Optical memory with pit depth encoding

Details Optical memory with pit depth encoding Optical memory with pit depth encoding

1994-05-04

1995-09-26

Nelms, David C.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369110, 369112, 3692751, 3692754, G11B 700

Patent

active

054539692

ABSTRACT:
An optical storage medium constitutes a substrate imprinted with optically detectable pits, each of the pits having one of a set of predetermined pit depths, each of the pits representing a number of binary bits corresponding to the number of the predetermined pit depths in the set. The pit depth is sensed unambiguously with a conoscopic holography sensor by changing the polarization of a polarized reflected beam in accordance with its angle of propagation and sensing an intensity pattern produced after the reflected beam passes through a polarized analyzer. Alternatively, using a confocal microscopy sensor, light from either the deepest or most shallow pit depth is focused on a small pin hole in an opaque surface, and a single detector measures the light intensity on the other side of the pin hole, the light intensity being a direct measure of the pit depth. The capacity of an optical memory such as a CD disk player is increased as much as four or five times by pit-depth encoding the disk, so that each pit location represent a number of bits. For example, a standard pit depth of 3 micrometers in a CD disk is divided into 0.1 micron steps so that each pit represents nearly 5 bits, providing a nearly five-fold increase in disk capacity.

REFERENCES:
patent: 5016240 (1991-05-01), Strandjord
patent: 5144552 (1992-09-01), Abe
patent: 5339304 (1994-08-01), Hanaoka

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