Wrap reduction algorithm for fringe projection profilometry

In phase measuring deflectometry (PMD), the fringe pattern deformed according to slope deviation of a specular surface is digitized employing a phase-shift technique. Without height-angle ambiguity, carrier-removal process is adopted to evaluate the variation of surface slope from phase distribution when a quasi-plane is measured. This paper investigates nonlinear carrier components introduced by the generalized imaging process in PMD and the nonlinear carrier removal methods. To remove the nonlinear carrier components in PMD, the reference subtraction technique, series-expansion technique and Zernike polynomials which are normally used in fringe projection profilometry are analyzed on accuracy, processing time and experimental simplicity. What’s more, a new nonlinear carrier removal technique is proposed according to the analytical expression of carrier phase. The theoretical analysis and the experiment results show that the new technique is accurate, simple and time-saving.

This paper proposes the use of the two‐dimensional continuous Paul wavelet transform to extract the phase of spatial carrier fringe patterns. The proposed algorithm has been tested using computer‐generated and real fringe patterns, and these tests have demonstrated the suitability of the proposed technique for the phase demodulation of fringe patterns. Additionally, this algorithm is compared to three two‐dimensional continuous wavelet algorithms that have figured prominently in the literature, specifically the Morlet, advanced Morlet and fan mother wavelets. This comparison has revealed that the proposed algorithm outperforms the other three mother wavelets in terms of its suitability for extracting the phase of fringe patterns that exhibit large phase variations.

A new technique for fringe pattern demodulation using a linear digital phaselocked loop (DPLL) is presented. The phase components of a fringe pattern arecalculated using a way similar to the Fourier fringe analysis technique and awrapped phase map is produced. The linear DPLL demodulates, tracks and unwrapsthe wrapped phase map simultaneously. Consequently, the proposed algorithm hasgood noise immunity. The proposed algorithm is tested using real fringepatterns and its suitability for demodulating real fringe patterns isconfirmed. Also, the proposed algorithm is compared with the Fourier fringeanalysis technique. The implementation of the linear DPLL in real time on acommercial parallel image processing system is described. Fringe patterns aregrabbed, processed and the resultant phase maps are displayed concurrently.The parallel system is capable of analysing 25 images per second. There is atwo-image delay between grabbed fringe patterns and displayed phase maps.

A transform-domain fringe pattern denoising technique is presented. The Discrete Cosine Transform (DCT) is applied in a sliding window manner to get an overcomplete image expansion, and then the transform coefficients are thresholded to reduce the noise. We investigate the proper size of the sliding window and the proper threshold level. The latter is determined individually for each window position using a local noise variance estimate. In order to deal with a rather inadequate but simplified noise model, a proportionality factor, related with the speckle size, is found by experiments with digitally simulated speckle fringes. Such a proportionality factor suggests that the technique could be made fully automatic. We demonstrate promising results in denoising of real speckle fringe patterns, obtained through an out-of-plane sensitive Digital Speckle Pattern Interferometry (DSPI) set-up in a process of non-destructive testing of reinforced composite materials deformation.

Mass loss from wall surface bulge deformation can be used to estimate the strength loss of reinforcement, bond reduction, and ductility degradation, so it is very important to accurately measure the three-dimensional (3D) shape of on-site wall surface bulge. In this paper, we try to solve the problem by use of fringe projection profilometry. In the fringe projection patterns of wall surface bulge, the contrast of the fringes is very weak, and there are sometimes cracks in patterns. We first present a preprocessing method to inpaint fringes if there are damaged fringes caused by cracks. Then we propose a new, to the best of our knowledge, image decomposition model, total generalized variation (TGV)-Hilbert-block-matching (BM)3D, to effectively extract the fringe component. Finally, we use Fourier transform, phase unwrapping, and carrier-removal methods to obtain the unwrapped phase. We test the proposed method on a simulated fringe projection pattern and two real fringe projection patterns of wall surface bulge. We compare our method with the advanced total variation space-generalized functions space-BM3D, TV-Hilbert-L2, and Beppo-Levi-space-Hilbert-BM3D methods. In addition, we perform ablation experiments to prove that our preprocessing method is necessary. The experimental results demonstrate that our method can effectively measure the 3D shape of wall surface bulge from a single fringe projection pattern for the first time, to our knowledge.

Cover crop species represent an affordable and effective weed control method in agroecosystems; nonetheless, the effect of its use on arbuscular mycorrhizal fungi (AMF) has been scantily studied. The goal of this study was to determine root colonization levels and AMF species richness in the rhizosphere of maize plants and weed species growing under different cover crop and weed control regimes in a long-term experiment. The treatment levels used were (1) cover of Mucuna deeringian (Muc), (2) "mulch" of Leucaena leucocephala (Leu), (3) "mulch" of Lysiloma latisiliquum (Lys), (4) herbicide (Her), (5) manual weeding (CD), (6) no weeding (SD), and (7) no maize and no weeding (B). A total of 18 species of AMF belonging to eight genera (Acaulospora, Ambispora, Claroideoglomus, Funneliformis, Glomus, Rhizophagus, Sclerocystis, and Scutellospora) were identified from trap cultures. Muc and Lys treatments had a positive impact on AMF species richness (11 and seven species, respectively), while Leu and B treatments on the other hand gave the lowest richness values (six species each). AMF colonization levels in roots of maize and weeds differed significantly between treatment levels. Overall, the use of cover crop species had a positive impact on AMF species richness as well as on the percentage of root colonized by AMF. These findings have important implications for the management of traditional agroecosystems and show that the use of cover crop species for weed control can result in a more diverse AMF community which should potentially increase crop production in the long run.

The article describes the clinical and genetic features of juvenile rheumatoid arthritis and the consequences of the disease after treatment with chronotherapy. The clinical features of the disease, the results of laboratory analysis are important when choosing an effective treatment method. An effective treatment method is characterized by a faster onset of remission, an extension of its duration and a decrease in the side effects of drug treatment. The benefits of breastfeeding for babies are well known, but there is growing evidence that breastfeeding has a positive impact on a mom's health as well. Research shows that breastfeeding lowers a risk for juvenile rheumatoid arthritis.

The article is devoted to the study of the concept of intellectual abilities of preschool children. It is determined that intellectual development is understood as a set of quantitative and qualitative changes that occur in the cognitive mental processes of a child under the influence of the child’s environment and own experience. The core of intellectual development is mental abilities. It is emphasized that the devel- opment of intellectual abilities occurs in various types of preschoolers’ activities: play, construction, and learning activities. The influence of STEM education on the development of preschool children’s intellectual abilities is investigated. It is proved that the use of STEM education contributes to the creation of a model of educational environment for the development of prerequisites for scientific and technical creativity and intellectual activity of preschoolers, variability of the content of the educational process in the group, which makes it possible to take initiative and independence in various activities. To achieve this goal, such research methods as analysis and generalization of philosophical and psychological-pedagogical literature, state documents on preschool education were used to determine the terminological field of the study. The classification and generalization of existing practical developments and own pedagogical experience in the implementaƟon of STEM education in the educational process of preschool education institutions are applied. Effective methods and means for the development of students’ intellectual abilities are substantiated: robotics, construction, mental arithmetic, logical tasks, experiments, research, etc. It has been established that STEM educaƟon has a positive impact on the development of a child’s cognitive processes: perception, memory, thinking, speech, imagination. The need to create appropriate curricula, laboratories, and centers for the development of STEM skills in preschoolers is emphasized.

Nitrogen content dependent microwave absorption property of nitrogen-doped SiC materials annealed in N2: Opposing trends for microparticles and nanowires

Fringe projection profilometry (FPP) has been one of the most popular non-contact methods for 3D surface measurement in recent years. In FPP, the quality of the fringe pattern determines the measurement accuracy and measurement range to a great extent. In this paper, we proposed a high-quality fringe projection method using a biaxial MEMS scanning mirror and a laser diode (LD). The fringe pattern is produced by a very low NA (numerical aperture) scanning laser beam. Compared with pixel array based fringe pattern generation method, such as DLP and LCOS, the generation method can produce higher performance fringe pattern, which is high contrast, narrow pitch and long depth. In this paper, we also did a contrast between different fringe pattern generation methods.

We present a method for automatic determination of isostatics from the photoelastic measurement of isoclinics obtained by phase-shifting techniques. The method is based on the integration of two difference equations by use of a multigrid algorithm, using a quality map obtained from experimental data by checking the consistency of the generated experimental differences. So-called isostatic surfaces are determined and, from them, the isostatics net can be drawn with any prescribed density and resolution. The algorithm is very robust and fast and has proven very efficient for working with real photoelastic fringe patterns.

Phase-shifting interferometry is a highly accurate technique for obtaining phase distribution from the recorded fringe patterns. Generally, phase-shifting interferometry requires recording several fringe patterns with varying phase shifts experimentally and during the acquisition, the object must be stable. Also, the atmospheric turbulence and mechanical conditions should also remain constant during this time. These requirements limit the use of these phase-shifting interferometric techniques in dynamic event studies. In the present work, we introduce Riesz transformed based digital four-step phase-shifting interferometer to obtain phase distribution from a single recorded fringe pattern. All the experimental phase-shifting setups necessary to realize the phase-shifting are removed. The idea is based on the recording of a single fringe pattern, and computes its Riesz transform at first, second and third-orders. The obtained Riesz transform components are combined to generate three π/2 phase-shifted fringe patterns, and then, the phase distribution is obtained from these phase-shifted fringe patterns. The performance of this method is demonstrated first by using numerical simulation and the quantitative appraisal is given by using image quality index. Further, we apply this technique on a real fringe pattern recorded in digital speckle pattern interferometry (DSPI). The obtained results reveal that our method provides a simple and accurate solution for phase evaluation, therefore, makes it suitable for real-time measurements.

A phase unwrapping method suitable for high frequency fringe based on edge feature

To reveal the fundamental aspects hidden behind a variety of transient events in mechanics, physics, and biology, the highly desired ability to acquire three-dimensional (3D) images with ultrafast temporal resolution has been long sought. As one of the most commonly employed 3D sensing techniques, fringe projection profilometry (FPP) reconstructs the depth of a scene from stereo images taken with sequentially structured illuminations. However, the imaging speed of current FPP methods is generally capped at several kHz, which is limited by the projector-camera hardware and the number of fringe patterns required for phase retrieval and unwrapping. Here we report a novel learning-based ultrafast 3D imaging technique, termed single-shot super-resolved FPP (SSSR-FPP), which enables ultrafast 3D imaging at 100,000 Hz. SSSR-FPP uses only one pair of low signal-to-noise ratio (SNR), low-resolution, and pixelated fringe patterns as input, while the high-resolution unwrapped phase and fringe orders can be deciphered with a specific trained deep neural network. Our approach exploits the significant speed gain achieved by reducing the imaging window of conventional high-speed cameras, while “regenerating” the lost spatial resolution through deep learning. To demonstrate the high spatio-temporal resolution of SSSR-FPP, we present 3D videography of several transient scenes, including rotating turbofan blades, exploding building blocks, and the reciprocating motion of a steam engine, etc., which were previously challenging or even impossible to capture with conventional methods. Experimental results establish SSSR-FPP as a significant step forward in the field of 3D optical sensing, offering new insights into a broad spectrum of dynamic processes across various scientific disciplines.

This research aims to gain insights into the influence of the Project-based learning model on the enhancement of creative thinking skills among high school students in the subject of biology. The low creative thinking skills of high school students and the teacher-centered learning model, which typically involves lectures, have prompted the need for a more active learning process that involves students in the learning process. The Project-based learning model has been identified as a suitable approach for this purpose. To conduct the research, an expost facto method was employed, involving a review of relevant literature on the topic. The findings of the study indicate that the Project-based learning model has a positive impact on the creative thinking skills of high school students, as evidenced by an increase in the average scores of the students. This research adds to the body of knowledge on effective learning methods and has practical implications for educators seeking to enhance the creative thinking skills of their students. Further research could be conducted to explore the potential of the Project-based learning model in other subjects and at different educational levels. Additionally, it would be valuable to examine the long-term effects of the Project-based learning model on the creative thinking skills of students, as well as its potential to foster other desirable outcomes such as critical thinking and problem-solving skills.