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Geometric Area Measurements of Circular Apertures for Radiometry at NIST



J B. Fowler, Maritoni A. Litorja


NIST has established a geometric aperture-area measurement facility for circular apertures. The instrument consists of an interferometrically controlled XY translation stage for high-accuracy positioning and a video microscope for detection fo the aperture edge. Least-squares fitting of the edge points located along the aperture's inner circumference to the equation of a circle is used to determine the geometric area. In this paper we describe the measurement method, based on the work started and described by Fowler, Durvasula and Parr [1]. Analysis and estimation of various contributions to the overall measurement uncertainty, including the effects of diffraction and partial coherence of light on the edge location are also discussed.
No. 1


apertures, metrology, microscopy, radiometry


Fowler, J. and Litorja, M. (2003), Geometric Area Measurements of Circular Apertures for Radiometry at NIST, Metrologia, [online], (Accessed April 14, 2024)
Created February 1, 2003, Updated June 2, 2021