A long-range high applicability length comparator for linear displacement sensor calibration

In this article, a long-range length comparator, applicable for both static- and dynamic-index calibrations of a linear displacement sensor, is presented. The comparator consists of an air-floating linear motion generator (LMG) and an interferometric optical length calibrator (OLC). A novel design of the LMG made by multisegment splicing is introduced, in which a two-level vibration isolation arrangement, a multiple sliders’ setup, and an exoskeleton framework are adopted. The resulting linear motion can be extremely ideal even with a large stroke. The angular error is within $11.89~\mu $ rad covering the 12-m range. The maximum operating speed and the acceleration of the LMG are 10 m/s and 20 m/s2, respectively. A dual-path optical design of the OLC is displayed, resulting in high environmental tolerance and a small trigger delay of 4.75 ns. The best accuracy of the comparator can be ±( $0.041+ 0.106L) \mu \text{m}$ with a resolution of 0.3 nm. The maximum error and operation speed of a 2-m range exposed encoder were successfully calibrated, and the grating pitch deviation was also found, by which the effectiveness of the comparator is proven. The proposed length comparator introduces a possible solution, for how a long-range linear displacement sensor, can be calibrated with high accuracy, efficiency, and applicability.