Nanometer-level agreement measurement and evaluation of multiple laser interferometric displacement sensor probes

In ultra-precision displacement measurement, employing multiple probes of a laser interferometric displacement sensor (LIDS) for differential measurement can significantly suppress the common-mode noises to improve the measurement quality. The efficacy of differential measurement is contingent upon the agreement among the LIDS probes. Therefore, it is crucial to scientifically evaluate this agreement. At the nanometer scale, it is challenging for multiple probes to simultaneously measure the same target and evaluate their agreement. Based on the Bland-Altman method (B-A method), we have extended the B-A method and developed a method that utilizing a single displacement reference measures and evaluates the agreement among the 4 LIDS probes. The proposed method facilitates nanometer-level quantification of multi-probe agreement. Besides, the inconsistency errors in agreement evaluation among the 4 probes were within ± 1 nm and the differential measurements with paired probes verified the results. Furthermore, the proposed method can be extended to evaluate the agreement of any number of LIDS probes.