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Polarization influence on reflectance measurements in the spatial frequency domain
J Wiest1, N Bodenschatz, A Brandes
1Institut für Lasertechnologien in der Medizin und Meßtechnik, Helmholtzstr. 12, D-89081 Ulm, Germany.
Physics in Medicine and Biology
|July 10, 2015
Summary
Using crossed polarizers for reflectance measurements can lead to significant errors (over 25%) in optical properties. A polarized theory is recommended for accurate spatial frequency domain analysis, as scalar theory is insufficient.
Area of Science:
- Optical Physics
- Biomedical Optics
- Materials Science
Background:
- Crossed polarizers are common for suppressing specular reflections in reflectance measurements.
- Scalar theory is often used to analyze these measurements, neglecting polarization effects.
- This discrepancy can lead to inaccuracies in derived optical properties.
Purpose of the Study:
- To quantify the errors in optical properties due to the discrepancy between crossed polarizers and scalar theory in spatial frequency domain measurements.
- To evaluate the effectiveness of reference measurements in mitigating these errors.
- To provide recommendations for accurate optical property derivation.
Main Methods:
- Polarized Monte Carlo simulations were used for forward calculation of reflectance.
- Mie theory was applied to calculate scattering functions for spherical scatterers.
- Scalar radiative transfer equation was used for deriving optical properties (reduced scattering coefficient [Formula: see text] and absorption coefficient μa).
Main Results:
- Scalar theory analysis of reflectance data obtained with crossed polarizers resulted in errors exceeding 25% for both [Formula: see text] and μa.
- Reference measurement methods did not consistently improve the accuracy of optical property derivation in the spatial frequency domain.
- Significant discrepancies were observed between polarized light interaction and scalar approximations.
Conclusions:
- The use of non-polarized scalar theory for analyzing reflectance measurements with crossed polarizers introduces substantial errors.
- Reference measurements are not a universally effective solution for correcting these polarization-induced errors.
- A polarized theory is essential for accurate optical property determination when employing crossed polarizers in spatial frequency domain measurements.
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