Patent ID: 7839731

Claim:
A finite optical system for recording data to and/or reproducing data from an optical disc having a numerical aperture on an optical disc side larger than or equal to 0.60, comprising: a light source that emits a diverging light beam; an objective lens that converges the diverging light beam onto a data recording surface of the optical disc; and a driving system that controls a position and an attitude of the objective lens, wherein the driving system operates to move the objective lens in a direction perpendicular to a central axis of the objective lens for a tracking operation, and to change the attitude of the objective lens during the tracking operation so that the central axis on a light source side tilts toward the light source, and wherein the driving system controls the position and the attitude of the objective lens to satisfy a condition: 0.25 ≦d· tan θ/ TR≦ 0.75 (1) where d (mm) represents a distance on an air basis between the light source and the data recording surface of the optical disc, TR (mm) represents a shifting amount of an object image caused by tracking shift movement of the objective lens by the tracking operation, and θ (°)represents a tilting amount of the objective lens with respect to a reference axis of the optical system.