| 摘要 |
PURPOSE:To decrease the deviation of a track or focus by setting the effective diameter of a lens in use so as to make the luminous flux passing through an optical path at a fixed side larger than the luminous flux passing through the optical path of an objective lens thereby correcting optically the deviation of the optical axis of the moving to the optical axis of the fixed part. CONSTITUTION:The titled device is constituted so that the luminous flux from the fixed part 10 whose width of luminous flux is decided by a collimator lens 12 in existing in the fixed part 10 is made narrower by a relay lens system comprised of the 1st and 2nd lenses 17, 18. Since the relation of L1>L2 exists even if the optical axis is deviated by a distance (a), the fluctuation of output difference of a 2-split light receiving face is decreased so as to decrease the deviation of track or focus caused by the deviation of position between the fixed part 10 and a moving part 9. |
