Aiming at the problem of insufficient similarity between the binary defocus fringe generated by the traditional dithering algorithm in the binary surface structured light coding technology and the standard sinusoidal fringe, a dynamic threshold dithering algorithm based on the traditional Floyd-Steinberg dithering algorithm is proposed, which can generate the binary fringe pattern with high sinusoidal similarity, improving the accuracy of structured light three-dimensional reconstruction. Considering the influence of the pixel gray value in the vicinity of the pixel point on the threshold of the dithering algorithm, the parameters α and edge sensitivity coefficient đť“‚ are introduced to dynamically adjust the dithering threshold to improve the sinusoidal similarity of the dithering stripes. In addition, a total error calculation and evaluation method that takes into account the effects of gray error and phase error is used to improve the robustness of the algorithm. The simulation shows that when the parameters α and đť“‚ in the algorithm are set to 0.68 and 0.20 respectively, the total error is reduced by 82.97% at the fringe period T = 20 pixel. Corresponding experiments have been established to verify that the dynamic threshold can be displayed more clearly in the small change area of the model, which improves the image quality of the three-dimensional reconstructed object.
Phase shifting profilometry (PSP) has been commonly used in three-dimensional shape measurement. However, image saturation is a challenging problem leading to phase and measurement errors when measuring the shiny surface. We propose a new method using pixel-wise composed fringe pattern based on multi-intensity matrix projection of neighborhood pixels. First, a multi-intensity projection matrix is established and projected onto the object. The optimal intensity (the maximum projection intensity without saturation) for each pixel and the mask of each intensity can be obtained by analyzing the proportion of saturated pixels in the captured matrix region. Then, a set of new fringe pattern images without saturation can be obtained with phase shifted sinusoidal fringe patterns of different intensity levels and the corresponding mask. With PSP, the object can be reconstructed. Compared with existing methods, the proposed method can significantly reduce the number of projection operations and time consumption. The performance of the proposed method is verified by the experiments.
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