Displacement Measurement by a Linear Encoder Using a Diode Array
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
A typical optical encoder consists of precisely spaced parallel lines and is attached to the workpiece for motion measurement. By counting the number of lines going past a fixed sensor, the displacement is computed. The accuracy of measurement depends largely on the precision of the encoder lines. Any stress that alters the geometry (e.g., spacing) of the lines degrades the measurement accuracy. The geometric distortion may be a result of the manufacturing process. An encoder embodiment is described herein where the accuracy depends far less on maintaining the geometry of the encoder; instead, accuracy depends upon the sensor (a diode array in this case). As illustrated in Fig. 1, three components constitute the measuring system. The encoder strip is attached to the workpiece and slides over the sensor array.