Patent ID: 7417939

Claim:
An optical pickup adapted to radiate a light beam which is eventually transformed into a plurality of beam spots on an optical recording medium and to record information on the optical recording medium and retrieve information from the optical recording medium by radiating the light beam on the optical recording medium, the optical pickup comprising: a light source for emitting the light beam; an object lens for converging the light beam into a convergent light beam to direct the convergent light beam to the optical recording medium; and an aberration correction lens assembly located between the light source and the object lens, the aberration correction lens assembly including at least one movable lens which is movable in an optical axis direction, the aberration correction lens assembly controlling a movement of the movable lens to correct spherical aberration, wherein a distance between a principal plane of a lens in the aberration correction lens assembly on the most light emergent side and a principal plane of the object lens is determined by the following equation: ( f 2 + f 3 ) - 10 ⁢ f 3 2 3 ⁢ NA 4 < e 2 < ( f 2 + f 3 ) + 10 ⁢ f 3 2 3 ⁢ NA 4 where e 2 represents the distance between the principal plane of the lens in the aberration correction lens assembly on the most light emergent side and the principal place of the object lens, NA represents a numerical aperture of the object lens, f 2 represents a focal length of the aberration correction lens assembly on the light emergent side, and f 3 represents a focal length of the object lens.