Fourier-transform speckle profilometry based on Michelson interference

A method of shape measurement based on ESPI carrier-frequency modulation is presented. In the typical setup of Michelson interferometer, turning the tested object a small angle generates an air wedge between the object plane and the reference plane. The wedge produces equal thickness interference fringes. A carrier fringe pattern containing height information is formed on the object surface. The carrier fringe pattern is captured by a CCD camera. The phase of the object can be derived by Fourier transform and the shape measurement is realized. The principle of the method is described and the experiment results are given. The results indicate that the method has the virtue of high sensitivity because speckle pattern interferometry is used.