| 摘要 |
PURPOSE:To make it possible to satisfactorily detect various signals such as a tracking signal, etc., by arranging a light detector at the position which in not affected by rotation of a movable mirror. CONSTITUTION:A half mirror 8 is mounted between movable mirror 2 and a condensing lens 3, and divides a reflected ray which comes from the information recording surface 4. And a point which is equivalent to an image point G' by the lense 3 is made G''', and when the mirror 2 has been rotated, a signal is detected by a light detector 7 which is mounted at the point G'''. Accordingly, a light spot of proper size which is not affected by rotation of the movable mirror 2 is formed on the light detector 7. |
