JP2015185190A - Optical recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve recording accuracy.SOLUTION: An optical recording device 100 records information in an optical information recording medium 118 by irradiating the optical information recording medium 118 with signal light and reference light modulated by a spatial light modulator 110 using a liquid crystal cell. The optical recording device 100 also converts, into an electric signal, reproduction light obtained by irradiating the optical information recording medium 118 with the reference light using an image pick-up device 121. An adjustment unit 122 adjusts the temperature of the spatial light modulator 110. A storage unit 124 stores control conditions that are selected based on control conditions of the adjustment unit 122 and on the electric signal obtained by the image pick-up device 121. A control unit 123 controls the adjustment unit 122 according to the control conditions stored in the storage unit 124.

Description

  The present invention relates to an optical recording apparatus that records information on an optical information recording medium.

  Conventionally, an information signal is recorded by irradiating a reference light and a signal light to an optical information recording medium to form an hologram, or an information signal is reproduced by irradiating a reference light to the hologram of the optical information recording medium. An optical pickup device is known (for example, see Patent Document 1 below). Further, as a spatial light modulator that can be used for an optical pickup device for a hologram or the like, LCOS (Liquid Crystal On Silicon) using a liquid crystal cell is known.

JP 2013-251025 A

  However, in the above-described prior art, the contrast of the spatial light modulator may be lowered due to factors such as mounting accuracy of a spatial light modulator using a liquid crystal cell, lot variation, temperature fluctuation, and the like. There is a problem that information recording accuracy is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical recording apparatus capable of improving the recording accuracy in order to solve the above-described problems caused by the prior art.

  In order to solve the above-described problems and achieve the object, an optical recording apparatus according to the present invention irradiates an optical information recording medium with signal light modulated by a spatial light modulator using a liquid crystal cell. An optical recording apparatus that records information on a medium and converts reproduction light obtained by irradiating the optical information recording medium with reference light into an electric signal by an image sensor, and adjusts the temperature of the spatial light modulator An adjustment unit, a storage unit that stores the control condition selected based on the control condition of the adjustment unit, and the electrical signal obtained by the imaging device, and the control condition stored by the storage unit And a control unit for controlling the adjustment unit.

  As a result, the temperature of the spatial light modulator can be controlled according to the control condition selected using the imaging device used for reproducing information from the optical information recording medium, and the contrast of the spatial light modulator can be improved.

  According to one aspect of the present invention, it is possible to improve the recording accuracy.

FIG. 1 is a diagram illustrating an example of an optical recording apparatus according to an embodiment. FIG. 2A is a diagram illustrating an example of a partial cross section of the spatial light modulator. 2B is a diagram illustrating an example of light in the spatial light modulator illustrated in FIG. 2A. FIG. 3 is a diagram showing an example of a liquid crystal molecular state of a liquid crystal cell using a ferroelectric liquid crystal. FIG. 4 is a diagram showing an example of the relationship between the liquid crystal molecular state of the ferroelectric liquid crystal layer and the incident polarization direction. FIG. 5 is a diagram illustrating an example of the configuration of the control unit. FIG. 6 is a flowchart illustrating an example of control signal selection processing by the control unit. FIG. 7 is a diagram illustrating a modification of the optical recording apparatus according to the embodiment. FIG. 8 is a diagram illustrating an example of a control unit according to a modification. FIG. 9 is a flowchart illustrating an example of target temperature selection processing by the control unit.

  Embodiments of an optical recording apparatus according to the present invention will be described below in detail with reference to the drawings.

(Embodiment)
(Optical Recording Device According to Embodiment)
FIG. 1 is a diagram illustrating an example of an optical recording apparatus according to an embodiment. An optical recording apparatus 100 according to an embodiment includes a light source 101, a collimator lens 102, a polarization variable element 103, a PBS prism 104, a beam expander 106, a phase mask 107, a relay lens 108, and a PBS prism 109. A spatial light modulator 110, a relay lens 111, a spatial filter 112, an objective lens 113, a mirror 114, a mirror 115, a galvano mirror 116, a scanner lens 117, an optical information recording medium 118, and 1 / 4 wavelength plate 119, galvanometer mirror 120, image sensor 121, adjustment unit 122, control unit 123, and storage unit 124.

  The optical recording apparatus 100 records information on the optical information recording medium 118 by irradiating the optical information recording medium 118 with the signal light spatially modulated by the spatial light modulator 110 and the reference light. Further, the optical recording apparatus 100 reads information by converting reproduction light obtained by irradiating the optical information recording medium 118 with reference light into an electric signal by the image sensor 121.

  The light source 101 emits a light beam to the collimating lens 102. The light beam emitted from the light source 101 can be, for example, a predetermined linearly polarized continuous light. For example, an LD (Laser Diode) can be used as the light source 101. The collimating lens 102 collimates the light beam emitted from the light source 101 into a light beam having a predetermined beam diameter, and emits the collimated light beam to the polarization variable element 103.

  The polarization variable element 103 and the PBS prism 104 constitute a shutter unit 105 that controls the irradiation of the signal light from the spatial light modulator 110 to the optical information recording medium 118 in accordance with the drive voltage supplied from the control unit 123.

  The polarization variable element 103 adjusts the polarization state of the light beam emitted from the collimating lens 102 in accordance with the drive voltage supplied from the control unit 123. For example, the polarization variable element 103 sets the polarization state of the light beam to a polarization state including P-polarized light and S-polarized light when recording information on the optical information recording medium 118.

  The polarization variable element 103 sets the polarization state of the light beam to S-polarized light when reproducing information from the optical information recording medium 118. The polarization variable element 103 emits a light beam whose polarization state is adjusted to the PBS prism 104. As the polarization variable element 103, for example, a liquid crystal cell can be used. For the liquid crystal cell, for example, FLC (Ferroelectric Liquid Crystal) can be used.

  The PBS prism 104 is a PBS (Polarization Beam Splitters) that transmits the P-polarized light beam emitted from the polarization variable element 103 and emits it as signal light to the beam expander 106. Further, the PBS prism 104 reflects the S-polarized light beam emitted from the polarization variable element 103 and emits it to the mirror 114 as reference light. Thus, when information is recorded on the optical information recording medium 118, P-polarized signal light is emitted to the beam expander 106, and S-polarized reference light is emitted to the mirror 114. Further, when reproducing information from the optical information recording medium 118, S-polarized reference light is emitted to the mirror 114.

  The beam expander 106 expands the beam length of the signal light emitted from the PBS prism 104 to a predetermined beam length, and emits the signal light having the expanded beam length to the phase mask 107. The signal light emitted from the beam expander 106 to the phase mask 107 is emitted to the PBS prism 109 via the phase mask 107 and the relay lens 108.

  The PBS prism 109 transmits the P-polarized signal light emitted from the relay lens 108 and emits it to the spatial light modulator 110. The PBS prism 109 reflects the signal light emitted from the spatial light modulator 110 and emits it to the relay lens 111. The signal light emitted from the PBS prism 109 to the relay lens 111 is emitted to the optical information recording medium 118 through the relay lens 111, the opening of the spatial filter 112, and the objective lens 113.

  The spatial light modulator 110 is a spatial light modulator using a liquid crystal cell, and spatially modulates the signal light emitted from the PBS prism 109 based on the modulation information. For example, the spatial light modulator 110 performs modulation based on the two-dimensional image data (modulation information) written from the control unit 123. Then, the spatial light modulator 110 emits the modulated signal light to the PBS prism 109. For example, LCOS using a ferroelectric liquid crystal cell can be used for the spatial light modulator 110 (see, for example, FIGS. 2A and 2B).

  The reference light emitted from the PBS prism 104 to the mirror 114 is emitted to the galvanometer mirror 116 via the mirrors 114 and 115. The galvanometer mirror 116 reflects the reference light emitted from the mirror 115 at a variable angle and emits it to the scanner lens 117. The angle control of the galvanometer mirror 116 can be performed by the control unit 123, for example. The scanner lens 117 emits the reference light emitted from the galvanometer mirror 116 to the optical information recording medium 118.

  As the optical information recording medium 118, for example, various optical information recording media such as a photorefractive crystal such as lithium niobate and a photosensitive resin material (photopolymer) can be used. Further, the optical information recording medium 118 may be displaceable under the control of the control unit 123, for example.

  At the time of information recording, the signal light emitted from the objective lens 113 and the reference light emitted from the scanner lens 117 are incident on the optical information recording medium 118 so as to overlap each other. Thereby, an interference fringe pattern is formed on the optical information recording medium 118, and the optical information recording medium 118 records the formed interference fringe pattern as a hologram. In addition, angle multiplex recording can be performed by changing the incident angle of the reference light to the optical information recording medium 118 by controlling the angle of the galvanometer mirror 116. In the present embodiment, this hologram is called a “page”, and a recording area where the page is angle-multiplexed is called a “book”.

  At the time of reproducing information, the reference light emitted from the scanner lens 117 enters the optical information recording medium 118. The quarter-wave plate 119 passes the reference light emitted from the scanner lens 117 and transmitted through the optical information recording medium 118 and emits it to the galvanometer mirror 120.

  The galvanometer mirror 120 reflects the reference light emitted from the quarter-wave plate 119 at a variable angle. The angle control of the galvanometer mirror 120 can be performed by the control unit 123, for example. At this time, the angle control of the galvanometer mirror 120 is performed in conjunction with the angle control of the galvanometer mirror 116, so that the reference light is reflected substantially vertically by the galvanometer mirror 120 and the reference light is folded back to the quarter-wave plate 119. .

  Accordingly, the reference light emitted from the scanner lens 117 and transmitted through the optical information recording medium 118 is converted from S-polarized light to P-polarized light by passing through the quarter-wave plate 119 twice, and emitted to the optical information recording medium 118. The As a result, the reproduction light corresponding to the information recorded on the optical information recording medium 118 is emitted to the objective lens 113 as P-polarized diffracted light.

  The reproduction light emitted from the optical information recording medium 118 to the objective lens 113 is emitted to the PBS prism 109 via the objective lens 113 and the relay lens 111. At this time, only the reproduction light that is diffracted light from the reproduction target book is transmitted to the PBS prism 109 through the opening of the spatial filter 112 between the relay lenses 111.

  The PBS prism 109 transmits the P-polarized reproduction light emitted from the relay lens 111 and emits it to the image sensor 121.

  The image sensor 121 converts the reproduction light emitted from the PBS prism 109 into an electric signal. Thereby, an electrical signal indicating information recorded on the optical information recording medium 118 is obtained. The image sensor 121 outputs the converted electrical signal to the control unit 123. As the image sensor 121, for example, a solid-state image sensor such as a CMOS (Complementary Metal Oxide Semiconductor: complementary metal oxide semiconductor) can be used.

  The adjustment unit 122 adjusts the temperature of the spatial light modulator 110 according to the control signal input from the control unit 123. For example, the adjustment unit 122 is provided in the vicinity of the spatial light modulator 110. In addition, various temperature adjusting devices such as a Peltier element, a heater, a blower, and a combination thereof can be used as the adjusting unit 122.

  The control unit 123 controls the spatial light modulator 110, the shutter unit 105, the adjustment unit 122, and the like when recording information on the optical information recording medium 118 or reproducing information from the optical information recording medium 118.

  For example, the control unit 123 writes information to be recorded (modulation information) to the spatial light modulator 110 and outputs signal light and reference light from the PBS prism 104 when recording information on the optical information recording medium 118. As described above, the drive voltage is supplied to the polarization variable element 103. However, even when information is recorded on the optical information recording medium 118, the control unit 123 applies the polarization variable element 103 so that signal light is not emitted from the PBS prism 104 when information is written to the spatial light modulator 110. Supply drive voltage.

  In addition, the control unit 123 supplies a drive voltage to the polarization variable element 103 so that only the reference light is emitted from the PBS prism 104 when reproducing information from the optical information recording medium 118.

  The control unit 123 controls the book to be recorded and the like by controlling the angle of the galvano mirror 116 when recording information on the optical information recording medium 118. In addition, the control unit 123 controls the book to be reproduced and the like by controlling the angle of the galvanometer mirrors 116 and 120 when reproducing the information from the optical information recording medium 118. In FIG. 1, the connection relationship between the control unit 123 and the galvanometer mirrors 116 and 120 is not shown. Further, the control unit 123 may move the book to be recorded by changing the position of the optical information recording medium 118 with respect to the objective lens 113.

  The storage unit 124 stores the control conditions of the adjustment unit 122 by the control unit 123. This control condition is a control condition selected based on the control condition of the adjustment unit 122 by the control unit 123 and the electric signal obtained by the image sensor 121. In the example illustrated in FIG. 1, it is assumed that the control condition is a control signal (for example, control voltage) input from the control unit 123 to the adjustment unit 122. In this case, the storage unit 124 stores a value indicating the control signal directly or indirectly. As the storage unit 124, for example, various nonvolatile memories can be used. Various volatile memories can also be used for the storage unit 124.

  The control unit 123 controls the temperature of the spatial light modulator 110 based on the control conditions stored in the storage unit 124. In the example illustrated in FIG. 1, the control unit 123 controls the temperature of the spatial light modulator 110 by inputting the control signal stored in the storage unit 124 to the adjustment unit 122. Further, the control unit 123 selects a control signal based on the electrical signal from the imaging element 121 monitored while switching the control signal to the adjustment unit 122, and performs a process of storing the selected control signal in the storage unit 124. Also good. Processing for selecting a control signal by the control unit 123 will be described later (see, for example, FIG. 6).

(Partial cross section of spatial light modulator)
FIG. 2A is a diagram illustrating an example of a partial cross section of the spatial light modulator. The spatial light modulator 110 shown in FIG. 1 can be realized by, for example, the reflective LCOS 200 shown in FIG. 2A. The reflective LCOS 200 includes a transparent electrode substrate 210, a ferroelectric liquid crystal layer 220, reflective electrodes 231 to 233, silicon oxide film layers 240, light shielding layers 251 to 254 that are reflective members, and silicon oxide film layers 260. Transistors 271 to 273, a silicon layer 280, contact holes 291 to 293, and vias 294 to 296. Here, the silicon oxide film layers 240 and 260 and the silicon layer 280 constitute a silicon substrate.

  In the reflective LCOS 200, the ferroelectric liquid crystal layer 220 is sandwiched between the silicon oxide film layer 240 on which the reflective electrodes 231 to 233 are provided and the transparent electrode substrate 210, and the transparent electrode substrate 210 and the ferroelectric liquid crystal layer 220 are sandwiched. This is a reflective liquid crystal optical element that reflects the transmitted light by the reflective electrodes 231 to 233 and emits the light from the transparent electrode substrate 210.

  The transparent electrode substrate 210 can be formed, for example, by overlapping a glass substrate and a transparent electrode. The transparent electrode can be formed of, for example, ITO (indium tin oxide). In this case, for example, the transparent electrode substrate 210 can be formed by coating ITO on a glass substrate. For example, a voltage is applied to the transparent electrode substrate 210 from a control substrate of the reflective LCOS 200.

  The ferroelectric liquid crystal layer 220 is a liquid crystal layer provided between the transparent electrode substrate 210 and the reflective electrodes 231 to 233 and having two stable states. In the ferroelectric liquid crystal layer 220, the liquid crystal alignment changes according to the voltage applied between the transparent electrode substrate 210 and the reflective electrodes 231 to 233.

  The reflective electrodes 231 to 233 are reflective pixel electrodes that reflect light. The reflective electrodes 231 to 233 are arranged on the silicon oxide film layer 240, for example, at equal intervals and with a gap. The reflective electrodes 231 to 233 can be formed of aluminum, for example.

  Since only a part of the reflective LCOS 200 is illustrated in FIG. 2A, only the reflective electrodes 231 to 233 are illustrated as reflective electrodes. However, the reflective LCOS 200 may include more reflective electrodes. . In FIG. 2A, only the reflective electrodes 231 to 233 arranged in the two-dimensional direction are illustrated, but each reflective electrode of the reflective LCOS 200 is two-dimensionally (that is, in a matrix) with respect to the silicon oxide film layer 240. Be placed.

The silicon oxide film layer 240 is a SiO ₂ (silicon dioxide) layer provided between the reflective electrodes 231 to 233 and the light shielding layers 251 to 254. The silicon oxide film layer 240 is provided with vias 294 to 296 that penetrate the silicon oxide film layer 240 and connect the reflective electrodes 231 to 233 and the contact holes 291 to 293.

  The light shielding layers 251 to 254 are light shielding layers that shield light from the silicon oxide film layer 240 to the silicon oxide film layer 260. The light shielding layers 251 to 254 are reflection members that reflect light that has passed through the gap between the reflection electrodes 231 to 233 out of the light transmitted through the ferroelectric liquid crystal layer 220. The light shielding layers 251 to 254 can be formed of aluminum, for example.

  Since only a part of the reflective LCOS 200 is illustrated in FIG. 2A, only the light shielding layers 251 to 254 are illustrated as the light shielding layer, but the reflective LCOS 200 may have more light shielding layers. . 2A shows only the light shielding layers 251 to 254 arranged in the two-dimensional direction, each light shielding layer of the reflective LCOS 200 is arranged in the two-dimensional direction with respect to the silicon oxide film layer 240.

The silicon oxide film layer 260 is a layer of SiO ₂ (silicon dioxide) provided between the light shielding layers 251 to 254 and the silicon layer 280. The silicon oxide film layer 260 is provided with contact holes 291 to 293 that penetrate the silicon oxide film layer 260 and connect the vias 294 to 296 to the transistors 271 to 273.

  Transistors 271 to 273 are provided in the silicon layer 280. The transistors 271 to 273 apply a voltage to the reflective electrodes 231 to 233 through the contact holes 291 to 293 and the vias 294 to 296, respectively.

  Since only a part of the reflective LCOS 200 is illustrated in FIG. 2A, only the transistors 271 to 273 are illustrated as transistors. However, the reflective LCOS 200 includes a transistor corresponding to a reflective electrode. In FIG. 2A, only the transistors 271 to 273 arranged in the two-dimensional direction are illustrated, but the transistors of the reflective LCOS 200 are arranged in the two-dimensional direction with respect to the silicon oxide film layer 240 corresponding to the reflective electrodes. Is done.

(Light in spatial light modulator)
2B is a diagram illustrating an example of light in the spatial light modulator illustrated in FIG. 2A. In FIG. 2B, the same parts as those shown in FIG. For example, light enters the reflective LCOS 200 vertically from the transparent electrode substrate 210. The light incident on the reflective LCOS 200 is, for example, a single wavelength laser beam oscillated by a laser light source.

  Lights 201 to 203 shown in FIG. 2B are light incident on the reflective electrodes 231 to 233 out of the light incident on the reflective LCOS 200 and transmitted through the ferroelectric liquid crystal layer 220, respectively. Lights 201 to 203 are reflected by the reflective electrodes 231 to 233, respectively, pass through the ferroelectric liquid crystal layer 220, and are emitted from the transparent electrode substrate 210. In addition, the liquid crystal alignment of each portion of the ferroelectric liquid crystal layer 220 through which the light 201 to 203 is transmitted is changed by each voltage applied to the reflective electrodes 231 to 233 by the transistors 271 to 273.

  Therefore, the light beams 201 to 203 are modulated in accordance with the voltages applied to the reflective electrodes 231 to 233 by the transistors 271 to 273, and the modulated light beams 201 to 203 are emitted from the transparent electrode substrate 210.

  2A and 2B are shown differently from actual dimensions.

(Liquid crystal molecular state of liquid crystal cell using ferroelectric liquid crystal)
FIG. 3 is a diagram showing an example of a liquid crystal molecular state of a liquid crystal cell using a ferroelectric liquid crystal. The liquid crystal molecular states 301 and 302 in the switching states 311 to 313 shown in FIG. 3 are two stable states of the liquid crystal molecules in the ferroelectric liquid crystal layer 220 of the reflective LCOS 200 shown in FIGS. 2A and 2B. The reflective LCOS 200 switches between the liquid crystal molecular states 301 and 302 according to the drive voltage supplied from the control unit 123. Thereby, the polarization state of the light (signal light) transmitted through the reflective LCOS 200 is switched.

  The switching angle θ is an angle difference in the molecular major axis direction in the liquid crystal molecular states 301 and 302. The control unit 123 switches between the liquid crystal molecular states 301 and 302 according to the driving voltage. At this time, the contrast of the signal light applied to the optical information recording medium 118 is maximized when the switching angle θ is 45 degrees, for example.

  Switching states 311 to 313 show liquid crystal molecular states 301 and 302 when the temperature of the spatial light modulator 110 (ferroelectric liquid crystal layer 220) is T0 to T2 (T0 <T1 <T2), respectively. As shown in switching states 311 to 313, the liquid crystal molecular states 301 and 302 of the ferroelectric liquid crystal layer 220 change depending on the temperature of the spatial light modulator 110.

(Relationship between liquid crystal molecular state of ferroelectric liquid crystal layer and incident polarization direction)
FIG. 4 is a diagram showing an example of the relationship between the liquid crystal molecular state of the ferroelectric liquid crystal layer and the incident polarization direction. An incident polarization direction 401 shown in FIG. 4 is a polarization direction of light incident on the reflective LCOS 200. In the reflective LCOS 200, the molecular major axis direction of one of the liquid crystal molecular states 301 and 302 of the ferroelectric liquid crystal layer 220 (the liquid crystal molecular state 301 in the example shown in FIG. 4) is parallel to the incident polarization direction 401. The maximum contrast can be obtained.

  However, the molecular major axis direction of the liquid crystal molecular state 301 and the incident polarization direction 401 may not be parallel depending on, for example, the mounting accuracy of the reflective LCOS 200 and lot variations. Further, as shown in FIG. 3, since the liquid crystal molecular states 301 and 302 change depending on the temperature of the reflective LCOS 200, even if the mounting accuracy of the reflective LCOS 200 is high and the lot variation is small, the molecular major axis of the liquid crystal molecular state 301 The direction and the incident polarization direction 401 may not be parallel.

  On the other hand, the control unit 123 controls the temperature of the reflective LCOS 200 based on the control condition based on the electrical signal obtained by the imaging element 121, thereby causing the molecular major axis direction and the incident polarization direction of the liquid crystal molecular state 301 to be controlled. 401 is kept parallel. Thereby, even if the mounting accuracy of the reflective LCOS 200 is low, the molecular major axis direction of the liquid crystal molecular state 301 and the incident polarization direction 401 can be made parallel by controlling the temperature of the reflective LCOS 200. Further, for example, even if the apparatus temperature of the optical recording apparatus 100 varies, the molecular major axis direction of the liquid crystal molecular state 301 and the incident polarization direction 401 can be kept parallel.

(Configuration of control unit)
FIG. 5 is a diagram illustrating an example of the configuration of the control unit. The control unit 123 illustrated in FIG. 1 includes, for example, a control circuit 501, a waveform generation circuit 502, a drive circuit 503, and an image analysis circuit 504, as illustrated in FIG.

  The control unit 123 controls the writing of modulation information (two-dimensional image data) to the spatial light modulator 110, the drive voltage supplied to the shutter unit 105, the adjustment unit 122, and the like. Although not shown, the control unit 123 may perform control such as angle control of the galvanometer mirrors 116 and 120 and movement of the optical information recording medium 118.

  For example, the control circuit 501 outputs a signal indicating the waveform pattern of the drive voltage of the polarization variable element 103 to the waveform generation circuit 502. The waveform generation circuit 502 generates a waveform signal having a voltage waveform based on the signal output from the control circuit 501, and outputs the generated waveform signal to the drive circuit 503. The drive circuit 503 supplies a drive waveform based on the waveform signal output from the waveform generation circuit 502 to the polarization variable element 103. In addition, the control circuit 501 outputs the control signal stored in the storage unit 124 to the adjustment unit 122.

  The image analysis circuit 504 analyzes the image information indicated by the electric signal output from the image sensor 121 in the process of selecting the control condition (for example, control signal) of the adjustment unit 122 by the control unit 123. For example, the image analysis circuit 504 calculates an evaluation value of information recording accuracy (for example, contrast) with respect to the optical information recording medium 118 based on the electric signal output from the image sensor 121.

  In the present embodiment, the evaluation value is a value that increases as the recording accuracy (for example, contrast) increases. However, the evaluation value may be a value that decreases as the recording accuracy (for example, contrast) increases. The image analysis circuit 504 outputs the calculated evaluation value to the control circuit 501. Calculation of the evaluation value by the image analysis circuit 504 will be described later.

  The control circuit 501, the waveform generation circuit 502, and the drive circuit 503 can be realized by, for example, one or a plurality of microcomputers or a custom IC (Integrated Circuit). The waveform generation circuit 502 may include a power source. The image analysis circuit 504 can be realized by an integrated circuit such as ASIC (Application Specific Integrated Circuit). However, the hardware configuration of each unit of the control unit 123 is not limited to these, and various hardware configurations may be used.

  Further, among the functions of the control circuit 501, for example, the control of the adjustment unit 122 may be performed by a control circuit different from the control circuit 501. In this case, the image analysis circuit 504 outputs the calculated evaluation value to the control circuit that controls the adjustment unit 122.

(Control signal selection processing by the controller)
FIG. 6 is a flowchart illustrating an example of control signal selection processing by the control unit. For example, the control unit 123 performs a selection process of a control signal (control condition) illustrated in FIG. When the optical recording apparatus 100 is not in operation, for example, there is no external recording (writing) request or reproduction (reading) request to the optical recording apparatus 100 (self apparatus), and the optical recording apparatus 100 is idle or the like. is there.

  First, the control unit 123 initializes k (k = 1) indicating a candidate index of a control signal (step S601). Next, the control unit 123 sets a control signal to the adjustment unit 122 to Vk (step S602). Next, the control unit 123 waits for a predetermined time (step S603). The standby time in step S603 is set to a time sufficient for the control signal set in step S602 to be reflected in the temperature of the spatial light modulator 110, for example.

  Next, the control unit 123 performs recording processing of predetermined data on the optical information recording medium 118 (step S604). The predetermined data is, for example, known pattern data. Next, the control unit 123 performs a reproduction process of the predetermined data recorded on the optical information recording medium 118 by the recording process of step S604 (step S605). Next, the control unit 123 calculates an evaluation value of information recording accuracy with respect to the optical information recording medium 118 based on the electrical signal from the image sensor 121 obtained in step S605 (step S606).

  Next, the control unit 123 determines whether k has reached n (step S607). n is the maximum value of the control signal candidate index. When k has not reached n (step S607: No), the control unit 123 increments k (k = k + 1) (step S608), and returns to step S602.

  In step S607, when k has reached n (step S607: Yes), the control unit 123 has the control signal with the highest evaluation value calculated in step S606 among the control signal candidates set in step S602. Is selected (step S609). If the evaluation value decreases as the recording accuracy increases, the control unit 123 selects a control signal having the lowest evaluation value in step S609. Next, the control unit 123 stores the control signal selected in step S609 in the storage unit 124 (step S610), and ends a series of selection processes.

  As described above, the control unit 123 selects the control signal to the adjustment unit 122 based on the electrical signal from the imaging element 121 monitored while switching the control signal to the adjustment unit 122, and stores the selected control signal in the storage unit 124. Remember me.

  For example, the control unit 123 records predetermined data on the optical information recording medium 118 while switching a control signal to the adjustment unit 122. Then, the control unit 123 selects a control signal based on an evaluation value for each control signal based on an electrical signal obtained by converting the reproduction light of the predetermined data recorded on the optical information recording medium 118 by the image sensor 121.

  The control unit 123 further increases the evaluation value by performing steps S601 to S608 by using the control signal selected in step S609 and each control signal obtained by increasing or decreasing the selected control signal as a candidate. A follow-up process for selecting a control signal may be performed.

  Further, when the control signal Vk is a control signal that monotonously increases or monotonously decreases with an increase in the index k, and the temperature of the spatial light modulator 110 monotonously increases or monotonously decreases with a change in the control signal, that is, the index. When the temperature of the spatial light modulator 110 monotonously increases or monotonously decreases as k increases, the evaluation value is considered to have a maximum value as the index k increases. For this reason, the control part 123 may make it transfer to step S608, even if k has not reached n, when the local maximum value of an evaluation value is detected. As a result, it is possible to shorten the control signal selection processing time and reduce power consumption.

  For example, the control unit 123 performs the process shown in FIG. 6 only when the optical recording apparatus 100 is activated for the first time, thereby selecting an appropriate control signal according to the mounting accuracy of the spatial light modulator 110 and lot variations. be able to. In this case, the storage unit 124 is a nonvolatile memory. Thereby, since it is not necessary to perform the processing shown in FIG. 6 after the next activation of the optical recording apparatus 100, power consumption can be reduced.

  Further, the control unit 123 may perform the processing illustrated in FIG. 6 every time the optical recording apparatus 100 is activated. Thereby, for example, even if the relationship between the temperature of the spatial light modulator 110 and the liquid crystal molecular states 301 and 302 of the spatial light modulator 110 changes due to aging of the spatial light modulator 110, appropriate control is performed each time. A signal can be selected.

  Further, the control unit 123 may perform the processing shown in FIG. 6 when the optical recording apparatus 100 is not in operation, such as when it is idle. Thereby, for example, even if the relationship between the temperature of the spatial light modulator 110 and the liquid crystal molecular states 301 and 302 of the spatial light modulator 110 changes due to aging of the spatial light modulator 110, appropriate control is performed each time. A signal can be selected.

(Calculation of evaluation value)
The calculation of the evaluation value in step S606 shown in FIG. 6 will be described. In step S606, for example, the control unit 123 acquires an electrical signal from the imaging device for the reproduction light obtained by the reproduction processing in step S605. Note that the electrical signal obtained by the reproduction process is, for example, temporally continuous image information. In this case, the control unit 123 may acquire, for example, image information indicating an average luminance change over time of the entire image, or acquire image information indicating an average luminance change over time of a part of the image. May be. In addition, the control unit 123 may acquire image information of the entire image at a certain time point, or may acquire image information of a part (a plurality of pixels) of the image at a certain time point.

  The control unit 123 compares the acquired image information data with the ideal image information corresponding to the predetermined data stored in the optical information recording medium 118 in step S604, and the closer the compared image information is, the closer the compared image information is. Calculate a high evaluation value. For comparison of image information, for example, comparison by image processing such as pattern matching can be used.

  Alternatively, the control unit 123 compares the data of the image information obtained by decoding the electrical signal obtained by the reproduction process in step S605 and the predetermined data recorded in step S604, and the evaluation value is higher as the compared data is closer. May be calculated. However, the calculation method of the evaluation value by the control unit 123 is not limited to these, and various calculation methods can be used.

(Modification of Optical Recording Apparatus According to Embodiment)
FIG. 7 is a diagram illustrating a modification of the optical recording apparatus according to the embodiment. In FIG. 7, the same parts as those shown in FIG. As shown in FIG. 7, the optical recording apparatus 100 may include a measurement unit 701 in addition to the configuration shown in FIG. For the measurement unit 701, various measurement units such as a semiconductor sensor can be used.

  The measurement unit 701 measures the temperature of the spatial light modulator 110. For example, the measurement unit 701 is provided at a position where the temperature of the spatial light modulator 110 (liquid crystal cell) can be measured directly or indirectly. The measurement unit 701 notifies the control unit 123 of the measured temperature. Note that the temperature notified from the measurement unit 701 is not limited to a numerical value represented by, for example, a Celsius temperature scale or a Fahrenheit temperature scale, and may be a signal that changes according to the temperature.

  In this case, the control condition stored in the storage unit 124 is a target value (target temperature) of the temperature measured by the measurement unit 701 in the control of the control signal input from the control unit 123 to the adjustment unit 122. it can. In this case, the storage unit 124 stores a value indicating the target temperature directly or indirectly. The control unit 123 adjusts the temperature of the spatial light modulator 110 by controlling a control signal to the adjustment unit 122 so that the temperature notified from the measurement unit 701 approaches the temperature stored in the storage unit 124. .

(Control section according to modification)
FIG. 8 is a diagram illustrating an example of a control unit according to a modification. In FIG. 8, the same parts as those shown in FIG. The control unit 123 illustrated in FIG. 7 can be realized by the control unit 123 illustrated in FIG. 8, for example. The control circuit 501 changes the control signal output to the adjustment unit 122 so that the temperature notified from the measurement unit 701 approaches the temperature stored in the storage unit 124.

  Thereby, even if the correspondence between the control signal output to the adjusting unit 122 and the temperature of the spatial light modulator 110 varies, the molecular major axis direction of the liquid crystal molecular state 301 and the incident polarization direction 401 become parallel. The state in which the contrast of the spatial light modulator 110 is high can be maintained. The change in the correspondence relationship is caused by, for example, a change in the apparatus temperature of the optical recording apparatus 100, a secular change in the adjustment unit 122, or the like.

(Target temperature selection processing by the control unit)
FIG. 9 is a flowchart illustrating an example of target temperature selection processing by the control unit. The control unit 123 illustrated in FIG. 7 performs, for example, a target temperature (control condition) selection process illustrated in FIG. 9 when the optical recording apparatus 100 is activated or not operated.

  First, the control unit 123 initializes k (k = 1) indicating a target temperature candidate index (step S901). Next, the control part 123 sets the target value (target temperature) of the temperature measured by the measurement part 701 in control of the control signal to the adjustment part 122 to Tk (step S902). Next, the control unit 123 waits for a predetermined time (step S903). The standby time in step S903 is, for example, a time sufficient for the target temperature set in step S902 to be reflected in the temperature of the spatial light modulator 110.

  Steps S904 to S908 shown in FIG. 9 are the same as steps S604 to S608 shown in FIG. In step S907, when k has reached n (step S907: Yes), the control unit 123 sets the target temperature having the highest evaluation value calculated in step S906 among the target temperature candidates set in step S902. Is selected (step S909). If the evaluation value decreases as the recording accuracy increases, in step S909, the control unit 123 selects a target temperature with the lowest evaluation value. Next, the control unit 123 stores the target temperature selected in step S909 in the storage unit 124 (step S910), and ends a series of selection processes.

  As described above, the control unit 123 selects the target temperature based on the electrical signal from the imaging element 121 monitored while switching the target temperature in the control of the control signal of the adjustment unit 122, and stores the selected target temperature in the storage unit 124. Remember.

  For example, the control unit 123 records predetermined data on the optical information recording medium 118 while switching the target temperature in the control of the control signal of the adjustment unit 122. Then, the control unit 123 selects a target temperature based on an evaluation value for each target temperature based on an electrical signal obtained by converting the reproduction light of the predetermined data recorded on the optical information recording medium 118 by the image sensor 121.

  The control unit 123 further increases the evaluation value by performing Steps S901 to S908 with the target temperature selected in Step S909 and each target temperature obtained by increasing or decreasing the selected target temperature as candidates. A follow-up process for selecting a target temperature may be performed.

  When the target temperature Tk is a target temperature that monotonously increases or monotonously decreases with an increase in the index k, the evaluation value is considered to have a maximum value with respect to the increase in the index k. For this reason, when detecting the maximum value of the evaluation value, the control unit 123 may shift to step S908 even if k has not reached n. As a result, it is possible to shorten the time for selecting the target temperature and reduce the power consumption.

  For example, the control unit 123 performs the process shown in FIG. 9 only when the optical recording apparatus 100 is activated for the first time, thereby selecting an appropriate target temperature according to the mounting accuracy of the spatial light modulator 110 and lot variations. be able to. In this case, the storage unit 124 is a nonvolatile memory. As a result, it is not necessary to perform the processing shown in FIG. 9 after the next activation of the optical recording apparatus 100, so that power consumption can be reduced.

  Further, the control unit 123 may perform the processing illustrated in FIG. 9 each time the optical recording apparatus 100 is activated. Thereby, for example, even if the relationship between the temperature of the spatial light modulator 110 and the liquid crystal molecular states 301 and 302 of the spatial light modulator 110 changes due to aging of the spatial light modulator 110, an appropriate target each time. The temperature can be selected.

  Further, the control unit 123 may perform the processing illustrated in FIG. 9 when the optical recording apparatus 100 is not in operation, such as when it is idle. Thereby, for example, even if the relationship between the temperature of the spatial light modulator 110 and the liquid crystal molecular states 301 and 302 of the spatial light modulator 110 changes due to aging of the spatial light modulator 110, an appropriate target each time. The temperature can be selected.

  As described above, according to the optical recording apparatus 100, the spatial light is controlled by controlling the adjustment unit 122 that adjusts the temperature of the spatial light modulator 110 according to the control condition based on the electrical signal obtained by the imaging element 121. The contrast of the modulator 110 can be improved. For this reason, it is possible to improve the recording accuracy.

  Further, the evaluation value of the control condition can be calculated using the image sensor 121 used for reproducing the information recorded on the optical information recording medium 118. For this reason, for example, the control condition of the adjusting unit 122 can be selected without separately providing a monitor unit for monitoring the characteristics of the spatial light modulator 110. In addition, since an evaluation value based on a reproduction result of information from the optical information recording medium 118 can be calculated, it is possible to select a control condition of the adjusting unit 122 that increases the actual recording accuracy.

  Further, the optical recording apparatus 100 can be used even when the image pickup device 121 used for reproducing information recorded on the optical information recording medium 118 is used by performing an operation of selecting a control condition when the optical recording apparatus 100 is activated or not operated. Can reduce the impact on the operation.

  As described above, the optical recording apparatus according to the present invention is useful for an optical recording apparatus that records information on an optical information recording medium. In particular, the hologram is formed by irradiating the optical information recording medium with reference light and signal light. It is suitable for a hologram pickup device that records an information signal by forming it or reproduces an information signal by irradiating a hologram of an optical information recording medium with reference light.

DESCRIPTION OF SYMBOLS 100 Optical recording device 101 Light source 102 Collimating lens 103 Polarization variable element 104,109 PBS prism 105 Shutter part 106 Beam expander 107 Phase mask 108,111 Relay lens 110 Spatial light modulator 112 Spatial filter 113 Objective lens 114,115 Mirror 116, DESCRIPTION OF SYMBOLS 120 Galvanometer mirror 117 Scanner lens 118 Optical information recording medium 119 1/4 wavelength plate 121 Imaging element 122 Adjustment part 123 Control part 124 Storage part 200 Reflective LCOS
210 Transparent electrode substrate 220 Ferroelectric liquid crystal layer 231 to 233 Reflective electrode 240 and 260 Silicon oxide film layer 251 to 254 Light shielding layer 271 to 273 Transistor 280 Silicon layer 291 to 293 Contact hole 294 to 296 Via 301, 302 Liquid crystal molecular state 311 313 Switching state 401 Incident polarization direction 501 Control circuit 502 Waveform generation circuit 503 Drive circuit 504 Image analysis circuit 701 Measurement unit

Claims (7)

It is obtained by irradiating the optical information recording medium with signal light modulated by a spatial light modulator using a liquid crystal cell to record information on the optical information recording medium and irradiating the optical information recording medium with reference light. An optical recording apparatus that converts reproduction light into an electrical signal by an image sensor,
An adjustment unit for adjusting the temperature of the spatial light modulator;
A storage unit that stores the control condition selected based on the control condition of the adjustment unit and the electrical signal obtained by the imaging device;
A control unit that controls the adjustment unit according to the control condition stored by the storage unit;
An optical recording apparatus comprising: The adjusting unit adjusts the temperature of the spatial light modulator according to the input control signal,
The control condition is the control signal input to the adjustment unit,
The control unit inputs the control signal stored by the storage unit to the adjustment unit.
The optical recording apparatus according to claim 1. A measurement unit for measuring the temperature of the spatial light modulator;
The control condition is a target value of the temperature in the control of the adjustment unit,
The control unit controls the adjustment unit such that the temperature measured by the measurement unit approaches the temperature stored by the storage unit.
The optical recording apparatus according to claim 1.   The said control part performs the process which memorize | stores in the said memory | storage part the said control conditions selected based on the said electrical signal monitored while switching the said control conditions. The optical recording apparatus described.   The optical recording apparatus according to claim 4, wherein the control unit performs the process when the apparatus is activated.   6. The optical recording apparatus according to claim 4, wherein the control unit performs the processing when there is no request to the apparatus from outside the recording or reproduction of the information.   The optical recording apparatus according to claim 1, wherein the liquid crystal cell is a ferroelectric liquid crystal cell.

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