| 摘要 |
PROBLEM TO BE SOLVED: To allow an objective lens to be focused to a high density disk and a standard density disk are reproduced in the case of reproducing the both disks by using the same objective lens when a focus signal is made zero. SOLUTION: A first light receiving section 70 is formed with central light receiving regions 73, 74 which are set to magnitude of a center section affected less by spherical aberration in reflected light from a standard density disk and peripheral light receiving regions 71, 72, when those photoelectric conversion signals are equal each other, a laser beam is focused on a surface of a recording member for a high density disk. Also, a second light receiving section 75 is formed with central light receiving regions 76, 77 being larger than the central light receiving regions 73, 74 and peripheral light receiving regions 78, 79, when these photoelectric conversion signals are equal each other, a laser beam is focused on a surface of a recording member for a standard density disk. |
