ABSOLUTE INTERFEROMETRY WITH TUNABLE SEMI CONDUCTOR-LASERS

In contrast to conventional length interferometry with frequency stabi lized helium-neon-lasers the absolute interferometry with tunable semi conductor lasers renders possible to detect distances in a static way without moving the measuring reflector. All commercial laser interfero meters are only able to measure changes in the pathlengh of the interf erometer. So the starting point of the measurement, to that the follow ing measurement results are related, is unknown. An interruption of th e laserbeam stops a measurement, because the relation to the preceding measurement results are irrecoverably lost. The report describes an a bsolute interferometric process, which causes a change of interference phase by continuous tuning of the wavelength of a semiconductor laser . This change of phase is related to that of an reference interferomet er with constant length. With the knowledge of the reference length th e absolute distance can be calculated.