Experimental study of temperature characteristics in a low-light-level CMOS system

The low-light-level sensing technology has been subject to the development of image sensors. The later, developed in the recent decades, has been improved from the low light level image intensifier, EBCCD, to recently, the CMOS technology. New technologies, for instance, APS(Active Pixel Sensor), back illuminated, etc. have been supplied following the CMOS process technology, resulting in a series of CMOS detectors with high sensitivity, lower noise and fewer operation restrictions. However, as a weak signal detection system, the operation condition, for example, the temperature characteristics related with the exposure time, ambient brightness, and target brightness, also cannot be ignored. In this paper, we presented a detailed temperature characteristic analysis based on a low-light-level CMOS system. The dark current was verified based on all black tests. The calculation as followed was drawn based on the varying ambient conditions and settings of the system:1, A typical dark current curve was obtained from the experiment, double every 9℃ with environment temperature increased.2, the information acquisition ability is affected by the exposure time, ambient brightness, and target brightness, reflected by the dark current and photon noise. Meanwhile, it was proofed in this paper, in a low light level system, the traditional signal to noise ratio calculation could not delaminate the brightness caused by the dominate photo noise, resulting an error strong enough to affect signal. Therefore, in this paper, a SNR evaluate method which could improve the objectivity of the evaluation of the low light level image was provided. It was believed to be helpful to the future research.