Absolute phase calculation for Fourier transform profilometry with colour coding grating

Aiming at the drawback of large time need for traditional phase unwrapping process, a novel method, absolute phase calculation for Fourier transform profilometry(FTP) with colour coding grating is proposed. Fourier is adopted to calculate the relative phase (wrapped phase) because of the least need of images. Color strips are used to mark each 2 phase-change period. With the two parts, relative phase and fringe orders, the absolute phase can be obtained directly. The fringe orders and the relative phase are calculated simultaneously, and this algorithm can circumvent phase unwrapping process. Moreover, errors can not diffuse, because no unwrapping process is needed in our algorithm, and also because the relative phase and fringe orders are uncorrelated. Besides, no need of unwrapping processing and calculating the absolute phase directly in our algorithm can lead to high speed in 3D profile measurement. Experimental results show the validity of our algorithm both for complex object and separate objects.