Patent ID: 6538746
Filing Date: 2003-03-25
Classification: G01B

Abstract:
In a method for optical interferometric length measurement in which a beam, or a beam component, of a laser of high coherence length, stabilized with respect to a reference section, is split into two partial beams, one of which is reunited after traversing a reference section and the other reunited after traversing a measuring section, the interference pattern is detected by a detector and the signal formed therefrom amplified and a measuring signal is generated in accordance with a prescribed modulation pattern, the laser being sequentially stabilized in time with respect to at least two different wavelengths &lgr;1[&phgr;1] and &lgr;2[&phgr;2] for absolute measurement of the length L of a measuring section, the number of &Dgr;n of the interferences traversing the detector counted during a transition from a first to a second wavelength, and the absolute length L of the measuring section then calculated as a function of phase measurements &phgr;1, &phgr;2 for the two stabilized wavelengths &lgr;1, &lgr;2, the improvement comprising the step of performing the phase measurement in a resetting control loop which compensates said phases.