Laser interferometry 1002002-86
A technique of detecting geometry, measuring accurate lengths and so
on by the interference of laser beam.
By producing interference between beams that are reflected on the reference
plane and the objective plane, geometry of a static planar or spherical
object can be measured at a resolution of λ/2 or better (Wavelength λ of
a typical He-Ne laser is 0.633 μm). By combining interference technology
with electronics, the measuring resolution of geometry can be improved
up to about λ/100 while the resolution in measurement of lengths can be
improved even to λ/1000. Relative distance from a moving object can be
measured by the beat interference technique that exploits the Doppler effect
of laser beam, at a resolution of λ/4 or better. Vibrational displacements
can also be measured by the holography interference technique.