Abstract

A new detection method for the reference position (zero position) of an optical encoder by using a diffraction grating with variable pitch is proposed. Movement of the diffraction grating changes the position of the grating relative to the radiating laser spot, altering the grating pitch that is illuminated by the laser and causing a change in the diffraction angle of the beam. The change is detected by two photodiodes. Our experiment shows that the method can provide highly accurate detection of the reference point in the submicrometer range.

© 1993 Optical Society of America

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