Cryptography – Electric signal modification – Having magnetic record carrier
Patent
1996-04-05
1998-11-03
Swann, Tod R.
Cryptography
Electric signal modification
Having magnetic record carrier
380 9, 380 10, 380 6, 380 3, 711163, G06F 500
Patent
active
058320881
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a data recording method for effectively preventing illegal data duplication (copy) between disk-like recording mediums such as a read-only optical disk (CD-ROM, etc.), a write once optical disk (CD-R, etc.), a recordable optical disk (magneto-optical disk, etc.) or magnetic disk, a data recording apparatus and disk-like recording medium which can realize the data recording method and a computer system and a data copy preventing method for preventing illegal data copy between the disk-like recording mediums when one system is arranged by using these disk-like recording mediums.
2. BACKGROUND ART
As a disk-like recording medium (referred to hereinafter as an optical disk) on and from which an information signal is recorded and reproduced by laser beam, there are now commercially available a so-called compact disc with audio data recorded therein, a CD-ROM in which computer data is recorded, a write once optical disk on which an information signal can be recorded once and a recordable optical disk in which an information signal can be reproduced, recorded and erased.
The read-only optical disk such as a compact disc or CD-ROM has tracks on which irregular patterns, i.e., phase pits are concentrically or spirally formed on the basis of a recorded information signal formed on one surface thereof. Specifically, the read-only optical disk is composed of a disk base plate made of a transparent synthetic resin such as polycarbonate or PMMA (polymethyl methacrylate), a reflection film made of a metal such as Al or Au formed so as to cover phase pits formed on one surface of the disk base plate and a protection layer formed so as to cover the reflection film in order to protect the reflection film.
When an information signal is reproduced from the read-only optical disk, laser beam from a laser light source is converged by an objective lens and irradiated on the read-only optical disk from the disk base plate side. Reflected light flux modulated by the phase pits on the optical disk is detected by a photodetector, for example, and converted into a detected signal having a signal level corresponding to an intensity of reflected light flux, thereby allowing a reproduced signal of the information signal recorded on the read-only optical disk to be obtained.
While the read-only optical disk can provide mass-produced products (optical disks) inexpensively on the market, it is not suitable for products of small demand. For this end, write once optical disks are prepared for optical disk products of small demand and a variety of data can be provided to the user easily.
As write once optical disks, there are available a write once optical disk of recording system using physical chemical change of pigment, a write once optical disk of a single layer hole forming recording system, a write once optical disk of multi-layer hole forming recording system, a write once optical disk of phase-change recording system and a write once optical disk of bubble-foaming system. Upon reproduction, in a manner similar to the read-only optical disk, a laser beam (having a weak reproduction laser power) from a laser light source is irradiated on the disk from the disk base plate side under the condition that the laser beam is converged by an objective lens. Then, reflected light flux that is modulated by previously-recorded pits is detected by a photodetector and the detected signal is converted into a detected signal having a signal level corresponding to an intensity of a reflected light bundle, thereby obtaining a reproduced signal of an information signal recorded on the write once optical disk.
When an information signal is recorded on the above write once optical disk, a laser beam (having a strong recording laser power) from a laser light source is irradiated on the optical disk from the disk base plate side under the condition that the laser beam is converged by an objective lens. Then, the power of the laser beam is turned on and off by modulating the laser beam in response to an inform
REFERENCES:
patent: 5414688 (1995-05-01), Inokuchi
patent: 5513260 (1996-04-01), Ryan
Kitada Takaharu
Nakajima Heitaro
Ogawa Hiroshi
Peikari J.
Sony Corporation
Swann Tod R.
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