# US 5,353,247 A · Optical mass storage system and memory cell incorporated therein > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,353,247 A - Document ID: US5353247A - Status: Granted - Kind: A - Application number: 07/889,490 - Filed: 1992-05-27 - Granted: 1994-10-04 - Earliest claimed: 1992-05-27 - Inventors: Sadeg M. Faris - Web page: https://patentgrep.com/patent/US5353247A ## CPC - G11B 7/245: containing a polymeric component - G11B 7/00455: {involving reflectivity, absorption or colour changes} - G11B 7/14: specially adapted to record on, or to reproduce from, more than one track simultaneously - G11B 7/24: Record carriers characterised by shape, structure or physical properties, or by the selection of the material (characterised by the arrangement of information on the carrier G11B7/007) - G11B 7/244: comprising organic materials only - G11B 7/25: containing liquid crystals - G11B 7/2532: comprising metals - G11B 7/2534: polycarbonates [PC] - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract This application relates to a new read-write optical storage technology which is based on the cholesteric liquid crystal (CLC) polymer property of selective reflection at a characteristic wavelength. Each layer in a multi-layer CLC storage arrangement has a different characteristic wavelength, making it possible to randomly select any layer for reading, writing or erasing. Each layer incorporates a plurality of memory cells, in a write/erase mode, disposed on a dye polymer material or having such dye polymer material integrated into the CLC material such that, in the presence of light and electric or magnetic fields, the molecules of the CLC material are heated and align themselves with the electric or magnetic field. To the extent that the CLC molecules align themselves with a magnetic field normal to the plane of a storage element, electromagnetic energy in the form of light or infrared radiation at a specific wavelength, in a read mode, will be reflected. Any other orientation whether due to the presence of a magnetic or electric field or heating alone will be transparent to any other wavelength and a circular polarization opposite to the polarization of an incident reading beam. Finally, a disk storage system and a multi-layered storage system for reading, displaying and printing stored information are shown to indicate applications of the cholesteric liquid crystal storage technology. ## Claims ### Claim 1 An optical memory comprising an information storage element which includes a plurality of information storage regions at least one of which, in one mode, causes a reflection of incident circularly polarized electromagnetic radiation of a given wavelength and, in another mode, transmits electromagnetic radiation, and, means associated with said storage element for reversibly switching said at least one of said storage regions between said modes. ### Claim 2 (depends on 1) An optical memory according to claim 1 further including means for detecting a reflection from said at least one of said storage regions. ### Claim 3 (depends on 1) An optical memory according to claim 1 further including means for projecting said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 4 (depends on 1) An optical memory according to claim 1 further including means for selecting said at least one of said storage regions. ### Claim 5 (depends on 1) An optical memory according to claim 1 further including means for detecting a reflection from said at least one of said storage regions and means for projecting said incident circularly polarized electromagnetic radiation to said information storage element. ### Claim 6 (depends on 1) An optical memory according to claim 1 further including means for detecting a reflection from said at least one of said storage regions, and, means for selecting said at least one of said storage regions. ### Claim 7 (depends on 1) An optical memory according to claim 1 further including means for projecting said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 8 (depends on 1) An optical memory according to claim 1 further including means for detecting a reflection from said at least one of said storage regions, means for projecting said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions to optically respond to one of said detecting and projecting means. ### Claim 9 (depends on 1) An optical memory according to claim 1 wherein said given wavelength of electromagnetic radiation is in the visible range. ### Claim 10 (depends on 1) An optical memory according to claim 1 wherein said given wavelength of electromagnetic radiation is in the range of 300 nm to 14,000 nm. ### Claim 11 (depends on 1) An optical memory according to claim 1 wherein said circular polarization of incident electromagnetic radiation is right-hand circularly polarized. ### Claim 12 (depends on 1) An optical memory according to claim 1 wherein said circular polarization of incident electromagnetic radiation is left-hand circularly polarized. ### Claim 13 (depends on 1) An optical memory according to claim 1 wherein said information storage element is a member in which said information storage regions are disposed. ### Claim 14 (depends on 1) An optical memory according to claim 1 wherein said information storage element further includes a support substrate on which said information storage regions are disposed. ### Claim 15 (depends on 1) An optical memory according to claim 1 wherein each of said storage region is a cholesteric liquid crystal region. ### Claim 16 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element. ### Claim 17 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes means for immersing said storage element in field and aligning said field in one of two mutually orthogonal directions. ### Claim 18 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions. ### Claim 19 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions. ### Claim 20 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes another means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 21 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes means for selecting said at least one of said storage regions. ### Claim 22 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes a radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element and switchable means for immersing said storage element in a field and aligning said field in one to two mutually orthogonal directions. ### Claim 23 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes a radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element and switchable means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions. ### Claim 24 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes a radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element and switchable means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions. ### Claim 25 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, and, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 26 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 27 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes a radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, switchable means for immersing said storage element in a field and aligning said field in one of two mutually orthogonal directions and, means for projecting said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 28 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes a radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, switchable means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions, and, means for projecting said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 29 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes a radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, switchable means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions and, means for projecting said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 30 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive compact with a surface of said information storage element, means for immersing said storage element in a field and aligning said field in one of two mutually orthogonal directions, and, means for selecting said at least one of said storage regions. ### Claim 31 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions, and, means for selecting said at least one of said storage regions. ### Claim 32 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions, and, means for selecting said at least one of said storage regions. ### Claim 33 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 34 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, means for immersing said storage element in a field and aligning said field in one of two mutually orthogonal directions, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 35 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 36 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said information storage element, means for immersing said storage element in an electric field and aligning said electric field and aligning said electric field in one of two mutually orthogonal directions, means for projecting circularly polarized electromagnetic radiation of said given wavelengths of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 37 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage region. ### Claim 38 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, and, means for immersing said storage element in a field and aligning said field in one of two mutually orthogonal directions. ### Claim 39 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, and, means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions. ### Claim 40 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, and, means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions. ### Claim 41 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, and, means for selecting said at least one of said storage regions. ### Claim 42 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in a magnetic field and aligning said field in one of two mutually orthogonal directions, and, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 43 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions, and, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 44 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions, and, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element. ### Claim 45 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in a field and aligning said field in one of two mutually orthogonal directions, and, means for selecting said at least one of said storage regions. ### Claim 46 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions, and, means for selecting said at least one of said storage regions. ### Claim 47 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions, and, means for selecting said at least one of said storage regions. ### Claim 48 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 49 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in a field and aligning said field in one of two mutually orthogonal directions, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 50 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 51 (depends on 1) An optical memory according to claim 1 wherein said means for switching includes an electromagnetic radiation absorbing substance integral with said plurality of information storage regions, means for immersing said storage element in an electric field and aligning said electric field in one of two mutually orthogonal directions, means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said information storage element, and, means for selecting said at least one of said storage regions. ### Claim 52 (depends on 2) An optical memory according to claim 2 wherein said means for detecting a reflection includes a solid state detector of said electromagnetic radiation at said given wavelength. ### Claim 53 (depends on 2) An optical memory according to claim 2 wherein said means for detecting a reflection includes a detector of said electromagnetic radiation at said given wavelength. ### Claim 54 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes at least a source of electromagnetic radiation which projects circularly polarized electromagnetic radiation. ### Claim 55 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes at least a source of electromagnetic radiation having an energy output sufficient to permit nondestructive reflection of said incident circularly polarized electromagnetic radiation. ### Claim 56 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes at least a source of electromagnetic radiation which projects unpolarized electromagnetic radiation. ### Claim 57 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes a source of electromagnetic radiation which projects unpolarized electromagnetic radiation and means for converting said unpolarized radiation to circularly polarized radiation. ### Claim 58 (depends on 2) An optical memory according to claim 2 wherein said means for projecting includes a solid state source of said electromagnetic radiation. ### Claim 59 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes a laser. ### Claim 60 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes a solid state laser. ### Claim 61 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes a laser which provides unpolarized electromagnetic radiation and means for converting said unpolarized radiation to one of two circular polarizations. ### Claim 62 (depends on 3) An optical memory according to claim 3 wherein said means for projecting includes means for focusing said electromagnetic radiation on said at least one of said storage regions. ### Claim 63 (depends on 4) An optical memory according to claim 4 wherein said means for selecting includes means for applying relative motion between said electromagnetic radiation and said information storage element. ### Claim 64 (depends on 4) An optical memory according to claim 4 wherein said means for selecting includes means for applying rotary motion to said information storage elements. ### Claim 65 (depends on 16) An optical memory according to claim 16 wherein said radiation absorbing medium is a dye polymer which is absorptive at said given wavelength. ### Claim 66 (depends on 16) An optical memory according to claim 16 wherein said radiation absorbing medium is a medium which converts electromagnetic radiation at said given wavelength to heat. ### Claim 67 (depends on 18) An optical memory according to claim 18 wherein said means for immersing and aligning includes a pair of orthogonally arranged solenoids disposed around said information storage element. ### Claim 68 (depends on 18) An optical memory according to claim 18 wherein said means for immersing and aligning includes a pair of orthogonally arranged electrodes disposed around said information storage elements. ### Claim 69 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes at least a source of electromagnetic radiation having an energy output at said given wavelength sufficient to cause heating of said at least an information storage region above its glass transition temperature. ### Claim 70 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes at least a source of electromagnetic radiation which projects circularly polarized electromagnetic radiation. ### Claim 71 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes a solid state source of said electromagnetic radiation. ### Claim 72 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes a laser. ### Claim 73 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes a solid state laser. ### Claim 74 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes a laser which provides unpolarized electromagnetic radiation and means for converting said unpolarized radiation to one of two circular polarizations. ### Claim 75 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes a source of electromagnetic radiation which provides unpolarized electromagnetic radiation and means for converting said unpolarized radiation to circularly polarized radiation. ### Claim 76 (depends on 20) An optical memory according to claim 20 wherein said another means for projecting includes means for focusing said electromagnetic radiation on said at least one of said information storage regions. ### Claim 77 (depends on 20) An optical memory according to claim 20 wherein said means for selecting includes means for applying relative motion between said electromagnetic radiation and said information storage element. ### Claim 78 (depends on 21) An optical memory element according to claim 21 wherein said means for selecting includes means for applying rotary motion to said information storage element. ### Claim 79 (depends on 37) An optical memory element according to claim 37 wherein said electromagnetic radiation absorbing substance is a dye polymer which is absorptive at said given wavelength. ### Claim 80 (depends on 37) An optical memory element according to claim 37 wherein said electromagnetic radiation absorbing substance is a substance which converts said electromagnetic radiation at said given wavelength to heat. ### Claim 81 (depends on 37) An optical memory element according to claim 37 wherein said electromagnetic radiation absorbing substance is a cholesteric liquid crystalline polysiloxane having approximately 10% benzophenone disposed therein. ### Claim 82 (depends on 37) An optical memory element according to claim 37 wherein said electromagnetic radiation absorbing substance is a cholesteric liquid crystalline polysiloxane having carbon black in concentrations in a range of 0.5% to 1% disposed therein. ### Claim 83 A memory cell comprising a cholesteric liquid crystal which is reflecting to incident circularly polarized electromagnetic radiation at a given wavelength, and, means for reversibly altering said crystal to change said crystal from reflecting to transparent to said incident electromagnetic radiation. ### Claim 84 (depends on 83) A memory cell according to claim 83 wherein said given wavelength is in the visible range. ### Claim 85 (depends on 83) A memory cell according to claim 83 wherein said given wavelength is in a range of 300 nm to 14,600 nm. ### Claim 86 (depends on 83) A memory cell according to claim 83 wherein said means for reversibly altering includes an electromagnetic radiation absorbing medium disposed in thermally conductive contact with a surface of said crystal. ### Claim 87 (depends on 83) A memory cell according to claim 83 wherein said means for reversibly altering includes an electromagnetic radiation absorbing substance integral with said crystal. ### Claim 88 (depends on 83) A memory cell according to claim 83 wherein said means for reversibly altering includes means for immersing said crystal in a field and aligning said field in one of two mutually orthogonal directions. ### Claim 89 (depends on 83) A memory cell according to claim 83 wherein said means for reversibly altering includes means for immersing said crystal in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions. ### Claim 90 (depends on 83) A memory cell according to claim 83 wherein said means for reversibly altering includes means for immersing said crystal in an electric field and aligning said electric field in one of two mutually orthogonal directions. ### Claim 91 (depends on 83) A memory cell according to claim 83 wherein said means for reversibly altering includes means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said crystal. ### Claim 92 (depends on 86) A memory cell according to claim 86 further including means for immersing said crystal in a field and aligning said field in one of two mutually orthogonal directions. ### Claim 93 (depends on 86) A memory cell according to claim 86 further including means for immersing said crystal in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions. ### Claim 94 (depends on 86) A memory cell according to claim 86 further including means for immersing said crystal in an electric field and aligning said electric field in one of two mutually orthogonal directions. ### Claim 95 (depends on 86) A memory cell according to claim 86 wherein said radiation absorbing medium is a dye polymer which is absorptive at said given wavelength. ### Claim 96 (depends on 87) A memory cell according to claim 87 further including means for immersing said crystal in a field and aligning said field in one of two mutually orthogonal directions. ### Claim 97 (depends on 87) A memory cell according to claim 87 further including means for immersing said crystal in a magnetic field and aligning said magnetic field in one of two mutually orthogonal directions. ### Claim 98 (depends on 87) A memory cell according to claim 87 further including means for immersing said crystal in an electric field and aligning said electric field in one of two mutually orthogonal directions. ### Claim 99 (depends on 87) A memory cell according to claim 87 wherein said radiation absorbing substance is a dye polymer which is absorptive at said given wavelength. ### Claim 100 (depends on 91) A memory cell according to claim 91 wherein said means for projecting includes a source of electromagnetic radiation having an energy output at said given wavelength sufficient to cause heating of said crystal above its glare transition temperature. ### Claim 101 (depends on 91) A memory cell according to claim 91 wherein said means for projecting includes a laser. ### Claim 102 (depends on 91) A memory cell according to claim 91 wherein said means for projecting includes a semiconductor laser. ### Claim 103 (depends on 95) A memory cell according to claim 95 wherein said electromagnetic radiation absorbing medium is a cholesteric liquid crystalline polysiloxane having approximately 10% benzophenone disposed therein. ### Claim 104 (depends on 95) A memory cell according to claim 95 wherein said electromagnetic radiation absorbing substance in a cholesteric liquid crystalline polysiloxane having carbon black in concentration in the range of 0.5% to 1% disposed therein. ### Claim 105 (depends on 96) A memory cell according to claim 96 wherein said means for reversibly altering includes means for projecting circularly polarized electromagnetic radiation of said given wavelength of a circular polarization opposite to that of said incident circularly polarized electromagnetic radiation at said crystal. ### Claim 106 (depends on 99) A memory cell according to claim 99 wherein said electromagnetic radiation absorbing medium is a cholesteric liquid crystalline polysiloxane having approximately 10% benzophenone disposed therein. ### Claim 107 (depends on 99) A memory cell according to claim 99 wherein said electromagnetic radiation absorbing medium is a cholesteric liquid crystalline polysiloxane having carbon black in concentrations in a range of 0.5% to 1% disposed therein. ### Claim 108 An optical memory comprising a plurality of information storage elements each of which includes a plurality of information storage regions at least one which is reflecting to a given circular polarization of incident electromagnetic radiation, said at least one of said storage regions of one of said plurality of storage elements being reflecting at one of a plurality of wavelengths of said incident electromagnetic radiation and at least one of said storage regions of another of said plurality of storage elements being reflecting at another of said plurality of wavelengths of incident electromagnetic radiation, and, means for projecting said plurality of wavelength of incident electromagnetic radiation at said plurality of information storage elements to provide reflections from said storage regions. ### Claim 109 (depends on 108) An optical memory according to claim 108 further including a means for detecting said reflections from said storage regions. ### Claim 110 (depends on 108) An optical memory according to claim 108 further including means associated with each of said memory elements for changing at least a selected one of said storage regions from a reflecting condition to a transmitting condition and from a transmitting condition to a reflecting condition. ### Claim 111 (depends on 110) An optical memory according to claim 110 wherein said plurality of wavelengths of electromagnetic radiation are in the visible range. ### Claim 112 (depends on 110) An optical memory according to claim 110 wherein said plurality of wavelength of electromagnetic radiation are in a range of 400 nm to 11,600 nm. ### Claim 113 (depends on 110) An optical memory according to claim 110 wherein said given circular polarization is right-hand circular polarization. ### Claim 114 (depends on 110) An optical memory according to claim 110 wherein said given circular polarization is left-hand circular polarization. ### Claim 115 (depends on 110) An optical memory according to claim 110 wherein each of said information storage elements further includes a support substrate on which said information storage regions are disposed. ### Claim 116 (depends on 110) An optical memory according to claim 110 wherein each of said information storage elements is a member in which said information storage regions are disposed. ### Claim 117 (depends on 110) An optical memory according to claim 110 wherein each of said information storage regions is a cholesteric liquid crystal region. ### Claim 118 (depends on 110) An optical memory according to claim 110 wherein information storage regions other than said at least one of said information storage regions are transparent to said plurality of wavelengths of incident electromagnetic radiation. ### Claim 119 (depends on 110) An optical memory according to claim 110 wherein said means for projecting includes at least a single laser. ### Claim 120 (depends on 110) An optical memory according to claim 110 wherein said means for projecting includes a tunable laser. ### Claim 121 (depends on 110) An optical memory according to claim 110 wherein said means for projecting includes a plurality of lasers each of which is at a wavelength within said plurality of wavelengths of incident electromagnetic radiation. ### Claim 122 (depends on 110) An optical memory according to claim 110 wherein said means for projecting is a source of said electromagnetic radiation which is unpolarized. ### Claim 123 (depends on 110) An optical memory according to claim 110 wherein said means for projecting includes a source of circularly polarized electromagnetic radiation. ### Claim 124 (depends on 110) An optical memory according to claim 110 wherein said plurality of information storage regions includes a further plurality of information storage regions disposed in alignment with said plurality of information storage regions at least one of said further plurality of information storage regions being aligned with said at least one of said storage regions, said at least one of said further plurality of storage regions being reflecting to a circular polarization opposite to said given circular polarization. ### Claim 125 (depends on 110) An optical memory according to claim 110 wherein said plurality of information storage regions includes a further plurality of information storage regions aligned with said plurality of information storage regions at least one of said further plurality of information storage regions being aligned with said at least one of said storage regions, said at least one of said further plurality of storage regions being reflecting to said given circular polarization, and a plate of thickness equal to one-half the wavelength of one of said plurality of wavelengths of electromagnetic radiation sandwiched between said plurality and said further plurality of information storage regions. ### Claim 126 (depends on 110) An optical memory according to claim 110 further including means for detecting reflections from said storage regions.