OPTICAL RECORDING/PLAYBACK DEVICE AND OPTICAL RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To improve recording capacity per one piece of an optical recording medium by conducting recording/playback of a multilayered optical recording medium by a near field optical recording method using an objective lens of a large numerical aperture exceeding 1.

SOLUTION: An optical recording/playback device emits a light beam from an optical head 30 to an optical recording medium 10 for conducting recording/playback. The optical recording medium has a plurality of information record layers 16, and the uppermost information record layer is covered with a transparent protection layer 20. The optical head is provided with: an optical system which emits a convergent light beam from a beam emission surface of the objective lens with a numerical aperture larger than 1 toward the optical recording medium; an air gap maintenance mechanism which maintains an air gap between the beam emission surface of the objective lens and the surface of the optical recording medium to a minute air gap in which light propagation by an evanescent wave is possible; a focal position controller which focuses the convergent light beam with a desired depth of the optical recording medium; and a spherical-aberration correction mechanism which corrects spherical aberration when the convergent light beam focuses within the optical recording medium.

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