JP2001176089A - Disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the rocking of an objective lens without separately providing a sensor, etc., for detecting the rocking of the objective lens. SOLUTION: The disk device 1 includes a DSP core 38a and the DSP core 38a sets a count value corresponding to the total number of tracks to be jumped in a counter 38b when an instruction for seeking such as the jumping of a piece of music, etc., is given during the time of reproducing an MO disk 44. During jumping, the DSP core 38a generates a tracking actuator control signal based on the DC component of a push-pull signal which is obtained from a sum signal detecting circuit 30 and corrects the rocking of the objective lens 14 in a radial direction. Accordingly, the number of the jumped tracks can be correctly counted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk drive,
In particular, the present invention relates to a disk device that detects a tracking error signal by, for example, a differential push-pull method and causes an objective lens provided in an optical pickup to follow a track.

[0002]

2. Description of the Related Art A conventional disk drive of this type is provided with a sensor for detecting a swing of an objective lens in a radial direction. Therefore, the swing of the objective lens is detected by the sensor during the jump, and the actuator coil is controlled based on the detection result. For this reason, the swing of the objective lens is eliminated, and the jumped tracks are accurately counted.

[0003]

However, in this prior art, since a sensor for detecting the swing of the objective lens is separately provided, it is necessary to provide a large space, and the apparatus body becomes large. Moreover, the cost was increasing.

[0004] Therefore, a main object of the present invention is to provide a disk device capable of eliminating the swing of the objective lens with a simple configuration.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a disk drive for detecting a tracking error signal by a differential push-pull method and for causing an objective lens provided in an optical pickup to follow a track, and for calculating a push-pull signal. The present invention is a disk apparatus comprising: a unit; a detection unit configured to detect a DC component of a push-pull signal; and a correction unit configured to correct a radial swing of an objective lens based on the DC component during a track jump.

[0006]

In this disk device, three spots of laser light are emitted from the optical pickup to the disk surface. Light reflected by the disk surface is detected by a photodetector provided in the optical pickup, and a tracking error signal is detected by a differential push-pull method. By controlling the tracking actuator based on this tracking error signal, the objective lens follows the track. For example, the calculating means calculates a push-pull signal, and a DC component included in the push-pull signal is detected. When a seek instruction such as skipping is given and the track jumps to the target position, it is possible to correct the radial fluctuation of the objective lens by controlling the tracking actuator with the detected DC component. it can.

More specifically, the detecting means adds a first push-pull signal detected from a main beam and a second push-pull signal detected from a sub-beam used in the differential push-pull system to thereby reduce a DC component. To detect.

[0008]

According to the present invention, the swing of the objective lens in the radial direction can be corrected only by controlling the tracking actuator with the DC component included in the push-pull signal. That is, shaking can be eliminated with a simple configuration. For this reason, the number of jumped tracks can be accurately counted, so that it is possible to accurately jump to the track including the target position. Therefore, a stable seek can be performed.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0010]

Referring to FIG. 1, a disk device 10 of this embodiment includes an optical pickup 12. Optical pickup 1
2 includes an optical lens (objective lens) 14, which is supported by a tracking actuator 16 and a focus actuator 18. Therefore, the laser light output from the laser diode 20 is
The light is converged by the objective lens 14 and the ASMO (Advanced Strag
The light is irradiated onto the reproducing surface of a magneto-optical disk (MO disk) 44 such as an eMagneto Optical) disk. Thus, a desired signal is read from the MO disk 44.

The MO disk 44 is a land / groove recordable disk. The optical pickup 12 is connected to the sled motor 42 by, for example, a rack and pinion method, and thus is moved in the outer circumferential direction and the inner circumferential direction (radial direction) of the MO disk 44.

Laser light (reflected light) reflected on the disk surface
Is irradiated on the photodetector 22 through the same objective lens 14. The output of the photodetector 22 is the TE signal detection circuit 2
4. The signals are input to the FE signal detection circuit 26 and the sum signal detection circuit 30, and the TE signal (tracking error signal), the FE signal (focus error signal), and the sum signal are detected respectively. The detected TE signal and FE signal are
The signals are supplied to A / D converters 36a and 36b provided in a DSP (Digital Signal Processor) 34, respectively. The detected sum signal has its high-frequency component removed by the LPF 32 and is supplied to the A / D converter 36 d provided in the DSP 34. The DSP 34 validates the output of the A / D converter 36d only when the optical pickup 12 is jumping a track (not shown) during a seek.

More specifically, the photodetector 22 is shown in FIG.
It is shown as (A). The light detector 22 has four regions A to D provided at the center and regions F and H and regions G and E provided above and below the four regions A to D. Each of the regions A to H is a light detection element 22a to 22h. It is formed. The laser light emitted from the laser diode 20 is diffracted by a diffraction grating (not shown), and three spot lights are applied to the reproduction surface of the MO disk 42 through the objective lens 14. That is, FIG.
As shown in (B), with respect to the rotation direction (tangential direction) of the MO disk 42, the spot light corresponding to the regions A to D is centered, and the spot light corresponding to the regions F and H The spot light corresponding to the regions G and E is irradiated. The spot light corresponding to the regions A to D is the main beam, and the spot light corresponding to the regions F and H and the regions G and E is the sub beam. Note that the reproduction signal is extracted by the main beam.
Also, in FIG. 2B, the gray part is the land (L).
And the white portion is the groove (G).

The reflected light reflected on the reproducing surface of the MO disk 44 is applied to the corresponding light detecting elements 22a to 22a.
22h. The outputs of the photodetectors 22a to 22h are output from the TE signal detection circuit 24 and the sum signal detection circuit 30.
And the outputs of the photodetectors 22a to 22d are FE
The signal is input to the signal detection circuit 26, and each circuit performs a different operation. That is, the TE signal detection circuit 24 detects the TE signal (difference signal) as shown in Expression 1 by the differential push-pull method. Further, the FE signal detection circuit 26 detects an FE signal as shown in Expression 2. further,
The sum signal detection circuit 30 detects the sum signal (DC component of the PP signal) as shown in Expression 3 by adding the push-pull (PP) signal of the main beam and the PP signal of the sub beam. Note that in Expressions 1 to 3, the outputs of the photodetectors 22a to 22h are indicated by the same characters as those in the regions A to H.

[0015]

## EQU1 ## TE = {(A + D)-(B + C)}-α} (F
+ G)-(E + H) where α ≒ 2.

[0016]

FE = (A + C)-(B + C)

[0017]

## EQU3 ## Sum signal = {(A + D)-(B + C)} + α
{(F + G)-(E + H)} where α ≒ 2.

The TE signal output from the TE signal detection circuit 24 is input to a tracking zero cross (TZC) signal generation circuit 28. TZC signal generation circuit 28
Generates a TZC signal that switches between high level (H) and low level (L) at the zero crossing of the input TE signal. The generated TZC signal is supplied to the A / D converter 36c.
Given to. Note that the DSP 34 validates the output of the A / D converter 36c only when performing a seek.

Further, the MO disk 44 is fixedly mounted on a turntable 46, and the spindle motor 4
8 rotates with the turntable 46. The spindle motor 48 generates an FG pulse related to the rotation speed, and this FG pulse is used by the A / D converter 36 of the DSP 34.
e. The MO disk 44 is a disk of a constant linear velocity (CLV) system, and the spindle motor 4
The number of rotations of 8 decreases as the optical pickup 12 moves in the outer peripheral direction.

Thus, the A / D converters 36a to 36a
e, the TE signal, the FE signal, the TZC signal, the sum signal, and the FG signal are converted into digital signals.
The data is input to the DSP core 38a. The DSP core 38a
Execute tracking servo processing based on the TE signal,
Further, it performs focus servo processing based on the FE signal, and further executes spindle servo processing based on the FG signal.

A tracking actuator control signal and a sled control signal are generated by the tracking servo processing, and the corresponding PWM signal is generated by the PWM driver 40a.
And 40c are output to the tracking actuator 16 and the sled motor 42. Further, a focus actuator control signal is generated by the focus servo process, and the corresponding PWM signal is output to the PWM driver 40.
b to the focus actuator 18. Further, a spindle servo motor control signal is generated by the spindle servo processing, and the corresponding PWM signal is
The signal is output from the M driver 40d to the spindle motor 48.

As described above, the TE signal detection circuit 24, DS
A tracking servo system is formed by the P30, the tracking actuator 16 and the sled motor 42, and the tracking of the objective lens 14 is appropriately controlled based on the TE signal. That is, the objective lens 14 follows the track. Further, the FE signal detection circuit 26, the DSP
A focus servo system is formed by the focus actuator 30 and the focus actuator 18, and the focus of the objective lens 14 is appropriately controlled based on the FE signal. Further, a spindle servo system is formed by the spindle motor 48 and the DSP 30, and the rotation of the spindle motor 48, that is, the rotation of the MO disk 44 is appropriately controlled based on the FG signal. As a result, the laser beam output from the laser diode 20 is irradiated on a desired track with a desired light amount,
Therefore, a desired signal is read from the disk surface.

For example, while a desired signal recorded on a land is being reproduced, when a seek instruction such as skipping music is given from a host computer (not shown), that is, the land between the current position and the destination position is given. Is given, the thread servo and the tracking servo are turned off in accordance with the instruction of the DSP core 38a. Then, TZ
The count value (2N-) is supplied to the down counter 38b for counting the rising edge and the falling edge of the C signal.
Set 1). When the setting of the count value is completed, DS
P38a supplies a kick pulse (PWM signal) to the sled motor 42 to actually move the optical pickup 12. If a seek is instructed while the groove is playing,
The number of grooves between the current position and the destination position is given to the DSP core 38a.

While the optical pickup 12 jumps the track, the DSP core 38a sets the down counter 38b at the rising edge and the falling edge of the TZC signal.
Is decremented, and when the count value becomes 0, a brake pulse (PWM signal) is given to the sled motor 42. The DSP 38a further turns on the tracking servo and the thread servo. As a result, reproduction of a desired signal is started from the target position.

Assuming that the objective lens 14 does not swing during the jump, a regular TE signal is detected as shown in FIG. Accordingly, a TZC signal as shown in FIG. 3 (B) is generated, and the DSP core 38a counts the number of tracks jumped based on the TZC signal. At this time, the static offset of the optical pickup 12, that is, the direct current (DC) component of the PP signal is as shown in FIG.
It is a constant voltage as shown in FIG. in this way,
In an ideal situation in which the objective lens 14 does not oscillate, the offset can be removed by controlling the tracking actuator 16 with the DC component once detected.

However, in practice, the objective lens 14 fluctuates due to acceleration / deceleration of the optical pickup 12 and the like.
The period of the signal fluctuates irregularly as shown in FIG.
The DC level also varies between positive polarity and negative polarity as shown in FIG. When the period of the TE signal becomes dense, the objective lens 14 swings in the same direction as the moving direction of the optical pickup 12, and when the period of the TE signal becomes coarse, the objective lens 14 moves in the direction opposite to the moving direction of the optical pickup 12. Swing. When the objective lens 14 swings in the opposite direction and crosses from the outer circumferential direction to the inner circumferential direction, the DSP core 38a counts the same track three times in total. When such an erroneous count of the number of tracks occurs, it is not possible to jump to a desired track, and it takes time to seek. In this embodiment, in order to avoid such inconvenience, a sum signal is taken in at the time of a track jump, and based on this, a swing of the objective lens 14 is prevented.

Specifically, the DSP core 38a processes the flowchart shown in FIG. 4 in response to a seek instruction. Note that the DSP core 38a actually has logic for executing the following processing, and for convenience of explanation,
This will be described with reference to a flowchart.

First, the DSP core 38a turns off the thread servo and the tracking servo in steps S1 and S3, respectively. In step S5, the number data N of the land (or groove) to be jumped is fetched from the host computer, and the count value (2N-1) is set in the down counter 38b. In the following step S7, in order to move the optical pickup 12, The thread control signal is transmitted to the thread motor 42 via the PWM driver 40c.
Output to

The number (N) of lands or grooves to be jumped is calculated by the host computer based on the address of the current position and the address of the destination position.

The DSP 38b then sets T in step S9.
The capture of the ZC signal is started. Down counter 38b
Is decremented at the rising edge and the falling edge of the fetched TZC signal.

In a succeeding step S11, it is determined whether or not the count value of the down counter 38b has become "0". Here, if the count value indicates a value equal to or more than "1", the process proceeds to step S19, and the DC component included in the PP signal is captured. That is, L input to the A / D converter 36d
The output (DC component) of the sum signal detection circuit 30 via the PF 32 is captured. Subsequently, in step S21, a DC component increase / decrease P × gain G is calculated.

Here, the DC component increase / decrease P is the direction and magnitude of the swing of the objective lens 14. However, since the objective lens 14 has an inherent static offset, D
The C component increase / decrease P is represented by the difference between the offset and the DC component. The reference value shown in FIG. 3E coincides with the static offset (DC component) in FIG. 3C, and the difference between the sum signal in the positive direction and the difference in the negative direction with respect to this reference value is D.
It becomes the C component difference amount P. When the optical pickup 12 is moving from the inner circumferential direction to the outer circumferential direction, when a positive difference amount is obtained, the objective lens 1 is moved by a distance corresponding to the difference amount.
4 oscillates (shifts) in the outer peripheral direction. On the other hand, when a negative difference amount is obtained, the objective lens 14 swings (shifts) in the inner circumferential direction by a distance corresponding to the difference amount. When the optical pickup 12 is moving from the outer circumferential direction to the inner circumferential direction, the swing direction of the objective lens 14 is reversed. The gain G is determined according to the sensitivity of the tracking actuator 16 and is a value obtained by an experiment or the like.

Then, in step S23, step S
The value (P × G) calculated in 21 is given as a tracking actuator control signal (track output) to the tracking actuator 16 via the PWM driver 40a, and the process returns to step S9. In this way, the swing of the objective lens 14 is corrected during the jump.

On the other hand, if "YES" is determined in the step S11, that is, if it is determined that the jump is completed, a thread control signal (PWM signal) for braking is determined in a step S13.
Is output. When the optical pickup 12 starts braking, the tracking servo is turned on in step S15, and the thread servo is turned on in step S17.
The seek process ends.

According to this embodiment, the DC component included in the PP signal is detected by adding the PP signal of the main beam and the PP signal of the sub beam used in the differential push-pull method, and this DC component is detected. Can be used to correct the fluctuation of the objective lens in the radial direction. That is, shaking can be eliminated with a simple configuration. For this reason, since the number of tracks is not erroneously counted, it is possible to accurately jump to the track where the target position exists. Therefore, the time required for the seek can be reduced.

Further, since a track can be reliably turned on to a desired land or groove, a stable seek can be executed.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention;

FIG. 2A is an illustrative view showing a photodetector;
(B) is an illustrative view showing laser light (spot light) applied to a track;

FIG. 3A is an illustrative view showing a TE signal when the objective lens does not shake, and FIG. 3B is an illustrative view showing a TZC signal generated based on the TE signal shown in FIG. (C) is an illustrative view showing a DC component included in the PP signal when no shake occurs in the objective lens;
(D) is an illustrative view showing a TE signal when the objective lens has a vibration, and (E) is an illustrative view showing a DC component included in the PP signal when the objective lens has a vibration. .

FIG. 4 is a flowchart showing seek processing of the DSP core shown in the embodiment in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Disc device 12 ... Optical pickup 14 ... Objective lens 24 ... TE signal detection circuit 26 ... FE signal detection circuit 28 ... TZC signal generation circuit 30 ... Sum signal detection circuit 34 ... DSP 38a ... DSP core 42 ... Thread motor 44 ... MO Disk 46… Spindle motor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D117 AA02 CC06 EE04 EE19 FF14 FF21 GG06 5D118 AA21 AA23 BA01 BF12 BF13 CA05 CD03 CF03 CF05 CF06 CF16 CG04 CG09 CG14 CG33 CG36 CG44 DA26 DA33 DA35 DA42 DC03

Claims (2)

[Claims] 1. A disk device for detecting a tracking error signal by a differential push-pull method and for causing an objective lens provided on an optical pickup to follow a track, calculating means for calculating a push-pull signal; Detecting means for detecting the component,
And a correcting unit for correcting a swing of the objective lens in a radial direction based on the DC component at the time of a track jump. 2. The apparatus according to claim 1, wherein said detecting means includes main detecting means for detecting a first push-pull signal from a main beam, and sub-detecting means for detecting a second push-pull signal from a sub-beam. 2. The disk device according to claim 1, wherein the DC component is detected by adding a second push-pull signal.