Research On Three-dimensional Absolute Displacement Measurement Method Based On Point-diffraction Interference Technique

Three-dimensional absolute displacement measurement plays an important role in precision measurement, design and manufacturing fields. However, the existing three-dimensional absolute displacement measuring systems(such as coordinate measuring machine and laser tracker, etc.) have many shortcomings such as high maintenance costs, huge equipment and complex structure. A three-dimensional absolute displacement measurement method based on the point diffraction interference technique has been presented in this paper which is one of the research hotspot in the optical precision testing field, the purpose is to design a low-cost, high-precision three-dimensional absolute displacement measurement system. The measuring principle of the system has been described, an experimental platform has been set up, and simulation and actual measurement experiments have been carried out in this paper to verify the feasibility of the system.Firstly, three-dimensional absolute displacement measurement system based on point diffraction interference technique has been presented, and the measuring principle of the system has been introduced, and the function and role of system building blocks have been described respectively, including system optical path, point diffraction probe, image acquisition, computer control and data processing.Secondly, according to the theory of point diffraction and measurement principles of this system establish mathematical model of the measurement system. For the calculating of phase demodulation in the system, two methods have been introduced including phase-shifting method and Fourier transform algorithm, this paper use phase-shifting algorithms for solving the phase information. Propose reconstruction optimization algorithm for the calculation of the three-dimensional absolute displacement, and introduce a variety of optimization methods, including algorithms principle and calculation process, the Particle Swarm Optimization(PSO) algorithm has been used in this paper for solving absolute displacement.Thirdly, using the measurement principle and the mathematical model presented in this paper measures three-dimensional absolute displacement. In order to verify the feasibility and robustness of PSO algorithm, conduct simulation analysis with noise and without noise; Carry out simulation analysis for parameters of the PSO on purpose of maximizing the measurement accuracy. The result show that the measurement system proposed in this paper can achieve measurement accuracy of nanoscale in the case of simulation.Finally, actual measurement of three-dimensional absolute displacement has been carried out by measurement system proposed, and compared with the CMM, the result show that the actual measurement accuracy of the system can reach the order of microns.Three-dimensional absolute displacement measurement system based on point-diffraction technique put forward in this paper has advantage which low cost, easy to carry, can achieve rapid high-precision measurement at the scene. This measurement system has good application value and development prospect.