JP2006350011A - Image exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image exposure device for preventing the quality of an exposure image from deteriorating, for example, when dust adheres to a microlens array. <P>SOLUTION: The image exposure device comprises a spatial light modulator comprising a two-dimensional arrangement of a great number of pixel portions each modulating irradiated light; a light source for applying light to the spatial light modulator; and an image-forming optical system that includes a microlens array 55 having an arrangement of a microlenses 55a each individually converging light from each pixel section of the spatial light modulator in an array and forms an image by light modulated by the spatial light modulator on a photosensitive material. The microlens array 55 is arranged so that a surface which carries the microlens 55a faces the side of the spatial light modulator, and has a thickness that is larger than the focal distance of the microlens. As a result, a focal position A in the microlens is inside the microlens array 55. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image exposure apparatus, and more particularly to image exposure 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. Relates to the device.

  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.

  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 rectangular 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, the first imaging optical system is arranged on the optical path of the light modulated by the spatial light modulation element, and the microscopic surface corresponding to each pixel portion of the spatial light modulation element is formed on the imaging surface by the imaging optical system. A microlens array in which lenses are arranged in an array is arranged, and in the optical path of the light that has passed through the microlens array, a second connection for forming an image of the modulated light on a photosensitive material or a screen. It is considered that an image optical system is disposed 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 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, an aperture array (aperture plate) having apertures (openings) corresponding to the microlenses of the microlens array is arranged on the rear side of the microlens array in the same type of image exposure apparatus. A configuration is shown in which only the light passing through the microlens 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 stray light can be prevented from entering the adjacent pixels. Even when the DMD pixel (micromirror) is turned off so that light is not irradiated onto the exposure surface, a slight amount of light may be incident on the exposure surface. As a result, the amount of light on the exposure surface when the DMD pixel is in the off state can be reduced.
JP 2001-305663 A JP 2004-122470 A

  As described above, in the conventional image exposure apparatus in which the spatial light modulation element and the microlens array are combined, dust (contaminants) due to impurities adheres to the microlens array. There is a problem that the image quality of the exposed image is deteriorated significantly. That is, at the position of the photosensitive material to be irradiated with the light passing through the microlens array to which dust is attached, the amount of exposure light is always extremely small regardless of the modulation state of the light, for example, an exposure image A situation occurs in which black dots are recorded on the screen.

  In addition, as shown in FIG. 21, the energy density is high at the position (focal position A) where the light transmitted through the microlens array 102 in which the microlenses 100 are arranged in an array is collected. There are cases where the air near the position A is contaminated and dust tends to collect. In this case, dust tends to adhere to the surface of the nearby microlens array 102, and there is also a problem that the amount of light is reduced and the quality of the exposed image is impaired.

  The present invention has been made in consideration of the above facts, and in an image exposure apparatus comprising a combination of a spatial light modulation element and a microlens array, the image quality of the exposed image is reduced even when dust adheres to the microlens array. An object of the present invention is to provide an image exposure apparatus that can prevent this from happening.

  In order to achieve the above object, the invention described in claim 1 is directed to a spatial light modulation element in which a large number of pixel portions each for modulating irradiated light are arranged two-dimensionally, and light to the spatial light modulation element. And a microlens array in which microlenses for condensing light from each pixel portion of the spatial light modulator are arranged in an array, and the light modulated by the spatial light modulator An image exposure apparatus comprising an imaging optical system that forms an image on a photosensitive material, wherein the microlens array is disposed such that a surface on which the microlens is formed faces the spatial light modulation element side. And a thickness greater than the focal length of the microlens.

  The spatial modulation element is a two-dimensional array of a large number of pixel units that modulate light emitted from a light source, and the imaging optical system collects light from each pixel unit of the spatial light modulation element. The microlens array includes a microlens array in which the microlenses are arranged in an array, and forms an image of light modulated by the spatial light modulator on the photosensitive material. According to a fourth aspect of the present invention, the spatial light modulation element is a DMD (digital micromirror device) in which micromirrors as the pixel unit are two-dimensionally arranged. it can.

  The microlens array is arranged so that the surface on which the microlens is formed faces the spatial light modulation element side. The microlens array has a thickness larger than the focal length of the microlens. Thereby, the focal position of the light transmitted through the microlens is inside the microlens array. Therefore, air is not polluted by the light dust collection effect, and it is effectively prevented that the image quality of the exposure image is deteriorated due to insufficient light quantity. Furthermore, even if dust (contaminants) due to impurities adheres to the microlens array, the energy of the light emitted from the microlens array is small, so the influence on the image quality of the exposure image is small. A reduction in image quality due to a decrease in the amount of light can be suppressed as much as possible.

  For example, when the wavelength of light passing through the microlens array 55 is in the short wavelength range of 350 nm to 450 nm, and the microlens array is arranged near or around the imaging position of the imaging lens that images light from the light source In particular, the surface of the microlens array near the imaging position that is in a high energy state is also in a very high energy state, and impurities are likely to adhere to the surface of the microlens array. By applying the present invention in such a case, it is possible to suppress the deterioration of the image quality of the exposure image.

  According to a second aspect of the present invention, there is provided a spatial light modulation element in which a large number of pixel portions that respectively modulate the irradiated light are two-dimensionally arranged, and a light source that irradiates the spatial light modulation element with light. A microlens array in which microlenses for condensing light from the respective pixel portions of the spatial light modulator are arranged in an array, and an image formed by the light modulated by the spatial light modulator is displayed on the photosensitive material. An image forming optical system that forms an image on the image exposure apparatus, further comprising: a transmissive member that transmits light from the microlens, wherein the transmissive member has a focal position of the microlens within the transmissive member. It is good also as a structure arrange | positioned in the position which becomes.

  In this case, as described in a third aspect, a light-shielding mask may be formed on the transmissive member.

  The mask may be an aperture array made of a light-shielding member and provided with an opening corresponding to each microlens. By providing such a mask, the extinction ratio can be effectively increased.

  According to the present invention, even when dust adheres to the microlens array, it is possible to prevent the image quality of the exposure image from being deteriorated.

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

(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 moving 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) described later for driving a moving stage 152 as a 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 movement 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 moving 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. Accordingly, as the moving 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 in accordance with 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 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 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 condensing 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 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. It comprises two image forming optical systems and a microlens array 55 inserted between these image forming optical systems.

  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 micro lens 55a has a focal length of 0.19 mm and an NA (numerical aperture) of 0.11. The shape of the microlens 55a is, for example, a semispherical shape. The beam diameter of the laser beam B at the position of each microlens 55a is 41 μm. Details of the focal position of the micro lens 55a will be described 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 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 rectangular 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.

  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. Further, by tilting the DMD 50, the pitch P ₁ of the scanning locus (scanning 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 tilt angle of the DMD 50 is very small, the scan width W ₂ when the DMD 50 is tilted and the scan width W ₁ when the DMD 50 is not tilted are substantially the same.

  Further, the same scanning line is overlapped and exposed (multiple exposure) by different micromirror rows. In this way, by performing multiple exposure, it is possible to control a minute amount of the exposure position 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. 9A, 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 ends of the optical fiber 31 opposite to the multimode optical fiber 30 are arranged along the main scanning direction orthogonal to the sub-scanning direction, and they are arranged in two rows. Thus, a laser emitting unit 68 is configured.

  As shown in FIG. 9B, the laser emitting portion 68 constituted by the end portion of the optical fiber 31 is sandwiched and fixed between two support plates 65 having a flat surface. Moreover, it is desirable to arrange a transparent protective plate such as glass on the light emitting end face of the optical fiber 31 for protection. The light exit end face of the optical fiber 31 has high light density and is likely to collect dust and easily deteriorate. However, by arranging the protective plate as described above, it is possible to prevent the dust from adhering to the end face and to delay the deterioration. Can do.

  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 multimode optical fiber 30 and the optical fiber 31 are coupled by fusing the incident end face of the optical fiber 31 to the outgoing end face of the multimode 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 multimode optical fiber 30 and the core diameter of the optical fiber 31 are matched.

  In the present invention, as described above, it is not always necessary to use two multimode optical fibers having different clad diameters, that is, optical fibers 31 by fusion (so-called different diameter fusion), and the clad diameter is constant. A fiber array light source may be configured by bundling a plurality of optical fibers (for example, the multimode optical fiber 30 in the example of FIG. 9A) as they are in a bundle.

  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 have substantially the same oscillation wavelength (for example, 405 nm), and all the maximum outputs are also almost the same (for example, about 100 mW for the multimode laser and about 50 mW for the single mode laser). Note that the outputs of the GaN-based semiconductor lasers LD1 to LD7 may be different from each other below the maximum output. Further, 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. 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 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 moving stage 152 is connected to the overall control unit 300.

  Next, the microlens array 55 will be described in detail.

  As shown in FIG. 5, the microlens array 55 is arranged such that the surface on which the microlens 55a is formed is on the lens system 54 side, that is, the light incident side.

  As shown in FIG. 17, the microlens array 55 has a thickness d such that the focal position A of each microlens 55 a is inside the microlens array 55. That is, the thickness d of the microlens array 55 is larger than the focal length of the microlens 55a. Here, the thickness d is a distance from the apex portion of the microlens 55a to the bottom surface of the microlens array 55 as shown in FIG.

  As described above, at the focal position A, the energy density is increased because the light transmitted through the lens system 54 is collected. However, in the microlens array 55 according to the present embodiment, the focal position A of each microlens 55a is a microlens. Since it exists inside the array 55, the phenomenon that the air is contaminated by the light dust collecting effect does not occur. Therefore, it is possible to effectively prevent the image quality of the exposure image from being deteriorated due to insufficient light quantity.

  In addition, even when contaminants (dust) adhere to other than the condensing position of the microlens, the light intensity is lower than in the vicinity of the condensing position except in the vicinity of the condensing position. Can be suppressed. Therefore, as shown in FIG. 17, even when dust 80 is attached to the bottom surface of the microlens array 55, the light spreads at that position and the light energy is small. Therefore, the influence on the image quality of the exposure image is small, and the deterioration of the image quality can be suppressed.

  In this embodiment, the wavelength of the laser beam B is 405 nm, and is included in the short wavelength range of 350 nm to 450 nm. Accordingly, since the energy of the laser beam B is high, impurities easily adhere to the surface of the microlens array 55 in particular. However, with the above configuration, it is possible to suppress a deterioration in image quality due to dust adhesion.

  Further, by making the microlens array 55 thick, it is possible to prevent the microlens array 55 from being deformed such as warpage due to a temperature change or the like. For this reason, it can prevent that the focal position of each micro lens 55a varies, and it can prevent that surface accuracy deteriorates.

(Operation of image exposure device)
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 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 moving stage 152 that adsorbs 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 end of the photosensitive material 150 is detected by the sensor 164 attached to the gate 160 when the moving stage 152 passes under the gate 160, the image data stored in the frame memory is sequentially read out for 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 13.7 μm × 13.7 μm.

  When the laser light B is irradiated from the fiber array light source 66 to the DMD 50, the laser light reflected when the micromirror of the DMD 50 is on is imaged on the photosensitive material 150 by the imaging optical system 51. 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. In addition, the photosensitive material 150 is moved at a constant speed together with the moving stage 152, so that 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 for each exposure head 166. 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 completed and the rear end of the photosensitive material 150 is detected by the sensor 164, the moving stage 152 is moved along the guide 158 by the stage driving device 304 on the most upstream side of the gate 160. Returned to the origin at the point, and again moved along the guide 158 from the upstream side to the downstream side of the gate 160 at a constant speed.

  Next, illumination that is configured by 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 irradiates the DMD 50 with the laser light B as 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 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.

  As described above, the thickness d of the microlens array 55 is larger than the focal length of the microlens 55a. Therefore, the light incident on the microlens 55a is collected inside the microlens array 55 and emitted from the microlens array 55 in a spread state. Therefore, air is not polluted by the light dust collection effect, and it is effectively prevented that the image quality of the exposure image is deteriorated due to insufficient light quantity.

  Further, even when dust adheres to the bottom surface or the like of the microlens array 55, the energy of the light emitted from the microlens array 55 is small, so that the influence on the image quality of the exposure image is small and the dust adheres. Therefore, it is possible to suppress the deterioration of the image quality due to the decrease in the amount of light as much as possible.

  Furthermore, since the microlens array 55 is thickened, it is possible to prevent the microlens array 55 from being deformed such as warpage due to a temperature change or the like. Therefore, it is possible to prevent the focal positions of the micro lenses 55a from varying, and it is possible to prevent the surface accuracy from deteriorating.

  In the present embodiment, the thickness d of the microlens array 55 is set to be larger than the focal length of the microlens 55a. However, the microlens array 55 is not thickened, but is positioned at the focal position A of the microlens 55a. Alternatively, a transmissive member that transmits light, such as glass, may be provided.

  For example, as shown in FIG. 18, a transmissive member 84 is provided separately from the microlens array 55, and is arranged so that the focal position A of the microlens 55 a is inside the transmissive member 84. Thereby, it is possible to prevent the air from being contaminated by the light dust collecting effect, and it is effectively prevented that the image quality of the exposure image is deteriorated due to insufficient light quantity.

  Further, when the transmissive member 84 is provided separately from the microlens array 55 as described above, the surface on which the microlens 55a of the microlens array 55 is formed faces the transmissive member 84 as shown in FIG. You may arrange in.

  Furthermore, as shown in FIG. 20, a mask 86 may be provided on the transmissive member 84. The mask 86 is an aperture array in which openings (apertures) are two-dimensionally arranged corresponding to the microlenses 55a of the microlens array 55. By providing such a mask 86, extra light transmitted through the portion other than the microlens 55a of the microlens array 55 is reflected by the mask 86, and the extinction ratio can be increased.

  As shown in FIG. 20, the mask 86 may be provided on the surface of the transmission member 84 on the side facing the microlens array 55, or on the surface opposite to the surface. Further, the mask 86 may be provided separately from the transmission member 84.

It is a perspective view which shows the external appearance of the image exposure apparatus which is one Embodiment of this invention. It is a perspective view which shows the structure of the scanner of the image exposure apparatus of FIG. (A) is a top view which shows the exposed area | region formed in a photosensitive material, (B) is a figure which shows the arrangement | sequence of the exposure area by each exposure head. It is a perspective view which shows schematic structure of the exposure head of the image exposure apparatus of FIG. It is sectional drawing of the said exposure head. It is the elements on larger scale which show the structure of a digital micromirror device (DMD). (A) And (B) is explanatory drawing for demonstrating operation | movement of DMD. (A) And (B) is a top view which compares the arrangement | positioning of an exposure beam, and a scanning line by the case where it does not incline and arranges DMD. (A) is a perspective view which shows the structure of a fiber array light source, (B) is a front view which shows the arrangement | sequence of the light emission point in the laser emission part of a fiber array light source. It is a figure which shows the structure of a multimode optical fiber. It is a top view which shows the structure of a combined laser light source. It is a top view which shows the structure of a laser module. It is a side view which shows the structure of the laser module shown in FIG. It is a partial front view which shows the structure of the laser module shown in FIG. It is a block diagram which shows the electric constitution of the said image exposure apparatus. (A) And (B) is a figure which shows the example of the use area | region of DMD. It is sectional drawing of a microlens array. It is sectional drawing of a microlens array and a transmissive member. It is sectional drawing of a microlens array and a transmissive member. It is sectional drawing of the permeation | transmission member provided with the micro lens array and the mask. It is a figure for demonstrating the condensing position of the microlens array which concerns on a prior art example.

Explanation of symbols

30 Multimode optical fiber 31 Optical fiber 50 Digital micromirror device (DMD)
51 Imaging optical system 55 Micro lens array 62 Micro mirror 64 Laser module 66 Fiber array light source 68 Laser emitting part 84 Transmission member 86 Mask 150 Photosensitive material 162 Scanner 166 Exposure head 300 Overall control part

Claims (4)

A spatial light modulation element in which a large number of pixel portions each modulating the irradiated light are two-dimensionally arranged;
A light source for irradiating light to the spatial light modulator;
Including a microlens array in which microlenses for condensing light from each pixel portion of the spatial light modulator are arranged in an array, and an image formed by the light modulated by the spatial light modulator is formed on a photosensitive material. An imaging optical system for imaging;
In an image exposure apparatus comprising:
The microlens array is disposed such that a surface on which the microlens is formed faces the spatial light modulation element side, and has a thickness larger than a focal length of the microlens. apparatus. A spatial light modulation element in which a large number of pixel portions each modulating the irradiated light are two-dimensionally arranged;
A light source for irradiating light to the spatial light modulator;
Including a microlens array in which microlenses for condensing light from each pixel portion of the spatial light modulator are arranged in an array, and an image formed by the light modulated by the spatial light modulator is formed on a photosensitive material. An imaging optical system for imaging;
In an image exposure apparatus comprising:
An image exposure apparatus comprising: a transmissive member that transmits light from the microlens, wherein the transmissive member is disposed at a position where a focal position of the microlens is inside the transmissive member.   The image exposure apparatus according to claim 2, wherein a light-shielding mask is formed on the transmissive member.   4. 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 unit are two-dimensionally arranged. The image exposure apparatus according to item.

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