JP2011146098A - Hologram recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording and reproducing device having a reproduction photodetector 46 that receives one of information reproducing light and reference reproducing light, irrespective of a sectional shape, and blocks the other one. <P>SOLUTION: A light-shielding liquid crystal panel 40 is arranged in front of a reproduction photodetector 46. Transmittance of a plurality of pixels arranged in the incident region of the light-shielding liquid crystal panel 40 is controlled by a light-shielding signal control circuit 208. The light-shielding signal control circuit 208 sets a pattern region S1 that receives the information reproducing light and a non-light shielding region S2 that receives reference reproducing light in the light-shielding liquid crystal panel 40, and sets the highest transmittance for the pixel of the pattern region S1 and sets the lowest transmittance for the pixel of the non-light shielding region S2. Regardless of a change in sectional shape of the information reproducing light and the reference reproducing light, the pattern region S1 and the non-light shielding area S2 are set according to the sectional shapes, thereby allowing the reproduction photodetector 46 to receive one of the light beams while blocking the other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hologram recording / reproducing apparatus for reproducing data recorded on a hologram recording medium. The present invention also provides a hologram recording / reproducing apparatus that records data on a hologram recording medium and reproduces the recorded data, and further compares the data recorded on the hologram recording medium with the reproduced data to obtain a hologram recording medium. It relates to a device to be evaluated.

  In order to increase the recording capacity of an optical disc, research on multiplex recording on a hologram recording medium is underway.

  The main methods for recording data on the hologram recording medium are two-beam interference recording and collinear recording. The collinear method uses information light having a common optical axis generated by optically modulating laser light emitted from a laser light source with a spatial light modulator (SLM) and a reference light on a hologram recording medium. This is a method for recording data. The information light and the reference light having a common optical axis are condensed on the recording layer of the hologram recording medium, so that the information light and the reference light interfere in the recording layer, and interference fringes resulting from the interference appear in the recording layer. To be recorded. Further, by adopting shift multiplex recording in which the interference fringe recording area is moved so as to overlap in parallel with the recording layer, the recording capacity to the hologram recording medium is remarkably increased.

  Usually, a liquid crystal panel or a DMD (Digital Micromirror Device) is used as a spatial light modulator during data recording by the collinear method. When a liquid crystal panel is used, information light and reference light are generated by passing one laser beam through a liquid crystal panel whose dot pattern is controlled by a plurality of transparent electrodes (pixels). When the DMD is used, information light and reference light are generated by reflecting one laser beam on the DMD in which the directions of the plurality of micromirrors (pixels) are controlled.

  When reproducing the data recorded on the hologram recording medium, only the reference light is irradiated to the hologram recording medium. Reproduction light (diffracted light) is generated by diffracting the reference light with the interference fringes recorded on the hologram recording medium. The generated reproduction light is received by a photodetector comprising a plurality of pixels such as a CCD or CMOS. Then, data is reproduced based on the light reception signal output from each pixel of the photodetector.

  The reproduction light generated from the hologram recording medium at the time of data reproduction includes information reproduction light including recording data and reference reproduction light not including recording data. Of these, reference reproduction light is not necessary for data reproduction. Therefore, it is necessary to block the reference reproduction light out of the reproduction light and allow only the information reproduction light to enter the photodetector. Patent Document 1 discloses a hologram recording / reproducing apparatus in which only a information reproducing light is incident on a photodetector by installing a ring mask in front of the photodetector and blocking the reference reproducing light by the ring mask (Patent Document 1). 1 and paragraph 0062).

  When the hologram recording / reproducing apparatus is applied to, for example, an authentication apparatus disclosed in Patent Document 2, light including information is irradiated onto a hologram recording medium on which a plurality of data is recorded at the time of authentication. Then, light including information and light not including information are generated from the hologram recording medium. Among these, the light containing information is shielded, and the light not containing information is received by the photodetector. Whether or not the original data represented by the light including information is the same as the data recorded on the hologram recording medium is determined based on the intensity of the light that does not include the received information. Specific data is authenticated from a plurality of data by this determination of coincidence. Such coincidence determination by the authentication device corresponds to data reproduction. This authentication device is characterized in that the hologram recording medium is irradiated with light containing information, and the light containing the information out of the light generated from the hologram recording medium is shielded, and the light containing no information is incident on the photodetector. Is different from the hologram recording / reproducing apparatus for reproducing However, the type of light to be irradiated and the type of light to be blocked are only different from those at the time of data reproduction. Therefore, light containing information can be shielded by light shielding means such as a ring mask installed in front of the photodetector during data reproduction.

  Hereinafter, for the sake of simplicity, even when the hologram recording / reproducing apparatus is applied to an authentication apparatus, light including information among information irradiated on the hologram recording medium during data recording is used as information light, and light including no information is used as reference light. Of the light generated from the hologram recording medium at the time of authentication, light including information is referred to as information reproduction light, and light not including information is referred to as reference reproduction light. Further, in this specification, “authentication” may be included in data reproduction. In order to avoid confusion, normal data reproduction may be referred to as “data reproduction”.

  The cross-sectional shape of the reproduction light generated from the hologram recording medium is the same as the cross-sectional shape of the laser light irradiated onto the hologram recording medium during data recording. However, since the reproduction light is enlarged or reduced by an optical system that passes through until the light is received by the photodetector, the cross-sectional shape of the reproduction light just before being received by the photodetector and the laser irradiated to the hologram recording medium at the time of data recording The cross-sectional shape of light is not completely the same. However, the similar relationship between the two is maintained. Therefore, based on this similarity, the cross-sectional shape of the reproduction light at the position immediately before being received by the photodetector can be grasped. The boundary position between the information reproduction light and the reference reproduction light is obtained from the sectional shape of the reproduction light thus obtained. By installing a ring mask based on the obtained boundary position, only the information reproduction light or only the reference reproduction light is incident on the photodetector.

  Patent Document 3 discloses a means for detecting a boundary position between information reproduction light and reference reproduction light corresponding to a boundary position between information light and reference light based on a reference mark formed in an invariant data area obtained from reference light. And a means for changing the position and opening diameter of the light shielding plate corresponding to the ring mask in accordance with the boundary position thus detected. According to this, even when the boundary position between the information beam and the reference beam fluctuates, only the information reproduction beam is reliably detected by detecting the boundary position between the information reproduction beam and the reference reproduction beam with reference to the reference mark. Can be incident on a photodetector.

JP 2006-39181 A JP 2008-233186 A JP 2008-197575 A

  As described above, the cross-sectional shape of the laser light generated from the hologram recording medium at the time of data reproduction or authentication is similar to the cross-sectional shape of the laser light irradiated onto the hologram recording medium at the time of data recording. Therefore, when only the information reproduction light (reference reproduction light at the time of authentication) is received by the photo detector during data reproduction, the aperture diameter is based on the boundary position between the information reproduction light and the reference reproduction light obtained based on this similarity relationship. By installing the determined light shielding means in front of the photodetector, the reference reproduction light (information reproduction light at the time of authentication) can be blocked.

  By the way, a hologram recording / reproducing apparatus having a function of recording and reproducing data on various hologram recording media and evaluating the hologram recording medium based on the result is a sectional shape of information light and reference light at the time of data recording. In some cases, the hologram recording medium is irradiated with laser light having variously changed values. In such a case, since the cross-sectional shapes of the information reproduction light and the reference reproduction light also change variously, the light to be shielded according to each cross-sectional shape only by changing the aperture diameter of the single light shielding means at the time of data reproduction ( In the data reproduction, the reference reproduction light and the information reproduction light in the authentication cannot be shielded. If light-shielding means corresponding to each cross-sectional shape is prepared in advance and the light-shielding means corresponding to each cross-sectional shape is used at the time of reproduction, the light to be shielded can be shielded according to each cross-sectional shape, It is uneconomical. In addition, when the light to be shielded is arranged inside the light that is not shielded, the light shielding means cannot be held, and as a result, the light that should be shielded cannot be sufficiently shielded.

  The present invention has been made to cope with the above-described problem. Regardless of how the cross-sectional shapes of the information reproduction light and the reference reproduction light change, any one of the information reproduction light and the reference reproduction light during data reproduction is provided. One light (information reproduction light at the time of data reproduction, reference reproduction light at the time of authentication) is received by the photodetector, and the other light (reference reproduction light at the time of data reproduction, information reproduction light at the time of authentication) It is an object of the present invention to provide a hologram recording / reproducing apparatus that can shield only light from being received by a photo detector.

  A feature of the present invention is that a laser light source (10) that emits laser light and a plurality of pixels that can modulate the laser light form an incident surface on which the laser light emitted from the laser light source (10) is incident. A spatial light modulator (16) for generating information light and / or reference light from the laser light, and irradiating the hologram recording medium (HK) with information light or reference light generated by the spatial light modulator (16) Receiving either one of the information reproduction light and the reference reproduction light generated by the light receiving device, and outputting a signal corresponding to the intensity of the received light, and the signal output from the light receiving device (46). And a reproducing means (216, 220) for reproducing data recorded on the hologram recording medium (HK), the information reproducing light and the reference A light-blocking optical member (40) having a plurality of pixels disposed in an incident area where the information reproduction light and the reference reproduction light are incident, and the light-blocking optical member (40). A light-shielding optical member control means (208) for controlling the optical characteristics of each pixel, and the light-shielding optical member control means (208) is arranged in the incident area at the time of data reproduction. A first area where light is incident on the light shielding optical member (40) and a second area where the other light is incident on the light shielding optical member are set, and light incident on the first area is The optical characteristics of the pixels arranged in the first area and the second area are arranged so that the light incident on the light receiver (46) and incident on the second area does not enter the light receiver (46). To control the optical characteristics of It is to a hologram recording and reproducing apparatus, characterized by.

  According to the hologram recording / reproducing apparatus of the present invention, during data reproduction, the light-shielding optical member control means causes the first region where one of the information reproduction light and the reference reproduction light is incident on the light-shielding optical member; The second region where the other light enters is set. Further, the optical characteristics of the pixels arranged in the first region are controlled so that the light incident on the first region is incident on the light receiver, and the light incident on the second region is not incident on the light receiver. The optical characteristics of the pixels arranged in the second region are controlled. Since the optical characteristics of each pixel of the light shielding optical member are controlled in this way, the light incident on the first region (one of the information reproduction light and the reference reproduction light) enters the light receiver. . On the other hand, the light incident on the second region (the other of the information reproduction light and the reference reproduction light) is not incident on the light receiver.

  Since the light shielding optical member of the present invention has a plurality of pixels arranged in the incident area where the information reproduction light and the reference reproduction light are incident, the light shielding optical member control means controls the optical characteristics of each pixel. The shape of the first region that is the incident region of the light that should be incident on the light receiver and the shape of the second region that is the incident region of the light that should not be incident on the light receiver can be arbitrarily set. Therefore, the first region and the second region can be set according to the cross-sectional shapes of the incident information reproduction light and reference reproduction light regardless of how the sectional shapes of the information reproduction light and the reference reproduction light are changed. Then, by controlling the optical characteristics of the pixels arranged in each set region, only one of the lights can be received by the light receiver, and the other light can be blocked from being received by the light receiver. it can.

  In the present invention, “data reproduction” refers to not only normal data reproduction (data reproduction) in which data at the time of recording is created from data recorded on a hologram recording medium, and this data is decoded, but also recorded on the hologram recording medium. It is assumed that “authentication” for determining the coincidence between the specific data of the plurality of pieces of data and a certain data is included. When “data reproduction” is executed, only the reproduction light is generated by the spatial light modulator. Also, the information reproducing light is received by the light receiver. Therefore, in this case, one of the lights is information reproducing light, and the other light is reference reproducing light. On the other hand, when “authentication” is executed, only the information light is generated by the spatial light modulator. Further, the reference reproducing light is received by the light receiver. Therefore, in this case, one of the lights is a reference reproduction light, and the other light is an information reproduction light.

  The “light-shielding optical member” may be any material as long as it is composed of a plurality of pixels and can optically change the light incident on each pixel. For example, a liquid crystal panel or DMD is exemplified as the light shielding optical member. The “optical characteristic” is a property that represents an optical influence of a pixel on incident light. For example, transmittance, reflection angle, refractive index, frequency, etc. are exemplified as the optical characteristics. “Pixel” refers to the smallest unit constituting a two-dimensional digital image (digital data). When the light shielding optical member is a liquid crystal panel, the pixels are transparent electrodes arranged in the liquid crystal panel, and when the light shielding optical member is a DMD, the pixels are micromirrors.

  The hologram recording / reproducing apparatus of the present invention records data on the hologram recording medium (HK) by irradiating the hologram recording medium (HK) with information light and reference light generated by the spatial light modulator (16). It is preferable to have a recording function and to reproduce the data recorded on the hologram recording medium (HK) using the data recording function by the reproducing means (216, 220). According to this, data recording and reproduction can be performed by one hologram recording / reproducing apparatus.

  Further, the light-shielding optical member control means (208) sets an additional region that is formed continuously with the second region and surrounds the second region, and light incident on the additional region is reproduced during data reproduction. The optical characteristics of the pixels arranged in the additional region may be controlled so as not to enter the light receiver (46). According to this, the light incident on the second region and the additional region surrounding the second region is not incident on the light receiver. Therefore, even if light that should not be incident on the light receiver due to the optical axis fluctuation of the laser light protrudes from the second region, the light that should not be incident on the light receiver as long as the protruding region is included in the additional region Is not incident on the receiver. As a result, the light blocking performance that should not be incident on the light receiver is improved.

  Further, the hologram recording / reproducing apparatus of the present invention provides a pattern region that is a region for generating information light on the incident surface of the spatial light modulator (16) and a reference light that is a region for generating reference light during data recording. An area setting means (206) for setting an area and a light-shielding area that is neither an information beam nor a reference beam; and at the time of data recording, information to be recorded is converted into two-dimensional data and the converted two-dimensional data is output A recording data generating means (204) for generating and generating a signal for controlling the pixels arranged in the pattern area based on the two-dimensional data output by the recording data generating means during data recording Together with a signal for controlling the pixels arranged in the reference light region and a signal for controlling the pixels arranged in the light shielding region, the spatial light modulator And recording signal generating means for force (206), further may be provided with. Then, the light shielding optical member control means (208) is configured to select the first area and the second area based on the pattern area and the reference light area set by the area setting means (206) during data reproduction. Should be set. In this case, when the light shielding optical member control means sets the additional area in addition to the first area and the second area, the light shielding optical member control means sets the first area based on the pattern area and the reference light area. , A second area and an additional area may be set.

  According to this, the light shielding optical member control means includes the first area and the second area on the light shielding optical member based on the pattern area and the reference light area of the spatial light modulator set by the area setting means at the time of data recording. (Additional area) is set. Since the information reproduction light is light obtained by reproducing the information light generated from the pattern area of the spatial light modulator, the cross-sectional shape of the information reproduction light is the same as or similar to the shape of the pattern area. Further, since the reference reproduction light is light obtained by reproducing the reference light generated from the reference light region of the spatial light modulator, the cross-sectional shape of the reference reproduction light is the same as or similar to the shape of the reference light region. Therefore, the light shielding optical member control means can more appropriately set the first region and the second region in the light shielding optical member based on the pattern region and the reference light region formed in the spatial light modulator. .

  In this case, when executing “data reproduction”, the light shielding optical member control means reproduces an area corresponding to the pattern area (information light generated in the pattern area) among the incident areas of the light shielding optical member. An area where the information reproduction light is supposed to enter the light shielding optical member) is set as the first area, and the area corresponding to the reference light area (the reference reproduction light obtained by reproducing the reference light generated in the reference light area is used for light shielding). The region considered to be incident on the optical member may be set as the second region. On the other hand, when “authentication” is executed, the light shielding optical member control unit may set the area corresponding to the pattern area as the second area and set the area corresponding to the reference light area as the first area. Since light is not incident on the light shielding optical member in principle in the area corresponding to the light shielding area, the light shielding optical member control unit does not need to control the pixels arranged in these areas. If there is a region surrounding the second region in the region corresponding to, the region may be set as an additional region. Of the regions corresponding to the light shielding regions, the regions other than the additional regions and in contact with the regions corresponding to the pattern regions have the same optical characteristics as the regions corresponding to the pattern regions (in data reproduction). If there is a first area, and if it is authentication, it may be set as an area having the same optical characteristics as the second area. Further, among the regions corresponding to the light shielding regions, the regions other than the additional region and not in contact with the region corresponding to the pattern region have the same optical characteristics as the region corresponding to the reference light region (data It is preferable to set the second area for reproduction and the area having the same optical characteristics as the first area for authentication.

  In order to set the first region and the second region in the light shielding optical member based on each region formed in the spatial light modulator, each pixel position of the spatial light modulator and each of the light shielding optical member are set. The correspondence relationship with the pixel position must be clarified, but this relationship can be grasped in advance by experiments or the like. Therefore, the light-shielding optical member control means determines the correspondence relationship between each pixel position of the spatial light modulator and each pixel position of the light-shielding optical member, and the pattern region set in the spatial light modulator and the reference. Based on the light region, the first region and the second region (or additional region) may be set.

  Further, the recording signal generation means (206) may include a positioning pattern image for representing the position of the pattern area in the information light generated from the light incident on the pattern area at the time of data recording. It is preferable to generate a signal for controlling the pixels arranged in the pattern region. The hologram recording / reproducing apparatus detects an actual position where a positioning pattern image included in the information reproducing light is incident on the light receiver (46) during data reproduction based on a signal output from the light receiver (46). By comparing the detected actual position with a normal position that is predetermined as a normal position where the positioning pattern image is incident on the light receiver (46), the real position and the normal position are It is preferable to provide position change amount detecting means (214) for detecting the change amount. Then, the light shielding optical member control means (208) sets the first region to be set in the light shielding optical member (40) and the light shielding based on the change amount detected by the position change amount detection means (214). Deviation from the incident region of any one of the lights incident on the optical member for light (40), and incident on the second region set on the optical member for light shielding (40) and the optical member for light shielding (40) Preferably, the positions of the first region and the second region to be set are corrected so that there is no deviation from the incident region of the other light.

  The amount of change between the actual position and the normal position of the positioning pattern image formed on the light receiver is the first area and the second area set in the light shielding optical member based on the formation positions of the pattern area and the reference light area. And the amount of deviation between the information reproduction light actually incident on the light shielding optical member and the incident position of the reference reproduction light. Based on the amount of change, the first region, the information reproduction light, and the reference reproduction light are shifted from the incident region of one of the lights (light to be incident on the light receiver), and the second region and the other of the other ones. The deviation from the incident area of the light (light that should not be incident on the light receiver) is corrected. Therefore, for example, even when the optical axis angle of the laser beam reflected by the hologram recording medium (HK) is greatly changed and the incident areas of the information reproduction light and the reference reproduction light are greatly deviated from the set areas, the above correction can be performed accurately. The setting positions of the first area and the second area can be matched with the incident positions of the information reproduction light and the reference reproduction light. Thereby, the light to be received can be surely received by the light receiver, and the light that should not be received can be blocked.

  The light shielding optical member control means (208) is configured to prevent the light incident on the light shielding optical member (40) from entering the light receiver (46) during data recording. It is preferable to control the optical characteristics of all the pixels to the same optical characteristics. According to this, laser light reflected or transmitted from the hologram recording medium during data recording and incident on the light shielding optical member can be prevented from being received by the light receiver, and the life of the light receiver can be extended. Can do.

  The optical characteristic of each pixel of the light shielding optical member (40) controlled by the light shielding optical member control means (208) may be a transmittance or a reflection angle. The light shielding optical member (40) may be a liquid crystal panel or DMD. When the light-shielding optical member is a liquid crystal panel, the light-shielding optical member control means (208) may control the transmittance of the pixels of the liquid crystal panel. When the light-shielding optical member is a DMD, the light-shielding optical member control means (208) may control the direction (reflection angle) of the DMD micromirror. The hologram recording / reproducing apparatus of the present invention is suitable for reproducing and evaluating a hologram recording medium recorded by a collinear method. This is because the information reproducing light and the reference reproducing light generated from the hologram recording medium recorded by the collinear method have a common optical axis, and therefore it is highly necessary to block one light before the photodetector.

1 is an overall configuration diagram of a collinear hologram recording / reproducing apparatus according to an embodiment. It is a flowchart which shows the flow of a condition setting program. It is a figure showing the example of designation | designated of a pattern area | region, a non-light-shielding area | region, and a light-shielding area | region. It is a figure showing the example of a setting of a transmissive area | region and a non-transparent area | region. It is a figure showing the other example of specification of a pattern area | region, a non-light-shielding area | region, and a light-shielding area | region. It is a figure showing the other example of a setting of a transmissive area | region and a non-transmissive area | region. It is a figure showing the other example of specification of a pattern area | region, a non-light-shielding area | region, and a light-shielding area | region. It is a figure showing the other example of a setting of a transmissive area | region and a non-transmissive area | region. It is a figure showing an example of the pattern area in which the positioning pattern was formed. It is a figure showing the state where the transmissive area | region and non-transmissive | permeability area | region which were set to the liquid crystal for light shielding were corrected based on the shift | offset | difference of the actual position and positioning position of a positioning pattern image.

  Hereinafter, a hologram recording / reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a collinear hologram recording / reproducing apparatus according to the present embodiment. The hologram recording / reproducing apparatus 1 has a data recording function of recording data on the hologram recording medium HK by irradiating the hologram recording medium HK with information light and reference light having a common optical axis. Further, data reproduction is performed in which information reproduction light generated from the hologram recording medium HK is received by irradiating the hologram recording medium HK on which data is recorded, and the data is reproduced (reproduced) based on the intensity of the received light. It has a function. Further, it has a function of evaluating the hologram recording medium HK by detecting the error rate of the reproduction data with respect to the recording data. In addition, the hologram recording / reproducing apparatus 1 records data related to authentication on the hologram recording medium HK, and detects the intensity of the reference reproduction light generated when the hologram recording medium HK is irradiated with information light, thereby matching the data. The present invention can also be applied to an authentication device that determines the property.

  As shown in FIG. 1, a hologram recording / reproducing apparatus 1 includes a pickup device 100, a hologram recording / reproducing evaluation circuit 200, a table control circuit 300, a focus / tracking control circuit 400, a controller 500, a turntable 601, A spindle motor 602, a feed motor 603, a display device 701, and an input device 702. The controller 500 is a control unit that controls all operations of the hologram recording / reproducing apparatus 1.

  The pickup apparatus 100 includes a main laser light source 10 and a servo laser light source 48, collimating lenses 12 and 50, mirrors 14, 24 and 30, DMD (Digital Micromirror Device) 16, relay lenses 18 and 22, a polarizing beam splitter 20, and a dichroic prism. 26, 1/4 wavelength plate 28, objective lens 32, focus actuator 34, tracking actuator 36, beam splitter 52, condensing lenses 38 and 54, light shielding liquid crystal panel 40, relay lenses 42 and 44, cylindrical lens 56, for reproduction A photo detector 46 and a servo photo detector 58 are provided.

  The main laser light source 10 is an element that records data on the hologram recording medium HK and emits laser light for reproducing (reproducing) or authenticating the data. The collimating lens 12, the mirror 14, the DMD 16, the relay lens 18, the polarization beam splitter 20, the relay lens 22, the mirror 24, the dichroic prism 26, the quarter wavelength plate 28, the mirror 30, and the objective lens 32, are emitted from the main laser light source 10. An optical system is configured until the holographic recording medium HK is irradiated with the laser beam.

  The laser light emitted from the main laser light source 10 passes through the collimator lens 12 to become parallel light, and this parallel light is reflected by the mirror 14 and enters the DMD 16 that is a spatial light modulator. The DMD 16 has an incident surface formed by a plurality of micromirrors (pixels) capable of modulating incident laser light, and the laser light emitted from the main laser light source 10 is incident on the incident surface. By controlling the direction of each micromirror in the incident plane, the laser light incident on the DMD 16 is spatially modulated. The DMD 16 generates information light and / or reproduction light (information light and reproduction light at the time of data recording, reference light or information light at the time of data reproduction (reproduction) or authentication). The light generated by the DMD 16 passes through the relay lens 18, the polarization beam splitter 20, and the relay lens 22, and is further reflected by the mirror 24 to change the traveling direction. Thereafter, the light enters the dichroic prism 26. Information light and / or reproduction light passes through the dichroic prism 26, enters the objective lens 32 through the quarter-wave plate 28 and the mirror 30, and is condensed on the recording layer of the hologram recording medium HK.

  Information reproduction light and reference reproduction light generated from the hologram recording medium HK are incident on the dichroic prism 26 via the objective lens 32, the mirror 30, and the quarter wavelength plate 28. After passing through the dichroic prism 26, it is reflected by the mirror 24, enters the polarization beam splitter 20 through the relay lens 22. Since the laser beam incident on the polarization beam splitter 20 from the relay lens 22 side passes through the quarter-wave plate 28 twice, the polarization direction changes by 90 °, so that most of the laser beam is reflected. The light reflected by the polarization beam splitter 20 enters the light shielding liquid crystal panel 40 via the condenser lens 38.

  The light-shielding liquid crystal panel 40 is interposed in the optical path of the information reproduction light and the reference reproduction light generated from the hologram recording medium HK, and has an incident region where the information reproduction light and the reference reproduction light are incident. A plurality of pixels (for example, transparent electrodes) are arranged in this incident region. At the time of data reproduction, either one of the information reproduction light and the reference reproduction light is transmitted through the light-shielding liquid crystal panel 40, and the light-shielding light described later is prevented so that either one of the light does not transmit through the light-shielding liquid crystal panel 40. The signal generation circuit 208 controls the transmittance of each pixel of the light shielding liquid crystal panel 40.

  The light transmitted through the light shielding liquid crystal panel 40 is received by the reproducing photodetector 46 through the relay lenses 42 and 44. The reproduction photodetector 46 outputs a signal corresponding to the intensity of the received light for each pixel.

  The servo laser light source 48 is an element that emits laser light for focus servo control and tracking servo control. Optical until the hologram recording medium HK is irradiated with the laser light emitted from the servo laser light source 48 by the collimating lens 50, the beam splitter 52, the dichroic prism 26, the quarter wavelength plate 28, the mirror 30, and the objective lens 32. A system is constructed.

The laser light emitted from the servo laser light source 48 becomes parallel light by passing through the collimating lens 50, passes through the beam splitter 52, and is reflected by the dichroic prism 26. The laser beam reflected by the dichroic prism 26 is condensed on a track formed on the hologram recording medium HK via the quarter-wave plate 28, the mirror 30, and the objective lens 32. The reflected light from the condensing position is collimated by the objective lens 32, reflected by the mirror 30, further passes through the quarter wavelength plate 28, is reflected by the dichroic prism 26, and then enters the beam splitter 52. About half of the incident light is reflected and about half is transmitted. The reflected light reflected by the beam splitter 52 is received by a servo photo detector (for example, a quadrant photo detector) 58 via a condenser lens 54 and a cylindrical lens 56.

  When the focus of the laser beam emitted from the servo laser light source 48 is aligned with the track position of the hologram recording medium HK, the cross-sectional shape of the light spot received by the light receiving surface of the servo photo detector 58 is circular. On the other hand, when the focus of the laser beam is deviated from the track position of the hologram recording medium HK in the optical axis direction, the cross-sectional shape of the light spot formed on the light receiving surface of the servo photo detector 58 is long on the diagonal of the light receiving surface. It has an elliptical shape with an axis. Therefore, the amount of defocus can be detected as a signal by comparing and calculating the intensity of light received in each of the divided areas obtained by dividing the light receiving surface of the servo photo detector 58 vertically and horizontally. Focus servo control is performed so as to eliminate this defocus. In the present embodiment, focus servo control is performed by the astigmatism method.

  Further, the focal point of the laser light emitted from the servo laser light source 48 is a direction perpendicular to the optical axis direction of the laser light from the track position of the hologram recording medium HK and a direction perpendicular to the groove direction of the track (hereinafter referred to as this). If the direction is deviated in the radial direction), that is, if the focal position is deviated in the radial direction, the amount of light received in one of the left and right divided areas of the light receiving surface of the servo photodetector 58 However, the amount of light received by one of the other divided regions is smaller. When there is no radial displacement of the focal position, the amount of light received in the left divided area of the light receiving surface of the servo photo detector 58 is equal to the amount of light received in the right divided area. Therefore, by comparing and calculating the intensity of the light received in each divided area of the light receiving surface of the servo photo detector 58, the radial deviation of the focal position can be detected as a signal. Tracking servo control is performed so that this radial deviation is eliminated. In this embodiment, tracking servo control is performed by a push-pull method.

  The focus actuator 34 drives the objective lens 32 in the direction of the optical axis of the laser light in accordance with a drive signal from a drive circuit 416 described later when focus servo control is executed. The tracking actuator 36 drives the objective lens 32 in the radial direction in accordance with a drive signal from a drive circuit 410 described later when executing tracking servo control.

  The turntable 601 is a table on which the hologram recording medium HK is placed. The spindle motor 602 is a motor for rotating the turntable 601. The feed motor 603 is a motor for moving the turntable 601 in the radial direction of the hologram recording medium HK placed on the turntable 601.

  The table control circuit 300 includes a spindle motor control circuit 302, a radial position detection circuit 304, and a feed motor control circuit 306. The spindle motor control circuit 302 rotates the spindle motor 602 so that the number of pulses per unit time of the pulse signal input from the encoder in the spindle motor 602 corresponds to the rotation speed input from the controller 500. To control.

  The radial position detection circuit 304 inputs a pulse signal from an encoder built in the feed motor 603. The radial position detection circuit 304 inputs a pulse signal from the encoder during the initial position return operation of the feed motor 603 which is started immediately after the hologram recording / reproducing apparatus 1 is turned on, and the input is stopped. If so, set the initial radius position. Then, the moving distance in the radial direction of the turntable 601 is calculated by counting the number of pulses of the pulse signal that is input thereafter, and the moving distance is adjusted to the initial radial position, so that the hologram recording medium HK is recorded. The actual radius position representing the radial position of the laser beam irradiated on the sensor is calculated, and the calculated actual radius position is output to the controller 500 and the feed motor control circuit 306. The controller 500 calculates the rotational speed of the turntable 601 corresponding to a predetermined linear speed from the actual radial position input from the radial position detection circuit 304, and outputs the calculated rotational speed to the spindle motor control circuit 302. .

The feed motor control circuit 306 functions as follows.
When the power of the hologram recording / reproducing apparatus 1 is turned on, the driving is started and the feed motor 603 is initially driven to the driving limit position (initial position returning operation).
A feed motor 603 is input so that the actual radial position is input from the radial position detection circuit 304 and the turntable 601 moves in the radial direction where the actual radial position matches the radial position input from the controller 50 during data recording and reproduction. Is driven at a predetermined feed rate. Further, when the actual radius position matches the irradiation end position input from the controller 50, the drive of the feed motor 603 is stopped.
When a thread servo start command is input from the controller 500, the number of pulses per unit time of the pulse signal input from the encoder built in the feed motor 603 corresponds to the feed speed input from the thread servo circuit 418 described later. The rotation of the feed motor 603 is controlled so as to be a number.

  The focus / tracking control circuit 400 is a circuit for executing focus servo control and tracking servo control, and includes a servo laser drive circuit 402, a signal amplification circuit 404, a tracking error signal (TE signal) generation circuit 406, and a tracking servo circuit. 408, a drive circuit 410, a focus error signal (FE signal) generation circuit 412, a focus servo circuit 414, a drive circuit 416, and a sled servo circuit 418.

  The servo laser drive circuit 402 supplies voltage and current to the servo laser light source 48 so that laser light with a predetermined intensity is emitted from the servo laser light source 48 when an operation start command is input from the controller 500. To do.

  The signal amplifying circuit 404 inputs a signal output from each divided region of the light receiving surface of the servo photo detector 58 and amplifies the input signal. The amplified signal is converted into a tracking error signal (TE signal) generating circuit 406 and a focus error. This is output to the signal (FE signal) generation circuit 412.

  The tracking error signal generation circuit 406 generates a tracking error signal by applying each amplified signal input from the signal amplification circuit 404 to an arithmetic expression (a + b) − (c + d) by a push-pull method, and tracks the generated tracking error signal. Output to the servo circuit 408. Note that a, b, c, and d in the above expression represent light reception signals output from the respective photodetectors arranged in the respective divided areas when the light receiving surface of the servo photodetector 58 is divided into four parts in the vertical and horizontal directions. Specifically, for servo, the direction corresponding to the groove direction of the track formed on the hologram recording medium HK placed on the turntable 601 is defined as the vertical direction, and the direction corresponding to the radial direction is defined as the horizontal direction. The output signal of the photodetector arranged in the divided area located in the upper right of the light receiving surface of the photodetector 58 is a, the output signal of the photodetector arranged in the divided area located in the lower right is b, and arranged in the divided area located in the lower left. The output signal of the photodetector is c, and the output signal of the photodetector arranged in the divided area located at the upper left is d.

  The tracking servo circuit 408 creates a tracking servo signal representing the amount of movement of the objective lens 32 in the radial direction necessary for setting the input tracking error signal to 0, and outputs the created tracking servo signal to the drive circuit 410. . The drive circuit 410 supplies a signal for driving the objective lens 32 in the radial direction to the tracking actuator 36 based on the input tracking servo signal. Tracking servo control is executed by driving the tracking actuator 36 based on the supplied signal.

  The focus error signal generation circuit 412 generates a focus error signal by applying each amplified signal input from the signal amplification circuit 404 to an arithmetic expression (a + c) − (b + d) based on the astigmatism method, and the generated focus error signal Output to the focus servo circuit 414.

  The focus servo circuit 414 receives a focus error signal, creates a focus servo signal that represents the amount of movement of the objective lens 32 in the optical axis direction necessary for setting the input focus error signal to 0, and creates the focus servo signal. Is output to the drive circuit 416. The drive circuit 416 supplies a signal for driving the objective lens 32 in the optical axis direction of the laser light to the focus actuator 34 based on the input focus servo signal. The focus servo control is executed by driving the focus actuator 34 based on the supplied signal.

  The sled servo circuit 418 receives the tracking servo signal from the tracking servo circuit 408, detects the DC component of the signal, and creates a signal representing the feed speed of the feed motor 603 necessary to make this DC component zero. The generated signal is output to the feed motor control circuit 306. The DC component of the tracking servo signal corresponds to a deviation from the neutral position of the objective lens 32. By driving the feed motor 603 so as to eliminate this deviation, the focal point of the servo laser beam moves in the radial direction following the track groove of the hologram recording medium HK.

  The hologram recording / reproducing evaluation circuit 200 records data on the hologram recording medium HK using the pickup device 100, reproduces (reproduces or authenticates) the recording data of the hologram recording medium HK, and based on the reproduction result, the hologram recording medium HK. It is a circuit for evaluating. The hologram recording / reproducing evaluation circuit 200 includes a main laser driving circuit 202, a recording binarized data generating circuit 204, a DMD control signal generating circuit 206, a shading signal generating circuit 208, a luminance data generating circuit 210, and a reproducing unit. A binarized data generation circuit 212, a position change amount detection circuit 214, a reproduction data generation circuit 216, an error rate detection circuit 218, and a light amount detection circuit 220.

  The main laser driving circuit 202 starts driving when an operation start command is input from the controller 500, and supplies voltage and current to the main laser light source 10 so that laser light with a predetermined intensity is emitted from the main laser light source 10. To do.

  The recording binarized data generation circuit 204 sets the number of units of recording data (original data) (data amount for each conversion into two-dimensional binarized data) according to a command from the controller 500. Also, recording data (original data) is input from the controller 500, and the recording data (original data) is converted into two-dimensional binarized data (“0”, “1” on the two-dimensional plane) for each set number of units. In the arranged data, the number of the data is converted (encoded) to correspond to the number of micromirrors in the pattern area described later. Then, the converted binarized data is output to the DMD control signal generation circuit 206.

  The DMD control signal generation circuit 206 has a memory. Then, according to a command from the controller 500, a pattern area, a non-light-shielding area, and a light-shielding area to be formed on the incident surface of the DMD 16 are set, and a part of the memory area is assigned to the pattern area, the non-light-shielding area, and the light-shielding area, respectively. Allocate to the memory area to output data. Further, the DMD control signal generation circuit 206 generates a signal for controlling the orientation of the micromirrors arranged in the pattern area based on the two-dimensional binarization data input from the recording binarization data generation circuit 204. create. The created data is stored in a memory area that outputs data to the pattern area.

  The pattern area, the non-light-shielding area, and the light-shielding area are all areas formed on the incident surface of the DMD 16. The direction of the micromirrors arranged in each region is controlled by data output from the memory of the DMD control signal generation circuit 206. At the time of data recording, the direction of the micromirror arranged in the pattern area is set to the two-dimensional binarization generated by the recording binary data generation circuit 204 by the laser beam reflected by the micromirror arranged in this area. Information light including a pattern image representing data is formed, and the information light is controlled by data output from the DMD control signal generation circuit 206 so as to enter the hologram recording medium HK. The direction of the micromirrors arranged in the non-light-shielding region is such that the reference light is formed by the laser light reflected in the region and the reference light is incident on the hologram recording medium HK. It is controlled by the data output from 206. The direction of the micromirrors arranged in the light shielding area is determined from the DMD control signal generation circuit 206 so that the laser light reflected in the area does not enter the hologram recording medium HK, that is, neither information light nor reference light is generated. Controlled by output data. In this embodiment, the orientation of the micromirrors arranged in the pattern area is controlled so that the information light generated in the pattern area of the DMD 16 includes a positioning pattern image for representing the position of the pattern area. Is done. This positioning pattern image is included in the information reproduction light at the time of data reproduction.

  The shading signal generation circuit 208 has a memory. Then, based on a command from the controller 500, a transmissive area and a non-transmissive area are set in the incident area of the light-shielding liquid crystal panel 40, and a part of the memory area represents the transmittance of pixels arranged in the transmissive area. The memory area for outputting data and the memory area for outputting data representing the transmittance of the pixels arranged in the non-transparent area are allocated. In the memory area for outputting data representing the transmittance of the transmissive area, data for setting the transmittance to the maximum value is stored, and in the memory area for outputting data representing the transmittance of the non-transmissive area. Stores data for setting the transmittance to the minimum value. The stored data is output to the light shielding liquid crystal panel 40 during data reproduction. The memory of the light shielding signal generation circuit 208 also stores data for setting the transmittance of all the pixels of the light shielding liquid crystal panel 40 to the minimum value. This data is output to the light-shielding liquid crystal panel 40 when data is recorded on the hologram recording medium HK.

  Further, the light shielding signal generation circuit 208 receives information indicating the correspondence between the position of each pixel of the light shielding liquid crystal panel 40 and the position of each pixel of the reproducing photodetector 46 from the controller 500 or the light shielding liquid crystal panel 40. Information indicating the relationship between the direction and distance and the direction and distance of the reproduction photodetector 46 is input. The shading signal generation circuit 208 stores such information in a memory.

  The luminance data generation circuit 210 starts operation when an operation command is input from the controller 500, converts the intensity value of the signal for each pixel output by the reproduction photodetector 46 into digital data (luminance data) related to luminance, and Data and pixel position data corresponding to the luminance data are output in association with each other.

  The light amount detection circuit 220 starts operation when an operation command is input from the controller 500, and based on the luminance data of each pixel output from the luminance data generation circuit 210, the reproduction light intensity for each recording data of the hologram recording medium HK. Is output to the controller 500. The controller 500 stores the input reproduction light intensity, determines the coincidence between the recording data and the authentication target data when the reproduction light intensity is equal to or greater than the threshold value, and when the authentication target data matches the recording data by the data processing A comparison result between the reproduction light intensity and the average value or maximum value of the reproduction light intensity when the data to be authenticated does not match the recorded data is acquired.

  The reproduction binarized data generation circuit 212 starts operation when an operation command is input from the controller 500, and the position data of each pixel of the reproduction photo detector 46 output from the luminance data generation circuit 210 and the position of the pixel are output. Two-dimensional binarized data is generated and output based on the corresponding luminance data. The two-dimensional binarized data is data corresponding to the data output from the recording binarized data generation circuit 204.

  The reproduction data generation circuit 216 starts operation when an operation command is input from the controller 500, and converts the two-dimensional binarized data output from the reproduction binary data generation circuit 212 into recording data (original data). Is converted (decoded) into data corresponding to the above, and the converted data is output.

  The error rate detection circuit 218 starts to operate when an operation command is input from the controller 500, and the data output from the reproduction data generation circuit 216 and the recording data (original data) input from the controller 500 and stored in the memory. ) And calculate the error rate by dividing the number of errors by the number of data. The calculated error rate is output to the controller 500.

  The position change amount detection circuit 214 inputs, from the controller 500, a position (normal position) obtained in advance as a normal position where the positioning pattern image included in the information reproduction light is to be received by the reproduction photodetector 46. Record. When the operation command is input from the controller 500, the operation is started. From the position data output from the luminance data generation circuit 210 and the luminance data corresponding to the position data, the reproduction pattern detector 46 actually receives the positioning pattern image. The detected position (actual position) is detected. Further, the position change amount detection circuit 214 moves the light receiving surface of the reproducing photodetector 46 in the X direction between the normal position and the actual position represented on the plane defined by the X direction (X axis) and the Y direction (Y axis). A deviation amount and a deviation amount in the Y direction are calculated. The shift amount in the X direction is output to the light shielding signal generation circuit 208 as the X direction position change data, and the shift amount in the Y direction is output as the Y direction position change data. The light shielding signal generation circuit 208 corresponds to the input X-direction position change data and Y-direction position change data, and the stored positions of the pixels of the light-shielding liquid crystal panel 40 and the positions of the pixels of the reproduction photodetector 46. With reference to the relationship or the like, the X direction position change data and the Y direction position change data are converted into X direction position change data and Y direction position change data in the incident region of the light shielding liquid crystal panel 40. Then, the set transmission region and non-transmission region are corrected so that the transmission region and the non-transmission region move by the amount of change represented by the converted X-direction position change data and Y-direction position change data.

  In the hologram recording / reproducing apparatus 1 configured as described above, when an operator evaluates the hologram recording medium HK, first, the instruction to set the hologram recording medium HK on the turntable 601 and set the conditions on the input device 702 is performed. Enter. As a result, the controller 500 starts the condition setting program shown in FIG. When the condition setting program is started, the controller 500 first evaluates “data reproduction” or “authentication” in step 102 (hereinafter, step number is abbreviated as S) 102 in FIG. Are displayed on the display device 701, and the operator is prompted to select one of them. Thereafter, the display is repeated until the input is completed (S104). The operator selects “data reproduction” when evaluating “data reproduction”, and selects “authentication” when evaluating “authentication”.

  After either “data reproduction” or “authentication” is selected, the controller 500 causes the display device 701 to display an area designation screen for the pattern area, the non-light-shielded area, and the light-shielded area in S106, and the operator selects it. Prompt for area specification. Thereafter, the display is repeated until the area designation by the operator is completed (S108). The operator designates each area using the display device 701. The designation method of each area may be a system in which “graphic”, “position”, “diameter”, etc. are designated by language or numerical value, or the DMD 16 is displayed on the display device 701 and each area is displayed on the displayed DMD 16. The method of designating may be used.

  Since the information light is generated from the pattern area and the reference light is generated from the non-shielding area, the pattern area and the non-shielding area are designated outside the incident range of the laser light incident on the DMD 16. Can not. Accordingly, the size and position of the cross section of the laser light incident on the DMD 16 are displayed on the display device 701 by numerical values such as “diameter” and “position”, or by graphic display, etc., so that the operator can recognize the incident range of the laser light. By doing so, it is possible to prevent the pattern area and the non-light-shielding area from being designated outside the laser light incident range.

  FIG. 3 is a diagram illustrating an example of the designated pattern area, non-light-shielding area, and light-shielding area. In the drawing, shaded areas are light shielding areas (inner light shielding areas and outer light shielding areas), areas indicated by dots are pattern areas, and non-pattern areas are non-light-shielding areas. In addition, an incident range of the laser beam is represented by a region surrounded by a dotted line. According to this example, the pattern region R1 is formed at substantially the center of the incident range of the laser beam, and the ring-shaped non-light-shielding region R2 is formed so as to surround the periphery thereof. An inner light-shielding region R3 is formed between the ring-shaped non-light-shielding region R2 and the pattern region R1. An outer light shielding region R4 is formed on the outer peripheral side of the non-light shielding region R2. The non-light-shielding region R2 corresponds to the reference light region of the present invention.

  In the pattern region R1, a positioning pattern for representing the position of the region is formed. FIG. 9 is a diagram illustrating a state in which the positioning pattern is formed in the pattern region R1. As shown in FIG. 9, the positioning pattern is formed in the pattern region R1 so that the positioning pattern having a simple shape becomes a dark portion (a portion where the laser beam reflected by the portion does not enter the hologram recording medium HK). . The shape and position of the positioning pattern may be designated by the operator, or may be preset and stored in the memory of the controller 500.

  When the designation of each area by the operator is completed (S108: Yes), the controller 500 outputs an area setting command to the DMD control signal generation circuit 206 in S110. Thereby, the DMD control signal generation circuit 206 calculates the positions of the pattern area, the non-light-shielding area, and the light-shielding area on the incident surface of the DMD 16 based on the pattern area, the non-light-shielding area, and the light-shielding area specified by the operator. A pattern area, a non-light-shielding area, and a light-shielding area to be formed on the incident surface of the DMD 16 are set. In addition, the DMD control signal generation circuit 206 allocates a part of the memory area to a memory area that outputs data to each area. Further, the DMD control signal generation circuit 206 empties the memory area for outputting data to the pattern area. Further, the output memory area outputs data to the non-light-shielding area. The laser light reflected by the micromirrors arranged in this area is irradiated with reference light to the hologram recording medium HK. Filled with certain data to control the orientation. The memory area that outputs data to the light shielding area is for controlling the orientation of the micromirrors arranged in this area so that the laser beam reflected by the micromirrors arranged in this area is not irradiated onto the hologram recording medium HK. Filled with certain data.

  Next, the controller 500 outputs a unit number setting command to the recording binary data generation circuit 204 in S112. Thus, the recording binarized data generation circuit 204 converts the recording data (original data) into two-dimensional binarized data based on the number of micromirrors arranged in the pattern area input from the controller 500. Set the number of units.

  Subsequently, the controller 500 outputs a transmission / non-transmission area setting command to the light shielding signal generation circuit 208 in S114. As a result, the light shielding signal generation circuit 208 sets a transmissive region and a non-transmissive region to be formed in the incident region of the light shielding liquid crystal panel 40. Specifically, each pixel of the light-shielding liquid crystal panel 40 is classified into a pixel arranged in the transmissive region and a pixel arranged in the non-transmissive region. At the same time, the light-shielding signal generation circuit 208 partially transmits the memory area for outputting data representing the transmittance of the pixels arranged in the transmissive area and the transmission of the pixels arranged in the non-transmissive area. It is allocated to the memory area for outputting data representing the rate. Further, the light-shielding signal generation circuit 208 fills the memory area for outputting data representing the transmittance of the pixels arranged in the transmissive area with data for setting the pixel transmittance to the maximum value, and the non-transmissive area. The memory area for outputting the data representing the transmittance of the pixels arranged in is filled with data for setting the transmittance of the pixel to the minimum value.

  The transmissive region and the non-transmissive region are determined based on the pattern region, the non-shielded region, and the shielded region set in the DMD 16. The correspondence relationship between the position of each micro mirror of the DMD 16 and the position of each pixel of the light shielding liquid crystal panel 40 is stored in the controller 500 in advance. Therefore, the light-shielding signal generation circuit 208 receives the correspondence relationship and the positional information of the pattern area, the non-light-shielding area, and the light-shielding area from the controller 500, and based on these input information, the light-transmitting area and the non-transparent area are determined. Can be set.

  4 (a) and 4 (b) show the signal generation for shading when “data reproduction” is selected in S102 and the pattern area, non-light-shielding area and light-shielding area are set as shown in FIG. FIG. 6 is a diagram illustrating a transmissive region and a non-transmissive region set in the incident region of the light-shielding liquid crystal panel by the circuit. In FIGS. 4A and 4B, the hatched area is a non-transmissive area, and the other area (non-pattern area) is a transmissive area. A region surrounded by two circles indicated by dotted lines is a region (non-shielding correspondence region) corresponding to the non-shielding region R2 formed in the DMD 16, and this non-shielding correspondence region S2 is included in the non-shielding correspondence region S2. Reference reproduction light generated by the hologram recording medium HK enters. Further, an area surrounded by a dotted line formed near the center of the figure is an area (pattern corresponding area) corresponding to the pattern area R1 formed in the DMD 16, and this pattern corresponding area S1 includes a hologram at the time of data reproduction. Information reproduction light generated on the recording medium HK enters.

  As can be seen from FIGS. 4A and 4B, the non-transmissive region is composed of a non-light-shielding corresponding region S2 and an additional non-transmissive region S4. The non-light-shielding corresponding region S2 is a region where the reference reproduction light is incident as described above. The additional non-transmissive region S4 is a region that is formed continuously with the non-light-shielding corresponding region S2 and surrounds the non-light-shielding corresponding region S2. Specifically, the additional non-transmissive region S4 is a region corresponding to the outer light shielding region R4 formed in the DMD 16 (outer light shielding corresponding region) and a part of the region corresponding to the inner light shielding region R3 formed in the DMD 16. Thus, the predetermined area is continuous from the inner boundary of the non-light-shielding corresponding area S2. Therefore, when the non-light-shielding corresponding region S2 is formed in a ring shape as shown in the figure, the additional non-transparent region S4 includes a region continuing from the inner boundary of the non-light-shielding corresponding region S2, and a region continuing from the outer boundary. It is divided into. In FIG. 4, the additional non-transparent area S4 that continues from the outer boundary of the non-light-shielding corresponding area S2 is set over the entire outer light-shielding corresponding area provided outside the non-light-shielding corresponding area S2. However, since light does not enter the outside of the region where the reference reproduction light is incident, it is not necessary to set the additional non-transmissive region S4 in the entire region in this way, and a predetermined region continuous from the outer boundary of the non-light-shielding corresponding region S2. An additional non-transparent area S4 may be set.

  In addition, a region other than the non-transmissive region is set as a transmissive region. Therefore, the transmissive area includes a pattern corresponding area S1 and an additional transmissive area S3 that is continuous with the pattern corresponding area S1 and surrounds the entire pattern corresponding area S1.

  When a light transmission signal generation circuit 208 receives a transmission / non-transmission area setting command from the controller 500, first, in the incident area of the light shielding liquid crystal panel 40, a pattern corresponding area that is an area where information reproduction light is incident upon data reproduction. S1 and a non-shielding-corresponding region S2, which is a region where reference reproduction light enters during data reproduction, are set. Next, an additional transmissive region S3 surrounding the pattern corresponding region S1 and an additional non-transmissive region S4 surrounding the non-light-shielding corresponding region S2 are set. Then, the pattern corresponding area S1 and the additional transmissive area S3 are set as transmissive areas, and the non-light-shielding corresponding area S2 and the additional non-transmissive area S4 are set as non-transmissive areas.

  Incidentally, the reason why the additional non-transmissive area S4 is set as the non-transmissive area is as follows. When reproducing the data of the hologram recording medium HK, the hologram recording medium HK rotates. However, the normal direction of the rotation peripheral surface of the hologram recording medium HK changes due to surface shake during rotation. When the normal direction changes, the optical axis position of the reproduction light generated from the hologram recording medium HK changes. When the optical axis position of the reproduction light changes, extra light may enter the reproduction photodetector 46. For this reason, the additional non-transmission region S4 is set so that excessive light does not enter the reproducing photodetector 46 even if the optical axis position changes.

  The additional non-transmissive region S4 is a part of a region corresponding to the light shielding region formed in the DMD 16 and is a region continuous with the non-light shielding corresponding region S2. Any shape may be used as long as it is a region surrounded from the inside. The boundary between the additional non-transmissive region S4 and the transmissive region (additional transmissive region S3) may be set along a circle representing the inner boundary of the non-light-shielding corresponding region S2, for example, as shown in FIG. Alternatively, as shown in FIG. 4B, it may be set along a line representing the boundary of the pattern corresponding region S1.

  In this example, the pattern corresponding region S1 that is a transmissive region corresponds to the first region of the present invention, and the non-light-shielding corresponding region S2 that is a non-transmissive region corresponds to the second region of the present invention. Further, the additional non-transmissive area S4 which is a non-transmissive area corresponds to the additional area of the present invention.

  When “authentication” is selected in S102, the light-shielding signal generation circuit 208 sets the transmission region (pattern corresponding region S1 and additional transmission region S3) shown in FIG. 4 as a non-transmission region. The transmissive area (non-light-shielding corresponding area S2 and additional non-transmissive area S4) is set as the transmissive area. Therefore, in this case, the non-light-shielding corresponding region S2 that is the transmissive region corresponds to the first region of the present invention, and the pattern corresponding region S1 that is the non-transmissive region corresponds to the second region of the present invention and is the non-transmissive region. The transmissive region S3 corresponds to the additional region of the present invention.

  The correspondence between the position of the micromirror arranged on the incident surface of the DMD 16 and the position of the pixel arranged on the incident area of the light shielding liquid crystal panel 40 can be determined in advance as follows. First, each micromirror of the DMD 16 is controlled so that the laser beam reflected from the DMD 16 forms a specific pattern on the hologram recording medium HK. By irradiating the DMD 16 controlled in this manner with laser light, the pattern is stored as interference fringes on the hologram recording medium HK. Further, the reproduction light (reference reproduction light and information reproduction light) generated from the hologram recording medium HK is received by the reproduction photodetector 46 with a certain point of the light-shielding liquid crystal panel 40 in a non-transmissive state. Then, in the pattern formed by the received light, a dark spot that is generated when one point of the light-shielding liquid crystal panel 40 is made non-transmissive is formed. By associating a specific position in the incident surface of the DMD 16 corresponding to the dark spot with a position in the incident area of the light shielding liquid crystal panel 40 that is in a light shielding state, the position of the micromirror of the DMD 16 and the light shielding liquid crystal panel 40 are matched. Are associated with each other. Further, by associating a specific position of a specific pattern formed on the reproduction photodetector 46 with a position on the incident surface of the DMD 16 corresponding to the specific position, the position of the micromirror of the DMD 16 and the reproduction photodetector 46 are correlated. The positions of the pixels arranged on the light receiving surface are associated with each other. The correspondence relationship between the position of each micromirror of the DMD 16 and each pixel position of the light shielding liquid crystal panel 40 and the correspondence relationship between each micromirror position of the DMD 16 and each pixel position of the reproduction photodetector 46 are stored in the controller 500 in advance. ing.

  Note that the example of area designation shown in FIG. 3 is merely an example, as long as data can be recorded as interference fringes due to interference between the information light and the reference light generated by the DMD 16 in the hologram recording medium HK. Each area may be designated as. For example, each area may be designated as shown in FIG. According to this, the rectangular pattern region R1 is formed substantially at the center of the incident surface, and the non-light-shielding region R2 having a rectangular outer shape is formed so as to surround the periphery. The light shielding area includes an inner light shielding area R3 and an outer light shielding area R4, and an inner light shielding area R3 is formed between the pattern area R1 and the non-light shielding area R2, and an outer light shielding area R4 is formed outside the non-light shielding area R2. The FIG. 6 is a diagram showing a non-transmissive region (shaded portion) and a transmissive region (portions other than the shaded portion) set in the light-shielding liquid crystal panel 40 when each region of the DMD 16 is designated and set as shown in FIG. It is.

  Further, the pattern area, the light shielding area, and the non-light shielding area formed on the DMD 16 can be designated as shown in FIG. According to FIG. 7, a circular non-light-shielding region R2 is formed beside the rectangular pattern region R1. That is, the non-light-shielding region R2 does not surround the pattern region R1. For this reason, the light-shielding region R5 is represented as a single region without being divided by the non-light-shielding region R2. FIG. 8 is a diagram showing a non-transmissive region (shaded portion) and a transmissive region (portions other than the shaded portion) set in the light-shielding liquid crystal panel 40 when each region designation and setting of the DMD 16 is performed as shown in FIG. It is. As can be seen from FIG. 8, the non-transmissive region is formed by a circular non-shielding corresponding region S2 and a ring-shaped additional non-transmissive region S4 that is continuous with the non-shielding corresponding region S2 and surrounds the non-shielding corresponding region. The In FIG. 8, all the areas outside the non-transmission area except the pattern corresponding area S1 are made the additional transmission area S3. However, the boundary between the additional transmission area S3 and the additional non-transmission area S4 is the pattern corresponding area S1. It may be set at any position between the non-light-shielding corresponding region S2 and may be set near the pattern corresponding region S1, for example, as in FIG. 4B.

After outputting the transmission / non-transmission area setting command in S114, the controller 500 proceeds to S116 and displays a condition input screen on the display device 701 so as to input other conditions. The operator inputs necessary conditions according to the condition input screen. Examples of the input conditions include the following conditions.
(1) Type of data to be recorded (2) Radiation start radius position (3) Radiation end radius position (4) Rotational speed of hologram recording medium HK placed on turntable 601 (5) Pattern formed on DMD 16 Change rate (6) Data to be authenticated when “authentication” is performed

  When the input of the above conditions is completed (S118: Yes), the controller 500 ends the condition setting program. This program is executed when it is necessary to set conditions to be input in S102, S106, and S116. If these conditions are already stored in the memory of the controller 500, the execution of this program can be omitted by using the stored conditions.

  After executing the condition setting program, the operator inputs a command representing “data recording” to the controller 500 from the input device 702. Then, the controller 500 outputs the recording data to the recording binary data generation circuit 204. Thus, the recording binarized data generation circuit 204 converts (encodes) the input recording data into two-dimensional binarized data, and outputs the two-dimensional binarized data to the DMD control signal generation circuit 206. The DMD control signal generation circuit 206 creates data for controlling the direction of the micromirrors arranged in the pattern region R1 of the DMD 16 based on the input two-dimensional binarized data. In this case, the DMD control signal generation circuit 206 creates data so that the positioning pattern is formed in a portion that does not affect the binarized data in the pattern area. The data thus created is stored in a memory area that outputs data to the pattern area.

As described above, in the memory of the DMD control signal generation circuit 206, the memory area that outputs data to the non-light-shielded area has a fixed data (the laser beam reflected by the micromirrors arranged in the non-light-shielded area is recorded on the hologram). The memory area where data is output to the light-shielding area is also reflected by the micromirrors arranged in the light-shielding area. The data is filled with data that controls the orientation of the micromirror so that the laser beam is not irradiated onto the hologram recording medium HK.

  Next, the controller 500 outputs a command indicating “data recording” to the light shielding signal generation circuit 208. When a command indicating “data recording” is input, the light shielding signal generation circuit 208 outputs data for setting the transmittance to the minimum value to each pixel of the light shielding liquid crystal panel 40. Thereby, all the incident areas of the light shielding liquid crystal panel 40 are set to the non-transmissive areas. Therefore, at the time of data recording, the light incident on the light shielding liquid crystal panel 40 from the polarization beam splitter 20 side is blocked by the light shielding liquid crystal panel 40 and does not enter the reproducing photodetector 46.

  Next, the controller 500 sets a time interval for outputting recording data to the DMD control signal generation circuit 206. This time interval is calculated based on the pattern change speed of the DMD 16 input when the condition setting program is executed. Thereafter, the controller 500 outputs a rotation command to the spindle motor control circuit 302 and a drive command to the feed motor control circuit 306. As a result, the drive of the feed motor 603 is controlled so that the irradiation position of the laser beam moves from the irradiation start radius position to the irradiation end radius position, and the hologram recording medium HK placed on the turntable 601 has a predetermined value. The rotational drive of the spindle motor 602 is controlled so as to rotate at the rotational speed. Further, the controller 500 outputs an operation start command to the servo laser drive circuit 402. As a result, servo laser light is emitted from the servo laser light source 48. The servo laser light is applied to the hologram recording medium HK through the optical system, and the reflected light is received by the servo photodetector 58. Focus servo control and tracking servo control are performed based on the intensity of light received by the servo photodetector 58.

  In addition, the controller 500 outputs a drive command to the main laser drive circuit 202. As a result, laser light is emitted from the main laser light source 10. Also, a command indicating “data recording” is output to the DMD control signal generation circuit 206. Thereby, the DMD control signal generation circuit 206 sets the data for controlling the orientation of the micromirrors arranged in the pattern area of the DMD 16 for each unit and the data for controlling the orientation of the micromirrors arranged in the non-shielding area and the light shielding area. Are output to the DMD 16 at set time intervals together with data for controlling the direction of the micromirrors arranged in the. The DMD 16 forms a pattern area, a non-light-shielding area, and a light-shielding area on its incident surface by controlling the orientation of each micromirror based on the input data.

  The laser light emitted from the main laser light source 10 enters the DMD 16 through the collimating lens 12 and the mirror 14. Information light representing recording data is generated by the light incident on the pattern area of the DMD 16, and reference light is generated by the light incident on the non-light-shielding area of the DMD 16. The information light includes a positioning pattern image. Information light and reference light generated by the DMD 16 enter the hologram recording medium HK placed on the turntable 601 via the optical system. Information light and reference light interfere with each other on the recording layer of the hologram recording medium HK. Interference fringes generated at the time of interference are recorded on the recording layer of the hologram recording medium HK. Since the recording data binarized at every set time interval is sequentially output from the DMD control signal generation circuit 206 to the DMD 16, information light and reference light representing the recording data are sequentially output to the hologram recording medium HK. The interference fringes generated by the interference with the shift multiple recording. Further, when the feed motor 603 is driven during data recording, the irradiation radius position of the laser beam on the turntable 601 approaches the irradiation end radius position from the irradiation start radius position. Data recording is completed when the irradiation radius position of the laser beam reaches the irradiation end radius position. When the data recording is completed, the emission of the laser beam for recording is stopped.

  When the recording of data on the hologram recording medium HK is completed, “recording complete” is displayed on the display device 701. Thereafter, the worker inputs a command representing “reproduction” from the input device 702 to the controller 500. At this time, if “data reproduction” is selected in the condition setting program, the controller 500 outputs a command representing “data reproduction” to the DMD control signal generation circuit 206. When the DMD control signal generation circuit 206 receives a command indicating “data reproduction”, the laser beam reflected by the micromirrors arranged in the non-shielding region among the regions formed on the DMD 16 during data recording is recorded on the hologram recording medium. Data for controlling each micromirror of the DMD 16 is output so that the laser beam incident on the HK and reflected by the micromirror disposed in the other region does not enter the hologram recording medium HK. In this case, the data is output only once.

  In addition, the controller 500 outputs a command indicating “data reproduction” to the light shielding signal generation circuit 208. When a signal indicating “data reproduction” is input, the light shielding signal generation circuit 208 outputs the data stored in the memory to the light shielding liquid crystal panel 40. As a result, among the pixels arranged in the incident area of the light-shielding liquid crystal panel 40, the transmittance of the pixels arranged in the transmission area set in S114 of the condition setting program is set to the maximum value, and the non-transmission area is set. The transmittance of the arranged pixels is set to the minimum value.

  In addition, the controller 500 outputs an operation command to the luminance data generation circuit 210, the position change amount detection circuit 214, the reproduction data generation circuit 216, and the error rate detection circuit 218. Then, the irradiation position of the main laser beam is returned to the irradiation start radius position, the laser beam is emitted from the main laser light source 10, and data reproduction is started.

  Laser light emitted from the main laser light source 10 during reproduction enters the DMD 16. At this time, the laser light reflected by the micromirrors arranged in the non-light-shielding region of the DMD 16 enters the hologram recording medium HK, and the laser light reflected by the micromirrors arranged in other regions is incident on the hologram recording medium HK. The direction of the micromirrors arranged in each region is controlled so as not to enter. Therefore, only the reference light reflected by the non-shielding region among the laser light incident on the DMD 16 is incident on the hologram recording medium HK via the optical system.

  When reference light is irradiated onto the hologram recording medium HK on which data has been recorded, the reference light is diffracted by the interference fringes formed in the recording layer of the hologram recording medium HK, thereby generating information reproduction light and reference reproduction light. Is done. The cross-sectional shape of the information reproduction light is the same as or similar to the cross-sectional shape of the information light, and the cross-sectional shape of the reference reproduction light is the same or similar to the cross-sectional shape of the reference light. The generated information reproduction light and reference reproduction light pass through the objective lens 32, the mirror 30, the quarter wavelength plate 28, the dichroic prism 26, the mirror 24, the relay lens 22, the polarization beam splitter 20, and the condenser lens 38. The light enters the light shielding liquid crystal panel 40.

  The light shielding liquid crystal panel 40 forms a transmissive region and a non-transmissive region based on data input from the light shielding signal generation circuit 208. Therefore, the laser light incident on the transmission region is transmitted through the light shielding liquid crystal panel 40, but the laser light incident on the non-transmission region is not transmitted through the light shielding liquid crystal panel 40. Although the reference reproduction light is incident on the non-shielding corresponding region S2 of the light shielding liquid crystal panel 40, the reference reproduction light is not transmitted through the light shielding liquid crystal panel 40 because the non-shielding correspondence region S2 is a non-transmissive region. On the other hand, the information reproducing light is incident on the pattern corresponding region S1 of the light shielding liquid crystal panel 40. Since the pattern corresponding area S1 is a transmission area, the information reproduction light is transmitted through the light shielding liquid crystal panel 40. That is, the reference reproduction light is blocked by the light shielding liquid crystal panel 40, and only the information reproduction light passes through the light shielding liquid crystal panel 40. In this case, the additional non-transmissive region S4 that is continuously provided so as to surround the non-light-shielding corresponding region S2 of the light-shielding liquid crystal panel 40 is also set as the non-transmissive region, so that it enters the light-shielding liquid crystal panel 40. Even when the position where the reference reproduction light is incident on the light-shielding liquid crystal panel 40 is slightly changed due to the change in the optical axis position of the laser light, the light is shielded by being incident on the additional non-transmissive region S4.

  The information reproduction light that has passed through the light shielding liquid crystal panel 40 is received by the reproduction photodetector 46. The reproduction photodetector 46 outputs a signal corresponding to the received light intensity to the luminance data generation circuit 210. The luminance data generation circuit 210 converts the input signal into luminance data, associates the luminance data with the position data corresponding to the luminance data, and outputs it to the binarized data generation circuit 212.

  The binarized data generation circuit 212 generates two-dimensional binarized data based on the position data of each pixel of the reproduction photodetector 46 input from the luminance data generation circuit 210 and the luminance data corresponding to the position of the pixel. The generated binarized data is output to the position change amount detection circuit 214 and the reproduction data generation circuit 216. The reproduction data generation circuit 216 decodes the two-dimensional binarized data input from the binarized data generation circuit 212 and outputs the decoded data to the controller 500 and the error rate detection circuit 218. The error rate detection circuit 218 compares the data input from the reproduction data generation circuit 216 with the original data input from the controller 500, and calculates an error rate by dividing the number of errors by the number of data. The calculated error rate is output to the controller 500. The controller 500 calculates a playback evaluation result based on the error rate, and outputs the evaluation result to the display device 701. This completes the data reproduction evaluation.

  Further, when data recording to the hologram recording medium HK is completed and the operator inputs a command indicating “reproduction” from the input device 702 to the controller 500, and “authentication” is selected in the condition setting program, The controller 500 outputs a command indicating “authentication” to the DMD control signal generation circuit 206. As a result, the DMD control signal generation circuit 206 causes the laser beam reflected by the micromirrors arranged in the pattern area among the areas formed in the DMD 16 at the time of data recording to become information light based on the data to be authenticated, and the hologram recording medium Data for controlling each micromirror of the DMD 16 is output so that the laser light incident on the HK and reflected by the micromirrors arranged in other areas does not enter the hologram recording medium HK.

  Further, the controller 500 outputs a command indicating “authentication” to the light shielding signal generation circuit 208. When a signal indicating “authentication” is input, the light shielding signal generation circuit 208 outputs data for controlling the transmittance of each pixel of the light shielding liquid crystal panel 40 to the light shielding liquid crystal panel 40. In this case, the light-shielding signal generation circuit 208 sets the non-light-shielding corresponding region S2 and the additional non-transmissive region S4 of the light-shielding liquid crystal panel 40 as transmissive regions, and other regions (pattern corresponding region S1 and additional transmissive region S3). ) Is set to the non-transmissive area, and the transmittance of each pixel is set so that the transmittance of the pixel arranged in the transmissive area becomes the highest value and the transmittance of the pixel arranged in the non-transmissive area becomes the lowest value. Data for control is output to the light-shielding liquid crystal panel 40.

  Further, the controller 500 outputs an operation command to the luminance data generation circuit 210 and the light amount detection circuit 220. Then, the irradiation position of the main laser light is returned to the irradiation start radius position, and the laser light is emitted from the main laser light source 10 to start authentication.

  Laser light emitted from the main laser light source 10 at the time of authentication enters the DMD 16. Only the information light is generated by the light reflected by the micromirrors arranged in the pattern area of the DMD 16. The generated information light is applied to the hologram recording medium HK on which data has been recorded via an optical system. The information reproduction light and the reference reproduction light are generated by diffracting the information light by the interference fringes formed in the recording layer of the hologram recording medium HK. The generated information reproduction light and reference reproduction light are incident on the light shielding liquid crystal panel 40.

  The light-shielding liquid crystal panel 40 is formed with a transmissive region and a non-transmissive region as described above. The transmissive area includes a non-light-shielding corresponding area S2 and an additional non-transmissive area S4, and the non-transmissive area includes a pattern corresponding area S1 and an additional transmissive area S3. Therefore, the reference reproduction light incident on the non-light shielding corresponding region S2 is transmitted through the light shielding liquid crystal panel 40, and the information reproduction light incident on the pattern corresponding region S1 is not transmitted through the light shielding liquid crystal panel 40. That is, only the reference reproduction light passes through the light shielding liquid crystal panel 40. The reference reproduction light that has passed through the light shielding liquid crystal panel 40 is received by the reproduction photodetector 46.

  The reproduction photodetector 46 that has received the reference reproduction light outputs a signal corresponding to the received light intensity to the luminance data generation circuit 210. The luminance data generation circuit 210 converts the input signal into luminance data, associates the luminance data with position data corresponding to the luminance data, and outputs the luminance data to the light amount detection circuit 220. The light amount detection circuit 220 calculates the reproduction light intensity for each recording data of the hologram recording medium HK based on the input signal and outputs it to the controller 500. The controller 500 stores the input reproduction light intensity, determines the coincidence between the recording data and the authentication target data when the reproduction light intensity is greater than or equal to the threshold value, and the data when the authentication target data matches the recording data. A comparison result between the reproduction light intensity and the average value or maximum value of the reproduction light intensity when the data to be authenticated does not match the recording data is acquired. Then, the controller 500 outputs the evaluation result of the hologram recording medium HK to the display device 701 based on the acquired coincidence determination result and comparison result. This completes the evaluation of authentication. Thus, at the time of authentication, the light amount detection circuit 220 and the controller 500 correspond to authentication means (reproduction means).

  Since the information light applied to the hologram recording medium HK during data recording includes a positioning pattern image representing the position of the pattern area, the information reproducing light generated during data reproduction also includes the positioning pattern image. Therefore, when “data reproduction” is selected, a positioning pattern image is formed on the light receiving surface of the reproduction photodetector 46. Based on the formation position of the positioning pattern image, the positions of the transmissive region and the non-transmissive region formed on the light-shielding liquid crystal panel 40 are corrected as follows.

  When “data reproduction” is performed, the position change amount detection circuit 214 forms a positioning pattern image on the light receiving surface of the reproduction photodetector 46 based on the binarized data input from the reproduction binary data generation circuit 212. The position (actual position) to be calculated is calculated. Then, the amount of deviation between this actual position and the normal position (normal position) where the positioning pattern image is to be formed on the light receiving surface of the reproducing photodetector 46 is calculated. The amount of deviation is expressed as X-direction position change data and Y-direction position change data when the light receiving surface of the reproduction photodetector 46 is defined in the X direction and the Y direction. Then, the position change amount detection circuit 214 outputs the calculated X direction position change data and Y direction position change data to the light shielding signal generation circuit 208.

The light-shielding signal generation circuit 208 corresponds to the correspondence between each pixel position of the light-shielding liquid crystal panel 40 and each pixel position of the reproduction photodetector 46, or the direction and distance of the light-shielding liquid crystal panel 40 and the direction of the reproduction photodetector 46. Based on the relationship with the distance, the X direction position change data and the Y direction position change data input from the position change amount detection circuit 214 are defined when the incident area of the light shielding liquid crystal panel 40 is defined in the X direction and the Y direction. The X direction position change data and the Y direction position change data in the incident area of the light shielding liquid crystal panel 40 are converted. The position change amount represented by the converted position change data is the amount of deviation between the pattern corresponding area S1 set in the light shielding liquid crystal panel 40 and the incident area of the information reproducing light actually incident on the light shielding liquid crystal panel 40, and The deviation amount between the non-light-shielding corresponding region S2 set in the light-shielding liquid crystal panel 40 and the incident region of the reference reproduction light that actually enters the light-shielding liquid crystal panel 40 is represented. Therefore, the light-shielding signal generation circuit 208 has the positions of the transmission region (pattern corresponding region S1 and additional transmission region S3) and the non-transmission region (non-light-shielding corresponding region S2 and additional non-transmission region S4) by the converted position change amount. Modify data stored in memory to move. By outputting the corrected data to the light shielding liquid crystal panel 40, the shift between the reference reproduction light incident area to the light shielding liquid crystal panel 40 and the non-light shielding corresponding area S2 and the light shielding liquid crystal panel 40 are output. The deviation between the incident area of the information reproducing light and the pattern corresponding area S1 is corrected.

  FIG. 10 is a diagram illustrating a state where the transmissive region and the non-transmissive region in which the above-described deviation is corrected are set in the light-shielding liquid crystal panel 40. In the figure, G1 represents the position (position corresponding to the actual position) where the positioning pattern image is actually formed on the light-shielding liquid crystal panel 40 before correcting the deviation, and G2 corresponds to the normal position of the positioning pattern image. This represents the normal position of the pattern image on the light-shielding liquid crystal panel 40. As can be seen, G1 and G2 are shifted in the X and Y directions. Therefore, the formation positions of the pattern corresponding area S1 and the non-light-shielding corresponding area S2 are corrected so that the position corresponding to G1 of the pattern corresponding area becomes G2, that is, the shift amount is eliminated, and accordingly, the additional transmission area S3 is corrected. And the formation position of the additional non-transmissive region S4 is also corrected. When the position of each region is corrected in this manner, the optical axis position of the reproduction light generated from the hologram recording medium HK changes by a predetermined range or more (that is, the reference reproduction light protrudes from the additional non-transmission region). Even when the position of the optical axis changes), only the information reproducing light can be accurately incident on the reproducing photodetector 46.

  According to the present embodiment, the light-shielding liquid crystal panel 40 as the light-shielding optical member is disposed in front of the reproducing photodetector 46. The light-shielding liquid crystal panel 40 has an incident area where information reproduction light and reference reproduction light are incident, and a plurality of pixels are arranged in the incident area. Further, the transmittance, which is one of the optical characteristics of each pixel, is controlled by the light shielding signal control circuit 208. The light-shielding signal control circuit 208 sets a pattern corresponding area S1 where information reproduction light is incident and a non-light-shielding corresponding area S2 where reference reproduction light is incident within the incident area of the light-shielding liquid crystal panel 40. The transmittance of the pixels arranged in the pattern corresponding region S1 is set to the highest value (the lowest value at the time of authentication) so that the information reproduction light incident on the region S1 enters the reproduction photodetector 46 (not to be incident at the time of authentication). The transmittance of the pixels arranged in the non-shielding corresponding region S2 is set to the lowest value (so that the reference reproduction light entering the non-shielding corresponding region S2 does not enter the reproducing photodetector 46 (so that it is incident upon authentication). Set to the highest value at the time of authentication. Therefore, no matter how the cross-sectional shapes of the information reproduction light and the reference reproduction light change, the pattern corresponding region S1 and the non-shielding corresponding region S2 are set according to the cross-sectional shapes of the incident information reproduction light and reference reproduction light. Thus, only one of the lights (information reproduction light at the time of data reproduction, reference reproduction light at the time of authentication) is received by the reproduction photodetector 46, and one of the other lights (reference at the time of data reproduction). Reproduction light, or information reproduction light at the time of authentication) can be shielded from being received by the reproduction photodetector 46.

  The hologram recording / reproducing apparatus 1 has a data recording function for recording data on the hologram recording medium HK by irradiating the hologram recording medium HK with information light and reference light generated by the DMD 16. The data recorded on the hologram recording medium HK can be reproduced. For this reason, data recording and reproduction can be performed by one hologram recording / reproducing apparatus.

  Further, the light-shielding signal control circuit 208 is continuously formed in the non-light-shielding corresponding region S2 and the additional non-transparent region S4 surrounding the non-light-shielding corresponding region S2 and the pattern corresponding region S1 during data reproduction. In addition, an additional transparent area S3 surrounding the pattern corresponding area S1 is set. Then, at the time of data reproduction, the transmittance of the pixels arranged in the additional non-transmissive region S4 is set to the lowest value so that the light incident on the additional non-transmissive region S4 does not enter the reproduction photodetector 46, and authentication is performed. If so, the transmittance of the pixels arranged in the additional transmission region S3 is set to the lowest value so that the light incident on the additional transmission region S3 does not enter the reproduction photodetector 46. For this reason, even if light that should not be incident on the reproduction photodetector 46 due to an optical axis fluctuation of the laser light protrudes from the non-shielding corresponding region S2 (or pattern corresponding region S1), the protruding region is an additional non-transmissive region. As long as it is included in S4 (or the additional transmission region S3), light that should not be incident on the reproduction photodetector 46 is not incident. As a result, the light blocking performance that should not be incident on the reproducing photodetector 46 is improved.

  Further, at the time of data recording, the DMD control signal generation circuit 206 uses the DMD 16 incident surface to generate information light on a pattern area, a non-light-shielding area to generate reference light, and information light and reference light. A light blocking area that is not generated is set. Further, at the time of data recording, the information to be recorded is converted into two-dimensional binary data by the binary data generation circuit 204, and the converted two-dimensional binary data is output to the DMD control signal generation circuit 206. Is done. Then, the DMD control signal generation circuit 206 generates a signal for controlling the micromirrors arranged in the pattern area of the DMD 16 based on the input two-dimensional binarized data, The signal is output to the DMD 16 together with a signal for controlling the micromirrors arranged in the light shielding area and a signal for controlling the micromirrors arranged in the light shielding area. Thereby, at the time of data recording, information light is generated from the pattern area of the DMD 16 and reference light is generated from the non-light-shielding area.

  Since the information reproduction light is light obtained by reproducing the information light generated from the pattern area of the DMD 16, the cross-sectional shape of the information reproduction light is the same as or similar to the shape of the pattern area. Further, since the reference reproduction light is light obtained by reproducing the reference light generated from the non-light-shielding region of the DMD 16, the cross-sectional shape of the reference reproduction light is the same as or similar to the shape of the non-light-shielding region. Therefore, the light shielding signal generation circuit 208 more appropriately determines the pattern corresponding region and the non-light shielding corresponding region to be set in the light shielding liquid crystal panel 40 during data reproduction based on the pattern region and the non-light shielding region formed in the DMD 16. Can be set.

  In addition, the DMD control signal generation circuit 206 includes a positioning pattern image for indicating the position of the pattern area in the information light generated from the light incident on the pattern area of the DMD 16 at the time of data recording. A signal for controlling the arranged micromirror is generated. Further, the position change amount detection circuit 214 is based on the signal output from the reproduction photo detector 46, and the actual position where the positioning pattern image included in the information reproduction light is formed on the reproduction photo detector 46 during data reproduction (reproduction). Is detected, and the detected actual position is compared with a normal position that is determined in advance as a normal position at which the positioning pattern image is to be formed on the reproduction photodetector 46, whereby the positioning formed on the reproduction photodetector 46 is detected. A change amount between the actual position and the normal position of the pattern image is detected. The light-shielding signal generation circuit 208 is based on the amount of change detected by the position change amount detection circuit 214 and the pattern corresponding region S1 set in the light-shielding liquid crystal panel 40 and the incident region of the information reproduction light incident on the light-shielding liquid crystal panel 40. The pattern corresponding region S1 to be set and the non-light shielding corresponding region S2 set in the light shielding liquid crystal panel 40 and the reference reproduction light incident region incident on the light shielding liquid crystal panel 40 are eliminated. The position of the non-light shielding corresponding region S2 is corrected. For this reason, even if the optical axis angle of the laser beam reflected by the hologram recording medium HK changes greatly and the incident area of the information reproduction light and the reference reproduction light deviates greatly from the set area, the above-described correction can accurately handle the pattern. The formation position of the area S1 and the incident position of the information reproduction light, and the formation position of the non-light-shielding corresponding area S2 and the incidence position of the reference reproduction light can be matched. As a result, it is possible to reliably block light that should not be received by the reproducing photodetector 46.

  Further, the light-shielding signal generation circuit 208 sets the transmittance of all the pixels of the light-shielding liquid crystal panel 40 to the lowest value so that light incident on the light-shielding liquid crystal panel 40 does not enter the reproduction photodetector 46 during data recording. To do. Therefore, it is possible to prevent the reproducing photodetector 46 from receiving the laser light reflected or transmitted from the hologram recording medium HK and entering the light shielding liquid crystal panel 40 during data recording.

  As mentioned above, although embodiment of this invention was described, this invention should not be limited to the said embodiment, A various change is possible. For example, although the DMD is used as the spatial light modulator in the above embodiment, a liquid crystal panel that transmits laser light may be used instead. In the case of a liquid crystal panel, a pattern area, a non-light-shielding area, and a light-shielding area are formed by setting the transmittance of each pixel to the highest value or the lowest value. In the above-described embodiment, a positioning pattern is formed in the pattern area, and a change in the position of the positioning pattern is detected by detecting the deviation between the actual position of the pattern image formed on the reproduction photodetector 46 and the normal position. The positions of the pattern corresponding area and the non-light-shielding corresponding area to be formed on the light-shielding liquid crystal panel 40 are corrected according to the deviation of the incident position of the laser light on the liquid crystal panel 40, but the reproduced light from the hologram recording medium HK If a mechanism for setting the hologram recording medium HK on the turntable 601 is provided so that the change in the optical axis is within a predetermined range, such correction is not necessary. In this case, it is possible to prevent excess light from entering the reproducing photodetector 46 due to the optical axis shift of the laser light only by forming the additional non-transmissive region in the light shielding liquid crystal panel 40. According to this, the cost of an apparatus can be suppressed.

  Further, according to the above embodiment, the light shielding liquid crystal panel 40 is used to shield unnecessary light out of the reproduction light generated from the hologram recording medium HK. Any means may be used as long as it can set the incident area of the light that should be incident on the reproducing photodetector 46 and the incident area of the light that should not be incident by controlling the optical characteristics. For example, DMD may be used.

  In the above embodiment, since the direction of the micromirrors arranged in the non-light-shielding region formed in the DMD 16 is controlled by the same data, the direction of the micromirrors arranged in this region is the same, and this region The light quantity distribution of the reference light generated from the laser beam remains the same as the laser light emitted from the laser light source. That is, the reference light is ordinary laser light. However, the DMD control signal generation circuit 206 outputs to the DMD 16 data for controlling the orientation of the micromirrors arranged in this area so that a predetermined pattern (a pattern representing the reference light) is formed in the non-light-shielding area. It may be a thing. In the above embodiment, the spindle motor 602 and the turntable 601 are moved by the feed motor 603 so that the laser light spot on the hologram recording medium HK is moved in the radial direction. You may make it the structure moved by the feed motor 603. FIG. Also by this, the same effect as the above embodiment can be obtained. As described above, the present invention can be variously modified without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 ... Hologram recording / reproducing apparatus, 10 ... Main laser light source, 16 ... DMD (spatial light modulator), 40 ... Light-shielding liquid crystal panel (light-shielding optical member), 46 ... Reproducing photo detector (light receiver), 100 ... Pick-up apparatus , 200 ... Hologram recording / reproduction evaluation circuit, 202 ... Main laser drive circuit, 204 ... Recording binary data generation circuit (recording data generation means), 206 ... DMD control signal generation circuit (area setting means, recording signal generation) Means), 208 ... Shading signal generation circuit (light shielding optical member control means), 210 ... Luminance data generation circuit, 212 ... Reproduction binary data generation circuit, 214 ... Position change amount detection circuit (position change amount detection means) 216: Reproduction data generation circuit (reproduction means) 218: Error rate detection circuit 220: Light quantity detection circuit (reproduction means) 300: Table Control circuit 400 ... Focus tracking control circuit 500 ... Controller 601 ... Turntable 602 ... Spindle motor 603 ... Feed motor 701 ... Display device 702 ... Input device R1 ... Pattern area R2 ... Non-shielding area , R3 ... inner light-shielding region, R4 ... outer light-shielding region, R5 ... light-shielding region, S1 ... pattern-corresponding region, S2 ... non-light-shielding region, S3 ... additional transmission region, S4 ... additional non-transmission region

Claims (6)

A laser light source (10) for emitting laser light;
A spatial light modulator for forming an incident surface on which laser light emitted from the laser light source (10) is incident by a plurality of pixels capable of modulating laser light, and generating information light and / or reference light from the incident laser light (16) and
Light received by receiving either information reproduction light or reference reproduction light generated by irradiating the hologram recording medium (HK) with information light or reference light generated by the spatial light modulator (16) A light receiver (46) for outputting a signal corresponding to the intensity of
In a hologram recording / reproducing apparatus comprising reproduction means (216, 220) for reproducing data recorded on the hologram recording medium (HK) based on a signal output from the light receiver (46),
A light-shielding optical member (40) having a plurality of pixels disposed in an incident region where the information reproduction light and the reference reproduction light are incident, and is interposed in an optical path of the information reproduction light and the reference reproduction light;
A light shielding optical member control means (208) for controlling the optical characteristics of each pixel of the light shielding optical member (40),
The light-shielding optical member control means (208) includes a first region in which the one light is incident on the light-shielding optical member (40) and the other light in the incident region during data reproduction. Sets a second region that is incident on the light shielding optical member, light incident on the first region is incident on the light receiver (46), and light incident on the second region is the light receiver (46). The hologram recording / reproducing apparatus controls the optical characteristics of the pixels arranged in the first area and the optical characteristics of the pixels arranged in the second area so as not to be incident on the first area. The hologram recording / reproducing apparatus according to claim 1,
A data recording function for recording data on the hologram recording medium (HK) by irradiating the hologram recording medium (HK) with information light and reference light generated by the spatial light modulator (16); A hologram recording / reproducing apparatus, wherein data recorded on a hologram recording medium (HK) using a function is reproduced by the reproducing means (216, 220). The hologram recording / reproducing apparatus according to claim 2,
The light-shielding optical member control means (208) sets an additional area that is formed continuously with the second area and surrounds the second area, and light incident on the additional area is received during data reproduction. A hologram recording / reproducing apparatus, wherein the optical characteristics of the pixels arranged in the additional region are controlled so as not to enter the device (46). The hologram recording / reproducing apparatus according to claim 2 or 3,
At the time of data recording, a pattern region that is a region for generating information light on the incident surface of the spatial light modulator (16), a reference light region that is a region for generating reference light, and neither information light nor reference light is generated. An area setting means (206) for setting a light shielding area, which is an area;
Recording data generating means (204) for converting information to be recorded into two-dimensional data at the time of data recording and outputting the converted two-dimensional data;
At the time of data recording, a signal for controlling the pixels arranged in the pattern area is generated based on the two-dimensional data output by the recording data generating means, and the generated signal is arranged in the reference light area. Recording signal generation means (206) for outputting to the spatial light modulator together with a signal for controlling the pixel and a signal for controlling the pixel arranged in the light shielding region,
The light shielding optical member control means (208) sets the first area and the second area based on the pattern area and the reference light area set by the area setting means (206) during data reproduction. A holographic recording / reproducing apparatus comprising: The hologram recording / reproducing apparatus according to claim 4,
The recording signal generating means (206) is arranged such that, during data recording, the information light generated from the light incident on the pattern area includes a positioning pattern image for representing the position of the pattern area. Generate a signal to control the pixels arranged in the area,
The hologram recording / reproducing apparatus detects and detects the actual position where the positioning pattern image included in the information reproducing light is incident on the light receiver (46) during data reproduction based on the signal output from the light receiver (46). The amount of change between the actual position and the normal position by comparing the actual position with a normal position that is predetermined as a normal position where the positioning pattern image is incident on the light receiver (46). A position change amount detecting means (214) for detecting
The light shielding optical member control means (208) is configured to set the first region and the light shielding optical to be set in the light shielding optical member (40) based on the change amount detected by the position change amount detection means (214). Deviation from the incident region of any one of the light incident on the member (40), and the second region set in the light shielding optical member (40) and the light incident on the light shielding optical member (40) A hologram recording / reproducing apparatus, wherein the positions of the first region and the second region to be set are corrected so that there is no deviation from the incident region of the other light. The hologram recording / reproducing apparatus according to any one of claims 2 to 5,
The light shielding optical member control means (208) is configured to prevent all light incident on the light shielding optical member (40) from entering the light receiver (46) during data recording. A hologram recording / reproducing apparatus, wherein the optical characteristics of the pixels are controlled to the same optical characteristics.

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