Electrophotographic optical memory system

United States Patent m

Magee et al.

[ii] Patent Number: 4,757,472 [45] Date of Patent: Jul. 12,1988

[54] ELECTROPHOTOGRAPHIC OPTICAL MEMORY SYSTEM

[75] Inventors: Frederick N. Magee, San Jose;

William M. Brooks, Aptos, both of
Calif.

[73] Assignee: Tecon Memory, Inc., Redmond,
Wash.

[21] Appl. No.: 948,385

[22] Filed:

Dec. 31,1986

[51] Int. G11C 13/00; G11C 13/04;

G11B 7/00; G11B 7/013

[52] U.S. CI 365/120; 365/126;

365/127

[58] Field of Search 365/120, 126, 127;

346/151, 135.1; 372/24; 369/100, 110, 111;

430/19, 350, 945

[56] References Cited

U.S. PATENT DOCUMENTS

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(List continued on next page.)

An optical memory system for storage and retrieval of digital data using a source of writing light in the visible light range and a separate source of near infrared, polarized reading light. The writing light is amplitude modulated by a signal containing the digital data to be stored. Horizontal and vertical deflectors deflect the beams to scan horizontally and vertically in response to control signals. The scanning beams are focused to a focal point to impinge upon a stationary medium manufactured of a dry film having submicron electrically photosensitive particles embedded in a thermoplastic layer mounted on a substantially transparent electrically conductive substrate. The particles are insensitive to light at the reading light wavelength. The particles are initially uncharged and the film is sensitive to light after receiving an initial surface charge. The regions of the medium with the charged particles and with the uncharged particles cause differing angular rotation of the electric and magnetic field vectors of the reading light, with the degree of rotation of the reading light after passing through the medium indicating whether a digital data bit of one or zero is recorded. A fixed mask is positioned in the focal plane of the lens and in juxtaposition with the medium. The mask is opaque to the writing and reading light beams and has a matrix of rows and columns of transparent apertures. The apertures define the extent of the regions of the medium with the charged and uncharged particles.

18 Claims, 2 Drawing Sheets

U.S. PATENT DOCUMENTS

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OTHER PUBLICATIONS

Xerox Dry Microfilm: A Versatile Camera-Film and Information-Recording Medium, SPSE, vol. 9, No. 1, Feb. 1983.

An Instant, Dry, Updatable Infrared Film with High Sensitivity and Resolution, SPSE, vol. 12, No. 1, Feb. 1986.

A Portable, Inexpensive Microfilm Camera-Processor-Viewer, Using Instant, Updatable Xerox Dry Microfilm, SPSE, vol. 6, No. 4, Aug. 1980. "AMEN" Imaging: The Last Word in Nonsilver Photography?, SPSE, vol. 28, No. 6, Nov./Dec. 1984.