Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1995-08-15
1998-05-26
Lee, Thomas D.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
382274, H04N 140
Patent
active
057575150
ABSTRACT:
An image reading apparatus can perform shading correction with a simple arrangement. Prior to an original read operation, a prescanning operation is performed using a white reference original. Shading data is formed by a shading correction circuit and held in both an internal shading memory and a memory in a shading data confirming unit. The shading data confirming unit compares the data in both the memories to detect whether the data is destroyed. If the data is destroyed, permanent shading data is used. When the image is a halftone image, the prescanning operation is performed again to form shading data. Therefore, a conventionally used prescanning mechanism for the reference white ground can be omitted. At the same time, even when the shading data is destroyed by an abnormal voltage or the like, processing can be normally performed.
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patent: 5091789 (1992-02-01), Haneda et al.
patent: 5253083 (1993-10-01), Hirota
patent: 5325210 (1994-06-01), Takashima et al.
patent: 5398119 (1995-03-01), Suzuki
patent: 5455690 (1995-10-01), Ishikawa
Canon Kabushiki Kaisha
Grant II Jerome
Lee Thomas D.
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