Angstrom level profilometry for submillimeter- to meter-scale surface errors

Paul E. Glenn

doi:10.1117/12.22817

1 November 1990 Angstrom level profilometry for submillimeter- to meter-scale surface errors

Paul E. Glenn

Proceedings Volume 1333, Advanced Optical Manufacturing and Testing; (1990) https://doi.org/10.1117/12.22817
Event: 34th Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, 1990, San Diego, CA, United States

Abstract

In this paper we define a versatile new noncontacting profilometry approach that offers significant advantages in terms of accuracy, robustness, and flexibility over conventional interferometric or slope measuring approaches. The approach involves measuring the local curvature of the test piece by simultaneously measuring its slope at two slightly displaced locations. As the pair of sensing beams is scanned along the test piece, a profile of curvature is built, from which the height profile is deduced. The sensing of curvature eliminates the need for an interferometric reference surface, and makes the approach insensitive to all types of vibration and drift, both in surface height and in surface slope. Thus, the approach is extremely robust. We have already demonstrated sub-Angstrom accuracy for typical mid-spatial period ranges extending from a fraction of a millimeter to tens of millimeters. In this paper, however, we emphasize several extensions of the measurement technique that make it an extremely versatile profiling approach for a variety of metrology needs. These extensions include beam expansion to make very long scans possible; measurement of circularity and cone angle of near cylindrical optics; and measurement of absolute flatness. We summarize our experimental results obtained to date, and define expected performance levels for these extended measurement functions.

Citation Download Citation

Paul E. Glenn "Angstrom level profilometry for submillimeter- to meter-scale surface errors", Proc. SPIE 1333, Advanced Optical Manufacturing and Testing, (1 November 1990); https://doi.org/10.1117/12.22817

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