DEFORMATION MEASUREMENT USING DUAL-FREQUENCY PROJECTION GRATING PHASE-SHIFT PROFILOMETRY

2π phase ambiguity problem is very important in phase measurement when a de- formed object has a large out of plane displacement.The dual-frequency projection grating phase- shifting profilometry (PSP) can be used to solve such an issue.In the measurement,two proper- chosen frequency gratings are utilized to synthesize an equivalent wavelength grating which ensures the computed phase in a principal phase range.Thus,the error caused by the phase unwrapping process with the conventional phase reconstruct algorithm can be eliminated.Finally,experimen- tal result of a specimen with large plastic deformation is given to prove that the proposed method is effective to handle the phase discontinuity.