Relevant bibliographies by topics / Unwrapped phase

Academic literature on the topic 'Unwrapped phase'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Unwrapped phase"

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Spagnolini, Umberto. "2-D phase unwrapping and phase aliasing." GEOPHYSICS 58, no. 9 (September 1993): 1324–34. http://dx.doi.org/10.1190/1.1443515.

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The phase of complex signals is measured modulo-2π (wrapped phase); continuous‐phase information is obtained by adding properly chosen multiples of 2π shift to the wrapped phase. Unwrapping searches for the 2π combinations that minimize the discontinuity of the unwrapped phase as only the unwrapped phase can be analyzed and interpreted by further processing. The key problem of phase unwrapping is phase aliasing, a condition mainly caused by rapid phase variations. The extension of the one‐dimensional (1-D) phase unwrapping algorithms to a two‐dimensional (2-D) domain by 1-D slicing gives unsatisfactory results even in the presence of low‐phase aliasing, whereas 2-D phase unwrapping deals with the complete problem, overcoming the limitations of 1-D unwrapping. The 2-D unwrapped phase is obtained as the solution of a variational problem that minimizes the differences between the gradients of the wrapped and unwrapped phase. The Euler equation is then integrated using the boundary conditions obtained from the wrapped phase. In addition to determining a unique unwrapped phase, this approach has the advantage that it limits the influence of phase aliasing. It is also more attractive than iterative 1-D unwrapping since it limits the propagation of unwrapping errors. Error propagation in phase unwrapping can strongly influence the result of any phase processing. Examples in this paper apply 2-D phase unwrapping to problems of refraction statics and interferometrical imaging using a remote system (SAR) and demonstrate how limited error propagation allows phase processing.
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Zhao, Xiaxia, Rong Mo, and Zhiyong Chang. "Enhanced geometric constraint-based phase unwrapping algorithm in binocular stereo vision fringe projection system." Insight - Non-Destructive Testing and Condition Monitoring 63, no. 9 (September 1, 2021): 540–46. http://dx.doi.org/10.1784/insi.2021.63.9.540.

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Phase unwrapping plays an important and central role in phase-based digital fringe projection profilometry. The unwrapping quality directly influences the three-dimensional measurement accuracy. Recently, an effective geometric constraint-based phase unwrapping algorithm has been proposed to obtain the continuous absolute phase map and the unwrapped phase accuracy was found to be high. However, in this technique the virtual depth plane at z = zmin is often created empirically, which increases the manual measurement error. For this reason, this paper proposes a method for accurately constructing the virtual plane and further applies it to phase unwrapping of objects with a larger depth range. In this method, a binocular stereo vision system is used as the measurement set-up for the virtual depth plane construction and a series of virtual depth planes at z = zimin (i ≥ 2) is automatically built using a computational framework. Then, the phase is unwrapped for each region according to the continuity of the unwrapped phase and a complete absolute phase map is obtained by merging the unwrapped phases in all regions for 3D reconstruction. In this process, the virtual depth planes are created automatically and quantitatively by the measurement system. No human intervention is required and it greatly reduces the manual measurement error. Experiments show that the artificial virtual planes can be built accurately and the phase is unwrapped correctly and readily.
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Dudczyk, J., and A. Kawalec. "Optimizing the minimum cost flow algorithm for the phase unwrapping process in SAR radar." Bulletin of the Polish Academy of Sciences Technical Sciences 62, no. 3 (September 1, 2014): 511–16. http://dx.doi.org/10.2478/bpasts-2014-0055.

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Abstract The last three decades have been abundant in various solutions to the problem of Phase Unwrapping in a SAR radar. Basically, all the existing techniques of Phase Unwrapping are based on the assumption that it is possible to determine discrete ”derivatives” of the unwrapped phase. In this case a discrete derivative of the unwrapped phase means a phase difference (phase gradient) between the adjacent pixels if the absolute value of this difference is less than π. The unwrapped phase can be reconstructed from these discrete derivatives by adding a constant multiple of 2π. These methods differ in that the above hypothesis may be false in some image points. Therefore, discrete derivatives determining the unwrapped phase will be discontinuous, which means they will not form an irrotational vector field. Methods utilising branch-cuts unwrap the phase by summing up specific discrete partial derivatives of the unwrapped phase along a path. Such an approach enables internally cohesive results to be obtained. Possible summing paths are limited by branch-cuts, which must not be intersected. These branch-cuts connect local discontinuities of discrete partial derivatives. The authors of this paper performed parametrization of the Minimum Cost Flow algorithm by changing the parameter determining the size of a tile, into which the input image is divided, and changing the extent of overlapping of two adjacent tiles. It was the basis for determining the optimum (in terms of minimum Phase Unwrapping time) performance of the Minimum Cost Flow algorithm in the aspect of those parameters.
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Yi, Tian, and Chang Li. "Phase Unwrapped Method of Modified Fringe Order." American Journal of Electrical and Computer Engineering 6, no. 1 (2022): 40. http://dx.doi.org/10.11648/j.ajece.20220601.15.

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Kam, Dong-Uk, Jeong Hee Kim, and Kunwoo Lee. "Unwrapped phase correction for robust 3D scanning." Applied Optics 58, no. 14 (May 2, 2019): 3676. http://dx.doi.org/10.1364/ao.58.003676.

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Choi, Yunseok, and Tariq Alkhalifah. "Unwrapped phase inversion with an exponential damping." GEOPHYSICS 80, no. 5 (September 2015): R251—R264. http://dx.doi.org/10.1190/geo2014-0498.1.

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Liu, Wanli, Jian Shao, Zhenguo Liu, and Yang Gao. "A Refined Phase Unwrapping Method for High Noisy Dense Fringe Interferogram Based on Adaptive Cubature Kalman Filter." Mathematical Problems in Engineering 2021 (August 9, 2021): 1–14. http://dx.doi.org/10.1155/2021/7141091.

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Cubature Kalman filter phase unwrapping (CKFPU) is an effective algorithm in unwrapping the interferograms. The local phase slope estimation is a key factor that affects the unwrapped accuracy. However, the estimation accuracy of local phase slop is relatively low in high noisy and dense stripes areas, which usually leads to the unsatisfactory unwrapped results. In order to effectively solve this issue, the rewrapped map of the unwrapped phase (obtained by CKFPU algorithm), which is a filtered interferogram with clearer fringes and more detailed information, is proposed in this paper to improve the phase slope estimation. In order to solve the problem of imprecise error variance for the new phase slope estimation, an adaptive factor is introduced into the CKFPU algorithm to increase the stability and reliability of the phase unwrapping algorithm. The proposed method is compared with the standard CKFPU algorithm using both simulated and real data. The experimental results validate the feasibility and superiority of the proposed method for processing those high noise dense fringe interferograms.
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Wu, Xinming, and Guangfa Zhong. "Generating a relative geologic time volume by 3D graph-cut phase unwrapping method with horizon and unconformity constraints." GEOPHYSICS 77, no. 4 (July 1, 2012): O21—O34. http://dx.doi.org/10.1190/geo2011-0351.1.

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Construction of a relative geologic time (RGT) volume is vital to seismic geomorphological and sedimentological interpretation. Seismic instantaneous phase unwrapping provides an excellent approach for generating an RGT volume. Although several 2D or 3D seismic phase unwrapping results have been published, there is a clear need for discussions on concrete methods for seismic phase unwrapping. We have developed the graph-cut phase unwrapping method, which performs well in the interferometric synthetic aperture radar image processing. It has advantages of strong discontinuity-preserving ability and high computing efficiency. To make it suitable for 3D seismic phase unwrapping, the method is improved by extending it from 2D to 3D, and by introducing the seismic horizon and unconformity constraints. The strong and continuous conformable seismic events, which can be easily tracked by certain autopicking methods, are introduced as horizon constraints for guiding the phase unwrapping to ensure a constant unwrapped phase on a constraining horizon. This idea is based on the fact that continuous seismic horizons are of time-stratigraphic significance. The horizon constraints can promise a correct unwrapped result on the constraining horizons and avoid the possible phase unwrapping errors propagating across a horizon. An unconformity represents a geologic time discontinuity, which is difficult to recover in an RGT volume by phase unwrapping. What’s worse, incorrect phase unwrapping on an unconformity will result in some discontinuities of unwrapped phase in the conformable data areas outside the unconformity. Interpreted unconformities are used as unconformity constraints to recover the discontinuities of the unwrapped phase at the constraining unconformities. As a test, our improved 3D graph-cut phase unwrapping method is successfully applied to the late Permian to early Triassic carbonate reservoirs in northern Sichuan Basin, southwest China. The results match well with the regional geologic background.
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Liu, Wei Ke, Gou Lin Liu, and Xiao Qing Zhang. "Least Squares Phase Unwrapping Algorithm Based on Topographic Factors." Applied Mechanics and Materials 105-107 (September 2011): 1876–79. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1876.

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The phase of complex signals is wrapped since it can only be measured modulo-2; unwrapping searches for the 2-combinations that minimize the discontinuity of the unwrapped phase, as only the unwrapped phase can be analyzed and interpreted by further processing. Weighted least squares phase unwrapping algorithm could avoid errors transmission in the whole phase images, but it could not avoid defect and overlay of interference fringes caused by topographic factors. Therefore, a new phase unwrapping and weights choosing method based on local phase frequency estimate of topographic factors was presented. Experiments show it is an efficient phase unwrapping method which well overcome the defect of under-estimate slopes by least squares algorithm, and has higher accuracy and stability than other methods.
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Draper, Douglas C., J. Fred Holmes, and John Peacock. "Unwrapped-phase distribution model for speckle and turbulence." Applied Optics 31, no. 18 (June 20, 1992): 3481. http://dx.doi.org/10.1364/ao.31.003481.

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Dissertations / Theses on the topic "Unwrapped phase"

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Karam, Zahi Nadim. "Computation of the one-dimensional unwrapped phase." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35601.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.
Includes bibliographical references (p. 101-102). "Cepstrum bibliography" (p. 67-100).
In this thesis, the computation of the unwrapped phase of the discrete-time Fourier transform (DTFT) of a one-dimensional finite-length signal is explored. The phase of the DTFT is not unique, and may contain integer multiple of 27r discontinuities. The unwrapped phase is the instance of the phase function chosen to ensure continuity. This thesis presents existing algorithms for computing the unwrapped phase, discussing their weaknesses and strengths. Then two composite algorithms are proposed that use the existing ones, combining their strengths while avoiding their weaknesses. The core of the proposed methods is based on recent advances in polynomial factoring. The proposed methods are implemented and compared to the existing ones.
by Zahi Nadim Karam.
S.M.
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Shah, Nikhil. "Seismic 'Full Waveform Inversion' of wrapped and unwrapped phase." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24849.

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Full Waveform Inversion (FWI) is a highly promising but far from robust and stable optimisation for computing the subsurface velocity model from seismic data acquired with long offsets and low frequencies. Mathematically, it solves the non-linear problem of matching model-predicted data to observed data with an iterative localised minimisation of the misfit. Therefore it is necessarily restricted by the need for an accurate starting model. In this thesis, we look at being able to relax the constraints on the starting model in FWI, obtain lower wavenumber updates from FWI, and in the process distinguish between adequate and inadequate starting models. Our approach here is to precede the conventional Born-based iterations with Rytov-based iterations which isolate discrete frequency phase. Here the misfit function being minimised is the norm of the phase residual which measures the difference in phase between observed and predicted data. Our treatment of the phase residual differs from previous work in two specific ways: i) we define the time-weighted phase residual, ii) we unwrap the residual thereby accounting for errors greater than half a cycle or 'cycle-skipped'. Previous work did (i) using the Laplace-Fourier domain i.e. using an exponential function. Here we use a more versatile time window which prepares the residual for (ii). Previous work in the context of FWI did not attempt (ii) at all. We find it is the combination of (i) and (ii) that provides the solution we are looking for. In this thesis we formulate the theory for inverting the time-weighted phase residual. We find this mismatch measure meets the requirement of being able to distinguish between adequate and inadequate starting models. Finally, we demonstrate that an 'unwrapped' solution deals with the latter. The unwrapped solution is shown to correctly invert cycle-skipped data and successfully update longer wavelengths than possible with conventional inversion when wide-angle data is available. This leads to a multi-scale approach which ends with conventional inversion but begins with phase-unwrapped inversion at the lowest useable frequency. It finds the global minimum solution to the full wavefield inverse problem down to a depth governed by the offset range of the survey using only a simple starting model.
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Draper, Douglas C. "Prediction and measurement of the unwrapped phase for speckle propagating in turbulence /." Full text open access at:, 1992. http://content.ohsu.edu/u?/etd,638.

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Suguna, Sree N. "Small Angle Sensing/Measurement Using 'Pattern Imaging' Method - Few Investigations." Thesis, 2008. http://hdl.handle.net/2005/753.

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The present thesis concerns with a few investigations on sensing/measurement of small angle rotation/tilt using Pattern Imaging Method. The methodology involves looking at the tailored-objects located adjacent to the observer (CCD camera) through a mirror and extracts the angular position of the mirror from their images by processing the latter through object specific algorithm. Its principal advantage stems from the fact that small-angle measurement can be done using ambient light which is neither collimated nor filtered for single wavelength. This makes the associated optical configuration not only simple but also robust for the said application, in comparison to currently competing technologies based on Autocollimation and Interferometry. The present thesis elaborates specifically four new Pattern-Designs proposed for tailoring the spatial-brightness of the objects. Introducing for the first time, processing algorithms based on ‘Modified Fringe-Processing Strategy’ and ‘Phase-Only-Correlation’, the investigations demonstrate enhanced performance for small angle measurement with all the proposed pattern designs. The first three designs for the pattern are evaluated for 1-D measurement through fringe processing approach while the fourth pattern design is evaluated for 2-D measurement through Phase-only-Correlation. The results of the investigations are utilized to propose, design and develop a novel optical inclinometer which can work with any of the proposed pattern designs as the object. The first three pattern-designs rely upon sinusoidal modulation of the object surface and utilize three custom developed algorithms -Algorithm-A, Algorithm-B and Algorithm-C -to extract two quantities namely wrapped phase Δαw and unwrapped phase Δαuw , from the captured images. Each of these quantities will have an associated measurement range and accuracy corresponding to any of the three pattern designs. All measurements are carried out keeping the object/camera to mirror distance constant at 250 mm. From wrapped phase measurement, all the three designs, each with pitch of 2mm for sinusoidal modulation and held at a distance of 250 mm from the mirror, have been found to facilitate reliable angle measurement over a range of 850 arc seconds with accuracy better than 1 arc second after curve fitting the experimentally obtained data. From unwrapped phase measurement, the color coded as well as BCD coded composite patterns, when tested using five bands of sinusoidal modulation (with a pitch of 2mm) and held at a distance of 250 mm from the mirror, facilitated reliable angle measurement over a larger range of nearly 10 . The 2-D angle measurement using fourth pattern-design and the Algorithm-D, facilitated measurement over a range of 10 with an accuracy of 9 arc seconds when the distance between the mirror and the pattern is held at 250 mm. A comparison of the results from the present investigation with the best performance from other investigators reveals the following. The proposed modifications in the processing algorithms as well as the pattern designs help to achieve a measurement range of 750 arc seconds with accuracy better than 1 arc second from this method, with an object pattern whose lateral size is smaller by a factor of nearly 15. Such a size reduction in the object as well as the associated mirror would help to construct angle measuring instruments that work on this method more compactly. The results of the investigation have been utilized to propose and demonstrate a novel prototype optical inclinometer which has been experimentally found to work in a range of 0.40 with accuracy nearly 6 arc seconds.
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Book chapters on the topic "Unwrapped phase"

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Bourgeat, Pierrick, Jurgen Fripp, Andrew Janke, Graham Galloway, Stuart Crozier, and Sébastien Ourselin. "The Use of Unwrapped Phase in MR Image Segmentation : A Preliminary Study." In Lecture Notes in Computer Science, 813–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/11566489_100.

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Iwanaga, Mauricio Kiotsune, Michael John Brennan, Oscar Scussel, Fabrício César Lobato de Almeida, and Mahmoud Karimi. "On the Pipe Localization Based on the Unwrapped Phase of Ground Surface Vibration Between a Roving Pair of Sensors." In Mechanisms and Machine Science, 1069–76. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-15758-5_110.

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Nico, G., L. Guerriero, G. Palubinskas, and M. Datcu. "Overview and Bayesian Perspective of Phase Unwrappin." In Maximum Entropy and Bayesian Methods Garching, Germany 1998, 301–8. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4710-1_29.

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Rastogi, Pramod. "Simultaneous estimation of unwrapped phase and its derivatives." In Single and Multicomponent Digital Optical Signal Analysis Estimation of phase and its derivatives. IOP Publishing, 2017. http://dx.doi.org/10.1088/978-0-7503-1469-5ch6.

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Conference papers on the topic "Unwrapped phase"

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Lin, Yuzhao, Kai Zhang, Zhenchun Li, Renwei Din, and Zhennan Yu. "Full unwrapped phase inversion in the phase space." In SEG Technical Program Expanded Abstracts 2019. Society of Exploration Geophysicists, 2019. http://dx.doi.org/10.1190/segam2019-3215652.1.

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Zhang, Feng, Yanghua Wang, and Xiangyang Li. "Mixed‐phase wavelet estimation using unwrapped phase of bispectrum." In Beijing 2009 International Geophysical Conference and Exposition. Society of Exploration Geophysicists, 2009. http://dx.doi.org/10.1190/1.3603775.

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Zhang, F., Y. Wang, and X. Li. "Mixed-phase Wavelet Estimation Using Unwrapped Phase of Bispectrum." In 71st EAGE Conference and Exhibition incorporating SPE EUROPEC 2009. European Association of Geoscientists & Engineers, 2009. http://dx.doi.org/10.3997/2214-4609.201400063.

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Karam, Zahi N., and Alan V. Oppenheim. "Computation of the One-Dimensional Unwrapped Phase." In 2007 15th International Conference on Digital Signal Processing. IEEE, 2007. http://dx.doi.org/10.1109/icdsp.2007.4288579.

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Cohen, David, and David C. Redding. "NGST high dynamic range unwrapped phase estimation." In Astronomical Telescopes and Instrumentation, edited by John C. Mather. SPIE, 2003. http://dx.doi.org/10.1117/12.461773.

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Choi, Yunseok, and Tariq Alkhalifah. "Unwrapped phase inversion for near surface seismic data." In SEG Technical Program Expanded Abstracts 2012. Society of Exploration Geophysicists, 2012. http://dx.doi.org/10.1190/segam2012-0356.1.

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Choi, Yunseok, and Tariq Alkhalifah. "Frequency‐domain waveform inversion using the unwrapped phase." In SEG Technical Program Expanded Abstracts 2011. Society of Exploration Geophysicists, 2011. http://dx.doi.org/10.1190/1.3627727.

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Alanazi, Nouf A., and Partha P. Banerjee. "Phase Retrieval using Transport of Intensity and Phase with Electrically Programmable Optical Path Lengths." In Digital Holography and Three-Dimensional Imaging. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/dh.2022.th3a.1.

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The principle of unwrapped phase retrieval using transport of intensity and phase equations with electrically programmable optical path lengths achieved employing liquid crystals is demonstrated by retrieving a Gaussian phase recorded with off-axis digital holography.
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Lin, Yuzhao, Zhenchun Li, and Kai Zhang. "Unwrapped instantaneous-phase inversion based on new decompose method." In SEG Technical Program Expanded Abstracts 2018. Society of Exploration Geophysicists, 2018. http://dx.doi.org/10.1190/segam2018-2996705.1.

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Ambale, Bharath, Thomas S. Denney, Himanshu Gupta, Steven Lloyd, and Louis Dell'Italia. "Measuring 3D left ventricular strain from unwrapped harmonic phase." In 2008 5th IEEE International Symposium on Biomedical Imaging (ISBI 2008). IEEE, 2008. http://dx.doi.org/10.1109/isbi.2008.4541276.

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