Improvement of measuring accuracy of spatial fringe analysis method using a Kalman filter and its application

Abstract

When the spatial fringe analysis method based on the moiré technique is applied to a noisy fringe image, problems arise in the processing with, for example, phase unwrapping, accuracy of analysis, and so on. A digital filter technique and a filter based on time series analysis are applied to the spatial fringe analysis method to solve these problems. In a simulation with a model of the fringe image, results show that the spatial fringe analysis method using digital filters is highly robust against a noise in an image, and that the method using a Kalman filter can smoothly and accurately detect the phase map of the object with a continuous phase distribution. Furthermore, the method is applied to analyze a speckle fringe image in ESPI. A new speckle interferometry based on the proposed method can analyze specklegrams with a normal ESPI system. The results show that a spatial fringe analysis method based on the moiré technique can analyze accurately the phase of a speckle fringe image using only a single fringe image. The proposed method can be anticipated to accelerate the use of ESPI in industry.