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EUROMET #610: Comparison of reference laser interferometer systems

Author(s): Petr Balling and Petr K?en
Affiliation(s): Czech Metrology Institute

Topic: 1. Interferometry & Optical Testing Techniques
Presentation: Poster

The laserinterferometers as the most precise displacement measuring devices serve as a basic tool for providing traceability from primary wavelength standards to broad area of dimensional measurements. In principle, the relative uncertainty of 1E-10 (0.1ppb) is possible in vacuum, where only wavelength uncertainty, alignment and diffraction contribute to uncertainty. But when measuring in air, the instability and uncertainty of refractive index correction are most significant. EUROMET project 610 was running in the years 2001-2006. It was an informal comparison with the goal to exchange experience in using and calibrating counting interferometers. Instruments HP/Agilent 5519 (A or B) of several national metrology institutes - OMH (Hungary, 2001), BEV (Austria, 2005), JV (Norway, 2005) and SMU (Slovakia, 2006) - were one by one compared with the laser-interferometric comparator IK-1 of CMI (Czech Republic), which provided sufficiently stable and homogenous environment and stabilized optical path. The results agreed to (14 to 460) nm per 1m, i.e. (14 to 460) ppb. Various sources of deviation and their corrections are discussed in detail. References: http://www.euromet.org/cgi-bin/projectfile.pl?prefno=610, www.euramet.org, http://kcdb.bipm.org