U.S. patent number 3,638,231 [Application Number 04/827,510] was granted by the patent office on 1972-01-25 for device for recording with electron rays.
This patent grant is currently assigned to Nederlands Centrale Organisatie voor Toegepast-Natuurwetenschappelijk. Invention is credited to Alfred B. Bok, Leendert A. Fontijn, Jan B. Le Poole.
United States Patent |
3,638,231 |
Le Poole , et al. |
January 25, 1972 |
DEVICE FOR RECORDING WITH ELECTRON RAYS
Abstract
A device is disclosed for recording image elements, by exposing
recording material, at constant current density with the aid of a
focused electron beam provided with means before the last focusing
device for varying the shape and/or size, in the recording plane,
the cross section of the electron beam in conformity with image
signals.
Inventors: |
Le Poole; Jan B. (Delft,
NL), Fontijn; Leendert A. (Maasdijk, NL),
Bok; Alfred B. (Berkel, NL) |
Assignee: |
Nederlands Centrale Organisatie
voor Toegepast-Natuurwetenschappelijk (The Hague,
NL)
|
Family
ID: |
19803740 |
Appl.
No.: |
04/827,510 |
Filed: |
May 26, 1969 |
Foreign Application Priority Data
|
|
|
|
|
May 27, 1968 [NL] |
|
|
6807439 |
|
Current U.S.
Class: |
347/123;
101/DIG.37; 219/121.12; 219/121.25; 219/121.26; 219/121.34;
358/302; 347/129 |
Current CPC
Class: |
G11C
13/04 (20130101); H01J 37/3002 (20130101); H01J
37/3007 (20130101); H01J 37/302 (20130101); H01J
2237/1514 (20130101); Y10S 101/37 (20130101) |
Current International
Class: |
H01J
37/302 (20060101); H01J 37/30 (20060101); G11C
13/04 (20060101); B23k 015/00 (); G01d 015/04 ();
G11c 013/00 () |
Field of
Search: |
;346/74EB,74ES,74CR
;328/123,124 ;219/121EB ;178/6.7R,6.6B |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Britton; Howard W.
Claims
We claim:
1. A device for binary recording with the aid of an electron beam
comprising an electron source for producing said electron beam, a
recording medium, a means for focusing the central axis of said
beam on said recording medium, electron optical means for shaping
said beam and for exposing said recording medium with said beam,
means for displacing said recording medium and said beam relatively
to each other, and means for varying the cross section of said
electron beam on said recording medium with respect to said central
axis to form an image thereon at substantially constant current
density.
2. A device as claimed in claim 1 further comprising two
electrostatic slit lenses located in succession in the direction of
said beam from said electron source to said recording medium.
3. A device as claimed in claim 1 wherein said electron source
includes a slit diaphragm.
4. A device as claimed in claim 1 further comprising a diaphragm
located in front of said recording medium.
5. A device as claimed in claim 1, wherein said means for varying
the cross section of the beam comprises a biprism located to
intersect said beam and a modulator for controlling said biprism to
deflect said beam.
6. A device as claimed in claim 5, wherein said means for varying
furthermore includes in succession from said electron source to
said recording image a mask located in the image plane of said
means for focusing, a second biprism, and a second focusing
means.
7. A device as claimed in claim 5, wherein said biprism is an
electrostatic prism in the form of a cylindrical condenser with an
inner conductor, and said modulator modulates the voltage
differential across said inner conductor.
8. A device as claimed in claim 1 further comprising two quadrupole
lenses located in succession in the direction of said beam from
said electron source to said recording medium.
9. A device as claimed in claim 8, wherein said quadrupole lenses
are magnetic lenses and further comprising means for rotating and
axially displacing said quadrupole lenses with respect to the
central axis of said beam.
10. A device as claimed in claim 8 further comprising a diaphragm
located in the principal plane of one of said quadrupole
lenses.
11. A device as claimed in claim 1, wherein said means for varying
the cross section of said beam are located between said electron
source and said means for focusing and comprise in succession from
said electron source to said recording medium a first diaphragm, a
deflector, a second focusing means and a second diaphragm in
alignment with said first diaphragm in the image plane of said
second focusing means.
12. A device as claimed in claim 11, wherein the diaphragms are
segments of a circle.
13. A device as claimed in claim 11, wherein the diaphragms are
gauzes.
Description
The invention relates to a device for binary recording with the aid
of an electron beam provided with an electron source for producing
the beam, a means for focusing the beam, electron optical means for
shaping the beam and for exposing the recording material with the
beam at virtually constant current density and means for displacing
the recording material and the beam relatively to each other.
Similar devices are known. On the one hand devices are known for
exposing a photographic emulsion or a photolacquer for making a
mask. On the other hand arrangements are known for exposing a
photographic emulsion or photolacquer for carrying out direct
processes on circuits.
In the case of the device for making a mask, the mask to be made is
a reduced image of a material mask previously placed between the
condenser lens and the intermediate lens. If, therefore, it is
desired to make masks of a different shape, the material mask must
be replaced by a material mask of that shape. In the case of the
device for carrying out processes on circuits, the processes are
guided by a computer control tape. During exposure the beam is
focused on the workpiece and then always has practically the same
shape and cross section. The required pattern is produced by
deflecting the focused beam.
It is the object of the invention to provide a different method of
making a pattern, which has proved to have many additional
advantages.
For this purpose, the invention is characterized by means of
varying the shape and/or size of the cross section of the electron
beam in the recording plane, forming the exposing part in an image
element.
The required pattern is produced by dividing this pattern into
image elements and by making exposures in these elements with the
beam, with a beam cross section varying locally in size and shape,
the beam being controlled for this by a programmed computer or by a
scanned model.
In one embodiment the electron beam cross section is controlled by
a biprism placed between the electron source and the focusing
device, the biprism being an electrostatic prism across which the
voltage differential can be modulated.
Application of this control system results in two point focuses of
the source at each side of the original focus, each having half the
intensity and the distance between them being proportional to the
modulation. By applying two quadrupole lenses in succession in the
direction of the beam, the point focuses are changed into line
focuses. Such a system with line focuses and a diaphragm located
before the recording plane is particularly suitable for use in
binary recording.
In another embodiment the electron beam cross section is controlled
by modulation of a deflecting device located between a diaphragm
and a focusing device with a second diaphragm aligned with the
first diaphragm and located in the image plane of this focusing
device.
The means used in this embodiment are applied instead of and in the
place of the biprism mentioned in the first embodiment.
The invention will be further elucidated by reference to a drawing
with nine figures for these and other embodiments and details.
FIG. 1 shows the path of the beam when imaging with two quadrupole
lenses.
FIG. 2 shows a quadrupole lens diagrammatically.
FIG. 3 shows a circuit for feeding a quadrupole lens.
FIG. 4 shows a biprism.
FIG. 5 is a sketch showing the principle of the path of the beam in
an exposure apparatus with a biprism and quadrupole lenses.
FIG. 6 shows a slightly different beam path diagrammatically in a
single plane and with means added for inverting the exposed
image.
FIG. 7 shows the beam path for an apparatus in which the means
comprise two half diaphragms, a deflector and a focusing
device.
FIGS. 7a and 7b show the operation of the regulated deflecting
system P in FIG. 7.
FIG. 8 shows three embodiments of diaphragms applicable in
apparatus with a beam as in FIG. 7.
FIG. 9 shows an exposure apparatus in perspective.
In the figures, identical numbers and letters relate to identical
elements.
FIG. 1 shows three rays, 1, 2 and 3 of a diverging beam transmitted
by source B and converging at point C.
Rays 1 and 3 and rays 2 and 3 are in planes which are at an angle
of 90.degree..
Lines A.sub.1 and A.sub.2 show diagrammatically the strength of the
quadrupole lenses and the quadrupole lenses themselves, which
provide the image C of source B.
The arrows 4, 5, 6 and 7 in lines A.sub. 1 and A.sub.2 indicate the
direction of focusing and defocusing of the beam.
Arrow 4, for instance, indicates that the beam in the plane of rays
2 and 3 is further diverged by the first lens and arrow 5 indicates
that the beam in the plane of rays 1 and 3 is converged by the
first lens.
The quadrupole lenses A.sub.1 and A.sub.2 therefore focus in one
plane and hence defocus in the plane practically perpendicular
thereto.
Each quadrupole lens A.sub.1 and A.sub.2 consists of four coils 8,
9, 10 and 11, see FIG. 2, designed separately.
The strength of the lens is calculated from the imaging and
enlarging requirements and is determined by the column
dimensions.
The current through a coil 8, 9, 10 and 11 of the lens is
determined with the aid of the formulae:
in which f.sub.x and f.sub.y are the focal lengths in the focusing
and defocusing direction and in which .beta..sup.2 is given as a
parameter of the lens by
in which
ni = the number of ampere windings per coil.
u = the accelerating potential of the electrons in volts.
1 = the length of the coil parallel to the system axis.
r = the distance from the coil to the axis.
The circuit for the coils of a lens is shown in FIG. 3.
In order to correct the first order deflection fault, both north
and south poles are included in a simple balanced circuit. The
location of the two lenses follows from the imaging and enlarging
requirements.
In the embodiment of an exposure installation shown in FIG. 5 a
biprism as shown in FIG. 4 is connected before the quadrupole
lenses A.sub.1 and A.sub.2.
The biprism consists of a hollow cylinder 15 and a tungsten wire
16.
The cylinder 15 is provided with an opening 17 to let through beam
19 and an opening 18 to let through beams 19.sub.1 and
19.sub.2.
Beams 19.sub.1 and 19.sub.2 are obtained by applying a voltage
differential across the biprism.
In this way, two virtual sources arise and, depending upon the
voltage differential, these virtual sources will either overlap or
not.
Owing to a slit diaphragm being applied as a Wehnelt opening in the
electron source of FIG. 5, an elliptical crossover of the source is
obtained.
The ratio between the two main axes is then about 1:3, which is an
improvement on the customary case with a round Wehnelt opening, in
which the ratio may be as high as 2:3.
The line source B so obtained forms, with the aid of the biprism of
which only wire 16 is shown, two virtual line sources B.sub.1 and
B.sub.2 for the quadrupole lenses A.sub.1 and A.sub.2 which image
the sources B.sub.1 and B.sub.2 at C.sub.1 and C.sub.2 on coated
roll 20.
Images C.sub.1 and C.sub.2 consist of line images about 100 microns
long and only a few microns wide.
Owing to the position and the energizing of the two quadrupole
lenses A.sub.1 and A.sub.2, the enlargement can be varied within
wide limits in both main axis directions.
For this purpose the quadripole lenses are rotatable about and
axially movable along a tube.
By regulating the voltage differential across the biprism, the
distance d between images C.sub.1 and C.sub.2 is regulated and
thereby the Kodak Photo Resist or some other exposable material
applied as a thin coating on roll 20 is exposed.
Coated roll 20 rotates at a constant speed under images C.sub.1 and
C.sub.2, moving axially at the rate of 0.14 mm. per rotation.
Because of the 0.14-mm. pitch of coated roll 20 and the track
thereby described on roll 20 of the line images C.sub.1 and
C.sub.2, a 0.15-mm. diaphragm D.sub.2 is applied immediately above
roll 20 to prevent the tracks overlapping.
Owing to the presence of diaphragm D.sub.2, the cross section of
the electron beam in the recording plane is varied owing to
modulation on roll 20 as shown (See exposed tracks E).
To limit the margin of error in imaging due to lens aberrations,
especially owing to spherical aberration, the beam is diaphragmed
through diaphragm D.sub.1.
The exposed coated roll 20 can if desired be gravured by etching,
the unexposed parts being etched after development of the K.P.R.
coating, each image element of a form thus containing for instance
one or more ink cells with different surface areas and/or different
depths.
FIG. 6 shows diagrammatically the path of the beam for a device
with inverted line imaging.
In this device the biprism 16 is located after the first quadrupole
lens A, in order to increase sensitivity. In the absence of
modulation of biprism 16, images C.sub.1 and C.sub.2 coincide on
mask F. There is then no exposure on the coated roll 20.
Upon modulation, images C.sub.1 and C.sub.2 fall partly or entirely
outside mask F.
The second biprism G and the rotational-symmetric lens H combine
these images C.sub.1 and C.sub.2 again to a line image I, whose
length is determined by modulation and with which coated roll 20 is
exposed.
FIG. 7 shows the path of the beam, again in a different
arrangement.
Source B is imaged by the rotational-symmetric lens K in the plane
of the rotational-symmetric lens N.
A diaphragm L, embodiments of which are drawn in FIG. 8, intercepts
part of the beam.
A deflection system M, to which a modulating signal can be
connected is located before lens N.
Behind lens N, there is a diaphragm O.
In the absence of modulation of system M, the image in the plane of
lens N will be imaged unimpeded through diaphragm O on roll 20,
with the aid of the rotational-symmetric lens H.
The continuous lines converging in image element R show the path of
the beam in this situation.
If the system M is modulated, however, part of the beam will be
intercepted by diaphragm O.
The broken lines converging in image element R' show the path of
the beam for this.
Deflection system P is coupled to system M and is applied to ensure
that the centers of gravity of the image elements are aligned on
the cylinder.
FIG. 7a gives an example of this for line image elements in the
absence of deflection system P.
FIG. 7b gives an example of image elements in the form of squares,
in which, with the regulated system P for example, the centers of
gravity are shown on a straight line z.
Upon application in FIG. 7 of a diaphragm L, O of the type shown in
FIG. 8a, image elements R are obtained in the form of a line whose
length varies with modulation.
Upon application of a diaphragm of the type shown in FIG. 8b, these
become squares whose size varies with modulation. And upon
application of a diaphragm of the type shown in FIG. 8c the image
elements form a squared pattern with a constant number of squares
varying in size with modulation.
FIG. 9 shows diagrammatically and in perspective an arrangement
according to the invention with a beam path corresponding to that
of FIG. 6 using slit lenses S and T instead of the quadrupole
lenses A.sub.1 and A.sub.2.
The modulating signal can, of course, be adapted electronically to
the standards required for good reproduction of the halftones in
the resulting print.
This is very important because the signal of the device scanning
the original will not be linear with the quantity of ink which must
be transferred per ink cell from the printing cylinder to the
copy.
With this system, local corrections are of course also
possible.
* * * * *