| 摘要 |
PURPOSE:To easily adjust an optical system of a focus servo-system, and a circuit system, by focusing an expanded image of a light spot separated by a diffraction lattice, to one point, and detecting the focusing. CONSTITUTION:A light beam from a semiconductor laser 7 of a focus servo-system is condensed onto a diffraction lattice 2 by a lens 1. Its spot is expanded by an optical system (for instance, a microscope) 3, and is observed with the naked eye 4 or a projecting observation system. In case when a position of the diffraction lattice is before and behind the spot, the spot is seen as if it is separated into 3 points or more, by 0-degree and primary diffracted light beam. Since the spot is condensed to one point at the focal position, the diffraction lattice 2 is focused to the focal position. In this way, an optical system of a focus servo-system, and a circuit system are adjusted easily. |
