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Surface and thickness measurement of a transparent film using wavelength scanning interferometry

Gao, F., Muhamedsalih, Hussam and Jiang, Xiangqian (2012) Surface and thickness measurement of a transparent film using wavelength scanning interferometry. Optics Express, 20 (19). p. 21450. ISSN 1094-4087

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    A wavelength scanning interferometer for measuring the surface
    and thickness of a transparent film has been studied. A halogen light source
    combined with an acousto-optic tuneable filter is used to generate a
    sequence of filtered light in a Linnik interferometer, which leads to a
    sequence of interferograms captured by a CCD camera. When a transparent
    thin film is measured, the reflection signals from both the top and bottom
    surfaces of the film will interfere with the reference signal. At the same
    time, the multiple reflection signals between the two film surfaces will also
    interfere with each other. Effective separation of the interference signals
    from each other is the key to achieving a successful measurement. By
    performing a frequency-domain analysis, these interference signals can be
    separated. An optimized Fourier transform method is used in the analysis.
    Measurements of the top and bottom surface finishes of the film, as well as
    the film thickness map, have been achieved. The film needs to be more than
    3 μm in optical path length, and must transparent with no absorption of
    light. The film’s refractive index needs to be known as a function of
    wavelength. In this paper, the theoretical analysis and simulation study of
    wavelength scanning interferometry for transparent film measurement is
    discussed. Experiments on thin film layers of Parylene N coated on a glass
    slide surface are studied and analyzed. Comparison study results with other
    contact and non-contact methods are also presented

    Item Type: Article
    Subjects: Q Science > Q Science (General)
    Q Science > QC Physics
    Schools: School of Computing and Engineering
    School of Computing and Engineering > Centre for Precision Technologies > Surface Metrology Group
    Related URLs:
    Depositing User: Feng Gao
    Date Deposited: 09 Oct 2012 16:43
    Last Modified: 12 Nov 2013 09:53


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