Design of an Optical Mechanical System for High-Resolution Encoders

Abstract

An optical mechanism composed of a movable part and a fixed part for the increment high-resolution optical displacement encoders is proposed in this paper. The parallel light emitted from the movable part passes through a double-concave lens and a specially designed optical grating; it is then projected onto a phototransistor array receiver to indicate the displacement of the movable part. The relationship equation of the lens is developed to design an optical mechanism which can enlarge the displacement so that it becomes observable. Based upon the simulation results, a specially designed optical grating is designed to compensate for the deviations on the detecting surface and to derive the increment movement of the light source. The simulation results indicated that the optical mechanism with 50 times magnification could make the 10 nm movement intervals of a light source be about 500 nm movement intervals in the detecting surface. Furthermore, an experimental system with a 200 nm resolution is established to verify the possibility of the proposed structure.