WO2006085660A1

WO2006085660A1 - Image exposing apparatus

Info

Publication number: WO2006085660A1
Application number: PCT/JP2006/302568
Authority: WO
Inventors: Shuichi Ishii; Koichi Kimura; Katsuto Sumi; Hiromi Ishikawa; Toshihiko Omori
Original assignee: Fujifilm Corporation
Priority date: 2005-02-10
Filing date: 2006-02-08
Publication date: 2006-08-17
Also published as: KR20070104642A; TW200636396A; JP2006251748A

Abstract

An image exposing apparatus, in which a photosensitive material is exposed by light modulated by a spatial optical modulation device, which is capable of securing high light utility efficiency and extinction ratio. In an image exposing apparatus including a spatial optical modulation device 50, such as a DMD having multitudes of reflective pixel sections disposed two-dimensionally, each for modulating light irradiated thereon; a light source 66 for irradiating light B on the spatial optical modulation device 50; and an imaging optical system 51 for focusing an image represented by the light B transmitted via the spatial optical modulation device 50 on a photosensitive material 150, each of the pixel sections (e.g., micromirrors of DMD) is shaped like a concave or convex mirror that converges the light B used for image exposure.

Description

DESCRIPTION

IMAGE EXPOSING APPARATUS

Technical Field

The present invention relates to an image exposing apparatus .

More specifically, the present invention is directed to an image exposing apparatus, in which a photosensitive material is exposed by focusing thereon an optical image represented by the light modulated by a spatial optical modulation device .

Background Art

Image exposing systems in which light modulated by a spatial optical modulation device is transmitted through an imaging optical system to focus an image represented by the light on a predetermined photosensitive material in order to expose the photosensitive material with the image are known. Basically, such image exposing system includes a spatial optical modulation device constituted by a plurality of pixel sections arranged in rows, each for modulating irradiated light in accordance with a control signal; a light source for irradiating light on the spatial optical modulation device; and an imaging optical system for imaging an optical image represented by the light modulated by the spatial optical modulation device on the photosensitive material . In such image exposing systems, a device such as a DMD (digital micromirror device) or the like may preferably be used as the spatial optical modulation device. The DMD described above is a mirror device in whichmultitudes of rectangularmicromirrors that change the angle of the reflecting surface according to a control signal are disposed two-dimensionally on a semiconductor substrate made of, for example, silicon or the like. Here, the micromirrors described above serve as reflective pixel sections .

In the image exposing system described above, it is often the case that an image needs to be enlarged before being projected on the photosensitive material . If that is the case, an image magnifying and focusing optical system is used as the imaging optical system. Simple passage of light propagatedvia the spatial optical modulation device through the image magnifying and focusing optical system may results in a broader light beam from each of the pixel sections of the spatial optical modulation device. Thus, the pixel size in the projected image becomes larger and the sharpness of the image is degraded.

Consequently, a consideration has been given to enlarge and project an image using first and second imaging optical systems . In this configuration, the first imaging optical system is disposed in the optical path of the light modulated by the spatial optical modulation device with a microlens array havingmicrolenses disposed in an array, each corresponding to each pixel section of the spatial optical modulation device, being disposed at the imaging plane of the first imaging optical system, and the second imaging optical system for focusing the image represented by the modulated light on a photosensitive material or screen is disposed in the optical path of the light transmitted through the microlens array. In the configuration described above, the size of the image projected on a photosensitive material or screen may be enlarged, and yet the sharpness of the image may be maintained at a high level, since the light from each of the pixel sections of the spatial optical modulation device is converged by each microlens of the microlens array, thereby the pixel size (spot size) in the projected image is narrowed down and maintained at a small size .

One of such image exposing systems that uses a DMD as the spatial optical modulation device in combination with a microlens array is described in Japanese Unexamined patent Publication No . 2001-305663. A similar type of image exposing system is described in Japanese Unexamined patent Publication No . 2004-122470. In the system, an aperture array (aperture plate) having apertures, each corresponding to each microlens of the microlens array, is provided on the rear side of the microlens array to allow only the light propagatedvia a correspondingmicrolens to pass through the aperture . This configuration prevents light from the adjacent microlenses that do not correspond to the aperture of the aperture plate from entering the aperture, so that stray light may be prevented from wandering into the adjacent pixels . Further, a small amount of light may sometimes be irradiated on the exposing surface even when the pixels

(micromirrors) of the DMD are turned off to shut out the light . In this case also, the configuration described above may reduce the amount of light present on the exposing surface when the pixels of the DMD are turned off. In the conventional image exposing system constituted by a combination of a spatial optical modulation device having reflective pixel sections such as a DMD, amicrolens array, and an imaging optical system, an image represented by each of the pixel sections such as the micromirrors or the like is focusedby the imaging optical system, and the microlens array is disposed such that each of the microlenses thereof is placed at the imaging plane formed by the imaging optical system.

The image exposing apparatus constructed in the manner as described above has problems that degraded optical utility efficiency and extinction ratio may result unless the relative positional relationship between the spatial modulation device and microlens array is maintained strictly in a predetermined fashion.

Detailed description on this point will be provided hereinbelow.

Squares indicated by the reference numeral 100 in Figure 18A are images represented by the pixel sections of a spatial optical modulation device, such as the micromirrors of a DMD focused by an imaging optical system. A rectangle indicated by the reference numeral 101 in Figure 18B is a microlens array having microlenses 102 disposed side by side. In providing such micromirror images 100 on a part of the respective microlenses 102 of the microlens array 101, if the micromirror images 100 are formed larger than the size of the microlenses 102, the relationship between the formed images and microlenses becomes like that shown in Figure 19A, and if the spatial modulation device and microlens array are misaligned in the direction that crosses the optical axis, the relationship becomes like that shown in Figure 19B. In both cases, a large eclipse occurs, and the light reflected on the edge portion of the micromirrors is no longer used for image exposure, resulting in low light utility efficiency. Generally, a mask for blocking unwanted light is provided integrally or separately on the exterior of the edge portion of the microlens 102. If such mask is provided, the light eclipsed in the manner as described above is blocked by the mask. Even if such mask is not provided, the light eclipsed in the manner as described above is deflected from the aperture of the microlens 102 and is not converged by , the microlens 102. Thus, the light is not available for the intended use .

Further, when the misalignment between the spatial modulation device and microlens array shown in Figure 19B becomes greater, a part of the micromirror image 100 which should be focused on a part of the microlens 102 called A is focused on a part of the adjacent microlens 102 called B. If that is the case, for example, when the light transmitting through B microlens 102 needs to be completely blocked, the light which should be inputted to Amicrolens 102 enters B microlens 102, thereby the extinction ratio of B microlens 102 is degraded.

In view of the circumstances described above, it is an object of the present invention to provide an image exposing apparatus having high light utility efficiency with a high extinction ratio.

Disclosure of Invention

An image exposing apparatus of the present invention comprises : a spatial optical modulation device having a plurality of reflective pixel sections disposed side by side, each for modulating light irradiated thereon according to a control signal; a light source for irradiating light on the spatial optical modulation device; and an imaging optical system for focusing an image represented by the light modulated by the spatial optical modulation device on a photosensitive material; wherein each of the pixel sections of the spatial optical modulation device is shaped like a concave or convex mirror.

In the image exposing apparatus constructed in the manner as described above, if the imaging optical system includes an optical system for receiving light transmitted via each of the pixel sections of the spatial optical modulation device and focusing an image of each of the pixel sections; and a microlens array having a plurality of microlenses disposed side by side, each for receiving light transmitted through the optical system and separately converging the light transmitted via each of the pixel sections of the spatial optical modulation device are provided, the microlens array is preferable to be disposed at a light converging plane, formed by the concavely or convexly shaped pixel sections and optical system, off the imaging plane of the pixel sections formed by the lens system.

Further, if the microlens array is provided, the imaging optical system is preferable to include an optical system for receiving light transmitted through the microlens array and focusing light received from each of the microlenses of the microlens array on the photosensitive material .

Further, instead of the microlens array, an aperture array having a plurality of apertures disposed side by side, each for separately transmitting the light transmitted via each of the pixel sections of the spatial optical modulation device may be provided. In this case, the aperture array is preferable to be disposed at a light converging plane, formed by the concavely or convexly shaped pixel sections and the optical system, off the imaging plane of the pixel sections formed by the lens system.

If the aperture array is provide, the imaging optical system is preferable to include an optical system for receiving light transmitted through the aperture array and focusing light received from each of the apertures of the aperture array on the photosensitive material .

Further, in the image exposing apparatus of the present invention, a DMD described above maypreferably be used as the spatial optical modulation device .

The image exposing apparatus according to another embodiment of the present invention comprises : a spatial optical modulation device having a plurality of reflective pixel sections disposed side by side, each for modulating light irradiated thereon according to a control signal; a light source for irradiating light on the spatial optical modulation device; and an optical system for focusing an image represented by the light modulated by the spatial optical modulation device on a photosensitive material, wherein: each of the pixel sections of the spatial optical modulation device is shaped like a curved surface; and when a primary ray of the light exiting from the spatial optical modulation device has a divergence angle, a convergence angle of the primary ray of the light provided by the pixel sections and the optical system is formed greater than the divergence angle of the primary ray.

Here, each of the pixel sections of the spatial optical modulation device mayhave any shape as long as it has a curved surface . It may be shaped like a concave or convex mirror.

A microlens array may be disposed at a light converging plane, formed by the pixel sections and the optical system, off the imaging plane formed by the pixel sections and optical system. In this case, the microlens array may be installed movable in optical axis directions of the light to allow focus adjustment .

The apparatus may further comprise an aperture array having a plurality of apertures disposed side by side, each for receiving light transmitted through the optical system and transmitting the light transmitted via each of the pixel sections of the spatial optical modulation device separately. Preferably, the aperture array is disposed at a light converging plane, formed by the pixel sections and the optical system, off the imaging plane of the pixel sections formed by the optical system. Preferably, a lighting angle, which is a divergence angle of a primary ray of the light is formed smaller than the difference between a convergence angle of the primary ray of the light and a diffraction angle formed by the spatial optical modulation device, in order to make the convergence angle of the primary ray of the light greater than the divergence angle thereof.

The referent of "light converging plane" as used herein means a plane where the light reflected by the pixel sections is converged separately, which is off the imaging plane formed by the pixel sections and the optical system. When performing image exposure by irradiating light transmitted via each of the pixel sections of the spatial optical modulation device on the photosensitive material, it is basically required to converge and focus light transmitted via each of the pixel sections . In the image exposing apparatus of the present invention, each of the pixel sections of the spatial optical modulation device is shaped like a concave or convex mirror which allows each of the pixel sections to converge the light separately. Further, the light cnverging capability on a pixel by pixel basis may also be provided by forming a convergence angle of a primary ray of the light, which is determined by the shape of each of the pixel sections and the optical system, greater than a divergence angle of the primary ray. Accordingly, if each of the light beams separately converged by the pixel sections has an intended beam diameter, the microlens array may be omitted. Thereby, degradation in the light utility efficiency and extinction ratio which may occur if the microlens array is provided as described above may be prevented.

Further, in the case where an optical system for receiving light transmitted via each of the pixel sections of the spatial optical modulation device and focusing an image represented by the pixel sections, and the microlens array described above for receiving light transmitted through the optical system are provided, degradation in the light utility efficiency and extinction ratio may be prevented by disposing the microlens array at a light converging plane, formed by the concavely or convexly shaped pixel sections, off the imaging plane of the pixel sections formed by the optical system described above . This will be elaborated with reference to Figures 20 and 21 hereinbelow.

Circles indicated by the reference numeral 110 in Figure 2OA are converged images produced by the concavely shaped pixel sections and the optical system. A rectangle indicated by the reference numeral 101 in Figure 2OB is a microlens array having microlenses 102 disposed side by side . The converged image described above is a small sized (converged size) light spot unlike the images of the pixel sections . Consequently, the relationship between such converged images and the microlenses 102 of the microlens array 101 becomes like that shown in Figures 21A and 21B. That is, even if the spatial modulation device and mierolens array is slightly misaligned as shown in Figure 21B, as well as they are in concentric relationship as shown in Figure 21A, eclipse of the converged image is prevented from occurring, or a converged image to be inputted to a certain microlens is prevented from wandering into adjacent microlenses . In this way, degradation in the light utility efficiency and extinction ration may be prevented. Further, only less distorted light beams converged by the concavely shaped pixel sections transmit through the microlenses, so that stray light not converged and reflecting distortions may be easily blocked by the aperture array or the like provided on the outside of the microlens array.

Brief Description of Drawings

Figure 1 is a perspective view of an image exposing apparatus according to a first embodiment of the present invention, illustrating the overview thereof. Figure 2 is a perspective view of a scanner of the image exposing apparatus shown in Figure 1, illustrating the construction thereof.

Figure 3A is a plan view of a photosensitive material, illustrating exposed regions thereof. Figure 3B is a drawing illustrating the disposition of the exposing area of each exposing head.

Figure 4 is a perspective view of an exposing head of the image exposing apparatus shown in Figure 1, illustrating the schematic construction thereof. Figure 5 is a schematic cross-section view of the exposing head described above .

Figure 6 is a partially enlarged view of a digital micromirror device (DMD) , illustrating the construction thereof.

Figure 7A is a drawing for explaining the operation of the DMD.

Figure.7B is a drawing for explaining the operation of the DMD.

Figure 8A is a plan view of the DMD, illustrating the arrangement of the exposing beams and scanning lines when the DMD is not inclined relative to the subscanning direction.

Figure 8B is a plan view of the DMD, illustrating the arrangement of the exposing beams and scanning lines when the DMD is inclined relative to the subscanning direction.

Figure 9A is a perspective view of a fiber array light source, illustrating the construction thereof.

Figure 9B is a front elevation view of the fiber array light source, illustrating the disposition of luminous points at the laser output section.

Figure 10 is a drawing illustrating the construction of a multimode optical fiber.

Figure 11 is a plan view of a beam-combining laser light source, illustrating the construction thereof.

Figure 12 is a plan view of a laser module, illustrating the construction thereof. Figure 13 is a side view of the laser module shown in Figure 12, illustrating the construction thereof.

Figure 14 is a partial front elevation view of the laser module shown in Figure 12, illustrating the construction thereof.

Figure 15 is a block diagram illustrating the electrical configuration of the image exposing apparatus described above . Figure 16A is a drawing illustrating an example area of use in the DMD.

Figure 16B is a drawing illustrating an example area of use in the DMD. Figure 17 is a schematic cross-sectional view of the exposing head used for the image exposing apparatus according to a second embodiment.

Figures 18A and 18B are illustrations for explaining problems of the conventional image exposing apparatus . Figures 19A and 19B are illustrations for explaining problems of the conventional image exposing apparatus .

Figures 2OA and 2OB are illustrations for explaining advantageous effects of the apparatus of the present invention.

Figures 2IA and 2IB are illustrations for explaining advantageous effects of the apparatus of the present invention.

Figure 22 is a schematic plan view of a DMD used for the image exposing apparatus of the present invention, illustrating the relevant part thereof.

Figure 23 is a schematic side view of the DMD shown in Figure 22, illustrating the relevant part thereof.

Figures 24A to 24F are illustrations for explaining the manufacturing process of the DMD shown in Figure 22.

Figure 25 is a schematic side view of a drive circuit board used for the DMD shown in Figure 22. Figure 26 a schematic plan view of an alternative DMD used for the image exposing apparatus of the present invention, illustrating the relevant part thereof .

Figure 27 is a schematic side view of the DMD shown in Figure 26, illustrating the relevant part thereof . Figures 28A to 28F are illustrations for explaining the manufacturing process of the DMD show in Figure 26.

Figure 29 is a schematic side view of a drive circuit board used for the DMD shown in Figure 26.

Figure 30 is a pattern diagram illustrating how light is convergedby the DMD andoptical system in the apparatus of the present invention.

Figure 31 is a pattern diagram illustrating how light is converged by the DMD and optical system in the conventional apparatus . Figure 32 is a pattern diagram illustrating another example of how light is converged by the DMD and optical system in the apparatus of the present invention.

Figures 33A and 33B are pattern diagrams illustrating the relevant part of the image exposing apparatus according to another embodiment of the present invention.

Figures 34A and 34B are pattern diagrams illustrating the relevant part of the image exposing apparatus according to still another embodiment of the present invention.

Best Mode for Carrying Out the Invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings . The image exposing apparatus according to a first embodiment will be described first . [Construction of the Image Exposing Apparatus]

As shown in Figure 1, the image exposing apparatus of the present embodiment includes a plate-like moving stage 152 for holding a sheet-like photosensitive material 150 thereon by suction. Two guides 158 extending ' along the moving direction of the stage are provided on the upper surface of a thick plate-like mounting platform 156 which is supported by four legs 154. The stage 152 is arranged such that its longitudinal direction is oriented to the moving direction of the stage, and movably supported by the guides 158 to allow back-and-forth movements . The image exposing apparatus of the present embodiment further includes a stage drive unit 304 (Figure 15) , which will be described later, for driving the stage 152 that serves as a subscanning means along the guides 158.

An inverse U-shaped gate 160 striding over the moving path of the stage 152 is provided at the central part of the mounting platform 156. Each of the ends of the inverse U-shaped gate 160 is fixedly attached to each of the sides of the mounting platform 156.

A scanner 162 is provided on one side of the gate 160, and a plurality of sensors 164 (e. g. two) for detecting the front and rear edges of the photosensitive material 150 is provided on the other side. The scanner 162 and sensors164 are fixedly attached to the gate 160 over the moving path of the stage 152. The scanner 162 and sensors

164 are connected to a controller (not shown) that controls them.

As shown in Figures 2 and 3B, the scanner 162 includes a plurality of exposing heads 166 (e . g. fourteen) arranged in matrix form in V rows and "n" columns . In this example, four exposing heads 166 are disposed in the third row in relation to the width of the photosensitive material 150. Hereinafter, the exposing head disposed at the n^th column of the m^th row will be designated as the exposing head 166,^. The exposing area 168 of each exposing head 166 has a rectangular form with the short side oriented in the subscanning direction. Accordingly, a stripe-shaped exposed region 170 is formed on the photosensitive material 150 by each of the exposing heads 166 as the stage 152 moves . Hereinafter, the exposing area of the exposing head disposed at the n^th column of the m^th row will be designated as the exposing area 168™.

As shown in Figures 3A and 3B, ^" each of the exposing heads 166 arranged linearly in a row is displaced by a predetermined distance (e . g. , a natural number multiple of the long side of the exposing area, twice the long side in this case) in the arrangement direction such that each of the stripe-shaped exposed regions 170 is disposed without any gap with the adjacent exposed regions 170 in the orthogonal direction to the subscanning direction. Consequently, the unexposed region of the photosensitive material which corresponds to the space between the exposing areas 168u and 168_i2 in the first row may be exposed by the exposing area 168₂i in the second row and exposing area I6831 in the third row.

As shown in Figures 4 and 5, each of the exposing heads 166_n to 166mn has a digital micromirror device (DMD) 50, which is available from U.S . Texas Instruments Inc. , as the spatial optical modulation device that modulates the incident light beam on a pixel by pixel basis according to image data. The DMD 50 is connected to a controller 302 (Figure 15) to be described later. The controller 302 includes a data processing section and a mirror drive controlling section. The data processing section of the controller 302 generates a control signal for drive controlling each of the micromirrors within an area of the DMD 50 to be controlled for each of the exposing heads 166 based on inputted image data. The meaning of the "area to be controlled" will be provided later. The mirror drive controlling section controls the angle of the reflecting surface of each of the micromirrors .of the DMD 50 for each of the exposing heads 166 based on the control signal generatedby the image data processing section. The method for controlling the angle of the reflecting surface of each of the micromirrors will be described later. A fiber array light source 66 having a laser output section in which output faces (luminous points) of optical fibers are arranged linearly along the direction corresponding to the direction of the long side of the exposing area 168; a lens system 67 for correcting and focusing the laser beamoutputted from the fiber array light source 66 on the DMD; and a mirror 69 for reflecting the laser beam transmitted through the lens system 67 toward the DMD 50 are disposed in this order on the light entry side of the DMD 50. In Figure 4, the lens system 67 is illustrated schematically.

As illustrated in detail in Figure 5, the lens system 67 includes a condenser lens 71 for condensing a laser beam B as the illuminating light emitted from the fiber array light source 66, a rod-shaped optical integrator 72 (hereinafter referred to as "rod integrator) placed in the light path of the light transmitted through the condenser lens 71, and an imaging lens 74 disposed ahead of the rod integrator 72, that is, on the side of the mirror 69. The laser beam emitted from the fiber array light source 66 is irradiated on the DMD 50 through the condenser lens 71, rod integrator 72, and^' imaging lens 74 as a substantially collimated light beam having homogeneous light intensity in the cross section. The shape and function of the rod integrator 72 will be described in detail later . The laser beam B exiting from the lens system 67 is reflected by the mirror 69, and irradiated on the DMD 50 through a TIR (total internal reflection) prism 70. In Figure 4, the TIR prism 70 is omitted. An imaging optical system 51 for focusing the laser beam B reflected by the DMD 50 on the photosensitive material 150 is disposed on the light reflecting side of the DMD 50. The imaging optical system 51 is schematically shown in Figure 4. As illustrated in detail in Figure 5, the imaging optical system 51 includes a first imaging optical system constituted by lens systems 52, 54, and a second imaging optical system constituted by lens systems 57, 58, with a microlens array 55 and an aperture array 59 disposed between the two optical systems .

As shown in Figure 6, the DMD 50 is a mirror-device constituted by multitudes (e . g. , 1024 x 768) of tiny mirrors (micromirrors) 62, each forming a pixel, are arranged in a lattice pattern on SRAM cells

(memory cells) 60. In each pixel, a rectangular micromirror is provided at the top, which is supported by a support post . A highly reflective material, such as aluminum or the like, is deposited on the surface of the micromirror. The reflectance of the micromirror is not less than 90% . The size of the mirror is, for example, 13μm in both vertical and horizontal directions, and the arranging pitch is, for example, 13.7μm in both vertical and horizontal directions. Each of the micromirrors 62 is formed like a concave mirror having a light condensing (focusing) capability by a method to be described later. A silicon-gate CMOS SRAM cell 60, which may be produced on a commonmanufacturing line for manufacturing semiconductormemories, is provided beneath each of the micromirrors 62 through the support post having a hinge and yoke . The entire DMD is constructed monolithically.

When a digital signal is written into the SRAM cell 60 of the DMD 50, the micromirror supported by the support post is inclined within the range of ± α degrees (e .g. , ± 12 degrees) centered on the diagonal line relative to the substrate on which the DMD 50 is mounted. Figure 7A shows the micromirror 62 inclined by + α degrees, whichmeans that it is in on-state, and Figure 7B shows the micromirror 62 inclined by - α degrees, which means that it is in off-state . Accordingly, by controlling the tilt of the micromirror 62 in each pixel of the DMD 50 according to image signals as shown in Figure 6, the laser beam B irradiated on the DMD 50 is reflected to the tilt direction of each of the micromirros 62.

Figure 6 is a partially enlarged view of the DMD 50, illustrating an example state in which some of the micromirrors in a portion of the DMD 50 are controlled to tilt by + or - α degrees . The on-off control of each of the miromirrors 62 is implemented by the controller 302 connected to the DMD 50. A light absorption material (not shown) is disposed in the propagating direction of the laser beamB reflectedby the micromirrors which are in off-state .

The microlens array 55 shown in Figure 5 includes multitudes of microlenses 55a arranged two-dimensionally, each corresponding to each pixel or micromirror 62 of the DMD 50. Each of the microlenses 55a is placed at a position where the laser beam B reflected by the correspondingmiromirror 62 enters, which is a light convergingplane formed by the micromirrors 62 and the lens systems 52, 54, off the imaging plane of the micromirrors 62 formed by the lens systems 52, 54. Although the DMD 50 has 1024 pieces x 768 columns of micromirrors in total, only 1024 pieces x 256 columns are driven in the present embodiment as will be described later. Thus, corresponding number of 1024 pieces x 256 columns of the microlenses 55a are disposed. The size of the microlens 55a is 41um in both vertical and horizontal directions . As an example, the microlens 55a is made of silica glass, and has a focal length of 0.23mm and a NA (numerical aperture) of 0.06.

In the mean time, the aperture array 59 is made of an opaque member with multitudes of apertures (openings) 59a formed therethrough, each corresponding to each of the microlenses of the microlens array 55. In the present embodiment, the diameter of each of the apertures 59a is 12um.

The image of the DMD 50 is focused on the microlens array by the first optical system constituted by the lens systems 52, 54 shown in Figure 5 by magnifying it three times, and the image formed after the microlens array is focused and projected on the photosensitive material 150 by the second optical system constituted by the lens systems 57, 58 by magnifying it 1.6 times . In the present embodiment, a prism pair 73 is disposed between the second optical system and photosensitive material 150, and the focus of the image on the photosensitive material 150 may be adjusted by moving the prism pair 73 in up and down directions in Figure 5. In Figure 5, the photosensitive material 150 is moved in the subscanning direction indicated by the arrow F.

Preferably, the DMD 50 is installed in slightly inclined manner so that the short side thereof forms a predetermined angle θ (e .g. , 0.1 to 5 degrees) with the subscanning direction. Figure 8A illustrates the scan trace of the reflected light image 53 (exposing beam) produced by each of the micromirrors when the DMD 50 is not inclined, and Figure 8B illustrates the scan trace of the exposing beam 53 from each of the micromirrors when the DMD 50 is inclined.

The DMD 50 includes multitudes of micromirror columns (e . g. , 756) disposed in the transverse direction, each having a multitude of micromirrors (e. g. , 1024) disposed in the longitudinal direction. As shown in Figure 8B, the pitch P₂ between the scan traces (scanning lines) of the exposing beams 53 produced by the micromirrors is narrower when DMD 50 is inclined than the pitch Pi when it is not inclined, and image resolution is improved significantly. In the mean time, the inclination angle of the DMD 50 relative to the subscanning direction is very small so that a scanning width W₂ when the DMD is inclined is approximately the same as a scanning width Wi when it is not inclined. Further, the same scanning line is exposed a plurality of times by the different micromirror columns (multiple exposures) . The multiple exposures allow fine control of exposing position and a high resolution exposure may be realized. Further, the seam between a plurality of exposing heads disposed in the main scanning direction may be smoothed out by the fine exposing position control . The similar effect may be obtained by arranging the micromirror columns in a zigzag pattern by displacing each of the micromirror columns by a predetermined distance in the direction which is orthogonal to the subscanning direction, instead of inclining the DMD 50.

As shown in Figure 9A, the fiber array light source 66 includes a plurality of laser modules 64 (e . g. , 14) , and one end of a length of multi-mode optical fiber 30 is connected to each of the laser modules 64. A length of optical fiber 31 having the same core diameter and smaller clad diameter than the multi-mode optical fiber 30 is spliced to the other end of each of the multi-mode optical fibers 30. As is illustrated in detail in Figure 9B, each end face of seven optical fibers 31 on the side opposite to the multimode fiber 30 is aligned along the main scanning direction which is orthogonal to the subscanning direction, and two arrays of the end faces are disposed to form a laser output section 68.

The laser output section 68 constituted by the end faces of the optical fibers 31 is fixedly sandwiched by two support plates 65, each having a flat surface. Preferably, a transparent protection plate made of glass or the like is provided on each of the light output faces of the optical fibers 31 for protection. The light output face of each of the optical fibers 31^" is likely to collect dust and prone to deterioration since it has a high optical density. Provision of the protection plate described above may prevent adhesion of dust and delay the deterioration.

In the present embodiment, the optical fiber 31 having a smaller clad diameter with the length of around 1 to 30 cm is spliced coaxially to the tip of the laser beam output side of the multimode fiber 30 having a greater clad diameter as ^'shown in Figure 10. The optical fibers 30, 31 are spliced together by fusion splicing the input face of the optical fiber 31 to the output face of the optical fiber 30 with the core axes being aligned. As described above, the optical fiber 31 has the same core diameter as the multimode optical fiber 30. As for the multimode optical fiber 30 and optical fiber 31, a step index type optical fiber, graded index type optical fiber, or hybrid type optical fiber may be used. For example, a step index type optical fiber available from Mitsubishi Cable Industries, Ltd. may be used. In the present embodiment, the multimode optical fiber 30 and optical fiber 31 are step index type . The Multimode optical fiber 30 has a clad diameter of 125um, a core diameter of 50μm, a NA of 0.2, and a transmittance for the coating of input face of not less than 99.5% . The optical fiber 31 has a clad diameter of 60um, a core diameter of 50um, and a NA of 0.2. However, the clad diameter of the optical fiber 31 is not limited to 60μm. The clad diameter of many optical fibers used for a conventional optical fiber light source is 125μm. Preferably, the clad diameter of the multimode optical fiber is not greater than 80um, and more preferably, not greater than 60um, since a smaller clad diameter results in a deeper focal depth. Preferably, the clad diameter of the optical fiber 31 is not less than lOμm, since a single mode optical fiber requires a core diameter of at least 3 to 4um. Preferably, the optical fibers 30, 31 have the same core diameter from the stand point of coupling efficiency. In the present invention, it is not necessarily required to use two different types of optical fibers 30, 31 having different clad diameters with each other by ^"fusion splicing them together

(so-called taper splicing) . The fiber array light source may be formed by bundling a^* plurality of optical fibers having the same clad diameter (e .g. , optical fibers 30 in Figure 9A) , each without a different type of optical fiber being spliced thereto.

The laser module 64 is constituted by a beam combining laser light source (fiber light source) . The beam combining laser light source includes a plurality of transverse multimode or single mode GaN system semiconductor laser chips LDl, LD2, LD3, LD4, LD5, LD6 and LD7 fixedly mounted on a heat block 10; collimator lenses 11, 12, 13, 14, 15, 16, and 17, each provided for each of the GaN system semiconductor lasers LDl to LD7; a condenser lens 20; and a multimode optical fiber 30. The number of the semiconductor lasers is not limited to seven, and different number of the semiconductor lasers may be employed. Further, instead of the seven separate collimator lenses 11 to 17, a collimator lens array in which these collimator lenses are integrated may be used.

Each of the GaN system semiconductor lasers LDl to LD7 has substantially the same oscillation wavelength (e . g. , 405nm) and maximum output (e . g. , around 10OmW for multimode laser, and 5OmW for single mode laser) . The output of each of the GaN system semiconductor lasers LDl to LD7 may differ with each other below the maximum output power. As for the GaN system semiconductor lasers LDl to LD7, a laser that oscillates at a wavelength in the wavelength range from 350 to 450nm other than at 405nm may also be used.

The beam combining laser light source is installed in a box type package 40 having a top opening together with other optical elements . The package 40 includes a package lid 41 formed to seal the opening of the package 40. A sealing gas is introduced into the package 40 after being deaerated, and the opening of the package 40 is sealed with the package lid 41 to air-tightly seal the beam combining laser light source within the closed space (sealing space) created thereby. A base plate 42 is fixedly attached on the bottom surface of the package 40, and the heat block 10, a collimator lens holder 45 for holding the collimator lens 20, and a fiber holder 46 for holding the input end of the multimode fiber 30 are attached on the upper surface of the base plate 42. The output end of the multimode fiber 30 is drawn outside through an aperture provided on the wall of the package 40.

A collimator lens holder 44 is attached to a lateral surface of the heat block 10, and the collimator lenses 11 to 17 are held thereat . An aperture is provided on a lateral side wall through which wiri'ng for supplying a drive current to the GaN system semiconductor lasers LDl to LD7 is drawn outside .

In Figure 13, only the GaN system semiconductor laser LDl out of the seven semiconductor lasers LDl to LD7, and the collimator lens 17 out of the seven collimator lenses 11 to 17 are shown for clarity. Figure 14 is a front view of the mounting section of the collimator lenses 11 to 17, illustrating the front geometry thereof. Each of the collimator lenses 11 to 17 is formed such that a region including the optical axis of a circular lens having an aspheric surface is sliced out by parallel planes in an elongated form. The elongated collimator lens may be formed, for example, by molding resin or optical glass . The collimator lenses 11 to 17 are disposed closely with each other in the arrangement direction of the luminous points of the GaN system semiconductor lasers LDl to LD7 (left-to-right direction in Figure 14) such that the length direction of the collimator lenses 11 to 17 is oriented in the direction which is orthogonal to the arrangement direction of the luminous points of the GaN system semiconductor lasers LDl to LD7.

In the mean time, as for the GaN system semiconductor lasers LDl to LD7, lasers that include an active layer with a luminous width of 2um and emit respective laser beams Bl to B7 with divergence angles of, for example, 10 degrees and 30 degrees respectively in the parallel and orthogonal directions to the active layer is used. The GaN system semiconductor lasers LDl to LD7 are disposed such that the luminous points thereof are aligned linearly in the direction parallel to the active layer .

Accordingly, the laser beams Bl to B7 emitted from the respective luminous points enter the respective elongated collimator lenses 11 to 17 with the direction having a larger divergence angle corresponds to the length direction and the direction having a smaller divergence angle corresponds to the width direction (direction orthogonal to the length direction) of the collimator lenses . That is, the width of each of the collimator lenses 11 to 17 is 1.1mm, the length thereof is 4.6mm, and the beam diameters of the laser beams Bl to B7 entering the collimator lenses 11 to 17 in the horizontal and vertical directions are 0.9mm and 2.6mm respectively. Each of the collimator lenses 11 to 17 has a focal length fi of 3mm and a NA of 0.6, which is arranged with a pitch of 1.25mm. The condenser lens 20 is formed such that a region including the optical axis of a circular lens having an aspheric surface is sliced out by parallel planes in an elongated form. It is disposed such that the long side thereof corresponds to the arrangement direction of the collimator lenses 11 to 17, i . e . , horizontal direction, and short side thereof corresponds to the direction orthogonal to the horizontal direction. The condenser lens 20 has a focal length I₂ of 23mm and a NA of 0.2. The condenser lens 20 is also formed by molding resin or optical glass .

The electrical configuration of the image exposing apparatus according to the present invention will be described with reference to Figure 15.. As shown in Figure 15, an overall control section 300 connects to a modulation circuit 301, which in turn connects to a controller 302 for controlling the DMD 50. The overall control section 300 also connects to an LD drive circuit 303 for driving laser modules 64. Further, it connects to a stage drive unit 304 for driving the stage 152. [Operation of the Image Exposing Apparatus]

The operation of the aforementioned image exposing apparatus will be described hereinafter. In each of the exposing heads of the scanner 162, each of the laser beams Bl, B2, B3, B4, B5, B6, and B7 emitted in diverging manner from each of the GaN system semiconductor lasers LDl to LD7 (Figure 11) , which constitute a beam combining light source of the fiber array light source 66, is collimated by each of the corresponding collimator lenses 11 to 17. The collimated laser beams Bl to B7 are condensed by the condenser lens 20 and focused on the input end face of a core 30a of the multimode optical fiber 30.

In the present embodiment, the collimator lenses 11 to 17 and condenser lens 20 constitute a condensing optical system, and the condensing optical system and multimode optical fiber 30 constitute a beam combining optical system. That is, laser beams Bl to B7 condensed by the condenser lens 20 in the manner as described above enter the core 30a of the multimode optical fiber 30 to propagate therethrough, and exit from the optical fiber 31, which is spliced to the output end face of the multimode optical fiber 30, as a single combined laser beam B.

In each of the laser modules 64, when the coupling efficiency of the laser beams Bl to B7 to the multiitiode optical fiber 30 is 0.9, and output power of each of the GaN system semiconductor lasers LDl to LD7 is 5OmW, a combined laser beam B having an output power of 315mW (5OmWxO .9x7) from each of the optical fibers 31 arranged in arrays . Accordingly, from the total number of 14 optical fibers, a laser beam B having an output power of 4.4W (0.315x14) may be obtained. When performing an image exposure, image data according to the image to -be exposed are inputted from the modulation circuit 301 shown in Figure 15 to the controller 302 of the DMD 50 and temporarily stored in the frame memory thereof. The image data are data in which the gray level of each of the pixels forming the image is represented by a binary value (presence/absence of a dot) .

The stage 152 with a photosensitive material 150 suctioned thereon is moved along the guides 158 at a constant speed from the upper stream to the down stream of the gate 160. When the stage 152 passes under the gate 160, and the front edge of the photosensitive material 150 is detected by the sensors 164 attached to the gate 160, the image data stored in the frame memory are sequentially read out for a plurality of lines at a time . Then, a control signal for each of the exposing heads 166 is generated on a head-by-head basis by the data processing section based on the readout image data, and each of the micromirrors of the DMD 50 in each of the exposing heads 166 is on-off controlled on a head-by-head basis by the mirror drive controlling section based on the generated control signal .

While the laser beam B is irradiated on the DMD 50 from the fiber array light source 66, a laser beam reflected by a micromirror of the DMD 50 driven to on-state is focused on the photosensitive material 150 through the lens system 51. In this way, the laser beam emitted from the fiber array light source 66 is on-off controlled on a pixel-by-pixel basis, and the photosensitive material 150 is exposed with the number of pixels (exposing areas 168) which is substantially equal to that of the pixels of the DMD used. The photosensitive material 150 is moved with the stage 152 at a constant speed so that the photosensitive material 150 is subscanned by the scanner 162 in the direction opposite to the stage moving direction, and a stripe-shaped exposed region 170 is formed by each of the exposing heads 166.

Although DMD 50 includes 768 arrays of micromirrros disposed in the subscanning direction, eachhaving 1024 pieces of microrαirrors disposed in the main scanning direction, only a part of the micromirror arrays (e . g. , 1024 pieces * 256 arrays) is drive controlled by the controller 302 in the present embodiment as shown in Figures 16A and 16B.

In this case, micromirror arrays disposed either in the central area (Figure 16A) , or top (or bottom) end area (Figure 16B) of the DMD 50 may be used. In addition, if some of the micromirrors become defective, a micromirror array or arrays having no defective micromirror may be used instead of the micromirror array or arrays having the defective micromirrors . In this way, the micromirror arrays may be changed accordingly depending on the situation.

The DMD 50 has a certain limited data processing speed. The modulation speed per line is inversely proportional to the number of pixels used. Therefore, the modulation speed per line may be increased by using only a part of the entire micromirror arrays. In the mean time, for the exposing method in which the exposing heads are moved continuously relative to the exposing surface, not all of the pixels located in the subscanning direction need to be used.

When the subscanning of the photosensitive material 150 by the scanner 162 is completed, and the rear edge of the photosensitive material 150 is detected by the sensors 164, the stage 152 is returned to the original position on the uppermost stream of the gate 160 along the guides 158 by the stage drive unit 304. Thereafter, it is moved again along the guides 158 from the upper stream to down stream of the gate 160 at a constant speed.

Illumination optics, which are constituted by the fiber array light source 66, condenser lens 71, rod integrator 72, image forming lens 74, mirror 69, and TIR prism 70 shown in Figure 5, for irradiating the laser beam B as illumination light on the DMD 50 will be described herein below. The rod integrator 72 is, for example, a transparent rod formed in a square pole. While the laser beam B propagates in the rod integrator 72 by total reflection, the intensity distribution within the cross-section of the laser beam B is homogenized. The input and output faces of the rod integrator 72 is provided with an antireflection coating to improve the transmittance . Provision of the laser beam B, which serves as the illumination light, having a highlyhomogenized intensity distributionwithin the cross-section in the manner as described above may result in the illumination light having a homogeneous light intensity, allowing a high resolution image to be exposed on the photosensitive material 150.

In the apparatus according to the present embodiment, each of the microlenses 55a of the microlens array 55 shown in Figure 5 is placed at a light converging plane, formed by the micromirrors and the lens systems 52, 54, off the imaging plane of the micromirrors formed by the lens systems 52, 54. This arrangement arrows light utility efficiency and extinction ratio to be maintained high even when a slight misalignment occurs between the DMD 50 and microlens array 55. The reason is as described above with reference to Figures 20 and 21.

Hereinafter, a second embodiment of the present invention will be described. Figure 17 is a schematic cross-sectional view of an exposing head of the image exposing apparatus according to the second embodiment . The exposing head of the second embodiment basically differs from the exposing head shown in Figure 5 in that it does not include the second optical system constituted by the lens systems 57, 58. That is, in the image exposing apparatus according to the second embodiment, the photosensitive material 150 is placed at the light converging plane formed by the microlenses 55a of the microlens array 55, and the image converged by the microlens array 55 is exposed directly on the photosensitive material .

In the present embodiment also, each of the microlenses 55a of the microlens array 55 is placed at a light converging plane, formed by the micromirrors 62 and the lens systems 52, 54, off the imaging plane of the micromirrors 62 formed by the lens systems 52, 54, so that light utility efficiency and extinction ratio may be maintained high even when a slight misalignment occurs between the DMD 50 and microlens array 55 as in the first embodiment . In the mean time, if the laser beam B converged by the micromirrors and lens systems 52, 54 has an intended beam diameter, the microlens array 55 may be omitted.

Further, it is also possible to use an aperture array having multitudes of apertures arranged side by side, instead of the microlens array 55 used in the two embodiments described above. In this case, the aperture array is disposed at a light converging plane formed by the micormirrors and lens systems 52, 54. Such aperture array may provide an advantageous effect of reshaping of the beam by the apertures, in addition to high light utility efficiency. ■ Hereinafter, an example method for manufacturing the DMD 50 will be described. Figure 22 is a detailed plan view of an element 400 of the DMD 50 described above, and Figure 23 is a cross-sectional side view of the element 400 taken along the line A-A .in Figure 22. First, the element 400 serving as a pixel section of the DMD 50 will be described.

The element 400 includes first and second lower electrodes 463a, 463b formed spaced apart with each other on a drive circuit substrate 451, first and second upper electrodes 467a, 467b formed spaced apart from the first and second lower electrodes 463a, 463b respectively, and a moving member 461 (which includes a hinge 455 and a mirror section 457) disposed between the lower electrodes 463a, 463b and upper electrodes 467a, 467b . The first upper electrode 467a is provided at a location corresponding to that of the first lower electrode 463a, and the second upper electrode 467b is provided at a location corresponding to that of the second lower electrode 463b. The sections indicatedby the reference numerals 479 and 483 in Figure 22 are support sections of the hinge 455 and support sections of the upper electrodes 467a, 467b respectively.

The micromirror 62 schematically shown in Figure 7 and other drawings corresponds to the central region (not blocked by the upper electrodes 467a, 467b) of the mirror section 457. In Figure 22, the central region of the mirror section 457 is indicated relatively small with respect to the entire size of the element 400 for clarity. In actuality, however, the central region of the mirror section 457 occupies a major portion of the element 400.

As shown in Figure 23, the first lower electrode 463a and second upper electrode 467b are connected to each other, and then connected to a first drive electrode 485, while the second lower electrode 463b and first upper electrode 467a are connected to each other, and then connected to a second drive electrode 487. The hinge 455 made of a conductive material is connected to a moving member electrode 489. The potentials Vl, V2, and Vm of the first drive electrode 485, second drive electrode 487, and moving member electrode 489 are controlled by a semiconductor integrated circuit, for example, a CMOS circuit provided in the drive circuit substrate .

Here, the potential difference of Vl with respect to Vm is expressed as V ( I) , and the potential difference of V2 with respect to Vm is express as V(2) . When the element 400 is set such that

V (1) =V (2) , the moving member, that is, mirror section 457 is maintained parallel to the drive circuit substrate 451. This is because the electrostatic force exerted between one end of the moving member 461 and first lower electrode 463a, and electrostatic force exerted between that end of the moving member 461 and first upper electrode 467a become equal with each other. Further, the electrostatic force exerted between the other end of the moving member 461 and second lower electrode 463b, and electrostatic force exerted between that other end of the moving member 461 and second upper electrode 467b become equal with each other. The parallel state is maintained stably by the elasticity of the hinge 455. When the element 400 is set such that V (I) >V (2) , the mirror section 457 is inclined as shown in Figure 23 with the hinge 455 being twisted. This is because the electrostatic force F exerted between one end of the moving member 461 and first lower electrode 463a, and electrostatic force F exerted between the other end of the moving member 461 and second upper electrode 467b become greater than the electrostatic force f exerted between one end of the moving member 461 and first upper electrode 467a, and electrostatic force f exerted between the other end of the moving member 461 and second lower electrode 463b. On the other hand, when the element 400 is set such that V(1) <V(2) , the mirror section 457 is inclined to the opposite direction to that shown in Figure 23. In this way, the mirror section 457 may be set either one of the two inclined positions .

Hereinafter, a method for producing the element 400 will be described with reference to Figures 24 and 25. In Figure 24, schematic cross-sectional side views of the element 400 taken along the line A-A in Figure.22 are shown on the left, and those taken along the line B-B in Figure 22 are shown on the right.

As shown in Figure 24A, a drive circuit substrate 451 is provided. As is detailed in Figure 25, the drive circuit substrate 451 includes CMOS circuits 471 and wiring circuits 473 constituting a drive circuit formed, for example, on a Si substrate 469. In addition, an insulation layer 475 is formed on top of the substrate, and contact holes for connecting the wiring circuits 473 to the respective electrodes are created after planarizing the surface of the insulation layer by CMP method or the like .

Then, a first aluminum thin film (preferably, an aluminum alloy containing a metal having a high melting point) is formed (not shown) on the drive circuit substrate 451 by sputtering, which is patterned by ordinary photolithographic etching to provide intended electrode shapes for creating the first and second lower electrode 463a, 463b . The first and second lower electrodes 463a, 463b are connected to the output side of the CMOS circuits through the wires passed through the contact holes and wiring circuits 473 and set at predetermined potentials respectively. Then, as shown in Figure 24B, a first positive resist 491 is applied on the substrate, which is subsequently hard baked after the areas 491a for providing the support sections 479 of the hinge 455 are patterned. The layer comprising the first resist 491 serves as a sacrifice layer and is removed in a process to be described later. Accordingly, the distance between the lower electrodes 463a, 463b and hinge 455 to be formed later depends on the thickness of the hard baked resist film. Here, instead of the positive resist 491, photosensitive polyimide or the like may also be used.

Then, as shown in Figure 24C, a second aluminum thin film (preferably, an aluminum alloy containing a metal having a high melting point) 493 from which the hinge 455 and support sections 479 thereof will be created is formed by sputtering. Thereafter, a Siθ₂ film (not shown) is formed by PE-CVD (plasma CVD) . The SiO₂ film serves as an etching mask for the second aluminum thin film 493. Then, the SiO₂ film is patterned to provide intended shapes for the hinge 455 and support sections thereof by photolithographic etching.

Then, a third aluminum thin film (preferably, an aluminum alloy containing a metal having a high melting point) 495 from which the mirror section 457 will be created is formed by sputtering. Thereafter, a SiO₂ film (not shown) is formed by PE-CVD (plasma CVD) . The SiO₂ film serves as an etching mask for the third aluminum thin film 495. Then, the SiO₂ film is patterned to provide an intended shape for the mirror section by photolithographic etching. Then, the third and second aluminum thin films 495, 493 are etched successively with the SiO₂ films as the etching masks, and the SiO₂ films are removed by plasma etching at the end. The etching of the aluminum thin films is performed by wet etching using aluminum etchant, which is a mixed aqueous solution of phosphoric acid, nitric acid, and acetic acid, plasma etching using chlorinated gas, or the like . A contact hole is created through the SiO₂ films, and the hinge 455 is connected to the output side of a CMOS circuit 471 through the wire passed through the contact hole and a wiring circuit 473 to be set at a predetermined potential . Then, as shown in Figure 24D, a second positive resist 497 is applied, which is patterned for providing the support sections 483 of the upper electrodes 467a, 467b, and thereafter the substrate is hard baked. The surface of the positive resist 497 is planarized by the reflow effect at the time of the hard baking regardless of the irregularity of the film therebelow. The layer comprising the second resist 497 serves as a sacrifice layer and is removed in a process to be described later. Accordingly, the distance between the hinge 455 and mirror section 457, and the upper electrodes 467a,

467b to be formed at a later stage is determined by the thickness of the hard baked resist film. Here, instead of the positive resist

497, photosensitive polyimide or the like may preferably be used.

Then, as shown in Figure 24E, a fourth aluminum thin film

(preferably, an aluminum alloy containing a metal having a high melting point) 499 from which the upper electrodes 467a, 467b and support sections thereof will be created is formed by sputtering. Thereafter, the fourth aluminum thin film 499 is patterned by photolithographic etching to provide intended shapes of the upper electrodes 467a, 467b and support sections thereof . The etching of the aluminum thin films is performed by wet etching using aluminum etchant, which is a mixed aqueous solution of phosphoric acid, nitric acid, and acetic acid, plasma etching using chlorinated gas, or the like. At this time, the first and second upper electrodes 467a, 467b are connected to the second and first lower electrodes 463b, 463a respectively. Then, as shown in Figure 24F, the second and first resist layers 497, 491 serving as the sacrifice layers are removed by plasma etching with oxygen gas to create airspaces 453, 465. This produces an element 400 that includes the substrate 451 having the first and second lower electrodes 463a, 463b formed thereon, with the moving member 461 (hinge 455 and mirror section 457) arranged thereabove through the intermediary of the airspace 453, and the first and second upper electrodes 467a, 467b arranged above the moving member 461 through the intermediary of the airspace 465. A plurality of such elements 400 is created simultaneously to produce a DMD 50. In producing the DMD 50 in the manner as described above, the mirror section 457 may be shaped like a concave mirror as described above by controlling the film-forming temperature to give stress distributions to the film when the third aluminum thin film 495 from which the mirror section 457 will be created is formed, and thereafter removing the layer of the first resist 491 serving as a sacrifice layer.

Alternatively, the mirror section 457 may be shaped like a concave mirror by the use of different materials for the third aluminum thin film 495 from which the mirror section 457 will be created, and the hinge 455 serving as the backing substrate thereof to bend the mirror section 457 by the difference in the thermal expansion coefficient of the materials .

Further, the surface of the first resist 491 serving as the backing substrate of the mirror section 457 and hinge 455 may be shaped like a concave mirror by providing a concave pattern, which will be removed with the first resist 491 at a later stage, on the surface on which the first resist 491 is applied prior to the application of the resist. In this way, the mirror section 457 to be formed on the surface of the first resist 491 may be shaped like a concave mirror. Here, the surface of the first resist 491 may become flattened depending on the viscosity thereof regardless of the surface contour of the backing substrate . Therefore, it is necessary to provide the first resist 491 having an appropriate viscosity.

Hereinafter, a method for manufacturing a DMD having different configuration will be described. Figure 26 is a detailed plan view of an element 500 of the alternative DMD, and Figure 27 is a cross-sectional side view of the element 500 taken along the line A-A in Figure 26. First, the element 500 serving as a pixel section of the DMD will be described. The element 500 includes first and second lower electrodes 543a, 543b formed spaced apart with each other on a drive circuit substrate 521, first and second upper electrodes 545a, 545b formed spaced apart from the first and second lower electrodes 543a, 543b respectively, and a moving member 531 (which includes a hinge 525 and a mirror section 527) disposed between the first lower and upper electrode pair 543a, 545a, and the second lower and upper electrode pair 543b, 545b . The first upper electrode 545a is provided at a location corresponding to that of the first lower electrode 543a with an intermediate insulation layer 549 between them, and the second upper electrode 545b is provided at a location corresponding to that of the second lower electrode 543b with the intermediate insulation layer 549 between them. The sections indicated by the reference numerals 551 and 553 in Figure 26 are support sections of the hinge 525 and support sections of the upper electrodes 545a, 545b respectively.

In the present example, the mirror section 527 corresponds to the micromirror 62 schematically shown in Figure 7 and other drawings . In Figure 26, the mirror section 527 is indicated relatively small with respect to the entire size of the element 500 for clarity. In actuality, however, the mirror section 527 occupies a major portion of the element 500.

As shown in Figure 27, the first lower electrode 543a and second upper electrode 545b are connected to each other, and then connected to a first drive electrode 555, while the second lower electrode 543b and first upper electrode 545a are connected to each other, and then connected to a second drive electrode 557. The hinge 455 and mirror section 527 integrally formed with a conductive material is connected to a moving member electrode 559. The potentials Vl, V2, and Vm of the first drive electrode 555, second drive electrode 557, and moving member electrode 559 are controlled by a semiconductor integrated circuit, for example, a CMOS circuit provided in the drive circuit substrate.

Here, the potential difference of Vl with respect to Vm is expressed as V(I) , and the potential difference of V2 with respect to Vm is express as V(2) . When the element 500 is set such that V(1) =V(2) , the moving member, that is, mirror section 527 is maintained parallel to the drive circuit substrate 521. This is because the electrostatic force exerted between one end of the moving member 531 and first lower electrode 543a, and electrostatic force exerted between that end of the moving member 531 and first upper electrode 545a become equal with each other. Further, the electrostatic force exerted between the other end of the moving member 531 and second lower electrode 543b, and electrostatic force exerted between that other end of the moving member 531 and second upper electrode 545b become equal with each other. The parallel state is maintained stably by the elasticity of the hinge 525.

When the element 500 is set such that V (I) >V (2) , the mirror section 527 is inclined as shown in Figure 27 with the hinge 525 being twisted. This is because the electrostatic force F exerted between one end of the moving member 531 and first lower electrode 543a, and electrostatic force F exerted between the other end of the moving member 531 and second upper electrode 545b become greater than the electrostatic force f exerted between one end of the moving member 531 and first upper electrode 545a, and electrostatic force f exerted between the other end of the moving member 531 and second lower electrode 543b. On the other hand, when the element 500 is set such that V (1) <V (2 ) , the mirror section 527 is inclined to the opposite direction to that shown in Figure 27. In this way, the mirror section 527 may be set either one of the two inclined positions . Hereinafter, a method for producing the element 500 will be described with reference to Figures 28 and 29. In Figure 28, schematic cross-sectional side views of the element 500 taken along the line A-A in Figure 26 are shown on the left, and those taken along the line B-B in Figure 26 are shown on the right. As shown in Figure 28A, a drive circuit substrate 521 is provided. As is detailed in Figure 29, the drive circuit substrate 521 includes CMOS circuits 537 and wiring circuits 539 constituting a drive circuit are formed, for example, on a Si substrate 535. In addition, an insulation layer 5^'41 is formed on top of the substrate, and contact holes for connecting the wiring circuits 539 to the respective electrodes are created after planarizing the surface of the insulation layer by CMP method or the like .

Then, a first aluminum thin film (preferably, an aluminum alloy containing a metal having a high melting point) is formed (not shown) on the drive circuit substrate 521 by sputtering, which is then patterned by ordinary photolithographic etching to provide intended electrode shapes for creating the first and second lower electrode 543a, 543b as shown in Figure 28B. The first and second lower electrodes 543a, 543b are connected to the wiring circuits 539 (Figure 29) through the contact holes so that they may be set at predetermined potentials . Here, the lower electrodes 543a, 543b need to be brought into close proximity to the hinge 525 and mirror section 527 to be described later with high precision. Therefore, it is preferable that the photolithography for the lower electrodes 543a, 543b is performed by stepper exposure, and the etching therefor is implemented by dry etching.

Then, as shown in Figure 28C, the insulation layer 549 made of SiO₂ or SiN is formed by PE-CVD (plasma CVD) . The insulation layer 549 serves as the interlayer insulation film between the lower electrodes 543a, 543b and upper electrodes 545a, 545b to be described later, and the position of the upper electrodes 545a, 545b is determined by the layer thickness of the insulation layer 549. Thereafter, the insulation layer is patterned in a predetermined shape by ordinary photolithographic etching. Here, the end faces of the insulation layer 549 need to be brought into close proximity to the hinge 525 andmirror section 527 with highprecision. Therefore, it is preferable that the photolithography for the insulation layer is performed by stepper exposure, and the etching therefor is implemented by dry etching. Then, as shown in Figure 28D, a positive resist 561 is applied to the substrate 521 and hard baked after the areas for providing the support sections 551 of the hinge 525 are patterned. The layer comprising the resist 561 serves as a sacrifice layer and is removed in a process to be described later to provide an airspace 523. Accordingly, the position of the moving member 531 (hinge 525 and mirror section 527) to be formed at a later stage is determined by the thickness of the hard baked resist 561. Here, instead of the resist 561, photosensitive polyimide or the like may preferably be used. Then, as shown in Figure 28E, a second aluminum thin film

(preferably, an aluminum alloy containing a metal having a high melting point) is formed, which is processed by ordinary photolithographic etching to provide the first and second upper electrodes 545a, 545b, hinge 525 (beam body) , support sections 551 of the hinge, and mirror section 527. Further, the first and second upper electrodes 545a, 545b are connected to the wiring circuits 539 (Figure 29) on the substrate 521 through the contact holes . In the present example, the first upper electrode 545a and second lower electrode 543b are connected to each other, and the second upper electrode 545b and first lower electrode 543a are connected to each other by the wiring circuits 539. The hinge 525 is connected to the CMOS circuit 537 shown in Figure 29 through a means not shown in the drawing.

Here, the upper electrodes 545a, 545b need to be brought into close proximity to the moving member 531 with high precision. Therefore, it is preferable that the photolithography for the upper electrodes 545a, 545b is performed by stepper exposure, and the etching therefor is implemented by dry etching.

Finally, as shown in Figure 28F, the resist 561 serving as a sacrifice layer is removed by plasma etching with oxygen gas to create the airspace 523. This allows the hinge 525 and mirror section 527 to move in seesaw fashion on an axis passing through the hinge 525.

This produces an element 500 that includes the hinge 525 disposed above the substrate 521 through the intermediary airspace 523, and the mirror section 527 constructed to move in seesaw fashion by the movement of the hinge 525. A plurality of such elements 500 is created simultaneously to produce a DMD 50.

When producing the DMD 50 in the manner as described above, the three methods described above for shaping the mirror section 457 like a concave mirror may be applied in a similar fashion to shape the mirror section 527 like a concave mirror .

The two elements 400 and 500 described above are configured to move the mirror section in seesaw fashion using two pairs of electrodes and do not include a beam at the underside of the mirror section for contacting an address electrode . The image exposing apparatus of the present invention may also be constructed using a DMD in which a pair of electrodes is used to move the mirror section in seesaw fashion and includes a beam at the underside of the mirror section for contacting an address electrode, as in the typical DMDs currently available for practical use .

Further, the image exposing apparatuses according to the embodiments described above use a DMD as the spatial optical modulation device . But, in image exposing apparatuses that use a reflective spatial optical modulation device other than a DMD, degradation in the light utility efficiency and extinction ratio may be prevented by applying the present invention.

A concrete description of how the light reflected by the DMD 50 is separately converged will be provided hereinbelow. Figure 30 is a pattern diagram illustrating how light is converged by the DMD 50 (spatial optical modulation device) shown in Figure 5 or 17. Each of the pixel sections 62 of the DMD 50 shown in Figure 30 is shaped like a convex mirror (e . g. , concave mirror formed on a curved surface) as described above . The light irradiated on the concave mirror-like pixel section 62 is converged by the concave mirror-like pixel section 62 and optical systems 52, 54, and focused at the imaging plane f1. The converged image 110 of each of the pixel sections 62 overlaps with each other at positions within the range from the optical systems 52, 54 to the imaging plane f1. On the other hand, the converged image 110 of each of the pixel sections 62 is separated from each other at positions off the imaging plane fl in the direction away from the optical systems 52, 54 (arrow Xl direction) . If each of the converged images 110 has an intended beam diameter, the images may be exposed directly on a photosensitive material from the optical systems 52, 54. Thus, the microlens array described above is not required any more, and thereby degradation in the light utility efficiency and extinction ratio caused by the microlens array may be prevented.

That is, if each of the pixel sections of the DMD 50 is formed to have a flat surface, each of the converged images 110a is disposed at the imaging plane f0 without any clearance gap between the images and overlaps with each other at any light converging plane off the imaging plane as shown in Figure 31. Thus, displacement of the microlens 102 and mask from the imaging plane f0 causes the problem of degraded light utility efficiency as described with reference to Figures 18 and 19. On the other hand, in Figure 30, each of the converged images 110 is converged separately at a light converging plane off the imaging plane f1. If the converged image has an intended beam diameter, therefore, the microlens array may be omitted Further, in Figure 30, if the microlens array 55 is provided at a light converging plane, formed by the concave mirror-like pixel sections 62, off the imaging plane of the pixel sections formed by the optical systems 52, 54, the degradation in the light utility efficiency and extinction ratio may be prevented as described above with reference to Figures 20 and 21.

Figure. 32 is a schematic diagram of the image exposing apparatus according to a third embodiment of the present invention. Hereinafter, the image exposing apparatus will be described with reference to Figure 32. In the image exposing apparatus shown in Figure 32, sections having identical configurations to those of the image exposing apparatus shown in Figure 30 are given the same reference numerals, and will not be elaborated upon further here .

The image exposing apparatus shown in Figure 32 differs from that shown in Figure 30, in that it includes a spatial optical modulation device including pixel sections, each shaped like a convex mirror. More specifically, each of pixel sections 262 of a DMD

(spatial optical modulation device) 250 is shaped like a convex mirror (e . g. , convex mirror formed on a convexly curved surface) .

The light irradiated on the convex mirror-like pixel section 262 is focused at the imaging plane f10 through imaging optical systems 52, 54.

Here, the converged image 210 of each of the pixel sections 262 is separated with each other at positions within the range from the optical systems 52, 54 to the imaging plane fl^'O . On the other hand, the converged image 210 of each of the pixel sections 262 overlaps with each other at positions off the imaging plane flO in the direction indicated by the arrow Xl . If each of the converged images 210 is separated with each other and has an intended beam diameter at a light converging plane off the imaging plane f10 within the range between the imaging plane flO and the optical systems 52, 54, the images may be exposed directly on the photosensitive material from the optical systems 52, 54. Thus, the microlens array 55 may be omitted, and thereby degradation in the light utility efficiency and extinction ratio which may occur if the microlens array 55 is provided as described above may be prevented.

Further, even in the case where the microlens array 55 that receives light transmitted through the optical systems 52, 54 is provided, degradation in the light utility efficiency and extinction ratio may be prevented by placing the microlens array 55 at a light converging plane, formed by the convex mirror-like pixel sections 262, off the .imaging plane flO formed by the optical systems 52, 54 (Figures 20 and 21) .

The DMD 250 having convex mirror-like pixel sections may be manufactured in the similar manner as the DMD 50 having concave mirror-like pixel sections described with reference to Figures 22 to 28.

In the mean time, the light entering the DMD 50 or DMD 250 is formed substantially in a collimated light beamhaving homogeneous light intensity in the cross section through the condenser lens 71, rod integrator 72, and imaging lens 74 (Figures 4 and 5) . In actuality, however, the light entering the DMD 50 or DMD 250 has a divergence angle . Consequently, the light exiting from the DMD 50 or DMD 250 has a certain divergence angle as well . The beam size converged by each of the pixel sections 62 or 262 and imaging optical systems 52, 54 depends on the divergence angle . Thus, a problem may arise that the light from each of the pixel sections 62 or 262 is not converged separately depending on the magnitude of the divergence angle .

Consequently, when a principal ray of the light entering the DMD 50 or DMD 250 has a predetermined divergence angle β, a convergence angle γ of the primary ray determined by each of the pixel sections 62 or 262 and the optical systems 52, 54 is formed greater than the divergence angle β of the primary ray (γ>β) as shown in Figures 30 and 32. Figures 33A and 33B are pattern diagrams illustrating the convergence angle Y and divergence angle β when each of the pixel sections 62 is formed like a concave mirror. As shown in Figure 33A, if the convergence angle y of the primary ray is greater than the divergence angle β thereof (γ>β) , the light reflected by each of the pixel sections 62 may be converged separately at a light converging plane off the imaging plane fl (Figure 30) . On the other hand, if the convergence angle γ of the primary ray is not greater than the divergence angle β thereof (γ≤β) as shown in Figure 33B, the light reflected by each of the pixel sections 62 may not be converged separately, and overlaps with each other before and after the imaging plane fl .

Likewise, as shown in Figure 34A, when each of the pixel sections 262 is formed like a convex mirror and if the convergence angle γ of the primary ray is greater than the divergence angle β thereof (γ>β) , the light reflected by each of the pixel sections 262 may be converged separately at a light converging plane off the imaging plane flO (Figure 32) . On the other hand, if the convergence angle γ of the primary ray is not greater than the divergence angle β thereof (y≤β) as shown in Figure 34B, the light reflected by each of the pixel sections 262 may not be converged separately, and converged light of each of the pixel sections overlaps with each other before and after the imagingplane flO . Thus, as shown in Figures 33A and 34A, the light reflected by each of the pixel sections 62 or 262 may be converged separately by forming the convergence angle Y greater than the divergence angle β .

Here, the convergence angle y of the primary ray is determined by the light collecting power of each of the pixel sections 62 or 262 and optical systems 52, 54. In the mean time, the divergence angle β may be expressed as the addition of a lighting angle βl and a diffraction angle β2 (β=βl+β2) . The lighting angle βl indicates the divergence angle of a primary ray of the light outputted to the DMD 50 through the condenser lens 71, rod integrator 72, and imaging lens 74. The diffraction angle β2 is_^the diffraction angle of a diffraction optical device disposed on the light exiting surface side of the DMD 50 as described, for example, in Japanese Unexamined Patent Publication Nos . 2004-133279 and 2000-338475 (not shown in Figures 30 and 32) .

Consequently, the light that satisfies the relationship of lighting angle βKconvergence angle Y - diffraction angle β2 is outputted to the DMD 50 through the condenser lens 71, rod integrator

72, and imaging lens 74 in order to satisfy the relationship of convergence angle γ>divergence angle β (Figures 4 and 5) .

By forming the convergence angle Y of a primary ray of the light becomes greater than the divergence angle thereof as described above, the light reflected by each of the pixel sections 62 or 262 may be converged separately. In particular, if each of the light beams 210 converged separately by each of the pixel sections 62 or 262 has an intended beam diameter, the light beams may be exposed directly on a photosensitive material from the optical systems 52, 54. Thus, the microlens array may be omitted, and thereby degradation in the light utility efficiency and extinction ratio which may occur if the microlens array 55 is provided as described above may be prevented.

Further, the microlens array 55 may be provided at a plane where the light reflectedby the pixel sections 62 or 262 is converged separately, which is off the imaging plane fl or flO of the pixel sections 62 or 262 formed by the optical systems 52, 54. This may prevent the degradation in the light utility efficiency and extinction ratio as described above with reference to Figures 20 and 21.

Further, if the microlens array 55 is installed movably in optical axis directions (arrow X directions) , the focal point of the light may be adjusted easily. In particular, placement of the microlens array 55 at a light converging plane instead of the imaging plane fl or flO may minimize the variation in the light utility efficiency when focus adjustment is made . That is, in Figure 30 or 32, the variation in the light utility efficiency between the light converging plane and a plane before or after thereof is smaller than that between the imaging plane f1 or f10_. and a plane before or after thereof. Thus, rapid changes in the light utility efficiency may be prevented when the microlens array 55 is moved in the arrow X directions .

If the image surface at the imaging plane fl or flO formed by the optical systems 52, 54 is curved as shown in Figures 34A, 34 (b) , the microlens array may be placed based on the averaged position at the imaging plane of the pixel sections or the apex of the imaging plane .

Further, an aperture array may be provided at a plane where the light reflected by the pixel sections 62 or 262 is converged separately, which is off the imaging plane fl or flO of the pixel sections 62 or 262 formed by the optical systems 52, 54. This arrangement may block the stray light as described above. Still further, both the aperture array and microlens array may be disposed at a light converging plane (Figures 20 and 21) .

Claims

1. An image exposing apparatus, comprising: a spatial optical modulation device having a plurality of reflective pixel sections disposed side by side, each for modulating light irradiated thereon according to a control signal; a light source for irradiating light on the spatial optical modulation device; and an imaging optical system for focusing an image represented by the light modulated by the spatial optical modulation device on a photosensitive material; wherein each of the pixel sections of the spatial optical modulation device is shaped like a concave or convex mirror.

2. The image exposing apparatus according to claim 1, wherein the imaging optical system includes : an optical system for receiving light transmitted via each of the pixel sections of the spatial optical modulation device and focusing an image of each of the pixel sections; and a microlens array having a plurality of microlenses disposed side by side, each for receiving light transmitted through the optical system and converging the light transmitted via each of the pixel sections of the spatial optical modulation device separately, the microlens array being disposed at a light converging plane, formed by the concavely or convexly shaped pixel sections and the optical system, off the imaging plane of the pixel sections formed by the optical system.

3. The image exposing apparatus according to claim 2, wherein the imaging optical system includes an optical system for receiving light transmitted through the microlens array and focusing light received from each of the microlenses of the microlens array on the photosensitive material .

4. The image exposing apparatus according to claim 1, wherein the imaging optical system includes : an optical system for receiving light transmitted via each of the pixel sections of the spatial optical modulation device and focusing an image of each of the pixel sections; and an aperture array having a plurality of apertures disposed side by side, each for receiving light transmitted through the optical system and transmitting the light transmitted via each of the pixel sections of the spatial optical modulation device separately, the aperture array being disposed at a light converging plane, formed by the concavely or convexly shaped pixel sections and the optical system, off the imaging plane of the pixel sections formed by the optical system.

5. The image exposing apparatus according to claim 4, wherein the imaging optical system includes an optical system for receiving light transmitted through the aperture array and focusing light received from each of the apertures of the aperture array on the photosensitive material .

6. The image exposing apparatus according to any of claims 1 to 5, wherein the spatial optical modulation device comprises a

DMD (digital micromirror device) having micromirrors that serve as the pixel sections disposed two-dimensionalIy.

7. An image exposing apparatus, comprising: a spatial optical modulation device having a plurality of reflective pixel sections disposed side by side, each for modulating light irradiated thereon according to a control signal; a light source for irradiating light on the spatial optical modulation device; and an optical system for focusing an image represented by the light modulated by the spatial optical modulation device on a photosensitive material, wherein: each of the pixel sections of the spatial optical modulation device is shaped like a curved surface; and when a primary ray of the light exiting from the spatial optical modulation device has a divergence angle, a convergence angle of the primary ray of the light provided by the pixel sections and the optical system is formed greater than the divergence angle of the primary ray.

8. The image exposing apparatus according to claim 7, wherein each of the pixel sections of the spatial optical modulation device is shaped like a concave or convex mirror.

9. The image exposing apparatus according to claim 7 or 8, wherein a microlens array is disposed at a light converging plane, formed by the pixel sections and the optical system, off the imaging plane formed by the pixel sections and the optical system.

10. The image exposing apparatus according to claim 9, wherein the microlens array is installed movably in optical axis directions of the light.

11. The image exposing apparatus according to claim 7, further comprising an aperture arrayhaving a plurality of apertures disposed side by side, each for receiving light transmitted through the optical system and transmitting the light transmitted via each of the pixel sections of the spatial optical modulation device separately, the aperture array being disposed at a light converging plane, formed by the pixel sections and the optical system, off the imaging plane of the pixel sections formed by the optical system.

12. The image exposing apparatus according to any of the claims 7 to 11, wherein a lighting angle, which is a divergence angle of a primary ray of the light to be irradiated on the spatial optical modulation device, is formed smaller than the difference between a convergence angle of the primary ray of the light and a diffraction angle formed by the spatial optical modulation device .