JP4122660B2 - Recording medium driving apparatus and tilt detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording medium driving apparatus for recording and / or reproducing digital data to and from a disk-shaped recording medium by rotationally driving the disk-shaped recording medium, and a tilt amount generated when the disk-shaped recording medium is rotationally driven. The present invention relates to a tilt detection method.
[0002]
[Prior art]
For example, optical disks such as so-called CDs (Compact Discs) and DVDs (Digital Versatile Discs or Digital Video Discs) are widely known as recording media on which digital data is optically recorded.
[0003]
An optical disc drive apparatus that records and / or reproduces digital data on such an optical disc irradiates a rotationally driven optical disc with a minute spot obtained by condensing laser light by an optical pickup at a desired position, Record and / or play back digital data. At this time, the optical pickup causes the laser beam to follow a track provided on the disk surface of the optical disc in order to stably record digital data on the optical disc and to faithfully reproduce the digital data recorded on the optical disc. Operate.
[0004]
[Problems to be solved by the invention]
By the way, in the above-mentioned optical disc, radial tilt occurs due to the influence of the environment such as temperature and humidity during use and / or storage, the warpage of the optical disc due to the handling condition, and the tilt of the optical pickup in the optical disc drive apparatus. There is. This tilt is known to cause aberrations in the reproduction optical spot, causing distortion in the reproduction signal, a decrease in MTF (Modulation Transfer Function), and a decrease in recording power efficiency.
[0005]
In recent years, there has been a tendency to increase the numerical aperture (NA) of an objective lens in an optical pickup for increasing the density of an optical disk. For example, in the case of a CD, the value of NA is increased. Is 0.45, and in the case of DVD, an objective lens having an NA value of 0.60 is used. In connection with this, the substrate thickness of the optical disc is reduced. For this reason, the optical disk is likely to be warped and has a large NA, so that the angle dependency of aberration is also increasing.
[0006]
On the other hand, in the optical disk drive device, in order to compensate for the tilt, there is a type in which a dedicated sensor is provided to detect the amount of tilt, and the objective lens or actuator in the optical pickup is tilted based on the detection signal. It has been put into practical use.
[0007]
However, when the optical disk has a small diameter, the conventional optical disk drive device cannot secure a sufficient place for installing the sensor for detecting the tilt amount, and it is difficult to detect the tilt amount.
[0008]
The present invention has been made in view of such circumstances, solves the problem of the tilt detection method in the conventional optical disk drive device, and detects the tilt amount quickly and accurately from the signal obtained by the optical pickup. It is an object to provide a recording medium driving device and a tilt detection method.
[0009]
[Means for Solving the Problems]
  A recording medium driving apparatus according to the present invention that achieves the above-mentioned object rotates 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 driving apparatus for recording and / or reproducing digital data, wherein a disk-shaped recording medium is irradiated with a laser beam that forms a main beam spot and two sub-beam spots, and a disk-shaped recording is performed. Based on optical pickup means for receiving the return light reflected and diffracted on the surface of the medium, and return light from the signal information recording side wall by the two target beam spots among the main beam spot and the two sub beam spotsExtracted signal information componentAmplitude detecting means for detecting the amplitude of the signal, and tilt detecting means for detecting the tilt amount based on the amplitude of the signal detected by the amplitude detecting means.The tilt detection means returns light from the signal information recording side wall when one of the two target beam spots detected by the amplitude detection means is located closer to the inner circumference side of the disc-shaped recording medium than the signal information recording side wall. Signal information when the other one of the two target beam spots detected by the amplitude detection means is positioned on the outer peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. A difference value from the amplitude of the second signal, which is a signal based on the return light from the recording side wall, is obtained as a tilt instruction value indicating the tilt amount.It is characterized by that.
  The recording medium driving apparatus according to the present invention rotationally drives a disc-shaped recording medium having a signal information recording side wall on which signal information distinguishable from the recording data is recorded, and the digital data is recorded on the disc-shaped recording medium. A recording medium driving apparatus for performing recording and / or reproduction, which irradiates a disk-shaped recording medium with a laser beam that forms a main beam spot and two sub beam spots, and on the surface of the disk-shaped recording medium. Optical pick-up means for receiving the reflected and diffracted return light, and amplitude detection for detecting the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots of the main beam spot and the two sub beam spots And a tilt detection means for detecting a tilt amount based on the amplitude of the signal detected by the amplitude detection means, and the disc-shaped recording medium comprises: No. information recording side wall is provided on one of the inner and outer peripheral sides of the disc-shaped recording medium, and guide grooves and land portions are alternately provided, and recording data is recorded in each of the guide grooves and land portions. Address information as signal information is recorded on the signal information recording side wall, and the optical pickup unit irradiates the main beam spot to the guide groove or land portion, and the guide groove to which the main beam spot is irradiated Alternatively, each of the land portion or guide groove adjacent to the land portion is irradiated with one of the two sub beam spots, and the amplitude detection means applies the return light from the signal information recording side wall by the two target beam spots. The amplitude of the signal based on 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 The tilt detecting means detects the width, and the tilt detecting means returns from the signal information recording side wall when the main beam spot detected by the amplitude detecting means 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 light, and one of the two sub beam spots detected by the amplitude detecting means 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. In this case, 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 is obtained as a tilt instruction value indicating the tilt amount.
[0010]
Such a recording medium driving apparatus according to the present invention irradiates the disc-shaped recording medium with the laser beam that forms the main beam spot and the two sub beam spots by the optical pickup unit, and the main unit by the tilt detection unit. The tilt amount is detected based on the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots among the beam spot and the two sub beam spots.
[0011]
  In addition, the tilt detection method according to the present invention that achieves the above-described object is a disk-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded. In addition to irradiating a laser beam that forms a beam spot and receiving a return beam reflected and diffracted by the surface of the disk-shaped recording medium, signal information by two target beam spots of the main beam spot and the two sub beam spots Based on return light from recording sidewallExtracted signal information componentDetects signal amplitude and detects tilt amount based on detected signal amplitudeThe first signal which is a signal based on the return light from the signal information recording side wall when one of the two detected 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. And a signal based on the return light from the signal information recording side wall when the other of the detected two 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. The difference value from the signal amplitude is obtained as a tilt instruction value indicating the tilt amount.It is characterized by that.
  Furthermore, the tilt detection method according to the present invention forms a main beam spot and two sub beam spots on a disc-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded. While irradiating a laser beam and receiving the return light reflected and diffracted on the surface of the disc-shaped recording medium, the return light from the signal information recording side wall by the two target beam spots of the main beam spot and the two sub beam spots. And detecting the amount of tilt based on the detected amplitude of the signal, and the disc-shaped recording medium has a signal information recording side wall on either the inner peripheral side or the outer peripheral side of the disc-shaped recording medium. The guide grooves and the land portions are provided alternately, and each of the guide grooves and the land portions is a recording area in which recording data is recorded, and the signal information is recorded on the signal information recording side wall. The address information is recorded, the main beam spot is irradiated to the guide groove or land portion, and 2 each of the land portion or guide groove adjacent to the guide groove or land portion irradiated with the main beam spot is recorded. A signal from the main beam spot and one of the two sub beam spots is used as the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots. The amplitude of the signal based on the return light from the information recording side wall is detected, and the detected main beam spot from the signal information recording side wall when the detected main beam spot is located on the inner peripheral side or the outer peripheral side of the disc-shaped recording medium from the signal information recording side wall. The amplitude of the first signal, which is a signal based on the return light, and one of the detected two sub beam spots is more circular than the signal information recording side wall. Obtaining 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 positioned on the outer peripheral side or the inner peripheral side of the recording medium, as a tilt instruction value indicating a tilt amount. It is a feature.
[0012]
Such a tilt detection method according to the present invention irradiates a disc-shaped recording medium with a laser beam that forms a main beam spot and two sub beam spots, and the main beam spot and the two sub beam spots, The tilt amount is detected based on the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.
[0014]
In this embodiment, the recording medium driving apparatus according to the present invention records digital data such as CD (Compact Disc), DVD (Digital Versatile Disc or Digital Video Disc), MD (Mini Disk, Sony Corporation). The present invention is applied to an optical disk reproducing apparatus that reproduces digital data from an optical disk that is a disc-shaped recording medium. Here, first, the principle regarding the tilt detection method by the optical disk reproducing apparatus will be described.
[0015]
An optical disk suitable for applying the present invention is shown in FIGS. 1 to 3 in accordance with the recording area.
[0016]
That is, the optical disk shown in FIG. 1 is called a straight groove SG (straight groove) SG which is a non-modulated guide groove having no wobble and a double spiral. For example, FM modulation (Frequency) is performed at about 80 kHz with respect to a standard linear velocity. The wobbled groove WG, which is a modulation guide groove having signal information recording side walls W wobbled on both sides, provided with address information, which is modulated signal information, is alternately provided, and these straight grooves An area sandwiched between the part SG and the wobbled groove part WG is provided as a land part L, and the straight substrate SG and the wobbled groove part WG are recording substrates.
[0017]
Further, the optical disc shown in FIG. 2 has a groove portion IG which is an inner peripheral side modulation guide groove in which, for example, a signal information recording side wall W wobbled with FM modulated address information is provided as an inner peripheral side wall of the optical disc. And groove portions OG, which are outer peripheral side modulation guide grooves provided with the signal information recording side wall W as the outer peripheral side wall of the optical disc, and an area sandwiched between the groove portions IG and the groove portion OG. A land substrate provided as a land portion L and having the land portion L as a recording area.
[0018]
Further, the optical disc shown in FIG. 3 has a groove portion which is a guide groove having a signal information recording side wall W wobbled with, for example, FM-modulated address information on either the inner peripheral side or the outer peripheral side of the optical disc. G and land portion L are alternately provided, and the groove portion G and land portion L are land / groove substrates each serving as a recording area. Note that the optical disk 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.
[0019]
An optical disk reproducing apparatus shown as an embodiment of the present invention irradiates laser light to these optical disks, and a main beam spot MS and two sub beam spots SS on the optical disk.₁, SS₂And form. Each of these beam spots is a Gaussian beam whose intensity distribution exhibits a Gaussian distribution. The optical disc reproducing apparatus detects the tilt amount based on the return light from two beam spots (target beam spots) among the three beam spots formed on the optical disc.
[0020]
That is, in the case of the optical disk of the groove substrate shown in FIG. 1, the optical disk reproducing apparatus has two sub beam spots SS irradiated to the land portion L.₁, SS₂And the amount of tilt is detected based on the return light from these target beam spots.
[0021]
Further, in the case of the land substrate optical disk shown in FIG. 2, the optical disk reproducing apparatus has two sub beam spots SS irradiated to the groove portions IG and OG.₁, SS₂And the amount of tilt is detected based on the return light from these target beam spots.
[0022]
Further, in the case of the land / groove substrate optical disk shown in FIG. 3, the optical disk reproducing apparatus has a main beam spot MS and two sub beam spots SS.₁, SS₂One of the sub beam spots is set as a target beam spot, and the tilt amount is detected based on the return light from these target beam spots.
[0023]
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 apparatus will be described as a main beam spot MS. Are there sub-beam spots SS₁, SS₂As shown in FIG. 4 (A), the beam in the case where the signal information recording side wall W is located on the inner peripheral side of the optical disc with respect to the laser beam from the optical pickup (not shown). Spot S_AAs shown in FIG. 5B, the beam spot when it is on the outer peripheral side of the optical disk is a spot S._BAnd In the following description, the spot S is used as necessary._ATrack T is irradiating track T_AAnd spot S_BTrack T is irradiating track T_BAnd
[0024]
Here, the result of the numerical calculation of the change in the intensity distribution of the laser beam due to the tilt is as shown in FIG.
[0025]
Spot S irradiated on the optical disk_BWhen the irradiation is normally performed without being affected by the tilt, that is, when the tilt amount is “0 °”, the solid line portion C in FIG._0BAs shown, the intensity distribution is a track T in the radial direction of the optical disk._BIt becomes symmetrical at the center position. Therefore, the return light reflected and diffracted by the disk surface is a track T in the radial direction of the optical disk._BIt becomes symmetrical at the center position.
[0026]
On the other hand, the spot S irradiated on the optical disc in a state tilted in the direction of the signal information recording side wall W due to distortion due to the influence of tilt._BFor example, the broken line portion C in FIG._0.6BThe chain line part C in the figure_1.2BAs shown. That is, the spot S irradiated on the optical disk_BWhen the tilt amounts are “0.6 °” and “1.2 °”, respectively, the broken line portion C in FIG._0.6B, Chain line C_1.2BAs shown, the intensity distribution of the track T in the radial direction of the optical disk is_BAsymmetrical on track T_BThe intensity of the laser beam irradiated on the side where the signal information recording side wall W is provided is lower than that when normally irradiated, and the track T_BThe intensity of the laser beam irradiated on the side where the signal information recording side wall W is not provided becomes higher than that when the signal information recording side wall W is not normally irradiated. The tendency becomes more prominent as the tilt amount increases. Therefore, the return light reflected and diffracted by the disk surface is the track T_BThe intensity I of the return light from the signal information recording side wall W becomes asymmetric._0.6B, I_1.2BWill also be different.
[0027]
Further, the spot S irradiated on the optical disk in the state tilted in the direction of the signal information recording side wall W under the influence of the tilt._AAlthough not shown, the intensity distribution is a track T in the radial direction of the optical disk._AAsymmetrical on track T_AThe intensity of the laser beam irradiated to the side where the signal information recording side wall W is provided becomes higher than that when normally irradiated, and the track T_AThe intensity of the laser beam irradiated to the side where the signal information recording side wall W is not provided is lower than that of normal irradiation. Therefore, the return light reflected and diffracted by the disk surface is the track T_AAs a result, the intensity of the return light from the signal information recording side wall W becomes different.
[0028]
FIG. 6 shows the result of numerical calculation of the signal characteristics based on the return light from the signal information recording side wall W when the optical disc 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 ADIP (ADress In Pre-groove) given to the signal information recording side wall W is reproduced. Signal.
[0029]
Spot S against tilt amount_AThe signal based on the return light from the signal information recording side wall W by the wobble component signal SIG_A) Is a curve in which the change in amplitude is plotted_AAnd spot S with respect to tilt amount_BThe signal based on the return light from the signal information recording side wall W by the wobble component signal SIG_B) Is a curve in which the change in amplitude is plotted_BThen, as shown in the figure, the wobble component signal SIG_AAmplitude and wobble component signal SIG_BBoth of these amplitudes depend on the tilt amount, and tend to be symmetric with respect to the case where the tilt amount is “0 °”. These wobble component signals SIG_AAnd the wobble component signal SIG_BThe signal represented by the difference between the tilt detection signal SIG_TThen, curve C_TAs can be seen, linear characteristics can be obtained in the range of “about −0.75 ° to about + 0.75 °” centering on the case where the tilt amount is “0 °”. The pull-in range is “about −1.2 ° to about + 1.2 °”.
[0030]
The optical disc reproducing apparatus 10 shown in FIG. 7 as an embodiment of the present invention detects and compensates for the tilt amount using such characteristics.
[0031]
As shown in the figure, the optical disk reproducing apparatus 10 includes an optical pickup 11 that reads digital data recorded on an optical disk (not shown), and IV that performs current-voltage conversion (IV conversion) on the signal output from the optical pickup 11. The conversion circuit 12 and the optical pickup 11 are tracked so that the distance between the optical pickup 11 and the optical disk 11 is kept constant, the servo circuit 13 for controlling the rotational drive operation of a spindle motor (not shown), and a band pass for passing a signal of a desired frequency component A filter (Band Pass Filter; BPF) 14, a peak envelope detection circuit 15 for detecting a peak envelope of the wobble component signal passed by the band pass filter 14, and a bottom envelope of the wobble component signal passed by the band pass filter 14 Detect bottom envelope Based on a loop detection circuit 16, a subtracter 17 that takes a difference between a peak envelope detected by the peak envelope detection circuit 15 and a bottom envelope detected by the bottom envelope detection circuit 16, and an output from the subtractor 17 The amplitude detection circuit 18 for detecting the amplitude of the wobble component signal and the wobble component signal passed by the band pass filter 14 are_AIs due to the return light from the track T_BA track discriminating circuit 19 for discriminating whether the light is from the return light, an address detecting circuit 20 for extracting and detecting an address recorded on the optical disc from the wobble component signal passed by the band-pass filter 14, and an IV conversion circuit 12, an equalizer 21 that performs waveform equalization processing on an RF (Radio Frequency) signal input from 12, a data determination circuit 22 that extracts data from the signal input from the equalizer 21 to determine data detection capability, and will be described later. A target value setting circuit 23 for setting a target value for compensating for a tilt instruction value indicating the tilt amount detected by the tilt detection circuit 24, a tilt detection circuit 24 for detecting the tilt amount, and a tilt compensation Therefore, a drive signal for driving the focus coils 27a and 27b of the optical pickup 11 is generated. And a live signal generating circuit 25.
[0032]
The optical pickup 11 includes an objective lens 26 that condenses the laser light from the laser diode 29, focus coils 27a and 27b for tilting the objective lens 26 with respect to the optical disc, and electromagnetic force generated by these focus coils 27a and 27b. The actuator 28 that drives the objective lens 26, a laser diode (LD) 29 that emits laser light, and the return light that is transmitted through the laser light emitted from the laser diode 29 and reflected and diffracted on the surface of the optical disk And a photodiode (PD) 31 that receives the return light reflected and diffracted by the surface of the optical disk and incident by the prism 30.
[0033]
The objective lens 26 condenses the laser light from the laser diode 29 and irradiates the optical disk (not shown).
[0034]
The focus coils 27a and 27b are for tilting the objective lens 26 with respect to the optical disc, respectively. A current of a magnitude based on the drive signal supplied from the drive signal generation circuit 25 flows through each of the focus coils 27a and 27b. The focus coils 27a and 27b drive the actuator 28 in a direction in which the tilt is compensated by an electromagnetic force generated by an effect with a magnet (not shown).
[0035]
The actuator 28 performs tracking driving of the objective lens 26 in order to track the objective lens 26 to a desired position on an optical disk (not shown). In addition, the actuator 28 tilts the objective lens 26 with respect to the optical disk by electromagnetic force generated by the focus coils 27a and 27b.
[0036]
The laser diode 29 has a light emitting unit made of, for example, a semiconductor laser and emits laser light. The laser light emitted from the laser diode 29 is incident on the prism 30.
[0037]
The prism 30 receives and transmits the laser light emitted from the laser diode 29, and outputs the laser light to the objective lens 26, and the return light reflected and diffracted on the surface of the optical disk is incident and internally reflected to the photodiode 31. Exit.
[0038]
The photodiode 31 has a photodetector and a photoelectric conversion unit, receives the return light that is reflected and diffracted on the surface of the optical disk and is incident on the prism 30, converts it into an electrical signal, and outputs it to the IV conversion circuit 12 at the subsequent stage.
[0039]
Such an optical pickup 11 irradiates an optical disk (not shown) with laser light emitted from the laser diode 29 to form a main beam spot MS, and receives return light that is reflected and diffracted by the main beam spot MS on the surface of the optical disk. By doing so, the digital data recorded in the track on the surface of the optical disk is read out. Further, as described above, the optical pickup 11 converts the laser light into the main beam spot MS and the two sub beam spots SS.₁, SS₂And an optical system for receiving the return light reflected and diffracted on the optical disk surface by irradiating the optical disk (not shown) with these beam spots. Sub beam spot SS₁, SS₂The return light reflected and diffracted on the surface of the optical disk is used for 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.
[0040]
The IV conversion circuit 12 performs current-voltage conversion on the signal output from the photodiode 31. The IV conversion circuit 12 outputs the signal obtained by the conversion to the subsequent servo circuit 13 and the band pass filter 14. 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.
[0041]
Based on the signal supplied from the IV conversion circuit 12, the servo circuit 13 drives the optical pickup 11 so that the distance from the optical disk is kept constant, or controls the rotational driving operation of a spindle motor (not shown).
[0042]
The band pass filter 14 cuts off the RF signal component and other noise components from the signal supplied from the IV conversion circuit 12 in order to extract the wobble component signal from the signal information recording side wall W, and the desired frequency component. Pass through the signal. The wobble component signal passed by the band pass filter 14 is supplied to the peak envelope detection circuit 15, the bottom envelope detection circuit 16, the track discrimination circuit 19, and the address detection circuit 20 at the subsequent stage.
[0043]
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 subtracter 17.
[0044]
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 the subsequent subtracter 17.
[0045]
The subtractor 17 takes 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.
[0046]
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.
[0047]
The track discrimination circuit 19 includes a sub beam spot SS passed by the band pass filter 14.₁, SS₂Based on the wobble component signal by, the track discrimination of the main beam spot MS is performed. The track discrimination circuit 19 outputs a track discrimination signal indicating the result of discriminating the track to the subsequent address detection circuit 20 and tilt detection circuit 24.
[0048]
The address detection circuit 20 extracts and detects the address recorded on the optical disc from the wobble component signal by the main beam spot MS passed by the band pass filter 14. At this time, the address detection circuit 20 uses the track discrimination signal supplied from the track discrimination circuit 19 to detect the detected address as the track T_AOr by the return light from the signal information recording side wall W constituting the track T_BIt is discriminated whether it is due to the return light from the signal information recording side wall W constituting the.
[0049]
The equalizer 21 receives the RF signal from the IV conversion circuit 12 and performs a waveform equalization process for correcting a jitter error of the RF signal, for example. The equalizer 21 adjusts the gain based on a tilt error signal supplied from a tilt detection circuit 24 described later, and compensates for a decrease in MTF (Modulation Transfer Function). The equalizer 21 outputs the signal subjected to the waveform equalization processing to the subsequent data discrimination circuit 22.
[0050]
The data discrimination circuit 22 extracts data from the signal input from the equalizer 21 and discriminates the data detection capability such as jitter error. The data determination circuit 22 outputs a data determination signal indicating the result of determining the data detection capability to the target value setting circuit 23 and the tilt detection circuit 24 at the subsequent stage.
[0051]
The target value setting circuit 23 sets a target value for compensating for the tilt instruction value indicating the tilt amount detected by the tilt detection circuit 24 based on the data determination signal supplied from the data determination circuit 22. The target value setting circuit 23 outputs the set target value to the subtracter 35 of the tilt detection circuit 24.
[0052]
The tilt detection circuit 24 includes a switch 32 that opens and closes based on a sample pulse generated from a sample pulse circuit (not shown), and a spot S._ATrack T like_AAn amplitude detection circuit 33a for detecting the amplitude of only the wobble component signal due to the return light from_BTrack T like_BAmplitude detection circuit 33b for detecting the amplitude of only the wobble component signal due to the return light from the track, and the track T detected by the amplitude detection circuit 33a_AAmplitude value of the wobble component signal due to the return light from the track T and the track T detected by the amplitude detection circuit 33b_BA subtractor 34 for obtaining a difference between the amplitude value of the wobble component signal due to the return light from the light and a subtractor for obtaining a difference between the difference value supplied from the subtracter 34 and the target value supplied from the target value setting circuit 23. 35.
[0053]
The switch 32 opens and closes based on a sample pulse generated from a sample pulse circuit (not shown), and connects or disconnects the amplitude detection circuit 18 and the amplitude detection circuit 33a or the amplitude detection circuit 33b.
[0054]
The amplitude detection circuit 33a receives an amplitude detection signal indicating the amplitude detected by the amplitude detection circuit 18, and the track T_AThe amplitude of only the wobble component signal due to the return light from is detected. The amplitude detection circuit 33a outputs an amplitude signal indicating the detected amplitude value to the subtractor 34 at the subsequent stage.
[0055]
The amplitude detection circuit 33b receives an amplitude detection signal indicating the amplitude detected by the amplitude detection circuit 18, and the track T_BThe amplitude of only the wobble component signal due to the return light from is detected. The amplitude detection circuit 33b outputs an amplitude signal indicating the detected amplitude value to the subtracter 34 at the subsequent stage.
[0056]
The subtractor 34 takes the difference between the amplitude value indicated by the amplitude signal supplied from the amplitude detection circuit 33a and the amplitude value indicated by the amplitude signal supplied from the amplitude detection circuit 33b. The subtractor 34 outputs the obtained tilt instruction value, which is a difference value, to the subsequent subtractor 35.
[0057]
The subtractor 35 takes 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 to the equalizer 21 and the subsequent stage 21. Output to the drive signal generation circuit 25.
[0058]
Such a tilt detection circuit 24 detects and generates a tilt amount 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. The tilt error signal is output to the equalizer 21 and the drive signal generation circuit 25.
[0059]
The drive signal generation circuit 25 includes an adder 36 that calculates the sum of the focus error signal supplied from the optical pickup 11 and the tilt error signal supplied from the tilt detection circuit 24, and the focus error signal supplied from the optical pickup 11. And a subtractor 37 that takes a difference between the tilt error signal supplied from the tilt detection circuit 24 and a drive signal that indicates the magnitude of the current that flows through the focus coil 27 a based on the added value supplied from the adder 36. And a drive circuit 38b that generates a drive signal indicating the magnitude of the current flowing through the focus coil 27b based on the difference value supplied from the subtractor 37.
[0060]
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 supplies the sum to the drive circuit 38a. Output.
[0061]
The subtractor 37 takes 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 sends the difference value to the drive circuit 38b. Output.
[0062]
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.
[0063]
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 subtractor 37. The drive circuit 38b outputs the generated drive signal to the focus coil 27b.
[0064]
Such a drive signal generation circuit 25 generates a drive signal for compensating for tilt and outputs the drive signal to the focus coils 27a and 27b.
[0065]
The optical disc playback apparatus 10 having the above-described units is the spot S described above._ATrack T like_AWobble component signal SIG when laser light is irradiated_AAnd spot S_BTrack T like_BWobble component signal SIG when laser light is irradiated_BAnd the tilt detection circuit 24_AWobble component signal SIG when laser light is irradiated_AAnd track T_BWobble component signal SIG when laser light is irradiated_BAnd 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.
[0066]
Here, in the optical disc playback apparatus 10, a value that is arbitrarily set in advance or a value recorded on a control track that is a control information recording area of the optical disc may be used as the target value. As an initial operation when loading an optical disc, a target value can be set by the following method.
[0067]
The optical disk reproducing apparatus 10 supplies a drive signal to the focus coils 27a and 27b when the optical disk is loaded, and drives the actuator 28 while changing the actuator 28 of the optical pickup 11. Then, the optical disc reproducing apparatus 10 obtains a tilt instruction value corresponding to the change in 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 disc reproducing apparatus 10 measures 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 by the target value setting circuit 23. To do. Then, the optical disk reproducing apparatus 10 sets the tilt instruction value that minimizes the data detection error as the target value by the target value setting circuit 23.
[0068]
In this way, the optical disc playback apparatus 10 can set an optimum target value based on the correlation between the tilt instruction value and the data detection error.
[0069]
Specifically, the optical disk reproducing apparatus 10 performs the wobble component signal SIG by the method described below._AAnd the wobble component signal SIG_BAnd the amount of tilt is detected.
[0070]
The optical disk reproducing apparatus 10 uses the optical pickup 11 to perform the main beam spot MS and the two sub beam spots SS as in the normal reproduction.₁, SS₂To the optical disc.
[0071]
At this time, spot S_AAnd spot S_BWhen the optical disc is normally irradiated without being affected by the tilt, that is, when the tilt amount is “0 °”, the wobble component signal passed by the band-pass filter 14 is the spot S_AWobble component signal SIG based on return light from signal information recording side wall W_AAnd spot S_BWobble component signal SIG based on return light from signal information recording side wall W_BIs equivalent in amplitude to each other.
[0072]
On the other hand, spot S_AAnd spot S_BIs affected by the tilt, and the optical disk is irradiated in a state tilted in the direction of one of the signal information recording side walls W, the wobble component signal passed by the band-pass filter 14 is the spot S_AWobble component signal SIG based on return light from signal information recording side wall W_AAnd spot S_BWobble component signal SIG based on return light from signal information recording side wall W_BAnd have different amplitudes.
[0073]
Therefore, the wobble component signal SIG_A, SIG_BThe amplitude signals detected by the amplitude detection circuits 33a and 33b of the tilt detection circuit 24 and supplied to the subtractor 34 change in amplitude in an edge shape according to the movement of the three beam spots. .
[0074]
The optical disc reproducing apparatus 10 detects a tilt instruction value that is a difference value obtained by the subtracter 34 of the tilt detection circuit 24 based on such an amplitude signal, and generates a tilt error signal. The optical disc playback apparatus 10 repeats such an operation a plurality of times.
[0075]
In this way, the optical disc playback apparatus 10 can detect and compensate for the tilt amount. By detecting the tilt amount in this manner, the optical disc reproducing apparatus 10 can quickly detect the tilt amount without waiting for the rotation of the optical disc. Further, since the optical disc reproducing apparatus 10 obtains a plurality of tilt instruction values during one rotation of the optical disc, it can detect the tilt amount with high accuracy.
[0076]
That is, for example, the track T_AAnd track T_BIn the case where the amplitude value of the wobble component signal is stored and calculated later, a tilt amount detection time and a calculation time of at least two rotations are required separately from the normal operation. When seeking from the innermost circumference where the tilt amount is small to the outermost circumference where the tilt amount is large, a rotation waiting time of 2 rotations + α is required, and the effective access speed is lowered.
[0077]
Further, when the tilt amount is detected based on one sample information during one rotation of the optical disk, there arises a problem that it cannot follow the circular fluctuation. For example, in the case of an optical disk rotating at 600 rpm, the time constant is There arises a problem that it becomes as large as about 2 seconds. In addition, track T_AAnd track T_BWhen only one of the tracks is continuously reproduced, there arises a problem that the tilt amount cannot be detected.
[0078]
The optical disc reproducing apparatus 10 can solve such a problem, and can perform tilt detection and compensation quickly and with high accuracy without the need to perform complicated operations.
[0079]
As described above, the optical disk reproducing apparatus 10 uses the optical pickup 11 to cause the main beam spot MS and the two sub beam spots SS.₁, SS₂Can be detected and compensated without providing a dedicated sensor for tilt detection by detecting the return light from two of the three beam spots. Therefore, the optical disk reproducing apparatus 10 can detect and compensate the tilt amount even for an optical disk that is thin and has a small diameter as the numerical aperture (NA) of the objective lens 26 is increased.
[0080]
The present invention is not limited to the above-described embodiment. For example, when the optical disc shown in FIG. 3 is applied, two sub beam spots SS are not necessarily used.₁, SS₂It is not necessary to provide a single sub-beam spot.
[0081]
Of course, the present invention can be applied not only to an optical disk reproducing apparatus for reproducing digital data from an optical disk, but also to a recording apparatus for recording digital data on an optical disk.
[0082]
Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.
[0083]
【The invention's effect】
As described above in detail, the recording medium driving apparatus according to the present invention rotationally drives 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. On the other hand, a recording medium driving apparatus for recording and / or reproducing digital data, which irradiates a disk-shaped recording medium with a laser beam that forms a main beam spot and two sub beam spots, and Optical pickup means for receiving the return light reflected and diffracted on the surface of the recording medium, and the signal based on the return light from the signal information recording side wall by the two target beam spots of the main beam spot and the two sub beam spots. Amplitude detection means for detecting amplitude, and tilt detection means for detecting a tilt amount based on the amplitude of the signal detected by the amplitude detection means Obtain.
[0084]
Therefore, the recording medium driving apparatus according to the present invention irradiates the disc-shaped recording medium with the laser beam forming the main beam spot and the two sub beam spots by the optical pickup means, and the main beam by the tilt detection means. 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 by the two target beam spots of the spot and the two sub beam spots, and a dedicated sensor for tilt detection is provided. Tilt detection can be performed promptly and with high accuracy without being provided.
[0085]
The tilt detection method according to the present invention forms a main beam spot and two sub beam spots on a disc-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded. While irradiating the laser beam and receiving the return light reflected and diffracted on the surface of the disk-shaped recording medium, the return light from the signal information recording side wall by the two target beam spots of the main beam spot and the two sub beam spots. Is detected, and the tilt amount is detected based on the detected amplitude of the signal.
[0086]
Therefore, the tilt detection method according to the present invention irradiates the disc-shaped recording medium with the laser beam that forms the main beam spot and the two sub beam spots, and 2 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 by one target beam spot, and the tilt detection can be performed quickly and highly without requiring a dedicated sensor for tilt detection. It becomes possible to carry out with 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, and is a diagram illustrating a state of a groove substrate in which straight groove portions and wobble groove portions are alternately provided.
FIG. 2 is an explanatory diagram of an optical disc applied to the optical disc reproducing apparatus, and shows a land substrate in which grooves that are inner modulation guide grooves and grooves that are outer modulation guide grooves are alternately provided. It is a figure explaining.
FIG. 3 is an explanatory diagram of an optical disk applied to the optical disk reproducing apparatus, and illustrates a state of a land / groove substrate in which groove portions and land portions are alternately provided.
FIG. 4 is a diagram illustrating the arrangement of beam spots.
FIG. 5 is a diagram for explaining a result obtained by numerical calculation of a change in intensity distribution of laser light due to tilt.
FIG. 6 is a diagram for explaining the relationship between a wobble component signal and a tilt amount, and results of numerically calculating the characteristics of a wobble component signal when a laser beam is irradiated onto an optical disc while actually changing the tilt amount; FIG.
FIG. 7 is a block diagram illustrating the configuration of the optical disc playback apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Optical disk reproducing apparatus, 11 Optical pick-up, 18, 33a, 33b Amplitude detection circuit, 19 Track discrimination circuit, 21 Equalizer, 22 Data discrimination circuit, 23 Target value setting circuit, 24 Tilt detection circuit, 25 Drive signal generation circuit, 26 Objective Lens, 29 Laser diode, 31 Photo diode

Claims (30)

Recording medium driving apparatus for rotating and driving a disc-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded, and recording and / or reproducing digital data with respect to the disc-shaped recording medium Because
An optical pick-up means for irradiating the disk-shaped recording medium with laser light for forming a main beam spot and two sub-beam spots, and receiving return light reflected and diffracted by the surface of the disk-shaped recording medium; ,
Amplitude detecting means for detecting the amplitude of a signal obtained by extracting the signal information component based on the return light from the signal information recording side wall by the two target beam spots from the main beam spot and the two sub beam spots;
A tilt detecting means for detecting a tilt amount based on the amplitude of the signal detected by the amplitude detecting means ,
The tilt detection unit is configured to record the signal information when one of the two target beam spots detected by the amplitude detection unit is located on the inner circumference 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 side wall, and the other of the two target beam spots detected by the amplitude detecting means is more of the disc-shaped recording medium than the signal information recording side wall. A recording medium drive characterized in that 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 positioned on the outer peripheral side, is obtained as a tilt instruction value indicating the tilt amount. apparatus. A recording medium driving apparatus for rotating and driving a disk-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recording data is recorded, and recording and / or reproducing digital data on the disk-shaped recording medium Because
An optical pick-up means for irradiating the disk-shaped recording medium with laser light for forming a main beam spot and two sub-beam spots, and receiving return light reflected and diffracted by the surface of the disk-shaped recording medium; ,
Amplitude detecting means for detecting the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots among the main beam spot and the two sub beam spots;
A tilt detecting means for detecting a tilt amount based on the amplitude of the signal detected by the amplitude detecting means,
The disc-shaped recording medium is provided with guide grooves and land portions alternately having the signal information recording side wall on either the inner peripheral side or the outer peripheral side of the disc-shaped recording medium, and the guide grooves and the land portions are provided. Each of which 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,
The optical pickup means irradiates the main beam spot to the guide groove or the land portion, and each of the guide groove or the land portion or guide groove adjacent to the land portion irradiated with the main beam spot. Irradiate one of the two secondary beam spots
The amplitude detecting means records the signal information recorded by the main beam spot and one of the two sub beam spots as the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots. Detect the amplitude of the signal based on the return light from the sidewall,
  The tilt detection unit is configured to detect the main beam spot detected by the amplitude detection unit from the signal information recording side wall when the disc information recording side wall is located on the inner peripheral side or the outer peripheral side of the signal information recording side wall. The amplitude of the first signal, which is a signal based on the return light, and one of the two sub beam spots detected by the amplitude detecting means is on the outer peripheral side of the disc-shaped recording medium from the signal information recording side wall or A recording medium characterized in that 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 inner peripheral side, is obtained as a tilt instruction value indicating the tilt amount. Drive device. The disc-shaped recording medium is provided with alternating modulation guide grooves that modulate the width or position on both side walls to form the signal information recording side walls and non-modulation guide grooves that do not modulate both side walls, and the modulation guide grooves and An area sandwiched between the non-modulation guide grooves is provided as a land portion, and the modulation guide grooves and the non-modulation guide grooves are used as recording areas in which the recording data is recorded, and the signal information is recorded on the side wall of the signal information as the signal information. 3. The recording medium driving apparatus according to claim 1, wherein address information is recorded. The optical pickup means irradiates the modulation guide groove or the non-modulation guide groove with the main beam spot, and is adjacent to the modulation guide groove or the non-modulation guide groove to which the main beam spot is irradiated. Irradiate one of the two sub beam spots to each of the two land portions,
The amplitude detection means is configured such that the amplitude of the signal based on the return light from the signal information recording side wall by the two sub beam spots is the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots. Detect
The tilt detection means is configured to record the signal information when one of the two sub beam spots detected by the amplitude detection means 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 side wall, and the other of the two sub beam spots detected by the amplitude detecting means is more of the disc-shaped recording medium than the signal information recording side wall. 4. A difference value from an amplitude of a second signal, which is a signal based on a return light from the signal information recording side wall when positioned on the outer peripheral side, is obtained as a tilt instruction value indicating the tilt amount. The recording medium driving device according to claim. The disc-shaped recording medium includes an inner peripheral modulation guide groove in which 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 an outer peripheral side wall of the disc-shaped recording medium. The outer peripheral modulation guide grooves provided alternately as the outer peripheral modulation guide grooves and the inner peripheral modulation guide grooves and the outer peripheral modulation guide grooves are provided as land portions, and the land portions are recorded with the recording data. 3. The recording medium driving apparatus according to claim 1, wherein address information as the signal information is recorded on the signal information recording side wall. The optical pickup means irradiates the land portion with the main beam spot, and the inner peripheral modulation guide groove and the outer peripheral modulation guide groove adjacent to the land portion irradiated with the main beam spot. Irradiate one of the two secondary beam spots to each,
The amplitude detection means is configured such that the amplitude of the signal based on the return light from the signal information recording side wall by the two sub beam spots is the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots. Detect
The tilt detection means is configured to record the signal information when one of the two sub beam spots detected by the amplitude detection means 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 side wall, and the other of the two sub beam spots detected by the amplitude detecting means is more of the disc-shaped recording medium than the signal information recording side wall. 6. The difference value with respect to the amplitude of the second signal, which is a signal based on the return light from the signal information recording side wall when positioned on the outer peripheral side, is obtained as a tilt instruction value indicating the tilt amount. The recording medium driving device according to claim.   The disc-shaped recording medium is provided with guide grooves and land portions alternately having the signal information recording side wall on either the inner peripheral side or the outer peripheral side of the disc-shaped recording medium, and the guide grooves and the land portions are provided. 2. The recording medium driving apparatus according to claim 1, wherein each of the recording information 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. The optical pickup means irradiates the main beam spot to the guide groove or the land portion, and each of the guide groove or the land portion or guide groove adjacent to the land portion irradiated with the main beam spot. Irradiate one of the two secondary beam spots
The amplitude detecting means records the signal information recorded by the main beam spot and one of the two sub beam spots as the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots. Detect the amplitude of the signal based on the return light from the sidewall,
The tilt detection unit is configured to detect the main beam spot detected by the amplitude detection unit from the signal information recording side wall when the disc information recording side wall is located on the inner peripheral side or the outer peripheral side of the signal information recording side wall. The amplitude of the first signal, which is a signal based on the return light, and one of the two sub beam spots detected by the amplitude detecting means is on the outer peripheral side of the disc-shaped recording medium from the signal information recording side wall or The 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 inner circumference side, is obtained as a tilt instruction value indicating the tilt amount. 8. The recording medium driving device according to 7. 3. The recording medium driving apparatus according to claim 1, further comprising target value setting means for setting a target value for compensating for the tilt instruction value.   The recording medium driving apparatus according to claim 9, wherein the target value is a value arbitrarily set in advance.   10. The recording medium driving apparatus according to claim 9, wherein the target value is a value recorded in a control information recording area of the disc-shaped recording medium. 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 discriminating the data detection capability for the recording data;
Drive signal generation means for generating a drive signal for compensating for 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; Prepared,
The drive signal generation means controls and drives the optical pickup means by changing a tilt amount based on the drive signal,
The tilt detection means obtains a tilt instruction value corresponding to a change in tilt amount,
The target value setting means sets the target value based on a tilt instruction value obtained by the tilt detection means and a data discrimination signal indicating a result of discriminating data detection capability by the data discrimination means. A recording medium driving apparatus according to claim 9. Drive signal generation means for generating a drive signal for compensating for 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. 3. A recording medium driving apparatus according to claim 1, wherein the recording medium driving apparatus is a recording medium driving apparatus.   14. The recording medium driving apparatus according to claim 13, wherein the optical pickup means is controlled based on the drive signal generated by the drive signal generating means so that the tilt instruction value approaches the target value. Waveform equalization means for performing waveform equalization processing on the RF signal based on the return light reflected and diffracted on the surface of the disk-shaped recording medium,
14. The recording medium driving apparatus according to claim 13, wherein the waveform equalizing means performs gain adjustment based on the tilt error signal obtained by the tilt detecting means. A disk-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recorded data is irradiated with a laser beam that forms a main beam spot and two sub-beam spots, and the disk-shaped recording is performed. Receive the return light reflected and diffracted by the surface of the medium,
Detecting the amplitude of the signal obtained by extracting the signal information component based on the return light from the signal information recording side wall by the two target beam spots from the main beam spot and the two sub beam spots;
The amount of tilt is detected based on the detected amplitude of the signal ,
The first signal is a signal based on the return light from the signal information recording side wall when 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 . And the return light from the signal information recording side wall when the other of the detected two 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. A tilt detection method characterized in that a difference value with respect to an amplitude of a second signal as a signal is obtained as a tilt instruction value indicating the tilt amount . A disk-shaped recording medium having a signal information recording side wall on which signal information distinguishable from recorded data is irradiated with a laser beam that forms a main beam spot and two sub-beam spots, and the disk-shaped recording is performed. Receive the return light reflected and diffracted by the surface of the medium,
Detecting the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots among the main beam spot and the two sub beam spots;
The amount of tilt is detected based on the detected amplitude of the signal,
The disc-shaped recording medium is provided with guide grooves and land portions alternately having the signal information recording side wall on either the inner peripheral side or the outer peripheral side of the disc-shaped recording medium, and the guide grooves and the land portions are provided. Each of which is a recording area in which the recording data is recorded, address information as the signal information is recorded on the signal information recording side wall,
The main beam spot is irradiated to the guide groove or the land portion, and two sub-portions are provided to each of the guide groove or land portion adjacent to the land portion or the guide groove irradiated with the main beam spot. Irradiate one of the 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 is the return light from the signal information recording side wall by one of the main beam spot and the two sub beam spots. Detect the amplitude of the signal based on
When the detected main beam spot is located on the inner circumference side or the outer circumference side of the disc-shaped recording medium with respect to the signal information recording side wall, the first signal is a signal based on the return light from the signal information recording side wall. Amplitude and return light from the signal information recording side wall when one of the detected two sub beam spots is located on the outer peripheral side or the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. A tilt detection method characterized in that a difference value with respect to the amplitude of a second signal, which is a signal based thereon, is obtained as a tilt instruction value indicating the tilt amount . The disc-shaped recording medium is provided with alternating modulation guide grooves that modulate the width or position on both side walls to form the signal information recording side walls and non-modulation guide grooves that do not modulate both side walls, and the modulation guide grooves and An area sandwiched between the non-modulation guide grooves is provided as a land portion, and the modulation guide grooves and the non-modulation guide grooves are used as recording areas in which the recording data is recorded, and the signal information is recorded on the side wall of the signal information as the signal information. tilt detection method according to claim 16 or 17, wherein that records the address information. The main beam spot is irradiated to the modulation guide groove or the non-modulation guide groove, and each of the two land portions adjacent to the modulation guide groove or the non-modulation guide groove irradiated with the main beam spot. Irradiate one of the two secondary beam spots
As the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots, the amplitude of the signal based on the return light from the signal information recording side wall by the two sub beam spots is detected,
The first signal is a signal based on the return light from the signal information recording side wall when one of the detected two sub beam spots is located on the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. And the return light from the signal information recording side wall when the other of the detected two sub beam spots 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 a difference value from the amplitude of the second signal, which is a signal, is obtained as a tilt instruction value indicating the tilt amount. The disc-shaped recording medium includes an inner peripheral modulation guide groove in which 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 an outer peripheral side wall of the disc-shaped recording medium. The outer peripheral modulation guide grooves provided alternately as the outer peripheral modulation guide grooves and the inner peripheral modulation guide grooves and the outer peripheral modulation guide grooves are provided as land portions, and the land portions are recorded with the recording data. that the recording area, the signal information recording claim 16 or 17 tilt detection method according to characterized in that it sidewall record address information as the signal information. The land portion is irradiated with the main beam spot, and two are provided for each of the inner peripheral modulation guide groove and the outer peripheral modulation guide groove adjacent to the land portion irradiated with the main beam spot. Irradiate one of the secondary beam spots,
As the amplitude of the signal based on the return light from the signal information recording side wall by the two target beam spots, the amplitude of the signal based on the return light from the signal information recording side wall by the two sub beam spots is detected,
The first signal is a signal based on the return light from the signal information recording side wall when one of the detected two sub beam spots is located on the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. And the return light from the signal information recording side wall when the other of the detected two sub beam spots is located on the outer peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. 21. The tilt detection method according to claim 20, wherein a difference value from the amplitude of the second signal, which is a signal, is obtained as a tilt instruction value indicating the tilt amount.   The disc-shaped recording medium is provided with guide grooves and land portions alternately having the signal information recording side wall on either the inner peripheral side or the outer peripheral side of the disc-shaped recording medium, and the guide grooves and the land portions are provided. 17. The tilt detection method according to claim 16, wherein each of the recording information 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. The main beam spot is irradiated to the guide groove or the land portion, and two sub-portions are provided to each of the guide groove or land portion adjacent to the land portion or the guide groove irradiated with the main beam spot. Irradiate one of the 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 is the return light from the signal information recording side wall by one of the main beam spot and the two sub beam spots. Detect the amplitude of the signal based on
When the detected main beam spot is located on the inner circumference side or the outer circumference side of the disc-shaped recording medium with respect to the signal information recording side wall, the first signal is a signal based on the return light from the signal information recording side wall. Amplitude and return light from the signal information recording side wall when one of the detected two sub beam spots is located on the outer peripheral side or the inner peripheral side of the disc-shaped recording medium with respect to the signal information recording side wall. 23. The tilt detection method according to claim 22, wherein a difference value with respect to the amplitude of the second signal that is a signal based thereon is obtained as a tilt instruction value indicating the tilt amount. Tilt detection method according to claim 16 or 17, wherein setting the target value to compensate for the tilt indication value.   The tilt detection method according to claim 24, wherein the target value is a value arbitrarily set in advance.   The tilt detection method according to claim 24, wherein the target value is a value recorded in a control information recording area of the disk-shaped recording medium. Extracting the recording data from the RF signal based on the return light reflected and diffracted on the surface of the disk-shaped recording medium, and determining the data detection capability for the recording data;
An optical pickup means for irradiating the disk-shaped recording medium with a laser beam that forms 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; The amount of tilt is changed based on a drive signal for compensating for a tilt generated 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. To obtain a tilt instruction value corresponding to a change in the tilt amount, and set the target value based on the obtained tilt instruction value and a data determination signal indicating a result of determining the data detection capability. The tilt detection method according to claim 24. A drive signal for compensating for tilt is generated 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. Item 18. The tilt detection method according to Item 16 or 17 .   An optical pickup means for irradiating the disk-shaped recording medium with a laser beam that forms 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; 29. The tilt detection method according to claim 28, wherein the tilt instruction value is controlled to approach the target value based on a drive signal.   29. The tilt according to claim 28, wherein gain adjustment is performed in a waveform equalization process performed on an RF signal based on return light reflected and diffracted on the surface of the disc-shaped recording medium based on the tilt error signal. Detection method.

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