Effect of CCD nonlinearity on spectrum distribution

The effect of spectrum distribution from CCD nonlinearity in Fourier transform profilometry is analyzed. Firstly, the spectrum distribution expression from deformed fringe acquired by actual CCD after Fourier transform is given. Secondly, the nonlinearity condition of output deformed fringe from CCD under the actual conditions is discussed, the relationship of spectrum overlapping between first-order spectra which contains object height information and higher-order spectra is analyzed, and its separation condition is discussed. Finally, the discrete deformed fringe expression after sampling aim at pixels signal intensity from CCD is deduced, the Fourier spectrum expression of deformed fringe is obtained, spectrum overlapping and separation caused by sampling are analyzed, and the sampling condition must be satisfied with sampling frequency is given. The results of computer simulation and experiment verify the correctness of the theory analysis.