Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-12-12
1992-02-18
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358166, 358174, 358172, H04N 5702, H04N 552
Patent
active
050898914
ABSTRACT:
A circuit for correcting a tone of a brightness signal generated by a television camera including an upper limiter for clipping off an upper portion of the brightness signal higher than an upper threshold level, and a lower limiter for clipping off a lower portion of the brightness signal lower than a lower threshold level which is automatically changed in accordance with a peak value of the black level of the brightness signal. A middle level brightness signal produced by the lower limiter is processeed by a non-linear circuit and then a difference between a non-linearly processed bright signal and the middle level brightness signal is derived to produce a tone correction signal. After the polarity and gain of the tone correction signal are manually adjusted, the tone correcting signal is added to the input brightness signal. In this manner the tone of a television image displayed on a television monitor screen can be corrected exclusively in a dark area without affecting the tone in a bright area. When the tone correction signal has the negative polarity, the dark background can be further darkened without decreasing the brightness in the bright area to attain a special production effect.
REFERENCES:
patent: 4038688 (1977-07-01), Chow et al.
patent: 4057828 (1977-11-01), Monahan
patent: 4589022 (1986-05-01), Prince et al.
patent: 4843472 (1989-06-01), Shinada
patent: 5021886 (1991-06-01), Shibuyama
Groody James J.
Ikegami Tsushinki Co. Ltd.
Murrell Jeffrey S.
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