Abstract:
The present invention provides a technology which estimates the most suitable cure time which changes with the environment when recording a hologram and adjusts the cure time in real time, thereby enabling a suitable pre-cure or post-cure. When irradiating an optical information recording medium with cure light, the light transmitted from the optical information recording medium is detected by a detector and the irradiation time is adjusted by continuing irradiation until the intensity of the transmitted light detected exceeds a prescribed reference value.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority from Japanese Patent Application No. 2011-216004, filed Sep. 30, 2011, the entire contents of which are incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a device, a method, and a medium for recording or reproducing information onto or from an optical information recording medium by using holography. 
       BACKGROUND ART 
       [0003]    At the present time, it is possible to commercialize an optical disc having a recording density of approximately 100 GB for the people&#39;s livelihood as well owing to Blu-ray Disc™ standards using a blue-violet colored semiconductor laser. In the future, a large capacity exceeding 500 GB is desired in optical discs as well. For implementing such an ultra-high density in optical discs, however, a density increasing technique using a new system different from the conventional density increasing technique using a shorter wavelength and a high NA is needed. 
         [0004]    Among studies conducted concerning storage techniques, the hologram recording technique for recording digital information by utilizing holography attracts attention. As for the hologram recording technique, for example, there is JP-A-2004-272268 (Patent Literature 1). The so-called angle multiplex recording system, in which different page data are displayed on a spatial light modulator while changing an incidence angle of a reference beam to an optical information recording medium and multiplex recording is conducted, is described in JPA-2004-272268. In addition, a technique of shortening the spacing between adjacent holograms by condensing a signal beam with a lens and disposing an aperture (spatial filter) in its beam waist is described in JP-A-2004-272268. Furthermore, as for the hologram recording technique, there is, for example, WO2004-102542 (Patent Literature 2). An example using a shift multiplex system is described in WO2004-102542. In one spatial light modulator, a beam from inner side pixels is used as a signal beam and a beam from outer side ring-shaped pixels is used as a reference beam. Both beams are condensed onto an optical information recording medium by using the same lens. A hologram is recorded by causing interference between the signal beam and the reference beam near a focus plane of the lens. 
         [0005]    Furthermore, for example, in JP-A-6-84762 (Patent Literature 3), there is the following description. “At the time of hologram recording, a monitor beam  40  differing in wavelength from a reference beam  18  and an object beam  28  is incident on a prism  16  obliquely. A hologram recording medium  17  is irradiated with the monitor beam  40 . A part of the monitor beam  40  reflected by an inner face of the hologram recording medium  17  is diffracted by a formed hologram. The monitor beam  40  that is not diffracted is transmitted by the hologram recording medium  17 , emitted from an oblique plane on the opposite side of the prism  16 , and detected by a detector  31 . The recording state of the hologram is detected by detecting at least one of the diffracted beam and the non-diffracted beam of the monitor beam  40 . The exposure condition can be optimized on the basis of the detected recording state of the hologram.” 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PATENT LITERATURE 1: JP-A-2004-272268 
         PATENT LITERATURE 2: WO2004-102542 
         PATENT LITERATURE 2: JP-A-6-84762 
       
     
       SUMMARY OF INVENTION 
     Technical Problem  
       [0009]    By the way, at the time of hologram information recording, pre-exposure processing or post-exposure processing called cure is needed. However, an optimum cure time changes depending upon an environment at the time of information recording. Therefore, it is difficult to conduct optimum cure, resulting in a problem in putting a holographic memory to practical use. 
         [0010]    In Patent Literature 3, cure processing in a device for storing information in a holographic memory is not considered at all. Especially, the pre-exposure processing is not considered at all. 
         [0011]    An object of the present invention is to provide a technique that makes optimum cure possible by adjusting the cure time in real time when recording information. 
       Solution to Problem  
       [0012]    The problem to be solved by the invention can be solved by the invention stated in claims. 
       Advantageous Effects of Invention  
       [0013]    According to the present invention, it becomes possible to conduct suitable cure irrespective of the environment at the time of recording by adjusting cure time in real time when conducting the pre-exposure processing. Or when conducting the post-exposure processing, it becomes possible to reduce excessive cure time and prevent insufficient cure. 
         [0014]    Other objects, features and advantages of the present invention will become apparent from ensuing description of embodiments of the present invention with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1  is a flow chart showing an embodiment of an operation (embodiment 1); 
           [0016]      FIG. 2  is a configuration diagram showing an embodiment of an optical information recording and reproduction device; 
           [0017]      FIG. 3  is a diagram showing an embodiment of a pickup in the optical information recording and reproduction device (at the time of recording); 
           [0018]      FIG. 4  is a diagram showing an embodiment of a pickup in the optical information recording and reproduction device (at the time of reproduction); 
           [0019]      FIG. 5  is a diagram showing an embodiment of operation flows of the optical information recording and reproduction device; 
           [0020]      FIG. 6  is a schematic diagram showing examples of accumulated exposure energy and an accumulated reproduction light quantity in an optical information recording medium (embodiment 1); 
           [0021]      FIG. 7  is a diagram showing an embodiment of a disc cure optical system in the optical information recording and reproduction device (embodiment 1); 
           [0022]      FIG. 8  is a diagram showing an embodiment of a disc cure optical system in the optical information recording and reproduction device (embodiment 2); 
           [0023]      FIG. 9  is a schematic diagram showing an example of a relation between cure exposure time and transmitted light quantity (embodiment 3); 
           [0024]      FIG. 10  is a flow chart showing an embodiment of operation (embodiment 3); 
           [0025]      FIG. 11  is a diagram showing an embodiment of the optical information recording medium (embodiment 4); 
           [0026]      FIG. 12  is a configuration diagram showing an embodiment of the optical information recording and reproduction device (embodiment 4); 
           [0027]      FIG. 13  is a configuration diagram showing an embodiment of an information reproduction circuit in the optical information recording and reproduction device (embodiment 4); 
           [0028]      FIG. 14  is a diagram showing an embodiment of an optical information recording medium (embodiment 5); and 
           [0029]      FIG. 15  is a flow chart showing an embodiment of operation (embodiment 6). 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0030]    Embodiments of the present invention will be described with reference to the accompanying drawings. 
         [0031]    The description is conducted for embodiments. However, it is apparent to those skilled in the art that the present invention is not restricted to the embodiments, but various changes and modifications can be made without departing from the spirit and scopes of appended claims of the present invention. 
         [0032]      FIG. 2  is a block diagram showing a configuration example of a recording and reproduction device of an optical information recording medium for recording and/or reproducing digital information by utilizing holography. 
         [0033]    An optical information recording and reproduction device  10  includes a pickup  11 , a phase conjugate optical system  12 , a disc cure optical system  13 , a disc rotation angle detection optical system  14 , and a rotation motor  50 . An optical information recording medium  1  is configured to be able to be rotated by the rotation motor  50 . 
         [0034]    The pickup  11  functions to emit a reference beam and a signal beam to the optical information recording medium  1  and record digital information in the optical information recording medium by utilizing holography. At this time, an information signal to be recorded is sent into a spatial light modulator in the pickup  11  via a signal generation circuit  86  by a controller  89 , and the signal beam is modulated by the spatial light modulator. 
         [0035]    When reproducing information recorded in the optical information recording medium  1 , a phase conjugate beam of the reference beam emitted from the pickup  11  is generated in the phase conjugate optical system  12 . Here, the phase conjugate beam is a light wave which advances in an opposite direction while holding the same wave surface as that of an input beam. A reproduced beam reproduced by using the phase conjugate beam is detected by a photo-detector included in the pickup  11  and described later, and a signal is reproduced by a signal processing circuit  85 . 
         [0036]    Irradiation time of the reference beam and the signal beam with which the optical information recording medium  1  is irradiated can be adjusted by the controller  89  which controls opening/closing time of a shutter in the pickup  11  via a shutter control circuit  87 . 
         [0037]    The disc cure optical system  13  functions to generate a light beam to be used in pre-cure and post-cure of the optical information recording medium  1 . The pre-cure is pre-exposure processing in which a desired position is irradiated with a predetermined light beam before the desired position is irradiated with the reference beam and the signal beam, when recording information in the desired position in the optical information recording medium  1 . The post-cure is post-exposure processing in which a desired position is irradiated with a predetermined light beam to make incremental recording in the desired position impossible, after information is recorded in the desired position in the optical information recording medium  1 . 
         [0038]    The disc rotation angle detection optical system  14  is used to detect a rotation angle of the optical information recording medium  1 . When adjusting the optical information recording medium  1  to a predetermined rotation angle, it is possible to detect a signal corresponding to a rotation angle by using the disk rotation angle detection optical system  14  and cause the controller  89  to control the rotation angle of the optical information recording medium  1  via a disc rotation motor control circuit  88  by using the detected signal. 
         [0039]    A light source drive circuit  82  supplies predetermined light source drive currents to light sources in the pickup  11 , the disc cure optical system  13  and the disc rotation angle detection optical system  14 . Each light source can emit a light beam with a predetermined light quantity. 
         [0040]    Furthermore, each of the pickup  11  and the disc cure optical system  13  has a mechanism capable of sliding a position in a radial direction of the optical information recording medium  1 . Position control is exercised via an access control circuit  81 . 
         [0041]    By the way, the recording technique using the principle of angle multiplex of holography has a tendency in which the allowable error for deviation of reference beam angle becomes extremely small. 
         [0042]    Therefore, it becomes necessary to provide a mechanism in the pickup  11  to detect a deviation quantity of a reference beam angle, cause a servo signal generation circuit  83  to generate a signal for servo control, and provide a servo mechanism in the optical information recording and reproduction device  10  to correct the deviation quantity via a servo control circuit  84 . 
         [0043]    Furthermore, as for the pickup  11 , the disc cure optical system  13 , and the disc rotation angle detection optical system  14 , some optical system configurations or all optical system configurations may be collected into one and simplified. 
         [0044]      FIG. 3  shows a recording principle in an example of a basic optical system configuration of the pickup  11  in the optical information recording and reproduction device  10 . A light beam emitted from a light source  201  is transmitted by a collimate lens  202 , and incident on a shutter  203 . When the shutter  203  is open, the light beam passes through the shutter  203 . Then, the light beam is controlled in polarization direction by an optical element  204  formed of, for example, a half-wave plate, to have a desired ratio in light quantity ratio between p polarized light and s polarized light, and then is incident on a PBS (Polarization Beam Splitter) prism  205 . 
         [0045]    The light beam transmitted by the PBS prism  205  functions as a signal beam  206 . After being expanded in light beam diameter by a beam expander  208 , the light beam is transmitted by a phase mask  209 , a relay lens  210 , and a PBS prism  211 , and is incident on a spatial light modulator  212 . 
         [0046]    The signal beam added with information by the spatial light modulator  212  is reflected by the PBS prism  211  and propagate through a relay lens  213  and a spatial filter  214 . Thereafter, the signal beam is condensed onto the optical information recording medium  1  by an object lens  215 . 
         [0047]    On the other hand, a light beam reflected by the PBS prism  205  functions as a reference beam  207 . The reference beam  207  is set to a predetermined polarization direction depending upon recording or reproduction by a polarization direction transform element  216 , and then incident on a galvanometer mirror  219  via a mirror  217  and a mirror  218 . Since the galvanometer mirror  219  can be adjusted in angle by an actuator  220 , an incidence angle of the reference beam incident on the optical information recording medium  1  after passing through a lens  221  and a lens  222  can be set to a desired angle. By the way, an element for transforming a wave surface of the reference beam may be used instead of the galvanometer mirror in order to set an incidence angle of the reference beam. 
         [0048]    In this way, the signal beam and the reference beam are incident on the optical information recording medium  1  so as to overlap with each other. As a result, an interference fringe pattern is formed in the optical information recording medium. Information is recorded by writing this pattern into the optical information recording medium. Furthermore, since the incidence angle of the reference beam incident on the optical information recording medium  1  can be changed by the galvanometer mirror  219 , recording using angle multiplexing is possible. 
         [0049]    Hereafter, in a hologram recorded in the same area by changing the reference beam angle, a hologram corresponding to each reference beam angle is referred to as page and a collection of pages angle-multiplexed in the same area is referred to as book. 
         [0050]      FIG. 4  shows a reproduction principle in an example of a basic optical system configuration of the pickup  11  in the optical information recording and reproduction device  10 . When reproducing recorded information, the reference beam is incident on the optical information recording medium  1 . A light beam transmitted by the optical information recording medium  1  is reflected by a galvanometer mirror  224  which can be adjusted in angle by an actuator  223 . As a result, a phase conjugate beam is generated as described earlier. 
         [0051]    The signal beam reproduced by using the phase conjugate beam propagates through the object lens  215 , the relay lens  213  and the spatial filter  214 . Thereafter, the signal beam is transmitted by the PBS prism  211  and incident on a photo-detector  225 . It is possible to reproduce the recorded signal. 
         [0052]      FIG. 5  shows operation flows of recording and reproduction in the optical information recording and reproduction device  10 . Here, flows concerning recording and reproduction utilizing holography will be described. 
         [0053]      FIG. 5(   a ) shows a flow of operation conducted until preparation of recording or reproduction is completed after the optical information recording medium  1  is inserted into the optical information recording and reproduction device  10 .  FIG. 5(   b ) shows a flow of operation conducted until information is recorded into the optical information recording medium  1  since a preparation completion state.  FIG. 5(   c ) shows a flow of operation conducted until information recorded into the optical information recording medium  1  is reproduced since the preparation completion state. 
         [0054]    As shown in  FIG. 5(   a ), a medium is inserted ( 401 ). The optical information recording and reproduction device  10  conducts disc discrimination to determine, for example, whether the inserted medium is a medium in which digital information is recorded or reproduced by utilizing holography ( 402 ) 
         [0055]    If it is determined as a result of the disc discrimination that the inserted medium is a medium in which digital information is recorded or reproduced by utilizing holography, the optical information recording and reproduction device  10  reproduces control data provided in the optical information recording medium ( 403 ), and acquires information, for example, concerning the optical information recording medium and information, for example, concerning various setting conditions at the time of recording and reproduction. 
         [0056]    After reproducing the control data, the optical information recording and reproduction device  10  conducts learning processing concerning various adjustments and the pickup  11  depending upon the control data ( 404 ), and the optical information recording and reproduction device  10  completes the preparation for recording or reproduction ( 405 ). 
         [0057]    As for the operation flow until information recording since the preparation completion state, first, data to be recorded is received as shown in  FIG. 5(   b ) ( 411 ), and information depending upon the data is sent into the spatial light modulator in the pickup  11 . 
         [0058]    Thereafter, various kinds of learning processing are conducted previously as occasion demands to make it possible to record high quality information in the optical information recording medium ( 412 ). Positions of the pickup  11  and the disc cure optical system  13  are disposed in predetermined positions of the optical information recording medium by seek operation ( 413 ). 
         [0059]    Thereafter, a predetermined area is pre-cured by using the light beam emitted from the disc cure optical system  13  ( 414 ). Data is recorded by using the reference beam and the signal beam emitted from the pickup  11  ( 415 ). 
         [0060]    After the data is recorded, data is verified as occasion demands ( 416 ), and post-cure is conducted by using the light beam emitted from the disc cure optical system  13  ( 417 ). 
         [0061]    As for the operation flow until information reproduction since the preparation completion state, as shown in  FIG. 5(   c ), various kinds of learning processing are conducted previously as occasion demands to make it possible to reproduce high quality information from the optical information recording medium ( 421 ). Thereafter, positions of the pickup  11  and the phase conjugate optical system  12  are disposed in predetermined positions of the optical information recording medium by seek operation ( 422 ). 
         [0062]    Thereafter, the reference beam is emitted from the pickup  11 , and information recorded in the optical information recording medium is reproduced ( 423 ). 
         [0063]    In the ensuing description of embodiments, description will be omitted as for parts overlapping the above-described operation. Furthermore, description “cure” represents both pre-cure and post-cure. 
       Embodiment 1 
       [0064]    A first embodiment in the present invention will now be described with reference to  FIG. 1 ,  FIG. 6  and  FIG. 7 . 
         [0065]      FIG. 6  is a schematic diagram showing examples of accumulated exposure energy and an accumulated reproduction light quantity in the optical information recording medium (embodiment 1). The ordinate axis represents a value obtained by adding up reproduction light quantities from pages in the same book, i.e., an accumulated reproduction light quantity. The abscissa axis represents a value obtained by adding up exposure energy at the time of recording into the optical information recording medium, i.e., accumulated exposure energy. In  FIG. 6 , results of the accumulated reproduction light quantity and accumulated exposure energy in two different optical information recording media are schematically shown as an example. In the optical information recording medium using photopolymer which is generally used in holographic memories, a reproduction beam is not generated even if recording is conducted unless the optical information recording medium is irradiated with a beam for some determinate time. When recording a page, therefore, it is necessary to conduct processing called pre-cure in which the optical information recording medium is exposed to light for some determinate time, as pre-processing. Energy required for the pre-cure differs depending upon the optical information recording medium. For example, in case of  FIG. 6 , pre-cure with energy of E 1  is needed for a medium  1  and pre-cure with energy of E 2  is needed for a medium  2 . In addition, even if the medium is the same, energy required for the pre-cure also changes depending upon differences in environment such as the temperature and humidity at the time of recording. In order to cope with these differences, it is necessary to change the pre-cure time depending upon a difference in medium and a difference in environment such as the temperature when conducting the pre-cure. As a matter of fact, however, it is difficult to incorporate pre-cure time into the optical information recording and reproduction device while taking differences in various environments into consideration. Therefore, a technique for adjusting the pre-cure time in real time is needed. The present invention relates to the adjustment of the cure time in real time. 
         [0066]      FIG. 7  shows an embodiment of a disc cure optical system in the optical information recording and reproduction device. A disc cure optical system  15  includes a cure light source  301 , a collimate lens  302 , an aperture  303 , a lens  304 , a lens  305 , and a photo-detector  306 . A laser beam emitted from the cure light source  301  is converted to parallel rays by the collimate lens  302 . Thereafter, the parallel rays are prescribed to have a desired shape and size by the aperture  303 . Thereafter, a 4-f system formed by the lens  304  and the lens  305  irradiates the optical information recording medium  1  with a beam having the shape and size prescribed by the aperture. A cure beam transmitted by the optical information recording medium  1  is detected by the photo-detector  306 . Intensity of the transmitted beam detected by the photo-detector  306  tends to increase with time. This is because continuation of exposure causes monomer and photosensitive materials in the optical information recording medium to continue reaction and decreases the number of monomers and photosensitive materials and consequently absorption of the beam decreases. In the present invention, this change of transmitted light quantity is utilized and the pre-cure time is adjusted in real time. In other words, irradiation with the cure beam is continued until the intensity of the transmitted beam detected by the photo-detector  306  reaches some reference value, and irradiation with the laser beam is terminated when the reference value is exceeded. By doing so, it becomes possible to confirm the situation of the pre-cure in real time and adjust the pre-cure time. By the way, the reference value of the transmitted beam intensity for each medium may be retained previously in a drive, or may be recorded in a device that controls the drive or in the optical information recording medium itself. 
         [0067]      FIG. 1  is a flow chart showing an embodiment of an operation at the time of pre-cure in the present invention. First, the optical information recording medium is irradiated with a pre-cure beam at  501 . Then, a transmitted beam from the optical information recording medium is detected by the photo-detector at  502 . Then, it is determined at  503  whether the intensity of the detected transmitted beam is at least the reference value. If the intensity of the transmitted beam is less than the reference value, irradiation with the pre-cure beam is continued at  505  and the processing returns to the operation at  502 . If the intensity of the transmitted beam is at least the reference value, irradiation of the optical information recording medium with the pre-cure beam is terminated at  504 . 
         [0068]    In the present embodiment, it is not indispensable to the photo-detector whether there is a detection capability of two-dimensional data. Therefore, it is possible to use high speed devices such as the OEIC (Opto-Electronic Integrated Circuit) used in the Blu-ray Disc™ and the like. Therefore, there is a merit that high precision adjustment of the pre-cure time is possible. Furthermore, in a case where the optical information recording and reproduction device has a configuration capable of conducting recording and reproduction with respect to both the holographic memory and a conventional optical disc such as a Blu-ray Disc™, the OEIC utilized when conducting reproduction on the conventional optical disc can be utilized for detection of the transmitted beam of the cure beam as well. 
         [0069]    In the embodiment, especially the pre-cure has been described. However, the present invention can be utilized in the post-cure as well, and the present invention is not restricted to the pre-cure. In a case where the present invention is executed in the pre-cure, it is possible to improve the recording quality because a difference in pre-cure time depending upon the medium can be coped with. In a case where the present invention is executed in the pre-cure, there is a merit that the speed up of recording becomes possible because wasteful irradiation in the post-cure can be reduced. Furthermore, there is a merit that it is possible to prevent monomer which becomes a noise source after recording from remaining, because it is possible to prevent incomplete post-cure. 
         [0070]    In the ensuing description of embodiments, description of parts common to those in the present embodiment will be omitted. 
       Embodiment 2 
       [0071]    A second embodiment in the present invention will now be described with reference to  FIG. 8 . 
         [0072]      FIG. 8  shows an embodiment of a disc cure optical system in the optical information recording and reproduction device. A disc cure optical system  16  includes a cure light source  301 , a collimate lens  302 , an aperture  303 , a lens  304 , a lens  305 , a mirror  307 , and a photo-detector  225  in the pickup  11 . A laser beam emitted from the cure light source  301  is converted to parallel rays by the collimate lens  302 , and then prescribed to have a desired shape and a desired size by the aperture  303 . Thereafter, a 4-f system formed of the lens  304  and the lens  305  irradiates the optical information recording medium  1  with a beam having the shape and size prescribed by the aperture. A cure beam transmitted by the optical information recording medium  1  is reflected by the mirror  307 . The photo-detector  225  in the pickup  11  is irradiated with the reflected beam. Intensity of the transmitted beam detected by the photo-detector  225  has a tendency to increase with time. This is because continuation of exposure causes monomer and photosensitive materials in the optical information recording medium to continue reaction and decreases the number of monomers and photosensitive materials and consequently absorption of the beam decreases. In the present invention, this change of transmitted light quantity is utilized and the pre-cure time is adjusted in real time. In other words, irradiation with the cure beam is continued until the intensity of the transmitted beam detected by the photo-detector  225  reaches some reference value, and irradiation with the laser beam is terminated when the reference value is exceeded. By doing so, it becomes possible to confirm the situation of the pre-cure in real time and adjust the pre-cure time. By the way, the reference value of the transmitted beam intensity for each medium may be retained previously in a drive, or may be recorded in a device that controls the drive or in the optical information recording medium itself. 
         [0073]    In the present embodiment, the pickup and the disc cure optical system share the photo-detector. Therefore, there is a merit that it is possible to decrease the number of components and shrink the size of the device. 
         [0074]    In the ensuing description of embodiments, description of parts common to those in the present embodiment will be omitted. 
       Embodiment 3 
       [0075]    A third embodiment in the present invention will now be described with reference to  FIG. 9  and  FIG. 10 . In the present embodiment, a technique for learning the reference value of the transmitted beam intensity which becomes a criterion for finishing the pre-cure, before disc recording or periodically will be described. 
         [0076]      FIG. 9  is a schematic diagram showing an example of a relation between cure exposure time and transmitted light quantity. For example, in a case where a reference value of transmitted light intensity that indicates the pre-cure termination is learned, a recording area for learning is previously provided on the disc and movement to the recording area for learning is first conducted. Thereafter, an initial value  11  of the transmitted beam in a case where the cure beam is applied to the recording area for learning and a saturation value  12  in a case where the cure beam is continued to be applied are detected. As for a method for determining the saturation value  12 , for example, a light quantity I at time when a displacement quantity dI/dT of a transmitted light quantity I for some time dT has become a definite quantity or less may be set as 12. At this time, a reference value I′ of the transmitted light quantity can be determined, for example, by the following Expression (1). 
         [0000]        I ′=(1− x/ 100)× I 1+ x/ 100× I 2   (1)
 
         [0077]    Here, x specifies a ratio of a displacement from the initial value I 1  of the transmitted light quantity I to the reference value I′ to the whole displacement of the transmitted light quantity. The ratio x may be previously retained in the optical information recording and reproduction device, a device that controls the optical information recording and reproduction device, or the optical information recording medium. Or the user may be caused to input the ratio x at the time of recording. By the way, the method for determining the reference value of the transmitted quantity is not restricted to the above-described method, but the reference value may be calculated by using a different method. For example, a light quantity at time when dI/dT for a displacement quantity of the transmitted light quantity I from the initial value I 1  has become at least a determinate quantity may be set as the reference value I′. 
         [0078]      FIG. 10  is a flow chart showing an embodiment of operation at the time of pre-cure in the present invention. First, it is determined at  601  whether to conduct learning of the reference value of the transmitted beam intensity that indicates the pre-cure termination. 
         [0079]    In case where learning of the reference value of the transmitted beam intensity is not to be conducted, ordinary recording and reproduction are executed at  602 , and the processing returns to determination whether to conduct learning of the reference value of the transmitted beam intensity at  601  again. In the case of learning of the reference value of the transmitted beam intensity, the disc is moved to the area for learning at  603 . Thereafter, the optical information recording medium is irradiated with the pre-cure beam at  604 . A transmitted beam from the optical information recording medium is detected by the photo-detector at  605 . After the optical information recording medium is irradiated with the pre-cure beam for a sufficient time, irradiation with the pre-cure beam is terminated at  606 . An optimum reference value of the transmitted beam intensity is calculated according to the above-described method at  607 . 
         [0080]    In the present embodiment, it is possible to cope with differences in transmittance and absorbance of the medium caused by differences in environment such as temperature and humidity. There is a merit that tolerance to an environment change can be enhanced. 
         [0081]    In the ensuing description of embodiments, description of parts common to those in the present embodiment will be omitted. 
       Embodiment 4 
       [0082]    A fourth embodiment in the present invention will now be described with reference to  FIG. 11  and  FIG. 12 . 
         [0083]      FIG. 11  shows an embodiment of the optical information recording medium. The present embodiment has a feature that an information recording area  2  is provided, for example, in an inner circumference part of the optical information recording medium  1 . The initial value and saturation value of the transmitted beam intensity and the reference value which becomes a criterion of the cure termination are retained in the information recording area  2 . When executing the cure, an information reproduction circuit which will be described later adjusts the cure time by referring to these values. As for a method for adjusting the cure time, the methods of the above-described embodiments 1 to 3 are utilized. By the way, the position of the information recording area is not restricted to the inner circumference part of the optical information recording medium, but may be located in any place as long as the position is located in the optical information recording medium. Furthermore, time that becomes a criterion of the actual cure may be previously recorded in the information recording area  2 . As for a method for retaining the transmitted beam intensity information in the information recording area  2 , the transmitted beam intensity information may be retained using a difference in pit or crystallinity in the same way as the conventional optical disc represented by the Blu-ray Disc™, may be retained by utilizing holography, or may be retained by using a bar code or the like. 
         [0084]      FIG. 12  is a configuration diagram showing an embodiment of the optical information recording and reproduction device.  FIG. 13  shows an embodiment of an information reproduction circuit in the optical information recording and reproduction device.  FIG. 12  differs in configuration from  FIG. 2  in that an information reproduction circuit  90  is added. When executing the cure, a pickup  92  in the information reproduction circuit  90  receives a command from the controller  89  and reads the transmitted beam intensity information recorded in the optical information recording medium  1 . In the information reproduction circuit  90 , a radial position control mechanism  91  capable of sliding the position in the radial direction of the optical information recording medium  1  is provided, and position control is exercised via the access control circuit  81 . In the information reproduction circuit  90 , a signal processing circuit  93  processes a signal reproduced by the pickup  92 , and then a light source drive signal generation circuit generates a signal for controlling the light source drive circuit  82  and sends the signal to the light source drive circuit  82 . The light source drive circuit  82  adjusts drive time of a light source in the disc cure optical system  13 . By the way, other operations are the same as those in the description of  FIG. 2 , and consequently description of them will be omitted, 
         [0085]    In the present embodiment, it is possible to provide each optical information recording medium with transmitted beam intensity information. Therefore, there is a merit that it is possible to cope with a difference in cure condition of every optical information recording medium in detail. 
         [0086]    In the ensuing description of embodiments, description for parts common to the present embodiment will be omitted. 
       Embodiment 5 
       [0087]    A fifth embodiment in the present invention will now be described with reference to  FIG. 14 . 
         [0088]      FIG. 14  shows an embodiment of the optical information recording medium. The present embodiment has a feature that an information recording circuit  4  is provided in an optical information recording medium cartridge  3  for preventing the optical information recording medium  1  from unnecessary exposure. 
         [0089]    An initial value and a saturation value of the transmitted beam intensity and a reference value that becomes a criterion of cure termination are retained in the information recording circuit  4 . When executing the cure, the above-described information reproduction circuit adjusts the cure time by referring to these values. As for a method for adjusting the cure time, for example, the above-described methods of the embodiments 1 to 3 are used. By the way, the position of the information recording circuit is not restricted to the illustrated position, but may be in an arbitrary place as long as the position is located in the optical information recording medium cartridge. As for a method for retaining the transmitted beam intensity information in the information recording circuit  4 , a method for using a chip capable of conducting wireless communication such as, for example, an RFID (Radio Frequency Identification) tag, or an IC chip that conducts contact type reading is conceivable. 
         [0090]    The optical information recording and reproduction device can be implemented with a configuration similar to that shown in  FIG. 12 . In the case of the present embodiment, the position adjustment in the information reproduction circuit  90  can be omitted. Therefore, communication between the access control circuit  81  and the information reproduction circuit  90  can be omitted. By the way, in a case where the RFID is used, the information reproduction circuit  90  needs to include an RFID reader capable of reading an RFID tag. In a case where a contact type IC chip is used, the information reproduction circuit  90  needs to be a device capable of reading a contact type IC chip and needs to be disposed in a position that beings about contact with the IC chip when inserted into the cartridge. 
         [0091]    In the present embodiment, an area in the optical information recording medium is not used to retain the transmitted beam intensity information. Therefore, there is a merit that it is not necessary to reduce the recording area. Furthermore, there is a merit that it is not necessary to conduct processing such as position alignment of the optical information recording medium and the information reproduction circuit. 
         [0092]    In the ensuing description of an embodiment, description for parts common to the present embodiment will be omitted. 
         [0093]    By the way, the above-described embodiments can also be represented as follows: an optical information recording device for recording information in a holographic memory includes a light source for generating a signal beam and a reference beam, a spatial light modulator for adding information to the signal beam generated by the light source, an exposure processing light source for conducting pre-exposure processing on the holographic memory, and a detector for detecting a beam emitted from the exposure processing light source and transmitted by the holographic memory, and the pre-exposure processing is controlled depending upon a detection result of the detector. 
       Embodiment 6 
       [0094]    A sixth embodiment in the present invention will now be described with reference to  FIG. 15 . In the present embodiment, a technique for adjusting cure time by using the transmitted light quantity of the cure beam at the time of the post cure as well will be described. 
         [0095]      FIG. 15  is a flow chart showing an embodiment of an operation at the time of the post cure in the present invention. First, the optical information recording medium is irradiated with a post cure beam at  701 . Then, a transmitted beam from the optical information recording medium is detected by the photo-detector at  702 . Then, it is determined at  703  whether the intensity of the detected transmitted beam is at least the reference value. If the intensity of the transmitted beam is less than the reference value, irradiation with the post-cure beam is continued at  705  and the processing returns to the operation at  702 . If the intensity of the transmitted beam is at least the reference value, irradiation of the optical information recording medium with the post-cure beam is terminated at  704 . 
         [0096]    In the present embodiment, there is a merit that the speed up of recording becomes possible because wasteful irradiation in the post-cure can be reduced. Furthermore, there is a merit that it is possible to prevent monomer which becomes a noise source after recording from remaining, because it is possible to prevent incomplete post-cure. 
       Reference Signs List 
       [0000]    
       
           1 : Optical information recording medium 
           2 : Information recording area 
           3 : Optical information recording medium cartridge 
           4 : Information recording circuit 
           10 : Optical information recording and reproduction device 
           11 : Pickup 
           12 : Phase conjugate optical system 
           13 : Disc cure optical system 
           14 : Disc rotation angle detection optical system 
           15 : Disc cure optical system 
           16 : Disc cure optical system 
           17 : Optical information recording and reproduction device 
           50 : Rotation motor 
           81 : Access control circuit 
           82 : light source drive circuit 
           83 : Servo signal generation circuit 
           84 : Servo control circuit 
           85 : Signal processing circuit 
           86 : Signal generation circuit 
           87 : Shutter control circuit 
           88 : Disc rotation motor control circuit 
           89 : Controller 
           90 : Information reproduction circuit 
           91 : Radial position control mechanism 
           92 : Pickup 
           93 : Signal processing circuit 
           94 : Light source drive signal generation circuit 
           201 : Light source 
           202 : Collimate lens 
           203 : Shutter 
           204 : Half-wave plate 
           205 : Polarization beam splitter 
           206 : Signal beam 
           207 : Reference beam 
           208 : Beam expander 
           209 : Phase mask 
           210 : Relay lens 
           211 : Polarization beam splitter 
           212 : Spatial light modulator 
           213 : Relay lens 
           214 : Spatial filter 
           215 : Object lens 
           216 : Polarization direction transform element 
           217 : Mirror 
           218 : Mirror 
           219 : Mirror 
           220 : Actuator 
           221 : Lens 
           222 : Lens 
           223 : Actuator 
           224 : Mirror 
           225 : Photo-detector 
           301 : Cure light source 
           302 : Collimate lens 
           303 : Aperture 
           304 : Lens 
           305 : Lens 
           306 : Photo-detector 
           307 : Mirror