| 摘要 |
PURPOSE:To detect the position of an objective lens by attaching a light reflecting body to a member that moves in a body with the objective lens of an optical head or to the objective lens itself and arranging an optically coupled element having a light emission element and a light receiving element at a position opposite to the light reflecting body. CONSTITUTION:A mirror 25 is installed in a member that moves in a body with an objective lens such as a movable magnetic body, and an optically coupled element 30 having a light emission element and four light receiving elements 33a-33d is installed at a position opposite to the mirror 25. Light emitted from the light emission element and reflected by the mirror 25 is received by light receiving elements 33a-33d, and the position of the objective lens 5 is detected. By controlling moving of the objective lens 5 in the direction of focusing direction and tracking direction basing on such detection, collision of the objective lens 5 and an information recording medium can be prevented surely.
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