JP2007033973A - Exposure head and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain substantially deep focal depth without using a complicated configuration while keeping high resolution in an exposure head and an exposure apparatus. <P>SOLUTION: The exposure head is equipped with a spatial optical modulator such as DMD 50 having a large number of arrayed pixels each modulating irradiating light according to control signals, and is relatively moved with respect to a photosensitive material 150 to perform multiple exposure on one position of the photosensitive material 150 to beams from a plurality of pixels, wherein a microlens array 55 having arrayed microlenses 56 condensing beams from the respective pixels of the spatial optical modulator is disposed on the optical path between the spatial optical modulator and the photosensitive material 150. The microlenses 56A to 56D used for multiple exposure at one position have different focal lengths from others. The exposure apparatus is equipped with the exposure head and a stage 152 to relatively move the exposure head with respect to the photosensitive material 150. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure head and an exposure apparatus, and in particular, an exposure head that includes a spatial light modulation element that modulates light according to a control signal, moves relative to the photosensitive material, and exposes the photosensitive material; The present invention relates to an exposure apparatus provided with the exposure head.

  Conventionally, various exposure heads for exposing a photosensitive material using light modulated by a spatial light modulator based on image data, and exposure apparatuses for forming an image pattern on the photosensitive material by scanning the exposure head are known. It has been. The spatial light modulation element is formed by arranging a large number of pixel units for modulating irradiated light according to control signals, and one example thereof is a DMD (digital micromirror device). The DMD is a mirror device in which a large number of micromirrors that change the angle of a reflecting surface according to a control signal are two-dimensionally arranged on a semiconductor substrate such as silicon.

In Patent Document 1 and Patent Document 2, DMD is used as a spatial light modulation element, and the light path modulated by the spatial light modulation element corresponds to each pixel part of the spatial light modulation element. An exposure apparatus having a configuration in which a microlens array in which microlenses that collect light are arranged in an array is arranged is described. Furthermore, in Patent Document 2, the DMD is arranged to be inclined with respect to the scanning direction, and exposure (multiple exposure) is performed on one scanning line so as to reduce image unevenness and the scanning line at the time of scanning. A technique for improving the resolution by narrowing the interval is described.
JP 2003-337425 A Japanese Patent Laid-Open No. 2004-9595

By the way, in an exposure apparatus using a microlens array as described above, light modulated by DMD is formed into dots by a microlens of the microlens array, and the light is projected onto a photosensitive material for exposure. The resolution R at this time depends on the NA (numerical aperture) of the microlens and is expressed by the following equation (1).
R = k1 × λ / NA (1)
Here, k1: constant, λ: wavelength, NA = n × sin θ, n: refractive index θ: an angle formula extending from the image point to the radius of the exit pupil (1), the lens shape is controlled. In order to improve the resolution, it is necessary to increase the NA. On the other hand, the focal depth Z is expressed by the following equation (2).
Z = k2 × λ / NA ² (2)
As can be seen from equation (2), the greater the NA, the shallower the focal depth.

  From the above, when the exposure wavelength is constant, increasing the NA to improve the resolution decreases the depth of focus. If the depth of focus is shallow, the amount of blur on the exposure surface caused by a slight positional shift in the optical axis direction of light incident on the photosensitive material increases, and the sharpness of the pattern formed on the photosensitive material deteriorates. . In particular, in the case of a substrate having a thick photosensitive layer, the problem of the positional deviation becomes large. Although the above problem can be solved by adding an autofocus mechanism, a substrate detection mechanism, a control mechanism, and the like are separately required, resulting in new problems such as a complicated structure and increased cost.

  The present invention has been made in view of the above circumstances, and provides an exposure head having a substantially deep depth of focus and a exposure apparatus including the exposure head without using a complicated configuration while maintaining high resolution. The purpose is to do.

  An exposure head according to the present invention includes a spatial light modulation element in which a large number of pixel portions for modulating irradiated light according to a control signal are arranged in parallel, and moves relative to the photosensitive material so that the same photosensitive material is used. In an exposure head that performs multiple exposure with light from a plurality of the pixel units, the light from each pixel unit of the spatial light modulator is condensed on an optical path between the spatial light modulator and the photosensitive material. A microlens array in which microlenses are arranged in an array is disposed, and at least two of the microlenses used for multiple exposure at the same position have different focal lengths. .

  Among the microlenses used for the multiple exposure at the same position, the focal lengths of at least three microlenses are different, and the difference in focal length between the microlenses having short focal lengths becomes smaller as the focal length of the microlenses is shorter. You may set so that.

  Alternatively, the focal lengths of at least three microlenses among the microlenses used for the multiple exposure at the same position are different, and the difference in focal length between the microlenses having short focal lengths is long. You may set so that it may become so small.

  Here, the different focal lengths mean that the other is not in focus when one is in focus, and is close to the optical axis direction so that the other is in focus when one is out of focus. To do.

  The exposure apparatus of the present invention comprises the exposure head and moving means for moving the exposure head relative to the photosensitive material.

  In the exposure head of the present invention, the same position is subjected to multiple exposure with light passing through a plurality of microlenses having different focal lengths, and these lights are focused on the point to be exposed and aligned in the optical axis direction. Both of which the focus position is slightly shifted are included. On the other hand, the optical power density is high at the focusing position of each microlens, and the optical power density decreases as the distance from the focusing position increases. If the exposure amount is set so that the photosensitive material is exposed and patterned at a high light power density at the in-focus position, the pattern is formed only by the light focused on the point to be exposed and is not in focus. Patterns are not formed by light. Therefore, even if the NA of the microlens is increased to improve the resolution and the depth of focus of each microlens becomes shallow, as a result, exposure with a high resolution and a substantially deep depth of focus becomes possible.

  In order to obtain lenses having different focal lengths, for example, in the case of a refractive lens, it is sufficient to simply form the lenses with different curvatures, which can be easily realized. Thereby, in the present invention, a substantially deep depth of focus can be obtained by a simple method.

  When the microlens is composed of the simplest plano-convex spherical lens and the aperture diameter is constant, the focal depth becomes shallower as the lens has a shorter focal length. On the other hand, in order to always focus on an arbitrary position in the thickness direction of the photosensitive agent, the arbitrary position needs to fall within the range of the focal depth of any microlens. That is, the entire range in the thickness direction needs to be covered by the range of the focal depth of any microlens. Therefore, when the focal lengths of at least three microlenses among the microlenses used for multiple exposure at the same position are different, the focal length difference between the microlenses having short focal lengths is short. If it is set so as to be smaller, the entire range in the thickness direction can be efficiently covered with the range of the focal depth of any microlens.

  On the other hand, the amount of exposure light absorbed by the photosensitive material increases as the photosensitive material becomes deeper. Therefore, if the difference in focal length between microlenses with close focal lengths is set to be smaller as the focal length of the microlenses is longer, it is possible to compensate for a reduction in light amount due to absorption of the photosensitive material.

  Hereinafter, an exposure head and an exposure apparatus according to an embodiment of the present invention will be described with reference to the drawings. The exposure head and the exposure apparatus of this embodiment perform multiple exposure using light passing through microlenses having different focal lengths. First, the overall configuration of the exposure apparatus of this embodiment will be described. FIG. 1 is a perspective view showing a schematic configuration of the exposure apparatus of the present embodiment.

  As shown in FIG. 1, the exposure apparatus 100 according to the present embodiment includes a stage 152 as a flat plate-like moving unit that holds and holds a photosensitive material 150 on the surface. Two guides 158 extending along the stage moving direction are installed on the upper surface of the thick plate-like installation table 156 supported by the four legs 154. The stage 152 is arranged so that the longitudinal direction thereof faces the stage moving direction, and is supported by a guide 158 so as to be reciprocally movable. This exposure apparatus is provided with a stage driving device (not shown) that drives a stage 152 as sub-scanning means along a guide 158.

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

  As shown in FIGS. 2 and 3B, the scanner 162 includes a plurality of (e.g., eight) exposure heads 166 arranged in an approximately matrix of m rows and n columns (e.g., 2 rows and 4 columns). . In the following description, when individual exposure heads arranged in the m-th row and the n-th column are shown, they are expressed as an exposure head 166 mn.

  As shown in FIG. 2, the exposure area 168 that is an area exposed by the exposure head 166 has a rectangular shape with a short side along the sub-scanning direction, and is inclined at a predetermined inclination angle θ with respect to the sub-scanning direction. ing. As the stage 152 moves, a strip-shaped exposed area 170 is formed for each exposure head 166 in the photosensitive material 150. As shown in FIGS. 1 and 2, the sub-scanning direction is opposite to the stage moving direction. In the following, when an exposure area by individual exposure heads arranged in the m-th row and the n-th column is shown, it is expressed as an exposure area 168 mn.

Further, as shown in FIGS. 3A and 3B, the exposure heads in the respective rows arranged in a line so that each of the strip-shaped exposed areas 170 partially overlaps the adjacent exposed areas 170. Each of 166 is arranged at a predetermined interval 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.}

  As shown in FIGS. 4 and 5, each exposure head 166 is a digital micromirror device (hereinafter, DMD) as a spatial light modulation element that modulates an incident light beam for each pixel unit according to image data. 50). 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 region to be controlled by the DMD 50 for each exposure head 166 based on the input image data. The mirror drive control unit controls the angle of the reflection surface of each micromirror of the DMD 50 for each exposure head 166 based on the control signal generated by the image data processing unit. The control of the angle of the reflecting surface will be described later.

  On the light incident side of the DMD 50, a fiber array light source 66 including a laser emitting portion 68 in which the emitting end portion (light emitting point) of the optical fiber is arranged in a line along a direction corresponding to the long side direction of the exposure area 168, A lens system 67 for correcting the laser light emitted from the fiber array light source 66 and condensing it on the DMD, and a mirror 69 for reflecting the laser light transmitted through the lens system 67 toward the DMD 50 are arranged in this order. In FIG. 4, the lens system 67 is schematically shown.

  As shown in detail in FIG. 5, the lens system 67 condenses the condensing lens 71 that condenses the laser light B as illumination light emitted from the fiber array light source 66, and is inserted into the optical path of the light that has passed through the condensing lens 71. The rod-shaped optical integrator 72 (hereinafter referred to as a rod integrator) 72 and a collimator lens 74 disposed on the light exit side of the rod integrator 72. The condensing lens 71, the rod integrator 72, and the collimator lens 74 cause the laser light emitted from the fiber array light source 66 to enter the DMD 50 as a light beam that is close to parallel light and has a uniform beam cross-sectional intensity.

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

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

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

  FIG. 7 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. Further, a light absorber (not shown) is arranged in the direction in which the laser beam B reflected by the off-state micromirror 62 travels.

  Here, the DMD 50 is assumed to be composed of K block regions each having L rows × M columns of micromirrors 62. FIG. 8 shows an exposure area 168 that is a two-dimensional image obtained by one DMD 50 and the block area in the exposure area 168. In FIG. 8, for the sake of simplicity, the number of matrices is reduced, L = 4, M = 16, K = 4, and four block areas are indicated as A, B, C, and D. .

As shown in FIG. 8, the DMD 50 is disposed so that the exposure area 168 is inclined at an inclination angle θ of θ = ± tan ⁻¹ (k / L) with respect to the sub-scanning direction. Here, k is a natural number relatively prime to L, or a number equal to L. By tilting the exposure area 168 in this manner, the pitch of the scanning trajectory (scanning line) of the exposure beam by each micromirror 62 becomes narrower than the pitch of the scanning line when the exposure area 168 is not tilted, thereby improving the resolution. be able to.

Further, by setting the inclination angle θ of the exposure area 168 to ± tan ⁻¹ (k / L) with respect to the sub-scanning direction, the light reflected by the plurality of micromirrors 62 is scanned on the same scanning line. For example, focusing on the scanning line L1 in FIG. 8, a total of four reflected light images (exposure beams) indicated by black circles in FIG. 8 are scanned on the scanning line L1. That is, as the exposure head 166 moves relative to the photosensitive material 150 (sub-scanning), the same position on the photosensitive material 150 is subjected to multiple exposure with the light reflected by the plurality of micromirrors 62.

  As shown in FIGS. 4 and 5, an imaging optical system 51 that images the laser beam B reflected by the DMD 50 onto the photosensitive material 150 is disposed on the light reflecting side of the DMD 50. Although this imaging optical system 51 is schematically shown in FIG. 4, as shown in detail in FIG. 5, an optical system comprising lens systems 52 and 54 and a microlens through which light transmitted through this optical system is incident An array 55 and an aperture array 59 are included.

  The optical system including the lens systems 52 and 54 enlarges an image formed by the DMD 50 and forms an image on the microlens array 55. The microlens array 55 corresponds to each pixel portion of the DMD 50, and is formed by two-dimensionally arranging a large number of microlenses 56 that collect the light from each pixel portion. Each microlens 56 is arranged in the vicinity of the imaging position of the micromirror 62 by the lens systems 52 and 54 at a position where the laser beam B from the corresponding micromirror 62 is incident. The aperture array 59 is formed by forming a large number of apertures (openings) corresponding to the microlenses 56 of the microlens array 55. In the figure, the photosensitive material 150 is sub-scanned in the direction of arrow F.

  As shown in FIG. 9, the microlens array 55 is divided into four block areas corresponding to the block areas A, B, C, and D of the DMD, and the focal length of the microlens is different for each block area. Hereinafter, the microlenses arranged in the block areas A, B, C, and D are referred to as microlenses 56A, 56B, 56C, and 56D, respectively. In FIG. 9, the number of matrices is shown smaller than the actual number for simplification.

  As schematically shown in FIGS. 10 and 11, the focal lengths of the microlenses 56A, 56B, 56C, and 56D increase in this order, and the range extends from the upper surface to the lower surface of the photosensitive layer 150a of the photosensitive material 150. The difference is almost equally spaced. FIG. 11 is a diagram showing the four types of microlenses 56A, 56B, 56C, and 56D in an overlapping manner.

  Similar to the tilt of the DMD 50 described above, the lens arrangement direction of the microlens array 55 also has a tilt angle θ with respect to the sub-scanning direction. Similarly to the multiple exposure of the micro mirror 62 of the DMD 50 described above, in the micro lens array 55, as indicated by the black circles in FIG. 9, the scanning lines L1 are arranged in the block areas A, B, C, and D. The microlenses 56A, 56B, 56C, and 56D are scanned one by one, and the same position on the photosensitive material 150 is subjected to multiple exposure with light from the microlenses 56A, 56B, 56C, and 56D having different focal lengths.

  The optical power density is high at the in-focus position of each microlens, and the optical power density decreases as the distance from the in-focus position increases. Therefore, if the exposure amount is set so that the photosensitive material is exposed and patterned at the light power density at the in-focus position, the pattern is formed and focused only by the microlens focused on the point to be exposed. Patterns are not formed by the microlenses that are not.

  If the number of exposures of multiple exposure is large, the integrated amount of exposure using only the microlenses that are not in focus exceeds the photosensitive threshold for patterning when the photosensitive material is exposed to light, which may degrade the resolution. Sex occurs. In such a case, at the point to be exposed, the integrated amount of exposure using only the unfocused microlens does not exceed the photosensitive threshold, and the exposure using the focused microlens and the unfocused microlens are not performed. The exposure amount is set so that the integrated amount with the exposure by means exceeds the photosensitive threshold. Thereby, a result similar to the above is obtained.

  From the above, even if the NA of the microlens is increased to improve the resolution and the depth of focus of each microlens becomes shallow, the multiple exposure with the lenses having different focal lengths as described above results in the resolution being reduced. High exposure enables a substantially deep focal depth.

  Next, an example of a design method and a manufacturing method of microlenses having different focal lengths as described above will be described. If a plano-convex spherical lens that is easy to manufacture is employed as the microlens, its focal length f is simply determined by the refractive index n and the curvature radius r, and is f = r / (n−1). For example, assuming that the material used is quartz glass having a refractive index of about 1.46 and a plano-convex spherical lens having a focal length of 100 μm, the radius of curvature is 46 μm. Further, assuming that the exposure wavelength is 405 nm, NA = 0.26, and the constant k2 = 0.2 determined by the resist and the development process, the depth of focus is about 1.2 μm.

Therefore, based on the lens having the curvature radius of 46 μm, lenses having slightly different curvature radii, for example, lenses having curvature radii of 44, 45, and 47 are assumed. Table 1 shows the results of calculating the focal length and the focal depth with these lenses having the same diameter aperture.

In order to produce such a lens, a known gray scale gradation pattern on a quartz glass substrate is controlled for each block region to produce a lens shape having a different curvature, or a resist pattern for each block region. Using a method of changing the size and performing heat reflow, a lens shape made of resist is formed. Thereafter, ICP (Inductively coupled plasma) dry etching is performed with a fluorine-based mixed gas such as CF ₄ , C ₂ F ₆ , or CHF ₃ , and transferred to quartz glass. At this time, by controlling the bias, the substrate temperature, and the mixing ratio of the etching gas, the selection ratio of the resist and the quartz glass can be adjusted to obtain the shape of the curvature radius.

  In the above-described embodiment, the change in the focal length is approximately equal. However, the present invention is not limited to this, and it is desirable that the focal length is appropriately set according to various conditions such as the type of photosensitive material and the exposure process. . When the focal lengths of at least three microlenses among the microlenses used for the multiple exposure at the same position are different, the value may be set by paying attention to the difference in focal length.

In the plano-convex spherical lens as described above, if the aperture diameter is constant, the shorter the focal length, the shallower the focal depth. Focusing on this point, the difference in focal length between microlenses with close focal lengths becomes smaller as the focal length of the microlenses is shorter so that the thickness direction of the photosensitive material is covered with the focal depth of the plurality of microlenses. You may set as follows. That is, a plurality of microlenses having different focal lengths are numbered in order of increasing focal length, and the focal length of the i-th (i = 1, 2, 3,...) Microlens having the short focal length is fi. To satisfy. FIG. 12 is a diagram schematically showing such four microlenses 56A ′ to 56D ′.
fi + 1−fi <fi + 2−fi + 1

Or conversely, paying attention to the fact that the deeper the photosensitive material, the more the amount of exposure light absorbed by the photosensitive material, the difference in the focal length between microlenses with close focal lengths, so as to compensate for the decrease in light quantity due to this absorption, You may set so that it may become so small that the focal distance of a micro lens is long. That is, numbers are assigned in order from the shortest focal length, and the focal length of the i-th (i = 1, 2, 3,...) Microlens with the shortest focal length is fi, so that the following equation is satisfied. FIG. 13 is a diagram schematically showing such four microlenses 56A ″ to 56D ″ in an overlapping manner.
fi + 1-fi> fi + 2-fi + 1
As described above, by appropriately selecting the configuration of the microlens, it is possible to cope with various resists and various exposure processes.

  The microlens to be used is not limited to the plano-convex spherical lens as described above, but may be a lens having another shape, and an aspherical lens, a gradient index lens, a diffractive optical element, or the like may be employed.

  In the above-described embodiment, the microlens array is divided into four block areas. However, the number of divisions of the block areas is not limited to this, and may be two or more according to the target patterning process. It is desirable to set the number of divisions. In the present embodiment, the focal length is different for each block region. However, when the number of block regions is large, there may be a plurality of block regions made of microlenses having the same focal length.

  Furthermore, the microlens array does not necessarily have to be divided into block-shaped block areas, and it is only necessary to configure the microlenses used for multiple exposure at the same position so that at least two focal lengths are different, and various arrangements are possible. It is. For example, microlenses having different focal lengths may be alternately arranged along the path of the scanning line, or four types of lenses a, b, c, d having different focal lengths as shown in FIG. A houndstooth arrangement may be used so that microlenses having the same focal length are arranged in an oblique direction. In the case where the outer diameters of the respective lenses are different, such as when lenses having the same NA and different focal lengths are configured, it is desirable to arrange them in consideration of these outer diameter sizes. Especially for microlenses formed by thermal reflow by changing the resist pattern size, a staggered lattice arrangement in which a large outer diameter lens and a small outer diameter lens are arranged adjacent to each other is effective to avoid contact between adjacent lenses. It is.

  Furthermore, instead of the imaging optical system 51 of the above-described embodiment, an imaging optical system in which an optical system including lens systems 57 and 58 for the purpose of magnification conversion or the like is inserted between the microlens 55 and the photosensitive material 150. The present invention can also be applied to the exposure head shown in FIG.

  In the above example, the exposure head provided with the DMD as the spatial light modulation element has been described. However, in addition to the reflective spatial light modulation element, a transmissive spatial light modulation element (LCD) can also be used. For example, a liquid crystal shutter such as a MEMS (Micro Electro Mechanical Systems) type spatial light modulator (SLM), an optical element (PLZT element) that modulates transmitted light by an electro-optic effect, or a liquid crystal light shutter (FLC). It is also possible to use a spatial light modulation element other than the MEMS type, such as an array. Note that MEMS is a general term for a micro system that integrates micro-sized sensors, actuators, and control circuits based on a micro-machining technology based on an IC manufacturing process, and a MEMS type spatial light modulator is an electrostatic force. It means a spatial light modulation element driven by an electromechanical operation using Further, a plurality of GLVs (GratingLightValves) arranged in a two-dimensional shape can be used. In the configuration using these reflective spatial light modulator (GLV) and transmissive spatial light modulator (LCD), a lamp or the like can be used as a light source in addition to the laser described above.

The perspective view which shows the exposure apparatus concerning one Embodiment of this invention 1 is a perspective view showing the configuration of a scanner of the exposure apparatus in FIG. (A) is a plan view showing an exposed area formed on a photosensitive material, and (B) is a view showing an arrangement of exposure areas by each exposure head. 1 is a perspective view showing a schematic configuration of an exposure head of the exposure apparatus of FIG. Sectional drawing which shows the structure of the exposure head of FIG. Partial enlarged view showing the configuration of a digital micromirror device (DMD) (A) And (B) is explanatory drawing for demonstrating operation | movement of DMD. Diagram showing exposure area by DMD Diagram showing the configuration of the microlens array Sectional view showing microlenses with different focal lengths Figure with the microlenses in Figure 10 superimposed Diagram of another example of microlenses with different focal lengths Diagram of another example of microlenses with different focal lengths The figure which shows another example of arrangement of micro lenses with different focal lengths Sectional drawing which shows the structure of another exposure head which can apply this invention

Explanation of symbols

50 Digital Micromirror Device (DMD)
51 Image forming optical system 52, 54 Lens system 55 Micro lens array 56, 56A, 56B, 56C, 56D Micro lens 59 Aperture array 62 Micro mirror 66 Fiber array light source 67 Lens system 68 Laser emitting unit 71 Condensing lens 72 Rod integrator 100 Exposure device 150 Photosensitive material 152 Stage 162 Scanner 164 Sensor 166 Exposure head 168 Exposure area 170 Exposed area A, B, C, D Block area

Claims (4)

A plurality of pixel units each including a spatial light modulation element in which a large number of pixel units for modulating irradiated light according to a control signal are arranged in parallel, and moving relative to the photosensitive material so that the same position of the photosensitive material is located; In the exposure head that performs multiple exposure with light from
In the optical path between the spatial light modulation element and the photosensitive material, a microlens array is arranged in which microlenses that collect light from each pixel portion of the spatial light modulation element are arranged in an array,
An exposure head characterized in that focal lengths of at least two microlenses among the microlenses used for the multiple exposure at the same position are different.   Among the microlenses used for the multiple exposure at the same position, the focal lengths of at least three microlenses are different, and the difference in focal length between the microlenses having short focal lengths becomes smaller as the focal length of the microlenses is shorter. 2. The exposure head according to claim 1, wherein the exposure head is set to be   Among the microlenses used for the multiple exposure at the same position, the focal lengths of at least three microlenses are different, and the difference in focal length between the microlenses having short focal lengths is smaller as the focal length of the microlenses is longer. 2. The exposure head according to claim 1, wherein the exposure head is set to be The exposure head according to any one of claims 1 to 3,
An exposure apparatus comprising: moving means for moving the exposure head relative to the photosensitive material.

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