Research And Improvement Of Three-Dimensional Absolute Measurement System Based On Point-Diffraction Interferometry

With increasing study of three-dimensional absolute displacement system,it can meet the needs of high-speed industrial measurement well.The three-dimensional measurement system which is based on point diffraction has become a feasible measurement system based on its portability and real-time performance.In this paper,aiming at the problem of low measurement precision in the transverse direction parallel to the stripe of the single fiber pair point-diffraction interferometer three dimension measurement system,a three dimensional absolute measurement system based on dual-path point-diffraction interferometer system is proposed.The main research contents are as follows:(1)The system model of single path diffraction interferometer is introduced,through the three-dimensional absolute measurement mathematical principle and mathematical model,the difference of displacement sensitivity in the two orthogonal directions of the point-diffraction interference system with only one fiber pair is analyzed.The overall design of dual-path point-diffraction interferencer system is presented,and the measurement flow of the whole experiment is outlined.(2)The fast particle swarm optimization algorithm is optimized and the setting of the optimal parameters are introduced to improve the anti-jamming ability,the measurement precision and the speed of the system in practical application.The accuracy of single path and dual-path point diffraction interferometry system is compared.In the simulation with 5nm random noise,the dual-path point-diffraction interferencer system achieves better than sub micron level in three directions simultaneously.(3)Analysis of several main factors of three dimensional absolute measurement system based on dual-path point-diffraction interferometer contributing to the difference between ideal and actual measuring range,including fiber point diffraction wavefront aperture angle,CCD performance,laser power and probe structure.(4)According to the theoretical simulation design,the hardware platform of dual-path point-diffraction interferometer is built,and a submicron aperture optical fiber probe is designed and fabricated.The software platform has been designed based on MATLAB,and the comparison of experiment result between point-diffraction interferometer and three-dimension measurement machine is carried out.Through the improvement of system model,measuring light path,measuring probe and reconstruction algorithm,the dual-path point-diffraction interferometer system proposed in this paper can solve the problem of measurement accuracy inconsistency in three directions of single path point-diffraction interferometer system,and finally achieve micrometer measurement in three directions.