JP2009020306A - Spatial light modulator and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new spatial light modulator, emitting an incident light with appropriate spatial modulation. <P>SOLUTION: The spatial light modulator 3 comprises a base part 31 formed of a material having a refractive index changed by electric field and an end surface through which light enters the inside. A plurality of electrodes 33 that is a group of electrode elements respectively arranged in an alignment direction vertical to the advancing direction is formed on the base part 31 zigzag in two lines, and by giving a voltage between electrode elements of each electrode 33, a periodic change of refractive index in the alignment direction is caused at a site within the base part 31 in the vicinity of the electrode 33 to diffract the light passing through the site. By similarly controlling each electrode 33 of one line and each electrode 33 of the other line adjacent in a predetermined direction to this electrode 33, the alignment directional width of an emitting area of refracted light on a plane conjugate with the spatial light modulator 3 is increased, compared with the case using only one electrode, and emission of the incident light with appropriate spatial modulation is achieved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spatial light modulator that spatially modulates incident light, and an image recording apparatus that records an image on a recording material by irradiating the recording material with light.

Conventionally, a method of performing light modulation using a material whose refractive index changes by an electric field such as lithium niobate (LiNbO ₃ ) is known. For example, Patent Document 1 discloses an optical modulator in which a plurality of electrode elements are arranged in one direction on the main surface of a thick plate-like electro-optic substrate. In this optical modulator, electrodes adjacent to each other are disclosed. By applying a voltage between the elements to generate an electric field inside the substrate, it is possible to diffract the light traveling inside the electro-optic substrate.
JP 2000-313141 A

  By the way, a spatial light modulator (that is, a multi-channel light modulator) is constructed by arranging a plurality of electrodes, each of which is a set of electrode elements arranged in a predetermined arrangement direction, on the electro-optic substrate in the arrangement direction. In this case, for example, in a plurality of electrodes, a voltage is applied to every other electrode in the arrangement direction, and a light diffracted by the action of the electrodes is applied to a spatial light modulator while no voltage is applied to the remaining electrodes. When irradiating on a predetermined optically conjugate exposure surface, the light irradiation area on the exposure surface (a region where the amount of light exceeds a certain amount, and if the exposure surface is a photosensitive surface, it exceeds the amount of light necessary for light exposure) The width in the direction corresponding to the arrangement direction of the region) becomes smaller than the width of the gap between the irradiation regions adjacent to each other. Therefore, even when trying to record, for example, a checkered pattern image using such a spatial light modulator, the image cannot be recorded with high accuracy.

  On the other hand, depending on the design of the spatial light modulator, in a plurality of electrodes arranged in the arrangement direction, a gap (that is, a gap larger than a gap between electrode elements included in the electrodes) is provided between adjacent electrodes. Sometimes. In this case, due to the influence of the gap, the pitch in the direction corresponding to the arrangement direction of the plurality of irradiation areas on the exposure surface becomes large, and image recording using such a spatial light modulator has a high recording resolution. The image cannot be recorded.

  Therefore, increase the width (in the direction corresponding to the arrangement direction) of the irradiation area on the plane conjugate with the spatial light modulator, or reduce the arrangement pitch of the irradiation area on the plane conjugate with the spatial light modulator. Therefore, a new spatial light modulator capable of achieving the above is required.

  The present invention has been made in view of the above problems, and has as its main object to provide a novel spatial light modulator that appropriately spatially modulates incident light and emits it, and a recording material using the spatial light modulator. The aim is also to properly record images on top.

  The invention according to claim 1 is a spatial light modulator, which is a plate-like member made of a material whose refractive index changes by an electric field, and transmits light incident on the inside from one end face. A base portion that leads to another end surface opposite to the end surface; and a plurality of electrodes each of which is a set of electrode elements arranged in an arrangement direction perpendicular to the light traveling direction on the main surface of the base portion. By arranging a voltage between the electrode elements included in each electrode, a periodic change in refractive index in the arrangement direction is caused in the base portion in the vicinity of each electrode. And a modulator that diffracts the light that is generated in the part and passes through the part.

  The invention according to claim 2 is the spatial light modulator according to claim 1, wherein in each of the plurality of electrodes, each electrode included in one column and each of the electrodes included in the other column The one adjacent to the electrode in the predetermined direction is similarly controlled as one modulation unit.

  A third aspect of the present invention is the spatial light modulator according to the second aspect, wherein the light is multiple-reflected on both principal surfaces of the base portion.

  According to a fourth aspect of the present invention, in the spatial light modulator according to the third aspect, the thickness of the base portion is 50 micrometers or less.

  The invention according to claim 5 is the spatial light modulator according to claim 3 or 4, wherein each of the plurality of electrodes is formed on each of the main surfaces with the base portion interposed therebetween. A set of element pairs.

  The invention according to claim 6 is the spatial light modulator according to claim 1, wherein in the plurality of electrodes, electrodes included in one row are arranged with a gap in the arrangement direction, and the other The electrodes included in the row are arranged with a gap in the arrangement direction.

  A seventh aspect of the present invention is the spatial light modulator according to the sixth aspect, wherein the light is multiple-reflected on both principal surfaces of the base portion.

  The invention according to claim 8 is the spatial light modulator according to claim 7, wherein the thickness of the base portion is 50 micrometers or less.

  The invention according to claim 9 is the spatial light modulator according to claim 7 or 8, wherein each of the plurality of electrodes is formed on each of the main surfaces with the base portion interposed therebetween. A set of element pairs.

  A tenth aspect of the present invention is an image recording apparatus for recording an image on the recording material by irradiating the recording material with light, wherein the light source section and the light from the light source section are incident thereon. 9. The spatial light modulator according to claim 9, an optical system that guides one of zero-order light and (± 1) -order diffracted light from the spatial light modulator onto a recording material, and the space on the recording material A scanning mechanism that moves the irradiation position of light from the light modulator relative to the recording material in a scanning direction perpendicular to a direction corresponding to the arrangement direction in the spatial light modulator; and A controller that controls the spatial light modulator in synchronization with the relative movement with respect to the recording material.

  The invention described in claim 11 is an image recording apparatus for recording an image on the recording material by irradiating the recording material with light, wherein the light source unit and the light from the light source unit are incident thereon. 5. The spatial light modulator according to claim 5, an optical system that guides one of zero-order light and (± 1) -order diffracted light from the spatial light modulator onto a recording material, and the space on the recording material A scanning mechanism that moves the irradiation position of light from the light modulator relative to the recording material in a scanning direction perpendicular to a direction corresponding to the arrangement direction in the spatial light modulator; and A controller that controls the spatial light modulator in synchronization with the relative movement with respect to the recording material, and records each of the plurality of modulation units arranged in the arrangement direction in the spatial light modulator independently on the recording material. When ON state to be performed Wherein the area to be recorded on the recording material as a unit recording area, a plurality of unit recording area corresponding to the plurality of modulation units are arranged in succession in the direction corresponding to the arrangement direction.

  The invention according to claim 12 is an image recording apparatus for recording an image on the recording material by irradiating the recording material with light, wherein the light source and the light from the light source enter. 9. The spatial light modulator according to claim 9, an optical system that guides one of zero-order light and (± 1) -order diffracted light from the spatial light modulator onto a recording material, and the space on the recording material A scanning mechanism that moves the irradiation position of light from the light modulator relative to the recording material in a scanning direction perpendicular to a direction corresponding to the arrangement direction in the spatial light modulator; and A control unit that controls the spatial light modulator in synchronization with the relative movement with respect to the recording material, and sets each of the plurality of electrodes of the spatial light modulator to an ON state in which recording is performed on the recording material alone. When recorded on the recording material The frequency as a unit recording area, a plurality of unit recording area corresponding to the plurality of electrodes are arranged in succession in the direction corresponding to the arrangement direction.

  A thirteenth aspect of the present invention is the image recording apparatus according to the eleventh or twelfth aspect, wherein widths of the plurality of unit recording areas in a direction corresponding to the arrangement direction are equal.

  The invention according to claim 14 is the image recording apparatus according to any one of claims 10 to 13, wherein the optical system is a reduction optical system.

  According to the first to ninth aspects of the invention, in the spatial light modulator, appropriately spatially modulated light can be emitted by using the electrodes arranged in a staggered pattern.

  Further, in the inventions according to claims 2 to 5, the combination of two electrodes in two rows is used as a unit of modulation control, so that compared to the case where only one electrode is used, the surface is conjugate with the spatial light modulator. And the width of the direction corresponding to the arrangement direction of the irradiation region when guiding the diffracted light can be increased, and in the inventions of claims 3 and 7, the length of the electrode in the light traveling direction is shortened, or The voltage applied to the electrode can be lowered.

  In the inventions of claims 5 and 9, the length of the electrodes in the light traveling direction can be further shortened, or the voltage applied to the electrodes can be further lowered. When a gap is provided between electrodes adjacent to each other in the direction, a plurality of electrodes are arranged in two rows in a staggered manner, so that the surface is conjugated with the spatial light modulator as compared with the case where the electrodes are arranged in one row. The arrangement pitch of the plurality of irradiation regions respectively corresponding to the plurality of electrodes can be reduced.

  According to the tenth to fourteenth aspects of the present invention, in the image recording apparatus using the spatial light modulator utilizing the electro-optic effect, an image can be appropriately recorded on the recording material.

  In the invention of claim 11, an image can be recorded on the recording material with high accuracy using the modulation unit as a unit of modulation control. In the invention of claim 12, an image is recorded on the recording material with high recording resolution. In the invention of claim 14, an image can be recorded with higher accuracy.

  FIG. 1 is a diagram showing a configuration of an image recording apparatus 1 according to the first embodiment of the present invention. The image recording apparatus 1 has an optical head 2 that emits drawing light along the Z direction in FIG. 1 (direction parallel to the optical axis J1 of the optical head 2), and a recording material 9 on which an image is recorded on the outer surface. A holding drum 70 that is a holding unit to hold, and a control unit 4 that performs overall control of the image recording apparatus 1 are provided. The recording material 9 is irradiated with drawing light from the optical head 2 while being scanned, whereby an image is recorded (that is, an image is drawn by light irradiation). As the recording material 9, for example, a photosensitive material such as a printing plate and a plate forming film is used. A photosensitive drum for plateless printing may be used as the holding drum 70. In this case, the recording material 9 corresponds to the surface of the photosensitive drum, and the holding drum 70 is regarded as holding the recording material 9 integrally. be able to.

  The holding drum 70 is rotated by the motor 81 about the central axis of the cylindrical surface, so that the optical head 2 is relative to the recording material 9 in the main scanning direction (that is, the direction perpendicular to the rotation axis of the holding drum 70). Move at a constant speed. The optical head 2 can be moved by a motor 82 and a ball screw 83 in a sub-scanning direction parallel to the rotation axis of the holding drum 70 (that is, the X direction in FIG. 1 perpendicular to the main scanning direction). Is detected by the encoder 84. Thus, the main scanning mechanism including the motor 81 moves the irradiation position of the light from the optical head 2 on the recording material 9 relative to the recording material 9 at a constant speed in the main scanning direction. The irradiation position on the recording material 9 is relatively moved in the sub-scanning direction intersecting the main scanning direction by the sub-scanning mechanism including the 82 and the ball screw 83.

  2 and 3 are diagrams showing the internal configuration of the optical head 2 in a simplified manner. 2 shows the optical head 2 upward (that is, the Y direction perpendicular to the Z direction and the X direction in FIG. 1) along the optical axis J1 and the sub-scanning direction of the optical head 2 in FIG. FIG. 3 shows the internal configuration of the optical head 2 when viewed from the (+ Y) side in FIG. 1, and FIG. 3 shows the optical head 2 side viewed from the side opposite to the motor 82 in FIG. 1 along the sub-scanning direction. 2 shows the internal configuration of the optical head 2 (when viewed from the (−X) side of the optical head 2 toward the (+ X) direction).

  The optical head 2 shown in FIGS. 2 and 3 is a semiconductor laser that emits a light beam having a predetermined wavelength (a semiconductor laser array in which a plurality of semiconductor lasers are arranged, or another type of light emitting element such as a lamp). And a multi-channel spatial light modulator 3 on which a light beam from the light source unit 21 is incident. The spatial light modulator 3 includes a base portion 31 that is a plate-like member formed of a material whose refractive index changes by an electric field, and a modulation portion 32 that modulates light incident into the base portion 31. The modulation unit 32 includes a plurality of electrodes that are a set of electrode elements arranged on the main surface 311 on the (+ Y) side of the base unit 31 in the arrangement direction (X direction in FIGS. 2 and 3) perpendicular to the optical axis J1. 33 (however, each electrode 33 is shown as one rectangle in FIG. 2), and the plurality of electrodes 33 are arranged in two rows in a staggered manner in the arrangement direction. In the following description, of the two columns of the electrodes 33 arranged in the arrangement direction, the (−Z) side column is referred to as a first electrode column, the (+ Z) side column is referred to as a second electrode column, and FIG. In FIG. 3, reference numerals 321 and 322 are assigned to the first and second electrode rows, respectively.

In the present embodiment, base portion 31 is formed of a single crystal of lithium niobate (LiNbO ₃ ) (that is, lithium niobate, abbreviated as LN). The base portion 31 is a single crystal of lithium tantalate (LiTaO ₃ ) (that is, lithium tantalate, abbreviated as LT), etc. It may be formed of the material.

  FIG. 4 is a plan view showing the spatial light modulator 3, and FIG. 5 is a cross-sectional view of the spatial light modulator 3. 5 shows a cross section of the spatial light modulator 3 at the position of the arrow AA in FIG. 4 (that is, the position of the first electrode row 321), and the lower stage of FIG. 5 shows the arrow B- in FIG. A cross section of the spatial light modulator 3 at the position B (that is, the position of the second electrode row 322) is shown. In the upper and lower stages of FIG. 5, illustration of parallel oblique lines in the cross section of the base portion 31 is omitted.

  4 and 5, in each of the first electrode row 321 and the second electrode row 322, the plurality of electrode elements 331 and 332 included in the plurality of electrodes 33 have a constant pitch in the X direction. The electrode element 331 (see FIG. 4) connected to the potential applying unit 41 included in the control unit 4 of FIG. 2 and the electrode element 332 connected to the ground unit 34 for applying a ground potential are Alternatingly arranged in the X direction. In the spatial light modulator 3, six electrode elements 331 and 332 (that is, three electrode elements 331 and three electrode elements 332) that are continuous in the arrangement direction are used as one electrode 33. It is possible to apply a potential to each electrode 33 individually. In FIG. 5, electrode elements 331 and 332 included in one electrode 33 are surrounded by a two-dot chain line rectangle (the same applies to FIG. 13 described later).

  In the present embodiment, the number of electrodes 33 in the first electrode row 321 and the number of electrodes 33 in the second electrode row 322 are the same, and as shown in the upper and lower stages of FIG. One electrode 33 (most (−X)) of the first electrode row 321 is located at the center between the centers of the two adjacent electrodes 33 (that is, the center between the electrode elements 331 and 332 adjacent to each other in the two electrodes 33). (Excluding the electrode 33 on the side) (that is, the center between the electrode elements 331 and 332 at both ends of the electrode 33), and each electrode 33 of the first electrode array 321 is in the second electrode array in the X direction. Each of the corresponding two electrodes 33 of 322 partially overlaps.

  As shown in FIG. 4, each electrode element 331, 332 has a long shape in the Z direction (light traveling direction) (for example, a length of 10 millimeters (mm)) and is adjacent to each other in the X direction. The distance between the elements 331 and 332 (center-to-center distance) is 5 to 20 micrometers (μm), and the width of the gap between the electrode elements 331 and 332 adjacent to each other is almost the same as the width of each electrode element 331 and 332. It is said. Further, the (+ Z) side end portion of the electrode element 331 included in the first electrode row 321 and the (−Z) side end portion of the electrode element 331 included in the second electrode row 322 are arranged in the Z direction. The distance is preferably 50 μm or more (10 mm or less). In FIG. 4, the scale is different between the X direction and the Z direction (the same applies to FIG. 10 described later). Of course, the size and arrangement pitch of the electrode elements 331 and 332 may be appropriately changed according to the design of the spatial light modulator.

  When a predetermined potential is applied from the potential applying section 41 to the plurality of electrode elements 331 of each electrode 33 in FIG. 5, an electric field is formed in the base section 31 from each electrode element 331 to the adjacent electrode element 332. Is done. The base portion 31 formed of lithium niobate has a refractive index greatly changed by an electric field in the Y direction (that is, the direction corresponding to the electro-optic coefficient r33) perpendicular to the arrangement direction (X direction) of the electrode elements 331 and 332. A voltage (potential difference) is applied between the electrode elements 331 and 332 included in each electrode 33, and the upper part of FIG. By generating an electric field in the Y direction as indicated by an arrow labeled E1 in the lower stage, a periodic refractive index change in the arrangement direction causes the vicinity of the main surface 311 in the base portion 31 in the vicinity of the electrode 33. It occurs at the site.

  The light source unit 21 shown in FIGS. 2 and 3 has a collimator lens (not shown), and the light beam emitted from the semiconductor laser is converted into parallel light through the collimator lens and enters the cylindrical lens 221. The light that has passed through the cylindrical lens 221 changes from a circular beam cross section perpendicular to the optical axis J1 to an ellipse that is long in the X direction. That is, the cylindrical lens 221 has a negative power only in the X direction, and the width of the light beam cross section of the light passing through the cylindrical lens 221 is (almost) constant with respect to the optical axis J1 and the Y direction perpendicular to the X direction. .

  The light from the cylindrical lens 221 is incident on the cylindrical lens 222 having a positive power only in the X direction, and the light that has passed through the cylindrical lens 222 is formed into an elliptical shape having a constant cross-section with a long beam cross section in the X direction. The light enters the lens 223. The cylindrical lens 223 has a positive power only in the Y direction. When attention is paid only to the Y direction, the light passing through the cylindrical lens 223 shown in FIG. 3 is condensed and the base portion of the spatial light modulator 3 is collected. 31 enters the (−Z) side end face (hereinafter referred to as “incident face”) 313. Regarding the X direction, the light from the cylindrical lens 223 shown in FIG. 2 enters the spatial light modulator 3 in a parallel state. Thus, in the optical head 2, the illumination optical system 22 is constructed by the cylindrical lenses 221 to 223.

  Here, in the spatial light modulator 3 of FIG. 3, in the base portion 31, the angle formed by the incident surface 313 and the end surface (hereinafter referred to as “output surface”) 314 opposite to the incident surface 313 and the main surface 311. Is set to an acute angle so that light incident from the incident surface 313 along the optical axis J1 parallel to the main surface 311 is guided to the output surface 314 while being reflected only once by the main surface 311. Emitting along a direction parallel to the surface 311 (that is, matching the incident optical axis and the outgoing optical axis) is realized. At this time, in each electrode 33 of the spatial light modulator 3 in FIG. 2, the electrode element 331 is not applied with the potential from the potential applying unit 41 (that is, the electrode element 331 is set to the ground potential). Then, the light passing through the portion in the base portion 31 near the electrode 33 travels inside the base portion 31 while being in a parallel state with respect to the X direction. In a state where the potential from the potential applying unit 41 is applied to the electrode element 331, a periodic refractive index change occurs in the arrangement direction in the arrangement direction due to the electro-optic effect, and in this case, in the base unit 31 In this case, a periodic phase difference is generated in the light passing through the portion in the vicinity of the electrode 33 and diffraction occurs (that is, the spatial light modulator 3 functions as a phase diffraction grating). As described above, each electrode 33 of the spatial light modulator 3 is emitted from the emission surface 314 as zero-order light in which the light passing through the portion in the base portion 31 in the vicinity of the electrode 33 is parallel to the X direction. And a state of being emitted from the emission surface 314 as (± 1) order diffracted light (of course, higher order diffracted light is also emitted) away from the optical axis J1 in the X direction as it travels along the optical axis J1. Transition between is possible.

  The zero-order light or (± 1) -order diffracted light emitted from the emission surface 314 while passing through each electrode 33 of the spatial light modulator 3 in FIG. 3 and diverges in the Y direction is indicated by a thin solid line in FIG. As shown in the outline, the cylindrical lens 231 having a positive power only in the Y direction makes the light substantially parallel to the Y direction and enters the lens 232 having a positive power. Here, the front focal point of the lens 232 is the base near the center between the (+ Z) side end of the electrode 33 of the first electrode row 321 and the (+ Z) side end of the electrode 33 of the second electrode row 322. A small shielding plate 233 is disposed at the rear focal point of the lens 232. Therefore, the 0th order light that is substantially parallel to both the X direction and the Y direction is condensed and shielded on the shielding plate 233 via the lens 232. Further, the (± 1) -order diffracted light enters a position away from the optical axis J1 of the lens 232 shown in FIG. 2, and enters the lens 234 along a path that does not overlap the shielding plate 233 (0th order). The path of light and (± 1) -order diffracted light will be described later.) The lens 234 is arranged so that the front focal point is located in the vicinity of the shielding plate 233 and the rear focal point is on the recording material 9 of the holding drum 70, and (± 1) -order diffracted light is exposed through the lens 234. The recording material 9 which is a surface is irradiated. Thus, in the optical head 2, the projection optical system 23 (which can also be regarded as a Schlieren optical system) is constructed by the cylindrical lens 231, the shielding plate 233, and the lenses 232 and 234.

  FIG. 6 is a diagram for explaining a light path between the spatial light modulator 3 and the recording material 9. In FIG. 6, the cylindrical lens 231 is not shown. As shown in FIG. 6, the lens 232 is actually sufficiently larger than the spatial light modulator 3, and any electrode 33 of the spatial light modulator 3 (in FIG. 6, each electrode 33 is replaced by one line segment). Light (0th-order light or (± 1) th-order diffracted light) also enters the lens 232. For example, in a state where no voltage is applied to all the electrodes 33 in the first electrode row 321, the 0th order light from the vicinity of the most (−X) side or the most (+ X) side electrode 33 in the second electrode row 322 is The lens 232 guides and shields the lens 232 along a path K2 indicated by a thin solid line in FIG. In addition, the (± 1) -order diffracted light is incident on a position away from the optical axis J1 of the lens 232 along a path K3 indicated by a thin broken line in FIG. 6, and enters the lens 234 without being blocked by the shielding plate 233. To reach. The optical system constructed by the lenses 232 and 234 is bilateral telecentric, and the (± 1) -order diffracted light is guided to a position where the zero-order light is guided onto the recording material 9 if the shielding plate 233 is omitted. It is burned.

  In FIG. 6, the principal ray of the 0th order light when the shielding plate 233 is omitted is indicated by a two-dot chain line denoted by reference numeral M <b> 1, and the principal ray M <b> 1 is perpendicular to the recording material 9. In the present embodiment, a reduction optical system is constructed by the lenses 232 and 234, and on the recording material 9, there are a plurality of positions to which light from the vicinity of the plurality of electrodes 33 of the second electrode row 322 is guided, respectively. They are arranged in the X direction perpendicular to the main scanning direction (that is, the direction corresponding to the arrangement direction of the electrodes 33) at a pitch smaller than the arrangement pitch of the electrodes 33 in the second electrode row 322.

  In the optical head 2, in the electrodes 33 included in the first electrode row 321, as in the second electrode row 322, a plurality of positions on the recording material 9 to which light from the vicinity of the plurality of electrodes 33 is guided are the first position. They are arranged in the sub-scanning direction at a pitch smaller than the arrangement pitch of the electrodes 33 in one electrode row 321. Therefore, on the recording material 9, the position where the light from the vicinity of the electrode 33 of the first electrode array 321 and the position of the light from the vicinity of the electrode 33 of the second electrode array 322 are alternately irradiated in the X direction. line up. At this time, in the vicinity of the recording material 9, the in-focus position of the (± 1) order diffracted light from the vicinity of the electrode 33 included in the first electrode array 321 and the (±) from the vicinity of the electrode 33 included in the second electrode array 322. 1) Although the in-focus position of the next diffracted light is slightly separated in the optical axis J1 direction, the center-to-center distance in the optical axis J1 direction between the first electrode array 321 and the second electrode array 322 in the spatial light modulator 3 is In addition, the difference in focus position in the optical axis J1 direction in the vicinity of the recording material 9 is slightly proportional to the square of the reduction magnification of the projection optical system 23, and therefore between the first electrode row 321 and the second electrode row 322. The difference in the in-focus position hardly affects the quality of an image recorded on the recording material 9 by an image recording operation described later.

For example, when the center distance in the Z direction between the first electrode array 321 and the second electrode array 322 is 20 mm and the reduction magnification of the projection optical system 23 is 1/20, the first electrode array 321 The difference in focus position with respect to the second electrode row 322 is 0.05 mm (= 20 × (1/20) ² ).

  Here, an area where recording is performed on the recording material 9 by the spatially modulated light from the spatial light modulator 3 will be described. FIG. 7 is a diagram for explaining a region where recording is performed on the recording material 9 by the light from the spatial light modulator 3. The uppermost stage and the second stage from the top of FIG. 7 show the electrodes 33 (however, abstractly shown in a rectangle) included in the first electrode row 321 and the second electrode row 322, respectively. The third and fourth stages from the top show the light quantity distribution in the X direction on the recording material 9 of the (± 1) order diffracted light from the vicinity of the electrodes 33 of the first electrode array 321 and the second electrode array 322, respectively. 7 shows the light amount distribution in the X direction on the recording material 9 of the (± 1) -order diffracted light from the vicinity of the electrodes 33 of both the first electrode row 321 and the second electrode row 322 (see below). 9).

  In the electrodes 33 of the first electrode row 321 shown in the uppermost stage of FIG. 7, it is assumed that every other electrode 33 exists in the arrangement direction of the electrodes 33 (in a rectangle with parallel diagonal lines in the uppermost stage of FIG. 7). When a voltage is applied to the electrodes 33) and no voltage is applied to the remaining electrodes 33 (however, it is assumed that no voltage is applied to all the electrodes 33 in the second electrode row 322). The distribution of the amount of light in the direction (X direction) corresponding to the arrangement direction of the light applied to the recording material 9 on the holding drum 70 rotating at the number of rotations (number of rotations per unit time) is from the top of FIG. This is indicated by a line denoted by reference numeral L11 in the third stage. At this time, the portion in the base portion 31 and the surface of the recording material 9 in the vicinity of the (+ Z) side end portion of the electrode 33 of the first electrode row 321 in FIG. A width obtained by multiplying the width of the applied electrodes 33 in the arrangement direction (equal to the arrangement pitch of the electrodes 33 in each electrode row) by the reduction magnification of the projection optical system 23 (hereinafter simply referred to as “width corresponding to the electrodes 33”). ”) In the range (approximately the range of the width). Note that the influence of the reduction magnification of the projection optical system 23 is ignored in the third, fourth, and bottom stages from the top of FIG. 7 (the same applies to FIGS. 9 and 11 described later).

  When the amount of light required for exposure in the recording material 9 (hereinafter referred to as “necessary amount of light”) is R, the width of the region recorded on the recording material 9 by the light from the vicinity of each electrode 33 to which a voltage is applied is W1. Usually, it becomes smaller than the width corresponding to the electrode 33.

  In addition, in the electrodes 33 of the second electrode row 322 shown in the second row from the top in FIG. 7, it is assumed that every other electrode 33 (in the second row from the top in FIG. When a voltage is applied to the electrodes 33 (shown by rectangles with parallel oblique lines) and no voltage is applied to the remaining electrodes 33 (however, no voltage is applied to all the electrodes 33 in the first electrode row 321). The distribution of the quantity of light in the X direction of the light irradiated on the recording material 9 on the holding drum 70 rotating at a predetermined number of revolutions is denoted by reference numeral L12 in the fourth row from the top in FIG. As shown by the attached line. Also in this case, the portion in the base portion 31 in the vicinity of the (+ Z) side end portion of the electrode 33 of the second electrode row 322 in FIG. 2 and the surface of the recording material 9 are regarded as almost conjugate, and the first electrode described above is used. As in the case of the column 321, the width of the region recorded on the recording material 9 by the light from the vicinity of each electrode 33 to which a voltage is applied is W 1, which is smaller than the width corresponding to the electrode 33.

  When the image recording apparatus 1 actually records an image on the recording material 9, each electrode 33 included in the first electrode array 321 of FIG. 2 and the first electrode array included in the second electrode array 322. The electrode 33 adjacent to the electrode 33 of 321 in the (+ X) direction and the (+ Z) direction (that is, in the uppermost stage and the second stage of FIG. 7, each electrode 33 of the first electrode row 321 and the electrode 33 The electrode 33 of the second electrode row 322 adjacent to the lower right of the same is controlled in the same manner as one modulation unit (denoted by reference numeral 330 in FIG. 7). Therefore, in the spatial light modulator 3, the electrodes 33 included in every other modulation unit 330 in the plurality of modulation units 330 arranged in the arrangement direction (X direction) (in the uppermost stage and the second stage in FIG. When a voltage is applied to the electrode 33) indicated by a rectangle with parallel diagonal lines, and no voltage is applied to the electrode 33 included in the remaining modulation unit 330, the light irradiated on the recording material 9 on the holding drum 70 The light quantity distribution in the X direction is indicated by a line denoted by reference numeral L13 at the bottom of FIG.

  The light quantity distribution shown at the bottom of FIG. 7 approximates to the sum of the light quantity distribution shown at the third stage of FIG. 7 and the light quantity distribution shown at the fourth stage of FIG. Actually, in the electrode 33 of the second electrode row 322 to which a voltage is applied, due to the influence of light diffraction by the electrode 33 of the first electrode row 321 of the same modulation unit 330, the (−X) side portion (electrode element) The portion corresponding to the modulation unit 330 to which a voltage is applied in the light amount distribution of the light actually irradiated on the recording material 9 is limited in the light passing through the vicinity, and the central portion in the X direction is substantially flat. It becomes a mountain shape. As a result, the width of the region recorded on the recording material 9 with respect to the modulation unit 330 to which the voltage is applied (that is, the width in the X direction of the portion where the light amount is larger than the necessary light amount R of the recording material 9 in the light amount distribution). ) Is W2 larger than W1.

  In the image recording apparatus 1, when the modulation unit 330 to which a voltage is applied and the modulation unit 330 to which no voltage is applied are alternately repeated in the arrangement direction, the light on the recording material 9 is irradiated by light from the vicinity of the modulation unit 330 to which a voltage is applied. The light quantity of the light beam from the light source unit 21, the voltage applied to each electrode 33, etc., so that the area recorded in the line is aligned in the X direction at a pitch twice the width W2 (see the bottom stage in FIG. 7). Has been adjusted. At this time, an area recorded on the recording material 9 for each modulation unit 330 to which a voltage is applied (each of the modulation units 330 present every other unit) is only the modulation unit 330 in the plurality of modulation units 330. Is the same as an area recorded on the recording material 9 when recording is performed on the recording material 9 alone (that is, an ON state described later). When each of the modulation units 330 is in a state of recording on the recording material 9 alone, an area recorded on the recording material 9 is defined as a unit recording area, and a plurality of unit recordings respectively corresponding to the plurality of modulation units 330 are performed. It can be said that various conditions are set so that the regions are arranged continuously in the X direction (that is, with almost no overlap or gap). In the following description, the electrode 33 (two electrodes 33 included in the modulation unit 330 in this embodiment and one electrode 33 in the second embodiment described later) serving as a unit of modulation control is recorded alone. An area recorded on the recording material 9 when recording is performed on the material 9 is defined as a unit recording area.

  If the reduction magnification of the projection optical system 23 is 1/20, and the distance between the centers of the electrodes 33 adjacent to each other in each of the electrode rows 321 and 322 is 212 μm, W2 at the bottom of FIG. 7 is 10 μm. In this case, an image can be recorded with a recording resolution (number of dots per unit length) of 2400 dpi (dot per inch) in the X direction.

  FIG. 8 is a diagram showing a flow of operations in which the image recording apparatus 1 records an image on the recording material 9. When recording an image, first, emission of light from the light source unit 21 is started (step S11). Subsequently, the holding drum 70 is rotated so that the optical head 2 is recorded at a constant speed in the main scanning direction. The optical head 2 moves in the sub-scanning direction in synchronization with the rotation of the holding drum 70 (step S12). In the control unit 4, the light irradiation position on the recording material 9 (that is, the irradiation position on the assumption that light from the entire spatial light modulator 3 is always guided to the recording material 9) relative to the recording material 9. On / off switching in each modulation unit 330 of the spatial light modulator 3 between an ON state in which light ((± 1) -order diffracted light) is guided to the recording material 9 and an OFF state in which the light is not guided in synchronization with the movement. Control is performed (step S13), and an image is recorded on the recording material 9. In this way, when an image is recorded on the entire recording material 9 while raster-scanning the light irradiation position from the optical head 2, the holding drum 70 is rotated, the optical head 2 is moved in the sub-scanning direction, and The emission of light from the light source unit 21 is stopped (steps S14 and S15), and the operation of recording an image in the image recording apparatus 1 is completed.

  Here, a spatial light modulator of a comparative example in which only the first electrode row 321 is provided on the base portion 31 is assumed, and in the spatial light modulator of the comparative example, one of the electrodes 33 included in the first electrode row 321. When recording is performed on the recording material 9 with only the electrodes 33 that are present every other one being in the ON state and the remaining electrodes 33 are in the OFF state, the light quantity distribution on the recording material 9 in the X direction is the third level from the top in FIG. As shown. In this case, the width in the X direction of the recording area recorded on the recording material 9 by the light from the vicinity of each electrode 33 to which a voltage is applied (the width that becomes W1) is the width of the gap between the adjacent recording areas ( The width becomes G1 at the third level in FIG. Therefore, even if an attempt is made to record a checkered pattern image on the recording material 9 using the spatial light modulator of the comparative example, the image cannot be recorded with high accuracy.

  On the other hand, in the spatial light modulator 3 according to the present embodiment, a plurality of electrodes 33 are formed in two rows in a staggered manner in the arrangement direction on the main surface 311 of the base portion 31, and each of the electrodes included in one row is included. The electrode 33 and the electrode 33 that is included in the other column and whose predetermined end portion overlaps the electrode 33 in the arrangement direction are similarly controlled as one modulation unit 330. In this way, by using the two electrodes 33 included in each of the two columns as a unit of modulation control, a surface conjugate with the spatial light modulator 3 as compared with the case where only one electrode 33 in one column is used. The irradiation area when the (± 1) -order diffracted light is guided upward (that is, an area where the amount of light exceeds a certain amount, and when the exposure surface is a photosensitive surface, the region where the amount of light exceeds the amount necessary for exposure) The width in the direction corresponding to the arrangement direction can be increased. A plurality of unit recording areas respectively corresponding to the plurality of modulation units 330 are continuously arranged with a width equal to the direction corresponding to the arrangement direction, so that the image recording apparatus 1 in FIG. It is possible to accurately record an image on the recording material 9 using 330 as a unit of modulation control.

  Further, in the optical head 2, when the projection optical system 23 constructed by the lenses 232 and 234 is telecentric on both sides, the distance in the optical axis J1 direction between the lens 234 and the recording material 9 slightly varies. However, the magnification of the image on the recording material 9 does not change, and highly accurate image recording is realized. Furthermore, by making the projection optical system 23 a reduction optical system, the influence on the image due to the difference in the focus position between the first electrode array 321 and the second electrode array 322 on the recording material 9 is suppressed. Thus, an image can be recorded on the recording material 9 with higher accuracy.

  In the spatial light modulator 3 of FIG. 5, a plurality of electrode elements 331 and 332 are arranged at a constant pitch in each electrode row 321 and 322 (that is, a plurality of electrodes 33 are arranged without a gap). The plurality of electrodes 33 included in each electrode row 321 and 322 may be arranged with a gap in the X direction (see FIG. 10 described later). FIG. 9 is a diagram for explaining a region where recording is performed on the recording material 9 by the light from the spatial light modulator 3 in which the electrodes 33 are arranged with a gap in each of the electrode rows 321 and 322. It is a figure corresponding to FIG.

  As shown in the uppermost part of FIG. 9, the plurality of electrodes 33 included in the first electrode row 321 are arranged at a constant pitch with a gap in the X direction, and exist every other one in the X direction. When a voltage is applied to the electrode 33 (the electrode 33 indicated by a rectangle with parallel oblique lines in the uppermost stage in FIG. 9) and no voltage is applied to the remaining electrodes 33, the recording material 9 is irradiated. The light quantity distribution in the X direction of light is indicated by a line denoted by reference numeral L21 in the third row from the top in FIG. 9, the plurality of electrodes 33 included in the second electrode row 322 are also arranged at the same pitch as the first electrode row 321 with a gap in the X direction. Temporarily, a voltage is applied to every other electrode 33 in the X direction (the electrode 33 indicated by a rectangle with a parallel diagonal line in the second stage in FIG. 9), and a voltage is applied to the remaining electrodes 33. If not, the light amount distribution in the X direction of the light applied to the recording material 9 is indicated by a line labeled L22 in the fourth row from the top in FIG.

  When an image is actually recorded on the recording material 9 by the image recording apparatus 1, each electrode 33 included in the first electrode array 321, and included in the second electrode array 322 and corresponding to the first electrode array 321. The electrode 33 adjacent to the electrode 33 in the (+ X) direction and the (+ Z) direction (that is, in the uppermost stage and the second stage in FIG. 9, each electrode 33 of the first electrode row 321 and the lower right of the electrode 33 The second electrode row 322 adjacent to the electrode 33) is similarly controlled as one modulation unit 330. Therefore, a voltage is applied to the electrodes 33 included in every other modulation unit 330 among the plurality of modulation units 330 arranged in the arrangement direction in the spatial light modulator 3, and the electrodes 33 included in the remaining modulation units 330 are applied. Assuming that no voltage is applied, the light quantity distribution in the X direction of the light irradiated on the recording material 9 is as shown by the line labeled L23 at the bottom of FIG. The width of the region recorded on the recording material 9 with respect to 330 (that is, the width in the X direction of the portion where the light amount is larger than the necessary light amount R of the recording material 9 in the light amount distribution) is W3.

  In the image recording apparatus 1, as shown in the bottom of FIG. 9, the area recorded on the recording material 9 by the light from the vicinity of the modulation unit 330 to which a voltage is applied is at a pitch twice the width W3. Various conditions are set to line up in the X direction. Thereby, when each of the plurality of modulation units 330 arranged in the arrangement direction is in an ON state in which recording is performed on the recording material 9 alone, an area recorded on the recording material 9 is defined as a unit recording area, and the plurality of modulation units is recorded. A plurality of unit recording areas respectively corresponding to 330 are continuously arranged with the same width in the X direction, and as a result, it is possible to accurately record an image on the recording material 9.

  On the other hand, when the electrodes 33 are arranged with a gap in each electrode row 321, 322, it is also possible to record an image on the recording material 9 with each electrode 33 as a unit of modulation control. FIG. 10 is a plan view showing a spatial light modulator 3a according to the second embodiment of the present invention.

  As shown in FIG. 10, the modulation unit 32a of the spatial light modulator 3a has an arrangement direction (in FIG. 10) that is perpendicular to the light traveling direction (Z direction in FIG. 10) on the main surface 311 of the base unit 31. A plurality of electrodes 33, which are a set of electrode elements 331 and 332 arranged in the (X direction), are arranged in two rows in a staggered manner in the arrangement direction, and each electrode row 321 and 322 has a space between adjacent electrodes 33. A plurality of electrodes 33 (five electrodes 33 in FIG. 10) are arranged in the arrangement direction with a gap (gap larger than the gap between the electrode elements 331 and 332 included in the electrode 33). Further, the first electrode row is located at the center between the centers of the two electrodes 33 adjacent to each other in the second electrode row 322 in the X direction (that is, between the electrode elements 331 and 332 adjacent to each other in the two electrodes 33). The center of one electrode 33 of 321 (excluding the most (−X) side electrode 33) (that is, the center between the electrode elements 331 and 332 at both ends of the electrode 33) is arranged, and the first electrode row 321 Each electrode 33 partially overlaps each corresponding two electrode 33 of the second electrode row 322.

  FIG. 11 is a diagram for explaining a region where recording is performed on the recording material 9 by the light from the spatial light modulator 3a, and corresponds to FIG. The uppermost stage and the second stage from the top in FIG. 11 show the electrodes 33 (however, abstractly shown in a rectangle) included in the first electrode row 321 and the second electrode row 322, respectively. The third row from the top and the bottom row show the light amount distribution in the X direction on the recording material 9 of the (± 1) order diffracted light from the vicinity of the electrodes 33 of the first electrode row 321 and the second electrode row 322, respectively. .

  As described above, the plurality of electrodes 33 included in the first electrode row 321 are arranged at a constant pitch with a gap in the arrangement direction (X direction) (see the uppermost stage in FIG. 11). When a voltage is applied to all the electrodes 33 in the first electrode array 321 (however, no voltage is applied to all the electrodes 33 in the second electrode array 322), the light applied to the recording material 9 The light quantity distribution in the X direction is indicated by a solid line denoted by reference numeral L31 in the third row from the top in FIG. In the image recording apparatus 1, the required light amount of the recording material 9 is R, and the width of the area recorded on the recording material 9 by light from the vicinity of the electrodes 33 of the first electrode array 321 (that is, the light amount distribution indicated by the line L31). The width of the portion of the recording material 9 in which the light amount is larger than the required light amount R in the X direction) is W4, and the distance between the adjacent regions is also W4, so that the light amount of the light beam from the light source unit 21 is also W4. The voltage applied to each electrode 33 is adjusted.

  As shown in the second row from the top in FIG. 11, the plurality of electrodes 33 included in the second electrode row 322 are also arranged at the same pitch as the first electrode row 321 with a gap in the arrangement direction. If a voltage is applied to all the electrodes 33 in the second electrode array 322 (provided that no voltage is applied to all the electrodes 33 in the first electrode array 321), the recording material 9 is irradiated. The light quantity distribution in the X direction of the emitted light is as shown by a broken line with a symbol L32 at the bottom of FIG. Also in this case, in the image recording apparatus 1, the width of the area recorded on the recording material 9 by the light from the vicinity of the electrode 33 of the second electrode row 322 is W4, and the distance between the adjacent areas is also W4. Various conditions are set so that Actually, as shown in the third and bottom stages of FIG. 11, on the recording material 9, the gap between the areas recorded with respect to the electrodes 33 of the first electrode array 321 is made to be a gap of the second electrode array 322. Interpolation is possible in the area recorded with respect to the electrode 33.

  As described above, in the spatial light modulator 3a of FIG. 10, when a gap is provided between the electrodes 33 adjacent to each other in the arrangement direction, the electrodes are arranged in one row by arranging the plurality of electrodes 33 in two rows in a staggered manner. The arrangement pitch of the plurality of irradiation regions respectively corresponding to the plurality of electrodes 33 on the plane conjugate with the spatial light modulator 3a (that is, the pitch in the direction corresponding to the arrangement direction) is reduced as compared with the arrangement in the arrangement. Is possible. Then, in the image recording apparatus 1 having the spatial light modulator 3a, an area recorded on the recording material 9 when each of the plurality of electrodes 33 is turned on to perform recording on the recording material 9 alone is unit-recorded. Various conditions are set so that a plurality of unit recording areas respectively corresponding to the plurality of electrodes 33 are continuously arranged with the same width in the X direction (that is, with almost no overlap and no gap). As a result, it is possible to accurately record an image on the recording material 9 at a high recording resolution in a direction corresponding to the arrangement direction.

  By the way, in the spatial light modulator 3 of FIG. 4 in which a plurality of electrodes 33 are arranged in two rows in a staggered manner without providing a gap between the electrodes 33 adjacent to each other in the arrangement direction, it is assumed that one electrode 33 is modulation-controlled. When recording an image on the recording material 9 as a unit of, for example, two continuous electrodes 33 of the first electrode array 321 are turned on, and the second electrode array 322 existing between these electrodes 33 in the X direction is used. Even if an electrode 33 is turned off and a pattern corresponding to ON / OFF / ON is to be recorded, the two electrodes 33 in the first electrode row 321 are actually turned on, so that 2 Periodic changes in refractive index occur at sites in the base portion 31 corresponding to the entire electrodes 33, and recording is performed on the recording material 9 in a range corresponding to the entire two electrodes 33 in the X direction. It would be carried out. Therefore, in a spatial light modulator in which a plurality of electrodes 33 are arranged in two rows in a staggered manner, when one electrode 33 is used as a unit for modulation control, the electrodes 33 are arranged with a gap in the arrangement direction. It is necessary to

  FIG. 12 is a diagram illustrating a part of another example of the optical head, and corresponds to FIG. 3. FIG. 13 is a cross-sectional view of the spatial light modulator 3b and corresponds to FIG. The optical head 2 of FIG. 12 differs from the optical head 2 of FIGS. 2 and 3 only in the configuration of the spatial light modulator 3b. Other configurations are the same, and are denoted by the same reference numerals.

  In the spatial light modulator 3b shown in FIG. 12, the base portion 31a is a thin plate member formed of lithium niobate. The base part 31a shown in FIG. 13 also has a refractive index that changes greatly due to the electric field in the Y direction in FIG. 13 perpendicular to the arrangement direction (X direction) of the electrode elements 331 and 332, as in the base part 31 in FIG. By applying a voltage (potential difference) between the electrode elements 331 and 332 of each electrode 33, an arrow E2 in FIG. 13 indicates the vicinity of the electrode elements 331 and 332 inside the base portion 31a. As shown, by generating an electric field in the Y direction, a periodic refractive index change occurs in the arrangement direction at a site in the base portion 31a near the electrode 33. In the present embodiment, the thickness of the base portion 31a (the thickness in the Y direction in FIG. 12) is 50 μm, and the range in the Y direction in which the refractive index changes inside the base portion 31a is from the main surface 311. The refractive index is changed by the electric field between the electrode elements 331 and 332 to the vicinity of the main surface 312 on the side opposite to the main surface 311.

  Further, when focusing only on the Y direction, in the optical head 2, the light that has passed through the cylindrical lens 223 shown in FIG. 12 is incident on the (−Z) side incident surface 313 of the base portion 31 a. As for the X direction, the light from the cylindrical lens 223 is incident on the spatial light modulator 3b in a parallel state as in the optical head 2 of FIG. The light incident on the inside of the base portion 31a is reflected along the optical axis J1 while being multiple-reflected by both parallel main surfaces 311 and 312 (main surfaces 311 and 312 whose normals are parallel to the Y direction) of the base portion 31a. And proceed.

  By the way, in the spatial light modulator 3 of FIG. 3, the thickness of the base portion 31 is relatively large (for example, several mm), and the light enters from the incident surface 313 and travels inside the base portion 31 as described above. The incident light is incident on the main surface 311 on which the plurality of electrodes 33 are arranged at a small angle (at a large incident angle), reflected by the main surface 311, and output from the other output surface 314. . In the base portion 31, the depth at which the refractive index changes due to the voltage between the electrode elements 331 and 332 adjacent to each other (depth from the main surface 311) is proportional to the square of the voltage, and the electrode elements 331 and 332 adjacent to each other. The voltage applied between the electrode elements 331 and 332 increases due to prevention of discharge between the electrode elements 331 and 332, difficulty in manufacturing, safety in use, and the like. There is a certain limit to shortening the distance between the elements 331 and 332. Therefore, in the spatial light modulator 3 of FIG. 3, the electrode elements 331 and 332 are elongated in the light traveling direction while light is incident at a small angle with respect to the main surface 311 on which the electrode elements 331 and 332 are formed. The phase difference required for diffracting the light traveling inside the base portion 31 is caused by the change in the refractive index inside the base portion 31 by increasing the distance causing the phase change in the light.

  On the other hand, in the spatial light modulator 3b shown in FIG. 12 and FIG. 13, the light incident on the inside from the incident surface 313 in the base portion 31a is repeatedly totally reflected by both the main surfaces 311 and 312 and both the main surfaces 311. , 312 in the direction of travel. As described above, by using the base portion 31a that is thin enough to allow the incident light to be multiple-reflected by the two main surfaces 311, 312, the electric field is almost entirely in the range in which each electrode 33 is formed in the light traveling direction. As a result, the phase of the light can be changed. In other words, the light is caused to enter the range where the refractive index change occurs in the thickness direction of the base portion 31a a plurality of times, or the light is allowed to stay within this range, and the distance at which the phase change occurs (due to the action of the electric field). By securing a distance (in which the change in the refractive index affects the light), the phase change of the light can be efficiently generated. Thereby, compared with the spatial light modulator 3 of FIG. 3, the length of the electrode elements 331 and 332 in the optical axis J1 direction in each electrode 33 is shortened, or (and) provided between the electrode elements 331 and 332. The voltage can be lowered, and as a result, it is possible to reduce the size and improve the safety of the spatial light modulator. Of course, the thin plate-like base portion 31a may be used for the spatial light modulator 3a in the second embodiment (the same applies to the spatial light modulators of FIGS. 14 to 17 described later).

  In the present embodiment, the voltage applied between the electrode elements 331 and 332 of the electrode 33 at the time of diffraction of incident light can be 60 volts (V) or less (40 V or less depending on various conditions) As a result, the voltage applied between the electrode elements can be lowered and the safety associated with the handling of the spatial light modulator 3b can be reliably improved. In addition, by making the electrode 33 longer in the direction of the optical axis J1, the potential applied to the electrode element 331 can be reduced to 15 V or less (10 V or less depending on various conditions). In this case, the spatial light modulator 3b It is possible to perform modulation at a high speed.

  In the spatial light modulator 3b shown in FIGS. 12 and 13, the electrode elements 331 and 332 are formed on the (+ Y) side main surface 311 of the base portion 31a (of course, they may be formed on the main surface 312). In the spatial light modulator, electrode elements 331 and 332 may be formed on both main surfaces 311 and 312 of the base portion 31a. FIG. 14 is a diagram for explaining another example of the electrode. 14 shows the electrode 33c on the base portion 31a, and is a cross-sectional view corresponding to the upper or lower stage of FIG. Further, the lower part of FIG. 14 is a diagram showing a change in the refractive index inside the base portion 31a caused by the electrode 33c. The vertical axis shows the amount of change in the refractive index, and the horizontal axis shows the position in the X direction. In the upper part of FIG. 14, illustration of parallel oblique lines showing the cross section of the base portion 31a is omitted (the same applies to the upper part of FIG. 15 described later).

  One electrode 33c of the spatial light modulator 3c shown in the upper part of FIG. 14 includes a plurality of electrode elements 331 formed on one main surface 311 of the base portion 31a and connected to the potential applying unit 41, and the other main element 31c. A plurality of electrode elements 332 formed on the surface 312 and connected to the ground part 34. The plurality of electrode elements 332 are respectively disposed at positions facing the plurality of electrode elements 331 across the base portion 31a. In the spatial light modulator 3c having the electrode 33c, the electrode elements 331 and 332 facing each other in the Y direction. A plurality of electrode element pairs are arranged in the X direction. In each electrode element pair, as indicated by an arrow with E3 in the upper part of FIG. 14, an electric field in a direction (Y direction) perpendicular to both the main surfaces 311 and 312 and the light traveling direction (Z direction) is generated. It is formed.

  Thus, in the spatial light modulator 3c, when diffracting the light incident on the inside of the base portion 31a, it is necessary to form an electric field in a direction perpendicular to the traveling direction of the light and both the main surfaces 311 and 312. In some cases, by forming each electrode 33c as a set of electrode element pairs formed on both main surfaces 311 and 312 with the base portion 31a interposed therebetween, as shown in the lower part of FIG. Thus, a periodic refractive index change in the arrangement direction (X direction) of the electrode element pairs can be efficiently generated. As a result, the length of the electrode 33c in the light traveling direction can be further shortened, or the voltage applied to the electrode 33c can be further reduced.

  FIG. 15 is a diagram for explaining still another example of the electrode. The upper part of FIG. 15 shows the electrode 33d on the base part 31a, and is a cross-sectional view corresponding to the upper part or the lower part of FIG. The lower part of FIG. 15 is a diagram showing a change in the refractive index inside the base portion 31a caused by the electrode 33d, where the vertical axis shows the amount of change in the refractive index and the horizontal axis shows the position in the X direction.

  In the electrode 33d of the spatial light modulator 3d shown in the upper part of FIG. 15, the electrode element 331 connected to the potential applying unit 41 and the electrode element 332 connected to the ground unit 34 are provided on each main surface 311, 312. They are alternately arranged at a constant pitch in the X direction. In addition, electrode elements 332 are arranged at positions on the main surface 312 facing each electrode element 331 on the main surface 311, and electrodes are arranged at positions on the main surface 312 facing each electrode element 332 on the main surface 311. An element 331 is arranged, and two electrode elements 331 and 332 facing each other are used as electrode element pairs, and a plurality of electrode element pairs are arranged in the X direction on the electrode 33d. In the plurality of electrode element pairs, as indicated by an arrow with symbol E4 in the upper part of FIG. 15, an electric field directed in the (+ Y) direction and an electric field directed in the (−Y) direction are generated in the X direction inside the base portion 31a. Are alternately formed. Thereby, in the spatial light modulator 3d having the electrode 33d, when diffracting the light incident on the inside of the base portion 31a, an electric field in the direction perpendicular to the traveling direction of the light and both the main surfaces 311 and 312 is formed. When it is necessary to perform this, as shown in the lower part of FIG. 15, the degree (amplitude) of the periodic refractive index change in the arrangement direction of the electrode elements 331 and 332 can be increased inside the base portion 31 a. The length of the electrode 33d in the light traveling direction can be further shortened, or the voltage applied to the electrode 33d can be further reduced.

  As described above, in the spatial light modulators 3b to 3d having the thin plate-like base portion 31a, at least one of the main surfaces 311 and 312 of the base portion 31a is perpendicular to the light traveling direction inside the base portion 31a. There are provided electrodes 33, 33c, 33d in which a plurality of electrode elements 331, 332 are arranged in the arrangement direction, and the electrodes 33, 33c, 33d are adjacent to each other. ), A periodic refractive index change in the arrangement direction is generated in a portion in the base portion 31a in the vicinity of the electrodes 33, 33c, 33d, and light incident on the base portion 31a is applied. Is diffracted.

  FIG. 16 is a diagram showing a configuration of still another example of the spatial light modulator, and FIG. 17 is an exploded view of the spatial light modulator 3e of FIG. The spatial light modulator 3e in FIG. 16 includes an auxiliary substrate 351 in which a plurality of electrode elements 331 are arranged in the X direction on one main surface, and a plurality of electrode elements 332 in the X direction on one main surface. As shown in FIGS. 16 and 17, the plurality of electrode elements 331 of the auxiliary substrate 351 abut on the main surface 311 of the base portion 31a, and the plurality of electrode elements of the auxiliary substrate 352 are provided. The spatial light modulator 3e is configured by sandwiching the base portion 31a between the two auxiliary boards 351 and 352 so that the 332 contacts the main surface 312 of the base portion 31a. In such a spatial light modulator 3e, since it is not necessary to directly form electrode elements on the thin plate-like base portion 31a, it is possible to easily manufacture the spatial light modulator. In addition, when forming an electric field inside the base part 31a using the electrode elements 331 and 332 formed on the auxiliary substrates 351 and 352, the electrode elements 331 and 332, the main surfaces 311 and 312 of the base part 31a, There may be a minute gap between them. Further, by alternately forming the electrode elements 331 and 332 on the auxiliary substrates 351 and 352, the same spatial light modulator 3d as shown in FIG. 15 may be manufactured.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible.

  In the first embodiment, each electrode 33 included in the first electrode row 321 in FIG. 2 and the (+ X) direction with respect to the electrode 33 included in the second electrode row 322 and the first electrode row 321. The electrodes 33 adjacent to each other in the (+ Z) direction are similarly controlled as one modulation unit 330. Depending on the arrangement of the electrodes 33 in the spatial light modulator 3, each electrode 33 in the first electrode row 321 and the corresponding electrode The electrode 33 of the second electrode array 322 adjacent to the (33) in the (−X) direction and the (+ Z) direction may be similarly controlled as one modulation unit 330. That is, in the spatial light modulator 3, among the plurality of electrodes 33 arranged in a staggered pattern in the arrangement direction in the two rows, each of the electrodes 33 included in one column and the one of the electrodes 33 included in the other column. The one adjacent to the electrode 33 in the predetermined direction is similarly controlled as one modulation unit. Thereby, the width in the direction corresponding to the arrangement direction of the irradiation region of the diffracted light on the plane conjugate with the spatial light modulator 3 can be increased as compared with the case where only one electrode 33 is used.

  Although the thickness of the thin plate-like base portion 31a is 50 μm, the light incident from the incident surface 313 is reflected by both the main surfaces 311 and 312 in a direction parallel to both the main surfaces 311 and 312. If guiding, the base portion 31a can be changed to various thicknesses. However, in a general spatial light modulator, the depth at which the refractive index changes inside the base portion is 30 to 50 μm, and therefore the refractive index is almost entirely inside the base portion 31a in the Y direction. In order to cause the change, the thickness of the base portion 31a is preferably 50 μm or less. Further, from the viewpoint of ensuring a certain strength of the base portion 31a during the manufacture of the spatial light modulator, it is preferable that the thickness of the base portion 31a be 3 μm or more.

  In the image recording apparatus 1, only the (± 1) -order diffracted light from the spatial light modulators 3, 3 a to 3 e is guided onto the recording material 9 by the projection optical system 23, but depending on the design of the image recording apparatus, spatial light The (± 1) order diffracted light from the modulators 3, 3a to 3e may be shielded, and the 0th order light may be guided onto the recording material. That is, one of the zero-order light and the (± 1) -order diffracted light from the spatial light modulators 3, 3 a to 3 e to which the light from the light source unit 21 is incident is guided onto the recording material 9 by the projection optical system 23. In the image recording apparatus, it is possible to record an image by modulation control of the spatial light modulators 3, 3a to 3e.

  The image recording apparatus provided with the spatial light modulators 3, 3a to 3e uses a scanning mechanism that moves the optical head relative to the plate-like recording material placed on the stage along the recording material. The spatial light modulators 3, 3 a to 3 e are moved relative to the recording material in the scanning direction perpendicular to the direction corresponding to the arrangement direction with the irradiation positions of the light from the spatial light modulators 3, 3 a to 3 e on the material. 3e may be controlled to appropriately record an image on the recording material.

  The recording material that holds the image information may be a photosensitive material such as a printed wiring board or a semiconductor substrate, or may be another photosensitive material, and is a material that reacts to heat due to light irradiation. It may be.

  In the spatial light modulators in the first and second embodiments, it is possible to emit appropriately spatially modulated light by using the electrodes 33 arranged in a staggered manner. The containers 3, 3a to 3e may be used for purposes other than image recording. In this case, the object to be irradiated with light may be other than the recording material.

1 is a diagram illustrating a configuration of an image recording apparatus according to a first embodiment of the present invention. It is a figure which shows the internal structure of an optical head. It is a figure which shows the internal structure of an optical head. It is a top view which shows a spatial light modulator. It is sectional drawing of a spatial light modulator. It is a figure for demonstrating the path | route of the light between a spatial light modulator and a recording material. It is a figure for demonstrating the area | region where recording is performed on a recording material. It is a figure which shows the flow of the operation | movement which records an image on a recording material. It is a figure for demonstrating the area | region where recording is performed on a recording material. It is a top view which shows the spatial light modulator which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the area | region where recording is performed on a recording material. It is a figure which shows the other example of an optical head. It is sectional drawing of a spatial light modulator. It is a figure which shows the other example of an electrode. It is a figure which shows the further another example of an electrode. It is a figure which shows the further another example of a spatial light modulator. It is an exploded view of a spatial light modulator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image recording device 3, 3a-3e Spatial light modulator 4 Control part 9 Recording material 21 Light source part 23 Projection optical system 31, 31a Base part 32, 32a Modulation part 33, 33c, 33d Electrode 81 Motor 311, 312 Main surface 313 Incident surface 314 Output surface 321, 322 Electrode array 330 Modulation unit 331, 332 Electrode element

Claims (14)

A spatial light modulator,
A plate-like member formed of a material whose refractive index changes by an electric field, and a base portion that guides light incident on the inside from one end face to another end face opposite to the one end face;
A plurality of electrodes, each of which is a set of electrode elements arranged in an arrangement direction perpendicular to the light traveling direction, are arranged in two rows in a staggered manner in the arrangement direction on the main surface of the base portion. By applying a voltage between the electrode elements included in the electrode, a periodic refractive index change in the arrangement direction is caused in a portion in the base portion in the vicinity of each electrode, and the light passing through the portion is diffracted. A modulation unit;
A spatial light modulator comprising: The spatial light modulator according to claim 1,
In the plurality of electrodes, each electrode included in one column and an electrode included in the other column adjacent to each electrode in a predetermined direction are similarly controlled as one modulation unit. A spatial light modulator characterized by. The spatial light modulator according to claim 2,
The spatial light modulator, wherein the light is multiple-reflected on both main surfaces of the base portion. The spatial light modulator according to claim 3,
A spatial light modulator, wherein the base portion has a thickness of 50 micrometers or less. The spatial light modulator according to claim 3 or 4,
Each of the plurality of electrodes is a set of electrode element pairs respectively formed on both the main surfaces with the base portion interposed therebetween. The spatial light modulator according to claim 1,
In the plurality of electrodes, the electrodes included in one row are arranged with a gap in the arrangement direction, and the electrodes contained in the other row are arranged with a gap in the arrangement direction. Light modulator. The spatial light modulator according to claim 6,
The spatial light modulator, wherein the light is multiple-reflected on both main surfaces of the base portion. The spatial light modulator according to claim 7,
A spatial light modulator, wherein the base portion has a thickness of 50 micrometers or less. The spatial light modulator according to claim 7 or 8,
Each of the plurality of electrodes is a set of electrode element pairs respectively formed on both the main surfaces with the base portion interposed therebetween. An image recording apparatus for recording an image on the recording material by irradiating the recording material with light,
A light source unit;
The spatial light modulator according to any one of claims 1 to 9, wherein light from the light source unit is incident;
An optical system for guiding one of zero-order light and (± 1) -order diffracted light from the spatial light modulator onto the recording material;
A scanning mechanism for moving the irradiation position of light from the spatial light modulator on the recording material relative to the recording material in a scanning direction perpendicular to a direction corresponding to the arrangement direction in the spatial light modulator. When,
A controller that controls the spatial light modulator in synchronization with the relative movement of the irradiation position with respect to the recording material;
An image recording apparatus comprising: An image recording apparatus for recording an image on the recording material by irradiating the recording material with light,
A light source unit;
The spatial light modulator according to any one of claims 2 to 5, wherein light from the light source unit is incident;
An optical system for guiding one of zero-order light and (± 1) -order diffracted light from the spatial light modulator onto the recording material;
A scanning mechanism for moving the irradiation position of light from the spatial light modulator on the recording material relative to the recording material in a scanning direction perpendicular to a direction corresponding to the arrangement direction in the spatial light modulator. When,
A controller that controls the spatial light modulator in synchronization with the relative movement of the irradiation position with respect to the recording material;
With
When each of the plurality of modulation units arranged in the arrangement direction in the spatial light modulator is in an ON state in which recording is performed on the recording material alone, an area recorded on the recording material is defined as a unit recording area. A plurality of unit recording areas respectively corresponding to a plurality of modulation units are continuously arranged in a direction corresponding to the arrangement direction. An image recording apparatus for recording an image on the recording material by irradiating the recording material with light,
A light source unit;
The spatial light modulator according to any one of claims 6 to 9, wherein light from the light source unit is incident;
An optical system for guiding one of zero-order light and (± 1) -order diffracted light from the spatial light modulator onto the recording material;
A scanning mechanism for moving the irradiation position of light from the spatial light modulator on the recording material relative to the recording material in a scanning direction perpendicular to a direction corresponding to the arrangement direction in the spatial light modulator. When,
A controller that controls the spatial light modulator in synchronization with the relative movement of the irradiation position with respect to the recording material;
With
When each of the plurality of electrodes of the spatial light modulator is in an ON state in which recording is performed on the recording material alone, an area recorded on the recording material is defined as a unit recording area, and each of the plurality of electrodes A plurality of corresponding unit recording areas are continuously arranged in a direction corresponding to the arrangement direction. The image recording device according to claim 11 or 12,
An image recording apparatus, wherein widths of the plurality of unit recording areas in a direction corresponding to the arrangement direction are equal. The image recording apparatus according to any one of claims 10 to 13,
An image recording apparatus, wherein the optical system is a reduction optical system.

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