Disk-based optical correlator and method

Apparatus for optically storing information comprising:

• an optical recording medium said medium comprising an optical recording layer of a sufficient thickness for recording volume holographic information throughout the volume of each of a plurality of spots therein;
• optical modulator means for modulating a coherent light beam in response to an image signal representing a successive one of a set of template images, so as to produce an image beam corresponding to said image signal;
• imaging and transforming means for imaging, in a first direction, said image beam on a selected spot on said optical recording medium while Fourier transforming, in a second direction orthogonal to said first direction, said image beam on said selected spot;
• recording reference beam source means for projecting a reference beam onto said selected spot, said reference beam being coherent with said coherent light beam, whereby to generate a hologram of a respective template image through the volume in said spot;
• means for multiplexing holograms of all of said set of template images in said spot;
• means for moving said medium whereby said image beam is imaged onto a successive spots on said medium, whereby successive sets of multiplexed holograms are recorded in said successive spots.

A method of performing correlation in an optical recording medium said medium comprising an optical recording layer of a sufficient thickness for recording volume holographic information throughout the volume of each of a plurality of spots therein, said method comprising:

• modulating a coherent light beam in response to an image signal representing one of (a) one of a set of template images or (b) an input image, so as to produce an image beam corresponding to said image signal;
• imaging, in a first direction, said image beam on a selected spot on said optical recording medium while Fourier transforming, in a second direction orthogonal to said first direction, said image beam on said selected spot;
• causing said image signal successively to represent respective ones of said set of template images, while successively projecting a reference beam onto said selected spot at respective angles relative to said optical recording medium, said reference beam being coherent with said coherent light beam, whereby to record respective angularly multiplexed volume holograms throughout the volume of said optical recording layer at said spot;
• after recording of said holograms in said optical recording layer, causing said image beam to represent said input image while detecting at plural line detectors aligned in said second direction at a correlation plane Fourier transformed versions of respective patterns of said image beam diffracted by respective volume holograms in said selected spot, each of said patterns corresponding to a one-dimensional slice of a two-dimensional correlation of said input image with a corresponding one of said template images;
• and, simultaneously,
• moving said optical recording medium in said first direction so as to scan said image beam across said spot, whereby to generate a two-dimensional correlation function for each one of said patterns.

A method of optically storing information in an optical recording medium said medium comprising an optical recording layer of a sufficient thickness for recording volume holographic information throughout the volume of each of a plurality of spots therein, comprising:

• modulating a coherent light beam in response to an image signal representing a successive one of a set of template images, so as to produce an image beam corresponding to said image signal;
• imaging, in a first direction, said image beam on a selected spot on said optical recording medium while Fourier transforming, in a second direction orthogonal to said first direction, said image beam on said selected spot;
• projecting a reference beam onto said selected spot, said reference beam being coherent with said coherent light beam, whereby to generate a hologram of a respective template image in said spot;
• multiplexing holograms of all of said set of template images in said spot;
• moving said medium whereby said image beam is imaged onto a successive spots on said medium, whereby successive sets of multiplexed holograms are recorded in said successive spots.

A method for optically recording and recovering information contained in a plurality of templates, comprising:

• providing a recording medium distributed over a surface and having a sufficient thickness to provide a volume of said surface for recording volume holograms throughout the volume of each of a plurality of regions therein,
• providing a first coherent light beam,
• modulating a second coherent light beam which is coherent with said first beam with successive one of said templates to produce a succession of image beams,
• imaging said modulated beam in a first direction,
• Fourier transforming said modulated beam in a second direction orthogonal from said first direction,
• forming a reference beam coherent with said first coherent light beam,
• simultaneously imaging said modulated beam and said reference beam onto said region in said medium to form a volume hologram therein,
• progressively changing the angle of impingement of said reference beam into the media so as to angularly multiplex the templates into said medium at said location, and
• moving said medium so that said beams are imaged in successive regions in said medium while changing said templates.

Apparatus for optical recording and recovering information contained in a plurality of templates, comprising

• means for providing a recording medium distributed over a surface and having a sufficient thickness and provide a volume of said surface for recording optical holograms throughout the volume of each of a plurality of regions therein,
• means for providing a first coherent light beam;
• means for modulating said coherent light beam with an image of one Of said templates to produce an image beam,
• means for imaging said modulated beam in a first direction
• means for Fourier transforming said modulated beam in a second direction different from said first direction,
• means for forming a reference beam coherent with said first coherent light beam,
• means for imaging said modulated beam and said reference beam onto a region in said medium to form a volume hologram therein, and
• means for moving said medium so that said beams are imaged in successive regions in said medium while changing said templates.

A method for optically recording and recovering information contained in a plurality of templates, comprising:

• providing a recording medium distributed over a surface and having a thickness to provide a volume for recording volume holograms throughout the volume of each of a plurality of regions therein,
• providing a first coherent reference light beam and a second coherent light beam coherent with said first beam,
• modulating said second coherent light beam with successive ones of said templates to produce a succession of image beams,
• imaging said modulated beam in a first direction,
• Fourier transforming said modulated beam in a second direction orthogonal from said first direction,
• simultaneously illuminating said modulated beam and said reference beam into said region in said medium to form a volume hologram therein,
• progressively changing the angle of said reference beam so as to angle multiplex the templates into said medium at said location,
• moving said medium so that said beams are illuminated in successive regions in said medium, and subsequently
• presenting a second coherent light beam with information from an unknown template,
• moving the medium relative to that beam to generate correlation functions for said unknown template,
• recovering a correlated template by
• illuminating the region with an unmodulated, coherent readout beam to generate a diffracted beam containing the correlated template information,
• imaging said diffracted beam in a first direction,
• Fourier transforming said diffracted beam in a second direction orthogonal to said first direction to reconstruct said correlated template.