PURPOSE: To enhance measuring accuracy by causing a measuring interferometer and a control interferometer to form at least one interference signal each, and calculating the length of a measuring area.
CONSTITUTION: A laser beam source 2 is modulated by a driving power supply within a skip-free wavelength range, and a laser beam source 3 is driven at a certain wavelength. Split beams 6, 7 are detected by respective photodetectors 11, 12. Further, the detectors 11, 12 are connected to a counting electronic circuit and the light sources 2, 3 to laser wavelength control devices. Near the center of a measuring interferometer 4, a control interferometer 13 is also provided, its control area 14 having a certain length shorter than half of the measuring area. Beams of the same beam sources 2, 3 are made to impinge on the interferometers 4, 13 by a beam splitter 15 and a reflector 16. Incidence of the beam on the light source 2 is achieved by a reflector 17. Since standard members are chiefly used, the entire laser interferometer device 1 can be constructed as an integrated optical system.
DEIITAA MITSUHIERU
ANDOREASU FURANTSU
FRAUNHOFER GES FORSCHUNG