Spatial binary coding method for stripe-wise phase unwrapping.

Binary coding methods have been widely used for three-dimensional (3D) shape measurement. However, traditional binary coding methods always require a sequence of binary patterns to encode the fringe order. This paper presents a spatial-temporal binary coding (STBC) method for 3D shape measurement with three binary patterns, including a spatial pattern and two temporal patterns. Specifically, the spatial pattern is used to encode a 4-bit spatial code, and the temporal patterns are used to encode the 2-bit temporal code. By combining the spatial code and the temporal code, 6-bit code words can be obtained that distinguish 26=64 fringe periods of sinusoidal phase-shifting patterns. A robust dual-region labeling decoding scheme is also developed to extract the 6-bit code word for fringe order determination, and then absolute-phase unwrapping can be carried out. Experiments have been conducted, and their results confirm that the STBC method can reliably reconstruct the 3D shapes of measured objects with only three binary patterns.

This paper used a robust mathematical way (binary coding method) to study shadow effect in photovoltaic arrays. Binary coding method provides a way to define power generation index (PGI) as a factor which shows the performance of arrays at shadow condition. Different configurations of photovoltaic (PV) array show different behavior at shadow condition. Configurations behavior depends on modules interconnections, bypass and blocking diodes, and etc. Configuration which has better working condition should be chosen for PV array. In this paper all conventional configurations are analyzed and compared by the use of value. Over currents which may create in some states of shadow is studied. Moreover, this paper deals with influence of working voltage range of inverter in maximum power point tracking. Finally, configurations are rated.

This paper proposes a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">binary</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coding</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">method</i> , a novel post classification change detection method that indexes multitemporal satellite images into a single information layer. As a case study, this method is applied to the production of a deforestation map and a tree age map of evergreen trees. Seven images of Landsat-5 Thematic Mapper (TM) and Landsat-7 Enhanced TM Plus of Kangwon province in Korea, all obtained in November from 1984 to 2005, were used. Seven forest/nonforest bitmaps were produced by the normalized difference vegetation index thresholding. After the maximum value composite, the binary coding method was applied to convert the five bitmaps into a single-layered binary index map. This simple but intuitive method produced a deforestation map and a tree age map. The deforestation map contains the history of forest fires and massive replantation while the tree age map shows the age of evergreen trees with 30 years of range, both in approximately five-year temporal resolution. Comparison of the results with a digital forest inventory, forest fire records, and field investigations showed good agreement on the south-facing sunny slopes. Errors from geometric and radiometric data processing and inaccuracies of the digital forest inventory were also identified.

This paper presents algorithms for parallel implementation of the recently reported binary tree triangular coding (BTTC ) method for lossy image compression. We present parallel BTTC algorithms for four models: (1) parallel random access machine (PRAM), (2) hypercube, (3) 2-D mesh, and (4) sparse mesh, with their respective time complexities as O((n/p) log(n/p)), O((n/p) (log(n/p) +log p)), O((n/p) (log(n/p)+log p)), and O((n/p) (log(n/p)+log p)) for encoding and θ(n/p), θ ((n/p) (1+log p)), θ((n/p) (1+log p)), and θ((n/p) (1+log p)) for decoding, wheren is total number of pixels in the image and p is number of processors.

This paper presents algorithms for parallel implementation of the recently reported binary tree triangular coding (BTTC ) method for lossy image compression. We present parallel BTTC algorithms for four models: (1) parallel random access machine (PRAM), (2) hypercube, (3) 2-D mesh, and (4) sparse mesh, with their respective time complexities as O((n/p) log(n/p)), O((n/p) (log(n/p) +log p)), O((n/p) (log(n/p)+log p)), and O((n/p) (log(n/p)+log p)) for encoding and θ(n/p), θ ((n/p) (1+log p)), θ((n/p) (1+log p)), and θ((n/p) (1+log p)) for decoding, wheren is total number of pixels in the image and p is number of processors.

Superfast 3D absolute shape measurement using five binary patterns

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

In order to obtain a higher quantity absolute phase, a novel phase unwrapping model by combination of dual-frequency heterodyne and segmented quantifization phase coding method is proposed in this research. This model also provides a generalized phase order error correction method for eliminate phase order jump errors. Only ten fringe patterns are used for the projection in this study. The workflow of the devised model starts with acquisition of the low frequency wrapped phase by using the classic double-frequency heterodyne method, and then it moves to obtain the fringe order of low frequency wrapped phase based on the projected segmented quantifization phase coding patterns. In this step, two-dimensional scanning lookup method is used to eliminate the noise points caused by the rounding operation. Then, new fringe order can be obtained by combination of the obtained fringe order of low frequency wrapped phase and the new projected binary fringe pattern with complementarity, and this new fringe order combined with the previous fringe order can be used to unwrap the heterodyne phase. Finally, the wrapped phase of the dual-frequency is unwrapped through unwrapped heterodyne phase and the highest frequency phase. This study applies metal workpiece measurements as case studies to test the validity of the proposed model. The experimental results show that the error effects of fringe order can be eliminated, and the high frequency fringes retain more information on the measure workpiece surfaces.

The structure and assembly process of Chip Shooter (CS) machine are studied. The factors of engineering practice such as the component size and machine structure etc. are considered. The assembly optimization model of Printed Circuit Board (PCB) on CS machine is formulated. A hybrid genetic algorithm (HGA) which combine with Polychromatic Sets (PS) and Genetic Algorithm (GA) is presented. A binary piece-wise coding method is proposed. In the individual chromosome, feeder arrangement and component placement sequence is described simultaneously. Constraint model is used to consider the impact of component size on the assembly speed and the feeder arrangement of CS machine. Meanwhile the constraint model improved the quality of initial population, ensured the effectiveness of GA operation and narrowed the search space of GA obviously. Calculation example indicated that HGA optimize the component sequence and feeder arrangement simultaneously and achieve excellent practicability. The assembly efficiency of CS machine is improved obviously.

A separable reversible data hiding scheme for encrypted JPEG bitstreams

BackgroundThe accuracy of three-dimensional measurement of object surface is always affected by the nonlinear gamma of the projector. The defocusing binary projection can overcome the nonlinear gamma distortion of the projector and reduce the effect of high harmonics without gamma calibration. Although researches have already reduced the errors to get a clear sinusoidal curve, there still leave room for improvement, especially when wide stripes are applied during the measurement.MethodsThis paper presents a kind of ellipse binary pattern. By analyzing the property and spectrum, the binary pattern can produce high quality sinusoidal curve and produce smaller errors. It has a better effect to use an ellipse pattern to overcome the nonlinear gamma distortion of the projector and it is suit to be used as wide stripes.ResultsSimulation and comparison experiments plus three-step phase shifted method are conducted to verify feasibility and accuracy of this binary pattern. The experimental results have indicated that this binary pattern can increase the accuracy of 3D measurement and reduce phase errors caused by the nonlinear gamma of the projector. The defocusing ellipse pattern is superior to traditional methods. In addition, the defocusing binary stripe is robust and suit to measure object with large period.ConclusionsIn this paper, an binary ellipse pattern is proposed for high-accuracy 3D measurement profilometry. It is easy to generate high-quality sinusoidal fringe pattern. Experiment results have demonstrated the feasibility and accuracy of the improved binary pattern besides it proved that the period of fringe pattern has little impact on the accuracy of measurement.

Three-dimensional (3D) measurement of complex surfaces is of great importance in industrial inspection and production. To solve the problem of high accuracy measurement on complex surfaces, a phase unwrapping method based on multi-frequency binary is proposed, which can directly calculate fringe order by using wrapped phase. First, the four-step phase shift fringe patterns whose period changes exponentially are projected onto the measured object (The base is 2, the index is n, n=1, 2, 3...). Then, the four-step phase shift algorithm is used to obtain the wrapped phase of each period. Binary fringe is generated by binarization of the wrapped phase of each period according to the threshold value of 0. The fringe order K is calculated by binary coding and decoding algorithm, and then the wrapped phase in the highest period is unwrapped by K which can obtain the continuous phase of the object. The simulation and experiment verify the validity of the proposed method, and it has high robustness for complex surface and isolated object. The proposed method is simple in calculation, flexible in control and easy to operate. It provides a simple and effective method for improving the accuracy and robustness of the fringe projection profilometry system.

An object-based region-growing phase unwrapping method for mapping vertical displacement in permafrost landscapes

A novel phase-shifting profilometry to realize temporal phase unwrapping simultaneously with the least fringe patterns

Recently, deep learning has attracted more and more attention in phase unwrapping of fringe projection three-dimensional (3D) measurement, with the aim to improve the performance leveraging the powerful Convolutional Neural Network (CNN) models. In this paper, for the first time (to the best of our knowledge), we introduce the Transformer into the phase unwrapping which is different from CNN and propose Hformer model dedicated to phase unwrapping via fringe order prediction. The proposed model has a hybrid CNN-Transformer architecture that is mainly composed of backbone, encoder and decoder to take advantage of both CNN and Transformer. Encoder and decoder with cross attention are designed for the fringe order prediction. Experimental results show that the proposed Hformer model achieves better performance in fringe order prediction compared with the CNN models such as U-Net and DCNN. Moreover, ablation study on Hformer is made to verify the improved feature pyramid networks (FPN) and testing strategy with flipping in the predicted fringe order. Our work opens an alternative way to deep learning based phase unwrapping methods, which are dominated by CNN in fringe projection 3D measurement.