Optical information playback device, optical information playback method, and information recording medium

Abstract

Provided are an optical information playback device, an optical information playback method, and an information recording medium, by which, if the size of a recording area is smaller than the diffraction limit of light, information can be favorably playbacked. An optical information playback device comprises a light source (14) which emits playback lights, and a resonance unit (22) arranged closely to a recording area (4) of a recording layer (2), wherein the resonance unit (22) is provided with a plasmon resonance element (9) which generates plasmon resonance between the recording area (4) and the resonance unit (22), a photodetector (17a) which detects reflection lights or transmitted lights from the plasmon resonance element (9) to which the playback lights are irradiated, and a playback unit (24) which assesses whether the recording area (4); is in a recorded state or in an unrecorded state on the basis of the detection signal from the photodetector (17a) and playbacks the information recorded in the recording area (4).

Description

technical field [0001] The present invention relates to an optical information reproducing device and an optical information reproducing method for optically reproducing information recorded on an information recording medium, and an information recording medium including at least a substrate and a recording layer. Background technique [0002] As an optical information reproducing device, an optical storage system using an optical disc such as a CD (Compact Disc), DVD, BD (Blu-ray Disc) or an optical card as an information recording medium has been put into practical use. [0003] The reproduction principle of the conventional optical storage system is simplified as Figure 10 shown. Figure 10 It is an explanatory diagram showing a part of the configuration of a conventional optical information recording and reproducing apparatus and a state of reproducing information from an information recording medium. [0004] In a conventional optical information recording and reprodu...

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Problems solved by technology

[0005] However, in conventional optical storage systems, there is a problem that the size of the recording mark that can be reproduced (recording mark length) is limited by the NA (numerical aperture) of the objective lens and the diffraction limit determined by the wavelength of the reproduction light. The optical limit size is limited, and it is difficult to further increase the density

[0010] As a result, there is a problem that the change in the intensity of stray light detected corresponding to the presence or absence of recording marks is less than 0.00001% relative to the amount of reproduction light, for example, which is too small to perform good information reproduction.

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