Non-Contact Sensor for Two-Dimensional Translation and Rotation
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Relative planar displacement and orientation of a moving part equipped with fixed light sources is measured with high resolution over a limited range by non-contact optical sensors. Two-dimensional optical position sensors, called lateral effect photodiodes, are well known and are commercially available. The position of the centroid of a spot of light is inferred from measured photocurrents (see the figure): x a (x1 - x2)/(x1 + x2), y a (y1 - y2)/(y1 + y2), Here, x1, x2, y1, y2 refer to the lateral cell currents. If the lateral cell 1 is attached to the fixed part, for example, and a light- emitting diode (LED) light source is attached to the moving part located above the cell surface, then x and y is the relative displacement of the two parts.