JPH1116174A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform excellent tracking control without an offset when tracking servo control by one beam push-pull method, etc. is performed. SOLUTION: This device is constituted so as to perform the tracking of a beam of an optical pickup 20 by using an optical disk in which a groove is continuously formed along a track and a pit is formed on a land part between this groove and a groove on the adjacent track. In this case, the peak position and the bottom position of a detected difference signal A (push-pull signal) are held by holding means 33 and 34, the difference between the peak position and the bottom position is detected by a detecting means 35 so that the tracking control of the beam of the optical pickup 20 is performed based on the detected difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for application to a recording device or a reproducing device for optically recording or reproducing disks such as optical disks and magneto-optical disks (hereinafter these disks are simply referred to as optical disks). Optical disk device.

[0002]

2. Description of the Related Art An optical disc apparatus for recording or reproducing data on or from an optical disc records data on the track while performing tracking servo control for following a track formed on the disc with a laser beam from an optical pickup. A process for reproducing data recorded on the track is performed.

There is a system in which a guide groove called a groove is provided on an optical disk in order to perform tracking control satisfactorily. FIG. 6 is a diagram showing an example of a disk on which the grooves are formed. In the disk, grooves g are arranged at a predetermined track pitch Tp.
A land l is formed between the adjacent track and the groove g. Data is recorded on the disk at any position of the groove g or the land l (here, the groove g).
Done in In the figure, the groove g is shown in a straight line for the sake of simplicity of description, but the track is actually formed in an annular or spiral shape along the circumference of the disk. Further, the groove g is formed in a meandering state called wobbling, and data necessary for reproduction such as a track address and a clock may be recorded in the wobbling state.

[0004] Further, there is a land portion l in which data such as a track address is previously recorded in pits. For example, as shown in FIG. 6, a recordable optical disk of a standard called DVD-R has a track formed by a groove g and a predetermined period on a land 1 between the groove g of an adjacent track. A pit p is provided (actually, a plurality of pits may be provided at one pit formation position p), and a track address and the like are recorded in advance by these pits.

FIG. 7 is a three-dimensional view showing an example of the state of formation of the grooves and pits.
Represents a straight line without wobbling, and the pit p
Are provided in a predetermined state on the land l between the grooves g of the two tracks. In an actual disk, as shown in FIG. 7, a transparent layer or a protective layer is formed on the groove g or the pit p, and on the surface of the disk, the depth of the groove g or the pit p is smaller. No corresponding grooves or holes are provided.

FIG. 8 shows the principle of detecting a tracking error signal for causing a track on which the groove g is formed to track. That is, the return light of the laser light emitted from the optical pickup is made incident on the light receiving section 82 via the objective lens 81 in the optical pickup. Light receiving section 82
Is composed of light receiving portions 82a and 82b divided into two in the direction orthogonal to the longitudinal direction of the track.
The detection output of 2b is supplied to the comparator 83. Comparator 83
Then, the difference between the detection outputs of the two light receiving sections 82a and 82b is obtained,
The difference signal is supplied to a tracking servo circuit (not shown) as a tracking error signal. In the tracking servo circuit, a tracking coil or the like of the optical pickup is driven in accordance with the level and polarity of the difference signal, and tracking control is performed so that the groove g is located at the center of the spot of the laser beam.

The tracking servo method shown in FIG. 8 is called a one-spot push-pull method. When the position on the disk irradiated with the laser beam is the position where the groove g is located at the center, the tracking servo method is divided into two. Light receiving sections 82a, 8
The light receiving levels of the laser light at 2b become equal, and the level of the detected tracking error signal becomes zero. When the groove g is shifted to one of the positions, a tracking error signal having a level corresponding to the shift amount is detected in the polarity of the shifted direction, and the servo is controlled so that the level of the tracking error signal is zero. By performing the control, good tracking servo control based on the groove is performed.

The tracking servo system shown in FIG.
This is called the PP (Differential Push Pull) method.
In this case, in addition to the main spot SP1 for recording and reproducing signals, two sub spots SP2 and S
The disk is irradiated with laser light of a total of three spots P3. In this case, the sub spot SP2 at a position preceding the main spot is set at a position shifted to one side by half the track pitch with respect to the main spot SP1, and the sub spot SP3 located after the main spot SP3.
Is 1/1 of the track pitch with respect to the main spot SP1.
It is set at a position shifted by two by the other. here,
The main spot SP1 is scanning the track n.

The return light of each spot is detected by the light receiving sections 91, 92 and 93 which are divided into two parts. That is, the light receiving section 91 for detecting the return light of the main spot SP1 is divided into two sections, a detecting section E1 and a detecting section F1, and a comparator 94 detects a difference signal TE1 between the detecting sections E1 and F1. Sub spot S
The light receiving section 92 for detecting the return light of P2 is divided into two sections, a detecting section E2 and a detecting section F2.
2 difference signal TE2 is detected. The light receiving unit 93 that detects the return light of the sub spot SP3 includes a detecting unit E3 and a detecting unit F3.
The comparator 96 detects the difference signal TE3 between the two detectors E3 and F3. This difference signal TE3 is supplied to the amplifier 9
8, the signal is amplified with a predetermined gain, and the amplified signal and the difference signal T are amplified.
E2 is added by the adder 97, and the added signal is output to the amplifier 9
9 and is amplified by a predetermined gain.
00 is supplied. Further, the difference signal TE1 is
The difference is detected by the comparator 100, and the detected output becomes a tracking error signal, and the tracking servo control is performed based on the tracking error signal.

[0010]

In the tracking servo control of the one-spot push-pull method shown in FIG. 8, an offset may occur in the position of the light spot. That is, for example, when using an optical device that drives only the objective lens 81 and following or accessing an eccentric disk, the center of the objective lens 81 shifts in the radial direction, so that the light receiving unit The spot position on 82 shifts, resulting in an offset.

In the case of the tracking servo control of the DPP method shown in FIG. 9, there is no such an offset problem, but the configuration is more complicated than the one-spot push-pull method, and the SN ratio and the use of laser light There is a problem with bad rates. That is, since the laser light is used by being divided into three spots, the light amount of the sub-spots SP2 and SP3 is 10% or less with respect to the light amount of the main spot SP1, but the contribution as the servo signal is made by the main spot and the sub-spot Since the ratios are the same, there is a problem that the SN ratio of the tracking servo signal is poor. Further, since the sub-spots SP2 and SP3 are used for purposes other than tracking servo control, there is a problem that the utilization rate of laser light is poor.

Therefore, although the one-spot push-pull method is originally preferred, there is a problem of causing an offset as described above. The push-pull method could not be actively adopted.

In view of the foregoing, an object of the present invention is to enable good tracking control without offset with a simple configuration such as the one spot push-pull method.

[0014]

According to the present invention, a groove is formed continuously along a track, and a pit is formed in a land portion between the groove and an adjacent track. In an optical disc device that performs tracking of a beam of an optical pickup by using the selected optical disc, a peak position and a bottom position of a detected difference signal (push-pull signal) are held, and a difference between the peak position and the bottom position is detected. The tracking control of the beam of the optical pickup is performed based on the detected difference.

According to the present invention, a pit provided on one side of the land with respect to a groove constituting a target track is detected by peak position detection and provided on the other side of the land. Pits are detected by bottom position detection, and tracking control can be favorably performed based on detection information of pits intermittently arranged on a track.

[0016]

Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing a tracking servo control configuration of the optical disk apparatus of the present embodiment. An optical disk 11 is driven to rotate by a spindle motor 12 and an optical pickup 20 is driven.
After the laser beam from the laser source 21 in the inside is reflected by the beam splitter 22, the laser beam is irradiated on the optical disk 11 through the objective lens 23, and the return light from the disk is detected by the laser light detection unit 25 inside the pickup 20. I do. The focus position of the objective lens 23 is driven by the focus coil 24. Regarding the laser beam detection unit 25, the direction perpendicular to the track forming direction of the disk (the circumferential direction of the disk) (that is, the radial direction of the disk)
The detection is performed by the divided detection units 25a and 25b.

The signal detected by the laser beam detector 25 is used as a reproduction signal from the optical disk 11. In this embodiment, a configuration for tracking servo control will be described below. That is, in order to perform tracking servo control,
The detection signals of the two divided detection units 25a and 25b are supplied to the subtractor 13 to obtain a difference signal (push-pull signal) between the two signals, and tracking servo control is performed based on the difference signal. The two divided detectors 25a, 25
The tracking servo control based on the difference signal of the detection signal 5b is basically the tracking servo control by the push-pull method described in FIG. 8 as a conventional example.

Here, the configuration of the optical disk 11 for which tracking control is performed by the apparatus of the present embodiment will be described. A groove wobbled at a predetermined frequency is formed on the optical disk 11 in advance, and a portion where the groove is formed is formed. To record a signal. In a land portion between a groove forming a track and a groove of an adjacent track, pits are formed at a predetermined period (that is, a disk having a configuration described in FIGS. 6 and 7 as a conventional example). use. As the optical disk 11 having such a configuration, there is, for example, a recordable optical disk called DVD-R.

In the following, a configuration for tracking servo control will be described. The difference signal (push-pull signal) output from the subtracter 13 based on the signal detected by the optical pickup 20 removes high-frequency components by a low-pass filter 14. And the difference signal from which the high-frequency component has been removed is
The signal is supplied to the tracking servo circuit 16 via the adder 15 as a tracking error signal. The high-frequency component removed by the low-pass filter 14 is a component including at least a frequency corresponding to the wobbling frequency of the groove formed on the optical disc 11.

In this embodiment, the difference signal output from the subtractor 13 is supplied to a high-pass filter 31 to remove the eccentric component of the disk 11, and the difference signal from which the eccentric component has been removed is converted to a band-eliminate filter 32. To remove only the frequency band corresponding to the wobbling frequency of the groove formed on the optical disk 11.

The difference signal from which the eccentric component and the wobbling component of the disk 11 have been removed is sent to a peak hold circuit 3.
3 and the bottom hold circuit 34. The peak hold circuit 33 performs processing for holding the position where the supplied difference signal has the highest level, and the bottom hold circuit 34 performs processing for holding the position where the supplied difference signal has the lowest level. Then, the signal of the level held by the peak hold circuit 33 and the signal of the level held by the bottom hold circuit 34 are subtracted by the subtractor 3
5 to detect the difference between the levels of the two signals. Therefore,
The subtracter 35 performs a process of detecting a difference between the peak and the bottom.

The signal of the difference between the peak and the bottom detected by the subtractor 35 is smoothed by a low-pass filter 36, supplied to the adder 15, added to the output of the low-pass filter 14, and added as a tracking error signal. This is supplied to the tracking servo circuit 16.

The tracking servo circuit 16 performs tracking servo control so that the value of the supplied tracking error signal becomes small. That is, a drive signal to be supplied to the tracking coil 24 in the optical pickup 20 is generated in accordance with the level of the supplied tracking error signal, and control is performed so that the value of the supplied tracking error signal approaches zero.

Next, the operation of the tracking servo control system configured as described above will be described with reference to FIGS. FIGS. 2 to 4 are diagrams showing examples of signal waveforms obtained by the circuit of the present embodiment. The symbols A to H given to the waveforms in the respective drawings are from A to H given in FIG. It corresponds to a signal obtained on the transmission path of the code indicated by H.

First, the signal state of the just-track state in which the spot of the laser beam from the optical pickup 20 correctly scans the groove formed on the optical disk 11 is shown in FIG.
This will be described with reference to FIG. The difference signal (push-pull signal) A detected by the subtractor 13 in the just track state is
The state shown in FIG. This signal is a signal in which a waveform of a fine frequency corresponding to the wobbling frequency of the groove is on a large undulation waveform corresponding to the eccentric component of the disk. Then, at a portion where a pit is formed beside the groove, there is a temporary level fluctuation corresponding to the pit formation state. That is, when scanning a place where a pit is formed on one side of the groove, the level temporarily increases, and when scanning a place where a pit is formed on the other side of the groove, The level goes down temporarily. The center of the push-pull signal A is at 0V level.

The push-pull signal A is obtained by removing the eccentric component of the disk by the high-pass filter 31 as shown in FIG.
As shown in B of FIG. 7, the level corresponding to the pit detection temporarily rises or falls on the waveform corresponding to the wobbling frequency of the groove. further,
By removing the wobbling component from this signal by the band luminescent filter 32, as shown in FIG.
Only a temporary rise or fall of the level corresponding to the pit detection is detected.

When this signal is supplied to the peak hold circuit 33, the peak value (maximum value) when the level temporarily rises is held, and a signal shown in D of FIG. 2 is obtained. Further, the signal shown in FIG. 2C is supplied to the bottom hold circuit 34, so that the bottom value (lowest value) when the level temporarily drops is held.
In the state shown in FIG. Here, the peak hold circuit 33 and the bottom hold circuit 34 have a characteristic that the hold value gradually decreases with a time constant.

A subtractor 35 for comparing the peak value and the bottom value.
2 is in the state shown in FIG. 2F, and in the case of the just track state, there is almost no difference between the peak value and the bottom value of the waveform that goes up and down around the 0 V level, and the low-pass filter 36 As shown in FIG. 2G, the signal smoothed by the above is a signal in which the 0 V level is maintained. The output of the low-pass filter 36 is added to the signal output by the low-pass filter 14 to generate the tracking error signal of the present example shown in FIG. A signal obtained by removing a high-frequency component including a wobbling component from a difference signal output from the subtractor 13 by a filter 14 is added to the tracking error signal, and a tracking error signal that follows the groove is added to the tracking servo circuit 16. Supplied.

When the scanning position of the laser beam goes off-track from the state shown in FIG. 2 to the outer periphery of the disk, for example, a pit detection signal included in the difference signal (push-pull signal) detected by the subtractor 13 is detected. Is a signal in which the upper and lower levels are out of balance in proportion to the off-track state (here, the peak level is higher than in the just-track state and the bottom level is closer to 0 V). For example, an eccentric component and a wobbling component 3 (the output of the filter 32) is in the state shown in FIG. At this time, the signal obtained by smoothing the difference signal between the peak value and the bottom value detected by the subtractor 35 becomes a signal having a level higher than 0 V as shown in FIG. The tracking error signal is a signal of a level higher than 0 V as shown in H of FIG. When such a signal is supplied to the tracking servo circuit 16, the drive signal supplied to the tracking coil 24 performs a process of correcting the tracking position to the inner peripheral side, and controls the tracking error signal to approach 0V. Is performed, and servo control for correcting to the just track state is performed.

When, for example, the scanning position of the laser beam goes off-track from the state shown in FIG. 2 to the inner peripheral side of the disk, a pit detection signal included in the difference signal (push-pull signal) detected by the subtractor 13 is detected. Is a signal in which the upper and lower levels are unbalanced in proportion to the off-track state (here, the peak level approaches 0 V and the bottom level is lower than in the just-track state), and for example, an eccentric component and a wobbling component 4 (the output of the filter 32) is in the state shown in FIG. At this time, the signal obtained by smoothing the difference signal between the peak value and the bottom value detected by the subtractor 35 becomes a signal having a level lower than 0 V as shown in FIG. The tracking error signal is a signal having a level lower than 0 V as shown in H of FIG. When such a signal is supplied to the tracking servo circuit 16, the tracking coil 2
The processing for correcting the tracking position in the opposite direction (outer circumference side) to the case of FIG. Servo control is performed.

As described above, by performing the tracking servo control of the present embodiment, good tracking servo control without offset can be performed using the pits formed beside the grooves of the disk. That is, when an offset occurs in any direction from the just track state, the signal waveform shown in FIG. 3 or FIG. 4 is detected from the detection state of the pit formed on the side of the groove, and the offset state is detected. The process of correcting the offset state is performed by the servo control, so that the state can be returned to the just track state. Therefore, it is possible to effectively remove the offset generated by the tracking servo control such as the one spot push-pull method.

In the configuration shown in FIG. 1, the push-pull signal output from the subtractor 13 is removed from the eccentric component of the disk by the high-pass filter 31 and then the wobbling component of the groove is removed by the band hermitate filter 32. However, instead of these two filters 31, 32,
The configuration may be such that one high-pass filter having a cutoff frequency higher than the wobbling frequency is used to simultaneously remove the eccentric component of the disk and the wobbling component of the groove.

However, when the eccentric component of the disk and the wobbling component of the groove are simultaneously removed by one high-pass filter, when the push-pull signal shown in FIG. The signals supplied to the peak hold circuit 33 and the bottom hold circuit 34 after passing through the high-pass filters have the opposite direction to the temporary fluctuation of the level corresponding to the pit detection direction, as shown in FIG. Although the waveform z called zaku appears slightly, the level of this waveform z is sufficiently lower than the detected waveform of the pit, so that it does not hinder the tracking servo described with reference to FIG.

In the above-described embodiment, the recording system and the reproducing system of the signal have not been described. However, as long as a recording medium having grooves and pits is used, any type of recording apparatus or system can be used. The present invention can also be applied to a playback device, and is not limited to the DVD-R recording device or playback device shown as an example in the above embodiment.

In the above-described embodiment, the pick-up detects the return light from the disk and performs tracking control. In the above-described embodiment, the control is performed by the one-spot push-pull method. Can be applied to other tracking control configurations as long as is obtained.

[0037]

According to the optical disk apparatus of the present invention, a pit provided on one side of a land is detected by a peak position detection with respect to a groove constituting a target track, and the other is formed by a pit provided on the other side. Pits provided on the side lands are detected by bottom position detection, and tracking control can be performed satisfactorily based on detection information of pits intermittently arranged on the track. For example, one spot push-pull By using the method, good tracking servo control without causing offset can be performed.

According to the optical disk apparatus of the present invention, the output of the peak / bottom difference detection means is added to the difference signal output by the beam detection means and the result is supplied to the tracking control means. While performing tracking control following the groove by the difference signal output by the detecting means, control can be performed so that no offset is caused by detecting a pit adjacent to the groove, and good tracking servo control can be performed.

According to the optical disk device of the present invention, the difference signal output from the beam detecting means is removed from the wobbling component of the groove by a filter for removing a predetermined band, and then output from the peak / bottom difference detecting means. And good tracking servo control without the influence of the wobbling component of the groove can be performed.

According to the optical disk device of the present invention, the difference signal output from the beam detecting means is peak-held after removing the wobbling component of the groove or the eccentric component of the disk by the filter for removing a predetermined band. With this configuration, the detection information of the pits adjacent to the groove is not affected by the wobbling component or the eccentricity component of the disk, and good tracking servo control based on the pit detection information can be performed.

According to the fifth aspect of the present invention, the output of the peak / bottom difference detecting means is smoothed by the low-pass filter and supplied to the tracking control means. Good tracking servo control that prevents the tracking error signal from being disturbed due to the execution is enabled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical disk device of the present invention.

FIG. 2 is a waveform diagram showing a reproduction signal waveform (in the case of a just track state) according to the embodiment of the optical disc apparatus of the present invention.

FIG. 3 shows a reproduction signal waveform according to an embodiment of the optical disc apparatus of the present invention (when an outer track is in an off-track state).
FIG.

FIG. 4 is a reproduction signal waveform according to an embodiment of the optical disc apparatus of the present invention (in the case where an inner track is in an off-track state).
FIG.

FIG. 5 is a waveform diagram showing a state of a reproduction signal waveform in another embodiment of the optical disk device of the present invention.

FIG. 6 is a plan view showing an example of a state where grooves and pits are formed on the optical disc.

FIG. 7 is a perspective view showing an example of a state in which grooves and pits are formed on an optical disc.

FIG. 8 is a configuration diagram illustrating detection processing of a tracking error signal by a push-pull method.

FIG. 9 is a configuration diagram showing detection processing of a tracking error signal by the DPP method.

[Explanation of symbols]

11 optical disc, 13 subtractor, 14 low-pass filter, 15 adder, 16 tracking servo circuit,
Reference Signs List 20 optical pickup, 21 laser source, 22 beam splitter, 23 objective lens, 24 focus coil, 25 laser light detection unit, 31 high-pass filter, 32 band band filter, 33 peak hold circuit, 34: bottom hold circuit, 35: subtractor, 36: low-pass filter

Claims (5)

[Claims] An optical pickup having a groove formed continuously along a track and having pits formed in a land between adjacent grooves of a track is used to track a beam of an optical pickup. In the optical disc apparatus, a return light of the beam from the optical disc is detected by a light receiving portion divided into two at least in a direction orthogonal to a longitudinal direction of a track, and a difference signal between detection signals of the light receiving portion divided into two is detected. Beam detecting means for detecting; peak holding means for holding a peak position of the difference signal output by the beam detecting means; bottom holding means for holding a bottom position of the difference signal output by the beam detecting means; Means for detecting the difference between the output of the means and the output of the bottom hold means. If, on the basis of the output of the peak and bottom difference detecting means, the optical disk apparatus having a tracking control means for performing tracking control of the beam of the optical pickup. 2. The optical disk device according to claim 1, wherein the difference signal output by the beam detecting means includes a peak signal and a peak signal.
An optical disc device to which the output of the bottom difference detecting means is added and supplied to the tracking control means. 3. The optical disc apparatus according to claim 2, wherein the difference signal output from the beam detecting means is used to remove the wobbling component of the groove by a filter for removing a predetermined band, and then the peak / bottom difference detection is performed. An optical disk device for adding to the output of the means. 4. The optical disk device according to claim 1, wherein the difference signal output from the beam detecting means is filtered by a filter for removing a predetermined band to remove a wobbling component of the groove or an eccentric component of the disk. An optical disc device for supplying the peak hold means and the bottom hold means. 5. The optical disk device according to claim 1, wherein an output of said peak / bottom difference detecting means is smoothed by a low-pass filter and supplied to said tracking control means.