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Fringe 2013 pp 623-628 | Cite as

Topography Measurements of High Gradient and Reflective Micro-structures by Digital Holography

  • Michał Józwik
  • Tomasz Kozacki
  • Kamil Liżewski
  • Maciej Barański
  • Christophe Gorecki

Introduction

Due to both, 100% fill factor and the high shape gradient, the silicon molds are difficult to fabricate and are also demanding in characterization by optical methods. In the paper we present a method that overcomes some of measurement problems and can be used for recovering high numerical aperture (NA) shape of reflective microstructures, such as silicon molds. To achieve this practical goal we use the digital holography in microscope configuration with afocal imaging system [1] working in reflection mode. The standard method for topography reconstruction in optical full field metrology uses thin element approximation (TEA). In this paper we deal with the high NA optical field generated by an object. TEA would produce significant errors and cannot be applied. There are two algorithms that allow shape reconstruction with smaller error: the extended depth of focus (EDOF) [2] and the local ray approximation (LRA) [3,4]. The first one computes the shape from unwrapped measured phase. The phase is used in a refocusing algorithm to obtain the local object height from the optical field. The phase in this plane is reconstructed by TEA algorithm. Second algorithm is based on analysis of a local ray’s optical path differences in object. Both algorithms can be applied under condition that entire optical field is transferred by the imaging system. Also the algorithms require knowledge of the precise location of the plane from which the phase originates [5].

Keywords

Fill Factor Optical Field Microlens Array Object Wave Digital Holography 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    Kozacki, T., Józwik, M., Jóźwicki, R.: Determination of optical field generated by a microlens using digital holographic method. Opto-Electronics Review 17, 58–63 (2009)CrossRefGoogle Scholar
  2. 2.
    Colomb, T., Pavillon, N., Kühn, J., Cuche, E., Depeursinge, C., Emery, Y.: Extended depth-of-focus by digital holographic microscopy. Optics Letters 35, 1840–1842 (2010)CrossRefGoogle Scholar
  3. 3.
    Kozacki, T., Liżewski, K., Kostencka, J.: Holographic method for topography measurement of highly tilted and high numerical aperture micro structures. Optics and Laser Technology 49, 38–46 (2013)CrossRefGoogle Scholar
  4. 4.
    Kozacki, T., Józwik, M., Liżewski, K.: High-numerical-aperture microlens shape measurement with digital holographic microscopy. Optics Letters 36, 4419–4421 (2011)CrossRefGoogle Scholar
  5. 5.
    Liżewski, K., Tomczewski, S., Kostencka, J., Kozacki, T.: Hybrid and transflective system based on digital holographic microscope and low coherent interferometer for high gradient shape measurement. In: Proc. of SPIE, vol. 8788, p. 87880A-87880A-7 (2013)Google Scholar
  6. 6.
    Baranski, M., Passilly, N., Albero, J., Gorecki, C.: Fabrication of 100% fill factor arrays of microlenses from silicon molds. In: Proc. of SPIE, vol. 8428, 84281G-1–84281G-7 (2012)Google Scholar
  7. 7.
    Liżewski, K., Kozacki, T., Kostencka, J.: Digital holographic microscope for measurement of high gradient deep topography object based on superresolution concept. Optics Letters 38, 1878–1880 (2013)CrossRefGoogle Scholar
  8. 8.
    Kozacki, T., Liżewski, K., Kostencka, J., Józwik, M.: Topography Measurement of High Numerical Aperture Microlenses with Digital Holographic Microscopy. Digital Holography and 3D Imaging Technical Digest, Optical Society of America Technical Digest (online), paper DTu2A.6 (2013)Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Michał Józwik
    • 1
  • Tomasz Kozacki
    • 1
  • Kamil Liżewski
    • 1
  • Maciej Barański
    • 2
  • Christophe Gorecki
    • 2
  1. 1.Institute of Micromechanics and PhotonicsWarsaw University of TechnologyWarsawPoland
  2. 2.Department of Micro Nano Sciences & SystemsFEMTO-ST Institute (CNRS UMR 6174)BesançonFrance

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