Optical disk including a barcode pattern formed by a laser using pulse width modulation

Abstract

An object of the present invention is to provide a marking forming apparatus, a method of forming a laser marking on an optical disk, a reproduction apparatus, an optical disk, and a method of manufacturing an optical disk, capable of providing a greatly improved copy prevention capability as compared to prior known construction. To achieve this object, in the optical disk of the invention, for example, a marking is formed by a laser on a reflective film of a disk holding data written thereon and at least position information of the marking or information concerning the position information is written on the disk in an encrypted form or with a digital signature appended thereto.

Description

[0001]This is a Reissue Divisional Application of U.S. patent application Ser. No. 09 / 588,364, filed Jun. 2, 2000, which is a Reissue Application of U.S. Pat. No. 5,761,301, issued Jun. 2, 1998.[0002]More than one reissue application has been filed for the reissue of U.S. Pat. No. 5,761,301. The reissue applications are U.S. application Ser. No. 10 / 183,205 (the present specification), Ser. Nos. 10 / 020,427, 10 / 017,973, 10 / 017,965, and 09 / 588,364, all of which are divisional reissues of U.S. Pat. No. 5,761,301.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]The present invention relates to a marking forming apparatus, a method of forming a laser marking to an optical disk, a reproduction apparatus, an optical disk, and a method of manufacturing an optical disk, which may be utilized, for example, to prevent duplication of optical disks.[0005]2. Description of the Prior Art[0006]With increasing use of ROM-type optical disks in recent years, pirated disks have also been ...

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Benefits of technology

[0022]In view of the above-outlined problems of the prior art, it is an object of the present invention to achieve a greatly improved copy prevention capability as compared to the prior art.

[0024]To overcome Problem 1, a piracy prevention method involving the use of a physical mark at a reflective film level, rather than the master disk level physical mark as used in the prior art, is provided wherein the physical mark is formed on a reflective film of a disk. This prevents the production of pirated disks if duplication is made at the master disk level.

[0025]To overcome Problem 2, a new ROM-recording means is used that performs secondary recording to a two-disk laminated ROM disk by using a laser. In a first step, physical marks are randomly formed, and in a second step, the physical marks are measured with a measuring accuracy as high as 0.13 μm. In a third step, their position information is encrypted and, using the secondary recording means, a barcode is recorded to the ROM disk with an accuracy of several tens of microns which is the usual processing accuracy. Optical mark position information can thus be obtained with an accuracy of, for example, 0.1 μm much higher than the processing accuracy of a conventional apparatus. Since optical marks cannot be formed with the accuracy of 0.1 μm by using commercially available equipment, production of pirated disks can be prevented.

[0026]To overcome Problem 3, both a first-generation cipher with a low degree of security and a second-generation cipher with a high degree of security, each enciphering the position information with a digital signature, are prerecorded on a medium and by using such a medium, piracy is prevented with the security corresponding to the applicable generation if the design of reproduction apparatus changes from one generation to the next.

[0029]To overcome Problem 6, position information of an antipiracy mark of the invention, which differs from one disk to another, is used as a disk identifier. The position information and the disk serial number, i.e., the disk ID, are combined and encrypted together with a digital signature, thus appending an unalterable disk ID to each disk. Since each completed disk has a different ID, the password is also different. The password does not work on other disks. This enhances password security.

Problems solved by technology

With increasing use of ROM-type optical disks in recent years, pirated disks have also been spreading, infringing the rights of copyright owners.

This necessarily means a financial loss to the copyright owner.

However, since it is possible to extract this physical mark by examining a legitimate disk, the prior art method has had the problem that pirated disks may be made if such a special mastering apparatus falls into the hands of an illegal person.

This method requires much time and cost to produce one master disk, but since hundreds of thousands of disks can be produced from one pirated master disk, the cost per pirated disk is low.

This has therefore given rise to the problem that as the replica method becomes widespread in the future, it may defeat the effectiveness of piracy prevention techniques at the master disk level.

As described above, the prior art piracy prevention techniques have several problems to be overcome.

Problem 1: The effectiveness of the master disk level piracy prevention techniques of the prior art is low since it is possible to replicate the physical mark.

Problem 2: In the prior art method that forms a physical mark based on physical mark design data, if a manufacturing apparatus of the same precision as the apparatus used by the legitimate disk manufacturer is obtained, illegal disks can be easily manufactured.

Problem 3: Since the security level provided by the prior art piracy prevention methods is fixed, its effectiveness decreases against constantly improving pirating techniques.

The use of copy protection is therefore limited to closed specifications such as game disks.

Problem 5: According to the prior art methods, a limited number of licensing companies possess the special manufacturing apparatus and do not make the apparatus public.

Therefore, software makers cannot make disks except at the licensing companies.

As a result, password security cannot be maintained unless a floppy disk or a communication line is used in combination.

Furthermore, the password has to be entered each time the disk is used since secondary recording is not possible.

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