Browse Prior Art Database

Electroluminescent Photoconductive Flying Spot Scanner

IP.com Disclosure Number: IPCOM000080433D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 4 page(s) / 105K

Publishing Venue

IBM

Related People

Schaaf, RL: AUTHOR

Abstract

This scanner generates a flying light spot which scans an image with a television type raster pattern. An electroluminescent-photoconductive (EL-PC) element is excited by internal or external light feedback, in order to generate the flying spot.

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Electroluminescent Photoconductive Flying Spot Scanner

This scanner generates a flying light spot which scans an image with a television type raster pattern. An electroluminescent-photoconductive (EL-PC) element is excited by internal or external light feedback, in order to generate the flying spot.

Figs. 1, 2 and 3 show an arrangement whereby a localized spot on the EL layer is excited by a sync pulse, and external optical feedback of the resulting light to the PC layer causes a light spot to travel, in raster fashion, across the EL layer.

Figs. 4, 5 and 6 show an alternate construction of an EL-PC device having internal optical feedback, wherein the EL layer is selectively excited and its resulting light is fed back to the PC layer by glass laminate fiber optic elements.

Figs. 7 and 8 show another construction of an EL-PC device having internal optical feedback, wherein a photoresistive (PC) layer and a phosphor (EL) layer are sandwiched between two transparent electrical conductors. The phosphor layer is first electrically charged and then optically excited in a raster pattern by an ultraviolet lamp. The transparent conductors are then shorted, and one end of the raster pattern is illuminated by a light beam. This results in a traveling light spot which follows the raster pattern.

With reference to Fig. 1, EL-PC panel 10 is shown in cross- section. PC layer 11 and EL layer 12 are separated by opaque electrically conductive layer 13. Transparent electrically conductive layers 14 and 15 complete the device.

A sync pulse applies voltage to corner 16 of the panel. As a result, corner 16 of the EL layer emits light. Most of this light illuminates point 57 of transparent object 17, through projection lens 25. However, a fraction of this light is feedback to point 18 on the PC layer, by way of a series of mirrors 19-22 and focusing lens
23.

The feedback light at point 18 causes the resistance of the PC layer at this localized point to decrease. As a result the supply voltage to the EL layer shifts to point 24, vertically above point 16, and point 24 begins to emit light.

Mirror 19 is a beam splitting mirror. Mirror 22 is Positioned to cause the light spot to move vertically up the PC layer, as the raster scan continues. When the light spot reaches to top of a line scan, the feedback light strikes mirror 22a. This mirror is positioned to reflect the light back to the bottom of the PC layer, but to a point vertically displaced from point 18. This raster scanning of object 16 continues until the feedback light runs off the far end of the panel, to complete a scan frame of the object.

Fig. 1 shows the scanner used as an input device which converts the image of object 17 into a video signal for storage or transmission. Fig. 3 shows the scanner used as an output device. A video input signal controls voltage controlled light scattering film 26. This film is sandwiched between two

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transparent electrical conductors 27 and 28. The...