JP2822859B2 - Optical disk recording medium and method for correcting reproduced information signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording medium, and more particularly to an optical disk recording medium capable of performing tracking control and constant linear velocity recording even if the track density is reduced in order to increase the recording density, and the reproduction information signal of the optical disk recording medium. It relates to a correction method.

[0002]

2. Description of the Related Art Generally, currently available CDs and LDs are commercially available.
And the like, the read-only optical disk has a track pitch of about 0.5 microns along a spiral track of about 1.6 microns.
Pits on the order of microns are recorded as information by changes in irregularities. Also, a write-once type that can be written once,
In a rewritable optical disk, a spiral guide groove is similarly formed at a track pitch of about 1.6 μm, and information is recorded in or between the guide grooves to form a track.

Recently, there has been an increasing demand for smaller recording media and higher image quality, and an improvement in recording density has been desired.
In order to improve the recording density, researches and developments on shortening the laser wavelength used for recording and reproduction, increasing the NA (aperture) of the lens, and the like have been made. However, development of a short-wavelength blue laser is difficult at the present stage, and its appearance is expected in the 21st century, and if a high NA lens is used, the precision of a disk used will be severe. Another method for increasing the recording density is to increase the track density.

[0004]

However, when the track density is increased, the amplitude of the tracking error signal becomes smaller, the influence of the track pitch unevenness becomes larger, and the tracking servo becomes unstable. In addition, there is a problem that crosstalk between adjacent tracks increases. As a countermeasure against the crosstalk, a method of reducing crosstalk between adjacent tracks by performing multi-beam reproduction has been proposed (Japanese Patent Laid-Open No. 232118/1991). However, this method is not preferable because the apparatus becomes complicated.

As another means for reducing the track density, a technique for recording information in both tracking guide grooves (grooves) and between guide grooves (lands) has been proposed (Japanese Patent Laid-Open Publication No. 59-1984).
-139147). Also, the groove depth is λ
/ 5, it is possible to reduce the crosstalk of the adjacent track even if information is recorded in both the groove portion and the land portion (1992 Japan Society of Applied Physics (Autumn) 18a-T-3) Etc. have been proposed. However, these methods also have problems such as unstable tracking servo.

In the field of MD (mini-disc), as a means for increasing the recording density, a synchronization signal is embedded in a disc by pits (concavities and convexities) or wobbles (guide grooves meandering) and rotated. When driving, the rotation is controlled so that the rotation reference signal and the disk synchronization signal are synchronized, and the linear velocity is kept constant.
LV (Constant Linear Veloci)
ty) Recording is being performed.

FIG. 26 shows a plan view of a conventional disk of this type. A spiral guide groove 2 is formed on the surface of the disk 1, and the guide groove 2 27 and 28, wobbling so as to meander based on address information and the like. In this case, the track pitch L1 is, for example, 1.6 μm
The wobbling amplitude L2 is set to, for example, 0.
It is set to about 06 μm, and the FM modulation carrier frequency of wobbling is constant. Wobbling here
Bling) is a technique employed in a write-once CD (CD-R) or a rewritable mini-disc (MD). The guide groove is slightly meandered, and a simultaneous signal of absolute time (or address) and CLV is simultaneously transmitted. Is to be embedded. For example, address data such as absolute time is frequency-modulated (FM), and the guide groove is slightly meandered by the signal. When recording with a drive, the error signal of the tracking servo includes an FM signal corresponding to the meandering of the guide groove. This is extracted by a band-pass filter or the like, and the FM carrier (the center frequency of the FM) is set to the CLV. The FM is demodulated to read the absolute time (or address). For CD-R and MD, a frequency that does not affect the tracking servo and data is selected as the FM of 22.05 KHz ± 1 KHz.

In order to increase the recording density, it is conceivable to record information in both the guide grooves (grooves) and between the guide grooves (lands) of the disk employing the wobbling as the guide grooves. In this case, as shown on the left side of FIG. 21, when tracing between the guide grooves, that is, the lands 3, the wobble signal 4 is output when the vibrations of the guide grooves 2 on both sides of the land 3 to be traced match. However, if the vibrations of the grooves 2 on both sides of the traced land portion 3 do not match as shown in the right part of FIG. 21, the phases of the wobble signals on both sides are shifted, and in particular, 180
When the phase is shifted by ° C., the amplitude of the wobble signal 4 becomes zero, so that address information and the like cannot be read, and there is a problem that CLV recording cannot be performed.

The present invention focuses on the above problems,
The purpose of this invention is to solve this problem effectively. The purpose is to record information in both the guide grooves and between the guide grooves, and to properly extract the wobble signal. It is to provide a correction method.

[0010]

According to a first aspect of the present invention, there is provided an optical disc recording medium for recording information or having a spiral guide groove on which information is recorded. The first and second FM are displaced in the groove width direction in accordance with the first or second FM modulated signal of two kinds of carrier frequencies and are modulated every rotation.
The modulation signal can be switched.

[0011]

According to a third aspect of the present invention, there is provided an optical disc recording medium having a spiral guide groove on which information is recorded or information is recorded, wherein one edge of the guide groove is provided. Is displaced in the groove width direction with the maximum amplitude smaller than the track pitch in accordance with the FM modulation signal FM-modulated at the predetermined carrier frequency, and the other edge of the guide groove is not displaced, or When reproducing an information signal from an optical disc recording medium displaced in the groove width direction with a maximum amplitude smaller than the track pitch in response to a different predetermined single frequency signal, the width of the guide groove or the width between the guide grooves fluctuates. In order to suppress the fluctuation of the amplitude of the reproduced information signal caused by the above, the sum or difference of the displacement signals extracted from the tracking error signal is calculated. And by forming an amplitude correction signal, which is constituted so as to correct the reproduced information signal based on the amplitude correction signal.

[0013]

According to the first aspect of the present invention, the guide groove is displaced in the groove width direction by the first and second FM modulation signals switched every one rotation, so that even when tracing between the guide grooves, The wobble signal can be extracted, and the polarity of the tracking servo is switched by extracting the information of the pit row to select the recording of the guide groove or the recording between the guide grooves.

[0014]

[0015] According to the third aspect of the present invention, the first issued the above-mentioned Akira
When reproducing information signals from an optical disk recording medium by, by the amplitude correction signal formed by taking the sum or difference between the displacement signal extracted from the tracking error signal, the amplitude variation since to correct the reproduced information signal Can be suppressed, and the information signal can be reproduced stably.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical disk recording medium according to the present invention will be described below with reference to the accompanying drawings. First, the optical disk recording medium of the first invention will be described. FIG. 1 is a partial cross-sectional perspective view showing an optical disc recording medium according to the first invention, FIG. 2 is a plan view for explaining a wobbling state of a guide groove of the recording medium shown in FIG. 1, and FIG. 3 is a guide shown in FIG. FIG. 4 is a plan view showing the switching portion of the wobble carrier in the groove, and FIG. 4 is a block diagram for generating a wobble signal when forming the guide groove of the recording medium shown in FIG.

As shown in the figure, the guide groove 5 of the optical disk recording medium is spirally formed on the disk surface as shown in FIG. 26, and the width L3 of the guide groove 5 is, for example, about 0.8 μm. The pitch L4 of the guide grooves 5 is set to, for example, about 1.6 μm, and the depth T of the guide grooves 5 is
For example, it is set to about 0.07 μm. Accordingly, a spiral guide groove (land portion) 13 having a convex cross section is formed between the adjacent guide grooves 5.

Particularly, in this embodiment, the guide groove 5
Are displaced in a meandering manner in the groove width direction, that is, wobbled, the first guide groove 5A and the second guide groove which are displaced in the groove width direction according to the FM-modulated first and second FM modulation signals having different carrier frequencies. The first and second guide grooves 5A and 5B are alternately formed every rotation (every round of the disk). A pit row 6 in which information pits for notifying the switching of the carrier frequency are arranged at the switching portions of the first and second guide grooves 5A and 5B as shown in FIG. I have.

A wobble signal for producing a master for forming such an optical disk recording medium is generated as shown in a block diagram of FIG. That is, the first carrier signal S1 having the frequency f1 is input to the first FM modulator 7, and a part of the first carrier signal S1 is frequency-divided into, for example, １ ／ through the frequency divider 8. To generate a second carrier signal S2 having a frequency f2, and the second carrier signal S2 is input to the second FM modulator 9.

On the other hand, the address information data S3 is bi-phase modulated by the digital modulator 10, and the modulated signal is input to the first and second FM modulators 7 and 9, respectively, and the first and second FM modulators 7 and 9 respectively have the frequency f1 ± ΔF. And a second FM modulation signal S5 having a frequency f2 ± ΔF. Note that ΔF indicates the deviation of the FM modulation signal.

These first and second FM modulated signals S4,
Each of the signals S5 is input to a switch section 11 composed of, for example, a semiconductor switch, selectively switched by the switch section 11, and output as a wobble signal S6.
The switching of the switch unit 11 is performed by applying a switching signal S7 for outputting one pulse per one rotation of the disk to the switch unit 11 via the switching circuit 11, and thereby, as described above, every one rotation of the disk. The guide grooves 5A and 5B in which the FM modulation signal is switched are formed alternately.

Next, recording / reproduction of the optical disk recording medium configured as described above will be described. In this embodiment, information is recorded not only in the guide grooves 5 of the recording medium but also between the guide grooves (lands) 13 to reduce the track density. FIG. 5 shows a block circuit for reading address information and performing CLV control for recording / reproducing the recording medium.

That is, the tracking error signal S7 obtained by driving the recording medium is branched into two, and they are passed through a first band-pass filter 14 having a frequency f1 and a second band-pass filter 15 having a frequency f2. Then, a first FM modulation signal S8 having a frequency f1 ± ΔF and a second FM modulation signal S9 having a frequency f2 ± ΔF are output. The first FM modulated signal S8 is the first FM modulated signal S8.
The output is input to the demodulation unit 16 and the output is input to the address discrimination unit 18 via the first digital demodulation unit 17.
The second FM modulation signal S9 is input to the second FM demodulation unit 19, and the output is input to the address discrimination unit 18 via the second digital demodulation unit 20. This address discriminator 1
Numeral 8 outputs address data S10 indicating a track number or the like based on the input signals from both demodulators 17 and 20.

On the other hand, the first and second FM demodulation sections 16, 1
9 are partially output from the first carrier extraction unit 21 respectively.
And the second carrier extraction unit 22 to extract each carrier frequency. The output of the first carrier extracting unit 21 is input to a switch unit 23 composed of, for example, a semiconductor switch, and the output of the second carrier extracting unit 22 is switched via a multiplier 24 for doubling the frequency. Input to the unit 23.

The output signal from each of the extraction units 21 and 23 is selectively switched from the switch unit 23, and is output as a spindle signal S11.
5, and a CLV control of a disk drive motor (not shown) is performed based on the servo reference signal S12 input from the controller 5 and an encoder (not shown).

On the other hand, in order to switch the switch section 23, the high frequency reproduction signal S13
The output is input to the switch unit 23 as the switching signal S14.

Now, based on such a block diagram,
When recording / reproduction is performed, the wobble signal is included in the tracking error signal, and the first guide groove 5A of the recording medium is provided.
When tracing (carrier frequency f1 = 2 · f2), the first band-pass filter (BPF) 14 outputs the first FM modulated signal, and the second band-pass filter (BPF) 15 outputs And the second guide groove 5
When tracing B (carrier frequency f2), the first
No output is output from the band-pass filter 14, and a second FM modulated signal is output from the second band-pass filter 15. Then, the center frequency of each of these carrier frequencies is used for CLV control.

Further, between the guide grooves (land portions) 1 of the recording medium 1
When tracing No. 3, since the carrier frequencies of the guide grooves at both ends of the land portion are picked up, the wobble signal is superimposed on the first carrier frequency f1 and the second carrier frequency f2. A first FM modulation signal and a second FM modulation signal are output from the first and second band pass filters 14 and 15, respectively, and these are used for CLV control.

FIG. 6 shows the amplitude of the wobble signal and the output of each band-pass filter at the time of tracing the land 13. FIG. 6A shows the displacement state of the land portion, and FIG. 6B shows the amplitude of the wobble signal corresponding thereto. This wobble signal has a waveform obtained by superimposing the first FM modulation signal and the second FM modulation signal as described above. Then, the output of the first band-pass filter (FIG. 6D) and the output of the second band-pass filter (FIG. 6C) through the wobble signal are the first FM modulated signal and the second FM signal, respectively. Of the FM modulation signal.

FIG. 7 shows the spectrum of a wobble signal during such a series of recording and reproduction. FIG. 7 (A)
Shows the spectrum when the first guide groove 5A is traced, and shows the amplitude value of the wobble signal at the first carrier frequency f1, and FIG. 7 (B) traces the second guide groove 5B. Shows the spectrum at the time of
The amplitude value of the wobble signal appears at the second carrier frequency f2. FIG. 7C shows a spectrum when the land portion, that is, the space 13 between the guide grooves is traced, and the amplitude value of the wobble signal appears at the first carrier frequency f1 and the second carrier frequency f2. I have.

Further, as the tracing is performed, pit information indicating the switching of the carrier frequency is read from the pit row 6 each time the disk makes one rotation, and a groove (guide groove) is switched by switching the polarity of the tracking servo. ) Recording or land recording is selected.

FIG. 8 shows the switching state of the carrier frequency. That is, FIGS. 8A and 8C show a state where the first carrier frequency f1 is switched to the second carrier frequency f2, and FIG. 8B shows a state where the second carrier frequency f2 is switched to the first carrier frequency. The state of switching to f1 is shown. As shown in the figure, since the first carrier frequency f1 and the second carrier frequency f2 are synchronized, the phase shifts stably even after switching regardless of where the pit portion is located. Therefore, the address information can be read stably. The address information (track number, etc.) of the land portion is determined by reading both address information of the adjacent grooves. For example, the track No. 1000 and No. 1002, the value between these, No. It is determined as 1001.

As described above, two different types of FM modulation signals are switched for each rotation so that the guide groove 5 is displaced in the groove width direction. Therefore, CLV recording is performed in both the guide groove 5 and the guide groove 13. As a result, the wobble signal can be stably taken out. In the above embodiment, the pit rows 6 are formed only in the guide grooves 5, but as shown in FIG. 9, a large number of pit rows 6A are provided between the guide grooves (lands) 13 so that this portion is formed. A partial ROM may be used to enable CLV recording.

Next, the optical disk recording medium of the second invention will be described. 10 is a partial cross-sectional perspective view showing an optical disk recording medium according to the second invention, FIG. 11 is a plan view for explaining a wobbling state of a guide groove of the recording medium shown in FIG. 10, and FIG. FIG. 13 is a block diagram for generating a wobble signal when forming a guide groove of a medium.
FIG. 1 is a waveform diagram of signals at various parts in the block diagram shown in FIG.
FIG. 4 is a diagram showing a trajectory of a laser beam and a guide groove formed when an optical disc master is produced.

The guide groove 27 of this optical disk recording medium is also spirally formed on the disk surface, as shown in FIG. The width L3, pitch L4, and depth T of the guide groove 27 are each set to 0.8 in the same manner as in the first embodiment.
μm, 1.6 μm and about 0.07 μm. Accordingly, a spiral guide groove (land portion) 29 having a convex cross section is formed between the adjacent guide grooves 27.

Particularly, in this embodiment, the guide groove 27 is used.
Is displaced in a meandering manner in the groove width direction, that is, wobbled by the first and second FM modulation signals having two different carrier frequencies. Specifically, the guide groove 27
One edge 28A is displaced in a meandering manner by a high frequency first FM modulation signal, and the other edge 28B is meandering by a low frequency, for example, half frequency, second FM modulation signal. Has been displaced. In this case, the maximum amplitude of the displacement is set to be smaller than the track pitch, and is preferably set to, for example, about 1 to 10% of the track pitch.

A wobble signal for producing a master for forming such an optical disk recording medium is generated as shown in the block diagram of FIG. That is, the frequency f
The first carrier signal S15 is input to the first FM modulation unit 30, and a part of the first carrier signal S15 is frequency-divided by, for example, し て through a frequency divider 31 to obtain a second frequency having a frequency f2. A second carrier signal S16 is generated and input to the second FM modulator 32.

On the other hand, the first address information data S17 is bi-phase modulated by the first digital modulator 33, and the modulated signal is input to the first FM modulator 30.
The first FM modulation signal S18 having a frequency f1 ± ΔF is output. The second address information data S19 is modulated by the second digital modulator 34, and the modulated signal is
Of the frequency f2 ± ΔF
Is output. The signal S1 at this time
8, the waveforms of S20 are shown in FIG.

Then, the first FM modulated signal S18 modulated with the first address information is supplied to the first AM amplitude modulator 3
5, an AM carrier signal S21 of, for example, 10 MHz or more.
A first amplitude modulation signal S that is amplitude-modulated and output
Reference numeral 22 denotes a first half-wave rectified signal S in a first half-wave rectifier 36.
23 is obtained. These signals S22 and S23 are shown in FIG.

The second FM modulated signal S20 modulated with the second address information is supplied to a second AM amplitude modulator 37.
Then, the second amplitude modulated signal S24 that is amplitude-modulated by the AM carrier signal S21 and output is obtained by the second half-wave rectification unit 38 to obtain a second half-wave rectified signal S25. These signals S24 and S25 are shown in FIG.

The half-wave rectified signals S23, S25
Is inverted, and these two signals are added by an adder 39 to obtain a wobble signal S26. After the signal S26 is amplified by the amplifier 40, it is supplied to the deflector 41, and the exposure beam is deflected with a small amplitude in a direction perpendicular to the track direction of the rotating recording surface of the disk, as shown in FIG.
A guide groove as shown in FIG. FIG. 14A shows a situation where the laser beam 42 oscillates along a trajectory 44 to irradiate the exposure region 43, and FIG.
9A shows a guide groove 27 formed by the operation shown in FIG. 9A. The frequency of one edge 28A is high and the other edge 2A is high.
The frequency of 8B is low, and each has a slight swell of amplitude ΔL. In FIG. 14, the amplitude .DELTA.L of the very small undulation at the edge of the guide groove is suppressed as the linear velocity at the time of recording the master is lower or as the amplitude modulation carrier frequency is higher. For example, if the linear velocity is 1 m / sec and the wobble amplitude is 30
In the case of forming a guide groove having a groove width of 0.8 μm in nm, if the amplitude modulation carrier frequency is 10 MHz, the amplitude of the minute undulation is about 3 nm, and the influence on the reading of the wobble signal is very small. .

Next, recording / reproduction of the optical disk recording medium configured as described above will be described. Also in this embodiment, similarly to the first aspect of the invention, information is recorded not only in the guide grooves 27 but also between the guide grooves (lands) 29 to increase the track density.

FIG. 1 is a block diagram of reading address information and CLV control for recording / reproducing the recording medium.
It is shown in FIG. That is, the tracking error signal S7 obtained by driving the recording medium is branched into two, and they are divided into the first bandpass filter 14 having the frequency f1 and the second bandpass filter 1 having the frequency f2.
5 to output a first FM modulated signal S8 having a frequency f1 ± ΔF and a second FM modulated signal S9 having a frequency f2 ± ΔF.

The first FM modulated signal S8 is split into two, one of which is input to the first FM demodulation unit 16, and the output of which is input to the switch unit 45, for example, a semiconductor switch. On the other hand, the second FM modulation signal S9 is branched into two, one of which is input to the second FM demodulation unit 19, and the output of which is input to the switch unit 45. The outputs from the two demodulation units 16 and 19 are selectively switched by the switch unit 45 and output, and output as address data S10 via the digital demodulation unit 46 and the address reading unit 47.

On the other hand, a part of the output of the first FM demodulation section 16 is reduced to half the frequency f2 by way of the frequency divider 48 for reducing the frequency f1 to 例 え ば, for example, and is input to the switch section 23. On the other hand, part of the output of the second FM demodulation unit 19 is input to the switch unit 23 with the frequency f2, and is selectively output by the switch unit 23. This output signal is used as the spindle signal S11 as the spindle C
The disk drive motor (not shown) is CLV-controlled based on a servo reference signal S12 input to the LV servo 25 and input from an encoder or the like (not shown).

On the other hand, the switches 23 and 45 are appropriately switched by a switching signal S27 indicating recording / reproducing of a groove (guide groove) or recording / reproducing of a land (guide groove). Further, the first FM modulation signal S8 and the second FM
The branched signal of the modulation signal S9 is input to a first amplitude detection unit 49 and a second amplitude detection unit 50, respectively, and each output is differentially obtained by a differential amplifier 51 to obtain a tracking DC offset correction signal. It will be output as S28.

When recording / reproducing is performed based on such a block diagram, as shown in FIG. 16A, the laser beam 52 is applied to the guide grooves 27 or between the guide grooves (land portions).
When the trace 29 is traced, the tracking error signal S7 includes two types of wobble signals having different carrier frequencies as shown in FIG. The spectrum of the wobble signal at this time is shown in FIG.
The amplitude value appears at 1, f2.

The tracking error signal S7 is branched into two and the first and second band pass filters 14 and 15
16C, a first FM modulated signal S8 having a frequency f1 shown in FIG. 16C and a second FM modulated signal S9 having a frequency f2 shown in FIG. 16D are output. Are separated.

Each of these wobble signals is demodulated and selectively taken out by the switch unit 45. For example, at the time of recording / reproducing on a land portion, address data obtained by demodulating an FM signal modulated at a frequency f1 is used. Guide groove) FM modulated at frequency f2 during recording and reproduction
The address data obtained by demodulating the signal is used. This allows
Address data corresponding to each of the groove and the land can be read. In this case, switching between groove recording and land portion recording is performed by switching the polarity of the tracking servo.

As another method of reading an address corresponding to each of the groove and the land, it is also possible to use an FM modulation signal modulated at the frequency f1 as the address of the groove and the land. That is, 28 shown in FIG.
Even if the groove and the land adjacent to the wobbling of A have the same address, the groove or the land can be distinguished by selecting the polarity of the tracking servo, so that the address can be shared. Further, the wobbling of 28B may not be modulated and may be a single frequency of f2. Alternatively, if the wobbling is not used for the DC offset correction of the tracking servo, the 28B wobbling may be omitted.

When the laser beam 52 traces the center of the track, the amplitudes of the outputs from the first and second band-pass filters 14 and 15 become equal. By comparing and outputting the signals by the differential amplifier 51, the signals can be used as a tracking DC offset correction signal. Therefore, for example, the DC offset of the tracking error by the push-pull method can be corrected, so that stable tracking can be performed.

As described above, according to this embodiment, the opposite edges of the guide grooves are modulated with different address information and wobbled at different FM carrier frequencies, so that not only the guide grooves but also the guide grooves ( When tracing the land, the wobble signal modulated by the address information can be detected, and the track density can be increased.

Next, a method of correcting a reproduced information signal according to the third invention will be described. This correction method is mainly performed when reproducing the information signal of the optical disk recording medium according to the second invention.

FIG. 18 is a schematic top view of the guide groove wobble of the optical disk recording medium of the second invention and a relation diagram showing a relationship between a groove width change and a reproduction signal amplitude fluctuation. FIG. 19 shows a conventional automatic threshold control circuit. FIG. 20 is a waveform diagram for explaining the responsiveness of the automatic threshold control circuit shown in FIG. 19, FIG. 21 is a block diagram showing a correction circuit for the reproduction information signal, and FIG.
2 is a block diagram showing a sampling pulse generating circuit in the circuit shown in FIG. 21, and FIG. 23 is a block diagram showing an amplitude fluctuation detecting circuit in the circuit shown in FIG.

The optical disc recording medium according to the second invention shown in FIGS. 10 and 11 has a common address in both the guide groove 27 and the guide groove (land portion) 29. While recording is possible, the amplitude of the reproduced information signal fluctuates at a frequency of about 100 KHz according to the change in the guide groove width or the width between the guide grooves when reproducing the recorded information, and adversely affects the reproduced signal. Become. That is,
FIG. 18A is a schematic top view of a guide groove of the optical disk recording medium shown in FIGS.
The first wobble having a low frequency of B is shown at the lower edge 2 in the figure.
A second wobble having a higher frequency of 8A is shown. The guide groove width L3 is set to 0.8 μm, and the maximum to maximum (PP) displacement of each wobble is about 60 nm. The upper and lower envelopes of the reproduced information signal at this time are respectively shown in FIG.
8 (B), and the difference signal (first wobble signal-second wobble signal) has a waveform as shown in FIG. 18 (C), which indicates a change in groove width. . Such a change in the groove width causes a change in the reproduced information signal as described above.

In general, when a modulated signal in which the time ratios of the high level and the low level of a digital signal per unit time are substantially equal to each other is recorded by PWM (pulse width modulation), the DC component is included in the reproduced signal output. , The original digital information can be obtained by zero-level comparison using a level comparator. However, if the reproduced signal output has an amplitude fluctuation, accurate original digital information cannot be obtained. For example, as shown in FIG. 19, an automatic threshold control circuit (see Japanese Patent Publication No. 3-21993) is used. . That is, the DC component contained in the output of the waveform shaping level comparator 60 is detected by the integrator 61, an output corresponding to the DC component is obtained by the differential amplifier 62, and this output is compared with the level comparator 60. The level is set as a threshold. As a result, when the DC component included in the output of the level comparator 60 increases in the positive direction, the time ratio of the high level of the reproduction input becomes large, so that the level comparator 6
If the threshold value of 0 is increased accordingly, the time ratio between the high level and the low level becomes substantially equal.

However, in this method, as in the envelope of the reproduced information signal shown in FIG. 20 (A), the threshold value changes in accordance with the correction of the amplitude fluctuation of the low frequency of 1 KHz or less, and good correction can be performed. As shown in FIG. 20B, in the case of an amplitude fluctuation of a high frequency of about 100 KHz, for example, like an envelope of an information signal reproduced from the recording medium of the present invention, the threshold value cannot follow and change, It cannot be corrected. Therefore, the correction method according to the present invention is used.

First, a description will be given of a circuit for correcting an amplitude fluctuation of a reproduction information signal for implementing the correction method according to the present invention. Here, the guide groove 27 (see FIGS. 10 and 11)
One edge 28A of the guide groove is displaced in the groove width direction with a maximum amplitude smaller than the track pitch in accordance with an FM modulation signal frequency-modulated at a predetermined carrier frequency, for example, frequency 117 KHz and deviation ± 5 KHz. The other edge portion 28B has a maximum amplitude smaller than the track pitch in the groove width direction according to a non-modulated single frequency signal different from the predetermined carrier frequency, for example, a frequency 78 KHz that is 2/3 of the carrier frequency. An embodiment for reproducing an information signal recorded on a displaced optical disk recording medium will be described.

First, the tracking error signal S30 is
The first wobble (78 KHz) and the second wobble (1
17 KHz) to detect the first BPF, respectively.
(Band pass filter) 63 and the second BPF 64 are input, and the respective outputs are connected to the first subtractor 65. The subtractor 65 outputs an amplitude correction signal S31. This output is commonly connected to each input of a gain control amplifier 66 and a sampling pulse generating circuit 67. The output of this amplifier 66 is Connected to one input and the other input of the second subtractor 68 is
The output of the delay element 69 for delaying the reproduction information signal is connected, and the second subtracter 68 outputs the reproduction information signal S32 whose amplitude fluctuation has been corrected.

On the other hand, the reproduced information signal S3 after the amplitude change
2 is fed back and input to the amplitude fluctuation detecting circuit 70, and the sampling pulse signal S33 from the sampling pulse generating circuit 67 is supplied to the detecting circuit 70.
Is also entered. The output of the detection circuit 70 is connected to the-terminal of a first differential amplifier 71 whose + terminal is grounded, and the output of this amplifier 71 is connected to the gain control amplifier 66.
, And transmits an amplitude fluctuation correction error signal S34.

On the other hand, the sampling generation circuit 67 is configured as shown in FIG.
31 is input to the input of the peak hold unit 72 and the + terminal of the second differential amplifier 73, and the output of the peak hold unit 72 is grounded via a series circuit of the resistors R1 and R2. The connection point of these two resistors R1 and R2 is connected to the minus terminal of the second differential amplifier 73,
The second differential amplifier 73 outputs a sampling pulse signal S33.

On the other hand, the amplitude fluctuation detecting circuit unit 70
3 and specifically, the reproduced information signal after the amplitude fluctuation correction fed back is connected to the respective inputs of the upper envelope detector 74 and the lower envelope detector 75. The outputs of the detectors 74 and 75 are input to the first adder 76, respectively, and the sum of the upper envelope signal S35 and the lower envelope signal S36, which are the output signals, is obtained. After the output of the first adder 76 is input to the attenuator 77, an amplitude fluctuation signal S37 of the reproduction information signal is output.
At 8, the timing is held at the timing of the sampling pulse signal S33. The output of the sample hold unit 78 is connected to the input of the integrator 79, and transmits the sample hold signal S38. The output of the integrator 79 is connected to the negative terminal of the first differential amplifier 71.

Next, an example of the method of the present invention, which is performed using the circuit configured as described above, will be described. FIG. 24 shows FIG.
FIG. 25 is a waveform chart showing the waveform of each signal in FIGS. 1 to 23, and FIG. 25 is a graph showing the relationship between the amplitude fluctuation correction error signal and the correction signal gain in the amplitude fluctuation detection circuit.

First, by inputting the tracking error signal S30 to the first and second BPFs 63 and 64,
The first BPF 63 extracts a first wobble signal due to the displacement of one edge of the guide groove, and the second BPF 64 extracts a second wobble signal due to the displacement of the other edge of the guide groove. Here, the first wobble is a 78 KHz single frequency signal, and the second wobble is 117 KHz ± 5.
Each is reproduced by an FM signal of KHz. The difference between these two wobble signals is obtained by a first subtractor 65, and an amplitude correction signal S31 (see FIG. 24A) is output. The signal of the difference between the first wobble and the second wobble corresponds to the amount of change in the guide groove width or the guide groove width. Each BPF is designed so that the delay time of each wobble signal obtained by the first and second BPFs 63 and 64 is equal to an integer multiple (1 to 3) of each wobble signal period. If unavoidable, use delay element 6
9, the reproduction information signal S29 is delayed, and the time axis is adjusted so that the difference signal between the respective wobble signals, that is, the amplitude correction signal S31 matches the phase of the amplitude fluctuation (envelope) caused by the wobble of the reproduction information signal S29.

The amplitude of the amplitude correction signal S31, which is the difference signal between the wobble signals, is automatically adjusted to an appropriate amplitude by the gain control amplifier 66 based on the gain determined by the amplitude fluctuation correction error signal S34 input thereto. The amplitude correction signal set to an appropriate amplitude and the reproduction information signal S after delay
The difference from the signal 29 is obtained by the second subtractor 68 to correct the amplitude fluctuation of this signal, and the reproduced information signal S32 (see FIG. 24C) after the amplitude fluctuation correction is output. Thereby, it is possible to obtain the reproduction information signal S32 in which the amplitude fluctuation is suppressed. FIG. 24C shows the reproduced information signal S32 when the amplitude fluctuation is insufficient.

Here, a method for setting the amplitude of the amplitude correction signal S31 to the optimum signal will be described. The reproduced information signal S32 after the amplitude fluctuation correction is fed back to the upper and lower envelope detectors of the amplitude fluctuation detection circuit 70. At 74 and 75, the upper envelope signal S35 and the lower envelope signal S
24 (see FIG. 24 (C)), and the sum is obtained by adding each of the envelope signals S35 and S36 by the first adder 76, and then the attenuator 77 sets the amplitude to 1 /
2, and the amplitude fluctuation signal S37 is detected. The waveform of the signal S37 is shown in FIG. 24 (D) by being classified into various modes, that is, when correction is insufficient, when correction is appropriate, and when correction is excessive.

On the other hand, as is apparent from FIG. 24D, the phase of the obtained amplitude fluctuation signal S37 is inverted when the amplitude fluctuation correction is insufficient and when the amplitude fluctuation correction is excessive. Therefore, in the sampling pulse generation circuit 67 shown in FIG.
A sampling pulse signal S33 corresponding to the maximum position of the amplitude of the amplitude correction signal S31 is generated. That is, the peak value of the amplitude correction signal S31, which is a difference signal between the first wobble signal and the second wobble signal, is held by the peak hold unit 72, and the obtained value is proportionally divided by the values of the resistors R1 and R2. 24 is compared with the amplitude correction signal S31 by the second differential amplifier 73 to obtain FIG.
A sampling pulse signal S33 as shown in FIG. By this signal S33, the sample hold unit 78
The amplitude fluctuation signal S37 can be sampled and held at the position where the guide groove width or the guide groove width is maximum,
The value at this time is the sample hold signal S38 (FIG. 24).
(See (D)). Then, the sample hold signal S38 is integrated by the integrator 79 to obtain an amplitude fluctuation correction error signal S34 that can be negatively feedback-controlled as shown in FIG. Then, based on the amplitude fluctuation correction error signal S34, the amplitude of the amplitude correction signal S31, which is the difference signal between the wobble signals, is calculated by the gain control amplifier 66.
As described above, it is possible to automatically control the reproduction information signal so as to minimize the fluctuation in amplitude. That is, the gain of the gain control amplifier 66 is determined based on the value of the amplitude fluctuation correction error signal S34 based on the graph shown in FIG. 25, and the reproduced information signal S32 in which the amplitude fluctuation is suppressed can be finally obtained.

As described above, a change in the width of the guide groove or the width between the guide grooves causes the amplitude fluctuation of the reproduced information signal to be disturbed. However, according to the present invention, the amplitude of the reproduced information signal fluctuates at a high frequency. Therefore, the original information signal can be accurately reproduced from the optical disk recording medium on which high-density recording has been performed, because the amplitude fluctuation can be greatly suppressed.

[0069]

As described above, according to the optical disk recording medium of the present invention, the following excellent functions and effects can be exhibited. According to the first aspect, since the guide groove is displaced in the groove width direction by two different types of FM modulation signals for each rotation, a wobble signal can be taken out even when tracing between the guide grooves. CLV control
Ru can be stably performed by the high-density recording. According to the third aspect, the amplitude correction signal is obtained from the tracking error signal, and the reproduced information signal is corrected using the amplitude correction signal. From which the original information signal can be obtained accurately.

[Brief description of the drawings]

FIG. 1 is a partial sectional perspective view showing an optical disk recording medium according to a first invention.

FIG. 2 is a plan view for explaining a wobbling state of a guide groove of the recording medium shown in FIG.

FIG. 3 is a plan view showing a switching portion of a wobble carrier in a guide groove shown in FIG. 2;

FIG. 4 is a block diagram for generating a wobble signal when a guide groove of the recording medium shown in FIG. 1 is formed.

FIG. 5 is a block circuit diagram of reading of address information and CLV control for performing recording / reproduction on the recording medium shown in FIG. 1;

FIG. 6 is a waveform chart for explaining a method of extracting a wobble signal at the time of tracing a land portion in the first invention.

FIG. 7 is a graph showing an amplitude spectrum of a wobble signal.

FIG. 8 is a waveform diagram for explaining switching of a carrier of a wobble signal.

FIG. 9 is an explanatory diagram showing a partial ROM.

FIG. 10 is a partial sectional perspective view showing an optical disk recording medium according to a second invention.

11 is a plan view for explaining a wobbling state of a guide groove of the recording medium shown in FIG.

FIG. 12 is a block diagram for generating a wobble signal when forming a guide groove of the recording medium shown in FIG. 10;

FIG. 13 is a waveform chart of a signal of each part of the block diagram in FIG. 12;

FIG. 14 is a diagram illustrating a trajectory of a laser beam and a formed guide groove when an optical disc master is manufactured.

FIG. 15 is a block circuit that performs address information reading and CLV control of the recording medium illustrated in FIG. 10;

16 is a waveform chart for explaining a method of extracting a wobble signal from the recording medium shown in FIG.

FIG. 17 is a graph showing the spectrum of the amplitude of the wobble signal shown in FIG. 16;

FIG. 18 is a schematic top view of a guide groove wobble of the optical disk recording medium of the second invention and a relation diagram showing a relation between a groove width change and a reproduction signal amplitude change.

FIG. 19 is a block diagram showing a conventional automatic threshold control circuit.

20 is a waveform chart for explaining responsiveness of the automatic threshold control circuit shown in FIG.

FIG. 21 is a block diagram showing a reproduction information signal correction circuit.

FIG. 22 is a block diagram showing a sampling pulse generation circuit in the circuit shown in FIG. 21;

FIG. 23 is a block diagram showing an amplitude fluctuation detecting circuit in the circuit shown in FIG. 21;

24 is a waveform chart showing waveforms of respective signals in FIGS. 21 to 23. FIG.

FIG. 25 is a graph showing a relationship between an amplitude fluctuation correction error signal and a correction signal gain in the amplitude fluctuation detection circuit.

FIG. 26 is a plan view showing a general optical disk recording medium.

FIG. 27 is a partial sectional perspective view of a conventional recording medium.

FIG. 28 is a plan view of the recording medium of FIG. 27.

FIG. 29 is a waveform diagram showing a wobble signal when a land portion of the recording medium of FIG. 27 is traced.

[Explanation of symbols]

5: guide groove, 5A: first guide groove, 5B: second guide groove, 6: pit row, 13: between guide grooves, 27: guide groove,
28 ... edge, 28A ... one edge, 28B ... the other edge, 29 ... between guide grooves (land), 63 ... first BP
F, 64: second BPF, 66: gain control amplifier, 6
7: sampling pulse generation circuit, 70: amplitude fluctuation detection circuit, 72: peak hold section, 74: upper envelope detection section, 75: lower envelope detection section, 78: sample hold section, S1: first carrier signal , S2: second carrier signal, S4: first FM modulation signal, S5: second FM modulation signal, S6: wobble signal, S15: first carrier signal, S16: second carrier signal, S18 ... The first F
M modulation signal, S20: second FM modulation signal, S29: reproduction information signal, S30: tracking error signal, S31
... amplitude correction signal, S32: reproduction information signal after amplitude fluctuation correction, S33: sampling pulse signal, S34: amplitude fluctuation correction error signal, S35: upper envelope signal, S36: lower envelope signal, S37: amplitude fluctuation signal , S38... Sample hold signals.

Claims (2)

(57) [Claims] 1. An optical disc recording medium having a spiral guide groove on which information is recorded or on which information is recorded,
The guide groove first has been FM-modulated two kinds of carrier frequencies, wherein every rotating the first and second FM-modulated signal is switched while being displaced in the groove width direction according to the second FM-modulated signal An optical disk recording medium characterized by being used. 2. An optical disc recording medium for recording information or having a spiral guide groove on which information is recorded,
One edge of the guide groove is FM at a predetermined carrier frequency.
The guide groove is displaced in the groove width direction with the maximum amplitude smaller than the track pitch in accordance with the modulated FM modulation signal, and the other edge of the guide groove is not displaced, or a predetermined single frequency different from the predetermined carrier frequency When reproducing an information signal from an optical disk recording medium displaced in the groove width direction with a maximum amplitude smaller than the track pitch in response to a signal, the information signal is generated due to a change in the width of the guide groove or the width between the guide grooves. In order to suppress the amplitude fluctuation of the reproduction information signal, an amplitude correction signal is formed by taking the sum or difference of each displacement signal extracted from the tracking error signal, and the reproduction information signal is corrected based on the amplitude correction signal. A method for correcting a reproduction information signal of an optical disk recording medium, wherein the method is configured as described above.