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BROAD CONTEXT BACKGROUND DETECTOR

IP.com Disclosure Number: IPCOM000025189D
Original Publication Date: 1983-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 99K

Publishing Venue

Xerox Disclosure Journal

Abstract

Referring to the drawings, an electronic page scanning system is shown with the document page 3 at object area or platen 4 imaged through a lens 5 onto either a raster imager or an area imager 6. At startup of the system, calibration for gain and offset is carried out by placing a known calibration target in the object area 4.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 58% of the total text.

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XEROX DISCLOSURE JOURNAL

BROADCONTEXTBACKGROUND Proposed Classification DETECTOR U.S. C1. 358/282 Douglas G. Wiggins Int. Cl. H04n 1/40

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Volume 8 Number 6 November/December 1983 525

 N GAl .--) m- CONTROL

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DIGITAL

  IMAGE ---C MEMORY PROCESSING

[This page contains 1 picture or other non-text object]

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BROAD CONTEXT BACKGROUND DETECTOR (Cont'd)

Referring to the drawings, an electronic page scanning system is shown with the document page 3 at object area or platen 4 imaged through a lens 5 onto either a raster imager or an area imager 6. At startup of the system, calibration for gain and offset is carried out by placing a known calibration target in the object area 4.

To detect background, a photodiode 7 is mounted in the optical path in front of the lens 5, photodiode 7 being mounted in such a way as to minimized the amount of light obstructed. Photodiode 7 operates to detect the average density of the document 3 being scanned over some suitable context which for text indicates background and for photographs indicates darkness. Photodiode 7 is calibrated in the same manner as the scanning system is calibrated.

As shown in Figure 2, the image signals from imager 6 are output via a gain control 11 to A/D 12 which converts the analog image signals to digital. Digital image signals from A/D 12 are thereafter processed by suitable digital signal processing circuitry 14 and output to a user such as memory 15. A feed back loop 16 with microprocessor 17 allows the microprocessor to sample each pixel and generate a gain correction value and thus regulate the amount of signal gain provided by circuit 11 in response to t...