JPH08279163A - Optical disk device and seeking method - Google Patents

Abstract

PURPOSE: To move relatively rapidly from a seeking time to a regular tracking control mode when a guide groove is provided on an optical disk and a one spot push-pull method for tracking control is used. CONSTITUTION: A DC offset generation circuit 100 obtaining a DC offset of a tracking error signal from a signal from an optical pickup at a seek time is provided. The DC offset generation circuit 100 generates a component of the common mode (or phase opposite to), the same frequency and the same amplitude as the tracking error signal TE from a regenerate high frequency signal RF at the seek time, and obtains the DC offset as a difference (addition) between the generated component and the tracking error signal at the seek time. Otherwise, the circuit 100 sample holds the tracking error signal at the seek time at the point of time correspond to a zero cross point of its high band component based on the regenerated high frequency signal. A tracking actuator is dumped by the signal based on the DC offset generated by the DC offset generation circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device and a seek method in this optical disk device, and more particularly to a so-called one-spot push-pull method as a tracking control method.

[0002]

2. Description of the Related Art In an optical disc apparatus, an optical beam is emitted from an optical pickup, the reflected light is received by the optical pickup and converted into an electric signal, and a reproduction high frequency signal is obtained from the signal from the pickup. A tracking error signal and a focus error signal are generated from the signal from the optical pickup to control the recording track so that the light beam scans stably and accurately.

In the case of an optical disk such as a magneto-optical disk capable of recording signals, a depth of λ / 8n (λ) is formed in advance in a spiral or concentric circle on the optical disk in order to generate a tracking error signal. Is a wavelength of the light beam, and n is a refractive index of the substrate. A groove (guide groove) is formed in advance, and the difference between the reflected light amount from this groove and the reflected light amount from the non-groove portion (land portion) is used. 1
The spot push-pull method (hereinafter referred to as the push-pull method) is used to perform tracking control on recording tracks (see the above-mentioned reference). In this case, the signal recording track may be formed in the groove or the land portion.

Incidentally, a tracking error detection method in the case of an actual WO (Write Once) or MO (magneto-optical) disk device is a developed version of the so-called push-pull method.

An outline of the push-pull method will be described with reference to FIG. In the push-pull method, the distribution of reflected light from the disk substrate 1 changes depending on the positional relationship between the light spot and the groove 2, and when a track deviation occurs, the tracking becomes asymmetric on the pupil of the objective lens, so that a tracking error is obtained. Is.

FIG. 11 shows a case where a signal is recorded in the groove 2, and the track center Tc coincides with the center of the groove 2. The width of one groove 2 and land 3 becomes the track pitch Pt.

In this case, as shown in FIG. 11, the reflected light from the disk substrate 1 is reflected in the direction perpendicular to the groove 2 mainly as 0th-order diffracted light and ± 1st-order diffracted light.
Now, the two-divided photodetector 4 is arranged on the pupil of the objective lens, and each of the two light receiving portions 4L and 4R has (0th order)
When + (+ 1st order) and (0th) + (-1st) luminous fluxes are detected separately, a tracking error is obtained by taking the difference signal between the outputs of these two light receiving units 4L and 4R.

That is, in the two-divided photodetector 4 of FIG. 11, S0 represents the area of the region where only the 0th order light exists, and S1 represents the area of the region where the 0th order and ± 1st order diffracted lights exist. Therefore, when the center of the groove 2 (track center Tc) coincides with the optical axis of the objective lens 3, the output difference between the two light receiving portions 4L and 4R becomes zero,
Further, when the center of the groove 2 is displaced from the optical axis, the output difference between the two light receiving portions 4L and 4R has positive and negative polarities according to the direction of the displacement and has a value according to the displacement amount. That is, a so-called S-shaped tracking error signal can be obtained.

A major drawback of this push-pull method is that, as shown in FIG. 12, the objective lens 5 moves in the direction orthogonal to the optical axis 6 so that the center of the two-divided photodetector 4 and the center of the diffracted light are aligned. Otherwise, a DC offset will occur in the tracking error signal. When the DC offset occurs in this way, the position where the tracking error signal becomes zero level deviates from the track center Tc.

Various measures have conventionally been taken against this problem. FIG. 13 shows an example of a tracking actuator which has taken the countermeasure. In this example, a moving amount of the objective lens 5 in a direction orthogonal to the optical axis is detected and corrected by a sensor having a mechanical structure.

That is, FIG. 13 is a view of the tracking actuator viewed from above, and windings 11 and 12 are provided on the side surface of the member 10 to which the objective lens 5 is attached. The permanent magnet 1 is opposed to the windings 11 and 12.
3, 14 are provided. The member 10 includes leaf springs 15 and 15
It is attached so as to be movable in the direction of the arrow. One end of each of the leaf springs 15 and 15 is attached to a fixing portion (not shown).

A position sensor 20 having a mechanical structure is provided to detect the position of the objective lens 3 in the arrow direction. In FIG. 13, the shutter piece 1 is attached to the member 10.
6 is attached, and this shutter piece 16
The tip of the LED (light emitting diode) 17 and this LE
The mechanical sensor 20 is formed by moving the spatial position between the photo sensor 18 and the photo sensor 18 facing the D17 in a direction parallel to the arrow direction. The LED 17 and the photodiode 18 are attached to an attachment member 19 fixed to a fixing portion (not shown).

The tip of the shutter piece 16 is LE
Made of a material that blocks the light from D17,
As the objective lens 5 moves, the tip of the shutter piece 16 moves in the direction of the arrow, and the amount of light reaching the photodiode 18 from the LED 17 changes. The light reception output of the photo sensor 18 becomes a position detection signal of the objective lens 5, and this position detection signal is derived as a displacement output signal of the tracking actuator of the sensor 20.

The position displacement of the objective lens 5 in the direction of the arrow is equal to the displacement of the tracking actuator, and the tracking error is exactly zero at the track center Tc.
At the position of, the displacement of the tracking actuator is also zero.

In the normal tracking control mode, the objective lens 5 attached to the leaf springs 15 and 15 is moved to the windings 11 and 12 according to the tracking error signal, so that the objective lens 5 attached to the leaf springs 15 and 15 is shown in the figure. , As shown by the arrow, the servo moves so as to move in the direction orthogonal to the optical axis and the tracking error becomes zero. In the just tracking state in this tracking control mode, the displacement of the tracking actuator becomes zero.

[0016]

By the way, in the optical disk device, when the so-called seek for moving the optical pickup in the radial direction of the optical disk to search for the track position is performed, the objective lens 5 attached to the leaf springs 15, 15 becomes It vibrates due to external force. Since the tracking actuator is a mechanical secondary system, a resonance frequency exists, so that the objective lens 5 resonates at the resonance frequency. For this reason,
The relative speed between the optical disk and the light spot increases, and tracking pull-in becomes worse.

In order to prevent this, conventionally, as described above, the position of the objective lens 5 is detected as the displacement of the tracking actuator by the sensor 20, and the tracking actuator is vibrated by the detection signal.

However, since the conventional sensor 20 has a mechanical structure, the shape of the tracking actuator becomes large and the apparatus becomes large in size, and a plurality of sensor parts are required, which is expensive. There is a drawback that it will end up.

In view of the above points, the present invention detects the position of the objective lens without using a special mechanical sensor, and the actuator can be damped by the position detection signal, and the optical disk device The purpose is to reduce the size and improve the performance.

[0020]

In order to solve the above problems, an optical disk device according to the present invention irradiates an optical disk having a guide groove with a light beam and receives reflected light from the optical disk through an objective lens. And an optical pickup that converts into an electric signal, the distribution of reflected light from the optical disc changes depending on the positional relationship between the light spot and the guide groove,
When a track deviation occurs, utilizing the fact that the pupil of the objective lens becomes asymmetrical, a means for generating a tracking error signal as an output difference between two light receiving regions of the optical pickup, and a control signal are received, A tracking actuator that displaces the objective lens in the radial direction of the disc by a direction and an amount according to the control signal, and the tracking actuator is controlled by the tracking error signal so that the light beam is emitted onto a track of the optical disc. And a tracking control system for controlling the scanning error of the light beam from a certain track position to a target track position so as to move the pickup so as to change the scanning track position of the light beam. DC offset of signal Comprising a DC offset generating circuit for obtaining, during the seek, the signal based on the DC offset generated by the DC offset generating circuit, and a damping control system for damping the tracking actuator.

The DC offset generation circuit generates a component having the same phase and the same frequency as the tracking error signal at the seek time from the reproduced high frequency signal which is the sum of the outputs of the two light receiving regions of the pickup at the seek time. A circuit for obtaining the DC offset as a difference between the generated component and the tracking error signal during the seek can be configured.

The direct-current offset generating circuit is also operable to change the reproduction high frequency signal, which is the sum of the outputs of the two light receiving regions of the pickup during the seek, to the zero-cross point of the high frequency component of the tracking error signal during the seek. It is configured by a circuit for generating a corresponding sampling clock and a sample hold circuit for sampling and holding the tracking error signal at the time of the seek by the sampling clock, and the DC offset is obtained from the sample hold circuit. You can also

[0023]

In the optical disk device of the present invention having the above structure, the displacement of the objective lens in the radial direction of the optical disk at the time of seeking is detected as the DC offset of the tracking error signal by the DC offset generating circuit. Then, the tracking actuator is damped based on the detected DC offset. Therefore, it is not necessary to provide a mechanical displacement sensor for the objective lens as in the prior art.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk device according to the present invention and a seek method in this device will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of an optical disk device according to the present invention. In FIG. 1, the optical disc 21 is a magneto-optical disc (MO) in this example, and the groove is formed in advance as described above. The optical disk 21 is driven by a spindle motor 22, but rotation is controlled by a spindle servo system (not shown) in a state of constant rotational angular velocity (CAV) or constant linear velocity (CLV).

The optical pickup 23 has an objective lens 23L.
In addition to the above, it has an optical system such as a laser light source and a photodetector for receiving reflected light.
Is irradiated with a light beam, and the reflected light is received by the photodetector through the objective lens 23L.

Although not shown, the optical pickup 23 controls the movement of the objective lens 23L in the radial direction of the optical disc 21 (for tracking control) and the movement of the objective lens 23L in the vertical direction relative to the optical disc 21 (for focus control). And a two-dimensional actuator. As the tracking control method in this case, the so-called one-spot push-pull method is used as described above.

In this example, the optical pickup 23
Can be moved in the radial direction of the optical disc 21 as a whole by a sled motor 24. A seek operation or the like is performed by the position control of the optical pickup 23 by the thread motor 24.

In the case of this example, the photodetector of the optical pickup 23 is constituted by a four-divided detector as shown in FIG. 2, and four photodetectors A, B, C, and
The received light outputs SA, SB, SC, SD from D are supplied to the RF circuit 25. In this case, if the set of the two light receiving portions A and B and the set of the two light receiving portions C and D are divided, the configuration becomes equal to the two-divided detector.

In the RF circuit 25, four received light outputs SA ...
A reproduction high-frequency signal RF is generated as a signal of the sum of SD (a sum signal of the outputs of the two light-receiving sections if it is a two-divided detector) and is supplied to the signal processing circuit 26. Signal processing circuit 2
6 reproduces a digital signal and supplies the digital signal to, for example, a host computer.

Further, in the RF circuit 25, (SA + SC)
The focus error signal FE is generated by the calculation of − (SB + SD) (however, this calculation is performed for each signal level). This focus error signal F
E is supplied to the drive coil of the actuator for focusing the two-dimensional actuator of the optical pickup 23 via the phase compensation circuit 27 and the drive amplifier 28, and focus control is performed.

In the RF circuit 25, (SA + S
The tracking error signal TE is generated by the calculation of B)-(SC + SD) (however, this calculation is performed for each signal level, and when it is a two-divided detector, it becomes a difference signal between two light receiving portions). The tracking error signal TE is supplied to one input terminal a of the switch circuit 29.

In this embodiment, since the DC offset of the tracking error signal TE at the time of seek is the positional displacement of the objective lens, the DC offset at the time of seek is referred to as the tracking error signal TE which is the output signal of the optical pickup. It is generated from the reproduction high frequency signal RF and the tracking actuator is controlled by the generated signal.

That is, the tracking error signal TE
Is supplied to the DC offset generating circuit 100 corresponding to the displacement of the objective lens at the time of seeking, and the RF circuit 2
The reproduced high frequency signal RF from 5 is supplied to the DC offset generation circuit 100. A specific example of this DC offset generation circuit 100 will be described later.

The DC offset generating circuit 10
The DC offset signal obtained from 0 is the switching circuit 2
9 is supplied to the other input terminal b.

The switch circuit 29 controls the entire operation of the optical disk device of this example, for example, at the time of recording or reproduction by a switching control signal from a control circuit 30 including a microcomputer. For example, when the normal tracking control should be performed, it is switched to the input end a side, and when seeking, it is switched to the input end b side.

Further, the control circuit 30 controls the sled motor 14 at the time of seek to move the pickup position so as to make a track jump from the current track position to the target track position.

When normal tracking control is to be performed, such as during recording or reproduction, a tracking error signal by the push-pull method is obtained from the switch circuit 29, which is the phase compensation circuit 31 and the drive amplifier 3.
2 is supplied to the drive coil of the tracking actuator of the two-dimensional actuator of the optical pickup 23, and tracking control is performed.

At the time of seeking, a component equal to the DC offset contained in the tracking error signal at that time is generated by the DC offset generating circuit 100, and this component is obtained from the switch circuit 29. The DC offset component is the phase compensation circuit 31 and the drive amplifier 32.
Is supplied to the drive coil of the tracking actuator of the two-dimensional actuator of the optical pickup 23, works in the direction of suppressing the displacement of the objective lens 23L, and the objective lens 23L is damped.

[First Embodiment of DC Offset Generating Circuit] The principle of the method of detecting the DC offset of the tracking error signal, which is the displacement of the objective lens at the time of seek, that is, the displacement of the tracking actuator, in the first embodiment. explain.

In this embodiment, a component equal to the DC offset contained in the tracking error signal TE at the time of seek is generated from the tracking error signal TE and the reproduction high frequency signal RF.

When observing the relationship between the level of the reproduction high frequency signal RF, that is, the envelope of the reproduction high frequency signal RF and the tracking error signal TE at the time of seek, FIG.
And as shown in FIG. 5, both have the same frequency,
They have a phase difference of 90 degrees with each other, and depending on the relative movement directions of the optical spots in the radial direction of the optical disk, the phase relationship between the lead and the lag is reversed.

Then, when the optical pickup is moved in the radial direction of the disk by the seek, the objective lens 23L
As a result, the tracking error signal TE has a DC offset as shown in FIG. That is, in FIG. 3, the solid line TEo represents the tracking error signal when there is no DC offset. For example, when the light spot position moves from the inner circumference side to the outer circumference side of the disc, the tracking error signal is indicated by the dotted line TEu in FIG. As shown in FIG. 3, a positive DC offset occurs, and conversely, when the light spot position moves from the outer circumference side to the inner circumference side of the disc, the tracking error signal becomes as shown by the alternate long and short dash line TEd in FIG. DC offset has occurred.

On the other hand, the reproduction high frequency signal RF is 2
Since it is a sum signal of two light receiving parts, no DC offset occurs in its envelope.

Therefore, at the time of seek, the reproduction high frequency signal RF
A component having the same frequency and phase as that of the tracking error signal TE is generated from the control signal, and the generated component is controlled to be equal to the amplitude of the high frequency component of the tracking error signal FE excluding the DC offset. Then, as a result of this control, if the obtained signal is subtracted from the tracking error signal TE, only the DC offset in the tracking error signal TE can be obtained.

If the tracking actuator is driven by this DC offset, the position of the objective lens is controlled in the direction of zero displacement, and the objective lens is damped so that resonance does not occur.

FIG. 6 is a circuit diagram of the first embodiment of the DC offset generating circuit 100, and FIG. 7 is a waveform diagram of each part of the circuit of FIG. 6 at the time of seek.

In the DC offset generating circuit 100 of this example, the tracking error signal T is input through the input terminal 101.
E (see FIG. 7A) is input, and a signal Erf (see FIG. 7B) obtained by envelope detection of the reproduction high frequency signal RF is input through the input terminal 102. As shown by the dotted line in FIG. 7A, the tracking error signal TE at the time of seeking contains a DC offset component Eof.

The tracking error signal TE input through the input terminal 101 is supplied to one input terminal of the subtraction circuit 110. In addition, the tracking error signal TE
Is supplied to a high-pass filter 113 including a capacitor 111 and a resistor 112, and the high-pass filter 2
From 13, a signal Ste (see FIG. 7C) obtained by removing the low frequency component of the tracking error signal TE is obtained. This signal Ste is converted into a rectangular wave signal C by the waveform shaping comparator 114.
te (see FIG. 7E).

The signal Erf input through the input terminal 102 is also supplied to a high-pass filter 123 composed of a capacitor 121 and a resistor 122. From the high-pass filter 123, a signal Srf (excluding the DC component of the signal Erf is output. 7D) is obtained. This signal Srf is
A rectangular wave signal Cte (see FIG. 7) is generated by the waveform shaping comparator 124.
E)).

Then, the rectangular wave signal Cte is supplied to the D terminal of the D flip-flop 125 and the rectangular wave signal Cte.
rf is supplied to the clock terminal of the D flip-flop 125. In the D flip-flop 125, the rectangular wave signal Cte is sampled at the falling edge of the rectangular wave signal Crf, for example. As a sampling output from the D flip-flop 125, a direction detection signal Dir (Fig. 7G) is obtained.

That is, as described above, the envelope of the reproduction high frequency signal RF and the tracking error signal TE
Has a phase difference of 90 degrees, and the advance and lag relationship between the two is reversed depending on the moving direction of the light spot in the radial direction of the disk. Therefore, for example, as shown in FIGS. 4 and 5, when the light spot position moves from the inner circumference side to the outer circumference side, the direction detection signal Dir becomes high level,
Further, when the light spot position moves from the outer peripheral side to the inner peripheral side, the direction detection signal Dir becomes low level.

Then, the signal Srf obtained by removing the low frequency component from the envelope detection signal Erf of the reproduction high frequency signal RF from the high pass filter 123 is the all pass filter 12
6. The all-pass filter 126 has a flat amplitude characteristic with respect to frequency and has a characteristic of shifting (delaying) all frequency components by a predetermined phase amount.

Now, assuming that the input of this all-pass filter 126 is ei and the output thereof is eo, the input / output characteristics thereof can be expressed by the following equation.

[0055]

[Equation 1] Here, ω is the angular frequency. Then, in the case of this example, the all-pass filter 126 uses a filter in which the phase difference between the input ei and the output eo is 90 degrees.

The output signal Ss (see FIG. 7H) of the all-pass filter 126 is supplied to one input terminal N of the switch circuit 127 and is converted into a signal Siv (see FIG. 7I) whose phase is inverted by the phase inverting circuit 128. , And is supplied to the other input terminal IV of the switch circuit 127.

The direction detection signal Dir described above is supplied as the switching control signal of the switch circuit 127. In this example, when the direction detection signal Dir is at the low level, the signal at the input terminal N is selected. However, when the selection direction detection signal Dir is at the high level, the signal is switched to the signal at the input terminal IV. As a result, from the switch circuit 127, a signal S having the same frequency and the same phase as the tracking error signal TE and only the amplitude being indefinite.
m is obtained.

This signal Sm is supplied to a voltage control type variable resistor (hereinafter, referred to as VCR) 131 to perform amplitude control. Then, as will be described later, this VC
The resistance value of R131 is controlled by the control signal from the VCR control voltage generation circuit 130,
From, a signal Sd (see FIG. 7J) equal to the signal obtained by removing the DC offset component from the tracking error signal TE input through the input terminal 101 is obtained.

The output signal Sd of the VCR 131 is supplied to the subtraction circuit 110 through the amplifier 132 and subtracted from the tracking error signal TE. Therefore, if the signal Sd is a signal equal to the signal obtained by removing the DC offset component from the tracking error signal TE, only the DC offset component Eof (see FIG. 7K) in the tracking signal TE is obtained from the subtraction circuit 110.

However, when the output of the subtraction circuit 110 is not only the DC offset component Eof, the resistance value of the VCR 131 is controlled as follows to remove the extra component.

That is, the output signal of the subtraction circuit 110 is
After being supplied to the high-pass filter 143 composed of the capacitor 141 and the resistor 142 to remove the DC offset component Eof, it is supplied to the VCR control voltage generation circuit 130 via the amplifier 144. On the other hand, a signal Cte from the comparator 114, which is obtained by waveform-shaping the signal obtained by removing the DC offset component from the tracking error signal TE, is supplied to the VCR control voltage generation circuit 130.

The VCR control voltage generation circuit 130 compares both input signals to form a control voltage for the VCR 131,
Controls the resistance value of CR131. By this control loop, the output signal of the amplifier 144 is made to be substantially zero. Therefore, the output signal of the subtraction circuit 110 is made to be only the DC offset component Eof in the tracking error signal TE, and this is obtained from the output terminal 103.

Then, in FIG. 1, at the seek time, the DC offset component obtained at the output terminal 103 is obtained through the switch circuit 29, and this is obtained.
1 and the drive circuit 32 to supply the tracking actuator to suppress the resonance of the objective lens 23L.

In the above example, the reproduction high frequency signal RF
Tracking error signal TE from the envelope Erf of
A component having the same phase, the same amplitude, and the same frequency as the high frequency component of is generated and the generated component is subtracted from the tracking error signal TE.
A component having the opposite phase, the same amplitude, and the same frequency as the high frequency component of 1 may be generated and added to the tracking error signal TE, and the high frequency component may be removed to generate the DC offset.

[Second Embodiment of DC Offset Generation Circuit] In the second embodiment, when the frequency, the phase and the amplitude of the envelope of the reproduced high frequency signal are matched with the tracking error signal as in the above-mentioned example. , This is an example of improving this because the circuit becomes complicated.

This example takes advantage of the fact that when the tracking error signal TE is sampled at the zero point of the high frequency component of the tracking error signal TE, a DC offset can be extracted, as indicated by the circle in FIG.

Since it is generally difficult to directly detect the zero point of the high frequency component of the tracking error signal TE, the zero point is detected using the envelope of the reproduced high frequency signal RF. Before the description of this embodiment, the detection accuracy in this case will be described.

When switching from the seek state to the normal tracking control ON, the relative speed Ve of the light spot crossing the groove in the immediately preceding tracking direction is 8 mm /
It is known that the tracking servo cannot be properly pulled in unless it is about sec or less.

The frequency ft of the tracking error signal at this time is ft = Ve / Tp (2), where Tp is the track pitch. Substituting Ve = 8 mm / sec into this equation (2), and substituting Tp = 1.3 μm, for example, ft
= 6.5 kHz. As shown in FIG. 8, since there are two sampling points per cycle of the tracking error signal TE, the sampling frequency fs is fs.
= 6.25 × 2 = 12.3 [kHz].

On the other hand, the resonance frequency of the tracking actuator is, for example, about 30 Hz. So now, 3
Considering that the resonance of the tracking actuator is suppressed by a servo loop having a gain of 40 dB or more at 0 Hz, in the case of the example of FIG.
Due to the effect of the phase compensation circuit 32, the open loop gain is 10 dB.
Since / oct is a normal characteristic, a servo loop having a servo band of 480 Hz may be designed. If the above-mentioned sampling frequency is 12.3 kHz, this characteristic can be sufficiently realized.

FIG. 9 shows an example of a circuit diagram in the case of the second embodiment, and FIG. 10 shows a waveform diagram of each part thereof.

As shown in FIG. 9, in this example, the tracking error signal TE (see FIG. 10A) input through the input terminal 41 is supplied to the sample hold circuit 43 through the amplifier 42. The sample hold circuit 43 includes a sampling switch circuit 431 and a charging / discharging capacitor 432.

On the other hand, a signal Erf (see FIG. 10B) obtained by envelope-detecting the reproduction high frequency signal RF is supplied through the input terminal 44 to the 90-degree phase shifter 4 having a high-pass filter configuration, for example.
5 and is made into a signal Rs (see FIG. 10C) which is in-phase or anti-phase with the tracking error signal FE. Then, this signal Rs is supplied to the waveform shaping comparator 46, and becomes a rectangular wave signal Cr (see FIG. 10D).

This rectangular wave signal Cr is supplied as it is to one input end of the exclusive OR gate 47, and the other of the exclusive OR gate 47 is passed through a delay circuit 48 having a sufficient pulse width as a sampling pulse. It is supplied to the input terminal. As a result, a pulse Sp (see FIG. 10E) is obtained from the exclusive OR gate 47 at the rising and falling edges of the rectangular wave signal Cr. In the tracking error signal TE, the pulse Sp is obtained at the zero cross point of the high frequency component.

This pulse Sp is supplied to the switch circuit 431 of the sample hold circuit 43, and the switch circuit 431 is turned on in the pulse width section. That is,
The tracking error signal TE is sampled by the pulse Sp, and the sampled value is stored in the capacitor 432. Then, the output signal of the sample hold circuit 43 is led to the output terminal 50 via the amplifier 49. Therefore, as described above, the DC offset component Eof (see FIG. 10F) in the tracking error signal TE is obtained at the output terminal 50.

Thus, in the case of the second embodiment,
The DC offset in the tracking error signal TE corresponding to the displacement of the objective lens at the time of seek can be extracted with a simple circuit configuration.

[0077]

As described above, according to the present invention, at the time of seek, a value equal to the DC offset component in the tracking error signal is generated and the tracking actuator is damped by using the value. The structure of the tracking actuator can be simplified, and the optical disk device can be manufactured at a low cost, as compared with the case where a mechanical sensor as in the related art must be used.

[Brief description of drawings]

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

FIG. 2 is a diagram illustrating an example of a configuration of a light receiving unit of an optical pickup.

FIG. 3 is a diagram showing an example of a DC offset of a tracking error signal.

FIG. 4 is a diagram for explaining a relationship between a tracking error signal and a reproduction high frequency signal.

FIG. 5 is a diagram for explaining a relationship between a tracking error signal and a reproduction high frequency signal.

FIG. 6 is a circuit diagram of an embodiment of a main part of the embodiment of FIG.

FIG. 7 is a waveform diagram of each part of the embodiment of FIG.

FIG. 8 is a diagram for explaining the principle of another embodiment of the main part of the embodiment of FIG.

FIG. 9 is a circuit diagram of another embodiment of the main part of the embodiment of FIG.

FIG. 10 is a waveform diagram of each part of the embodiment of FIG.

FIG. 11 is a diagram for explaining a method of acquiring a tracking error by the one-spot push-pull method in the optical disc device.

FIG. 12 is a diagram for explaining a DC offset which is a defect in the one-spot push-pull method.

FIG. 13 is a diagram for explaining a conventional method for detecting displacement of an objective lens during seek.

[Explanation of symbols]

 21 optical disc 23 optical pickup 25 RF circuit 29 switch circuit 31 phase compensation circuit 32 drive circuit 100 DC offset generation circuit TE tracking error signal RF reproduction high frequency signal Erf envelope detection output signal of reproduction high frequency signal Eof DC offset component

Claims (4)

[Claims] 1. An optical pickup for irradiating an optical disc having a guide groove with a light beam and receiving reflected light from the optical disc through an objective lens to convert it into an electric signal, and a distribution of reflected light from the optical disc. Changes depending on the positional relationship between the light spot and the guide groove, and when a track is deviated, the fact that it becomes asymmetric on the pupil of the objective lens is used to track as an output difference between two light receiving regions of the optical pickup. Means for generating an error signal; a tracking actuator which receives the control signal and displaces the objective lens in the radial direction of the disk by a direction and an amount according to the control signal; and the tracking actuator by the tracking error signal. Control so that the light beam scans the track of the optical disk correctly. And a tracking control system for controlling the tracking error signal, and a DC offset of the tracking error signal from the signal from the optical pickup at the time of seeking to move the pickup so as to change the scanning track position of the light beam from a certain track position to a target track position. An optical disk device comprising: a DC offset generating circuit to be obtained; and a vibration damping control system for damping the tracking actuator by a signal based on the DC offset generated by the DC offset generating circuit during the seek. 2. The direct current offset generation circuit is in-phase or anti-phase with a high frequency component of the tracking error signal at the seek time from a reproduced high frequency signal which is a sum of outputs of the two light receiving areas of the pickup at the seek time. 2. The optical disk device according to claim 1, wherein the components having the same amplitude and the same frequency are generated, and the DC offset is obtained as a difference between the generated component and the tracking error signal during the seek. 3. The direct current offset generation circuit, from the reproduction high frequency signal which is the output sum of the two light receiving regions of the pickup at the time of the seek, to the zero cross point of the high frequency component of the tracking error signal at the time of the seek. It comprises a circuit for generating a corresponding sampling clock and a sample hold circuit for sampling and holding the tracking error signal at the time of the seek with the sampling clock, and the DC offset is obtained from the sample hold circuit. The optical disk device according to claim 1. 4. A distribution of reflected light from an optical disk changes depending on a positional relationship between a light spot and a guide groove provided on the optical disk, and when a track deviation occurs, it becomes asymmetric on a pupil of an objective lens. Utilizing this, a tracking error signal is generated as an output difference between two light receiving regions of the optical pickup, and the tracking error signal controls a tracking actuator for displacing the objective lens in the radial direction of the optical disc to perform tracking control. In the optical disc device for performing the following, during the seek for moving the optical pickup from a certain track position to the target track position, the reproduction is a sum of the tracking error signal at the seek time and the output of the two light receiving areas of the optical pickup. From the high frequency signal, A DC offset included in the racking error signal is obtained, and the tracking actuator is controlled by the signal based on the DC offset to suppress the displacement of the objective lens in the radial direction of the optical disc. How to seek.