Improved composite Fourier transform profilometry

An improved composite Fourier transform profilometry (ICFTP) is proposed through optimizing the composite grating. Compared with the composite Fourier transform profilometry (CFTP), the frequencies of the two sinusoidal images modulated along the orthogonal direction in the optimized composite grating are not equal. The overlapping degree of Fourier spectrum of the optimized grating is lowered. The measuring accuracy is improved because two frequencies are used to calculate phase more accurately. By using a more advantageous flat image extracted ingeniously from the optimized grating, the zero component of the lower frequency sinusoidal image in the Fourier spectrum can be eliminated. So the measuring range is extended the same as that by the π phase shifting technique. Both numerical simulation and experiment demonstrate the feasibility and validity of the proposed method.

► The composite Fourier transform profilometry is improved by optimizing the projection grating. ► The overlapping degree of Fourier spectrum is lowered in the optimized composite grating. ► The measuring range is extended by using a flat image extracted ingeniously from the optimized grating. ► The measuring accuracy is improved because two frequencies are used to calculate phase more accurately.