JP2006085071A - Multi-beam exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-beam exposure device for recording an expression using an FM screen by using an two-dimensional optical modulator, increasing the number of exposable dots at once in a direction orthogonal to the scanning direction, and using a beam spot that has become rectangular by beam splitting. <P>SOLUTION: The multi-beam exposure device divides a plurality of exposure beam spots BS, projected to an exposure face so as to be arranged in parallel to the scanning direction from the two-dimensional optical modulator into a plurality of blocks G1, G2 and G3 in the scanning direction, is mutually shifted in the direction orthogonal to the scanning direction, and scans and exposes, in a state in which the exposure beam spot BS concerning at least one block G and the exposure beam spot BS concerning the other blocks G are shifted. Furthermore, the multi-beam exposure device scans and exposes an edge part by a steep beam spot BS by transmitting a plurality of optical beams in an optical element of a uniaxial crystal and distributing each optical beam with equal intensity in the form of a substantially rectangle at a focused point, as a normal beam and as an abnormal beam separated in a sub-scanning direction so as to partly overlap. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention collects each light beam emitted from a two-dimensional light modulator, which is a spatial light modulation element, on a pixel-by-pixel basis by an optical element based on image data (pattern data). The present invention relates to a multi-beam exposure apparatus that exposes with a predetermined pattern by irradiating a recording medium with light.

  In recent years, a recording medium such as a lithographic printing plate using a spatial light modulation element (two-dimensional light modulator) such as a digital micromirror device (DMD) as a pattern generator and a light beam modulated according to image data Development of a multi-beam exposure apparatus that performs image exposure on the top is in progress. Since this spatial light modulation element (two-dimensional light modulator) has a configuration in which pixels that modulate incident light are two-dimensionally arranged, it has the merit that it can also be used in a spatially incoherent light source, a so-called lamp. Have. Further, the spatial light modulation element (two-dimensional light modulator) can reduce the light power irradiated per unit pixel as compared with the one-dimensional light modulator arranged in one dimension depending on the method of use. Therefore, it is expected to be widely used for multi-beam exposure apparatuses.

  This DMD is a mirror device in which a large number of micromirrors whose reflecting surfaces change in response to a control signal, for example, are two-dimensionally arranged on a semiconductor substrate such as silicon, and the electrostatic force generated by charges stored in each memory cell. Thus, the angle of the reflection surface of the micromirror is changed.

  In such a multi-beam exposure apparatus using a DMD, for example, a laser beam emitted from a laser light source is collimated by a lens system, and the laser beam is emitted from a plurality of DMD micromirrors arranged at a substantially focal position of the lens system. Each beam emitted after being modulated two-dimensionally by reflecting the light is condensed for each pixel by a lens system to reduce the spot diameter on the exposure surface of a recording medium (lithographic printing plate) which is a photosensitive material. Then, an image is formed and image exposure is performed.

  That is, in this multi-beam exposure apparatus, each of the DMD micromirrors is controlled on / off by a control device (not shown) based on a control signal generated according to image data or the like to modulate (deflect) the laser beam. Then, exposure is performed by irradiating the exposure surface (recording surface) with the modulated laser beam.

  In this multi-beam exposure apparatus, a lithographic printing plate or the like is arranged on the recording surface, and a laser beam is irradiated onto each of the lithographic printing plate or the like from a plurality of exposure heads provided in the exposure apparatus, and the position of the beam spot imaged. The pattern exposure is performed on the flat printing plate or the like by modulating each DMD according to the image data while moving the plate relative to the flat printing plate or the like. Note that a recording medium such as a lithographic printing plate on which an image is exposed and recorded is subjected to an automatic developing machine as necessary, and a latent image formed on the recording medium such as a lithographic printing plate is converted into a visible image.

  Conventionally, a DMD used in such a multi-beam exposure apparatus is configured to arrange m rows in the scanning direction and n columns in a direction orthogonal to the scanning direction. Further, this DMD is arranged so that the row of pixels is inclined at a predetermined angle with respect to the scanning direction of the exposure head, and by performing multiple exposures N times at different times in the scanning direction, m / N-1 dots can be formed. As described above, it has been proposed to change the dot pitch and increase the resolution in the direction orthogonal to the scanning direction by adjusting the number of multiple exposures in the scanning direction (see, for example, Patent Document 1).

  However, in such a multi-beam exposure apparatus, when a row of DMD pixels is arranged so as to be inclined at a predetermined angle with respect to the scanning direction of the exposure head, and recording is performed by N times multiple exposure while shifting the time in the scanning direction. Then, exposure is performed a plurality of times by shifting the time with pixels inclined obliquely with respect to the main scanning line to form one dot on the lithographic printing plate. At this time, the position of each beam spot subjected to multiple exposure for recording one dot on the lithographic printing plate is shifted in the sub-scanning direction. For this reason, the exposure amount distribution in the recorded dots spreads in the sub-scanning direction, and the recorded dots have a so-called blurred shape in the sub-scanning direction.

  In addition, in a conventional multi-beam exposure apparatus that exposes an image to a lithographic printing plate, an AM screen (a method for forming a gray image by a halftone image) is used when a halftone is expressed by exposing the lithographic printing plate. In general, halftones are expressed in a net shape (so-called minimal checkered pattern). That is, in the AM screen, the halftone dot image of the minimum unit is composed of a relatively large number of dots, for example, a total of 196 dots of 14 (number of dots in the horizontal direction) × 14 (number of dots in the vertical direction). A grayscale image is recorded by recording point images in a two-dimensional plane. However, when halftones are expressed using this AM screen, moire fringes or tone jumps may occur.

  Further, as a technique for forming a grayscale image using a halftone dot image, there is a technique called FM screen (FM Screen). This FM screen expresses the density of a recorded image by a set density of irregular dots having no regularity. For example, an image composed of a relatively small number of dots such as 2 × 2 total 4 dots is displayed. Gradation is expressed by being distributed in a two-dimensional plane. This FM screen has the advantage that the generation of moire fringes can be suppressed in principle.

  Therefore, in a multi-beam exposure apparatus that performs image exposure on a recording medium such as a lithographic printing plate, it is desired to form a halftone with a small net shape using an FM screen.

  However, in a multi-beam exposure apparatus, when recording is performed by a system in which DMD pixel rows are arranged so as to be inclined at a predetermined angle with respect to the scanning direction of the exposure head and the time is shifted in the scanning direction and multiple exposure is performed N times. When multiple exposure is performed to record one dot on a recording medium such as a printing plate, the positions of a plurality of beam spots subjected to multiple exposure with respect to the same exposure point to be one dot are shifted in the sub-scanning direction and recorded. There is a case where the exposure amount distribution of the dots spread in the sub-scanning direction and one recorded dot becomes a so-called blurred shape in the sub-scanning direction.

One dot recorded in this way has a shape that is blurred in the sub-scanning direction, and the image when the FM screen is recorded by exposure in a state where the so-called edge cannot be kept sharp is recorded such as fluctuations in optical power and the number of printed sheets. If the circumference of the recording pixel changes even a little depending on the conditions and development conditions such as the degree of development of the automatic developing machine, the ratio of halftone images (halftone area ratio characteristic) is likely to change abruptly, and density fluctuations are likely to occur. For this reason, the conventional multi-beam exposure apparatus that arranges the rows of DMD pixels so as to be inclined at a predetermined angle with respect to the scanning direction of the exposure head and shifts the time in the scanning direction N times, uses an FM screen. There is a problem that it is difficult to do.
JP 2004-62156 A

  In the present invention, in view of the above-described problems, the number of dots (number of beam spots) that can be exposed at a time in the direction orthogonal to the scanning direction when performing exposure processing using a DMD or the like that is a two-dimensional optical modulator. And a multi-beam exposure apparatus capable of recording a stable halftone expression using an FM screen.

  The multi-beam exposure apparatus according to claim 1 of the present invention is projected onto the exposure surface of the recording medium in the multi-beam exposure apparatus that scans and exposes the exposure surface of the recording medium with a plurality of exposure beam spots. A two-dimensional light modulator arranged to align a plurality of two-dimensionally arranged exposure beam spots in parallel with the scanning direction, and a plurality of exposure beams emitted from the two-dimensional light modulator It is placed on the projection optical system that forms an image on the top, and the plurality of exposure beams are divided into a plurality of blocks with respect to the scanning direction, and the relative position between the blocks is shifted in a direction perpendicular to the scanning direction. By projecting onto the exposure surface, the position during exposure with the exposure beam spot adjacent in the direction orthogonal to the scanning direction projected onto the exposure surface by at least one block is changed to the other. A part of the pixel shift member that is exposed by the exposure beam spot projected onto the exposure surface by the block, and a part of the projection optical system that extends from the pixel shift member to the exposure surface, and the exposure beam is abnormal from the ordinary ray And an optical element of a uniaxial crystal provided so as to form a beam spot shape adjacent to each other so that the two beam spots are partially overlapped with each other by a substantially equal amount of light and are aligned in a direction orthogonal to the scanning direction. It is characterized by that.

  By configuring as described above, in this multi-beam exposure apparatus, the multi-beam emitted from the two-dimensional optical modulator is divided into a plurality of blocks in the scanning direction by a partial pixel shift member, and the blocks are scanned with each other. By shifting in a direction orthogonal to the direction and projecting onto the exposure surface, exposure is performed, and multiple exposure is performed for each row by each of a plurality of rows of exposure beam spots arranged in the scanning direction to be exposed in one block, and two-dimensionally. Thus, each dot can be recorded. Therefore, the position of each beam spot subjected to multiple exposure for recording each dot is accurately matched to prevent the spread of the exposure amount distribution in each dot, and the FM screen while keeping the edge of the recorded dot shape sharp. Can be recorded. In addition, the number of dots that can be exposed at one time (the number of beam spots) can be increased in the direction orthogonal to the scanning direction. For this reason, in this multi-beam exposure apparatus, for example, an enlargement optical system is used to enlarge the area of the exposure area when the beam spot is projected onto the exposure surface by the two-dimensional optical modulator, and the scanning process for the recording medium is performed. The efficiency of the exposure process can be improved by improving the speed. In this multi-beam exposure apparatus, for example, the exposure process is performed in a state where the pitch between adjacent beam spots is reduced in the direction orthogonal to the scanning direction when the beam spot is projected onto the exposure surface by the two-dimensional optical modulator. Thus, so-called resolution (positional resolution) can be improved. Further, when a plurality of light beams are transmitted through a uniaxial crystal optical element disposed on the optical path from a part of the pixel shift member to the exposure surface, each light beam is separated into an ordinary ray and an extraordinary ray. . The separated ordinary ray and extraordinary ray have the same intensity, and are separated, for example, in a direction orthogonal to the scanning direction (sub-scanning direction). The ordinary ray and the extraordinary ray separated in the sub-scanning direction with the same intensity are, for example, a beam spot having a substantially rectangular distribution in the condensing point on the recording medium, for example, in the sub-scanning direction and having a sharp edge. It is focused on. In this multi-beam exposure apparatus, the beam spot is divided into a substantially rectangular distribution and the beam spot having a sharp edge is exposed in a state where the longitudinal direction of the substantially rectangular distribution is along the scanning direction. Therefore, the intensity distribution of the beam spot on the recording medium is substantially rectangular in the sub-scanning direction, and the edges on both sides of the focal point are sharpened. The image unevenness in the sub-scanning direction is preferably suppressed. Therefore, the image when the FM screen is recorded has a halftone dot so that the circumference of the recording pixel does not fluctuate at all due to recording conditions such as light power fluctuation and the number of printed sheets, development conditions such as the degree of development of the automatic processor, and the like. It is possible to prevent the image ratio (halftone dot area ratio characteristic) from changing abruptly to make it difficult to cause density fluctuations, and to record halftones stably using an FM screen.

  According to a second aspect of the present invention, in the multi-beam exposure apparatus according to the first aspect, the partial pixel shift member is configured as an optical element using polarization of light, and the partial pixel shift member and the uniaxial crystal are formed. A polarization adjusting means is provided on a projection optical system between the optical element and the optical element so that an ordinary ray and an extraordinary ray are emitted from the optical element of the uniaxial crystal with the same amount of light.

  With the configuration described above, in addition to the operation and effect of the invention according to claim 1, the polarization direction is constant by passing through the uniaxial crystal optical element configured as an optical element utilizing the polarization of light. Are converted into a predetermined polarization state such as circularly polarized light by a polarization adjusting means such as a quarter-wave plate and then incident on the optical element of the uniaxial crystal. When the light beams are transmitted, each light beam is separated into an ordinary ray and an extraordinary ray shifted in the sub-scanning direction with equal intensity, and an appropriate exposure process can be performed.

  The multi-beam exposure apparatus of the present invention can increase the number of dots (number of beam spots) that can be exposed at a time in the direction orthogonal to the scanning direction when performing exposure processing using a two-dimensional optical modulator. Moreover, there is an effect that a stable halftone expression can be recorded using an FM screen.

  Embodiments relating to the multi-beam exposure apparatus of the present invention will be described with reference to FIGS.

  The image forming apparatus as the multi-beam exposure apparatus according to the embodiment of the present invention is not illustrated, but is configured as, for example, a so-called flatbed type image forming apparatus (setter) that is driven and controlled by a control unit. As shown, a recording medium 12 such as a lithographic printing plate (PS plate) is placed on a moving stage 10, and the moving head 10 controls the exposure head 14 while moving the recording medium 12 in the main scanning direction. The multi-beam emitted from the light source side is spatially modulated on the basis of the modulation signal generated from the image data by the unit, and the exposure process is performed by irradiating the exposure area 16 on the recording medium 12.

  The exposure area 16 by the exposure head 14 is configured in a rectangular shape having a short side in the feed direction (main scanning direction), for example. In this case, a strip-shaped exposed region 18 is formed on the recording medium 12 in accordance with the scanning exposure moving operation. In the image forming apparatus (setter), a plurality of exposure heads 14 are arranged in a substantially matrix form of m rows and n columns (for example, 2 rows and 4 columns), and a plurality of (for example, 8) exposure heads 14 are simultaneously used. You may comprise so that an exposure process may be performed.

  As shown in FIG. 1, this exposure head 14 uses a digital micromirror device as a spatial light modulator (two-dimensional light modulator) that modulates an incident light beam for each pixel in accordance with image data. (DMD) 20 is provided. The DMD 20 which is a two-dimensional optical modulator is driven and controlled by a control unit (control means) 22 having data processing means and mirror drive control means.

  The data processing unit of the control unit 22 controls driving of the micromirrors in the region to be controlled by the DMD 20 to the exposure head 14 based on the input image data (control of the angle of each micromirror reflecting surface). Control signal is generated.

  Connected to the light incident side of the DMD 20 in the exposure head 14 are bundle optical fibers 28 each drawn from a light source unit 24 that is an illumination device that emits multi-beams as laser light.

  The light source unit 24 is provided with a plurality of multiplexing modules 26 that combine laser beams such as ultraviolet rays emitted from a plurality of semiconductor laser chips and input them to an optical fiber. The optical fiber extending from each multiplexing module 26 is a multiplexing optical fiber that propagates the combined laser beam, and a plurality of optical fibers are bundled into one to form a bundle-shaped optical fiber (fiber bundle) 28. The laser beam is configured to improve the intensity of the emitted laser beam.

  On the light incident side of the DMD 20 in the exposure head 14, there is provided a mirror 32 that reflects the laser light emitted from the connection end of the bundle optical fiber 28 toward the DMD 20 through an optical lens having a rod lens or the like. Arrange the illumination optical system.

  As shown in FIG. 10, the DMD 20 is entirely monolithic as a mirror device in which a plurality of micromirrors 36 (for example, 600 × 800) constituting a pixel (pixel) are arranged in a lattice pattern. (Integrated type).

  A material having high reflectivity such as aluminum is deposited on the surface of the micromirror 36 disposed at the top of each pixel. In addition, a column 34 projects from the center of the lower surface of each micromirror 36.

  This DMD 20 is provided with a pillar 34 projecting from a micromirror 36 on a hinge 40 provided on a silicon gate CMOS SRAM cell 38 which is manufactured in a normal semiconductor memory manufacturing line corresponding to each pixel. And the micromirror 36 is mounted so as to be tiltable by ± a degrees (± 10 degrees) in the diagonal direction about the hinge 40 as an axis.

  Further, in this DMD 20, static electricity due to charges accumulated on one side or the other side of each of the mirror address electrodes 42 respectively formed at both ends in the diagonal direction in which the micromirrors 36 on the SRAM cell 38 are inclined. Utilizing force, the micromirror 36 is configured to be driven and controlled to be in a state tilted to + a degrees when the micromirror 36 is in an on state or in a state tilted to -a degrees when the micromirror 36 is in an off state.

  In the DMD 20 configured as described above, when a digital signal is written to the SRAM cell 38, the micromirrors 36 in the respective pixels of the DMD 20 correspond to the substrate side on which the DMD 20 is disposed with the diagonal line as the center in accordance with the image signal. Thus, the light is incident on the DMD 20 and is reflected in the tilt direction of each micromirror 36.

  The light reflected by the on-state micromirror 36 is modulated into an exposure state and enters a projection optical system (see FIG. 1) provided on the light exit side of the DMD 20. The light reflected by the micromirror 36 in the off state is modulated into a non-exposure state and enters a light absorber (not shown).

  Next, a projection optical system (imaging optical system) provided on the light reflection side of the DMD 20 in the exposure head 14 will be described. As shown in FIG. 1, the projection optical system (imaging optical system) provided on the light reflection side of the DMD 20 in the exposure head 14 forms a light source image on the recording medium 12 on the exposure surface on the light reflection side of the DMD 20. Therefore, in order from the DMD 20 toward the recording medium 12, the first imaging optical lens systems 44 and 46, a microlens array 48 that is an intermediate imaging unit, and a rear vicinity on the optical path from the microlens array 48 A partial pixel shift member 50 disposed at a position, a uniaxial crystal optical element 55 disposed at a position near the rear of the partial pixel shift member 50 on the optical path, second imaging optical lens systems 52, 54, and The optical member for each exposure with the prism pair 56 for autofocus is arrange | positioned and comprised.

  Note that the first imaging optical lens systems 44 and 46 and the second imaging optical lens systems 52 and 54 in the projection optical system are each shown as one lens in FIG. A lens (for example, a convex lens and a concave lens) may be combined.

  In the projection optical system of the exposure head 14, the first imaging optical lens systems 44 and 46, the second imaging optical lens systems 52 and 54, and other lens systems not shown are configured so as to be conjugate with each other. Has been.

  In the projection optical system of the exposure head 14, each micromirror 36 of the DMD 20 is disposed at the front focal position of the lens system 44. Further, the first imaging optical lens systems 44 and 46 are arranged at confocal positions that share the rear focal position and the front focal position, respectively. The microlens array 48 is disposed at the rear focal position of the lens system 46. A microlens array 48 that is an intermediate image forming unit used here includes a plurality of microlenses that correspond one-to-one to each micromirror 36 of the DMD 20 that reflects the laser light emitted from the light source unit 24 through the optical fiber 28. Each microlens is disposed on the optical axis of each laser beam that has passed through the first imaging optical lens systems 44 and 46, respectively. The microlens provided in the microlens array 48 has a positive lens power and has a function of reducing the beam diameter of the laser beam. Each micromirror 36 and microlens array 48 are conjugated with each other.

  In the projection optical system of the exposure head 14, for example, as shown in FIG. 1, the back focal position of the micromirror 36 in the microlens array 48 at the rear focal position of the lens system 46 (the second imaging optical lens system 52). A partial pixel shift member 50 (for increasing the number of channels) is disposed at the front focal position), and further, on the optical path between the partial pixel shift member 50 and the second imaging optical lens systems 52 and 54, A uniaxial crystal optical element 55 (for beam splitting) is arranged.

  The partial pixel shift member 50 used in the exposure head 14 of this image forming apparatus has the number of dots that can be exposed at one time in the direction orthogonal to the scanning direction (beam spot number) when performing exposure processing using the DMD 20. This is an optical member for increasing the number of channels, which is a number) by effectively utilizing the vertical pixels of the DMD 20 and recording a stable halftone expression using an FM screen.

  The partial pixel shift member 50 has a plurality of exposure beam spots projected onto the exposure surface (the surface of the recording medium 12) from a group of micromirrors 36 arranged in a two-dimensional grid of M rows and N columns in the DMD 20. Are divided into a plurality of blocks with respect to the scanning direction (main scanning direction which is the feed direction) on the exposure surface, and the relative positions between these blocks are orthogonal to the scanning direction (main scanning direction) ( The DMD 20 is used so that the gap in the feed direction at the position of the plurality of exposure beam spots exposed in one block is exposed with the plurality of exposure beam spots in the other block. During the exposure process, the number of dots that can be exposed at one time (the number of channels that is the number of beam spots) is increased in the direction orthogonal to the scanning direction.

  Note that the number of dots that can be exposed at one time (by dividing the position of the exposure beam spot projected onto the exposure surface from the exposure head 14 into a plurality of blocks on the exposure surface in a direction orthogonal to the scanning direction ( The increase rate of the number of dots that can be exposed when increasing the number of beam spots (the number of beam spots) is divided into blocks and shifted so that the exposure positions of the blocks do not overlap each other (for example, at equal intervals). Since it is proportional to the number of divisions of the shifted block, the increase rate of the required number of dots that can be exposed (the number of channels that is the number of beam spots) is selected by appropriately adjusting the number of divisions and the shift amount. Can be set.

  The partial pixel shift member 50 can be configured as an optical element using light refraction, an optical element using light diffraction, or an optical element using light polarization.

  When the partial pixel shift member 50 is configured as an optical element using refraction of light, for example, the partial pixel shift member 50 is configured as shown in FIGS. 2, 3, and 7. A plurality of optical materials such as optical glass formed on a planar member having the same thickness (three in the partial pixel shift member 50 shown in FIGS. 2, 3 and 7) May be used). That is, as shown in FIG. 2, the partial pixel shift member 50 moves the first optical member 50A, the second optical member 50B, and the third optical member 50C in the scanning direction (feeding direction) on the optical path. ), The second optical member 50B is arranged so as to be orthogonal to the optical axis, and the first optical member 50A is inclined at a predetermined angle with respect to the optical axis. The third optical member 50C is disposed at a predetermined angle with respect to the other optical axis. In other words, the partial pixel shift member 50 is provided with the first optical member 50A for refraction, the second optical member 50B, and the third optical member 50C at positions located on the upper, middle, and lower stages on the optical path. The upper and lower first optical members 50A and the third optical member 50C are installed in a state (shown in FIG. 3) rotated by a predetermined angle about the scanning direction.

  Further, the second optical member 50B has a length (distance between the first optical member 50A and the third optical member 50C) with respect to the scanning direction (feeding direction) of the DMD 20 at the position where the partial pixel shift member 50 is disposed. The optical path width corresponding to the scanning direction (feeding direction) of the optical path from all the micromirrors 36 to the exposure surface (the surface of the recording medium 12) is set to a length equal to three. Further, the second optical member 50B has an optical path whose central position in the scanning direction corresponds to the scanning direction of the optical path from all the micromirrors 36 of the DMD 20 to the exposure surface at the position where the partial pixel shift member 50 is disposed. Arrange to match the center of the width.

  With this arrangement and configuration, the partial pixel shift member 50 divides the group of micromirrors 36 two-dimensionally arranged in the DMD 20 into three equal parts in the scanning direction on the exposure surface (the beam in the scanning direction). It is possible to set three blocks G1, G2, and G3 that are equally divided as illustrated in FIG.

  Further, in the partial pixel shift member 50 configured as an optical element using light refraction, the angle at which the first optical member 50A is inclined to the one side with respect to the optical axis is appropriately adjusted and set as shown in FIG. As shown, the multi-beam of laser light is refracted so that the beam spot group BS1 of the first block G1 is arranged adjacent to each other in the direction orthogonal to the scanning direction of the beam spot group BS2 in the second block G2. It is configured to shift to one side by a distance of 1/3 (for example, 1/3 pitch shift to the left in FIG. 2).

  Further, in this partial pixel shift member 50, the multi-beam of laser light is refracted as shown in FIG. 3 by appropriately adjusting and setting the angle at which the third optical member 50C is inclined to the other with respect to the optical axis. Then, the beam spot group BS3 of the third block G3 is shifted to the other side by a distance of 1/3 between each other arranged adjacent to each other in the direction orthogonal to the scanning direction of the beam spot group BS2 in the second block G2. For example, it is configured to shift 1/3 pitch to the right as viewed in FIG.

  By disposing the partial pixel shift member 50 in this way, the exposure head 14 of this image forming apparatus is configured so that the beam spots BS2 in the second block G2 are adjacent to each other with respect to the direction orthogonal to the scanning direction. Furthermore, the exposure processing can be performed in a state where the beam spots BS1 of the first block G1 and the beam spots BS3 of the third block G3 are arranged at equal intervals. Therefore, in the exposure head 14 in which the partial pixel shift member 50 is arranged and configured as described above, as a result of performing scanning exposure on the exposure surface as shown in FIG. 8, once with respect to a position on a straight line in a direction orthogonal to the scanning direction. The number of dots that can be exposed to (number of channels, which is the number of beam spots) is increased by a factor of three (the pitch between adjacent beam spots has been reduced to ３, so-called resolution (positional resolution) has been improved by a factor of three. State).

  In the exposure head 14 that sets the three blocks G1, G2, and G3 that are mutually shifted by the partial pixel shift member 50, the second imaging optical lens systems 52 and 54 are configured as, for example, an enlargement optical system, By enlarging the cross-sectional area of the light beam reflected by the DMD 20, the area of the exposure area 16 (shown in FIG. 11) by the light beam reflected by the DMD 20 on the recording medium 12 is latticed. It is configured to expand to three times the area of the light reflecting surface arranged in a shape.

  Note that when the second imaging optical lens systems 52 and 54 are configured as magnifying optical systems, an image is formed on the exposure surface of the recording medium 12 using, for example, the microlens array 48 or other optical members. Each beam spot may be condensed so as to be reduced in size so as to have a predetermined beam spot diameter.

  Further, in the exposure head 14, the light beam projected from the second imaging optical lens system 52, 54 is focused on the recording medium 12 placed on the exposure surface by the autofocus function of the prism pair 56. To form an image.

  When the exposure head 14 is configured as described above, scanning is performed once in the direction orthogonal to the scanning direction on the exposure surface of the recording medium 12 under the condition that the feed speed in the scanning direction is the same. Comparison in the case where scanning exposure is performed with only a predetermined number of micromirrors 36 arranged in a direction orthogonal to the scanning direction of DMD 20 shown in FIG. 9 (when DMD 20 is tilted in the scanning direction and exposure processing is not performed). Can be 3 times the example.

  Therefore, when performing exposure processing on the entire exposed surface of the recording medium 12 while reciprocating the recording medium 12 in the scanning direction using the same number of exposure heads 14, the scanning processing speed (the same number of exposures). The efficiency of the exposure process can be improved by using the head 14 to improve the speed from the start to the completion of the exposure process for one recording medium 12.

  Further, in the exposure head 14 for setting a plurality of (here, three) blocks G1, G2, and G3 that are mutually shifted by the partial pixel shift member 50, the second imaging optical lens systems 52 and 54 are shifted. It is configured as an optical system having an enlargement ratio less than the number of blocks (here, an enlargement ratio less than 3 times), and is scanned only by a predetermined number of micromirrors 36 arranged in a direction perpendicular to the scan direction of the DMD 20 shown in FIG. Compared to the case of exposure processing in the comparative example in the case of exposure, the pitch between adjacent beam spots in the direction orthogonal to the scanning direction may be reduced to improve the so-called resolution (positional resolution). Of course.

  In the exposure head 14 for setting a plurality of (here, three) blocks G1, G2, and G3 that are mutually shifted by the partial pixel shift member 50, the three blocks G1 and G2 are formed on the exposure surface of the recording medium 12. , It is impossible to perform exposure processing by clearly distinguishing the pixels at the boundary of G3 (exposure processing by clearly separating pixels at the boundary of the three blocks G1, G2, and G3). , Crosstalk may occur between pixels at the boundary of G3. In such a case, in order to reduce the crosstalk, it is possible to cope with not using the pixel on the DMD 20 that hits the boundary.

  The partial pixel shift member 50 is configured to be divided into two blocks and shifted by a combination of the first optical member 50A or the third optical member 50C and the second optical member 50B, or the partial pixel shift. The member 50 may be configured to be divided into two blocks and shifted by a combination of the first optical member 50A and the third optical member 50C.

  Next, the partial pixel shift member 50 described above may be configured as an optical element using light diffraction. As an element utilizing light diffraction, there are a hologram and a binary optical element blazed. Here, a configuration example using a binary optical element will be described with reference to FIGS.

  The partial pixel shift member 50 configured as an optical element using light diffraction shown in FIG. 4 is a single flat plate made of optical glass or the like formed on a transparent flat member having the same thickness. It is divided into three areas (parts) of an upper stage, a middle stage, and a lower stage with respect to the scanning direction).

  The second transmission unit 50E is configured to transmit a light beam along a straight optical path, and has a length (between the first diffraction unit 50D and the third diffraction unit 50F) with respect to the scanning direction (feed direction). The optical path width corresponding to the scanning direction (feeding direction) of the optical path from all the micromirrors 36 of the DMD 20 at the arrangement position of the partial pixel shift member 50 to the exposure surface (the surface of the recording medium 12). Set the length to Further, the second transmission portion 50E has an optical path whose central position in the scanning direction corresponds to the scanning direction of the optical path from all the micromirrors 36 of the DMD 20 to the exposure surface at the position where the partial pixel shift member 50 is disposed. Arrange to match the center of the width.

  With this arrangement and configuration, the partial pixel shift member 50 divides the group of micromirrors 36 two-dimensionally arranged in the DMD 20 into three equal parts in the scanning direction on the exposure surface (the beam in the scanning direction). It is possible to set three blocks G1, G2, and G3 that are equally divided as illustrated in FIG.

  In the partial pixel shift member 50 configured as an optical element using this light diffraction, the front and back surfaces of the first diffractive portion 50D diffract the light beam in the direction orthogonal to the scanning direction as shown in FIG. On the other hand, the first BOE (binary optics element) 51 is provided which has an effect of shifting the beam spot by a predetermined amount.

  Further, a second BOE (binary optics element) that acts to diffract the light beam on the front and back surfaces of the third diffractive portion 50F and shift the beam spot by a predetermined amount in the other direction orthogonal to the scanning direction as shown in FIG. ) 53.

  The first BOE 51 and the second BOE 53 are processed and formed as commonly used binary optics elements. For example, the first diffractive portion in the plate-shaped optical glass that partially forms the entire pixel shift member 50 is used. The front and back both surface portions of the 50D and the third diffractive portion 50F are formed by processing inclined surfaces that are fine in sectional view (actually, a so-called etching process is repeated to form a fine step-like inclination in the recesses). be able to.

  The first BOE 51 and the second BOE 53 are finely extending linearly from one end to the other end in the direction orthogonal to the scanning direction on both the front and back surfaces of the first diffractive part 50D and the third diffractive part 50F. It is configured as an inclined surface having a substantially triangular cross section. In the first BOE 51 and the second BOE 53, the height of the fine substantially sectional triangle (height of the step) is n, the refractive index of the diffractive member, the refractive index of air, the light wavelength λ, and the number of steps. When N, it is formed to be an integral multiple of the following formula.

  formula

これら第１ＢＯＥ５１と、第２ＢＯＥ５３とは、理論的に、それぞれの凹部内の傾斜に形成された微細な階段部分の段数（レベル）が８レベルの傾斜面の場合に、第１ＢＯＥ５１と、第２ＢＯＥ５３とで所定の方向に回折される光の割合が約９５％となり、１６レベルの傾斜面の場合に約９８．７％，３２レベルで９９．５％となる。従って、第１ＢＯＥ５１と、第２ＢＯＥ５３とは、露光面上での迷光限界に応じて１６レベルあるいは３２レベル程度に加工することで、十分実用に耐え得るものとなる。

In theory, the first BOE 51 and the second BOE 53 are the first BOE 51, the second BOE 53, Thus, the ratio of light diffracted in a predetermined direction is about 95%, about 98.7% in the case of a 16-level inclined surface, and 99.5% in 32 levels. Therefore, the first BOE 51 and the second BOE 53 can be sufficiently put into practical use by processing them at 16 levels or 32 levels according to the stray light limit on the exposure surface.

  Further, the first diffractive portion 50D provided with the first BOE 51 and the third diffractive portion 50F provided with the second BOE 53 can be understood by comparing FIGS. 5 and 6 with the binary optics element. The direction of inclination is reversed, and the direction in which the light beam is diffracted by the first BOE 51 to shift the position of the beam spot, and the direction in which the light beam is diffracted by the second BOE 53 to shift the position of the beam spot. It is configured to be in the reverse direction.

  Furthermore, the first diffractive portion 50D provided with the first BOE 51 and the third diffractive portion 50F provided with the second BOE 53 are irradiated with beams on the exposure surface of the recording medium 12 by changing and adjusting the respective thicknesses. The shift amount of the spot position can be set to a predetermined amount.

  In addition, when the partial pixel shift member 50 provided in the exposure head 14 of the multi-beam exposure apparatus is configured as an optical element using light diffraction, the partial pixel shift member 50 described above uses light refraction. Functions and effects similar to those of the optical element can be obtained.

  Further, the partial pixel shift member 50 is configured to be divided and shifted into two blocks by a combination of the first diffractive part 50D or the third diffractive part 50F and the second transmissive part 50E, or a partial pixel shift. The member 50 may be configured to be divided into two blocks and shifted by a combination of the first diffractive part 50D and the third diffractive part 50F.

  Next, a configuration example in which the partial pixel shift member 50 described above is configured as an optical element using polarization of light will be described with reference to FIG.

  The partial pixel shift member 50 configured as an optical element using the polarization of light shown in FIG. 7 is formed on a transparent flat plate having the same thickness, and has an upper stage, a middle stage, and a scanning direction (main scanning direction). The upper stage divided into the lower three areas (parts) is the first polarizing section 50G, the middle stage is the second transmitting section 50H, and the lower stage is the third polarizing section 50I.

  The second transmission unit 50H is configured to transmit the light beam through a straight optical path, and has a length with respect to the scanning direction (feed direction) (distance between the first polarization unit 50G and the third polarization unit 50I). Is a length obtained by equally dividing the optical path width corresponding to the scanning direction (feeding direction) of the optical path from all the micromirrors 36 of the DMD 20 at the arrangement position of the partial pixel shift member 50 to the exposure surface (the surface of the recording medium 12). Set to Further, the second transmission portion 50H has an optical path whose center position in the scanning direction corresponds to the scanning direction of the optical path from all the micromirrors 36 of the DMD 20 at the arrangement position of the partial pixel shift member 50 to the exposure surface. Arrange to match the center of the width.

  With this arrangement and configuration, the partial pixel shift member 50 divides the group of micromirrors 36 two-dimensionally arranged in the DMD 20 into three equal parts in the scanning direction on the exposure surface (the beam in the scanning direction). It is possible to set three blocks G1, G2, and G3 that are equally divided as illustrated in FIG.

  Hereinafter, a case where light having polarized light parallel to the shift direction partially enters the pixel shift member will be considered.

  In the partial pixel shift member 50 configured as an optical element using the polarization of the light, the first polarization unit 50G is formed by a generally used beam display sensor, and a light beam (light beam) is formed on the beam display sensor. ) Is shifted to one of the directions orthogonal to the scanning direction. The beam displacer is configured such that the crystal optical axis is inclined by 45 ° in the direction of shifting the beam with respect to the incident surface normal.

  In addition, the third polarizing section 50I is formed by a generally used beam displacer, and the emission direction of the extraordinary ray generated by transmitting the ray (light beam) to the beam displacer is a direction orthogonal to the scanning direction. It is comprised so that there exists an effect | action which shifts to the other of these. That is, the light beam is polarized by the first polarizing unit 50G and the position of the beam spot projected on the exposure surface is shifted, and the light beam is polarized by the third polarizing unit 50I and projected on the exposure surface. The beam spot position is shifted in the opposite direction. Further, the first polarizing unit 50G and the third polarizing unit 50I change and adjust the thicknesses of the first polarizing unit 50G and the third polarizing unit 50I so that the shift amount of the position of the beam spot projected on the exposure surface of the recording medium 12 is set to a predetermined amount. Can be set.

  Various methods are conceivable as a method for making the polarization direction of the light parallel to the shift direction. For example, the polarizing plate member 58 may be installed before entering the pixel shift member 50 partially. .

  Note that the partial pixel shift member 50 provided in the exposure head 14 of the multi-beam exposure apparatus is configured as an optical element using polarization of light, and the partial pixel shift member 50 described above utilizes refraction of light. Functions and effects similar to those of the optical element can be obtained.

  Further, the partial pixel shift member 50 is configured to be divided into two blocks and shifted by a combination of the first polarizing unit 50G or the third polarizing unit 50I and the second transmission unit 50H, or the partial pixel shift The member 50 may be configured to be divided into two blocks and shifted by a combination of the first polarizing unit 50G and the third polarizing unit 50I.

  Further, in the exposure head 14 of this multi-beam exposure apparatus, the shape of the beam spot projected on the exposure surface is made rectangular, so that an FM screen can be formed satisfactorily. The recording surface is scanned.

  For this reason, the uniaxial crystal optical element 55 is disposed in the exposure head 14 at a position between the partial pixel shift member 50 and the second imaging optical lens systems 52 and 54 on the optical path of the imaging optical system. Set up. In this exposure head 14, various types of optical elements 55 of a uniaxial crystal are used, for example, those using an angle division method such as a Rohon or Wollaston prism, or those using a parallel division method such as a beam display prism. You may comprise. Here, as the optical element 55 of the uniaxial crystal, a beam displacer in which the crystal optical axis is inclined by 45 degrees with respect to the incident surface and the normal line is used.

  When a circularly polarized light beam (which may be a randomly polarized light beam) is incident on the uniaxial crystal optical element 55, the light beam is equal in intensity to an ordinary ray Po and an extraordinary ray Pe as shown in FIG. To separate. In this case, the ordinary ray Po and the extraordinary ray Pe are shifted in parallel with each other. For example, when the optical element 55 of the uniaxial crystal has a light wavelength of 405 nm and the shift amount (division width) is set to 5.5 μm, quartz is used as the material of the optical element 55 of the uniaxial crystal, and the thickness thereof. Is about 0.904 mm. The crystal used as the material of the uniaxial crystal optical element 55 is advantageous in that it is stable in material and low in cost, and can cope with a circle having a diameter of 30 mm. The refraction angle of the extraordinary ray Pe can be arbitrarily adjusted by the thickness and material of the optical element 55 of the uniaxial crystal with respect to the optical axis direction.

  In this way, when a light beam is separated into an ordinary ray Po and an extraordinary ray Pe with equal amounts of light and parallel-shifted (an angle division method may be used) to form a beam spot shape that overlaps two (so-called beam division) 13), for example, as shown in FIG. 13, two Gaussian beams having a half width of 5 μm are shifted by 5.5 μm and are superposed (divided into two beams), and in the sub-scanning direction. On the other hand, it becomes a state closer to a rectangular shape, and also becomes sharp in the main scanning direction (the edge portion of the beam spot becomes steep).

  Compared with the comparative example of FIG. 14 which shows a case where the half-value width is 8.8 μm (1 / e2 width 15 μm) which is a Gaussian beam spot shape generally used in the past, this is a Gaussian beam spot beam which is generally used in the past. The shape is circular in cross section and does not extend in the sub-scanning direction, and the beam spot shape gently spreads out, so that it is gentle in the main scanning direction (the edge of the beam spot is in a gentle state). From this, the difference in effect is clear.

  In the exposure head 14 of this multi-beam exposure apparatus, the plane (see FIG. 12) including the crystal optical axis and the normal line in the optical element 55 of the uniaxial crystal corresponds to the direction orthogonal to the scanning direction on the exposure surface. By disposing the uniaxial crystal optical element 55, two beam spots are superposed in a direction orthogonal to the scanning direction (sub scanning direction) (sub scanning is performed adjacent to each other so that the two beam spots partially overlap). (A state of being aligned in the direction). Further, in this exposure head 14, since the spot shape of the exposure beam spot is narrowed down in the scanning direction to obtain a pseudo rectangular shape, a direction orthogonal to the scanning direction in which one dot is formed on the recording medium 12 ( The edge portion of the exposure amount distribution in the sub-scanning direction can be sharpened, and the edge of the exposure amount distribution after scanning in the scanning direction can also be sharpened.

  Further, in this exposure head 14, in order to perform beam splitting during the exposure process, a means using refraction or a means using diffraction may be used in addition to the uniaxial crystal optical element 55. Further, in this exposure head 14, the uniaxial crystal optical element 55 may be disposed closer to the recording medium 12 than the second imaging optical lens systems 52 and 54.

  In the exposure head 14, when the partial pixel shift member 50 shown in FIG. 7 is configured as an optical element using the polarization of light, the polarization direction of the light beam that has passed through the partial pixel shift member 50. 1 is only linearly polarized light that generates an extraordinary ray, and as shown by an imaginary line in FIG. 1, the optical element 55 of the uniaxial crystal on the optical path is on the front side (partially on the rear side of the pixel shift member 50). For example, a quarter-wave plate 57 is disposed as a polarization adjusting unit, and a laser beam composed of linearly polarized light that has been transmitted through a part of the pixel shift member 50 using the polarization of light is transmitted through the quarter-wave plate 57. To be converted into circularly polarized light. In the exposure head 14, the polarization direction is adjusted using a half-wave plate instead of the quarter-wave plate 57 as a polarization adjusting unit, and then incident on the uniaxial crystal optical element 55. The ordinary light Po and the extraordinary light Pe may be emitted from the uniaxial crystal optical element 55 with the same amount of light. Further, in the exposure head 14, as polarization adjusting means, means for randomly polarizing a part of the pixel shift member 50 on the rear side in the optical path is provided so that the randomly polarized light beam is incident on the optical element 55 of the uniaxial crystal. You may comprise.

  Next, operations and effects when the exposure head 14 configured as described above performs exposure processing on the recording medium 12 will be described.

  In the exposure head 14, the arrangement of the grid-like arrangement of the micromirrors 36 (shown in FIG. 10) is aligned with the scanning direction and the direction orthogonal to the scanning direction. The group of micromirrors 36 arranged in the same manner is divided into three on the exposure surface with respect to the scanning direction, and three blocks G1, G2, and G3 that are equally divided as shown in FIG. Each beam spot is formed in a rectangular shape by an optical element 55 made of a crystalline crystal and exposed to the recording medium 12.

  Therefore, the exposure head 14 performs multiple exposure with the three beam spot groups BS1 belonging to the block G1, for example, when exposing a first exposure point position arranged in a direction orthogonal to the scanning direction. Further, when exposing the second exposure point position adjacent to the first exposure point position (position on the right side in FIG. 8), multiple exposure is performed with the three beam spot groups BS2 belonging to the block G2. To do. Further, when exposing a third exposure point position adjacent to the second exposure point position (position on the right side in FIG. 8), multiple exposure is performed with the three beam spot groups BS3 belonging to the block G3. . A plurality of predetermined exposure points arranged in the direction orthogonal to the scanning direction in this way are selected and subjected to multiple exposure, and the recording medium 12 is moved in the scanning direction to thereby adjust the exposure range of the recording medium 12. An exposure process is performed on the whole.

  Therefore, when the above-described grid-like arrangement of the group of micromirrors 36 is arranged so as to coincide with the scanning direction and exposure processing is performed on the recording medium 12 by the exposure head 14 provided with a partial pixel shift member 50, the main scanning line. Thus, exposure is performed a plurality of times while shifting the time at the pixels arranged along the line to form one dot on the recording medium 12. At this time, since one dot is recorded on the recording medium 12, the position of each beam spot subjected to multiple exposure can be accurately matched, so that the exposure amount distribution in one recorded dot does not spread, and the recorded dot The edge of the shape can be kept sharp.

  Combined with this, in this exposure head 14, as shown in FIG. 8, each beam spot on the recording surface of the recording medium 12 is caused by the action of the optical element 55 of a uniaxial crystal, so that each light beam has an equal amount of light. Two beam spots are overlapped in the direction perpendicular to the scanning direction (sub-scanning direction) on the exposure surface, and are separated from each other in parallel, and the distribution of the rectangular shape in the sub-scanning direction at the condensing point on the recording medium 12 It becomes. Therefore, in this exposure head 14, the beam is split into a substantially rectangular distribution, and the beam spot whose edge portion is steep has the longitudinal direction of the substantially rectangular distribution in the main scanning direction (sub-scanning direction). Since the exposure process is performed in a state along the (perpendicular direction), the image when the FM screen is recorded depends on the recording conditions such as the light power fluctuation and the number of prints, the development conditions such as the degree of development of the automatic processor, etc. The halftone image ratio (halftone dot area ratio characteristic) is prevented from changing abruptly so that the perimeter does not change at all, making it difficult for density fluctuations to occur, and a halftone is stably expressed using an FM screen. Can be recorded.

  Next, the operation of the multi-beam exposure apparatus configured as described above will be described.

  In this multi-beam exposure apparatus, image data corresponding to the exposure pattern is input to the control unit 22 connected to the DMD 20 and temporarily stored in a memory in the control unit 22. This image data is data representing the density of each pixel constituting the image by binary values (whether or not dots are recorded).

  The recording medium 12 is moved after the exposure head performs one scan from the upstream side to the downstream side in the scanning direction while being attracted to the surface of the moving stage (not shown) (the moving stage is stopped during scanning). When the recording medium 12 on the moving stage passes under the exposure head 14, the image data stored in the memory is sequentially read out for each of a plurality of lines, and the read image data is read by a control device as a data processing unit. The two-dimensional arrangement of the exposure beam spot is divided into a plurality of blocks and shifted to each other by a predetermined distance in the direction orthogonal to the scanning direction, and the two exposure beam spots overlap, A control signal (control data) corresponding to the fact that the light distribution point on the recording medium 12 has a substantially rectangular distribution in the sub-scanning direction is generated.

  Based on the generated control signal, each of the micromirrors of the DMD 20 installed in the exposure head 14 is on / off controlled. When the control unit 22 is irradiated with laser light from the light source unit 24, each light beam reflected when the micromirrors of the DMD 20 are in the ON state has a substantially rectangular distribution at the corresponding required exposure beam spot position. Imaged and exposed.

  As shown in FIG. 11, the recording medium 12 is two-dimensionally exposed by the exposure head 14 by repeatedly moving the exposure head together with the moving stage after the exposure head performs one scan.

  In the multi-beam exposure apparatus according to the present embodiment, the DMD is used as the spatial light modulation element used in the exposure head 14. For example, a micro light mechanical modulation element (SLM) special light is used. A spatial light modulator other than the MEMS type, such as a modulator, an optical element (PLZT element) that modulates transmitted light by an electro-optic effect, or a liquid crystal light shutter (FLC) can be used instead of the DMD.

  In addition to the spatial light modulation element that takes only the on / off state, a spatial light modulation element that takes a plurality of intermediate values and can express gradation in addition to the on / off state may be used.

  Note that MEMS is a general term for a micro system that integrates micro-size sensors, actuators, and control circuits based on a micro-machining technology based on an IC manufacturing process. It means a spatial light modulator driven by electromechanical operation using

  In the multi-beam exposure apparatus according to this embodiment, the DMD 20 that is a two-dimensional light modulator used in the exposure head 14 may be replaced with a unit that selectively turns on / off a plurality of pixels. In other words, in the present specification, a two-dimensional optical modulator includes means for selectively turning on / off a plurality of pixels. The means for selectively turning on / off the plurality of pixels includes, for example, a laser light source that can selectively emit on / off a laser beam corresponding to each pixel, or each minute laser emission surface. Is arranged corresponding to each pixel to form a surface-emitting laser element, and each micro-laser light-emitting surface can be selectively turned on / off so as to be able to emit light.

  The multi-beam exposure apparatus according to the present invention is not limited to the above-described embodiment, but may be configured as a PS plate exposure setter. Various other configurations can be used without departing from the scope.

It is a schematic block diagram which shows the exposure head part of the multi-beam exposure apparatus based on Embodiment regarding the multi-beam exposure apparatus of this invention. It is a schematic structure perspective view which takes out and shows the one part pixel shift member using the refraction of the light used for the exposure head of a multi-beam exposure apparatus based on embodiment regarding the multi-beam exposure apparatus of this invention. It is a schematic explanatory drawing which shows the effect | action of the partial pixel shift member using the refraction | bending of the light used for the exposure head of the multi-beam exposure apparatus based on Embodiment regarding the multi-beam exposure apparatus of this invention. It is a schematic structure perspective view which takes out and shows the one part pixel shift member using the diffraction of the light used for the exposure head of the multi-beam exposure apparatus based on Embodiment regarding the multi-beam exposure apparatus of this invention. It is a schematic explanatory drawing which shows the effect | action of the 1st diffraction part in the partial pixel shift member using the diffraction of the light used for the exposure head of a multi-beam exposure apparatus based on embodiment regarding the multi-beam exposure apparatus of this invention. It is a schematic explanatory drawing which shows the effect | action of the 3rd diffraction part in the partial pixel shift member using the diffraction of the light used for the exposure head of a multi-beam exposure apparatus based on embodiment regarding the multi-beam exposure apparatus of this invention. It is a schematic structure perspective view which takes out and shows the one part pixel shift member using the polarization of the light used for the exposure head of a multi-beam exposure apparatus based on embodiment regarding the multi-beam exposure apparatus of this invention. It is a schematic explanatory drawing which shows the state which superimposes an exposure beam spot and exposes as a substantially rectangular distribution with the exposure head of the multi-beam exposure apparatus which concerns on embodiment regarding the multi-beam exposure apparatus of this invention. Schematic showing a comparative example of the state of a beam spot projected on an exposure surface for comparatively explaining the effect when exposure is performed by the exposure head of the multi-beam exposure apparatus according to the embodiment of the multi-beam exposure apparatus of the present invention. It is explanatory drawing. It is a perspective view which shows schematic structure of DMD used for the exposure head of the multi-beam exposure apparatus based on Embodiment regarding the multi-beam exposure apparatus of this invention. It is a perspective view of the principal part which shows the state which is performing the exposure process with the exposure head of the multi-beam exposure apparatus based on Embodiment regarding the multi-beam exposure apparatus of this invention. It is explanatory drawing which shows the effect | action of the optical element of the uniaxial crystal used for the exposure head based on Embodiment regarding the multi-beam exposure apparatus of this invention. It is explanatory drawing which shows the light quantity distribution of the beam spot divided by the exposure head based on Embodiment regarding the multi-beam exposure apparatus of this invention. FIG. 6 is an explanatory diagram showing a Gaussian-distributed light amount distribution of a beam spot shape generally used in the past for comparison with the light amount distribution of a beam spot divided by an exposure head according to an embodiment of the multi-beam exposure apparatus of the present invention. is there.

Explanation of symbols

12 Recording medium 14 Exposure head 16 Exposure area 24 Light source unit 36 Micro mirror 48 Micro lens array 50 Partial pixel shift member 50A First optical member 50B Second optical member 50C Third optical member 50D First diffractive part 50E Second transmission part 50F Third diffraction section 50G First polarization section 50H Second transmission section 50I Third polarization section 55 Uniaxial crystal optical element 57 1/4 wavelength plate (polarization adjusting means)
58 Polarizing plate member G1 Block G2 Block G3 Block

Claims (2)

In a multi-beam exposure apparatus that scans and exposes an exposure surface of a recording medium with a plurality of exposure beam spots,
A two-dimensional light modulator arranged to align a plurality of two-dimensionally arranged exposure beam spots projected onto the exposure surface of the recording medium in parallel with the scanning direction;
The plurality of exposure beams emitted from the two-dimensional light modulator are arranged on a projection optical system that forms an image on an exposure surface, and the plurality of exposure beams are divided into a plurality of blocks in the scanning direction. A direction perpendicular to the scanning direction projected onto the exposure surface by at least one of the blocks is shifted by projecting the relative position between the blocks in the direction orthogonal to the scanning direction and projecting onto the exposure surface. A partial pixel shift member that exposes a position during exposure with the exposure beam spot adjacent to the exposure beam spot projected onto an exposure surface by the other block;
It is disposed on the projection optical system from the partial pixel shift member to the exposure surface, and the exposure beam is separated into an ordinary ray and an extraordinary ray with substantially equal light amount so that two beam spots partially overlap. An optical element of a uniaxial crystal provided so as to form a beam spot shape that is adjacent and arranged in a direction orthogonal to the scanning direction;
A multi-beam exposure apparatus comprising: The partial pixel shift member is configured as an optical element using polarization of light, and the optical of the uniaxial crystal is formed on a projection optical system between the partial pixel shift member and the optical element of the uniaxial crystal. 2. The multi-beam exposure apparatus according to claim 1, further comprising a polarization adjusting means for causing the ordinary ray and the extraordinary ray to be emitted from the element at an equal light amount.

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