A system for scanning an illuminated area

This invention relates to a system for scanning an illuminated area (20) in which a linear image sensor (18) and the video channel (22, 12, 26 and 16) associated with the sensor are calibrated to maximize the video signal available. The sensor is limited in output by saturation of the CCD analog shift registers in the sensor. The channel is limited by the range of the analog-to-digital converter (16) in the channel. The useable video signal is maximized by calibrating the sensor (18) relative to its saturation condition and by adjusting the gain of the video channel relative to the range of the analog-to-digital converter (16). The sensor is calibrated by adjusting its exposure to illumination. The adjustment may be made by adjusting the illumination source (10) or by changing the sampling interval T for the sensor (18). The gain is adjusted by using a variable gain amplifier (12). A microprocessor (14) monitors the digitized video signal and controls the exposure and gain to calibrate the sensor and channel.