Video amplifier for optical scanners
    5.
    发明授权
    Video amplifier for optical scanners 失效
    用于光学扫描仪的视频放大器

    公开(公告)号:US3626092A

    公开(公告)日:1971-12-07

    申请号:US3626092D

    申请日:1969-07-15

    Applicant: IBM

    Inventor: WILSON MELVIN G

    CPC classification number: H04N1/401 G06G7/24 G06K9/20

    Abstract: To correct for intensity variations in an optical scan generator, a first photodetector receives a light input directly from the generator, while a second photodetector receives light reflected from a document. A converter produces logarithmic representations of both photodetector outputs, and feeds them to a differential amplifier for subtraction. A video processor then produces a digitized video signal from the amplifier output. A low-frequency level control feeds the amplifier output back to its input to provide drift compensation by referencing the average background to a specified output level. The level control may be disabled by certain values of the digitized video signal.

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