Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1999-05-20
2001-07-24
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
active
06266299
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical disk for recording, reproducing and erasing information. In particular, the present invention relates to an optical disk comprising write-once information that can be used for copyright protection, for example for copy-protection or protection from unauthorized use of software. Throughout this specification, “write-once information” refers to information that is recorded after finishing the disk manufacturing process. The present invention relates further to a method for recording and a method for reproducing write-once information on the optical disk, an apparatus for reproducing the optical disk, an apparatus for recording and reproducing the optical disk, an apparatus for recording write-once information on the optical disk, and an apparatus for recording on the optical disk.
BACKGROUND OF THE INVENTION
In recent years, the speed with which electronic calculators and information processing systems can process ever greater amounts of information has increased sharply. Together with the digitalization of audio and video information, this gave rise to the rapid dissemination of low-cost, high-volume auxiliary storage devices and recording media therefor, especially optical disks, which can be accessed with high access speeds.
The basic configuration of conventional optical disks is as follows: A dielectric layer is formed on top of a disk substrate, and a recording layer is formed on top of the dielectric layer. On top of the recording layer, an intermediate dielectric layer and a reflecting layer are formed in that order. An overcoat layer is formed on top of the reflecting layer.
The following is an explanation of how an optical disk with the above configuration is operated.
In the case of an optical disk having, in its recording layer, a magneto-optical layer with perpendicular magnetic anisotropy, the recording and erasing of information is performed by locally (a) heating the recording layer with a laser beam to a temperature with small coercive force above the compensation temperature or to a temperature near or above the Curie temperature to decrease the coercive force of the recording layer in the irradiated portion, and (b) magnetizing the recording layer in the direction of an external magnetic field. (This is also called “thermomagnetic recording” of information.). Moreover, for the reproduction of the recording signal, a laser beam with less intensity than the laser beam for recording or erasing irradiates the recording layer. The recording state of the recording layer, that is, the rotation of the polarization plane of the light that is reflected or transmitted in accordance with the orientation of the magnetic field (this rotation occurs mainly due to two magneto-optical effects—the Kerr effect and the Faraday effect), is detected by a photodetector through the change in the intensity of the irradiated light. In order to decrease the interference between opposite magnetizations and allow high-density recordings, a magnetic material with perpendicular magnetic anisotropy is used for the recording layer of the optical disk.
Moreover, when the data is reproduced, the reproduction signal level during data reproduction can be raised to detect the reproduction signal by using a layered structure for the recording layer: Several magnetic thin films comprising an exchange coupling multilayer or a magneto-static coupling multilayer.
For the recording layer, a material is used that can record information by locally raising the temperature or inducing a chemical reaction due to absorption of the irradiated laser light. The local variations in the recording layer can be detected by irradiating laser light of a different intensity or wavelength than that used for the recording and detecting the reproduction signal using the reflected or the transmitted light.
Regarding such optical disks, there is a need for a way to protect the data on the disk with write-once information (identification data) that allows for copyright protection, for example copy protection and protection against unauthorized use of software.
With the above configuration, it is possible to record disk information in TOC (or control data) areas, but when disk data is recorded with pre-pits, the disk information has to be administered stamper by stamper and cannot be administered user by user.
Moreover, when information is recorded using a magnetic film or a film of a phase-reversible material, administrative information easily can be changed, which means that it easily can be rewritten (manipulated), so that the contents on the optical disk cannot be copyright protected.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problems of the prior art. It is a further object of the present invention to provide an optical disk comprising write-once information that can be used for copyright protection, for example for copy-protection or protection from unauthorized use of software, a method for recording write-once information on an optical disk, a method for reproducing write-once information from an optical disk, an apparatus for reproducing optical disks, an apparatus for recording and reproducing optical disks, an apparatus for recording write-once information on optical disks, and an apparatus for recording on optical disks.
In order to attain these objects, a first configuration of an optical disk in accordance with the present invention comprises a disk substrate and a recording layer on the disk substrate. The recording layer includes a magnetic film with a magnetic anisotropy in a direction perpendicular to a surface of the magnetic film. The optical disk stores write-once information formed by first recording areas and second recording areas in a pre-determined portion of the recording layer. A magnetic anisotropy in a direction perpendicular to a surface of the second recording areas is smaller than a magnetic anisotropy in a direction perpendicular to a surface of the first recording areas. The second recording areas are formed as stripe-shaped marks that are oblong in a radial direction of the disk. A plurality of the marks is arranged in a circumferential direction of the disk, the arrangement being based on a modulation signal of the write-once information. In accordance with this first configuration, an optical disk can be achieved, which comprises write-once information that can be used for copyright protection, for example for copy-protection or protection from unauthorized use of software.
It is preferable that the optical disk according to the first configuration further comprises an identifier indicating whether there is a row of a plurality of marks arranged in a circumferential direction of the disk. With this configuration, the system can be started in a short time. Moreover, in this configuration, it is preferable that the identifier indicating the row of marks is stored among control data. With this configuration, it is known when the control data is reproduced whether write-once information is stored, so that the write-once information can be reproduced reliably.
It is preferable that in the optical disk according to the first configuration, the pre-determined portion comprising write-once information is at an inner perimeter portion of the disk. With this configuration, the position of the optical head with respect to a radial direction of the disk can be determined with an optical head stopper or address information of a bit signal.
It is preferable that in the optical disk according to the first configuration, a difference between a luminous energy that is reflected from the first recording areas and a luminous energy that is reflected from the second recording areas is below a certain value. It is particularly preferable that the difference between luminous energy that is reflected from the first recording areas and luminous energy that is reflected from the second recording areas is not more than 10%. With this configuration, variations of the reproduction waveform accompanying changes of
Gotoh Yoshiho
Koishi Kenji
Konishi Shinichi
Miyatake Norio
Moriya Mitsurou
Dinh Tan
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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