JPH09147384A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the recording and reproducing of information to an optical disk while changing the direction of the incident light on an objective lens by mounting galvano-mirrors for reflecting a laser beam to prescribed directions. SOLUTION: Respective control signals of the focusing coil and the tracking coil constituting the fine moving mechanism of an objective lens, the linear motor 12 constituting the fine moving mechanism of the objective lens and the galvano-mirror 9 for positioning the spot of the laser beam are supplied by interposing a first filter 41, a second filter 42 and a third filter 43. The first filter 41 adopts a low-pass filter, the second filter 42 and the third filter 43 adopt band-pass filters. Frequency areas of signals to be grabbed are made to be the second filter 42, the third filter 43 and the first filter 41 in the order of heights of frequencies. Consequently, since this device can control respective parts of the device with extremely high accuracy, this device can cope with the increasing of the density of the disk of a future.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc having a galvanometer mirror for reflecting a laser beam in a predetermined direction and recording / reproducing information on / from the optical disc while changing the direction of light incident on an objective lens. Regarding the device.

[0002]

2. Description of the Related Art As is well known, a compact disk (C
As represented by D) and a laser disk (LD), an optical disk device that reproduces information using a laser beam is widely used. Recently, the optical disk device has been used as a storage device of a computer.

In addition, high-speed movement of an optical head equipped with an optical system has been required so that high-speed recording and reproduction of data can be performed. In response to such a demand for high-speed movement of the optical head, a method has been proposed in which the mass of the optical head is reduced as much as possible to realize a quick seek. As such a method, a separation optical method is adopted in which a semiconductor laser (light source) or a photodetector (detector) is not mounted on an optical head, and only an objective lens for forming a focal point on an optical disk is mounted on an optical head and moved. ing.

An example of a conventional optical disk device adopting the separation optical system will be described below with reference to FIG. Fixed optical system 113 such as semiconductor laser 111 and photodetector 112
Is fixed to a base or the like (not shown). The laser light L emitted from the semiconductor laser 111 is given to the objective lens 116 mounted in the optical head 115 via the galvano mirror 114 also fixedly arranged. The objective lens 116 forms a focal point on a pit on the optical disk D, and guides the reflected light to the photodetector 112 again in the reverse path.
The optical head 115 is driven in a tracking direction X and a focusing direction Y by driving means (not shown).

According to such a system, the optical head 115
Can be corrected by controlling the swing angle of the fixedly disposed galvanometer mirror 114 when the optical path is tilted in the tracking direction X (a change in the incident angle of the laser beam on the objective lens 116). it can. Therefore, it is not necessary to mount a means for tilting the objective lens 116 itself on the optical head 115, so that the mass of the entire optical head 115 can be reduced, and a quick seek can be realized.

The conventional galvanometer mirror 114 used in this manner has the structure shown in FIGS. 10 to 12. Here, FIG. 10 is a plan view of the galvano mirror 114, FIG. 11 is a sectional view taken along the line AA in FIG. 10, and FIG. 12 is B in FIG.
FIG. 4 is a cross-sectional view taken along line B.

The galvano mirror 114 includes a reflecting mirror 117 for reflecting the laser beam, an oscillator 118 to which the reflecting mirror 117 is fixed, and two supporting members for supporting the oscillator 118 with respect to the fixed portion 119. 120a and 120b. The fixing portion 119 is composed of a yoke 121 and a magnet 122, and applies a magnetic field to a coil 123 fixed to the side surface of the oscillating body 118 to support the reflecting mirror 117.
It can be swung around the axes 120a and 120b.

[0008]

However, there is a danger that the surface of the reflecting mirror 117 of the galvanometer mirror 114 will gradually tilt due to temperature changes and aging. If such an inclination occurs, it becomes difficult to accurately guide the reflected light from the galvanometer mirror 114 to the objective lens 116, and this may cause a tracking offset, which may hinder accurate tracking operation. is there. In addition, the influence of this inclination changes according to the distance from the galvano mirror 114 to the objective lens 116, so that complicated control such as further correcting the swing angle of the galvano mirror 114 by the current position of the optical head 115 is required. It will be necessary.

Therefore, only the galvanometer mirror 114 is mounted on the optical head 115, and the galvanometer mirror 114 and the objective lens are mounted.
There is a demand for a fixed optical system in which the distance from the optical system is kept constant.

However, as described above, the conventional galvanomirror 114 has a large mass since it has the yoke 121, the magnet 122, the coil 123, and the like, and when mounted on the optical head 115, the high-speed seek of the optical head 115 is hindered. It was virtually impossible.

Therefore, it is an object of the present invention to provide an optical disk device which is equipped with a lightweight and small-sized galvanometer mirror and which is capable of high-speed seek and is compatible with high disk density.

[0012]

In order to achieve the above object, in the present invention, a light source for generating a laser beam, a galvano mirror for reflecting the laser beam from the light source, and a laser beam reflected by the galvano mirror are provided. In response, an objective lens that forms a focus on the optical disc, a carriage that mounts the galvano-mirror and the objective lens, a first drive mechanism that finely drives the objective lens in the radial direction of the optical disc, and a carriage that drives the objective lens A second drive mechanism for coarsely driving in the direction, signal processing of reflected laser light from the optical disk, and the galvano mirror, the first drive mechanism,
An optical disk device having a signal processing means for generating a control signal to the second drive mechanism.

The signal generated by the signal processing means is preferably obtained by processing the reflected laser light from the optical disk according to its frequency range. Further, the signal processing means processes the reflected laser light from the optical disc as a first processed signal, a second processed signal and a third processed signal in the order of increasing frequency region thereof, and the first processed signal is transmitted to the galvanometer mirror. It is preferable that the second processing signal be output to the first drive mechanism and the third processing signal be output to the second drive mechanism. Further, the galvano mirror can be formed of a material mainly containing silicon.

According to the present invention as described above, since the galvano mirror is electrostatically driven, elements such as a yoke, a magnet and a coil having a large mass are not included. Therefore,
The Galvano mirror will be lighter and smaller, and an optical disk device that can perform high-speed seek will be realized.

Further, according to the present invention, it is possible to generate a control signal for each part of the apparatus (first drive mechanism, second drive mechanism, galvano mirror) according to a frequency band. Therefore, each part of the device can be controlled with extremely high accuracy using a single input signal. Therefore, it is possible to sufficiently cope with the future increase in the density of the disk, that is, the case where the track pitch of the disk becomes narrower than the conventional one.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, the optical disk device of the present invention will be described with reference to FIGS. Here, FIG. 1 is a sectional view showing the internal structure of the optical disk device, FIG. 2 is a plan view of a drive system including an optical head, FIG. 3 is a sectional view of the optical head, and FIG. 4 is a sectional view of an optical unit.

The disk 1 (optical disk, magneto-optical disk, etc.) used for recording and reproducing information is held by chucking means such as a magnet chuck with respect to a spindle motor 2 fixed to a base (not shown), During reproduction, the spindle motor 2 stably drives the rotation.

A semiconductor laser 3 for generating a laser beam for irradiating the disk 1 includes a photodetector 4 and a HOE (Ho
logramic Optical Element) Element 5, collimating lens
An optical unit 6 is configured with 50 and the like, and the optical unit 6 is fixed inside an optical head (carriage) 7. As shown in FIG. 4, the optical unit 6
A plurality of irregularities are formed in the lower part of the for the purpose of enhancing heat dissipation.

The laser light emitted from the semiconductor laser 3 passes through the HOE element 5 formed on the glass surface, becomes parallel light by the collimator lens 50, is reflected by the galvano mirror 9 at an angle of about 45 °, and is reflected by the optical head. It is guided to the objective lens 10 held by the objective lens holder 13 arranged on the upper part of 7. Then, the laser light is focused on the recording track of the disc 1 by the objective lens 10 to form a focus.

The reflected light from the disk 1 returns to the objective lens 10, and the galvano mirror 9, collimating lens 50,
It is returned to the photo detector 4 via the HOE element 5.
A recording information signal, a focus offset signal, a track offset signal, etc. are generated from the reflected light taken into the photodetector 4. Then, by using the focus offset signal, a positional deviation of the objective lens 10 in the focusing direction is detected, and a control operation is performed in which a current is passed through the focus coil 11 so as to correct this positional deviation. Further, by using the track offset signal, a positional deviation of the objective lens 10 in the track direction is detected, and a voltage is applied to the linear motor coil 12 and the galvano mirror 9 so as to correct the positional deviation, and a control operation is performed.

The objective lens 10 is held by an objective lens holder 13 made of a plastic magnet. This objective lens holder 13 has one end engaged with the slide shaft 14 via a slide bearing fixed to the optical head 7,
It constitutes a so-called plain bearing mechanism. Further, a pair of focus coil and tracking coil 11 are wound and attached to the objective lens holder 13 one by one.

A pair of magnetic circuits 51 are erected and fixed around the objective lens holder 13 to supply magnetic flux to the focus coil and the tracking coil 11. Then, an electromagnetic action acts between the focus coil wound around and fixed to the optical head 7 and the current flowing through the tracking coil 11 to cause the objective lens 10 to generate the focus driving force and the tracking driving force. The tracking driving force here is a driving force for finely driving the objective lens holder 13 in the radial direction of the disk 1, and the focus coil and the tracking coil 11 and a pair of magnetic circuits.
51 constitutes the first drive mechanism.

The linear motor coils 12 are formed in a tubular shape, and one each is fixed to both side surfaces of the optical head 7. A total of four slide bearings 15 are formed on both sides of the optical head 7 with the linear motor coil 12 sandwiched between them.
The two guide shafts 16 extending in the radial direction are engaged with each other. This allows the optical head 7 to
It is supported so that it can move in the radial direction.

The guide shaft 16 is made of a magnetic material and also serves as a yoke of a magnetic circuit. Then, U-shaped back yokes 17 are fixed to both ends of the guide shaft 16.

A radial magnet 18 is arranged at a position facing the linear motor coil 12 with a magnetic gap in between.
It is fixed to the back yoke 17. The guide shaft 16, the back yoke 17, and the radial magnet 18 form a radial magnetic circuit 19, which causes a magnetic field to act on the linear motor coil 12 and an electromagnetic action with the current flowing through the linear motor coil 12 to cause the optical head 7 to move. The driving force for the coarse movement of the disk 1 in the radial direction is generated.

Here, the linear motor coil 12 and the radial magnetic circuit 19 constitute a second drive mechanism. A positioning member 52 made of an elastic material such as rubber is fixed on the optical head 7, and a part of the positioning member 52 is connected to the objective lens holder 13. The positioning member 52 positions the objective lens holder 13 at its neutral position when the focus coil and the tracking coil 11 are not energized.

Next, a specific structure of the galvano mirror 9 will be described with reference to FIGS. 6 to 8. 6 is an exploded perspective view showing a galvano mirror used in the present invention, FIG. 7 is a sectional view thereof, and FIG. 8 is a plan view of a second plate.

As shown in FIG. 5, the galvanometer mirror 9 has a structure in which a first plate 21 and a second plate 22 are laminated. The first plate 21 has a hollow structure that is square-shaped. A semiconductor laser
A reflecting mirror 24 for reflecting the laser light from the laser beam 3, a swinging body 25 having the reflecting mirror 24 formed on its surface, and two elastic bodies for connecting the swinging body 25 to the first plate 21 ( And a support member) 26.

Here, the center of gravity of the mass of the movable portion, which is the total of the reflecting mirror 24 and the oscillating body 25, is configured to be near the middle of the line connecting the two elastic bodies 26. The reflection mirror 24, the oscillating body 25, and the elastic body 26 are integrally formed by anisotropic etching of a semiconductor mainly composed of silicon. Directly manufactured on.

The reflecting mirror 24 is formed so as to project from the rocking body 25 by a distance of 2 to 3 μm. Also, the elastic body 26
Are formed of a material that electrically insulates the oscillator 25 and the first plate 21.

The second plate 22 is bonded to the first plate 21 by means such as diffusion bonding or anodic oxidation bonding. The second plate 22 is formed of a glass-based member, and is electrically insulated from the first plate 21.

The first plate 21, the oscillator 25, and the second plate 22 are made of a material having substantially the same coefficient of thermal expansion, so that the influence of thermal strain on the oscillator 25 due to temperature changes. It is designed to prevent That is, as the second plate 22, a glass member having substantially the same coefficient of thermal expansion as that of the first plate 21 is selected.

On the other hand, at a portion of the second plate 22 facing the oscillator 25, a total of 2 portions are symmetrical with respect to a line connecting the two elastic bodies 26 (center line of the first plate 21). 2 electrodes
8,29 are provided. These electrodes 28 and 29 are formed on the second plate 22 by means such as vapor deposition and sputtering. The electrodes 28 and 29 may be transparent electrodes.

Galvanometer mirror 9 configured as described above
The driving method of will be described. First, the oscillator 25 formed of a semiconductor is charged to the positive pole, the electrode 29 is charged to the negative pole, and the electrode 28 is charged to the positive pole. Then, the oscillating body 25 and the electrode 29 attract each other by an electrostatic force, and the two elastic bodies 26 are twisted and deformed, whereby the oscillating body 25 rotates. Similarly, the oscillator 25 is charged to the negative pole, and the electrode 29 is charged to the positive pole.
-Is charged to the pole. Then, the two elastic bodies 26 are twisted and deformed, so that the rocking body 25 is rotated in the opposite direction.

In the above example, the oscillator 25 is positively charged and the first electrode 28 and the second electrode 29 are negatively charged. However, for example, the oscillator 25 is negatively charged. ,
The same effect can be obtained by charging the first electrode 28 and the second electrode 29 to +. Further, when the oscillator 25 is connected to the ground and set to the state of zero potential, the electrodes 28, 29
The same effect can be obtained if both are charged to + or both are charged to-.

Here, by measuring the capacitance between the oscillator 25 and the electrodes 28, 29, the oscillator 25 and the second plate 22 are measured.
It is possible to detect the gap length between and, and thereby the rotation (swing) angle of the oscillating body 25 can be accurately detected. Then, by electrically correcting the tracking offset using the detected value, the restriction on the rotation angle peculiar to the galvanometer mirror can be almost eliminated, and stable and highly accurate tracking control can be performed.

Further, by using the change in the gap length between the oscillator 25 and the second plate 22 measured from the change in capacitance, the inclination of the surface of the reflecting mirror 24 due to temperature rise or aging can be corrected. it can.

Next, the procedure of signal processing in the present invention will be described. FIG. 5 is a block diagram showing the internal structure of the signal processing means, that is, the processing procedure of the track offset signal.

First, the track offset signal is input to the first filter 41, the second filter 42, and the third filter 43, respectively. Here, a kind of low-pass filter is adopted as the first filter 41. Therefore, the signal passing through the first filter 41 becomes a signal in the low frequency region, and the linear motor driver 44 and the linear motor coil are
Used as a signal for 12.

The third filter 43 is a galvanometer mirror.
In order to control the rotation (oscillation) of 9, it is set to configure a bandpass filter that captures signals in the high frequency range. This high frequency signal is used as a signal for the galvanometer mirror unit driver 46 and the galvanometer mirror 9.

Further, the signal passing through the second filter 42 should be configured as a bandpass filter so as to take in a signal in the frequency domain located just in the middle of the first filter 41 and the third filter 43. It is set. Then, it is used as a signal for the objective lens drive driver 45 and the focus coil and tracking coil 11.

The signal processed in this way urges the linear motor coil 12 to serve as a coarse drive signal for the optical head 7 and also to the focus coil and the tracking coil.
It is used as a fine movement drive signal of the objective lens holder 13 by urging 11 and as a control signal of the swing angle of the galvanometer mirror 9 (spot position control signal of laser light). In this way, information is recorded on the recording track of the disk 1, and the information is read from the recording track of the disk 1.

According to the present invention having the signal processing means as described above, it is possible to generate the control signals of the respective parts of the apparatus (the first drive mechanism, the second drive mechanism, the galvano mirror) according to the frequency band. Therefore, each part of the device can be controlled with extremely high accuracy using a single input signal. Therefore, it is possible to obtain a practically great effect that it is possible to sufficiently cope with the future increase in the density of the disk, that is, even when the track pitch of the disk becomes narrower than in the past.

Further, the galvano mirror used in this embodiment
According to 9, the weight is significantly reduced as compared with the conventional one because it does not have elements with a large mass such as a yoke, a magnet, and a coil. Therefore, the optical head 7 has a galvanometer mirror.
Even if 9 is mounted, the optical head 7 can be kept lightweight and compact, and the optical head 7 can perform high-speed seek.

Since the driving force is generated by utilizing the electrostatic force, the power consumption can be reduced and the optical unit 6 and the objective lens 10 mounted on the optical head 7 can be reduced.
Thermal adverse effects on such devices can be avoided as much as possible.

The center of gravity of the oscillating body 25 is arranged on the rotation axis of the oscillating body 25, that is, on the line connecting the two elastic bodies 26, and rotation (swing) is realized by the torsional deformation of these elastic bodies 26. Therefore, even if the disturbance acceleration acts, it does not affect the rotational deformation.

Further, a galvanometer mirror composed of an electrostatic drive element that does not require any electromagnetic force is used for an electromagnetic drive element such as a coil or a magnet used to drive the objective lens 10. That is, by using the electromagnetic force and the electrostatic force, it is possible to almost completely prevent problems such as mutual interference of the driving forces. Therefore, the adverse effect of mounting the galvanometer mirror 9 on the optical head 7 can be eliminated, and the galvanometer mirror 9 can be removed.
It is also easy to arrange 9 and the objective lens 10 at extremely close positions (for example, directly below the objective lens), and the degree of freedom in device design is greatly improved. Further, it is possible to suppress the movement of the optical axis center at the objective lens position due to the rocking and tilting of the galvanometer mirror, and as a result, it is possible to reduce the offset generated in the tracking and focus control signals and to reduce the spot position. It becomes possible to determine with higher accuracy.

Further, conventionally, the galvanometer mirror and the oscillator were joined together and the coil and the oscillator were joined together with an adhesive or the like, but in the present invention, no inclusion such as an adhesive is used. . Therefore, the torque generated by the coil or the magnet is not transmitted through the adhesive layer, and the vibration frequency can be set to be extremely high. That is,
The drive frequency characteristics of the galvano mirror are not deteriorated due to insufficient rigidity of the adhesive part (for example, the resonance point is around 20kHz and it is impossible to servo to the high range). The control operation becomes extremely easy, and the positioning operation with high accuracy becomes possible.

The rotation axis of the oscillating body 25 and the longitudinal direction of the elastic body 26 are substantially coincident with each other, and the center of mass of the oscillating portion 25 (movable portion) is on the line connecting the two elastic portions 26. It is configured to be near the middle of the. Therefore, even if disturbance acceleration acts on the device, it does not affect the rotational movement of the oscillating body 25.

In the above-mentioned embodiment, the second plate 22 is made of an electrically insulating material such as a glass plate. However, for example, an insulating layer made of an oxide film is provided on the surface of a semiconductor mainly composed of silicon. You may use the thing. Even with such a configuration, a similar effect can be obtained. It is needless to say that the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made without departing from the spirit of the invention.

[0051]

As described above, according to the present invention, since the galvano mirror is electrostatically driven, it does not include a large mass element such as a yoke, a magnet and a coil. Therefore, the galvanometer mirror is lightened and miniaturized, and an optical disk device capable of high-speed seek is realized.

Further, in the present invention, it is possible to generate the control signals of the respective parts of the device (the first drive mechanism, the second drive mechanism, the galvano mirror) according to the frequency band. Therefore, each part of the device can be controlled with extremely high accuracy using a single input signal. Therefore, it is possible to sufficiently cope with the future increase in the density of the disk, that is, the case where the track pitch of the disk becomes narrower than the conventional one.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the internal structure of an optical disk device according to the present invention.

FIG. 2 is a plan view of a drive system including an optical head.

FIG. 3 is a sectional view of an optical head.

FIG. 4 is a cross-sectional view of the optical unit.

FIG. 5 is a block diagram showing a processing procedure of a track offset signal.

FIG. 6 is an exploded perspective view showing a galvanometer mirror.

FIG. 7 is a sectional view of a galvanometer mirror.

FIG. 8 is a plan view of a second plate.

FIG. 9 is a configuration diagram showing an example of a conventional optical disc device.

FIG. 10 is a plan view showing a conventional galvanometer mirror.

11 is a sectional view taken along the line AA in FIG.

12 is a sectional view taken along line BB in FIG.

[Explanation of Codes] 1 ... Disk 2 ... Spindle motor 3 ... Semiconductor laser 4 ... Photo detector 5 ... HOE element 6 ... Optical unit 7 ... Optical head 8 ... Prism 9 ... Galvano mirror 10 ... Objective lens 11 ... Focus coil and tracking coil 12 Linear motor coil 13 Objective lens holder 14 Sliding shaft 15 Sliding bearing 16 Guide shaft 17 Back yoke 18 Radial magnet 19 Radial magnetic circuit 21 First plate 22 Second plate 24 Reflection Mirror 25 ... Oscillator 26 ... Elastic body 28, 29 ... Electrode 41 ... First filter 42 ... Second filter 43 ... Third filter 44 ... Linear motor driver 45 ... Objective lens driver 46 ... Galvano mirror unit 51 ... Magnetic circuit 52 ... Positioning member

Claims (4)

[Claims] 1. A light source for generating a laser beam, a galvano mirror for reflecting and controlling the laser beam from the light source by electrostatic driving, and an objective lens for receiving a laser beam reflected by the galvano mirror and forming a focus on an optical disk. A carriage on which the galvanometer mirror and the objective lens are mounted, a first drive mechanism for finely driving the objective lens in the radial direction of the optical disc, and a second drive mechanism for coarsely driving the carriage in the radial direction of the optical disc. An optical disk device comprising: a signal processing unit that processes a reflected laser beam from the optical disk and generates a control signal to the galvano mirror, the first drive mechanism, and the second drive mechanism. 2. The optical disk apparatus according to claim 1, wherein the signal generated by said signal processing means is the reflected laser light from the optical disk processed according to its frequency range. 3. The signal processing means outputs the reflected laser light from the optical disk as a first processed signal in descending order of frequency range thereof.
Signal processing is performed as a second processed signal and a third processed signal, the first processed signal is applied to the galvanomirror, the second processed signal is applied to the first drive mechanism, and the third processed signal is applied to the second drive mechanism. The optical disk device according to claim 1, wherein the optical disk device outputs the respective data. 4. The optical disk device according to claim 1, wherein the galvano mirror is made of a material mainly containing silicon.