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From Veeco Instruments
Absolute flatness testing is an interferometric method for obtaining the surface shape of flats, independent of the shape of the reference flat used in the test. In this method, a user measures three flats in a series of configurations, rotating and replacing flats between measurements in a prescribed order to eliminate the reference surface as an error source. In this paper we describe the theory of the three flat test, the test procedure, and techniques for minimizing measurement error. We include an example measurement using 4-inch diameter transmission flats. The real benefit of absolute testing occurs when you use a tested flat as a reference surface during subsequent measurements. The extremely accurate surface data can be subtracted during these measurements, allowing high-accuracy characterization of other optical surfaces. Product Announcements
Topics of Interest
An optical flat is a precisely polished flat surface, used as a reference against which the flatness of an unknown surface may be compared. Edmund Optics offers both single surface and dual surface...
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An optical flat is a precisely polished flat surface, used as a reference against which the flatness of an unknown surface may be compared. Edmund Optics offers both single surface and dual surface...
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Flatness places all of the points on a part's surface within a single plane. Flatness is often quantified by comparing a part's surface to a reference plane or optical flat. Typically, a least-squares...
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2.5. COMPENSATION OF INTRINSIC ABERRATIONS IN THE
INTERFEROMETER
A Twyman–Green interferometer may easily have aberrations of its own due to
defective optical components, so that the...
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6.1 Introduction
As shown in Chapter 5, for plane rectilinear near-field scanning, probe pattern characterisation errors contribute to the overall facility error budget as a singular mapping.
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