Methods for converting a video signal into a black/white signal
US4315285A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 1, 1979 |
| Grant date | Feb 9, 1982 |
| Priority date | — |
| Expiry date | Aug 1, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/403
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The invention relates to facsimile reproduction and particularly to a method for converting a video signal obtained by scanning an original dot by dot and line by line, into a bilevel black/white signal. In the black/white recording of colored originals in which both the background and the information can be white, black, grey or colored, grey/black transitions coming from "white" and grey/white transitions coming from "black" are frequently not evaluated correctly by the dynamic threshold so that information is lost in the copy. In order that these types of transitions are also detected, it is suggested to eliminate the DC component of the video signal and to compare the video signal modified in this way with a second dynamic threshold signal derived from it. The comparison signal is logically linked to the customary black/white signal in such a manner that the black/white signal is flipped to "white" at a grey/black transition and to "black" at a grey/white transition in each case for a specified time interval. In this manner, for example between a colored area in the original recorded as "black" and a black letter in this area, a white boundary line is created which makes the fr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.