Encrypted holographic data storage based on orthogonal phase code multiplexing
US5940514A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 30, 1996 |
| Grant date | Aug 17, 1999 |
| Priority date | — |
| Expiry date | Apr 30, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03H2001/2675
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An encryption method and apparatus for holographic data storage are disclosed. In a system using orthogonal phase-code multiplexing, data is encrypted by modulating the reference beam using an encryption key K represented by a unitary operator. In practice, the encryption key K corresponds to a diffuser or other phase-modulating element placed in the reference beam path, or to shuffling the correspondence between the codes of an orthogonal phase function and the corresponding pixels of a phase spatial light modulator. Because of the lack of Bragg selectivity in the vertical direction, the phase functions used for phase-code multiplexing are preferably one dimensional. Such phase functions can be one-dimensional Walsh functions. The encryption method preserves the orthogonality of reference beams, and thus does not lead to a degradation in crosstalk performance.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.