Optical information recorder/reproducer, optical information recording/reproducing method and control circuit

Abstract

The invention provides an optical information recorder / reproducer, an optical information recording / reproducing method and a control circuit. A distance control circuit (23) keeps the constant distance between a condensing member (11) and the surface of an optical disc (1) using return light from a region where proximity field light is generated. Under that state, a focus control circuit (27) focus-controls the focus position of the proximity field light to sustain it at the position of an information layer using reflection light from the information layer. Consequently, information can be recorded and reproduced stably with the proximity field light without causing erroneous erasure or destruction of information recorded on the recording layer (2) even if locally varying irregularities occur on the surface of the optical disc (1) or uneven thickness exists in the protective layer (3).

Description

technical field [0001] The present invention relates to a recording and reproducing device and a recording and reproducing method of an optical information recording medium for optically recording and / or reproducing information, and particularly relates to focus control of a recording and reproducing device using near-field optics (Near-Field Optics). Background technique [0002] A technique utilizing near-field light has been proposed as a method capable of recording and reproducing data on and from an optical disc at a higher density. As a condensing member for generating near-field light, an optical system combining a condensing lens and a solid immersion lens (Solid Immersion Lens, SIL) has attracted attention in recent years. With this combination, a numerical aperture higher than the NA (numerical aperture) of the condenser lens can be realized. If the numerical aperture of the optical system is increased, the size of the spot (spot) can be reduced, so higher-density...

AI Technical Summary

Problems solved by technology

In this case, even if the gap can be kept constant, the change of the focus state of the information layer cannot be avoided.

[0011] The second problem is that there will be problems in the recording and reproduction of so-called multi-layer disks with multiple information layers arranged in the direction of the optical axis.

Therefore, in the case of accidentally focusing on a certain layer of the information layer when the gap servo is operated, it is possible to erase or destroy the information recorded in the information layer by mistake, and the greater the number of information layers, the higher the probability.

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