Differential video image compression in holographic media
US5877873A · kind A · utility
Inventors
Key dates
| Filing date | Jul 24, 1996 |
| Grant date | Mar 2, 1999 |
| Priority date | — |
| Expiry date | Jul 24, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03H2260/54
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A video image Fk! is identified as a basis image and stored as a basis page Sk! in a holographic storage medium. A subsequent image Fk+n! is stored by recording in the medium a page Sk+n!=Fk+n!-ak!Fk!, where ak!.noteq.0 and preferably ak!=1. The page Sk! is recorded with a reference beam Rk!, while Sk+n! is recorded with a reference beam Rk+n! orthogonal to Rk!. The basis page is reset whenever the average intensity of a page to be stored exceeds a predetermined threshold. An image F'k! is retrieved by reading basis page Sk! and letting F'k!=Sk!. Subsequent images F'k+n! are retrieved as Sk+n!+bk!Sk!, where bk!.noteq.0 and preferably bk!=ak!=1. The page addition step is performed coherently, i.e. by accessing the medium with a reference wave function Rk+n!+bk!Rk!. The coherent addition is achieved by using a compound phase-and-amplitude modulator in a phase-code-multiplexed system, and by simultaneously accessing the storage medium at two different angles in an angle-multiplexed system. Differential video compression leads to a reduction in interpage crosstalk and to a capacity increase in crosstalk-limited memories. Optical page-by-page addition allows fast readout and eliminates …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.