Automatic camera exposure control using variable exposure index CCD sensor

摘要

An improved automatic exposure control system for an electronic still camera which uses a variable amplifier to amplify the output signal of an image sensor. A low electrical gain is used when the scene is bright enough to provide a sufficiently fast shutter speed and depth of field in order to keep from blurring the image to be captured. The gain is increased as the scene illumination decreases. Some amount of increased gain is preferably used even before the aperture of the camera is fully opened. The gain of the variable gain amplifier is adjusted as the user changes the focal length (zoom) setting, as the required shutter speed and f-number needed to provide a blur-free image depends on the lens focal length. The gain may also be adjusted as a function of focus distance setting.