| 摘要 |
PURPOSE:To provide a displacement information detector and a speedometer which permits to obtain a Doppler signal corresponding to speed independent of the wave length a highly precise speed signal. CONSTITUTION:An illumination means for generating a light of wave length lambda, an optical means, which has a wave guide part, for making light from the illumination means incident on an object, a diffraction grating 10 integrally provided in the wave guide part for the purpose of diffracting light from the illumination means, an optical element integrally provided in the wave guide part for the purpose of making two pieces 5a, 5b of diffracted light from the diffraction grating 10 incident on the object, and an optical detection means for detecting light from the object that the optical means is made incident for the purpose of detecting information in regard to the displacement of the object are equipped for the displacement information detector and the speed meter. The two pieces 5a, 5b of diffracted light are made incident on the object so that the two pieces 5a, 5b of diffracted light to the vertical direction of the specified direction may be an angle theta in a plane including the specified direction and a diffracted route by the use of the optical element, and the diffraction grating 10 and the optical element are arranged so that sin theta/lambda is substantially constant independent of the change of the wave length lambda of light emitted from the illumination means. |
