JP2001118273A - Recording medium drive device and tilt detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and precisely detect a tilt amount without an exclusive sensor. SOLUTION: An optical disk reproducing device 10 is provided with an optical pickup 11 reading out the digital data recorded on an optical disk an amplitude detection circuit 18 detecting the amplitude of a wobble component signal passed by a band-pass filter 14 and a tilt detection circuit 24 detecting the tilt amount. The optical disk reproducing device 10 irradiates the optical disk, with a laser beam forming a main beam spot and two sub-beam spots, and detects the amplitude of respective wobble component signals based on return beams from a signal information recording side wall by two objective beam spots among the main beam spot and two sub-beam spots and obtains the difference values of the amplitude of respective wobble component signals as a tilt instruction value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium drive for rotating a disc-shaped recording medium to record and / or reproduce digital data on the disc-shaped recording medium, and to rotate the disc-shaped recording medium. The present invention relates to a tilt detection method for detecting a tilt amount generated at the time.

[0002]

2. Description of the Related Art For example, a so-called CD (Compact Disc), DVD (Digital Versatile Disc or Digital Video) is used as a recording medium on which digital data is optically recorded.
Disc) and other optical discs are widely known.

An optical disk drive for recording and / or reproducing digital data on and from such an optical disk has a small spot where a laser beam is condensed by an optical pickup on a rotationally driven optical disk at a desired position. Irradiate and record and / or reproduce digital data. At this time, in order to stably record digital data on the optical disk or to faithfully reproduce the digital data recorded on the optical disk, the optical pickup makes the laser beam follow a track provided on the surface of the optical disk. Operate.

[0004]

However, in the above-mentioned optical disk, the optical disk may be warped by the influence of the environment such as temperature and humidity during use and / or storage, and may be caused by the warp of the optical disk due to the handling state or the tilt of the optical pickup in the optical disk drive. As a result, radial tilt may occur. Since this tilt causes aberration in the reproduction optical spot, distortion of the reproduction signal and MTF (Modulati
On transfer function) and recording power efficiency are known to be reduced.

In recent years, in order to increase the density of an optical disk, a numerical aperture (numerical aperture) of an objective lens in an optical pickup has been used in an optical disk drive.
e; NA) tends to be increased. For example, an objective lens having an NA value of 0.45 for a CD and an NA value of 0.60 for a DVD is used. Along with this, the thickness of the substrate of the optical disk has been reduced. For this reason, in the current situation, the optical disc is likely to be warped and has a large NA, so that the angle dependence of the aberration is also increasing.

On the other hand, in an optical disk drive, a dedicated sensor is provided to detect a tilt amount in order to compensate for the tilt, and an objective lens, an actuator and the like in an optical pickup are tilted based on the detected signal. Has been put to practical use.

However, in the conventional optical disk drive, if the optical disk has a small diameter, a place for installing a sensor for detecting the amount of tilt cannot be sufficiently secured, and it is difficult to detect the amount of tilt. there were.

The present invention has been made in view of the above circumstances, and solves the problem of the tilt detection method in the conventional optical disk drive, and quickly and accurately detects a tilt amount from a signal obtained by an optical pickup. And a tilt detection method.

[0009]

According to the present invention, there is provided a recording medium driving apparatus for rotating a disk-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded. A recording medium drive for recording and / or reproducing digital data on a disk-shaped recording medium, wherein the laser forms a main beam spot and two sub-beam spots on the disk-shaped recording medium An optical pickup means for irradiating light and receiving return light reflected and diffracted on the surface of the disc-shaped recording medium; and a signal information recording side wall formed by two target beam spots out of a main beam spot and two sub beam spots. Amplitude detecting means for detecting the amplitude of the signal based on the return light of the light, and detecting the amount of tilt based on the amplitude of the signal detected by the amplitude detecting means. It is characterized in that it comprises a tilt detector for.

In the recording medium driving apparatus according to the present invention, the optical pickup means irradiates the disk-shaped recording medium with laser light for forming a main beam spot and two sub-beam spots, and tilt detection means. Thus, the tilt amount is detected based on the amplitude of the signal based on the return light from the signal information recording side wall due to two target beam spots among the main beam spot and the two sub beam spots.

Further, the tilt detecting method according to the present invention for achieving the above object provides a tilt detection method for a disc-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded. A laser beam forming two sub-beam spots is radiated, and return light reflected and diffracted on the surface of the disk-shaped recording medium is received, and two target beam spots are selected from the main beam spot and the two sub-beam spots. , The amplitude of the signal based on the return light from the signal information recording side wall is detected, and the amount of tilt is detected based on the amplitude of the detected signal.

In the tilt detecting method according to the present invention, a laser beam forming a main beam spot and two sub-beam spots is irradiated on a disc-shaped recording medium, and the main beam spot and the two sub-beam spots are irradiated. Among them, the tilt amount is detected based on the amplitude of the signal based on the return light from the signal information recording side wall due to the two target beam spots.

[0013]

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

In this embodiment, a recording medium driving apparatus according to the present invention is applied to, for example, a CD (Compact Disc) or a DVD.
(Digital Versatile Disc or Digital Video Dis
c) The present invention is applied to an optical disk reproducing apparatus for reproducing digital data from an optical disk which is a disk-shaped recording medium on which digital data such as MD (Mini Disk, a product name of Sony Corporation) is recorded. First, the principle of the tilt detection method performed by the optical disc reproducing apparatus will be described.

An optical disk suitable for applying the present invention is shown in FIGS. 1 to 3 according to the recording area.

That is, the optical disk shown in FIG. 1 is referred to as a straight groove SG which is a non-modulation guide groove having no wobble, and a double spiral. For example, FM at about 80 kHz with respect to a standard linear velocity. A wobble groove portion (wobbled groove) WG, which is a modulation guide groove having signal information recording side walls W on both sides to which address information which is modulated signal information is added and wobbled, is provided alternately. An area sandwiched between the straight groove portion SG and the wobble groove portion WG is provided as a land portion L, and the straight groove portion SG and the wobble groove portion WG are a recording substrate having a recording area.

The optical disk shown in FIG.
A groove portion IG which is an inner peripheral modulation guide groove for providing a signal information recording side wall W to which the M-modulated address information is added and wobbled as an inner peripheral side wall of the optical disc.
And a groove portion OG serving as an outer modulation guide groove for providing a signal information recording side wall W as an outer side wall of the optical disc.
Are alternately provided, and a region sandwiched between the groove portion IG and the groove portion OG is provided as a land portion L, and the land portion L is a land substrate having a recording area.

Further, the optical disk shown in FIG. 3 is a guide groove having, for example, a signal information recording side wall W to which FM-modulated address information is added and wobbled on either the inner peripheral side or the outer peripheral side of the optical disk. This is a land / groove substrate in which certain groove portions G and land portions L are provided alternately, and these groove portions G and land portions L are each a recording area. It should be noted that the optical disk shown in the figure is provided with a groove portion G having a signal information recording side wall W on the outer peripheral side of the optical disk.

An optical disk reproducing apparatus shown as an embodiment of the present invention irradiates these optical disks with laser light to form a main beam spot MS and two sub-beam spots SS ₁ and SS ₂ on the optical disk. Each of these beam spots is a Gaussian beam whose intensity distribution exhibits a Gaussian distribution. The optical disc reproducing device detects the amount of tilt based on the return light from two beam spots (target beam spots) among the three beam spots formed on the optical disc.

That is, in the case of the optical disk reproducing apparatus having the groove substrate shown in FIG. 1, the optical disk reproducing apparatus has two sub-beam spots SS ₁ and SS ₂ illuminated on the land portion L.
Are the target beam spots, and the amount of tilt is detected based on the return light from these target beam spots.

In the case of the optical disk reproducing apparatus of the land substrate shown in FIG.
G, OG, two sub-beam spots S
S ₁ and SS ₂ are set as target beam spots, and the amount of tilt is detected based on the return light from these target beam spots.

Further, in the case of the land / groove substrate optical disk shown in FIG. 3, the optical disk reproducing apparatus uses a main beam spot MS and two sub beam spots S.
One of the sub-beam spots S ₁ and SS ₂ is set as a target beam spot, and the tilt amount is detected based on the return light from the target beam spot.

In the following description, in order to generally describe the case where the optical disk shown in FIGS. 1 to 3 is used, two beam spots used when the tilt amount is detected by the optical disk reproducing device are described with the main beam. Spot MS or sub beam spot SS ₁ , S
Not bound by either a S _2, if necessary, as shown in FIG. 4 (A), if the signal information recording sidewall W is located on the inner peripheral side of the optical disc than the laser beam from the optical pickup (not shown) The beam spot at is assumed to be spot S _A ,
As shown in FIG. (B), a beam spot in the case on the outer peripheral side of the optical disk and the spot S _B. In the following description, if necessary, the track the spot S _A is irradiated with the track T _A, the track the spot S _B is irradiated with the track T _B.

FIG. 5 shows a result obtained by numerical calculation of a change in the intensity distribution of the laser beam due to the tilt.

[0025] The spot S _B to be irradiated on the optical disk,
When the irradiation is normally performed without being affected by the tilt, that is, when the tilt amount is “0 °”, the intensity distribution in the radial direction of the optical disc is changed as indicated by a solid line portion C _0B in FIG. It is symmetrical at the center position of the track T _B.
Therefore, the return light reflected and diffracted on the disk surface is
It is symmetrical at the center position of the track T _B in the radial direction of the optical disk.

On the other hand, due to the distortion due to the aberration influenced by a tilt, the signal information recording sidewall W spot S _B irradiated on the optical disc in a state inclined in the direction of, for example the broken line in the drawing section C _0.6B and as shown in the drawing chain line portion C _1.2B. That is, the spot S irradiated on the optical disc
_B, when the tilt amount "0.6 °" is "1.2 °", respectively, the broken line in the drawing unit C _0.6B, chain line portion C _1.2B
As shown in both its intensity distribution becomes asymmetric on the track T _B in the radial direction of the optical disk, the intensity of the laser light to the signal information recording sidewall W in the track T _B is irradiated on the side that is provided, normally illuminated is lower than if the signal information recording sidewall W in the track T _B
The intensity of the laser beam irradiated on the side where no is provided is higher than when the laser beam is normally irradiated. This tendency becomes more remarkable as the tilt amount increases. Therefore, the return light reflected and diffracted by the disc surface is made asymmetrical on the track T _B, the signal information recording return light intensity I _0.6B from the side wall W, I _1.2B also different from each other.

Further, although not shown, the spot S _A irradiating the optical disc in a state of being tilted in the direction of the signal information recording side wall W due to the tilt has an intensity distribution on the track T _A in the radial direction of the optical disc. in becomes asymmetrical, the intensity of the laser light signal information recording sidewall W in the track T _a is irradiated on the side provided becomes higher than when it is properly illuminated, signal information recording sidewall W is provided in the track T _a The intensity of the laser beam irradiated on the non-exposed side is lower than that when the laser beam is normally irradiated. Therefore, the return light reflected and diffracted by the disc surface is made asymmetrical on the track T _A, the respective even intensity of return light from the signal information recording sidewall W different.

FIG. 6 shows the results of numerical calculation of the signal characteristics based on the return light from the signal information recording side wall W when the optical disk is irradiated with laser light while actually changing the tilt amount. Here, the wobble component signal which is a signal based on the return light from the signal information recording side wall W with respect to the tilt amount is obtained when reproducing the ADIP (ADress In Pre-groove) given to the signal information recording side wall W. Signal.

[0029] The curve obtained by plotting the change in the amplitude of the signal based on the return light from the signal information recording sidewall W by spot S _A for the amount of tilt (wobble component signal SIG _A) and curve C _A, according to the spot S _B for the amount of tilt When the curve obtained by plotting the change in the amplitude of the signal information recording sidewall W signal based on the return light from (the wobble component signal SIG _B) and the curve C _B, as shown in the figure, the wobble component signal S
Both the amplitude of IG _{A and} the amplitude of wobble component signal SIG _B depend on the amount of tilt, and tend to be symmetric about the case where the amount of tilt is “0 °”. The signal represented by the difference between the wobble component signal SIG _A and the wobble component signal SIG _B is converted to a tilt detection signal SI.
Assuming that G _T , as shown by a curve C _T , a characteristic having linearity in a range of “about −0.75 ° to about + 0.75 °” around the case where the tilt amount is “0 °”. Can be obtained. Note that the pull-in range is “about -1.2 ゜ to about +
1.2 ゜ ”.

The optical disk reproducing apparatus 10 shown in FIG. 7 as an embodiment of the present invention detects the amount of tilt by using such characteristics and compensates for it.

As shown in FIG. 1, an optical disk reproducing apparatus 10 includes an optical pickup 11 for reading digital data recorded on an optical disk (not shown) and a current-voltage conversion (IV conversion) of a signal output from the optical pickup 11. Iv) an IV conversion circuit 12, a servo circuit 13 for controlling the optical pickup 11 to keep the distance to the optical disk constant, and controlling a rotation driving operation of a spindle motor (not shown), and passing a signal of a desired frequency component. Band Pass Filter
r; BPF) 14, a peak envelope detection circuit 15 for detecting the peak envelope of the wobble component signal passed by the band-pass filter 14, and a bottom for detecting the bottom envelope of the wobble component signal passed by the band-pass filter 14. Envelope detection circuit 1
6, the peak envelope and the bottom envelope detection circuit 1 detected by the peak envelope detection circuit 15
6, a subtractor 17 for obtaining a difference from the bottom envelope detected by the control unit 6, an amplitude detection circuit 18 for detecting the amplitude of the wobble component signal based on an output from the subtractor 17,
A track discrimination circuit 19 for the wobble component signal passed by the band pass filter 14 to determine due to return light from either the track T _B is due to return light from the track T _A, is passed by the band pass filter 14 An address detection circuit 20 for extracting an address recorded on the optical disk from the wobble component signal and detecting the address.
RF (Radio Frequency) input from V conversion circuit 12
An equalizer 21 for performing a waveform equalization process on the signal; a data determination circuit 22 for extracting data from the signal input from the equalizer 21 to determine a data detection capability; and a tilt detected by a tilt detection circuit 24 described later. A target value setting circuit 23 for setting a target value for compensating a tilt instruction value indicating the amount, a tilt detection circuit 24 for detecting a tilt amount, and a focus coil 27a of the optical pickup 11 for tilt compensation. , 27b for generating a drive signal for driving the drive signals.

The optical pickup 11 has an objective lens 26 for condensing laser light from a laser diode 29, focus coils 27a and 27b for tilting the objective lens 26 with respect to the optical disk, and these focus coils 27a and 27b. Objective lens 2 by electromagnetic force
6, a laser diode (LD) 29 that emits laser light, and internally reflects the return light that transmits the laser light emitted from the laser diode 29 and is reflected and diffracted on the optical disk surface. And a photodiode (PD) 31 for receiving return light reflected and diffracted on the optical disk surface and incident by the prism 30.

The objective lens 26 includes a laser diode 29
From the laser beam and irradiates the optical disk (not shown).

The focus coils 27a and 27b are for tilting the objective lens 26 with respect to the optical disk. These focus coils 27a, 27
A current having a magnitude based on the drive signal supplied from the drive signal generation circuit 25 flows through b. The focus coils 27a and 27b respectively drive the actuator 28 in a direction to compensate for tilt by an electromagnetic force generated by an effect with a magnet (not shown).

The actuator 28 drives the objective lens 26 to track the objective lens 26 at a desired position on an optical disk (not shown).
Further, the actuator 28 includes the focus coil 27
The objective lens 26 is tilted with respect to the optical disk by the electromagnetic force of a and 27b.

The laser diode 29 has, for example, a light emitting portion made of a semiconductor laser, and emits laser light. The laser light emitted from the laser diode 29 enters the prism 30.

The prism 30 receives and transmits the laser light emitted from the laser diode 29 and
6, the return light reflected and diffracted on the surface of the optical disk is incident and internally reflected, and the photodiode 3
Emitted to 1.

The photodiode 31 has a photodetector and a photoelectric converter, receives the return light reflected and diffracted on the optical disk surface and incident by the prism 30, converts the return light into an electric signal, and outputs the electric signal to the IV conversion circuit 12 at the subsequent stage. I do.

The optical pickup 11 forms a main beam spot MS by irradiating the laser beam emitted from the laser diode 29 to an optical disc (not shown), and the main beam spot MS is reflected and diffracted on the optical disc surface. By receiving light, digital data recorded on tracks on the optical disk surface is read. Further, as described above, the optical pickup 11 divides the laser beam into a main beam spot MS and two sub-beam spots SS ₁ and SS ₂ , irradiates these beam spots to an optical disc (not shown), and reflects the beam spot on the optical disc surface. An optical system for receiving the diffracted return light is provided. The return light obtained by reflecting and diffracting the sub beam spots SS ₁ and SS ₂ on the optical disk surface is used for the track discrimination of the main beam spot MS by the track discrimination circuit 19. Further, the optical pickup 11 outputs a focus error signal indicating a focus error of the objective lens 26 to the drive signal generation circuit 25.

The IV conversion circuit 12 includes the photodiode 3
The signal output from 1 is subjected to current-voltage conversion. The IV conversion circuit 12 converts the signal obtained by the conversion into a servo circuit 13 in the subsequent stage.
And output to the bandpass filter 14. In addition, the IV conversion circuit 12 outputs an RF signal obtained by converting a signal based on the return light from the main beam spot MS to the equalizer 21 at the subsequent stage.

The servo circuit 13 drives the optical pickup 11 based on the signal supplied from the IV conversion circuit 12 so as to focus the optical pickup 11 so as to keep the distance from the optical disk constant, and controls the rotational driving operation of a spindle motor (not shown). I do.

The band pass filter 14 is an IV conversion circuit 1
In order to extract a wobble component signal from the signal information recording side wall W out of the signals supplied from 2, the RF signal component and other noise components are cut off, and a signal of a desired frequency component is passed. The wobble component signal passed by the band-pass filter 14 is supplied to a peak envelope detection circuit 15, a bottom envelope detection circuit 16, a track discrimination circuit 19, and an address detection circuit 20 at the subsequent stage.

The peak envelope detection circuit 15 detects the peak envelope of the wobble component signal passed by the band pass filter 14. The peak envelope detection circuit 15 outputs the detected peak envelope to the subsequent-stage subtractor 17.

The bottom envelope detection circuit 16 detects the bottom envelope of the wobble component signal passed by the band pass filter 14. The bottom envelope detection circuit 16 outputs the detected bottom envelope to a subtractor 17 at the subsequent stage.

The subtractor 17 calculates the difference between the peak envelope supplied from the peak envelope detection circuit 15 and the bottom envelope supplied from the bottom envelope detection circuit 16, and outputs the obtained difference signal to the amplitude detection circuit 18 at the subsequent stage. Output.

The amplitude detection circuit 18 detects the amplitude of the wobble component signal based on the difference signal supplied from the subtracter 17. The amplitude detection circuit 18 outputs an amplitude detection signal indicating the detected amplitude to the subsequent tilt detection circuit 24.

The track discriminating circuit 19 determines whether the sub-beam spots SS ₁ and S pass through the band-pass filter 14.
Based on the wobble component signal by the S _2, performs track discrimination of the main beam spot MS. The track discriminating circuit 19 outputs a track discriminating signal indicating the result of discriminating the track to the address detecting circuit 20 and the tilt detecting circuit 2 in the subsequent stage.
4 is output.

The address detection circuit 20 extracts and detects the address recorded on the optical disk from the wobble component signal of the main beam spot MS passed by the band pass filter 14. At this time, based on the track discrimination signal supplied from the track discrimination circuit 19, the address detection circuit 20 converts the detected address into the track T _A.
If by return light from the signal information recording sidewall W constituting the signal information recording sidewall W constituting the track T _B
It is determined whether or not this is due to the return light from the camera.

The equalizer 21 receives the RF signal from the IV conversion circuit 12 and performs a waveform equalization process for correcting, for example, a jitter error of the RF signal. This equalizer 21
Adjusts the gain based on a tilt error signal supplied from a tilt detection circuit 24 described later,
Compensation for lowering of Transfer Function). The equalizer 21 outputs the signal on which the waveform equalization processing has been performed to the data determination circuit 22 at the subsequent stage.

The data discriminating circuit 22 extracts data from the signal input from the equalizer 21 and discriminates a data detecting ability such as a jitter error. Data discrimination circuit 22
A data determination signal indicating the result of determining the data detection capability is provided to a target value setting circuit 23 and a tilt detection circuit 24 in the subsequent stage.
Output to

The target value setting circuit 23 includes a data discriminating circuit 2
2, a target value for compensating for a tilt instruction value indicating the tilt amount detected by the tilt detection circuit 24 is set. The target value setting circuit 23 outputs the set target value to the subtractor 35 of the tilt detection circuit 24.

[0052] tilt detection circuit 24 includes a switch 32 for opening and closing based on the sample pulses generated from the sample pulse circuit, not shown, the amplitude of the wobble component signal only by the return light from the track T _A like the spot S _A an amplitude detection circuit 33a for detecting, from the track T _B like the spot S _B and an amplitude detection circuit 33b for detecting the amplitude of the wobble component signal only by the return light, from the track T _a detected by the amplitude detection circuit 33a The amplitude value of the wobble component signal due to the return light and the amplitude detection circuit 33b
A subtractor 34 for obtaining the difference between the amplitude value of the wobble component signal by the return light from the track T _B detected by the difference value and the target value setting circuit 2 which is supplied from the subtractor 34
And a subtractor 35 for obtaining a difference from the target value supplied from the third unit.

The switch 32 opens and closes based on a sample pulse generated from a sample pulse circuit (not shown), and connects or cuts off the amplitude detection circuit 18 and the amplitude detection circuit 33a or 33b.

The amplitude detection circuit 33a includes the amplitude detection circuit 18
Enter the amplitude detection signal indicating the detected amplitude by, detecting the amplitude of the wobble component signal only by the return light from the track T _A. The amplitude detection circuit 33a outputs an amplitude signal indicating the detected amplitude value to the subsequent-stage subtractor 34.

The amplitude detection circuit 33b includes the amplitude detection circuit 18
Enter the amplitude detection signal indicating the detected amplitude by, detecting the amplitude of the wobble component signal only by the return light from the track T _B. The amplitude detection circuit 33b outputs an amplitude signal indicating the detected amplitude value to the subsequent subtractor.

The subtractor 34 calculates the amplitude value indicated by the amplitude signal supplied from the amplitude detection circuit 33a and the amplitude detection circuit 33b.
And the difference from the amplitude value indicated by the amplitude signal supplied from.
The subtractor 34 outputs the tilt instruction value, which is the obtained difference value, to the subtractor 35 at the subsequent stage.

The subtractor 35 calculates a difference between the tilt instruction value supplied from the subtractor 34 and the target value supplied from the target value setting circuit 23, and outputs a tilt error signal represented by the difference value in the subsequent stage. The signal is output to the equalizer 21 and the drive signal generation circuit 25.

The tilt detection circuit 24 detects the amount of tilt based on the amplitude detection signal of the wobble component signal supplied from the amplitude detection circuit 18 and the track discrimination signal supplied from the track discrimination circuit 19. , And outputs the generated tilt error signal to the equalizer 21 and the drive signal generation circuit 25.

The drive signal generation circuit 25 adds the focus error signal supplied from the optical pickup 11 and the tilt error signal supplied from the tilt detection circuit 24, and the adder 36 supplied from the optical pickup 11. A subtractor 3 that calculates the difference between the focus error signal and the tilt error signal supplied from the tilt detection circuit 24
7, a drive circuit 38a that generates a drive signal indicating the magnitude of the current flowing through the focus coil 27a based on the added value supplied from the adder 36, and a focus coil based on the difference value supplied from the subtractor 37. And a drive circuit 38b for generating a drive signal indicating the magnitude of the current flowing through 27b.

The adder 36 calculates the sum of the focus error signal indicating the focus error of the objective lens 26 supplied from the optical pickup 11 and the tilt error signal supplied from the tilt detection circuit 24, and drives the added value. Output to the circuit 38a.

The subtractor 37 calculates the difference between the focus error signal indicating the focus error of the objective lens 26 supplied from the optical pickup 11 and the tilt error signal supplied from the tilt detection circuit 24, and drives the difference value. Output to the circuit 38b.

The drive circuit 38a generates a drive signal indicating the magnitude of the current flowing through the focus coil 27a based on the added value supplied from the adder 36. The drive circuit 38a outputs the generated drive signal to the focus coil 27a.

The drive circuit 38b generates a drive signal indicating the magnitude of the current flowing through the focus coil 27b based on the difference value supplied from the subtracter 37. The drive circuit 38b outputs the generated drive signal to the focus coil 27b.

Such a drive signal generation circuit 25
A drive signal for compensating tilt is generated and output to the focus coils 27a and 27b.

The optical disc reproducing apparatus 10 having the above-described components is configured to operate the track T _A like the spot S _A described above.
The wobble component signal SIG _A in the case where the laser beam is irradiated, the wobble component signal in the case where the laser beam is irradiated on the track T _B like the spot S _B SIG _B
Sampling the bets, the difference by the tilt detection circuit 24, a wobble component signal SIG _A in the case where the laser beam is irradiated on the track T _A, a wobble component signal SIG _B in the case where the laser beam is irradiated on the track T _B A tilt instruction value represented by a value is obtained, and the optical pickup 11 is controlled and driven so that the tilt instruction value approaches the target value set by the target value setting circuit 23.

Here, in the optical disk reproducing apparatus 10, a preset value or a value recorded in a control track which is a control information recording area of the optical disk may be used as the target value. 1
0 is an initial operation at the time of loading the optical disc,
The target value can be set by the following method.

The optical disk reproducing apparatus 10 transmits a drive signal to the focus coil 2 when loading the optical disk.
7a and 27b, and drive the actuator 28 of the optical pickup 11 while changing it. Then, the optical disc reproducing apparatus 10 obtains a tilt instruction value according to the change of the tilt amount by the tilt detection circuit 24, and sequentially supplies the tilt instruction value to the target value setting circuit 23. Further, the optical disk reproducing device 10 includes a target value setting circuit 23.
Thus, the correlation between the tilt instruction value supplied from the tilt detection circuit 24 and the data detection error based on the data determination signal supplied from the data determination circuit 22 is measured.
Then, the optical disk reproducing device 10 sets the target value setting circuit 2
According to 3, the tilt instruction value that minimizes the data detection error is set as the target value.

As described above, the optical disk reproducing apparatus 10
Can set an optimal target value based on the correlation between the tilt instruction value and the data detection error.

The optical disk reproducing device 10 is, specifically,
According to the method described below, the wobble component signal
_A and the wobble component signal SIG _B are sampled to detect a tilt amount.

The optical disc reproducing apparatus 10 irradiates the main beam spot MS and the two sub-beam spots SS ₁ and SS ₂ onto the optical disc by the optical pickup 11 as in the case of the normal reproduction.

At this time, when the spots S _A and S _B are normally irradiated on the optical disk without being affected by the tilt, that is, when the tilt amount is “0 °”, the band pass filter 14 wobble component signal passed by the spot S _A according to the signal information recording sidewall W
The wobble component signal SIG _A based on the return light from the wobble component signal SIG _B based on the return light from the signal information recording sidewall W by spot S _B, becomes amplitude equal to each other.

On the other hand, when the spots S _A and S _B are affected by the tilt and are irradiated on the optical disc in a state of being inclined in the direction of any of the signal information recording side walls W, the band pass filter 14 passes the spots. wobble component signal, a wobble component signal SIG _a based on the return light from the signal information recording sidewall W by spot S _a, a wobble component signal SIG _B based on the return light from the signal information recording sidewall W by spot S _B Have different amplitudes from each other.

Therefore, the wobble component signals SIG _A ,
The amplitude signal supplied to the subtractor 34 by detecting the amplitude of each of the SIG _B by the amplitude detection circuits 33a and 33b of the tilt detection circuit 24, the amplitude of which changes in an edge shape in accordance with the movement of the three beam spots. Becomes

The optical disk reproducing apparatus 10 detects a tilt instruction value, which is a difference value obtained by the subtractor 34 of the tilt detection circuit 24, based on such an amplitude signal, and generates a tilt error signal. The optical disc reproducing device 10
Such an operation is repeated a plurality of times.

As described above, the optical disk reproducing apparatus 10
Can be compensated by detecting the amount of tilt. By detecting the amount of tilt in this way, the optical disk reproducing device 10 can quickly detect the amount of tilt without waiting for the rotation of the optical disk. In addition, the optical disk reproducing device 10 obtains a plurality of tilt instruction values during one rotation of the optical disk, so that the tilt amount can be detected with high accuracy.

That is, for example, when the amplitude values of the wobble component signals in the tracks T _A and T _B are stored and later calculated, the tilt amount of at least two rotations is detected separately from the normal operation. Since it requires time and calculation time, when seeking from the innermost circumference where the tilt amount is small to the outermost circumference where the tilt amount is large on the optical disc,
A rotation waiting time of 2 rotations + α is required, which causes a problem of lowering the effective access speed.

Further, when the tilt amount is detected based on one sample information during one rotation of the optical disk, a problem arises in that the optical disk cannot follow the rotation fluctuation. For example, in the case of an optical disk rotating at 600 rpm, There is a problem that the time constant is increased to about 2 seconds. Further, in a case where only one of the tracks T _A and T _B is continuously reproduced,
There is a problem that the tilt amount cannot be detected.

The optical disk reproducing apparatus 10 can solve such a problem and can quickly and accurately detect tilt and compensate without any complicated operation.

As described above, the optical disc reproducing apparatus 10 irradiates the main beam spot MS and the two sub-beam spots SS ₁ and SS ₂ onto the optical disc by the optical pickup 11 and emits two of the three beam spots. By detecting the return light due to the beam spot, tilt detection and compensation can be performed without providing a dedicated sensor for tilt detection. Therefore, the optical disk reproducing apparatus 10 controls the numerical aperture (Nu
The tilt amount can be detected and compensated even for an optical disc that is thin and has a small diameter with an increase in merical aperture (NA).

The present invention is not limited to the embodiment described above. For example, when the optical disk shown in FIG. 3 is applied, it is necessary to provide _two sub-beam spots SS ₁ and SS _2. However, only one sub-beam spot may be used.

The present invention is not limited to an optical disk reproducing apparatus for reproducing digital data from an optical disk,
Of course, the present invention is also applicable to a recording device for recording digital data on an optical disk.

As described above, it is needless to say that the present invention can be appropriately changed without departing from the gist of the present invention.

[0083]

As described in detail above, the recording medium driving apparatus according to the present invention drives the disk-shaped recording medium having the signal information recording side wall on which the signal information that can be distinguished from the recording data is recorded. A recording medium drive for recording and / or reproducing digital data on a disk-shaped recording medium, comprising: a laser beam forming a main beam spot and two sub-beam spots on the disk-shaped recording medium; An optical pickup means for irradiating and receiving return light reflected and diffracted on the surface of the disc-shaped recording medium, and return from the signal information recording side wall by two target beam spots of the main beam spot and the two sub beam spots Amplitude detecting means for detecting the amplitude of a signal based on light, and til for detecting a tilt amount based on the amplitude of the signal detected by the amplitude detecting means And detection means.

Therefore, the recording medium driving device according to the present invention irradiates the disk-shaped recording medium with the laser beam forming the main beam spot and the two sub-beam spots by the optical pickup means, and by the tilt detection means. Out of the main beam spot and the two sub beam spots, the tilt amount can be detected based on the amplitude of the signal based on the return light from the signal information recording side wall due to the two target beam spots. The tilt detection can be performed promptly and with high accuracy without providing the above sensor.

Further, the tilt detecting method according to the present invention comprises:
A disk-shaped recording medium having a signal information recording side wall on which signal information that can be distinguished from recording data is recorded is irradiated with laser light that forms a main beam spot and two sub-beam spots. Of the main beam spot and the two sub beam spots, the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots was detected and detected. The amount of tilt is detected based on the amplitude of the signal.

Therefore, the tilt detecting method according to the present invention irradiates a laser beam forming a main beam spot and two sub-beam spots to a disc-shaped recording medium, and outputs the main beam spot and the two sub-beam spots. Of which 2
The tilt amount can be detected based on the amplitude of the signal based on the return light from the signal information recording side wall due to the two target beam spots, and the tilt detection can be performed quickly and efficiently without the need for a dedicated sensor for tilt detection. It can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical disk applied to an optical disk reproducing device shown as an embodiment of the present invention, illustrating a state of a groove substrate in which straight groove portions and wobble groove portions are provided alternately.

FIG. 2 is an explanatory diagram of an optical disk applied to the optical disk reproducing apparatus, showing a state of a land substrate in which groove portions as inner side modulation guide grooves and groove portions as outer side modulation guide grooves are alternately provided. FIG.

FIG. 3 is an explanatory diagram of an optical disk applied to the optical disk reproducing device, illustrating a state of a land / groove substrate in which groove portions and land portions are provided alternately.

FIG. 4 is a diagram illustrating the arrangement of beam spots.

FIG. 5 is a diagram illustrating a result obtained by numerical calculation of a change in the intensity distribution of laser light due to tilt;

FIG. 6 is a diagram for explaining a relationship between a wobble component signal and a tilt amount, and is a result obtained by numerical calculation of a characteristic of a wobble component signal when an optical disk is irradiated with laser light while actually changing the tilt amount. FIG.

FIG. 7 is a block diagram illustrating a configuration of the optical disc reproducing device.

[Explanation of symbols]

Reference Signs List 10 optical disk reproducing device, 11 optical pickup, 18, 33a, 33b amplitude detecting circuit, 19
Track discriminating circuit, 21 equalizer, 22 data discriminating circuit, 23 target value setting circuit, 24 tilt detecting circuit, 25 drive signal generating circuit, 26 objective lens, 29 laser diode, 31 photodiode

Claims (30)

[Claims] 1. A disk-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded, and a digital data is recorded and / or reproduced on and from the disk-shaped recording medium. A recording medium driving device for performing irradiation of a laser beam that forms a main beam spot and two sub-beam spots onto the disc-shaped recording medium, and the laser beam is reflected and diffracted on the surface of the disc-shaped recording medium. Optical pickup means for receiving return light; and amplitude detection means for detecting an amplitude of a signal based on return light from the signal information recording side wall due to two target beam spots among the main beam spot and the two sub beam spots. And tilt detection means for detecting a tilt amount based on the amplitude of the signal detected by the amplitude detection means, Recording medium drive. 2. The tilt detecting means according to claim 1, wherein one of said two target beam spots detected by said amplitude detecting means is located on an inner peripheral side of said disc-shaped recording medium with respect to said signal information recording side wall. And the other of the two target beam spots detected by the amplitude detecting means, which is a signal based on the return light from the signal information recording side wall, is larger than the signal information recording side wall. A difference value from the amplitude of a second signal, which is a signal based on the return light from the signal information recording side wall when located on the outer peripheral side of the disc-shaped recording medium, is obtained as a tilt instruction value indicating the tilt amount. 2. The recording medium driving device according to claim 1, wherein: 3. The disc-shaped recording medium, wherein modulation guide grooves whose width or position is modulated on both side walls to serve as the signal information recording side walls and non-modulation guide grooves which do not modulate both side walls are provided alternately. An area sandwiched between the modulation guide groove and the non-modulation guide groove is provided as a land portion, the modulation guide groove and the non-modulation guide groove are set as a recording area where the recording data is recorded, and the signal information recording side wall is provided. 2. The recording medium driving device according to claim 1, wherein address information as said signal information is recorded. 4. The optical pickup means irradiates the modulation guide groove or the non-modulation guide groove with the main beam spot, and irradiates the main beam spot with the modulation guide groove or the non-modulation guide groove. One of two sub-beam spots is radiated to each of the two land portions adjacent to the groove, and the amplitude detecting means returns light from the signal information recording side wall due to the two target beam spots. The tilt detection means detects the amplitude of the signal based on the return light from the signal information recording side wall due to the two sub beam spots as the signal amplitude based on the two sub beam spots, and the tilt detection means detects the two sub beam spots detected by the amplitude detection means. The signal information when one of the beam spots is located on the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. The amplitude of the first signal, which is a signal based on the return light from the recording side wall, and the other of the two sub-beam spots detected by the amplitude detecting means is larger than the signal information recording side wall in the disc-shaped recording medium. A difference value from an amplitude of a second signal, which is a signal based on return light from the signal information recording side wall when located on the outer peripheral side of the signal information recording side, is obtained as a tilt instruction value indicating the tilt amount. 4. The recording medium driving device according to 3. 5. The disc-shaped recording medium, wherein the signal information recording side wall is provided as an inner peripheral side wall of the disc-shaped recording medium, and the signal information recording side wall is provided by the disc-shaped recording medium. The outer peripheral side modulation guide grooves provided as the outer peripheral side walls are alternately provided, and a region sandwiched between the inner peripheral side modulation guide groove and the outer peripheral side modulation guide groove is provided as a land portion, and the land portion is provided as the land portion. 2. The recording medium drive according to claim 1, wherein a recording area in which recording data is recorded, and address information as the signal information is recorded on the signal information recording side wall. 6. The optical pickup means irradiates the land portion with the main beam spot, the inner peripheral side modulation guide groove adjacent to the land portion irradiated with the main beam spot, and the outer peripheral portion. Irradiating one of the two sub-beam spots to each of the side modulation guide grooves, wherein the amplitude detecting means detects an amplitude of a signal based on a return light from the signal information recording side wall by the two target beam spots. And detecting the amplitude of the signal based on the return light from the signal information recording side wall due to the two sub-beam spots, wherein the tilt detecting means detects the amplitude of the two sub-beam spots among the two sub-beam spots detected by the amplitude detecting means. Returning from the signal information recording side wall when one is located on the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall The amplitude of the first signal, which is a signal based on light, and the other of the two sub-beam spots detected by the amplitude detection means is located closer to the outer periphery of the disc-shaped recording medium than the signal information recording side wall. 6. The recording medium according to claim 5, wherein a difference value from an amplitude of a second signal, which is a signal based on the return light from the signal information recording side wall, is obtained as a tilt instruction value indicating the tilt amount. Drive. 7. The disc-shaped recording medium, wherein a guide groove having the signal information recording side wall on one of an inner peripheral side and an outer peripheral side of the disc-shaped recording medium and lands are alternately provided,
2. The recording according to claim 1, wherein each of the guide groove and the land is a recording area in which the recording data is recorded, and address information as the signal information is recorded on the signal information recording side wall. Medium drive. 8. The optical pickup means irradiates the guide groove or the land with the main beam spot, and irradiates the main beam spot with the guide groove or a land adjacent to the land. Alternatively, each of the guide grooves is irradiated with one of the two sub-beam spots, and the amplitude detecting means calculates the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots. Detecting the amplitude of the signal based on the return light from the signal information recording side wall by the main beam spot and one of the two sub beam spots, wherein the tilt detection means is detected by the amplitude detection means. When the main beam spot is located on the inner or outer peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall, The amplitude of the first signal, which is a signal based on the return light from the signal information recording side wall, and one of the two sub-beam spots detected by the amplitude detecting means is greater than the signal information recording side wall in the disk. A difference value from the amplitude of the second signal, which is a signal based on the return light from the signal information recording side wall when located on the outer peripheral side or the inner peripheral side of the linear recording medium, is obtained as a tilt instruction value indicating the tilt amount. The recording medium driving device according to claim 7, wherein: 9. The recording medium driving device according to claim 1, further comprising target value setting means for setting a target value for compensating for the tilt instruction value. 10. The recording medium drive according to claim 9, wherein the target value is a value arbitrarily set in advance. 11. The recording medium drive according to claim 9, wherein the target value is a value recorded in a control information recording area of the disk-shaped recording medium. 12. A data discriminating means for extracting the recording data from an RF signal based on the return light reflected and diffracted on the surface of the disc-shaped recording medium, and for discriminating a data detection capability for the recording data, and a tilt indication value. And a drive signal generating means for generating a drive signal for compensating tilt based on a tilt error signal represented by a difference value between the tilt instruction value and a target value for compensating for the tilt instruction value; The signal generating means changes the amount of tilt based on the drive signal and controls and drives the optical pickup means. The tilt detecting means obtains a tilt instruction value according to the change in tilt amount, and the target value The setting means includes a data indicating the tilt instruction value obtained by the tilt detecting means and a result of determining the data detecting ability by the data determining means. Based on the data discrimination signal, a recording medium driving apparatus according to claim 9, wherein the setting the target value. 13. A drive for generating a drive signal for compensating tilt based on a tilt error signal represented by a difference value between the tilt command value and a target value for compensating the tilt command value. 2. The recording medium driving device according to claim 1, further comprising signal generation means. 14. The optical pickup device according to claim 13, wherein the optical pickup device is controlled based on the drive signal generated by the drive signal generation device so that the tilt instruction value approaches the target value. Recording medium drive. 15. A waveform equalizer for performing a waveform equalization process on an RF signal based on return light reflected and diffracted on the surface of the disk-shaped recording medium, wherein the waveform equalizer comprises the tilt detector 14. The recording medium driving device according to claim 13, wherein gain adjustment is performed based on the tilt error signal obtained by the following. 16. A laser beam forming a main beam spot and two sub beam spots is irradiated on a disc-shaped recording medium having signal information recording side walls on which signal information distinguishable from recording data is recorded. Receiving the return light reflected and diffracted on the surface of the disc-shaped recording medium, based on the return light from the signal information recording side wall by two target beam spots among the main beam spot and the two sub beam spots. A tilt detection method, comprising: detecting an amplitude of a signal; and detecting a tilt amount based on the detected amplitude of the signal. 17. A method according to claim 1, wherein one of the detected two target beam spots is located on the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall, based on the return light from the signal information recording side wall. The amplitude of the first signal, which is a signal, from the signal information recording side wall when the other of the two detected target beam spots is located on the outer peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. 17. The tilt detecting method according to claim 16, wherein a difference value from the amplitude of the second signal, which is a signal based on the returning light, is obtained as a tilt instruction value indicating the tilt amount. 18. The disc-shaped recording medium, wherein modulation guide grooves which modulate the width or position on both side walls to serve as the signal information recording side walls and non-modulation guide grooves which do not modulate both side walls are provided alternately. An area sandwiched between the modulation guide groove and the non-modulation guide groove is provided as a land portion, the modulation guide groove and the non-modulation guide groove are set as a recording area where the recording data is recorded, and the signal information recording side wall is provided. 17. The tilt detecting method according to claim 16, wherein address information as the signal information is recorded. 19. The modulation guide groove or the non-modulation guide groove is irradiated with the main beam spot, and the modulation guide groove or the non-modulation guide groove adjacent to the modulation guide groove or the non-modulation guide groove irradiated with the main beam spot is illuminated. Each of the land portions is irradiated with one of the two sub-beam spots, and the two sub-beams are used as the amplitude of a signal based on the return light from the signal information recording side wall due to the two target beam spots. Detecting the amplitude of the signal based on the return light from the signal information recording side wall due to the spot; one of the detected two sub beam spots being closer to the inner circumference of the disc-shaped recording medium than the signal information recording side wall; The amplitude of the first signal, which is a signal based on the return light from the signal information recording side wall when it is located, and the two detected sub beam spots The difference value between the amplitude of a second signal, which is a signal based on the return light from the signal information recording side wall when the other of the signal information recording side walls is located on the outer peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall, 19. The tilt detection method according to claim 18, wherein the tilt detection value is obtained as a tilt instruction value indicating the tilt amount. 20. The disc-shaped recording medium, wherein the signal information recording side wall is provided as an inner peripheral side wall of the disc-shaped recording medium, and the signal information recording side wall is provided by the disc-shaped recording medium. The outer peripheral side modulation guide grooves provided as the outer peripheral side walls are alternately provided, and a region sandwiched between the inner peripheral side modulation guide groove and the outer peripheral side modulation guide groove is provided as a land portion, and the land portion is provided as the land portion. 17. The tilt detection method according to claim 16, wherein the recording information is recorded in a recording area, and address information as the signal information is recorded on the signal information recording side wall. 21. The land beam is irradiated with the main beam spot, and each of the inner peripheral side modulation guide groove and the outer peripheral side modulation guide groove adjacent to the land part irradiated with the main beam spot is provided. Irradiates one of each of the two sub-beam spots to the signal information by the two sub-beam spots as an amplitude of a signal based on return light from the signal information recording side wall by the two target beam spots. Detecting the amplitude of the signal based on the return light from the recording side wall, and detecting one of the two detected sub-beam spots on the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall; The amplitude of the first signal, which is a signal based on the return light from the signal information recording side wall, and the other of the two detected sub-beam spots are higher. The difference value between the amplitude of a second signal, which is a signal based on the return light from the signal information recording side wall when the signal information recording side wall is located on the outer peripheral side of the signal information recording side wall, and the tilt amount indicating the tilt amount 21. The tilt detecting method according to claim 20, wherein the tilt value is obtained as an instruction value. 22. The disc-shaped recording medium, wherein a guide groove having the signal information recording side wall on one of an inner peripheral side and an outer peripheral side of the disc-shaped recording medium and lands are alternately provided. 17. The tilt detecting method according to claim 16, wherein each of the groove and the land is a recording area where the recording data is recorded, and address information as the signal information is recorded on the signal information recording side wall. . 23. Irradiating the main beam spot on the guide groove or the land, and irradiating the land or the guide groove adjacent to the guide groove or the land with the main beam spot. The main beam spot and the two sub-beam spots are radiated as one of the two sub-beam spots, respectively, as an amplitude of a signal based on the light returned from the signal information recording side wall by the two target beam spots. And detecting the amplitude of the signal based on the return light from the signal information recording side wall due to one of the signal information recording side walls, and detecting the main beam spot on the inner side or outer side of the disc-shaped recording medium with respect to the signal information recording side wall. , The amplitude of the first signal which is a signal based on the return light from the signal information recording side wall, and the two detected sub-signals. Amplitude of a second signal which is a signal based on the return light from the signal information recording side wall when one of the beam spots is located on the outer peripheral side or inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. 23. The tilt detecting method according to claim 22, wherein a difference value from the tilt angle is obtained as a tilt instruction value indicating the tilt amount. 24. The tilt detecting method according to claim 16, wherein a target value for compensating the tilt instruction value is set. 25. The tilt detecting method according to claim 24, wherein the target value is a value arbitrarily set in advance. 26. The tilt detecting method according to claim 24, wherein the target value is a value recorded in a control information recording area of the disc-shaped recording medium. 27. The recording data is extracted from an RF signal based on return light reflected and diffracted on the surface of the disc-shaped recording medium, and a data detection capability for the recording data is determined. The optical pickup means for irradiating a laser beam forming a main beam spot and two sub-beam spots and receiving return light reflected and diffracted on the surface of the disk-shaped recording medium is provided with the tilt instruction value and the tilt instruction value. The tilt amount is changed based on the drive signal for compensating for the tilt generated based on the tilt error signal represented by the difference value from the target value for compensating the value, and the drive is performed. A tilt instruction value according to the change is obtained, and the obtained tilt instruction value and
The tilt detection method according to claim 24, wherein the target value is set based on a data determination signal indicating a result of determining the data detection capability. 28. A drive signal for compensating tilt is generated based on a tilt error signal represented by a difference value between the tilt command value and a target value for compensating the tilt command value. 17. The tilt detecting method according to claim 16, wherein: 29. An optical system for irradiating the disc-shaped recording medium with laser light for forming a main beam spot and two sub-beam spots and receiving return light reflected and diffracted on the surface of the disc-shaped recording medium. Pickup means,
29. The tilt detecting method according to claim 28, wherein control is performed such that the tilt instruction value approaches the target value based on the drive signal. 30. A gain adjustment in a waveform equalization process performed on an RF signal based on return light reflected and diffracted on the surface of the disk-shaped recording medium based on the tilt error signal. Item 30. The tilt detecting method according to Item 28.