Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1979-01-03
1980-11-18
Britton, Howard W.
Facsimile and static presentation processing
Facsimile
Recording apparatus
358280, H04N 140
Patent
active
042348951
ABSTRACT:
A facsimile scanning method for converting a video signal obtained by opto-electronic scanning of an original into a two-level signal suitable for transmission.
A first companion signal is first generated which lies essentially above the video signal and which follows the video signal when it rises but when the video signal declines remains at the voltage reached when the video signal was at a maximum until a difference value between the first companion signal and a reference signal is reached, which then comes close to the declining video signal until the difference value is reached, which remains at the voltage value then reached until the first companion coincides with the video signal, and which then follows the rising video signal.
At the same time a second companion signal is generated which lies substantially below the video signal and which progresses accordingly. From the first and second companion signals is derived a threshold signal which follows the video signal dynamically. The two-level signal is obtained by comparing the threshold signal with the video signal.
The reference signal may be the video signal or one of the companion signals. The difference values are preset at constant levels or are proportional to the mean brightness of the background of the original.
REFERENCES:
patent: 3159815 (1964-12-01), Groce
patent: 3472958 (1969-10-01), Estock
patent: 3566281 (1971-02-01), Baumann
patent: 3952144 (1976-04-01), Kolker
Sommer Rudiger
Wischer Hermann
Britton Howard W.
Dr. -Ing. Rudolf Hell GmbH
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