JPH10124892A - Disk drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reproducing operation performance by allowing the low frequency components of a tracking error signal to control a variable gain amplifier circuit, while a tracking servo loop is off, and thereby quickly precisely drawing a servo. SOLUTION: During the period that a switch 22 is connected to a TA terminal, a tracking error signal STE from a tracking error amplifier circuit 1 controls a variable gain amplifier circuit 3B through a buffer amplifier 24, with low frequency components extracted by LPF 23. As a result, the output of a direct detecting means can be detected at an offset level, enabling balance adjustment automatically. Meantime, during the period that the switch 22 is connected to a TB terminal, the variable gain amplifier circuit 3B is grounded through a resistance R5, with its amplification factor adjusted by the operation of a variable resistance VR. In this case, the switch 22 is controlled by a control signal CNTSW from a system control circuit 20, and is connected to the TA terminal while the tracking servo loop is off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk drive, and more particularly to a circuit system for executing a tracking servo.

[0002]

2. Description of the Related Art For example, a disk drive such as a compact disk player is known. As this type of disk drive, a recording track on a compact disk is irradiated with three laser spots, and a return track obtained by the laser spot is obtained. There is an apparatus in which tracking control is performed by a so-called three-beam method in which tracking control is performed using light.

As shown in FIG. 3, in the tracking servo system based on the three-beam method, a laser beam emitted from a semiconductor laser is divided into a main beam consisting of a 0th-order diffraction beam and a ± 1st-order beam using a diffraction grating. The light is separated into two sub-beams composed of the analyzed light. Then, the main beam is applied to the recording pit PT formed on the recording track TRK on the compact disk as a reproducing laser spot SP _MAIN , thereby reproducing the recorded information and, at the same time, the two sub beams SP _SUB1 and SP _SUB2 are formed. Reproduction laser spot SP as viewed in the traveling direction of recording track TRK (indicated by arrow a)
Irradiate before and after _MAIN . These two sub beams S
P _SUB1 and SP _SUB2 are first and second tracking laser spots.

In the first and second tracking laser spots SP _SUB1 and SP _SUB2 , for example, the just tracking state in which the center of the reproducing laser spot SP _MAIN is positioned at the track center TRK _CTR of the recording track TRK (FIG. 3) In the case of (a)), the centers SP _CTR1 and SP _{CTR2 of} the first and second tracking laser spots SP _SUB1 and SP _SUB2 are the same amount Δx on the inner and outer sides (in FIG. 3, the track center TRK _CTR (The right side is the inner side and the left side is the outer side).

Incidentally, the tracking error signal is composed of first and second tracking laser spots SP _SUB1 and SP _SUB1 .
The return light of _SUB2 is received by the first and second tracking light detectors, respectively, and the difference between the respective light receiving outputs obtained as a result is calculated and obtained. The tracking error signal obtained in the tracking state becomes 0 level.

On the other hand, a reproducing laser spot
SP_MAINIs the track center T of the recording track TRK
RK_CTR A predetermined amount Δz on the outer circumference (or inner circumference).
In the state (Fig. 3 (b) or Fig. 3 (c))
Correspond to the first and second tracking lasers
Spot SP_SUB1, SP_SUB2Center SP_CTR1, SP_{CT R2}
As a result, there is a light amount difference between the respective return lights,
Therefore, the tracking error signal
A positive (or negative) signal level results.

For this reason, in a compact disk player, a tracking control circuit is used so that the signal level of a tracking error signal is always set to 0 level.
An appropriate tracking servo is performed by driving the tracking coil of the biaxial device holding the objective lens in the tracking direction (the direction orthogonal to the traveling direction a of the recording track).

In practice, however, signals obtained from the first and second tracking optical detectors even in the just tracking state due to differences in the characteristics of the tracking optical detector and misalignment of the entire optical system. In some cases, a difference occurs, that is, the tracking error signal does not become 0 level even in the just tracking state.

In view of the above, characteristics and alignment errors can be absorbed by making it possible to adjust the amplification level of one of the outputs of the first and second tracking optical detectors (for example, by providing an adjusting means such as a semi-fixed resistor). I was doing it. That is, the adjustment is performed so that the tracking error signal becomes 0 level in the just tracking state.

Further, the present applicant has previously proposed a tracking control circuit for automatically realizing the balance adjustment of the first and second tracking optical detectors. FIG. 4 shows a tracking control circuit previously proposed by the present applicant.

In the tracking control circuit shown in FIG. 4, tracking optical detectors 2A and 2B (hereinafter, detectors) are respectively provided with tracking laser spots SP.
Light reflected by _SUB1 and SP _SUB2 is received, and light receiving outputs S _PD1 and S _{PD2 corresponding} to the _{amounts of} light are supplied to the tracking error amplifier circuit 11.

The tracking error amplifier circuit 11 is provided with a buffer circuit 11A having an operational amplifier configuration and connected to a feedback resistor R11. The light receiving output _SPD1 from the detector 2A is converted from a current value to a voltage value by the buffer circuit 11A. Then, the signal is input to the inverting input terminal of the subtraction circuit 11C via the input resistor R13. On the other hand, the received light output _SPD2 input from the detector 2B is _equal to the variable gain amplifier circuit 11B.
And is amplified at a predetermined amplification factor, converted from a current value to a voltage value, and input to the non-inverting input terminal of the subtraction circuit 11C via the input resistor R14.

A negative feedback resistor R15 is connected to an inverting input terminal of the subtraction circuit 11C, and a non-inverting input terminal is grounded via a resistor R16. The output end of the subtracting circuit 11C, that is, as the output of the tracking error amplifier 11 becomes a tracking error signal S _TE by the difference calculation of the light-receiving output S _PD1, S _PD2.

The tracking error signal _STE is A /
Is D converter 12, is converted into the tracking error data DT _TE by a digital value is sent to the servo data forming circuit 13 comprising a digital signal processor of the microcomputer configuration. Servo data forming circuit 13, the tracking error data DT _TE input, digital level adjustment performs servo data forming processing such as phase compensation, the result generated tracking servo data DT _SB, followed by a 1 PWM (pulse wi
dth modulation) is transmitted to the tecode circuit 14.

Thus, the first PWM decoding circuit 14
PW input tracking servo data DT _SB
The signal is decoded by the M modulation method, and the resulting decoded signal is sent to the tracking coil drive circuit 15 as the tracking coil drive signal _SDV . Thus, the tracking coil drive signal S _DV is transmitted via the tracking coil drive circuit 15 to the tracking coil 1 of the two-axis device 16.
6A, whereby the biaxial device 16, that is, the objective lens of the optical head, is driven and controlled in the tracking direction according to the tracking servo data DT _SB , and the tracking servo is executed.

The first PWM decoding circuit 14 receives jump data DT _JP in addition to the tracking servo data DT _SB inputted from the servo data forming circuit 13. The jump data DT _JP shown in FIG. 3 is based on a jump control signal CNT _JP given from a system control circuit 20 having a microcomputer configuration.
Jump control circuit 2 for executing the track jump operation of the light spots SP _MAIN , SP _SUB1 , SP _SUB2
1 is a signal to be generated. Thereby, the first PWM
The decoding circuit 14 decodes the input jump data DT _JP by a PWM modulation method, and sends out a decoding signal obtained as a result to the tracking coil driving circuit 15 as a tracking coil driving signal _SDV .

Thus, the tracking coil drive signal S
_DV is supplied to the tracking coil 16A of the two-axis device 16. Thereby, according to the jump data DT _JP ,
The biaxial device 6, that is, the objective lens of the optical head is driven and controlled in the tracking direction, and the three light spots S
Track jump operations of P _MAIN , SP _SUB1 and SP _SUB2 are executed.

The tracking error data DT _TE obtained from the A / D converter 12 is used for the servo data forming circuit 1
In addition to 3, the signal is sent to a balance control circuit 17 comprising a digital signal processor having a microcomputer configuration. The balance control circuit 17 performs a balance control operation based on a control signal CNT _BC of the system control circuit 20, for example, when the tracking servo is off. It calculates the average value data for the tracking error data DT _TE comprised in average during a predetermined period, the variable gain amplifier circuit 1 as the average value data is a value "0"
The control data DT _CNT for controlling the gain of 1B is
The data is sent to the second PWM decoding circuit 18.

The second PWM decoding circuit 18 decodes the input control data _DTCNT by a modulation method, and supplies the resulting decoded signal to a low-pass filter circuit 19 including a resistor R17 and a capacitor C11. The decoded signal smoothed by the low-pass filter circuit 19 is supplied to the variable gain amplifier circuit 11B as a control voltage _VCNT for variably controlling the gain.

In the above configuration, for example, after power is turned on,
First, a compact disc is loaded into a CD player,
The traverse signal is generated when the focus servo is turned on and the spindle servo is turned on by the start-up process (when the tracking servo is still controlled to be in the off state). In such a case, the system control circuit 20 causes the balance control circuit 17 to start the balance control processing. Then, based on the average value data obtained by the balance control circuit 17, the variable gain amplifying circuit 11
The gain of B is adjusted.

That is, the balance control circuit 17 sets the variable gain amplifying circuit 11B to an arbitrary gain when the tracking servo is in an off state (a period in which the servo loop is off), and the tracking error obtained as a result is obtained. By automatically adjusting the gain of the variable gain amplifier circuit 11B so that the average value data, which is the average value of the data _{DTTE for} a predetermined period, becomes the value “0”, the detectors 2A, 2
B, the first and second light receiving outputs S _PD1 , S _PD2
To be able to adjust the balance.

[0022]

By using the tracking control circuit as described above, errors due to optical alignment and the characteristics of the detectors 2A and 2B can be adjusted, and the processing of the balance control circuit 17 can be executed at any time to change over time. State that may occur due to changes in characteristics due to temperature or temperature conditions, or even environmental factors (such as the attitude of a portable disc player) (the generation of a DC offset superimposed on the tracking error signal _STE )
Can also be absorbed.

However, to realize such automatic balance adjustment, relatively large-scale circuit units such as the balance control circuit 17 and the PWM decode circuit 18 are required, and the circuit configuration becomes large-scale. The balance control circuit 1
In No. 7, since the average value calculation is repeated to drive the gain of the variable gain amplifier circuit 11B, a considerably high digital calculation processing capability is required. from these things,
Actually, there is a problem that an automatic balance adjustment function cannot be adopted in a small-sized CD player, a low-priced player, and the like.

[0024]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made to enable automatic balance adjustment even in a small or low-cost disk drive.
An object of the present invention is to make it possible to realize an improvement in reproduction capability.

For this reason, as a disk drive device, first, a recording track of a disk-shaped recording medium is irradiated with light from an objective lens, and reflected light information is detected in accordance with a state of displacement of a relative position between the objective lens and the recording track. First and second detecting means for generating a tracking error signal based on the difference between the output of the first detecting means and the output of the second detecting means. And extracting means for extracting a low-frequency component of the generated tracking error signal, and correcting one of the output of the first detecting means and the output of the second detecting means based on the output of the extracting means. Correction means is provided. Further, there is provided control means for executing a correction operation by the correction means when the tracking servo loop is open. That is, by extracting a low-frequency component from the tracking error signal, an offset level superimposed on the tracking error signal is obtained, and the output of the first or second detection means is directly corrected by the offset level, thereby providing a simple circuit. The configuration allows automatic balance adjustment to be realized.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a disk drive according to the present invention will be described below with reference to FIGS. FIG. 1 shows a configuration of a tracking control circuit 10 mounted on a disk drive device. The same reference numerals are given to the same functional parts as those in FIG.

In the tracking control circuit 10 shown in FIG. 1, the detectors 2A and 2B cause the light receiving outputs S _PD1 and S _PD2 corresponding to the amounts of reflected light from the tracking laser spots SP _SUB1 and SP _SUB2 (see FIG. 3) to have tracking errors. The signal is supplied to the amplifier circuit 1.

The tracking error amplifying circuit 1 is provided with a buffer circuit 3A to which a feedback resistance value is set by resistors R1, R2 and R3 and to which a capacitor C1 for limiting a low frequency gain is connected. Then, the light receiving output _SPD1 from the detector 2A is supplied to the inverting input terminal of the buffer circuit 3A. The non-inverting input terminal of the buffer circuit 3A supply voltage V _D is supplied. The light receiving output _SPD1 is converted from a current value to a voltage value by the buffer circuit 3A, and is input to the inverting input terminal of the subtraction circuit 3C via the input resistor R6.

On the other hand, the light receiving output _SPD2 input from the detector 2B is input to the inverting input terminal of the variable gain amplifier 3B. The power supply voltage V _D is supplied to the non-inverting input terminal of the variable gain amplifier circuit 3B. In the variable gain amplifying circuit 3B, the feedback resistance value is set by the resistors R4 and R5 and the variable resistor R5, and the low frequency gain is limited by the capacitor C2.

The light receiving output S _PD2 is a variable gain amplifier 3B
And is amplified at a predetermined amplification factor set by the feedback resistance value, and is converted from a current value to a voltage value. That is, the amplification factor is basically adjusted and set according to the value of the variable resistor R5 (for example, a semi-fixed resistor). Although the operation function will be described later, the resistor R5 is connected to the switch 22,
When 2 is connected to the T _B terminal, the variable gain amplifier circuit 3B is grounded through a resistor R5, whereas the switch 22
There when connected to T _A terminal, an output of the low-pass filter 23 is to be supplied to the resistor R5.

The output of the variable gain amplifier circuit 3B is input to the non-inverting input terminal of the subtraction circuit 3C via the input resistor R7. The inverting input terminal of the subtracting circuit 3C negative feedback resistor R9 is connected, also the non-inverting input terminal is connected through a resistor R8 to the power supply voltage V _D. And the output terminal of the subtraction circuit 3C,
That is, as the output of the tracking error amplifying circuit 1, the tracking error signal S _TE by the difference calculation of the light-receiving output S _PD1, S _PD2.

The tracking error signal _STE is A /
Is D converter 12, is converted into the tracking error data DT _TE by a digital value is sent to the servo data forming circuit 13 comprising a digital signal processor of the microcomputer configuration. Servo data forming circuit 13, the tracking error data DT _TE input, digital level adjustment performs servo data forming processing such as phase compensation, the result generated tracking servo data DT _SB, PWM Tekodo It is sent to the circuit 14.

The PWM decoding circuit 14 decodes the input tracking servo data DT _SB by the PWM modulation method, and sends out a tracking coil drive signal S _DV obtained as a result to the tracking coil drive circuit 15.
That tracking error first signal S tracking coil drive signal is generated based on the _TE S _DV is supplied to the tracking coils 16A of the biaxial device 16 via the tracking coil driving circuit 15, thereby the biaxial device 16 that is, the optical head Are driven and controlled in the tracking direction. That is, as the operation of the tracking servo loop, Deitekuta 2A, the light receiving output S _PD1 of 2B, S
_The tracking servo based on _PD2 is executed.

The jump data DT _JP is input to the PWM decoding circuit 14 in addition to the tracking servo data DT _SB input from the servo data forming circuit 13. The jump data DT _JP performs a track jump operation of the three light spots SP _MAIN , SP _SUB1 , and SP _SUB2 shown in FIG. 3 based on a jump control signal CNT _JP given from a system control circuit 20 having a microcomputer configuration. Jump control circuit 21 for execution
Is a signal to be generated. The system control circuit 20
Means that the PWM decode circuit 14 is controlled so that the tracking servo loop is opened (turned off) when the track jump operation (access operation) is performed.

At the time of access, etc., jump data D
When T _JP is input, the PWM decoding circuit 14 decodes the jump data DT _JP by the PWM modulation method, and sends out the resulting decoded signal to the tracking coil drive circuit 15 as the tracking coil drive signal S _DV .

The tracking coil drive signal S _DV is supplied to the tracking coil 16 A of the two-axis device 16.
Thus, the two-axis device 6, that is, the objective lens of the optical head is driven and controlled in the tracking direction according to the jump data DT _JP , and the three light spots SP _MAIN , S
The track jump operation (access operation) of P _SUB1 and SP _SUB2 is executed.

[0037] In the present embodiment, the tracking error signal S _TE output from the tracking error amplifying circuit 1 is also supplied to the low-pass filter 23. Then, a low-pass component of the tracking error signal _STE is extracted by the low-pass filter 23, and the buffer amplifier 2 for impedance matching is extracted.
4 to the T _A terminal of the switch 22. Therefore, the period during which the switch 22 is connected to the T _A terminal,
A low-frequency component of the tracking error signal S _TE is applied to the resistor R5 side, i.e. a low-frequency component of the tracking error signal S _TE is supplied to the gain as the control voltage V _CNT to variably control the variable gain amplifier circuit 3B .

Meanwhile T _B terminal of the switch 22 is grounded, the period during which the switch 22 is connected to the T _B terminal, the variable gain amplifier circuit 3B is grounded through a resistor R5. Usually switch 22 is connected to T _B terminal,
Therefore, the gain of the variable gain amplifier circuit 3B is equal to the variable resistance VR.
(Semi-fixed resistance).

The switch 22 is is switching control by a control signal CNT _SW from the system control circuit 20, the system control circuit 20 so as to connect the switch 22 to T _A terminal during a period in which to turn off the tracking servo loop ing.

FIG. 2 shows a process at the time of executing access, for example. Proceeds accessed when executing the (track jump) the processing of the system control circuit 20 from step F101 to F102, with to the tracking servo loop off the PWM decoder circuit 14, the switch 22 T _A terminal in step F103 To be connected. And step F1
At step 04, a jump control signal CNT _JP is output to execute the track jump operation of the three light spots SP _MAIN , SP _SUB1 and SP _SUB2 shown in FIG.

Although the access operation itself will not be described in detail, at the time of access, the objective lens moves or slides while controlling such as detecting that a required number of track jumps have been crossed by means such as counting a traverse signal. Is performed to move the entire optical head. Then, when the disk reaches the target track on the disk, the pull-in operation (settling of the spindle motor rotation speed, focus servo on, tracking servo on) is executed, and data can be read. When such access is completed, the process proceeds from step F105 to F106,
Thereby terminating the process related to access return the switch 22 to T _B terminal.

[0042] In this way, for example, when accessing the switch 22 in a period during which the tracking servo loop is turned off are connected to the T _A terminal, thus the period tracking servo loop is turned off, the tracking error signal S The low-frequency component of _TE is applied to the resistor R5 as a control voltage _VCNT for variably controlling the gain of the variable gain amplifier circuit 3B.

In this period, a traverse signal waveform accompanying the light spot crossing the track is observed as the tracking error signal _STE .
Therefore, the low-frequency component extracted by the low-pass filter 23 is a DC component superimposed on the traverse signal waveform, that is, an offset component during a period when the tracking servo loop is off.

The offset component includes various causes such as errors due to the optical system alignment of the optical head and the characteristics of the detectors 2A and 2B, changes in characteristics due to aging and temperature conditions, and environmental factors such as the posture of the device during use. It occurs in. If such a DC offset becomes large due to various situations, it becomes difficult to pull in the tracking servo at the end of the access or the like, and the subsequent reproduction start is delayed.

However, in this embodiment, the DC offset component is supplied as the control voltage _VCNT to the variable gain amplifier circuit 3B via the buffer amplifier 24, so that the DC offset component is supplied.
The gain is adjusted according to the C offset value, that is, the balance between the light receiving outputs S _PD1 and S _PD2 supplied to the subtraction circuit 3C is adjusted. That is, the gain of the variable gain amplifier circuit 3B is adjusted so that the DC offset component converges to zero.

Therefore, if the tracking control circuit of this embodiment is used, every time the tracking servo loop is turned off, errors due to optical alignment and the characteristics of the detectors 2A and 2B, changes over time and characteristics due to temperature conditions, and environmental factors. As a result, the imbalance state (DC offset on the traverse signal) is absorbed, so that quick and accurate tracking servo pull-in is possible, and accordingly, the reproduction operation performance is improved.

Further, since the traverse signal is always fixed at the center (offset zero), it is advantageous in terms of a dynamic range, and a stable servo operation can be realized in a low-voltage system. Of course, at the time of normal operation (tracking servo loop on), there is also an advantage that operation performance such as servo characteristics is not affected at all.

In the case of this embodiment, such automatic balance adjustment is performed by using the low-pass filter 23, the buffer amplifier 24,
This is realized only by providing a simple circuit unit called the switch 22, and does not require a circuit system such as the balance control circuit 17 and the PWM decode circuit 18 shown in FIG. . From these facts, it is possible to reduce the size and cost of the circuit,
Can be used in D players and low-priced players, etc.
That is, the automatic balance adjustment function can be adopted.

In the example of FIG. 1, the gain is adjusted for the light receiving output _SPD2 of the detector 2B.
Configurations are of course contemplated that perform gain adjustment with respect to the light receiving output S _PD1 detector 2A. However,
In the case where the subtraction circuit 3C performs the operation of (S _PD2 −S _PD1 ) as shown in FIG. 1, the polarity adjustment is performed to adjust the gain of the light receiving output S _PD1 of the detector 2A with the output of the low-pass filter 23. Therefore, it is necessary to perform -1 multiplication (polarity inversion) in the buffer amplifier 24.

[0050]

As described above, according to the disk drive of the present invention, during the period when the tracking servo loop is off, the low frequency component is extracted from the tracking error signal by the extracting means so that the low frequency component is superimposed on the tracking error signal. The automatic balance adjustment can be realized with a very simple circuit configuration by calculating the offset level that has been set and directly correcting the output of the first or second detection means with the offset level.

Therefore, DC offset on the traverse signal due to mechanical errors, changes in electrical characteristics due to aging and temperature conditions, and environmental factors are absorbed, and the center value of the traverse signal is fixed at the center level. Therefore, it is possible to quickly and accurately perform tracking servo pull-in at the end of access and the like, and accordingly, the reproducing operation performance is improved. Since the automatic balance adjustment for improving the performance is realized by a small-scale circuit system, there is a great effect that the automatic balance adjustment function can be added even to a small-sized or low-cost disk drive device. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram of a tracking control circuit of a disk drive device according to an embodiment of the present invention.

FIG. 2 is a flowchart of a process at the time of access of a tracking control circuit of the disk drive device of the embodiment.

FIG. 3 is an explanatory diagram of tracking control by a three-beam method.

FIG. 4 is a block diagram of a tracking control circuit according to the prior art.

[Explanation of symbols]

1 tracking error amplifier circuit, 2A, 2B detector, 3A buffer circuit, 3B variable gain amplifier circuit,
3C subtraction circuit, 12 A / D converter, 13 servo data formation circuit, 14 PWM decoding circuit, 15 tracking coil drive circuit, 16 2-axis mechanism, 20 system control circuit, 21 jump control circuit, 22 switch, 23 low-pass filter, 24 buffer amplifier

Claims (1)

[Claims] 1. A first method for irradiating a recording track of a disk-shaped recording medium with light from an objective lens and detecting reflected light information according to a state of deviation of a relative position between the objective lens and the recording track. And a second detection unit, a generation unit that generates a tracking error signal based on a difference between an output of the first detection unit and an output of the second detection unit, and a tracking error generated by the generation unit. Extracting means for extracting a low-frequency component of the signal; correcting means for correcting one of the output of the first detecting means and the output of the second detecting means based on the output of the extracting means; When the tracking servo loop is open, the correction operation by the correction means is executed, and when the tracking servo loop is closed, the correction operation by the correction means is executed. Disk drive apparatus characterized by comprising a controller that controls so as not.