Browse Prior Art Database

Image Equalizer

IP.com Disclosure Number: IPCOM000041676D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Kobayashi, Y: AUTHOR

Abstract

This article describes the concept of compensating the unflatness of an image output signal of an image sensor. A portion of an input signal to a digital-to-analog converter, to which the image output signal is applied, is blended to its output signal, or a current is fed back to the input of the digital-to-analog converter from its output to realize the optimized compensation. An image sensor 1 in a document-reading apparatus has plural sensor elements arranged in a line along the width of a document 2. A light from a fluorescent lamp 3 is reflected from the document 2. The reflected light through a lens 4 is sensed by the sensor elements to produce image signals, which are serially supplied to a sample and hold circuit 5 and a black level clamp circuit 6.

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Image Equalizer

This article describes the concept of compensating the unflatness of an image output signal of an image sensor. A portion of an input signal to a digital-to- analog converter, to which the image output signal is applied, is blended to its output signal, or a current is fed back to the input of the digital-to-analog converter from its output to realize the optimized compensation. An image sensor 1 in a document-reading apparatus has plural sensor elements arranged in a line along the width of a document 2. A light from a fluorescent lamp 3 is reflected from the document 2. The reflected light through a lens 4 is sensed by the sensor elements to produce image signals, which are serially supplied to a sample and hold circuit 5 and a black level clamp circuit 6. Due to a decrease of light intensity at both ends of the fluorescent lamp and the shading effect of the lens 4, the image output signal of the image sensor 1 indicating the reflected light from the white document becomes unflat, as shown in Fig. 1. Prior technology has tried to compensate the unflatness of the image signal by the provision of a digital-to-analog (D/A) converter 7, a comparator 8, an up/down counter 9 and a random access memory 10. During the calibration mode, under the control of a control unit 11 the unflat image output signal, indicating a top white margin of the document 2, is serially applied to the comparator 8 through the sample and hold circuit 5 and the black level cla...