Method and apparatus of controlling a pixel reset level for reducing an image lag in a CMOS sensor
US6958776B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 21, 2001 |
| Grant date | Oct 25, 2005 |
| Priority date | — |
| Expiry date | Aug 23, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N25/779
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The invention provides a method and apparatus for reducing image lag in CMOS active pixel sensors at low light levels by controlling the reset level. By ensuring that the reset level is independent of the preceding signal level, the problem of image lag can be avoided. Always resetting a photodiode to a fixed voltage is a hard reset. The maximum signal swing is limited by the reset level and the column readout amplifier. If the column circuits are not modified, using hard reset can reduce the maximum signal swing. However in dark images only a portion of the full scale is used. Therefore the amplifier gain setting can be used to determine whether to use a hard reset or soft reset. This method and apparatus for using hard or soft reset dependent on signal level improves image quality at low light levels without compromising performance at high illumination.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.