Patent ID: 6459509
Filing Date: 2002-10-01
Classification: H04N

Abstract:
The optical reading head system having a read head pixel output and means for monitoring unacceptable pixel output error status during scanning operations, the system comprising:a scanning station for receiving a document to be scanned, the scanning station including an exposure region, the exposure region including the image region and an error-detect line, the error-detect line having a relatively high reflectivity with respect to its bordering portions of the exposure region; a detector including an array of photosensitive sites that sense reflected light from the exposure region during a detector exposure period to generate a pixel output profile of (1) the image region when a document is being scanned, whereby the error-detect line is shielded from the detector by the document, and (2) the error-detect line at a selected time when it is not being obscured by a document; a plurality of light sources for lighting the exposure region, wherein the light sources each emit an individually controllable amount of light to the exposure region during a detector exposure period such that the system's pixel output is acceptably calibrated; and a processor for (1) causing the detector to generate a pixel output image of the error-detect line while a document is not being scanned, (2) comparing the resulting pixel output image of the error-detect line with a previously obtained pixel output image of the error-detect line that was taken when the system's pixel output was acceptably accurate, and (3) generating an unacceptable error-detect signal when the compared error-detect line pixel output images are unacceptably different from one another.