Standardizing Interferometric Measurement

Because the U.S. supplies much of the interferometric measurement hardware and software used these days, the ANSI/NAPM IT.11 Subcommittee on Interferometric Testing has been asked to take the lead in formulating standards for interferometric measurement of wavefront error and surface roughness. As OPN went to press, the committee was scheduled to discuss several related isssues at the OSA Annual Meeting Oct. 3-8 in Toronto. One item the committee is considering is the rather mundane question of how to define "peak-to-valley" error. The widely used but naive answer is the lowest valley subtracted from the highest peak. A little thought shows that finding these two extremes depends on the spatial sampling density and the alignment of the sampling grid with the surface in question.

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