Dual-path point-diffraction interference system for three-dimensional measurement

In the single-path point-diffraction three-dimensional measurement system with only one fiber pair, the measurement accuracy in the lateral direction parallel to the fringle direction is poor. To solve this problem, a dual-path point-diffraction interference system is proposed to enhance the accurate three-dimensional measurement in this study. The influence of point-diffraction wavefront error, structural layout of measuring probe and three-dimensional iterative reconstruction algorithm on the three-dimensional measurement accuracy is analyzed. Based on the analysis, the optimal system parameters (e.g., point-diffraction source structure and structural layout of probe) are determined. The experimental results show that the accuracy of the single-path point-diffraction interference system for three-dimensional measurement in the x and y directions are in the order of submicrons and microns, respectively. In comparison, the dual-path point-diffraction interference system can reach the order of submicrons at three directrions. The feasibility and accuracy of the proposed system are verified. It provides a feasible method for the measurement three-dimensional displacement and size without guide rail.