| 摘要 |
PURPOSE:To obtain a measuring instrument with the straight-advance accuracy for a traveling body without any possibility of generating measurement error due to the fluctuation, etc., of laser beams. CONSTITUTION:Laser beams L1 generated from a laser light source 3 are expanded by an expansion optical system 4, are split into two split beams LP by a half mirror 5e of a prism unit 5 and are reflected by both oblique surfaces 5c and 5d, cross each other at an angle of 2 theta, and a synthetic wave L0 with a light intensity distribution in the direction of X axis by interference. A pin photodiode 1 which is split into two portions and are in one piece with a traveling body M1 detects the light intensity of the synthetic wave L0 and then measures the displacement in the direction of X axis of the traveling body M1 base on the change. |
