Optical memory with pit depth encoding
US5453969A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 4, 1994 |
| Grant date | Sep 26, 1995 |
| Priority date | — |
| Expiry date | May 4, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03H1/0493
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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, …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.