Improved method for three-dimensional profile measurement based on grating projection

The traditional Fourier transform profilometry (FTP) is not applicable to unwrap the wrapped-phase correctly when the depth continuity phase of the detected object is interrupted by its abrupt height change. The problem can be solved by using the two-frequency grating projection. By summarizing the traditional measurement method and the two-frequency grating measurement method, a novel technique based on the color composite grating projection was introduced, which could eliminate the effects of the background spectra and high-order components on the measurement with only one collection, expand the scope of measurement, and solve the problem of phase interruption. The measured results of the three methods were analyzed and compared. It shows that the accuracy of the color composite grating projection method is the best.