Christopher M Carpenter

US Patent:

57777608, Jul 7, 1998

Filed:

May 10, 1996

Appl. No.:

8/644810

Inventors:

Nathan J. Hays - San Francisco CA
James A. Henson - Morgan Hill CA
Christopher M. Carpenter - Sunnyvale CA
William R. Akin - Morgan Hill CA
Richard M. Ehrlich - Saratoga CA
Lance D. Beazley - San Jose CA

Assignee:

Quantum Corporation - Milpitas CA

International Classification:

G03H 102
G03H 128
G11C 1304
G11B 724

US Classification:

359 7

Abstract:

A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e. g. voice coil motor) which respond to position feedback information and adjust the angular position of the reference angle of a reference beam to maximize SNR by reducing crosstalk, thereby improving storage capacity.