Optical characterization of thin layers grown on metal components

Franz Christian Mayrhofer, Gerald Zauner, Günther Hendorfer

Research output: Chapter in Book/Report/Conference proceedingsConference contribution

2 Citations (Scopus)


In this work a new method for calculating the optical properties of an absorbing film grown on substrates, including the real and imaginary part of the index of refraction is shown. In particular the thermal radiation of a growing oxide-film on a heated steel specimen is measured by a CCD camera with a near infrared (1000nm) band-pass filter. The observed radiation-signal shows significant temporal patterns due to interferences in the growing oxide film. Under the assumptions of known specimen temperature, constant optical properties (dielectric functions) of each layer and semitransparent films, it is possible to develop a model by which variations of the resulting emissivity with varying film-thickness can be explained. From this model, which is derived from the calculation of the reflectance of a thin absorbing film on an absorbing substrate, the complex index of refraction of the film can be determined without explicit knowledge of the optical constants of the respective layers. Since a matrix-camera is used to monitor the process changes of the emissivity over time, spatial information may also be derived. In this way it is possible to detect spatial inhomogeneities in the film and to determine the cause (either inhomogeneous growth rates or spatial variations of material properties). In addition, these results can be used for emissivity correction in non-contact thermal imaging. This method is not limited to oxide films and can be used for other heat treatment processes that deposit semitransparent films as well.

Original languageEnglish
Title of host publicationOptical Sensors 2008
PublisherSPIE Press
Number of pages12
ISBN (Print)9780819472014
Publication statusPublished - 2008
EventSPIE Photonics Europe 2008 - Strassburg, France
Duration: 7 Apr 200811 Apr 2008

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceSPIE Photonics Europe 2008


  • CCD camera
  • Dielectric function
  • Emissivity
  • Optical properties
  • Oxide films
  • Thermal imaging
  • Thin films


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