| 摘要 |
PURPOSE:To extend an effective tracking width by allowing the optical reflection axis of a mobile mirror to pass always the rear focus of a focusing lens when the mobile mirror is moved in accordance with the rotation of a revolving shaft. CONSTITUTION:An optical head consists of a mobile mirror 7 provided on a rotating body 6 having a revolving shaft 5, an independent fixed mirror 9 which receives the reflected light of the light incident on the mirror 7, and a focusing lens 2 which receives the reflected light reflected in the direction parallel with the revolving shaft 5 by the fixed mirror 9. The focussing lens 2 is attached to the rotating body 6, and the mobile mirror 7 is so provided that the length between the reflection point of the mobile mirror 7 and the center of the revolving shaft 5 is a prescribed value. When the mobile mirror 7 is moved in accordance with turning of the revolving shaft 5, the optical axis of reflection of the mobile mirror 7 passes always the rear focus of the focusing lens 2. |
