JP4450689B2 - Exposure head - Google Patents

Description

  The present invention relates to an exposure head for exposing an exposure surface of a photosensitive material or the like with a bundle of light beams modulated by a spatial light modulator in accordance with image data.

  Conventionally, various exposure heads have been proposed for performing image exposure with a light beam modulated in accordance with image data using a spatial light modulator such as a digital micromirror device (DMD).

  The DMD uses a mirror device in which a large number of micromirrors whose reflection surfaces change in response to a control signal are two-dimensionally arranged on a semiconductor substrate such as silicon. The exposure head using this DMD is, for example, a light source that emits a laser beam, a collimating lens system that collimates the laser beam emitted from the light source, a DMD that modulates the laser beam, and a laser beam reflected by this DMD. An imaging optical system that forms an image on top is provided. In this exposure head, each micromirror of the DMD is controlled to be turned on / off by a control device in accordance with a control signal generated according to image data or the like, and the laser beam is modulated (deflected) into an exposure state or a non-exposure state. The exposure surface is exposed by a laser beam modulated in a state (hereinafter referred to as “beam bundle”). Here, the imaging optical system is usually configured as an enlargement optical system, and the exposure area on the exposure surface is enlarged with respect to the area of the effective area of the DMD in which micromirrors are two-dimensionally arranged. Yes. However, when the area of the exposure area with respect to the exposure surface is enlarged with respect to the area of the effective area of the DMD by the imaging optical system, the area (spot diameter) of the beam spot on the exposure surface is also enlarged according to the enlargement ratio. The MTF (Modulation Transfer Function) characteristic on the surface is lowered in accordance with the enlargement ratio of the exposure area.

  Therefore, as an exposure head capable of solving the above-described problems, for example, there are those having configurations as shown in Patent Document 1 and Patent Document 2.

  Patent Document 1 discloses a double-telecentric projection optical system having a small numerical aperture but a large image field, and an array of microlenses each having a large numerical aperture and a small field. And an optical system combining a microlens aperture array, and an optical scanning device (microlens scanner) equipped with this optical system exposes an exposure surface by an exposure spot formed by the microlens array. Scan exposure on the (printing surface). However, in such an optical system, there is a trade-off between the uniformity of illumination on the microlens aperture and the suppression of light leakage (crosstalk) to the adjacent aperture, and a uniform exposure spot on the exposure surface. There is a problem that it is difficult to achieve both light efficiency and light utilization efficiency.

  Also, for example, FIG. 15 includes a group of lenses and a point such as a microlens array in order to image pattern information displayed on the pixel panel on a subject such as a wafer. A configuration using an array (point array), a grating, and an additional lens group is shown. Here, the grating is for reducing the crosstalk light and noise light due to the scattering component of the light that illuminates the pixel panel and the diffraction and scattering from the pixel panel by the shielding effect.

However, when the grating is arranged at a position before the focused light beam by the microlens array is converged, that is, in a so-called Fresnel diffraction region, it reduces crosstalk light and scattered light. The effect is not enough. Also, if the grating is placed at the convergence position of the convergent light beam, so-called Fraunhofer diffraction, the working distance cannot be secured, so the material cannot be placed directly at the beam convergence position. It is necessary to form an image on the material via an additional lens group (imaging lens system). This imaging lens system has a drawback that a large number of element lenses are required particularly when high-resolution imaging is performed, which increases the cost and requires a large space.
US Pat. No. 6,133,986 (FIG. 14) US Pat. No. 6,473,237 B2 (FIG. 15)

  An object of the present invention is to provide an exposure head capable of exposing optical pattern information displayed by a spatial light modulator with high resolution and high resolution over a wide exposure area in consideration of the above facts. is there.

  In order to achieve the above object, an exposure head according to the present invention comprises a light beam arranged along a row direction intersecting the scanning direction while moving relative to the exposure surface along the scanning direction. An exposure head for two-dimensionally exposing an exposure surface with a bundle of light sources, wherein a plurality of pixel portions whose light modulation states change according to a control signal are arranged one-dimensionally or two-dimensionally, and a light source portion A spatial light modulation element that selectively divides the plurality of pixel beams into one of an exposure state and a non-exposure state, respectively, A first micro-focusing element array in which a plurality of first micro-focusing elements are arranged so as to correspond to a plurality of pixel portions in the spatial light modulation element, and a Fraunhofer of the pixel beam modulated in the exposure state A diffraction pattern is arranged in the vicinity of the rear focal plane of the first micro-focusing element formed by the first micro-focusing element, and corresponds to each of the plurality of first micro-focusing elements. A plurality of apertures are arranged, an aperture array that transmits only a main part of the Fraunhofer diffraction image by the apertures, and a plurality of second micro-focusing elements are arranged so as to correspond to the plurality of apertures, And a second micro-focusing element array that forms a real image of the pixel beam respectively transmitted through the aperture on the exposure surface by the plurality of second micro-focusing elements.

  In the exposure head according to the present invention, a plurality of first micro-focusing elements are arranged in the first micro-focusing element array so as to correspond to the plurality of pixel portions in the spatial light modulation element, and the first micro-focusing elements are arranged. A Fraunhofer in which a plurality of apertures arranged so that aperture arrays arranged in the vicinity of the rear focal plane of the focusing element respectively correspond to the plurality of first micro focusing elements are formed by the plurality of first microlens arrays -By transmitting only the main part of the diffracted image, the beam diameter of the pixel beam modulated into the exposure state by each pixel portion of the spatial light modulator can be reduced, so that it is projected onto the exposure surface through the second microlens array. The beam diameter of the generated beam spot can be adjusted to a required size.

  In the exposure head according to the present invention, the second micro-focusing element array forms the real image of the pixel beam that has passed through each of the plurality of apertures on the exposure surface by using the plurality of second micro-focusing elements. The pixel beam whose beam diameter has been reduced by passing through the first micro-focusing element of the micro-focusing element array and the aperture of the aperture array is placed at a position determined by the focal length and imaging magnification of the second micro-focusing element. Since the image can be formed as a beam spot, the exposure surface can be set directly at the convergence position of the pixel beam while ensuring the required working distance while effectively reducing crosstalk light and scattered light by the action of the aperture. become.

  In the exposure head according to the present invention, the second micro-focusing element array forms the real image of the pixel beam that has passed through each of the plurality of apertures on the exposure surface by using the plurality of second micro-focusing elements. The beam diameter is reduced by the first micro-focusing element of the micro-focusing element array, and the pixel beam transmitted through the aperture of the aperture array is formed as a beam spot at a position determined by the focal length and the imaging magnification of the second micro-focusing element. Since the image can be formed, the exposure surface can be directly placed at the convergence position of the pixel beam while ensuring the required working distance while effectively reducing the crosstalk light and the scattered light by the action of the aperture.

  Here, in order to secure a working distance, a micro-converging element array such as a micro-lens array is used, so the number of parts of the apparatus is reduced compared to the case where an imaging lens system composed of a plurality of element lenses is used. In addition to being able to greatly reduce the installation space, the apparatus cost can be reduced and the apparatus can be downsized.

  In the exposure head according to the present invention described above, an aspherical lens such as a toric lens can be used as at least one of the first microfocusing element and the second microfocusing element.

  As described above, according to the exposure head of the present invention, the optical pattern information displayed by the spatial light modulator can be exposed with high resolution and high resolution over a wide exposure area.

Specifically, according to the exposure head of the present invention, the pixel size of the spatial light modulator is reduced for each pixel using a microlens array or the like to increase the resolution on the exposure surface (high resolving power), The exposure surface is scanned along a straight line that forms a certain angle θ (0 ° <θ <90 °) with respect to one pixel column of the spatial light modulator, thereby increasing the exposure density and increasing the resolution (high resolution). In the exposure head aiming at
(A) A high-resolution exposure beam is obtained by almost completely blocking noise components such as scattering components contained in light illuminating the spatial light modulation device and crosstalk components caused by diffraction and scattering from the spatial light modulation device. be able to.

  (B) A working distance can be secured by transmitting the exposure beam spatially to another surface, and an actual exposure object can be disposed on the transmitted surface.

  (C) The above (B) can be realized at a low cost and in a small space.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Configuration of exposure apparatus]
As shown in FIG. 1, an exposure apparatus 142 to which an exposure head according to an embodiment of the present invention is provided includes a flat stage 152 that holds a sheet-like photosensitive material 150 by adsorbing to the surface. 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 legs 154, and the stage 152 is supported by the guides 158 so as to be reciprocally movable. ing. The exposure device 142 is provided with a drive device (not shown) for driving the stage 152 along the 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 gate 160 is fixed to both side surfaces of the installation table 156. A laser scanner 162 is provided on one side of the gate 160, and a plurality of (for example, two) detection sensors 164 for detecting the front and rear ends of the photosensitive material 150 are provided on the other side. . The laser scanner 162 and the detection sensor 164 are respectively attached to the gate 160 and fixedly arranged above the moving path of the stage 152. The laser scanner 162 and the detection sensor 164 are connected to a controller (not shown) that controls them.

  As shown in FIGS. 2 and 3B, the laser scanner 162 has a plurality of (for example, 14) exposure heads 166 arranged in a substantially matrix of m rows and n columns (for example, 3 rows and 5 columns). It has. 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 166mn.

  An exposure area 168 by the exposure head 166 has a rectangular shape with a short side in the scanning direction. Therefore, as the stage 152 moves, a strip-shaped exposed area 170 is formed for each exposure head 166 in the photosensitive material 150. In addition, when showing the exposure area by each exposure head arranged in the mth row and the nth column, it is expressed as an exposure area 168mn.

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 scanning direction without gaps. These are arranged with 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 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 FIG. 4, each of the exposure heads 166 _{11 to} 166 mn uses a digital micromirror device (DMD) 50 as a spatial light modulation element that modulates an incident light beam for each pixel in accordance with image data. I have. The DMD 50 is connected to a controller (not shown) including a data processing unit and a mirror drive control unit. The data processing unit of this controller generates a control signal for driving and controlling each micromirror in the area (effective area) to be controlled by the DMD 50 for each exposure head 166 based on the input image data. The effective area of the DMD 50 will be described later. The mirror drive control unit controls the angle of the reflection surface of each micromirror in 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.

  As shown in FIG. 4, the exposure head 166 includes a laser emission portion in which the emission end portion (light emission point) of the optical fiber is arranged in a line along the direction corresponding to the long side direction of the exposure area 168. A fiber array light source 66, an illumination optical system 67 that irradiates the laser beam emitted from the fiber array light source 66 onto the DMD 50 as uniform illumination light, a folding mirror 74 that reflects the laser beam transmitted through the illumination optical system 67 toward the DMD 50, A TIR (total reflection) prism 76 that separates the laser beam reflected by the folding mirror 74 and incident on the DMD 50 and the laser beam reflected by the DMD 50 with high efficiency is arranged in this order. Here, in the illumination optical system 67, a micro rod lens 71 is disposed as an element lens in an intermediate portion along the optical axis direction, and the laser beam from the fiber array light source 66 is transmitted through the micro rod lens 71. As a result, the illumination light is made uniform.

  As shown in FIG. 6, the DMD 50 is configured such that a micromirror 62 is supported on a SRAM cell (memory cell) 60 by supporting columns, and a large number of pixels (pixels) are formed. This is a mirror device configured by arranging (for example, 600 × 800) micromirrors in a lattice pattern. Each pixel is provided with a micromirror 62 supported by a support column at the top, and a material having a high reflectance such as aluminum is deposited on the surface of the micromirror 62. The reflectance of the micromirror 62 is 90% or more. A silicon gate CMOS SRAM cell 60 manufactured in a normal semiconductor memory manufacturing line is disposed directly below the micromirror 62 via a support including a hinge and a yoke, and is entirely monolithic (integrated type). ).

  When a digital signal is written in the SRAM cell 60 of the DMD 50, the micromirror 62 supported by the support is inclined within a range of ± α degrees (for example, ± 10 degrees) with respect to the substrate side on which the DMD 50 is disposed with the diagonal line as the center. It is done. FIG. 7A shows a state in which the micromirror 62 is tilted to + α degrees in the on state, and FIG. 7B shows a state in which the micromirror 62 is tilted to −α degrees in the off state. Therefore, by controlling the inclination of the micromirror 62 in each pixel of the DMD 50 according to the image signal as shown in FIG. 6, the light incident on the DMD 50 is directed in a direction corresponding to the inclination of each micromirror 62. Reflected.

  FIG. 6 shows an example of a state in which a part of the DMD 50 is enlarged and the micromirror 62 is controlled to + α degrees or −α degrees. On / off control of each micromirror 62 is performed by a controller (not shown) connected to the DMD 50. Here, the light reflected by the on-state micromirror 62 is modulated into an exposure state, and enters an illumination optical system 67 (see FIG. 4) provided on the light exit side of the DMD 50. The light reflected by the micromirror 62 in the off state is modulated into a non-exposure state and enters a light absorber (not shown).

  The DMD 50 is preferably arranged with a slight inclination so that the short side direction (row direction) forms a predetermined angle θ (for example, 0.1 ° to 0.5 °) with the scanning direction. FIG. 8A shows the scanning trajectory of the beam spot (laser beam) 53 on the exposure surface by each micromirror when the DMD 50 is not tilted, and FIG. 8B is the exposure track when the DMD 50 is tilted. A scanning locus of the beam spot 53 is shown.

  In the DMD 50, a number of micromirror arrays in which a large number (for example, 800) of micromirrors are arranged along the longitudinal direction (row direction) are arranged in a short direction (for example, 600 sets). As shown in FIG. 8B, by tilting the DMD 50, the pitch P ′ of the scanning trajectory (scanning line) of the exposure beam 53 by each micromirror is greater than the pitch P of the scanning line when the DMD 50 is not tilted. It becomes narrower and the resolution can be greatly improved. On the other hand, since the tilt angle of the DMD 50 is very small, the scan width W ′ when the DMD 50 is tilted and the scan width W when the DMD 50 is not tilted can be regarded as substantially the same. Note that the same effect can be obtained by arranging the micromirror rows in a staggered manner by shifting the micromirror rows by a predetermined interval in a direction orthogonal to the scanning direction instead of inclining the DMD 50.

  For example, as shown in FIG. 9A, the fiber array light source 66 includes a plurality of (for example, six) laser modules 64, and each laser module 64 includes one end of the multimode optical fiber 30. Are combined. 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 FIG. 9C. The laser emitting portion 68 is configured by arranging the emitting end portions (light emitting points) of the optical fiber 31 in a line along a direction orthogonal to the scanning direction. As shown in FIG. 9D, the light emitting points can be arranged in two rows along a direction orthogonal to the scanning direction.

  The exit end (see FIG. 9) of the optical fiber 31 is sandwiched and fixed between two support plates (not shown) having a flat surface. Further, as shown in FIG. 9B, a transparent protective plate 63 such as glass is disposed on the light emitting side of the optical fiber 31 in order to protect the end face of the optical fiber 31. The exit end of the optical fiber 31 is easily deteriorated because of its high light density and easy dust collection. However, the protective plate 63 can prevent dust from adhering to the end face and delay the deterioration. .

  The multimode optical fiber 30 and the optical fiber 31 may be any of a step index type optical fiber, a graded index type optical fiber, and a composite type optical fiber. 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 30 and the optical fiber 31 are step index type optical fibers, and the multimode optical fiber 30 has a cladding diameter = 125 μm, a core diameter = 25 μm, NA = 0.2, and an incident end face coat. The optical fiber 31 has a cladding diameter = 60 μm, a core diameter = 25 μm, and NA = 0.2.

  The laser module 64 is configured by a combined laser beam source (fiber light source) shown in FIG. This combined laser beam 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 arranged and fixed on the heat block 10. , LD7, collimator lenses 11, 12, 13, 14, 15, 16, and 17 provided corresponding to each of the GaN-based semiconductor lasers LD1 to LD7, one condenser lens 20, and one And a multimode optical fiber 30. The number of semiconductor lasers is not limited to seven.

  Next, the configuration of the optical system on the light reflection side of the DMD 50 in the exposure head 166 will be described.

  As shown in FIG. 5, the exposure head 166 includes an imaging lens system 200, a first microlens array 206, an aperture array 210, and a second microlens array along the traveling direction of the pixel beam on the light reflection side of the DMD 50. 214 are provided in order. Here, the DMD 50 is disposed on the surface (X1, Y1), and each micromirror 62 of the DMD 50 is disposed along the surface (X1, Y1). The imaging lens system 200 is preferably a telecentric optical system on both the incident side (object side) and exit side (image side) of the pixel beam, and the focal lengths of the element lenses 202 and 204 are f1 and f2, respectively. Yes.

  In FIG. 5, 220A, 220B, and 220C are pixel beams that are modulated by the micromirrors 62A, 62B, and 62C, respectively, and 222A, 222B, and 222C are pixel beams that have passed through the imaging lens system 200, 224A, and 220C, respectively. 224B and 224C are real images of the micromirrors 62A, 62B, and 62C formed by the imaging lens system 200, respectively.

  FIG. 5 shows only two element lenses 202 and 204 arranged at both ends of the imaging lens system 200 in the optical axis direction. In order to form an image with sufficiently high resolution, it is generally composed of a plurality of element lenses such as 5 to 15 elements, or a plurality of element lenses including an aspheric lens that is difficult to manufacture. is there.

  In the imaging lens system 200, each micromirror 62 (only three micromirrors 62A, 62B, and 62C are shown in FIG. 5) constituting the DMD 50 is placed on the incident surface of the first microlens array 206. Form an image. That is, the reflecting surfaces of the micromirrors 62A, 62B, and 62C and the incident surface of the first microlens array 206 on which these real images 224A, 224B, and 224C are formed are in a conjugate relationship with each other with respect to the imaging lens system 200. ing.

  In FIG. 5, the pixel beams 220A, 220B, and 220C modulated in the exposure state by the micromirrors 62A, 62B, and 62C in the DMD 50 are indicated by solid lines, and the conjugate relationship with respect to the imaging lens system 200 is indicated by a broken line. For simplification of explanation, FIG. 5 shows only three micromirrors 62A, 62B, and 62C, but the exposure head 166 has all (for example, 800 × 600, 1024 × 256) in the DMD 50. The required effective area is selected from the light reflecting surface constituted by the micromirrors 62), and the laser beams are respectively modulated by a large number (for example, 200 × 600) of micromirrors 62 included in the effective area.

  The first microlens array 206 is provided with a plurality of microlenses 208, and these microlenses 208 are formed with real images 224A, 224B, and 224C of the light incident surfaces of the micromirrors 62A, 62B, and 62C. Are arranged so as to coincide with the surface (X2, Y2). Each microlens 208 of the first microlens array 206 has a one-to-one correspondence with the plurality of micromirrors 62 arranged in the effective area of the DMD 50. That is, for example, when the laser beam is modulated using the 800 × 600 micromirror 62 in the DMD 50, 800 × 600 microlenses 208 correspond to the micromirrors 62 in the first microlens array 206. Are arranged two-dimensionally.

  Here, the focal length of the microlens 208 of the first microlens array 206 is f3, and 226A, 226B, and 226C are pixel beams (Fraunhofer) converged by the microlens 208 of the first microlens array 206. (Diffraction images) are shown respectively.

  In other words, the laser beam modulated by the DMD 50 is normally emitted as substantially collimated pixel beams 220A, 220B, and 220C, and passes through the imaging lens system 200 to be substantially collimated pixel beams 222A, 222B, and 222C. The light enters each microlens 208 of the lens array 206. These pixel beams 222A, 222B, and 222C are converged by the microlens 208 of the first microlens array 206, respectively, and form a Fraunhofer diffraction image on the focal plane (X3, Y3) of the first microlens array 206.

  As shown in FIG. 5, the aperture array 210 is disposed on the focal plane (X3, Y3) of the first microlens array 206. Apertures 212 are two-dimensionally arranged in the aperture array 210 so as to correspond to the microlenses 208 of the first microlens array 206 on a one-to-one basis. These apertures 212 have a size and a shape that substantially transmits only the 0th-order diffraction image of the Fraunhofer diffraction image formed by each microlens 208 of the first microlens array 206. Thereby, noise components included in the diffraction image formed by the first microlens array 206, for example, scattering components included in the laser beam that illuminates the DMD 50, scattering components generated from the DMD 50, or crosses generated by diffraction from the DMD 50. Talk components and the like are blocked.

  The pixel beam that has passed through the aperture array 210 and from which noise components have been removed is imaged by the microlenses 216 of the second microlens array 214 to form exposure spots 228A, 228B, and 228C on the exposure surface 56. At this time, since a certain space (working distance) is ensured between the second microlens array 214 and the exposure surface 56, the photosensitive material arranged on the exposure surface 56 is exposed to the high-resolution exposure spots 228A, 228A, Exposure can be performed using 228B and 228C. Further, since the focal lengths of the microlenses 208 and 216 of the first and second microlens arrays 206 and 214 can be normally set to about 0.1 to 1 mm, the real images 224A and 224A of the micromirrors 62 of the DMD 50 can be obtained. The distance L from the surface on which 224B and 224C are formed to the exposure surface 56 can be 10 mm or less.

  Next, a theoretical description will be given of the resolution obtained by the optical system including the DMD 50, the first microlens array 206, the aperture array 210, and the second microlens array 214 configured as described above.

  FIG. 11A shows the DMD 50 arranged on the conjugate plane (X1, Y1) shown in FIG. However, only a part (5 rows × 5 columns) of micromirrors 62 in the DMD 50 is illustrated here. Typically, in the DMD 50, the micromirrors 62 are arranged in 600 rows × 800 columns. Here, P1 is the pixel period, W1 is the pixel size, and the pixel size W1 is the same size in both the row direction (X1 direction) and the column direction (Y1 direction).

  FIG. 11B shows a real image 224 of each micromirror 62 formed on the conjugate plane (X2, Y2). Here, the imaging magnification a of the imaging lens system 200 is calculated by f2 / f1, the pixel period P2 of the real image 224 is calculated by a · P1, and the pixel size W2 is calculated by a · W1.

  FIG. 11C shows the aperture array 210 arranged on the focal plane (X3, Y3). As described above, Fraunhofer diffraction images of the pixel beams 222A, 222B, and 222C that have entered the microlenses 208 in the first microlens array 206 are formed on the focal plane (X3, Y3). Here, assuming that the effective aperture of each microlens 208 in the first microlens array 206 covers the incident pixel beams 222A, 222B, and 222C, a diffraction image formed on the focal plane (X3, Y3). Can be considered as a diffracted image when a rectangular aperture having the same size as the pixel beams 222A, 222B, and 222C is uniformly illuminated. At this time, the intensity distribution I (X3, Y3) when the origin of the coordinates is set at the center of each pixel has a wavelength of light λ and a focal length of each microlens 208 of the first microlens array 206 as f3. In this case, it is expressed by the following formula (7).

I (X ₃ , Y ₃ ) = C · sinc ² (W 2 · X 3 / λ · f 3) · sinc ² (W 2 · Y 3 / λ · f 3) (7)
However, C is a constant, sinc (ω) = sin (πω) / (πω).

  The intensity distribution I (X3, Y3) has a main maximum at the center (ω = 0) (0th order diffraction image), and becomes 0 at ω = 1, 2, 3,. A sub-maximum appears between ω = 1, 2, 3,..., but the intensity is much lower than that of the main maximum, and a large part of the total energy is included in the zero-order diffraction image.

Further, the coordinates (X3 ₁ , Y3 ₁ ) at which ω = 1 giving the periphery of the 0th-order diffraction image are | X3 ₁ | = | Y3 ₁ | = λ · f3 / W2. Here, an aperture array 210 having a square aperture 212 of s = 2 · | X3 ₁ | = 2 · | Y3 ₁ | = 2λ · f3 / W2 in the X direction and the Y direction is arranged at each pixel position. When only the next diffraction image is transmitted, immediately after transmitting through the aperture array 210, the pixel period is P3 = P2 = a · P1, and the pixel size is W3 = s.

  FIG. 11D shows a real image (pixel beam) 228 of each micromirror 62 formed on the exposure surface (X4, Y4) 56 by the second microlens array 214. Each microlens 216 of the second microlens array 214 forms an actual image on the exposure surface (X4, Y4) 56 by imaging each pixel beam immediately after passing through each aperture 212 of the aperture array 210. At this time, if the imaging magnification is b, the pixel period is P4 = P3 = P2 = a · P1, and the pixel size is W4 = b · s.

(Calculation results based on specific numerical examples)
Next, an example of a resolution calculation result obtained by substituting specific numerical values for the above-described theoretical calculation formula will be described.

In the exposure head 166, the pixel period P1 in the DMD 50 is 13.7 μm, the pixel size W1 is 13.0 μm,
The focal lengths f1 and f2 of the element lenses 202 and 204 of the imaging lens system 200 are 20 mm and 40 mm, respectively.
The wavelength λ of the laser beam emitted from the fiber array light source 66 is 0.4 μm,
The focal length f3 of each microlens 208 of the first microlens array 206 is 0.2 mm,
The dimension of one side of each aperture 212 of the aperture array 210 is s (where s is a theoretical dimension for making the shape of the aperture 212 square and allowing only the 0th-order diffraction image to pass through),
When the imaging magnification b for real image formation by each microlens 216 of the second microlens array 214 is 1, the pixel size W4 and the pixel period P4 on the exposure surface (X4, Y4) 56 are obtained as follows. .

a = f2 / f1 = 40/20 = 2
W1 = 13.0 μm, P1 = 13.7 μm, W2 = 26.0 μm, P2 = 27.4 μm
| X31 | = | Y31 | = λ · f3 / W2 = 0.4 × 0.2 / 26.0 = 3.1 μm
s = 2 · | X3 1 | = 2 · | Y 3 1 | = 6.2 μm
W3 = s = 6.2 μm, P3 = P2 = 27.4 μm
W4 = b · s = 1 × 6.2 = 6.2 μm, P4 = P3 = 27.4 μm.

  That is, the pixel beam size W4 on the exposure surface (X4, Y4) 56 is 6.2 μm, which is sufficiently smaller than the pixel size W1 (= 13.0 μm) of the DMD 50, and the resolution is increased.

(Resolution improvement effect by tilt scanning)
Next, the theoretical improvement effect of the resolution when the row direction of the DMD 50 is inclined by a predetermined angle θ with respect to the scanning direction will be described.

  As shown in FIG. 12, the exposure surface (X4, Y4) 56 in the case where scanning is performed with the row direction of the DMD 50 inclined at an angle θ that is tan θ = 1 / n (n is the number of columns) with respect to the scanning direction. Consider the scanning mode of the pixel beam above.

Here, the angle θ is an angle (0 ° <θ <90 °) formed by the row direction (arrow X direction) of the DMD 50 and the scanning direction with respect to the exposure surface 56 (arrow t direction shown in FIG. 12),
P4 is a pixel period on the exposure surface (X4, Y4) 56,
W4 is the pixel size on the exposure surface (X4, Y4) 56. However, the pixel referred to here is an image formed on the exposure surface (X4, Y4) 56 by exposure of the exposure spot 228 (see FIG. 11D). The pixel period and pixel size of this pixel are the same as the period and size of the exposure spot 228 (see FIG. 11D) imaged on the exposure surface (X4, Y4) 56. The following description will be made assuming that they are equal.

  As shown in FIG. 12, in the exposure head 166 of the present embodiment, n scanning line groups of n pixels included in any one row in the DMD 50 are arranged at an interval of P4 · sin θ. Further, the adjacent interval between the n pixels included in the next adjacent row and the n scanning line group is also P4 · sin θ, and the scanning line having the interval P4 · sin θ is formed as a whole.

At this time, if modulation control is performed so that the exposure pixels are arranged at the same interval as the scanning line interval, the exposure pixel period becomes P4 · sin θ. Applying the numerical example mentioned above to this,
θ = tan-1 (1 / n) = tan-1 (0.2) = 11.3 °
Exposure pixel period = P4 · sin θ = 27.4 × sin 11.3 ° = 5.4 μm
The exposure pixel beam size on the exposure surface (X4, Y4) 56 is W4 = b · s = 1 × 6.2 μm = 6.2 μm. Accordingly, appropriate exposure can be performed with a pixel period of 5.4 μm while performing a slight overlap exposure with a sufficiently small exposure beam of 6.2 μm. That is, the exposure pixel period P4 · sin θ = 5.4 μm of the exposure surface 56 is smaller than the pixel period P1 = 13.7 μm of the DMD 50, and the resolution is increased.
[Modification of micro lens array]
In the exposure head 166 according to the present embodiment described above, spherical lenses are used as the microlens 208 of the microlens array 206 and the microlens 216 of the microlens array 214, respectively. As the microlens, an aspherical lens, specifically, for example, a toric lens can be used. At least one of the microlens arrays 206 and 216 uses a toric lens as the microlens, so that the influence of the distortion of the DMD 50 can be eliminated.

  That is, the micromirror 52 of the DMD 50 may be distorted, and due to the distortion, the light modulated by the micromirror 52 in the on state is a beam whose shape is disordered even if it is focused by the microlens array 206. There is a possibility that the beam cannot be condensed into a sufficiently small beam. If this is the case, there is a concern that the beam diameter may not be sufficiently small on the exposure surface 56, or that light that does not pass through the aperture 210 increases, resulting in a decrease in light utilization efficiency. Therefore, in the exposure head 166 according to the present embodiment, when the above-described problem is particularly concerned, the microlens arrays 206 and 214 including aspherical microlenses (here, toric lenses) are employed. Therefore, the occurrence of such a problem is avoided.

  Of the microlens array 206 and the microlens array 214, the microlens array 214 on the downstream side may be a microlens array in which toric lenses are arranged (hereinafter referred to as “toric lens array”), but the aperture 210. In view of the fact that it is more preferable to shape the beam on the upstream side, it is preferable to use the microlens array 206 as a toric lens array. In this case, since the shape and size of the incident beam to the aperture 210 are improved, there is an advantage that the vignetting of the beam is reduced. Therefore, here, a microlens array arranged upstream of the aperture 210 is a microlens array in which a plurality of toric lenses are two-dimensionally arranged (hereinafter referred to as “microlens array 260”). The case will be described.

  The toric lens array used as the microlens array according to the present embodiment will be described in detail.

  FIG. 14 shows an example of the result of measuring the flatness of the reflecting surface of the micromirror 62 constituting the DMD 50. In the figure, the same height positions of the reflecting surfaces are shown connected by contour lines, and the pitch of the contour lines is 5 nm. Note that the x direction and the y direction shown in the figure are two diagonal directions of the micromirror 62, and the micromirror 62 is configured to rotate around a rotation axis extending in the y direction. FIGS. 15A and 15B show the height position displacement of the reflecting surface of the micromirror 62 along the x direction and the y direction, respectively.

  As shown in FIG. 14 and FIG. 15, there is distortion on the reflection surface of the micro mirror 62, and when attention is paid particularly to the center of the mirror, distortion in one diagonal direction (y direction) It is larger than the distortion in the diagonal direction (x direction). Therefore, there may be a problem that the shape of the laser beam (pixel beam) collected by the spherical microlens 208 (see FIG. 5) of the microlens array 206 is distorted.

  In the exposure head 166 according to the present embodiment, an aspherical lens (toric lens) can be used as the microlens 262 of the microlens array 260 in order to prevent the above-described problem.

  FIGS. 16A and 16B show a front shape and a side shape of a microlens array using a toric lens, respectively. In these drawings, the dimensions of each part of the microlens array 260 are also written, and the unit thereof is mm. Here, it is assumed that the 1024 × 256 rows of micromirrors 62 of the DMD 50 are driven, and the microlens array 260 correspondingly corresponds to the row of 1024 microlenses 262 arranged in the horizontal direction. It is configured in parallel. In FIG. 16A, the arrangement order of the micro lens array 260 is indicated by j in the horizontal direction and k in the vertical direction.

  FIGS. 17A and 17B show a front shape and a side shape of one microlens 262 in the microlens array 260, respectively. In FIG. 17A, contour lines of the microlens 262 are also shown. The end surface of each microlens 262 on the light emission side has an aspherical shape that corrects the aberration caused by the distortion of the reflection surface of the micromirror 62 described above. More specifically, the microlens 262 is a toric lens, the radius of curvature Rx in the direction optically corresponding to the x direction is −0.125 mm, and the radius of curvature Ry in the direction corresponding to the y direction is −0. .1 mm.

  Accordingly, the condensing state of the pixel beam B in the cross section parallel to the x direction and the y direction is roughly as shown in FIGS. 18A and 18B, respectively. That is, comparing the cross section parallel to the x direction and the cross section parallel to the y direction, the radius of curvature of the microlens 262 is smaller and the focal length is shorter in the latter cross section. .

  FIGS. 19A, 19B, 19C, and 19D show the simulation results of the beam diameter in the vicinity of the condensing position (focal position) of the microlens 262 when the microlens 262 has the above shape, respectively. For comparison, the results of similar simulations for the case where the microlenses of the microlens array have a spherical shape with a radius of curvature Rx = Ry = −0.1 mm are shown in FIGS. 20A, 20B, 20C, and 20D. Shown in Note that the value of z in each figure indicates the evaluation position in the focus direction of the microlens by the distance from the beam exit surface of the microlens.

  The surface shape of the microlens 262 used in the simulation is expressed by the following equation (8).

  In the above equation, Cx: curvature in the x direction (= 1 / Rx), Cy: curvature in the y direction (= 1 / Ry), X: distance from the lens optical axis O in the x direction, Y: lens in the y direction This is the distance from the optical axis O.

  As is apparent from a comparison between FIGS. 19A to 19D and FIGS. 20A to 20D, in the exposure head 166 according to the present embodiment, the microlens 262 has a focal length in a cross section parallel to the y direction parallel to the x direction. By using a toric lens smaller than the focal length in the cross section, distortion of the beam shape in the vicinity of the condensing position is suppressed. If so, the photosensitive material 150 can be exposed to a higher-definition image without distortion. It can also be seen that the microlens 262 shown in FIGS. 19A to 19D has a wider region with a smaller beam diameter, that is, a greater depth of focus, than when a spherical lens is used as the microlens.

  In addition, when the magnitude relation of the distortion of the center part in the x direction and the y direction of the micromirror 62 is opposite to the above, the focal length in the cross section parallel to the x direction is in the cross section parallel to the y direction. If the microlens 262 is composed of a toric lens that is smaller than the focal length, similarly, a higher-definition image without distortion can be exposed to the photosensitive material 150.

  In addition, the aperture array 210 disposed in the vicinity of the condensing position of the microlens array 260 is disposed such that only light having passed through the corresponding microlens 262 is incident on each aperture 212. That is, by providing this aperture array 210, it is possible to prevent light from adjacent microlenses 262 not corresponding to each aperture 212 from entering, and to increase the extinction ratio.

  Originally, if the diameter of the aperture 212 of the aperture array 210 installed for the above purpose is reduced to some extent, the effect of suppressing the distortion of the beam shape at the condensing position of the microlens 262 can also be obtained. However, in such a case, the amount of light blocked by the aperture array 210 is increased, and the light use efficiency is reduced. On the other hand, when the microlens 262 has an aspherical shape, the light utilization efficiency is kept high because light is not blocked.

  Here, in the exposure head 166 according to the present embodiment, the case where the microlens 262 of the microlens array 260 is a toric lens having a secondary aspherical shape has been described, but higher order (fourth order, By adopting a sixth-order aspherical lens, the beam shape can be further improved.

  Further, in the microlens array 260 according to the modification, the end surface on the light emitting side of the microlens 262 is an aspheric surface (toric surface), but one of the two light passing end surfaces is a spherical surface and the other is a cylindrical surface. Even if the microlens array is constituted by the microlenses, the same effect as that of the microlens 262 can be obtained.

  Further, in the microlens array 260 according to the modified example, the microlens 262 has an aspherical shape that corrects aberration due to distortion of the reflection surface of the micromirror 62. Instead of adopting such an aspherical shape, The same effect can be obtained even if each microlens 262 constituting the microlens array 260 has a refractive index distribution that corrects aberration due to distortion of the reflection surface of the micromirror 62.

  An example of such a microlens 264 is shown in FIG. FIGS. 4A and 4B show the front and side shapes of the microlens 264, respectively. As shown in the drawing, the outer shape of the microlens 264 is a parallel plate. The x and y directions in the figure are as described above.

  22A and 22B schematically show the condensing state of the pixel beam B in the cross section parallel to the x direction and the y direction by the microlens 264 shown in FIG. The microlens 264 has a refractive index distribution that gradually increases outward from the optical axis O. In the drawing, the broken line shown in the microlens 264 indicates that the refractive index is predetermined from the optical axis O. The position changed with the pitch is shown. As shown in the drawing, when comparing the cross section parallel to the x direction and the cross section parallel to the y direction, the ratio of the refractive index change of the microlens 264 is larger in the latter cross section, and the focal length is larger. It is shorter. Even when a microlens array including such a gradient index lens is used, it is possible to obtain the same effect as when the microlens array 260 according to the modification is used.

  In addition, in the microlens whose surface shape is aspherical like the microlens 262 previously shown in FIGS. 17 and 18, a refractive index distribution as described above is given together, and both by the surface shape and the refractive index distribution. The aberration due to the distortion of the reflection surface of the micromirror 62 may be corrected.

  Further, the microlens 266 shown in FIGS. 23A and 23B may be adopted instead of the microlens 262 shown in FIGS. 17A and 17B. The distribution of the contour lines of the microlens 266 is such that the microlens 262 is rotated around the optical axis in accordance with the change in the distortion direction of the mirror of the DMD 50. That is, in the present embodiment, a microlens can be formed and the mounting direction around the optical axis can be set so that an optimal contour line distribution corresponding to the distortion shape of the DMD 50 can be obtained.

  Here, the case where the microlens array 260 made of an aspherical lens is used as the microlens array disposed on the upstream side of the aperture 210 has been described. However, the microlens array disposed on the upstream side of the aperture 210 is spherical. A microlens array 216 made of lenses may be used, and a microlens array made of aspherical lenses may be used as a microlens array arranged on the downstream side of the aperture 210. In this case, the vignetting of the incident beam due to the aperture 210 may slightly increase, but the beam shape and size on the exposure surface 56 are improved as in the case where the microlens array 260 is arranged on the upstream side of the aperture 210. it can.

In addition, both the two microlens arrays respectively arranged on the upstream side and the downstream side of the aperture 210 are made into microlens arrays composed of aspherical lenses, and the reflection surfaces of the micromirrors 62 are respectively arranged on the upstream side and the downstream side of the aperture 210. You may make it correct | amend the aberration by distortion.
[Modification of exposure head]
Next, an exposure head according to a modification of the embodiment of the present invention will be described.

  FIG. 13 shows a configuration on the light reflection side of the DMD in an exposure head according to a modification of the embodiment of the present invention. The exposure head 250 according to this modification differs from the exposure head 166 shown in FIG. 5 in that the imaging lens system 200 is omitted.

  In the exposure head 250 shown in FIG. 13, the pixel beams 220A, 220B, and 220C from the micromirrors 62A, 62B, and 62C of the DMD 50 are substantially collimated, and these pixel beams 220A, 220B, and 220C are the first micromirrors. The light enters the microlenses 208 of the lens array 206, and Fraunhofer diffraction images 226A, 226B, and 226C are formed at the focal positions of the microlenses 208. These diffraction images 226A, 226B, and 226C pass through an aperture array 210 having an aperture 212 having the same size as that of the zeroth-order diffraction image, so that noise components are removed and each microlens 216 of the second microlens array 214 is removed. Is incident on. Thereby, real images 228A, 228B, and 228C are formed as exposure beam spots on the exposure surface (X4, Y4) 56 as in the case shown in FIG. In this exposure head 250, substantially the same optical characteristics as in the case of using the imaging lens system 200 with the magnification a = 1 in the exposure head 166 shown in FIG. 5 can be obtained.

  The exposure head 250 according to the modified example described above can be suitably used when the distance from the DMD 50 to the exposure surface 56 is short, and the imaging lens system 200 can be omitted as compared with the exposure head 166. As a result, the manufacturing cost can be reduced and the apparatus can be downsized.

In the exposure head 250 according to the modified example, at least one of the two microlens arrays arranged on the upstream side and the downstream side of the aperture array 210 is a microlens array made of an aspheric lens such as a toric lens array, Aberration due to distortion of the reflection surface of the micromirror 62 may be corrected by the microlens array including the aspherical lens.
[Generalization of high resolution conditions]
Next, generalized conditions for obtaining a high resolution when the exposure surface 56 is scanned and exposed using the exposure heads 166 and 250 according to the embodiment of the present invention described above will be described.

(1) Exposure beam size and scanning line interval The exposure beam size W4 is obtained by the following equation (9).

W4 = b · W3 = b · s = b · (2λ · f3 / W2) = b · (2λ · f3 / a · W1) = 2b · λ · f3 / a · W1 (9)
Further, the scanning line interval when scanning and exposing in the direction of angle θ where tan θ = 1 / n with respect to the row direction having n pixels of DMD 50 is obtained by the following equation (10).

P4 · sin θ = a · P1 · sin [tan ⁻¹ (1 / n)] ≈a · P1 · (1 / n) = a · P1 / n (10)
(2) Generalized conditional expression for obtaining high resolution In order to obtain high resolution, it is necessary to satisfy the conditions described in any of the following (a) to (c).

(A) the exposure beam size is equal to or smaller than the pixel size of the original spatial light modulator, ie, W4 ≦ W1,
From the above equation (9), 2b · λ · f3 / a · W1 ≦ W1
Therefore, 2b · λ · f3 ≦ a · W1 ²
(B) The scanning line interval is equal to or smaller than the exposure beam size. That is, P4 · sin θ ≦ W4
From the above equation (10), a · P1 / n ≦ 2b · λ · f3 / a · W1
Therefore, a ² · P1 · W1 / n ≦ 2b · λ · f3
(C) The above conditional expressions (a) and (b) hold simultaneously, that is, a ² · P 1 · W 1 / n ≦ 2b · λ · f 3 ≦ a · W 1 ²
In the exposure head 250 shown in FIG. 13, if a = 1 in the above (a) and (b), generalized conditions for obtaining a high resolution can be obtained.

  In the exposure heads 166 and 250 of this embodiment, only the case where the DMD 50 is used as the spatial light modulation element has been described. However, as such a spatial light modulation element, a laser beam emitted from the optical fiber light source 66 is used. Any device other than the DMD 50 can be used as long as it can be divided into a plurality of pixel beams (light beam groups) having a desired pixel pitch and can selectively modulate these pixel beams into either an exposure state or a non-exposure state. For example, a micro electro mechanical systems (MEMS) type spatial modulation element, an optical element (PLZT element) that modulates transmitted light by an electro-optic effect, a liquid crystal light shutter (LCD), and the like are also applicable. However, an illumination optical system for obtaining a light beam group spatially modulated for each pixel needs to be individually optimized depending on the type of the spatial light modulator.

  In addition, the spatial light modulation element as described above does not necessarily have to be two-dimensionally arranged with pixels such as micromirrors, but has one-dimensionally arranged pixels, that is, n pixels are arranged in rows. It may be arranged linearly along the direction.

  In the exposure heads 166 and 250 according to the present embodiment, the real image of the spatial light modulator formed on the incident surface of the first microlens array 206 is used as an equal-magnification image (magnification a = 1 of the imaging lens system 200). Alternatively, an enlarged image (a> 1) may be used, and the imaging magnification b by each microlens 216 of the second microlens array 214 may be set to a value other than 1.

  In the exposure heads 166 and 250 according to the present embodiment, the microlens arrays 206 and 214 are used. However, the microlens arrays 206 and 214 having the refractive microlenses 208 and 216 are not limited to the microlens arrays 206 and 214. For example, a GRIN (graded index) type microlens array, a diffraction type microlens array such as a hologram, a reflection type micro concave reflection mirror array, and the like are also applicable.

1 is a perspective view showing an appearance of an exposure apparatus to which an exposure head according to an embodiment of the present invention is applied. It is a perspective view which shows the structure of the scanner of the exposure apparatus shown by FIG. (A) is a top view which shows the exposed area | region formed in a photosensitive material, (B) is a figure which shows the arrangement | sequence of the exposure area by each exposure head. 1 is a side view showing a schematic configuration of an exposure head according to an embodiment of the present invention. FIG. 5 is a side view showing a configuration of an optical system arranged on the light reflection side of the DMD in the exposure head shown in FIG. 4. It is the elements on larger scale which show the structure of a digital micromirror device (DMD). (A) And (B) is explanatory drawing for demonstrating operation | movement of DMD. (A) And (B) is a top view which compares and shows the arrangement | positioning of an exposure beam, and a scanning line by the case where it does not arrange | position inclined DMD and the case where it arranges inclined. (A) is a perspective view which shows the structure of a fiber array light source, (B) is the elements on larger scale of (A), (C) and (D) is a top view which shows the arrangement | sequence of the light emission point in a laser emission part. It is. It is a side view which shows the structure of a combined laser beam source. 6 is a plan view showing the relationship between the size and pitch of the exposure beam in the planes (X1, Y1), (X2, Y2) (X3, Y3) and (X4, Y4) shown in FIG. It is a top view for demonstrating the improvement effect of the resolution in the exposure surface (X4, Y4) at the time of inclining DMD with respect to the scanning direction. It is a side view which shows the structure of the optical system arrange | positioned at the light reflection side of DMD in the exposure head which concerns on the modification of embodiment of this invention. It is the top view which showed the result of having measured the flatness of the reflective surface of the micromirror which comprises DMD by the contour line. It is a graph which shows the height position displacement of the reflective surface in the micromirror shown by FIG. It is the front view and side view which show the structure of the micro lens array using a toric lens. It is the front view and side view which show the structure of the toric lens in the micro lens array shown by FIG. It is a side view which shows the condensing state of the pixel beam by the toric lens shown by FIG. It is a graph which shows the simulation result of the beam diameter in the vicinity of a condensing position at the time of using a toric lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to an evaluation position is 0.18 mm. ing. It is a graph which shows the simulation result of the beam diameter in the vicinity of a condensing position at the time of using a toric lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to the evaluation position is 0.2 mm. ing. It is a graph which shows the simulation result of the beam diameter near the condensing position at the time of using a toric lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to the evaluation position is 0.22 mm. ing. It is a graph which shows the simulation result of the beam diameter in the vicinity of a condensing position at the time of using a toric lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to an evaluation position is 0.24 mm. ing. It is a graph which shows the simulation result of the beam diameter near the condensing position at the time of using a spherical lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to an evaluation position is 0.18 mm. ing. It is a graph which shows the simulation result of the beam diameter in the vicinity of a condensing position at the time of using a spherical lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to the evaluation position is 0.2 mm. ing. It is a graph which shows the simulation result of the beam diameter in the vicinity of a condensing position at the time of using a spherical lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to an evaluation position is 0.22 mm. ing. It is a graph which shows the simulation result of the beam diameter in the vicinity of a condensing position at the time of using a spherical lens as a micro lens of a micro lens array, and shows the case where the distance from the beam emission surface of a micro lens to an evaluation position is 0.24 mm. ing. It is the front view and side view which show the structure of the micro lens at the time of giving refractive index distribution to the micro lens of a micro lens array. It is a side view which shows the condensing state of the pixel beam by the micro lens shown by FIG. It is the front view and side view of a toric lens from which the distribution of a contour line differs from the toric lens shown by FIG.

Explanation of symbols

50 DMD (Spatial Light Modulator)
53 Beam spot 56 Exposure surface 62 Micro mirror 66 Optical fiber light source 166 Exposure head 200 Imaging lens system 206 First micro lens array (first micro focusing element array)
208 micro lens (first micro focusing element)
210 Aperture array 212 Aperture 214 Second microlens array (second microfocusing element array)
216 micro lens (second micro convergence element)
250 exposure head 260 micro lens array 262 micro lens (toric lens)
H.264 Micro Lens (Aspherical Lens)

Claims (8)

Exposure for two-dimensional exposure of an exposure surface by a bundle of light beams arranged along a row direction intersecting the scanning direction while moving relative to the exposure surface along the scanning direction. Head,
A plurality of pixel portions whose light modulation states change according to a control signal are arranged one-dimensionally or two-dimensionally, and a light beam incident from a light source portion is divided into a plurality of pixel beams by the plurality of pixel portions. And a spatial light modulation element that selectively modulates the plurality of pixel beams to either the exposure state or the non-exposure state,
A first micro-focusing element array in which a plurality of first micro-focusing elements are arranged so as to correspond to a plurality of pixel portions in the spatial light modulation element;
A Fraunhofer diffraction image of the pixel beam modulated into the exposure state is disposed in the vicinity of a rear focal plane of the first microfocusing element formed by the first microfocusing element, and the plurality of first A plurality of apertures are arranged so as to correspond to the microfocusing elements of the aperture array, and the aperture array that transmits only the main part of the Fraunhofer diffraction image by the apertures,
A plurality of second micro-focusing elements are arranged so as to correspond to the plurality of apertures, and a real image of a pixel beam respectively transmitted through the plurality of apertures is formed on the exposure surface by the plurality of second micro-focusing elements. A second micro-focusing element array that
An exposure head comprising: An imaging lens system is provided between the spatial light modulation element and the micro focusing element array,
The spatial light modulation element and the spatial light modulation element and the pixel beam exit surface of the pixel unit and the incident surface of the pixel beam of the first micro focussing element are in a conjugate relationship with respect to the imaging lens system. 2. The exposure head according to claim 1, further comprising a first micro-focusing element array.   3. The exposure head according to claim 1, wherein the aperture has a size and a shape that substantially transmits only the 0th-order diffraction image of the Fraunhofer diffraction image formed by the first microfocusing element. . The aperture has a size and shape that substantially transmits only the 0th-order diffraction image of the Fraunhofer diffraction image formed by the first micro-focusing element;
The pixel period of the plurality of pixel portions in the spatial light modulator is P1, the pixel size is W1, the number of pixels of the pixel portions arranged along the row direction substantially orthogonal to the scanning direction is n,
The focal length of the first microfocusing element is f3,
An optical magnification at which the second micro-focusing element forms an actual image of the pixel beam transmitted through the aperture on the exposure surface; b,
When the wavelength of the light beam emitted from the light source unit is λ,
The angle formed by the row direction and the scanning direction is tan ^-1 (1 / n), and any one of the following formulas (1) to (3) is satisfied. Exposure head.
2b ・ λ ・ f3 ≦ W12 (1)
P1 · W1 / n ≦ 2b · λ · f3 (2)
P1 · W1 / n ≦ 2b · λ · f3 ≦ W12 (3) The aperture has a size and a shape that substantially transmits only the 0th-order diffraction image of the Fraunhofer diffraction image emitted from the micro-focusing element;
The pixel period of the plurality of pixel portions in the spatial light modulator is P1, the pixel size is W1, the number of pixels of the pixel portions arranged along the row direction substantially orthogonal to the scanning direction is n,
The focal length of the first microfocusing element is f3,
An optical magnification at which the second micro-focusing element forms an actual image of the pixel beam transmitted through the aperture on the exposure surface; b,
A magnification at which the imaging lens system forms a real image on an emission surface of the pixel beam in the pixel unit on an incident surface of the pixel beam in the first micro-converging element array;
When the wavelength of the light beam emitted from the light source unit is λ,
The angle formed by the row direction and the scanning direction is tan ^-1 (1 / n), and satisfies any one of the following expressions (4) to (6): Exposure head.
2b · λ · f3 ≦ a · W12 (4)
a 2 · P 1 · W 1 / n ≦ 2b · λ · f 3 (5)
a 2 · P 1 · W 1 / n ≦ 2b · λ · f 3 ≦ a 2 · W 12 (6)   6. The exposure head according to claim 1, wherein at least one of the first micro focus element and the second micro focus element is an aspheric lens.   7. The exposure head according to claim 6, wherein the first micro focusing element is an aspheric lens.   8. The exposure head according to claim 7, wherein the aspheric lens is a toric lens.