Three-dimensional measurement method of highly reflective surface based on per-pixel modulation

The three-dimensional (3D) shape measurement of highly reflective surface is one of the common problems in the field of optical 3D measurement. In this paper, a 3D measurement method of highly reflective surface based on per-pixel modulation was proposed to solve the problem that the phase information could not be obtained due to overexposure. Firstly, the positions of saturated pixels were identified by the projecting maximum gray image. Then, the coordinate matching was carried out by projecting horizontal and vertical fringes under low gray-level condition, and the optimal projecting gray value of supersaturated pixels would be per-pixel modulated by combining with a new intensity mapping relationship between camera and projector. Finally, the reconstructed and adaptive fringe projection sequences were projected, phase recovery and 3D reconstruction were realized by using the multi-frequency heterodyne phase shift method. The experimental results showed that the average error and standard deviation of the proposed method were less than the measured values obtained by other methods, and compared with the traditional method, the average error was reduced by 61.9% and the standard deviation was reduced by 67.7%. The proposed method has the advantages of high modulation, fast speed and can ensure high measurement accuracy.