Air flow and length noise in displacement interferometry

0441268 - ÚPT 2015 RIV US eng C - Conference Paper (international conference)
Holá, Miroslava - Číp, Ondřej - Šarbort, Martin - Lazar, Josef
Air flow and length noise in displacement interferometry.
Optics and Measurement Conference 2014 (Proceedings of SPIE 9442). Bellingham: SPIE, 2014, 94420D: 1-7. ISBN 9781628415575. ISSN 0277-786X.
[Optics and Measurement Conference 2014 (OaM 2014). Liberec (CZ), 07.10.2014-10.10.2014]
R&D Projects: GA ČR GB14-36681G; GA TA ČR TA02010711; GA TA ČR TA01010995; GA TA ČR TE01020233; GA MŠMT(CZ) LO1212; GA MŠMT ED0017/01/01
Institutional support: RVO:68081731
Keywords : refractometry * refractive index of air * interferometer * measuring system
Subject RIV: BH - Optics, Masers, Lasers

We report on an evaluation of the influence that fast changes of the refractive index has on the uncertainty of interferometric displacement measurement. Measurement of position within a limited range is typical for coordinate measuring systems such as nanometrology standards combining scanning probe microscopy (SPM) with precise positioning. For long-range systems the varying refractive index of air contributes the most to the overall uncertainty. We proposed to extend the principle of compensation of the fluctuations of the refractive index of air through monitoring the optical length within the measuring range of the displacement measuring interferometer. In this contribution we evaluate the level of uncertainty associated with the nature of the fluctuations of the refractive index of air in laser interferometry. We have observed that its fast variations, seen as length noise, are not linearly proportional to the measuring beam path but play a significant role only over distances longer than 50 mm. Over longer distances the length noise rises proportionally. The measurements were performed under conditions typical for metrology SPM systems.
Permanent Link: http://hdl.handle.net/11104/0245284