Angle Measurement Using Ring Laser

Abstract

An experimental study for high precision digital angle measurement by using a He-Ne ring laser is described. The triangular ring laser, which is composed of an invar framework with a cavity length of 180 cm and two plasma tubes filled with 14 : 1 : 1 mixture of He : Ne²⁰ : Ne²² discharged with current-stabilized power supplies is used. Angles (30°) of twelve sides constituting a polygon are measured applying the principle that the integral of beat signal of the ring laser is directly proportional to the angle of rotation of the ring laser. The dispersion of the measured values is found to be 10"-45" for 30°. It has become clear that it is important to supress fluctuation of cavity length much less than the present level and to operate on stable single mode for better accuracy.