Two-wavelength micro-interferometry for 3-D surface profiling |
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Authors: | U. Paul Kumar Basanta Bhaduri M.P. Kothiyal N. Krishna Mohan |
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Affiliation: | Applied Optics Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai, TN 600 036, India |
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Abstract: | Three-dimensional non-contact optical techniques for rapid and accurate mapping of micro-machined surfaces are important for the optoelectronic industry. Interferometry is a well-established technique for 3-D surface profiling. The conventional interferometric surface profilers using a single wavelength offer excellent vertical resolution, but a serious limitation to their use is that they can only handle smooth profiles and step heights less than half a wavelength. In this paper we describe a two-wavelength micro-interferometric setup for 3-D surface profile characterization of smooth as well as rough micro-specimens. The method removes ambiguity associated with the single-wavelength data and also extends the phase measurement range compared to the conventional single-wavelength interferometry. Seven-phase step algorithm is used for quantitative fringe analysis. The design of the system along with experimental results on smooth and rough micro-specimens is presented. |
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