Absolute phase analysis method for three-dimensional surface profilometry using frequency-modulated grating

Wakayama UniversityDepartment of Opto-Mechatronics930 SakaedaniWakayama 640 8510, JapanE-mail: yoneyama@sys.wakayama-u.ac.jpAbstract. The authors propose a new high-speed and accurate phaseanalysis and subsequent phase unwrapping method for grating projec-tion surface profilometry. In the proposed method, a special grating pat-tern is used for the projection. The light intensity distribution of this grat-ing pattern has a form of a frequency modulated sinusoidal wave. In thisgrating pattern, two different phase distributions are included. The fre-quency modulated grating, which can be generated with an LCD projec-tor or a film projector easily, is projected onto an object. Then, nineframes with phase stepping at a regular interval for a cycle are taken bya CCD camera. From these nine pictures, the two wrapped phase distri-butions are analyzed simultaneously. Then, using these phase distribu-tions, phase unwrapping is carried out at each pixel independently. The3-D profile of the object can be reconstructed using the absolute phasedistribution. Since this method is suitable for high-speed shape measure-ment, applications to various inspections and 3-D surface digitizing areexpected.