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AREA BRIGHTNESS AVERAGE THROUGH PHOTO-GATE CURRENT

IP.com Disclosure Number: IPCOM000024856D
Original Publication Date: 1982-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 62K

Publishing Venue

Xerox Disclosure Journal

Abstract

There are several applications in the processing of video data from an imaging array such as a Charge Coupled Device (CCD) where an average signal value would be useful, i.e., Automatic Gain Control (AGC), automatic thresholding, etc. To date, several approaches have been used; namely, integrating elements which identify past occurrences only and time delay through memory elements which is expensive.

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L 'EROX DISCLOSURE JOURNAL

AREA BRIGHTNESS AVERAGE THROUGH PHOTO-GATE CURRENT U.S. C1. 358/282 Richard H. Tuhro

Proposed Classification

Int. C1. H04n 1/40

There are several applications in the processing of video data from an imaging array such as a Charge Coupled Device (CCD) where an average signal value would be useful, i.e., Automatic Gain Control (AGC), automatic thresholding, etc. To date, several approaches have been used; namely, integrating elements which identify past occurrences only and time delay through memory elements which is expensive.

It is proposed here that a signal derived from the CCD photo current be used to provide average brightness information on the scan line currently being integrated. This information would be available when the scan line is shifted out.

In any solid state imaging array such as a CCD, photons create hole-electron pairs in the semi-conductor. Depending on array design, the current from either the holes or electrons is shifted to the output and sensed. The other current flows during the charge integration period but is typically not sensed.

It is proposed that this current e sensed as a measure of average line density. For a typical CCD application, 10 electrons per8cell are collected. In a CCD array having 1760 cells, there would be 1.76 x 10 electrons (or holes) flowing every integration time. If the integration time were 1 ms, there would be 1.76 x 10 electrons per second or:

9

(1.76 x loll) (1.6 x = 2.8 x coul/sec....