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Absolute Alignment of the Reference Retroreflectometer at NIST



Carl C. Miller


The National Cooperative Highway Research Program (NCHRP Project 05-16) awarded The National Institute of Standards and Technology (NIST) a contract to develop a dedicated reference instrument for measuring retroreflective materials, and a calibration program that provides traceability to the relevant national scales maintained by NIST. The most critical aspect of the NIST Reference Retroreflectometer is the absolute alignment of the three components: thesource, the goniometer, and the detector. Presented are the methods for aligning the components and the uncertainty of the four angles defined as the CIE goniometer system. The expanded uncertainty (k=2) for the observation angle, alpha, is 0,00057 ; for the entrance angle components, beta 1 and beta 2, is 0,0090 ; and for the rotation angle, epsilon, is 0,061 .
Proceedings Title
Commission Internationale de L'eclairage | 25th | | CIE
Conference Dates
June 25-July 2, 2003
Conference Title
Publications Commission Internationale De L'Eclairage CIE


calibration standard, retroreflection, retroreflectometer, uncertainty


Miller, C. (2003), Absolute Alignment of the Reference Retroreflectometer at NIST, Commission Internationale de L'eclairage | 25th | | CIE (Accessed June 23, 2024)


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Created June 1, 2003, Updated February 17, 2017