Efficient approach for three-dimensional shape measurement using fringe projection by complex coefficient FIR band-pass filter

An efficient approach for three-dimensional (3D) shape measurement is proposed. Phase distribution is obtained directly by filtering deformed fringe pattern with complex coefficient finite impulse response (FIR) band-pass filter. Firstly, a FIR low-pass filter is designed; its bandwidth is half of that of the deformed fringe pattern. Secondly, the complex coefficient FIR band-pass filter is gained by moving the frequency spectrum of low-pass filter to the position where the frequency spectrum of deformed fringe pattern located. Finally, the phase distribution is obtained by filtering the deformed fringe pattern with designed filter and calculating the argument of the filtered pattern. The experimental results reveal that a high resolution 3D image with texture can be obtained. Compared with conventional Fourier transform profilometry (FTP), the standard deviation of phase difference between these two methods reaches only 0.75%. As a result, this approach provides a new way to obtain phase distribution of deformed fringe pattern in spatial domain instead spatial frequency domain.