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A newly developed practical sphericity measurement system by means of stitching interferometry is described in this paper. Spheres are widely used in industry. In particular, spheres with stem are usually used in metrological applications such as reference sphere for Coordinate Measuring Machines. It is common to calibrate form of spheres with tactile roundness measurement, however a comprehensive form measurement is desired for evolving high precision applications. The developed system consists of commercial base Fizeau type interferometer to capture partial surface areas of sphere and five axes stages to handle sphere with stem. Hence the system is very suitable for measurement of such stemmed spheres. This system yields three dimensional form maps of stitched sphere and peak to valley sphericity. Standard deviation of sphericity value yielded using this system is less than 5 nm in 8 times repetition. Finally, an equatorial profile clipped from stitched sphere shows good agreement with a result of tactile roundness measuring method within 10 nm typically.

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