JPH10149543A - Optical recording medium and tracking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium capable of suppressing the occurrence of a track offset without lowering recording density and a tracking device performing tracking of a light beam for the optical recording medium without causing the track offset. SOLUTION: The optical recording medium is provided with first meandering bits 1a... formed discontinuously at a prescribed period on one side side wall 1 of a groove 4 by that the side walls 1 are meandered, and second meandering bits 2a... formed discontinuously at the prescribed period on the other side side wall 2 by that the side walls 2 are meandered. When the light beam 3a performs the tracking in the state shifting from the center of the groove 4 e.g. to the side wall 1 side, a difference (V1 -V2 ) between amplitude values obtained by the amplitude values of the regenerative signals of the meandering bits becomes the positive value increasing according to a shifted amount from the center. Thus, by detecting the difference between the amplitude values as a tracking error signal, the tracking is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical recording medium having a groove and a tracking device for tracking a light beam on the optical recording medium.

[0002]

2. Description of the Related Art Conventionally, at least one side wall of a groove of an optical recording medium is continuously meandered to record address information and rotation control information. In the optical recording medium, the meandering frequency is set so that the tracking servo band and the meandering frequency band do not overlap. Thus, for example, while tracking the light beam by a push-pull method or the like, the tracking error signal is passed through a band-pass filter to extract only the meander frequency component,
Address information can be reproduced.

As such an optical recording medium, for example, Japanese Patent Laying-Open No. 5-314538 discloses an optical disk in which only one of the side walls of a groove is meandered according to address information. Since the optical disc can record information on both the groove and the land, high-density recording is possible. The above publication also describes an optical disk having both side walls of a groove meandering.

[0004]

However, when tracking is performed using the above-described push-pull method, if the objective lens has an optical axis shift, a track offset occurs due to the optical axis shift, and the optical axis shifts. There is a problem that the beam is tracked while being deviated from the center of the track in a DC manner.

That is, a data error occurs at the time of recording or reproducing information due to the track offset.
Therefore, a method capable of performing tracking so that a track offset does not occur is desired.

Incidentally, as a method for solving the above problem, a tracking method employing a sample servo method has been conventionally known. In the above method, instead of the groove, two types of marks are recorded on the optical recording medium so as to be meandering to the left and right around the center of the track (symmetric), and a reproduction signal obtained from these two types of marks is obtained. This is a method for performing tracking control so that the amplitude values of the signals become the same. According to the above method, a tracking error signal can be obtained using two types of marks, so that the occurrence of a track offset can be suppressed.

However, for example, when the width of the mark is 0.7 μm,
m, the meandering amplitude is ± 0.2 μm, and the track pitch requires a minimum width of 1.1 μm. Therefore, the track pitch cannot be made narrower than the interval between the two types of marks recorded in a meandering state.
Therefore, the optical recording medium has a new problem that the recording density is lower than that of an optical recording medium having a track pitch equal to the width of a recording mark.

Therefore, an optical recording medium capable of suppressing the occurrence of a track offset without lowering the recording density, and a tracking device for tracking a light beam without causing a track offset with respect to the optical recording medium Is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an optical recording medium capable of suppressing the occurrence of track offset without lowering the recording density, and an optical recording medium. An object of the present invention is to provide a tracking device for tracking a light beam without causing a track offset with respect to a medium.

[0010]

According to a first aspect of the present invention, there is provided an optical recording medium having a groove, wherein at least one side wall of the groove is provided on the side wall of the groove.
A first meandering bit formed discontinuously at a predetermined period by meandering the side wall, and the other side wall includes:
The side wall includes a second meandering bit formed discontinuously at a predetermined period by meandering at an amplitude equal to the amplitude of the meandering.

According to the above configuration, the optical recording medium includes the meandering bits formed discontinuously at a predetermined period on the side walls on both sides of the groove. Therefore, when performing tracking by irradiating the optical recording medium with a light beam, if tracking is performed with the center of the light beam deviated from the center line in the tracking direction of the groove, the tracking is obtained from the first meandering bit. The amplitude value of the signal and the amplitude value of the signal obtained from the second meandering bit are detected as different values. Therefore, tracking can be performed based on the detection results of these amplitude values.

The first meandering bit and the second meandering bit are formed by meandering side walls. Therefore, the first meandering bit and the second meandering bit can be formed without making the track pitch wider than the conventional track pitch. Thus, it is possible to provide an optical recording medium capable of suppressing the occurrence of track offset without lowering the recording density of the track.

According to a second aspect of the present invention, there is provided an optical recording medium according to the first aspect, wherein the first meandering bit or the second meandering bit is formed on a side wall of the groove. It is characterized in that information is recorded in a non-recorded area.

According to the above configuration, since information is recorded in an area where the first meandering bit or the second meandering bit is not formed on the side wall of the groove, the vicinity of the first meandering bit and the second meandering bit is recorded. It is possible to prevent an information recording / reproducing error from occurring. Further, since the meandering amounts of the first meandering bit and the second meandering bit can be increased, it is possible to improve the S / N ratio (Signal-to-Noise ratio) of the tracking error signal. Become.

If the length of the meandering bit is shorter than the diameter of the light spot, the reproduced signal amount decreases. To compensate for this, the amplitude of the meandering bit is increased. Therefore, if the recording of information is prohibited in the vicinity, the amplitude of the meandering bit can be freely adjusted.

According to a third aspect of the present invention, there is provided an optical recording medium according to the first or second aspect, wherein the optical recording medium has at least one zone in a radial direction of the disk. The optical disk has a first meandering bit and a second meandering bit recorded in the zone by a CAV method.

According to the above configuration, the disk has at least one zone in the radial direction, and the first and second meandering bits are recorded in the zone by the CAV method. The phases of the grooves match. Therefore, the land can be tracked in the same way as the groove is tracked. As described above, since both the groove and the land can be tracked, it is possible to provide an optical disk capable of recording information on both the groove and the land.

According to a fourth aspect of the present invention, there is provided an optical recording medium according to the second aspect, wherein at least one of the side walls continuously meanders at a predetermined period. It is characterized in that the amplitude is smaller than the amplitude of the meandering bit formed on the side wall.

According to the above arrangement, for example, when one side wall of the groove is continuously meandering according to the rotation synchronization signal or the address information as the information for rotation control, it is obtained from the side wall. The amplitude value of the signal is smaller than the amplitude value of the signal obtained from the meandering bit formed on the side wall. Therefore, it is possible to prevent information recorded near the side wall from causing a reproduction error due to a signal obtained from the side wall. Further, only the amplitude of the meandering bit can be increased, and the ability to detect the meandering bit can be improved. Further, when the length of the meandering bit is smaller than the diameter of the light spot, the amount of the reproduction signal from the meandering bit decreases. Therefore, the amplitude of only the meandering bit can be increased to compensate for the reproduction signal amount.

According to a fifth aspect of the present invention, there is provided a tracking apparatus for tracking a light beam on an optical recording medium having a groove, wherein the side wall is meandering on one side wall of the groove. A first meandering bit formed discontinuously at a predetermined period, and the other side wall meanders at a predetermined period by meandering at an amplitude equal to the amplitude of the meandering. A light beam irradiating means for irradiating an optical recording medium provided with two meandering bits with a light beam, a reproduced signal amount detecting means for detecting a reproduced signal amount obtained from reflected light or transmitted light of the light beam; Comparing means for comparing the reproduced signal amount of the first meandering bit detected by the amount detecting means with the reproduced signal amount of the second meandering bit; Serial it is characterized in that a tracking means for tracking the light beam so that both the reproduction signal amount is equal.

According to the above arrangement, the optical recording medium is irradiated with the light beam by the light beam irradiating means, and the reproduction signal amount (for example,
(Amplitude value) is detected by the reproduced signal amount detecting means. At this time, when tracking is performed with the center of the light beam deviated from the center line in the tracking direction of the groove, the amplitude value of the reproduced signal obtained from the first meandering bit of the optical recording medium and the amplitude obtained from the second meandering bit are obtained. The amplitude value of the reproduced signal is detected as a value different from each other. And
The comparison means compares the two amplitude values, and the tracking means tracks the light beam based on the output of the comparison means so that the two amplitude values become equal.
That is, the center line of the groove in the tracking direction can be matched with the center of the light beam. This allows
Tracking can be performed on the optical recording medium without causing a track offset.

According to a sixth aspect of the present invention, in the tracking apparatus of the fifth aspect, the reproduction signal amount detecting means is configured to detect the first meandering bit and / or the second meandering bit. It is characterized by comprising clock generation means for generating a clock synchronized with the obtained reproduction signal, and sampling the reproduction signal amount based on the clock.

According to the above configuration, it is possible to easily obtain a timing signal for detecting a reproduction signal amount (for example, an amplitude value) from the first meandering bit and / or the second meandering bit. Therefore, since the amplitude value is sampled by the timing signal, a more accurate amplitude value can be detected, and the tracking accuracy can be further improved.

According to a seventh aspect of the present invention, there is provided an optical recording / reproducing apparatus including the tracking device according to the sixth aspect and recording / reproducing means for recording / reproducing information based on the clock. It is characterized by having.

According to the above arrangement, the recording / reproducing means records / reproduces information based on the clock synchronized with the reproduction signal obtained from the first meandering bit and / or the second meandering bit. This makes it possible to provide a recording / reproducing apparatus capable of recording / reproducing information with higher precision than before.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIGS. 1A and 1B, the optical recording medium according to the present invention has grooves 4 and lands 5. On the one side wall 1 of the groove 4, first meandering bits 1 a for performing tracking are formed discontinuously at a certain period (predetermined period), and on the other side wall 2 of the groove 4. Are formed such that the second meandering bits 2a for performing tracking are discontinuous at a certain fixed period (predetermined period). The first meandering bits 1a and the second meandering bits 2a are formed so as to have equal amplitudes and are provided alternately.

When tracking the groove 4, the first meandering bit 1a... And the second meandering bit 2a... Tracking is performed by detecting a reproduction signal. When tracking the land 5, the grooves 4.4 provided on both sides of the land 5 are used.
, And the reproduction signal from one of the first meandering bits 1a... And the other second meandering bit 2a.

In the optical recording medium, a large number of grooves 4 and a large number of lands 5 are provided over the entire recording area. Specific examples of the optical recording medium include an optical disk, an optical card, and an optical tape.

For example, as shown in FIG. 2, when the optical recording medium is the optical disk 9, the meandering bits are recorded by the following method. That is, the optical disc 9 is
(Zone constant angular ve
location) (or ZCLV (Zone con
The disk is of a type (start linear velocity)), and is divided into, for example, four zones Z1 to Z4 sequentially from the center of the disk in the radial direction. In the four zones Z1 to Z4, meandering bits are recorded by the CAV method. Thereby, in the same zone Z1 to Z4, adjacent grooves 4
4 are in phase. Therefore, the land 5 can be tracked in the same way as the groove 4 is tracked, so that the reproduced signal of the meandering bit can always be detected at the same timing.

When the meandering bits are recorded by the CLV method, the phase of the playback signal of the meandering bit in one groove 4 and the phase of the playback signal of the meandering bit in the adjacent groove 4 gradually shift. Therefore, it is not possible to detect reproduced signals from all the meandering bits at the same timing, which is not preferable.

Here, as shown in FIG. 1B, when the light beam 3a is tracked at the center of the groove 4 on the optical recording medium, the reproduced signal X ₁ (shown by a solid line) is shown in FIG. ) as shown, the first serpentine bit 1a ... reproduction signal (hereinafter, the signal of the first referred to as reproduction signal), for example, the amplitude value V _1, a second serpentine bit 2a ... reproduction signal (hereinafter, the second Reproduction signal), for example, the amplitude value V
It is equal to ₂ . However, as shown in FIG. 2B, from the center of the groove 4, for example, the second meandering bit 2
The light beam 3b is shifted to the side wall 2 on which
Is tracked, the light beam 3b is
Are approaching the meandering bits 2a. For this reason, as shown by the reproduction signal X ₃ (indicated by a broken line) in FIG. 7C, the amplitude value V ₂ of the second reproduction signal is larger than that when the tracking is performed at the center. Meanwhile, since the light beam 3b are away from the first serpentine bit 1a ..., amplitude V ₁ of the first reproduction signal is smaller compared with the case where the tracking center. That is, the difference between the amplitude values (V ₁ −V
₂ ) is a negative value that increases as the light beam 3a shifts toward the side wall 2 and increases according to the shift amount.

On the other hand, when the light beam 3a is tracked while being shifted from the center of the groove 4 toward the side wall 1, as shown by the reproduced signal X ₂ (indicated by a broken line) in FIG. , the amplitude value V ₁ of the first reproduced signal becomes large, the amplitude value V ₂ of the second reproduction signal is reduced. That is, the difference between the amplitude values (V ₁ -V ₂ ) is a positive value that increases in accordance with the amount of shift as the light beam 3 a shifts toward the side wall 1. Therefore, by calculating the difference between the amplitude values, the difference can be used as a tracking error signal. That is, tracking can be performed using the signal.

Then, Nyquist sampling theorem
By setting the frequency band of the repetition frequency of all the meandering bits higher than the tracking servo band based on the above, it is possible to eliminate disturbances caused by track fluctuations of the optical disk and the like, so that information can be completely reproduced. That is, tracking servo can be performed. Thus, tracking control can be performed by a tracking device described later.

According to the above configuration, for example, the meandering of the meandering bit can be freely increased to a range reaching the side wall 1 (2) on the opposite side of the groove 4. For example, when the track pitch is 0.7 μm, the amplitude of the meandering bit can be set to 0.7 μmp-p. Thereby, the amplitude of the meandering bit can be freely formed without making the track pitch wider than the conventional track pitch. Thus, it is possible to provide an optical recording medium capable of suppressing the occurrence of track offset without lowering the recording density of the track. Further, information can be recorded in both the groove 4 and the land 5.

In addition to the above method, it is also possible to perform tracking by a push-pull method and to perform offset correction of tracking by using a reproduced signal of meandering bits. In this case, the frequency band of the repetition frequency of all the meandering bits may be reduced to the track offset frequency band. In the most extreme cases, one per track
A set of meandering bits may be provided.

As shown in FIG. 3, an optical recording / reproducing apparatus according to the present invention comprises a semiconductor laser 6 and an A / D converter 1.
2, CPU 13, D / A converter 14, PLL circuit 1
7, a tracking device comprising a timing adjustment circuit 18 and the like; and a recording / reproducing means comprising a recording circuit 29 and a reproducing circuit 30.

The semiconductor laser 6 emits the light beam 3 to the optical disk 9. The beam splitter 7 transmits the light beam 3 and reflects the light reflected by the optical disc 9 toward the photodetector 10. Objective lens 8
Focuses the light beam 3 on the optical disc 9. The semiconductor laser 6, the beam splitter 7, and the objective lens 8 constitute a light beam irradiation unit.

The output side of the photodetector 10 is an amplifier 1
1 is connected to the input side. The above photodetector 1
0 converts the reflected light of the light beam 3 into a reproduction signal c (FIG. 4). The output side of the amplifier 11 is connected to the A / D converter 12, the hysteresis comparator 16, and the input side of the timing adjustment circuit 18. The amplifier 11 amplifies the input reproduction signal c. A / D converter 12
Is connected to the input side of the CPU 13. The A / D converter 12 includes a timing adjustment circuit 18
, A timing clock p (described later) is input.
The A / D converter 12 converts the analog reproduction signal c into a digital reproduction signal g using the timing clock p. The output side of the CPU 13 is connected to the input side of the D / A converter 14. CPU 13
Is a digital arithmetic unit, compares the amplitude value V ₁ of the first reproduction signal in the reproduction signal g with the amplitude value V ₂ of the second reproduction signal, and uses the result as a digital tracking error signal h as D / D Output to the A converter 14.

The output side of the D / A converter 14 is connected to the input side of the objective lens actuator 15. The D / A converter 14 outputs the tracking error signal h
Into an analog tracking error signal e. Then, the objective lens actuator 15 drives the objective lens 8 based on the tracking error signal e to perform tracking. The output side of the hysteresis comparator 16 is connected to the input side of the PLL circuit 17. The hysteresis comparator 16 compares the reproduction signal c with a threshold voltage, and outputs a binarized signal o (FIG. 4) to the PLL circuit 17. The PLL circuit 17 is a clock generating means for generating a clock q (FIG. 4) synchronized with the rise and fall of the binarized signal o. The output side of the PLL circuit 17 includes a timing adjustment circuit 18, a recording circuit 29, and a reproduction circuit 3.
0 is connected to the input side.

The timing adjusting circuit 18 comprises a delay circuit 19, a comparator 21, an inverter 27, and an AND gate 20, as shown in FIG. The input side of the delay circuit 19 is connected to the output side of the PLL circuit 17. The output side of the delay circuit 19 is an AND gate 2
0 is connected to the input side. The delay circuit 19 adjusts the phase of the clock q and inputs the clock q to the AND gate 20. The comparator 21 is connected to the amplifier 11 and to the inverter 27. The comparator 21 has the reproduction signal c and the slice level signal s
(FIG. 4) is input. After slicing the reproduction signal c with the slice level signal s, the comparator 21 outputs the signal to the inverter 27.

The inverter 27 is connected to the comparator 21 and to the AND gate 20. The inverter 27 converts the sliced reproduction signal c into a gate signal r (FIG. 4), and inputs the gate signal r to the AND gate 20.

The AND gate 20 is connected to the delay circuit 19 and the inverter 27, and is also connected to the A / D converter 12. The AND gate 20 generates a timing clock p (FIG. 4) by taking the product of the clock q and the gate signal r.
To the A / D converter 12.

The A / D converter 12, the hysteresis comparator 16, the PLL circuit 17, and the timing adjusting circuit 18 constitute a reproduced signal amount detecting means.

The CPU 13 is a comparing means. Further, the tracking means is constituted by the CPU 13, the D / A converter 14 and the objective lens actuator 15. Further, the A / D converter 12, C
The PU 13 and the D / A converter 14 also constitute a tracking signal detection circuit.

The recording circuit 29 records information based on the clock q. The reproduction circuit 30 reproduces information based on the clock q. The recording circuit 29 and the reproducing circuit 30 constitute recording / reproducing means.

In the above configuration, the light beam 3 emitted from the semiconductor laser 6 is applied to the optical disk 9 via the beam splitter 7 and the objective lens 8. In addition,
The light beam 3 irradiates the groove 4 of the optical disc 9.

Then, the reflected light of the light beam 3 reflected by the optical disk 9 is incident on the beam splitter 7 via the objective lens 8, and the optical path is bent by the beam splitter 7. The reflected light whose optical path has been bent enters the photodetector 10, is converted into a reproduction signal c, and is amplified by the amplifier 11. On the side walls 1 and 2 of the groove 4, meandering bits are formed discontinuously at a constant period. For this reason, by taking out the instantaneous amplitude value, it is possible to obtain the intermittent first reproduction signal and second reproduction signal, that is, the discontinuous first reproduction signal and second reproduction signal. Note that the tracking device may have a configuration in which the transmitted light of the light beam 3 on the optical disk 9 is incident on the photodetector 10.

The reproduction signal c is input to the hysteresis comparator 16 and the hysteresis comparator 16
Is compared with the threshold voltage and output as a binary signal o. The binarized signal o is converted in the PLL circuit 17 into a clock q synchronized with the rise and fall of the binarized signal o, that is, a clock q synchronized with the meandering bit, and the delay circuit of the timing adjustment circuit 18 19
Output to

The reproduction signal c is supplied to the timing adjustment circuit 1
8 and is sliced by the slice level signal s, and then input to the inverter 27.
The reproduced signal input to the inverter 27 is a gate signal r
And input to the AND gate 20. And
In the AND gate 20, the product of the clock q whose phase has been adjusted in the delay circuit 19 and the gate signal r is obtained, and a timing clock p matching the negative peak position of the amplitude of the reproduced signal c is output. The timing clock p is A
/ D converter 12.

The reproduced signal c is supplied to the A / D converter 12
And converted into a digital reproduction signal g by the timing clock p. Thus, the amplitude V ₁ of the first serpentine bit 1a ..., an amplitude value V ₂ of the second serpentine bit 2a ... can be accurately detected, the tracking accuracy can be further improved. The amplitude value V ₁ of the first reproduced signal and the amplitude value V ₂ of the second reproduced signal are C
The tracking error signal h is compared by the PU 13 and
It is input to the D / A converter 14. The tracking error signal h is converted into an analog tracking error signal e by the D / A converter 14 and input to the objective lens actuator 15.

Next, a method of calculating the tracking error signal e will be described with reference to the flowchart shown in FIG. First, the amplitude value V ₁ of the first reproduced signal from the first serpentine bit 1a ... detected by the A / D converter 12 (S1). Similarly detecting the amplitude V ₂ of the second reproduction signal from the second serpentine bit 2a ... (S2).

Next, the amplitude value V _{1 is} set by the CPU 13.
And the difference (V ₁ −V ₂ ) (hereinafter referred to as δV) between the amplitude value and the amplitude value V ₂ is obtained (S 3). Then, the difference δV is used as the tracking error signal e and the D / A converter 14
Is output to the objective lens actuator 15 through the step (S4). Thereafter, the procedure returns to (S1) again, and the above procedure is repeated. Accordingly, tracking control can be performed so that the difference δV between the amplitude value V ₁ of the first reproduction signal and the amplitude value V ₂ of the second reproduction signal becomes zero.

It should be noted that the photodetector 10 can be replaced with a two-segment photodetector, and the detection signal (reproduction signal) can be differentially amplified to output a push-pull signal. In this case, the amplitude value of the first reproduction signal and the amplitude value of the second reproduction signal are detected from the push-pull signal, and based on the difference between the amplitude value of the first reproduction signal and the amplitude value of the second reproduction signal. Then, the tracking may be performed by outputting the tracking error signal e.

The clock q is also input to the recording circuit 29 and the reproducing circuit 30. As a result, the reproduction of the information recorded on the optical disk 9 and the recording of the information on the optical disk 9 are performed based on the accurate clock q synchronized with the first meandering bit 1a and the second meandering bit 2a. Therefore, it is possible to reduce the occurrence of bit jitter due to the rotation fluctuation of the optical disc 9 and to set a margin area for the rotation fluctuation on the optical disc 9. Therefore, the recording capacity of the optical disc 9 can be further improved.

Instead of the timing adjusting circuit 18 comprising the delay circuit 19, the AND gate 20, the comparator 21 and the inverter 27, as shown in FIG. 6, the delay circuit 19, the AND gate 20, and the comparators 21 and 2 are provided.
6, it can be composed of an inverter 27 and an OR gate 28.

The output side of the comparator 21 is connected to the input side of the inverter 27. The output side of the inverter 27 is connected to the input side of the OR gate 28. The output side of the comparator 26 is connected to the input side of the OR gate 28. Further, the output side of the delay circuit 19 and the OR gate 28 are connected to the input side of the AND gate 20. The comparator 26 slices the reproduction signal c input to the comparator 26 with a slice level signal s ′ (FIG. 4). The OR gate 28
When a signal is input from the comparator 26 or the inverter 27, the gate signal r 'is input to the AND gate 20. The AND gate 20 outputs the timing clock p ′
(FIG. 4) is input to the A / D converter 12.

In the above configuration, the reproduction signal c is sliced by the comparator 21 with the slice level signal s and output to the inverter 27. The sliced reproduction signal c is input to the OR gate 28 via the inverter 27. The reproduction signal c is sliced by the comparator 26 using the slice level signal s ′ and input to the OR gate 28. Then, the gate signal r 'is output from the OR gate 28. The gate signal r 'is shown in FIG.
As shown in (1), they correspond to a positive peak position and a negative peak position in the reproduction signal c. Timing lock p '
Is obtained by multiplying the clock signal q whose phase has been adjusted by the delay circuit 19 and the gate signal r ′ in the AND gate 20. Thereby, the peak-to-peak of the reproduction signal c, that is, the amplitude value from one peak to the next peak is detected.

The clock q is an accurate clock synchronized with the meandering bit. If the information recorded in the groove 4 is recorded / reproduced based on the clock q, occurrence of bit jitter due to rotation fluctuation of the optical disk 9 can be reduced, and a margin area for rotation fluctuation information needs to be provided on the optical disk 9. Therefore, the recording capacity can be increased.

Instead of using the A / D converter 12, the CPU 13 and the D / A converter 14 as the tracking error signal detection circuit, as shown in FIG. 8, the sample and hold circuits 22 and 23, the clock distribution circuit 25 and the subtractor 24.

The input side of the clock distribution circuit 25 is connected to the output side of the timing adjustment circuit 18. The clock distribution circuit 25 converts the timing clock p input to the clock distribution circuit 25 into a timing clock p _1.
distributed to p _2. The input sides of the sample hold circuits 22 and 23 are connected to the amplifier 11 and the output side of the clock distribution circuit 25. The output side of the sample and hold circuit 22 is connected to the positive input side of the subtractor 24, and the output side of the sample and hold circuit 23 is connected to the negative input side of the subtractor 24. The sample hold circuit 22 holds the amplitude value V ₁ of the first reproduced signal based on the timing clock p ₁ input thereto. The sample hold circuit 23 holds the amplitude value V ₂ of the second reproduced signal based on the input timing clock p ₂ . The output side of the subtractor 24 is connected to the input side of the objective lens actuator 15. The subtractor 24 calculates a difference δV between the amplitude values V ₁ and V ₂ and converts the difference δV into a tracking error signal e.

[0062] In the above configuration, the reproduction signal c output from the amplifier 11 is input to the sample-and-hold circuit 22, an amplitude value V ₁ of the first reproduced signal is held on the basis of the timing clock p _1.

On the other hand, the reproduced signal c is also inputted to the sample hold circuit 23, and the amplitude value V ₂ of the second reproduced signal is held based on the timing clock p ₂ . The amplitude value V ₁ and the amplitude value V ₂ are input to the subtractor 24, converted into a tracking error signal e, and input to the objective lens actuator 15.

In the above embodiment, since the tracking error signal e is obtained from the meandering bit, the larger the amplitude of the meandering bit, the better. Further, when tracking the light beam 3 in the vicinity of the meandering bit, an information error is likely to occur. Therefore, information is not recorded in the vicinity of the meandering bit, and the information is recorded in an area where no meandering bit is formed. It is preferable to record.

[Second Embodiment] The following will describe another embodiment of the present invention with reference to FIG. For convenience of description, the same members as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The optical disk according to the present embodiment is shown in FIG.
As shown in FIG. 1, a side wall 31 is provided instead of the side wall 1. The side wall 31 has a certain period (predetermined period) according to a rotation synchronization signal or address information which is information for rotation control.
And meanders continuously. That is, in the optical disk, the side wall 31 is continuously meandered,
, A rotation synchronizing signal and address information are recorded.

According to the above configuration, for example, the groove 4
To track the light beam 3 at the side wall 3
The frequency band of the meandering bit and the frequency band of the meandering bit are set so as not to overlap. As a result, the reproduced signal c is separated for the meandering bit and the side wall 31 respectively.
Is detected. Therefore, the reproduced signal from the meandering side wall 31 can be used for controlling the rotation of the optical disk and accessing the pickup. On the other hand, the first reproduced signal and the second reproduced signal from the meandering bits can be used for tracking control.

It is more preferable that the amplitude of the meandering side wall 31 formed in accordance with the rotation synchronization signal and the address information is made smaller to suppress the information recording / reproducing error.
In order to suppress the information recording / reproducing error, it is preferable that the amplitude of the meandering bit for tracking control is larger than the amplitude for the rotation synchronization signal and the address information.

[0069]

According to the first aspect of the present invention, there is provided an optical recording medium comprising:
As described above, in an optical recording medium having a groove,
One side wall of the groove includes a first meandering bit formed discontinuously at a predetermined period by meandering the side wall, and the other side wall has an amplitude equal to the meandering amplitude. And a second meandering bit discontinuously formed at a predetermined period by meandering.

Therefore, when performing tracking by irradiating the optical recording medium with a light beam, if the center of the light beam is displaced from the center line in the groove tracking direction, the first meandering bit And the amplitude value of the signal obtained from the second meandering bit are detected as different values.
Therefore, tracking can be performed based on the detection results of these amplitude values.

The first meandering bit and the second meandering bit can be formed without making the track pitch wider than the conventional track pitch. As a result, it is possible to provide an optical recording medium capable of suppressing the occurrence of track offset without lowering the recording density of the track.

As described above, in the optical recording medium according to the second aspect of the present invention, information is recorded in an area where the first meandering bit or the second meandering bit is not formed on the side wall of the groove. It is.

As a result, it is possible to prevent occurrence of an information recording / reproducing error in the vicinity of the first meandering bit and the second meandering bit. Furthermore, since the amount of meandering of the first meandering bit and the second meandering bit can be increased, there is an effect that the S / N ratio of the tracking error signal can be improved.

If the length of the meandering bit is shorter than the diameter of the light spot, the reproduced signal amount is reduced. To compensate for this, the amplitude of the meandering bit is increased. Therefore, if the recording of information is prohibited in this vicinity, the effect of freely adjusting the amplitude of the meandering bit is achieved.

As described above, the optical recording medium according to the third aspect of the present invention is an optical recording medium having at least one zone in the radial direction of the disk, and the first optical recording medium having the first zone in the zone. In this configuration, the meandering bit and the second meandering bit are recorded by the CAV method.

As a result, the phases of adjacent grooves do not shift. Therefore, the land can be tracked in the same way as the groove is tracked. As described above, since both the groove and the land can be tracked, it is possible to provide an optical disk capable of recording information on both the groove and the land.

As described above, according to the optical recording medium of the present invention, at least one of the side walls continuously meanders at a predetermined period, and the amplitude of the meandering bit is formed on the side wall. Is smaller than the amplitude.

For example, when one side wall of the groove continuously meanders according to a rotation synchronization signal or address information which is information for rotation control, the amplitude value of a signal obtained from the side wall is It becomes smaller than the amplitude value of the signal obtained from the meandering bit formed on the side wall. Therefore, it is possible to prevent information recorded near the side wall from causing a reproduction error due to a signal obtained from the side wall. Further, only the amplitude of the meandering bit can be increased, and the ability to detect the meandering bit can be improved. Further, when the length of the meandering bit is smaller than the diameter of the light spot, the amount of the reproduction signal from the meandering bit decreases. Therefore, the amplitude of only the meandering bit can be increased to compensate for the reproduction signal amount.

According to a fifth aspect of the present invention, there is provided a tracking apparatus for tracking a light beam on an optical recording medium having a groove, as described above.
A first meandering bit formed discontinuously at a predetermined period on one side wall of the groove by meandering the side wall;
Light beam irradiation is performed to irradiate an optical recording medium with a second meandering bit formed discontinuously at a predetermined period by meandering the other side wall with an amplitude equal to the meandering amplitude. Means, a reproduced signal amount detecting means for detecting a reproduced signal amount obtained from reflected light or transmitted light of the light beam, a reproduced signal amount of the first meandering bit detected by the reproduced signal amount detecting means, A comparison means for comparing the reproduced signal amount of the meandering bit and a tracking means for tracking the light beam based on the output of the comparison means so that the reproduced signal amounts become equal to each other.

Therefore, when tracking is performed with the center of the light beam deviated from the center line in the groove tracking direction, the reproduction signal amount obtained from the first meandering bit of the optical recording medium, for example, the amplitude value, Since the reproduced signal amount obtained from the two meandering bits, for example, the amplitude value is detected as different values from each other, the light beam is tracked so that these two amplitude values become equal to each other, so that the center line in the tracking direction of the groove can be obtained. And the center of the light beam. Thereby, there is an effect that tracking can be performed on the optical recording medium without causing a track offset.

As described above, in the tracking device according to the sixth aspect of the present invention, the reproduced signal amount detecting means generates a clock synchronized with the reproduced signal obtained from the first meandering bit and / or the second meandering bit. Clock generating means for sampling the reproduced signal amount based on the clock.

Therefore, it is possible to easily obtain the timing signal for detecting the reproduced signal amount, for example, the amplitude value from the first meandering bit and / or the second meandering bit.
Therefore, since the amplitude value is sampled by the timing signal, a more accurate amplitude value can be detected, and the tracking accuracy can be further improved.

An optical recording / reproducing apparatus according to a seventh aspect of the present invention includes the tracking apparatus according to the sixth aspect and a recording / reproducing means for recording / reproducing information based on the clock. Configuration.

Therefore, the recording / reproducing means records / reproduces information based on the clock synchronized with the reproduction signal obtained from the first and / or second meandering bits.
As a result, it is possible to provide a recording / reproducing apparatus capable of recording / reproducing information with higher precision than before.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of an optical recording medium according to the present invention, wherein (a) is a schematic sectional view of the optical recording medium,
FIG. 3B is a plan view of a main part of the optical recording medium, and FIG. 3C is an explanatory diagram of a reproduction signal obtained from the optical recording medium.

FIG. 2 is a plan view showing a schematic configuration of an optical recording medium according to the present invention.

FIG. 3 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus according to the present invention.

FIG. 4 is a timing chart of various signals in a tracking device provided in the optical recording / reproducing device.

FIG. 5 is a block diagram illustrating a configuration of a timing adjustment circuit included in the tracking device.

FIG. 6 is a block diagram showing another configuration of the timing adjustment circuit.

FIG. 7 is a flowchart illustrating a tracking method.

FIG. 8 is a block diagram showing another configuration of the tracking error signal detection circuit provided in the tracking device.

FIG. 9 is a plan view showing another configuration of the optical recording medium according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Side wall 1a 1st meander bit 2 Side wall 2a 2nd meander bit 3 Light beam 4 Groove 5 Land 6 Semiconductor laser (light beam irradiation means) 12 A / D converter (reproduction signal amount detection means) 13 CPU (comparison means, tracking means) 16 Hysteresis comparator (reproduction signal amount detection means) 17 PLL circuit (reproduction signal amount detection means, clock generation means) 18 Timing adjustment circuit (reproduction signal amount detection means) 25 Clock distribution circuit 29 Recording circuit (recording / reproduction means) 30 reproduction circuit (reproducing means) 31 sidewall e tracking error signal p · p 'timing clock q clock r gate signal V ₁ amplitude V ₂ amplitude value

Claims (7)

[Claims] 1. An optical recording medium having a groove, wherein one side wall of the groove is provided with a first meandering bit formed discontinuously at a predetermined period by meandering the side wall, and the other side wall is provided. The optical recording medium according to claim 1, further comprising a second meandering bit formed discontinuously at a predetermined period by said side wall meandering at an amplitude equal to said meandering amplitude. 2. The optical recording medium according to claim 1, wherein information is recorded in an area where the first meandering bit or the second meandering bit is not formed on a side wall of the groove. 3. The optical recording medium is an optical disk having at least one zone in a radial direction of the disk, and a first meandering bit and a second meandering bit are recorded in the zone by a CAV method. 3. The optical recording medium according to claim 1, wherein: 4. The method according to claim 2, wherein at least one of the side walls meanders continuously at a predetermined period, and the amplitude of the meandering is smaller than the amplitude of the meandering bit formed on the side wall. Optical recording medium. 5. A tracking device for tracking a light beam on an optical recording medium having a groove, wherein the first meandering bit is formed discontinuously at a predetermined cycle by meandering the side wall on one side wall of the groove. With
Light beam irradiation is performed to irradiate an optical recording medium with a second meandering bit formed discontinuously at a predetermined period by meandering the other side wall with an amplitude equal to the meandering amplitude. Means, a reproduced signal amount detecting means for detecting a reproduced signal amount obtained from reflected light or transmitted light of the light beam, a reproduced signal amount of the first meandering bit detected by the reproduced signal amount detecting means, Light comprising: comparing means for comparing a reproduced signal amount of a meandering bit; and tracking means for tracking a light beam based on an output of the comparing means so that the reproduced signal amounts are equal. Tracking device for recording media. 6. The reproduction signal amount detection means includes clock generation means for generating a clock synchronized with the reproduction signal obtained from the first meandering bit and / or the second meandering bit, and based on the reproduction signal. 6. The tracking device according to claim 5, wherein the amount is sampled. 7. An optical recording / reproducing apparatus comprising: the tracking device according to claim 6; and recording / reproducing means for recording / reproducing information based on the clock.