25 October 2016 Comparison of small angle deflectometric measurements with different apertures down to the sub-millimetre range
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Abstract
The Physikalisch-Technische Bundesanstalt (PTB) has developed and set up a deflectometer with sub-millimetre lateral resolution. This device uses an enhanced deflectometric method called ‘Exact Autocollimation Deflectometric Scanning’ (EADS), which makes use of two angle sensors. One angle sensor has a small beam aperture and scans the specimen by using a pentaprism or a double mirror unit. It operates as a null angle sensor and controls the tilting of the specimen by means of a piezo actuator, so that the reflected beam of the specimen always propagates back in the same direction. The null-angle sensor allows sub-millimetre apertures with sensitivities of better than 0.01 arcsec to be achieved. The tilt of the specimen is measured with the second angle sensor – usually a commercially available autocollimator – with a large aperture at a fixed distance. The surface topography is obtained by the numerical integration of the measured tilt angles. The measurement uncertainty associated with the resulting topography typically scales with the scan length. Here, we present measurements with different lateral resolutions down to 0.3 mm.
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Gerd Ehret, Gerd Ehret, Susanne Quabis, Susanne Quabis, Michael Schulz, Michael Schulz, } "Comparison of small angle deflectometric measurements with different apertures down to the sub-millimetre range ", Proc. SPIE 9687, 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Subnanometer Accuracy Measurement for Synchrotron Optics and X-Ray Optics, 968702 (25 October 2016); doi: 10.1117/12.2243608; https://doi.org/10.1117/12.2243608
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