JP4208141B2 - Image exposure method and apparatus - Google Patents

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.

  The present invention also relates to an exposure method using the image exposure apparatus as described above.

  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. Note that Non-Patent Document 1 and Japanese Patent Application No. 2002-149886 by the applicant of the present application show an example of an image exposure apparatus having the above basic configuration.

As one of the spatial light modulation elements suitably used in this type of image exposure apparatus, there is a DMD (digital micromirror device). The DMD is a mirror device in which a large number of micromirrors that swing according to a control signal and change the angle of a reflecting surface 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 the specification of Japanese Patent Application No. 2002-149886, a first imaging optical system is disposed in the optical path of the light modulated by the spatial light modulation element, and an imaging surface formed by this imaging optical system. Includes a microlens array in which microlenses corresponding to the respective pixel portions of the spatial light modulator are arranged in an array, and the optical path of the light that has passed through the microlens array depends on the modulated light. It has been considered that a second imaging optical system that forms an image on a photosensitive material or a screen is disposed, and the 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 1 shows an example of an image exposure apparatus using DMD as a spatial light modulation element and combining it with a microlens array. In Patent Document 2, in the same type of image exposure apparatus, an aperture plate having an aperture corresponding to each microlens of the microlens array is disposed on the rear side of the microlens array, and the corresponding microlens is passed through. A configuration is shown in which only light passes through the aperture. In this configuration, light from adjacent microlenses that do not correspond to each aperture of the aperture plate is prevented from entering, so that the extinction ratio is increased.
JP 2001-305663 A Special table 2001-500628 gazette Akihito Ishikawa "Development shortening and mass production application by maskless exposure", "Electrotronics packaging technology", Technical Research Committee, Vol.18, No.6, 2002, p.74-79

  By the way, in the conventional image exposure apparatus in which the DMD and the microlens array are combined as described above, there is a problem that the shape of the beam condensed by each microlens of the microlens array is distorted. It recognized.

  The present invention has been made in view of the above circumstances, and an object thereof is to prevent distortion of a beam condensed by a microlens in an image exposure apparatus in which a DMD and a microlens array are combined.

  Another object of the present invention is to provide an image exposure method capable of preventing the beam distortion.

An image exposure apparatus according to the present invention comprises:
As described above, a plurality of oscillating rectangular micromirrors are arranged two-dimensionally, and DMD (digital micromirror device) that spatially modulates incident light for each micromirror;
A light source for irradiating the DMD with light;
Imaging optics that includes a microlens array in which microlenses that collect light from each micromirror of the DMD are arranged in an array, and forms an image of light modulated by the DMD on a photosensitive material In an image exposure apparatus comprising a system,
An aperture plate having a long and narrow opening that is separated from the microlens array on the DMD side or integrated with the microlens array is a mirror oscillation axis of two diagonal lines of the rectangular micromirror. It is characterized in that it is provided for each microlens with the minor axis of the aperture substantially corresponding to the direction of the diagonal line parallel to the microlens.

  As the aperture plate, a plate having an elliptical opening, a plate having an oval opening, a plate having a polygonal opening, or the like can be suitably used. The aperture plate is preferably formed as an aperture array in which a plurality of apertures are arranged two-dimensionally.

  On the other hand, an image exposure method according to the present invention is characterized in that a predetermined pattern is exposed on a photosensitive material using the image exposure apparatus according to the present invention described above.

  According to the inventor's research, the above-mentioned problem that the shape of the beam condensed by the microlens is distorted is caused by the distortion of the reflection surface of the micromirror constituting the DMD. found. Conventionally, the reflection surface of a micromirror serving as a pixel portion in a DMD has been considered to be formed with high precision and flatness, but according to the analysis of the present inventors, this reflection surface is considerably distorted. It was found that basically has a distribution as shown in FIGS. 18 (A) and 18 (B). Hereinafter, this distortion distribution will be described in detail.

Rectangle micromirrors constituting the DMD are swung Suruga about one parallel to the oscillation axis of the two diagonals, Figure 18 (A) in the x-direction intersecting with the pivot shaft (swing direction) the strain distribution in cross section along the diagonal line, and FIG. (B) shows the strain distribution in the cross section along the diagonal line of the pivot shaft parallel to the y direction (the direction of the oscillation axis). In these drawings, the horizontal axis indicates the position from the mirror center. As shown here, there is an inflection point of distortion at a position near ± 5100 nm from the mirror center in the x direction, while there is an inflection point of distortion at a position near ± 4500 nm from the mirror center in the y direction. The distortion changes gently in the region on the mirror center side from each inflection point, and the distortion changes relatively greatly in the region outside it.

In view of the above knowledge, in the image exposure apparatus according to the present invention, an aperture plate having an elongated opening having a long axis, separated from the microlens array on the DMD side or integrally with the microlens array, Of the two diagonal lines of the rectangular micromirror, each microlens is provided in a state in which the short axis of opening corresponds to the direction of the diagonal line parallel to the mirror swing axis, that is, the y direction. When such an aperture plate is provided, most of the light reflected by the peripheral portion of the mirror (that is, the portion outside the inflection point) having a relatively large change in distortion is blocked by the aperture plate. The problem that the shape at the condensing position of the beam condensed by the lens is distorted can be prevented.

  As described above, if it is possible to prevent the shape of the beam collected by each microlens of the microlens array from being distorted, a higher-definition image without distortion can be exposed.

Of course, the basic action of the aperture plate can be obtained over the entire circumference of the aperture. However, in the image exposure apparatus of the present invention, the aperture plate is oriented in a diagonal direction parallel to the oscillation axis of the micromirror. Since it is arranged with the aperture short axis almost corresponding, light reflected in a relatively short range (this is a region with relatively little distortion change) from the center of the micromirror in this diagonal direction and its vicinity. Only passes through the opening, and the effect of preventing distortion of the beam shape is more certain. On the other hand, in the diagonal direction different from the above and in the vicinity thereof, light reflected in a relatively long range from the center of the micromirror (again, a region where the change in distortion is relatively small and the distortion itself is also small). Since the light passes through the opening, it is not necessary to squeeze an unnecessarily large amount of light in this direction, and the light utilization efficiency can be kept high as a whole.

  In the configuration described in Patent Document 2 described above, if the aperture diameter of the aperture plate installed for the purpose of increasing the extinction ratio is reduced to some extent as a whole, the beam shape at the condensing position of the microlens The effect which suppresses distortion of this is also acquired. However, in such a case, the amount of light blocked by the aperture plate increases, and the light utilization efficiency decreases. On the other hand, as described above, the image exposure apparatus of the present invention also maintains high light utilization efficiency.

  On the other hand, since the image exposure method according to the present invention exposes a predetermined pattern onto a photosensitive material using the image exposure apparatus according to the present invention described above, the shape of the condensed beam at the condensing position is distorted. This makes it possible to expose a high-definition pattern.

  An image exposure apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[Configuration of image exposure apparatus]
As shown in FIG. 1, the image exposure apparatus includes a flat plate-shaped 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 disposed 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 drive unit 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 end portions 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 mth row and the nth column, it is expressed as an exposure head 166 _mn .

An exposure area 168 by the exposure head 166 has a rectangular shape with the short side in the sub-scanning direction. Therefore, as the stage 152 moves, a strip-shaped exposed area 170 is formed on the photosensitive material 150 for each exposure head 166. 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 manufactured by Texas Instruments, Inc. as a spatial light modulation element that modulates an incident light beam for each pixel according to image data. 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 portion in which an emitting end portion (light emitting point) of an optical fiber is 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 the 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 includes a condenser 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 condenser lens 71. The rod-shaped optical integrator 72 (hereinafter referred to as a rod integrator) 72 and an imaging lens 74 disposed in front of the rod integrator 72, that is, on the mirror 69 side. The condenser lens 71, the rod integrator 72, and the imaging 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 this rod integrator 72 will be described in detail later.

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

  On the light reflection side of the DMD 50, an imaging optical system 51 that images the laser light B reflected by the DMD 50 on the photosensitive material 150 is disposed. The 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 56.

  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 will be described later, only 1024 × 256 rows of the 1024 × 768 rows of micromirrors of 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 micro lens 55a has a focal length of 0.19 mm, an NA (numerical aperture) of 0.11, and is formed of 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 micro lens 55a is 41 μm.

  The aperture array 56 is formed with a large number of apertures (openings) 56a corresponding to the respective microlenses 55a of the microlens array 55, and is arranged in the vicinity of the condensing position of the laser beam B by the lens system 54. ing. The aperture array 56 will be described in detail later.

  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 enlarged and enlarged by 4.8 times 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, a large number (for example, 1024 × 768) of micromirrors (micromirrors) 62 constituting pixels (pixels) are arranged on a SRAM cell (memory cell) 60 in a lattice pattern. This is a mirror device. In each pixel, a rectangular micromirror 62 supported by a support column is provided at the top, and a material having a 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. Directly below the micromirror 62, a silicon gate CMOS SRAM cell 60 manufactured on a normal semiconductor memory manufacturing line is disposed via a support including a hinge and a yoke, and the entire structure is monolithic. ing.

  When a digital signal is written to the SRAM cell 60 of the DMD 50, the micromirror 62 supported by the support is tilted within a range of ± α degrees (eg, ± 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. 7A shows a state where the micromirror 62 is tilted to + α degrees when the micromirror 62 is in the on state, and FIG. 7B shows a state where the micromirror 62 is tilted to −α degrees when the micromirror 62 is 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. The 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 micromirror 62 in the off state travels.

  Further, it is preferable that the DMD 50 is disposed 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. Further, by tilting the DMD 50, the pitch P ₁ of the scanning trajectory (scan line) of the exposure beam 53 by each micromirror becomes narrower than the pitch P ₂ of the scanning line when the DMD 50 is not tilted, and the resolution is greatly improved. Can be made. On the other hand, since the inclination angle of the DMD 50 is very small, the scanning width W ₂ when the DMD 50 is inclined and the scanning width W ₁ when the DMD 50 is not inclined are substantially the same.

  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 the 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 a multimode optical fiber 30 is coupled to each laser module 64. The other end of the multimode optical fiber 30 is coupled with an optical fiber 31 having the same core diameter as the multimode optical fiber 30 and a cladding diameter smaller than the multimode optical fiber 30. As shown in detail in FIG. 9b, seven end portions of the multi-mode optical fiber 31 opposite 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. Further, it is desirable that a transparent protective plate such as glass is 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 is easily collected and easily deteriorated due to its high light density.However, the protective plate as described above prevents the dust from adhering to the end face. 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 light 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 31a of the optical fiber 31 is the same as the diameter of the core 30a 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. 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. Further, 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 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, 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. On the top surface of the base plate 42, the heat block 10, a condensing lens holder 45 for holding the condensing lens 20, and a multimode optical fiber 30 are provided. 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 through 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 the 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 is numbered among the plurality of GaN semiconductor lasers, and only the collimator lens 17 is numbered among the plurality of collimator lenses. 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 in which a region including the optical axis of a circular lens having an aspherical surface is cut out in a parallel 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 the laser beams B1 to 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.

Accordingly, 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. The 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 for controlling 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. Further, 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 collimator lenses 11 to 17 and the condenser 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, propagate through the optical fiber, and merge 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 provide a laser beam B with 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 having the photosensitive material 150 adsorbed on 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 DMD 50 is irradiated with the laser beam B from the fiber array light source 66, 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 a pixel unit (exposure area 168) that is approximately the same number as the number of used pixels of 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. 16A may be used, and the micromirror arranged at the end of the DMD 50 as shown in FIG. 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-scanning of the photosensitive material 150 by the scanner 162 is completed and the rear end of the photosensitive material 150 is detected by the sensor 164, the stage 152 is moved to the most upstream side of the gate 160 along the guide 158 by the stage driving device 304. It returns to a certain origin and is moved again along the guide 158 from the upstream side to the downstream side of the gate 160 at a constant speed.

  Next, the illumination comprising the fiber array light source 66, the condensing lens 71, the rod integrator 72, the imaging 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 the illumination light. The optical 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 as 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.

FIG. 17 shows the result of measuring the flatness of the reflecting surface of the micromirror 62 constituting the DMD 50. In the figure, the same height positions of the reflecting surfaces are shown connected by contour lines, and the pitch of the contour lines is 5 nm. Note x and y directions shown in the figure is a two diagonal directions of the micromirrors 62, the micro mirror 62 is swung as described above about a pivot shaft extending parallel to the y-direction. 18A and 18B show the height position displacement of the reflecting surface of the micromirror 62 along the x direction and the y direction, respectively.

As shown in FIGS. 17 and 18, there is distortion on the reflecting surface of the micromirror 62. 18A and 18B, when this change in distortion is examined closely, there is an inflection point of distortion at a position near ± 5100 nm from the mirror center in the x direction intersecting with the oscillation axis of the micromirror 62. In the y direction parallel to the oscillation axis, there is an inflection point of distortion at a position near ± 4500 nm from the mirror center, and the distortion changes gradually in the region closer to the mirror center than those inflection points. In the outer region, the strain changes relatively greatly. In addition, the change in the distortion in the y direction is significantly larger than the change in the distortion in the x direction, and the above tendency is more remarkable. If the above-described distortion exists on the reflection surface of the micromirror 62, there may be a problem that the shape of the laser beam B collected by the microlens 55a of the microlens array 55 is distorted. As shown in FIG. 18A, the distortion in the x direction of the reflection surface is relatively small in the region near the center of the micromirror 62.

  In the image exposure apparatus of the present embodiment, the above-described aperture array 56 (see FIG. 5) is provided in order to cope with the above-described problem. As shown in FIG. 19, the aperture array 56 has a large number of elliptical apertures 56a arranged two-dimensionally. The same number of the apertures 56a as the microlenses 55a are provided so as to correspond to the microlenses 55a of the microlens array 55, respectively. The aperture array 56 is in a state in which each aperture 56a is aligned with the optical axis of the micro lens 55a, and the short axis of the elliptical aperture 56a corresponds to one diagonal direction (y direction) of the micro mirror 62. It is arranged. Here, “the short axis of the aperture 56a corresponds to the y direction of the micromirror 62” means that both are aligned in the optical positional relationship between the aperture 56a and the micromirror 62.

  When the aperture array 56 as described above is provided, most of the laser light B reflected by the peripheral portion of the micromirror 62 having a relatively large distortion change is blocked by the aperture array 56. The problem that the shape at the condensing position of the condensed laser beam B is distorted can be prevented. If so, the laser beam B can expose a higher-definition image without distortion.

  Of course, the basic action of the aperture array 56 is obtained over the entire circumference of the aperture 56a. In the present embodiment, the aperture array 56 has a short axis as a micromirror as shown in FIG. 62 is arranged in a state corresponding to one diagonal direction (y direction), and therefore, in the y direction and the vicinity thereof, a relatively short range from the center of the micromirror 62 (here, a change in distortion is relatively small). Only the laser beam B reflected in the region) passes through the aperture 56a, and the effect of preventing the distortion of the beam shape is more certain.

  On the other hand, in the diagonal direction different from the above, that is, the diagonal direction (x direction) in which the change in distortion of the reflecting surface is smaller and the vicinity thereof, a relatively long range from the center of the micromirror 62 (again, the change in distortion) Since the laser beam B reflected by the relatively small amount of distortion and the distortion itself passes through the aperture 56a, it is not necessary to squeeze an unnecessarily large amount of light in this direction. Can be kept high. If the light utilization efficiency can be ensured in this way, the number of laser beams to be combined can be reduced, and therefore generation of excess heat can be suppressed.

  Of course, even if the aperture 56a is arranged in a state in which the minor axis thereof is slightly deviated from the state in which the minor axis accurately corresponds to the y direction of the micromirror 62, the above-described effect can be basically obtained. It is.

  Further, in the present embodiment, the aperture 56a of the aperture array 56 is elliptical, but an oval aperture 56b shown in FIG. 20 or an elongated polygonal aperture 56c shown in FIG. 21 may be employed. In this case, basically the same effect as that obtained when the aperture 56a is elliptical can be obtained.

  In addition, the aperture plate used in the image exposure apparatus of the present invention is separated from the microlens array 55 like the aperture array 56 in the above-described embodiment and arranged on the DMD 50 side further than that, and is integrated with the microlens array 55. It may also be formed. 22 and 23 show examples of the aperture plate formed as described above. In the configuration shown in FIG. 22, a light-shielding mask 356 having an elongated opening 356a is formed on the surface opposite to the surface on which the microlens 55a of the microlens array 55 is formed (DMD side) by, for example, vapor deposition. The light shielding mask 356 functions as an aperture plate. In the configuration shown in FIG. 23, a light-shielding mask 356 similar to the above is formed on the surface of the microlens array 55 where the microlenses 55a are formed, and the light-shielding mask 356 functions as an aperture plate. Yes.

  Further, when the aperture plate is formed separately from the microlens array in the image exposure apparatus of the present invention, the installation position is not limited to between the DMD and the microlens array, and the aperture plate is disposed on the light source side from the DMD. May be installed.

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 distortion of the reflective surface of the micromirror which comprises DMD with a contour line The graph which shows distortion of the reflective surface of the said micromirror about two diagonal directions of this mirror The front view which shows the aperture plate used for the image exposure apparatus of FIG. Schematic showing another example of aperture shape of aperture plate Schematic showing yet another opening shape example of the opening plate Side view showing another example of aperture plate Side view showing still another example of aperture plate

Explanation of symbols

LD1-LD7 GaN semiconductor laser
30, 31 Multimode optical fiber
50 Digital micromirror device (DMD)
51 Magnification optical system
52, 54 Lens of the first imaging optical system
55 Micro lens array
56 Aperture array
56a, 56b, 56c Aperture (opening)
57, 58 Second imaging optical system lens
66 Laser module
66 Fiber array light source
68 Laser emission part
72 Rod integrator
150 photosensitive material
152 stages
162 Scanner
166 Exposure head
168 Exposure area
170 Exposed area
356 Shading Mask
356a Opening of shading mask

Claims (6)

A plurality of oscillating rectangular micromirrors arranged two-dimensionally, DMD (digital micromirror device) that spatially modulates the incident light for each micromirror,
A light source for irradiating the DMD with light;
Imaging optics that includes a microlens array in which microlenses that collect light from each micromirror of the DMD are arranged in an array, and forms an image of light modulated by the DMD on a photosensitive material In an image exposure apparatus comprising a system,
An aperture plate having an elongated opening having a short axis and a long axis, separated from the microlens array on the DMD side or integrally with the microlens array, is one of the two diagonal lines of the rectangular micromirror. An image exposure apparatus provided for each microlens in a state in which a minor axis of an opening substantially corresponds to a diagonal direction parallel to a mirror swing axis.
  2. The image exposure apparatus according to claim 1, wherein the aperture plate has an elliptical aperture.   2. The image exposure apparatus according to claim 1, wherein the aperture plate has an oval aperture.   2. The image exposure apparatus according to claim 1, wherein the aperture plate has a polygonal aperture.   5. The image exposure apparatus according to claim 1, wherein the aperture plate forms an aperture array in which a plurality of apertures are arranged in a two-dimensional manner.   6. An image exposure method comprising exposing a predetermined pattern onto a photosensitive material using the image apparatus according to claim 1.

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