| 摘要 |
PURPOSE: To make it possible to read a whole information band of a disk without moving an optical head by setting up a light receiving device provided with a means capable of detecting a focusing error and a tracking error on a path of a laser beam reflected by a reflection mirror and correcting the focusing error with an optical scanner. CONSTITUTION: The laser beam outgoing from a laser diode 51 advances in order of a partial reflection mirror 52 → a convergence lens 53 → a focusing error correcting lens 54 → the optical scanner 55 → an objective lens 57 →a disk 56 to arrive at an image point 60. The laser beam reflected by the disk 56 is sensed by the light receiving device 58 further through the objective lens 57 → the optical scanner 55 → the focusing error correcting lens 54 → the convergence lens 53 → the partial reflection mirror 52. Then, the lens size of the objective lens 57 is made larger than an interval between the track start point 56A and the last stop 56B of the disk 56, and the Laser beam is scanned to left/right around the optical axis 55A of the objective lens 57 from the optical scanner 55. Thus, the whole information band of the disk are read without moving the optical head. |
