| 摘要 |
PURPOSE:To measure displacement angle with high accuracy by passing a laser light that is reflected from an object to be measured that makes extremely small angular displacement and modulated through a prism at an angle near the critical angle and detecting beats between this laser light and a stabilized laser light. CONSTITUTION:Laser light from variable frequency laser 1 that is minutely modulated by an oscillator 5 and a driving device 4 is reflected at an object 3 to be measured and gets into a prism 7 via a lens 6, and the light passes the bottom face 8 of the prism 7 at an angle close to the critical angle and reflected at a half-mirror 9 to get into a light detector 10. On the other hand laser light from a laser in which its wave length is stabilized gets into the light detector 10 through a half-mirrors 12 and 9, and beats of two indident lights are detected. This heat signal is resonated with the frequency of the oscillator 5 and detected by means of a lock-in amplifier 13, and at a calculator 14 angle of displaccement is sought from the difference of frequencies and it is displayed at a display unit 15. Accordingly displacement angles are measured with high accuracy. |
