KEYWORDS: Reconstruction algorithms, Calibration, High dynamic range imaging, Cameras, Matrices, 3D modeling, Projection systems, Image fusion, Structured light, Point clouds
In the field of 3D reconstruction technology, the 3D measurement of high-dynamic-range objects has always attracted the attention of many scholars. This paper proposes a exposure algorithm for high-dynamic-range objects structured light reconstruction based on the local homography matrix. By improving the traditional calibration method and introducing the concept of the homography matrix, this method significantly enhances the calibration accuracy, which in turn determines the reconstruction accuracy of high-dynamic-range objects. Then, by utilizing the functional relationship of the camera response curve to analyze the relationship between image pixel values, illumination values, and exposure time, the algorithm automatically calculates the exposure time series for image fusion. Combined with high-precision calibration results for 3D reconstruction, it can effectively restore the lost point cloud information in high-dynamic-range areas, thereby improving the accuracy and adaptability of the reconstruction. Experimental results show that this method greatly reduces the re-projection error, making the error distribution more concentrated. Through 3D reconstruction experiments on high-dynamic-range objects, the effectiveness of the algorithm in this paper is verified, which can solve the problems encountered in traditional 3D reconstruction when dealing with high-dynamic-range objects and greatly improve the level of automation.
In the field of non-contact 3D reconstruction, structured light 3D reconstruction combining phase-shifting and Gray code is a high-precision reconstruction method. To address the problem of phase jumps easily occurring during phase unwrapping with traditional Gray codes, this paper proposes a cyclic complementary Gray code phase unwrapping algorithm based on gradient correction. Firstly, the wrapped phase image is converted based on the cyclic complementary Gray code to obtain the absolute phase image. For fixed-value phase jumps caused by blurred fringe order edges, phase jump points and their directions are determined through the second-order gradient of absolute phase, followed by phase correction to obtain smooth and continuous absolute phases. In the reconstructed 3D point cloud of the gypsum sculpture, the number of discrete points decreased by 96%. The experimental results indicate that the algorithm effectively discriminates phase jump points and corrects phase jumps without relying on pre-calibrated threshold values.
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