Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1989-02-06
1990-11-13
Coles, Sr., Edward L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358464, 358466, H04N 140
Patent
active
049706055
ABSTRACT:
The background compensation circuit defines a background threshold signal in dependence on an average value between the positive-peak and negative-peak signals previously received from the elements for scanning the pixels of the image, and in dependence on the analog signal (AS) of the pixel added to a reference signal. The circuit comprises two detectors (21, 22) for respectively detecting a positive peak and a negative peak and which each have a short charge time constant and a long discharge time constant. A summing circuit (25) generates a threshold signal (V.sub.s) as a linear combination of the signals (V.sub.max, V.sub.min) of the detectors (21, 22) the analog signal (AS) of the pixel and a reference signal (V.sub.r). Finally the threshold signal is compared (26) to the analog signal (AS) of the pixel to produce a binary reading signal which is at "one" level when the threshold signal is greater than the analog signal and is at "zero" level when the threshold signal is less than the analog signal.
REFERENCES:
patent: 3723649 (1973-03-01), Pitegoff et al.
patent: 3790706 (1974-02-01), Gubala et al.
patent: 3965290 (1976-06-01), Tisue
patent: 4234895 (1980-11-01), Sommer et al.
patent: 4468704 (1984-08-01), Stoffel et al.
Fogaroli Giuseppe
Sgreccia Ennio
Tadini Giorgio
Coles Sr. Edward L.
Ing. C. Olivetti & C. S.p.A.
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