Interferometric
measurement of angle
With laser
interferometer it is possible to measure length to accuracy of 1 part in 106 on
a routine basis. With the help of two retro reflectors placed at a fixed
distance and a length measuring laser interferometer the change in angle can be
measured to an accuracy of 0.1 second.
The device uses sine
Principle. The line joining the poles the retro-reflectors makes the hypotenuse
of the right triangle. The change in the path difference of the reflected beam
represents the side of the triangle opposite to the angle being measured. Such
laser interferometer can be used to measure an angle up to ± 10 degrees with a
resolution of 0. 1 second. The principle of operation is shown in fig.
