JPH09146033A - Galvanometer mirror and optical disk device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a galvanometer mirror whose initial tilt angle can be made as small as possible and to provide an optical device capable of supplying a playback signal of high reliability by mounting the galvanometer mirror. SOLUTION: A prism mirror 23, which reflects laser light, is supported elastically by a leaf spring 24. Further, coils 25a and 25b are fixed to the prism mirror 23, permanent magnets 29a and 29b face each other across a specific magnetic gap, and the prism mirror 23 is driven with a Lorenz's force. At this time, the prism mirror 23 rotates on the optical axis of an objective. Further, a magnetic body 30 is fixed right in the space part of the coil 25b. The prism mirror 23 can be rotated finely on the optical axis of the objective by finely moving the permanent magnet 29b in X direction, and the initial tilt angle of the prism mirror 23 can be corrected.

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 11 such as semiconductor laser 111 and photodetector 112
3 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 a concrete structure shown in FIGS. 11 to 13. Here, FIG. 11 is a plan view of the galvano mirror 114, FIG. 12 is a sectional view taken along the line AA in FIG. 11, and FIG. 13 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, when the surface of the reflecting mirror 117 of the galvano mirror 114 has a large initial tilt angle (deviation amount from the reference position), an offset occurs in the tracking error signal or spot quality. However, there is a problem in that the error rate becomes low and becomes uncontrollable, or the error rate of the reproduced signal becomes extremely high.

It is therefore an object of the present invention to provide a galvano mirror capable of reducing the initial tilt angle of the galvano mirror as much as possible, and an optical disk device equipped with this galvano mirror for supplying a highly reliable reproduction signal.

[0010]

To achieve the above object, the present invention provides a reflection mirror, a coil fixed to the reflection mirror, a magnetic circuit for applying a magnetic field to the coil, and a magnetic circuit for the magnetic circuit. A galvano mirror having a magnetic body connected to the reflection mirror under the influence of a magnetic field is used.

Further, a reflecting mirror, a permanent magnet fixed to the reflecting mirror, a coil for generating a driving force in the permanent magnet by the interaction of the permanent magnet, and a state of being affected by the magnetic field of the permanent magnet. And a magnetic body connected to the reflection mirror.

Further, a light source for generating a laser beam, a galvano mirror for reflecting the laser beam from the light source, an objective lens for receiving a laser beam reflected by the galvano mirror to form a focus on an optical disc, and the objective lens. An optical disc device having means for driving the optical disc in the radial direction of the optical disc, and signal processing means for processing reflected light from the optical disc to generate a drive signal to the drive means and a reproduction signal from the optical disc. The galvano mirror is a reflection mirror, a coil fixed to the reflection mirror, a magnetic circuit for applying a magnetic field to the coil, and a magnetic circuit connected to the reflection mirror in a state of being affected by the magnetic field of the magnetic circuit. An optical disc device having a body.

Further, a light source for generating a laser beam, a galvano mirror for reflecting the laser beam from the light source, an objective lens for receiving a laser beam reflected by the galvano mirror to form a focus on an optical disc, and the objective lens. An optical disc device having means for driving the optical disc in the radial direction of the optical disc, and signal processing means for processing reflected light from the optical disc to generate a drive signal to the drive means and a reproduction signal from the optical disc. The galvanometer mirror is a state in which a reflection mirror, a permanent magnet fixed to the reflection mirror, a coil for generating a driving force in the permanent magnet by interaction of the permanent magnet, and a magnetic field of the permanent magnet are applied. And a magnetic body connected to the reflection mirror.

According to the present invention as described above, the reflecting mirror can be finely rotated around the optical axis of the objective lens by finely moving the permanent magnet, and the initial tilt angle of the reflecting mirror can be corrected. Becomes

[0015]

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

A disk 1 (optical disk, magneto-optical disk, etc.) used for recording and reproducing information is held by a 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 constitutes an optical unit 8 together with a photodetector 4, a collimator lens 5, a condenser lens 6, a deflecting prism 7 and the like.
Is fixed on the base.

The laser light emitted from the semiconductor laser 3 passes through the collimator lens 5 and is deflected by the deflection prism 7 to 45
Outputs from the optical unit 8 after changing the direction to °.
This laser light is reflected by a reflection mirror 22 (described later) fixed inside the optical head 20 in the 90 ° direction, and then by a galvanometer mirror.
A reflecting mirror surface 9 (described later) turns the direction again to 90 ° and guides it to the objective lens 10 arranged above the optical head 20. 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, passes through the galvanometer mirror 9 and the reflection mirror 22, passes through the deflection prism 7, and is returned to the photodetector 4. 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, the track offset signal is used to detect the positional deviation of the objective lens 10 in the track direction, and a control operation is performed by applying a voltage to the linear motor coil 12 and the galvano mirror 9 so as to correct this positional deviation.

The objective lens 10 is held by an objective lens holder 13 around which a focus coil 11 is wound. Further, one end of the parallel leaf spring 14 is fixed to the objective lens holder 13 and the other end of the parallel leaf spring 14 is fixed to the optical head 20, so that the objective lens 10 is supported so as to be movable in the optical axis direction. . Then, a focus magnetic circuit 21 provided upright on the optical head 20 so as to surround the objective lens holder 13,
Focus coil wound around and fixed to the objective lens holder 13
Electromagnetic action acts between the current flowing in 11 and the objective lens
Generates focus drive force to 10.

The linear motor coils 12 are formed in a tubular shape, and one each is fixed to both side surfaces of the optical head 20. In addition, a total of three plain bearings are provided at both ends of one linear motor coil 12 and one end of the other linear motor coil 12.
15 are formed and are engaged with two guide shafts 16 extending in the radial direction of the disk 1, respectively. As a result, the optical head 20 is supported so as to be movable in the radial direction of the disk 1.

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 the magnetic gap interposed therebetween, and 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, and the linear motor coil
A magnetic field is applied to 12 and an electromagnetic action with the current flowing through the linear motor coil 12 causes the optical head 20 to generate a driving force in the radial direction of the disk 1.

Next, a specific structure of the galvano mirror 9 according to the present invention will be described with reference to FIGS. FIG.
Is a perspective view showing a galvanometer mirror, and FIG. 4 is a sectional view thereof. What is indicated by an arrow in the figure is a path through which the laser light reaches the objective lens 10. That is, the laser light emitted from the optical unit 8 is 90 ° at the reflection mirror 22.
The direction is changed to 90 °, and the direction is changed again to 90 ° by the reflecting surface of the prism mirror (reflection mirror) 23. In FIG. 3, the laser light travels while changing the moving direction in three orthogonal directions.

On one side surface of the prism mirror 23, a leaf spring (supporting means) 24 having a substantially V shape is adhered and fixed. The direction from the prism mirror 23 to the side plate 27b corresponds exactly to the spindle motor 2 side (that is, the disk 1 side). Although the leaf spring 24 is made of a single steel material here, it may be made of a plurality of steel materials.
The end of the leaf spring 24 is fixed to the side plate 27b formed by bending the galvano-mirror base 26 made of a magnetic material by means such as adhesion or welding. Similarly, the back surface of the reflection mirror 22 is held and fixed to the side plate 27a.

The prism-shaped portion of the leaf spring 24 is elastically deformed so that the prism mirror 23 can rotate (swing) around the optical axis of the objective lens 10.
On the other hand, on both side surfaces of the prism mirror 23, a pair of coils 25a, 25b wound in a substantially circular shape are adhered and fixed. (For the coil 25b, the prism mirror 23
It is fixed to. ) A permanent magnet is placed at a position facing the coils 25a and 25b with a magnetic gap of a predetermined length.
29a and 29b are arranged. The permanent magnets 29a and 29b are the coil effective areas of the coils 25a and 25b (the coil winding is the objective lens).
The optical axis direction of the objective lens 10 is divided into two parts so as to be opposed to a region (extending in the optical axis direction of 10) and magnetized in a direction facing the prism mirror 23. In addition,
The permanent magnet 29a is adhered and fixed to the side plate 27b, and the permanent magnet 29b is adhered and fixed to the side plate 27c.

The Lorentz force is generated by the interaction between the magnetic field generated by the permanent magnets 29a and 29b and the current flowing through the coils 25a and 25b. By this Lorentz force,
The prism mirror 23 applies driving forces in opposite directions to the two coils 25a and 25b so as to rotate around the optical axis of the objective lens 10.

Then, by causing the rotational movement of the prism mirror 23, the incident angle of the laser light incident on the prism mirror 23 from the reflection mirror 22 is changed.
It becomes possible to make a minute change with respect to the moving direction of. That is, the spot position focused on the disc 1 by the objective lens 10 can be slightly displaced with respect to the tracking direction, that is, the moving direction of the carriage 20.

Further, as shown in FIG. 4, on the side of the coil 25b on the side surface of the prism mirror 23, a magnetic body 30 made of iron piece or the like is attached. The magnetic body 30 is arranged at a position just corresponding to the space of the wound coil 25b. Therefore, the magnetic body 30 has a permanent magnet.
The magnetic attraction force of 29b acts, and if the permanent magnet 29b can be moved in the X direction in the figure, the prism mirror 23 can be rotated around the optical axis of the objective lens 10.

According to the present invention configured as described above,
By attaching the magnetic body 30 to the prism mirror 23 in advance, the prism mirror 23 can be finely positioned. That is, first, with the permanent magnet 29b remaining, all the constituent elements are assembled (initial state).
Fix b to side plate 27c while slightly moving it in the X direction in the figure. At this time, the magnetic body 30 is magnetically attracted and moves according to the position of the permanent magnet 29b in the X direction, so that the prism mirror 23 slightly rotates around the optical axis of the objective lens 10 as described above. Therefore, it is possible to obtain a practically great effect that the initial tilt angle of the prism mirror 23 in the initial state can be corrected later. Further, this makes it possible to remarkably improve the reliability of the reproduced signal.

Further, the position where the magnetic body 30 is attached corresponds to a surface of the side surface of the prism mirror 23 opposite to the leaf spring 24. Therefore, the tension is always applied to the leaf spring 24 when the initial tilt angle of the prism mirror 23 is corrected. Therefore, the magnetic attraction force to the magnetic body 30 is applied to the leaf spring 24.
By emphasizing the restorative force, the positioning operation becomes extremely stable.

Further, the prism mirror 23 is almost the same as its reflecting surface.
It is elastically supported so that it can rotate around an axis that forms an angle of 45 °. Therefore, even if the leaf spring 24 expands due to thermal expansion or the like, this expansion only causes movement within a plane parallel to the reflecting surface of the prism mirror 23, which causes tilting of the reflected light and parallel movement. Since it does not occur, tracking offset does not occur due to temperature changes and aging changes.

Further, since the C-shaped leaf spring 24 is arranged in line symmetry with respect to the moving direction of the carriage 22,
The reflecting surface of the prism mirror 23 does not tilt due to the inertial force caused by the high speed movement of the carriage 22. Therefore, the control of the linear motor and the control operation of the galvanometer mirror do not interfere with each other, and a stable tracking operation can be realized.

Next, a second embodiment of the present invention will be described with reference to FIG. In each of the following examples, the first
The same components as those in the embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The present embodiment differs from the first embodiment in the mounting position of the permanent magnet and the coil. That is, in this embodiment, the permanent magnets 29a and 29b are directly adhered to the prism mirror 23, the coils 25a and 25b are arranged at positions facing each other through a magnetic gap of a predetermined length, and fixed to the side plates 27b and 27c. There is. In addition, slits 28 are provided at both ends of the leaf spring 24 (near the connection portion between the prism mirror 23 and the side plate 27b).
Is provided. Although a total of eight slits 28 are formed here, the number and shape of the slits 28 need not be limited to the illustrated form.

Further, in this embodiment, the coil 25 of the side plate 27c is
b The magnetic body 30 is fixed to the surface opposite to the mounting surface. According to the present embodiment configured as described above, not only the same effects as those of the above-described first embodiment but also the following effects can be obtained.

That is, in this embodiment, the permanent magnets 29a and 29b are used.
Since it is a direct connection between the prism and the prism mirror 23, the coil 25
As compared with the case where the a, 25b and the prism mirror 23 are joined, the joining can be performed with higher flatness. Therefore, bonding with a relatively thin adhesive layer is possible, and high bonding strength can be obtained. This makes it possible to obtain a good vibration characteristic without resonance up to a high frequency range, and a highly accurate control operation becomes possible.

In addition, the coils 25a and 25b are attached to the prism mirror 23.
Therefore, there is no concern that the prism mirror 23 will be distorted due to the generation of heat due to the power supply to the coils 25a and 25b. Further, since the flexible printed circuit board (not shown) for supplying electric power to the coils 25a and 25b is not connected to the prism mirror 23, the thermal effect of the flexible printed circuit board or the adverse effect of the tensile force acts on the prism mirror 23. Never.

Further, in this embodiment, the permanent magnets 29a, 29b are each divided into two with the optical axis direction of the objective lens 10 as an axis so as to face the coil effective areas of the coils 25a, 25b.
The pair of divided magnets are magnetized in opposite directions. That is, the permanent magnets 29a, 29b facing each other with the prism mirror 23 interposed therebetween are magnetized so as to have a symmetrical relationship with the optical axis direction of the objective lens 10 as an axis. Therefore, the influences of changes in the magnetic field due to the focus coil 11 cancel each other out, interference with the focus driving force is suppressed, and stable tracking control and focus control are possible.

Further, by providing the slit 28 in the leaf spring 24, stress is concentrated on the slit 28 portion when the leaf spring 24 is elastically deformed. Therefore, the movement of the instantaneous rotation center of the prism mirror 23 can be reduced, and more stable tracking control can be performed.

Next, a third embodiment of the present invention will be described with reference to FIGS. 6 and 7. Although the components of this embodiment are different in shape from the first embodiment, their basic functions are almost the same. The major difference between this embodiment and the first embodiment is the arrangement of the leaf springs.

In this embodiment, the reflection mirror 32 fixed to the mirror holder 31 is elastically supported by the two leaf springs 24a and 24b. The leaf springs 24a and 24b are connected to the mirror holder 31 at one end and to the holding portions 33a and 33b at the other end, respectively, in a state in which the plane directions of the leaf springs are the same. The holding portions 33a and 33b are adapted to be fitted into the cutout portions 34a and 34b provided in the galvano mirror base 26.

Also in this embodiment, the magnetic body 30 is fixed to the center of the space of the wound coil 25b. According to the present embodiment configured as described above,
In addition to the same effects as those of the first embodiment described above, the following effects can be obtained.

That is, in this embodiment, even if the leaf springs 24a and 24b are stretched and distorted due to thermal deformation, the reflection mirror 32
Since only the displacement that rotates around an axis orthogonal to the mirror surface acts on the mirror surface, the mirror surface does not tilt. Therefore, the positioning operation of the laser light can be stably maintained.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. This embodiment differs from the third embodiment in the arrangement of leaf springs and the number of magnetic bodies.

That is, in the present embodiment, the leaf springs 24a,
Although the surface directions of 24b are the same as each other, the direction of 24b is maintained in a state different from that of the third embodiment by 90 °. Two to four magnetic bodies 30 are prepared and fixed not only on both sides of the hollow portion of the coil 25b shown in FIG. 9 but also on both sides of the hollow portion of the coil 25a.

According to the present embodiment configured as described above,
In addition to the same effects as those of the first embodiment described above, the following effects can be obtained. That is, in the present embodiment, by adjusting the mutual positions (inclinations) of the magnetic bodies 30a and 30b in the Z-axis direction, rotation adjustment about the X-axis can be performed, and
By adjusting the positions of the magnetic bodies 30 on both sides in the Z-axis direction as one set, rotation adjustment about the Y-axis can be performed.

It is needless to say that the present invention is not limited to the above-described embodiments and modified examples, and various modifications can be made without departing from the spirit of the invention.
For example, the optical unit 8 is mounted on the optical head 20,
It goes without saying that the same effect can be obtained with an optical disk device of the so-called "fixed optical system" system.

[0048]

As described above, according to the present invention, a galvanometer mirror capable of reducing the initial tilt angle of the galvanometer mirror as much as possible, and an optical disk device equipped with this galvanometer mirror for supplying a highly reliable reproduction signal. Will be provided.

[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 perspective view of a drive system including an optical head.

FIG. 3 is a perspective view showing a galvanometer mirror according to the present invention.

FIG. 4 is a sectional view of a galvanometer mirror.

FIG. 5 is a perspective view of a galvanometer mirror according to a second embodiment of the present invention.

FIG. 6 is a perspective view of a galvanometer mirror according to a third embodiment of the present invention.

7 is an exploded perspective view of the galvanometer mirror shown in FIG.

FIG. 8 is a perspective view of a galvanometer mirror according to a fourth embodiment of the present invention.

9 is an exploded perspective view of the galvano mirror shown in FIG.

FIG. 10 is a block diagram showing an example of a conventional optical disc device.

FIG. 11 is a plan view showing a conventional galvanometer mirror.

12 is a cross-sectional view taken along the line AA in FIG.

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

[Explanation of symbols]

 1 ... Disk 2 ... Spindle motor 3 ... Semiconductor laser 4 ... Photodetector 5 ... Collimating lens 6 ... Condensing lens 7 ... Deflection prism 8 ... Optical unit 9 ... Galvano mirror 10 ... Objective lens 11 ... Focus coil 12 ... Linear motor coil 13 ... Objective lens holder 14… Parallel leaf spring 15… Slide bearing 16… Guide shaft 17… Back yoke 18… Radial magnet 19… Radial magnetic circuit 20… Optical head 21… Focus magnetic circuit 22… Reflecting mirror 23… Prism mirror (Reflecting mirror) 24, 24a, 24b ... Leaf spring (supporting means) 25a, 25b ... Coil 26 ... Galvano mirror base 27a, 27b, 27c ... Side plate 28 ... Slit 29a, 29b ... Permanent magnet 30, 30a, 30b ... Magnetic body 31 ... Mirror holder 32 ... Reflecting mirror 33 ... Holding parts 34a, 34b ... Notch parts

Claims (4)

[Claims] 1. A reflection mirror, a coil fixed to the reflection mirror, a magnetic circuit for applying a magnetic field to the coil, and a magnetic circuit connected to the reflection mirror in a state of being affected by the magnetic field of the magnetic circuit. A galvanometer mirror having a body. 2. A reflection mirror, a permanent magnet fixed to the reflection mirror, a coil for generating a driving force in the permanent magnet by interaction of the permanent magnet, and a state of being affected by a magnetic field of the permanent magnet. And a magnetic substance connected to the reflection mirror. 3. A light source that emits laser light, a galvano mirror that reflects the laser light from the light source, an objective lens that receives the laser light reflected by the galvano mirror and forms a focus on an optical disc, and the objective lens. An optical disc device comprising: a means for driving the optical disc in a radial direction of the optical disc; and a signal processing means for processing reflected light from the optical disc to generate a drive signal to the drive means and a reproduction signal from the optical disc. The galvano-mirror includes a reflection mirror, a coil fixed to the reflection mirror, a magnetic circuit for applying a magnetic field to the coil, and a magnetic circuit connected to the reflection mirror in a state of being affected by the magnetic field of the magnetic circuit. An optical disk device having a body. 4. A light source that generates a laser beam, a galvano mirror that reflects the laser beam from the light source, an objective lens that receives the laser beam reflected by the galvano mirror and forms a focus on an optical disc, and the objective lens. An optical disc device comprising: a means for driving the optical disc in a radial direction of the optical disc; and a signal processing means for processing reflected light from the optical disc to generate a drive signal to the drive means and a reproduction signal from the optical disc. The galvanometer mirror includes a reflection mirror, a permanent magnet fixed to the reflection mirror, a coil for generating a driving force in the permanent magnet by interaction with the permanent magnet, and a state in which a magnetic field of the permanent magnet is applied. And a magnetic body connected to the reflection mirror.