A primary-level comparator, with a reproducibility of 0.2 nm and intended for realization of a Systeme International length unit in the range of 1–100 mm, is reported. High-precision differential measurements of phase change on reflection from blocks and end plates are demonstrated. A set of experiments has been developed to measure systematic error associated with nonideal interferometer optics and deviations from flatness of an auxiliary plate. For specially selected high-grade 6-mm blocks, reproducible wringing has been achieved with a random uncertainty in length measurements of 0.1–0.2 nm. Subnanometer wear-off of the blocks as a result of the cleaning has been detected. Under the conditions of reproducible wringing, the accuracy of the length measurements is evaluated to be in the 2–3-nm range for 6-mm blocks.
© 1999 Optical Society of America
(120.2650) Instrumentation, measurement, and metrology : Fringe analysis
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.3940) Instrumentation, measurement, and metrology : Metrology
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
(120.6660) Instrumentation, measurement, and metrology : Surface measurements, roughness
Igor Malinovsky, Alexander Titov, Jorge Augusto Dutra, Hakima Belaïdi, Ricardo dos Santos Fraņa, and Carlos Alberto Massone, "Toward Subnanometer Uncertainty in Interferometric Length Measurements of Short Gauge Blocks," Appl. Opt. 38, 101-112 (1999)