Ambient light automatic gain control for electronic imaging cameras and the like
US5742340A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 6, 1995 |
| Grant date | Apr 21, 1998 |
| Priority date | — |
| Expiry date | Jun 6, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N23/71
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Apparatus that performs automatic gain control (AGC) for an electronic imaging camera, especially in outdoor surveillance applications. A fiber optic link is used to collect ambient light and couple this light onto a small portion of a light sensing array of the camera. A reference voltage produced by the light sensing array in response to the light from the fiber is used by AGC circuits in the camera to control the integration time of light sensing elements of the array, the gain of the camera's video amplifier, and lens aperture, if necessary. These camera gain controls are adjusted to maintain the reference voltage derived from the light provided by the fiber optic link to be within a predefined range as the ambient light level varies due to weather conditions and time of day. Methods of providing automatic gain control correction are also disclosed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.