Non-volatile readout of shift multiplexed holograms

A method of reconstructing successive holograms previously recorded by a recording reference beam in a recording medium having a z axis perpendicular to said recording medium, each previously recorded successive hologram being spaced apart a recording displacement, and wherein said recording reference beam has a recording wavelength in the range where the recording medium is photosensitive and said recording reference beam forms a recording angle with said signal beam, said method comprising the steps of:

• (a) providing a reconstruction reference beam having a reconstruction wavelength in the range where the recording medium is relatively photo-insensitive and a reconstruction propagation angle fixed with respect to said z axis onto said recording medium;
• (b) producing a succession of relative displacements in said recording medium, each of said displacements being equal to the distance of said recording displacements with which said holograms were previously recorded;
• and
• (c) detecting reconstruction of said previously recorded holograms at said reconstruction wavelength.

A holographic storage device for recording and reconstructing successive holograms in a recording medium having a z axis perpendicular to said recording medium, said device comprising:

• a recording mechanism comprising,
• a means for generating a recording reference beam, said reference beam having a recording wavelength in the range where said recording medium is photosensitive, a recording propagation angle for providing said recording reference beam to a diffraction grating and said recording medium incident at an oblique angle, and a succession of signal beams intersecting said recording reference beam within said recording medium to thereby record successive holograms, each being spaced apart a recording displacement;
• a reconstruction mechanism comprising,
• a means for generating a reconstruction reference beam, said reconstruction reference beam having a reconstruction wavelength in the range where said recording medium is relatively photo-insensitive, a reconstruction propagation angle for providing said reconstruction reference beam to said diffraction grating and to said recording medium incident at a fixed angle, and means for producing a succession of relative displacements in said recording medium, each of said displacements being appropriate for Bragg-matching the previously recorded said holograms at said reconstruction wavelength;
• and
• detection means for detecting reconstruction of said previously recorded holograms at said reconstruction wavelength.

A method for recording and reconstructing successive holograms in a recording medium having a z axis perpendicular to said recording medium, said method comprising the steps of:

• (a) providing a recording reference beam, having a recording wavelength in the range where the recording medium is photosensitive and a recording propagation angle, to a diffraction grating and to said recording medium incident at an oblique angle;
• (b) providing a succession of signal beams intersecting said recording reference beam within said recording medium to thereby record successive holograms, each being spaced apart a recording displacement;
• (c) providing a reconstruction reference beam, having a reconstruction wavelength in the range where the recording medium is photo-insensitive and a reconstruction propagation angle, to said diffraction grating and to said recording medium incident at a fixed angle;
• (d) producing a succession of relative displacements in said recording medium, each of said displacements being equal to the distance of said recording displacements with which said holograms were previously recorded by said recording reference beam;
• and
• (e) detecting reconstruction of said previously recorded holograms at said reconstruction wavelength.

A holographic recording device for recording successive holograms in a recording medium, comprising:

• a recording mechanism for providing at least a fan of M amount of waves along at least a first axis with a separation angle between adjacent waves and directing said fan of M waves as a reference beam along a reference beam path onto said recording medium;
• signal means for successively modulating a wave with a succession of images to produce a succession of signal beams along a signal beam path lying at a propagation angle relative to said reference beam path so that said signal and reference beams intersect at a beam intersection lying within said medium, said beam intersection having a size corresponding to beam areas of said reference and signal beams;
• and
• displacement means for producing a succession of relative displacements a direction parallel to said first axis between said recording medium and said beam intersection of said signal and reference beam paths in synchronism with said succession of signal beams, each of said displacements being less than said size of said intersection whereby to record successive holograms partially overlapped along a direction of said displacements.

A holographic reconstruction device for reconstructing at a detection plane successive holograms previously recorded in a recording medium by means for diffracting a succession of signal beams along a signal beam path lying at a propagation angle relative to a reference beam including a fan of M amount of waves, said fan being parallel to the path of said signal beams and having a separation angle between adjacent waves of the fan and displacement means for successively displacing said medium relative to said signal and reference beams in a direction parallel to said first axis by a distance less than the intersection of said reference and signal beams in said recording medium in synchronism with said succession of signal beams, said reconstruction device comprising:

• a reconstruction mechanism for providing at least a fan of M waves along at least a first axis corresponding to the direction of the reference beam with which said holograms were previously recorded with a separation angle between adjacent waves and directing said fan of M waves as a reference beam along a reference beam path onto said recording medium;
• displacement means for producing a succession of relative displacements a direction parallel to said first axis between said recording medium and said beam intersection of said signal and reference beam paths in synchronism with said succession of signal beams, each of said displacements being equal to the distance of said displacements with which said holograms were previously recorded;
• and
• detection means for detecting at said detection plane light diffracted from said reference beam by a succession of said previously recorded holograms.