Abstract: The invention is a system and method for automatically determining a resolution of an encoder, automatically calibrating the encoder resolution, and automatically determining a length of a workpiece from the encoder resolution and encoder count. The system comprises an encoder for generating an encoder signal indicative of linear movement of a moving workpiece traveling along a path. The system also comprises a first sensor positioned along the path traveled by the workpiece, the first sensor generating a first sensor signal in response to sensing an identifying characteristic of the workpiece. The system further comprises a second sensor positioned along the path traveled by the workpiece, the second sensor generating a second sensor signal in response to sensing the identifying characteristic of the workpiece, said second sensor being positioned a known distance from the first sensor along the path traveled by the workpiece.

Abstract: A backlit display apparatus illuminates a film for displaying one or more images. The film has a series of frames and at least one mark printed on it corresponding to each frame. The marks provide information representative of frame position relative to the film or otherwise identifying the image displayed by the frame when illuminated. A light source, positioned behind the film relative to an intended viewer in front of the film, illuminates the frames. A detector detects the marks printed on the film as the film is advanced by a motor. An encoder associated with the motor detects the position of the frames as a function of the angular position of the motor when each mark on the film is detected. In response, the encoder generates a position signal representative of the detected positions of the frames. A processor controls the motor in response to the position signal to advance the film so that a selected frame is within the desired viewing area for a predetermined interval of time.