U.S. patent application number 09/843950 was filed with the patent office on 2001-09-20 for gas laser oscillator.
Invention is credited to Eguchi, Satoshi, Hayashikawa, Hiroyuki, Yamashita, Takayuki.
Application Number | 20010022798 09/843950 |
Document ID | / |
Family ID | 27328268 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010022798 |
Kind Code |
A1 |
Hayashikawa, Hiroyuki ; et
al. |
September 20, 2001 |
Gas laser oscillator
Abstract
A gas laser oscillator having at least three discharge tubes
disposed along the optical axis, and a spacer having an opening
centered on the optical axis. The spacer is disposed between a
partially reflective mirror and the closest discharge tube.
Further, the discharge tubes are disposed in series along the
optical axis, and satisfy the following three formulas
simultaneously: r1/r2>1.0 Formula 1 L2/(L1+L2)<0.85 Formula 2
r3/r2<1.4 Formula 3 where the sum of lengths of a pair of
discharge tubes disposed at both ends in optical axis direction is
L1, the inside diameter of these discharge tubes is r1, the sum of
lengths of the other discharge tubes in the optical axis direction
is L2, the inside diameter of these discharge tubes is r2, and the
inside diameter of the opening of the spacer is r3.
Inventors: |
Hayashikawa, Hiroyuki;
(Toyonaka-shi, JP) ; Eguchi, Satoshi;
(Takatsuki-shi, JP) ; Yamashita, Takayuki;
(Toyonaka-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
27328268 |
Appl. No.: |
09/843950 |
Filed: |
April 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09843950 |
Apr 30, 2001 |
|
|
|
09120886 |
Jul 23, 1998 |
|
|
|
6249535 |
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Current U.S.
Class: |
372/55 ;
372/62 |
Current CPC
Class: |
H01S 3/097 20130101;
H01S 3/073 20130101; H01S 3/041 20130101 |
Class at
Publication: |
372/55 ;
372/62 |
International
Class: |
H01S 003/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 1997 |
JP |
9-203669 |
Aug 5, 1997 |
JP |
9-210669 |
Aug 5, 1997 |
JP |
P-210672 |
Claims
1. A gas laser oscillator comprising: (a) discharge tubes disposed
along the optical axis of laser beam for forming a discharge space
inside, (b) a fully reflective mirror disposed toward one opening
of said discharge space for composing a terminal mirror, (c) a
partially reflective mirror disposed toward other opening of said
discharge space for composing an output mirror, (d) a switching
power source for composing a high voltage power source for
generating discharge inside said discharge tubes, (e) a step-up
transformer for composing a high voltage power source for
generating discharge inside said discharge tubes, this step-up
transformer including the following: (1) a step-up transformer main
body, (2) a transformer container for storing insulating oil inside
for immersing said step-up transformer main body in the inside
insulating oil, and (3) an oil cap having a penetration hole and
also including a filter having resistance to passing of insulating
oil in the penetration hole, being fitted to said transformer
container; and (f) a rectifying and smoothing circuit for composing
a high voltage power source for generating discharge inside said
discharge tubes.
2. A gas laser oscillator of claim 1, wherein the oil cap disposed
in the transformer container is provided with a penetration hole in
the vertical direction.
3. A gas laser oscillator of claim 1, wherein the oil cap disposed
in the transformer container is provided with a penetration hole
having one end opened to the lower end of the oil cap, and other
end opened to the outer circumference of the upper part of the oil
cap.
4. A gas laser oscillator of claim 1, wherein the oil cap disposed
in the transformer container is provided with a penetration hole
having one end opened to the upper end of the oil cap, and other
end opened to the outer circumference of the lower part of the oil
cap.
5. A gas laser oscillator of claim 1, wherein the diameter of pores
of the filter fitted to the oil cap disposed in the transformer
container is 0.55 mm or less.
Description
[0001] This is a divisional application of Ser. No. 09/120,886,
filed Jul. 23, 1998.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a gas laser oscillator
having an optical axis that is matched with the axial direction of
the discharge tube, and more particularly to a gas laser oscillator
capable of obtaining a laser beam of high quality.
[0003] FIG. 4 is a schematic block diagram of a conventional gas
laser oscillator. In FIG. 4, reference numeral 1 is a discharge
tube made of glass or other dielectric material, and the inside of
the discharge tube 1 is filled with laser gas, or laser gas is
circulated by a gas circulating apparatus not shown in the drawing.
Reference numerals 2 and 3 are electrodes disposed at both ends of
the discharge tube 1, reference numeral 4 is a high voltage power
source connected to the electrode 2 and electrode 3, and reference
numeral 5 is a discharge space inside the discharge tube 1 lying
between the electrode 2 and electrode 3. Reference numeral 6 is a
fully reflective mirror disposed toward one opening of the
discharge space 5, and reference numeral 7 is a partially
reflective mirror disposed toward the other opening of the
discharge space 5, and the fully reflective mirror 6 and partially
reflective mirror 7 form an optical resonator. Reference numeral 8
is a laser beam emitted from the partially reflective mirror 7.
[0004] In the conventional gas laser oscillator, the operation is
described below. Discharge occurs in the discharge space 5 between
the electrode 2 and electrode 3 connected to the high voltage power
source 4. By this discharge, the laser gas in the discharge space 5
is excited by the discharge energy. The excited laser gas is set in
a state of resonance by the optical resonator formed by the fully
reflective mirror 6 and partially reflective mirror 7, and being
optically amplified by this resonance, the laser beam 8 is issued
from the partially reflective mirror 7. This laser beam 8 is used
in various applications of laser processing.
[0005] FIG. 5(a) and FIG. 5(b) are diagrams for explaining the
operation of the optical resonator in the gas laser oscillator,
showing more specifically the structure of the gas laser
oscillator. In FIG. 4, only one discharge tube is shown, but
generally, as shown in FIG. 5(a) and FIG. 5(b), plural discharge
tubes 1 are disposed in series along the optical axis. Although
mere cylindrical forms are expressed in FIG. 5(a) and FIG. 5(b),
same as the discharge tube 1 in FIG. 4, an electrode 2 and an
electrode 3 are disposed at both ends of each discharge tube 1, and
a high voltage power source 4 is connected between each pair of
electrodes, that is, electrode 2 and electrode 3, and a discharge
space is formed inside of each discharge tube 1.
[0006] In the gas laser oscillator shown in FIG. 5(a) and FIG.
5(b), when discharge occurs in the discharge space 5, a standing
wave 10 is formed. The property of this standing wave 10 is
determined by the size of the resonance space 9 and the curvature
of the fully reflective mirror 6 and partially reflective mirror 7.
This property of standing wave is known as TEM (transverse
electromagnetic) mode order. Generally the lower the TEM mode
order, the better is the laser beam converging, and it is known
that higher processing performance is obtained. For example, the
smaller the inside diameter of the discharge tube 1, the narrower
is the resonance space, and therefore oscillation of high-order TEM
mode is suppressed, the TEM mode order becomes lower and light
converging is enhanced, so that a laser beam of high processing
performance is obtained.
[0007] On the other hand, in the gas laser oscillator having thus
explained construction, of the electric energy supplied from the
high voltage power source 4, all energy excluding the portion
converted into the laser beam 8 becomes heat. Therefore, to
maintain the parallelism between the fully reflective mirror 6 and
partially reflective mirror 7 by preventing deformation due to this
generated heat, it is necessary to cool the fully reflective mirror
6 and partially reflective mirror 7 and the peripheral parts
supporting them.
[0008] Concerning cooling of the fully reflective mirror 6 and
partially reflective mirror 7 and their peripheral parts in the
conventional gas laser oscillator, as disclosed in Japanese
Laid-open Patent No. 56-90588, the construction being shown in FIG.
8. As shown in FIG. 8, the fully reflective mirror 6 and partially
reflective mirror 7 for resonance are respectively held by a flange
31 and a flange 32. By coupling these flanges 31 and 32 through a
support element 33, the parallelism of the fully reflective mirror
6 and partially reflective mirror 7 necessary for laser oscillation
is maintained. A passage 35 is provided inside the support element
33, and it is intended to cool by passing oil or other cooling
medium in this passage 35. In the conventional gas laser
oscillator, the passage 35 of the cooling medium inside the support
element 33 was straight from the inlet to the outlet of the cooling
medium.
[0009] The high voltage power source 4 is, as shown in FIG. 15,
composed of a switching power source 44, a step-up transformer 45,
and a rectifying and smoothing circuit 46. Generally, the gas laser
oscillator is composed of plural discharge tubes, and each
discharge tube requires the step-up transformer 45 and rectifying
and smoothing circuit 46. In one switching power source 44, the
primary side of plural step-up transformers 45 can be connected,
and therefore only one switching power source 44 is enough for
plural discharge tubes.
[0010] The step-up transformer 45 is composed of a step-up
transformer main body 49 and a transformer container 47 as shown in
FIG. 16, and the transformer container 47 is filled with insulating
oil 48, and the step-up transformer main body 49 composed of coil
and core is immersed in the insulating oil 48. A top plate 50 is
disposed in the upper part of the transformer container 47, and an
oil feed port 51 provided in the top plate 50 is sealed with an oil
cap 52 except when feeding oil, so that the entire step-up
transformer 44 is in a sealed structure.
[0011] The conventional gas laser oscillator thus constructed had
several problems.
[0012] First, to lower the TEM mode order, in the discharge tube 1
shown in FIG. 5(a), when the inside diameter of the discharge tube
1 is reduced as shown in FIG. 5(b), scattered beam 8a is likely to
occur in the resonance space 9, and scattered beam 8a mixes into
the laser output. FIG. 6 shows an output mode in a conventional gas
laser oscillator. The axis of abscissas in FIG. 6 denotes the
distance toward outside from the center of the output laser beam,
and position 0 indicates the center. The axis of ordinates
represents the energy density of the laser beam. FIG. 6 shows that
scattered beam 8a is present in the peripheral region A of the
laser beam 8. Laser cutting by using such a laser beam causes an
increase in the thermal effects around the cut section due to the
scattered beam 8a included in the peripheral region, and lowers the
cutting quality. As explained above, when attempting to improve the
light converging and enhance the processing performance by lowering
the TEM mode order, the scattered beam mixes into the output laser
beam to increase the thermal effect range, which leads to a first
problem of deterioration of processing quality.
[0013] As mentioned herein, in the gas laser oscillator, of the
electric energy supplied from the high voltage power source 4, all
energy except for the portion converted into the laser beam becomes
heat 36. Such heat 36 was dissipated, conducting to the parts
composing the gas laser oscillator, such as flanges 31 and 32
existing around the resonance space 9 or the support element 33 for
coupling them, through the laser gas filling the resonance space 9
as shown in FIG. 9.
[0014] The support element 33 is a member for maintaining the
parallelism between the fully reflective mirror 6 and partially
reflective mirror 7, and when uniformity of temperature
distribution in the support element 33 is lost due to the
conducting heat 36, the support element 33 is thermally deformed,
and accurate parallelism between the fully reflective mirror 6 and
partially reflective mirror 7 cannot be maintained. To avoid this
inconvenience, it was designed to cool by passing a cooling medium
in the support element 33. However, in the conventional gas laser
oscillator, the passage 35 of the cooling medium was straight from
the inlet to the outlet of the cooling medium inside the support
element 33. Accordingly, heat convection occurs in the cooling
medium inside the passage 35, and temperature distribution of the
cooling medium itself is not uniform. Due to heat convection of the
cooling medium itself, the temperature is higher in the upper part
and the temperature is lower in the lower part of the support
element 33, and the temperature distribution is uneven, and thermal
distortion occurs. This thermal distortion leads to a second
problem of making it difficult to maintain the accurate parallelism
between the fully reflective mirror 6 and partially reflective
mirror 7.
[0015] In the step-up transformer 45 of the conventional high
voltage power source, the step-up transformer main body 49 was
contained in the transformer container 47, and the transformer
container 47 was in a sealed structure. Due to the heat generated
in the step-up transformer main body 49, the temperature of the
insulating oil 48, in which the transformer main body 49 is
immersed, and the air 53 in the transformer container 47 are
raised. When the transformer container 47 is enclosed by the top
plate 50 and oil cap 52, the internal atmospheric pressure in the
transformer container is raised, and a pressure difference occurs
between the inside and outside of the transformer container 47.
This pressure difference causes the insulating oil 48 to leak out
of the transformer container 47.
[0016] To eliminate the pressure difference between the inside and
outside of the transformer container 47, as shown in FIG. 17, a
penetration hole was provided in the oil cap 52. As a result,
occurrence of a pressure difference between the inside and outside
of the transformer container 47 could be prevented, but the
insulating oil 48 splashed up and leaked during transportation.
FIG. 18 and FIG. 19 are modified examples of the penetration hole
provided in the oil cap 22, but it was a third problem that leakage
of the insulating oil 48 could not be prevented completely.
SUMMARY OF THE INVENTION
[0017] The invention is devised to solve these problems, and it is
a first object thereof to offer a gas laser oscillator capable of
obtaining a laser beam of high quality by suppressing occurrence of
scattered beam while lowering the output laser TEM mode order.
[0018] It is a second object of the invention to offer a gas laser
oscillator capable of maintaining parallelism of fully reflective
mirror and partially reflective mirror for composing an optical
resonator, and obtaining a stable laser beam, by preventing thermal
deformation of support element and other members due to heat
generated by laser oscillation.
[0019] It is a third object of the invention to offer a gas laser
oscillator capable of preventing occurrence of pressure difference
between inside and outside of the transformer container, and also
preventing the insulating oil in the transformer container from
leaking out during transportation.
[0020] The gas laser oscillator, constructed in accordance with a
first embodiment of the invention, comprises:
[0021] at least three discharge tubes disposed in series along the
optical axis of laser beam for forming a discharge space
inside,
[0022] a fully reflective mirror disposed toward one opening of the
discharge space for composing a terminal mirror,
[0023] a partially reflective mirror disposed toward other opening
of the discharge space for composing an output mirror, and
[0024] a spacer disposed between the partially reflective mirror
and the closest discharge tube, having an opening in the center of
the optical axis of laser beam,
[0025] in which of the discharge tubes disposed in series along the
optical axis, the sum of lengths of a pair of discharge tubes
disposed at both ends in the optical axis direction supposed to be
L1, the inside diameter of these discharge tubes supposed to be r1,
the sum of lengths of the other discharge tubes in the optical axis
direction supposed to be L2, the inside diameter of these discharge
tubes supposed to be r2, and the inside diameter of the opening of
the spacer supposed to be r3 satisfy the following three formula
simultaneously.
r1/r2>1.0 Formula 1
L2/(L1+L2)<0.85 Formula 2
r3/r2<1.4 Formula 3
[0026] The gas laser oscillator of another embodiment of the
invention comprises:
[0027] discharge tubes disposed along the optical axis of laser
beam for forming a discharge space inside,
[0028] a fully reflective mirror disposed toward one opening of the
discharge space for composing a terminal mirror,
[0029] a partially reflective mirror disposed toward other opening
of the discharge space for composing an output mirror,
[0030] a first flange for holding the fully reflective mirror,
[0031] a second flange for holding the partially reflective mirror,
and
[0032] a support element, being a member for keeping parallelism
between the fully reflective mirror and the partially reflective
mirror by coupling the first flange and the second flange, and
having a spiral medium passage for passing cooling medium disposed
inside thereof.
[0033] In the support element of the gas laser oscillator of claim
2, plural spiral cooling medium passages are provided for passing
cooling medium.
[0034] The gas laser oscillator as set forth in claim 3
comprises:
[0035] discharge tubes disposed along the optical axis of laser
beam for forming a discharge space inside,
[0036] a fully reflective mirror disposed toward one opening of the
discharge space for composing a terminal mirror,
[0037] a partially reflective mirror disposed toward other opening
of the discharge space for composing an output mirror, and
[0038] a high voltage power source including a switching power
source for generating discharge inside the discharge tubes, a
step-up transformer, and a rectifying and smoothing circuit,
[0039] in which the step-up transformer includes:
[0040] a step-up transformer main body,
[0041] a transformer container for storing insulating oil inside
for immersing the step-up transformer main body in the inside
insulating oil, and
[0042] an oil cap having a penetration hole and also including a
filter having resistance to passing of insulating oil in the
penetration hole, being fitted to the transformer container.
[0043] In the gas laser oscillator of the invention, the
penetration hole provided in the oil cap of the transformer
container penetrates the oil cap in the vertical direction, and is
provided with a filter having resistance to passing of insulating
oil at a lower portion in the penetration hole.
[0044] In the gas laser oscillator of the invention, the
penetration hole provided in the oil cap of the transformer
container has one end opened to the lower end of the oil cap, and
other end opened to the outer circumference of the upper part of
the oil cap, and is provided with a filter having resistance to
passing of insulating oil at a lower portion in the penetration
hole.
[0045] In the gas laser oscillator of the invention, the
penetration hole provided in the oil cap of the transformer
container has one end opened to the upper end of the oil cap, and
other end opened to the outer circumference of the lower part of
the oil cap, and is provided with a filter having resistance to
passing of insulating oil at a lower portion in the penetration
hole.
[0046] In the gas laser oscillator of the invention, the pore size
of the filter of the oil cap disposed in the transformer container
is 0.55 mm or less.
[0047] According to the first embodiment of the gas laser
oscillator, of the series of discharge tubes arranged in series,
the resonance space formed in the other discharge tubes other than
a pair of discharge tubes disposed at both ends is relatively
narrowed, the TEM mode order of the laser beam is lowered. Besides,
since scattered beam caused in the discharge tubes disposed at ends
is intercepted by the spacer and is not delivered outside, so that
mixing of scattered beam into the laser beam is prevented. The TEM
mode order of the laser beam is lowered, light converging is
improved, and mixing of scattered beams into the laser beam is
prevented, so that an excellent laser beam high in processing
performance and small in thermal effects in the processing
peripheral area is obtained.
[0048] According to the gas laser oscillator of the second
embodiment, by forming the passage for cooling medium inside the
supporting element spirally, the temperature distribution of the
support element is uniform, and thermal distortion of the support
element can be eliminated. Since the support element is formed by
coupling the flange for holding the fully reflective mirror and the
flange for holding the partially reflective mirror, as the thermal
distortion of the support element is eliminated, it is easier to
maintain the parallelism between the fully reflective mirror and
partially reflective mirror, so that a stable laser beam can be
obtained.
[0049] According to the gas laser oscillator of the second
embodiment, by forming a penetration hole in the oil cap of the
transformer container, and disposing a filter for resisting passing
of insulating oil in this penetration hole, if the insulating oil
splashes due to vibration during transportation, the insulating oil
will never leak out of the transformer container. Besides, since
the oil film formed in the filter provided in the penetration hole
is easily broken by the pressure difference between inside and
outside of the transformer container, the internal pressure of the
transformer container is nearly kept constant, and insulating oil
will not leak out due to the pressure difference between inside and
outside.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 is a sectional view of a gas laser oscillator
constructed in accordance with a first embodiment of the
invention.
[0051] FIGS. 2(a)-(c) are diagrams showing the effects of a
discharge tube and spacer shape on convergence of a laser beam in
the gas laser oscillator in the first embodiment of the
invention.
[0052] FIGS. 3(a)-(b) are diagrams showing effects by the gas laser
oscillator in the first embodiment of the invention.
[0053] FIG. 4 is a sectional view showing a schematic
representation of a conventional gas laser oscillator.
[0054] FIGS. 5(a)-(b) are structural diagrams explaining the
operation of an optical resonator in the conventional gas laser
oscillator.
[0055] FIG. 6 is a diagram showing the output mode of laser beam in
the conventional gas laser oscillator.
[0056] FIGS. 7(a)-(b) are sectional views showing a construction of
a gas laser oscillator constructed in accordance with a second
embodiment of the invention.
[0057] FIG. 8 is a structural diagram explaining the cooling medium
passage of support element in the conventional gas laser
oscillator.
[0058] FIG. 9 is a partial diagram showing conduction and radiation
of heat in a gas laser oscillator.
[0059] FIG. 10 is a sectional view showing a structure of a step-up
transformer of a gas laser oscillator in a third embodiment of the
invention.
[0060] FIG. 11 is a sectional view showing a first embodiment of an
oil cap used in a step-up transformer of a gas laser oscillator of
the invention.
[0061] FIG. 12 is a sectional view showing a second embodiment of
an oil cap used in a step-up transformer of a gas laser oscillator
of the invention.
[0062] FIG. 13 is a sectional view showing a third embodiment of an
oil cap used in a step-up transformer of a gas laser oscillator of
the invention.
[0063] FIG. 14 is a diagram showing the relation of pore size of
the filter of the invention and the leak amount of insulating oil
during transportation.
[0064] FIG. 15 is a block diagram showing a high voltage power
source used in a gas laser oscillator.
[0065] FIG. 16 is a sectional view showing a structure of a step-up
transformer of a conventional gas laser oscillator.
[0066] FIG. 17 is a sectional view of a conventional oil cap having
a straight penetration hole.
[0067] FIG. 18 is a sectional view of a conventional oil cap having
an inverted L-shaped penetration hole.
[0068] FIG. 19 is a sectional view of a conventional oil cap having
a lateral U-shaped penetration hole.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0069] FIG. 1 shows a construction of a first embodiment of a gas
laser oscillator of the present invention. Same members as the
members in FIG. 4 and FIG. 5 are identified with same reference
numerals also in FIG. 1 and their explanations are omitted. FIG. 1
is a sectional view of a gas laser oscillator, and in FIG. 1,
reference numeral 21 is a spacer having an opening having a
specified inside diameter with the center on the optical axis of a
laser beam 8, and reference numerals 22 and 23 are a plurality of
(six in FIG. 1) discharge tubes disposed in series along the
optical axis of the laser beam, and a pair of discharge tubes 22
out of these discharge tubes are disposed at both ends of the
optical axis, that is, at both ends closest to a fully reflective
mirror 6 and a partially reflective mirror 7, while the other
discharge tubes 23 are disposed between the pair of discharge tubes
22.
[0070] In FIG. 1, the discharge tubes 22 and discharge tubes 23 are
shown as mere tubular bodies, but in the individual discharge tubes
22 and discharge tubes 23, same as the discharge tubes 1 shown in
FIG. 4, a pair of electrodes, equivalent to electrode 2 and
electrode 3, are disposed at both ends of each tubular body. A high
voltage power source is connected between each pair of electrodes,
and a discharge space is formed individually in the discharge tubes
22 and discharge tubes 23. However, such arrangement is riot
directly related to the nature of the invention, in FIG. 1, the
discharge tubes 22 and discharge tubes 23 are expressed as mere
tubular bodies.
[0071] Herein, supposing the inside diameter of the pair of
discharge tubes 22 disposed at both ends of the optical axis to be
r1,
[0072] the sum of the lengths of the pair of discharge tubes to be
L1 (=11+12),
[0073] the inside diameter of the other discharge tubes 23 except
for the pair of discharge tubes 22 to be r2,
[0074] the sum of the length of the other discharge tubes 23 except
for the pair of discharge tubes 22 to be L2 (=13+14+15+16), and
[0075] the inside diameter of the opening of the spacer to be
r3,
[0076] the gas laser oscillator of the first embodiment is composed
so as to satisfy the following three formulas simultaneously.
r1/r2>1.0 Formula 1
L2/(L1+L2)<0.85 Formula 2
r3/r2<1.4 Formula 3
[0077] Thus, as long as the shapes of the discharge tubes 22,
discharge tube 23 and spacer 21 simultaneously satisfy the three
formulas (formula 1, formula 2, and formula 3), the inside diameter
r2 of the discharge tubes 23 is smaller than the inside diameter r1
of the discharge tubes 22. As a result, the internal portion of the
discharge tubes 23 in the resonance space 9 is relatively narrower
than the internal portion of the discharge tubes 22, and the TEM
mode order of the laser beam 8 is lowered. On the other hand, the
inside diameter r1 of the discharge tubes 22 disposed at both ends
in the optical axis direction is larger than the inside diameter of
the discharge tubes 23 disposed in the middle, and therefore when
the scattered beam 8a generated in the resonance space 9 inside the
discharge tubes 23 passes through the inside of the discharge tubes
22, it diverges toward the outside of the resonance space due to
diffraction. This scattered beam 8a diverging toward the outside is
intercepted by the spacer 21, and is not delivered outside, thereby
preventing the scattered beam 8a from mixing into the output laser
beam 8.
[0078] FIGS. 2(a), (b) and (c) are diagrams showing the effects of
the inside diameter and length of the discharge tubes 22 and
discharge tubes 23 and inside diameter of the spacer 21 on the
converging performance of laser beam. In these diagrams, as the
parameters for evaluating the converging performance of laser beam,
the width of the heat affected zone by cutting a mild steel plate
by laser beam was used. The width of the heat affected zone was
measured on the basis of the cut-off line.
[0079] FIG. 2(a) shows the relation between r1/r2 change and heat
affected width, supposing L2/(L1+L2) to be 0.5 and r3/r2 to be 1.
As clear from this diagram, when the value of r1/r2 is larger than
1, that is, when the inside diameter r1 of the discharge tubes 22
disposed at both ends in the optical axis direction is larger than
the inside diameter r2 of the discharge tubes 23 disposed in the
middle, the occurrence of scattered beams 8a is suppressed, and the
heat affected width is smaller.
[0080] FIG. 2(b) shows the relation between L2/(L130L2) change and
heat affected width, supposing r1/r2 to be 1.11 and r3/r2 to be 1.
As clear from this diagram, when the value of L2/(L1+L2) exceeds
0.85, the heat affected width increases suddenly, and hence the
value of L2/(L1+L2) should be less than 0.85.
[0081] FIG. 2(c) shows the relation between r3/r2 change and heat
affected width, supposing r1/r2 to be 1.11 and L2/(L1+L2) to be
0.5. As clear from this diagram, when the value of r3/r2 exceeds
1.4, the heat affected width increases suddenly. Hence, the value
of r3/r2 must be set at less than 1.4. It suggests that the
intercepting effect of scattered beam 8a by the spacer 21 is
reduced when the inside diameter r3 of the opening of the spacer 21
is too large compared with the inside diameter r2 of the discharge
tubes 23. In other words, the spacer 21 having an opening of an
appropriate inside diameter is effective for intercepting the
scattered beam 8a.
[0082] FIG. 3 is a diagram that explains the effect of the first
embodiment of the gas laser oscillator of the invention. FIG. 3(a)
shows the output mode of the output laser beam 8 of the gas laser
oscillator according to the first embodiment of the invention. As
is clear from a comparison between FIG. 3(a) and FIG. 6, the laser
beam issued from the gas laser oscillator of the invention is free
from scattered beam in the peripheral region A, and a laser beam of
high quality is obtained.
[0083] FIG. 3(b) compares with heat affected width by cutting of
mild metal plate, between the conventional gas laser oscillator and
gas laser oscillator in the first embodiment of the invention. The
embodiment of the invention and the prior art is compared by
representing the heat affected width on the axis of ordinates. As
is clear from FIG. 3(b), in the gas laser oscillator of the
invention, the heat affected width can be notably decreased as
compared with the conventional gas laser oscillator.
[0084] As explained herein, according to the gas laser oscillator
of the first embodiment of the invention, the TEM mode order of
output laser beam can be lowered, and mixing of scattered beam into
the output laser beam can be prevented, so that an output laser
beam of high converging performance and high quality can be
obtained. Therefore, by using this gas laser oscillator, a high
processing performance is obtained, and laser processing of high
quality is realized.
[0085] FIG. 7(a) shows a structural example of a gas laser
oscillator constructed in accordance with a second embodiment of
the invention. The basic components are same as in the conventional
gas laser oscillator explained in FIG. 4, but the construction is
newly described below including the basic components. In FIG. 7(a),
reference numeral 1 is a discharge tube, 2 and 3 are electrodes, 4
is a high voltage power source for supplying electric power for
discharging between the electrodes 2 and 3, 6 is a fully reflective
mirror, and 7 is a partially reflective mirror, and the fully
reflective mirror 6 and partially reflective mirror 7 are combined
to form an optical resonator. Reference numeral 8 is a laser beam
issued through the partially reflective mirror 7, reference numeral
9 is a resonance space, reference numeral 31 is a flange for
holding the fully reflective mirror 6, reference numeral 32 is a
flange for holding the partially reflective mirror 7, reference
numeral 33 is a support element coupling the flange 31 and flange
32, and reference numeral 34 is a passage for passing cooling
medium disposed inside the support element 33.
[0086] In this embodiment, the passage 34 of cooling medium is
formed spirally inside the support element 33. In such passage 34,
the cooling medium flows spirally inside the support element 33,
and thereby the support element 33 is cooled uniformly without
causing a temperature difference between upper part and lower part
of the support element 33 due to convection of cooling medium.
Therefore, thermal distortion, conventionally induced by
temperature difference in the parts of the support element 33, does
not occur in the present invention. As a result, it is easy to
maintain the parallelism between the fully reflective mirror 6 and
partially reflective mirror 7 held by the flange 32 and flange 33
coupled by the support element 33.
[0087] FIG. 7(b) shows a modified example of the gas laser
oscillator in the second embodiment of the invention. In the
structural example shown in FIG. 7(a), the passage 34 for cooling
medium provided in the support element 33 was one system of spiral
passage, but plural systems may be formed as in a passage 35 shown
in FIG. 7(b). For example, a passage 35a is provided inside the
support element 33, a second passage 35b and a third passage 35c
are disposed on the parts close to the surface of the support
element 33. By forming plural systems of the passage 35 for the
cooling medium, the cooling effect is enhanced and more uniform
cooling is realized. In FIG. 7(b), the inlets and outlets of the
plural systems of passages 35a, 35b, 35c are gathered at one
position each, but the inlets and outlets of plural systems of
passages for cooling medium may be also located independently in
each passage. Therefore, the inlets and outlets of plural systems
of passages for cooling medium are also located independently in
each passage, and the cooling medium flowing direction may be
reverse in each passage, and the temperature distribution of the
support element 33 may be more uniform.
[0088] Alternatively, the support element 33 may be divided into a
plurality of sections, and at least one system of spirally formed
passage for cooling medium may be provided for each divided section
of the support element.
[0089] As explained herein, according to the gas laser oscillator
of the second embodiment of the invention, since the support
element can be cooled uniformly, the temperature distribution is
uniform, the support element is free from thermal distortion, and
it is easy to maintain the parallelism between the fully reflective
mirror and partially reflective mirror for composing the optical
resonator, so that a stable laser beam may be obtained.
[0090] FIG. 10 shows a step-up transformer 45 used in a gas laser
oscillator in a third embodiment of the invention. In FIG. 10, a
transformer container 47 contains an insulating oil 48, and a
step-up transformer main body 49 is fixed in the transformer
container 47 so as to be completely immersed in the insulating oil
48. The transformer container 47 has a top plate 50 so as to keep
airtight at the junction, and an oil cap 52 having a vertical
penetration hole 54 is fitted to the top plate 50 so as to keep
airtight at the junction. A filter 55 having resistance to passing
of the insulating oil 48 is provided in the vertical penetration
hole 54 provided in the oil cap 52. The filter 55 is made of foamed
urethane or a similar material that has resistance to oil.
[0091] Thus, in this step-up transformer 45, the insulating oil 48
splashing up due to vibration during transportation sticks to the
top plate 50, or partly invades into the penetration hole 54 in the
oil cap 52 to be absorbed on the filter 55. On the pores of the
filter 55 absorbing the insulating oil 48, an oil film is formed
due to surface tension of the insulating oil 48 itself. By this oil
film, passing of insulating oil 48 is blocked, and leak of
insulating oil from the transformer container 47 is prevented.
[0092] However, if the pore size is too large, forming of oil film
of insulating oil 48 on the filter 55 is impaired, and the effect
of arresting passing of insulating oil 48 by the oil film is lost.
FIG. 14 is a diagram showing the relation between the pore size of
filter material and leak of insulating oil during transportation.
According to FIG. 14, when the pore size of the filter material
exceeds 0.55 mm, the insulating oil leaks during transportation,
and it is known that, as the material for the filter 55, an oil
resistant and foaming material with pore size of 0.55 mm or less
must be selected.
[0093] On the other hand, due to heat generation of the step-up
transformer main body 49, the atmospheric pressure in the
transformer container 47 is raised, and an atmospheric pressure
difference occurs between the inside and outside of the transformer
container 47. Due to this atmospheric pressure difference between
the inside and outside of the transformer container 47, the oil
film formed in the pores of the filter 55 is broken, and only the
air inside the transformer container 47 is discharged outside, so
that the atmospheric pressure in the transformer container is kept
almost constant.
[0094] The filter 55 is provided only in a lower portion of the
penetration hole 54 of the oil cap 52, and a space is left in the
upper part of the penetration hole 54. This space is provided so
that oil drops may not pop out of the penetration hole if the oil
film is broken and oil drops splash upward. Part of the insulating
oil 48 splashing out as the oil film is torn by the atmospheric
pressure difference sticks to the inner wall of the penetration
hole 54, but moves downward due to gravity, and is absorbed on the
filter 55, and forms an oil film again.
[0095] It is effective whether the shape of the penetration hole 54
is an inverted L-form as shown in FIG. 18 relating to the prior art
or a lateral U-form as shown in FIG. 19, and still more FIG. 12 and
FIG. 13 show the shapes of the penetration hole in consideration of
the effect of recovering the insulating oil 48 sticking to the
inner wall of the penetration hole 54 to the filter 55.
[0096] The penetration hole shown in FIG. 12 is composed of a
vertical portion 54a and a slope 54b. The vertical portion 54a is
opened only beneath the oil cap 52, and does not penetrate upward.
The slope 54b penetrates obliquely upward starting from the upper
end of the vertical portion 54a, and is opened to the outside of
the transformer container. The filter 55 is inserted only in the
vertical portion 54a.
[0097] When the penetration hole is thus formed, since the filter
55 is inserted only in the vertical portion 54a, it is advantageous
that the space from the filter 55 to the outside is kept wide. If
the oil film of the filter 55 is broken, oil drops only splash
around the filter 55, not reaching to outside of the transformer
container 47. Part of oil drops sticking to the inner wall of the
slope 54b moves downward by the gravity, and is absorbed in the
filter 55 in the vertical portion 54a.
[0098] The penetration hole shown in FIG. 13 is formed of a
vertical portion 54a and a slope 54b. The vertical portion 54a is
opened only above the oil cap 52, and does not penetrate downward.
The slope 54b penetrates obliquely downward starting from the lower
end of the vertical portion 54a, and is opened to the inside of the
transformer container. The filter 55 is inserted only into the
slope 54b.
[0099] When the penetration hole is thus formed, since the filter
55 is inserted only in the slope 54b, it is advantageous that the
space from the filter 55 to the outside is kept wide. If the oil
film of the filter 55 is broken, oil drops only splash around the
filter 55, not reaching to outside of the transformer container 47.
Part of oil drops sticking to the inner wall of the vertical
portion 54a moves downward by gravity, and is absorbed in the
filter 55 in the slope 54b.
[0100] In the gas laser oscillator in the third embodiment of the
invention, as described herein, by installing an oil resistant
filter of an appropriate pore size, having resistance to passing of
insulating oil, in the penetration hole of the oil cap, it is
effective to prevent insulating oil from leaking out of the oil cap
due to vibration during transportation. Besides, since the oil film
formed in the filter is broken by a slight atmospheric pressure
difference between the inside and outside of the transformer
container, the atmospheric pressure in the transformer container is
almost kept constant, and therefore leakage of insulating oil due
to the pressure difference between the inside and outside the
transformer container does not occur.
* * * * *