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Browse Prior Art Database

Technique for Varying Optical Density of Holographic Disk

IP.com Disclosure Number: IPCOM000060458D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Cato, RT: AUTHOR

Abstract

This article describes a technique for varying the optical density of individual facets of a multi-faceted holographic disk. The disk is made with photochromic glass. The optical density of the glass is varied by using a high intensity strobe light, which is controlled by a microprocessor. Referring to the drawing, the holographic disk 10 is similar to those in use today except that the glass substrate is made of photochromic glass. The optical density of such glass can be varied by exposing it to ultraviolet (UV) light for different periods of time. A high intensity UV source 12 is located adjacent disk 10 in a chamber 14 which is light-tight except for an optical window 16 facing the surface of the disk 10.

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Technique for Varying Optical Density of Holographic Disk

This article describes a technique for varying the optical density of individual facets of a multi-faceted holographic disk. The disk is made with photochromic glass. The optical density of the glass is varied by using a high intensity strobe light, which is controlled by a microprocessor. Referring to the drawing, the holographic disk 10 is similar to those in use today except that the glass substrate is made of photochromic glass. The optical density of such glass can be varied by exposing it to ultraviolet (UV) light for different periods of time. A high intensity UV source 12 is located adjacent disk 10 in a chamber 14 which is light-tight except for an optical window 16 facing the surface of the disk 10. The source 12 is strobed under the control of a microprocessor 18 to expose each facet of disk 10 to a specific amount of UV energy as the facet passes beneath the window 16. The response time of the photochromic glass is relatively slow. If a UV pulse of a given duration is applied to a facet once each revolution, the optical density of that facet can be maintained at or near a given level. The optical density of a facet determines how much light generated by a laser 20 will be transmitted through disk 10. Light passing through disk 10 will either be diffracted (bent) into a first-order output beam 22 or will continue in a straight line in a zero-order beam 24 towards a photodetector 26. The techniqu...