Dynamic aperture holographic multiplexing

Abstract

Systems and methods for dynamic aperture holographic multiplexing are disclosed. One example process may include recording a set of holograms in a recording medium by varying both the reference beam angular aperture and the signal beam angular aperture. The angular aperture of the signal beam may be dynamically changed such that the closest edge of each signal beam angular aperture is selected to be a threshold angle different than the angular aperture of the reference beam used to record it. In some examples, the dynamic aperture holographic multiplexing process may include dynamic aperture equalization to reduce cross-talk, to improve error correction parity distribution for improved recovery transfer rate, to provide multiple locus aperture sharing for increased recording density, and to provide polarization multiplexed shared aperture multiplexing for increased transfer rate in both recording and recovery.

What is claimed is: 
     
         1 . A method for recording a set of multiplexed holograms, the method comprising:
 recording a first hologram of the set of multiplexed holograms to a recording medium using a first signal beam angular aperture and a first reference beam; and   recording a second hologram of the set of multiplexed holograms to the recording medium using a second signal beam angular aperture and a second reference beam, wherein the second signal beam angular aperture is varied in at least one characteristic from the first signal beam angular aperture.   
     
     
         2 . The method of  claim 1 , wherein the first hologram and the second hologram each comprise a data page of pixel information. 
     
     
         3 . The method of  claim 1 , wherein the first signal beam angular aperture and the second signal beam angular aperture vary in one or more of shape, size, and position. 
     
     
         4 . The method of  claim 1 , further comprising:
 recording a third hologram of the set of multiplexed holograms to the recording medium using a third signal beam angular aperture and a third reference beam, wherein the third signal beam angular aperture is varied in at least one characteristic from the first signal beam angular aperture and the second signal beam angular aperture; and   recording a fourth hologram of the set of multiplexed holograms to the recording medium using a fourth signal beam angular aperture and a fourth reference beam, wherein the fourth signal beam angular aperture is varied in at least one characteristic from the first signal beam angular aperture, second signal beam angular aperture, and the third signal beam angular aperture.   
     
     
         5 . The method of  claim 4 , wherein:
 an edge of the first signal beam angular aperture is separated from an angular aperture of the first reference beam by a first angle;   an edge of the second signal beam angular aperture is separated from an angular aperture of the second reference beam by a second angle;   an edge of the third signal beam angular aperture is separated from an angular aperture of the third reference beam by a third angle; and   an edge of the fourth signal beam angular aperture is separated from an angular aperture of the fourth reference beam by a fourth angle.   
     
     
         6 . The method of  claim 5 , wherein the first angle, the second angle, the third angle, and the fourth angle are substantially equal. 
     
     
         7 . The method of  claim 5 , wherein:
 the first angle and the third angle are substantially equal;   the second angle and the fourth angle are substantially equal; and   the first angle and the third angle are different than the second angle and the fourth angle.   
     
     
         8 . The method of  claim 1 , wherein using the first signal beam angular aperture comprises using a signal beam with an angular range. 
     
     
         9 . The method of  claim 1 , wherein at least a portion of an angular locus of a set of reference beams used to record the set of multiplexed holograms overlaps at least a portion of an angular locus of a set of signal beams used to record the set of multiplexed holograms. 
     
     
         10 . The method of  claim 1 , wherein a first portion of the set of multiplexed holograms are used to store error parity data and a second portion of the set of multiplexed holograms are used to store input data, wherein the holograms of the first portion are smaller than the holograms of the second portion. 
     
     
         11 . A system for recording a set of multiplexed holograms, the system comprising:
 an aperture sharing element configured to output a modulated signal beam and a reference beam;   a recording medium; and   a controller configured to:
 cause the recording of a first hologram of the set of multiplexed holograms to the recording medium by causing the aperture sharing element to output a first signal beam having a first signal beam angular aperture and a first reference beam having a first reference beam angular aperture; and 
 cause the recording of a second hologram of the set of multiplexed holograms to the recording medium by causing the aperture sharing element to output a second signal beam having a second signal beam angular aperture and a second reference beam having a second reference beam angular aperture, wherein the second signal beam angular aperture is varied in at least one characteristic from the first signal beam angular aperture. 
   
     
     
         12 . The system of  claim 11 , wherein the aperture sharing element comprises a spatial light modulator, and wherein causing the aperture sharing element to output the first signal beam having the first signal beam angular aperture and the first reference beam having the first reference beam angular aperture comprises controlling the spatial light modulator to output the first signal beam having the first signal beam angular aperture and the first reference beam having the first reference beam angular aperture. 
     
     
         13 . The system of  claim 11 , further comprising:
 a laser source for generating a beam;   a beam directing device coupled to receive the beam; and   a spatial light modulator coupled to receive the beam, wherein:
 causing the aperture sharing element to output the first signal beam having the first signal beam angular aperture comprises controlling the spatial light modulator to cause the aperture sharing element to output the first signal beam having the first signal beam angular aperture; and 
 causing the aperture sharing element to output the first reference beam having the first reference beam angular aperture comprises controlling the beam directing device to output the first reference beam having the first reference beam angular aperture 
   
     
     
         14 . The system of  claim 11 , wherein the controller is further configured to:
 cause the recording of a third hologram of the set of multiplexed holograms to the recording medium by causing the aperture sharing element to output a third signal beam having a third signal beam angular aperture and a third reference beam having a third reference beam angular aperture, wherein the third signal beam angular aperture is varied in at least one characteristic from the first signal beam angular aperture and the second signal beam angular aperture; and   cause the recording of a fourth hologram of the set of multiplexed holograms to the recording medium by causing the aperture sharing element to output a fourth signal beam having a fourth signal beam angular aperture and a fourth reference beam having a fourth reference beam angular aperture, wherein the fourth signal beam angular aperture is varied in at least one characteristic from the first signal beam angular aperture, second signal beam angular aperture, and the third signal beam angular aperture.   
     
     
         15 . The system of  claim 14 , wherein:
 an edge of the first signal beam angular aperture is separated from an angular aperture of the first reference beam by a first angle;   an edge of the second signal beam angular aperture is separated from an angular aperture of the second reference beam by a second angle;   an edge of the third signal beam angular aperture is separated from an angular aperture of the third reference beam by a third angle; and   an edge of the fourth signal beam angular aperture is separated from an angular aperture of the fourth reference beam by a fourth angle.   
     
     
         16 . The system of  claim 15 , wherein the first angle, the second angle, the third angle, and the fourth angle are substantially equal. 
     
     
         17 . The system of  claim 15 , wherein:
 the first angle and the third angle are substantially equal;   the second angle and the fourth angle are substantially equal; and   the first angle and the third angle are different than the second angle and the fourth angle.   
     
     
         18 . The system of  claim 11 , wherein the first signal beam angular aperture comprises an angular range of the signal beam. 
     
     
         19 . The system of  claim 11 , wherein at least a portion of an angular locus of a set of reference beams used to record the set of multiplexed holograms overlaps at least a portion of an angular locus of a set of signal beams used to record the set of multiplexed holograms. 
     
     
         20 . The system of  claim 11 , wherein a first portion of the set of multiplexed holograms is used to store error parity data and a second portion of the set of multiplexed holograms is used to store input data, wherein the holograms of the first portion are smaller than the holograms of the second portion.