The phase-coding method is widely used during 3D measurement for attaining absolute phase retrieval. However, traditional the phase-coding method still suffers from low accuracy and insufficient reliability. To addres...
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The phase-coding method is widely used during 3D measurement for attaining absolute phase retrieval. However, traditional the phase-coding method still suffers from low accuracy and insufficient reliability. To address these issues, a phase-shifting segmented phasecodingmethod was proposed in this work for absolute phase retrieval in complex object measurements, which specifically improved upon the segmented method of phasecoding. coding patterns with different phase-shifting were obtained by embedding the codeword into the phaseshifting phase. These patterns were also combined and arranged to create novel segmented coding patterns. In addition, this segmented encoding can be self-connected based on its different phase-shifting information to obtain the complete fringe order, achieving thus absolute phase retrieval of over 36 codewords. To solve the problem of the periodic misalignment of the wrapped phase and fringe order, the complementary phasecodingmethod was encoded by the bidirectional codingmethod, and the separation method of the bidirectional coding was improved. From experimental results, it was demonstrated that the proposed method has high measurement accuracy and reliability.
The phase-coding method is useful in 3D shape measurement due to its low sensitivity to surface contrast and camera noise. However, as the number of fringe periods increases, the wrapped phase recovered from the sinus...
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The phase-coding method is useful in 3D shape measurement due to its low sensitivity to surface contrast and camera noise. However, as the number of fringe periods increases, the wrapped phase recovered from the sinusoidal phase-shifting patterns is always misaligned with the fringe order calculated by the stair-coding patterns. To solve this, an improved dual-frequency phase-coding fringe projection method is designed to realize absolute phase retrieval. Specifically, the auxiliary fringe order determined by phase-shifting is used to get the absolute phase, which can eliminate fringe-order errors. Moreover, to increase speed and the number of codewords, this paper presents a scheme that only requires seven patterns, including a uniform gray image, two high-frequency sinusoidal fringe patterns, two low-frequency sinusoidal fringe patterns and two phase-coding fringe patterns. Therefore, this method requires fewer patterns to realize high-resolution measurement than existing methods. The success of the proposed method can be proved by experiments.
Stereo cameras have been widely used in three-dimensional (3D) reconstruction, target ranging and environment perception. The calibration of stereo cameras is the key technology of vision system. Most of the existing ...
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Stereo cameras have been widely used in three-dimensional (3D) reconstruction, target ranging and environment perception. The calibration of stereo cameras is the key technology of vision system. Most of the existing methods are not flexible due to limitations of the size of the cameras' overlapping fields of view (FOV) and the degree of defocus. This paper presents a stereo calibration method in which the feature points on the target are globally encoded by the phase-coding method. Each feature point has a specific code, and the mapping relationship between image coordinates and world coordinates can be uniquely determined. So, the stereo cameras whether or not capture the same area of the target, both the camera coordinate systems can be unified under one global coordinate system. In addition, calibration can be accomplished when cameras are out of focus seriously, for the coding and extraction of feature points are phase-based. Simulations and experiments were carried out to prove flexibility and robustness of the proposed method.
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