JPH023006A - Laser exposing method for image scanning recorder - Google Patents

Abstract

PURPOSE:To realize an overlap printing exposure by a multi-beam by a comparatively simple constitution by allowing the multi-beam to execute sub-scanning so as to fill up between beam spots of the first half part which is brought to main scan first by the latter half part of a beam spot train which is brought to main scan afterward. CONSTITUTION:A multi-beam is allowed to execute a sub-scanning so as to fill up between beam spots 1, 3, 5, 7 and 9 of the first half part which is brought to main scanning first, by the latter half parts 2, 4, 6 and 8 of a beam spot train which is brought to main scanning afterward. Accordingly, it is made unnecessary to provide a means for preventing an interference between each laser recording beam for constituting the multi-beam, and also, a delicate adjustment of an output timing of data becomes unnecessary. In such a way, the multi-beam can be brought to overlap printing exposure by comparatively simple constitution.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a laser exposure method that is used in image scanning recording devices such as laser plotters for manufacturing printed wiring boards, color scanners for plate making, or laser printers. In particular, multiple laser recording beams (multibeams)
This invention relates to a laser exposure method for scanning an image recording surface in parallel.

<Prior Art> FIG. 14 is a schematic block diagram of a laser plotter as an example using a conventional laser exposure method.

The laser plotter can be roughly divided into an image data creation section 10;
It is composed of a data conversion section 70 and an image recording section 80. The image data creation unit 10 creates contour edge vector data of a figure from CAD data, and includes a minicomputer 11. for calculating the vector data. CRT
12, a keyboard 13, and a magnetic tape 14 and a magnetic disk 15 for storing CAD data. The data conversion section 70 converts vector data given from the image data creation section 10 into dot data. It prints both images by scanning the photosensitive material (image recording surface) in a band shape while individually controlling the ON10 F F of the beam.
It is composed of a recording cylinder (or a table driven in a plane) 82 which is rotatably driven with a paper attached thereto.

In an apparatus that performs simultaneous recording using such multi-beams, the beam spots BS are usually placed adjacent to each other in the axial direction (sub-scanning direction) of the recording cylinder 82, as shown in FIG. array and recording cylinder 82
By rotating the beam spot array, the beam spot array is relatively displaced in the circumferential direction (main scanning direction) of the recording cylinder 82 to perform recording.

By the way, the light intensity distribution of the laser recording beam is not uniform, but has a Gaussian distribution in which the light intensity is extremely reduced at the periphery. When scanning, there is a tendency for so-called scanning line cracks to occur, where the exposure amount is insufficient in adjacent areas of each beam spot and the density in those areas becomes low.Also, as shown in A decline in image quality, such as jitter in the border lines, is unavoidable.

Therefore, in order to improve the quality of images recorded by multi-beams, a method can be considered in which parts of the beam BSs arranged in series are overlapped with each other for exposure as shown in Fig. 17. Since this is coherent light, if adjacent beam spots are simply superimposed, light interference will occur in that area and exposure and recording will not be performed properly. Therefore, various methods have been proposed to avoid such interference of laser recording beams and realize multi-beam overprinting.

The first method is to overlap the beam spots by making adjacent laser recording beams form a pair of orthogonal polarizations, and the second method is to provide an optical path length difference between adjacent laser recording beams that is greater than the coherence distance. The third method is to scan a plurality of beam spots BS by arranging them in a staggered manner, as shown in FIG. A fourth method is to overlap the beam spots of laser recording beams emitted from individual laser light sources.

According to this overprinting exposure method, as shown in FIG. 19, scanning line cracks do not occur in the recorded image, and
Moreover, smooth border lines can be obtained.

<Problems to be Solved by the Invention> However, each of the above exposure methods has the following problems.

According to the first exposure method, an optical means such as a half-wave plate for rotating the polarization plane of the laser recording beam by 90 degrees is indispensable, leading to the complexity of the optical device. According to the above, due to the need to provide a difference in optical path length, the optical path length of the optical system becomes extremely long, which makes it vulnerable to vibrations.According to the third exposure method, since adjacent laser recording beams are shifted vertically, The timing of data output for 0N10FF control of the laser recording beam must be delicately adjusted, which complicates the circuit configuration.According to the fourth exposure method, two light sources are used.
There are problems such as complicating the device and increasing costs.

The present invention was developed in light of these circumstances, and avoids complicating the optical system and delicately adjusting the data output timing, and enables multi-beam overprint exposure with a relatively simple configuration. It is an object of the present invention to provide a laser exposure method for an image scanning recording device that can realize the following.

Means for Solving the Problems> In order to achieve the above objects, the present invention has the following configuration.

That is, the present invention irradiates an image recording surface with a plurality of independently controlled laser recording beams (multi-beams) to form a series of beam spots, and directs the multi-beams onto the image recording surface. In a laser exposure method for an image scanning recording device that performs exposure recording on a recording medium by performing relative scanning (main scanning) in a direction crossing the spot arrangement direction and relative scanning (sub-scanning) in the spot arrangement direction, In successive main scans, the multi-beams are sub-scanned so that the second half of the beam spot row that is scanned later fills the space between the beam spots of the first half of the beam spot row that was scanned first. .

Specifically, there are cases where the multi-beam is composed of an odd number of laser recording beams and cases where it is composed of an even number of laser recording beams. do.

Note that in this specification, the first half of a beam spot row refers to the leading front half of the beam group in the sub-scanning direction in which the beam spots are arranged, and the second half of the beam spot row refers to the rear half of the beam group. beam group.

According to the present invention, in successive main scans, the second half of the beam spot row that is main scanned later fills the space between the beam spots of the first half of the beam spot row that was main scanned first. Since the multi-beams are sub-scanned, there is no interference between the laser recording beams, and the multi-beams are used for overlapping exposure.

<Example> Embodiments of the present invention will be described below with reference to the drawings.

The laser exposure method according to the example of "Kaya" J01 Masumoto is a method of exposure recording using a multi-beam consisting of an odd number of laser recording beams, and when the array pitch of the beam spots is P1 and the number of beam spots is N, Abbreviation for multi-beam (PXN)/
The sub-scanning is performed at a pitch of 2.

An example in which the multi-beam is composed of nine laser recording beams will be described below.

FIG. 1 is a schematic diagram of a laser protector as an example of an image recording apparatus using the exposure method according to the present embodiment.

This laser plotter is composed of an image data creation section 10, a data conversion section 20, and an image recording section 30. Of these, the image data creation section 10 has the same configuration as the conventional device explained in FIG. Therefore, I will omit the explanation here.

The data converter 20 is configured as follows.

The vector data created by the image data creation unit 1O is
The intersection data processing circuit 21 converts the data into intersection data indicating the intersections between the drawing pattern and each scanning line, and then provides the data to the memory controller 22 . The memory controller 22 is
This is for controlling writing/reading of intersection data to/from the buffer memory circuit 23.

As shown in FIG. 2, the buffer memory circuit 23 is composed of five buffer memories 23A, 23B, and 23C that are individually controlled by the memory controller 22. Each of the buffer memories 23A, 23B, and 23C includes 9 line memories 1 to 9 corresponding to each laser recording beam of the multi-beam. Each line memory is set with an area large enough to store the same number of bit data (intersection data) as the number of pixels included in the -scanning line.

The dot data creation circuit 24 includes a buffer memory circuit 23
This is a circuit for converting the intersection point data read from the line memories 1 to 9 into dot data, and includes AND gates Gl, G2 . ..., G9, and JK flip-flops FFI, FF2, etc. connected to each AND gate.
・It is composed of FF9.

The modulator control circuit 25 individually performs 0N10FF control of the 9-channel acousto-optic modulator provided in the image recording section 30, which will be described later, based on the 9 lines of dot data given from the dot data creation circuit 24. Outputs the signal.

The image recording section 30 is configured as follows.

As shown in FIG. 3(a), the exposure head 31 provided in the image recording unit 30 includes a plurality of beam splitters 33 that split the laser beam irradiated from the laser light source 32 into nine laser recording beams; Each laser recording beam is individually set to zero according to the dot data given from the modulator control circuit 25.
9-channel acousto-optic modulator (A
OM) 34, a reflecting mirror 35, and an optical system 36 that focuses the modulated multi-beams and irradiates them onto the image recording surface.

FIG. 3 (bl shows the beam spot array of the multi-beam obtained by the above-mentioned optical means. The array pitch P of the beam spot is set approximately equal to the beam spot diameter. Here, the beam spot diameter In the case of a laser recording beam with a Gaussian distribution, for example, is defined by the beam diameter corresponding to a light intensity distribution of 1/e"l (approximately 13.5%) with respect to the light intensity at the center of the beam. In other words, The array pitch of the beam spots is set at a distance that does not cause interference between adjacent laser recording beams (therefore, the array pitch P may be set slightly larger than the beam diameter), and in this respect, the The same applies to the second embodiment.

The exposure head 31 is attached to a screw rod 37, and the screw rod 3
By rotating the exposure head 7 with a motor 38, the exposure head 3I is pitch-fed intermittently or continuously in the axial direction of the recording cylinder 40. motor 38
The rotational speed of the motor is controlled by a motor control circuit 39 which receives a speed command pulse from the memory controller 22.

The recording cylinder 40 is driven by a drive mechanism (not shown).
It is rotated at a constant speed, and the rotational speed is detected by a rotary encoder 41. The detection signal of the rotary encoder 41 is given to a timing generation circuit 42. The timing generation circuit 42 creates an output timing signal based on this detection signal and outputs it to the memory controller 22.

Next, the operation of this embodiment will be explained.

Please refer to FIG. Figure (a) is a diagram schematically showing the calculation process of intersection point data, and Figure (b) is a diagram schematically showing the line memory in the buffer memory 23 in which the calculated intersection data is stored. be.

The intersection data processing circuit 21, which is given the vector data of the drawing pattern from the image data creation unit IO, processes the scanning line (1
), (2), (3), ... and the drawing pattern indicated by the hypotenuse area in the figure, calculate the Y address of the intersection (white/black change point), and send this to the memory controller 22 as intersection data. Output.

The memory controller 22 (see FIG. 2) takes in the intersection data based on the data request signal (DReq) transmitted from the intersection data processing circuit 21, and stores it at the corresponding address on the corresponding line memory of the buffer memory circuit 23. , rlj, and outputs a data request acknowledge signal (D ReqAck) to the intersection data processing circuit 21. D.R.
The intersection data processing circuit 21 that has received the eqAck signal outputs the next intersection data together with the DReq signal.

When the intersection data for 1947 minutes is output from the intersection data processing circuit 21, the intersection data processing circuit 21 outputs an end signal (
END). The memory controller 22 receiving this END signal changes the line of the PanorMemo 1 circuit 23 and writes to the next line memory. When a line feed is performed, the memory controller 22 sends an end acknowledge signal (ENDAc) to the intersection data processing circuit 21.
k).

By receiving this E N D Ack signal, the intersection data processing circuit 21 starts outputting the intersection data of the next line.

Reading of the intersection data from the buffer memory circuit 23 is performed at the following timing. The following description will be made mainly with reference to FIG.

The memory controller 22 receives an output timing signal as shown in FIG. 5 (al) from the timing generation circuit 42. One cycle of this output timing signal corresponds to a pixel pitch. Specify the buffer memory from which the data is to be read using the C5 signal, and specify the address of the line memory in synchronization with the output timing signal (see FIG. 5, etc.);
Then, when the R/W signal shown in FIG. 5(C) is at rH level, the intersection data are read out in order according to the respective designated addresses (see FIG. 5(d)). Reading is performed in parallel for each line memory within the designated Batza memory.

Each read intersection data is sent to the don't data creation circuit 2.
It is given as one input of the A N D gate C (Gl-C9) of 4. The AND gate G receives a timing pulse (FIG. 5(e)) given from the memory controller 22.
), the intersection data as shown in 511J(f) is input to the next stage JK flimp flop FF (FFI to FF9).

As a result, the level of the output Q of the JK frimb flop FF changes at each data change point, as shown in FIG. 5 (80).

That is, the first intersection data rlJ shown in FIG. 5(d) is the changing point where the ti 1iii pattern changes from white to black, and the next intersection data rlJ is the changing point where the ti 1iii pattern changes from black to white. Then, the rHJ level region of the Q output of the JK flip-flop FF shown in FIG. 5Fg) corresponds to the period in which the laser recording beam is turned on (exposed state). . The output Q of each JK flip-flop FF obtained in this manner is applied as dot data to the modulator control circuit 25 at the next stage.

While the intersection data is being read from each line memory of the buffer memory circuit 23, the memory controller 22
Input rQ into the line memory as shown in FIG. As a result, after the intersection data is read out,
During the "L level" period of the R/W signal shown in FIG. 5(C), the data in that address is rewritten to rQl.

Next, with reference to FIG. 6, the order of writing and reading data into each line memory of the buffer memory will be described.

FIG. 6 shows buffers and memories 23A, 23B, 23
This is an explanatory diagram schematically showing the input/output of line data to C. Also, here, inline data is a general term for intersection data for ■scanning, and in the figure, ■, ■, ■ .

It is indicated by...

When writing data to the buffer memory circuit 23,
As shown in FIG. 6(a), first, the buffer memory 23
All contents of line memories 1 to 4 of A are initially cleared to rQJ. Then, among the line data from ■ to ■ sequentially obtained from the intersection data processing circuit 21, the odd numbered line data ■, ■, ■■, ■ are stored in each of the buffer memory 23A at 5.6.7.89.・Write to in-memory and write even numbered line data ■, ■, ■, ■ to buffer memory 23
Write to each line memory in 12.3.4 of B.

Preparation for drawing is completed by writing the data as described above, and the line data is read out and drawn at the same time as the next line data is written.

That is, as shown in FIG. 6 (bl), the buffer memory 23
A] While the contents of the two memories 1 to 9 are being read out, line data [phase], 0, 0.0 . [Phase] is buffer-,
, y Line data ①, ②, ②, ② are respectively written into the line memories 1 to 4 of the PIJ 23C.

When the first main scan is completed, the buffer memory 2 is opened for the second main scan as shown in FIG. 6(C).
Line data ■, ■, ..., ■ are read from 3B, and the buffer memories 23C and 23
The next line data is written to A. Thereafter, line data is similarly read and written to the buffer memories 23A, 23B, and 23C in parallel.

Note that each main scan corresponds to one rotation of the recording cylinder 40, and during one rotation of the recording cylinder 40, the exposure head 31 moves approximately 4.5×P (P is the beam spot In other words, the memory controller 22 outputs a speed command pulse to the motor control circuit 39 so that the multi-beam is sub-scanned at a pitch of approximately 4.5×P. .

As a result, as shown in FIG. 7, in successive main scans, the latter part of the beam spot row that is main scanned later fills the space between the beam spots of the first half of the beam spot row that was main scanned first. (See Fig. 19). However, in FIG. 7, for ease of understanding, the multi and one frames corresponding to each main scan are drawn shifted vertically. Further, the numbers in FIG. 7 correspond to the line data shown in FIG. 6.

The laser exposure method according to this embodiment is a method of exposure recording using a multi-beam consisting of an even number of laser recording beams, and the arrangement pitch of the beam spots is P and the number of beam spots is N. In this case, the multi-beam is divided into a first half and a second half each consisting of the same number of beam groups so that the distance between the centers of adjacent beam spots in the divided portions is approximately 1.5×P, and these beam groups are Sub-scanning is performed at a pitch of approximately (p×N)/2.

Hereinafter, a case will be described using as an example a case where the multi-beam is composed of 10 laser recording beams.

Since the schematic structure of the device is almost the same as that of the first embodiment shown in FIG. 1, illustration is omitted, and only the parts different from the first embodiment will be explained here.

In this example, since 10 laser recording beams are used, the buffer memories 23A, 23B 23C
are each equipped with 10 line memories, and correspondingly, the dot data creation circuit 1524 is equipped with 10 AND gates and 10 JK flip-flops.

Further, in order to divide the multi-beam into five beam groups each, the exposure head 31 is constructed as shown in FIG. 8. - Two laser beams B2°B are emitted from the laser light source 32 by the laser beam B1 and the heem portion IPI n51.
It is divided into 3 parts. One laser beam B2 is reflected by a reflection mirror 52, and then divided into five laser recording beams by a plurality of beam splitters 53.The zero-divided beam group B4 is individually divided into 0N10F beams by an acousto-optic modulator 54.
F controlled. The beam group B5 emitted from the acousto-optic modulator 54 is reflected by a reflecting mirror 557 and is incident on the polarizing beam splitter 56.

On the other hand, the other laser beam B3 split by the beam splitter 51 is reflected by reflection mirrors 57 and 58, so that the plane of polarization is displaced by 90 degrees, and then the multiple beam splitter 59 records five laser beams. divided into beams. The divided beams 9B6 are individually 0N10FF controlled by the acousto-optic modulator 60. The beam group B7 emitted from the acousto-optic modulator 60 is reflected by a reflection mirror 61, and then enters the polarization beam splinter 56 via the beam shifter 62.

The beam shifter 62 is composed of a transparent parallel plane plate as shown in FIG. The emitted light can be shifted parallel to the incident light by a distance L (in this case, P/2).

L=t(1-cos θ/F■17π sti)-sin
θ However, L indicates the thickness of the parallel plane plate, and n indicates its refractive index.

Therefore, as shown in FIG.
By setting the angle to a predetermined angle θ, the beam group B is installed by displacing the incident beam group B7 by P/2.
It can be injected as 7'. FIG. 11 shows the multi-beam beam spot array obtained in this way, and by displacing the incident beam group B7 by P/2 in the sub-scanning direction, adjacent beam groups B
5. The distance between the centers of the beam spots of the nearest beam B7' is approximately 1.5×P.

In FIG. 8, two beam groups B5. By making each polarization plane of B7 orthogonal,
The loss of the amount of light BL in the polarizing beam splinter 56 is reduced. However, if the loss of light quantity is acceptable, a normal beam splitter may be used, and in this case there is no need to provide a reflecting mirror 57 or the like for orthogonally displacing the plane of polarization.

Further, the optical means for displacing one beam group is the eighth beam group.
The present invention is not limited to the example shown in the figure, and various modifications can be made. For example, if the beam shifter 62 is not used (but if the reflecting mirror 55 is mounted with a displacement of P/2 along the optical axis of the beam group B5, the reflected beam group B5 will be shifted by P/2 with respect to the other beam JffB7). Therefore, in this case as well, a predetermined split beam group as shown in Fig. 11 can be obtained.Also, a multi-AOM with the optical distance in each modulation channel set to 3P/2 only in the center can be fabricated. It can also be used.

Next, the human output of line data to each buffer memory 23A, 23B, and 23C will be explained.

The procedure for writing/extracting line data into each buffer memory is performed in the same manner as in the first embodiment, so the order is shown in FIG. 12 and the explanation here will be omitted. Note that Fig. 12 (a) shows the acquisition of initial data, and Fig. 12 (bl, (c), fd) shows the reading of brown line data in the first, second, and third main scans. The writing state is schematically shown.

In this embodiment, the speed command pulse is sent from the memory controller 22 to the motor control circuit 39 so that the amount of movement of the exposure head 31 per rotation of the recording cylinder 40, that is, the sub-scanning pitch is approximately 5×P. Output.

As a result, as shown in FIG. 13, in successive main scans, the latter half of the beam spot row that is scanned later fills in the space between the beam spots of the first half of the beam spot row that is scanned first. The exposure is recorded as follows (first
(See Figure 9). In FIG. 13, for ease of understanding, the multi-beams corresponding to each main scan are drawn shifted vertically, and the numbers in the figure correspond to the line data shown in FIG. 12.

In the first embodiment, a multi-beam consisting of 9 laser recording beams is used, and in the second embodiment, a multi-beam consisting of 10 laser recording beams is used to perform exposure recording. It goes without saying that the number of laser recording beams constituting a multi-beam in the present invention is not limited.

Furthermore, although the embodiments have been described using a laser printer as an example, the present invention can also be applied to other image scanning and recording apparatuses such as a color scanner for plate making and a laser printer.

Further, in the above embodiment, the recording cylinder 40 is used to form the image recording surface into a curved surface, but a table driven in a plane may be used to form the image recording surface into a flat surface.

<Effects of the Invention> As is clear from the above description, according to the present invention, in successive main scans, the latter half of the beam spot row that is scanned later is the same as the beam spot row that was scanned first. Since the multi-beam is sub-scanned so as to fill the spaces between the beam spots in the first half, there is no need to provide special optical means for preventing interference for each laser recording beam that makes up the multi-beam. There is no need to make delicate adjustments to the data output timing, which is required when overprinting multiple beams with multiple beam spots arranged in a staggered manner, and it is possible to overprint multiple beams using a relatively simple configuration. I can do it.

[Brief explanation of the drawing]

1 to 7 are explanatory diagrams of the first embodiment of the present invention,
Figure 1 is a schematic block diagram of the laser plotter, Figure 2 is a detailed block diagram around the buffer memory circuit, and Figure 3 (a).
is a perspective view showing an example of the configuration of the exposure head, FIG. 3(B) is an explanatory diagram of the arrangement state of beam spots, FIG. 4 is an explanatory diagram of the operation of writing intersection data to the line memory, and FIG. FIG. 6 is an explanatory diagram of the operation to read/write line data to the buffer memory; FIG. 7 is an explanatory diagram of the multi-beam scanning state. 8 to 13 are explanatory diagrams of a second embodiment of the present invention, in which FIG. 8 is a perspective view showing an example of the configuration of an exposure head, FIG. 9 and FIG. 10 are explanatory diagrams of a beam shifter, and FIG. 12 is an explanatory diagram of the arrangement state of beam spots, FIG. 12 is an explanatory diagram of the writing/reading operation of line data to the buffer memory, and FIG. 13 is an explanatory diagram of the multi-beam scanning state. 14 to 19 are explanatory diagrams of the conventional example, and FIG. 14 is a schematic block diagram of the laser plotter according to the conventional example.
Fig. 5 is an explanatory diagram of the arrangement of a general non-overlapping beam spot array, Fig. 16 is an explanatory diagram of an example of a recorded image exposed by non-overlapping beam spots, and Fig. 17 is an explanatory diagram of the arrangement of an overlapping beam spot array. FIG. 18 is an explanatory diagram of beam spot arrays arranged in a staggered manner, and FIG. 19 shows an example of a recorded image exposed by overlapping beam spot arrays. 10... Image data creation unit 20... Data changing unit 21... Intersection data processing circuit 22... Memory controller 23... Buffer memory circuits 23A, 23B, 23C... Buffer memory 24...
・Dot data creation circuit 25...Modulator control circuit 30...Image recording unit 31...Exposure head 40...Recording cylinder Applicant Dainippon Screen Mfg. Co., Ltd. Agent Patent attorney Tsutomu Sugitani Figure (Bar/7F voice mo.) 23A) (Tsuma 1 Fushiru Esu 23B) 71 voices e923B) (8゛) 1 voice also 23C) ± 2nd number 371

Claims (3)

[Claims] (1) Multiple independently controlled laser recording beams (hereinafter referred to as multi-beams) are irradiated onto the image recording surface to form a series of beam spots, and the multi-beam beams are directed onto the image recording surface. An image that is exposed and recorded on a recording medium by performing relative scanning (hereinafter referred to as main scanning) in a direction crossing the spot arrangement direction and relative scanning (hereinafter referred to as sub-scanning) in the spot arrangement direction. In a laser exposure method for a scanning recording device, in successive main scans, the latter part of the beam spot row that is main scanned later fills the space between the beam spots of the first half of the beam spot row that is main scanned first. A laser exposure method for an image scanning recording device characterized by performing sub-scanning with multi-beams. (2) In the laser exposure method for an image scanning recording device according to claim (1), the multi-beam consists of an odd number of laser recording beams,
The array pitch of the beam spots of this multi-beam is P,
When the number of beam spots is N, approximately (P×N)/
A laser exposure method for an image scanning recording device that performs sub-scanning with a multi-beam at a pitch of 2. (3) In the laser exposure method for an image scanning recording device according to claim (1), the multi-beam consists of an even number of laser recording beams,
The array pitch of the beam spots of this multi-beam is P,
When the number of beam spots is N, the multi-beam is divided into a first half and a second half each consisting of the same number of beam groups so that the distance between the centers of adjacent beam spots in the divided portion is approximately 1.5×P. A laser exposure method for an image scanning and recording apparatus in which the beams are divided into two beam groups and sub-scanned with these beam groups at a pitch of approximately (P×N)/2.