Adaptive high dynamic range 3D measurement method based on speckle-assisted fringe projection

Conventional phase-shift method can obtain the topography information of the object surface by projecting phase-shift fringe sequence and capturing deformed pictures. However, overexposure on shiny surfaces causes the loss of fringe information received by the camera, thus reducing the measurement accuracy and integrity. To solve this problem, an adaptive fringe projection method based on speckle-assisted fringes and mask fusion is proposed. Firstly, the optimal projection intensities are obtained by fusing multiple mask images. Then, the pixel-by-pixel mapping relationship between the camera and projector is established by using speckle-assisted phase shift method under unsaturated condition. Finally, the adaptive intensity fringe is generated and projected by the constraint of the mapping relationship. The 3D reconstruction is performed by the speckle-assisted phase shift method. Experimental results show that the RMS phase error of the proposed method is reduced by 94%, 33% and 12% compared with the contrast methods. The proposed method can accurately match the phase information of the overexposed surface and reconstruct objects with large surface fluctuations, thereby effectively solving the problem of 3D reconstruction of high reflective objects.