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Photoconductive Laser Scanned Panchromatic Image Transducer

IP.com Disclosure Number: IPCOM000084682D
Original Publication Date: 1975-Dec-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hovel, H: AUTHOR [+3]

Abstract

An image transducer is described which comprises a photoconductor layer of high resistivity, direct band-gap material contacted on both sides by transparent ohmic contacts. The transducer is so constructed that it can sense a panchromatic light image on one side and this image, in turn, can then be read out by a monochromatic or easily deflectable laser beam. The resistivity of the layer, the dimensions of the layer and the voltage applied to the contacts are designed to provide an output current proportional to the input intensity on the first side, to optimize the signal amplitude and to maximize the speed consistent with obtaining sufficient signal amplitude.

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Photoconductive Laser Scanned Panchromatic Image Transducer

An image transducer is described which comprises a photoconductor layer of high resistivity, direct band-gap material contacted on both sides by transparent ohmic contacts. The transducer is so constructed that it can sense a panchromatic light image on one side and this image, in turn, can then be read out by a monochromatic or easily deflectable laser beam. The resistivity of the layer, the dimensions of the layer and the voltage applied to the contacts are designed to provide an output current proportional to the input intensity on the first side, to optimize the signal amplitude and to maximize the speed consistent with obtaining sufficient signal amplitude.

Light incident on the first side creates hole-electron pairs on that side. Since the opposite side of the device is still high resistivity, the electric field then becomes high on the dark side and low on the illuminated side.

If both sides are illuminated and if the intensity on the second side is high (by a laser for example) the conductivity on that side is much higher than on the first side. The electric field becomes high on the first side and the output current is proportional to the intensity on the first side.

In use a voltage is applied across the entire area of the imaging device, light is incident on the first side in an applied pattern and a laser spot is incident on the second side for reading the pattern on the first side. When the...