Abstract: A single pass ROS system provides a plurality of latent images which may subsequently be developed in different colors. The ROS units are initially aligned so that each color image is precisely registered at the same relative position along the exposed area of a photoreceptor belt. The alignment is accomplished by forming a pair of opposed alignment apertures in the surface of the belt and detecting coincidence or lack of coincidence of signals generated by the beginning and end of each scan line. The correction is enabled by rotating the output window in the ROS system, a transmissive optical component with no optical power, subsequent to the ROS, to create the required rotation of the projected scan line. Once the initial X and Y-axis alignments are complete, subsequent alignment is maintained through subsequent passes by checking the positions of the previously identified pixels as they advance past additional lead edge apertures formed in the process direction along the belt surface.

Abstract: The present invention is directed to a precise method of registering a plurality of ROS imagers, so as to form sequential registered images on a photoreceptor belt in a single pass. Pairs of belt holes are formed in the photoreceptor belt, outside the image area and outside of the scan width of the ROS imagers. A pair of light sources are incorporated into the post polygon optics of each ROS imager so as to produce a light spot at the photoreceptor surface which will periodically illuminate the holes on the belt. As the leading edge of the belt holes advances into the beams, detectors placed beneath the belt and beneath the exposure station provide signals representing the exposure level of the light source output. The position of a transmissive optical element with no optical power, subsequent to each of said ROS imagers, is adjusted in response to registration error signals generated by said photodetecting means to adjust the position of said scan lines.