Hologram recording/reproducing device and hologram recording medium

Abstract

A holographic recording and reproducing apparatus comprises: a pickup for moving an objective lens that focuses a coherent light beam along a recording track on a holographic recording medium and for detecting reflected light from the recording track to perform focus- and tracking-servo control; a relative velocity determination unit for determining a relative velocity of a converging position of the objective lens with respect to the holographic recording medium; a driving unit for changing a relative position of the objective lens with respect to an optical path of the coherent light beam so as to make the relative velocity fall within a predetermined range at least during a predetermined period; and a control unit for performing recording or reproduction for a recording layer during the predetermined period. The holographic recording medium includes a plurality of markers used for positioning an optical interference pattern of the coherent light beam.

1 . A holographic recording apparatus for recording data on a holographic recording medium in the form of a flat plate which includes a recording layer comprising a photosensitive material and for which recording is achieved by an interference pattern of a coherent light beam, the apparatus comprising: 
 a pickup including an objective lens which focuses the coherent light beam, for moving the objective lens along a recording track of the holographic recording medium and detecting reflected light from the recording track to perform focus- and tracking-servo control;    a relative velocity determination unit for determining a relative velocity of a converging position of the objective lens with respect to the holographic recording medium;    a driving unit for changing a relative position of the objective lens with respect to an optical path of the coherent light beam in such a manner that the relative velocity falls within a predetermined range at least during a predetermined period; and    a control unit for performing recording for the recording layer during the predetermined period.    
   
   
       2 . The holographic recording apparatus according to  claim 1 , wherein the relative velocity determination unit determines the relative velocity based on address information obtained from the holographic recording medium.  
   
   
       3 . The holographic recording apparatus according to  claim 2 , wherein the address information is pre-pit information.  
   
   
       4 . The holographic recording apparatus according to  claim 1 , wherein the relative velocity determination unit determines the relative velocity based on a detection signal of markers arranged at predetermined intervals in the holographic recording medium.  
   
   
       5 . The holographic recording apparatus according to  claim 1 , wherein the driving unit drives the objective lens so that the relative velocity falls within a predetermined range at least during a predetermined period.  
   
   
       6 . The holographic recording apparatus according to  claim 5 , wherein the driving unit drives the objective lens to bring the coherent light beam into focus on the marker.  
   
   
       7 . The holographic recording apparatus according to  claim 5 , wherein the driving unit drives the objective lens in such a manner that a relative velocity of the converging position of the objective lens with respect to the maker falls within a predetermined range at least during a predetermined period while the converging position of the objective lens is shifted from the marker by a predetermined distance.  
   
   
       8 . The holographic recording apparatus according to  claim 1 , wherein the driving unit moves an incident optical path of the coherent light beam to the objective lens to make the relative velocity fall within a predetermined range at least during a predetermined period.  
   
   
       9 . The holographic recording apparatus according to  claim 8 , wherein the driving unit rotates a mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       10 . The holographic recording apparatus according to  claim 8 , wherein the driving unit rotates a polygon mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       11 . A holographic reproducing apparatus for reproducing data recorded on a holographic recording medium in the form of a flat plate which includes a recording layer comprising a photosensitive material and for which recording is achieved by an interference pattern of a coherent light pattern, the apparatus comprising: 
 a pickup including an objective lens focuses the coherent light beam, for moving the objective lens along a recording track of the holographic recording medium and detecting reflected light from the recording track so as to perform focus- and tracking-servo control;    a relative velocity determination unit for determining a relative velocity of a converging position of the objective lens with respect to the holographic recording medium;    a driving unit for changing a relative position of the objective lens with respect to an optical path of the coherent light beam in such a manner that the relative velocity falls within a predetermined range at least during a predetermined period; and    a control unit for performing reproduction from the recording layer during the predetermined period.    
   
   
       12 . The holographic reproducing apparatus according to  claim 11 , wherein the relative velocity determination unit determines the relative velocity based on address information obtained from the holographic recording medium.  
   
   
       13 . The holographic reproducing apparatus according to  claim 12 , wherein the address information is pre-pit information.  
   
   
       14 . The holographic reproducing apparatus according to  claim 11 , wherein the relative velocity determination unit determines the relative velocity based on a detection signal of markers arranged at predetermined intervals in the holographic recording medium.  
   
   
       15 . The holographic reproducing apparatus according to  claim 11 , wherein the driving unit drives the objective lens so that the relative velocity falls within a predetermined range at least during a predetermined period.  
   
   
       16 . The holographic reproducing apparatus according to  claim 15 , wherein the driving unit drives the objective lens to bring the coherent light beam into focus on the marker.  
   
   
       17 . The holographic reproducing apparatus according to  claim 15 , wherein the driving unit drives the objective lens in such a manner that a relative velocity of the converging position of the objective lens with respect to the maker falls within a predetermined range at least during a predetermined period while the converging position of the objective lens is shifted from the marker by a predetermined distance.  
   
   
       18 . The holographic reproducing apparatus according to  claim 11 , wherein the driving unit moves an incident optical path of the coherent light beam to the objective lens to make the relative velocity fall within a predetermined range at least during a predetermined period.  
   
   
       19 . The holographic reproducing apparatus according to  claim 18 , wherein the driving unit rotates a mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       20 . The holographic reproducing apparatus according to  claim 18 , wherein the driving unit rotates a polygon mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       21 . A holographic recording method for recording data on a holographic recording medium in the form of a flat plate which includes a recording layer comprising a photosensitive material and for which recording is achieved by an interference pattern of a coherent light beam, the method comprising: 
 a step of focusing the coherent light beam by an objective lens;    a step of moving the objective lens along a recording track of the holographic recording medium and detecting reflected light from the recording track to perform focus- and tracking-servo control;    a relative velocity determination step of determining a relative velocity of a converging position of the objective lens with respect to the holographic recording medium;    a driving step of changing a relative position of the objective lens with respect to an optical path of the coherent light beam in such a manner that the relative velocity falls within a predetermined range at least during a predetermined period; and    a step of performing recording for the recording layer during the predetermined period.    
   
   
       22 . The holographic recording method according to  claim 21 , wherein the relative velocity determination step determines the relative velocity based on address information obtained from the holographic recording medium.  
   
   
       23 . The holographic recording method according to  claim 22 , wherein the address information is pre-pit information.  
   
   
       24 . The holographic recording method according to  claim 21 , wherein the relative velocity determination step determines the relative velocity based on a detection signal of markers arranged at predetermined intervals in the holographic recording medium.  
   
   
       25 . The holographic recording method according to  claim 21 , wherein the driving step drives the objective lens so that the relative velocity falls within a predetermined range at least during a predetermined period.  
   
   
       26 . The holographic recording method according to  claim 25 , wherein the driving step drives the objective lens to bring the coherent light beam into focus on the marker.  
   
   
       27 . The holographic recording method according to  claim 25 , wherein the driving step drives the objective lens in such a manner that a relative velocity of the converging position of the objective lens with respect to the maker falls within a predetermined range at least during a predetermined period while the converging position of the objective lens is shifted from the marker by a predetermined distance.  
   
   
       28 . The holographic recording method according to  claim 21 , wherein the driving step moves an incident optical path of the coherent light beam to the objective lens to make the relative velocity fall within a predetermined range at least during a predetermined period.  
   
   
       29 . The holographic recording method according to  claim 28 , wherein the driving step rotates a mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       30 . The holographic recording method according to  claim 28 , wherein the driving step rotates a polygon mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       31 . A holographic reproducing method for reproducing data recorded on a holographic recording medium in the form of a flat plate which includes a recording layer comprising a photosensitive material and for which recording is achieved by an interference pattern of a coherent light pattern, the method comprising: 
 a step of focusing the coherent light beam by an objective lens;    a step of moving the objective lens along a recording track of the holographic recording medium and detecting reflected light from the recording track so as to perform focus- and tracking-servo control;    a relative velocity determination step of determining a relative velocity of a converging position of the objective lens with respect to the holographic recording medium;    a driving step of changing a relative position of the objective lens with respect to an optical path of the coherent light beam in such a manner that the relative velocity falls within a predetermined range at least during a predetermined period; and    a step of performing reproduction from the recording layer during the predetermined period.    
   
   
       32 . The holographic reproducing method according to  claim 31 , wherein the relative velocity determination step determines the relative velocity based on address information obtained from the holographic recording medium.  
   
   
       33 . The holographic reproducing method according to  claim 32 , wherein the address information is pre-pit information.  
   
   
       34 . The holographic reproducing method according to  claim 31 , wherein the relative velocity determination step determines the relative velocity based on a detection signal of markers arranged at predetermined intervals in the holographic recording medium.  
   
   
       35 . The holographic reproducing method according to  claim 31 , wherein the driving step drives the objective lens so that the relative velocity falls within a predetermined range at least during a predetermined period.  
   
   
       36 . The holographic reproducing method according to  claim 35 , wherein the driving step drives the objective lens to bring the coherent light beam into focus on the marker.  
   
   
       37 . The holographic reproducing method according to  claim 35 , wherein the driving step drives the objective lens in such a manner that a relative velocity of the converging position of the objective lens with respect to the maker falls within a predetermined range at least during a predetermined period while the converging position of the objective lens is shifted from the marker by a predetermined distance.  
   
   
       38 . The holographic reproducing method according to  claim 31 , wherein the driving step moves an incident optical path of the coherent light beam to the objective lens to make the relative velocity fall within a predetermined range at least during a predetermined period.  
   
   
       39 . The holographic reproducing method according to  claim 38 , wherein the driving step rotates a mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       40 . The holographic reproducing method according to  claim 38 , wherein the driving step rotates a polygon mirror arranged in an optical path of the coherent light beam to move the incident optical path of the coherent light beam to the objective lens.  
   
   
       41 . A holographic recording medium on which an optical interference pattern of a coherent light beam is recorded as a spatial change of a refractive index, comprising a plurality of markers for positioning the optical interference pattern.  
   
   
       42 . The holographic recording medium according to  claim 41 , comprising a substrate and a recording layer comprising a photosensitive material formed to be adjacent to the substrate, wherein the markers are formed in the substrate.  
   
   
       43 . The holographic recording medium according to  claim 41 , comprising: a substrate; a burying layer for burying said substrate to flatten the substrate, the burying layer being adjacent to the substrate and having a different refractive index from the substrate; and a recording layer comprising a photosensitive material to be adjacent to the burying layer, wherein the markers are formed in the burying layer.  
   
   
       44 . The holographic recording medium according to  claim 41 , comprising a recording layer including a photosensitive material, wherein the markers are formed in the recording layer.  
   
   
       45 . The holographic recording medium according to  claim 42 , wherein the markers are arranged at predetermined intervals to form a recording track on a plane of the recording medium.  
   
   
       46 . The holographic recording medium according to  claim 45 , wherein the markers are arranged concentrically on the plane of the recording medium.  
   
   
       47 . The holographic recording medium according to  claim 45 , wherein the markers are arranged spirally on the plane of the recording medium.  
   
   
       48 . The holographic recording medium according to  claim 41 , comprising a substrate having a groove for indicating a recording track formed thereon, and a recording layer comprising a photosensitive material to be adjacent to the substrate, wherein the markers are formed in the substrate along the groove.  
   
   
       49 . The holographic recording medium according to  claim 41 , comprising: a substrate having a groove for indicating a recording track formed thereon; a burying layer for burying the substrate to flatten the substrate, the burying layer being adjacent to the substrate and having a different refractive index from the substrate; and a recording layer comprising a photosensitive material to be adjacent to the burying layer, wherein the markers are formed in the substrate along the groove.  
   
   
       50 . The holographic recording medium according to  claim 48 , wherein the groove is wobbled and the markers are formed at predetermined positions in wobbling of the groove.  
   
   
       51 . The holographic recording medium according to  claim 41 , wherein the markers have a transmittance of a predetermined value or more with respect to a wavelength of the coherent light beam that has generated the optical interference pattern.  
   
   
       52 . The holographic recording medium according to  claim 51 , wherein the markers have a thickness so as to provide the markers with a transmittance of a predetermined value or more with respect to a wavelength of the coherent light beam that has generated the optical interference pattern.  
   
   
       53 . The holographic recording medium according to  claim 48 , wherein the groove has such a phase depth that the groove has no effect on transmitted and reflected light at a wavelength of the coherent light beam that has generated the optical interference pattern.