Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1987-02-17
1987-11-24
Chin, Tommy P.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358 36, 455306, H04N 5213
Patent
active
047092696
ABSTRACT:
A noise reduction circuit for video signal comprises first through third circuits each for obtaining from an input video signal a high frequency component including a noise component and for limiting large amplitude parts thereof, where a filter part of the second circuit has an impulse response characteristic wherein an amplitude increases or decays with time and is complementary to that of a filter part of the first circuit and a filter part of the third circuit has an impulse response characteristic which is essentially a combination of the two impulse response characteristics, and a fourth circuit for carrying out a subtraction between the input video signal and an output signal of the first circuit so as to obtain a first signal which is substantially eliminated of the noise component except for a noise component and distortion remaining at parts in vicinities of rises and falls in the video signal caused by the amplitude limitation carried out in the first circuit, carrying out a subtraction between output signals of the second and third circuits so as to obtain a second signal which includes the noise component and the waveform distortion of the first signal with an inverted phase, and for adding the first and second signals so as to produce an output video signal which has been substantially eliminated of all the noise component.
REFERENCES:
patent: 4216570 (1980-08-01), Nakagaki
patent: 4563704 (1986-01-01), Hirota
patent: 4646153 (1987-02-01), Fukuda
patent: 4652922 (1987-03-01), Ozaki
Chin Tommy P.
Meller Michael N.
Victor Company of Japan Ltd.
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