Research On The Zero Alignment Technology For Plane Grating Measurement System

Grating due to its high precision, less susceptible to environmental interference, small size, easy to operate, cost advantages are not widely used as one of the ultraprecision measuring tools. Alignment accuracy is incremental encoders important indicator, so how to improve the alignment accuracy is a raster measure important aspects of technology development.This paper presents a double grating zero alignment system, including scanning grating and scale grating. Design of a dual grating structure and optical structure, followed by photoelectric conversion through the design and data collection related to basic circuit output signal, designed to filter the signal processing algorithm, achieved a greater working distance(≥20mm) reached premise alignment precision micron(≤1μm).The main research topics are as follows,First, designed the important parameter of the scanning grating and scale grating by use of relevant theory. With the imaging scanning principle,designed coding structure of the double grating and simulation; Simulation Fresnel diffraction effects, designed the basic groove width of double grating; Derivation diffraction efficiency formula, set the internal cycle reticle grating structure.Secondly, designed the optical structure,based on double grating zero alignment system.,achieved a light signal detection of parallel light is incident on the positive.Then, photoelectric converting circuit and arithmetic circuit is designed. After the realization of signal acquisition, For larger output signal noise disadvantages,designed a variable compression enjoyed filtering algorithm,the signals are filtered success. And Kalman filter method were compared.Finally, verify the double grating zero alignment system through experiments.The distance of the scanning grating and scale grating is 21 mm, Match a larger working distance condition. Used Single-frequency laser interferometer to measure, after Kalman Filter and variable compression enjoyed filtering algorithm, alignment accuracy are 0.72μm. Finally successfully achieved micron alignment accuracy.