COMPENSATION OF EFFECTS OF ATMOSPHERIC PERTURBATIONS IN OPTICAL METROLOGY

摘要

In general, in a first aspect, the invention features a method that includes using an interferometry assembly (100) to provide three different output beams (181-183, 191-193), each output beam including an interferometric phase related to an optical path difference between a corresponding first beam and a corresponding second beam, each first beam contacting a measurement object (120) at least once, monitoring the interferometric phases for each of the three different output beams, and deriving information about variations in the optical properties of a gas in the first beam paths from the three monitored phases.