JP2006337528A - Image exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain highly fine images even when a pixel part of a spatial light modulation element has anisotropic torsion. <P>SOLUTION: An image exposure system comprises the spatial light modulation element 50 such as DMD two-dimensionally arranging a great number of pixel parts modulating emitted light respectively, a light source 66 for irradiation with light B on the spatial light modulation element 50, an imaging optical system 51 for imaging an image of the pixel part by receiving light passing through each pixel part of the spatial light modulation element 50, and a microlens array 55 for arranging a microlens 55a condensing light B from each pixel part of the spatial light modulation element 50 respectively in the form of an array. The microlens array 55 is arranged in the vicinity of an imaging position of the pixel part by an imaging optical system 51. Each microlens 55a of the microlens array 55 has powers different in two directions in a vertical face on an optical axis so as to correct aberration due to anisotropic torsion of the pixel part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image exposure apparatus, and more particularly, an image in which light modulated by a spatial light modulation element is passed through an imaging optical system and an image formed by the light is formed on a photosensitive material to expose the photosensitive material. The present invention relates to an exposure apparatus.

  2. Description of the Related Art Conventionally, there has been known an image exposure apparatus that passes light modulated by a spatial light modulation element through an imaging optical system, forms an image of this light on a predetermined photosensitive material, and exposes the photosensitive material. This type of image exposure apparatus basically includes a spatial light modulation element in which a large number of pixel units that modulate irradiated light according to a control signal are two-dimensionally arranged, and the spatial light modulation element. A light source for irradiating light and an imaging optical system for forming an image of light modulated by the spatial light modulation element on a photosensitive material are provided. Non-Patent Document 1 and Patent Document 1 show an example of an image exposure apparatus having the above basic configuration.

  In this type of image exposure apparatus, as the spatial light modulation element, for example, an LCD (liquid crystal display element), a DMD (digital micromirror device), or the like can be suitably used. The DMD is a mirror device in which a number of micromirrors that change the angle of the reflecting surface in accordance with a control signal are two-dimensionally arranged on a semiconductor substrate such as silicon.

  In the image exposure apparatus as described above, there is often a demand for enlarging an image projected on a photosensitive material, and in that case, an enlarged imaging optical system is used as an imaging optical system. In doing so, simply passing the light that has passed through the spatial light modulation element through the magnification imaging optical system expands the luminous flux from each pixel portion of the spatial light modulation element, and the pixel size in the projected image is reduced. The image becomes larger and the sharpness of the image decreases.

  Therefore, as shown in Patent Document 1, the first imaging optical system is disposed in the optical path of the light modulated by the spatial light modulator, and the spatial light modulation is formed on the imaging surface by the imaging optical system. A microlens array in which microlenses corresponding to each pixel portion of the element are arranged in an array is arranged, and in the optical path of the light that has passed through the microlens array, an image of the modulated light is transferred to a photosensitive material or It is considered that a second imaging optical system that forms an image on a screen is arranged and an image is enlarged and projected by the first and second imaging optical systems. In this configuration, the size of the image projected on the photosensitive material and the screen is enlarged, while the light from each pixel portion of the spatial light modulator is condensed by each microlens of the microlens array. Since the pixel size (spot size) in the image is reduced and kept small, the sharpness of the image can be kept high.

Patent Document 2 shows an example of an image exposure apparatus using a DMD as a spatial light modulation element and combining it with a microlens array.
JP 2004-1244 A JP 2001-305663 A Akihito Ishikawa “Development shortening and mass production application by maskless exposure”, “Electronics packaging technology”, Technical Research Co., Ltd., Vol. 18, no. 6, 2002, p. 74-79

  However, in the image exposure apparatus as described above, an astigmatic difference occurs in the beam condensed by each microlens of the microlens array via each pixel portion of the spatial light modulator, and the cross section is elliptical. It sometimes became a beam. As a result, the pixel size in the projected image cannot be kept small, resulting in a problem that the sharpness of the image is deteriorated. The astigmatic difference is mainly caused by the distortion of the surface of the pixel portion of the spatial light modulation element, and when the DMD is used as the spatial light modulation element, the distortion of the reflection surface of the DMD pixel portion is the main cause.

  In particular, when there is an anisotropic distortion in which the reflective surface of the pixel portion is a rotationally asymmetric surface with respect to the optical axis, an optical system that generates astigmatism is generated, and the microscopic surface passes through the reflective surface of the pixel portion. The beam condensed by the lens has a phenomenon that the position in the optical axis direction (beam waist position) at which the beam diameter becomes the smallest differs depending on the in-plane direction perpendicular to the optical axis.

  Specifically, assuming that two different directions in the plane perpendicular to the optical axis are the x direction and the y direction, respectively, the beam in the y direction spreads at the beam waist position in the x direction where the beam diameter in the x direction is minimum. Since the beam diameter in the y direction is not minimized, the cross sectional shape of the beam is an ellipse. Similarly, at the beam waist position in the y direction where the beam diameter in the y direction is minimum, the beam in the x direction is expanded and the cross-sectional shape of the beam is an ellipse. Since the image formation on the photosensitive material is performed on a two-dimensional surface, the sharpness decreases when an image is formed using such a beam as it is.

  The present invention has been made in view of the above circumstances, and provides an image exposure apparatus capable of obtaining a high-definition image even when a pixel portion of a spatial light modulator has an anisotropic distortion. With the goal.

  An image exposure apparatus according to the present invention includes a spatial light modulation element in which a plurality of reflective pixel units that modulate irradiated light according to control signals, and a light source that emits light to the spatial light modulation element. And an optical system that receives light that has passed through each pixel portion of the spatial light modulator and forms an image of the pixel portion, and light that has passed through the optical system via each pixel portion of the spatial light modulator. An image exposure apparatus including a microlens array in which a plurality of individually incident microlenses are arranged in parallel, and an imaging optical system that forms an image of light modulated by the spatial light modulator on a photosensitive material The microlens array is disposed in the vicinity of the imaging position of the pixel unit by the optical system, and each microlens of the microlens array corrects aberration due to anisotropic distortion of the pixel unit. axis It is characterized in that those having different powers in two directions perpendicular plane.

  In the image exposure apparatus, the microlens may be not only a normal refractive lens but also a gradient index lens or a diffractive lens. The microlens may be a lens configured by combining at least two of a refractive lens, a gradient index lens, and a diffractive lens. The combination here means not only a cemented lens but also a single lens having a plurality of functions. For example, as a combination of a refractive lens and a diffractive lens, a Fresnel lens having a refractive action and a diffractive action can be considered. Further, as a combination of the refractive lens and the refractive index distribution type lens, for example, a spherical lens having a refractive index distribution can be adopted.

  In the image exposure apparatus, the light that has passed through each pixel unit is individually collected at a condensing position by the pixel unit, the optical system, and the microlens array that is out of the imaging position of the pixel unit by the optical system. It is desirable that a condensing microlens array in which a plurality of light-emitting microlenses are arranged in parallel is further provided.

  The condensing microlens array is preferably arranged so as to be movable in the optical axis direction of the light.

  Further, in the image exposure apparatus, the light that has passed through each pixel unit is individually applied to the light collection position by the pixel unit, the optical system, and the microlens array that is out of the imaging position of the pixel unit by the optical system. It is desirable that an aperture array in which a plurality of apertures through which light passes is arranged is further provided.

  Furthermore, it is desirable that the spatial light modulation element is a DMD (digital micromirror device) in which micromirrors as the pixel portion are two-dimensionally arranged.

  Note that the light condensing position described above is separated from the light reflected from each pixel unit by the pixel unit, the optical system, and the microlens array at a position deviating from the image forming position of the pixel unit by the optical system. Means the position.

  In the image exposure apparatus according to the present invention, each microlens of the microlens array has different powers in two directions in a plane perpendicular to the optical axis so as to correct aberration due to anisotropic distortion of the pixel portion. Thereby, even when the pixel portion of the spatial light modulation element has anisotropic distortion, each microlens of the microlens array corrects astigmatism generated by the distortion and passes through each pixel portion. The beam waist positions in the x direction and the y direction of the beams condensed by the microlenses can be matched. Therefore, according to the image exposure apparatus of the present invention, a beam which is condensed and has a uniform beam waist position in the x direction and the y direction can be used for image formation, so that a high-definition image can be obtained.

  Further, in the image exposure apparatus according to the present invention, since the astigmatism is corrected by arranging the microlens array in the vicinity of the image forming position of the pixel portion, the light reflected from each pixel portion is separated and condensed. The condensing position range can be widened.

  If a condensing microlens array that condenses the light that has passed through each pixel section is further arranged at this condensing position, the spot size can be further reduced, contributing to the improvement of image sharpness. it can. Further, since the light is collected by the microlens array arranged in the vicinity of the imaging position, the beam diameter incident on the condensing microlens array arranged at the focusing position is the beam diameter at the imaging position. Even smaller. Therefore, even if the spatial light modulator and the condensing microlens array are slightly shifted, the beam at the condensing position is vignetted or the beam to be incident on the microlens with the condensing microlens array is adjacent to the microlens array. Without entering the lens, it is possible to prevent a decrease in light use efficiency and extinction ratio, which are a concern when arranging the condensing microlens array.

  If this condensing microlens array is arranged so as to be movable in the direction of the optical axis of light, it is possible to easily adjust the focus of light. In particular, since the amount of change in light utilization efficiency before and after the focusing position is smaller than the amount of change in light utilization efficiency before and after the imaging position, the change in light utilization efficiency when focus adjustment is performed The amount can be kept to a minimum.

  When an aperture array is disposed at this condensing position, only the light collected through each pixel portion passes through each aperture, so that stray light can be blocked and the extinction ratio can be improved.

  If a gradient index lens is used for the microlens, the outer shape can be a parallel plate. If a diffractive lens is used, the outer shape can be a parallel plate and a normal refractive lens. Thus, the thickness in the optical axis direction can be reduced. In the case where a lens configured by combining at least two of a refractive lens, a gradient index lens, and a diffractive lens is employed as the microlens, the degree of freedom in design is increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, an image exposure apparatus according to a first embodiment of the present invention will be described.

[Configuration of image exposure apparatus]
As shown in FIG. 1, the image exposure apparatus includes a flat plate-like moving stage 152 that holds a sheet-like photosensitive material 150 on the surface thereof. Two guides 158 extending along the stage moving direction are installed on the upper surface of the thick plate-shaped installation table 156 supported by the four legs 154. The stage 152 is arranged so that the longitudinal direction thereof faces the stage moving direction, and is supported by a guide 158 so as to be reciprocally movable. The image exposure apparatus is provided with a stage driving device 304 (see FIG. 15), which will be described later, that drives a stage 152 as sub-scanning means along a guide 158.

  A U-shaped gate 160 is provided at the center of the installation table 156 so as to straddle the movement path of the stage 152. Each of the ends of the U-shaped gate 160 is fixed to both side surfaces of the installation table 156. A scanner 162 is provided on one side of the gate 160, and a plurality of (for example, two) sensors 164 for detecting the front and rear ends of the photosensitive material 150 are provided on the other side. The scanner 162 and the sensor 164 are respectively attached to the gate 160 and fixedly arranged above the moving path of the stage 152. The scanner 162 and the sensor 164 are connected to a controller (not shown) that controls them.

As shown in FIGS. 2 and 3B, the scanner 162 includes a plurality of (for example, 14) exposure heads 166 arranged in an approximately matrix of m rows and n columns (for example, 3 rows and 5 columns). . In this example, four exposure heads 166 are arranged in the third row in relation to the width of the photosensitive material 150. In addition, when showing each exposure head arranged in the m-th row and the n-th column, it is expressed as an exposure head 166 _mn .

An exposure area 168 by the exposure head 166 has a rectangular shape with a short side in the sub-scanning direction. Therefore, as the stage 152 moves, a strip-shaped exposed area 170 is formed for each exposure head 166 in the photosensitive material 150. In addition, when showing the exposure area by each exposure head arranged in the m-th row and the n-th column, it is expressed as an exposure area 168 _mn .

Further, as shown in FIGS. 3A and 3B, each of the exposure heads in each row arranged in a line so that the strip-shaped exposed regions 170 are arranged in the direction orthogonal to the sub-scanning direction without gaps. These are arranged with a predetermined interval (natural number times the long side of the exposure area, twice in this example) in the arrangement direction. Therefore, can not be exposed portion between the exposure area _{168 11} in the first row and the exposure area _{168 12,} it can be exposed by the second row of the exposure area _{168 21} and the exposure area _{168 31} in the third row.

As shown in FIGS. 4 and 5, each of the exposure heads 166 _{11 to} 166 _mn is a spatial light modulation element that modulates an incident light beam for each pixel according to image data, and is manufactured by Texas Instruments Incorporated. Digital micromirror device (DMD) 50. The DMD 50 is connected to a controller 302 (see FIG. 15), which will be described later, provided with a data processing unit and a mirror drive control unit. The data processing unit of the controller 302 generates a control signal for driving and controlling each micromirror in the region to be controlled by the DMD 50 for each exposure head 166 based on the input image data. The area to be controlled will be described later. The mirror drive control unit controls the angle of the reflection surface of each micromirror of the DMD 50 for each exposure head 166 based on the control signal generated by the image data processing unit. The control of the angle of the reflecting surface will be described later.

  On the light incident side of the DMD 50, a fiber array light source 66 including a laser emitting section in which emission ends (light emitting points) of an optical fiber are arranged in a line along a direction corresponding to the long side direction of the exposure area 168, a fiber A lens system 67 that corrects laser light emitted from the array light source 66 and collects it on the DMD, and a mirror 69 that reflects the laser light transmitted through the lens system 67 toward the DMD 50 are arranged in this order. In FIG. 4, the lens system 67 is schematically shown.

  As shown in detail in FIG. 5, the lens system 67 condenses the condensing lens 71 that condenses the laser light B as illumination light emitted from the fiber array light source 66, and is inserted into the optical path of the light that has passed through the condensing lens 71. The rod-shaped optical integrator (hereinafter referred to as a rod integrator) 72 and a collimator lens 74 disposed on the downstream side of the rod integrator 72, that is, on the mirror 69 side. The condensing lens 71, the rod integrator 72, and the collimator lens 74 cause the laser light emitted from the fiber array light source 66 to enter the DMD 50 as a light beam that is close to parallel light and has a uniform beam cross-sectional intensity. The shape and action of the rod integrator 72 will be described in detail later.

  The laser beam B emitted from the lens system 67 is reflected by the mirror 69 and irradiated to the DMD 50 through a TIR (total reflection) prism 70. In FIG. 4, the TIR prism 70 is omitted.

  An imaging optical system 51 that images the laser beam B reflected by the DMD 50 on the photosensitive material 150 is disposed on the light reflection side of the DMD 50. This imaging optical system 51 is schematically shown in FIG. 4, but as shown in detail in FIG. 5, a first imaging optical system comprising lens systems 52 and 54 and a first imaging system comprising lens systems 57 and 58 are shown. The image forming optical system includes two image forming optical systems, a microlens array 55 inserted between these image forming optical systems, and an aperture array 59.

  The microlens array 55 is formed by two-dimensionally arranging a number of microlenses 55a corresponding to each pixel of the DMD 50. In this example, as described later, only 1024 × 256 rows of the 1024 × 768 rows of micromirrors of the DMD 50 are driven, and accordingly, 1024 × 256 rows of microlenses 55a are arranged. The arrangement pitch of the micro lenses 55a is 41 μm in both the vertical and horizontal directions. As an example, the microlens 55a has a focal length of 0.19 mm, an NA (numerical aperture) of 0.11, and is formed from the optical glass BK7. The shape of the micro lens 55a will be described in detail later. The beam diameter of the laser beam B at the position of each microlens 55a is 41 μm.

  The aperture array 59 is formed by forming a large number of apertures (openings) 59a corresponding to the respective microlenses 55a of the microlens array 55. In the present embodiment, the diameter of the aperture 59a is 10 μm.

  The first image-forming optical system forms an image on the microlens array 55 by enlarging the image by the DMD 50 three times. The second imaging optical system enlarges the image passing through the microlens array 55 by 1.6 times, and forms and projects the image on the photosensitive material 150. Therefore, as a whole, the image formed by the DMD 50 is magnified 4.8 times and formed on the photosensitive material 150 and projected.

  In this example, a prism pair 73 is disposed between the second imaging optical system and the photosensitive material 150, and the prism pair 73 is moved in the vertical direction in FIG. The focus can be adjusted. In the figure, the photosensitive material 150 is sub-scanned in the direction of arrow F.

  As shown in FIG. 6, in the DMD 50, on a SRAM cell (memory cell) 60, a large number (for example, 1024 × 768) of micromirrors (micromirrors) 62 constituting pixels (pixels) are arranged in a grid pattern. This is a mirror device. In each pixel, a micromirror 62 supported by a support column is provided at the top, and a material having high reflectance such as aluminum is deposited on the surface of the micromirror 62. The reflectance of the micromirror 62 is 90% or more, and the arrangement pitch is 13.7 μm as an example in both the vertical and horizontal directions. A silicon gate CMOS SRAM cell 60 manufactured in a normal semiconductor memory manufacturing line is disposed directly below the micromirror 62 via a support including a hinge and a yoke, and the entire structure is monolithic. ing.

  When a digital signal is written in the SRAM cell 60 of the DMD 50, the micromirror 62 supported by the support is tilted in a range of ± α degrees (for example, ± 12 degrees) with respect to the substrate side on which the DMD 50 is disposed with the diagonal line as the center. It is done. FIG. 7A shows a state in which the micromirror 62 is tilted to + α degrees in the on state, and FIG. 7B shows a state in which the micromirror 62 is tilted to −α degrees in the off state. Therefore, by controlling the tilt of the micromirror 62 in each pixel of the DMD 50 according to the image signal as shown in FIG. 6, the laser light B incident on the DMD 50 is reflected in the tilt direction of each micromirror 62. The

  FIG. 6 shows an example of a state in which a part of the DMD 50 is enlarged and the micromirror 62 is controlled to + α degrees or −α degrees. On / off control of each micromirror 62 is performed by the controller 302 connected to the DMD 50. Further, a light absorber (not shown) is arranged in the direction in which the laser beam B reflected by the off-state micromirror 62 travels. The micromirror 62 in the present embodiment has a distortion on its reflection surface, but the distortion is omitted in FIGS.

  Further, it is preferable that the DMD 50 is arranged with a slight inclination so that the short side forms a predetermined angle θ (for example, 0.1 ° to 5 °) with the sub-scanning direction. 8A shows the scanning trajectory of the reflected light image (exposure beam) 53 by each micromirror when the DMD 50 is not tilted, and FIG. 8B shows the scanning trajectory of the exposure beam 53 when the DMD 50 is tilted. Show.

In the DMD 50, a number of micromirror arrays in which a large number (for example, 1024) of micromirrors are arranged in the longitudinal direction are arranged in a short direction (for example, 756 sets). As shown in FIG. in significantly improved by tilting the DMD 50, the pitch P ₁ of the scanning locus of the exposure beams 53 from each micromirror (scan line), it becomes narrower than the pitch P ₂ of the scanning lines in the case of not tilting the DMD 50, the resolution Can be made. On the other hand, the inclination angle of the DMD 50 is small, the scanning width _{W 2} in the case of tilting the DMD 50, which is substantially equal to the scanning width _{W 1} when not inclined DMD 50.

  Further, the same scanning line is overlapped and exposed (multiple exposure) by different micromirror rows. Thus, by performing multiple exposure, it is possible to control a minute amount of the exposure position with respect to the alignment mark, and to realize high-definition exposure. Further, joints between a plurality of exposure heads arranged in the main scanning direction can be connected without a step by controlling a very small amount of exposure position.

  Note that the same effect can be obtained by arranging the micromirror rows in a staggered manner by shifting the micromirror rows by a predetermined interval in a direction orthogonal to the sub-scanning direction instead of inclining the DMD 50.

  As shown in FIG. 9 a, the fiber array light source 66 includes a plurality of (for example, 14) laser modules 64, and one end of the multimode optical fiber 30 is coupled to each laser module 64. An optical fiber 31 having the same core diameter as that of the multimode optical fiber 30 and a smaller cladding diameter than the multimode optical fiber 30 is coupled to the other end of the multimode optical fiber 30. As shown in detail in FIG. 9b, seven end portions of the multimode optical fiber 31 on the opposite side to the optical fiber 30 are arranged along the main scanning direction orthogonal to the sub-scanning direction, and are arranged in two rows to form a laser. An emission unit 68 is configured.

  As shown in FIG. 9B, the laser emitting portion 68 constituted by the end portion of the multimode optical fiber 31 is sandwiched and fixed between two support plates 65 having a flat surface. In addition, a transparent protective plate such as glass is preferably disposed on the light emitting end face of the multimode optical fiber 31 for protection. The light exit end face of the multimode optical fiber 31 has high light density and is likely to collect dust and easily deteriorate. However, the protective plate as described above prevents the dust from adhering to the end face and deteriorates. Can be delayed.

  In this example, as shown in FIG. 10, an optical fiber 31 having a small cladding diameter of about 1 to 30 cm is coaxially coupled to a tip portion on the laser beam emission side of a multimode optical fiber 30 having a large cladding diameter. Yes. The optical fibers 30 and 31 are coupled by fusing the incident end face of the optical fiber 31 to the outgoing end face of the optical fiber 30 in a state where the respective core axes coincide. As described above, the diameter of the core 31 a of the optical fiber 31 is the same as the diameter of the core 30 a of the multimode optical fiber 30.

  As the multimode optical fiber 30 and the optical fiber 31, any of a step index type optical fiber, a graded index type optical fiber, and a composite type optical fiber can be applied. For example, a step index type optical fiber manufactured by Mitsubishi Cable Industries, Ltd. can be used. In this example, the multimode optical fiber 30 and the optical fiber 31 are step index type optical fibers, and the multimode optical fiber 30 has a cladding diameter = 125 μm, a core diameter = 50 μm, NA = 0.2, and transmission of the incident end face coating. The ratio is 99.5% or more, and the optical fiber 31 has a cladding diameter = 60 μm, a core diameter = 50 μm, and NA = 0.2.

  However, the cladding diameter of the optical fiber 31 is not limited to 60 μm. The clad diameter of many optical fibers used in conventional fiber light sources is 125 μm. However, the smaller the clad diameter, the deeper the depth of focus. Therefore, the clad diameter of the multimode optical fiber is preferably 80 μm or less, preferably 60 μm or less. Is more preferable. On the other hand, in the case of a single mode optical fiber, the core diameter needs to be at least 3 to 4 μm, and therefore the cladding diameter of the optical fiber 31 is preferably 10 μm or more. In addition, it is preferable from the viewpoint of coupling efficiency that the core diameter of the optical fiber 30 and the core diameter of the optical fiber 31 are matched.

  The laser module 64 is configured by a combined laser light source (fiber light source) shown in FIG. The combined laser light source includes a plurality of (for example, seven) chip-like lateral multimode or single mode GaN-based semiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6, and the like arranged and fixed on the heat block 10. LD 7, collimator lenses 11, 12, 13, 14, 15, 16 and 17 provided corresponding to each of GaN-based semiconductor lasers LD 1 to LD 7, one condenser lens 20, and one multimode light And fiber 30. The number of semiconductor lasers is not limited to seven, and other numbers may be adopted. Further, instead of the seven collimator lenses 11 to 17 as described above, a collimator lens array in which these lenses are integrated can be used.

  The GaN-based semiconductor lasers LD1 to LD7 all have a common oscillation wavelength (for example, 405 nm), and the maximum output is also all common (for example, about 100 mW for a multimode laser and about 50 mW for a single mode laser). As the GaN-based semiconductor lasers LD1 to LD7, lasers that oscillate at wavelengths other than 405 nm in the wavelength range of 350 nm to 450 nm may be used.

  As shown in FIGS. 12 and 13, the above-described combined laser light source is housed in a box-shaped package 40 having an upper opening together with other optical elements. The package 40 includes a package lid 41 created so as to close the opening thereof, and is formed by introducing a sealing gas after the deaeration process and closing the opening of the package 40 with the package lid 41. The combined laser light source is hermetically sealed in a closed space (sealed space).

  A base plate 42 is fixed to the bottom surface of the package 40, and the heat block 10, a condensing lens holder 45 that holds the condensing lens 20, and the multimode optical fiber 30 are disposed on the top surface of the base plate 42. A fiber holder 46 that holds the incident end is attached. The exit end of the multimode optical fiber 30 is drawn out of the package from an opening formed in the wall surface of the package 40.

  A collimator lens holder 44 is attached to the side surface of the heat block 10, and collimator lenses 11 to 17 are held there. An opening is formed in the lateral wall surface of the package 40, and wiring 47 for supplying a driving current to the GaN-based semiconductor lasers LD1 to LD7 is drawn out of the package through the opening.

  In FIG. 13, in order to avoid complication of the drawing, only the GaN semiconductor laser LD7 among the plurality of GaN semiconductor lasers is numbered, and only the collimator lens 17 among the plurality of collimator lenses is numbered. is doing.

  FIG. 14 shows the front shape of the attachment part of the collimator lenses 11-17. Each of the collimator lenses 11 to 17 is formed in a shape obtained by cutting a region including the optical axis of a circular lens having an aspherical surface into a long and narrow plane. This elongated collimator lens can be formed, for example, by molding resin or optical glass. The collimator lenses 11 to 17 are closely arranged in the arrangement direction of the light emitting points so that the length direction is orthogonal to the arrangement direction of the light emitting points of the GaN-based semiconductor lasers LD1 to LD7 (left and right direction in FIG. 14).

  On the other hand, each of the GaN-based semiconductor lasers LD1 to LD7 includes an active layer having a light emission width of 2 μm, and each of the laser beams B1 to B1 having a divergence angle in a direction parallel to the active layer and a direction perpendicular thereto, for example A laser emitting B7 is used. These GaN-based semiconductor lasers LD1 to LD7 are arranged so that the light emitting points are arranged in a line in a direction parallel to the active layer.

Therefore, in the laser beams B1 to B7 emitted from the respective light emitting points, the direction in which the divergence angle is large coincides with the length direction and the divergence angle is small with respect to the elongated collimator lenses 11 to 17 as described above. Incident light is incident in a state where the direction coincides with the width direction (direction perpendicular to the length direction). That is, the collimator lenses 11 to 17 have a width of 1.1 mm and a length of 4.6 mm, and the horizontal and vertical beam diameters of the laser beams B1 to B7 incident thereon are 0.9 mm and 2. 6 mm. Each of the collimator lenses 11 to 17 has a focal length f ₁ = 3 mm, NA = 0.6, and a lens arrangement pitch = 1.25 mm.

The condensing lens 20 is formed by cutting a region including the optical axis of a circular lens having an aspheric surface into a long and narrow shape in parallel planes, and is long in the arrangement direction of the collimator lenses 11 to 17, that is, in a horizontal direction and short in a direction perpendicular thereto. Is formed. This condenser lens 20 has a focal length f ₂ = 23 mm and NA = 0.2. The condensing lens 20 is also formed by molding resin or optical glass, for example.

  Next, the electrical configuration of the image exposure apparatus of this example will be described with reference to FIG. As shown here, a modulation circuit 301 is connected to the overall control unit 300, and a controller 302 that controls the DMD 50 is connected to the modulation circuit 301. The overall control unit 300 is connected to an LD drive circuit 303 that drives the laser module 64. Furthermore, a stage driving device 304 that drives the stage 152 is connected to the overall control unit 300.

[Operation of image exposure apparatus]
Next, the operation of the image exposure apparatus will be described. In each exposure head 166 of the scanner 162, laser light B1, B2, B3 emitted in a divergent light state from each of the GaN-based semiconductor lasers LD1 to LD7 (see FIG. 11) constituting the combined laser light source of the fiber array light source 66. Each of B4, B5, B6, and B7 is collimated by the corresponding collimator lenses 11-17. The collimated laser beams B <b> 1 to B <b> 7 are collected by the condenser lens 20 and converge on the incident end face of the core 30 a of the multimode optical fiber 30.

  In this example, the collimating lenses 11 to 17 and the condensing lens 20 constitute a condensing optical system, and the condensing optical system and the multimode optical fiber 30 constitute a multiplexing optical system. That is, the laser beams B1 to B7 collected as described above by the condenser lens 20 enter the core 30a of the multimode optical fiber 30 and propagate through the optical fiber to be combined with one laser beam B. The light is emitted from the optical fiber 31 coupled to the output end of the multimode optical fiber 30.

  In each laser module, when the coupling efficiency of the laser beams B1 to B7 to the multimode optical fiber 30 is 0.9 and each output of the GaN-based semiconductor lasers LD1 to LD7 is 50 mW, the light arranged in an array For each of the fibers 31, a combined laser beam B having an output of 315 mW (= 50 mW × 0.9 × 7) can be obtained. Therefore, the entire 14 multi-mode optical fibers 31 can obtain a laser beam B having an output of 4.4 W (= 0.315 W × 14).

  At the time of image exposure, image data corresponding to the exposure pattern is input from the modulation circuit 301 shown in FIG. 15 to the controller 302 of the DMD 50 and temporarily stored in the frame memory. This image data is data representing the density of each pixel constituting the image by binary values (whether or not dots are recorded).

  The stage 152 that has adsorbed the photosensitive material 150 to the surface is moved at a constant speed from the upstream side to the downstream side of the gate 160 along the guide 158 by the stage driving device 304 shown in FIG. When the leading edge of the photosensitive material 150 is detected by the sensor 164 attached to the gate 160 when the stage 152 passes under the gate 160, the image data stored in the frame memory is sequentially read out for each of a plurality of lines. A control signal is generated for each exposure head 166 based on the image data read by the data processing unit. Then, each of the micromirrors of the DMD 50 is controlled on and off for each exposure head 166 based on the generated control signal by the mirror drive control unit. In the case of this example, the size of the micromirror serving as one pixel portion is 14 μm × 14 μm.

  When the laser beam B is irradiated from the fiber array light source 66 to the DMD 50, the laser beam reflected when the micromirror of the DMD 50 is in an on state is imaged on the photosensitive material 150 by the lens systems 54 and 58. In this manner, the laser light emitted from the fiber array light source 66 is turned on and off for each pixel, and the photosensitive material 150 is exposed in pixel units (exposure area 168) that is approximately the same number as the number of pixels used in the DMD 50. Further, when the photosensitive material 150 is moved at a constant speed together with the stage 152, the photosensitive material 150 is sub-scanned in the direction opposite to the stage moving direction by the scanner 162, and a strip-shaped exposed region 170 is formed for each exposure head 166. It is formed.

  In this example, as shown in FIGS. 16A and 16B, the DMD 50 has 768 pairs of micromirror arrays in which 1024 micromirrors are arranged in the main scanning direction. In this example, the controller 302 performs control so that only a part of micromirror rows (eg, 1024 × 256 rows) are driven.

  In this case, a micromirror array arranged at the center of the DMD 50 as shown in FIG. 16 (A) may be used, and the micromirror arranged at the end of the DMD 50 as shown in FIG. 16 (B). A column may be used. In addition, when a defect occurs in some of the micromirrors, the micromirror array to be used may be appropriately changed depending on the situation, such as using a micromirror array in which no defect has occurred.

  Since the data processing speed of the DMD 50 is limited and the modulation speed per line is determined in proportion to the number of pixels used, the modulation speed per line can be increased by using only a part of the micromirror rows. Get faster. On the other hand, in the case of an exposure method in which the exposure head is continuously moved relative to the exposure surface, it is not necessary to use all the pixels in the sub-scanning direction.

  When the sub-scan of the photosensitive material 150 by the scanner 162 is finished and the rear end of the photosensitive material 150 is detected by the sensor 164, the stage 152 is moved to the uppermost stream side of the gate 160 along the guide 158 by the stage driving device 304. It returns to a certain origin, and again moves along the guide 158 from the upstream side to the downstream side of the gate 160 at a constant speed.

  Next, illumination optics configured by the fiber array light source 66, the condensing lens 71, the rod integrator 72, the collimator lens 74, the mirror 69, and the TIR prism 70 shown in FIG. 5 and irradiating the DMD 50 with the laser light B as illumination light. The system will be described. The rod integrator 72 is a translucent rod formed in, for example, a rectangular column shape, and the intensity distribution in the beam cross section of the laser beam B is made uniform while the laser beam B travels while totally reflecting inside the rod integrator 72. The entrance end face and exit end face of the rod integrator 72 are coated with an antireflection film to increase the transmittance. As described above, if the intensity distribution in the beam cross section of the laser beam B that is illumination light can be made highly uniform, non-uniform illumination light intensity can be eliminated and a high-definition image can be exposed on the photosensitive material 150.

  Here, FIG. 17 shows the direction of the deflection axis that becomes the central axis when the micromirror 62 constituting the DMD 50 rotates. In the present embodiment, one diagonal direction of the reflection surface of the micromirror 62 is the direction of the deflection axis, the direction is the y direction, and the other diagonal direction is the x direction. That is, the x direction and the y direction are two different directions in a plane perpendicular to the optical axis O. In the present embodiment, these directions are orthogonal to each other.

  FIGS. 18A and 18B respectively show schematic views of the height position displacement of the reflecting surface of the micromirror 62 in the cross section parallel to the x direction and the y direction. In FIG. 18, the horizontal axis represents the position in each direction from the center of the reflecting surface, and the vertical axis represents the displacement in the optical axis direction. As shown in FIGS. 18A and 18B, the reflecting surface of the micromirror 62 is a rotationally asymmetric curved surface having a concave shape in the x direction and a convex shape in the y direction. Have.

  When parallel light is incident on such a surface, the reflected light becomes convergent light in the x direction and becomes divergent light in the y direction. When this light is collected by a normal lens having a rotationally symmetric power with respect to the optical axis, the position in the optical axis direction (beam waist position) at which the beam diameter becomes the smallest differs between the x direction and the y direction. A phenomenon, that is, astigmatism occurs, which hinders high definition of an image.

  Therefore, in the image exposure apparatus of the present embodiment, in order to prevent the above-described problem, each micro lens 55a of the micro lens array 55 has a special shape different from the conventional one. Hereinafter, this point will be described in detail.

  FIGS. 19A and 19B respectively show the front and side shapes of the entire microlens array 55 in detail. These drawings also show the dimensions of each part of the microlens array 55, and the unit thereof is mm. In this embodiment, as described above with reference to FIG. 16, the 1024 × 256 micromirrors 62 of the DMD 50 are driven. Correspondingly, the microlens array 55 is 1024 in the lateral direction. The microlenses 55a arranged in a row are arranged in 256 rows in the vertical direction. In FIG. 6A, the arrangement order of the microlens array 55 is indicated by j in the horizontal direction and k in the vertical direction.

  Each micro lens 55a has a different power in the x and y directions and is rotationally asymmetric with respect to the optical axis so as to correct the aberration caused by the anisotropic distortion of the reflection surface of the micro mirror 62 described above. Yes. More specifically, the microlens 55a in the present embodiment is a cylindrical lens having 0 in the x direction and a positive value in the y direction. The value of the power in the y direction reflects the curvature of the reflection surface of the micromirror 62 and reflects the beam after passing through the lens systems 52 and 54 of the first imaging optical system and the microlens 55a. The difference between the beam waist positions in the x direction and the y direction (astigmatism difference) is substantially zero.

  FIG. 20A shows a perspective view of the microlens 55a as described above as an example. The microlens 55a has a square with diagonal lines in the x direction and the y direction as its bottom surface, and its upper surface has a curved surface shape. 20B and 20C, the micro lens 55a has a rectangular shape in a cross section passing through the optical axis and parallel to the x direction, and in a cross section passing through the optical axis and parallel to the y direction. A plano-convex shape in which the bottom surface is a straight line and the top surface is an arc.

  The manner in which the aberration due to the distortion of the reflection surface of the micromirror 62 is corrected by the microlens 55a will be described more specifically. FIGS. 21A and 21B are schematic diagrams showing how the light reflected by the micromirror 62 described above is corrected by the microlens 55a in a cross section passing through the optical axis and parallel to the x and y directions. FIG. The microlens array 55 is disposed in the vicinity of the imaging position where the image of the micromirror 62 is formed by the first imaging optical system.

  In FIG. 21, the TIR prism 70 is omitted. In FIG. 21, three adjacent micromirrors are illustrated, and light reflected at the center and both ends of one central micromirror is indicated by a solid line. FIG. 21 schematically shows a state where the beam diameter of the beam reflected by the three micromirrors changes on the downstream side of the lens system 54 by a dotted-line ellipse.

  In the x direction, as shown in FIG. 21 (A), the light reflected by the concave micromirror 62 becomes convergent light, passes through the lens systems 52 and 54, and then enters the microlens 55a. To do. Since the power in the x direction of the micro lens 55a is 0 as described above, the light incident on the micro lens 55a travels in the x direction without changing the angle with the optical axis, and the beam diameter is at the beam waist position. The smallest.

  On the other hand, in the y direction, as shown in FIG. 21B, the light reflected by the convex micromirror 62 becomes divergent light, passes through the lens systems 52 and 54, and then microlenses 55a. Is incident on. As described above, since the micro lens 55a has a positive power in the y direction, the light incident on the micro lens 55a is condensed in the y direction, and the beam is located at the same position as the beam waist position in the x direction. The diameter becomes the smallest.

  As described above, the astigmatism can be corrected by configuring the micro lens 55a to have different powers in the x direction and the y direction according to the anisotropic shape of the reflection surface of the micro mirror 62. It is possible to prevent the cross-sectional shape of the beam from becoming an ellipse. Therefore, the beam waist positions in the x direction and the y direction are aligned, the cross-sectional shape of the beam is shaped, and the focused beam can be used for image formation, so that a high-definition image can be obtained.

  In the above description, the example in which the reflection surface of the micromirror 62 has a concave shape and a convex shape in the x direction and the y direction, respectively, has been described, but one of the x direction and the y direction is a planar shape and the other is a concave shape or a convex shape. However, astigmatism due to the reflecting surface of the micromirror can be corrected in the same manner. Next, these cases will be described.

  First, a case where an image is formed using a DMD 250 in which a plurality of micromirrors 262 having a reflecting surface having a concave shape and a planar shape in the x direction and the y direction, respectively, will be described. For simplicity, the concave shape of the micromirror 262 in the x direction is the same as the concave shape of the micromirror 62 in the x direction.

  In this case, a microlens array 55 'in which a plurality of microlenses 55a' are arranged in parallel is used in place of the microlens 55a. The microlens 55a 'is a cylindrical lens that has zero power in the x direction and a smaller positive power than the microlens 55a in the y direction. That is, it can be considered that the micro lens 55a 'has a larger radius of curvature in the y direction of the micro lens 55a shown in FIG. The value of the power in the y direction of the micro lens 55a ′ is determined by reflecting the micro mirror 262 in consideration of the curvature of the reflection surface of the micro mirror 262, and the lens systems 52 and 54 of the first imaging optical system and the micro lens 55a ′. Is determined so that the difference (astigmatism difference) between the beam waist positions in the x direction and the y direction of the beam after passing through is substantially zero.

  The manner in which the aberration due to the distortion of the reflection surface of the micromirror 262 is corrected by the microlens 55a 'will be described with reference to FIGS. FIG. 21C is a schematic diagram showing how the light reflected by the micromirror 262 is corrected by the microlens 55a ′ in a cross section passing through the optical axis and parallel to the y direction. The way of illustration is as described above. Also in this case, the microlens array 55 ′ is disposed in the vicinity of the imaging position where the image of the micromirror 262 is formed by the first imaging optical system.

  In the x direction, the micromirror 62 and the microlens 55a described with reference to FIG. 21A are exactly the same as those in the x direction, and the beam diameter in the x direction is the same as that of the micromirror described above. The beam waist position is minimum when 62 and the micro lens 55a are used.

  On the other hand, in the y direction, as shown in FIG. 21C, the light reflected by the micromirror 262 having a planar shape remains parallel and passes through the lens systems 52 and 54, and then the microlens. Incident at 55a '. As described above, since the microlens 55a ′ has a positive power in the y direction, the light incident on the microlens 55a is collected in the y direction and is at the same position as the beam waist position in the x direction. The beam diameter is the smallest.

  As described above, even when the reflecting surface of the micromirror has a concave shape and a planar shape in different directions in the plane perpendicular to the optical axis, astigmatism is obtained by using the microlens according to the shape of the reflecting surface. Can be corrected, and the same effect can be obtained.

  In addition, the shape in the cross section parallel to the y direction of the micro lenses 55a and 55a 'is not limited to the plano-convex shape shown in FIG. 20C, and may be a meniscus shape. In the above embodiment, the power of the microlens is set to 0 in the direction in which the reflecting surface of the micromirror has a concave shape. However, the present invention is not limited to this, and the light after passing through the microlens becomes convergent light. If the astigmatism caused by the above can be corrected, the microlens may have positive or negative power in the direction in which the reflection surface of the micromirror has a concave shape.

  Next, the case where the reflection surface of the micromirror has a planar shape and a convex shape in the x direction and the y direction will be described. In this case, instead of the above-described microlenses 55a and 55a 'that are cylindrical lenses, a microlens having positive power in both the x direction and the y direction and having a power in the x direction smaller than that in the y direction is used. As an example of such a microlens, there is a lens configured such that a shape in a cross section parallel to the x direction and the y direction is equal to a cross sectional shape of a spherical lens having a different curvature radius.

  The power values in the x and y directions of the microlens are reflected by the micromirror in consideration of the curvature of the reflecting surface of the micromirror, as in the above example, and the lens system 52 of the first imaging optical system. , 54 and the beam waist after passing through the microlens is determined so that the difference between the beam waist positions in the x direction and the y direction (astigmatic difference) becomes substantially zero.

  In this case, the x direction can be considered in the same way as the y direction when the above-described micromirror 262 and microlens 55a 'described with reference to FIG. Further, the y direction can be considered in the same manner as that in the y direction when the above-described micromirror 62 and microlens 55a described with reference to FIG. Therefore, also in this case, the beam waist positions in the x direction and the y direction can be matched.

  Thus, even when the reflective surface of the micromirror has a planar shape and a convex shape in different directions in the plane perpendicular to the optical axis, by using a microlens corresponding to the shape and curvature of the reflective surface, Astigmatism can be corrected, and the same effect can be obtained.

  From the above, even if the reflection surface of the micromirror has different shapes in the x direction and the y direction, the power of the microlens in the x direction and the y direction can be set to different values, thereby reducing the astigmatism caused by the micromirror. Aberration can be corrected and a higher definition image can be formed.

  In the above description, the curved surface shape of the microlens is a spherical shape, but the invention is not limited to this, and a higher order (4th order, 6th order, ...) aspherical shape may be adopted.

  In the embodiment described above, each microlens constituting the microlens array has been described as a refractive lens, but the same effect can be obtained by using a gradient index lens instead. A microlens 155a is shown in FIG. 22 as an example of a gradient index lens. (A) and (B) of the figure respectively show the front shape and the side shape of the micro lens 155a, and the outer shape of the micro lens 155a is a parallel plate shape as shown in the figure. The x and y directions in the figure are as described above.

  23A and 23B schematically show the state of the laser beam B in the cross section parallel to the x direction and the y direction by the microlens 155a. The microlens 155a has a uniform refractive index distribution in the x direction and has a refractive index distribution that gradually increases outward from the optical axis O in the y direction. In FIG. A broken line shown in the microlens 155a indicates a position where the refractive index changes from the optical axis O at a predetermined equal pitch.

  As shown in the drawing, when the cross section parallel to the x direction is compared with the cross section parallel to the y direction, the parallel light incident on the micro lens 155a is emitted as parallel light in the x direction and becomes convergent light in the y direction. And exit. Even when a microlens array composed of such a gradient index lens is used, the same effects as those obtained when the microlens array using the above-described microlenses 55a and 55a 'can be obtained.

  Further, instead of a microlens having positive power in both the x-direction and y-direction and having power in the x-direction smaller than that in the y-direction, it has a refractive index distribution in both the x-direction and y-direction, A microlens 255a having a smaller refractive index change rate in the x direction and a longer focal length is used than in the y direction. 24A and 24B schematically show the condensing state of the laser beam B in the cross section parallel to the x and y directions by the microlens 255a. The microlens 255a has a refractive index distribution that gradually increases outward from the optical axis O. In the drawing, the broken line shown in the microlens 255a indicates that the refractive index is predetermined from the optical axis O. The position changed with the pitch is shown.

  As shown in the figure, when the cross section parallel to the x direction is compared with the cross section parallel to the y direction, the ratio of the refractive index change of the microlens 255a is larger in the latter cross section, and the focal length is larger. It is shorter. Even when a microlens array composed of such a gradient index lens is used, the microlens has positive power in both the x-direction and y-direction, and the power in the x-direction is smaller than the power in the y-direction. It is possible to obtain the same effect as when a microlens array composed of

  Further, a diffractive lens may be used in place of the above refractive lens or gradient index lens. An example of such a microlens 355a is shown in FIG. (A) and (B) of the same figure respectively show the front shape and the side shape of the micro lens 355a, and the outer shape of the micro lens 355a is a parallel plate shape as shown in the figure. The x and y directions in the figure are as described above. As schematically shown in FIG. 6A, the microlens 355a has diffraction gratings formed at a pitch of a predetermined interval in the y direction, the power in the x direction is 0, and positive power in the y direction. It is what you have. Even when a microlens array composed of such microlenses 355a is used, it is possible to obtain the same effect as in the case of using a microlens array using the aforementioned microlenses 55a and 55a '.

  Further, instead of the lens having positive power in both the x direction and the y direction and having a power in the x direction smaller than that in the y direction, a diffractive lens 455a illustrated in FIG. 26 can be used. . (A) and (B) of the same figure respectively show the front shape and the side surface shape of the micro lens 455a, and the outer shape of the micro lens 455a is a parallel plate shape as shown in the figure. The x and y directions in the figure are as described above. As schematically shown in FIG. 6A, the pitch interval of the diffraction grating of the microlens 455a is larger in the x direction than in the y direction, and the power in the x direction is smaller than the power in the y direction. It is comprised so that it may become. Even when a microlens array composed of such a diffractive lens 455a is used, the microlens array has a positive power in both the x-direction and the y-direction, and the power in the x-direction is smaller than the power in the y-direction. It is possible to obtain the same effect as when the constructed microlens array is used.

  Furthermore, instead of the microlens, a composite lens configured by combining at least two of a refractive lens, a gradient index lens, and a diffractive lens may be used. For example, a Fresnel lens can be considered as a lens in which a refractive lens and a diffractive lens are combined. As a lens that combines a refractive lens and a refractive index distribution type lens, for example, a lens having a curved surface shape such as a spherical surface is used, and a lens having a refractive index distribution is used. Aberration due to distortion of the reflecting surface may be corrected.

  In the present embodiment, the x and y directions are taken along the two diagonal directions of the micro mirror 62, and the micro lens 55a is configured to have different powers along that direction. It is desirable to determine according to the strain distribution of the micromirror 62. For example, unlike the present embodiment, when there are significantly different curved shapes along the two side directions of the micromirror, the microlens may be configured to have different powers along the two side directions. desirable.

  Here, the condensing position will be described with reference to FIG. On the upstream side of the microlens 55a, the light reflected by the micromirrors 62 spreads and overlaps, as schematically shown by the overlapping dotted ellipses in FIG. On the other hand, on the downstream side of the micro lens 55a, the light reflected by the adjacent micro mirrors 62 is separated and condensed, as schematically shown by the dotted dotted ellipses in FIG. Yes. Referring to FIG. 21B, the light reflected by each micromirror 62 is separated and collected on the downstream side of the microlens 55a.

  That is, from the downstream side of the microlens 55a to a predetermined range, the condensing position where the light reflected by each micromirror 62 is separated and condensed by the micromirror 62, the lens systems 52 and 54, and the microlens 55a. It has become.

  In the present embodiment, an aperture array 59 is disposed at this condensing position, and only light that has passed through the corresponding microlens 55a is incident on and transmitted through each aperture 59a. Thereby, it is possible to prevent the incidence of light and stray light from the adjacent microlenses 55a not corresponding to the respective apertures 59a, and the extinction ratio can be increased. Moreover, such an aperture array 59 has high light utilization efficiency, and also has an effect that the beam shape can be shaped by the opening.

  Next, an image exposure apparatus according to a second embodiment of the present invention will be described. FIG. 27 is a schematic sectional view showing an exposure head of an image exposure apparatus according to the second embodiment of the present invention. Compared with the exposure head in the first embodiment shown in FIG. 5, this exposure head replaces the imaging optical system 51 in the first embodiment with a lens system from the imaging optical system 51 in the first embodiment. This is basically different in that an image forming optical system 51 ′ without the second image forming optical system 57 and 58 is used. Since other configurations are the same as those in the above-described embodiment, a duplicate description is omitted.

  That is, in this embodiment, the light collected by the microlens array 55 is directly exposed to the photosensitive material 150. Also in this embodiment, it is possible to obtain the same effect as that of the first embodiment.

  Next, an image exposure apparatus according to a third embodiment of the present invention will be described. FIG. 28 is a schematic sectional view showing an exposure head of an image exposure apparatus according to the third embodiment of the present invention. The image exposure apparatus of this embodiment is basically different in that a condensing microlens array 56 is further disposed at the condensing position of the image exposure apparatus of the first embodiment shown in FIG. In the present embodiment, an imaging optical system 151 is used instead of the imaging optical system 51 of the first embodiment. The image forming optical system 151 includes a first image forming optical system including lens systems 52 and 54, a second image forming optical system including lens systems 57 and 58, and a microscopic lens inserted between these image forming optical systems. The lens array 55, the condensing microlens array 56, and the aperture array 159 are configured. Since other configurations are the same as those in the above-described embodiment, a duplicate description is omitted.

  The condensing microlens array 56 includes a plurality of microlenses 56 a that individually collect the light that has passed through each pixel portion, and each microlens 56 a of the microlens array 55 is arranged in each microlens 56 a. Thus, the light that has been corrected for aberration and collected is made incident. Similarly to the aperture array 59, the aperture array 159 is formed by forming a large number of apertures (openings) 159a corresponding to the microlenses 56a of the condensing microlens array 56 on the light shielding member. It arrange | positions so that only the light which passed through each corresponding micro lens 56a may inject.

  In this embodiment, the same effect as that of the first embodiment can be obtained, and according to the configuration of the present embodiment, the beam condensed by the microlens array 55 and shaped in cross-section is condensed. Since the spot size can be controlled to be further reduced by collecting light by the micro lens array 56, the sharpness can be further improved.

  Next, an image exposure apparatus according to a fourth embodiment of the present invention will be described. FIG. 29 is a schematic sectional view showing an exposure head of an image exposure apparatus according to the fourth embodiment of the present invention. Compared with the exposure head in the third embodiment shown in FIG. 28, this exposure head replaces the imaging optical system 151 in the third embodiment with the lens system 57 from the imaging optical system 151 in the third embodiment. , 58 is basically different in that an imaging optical system 151 ′ is used without the second imaging optical system. Since other configurations are the same as those in the above-described embodiment, a duplicate description is omitted.

  That is, in this embodiment, the light collected by the microlens array 55 is directly exposed to the photosensitive material 150. Also in this embodiment, it is possible to obtain the same effect as that of the third embodiment.

  Furthermore, in the present embodiment, if the arranged condensing microlens array 56 is arranged so as to be movable in the optical axis direction of the light, the light focus can be easily adjusted. In particular, since the condensing microlens array 56 is arranged not at the image forming position but at the condensing position, it is possible to minimize the amount of change in the light utilization efficiency when performing the focus adjustment. That is, the amount of change in the light utilization efficiency before and after the focusing position is smaller than the amount of change in the light utilization efficiency before and after the imaging position. Therefore, when the condensing microlens array 56 is moved in the optical axis direction, it is possible to prevent the light utilization efficiency from changing suddenly.

  In the above-described embodiment, a laser light source is used as a light source for irradiating light to the spatial light modulation element. However, the present invention is not limited to this, and a lamp light source such as a mercury lamp can also be used.

  In the above embodiment, the DMD is used as the spatial light modulation element. However, the same effect can be obtained by applying the present invention to an image exposure apparatus using a reflective spatial light modulation element other than the DMD. It is done.

The perspective view which shows the external appearance of the image exposure apparatus which is one Embodiment of this invention 1 is a perspective view showing a configuration of a scanner of the image exposure apparatus in FIG. (A) is a plan view showing an exposed area formed on a photosensitive material, and (B) is a view showing an arrangement of exposure areas by each exposure head. 1 is a perspective view showing a schematic configuration of an exposure head of the image exposure apparatus of FIG. Cross section of the above exposure head Partial enlarged view showing the configuration of a digital micromirror device (DMD) (A) And (B) is explanatory drawing for demonstrating operation | movement of DMD. (A) and (B) are plan views showing the arrangement of the exposure beam and the scanning line in a case where the DMD is not inclined and in a case where the DMD is inclined. The perspective view which shows the structure of a fiber array light source Front view showing arrangement of light emitting points in laser emitting section of fiber array light source Diagram showing the configuration of a multimode optical fiber Plan view showing the configuration of the combined laser light source Plan view showing the configuration of the laser module Side view showing the configuration of the laser module shown in FIG. The partial front view which shows the structure of the laser module shown in FIG. Block diagram showing the electrical configuration of the image exposure apparatus (A) And (B) is a figure which shows the example of the use area | region of DMD. The figure which shows the direction of the deflection axis of the micromirror which comprises DMD The schematic diagram which shows distortion of the reflective surface of the said micromirror about two diagonal directions of this mirror Front view (A) and side view (B) of the microlens array used in the image exposure apparatus The perspective view (a) of the microlens which comprises the said microlens array, sectional drawing (b) in a cross section parallel to x direction, sectional drawing (c) in a cross section parallel to y direction Explanatory drawing explaining how aberration is corrected by a microlens Front view (A) and side view (B) showing another example of a microlens FIG. 22 is a schematic diagram showing a light collection state by the microlens of FIG. 22 in one cross section (A) and another cross section (B). Furthermore, the schematic which shows the condensing state by the micro lens of another example in one cross section (A) and another cross section (B) Front view (A) and side view (B) showing still another example of a microlens Front view (A) and side view (B) showing still another example of a microlens Sectional drawing of the optical head with which the image exposure apparatus of the 2nd Embodiment of this invention is provided Sectional drawing of the optical head with which the image exposure apparatus of the 3rd Embodiment of this invention is provided Sectional drawing of the optical head with which the image exposure apparatus of the 4th Embodiment of this invention is provided

Explanation of symbols

LD1 to LD7 GaN semiconductor laser 30, 31 Multimode optical fiber 50, 250 Digital micromirror device (DMD)
51 Imaging optical system 52, 54 Lens system 55, 55 ′ Micro lens array 55a, 55a ′, 56a, 155a, 255a, 355a, 455a Micro lens 56 Condensing micro lens array 57, 58 Lens system 59, 159 Aperture array 59a, 159a Apertures 62, 262 Micromirror 64 Laser module 66 Fiber array light source 68 Laser emitting unit 72 Rod integrator 150 Photosensitive material 152 Stage 162 Scanner 166 Exposure head 168 Exposure area 170 Exposed area

Claims (9)

A spatial light modulation element in which a plurality of reflective pixel portions each for modulating irradiated light according to a control signal are arranged in parallel;
A light source for irradiating light to the spatial light modulator;
An optical system that receives light that has passed through each pixel portion of the spatial light modulator and forms an image of the pixel portion, and light that has passed through the optical system via each pixel portion of the spatial light modulator is individually In an image exposure apparatus comprising a microlens array in which a plurality of incident microlenses are arranged side by side, and an imaging optical system that forms an image of light modulated by the spatial light modulator on a photosensitive material,
The microlens array is disposed in the vicinity of the imaging position of the pixel unit by the optical system,
Each microlens of the microlens array has different power in two directions in a plane perpendicular to the optical axis so as to correct aberration due to anisotropic distortion of the pixel portion. Exposure device.   The image exposure apparatus according to claim 1, wherein the microlens is a refractive lens.   The image exposure apparatus according to claim 1, wherein the microlens is a gradient index lens.   The image exposure apparatus according to claim 1, wherein the microlens is a diffractive lens.   2. The image exposure apparatus according to claim 1, wherein the microlens is a lens configured by combining at least two of a refractive lens, a gradient index lens, and a diffractive lens.   A plurality of microlenses for individually condensing light that has passed through each pixel unit at a condensing position by the pixel unit, the optical system, and the microlens array that are out of the imaging position of the pixel unit by the optical system. 6. The image exposure apparatus according to claim 1, further comprising a condensing microlens array arranged in parallel.   The image exposure apparatus according to claim 6, wherein the condensing microlens array is arranged to be movable in an optical axis direction of the light.   A plurality of apertures for individually transmitting the light passing through each pixel unit are arranged in parallel at the condensing position by the pixel unit, the optical system, and the microlens array, which are out of the imaging position of the pixel unit by the optical system. 8. The image exposure apparatus according to claim 1, further comprising an aperture array.   9. The spatial light modulation element according to claim 1, wherein the spatial light modulation element is a DMD (digital micromirror device) in which micromirrors as the pixel portions are two-dimensionally arranged. Image exposure equipment.

Images