HIGH-NUMERICAL-APERTURE OPTICAL SYSTEM AND OPTICAL INFORMATION RECORDING AND REPRODUCING DEVICE USING SAME

摘要

PROBLEM TO BE SOLVED: To provide a high-NA(numerical aperture) optical system with good image forming performance and the optical information recording and reproducing device using this optical system by suppressing small a spherical aberration generated owing to variation in the thickness of the transparent protection substrate part of a recording medium. ;SOLUTION: This high-numerical-aperture optical system converges the luminous flux from a light source on the information surface of the recording medium through the transparent protection substrate part 16 of the recording medium 6. The optical system has optical elements, such as a nearly hemispherical convex lens and an objective, arranged along the optical path, at a fine air interval on the transparent protection substrate part 16 and the respective optical elements of the optical system are so positioned that the spherical aberration generated by the optical system is less than a specific value against specific thickness variation of the transparent protection substrate part 15.;COPYRIGHT: (C)1999,JPO