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Proceedings Paper

Adaptive interferometric metrology system (AIMS) based on an interferometer employing a "common-path" optical configuration
Author(s): Michael J. Downs
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Paper Abstract

The invention ofthe gas laser in the 1960's provided a robust and relatively inexpensive radiation source, which frirnished an intense collimated coherent beam ideally suited for use in optical mterferometer systems. The inherent accuracy and resolution ofthese laser based instmments making them the ultimate tool both for the precision measurement of geometric parameters and motion control. At the Conference Generate des Poids et Mesures in 1983 the International standard oflength the Metre was redefmed as the distance travelled by light in free space during 1/c of a second, where c is the defmed speed of light [ 299,792,458 Kms ]. Optical mterferometers are employed worldwide for precision positioning and calibration, achieving direct traceability to this length standard by using lasers as precision reference standards of frequency. The source most commonly utilised in commercial interferometers is the red Helium-Neon laser with a wavelength of633nm. The coherence ofthe light emitted from frequency stabilised versions ofthese lasers permits bi-directional fringe counting interferometer systems with measurement ranges ofup to 50 metres or more in the free atmosphere and experience has shown that the frequencies ofthese lasers do not change by more than a few parts in ten to the eight over the lifetime ofthe tube [Typically several years ]. The coherence length of the light emitted from the lower cost nonfrequency stabilised Helium-Neon tubes provides a measurement range of several centimetres with a frequency known to better than one part in ten to the six, properties which make these lasers a suitable source for short range interferometric metrology applications.

Paper Details

Date Published: 22 October 2001
PDF: 7 pages
Proc. SPIE 4401, Recent Developments in Traceable Dimensional Measurements, (22 October 2001); doi: 10.1117/12.445612
Show Author Affiliations
Michael J. Downs, Interferomet, Ltd. (United Kingdom)


Published in SPIE Proceedings Vol. 4401:
Recent Developments in Traceable Dimensional Measurements
Jennifer E. Decker; Nicholas Brown, Editor(s)

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