DISPLACEMENT DETECTION APPARATUS, DISPLACEMENT GAUGING APPARATUS AND FIXED POINT DETECTION APPARATUS

摘要

A displacement detecting apparatus, a displacement gauging apparatus and a fixed point detection apparatus can highly accurately detect a fixed point or gauge a displacement by reducing the disturbances of polarization due to the stress and the buckling of the optical fiber for transmitting a light beam emitted from a light source to the detecting side. The displacement detection apparatus includes a light source for emitting a light beam, an extinction ratio converting unit that raises the extinction ratio of the light beam emitted from the light source to not less than 20 dB, a focusing lens for focusing the light beam of an extinction ratio raised to not less than 20 dB by the extinction ratio converting unit, an optical fiber of the polarization holding type for transmitting the light beam focused by the focusing lens, a diffraction grating fitted to an object of measurement so as to be irradiated with and diffract the light beam transmitted through the optical fiber, and a light receiving unit that receives the light beam diffracted by the diffraction grating, the light beam focused by the focusing lens with the extinction ratio raised to not less than 20 dB by the extinction ratio converting unit being made to enter the optical fiber with its axis of polarization made to agree with the optical axis of the optical fiber or an axis orthogonally intersecting the optical axis, the light receiving unit being adapted to detect the displacement of the object of measurement by means of the level of the rate of receiving the diffracted light beam.