Patent ID: 6254003
Filing Date: 2001-07-03
Classification: G06K

Abstract:
An apparatus for optically scanning encoded data from an optically readable indicia and converting said data into an electrical signal that may be decoded to recover said data, said apparatus being of the type which continues scanning, without substantial interruption, until scanning is discontinued, including, in combination:a) an image sensor, having a pixel array that includes a plurality of pixels, for receiving an image of said indicia and for generating an image sensor signal that varies in accordance with the intensity of light incident on said pixel array and the exposure time of said sensor, said image sensor having an exposure time that can be varied over a dynamic range;b) illumination signal generating means responsive to said image sensor signal for generating an illumination signal that varies in accordance with said image sensor signal;c) exposure control means for controlling the exposure time of said image sensor, including:(i) means for storing, at a plurality of sequentially selectable storage locations, a plurality of exposure control values that correspond to different respective exposure times for said image sensor, said exposure control values being selected to make available, for exposure control purposes, approximately all of said dynamic range;(ii) means for establishing a pointer for identifying the storage location that stores the exposure control value to be used during each scan;(iii) adjusting means for advancing said pointer in a first direction if said illumination signal is greater than a maximum illumination value during a predetermined portion of a scan, and for advancing said pointer in a second, opposite direction if said illumination signal is less than a minimum illumination value during said predetermined portion of a scan;whereby the magnitude of said illumination signal changes in a stepwise manner until it remains between said maximum and minimum illumination values.