Television gamma corrector with symmetrical response about black-level
US4499494A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 27, 1982 |
| Grant date | Feb 12, 1985 |
| Priority date | — |
| Expiry date | Sep 27, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N23/83
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A television camera or other source of color-representative signals such as R, G and B includes a matrix to which the R, G and B signals are applied to form luminance (Y) and color-difference (I,Q) signals. The source and matrix are coupled together by way of a signal path having a particular response or transfer function for the R, G and B signals over their normal range. Unavoidable noise occurring in the signals near black level may perturb the color-representative signals, and causes color errors. The errors are reduced by arranging the coupling to have a response to negative noise peaks into the blacker-than-black region. The response outside this normal range is complementary to the response within the normal range. In a particular embodiment the coupling includes a gamma corrector which has complementary response in the blacker-than-black region.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.