Optical scanner including exposure control

摘要

A scanner includes a photodetector, and encoder and an exposure control. For each line of pixels detected by the photodetector, the exposure control starts the exposure time and then stops the exposure time after a specified amount of relative motion has been detected. Thus, variations in the amount of relative motion cause inversely proportional variations in the exposure time to ensure that exposure time for each line of pixels corresponds to the same displacement. The exposure control can compensate for unavoidable position and velocity errors encountered in a dc motor drive and thereby allows a dc motor drive to be used in low cost commercial scanning products.