Optical communication of video information with distortion correction
US4654891A · kind A · utility
Inventor
Key dates
| Filing date | Sep 12, 1985 |
| Grant date | Mar 31, 1987 |
| Priority date | — |
| Expiry date | Sep 12, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/58
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A predistortion circuit is disclosed for correcting distortions in an optical communication system caused by the characteristics of a light-emitting diode. The invention makes use of the existence of automatic gain control circuitry in the receiver portion of an optical communication system to assist in correction of distortions which occur at the transmitter end. In particular, the present invention provides passive pre-distortion circuitry in the transmitter which dynamically modifies the level with respect to which the video signal in the transmitter is clamped. The automatic gain control circuit in the receiver will detect the DC level of the received video. A shift in the DC reference level transmitted causes the receiver AGC to correct the receiver gain. Since the invention operates to appropriately adjust the clamping reference at the transmitter end in a manner which compensates for distortions introduced by the light-emitting diode, the gain correction at the receiver will be responsive to this change in clamping level and therefore tend to correct for the distortions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.