HK1046764B - Optical disk apparatus, optical disk recording method, and optical disk - Google Patents

Description

Optical disc apparatus, optical disc recording method, and optical disc

Technical Field

The present invention relates to an optical disc apparatus, an optical disc accessing method and an optical disc, and more particularly, to an optical disc apparatus, an optical disc accessing method and an optical disc which are suitable for application to a disc recording/reproducing apparatus designed for a compact disc (MD), a read-only disc (CD), a Digital Video Disc (DVD), and the like. The invention is conceived as follows: when copyright information is recorded by repeatedly forming partial areas that cause a larger variation in the return light reception result than pits or marks, the existence ratio (existence ratio) of such partial areas in the circumferential direction of the optical disc is set to less than 0.3, thereby ensuring accurate reproduction of copyright information recorded as, for example, a barcode.

Background

Recently, it has been noted that a small-sized optical disc apparatus, which is conventionally used as an optical disc apparatus, is rapidly spread for use because it has advantages of simply and easily copying music from various contents and preventing deterioration of sound quality. More specifically, in the compact disc apparatus, music information distributed via the internet may be recorded on a compact disc for trial listening, or music on a read-only compact disc borrowed from friends or the like may be recorded on a compact disc for trial listening.

However, in such a simple and easy reproduction process that prevents any deterioration of the sound quality, although there is an advantage in that convenience is brought to the user, the interests of the copyright holder or the music creator may be impaired, which is highly likely. For this reason, various worldwide groups and forums, such as RIAA (american recording industry association), SDMI (protected digital music creation rights organization), CPTWG (copyright protection technology working group), and the like, are now under discussion for various measures to protect the interests of copyright holders.

As one of these measures, a method of recording music information after encrypting it with copyright protection information unique to each recording medium has been proposed. According to this method, when music information has been copied to another recording medium, it is difficult to decrypt the information because copyright protection information is different in each recording medium, thereby preventing unlimited copying and protecting the interests of the copyright holder.

For such a copyright-protected information recording system, a method of forming a sector which is difficult to be accessed by a user and recording copyright-protected information in this sector is proposed, and a method of recording such information as a bar code by partially removing a reflective film with respect to main data in the form of a recorded pit row is proposed (international publication No. WO 97/14144).

In the latter method (recording copyright protection information like a barcode by partially removing the reflective film), a laser beam is modulated by a predetermined modulation signal and then repeatedly irradiated onto an optical disc, wherein data to be recorded is processed by PE (phase encoding) to generate a modulation signal, thereby generating a clock pulse from the reproduced signal and realizing reproduction of data recorded in units of one bit like a barcode.

In such a barcode recording process based on the known conventional method, there is a problem in that: the operation of the optical pickup is unstable, resulting in the inability to accurately reproduce copyright protection information.

More specifically, in the above-described recording method, the optical characteristics of the information recording film are locally and irreversibly changed by irradiation of a laser beam. Therefore, in the irreversible change of the optical characteristics by the irradiation of the laser beam, one notable feature is: the change in optical characteristics on the information recording plane becomes large, eventually causing a significant change in the amount of returned light obtained by irradiating the laser beam in the playback mode. In addition, in this barcode recording method, another feature is: the local changes extend over a relatively long distance in the circumferential direction of the optical disc compared to the case of using a mark row or the like. When access is made to the area where the copyright protection information is recorded in the above-described manner, the time period during which a sufficient amount of return light cannot be received in the optical disc apparatus becomes relatively long, so that an error occurs in performing appropriate focus control. If such proper focus control is difficult to achieve, correct playback of the copyright protection information in the optical disc device is also difficult to achieve.

Disclosure of Invention

An object of the present invention is to provide an optical disc apparatus, an optical disc recording method, and an optical disc in which copyright information can be accurately reproduced when such copyright information is recorded by repeatedly forming partial areas that cause a change in return light reception result larger than pits or marks.

To achieve the above object, according to a first aspect of the present invention, there is provided an optical disc apparatus for recording copyright information on an optical disc on which desired data is recorded by repetition of pits or marks, the apparatus comprising: the signal source is used for providing copyright information; an error correction code circuit for attaching an error correction code to the copyright information; a modulator for generating a modulated signal according to the copyright information and an error correction code; and an optical system for irradiating a laser beam onto an optical disc in response to the modulation signal to record the copyright information, wherein the copyright information is recorded by irradiating the laser beam onto the optical disc in such a manner that: dividing a predetermined area of the optical disc into a plurality of minute sub-areas in a circumferential direction, and forming partial areas regarding copyright information in the n minute sub-areas among consecutive m minute sub-areas, which cause a larger change in a return light reception result than pits or marks, wherein an existence ratio of the partial areas is set to be less than 0.3 in the circumferential direction of the optical disc, the partial areas being repeatedly formed in the predetermined area of the optical disc by laser beam irradiation, m and n are positive integers, where n < m.

An optical disc recording method of the present invention for recording copyright information on an optical disc on which desired data is recorded by repetition of pits or marks to be played back, said recording method comprising the steps of: irradiating a laser beam on the optical disc in such a manner that: dividing a predetermined area of the optical disc into a plurality of minute sub-areas in a circumferential direction, and among consecutive m minute sub-areas, partial areas causing a larger change in a return light reception result than pits or marks are formed among n minute sub-areas corresponding to copyright information, thereby recording the copyright information in the partial areas, wherein an existence ratio of the partial areas in the circumferential direction of the optical disc is set to be less than 0.3, the partial areas are repeatedly formed in the predetermined area of the optical disc by laser beam irradiation, m and n are positive integers, where n < m.

The optical disc apparatus and the optical disc recording method of the present invention repeatedly form local areas in a predetermined area of the optical disc by irradiating a laser beam, the local areas cause a larger change in the return light reception result than pits or marks, and copyright information is recorded in such local areas. The existence ratio of the local area is set to be less than 0.3 in the circumferential direction of the optical disc.

According to a second aspect of the present invention, there is provided an optical disc on which desired data is recorded by repetition of pits or marks and data recorded by the repetition of pits or marks is reproduced by processing a return light reception result obtained by irradiation of a laser beam, wherein the optical disc comprises: a user area for recording user data therein; and a barcode region formed inside the user region and within a radius of 22.9 mm, the barcode region having minute sub-regions divided into partial regions repeatedly formed in a circumferential direction of the optical disc, the partial regions being formed in n minute sub-regions among consecutive m minute sub-regions, causing a larger change in a return light reception result than pits or marks, wherein an existence ratio of the partial regions in the circumferential direction of the optical disc is set to be less than 0.3, and m and n are positive integers, where n < m.

In the optical disk of the present invention, copyright information is recorded in partial areas which are repeatedly formed in a predetermined area of the optical disk by laser beam irradiation and cause a change in return light reception result larger than pits or marks in such a manner that the existence ratio of the partial areas is less than 0.3 in the circumferential direction of the optical disk.

According to a third aspect of the present invention, there is provided an optical disc apparatus for accessing an optical disc on which data is recorded by a plurality of rows of pits or marks, the apparatus comprising: an optical system for irradiating a laser beam onto the optical disc and outputting a result of receiving return light from the optical disc; a copyright information reproducing device for reproducing copyright information, the copyright information being recorded on the optical disc based on a sampling result obtained by sampling a return light reception result at a predetermined timing; and a control means for controlling access to said optical disc based on the copyright information, wherein by recording the copyright information on said optical disc in such a manner that: dividing a predetermined area of the optical disc into a plurality of minute sub-areas in a circumferential direction, and forming local areas on copyright information in n minute sub-areas among consecutive m minute sub-areas, wherein the local areas cause a larger change in a return light reception result than pits or marks, an existence ratio of the local areas is set to less than 0.3 in the circumferential direction of the optical disc, the local areas are repeatedly formed in the predetermined area of the optical disc by laser beam irradiation, m and n are positive integers, wherein n < m.

Wherein the copyright information recorded on the optical disc is reproduced by comparing sampling results obtained by sampling the return light reception results at predetermined timings.

With this structure, since the local region causing a larger change in the return light reception result is repeatedly formed in such a manner that: the existence ratio thereof is less than 0.3 in the circumferential direction of the optical disk, and therefore even if the time period during which a sufficient amount of return light cannot be received is long, the time period during which such an amount of light is insufficient can be shortened as a whole as compared with the time period during which a sufficient amount of return light can be received. Therefore, it is possible to obtain an appropriate setting to completely avoid an undesirable situation in which it is difficult to achieve correct focus control, thereby enabling accurate playback of copyright protection information.

Accordingly, the present invention can realize a satisfactory optical disc suitable for realizing reliable playback of copyright information.

In addition, according to the present invention, the copyright protection information recorded on the optical disc can be reproduced by comparison of the sampling result obtained by sampling the return light reception result at a predetermined timing, so that even when any change in the low-frequency signal level occurs in the return light reception result, the point in time at which the sampling result of the highest signal level is obtained can be determined. Therefore, by applying the above-described playback method to a case where copyright information is recorded in a repeatedly formed partial area causing a large change in the return light reception result, it is possible to effectively avoid any harmful effect by a change in the level of a low-frequency signal even when 1-bit recording has a long distance in the circumferential direction, thereby reliably achieving accurate playback of the copyright information.

According to a fourth aspect of the present invention, there is provided an optical disc manufacturing method comprising the steps of: modulating a recording laser beam with the address information and irradiating the modulated laser beam onto a main disc, and exposing the main disc to record the address information; developing the main disc to form fine concavo-convex portions corresponding to the pit rows or grooves; plating the master disc to form a master disc, and making a stamper from the master disc; mass-producing disk substrates each having a fine concave-convex portion reproduced from a master disk by molding the stamper; forming a magneto-optical film as an information recording film on the disk substrate; forming a protective film on the information recording film; recording copyright protection information on the optical disc by a bar code writer, wherein the copyright protection information is recorded by irradiating a laser beam on the optical disc in such a manner that: dividing a predetermined area of the optical disc into a plurality of minute sub-areas in a circumferential direction, and among consecutive m minute sub-areas, partial areas causing a larger change in a return light reception result than pits or marks are formed among n minute sub-areas corresponding to copyright information, thereby recording the copyright information in the partial areas, wherein an existence ratio of the partial areas in the circumferential direction of the optical disc is set to be less than 0.3, the partial areas are repeatedly formed in the predetermined area of the optical disc by laser beam irradiation, m and n are positive integers, where n < m.

Drawings

Fig. 1A to 1D are schematic views for explaining a compact disc used in the present invention;

FIG. 2 is a flow chart showing a process of manufacturing the compact disc of FIG. 1;

FIG. 3 is a block diagram showing a bar code writer in one embodiment of the invention;

FIG. 4 is a block diagram showing a 4-1 modulator in the bar code writer of FIG. 3;

fig. 5 is a block diagram showing an optical disc apparatus for accessing the compact disc of fig. 1;

fig. 6 is a block diagram showing a second decoder in the optical disc apparatus of fig. 5;

fig. 7 is a block diagram showing a maximum detector in the second decoder of fig. 6.

Detailed Description

Some preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

(1) Structure of the embodiment

Fig. 2 is a flowchart showing a process of manufacturing an optical disc according to an embodiment of the present invention. In the present embodiment, the optical disc manufacturing process 1 is adopted to manufacture the compact disc 2 containing the recorded copyright protection information ED.

The copyright protection information ED is used for encrypting audio data and the like to be recorded on the compact disc 2 and also for decrypting audio data and the like recorded on the compact disc 2. For example, the copyright protection information ED is composed of ID information unique to each compact disc, information on the relevant manufacturer, information on the date of manufacture, and information controlling whether to permit copying or prohibit copying. In the present embodiment, the copyright protection information ED is composed of, for example, 128 bits of digital information, in which a unique value different from any other disc is set for each small optical disc.

In the optical disc manufacturing process 1, the address encoder 6 supplies address information SA to a groove cutter 7, which then modulates a recording laser beam with such address information SA and irradiates the modulated laser beam onto a master (disk master) 8. Then, the master 8 is exposed by the notching machine 7 to thereby record address information SA in the shape of a curved groove or pit row. The recorded address information SA is used for tracking control of the small optical disc 2 and also for access to the small optical disc 2.

In the optical disc manufacturing process 1, the main disc 8 exposed by the notching machine 7 as described above is developed in the subsequent developing step 9, thereby forming fine concave-convex portions corresponding to the pit rows or grooves in the exposed tracks.

In a following plating step 10, the master disc 8 is plated to form a master disc (motherdisk) 12. In the optical disc manufacturing process 1, a stamper is manufactured from a master 12, and in an injection molding step 13, disc substrates 14 each having fine concave-convex portions reproduced from the master 12 are mass-manufactured by molding the stamper by an injection molding machine.

In the subsequent recording film forming step 15, a magneto-optical film is formed as an information recording film on the disk substrate 14 by sputtering or the like. And in the next protective film forming step 17, a protective film is formed on the information recording film so as to ensure environmental resistance of the small optical disc 2.

In the next step of the optical disc manufacturing process 1, copyright protection information ED output from a signal source 16 is recorded by a bar code writer 18, and then the compact disc 2 is shipped.

The barcode writer 18 modulates a high-power laser beam emitted from a YAG (yttrium aluminum garnet) laser or the like with the copyright protection information ED and then irradiates the modulated laser beam to an inner area of the compact disc 2 to locally and irreversibly change the information recording plane of the compact disc 2 by the copyright protection information ED, thereby recording the copyright protection information ED. At this time, the barcode writer 18 records the copyright protection information ED by irradiating a laser beam of a radially long and narrow shape, thereby recording the copyright protection information ED like a barcode on a predetermined inner area of the compact disc 2. At this stage, the barcode writer 18 irreversibly changes the information recording film composed of one reflective film by irradiation of the laser beam, thereby irreversibly changing the optical characteristics of the information recording plane.

Fig. 1A is a perspective view of such a compact disc 2 containing copyright protection information ED as described above. Copyright protection information ED is recorded in a predetermined internal area ard of the small optical disc 2 like a bar code. The area ARED for recording the copyright protection information ED is set to be 0.8mm wide around a radius of 22.1 mm.

The copyright protection information ED is repeatedly recorded four times along a week of the compact disc 2, so that the copyright protection information ED can be reliably reproduced even if a local defect or the like occurs. In the copyright protection information ED, as shown in fig. 1B, a header (header) is assigned to its top so that the start of recording the copyright protection information ED can be detected from the header. In addition, a 40-bit error correction code is assigned to the end of the copyright protection information ED to prevent any bit error. In the present embodiment, the error correction code is composed of, for example, a Reed-Solomon (Reed-Solomon) code.

Among various data to be set, a header is represented by a logic level pattern (pattern) (e.g., 010001000100), which is not generated in the subsequent copyright protection information ED or error correction code. As shown in fig. 1D-1 to 1D-4, each bit represented by a logic level corresponds to a minute sub-area 50 μm wide formed by radially dividing a recording area ard of copyright protection information ED approximately in units of 50 μm. In the present embodiment, the light amount of the laser beam is increased for each minute sub-area of the corresponding logical 1, and thus the information recording plane associated with the minute sub-area is irreversibly changed. Therefore, the circumference of 50 μm corresponding to the width of the minute sub-area is much larger than the length of each mark recorded on the small optical disc 2 as user data by EFM (8-14) modulation. In the present embodiment, the circumference of the minute sub-area is set to 50 μm, and the laser beam emitted from a high-power YAG laser is irradiated onto the small-sized optical disc 2 through an objective lens (which has a relatively small numerical aperture NA), thereby achieving irreversible change of the optical characteristics of the information recording plane with sufficiently high accuracy.

Meanwhile, the copyright protection information ED and the error correction code are processed in units of 2 bits by 4-1 modulation and then sequentially recorded with a synchronization pattern inserted therein. In the synchronization pattern, three of the above-described minute sub-areas are successively allocated as shown in fig. 1C, and the optical characteristics of the information recording plane are irreversibly changed only for the central sub-area among such successive three minute sub-areas. Thus, in the present embodiment, it is possible to obtain proper timing consistency in the playback mode, and since one synchronization pattern is inserted per 2-bit recording, more accurate timing consistency can be reliably obtained.

In comparison with the above case, the 4-1 modulation is performed in such a manner that: that is, as shown in fig. 1D-1 to 1D-4 explaining the mutual correspondence relationship of the logical values of the copyright protection information ED and the error correction code, the copyright protection information ED and the error correction code are divided in units of 2 bits, and bit strings are generated accordingly for irreversibly changing the optical characteristics of the information recording plane thereof selectively for one of four minute sub-areas following the synchronization pattern in accordance with the logical values of the copyright protection information ED and the error correction code.

More specifically, 4-1 modulation is performed such that: when the copyright protection information ED and the 2-bit data (b1, b0) of the error correction code are logic 00, as shown in fig. 1D-1, the data (b1, b0) are converted into logic 1000 so that the change of the information recording plane is formed only in the first sub-area of the four minute sub-areas. When the 2-bit data (b1, b0) is logic 01, as shown in fig. 1D-2, the data (b1, b0) is converted to logic 0100 to form a change of the information recording plane only in the second sub-area of the four minute sub-areas. Meanwhile, when the 2-bit data (b1, b0) is logic 10, as shown in fig. 1D-3, the data (b1, b0) is converted into logic 0010 so that a change of the information recording plane is formed only in the third sub-area of the four minute sub-areas. When the 2-bit data (b1, b0) is logical 11, as shown in fig. 1D-4, the data (b1, b0) is converted to logical 0001 so as to form a change of the information recording plane only in the last one of the four minute sub-areas.

Therefore, in the present embodiment, the copyright protection information ED is recorded like a barcode by irreversible change of the local information recording plane, and the existence ratio of such local areas having optical characteristic variation is set to be less than 0.3 in the circumferential direction of the optical disc.

That is, when information is recorded by 4-1 modulation with the synchronization pattern assigned as described above, irreversible changes are made to two sub-areas of seven consecutive minute sub-areas on the compact disc 2, and then the existence ratio of such areas eventually becomes 2/7 ═ 0.285 in the circumferential direction of the optical disc 2. Therefore, in the present embodiment, accurate focus control can be reliably obtained even when the copyright protection information ED is recorded over a relatively long distance as compared with marks or the like recorded on the small optical disc 2, or optical (characteristic) changes much larger than those marks. Therefore, even in the case where the optical (characteristic) change reaches such a level that no return light is obtained from the information recording plane, if the presence ratio is set to be less than 0.3, it is possible to perform appropriate focus control in virtually any optical disc apparatus. As a result, in the present embodiment, accurate focus control can be achieved with a wide margin.

Fig. 3 is a block diagram of a bar code writer for recording such copyright protection information ED. In this barcode writer 18, the spindle motor 22 drives the small optical disc 2 at a predetermined rotational speed under the control of the spindle servo circuit 23, wherein an FG signal generator mounted at the bottom generates an output FG signal FG whose level rises as the small optical disc 2 passes through a predetermined angle per rotation. The spindle servo circuit 23 controls the operation of the servo motor 22 in such a manner that: the small optical disk 2 is rotated at a predetermined speed based on the FG signal FG.

The laser beam source 24 is constituted by a YAG laser, and intermittently emits a high-power laser beam L1 in response to a modulation signal PM.

The mirror 25 refracts the optical path of the laser beam L1 and projects it onto the compact disc 2. The objective lens 26 is composed of, for example, a cylindrical lens, and condenses the light reflected from the mirror 25 onto the information recording plane of the compact disc 2. Next, the barcode writer 18 semi-permanently changes the information recording film by changing the composition of the information recording film in accordance with the modulation signal PM or by evaporating the information recording film, thereby recording the copyright protection information ED like a barcode. In the case where the copyright protection information ED is not recorded in a sufficient width in the radial direction, the recording position can be continuously moved in the radial direction of the compact disc 2, so that it becomes possible to record the copyright protection information ED like a barcode by repeating such recording operation.

An ECC (error correction code) circuit 27 appends an error correction code, which has been described in conjunction with fig. 1, to the copyright protection information ED output from the signal source 16, and then transfers its output data. The 4-1 modulator 28 generates a modulation signal PM from the output data SB of the ECC circuit 27.

Fig. 4 is a block diagram showing the detailed structure of the 4-1 modulator 28. The serial-parallel converter 31 in the 4-1 modulator 28 receives serial data SB composed of copyright protection information ED and an error correction code from the ECC circuit 27, and after dividing the data SB in units of 2 bits, transmits the 2-bit data (b1, b0) as its output.

The fixed pattern generator 32A repeatedly outputs a fixed pattern of logic 1000, which corresponds to logic 00 of the data (b1, b0) described in connection with fig. 1, in synchronization with clock pulses obtained from a clock generator, not shown. Similarly, fixed pattern generators 32B through 32D iteratively output fixed patterns of logic 0100, 0010, and 0001, which correspond to logic 01, 10, and 11, respectively, of the data (B1, B0) described in connection with fig. 1.

The data selector 33 selectively transfers the output data of the fixed pattern generators 32A to 32D according to the logical value of the data (b1, b 0).

The synchronization pattern generator 34 repeatedly outputs a bit pattern of the logic 010 in synchronization with the clock pulses, which corresponds to the synchronization pattern described in connection with fig. 1.

Under the control of the controller 36, the data selector 35 selectively switches the output data of the data selector 33 or the output data of the sync pattern generator 34 and then transmits the selected output data. Therefore, the 4-1 modulator 28 configures one synchronization pattern for every 2-bit recording of the copyright protection information ED and the error correction code.

The banner generator 37 outputs a fixed pattern of logic 010001000100, which corresponds to the banner described in connection with fig. 1. The data selector 38 selectively transmits the output data of the header generator 37 or the output data of the data selector 35, thereby generating such a modulation signal PM: the title is arranged on top of the copyright protection information ED.

The controller 36 is a circuit for controlling the overall operation of the 4-1 modulator 28, and controls the operation of the data selectors 35 and 38 in such a manner that: the header, copyright protection information ED, and error correction code are configured as described in conjunction with fig. 1.

Fig. 5 is a block diagram of an optical disc apparatus for recording and reproducing the compact disc 2 manufactured in the above-described manner. In this optical disc apparatus 41, the spindle motor 42 drives the small optical disc 2 at a predetermined rotational speed under the control of the servo circuit 43.

The optical pickup 44 is supported by a predetermined slider (slid) mechanism in such a manner as to be movable in the radial direction of the compact disc 2. The optical pickup 44 irradiates a laser beam onto the small optical disc 2 and outputs the result of receiving light after receiving back light from the optical disc 2. In the recording mode, the optical pickup 44 applies a modulation magnetic field while intermittently increasing the light flux of the laser beam beyond that in the playback mode, thereby thermomagnetic-recording various information by a so-called pulse train method.

A Matrix Amplifier (MA)45 processes the output signal of the optical pickup 44 to generate: a wobble signal whose level changes with the meandering of the groove; a tracking error signal TK of which the level changes in accordance with the magnitude of the tracking error; a focus error signal FS whose level varies with the magnitude of a focus error; a playback signal MO whose level changes in accordance with the polarization plane of the return light from the compact disc 2 by utilizing the magnetic Kerr effect; and a playback signal HF whose level changes with the recording film and the pit row on the small optical disc 2.

By using such a tracking error signal TK and a focus error signal FS, the servo circuit 43 performs tracking control and focus control of the optical pickup 44. The servo circuit 43 also controls the rotation speed of the spindle motor 42 in the following manner: the clock pulse generated from the wobble signal has a predetermined frequency. Further, under the control of a Central Processing Unit (CPU)46, the servo circuit 43 acquires address information from the wobble signal and causes the optical pickup 44 to search for a predetermined position.

A Low Pass Filter (LPF)47 limits the pass band of the playback signal HF so as to suppress any deviation caused by noise of the playback signal HF and output the playback signal HF.

An analog-to-digital (AD) converter 48 converts the analog reproduction signal HF output from the low-pass filter 47 into a digital signal according to a predetermined sampling clock, and then outputs an 8-bit digital reproduction signal DX.

The second decoder 49 processes the digital playback signal DX to thereby play back the data SB composed of the copyright protection information ED and the error correction code. An Error Correction Circuit (ECC)50 performs error correction of the output data SB obtained from the second decoder 49, and then outputs copyright protection information ED.

The CPU46 constitutes a control circuit for controlling the operation of the optical disc apparatus 41. In response to detection of the loaded compact disc 2 by a compact disc detection mechanism, not shown, the CPU46 causes the optical pickup 44 to search for the lead-in area under the control of the servo circuit 43, as in a normal compact disc apparatus, thereby obtaining TOC data necessary for access to the compact disc 2. Subsequently, the CPU46 causes the optical pickup 44 to search for the area ARED where the copyright protection information ED is recorded, thereby obtaining the copyright protection information ED from the error correction circuit 50. At this time, the CPU46 instructs the servo circuit 43 to perform access only with focus control while stopping the tracking control operation, because tracking control is difficult in the area ARED where the copyright protection information ED is recorded like a barcode.

The CPU46 instructs the recording/playback section to perform encryption by the copyright protection information ED thus obtained, thereby controlling access to the compact disc 2, thereby achieving effective protection of the interests of the copyright holder.

More specifically, in the playback section, the decoder 51 plays back the clock signal by processing the playback signal MO, then 8-14 demodulates the playback signal MO in accordance with the clock signal, and outputs the played back data.

The decryptor 52 decrypts and outputs the reproduced data according to the copyright protection information ED, and an Error Correction Circuit (ECC)53 performs error correction of the output data obtained from the decryptor 52. Such errors are due to some defects or similar problems on the compact disc 2. Therefore, in the optical disc device 41, audio data and the like are reproduced by uniquely decrypting the small optical disc 2 based on the copyright protection information ED.

Meanwhile, in the recording portion, an Error Correction Circuit (ECC)55 appends an error correction code to input data received successively, and then transfers output data. The encryptor 56 at the next stage encrypts the output data from the error correction circuit 55 in accordance with the copyright protection information ED, and the modulator 57 performs 8-14 modulation (EFM) on the output data from the encryptor 56, thereby generating a modulated signal. The modulation signal is used to drive the modulation coil of the optical pickup 44. In this way, the optical disc device 41 records audio data and the like by unique encryption of the small optical disc 2 based on the copyright protection information ED.

Fig. 6 is a block diagram of the second decoder 49. In the second decoder 49, the PLL circuit 60 reproduces the channel clock signal CK from the digital reproduction signal DX.

The sync detector 61 determines the level of the digital reproduction signal DX based on the channel clock signal CK, thereby detecting a sync pattern and outputting a reset pulse SY.

The timing generator 62 generates sampling pulses T1 to T4 whose signal levels rise at timings approximately corresponding to the centers of each of the first to fourth minute sub-regions following the synchronization pattern described in conjunction with fig. 1, in accordance with the reset pulse SY.

The flip-flop circuits (FF)63A to 63D latch the digital reproduction signal DX in accordance with the sampling pulses T1 to T4, respectively, so that the second decoder 49 enables the flip-flop circuits (FF)63A to 63D to latch and hold the levels of the reproduction signals obtained from four minute sub-areas, respectively, which are assigned to two bits of copyright protection information ED and error correction code.

The max detector 64 decodes the copyright protection information ED and the 2-bit data (b1, b0) of the error correction code according to the determined values of the four latch results D1-D4. And, the parallel-to-serial converter (PS)65 converts the parallel 2-bit data (b1, b0) successively output from the maximum detector 64 into serial data.

Therefore, in the second decoder 49, the copyright protection information ED is decoded in accordance with the determined signal level value of the playback signal obtained in correspondence with the four minute sub-areas allocated for recording the copyright protection information ED, and it is possible to reliably achieve accurate playback of the copyright protection information ED even when a certain degree of signal level variation at low frequencies is contained in the playback signal.

In processing a playback signal on an optical disc, a binary discrimination method using a predetermined threshold value is generally applied. Therefore, even when the optical characteristics of the information recording plane of one of the four minute sub-areas are selectively changed, the copyright protection information ED can be decoded by performing binary discrimination on the playback signal and detecting the timing at which the binary discrimination result rises to logic 1 or the timing at which it falls to logic 0.

However, the playback signal on the optical disc includes a certain degree of low-frequency signal level variation, and when four minute sub-areas extend a long distance in the radial direction of the compact disc 2 as in the present embodiment, such low-frequency signal level variation may also adversely affect the decoding result. Therefore, in the present embodiment, the copyright protection information ED is decoded by: signal level sampling is performed corresponding to the respective areas and then the sampling results are compared with each other, whereby the copyright protection information ED can be reliably decoded. In addition, the pass band is limited beforehand by the low-pass filter 47, so that no errors are caused, which otherwise might be caused by some noise in the digital determination of the signal level values.

Fig. 7 is a block diagram of a maximum detector 64 that performs such digital determination of signal level values. In the maximum detector 64, the digital comparator 71 numerically determines the level value in response to the latch results D1 and D2 corresponding to the two minute sub-regions close to the synchronization pattern out of all the four latch results D1-D4. If the latch result D1 near the synchronization pattern has a larger value among the two latch results D1 and D2, the digital comparator 71 raises the logic value of the comparison result H1.

According to the comparison result H1, the data selector 72 selectively outputs the latch result of the larger value of the latch results D1 and D2 input to the digital comparator 71. When the logic value of the comparison result H1 is high, the latch result D1 close to the synchronization pattern is output. Meanwhile, when the logic value of the comparison result H1 is low, the latch result D2 distant from the synchronization pattern is output.

The digital comparator 73 numerically decides the level value in response to the latch results D3 and D4 corresponding to two minute sub-regions distant from the synchronization pattern out of all four latch results D1-D4. When the latch result D3 close to the synchronization pattern of the two latch results D3 and D4 has a large value, the digital comparator 71 raises the logic value of the comparison result H2.

According to the comparison result H2, the data selector 74 selectively outputs the latch result of the larger value of the latch results D3 and D4 input to the digital comparator 73. When the logic value of the comparison result H2 is high, the latch result D3 close to the synchronization pattern is output. Meanwhile, when the logic value of the comparison result H2 is low, the latch result D4 distant from the synchronization pattern is output.

In response to the output data of the data selectors 72 and 74, the digital comparator 75 numerically determines a level value. When the output data of the data selector 72 corresponding to the latched result close to the synchronization pattern has a larger value among the output data of the data selectors 72 and 74, the digital comparator 75 raises the logic value of the comparison result H3.

Based on the obtained three comparison results H1-H3, the decision circuit 76 decodes the 2-bit data (b1, b0) obtained from the detection results, and then transmits its decoded output. More specifically, when the third comparison result H3 is a logic 1, the maximum latched result D1 or D2 is indicated by the first comparison result H1. Therefore, in the case where the first comparison result H1 is logic 1, the circuit 76 determines that the pattern of the logic 1000 is allocated to four minute sub-areas, and transfers the output data of logic 00 (b1, b 0). When the first comparison result H1 is logic 0, the circuit 76 determines that the pattern of logic 0100 is allocated to four minute sub-areas, and transfers the output data of logic 01 (b1, b 0).

Meanwhile, when the third comparison result H3 is a logic 0, the maximum latched result D3 or D4 is indicated by the second comparison result H2. Therefore, when the second comparison result H2 is logic 1, the circuit 76 determines that the pattern of logic 0010 is allocated to four minute sub-areas, and transfers the output data of logic 10 (b1, b 0). And when the second comparison result H2 is logic 0, the circuit 76 determines that the pattern of logic 0001 is allocated to four minute sub-areas, and transfers the output data of logic 11 (b1, b 0). Such a relationship as described above can be expressed as follows:

when H1 is 1, H2 is 1, H3 is 1: b 0-0, b 1-0

When H1 is 0, H2 is 1, H3 is 1: b 0-1, b 1-0

When H1 ═ H2 ═ 1, H3 ═ 0: b0 ═ 0, b1 ═ 1

When H1 ═ 0, H2 ═ 0, H3 ═ 0: b 0-1, b 1-1

…(1)

(2) Operation of the embodiments

In the above-described structure, the small optical disc 2 (fig. 2) is manufactured by: the master disk 8 is first exposed by the notching machine 7, then the master disk 12 is formed by performing the developing step 9 and the plating step 10, and the disk substrate 14 is manufactured on a large scale using one stamper made of the master disk 12. Further, a magneto-optical recording film and a protective film are formed on each disk substrate 14, and after the copyright protection information ED is recorded like a barcode by the barcode writer 18, the disk substrate 14 is shipped.

In the barcode writer 18, the small optical disc 2 (fig. 3) is processed as follows: an error correction code is added to the copyright protection information ED outputted from the signal source 16 by the ECC circuit 27, then a predetermined modulation signal PM is generated by the 4-1 modulator 28, and the laser beam L1 emitted from the laser beam source 24 is irradiated after intermittently rising in accordance with the modulation signal PM (compact disc 2). Therefore, on the small optical disc 2, the copyright protection information ED is recorded in a predetermined inner area ard with the local and irreversible change of the information recording film by irreversibly changing the reflective film or locally removing the reflective film. That is, the copyright protection information ED is recorded on the small optical disc 2 by repetition of a local area that causes a larger change in the result of light received in the playback mode than pits or marks. Since the objective lens 26 for converging the laser beam L1 is composed of a cylindrical lens, the laser beam L1 is irradiated in a radially elongated shape, so that the copyright protection information ED is recorded like a barcode.

In the small-sized optical disc 2 (fig. 1), the pled area for recording the copyright protection information ED is sequentially divided in the circumferential direction at a pitch of approximately 50 μm, thereby defining a plurality of minute sub-areas. For three of the total 12 consecutive tiny sub-areas, a local change of the information recording plane is formed at the header by a pattern that is not generated during recording of the subsequent copyright protection information ED and error correction codes.

Meanwhile, as for the copyright protection information ED and the error correction code, the continuous minute sub-area behind the header is divided in units of seven, and the two-bit synchronization pattern, the copyright protection information ED, or the error correction code is recorded in the seven minute sub-areas. That is, for one sub-area of three minute sub-areas at the beginning of seven consecutive minute sub-areas, a local change for recording the synchronization pattern is formed. One of the remaining four minute sub-areas is selected in accordance with the copyright protection information ED or the error correction code, and a local change is formed in the selected minute sub-area, thereby recording two bits of the copyright protection information ED or the error correction code.

The copyright protection information ED is recorded as viewed from the radial direction of the recording area ard for the copyright protection information ED on the compact disc 2: the region in which the local change is formed is present at a ratio of 0.285, which is less than (the ratio setting of) 0.3 for the whole. Even when the copyright protection information ED is recorded by repetition of local areas, and these areas cause a larger variation in light reception results than pits or marks, the copyright protection information can be reliably reproduced under accurate focus control. Since one synchronization pattern of three minute sub-areas is arranged every four consecutive minute sub-areas, the copyright protection information ED can be reliably reproduced regardless of any rotation change or the like.

More specifically, in the conventional barcode recording, data to be recorded is processed by PE modulation to generate a modulation signal according to which a laser beam is irradiated, so that a local change formed in the circumferential direction of the optical disc is finally present at a rate of 0.5. However, in the present embodiment, the presence ratio is 0.285 which is less than 0.3, thereby reducing the ratio of the time period in which a sufficient amount of return light cannot be detected. In response to this (ratio of time period) reduction, any harmful influence on the focus servo and the like can be reduced, so that the recording of copyright protection information on the compact disc 2 can be satisfactorily realized. Therefore, it is possible to obtain stable operation of the focus servo and the like in the playback mode, and the design of the focus servo and the like in the playback apparatus can further simplify the structure.

The compact disc 2 shipped after the copyright protection information ED is thus recorded is loaded into the optical disc device 41 (fig. 5), wherein a playback signal HF representing a return light reception result obtained by irradiation of a laser beam is converted into a digital playback signal DX by the analog-to-digital converter 48, and then processed in the second decoder 49, thereby playing back the copyright protection information ED. Further, the audio data and the like are encrypted and recorded according to the reproduced copyright protection information ED, or the reproduced audio data and the like are decrypted according to the information.

Due to the above-described processing, the encrypted data can be correctly decrypted on the compact disc 2 legally recorded with the copyright protection information ED, thereby enabling the user to enjoy the musical performance recorded on the compact disc 2 without hindrance. Meanwhile, on any small optical disc (i.e., pirate disc) on which the copyright protection information ED is not legally recorded, the encrypted data cannot be correctly decrypted, and it is difficult for the user to enjoy the music recorded on the small optical disc 2, thereby losing the value of the pirate disc. Therefore, with the small-sized optical disk 2, it is possible to prevent the spread of pirated disks and ultimately protect the interests of copyright holders.

Also, when some user data is to be re-recorded, the data is encrypted according to the copyright protection information ED, thereby preventing illegal copying of the data onto any pirated disc or the like.

In the second decoder 49 (fig. 6) for the compact disc 2, the synchronization pattern is detected by the synchronization detector 61, and then the digital playback signal DX is sequentially sampled by the flip-flop circuits 63A to 63D in response to the sampling pulses T1 to T4 based on the detection of the synchronization pattern, thereby detecting the level of the playback signal HF for each of the four minute sub-areas allocated for recording the copyright protection information ED and the error correction code. In addition, in the maximum detector 64 (fig. 7), the four sampling results thus obtained are successively compared, and then it is determined which sub-region of the four minute sub-regions is allocated as the locally changed region, and according to the result of such determination, the copyright protection information ED and the error correction code root are successively decoded.

Therefore, on the compact disc 2, since erroneous decoding, which may be caused by a DC level variation as in the case where the copyright protection information ED is decoded only by binary discrimination, can be effectively avoided, even when the copyright protection information ED is recorded at a low transmission rate like a barcode, correct playback of the copyright protection information ED can be realized.

(3) Effects of the embodiments

According to the above-described structure, when copyright information is recorded by repetition of partial areas (which cause larger variations than the light reception results of pits or marks), the existence ratio of such partial areas in the circumferential direction is set to be less than 0.3, so that even when copyright information is recorded like a barcode, for example, any abnormal operation of focus servo or the like can be effectively avoided, thereby ensuring accurate reproduction of the copyright protection information ED.

In addition, a sync pattern is configured when four consecutive minute sub-areas are recorded in units of two bits, whereby the copyright protection information ED can be reliably reproduced regardless of any rotation change or the like.

Further, the copyright information recorded on the compact disc is reproduced by comparing sampling results obtained by sampling the light reception results at predetermined timings, so that erroneous decoding due to DC level variations as may be caused when the copyright protection information ED is decoded only by binary discrimination can be effectively avoided. Therefore, even when the copyright protection information ED is recorded at a low transmission rate like a barcode, correct playback of the copyright protection information ED can be achieved.

(4) Other embodiments

The above-described embodiment represents a typical example in which two bits of copyright protection information ED are assigned to four continuous minute sub-regions and one of the four minute sub-regions is selected to cause a local change in the information recording film. However, the present invention is not limited thereto, and such values may be changed according to various requirements.

Also in the above-described embodiment, the case where one minute sub-area is changed as a whole is explained. However, the present invention is not limited to this example only, and a minute sub-area may be partially changed to further reduce the influence on the focus servo and the like.

In addition, in the above-described embodiment, a case where the copyright protection information ED is recorded by changing or removing the reflective film to form a local change is described. However, the present invention is not limited to this, and the copyright protection information ED may be recorded like a bar code: for example, the surface of the disc substrate 14 is locally roughened or some pit rows are locally removed, thereby changing the information recording plane in terms of optical (characteristics).

Further, in the above-described embodiment, a case where the copyright protection information ED is recorded by irradiation with the YAG laser is described. However, the present invention is not limited to this example, and carbon dioxide (CO) may be used₂) A laser, a high power semiconductor laser or the like.

In addition, in the above-described embodiment, a case is described in which the copyright protection information ED is decoded in the following manner: in a reproduction system in which the level of the reproduction signal HF rises in the region where the change of the reflective film occurs, a maximum value is detected in the maximum detector 64. However, the present invention is not limited to this example, and in a playback system, another case opposite to the above may be also possible: the level of the playback signal HF drops in the region where the reflective film changes. In this case, the copyright protection information ED can be reliably reproduced by detecting the minimum value in the maximum detector instead of the maximum value, or by inserting an inverting amplifier in the reproduction signal processor.

Further, in the above-described embodiment, a case where the present invention is applied to a small optical disc, which is an optical disc suitable for recording and playback, has been described. However, the present invention is not limited to this example, and may be applied to a magneto-optical disc or a phase-change type optical disc that is also suitable for recording and playback, and may also be applied to a write-once type optical disc or a read-only (reproduction-only) type optical disc.

In addition, in the above-described embodiment, a case has been described in which access to an optical disc is controlled by an encryption process using copyright information. However, the present invention is not limited to this example, and can be widely applied to control of access to an optical disc by stopping, controlling the operation of the recording/reproducing section, or to control of access to an optical disc by stopping the output of the reproduction signal.

In addition, in the above-described embodiment, a case where unique information is configured as copyright information to an optical disc has been described. However, the present invention is not limited thereto. When audio data or the like is recorded for sale, the copyright information may be composed of, for example, specific information unique to the relevant artist.

Therefore, according to the present invention, in which copyright information is recorded by repeatedly forming local areas that cause a larger variation in light reception result than pits or marks, the existence ratio of such local areas in the circumferential direction is set to be less than 0.3. Therefore, even when copyright information is recorded like a barcode, for example, the information can be reliably and accurately reproduced.

Although the preferred embodiments of the present invention have been described using specific conditions, such description is for illustrative purposes only, and it is to be understood that various changes and modifications may be made without departing from the spirit or scope of the appended claims.

Claims (20)

1. An optical disc apparatus for recording copyright information on an optical disc on which desired data is recorded by repetition of pits or marks, said apparatus comprising:

the signal source is used for providing copyright information;

an error correction code circuit for attaching an error correction code to the copyright information;

a modulator for generating a modulated signal according to the copyright information and an error correction code; and

an optical system for irradiating a laser beam onto the optical disc in response to the modulation signal to record the copyright information,

wherein the copyright information is recorded by irradiating a laser beam onto the optical disc in such a manner that: a predetermined area of the optical disc is divided into a plurality of minute sub-areas in a circumferential direction, and partial areas regarding copyright information are formed in n number of minute sub-areas among m number of successive minute sub-areas, the partial areas causing a larger change in a return light reception result than pits or marks,

wherein an existence ratio of the partial region is set to less than 0.3 in a circumferential direction of the optical disc, the partial region being repeatedly formed in the predetermined region of the optical disc by laser beam irradiation,

m and n are positive integers, wherein n < m.

2. The optical disc apparatus according to claim 1, wherein said m is 4 and said n is 1.

3. The optical disc apparatus according to claim 1, wherein said optical disc apparatus places a synchronization pattern by selectively forming a partial area in at least one of a predetermined number of consecutive minute sub-areas immediately before said m minute sub-areas.

4. An optical disc apparatus according to claim 1, wherein the optical disc apparatus forms the partial region by irreversibly changing a reflective film of the optical disc.

5. The optical disc apparatus according to claim 1, wherein the optical disc apparatus forms the partial area by partially removing a reflective film of the optical disc.

6. The optical disc apparatus according to claim 1, wherein the optical disc apparatus forms the partial region by locally changing a disc substrate of the optical disc.

7. The optical disc apparatus according to claim 1, wherein said optical disc apparatus records copyright information as a barcode by forming said partial area.

8. An optical disc recording method for recording copyright information on an optical disc on which desired data is recorded by repetition of pits or marks to be played back, said recording method comprising the steps of:

irradiating a laser beam on the optical disc in such a manner that: dividing a predetermined area of the optical disc into a plurality of minute sub-areas in a circumferential direction, and among consecutive m minute sub-areas, partial areas causing a larger change in a return light reception result than pits or marks are formed among n minute sub-areas corresponding to copyright information, thereby recording the copyright information in the partial areas,

wherein an existence ratio of the partial region in a circumferential direction of the optical disc is set to be less than 0.3, the partial region being repeatedly formed in the predetermined region of the optical disc by laser beam irradiation,

m and n are positive integers, wherein n < m.

9. An optical disc on which desired data is recorded by repetition of pits or marks and data recorded by repetition of pits or marks is reproduced by processing a return light reception result obtained by irradiation of a laser beam,

wherein the optical disc includes:

a user area for recording user data therein; and

a barcode area formed inside the user area and within a radius of 22.9 mm, the barcode area having minute sub-areas divided into partial areas repeatedly formed in a circumferential direction of the optical disc, the partial areas being formed in n minute sub-areas of consecutive m minute sub-areas, causing a larger change in a return light reception result than pits or marks,

wherein the existence ratio of the local area in the circumferential direction of the optical disc is set to be less than 0.3, and m and n are positive integers, where n < m.

10. The optical disc of claim 9, wherein m is 4 and n is 1.

11. The optical disc according to claim 9, wherein one synchronization pattern is placed by selectively forming a partial region in at least one of k consecutive minute sub-regions immediately before the m minute sub-regions, where k is a positive integer.

12. The optical disc of claim 11, wherein k is 3.

13. The optical disc according to claim 9, wherein the partial area is formed by irreversibly changing a reflective film of the information recording plane.

14. The optical disc of claim 9, wherein the partial area is formed by partially removing the reflective film of the information recording plane.

15. The optical disc of claim 9, wherein the local area is formed by a local modification of the disc substrate.

16. The optical disc according to claim 9, wherein in the local area, copyright information is recorded as a barcode.

17. An optical disc apparatus for accessing an optical disc on which data is recorded by a plurality of rows of pits or marks, the apparatus comprising:

an optical system for irradiating a laser beam onto the optical disc and outputting a result of receiving return light from the optical disc;

a copyright information reproducing device for reproducing copyright information, the copyright information being recorded on the optical disc based on a sampling result obtained by sampling a return light reception result at a predetermined timing; and

a control means for controlling access to said optical disc based on the copyright information,

wherein by recording copyright information on the optical disc in such a manner: dividing a predetermined area of the optical disc into a plurality of minute sub-areas in a circumferential direction, and forming local areas on copyright information in n minute sub-areas out of m successive minute sub-areas, wherein the local areas cause a larger change in a return light reception result than pits or marks,

the existence ratio of the partial region is set to be less than 0.3 in the circumferential direction of the optical disc, the partial region is repeatedly formed in the predetermined region of the optical disc by laser beam irradiation,

m and n are positive integers, wherein n < m.

18. The optical disc device according to claim 17, wherein the copyright information playback apparatus comprises: a synchronization pattern detection means for detecting one synchronization pattern included in the copyright information from the light reception result; sampling pulse generating means for generating a plurality of sampling pulses based on a detection result obtained from the synchronization pattern detecting means; a plurality of sampling means for sampling the light reception result with reference to each sampling pulse; and a comparing means for comparing sampling results obtained from said plurality of sampling means and outputting a comparison result;

wherein the copyright information is output based on the comparison result obtained from the comparing means.

19. The optical disc device according to claim 17, wherein access to the optical disc is controlled by encrypting input/output data of the optical disc according to copyright information.

20. A method of manufacturing an optical disc, comprising the steps of:

modulating a recording laser beam with the address information and irradiating the modulated laser beam onto a main disc, and exposing the main disc to record the address information;

developing the main disc to form fine concavo-convex portions corresponding to the pit rows or grooves;

plating the master disc to form a master disc, and making a stamper from the master disc;

mass-producing disk substrates each having a fine concave-convex portion reproduced from a master disk by molding the stamper;

forming a magneto-optical film as an information recording film on the disk substrate;

forming a protective film on the information recording film;

copyright protection information is recorded on the optical disc by a bar code writer,

wherein the copyright protection information is recorded on the optical disc by irradiating a laser beam in such a manner that:

dividing a predetermined area of the optical disc into a plurality of minute sub-areas in a circumferential direction, and among consecutive m minute sub-areas, partial areas causing a larger change in a return light reception result than pits or marks are formed among n minute sub-areas corresponding to copyright information, thereby recording the copyright information in the partial areas,

wherein an existence ratio of the partial region in a circumferential direction of the optical disc is set to be less than 0.3, the partial region being repeatedly formed in the predetermined region of the optical disc by laser beam irradiation,

m and n are positive integers, wherein n < m.