Patent attributes
An optical pickup device is applied to DVD recorders and includes a beam expander unit. A drive coil wound around a lens holder within the beam expander unit, is located in a magnetic field formed by a magnet. When an electric current is passed through the drive coil, the drive coil moves an expander second lens in a direction of an optical axis, receiving a force based on interaction between the electric current and the magnetic field. This changes a distance between an expander first lens and the expander second lens, and thus light emitted from the beam expander unit toward an object lens becomes diffused light or converged light. Consequently, the objective lens generates a spherical aberration in a reverse direction of a spherical aberration that has occurred owing to a deviation of a cover layer in film thickness from a reference value, which cancels the latter spherical aberration.