13 May 2013 Hybrid and transflective system based on digital holographic microscope and low coherent interferometer for high gradient shape measurement
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The most suited techniques for quantitative and accurate determination of the phase distribution in a phase photonic microstructures are based on the interferometry, especially the digital holography (DH) in microscopic configuration. However there is well known limitation of the coherent full- field interferometric measurements: the phase difference between the neighboring samples cannot be larger than 2π, or objects shape have to generate light that can be collected by used optical system. This limitation might be overcame by use of a well-known technique called low-coherence interferometry (LCI) which allows for absolute shape measurements with a nanometer resolution and does not have 2π limitation of coherent interferometric techniques. In this work a dual channel measurement system for characterization of a high numerical aperture objects is presented. The system combines functionalities of the LCI system based on Twyman-Green configuration and the DHM system based on Mach-Zehnder configuration. The DHM allows to measure sample in transmission while LCI setup provides reflective measurement data and, therefore, provides a more complete tool for topography characterization. In presented paper we focus on the measurement of high gradient objects were both methods fail if applied independently: the LCI gives measurement only in the object area of low NA while the DHM cannot provide absolute shape characterization due to limited NA of imaging system. The dual channel system extends capabilities of both methods. In our paper we present experimental results for topography measurement of high NA microlenses. The accuracy of the development method is discussed and both simulation and experimental data are provided.
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K. Liżewski, K. Liżewski, S. Tomczewski, S. Tomczewski, J. Kostencka, J. Kostencka, T. Kozacki, T. Kozacki, } "Hybrid and transflective system based on digital holographic microscope and low coherent interferometer for high gradient shape measurement", Proc. SPIE 8788, Optical Measurement Systems for Industrial Inspection VIII, 87880A (13 May 2013); doi: 10.1117/12.2020980; https://doi.org/10.1117/12.2020980

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