Correction of the calibration measurement by taking into account the Spectralon spectro-polarimetric BRDF model

Martin P. Levesque; Maria Dissanska

doi:10.1117/12.2323603

4 September 2018 Correction of the calibration measurement by taking into account the Spectralon^TM spectro-polarimetric BRDF model

Martin P. Levesque, Maria Dissanska

Author Affiliations +

Proceedings Volume 10750, Reflection, Scattering, and Diffraction from Surfaces VI; 107500H (2018) https://doi.org/10.1117/12.2323603
Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States

Abstract

The Spectralon is one of the best materials for the calibration of spectral measurements. Normally, the Spectralon must be illuminated and measured at right angle, but, this is not always possible, particularly for outdoor measurements where we cannot control the Sun position. A Spectralon plate has a BRDF (Bidirectional Reflectance Distribution Function), which is not completely flat as a perfect Lambertian surface and this affects the calibration. Furthermore, when illuminated or observed at angles, the Spectralon polarizes the light and it can also create reddening effects in some conditions. Moreover, several sensors (most of the spectrometers) are sensitive to the polarization and are prone to create reading artefacts. First, this paper presents a calibration procedure adapted to these situations; it takes into account the polarization and the Spectralon BRDF. Second, this paper presents also a Spectralon BRDF model that is required to calculate its reflectance at the encountered angular conditions. This BRDF model is an algorithm framework (based on curve fitting methods) that was deduced from the analysis of thousands Spectralon measurements done with various illumination, viewing and polarization angles. The model is decomposed into several sub-models for the various encountered scattering types (backscattering and deep, forward and sub-surface scatterings), plus models for the polarization contrast and reddening.

Conference Presentation

Citation Download Citation

Martin P. Levesque and Maria Dissanska "Correction of the calibration measurement by taking into account the Spectralon^TM spectro-polarimetric BRDF model", Proc. SPIE 10750, Reflection, Scattering, and Diffraction from Surfaces VI, 107500H (4 September 2018); https://doi.org/10.1117/12.2323603

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