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Producing Half Tone Images for Optical Display

IP.com Disclosure Number: IPCOM000075859D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

von Gutfeld, RJ: AUTHOR [+2]

Abstract

It is well known that a laser beam of moderate power (< 0.5W) can be used to alter the reflectivity of a chalcogenide glass, by transforming the material from an amorphous to a crystalline-like material. Furthermore, it has been shown that for thin films of GeTe and mixtures of GeTeAs, that the area of the transformed region is, within certain limits, approximately proportional to the laser amplitude and/or time of exposure. This effect can be used to create quasi-continuous regions of variable reflectivity without any intermediate developing step, such as typically employed in photographic half-tone processes.

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Producing Half Tone Images for Optical Display

It is well known that a laser beam of moderate power (< 0.5W) can be used to alter the reflectivity of a chalcogenide glass, by transforming the material from an amorphous to a crystalline-like material. Furthermore, it has been shown that for thin films of GeTe and mixtures of GeTeAs, that the area of the transformed region is, within certain limits, approximately proportional to the laser amplitude and/or time of exposure. This effect can be used to create quasi-continuous regions of variable reflectivity without any intermediate developing step, such as typically employed in photographic half-tone processes.

The present schemes utilize a thin film of chalcogenide on a transparent substrate which (1) moves on a belt positioned in front of an array of laser beams, or (2) is stationary, in front of a laser beam that is deflected or which can be scanned.

In scheme (1), the laser beam array is pulsed at a constant repetition rate while the chalcogenide film moves past it at a constant rate. Each beam is focused down to ~ a 1 mu diameter size and is amplitude modulated. The resulting pattern for a single beam is shown in the Figure. The fiducial marks 1 are spaced at intervals equivalent to the laser period, times the velocity of the moving film. The spots 2 vary in size approximately proportional to the laser amplitude. The resulting contrast over a small region may be even greater than that afforded by conventional ha...