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Aperture correction for a sphere interferometer

R Arnold Nicolaus and Gerhard Bönsch

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Considerations have been made to derive a correction for the diameter measurements of a sphere by means of a special sphere interferometer. This correction is caused by the finite diameter of the light source acting as the entrance 'pinhole' aperture in the light collimating system. The finite diameter has the effect that the wave which is incident on the sphere is a superposition of spherical waves which are slightly inclined with respect to each other. The resulting correction is essential for high accuracy dimensional measurements of silicon spheres to determine the Avogadro constant—a new determination of which is a contribution to a new definition of the kilogram.


PACS

07.60.Ly Interferometers

06.20.Jr Determination of fundamental constants

42.15.Fr Aberrations

06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

06.20.fa Units

Subjects

Instrumentation and measurement

Optics, quantum optics and lasers

Dates

Issue 6 (December 2009)

Received 18 May 2009, in final form 12 October 2009

Published 9 November 2009



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