21 August 2009 High-resolution measurement of internal interface of optically transparent materials
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The measurement of surface morphology of a material with high resolution is important in both the industrial and biomedical applications. Furthermore, a precise measurement of the morphology of the internal interface is usually needed for materials with multilayered structures. Although some optical techniques can provide subsurface imaging of materials, their resolutions are difficult to achieve nanometer scale. In our research, an optical system based on a composite interferometer which can image the internal interface of a material with nanometer resolution is proposed and demonstrated. The system consists of a Michelson interferometer and a Mach-Zehnder interferometer. The Michelson interferometer with a broadband light source is used for three-dimensional imaging of the sample. In the Mach-Zehnder interferometer, a prism and a retro-reflector are arranged for an optical delay line with adjustable length. The two interferometers share common light source and a rapid scanning optical delay system used for axial scanning. In the experiment, the adjustable optical delay line in the second interferometer is adjusted for the optical path lengths to match that relative to the interface under investigation. With a phase compensation mechanism, the interface can be imaged with an axial accuracy at nanometer scale.
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Chun-Wei Chang, Chun-Wei Chang, I-Jen Hsu, I-Jen Hsu, } "High-resolution measurement of internal interface of optically transparent materials", Proc. SPIE 7426, Optical Manufacturing and Testing VIII, 742602 (21 August 2009); doi: 10.1117/12.825199; https://doi.org/10.1117/12.825199

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