Method for three dimensional optical data storage and retrieval
First Claim
1. A method for writing optical data with three-dimensional resolution, comprising:
- producing a single, intense beam of focusable, coherent light;
focussing the beam on a photosensitive material to produce two-photon excitation of said material at the focal point of the beam to thereby produce a detectable characteristic change in said material.
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Accused Products
Abstract
In a method of high density (>1012 bits/cc) optical recording of information in a three-dimensional multilayered format, information is written in a photopolymer as submicron volume elements of altered index of refraction. The index change results from alteration of the photopolymer induced by two-photon excitation of the photo-sensitizer at the waist of a highly focused beam from a subpicosecond colliding pulse modelocked laser. Quadratic dependence of two-photon excitation on incident instantaneous intensity serves to confine crosslinking of the polymer to the focal volume; hence, bit array layers may be written with thicknesses on the order of the confocal parameter. As an example, eight well resolved bit planes can be written in a olymer film about 30 microns thick. Information written in this manner may be read with sufficient axial resolution by differential interference contrast (DIC) or confocal microscopy. This technique may be employed in multilayered write once read many (WORM) optical storage discs, for example.
166 Citations
27 Claims
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1. A method for writing optical data with three-dimensional resolution, comprising:
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producing a single, intense beam of focusable, coherent light; focussing the beam on a photosensitive material to produce two-photon excitation of said material at the focal point of the beam to thereby produce a detectable characteristic change in said material. - View Dependent Claims (2, 3, 4, 5, 6, 15, 16, 17, 18, 19, 20, 21)
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7. A method of reading optical data stored as a refractive index inhomogeneity in a medium, comprising:
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producing a polarized laser read beam; producing from said read beam a pair of focused cross-polarized component beams; focussing said component beam pair at adjacent locations in a medium containing inhomogeneities, and scanning said focussed beams through said medium to produce an optical interference signal indicative of inhomogeneities in said medium.
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8. A method of writing and subsequently reading optical data with three-dimensional resolution, comprising:
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providing a three-dimensional medium of photosensitive material capable of modification by the application of light of a predetermined intensity; producing a single, intense beam of light; focussing said beam of light at a focal point within said medium; scanning said focal point through said medium to produce at selected points in said medium two-photon excitation of said medium to produce a modification of a selected characteristic of the medium, each such modification representing an optical data bit in said medium; and thereafter reading optical data bits produced in said medium by scanning a focused reading beam through said medium to produce an interference pattern corresponding to said optical data bits.
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9. A method of reading optical data stored as a refractive index inhomogeneity in a medium, comprising:
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producing a polarized laser read beam; producing from said read beam a pair of divergent cross-polarized component beams; focusing said component beam pair at adjacent locations in a medium containing index inhomogeneities; collecting the component beam pair transmitted through said medium; recombining the transmitted component beam pair to produce a recombined beam; and analyzing polarization of the recombined beam to produce a signal beam indicative of refractive index inhomogeneities in the medium. - View Dependent Claims (10, 11, 12, 13, 14)
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22. A method for storing data with three-dimensional resolution, comprising:
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selectively producing a single, intense beam of coherent light representing data to be stored; focussing said beam to produce a focal region within a three-dimensional photosensitive optical storage material capable of optically sensible characteristic changes upon two-photon excitation; scanning said focal region within said storage material to plural locations in said material and causing said beam to produce two-photon excitation at selected locations within said material to produce at said selected locations characteristic changes in said material representing said data to be stored. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification