3D measurement method based on binary fringe plusphase coding fringe defocus projection

Precision three-dimensional measurement of complex surface is very significant in industrial non-destructive testing. The method of binary fringe defocus projection has important application prospects in fast three-dimensional measurement; however, it is difficult to realize high precision three-dimensional measurement on complex surface.For this reason, a complex surface 3D measurement method based on binary fringe plus phase coding fringe defocus projection is proposed. Because of defocus, the high harmonics and high-frequency noise are filtered out, the nonlinear Gamma effect of the projector can be overcome, its measurement accuracy can be improved, compared with the traditional projection sinusoidal fringe method. For the out-of-focus projection, as the frequency of the phase coding fringe increases, the fringe order decision becomes difficult, the periodic dislocation occurs which can lead to the errors of phase unwrapping.In order to solve the problem, the principle of phase-shift coding method is proposed to correct the periodic dislocation and make the fringe order decision accurate, so the measurement accuracy is further improved. The experimental results show that the accuracy of this method can reach 0.044 mm, which verifies the validity and practicability of the method.