| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a small optical pickup unit capable of correcting spherical aberration with respect to the optical pickup unit that can correct spherical aberration that occurs when the thickness of an enclosure layer from the surface of an optical disk deviates from a standard value. <P>SOLUTION: A drive coil 44 wound around a lens holder 40 in a beam expander unit 20 is arranged in a magnetic field formed by a magnet 46. Therefore, when current is applied to the drive coil 44, current receives force from the magnetic field, and the secondary lens 24 of the expander is moved in the X axis direction, which is the direction of the optical axis. As a result, the distance between the primary lens 22 of the expander and the secondary lens 24 of the expander changes, light injected to the objective lens from the beam expander unit 20 becomes diffused light or convergence light. Therefore, the objective lens causes spherical aberration in the opposite direction from the spherical aberration that happens as the thickness of the enclosure layer deviates from the standard value, which cancels the spherical aberration. Since the moving part is not moved, and a stepping motor is not needed, the physical size of the optical pickup unit capable of correcting the spherical aberration can be made smaller. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
