| 摘要 |
<P>PROBLEM TO BE SOLVED: To correct an unnecessary aberration which is generated accompanying the movement of an objective lens when a correcting means for aberration symmetrical to an optical axis is arranged outside an objective lens movable part. <P>SOLUTION: When an aberration occurs, a concentric circular "wave surface delay" is generated around an optical axis with respect to the reference wave surface of a return luminous flux. The "occurrence situation of spherical aberration" is detected by a beam splitter 112 for reflecting a concentric circular inner peripheral side from the reflected light of an optical recording medium 109 and passing through an outer peripheral side, and light receiving elements 114 and 116 based on a difference between the outer and inner peripheral parts. A relative positional shift between a liquid crystal element 105 and an objective lens 107 for correcting a wave surface shape symmetrically to the optical axis generates unnecessary coma aberration (residual aberration). The coma aberration is detected by the detection optical system of a condenser lens 110 and a light receiving element 117 and, by a 3-axis actuator 108 capable of controlling the tilting of the objective lens 107, the tilting of the objective lens 107 is changed to cancel the coma aberration of the passing luminous flux. <P>COPYRIGHT: (C)2004,JPO |
