Accounting for polarization–related effects in the measurement of the bidirectional reflectance distribution function

A Calderón,J Campos,A Ferrero

doi:10.1088/1681-7575/ab804f

Abstract

When measuring the Bidirectional Reflectance Distribution Function (BRDF) to characterize typical materials, the effect of the polarization of the light source or the dependence of the detector on the polarization is not usually considered, even though many studies have proven their impact in the uncertainty of the BRDF of most materials, including diffuse reflectance standards. A methodology to assess polarization-related effects proposed by other authors has been tested in this work for the measurement of the BRDF of four typical materials used for realizing white diffuse reflectance standards (ceramic tile, barium sulfate, Spectralon and Russian opal glass). Relative systematic error due to polarizing conditions is calculated as a combination of the instrument polarization bias and sample-based coefficients, and the impact of the proposed methodology on the uncertainty is discussed.

Highlights

A methodology to assess polarization-related effects proposed by other authors has been tested in this work for the measurement of the Bidirectional Reflectance Distribution Function (BRDF) of four typical materials used for realizing white diffuse reflectance standards
In order to improve the measurement of materials reflectance, national metrology institutes (NMIs) and other research centers have developed in recent years complex robot–based goniospectrophotometers to measure the bidirectional reflectance of surfaces with as few geometrical restrictions as possible [1,2,3,4,5,6,7,8,9,10]
This approach was experimentally tested on four typical materials for realizing white diffuse reflectance standards, which are used as 0◦: 45◦ bidirectional reflectance factor standards in BRDF measurements

Summary

Introduction

In order to improve the measurement of materials reflectance, national metrology institutes (NMIs) and other research centers have developed in recent years complex robot–based goniospectrophotometers to measure the bidirectional reflectance of surfaces with as few geometrical restrictions as possible [1,2,3,4,5,6,7,8,9,10]. The principal objective of this work was to assess polarization-related effects in the measurement of the BRDF, and to provide an approach to account for systematic errors This approach was experimentally tested on four typical materials for realizing white diffuse reflectance standards (ceramic tile, barium sulfate, Spectralon and Russian opal glass), which are used as 0◦: 45◦ bidirectional reflectance factor standards in BRDF measurements. Since they are not perfect reflecting diffusers (PRD, diffuser exhibiting isotropic diffuse reflection with a reflectance equal to one [16]), they need to be spectrophotometrically characterized in order to account for their deviation from ideality.

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