JP2605724B2 - Optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track following control method for an optical disk device having a plurality of heads mounted on the same slider.

(Prior Art) Conventionally, in a track following control method of an optical disk device, a slider movable in a radial direction of an optical disk is
Equipped with a head equipped with a tracking actuator that can scan the light beam in the radial direction on the disk surface by driving a galvanomirror, etc., controlling the slider position and the head tracking actuator at the same time to request the light beam Two-stage servo tracking control for following a track is performed.

For example, taking slider control by a sense signal for detecting a beam tilt as an example, the slider position is controlled based on a sense signal serving as a beam tilt detection signal after completion of access to a desired track (fixed position control), while a tracking error signal is controlled. Based on the signal (detecting how much the light beam deviates from the desired track), the change in track position that cannot be followed by the slider control is used to drive the galvanomirror by the tracking actuator provided on the head to precisely shift the light beam to the desired track. I am following.

In addition, in the slider position control based on the tracking error signal, in addition to the slider fixed position control based on the sense signal, the slider position control is performed for temporally gradual track position changes caused by eccentricity of the optical disk. The track is made to follow the light beam, and on the other hand, when the track position is short in time, the track beam is driven precisely by the drive of the galvanometer mirror by the track actuator provided on the head, which cannot be tracked by the slider control. To follow.

Furthermore, in recent years, in order to improve the writing / reading speed of information, an optical disk apparatus in which two heads are mounted on the same slider and the light beam of each head follows two tracks at the same time. It has been known.

In an optical disk drive having two heads mounted on a slider as described above, for example, as shown in FIG. 3, the light beam 2a from the head 1a is made to follow the track T1 of the optical disk 3, and at the same time, from the head 1b. The light beam 2b is made to follow a different track T2 of the optical disk 3. In the track following control in this case, first, for the slider 4, for example, the head 1a is detected by using a sense signal for detecting the position of the head 1a.
The slider 5 is controlled so that the light beam 2a is positioned immediately below the track T1. At the same time, the galvanomirrors 6a, 6b of the track actuators 4a, 4b incorporated in the respective heads 1a, 1b are driven based on the tracking error signals for the tracks T1, T2 of the light beams 2a, 2b to change the directions of the light beams 2a, 2b. However, track following control (fine control) for controlling the light beams 2a and 2b to precisely follow the tracks T1 and T2 of the optical disk 3 is performed (problems to be solved by the invention). In the track following control method, when the fine control is performed by the track actuator of the head, the slider is controlled to the position based on the sense signal indicating one of the beam inclinations, so that the heads 1a, 1b In the case where the track position to be accessed by the above is greatly shifted, the position of the slider 5 is controlled by, for example, a sense signal of the head 1a. Therefore, although the movement of the galvanometer mirror 6a of the tracking king actuator 4a that causes the light beam 2a of the head 1a to follow the track T1 is small, the tracking actuator 4b of the other head 1b that does not use the sense signal for controlling the position of the slider 5 is used. Must swing the galvanomirror 6b greatly.

Therefore, the light beam from the galvanomirror 6b is converged at a peripheral position off the center of the optical axis of the objective lens 7b to form a beam spot on the optical disk 3, and astigmatism due to the convergence of the light beam 2b increases. In addition, since the movement of the tracking actuator 4b increases, the mechanical loss increases, and the control accuracy decreases. Therefore, there is a problem that high-accuracy tracking control cannot be performed on the head 1b side.

(Means for Solving the Problems) The present invention has been made in view of such conventional problems, and has a high-accuracy track following for all heads even if a plurality of heads are mounted on the same slider. It is an object of the present invention to provide a track following control method for an optical disk device that enables control.

In order to achieve this object, the present invention provides an optical disc apparatus having a plurality of heads provided with a tracking actuator for moving a beam spot irradiated on a disc surface within a predetermined range on a slider movable in a disc radial direction. And detecting means for detecting a head position or a tracking error of the plurality of heads; and a movement amount of a beam spot by a tracking actuator provided on the plurality of heads based on a detection signal of the detecting means. And a slider control means for controlling the position of the slider at a position.

(Operation) In the track following control system of the present invention having such a configuration, for example, in a case where two heads are mounted on a slider, when the track following control is performed, the sliders use the beam of both heads. Based on the tilt detection signal or the tracking error detection signal, control is performed so that the movement of the tracking actuator of each head is substantially the same, in other words, the movement amount of the beam spot by each head is substantially the same.

That is, in the slider position control based on the sense signal for detecting the beam inclination, the slider is controlled to a position where the average value (S1 + S2) / 2 of the sense signals S1 and S2 of both heads is obtained.
As a result, the deflection angle of the galvanomirror by the tracking actuator that directs the light beam from each head to a different track position becomes the same if the change due to the tracking error signal is ignored, and the light beam may deviate significantly from the optical axis center of the objective lens. In addition, since the movement of the tracking actuator can be reduced by half compared to the related art, high-accuracy track following control can be performed for all heads.

(Embodiment) FIG. 1 is an explanatory view showing an embodiment of the present invention.

In FIG. 1, reference numeral 3 denotes an optical disk, which is an optical disk on which information is recorded by physical uneven pits or a magneto-optical disk on which information bits are recorded by a perpendicular magnetization direction. The recording track is formed in a spiral shape.

Reference numeral 5 denotes a slider, which is installed so as to be movable in the radial direction of the optical disk 3 by a voice coil type linear motor (not shown) or the like. On this slider 5, two heads 1a and 1b are mounted in this embodiment.

The heads 1a and 1b have built-in tracking actuators 4a and 4b. Galvano mirrors 6a and 6b for moving a beam spot in the radial direction of the optical disc 3 are incorporated in the tracking actuators 4a and 4b, and the galvanometer mirrors 6a and 6b The light beams 2a, 2b rotated by the drive circuits 8a, 8b and converged by the objective lenses 7a, 7b in a direction determined by the rotation position
Is irradiated.

Further, each of the heads 4a and 4b is provided with position sensors 11a and 11b for detecting a galvanomirror rotation angle based on a predetermined position in the movement range of the slider 5, and beams 2a and 2b from the position sensors 11a and 11b. Signal indicating the slope of
S1 and S2 are output.

The sense signals S1 and S2 from the position sensors 11a and 11b provided on the heads 1a and 1b are added by an adder 9, and an added signal (S1 + S2) is obtained.
Is input to the slider drive circuit 10. The slider drive circuit 10 controls the position of the slider 5 to a position where the average value (S1 + S2) / 2 of the addition signals obtained from the adder 9 is used in the track following control after the heads 1a and 1b have completed the access to the desired track.

Next, the track following control according to the embodiment of FIG. 1 will be described with reference to the flowchart of FIG.

In FIG. 2, first, in step S1, the access tracks T1 and T2 of the heads 1a and 1b are commanded. The command for the access tracks T1 and T2 is specified, for example, as the number of tracks from the reference position on the optical disc 3.

When the command for the access tracks T1 and T2 is received in step S1, the slider drive circuit 10 moves the slider to the intermediate track (T1 + T2) / 2 between the access tracks T1 and T2 as shown in step S2, and in step S3 the intermediate track position , The access control is terminated, and the head fine control in step S4, that is, the track following control based on the track error signal in the heads 1a and 1b is performed.

The track following control of the heads 1a and 1b based on the track error signal in step S4 irradiates the tracks T1 and T2 accessed by the slider 5 with the light beams 2a and 2b,
The track error is calculated from the track position information obtained by receiving the reflected light or the diffracted light, and the galvanometer mirrors 6a, 8b are operated by the carbano drive circuits 8a, 8b so as to eliminate the track error.
Drive 6b to precisely drive light beams 2a and 2b to access track T
Try to follow 1, T2.

In the head fine control in step S4,
As shown in the next step S5, the sense signals S1 and S2 from the position sensors 11a and 11b provided on the heads 1a and 1b are detected, and in step S4, the average value (S1 + S2) / 2 of the sense signals S1 and S2 is obtained. The position of the slider 5 is controlled by the slider drive circuit 10 so as to obtain this average value, and the head 5a is controlled by the sense signals S1 and S2 simultaneously with the head fine control in step S4 until the tracking end is determined in step S7.
Slider control to maintain the intermediate position between 1 and 1b is performed simultaneously.

In the position control of the slider 5 during the tracking control based on the sense signals S1 and S2, if the movement of the galvanometer mirrors 6a and 6b due to the tracking error signal is ignored, the galvanometer mirror 6a of the head 1a and the galvanometer mirror 6b of the head 1b are ignored. The position of the slider 5 is controlled to a position where the movement of the slider 5 becomes the same.

Therefore, even if the access tracks T1 and T2 are largely separated from each other, compared with the conventional case where the position of the slider 5 is controlled based on, for example, the sense signal of the access rack T1 of the head 1a, the galvanomirror 6b of the other head 1b is Movement is halved. Of course, the galvanometer mirror 6a of the head 4a compared to the conventional
Movement is large, but the movement is halved compared to the conventional case, the deflection of the galvanometer mirrors 6a, 6b of both heads 1a, 1b does not become extremely large, and the light beams 2a, 2b are changed to the objective lenses 7a, 7b. Does not deviate significantly from the center of the optical axis. Therefore, the occurrence of astigmatism due to beam convergence is suppressed,
Further, since the movements of the galvanometer mirrors 6a and 6b are small, errors due to mechanical loss are small, and highly accurate track following control can be realized based on the tracking error signal.

Further, as another embodiment of the present invention, the slider 5 may be driven based on a tracking error signal of each of the heads 1a and 1b obtained during the tracking control. In this case, as in the case of the sense signals, the sliders 5 are position-controlled so that the average value (E1 + E2) / 2 of the tracking error signals E1 and E2 of the heads 1a and 1b is provided on the tracking actuators 4a and 4b. The movements of the galvanomirrors 6a and 6b can be made substantially the same. In the position control of the slider 5 by the tracking error signal, since the movement of the slider 5 cannot follow the tracking error signal based on the change of the track position which is short in time, the average value is obtained after integrating the tracking error signal. And a slider 5 based on a tracking error signal that is gradual in time.
It is desirable to control the position.

Further, in the above embodiment, the case where two heads 1a and 1b are mounted on the slider 5 is taken as an example. However, the present invention is not limited to this, and three heads, 4 A plurality of units may be mounted such as a unit. When three or more heads are mounted on the slider 5 as described above,
The position of the slider 5 is controlled based on the average value of the sense signals or the tracking error signals of all the heads, whereby the movements of the tracking actuators provided on the plurality of heads can be made substantially the same.

Further, in the flowchart of FIG. 2, in the track access from steps S1 to S3, the access track T
The slider 5 is accessed to the intermediate position between 1 and T2 to shift to the track following control. However, as in the conventional example shown in FIG. 3, the head position obtained by the specific head track access is used. The slider 5 may be moved based on the indicated sense signal, and after the access is completed, the control may be shifted to the track following control shown in steps S4 to S7. In this case, the slider 5 moves to a position determined by the sense signal S1 from the position sensor 11a corresponding to the access track T1 of the head 1a shown in FIG.
The light beam 2b of 1b causes the galvanomirror 6b to swing greatly to access the track T2, but when the process shifts to track following control after the access is completed, the position sensor 11b
By shifting to the position control of the slider 5 based on the average value of the sense signals S1 and S2 from a and 11b, the slider 5 returns to the position where the movements of the galvanometer mirrors 6a and 6b are the same.

(Effects of the Invention) As described above, according to the present invention, in an optical disk device having a plurality of heads mounted on the same slider, when performing different track following control with each head, the position of each head or The position of the slider 5 is controlled to a position where the movement amount of the beam spot by each head is substantially the same based on the detection signal of the track error, so that the movement of the track actuator in each head is minimized, and the track following accuracy is improved. It can be greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of the present invention, FIG. 2 is a flowchart showing track following control of the present invention, and FIG.
The figure is an explanatory view showing a conventional example. 1a, 1b: Head 2a, 2b: Light beam 3: Optical disk 4a, 4b: Tracking actuator 5: Slider 6a, 6b: Galvano mirror 7a, 7b: Objective lens 8a, 8b: Galvano drive circuit 9: Adder 10: Slider drive Circuit 11a, 11b: Position sensor

Claims (2)

(57) [Claims] 1. An optical disk apparatus comprising: a plurality of heads provided with a track actuator for moving a beam spot for irradiating a disk surface within a predetermined range on a slider movable in a disk radial direction, the head being displaced in the disk radial direction. Detecting means for detecting a beam inclination or a tracking error of the plurality of heads; and a position at which the movement amount of a beam spot by a track actuator provided on the plurality of heads is substantially the same based on a detection signal of the detecting means. And a slider control means for controlling the slider. 2. A slider movably in a radial direction of a disk, an irradiating means provided on the slider, for irradiating the disk surface with a plurality of light beams, and irradiating a predetermined position of the light beam on the disk surface. A track actuator that moves within a range, a detecting unit that detects a tilt or a tracking error of the plurality of light beams, and a moving amount of the irradiation position of each of the light beams by the track actuator based on an output of the detecting unit. An optical disk device, comprising: slider control means for controlling the slider at substantially the same position.