Dynamic Three-dimensional Shape Measurement Research Articles

Dynamic three-dimensional shape measurement based on an adaptive phase unwrapping method

Dynamic three-dimensional shape measurement based on an adaptive phase unwrapping method

High-precision dynamic three-dimensional shape measurement of specular surfaces based on deep learning.

In order to solve the difficulty of traditional phase measuring deflectometry (PMD) in considering precision and speed, an orthogonal encoding PMD method based on deep learning is presented in this paper. We demonstrate for, what we believe to be, the first time that deep learning techniques can be combined with dynamic-PMD and can be used to reconstruct high-precision 3D shapes of specular surfaces from single-frame distorted orthogonal fringe patterns, enabling high-quality dynamic measurement of specular objects. The experimental results prove that the phase and shape information measured by the proposed method has high accuracy, almost reaching the results obtained by the ten-step phase-shifting method. And the proposed method also has excellent performance in dynamic experiments, which is of great significance to the development of optical measurement and fabrication areas.

Dynamic Three-Dimensional Shape Measurement Method Based on Misaligned Gray Code

Dynamic Three-Dimensional Shape Measurement Method Based on Misaligned Gray Code

High-efficiency dynamic three-dimensional shape measurement based on misaligned Gray-code light

The combination of Gray-code method with phase-shifting algorithm has been widely used in three-dimensional (3D) shape measurement. However, the non-uniform surface reflectance, the defocus of the projector and the object motion will cause order jump error at the boundary of adjacent Gray-code. This paper proposes a 3D shape measurement method based on misaligned Gray-code (MGC) light to avoid this kind of error. In this method, all the traditional Gray-code patterns are pre-moved by half fringe period before projection so that the edges of the decoding order and the wrapped phase are staggered exactly, and then each period of decoding order is divided into four sub-regions to construct correct phase order and unwrap the wrapped phase. In addition, the fringe period number can be further expanded by introducing the virtual plane to improve the measurement efficiency and accuracy simultaneously. Two sets of comparative experiments on static scenes confirm that our method can successfully avoid the order jump error without projecting additional Gray-code pattern. And the dynamic experimental results demonstrate that proposed method can especially realize high-efficiency and high-speed 3D shape measurement at a rate of 2381 fps by labeling 32-period fringe patterns with only 4 misaligned Gray-code patterns.

Dynamic shape measurement for objects with patterns by Fourier fringe projection profilometry based on variational decomposition and multi-scale Retinex.

In practical measurement, we often need to measure the shape of objects with patterns or letters. As far as we know, no paper has ever reported the shape measurement for objects with patterns or letters by Fourier fringe projection profilometry (FPP). In this paper, we propose a method based on the variational decomposition TV-Hilbert-L2 model and multi-scale Retinex (MSR) to measure the shape of objects with patterns and letters by Fourier FPP. In this method, we first use the TV-Hilbert-L2 model to obtain the fringe part, then perform MSR enhancement on the fringe part, and finally decompose the enhanced fringe part with TV-Hilbert-L2 again. We evaluate the performance of this method via application to one computer-simulated noisy fringe projection pattern and two experimental fringe projection patterns with different types of patterns or letters, and comparison with the Fourier transform method, the variational image decomposition TV-Hilbert-L2 model. Furthermore, we apply the proposed method to the dynamic three-dimensional shape measurement of hand posture with pattern. The experimental results show that our method can effectively measure the dynamic shape of objects with patterns or letters from a single-frame fringe projection pattern.

Modified three-wavelength phase unwrapping algorithm for dynamic three-dimensional shape measurement

Digital fringe projection (DFP) method has been widely used in three-dimensional (3D) shape measurement. Lots of studies have been conducted to enhance the measurement accuracy and speed by modulating the patterns. However, it is still hard to acquire enough number of 3D results to ensure the continuity of dynamic 3D shape measurement when phase shifting profilometry and temporal phase unwrapping algorithm is adopted. Besides, object motion can introduce phase error and thus measurement error for phase shifting profilometry. To this end, a dynamic 3D reconstruction framework based on modified three-wavelength phase unwrapping algorithm and phase error compensation method is proposed to solve this problem. By redefining the order of fringe patterns projected by the digital light processing (DLP) projector, the number of required patterns for 3D reconstruction can be reduced and the speed of dynamic 3D shape measurement can be improved. And using phase error compensation method based on Hilbert transform, the accuracy of 3D reconstruction can also be improved. Experiments were carried out to demonstrated the effectiveness of the proposed framework. And the modified algorithm successfully improved the speed of dynamic 3D shape measurement by 1∕3.

Dynamic three-dimensional shape measurement with a complementary phase-coding method

The traditional phase-coding (TPC) method has been widely used for three-dimensional (3D) shape measurement. However, the fringe order determined from the coding patterns cannot be precisely aligned with the wrapped phase calculated from the sinusoidal patterns when measuring dynamic objects. Consequently, phase unwrapping errors will occur around the 2π phase jumps of the wrapped phase. To address this problem, the present work proposes a complementary phase-coding (CPC) method for dynamic 3D shape measurement. Specifically, the projection of the sinusoidal and coding patterns forms a cycle and the se patterns are shifted by a half-period between even and odd cycles. Combining two fringe orders of adjacent even and odd cycles, the absolute phase map can be correctly recovered. Moreover, to improve the measurement speed, all 8-bit gray patterns are converted into 1-bit binary patterns by a binary dithering technique. Both simulations and experiments demonstrate the robustness and efficiency of the proposed method.

基于区域二值编码方法的动态三维形貌测量

基于区域二值编码方法的动态三维形貌测量

动态三维面形测量的研究进展

动态三维面形测量的研究进展