Day/Night Low Light Level (LLL) TV Sensors

A low-cost, miniaturized Low Light Level (LLL) CCD TV camera system capable of more than 400 TV lines per picture height at an illumination level ranging from moonless starlight (10 E-4 foot candles) is proposed. The electro-optical portion of the system will incorporate an input lens with an electrically controllable iris, a GEN III image intensifier, a coupling lens and a 2/3-inch CCD. With careful design and component selection, a signal-to-noise ration of 9 or better can be achieved at low light level conditions while maintaining daylight operability. Digital techniques will be employed both to optimize image exposure and to reduce noise. Iris diameter, intensifier gain and shutter duration will be set through multi-zone metering and fuzzy logic control. Fixed pattern noise will be filtered by temporal averaging and edge-preserving spatial smoothing tehcniques. Multi-zone metering and all noise filtering algorithms will be implemented in hardware for video rate output. Performance of the final electro-optical design will be verified through a detailed math model, and that of exposure control and noise filtering will be verified through extensive computer simulation.