JP2791825B2 - Optical beam tracking control method for optical disk device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a light beam tracking control method for an optical disc device having two focusing actuators in one position.

[Prior Art] FIG. 3 shows a schematic configuration of a conventional magneto-optical disk device. In FIG. 1, reference numeral 1 denotes a disk medium on which tracks for recording information are spirally formed in a radial direction, and reference numeral 2 denotes a spindle which rotates the disk medium once. Reference numeral 3 denotes an optical unit, which includes a semiconductor laser 4 as a light source having one light-emitting point, optical components 5 such as a coupling lens, a split-type photodetector 6 for detecting information, focus, and track signals. You. Numeral 7 denotes a focusing actuator which drives an objective lens 8 for condensing a light beam from the optical unit 3 on the surface of the disk medium 1 in a direction in which the disk medium 1 fluctuates. Reference numeral 9 denotes a tracking actuator which drives a light beam in the radial direction of the disk medium 1 by rotating a mirror. Reference numeral 10 denotes a positioner, which controls the optical unit 3, the focusing actuator 7, the tracking actuator 9 and the like on the disk medium 1.
To move in the radial direction. Numeral 11 denotes a position detecting device comprising a detecting unit for detecting a rotational displacement of the mirror with respect to the positioner 10 and an amplifying unit, 12 a base of the device, and 13 an electromagnetic device for changing a magnetic field near the surface of the disk medium 1.

Next, a description will be given of a light beam follow-up control method for causing the light beam of the optical disk device to follow the surface deflection of the disk medium 1 and the eccentricity of the track.

A focus signal generated from the disc medium reflected light by the photodetector 6 is processed by a control circuit (not shown) and supplied to the focusing actuator 7 as a drive signal, and the objective lens 8 is driven to follow the surface deflection of the disc medium 1.
The spot side of the light beam on the surface of the disk medium 1 is kept almost constant.

Similarly, a track signal generated from the disk medium reflected light by the photodetector 6 is processed by a control circuit (not shown) and supplied to the tracking actuator 9 as a drive signal, and the mirror is rotationally driven to follow the eccentricity of the track.
Continue to hold the light beam approximately at the center of the track.

At this time, if the track following is performed by rotating only the mirror from the mechanical equilibrium position and displacing the light beam with respect to the positioner 10, the reflected light of the disk medium becomes large on the photodetector 6 as shown by the broken line in the figure. Moving.

This reflected light movement is manifested as a track error signal in a method of generating a track signal by detecting a change in the diffraction pattern of the light beam generated when the light beam crosses the track by the split-type photodetector 6.

Therefore, by causing the positioner 10 to follow the movement of the tracking actuator 9, the displacement of the mirror from the mechanical equilibrium position is reduced, and the movement of the reflected light on the photodetector 6, that is, the control for suppressing the error detection of the track signal, is controlled. Is performed.

This control is performed by processing a signal of the position detecting device 11 by a control circuit (not shown), supplying the signal to the positioner 10 as a drive signal, and driving the positioner 10. This control is performed by the positioner 10
There is also an advantage that the total track following performance is improved by following the movement of the tracking actuator 9.

By the way, in the optical disk device shown in FIG. 3, when rewriting information, it is necessary to temporarily erase a signal before being recorded.

This erasing is an operation to make the magnetization direction of the disk medium 1 uniform, and irradiates a strong optical power to the surface of the disk medium 1 while applying a magnetic field in one direction by the electromagnet 13 to raise the medium temperature to the Curie point or higher. It is done by things.

On the other hand, recording is an operation in which the magnetization direction of the disk medium 1 is partially reversed in the direction opposite to the erasure, the magnetic field of the electromagnet 13 is reversed from that in the erasure, and strong optical power is applied to the surface of the disk medium 1 in a pulsed manner. To increase the medium temperature partially above the Curie temperature.

Further, whether or not the signal has been correctly recorded is confirmed by irradiating the medium surface with a weak optical power and reproducing the signal from the disk medium reflected light.

As a result, the disk medium 1 for rewriting information
At least three turns are required, and the information transfer rate is greatly reduced. This is a single light beam that erases,
This is because each function of recording and reproduction is realized. Therefore, by allowing the three light beams to share the respective functions, the signal can be rewritten within the time of one rotation of the disk medium, and the information transfer speed can be reduced. Preventing the decline is easily speculated.

However, when a total of three sets of actuators and positioners shown in FIG. 3 are arranged along the circumferential direction of the disk medium for each beam, there is a problem that the device becomes large.

[Problems to be Solved by the Invention] In order to reduce the size of the apparatus, two focusing actuators are arranged on one positioner, and an erasing beam is moved by an objective lens driven by one focusing actuator, and the other focusing actuator is moved by another focusing actuator. The configuration of an optical disk device that focuses a recording beam and a reproduction beam on the surface of a disk medium by an objective lens driven by the optical disk is conceivable.

However, in this configuration, although there are three light beams to be controlled, since there is only one positioner, the conventional light beam tracking control method cannot be applied as it is, and the track signal detection error can be reduced. It is necessary to improve suppression and track following performance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disc apparatus for arranging two focusing actuators on one positioner and condensing a plurality of light beams on a disk medium surface, so that the plurality of light beams follow a track with high accuracy. An object of the present invention is to provide a light beam tracking control method.

[Means for Solving the Problems] For this purpose, the present invention relates to a method in which a first objective lens and a second objective lens which are positioned substantially symmetrically with respect to a center line of a radial line of a disk medium passing through the center of a spindle are provided. Arranged on a positioner movable in the radial direction, the first objective lens focuses an erasing beam, the second objective lens focuses a recording beam and a reproducing beam on the surface of the disk medium, and An optical disc apparatus including a third tracking actuator for controlling a position of one of the recording beam and the reproduction beam condensed by the second objective lens with respect to one of the other light beams in a radial direction of the disc medium; For either the storage beam or the reproduction beam focused by the objective lens, a second tracking common to both beams is used. The positioner is driven using the output signal of the position detecting device of the actuator, and control for making the relative displacement of the light beam with respect to the positioner substantially zero is performed while the light beam follows the track. With respect to both of the erasing beams or one of the erasing beams condensed by the objective lens, the driving is substantially equal to the relative displacement generated when the erasing, recording, and reproducing beams follow the track. The control of applying the signal as a predicted amount to the third tracking actuator and / or the first tracking actuator for the erase beam is performed while the light beam follows the track.

[Example] Hereinafter, an example of the present invention will be described. FIG. 1 is a plan view of the optical disk device of the embodiment, and FIG. 2 is a diagram for explaining the operation of the optical disk device.

51 is a disk medium, and 52 is a spindle for rotating the disk medium 51. 53 is an optical unit,
A semiconductor laser that emits light beams for erasure, recording, and reproduction;
Optical components such as coupling lenses, information / focus /
It is composed of a split-type photodetector for detecting a track signal.

Reference numeral 54 denotes a first objective lens on which the erasing beam 40 from the optical unit 53 is applied to the surface of the disk medium 51, and reference numeral 55 denotes a first objective lens 54.
Is a first focusing actuator that drives the erase beam 40 in the radial direction of the disk medium 51 by rotation of a mirror, and 57 is a first tracking actuator 56 1 is a first position detection device including a detection unit for detecting a mirror rotational displacement and an amplification unit.

58 is a recording beam 41 and a reproduction beam from the optical unit 53
The second objective lens 42 focuses the light on the surface of the disk medium 51. The second objective lens is located at a position substantially symmetric with respect to the first objective lens 54 with respect to a center line of a straight line in the disk medium radial direction passing through the center of the spindle. 59 is a second focus sync actuator that drives the second objective lens 58 in the direction of the surface deflection of the disk medium 51,
Reference numeral 60 denotes a second tracking actuator that collectively drives the recording and reproducing light beams 41 and 42 in the radial direction of the disk medium 51 by rotating the mirror, and 61 detects a mirror rotation displacement of the second tracking actuator 60. It is a second position detection device including a unit and an amplification unit.

62 is a third tracking actuator for displacing the position of the recording beam 41 in the radial direction of the disk medium 1 with respect to the reproduction beam 42 by rotation of the mirror, 64 is a mirror for combining the recording beam 41 and the reproduction beam 42, and 65 is a disk medium 1 The positioner 66 that can move in the radial direction of the
, 67 is a driving device of the positioner 65, 68 is a base of the device, 69 is a magnet for generating an erasing magnetic field, and 70 is a magnet for generating a recording magnetic field.

80 is an optical disk control device for managing each operation, 81 is the first
A focus control device for driving the focusing actuator 55, and a second focusing actuator 82
A focus control device for driving 59; a track control device for driving the first tracking actuator 56;
Is a track control device for driving the second tracking actuator 60, and 85 is a third tracking actuator
Track control device for driving 62, 86 for positioner position control device, 87 for positioner speed control device, 88 for recording device,
89 is a relative displacement conversion device. The third tracking actuator 62 does not have a position detecting device mounted thereon, but may be provided.

Arrow A indicates the erase beam focus signal, B indicates the first focusing actuator drive signal, C indicates the read beam focus signal, D indicates the second focus actuator drive signal, E indicates the read beam track signal, and F indicates the read beam track signal.
Is a second tracking actuator drive signal, G is a second position detection signal, H is a positioner drive signal, 1 is an erase beam track signal, J is a first tracking actuator drive signal, K is a recording beam track signal, L
Is a third tracking actuator drive signal, M is a first position detection signal, N is a drive signal equivalent to generating a relative displacement of the erase beam, O is a drive signal equivalent to generate a relative displacement of the recording beam, The flow of is shown.

The light beam follow-up control method according to the present embodiment is substantially as follows.

When the disk medium 51 is loaded on the spindle 52 and reaches a certain number of rotations, a light beam is applied to the disk medium 51.
Position on the surface. This positioning is performed by the following operation.

The focus signal A of the erasing beam is input to the first focus control device 81, and the first focusing actuator 55 is driven to perform the focus tracking control of the erasing beam 40. Also, the focus signal C of the reproduction beam is input to the second focus control device 82, and the second focusing actuator 59 is driven to perform the focus follow-up control of the recording and reproduction beams 41 and 42. At this time, instead of the focus signal C of the reproduction beam 42, the recording beam 41
May be input.

Then, the track signal E of the reproduction beam is input to the second track control device 84 to drive the second tracking actuator 60 to perform the track following control of the reproduction beam 42 and to transmit the second position detection signal G to the positioner. An input to the position control device 86 causes the positioner 65 to follow the movement of the second tracking actuator 60.

Next, the relative displacement of the erase beam 40 and the recording beam 41 with respect to the positioner 65 at the time of positioning the same track is recorded.
The relative displacement is caused by track eccentricity, erasing, recording, and reproducing beams 40 to 42 for the spindle 52, a position adjustment error, and the like.

First, the reproducing beam 42 is moved to the inner periphery of the disk medium 51 by a known moving method used in the conventional optical disk device shown in FIG. After the reproduction beam 42 is made to follow a predetermined track, the erase beam 40 and the recording beam 41
Is operated to follow the predetermined track.

The track following control of the erase beam 40 is performed by inputting the track signal I of the erase beam 40 to the first track control device 83 and driving the first tracking actuator 56.

The track following control of the recording beam 41 is performed by inputting the track signal K of the storage beam 41 to the third track control device 85 and driving the third tracking actuator 62.

The relative displacement of the light beam with respect to the positioner 65 can be calculated from the position detection signal and the displacement calculation signal of the tracking actuator drive signal.

Here, the first position detection signal M as a displacement calculation signal of the erasing beam 40 is separated into a DC component and an AC component by a filter and recorded in the recording device 88. The AC component is recorded in synchronization with the rotation of the disk medium 51. As the displacement calculation signal of the recording beam 41, the third tracking actuator drive signal L is separated into a DC component and an AC component by a filter and recorded.

By the way, the relative displacement of the reproduction beam 42 is
Are minute because they follow the movement of the second tracking actuator 60 and do not need to be recorded. The relative displacement of the recording beam 41 is dominated by the DC component due to the position adjustment error, and the AC component due to the track eccentricity is
Since the beam interval between the recording beam 41 and the recording beam 41 is about 10 μm, it is very small. Therefore, the AC component does not necessarily need to be recorded. The above-described series of recording operations is performed at a plurality of locations from the inner circumference to the outer circumference of the disk medium 51, and the operation ends.

By the way, since the track eccentricity does not have a large difference between the inner circumference and the outer circumference, in the arrangement shown in FIG.
When the track eccentricity is described by Xsin (ωt−δ), the relative displacement of the erasing beam 40 caused by the track eccentricity is approximately −2 · X · sinδ · cosωt (1) As a result, the AC component of the displacement calculation signal of the erasing beam 40 records the value of one location on the disk medium 51, and the AC component at any other position can be calculated using the equation (1). The memory and the like of the recording device 88 can be saved, and the device becomes simple and inexpensive.

Next, a light beam follow-up control method using a displacement calculation signal indicating a relative displacement of the light beam recorded on the recording device 88 will be described.

When a command to move the light beam to a predetermined track is issued from the optical disc control device 80, the track following control of the light beam is released, and the positioner 65 is driven, for example, while calculating the number of tracks traversed by the reproduction beam. Move the light beam to a predetermined track. Since a specific moving method is out of the scope of the present invention, detailed description is omitted.

First, when the required number of tracks to be traversed by the reproduction beam 42 reaches the predetermined track is equal to the number of tracks already traversed, the track signal E of the reproduction beam 42 is input to the second track control device 84, and the second The tracking actuator 60 is driven to start the track following control of the reproduction beam 42, and the second position detection signal G is input to the positioner position controller 86 so that the positioner 65 follows the movement of the second tracking actuator 60. .

Next, the track signal I of the erase beam 40 is input to the first track control device 83, and the first tracking actuator 56 is driven to follow the erase beam 40. at the same time,
A drive signal N equivalent to the relative displacement of the light beam generated when the erase beam 40 is positioned on the predetermined track.
Is input from the relative displacement conversion device 89 to the first track control device 83 as a predicted amount, and feedforward control is performed.
Further, the track signal K of the recording beam 41 is input to the third track control device 85, and the third tracking actuator 62 is driven to make the recording beam follow the track. At the same time, a drive signal O equivalent to generating a relative displacement of the light beam generated when the recording beam 41 is positioned on the predetermined track is input from the relative displacement conversion device 89 to the third track control device 85 as a predicted amount. , Perform feedforward control.

At this time, if the track following the light beam is different from the predetermined track, the tracking actuator moves the light beam one track at a time in the radial direction of the disk medium to position the light beam on the predetermined track.

The relative displacement conversion device 89 is equivalent to generating a relative displacement of the light beam that occurs when the light beam is positioned on the predetermined track, based on the displacement calculation signal at the disk reference position stored in the storage device 88. Calculate and output an appropriate drive signal. An operation such as linear interpolation is performed for the DC component, and the amplitude is calculated for the AC component using the above equation (1).

The above is the light beam tracking control method of the present embodiment. By the way, the recording beam for generating a minute magnetization reversal region having a diameter of 1 μm or less on the medium surface and the reproducing beam for detecting the minute magnetization reversal region have a higher track than an erase beam for aligning the magnetization direction of the medium surface in one direction. Control accuracy is required.

In this regard, in the present embodiment, since the positioner 65 follows the movement of the tracking actuator 60 common to both the reproduction and recording beams, the movement of the reflected light of the disk medium on the photodetector of both beams can be suppressed, and the track The detection error can be reduced, and the total track following performance can be improved. As a result, it is possible to improve the track following accuracy of the reproducing and recording beams, which requires higher positioning accuracy than the erasing beam.

Further, since the storage beam inputs a drive signal O equivalent to generating a relative displacement of the light beam from the relative displacement conversion device 89 to the third track control device 85 as a predicted amount and performs feedforward control, Tracking control is further improved. Although the track detection error of the erase beam slightly increases due to the movement of the reflected light from the disk medium on the photodetector, a drive signal N equivalent to the relative displacement of the light beam is supplied from the relative displacement conversion device 89 to the first track control device. There is no problem in accuracy since the prediction amount is input to 83 and feedforward control is performed to improve the tracking performance.

[Effects of the Invention] As described above, according to the present invention, two focusing actuators are arranged on one positioner,
It is possible to improve the track following accuracy of each light beam of the optical disk device in which a plurality of light beams are focused on the disk medium surface. As a result, there is an advantage that a compact, high-performance optical disk device capable of rewriting signals at high speed can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view of an optical disk device according to an embodiment of the present invention,
FIG. 2 is a schematic configuration diagram viewed from II-II in FIG. 1, and FIG. 3 is a schematic configuration diagram of a conventional optical disk device. DESCRIPTION OF SYMBOLS 1 ... Optical disk medium, 2 ... Spindle, 3 ... Optical unit, 4 ... Semiconductor laser, 5 ... Optical components, 6 ...
... Photodetector, 7 Focusing actuator, 8
…… Objective lens, 9 …… Tracking actuator,
10 positioner, 11 position detecting device, 12 device base, 40 erase beam, 41 recording beam, 42 reproducing beam, 51 disk medium, 52 spindle, 53 ... optical unit, 54 ... first objective lens, 55 ... first focusing actuator, 56 ... first tracking actuator, 57 ... first position detecting device, 58 ... second
, The second focusing actuator, 60 ... the second tracking actuator, 61 ...
... second position detecting device, 62 ... third tracking actuator, 64 ... mirror, 65 ... positioner, 66 ...
Positioner guide, 67 …… Positioner drive, 68 ……
Base of device, 69: magnet for generating erasing magnetic field, 70: magnet for generating magnetic field, 80: optical disk control device, 81: focus control device, 82: focus control device, 83: track drive device, 84 ... Track drive device, 85 ... Track drive device, 86 ... Positioner position control device, 87 ... Positioner speed control device, 88 ... Storage device, 89 ... Relative displacement conversion device, A ... Erase beam focus signal , B... A first focusing actuator drive signal, C... A reproduction beam focus signal, D... A second focusing actuator drive signal, E.
F: second tracking actuator drive signal, G
... A second position detection signal, H... A positioner drive signal,
I: Track signal of erase beam, J: First tracking actuator drive signal, K: Track signal of recording beam, L: Third tracking actuator drive signal, M: First position detection signal, N: a drive signal equivalent to generating a relative displacement of the erasing beam, O: a drive signal equivalent to generating a relative displacement of the recording beam.

Claims (1)

(57) [Claims] 1. A first objective lens and a second objective lens which are positioned substantially symmetrically with respect to a center line about a straight line in a disk medium radial direction passing through the center of a spindle are disposed on a positioner movable in the disk medium radial direction. An erasing beam is focused by the first objective lens, a recording beam and a reproduction beam are focused on the surface of the disk medium by the second objective lens, and a recording beam focused by the second objective lens. In an optical disc apparatus provided with a third tracking actuator for controlling the position of one of the reproduction beams relative to one of the light beams in the radial direction of the disc medium, the recording beam and the reproduction beam condensed by the second objective lens The output signal of the position detection device of the second tracking actuator common to both beams. The positioner is driven using the signal, and control for making the relative displacement of the light beam with respect to the positioner substantially zero is performed while the light beam follows the track, and the other light beam is focused by the first objective lens. For both or one of the erasing beams, a drive signal that is substantially equal to the relative displacement generated when the erasing, recording, and reproducing beams follow the track is used as the predicted amount. 3. A light beam tracking control method for an optical disk device, wherein the control for applying to the tracking actuator and / or the first tracking actuator for the erase beam is performed while the light beam follows the track.