JPS63766B2 - - Google Patents

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.

The work essential to the production of conventional and modern engravings includes:
It involves shining a photo of the subject on a copyboard with a high-intensity light bulb and 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 described below, the type of printing plate produced is not limited to the scope of the present invention, and may be of any type. In recent years, phototypesetting has come back into use in newspaper and various types of commercial printing, particularly with the use of printing plate materials based on photopolymer systems. A typical process involves directly imaging a negative image as described above onto a photopolymer layer supported on a suitable substrate, and then processing the exposed polymer layer and substrate to remove the unexposed photopolymer layer. Portions are selectively removed to create a photoengraved printing plate.

In some systems, the negative is printed contact-printed on 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 processes are of good quality, they require materials such as negatives and chemicals, expensive camera equipment, and a large amount of time, making them expensive to perform.

Various methods have been proposed for directly manufacturing printing plates by etching them with laser beams or electron beams, but the optical systems used for detection and etching have inherent non-linearity, resulting in poor resolution. The proposed method was not satisfactory as the yield 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 transfer this information to the surface of the photosensitive plate with identical or corresponding information. The object of the present invention is to provide a laser reading/writing device of the above-mentioned nature which can be directly converted into a laser beam.

Another object of the invention is to provide highly accurate, rapid and
It is an object of the present invention to provide a laser reading/writing device of the above-mentioned nature that does not feel vibrations and can engrave copyboard paste-ups linearly and correctly.

The above general object is achieved by the present invention, according to which the copyboard is an integral part of a laser scanning means consisting of an input laser beam focused as a suitably small resolution spot onto the copyboard. It's summery. Means is provided for causing the spots to scan the copyboard in a predetermined pattern, such as a raster scan. The sensing means is adapted to receive light reflected from the copyboard at a location struck by the input or read 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 adapted to control the amplitude or power provided to the second laser beam. 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 photosensitive surface to be exposed, which are oriented either read-write or read-long with respect to each other. It is separated so that it hits. Generally, the faces or surfaces of the copyboard and photosensitive plate face each other or are oriented in a predetermined direction that determines whether exposure is read-write or read-long. 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 to the copyboard and the write beam is directed to the photosensitive surface. In this way, the beams are interlocked and irregularities in the motion of the scanning optics affect the read and write beams in the same way.

Embodiments of the invention will now be described with reference to the accompanying drawings, from which other objects and features of the invention will become apparent.

As shown in FIGS. 1 and 2, the main elements of the laser reading/writing apparatus of the present invention are maintained as subsystems within a suitable framework 20. As shown in FIGS.
These subsystems include the copyboard holder 22
and a photosensitive plate 24, a reading optical subsystem 26,
Writing laser beam subsystem 28 and reading optics input and/or output across copyboard 40 and photosensitive plate 24 to provide a common optical path for receiving and scanning both beam 31 and writing laser beam 32 optical subsystem 30. 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 mounting 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 has a photosensitive polymer layer 36 coated on one surface thereof, which layer is polymerized when exposed to radiation of a suitable color range and intensity. do.

Means 2 for holding the copyboard 40 parallel to and spaced from the photosensitive plate 24 and above the photosensitive plate 24;
2 are provided, which means 22 may be suitable holding means, such as, for example, a plate having grooves 42 connected to a plurality of channels (not shown) leading to a vacuum pump 44. By positioning the paste up on this plate downward above the photosensitive plate 24, the paste up can be held firmly and uniformly. The copyboard holder 22 is mounted on a suitable numbering means 46;
The device as a whole can be opened and closed.

The reading optics subsystem 26 includes a helium-neon laser 50, and the output of the laser 50 is input to the scanning optics subsystem 30 through a beam expander 52, a beam directing mirror 54, and a back beam splitter 56. beam combiner 58. Scanning optical subsystem 30
includes a galvanometer mirror 62 or other means for sweeping the incident input beam laterally across the width of copyboard 40 and photosensitive plate 24. The output of galvanometer mirror 62 passes through scanning objective lens 64 . Lens 64 generally focuses the passing beam onto copyboard 40 or photosensitive plate 24, as described below.

The writing laser subsystem 28 is a high power
Laser 6 capable of generating UV beams 70, 72
Contains 6,68. 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 from one side for one polarization direction and reflective for orthogonally polarized light such as beam 72. It is reflective because it is positioned. In this way, almost all the light from the UV laser is mixed with high efficiency. To do this, the output of one laser must be physically connected to the other laser.
90° or by incorporating a quarter-wave polarizer (not shown) that retards the phase of the light from one laser by 90° (i.e., effectively rotates the polarization by this amount). be rotated. The combined energy of the UV laser is sent from polarization beam combiner 74 to optical modulator 76 . The modulator 76 may be electro-optical or acousto-optic, such as the Zenith M70 (acoustic
Optical), Datalight DLM1-UV (acoustic)
(optical) or manufactured by Coherent Associates (electric/optical). 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-optic modulator 76 is to pass the light beam as an acoustic wave generated in a transparent material, which causes some or all of the energy in the UV light beam to be diffracted at an angle and transmitted to other parts of the optical system. It is important not to fall into this part. 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 to 35 mm and is passed through a scanning optics 30 by mirrors 78 and 79.
directed towards.

Scanning optical system 30 includes a beam combiner 58 . Beam combiner 58 also includes a first surface dichroic mirror that transmits the helium-neon beam incident on its back surface but
It has a dichroic coating that is highly reflective to UV radiation incident on the surface. Therefore, each beam is directed from the combiner 58 to the galvanometer mirror 62 and the scanning objective lens 64 in a nearly coincident state. In more detail in this regard, the directing mirror 54 of the reading optics is tilted slightly upward to direct the helium-neon beam upwardly at a small angle (~1°) relative to the horizontal centerline of the device. ,
On the other hand, the dichroic mirror surface of combiner 58 directs the UV radiation at a small angle (~1°) to the horizontal centerline of the device.
It is tilted slightly downward so that it points downward. In this way, the beams 31 and 32 diverge in the vertical direction while remaining in the same vertical plane as they travel from the scanning objective lens 64 toward the copyboard 40 and photosensitive plate 24. The beams arrive at the dihedral prism 80 separated from each other by approximately 1-2 inches. prism 80
The top surface 82 of the copyboard 40 is inclined at approximately 45 degrees so that the incoming read beam 31 is bent upwardly toward the copyboard 40. The lower surface 84 of prism 80 is also angled at a 45° angle so that writing beam 32 is directed toward photosensitive plate 24. The dihedral prism 80 has 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. It has been done.

Vibrations in the galvanometer mirror 62 or associated optical system components cause the combined beams to move together upwardly or downwardly, and this movement causes the beams to be out of phase (i.e., generally causing an upward motion). Note that the writing beam 32 moves to the right, causing the reading beam 31 to move to the left. In order to keep the beam synchronized and to move in the same direction in the event of vibrations, an anti-vibration optic 87 with a first reflecting plane, such as an aluminum mirror, is placed in the path of the reading beam 31 by suitable means. The mirror prism 80 is mounted so that the reflected beam therefrom is directed to a triplane mirror prism 80. In this way, even if the beam moves upward, when it hits the surface of the dihedral mirror, both beams will make the same translational movement, moving away from each other by the same amount or approaching each other, and therefore the vibrations of the beams will be in phase. , resulting in equal translational motion for each of the aforementioned surfaces.

The reading optical subsystem 26 is connected to the copyboard 4
It also includes means for regressively viewing small spots on 0. This means uses the beam splitter 5
6 includes a read lens 88 positioned to receive light from 6 and focus it as a spot onto a photomultiplier tube 90. The output of photomultiplier tube 90 is used to generate an electrical signal to operate modulator 76. In many applications, it will be desirable to position spatial filter 91 in front of photomultiplier tube 90 so that the spot on copyboard 40 that is visible at any given time is extremely small.

The means for moving the scanning optical subsystem comprises:
A suitable mounting plate 92 is included. The plate 92 is made of rods 102, 104 made by, for example, thorough polishing.
a suitable bearing 98, such as a ball bushing bearing running above;
It is mounted on a subcarriage 96 which is held on a subcarriage 99. A plate or carriage 92 holds the full readout optical subsystem 26 and the full scanning optical subsystem 30 and translates back and forth toward and away from the copyboard 40 and photosensitive plate 24. A suitable drive screw 106 is coupled to a nut 108 mounted on the underside of the carriage 92 (approximately below the objective lens 64). As will be described later, each time the mirror 62 finishes scanning the field, the screw 106 closes the stepping motor 1.
10 and is advanced by one increment. Second electric motor 112 that is normally not engaged
the carriage 9 when each scan sequence is completed.
It operates to quickly return 2. The electric motor 112 is adapted to operate via a unidirectional coupling 114. The operation of the device is described below along with some other components within the device.

In operation, the copyboard holder 22 is opened and the paste up is mounted directly over and facing the printing plate 24 by vacuum. To begin the scanning sequence, the carriage 92 is advanced to the point where the two-way mirror 80 is located just between the beginning of the paste 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. Carriage 92 is driven by motor 110 and screw 106 at a speed corresponding to half the diameter of the blurred circle for each scan. In this system, the diameter of the blurred circle is approximately 0.025-0.076 mm (1-3 mils) and represents the smallest spot that can actually be resolved by this optical system. Galvanometer mirror 62 scans in both directions during operation. At the end of each scan, the carriage 92, which holds the read/write subsystem and the scanning subsystem, is advanced. The small read dots created by the read beam 31 as it scans across the copy are approximately 0.05 mm (2 mils) in diameter and traverse areas of alternating light and dark. The dark areas may be typewritten text, line drawings, appropriately halftoned and screened photographs, or conventional material incorporated into a pasteup. The amount of light reflected by the copy varies significantly as a function of the reflectance density of the paste-up;
Dark areas reflect very little while bright areas reflect mostly. Note that the reading beam 31 is 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. The non-specular reflection is received by objective lens 64, reflected by scanning mirror 62, passes through beam combiner 58, and is reflected by beam splitter 56 into photomultiplier tube 90. A lens 88 placed in front of the tube 90 breaks the parallelism of the energy and
Focus on the 0 entrance slit. If desired, a spatial filter 91 may be incorporated into the entrance slit of tube 90 to provide high resolution by eliminating stray reflections and unwanted light. A photomultiplier tube 90 detects changes in reflected light energy as the dot scans across the light and dark areas of the paste up and generates a high and low signal. This signal is amplified and
Comparison is made at preset threshold 95. The output from high frequency signal generator 93, which is normally blocked when the signal exceeds the threshold, is provided to modulator 76 through gate 94. If the signal is below the threshold level, meaning that a dark area is being scanned, modulator 76 serves to deflect the writing laser beam. As the dot of the reading optics is scanned across the paste-up as described above, the ultraviolet writing laser beam 32 simultaneously strikes the printing plate 2 to be exposed.
Scan across 4. In summary, the beams are coaxial in the vertical plane but spatially separated by about 2-5° apart in the aforementioned reflective elements;
The mirror 80 is configured so that the light can be reflected upwardly and downwardly. After being deflected by scanning galvanometer mirror 62, both beams are focused by objective lens 64. This lens 64 is a flat field lens that converges to an angle of approximately 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, the reading beam 3
1 traverses each dark area of the paste-up, the ultraviolet beam 32 simultaneously exposes a segment of the photosensitive plate 24. This exposed area becomes the area where ink is transferred to, for example, newspaper 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 image reductions of 0 to 10% in width and up to 3% in length are desirable, and this can readily be achieved in the apparatus of the invention. The width expansion (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, the width is reduced. The length scale can be changed by providing a carriage which runs on ball bearings on the rails or rods 102, 104 held in the framework 20, on which the board to be prepared is placed. and achieve it. 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 in the same proportion as the desired scaling factor with respect 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 includes photomultiplier tube 90 and threshold 9 in the circuit that controls modulator 76.
This is achieved by incorporating a memory 97 in the signal path between the 5 and 5. This memory 97 stores all the information contained within a single width 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. It is also possible to use electro-optic deflectors in the write beam circuit if resolution is less of an issue. A vibrating mirror operated by a tuning fork may also be used.

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

Copies can be detected using the same apparatus as shown in FIGS. 1 and 2 (with the exception of changing the reading beam) with general illumination. The paste-up copy is generally illuminated using a non-actinic radiation bulb and a pinhole is used as a spatial filter in the photomultiplier tube entrance slit to determine the resolution of the readout system. In a sense, this creates a passive reading beam that is scanned by the optics. However, it will be appreciated that the reversing system using a reading 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 reading system. The advantage of optical fiber sensing is that it provides a high signal-to-noise ratio, but at the expense of considerable sensitivity to ambient light. Passive systems using full-light bulbs make alignment of the device less sensitive, 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.

Although the copyboard has been described above as holding a paste-up 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 as required in facsimile transmissions. In such devices, the paste-up 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 up-down counter to produce a binary number corresponding to the position of the reading beam. is obtained. The reading beam is optically coupled to the writing beam, so
This number provides accurate 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, and FIG. 2 is an optical schematic diagram of the device of FIG. 36... Photosensitive surface, 24... Board, 32... Writing laser beam, 66, 68... Writing laser beam generating means, 62, 64, 80... Scanning means, 40... Copy board, 22, 33... ...Holding means, 58, 56, 88, 90, 91... Detection means, 93, 94, 95, 76... Writing laser beam intensity control means, 92, 96, 98, 9
9... Means of transportation.

Claims (1)

[Scope of Claims] 1. A device for producing 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; an apparatus for adjusting the modulator to vary the intensity of the writing beam in response to energy received from the object to form an image of the object on the writing surface; a beam combining device for sending the combined beam along a common path; a scanning device disposed along said common path for deflecting the combined beam and performing synchronous scanning of the object and the writing surface with the reading beam and the writing beam; an objective lens that sends out the modulated writing and reading beams with a slight spread; a reflector that reflects one of the spread beams toward the other; and a reflector that reflects one of the spread beams toward the other; An apparatus for forming an image of an object on a writing surface, comprising a beam separation device including a beam separation device having a deflector having first and second surfaces for reflecting the object toward the writing surface.