JPH1186310A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a skew servo control with a simple configuration without necessitating a sensor exclusive for detecting the inclination of a disk. SOLUTION: In this device for performing the tracking of the beam of an optical pickup by using an optical disk on which a groove is continuously formed along a track and also pits are formed on the land part between grooves of adjacent tracks, the peak position and bottom position of a detected difference signal A are held by hold means 33, 34 and the difference between the peak position and the bottom position is detected in a detection means 35 to perform a skew servo control for correcting the inclination with respect to the optical disk 11 of an optical pickup 20 based the detected difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus and a reproducing apparatus for optically recording and reproducing disks such as an optical disk, a magneto-optical disk, and a phase change disk (hereinafter, these disks are simply referred to as optical disks). The present invention relates to an optical disk device suitable for application, and more particularly, to a skew servo control technique of a laser beam applied to a disk.

[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.

Although the tracking servo control of the one-spot push-pull method shown in FIG. 8 requires only dividing the light receiving section 82 into two parts and has a simple structure, 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.

As a tracking servo system which solves the problem of occurrence of the offset, a DPP (Diff) shown in FIG.
erential Push Pull) method.
In the case of the DPP method, in addition to the main spot SP1 for recording and reproducing a signal, a laser beam of a total of three spots of two sub spots SP2 and SP3 is irradiated on the disk before and after the main spot SP1. Here, 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 is The main spot SP1 is set at a position shifted by half the track pitch to the other. Here, the main spot SP1 is scanning the track n.

The return light of each spot is detected by light receiving sections 91, 92, and 93 which are divided into two. 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.

[0011]

By adopting the DPP method as described above, it is possible to favorably follow tracks formed on an optical disk.
In order to reproduce recorded data well on an optical disc with a very high recording density, it is necessary to not only increase the accuracy of the tracking servo control but also to correct the angle between the disc and the optical pickup. Servo control must be performed. That is, when irradiating a laser beam to a track originally formed on an optical disk, it is necessary to irradiate the laser beam in a state perpendicular to the signal recording surface on which the track is formed. On the other hand, an optical disk molded of a resin material or the like often causes warpage in a storage state or the like.In the case of a disk with this warpage, when a laser beam scans a warped portion of a track,
The state between the laser beam and the signal recording surface does not become orthogonal,
The recorded data cannot be read correctly.

For this reason, the distance or inclination between the disk surface (or signal recording surface) and the optical pickup is detected by some kind of sensor, and the inclination of the optical pickup is corrected in accordance with the detected signal. Skew servo control is performed so that irradiation is performed in a state perpendicular to the recording surface.

However, if a dedicated sensor or the like is provided for performing the skew servo control, the configuration of the optical pickup becomes more complicated, the manufacturing cost of the optical pickup increases, and the shape of the optical pickup also increases. There was a problem.

In view of the above, it is an object of the present invention to enable skew servo control with a simple configuration.

[0015]

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 using the selected optical disc, a peak position and a bottom position of the detected difference signal are held, and a difference between the peak position and the bottom position is detected. The skew servo control for correcting the tilt of the optical pickup based on the difference is performed.

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. The pits are detected by the bottom position detection, the inclination of the disk is detected based on the detection information of the pits intermittently arranged on the track, and the skew servo control can be favorably performed.

[0017]

Embodiments of the present invention will be described below.

First, the configuration of the optical disk 11 for performing tracking control and skew servo control in the apparatus of the present embodiment will be described. The signal is recorded at the designated location. 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, for example, a DVD-R
There is a recordable optical disc referred to as "recordable optical disc".

FIG. 1 is a diagram showing a configuration of tracking servo control and skew servo control of the optical disk device of this embodiment. The optical disk 11 is driven to rotate by a spindle motor 12 and an optical pickup 20 The laser light from the laser source 21 in the
After being reflected by the beam splitter 22, the light is irradiated on the optical disk 11 via the objective lens 23, and the return light from the disk is detected by the laser light detection unit 25 inside the pickup 20. The focus position of the objective lens 23 is driven by the focus coil 24. Also,
One end 26 of the optical pickup 20 is rotatably supported at a predetermined position, and a rack 27 is provided at an end opposite to the one end 26. A gear 28 screwed with the rack 27 is provided. Is rotated by the drive of the skew motor 38 so that the optical pickup 20 is inclined in the direction indicated by the arrow a with the one end 26 as a fulcrum.

Here, as the tracking servo control applied to the apparatus of the present embodiment, the DPP method described with reference to FIG.
There is a three-spot configuration that irradiates two sub-spots at positions shifted by two track pitches.
The detection unit is divided into two sections in a direction perpendicular to the track forming direction of the disc (the circumferential direction of the disc) (ie, in the radial direction of the disc).

The signal detected by the laser beam detector 25 is used as a reproduction signal from the optical disk 11. In order to obtain a tracking error signal, detection signals of three spots are supplied to the tracking error signal generation circuit 13, respectively. Then, a tracking error signal is generated by the DPP method. The configuration in which the tracking error signal is generated by the tracking error signal generation circuit 13 is the same as that described with reference to FIG.

The tracking error signal output from the tracking error signal generation circuit 13 is supplied to a tracking servo circuit 15 via a low-pass filter 14. Here, the high-frequency component removed by the low-pass filter 14 is a component including at least a frequency corresponding to a wobbling frequency of a groove formed on the optical disc 11. The tracking servo circuit 15 performs tracking servo control such that the value of the supplied tracking error signal becomes smaller. That is, according to the level of the supplied tracking error signal, the optical pickup 2
A drive signal to be supplied to the tracking coil 24 within 0 is generated, and control is performed so that the value of the supplied tracking error signal approaches 0.

Next, a configuration for skew servo control will be described below. In order to perform this skew servo control, each of the two divided detection units (the detection unit 91 in FIG. 9) for detecting the main spot in the detection unit 25 for detecting the laser light reflected on the signal recording surface of the optical disk. E that constitutes
The detection signal (corresponding to 1 and F1) is supplied to a subtractor 30 to obtain a difference signal (push-pull signal) between the two signals, and skew servo control is performed based on the difference signal.

In this embodiment, the difference signal output from the subtractor 30 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-eliminating 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 of the disk 11 from which the eccentric component and the wobbling component 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 to form a skew error signal, and this skew error signal is supplied to a skew servo circuit 37. Skew servo circuit 3
In step 7, skew servo control is performed so that the value of the supplied skew error signal is reduced. That is, in accordance with the level and polarity of the supplied skew error signal, a rotation drive signal for rotating the skew motor 38 in the direction corresponding to the polarity by an amount corresponding to the level is supplied, and the optical pickup is moved along the arrow a. The skew servo control is performed such that the laser beam emitted from the optical pickup 20 to the optical disk 11 and the signal recording surface of the optical disk 11 are always orthogonal to each other by performing a correction process for tilting the optical disk 20.

Next, the operation of the skew 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, a signal state in a state where the optical disk 11 has no warp and the laser beam from the optical pickup 20 is orthogonal to the signal recording surface of the optical disk 11 will be described with reference to FIG. The states shown in FIGS. 2, 3 and 4 are all in the just-track state for the tracking servo control, and it is assumed that only the angle formed between the disk 11 and the laser beam has changed. The difference signal (push-pull signal) A detected by the subtractor 30 is in 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 undulating 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 detected component of the pit in the land corresponds to the skew error signal component,
The processing of extracting only the skew error signal component from this signal in the processing after 1 is performed. Note that the center of this signal A is 0
V level.

By removing the eccentric component of the disk by the high-pass filter 31, the signal A has a level corresponding to the pit detection on a waveform corresponding to the wobbling frequency of the groove as shown in FIG. 2B. There is a temporary rise or fall. Further, by removing the wobbling component from this signal by the band luminescent filter 32, as shown in FIG. 2C, a signal is obtained in which 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 FIG. 2D 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.

Subtractor 35 for comparing peak value and bottom value
In the state shown in FIG. 2F, when the disk and the laser beam are orthogonal, the difference signal between the peak value and the bottom value of the waveform that goes up and down around the 0 V level is There is almost no signal smoothed by the low-pass filter 36, as shown in FIG. 2G. The output of the low-pass filter 36 is supplied to the skew servo circuit 37 as a skew error signal, and skew servo control is performed.

Then, from the state shown in FIG. 2, the laser beam and the signal recording surface of the disk are no longer orthogonal to each other.
For example, when the outer peripheral side of the disk is inclined lower than the inner peripheral side, the pit detection signal included in the difference signal detected by the subtractor 30 loses the balance between the upper and lower levels in proportion to the inclined state. (In this case, the peak level is higher and the bottom level is closer to 0 V as compared to a state where there is no skew error). For example, a signal (filter 32) from which the eccentric component and the wobbling component are removed
3), the state shown in FIG. 3C is obtained. At this time, the skew error 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. When the skew error signal is supplied to the skew servo circuit 37, the skew error signal is supplied to the skew motor 38 by a rotation drive signal.
A correction process for tilting the optical pickup 20 so as to follow the tilt of the disk is performed, and the skew error signal is set to 0.
V is controlled so that the signal recording surface of the disk and the laser beam are orthogonal to each other.

Also, for example, when the disk is inclined from the state shown in FIG. 2 such that the inner peripheral side of the disk is lower than the outer peripheral side (ie, a state in which the inclination opposite to the state described with reference to FIG. 3 occurs).
The pit detection signal included in the difference signal detected by the subtractor 30 is a signal in which the upper and lower levels are out of balance in proportion to the inclination state (in this case, the peak level is lower than in the state where there is no skew error). Becomes closer to 0 V and the bottom level becomes lower), and a state shown in FIG. 4C is obtained, for example, as a signal (output of the filter 32) from which the eccentric component and the wobbling component have been removed. At this time, the subtractor 35
The skew error signal obtained by smoothing the difference signal between the peak value and the bottom value detected at 0 V is 0 V as shown in FIG.
Signal at a lower level. When the skew error signal is supplied to the skew servo circuit 37, a correction process for inclining the optical pickup 20 in a direction opposite to that in FIG. Control is performed to bring the signal closer to 0 V, and skew servo control is performed so that the signal recording surface of the disk and the laser beam are orthogonal.

As described above, by performing the skew servo control of the present embodiment, a skew error signal for detecting the inclination of the disk is obtained by using the pits formed beside the grooves of the disk. Good skew servo control based on this is possible. That is, when the disk tilts in any direction from the state where the signal recording surface of the disk and the laser beam are orthogonal to each other, the state of detection of the pit formed on the side of the groove is changed to that shown in FIG. 3 or FIG. The skew is detected by detecting the signal waveform shown, and the skew correction process is performed by the servo control, so that a correct state can be returned. Therefore, in order to generate a reproduction RF signal, a tracking error signal by the DPP method, and the like, a detection signal of a part of a detection unit that detects return light of a laser beam applied to a disc is used.
An accurate skew error signal can be detected, and there is no need to detect the tilt of the optical pickup with a separate sensor as in the related art, and skew servo control can be performed with a simple configuration.

In the configuration of FIG. 1, the push-pull signal output from the subtracter 30 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 eccentricity component of the disk and the wobbling component of the groove are simultaneously removed by one high-pass filter as described above, for example, when the difference signal shown in FIG. The signal supplied to the peak hold circuit 33 and the bottom hold circuit 34 after passing through the one high-pass filter is, as shown in FIG. 5C, a temporary fluctuation of the level corresponding to the pit detection direction. In the opposite direction, a waveform z called slightly zag appears, but since the level of this waveform z is sufficiently lower than the pit detection waveform, it does not become an obstacle when performing the skew 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.

[0038]

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 a skew error signal can be detected satisfactorily based on detection information of pits intermittently arranged on the track. Skew servo control can be performed well, and good skew servo control can be easily performed without providing a separate tilt sensor or the like.

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

According to the third 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, so that the pits are detected intermittently. Good skew servo control that prevents disturbance of the skew error signal 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 reproduced signal waveform (in a state where there is no skew) according to the embodiment of the optical disk device of the present invention.

FIG. 3 shows a reproduction signal waveform according to the embodiment of the optical disc apparatus of the present invention (in a case where skew occurs on the outer peripheral side).
FIG.

FIG. 4 is a reproduction signal waveform according to an embodiment of the optical disk device of the present invention (in a state where skew occurs on the inner peripheral side).
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 disk, 13 tracking error signal generation circuit, 14 low-pass filter, 15 tracking servo circuit, 20 optical pickup, 21 laser source,
Reference numeral 22: beam splitter, 23: objective lens, 24: focus coil, 25: laser beam detector, 26: one end (rotation fulcrum), 27: rack, 28: gear, 30: subtractor, 31: high-pass filter .., 32 ... Band Hermitate Filter, 33 ... Peak Hold Circuit, 34 ... Bottom Hold Circuit, 35 ... Subtractor, 36 ... Low Pass Filter, 37 ... Skew Servo Circuit, 38 ... Skew Motor

Claims (3)

[Claims] 1. A skew servo for a beam of an optical pickup using an optical disk in which a groove is continuously formed along a track and a pit is formed in a land portion between the groove of an adjacent track. In the optical disk device that performs control, a return light of the beam from the optical disk is detected by a light receiving unit divided into two at least in a direction orthogonal to the longitudinal direction of the track, and a difference between detection signals of the two divided light receiving units is detected. Beam detection means for detecting a signal; peak hold means for holding a peak position of the difference signal output by the beam detection means; bottom hold means for holding a bottom position of the difference signal output by the beam detection means; Peak / bottom difference for detecting the difference between the output of the peak hold means and the output of the bottom hold means It means out, based on the output of the peak and bottom difference detecting means, the optical disk apparatus and a skew servo control means for performing skew servo control for correcting the inclination to the disk of the optical pickup. 2. The optical disc 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 disc. An optical disc device for supplying the peak hold means and the bottom hold means. 3. 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 skew servo control means.