U.S. patent application number 10/909670 was filed with the patent office on 2005-01-20 for laser radiation source.
Invention is credited to Jurgensen, Heinrich.
Application Number | 20050013328 10/909670 |
Document ID | / |
Family ID | 7880183 |
Filed Date | 2005-01-20 |
United States Patent
Application |
20050013328 |
Kind Code |
A1 |
Jurgensen, Heinrich |
January 20, 2005 |
Laser radiation source
Abstract
In a method and system for processing a processing surface of a
material, a mounting receives the material with the processing
surface. At least one fiber laser comprising a pump source and a
laser fiber has an infeed end, an outfeed end, and a core
surrounded by a pump core, the pump source being positioned at the
infeed end, and the laser fiber outputting a continuous wave laser
beam at the outfeed end. At least one of the laser beam and the
processing surface are laterally movable with respect to each
other. A focusing optics is provided through which the laser beam
passes. The laser beam output from the laser fiber is
diffraction-limited to permit the focusing optics to focus the
laser beam onto the processing surface as a spot having a spot size
sufficiently small to create a fine structure by processing
material at the processing surface.
Inventors: |
Jurgensen, Heinrich;
(Raisdorf, DE) |
Correspondence
Address: |
SCHIFF HARDIN, LLP
PATENT DEPARTMENT
6600 SEARS TOWER
233 SOUTH WACKER DRIVE
CHICAGO
IL
60606-6473
US
|
Family ID: |
7880183 |
Appl. No.: |
10/909670 |
Filed: |
July 30, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10909670 |
Jul 30, 2004 |
|
|
|
09786742 |
Sep 14, 2001 |
|
|
|
09786742 |
Sep 14, 2001 |
|
|
|
PCT/DE99/02721 |
Sep 1, 1999 |
|
|
|
Current U.S.
Class: |
372/6 ; 372/24;
372/9 |
Current CPC
Class: |
B23K 26/0884 20130101;
B23K 2103/50 20180801; B23K 26/382 20151001; B23K 26/389 20151001;
B23K 26/0643 20130101; B23K 26/0861 20130101; B23K 26/0608
20130101; B23K 26/0676 20130101; B23K 26/142 20151001; B41C 1/05
20130101; B23K 26/0665 20130101; B23K 2101/40 20180801; B23K 26/064
20151001; B23K 26/0613 20130101; B23K 26/082 20151001; B23K 26/0622
20151001; B23K 26/40 20130101; B23K 26/0652 20130101; B23K 26/0604
20130101; B23K 26/067 20130101; B23K 26/0648 20130101; B23K 26/1462
20151001 |
Class at
Publication: |
372/006 ;
372/009; 372/024 |
International
Class: |
H01S 003/30; H01S
003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 8, 1998 |
DE |
198 40 926.5 |
Sep 8, 1998 |
DE |
198409265 |
Claims
1-263. (cancelled).
264. A material processing system for processing a processing
surface of a material, comprising: a mounting which receives said
material with the processing surface; at least one fiber laser
comprising a pump source and a laser fiber having an outfeed end
and a core surrounded by a pump core, said pump source being
positioned at said laser fiber, and said laser fiber outputting a
laser beam at said outfeed end; said laser fiber outfeed end being
spaced from said surface, and at least one of said laser beam and
said processing surface being laterally movable with respect to
each other; focusing optics through which said laser beam passes;
and the laser beam output from said laser fiber outfeed end being
diffraction-limited to permit said focusing optics to focus the
laser beam onto said processing surface as a spot having a spot
size sufficiently small to create a fine structure by removing
material at said processing surface.
265. A system according to claim 264 wherein said focusing optics
comprises a lens on a terminator connected to said laser fiber
outfeed end.
266. A system according to claim 264 wherein said focusing optics
comprises a laser gun having a lens.
267. A system according to claim 266 wherein said laser gun has a
modulator which controls the laser beam.
268. A system according to claim 264 wherein the spot size is equal
to or less than approximately 10 micrometers in diameter.
269. A system according to claim 264 wherein the spot size is equal
to or less than approximately 20 micrometers in diameter.
270. A system according to claim 264 wherein the laser beam at the
spot has a power of at least approximately 100 watts at full beam
intensity.
271. A system according to claim 264 wherein the laser beam at said
spot has a power density of at least approximately
10.sup.7W/cm.sup.2 at full beam intensity.
272. A system according to claim 264 wherein said pump source
comprises at least one laser diode.
273. A system according to claim 266 wherein: a housing is provided
having said mounting for the processing surface; the pump source
and an end of the laser fiber opposite the outfeed end are mounted
in a fixed position with respect to said housing; the laser gun is
mounted for lateral movement parallel to said processing surface;
and said laser gun having at an output end adjacent said processing
surface said lens and at an input end said modulator, said laser
fiber outfeed end being connected to said input end of said laser
gun and moveable as said laser gun moves.
274. A system according to claim 273 wherein one of said laser
fiber outfeed end and an outfeed end of a passive fiber connected
to said laser fiber are at said input end of said laser gun.
275. A system according to claim 264 wherein a reflection surface
is positioned to deflect the laser beam when it is intended that it
not strike said processing surface.
276. A system according to claim 264 wherein a sump is positioned
to receive the laser beam when it is intended that it not strike
said processing surface.
277. A system of claim 276 wherein a reflection surface is
positioned to deflect said laser beam to said sump when it is
intended that the laser beam should not strike said processing
surface.
278. A system according to claim 277 wherein said reflection
surface and sump are positioned on a laser gun after the outfeed
end of the laser fiber.
279. A system according to claim 267 wherein a diffraction optics
is provided between said lens and an output of said modulator.
280. A system of claim 264 wherein a modulator is located to
modulate said laser beam from said outfeed end.
281. A system according to claim 264 wherein said pump source
comprises a plurality of laser diodes having light outputs directed
to said laser fiber.
282. A system according to claim 264 wherein said laser fiber
comprises two surfaces positioned to reflect laser light in said
laser fiber.
283. A system according to claim 264 wherein at least one of said
laser fiber and a passive fiber connected to said laser fiber has a
length which is significantly greater than a distance between said
pump source and an input end of a laser gun.
284. A system according to claim 264 wherein said laser fiber is
flexibly arranged in a pattern with bends to take up an excess
length of said laser fiber between a laser gun and said pump
source.
285. A system according to claim 273 wherein said housing has a
controller, and wherein at a top side of said housing said flat
processing surface is positioned along with said laterally moveable
laser gun.
286. A system according to claim 264 wherein said laser fiber
comprises an outfeed reflection surface and another reflection
surface spaced from said outfeed reflection surface.
287. A system according to claim 267 wherein at one of said outfeed
end of said laser fiber and an outfeed end of a passive fiber a
terminator is connected with an optics adjacent an input of said
modulator which converts the laser beam exiting the laser fiber
with diverging rays to parallel rays which enter at the input of
the modulator.
288. A system according to claim 264 wherein a terminator having an
optics is adjustably attached to said laser fiber at said outfeed
end to set a distance between an end of said core of said laser
fiber and said terminator optics.
289. A system according to claim 267 wherein said modulator
comprises an acousto-optical modulator which receives a control
signal having a frequency which controls a deflection angle of the
laser beam output from said modulator.
290. A system according to claim 267 wherein said modulator
comprises an acousto-optical modulator and an amplitude of a
control signal fed to said modulator controls an amplitude of the
laser beam exiting from the modulator.
291. A system according to claim 275 wherein said reflection
surface is positioned after an output of a modulator and is angled
so as to direct said laser beam deflected by the reflection surface
to a sump, said sump being attached to a laser gun radially
outwardly from a longitudinal axis of said laser gun.
292. A system according to claim 275 wherein said reflection
surface is positioned on a laser gun with respect to a longitudinal
axis of said laser gun between an output of a modulator and a
diffraction optics in said laser gun.
293. A system according to claim 267 wherein said modulator
comprises an acousto-optical modulator on said laser gun and is
positioned such that a control signal fed to said modulator
controls an output angle of said laser beam from said modulator by
a frequency of said control signal to selectively strike said
processing surface through the lens.
294. A system according to claim 267 wherein said modulator
comprises an acousto-optical modulator positioned in said laser gun
such that given no control signal fed to said modulator the output
laser beam from the modulator hits a reflection surface and given
presence of the control signal with a prescribed frequency said
laser beam output from said modulator passes through said focusing
lens and hits said processing surface.
295. A system according to claim 279 wherein said diffraction
optics is mounted in said laser gun, and, relative to a traveling
direction of the laser beam, said diffraction optics causes a laser
beam output from said modulator to diverge prior to passing through
said lens.
296. A system according to claim 264 wherein said focusing optics
comprises at least one lens and focuses the laser beam onto said
processing surface to form a laser spot at said processing surface
having a diameter equal to or less than approximately 10 um.
297. A system according to claim 264 wherein said material
processing surface comprises a semiconductor.
298. A system according to claim 297 wherein said semiconductor
comprises a wafer.
299. A system according to claim 264 wherein said laser beam is
oriented so that the laser beam strikes said processing surface at
an angle which is less than 90.degree. relative to a perpendicular
of said processing surface.
300. A system according to claim 264 wherein said laser fiber
converts a relatively large diameter of a pump spot at said infeed
end to a relatively much smaller diameter of the output laser beam
from said core at said outfeed end of said laser fiber.
301. A system according to claim 264 wherein said laser fiber at
said outfeed end connects to a passive fiber.
302. A system according to claim 264 wherein said laser fiber at
said outfeed end connects to a terminator, said terminator having
an open portion a lens.
303. A system according to claim 266 wherein a plurality of laser
fibers are provided between said pump source and said laser gun,
and a coupler which combines outfeed ends of said plurality of
laser fibers being connected to said laser gun.
304. A system according to claim 264 wherein a plurality of fiber
lasers are provided.
305. A system according to claim 266 wherein said laser fiber
connects to a coupler having at its output end a plurality of
passive fibers, output ends of said passive fibers being connected
to said laser gun.
306. A system according to claim 267 wherein said modulator
comprises an electro-optical modulator which changes a polarization
direction of a laser beam passing therethrough, and wherein a
polarization direction sensitive element follows said
electro-optical modulator so that depending upon a polarization
direction, the element either transmits a laser beam which is
communicated to said lens and then to said processing surface, or
deflects the laser beam.
307. A system according to claim 266 wherein a plurality of said
laser fibers are provided connected to said laser gun for
outputting onto said processing surface a plurality of said laser
beams.
308. A system according to claim 307 wherein said plurality of
laser beams are focused to a common spot.
309. A system according to claim 307 wherein said plurality of
laser beams are arranged to provide spots along a line next to one
another on said processing surface.
310. A laser system according to claim 266 wherein a plurality of
said laser guns are provided spaced from each other adjacent to
said processing surface and in a direction along and parallel to
said processing surface, each laser gun being fed by at least one
laser fiber.
311. A system according to claim 266 wherein in said laser gun
between said focusing optics and said processing surface a base
member having an inner cavity is provided with a transparent plate
through which said laser beam passes on its way to said processing
surface through said cavity, and after said transparent plate at
least one extraction channel which extracts unwanted eroded
material from said cavity.
312. A system according to claim 273 wherein the housing has at an
upper side said mount and said movable laser gun positioned
adjacent thereto, and wherein a lower portion of said housing has a
controller, modulation signal unit, and a cooling system, the
cooling system being connected to cool said pump source, and
wherein said laser fiber extends between said pump source fixedly
mounted in said lower portion of said housing up to said laser gun
at said upper portion of said housing.
313. A system according to claim 264 wherein said laser beam
striking said processing surface creates said fine structure as at
least one of the laser beam and the processing surface move
laterally with respect to each other.
314. A system according to claim 264 wherein said laser beam
striking the processing surface is amplitude modulated to cause a
changing intensity of said laser light beam for causing different
amounts of said material to be eroded depending on an intensity of
said laser light beam.
315. A system according to claim 264 wherein a penetration depth of
said fine structure changes dependent upon an intensity of said
laser light beam.
316. A system according to claim 264 wherein said fine structure
comprises holes.
317. The system according to claim 264 wherein an intensity of said
laser beam is controlled by a modulator in accordance with at least
an 8-bit signal fed to said modulator.
318. A system according claim 264 wherein said structure comprises
eroded material forming a line in the processing surface.
319. A system according to claim 264 wherein said material is used
for creating a printed circuit board.
320. A system according to claim 264 wherein a modulation control
of said laser beam allows adjusting a depth of said fine structure
within a fraction of a micrometer.
321. A system according to claim 264 wherein the processing of the
material comprises individual circuits cut from a semiconductor
wafer.
322. A system according to claim 267 wherein the modulator is
located on the laser gun and an optics is provided such that
parallel rays of the laser beam leaving the modulator diverge and
when the laser beam passes through the focusing optics rays of the
laser beam converge.
323. A system according to claim 264 wherein the fine structure
comprises eroded holes.
324. A system according to claim 264 wherein the laser beam erodes
the processing surface as the mount moves the processing
surface.
325. A system according to claim 264 wherein at least one of the
outfeed end of the laser fiber and an outfeed end of a passive
fiber connected to said laser fiber is moved during the
structuring.
326. A system according to claim 264 wherein the processing surface
comprises at least one of metal, ceramic, glass, semiconductor,
rubber, and plastic.
327. A system according to claim 264 wherein the laser beam
impinging on the processing surface creates the structure such that
a shape of the structure is created independently of a size of the
structure at the processing surface.
328. A system according to claim 264 wherein the laser beam
impinging on the processing surface creates an area of the
structure at the processing surface which is independent of its
depth.
329. A system according to claim 264 wherein the laser fiber has an
absorption efficiency of more than 60%.
330. A system according to claim 264 wherein the laser fiber core
has a diameter which creates a laser radiation beam at its outfeed
end having a diameter of approximately 10 .mu.m or less.
331. A system according to claim 264 wherein said processing
surface is substantially flat, and said mount moves the processing
surface in at least two dimensions.
332. A system according to claim 273 wherein one of the laser fiber
outfeed end and an outfeed end of a passive fiber connected to said
laser fiber is directly connected at the input end of the movable
laser gun and proceeds in a pattern with bends back to the pump
source at a fixed location on the housing.
333. A system according to claim 264 wherein said material
comprises at least a layer of a printed circuit board and the
material at the processing surface is eroded to form at least one
of bores and patterns of interconnects for the printed circuit
board.
334. A system according to claim 264 wherein the laser beam at said
spot has a power density of at least approximately 10.sup.7
W/cm.sup.2.
335. A system according to claim 264 wherein the processing surface
comprises a semiconductor wafer which is at least one of excised
and cut to provide differing fine patterns on the surface.
336. A system according to claim 264 wherein the processing surface
comprises a display screen structured by the laser beam.
337. A system according to claim 265 wherein said terminator
comprises a body with an aperture receiving one of said outfeed end
of said laser fiber and an outfeed end of a passive fiber connected
to said laser fiber, the lens being provided at an end of said
body, and said body being adjustable and positioned to adjust a
spacing of said lens from one of said outfeed end of said laser
fiber and said passive fiber outfeed end.
338. A system according to claim 264 wherein a plurality of fiber
lasers are provided and wherein at least one of the outfeed end of
said laser fiber and an outfeed end of a passive fiber connected to
said laser fiber of each laser being arranged along a line and at a
substantially same distance from said processing surface.
339. A system according to claim 338 wherein each of the laser
fiber outfeed ends has a respective terminator with a lens thereon
connected to the laser fiber.
340. A system according to claim 338 wherein said material
comprises a semiconductor which is cut by each of the laser beams
from the respective fiber lasers.
341. A system according to claim 264 wherein a plurality of fiber
lasers are provided and respective outfeed ends thereof are
commonly connected to a carrier.
342. A system according to claim 341 wherein the carrier is
rotatable so that a spacing between the laser beams can be changed
on the processing surface by rotating the carrier.
343. A system according to claim 341 wherein the carrier has a
guide, each of at least one of the outfeed ends of the fiber lasers
and outfeed ends of passive fibers connected to said laser fibers
being mounted adjustably to the guide so that a spacing between the
laser beams can be adjusted.
344. A system according to claim 341 wherein each of the laser
fiber outfeed ends has a connected terminator and the terminator is
mounted by a mounting element in adjustable fashion to the
carrier.
345. A system according to claim 341 wherein the carrier is
connected to a laser carrier guiding machine which allows movement
of the carrier towards and away from the processing surface and
also movement of the carrier in a direction parallel to the
processing surface.
346. A system according to claim 345 wherein said carrier is
rotatable by said machine about a vertical axis perpendicular to
said processing surface.
347. A system according to claim 264 wherein the processing surface
is substantially flat and the mounting comprises a table on which
the material with the processing surface is positioned.
348. A system according to claim 264 wherein the mounting is
moveable in at least one dimension.
349. A system according to claim 264 wherein the mounting is
movable in at least two dimensions.
350. A system according to claim 264 wherein the mounting is
movable in at least three dimensions.
351. A system according to claim 264 wherein the laser fiber
outfeed end is stationary, the processing surface is stationary,
and at least one optical element is employed which causes movement
of the laser beam across the processing surface in at least one
dimension.
352. A system according to claim 351 wherein the movement is in at
least two dimensions.
353. A system according to claim 264 wherein the mounting is
movable in at least in one dimension with the laser fiber outfeed
end being stationary and at least one optical element is provided
which moves the laser beam in at least one different dimension
relative to the processing surface.
354. A system according to claim 264 wherein optical elements
comprising a rotating mirror, a deflection mirror, and an optics
are utilized to move the laser beam relative to the processing
surface while the laser fiber outfeed end remains stationary.
355. A system according to claim 264 wherein a chamber is provided
adjacent the processing surface through which the laser beam passes
and which collects eroded material.
356. A system according to claim 355 wherein the chamber comprises
a suction outlet.
357. A system according to claim 355 wherein the chamber comprises
a gas inlet which, combined with a gas outlet, removes eroded
material during the fine structuring.
358. A system according to claim 355 wherein said chamber comprises
a glass plate closing off an end of the chamber and through which
said laser beam passes.
359. A system according to claim 264 wherein the material with the
processing surface comprises a pattern of photo-voltaic cells and a
plurality of fiber lasers with respective laser beams are employed
for the processing.
360. A material processing system for processing a processing
surface of a material, comprising: a mounting which receives said
material with the processing surface; at least one fiber laser
comprising a pump source and a laser fiber having an outfeed end
and a core surrounded by a pump core, said pump source being
positioned at said laser fiber, and said laser fiber outputting a
laser beam at said outfeed end; at least one of said laser beam and
said processing surface being movable with respect to each other;
focusing optics through which said laser beam passes; and the laser
beam output from said laser fiber outfeed end being
diffraction-limited to permit said focusing optics to focus the
laser beam onto said processing surface as a spot having a spot
size sufficiently small to create a fine structure by removing
material at said processing surface.
361. A material processing system for processing a processing
surface of a material, comprising: a mounting which receives said
material with the processing surface; at least one fiber laser
comprising a pump source and a laser fiber having an outfeed end
and a core surrounded by a pump core, said pump source being
positioned at said laser fiber, and said laser fiber outputting a
laser beam at said outfeed end; said laser fiber outfeed end having
a connected terminator with a lens, and the terminator being
connected to a laser gun, said laser gun having an optics through
which said laser beam directed through said terminator lens passes
on its way to said processing surface, and wherein said terminator
lens and said laser gun optics comprise a focusing optics; at least
one of said laser gun and said processing surface being movable
with respect to each other; the laser beam output from said laser
fiber outfeed end being diffraction-limited to permit said focusing
optics to focus the laser beam onto said processing surface as a
spot having a spot size sufficiently small to create a fine
structure by removing material at said processing surface.
362. A material processing system for processing a substantially
flat processing surface of a material, comprising: a mounting which
receives said material with the substantially flat processing
surface, said material comprising at least one of a metal, a
semiconductor, ceramic, plastic, and a rubber; at least one fiber
laser comprising a pump source and a laser fiber having an outfeed
end and a core surrounded by a pump core, said pump source being
positioned at said laser fiber, and said laser fiber outputting a
laser beam at said outfeed end; said laser fiber outfeed end being
spaced from said flat surface, and at least one of said laser beam
and said substantially flat processing surface being laterally
movable with respect to each other; focusing optics through which
said laser beam passes; and the laser beam output from said laser
fiber outfeed end being diffraction-limited to permit said focusing
optics to focus the laser beam onto said processing surface as a
spot having a spot size sufficiently small to create a fine
structure by processing material at said material processing
surface.
363. A system according to claim 362 wherein said fine structure
comprises cuts in a semiconductor material to divide up said
semiconductor material into pieces.
364. A system according to claim 362 wherein said fine structure
comprises holes in a semiconductor material.
365. A system according to claim 362 wherein said fine structure
comprises eroded lines in said processing surface.
366. A method for processing a processing surface of a material,
comprising the steps of: providing a mounting to receive said
material with the processing surface; providing at least one fiber
laser comprising a pump source and a laser fiber having an outfeed
end and a core surrounded by a pump core, said pump source being
positioned at said laser fiber, and said laser fiber outputting a
laser beam at said outfeed end; providing a focusing optics through
which said laser beam passes; providing the laser beam output from
said laser fiber outfeed end as diffraction-limited to permit said
focusing optics to focus the laser beam onto said processing
surface as a spot having a spot size sufficiently small to create a
fine structure by removing material at said processing surface;
providing said laser fiber outfeed end at a spacing from said
processing surface; and moving at least one of said laser beam and
said processing surface with respect to each other and creating
said fine structure by removing material at said processing
surface.
367. A method according to claim 366 wherein the moving occurs
during said removing of the material when creating at least a
portion of said fine structure.
368. A method according to claim 366 wherein the fine structure
comprises making holes in the processing surface.
369. A method according to claim 366 wherein said fine structure
comprises cutting off pieces of said material at said processing
surface.
370. A method according to claim 366 wherein said fine structure
comprises eroding lines into said processing surface.
371. A method according to claim 366 wherein the spot size is equal
to or less than approximately 20 micrometers diameter.
372. A method according to claim 366 wherein the spot size is equal
to or less than approximately 10 micrometers diameter.
373. A method according to claim 366 wherein the laser beam at the
spot has a power of at least approximately 100 watts at full beam
intensity.
374. A method according to claim 366 wherein the laser beam at said
spot has a power density of at least approximately 10.sup.7
W/cm.sup.2 at full beam intensity.
375. A method according to claim 366 wherein said pump source
comprises at least one laser diode.
376. A method according to claim 366 including the steps of:
providing a housing for said processing surface mounting; mounting
the pump source and an end of said laser fiber opposite said
outfeed end in a fixed position with respect to said housing;
connecting the laser outfeed end to a laser gun positioned adjacent
said processing surface; and providing said laser gun at an output
end adjacent said drum with a lens, and at an input end with a
modulator, and providing at least one of said laser fiber outfeed
end connected to said input end of said laser gun and an outfeed
end of a passive fiber connected to said laser fiber and connected
to said laser gun so that as the laser gun moves at least one of
the laser fiber outfeed end and passive fiber outfeed end also
moves.
377. A method according to claim 376 wherein one of said laser
fiber outfeed end and passive fiber outfeed end is secured at said
input end of said laser gun and moves along with said laser gun
during the processing.
378. A method according to claim 376 wherein a reflection surface
is positioned in said laser gun after an output of said modulator,
a sump is positioned on said laser gun, and as said material is
being processed, a laser beam from said modulator is deflected by
said reflection surface to said sump.
379. A method according to claim 366 including providing a lens in
front of a modulator through which said laser beam passes so that
parallel rays from said modulator diverge prior to the laser beam
entering the focusing optics.
380. A method according to claim 366 including providing a
plurality of laser diodes having outputs directed to said laser
fiber.
381. A method of claim 366 including the step of providing at least
one of said laser fiber and a passive fiber connected to said laser
fiber with a length sufficiently greater than a distance between
said pump source and an input end of a laser gun.
382. A method according to claim 366 wherein after said outfeed end
of said laser fiber a lens is provided so that the laser beam
entering an input to a modulator has parallel rays.
383. A method according to claim 366 including the step of
connecting said laser fiber at said outfeed end to a passive
fiber.
384. A method according to claim 366 wherein a modulator is
provided which comprises an acousto-optical modulator mounted in a
laser gun and providing a control signal having a frequency which
controls a deflection angle of the laser beam output from said
modulator.
385. A method according to claim 366 wherein an amplitude of a
control signal fed to a modulator controls an amplitude of the
laser beam exiting from the modulator.
386. A method according to claim 366 wherein a modulator is
provided which comprises an acousto-optical modulator and a control
signal fed to said modulator controls by its frequency an output
angle of said laser beam from said modulator to selectively strike
said processing surface through said focusing optics.
387. A method according to claim 366 wherein a modulator is
provided through which said laser beam passes.
388. A method according to claim 366 wherein said processing
surface comprises a semiconductor.
389. A method according to claim 366 including the step of having
said laser beam strike said processing surface at an angle which is
less than 90 degrees relative to a perpendicular to a said
processing surface.
390. A method according to claim 366 including the step of
providing a plurality of fiber lasers.
391. A method according to claim 366 wherein an optics is provided
so that diverging rays of the laser beam exiting the core of the
laser fiber enter a modulator in parallel.
392. A method according to claim 366 wherein a modulator is
provided which comprises an electro-optical modulator which changes
a polarization direction of the laser beam passing there through,
and wherein a polarization direction sensitive reflection surface
follows said electro-optical modulator.
393. A method according to claim 366 wherein a laser gun connected
to at least one of said fiber lasers outputs onto said processing
surface a plurality of laser beams.
394. A method according to claim 393 wherein said plurality of
laser beams are focused to a common spot.
395. A method according to claim 366 wherein a plurality of laser
beams provide spots along a line next to one another on said
processing surface.
396. A method according to claim 366 wherein a plurality of fiber
lasers are provided spaced apart from each other adjacent to said
processing surface.
397. A method according to claim 366 wherein said laser beam
striking the processing surface is amplitude modulated to cause a
changing intensity of said laser light beam for causing different
amounts of said surface to be eroded depending on an intensity of
said laser beam.
398. A method according to claim 366 including the step of
providing a plurality of said fiber lasers each having a connected
terminator at an end thereof, each terminator having a lens.
399. A method according to claim 398 wherein the terminators are
positioned a same distance from said processing surface.
400. A method according to claim 366 including the step of
connecting a terminator to the laser fiber.
401. A method according to claim 400 including the step of rotating
the carrier to change a spacing between the laser beams from the
respective terminators.
402. A method according to claim 366 including the step of
providing a chamber which removes eroded material from the
processing surface, said laser beam passing through said
chamber.
403. A method according to claim 402 including the step of
providing a vacuum in the chamber to remove the eroded
material.
404. A method according to claim 366 wherein the mounting is moved
in at least two dimensions.
405. A method according to claim 366 including the step of moving
at least one of the outfeed end of the laser fiber and an outfeed
end of a passive fiber connected to the laser fiber in at least one
dimension.
406. A method according to claim 366 including the step of moving
at least one of the outfeed end of the laser fiber and an outfeed
end of a passive fiber connected to the laser fiber in at least two
dimensions.
407. A method according to claim 366 including the step of
providing at least one of the outfeed end of the laser fiber and an
outfeed end of a passive fiber connected to the laser fiber in a
fixed position and moving the laser beam with optical elements
across said processing surface.
408. A method according to claim 407 including the step of moving
the mounting in at least one dimension.
409. A method for processing a processing surface of a material,
comprising the steps of: providing a mounting to receive said
material with the processing surface; providing at least one fiber
laser comprising a pump source and a laser fiber having an outfeed
end and a core surrounded by a pump core, said pump source being
positioned at said laser fiber, and said laser fiber outputting a
laser beam at said outfeed end; providing a focusing optics through
which said laser beam passes; providing the laser beam output from
said laser fiber outfeed end as diffraction-limited to permit said
focusing optics to focus the laser beam onto said processing
surface as a spot having a spot size sufficiently small to create a
fine structure by removing material at said processing surface; and
moving at least one of said laser beam and said processing surface
with respect to each other.
410. A method for processing a substantially flat processing
surface of a material, comprising the steps of: providing a
mounting to receive said material with the substantially flat
processing surface, the material comprising at least one of a
metal, a semiconductor, a ceramic, and a rubber; providing at least
one fiber laser comprising a pump source and a laser fiber having
an outfeed end and a core surrounded by a pump core, said pump
source being positioned at said laser fiber, and said laser fiber
outputting a laser beam at said outfeed end; providing focusing
optics; providing the laser beam output from said laser fiber
outfeed end as diffraction-limited to permit said laser gun to
focus the laser beam onto said processing surface with the focusing
optics as a spot having a spot size equal to or less than 20 .mu.m
to create a fine structure by processing material at said
processing surface; providing said laser fiber outfeed end at a
spacing from said processing surface; and moving at least one of
said laser beam and said processing surface laterally with respect
to each other and creating said fine structure by processing
material at said processing surface.
411. A material processing system for processing a surface of a
material, comprising: at least one fiber laser comprising a pump
source and a laser fiber having an outfeed end and a core
surrounded by a pump core, said pump source being positioned at
said laser fiber, and said laser fiber outputting a continuous wave
laser beam at said outfeed end; said laser fiber outfeed end being
spaced from said surface, and at least one of said laser beam and
said surface being movable with respect to each other; focusing
optics through which said laser beam passes; and the laser output
from said laser fiber outfeed end being diffraction-limited to
permit said focusing optics to focus the laser beam onto said
surface as a spot having a spot size sufficiently small to create a
fine structure by processing material at said surface.
412. A system according to claim 411 wherein a modulator is
provided after said outfeed end of said laser fiber to control said
continuous wave laser beam.
413. A system according to claim 412 wherein said modulator changes
an intensity of said laser beam.
414. A system according to claim 412 wherein said modulator
controls whether or not the laser beam strikes said surface.
415. A system according to claim 411 wherein said surface comprises
a printing form.
416. A method for processing a surface of a material, comprising
the steps of: providing at least one fiber laser comprising a pump
source and a laser fiber having an outfeed end and a core
surrounded by a pump core, said pump source being positioned at
said laser fiber, and said laser fiber outputting a continuous wave
laser beam at said outfeed end; providing a focusing optics through
which said laser beam passes; providing the laser beam output from
said laser fiber outfeed end as diffraction-limited to permit said
focusing optics to focus the laser beam onto said surface as a spot
having a spot size sufficiently small to create a fine structure by
processing material at said surface; providing said laser fiber
outfeed end at a spacing from said surface; and moving at least one
of said laser beam and said surface with respect to each other.
417. A method of claim 416 including providing a modulator through
which said laser beam from the outfeed end of said laser fiber
passes.
418. A method of claim 417 wherein the modulator changes an
intensity of the laser beam.
419. A method of claim 417 wherein the modulator determines whether
or not the laser beam reaches the surface.
420. A method according to claim 416 wherein the surface comprises
a printing form.
421. A material processing system for processing a surface of a
material, comprising: at least one fiber laser comprising a pump
source and a laser fiber having an outfeed end and a core
surrounded by a pump core, said pump source being positioned at
said laser fiber, and said laser fiber outputting a pulsed laser
beam at said outfeed end; said laser fiber outfeed end being spaced
from said surface, and at least one of said laser beam and said
surface being movable with respect to each other; focusing optics
through which said laser beam passes; and the laser output from
said laser fiber outfeed end being diffraction-limited to permit
said focusing optics to focus the laser beam onto said surface as a
spot having a spot size sufficiently small to create a fine
structure by processing material at said surface.
422. A system according to claim 421 wherein a modulator is
provided which internally modulates the pulsed laser beam.
423. A system according to claim 421 wherein a modulator externally
modulates the pulsed laser beam.
424. A system according to claim 421 wherein an acousto-optical
modulator within a laser resonator of the laser fiber modulates the
pulsed laser beam.
425. A system according to claim 421 wherein said surface comprises
a printing form.
426. A system according to claim 421 wherein said pulsed laser beam
comprises a quality-switched laser beam.
427. A method for processing a surface of a material, comprising
the steps of: providing at least one fiber laser comprising a pump
source and a laser fiber having an outfeed end and a core
surrounded by a pump core, said pump source being positioned at
said laser fiber, and said laser fiber outputting a pulsed laser
beam at said outfeed end; providing a focusing optics through which
said laser beam passes; providing the laser beam output from said
laser fiber outfeed end as diffraction-limited to permit said
focusing optics to focus the laser beam onto said surface as a spot
having a spot size sufficiently small to create a fine structure by
processing material at said surface; providing said laser fiber
outfeed end at a spacing from said surface; and moving at least one
of said laser beam and said surface with respect to each other.
428. A method according to claim 427 wherein a modulator is
provided which internally modulates the pulsed laser beam.
429. A method according to claim 427 wherein a modulator externally
modulates the pulsed laser beam.
430. A method according to claim 427 wherein an acousto-optical
modulator within a laser resonator of the laser fiber modulates the
pulsed laser beam.
431. A method according to claim 427 wherein said surface comprises
a printing form.
432. A method according to claim 427 wherein said pulsed laser beam
comprises a quality-switched laser beam.
433. A material processing system for processing a surface of a
material, comprising: at least one fiber laser comprising a pump
source and a laser fiber having an outfeed end and a core
surrounded by a pump core, said pump source being positioned at
said laser fiber, and said laser fiber outputting a laser beam at
said outfeed end; at least one of said laser beam and said surface
being movable with respect to each other; and the laser beam output
from said laser fiber outfeed end being diffraction-limited to
permit said laser beam impinging onto said surface as a spot to
have a spot size sufficiently small to create a fine structure by
processing material at said surface.
434. A method for processing a surface of a material, comprising
the steps of: providing at least one fiber laser comprising a pump
source and a laser fiber having an outfeed and a core surrounded by
a pump core, said pump source being positioned at said laser fiber,
and said laser fiber outputting a laser beam at said outfeed end;
providing the laser beam output from said laser fiber outfeed end
as diffraction-limited to permit said laser beam impinging onto
said surface to have a spot with a spot size sufficiently small to
create a fine structure by processing material at said surface; and
moving at least one of said laser beam and said surface with
respect to each other.
435. A method of claim 434 wherein said surface comprises at least
a layer of a printed circuit board.
436. A method of claim 434 wherein at least two fiber lasers are
provided outputting respective laser beams of at least one of
different wavelengths and different polarization directions, and
wherein the two laser beams are combined at said spot.
Description
BACKGROUND OF THE INVENTION
[0001] The invention is directed to a laser radiation source,
preferably for processing materials, as well as to an arrangement
for processing material comprising a laser radiation source and to
the operation thereof.
[0002] When processing materials with focused energy beams such as,
for example, electron beams or laser beams, there are applications
wherein structures must be produced that make high demands of the
focused energy beam with respect of its beam geometry and the
focusability of the beam. At the same time, however, a high beam
power is required.
[0003] A typical case wherein extremely fine structures must be
produced on a processing surface is the production of printing
forms, whether for rotogravure, offset printing, letter press
printing, silk screening or flexo-printing or for other printing
processes. In the production of printing forms, it is necessary to
produce extremely fine structures on the surface of the printing
forms, since highly resolved image information such as text,
screened images, graphics and line work must be reproduced with the
surface of the printing forms.
[0004] In rotogravure, the printing forms were produced in the past
with etching, which had led to good results; the etching, however,
was replaced over the course of time by more environmentally
friendly engraving with electromagnetically driven diamond styli.
Printing cylinders whose surface is composed of copper are normally
employed as printing forms in rotogravure, these fine structures
required for the printing being engraved thereinto in the form of
cups with the diamond stylus. The printing cylinders are introduced
into a printing press after they are produced, the cups being
filled with ink therein. Subsequently, the excess ink is removed
with a doctor blade and the remaining ink is transferred onto the
printed matter during the printing process. Copper cylinders are
thereby employed because of their long service life in the printing
process. A long service life is required given large editions, for
example, in particular, in magazine printing or packaging printing,
since the surface of the printing form wears in the printing
process as a result of the influence of the doctor blade and of the
printed matter. In order to extend the service life even further,
the printing cylinders are provided with a copper layer that has
been galvanized on; on the other hand, solid cylinders of copper
are employed. Another possibility of making the service life even
longer is comprised in galvanically chrome plating the copper
surface after the engraving. In order to achieve an even longer
service life, what is referred to as "hot chrome plating" is
additionally applied, whereby the galvanic process is carried out
under elevated temperature. The longest service lives that could
previously be obtained were achieved therewith. Deriving therefrom
is that copper is the most suitable as the material for the surface
of rotogravure cylinders. Materials other than copper have not
hitherto proven themselves for large editions.
[0005] When producing the cups, the drive of the diamond stylus
occurs via an electromechanically driven magnet system having an
oscillating armature to which the diamond stylus is secured. Such
an electromechanical oscillatory system cannot be made arbitrarily
fast because of the forces that must be exerted in order to engrave
the cups. This magnet system is therefore operated above its
resonant frequency so that the highest engraving frequency, i.e.
the highest engraving speed can be achieved. In order to increase
the engraving speed even further, a number of such engraving
systems have been arranged side-by-side in the axial direction of
the copper cylinder in given current engraving machines. This,
however, still does not suffice for the short engraving time of the
printing cylinders required currently, since the engraving time
directly influences the actuality of the printing result. For this
reason, rotogravure is not employed for newspaper printing but
mainly for magazine printing.
[0006] Upon utilization of a plurality of engraving systems, a
plurality of what are referred to as lanes are simultaneously
engraved into the surface of the printing cylinder. For example,
such a lane contains one or more entire magazine pages. One problem
that thereby arises is that cups having different volumes are
generated in the individual lanes given the same tone value to be
engraved, this occurring because of the different engraving systems
that are driven independently of one another and leading to
differences in the individual lanes that the eye detects during
later observation. For this reason, for example in packaging
printing, only one engraving system is employed so that these
errors, which are tolerated in magazine printing, do not occur.
[0007] When engraving the cups, the cup volume is varied dependent
on the image content of the master to be printed. The respective
tone value of the master should thereby be reproduced as exactly as
possible during printing. When scanning the masters, the
analog-to-digital converters having, for example, a resolution of
12 bits are utilized for recognizing the tone value gradations for
reasons of image signal processing (for example, gradation
settings), this corresponding to a resolution of 4096 tone values
in this case. The signal for the drive of the electromagnetic
engraving system is acquired from this high-resolution image
information, said signal usually being an 8-bit signal
corresponding to a resolution into 256 tone value gradations. In
order to generate the corresponding volumes that are required for
achieving this scope of gradations, the penetration depth of the
diamond stylus into the copper surface is varied with the drive of
the magnet system, whereby the geometry of the cups changes between
approximately 120 .mu.m diameter given a depth of 40 .mu.m and
approximately 30 .mu.m diameter given a depth of 3 .mu.m. Because
only an extremely small range of variation in the depth of the cups
between 40 .mu.m and 3 .mu.m is available, the penetration depth of
the stylus with which the cups are engraved must be exactly driven
to fractions of a .mu.m in order to reproducibly achieve the
desired range of gradation. As can be seen therefrom, an extremely
high precision is required in the engraving of the cups, at least
as regard to the generation of the required diameters and depths of
the cups. Since the geometry of the engraved cups is directly
dependent on the shape of the stylus, extremely high demands are
also made of the geometry of the diamond stylus which, as has been
shown, can only be achieved with extremely high expense and with a
high rejection rate in the manufacture of the styli. Moreover, the
diamond stylus is subject to wear since, when engraving a large
printing cylinder having fourteen lanes, a circumference of 1.8 m
and a length of 3.6 m given a screen of 70 lines/cm--which
corresponds to a plurality of 4900 cups/cm.sup.2, a stylus must
engrave approximately 20 million cups. When one of the diamond
styli breaks off during the engraving of a printing cylinder, then
the entire printing cylinder is unuseable. On the one hand, this
causes a considerable financial loss and, on the other hand,
represents a serious loss of time since a new cylinder must be
engraved, postponing the start of printing by hours. For this
reason, users frequently replace styli earlier than necessary. As
can also be seen therefrom, the endurance of the diamond styli is
also a critical concern.
[0008] All in all, electromagnetic engraving is well-suited for
producing high-quality rotogravure cylinders; however, it has a
number of weak points and is extremely complicated and one would
like to eliminate these disadvantages with a different method.
[0009] The cups produced in this way, which are intended to accept
the ink later, are also arranged on the surface of the printing
form in conformity with a fine, regular screen, namely the printing
screen, whereby a separate printing cylinder is produced for each
ink, and whereby a different screen having a different angle and
different screen width is respectively employed. When printing in
the printing press, given these screens, narrow bridges remain
between the individual cups, these supporting the doctor blade that
removes the excess ink after the inking. Another disadvantage of
this operating mode of this electromechanical engraving is that
texts and lines must also be reproduced in screened fashion, which
leads to step-patterns in the contours of the written characters
and the lines that the eye perceives as being disturbing. This is
one disadvantage compared to the widespread offset printing wherein
this stepping can be kept an order of magnitude lower, which can
then no longer be perceived by the eye, and which leads to a better
quality that rotogravure could hitherto not achieve. This is a
serious disadvantage of the rotogravure process.
[0010] In rotogravure, no stochastic screens can be generated
wherein the size of the cups and the position of the cups can be
randomly distributed corresponding to the tone value; this is not
possible when engraving with the diamond stylus. Such stochastic
screens are also frequently referred to as "frequency-modulated
screens" that have the advantage that details can be reproduced far
better with no Moir, this also leading to a better image quality
than in rotogravure.
[0011] It is also known to utilize the electron beam engraving
method applied in the processing of materials for generating the
cups, this having exhibited extremely good results because of the
high energy of the electron beam and the incredible precision with
respect to the beam deflection and beam geometry.
[0012] This method is described in the publication, "Schnelles
Elektronenstrahlgravierverfahren zur Gravur von Metallzylindern",
Optik 77, No. 2 (1987) pages 83-92, Wissenschaftliche
Verlagsgesellschaft mbH Stuttgart. Due to the extremely high
expense that is required for the hardware and electronics, electron
beam engraving has hitherto not prevailed in practice for the
engraving of copper cylinders for rotogravure but only in the steel
industry for surface engraving of what are referred to as textured
drums for sheet metal manufacture wherein textures are rolled into
the sheets.
[0013] It has been repeatedly proposed in the trade literature as
well as in the patent literature to engrave copper cylinders with
lasers. Since copper, however, is an extremely good reflector for
laser radiation, extremely high powers and, in particular,
extremely high power densities of the lasers to be employed are
required in order to penetrate into the copper and melt it. There
has hitherto not been any laser engraving unit with laser radiation
sources having a correspondingly high power density and energy with
which one succeeds in providing the copper cylinders for
rotogravure with the required cup structure in the copper
surface.
[0014] Attempts have nonetheless been made to utilize lasers for
rotogravure in that a switch has been made to materials other than
copper. Thus, for example, the publication DE-A-19 20 323 has
proposed to prepare copper cylinders with chemical etching such
that the surface of the copper cylinder already comprises cups that
have a volume that corresponds to the maximum printing density.
These cups are filled with a solid filler material, for example
plastic. Much of the filler material is then removed with a laser
until the desired cup volume has been achieved. This method in fact
manages with a lower laser power than would be necessary in order
to melt and evaporate the copper as in electron beam engraving. In
this method, however, the remaining plastic is attacked by the
solvent of the ink in the printing process and is decomposed, so
that only a low print run is possible. This method has not proven
itself in practice and has thus not been utilized.
[0015] The publication of the VDD Seminar Series, "Direktes
Lasergravierverfahren fur metallbeschichtete Tiefdruckzylinder",
published within the framework of a "Kolloquium vom Verein
Deutscher Druckingenieure e.V. und dem Fachgebiet Druckmaschinen
und Druckverfahren, Fachbereich Maschinenbau, Technische Hochschule
Darmstadt", by Dr. phil. Nat. Jakob Frauchiger, MDC Max Dtwyler, A
G, Darmstadt, 12 Dec. 1996, has proposed that rotogravure cylinders
plated with zinc be engraved by a quality-switched Nd:YAG
high-power solid-state laser pumped with arc lamps. In this method,
the volume of the cups is defined by the optical power of the
laser. The laser power required for the engraving is transmitted
onto the cylinder surface via an optical fiber whose output is
imaged onto the cylinder surface through a variable focusing
optics. One disadvantage of this method is that the arc lamps
required for pumping the laser have a relatively short service life
and must be replaced after approximately 500 hours of operation.
The engraving cylinder becomes unuseable given a failure of the
pump light source during the engraving. This corresponds to a
failure of the diamond stylus in electromechanical engraving and
results in the same disadvantages. A preventative replacement of
the arc lamps is cost-intensive and work-intensive, particularly
since one must count on the fact that the laser beam must be
re-adjusted in position after the replacement of the lamps. These
lamp-pumped solid-state lasers also have a very poor efficiency
since the laser-active material absorbs only a slight fraction of
the available energy from the pump source, i.e. from the arc lamp
here, and converts into laser light. Particularly given high laser
powers, this means a high electrical connection cost, high
operating costs for electrical energy and cooling and, in
particular, a considerable expense for structural measures due to
the size of the laser and the cooling unit. The space requirements
are so high that the laser unit must be located outside the machine
for space reasons, this in turn being accompanied by problems in
bringing the laser output onto the surface of the printing
cylinder.
[0016] A critical disadvantage of this method is that zinc is
significantly softer than copper and is not suitable as a surface
material for printing cylinders. Since the doctor blade with which
the excess ink is removed before printing in the printing press is
a steel blade, the zinc surface is damaged after a certain time and
the printing cylinder becomes unuseable. A printing cylinder having
a surface of zinc therefore does not even begin to approach as long
a service life in printing as a printing cylinder having a surface
of copper. Printing forms having a zinc surface are therefore not
suitable for high press runs.
[0017] Even if the zinc surface is chrome-plated after the
engraving, as has been also proposed in order to lengthen the
service life, the durability does not come close to that of normal
copper cylinders. Chrome does not adhere to zinc as well as it
adheres to copper and what is referred to as "hot chrome plating",
which is successfully employed given copper cylinders in order to
achieve an optimum adhesion of the chromium on the copper, is not
possible given zinc since the zinc would thereby melt. Since the
chrome layer does not adhere very well on the zinc, it is likewise
attacked by the doctor blade, which leads to a relatively early
failure of the printing cylinders. When, in contrast thereto,
copper cylinders are chrome-plated according to this method, then
incredibly high press runs are possible since the chromium firmly
adheres on the copper surface, so that these copper cylinders out
perform the chrome-plate zinc cylinders by far.
[0018] It proceeds from the publication EP-B-0 473 973, which is
likewise directed to the method described above, that an energy of
6 mWsec is required in this method given zinc for cutting a cup
having a diameter of 120 .mu.m and a depth of 30 .mu.m. An energy
of 165 mWsec is recited in this publication for copper, this
amounting to a factor of 27.5 for the required laser power. Lasers
having a continuous-wave performance of several kilowatts given
good beam quality are thus required in order to produce cups in
copper with a speed that is accessible for the printing industry.
Such a power, however, cannot be produced with the laser
arrangement described above. For this reason, it is likewise only
possible to engrave a zinc surface.
[0019] Such a laser arrangement, which is composed of a single
solid-state laser, in fact makes it possible to process rotogravure
cylinders having a zinc surface; if, however, one wishes to utilize
the advantages of the copper surface and stay with copper cylinders
and engrave these with a laser, the high power density required for
penetration into the surface of the copper and the high energy
required for melting the copper must be inevitably exerted. This,
however, has not hitherto been successfully done with a solid-state
laser.
[0020] It is known that the beam quality in solid-state lasers,
i.e. the focusability, decreases with increasing power. Even if the
power of the solid-state lasers were to be driven up or if a
plurality of solid-state lasers were directed onto the same cup or
parts thereof, it would therefore not be possible to satisfactorily
engrave copper cylinders for rotogravure with such a laser because
the precision of the laser beam, as offered by the electron beam,
required for generating the fine structures cannot be achieved. If
the laser power were increased given this apparatus, then a further
problem would arise: the focusing of high radiant intensity into
optical fibers is, as known, difficult. The fibers burn at high
power as a consequence of misadjustment at the infeed location. If
one wishes to avoid this, however, the fiber diameter would have to
be enlarged which, however, in turn has the disadvantage that the
fiber diameter would have to be imaged onto the processing material
with even greater demagnification. A demagnified imaging, however,
leads to an increase in the numerical aperture on the processing
surface and, consequently, to a reduced depth of field on the
processing surface. As proposed, the distance from the processing
surface could be kept constant. When, however, the beam penetrates
into the surface of the material, then a defocusing automatically
derives. This has a disadvantageous influence on the required power
density and on the exact dot size. Since, however, the diameter of
the processing spot and the energy of the beam determine the size
of the cup, it then becomes difficult to make the cup size as
exactly as required by the desired tone value. For this purpose, it
would also be necessary that the laser power is exactly constant
and also remains constant over the entire time that is required for
a cylinder engraving. When this is not the case, the cup size
changes and the cylinder becomes unuseable. This cannot be
compensated by varying the size of the processing spot since it is
not possible to adequately vary the processing spot in shape.
[0021] Further, a complicated modulator is required given such an
arrangement. As known, modulators for extremely high laser powers
are slow, this leading to a reduction of the modulation frequency
and, thus, of the engraving frequency. When, however, the engraving
frequency is too low, the energy diffuses into the environment of
the processing spot on the processing surface without cutting out a
cup. It is therefore necessary to also exert a high power in
addition to the high energy for the cutting.
[0022] The publication "Der Laser in der Druckindustrie", by Werner
Hulsbusch, page 540, Verlag W. Hulsbusch, Konstanz, describes that
it is particularly a matter of a high power density in processing
materials. Given power densities of typically above 10.sup.7
through 10.sup.8 W/cm.sup.2, a spontaneous evaporation of the
material occurs in all materials, this being accompanied by a
sudden absorption rise, which is especially advantageous since the
laser power is then no longer reflected from the metal surface.
When, for example, a laser source of 100 W is available, then the
processing spot diameter may not be larger than 10 .mu.m in order
to arrive at these values in the region, as proceeds from the
following equation: 100 W: (0.001 cm.times.0.001 cm)=10.sup.8
W/cm.sup.2.
SUMMARY OF THE INVENTION
[0023] One object of the present invention is to improve a laser
radiation source, preferably for processing materials as well as an
arrangement for processing materials having a laser radiation
source and the operation thereof such that an extremely high power
density and energy are achieved in a cost-beneficial way.
[0024] A material processing system and method is provided for
processing a processing surface of a material. A mounting receives
the material. At least one fiber laser comprising a pump source and
a laser fiber having an infeed end, outfeed end, and a core
surrounded by a pump core is provided. The pump source is
positioned at the infeed end and the laser fiber outputs a
continuous wave laser beam at the outfeed end. The laser fiber
outfeed end is spaced from the processing surface and at least one
of the laser beam and the processing surface are laterally movable
with respect to each other. A focusing optics is provided through
the laser beam passes. The laser beam output from the laser fiber
outfeed end is diffraction-limited to permit the focusing optics to
focus the laser beam onto the processing surface as a spot having a
spot size sufficiently small to create a fine structure by
processing material at the processing surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic illustration of the laser radiation
source;
[0026] FIG. 2 is a fundamental illustration of the fiber laser
(prior art);
[0027] FIG. 2a is a truncated illustration of the fiber of the
fiber laser (prior art);
[0028] FIG. 3 is a cross-section through an arrangement for
processing material with a laser radiation source of one preferred
embodiment;
[0029] FIG. 4 is an illustration of a laser gun for the laser
radiation source having a multiple arrangement of fiber lasers;
[0030] FIG. 4a is a perspective illustration relating to FIG.
4;
[0031] FIG. 4b is a version of FIG. 4;
[0032] FIG. 4c is a further version of FIGS. 4 and 4b;
[0033] FIG. 5 is an example of a terminator for the outfeed of the
radiation from a fiber or, respectively, from the fiber of a fiber
laser;
[0034] FIG. 5a is an example of a multiple arrangement for a
plurality of terminators;
[0035] FIG. 5b is an example of a terminator having adjustment
screws;
[0036] FIG. 5c is a cross-section through the terminator according
to FIG. 5b in the region of the adjustment screws;
[0037] FIG. 6 is an example of a terminator having spherical
adjustment elements;
[0038] FIG. 6a is a cross-section through the terminator according
to FIG. 6 in the region of the spherical adjustment elements;
[0039] FIG. 7 is an example of an embodiment of a terminator having
a conical fit for insertion into a mount;
[0040] FIG. 8 is an example of a multiple mount for a plurality of
terminators;
[0041] FIG. 8a shows the rear fastening of the terminators
according to FIG. 8;
[0042] FIG. 9 is an example of an embodiment having quadratic
cross-section;
[0043] FIG. 9a is a cross-section through the terminator according
to FIG. 9;
[0044] FIG. 10 is an example of a terminator having rectangular
cross-section and a trapezoidal plan view;
[0045] FIG. 10a is a longitudinal section through the terminator
according to FIG. 10;
[0046] FIG. 10b is a cross-section through the terminator according
to FIG. 10;
[0047] FIG. 11 is an example of a terminator having trapezoidal
cross-section;
[0048] FIG. 11a is an example of a terminator having triangular
cross-section;
[0049] FIG. 12 is an example of a terminator having
honeycomb-shaped cross-section;
[0050] FIG. 13 is a modular implementation of the fibers of the
fiber laser according to FIG. 1;
[0051] FIG. 14 is an example of the infeed of the pump energy into
the fibers of the fiber laser according to FIG. 13;
[0052] FIG. 15 is an example of a fiber laser having two
outputs;
[0053] FIG. 16 is an example of the merging of two fiber
lasers;
[0054] FIG. 17 is a schematic illustration of the beam path through
an acousto-optical deflector or, respectively, modulator;
[0055] FIG. 18 shows blanking out unwanted sub-beams of an
acousto-optical deflector or, respectively, modulator;
[0056] FIG. 18a is an arrangement having an electro-optical
modulator;
[0057] FIG. 19 is a plan view onto a four-channel acousto-optical
modulator;
[0058] FIG. 19a is a section through the modulator according to
FIG. 19;
[0059] FIG. 20 is a schematic beam path for a plan view for FIG.
4;
[0060] FIG. 21 is a schematic beam path for a plan view for FIG.
4b;
[0061] FIG. 22 is a schematic beam path for a plan view for FIG.
4c;
[0062] FIG. 23 shows a beam path for terminators that are arranged
at an angle relative to one another;
[0063] FIG. 24 is a version of FIG. 23 that contains a
multi-channel acousto-optical modulator;
[0064] FIG. 24a is a version for FIG. 24;
[0065] FIG. 25 is an intermediate imager for matching the fiber
lasers or, respectively, their terminators to, for example, the
modulator;
[0066] FIG. 26 shows the merging of twice four tracks of the beam
path from terminators with a strip mirror arrangement;
[0067] FIG. 26a is a plan view for FIG. 26;
[0068] FIG. 27 is a view of a strip mirror;
[0069] FIG. 27a is a sectional drawing through the strip mirror
according to FIG. 27;
[0070] FIG. 27b is another example of a strip mirror;
[0071] FIG. 28 shows the combining of twice four tracks of the beam
bundle from terminators with a wavelength-dependent mirror;
[0072] FIG. 28a is a plan view of FIG. 28;
[0073] FIG. 29 is an arrangement of a plurality of terminators in a
plurality of tracks and in a plurality of planes;
[0074] FIG. 30 is an arrangement of a plurality of terminators in a
bundle;
[0075] FIG. 31 is a sectional view through the beam bundle from the
terminators of the fiber lasers F1 through F3 according to FIG. 29
or FIG. 30;
[0076] FIG. 32 is an arrangement having a plurality of terminators
in a plurality of tracks and a plurality of levels having a
cylindrical optics for matching, for example, to the modulator;
[0077] FIG. 33 is a modification of FIG. 32;
[0078] FIG. 34 shows a mouthpiece for the laser gun with
connections for compressed air and for extracting the material
released by the beam;
[0079] FIG. 35 shows a turning of the laser gun for setting the
track spacings;
[0080] FIG. 36 is an illustration for generating four tracks with
an acousto-optical multiple deflector or multiple modulator;
[0081] FIG. 36a is a spatial presentation of an acousto-optical
multiple deflector or multiple modulators;
[0082] FIG. 36b is an expanded embodiment related to FIG. 36a;
[0083] FIG. 36c is a plan view of FIG. 36b;
[0084] FIG. 37 is an illustration for generating multiple tracks
with the assistance of an acousto-optical multiple deflector or
multiple modulator;
[0085] FIG. 38 is an advantageous arrangement for avoiding
reflections back into the lasers;
[0086] FIG. 39 shows a lens that has coolant flowing around it;
[0087] FIG. 39a is a section through a mount for an objective
lens;
[0088] FIG. 40 shows a fiber laser or a fiber that have been
clearly reduced in cross-section at their exit end;
[0089] FIG. 40a is a plan view onto the end of the fiber laser or
the fiber according to FIG. 40;
[0090] FIG. 40b is a side view of the fiber end wherein the axes of
the emerging beam bundles proceed nearly parallel;
[0091] FIG. 40c is a side view of the fiber end wherein the axes of
the emerging beam bundles overlap outside the fiber bundle;
[0092] FIG. 40d is a side view of the fiber end wherein the axes of
the emerging beam bundles overlap within the fiber bundle;
[0093] FIG. 41 shows an arrangement of fiber lasers or fibers
according to FIG. 40 in a plurality of tracks and levels;
[0094] FIG. 42 shows a further embodiment of the laser radiation
source;
[0095] FIG. 42a shows a further embodiment according to FIG.
42;
[0096] FIG. 42b is a sectional view of FIG. 42a;
[0097] FIG. 42c is an illustration of a robot;
[0098] FIG. 43 shows a flat bed arrangement having one preferred
embodiment of a laser beam source;
[0099] FIG. 43a is an addition to FIG. 43;
[0100] FIG. 43b is a sectional drawing through an arrangement for
removing the material released during the processing;
[0101] FIG. 44 is a hollow bed arrangement having one preferred
embodiment of a laser beam source; and
[0102] FIG. 44a shows an addition to FIG. 44.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0103] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to
preferred embodiments illustrated in the drawings and specific
language will be used to describe the same. It will nevertheless be
understood that no limitation of the scope of the invention is
thereby intended, such alterations and further modifications in the
illustrated device, and such further applications of the principles
of the invention as illustrated therein being contemplated as would
normally occur to one skilled in the art to which the invention
relates.
[0104] The laser radiation source comprises at least one
diode-pumped fiber laser, or a plurality of diode-pumped fiber
lasers whose output radiation beams impinge the processing location
next to one another and/or over one another or in a point or bundle
and thus enables the generation of a processing spot that is
designationally variable in shape and size, even given extremely
high laser powers and extremely high power densities. According to
preferred embodiments, these fiber lasers can be implemented as
continuous wave lasers or as quality-switched lasers, also referred
to as Q-switch lasers, whereby they are advantageously internally
or externally modulated and/or comprise an additional modulator.
Q-switch lasers have an optical modulator available to them within
the laser resonator, for example an acousto-optical modulator,
that, in its opened condition, interrupts the laser effect given a
pump radiation that continues to exist. As a result thereof, energy
is stored within the laser resonator, this being output as a short
laser pulse having high power when the modulator is closed in
response to a control signal. Q-switch lasers have the advantage
that they emit short pulses having high power, which briefly leads
to a high power density. An advantageous elimination of the molten
and evaporated material is enabled in the pulsed mode due to the
brief-term interruptions in the processing event. Instead of
switching the quality, a pulsed mode can also be generated with
internal or external modulation.
[0105] The processing spot can be designationally modified in shape
and size in that different numbers of lasers are provided that can
be switched on for shaping the processing spot. It is thereby
especially advantageous that the depth of the cut cup can be
determined by the laser energy independently of its shape and size.
Further, a control of the energy of the individual lasers can also
generate any arbitrary beam profile within the processing spot and,
thus, any arbitrary profile within the cup as well.
[0106] Further advantages of the present preferred embodiments
compared to known laser radiation sources are comprised therein
that the infeed of the radiant power from a solid-state laser into
an optical fiber can be eliminated but the exit of the fiber laser
supplies diffraction-limited radiation that, according to the
preferred embodiments can be focused onto less than a 10 .mu.m
diameter, as a result whereof an extremely high power density is
achieved given the greatest possible depth of field.
[0107] Given a traditional arrangement with solid-state lasers, the
size of the processing spot lies in the region of approximately 100
.mu.m. Given the present preferred embodiments, thus a power
density that is improved by the factor 100 derives, and a design
possibility in the area of the processing spot that is improved by
the factor 100 derives.
[0108] Due to the high precision and due to the shape of the
processing spot that can be designed in very fine fashion,
extremely fine screens, also including the stochastic screens that
are also called frequency-modulated screens (FM screens) and, thus
extremely smooth edges in lines and written characters can be
economically produced, so that rotogravure no longer need be
inferior to offset printing in terms of printing quality.
[0109] Due to the operating mode of the laser radiation source of
the preferred embodiments, it is also possible to link arbitrary
raster widths to arbitrary screen angles and apply arbitrary
different screen widths and arbitrary different screen angles at
arbitrary locations on the same printing cylinder. Line patterns
and text can also be applied independently of the printing screen
as long as one sees to sufficient supporting locations for the
doctor blade.
[0110] One advantage of the preferred embodiments is that the
differences in the data editing for the production of the printing
form are reduced to a minimum between rotogravure and offset
printing, this yielding substantial cost and time savings. Up to
now, the data for the rotogravure are acquired by conversion from
the data already present for the offset printing because a signal
is required for the drive of the engraving system that defines the
volume of a cup, whereby the area of a screen dot is determined in
offset printing. As a result of the multiple arrangement of lasers,
the laser beam source of the preferred embodiments makes it
possible to vary the area of a cup given constant depth, for which
reason it is no longer required to convert the data for offset
printing into data for the rotogravure. The data for the offset
printing can be directly employed for engraving the rotogravure
forms.
[0111] Another advantage of the preferred embodiments is that both
the area of a cup as well as the depth can be controlled
independently of one another with this laser radiation source, this
leading to a greater number of tone value gradations that can be
reproducibly generated, this leading to a more stable manufacturing
process for the printing cylinders and to an improved printing
result.
[0112] It is also an essential advantage that the energy can be
unproblemmatically transported from the pump source to the
processing point with the fiber, namely the fiber laser itself, or
with a fiber that is welded on or, respectively, attached in some
other way, this yielding an especially simple and space-saving
structure.
[0113] Another advantage of the preferred embodiments is that the
efficiency of such an arrangement with fiber lasers is
significantly higher than the efficiency of solid-state lasers,
since absorption efficiencies of more than 60% are achieved for
fiber lasers, these lying only at approximately half given
traditional diode-pumped solid-state lasers and being even far
lower given lamp-pumped solid-state lasers. Given the required
power of several kilowatts for an efficient engraving of
rotogravure cylinders, the efficiency of the lasers is of
incredible significance for the system costs and the operating
costs.
[0114] Further, a multiple arrangement of lasers yields the
advantage that the outage of a laser is less critical than given a
single-channel arrangement. When the only laser that is present
given the single-channel arrangement fails during the engraving of
a printing cylinder, the entire printing cylinder is unuseable.
When, however, a laser fails given a multiple arrangement, then the
power of the remaining lasers can, for example, be slightly boosted
in order to compensate the failure. After the end of the engraving,
the laser that has failed can then be replaced.
[0115] The dissertation, "Leistungsskalierung von Faserlasern",
Physics Department of the University of Hannover, Dipl.-Phys.
Holger Zellmer 20 Jun. 1996, fiber lasers are discussed as being
known. These lasers, however, had already been proposed in 1963 by
Snitzer and Koster, without these having been previously utilized
for processing materials given high powers. Although powers of up
to 100 W can be fundamentally achieved with the lasers described in
this dissertation, no useable arrangements are known for utilizing
these lasers for purposes of the present preferred embodiments.
[0116] The publication WO-A-95/16294 has already disclosed
phase-coupled fiber lasers; however, these are extremely involved
in terms of manufacture and are not suitable for industrial
employment. It had hitherto not been recognized to bring lasers of
this simple type to high power density and energy in the proposed,
simple way and to utilize them for erosive processing of
materials.
[0117] For example, the resonator length of the individual lasers
must be kept exactly constant to the fraction of a micrometer, for
which purpose what are referred to as "piezoelectric fiber
stretchers" are utilized. As a result of the complex structure, it
is likewise not possible to construct the laser unit modularly,
i.e. of components that are simple to assemble and to be multiply
employed or to replace individual laser components as needed on
site as a consequence of the great number of optical components
within a phase-coupled laser. Moreover, the optical losses are
extremely high, and the pump radiation absorption of the
laser-active medium is low, which results in a low efficiency of
the arrangement. Although fiber lasers are not particularly
susceptible to back-reflections in and of themselves, phase-coupled
lasers exhibit a great sensitivity to back-reflections due to their
very principle, i.e. when portions of the emitted radiation proceed
back into the laser resonator due to reflection or dispersion, as
is unavoidable when processing materials. These back-reflections
lead to uncontrolled output amplitudes and cause the laser to shut
down. Although what are referred to as optical isolators are known,
these being intended to attenuate such back-reflections, these
involve a number of disadvantages in practice, which, for example,
include the optical losses, the high price and the inadequate
attenuation properties. The lasers for the purpose of the present
preferred embodiments of processing materials need not only exhibit
a high power density but also must be able to supply the required
energy for cutting out the cups, must be extremely stable in terms
of the emitted radiation and must have a very good efficiency.
[0118] Further, U.S. Pat. No. 5,694,408 has disclosed a laser
system wherein a master oscillator generates low-power radiation
energy at a specific wavelength, this being optically intensified
and it being distributed for further post-amplification onto a
plurality of post-amplifiers, in order to then be in turn united to
form a common beam, a precise phase readjustment of the individual
post-amplified signals being required for this purpose in order to
avoid interferences in the output signal. This requires complicated
measuring and control procedures and involved actuating elements,
for which purpose, for example, electro-optical phase modulators
must be utilized, these being extremely expensive and having to be
operated with extremely high voltages.
[0119] Further, U.S. Pat. No. 5,084,882 discloses a phase-coupled
laser system that employs a plurality of fibers or fiber cores in a
bundle, the core thereof being, on the one hand, large compared to
its cladding or its spacing in order to achieve the phase coupling;
on the other hand, this should only have a diameter of a few
micrometers since it is a matter of single-mode fibers. This system
is mainly provided as an optical intensifier.
[0120] Another phase-coupled laser system that is likewise
implemented in an extremely complex way and that is composed of a
plurality of what are referred to as "sub-oscillators" is disclosed
by GB-A-21 54 364 under the title "Laser Assemblies", having
already been disclosed in 1984; however, no industrial realizations
with such phase-coupled laser systems have become known up to
now.
[0121] It has also not been previously proposed to combine a number
of the initially cited fiber lasers in a simple way, i.e. without a
complex phase coupling or the like, to form a compact, rugged and
service-friendly radiation source for processing materials and, for
example, to employ this for multi-track recording. A multiple
arrangement of such simple lasers that can be cost-beneficially
manufactured in quantity in several tracks and levels yields
enormous advantages for the purposes of the preferred embodiments
that would certainly not have escaped attention if the preferred
embodiments solution had been known.
[0122] A further advantage of fiber lasers is their clearly lower
tendency to oscillate when energy proceeds back into the laser.
Compared to traditional solid-state lasers, fiber lasers have a
resonance overshooting that is lower by an order of magnitude in
terms of its transfer function, this having been very positively
proven during operation. When processing materials, namely, one
cannot always prevent energy from being reflected from the
processing location back into the laser because the melting
material is explosively hurled in unpredictable directions and
thereby flies through the laser beam before it can be removed and
neutralized by particular techniques that are presented in one
embodiment of the invention.
[0123] An essential advantage of the multiple arrangement of fiber
lasers without phase coupling is that the individual lasers behave
differently in case of a back-reflection. This is related to the
fact that, for example, some of the lasers are not affected at all
by a back-reflection and others may possibly be effected only with
a delay. The probability is therefore high that oscillations of the
individual lasers, if they occur at all, are superimposed such that
they have no negative influence on the quality of the results of
the engraving.
[0124] The laser radiation source of the preferred embodiments can
also be advantageously utilized for all other types of processing
materials or transferring materials wherein high power density,
high energy and great precision or, too, high optical resolution
are important. In addition to engraving rotogravure cylinders
having a copper surface, other materials such as, for example, all
metals, ceramics, glass, semiconductor materials, rubber or
plastics can be processed and/or materials can be stripped from
more specifically prepared carrier materials and transferred onto
other materials at high speed and with high precision. In addition
to those that are uncoated, moreover, rotogravure cylinders,
printing plates or printing cylinders that are coated with masks as
well as all types of printing forms can also be produced or,
respectively, processed at high speed and with high resolution for
offset printing, letter press printing, silk screening,
flexo-printing and all other printing processes. For example, the
offset printing plates having metal coating (bi-metal plates) that
are employed for printing extremely large print runs in offset
printing and similar materials can be provided with images in an
environmentally friendly way, this having been hitherto possible
only with etching.
[0125] Further, materials can be processed that contain a
magnetizable surface, in that the parts of the material magnetized
in large-area fashion by a pre-magnetization process are
de-magnetized by briefly heating selected processing points to
temperatures that lie above the Curie point, when heated with the
laser radiation source of the preferred embodiments. The material
provided with images in this way for applications in printing
technology can serve as a print master in conjunction with a
corresponding toner.
[0126] As a result of the high power density of the inventive laser
radiation source of the preferred embodiments, it is also possible
to directly process chromium. Thus, for example, printing cylinders
of copper can already be chrome-plated for rotogravure before the
laser engraving, this eliminating a work step after the engraving
and benefiting the timeliness. Since the printout behavior of a cup
engraved in copper is also better than that of a chrome-plated cup
and its volume is more precise, this method also yields even better
printing results in addition to the high service life as a result
of the remaining chromium layer and the improved timeliness.
[0127] The employment of the laser radiation source of the
preferred embodiments, however, is not limited to employments in
printing technology but can be utilized anywhere that it is
important to erode material or change the properties of the
material by energy irradiation with lasers given high resolution
and high speed. Thus, for example, the aforementioned texture drums
can also be produced with the radiation source of the preferred
embodiments. Further, the patterns of interconnects for printed
circuit boards, including the boards for the components, preferably
for multi-layer printed circuit boards, can be produced by eroding
the copper laminate and allowing the interconnects to stand, and by
eroding copper laminate and carriers at the locations of the bores.
Further, the surface structure of material surfaces can be
partially modified by partial heating. For example, extremely fine
structures in the hardness of material surfaces can be produced in
large-area fashion in this way, this being particularly
advantageous for bearing surfaces since the bearing properties can
be intentionally influenced in this way. Further, there are
non-conductive ceramic materials at whose surface metal
crystallizes out due to energy irradiation, this being capable of
being utilized in conjunction with the laser radiation source of
the preferred embodiments for applications that require a high
resolution, for example for producing interconnects.
[0128] The laser beams can thereby be guided to the processing spot
and can be moved across the material in the greatest variety of
ways for example, the material to be processed can be located on a
rotating drum past which the radiation source is conducted in
relative fashion. However, the material can also be located in a
plane over which the laser radiation source or its output radiation
is conducted past in relative fashion. In a flat bed arrangement as
presented in the aforementioned publication "Der Laser in der
Druckindustrie" von W. Hulsbusch, FIG. 7-28 on page 431 and as
likewise disclosed in the publication EP-A-0 041 241, the radiation
source presented therein as argon or He Ne laser or, respectively,
as laser light source (4) in FIG. 3 of the publication can be
replaced by the laser radiation source of the preferred embodiments
in order to utilize the advantages of the laser radiation source of
the preferred embodiments. Further, the material to be processed
can be located within a hollow cylinder over which the laser
radiation source or its output radiation sweeps in a relative
motion.
[0129] The output of the laser radiation source can also be
implemented with a variable number of tracks whose mutual spacings
are variable, preferably similar to a long comb, this moving
relative to the material to be provided with images. Such an
arrangement is disclosed by U.S. Pat. No. 5,430,816. It is
disclosed therein to direct the radiation of an excimer laser
having a strength of approximately 50 watts onto a bundle of what
are referred to as stepped index fibers having diameters of 50
through 800 micrometers and to respectively couple a part of the
radiation into the individual fibers. The exit of each fiber is
then imaged onto the work piece via a respective positive lens
having a diameter of 60 mm, whereby the spacing between the
individual processing points must amount to at least 60 mm and a
protective mechanism to prevent contamination is required per
positive lens. What is disadvantageous is that only a fraction of
the laser energy thus proceeds into the respective fibers. The
energy distribution turns out very differently and changes in the
exit power derive given movement of the fibers, for which reason
what are referred to as scramblers must be utilized in order to
avoid this. These scramblers, however, disadvantageously influence
the efficiency of the system and increase the costs. Only
relatively imprecise bores having a diameter of approximately 130
micrometers can be produced in plastic with such an arrangement.
The pulse rate of the laser is the same for all simultaneously
produced bores, so that all bores must be implemented of the same
size. Moreover, the system is relatively slow since a boring
processing lies between one and two seconds. An arrangement having
fiber lasers yields tremendous advantages compared thereto: the
speed can be increased by several orders of magnitude and metals
can also be processed; the precision is substantially greater since
fiber lasers also exhibit a stable output power given movement of
the laser fibers; and bores having diameters below 10 micrometers
can also be unproblemmatically produced. Since each fiber laser can
be separately modulated, different processing patterns are
possible. Further, the end sections of the fiber lasers can be
unproblemmatically implemented smaller than 2.5 mm in diameter,
this enabling a clearly smaller spacing between the processing
tracks. As a result thereof, it is also possible to employ a shared
protective mechanism to prevent contamination of the optics.
[0130] Another example for the application of the laser beam source
of the preferred embodiments wherein the material is preferably
arranged in a plane derives in the semiconductor industry in the
processing of what are referred to as wafers, i.e. usually circular
disks of suitable semiconductor material that, for example, are
incised or cut or can be provided with all conceivable patterns in
the surface, of a type that could previously be manufactured only
by time-consuming chemical etching processes that were also not
environmentally friendly.
[0131] For the multi-channel cutting and in sizing of materials, a
simplified embodiment of the laser radiation source is possible, as
disclosed in the German Patent Application P 198 40 936.2 of the
assignee, "Anordnung zum mehrkanaligen Schneiden und Ritzen von
Materialien mittels Laserstrahlen".
[0132] A further application of the laser radiation source is
established in the manufacture of monitors and displays. For
example, the apertured masks for color picture screens as well as
the masks of what are referred to as flat picture screens or LCD
displays can be manufactured in a more environmentally friendly way
with laser processing than with the chemical etching processes that
were previously employed, in that the laser radiation source is
applied.
[0133] A considerable advantage of the laser radiation source is
that it has a small volume and has a flexible connection, namely
the laser fibers or fibers connected thereto between the pump
source and the exit of the radiation at the processing location and
thus allows all conceivable operating positions of the laser
radiation source or of its beam exit. There are therefore also no
limitations for the spatial arrangement of the processing surface,
since they can be arranged in an arbitrary attitude in space.
[0134] Another advantage of the preferred embodiments is comprised
therein that the radiation beam of the individual lasers with
defined values in beam diameter, beam divergence centering and
angular direction can be exactly and durably acquired in a
terminating section (terminator), as a result whereof a
fabrication-suited and service-suited arrangement for forwarding
the laser radiation onto the processing surface can be created. The
radiation beams can thereby be coupled into the fiber dependent on
the application, for example as pump spot and/or can be coupled out
as parallel laser beam, can diverge at the exit location or, for
example, can be focused in a certain distance from the exit point.
There is thus a desire to fashion the terminator as small as
possible and to provide it with one or more fits as a reference
surface or reference surfaces for the alignment of the laser
beam.
[0135] According to the preferred embodiments, this is achieved in
that the optical fibers are set in the terminator and the position
of the optical fibers and/or the position of the emerging radiation
beam is exactly adjusted. On the basis of the exact adjustment and
of a correspondingly spatially small embodiment of the terminators
which can also be attached to one another in an especially simple
way as a result of a special shaping, it becomes possible to
combine the radiation beams of a plurality of fiber lasers and
focus them such that the respectively encountered object is
achieved and, at the same time, an economical manufacture as well
as a cost-beneficial maintenance of the laser radiation source is
enabled.
[0136] FIG. 1 shows a laser radiation source 1 that is comprised of
at least one or a plurality of diode-pumped fiber lasers 2, also
called fiber lasers, implemented preferably as modules, these being
charged with electrical energy by a preferably modular supply 32
that is largely converted into laser radiation. Further, a
controller 33 is provided via which the modulation of the radiation
is undertaken and that provides to the interaction of the laser
radiation source with its periphery. The output rays of the laser
enter into an optical unit 8 at the radiation entry 9 and emerge
from the optical unit at the radiation exit 10. The job of the
optical unit 8 is to shape the laser radiation to form a processing
spot 24 on a processing surface 81; however, the laser radiation
can also be directly directed on to the processing surface without
the optical unit.
[0137] FIGS. 2 and 2a show the fundamental structure of a fiber
laser arrangement 2. In FIG. 2, the energy of a pump source such
as, for example, a laser diode, called a pump source 18 here, is
shaped via an infeed optics 3 to form a suitable pump spot 4 and is
coupled in to the laser fiber 5. Such pump sources are disclosed,
for example, in German Patent Application P 196 03 704 of the
assignee. Typical pump cross-sections of the laser fibers lie
approximately between 100 .mu.m and 600 .mu.m in diameter given a
numerical aperture of approximately 0.4. The laser fiber 5 is
provided with an infeed mirror 7 at the infeed side 6 that allows
the pump radiation to pass unimpeded but which exhibits 100%
reflection for the laser radiation. The infeed mirror 7 can be
secured to the fiber end with a suitable mount or by gluing;
however, it can also be realized on the fiber end by direct
vapor-deposition of a suitable layer as employed given infeed
mirrors for lasers. An outfeed mirror 12 that is partially
reflective for the laser radiation is attached to the outfeed side
11 of the laser fiber 5, the laser radiation 13 being coupled out
through the outfeed mirror 12. Advantageously, the outfeed mirror
exhibits 100% reflection for the pump radiation. As a result
thereof, the remaining pump radiation is reflected back into the
optical fiber, which is advantageous since the pump energy is
utilized better and, further, does not represent a disturbing
factor in the application of the laser radiation. The outfeed
mirror can, like the infeed mirror, likewise be produced by
vapor-deposition.
[0138] The infeed event of the pump radiation into the pump
cross-section 14 of the laser fiber 5 is shown in greater detail in
FIG. 2a. The energy in the pump spot 4 excites the laser radiation
in the core 15 of the laser fiber 5 on its way through the fiber.
The pump core 16 is surrounded by a cladding 17. The core of the
laser fiber that is approximately 5 .mu.m through 10 .mu.m thick is
doped mainly with rare earths.
[0139] The relatively large pump cross-section 14 simplifies the
infeed of the pump energy and enables the use of a connection
between pump source and laser fiber that is simple to release, as
shown in FIGS. 13 and 14. The terminator of the laser fiber at the
side of the pump source can thereby be advantageously structurally
the same as the terminator at the outfeed side; however, it need
not be. A precise plug-type connection between pump source and
laser fiber offers considerable advantages in the manufacture of
the fiber laser and in case of service. The laser fiber, however,
can also be firmly connected to the pump source to form a laser
module. As a result of the intentionally manufactured, extremely
small fiber core diameter, the fiber laser supplies a practically
diffraction-limited laser radiation 13 at the exit.
[0140] FIG. 3 shows a cross-section through one of the embodiments
of an arrangement for processing materials with the inventive laser
radiation source 1. A drum 22 is rotatably seated in a housing 21
and is placed into rotation by a drive (not shown). A laser gun 23,
which is conducted along the drum in the axial direction with a
carriage (not shown), is located on a prism (likewise not
shown).
[0141] The laser radiation emerging from the laser gun 23 impinges
the surface of the drum at the processing location in the
processing spot 24. Either the surface of the drum as well as a
material clamped onto the drum surface can be processed. The fiber
lasers, whose laser fibers 5 are respectively wound to a form, for
example, an air-permeated coil 25, are supplied into the laser gun
23 with the terminators 26, 94. Advantageously, however, passive
single-mode fibers or other passive optical fibers, referred to in
brief as fibers 28, can also be welded to the fiber lasers or
coupled thereto in some other way before the terminators 26, 94 are
attached, as described in FIGS. 15 and 16.
[0142] The pump sources 18 of the fiber lasers are attached on a
cooling member 27 that diverts the waste heat via a cooling system
31. The cooling system 31 can be a matter of a heat exchanger that
delivers the waste heat to the surrounding air; however, it can
also be a matter of a cooling unit. The laser gun 23 can also be
connected to the cooling system, but this is not shown. The driver
electronics for the pump sources 18, which belong to the supply 32
(not shown in further detail), are preferably situated on the
cooling member. A machine control is provided for the drives but is
not shown in FIG. 3. The structure of the pump sources, fiber laser
and corresponding power electronics is preferably modularly
implemented, so that corresponding pump sources and power modules
of the driver electronics that are separate or combined into groups
belong to the individual fiber lasers, these being capable of being
connected to one another via a bus system. As explained in greater
detail in FIG. 13 and FIG. 14, the laser fibers 5 and the pump
sources 18 can be connected to one another via a releasable
connection. It is also possible to couple a slight part of the pump
radiation out of the laser fiber 5, for example as a result of a
slight injury to the cladding 14, and to conduct this via an
optical fiber onto a measuring cell in order to offer a signal
therefrom that can be employed for the control or, respectively,
regulation of the pump radiation.
[0143] The modulation signals for the laser radiation are generated
in the controller 33 and the interaction of the laser radiation
source with the machine control and with the supply 32 as well as
the executive sequence of the calibration events as well as of the
control and regulation events are managed in the controller 33. A
safety circuit (not shown), for example, switches the pump sources
permanently off when there is danger.
[0144] Although a horizontally seated drum is shown in FIG. 3, the
drum can be arranged in any arbitrary attitude since the laser
radiation source is completely directionally insensitive in terms
of its attitude and is very compact in terms of structure and,
moreover, since the laser fibers 5 of the fiber laser or fibers 28
coupled to the laser fibers can be arbitrarily laid; for example,
the shaft of the drum can also be seated vertically or inclined
from the perpendicular, which yields an especially small floor
space. As a result thereof, moreover, the operation of a plurality
of arrangements or a system having a plurality of drums is possible
on the same floor space as would be required by an arrangement
having a horizontally seated drum. As a result thereof, the
printing forms can be manufactured faster; in particular, all
printing forms for a color set can be produced in a single,
parallel pass, which is advantageous especially with respect to the
uniformity of the final result. Further, an automatic charging with
printing forms for provision with images can be realized better
given a system erected on a small floor space than given a
spatially larger system. One or more laser radiation sources and,
additionally, one or more further lasers can be directed onto the
same printing form in order to accelerate the production thereof.
One advantage of the multi-track arrangement having the very fine
and precise tracks is that potential seams are clearly less
disturbing then when recording is carried out with coarser tracks.
As described under FIG. 37, further, the position of the tracks can
be precisely re-adjusted, so that residual errors become clearly
smaller than a track width. The inventive laser radiation sources
can thereby be preferably utilized for processing the finer
contours and the further laser or lasers can be utilized for
processing rougher contours, which can be particularly employed
given printing forms that, for example, are composed of plastic or
rubber.
[0145] Instead of one or each of the provided fiber lasers 2, it is
conceivable to provide a laser system with a terminator into the
laser radiation source and alternative supply to the laser gun 23,
whereby the fiber laser described in detail under FIG. 2, however,
represents the more cost-beneficial solution. When processing
materials, namely, if the radiant power of a plurality of lasers
that are not coupled to one another and that naturally emit with a
slight wavelength difference are directed onto a processing spot, a
phase equality of the individual lasers can be foregone and an
expensive control and regulation technology for a phase coupling
that is susceptible to malfunction can be avoided.
[0146] Such a laser system that, for example, is disclosed by U.S.
Pat. No. 5,694,408 contains an optical post-amplification and
comprises a radiation output composed of a fiber. A terminator is
described in greater detail later in one of the FIGS. 5, 5a, 5b,
5c, 6, 6a, 7, 9, 9a, 10, 10a, 10b, 11, 11a or 12.
[0147] Instead of employing the laser system disclosed by U.S. Pat.
No. 5,694,408, it is also conceivable to employ a phase-coupled
laser system according to U.S. Pat. No. 5,084,882. An image of the
fiber bundle then results on the processing surface as the
respective processing spot. Alternatively, a single-mode fiber
could be welded to each fiber at the exit of the bundle, this being
provided with the respective terminators, and supply the laser gun.
However, it is extremely difficult and complicated to manufacture
such phase-coupled laser systems and they would be correspondingly
expensive. Up to now, such phase-coupled laser systems have also
not been commercially available.
[0148] FIG. 4 is a section through an applied example of a laser
gun having sixteen fiber lasers that are coupled via terminators 26
and having a modulation unit composed of two multi-channel
acousto-optical modulators 34. The laser gun is a multi-part
receptacle for the adaptation of the optical unit and contains
mounts 29 (FIG. 4a) with fitting surfaces for the fits of the
terminators 26, means for combining the individual laser beams, the
modulation unit, a transmission unit for the transmission of the
laser radiation that is intended to produce a processing effect
onto the processing surface, and an arrangement for neutralizing
the laser radiation that is not intended to produce a processing
effect. An arrangement for removing the material eroded from the
processing surface can be arranged at the laser gun; this, however,
can also be arranged in the proximity of the processing surface in
some other way.
[0149] FIG. 4a shows a perspective illustration relating to FIG.
4.
[0150] FIG. 4b shows a modification of FIG. 4 wherein the beam
bundle of the individual fiber lasers do not proceed parallel as in
FIG. 4 but at an angle relative to one another; this, however,
cannot be seen from the sectional view in FIG. 4b and is therefore
explained in greater detail in FIGS. 21, 22 and 24.
[0151] FIG. 4c shows a modification of FIG. that enables an
advantageous, significantly more compact structure as a result of a
differently implemented transmission unit.
[0152] FIG. 4 shall be explained in detail first with the
assistance of FIG. 4a. These explanations apply analogously to
FIGS. 4b and 4c.
[0153] In a housing 35, 4 fiber lasers F.sub.HD1 through F.sub.HD4,
F.sub.VD1 through F.sub.VD4, F.sub.HR1 through F.sub.HR4, F.sub.VR1
through F.sub.VR4 via terminators 26 with mounts 29 (FIG. 4a) are
arranged in respectively four tracks of one beam packet, being
arranged side-by-side in a plane. The embodiment of the terminators
26 employed in FIG. 4 is described in greater detail in FIG. 9. The
terminators should preferably be inserted gas-tight into the
housing 35, to which end seals 36 (FIG. 4a) can be employed.
Instead of the terminators shown in FIGS. 4 and 4a, differently
shaped terminators can also be employed, as described in FIGS. 5,
5a, 5b, 5c, 6, 6a, 7, 9, 9a, 10, 10a, 10b, 11, 11a and 12, when
corresponding mounts 29 are provided in the housing 35. However, as
also described under FIG. 3, single-mode fibers or other fibers 28
can be attached to the fiber lasers before the terminators 26 are
attached. However, an arrangement of the laser fibers 5 or fibers
28 according to FIGS. 40, 40a, 40b, 40c, 40d and 41 can also be
employed. For example, the fiber lasers F.sub.HD1 through F.sub.HD4
or, respectively, F.sub.VR1 through F.sub.VR4 should have a
different wavelength than the fiber lasers F.sub.VD1 through
F.sub.VD4 or, respectively, F.sub.HR1 through F.sub.HR4. For
example, F.sub.HD1 through F.sub.HD4 and F.sub.VR1 through
F.sub.VR4 should have a wavelength of 1100 nm whereas F.sub.VD1
through F.sub.VD4 or, respectively, F.sub.HR1 through F.sub.HR4
should have a wavelength of 1060 nm, which can be achieved by a
corresponding doping of the laser-active core material of the laser
fibers 5. However, all fiber lasers can also exhibit different
wavelengths when they are correspondingly compiled.
[0154] As explained in greater detail in FIGS. 28 and 28a, the beam
packets of the fiber lasers F.sub.HD1 through F.sub.HD4 are united
with those of the fiber lasers F.sub.VD1 through F.sub.VD4 and the
beam packets of the fiber lasers F.sub.VR1 through F.sub.VR4 are
united with those of the fiber lasers F.sub.HR1 through F.sub.HR4
to form a respective beam packet F.sub.D1 through F.sub.D4 as well
as F.sub.R1 through F.sub.R4 (FIG. 4a) via wavelength-dependent
mirrors 37 as means for the combining. There are also other
possibilities of influencing the wavelength of the fiber lasers;
for example, wavelength-selecting elements such as Brewster plates,
diffraction gratings or narrowband filters can be introduced in the
region of the laser fibers between infeed mirror 7 and outfeed
mirror 12. It is also possible to provide at least one of the two
laser mirrors 7 or 12 with a mirror layer of a type that is
adequately highly reflective only for the desired wavelength. The
execution of the beam merging, however, is not limited to the
employment of fiber lasers with different wavelengths. In addition
to fiber lasers that have no privileged direction in the
polarization of the laser emission that is output, fiber lasers can
also be employed that output a polarized laser emission. When the
wavelength-dependent mirror is replaced by a mirror that is
polarization-dependent such that it allows one polarization
direction to pass whereas it reflects the other polarization
direction, only two differently polarized laser types need be
employed in order to unite the two with the polarization-dependent
mirror. In this case, the employment of the terminator 26 according
to FIG. 9 having a quadratic cross-section is especially suitable,
since the one or the other polarization direction can be
respectively produced with the same fiber laser by turning the
terminator by 90.quadrature. before being mounted into the housing
35.
[0155] A particular advantage of the combining of a plurality of
lasers to form a single spot, namely to each of the individual
processing points B.sub.1 through B.sub.n (for example B.sub.1
through B.sub.4 in FIGS. 20 through 22) is that a higher power
density is achieved given a predetermined spot size on the
processing surface 81.
[0156] The laser emission of the individual fiber laser can also be
distributed onto a plurality of terminators, this being described
in FIG. 15. This is particularly useful when materials are to be
processed that manage with a low laser power or when the power of
an individual fiber laser is adequately high. In such a case, it is
conceivable that a laser gun 23 is equipped with only four
terminators, for example F.sub.HD1 through F.sub.HD4, for this
purpose, F.sub.HD1 and F.sub.HD2 thereof, for example, being
supplied by one fiber laser and F.sub.HD3 and F.sub.HD4 being
supplied by a further fiber laser according to FIG. 15. When the
principle described in FIG. 15 is applied twice, all four tracks
F.sub.HD1 through F.sub.HD4 can be supplied by one fiber laser,
this leading to an extremely cost-beneficial arrangement,
particularly since further component parts such as
wavelength-dependent mirrors and strip mirrors can be eliminated
and, thus, an especially economical embodiment of the laser
radiation source can be created.
[0157] By omitting fiber lasers or, respectively, tracks, further,
the acquisition costs for such an arrangement can be lowered as
needed and fiber lasers can be retrofitted later as needed. For
example, one can begin with one fiber laser and one track. The
lacking terminators of the fiber lasers that are not introduced are
replaced for this purpose by structurally identical terminators
that, however, do not contain a through opening and no laser fibers
and only serve for termination in order to close the housing 35 as
though it were equipped with all terminators.
[0158] However, the laser radiation of a plurality of fiber lasers
can also be combined and conducted into a single terminator, this
being described in FIG. 16. For example, one can work with a
plurality of fiber lasers combined in this way and with one track
when, as described, the missing terminators are replaced by
structurally identical terminators that, however, do not contain a
through opening and no laser fibers in order to close the housing
35 as though it were equipped with all terminators.
[0159] Immediately after the beam bundle has left the respective
terminator, a part of the laser emission can be coupled out via a
beam splitter (which, however, is not shown) and can be conducted
onto a measuring cell that is not shown in the FIGS. in order to
produce a measured quantity therefrom that can be used as
comparison value for a control of the output power of each and
every fiber laser. However, laser emission can also already be
coupled out of the laser fiber for the acquisition of a measured
quantity before the terminator, this also not being shown.
[0160] The plurality of planes wherein the terminators are arranged
is not limited to the one plane as described. For example,
arrangements having three planes are recited in FIGS. 29, 32, 33
and 41. An arrangement having two planes is shown in FIG. 38.
[0161] The respective beam packets of the fiber lasers are
modulated via a respective four-channel acousto-optical modulator
34 whose functioning and embodiment is explained in greater detail
in FIGS. 17, 18, 19 and 19a. Using the acousto-optical modulator
34, which is a deflector in terms of principle, the unwanted energy
in the case illustrated here is deflected out of the original beam
direction 10 into the beam direction I.sub.1 (FIG. 4a), so that it
can be simply intercepted later in the beam path and neutralized.
The modulation can preferably occur digitally, i.e. a distinction
is made between only two conditions in the individual modulator
channels, namely "on" and "off", this being especially simple to
control; however, it can also occur in analog fashion since the
laser power in each modulator channel can be set to arbitrary
values. The modulation is not limited thereto that the energy from
the beam direction I.sub.0 is employed for the processing and the
energy from the direction I.sub.1 is neutralized. FIGS. 36, 36a,
36b, 36c and 37 recite examples wherein the beam direction 1.sub.1
that is diffracted off is employed for processing and the energy
from the direction I.sub.0 is neutralized. Further, a slight part
of the modulated radiant power of the individual modulator channels
can be forwarded onto a respective measuring cell via a beam
splitter (not shown) in order to generate a measured quantity that
is used as a comparison value in a control circuit for the exact
regulation of the laser energy of each track on the processing
surface.
[0162] The multi-channel acousto-optical modulator 34 is preferably
secured on a cylindrical modulator housing 41 that is rotatably
seated in an opening 48 in the housing 35. After the modulator
housing has been adjusted to the required Bragg angle
.alpha..sub.B, the modulator housing is fixed with a connection 42.
A seal 43 sees to it that each modulator housing terminates
gas-tight relative to the housing 35. A specifically prepared
printed circuit board 171 projects from the modulator housing 41
into the interior space 44 of the housing 35, electrical
connections to the piezo-electric transducers 45 being produced
thereover. The preferred embodiment of the modulators is described
in greater detail in FIGS. 19 and 19a.
[0163] After passing through the acousto-optical modulators, the
beam packets F.sub.D1 through F.sub.D4 and F.sub.R1 through
F.sub.R4 are conducted to a strip mirror 46 that is described in
greater detail in FIGS. 26, 26a, 27, 27a and 27b. The beam packet
F.sub.D1 through F.sub.D4 is arranged with respect to the strip
mirror 46 such that it can pass through the strip mirror unimpeded.
The laser beam bundles of the beam packet F.sub.R1 through
F.sub.R4, however, are offset by half a track spacing compared to
the beam packet F.sub.D1 through F.sub.D4 and impinge the strips of
the strip mirror arranged in strip-shaped fashion. As a result
thereof, they are redirected in terms of their direction and now
lie in one plane with the laser beam bundles F.sub.D1 through
F.sub.D4. An eight-track arrangement thus derives, whereby two
lasers of different wavelengths are also superimposed in each
track, so that a total of sixteen lasers have been merged and take
effect. The beams I.sub.1 that have been diffracted off in the
acousto-optical modulator 34 are located above this plane I.sub.0.
Given a different adjustment of the acousto-optical modulator 34,
the rays that are diffracted off can also lie under the plane of
I.sub.0, as shown in FIGS. 4b and 4c.
[0164] A significant advantage of the arrangement is that the
symmetry axis of the beam packets F.sub.HD1 through F.sub.HD4 and
F.sub.D1 through F.sub.D4 lie on the axis of the housing 35 that is
defined by the bore 47, and the beam axes of the corresponding beam
packets respectively lie parallel or at a right angle to this axis,
which allows a simple and precise manufacture. However, it is also
possible to arrange the beam packets asymmetrically and at
different angles. Further, it is possible to correct small
differences in the position of the beam packets by adjusting the
wavelength-dependent mirrors 37 and of the strip mirror 46. It is
possible to still re-adjust the terminators in position after they
are mounted and in terms of their angular allocation, for example
for individual optimization of the Bragg angles in the individual
channels; this, however, is not shown in the Figures.
[0165] It lies within the scope of the preferred embodiments that
the plurality of tracks is reduced but can also be increased
further; for example, by joining respectively eight instead of four
terminators that are connected to fiber lasers to form a beam
packet, a doubling of the number of tracks can be undertaken. For
this purpose, two eight-channel acousto-optical modulators would
have to be utilized. Acousto-optical modulators having 128 separate
channels on a crystal can be commercially obtained.
[0166] Within the framework of the preferred embodiments, it is
likewise possible to arrange the fiber lasers in different planes
for increasing the power per track and to superimpose their power
on the processing surface, this being explained in greater detail
in FIGS. 29, 31, 32, 33 and 41 and/or to arrange a plurality of
fiber lasers in bundles in order to superimpose their energy on the
processing surface, this being described in FIGS. 30 and 31.
[0167] Another possibility for increasing the number of tracks is
described in FIG. 37.
[0168] Directly modulatable fiber lasers can also be utilized, this
being described in greater detail in FIG. 23. In this case, the
acousto-optical modulators are omitted and an especially simple
structure derives.
[0169] Operation with a plurality of tracks of lasers and a
plurality of lasers in a track enables high processing speeds given
low relative speed between the laser gun and the work piece. The
processing speed can also thus be optimally adapted to the time
constant of the heat absorption of the material. Given a longer
operating time, too much energy uselessly flows off into the
environment.
[0170] The housing 35 is closed gas-tight with a cover and a seal,
neither being shown in the Figures. A cylindrical tube 51 is
flanged to the housing 35 in the region of the bore 47 and is
sealed via a seal 52. The cylindrical tube contains as an optical
transmission unit two tubes 53 and 54 each having a respective
optical imaging system that image eight laser beam bundles F.sub.D1
through F.sub.D4 and F.sub.R1 through F.sub.R4 at the radiation
exit 10 (FIG. 1) onto the processing surface in the correct scale.
Two optical imaging systems are preferably arranged following one
another, since an extremely great structural length or a very small
distance between the objective lens and the processing surface
would otherwise derive, both being disadvantageous since a long
beam path must be folded with mirrors and too small a spacing
between objective lens and processing surface could lead to a high
risk of contamination for the objective lens.
[0171] The beam path is shown as a side view in FIG. 4. The
fundamental beam path is shown in FIG. 20 as a plan view for the
beam packet F.sub.HD1 through F.sub.HD4. The wavelength-dependent
mirrors, the modulators and the strip mirrors are not shown
therein. The Figures mainly show plano-convex lenses; however, it
is also possible to utilize other lens forms such as, for example,
biconvex or concave-convex lenses or lenses having an spherical
shape in all figures. Lens systems that are respectively composed
of a plurality of lens combinations can also be employed.
[0172] In order to transmit the laser energy as efficiently as
possible and keep the heating of the optical components within
limits, all optical surfaces occurring in the various embodiments
of the laser radiation source are anti-reflection coated with
outmost quality for the wavelength range coming into consideration.
The optical imaging systems can preferably be telecentrically
implemented.
[0173] There are also other advantageous solutions for the
transmission unit in order to shorten the structural length of the
transmission unit and thereby nonetheless achieve a large spacing
between the objective lens and the processing surface, as is shown
in even greater detail in, among others, FIGS. 4b and 4c. The
lenses 55 and 56 can be connected to the tube 53 by screwed
connections or by gluing; however, they can also be preferably
metallized at their edges and soldered to the tube 53. The same is
true of the lenses 57 and 61 in the tube 54. A gas-tight seal of
the lenses and a good heat transmission from the lenses to the
tubes thus derives. The tube 54 is preferably terminated gas-tight
relative to the cylindrical tube 51 with a seal 62. With respect to
tightness and cleanliness, the same conditions apply to the space
63 as apply to the space 44 and, likewise, to the spaces 64 and 65
within the tubes 53 and 54. The chambers 66 and 67 are preferably
connected to the spaces 44 and 63 via bores 71. The tubes 53 and 54
can preferably comprise openings 72.
[0174] An intercept arrangement 73 for neutralizing the laser
radiation that is not intended to produce any processing effect on
the processing surface and that comprises a high-reflectivity
mirror 74 and a dispersion lens (concave lens) 75 projects into the
space 63. The principle of the intercept arrangement 73 is
described in greater detail in FIG. 18. The intercept arrangement
73 is introduced with a seal 76, and the concave lens 75, which can
also be replaced by some other optical element, for example a glass
plate, is glued into the intercept arrangement or is preferably
metallized at an image edge zone and soldered to the intercept
arrangement for better heat elimination. The space 63 is thus
closed off gas-tight from the environment. What derives as a result
of the described techniques is that the entire interior of the
laser gun is sealed gas-tight from the environment. The spaces 44,
63, 64 and 65 and the chambers 66 and 67, i.e. the entire interior
of the laser gun, can be preferably evacuated or filled with a
protective atmosphere. The spaces and chambers should be as free as
possible of components that output gases or particles because dirt
could otherwise settle on the highly stressed optical surfaces,
which would lead to a premature failure of the arrangement. The
seals to be employed should not give off any particles or gases.
Ultimate cleanliness of the parts to be assembled and of the
environment has great value associated with it during assembly
until the laser gun has been closed. After the closing of the laser
gun 23, an evacuation of the entire interior can be undertaken via
the valve 77 or a protective atmosphere can be filled in. The
advantage of filling the interior with protective atmosphere is
that it is simpler to replenish in that a gas bottle (not shown) is
connected to the valve 77 during operation via a pressure-reducing
valve, gas being capable of being refilled into the housing
therefrom as needed. Another advantage is that, when a terminator
is to be removed from the housing for the replacement of a fiber
laser and is to be replaced by another or when the housing or,
respectively, the cylindrical tube must be opened by the user for
some reason or other, a slight quantity of the protective
atmosphere can be allowed to flow through the housing during the
procedure in order to thus prevent the penetration of dirt
particles into the protected space. A slight quantity of the gas
can also be allowed to constantly flow through the housing and
escape such through openings, preferably in the proximity of the
objective lens. This flow also prevents a contamination of the
objective lens by dirt particles that are released during the
processing event (FIG. 39a). The evacuation or the filling with
protective atmosphere can also be foregone when a shorter service
life of the laser radiation source is accepted.
[0175] It is advantageous in the arrangement according to FIG. 4
that the angle between the beam packets of the original beam
direction I.sub.0 of the acousto-optical modulator and the beam
direction I.sub.1 that is diffracted off is noticeably increased by
the imaging system composed of the lenses 55 and 56, so that it is
simple to intercept the unwanted radiation packet of the deflected
beam direction with the highly reflective mirror 74 at the
intercept arrangement 73. The mirror 74 is preferably fabricated of
metal and is provided with a highly reflective layer in order to
keep the heating as a consequence of absorbed laser energy low. For
better heat elimination, it is connected via a strong flange of the
intercept arrangement 73 to the tube 51. However, the intercept
arrangement can also be foregone when the highly reflective mirror
is replaced with an optical component such as, for example, a lens
that slightly modifies the optical properties of the laser
radiation to be intercepted such that the focus of the radiation
that is diffracted off is different from the focus of the radiation
employed for processing the material. If the radiation to be
intercepted would then also be conducted onto the processing
surface, the radiation to be intercepted would not have the
required power density in order to erode material but would be
uselessly absorbed and reflected. The advantage of the arrangement
according to FIG. 4 is that low demands are made of the optical
components in the two tubes. The two tubes could also be
implemented completely the same. Another advantage is that the axes
of the terminators 26 lie parallel to one another. The distance
between the objective lens 61 and the processing surface 81 dare
not be too small, so that particles that fly off from the material
surface do not proceed onto the objective lens. When it is
contaminated, it then absorbs the laser energy that passes, is
destroyed, and is thus unuseable. In order to prevent the
contamination, a special mouthpiece 82 is arranged between the
objective lens 61 and the processing surface 81, this being
described in greater detail under FIG. 34.
[0176] The laser gun 23 of the laser radiation source is rotatable
around the optical axis that is identical to the axis of the
cylindrical tube 51, 95 within the arrangement for processing
materials (FIG. 3), for example on a prism 83, and is seated
displaceable in the direction of the optical axis and fixed in its
position with a strap retainer 85 or with a plurality of strap
retainers. As a result thereof, an exact adjustment of the laser
gun to the processing surface 81 is possible. A plate 86 that
comprises openings 87 through which a coolant can be pumped is
located outside the prism 83. The job of this plate 86 is to
intercept and divert the laser energy intercepted from the beam
path of the transmission unit, this being shown in greater detail
in FIG. 18. A heat dam that, however, is not shown in the FIGS., is
located between the plate 86 and the tube 51, 95, 113. The plate is
connected to the tube 51, 95, 113 via insulating flanges 91. The
flanges 91 also prevent the emergence of laser radiation.
[0177] By turning the laser gun 23 around its optical axis, the
track spacing of the laser tracks on the processing surface 81 can
be modified, this being shown in greater detail in FIG. 35. It lies
within the scope of the preferred embodiments that the turning of
the laser gun for setting the track spacing as well as the setting
of its spacing from the processing surface can be implemented not
only exclusively manually but with the assistance of a suitable,
preferably electronic control and/or regulation. Suitable measuring
devices (not shown) can also be provided for this purpose, these
being located in the proximity of the processing surface and being
capable of being approached by the laser gun as needed. A further
possibility for adjusting the track spacing is described in FIGS.
36, 36a, 36b, 36c and 37. A manually or motor-adjustable
vario-focusing optics can also be utilized for setting the track
spacing. Such a vario-focusing optics, in addition to permanently
arranged lenses, preferably has two movable lens systems, whereby
an adjustment of the first lens system mainly effects an adjustment
of the imaging scale, with which the track spacing can be
influenced, and whereby an adjustment of the second lens system
mainly effects an adjustment of the focusing. An iterative setting
can be undertaken for optimizing track spacing and best focus. It
is also possible to arrange a displaceable lens (not shown) having
a long focal length, preferably between the lenses 57 and 61, with
which the focusing of the processing points on the processing
surface can be finely readjusted without having to displace the
radiation source because the resultant focal length of two lenses
is dependent on their spacing.
[0178] As a result of the high laser power, the optical elements in
the beam path will heat, since they absorb a part, even though a
slight part, of the laser energy. Preferably, the critical optical
components are therefore not made of glass but of a material having
better thermal conductivity, for example of sapphire. The waste
heat, given metallization of the connecting surfaces of the optical
components, is eliminated by the solder connections to the mounts
and to the housing. For better heat output, the housing is
implemented with cooling fins 92 that can be cooled by a ventilator
(not shown). A permeation of the housing 35 as well as of the other
component parts of the laser radiation source with bores is also
possible, particularly in the critical regions at the lens mounts
and mounts for the terminators 26, a coolant being capable of being
pumped therethrough, as shown in FIGS. 8 and 39.
[0179] Since, as presented above, extremely high laser powers are
required in processing of materials, it is critical to the
preferred embodiments to keep the number of optical elements,
particularly lenses, in the beam path as low as possible in order
to keep the optical losses and the risk of contamination of the
optics, which would always lead to a premature failure, as low as
possible. It is also lies within the scope of the preferred
embodiments that the objective lens (61, 103 and 112) is equipped
with an interchangeable mount so that it can be quickly replaced by
the user of the laser radiation source as needed, whether because
it has been contaminated during operation or because a different
imaging scale is requested. In this case, it is advantageous that
the bore 72 and the tube 54 is not implemented.
[0180] It also lies within the scope of the preferred embodiments
that techniques are undertaken in the optical beam path so that no
laser energy can proceed back into the lasers. It is shown in FIG.
3 that the laser radiation impinges the material to be processed
not perpendicularly but at an angle, so that the radiation
reflected at the material surface cannot proceed back into the
laser radiation source. It is also shown in FIGS. 4, 4b, 4c and
FIG. 18 that the laser radiation to be destroyed can be conducted
by an obliquely placed concave lens 75 into a sump composed of an
obliquely placed plate 86 that can be cooled. Instead of the
concave lens of 75, some other optical component, for example a
plate or a diaphragm, can also be inventively employed. The
effective diameter of this optical component is thereby dimensioned
such that the laser radiation conducted into the sump can just
pass, whereas radiation that is reflected back from the sump or is
dispersed back, is largely retained, so that no energy can proceed
back into the laser. The surface of the plate 86, which is shown as
a planar surface in the Figures, can also be implemented crowned or
hollow and can be preferably roughened in order to absorb a maximum
of radiation and reflect or, respectively, disperse a minimum of
radiation.
[0181] It is also shown for two planes in FIG. 38 that, as a result
of a slight parallel offset of the beam axes of the beam bundles
emerging from the terminator, an oblique incidence onto all
effected lens surfaces can be achieved. This also applies for the
arrangement having one or more planes. The acousto-optical
modulator 34 is already rotated by the angle .alpha..sub.B relative
to the axis of the beam bundle; however, it can also be
additionally rotated by the angle .gamma. relative to the symmetry
axis of the beam bundle or an arrangement according to FIG. 24 can
be employed wherein the axes of the ray beams emerging from the
terminators proceed at an angle relative to one another. It has
been shown in practice that angular differences of 1 through 2
degrees between the perpendicular onto the optical surface and the
axis of the beam bundle are already adequate in order to achieve
protection against radiation reflected back into the laser.
[0182] It lies within the scope of the preferred embodiments to
select embodiments of the optical, mechanical and electrical
arrangement for FIG. 4 deviating from the described embodiment. For
example, the beam packets F.sub.D1 through F.sub.D4 and F.sub.R1
through F.sub.R4 could be focused onto the processing surface by a
shared lens, similar to that shown in FIG. 31, which in fact yields
a very high powered density but cannot present the shape of the
processing spot as well since all processing points lie on one
another and are united to form a common spot.
[0183] FIG. 4b shows another laser gun for a laser radiation source
that differs from the laser gun shown in FIG. 4 on the basis of a
housing 93, terminators 94, a cylindrical tube 95, a tube 96 and on
the basis of a highly reflective mirror 97.
[0184] The housing 93 has mounts 29 fitting the terminators 94. The
terminators 94 preferably correspond to those of FIGS. 10, 10a and
10b; the axes of the beam bundles do not proceed parallel in the
corresponding beam packets. Rather, they proceed somewhat toward
the center of the concave lens 101, which is shown in the plan view
21. However, all other terminators according to FIGS. 5, 5a, 5b,
5c; 6, 6a; 7, 9, 9a; 11, 11a and 12 can also be employed when it is
insured that the mounts 29 therefore are arranged at a
corresponding angle. The transmission unit is located in the tube
96, this transmission unit being composed of three lenses, namely a
dispersion lens, i.e. a concave lens 101, and two positive lenses,
i.e. convex lenses 102 and 103, whereby the convex lens 103 is
preferably implemented as an interchangeable objective lens. For
the mounting of the lenses with respect to tightness and heat
elimination, what was stated as to FIG. 4 and FIG. 4a applies, as
it does for the selection of material with respect to the heat
conduction.
[0185] The tube body 96 can be evacuated in the space between the
lenses 101 and 102 or can be filled with a protective atmosphere
or, preferably, be connected to the space 105 via a bore 104, said
space 105 being in turn connected via a bore 106 to the space 107.
The space 107 is connected to the space 111 via the bore 47, said
space 111 being in turn terminated gas-tight, as described under
FIG. 4 and FIG. 4a. The space between the lenses 102 and 103 can be
connected via a bore (not shown) to the space 105, particularly
when the mount of the objective is closed gas-tight or, as
described under FIG. 4, when a slight amount of the protective
atmosphere constantly flows through the laser gun and emerges in
the proximity of the objective lens, this, however, not being shown
in FIG. 4b. The entire interior of the laser gun, composed of the
spaces 111, 105, 107, is preferably evacuated or filled with a
protective atmosphere or, respectively, flooded by a protective
atmosphere, as was described in detail under FIG. 4 and FIG. 4a.
The undesired beam bundles are intercepted with a highly reflective
mirror 97; in contrast to FIG. 4, however, no lens system is
present that has an angle-enlarging effect, so that the distance
between the highly reflective mirror and the modulators is kept
correspondingly large here in order to achieve an adequate spatial
separation of the beam packets I.sub.0 and I.sub.1. Nonetheless,
the entire structural length of the laser gun is similar here to
the arrangement of FIG. 4. The optical beam path of the
transmission unit in FIG. 4 represents a side view. FIG. 21
indicates a fundamental beam path for a plan view relating to FIG.
4b. The beam path of the lenses 101 and 102 corresponds to that of
an inverted Galileo telescope; however, it can also be implemented
as an inverted Kepler telescope when the concave lens 101 having a
short focal length is replaced by a convex lens. Such telescopes
are described in the textbook "Optik" by Klein and Furtak, Springer
1988, pages 140 through 141. The advantage of the arrangement
according to FIG. 4b is that only three lenses are required for the
transmission unit. The disadvantage, to wit that the ray beams of
the individual terminators do not proceed parallel, is eliminated
by terminators according to FIGS. 10, 10a and 10b.
[0186] A lens 55 could also be employed in order to deflect the
beam bundles into the desired direction, as was shown in FIG. 20.
The individual laser beam bundles would then proceed parallel to
one another between the terminators 26 and the lens 55, that is
arranged as in FIG. 4, and no difference from FIG. 4 derives with
respect to the housing and the terminators or, respectively, their
arrangement. Since, however, the lens 55 also exercises a
collecting effect on the individual beam bundles in addition to the
deflecting effect, the same conditions as in FIG. 21 would not
arise at the location of the concave lens 101. This, however, can
be compensated by a different adjustment of the spacing of the
fiber 28 or, respectively, of the laser fiber 5 from the lens 133
or by a modification of the lens 133 in the terminators 26, i.e.
the ray cone of the laser beam bundle from the individual
terminators would be respectively set such that a sharp image
respectively derives on the processing surface at the location of
the points B.sub.1 through B.sub.n.
[0187] According to the preferred embodiments, it is also possible
to combine the lenses 102 and 103 to form a single, combined lens.
A transmission unit having only two lenses then derives. It is also
possible to arrange a displaceable lens (not shown) with a long
focal length between the lenses 101 and 102, the focusing of the
processing points on the processing surface being capable of being
finely readjusted therewith without displacing the radiation
source. A vario-focusing optics can also be employed, as was
mentioned under FIG. 4.
[0188] A special mouthpiece 82 is provided at the laser gun 23 that
is intended to prevent a contamination of the objective lens 112
and that is described in greater detail under FIG. 34.
[0189] FIG. 4c shows a laser gun that is even more significantly
compactly implemented than that of FIG. 4 and FIG. 4a. In
combination with a mirror arrangement, an objective lens 112 is
employed as transmission unit and this can be interchanged for
achieving different imaging scales. As already described under FIG.
4, a vario-focusing optics can also be employed. However, an
imaging can occur with the mirror arrangement by itself without
additional objective lens 112.
[0190] FIG. 4c differs from FIG. 4b in terms of the following
points: The cylindrical tube 95 is replaced by an eccentric tube
113. The tube body 96 is preferably replaced by a plate 114 having
a concave mirror 115 and a mount 116 with an objective lens 112 and
a highly anti-reflection coated plate 117. The intercept unit 73 is
given an arced (convex) mirror 121 above the highly reflective
mirror 97. The eccentric tube is connected to the housing 93 at one
side. A seal 52 sees to the required tightness. The plate 114 is
introduced into the eccentric tube 113, said plate 114 containing a
passage for the beam packets I.sub.0 and I.sub.1 and carrying the
concave mirror 115 whose dissipated heat can thus be diverted well
to the eccentric tube. The eccentric tube has two axes that are
preferably parallel to one another, namely, first the symmetry axis
of the entering beam packets having the direction I.sub.0 that are
directed onto the arced mirror and, second, the axis between
concave mirror and objective lens 112 that can be considered as an
optical symmetry axis for the emerging laser radiation.
[0191] The beam path is folded with the two mirrors 121 and 115.
The arced mirror 121 is preferably fabricated of metal. It is
intimately connected to the highly reflective mirror 97 and is
preferably fabricated of one piece therewith. The convex surface of
the arced mirror can be spherically or spherically shaped. The
mirror 115 is concavely shaped, i.e. a concave mirror. Its surface
can be spherically shaped but is preferably ly shaped. It is
preferably composed of metal. Metal has the advantage of good
elimination of the waste heat. A considerable advantage given
manufacture of metal also derives in the production of surfaces,
which, in this case, can be produced by known diamond polishing
lathing methods, as can also spherical and planar surfaces. As a
result thereof, the highly reflective mirror 97 and the arc mirror
121 can be manufactured of one piece and, preferably, in one work
pass having the same shape of the surface and can be mirrored in
common, which is particularly simple in terms of manufacture and
very advantageous for the positional stability of the arced mirror.
In the modulation of the laser energy with the acousto-optical
modulator, it impinges either the arc mirror 121 or the highly
reflective mirror 97. The waste heat that is produced remains the
same in any case and the arced mirror stays at its temperature and,
thus, its position, which is very important since it is preferably
implemented with a short focal length and the imaging quality of
the arrangement is therefore very dependent on its exact position.
In this case, the arced mirror 121 has advantageously co-assumed
the function of the highly reflective mirror 97. The highly
reflective mirror 97 can, however, also have some other form of
surface than the arced mirror 121 and, for example, can be a plane
mirror.
[0192] The beam path is similar to that of an inverted mirror
telescope after Herschel that, however, contains a convex lens
instead of the arced mirror and that is described in greater detail
in FIG. 22. Mirror telescopes are described on page 152 in the
"Lehrbuch der Experimentalphysik Band III, Optik" by
Bergmann-Schfer, 7.sup.th edition De Gruyter 1978. The arced mirror
can also be replaced by a concave mirror having a short focal
length. As a result thereof, the structural length would be
slightly enlarged and different ray cones of the ray bundles
emerging from the terminator would have to be set in order to
obtain a sharp image in the image plane. The arced mirror could
also be replaced by a convex lens having a short focal length.
Another folded mirror would then have to be utilized in order to
preserve the compact structure. The intercept arrangement 73 is
attached gas-tight to the eccentric tube via a seal 76 the
undesired laser energy, as described under FIGS. 4, 4b and 18,
being diverted via said intercept arrangement 73 to a cooling plate
86 with bores 87 and being neutralized. It is also possible to
already intercept the undesired laser radiation from the beam
packet I.sub.1 at the location of plate 114 and neutralize it.
[0193] The space 111 in the housing 93 is connected to the cavity
123 via the bore 122. Both spaces can be evacuated, filled with a
protective atmosphere, or flooded by a protective atmosphere, as
already described. The mount 116 that accepts the interchangeable
objective lens 112 is attached to the end of the eccentric tube 113
that resides opposite the housing 93. A seal 124 closes the cavity
123 gas-tight. The mount can also accept an anti-reflection coated
plate 117 whose edge is preferably metallized and that is
preferably soldered gas-tight to the mount. Its job is to keep the
cavity 123 gas-tight when the objective lens was removed for
cleaning or when an objective lens having a different focal length
is to be introduced in order to generate a different imaging scale.
The space between the objective lens 112 and the highly
anti-reflection coated plate 117 can also be connected to the space
123 via bore (not shown), particularly when the entire laser gun,
as described under FIG. 4, constantly has a protective atmosphere
flowing through it, this emerging in the proximity of the objective
lens 112, which is shown in FIG. 39a. The highly anti-reflection
coated plate 117, however, can also contain optical correction
functions, as known for the Schmidt optics known from the
literature, in order to thus improve the optical imaging quality of
the arrangement. However, it is also possible to omit the highly
anti-reflection coated plate, particularly when it contains no
optical correction function and the objective lens was introduced
gas-tight or a protective atmosphere flowing therethrough sees to
it that no dirt can enter into the space 123 when the objective
lens is replaced. A special mouthpiece 82 is provided at the laser
gun 23, this being intended to prevent a contamination of the
objective lens 112 and being described in greater detail under FIG.
34.
[0194] The eccentric tube can be provided with cooling fins 92 over
which a ventilator (not shown) can blow in order to eliminate the
waste heat to the environment better. The laser gun is rotatably
seated in a prism around the axis between concave mirror and
objective lens in order, as described under FIG. 4, to make the
track spacing adjustable and in order to set the correct distance
from the processing surface 81. The laser gun can be fixed with a
strap retainer 85.
[0195] It is possible to arrange a displaceable lens (not shown)
having a long focal length between, preferably, the concave mirror
115 and the objective lens 112, the focusing of the processing
points onto the processing surface being capable of being finely
readjusted therewith without displacing the laser gun. However, a
variable focusing optics (zoom lens) can also be utilized, as was
described under FIG. 4. All descriptions that were provided for
FIGS. 4, 4a and 4b also apply analogously.
[0196] FIG. 5 shows a preferred embodiment of a terminator 26 for a
fiber 28 or laser fiber 5, which is also a fiber. Plug-type
connections for optical fibers for low powers are known in optical
communications technology, in sensor applications and measurement
technology; these, however, are not suitable for high powers
because too much heating occurs, this leading to destruction. For
example, such laser diode collimator systems, beam shaping optics
and coupling optics are described in the catalog 1/97 of Schfter
& Kirchhoff, Celsiusweg 15, 22761 Hamburg, pages A1 through A6.
However, the power of these systems is limited to 1000 mW and is
thus below the demands for the desired applications in processing
materials by a factor of 100 because an adequate heat elimination
is not assured. Further, these systems are relatively large in
diameter, so that no high packing density of the laser outputs can
be achieved. Another great disadvantage is that these systems are
not adequately sealed; they would get dirty very quickly and burn
up due to an increased absorption of the laser radiation. Last but
not least, it should also be mentioned that the precision of the
mount for fibers and the lens are inadequate for the desired
application. Terminators according to this patent application are
therefore significantly more advantageous. Such terminators can be
advantageously employed for coupling laser radiation out of a fiber
5, 28, as disclosed in the German Patent Application P 198 40 935.4
of the assignee "Abschlussstuck fur Lichtleitfasern".
[0197] This terminator 26 can be fundamentally used for all
applications wherein the matter of concern is that the ray bundle
emerging from a fiber 5, 28 be precisely coupled with a releasable
connection. It is likewise possible with the assistance of this
terminator to produce a precise, releasable connection of the fiber
5, 28 to the remaining optics. The terminator is composed of an
oblong housing 132 that comprises a through cylindrical opening 130
extending in axial direction. The housing is preferably
manufactured of prefabricated, for example drawn material that can
preferably be composed of glass. The laser fiber 5 of the fiber
laser is preferably stripped off its cladding at its ultimate end
and is preferably roughened at its outside surface, this being
disclosed in German Patent Application P 197 23 267, so that the
remaining pump radiation leaves the laser fiber before the entry of
the laser fiber into the terminator. The fiber 5, 28 can also be
additionally surrounded by a single-layer or multi-layer protective
sheath 131 that can be connected to the housing 132 of the
terminator, for example with a glued connection 142. The housing
132 comprises fits 134 with which the housing can be exactly
introduced in a mount 29 (FIG. 5a, FIG. 7, FIG. 8, FIG. 14). The
fits can thereby extend over the entire length of the housing
(FIGS. 5b, 9, 10); however, it can also be attached in limited
regions of the housing (FIGS. 5, 6, 7). One or more seals 36 can be
provided that, for example, are connected to the housing 132 with
glue connections 142. The job of the seals is to enable a gas-tight
connection of the terminators to the mounts 29. The housing can
have a different diameter, for example a smaller diameter, in the
region of the protective cladding 131 and of the seal 36 than in
the region of the fits. At the end of the housing 132, the end of
the fiber 28 or, respectively, of the laser fiber 5 is accepted and
conducted within the housing in the opening 130. A lens 133 having
a short focal length is secured to the other end of the housing
132, whereby the housing can comprise a conical expansion 139 so as
not to impede the laser radiation 13. Means can be provided for
adjusting the position of the fiber 5, 28 within the terminator in
order to adjust the position of the fiber relative to the lens 133
within the terminator and with reference to the fits 134, as shown
in FIGS. 5b, 5c, 6, 6a, 7, 9, 9a, 10a, 10b, 11, 11a and 12. The
radial position of the fiber 5, 28 can also be defined by the
cylindrical opening 130, whereby the fiber is axially displaceable
within the opening. The position of the lens 133 can either be
adequately precisely mounted during assembly or can be axially
and/or radially adjusted and fixed with suitable means (not shown)
with reference to the fiber 5, 28 and to the fits 134, whereby the
fiber can also be axially displaced (FIG. 5b). The adjustments are
advantageously undertaken with a measuring and adjustment device.
What the adjustment is intended to achieve is that the beam bundle
144 emerging from the lens 133 is brought into a predetermined
axial and focus position with a defined cone relative to the fits
134. After a fixing of the fiber 5, 28 within the housing 132 and
of the lens 133 at the housing, the measuring and adjustment device
is removed. Inventively, it is also possible to provide the end of
the fiber 5, 28 with a suitable coating, for example a
correspondingly thickly applied metallization 141, in the region of
the terminator before assembly in order to further improve the
durability of the adjustment. The fixing of the fiber 5, 28 within
the housing 132 can occur with suitable means such as gluing,
soldering or welding. An elastic compound 138 that represents an
additional protection for the fiber is preferably provided at the
transition between the housing 132 and the protective sheath 131.
It is also possible to fashion and align the lens 133 by
corresponding shaping and vapor-deposition of a corresponding
layer, preferably at its side facing toward the fiber end, such
that it co-assumes the function of the outfeed mirror 12 for the
fiber laser.
[0198] FIG. 5a shows a multiple arrangement of fiber laser outputs
with the terminators from FIG. 5. Bores 150 for the acceptance of
two terminators 26 for two tracks are provided in a housing 145.
Further, respectively three pins 148 and 149 are attached in rows
such within the housing 145 in extension of the bores that they
represent a lateral limitation as mount 29 for the terminators and
see to a precise guidance and alignment of the terminators. The
diameters of the pins 148 are referenced d.sub.1 and are preferably
identical to one another. The diameters of the pins 149 are
referenced d.sub.2 and are preferably likewise identical to one
another. If the diameters of the pins 148 were the same as the
diameters of the pins 149, the axes of the ray beams of both tracks
would lie parallel to one another in the plane of the drawing since
the terminators 26 comprise cylindrical fits 134. In FIG. 5a,
however, the diameters of the pins 149 are shown larger than the
diameters of the pins 148, this resulting in the axes of the two
ray beams proceeding at an angle relative to one another in the
plane of the drawing. The angle between the ray beams is dependent
on the diameter difference d.sub.2-d.sub.1 and on the
center-to-center spacing M of the two pin rows. The terminators are
conducted through the housing 145 at the underside in one plane and
are conducted from above through a cover (not shown) of the housing
that is secured to the housing and can close it gas-tight with a
seal (not shown). The housing 145 can be part of a receptacle for
an optical unit for shaping the laser radiation. The terminators
are secured to the housing 145 with clips 147 and screws (not
shown), whereby the seals 36 see to a gas-tight closure. The
arrangement is not limited to two tracks; further bores 150 can be
provided and further pins 148 and 149 can be introduced in order to
insert further terminators for further tracks. The arrangement is
not limited to the one plane as described; further bores 150 can be
inserted into the housing 145 in further tracks and in one or more
further planes, these lying above or below the plane of the
drawing, and the pins 148 and 149 are lengthened to such an extent
that they represent mounts 29 for all tracks and all planes. Pins
148 and 149 are likewise employed for producing a defined spacing
between the planes. In this case, the pins proceed horizontally
between the terminators. For example, the horizontally arranged
pins 149 proceed between the wall of the housing 145 wherein the
bores 150 lie and the row of illustrated, vertically arranged pins
149. The horizontally arranged pins 148 preferably proceed at a
spacing M parallel to the horizontally arranged pins 149.
Horizontally arranged pins are not shown in FIG. 2a. The pins 148,
149 are preferably fabricated of drawn steel wire; however, they
can also be composed of other materials, for example of drawn
glass. An advantage given the arrangement with a plurality of
tracks and/or planes in the illustrated way is that the pins 148,
149 exhibit a certain flexibility. As a result thereof, it is
possible to press the entire packet of the terminators together in
the direction of the tracks and in the direction of the planes such
that the terminators 26 with their fittings 134 lie against the
pins without spacing, this being desirable for achieving utmost
precision.
[0199] FIG. 5b shows a terminator 26, whereby means for adjusting
the position of the fiber 5, 28 within the terminator are provided
in order to be able to adjust the position of the fiber 5, 28
relative to the lens 133 within the terminator and with respect to
the fittings 134. The position of the lens can also be adjusted.
The adjustments are advantageously undertaken with an adjustment
device. Adjustment screws 135, 136 (FIGS. 5b, 5c, 9, 9a, 10a, 10b,
11, 11a, 12) and/or balls 137 (FIGS. 6, 6a, 7) can be provided for
the adjustment of the position of the fiber 5, 28 in the housing
132. The fiber 28 or laser fiber 5 can also be axially displaced
within the adjustment screws 135, 136 or balls 137. The position of
the lens 133 can either be adequately precisely mounted during
assembly or axially and/or radially adjusted and fixed by means
(not shown) with reference to the fiber 5, 28 and with reference to
the fittings 134, whereby the fiber can also be axially displaced.
The adjustments are advantageously undertaken with a measuring and
adjustment device. What the adjustment is intended to achieve is
that the beam bundle 144 emerging from the lens 133 is brought into
a predetermined axial and focus position with a defined cone on the
basis of a relative adjustment of lens 133 and fiber 5, 28 toward
the fits 134. After a fixing of the fiber 5, 28 within the housing
132 and of the lens 133 to the housing, the measuring and
adjustment device is removed. That stated under FIG. 5 for this and
the other embodiments continues to apply, for example regarding the
metallization 141, the elastic compound 138 and the employment of
the lens 133 as laser mirror.
[0200] FIG. 5c shows a cross-section through the terminator 26 in
the region of the adjustment screws, from which it can be seen that
preferably three adjustment screws 135 are provided distributed
over the circumference, the fiber 28 or, respectively, the laser
fiber 5 being adjustable in fine fashion in the housing therewith.
Further, further adjustment screws 136, as shown in FIG. 5b, can be
provided within the terminator at the end of the terminator at
which the fiber 28 or, respectively, the laser fiber 5 enters.
These adjustment screws are designed like the adjustment screws
135. When only one set of adjustment screws 135 is employed, the
fiber 28 or the laser fiber 5 can only be adjusted with respect to
the angle. When two sets of adjustment screws are employed, they
can also be displaced parallel to their axis. The fixing of the
fiber 5, 28 within the housing 132 can occur with suitable means
such as gluing, soldering or welding.
[0201] FIG. 6 shows an embodiment of the terminator 26 wherein
small balls 137 of metal or, preferably, metallized glass are
employed instead of adjustment screws, these being brought into
their position in the housing and being subsequently glued or
soldered. A plurality of sets of balls can also be applied.
[0202] FIG. 6a shows a cross-section through the terminator in the
region of the balls 137.
[0203] In order to prevent the optical surfaces on the optical
fiber and the side of the lens 133 that faces toward the optical
fiber from contaminating biparticles in the ambient air, the
connections in FIGS. 5, 5b, 5c, 6, 6a, 7, 9, 10, 11, 11a and 12
between the lens 133 and the housing 132 as well as between the
adjustment screws 135 and 136 or, respectively, the balls 37 and
the housing 132 can be hermetically closed. This can occur with
suitable glued or soldered connections 142. When a soldered
connection is preferred, the glass parts are previously metallized
at the corresponding locations 141. In order to achieve a greater
strength, the glued or soldered connections can also entirely or
partially fill the remaining gap between the fiber 28, the laser
fiber 5 and the housing 132, or the protective sheath 131 in the
proximity of the terminator, this being shown, by way of example,
in FIG. 5. It is also possible to durably evacuate the interior 143
of the housing or fill it with a protective atmosphere.
[0204] FIG. 7 shows a further embodiment of a terminator 26 that is
introduced in a housing 145 with a mount 29. Given this embodiment,
the front, outer fitting 134 in the region of the lens 133 is
conically implemented for better sealing and for better heat
elimination. Additionally, a seal 146 can be provided that instead
of being attached to the lens-side end of the terminator as shown,
can also be attached to the fiber-side end thereof.
[0205] FIG. 8 shows mounts 29 in a housing 145 for a plurality of
conically implemented terminators 26 according to FIG. 7. Such
mounts are advantageous when a plurality of outputs of fibers or
fiber lasers are to be arranged next to one another or next to one
another and above one another. The axes of the mounts can thereby
be arranged such that the axes of the beam bundles emerging from
the terminators of the terminators lying side-by-side and/or above
one another proceed parallel to one another or at an angle. In
order to eliminate the waste heat, the housing 145 can be provided
with bores through which a coolant is conducted.
[0206] FIG. 8a shows the rear fastening of the terminators 26 in
the housing 145. For fixing the terminators 26, 94, clips 147 are
provided that fix the ends of the terminators with screws 151 in
the housing at the locations at which the fibers respectively enter
into the housing of the terminators 26, 94.
[0207] FIG. 9 shows an embodiment of a terminator 26 having a
quadratic or rectangular cross-section, whereby all outside
surfaces lie opposite one another proceed parallel and can be
fittings 134. FIG. 9a shows a cross-section through the terminator
26 according to FIG. 9 having a quadratic cross-section.
[0208] FIG. 10 shows an embodiment of the terminator 94 with
rectangular cross-section, whereby two outside surfaces lying
opposite one another proceed trapezoidally and two outside surfaces
lying opposite one another proceed parallel to one another. The
outside surfaces can be fittings 134.
[0209] FIG. 10a shows a longitudinal section and FIG. 10b a
cross-section through the terminator according to FIG. 10.
[0210] FIG. 11 shows terminators 26 having trapezoidal
cross-sections, so that a row of terminators arises by successive
turning of the terminators by 180.quadrature. when a plurality of
terminators are joined to one another, whereby the center points of
the terminators lie on a central line. When desired, a plurality of
such rows can be arranged above one another, which is indicated
with broken lines in FIG. 11.
[0211] FIG. 11a shows terminators 26 with a triangular
cross-section that can likewise be arranged in a plurality of rows
above one another, this being indicated with broken lines.
[0212] FIG. 12 shows terminators 26 having a hexagonal
cross-section that can be arranged honeycomb-like for increasing
the packing density.
[0213] The inventive terminators advantageously enable the laser
radiation source to be built of individual modules.
[0214] FIG. 13 shows an applied example of the terminator 26 or 94
given a fiber 28 or a laser fiber 5 that have both ends provided
with a respective, terminator.
[0215] According to the preferred embodiments, it is possible to
preferably implement the lens 133 at its side facing toward the
fiber end on the basis of a corresponding shape being and
vapor-deposition of a corresponding layer such that it co-assumes
the function of the outfeed mirror 12. According to the preferred
embodiments, it is also possible to implement the lens 3, 154 by
corresponding shaping and vapor-deposition of a corresponding layer
that it co-assumes the function of the infeed mirror 7.
[0216] It is fundamentally possible to combine a plurality of the
terminators described above in a plurality of tracks side-by-side
and above one another in a plurality of planes to form a
packet.
[0217] It is also possible to implement the shape of the
terminators differently from that shown in the Figures, for example
that a cylindrical shape according to FIG. 6 is lent trapezoidal or
rectangular fits according to FIG. 9 or FIG. 10.
[0218] FIG. 14 shows a coupling of the laser fiber 5 to a pump
source with the terminator 26 via the housing 152 in which the pump
source 18 is accommodated in a recess 153, preferably gas-tight. A
seal 146 assures that the terminator 26 likewise terminates
gas-tight, so that no dirt particles can penetrate into the recess
from the outside and, as needed, it can be evacuated or filled with
a protective atmosphere. A constant current of a protective
atmosphere can also flow through the recess 153, particularly given
temporary removal of the terminator 26. The radiation of the pump
source 18 is focused onto the pump cross-section of the laser fiber
5 via a lens 154. The pump source can be composed of one or more
laser diodes; however, it can also be composed of an arrangement of
one or more lasers, particularly fiber lasers as well, whose output
radiation was united such with suitable means that a suitable pump
spot arises.
[0219] FIG. 15 shows the branching of the output radiation from the
laser fiber 5 of a fiber laser with a fused fiber coupler 155. Such
fused fiber couplers are described for single-mode fibers on Page
G16 of the catalog of Spindler and Hoyer specified in greater
detail under FIG. 20 and can be directly fused to the output of the
laser fiber 5 after correspondingly precise alignment. In this
case, thus, the terminator 26, 94 is connected to a passive
single-mode fiber or, respectively, to a different fiber 28 and not
directly to a fiber laser with the active laser fiber 5. There are
also other possibilities of splitting the laser beam into a
plurality of sub-beams such as, for example, beam splitter mirrors
or holographic beam splitters. The advantage of the described fused
fiber coupler, however, is that the laser radiation can be brought
to the processing point guided within fibers insofar as possible,
this leading to a considerable simplification of the
arrangement.
[0220] FIG. 16 shows the uniting of the radiation from the laser
fibers 5 of two fiber lasers via a fused fiber coupler 156. The
cross-sections of the two input fibers are united to form one fiber
in the fused fiber coupler 156. For example, the diameter of the
fibers at the two inputs of the fused fiber coupler amounts to 6
.mu.m and the core diameter of the two laser fibers to be fused on
likewise amounts to 6 .mu.m. A core diameter of the single-mode
fiber at the output of the fused fiber coupler thus becomes 9
.mu.m, which still allows a faultless guidance of a single mode for
the corresponding wavelength. The diameter at the output of the
fused fiber coupler, however, can also be greater than 9 .mu.m, and
more than two outputs of fiber lasers or, respectively, fibers can
be united. The terminator 26, 94 in this case is thus connected to
a passive single-mode fiber or other passive fiber 28 and not to a
fiber laser with the active laser fiber 5.
[0221] However, all other types of light waveguides can be welded
to the fiber laser or coupled thereto in some other way, for
example via optics.
[0222] One or more passive single-mode fibers or one or more other
passive fibers 28 can also be coupled to an individual fiber laser
instead of a brancher according to FIG. 15 or a combiner according
to FIG. 16, being coupled via optics in order to then connect the
terminator to this single-mode fiber or other fiber.
[0223] However, it is also possible to unite the outputs of a
plurality of fiber lasers or single-mode fibers or other suitable
fibers into which laser radiation can be coupled via
wavelength-dependent or polarized beam combiners or other suitable
techniques, and to in turn couple into single-mode fibers or other
fibers that can be provided with a respective, corresponding
terminator at one or both ends.
[0224] The described possibilities of branching and uniting fibers
can be particularly advantageously employed when the modular
structure is applied to the laser radiation source.
[0225] FIG. 17 shows the principle of an acousto-optical deflector.
A piezo-electric transducer 45 is applied on a substrate 161 that
is also referred to as crystal, said piezo-electric transducer 45
being supplied with electrical energy from a high-frequency source
162. The laser beam 163 incident at a Bragg angle .alpha..sub.B is
deflected out of its direction proportionably to the frequency of
the high-frequency source by interaction with the ultrasound field
164 within the crystal. When the beam that is not deflected and
that passes through the modulator in a straight line is referenced
I.sub.0 (beam of the zero order), then the frequency f.sub.1 yields
a direction I.sub.11 (first beam of the first order), and the
frequency f.sub.2 yields a direction I.sub.12 (second beam of the
first order). Both frequencies can also be simultaneously present
and the beams I.sub.11 and I.sub.12 arise simultaneously, these
being capable of being modulated by varying the amplitudes of the
high-frequency sources. An optimum transmission efficiency for the
infed radiation respectively derives when the Bragg angle amounts
to half the angle between the direction of the beam bundle I.sub.0
and the direction of the deflected beam bundle. For use as
acousto-optical modulator, only one of the sub-beams is used. It is
mostly effective for processing materials to employ the beam of the
zero order because it has the higher power. However, it is also
possible to use one or more beams of the first order. The energy of
the beams that is not used is neutralized in that, for example, it
is converted into heat on a cooling surface. Only one
piezo-electric transducer 45 is provided in FIG. 17, for which
reason only one laser beam 163 can be deflected or modulated.
However, a plurality of piezo-electric transducers can also be
attached on the same substrate in order to thus simultaneously
provide a plurality of laser beams, i.e. a plurality of channels,
with different deflection or modulation signals. The individual
channels are referenced T.sub.1 through T.sub.n. When, as shown in
FIG. 17, the acousto-optical modulator is placed into a focal point
of the lens 165 and the beam path is implemented nearly parallel
through the acousto-optical modulator, the beams in the other focal
point of the lens 165 are focused on the processing surface
arranged here, and the beam axes between the lens 165 and the
processing surface 81 proceed parallel and impinge the processing
surface perpendicularly. Such an arrangement is called telecentric;
the advantage is that the spacing between the beam axes remains
constant when the position of the processing surface changes. This
is of great significance for a precise processing of material.
[0226] FIG. 18 shows how the unused beam is neutralized. The unused
beam is intercepted and deflected via a highly reflective mirror
166, which is preferably manufactured of metal for better heat
elimination, is dispersed by a concave lens 75 and is directed onto
an obliquely arranged plate 86 having bores 87 such that no energy
can be reflected back into the laser. The plate 86 and,
potentially, the mirror 166 are also cooled via a cooling system
that is operated by a pump 167. It is also possible to utilize a
convex lens on a glass plate instead of the concave lens. The
convex lens, particularly when a dispersion of the beam bundle to
be neutralized can be undertaken with other techniques, which can
occur, for example, by special shaping of the highly reflective
mirror 166, is described under FIG. 4c. The concave lens 75 can
also be omitted when one foregoes the advantage of the complete
sealing of the laser gun. The plate 86 is shown with a planar
surface at an angle. A plate having an arc or a cavity can also be
employed. The surface can be roughened in order to absorb the laser
energy well which is conducted to the coolant.
[0227] It is advantageous for an arrangement having a plurality of
tracks to arrange a plurality of such modulators on a common
crystal 34 according to FIGS. 19 and 19a. The individual modulators
cannot be arranged arbitrarily close to one another because of too
much heating. A modulator of Crystal Technology Incorporated, Palo
Alto, USA, is especially suited for the arrangement, this being
distributed under the designation MC 80 and containing five
separate deflection or modulator channels. In this case, the
spacing of the channels is predetermined at 2.5 mm, whereby the
beam diameter is recited as 0.6 mm through 0.8 mm. A similar
product by the same company is equipped with ten channels having a
spacing of 2.5 mm. The spacing of the channels of 2.5 mm requires
the diameter or the edge length of the terminators 26,94 is
implemented smaller than 2.5 mm. When the terminator 26, 94,
however, is greater in diameter or in edge length than the spacing
of the channels in acousto-optical deflector or modulator, an
adaptation can be undertaken with an intermediate imaging, as shown
in FIG. 25. Such a multi-channel deflector or modulator can also be
employed in the exemplary embodiments according to FIGS. 4, 4a, 4b,
4c, 36, 36a and 37. Dependent on the requirement of the
application, all channels need not be used. Only four channels are
shown in the illustrated applied examples.
[0228] Instead of the acousto-optical modulator, however, it is
also possible to utilize other modulators, for example what are
referred to as electro-optical modulators. Electro-optical
modulators are described under the terms "laser modulators", "phase
modulators" and "Pockels cells" on pages F16 through F33 of the
overall catalog G3, Order No. 650020 of Laser Spindler & Hoyer,
Gottingen. Multi-channel electro-optical modulators have also been
possibly employed, which is shown in the publication "Der Laser in
der Druckindustries" by Werner Hulsbuch, Verlag W. Hulsbusch,
Constance, page 523, FIG. 8-90a. When a one-channel or
multi-channel electro-optical modulator is employed in combination
with a birefringent material, then each laser beam can be split
into two beams that can be separately modulated via further
modulators. Such an arrangement is also referred to as an
electro-optical deflector in the literature.
[0229] FIG. 18a shows an arrangement having an electro-optical
modulator 168. In an electro-optical modulator, for example, the
polarization direction of the laser radiation that is not wanted
for processing is separated from the incident beam bundle 163, and
turned (P.sub.b), and subsequently, the laser radiation P.sub.b not
wanted for the processing is separated off in a
polarization-dependent beam splitter, which is also referred to as
polarization-dependent mirror 169, and is conducted into a sump,
for example into a heat exchanger that can be composed of a cooled
plate 86. The radiation P.sub.a wanted for processing is not turned
in terms of polarization direction and is supplied to the
processing surface via the lens 165. In the exemplary embodiments
according to FIGS. 4, 4b and 4c, the single-channel or
multi-channel acousto-optical modulators 34 can be replaced by
corresponding, single-channel or multi-channel electro-optical
modulators. In the exemplary embodiments according to FIGS. 4, 4b
and 4c, the highly reflective mirror 74, 97 can likewise be
replaced by the polarization-dependent mirror 169 (FIG. 18a),
wherefrom an intercept arrangement 78 derives, and whereby the
polarization-dependent mirror extends into the beam path desired
for the processing.
[0230] The fiber laser can also be directly modulated. Such
directly modulatable fiber lasers that have a separate modulation
input available to them are offered, for example, by IPG Laser GmbH
D-57299 Burbach, under the designation "Modell YLPM Series". The
advantage is that the acousto-optical modulators and the
corresponding electronics for the high-frequency sources can be
omitted. Moreover, the transmission unit can be simplified, as
shown in FIG. 23.
[0231] FIG. 19 shows a plan view onto an acousto-optical deflector
or modulator. It is mentioned in the description of FIGS. 4, 4b and
4c that the space 44 or 111 according to FIGS. 4, 4b and 4c wherein
the modulators are arranged should be optimally free of those
components that give off particles or gases because particles could
thus settle onto the highly stressed optical surfaces, which would
lead to the premature failure of the arrangement. For this reason,
the electrical components of the arrangement in FIGS. 19 and 19a
are arranged on a separate printed circuit board 171 that merely
has two arms projecting into the sealed space and produces the
electrical connections to the piezo-electrical transducers 45. The
printed circuit board 171 is sealed relative to the modulator
housing 172, preferably with a solder location 173. The end face of
the printed circuit board is preferably sealed by a metal band (not
shown) that is soldered on in the region of the space 44 or 111.
The printed circuit board is implemented in multi-layer fashion in
order to shield the individual high-frequency channels by
interposed connections to ground. Instead of a printed circuit
board, some other line arrangement can also be utilized. For
example, each radio frequency channel can be connected by its own
shielded line. The modulator housing 172 contains an access opening
174 to the electrical components. The modulator crystal 34 can be
metallized at its base area and is preferably secured on the
modulator housing with a solder point or a glued connection 175. A
connection 176 to a cooling system can be located directly under
the fastening location in order to carry the waste heat off via the
openings 87 with a coolant. The modulator housing 172 is preferably
closed by a cover 177 that carries the electrical terminals 181 and
also contains the connections for the cooling system, but this is
not shown. A seal 43 sees to it that the modulator housing 172 is
inserted gas-tight into the housing 35 or 93 of FIGS. 4, 4a, 4b and
4c and is secured with the connection 42.
[0232] It is possible to secure the electro-optical modulator 168
to the modulator housing (172) in a similar way and to contact it
via the printed circuit board 171.
[0233] FIG. 20 indicates that the basic beam path for the exemplary
embodiment of FIG. 4 for the beam bundles 144 of the corresponding
fiber lasers F.sub.HD1 through F.sub.HD4. The beams bundles of the
fiber lasers F.sub.VD1 through F.sub.VD4 proceed partially
congruently with the indicated rays but, inventively, have a
different wavelength and, as can be seen from FIG. 4a, are united
via a wavelength-dependent mirror 37 (not shown in FIG. 20) with
the beam packet F.sub.HD1 through F.sub.HD4 to form the beam packet
F.sub.D1 through F.sub.D4. Further, FIG. 20 does not show the beam
packets of the fiber lasers F.sub.VR1 through F.sub.VR4 and
F.sub.HR1 through F.sub.HR4 that, as can be seen from FIG. 4a, are
likewise combined via a wavelength-dependent mirror to form the
beam packet F.sub.R1 through F.sub.R4. As can be seen from the
arrangement of the strip mirror 46 in FIG. 4a, the beam bundles of
the beam packet F.sub.R1 through F.sub.R4 in FIG. 20 would proceed
offset by half a track spacing from the indicated rays. Instead of
containing the indicated four beam bundles, thus the complete beam
path contains a total of eight beam bundles that yield a total of
eight separate tracks on the processing surface. FIG. 20 only shows
the two beam bundles 144 of the fiber lasers F F.sub.HD1 and
F.sub.HD4. As already mentioned under FIG. 4, however, a plurality
of tracks can also be arranged; for example, the plurality of
tracks on the processing surface can also be increased to sixteen
separately modulatable tracks. On the basis of a digital modulation
of the respective laser, i.e. the laser is operated in only two
conditions as a result of turn-on and turn-off, this arrangement
enables an especially simple control and a good shaping of the
processing spot on the processing surface. This digital type of
modulation requires only an especially simple modulation
system.
[0234] A distinction between more than 100 tonal value levels is
required in high-grade multi-color printing in order to obtain
adequately smooth color progressions; more than 400 tonal value
stages would be optimum. When, for example, a cup in rotogravure
wherein the volume of the cups determines the amount of ink applied
onto the material being printed is composed of 8.times.8 or
16.times.16 small individual cups and the cup depth is kept
constant, the processed surface can be quantitized into 64 or 256
stages. When, however, the cup depth is controlled by additional,
analog or digital amplitude modulation or by a pulse-duration
modulation of the laser energy, the volume of the cups can be
arbitrarily finely quantized even given a low plurality of tracks.
If, for example, the cup depth were digitally controlled in only
two stages, as described in greater detail under FIG. 28, a cup
could be composed of 8.times.8 individual cups given eight tracks,
these potentially having respectively two different depths. For
example, the volume of the cups in this case could be quantized in
128 stages without losing the advantage of purely digital
modulation, which yields a considerable advantage for the stability
of the method. Given 16 tracks and 2 stages in the cup depth, the
number of digitally possible quantization stages already amounts to
512. It is also possible to generate the cups in two processing
passes in order to increase the number of tonal value steps.
[0235] The modulators 34 as well as the strip mirror 46 are not
shown in FIG. 20. For a better illustration, the cross-section of
the beam bundle 144 from the terminator of the fiber laser
F.sub.HD1 that is congruent with the ray beam F.sub.D1 after
passing the wavelength-dependent mirror is designed with a
hatching. Like all other illustrations, this illustration is not to
scale. The two illustrated beam bundles 144 yield the processing
points B.sub.1 and B.sub.4 on the processing surface 81 that
contribute to the built-up of the processing spot 24 and generate
corresponding processing tracks on the processing surface 81. The
axes of the terminators 26 and of the beam bundles 144 of the
individual fiber lasers proceed parallel to one another in FIG. 20.
The beam cones of the terminators, i.e. the shape of the ray beam
144, are shown slightly divergent. In the Figure, a beam narrowing
within the lens 133 is assumed in the Figure. The divergence angle
is inversely proportional to the diameter of the beam bundle in the
corresponding beam narrowing. The position of the beam narrowing
and its diameter, however, can be influenced by varying the lens
133 in the terminator 26, 94 and/or its distance from the fiber 28
or from the laser fiber 5. The calculation of the beam path occurs
in the known way. See the technical explanations on pages K16 and
K17 of the general catalog G3, Order No. 650020 of Laser Spindler
& Hoyer, Gottingen. The objective is that the processing points
B.sub.1 through B.sub.n of the processing surface 81 respectively
become beam narrowings in order to obtain the highest power density
in the processing points. With the assistance of the two lenses 55
and 56, beam narrowings and track spacings from the object plane
182 wherein the lenses 133 of the terminators 26 lie are imaged in
demagnified fashion in an intermediate image plane 183
corresponding to the ratio of the focal lengths of the lenses 55
and 56. When, in this case, the distance of the lens 55 from the
terminator 26 and from the crossing point 184 is equal to its focal
length and when the distance of the lens 56 from the intermediate
image plane 183 is equal to its focal length and equal to its
spacing from the crossing point 184, what is referred to as a
telecentric imaging is obtained, i.e. the axes of the beam bundles
belonging to the individual tracks begin to proceed parallel in the
intermediate image plane. The divergence, however, has been
noticeably increased. The preferably telecentric imaging has the
advantage that the diameters of the following lenses 57 and 61 need
only be insignificantly larger than the diameter of a beam bundle.
The lenses 57 and 61 demagnify the image from the intermediate
image plane 183 in a second stage onto the processing surface 81 in
the described way. A preferably telecentric imaging, namely that
the axes of the individual beam bundles proceed parallel between
the objective lens 61 and the processing surface 81, has the
advantage here that changes in spacing between the processing
surface and the laser gun produce no change in the track spacing,
which is very important for a precise processing. The imaging need
not necessarily occur in two stages with two lenses each; there are
other arrangements that can also generate parallel beam axes
between objective lens and processing surface, as shown in FIGS. 21
and 22. Deviations in the parallelism of the beam axes between the
objective lens 61 and the processing surface 81 can also be
tolerated as long as the result of the processing of the material
is satisfactory.
[0236] FIG. 21 shows a fundamental beam path for the exemplary
embodiment of FIG. 4b. The illustration is not to scale. As was
already the case in FIG. 20, the two beam bundles 144 of the lasers
F.sub.HD1 and F.sub.HD4 are only a matter of a sub-set of the beam
bundles of all existing lasers in order to explain the principle.
In contrast to FIG. 20, however, the axes of the individual beam
bundles of the terminators in FIG. 21 are not parallel but are
arranged at an angle relative to one another, which is shown in
greater detail in FIG. 24, and which is advantageously achieved by
terminators 94 according to FIGS. 10, 10a and 10b. As a result of
this arrangement, the individual beam bundles 144 would cross
similar to the case in FIG. 20 without a lens 55 being required. In
the region of the imaginary crossing point, the dispersive lens
with a short focal length, i.e. a concave lens 101 is inserted,
this bending of the incoming rays off and rendering of the beam
bundles divergent is shown, i.e. widening them. The convex lens 102
is preferably arranged in the intersection of the axial rays and,
together with the lens 101, forms an inverted Galileo telescope. As
a result thereof, for example, parallel input beam bundles are
converted into parallel output beam bundles having an enlarged
diameter between the lenses 102 and 103. The desired parallelism of
each input beam bundle can, as already described, be undertaken by
a suitable selection of focal length and spacing of the lens 133
from the fiber 28 or laser fiber 5 in the terminators 26, 94. The
objective lens 103 focuses the enlarged beam bundle onto the
processing surface 81 at the processing points B.sub.1 through
B.sub.4 that contribute to the build-up of the processing spot 24
and generate corresponding processing tracks on the processing
surface 81. The imaging scale can be modified in a simple way by
modifying the focal length of the lens 103. It is therefore
advantageous when the lens 103 is implemented as an interchangeable
objective lens. As already described, however, a vario-focusing
optics can also be employed. When the position of the lens 103 is
selected such that the distance between the lenses 102 and 103
corresponds to the focal length of the lens 103, the axes of the
beam bundles between the lens 103 and the processing surface are
parallel and yield constant spacings of the tracks of the
processing surface, even given a modified distance between the
laser gun and the processing surface.
[0237] FIG. 22 indicates the fundamental beam path for the
exemplary embodiment of FIG. 4c. Like all other figures, the
illustration is not to scale. The beam path is very similar to that
of FIG. 21, with the difference that an arced mirror 121 is
employed instead of the lens 101 and a concave mirror 115 is
employed instead of the lens 102. The beam path is considerably
shorter due to the folding that derives. The beam path
approximately corresponds to that of an inverted mirror telescope.
Mirror telescopes are independent of the wavelength which is
advantageous given employment of lasers having different
wavelength. The imaging errors can be reduced by employing surfaces
or with an optical correction plate 117 that, however, is not shown
in FIG. 22. It is advantageous when the focal length of the
objective lens 112 is equal to its spacing from the concave mirror.
The axes of the ray bundles are then parallel between the lens 112
and the processing surface 81 and yield constant spacings of the
tracks on the processing surface, even given a modified distance
between the laser gun and the processing surface. Moreover, an
advantageously large spacing of the objective lens from the
processing surface derives. As described a vario-focusing optics
can also be utilized.
[0238] FIG. 23 shows an arrangement having a plurality of lasers,
whereby the individual laser outputs in the form of the terminators
26 are arranged on a circular segment and aim at a common
cross-over point 185. This arrangement is particularly suitable for
directly modulatable lasers since a very low expense then results.
In such an arrangement, the imaging on the processing surface 81
can occur with only a single lens 186. However, an arrangement
according to FIGS. 4b or 4c can also be employed for imaging. The
ray cones of the beam bundles from the terminators are set such
that a beam narrowing and, thus, a sharp image derives for all
lasers on the processing surface 81. Preferably, the spacings
between the cross-over point 185 and the lens 186 as well as
between the lens 186 and the processing surface 81 are of the same
size and correspond to the focal length of the lens 186. In this
case, the axes of the individual ray bundles between the lens 186
and the processing surface 81 are parallel and yield constant
spacings between the processing tracks, even given a modified
distance between the laser gun and the processing surface. Although
not shown, a plurality of levels of lasers can also be arranged
above one another in order to increase the power density and the
power of the laser radiation source. The planes of the lasers are
preferably arranged parallel to one another. As shown in FIGS. 29
and 31, it then derives that the individual ray bundles from the
individual planes meet on a spot in the processing points on the
processing surface 81 and thus generate an especially high power
density.
[0239] FIG. 24 shows a modification relating to FIG. 23. Four fiber
lasers F.sub.HD1, F.sub.HD2, F.sub.HD3, F.sub.HD4 have their
terminators 94, which are described in greater detail in FIGS. 10,
10a and 10b, joined to one another on a circular segment. The
terminators 94 are particularly suited for joining to one another
as a result of their shape. Since no directly modulatable fiber
lasers are employed here, a four-channel acousto-optical modulator
34 is inserted. The piezo-electric transducers 45 can, as shown in
FIG. 24, likewise be arranged on a circular segment. As shown in
FIG. 24a, however, they can also be arranged parallel as long as
the ray bundles are still adequately acquired by the acoustic field
of the piezo-electric transducers 45. Instead of the lens 186, a
transmission unit as described in FIGS. 4b and 4c is advantageously
employed.
[0240] FIG. 25 indicates a demagnifiying intermediate imager with
the lenses 191 and 192, so that the distance between the individual
terminators 26, 94 can be greater than the distance between the
individual modulator channels T1 through T4 on the multi-channel
acousto-optical modulator 34. The imaging ratio corresponds to the
relationship of the focal lengths of the two lenses 191 and 192.
The intermediate image is preferably telecentrically designed in
that the distance of the lens 191 from the lenses 133 of the
terminators 26 or 94 and from the cross-over point 193 is equal to
its focal length, and in that the distance from the crossing point
193 to the lens 192 as well as the distance of the lens 192 from
the modulator crystal 34 is equal to its focal length. By adjusting
the distance between the two lenses, however, one can also achieve
that the rays emerging from the lens 192 no longer proceed parallel
but at an angle relative to one another in order to connect the
beam path according to FIGS. 21 or 22 thereto. An intermediate
image according to FIG. 25 can also be employed in combination with
an arrangement of the terminators on a circular segment according
to FIGS. 23 and 24.
[0241] The intermediate imager (191, 192) is shown in FIG. 25
between the terminators (26, 94) and the modulator (34). However, a
wavelength-dependent or polarization-dependent mirror 37 can also
be arranged preceding or following the intermediate imager in the
beam direction. An intermediate imager (191, 192) can also be
arranged in the beam path following the modulator, before or after
the strip mirror 46. Preferably, the intermediate imager in the
beam path is inserted at the locations referenced "E" in FIG.
4a.
[0242] FIGS. 26 and 26a show how the distance between the tracks in
the processing plane can be reduced. FIG. 26 is a side view and
FIG. 26a is the appertaining plan view. Since the beam bundles 144
emerging from the terminators 26, 94 have a smaller diameter than
the housing of the terminators, interspaces remain that are not
utilized. Moreover, the minimum distances between the tracks and
the maximum diameters of the beam bundles are prescribed by the
multi-channel acoustic-optical modulators 34. In order to decrease
the distances between the tracks, a strip mirror 46 is provided
that is transparent and mirrored in alternating fashion in
stripe-shaped fashion at intervals. The strip mirror 46 and the
modulators are not shown in FIG. 26a. Such a strip mirror 46 is
shown in FIGS. 27 and 27a, whereby FIG. 27a shows a side view of
FIG. 27. Highly reflective strips 195 are applied on a suitable
substrate 194 that is transparent for laser radiation. The
interspaces 196 as well as the backside are preferably provided
with a reflection-reducing layer. The beam bundles 144 from the
terminators 26, 94 of the fiber lasers F.sub.D1 through F.sub.D4
pass unimpeded through the transparent part of the strip mirror 46.
The beam bundles 144 from the terminators 26, 94 of the fiber
lasers F.sub.R1 through F.sub.R4 are arranged such that they are
reflected at the strips of the strip mirror such that that they lie
in a row with the ray bundles F.sub.D1 through F.sub.D4. The
distance between the tracks has thus been cut in half.
[0243] FIG. 27b shows a strip mirror 46, whereby the substrate of
the mirror was removed in the interspaces 196, and the entire,
remaining surface is preferably highly reflectively mirrored, so
that strips 195 derive. In this case, the strip mirrors can be
preferably manufactured of metal, which is especially advantageous
given high powers and the heating connected therewith.
[0244] An arrangement having strip mirrors can be combined very
well with an arrangement having wavelength-dependent mirrors, as
shown, for example, in FIGS. 4, 4a, 4b, 4c. The further beam path
according to FIG. 20 can be connected via the lens 55. The axes of
the individual terminators 26, 94, however, can also be arranged at
an angle, as shown in FIGS. 23 and 24. In this case, the further
beam path can proceed according to FIG. 21 or 22 and the lens 55 is
omitted.
[0245] FIGS. 28 and 28a show how fiber lasers of different
wavelength, for example Nd:YAG lasers having 1060 nm and those
having a different doping with 1100 nm are combined with one
another via a wavelength-dependent mirror 37. The wavelength
difference can be less but can also be greater.
[0246] The modulators and the wavelength-dependent mirror are not
shown in FIG. 28a. Preferably, wavelength-dependent mirrors are
optical interference filters that are manufactured by
vapor-deposition of suitable dielectric layers onto a substrate
that is transparent for the corresponding wavelengths and can have
very steep filter edges as high-pass or low-pass filters.
Wavelengths up to the filter edge are allowed to pass; wavelengths
beyond the filter edge are reflected. Band-pass filters are also
possible. Likewise, lasers of the same wavelength but a different
polarization direction can be combined via polarized beam
combiners, preferably polarization prisms. A combination of
polarized beam combiners and wavelength-dependent mirrors is also
possible. In FIG. 28, the beam bundles 144 emerging from the
terminators 26, 94 of the fiber lasers F.sub.HD1 through F.sub.HD4
with the wavelength .lambda..sub.1, pass unimpeded through a
wavelength-dependent mirror 37, whereas the beam bundles F.sub.VD1
through F.sub.VD4 having the wavelength .lambda..sub.2 are
reflected at it and, thus, the two beam bundles are united in one
another following the mirror. Each beam bundle can be separately
modulated via a respective multi-channel, acousto-optical modulator
34. Since respectively two lasers of different wavelengths process
the same track in the same processing point on the processing
surface, a digital amplitude modulation in 2 stages is possible in
a simple way in order, for example, to control the depth of the
cups when producing printing forms for rotogravure when the two
participating beam bundles are respectively merely turned on or
off. However, a shared modulator for the two united beam bundles
can also be employed. In this case, the modulator is arranged
between the wavelength-dependent mirror 37 and the lens 55, as
shown in FIGS. 4, 4a, 4b, 4c. The further beam path of the
transmission unit according to FIG. 20 connects via the lens 55.
However, the axes of individual terminators 26, 94 can also be
arranged at an angle relative to one another, as shown in FIGS. 23
and 24. In this case, the further beam path can proceed according
to FIG. 21 or 22 and the lens 55 can be omitted.
[0247] FIG. 29 shows how fiber lasers with their terminators 26, 94
(FIG. 31) can be arranged in a plurality of planes. Three planes of
terminators that are connected to fiber lasers lie above one
another. The first track is referenced F.sub.1 for the first plane,
with F.sub.2 for the second plane and with F.sub.3 for the third
plane. The numerals 11, 12 and 13 reference the first plane of the
further tracks. The axes of the beam bundles 144 emerging from the
terminators are directed parallel to one another in the individual
planes. The axes of the beam bundles of the individual tracks can
proceed parallel to one another, as shown in FIG. 20, or at an
angle relative to one another according to FIG. 23 or 24.
[0248] In FIG. 30, the terminators 26, 94 (FIG. 31) of, for
example, seven fiber lasers F.sub.1 through F.sub.7 are arranged in
a hexagon such that the axes of their ray bundles 144 are parallel
to one another. To this end, terminators according to FIG. 12 can
be advantageously employed. As a result thereof, the smallest
possible diameter of a common ray bundle composed of seven
individual ray bundles derives.
[0249] First, FIG. 31 is first a sectional view through the three
planes of the first track of FIG. 29. A lens 107 collects all
incoming parallel rays in its focal point 201 on the processing
surface 81. As a result thereof, power and power density are
multiplied by the plurality of lasers united in the focal point,
i.e. are tripled given three planes. When the axes of the beam
bundles emerging from the terminators 26, 94 proceed parallel to
one another for tracks and planes, the beam bundles of all tracks
would likewise be additionally united in the focal point, and a
common processing point would arise on the processing surface that
generates a processing track. When the axes of the beam bundles
emerging from the terminations 26 proceed under an angle as shown
in FIG. 23 or 24, every track of termination will generate a
processing point, which generates a processing track I.e., the same
number of processing tracks are registered next to one another as
there are tracks of terminators. The power of the beam beams of the
various planes is superimposed in the respective processing point
and the power density is tripled in the illustrated example. The
individual fiber lasers can thereby be directly modulated; however,
external modulators can also be employed. FIGS. 32 and 33 describe
how a multiple-channel acousto-optical modulator corresponding to
the number of tracks can be preferably employed for the
simultaneous modulation of all ray bundles of the various
planes.
[0250] FIG. 31 is also a sectional view through the bundle
arrangement according to FIG. 30. It is known that parallel ray
bundles that are incident into a lens have a common focus. Page 13,
FIG. 2.21 in the book "Optik und Atomphysik" by R. W. Pohl,
13.sup.th edition, 1976, Springer Verlag shows such an arrangement.
Further, DE-A-196 03 111 discloses an arrangement wherein, as can
be seen from FIG. 1 therein, the radiation from a plurality of
laser diodes is respectively coupled into a single-mode fiber, the
radiation at the output of each fiber is collimated to a
respective, parallel beam bundle, and all parallel beam bundles are
directed onto a common spot with a shared lens in order to achieve
an increased power density. Compared to the arrangement shown in
FIG. 31 with fiber lasers, however, this arrangement has serious
disadvantages. When radiation is to be efficiently coupled into
single-mode fibers, single-mode laser diodes are required for this
purpose so that the aperture of the single-mode fibers is not
overfilled and the total radiation can be transmitted into the core
of the single-mode fiber. Single-mode laser diodes, however, can
only be manufactured with extremely limited power because the
loadability of the minute laser mirrors represents a technological
barrier. Single-mode laser diodes are therefore only available up
to an output power of approximately 200 mW and are far more
expensive per watt than multi-mode diodes that are offered with
radiation powers of up to several kilowatts. Given single-mode
fibers for 800 nm wavelength, the product of core diameter and
numerical aperture amounts to approximately 5 .mu.m.times.0.11=0.55
.mu.m, whereas this lies at 300 .mu.m.times.0.4=120 .mu.m given a
fiber laser having a typical diameter of the pump fiber of 300
.mu.m and a numerical aperture of 0.4, which amounts to a factor of
220. When the area ratio of the two fibers is considered, then a
factor of (300/5).sup.2=3600 derives. Even when a reduction of the
laser radiation by the factor of the absorption efficiency of
approximately 0.6 is assumed given the fiber laser, this being the
efficiency with which the pump radiation is converted into laser
radiation, the power of the laser radiation that can be achieved at
the output of a fiber laser is several orders of magnitude higher
than the power at the output of a single-mode fiber. Even if
single-mode diodes or other laser radiation sources having very
high power were available, it would nonetheless not be possible to
couple this satisfactorily into single-mode fibers, since the
fibers would burn given the slightest misadjustment at the fiber
entry. This problem does not exist given fiber lasers since a
relatively large fiber diameter is available for the pumping and
the energy is transmitted into the single-mode core of the laser
fibers only within the laser fiber, which is possible
unproblemmatically and with good efficiency.
[0251] The lens 197 in FIG. 31 unites the entire power of all seven
beam bundles F.sub.1 through F.sub.7 of the corresponding fiber
lasers in its focal point 201 which represents the processing spot
24 on the processing surface 81. The power and the power density in
the focal point thus become higher by the factor of 7 than is the
case given an individual beam bundle. When, for example, 100 W are
required in order to generate a required power density on the
processing surface, then seven lasers having a radiant power of
approximately 15 watts each suffice in this case. However, more
than seven lasers can be provided. The lasers can preferably be
directly modulated. However, it is also possible to modulate all
seven beam bundles separately or overall with an external modulator
or to supply a plurality of such bundle arrangements to a
multi-channel modulator in such a way that the modulator channels
are preferably arranged in the focal point of a uniting lens 197
that is allocated to each bundle. It is also possible to couple the
multiplied power of each and every bundle into fibers before or
after the modulation. Further, such bundle arrangements can be
advantageously utilized in laser guns according to FIGS. 4, 4a, 4b,
4c.
[0252] It is advantageous to separately modulate the individual
lasers. This is especially suitable when a high number of lasers is
employed, since, for example, a quantized modulation that is
similar to an analog modulation, a quasi-analog modulation of the
united laser radiation is then enabled by digital modulation of the
individual lasers. However, it is also possible to modulate the
beam bundles 144 of all lasers in common, for example with an
acousto-optical modulator. In this case, the ultrasound field of
the modulator cell must exhibit such a size that the overall beam
bundle shown in FIG. 30 can be modulated. However, the switching
time of the acousto-optical modulator becomes so great as a result
thereof that the shape of the cups to be engraved is disturbed as a
consequence of the rotational movement of the drum containing the
processing surface. However, it is possible to entrain the laser
beam with a deflection motion in the direction of the rotary motion
of the printing cylinder to be engraved during the engraving and to
thereby achieve a processing spot 24 that is stationary on the
processing surface. The deflection motion can occur with the same
acousto-optical modulator with which the amplitude modulation
occurs. However, another acousto-optical cell can also be utilized,
the deflection occurring therewith.
[0253] FIG. 32, in a farther-reaching example, shows how the power
density on the processing surface can be considerably increased by
providing terminators 26, 94 with the corresponding fiber lasers in
a plurality of planes, but a modulation of all beam bundles 144
belonging to a track can be simultaneously implemented with a
single-multi-channel, acousto-optical modulator 34 corresponding to
the plurality of tracks. In this example, the terminators are
arranged in three planes of n tracks each that lie above one
another. The power of all ray bundles 144 of all planes should be
largely focused in a processing point in the processing surface for
each track in order to achieve a high power density. The
terminators 26, 94 are arranged parallel to one another in tracks
and planes, since the terminators 26 are joined to one another in
close proximity. As shown, terminators having a round cross-section
can be employed for this purpose; preferably, however, terminators
having a quadratic cross-section according to FIGS. 9 and 9a are
utilized. Given the parallel arrangement of the tracks, the
illustrated imaging system having the cylindrical lenses 202 and
203, also refer to as cylinder optics, can, for example, be added
analogous to an arrangement like that of FIG. 4. When the
individual tracks are to proceed at an angle according to FIGS. 23
or 24, terminators 94 according to FIGS. 10, 10a and 10b are
preferably employed. In this arrangement, too, the beam bundles of
the individual planes remain parallel; the fits of the terminators
94 should proceed parallel in the side view of FIG. 10a for this
purpose. When the axes of the ray bundles for the tracks proceed at
an angle relative to one another, the cylinder optics having the
lenses 202 and 203 can be added, for example analogous to the
arrangements according to FIGS. 4b or 4c. The beam bundles 144
emerging from the terminators are directed onto the convex cylinder
lens 202 that would combine the rays in its focus to form a line
having the length of the beam diameter. A concave cylinder lens 203
having a shorter focal length then the cylinder lens 202 is
attached such in the region of the focus of the cylinder lens 202,
203 having a long focal length such that its focus coincides with
the focus of the cylinder lens 202. As a result thereof, the rays
that leave the lens 203 become parallel again. The spacings between
the individual planes, however, have been reduced by the ratio of
the focal lengths of the two cylinder lenses compared to the
spacings that the beam bundles had when they left the terminators
26, 94. The spacings of the beam bundles have remained unmodified
in the direction of the tracks since the cylinder lenses exhibit no
refractive effect in this direction. As a result thereof,
elliptical beam cross-sections derive in the modulator. The purpose
of this arrangement is to make the overall height of the three
ellipses lying above one another so small that it approximately
corresponds to the major axis of the ellipses in order to create
conditions in the channels of the acousto-optical modulator similar
to those achieved given a round beam cross-section so that, for
example, similarly short switching times can be achieved.
[0254] FIG. 33 shows that, however, the spacing of the two cylinder
lenses can also be modified somewhat so that all three elliptical
beam bundles overlap in the modulator, this is in fact yielding a
shorter switching time in the acousto-optical modulator but also
yielding an increased power density in the modulator crystal. The
cylinder lens 203 can also be omitted for this purpose.
[0255] The cylinder optics (202, 203) is shown in FIG. 25 between
the terminators (26, 94) and the modulator 3. However, a
wavelength-dependent or polarization-dependent mirror 37 can also
be arranged preceding or following the cylinder optics in beam
direction. A cylinder optics (202, 203) can also be introduced in
the beam path following the modulator, preceding or following the
strip mirror 46. Preferably, the intermediate image is inserted in
the beam path at the locations references "E" in FIG. 4a.
[0256] For removing the material eroded from the processing
surface, FIG. 34 shows a mouthpiece 82 whose main job is to use a
directed flow to take care that optimally no clouds of gases and/or
eroded material form in the optical beam path between objective
lens and processing surface 81, these clouds absorbing a part of
the laser energy and depositing on the processing surface and thus
negatively influencing the work result.
[0257] As a result of its specific shaping, the mouthpiece 82
prevents the described disadvantages. Preferably, it is secured to
the laser gun with connections 204 that are simple to release, so
that it can be removed and cleaned in a simple way and also enables
a simple cleaning as well as a simple replacement of the objective
lens (not shown) 61, 103, 112. A cylindrical bore 206 for
adaptation to the objective lens and a preferably conical bore 207
as passage for the beam bundle as well as another preferably
cylindrical bore that represents the processing space 211 are
located in a preferably cylindrical base member 205. The distance
of the base member 205 from the processing surface 81 should not be
excessively great. The processing points (not shown) for producing
the individual processing tracks on the material to be processed
lie in the processing spot 24. A broad, all around extraction
channel 212 is preferably located in the base member, this channel
212 being connected to the processing space 211 via a plurality of
extraction channels 213 that should have a large cross-section.
Preferably, 3 through 6 extraction channels 213 are present. A
further, preferably all around admission channel 214 is located in
the base member, this channel 214 being connected via nozzle bores
215 to the processing space 211 and to the conical bore 207 via
smaller bypass bores 216. 3 to 6 nozzle bores 215 and 3 to 20
bypass bores 216 are preferably distributed over the circumference
of the admission channel 214. All bores can be offset relative to
one another and relative to the extraction channels 213 on the
circumference. Further bypass bores can also be attached and
directed onto the objective lens. This, however, is not shown. The
base member is surrounded by a ring 217 applied gas-tight that
contains a plurality of extraction connectors 221 in the region of
the channel 212 to which extraction hoses are connected, these
being conducted via an extraction filter to a vacuum pump. The
extraction hoses, the extraction filter and the vacuum pump are not
shown in FIG. 34. In the region of the channel 214, the ring
contains at least one admission connector 222 via which compressed
air filtered with an admission hose is supplied. The quantity of
admitted air can be set with a valve such that it is just adequate
in order to adequately rinse the processing space and such that it
generates a slight air stream along the conical bore via the bypass
bores that largely prevents a penetration of particles into the
conical bore. The admission hose, the valve and the filter are not
shown in FIG. 3 4. The nozzle bores 215 are directed such onto the
processing spot 24 such that the clouds of gas, solid and molten
material arising in the processing are quickly blown out of the
beam path so that these absorb as little laser energy as possible
and cannot negatively influence the processing result.
Oxidation-promoting or oxidation-inhibiting gases or other gases
can also be blown in with the admission air, these having a
positive influence on the processing process. A slight quantity of
air from the environment co-flows through the processing space to
the extraction channels through the gap between the processing
surface and the base member 205; this, however, is not shown. The
filter in the extraction line is attached easily accessible in the
proximity of the mouthpiece and sees to keeping the vacuum pump
clean. It is also possible to introduce the filter directly in the
extraction channel 212. As described under FIG. 39a, it is useful
when a protective atmosphere is additionally conducted over the
objective lens. If the mouthpiece 82 becomes too hot due to the
laser radiation reflected from the processing surface and the air
that flows through does not suffice for cooling, then the
mouthpiece can be provided with additional bores through which a
coolant is pumped; this, however, is not shown in the FIGS. A glass
plate 218 that is highly anti-reflection coated on both sides and
is simple to change can also be located within the cylindrical bore
205, this glass plate 218 keeping dirt particles away from the
objective lens. The shape of the mouthpiece can also deviate from
the form that is described and shown. For example, the bores need
not be cylindrically or conically implemented, as described; they
can be varied in shape. Likewise, for example, the nozzle bores and
extraction channels can assume arbitrary shapes and can also be
asymmetrically arranged. For example, the nozzle bores in FIG. 34
can be arranged more in the upper part of the FIG., whereas the
extraction channels lie more in the lower part of the Figure. For
example, the nozzle bores and/or the bypass bores can also be
foregone. The shape of the mouthpiece can also be modified,
particularly when the shape of the processing surface and the type
of relative motion between processing surface and laser radiation
source demand this. It is conceivable to utilize a modified form of
the described mouthpiece when the material to be processed is
located, for example, on a planar surface instead of on a drum
surface, and the laser radiation is conducted past this
line-by-line. In this case referred to as flatbed arrangement,
which is shown in greater detail in FIGS. 43, 43a and 43b, the
mouthpiece is implemented elongated corresponding to the line
length and is provided with an elongated processing space
corresponding to its length. The mouthpiece is equipped with nozzle
bores and extraction channels from one or from both sides. In this
case, the glass plate would be given a rectangular shape and would
extend over the entire length of the arrangement. In this case,
FIG. 34 could be analogously considered as a cross-section of the
elongated mouthpiece. Even when the material to be processed is
located in a hollow cylinder, which is not shown in detail in FIGS.
44a and 44b, a similar mouthpiece can be produced in that the
mouthpiece described for the flatbed arrangement is adapted in the
longitudinal direction to the shape of the hollow cylinder such
that a slight gap between the processing surface and the mouthpiece
derives over the entire length. The glass plate would be given a
rectangular shape in this case and would be curved over the entire
length of the arrangement.
[0258] A generally known scraper device that, however, is not shown
in the figures can be located in the proximity of the mouthpiece
but need not necessarily be connected to it or to the laser gun.
For example, the job of the scraper device is to scrape off the
ejects arising at the edges of the cups during the processing
process at rotogravure forms. Further, a brush device (not shown)
can preferably be located in the proximity of the laser gun, this
brushing out the cups that have been cut and ridding them of
adhering dirt. Further, a measuring device (not shown) can be
preferably inventively located at the laser gun, this measuring the
position and/or the volume of the cups immediately after they are
produced. In contrast to cups that have been manufactured by
electromechanical engraving or with a single laser beam, the volume
can be inventively more precisely identified for cups that are
produced with the inventive laser radiation source and have steep
edges and constant depth, in that the area of the cup is determined
with a specific, fast camera and the volume is derived therefrom.
It is thereby advantageous to measure a series of cups in order to
reduce measuring errors. It lies within the framework of the
preferred embodiments that specific control fields are engraved in
a region of the rotogravure cylinder, this being provided for
monitoring measurements and/or for monitoring prints. A
rated/actual comparison can be produced with this measured quantity
for the generated cups and with the cup size prescribed for this
location. The result can then be employed in order to correct the
position and/or the volume of the subsequently produced cups.
[0259] FIG. 35 shows the conditions on the processing surface. The
processing points are identified with the indices that indicate the
ray bundles of the fiber lasers according to FIGS. 4, 4a, 4b and 4c
that produce them. For example, the ray bundles of the fiber lasers
F.sub.VR1 and F.sub.HR1 generate the processing point
B.sub.FVR1+FHR1 in common to the diameter of the processing points
is referenced B, and their spacing is referenced A. In the
multi-channel, acousto-optical modulator described under FIGS. 19
and 19a, the allowable diameter of the beam bundle 144 is smaller
than the spacing of the channels of the modulator. The diameter of
the ray bundle 144 in the terminators 26, 94 cannot be made just as
large as the outside diameter of the terminators without great
expense. It follows therefrom that A is thus greater than B. This
leads to undesired interspaces at the processing tracks 224 that
derive as a result of the relative motion between the material to
be processed and the laser gun. The processing tracks have a track
width D that corresponds with the diameter of the processing points
B and are referenced as 1 through 8 in FIG. 35. In order to reduce
these interspaces, two beam packets were already nested inside one
another with the strip mirror, as described under FIGS. 4, 4a, 26
and 26a, in order to cut the interspaces in half. In order to
reduce the remaining interspaces even more, or to entirely avoid
them or cause the processing tracks 224 to overlap, the laser gun
can be turned such compared to the relative motion direction
between the material to be processed and the laser gun such that
the tracks come closer to one another, this being shown in FIG. 35.
In order, for example, to achieve a spacing C of the processing
tracks 224 that is equal to the diameter B of the processing
points, the laser gun must be turned by the angle .beta. according
to the relationship cos .beta.=B/A. Distortions in the image
information arise on the processing surface due to the rotation of
the laser gun, since the starts in the individual processing tracks
are now shifted relative to one another. These distortions,
however, are already compensated in the editing of the processing
data. It is also possible to undertake this compensation by an
adjustable, different delay of the signals in the individual data
channels immediately before the modulation or to simply accept the
distortions. Further possibilities for setting and reducing the
spacings of the processing tracks are presented in FIGS. 36, 36a,
36b, 36c and 37.
[0260] FIG. 36 shows the principle of how processing points B.sub.1
. . . B.sub.4 derive on the processing surface 81 when the
individual channels are charged with different frequencies f.sub.1
through f.sub.4 in a multi-channel acousto-optical modulator 34
having four separate channels. For example, the modulator channel
T.sub.1 (FIG. 36a) is thereby supplied with a frequency f.sub.1,
whereby f.sub.1 is provided with a higher frequency compared to
f.sub.4 in the modulator channel T.sub.4 (FIG. 36a), so that a
greater spacing of lo derives for the processing track 1 than for
the processing track 4. The channels T.sub.2 and T.sub.3 are
provided with corresponding frequencies f.sub.2 and f.sub.3 in
order to achieve the illustrated arrangement of the processing
tracks 224. However, the frequencies can also be arranged such that
the frequency f.sub.1 is lower then the frequency f.sub.4. It is
also possible to arbitrarily allocate the frequencies f.sub.1
through f.sub.4 to the individual modulator channels T.sub.1
through T.sub.4. In this case, a lens 165 as shown in FIG. 17 and
FIG. 36a is not absolutely necessary; rather, the laser radiation
emerging from the terminators can be focused such that a sharp
image derives in the processing points on the processing
surface.
[0261] How the beam bundles focused by the lens 165 impinge the
generated line M of the drum is shown in FIG. 36a with reference to
an example (not to scale) with the rotating drum on which the
processing surface 81 lies. The position of the puncture points P
of the ray axes with the plane of the lens 165 thereby corresponds
to the principle of FIG. 36. For that purpose, the modulator 34
with the channels T.sub.1 through T.sub.4 is correspondingly
arranged relative to the beam bundles 144 of the fiber lasers
F.sub.1 through F.sub.4. What is achieved by a suitable selection
of the frequencies f.sub.1 through f.sub.4 is that the partial rays
that generate the processing points B.sub.1 through B.sub.4 lie at
desired distances from one another in the direction of the
generated line M. This has the advantage that the position of each
processing point and, thus, of each processing track 224 can be
individually set by adjusting the corresponding frequency. A
particular advantage of the arrangement derives when, as indicated
in FIG. 17, the multi-channel acousto-optical modulator is arranged
approximately in the one and the processing surface is arranged
approximately in the other focal point of the lens 165, and the
axes of the beam bundles of the fiber lasers F.sub.1 through
F.sub.4 are arranged approximately in parallel planes. The
processing points B.sub.1 through B.sub.4 then lie in a row on the
generated line M (FIG. 36a), and the axes of the partial rays that
form the processing points are parallel and reside perpendicularly
on the processing surface (FIG. 17). Another advantage of the
arrangement is that the Bragg angle for optimizing the efficiency
can be individually set for each modulator channel, but this is not
shown in the Figures. In this example, the deflected rays are used
for processing material, whereas the non-deflected rays I.sub.0 are
blanked out by an intercept arrangement similar to that shown in
FIG. 18. In contrast to the arrangement in FIG. 18, it is shown
here that the mirror 166 acting as intercept arrangement can also
be arranged between the lens 165 and the processing surface. As
described under FIG. 4, however, the intercept arrangement can also
be foregone when a symmetrical or asymmetrical defocusing reduces
the radiation that is contained in I.sub.0 and is unwanted for
processing in terms of its power density to such an extent that no
processing effect is produced when it is directed onto the
processing surface.
[0262] FIG. 36b shows an expanded embodiment of FIG. 36a in a side
view. The lenses 202 and 203 are inserted between the multi-channel
modulator with the channels T.sub.1 through T.sub.n, said lenses
202 and 203 being preferably cylinder lenses and forming a cylinder
optics, as described under FIG. 32 and FIG. 33. This cylinder
optics demagnifies the distance between the channels T.sub.1 and
T.sub.n at the location of the lens 166 and, given a predetermined
focal length of the lens 165, thus, the angle at which the rays of
the individual channels T.sub.1 through T.sub.n impinge the
processing surface, is particularly significant given a great
number of channels and significantly favors the costs for the lens
165, which can also be a system composed of a plurality of lenses,
as well as its makeability.
[0263] FIG. 36c shows a plan view relating to FIG. 36b, from which
it can be seen that the cylinder optics exhibits essentially no
effect in this view. The ray bundles F.sub.1 through F.sub.n
coupled into the acousto-optical modulator 161 are in fact shown
under the same Bragg angle; however, they can also, however, be
coupled in individually differently under the respectively optimum
Bragg angle.
[0264] FIG. 37 emphasizes another advantage of the arrangements
according to FIGS. 36, 36a, 36b and 36c, namely that respectively
two processing points B.sub.11, B.sub.12 through B.sub.41, B.sub.42
can now be generated instead of the processing points B.sub.1
through B.sub.4 by simultaneous application of two different
frequencies to the respective modulator channels. Instead of four
processing tracks, eight separately modulatable processing tracks
224 have now arisen without increasing the number of lasers and/or
the number of modulator channels. It lies within the scope of the
preferred embodiments to also employ more than two frequencies per
modulator. Twelve different frequencies with a single modulator
channel have already been realized for a similar purpose. Another
advantage in the generation of processing points with
acousto-optical deflection is the possible shift of the processing
points at high deflection speed. By modifying the applied
frequencies, individual or all processing tracks 224 can be very
quickly displaced relative to their previous position and there is
thus a further possibility of beneficially influencing the position
and shape of the cups. With this technique, in particular, the
position of the processing tracks can be correspondingly readjusted
to a rated quantity with high precision. Precisions of a fraction
of a track width are thereby possible. The actual position of the
individual processing tracks can be precisely determined with a
known, interferometrically functioning measuring system in that,
for example, the actual position of the laser radiation source is
registered during the processing event and a correction signal for
the required displacement and readjustment of the processing tracks
is generated by comparison to the rated position of the processing
tracks. This can be of interest particularly when a seamless joint
is to be made to a processing pattern that already exists or when a
pattern that already exists is to be post-processed. Another
enormous advantage of the arrangement is that the Bragg angle can
be individually set for optimizing the efficiency for each
modulator channel, which, however, is not shown in the Figures. Up
to now, acousto-optical arrangements wherein a plurality of
sub-beams are generated from a laser beam by applying a plurality
of frequencies wherein all of these have a shared Bragg angle for
all sub-beams, has not yet made a breakthrough in processing of
materials because the efficiency is too low. When, however, a
combination of a number of laser beams having respectively
individually set Bragg angle and a number of acousto-optically
generated sub-beams per laser beam is selected as proposed, then a
clearly higher efficiency can be achieved, so that a great
plurality of simultaneously acting processing tracks can be
realized for processing material.
[0265] As described under FIGS. 18 and 18a, however, single-channel
or multi-channel electro-optical modulators can also be utilized in
conjunction with a birefringent material in order to split each
laser beam into two beams that can be separately modulated via
further electro-optical or acousto-optical modulators.
[0266] It has been emphasized that the processing of the material
in FIGS. 36, 36a, 36b, 36c and 37 should occur with the deflected
laser beams and that the radiation contained the non-deflected ray
laser beam is to be neutralized, so that no processing effect is
produced. This, however, is not absolutely necessary, and instances
are conceivable wherein one works conversely. A further advantage
of the arrangement shall therefore be cited and explained with
reference to FIG. 36a wherein one wishes to employ the radiation
contained in the laser beams lo for processing material, the mirror
166 is removed. The entire radiant power from all four lasers
F.sub.1 through F.sub.4 thus derives on the generated line in a
spot. More than four times the power density thus derives in the
spot compared to the previous processing points B.sub.1 through
B.sub.4, and it can be assumed that no processing effect arises in
B.sub.1 through B.sub.4 given specific materials and process
parameters. Ie., the processing surface simultaneously serves as a
sump for the radiation that is not intended to produce any
processing effect. This is advantageous since a thermal equilibrium
occurs on the processing surface since the entire laser energy is
supplied to the processing surface in every case. It lies within
the scope of the preferred embodiments that fewer or more than four
lasers with corresponding modulator channels are utilized and that
the difference in the power density between the radiation that is
intended to produce a processing effect and the radiation that
should not produce any processing effect is increased per
modulation channel by employing more than one frequency per
modulator channel. It also lies within the framework of the
preferred embodiments that the described principle can be
advantageously applied when the laser beam incident into the
acousto-optical modulator has high divergence, as is the case, for
example, when the acousto-optical modulator in an arrangement
according to FIG. 31 is to be arranged in the proximity of the
focal point 201 or in arrangements wherein the laser has an
especially great divergence. In FIG. 31, for example, the axis of
the beam bundle emerging from the laser F.sub.2 is intended to
represent the position of the optimum Bragg angle for a specific
frequency. In this case, the Bragg condition is met far more poorly
for the one frequency for the rays at the edge of the ray bundle,
for example of the lasers F.sub.1 and F.sub.3, than for the central
rays of, for example, the laser F.sub.2, and only a slight part of
the radiation is deflected, which means low contrast for the
modulator. When, however, a plurality of frequencies are
simultaneously applied to the acousto-optical modulator and when
these frequencies are selected such that they are optimum both for
the outer as well as for the middle incident beam bundle with
respect to the Bragg angle, the highest possible contrast derives
and the highest possible difference in the power density arises on
the processing surface between the radiation that is intended to
produce a processing effect and the radiation that should not
produce any processing effect.
[0267] FIG. 38 shows how a smart arrangement of the components in
the optical beam path can see to it that the laser beam bundles
never perpendicularly impinge the optical surfaces. This prevents a
part of the radiation from being reflected from these surfaces back
into the lasers. When energy proceeds back into a laser, an
excitation occurs in the laser and the laser begins to oscillate in
terms of the amplitude of the radiation that is output. The output
power is thus no longer constant and patterns are formed in the
process surface that can make the result unuseable. FIG. 38 shows
the axial rays of two planes; the lasers, however, can also be
arranged in one or more planes as long as the symmetry axis for the
two axes that are shown is not used. For reasons of function, the
acousto-optical modulator is already turned by the angle
.alpha..sub.B. In order, however, to be certain that energy is not
reflected back into the laser as a consequence of the changing
ultrasound field, the modulator can be additionally turned by the
angle .gamma., as shown in FIG. 38. Another possibility for
avoiding oscillations of the laser is the insertion of one or more
optical components at suitable locations in the beam path that only
allow laser radiation to transmit in one direction. For example,
what are referred to as Faraday isolators can be employed for this
purpose, as described under FIG. 20 in the catalog of Spindler and
Hoyer on page F2. Such isolators are not shown in the Figures.
[0268] FIG. 39 shows a lens 101 whose mount contains bores 87 that
preferably surround the lens in a plurality of turns and have a
coolant flowing through them. Given high-power arrangements, the
absorption of the optical medium of the lenses cannot be left out
of consideration. Moreover, a slight part of the radiation is
dispersed by every optical surface even given the best
anti-reflection coated and is absorbed by the mount parts. A
cooling of the lens mounts is therefore meaningful. It has already
been mentioned that materials having high thermal conductivity and
low absorption such as, for example, sapphire are advantageous for
the most stressed lenses. Sapphire also has the advantage that the
lens surface does not scratch when cleaning due to the greater
hardness of the material. One should also see to a good contacting
of the optical medium with the mount. This is advantageously
achieved by a metallization of the edge zone of the optical element
and by a soldering 223 to the mount. Metallic solders contain a
better heat conduction than glass solders.
[0269] It is also possible to cool the critical component parts of
the laser gun 23 and of the pump source 2 with the assistance of
what are referred to as micro-channel coolers, as described in the
article "Lasers in Material Processing" in the publication SPIE
Proceedings, Vol. 3097, 1997.
[0270] FIG. 39a shows a section through a mount 118 for the
objective lens 61, 103, 112 that, for example, is secured with a
thread to the tube body 95, 96 or to the mount 116 and is sealed
with a seal 125. The objective lens can be glued into the mount or,
preferably can be metallized at its edge and soldered into the
mount. The mount can be provided with one or more bores 120 through
which a protective atmosphere that comes from the interior of the
optical unit 8 flows and, for example using a channel 119, is
conducted via the side of the objective lens 61, 103, 112 pointing
toward the processing surface in order to prevent a contamination
of the objective lens by particles of material or by gases that are
released during the processing.
[0271] FIG. 40 describes a further possibility for preparing fiber
lasers or optical fibers, preferably single-mode fibers, for an
arrangement in tracks and planes with small spacing. The fiber 28
or laser fiber 5 is ground on all sides at the last end to such an
extent that a side length arises that is reduced to such an extent
that the exit points of the laser radiation 13 lie at a required,
slight spacing. In this case, the terminators 26, 94 can be
omitted, and an especially simple structure derives. The surfaces
that reside opposite can thereby proceed in pairs parallel to one
another or at an angle, or one pair proceeds parallel and the other
pair proceeds at an angle relative to one another, as was already
described for the terminators under FIGS. 9 and 10.
[0272] FIG. 40a shows a plan view onto, or a cross-section through
the ground laser fiber. The cross-section can preferably be
rectangular or quadratic; however, it can also have all other
shapes.
[0273] FIG. 40b shows a side view of the fiber bundle wherein the
fibers were processed similar to FIG. 40, so that the axes of the
individual beam bundles 13 proceed nearly parallel.
[0274] FIG. 40c represents a side view of the fiber bundle wherein
the fibers were processed wedge-shaped, so that the axes of the
individual ray bundles 13 intersect outside the fiber bundle.
[0275] FIG. 40d again shows a side view of the fiber bundle wherein
the axes of the individual fibers in fact proceed parallel but the
exit faces of the individual fibers are arranged at different
angles .epsilon. relative to the fiber axis, so that the axes of
the individual ray bundles 13 intersect within the fiber
bundle.
[0276] FIG. 41 shows how a receptacle with four tracks can be
produced from ground fibers or laser fibers according to FIG. 40
and FIG. 40a, FIG. 40b, FIG. 40c, 40d. A receptacle in a plurality
of planes is shown in broken lines in FIG. 41 in the form of two
further planes. The receptacle is also not limited to four tracks
and three planes; the laser outputs can be arranged in an arbitrary
number of tracks and planes according to this principle. On the
basis of a corresponding shaping when grinding the fibers, it is
possible to determine the spacings between the exit points of the
laser radiation 13. For example, the spacing can be implemented
such that the laser radiation of the individual plans overlaps on
the processing surface 81 such that only tracks derive or such that
the individual tracks overlap so that only planes derive. The
spacings between the exit points of the laser radiation 13,
however, can also be selected such that the laser rays of all
tracks and all planes overlap in a point on the processing surface.
For this purpose, the fiber lasers or optical fibers can also be
arranged in a bundle.
[0277] The principle of the described arrangement of laser outputs
in a plurality of planes or in a plurality of tracks or in a
plurality of tracks and in a plurality of planes or overlapping in
a point also applies to the laser rays incident on the processing
surface 81. A plurality of tracks or a plurality of levels or a
plurality of tracks and a plurality of levels of laser beams can
likewise be arranged on the processing surface according to this
ordering principle or the laser beams can be arranged overlapping
in a point.
[0278] The arrangement according to FIGS. 40, 40a, 40b, 40c, 40d
and 41 is particularly suited for directly modulatable lasers.
However, external modulators can also be employed. The emerging
beam bundles can be imaged into the processing surface with the
known arrangements; however, a receptacle can also be implemented,
whereby the beam bundles are directly directed onto the processing
surface, i.e. without transmission unit, in that, for example, the
outputs of a laser radiation source according to FIG. 41 are
brought extremely close to the processing surface or lie on the
surface of the material in sliding fashion, this yielding an
especially simple arrangement. Such a method can be employed, for
example, when changes in the surface of the material are to be
excited by energy irradiation or when a material transfer is to be
undertaken. In the example of a material transfer, a thin film is
placed onto the material to be provided with images that, for
example, can be a printing cylinder, an offset plate, an
intermediate carrier or the material to be printed itself, a layer
being applied to the underside of said thin film that faces to the
material to be provided with images and that is stripped by energy
irradiation and can be transferred onto the material to be provided
with images.
[0279] FIG. 42 shows another embodiment of the laser radiation
source that can be employed for multi-channel cutting and incising
of, for example, semiconductor materials and as disclosed in German
Patent Application P 198 40 936.2 of the assignee "Anordnung zum
mehrkanaligen Schneiden und Ritzen von Materialien mittels
Laserstrahlen" running parallel with and filed simultaneously with
the present patent application. The terminators 26, 94 of the
fibers or, respectively, fiber lasers F.sub.a through F.sub.n have
ray bundles 144 that are focused with the lens 133 at a
predetermined distance from the terminator. The diameter of the
processing points B.sub.a through B.sub.n amounts, for example, to
20 .mu.m; however, it can also lie thereabove or therebelow.
Further, the terminators are arranged on a profiled rail 256
described in greater detail in FIGS. 42 and 42b such that their
mutual spacing "A" can be set to arbitrary values until the
terminators meet one another. The profile rail is preferably
secured to an arm of a robot (FIG. 42c) and can, for example, be
moved in the directions x, y, z relative to ta table 225 with
actuating drives that are shown in FIG. 42c: Moreover, the profiled
rail can be turned relative to the table by an angle .phi. having
the axis z=(FIG. 42c), which can also be utilized for determining
the mutual spacing of the processing tracks. In the exemplary
embodiments according to FIGS. 4, 4b, 4c, 43, 44, the laser gun is
turned around the axis of the tube 51, 95, 113 in order to vary the
spacings between the processing tracks. Further, the table can be
moved in the directions x, y, z and can be turned by an angle .phi.
with the axis z. The material to be processed, for example one or
more, what are referred to as "wafers" separated from a drawn
semiconductor ingot, can be secured on the table 225 with clamp or
suction devices (not shown). For example, fine, parallel tracks as
needed, for example, for contacting photo-voltaic cells, can be
incised into the semiconductor material with the laser energy in
the individual processing points B.sub.1 through B.sub.n. However,
fine bores can also be introduced into the semiconductor material
or it can be cut with the laser in order, for example, to thus
separate electrical circuits from one another. An arrangement for
removing the material 249 (FIG. 42c) eroded from the processing
surface is attached close to the processing surface 81 for each
processing track 224 separately or for a plurality of processing
tracks 224 in common, the functioning of said arrangement being
described in detail in FIG. 34. When the profiled rail with the
terminators is turned relative to the table in order to modify the
spacing between the processing tracks, it is expedient to
compensate the distortion of the pattern to be registered that
arises due to the relative rotation by a pre-distortion of the
pattern to be applied and/or to compensate it with a time control
of the data stream. On the basis of the turning, it is also
possible to intentionally provide different line spacings given
relative motions in x-direction and in y-direction. For contacting
of the photo-voltaic cells, for example, two different line
patterns are required: a first pattern wherein the incised lines
following the metallization produce the contact to the
semiconductor material should have spacings of a few millimeters
between the individual lines and should, for example, proceed in
the x-direction. Further, what are referred to as bus bars are
required that proceed at a right angle relative to the contact
lines and connect these to one another. These lines forming the bus
bars should, for example, proceed in the y-direction and lie close
to one another so that they act like a closed band following the
metallization. Such a pattern can be very simply manufactured in
that the profiled rail with the terminators is turned to such an
extent until the desired pattern results. Due to the parallel
arrangement of a plurality of fiber laser outputs, the time
required for the processing can be considerably shortened; for
example, ten laser outputs can be employed in parallel for the
incising of the photo-voltaic elements 10, this increasing the
output by the factor of 10.
[0280] The described arrangement for cutting and incising is not
only suitable for processing semiconductor materials but can be
employed for all materials wherein the precise production of
patterns is important such as, for example, in manufacturing
printing forms.
[0281] FIG. 42a and the corresponding sectional view of FIG. 42b
show how the terminators 26 of the individual fiber lasers F.sub.a
through F.sub.n are secured. The profiled rail 256 is secured to a
carrier 260 with connections 261, the carrier potentially being,
for example, the arm of a robot. The terminators 26 are accepted in
mounts 257 and fixed with screw 259. The mounts 257 are provided
with a profile mating with the profiled rail 256, are placed in a
row onto the profiled rail 256, are set at predetermined intervals
"A" from one another and are fixed with the screws 259. Due to an
inventively small structure of the terminators 26 and of the mounts
257, a very slight spacing "A" is possible. The profiled rail with
the terminators can be conducted across the processing surface with
the robot for the purpose of processing the material, as shown in
FIG. 42 and described in detail. The required movements for
producing the processing tracks can be executed by the table 225
described in FIG. 42 that can also be carried out by the arm of the
robot. Preferably, the arm of the robot can also undertake a
rotatory motion around the rotational axis z=of the arrangement
that is approximately parallel to the axis of the terminators. With
this rotation and a relative displacement between the arm of the
robot and the table 225, it is possible to modify the spacing of
the processing tracks generated on the processing surface 81 and to
preferably set them smaller than corresponds to the dimension "A"
that has been set.
[0282] FIG. 42c indicates an example of the robot that can be
constructed, for example, of components of Montech-Deutschland
GmbH, Postfach 1949, 79509 Lorrach. A horizontal-linear unit 263 is
secured on a stand system "Quickset" 262, the unit 263 in turn
accepting a vertical-linear unit 264 having a rotatory drive 265.
The actual robot arm 260 is seated at the rotatory drive, the
profiled rail 256 being secured to the arm 260 with the connection
261. Another horizontal-linear unit is possible but not shown.
[0283] The various motion directions of the table 225 can be
realized with the same element, whereby the motion directions can
also be partly allocated to the table and partly to the profiled
rail. The housing for the acceptance of individual components, the
cooling system, the control for the lasers, the pump sources for
the fiber lasers, and the terminators 26, 94 are shown, the
arrangement for removing the material eroded from the processing
surface and the machine control for the drives are not shown in the
Figures.
[0284] FIG. 43 shows a further flatbed arrangement with the laser
radiation source. The material to be processed with the processing
surface 81 is located on a table 247 that is seated on guides 251
and can be moved in the feed direction u precisely with a spindle
252. The spindle 252 is placed into rotation by a motor 254 via a
gearing 253 that is driven proceeding from a control electronics
255. The laser radiation emerging from the laser gun 23 generates
the processing points B.sub.1 through B.sub.n in an intermediate
image plane 228 (not shown here) that, for example, is shown in
FIG. 44. The laser radiation is conducted via deflection mirror 241
and an optics 242 belonging to an optical unit onto a rotating
mirror 243 that, for example, can have one mirror face that,
however, can also be designed as a rotating mirror having a
plurality of mirror faces and that is placed into a rotatory motion
by a motor 244 driven proceeding from the control electronics 255.
The rotating mirror 243 steers the laser radiation over the
processing surface line-by-line in arrow direction v. An optics 245
belonging to the optical device is located between the rotating
mirror and the processing surface, the job of the optics 245 being
to generate a sharp processing spot on the processing surface over
the entire line length, this processing spot being potentially
composed of a plurality of processing points B.sub.1' through
B.sub.n=that are shown in FIG. 43. As a result of the rotation of
the rotating mirror, the processing points generate processing
tracks 224 on the processing surface 81 as shown, for example, in
FIGS. 35, 36 and 37. Preferably, a long deflection mirror 246 is
provided between the processing surface 81 and the optics 245 in
order to achieve a compact structure. The laser gun 23 is
preferably turned in the prism 248 such that the processing tracks
have the desired spacing from one another on the processing
surface, this being shown in FIG. 35. The fixing of the laser gun
can occur with a strap retainer (not shown). An arrangement 249 for
removing the material eroded from the processing surface is
attached close to the processing surface 81 over the entire line
length, the arrangement 249 being capable of being provided with a
glass plate 230 over the entire length and being shown in greater
detail in FIG. 43b. In FIG. 43, a laser gun with the lenses 102 and
103 according to FIG. 4b and a beam path illustrated in FIG. 20 can
be provided; however, all other types of laser guns can also be
used. Further, a plurality of laser radiation sources can be
attached in such a flat bed arrangement in order to speed the
processing procedure up. A second laser radiation source with the
corresponding optics and the arrangement 249 for removing the
material eroded from the processing surface can be attached
opposite the illustrated arrangement such that further processing
tracks derive on the processing surface.
[0285] It lies within the framework of the preferred embodiments
that the rotating mirror can also be replaced by an oscillating
mirror. It also lies in the scope of the preferred embodiments that
the rotating mirror can be replaced by two oscillating mirrors,
whereby the oscillatory direction of the one mirror, called "mirror
u", lies on the processing surface 81 in the direction referenced
u, and whereby the oscillating direction of the other mirror called
"mirror v", lies on the processing surface 81 in the direction
referenced v.
[0286] An arrangement having oscillating mirrors is especially
well-suited for fast incising of photo-voltaic cells, as was
described in detail under FIG. 42. The cell to be incised is placed
onto the table 247 with, for example, a loading device that is not
shown in FIG. 43 and is brought into the correct position. The
laser gun 23 is turned such that the desired spacings in the
processing tracks arise in the two processing directions u and v.
In a first processing event, for example, mirror u draws the
contact lines, whereas mirror v undertakes the correct positioning
of the contact line packets. In a second processing event, mirror v
draws the bus bars, whereas mirror u undertakes the correct
positioning of the line packets. In these processing events, the
photo-voltaic cell is not moved. It lies within the scope of the
preferred embodiments that the table 247 can be replaced by a
magazine (not shown) wherein a specific number of photo-voltaic
cells are delivered for processing, that the processing of the
respective cell occurs directly in the magazine, and that the
processed cell is automatically removed from the magazine after the
processing and is transferred into a second magazine, whereby the
next, unprocessed cell for processing moves forward to take the
place of the removed cell.
[0287] As a result of the extremely high beam quality of the laser
radiation source that derives due to the fiber laser working
diffraction-limited, a nearly parallel laser beam bundle can be
generated, as shown in FIG. 43 between the optics 242 and rotating
mirror 243 and as can also be seen in FIG. 4 between the lenses 57
and 61. Consequently, it is also possible to remove the optics 245,
the rotating mirror 243 and the deflection mirror 246 in FIG. 43
and replace them by a deflection mirror (not shown) that deflects
the nearly parallel laser beam bundle emerging from the optics 242
in the direction of the processing surface 81 and onto an objective
lens (not shown) having a short focal length that is implemented
similar to the objective lenses 61, 103 or 112.
[0288] The deflection mirror and the objective lens are inventively
combined with one another to form a unit and slide back and forth
on a guide rail (not shown) in the direction v, so that a number of
parallel processing tracks corresponding to the number of channels
in the laser radiation source are registered on the processing
surface (81) similar to previously with the rotating mirror 243 and
the optics 245.
[0289] The guide rail is implemented as a bearing having very low
friction, for example as an air bearing or as a magnetic bearing.
The drive of the unit composed of the objective lens and the
deflection mirror in the direction v and back respectively occurs
with a thrust into the corresponding direction that, for example,
is carried out by a preferably contact-free electromagnetic system,
whereby the energy acquired from the deceleration of the moving
unit is partially re-employed for the drive. Parts of the guide
rail, deflection mirror and objective lens are, for example,
accommodated in a closed space that contains windows for the entry
and the exit of the laser radiation and can be evacuated in order
to reduce frictional losses. The drive and guide rail represent a
linear drive for the unit composed of the objective lens and the
deflection mirror.
[0290] It lies within the framework of the preferred embodiments
that the respective, true position of the moving unit can be
determined for correction purposes via, for example, an optical
reference track. An arrangement 249 serves for the removal of the
material eroded from the processing surface 81. The advantage of
such an arrangement is that it can be very cost-beneficially
realized for long path lengths and high resolutions, and that it
can be set to various formats by displacement of the one and/or
other drive. A plurality of such units can also be arranged in
parallel in order to increase the processing speed.
[0291] FIG. 43a shows a simplification of the arrangement according
to FIG. 43 in that the two lenses 102 and 103 have been removed
from the laser gun. Given a corresponding spacing of the laser gun
from the deflection mirror 241, the divergent laser ray bundles
emerging from the lens 101 are focused onto the processing surface
81 with the lenses 241 and 245 and generate the processing points
B.sub.1 through B.sub.n that are identical to the processing points
B.sub.1' through B.sub.n=in this case.
[0292] FIG. 43b shows the arrangement 249 for removing the material
eroded from the processing surface in greater detail. The
functioning has been described in detail in FIG. 34.
[0293] FIG. 44 shows a hollow bed arrangement for processing
material with the laser radiation source. Hohlbett arrangements are
known; for example, two arrangements having hollow bed are
described in the publication "Der Laser in der Druckindustrie" by
Werner Hulsbuch, Verlag W. Hulsbusch, Konstanz, pages 461 and 562.
The material to be processed with the processing surface 81 is
located in a cylinder or, preferably, a part of a cylinder 236
having the radius R. This arrangement is referred to as a hollow
bed on whose axis a bearing 229 with a rotating mirror 233 is
arranged. The rotating mirror can, for example, have one mirror
face but can also be designed with a plurality of mirror faces and
can be placed into rotation by a motor 234 and be arranged on a
carriage (not shown) displaceable in the direction of the cylinder
axis relative to the cylinder 236. An optics 231 belonging to an
optical device and a mirror 232 are arranged as well on the
carriage (not shown) in the proximity of the processing surface 81.
Further, a deflection mirror 227 and the laser gun 23 as well as an
arrangement 235--close to the processing surface 81--for removing
the material eroded from the processing surface, which is described
in greater detail in FIG. 34, are located on the carriage. The ray
bundles 226 emerging from the laser gun generate processing points
B.sub.1 through B.sub.n in an intermediate image plane 228 that are
transmitted onto the processing surface 81 with the deflection
mirror 227, the mirror optics 231, 232 and the rotating mirror 233.
Here, they generate the processing points B.sub.1' through
B.sub.n=. The processing points B.sub.1 through B.sub.n=that form
the processing spot generate processing tracks 224 (FIGS. 35, 36
and 37) across the entire line length that are registered sharply
focused over the entire line length as a result of the constant
radius of the hollow bed. The advantage of the illustrated
arrangement is that a compact structure can be achieved. In
particular, the illustrated arrangement enables a small angle
.delta. between the axis of the ray bundle incident onto the
rotating mirror 233 and the ray bundle that is reflected by the
rotating mirror onto the processing surface, which is desirable for
low distortion in the recording geometry on the processing surface.
The laser gun is preferably seated in a prism (not shown) and is
secured with a fastening strap (likewise not shown). The laser gun
can be turned around its axis and can be displaced in the axial
direction. As a result of the rotation, the distance between the
processing tracks can be modified, this being shown in FIG. 35. The
spacing from the processing surface can be modified by the
displacement. An arrangement 235 for removing the material eroded
from the processing surface is attached over the entire line length
close to the processing surface 81, the arrangement 235 being
capable of being designed similar to what is shown in FIG. 43b,
whereby it is implemented in curved fashion corresponding to the
radius R of the cylinder 236 and can be provided with a curved
glass plate 237 (not shown) over the entire length, the functioning
thereof having been described in detail under FIG. 34. In FIG. 44,
a laser gun having the lenses 102 and 103 according to FIG. 4b and
a beam path shown in FIG. 20 are provided. However, all other types
of the inventive laser gun can be utilized. Further, a plurality of
laser radiation sources can also be attached in such a hollow bed
arrangement in order to speed the processing event up. For example,
a second rotating mirror and a second laser radiation source as
well as a second arrangement 235 for removing the material eroded
from the processing surface can be attached opposite the
illustrated arrangement such that further processing tracks derive
on the processing surface.
[0294] FIG. 44a shows a simplification of the arrangement according
to FIG. 44, in that the two lenses 102 and 103 were removed from
the laser gun. Given a corresponding spacing of the laser gun from
the deflection mirror 227, the divergent laser ray beams emerging
from the lens 101 are focused onto the processing surface 81 with
the lens 231 and generate the processing points B.sub.1 through
B.sub.n that are identical to the processing points B.sub.1'
through B.sub.n=in this case.
[0295] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only the preferred embodiments have been
shown and described and that all changes and modifications that
come within the spirit of the invention are desired to be
protected.
* * * * *