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2 September 2010 PASCAL: instrument for accurate precise characterization of Lambertian materials
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Accurate characterization of the reflection and scatter properties of materials is critical for their use in optical systems. PASCAL (Polarization And Scatter Characterization and Analysis of Lambertian materials) makes BRDF (Bidirectional Reflection Distribution Function) measurements with a polarized light source and can measure with / without an analyzer in series with the detector in the 400 - 1700 nm wavelength range. The entire incident light beam is collected by the detector assembly. With the sample in place, a precision circular aperture is used to collect the light. BRDF is calculated on the basis of the incident power and geometric factors eliminating the need for a standard characterized at another laboratory. The measured uncertainties of the geometric factors are comparable to those of the National Institute of Standards and Technology (NIST) Spectral Tri-function Automated Reflectance Reflectometer (STARR) facility. Spectral definition is achieved with band pass filters. As in typical BRDF instruments, the detector rotates about the sample in the plane defined by the source beam and the azimuth rotation of the sample. Unique additional features of this instrument include the ability to vary the sample elevation and sample roll. Comparisons with measurements made at NIST are presented. Measurements with this instrument demonstrate the importance of sample orientation, roll, with variations of 2.5% observed. The roll dependence can vary with polarization. The minimum sample size measurable is 5 cm diameter with the maximum sample size of 22 X 27 cm.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Vijay Murgai, John M. Nixt, Eric M. Moskun, Christopher M. Jones, Chad E. Payton, and Jacob D. CdeBaca "PASCAL: instrument for accurate precise characterization of Lambertian materials", Proc. SPIE 7792, Reflection, Scattering, and Diffraction from Surfaces II, 77920X (2 September 2010);


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