Dynamic noise reduction circuit for image luminance signal

Details Dynamic noise reduction circuit for image luminance signal Dynamic noise reduction circuit for image luminance signal

1989-04-07

1990-10-09

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358166, H04N 521, H04N 514

Patent

active

049624261

ABSTRACT:
A noise reduction circuit comprising: a high-pass filter for extracting the high-frequency component of an image signal; a coring circuit for extracting a faint signal component included in the extracted high-frequency component as noise; a low-pass filter for extracting the low-frequency component of the image signal; an adder for adding the cored high-frequency component and the low-frequency component extracted by the low-pass filter; and a coring control circuit which detects the level of a luminance signal and controls the coring range of the coring circuit according to the level of the luminance signal. Since noise is visually more conspicuous in a dark portion of a picture than in a bright portion of a picture, the coring control circuit increases the coring range when the level of the luminance signal is low, namely, for a dark portion of a picture, and decreases the coring range when the level of the luminance signal is high, namely, for a bright portion of a picture to make noise indistinct over the entire area of a picture plane.

REFERENCES:
patent: 4437123 (1984-03-01), Harlan
patent: 4509080 (1985-04-01), Lagoni
patent: 4520396 (1985-05-01), Dischert
patent: 4536796 (1985-08-01), Harlan
patent: 4587561 (1986-05-01), Kudo

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