| 摘要 |
PURPOSE:To always attain the trace of the same guide track, by providing a means to detect the moving position of a movable body of a driving means which moves plural optical spots independently in a direction almost vertical to the guide track. CONSTITUTION:The light of a light emitting element 1 is projected on the turning mirror 22 of the driving means which performs the tracking of an optical spot M, and reflected light beams are received by an optical detector 2. At the time of turning the turning mirror 22, the light beams from the light emitting element 1 are displaced on the optical detector 2 corresponding to a turning angle, and the optical detector 2 is the two-division one, and in which dividing direction is set at displacement direction, and by taking a difference between divided photoreceiving quantities, the quantity of displacement can be detected efficiently. Also relation between the turning mirror 22, and the relative aberration of two optical spots L and M, is set at constant relation, and the output of the optical detector 2 operates the turning mirror 22 only when the relative aberration of those two optical spots is less than 1/2 of the pitch of a guide track 3, thereby, the tracking control of the optical spot M can be performed. In this way, it is possible to always trace the same guide track by the plural optical spots. |
