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Design of a dual wavelength digital holographic imaging system for the examination of layered structures
Author(s): John C. McFarland; Ting Chean Khoo; Anna Sharikova; Alexander Khmaladze
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Paper Abstract

Digital holographic microscopy uses interference patterns produced by the object and reference waves to computationally reconstruct both amplitude and phase of light reflected from a sample under study. The phase information recorded for each pixel can be converted to a height profile map, yielding a three-dimension image of the sample. Holographic imaging of layered structures, where layers are separated from one another by the axial distances exceeding the wavelength of imaging light, is challenging. Software based 2π phase discontinuity unwrapping, which relies on the gradients produced by the slowly varying sloped surfaces in the sample, is generally impossible. Additionally, dual wavelength phase unwrapping is complicated by the fact that if the layers are not sufficiently reflective, the unwrapping based on the comparison of two single wavelength phase images is unreliable. We present the design of a simultaneous dual wavelength digital holographic microscope, where the phase imaging of each individual layer is performed by a single wavelength, and then the axial distance between all layers is determined based on the comparison between the phase maps produced by each wavelength. By combining two interferometers within one setup, we could acquire two phase profiles simultaneously, enabling fast measurements. We demonstrate that this method is particularly well-suited for imaging of multilayered electrode structures embedded in glass, which contain both high and low reflectivity features.

Paper Details

Date Published: 5 June 2018
PDF: 7 pages
Proc. SPIE 10690, Optical Design and Engineering VII, 1069013 (5 June 2018); doi: 10.1117/12.2312274
Show Author Affiliations
John C. McFarland, Univ. at Albany (United States)
Ting Chean Khoo, Univ. at Albany (United States)
Anna Sharikova, Univ. at Albany (United States)
Alexander Khmaladze, Univ. at Albany (United States)

Published in SPIE Proceedings Vol. 10690:
Optical Design and Engineering VII
Laurent Mazuray; Rolf Wartmann; Andrew P. Wood, Editor(s)

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