A high precision three-dimensional optical sensor using Fourier transform profilometry

Automatic measurement of an object shape is very important in solid modeling, machine vision, industrial inspection, and medical diagnostics, etc. We propose an optical sensor, which comprises a telecentric projector with a sinusoidal grating and a linear CCD camera. We use the FTP (Fourier transform profilometry) method to make a measurement on three-dimensional object. In the FTP method, a grating pattern projected onto the object surface is modulated by the height distribution of the object. The deformed fringe pattern is Fourier transformed and processed in the spatial frequency domain as well as in the space signal domain to demodulate the object shape from the main frequency component in the Fourier spectra. This optical sensor provides a rapid and non-invasive three-dimensional image acquisition. The repeatability is better than 5 mu m within the 3 sigma limits.