Precision positioning with suppression of the influence of refractive index of air

0421238 - ÚPT 2014 RIV US eng C - Conference Paper (international conference)
Holá, Miroslava - Hrabina, Jan - Oulehla, Jindřich - Čížek, Martin - Mikel, Břetislav - Řeřucha, Šimon - Buchta, Zdeněk - Číp, Ondřej - Lazar, Josef
Precision positioning with suppression of the influence of refractive index of air.
Optical Measurement Systems for Industrial Inspection VIII (Proceedings of SPIE Vol. 8788). Bellingham: SPIE, 2013, 878831:1-7. ISBN 978-0-8194-9604-1.
[Optical Measurement Systems for Industrial Inspection /8./. Munich (DE), 13.05.2013-16.05.2013]
R&D Projects: GA ČR GA102/09/1276; GA ČR GPP102/11/P820; GA TA ČR TA02010711; GA TA ČR TE01020233; GA MŠMT ED0017/01/01
Institutional support: RVO:68081731
Keywords : nanometrology * refractometry * interferometry * refractive index * nanoscale
Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

We present an interferometric technique based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. One of the important limiting factors in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty traditionally compensated when the index is evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where a reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 1xE-8 level. The technique allows to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range acting as a tracking refractometer. The principle is demonstrated on an experimental setup and a set of measurements describing the performance is presented.
Permanent Link: http://hdl.handle.net/11104/0227647