Stereo digital image correlation technique (stereo-DIC or 3D-DIC) has been widely used in three-dimensional (3D) shape and deformation measurement due to its high accuracy and flexibility. But it is ...a tough task for it to deal with complex structure components because of the severe perspective distortion in two views. This paper seeks to resolve this issue using a single-camera system based on DIC-assisted fringe projection profilometry (FPP). A pixel-wise and complete 3D geometry of complex structures can be reconstructed using the robust and efficient Gray-coded method based on a FPP system. And then, DIC is just used to perform the temporal matching and complete full-field pixel-to-pixel tracking. The in- and out-of-plane deformation are obtained at the same time by directly comparing the accurate and complete 3D data of each corresponding pixel. Speckle pattern design and fringe denoising methods are carefully compared and chosen to simultaneously guarantee the measuring accuracy of 3D shape and deformation. Experimental results demonstrate the proposed method is an effective means to achieve full-field 3D shape and deformation measurement on complex parts, such as honeycomb structure and braided composite tube, which are challenging and even impossible for the traditional stereo-DIC method.
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•A fast reconstruction method for three-dimensional shape measurement.•Utilizing dual-frequency grating to expand measureable depth with high accuracy.•Mapping the height from the ...wrapped phase without phase unwrapping.•Realization of high-speed dynamic 3D shape measurement by GPU.
Phase-to-height mapping is indispensable part of three-dimensional (3D) shape measurement system based on phase analysis, which guarantees the accuracy of 3D reconstruction. In this paper, a fast 3D shape reconstruction method based on dual-frequency grating projection and phase-to-height lookup table is proposed. In this proposed method, the reference plane is moved with known interval along the measurement depth direction to establish the mapping lookup table between the phase of the high and low frequency projected grating and their corresponding spatial height pixel by pixel respectively. Then, two methods to establish the lookup table with the unwrapped and the wrapped phase have been respectively introduced according to the characteristics of dual-frequency grating. The actual experimental results show that the two methods can effectively extend the measurement range of the current wrapped phase-to-height lookup method, and the reconstruction accuracy is better than the traditional phase-to-height quadratic fitting method. At the same time, the consumed time for 3D shape reconstruction of the tested object by the two methods is compared and analyzed. Finally, combining the high performance parallel computation of GPU, the fast 3D shape reconstruction is realized with the speed of 60fps.
The high-speed three-dimensional (3-D) shape measurement technique has become more and more popular recently, because of the strong demand for dynamic scene measurement. The single-shot nature of ...Fourier Transform Profilometry (FTP) makes it highly suitable for the 3-D shape measurement of dynamic scenes. However, due to the band-pass filter, FTP method has limitations for measuring objects with sharp edges, abrupt change or non-uniform reflectivity. In this paper, an improved Temporal Fourier Transform Profilometry (TFTP) algorithm combined with the 3-D phase unwrapping algorithm based on a reference plane is presented, and the measurement of one deformed fringe pattern producing a new 3-D shape of an isolated abrupt objects has been achieved. Improved TFTP method avoids band-pass filter in spatial domain and unwraps 3-D phase distribution along the temporal axis based on the reference plane. The high-frequency information of the measured object can be well preserved, and each pixel is processed separately. Experiments verify that our method can be well applied to a dynamic 3-D shape measurement with isolated, sharp edges or abrupt change. A high-speed and low-cost structured light pattern sequence projection has also been presented, it is capable of projection frequencies in the kHz level. Using the proposed 3-D shape measurement algorithm with the self-made mechanical projector, we demonstrated dynamic 3-D reconstruction with a rate of 297 Hz, which is mainly limited by the speed of the camera.
Phase-shifting profilometry (PSP) has been widely used in the measurement of dynamic scenes. However, the object motion will cause a periodical motion-induced error in the phase map, and there is ...still a challenge to eliminate it. In this paper, we propose a method based on three-stream neural networks to reduce the motion-induced error, while a general dataset establishment method for dynamic scenes is presented to complete three-dimensional (3D) shape measurement in a virtual fringe projection system. The numerous automatically generated data with various motion types is employed to optimize models. Three-step phase-shift fringe patterns captured along a time axis are divided into three groups and processed by trained three-stream neural networks to produce an accurate phase map. The actual experiment’s results demonstrate that the proposed method can significantly perform motion-induced error compensation and achieve about 90% improvement compared with the traditional three-step phase-shifting algorithm. Benefiting from the robust learning-based technique and convenient digital simulation, our method does not require empirical parameters or complex data collection, which are promising for high-speed 3D measurement.
Background
Cow’s milk protein allergy (CMPA) is a common allergy. Immunoglobulin E (IgE)-mediated cow’s milk allergy is associated with a high mortality risk and poor prognosis. The study aims to ...investigate whether there are different clinically CMPA phenotypes in China and to explore the association between CMPA phenotypes and specific IgE (sIgE) antibodies against different dairy products.
Methods
Serum sIgE against different animal milk and cow’s milk products and different milk components was measured by an allergen array. Four CMPA classifications were identified by the presence of serum sIgE: boiled milk-positive, yogurt-positive, buttermilk-positive, and raw milk-positive.
Results
Among the 234 participants included in the study, 9 were boiled milk sIgE-positive, 50 were yogurt sIgE-positive, 17 were buttermilk sIgE-positive, and 158 were only raw milk sIgE-positive. The boiled milk-positive group had the highest levels of raw milk sIgE and casein sIgE antibodies, followed sequentially by the yogurt-positive, buttermilk-positive, and raw milk-positive groups. The boiled milk group observed the highest levels of sIgE against raw milk, casein, α-lactalbumin, and β-lactoglobulin. These levels differed significantly from those in the other three groups. Allergic symptoms were distributed differently among the four study groups. The percentages of allergic patients with gastrointestinal tract symptoms in the above mentioned four groups ranged from high to low, and the percentages of patients with skin symptoms in the four groups ranged from low to high, respectively.
Conclusion
Based on dairy product sIgE antibody levels associated with different milk components and various clinical allergic symptom tendencies, we could distinguish four CMPA phenotypes.
This paper considers the three-dimensional (3D) shape measurement of metal parts during an additive manufacturing process in a direct energy deposition (DED) printing system with high temperature and ...strong light; a binocular measurement system based on ultraviolet light source projection is built using fringe projection and Fourier analysis. Firstly, ultraviolet light projection and an optical filter are used to obtain high-quality fringe patterns in an environment with thermal radiation. Then, Fourier analysis is carried out by using a single deformed fringe, and a spatial phase unwrapping algorithm is applied to obtain an unambiguous unwrapping phase, which is used as the guiding basis for the binocular matching process and 3D shape reconstruction. Finally, the accuracy of the measuring system is evaluated using a standard ball-bar gauge and the measurement error of this system is within 0.05 mm @ 100 × 100 mm. The results show that the system can measure 3D shape changes of metal parts in the additive manufacturing process. The proposed method and system have the potential to be used for online inspection and quality control of additive manufacturing.
The measuring technique combining a phase-shifting algorithm and Gray-code light has been widely used in three-dimensional (3D) shape measurement for static scenes because of its high robustness and ...anti-noise ability. However, in the high-speed measurement, phase unwrapping errors occur easily on the boundaries of adjacent Gray-code words because of the defocus of the projector, the motion of the objects and the non-uniform reflectivity of the surface. To overcome this challenge, a high-speed 3D shape measurement method based on shifting Gray-code light has been proposed in this paper. Firstly, the average intensity of three captured phase-shifting fringe images are used as a pixel-wise threshold to binarize the Gray codes and to eliminate most phase unwrapping errors caused by the non-uniform reflectivity, ambient light variations, and the defocus of projector. Then, the shifting Gray-code (SGC) coding strategy is proposed to avoid the remaining errors of phase unwrapping on the edge of the code words. In this strategy, no additional patterns are projected, and two sets of decoding words with staggered boundaries are built in the temporal sequences for one wrapped phase. Finally, the simple, efficient, and robust phase unwrapping can be achieved in the high-speed dynamic measurement. This proposed method has been applied to reconstruct 3D shape of randomly collapsing objects in a large depth range, and the experimental results demonstrate that it can reliably obtain high-quality shape and texture information at 310 frames per second.
House dust mite (HDM) is the most common airborne source causing complex allergy symptoms. There are geographic differences in the allergen molecule sensitization profiles. Serological testing with ...allergen components may provide more clues for diagnosis and clinical management.
This study aims to investigate the sensitization profile of eight HDM allergen components in a large number of patients enrolled in the clinic and to analyze the relation of gender, age, and clinical symptoms in North China.
The 548 serum samples of HDM-allergic patients (ImmunoCAP
d1 or d2 IgE ≥0.35) were collected in Beijing City and divided in four different age groups and three allergic symptoms. The specific IgE of HDM allergenic components, Der p 1/Der f 1, Der p 2/Der f 2, Der p 7, Der p 10, Der p 21, and Der p 23, was measured using the micro-arrayed allergen test kit developed by Hangzhou Zheda Dixun Biological Gene Engineering Co., Ltd. The new system was validated by comparing to single-component Der p 1, Der p 2, and Der p 23 tests by ImmunoCAP in 39 sera. The epidemiological study of these IgE profiles and the relation to age and clinical phenotypes were analyzed.
A greater proportion of male patients was in the younger age groups, while more female patients were in the adult groups. Both the sIgE levels and the positive rates (approximately 60%) against Der p 1/Der f 1 and Der p 2/Der f 2 were higher than for the Der p 7, Der p 10, and Der p 21 components (below 25%). The Der f 1 and Der p 2 positive rates were higher in 2-12-year-old children. The Der p 2 and Der f 2 IgE levels and positive rates were higher in the allergic rhinitis group. The positive rates of Der p 10 increased significantly with age. Der p 21 is relevant in allergic dermatitis symptom, while Der p 23 contributes to asthma development.
HDM groups 1 and 2 were the major sensitizing allergens, with group 2 being the most important component relevant to respiratory symptoms in North China. The Der p 10 sensitization tends to increase with age. Der p 21 and Der p 23 might be associated with the development of allergic skin disease and asthma, respectively. Multiple allergen sensitizations increased the risk of allergic asthma.
•This paper provides a detailed comparison of two typical temporal phase unwrapping methods including the two-frequency phase-shifting method and the Gray-coded-based method.•The basic principles and ...recent developments of the six approaches (hierarchical, number-theoretical and heterodyne approaches in two-frequency phase-shifting method; traditional Gray code approach, complementary Gray code approach and Gray code approach with tripartite phase unwrapping (Tri-PU) in Gray-coded-based method) are reviewed.•The performance of six approaches on measuring anti-noise ability, efficiency and robustness to motion are compared in detail based on proposed rigorous noise-induced error model and motion-induced error model.•Theoretical analysis, numerical simulation and experimental results are consistent and demonstrate that (a) Gray-coded-based method has better anti-noise ability than two-frequency phase-shifting method; (b) two-frequency phase-shifting method is more efficient than Gray-coded-based method when the number of encoding fringe periods exceeds 8; (c) hierarchical approach and Gray-coded approach with Tri-PU have best performance to resist motion-induced error in their respective types of methods.•Comparative results can give a helpful guidance to choose the “best” approach in different application scenes and quantitatively determine the projected fringe periods and imaging or projecting speed in dynamic measurement for FPP.
Two-frequency phase-shifting phase unwrapping and Gray-coded-based phase unwrapping are two typical temporal phase unwrapping methods to recover discontinuous or spatially isolated surfaces in fringe projection profilometry (FPP). But in dynamic measurement, environmental noise, required number of patterns and inter-frame motion affect the performance of these two methods on measuring anti-noise ability, efficiency and robustness in varying degrees. So, it is a challenge to quantitatively compare these methods’ abilities and determine the optimum one with appropriate system parameters and under a certain condition. In this paper, a detailed comparative study is conducted for the two-frequency phase-shifting method including hierarchical, number-theoretical and heterodyne approaches and the Gray-coded-based method including traditional Gray code approach, complementary Gray code approach and Gray code approach with tripartite phase unwrapping (Tri-PU). First, the principles of six approaches are reviewed; then, their anti-noise ability was quantitatively compared based on the proposed noise model; next, theoretical comparison of measuring efficiency, comparative review of improved methods and recommendation on usage are given to boost their efficiency; finally, motion-induced error model in phase unwrapping was presented to determine the appropriate system parameters in dynamic measurement. Theoretical analysis, numerical simulation and experimental results are consistent and demonstrate that (i) Gray-coded-based method has better anti-noise ability than two-frequency phase-shifting method; (ii) two-frequency phase-shifting method is more efficient than traditional Gray-coded-based method when the number of encoding fringe periods exceeds 8; (iii) hierarchical approach and Gray-coded approach with Tri-PU have best performance to resist motion-induced error in their respective types of methods. Comparative results can give a helpful guidance to choose the “best” approach in different application scenes and quantitatively determine the projected fringe periods and imaging or projecting speed in dynamic measurement for FPP.
The binary defocusing technique has been widely used in high-speed three-dimensional (3D) shape measurement because it breaks the bottlenecks in high-speed fringe projection and the projector's ...nonlinear response. However, it is challenging for this method to realize a two- or multi-frequency phase-shifting algorithm because it is difficult to simultaneously generate high-quality sinusoidal fringe patterns with different periods under the same defocusing degree. To bypass this challenge, we proposed a high-speed 3D shape measurement technique for dynamic scenes based on cyclic complementary Gray-code (CCGC) patterns. In this proposed method, the projected phase-shifting sinusoidal fringes kept one same frequency, which is beneficial to ensure the optimum defocusing degree for binary dithering technique. The wrapped phase can be calculated by phase-shifting algorithm and unwrapped with the aid of complementary Gray-code (CGC) patterns in a simple and robust way. Then, the cyclic coding strategy further extends the unambiguous phase measurement range and improves the measurement accuracy compared with the traditional Gray-coding strategy under the condition of the same number of projected patterns. High-quality 3D results of three complex dynamic scenes-including a cooling fan and a standard ceramic ball with a free-falling table tennis, collapsing building blocks, and impact of the Newton's cradle-were demonstrated at a frame rate of 357 fps. This verified the proposed method's feasibility and validity.
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