JP2006301062A - Mounting structure of digital micromirror device and image exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deviation of an optical axis of a digital micromirror device (DMD) in the structure for mounting the DVD on an optical apparatus. <P>SOLUTION: In a structure for mounting the DMD 50 having a substantially rectangular contour using region 50c onto an optical apparatus using the DMD 50, the DMD 50 is fixed at three points on the side of optical apparatus: a first fixing point 90a and a second fixing point 90b, which are located at mutually axial symmetric positions with respect to a straight line CL1 which passes the center O of a using region 50c and in parallel to one side of the using region 50c; a third fixing point 90c located at a position which is point symmetric to the intersection of the line connecting the two fixing points 90a and 90b and the straight line CL1 with respect to the center O of the using region 50c. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure in which a digital micromirror device in which a large number of micromirrors that change the angle are arranged in an array is attached to an optical apparatus.

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

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

  Recently, in this type of image exposure apparatus, a digital micromirror device (hereinafter referred to as DMD) is often used as a spatial light modulation element. The DMD is a mirror device in which a large number of rectangular micromirrors that change the angle of a reflecting surface in accordance with a control signal are two-dimensionally arranged on a semiconductor substrate such as silicon.

  It should be noted that this DMD usable area, that is, the area where the micromirror is disposed, generally has a generally rectangular outline as a whole. Further, in order to improve responsiveness, only a part of the usable area is used, but in this case as well, the use area is generally set to a substantially rectangular shape.

  By the way, 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.
JP 2001-305663 A

  As described above, in an image exposure apparatus that uses a combination of a DMD and a microlens array, the optical axis of the DMD (the axis extending in the light traveling direction through the center of the use area) matches the optical axis of the microlens array. After being aligned as described above, it is fixed to a predetermined position of the image exposure apparatus main body by bonding or the like.

  However, in the conventional image exposure apparatus, there has been a problem that the DMD is displaced while being used repeatedly, and the optical axis thereof is deviated from the optical axis of the microlens array, so that the image quality of the exposure image is impaired. .

  The DMD is used not only in the above-described image exposure apparatus but also in other various optical apparatuses such as an image display unit. In these apparatuses, if the optical axis of the DMD is shifted from a predetermined position, Similarly, the optical performance of the device is often impaired.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a DMD mounting structure that can prevent an optical axis shift of a DMD mounted on an optical device.

  It is another object of the present invention to provide an image exposure apparatus capable of preventing a DMD optical axis shift as described above and exposing a high-quality image.

The first DMD mounting structure according to the present invention comprises:
As described above, in a structure in which a DMD whose outline of a use area is substantially rectangular is attached to an optical device using the DMD,
The first and second fixed points set at positions where the DMD is symmetrical with respect to a straight line passing through the center of the use area and parallel to one side of the use area, and a line segment connecting the two fixed points Are fixed at three points on the optical device side through a point intersecting with the straight line and a third fixed point set at a point-symmetrical position with respect to the center of the use area. Is.

  The DMD mounting structure according to the present invention may be applied when the DMD use area is set as a part of the usable area and the center of the use area is deviated from the center of the entire DMD. desirable.

The second DMD mounting structure according to the present invention is as follows.
In a structure for attaching a DMD to an optical device using the DMD,
The DMD is fixed at least at three points to the holding member of the optical device;
The holding member includes an elastic portion that can be elastically deformed in the vicinity of at least one of the fixed points.

In the DMD mounting structure, particularly when the DMD has a substantially rectangular outline of the use area,
The DMD is connected to the first and second fixed points set at positions opposite to each other with a straight line passing through the center of the used area and parallel to one side of the used area, and a line connecting the two fixed points. Fixed at three points on the optical device side through a point where the minute intersects with the straight line and a third fixed point set on the opposite side across the center of the use area,
First, second, and third elastic portions are formed in the vicinity of the first, second, and third fixing points, respectively.
The distance from the center of the use area to the point where the line segment intersects the straight line and the distance to the third fixed point are A and B, respectively, the distance from the straight line to the first fixed point, the second C, D respectively, and the spring constants of the first, second, and third elastic portions in the direction in which the straight line extends are kax, kbx, and kcx, respectively. When the spring constants of the first and second elastic portions with respect to the arrangement direction are set to kay and kby, respectively,
kax · A / (A + B) + kbx · A / (A + B) + kcx · B / (A + B) = 0
kay · C / (C + D) + kby · D / (C + D) = 0
It is desirable that this relationship is almost satisfied.

  The elastic portion as described above can be formed by providing elasticity to a part of the holding member, for example, by providing a notch in the holding member in the vicinity thereof. In such a case, the spring constants kax, kbx and kcx, and kay and kby can be set to desired values by adjusting the length of the notch, the position thereof, the thickness of the holding member, and the like.

  The image exposure apparatus according to the present invention is characterized in that the DMD is attached to the holding member by the above-described first or second attachment structure of the present invention.

  According to the inventor's research, as described above, the main cause of misalignment of DMD is the coefficient of linear expansion between the DMD usually formed of alumina or the like and the holding member of the optical device using the DMD. It turns out that there is a difference. That is, if the linear expansion coefficients of these two are different, there will be a difference in the amount of expansion and contraction when they undergo a temperature change. Therefore, especially when both are bonded, the DMD is deformed while deforming the bonded portion. Will move.

  The DMD mounting structure according to the present invention has been obtained based on the above knowledge. In particular, in the first mounting structure, as described above, the DMD passes through the center of the use area and one side of the use area. With respect to a straight line parallel to the first and second fixed points set at positions that are line-symmetric with each other, a point where a line segment connecting these two fixed points intersects with the straight line, and a point symmetric with respect to the center of the use area Are fixed at three points on the optical device side via a third fixed point set at a position where (Corresponding to the straight line) and each fixed point with respect to the second center line, the first fixed point and the second fixed point are equidistant from the first center line and opposite to each other, and the third fixed point. Exists at a position on the first centerline and the first 2) fixed point and the third fixed point will be located at a position opposite to each other at equal distances from the second center line.

  In addition, expansion and contraction due to a temperature change in one homogeneous member occurs isotropically regardless of which part of the member is considered as a reference, and this can be said to be true in a monolithically formed DMD. . Therefore, as described above, when the DMD expands and contracts due to a temperature change, basically, the DMD expands and contracts around the second center line in the extending direction of the first center line, while the second center line extends and contracts. Since it extends and contracts around the first center line in the extending direction, the DMD does not move at the position where these two center lines intersect. Since the position where these two center lines intersect, that is, the position where the optical axis of the DMD usage region passes, the optical axis shift of the DMD is prevented in the end.

  If the DMD use area is set as a part of the usable area and the center of the use area is deviated from the center of the entire DMD, the entire DMD is placed on the optical device side with three points in good balance. Even if it is fixed, the center of the use area is easy to move when subjected to a temperature change, so that an optical axis shift is likely to occur. Therefore, if the first mounting structure of the present invention is applied in such a case, the effect of suppressing the optical axis deviation is particularly high.

  In the second DMD mounting structure according to the present invention, the holding member of the optical device to which the DMD is mounted includes an elastic portion that can be elastically deformed in the vicinity of at least one of the three or more fixing points. Since the difference in expansion / contraction amount due to the difference in linear expansion coefficient between the holding member of the optical device and the DMD is easily absorbed by the elastic deformation on the holding member side, the adhesive layer between the two is destroyed by this difference in expansion / contraction amount. Such a problem can be prevented.

In this case, the DMD in which the outline of the use area is substantially rectangular is set at positions opposite to each other across a straight line that passes through the center of the use area and is parallel to one side of the use area. And a fixed point of 2 and a point where a line segment connecting these two fixed points intersects with the straight line and a third fixed point set on the opposite side across the center of the use area, It is fixed at 3 points on the optical device side,
First, second, and third elastic portions are formed in the vicinity of the first, second, and third fixing points, respectively.
The distance from the center of the use area to the point where the line segment intersects the straight line and the distance to the third fixed point are A and B, respectively, the distance from the straight line to the first fixed point, the second C, D respectively, and the spring constants of the first, second, and third elastic portions in the direction in which the straight line extends are kax, kbx, and kcx, respectively. When the spring constants of the first and second elastic portions with respect to the arrangement direction are set to kay and kby, respectively,
kax · A / (A + B) + kbx · A / (A + B) + kcx · B / (A + B) = 0
kay · C / (C + D) + kby · D / (C + D) = 0
If the above relationship is substantially satisfied, it is possible to prevent the optical axis shift of the DMD. In other words, in such a configuration, assuming that the expansion and contraction due to the temperature change of the DMD occurs isotropically as described above, the elastic forces that the three fixing points receive from the respective elastic portions also in the x direction Since the tangles can be obtained in the y direction, it is possible to prevent the DMD optical axis shift from being newly induced by providing these elastic portions.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, as an example, the DMD mounting structure applied to the image exposure apparatus will be described. First, the image exposure apparatus will be described.

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

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

As shown in FIGS. 2 and 3B, the scanner 162 includes a plurality of (for example, 14) exposure heads 166 arranged in an approximately matrix of m rows and n columns (for example, 3 rows and 5 columns). . In this example, four exposure heads 166 are arranged in the third row in relation to the width of the photosensitive material 150. In addition, when showing each exposure head arranged in the 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 the short side in the sub-scanning direction. Therefore, as the stage 152 moves, a strip-shaped exposed area 170 is formed on the photosensitive material 150 for each exposure head 166. In addition, when showing the exposure area by each exposure head arranged in the m-th row and the n-th column, it is expressed as an exposure area 168 _mn .

Further, as shown in FIGS. 3A and 3B, each of the exposure heads in each row arranged in a line so that the strip-shaped exposed regions 170 are arranged in the direction orthogonal to the sub-scanning direction without gaps. These are arranged with a predetermined interval (natural number times the long side of the exposure area, twice in this example) in the arrangement direction. Therefore, can not be exposed portion between the exposure area 168 ₁₁ in the first row and the exposure area 168 _12, it can be exposed by the second row of the exposure area 168 ₂₁ and the exposure area 168 ₃₁ in the third row.

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

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

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

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

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

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

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

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

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

In the DMD 50, a number of micromirror arrays in which a large number (for example, 1024) of micromirrors are arranged in the longitudinal direction are arranged in a short direction (for example, 756 sets). As shown in FIG. Further, by tilting the DMD 50, the pitch P ₁ of the scanning trajectory (scan line) of the exposure beam 53 by each micromirror becomes narrower than the pitch P ₂ of the scanning line when the DMD 50 is not tilted, and the resolution is greatly improved. Can be made. On the other hand, since the inclination angle of the DMD 50 is very small, the scanning width W ₂ when the DMD 50 is inclined and the scanning width W ₁ when the DMD 50 is not inclined are substantially the same.

  Further, the same scanning line is overlapped and exposed (multiple exposure) by different micromirror rows. 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 the direction orthogonal to the sub-scanning direction instead of inclining the DMD 50.

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

  As shown in FIG. 9B, the laser emitting portion 68 constituted by the end portion of the multimode optical fiber 31 is sandwiched and fixed between two support plates 65 having a flat surface. Further, it is desirable that a transparent protective plate such as glass is disposed on the light emitting end face of the multimode optical fiber 31 for protection. The light exit end face of the multimode optical fiber 31 is easily collected and easily deteriorated due to its high light density.However, the protective plate as described above prevents the dust from adhering to the end face. Can be delayed.

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

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

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

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

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

  The GaN-based semiconductor lasers LD1 to LD7 all have a common oscillation wavelength (for example, 405 nm), and the maximum output is also all common (for example, about 100 mW for a multimode laser and about 50 mW for a single mode laser). 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 combined laser light source is housed in a box-shaped package 40 having an upper opening together with other optical elements. The package 40 includes a package lid 41 created so as to close the opening, and is formed by introducing a sealing gas after the deaeration process and closing the opening of the package 40 with the package lid 41. The combined laser light source is hermetically sealed in a closed space (sealed space).

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

  Further, 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 drive current to the GaN-based semiconductor lasers LD1 to LD7 is drawn out of the package through the opening.

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

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

  On the other hand, each of the GaN-based semiconductor lasers LD1 to LD7 includes an active layer having a light emission width of 2 μm, and 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.

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

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

  The microlens array 55 shown in FIG. 5 is formed by two-dimensionally arranging a number of microlenses 55a corresponding to each pixel of the DMD 50. In this example, as will be described later, only 1024 × 256 rows of the 1024 × 768 rows of micromirrors of DMD 50 are driven, and accordingly, 1024 × 256 rows of microlenses 55a are arranged. The arrangement pitch of the micro lenses 55a is 41 μm in both the vertical and horizontal directions. As an example, the micro lens 55a has a focal length of 0.19 mm, an NA (numerical aperture) of 0.11, and is formed of the optical glass BK7.

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

  Further, the first imaging optical system including the lens systems 52 and 54 shown in FIG. 5 enlarges the image by the DMD 50 three times and forms an image on the micro lens array 55. The second imaging optical system including the lens systems 57 and 58 enlarges the image that has passed through the microlens array 55 by 1.6 times and forms and projects it on the photosensitive material 150. Therefore, as a whole, the image formed by the DMD 50 is enlarged and enlarged by 4.8 times on the photosensitive material 150 and projected.

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

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

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

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

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

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

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

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

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

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

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

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

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

  Next, the DMD 50 mounting structure will be described in detail. 17 and 18 are exploded perspective views showing the DMD holding member 90 fixed to the exposure apparatus main body side and the DMD 50 fixed thereto as viewed from the front surface side and the back surface side of the DMD 50, respectively. As shown in these drawings, the DMD holding member 90 has three DMD fixing protrusions (hereinafter simply referred to as protrusions) 90a, 90b, and 90c, and the DMD 50 has a DMD holding surface at three points through them. The member 90 is fixedly bonded.

  The DMD holding member 90 has a substantially rectangular opening 90d that exposes a usable area of the DMD 50, that is, an area where the above-described micromirrors 62 are juxtaposed. Further, the DMD holding member 90 is formed with notches 90e, 90f, and 90g that are elongated at positions close to the sides of the opening 90d. And a portion extending thinly between the side of the opening 90d.

  The DMD 50 is basically made of alumina, while the DMD holding member 90 is made of aluminum. Since alumina and aluminum have different linear expansion coefficients, the DMD 50 may move relative to the DMD holding member 90 due to the difference in linear expansion coefficient when both of them undergo a temperature change. obtain.

  FIG. 19 is a plan view showing in detail the positional relationship between the DMD 50 and the protrusions 90a, 90b and 90c. In this embodiment, a part of the usable area (area in which the micromirrors 62 are arranged in parallel) 50b in the DMD main body 50a is selected as the used area 50c in the form of FIG. 16B described above. used. The DMD main body 50a is bonded and fixed to the protrusions 90a, 90b, and 90c at the outer portion outside the usable area 50b. The DMD main body 50a is positioned and fixed so that the optical axis of the use area 50c coincides with the optical axis of the microlens array 55.

  In the present embodiment, the portions of the DMD main body 50a that are bonded and fixed to the protrusions 90a, 90b, and 90c are the first, second, and third fixing points described above. That is, the protrusions 90a and 90b are set at positions that are symmetrical with each other with respect to a straight line (first center line CL1) that passes through the center O of the use area 50c of the fixed DMD 50 and is parallel to one side of the use area 50c. ing. The other protrusion 90c is set at a point symmetrical with respect to the point where the line connecting the protrusions 90a and 90b intersects the first center line CL1 and the center O of the use area 50c.

  Accordingly, when the relationship between the projections 90a, 90b and 90c with respect to the first center line CL1 and the second center line CL2 which divides the use area 50c of the DMD 50 in line symmetry, the projections 90a and 90b are equidistant from the first center line CL1. And the projection 90c is located on the first center line CL1, and the projection 90a (90b) and the projection 90c are equidistant from the second center line CL2 and opposite to each other. It will be.

  Further, as described above, the expansion and contraction due to the temperature change of the DMD 50 formed monolithically occurs basically isotropically regardless of which portion of the DMD 50 is taken as a reference. Therefore, when the DMD 50 moves relative to the DMD holding member 90 for the reason described above, the DMD 50 basically extends and contracts around the second center line CL2 in the direction in which the first center line CL1 extends, Since the second center line CL2 extends and contracts around the first center line CL1, the DMD 50 does not move at the position where the two center lines CL1 and CL2 intersect. Since the position where the two center lines CL1 and CL2 intersect is the position where the optical axis of the use area 50c of the DMD 50 passes through, the optical axis shift of the DMD 50 is eventually prevented.

  When the use area 50c of the DMD 50 is set as a part of the usable area 50b and the center O of the use area 50c is off the center of the entire DMD 50 as in the present embodiment, the entire DMD 50 is Even if the DMD holding member 90 is fixed at three points in a well-balanced manner, the center O of the use area 50c is easy to move when subjected to a temperature change. Therefore, in this embodiment in which the mounting structure of the present invention is applied in such a case, the effect of suppressing the optical axis deviation is particularly high.

  In the present embodiment, the protrusions 90a, 90b, and 90c of the DMD holding member 90 are formed in portions that extend thinly between the notches 90e, 90f, and 90g and the sides of the opening 90d. The portion between the protrusion 90a and the notch 90e, the portion between the protrusion 90b and the notch 90f, and the portion between the protrusion 90c and the notch 90g (since these portions are elastic portions, The first elastic portion, the second elastic portion, and the third elastic portion in this order) are more easily elastic in the plane including the three fixing points of the DMD 50 than when the notches 90e, 90f, and 90g are not provided. Deformable. If so, the difference in expansion and contraction due to the difference in linear expansion coefficient between the DMD holding member 90 and the DMD 50 is easily absorbed by the elastic deformation on the DMD holding member 90 side. It is possible to prevent the problem that the adhesive layer is destroyed.

In the present embodiment, in particular, the distance from the center O of the use area 50c to the point where the line segment connecting the protrusions 90a and 90b intersects the first center line CL1, and the distance to the protrusion 90c are A and B, respectively. The distance from one center line CL1 to the protrusion 90a and the distance from the protrusion 90b are C and D, respectively, and the spring constants of the first, second, and third elastic portions in the direction (x direction) in which the first center line CL1 extends are respectively shown. When kax, kbx, and kcx are set, and the spring constants of the first and second elastic portions with respect to the alignment direction (y direction) of the protrusion 90a and the protrusion 90b are respectively set to kay and kby,
kax · A / (A + B) + kbx · A / (A + B) + kcx · B / (A + B) = 0
kay · C / (C + D) + kby · D / (C + D) = 0
The relationship is almost satisfied. Therefore, assuming that the expansion and contraction due to the temperature change of the DMD 50 occurs isotropically as described above, the elastic forces that the three fixing points receive from the respective elastic portions are entangled in the x direction and also in the y direction. Therefore, it is possible to prevent the DMD 50 from newly inducing an optical axis shift by providing these elastic portions.

  In this embodiment, since A = B and C = D in particular, it is sufficient that the relationship of kax + kbx + kcx = 0 and kay + kby = 0 is substantially satisfied. In the case of A ≠ B or C ≠ D, the values of A and B and the values of C and D may be substituted into the above equations, and the necessary spring constant may be obtained by, for example, simulation using a computer. Further, the spring constants kax, kbx and kcx, and kay and kby are set to desired values by adjusting the lengths and positions of the notches 90e, 90f and 90g, and the thickness of the DMD holding member 90, respectively. Can do.

  Here, in the case of A = B and C = D, it is not always necessary to provide the elastic portion as described above, and only by setting A = B and C = D, the light is transmitted as described above. An effect of suppressing the axial deviation is obtained. In addition, the configuration provided with the elastic portion as described above is applied not only when A = B and C = D, but also when the DMD 50 is fixed at 3 points (when fixed at 4 points or more). In such a case, it is possible to prevent a problem that the adhesive layer between the DMD holding member 90 and the DMD 50 breaks due to a difference in expansion / contraction due to a difference in linear expansion coefficient.

  The present invention is also applicable to the case where all the usable areas 50b of the DMD 50 are used areas, and in this case, the effects described above are similarly produced. Another embodiment of the present invention so formed is shown in FIG. In FIG. 20, the same elements as those in FIG. 19 are denoted by the same reference numerals, and redundant description thereof will be omitted (the same applies hereinafter).

  FIG. 21 shows a further different embodiment of the present invention. In this embodiment, as compared with the embodiment of FIG. 20, the first center line CL1 and the second center line CL2 are interchanged, and the protrusions 90a and 90b are the upper side of the usable area 50b of the DMD 50. Are arranged in parallel with each other.

  Also in this embodiment, the protrusions 90a and 90b are symmetrical with respect to a straight line (first center line CL1) passing through the center O of the use area 50c of the fixed DMD 50 and parallel to one side of the use area 50c. Set to position. The other projection 90c is set at a point symmetrical with respect to the point where the line segment connecting the projections 90a and 90b intersects the first center line CL1 and the center O of the use region. Thereby, also in this embodiment, the same effect as in the two embodiments described above can be obtained.

The perspective view which shows the external appearance of the image exposure apparatus to which the attachment structure of DMD by one Embodiment of this invention was applied 1 is a perspective view showing a configuration of a scanner of the image exposure apparatus in FIG. (A) is a plan view showing an exposed area formed on a photosensitive material, and (B) is a view showing an arrangement of exposure areas by each exposure head. 1 is a perspective view showing a schematic configuration of an exposure head of the image exposure apparatus of FIG. Cross section of the above exposure head Partial enlarged view showing the configuration of a digital micromirror device (DMD) (A) And (B) is explanatory drawing for demonstrating operation | movement of DMD. (A) and (B) are plan views showing the arrangement of the exposure beam and the scanning line in a case where the DMD is not inclined and in a case where the DMD is inclined. The perspective view which shows the structure of a fiber array light source Front view showing arrangement of light emitting points in laser emitting section of fiber array light source Diagram showing the configuration of a multimode optical fiber Plan view showing the configuration of the combined laser light source Plan view showing the configuration of the laser module Side view showing the configuration of the laser module shown in FIG. The partial front view which shows the structure of the laser module shown in FIG. Block diagram showing the electrical configuration of the image exposure apparatus (A) And (B) is a figure which shows the example of the use area | region of DMD. The exploded perspective view which shows the state which looked at DMD and its holding member from the surface side of DMD The exploded perspective view which shows the state which looked at DMD and its holding member from the back side of DMD The top view which shows the positional relationship of the said DMD and a holding member The top view which shows the positional relationship of DMD and holding member in another embodiment of this invention, The top view which shows the positional relationship of DMD and holding member in further another embodiment of this invention, Explanatory drawing explaining the effect of this invention

Explanation of symbols

LD1-LD7 GaN semiconductor laser
50 Digital micromirror device (DMD)
50b DMD usable area
50c DMD usage area
55 Micro lens array
66 Laser module
66 Fiber array light source
90 DMD holding member
90a, 90b, 90c DMD fixing protrusion
90e, 90f, 90g Notch

Claims (6)

In a structure in which a digital micromirror device having a substantially rectangular outline of a use area is attached to an optical apparatus using the device,
The digital micromirror device includes first and second fixed points that are set to be symmetrical with each other with respect to a straight line that passes through the center of the use area and is parallel to one side of the use area. It is fixed at three points on the optical device side through a point where a line segment connecting fixed points intersects the straight line and a third fixed point set at a point-symmetrical position with respect to the center of the use area. A mounting structure for a digital micromirror device, characterized in that   The usage area of the digital micromirror device is set as a part of the usable area, and the center of the usage area is off the center of the entire digital micromirror device. The mounting structure of the digital micromirror device according to 1. In a structure for attaching a digital micromirror device to an optical apparatus using the device,
The digital micromirror device is fixed at least three points to the holding member of the optical device;
The digital micromirror device mounting structure, wherein the holding member includes an elastic portion capable of elastic deformation near at least one of the fixed points. The digital micromirror device is such that the outline of the use area is substantially rectangular,
The digital micromirror device includes first and second fixed points set at positions opposite to each other across a straight line passing through the center of the use area and parallel to one side of the use area. It is fixed at three points on the optical device side through a point where a line segment connecting fixed points intersects the straight line and a third fixed point set on the opposite side across the center of the use area. ,
First, second, and third elastic portions are formed in the vicinity of the first, second, and third fixing points, respectively.
The distance from the center of the use area to the point where the line segment intersects the straight line and the distance to the third fixed point are A and B, respectively, the distance from the straight line to the first fixed point, the second C, D respectively, and the spring constants of the first, second, and third elastic portions in the direction in which the straight line extends are kax, kbx, and kcx, respectively. When the spring constants of the first and second elastic portions with respect to the arrangement direction are set to kay and kby, respectively,
kax · A / (A + B) + kbx · A / (A + B) + kcx · B / (A + B) = 0
kay · C / (C + D) + kby · D / (C + D) = 0
4. The structure for mounting a digital micromirror device according to claim 3, wherein the relationship is substantially satisfied.   5. The digital micromirror according to claim 3, wherein the elastic portion is provided with elasticity in a part of the holding member by forming a notch in the holding member in the vicinity thereof. -Device mounting structure. A light source;
A digital micromirror device that modulates the light emitted from this light source;
A microlens array in which microlenses for condensing light passing through each micromirror of the digital micromirror device are arranged in an array,
In an image exposure apparatus comprising an imaging optical system that forms an image by light passing through the microlens array on a predetermined photosensitive material,
An image exposure apparatus, wherein the digital micromirror device is attached to a holding member by the attachment structure according to any one of claims 1 to 5.

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