Converting a video signal into a two-level signal
US4234895A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 3, 1979 |
| Grant date | Nov 18, 1980 |
| Priority date | — |
| Expiry date | Jan 3, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/403
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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 pre…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.