Patent ID: 7304745
Filing Date: 2007-12-04
Classification: G01B

Abstract:
1. A multi-frequency interferometry method for measuring the absolute phase of an electromagnetic wave, wherein the method comprises: selecting a target measurement range, L, within which absolute phase measurements are desired to be made, said phase measurements being related to a desired measurand of an object; determining a level of phase noise which will be present in wrapped phase measurements which will be made; for the selected target measurement range, and the determined phase noise level, calculating an optimum number, N, of wavelengths of electromagnetic radiation to be used in the multi-frequency interferometry, where N≧3; selecting an optimum series of values of said N wavelengths to achieve optimum noise immunity in wrapped phase measurements to be made; and using a computer system to carry out multi-frequency interferometry at the selected values of the N wavelengths so as to produce and record at least one wrapped phase measurement at each of the N wavelengths, which recorded wrapped phase measurements are thereafter processed by the computing system to obtain an absolute phase measurement related to the desired measurand of the object.