Sheet registration reticles were scanned automatically by detectors of linear array CCDs. The color of registration reticles was identified by red, green and blue filters arranged in turn on photosensitive surface of CCDs. Deviation direction of CMYK plates was recognized by CCD output level under different color filters. A / D conversion of CCD output level was realized with parallel comparison A / D conversion circuit. The registration error and deviation direction of detected plates were displayed on the screen directly.