| 摘要 |
PURPOSE:To adjust an optical axis made incident on an objective lens and to improve optical transmission efficiency and the balance of a tracking error signal, by varying the angle of the reflection optical axis of a mirror which reflects a parallel ray from a collimator lens, or performing the parallel displacement of the mirror. CONSTITUTION:Divergent rays from a semiconductor laser 21 are changed to parallel rays by a collimator lens 40, and are reflected on the mirror 50, and are made incident on the objective lens via a half mirror 51 having a refractive plane. At this time, since exact coincidence between the central point of the lens and the optical axis cannot be obtained generally, adjustment is performed by varying the angle of the plane A of the mirror 50 by an angle varying means 60, or performing the parallel displacement of the mirror 50. In such way, it is possible to coincide the center of the objective lens with an incident optical beam. Therefore, it is possible to improve the transmission efficiency and to balance the tracking error signal.
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