| Zugriffsnummer | 13693 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Tracing back radius of curvature and topography to the base unit of length with ultra-precision |
| Autor(in); Institution |
Weingärtner, Ingolf; 4.21, Bildoptik und Spektrometrie, PTB-Braunschweig
Schulz, Michael; 4.21, Bildoptik und Spektrometrie, PTB-Braunschweig
Geckeler, Ralf D.; 4.21, Bildoptik und Spektrometrie, PTB-Braunschweig
Jusko, Otto; 5.31, Maß und Form, PTB-Braunschweig
Neugebauer, Michael; 5.31, Maß und Form, PTB-Braunschweig
Nicolaus, Arnold; 5.13, Interferentielle Längenmessung, PTB-Braunschweig
Bönsch, Gerhard; 5.13, Interferentielle Längenmessung, PTB-Braunschweig
|
| Quelle/Jahr | Recent developments in traceable dimensional measurements:(2001), 175 - 183 |
| Schriftenreihe | Proceedings of SPIE: 4401 |
| Herausgeber(in) |
Decker, Jennifer E.
|
| ISSN | 0277-786X |
| ISBN | 0-8194-4096-5 |
| Verlag | Bellingham, Wash.: SPIE |
| Konferenzangaben | Recent developments in traceable dimensional measurements, Munich, 20-21, June, 2001, Germany |
| Freie Schlagworte | nanometrology ; traceability ; length ; dimensional metrology ; radius of curvature ; topography ; intrinsic standard |
| Zusammenfassung | Very recently, in the context of measuring aspheres and complex surfaces with ultra-precision, a particular measurement principle was developed which determines the form (topography) of extended test samples by first making scanning measurements of curvature, being the reciprocal of the radius of curvature. The curvature sensor must be traceably calibrated witha low uncertainty. This back tracing can be done, first, by measuring radius of full spheres with a highly accurate sphere interferometer, second, by measuring roundness with highly accurate methods, and third, by measuring specially designed calibration aspheres. These procedures for traceably calibrating the curvature sensor will be described. The determination of the radius of curvature for optical elements (lenses and mirrors) or other technical surfaces can today be performed with an uncertainty which is far higher than the uncertainty which can be reached by the definition and realisation of the base unit of length. Basically, the base unit of length can be traced back to time (with the well-defined defined value for the velocity of light in vacuum) via the wavelength with a relative uncertainty of 10-13. Practically, the length can be traced back to solid bodies (e.g. gauge blocks, spheres, cylinders) via the wavelength with a relative uncertainty of approximately 10-7 to 10-8. This measurement technique uses a curvature sensor which mainly consists of a device for determining the local surface topography over a relatively large area with a high lateral resolution. The curvature is then derived from these data by complex mathematical algorithms. Such a curvature sensor can be traceably calibrated with a low uncertainty. Generally speaking, radius or diameter of full spheres can be measured by various methods. First, with a special highly accurate sphere interferometer which is intended to be used in the context of the so-called "Avogadro experiment", and second, with roundness measurement methods which are highly accurate like all methods measuring over the full circle, as in these cases errors of the measurement facilities can be separated from the measurands and then eliminated. Measurement of a sphere with these methods represents the first step of the calibration of the curvature sensor. In a second step, the sphere will be measured with the curvature sensor itself, also over the full circle. By comparison of the two measurements the curvature sensor can be traceably calibrated with a low uncertainty. The procedure for traceably calibrating the curvature sensor as well as the hardware of the curvature sensor and the algorithms for evaluation will be described. At the end, an alternative method will be presented and described which uses specially designed aspheres for the calibration of curvature sensors and an application for ultra-precise measurement of steep aspheres and complex surfaces. |
Zitierung
Weingärtner, I., Schulz, M., Geckeler, R. D., Jusko, O., Neugebauer, M., Nicolaus, A., & Bönsch, G. (2001). Tracing back radius of curvature and topography to the base unit of length with ultra-precision. Recent developments in traceable dimensional measurements, Munich, 20-21, June, 2001, Germany.