Optical information storage medium reproduction apparatus and control method of the same

Abstract

In an optical information storage medium reproduction apparatus (10) for reproducing an optical information storage medium including a plurality of information recording layers each including a recording mark having a length shorter than an optical system resolution limit, reproduction laser power for reading an information recording layer closest to a reproduction-laser-incident surface of the optical information storage medium is set to be lower than reproduction laser power for reading an information recording layer farthest from the reproduction-laser-incident surface but not lower than minimum reproduction laser power that satisfies a reproduction signal characteristic that the optical information storage medium reproduction apparatus (10) requires. With the arrangement, it is possible to prevent that the information recording layer closest to the reproduction-laser-incident surface is irradiated wrongly with reproduction laser having high reproduction laser power, thereby making it possible to obtain successful reproduction quality. That is, it is possible to realize the optical information storage medium reproduction apparatus (10) that can set optimum reproduction laser power and perform stable super resolution reproduction.

Description

TECHNICAL FIELD[0001]The present invention relates to an optical information storage medium reproduction apparatus for reproducing an optical information storage medium by use of a super resolution reproduction technique, and a control method of the optical information storage medium reproduction apparatus.BACKGROUND ART[0002]In recent years, information technology, information communication technology, and multimedia technology have been greatly advanced. This increases demand for an increase in density and capacity of an optical information storage medium.[0003]To cope with such demand, there have been developed various techniques, such as multilayer techniques for forming information recording layers in a multilayered manner and super resolution techniques using a reproduction layer that allows reading of a recording mark shorter than a resolution limit of an optical information storage medium reproduction apparatus.[0004]Initially explained is one of the multilayer techniques. T...

AI Technical Summary

Benefits of technology

The present invention provides an optical information storage medium reproduction apparatus and control method that can stably reproduce high-density optical information storage media, such as multilayer super resolution optical information storage media, without damaging the recording marks of the first information recording layer and maintaining good reproduction signal characteristics. This is achieved by setting the reproduction laser power to be lower than the minimum required for the reproduction signal characteristic of the optical information storage medium reproduction apparatus. The invention also includes an optical system and objective lens with a specific numerical aperture.

Problems solved by technology

Further, the above optical information storage media do not employ any super resolution techniques.

However, by using Mo, W, Si, Ge, and the like material instead of Al and Au, which are conventionally used, to form a reflection layer of a read-only disk, it is possible to read a signal having a recording pit length shorter than the resolution limit, which signal cannot be read by a conventional optical system.

Images