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Sphere Diameter Interferometry with Nanometer Uncertainty



Eric S. Stanfield, John R. Stoup, Michael P. Braine, Theodore D. Doiron


In this paper we present both the design details and uncertainty budget for a National Institute of Standards and Technology (NIST)-developed high-accuracy Fizeau-type interferometer specifically adapted to measurement sphere diameter. To do this, we provide some historic details of the instrument's origins, an explanation of the clever accuracy-improving enhancements integrated into the design over the past several decades, and a detailed discussion of the role automation has played in achieving its current world-class accuracy. With utmost attention to the dominating components of a detailed uncertainty budget, we methodically improved a rather dated instrument design into a high-accuracy state-of-the-art system for sphere diameter measurement with an expanded uncertainty, U(k=2), of less than ± 10 nm for spheres with nominal diameters of between 0.4 mm and 26 mm. We conclude with a brief description of a novel application of this instrument for determining the phase-change upon reflection correction for both gauge blocks and gauge block platens. Applying corrections for phase-change upon reflection differences between different surfaces, gauge block and platen, is critically important for high-accuracy interferometric gauge block length measurements.


ball diameter, sphere diameter, ball interferometry, sphere interferometry, strang viewer, gage block phase correction, gauge block phase correction, platen phase correction, elastic deformation, elastic compression


Stanfield, E. , Stoup, J. , Braine, M. and Doiron, T. (2020), Sphere Diameter Interferometry with Nanometer Uncertainty, Metrologia, [online],, (Accessed July 24, 2024)


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Created February 19, 2020, Updated May 22, 2024