OPTICAL DISC DEVICE, FOCAL POINT POSITION CONTROL METHOD, AND RECORDING MEDIUM

摘要

It is possible to accurately record or reproduce a hologram expressing information onto/from an optical disc. When recording information onto the optical disc (100), the position of an objective lens (OL1) is controlled according to the detection result of a red color reflected light beam (Lr2) so that a focal point (Fr) follows a target track and a focal point (Fb1) of a blue color light beam (Lb1) is matched with a target mark position by the objective lens (OL1). According to the detection result of the blue color light beam (Lb1) via the objective lens (OL1) and an objective lens (OL2), the position of the objective lens (OL2) is controlled and the focal point (Fb2) is matched with the target mark position, so that the focal point (Fb1) of the blue color light beam (Lb1) and the focal point (Fb2) of the blue color light beam (Lb2) are matched with the target mark position so as to interfere each other. Thus, it is possible to record a recording mark (RM) at the target mark position.