HETERODYNE LASER INTERFEROMETER USING HETEROGENEOUS MODE HELIUM-NEON LASER AND SUPER HETERODYNE PHASE MEASURING METHOD

Abstract

Disclosed are a method and a device for detecting the phase of a moving object using

a heterodyne interferometer. A heterogeneous mode helium-neon laser is used

in the heterodyne interferometer as a direct light source to increase a measuring

speed and a measuring resolution performance as well as minimizing the loss of

the light source. Signals, which have only a frequency difference between reference

signals or measured signals and arbitrary signals, are extracted from signals

which are obtained by multiplying the arbitrary frequency signals by the reference

signals or the measured signals. After frequencies of the reference signals

and the measured signals are converted, a phase difference of the extracted signals

is measured, and a displacement of the moving object is measured. The laser interferometer

system of the present invention includes a laser light source part, an optical

interferometer, a frequency converter, and a phase measurer. The light source

used in the heterodyne interferometer uses output light emitted from a heterogeneous

mode helium-neon laser generator, which is stabilized in frequency, and such

output light have two frequencies which are at right angles to each other and linearly

polarized.