Laser for Measurement of Length
The large coherence length and high output intensity coupled with a low divergence enables the laser t find applications in precision length measurements, using interfermetric techniques. Here the laser beam is split into two parts, and they are made to interfere after transversing two different paths. One of the beam emerging from the beam splitter is reflected by a fixed reflector and the other by a cube corner reflector. The two reflected beam interfere to produce either constructive or destructive interference.
As the reflecting surface is moved one would get alternatively constructive and destructive interference which can be detected with the help of a photo detector. Since the change from a constructive to a constructive and destructive interference corresponds to a change of a distance of half a wave length. One can measure the distance transverse by the surface on which the reflector is mounted by counting the number of fringes which have crossed the photo detector.
Accuracies upto 0.1µm can be obtained by using such a technique. This technique is used can be obtained by using such a technique. This technique is used for accurate positioning of aircraft components
On a machine tool, for calibration and testing of testing of machine tools, for comparision with standards