| 摘要 |
PURPOSE:To enable not only the change in the position of a light reflecting face but also the position itself to be detected readily and accurately by oscillating the light transmittable plate form body disposed on the optical path of the luminous flux incident to the light reflecting face to be measured at the time of optically detecting the position of the face having light reflectiveness such as in a video disc, etc. CONSTITUTION:A light transmittable plate from body 12 such as glass plate is disposed on the optical path of the luminous flux 11 which is made approximately parallel to at least one direction perpendicular to the advancing direction incident to the light reflecting face to be measured 17. The plate form body 12 is provided oscillatably about the axis 13 which is approximately perpendicular to the advancing direction of the luminous flux 11 and is approximately parallel to the direction where the luminous flux 11 is made to the parallel luminous flux. Since this causes the luminous flux 21 reflected by the light reflecting face 17 and incident to a photo detctor 20 to vary at the amplitude according to the position of the light reflecting face and the output of the photo detector 20 to vibrate according to the position change of the incident luminous flux 11, the position of the light reflecting face 17 may be directly obtained from the output amplitude of the photo detector 20. |
