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Speckle patterns for tailorable and multiscale optical metrology measurements
Dissertation   Open access

Speckle patterns for tailorable and multiscale optical metrology measurements

Melvin Domin Mathew
Doctor of Philosophy (Ph.D.), Drexel University
Sep 2020
DOI:
https://doi.org/10.17918/00000186
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Abstract

Digital image correlation Multispectral imaging Nondestructive testing Speckle metrology Structural analysis (Engineering)
Optical metrology has been used in measuring distances and assessing movements and deformations for hundreds of years. With the advent of economically available high-end imaging systems and computer hardware systems, optical techniques for measuring the conditions of structures have increased. This technique is particularly useful given its non-contact nature and its versatility of scale independence. In comparison to other optical metrology techniques, such as point trackers or crack detection algorithms, digital image correlation (DIC) provides full field three-dimensional displacement and strain measurements. This matching and tracking algorithm depends on textures present or applied on the surfaces of the specimens under investigation to deform during the loading process. The quality of the results derived from this method thus depends on the quality of the pattern being tracked. Current speckle pattern application techniques predominantly generate spatially uncontrollable speckles and is dependent on the skill and experience of the operator. The proposed speckle pattern generation technique develops a methodology to create customizable patterns that are optimized to improving the quality of DIC results obtained. This technique leverages patterns inspired from natural bio-templates alongside DIC algorithmic quality metrics and imaging system based spatial constraints to parameterize, create and apply speckle pattern to attain high quality DIC displacement results.

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