Motion Sensor Featuring Triangular Aperture,
Original Publication Date: 1979-Apr-01
Included in the Prior Art Database: 2005-Feb-20
To sense the motion of an illuminated surface and measure its displacement or velocity, a photocell can be used with an aperture in a mask to monitor the passage of lines or registration marks on the moving surface. The relative size and shape of the sense mark and the aperture determine the accuracy and usefulness of the output signal from the photocell. For example, a triangular aperture is very effective for monitoring the passage of lines essentially rectangular marks on material such as paper.