Method and apparatus for reading coded labels

Abstract

Method and apparatus for reading machine readable coded labels on merchandise at a check-out station. A window is associated with the check-out station, together with means for supporting merchandise for movement past the window. A laser source having an output beam focused at a plane slightly beyond the window produces multiple vertical beams V.sub.1, V.sub.2, V.sub.3 having predetermined angular divergence and a horizontal beam H. Scanning optics, including a mirror wheel having a plurality of mirrors thereon, provides a raster location and a sub-raster location. Relay optics accept and inject the horizontal beam into the raster location movement of the wheel causing the horizontal movement of the H scan line at the window. The vertical beams impinge upon the sub-raster location from which the relay optics accept and inject the beams V.sub.1, V.sub.2, V.sub.3 over to the raster location. The relay optics serve to transform the motion of the wheel at the sub-raster location into a vector cancelling the horizontal scanning component at the raster location while adding a resultant of the sub-raster scan into a point image with a purely angular scan component at the raster location. Gating means is provided for permitting only one of the beams V.sub.1, V.sub.2, V.sub.3, or H to pass through the system at a time. Retrodirective viewing means receives reflective light from the area of impingement of the beam on the label, the reflected light being converted into electric signals indicative of the strength of reflection.