TW345615B - Diffractive grating rotary optical encoder with high tolerance to grating defects and misalignment - Google Patents

Abstract

A diffractive grating rotary optical encoder with high tolerance to grating defects and misalignment, having a unique structural design described in the embodiments of the invention; two light beams being incident in two different directions on an identical light point on the diffractive grating or forming two light points on the grating using a minute shifting of the light source, the angles between the two incident directions and the normal direction of the grating plane separately being approximately equal to the positive/negative first step diffraction angles of the grating; when inference stripes are formed by the diffraction beams generated by the incident lights on the diffraction grating, the conversion of photoelectrical signals of the system being used to obtain the displacement of the diffractive grating; the assembly components comprising: a diffractive grating attached to a moving article and having a relative motion with the incident light point as the measurement ruler of displacement; a measurement light beam sub-system generating first and second light beams and directly impinging on the diffractive grating thereby generating a diffractive light; a set of Fourier transform optical sub-system located on a common light path of the positive/negative first step diffractive light generated by the diffractive grating; a set of signal receiving optical sub-system for detecting the inference light signals generated by the secondary diffraction light of the diffractive grating.