CCD dark mean level correction circuit employing digital processing and analog subtraction requiring no advance knowledge of dark mean level
US5659355A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 31, 1994 |
| Grant date | Aug 19, 1997 |
| Priority date | — |
| Expiry date | Oct 31, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N25/633
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A digital black clamp circuit for calibrating the black level of an image signal produced by an imaging device, such as a CCD sensor. The digital black clamp circuit comprises a source of a video signal having a first interval of black level pixels and a second interval of image pixels; a differential amplifier having first and second inputs and an output, wherein the source is coupled to one of the first and second inputs; an A/D converter coupled to the output of the differential amplifier; a digital signal processor coupled to the A/D for accumulating and averaging digital black level pixels; a D/A converter coupled to the digital signal processor; and a control for selectively uncoupling the D/A converter to the other of the first and second inputs of the differential amplifier during the first interval of the video signal; and for coupling the D/A converter to the other of the first and second inputs during the second interval of the video signal to clamp the image pixels to an average black level.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.