Fast high-precision displacement measurement system based on fringe image analysis techniques

Abstract

Measurement systems with high precision, fast speeds, and large ranges are required in current technological and industrial fields. In this work, a system was constructed based on the Michelson interferometer and a “soft tracking” measurement scheme. First, an algorithm based on the Radon transform and grayscale projection was proposed to detect the inclination angle of the interference fringe. Next, a raw interference image was rotated to be vertical and projected to a one-dimensional form so that the fringe pitch could be calculated using the algorithm based on Fourier spectrum analysis. Finally, a spatial similarity matching method was developed to obtain the amount of fringe shifting. Each component of the algorithm is discussed, and experimental results are presented. The results showed the effectiveness of the measurement system. The system could measure a displacement of 40 μm within 100 ms, which was 35 times improvement in the system efficiency compared to our previous work. Finally, discussions of the measurement errors and the analysis of the influence factors are presented to comprehensively introduce the properties of the measurement system.

Keywords

• Displacement tracking
• Image analysis
• Michelson interferometer
• Out-of-plane displacement