Absolute measurement methods for reflectance and fluorescence

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Doctoral thesis (article-based)
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Date
2009
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Degree programme
Language
en
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Verkkokirja (513 KB, 52 s.)
Series
TKK dissertations, 166
Abstract
Reflectance and fluorescence are important properties when determining the colour and appearance of solid opaque material. They are also useful in several other industrial applications such as those in biochemical and medical industry and in remote sensing. In most industrial applications, the reflectance and / or fluorescence characteristics of samples are measured relative to a known reference standard. The uncertainty of the measurements is naturally dependent on the uncertainty of the reference standard and therefore it is vital to have high-accuracy calibration instruments capable of absolute measurements. In addition, the standards should be calibrated in the same measurement geometry as the application where they are used. Particularly, instruments capable of absolute fluorescence measurements commonly use a fixed measurement geometry and therefore there is a need for an instrument that does not have this limitation. In the thesis, goniometric measurement facilities for measuring reflectance and fluorescence characteristics of reference standards have been designed and developed. The significance of light scattering in goniometric diffuse reflectance measurements has been studied. The effect can cause errors of the order of 1 % in the measurements if it is not properly taken into account. Also, this effect may be at least partly responsible for the discrepancies reported earlier between goniometric and integrating-sphere-based diffuse reflectance measurements. The wavelength range of an existing gonioreflectometer for calibrating reflectance and radiance factors has been extended and an extensive bilateral comparison in the wavelength range 250 nm - 1650 nm is reported. Such extensive comparisons between goniometric instruments are very rare even though it is the only way to verify the reliability of the absolute scales in National Metrology Institutes. A goniofluorometer has been designed and developed for measuring bispectral luminescent radiance factors in various measurement geometries. Also, the theory and mathematics of a new method for measuring absolute fluorescence quantum yield based on goniometric measurements has been derived. One of the most significant results of this thesis is the discovery of non-Lambertian behaviour of fluorescence emission from solid amorphous material. In addition, it has been observed that the angular pattern of fluorescence emission is not very tightly linked to the angular pattern of reflectance. This is an important result since most commercial and research instruments are only capable of measurements in a fixed geometry and usually rely on the assumption of Lambertian emission of fluorescence.
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Keywords
diffuse reflectance, radiance factor, bispectral luminescent radiance factor, fluorescence quantum yield
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Parts
  • [Publication 1]: Silja Holopainen, Farshid Manoocheri, Saulius Nevas, and Erkki Ikonen. 2007. Effect of light scattering from source optics in goniometric diffuse reflectance measurements. Metrologia, volume 44, number 3, pages 167-170. © 2007 Institute of Physics Publishing. By permission.
  • [Publication 2]: Silja Holopainen, Farshid Manoocheri, Erkki Ikonen, Kai-Olaf Hauer, and Andreas Höpe. 2009. Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflectance. Applied Optics, volume 48, number 15, pages 2947-2957. © 2009 Optical Society of America (OSA). By permission.
  • [Publication 3]: Silja Holopainen, Farshid Manoocheri, and Erkki Ikonen. 2008. Goniofluorometer for characterization of fluorescent materials. Applied Optics, volume 47, number 6, pages 835-842; volume 47, number 36, page 6880. © 2008 Optical Society of America (OSA). By permission.
  • [Publication 4]: Silja Holopainen, Farshid Manoocheri, and Erkki Ikonen. 2009. Non-Lambertian behaviour of fluorescence emission from solid amorphous material. Metrologia, volume 46, number 4, pages S197-S201. © 2009 by authors and © 2009 Institute of Physics Publishing. By permission.
  • [Errata file]: Errata of publication 3
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