JP2005275325A - Image exposing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a stray light from being generated around a light converged by each microlens of a microlens array without exerting any adverse influence on the optical performance of an image exposing device which uses a spatial optical modulating element and the microlens array in combination. <P>SOLUTION: In front of the microlens array 64, an aperture array 66 is provided which is arranged spatially apart from the microlens array 64. Respective apertures 66 of the aperture array 66 are made large enough to pass at least a light of (0)th order and diffracted lights of (±1)th order of components of a light reflected nearby the center of a micromirror 74 on a DMD 34 corresponding to the apertures 66a including spread components corresponding to the numerical aperture of a 1st imaging optical system 52. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image exposure apparatus, and more particularly to an image exposure apparatus that includes an exposure head and exposes a desired pattern onto a photosensitive material by the exposure head.

  2. Description of the Related Art Conventionally, there has been known an image exposure apparatus that includes an exposure head and exposes a desired pattern onto a photosensitive material by the exposure head. An exposure head of this type of image exposure apparatus basically includes a light source and a spatial light modulation element in which a large number of pixel portions that independently modulate light emitted from the light source in accordance with a control signal are arranged. And an imaging optical system that forms an image of the light modulated by the spatial light modulation element on the photosensitive material. This basic configuration is described in Non-Patent Document 1, for example.

Further, as another configuration of the exposure head of the image exposure apparatus, for example, as described in Patent Document 1, a digital micromirror device (hereinafter referred to as “a light modulation element including a light source and a number of micromirrors”). DMD ”), a magnifying optical system for enlarging each light beam modulated by the many micromirrors, and a microlens array in which a large number of microlenses corresponding to each modulated and magnified light beam are arranged. Other configurations are also known. According to the configuration using such a microlens array, even if the size of the image exposed on the photosensitive material is enlarged, the light from each pixel portion of the spatial light modulator is transmitted by each microlens of the microlens array. Since the light is condensed, the pixel size (spot size of each light beam) of the exposure image on the photosensitive material is reduced and kept small, and there is an advantage that the sharpness of the image can be kept high. The DMD used as a spatial light modulation element in the above configuration is configured such that a number of micromirrors whose reflection surfaces are independently changed according to a control signal are arranged on a semiconductor substrate such as silicon. This is a mirror device.
JP 2001-305663 A Akihito Ishikawa "Development shortening and mass production application by maskless exposure", "Electrotronics packaging technology", Technical Research Committee, Vol.18, No.6, 2002, p.74-79

  However, an image exposure apparatus using a combination of a spatial light modulation element and a microlens array has the advantages described above, but stray light is generated around the light collected by each microlens of the microlens array. There was a problem. If such stray light reaches the photosensitive material, problems such as a decrease in the sharpness of the exposed image are caused.

  In view of the above circumstances, the present invention is an image exposure apparatus that uses a combination of a spatial light modulator and a microlens array, and is focused on each microlens of the microlens array without adversely affecting the optical performance of the apparatus. The object is to prevent stray light from being generated around the light.

That is, the image exposure apparatus of the present invention is an image exposure apparatus that includes an exposure head and exposes a desired pattern onto the photosensitive material by the exposure head. The exposure head includes a light source and light from the light source. A spatial light modulation element in which a large number of pixel portions each independently modulates and a plurality of light beams modulated by the large number of pixel portions are condensed and imaged on the same focal plane An optical system, an aperture array in which a large number of apertures corresponding to each of a large number of light beams that have passed through the imaging optical system are arranged, and a large number of light beams that are arranged on the focal plane and pass through the aperture array A microlens array in which a number of microlenses corresponding to each of the microlens arrays is arranged in this order on the optical path, and the aperture array and the microlens array are arranged spatially separated from each other. Ri, the distance d ₁ between the front surface of the radius R, the aperture array and the microlens array of each of the multiple openings of the _distance d ₂ between the front surface and the focal _plane, a large number of exit from the imaging optical system Angle θ ₁ formed by the center of the zero-order light from the spatial light modulator and the center of the first-order diffracted light, the half angle θ ₂ of the maximum cone angle of the zero-order light, and the aperture Between the refractive index n ₁ of the medium between the array and the micro lens array and the refractive index n ₂ of the material constituting each of the micro lenses,
R ≧ d ₁ (tan θ ₁ + tan θ ₂ ) + d ₂ (tan θ ₁ ′ + tan θ ₂ ′)
However, θ ₁ ′ = arcsin (n ₁ / n ₂ × sin θ ₁ )
θ ₂ ′ = arcsin (n ₁ / n ₂ × sin θ ₂ )
It is characterized in that

  Here, in the present invention, the microlens array is “arranged on the focal plane” of the imaging optical system means that the focal plane of the imaging optical system is on the front surface or the rear surface of the microlens array, or those It means that it exists between the front surface and the rear surface. In addition, the front surface (or rear surface) of the microlens array refers to a surface that is in contact with the apex of each convex surface when the front surface (or rear surface) of each microlens is a convex surface. In both the microlens array and the microlens, the “front surface” refers to the incident surface near the light source and the imaging optical system, and the “rear surface” refers to the emission surface far from the light source and the imaging optical system. .

  In the image exposure apparatus of the present invention described above, the radius R of the opening is preferably ½ or less of the product of the length of the short side of each pixel portion and the magnification of the imaging optical system. Here, “the length of the short side of the pixel portion” is referred to. For example, when each pixel portion has a square shape, this indicates the length of one side which is equal.

  The spatial light modulation element may be a digital micromirror device including a large number of micromirrors that reflect light from a light source as the large number of pixel portions. In that case, it is more preferable that the radius R of the opening is small enough to block the reflected light (at least the 0th-order light) from the peripheral portion where the amount of change in the geometric distortion of each micromirror is large.

  Further, in the image exposure apparatus of the present invention, each of the plurality of microlenses is a planoconvex lens having a flat front surface and a convex rear surface, and the focal plane of the imaging optical system is a microlens. It may coincide with the lens mounting surface on the rear side of the array.

  The image exposure apparatus of the present invention may include a plurality of exposure heads as described above.

  According to the image exposure apparatus of the present invention, by providing the aperture array in front of the microlens array, components that cause stray light such as light coming from the adjacent pixel portion of the corresponding pixel portion of the spatial light modulator are blocked. can do. Accordingly, stray light is prevented from being generated around the light collected by each microlens, and a high-definition image without distortion can be exposed on the photosensitive material.

  In addition, since the aperture array is arranged spatially separated from the microlens array, even if the components of the aperture array are heated by light, the heat is hardly transmitted to the microlens array, and the microlens array There is no risk of adversely affecting the optical performance of the lens array.

Further, the radius R of each aperture, the distance d ₁ between the aperture array and the front surface of the microlens array, the distance d ₂ between the front surface of the microlens array and the focal plane of the imaging optical system, and a number of light beams emitted from the imaging optical system The angle θ ₁ formed by the center of the zero-order light from the spatial light modulator and the center of the first-order diffracted light, the half angle θ ₂ of the maximum cone angle of the zero-order light, the aperture array, and the microlens array. Between the refractive index n ₁ of the medium between and the refractive index n ₂ of the material constituting each of the microlenses,
R ≧ d ₁ (tan θ ₁ + tan θ ₂ ) + d ₂ (tan θ ₁ ′ + tan θ ₂ ′)
However, θ ₁ ′ = arcsin (n ₁ / n ₂ × sin θ ₁ )
θ ₂ ′ = arcsin (n ₁ / n ₂ × sin θ ₂ )
Therefore, each microlens receives at least the 0th-order light and the ± 1st-order diffracted light of the light component reflected in the portion near the center of the corresponding pixel portion of the spatial light modulator. In addition, it is possible to enter even the spreading component corresponding to the numerical aperture of the imaging optical system, and it is possible to maintain good imaging performance while blocking the component causing stray light.

  Further, when the radius R of each aperture of the aperture array is set to 1/2 or less of the product of the short side length of each pixel portion of the spatial light modulator and the magnification of the imaging optical system, While causing the light reflected at the portion near the center of the corresponding pixel portion to be transmitted sufficiently and sufficiently, the component causing stray light derived from the light coming from the adjacent pixel portion is effectively blocked.

  Further, when a DMD having a large number of micromirrors is used as the spatial light modulation element, the radius R of each opening is set to the reflected light (at least the zeroth order) from the peripheral portion where the change in the geometric distortion of each micromirror is large. When it is small enough to block light), the components that cause stray light derived from the geometric distortion of the peripheral portion of each micromirror can be blocked in a necessary and sufficient range.

Further, if each microlens is a plano-convex lens having a flat front surface and a convex rear surface, and the focal plane of the imaging optical system coincides with the lens mounting surface on the rear side of the microlens array, R, d ₁ and d ₂ Adjustment for satisfying the above-described conditional expression is facilitated.

  Furthermore, if a plurality of the exposure heads are provided, the exposure efficiency can be improved.

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

[Configuration of image exposure apparatus]
As shown in FIG. 1, the image exposure apparatus 10 according to the present embodiment includes a flat plate-like moving stage 14 that holds a sheet-like photosensitive material 12 by adsorbing to the surface. Two guides 20 extending along the stage moving direction are installed on the upper surface of the thick plate-shaped installation table 18 supported by the four legs 16. The stage 14 is arranged so that the longitudinal direction thereof faces the stage moving direction, and is supported by the guide 20 so as to be reciprocally movable. The image exposure apparatus 10 is provided with a later-described stage driving device 116 (see FIG. 19) that drives the stage 14 as sub-scanning means along the guide 20.

  A U-shaped gate 22 is provided at the center of the installation base 18 so as to straddle the movement path of the stage 14. Each end of the U-shaped gate 22 is fixed to both side surfaces of the installation base 18. A scanner 24 is provided on one side of the gate 22 and a plurality of (for example, two) sensors 26 for detecting the front and rear ends of the photosensitive material 12 are provided on the other side. The scanner 24 and the sensor 26 are respectively attached to the gate 22 and fixedly arranged above the moving path of the stage 14. The scanner 24 and the sensor 26 are connected to a controller (not shown) that controls them.

As shown in FIGS. 2 and 3B, the scanner 24 includes a plurality of (for example, 14) exposure heads 28 arranged in an approximately matrix of m rows and n columns (for example, 3 rows and 5 columns). . In this example, only four exposure heads 28 are arranged in the third row in relation to the width of the photosensitive material 12. In the following, when individual exposure heads arranged in the m-th row and the n-th column are shown, they are expressed as the exposure head 28 _mn .

The exposure area 30 by each exposure head 28 has a rectangular shape with the short side in the sub-scanning direction. Accordingly, as the stage 14 moves, a strip-shaped exposed region 32 is formed in the photosensitive material 12 for each exposure head 28. In the following, when an exposure area by individual exposure heads arranged in the m-th row and the n-th column is indicated, it is expressed as an exposure area 30 _mn .

Further, as shown in FIGS. 3A and 3B, each of the exposure heads 28 in each row arranged in a line so that the strip-shaped exposed regions 32 are arranged without gaps in the direction orthogonal to the sub-scanning direction. Are arranged at a predetermined interval (natural number times the long side of the exposure area, twice in this embodiment) in the arrangement direction. Therefore, can not be exposed portion between the exposure area _{30 11} in the first row and the exposure area _{30 12,} it can be exposed by the second row of the exposure area _{30 21} and the exposure area _{30 31} in the third row.

As shown in FIGS. 4 and 5, each of the exposure heads 28 ₁₁ to 28 _mn is a spatial light modulation element that modulates an incident light beam for each pixel unit according to image data, and is manufactured by Texas Instruments Incorporated. DMD34. The DMD 34 is connected to a later-described controller 112 (see FIG. 19) that includes a data processing unit and a mirror drive control unit. The data processing unit of the controller 112 generates a control signal for driving and controlling each micromirror in the use area on the DMD 34 for each exposure head 28 based on the input image data. The use area on the DMD 34 will be described later. The mirror drive control unit controls the angle of the reflection surface of each micromirror of the DMD 34 for each exposure head 28 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.

  As shown in FIG. 4, on the light incident side of the DMD 34, there is provided a laser emitting portion in which the emitting end portion (light emitting point) of the optical fiber is arranged in a line along the direction corresponding to the long side direction of the exposure area 30. The fiber array light source 36, the lens system 38 that corrects the laser light emitted from the fiber array light source 36 and collects the light on the DMD, and the mirror 40 that reflects the laser light transmitted through the lens system 38 toward the DMD 34. Arranged in order. In FIG. 4, the lens system 38 is schematically shown.

  As shown in detail in FIG. 5, the lens system 38 is inserted into a condensing lens 42 that condenses the laser light B as illumination light emitted from the fiber array light source 36, and an optical path of the light that has passed through the condensing lens 42. The rod-shaped optical integrator (hereinafter referred to as “rod integrator”) 44 and an imaging lens 46 disposed in front of the rod integrator 44, that is, on the mirror 40 side. The rod integrator 44 is a translucent rod formed in, for example, a quadrangular prism shape. As the laser beam B emitted from the fiber array light source 36 travels while totally reflecting inside the rod integrator 44, the intensity distribution in the beam cross section is made uniform, and it is close to parallel light and the intensity in the beam cross section is made uniform. Is incident on the DMD 34 as a reflected light beam. As a result, non-uniform illumination light intensity can be eliminated and a high-definition image can be exposed on the photosensitive material 12. The entrance end face and the exit end face of the rod integrator 44 are coated with an antireflection film to enhance the transmittance.

  The laser beam B emitted from the lens system 38 is reflected by the mirror 40 and irradiated to the DMD 34 via a TIR (total reflection) prism 48. In FIG. 4, the TIR prism 48 is omitted.

  On the light reflection side of the DMD 34, a main optical system 50 that images the laser light B reflected by the DMD 34 on the photosensitive material 12 is disposed. The main optical system 50 is schematically shown in FIG. 4, but as shown in detail in FIG. 5, the first imaging optical system 52 including lenses 54 and 56 and the second connection including lenses 60 and 62 are provided. An image optical system 58, a microlens array 64 inserted between these image forming optical systems and disposed on the focal plane of the first image forming optical system 52, and a first lens disposed before the microlens array 64. 1 aperture array 66 and a second aperture array 68 disposed downstream of the microlens array 64.

  The microlens array 64 is formed by two-dimensionally arranging a large number of microlenses 64a corresponding to the respective micromirrors driven by the DMD 34. In this example, as will be described later, only 1024 × 256 rows of the 1024 × 768 rows of micromirrors of the DMD 34 are driven, and accordingly, 1024 × 256 rows of microlenses 64a are arranged. In FIG. 5, only three microlenses 64a are shown, but this is simplified for the sake of explanation. The arrangement pitch of the microlenses 64a is 41 μm in both the vertical and horizontal directions. In the present embodiment, each micro lens 64a is a plano-convex lens having a flat front surface and a convex rear surface, and is formed from an optical glass BK7 having a focal length of 0.19 mm and an NA (numerical aperture) of 0.11, for example. A plano-convex lens can be used. Note that the present invention is not limited to the above example, and a biconvex lens or the like may be used. In addition, each microlens 64a and a connecting portion that connects them in an array may be integrally formed of the same material to form a microlens array 64, or each microlens 64a may be formed on a base provided with a large number of openings. May be inserted.

  The first aperture array 66 and the second aperture array 68 are provided with a large number of apertures corresponding to the microlenses 64a on a plate made of a light shielding material mainly for the purpose of removing stray light. Both are arranged spatially separated from the microlens array 64. The first opening array 66 and the second opening array 68 will be described in detail later.

  The first imaging optical system 52 forms an image on the microlens array 64 by enlarging the image by the DMD 34 three times. The second imaging optical system 58 enlarges the image that has passed through the microlens array 64 by 1.6 times, and forms and projects the image on the photosensitive material 12. Therefore, as a whole, the image obtained by the DMD 34 is magnified 4.8 times and formed on the photosensitive material 12 and projected.

  In the present embodiment, a prism pair 70 is disposed between the second imaging optical system 58 and the photosensitive material 12, and the prism pair 70 is moved in the vertical direction in FIG. The focus of the image can be adjusted. In the figure, the photosensitive material 12 is sub-scanned in the direction of arrow F.

  As shown in FIG. 6, in the DMD 34, a large number (eg, 1024 × 768) of micromirrors (micromirrors) 74, each of which constitutes a pixel (pixel), are arranged in a lattice pattern on an SRAM cell (memory cell) 72. This is a mirror device. In each pixel, a rectangular micromirror 74 supported by a support is provided at the top, and a material having a high reflectance such as aluminum is deposited on the surface of the micromirror 74. In the present embodiment, the reflectance of each micromirror 74 is 90% or more, and the arrangement pitch is 13.7 μm as an example in both the vertical and horizontal directions. Since there is a slight gap between the micromirrors 74, the size of each micromirror 74 itself is 13.0 μm in both length and width. The SRAM cell 72 is a CMOS of a silicon gate manufactured on a normal semiconductor memory manufacturing line via a support including a hinge and a yoke, and is entirely configured monolithically.

  When a digital signal is written in the SRAM cell 72 of the DMD 34, each micromirror 74 supported by the support is either ± α degrees (for example, ± 12 °) with respect to the substrate side on which the DMD 34 is disposed with the diagonal line as the center. Tilt to. FIG. 7A shows a state in which the micromirror 74 is tilted to + α degrees in the on state, and FIG. 7B shows a state in which the micromirror 74 is tilted to −α degrees in the off state. Therefore, by controlling the tilt of the micromirror 74 in each pixel of the DMD 34 according to the image signal as shown in FIG. 6, the laser light B incident on the DMD 34 is reflected in the tilt direction of each micromirror 74. The

  FIG. 6 shows an example in which a part of the DMD 34 is enlarged and each micromirror 74 is controlled to + α degrees or −α degrees. The on / off control of each micromirror 74 is performed by the controller 112 connected to the DMD 34. Further, a light absorber (not shown) is disposed in the direction in which the laser beam B reflected by the micromirror 74 in the off state travels.

  Further, it is preferable that the DMD 34 is disposed slightly obliquely so that its short side forms a predetermined angle θ (for example, 1 ° to 5 °) with the sub-scanning direction. FIG. 8A shows the scanning trajectory of each light beam (exposure beam) 76 reflected and modulated by each micromirror when DMD 34 is not inclined, and FIG. 8B shows the case where DMD 34 is inclined. The scanning trajectory of the exposure beam 76 is shown.

In the DMD 34, a number of micromirror arrays in which a large number (for example, 1024) of micromirrors 74 are arranged in the longitudinal direction are arranged in a short direction (for example, 768 sets). as described above, by the DMD34 obliquely oriented, the pitch P ₂ of the scanning locus of the exposure beams 76 from each micromirror (scan line), it becomes narrower than the pitch P ₁ of the scanning line when not the DMD34 diagonally oriented, The resolution can be greatly improved. On the other hand, since the angle at which DMD 34 is inclined is very small, the scanning width W ₂ when DMD 34 is inclined and the scanning width W ₁ when DMD 34 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, the joints between the plurality of exposure heads 28 arranged in the main scanning direction can be connected without a step by a very small exposure position control.

  Note that the same effect can be obtained by arranging the micromirror rows in a staggered manner at a predetermined interval in the direction orthogonal to the sub-scanning direction instead of making the DMD 34 oblique.

  As shown in FIG. 9 a, the fiber array light source 36 includes a plurality of (for example, 14) laser modules 78, and one end of a multimode optical fiber 80 is coupled to each laser module 78. A multimode optical fiber 82 having a smaller cladding diameter than that of the multimode optical fiber 80 is coupled to the other end of the multimode optical fiber 80. As shown in detail in FIG. 9b, seven ends of the multimode optical fiber 82 opposite to the multimode optical fiber 80 are arranged along the main scanning direction orthogonal to the sub-scanning direction, and are arranged in two rows. Thus, a laser emitting portion 84 is configured.

  As shown in FIG. 9B, the laser emitting portion 84 formed by the end portion of the multimode optical fiber 82 is sandwiched and fixed between two support plates 86 having a flat surface. In addition, a transparent protective plate such as glass is preferably disposed on the light emitting end face of the multimode optical fiber 80 for protection. The light exit end face of the multimode optical fiber 80 has a high light density and is likely to collect dust and easily deteriorate. However, the protective plate as described above prevents the dust from adhering to the end face and deteriorates. Can be delayed.

  In this embodiment, as shown in FIG. 10, an optical fiber 82 having a length of about 1 m to 30 cm and having a small cladding diameter is coaxially coupled to a tip portion on the laser light emission side of a multimode optical fiber 80 having a large cladding diameter. ing. The optical fibers 80 and 82 are coupled by fusing the incident end face of the optical fiber 82 to the outgoing end face of the optical fiber 80 in a state where the respective core axes coincide.

  As the multimode optical fiber 80 and the optical fiber 82, 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 the present embodiment, the multimode optical fiber 80 and the optical fiber 82 are step index type optical fibers. The multimode optical fiber 80 has a cladding diameter = 125 μm, a core diameter = 50 μm, NA = 0.2, and an incident end face coating. The transmittance is 99.5% or more, and the optical fiber 82 has a clad diameter = 60 μm, a core diameter = 50 μm, and NA = 0.2.

  However, the cladding diameter of the optical fiber 82 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, since the core diameter needs to be at least 3 to 4 μm, the cladding diameter of the optical fiber 82 is preferably 10 μm or more. From the viewpoint of coupling efficiency, it is preferable to match the core diameters of the optical fibers 80 and 82.

  Further, in the present invention, it is not always necessary to use the two types of optical fibers 80 and 82 having different clad diameters as described above by fusion (so-called different diameter fusion). A fiber array light source may be configured by bundling a plurality of fibers (for example, optical fiber 80 in FIG. 9a) as they are in a bundle.

  The laser module 78 includes 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 88. LD 7, collimator lenses L 1, L 2, L 3, L 4, L 5, L 6, and L 7 provided corresponding to each of GaN-based semiconductor lasers LD 1 to LD 7, one condenser lens 90, and one multimode And an optical fiber 80. The number of semiconductor lasers is not limited to seven, and other numbers may be adopted. Further, instead of the seven collimator lenses L1 to L7 as described above, a collimator lens array in which these lenses are integrated may be used.

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

  As shown in FIGS. 12 and 13, the combined laser light source 78 is housed in a box-shaped package 92 having an upper opening together with other optical elements. The package 92 includes a package lid 94 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 92 with the package lid 94. The combined laser light source 78 is hermetically sealed in a closed space (sealed space).

  A base plate 96 is fixed to the bottom surface of the package 92, and the heat block 88, the condensing lens holder 98 that holds the condensing lens 90, and the multimode optical fiber 80 are disposed on the top surface of the base plate 96. A fiber holder 100 that holds the incident end of the optical fiber is attached. The exit end of the multimode optical fiber 80 is drawn out of the package from an opening formed in the wall surface of the package 92.

  A collimator lens holder 102 is attached to the side surface of the heat block 88, and collimator lenses L1 to L7 are held there. An opening is formed in the lateral wall surface of the package 92, and a wiring 104 for supplying a driving current from the GaN-based semiconductor laser 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 L7 is numbered among the plurality of collimator lenses. doing.

  FIG. 14 shows the front shape of the attachment part of the collimator lenses L1 to L7. Each of the collimator lenses L1 to L7 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. The elongated collimator lens can be formed, for example, by molding resin or optical glass. The collimator lenses L1 to L7 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 has a divergence angle of, for example, 10 ° and 30 ° in a direction parallel to the active layer. A laser emitting B7 is used. These GaN-based semiconductor lasers LD1 to LD7 are arranged so that the light emitting points are arranged in a line in a direction parallel to the active layer.

Therefore, in the laser beams B1 to B7 emitted from the respective light emitting points, the direction in which the divergence angle is large coincides with the length direction and the divergence angle is small with respect to the elongated collimator lenses L1 to L7 as described above. Incident light is incident in a state where the direction coincides with the width direction (direction perpendicular to the length direction). In this embodiment, the collimator lenses L1 to L7 have a width of 1.1 mm and a length of 4.6 mm, and the laser beam B1 to B7 incident thereon has a horizontal and vertical beam diameter of 0.9 mm, respectively. 2.6 mm. In addition, each of the collimator lenses L1 to L7 has a focal length f ₁ = 3 mm, NA = 0.6, and a lens arrangement pitch = 1.25 mm.

The condensing lens 90 is formed by cutting a region including the optical axis of a circular lens having an aspherical surface into a long and narrow plane parallel to the arrangement direction of the collimator lenses L1 to L7, that is, long in the horizontal direction and short in a direction perpendicular thereto. Is formed. The condenser lens 90 has a focal length f ₂ = 23 mm and NA = 0.2. This condensing lens 90 is also formed, for example, by molding resin or optical glass.

  Next, the configuration of the first opening array 66 and the second opening array 68 will be described with reference to FIGS.

FIG. 15 is an enlarged cross-sectional view showing the periphery of a set of microlenses 64a, openings 66a, and openings 66b constituting the microlens array 64, the first opening array 66, and the second opening array 68. . In FIG. 15, the light centers C ₀ and C of the 0th-order light, the + 1st-order diffracted light, and the −1st-order diffracted light that are modulated by one micromirror on the DMD 34 and collected by the first imaging optical system 52 are further illustrated. _{The +1} and C ₋₁ trajectories are shown, respectively. As described above, in the present embodiment, each micro lens 64a is a plano-convex lens having a flat front surface and a convex rear surface. The surface 106 is a lens attachment surface on the rear side of the microlens array 64 and at the same time is a focal plane of the first imaging optical system 52. As shown in the figure, the distance between the first aperture array 66 and the front surface of the microlens array 64 is d ₁ , and the front surface of the microlens array 64 and the focal plane of the first imaging optical system 52 (that is, the surface 106 in this embodiment). ) Is the distance d ₂ , the angle formed by the light center of the 0th order light from the corresponding micromirror of the DMD 34 and the light center of the ± 1st order diffracted light is θ ₁ , and between the first aperture array 66 and the microlens array 64. If the refractive index of the medium (air in this embodiment) is n ₁ , and the refractive index of the material constituting the microlens 64 a is n ₂ , the light beam center of the 0th order light at the position of the first aperture array 66 and the next time The distance s _{1 from} the light beam center of the folding light is

It can be expressed as.

FIG. 16A is an enlarged sectional view showing the periphery of the same set of microlens 64a, opening 66a and opening 66b as in FIG. 15, and corresponds to the numerical aperture of the first imaging optical system 52. 0-order light of the spread component from the corresponding micromirrors DMD34 (indicated by hatching), is a depiction with the trajectory of the beam center C _0. As shown in the figure, when the half cone angle of the maximum cone angle of the 0th-order light spreading component corresponding to the numerical aperture of the first imaging optical system 52 is θ ₂ , the 0th-order light spreading distance at the position of the first aperture array 66. s ₂ is

It can be expressed as. The numerical aperture NA of the first imaging optical system 52 and the angle θ ₂ are
NA = n ₁ sin θ ₂ (3)
Satisfy the relationship.

FIGS. 16B and 16C are cross-sectional views similar to FIG. 16A, and ± first-order diffracted light from corresponding micromirrors of DMD 34 corresponding to the numerical aperture of first imaging optical system 52. Are shown together with the trajectories of their ray centers C _{+ 1} and C- ₁ , respectively. The distances indicated by s ₃ in FIGS. 16B and 16C are the locus of the 0th-order light beam center C ₀ and the outermost spreading component of the 1st-order diffracted light at the position of the first aperture array 66. , Which is approximately equal to the sum of the distances s ₁ and s ₂ described above. Therefore, if the radius R of each opening 66a of the first opening array 66 is made larger than (s ₁ + s ₂ ), each microlens 64a is reflected at a portion close to the center of the corresponding micromirror of the DMD 34. The incident light component can include at least 0th-order light and ± 1st-order diffracted light including a spreading component corresponding to the numerical aperture of the first imaging optical system 52, and can obtain good imaging performance. Can do. Therefore, in the exposure apparatus of the present invention,
R ≧ d ₁ (tan θ ₁ + tan θ ₂ ) + d ₂ (tan θ ₁ ′ + tan θ ₂ ′) (4)
However, θ ₁ ′ = arcsin (n ₁ / n ₂ × sin θ ₁ )
θ ₂ ′ = arcsin (n ₁ / n ₂ × sin θ ₂ )
R, d ₁ and d ₂ are adjusted so as to satisfy the conditional expression

As an example, in the present embodiment, if the angle θ ₁ determined mainly by the pitch of the DMD 34 is 0.57 ° and the numerical aperture of the first imaging optical system 52 is NA = 0.005, each micro The lens 64a is made of quartz glass having a refractive index n ₂ = 1.47 and is adjusted so that R = 16 μm, d ₁ = 360 μm, d ₂ = 1000 μm, thereby satisfying the condition of the above formula (4). Is done. As described above, in this embodiment, since the medium between the first aperture array 66 and the microlens array 64 is air, n ₁ = 1.0.

Here, the purpose of providing the first aperture array 66 is to block components that cause stray light from entering the microlens array. Therefore, if the radius R of each aperture 66a is too large, this purpose is achieved. Is not preferable. Therefore, it is preferable that the radius R is fixed to a value equal to or less than an appropriate upper limit, and the distances d ₁ and d ₂ are adjusted so as to satisfy the condition of the above expression (4). In addition, since the thinner each micro lens 64a is, the easier it is to adjust the deviation of the optical path in the horizontal direction, it is preferable to adjust the thickness of the micro lens 64a (approximately d _{2 in} this embodiment) to be as thin as possible.

Regarding the upper limit of the radius R of the opening 66a described above, the cause of stray light derived from the light coming from the adjacent micromirror while transmitting the light reflected at the portion near the center of the corresponding micromirror of the DMD 34 sufficiently and sufficiently. In order to effectively block this component, it is preferable to set the upper limit to ½ of the product of the length of the short side of each micromirror 74 of the DMD 34 and the magnification of the first imaging optical system 52. In the present embodiment, as described above, each micromirror has a square shape of 13.0 μm × 13.0 μm, and the magnification of the first imaging optical system 52 is 3. Therefore, the radius R of each opening 66a is 19 .5 μm or less. As described above as an example, this condition is satisfied when adjustments are made so that R = 16 μm, d ₁ = 360 μm, and d ₂ = 1000 μm.

  In addition, when the DMD is used as a spatial light modulation element as in the present embodiment, the component that causes stray light is mainly generated due to the geometric distortion of the peripheral portion of each micromirror constituting the DMD. I found out. FIG. 17 is a diagram illustrating a result of actually measuring the flatness of the reflection surface of the micromirror 74 constituting the DMD 34 of the present embodiment. In this figure, the same height positions of the reflecting surfaces are shown connected by contour lines, and the pitch of the contour lines is 5 nm. Note that the x direction and the y direction shown in the figure are two diagonal directions of the micromirror 74, and the micromirror 74 rotates as described above about the rotation axis extending in the y direction. 18A and 18B show the height position displacement of the reflecting surface of the micromirror 74 along the x direction and the y direction, respectively. As shown in FIGS. 17 and 18, there is distortion on the reflection surface of the micromirror 74, and the amount of change in the distortion tends to gradually increase from the center of the micromirror 74 toward the peripheral edge. . The distortion in the rotation axis direction (y direction) of the micromirror 74 is larger than the distortion in the other diagonal direction (x direction).

  Therefore, in the present embodiment using the DMD 34, the radius R of each opening 66a of the first opening array 66 is the reflected light (at least the 0th order) from the peripheral portion where the change amount of the geometric distortion of each micromirror 74 is large. It is small enough to block light).

  By providing the first aperture array 66 configured as described above, in the exposure apparatus 10 of the present embodiment, the stray light derived from the light from the adjacent micromirrors and the geometric distortion of the peripheral portion of each micromirror 74 is obtained. It is possible to maintain good imaging performance while blocking the component causing the above in a necessary and sufficient range. In addition, since the first aperture array 66 is spatially spaced from the microlens array 64, even if the constituent members of the first aperture array 66 are heated by light, the heat is microscopic. There is no possibility that the optical performance of the microlens array 64 will be adversely affected by being hardly transmitted to the lens array 64.

  It should be noted that the size of each opening 68a of the second opening array 68 is sufficient to ensure a sufficient light amount ratio between when all the micromirrors 74 are in the on state and when all the micromirrors 74 are in the off state, and for stray light. The size is adjusted so that there is no problem in the shut-off performance.

  Next, with reference to FIG. 19, the electrical configuration of the image exposure apparatus 10 of the present embodiment will be described. As shown here, a modulation circuit 110 is connected to the overall control unit 108, and a controller 112 that controls the DMD 34 is connected to the modulation circuit 110. The overall control unit 108 is connected to an LD drive circuit 114 that drives the laser module 78. Further, a stage driving device 116 for driving the stage 14 is connected to the overall control unit 108.

[Operation of image exposure apparatus]
Next, the overall operation of the image exposure apparatus 10 will be described. In each exposure head 28 of the scanner 24, laser beams B1, B2, B3 emitted in a divergent light state from GaN-based semiconductor lasers LD1 to LD7 (see FIG. 11) constituting the combined laser light source of the fiber array light source 36. Each of B4, B5, B6, and B7 is collimated by the corresponding collimator lenses L1 to L7. The collimated laser beams B <b> 1 to B <b> 7 are collected by the condenser lens 90 and converge on the incident end face of the core 80 a of the multimode optical fiber 80.

  In the present embodiment, a condensing optical system is configured by the collimator lenses L1 to L7 and the condensing lens 90, and a combining optical system is configured by the condensing optical system and the multimode optical fiber 80. That is, the laser beams B1 to B7 collected as described above by the condenser lens 90 enter the core 80a of the multimode optical fiber 80, propagate through the optical fiber, and combine with one laser beam B. The light is emitted from the optical fiber 82 coupled to the output end of the multimode optical fiber 80.

  In each laser module, when the coupling efficiency of the laser beams B1 to B7 to the multimode optical fiber 80 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 82, 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 82 can obtain 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 110 shown in FIG. 19 to the controller 112 of the DMD 34 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). In accordance with this binary data, each micromirror 74 of DMD 34 is tilted to any one of ± α degrees.

  The stage 14 that has adsorbed the photosensitive material 12 to the surface is moved at a constant speed from the upstream side to the downstream side of the gate 22 along the guide 18 by a stage driving device 116 shown in FIG. When the leading edge of the photosensitive material 12 is detected by the sensor 26 attached to the gate 22 as the stage 14 passes under the gate 22, 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 28 based on the image data read by the data processing unit. Then, each of the micromirrors of the DMD 34 is controlled on and off for each exposure head 28 based on the generated control signal by the mirror drive control unit.

  When the laser light B is irradiated from the fiber array light source 36 to the DMD 34, the laser light reflected when the micromirror of the DMD 34 is in the on state is reflected in the first imaging optical system 52, the first aperture array 66, and the microlens. An image is formed on the photosensitive material 12 through the array 64, the second aperture array 68, the second imaging optical system 58 and the prism pair 70. In this manner, the laser light emitted from the fiber array light source 36 is turned on and off for each pixel, and the photosensitive material 12 is exposed in a pixel unit (exposure area 30) that is approximately the same number as the number of micromirrors used in the DMD 34. Further, when the photosensitive material 12 is moved at a constant speed together with the stage 14, the photosensitive material 12 is sub-scanned in the direction opposite to the stage moving direction by the scanner 24, and a strip-shaped exposed region 32 is formed for each exposure head 28. It is formed.

  In this example, as shown in FIGS. 20A and 20B, the DMD 34 has 768 sets of micromirror arrays in which 1024 micromirrors are arranged in the main scanning direction. In this example, the controller 112 performs control so that only a part of the micromirror rows (for example, 1024 × 256 rows) is driven.

  In this case, a micromirror array arranged at the center of the DMD 34 as shown in FIG. 20 (A) may be used, and a micromirror arranged at the end of the DMD 34 as shown in FIG. 20 (B). A column may be used. In addition, when a defect occurs in some of the micromirrors, the micromirror array to be used may be appropriately changed depending on the situation, such as using a micromirror array in which no defect has occurred.

  Since the data processing speed of the DMD 34 is limited and the modulation speed per line is determined in proportion to the number of micromirrors used, the modulation speed per line can be obtained by using only a part of the micromirror rows. Will be 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 micromirrors in the sub-scanning direction.

  When the sub scanning of the photosensitive material 12 by the scanner 24 is completed and the rear end of the photosensitive material 12 is detected by the sensor 26, the stage 14 is moved to the most upstream side of the gate 22 along the guide 20 by the stage driving device 116. It returns to a certain origin, and again moves along the guide 20 from the upstream side of the gate 22 to the downstream side at a constant speed.

  Although the embodiment of the present invention has been described in detail above, this embodiment is merely an example, and the technical scope of the present invention should be defined only by the claims in this specification. Needless to say.

The perspective view which shows the external appearance of the image exposure apparatus which is one Embodiment of this invention 1 is a perspective view showing a configuration of a scanner of the image exposure apparatus in FIG. (A) is a plan view showing an exposed area formed on the photosensitive material, and (B) is a plan 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. Sectional drawing of the exposure head of the image exposure apparatus of FIG. The elements on larger scale which show the structure of DMD of the image exposure apparatus of FIG. Explanatory diagram for explaining the operation of DMD A plan view showing the arrangement of exposure beams and scanning lines in a case where the DMD is not inclined and in a case where the DMD is not 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 Partial enlarged sectional view showing the configuration of the 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. Partial enlarged cross-sectional view illustrating the configuration of the microlens array and aperture array, and the locus of light rays incident on them Partially enlarged sectional view illustrating the configuration of the microlens array and the aperture array, and the spread of light incident on them The figure which shows the distortion of the reflective surface of the micromirror which comprises DMD with a contour line The graph which shows distortion of the reflective surface of the above-mentioned micromirror about two diagonal directions of the mirror 1 is a block diagram showing an electrical configuration of the image exposure apparatus in FIG. Plan view showing examples of DMD usage areas

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 12 Photosensitive material 14 Moving stage 18 Installation stand 20 Guide 22 Gate 24 Scanner 26 Sensor 28 Exposure head 34 DMD
36 Fiber array light source 48 TIR prism 50 Main optical system 52 First imaging optical system 58 Second imaging optical system 64 Micro lens array 66 First aperture array 68 Second aperture array 70 Prism pair

Claims (5)

An image exposure apparatus comprising an exposure head and exposing a desired pattern onto the photosensitive material by the exposure head,
The exposure head comprises:
A light source;
A spatial light modulation element in which a large number of pixel units that independently modulate light from the light source are arranged;
An imaging optical system that focuses each of a plurality of light beams modulated by the plurality of pixel units and forms an image on the same focal plane;
An aperture array in which multiple apertures corresponding to each of the multiple light beams that have passed through the imaging optical system are arranged;
A microlens array arranged on the focal plane and arranged with a plurality of microlenses corresponding to each of the plurality of light beams that have passed through the aperture array, in this order on the optical path,
The aperture array and the microlens array are arranged spatially separated from each other,
The radius R of each of the multiple apertures, the distance d ₁ between the aperture array and the front surface of the microlens array, the distance d ₂ between the front surface and the focal plane, and the multiple light beams emitted from the imaging optical system , The angle θ ₁ formed by the center of the zeroth-order light from the spatial light modulator and the center of the first-order diffracted light, the half angle θ ₂ of the maximum cone angle of the zeroth-order light, the aperture array, and the micro Between the refractive index n ₁ of the medium between the lens arrays and the refractive index n ₂ of the material constituting each of the microlenses,
R ≧ d ₁ (tan θ ₁ + tan θ ₂ ) + d ₂ (tan θ ₁ ′ + tan θ ₂ ′)
However, θ ₁ ′ = arcsin (n ₁ / n ₂ × sin θ ₁ )
θ ₂ ′ = arcsin (n ₁ / n ₂ × sin θ ₂ )
An image exposure apparatus characterized in that   The image exposure apparatus according to claim 1, wherein the radius R of the opening is equal to or less than ½ of a product of a length of a short side of the pixel portion and a magnification of the imaging optical system.   3. The image according to claim 1, wherein the spatial light modulation element is a digital micromirror device including a large number of micromirrors that reflect light from the light source as the large number of pixel portions. Exposure device. Each of the plurality of microlenses is a planoconvex lens having a flat front surface and a convex rear surface,
4. The image exposure apparatus according to claim 1, wherein the focal plane coincides with a lens-attaching surface on the rear side of the microlens array. 5.   The image exposure apparatus according to claim 1, comprising a plurality of the exposure heads.

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