Method and apparatus for raster scanning of images

摘要

A scanner has a window in its housing through which the scanning beam emerges to impinge upon an indicia to be read. The beam scans in a raster fashion over the window, and as it does so it impinges upon beam position indicating means which locate the position of the beam with respect to the scanner in at least certain portions of the scan pattern. Specifically, the beam position indicating means determines the position of the beam in a direction perpendicular to the overall scanning direction. In a preferred embodiment, the beam position indicating means may comprise one or more CCD's which provide electrical output signals dependent upon the position of the beam when it impinges upon them. Alternatively, the beam position indicating means may comprise passive code means such as a stacked series of bar code symbols. The location of the beam when it scans across the symbol can be determined by the unique pattern of reflections.