| 摘要 |
PURPOSE:To obtain the title apparatus receiving no effect of the fluctuation of air or temperature and preventing the adhesion of dust to the surface of a reflecting mirror, by performing operation, which irradiates the reflecting mirror operating in conjunction with an object to be measured and receives signal light, in a hermetically closed space. CONSTITUTION:A cylindrical guide 30 has such a structure that one end thereof is connected to a light projecting and receiving system 20 and the other end thereof is hermetically closed by a bush 32 and a cylindrical movable body 31 equipped with a reflecting mirror surface 29 is arranged in the hollow interior of the guide 30 in a freely reciprocally movable manner. One end of a detection shaft 33 is connected to the movable body 31 and the other end thereof passes through a bush 32 to protrude to the outside and the leading end thereof is brought into contact with an object 28 to be measured. By this constitution, the hollow interior of the guide is blocked from the effect of the fluctuation of the open air or temp. and the adhesion of dust or contamination to the mirror surface 29 is prevented. When the object 28 displaces in the axial direction, the detection shaft 33 operates in conjunction with said object and the movable body 31 moves corresponding to displacement quantity. At this time, an interference wave form detector 22 separates the interference light obtained by the light projecting receiving system 20 into respective components to form an interference light signal which is, in turn, operationally processed to calculate the displacement direction and displacement quantity of the object 28.
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