Study of a new design of an incremental optical encoder

摘要

A new design of an incremental optical encoder with a sub-micrometric resolution, composed of a divergent beam coming from an uncollimated laser diode, a sinusoidal phase diffraction grating and a detector consisting of a mask and a photodiode array is presented. It is modeled by the scalar theory of diffraction in the Fresnel approximation, obtaining the expression for the field at the detector plane. The tolerance of the system to rotations or displacements of its elements is analyzed. The output of the photodiode array is connected to an electronic interpolation circuit in order to verify the viability of the design.