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 . 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.
Issue: No. 1
Pub Type: Journals
apertures, metrology, microscopy, radiometry