Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-06-29
1992-05-05
Brinich, Stephen
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358163, H04N 140
Patent
active
051113112
ABSTRACT:
An image reading apparatus capable of operating in a normal reading mode for outputting a digital image signal and a test mode for preparing a black correction signal, comprises an image reading device for photoelectrically reading an image and outputting an analog image signal; an A/D converter for converting the analog image signal into a digital image signal, the A/D converter being selectively provided with either a high or low reference potential to select either a wide or narrow conversion scale range, respectively; a producing circuit for producing a black level correction signal; a correction circuit for correcting an analog image signal based on the black level correction signal; and a controller for controlling the image apparatus to operate in the test mode or the normal reading mode. In the test mode, the image reading device reads a black image and outputs a black analog signal, the A/D converter is provided with the low reference potential and converts the black analog signal into a black digital signal, and the producing circuit produces a black level correction signal on the basis of the black digital signal. In the normal reading mode, the correction circuit corrects an analog image signal on the basis of the black level correction signal, and the A/D converter is provided with the high reference potential and converts the corrected analog image signal into a digital image signal.
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Brinich Stephen
Konica Corporation
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