Automatic gain control for image-intensified camera

Stability of a nonlinear, sampled-data automatic gain control (AGC) for image-intensified cameras is described. The AGC increases the intensifier gain if the video scene is too dim and decreases the gain if the video scene is too bright. Otherwise, the AGC does not alter the gain. The gain of the system is stable, i.e., the gain does not oscillate between two values, for all possible static video scenes if the thresholds for defining both dim and bright scenes and the gain factor are chosen properly. This paper derives the regions for gain stability and provides the criteria for choosing the thresholds and the gain factor.