Bar code reader with closed-loop scan beam focusing

摘要

A bar code reader including automatic scan beam focusing based upon decoding performance is disclosed herein. The bar code reader includes a focusing lens which is movably supported along the light path of the scanning beam. An electric motor is coupled to the lens support to move the lens relative to the light beam source in response to control signals. The control signals are produced based upon the data error rate for the data produced by the decoding circuit of the reader from the signals produced by the photodetector therein. Based upon the data error rate, the electric motor is controlled to move the lens to focus the light beam and reduce or eliminate the data error.