JPH1139721A - Optical disk and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily identify that a reproduced data stream is an illegal copy even when the reproduced data stream is copied with a bit stream by frequency- modulating a reference clock for forming pits and lands at the time of manufacturing with a sub-data of a specified frequency consisting of the text data showing copyright of a file. SOLUTION: An EFM circuit 14 sends a modulation signal S1 modulating a bit stream consisting of main data to be recorded with a frequency modulation clock CKF to an optical modulator 8. The optical modulator 8 turns a laser beam L on/off with the modulation signal S1 and exposes a master disk 2 to form a pit and land. Sub-data D2 are set so that the distribution of the side band of the frequency modulation clock CKF is 1 kHz or below from a central frequency, and doesn't become 10 Hz or below. In a regular spindle motor servo having inertia, it is difficult to follow fluctuations in high frequency of a regenerative clock.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and an optical disk apparatus, for example, a CD-ROM (compact disk).
sc read only memory) and its recording / reproducing system. The present invention frequency-modulates a reference clock for forming pits and lands, or changes the ratio of the lengths of pits and lands, and records secondary data related to main data recorded by pits and lands. Make illegal copies easily recognizable.

[0002]

2. Description of the Related Art Conventionally, a CD-ROM has been subjected to data processing for data to be recorded, and then to EFM (eight-to-fourteen).
By performing the modulation, pits and lands corresponding to periods 3T to 11T are sequentially formed in units of a predetermined reference period T, whereby various data are recorded.

In response to this, the CD-ROM player irradiates the CD-ROM with a laser beam and receives the return light, thereby obtaining a reproduction signal whose signal level changes in accordance with the amount of the return light. The reproduced signal is binarized at a predetermined slice level to generate a binarized signal.
Further, the PLL circuit is driven from the binarized signal to generate a reproduced clock, and the binarized signal is sequentially latched by the reproduced clock. As a result, the CD-ROM player generates reproduction data in which the signal level switches at a period of 3T to 11T in accordance with the repetition of pits and lands formed on the CD-ROM.

[0004] The CD-ROM player processes the reproduced data generated in this way in accordance with the data processing at the time of recording, and reproduces various files recorded on the CD-ROM.

[0005]

By the way, this kind of CD
-ROM stores not only copyrighted works such as programs, but also copyrights and the like of these copyrighted works, thereby clarifying the location of copyrights and the like to prevent illegal duplication.

However, in illegal copying, CDs
-A data stream reproduced from the ROM is supplied to the optical disk device in a bit stream to form a CD-R (compact disc).
-recordable).

The CD-R illegally copied in this way
In this case, there is a problem that since the record of the copyright or the like is copied as it is, it cannot be identified as an illegal copy.

The present invention has been made in consideration of the above points, and enables an optical disk and an optical disk which can easily identify illegal duplication even when a data stream reproduced from a CD-ROM is duplicated by a bit stream. It is intended to propose a device.

[0009]

According to the present invention, there is provided an optical disk in which a reference period, which is a basic unit of pits and lands, is frequency-modulated to record sub data related to main data. .

[0010] Alternatively, in an optical disc,
The secondary data related to the main data is recorded by changing the length ratio of the pit and the land.

Alternatively, when the present invention is applied to an optical disk device and pits and lands are sequentially formed by a reference clock and main data is recorded, according to sub data related to the main data, Displace the frequency of the reference clock.

Instead of this, the present invention is applied to an optical disk device, and has a pit length modulating means for changing the ratio of the length of pits and lands according to sub data related to main data.

Instead of this, in addition to the main data reproducing means for reproducing main data applied to an optical disk device, a period detection in which a signal level changes according to a displacement of a reference period from a binarized signal. There is provided a sub data reproducing means for generating a signal, frequency modulating a reference period based on the period detection signal, and reproducing sub data recorded on the optical disk.

Alternatively, the present invention is applied to an optical disk apparatus, and in addition to the main data reproducing means, generates an asymmetry detection signal whose signal level changes in accordance with the asymmetry of the reproduction signal.
A secondary data reproducing means for reproducing secondary data recorded on the optical disk by changing the length ratio of the pits and lands is provided.

In an optical disk, if a reference period, which is a basic unit of pits and lands, is frequency-modulated to record sub-data related to main data, the main data is recorded by pits and lands. Data can be recorded. The secondary data will be separately reproduced by a dedicated reproducing system different from the main data reproducing system. If only the main data is duplicated as it is, the sub data will be lost and duplicated. Will be done. This makes it possible to determine whether or not the copy is illegal based on whether or not the sub data can be reproduced.

Alternatively, in an optical disc,
Even if the sub data related to the main data is recorded by changing the length ratio of the pits and lands, the sub data can be recorded in addition to the main data by the pits and lands. Data is separately reproduced by a dedicated reproduction system different from the main data reproduction system. As a result, when only the main data is copied as it is, the sub data is lost and copied, whereby it is possible to determine whether or not the sub data can be reproduced to determine whether it is an illegal copy. it can.

From these facts, when the present invention is applied to an optical disk apparatus and pits and lands are sequentially formed by a reference clock and main data is recorded, the reference data is used in accordance with the sub data related to the main data. By displacing the frequency of the clock, an optical disk can be created in which sub data is recorded in addition to main data.

Instead of this, the present invention is similarly applied to an optical disk apparatus, and has a pit length modulation means for changing the ratio of the lengths of pits and lands according to sub data related to main data. Then, the sub data can be recorded by changing the length ratio of the pit and the land.

On the other hand, on the reproducing side, a period detection signal whose signal level changes in accordance with the displacement of the reference period is generated from the binarized signal, and the reference period is frequency-modulated based on the period detection signal to be applied to the optical disk. The recorded sub data can be reproduced.

Alternatively, the present invention is similarly applied to an optical disk device on the reproducing side to generate an asymmetry detection signal whose signal level changes in accordance with the asymmetry of the reproduction signal, and the pit and land are detected based on the asymmetry detection signal. By changing the length ratio, it is possible to reproduce the sub data recorded on the optical disk.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(1) First Embodiment FIG. 1 is a block diagram showing an optical disk device according to a first embodiment of the present invention. This optical disc device 1
In the manufacturing process of the CD-ROM, it is used for exposing the disk master 2, and in this manufacturing process, the disk master 2 is used.
Is developed and then electroformed to form a mother disk.
Create an OM.

That is, in the optical disk device 1,
The spindle motor 4 drives the disk master 2 to rotate,
The FG signal generator held at the bottom outputs an FG signal FG whose signal level rises at every predetermined rotation angle. The spindle servo circuit 5 drives the spindle motor 4 in accordance with the exposure position of the master disc 2 so that the frequency of the FG signal becomes a predetermined frequency, thereby rotating the master disc 2 under the condition of a constant linear velocity. I do.

The recording laser 7 is constituted by a gas laser or the like, and emits a laser beam L for exposing the master disk. The optical modulator 8 is configured by an electroacoustic optical element, and emits the laser beam L by controlling on / off of the laser beam L by a modulation signal S1. The mirror 10 bends the optical path of the laser beam L and emits it toward the master disc 2, and the objective lens 11 condenses the reflected light of the mirror 10 on the master disc 2. Further, the mirror 10 and the objective lens 11 are sequentially moved to the outer peripheral side of the master disc 2 by a thread mechanism (not shown).
Are sequentially moved to the outer peripheral side of the master disc 2. As a result, in the optical disc device 1, tracks are formed spirally from the inner circumference to the outer circumference of the master disc 2,
The track is sequentially and intermittently irradiated with a laser beam in accordance with the modulation signal S1, thereby forming pits and lands alternately.

The data streamer 12 supplies user data D1 to be recorded on a CD-ROM by pits and lands. Thus, this user data D1 is
It constitutes main data to be recorded on a CD-ROM. The data processing circuit 13 adds an error correction code to the user data D1 according to a format specified for the CD-ROM, and then performs an interleaving process and outputs the result.

The EFM circuit 14 is provided with the data processing circuit 1
3 is EFM-modulated. At this time, the EFM circuit 14 adds additional data such as a subcode to the output data, thereby forming a bit stream in a format specified for the CD-ROM. Further, the EFM circuit 14 generates and outputs a modulated signal S1 whose signal level changes according to the bit stream. At this time, the EFM circuit 14 generates the modulation signal S1 so that the signal level switches in synchronization with the frequency modulation clock CKF output from the frequency modulation circuit 15.

Thus, in the optical disc apparatus 1, one cycle of the frequency modulation clock CKF is set as the reference cycle T, and the disc master 2 is exposed by the modulation signal S1 whose signal level switches between the cycles 3T to 11T. 3T ~
Pits and lands are sequentially formed with a length corresponding to 11T.

The frequency modulation circuit 15 controls the frequency modulation clock C so that the frequency is shifted within a predetermined frequency shift range from the center frequency in accordance with the logical level of the sub data D2.
Generate KF. Here, the sub data D2 is composed of text data indicating the copyright of each file composed of the user data D1 and the repetition of the error correction code and bit-reversed data of the text data, for example, NRZI (No.
n Return to Zero Inverted) Generated by modulation.

The sub data D2 is a frequency modulation clock C
The KF is supplied to the frequency modulation circuit 15 at a frequency higher than the response frequency of the spindle servo system so that the spindle servo system of the playback apparatus does not respond to the deviation of KF. That is, the sub data D2 is supplied to the frequency modulation circuit 15 at a frequency higher than a noise component generated by rotation of the CD-ROM when the CD-ROM is driven to rotate.

In the optical disk device 1, the playback device P
In the LL circuit, the shift frequency and the transmission speed of the sub data D2 are set so that the frequency modulation clock CKF can be reproduced faithfully. That is, in the reproducing device, the shift frequency and the transmission speed are set to be sufficient to generate a reproduced clock that follows the change in the signal level of the reproduced signal and that sufficiently suppresses the jitter with respect to the frequency modulation clock CKF. Specifically, since the noise component due to the rotation of the CD-ROM has a frequency of 10 [Hz], the sub data D2
Is that the spectrum distribution of the main side band of the frequency modulation clock CKF is 1 kHz from the center frequency.
The frequency is set so that the frequency distribution does not fall below 10 Hz from the center frequency. As a result, in the optical disk device 1, the reproduction system of the reproduction device can reproduce the user data D1 with a sufficient phase margin.

Thus, in the optical disk device 1, the reference period of pit and land formation is frequency-modulated by the sub data D2, and the sub data D2 related to the main data D1 is recorded on the CD-ROM. .

FIG. 2 shows the CD-ROM thus created.
FIG. 2 is a block diagram illustrating an optical disk device that plays a ROM. In the optical disc device 20, a sub-playback system 21 is added to the configuration of a normal CD-ROM player. That is, in the optical disk device 20, the spindle motor 2
2 drives the CD-ROM 23 to rotate.

The optical pickup 24 has a CD-ROM 23
Is irradiated with the laser beam L, and the return light of the laser beam L whose light amount changes according to the pit and the land is received. Further, the optical pickup 24 includes a reproduction signal RF whose signal level changes according to the amount of the return light, a tracking error signal whose signal level changes according to the tracking error amount, and a focus whose signal level changes according to the focus error amount. Generate an error signal. In the optical disk device 20, tracking control and focus control of the optical pickup 24 are performed based on the tracking error signal and the focus error signal.

The amplification circuit 25 amplifies the reproduced signal RF with a predetermined gain and outputs it. The binarization circuit 26 binarizes the reproduction signal RF based on a predetermined threshold and outputs a binarization signal S2.

The PLL circuit 28 reproduces a reproduction clock CK which is phase-synchronized with the frequency modulation clock CKF from the binary signal S2. That is, in the PLL circuit 28,
The phase comparison circuit 28A is a voltage-controlled oscillation circuit (VCO)
The reproduction clock CK and the binarized signal S output from 28C
2 and a phase comparison result is output. The low pass filter (LPF) 28B band-limits the phase comparison result to generate a phase error signal. The voltage controlled oscillation circuit (VCO) 28C generates a reproduction clock CK based on the phase error signal. Thereby, the PLL circuit 28
Generates a reproduction clock CK synchronized with a reference period T for forming pits and lands.

The spindle servo circuit 29 controls the rotation speed of the spindle motor 22 so that the reproduced clock CK is in phase with the system clock SCK. As a result, the optical disk device 20 drives the CD-ROM 23 to rotate under the condition that the linear velocity is constant.

At this time, the spindle servo circuit 29 controls the rotation of the spindle motor 22 having inertia and the CD-ROM 23 to respond to a noise component having a frequency of about 10 [Hz] accompanying the rotation of the CD-ROM 23. Control the rotation speed of the spindle motor 22 by using the frequency modulation clock CKF having a higher frequency than this.
Of the spindle motor 22
, It becomes difficult to control the rotation speed.

As a result, the spindle servo circuit 29
Although the rotation speed of the spindle motor 22 is controlled so that the phase of the reproduction clock CK corresponding to the change of the frequency modulation clock CKF is phase-synchronized with the system clock SCK, the phase cannot be completely synchronized.
The carrier signal of the reproduction clock CK is changed to the system clock S
The phase is synchronized with CK. The PLL circuit 28
, The frequency modulation clock CK of the optical disc device 1
The reproduction clock CK synchronized with F is reproduced.

The latch circuit 30 controls the reproduction clock CK
, The binary signal S2 is sequentially latched, thereby reproducing the reproduction data D3 from the reproduction signal RF. The data processing circuit 31 corrects the timing of the reproduced data D3 to a timing synchronized with the system clock SCK by sequentially latching the reproduced data D3 with the system clock SCK. Further, the data processing circuit 31
After the reproduction data D3 is subjected to EFM demodulation, a deinterleave process is performed. Further, the data processing circuit 31 performs an error correction process on the reproduced data, thereby demodulating and outputting the user data D1.

The secondary reproduction system 21 compares the phase of the reproduction clock CK with the phase of the system clock SCK in the phase comparison circuit 21A, and limits the band of the phase comparison result by the following low-pass filter 21B. Thereby, the secondary reproduction system 21
A sub reproduction signal RFS whose signal level changes according to the logical level of the sub data D2 is reproduced. Data processing circuit 2
1C reproduces a sub-reproduction clock by binarizing the sub-reproduction signal RFS.
The sub-data D2 is reproduced by sequentially latching the digitized reproduction signal RFS, and the sub-data D2 is subjected to error correction processing and output.

In the optical disk device 20, a system control circuit (not shown) performs, based on the sub data D2,
The copyright is displayed on a predetermined display device. Further, based on a comparison result between the sub data D2 and the user data D1,
It is determined whether or not the CD-ROM 23 is an illegally copied product. If the CD-ROM 23 is an illegally copied product, the reproduction of the CD-ROM 23 is stopped.

In the above configuration, the data streamer 1
After receiving predetermined data processing in the data processing circuit 13, the user data D1 supplied from
The subsequent EFM circuit 14 performs EFM modulation, thereby converting the bit stream into a bit stream in a CD-ROM format, and generates a modulated signal S1 whose signal level changes according to the bit stream. At this time, a frequency modulation clock CKF is generated for the main data composed of the user data D1 by the sub data D2 representing the copyright of the main data, and the frequency modulation clock CK is generated.
F so that the signal level changes in synchronization with F
1 is generated.

The modulation signal S1 causes the laser beam L
Are turned on and off, and the master disc 2 is sequentially exposed,
When a CD-ROM is created from the master disc 2, a period T, which is a reference period for forming pits and lands, is used.
On the other hand, pits and lands having a period of 3T to 11T are sequentially formed.
The user data D1.

Further, the frequency of the frequency modulation clock CKF, which is a reference for forming the pits and lands, is frequency-modulated by the auxiliary data D2, so that the reference period T is frequency-modulated. Is C
It is recorded on the D-ROM.

At this time, the speed and the amount of frequency shift of the frequency modulation clock CKF follow the change in the signal level of the reproduced signal in the PLL circuit of the reproducing apparatus.
Since the speed and the amount of deviation are set to be sufficient to generate a reproduced clock with sufficiently suppressed jitter with respect to the frequency modulation clock CKF, the main data D1
In order to ensure sufficient phase margin in normal CD-ROM players for playback,
Recorded in M.

On the other hand, since the secondary data must be reproduced by detecting a change in the reference cycle T, it cannot be reproduced unless a dedicated reproducing device is used, and it is assumed that the reproduced data can be reproduced. However, it is difficult to copy unless the optical disk device has the same configuration as the optical disk device 1. This makes it possible to determine whether the product is a duplicate product based on the presence or absence of the sub data.

That is, as shown in FIG.
At 23, the reproduction signal RF is rotationally driven by the spindle motor 22, and the reproduction signal RF is detected from the return light of the laser beam L.
Valued. Further, the binary signal S2 is input to the PLL circuit 28, where the reproduced clock CK is reproduced.

At this time, since the frequency modulation clock CKF is set to a frequency shift speed and a shift amount sufficient to generate a reproduction clock with sufficiently suppressed jitter, the reproduction reproduced in this manner. In the clock CK, the signal level changes in synchronization with the frequency modulation clock CKF.

In the optical disk device 20, the spindle motor 22 is controlled by the spindle servo circuit 29 so that the carrier frequency of the reproduced clock CK becomes a predetermined frequency, whereby the CD-ROM 23 is driven to rotate under the condition of a constant linear velocity. Will be. Ordinary CD-
In a ROM player, a CD-ROM
The ROM 23 is rotationally driven under the condition that the linear velocity is constant.

At this time, since the speed of the frequency shift of the frequency modulation clock CKF is set to a speed at which the spindle servo system is difficult to respond, the spindle servo circuit 2
In No. 9, although the CD-ROM 23 is driven to rotate under the condition of a constant linear velocity, it becomes difficult to control the rotational speed of the CD-ROM 23 following the displacement of the pit and land formation reference period T. .

Thus, the frequency modulation clock CKF is faithfully reproduced from the CD-ROM 23 in the optical disk device 20. Further, even in a normal CD-ROM player, the frequency modulation clock CKF is faithfully reproduced because these reproduction systems have substantially the same configuration.

When the reproduction clock CK is reproduced in this manner, the optical disk device 20 reproduces the reproduction clock CK.
The binary signal S2 is sequentially latched by K, and the reproduction data D3 is demodulated. The reproduction data D3 is corrected by the data processing circuit 31 to a timing synchronized with the system clock SCK. Further, the data processing circuit 31 receives predetermined data processing and reproduces the user data D1.

Thus, the reproduction system of the reproduction clock CK and the reproduction signal RF in a normal CD-ROM player
Since the processing system has the same configuration as the optical disk device 20, the user data D1 can be correctly reproduced in the same manner as the optical disk device 20. Therefore, this user data D1 is
-R to make a duplicate product. If the bit stream extracted from the process of the data processing circuit 31 is recorded on a CD-R, even if the user data D1 is encrypted, the main data is recorded in the same manner as a CD-ROM. CD-R can be created.

On the other hand, in the optical disc device 20, after the reproduction clock CK is compared in phase with the system clock SCK in the phase comparison circuit 21A, the band is limited by the low-pass filter 21B, so that the frequency deviation in the frequency modulation clock CKF is adjusted. A shift is detected. Further, after the output signal of the low-pass filter 21B is binarized in the subsequent data processing circuit 21C, the clock is reproduced and sequentially latched, whereby the sub data D2 is reproduced. Further, the sub data D2 is the user data D
The reproduction of the CD-ROM 23 is stopped if the contents are compared with the contents of No. 1 and the copy is determined to be illegal.

Thus, in a general CD-R player, the user data D1 is
Although it is possible to record the data D-R, it is difficult to record the sub data D2 by modulating the reference period T, thereby making it possible to record the sub data D2 on the CD-R.
It becomes difficult to duplicate the ROM 23. Further, in such a duplicated CD-ROM, since such sub data D2 cannot be reproduced, the optical disk device 20 can easily detect an illegal duplicate and make it difficult to reproduce.

According to the above configuration, with reference to the frequency modulation clock CKF frequency-modulated by the sub data D2,
By forming a CD-ROM by sequentially exposing the master disc, it is difficult for a normal CD-ROM player to reproduce the sub data and to reproduce the main data.
A D-ROM can be formed. In addition, depending on the recording device of a normal CD-R, the main data can be duplicated, the sub data cannot be easily recorded, and
A D-ROM can be formed. This makes it possible to easily reproduce an illegal copy by reproducing the sub data.

Further, by detecting the change in the frequency of the reproduction clock reproduced from the CD-ROM and reproducing the sub data, it is possible to obtain an optical disk apparatus capable of easily discriminating this kind of illegal duplication. .

(2) Second Embodiment FIG. 3 is a block diagram showing an optical disk device according to a second embodiment of the present invention. In the optical disk device 41, the same components as those of the optical disk device 1 described above with reference to FIG. 1 are denoted by the corresponding reference numerals, and duplicate description will be omitted.

In the optical disc device 41, the pulse width modulation circuit 42 performs pulse width modulation on the modulation signal output from the EFM circuit 14 according to the sub data D4 and outputs the result. Thereby, in the optical disk device 41, the sub data D
The sub data D4 is recorded by changing the ratio between the pit length and the land length according to the data No.

As in the first embodiment, the sub data D4 is obtained by subjecting the text data indicating the copyright of the user data D1, the error correction code of this text data, and the repetition of bit-inverted data to NRZI modulation. It is formed.

Here, in the optical disk device 41, the frequency spectrum of the reproduced signal, which is changed by changing the ratio between the pit length and the land length according to the sub data D2, is mainly
The frequency band higher than the frequency band (10 [Hz]) of the noise component generated by the rotation of the CD-ROM, and the reproducing apparatus can sufficiently cope with the asymmetry changing according to the ratio of the pit length and the land length. The sub-data D4 is set so that the frequency band becomes possible (1 kHz or less), and the modulation degree in the pulse width modulation circuit 42 is set.

Thus, also in this embodiment, in the optical disc apparatus 41, the main data D1
Although the data can be reproduced by the D-ROM player, the sub-data D4 can be reproduced only by a special reproducing device.

FIG. 4 is a block diagram showing an optical disk device for reproducing a CD-ROM created by the optical disk device 41. In FIG. 4, the same components as those of the optical disk device described above with reference to FIG. 2 are denoted by the corresponding reference numerals, and redundant description will be omitted.

In the optical disk device 50, a CD
The ROM 52 is driven to rotate by the spindle motor 22 under the condition of a constant linear velocity, and the reproduction signal RF obtained from the optical pickup 24 is amplified by the amplifier 25. Thereafter, in the optical disk device 50, the reproduction signal RF is binarized by the binarization circuit 26.

As shown in FIG. 5A, the reproduced signal RF
Is that the peak value of the signal level corresponding to the pit and land (particularly in the short period 3T to 6T) changes in accordance with the ratio of the pit length and land length changing in the CD-ROM 52, whereby the asymmetry changes. Will be observed. The binarization circuit 26 sets a slice level SL (FIG. 5B) for binarizing the reproduction signal RF in accordance with the pulsation of the reproduction signal RF in the slice level setting circuit 26A. Further, in the comparison circuit 26B, the reproduction signal RF is sequentially binarized by the slice level SL. Slice level setting circuit 2
6A indicates that the duty ratio of the binarized signal S2 is 50
An asymmetry detection signal whose signal level changes in accordance with the asymmetry of the reproduction signal RF is generated so as to be [%], and this asymmetry detection signal is output as the slice level SL.

In the optical disk device 50, after reproducing the reproduction clock from the binarized signal S2, the binarized signal S2 is sequentially latched to demodulate the reproduction data D3. Thus, the configuration from the optical pickup 24 to the data processing circuit 31 is a normal CD-RO
With the same configuration as the M player, also in this embodiment, the CD-ROM 52 is a normal CD-ROM.
It can be played on the player and may create illegal duplicates.

In the binarizing circuit 51A, the sub reproducing system 51 binarizes the slice level SL with a predetermined slice level SL1 and outputs a binarized signal S5 (FIG. 5C). The data processing circuit 51B outputs the binary signal S5
The clock is reproduced, and the sub data is reproduced by the clock.

According to the above configuration, the same effect as in the first embodiment can be obtained even when the sub data is recorded by changing the ratio between the pit length and the land length.

(3) Other Embodiments In the first embodiment, the phase of the reproduction clock obtained from the reproduction signal and the system clock are compared to detect the displacement of the frequency modulation clock CKF. However, the present invention is not limited to this, and the displacement of the frequency modulation clock CKF may be detected by performing band separation from the phase comparison result of the PLL circuit that reproduces the reproduction clock.

In the second embodiment described above,
Although the case where the ratio of the pit length and the land length is changed by pulse width modulation has been described, the present invention is not limited to this.
The ratio between the pit length and the land length may be changed by changing the amount of the laser beam L.

In the second embodiment described above,
Although the description has been given of the case where the sub data is reproduced from the slice level set by the binarization circuit, the present invention is not limited to this. May be played.

Further, in the above-described embodiment, a case has been described where text data indicating the copyright of the main data is recorded as sub-data. However, the present invention is not limited to this. For example, all or a part of the main data may be recorded. May be encrypted, and the key data for this encryption may be recorded as sub data.

Further, in the above-described embodiment, a case has been described in which the present invention is applied to create and reproduce a CD-ROM. However, the present invention is not limited to this, and a compact disc, a mini disc exclusively for reproduction For example, the present invention can be widely applied to various optical disks and their recording / reproducing devices.

[0074]

As described above, according to the present invention, the reference clock for forming the pits and lands is frequency-modulated, or the ratio of the pit length to the land length is changed, and the data is related to the main data recorded by the pits and lands. By recording additional data, illegal duplication can be easily identified.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an optical disc device according to a first embodiment of the present invention.

FIG. 2 shows a CD-ROM created by the optical disk device of FIG.
FIG. 2 is a block diagram illustrating an optical disk device that plays a ROM.

FIG. 3 is a block diagram illustrating an optical disc device according to a second embodiment of the present invention.

FIG. 4 shows a CD-ROM created by the optical disk device of FIG.
FIG. 2 is a block diagram illustrating an optical disk device that plays a ROM.

FIG. 5 is a signal waveform diagram for explaining the operation of the optical disc device of FIG. 4;

[Explanation of symbols]

1, 20, 41, 50 ... optical disk device, 2 ... disk master, 4, 22 ... spindle motor, 5, 29 ...
... Spindle servo circuit, 8 ... Optical modulator, 13, 21
C, 31, 51B: data processing circuit, 15: frequency modulation circuit, 21: auxiliary reproduction system, 21A, 28A: phase comparison circuit, 21B, 28B: low-pass filter, 2
3 ... CD-ROM, 26, 51A ... Binarization circuit, 2
6A: slice level setting circuit, 26B: comparison circuit, 28: PLL circuit, 28C: voltage-controlled oscillation circuit, 42: pulse width modulation circuit

Claims (6)

[Claims] 1. An optical disk in which pits and lands are repeatedly formed on a disk-shaped recording medium in units of a predetermined reference period, and main data is recorded by the pits and lands. An optical disc on which sub-data related to said data is recorded. 2. An optical disk in which pits and lands are repeatedly formed on a disk-shaped recording medium in units of a predetermined reference period, and the main data is recorded by the pits and lands. An optical disc characterized by recording sub-data related to said main data by changing. 3. A modulating means for generating a modulation signal whose signal level switches in accordance with main data in synchronization with a predetermined reference clock; An optical disc device, comprising: a light modulating unit that irradiates a disc-shaped recording medium with light; and a frequency modulating unit that shifts the frequency of the reference clock in accordance with sub data related to the main data. 4. Modulation means for generating a modulation signal whose signal level switches in accordance with main data in synchronization with a predetermined reference clock; and controlling the on / off of the laser beam in accordance with the modulation signal to produce a laser beam. Irradiating the disk-shaped recording medium with the light modulation means for sequentially forming pits and lands on the disk-shaped recording medium; and adjusting the ratio of the lengths of the pits and lands according to the sub data related to the main data. An optical disk device, comprising: a pit length modulation means for changing the pit length. 5. An optical disk apparatus for reproducing an optical disk in which pits and lands are repeatedly formed in units of a predetermined reference period, wherein the optical disk is irradiated with a laser beam to receive return light, and the amount of return light A reproducing means for outputting a reproduced signal whose signal level changes in accordance with the change of the signal; and a binarized signal obtained by binarizing the reproduced signal, and repeating the pits and lands on the optical disc based on the binarized signal. A main data reproducing means for reproducing recorded main data; a period detection signal whose signal level changes in accordance with a displacement of the reference period from the binarized signal; and the reference period from the period detection signal. And an auxiliary data reproducing means for reproducing sub data recorded on the optical disk by frequency-modulating the data. 6. An optical disk apparatus for reproducing an optical disk in which pits and lands are repeatedly formed in units of a predetermined reference period, wherein the optical disk is irradiated with a laser beam to receive return light, and the amount of return light A reproduction means for outputting a reproduction signal whose signal level changes in accordance with the change of the data; a main data reproduction means for reproducing main data recorded on the optical disk by repeating the pits and lands from the reproduction signal; An asymmetry detection signal whose signal level changes in accordance with the asymmetry of the reproduction signal is generated. From the asymmetry detection signal, the sub data recorded on the optical disk is reproduced by changing the ratio of the pit and land lengths. An optical disc device comprising: a sub data reproducing unit.