US 5,471,455 A · High density optical storage system

Abstract

Digital information is represented by surface steps orthogonal to the surface of a record carrier, said steps having a plurality of values between one tenth and 10,000 nanometers. The steps are read out by an optical differential interference method that is capable of resolving one tenth of a nanometer. The steps are written by a repeated masking and etching technique to form a master record carrier on glass from which a stamper is formed by molding and used to stamp replicate record carriers in polymeric material. In a different embodiment of the record carrier the surface steps are created by a modulated laser beam that ablates an integral number of layers from a pre-coated multilayer structure. In a third embodiment the data is represented by modulating the index of refraction between spots on a thin material film. The index difference is written optically. An extension to multiple thin film layers is also disclosed. An optically writeable embodiment of the invention is presented wherein the surface steps are produced by ablating a surface, utilising optical energy pulses.

Claims19

Dependent claims

In a high density optical information storage system having a light source that generates partially coherent incident light of a characteristic wavelength for illuminating simultaneously a plurality of adjacent track regions and decoding compressed information stored in said system, wherein an atomic unit of said compressed information corresponds to an M-bit word of decoded information, M being a fixed integer greater than 1, an information storage record carrier comprising:

a track structure defined on a substrate consisting of a plurality of said track regions, said M-bit word being uniquely encoded and stored as an optically-detectable difference in a common physical characteristic of adjacent, first and second track regions;
such that, when said first and second track regions are illuminated simultaneously by said partially coherent incident light, a reflected light signal with corresponding first and second reflected beams results, said first and second reflected beams having, respectively, a first and second phase with a phase difference uniquely determined by said optically-detectable difference;
said phase difference uniquely corresponding to said M-bit word of decoded information.

Dependencies are inferred from the claim text.

High density optical storage system

Life of this patent

High density optical storage system

Life of this patent

Abstract

Claims19