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Enhancing the robustness of ESPI measurements using digital image correlation Bingleman, Luke
Abstract
Electronic Speckle Pattern Interferometry (ESPI) provides a sensitive technique for measuring surface deformations. The technique involves comparison of the speckle phase angles within surface images measured before and after material deformation. This phase angle comparison requires that the speckle positions be consistent in all images. A lateral shift between images by just one pixel substantially degrades ESPI measurements, while a shift of two or more pixels typically causes complete speckle decorrelation and compromises the measurement entirely. To prevent such lateral motions, the specimen and the optical system must be rigidly fixed. This requirement typically prevents use of the ESPI method in applications outside laboratories or where it is necessary to remove the specimen from the optical setup between ESPI measurements. Here, Digital Image Correlation (DIC) is used to track speckle motion caused by specimen displacement between ESPI measurements. The measured images can then be mathematically shifted to restore the original speckle locations, thereby recorrelating the ESPI measurements. Examples are presented where ESPI measurements are successfully made with specimen shifts in excess of 60 pixels. A novel ESPI measurement technique where the specimen is removed in between ESPI measurements is also developed and validated.
Item Metadata
Title |
Enhancing the robustness of ESPI measurements using digital image correlation
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2010
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Description |
Electronic Speckle Pattern Interferometry (ESPI) provides a sensitive technique for measuring
surface deformations. The technique involves comparison of the speckle phase angles within
surface images measured before and after material deformation. This phase angle comparison
requires that the speckle positions be consistent in all images. A lateral shift between images
by just one pixel substantially degrades ESPI measurements, while a shift of two or more pixels
typically causes complete speckle decorrelation and compromises the measurement entirely.
To prevent such lateral motions, the specimen and the optical system must be rigidly fixed.
This requirement typically prevents use of the ESPI method in applications outside laboratories
or where it is necessary to remove the specimen from the optical setup between ESPI
measurements. Here, Digital Image Correlation (DIC) is used to track speckle motion caused by
specimen displacement between ESPI measurements. The measured images can then be
mathematically shifted to restore the original speckle locations, thereby recorrelating the ESPI
measurements. Examples are presented where ESPI measurements are successfully made with
specimen shifts in excess of 60 pixels. A novel ESPI measurement technique where the specimen
is removed in between ESPI measurements is also developed and validated.
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Genre | |
Type | |
Language |
eng
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Date Available |
2010-08-20
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivs 3.0 Unported
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DOI |
10.14288/1.0071157
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2010-11
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
Attribution-NonCommercial-NoDerivs 3.0 Unported