Free-form surface measurement based on fringe reflection

Abstract

This paper describes the principles and methods of free-form Surface measurement which is based on fringe reflection technique (PMD). This technique is based on incoherent imaging and phase-shfit. CCD camera was used to record images of sinusoid fringes pattern which is generated by computer monitor and reflected respectively by reflector tested. The phase of modulated fringes that test the mirror collected by CCD can be obtained through the phase-shifting algorithm, and the phase of the reference mirror can be calculated according to the structure, so the altitude difference between the two surface shape mentioned above can be obtained by the phase difference between them. The experiment fit the tested surface by 36 zernike polynomial and substitute the gradient data into equations to obtain the measured surface shaped by the least squares solution.