An official website of the European Union How do you know?      
European Commission logo
JRC Publications Repository Menu

Functional Machine Vision Utilizing Full-Field Low-Coherence Interferometry

cover
Presented is an investigation of noncontact micrometer profilometry through fullfield low-coherence interferometry, focusing on a functional machine vision approach. Thus, the goals of the research were: simplicity yet functionality, robustness yet versatility, and precision yet cost-effectiveness. Most modern low-coherence interferometry techniques use analog electromechanical scanning in either lateral or axial dimensions to perform three-dimensional measurement-this is burdensome and inefficient if approximate knowledge of the sample exists before measurement. This work innovates with the achievement of true random access full-field measurement without analog electromechanical scanning. Lateral scanning was implemented by electronically accessing small random regions of interest on a complementary metal-oxide semiconductor camera at very fast frame rates. By decoupling optical carrier generation from axial scanning, two previously unreported random depth access techniques are demonstrated that feature a digital stepper motor. One method utilized a beat frequency between two acousto-optic modulators and a complementary metal-oxide semiconductor camera; the other employed a charge-coupled device camera and linear piezoelectric transducer scanning over 4 periods of the optical carrier. A significant benefit of the these techniques is the possibility of full-field phase retrieval of the interferometric signal inside a 14 µm coherence envelope without electromechanical stepping. This is highlighted with the nanometer surface profile of a standard engineering gauge block by a novel heterodyne phase retrieval algorithm. Specific application of the work is to inexpensive and functional full-field dimensional metrology demanding micrometer resolution over millimeter ranges. Previously unreported application of random depth access full-field low-coherence interferometry to a small punch test is reported. Rapid, noncontact, threedimensional profiling of a mild steel disk deformed with an applied force is illustrated. The benefits of this approach over conventional maximum displacement measurements are noncontact full-field measurement, averaged cross-sectional profiling, uniform deformation analysis, and applied force calibration. This Thesis presents experimental work, signal processing techniques, and theoretical considerations, from a single point low-coherence interferometer through to the development of a three-dimensional random access functional machine vision system.
2007-02-13
JRC36265
Language Citation
NameCountryCityType
Datasets
IDTitlePublic URL
Dataset collections
IDAcronymTitlePublic URL
Scripts / source codes
DescriptionPublic URL
Additional supporting files
File nameDescriptionFile type 
Show metadata record  Copy citation url to clipboard  Download BibTeX
Items published in the JRC Publications Repository are protected by copyright, with all rights reserved, unless otherwise indicated. Additional information: https://ec.europa.eu/info/legal-notice_en#copyright-notice