Phase Unwrapping By Regions

Gierloff, Jeffrey J.

doi:10.1117/12.967466

Cited by 42 publications

(10 citation statements)

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“…Since successive frames are recorded with constant increments in load, this result inters the model exhibiting an elastic behavior under compression. Stresses calculated using the stress-optic relation given in eq (8) are compared with computations obtained from the relationship between load and applied stress from the theory of elasticity described in eq (9). The results are graphically tab- Fig.…”

Section: Figures 2 (A)-(b)mentioning

confidence: 99%

Photoelastic stress analysis using an object step-loading method

1997

Experimental Mechanics

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ABSTRACT--Sensitive, computer-aided retardation phase measurement methods suffer from the problem of discontinuity, which, in turn, hinders faultless phase unwrapping for stress determination in photoelasticity. An object steploading method is introduced in this paper to overcome such a problem. One advantage of the technique is that the entire loading-to-stress history is computed. In this paper, the theoretical aspects related to implementation of the object step-loading method in computer-aided photoelasticity are outlined, and experimental verification is performed on a birefringent model subjected to compressive loading by comparing stress values with those computed using the theory of elasticity.

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Section: Figures 2 (A)-(b)mentioning

confidence: 99%

Photoelastic stress analysis using an object step-loading method

1997

Experimental Mechanics

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“…A large number of decisions must be made and any errors can be propagated throughout the entire image. Numerous algorithms have expanded on the basis idea, the most robust utilising regional rather than global analysis [6,7,8]. However, no unwrapper is completely noise-immune.…”

Section: The Phase Unwrapping Problemmentioning

confidence: 99%

A Neural Network Approach to the Phase Unwrapping Problem in Fringe Analysis

Tipper

Burton

Lalor

1996

Nondestructive Testing and Evaluation

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This paper presents a novel approach to the phase unwrapping problem by employing a back-propagation neural network to detect the presence of phase wraps in an image. The philosophy behind the approach is to keep the analysis simple by using a small network consisting only of six input. six hidden and six output neurons. Each input neuron is assigned to one pixel and this input "window" is convolved with an image to analyse only six pixels at a time. The unwrapped phase distribution is reconstructed from this series of analyses. It is shown that after training for approximately two hours. the network can successfully unwrap a one-dimensional phase distribution in 0.5 seconds and that this method could prove 10 be the basis for a robust two dimensional phase unwrapper.

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“…this condition is not fulfilled because of the time-dependent character of electronic noise. Various noise-immune algorithms have been proposed to cope with the inconsistent points (79), (83)(84)(85)(86)(87)(88)(89)(90)(91)(92)(93)(94)(95)(96)(97)(98)(99)(100)(101)(102). Hence, computed principal phases values are corrupted by noise to such an extent that locally inconsistent regions are caused.…”

Section: Unwrapping Of Mod2n-phase Disributionsmentioning

confidence: 99%

“…speckle displacements and so on. Typical examples of these are' the region oriented method by GIERLOFF (99), the cut-line method by HUNTLEY (87) 1 02). Following the statistics of speckle fields it is obvious that dark speckles dominate in the image.…”

Section: Unwrapping Of Mod2n-phase Disributionsmentioning

confidence: 99%

Optical Methods in Experimental Solid Mechanics

Laermann¹

2000

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This volume contains 266 illustrationsThis work is subject to copyright.All rights are reserved, whether the whole or part of the material is concerned specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction hy photocopying machine or similar means. and storage in data hanks. PREFACE Recent developments and achievements inmeasurement techniques especially in optical and electro-optical methods like holography, shearography, speckle interferometry, grid-methods, modern modification of photoelasticity and photoviscoelasticity have opened new fields of applying experimental analysis in solid mechanics, in research as well as in industrial practice. Combined with computer techniques in digital image processing, data recording and data evaluation complex measuring systems can be realised nowadays with the possibility of far-reaching automation of the entire analysing processes. The sensitivity and the high resolving power of recording equipment requires thorough investigation of any effects on the precision and reliability of the measurements. Therefore it is necessary, to deal with the physics and the theories of the measurement methods in order to interpret the observed phenomena correctly. Furthermore proper algorithms must be available to evaluate the measured data to get the finally wanted infonnation, which generally do not coincide with the quantities taken from the measurements originally. This fact requires complementary scientific considerations of the theories concerning the problems to be analysed. At least the combination of experimental and mathematical/numerical procedures for evaluation and interpretation, known as "hybrid technique", demands additional contemplation. The lectures cover i. the theory and the physics of advanced optical measuring methods and problems of experimental performance, recent achievements in 2and ]-dimensional linear/non-linear photoelasticity including photovisco-elasticity, Moire-and grid-techniques, illfe1jerometric methods (holography. speckle inte1.ferometry, shearography): 11.the theory (~f digital image processing and its pe1jomwnce. data-recording, -compression, -processing, -l'isuali:::ation:iii. mathematical and numerical procedures. il{formatics for emluation of measured, digiti:;,ed data.As the co-ordinator (~f the CISM-course "Modem Optical Methods in Experimellfal Solid Mechanics .. and the editor (~f the lecture notes I grate.fitlly thank the lecturers/autlwrsfor the e.fjectil'e co-operation and thorough re\·ising the manuscripts. the resident Rector. the General Secretary. the ChiefEditor.and explicitly the st(!ffmemhers (~f CISM Secretariat.f(Jr support and excellent organisation (~f the course. Many thanks to the Springer-Verlag .f(Jr publishing the lecture notes. Karl-Hans LaennannABSTRACT Optical methods in experimental solid mechanics, yielding field information, combined with digital image processing and on-line evaluation of the experimentally obtained data by means of numerical procedures enable the stress-stra...

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Phase Unwrapping By Regions

Cited by 42 publications

References 0 publications

Photoelastic stress analysis using an object step-loading method

Photoelastic stress analysis using an object step-loading method

A Neural Network Approach to the Phase Unwrapping Problem in Fringe Analysis

Optical Methods in Experimental Solid Mechanics

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