Patent ID: 8233372
Filing Date: 2012-07-31
Classification: G11B

Abstract:
1. An optical system for optical pickup, the optical system being used in an optical pickup device that performs at least one of reading, writing, and erasing of information on a recording layer within an optical recording medium, the optical system comprising: a wavefront conversion optical system that includes a first lens element movable in a direction perpendicular to an optical axis and converts a wavefront of a light beam emitted from an external light source; and an objective optical system that converges a light beam emitted from the wavefront conversion optical system, irradiates the recording layer with converged light as evanescent light, and forms a spot on the recording layer, wherein the wavefront conversion optical system compensates a coma aberration of the spot on the recording layer in a state where an interval between a surface of the optical recording medium and a lens element of the objective optical system that is nearest to the surface is maintained constant, by moving the first lens element in the direction perpendicular to the optical axis, and the wavefront conversion optical system further includes a second lens element that is movable in a direction parallel to the optical axis and different from the first lens element, and adjusts a focal point of the spot on the recording layer and compensates a spherical aberration of the spot in a state where the interval between the surface of the optical recording medium and the lens element of the objective optical system that is nearest to the surface is maintained constant, by changing an interval in an optical axis direction between the light source and the second lens element.