METHODS AND APPARATUS FOR PROVIDING WIDE RANGE EXPOSURE CONTROL FOR IMAGE INTENSIFIER CAMERAS

The dynamic range of an image intensifier camera may be extended by using an automatic exposure control system which, in response to imager output (for example, the output of a charge coupled device (CCD) imager included in a solid state image intensifier camera), (a) generates a first control signal that controls the gain of the I.sup.2 Tube itself; (b) generates a second control signal for selectively gating the I.sup.2 Tube on or off; and (c) generates a third control signal for controlling a light attenuator that, according to a preferred embodiment of the invention, is included in the camera. The automatic exposure control system contemplated by the invention has a control range in excess of 10.sup.10 .times.; takes a measurement of the exposure from an imager (again, for example, a CCD sensor) for comparison to a desired setpoint; the measurement used may be a peak, an average or some weighted function and the automatic exposure control logic then adjusts, in order, the I.sup.2 Tube gain, the I.sup.2 Tube gating and the light attenuator (using the aforementioned first, second and third control signals), to adjust for steadily increasing light from the object under observation. In addition to automatic exposure control systems per se, the invention is also directed to camera systems which incorporate such automatic exposure control systems and to methods for realizing the automatic exposure control systems of the type described hereinafter.