27 December 2001 Stitching interferometry and absolute surface shape metrology: similarities
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Stitching interferometry is a method of analysing large optical components using a standard small interferometer. This result is obtained by taking multiple overlapping images of the large component, and numerically stitching these sub-apertures together by computing a correcting Tip- Tilt-Piston correction for each sub-aperture. All real-life measurement techniques require a calibration phase. By definition, a perfect surface does not exist. Methods abound for the accurate measurement of diameters (viz., the Three Flat Test). However, we need total surface knowledge of the reference surface, because the stitched overlap areas will suffer from the slightest deformation. One must not be induced into thinking that Stitching is the cause of this error: it simply highlights the lack of absolute knowledge of the reference surface, or the lack of adequate thermal control, issues which are often sidetracked... The goal of this paper is to highlight the above-mentioned calibration problems in interferometry in general, and in stitching interferometry in particular, and show how stitching hardware and software can be conveniently used to provide the required absolute surface shape metrology. Some measurement figures will illustrate this article.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael Bray, Michael Bray, } "Stitching interferometry and absolute surface shape metrology: similarities", Proc. SPIE 4451, Optical Manufacturing and Testing IV, (27 December 2001); doi: 10.1117/12.453636; https://doi.org/10.1117/12.453636

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