| 摘要 |
PURPOSE:To control a luminous flux position with high precision while eliminating interference disturbance to focus control even while track follow-up control is carried out in combination, by setting the rotating shaft of a rotary mirror for luminous flux deflection off an optical axis closely to the rear-side focal plane of an objective practically. CONSTITUTION:When a rotary mirror 13 is turned at theta while its axis is set at the rear-side focus F0 of an objective 14, incident luminous flux 30 is deflected by 2theta and focused on a disk 22 as shown by a light spot 31' through the objective 14. Since the rotating shaft of the mirror is on the focus of the objective 14, the optical axis of the incident luminous flux passing through the focus is at right angles to the disk, and the reflected luminous flux by the disk travels backward through the same path with the incident luminous flux. In practice, as the rotating shaft of the mirror is put closer to the rear-side focal plane of the objective, interference disturbance to focus control by track follow-up control, etc., is reduced to perform high-precision luminous flux position contorl. |
