Self-adaptive, all-or-nothing converter of an analog image analy

Details Self-adaptive, all-or-nothing converter of an analog image analy Self-adaptive, all-or-nothing converter of an analog image analy

1979-05-11

1981-01-27

Britton, Howard W.

Facsimile and static presentation processing

Facsimile

Recording apparatus

3401463AG, H04N 140

Patent

active

042478731

ABSTRACT:
In a facsimile system, for example, a document is scanned along successive scan lines and is analyzed by a photosensitive reader to produce an analog image analysis signal (V.sub.a). This signal is then converted into a two-value (i.e. black and white) signal by an all-or-nothing converter. This is done by a comparator (1) comparing the analog signal (V.sub.a) with a threshold (V.sub.d); and to avoid losing wanted information, in spite of varying background densities, it is necessary for the relative values of the analog signal (V.sub.a) and the threshold (V.sub.d) to vary so that the threshold remains somewhere between local maximum and minimum modulation levels over a range of absolute values.
In the present invention successive modulation peaks are detected by a peak detector (2) and their values stored e.g. on a capacitor. First means (a resistor 3) decay the stored value slowly so that while pale image representing peaks occur frequently the threshold as applied by circuit (6) at a value slightly below the peak value. Second means (transistor switch 4) are controlled to cause rapid decay of the stored peak value after the binary output signal has remained at black level for a run of more than 10 or so image points. Switch (5) serves to clear memory between successive scan lines.

REFERENCES:
patent: 3415950 (1963-12-01), Bartz
patent: 3696253 (1972-10-01), Deisch
patent: 3723649 (1973-03-01), Pitegoff
patent: 3912943 (1975-10-01), Wilson
patent: 3934136 (1976-01-01), Schoon
patent: 3976833 (1976-08-01), Lavery
patent: 4001500 (1977-01-01), Lavery
"IBM Technical Disclosure Bulletin," vol. 18, No. 6, Nov. 1975, New York, Penny, pp. 1962-1965.

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