Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1085;~07
This invention relates to engraving and more
particularly to the sensing and reproduction of patterns
onto photosensitive surfaces, as in the production of
printing plates.
Heretofore, the essential operations in the pro-
duction of modern engravings have included photography by
which material assembled on the copy board is illumined
by high intensity lamps and converted to a negative. The
negative is then used to expose a photo-~eceptive print-
ing plate, which is either composed of or coated with a
photosensitive material. Examples of such photosensitive
plates have been in the past of many kinds, some adapted
particularly for relief printing, while others are
adapted for intaglio (gravure) printing. The present
invention will find a wide variety of applications and,
as will become apparent, the type of printing plate to be
;~ produced is not limited in the present invention, but may
~; ~ be of any usual type. In recent years, newspapers and
~;~ commercial printing of various types have resorted to
;20 ~ photo-composition and, particularly, in the~utilization
of printing plate materials based on photosensitive
polymeric systems. A typical process consists of the
dir ct imaging of a photopolymer layer carried on a suit-
able substrat- to a negative prepared in the manner pre-
viously discussed, after which the exposed polymer layer
and sobstrate are processed to selectively remove those
portions which have not been exposed to develop the
photo-engraved printing plate. i
~ In certain systems, the negative is contact s
; 30`~ printed to the plate while in others it is imaged by a
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suitable l~ns and camera apparatus. While considerable
forward ~trides have been made in the art of producing
printing plates, it has still been required that such
plates be produced from negatives generated by photo-
graphic process. While quality is high, such negative
using processes require materials such as negatives and ~-
chemicals, expensive camera equipment, and numerous time
consuming and costly operations to accomplish.
While there have been proposals for direct pro-
duction of printing plates using a laser beam or electron
beam for etching the same, the systems proposed have not
been satisfactory due to inherent non-linearities of the
optical system used for the sensing and etching operations,
resulting in low resolution and low production. ~uch sys-
tems have also been unduly sensitive to small vibration
resulting in degradation of image quality.
In general, it is an object of the present inven-
tion to provide a laser read-write system for the produc-
tion of engravings on photosensitive surfaces which will
overcome the above limitations and disadvantages and
which will eliminate the need and use of the photographic
step in the production of printing p]ates.
.
Another object of the invention is to provide a
laser read-write system of the above character which is
capable of reading any information capable of being
assembled at the copy boa~d, whether of printed letters or
pictoral material, and directly translating the same into
identical or corresponding information onto the surface
of a photosensitive plate.
Another object of the invention is to provide a
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laser read-write system of the above character which is
highly accurate, rapid, insensitive to vibration, and
which can produce a linear, exact engraving of a copy
board paste-up.
The foregoing general objects have been achieved
in accordance with the present invention in which the
copy board becomes an integral part of a laser scanning
system consisting of an input laser beam which is focused
down to a suitably small resolving spot upon a copy board.
Means are provided for causing this spot to scan the copy
board in a predetermined pattern, which may, for example,
be 6imilar to a raster-like scan. A sensing system is
provided for receiving light reflected from the copy
board at the position of impingement of the reading laser
beam as it scans across the copy board surface. The out-
put on the means for sensing the reflected light is used
to control a modulator through which a second laser beam
passes. The modulator is designed to control the ampli-
tude or power delivered to the second laser beam. Both
the read laser beam and the write laser beam are caused
to pass through the same deflection optics, but are sub-
sequently separated to impinge on different planes in
space in such a way that the copy board and photosensitive
surface to be exposed are oriented either in a read-right
or read-wrong relation to each other. In general, the
planes or surfaces of the copy board and photosensitive
surface will be either facing each other or facing in a
predetermined direction which will determine whether or
not the resultant exposure is read-right or read-wrong.
In either event, the write beam is passed through the
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108~
same scanning optics as the read beam and its return. Special
routing optics subsequent to the scanning optics are used to
separate the beams so that the read beam is passed to the copy
board and the write beam is passed to the photosensitive :
surface. In this way, the beams are interlocked together and
any irregularity in the movement of the scanning optics equally
affects the read beam and the write beam.
According to a broad aspect of the present invention,
there is provided in a system for forming an image of an object
on a writing surface: means for producing a reading beam and a
writing beam for scanning of the object and the writing surface
respectively, modulator means for varying the intensity of
the writing beam, beam combiner means for directing the reading .
beam and the modulated writing beam generally together along
a common path, beam separator means for directi.ng the reading
and writing beams from the common path respectively toward t~e
object and the writing surface, scannîng means positioned
along the common path for diverting the combined beams across
a predetermined portion of the path to effect synchronous
2Q scanning of the object and the writing surface by the separated
beams, and means responsive to information obtained from the
object aæ it is scanned by the reading beam for conditioning .
the modulator means to vary the intens.ity of the wri.ting
beam to form an image of the object on the wri.ting surface. .
According to another broad aspect of the present ~: .
invention, thexe is provided in a method for scanning an object
and recording information obtained from scanning of the object
on a recording medium, utilizing a laser beam and a scanning
element having at least one reflective facet, the steps of:
3Q providing a first source of coherent radiation for forming a
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read beam, providing a second source of coherent radiation
for forming a write beam, combining the read and write beams
so that they travel along a common path, separating the read
and write beams after they have been com~ined and directing
the separated read and write beams so that the read beam is
directed to the object and the write ~eam is directed to the
recording medium, directing the combined read and write beams
simultaneously onto a facet of the scanning element, moving
the scanning element to cause the read and write beams to
simultaneously scan the object and the recording medium,
detecting information from the object being scanned by the read
beam and modulating the write beam in accordance with said
information to cause information about the scanned object to
be recorded on the recording medium.
The invention will now be described in greater detail
with re~erence to the accompanying dra~ings:
BRIEF DESCRIPTION OF THE DRA~INGS
FIGURE 1 is an isometric drawing with the portions
removed illustrating the laser read-write system for producing
patterns on the photosensitive surfaces as constructed in
accordance w~th t~e present invention.
FIGURE 2 is an optical schematic of the apparatus of
Figure 1.
FIGURE 3 is an isometric drawing of another embodiment
o a laser xead-write system with portions removed constructed
in accordance with the present invention.
FIGURE 4 is an optical schematic of the apparatus of
Figure 3.
Referxing no~-more particularly to Figures 1 and 2,
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the major elements of the laser read-write apparatus of the
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present invention are shown supported as sub-systems in a
suitable framework 20. These sub-systems include copy board
support 22 and photosensitive plate 24, p
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a read optical sub-s~stem 26, a write laser beam sub-
system 28, and a scan optical sub-system 30 providing a
common optical path for receiving and scanning both a
read optical system input and/or output beam 31, and a
write laser beam 32 across respective ones of the copy
board 22 and photosensitive plate 24. Each of these sub-
systems will now be described in detail, after which the
operation of the entire apparatus will be set forth.
Means is provided for supporting a photosensitive
plate at one end of the framework. It can, for example,
consist of any suitable mounting structure, such as a
flat plate 33 having an upwardly facing support surface
indicated at 34, underlying the photosensitive plate. In
~ne application, photosensitive plates can be made of
aluminum and have a photosensitive polymer layer 36
applied to one surface thereof which is polymerized upon
application of radiation of a suitable chromatic range
and intensity.
Means 22 is provided for supporting a copy board
40 in a plane spaced parallel to and located above the
photosensitive plate and can consist of any suitable
support means, as for example, a plate having grooves 42
therein connected through a plurality of channels (not
shown) to a vacuum pump 44 so that application of a paste-
up thereto permits the same to be rigidly and uniformly ~ -
supported when positioned face down over the photosensi-
tive plate. The copy board holder is supported on a
suitable hinge means 46 for permitting the same to be
opened and closed in relation to the apparatus as a whole.
~0 A read optical sub-system 26 consists of a helium-
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neon laser 50, the output of which is taken through a beam
expander 52, a beam routing mirror 54 and reverse beam
splitter 56 to a beam combiner 58 serving as the input to '
the scanning optical sub-system 30. The scanning sub-
system 30 includes a galvanometer mirror 62 or other means
for causing the input beam~ impinging thereon to scan ' -
laterally across the width of the copy board and photo-
sensitive plate. The output of the galvanometer mirror
62 i8 passed through a scanning objective lens 64 which
brings the beams passed therethrough into focus approxi-
mately at the copy board or photosensitive plate,'as will
be described. '~ '
'~ ' The write laser sub-system 28 consists of lasers '~ ' '
~ ' 66, 68 capable of developing high power W beams /o~ 72.
~ .
The output beams of each of the lasers are combined by
causing the respective output to be cross-polarized with
'; respect to the other. The combination is accomplished by
., ~, , .
passing the beams of each polarization through a polariza- '~
~' ~ tion sensitive beam combiner 74 which is transparent from
i, .
one side to radiation of one polarization direction and
S'~ , reflective by virtue of a diagonally positioned inner
surface~75 having a multi-layered dielectric coating
whlch is reflectlve'to light of the cross-polarization as
ln beam 72. In this way, substantially all of the light
from the W lasers is combined with high efficiency~ To
; 'effect the foregoing, the'output of one of the lasers i8 '
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rotated by either physically mounting that laser at 90
to the other or by incorporating'a quarter wave polarizer
not shown) which retards the phase of the light from one
of the lasers by 90, i.e., effectively rotating the
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108S3~7
"
polarization by that amount. The combined energy of the
uv lasers is then passed from the polarization beam com- ~
biner 74 through an optical modulator 76 either of an ~,
electro-optical or acousto-optical type. Examples
include Zenith M70 ~acousto-optical); Datalite DL~ 1- W
- (acousto-optical); Coherent Associates (electro-optical).
Assuming the modulator to be accoustic'al, it is manufac-
tured with coatings optimized for transmission in the ul-
traviolet,,region so as to be selectively transmissive to
light of that frequency depending upon the application of
an eIectrical control signal. A function of the accousti-
cal optical modulator is to pass a light beam through a
sound wave generated in a transparent material, the sound
wave diffracting part or all of the energy in the llV light
beam off at an angle so as not to enter the remainder of
the optical system. This results in the capability of
effectively turning the write beam completely off or com- '
pletely on with respect to the remainder of the s~stem in
response'to an applied electrical signal. When undeflect-
ed, the write'laser beam 32 passes through the remainder
of the optical system by traversing a beam expander which
enlarges the beam to 35 mm. and collimates it after ~hich
the beam is rerouted to the scannin,g optical system 30 by -
turning mirrors 78, 79.
The scanning optical system 30 includes beam
combiner 58, also including a first surface dichroic
mirror, which is transmissive for through transmission of
the helium-neon beam impinging on its back surface, but is
given a dichroic coating highly reflective as to W radi- ~ ,
ation impinging on its first surface. Thus, each of the ~'
beams is redirected in near coincidence from the combiner
58 to the galvanometer mirror 62 and the scanning
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~085307
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objective lens 54. In that connection, the routing mirror
54 of the read optical system in inclined upwardly
slightly so as to direct the helium-neon beam upwardly at
a small angle (~1) with respect to the horiæontal center
line of the system. The dichroic mirror surface of com-
biner 58 is inclined slightly downwardly so as to direct
the W radiation downwardly at a small angle (-1) with
respect to the horizontal center line of the system. In
this way, beams 31, 32 are vertically diverging as they
pass from the scan objective lens toward the copy board
and photosensitive plate, although still lying in a
single vertical plane. The beams diverge from each other
by about 1 to 2 inches and are intercepted by dihedral
mirror prism 80 which is arranged to have an upper sur-
face 82 arranged at an approximately 45 angle to the in-
coming beams so as to deflect the read beam 31 upwardly
to the copy board. The mirror has a lower surface 84 at
a 45 angle, aiming downwardly so as to deflect the write
beam 32 to the photosensitive plate. The dihedral mirror
i8 provided with suitable surface coatings to maximize
these reflections which may, for example, be an aluminum
coating on its upper surface 82 and a multi-layer dielec-
tric coating maximized for W reflection on its lower
surface 84.
It will be noted that any vibration in the galvano-
meter mirror system or in the relationship of the optical
components will result in the combined beams being
shifted upwardly or downwardly together which results in
such movement causing the beams to move out of phase,
i.e., generally upward motion causes the write bea~ 32 to
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108~307
move to the right while the read beam 31 moves to the left.
In order to maintain the beams in synchronism so that they
move in the same direction upon any vibration r an anti-
vibration optic is incorporated and consists of a first
surface xeflecting plane surface, such as an aluminum
mirror mounted by suitable means in the path of the read -
beam so as to cause a reflection thereof on route to the
dihedral mirror. In this way, movement of the beams up-
wardly causes equal translation o~ both beams apart ~rom
each other or towards each other an equal amount as they
impinge the dihedral mirror surfaces and, therefore,
causes any vibration in each beam to be in phase and cause
equal translation at each of said surfaces.
The read optical sub-system 26 also includes
means for retrodirectively viewing a small spot on the
copy board consisting of a read lens 88 positioned to
receive light from beam splitter 56 and focus the same
to a spot on a photo-multiplier 90. The output of the
photo-multiplier is sensed and used to provide an electri-
cal signal for operating modulator 76. In many applica-
tions it will be desirable to position a spatial filter
91 before the photo-multiplier tube so as to define a
very small spot on a copy board which can be viewed at any
particular moment.
Means are provided for moving the scan optical
sub-system and consists of suitable mounting plates 92,
94 carried on a sub-carriage 96 which is supported on
suitable bearings 98, 99, such as ball bushing bearings
running on rods 102, 104 which, for example, have been
manufactured by centerless grinding. Carriage 96
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supports the entire read optical sub-system 26, as well
as the entire scanning optical sub-system for translatory
movement back and forth towards and away from the cop~
board and photosensitive plate. A suitable drive screw
106 is connected to a nut 108 carried on a lower side of ;
the carriage approximately beneath the objective lens.
Screw 106 is rotated by a stepping motor 110 so that after
each scan of the mirror 62 across the field, the stepping
motor is advanced one increment, as will be described. A
10' second motor 112, which is normally disengaged, is pro-
vided for rapid return of the carriage after completion
of each scan sequence.' Motor 112 operates through a uni-
directional coupling 114. The operation of the device
will now be set forth, together with certain additional
details of the system.
In operation, the'copy board 22 is opened and a
paste-up mounted by vacuum directly over and opposité to
the printing plate'36. At the start of the scan sequence,
the moving carriage'is advanced until a point where the
dihedral mirror 80 is directly between the beginning of
the paste-up on the copy board and the beginning of the
printing plate. At this point, the'operator can visually
percei've the'red helium-neon line being scanned across the
start of the paste-up copy. The carriage 96 is driven
forward by motor 110 and screw 106 at ~ rate'corresponding
to one-half of a blur circle diameter per scan. A blur
circle'in the present instrument is approximately 1-3 mils
in diameter and represents the smallest practical resolved
spot achieved with thi's optical system. The galvanometer
mirror 62 scans in both directions during operation. At
the end of each scan, the entire carriage 96 supporting
the read-
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write system and scanning system is advanced. As the
read beam scans across the copy, the small read dot pro-
duced by the read beam will be about two mils in diameter
and cxosses areas which are alternately dark or light. ~
The dark areas may be typing, line art, photographs suit- -
ably half-toned screened, or any conventional subject
matter usual for incorporation in paste-up~ Th~ amount
of light reflected by the copy changes markedly as a func- ~ -
tion of the reflectivity density of the paste-up, the dark
areas reflecting very little, and the light areas reflect
significantly. It will be noted that the impingement of
the read beam upon the copy board is-arranged to be at an
angle so that specular reflection is avoided. In this
way, reflected light can be sensed retrodirectively with- -
out specular reflection by the same optical system which
. .
is transmitting the read beam. The non-specular reflec-
tion is received by the objective lens, reflected off the
s~anning mirror 62, passed through beam combiner 58 and
reflected off beam splitter 56 into the photomultiplier
tube. Lens 88 preceding the tube serves to decollimate ;
the energy and to bring it to a focus at the entrance
slit of the photo-multipler. If desired, spatial filter
91 may be incorporated at the entrance slit of the photo-
multiplier to achieve greater resolution by excluding
stray reflections and unwanted light. Photo-multiplier ~-
tube senses the change in reflected light energy as the
dot scans across the light and dark areas of the paste-
up so that a high and low signal is received. This ~
signal is amplified and compared in a preset threshold 92
so that whenever the threshold is exceeded, the RF
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oscillator signal generator 93 output normally blocked from passing to
modulator 76 by gate 94 will be passed. If the signal is less than the
threshold level, it is then responsive to a dark scanning area and thereby
turns the modulator on so as to deviate the write laser beam. If the signal
to the modulator is inverted, making it in effect responsive to a light
scanning area, the modulator is thereby turned off, exposing those areas on
the print plate corresponding to white areas on the copy and thereby creating
a negative image. As has been set forth in the previous description, as
the read system dot is scanning across the paste-up, the ultraviolet write
laser beam 32 is simultaneously scanned across the printing plate to be
exposed. In general, the beams are coaxial in a vertical plane and separated
from their reflective elements previously described from about 2 to 5 to
permit their spatial separation and separate reflection upwardly and down-
wardly at mirror 80. After being deflected by the scanning galvanometer
mirror, both the beams are focused by the objective lens. This lens is a flat
field lens covering an angle of about 25 and is designed to operate at near
diffraction limit resolution. The objective lens brings each of the beams to
~ a sharp focus at approximately the respective copy board or photosensitive
¦~ plane. Thus, as the read beam crosses each dark area of the paste-up, the
`20 ultraviolet beam is simultaneously exposing a segment of the photosensitive
!~ plate. This exposed area then becomes an area of type which will transfer
j ink to a newspaper page, for example, in normal printing.
In many applications, particularly in the newspaper printing
trade, it is desirable to obtain image demagnification of a slight amount
between the paste-up at the copy board and the plate being prepared. Such
image demagnification is desired in a range of from 0 to 10% in
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` 108530~ ,
width and up to 3% in length and is directly achievable
with the apparatus of the present invention. Width ~ag-
nification is controlled by the throw distance from the
scan objective to the respective plane. If this distance
/~5 ' .
A is shortened between the scan objective~64 and~the plate
surface 34 being preparedj width demagnification will ;
occur. Changes in length magnification are achieved in
accordance with the present invention by providing a
carriage running on ball bushings set on.rails or rods
supported in the framework and upon which the plate to be
prepared rests. This carriage is slowly driven by a screw
and ball nut arrangement similar to that previously des-
; cribed in connection with carriage 96. Obviously, ~he
driving speed of the for~going arrangement is arranged to
be a percentage of the driving speed o~ carriage 96 in
the same proportion as the desired change in magnification.
~n accordance with the present invention, it also
may be desired that the plate be prepared in read-right
relationship rather than read-wrong relationship in
aacordance with the printing practice being utilized.
This is accomplished by incorporating a memory 95 in the
circuit controlling modulator 76 and in the signal path
from the photo-multiplier tube to the threshold, which
memory is required to store the entire information con-
: . . .
tained in a single width scan of the read beam and read
it out in reverse order in the adjacent scan of the write
ç
; beam 32.
Many changes and modifications of the present
invention are to be understood as incorporated within the
~30 ~ general concept thereof, of which mention of a few will
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now be mad~, and after which an example of a substantially
different system will be set forth in detail in conjunc-
tion with an alternative embodiment of the invention incor-
porating many of the alternatives suggested. In the
present system, the horizontal scanner is shown as a
gal~ansmeter mirror which oscillates about a vertical
axis backwardly and forwardly. Such a mirror has inherent
high efficiency since it provides for read and write
function in both direction, and, therefore, its duty cycle
time is quite high. However, such a mirror could be re-
placed by a multi-facet rotating mirror or polygon mirror.
If the resolution requirements are not unduly strict, it
would be possible to substitute the electro-optical
~eflector in the write beam circuit as previously suggest-
ed. Alternatively, an oscillating mirror operated by a
tuning fork system could be utilized.
In the read system, the method of fiensing the
reflected light from the paste-up is variable. In the
just described, retrodirective sensing is utilized.
However, the light reflected from the paste-up could be
sensed by a fiber-optic array positioned across the entire
scan line and above the dihedral mirror. Such a fibex-
optic array could consist of a line of fibers facing the
scan line at the point of focus of the read laser beam.
This line of fibers picks up any reflected light from any
position along the scan line after which the fibers can
be bundled together to collect any light along this line
into a narrow bundle and passed to a detector in a manner
similar to that disclosed herein.
It is also possible to sense the copy by general
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illumination, utilizing the system exactly as shown,
except that in place of a read beam, the paste-up copy
can be generally illuminated by a non-actinic lamp system,
a pin hole being used as a spatial filter at the photo- -
multiplier tube entrance slit to determine the resolution
of the read system. This, in a sense, amounts to estab-
lishing a passive read beam which is scanned by the optics~
However, it will be found that by using a read laser as -
disclosed hereinbefore, the retroairective system becomes
relatively immune to ambient light and by utiliæing a
e/~ o~c
spatial filter, it is possible to climlinAt~ almost all
stray light from the read system. The advantage of a
fiber-optic sensing system is that a higher signal to
noise ratio is obtained, but at the sacrifice of greater
sensitivity to ambient light. In a passive system using
a lamp generally illumined system, the optical alignment
of the device is non-critical, but it is more difficult
to obtain a good signal to noise ratio.
In the present system, it is noted that the output
~0 as developed on the printing plate is the opposite from
the input and, therefore, is termed as a read-wrong -
system. Should a read-right system be desired, there are
several possibilities. One, is that a small memory can
be incorporated in the circuit so that an inversion can
be obtained by scanning a line ahead, remembering the
line in a suitable memory bank, and reading it out in
reverse order. Where the scanning mirror system operates
in both directions as shown, each line need only be read
out in the subsequent scan. The geometry of the system
just disclosed has each read and write surface arranged
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opposed to cach othcr. An alternative arrangement could
be provided in which the planes to be scanned both in
read and write are arranged side by side or in tandem. A
system designed with many of the alternative m~asures just
discussed will now be described.
Referring now to Figures 3 and 4, there is shown
an alternative embodiment of the present invention which
generally is supported within a suitable framework 120.
In the following description, like parts will be given
like numbers to those of Figures 1 and 2 eIevated by one
hundred to facilitate identification with respect to the
previous embodiment. Thus, sub-systems include copy
board 122 and photosensitive plate 124, a read optical
sub-system 126, a write laser beam sub-system 128 and a
scan sub-system 130 providing a common optical path for
receiving and scanning both the read optical system out-
put beam 131 and a write-laser-beam 132 across respective
ones of the copy board 122 and plate 124. The read opti-
cal system includes a helium-neon read laser 150, for
example, which is imaged to a turning mirror 154 through
a beam combiner 15~ transmissive thereto. The output of
a write laser 166 is taken through an intensity modulator
17~, a turning mirror 171 and is reflected off a dichroic
first surface of the beam combiner 158. Each of the beams
is coincident and need not contain any vertical divergence.
The beams are passed thence via a set of spherical mirrors
, ~ which serve as a beam expander. After being
reflected from an additional turning mirror 200, the
~ beams are coincident and collimated to an appropriate
diameter. They are then scanned and reflected off of
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successive mirror surfaces of a cylindrical drum 162
carrying a plurality of plane mirror surfaces 162a, 162b
thereon arranged in a polygonal fashion and through an
objective lens. The objective lens 164 brings ~he beams
to focus at the surfaces of the respective plates as here-
inbefore described.
A sub-frame 196 is provided for carrying copy
board 122 and the plate 124 in generally in-line relation
to each other with respect to the beams 131, 132. A first
dichroic beam splitter 184 serves as a W scanning mirror -
by reflecting the ultraviolet energy of the write laser
beam 132 downwardly toward the surface of the plate 1~4,
- while permitting the read beam 131 to pass to a second
scanning mirror 182 which redirects it downwardly to ;
impinge upon the paste-up at the copy board. The optical '-
distances from the scanning polygon to the respective
plate or copy board are arranged to be approximately the
same in order to maintain unity image magnification. The
non-specular reflected output from the paste-up is
received by a fiber-optic array 188 which is positioned
at an angle and aimed toward the line of scan immediately
below the scanning mirror. The fiber-optic array is -~
arranged in a linear fasion as a line-to-point converter
so that all possible r~flective elements of the paste-up
scan are being seen simultaneously. The array is then
regrouped into a small spot serving as the input to photo-
multiplier tube 190 which in turn controls the intensity
permitted to be passed by modulator 176.
:: ~
The paste-up and copy board are mounted in sub-
frame 196 carried on ball bushing-198 set on rods 202 and
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1085307
driven by screw 208 motor rotated so that the scanning
proceeds as increments as heretobefore described.
Since the read and write beams are both directed
in the same direction, the resultant pattern reproduced
on the photosensitive plate will be in read-write relation
to the paste-up and, therefore, the resultant engraving
is directly usable for offset printing. Additionally,
since the beams are deflected by the scanning optics in
the same direction, there will be no necessity fox anti-
vibration optics.
While there has been disclosed herein a copy board
supported paste-up which it is desired to reproduce, it is;
desirable to point out that the same apparatus-and proce-
ure can be used for positional informational encoding,
such as required in facsimilie transmissions~ In such an
apparatus, the paste-up becomes a grid or other position
~; indicating network which when passed by the read beam
generates output pulses which are counted in an up-down
counter to generate a binary memher-corresponding to the
position of the read beam. Since the read beam is
optically interlocked to the write beam, this member pro-
vides the accurate positional data required for high-
quality data transmission.
;:: : ' . .: ,.
~:: . .
~ 30
~: . ... ..
19
'~ '
' ' ' , ' ' ' ' ' ' .: ' : ' : '' ' .. ' ' . ' ' . . ' ' . ' '
