| 摘要 |
PURPOSE:To eliminate adverse influences upon a tracking error signal by moving the laser light, which is made incident on a center shaft of an objective lens holding cylinder, in parallel and making this laser light incident on an objective lens. CONSTITUTION:A trapezoid prism 3 and an objective lens 4 are provided in an objective lens holding cylinder 8 which can be rotated around a center shaft 2. In this device, the laser light incident from the external is turned by 90 deg. by a right-angled prism 1 and has the optical axis coincident with the center shaft 2 and is made incident on the trapezoid prism 3, and the laser light which is discharged from the trapezoid prism 3 after reflected twice is made incident on the objective lens 4 as a light which has a direction opposite to that of the incident light and is parallel with it. In this case, even if the objective lens 4 is moved for tracking adjustment, the trapezoid prism 3 is rotated together to make always the incident light incident on the center of the objective lens 4, and thus, adverse influences upon the tracking signal are eliminated. |
