| 摘要 |
PURPOSE:To enhance the resistance of the titled apparatus against a change with, time, by simplifying a mechanism so that the beam from an object to be detected converged by the hologram of a recording medium and the ratio of the converged beam and transmitted beam is changed on the basis of the change in the incident angle to the hologram due to the change in an optical axis direction to detect displacement. CONSTITUTION:The coherent beam 2 of a semiconductive laser 1 is converged to an optical disc 5 by a lens 4 through a beam splitter 3 and the reflected beam thereof is reflected by the splitter 3 through the lens 4 to be incident to a beam detector 7 through a recording medium on which a hologram was recorded. In this case, the hologram of the recording medium 6 is recorded by the interference of beams 8a, 8b and the beam 8a is allowed to be incident to the medium 6 at an incident angle theta from the converging point F1 on the recording surface of the disc 5 through a beam splitter 9 while the beam 8b is converged at a converging point F2 in this side of the medium 6 through a lens 10 and the splitter 9. Then, the detector 7 is arranged in the vicinity of the point F2 and, at the max. position of the output thereof, the position free from displacement on the recording surface of the disc 5 is determined. |
