Calibration of linear encoders with sub-nanometer uncertainty using an optical-zooming laser interferometer

• A length calibrator with sub-nanometer uncertainty was developed.
• The calibrator was based on the optical zooming laser interferometer.
• An optical comb was used for stabilization of optical sources of the calibrator.
• Linear encoders with the resolution of several tens of nanometers were calibrated.
• The calibration uncertainties were smaller than 0.55 nm (k = 2).

The nonlinear errors of high-precision linear encoders were calibrated by using a nanometer-length calibrator that was based on the optical-zooming laser interferometer with an optical frequency comb. A transmission-type linear encoder and a reflection-type linear encoder were calibrated, and the cyclic nonlinear errors were evident. The magnitudes of the observed cyclic errors were 0.1 nm and 0.2 nm, respectively, and the best calibration uncertainties were 0.55 nm (k = 2). A traceable calibration service for linear encoders with the best calibration uncertainty in the sub-nanometer range has started based on this work.