| 摘要 |
<p>Provided is an optical pickup device which can record/reproduce information appropriately at the time of temperature change or when a multilayer disc is used. Also provided is an objective lens for use therein. Since spherical aberration resulting from a change in refractive index of an objective lens (OBJ) increases when a temperature change occurs, a finite luminous flux is made to impinge on the objective lens (OBJ) by moving a collimate lens (CL) in the direction of the optical axis by means of a uniaxial actuator (AC1), thus minimizing spherical aberration. Since spherical aberration also increases when a (BD) is a multilayer optical disc and when an interlayer jump from a layer to a second layer of a plurality of information recording surfaces takes place, the collimate lens (CL) is moved accordingly in the direction of the optical axis. In contrast, since the tilt sensitivity of the objective lens (OBJ) is increased, occurrence of third-order comatic aberration is limited effectively even when a finite luminous flux is made to impinge on the objective lens (OBJ).</p> |
