Laser interferometry


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.


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