JPS60104917A - Laser reader and writing unit for carved plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the detection and reproduction of patterns onto photosensitive surfaces, such as in the case of engraving, particularly the production of printing plates.

An essential step in the production of traditional modern engravings involves exposing a photo of the subject on a copyboard to a high-intensity light bulb, converting it into a negative image. This negative image is used to expose a photosensitive printing plate made of or coated with a light-sensitive material. Examples of these photosensitive printing plates are conventionally diverse, some being used specifically for letterpress printing and others for intaglio (gravure) printing.

The applications of the present invention are wide-ranging, and as will be described later, the type of printing plate produced is not limited to the scope of the present invention (any type may be used). In recent years, phototypesetting has come back into use in newspaper and various types of commercial printing, particularly with printing plate materials based on photopolymer systems. A negative image as described above is directly imaged onto a photosensitive polymer layer supported on a transparent substrate, and the exposed polymer layer and substrate are then processed to selectively remove the unexposed areas. Then, a photoengraved printing plate is created.

In some systems, the negative is contact printed onto the plate, and in others it is imaged by a suitable lens and camera arrangement.

Although printing plate manufacturing technology has made great strides, it is still necessary to make printing plates from negative images created by a photographic process. Although these negative-based processes are of good quality, they require materials such as negatives and chemicals, expensive camera equipment, and often [1], and are expensive to perform.

Various methods have been proposed for directly manufacturing printing plates by etching them using laser beams or electron beams, but there are inherent nonlinearities in the optical systems used for detection and etching, and The proposed method was not satisfactory because the resolution was low and the production volume was low. These systems are also overly sensitive to small vibrations, resulting in image degradation.

In general, it is an object of the present invention to overcome the above-mentioned limitations and deficiencies, to eliminate the need for and use of a photographic step in printing plate production, and to provide a laser reading and writing device for producing engravings on photosensitive surfaces. It is to provide.

Another object of the present invention is to be able to read any information that can be assembled on a copyboard, whether printed text or art materials, and to transfer this information onto the surface of a photosensitive plate in the same manner.
That is to say, the object is to provide a laser reading and writing device of the above-mentioned nature which can be converted directly into corresponding information.

Another object of the present invention is to provide a laser reading and writing device of the above-mentioned nature which is extremely positive, rapid, vibration-free and capable of linearly and correctly engraving copyboard paste amplifiers. .

The above general object is achieved by the present invention, according to which the copyboard becomes an integral part of a laser scanning means consisting of an input laser beam focused as a suitably small resolved spot onto the copyboard. There is. Means are provided for scanning this spot in a predetermined pattern, such as raster scanning, =1 p-board. The sensing means is adapted to receive light reflected from the copyboard at locations struck by the input or readout laser beam as it scans across the surface of the copyboard. The output of the means for detecting reflected light controls a modulator through which the second laser beam is passed. The modulator is the second
The amplitude or power supplied to the laser beam is controlled. Both the read laser beam and the second or write laser beam are passed through the same deflection optics, but are then passed through the copyboard and the photoreceptor to be exposed, which are oriented either read-write or read-long with respect to each other. It is separated so that it hits the surface. Generally, the faces or surfaces of the copy baud F and the photosensitive plate face each other, or are oriented in a predetermined direction that determines whether exposure is performed by read-write or by long-lead. In either case, the writing beam is passed through the same scanning optics as the reading beam and its return. Special destination optics are used after the scanning optics to separate the beams so that the read beam is directed toward the copyboard and the write beam is directed toward the hard light surface. In this way, the beams are interlocked and any irregularities in the movement of the scanning optics will affect the reading beam 1 and the writing beam in the same way.

The present invention will be described in detail below with reference to the accompanying drawings.
Other objects and features of the invention will become apparent from this description.

As shown in FIGS. 1 and 2, the main elements of the laser reading/writing apparatus of the present invention are held within a suitable framework 20 as a subsystem.

These subsystems include copyboard holder 22 and photosensitive plate 24, read optics subsystem 26, write laser beam subsystem 28, and read optics input and/or output across copyboard 40 and photosensitive plate 24. It includes a scanning optical subsystem 30 that receives both one beam 31 and a writing laser beam 32 and provides a common optical path for scanning. First, the details of each of these subsystems will be explained, and then the operation of the entire device will be explained.

Means are provided for holding the photosensitive plate 24 to one end of the framework 20. This may be any suitable single-piece structure, such as a flat plate 33 with an upwardly facing retaining surface 34 lying beneath the photosensitive plate 24. In one application, the photosensitive plate 24
is made of aluminum and coated on one surface with a photopolymer layer 36 which polymerizes when exposed to radiation of the appropriate color range and intensity.

Means 22 for holding the copyboard 40 spaced parallel to and above the photosensitive plate 24 is provided, the means 22 including, for example, a plurality of channels (not shown) leading to a vacuum pump 44. It may be any suitable retaining means such as a plate having grooves 42 connected to the grooves. By positioning the paste amplifier on this plate facing downward on three sides of the photosensitive plate 24, the paste-up can be held firmly and evenly. The copyboard holder 22 is optionally mounted on a guard means 46 and is operable to open and close the apparatus as a whole.

The reading optical subsystem 26 includes a helium-neon laser 50, and the output of the laser 5o is connected to a beam expander 52, a beam directing mirror 54, and a back beam splitter 56.
through to a beam combiner 58 which is the input to the scanning optical subsystem 30. The scanning optical subsystem 3° converts the incoming input beam into a copy baud 1”.
40 and a galvanometer mirror 62 or other means for sweeping laterally across 111 of photosensitive plate 24.

The output of galvanometer mirror 62 passes through scanning objective lens 64 . Lens 64 generally focuses the passing beam onto copyboard 4o or photosensitive 4Ji, 24, as described below.

The write laser subsystem 28 includes a laser 66.68 capable of generating a high power tJV beam 70.72. The output beams of each of these lasers are mixed with the output of one orthogonally polarized to the other. This mixing is accomplished by passing the beams of each polarization through a polarization sensitive beam combiner 74. Beam combiner 74 has an inner surface 75 with a multilayer dielectric coating that is transparent for one polarization direction from one side and reflective for orthogonally polarized light such as beam 72. It is reflective because it is positioned diagonally. In this way, U■
Almost all the light from the laser is mixed with high efficiency. This can be done either by physically mounting the output of one laser at 90° relative to the other laser, or by retarding the phase of the light from one laser by 90° (i.e., changing the polarization by this amount). Rotation is effected by incorporating a V4 wavelength polarizer (shown in the figure). L.I.
The combined energy of the V-laser is sent from polarization beam combiner 74 to optical modulator 76 . The modulator 76 may be electro-optical or acoustic-optical, such as Zenith's M70 (acoustic-optical), Datalight's DLMI-UV (acoustic-optical), coherent・Product made by Associates (electrical/optical type) may be used. If the modulator 76 is acoustic, it is coated with a coating that optimizes its transparency in the ultraviolet range so that it selectively transmits light at ultraviolet frequencies depending on the applied electrical control signals. . The function of the acousto-optical modulator 7G is to pass the light beam as an acoustic wave generated in the transparent material, and this acoustic wave diffracts some or all of the energy in the UV light beam to a certain angle and causes the optical system to This is to prevent it from entering other parts. This provides the ability to completely block or completely pass the beam to other parts of the optical system in response to applied electrical signals. If undeflected, the writing laser beam 32 passes through a beam expander 77 that expands and collimates the beam by 35 degrees and is directed by mirrors 78, 79 onto the scanning optics 30.

Scanning optical system 30 includes a beam combiner 58 .

Beam combiner 58 also includes a first surface dichroic mirror that is transparent for the helium-neon beam incident on its back surface, but highly reflective for UV radiation incident on its first surface. A dichroic coating is applied. Therefore, each beam is directed from the compiler 58 to the galvanometer mirror 62 and the scanning objective lens 64 in a substantially coincident state.

To elaborate on this matter, the directing mirror 54 of the reading optical system
is tilted slightly upward to direct the helium-neon beam upward at a small angle (~1°) relative to the horizontal centerline of the device, while the dichroic mirror surface of combiner 58 directs the UV radiation. It is tilted slightly downward so that it points downward at a small angle (~1°) relative to the horizontal centerline of the device. In this way, the beams 31, 32 diverge vertically while remaining in the same vertical plane as they travel from the scanning objective lens 64 towards the copyboard 40 and photosensitive plate 24. The beams are about 2.
It opens 5-5 cm (1-2 inches) to reach the three-sided mirror prism 80. The top surface 82 of the prism 80 is sloped approximately 456 degrees so that the incoming read beam 31 is bent upwardly toward the copyboard 40. Lower surface 8 of prism 80
4 is also inclined at an angle of 45'', so the writing beam 32
is directed toward the photosensitive plate 24. The three-sided mirror prism 80 is provided with a suitable surface coating to maximize these reflections, such as an aluminum coating on the top surface 82 and a multilayer dichroic coating on the bottom surface 84 to maximize UV reflection. is alms.

Vibrations in the galvanometer mirror 62 or associated optical system components cause the combined beams to move upward or downward together, and this movement causes the beams to be out of phase (i.e., generally in a three-way motion). Note that the striking beam 32 moves to the right and the reading beam 31 moves to the left. In order to keep the beam synchronized and move in the same direction even when vibration occurs, an anti-vibration optical system 8 having a first reflecting surface such as an aluminum mirror is used.
7 is mounted by suitable means in the path of the reading beam 31 so that the reflected beam therefrom is directed to the double-sided mirror prism 80. In this way, even if the beam moves upward, the beams that hit the surface of the dihedral mirror move away from each other by the same amount, or approach each other (so that they move in the same translational motion, and therefore the beam vibrations are in phase. , resulting in equal translational motion for each of the aforementioned surfaces.

The reading optics subsystem 26 also includes means for retrogradely viewing a small spot on the copyboard 40.

This means includes a reading lens 88 positioned to receive the light from beam splitter 56 and focus it as a spot on photomultiplier tube 90 at LJ. The output of photomultiplier tube 90 is used to generate an electrical signal that operates modulator 76. In many applications,
It may be desirable to position the spatial filter 91 in front of the photomultiplier 90 so that the spot of the copy holder 40 that is visible at any given time is extremely small.

The means for moving the scanning optical subsystem includes a suitable mounting plate 92. The temporary 92 is mounted on a sub-carriage 96 which is held in suitable bearings 98,99'', such as ball bush bearings running on rods 102,104 made by ground grinding, for example. A copy board 4 is mounted holding a plate or carriage 91, 1 full reading optical reader system 26, and full scanning optical reader system 30.
o and the photosensitive plate 24, and move back and forth in translation so as to approach or move away from the photosensitive plate 24. A suitable drive screw 106 is mounted on the underside of the carriage 92 (approximately below the objective lens 64) and is coupled to a screw nut 108. As will be described below, the screw 106 is driven by 106 is driven by a stepping motor n110 and is advanced by 1 or 11:1.

A second electric motor 112, which is normally uncoupled, operates to rapidly return the unidirectional joint 1 upon completion of each scan sequence.
It operates via 14. The operation of the device is described below along with some other components within the device.

To operate, open the copy boat holder 22 and place the paste amplifier above and facing the printing plate 24.
Mounts directly by vacuum. Start scanning sequence
1, the carriage 92 is advanced to the point where the two-way mirror 80 is located just between the beginning of the base up on the copyboard 40 and the beginning of the printing plate 24. This point can be visually recognized as a red helium neon line scans across the beginning of the paste-up copy. The carriage 92 is driven by the electric M-wheel 110 and the screw 106 at a speed corresponding to half the diameter of the blurred circle for each scan. In this device, the diameter of the +) ellipse is approximately 0.02
5 to 0.076 IIm (1 to 3 mils), representing the smallest spot actually resolved by this optical system. Galvanometer mirror 62 scans in both directions during operation.

At the end of each scan, the 11-yield 92 that holds the read/write subsystem and scanning subsystem
moves forward. Read be l, 3I cross copy “ζ
The diameter of the small reading produced by the beam when scanning is approximately 0.05+1 IN (2 mils);
Move across an area of alternating light and dark. 11,3
The desired area may be typewritten text, line drawings, appropriately halftoned and screened photographs, or conventional material incorporated into a paste-up.

The light foot reflected by the copy varies markedly as a function of the reflectance density of the paste amplifier, with dark areas having very little fouling, whereas bright areas reflect most of it.

Note that the read beam 31 is intended to be incident on the copyboard at an angle that avoids specular reflections. In this way, the reflected light without specular reflection can be detected retrogradely by the same optical system that transmits the reading beam 31. Objective lens 64 for non-specular reflection
, reflected by scanning mirror 62 , passed through beam combiner 58 , and beam splinter 5
6 and enters the photomultiplier tube 90. tube 90
A lens 88, placed in front of the tube 9o, deparallels the energy and focuses it on the entrance slit of the tube 9o. If desired, a spatial filter 91 may be incorporated into the I'' slit of tube 90 to provide high resolution by eliminating stray reflections and unwanted light. Photoelectronic 4H'5 intensifier 90
When the dot scans across the bright and dark areas of the paste amplifier, it detects changes in the reflected light energy and generates a high/low signal. This signal is amplified and compared at the precent threshold 95. The output from high frequency signal generator 93, which is normally blocked when the signal exceeds a threshold, is provided to modulator 76 through gate 94. If the signal is below the threshold level, which means we are scanning a dark area, the modulator 76
acts to deflect the writing laser beam.

As the read optics dot scans across the base up as described above, the ultraviolet writing laser beam 32
simultaneously scan across the printing plate 24 to be exposed. In summary, the beams are coaxial in the vertical plane but spatially separated by about 2 to 5 degrees apart in the aforementioned reflective elements, and can be reflected upwardly and downwardly at the mirror 80. It looks like this. After being deflected by a scanning galvanometer mirror 62, both beams are focused by an objective lens 64. This lens 64 is a flat field lens that converges to an angle of about 25 degrees and is designed to operate near diffraction limited resolution. Objective lens 64 sharply focuses each beam approximately onto copyboard 40 or photosensitive plate 24. In this way, as the reading beam 31 traverses each dark area of the paste amplifier,
Ultraviolet beam 32 simultaneously exposes segments of photosensitive plate 24. This exposed area becomes, for example, an area where ink will be transferred to the new sheet of paper to be printed.

In many applications, particularly in the news printing industry, it is desirable to obtain a somewhat scaled image between the copyboard 40 and the prepared printing plate 24. Such an image reduction is preferably between 0 and 10 in [11] and up to 3% in length, and this can readily be achieved in the apparatus of the invention. +l+ Magnification (reduction) is controlled by the distance from the objective lens 64 to the corresponding surface. By shortening this distance between the objective lens 64 and the plate surface 34, rl is reduced. The length scale can be changed by providing a carriage which runs by means of ball bushing bearings on rails or rods 102, 104 held in the framework 20, on which the plate 11 is placed. achieve. This carriage is slowly driven by a screw and ball nut similar to carriage 92. It goes without saying that this drive speed should be set to the same ratio as the desired scale factor to the drive speed of the carriage 96.

According to the present invention, one may wish to produce plates in a read-write relationship rather than a lead-long relationship, depending on the printing press used. This is accomplished by incorporating memory 97 in the signal path between photomultiplier tube 90 and threshold 95 in the circuit that controls modulator 76. This memory 97 stores all the information contained within a single intermediate scan of the reading beam 31 and must be able to be read out in reverse order during the next scan of the writing beam 32.

It is clear that the invention is susceptible to many modifications within the inventive concept, a few examples of which will be described below, followed by a detailed description of other embodiments with many modifications. In the previous example, the horizontal scanner was a galvanometer mirror that oscillated back and forth about a vertical axis.

This mirror is highly efficient as it provides reading and writing in both directions, so its duty cycle time is extremely high. However, this mirror can be replaced by a polygonal mirror. If resolution is not so much of an issue, it is also possible to use an electro-optic deflector in the writing circuit. Also, using a vibrating mirror operated by a tuning fork, °ζ
Good too.

In the reading system, there are many methods for detecting the reflected light from the base amplifier. In the previous example, a backward detection method was used. However, the light reflected from the paste amplifier can also be detected by an optical fiber array positioned across the pre-scan line and above the three-way mirror. The optical fiber array may consist of lines of fibers facing the scan line at the focus of the reading laser beam. This fiber line picks up reflected light from locations along the scan line. The fibers can then be bundled together and the light along this strand is collected into a narrow bundle and sent to a detector as described above.

Copies can be detected using the same apparatus shown in FIGS. 1 and 2 (with the exception of changing the reading beam) and by general illumination. The paste-up copy is generally illuminated using a non-actinic radiation bulb and a pinball is used as a spatial filter in the photomultiplier entrance slit to determine the resolution of the reading system. In a sense, this is creating a passive reading beam that is scanned by the optics. However, it will be appreciated that the reversing system using a readout laser as described above is relatively immune to ambient light, and that by using a spatial filter almost all stray light can be removed from the readout system. The advantage of fiber optic sensing is that it provides a high signal-to-noise ratio, but at the expense of considerable sensitivity to ambient light.

In passive systems using full-light bulbs, alignment of the device is less delicate (but it is more difficult to obtain a good signal-to-noise ratio).

In the previous example, the output obtained on the printing plate was the opposite of the input, hence the name lead-long method. If a read/write method is desired, several methods can be considered. One method is to incorporate a small memory into the circuit and store the information obtained by scanning a line in this memory and read it out in reverse order. If the scanning mirror operates in both directions as shown, each line need only be read out during the next scan. The geometry of the previous device is arranged such that the reading and writing surfaces face each other. The surfaces scanned during reading and writing may be arranged side by side or vertically. An example of a device that has undergone many changes as described above will be described below.

Another embodiment of the invention shown in FIGS. 3 and 4 is held within a suitable framework 120. For parts similar to those in FIGS. 1 and 2, similar numbers with 100 added are flashed for ease of understanding. That is, the subsystems include a copy board 122 and a photosensitive plate 124, a read optical subsystem 126, a write laser beam subsystem 128, and a read optical system output beam 131 and a write laser beam 132 which are alternately connected to the copy board 122.
and a scanning subsystem 130 that provides a common optical path for scanning across the photosensitive plate 124.

The reading optical system includes, for example, a helium-neon reading laser 150, and the output of the laser 150 is transmitted through a refracting mirror 1.
54 and is sent to a beam combiner 158 that transmits this laser beam. The output of the writing laser 166 is extracted through an intensity modulator 176, a refractor mirror 171, and reflected off the dichroic first face of the beam combiner 158. The two beams are matched and need not be vertically divergent. The beam then passes through a pair of spherical mirrors 177A, 177B which act as beam expanders. The beams after being reflected by another refractor mirror 200 are coincident and collimated to the appropriate diameter. The beam is then scanned and reflected by successive mirror surfaces of a cylindrical drum 162 mounted with a plurality of plane mirror surfaces 162a, 162b, etc., and then passes through an objective lens 164.

Objective lenses 164 focus the beams onto the respective plate surfaces as described above.

Beam 131.13 copy board 122 and board 124
2 is provided with a subframe 19G for supporting them generally in-line with each other. First surface dichroic beam splinter 184 acts as a UV scanning mirror by reflecting the ultraviolet energy of writing laser beam 132 down toward the surface of plate 124 . Beam splitter 184 is transparent to read beam 131 and passes the beam to second scanning mirror 182;
The mirror 182 refracts the beam downward.
Turn to 22 paste up.

From the scanning optical system 162 to the plate 124 or copyboard 1
The optical distances to 22 are kept approximately the same in order to keep the image scale factor at unity. The non-specular output from the paste-up is received by an optical fiber array 188 that is positioned at an angle and aimed toward the scan line directly below the scanning mirror 182. Since the optical fiber array 188 is arranged linearly as a cotton-oat exchanger, all possible reflective elements of the paste amplifier scan will be viewed simultaneously. Array 188 is grouped into a small spot to serve as input to photomultiplier tube 190 and modulator 176.
Controls the strength that can pass through.

Paste-up and copyboard 122 is supported by soil bushings 198 on rods 202 on subframe 1
96 and is driven by the screw 20B so that the scanning progresses in stages as described above.

Since both the read and write beams are directed in the same direction,
The pattern reproduced on the photosensitive plate 124 is read-write for paste-up, so the resulting engraving can be used immediately for offset printing. Also, since the beams are deflected in the same direction by the scanning optics, there is no need to use anti-vibration optics.

Although the copyboard has been described above as holding a paste amplifier that one wishes to reproduce, it should be pointed out that the present apparatus and procedure can be used, for example, for positional information encoding required for facsimile transmissions. In such devices, the paste amplifier is a grid or other position-indicating network that generates output pulses as the reading beam passes through it, and these pulses are counted by an amplifier down counter to produce a binary number corresponding to the position of the reading beam. can get. Since the read beam is optically coupled to the write beam, this number provides the precise positional data necessary for high quality data transmission.

[Brief explanation of the drawing]

1 is a partially cutaway perspective view of a laser reading and writing device according to the invention for producing a pattern on a photosensitive surface; FIG. 2 is an optical schematic diagram of the device of FIG. 1; FIG. 4 is a partially cut away perspective view of another embodiment of a laser reading/writing device according to the invention, and FIG. 4 is an optical schematic diagram of the device of FIG. 3. FIG. 36...Photosensitive surface 24...Plate 32
...Writing laser beam 66.68...
・Writing laser beam generation means 62.64.80・
... Scanning means 40 ... Copy board 22.33 ... Holding means 58.56.88.90.91 ... Detection means 9
3.94.95.76... Writing laser beam intensity control means 92.96.98.99.102.104.110.1
12.114...Transportation means 1, incident display Patent Application No. 76402 of 1982 3. Relationship with the case of the person making the amendment Applicant Name American Hoechst Corporation 4;
agent

Claims (1)

[Claims] (1) A device for creating a reading beam for scanning an object and a writing beam for scanning a writing surface, a modulation device for varying the intensity of the writing beam, and a modulated writing beam and a reading beam together. a beam combining device that directs the spread beams slightly apart along two common paths; a beam separation device that includes a deflector between the spread beams and having first and second surfaces for deflecting each beam toward the target and writing surface; an apparatus, a reflector for reflecting one beam toward the other beam before both beams impinge on the face of the deflector, placed along a common path, and directing the combined beam across a predetermined portion of which common path; Scanning for synchronized scanning with a deflected beam separating the object from the writing surface and writing for forming an image of the object on the portrait surface in response to energy received from the object as the reading beam scans the object. Apparatus for forming an image of an object on a writing surface, comprising means for adjusting a modulator to vary the intensity of the focused beam.