CA1085307A - Laser read-write system for the production of engravings - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Engraving apparatus with particular reference to a plate to be engraved having a photosensitive surface in which a write laser beam exposes ? surface by scanning the same in conjunction with a read optical path asso-ciated with a copy board positioned proximate the plate.
Means, for example, such a read laser beam scans the copy board, the reflection therefrom being noted and used to control the intensity of the write beam. The optical scanning elements of both the read optical path and the write beam are common to each so that positional error due to vibrations in the optical components is eliminated.
Provision is made for read-right conversion to read-wrong during preparation of a plate, both by use of memory circuits and by geometrical arrangement. Independent width and length magnification, other than unity, are also provided.

Description

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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`- 1085307 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.
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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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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 ~ ~ -5-~. .~

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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, , .. .. .
the major elements of the laser read-write apparatus of the C ~ -5a-.
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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 ~5h-s3a7 ~
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--6- ` ;
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-~- 1085307 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.
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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 ' :` . '. . . ~.
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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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 -8- - ' * ~"~(e~q4~

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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 .. . , ~ ~ ~ , ' ' 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 -10- ` ,, - .. .
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~ lV~3~3~7 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 :

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 : - - . : .: . .

~ - 1085307 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 ''.' . ~ ' -17- ~ ;

' lOB530 7 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.
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The paste-up and copy board are mounted in sub-frame 196 carried on ball bushing-198 set on rods 202 and ,, . ~ . . .

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.

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Claims (59)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. 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 sur-face 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 directing the reading and writing beams from the common path respectively toward the object and the writing surface, scanning means pos-itioned along the common path for diverting the combined beams across a predetermined portion of the path to effect synchron-ous scanning of the object and the writing surface by the sep-arated beams, and means responsive to information obtained from the object as it is scanned by the reading beam for condition-ing the modulator means to vary the intensity of the writing beam to form an image of the object on the writing surface.

2. The system of Claim 1 wherein the means for producing the reading and writing beams comprises a first laser for generating a non-actinic laser beam for scanning the object and a second laser for generating an actinic laser beam for scanning the writing surface.

3. The system of Claim 1 together with means for holding the writing surface and the object in spaced apart generally parallel positions with the common path extending between the same.

4. The system of Claim 1 wherein the reading and writing beams contain energy of first and second wavelengths, respectively, energy of the first wavelength being directed toward the object and energy of the second wavelength being directed toward the writing surface.

5. The system of Claim 1 wherein the beam combiner means provides a small divergence of the beams along the com-mon path and the beam separator includes a deflector positioned between the diverging beams with first and second surfaces for reflecting the respective beams toward the object and the writ-ing surface.

6. The system of Claim S further including a re-flector for reflecting one of the diverging beams back toward the other before the beams impinge upon the surfaces of the reflector.

7. The system of Claim 1 including mounting means permitting positional adjustment of the writing surface rela-tive to the object, such adjustment determining the relative sizes of the images and the object.

8. The system of Claim 1 wherein the scanning means is mounted in a stationary position and the object and the writing surface are mounted on a carriage movable along an axis generally perpendicular to the paths of the scanning beams to effect scanning of the object and the writing sur-face along successive lines.

9. The system of Claim 1 wherein the scanning means comprises an oscillating galvanometer mirror disposed in the common path.

10. The system of Claim 1 including a fiber-optic array positioned adjacent to the object for receiving light energy therefrom.

11. The system of Claim 1 wherein the means re-sponsive to information from the object includes a memory for storing data corresponding to said information.

12. In a read/write system for scanning an object and recording information about the object on a recording medium: a first source of coherent radiation for forming a write beam, a second source of coherent radiation for form-ing a read beam, modulator means for modulating the write beam, means for combining the read and write beams so that they travel along a common path, means for separating the read and write beams after they have traveled in the common path and for directing the read beam to the object to be scanned and the write beam to the recording medium, scanning means having at least one reflective facet for simultaneously receiving said read and write beams at least periodically on said one facet, means for causing movement of said scanning means for causing said read and write beams to simultaneously scan the object and the recording medium, and means responsive to the information being obtained from the object while it is being scanned by the read beam for controlling the modulator means so that the write beam records on the recording medium information obtained from the scanning of the object by the read beam.

13. A system as in Claim 12 wherein first and sec-ond sources are two separate lasers having different output frequencies.

14. A system as in Claim 12 wherein said scanning means is a mirror and wherein said means for causing movement of said scanning means includes means for causing oscillations of said mirror.

15. A system as in Claim 12 wherein said scanning means is in the form of a multi-faceted polygon and wherein said means for causing movement of said scanning means con-sists of means for causing rotation of said multi-faceted polygon.

16. A system as in Claim 12 wherein said means for separating the read and write beams includes means for causing at least one of said read and write beams to be di-verted by a small angle with respect to the other beam, and a dihedral member disposed between the diverged read and write beams and having first and second surfaces inclined at an angle with respect to each other to direct the read and write beams respectively to the object to be scanned and the recording medium.

17. A system as in Claim 16, including means for supporting the object and the means for supporting the re-cording medium lie in substantially parallel superimposed planes, and means for causing movement of the means for sup-porting the object to be scanned and the means for supporting the recording medium with respect to the dihedral member.

18. A system as in Claim 17 wherein said means for supporting the object to be scanned remains stationary.

19. A system as in Claim 12 together with flat field lens means along the common path for focusing the com-bined beams onto the object being scanned and onto the re-cording medium.

20. A system as in Claim 17 together with rela-tively movable means for supporting the object and the means for supporting the recording medium.

21. 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: providing a first source of coherent radiation for forming a read beam, providing a second source of coherent radiation fox 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 combined and directing the separated read and write beams so that the read beam is directed to the object and the write beam 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.

22. A method as in Claim 21 wherein the read and write beams are separated after being combined by spatially separating the same by a small angle.

23. In a scanning and recording device for making an image of an object including;
means for simultaneously linearly advancing the object and a photo-sensitive recording surface disposed in parallel spaced apart facing arrange-ment on opposite sides of a rectilinear scan deflector means;
means for providing a first modulatable beam of coherent laser radiation;
means for providing a second beam of focusable radiation;
optical scanning means for receiving said first and second beams and for causing said beams to be directed along narrowly divergent paths to-ward said rectilinear deflector means and then directing said first beam toward said photosensitive surface while simultaneously directing said second beam toward said object in cooperation with said advancing means to form a simultaneous rectilinear scanning raster pattern of said beams across said surface and said object respectively;
said optical scanning means further comprising flat field lens means to simultaneously focus both beams;
photodetector means for receiving radiation from the object and for generating an electrical signal representative of said radiation;
means responsive to said electrical signal for modulating said first beam; and a fiber optic line-to-spot converter having a plurality of internally-reflecting light-transmitting fibers arranged in a linear array adjacent the rectilinear scan deflector means to transmit radiation from the object to the photodetector means.

24. A device according to claim 23 wherein said optical scanning means comprises:
means for combining said first and second beams along narrowly con-verging paths;
said optical scanning comprising mirror means; and means for directing said combined beams toward said mirror means and by reflection from said mirror means toward said flat field lens means.

5. 25. The device of claim 23 wherein:
said photosensitive recording surface comprises a planar substrate at a normal angle and in said rectilinear raster; and means for mounting the object in opposing planar position above said substrate for motion together with said substrate.

26. A device according to claim 23, wherein said first beam comprises actinic laser light having an ultraviolet wavelength and said second beam comprises visible light for reading the object.

27. A device according to claim 26 wherein said optical scanning means comprises:
dichroic means for reflecting one of said beams while transmitting the other of said beams to separate said combined first and second beams.

8. 28. The device of claim 23, said optical scanning means comprising:

a regular polygonal mirror structure having a plurality of equally spaced mirrors and means for rotating said polygonal mirror structure at a constant rate.

29. The device of claim 28 including means for reflecting said first and second beams simultaneously from a single mirror facet.

30. The device of claim 23 wherein the flat field lens means has a non-uniform focal length and includes:
means for focusing scanned beams as a uniform spot in said recti-linear raster on said photosensitive surface and on said object.

31. The device of claim 30 further comprising means for correlating said optical scanning means and said advancing means.

2. 32. A system for imaging an object comprising:
means for producing a first bright narrow beam of radiant energy;
first deviating means for causing said radiant energy beam to scan the object in a rectilinear raster pattern;
fiber optic means for receiving radiant energy from said object and for transmitting said energy;
signal producing means adapted to receive said transmitted energy and to produce a signal proportional thereto;
means for producing a second beam of laser radiation;
modulating means responsive to said signal producing means for causing the intensity of said laser beam to vary substantially as a function of said received radiant energy;
and second deviating means for causing said laser beam to scan a photosensitive medium in a raster pattern similar to that caused by said first deviating means;
said first and said second deviating means comprising at least one common major component to effect synchronous operation;
whereby an accurate image of said object is created on said photo-sensitive medium.

33. A method for optically scanning an object which comprises: generat-ing a collimated beam of scanning energy;

directing the beam to an optical deviating means for scanning the beam across the object;
focussing the beam from the optical deviating means to form a straight line scan side-to-side across the object;

providing relative linear motion between the object and the optical deviating means to form a rectilinear raster pattern;
receiving light from the object adjacent the scan line and trans-mitting said received light by multiple internal reflection to a signal means responsive to said light;
generating an electrical signal representative of said received light from the object;
generating a recording beam of energy and optically deviating said beam using said optical deviating means;
focusing the recording beam to form a rectilinear scan line across a photosensitive recording medium;
providing a rectilinear raster pattern of the recording beam in coordination with the object pattern;
modulating the recording beam as a function of the electrical signal to record a facsimile of the object in the photosensitive medium;
wherein the steps of directing and deviating said scanning and recording beams includes the use of at least one common reflective element of said optical deviating means; and wherein the steps of focusing said beams include the use of at least one common lens means.

34. The method of claim 33 further comprising the step of: providing a fiber optic line-to-spot converter for transmitting said light received from the object to said signal means.

35. The method of claim 33 wherein the recording medium consists essen-tially of a photoresist coating on a substrate.

36. The method of claim 33 further comprising the step of modulating the recording beam by driving an acousto-optic modulator in response to the electrical signal.

37. The method of claim 33 which further comprises the step of recording a relief pattern in a photocurable polymer recording medium wherein the record-ing beam includes ultra violet radiation.

38. The method of claim 33 further comprising the step of: directing the beams toward a common scanning mirror surface and thence through a flat field lens to provide autosynchronous scanning of said scanning energy beam and said recording beam.

39. The method of claim 38 including the steps of:
disposing the object and recording medium in spaced apart facing planar relationship;
directing the scanning energy beam and recording beam from the scanning mirror and flat field lens at narrowly diverging angles toward a dihedral mirror between the object and recording medium;
directing the scanning energy beam at a substantially perpendicular angle from the dihedral mirror toward the object;
directing the recording beam at a substantially perpendicular angle from the dihedral mirror in a direction essentially opposite to the scanning energy beam toward the recording medium; and moving the object, the recording medium, and the optical deviating means together parallel to the optical axis through the flat field lens to form a rectilinear raster pattern.

40. The method of claim 39 wherein the photosensitive recording medium consists essentially of an ablative medium comprising a thin uniform metal coating on a transparent substrate.

41. A laser recording system including a source of coherent radiation comprising an acousto-optic modulator disposed in a laser cavity, said modulator deflecting said coherent radiation in response to an electrical signal;
means for directing an expanded and modulated coherent recording beam from said source of coherent radiation together with an interrogating beam;
multi-faceted polygon mirror scanning means adapted to scan said interrogating beam and said recording beam simultaneously;
means for focusing the scanned interrogating beam in a linear spot sweep position along an object plane perpendicular to an optical axis through said polygon mirror;
means for focusing the scanned recording beam in a linear spot sweep position along an image plane perpendicular to said optical axis and parallel to said object plane;
means for detecting interrogating beam radiation directly adjacent the linear sweep position of the object plane and generating an electrical signal representative of said detected radiation; and optical means for feeding back said electrical signal to operate said modulator.

42. An optical scanning and recording system comprising:
an object to be recorded and a photosensitive image recording medium;
a first source for a modulatable beam of coherent radiation;
a second source for a second beam of radiation;
means for combining said first and second beams of radiation;
optical scanning means disposed to receive said combined first and second beams of radiation to provide autosynchronous deflection of said first and second beams of radiation;
means for directing said first beam towards a photosensitive medium;
means for directing said second beam toward the object to be recorded;
means for creating relative linear motion along the scanning means axis between the object and the photosensitive medium) and the optical scan-ning means;
flat field lens means disposed to receive radiation from said optical scanning means and to focus said first and second beams of radiation to form diffraction-limited spots along scan lines corresponding to object and image planes;
means for separating said first and second beams of scanned and focused radiation and means to direct said first and second beams of scanned and focused radiation along separate paths, whereby said first beam of radia-tion scans the image plane and said second beam scans the object plane;
internal reflection means disposed to receive radiation from the object; photodetector means for generating an electrical signal which varies substantially in proportion to the intensity of radiation received from said internal reflection means; and electrical processing means responsive to the electrical signal for generating an electrical signal for modulating said first beam intensity, whereby data representative of the imagery content of said object is recorded.

43. A recording system comprising a flat object plane and a flat record-ing plane, a first beam to interrogate said object plane, a second beam to record an image of the object plane in the recording plane, means to simultaneously scan said first and second beams across their respective planes, said scanning means including mirror means which simultaneously reflects said first and second beams, flat field lens means to simultaneously focus said beams onto their respective flat planes;
means to modulate said recording beam, and fiber optic feedback means adapted to detect a spot on said object-plane struck by said interrogation beam and to modulate said recording beam in its striking the corresponding spot in said recording plane, whereby a spot by spot accurate image of said object is created in said recording plane.

44. The combination of claim 43, wherein said mirror means comprises a rotating polygon mirror, and wherein said first and second beams are simul-taneously reflected from a single facet of said rotating polygon mirror to thereby generate a line of spots in said scan.

45. The combination of claim 43, wherein said interrogating beams com-prises visible light and said recording beam comprises laser light.

46. The combination of claim 43 and a carriage, means to mount said planes in spaced apart parallel relation to each other, means to move said carriage along a line parallel to and between said planes, said scanning means comprising raster scanning means at least partially mounted on said carriage and formed by said linear carriage motion means together with said mirror means which sweeps both said beams in a plane parallel to said object and recording planes, said scanning means comprising means to direct said beams onto said mirror means along narrowly convergent angles and thence off said mirror means along narrowly divergent angles, and deflection means on said carriage adapted to separate and reflect said beams onto their respective planes.

47. The combination of claim 43, said fiber optic feedback means com-prising a line-to-spot converter bundle, means to mount the line array end of said bundle in closely spaced relation to the portion of said optic plant being struck by said interrogating beam in said object plane is detected by a relatively large number of the fibers in said bundle.

48. A method of making an image of a flat object plane in a flat record-ing plane comprising the steps of generating an interrogating beam and a recording beam, simultaneously focusing both said beams with a single flat field lens means before directing said beams onto their respective planes, simultaneously scanning both said beams over their respective planes, detect-ing each spot in said object plane-struck by said interrogating beam with a plurality of fibers in the line end of a fiber optic line to spot converter, directing the detected light from the spot end of said converter into integrat-ing and signal producing means, and modulating said recording beam when it strikes each corresponding spot in said recording plane with said signal produced by the corresponding spot in said object plane.

49. The method of claim 48, wherein said scanning step is a raster scan formed by relative motion of said beams with respect to said planes together with simultaneous sweeping motion of both said beams reflected from a single mirror.

50. A method of making an image of a flat object plane in a flat record-ing plane comprising the steps of generating an interrogating beam and a recording beam, simultaneously focusing both said beams with a single flat field lens means before directing said beams onto their respective planes, scanning both said beams over their respective planes, detecting each spot in said object plane struck by said interrogating beam with a plurality of fibers in the line end of a fiber optic line to spot converter, directing the detected light from the spot end of said converter into integrating and signal producing means, and modulating said recording beam when it strikes each corresponding spot in said object plane.

51. The method of claim 50, wherein said scanning step is an auto-synchronous raster scan of both said beams over their respective planes formed by relative motion of said beams with respect to said planes together with simultaneous sweeping motion of both said beams reflected from a single mirror.

52. A method which comprises the steps of: generating a beam of scanning energy and a beam of recording energy;
directing the beams to an optical deviating means for scanning the beams together;
focusing the beams from the optical deviating means;
separating the beams;
directing the scanning beam to an object plane and the recording beam to a photosensitive recording medium plane;
providing relative motion between said planes and the optical deviating means to form rectilinear raster pattern;
received light from the object plane adjacent the scan line;
transmitting said received light by multiple internal reflection to a signal means responsive to said light;
generating an electrical signal representative of said received light from the object; and modulating the recording beam using said electrical signal to record a facsimile of the object in the photosensitive medium.

53. The method of claim 52 further comprising the step of providing a fiber optic line-to-spot converter for transmitting said light received from the object to said signal means.

54. The method of claim 52 further comprising the step of modulating the recording beam by driving an acousto-optic modulator in response to the electrical signal.

55. The method of claim 52 wherein said medium comprises a photocurable polymer recording medium, and wherein the recording beam includes ultra violet radiation.

56. The method of claim 52, further comprising the step of directing the beams toward a common scanning mirror surface and thence through a flat field lens to provide autosynchronous scanning of said scanning energy beam and said recording beam.

7. 57. The method of claim 56 including the steps of:
disposing the object and recording planes in spaced apart facing relationship;
directing the scanning energy beam and recording beam from the scanning mirror and flat field lens at narrowly diverging angles toward a dihedral mirror between the object and recording medium;
directing the scanning energy beam at a substantially perpendicular angle from the dihedral mirror toward the object;
directing the recording beam at a substantially perpendicular angle from the dihedral mirror in a direction essentially opposite to the scanning energy beam toward the recording medium; and moving the object, the recording medium, and the optical deviating means together parallel to the optical axis through the flat field lens to form a rectilinear raster pattern.

58. The method of claim 57 wherein the photosensitive recording medium consists essentially of an ablative medium comprising a thin uniform metal coating on a transparent substrate.

59. The method of claim 57 wherein the photosensitive recording medium consists essentially of photoresist coating on a substrate.