Approach for obtaining phase distribution of fringe pattern with complex coefficient FIR band-pass filter

Three dimension measurements with projected fringe is the important method of optical 3D sensing. The approach for obtaining phase distribution of deformed fringe pattern is a key technology of this method. In this paper, a new method for obtaining phase distribution of deformed fringe pattern is proposed. In the proposed method, phase distribution is obtained directly by filtering deformed fringe pattern with complex coefficient finite impulse response (FIR) band-pass filter. The detail of this method is expressed as following: Firstly, a FIR low-pass filter is designed whose band width is half of the width of first order spectrum of the deformed fringe pattern. Secondly, the complex coefficient FIR band-pass filter is gained by moving the spectrum of low-pass filter to the position of the first order spectrum of the deformed fringe pattern. Finally, the phase distribution is obtained by filtering the deformed fringe pattern with designed filter and calculating the argument of the filtered pattern. The theory and experimental results are presented. In experiment, compared with FTP, the standard deviation of phase measurement reaches 0.75%. As a result, this approach provides a new way to obtaining phase distribution of deformed fringe pattern.