Computer-generated frequency-carrier moiré profilometry

Abstract A three-dimensional measurement method based on frequency-carrier computer-generated moire fringe is proposed. By projecting two sinusoidal gratings with π phase difference each other onto the measured object respectively and capturing the corresponding deformed patterns, the AC component of the deformed pattern can be extracted. When this AC component is respectively multiplied by actively designed computer-generated sinusoidal grating and cosinoidal grating with the same frequency, two new fringes containing frequency-carrier moire components can be obtained. After low-pass filtering, the frequency-carrier moire fringes can be extracted to achieve object’s phase retrieval. As long as the DC component of the actively designed sinusoidal grating and cosinoidal grating are all controlled to be zero, the effect of inaccuracy elimination of the deformed pattern’s background light component on measuring accuracy can be reduced evidently. The frequency of the actively designed grating can be determined as 1/4 lines per pixel to ensure the maximum distance between each adjacent spectrum peaks of the new generated fringe so as to get the best measurement effect. The proposed method has good application ability in the limited number of projection frames and other scenes, and can achieve high measurement accuracy by projecting only two fringe patterns. Experimental results verify the feasibility and validity of the proposed method.