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Proceedings Paper

Development of a low-cost, 11 µm spectral domain optical coherence tomography surface profilometry prototype
Author(s): Nyasha J. Suliali; Peter Baricholo; Pieter H. Neethling; Erich G. Rohwer
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Paper Abstract

A spectral-domain Optical Coherence Tomography (OCT) surface profilometry prototype has been developed for the purpose of surface metrology of optical elements. The prototype consists of a light source, spectral interferometer, sample fixture and software currently running on Microsoft® Windows platforms. In this system, a broadband light emitting diode beam is focused into a Michelson interferometer with a plane mirror as its sample fixture. At the interferometer output, spectral interferograms of broadband sources were measured using a Czerny-Turner mount monochromator with a 2048-element complementary metal oxide semiconductor linear array as the detector. The software performs importation and interpolation of interferometer spectra to pre-condition the data for image computation. One dimensional axial OCT images were computed by Fourier transformation of the measured spectra. A first reflection surface profilometry (FRSP) algorithm was then formulated to perform imaging of step-function-surfaced samples. The algorithm re-constructs two dimensional colour-scaled slice images by concatenation of 21 and 13 axial scans to form a 10 mm and 3.0 mm slice respectively. Measured spectral interferograms, computed interference fringe signals and depth reflectivity profiles were comparable to simulations and correlated to displacements of a single reflector linearly translated about the arm null-mismatch point. Surface profile images of a double-step-function-surfaced sample, embedded with inclination and crack detail were plotted with an axial resolution of 11 μm. The surface shape, defects and misalignment relative to the incident beam were detected to the order of a micron, confirming high resolution of the developed system as compared to electro-mechanical surface profilometry techniques.

Paper Details

Date Published: 26 June 2017
PDF: 8 pages
Proc. SPIE 10329, Optical Measurement Systems for Industrial Inspection X, 103292Q (26 June 2017); doi: 10.1117/12.2268064
Show Author Affiliations
Nyasha J. Suliali, National Univ. of Science and Technology (Zimbabwe)
Peter Baricholo, National Univ. of Science and Technology (Zimbabwe)
Pieter H. Neethling, Stellenbosch Univ. (South Africa)
Erich G. Rohwer, Stellenbosch Univ. (South Africa)

Published in SPIE Proceedings Vol. 10329:
Optical Measurement Systems for Industrial Inspection X
Peter Lehmann; Wolfgang Osten; Armando Albertazzi Gonçalves Jr., Editor(s)

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