Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1999-06-15
2001-01-16
Neyzari, Ali (Department: 2752)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S275400
Reexamination Certificate
active
06175548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical recording medium and an optical recording and reproducing apparatus (the optical recording and reproducing apparatus in the present specification indicates an apparatus for optically performing a reproduction and/or recording for the optical recording medium) and particularly is to realize a large recording capacity using red and blue laser lights.
2. Description of the Related Art
The feature, when a disk shape is employed as the optical recording medium, resides in that a recording and reproducing apparatus speedy in access, small in size and convenient can be arranged. For example, in order to realize a disk which can carry out a recording and reproducing of NTSC in four hours on its one side face and can replace an existing video tape recorder (VTR), a memorizing capacity equal to or more than 8 GB (giga byte) is required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical recording medium whose memorizing capacity can be made equal to or more than 8 GB and whose fundamental structure is an optical disk having a ROM (Read Only Memory) portion at least in its part and an optical recording and reproducing apparatus which optically carries out a reproducing and/or recording for the optical recording medium.
According to an optical recording medium of the present invention, a light transmission layer is formed on an informaiton recording surface on which an information recording pit is formed, and a laser light with a wavelength &lgr; of 380 nm≦&lgr;≦450 nm is irradiated from the light transmission layer side through a lens system having an N.A. (numerical aperture) of equal to or more than 0.76 to thereby read out the information. The optical recording medium has such an arrangement that the thickness of its light transmission layer is 3 &mgr;m to 182 &mgr;m, a thickness irregularity of the light transmission layer is within ±5.26 &lgr;/(N.A.)
4
, a track pitch is set to be 0.27 &mgr;m to 0.404 &mgr;m, the shortest or minimum pit length of information recording pit is 0.13 &mgr;m to 0.219 &mgr;m, the recording line density is made as a pit string equal to or less than 0.146 &mgr;m/bit, and the depth of recording pit is set to be 31 nm to 75 nm.
The optical recording and reproducing apparatus of the present invention uses the above-mentioned optical recording medium of the invention and irradiates a laser light with the wavelength &lgr; of 380 nm≦&lgr;≦450 nm on the optical recording medium through an optical system with the N.A. equal to or more than 0.76 from the light transmission layer side to thereby reproduce a recorded information from the information recording surface.
In the optical recording medium of the present invention, a light transmission layer is formed on the information recording surface, the laser light is irradiated from the light transmission layer side, and the information recording surface is arranged such that a first information recording surface and a second information recording surface, each having at least one, are laminated via an intermediate layer serving as the light transmission layer.
The sum of thickness of light transmission layer and intermediate layer interposed between the surfaces to which the laser light is incident from each information recording surface is set to be 3 &mgr;m to 182 &mgr;m. That is, in such a case where only the light transmission layer exists between the surfaces to which the laser light is made incident from the information recording surface, its thickness is made to be 3 &mgr;m to 182 &mgr;m, while in the case where the light transmission layer and the intermediate layer are interposed, the sum of the thickness of them is made to be 3 &mgr;m to 182 &mgr;m. Then, a thickness irregularity from the surface to which the laser light is made incident to each information recording layer is set within ±5.26 &lgr;/(N.A.)
4
.
The track pitch on the first information recording surface is set to be 0.27 &mgr;m to 0.404 &mgr;m, and the track pitch on the second information recording surface is set to be 0.45 &mgr;m to 0.57 &mgr;m.
The laser light with the wavelength &lgr; of 380 nm≦&lgr;≦450 nm is irradiated on the first information recording surface through the optical system with the N.A. (numerical aperture) of equal to or more than 0.76, and the laser light with the wavelength &lgr; of 635 nm ≦&lgr;≦680 nm is irradiated on the second information recording surface through the optical system with the N.A. of equal to or more than 0.76 to perform at least any of recording or reproduction for them, respectively.
The optical recording and reproducing apparatus according to the present invention uses the optical recording medium having the first information recording surface and the second information recording surface mentioned above, and irradiates the first laser light with the wavelength &lgr; of 380 nm≦&lgr;≦450 nm and the second laser light with the wavelength &lgr; of 635 nm≦&lgr;≦680 nm on the first information recording surface and the second information recording surface through the optical system with the N.A. of equal to or more than 0.76, respectively, to thereby carry out at least any of recording or reproduction for them, respectively.
According to the above arrangement, it is possible to realize a large memorizing capacity equal to or more than 8 GB.
REFERENCES:
patent: 5432774 (1995-07-01), Fukumoto et al.
patent: 5764619 (1998-06-01), Nishiuchi et al.
Limbach & Limbach L.L.P.
Neyzari Ali
Sony Corporation
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