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Publication Citation: A Simple Ball Averager for Reference Sphere Calibrations

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Author(s): Ulf Griesmann; Quandou (. Wang; Johannes A. Soons; Remi Carakos;
Title: A Simple Ball Averager for Reference Sphere Calibrations
Published: January 01, 2005
Abstract: When measuring the form errors of precision optics with an interferometer, the calibration of the reference wavefront is of central importance.  Ball averaging, or random ball testing, has in recent years emerged as a robust method for calibrating spherical reference wavefronts in coverging beams.  We describe a simple instrument, consisting of an air bearing and two electric motors, that can rotate the test ball around three axes as required for a ball averaging test.  The performance of the instrument is demonstrated by isng it to calibrate a concave transmission sphere.  Further we discuss the effects of image sampling at random locations or on uniform grids, and the effect of correlated measurements due to partial image overlap.  Finally, we describe a method to determine the number of measurements which are sufficient for a ball averaging calibration.
Conference: SPIE Optics and Photonics 2005 Conference
Volume: 5869
Location: San Diego, CA
Dates: July 31-August 4, 2005
Keywords: ball averaging test,Transmission sphere calibration
Research Areas: Dimensional Metrology
PDF version: PDF Document Click here to retrieve PDF version of paper (516KB)