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Development of a robot-based gonioreflectometer for spectral BRDF measurement

A new gonioreflectometer has been developed at the National Research Council of Canada to measure spectral bidirectional reflectance distribution functions (BRDF). It incorporates a five-axis robot manipulator that holds the sample, and a rotation stage that holds an extended uniform light source of precisely known emitting solid angle. An array spectroradiometer is used to measure the reflected spectral radiance from the sample, which is compared to the spectral radiance of the source itself, allowing the calculation of the BRDF from first principles. The system has been designed in anticipation of a growing demand for traceable spectral BRDF measurements from sectors such as machine vision, remote sensing and color imaging. Capabilities of the system are demonstrated for diffuse reflectance material, vapor-blasted aluminum, and light interference pigments.