Calibration of an Internal-Length Standard by Angle-Stepping Gap Interferometry

Abstract We demonstrate a simple interferometric method for calibrating the length of an uncoated Fabry-Pérot etalon, using a rotary analog of phase-stepping interferometry. The interferometric method is designed to realize nearly the same measurand as a subsequent measurement in a tactile instrument. The estimated expanded uncertainty of 4 nm for the optical calibration, together with the well-matched measurands, make the etalon a promising transfer standard for the calibration of bidirectional corrections in tactile probing systems.