Although promised to be a fast and accurate three-dimensional shape measurement technique, grating projection profilometry based on phase measurement has been frequently baffled by the difficulty in phase unwrapping. We introduce the conventional excess fraction method into profilometry and extend it to nonlinear domain. Nonlinear excess fraction method (NLEFM), on the basis of which a multifrequency grating projection profilometry is developed, can work as a robust temporal phase unwrapper, which may extend the reliable measuring range by dozens of times at no cost of accuracy. The principle of NLEFM is detailed, and experimental results are given in which complex profiles are reliably measured with the novel system.
© 1999 Optical Society of America
(120.2650) Instrumentation, measurement, and metrology : Fringe analysis
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
(150.6910) Machine vision : Three-dimensional sensing
Yudong Hao, Yang Zhao, and Dacheng Li, "Multifrequency Grating Projection Profilometry Based on the Nonlinear Excess Fraction Method," Appl. Opt. 38, 4106-4110 (1999)