Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1984-12-11
1986-12-02
Britton, Howard W.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358152, 358160, 358178, 360 111, H04N 701, H04N 553
Patent
active
046269100
ABSTRACT:
In a field signal-frame signal conversion system including means for applying a delayed field signal delayed by 1/2 of one horizontal scanning period and a thru field signal, which is the same as the above field signal but not delayed, and switching means for alternately selecting the field signals at a time interval of one vertical scanning period to provide a frame signal, a circuit for preventing appearance of flicker attributable to the field signal-frame signal conversion, said circuit comprising a synchronizing signal separating circuit separating a synchronizing signal from the frame signal appearing at the output of said switching means, a sampling pulse generating circuit generating, in response to the application of the separated synchronizing signal, a sampling pulse signal synchronous with the change points from the sync tip level to the pedestal level and having a pulse width equal to or smaller than that of the serrating pulses, a sample and hold circuit operating in response to the sampling pulse signal for sampling the frame signal appearing at the output of said switching means, a clamping voltage generating circuit comparing the output signal of said sample and hold circuit with a reference value thereby generating a voltage signal proportional to the difference therebetween, and two clamping circuits connected to the thru and delayed field signal lines respectively and controlled by the output signal of said clamping voltage generating circuit for maintaining constant the pedestal level of the thru and delayed field signals.
REFERENCES:
patent: 4175272 (1979-11-01), Numakura
patent: 4213151 (1980-07-01), Harford
patent: 4298896 (1981-11-01), Heitmann
patent: 4386367 (1983-05-01), Peterson
Britton Howard W.
Fuji Photo Film Co. , Ltd.
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