Picture contrast-increasing arrangements

Details Picture contrast-increasing arrangements Picture contrast-increasing arrangements

1979-02-01

1981-07-14

Orsino, Jr., Joseph A.

Facsimile and static presentation processing

Facsimile

Recording apparatus

H04N 140

Patent

active

042790034

ABSTRACT:
Contrast is increased when reproducing originals, by using a first correcting signal for continuous-tone areas in the original and a second correcting signal which affects only line elements (narrow lines) in it. To generate a picture signal and a surrounding-area signal, an opto-electronic scanning member having a picture-point aperture and a surrounding-area aperture is provided. The diameter of the picture-point aperture is approximately equal to the width of the line elements in the original which are to be corrected.
The first correcting signal is obtained from the picture signal and the surrounding area signal in a difference stage, and a selectable proportion of it is superimposed on the picture signal to increase sharpness.
The difference stage is followed by a threshold circuit which allows positive parts of the first correcting signal lying above a first threshold and negative parts of the first correcting signal lying below a second threshold value to pass through, the parts which are allowed to pass through being superimposed on the picture signal as a second correcting signal, to increase sharpness for line elements.
With the arrangement, the reproduction of line elements can be optimized and the increase of contrast in continuous-tone areas can be selected so that no unsightly seams occur at jumps in tonal values.

REFERENCES:
patent: 2892887 (1959-06-01), Hell
patent: 2962548 (1960-11-01), Taudt
patent: 3197939 (1965-07-01), Ernst
patent: 3887939 (1975-06-01), Hunt

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