Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-02-20
1992-07-14
Coles, Sr., Edward L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358463, H04N 140
Patent
active
051308223
ABSTRACT:
A digital signal is provided by correcting image signal distortions contained in an image signal outputted from an elongated direct contact type image sensor in an image reader such as a facsimile device, which image sensor reads patterns on a document in contact with the document. The image signal distortions of the sensor output are so-called shading distortions due to sensitivity distribution of sensor elements or distribution of light from light sources onto the document. Signal distortions are corrected from both a white signal outputted from the sensor when a white document is read and a black signal outputted when a black document is read. The white signal and the black signal are stored and reproduced to generate a reference signal which is obtained by dividing the voltage range across both the signals at a predetermined ratio. The digital signal is obtained by comparing the sensor output with the reference signal. If necessary, a pseudo-black signal may be produced by dividing the voltage of the white signal.
REFERENCES:
patent: 3723649 (1973-03-01), Pitegoff et al.
patent: 4525741 (1985-06-01), Chahal et al.
patent: 4578711 (1986-03-01), White et al.
patent: 4961117 (1990-10-01), Rumley
Hara Eiichi
Nagata Tatsuya
Watanabe Michihiro
Yamada Takehiko
Coles Sr. Edward L.
Grant II Jerome
Hitachi , Ltd.
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