Browse Prior Art Database

Effective Automatic Aperture for Room Light C:CD Scanner Camera

IP.com Disclosure Number: IPCOM000045359D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Giordano, FP: AUTHOR

Abstract

A photodetector is placed in proximity to a CCD (charge-coupled device) scanner array to monitor the incoming light intensity which would be seen by the CCD array during scanning. This arrangement provides an automatic aperturing for the CCD scanning array so as to compensate for variation in room light intensity.

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Effective Automatic Aperture for Room Light C:CD Scanner Camera

A photodetector is placed in proximity to a CCD (charge-coupled device) scanner array to monitor the incoming light intensity which would be seen by the CCD array during scanning. This arrangement provides an automatic aperturing for the CCD scanning array so as to compensate for variation in room light intensity.

The proposed idea is to incorporate a photosite or photodetector either on the CCD scanner chip or discretely in the plane of the CCD scanner array to control the clocking rate of the array. This photo detector monitors incoming light intensity that would be seen by the C:CD array during scanning and correspondingly, through a current to voltage converter, produces an output voltage related to that intensity. This output voltage is converted to a digital value which is used to program a clock divider network for varying the clocking rate of the CCD scanner array. Depending on the light intensity, the sampling time for each pel (picture element) either increases or decreases, having a net effect of aperturing the incoming light level to the device. The photodetector output could be tailored linearly or logarithmically to provide the desired relationship between image brightness and sampling rate within the dynamic range of the CCD device.

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