Patent ID: 7020051
Filing Date: 2006-03-28
Classification: G11B

Abstract:
1. An optical pickup for a recording medium, comprising: a light source generating and emitting a light beam; an objective lens focusing the light beam from the light source to form a light spot on the recording medium; an optical path changer disposed on an optical path between the light source and the objective lens, altering a traveling path of the light beam; a light beam division and detection unit dividing a particular light beam portion of the light beam passed through the objective lens after being reflected and/or diffracted from the recording medium into sub-divided first, second and third light beam portions, and detecting a first detection signal from the first light beam portion and a second detection signal from the second and third light beam portions; and a spherical aberration detection circuit processing the first and second detection signals resulting from the sub-divided first, second and third light beam portions to detect spherical aberration caused by thickness variation of the recording medium, wherein the particular light beam portion divides into the first light beam portion on an axis crossing an optical axis parallel to a radial direction or a tangential direction of the recording medium, and the second and third light beam portions, one at either side of the first light beam portion in the tangential direction or the radial direction of the recording medium.