Workpiece identification for high lateral resolution - using two pointwise scannings of each line and stored reference

The method is for identification of workpieces, in partic. from workpiece geometry and/or position, in which at least one characteristic parameter is sensed and compared with a reference image as the piece moves relative to the scanner, are designed for high resolution perpendicular to the direction of motion. If the scanned image and the reference image do not coincide an error signal is generated. The piece is scanned twice pointwise along the same line, but with a sidewise displacement between scannings. A number of reference points corresp. to all sequentially scanned points of each line of the piece is held in store, and each recorded point is compared with its corresp. reference point.