JPH0714200A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To prevent vibration resistance of the objective lens driving device from deteriorating when an optical disk device concerned is vertically installed. CONSTITUTION:A magnetic material 12 is provided on a vertical surface of a lens holder 2 positioned on the side opposite to an objective lens 1 respect to a supporting shaft 10 and parallel to the supporting shaft 10, while a permanent magnet 13 is provided to be opposite to the magnetic material 12 from an outside fixed part of the lens holder 2. Moreover, a mechanism for adjusting a distance between a pole of the permanent magnet 13 and the magnetic material 12 is provided, and a mechanism for making the pole of the permanent magnet 13 horizontal and vertical to the magnetic material 12 is provided. Consequently, when the optical disk device is vertically installed, since the dead weight of the lens holder does not act upon the supporting shaft as a load, frictional force between the supporting shaft and a bearing is abated, and the vibration resistance of the objective lens driving device can thus be prevented from deteriorating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device mounted on an optical disk device for reproducing and recording information by irradiating a rotating information recording medium with condensed laser light.

[0002]

2. Description of the Related Art In order to realize high performance of an optical disk device, laser light is condensed to form a minute spot,
There is a need for an objective lens driving device that has a function of irradiating the surface of a disc-shaped information recording medium and causing the laser light to follow the movement of the rotating disc-shaped information recording medium with high accuracy. ◆ Hereinafter, the objective lens driving device shown in FIG. 15 will be described. In FIG. 15, although not shown, a disc-shaped information recording medium is mounted on the objective lens 1. The objective lens 1 is driven in its focal direction by the movement in the Z direction along the support shaft 10 to follow the focal point on the disk-shaped information recording medium surface 15. Further, the objective lens 1 is rotationally driven by the rotational movement around the support shaft 10 to follow the track on the disk-shaped information recording medium surface 15. Basically, the objective lens driving device shown in FIG. 15 is designed and manufactured so that a load is not applied to the support shaft 10 by balancing the mass of the support shaft 10 in the front-rear direction and the left-right direction. Therefore, when the optical disk device equipped with the objective lens driving device of FIG. 15 is installed horizontally, that is, when the Z direction of FIG. 15 and the focus driving direction of the objective lens 1 coincide with each other, the spindle 10 and the bearing 11 hardly contact each other.

However, when the optical disk device is installed vertically, that is, when the X direction in FIG. 15 and the gravity direction coincide with each other, the weight of the lens holder 2 always acts as a load on the support shaft 10, so that the objective lens 1 At the time of driving, frictional force is generated between the support shaft 10 and the bearing 11, and wear is further generated. This frictional force adversely affects the tracking accuracy, especially when the objective lens 1 is driven in the focal direction to follow the focus on the disk-shaped information recording medium surface 15. Further, when the clearance between the support shaft 10 and the bearing 11 increases due to wear, the inclination of the optical axis of the objective lens 1 increases. This inclination causes aberration and causes distortion in the reproduced signal. Japanese Patent Application Laid-Open No. 4-184723 discloses an objective lens driving device having a support shaft and a bearing as in FIG.

[0004]

Problems in the prior art will be described in detail below. When the objective lens driving device shown in FIG. 15 is installed vertically, that is, when the X direction and the gravitational direction in FIG. The frictional force between the shaft 10 and the bearing 11 increases, causing an increase in positioning tracking error of the objective lens 1. The first problem is to prevent deterioration of the durability of the objective lens driving device due to friction between the support shaft 10 and the bearing 11.

Further, when the support shaft 10 and the bearing 11 come into contact with each other when the objective lens 1 is driven, the support shaft 10 vibrates, and the vibration is transmitted to the objective lens 1 to deteriorate the dynamic characteristics of the objective lens 1. A second problem is to prevent deterioration of vibration resistance of the objective lens driving device due to contact between the support shaft 10 and the bearing 11.

In order to solve the first and second problems, a magnetic attraction force acts on the lens holder 2 from the attraction mechanism by the permanent magnet provided from the outer fixed portion of the lens holder 2.
The objective lens driving device is installed horizontally, that is, Z in FIG.
When the direction matches the focus driving direction of the objective lens 1, an extra load acts on the support shaft 10. Therefore, the frictional force between the support shaft 10 and the bearing 11 generated when the objective lens 1 is driven increases, and the vibration of the support shaft 10 is transmitted to the objective lens driving device, which may deteriorate the dynamic characteristics of the objective lens 1. The third problem is to stabilize the driving of the objective lens 1 and prevent the vibration resistance of the device from being lowered even when the objective lens driving device provided with the suction mechanism is installed horizontally.

An object of the present invention is to provide an objective lens driving device which prevents deterioration of durability due to friction between a support shaft and a bearing. Another object of the present invention is to provide an objective lens driving device which prevents deterioration of vibration resistance due to friction between a support shaft and a bearing. Another object of the present invention is also to provide an objective lens driving device provided with a suction mechanism in a horizontal position.
(EN) An objective lens driving device which stabilizes driving of the objective lens 1 and prevents deterioration of vibration resistance of the device.

[0008]

In order to solve the above-mentioned first problem of the objective lens driving device, in the present invention, the support is provided on the vertical surface of the upper surface of the lens holder located on the side opposite to the objective lens with respect to the support shaft. A magnetic attraction mechanism (hereinafter referred to as a gravity compensating mechanism) in which a magnetic material is provided parallel to the axis and a permanent magnet is attached to the fixed portion outside the lens holder facing the magnetic material to drive the objective lens Provided from outside the device.

In order to solve the second problem, the gravity compensation mechanism is provided with a mechanism for adjusting the distance between the pole of the permanent magnet and the magnetic material attached to the lens holder.

In order to solve the third problem, the gravity compensating mechanism for rotating the permanent magnet pole from a vertical state to a horizontal state with respect to the magnetic material provided on the vertical surface of the upper surface of the lens holder. It was installed in the mechanism.

[0011]

In the present invention, since the objective lens driving device is provided with the gravity compensation mechanism composed of the magnetic material and the permanent magnet from the outside thereof, when the objective lens driving device is installed vertically, the lens holder provided with the magnetic material is provided. Is lifted by its own weight due to the magnetic attraction force, and the own weight of the lens holder does not act as a load on the support shaft.

If the gravity compensation mechanism is provided with a mechanism for adjusting the distance between the pole of the permanent magnet and the magnetic material attached to the lens holder, the magnetic attraction force acting on the lens holder can be adjusted. The shaft and bearing do not contact.

Further, when the rotating mechanism of the permanent magnet is provided in the gravity compensating mechanism, when the objective lens driving device provided with the gravity compensating mechanism is installed horizontally, the extra magnetic attraction that acts on the lens holder from the gravity compensating mechanism. The force can be suppressed and the extra load acting on the support shaft is reduced.

[0014]

1 is a perspective view of an objective lens driving device according to an embodiment of the present invention, and FIG. 2 is a magnetic circuit perspective view of the objective lens driving device. First, the structure of the objective lens driving device will be described with reference to FIG. Reference numeral 1 denotes an objective lens that collects laser light and is held by a lens holder 2. The lens holder 2 has fixing members 14a, 14b,
Elastic support members 3a, 3 attached to 14c, 14d
It is supported by b, 3c and 3d, and is in contact with the support shaft 10 via a bearing 11 provided at the drive center thereof. The lens moving part is composed of an objective lens 1, a lens holder 2, and elastic supporting members 3a, 3b, 3c and 3d. The objective lens 1 is a lens holder 2 which is symmetrical with respect to the spindle 10.
Focus coils 4a, 4b mounted on the upper surface of the
Tracking coils 5a, 5 mounted on the surface perpendicular to the upper surface of the lens holder 2 symmetrically with respect to the spindle 10.
b and the magnetic circuit of FIG. 2 provided thereunder, it is possible to operate in the focal direction (Z direction) and the rotational direction (XY plane). ◆ Focus coil 4a (4b) is inserted so as to surround inner yoke 8a (8b), and tracking coil 5a (5b) is placed between inner yoke 8a (8b) and outer yoke 7a (7b). It is located in.

As shown in FIG. 2, the permanent magnet 6a (6b)
Is attached to the outer yoke 7a (7b) and its pole is directed to the inner yoke 8a (8b) side. The gravity compensation mechanism includes a magnetic material 12 provided over a vertical surface of the upper surface of the lens holder 2 located on the opposite side of the support shaft 10 from the objective lens 1.
And a permanent magnet 13 mounted so as to face the magnetic material 12 from a carriage case 16 outside the lens holder 2.

Next, the operation of this objective lens driving device will be described. In the magnetic circuit of FIG. 2, the outer yoke 7a (7
b) and the inner yoke 8a (8b), a magnetic flux flows in the Y direction, and a current in the X direction flows in the portion of the focus coils 4a, 4b located between the gaps, according to Fleming's law. An electromagnetic force is generated in the objective lens 1, and the objective lens 1 is driven in the focal direction (Z direction). On the other hand, when a current in the Z direction flows through the portions of the tracking coils 5a and 5b located between the gaps, electromagnetic force is generated in the X direction in the portion 5a and in the −X direction in the portion 5b. 1 rotates about a spindle 10 and drives in the XY plane.

FIG. 3 is a perspective view of a mechanism portion of the magneto-optical disk device in the embodiment, and FIG. 4 is a view showing an optical path of a laser in the magneto-optical disk device. In this apparatus, the objective lens driving device and the bias magnet device 18 are housed in the carriage case 17 to reduce the thickness of the device. In FIG. 3, reference numeral 15 is a disk-shaped information recording medium which is fixed to a spindle motor 16 and rotates at high speed. Carriage case drive coil 19
a and 19b are yokes 21a and 2 fixed to the base 20.
1b, 21c, 21d and permanent magnets 22a, 22b are arranged in a magnetic circuit.

The function of this device will be described below. In order to record or erase information on the surface of the disk-shaped information recording medium 15, the condensed laser light is applied to the surface of the disk-shaped information recording medium 15 and the cylindrical bias magnet device 18 is driven to rotate. As a result, a magnetic field is applied to the surface of the disc-shaped information recording medium 15. At that time, in order to move the objective lens 1 to the target position on the surface of the disc-shaped information recording medium 15, the carriage case 17 is moved to the carriage case.
Of the objective lens 1 in the radial direction (Y direction) of the disc-shaped information recording medium 15 by causing the objective lens 1 to travel on the guide rails 24a and 24b through the guide bearings 23a, 23b, 23c and 23d by the drive coils 19a and 19b. To move. Further, by driving the above-mentioned objective lens driving device provided in the carriage case 17, the objective lens 1 is moved in the focal direction (Z direction) of the disc-shaped information recording medium 15 in the radial direction (Y direction) about the support shaft 10. Direction).

Next, the path through which the surface of the disc-shaped information recording medium 15 is irradiated with laser light will be described. As shown in FIG. 4, the laser light emitted from the semiconductor laser 26 passes through the fixed optical system 27 and the laser passage hole 25 provided on the side surface of the carriage case 17 and then directly below the objective lens 1. Is incident on a rising prism 28 fixed to the bottom of the carriage case 17, is bent in a direction perpendicular to the surface of the disc-shaped information recording medium 15, is condensed by the objective lens 1, and is disc-shaped information recording medium. Irradiated on 15.

The objective lens driving device of the present invention is provided in the above optical head configuration, and the structure thereof will be described in detail below. A first example of the invention is shown in FIG. An iron round bar 12 having a diameter of dmm is arranged behind the lens holder 2 so as to be parallel to the support shaft 10. The height is made to match the height of the lens holder 2. This central axis is located on the extension of the line connecting the centers of the objective lens 1 and the support shaft 10, and the pole of the permanent magnet 13 is directed from the fixed side of the carriage case 16 near the center. The magnetic attraction force acting between the permanent magnet 13 and the iron round bar 12 is of a magnitude that cancels the weight of the lens holder 2 itself.

5 and 6, the magneto-optical disk device shown in FIG. 3 is installed vertically, that is, the X direction in FIG. 3 is aligned with the direction of gravity, and the objective lens 1 is located directly below the support shaft 10. Is a frequency response characteristic in the focal direction of the objective lens 1 when the objective lens 1 is driven in the focal direction. 5 and 6, the curve (a) represents the amplitude ratio (dB) and the curve (b) represents the phase (deg). If the gravity compensation mechanism is not installed from outside the objective lens drive,
As shown in FIG. 5, the frequency f1 between the frequency f0 (Hz) at which the primary resonance occurs and the frequency f2 (Hz) at which the secondary resonance occurs.
(Hz) has a large phase delay. This phase delay causes a large frictional force between the support shaft 10 and the bearing 11 as the objective lens 1 is driven, and the support shaft 10 is supported to excite the resonance of the structure, and the resonance causes the objective lens 1 to be excited. Is the cause. On the other hand, when the gravity compensation mechanism is provided from the outside of the objective lens driving device, no phase delay occurs at the frequency f1 (Hz) as shown in FIG. This is because almost no frictional force is generated between the support shaft 10 and the bearing 11. From the above results, by providing the gravity compensation mechanism from the outside of the objective lens driving device, the frictional force generated between the support shaft 10 and the bearing 11 is reduced, and the frequency response characteristic of the objective lens 1 in the focal direction is significantly increased. It can be seen that it will be improved.

Next, another embodiment of the gravity compensation mechanism will be described. When the magneto-optical disk device shown in FIG. 3 is installed vertically, in order to further improve the frequency response characteristic of the objective lens 1, it is necessary to make adjustment so that the support shaft 10 and the bearing 11 do not always come into contact with each other. is there.

7 and 8 are fine adjustment mechanism diagrams of the distance lx from the pole of the permanent magnet 13 to the magnetic material 12 provided on the lens holder 2, FIG. 7 being a top view and FIG. 8 being a sectional view. Shows. In the figure, 13 is a permanent magnet, and 29 is a hole provided in the wall of the carriage case 16. Reference numeral 30 denotes a guide mechanism provided in the carriage case 17, and the guide mechanism 30 is provided with a groove 31 having a depth in which the permanent magnet 13 is accommodated. Reference numeral 12 is a magnetic material attached to the vertical surface of the upper surface of the lens holder 2, and for example, a round bar made of iron is used. The permanent magnet 13 has its pole aligned with the center of the magnetic material 12 in the Z direction, and is attached perpendicularly to the magnetic material 12.
The adjusting member 32 at the distance lx is threaded with diagonal lines, and the adjusting member 32 is rotated from the outside of the carriage case 17 along the guide mechanism 30 to adjust the distance lx. Move in the direction indicated by the arrow in the figure.

The assembly procedure is shown below. For example, while observing the frequency characteristic of the objective lens 1 in real time with a measurement system including a laser Doppler meter or a laser displacement meter and an FFT, the distance lx is adjusted so that the frequency response characteristic becomes the best. Then, the permanent magnet 13 is fixed by adhering the nonmagnetic plastic plate 33 attached to the upper surface of the permanent magnet 13 to the guide mechanism 30.

FIG. 9 is an enlarged view of the portion surrounded by the dotted line in FIG. 8. However, if the magnetic material 12 is formed into a U-shape when viewed from above, most of the magnetic flux emitted from the permanent magnet 13 is the magnetic material 12.
Is absorbed by the permanent magnet 13 compared to the case of FIG.
The magnetic flux leaking from the magnetic field to the magnetic circuit is further reduced, and the frequency response characteristic of the objective lens 1 can be further improved.

Next, an embodiment for the third problem will be described. When the magneto-optical disk device shown in FIG. 3 is installed horizontally, the load due to the own weight of the lens holder 2 does not act on the support shaft 10, but the gravity compensation mechanism is composed of a permanent magnet, and the magnetic field leaking from it is present. Acts on the lens holder 2, so that an extra load acts on the support shaft 10 in the −X direction. Therefore, a frictional force is generated between the support shaft 10 and the bearing 11, and the support shaft 10 vibrates. The vibration is the objective lens 1
And the objective lens 1 resonates.

FIG. 10 is a side view showing a mechanism for suppressing the magnetic attraction force acting on the lens holder 2 from the gravity compensation mechanism. Reference numeral 34 is a holder for positioning the rotation stop of the permanent magnet 13, and reference numeral 35 is a magnetic material for holding the rotated permanent magnet 13 in the state (B). 36 is the center of rotation of the permanent magnet 13 and is provided outside the permanent magnet 13. When the magneto-optical disk device shown in FIG. 3 is installed vertically, the poles of the permanent magnets 13 are oriented vertically with respect to the magnetic material 12 attached to the lens holder 2 (state (A)). When the apparatus is installed horizontally, the permanent magnet 13 is rotated 90 degrees so that the poles of the permanent magnet 13 are oriented horizontally with respect to the magnetic material 12 attached to the lens holder 2 (state (B)). In order to switch the permanent magnet 13 from the state (A) to the state (B) or from the state (B) to the state (A), for example, the permanent magnet 1 is provided from the outside of the rotation stop positioning holder 34.
Apply magnetic field to 3. Here, since the rotation center 36 of the permanent magnet 13 is provided outside the permanent magnet 13, the poles of the magnetic material 12 and the permanent magnet 13 can be separated in the state (B), and the magnetic attraction acting on the lens holder 2 can be obtained. The force can be greatly reduced. With this rotation mechanism,
Even when the magneto-optical disk device shown in FIG. 3 is installed horizontally, the frequency response characteristic of the objective lens 1 is not disturbed.

In FIG. 10, since the permanent magnet 13 is switched from the state (A) to the state (B), the permanent magnet 13
Was rotated 90 degrees upward, but the permanent magnet 13 was moved downwards by 9 degrees.
You may rotate 0 degree. Further, when the magnetic material 37 is arranged on the entire rear surface of the permanent magnet 13 as shown in FIG. 11, when the permanent magnet 13 is in the state (B), the magnetic flux emitted from the permanent magnet 13 is absorbed by the magnetic material 37. As compared with the case of FIG. 10, the magnetic attraction force acting on the lens holder 2 becomes smaller. Therefore, the load acting on the support shaft 10 is further reduced, and the frequency response characteristic of the objective lens 1 can be further improved.

FIG. 12 shows another embodiment of the gravity compensation mechanism. Here, the iron core 38, the coil 39, and the AC power supply 43 form an electromagnet. The center of the iron core 38 is aligned with the center of the magnetic material 12 attached to the lens holder 2. 40a, 40
b is an electrical contact, 42a and 42b are conductive plates, and 40a and 42a, 40b and 42b constitute a microswitch. 41a and 41b are conductive plates, respectively.
Carriage cases 17 for supporting the carriages 42a and 42b.
It is a positioning member for positioning the conductive plates 42a, 42b in the + X and -X directions at the bottom.

In FIG. 12, the procedure for adjusting the positional relationship between the support shaft 10 and the bearing 11 will be described below. First, the contact 40a and the conductive plate 42 are placed in a state where the device is installed horizontally.
After contacting a, the device is installed vertically, that is, so that the X direction in the figure and the gravity direction match. At this time, the weight of the lens holder 2 acts as a contact force on the conductive plate 42a via the contact 40a. Next, when the positioning member 41a is moved in the + X direction on the carriage case 17, the contact force to the conductive plate 42a decreases and finally becomes 0. −
42a is cut off. At this time, the weight of the lens holder 2 acts as a load on the upper portion of the support shaft 10 via the bearing 11. As described above, the positioning member 4
After positioning 1a, attach it to the carriage case 17
Adhesively fixed to the bottom of. ◆ Next, the contact 40b and the conductive plate 42b are kept in contact with each other, and the coil 39 is energized,
An attractive force is applied between the magnetic material 12 attached to the lens holder 2 and the electromagnet to lift the lens holder 2 in the −X direction. When the positioning member 41b is moved in the -X direction on the carriage case 17, the contact force to the conductive plate 42b decreases and finally becomes zero, and the contact 40b and the conductive plate 42b are reached. Is cut off. At this time, spindle 1
A load acts on the lower part of 0 via the bearing 11.
After positioning the positioning member 41b as described above, it is adhesively fixed to the bottom of the carriage case 17. Based on the above adjustment, the contact 40a and the conductive plate
The spindle 10 and the bearing 11 can be prevented from contacting each other by adjusting the value of the current flowing through the coil 39 so that the conductive plate 42b and the contact 42a and the contact 40b do not contact each other.

The above is the adjustment procedure in the assembly. When the objective lens 1 is driven, the contact 40a and the conductive plate 42 are connected.
The contact between the support shaft 10 and the bearing 11 is detected by a, the contact 40b and the conductive plate 42b, and the current flowing through the coil 39 is controlled so that the support shaft 10 and the bearing 11 do not contact each other.

13 and 14 show another embodiment of the gravity compensation mechanism. FIG. 13 is a top view and FIG. 14 is a side view. The lens holder 2 has a fixing member 4 on the outside thereof.
4a, 44b, 44c to three elastic support members 45a,
It is supported by 45b and 45c. Reference numeral 46 denotes a member for moving the elastic support member 40c, which has a thread shown by a hatched portion. By rotating 46 from the outside of the carriage case 17, the elastic support member 45c is moved along the holders 47a and 47b in the direction of the arrow in the figure. ◆ When the device is installed vertically, that is, when the + X direction in the figure and the gravity direction are matched, the elastic support member 45c is in the -X direction in the figure, and when installed horizontally, 45c is + X in the figure.
Move in the direction. The elastic support member 45c is, for example, a rathe.
While observing the frequency characteristic of the objective lens 1 in real time with a measurement system including a Doppler meter or a laser displacement meter and an FFT, the frequency response characteristic is adjusted to be the best. After that, the nonmagnetic plastic plate 48 attached to the upper surface of the fixing member 44c is fixed to the holders 44a and 44b. With this elastic support member moving mechanism, it is possible to adjust the support shaft 10 and the bearing 11 so as not to contact each other.
The frequency response characteristic of the objective lens 1 is improved.

[0033]

As described above, according to the present invention, when the optical disk device is installed vertically, the frictional force generated between the support shaft of the objective lens driving device and the bearing is reduced. It is possible to prevent the deterioration of the vibration resistance while improving the durability of the.

[0034]

[Brief description of drawings]

FIG. 1 is a perspective view of an objective lens driving device that is an embodiment of the present invention.

FIG. 2 is a perspective view of the magnetic circuit in FIG.

FIG. 3 is a perspective view of a mechanism portion of a magneto-optical disk device including the objective lens driving device shown in FIG.

FIG. 4 is a diagram showing an optical path of laser light in FIG.

5 is a diagram showing the response characteristic in the focal direction of the objective lens when the magneto-optical disk device shown in FIG. 3 is installed vertically and the gravity compensation mechanism is not provided.

6 is a focal direction response characteristic diagram of an objective lens when the magneto-optical disk device shown in FIG. 3 is installed vertically and a gravity compensation mechanism is provided.

FIG. 7 is a top view showing a configuration of an example of a distance lx adjusting mechanism according to the present invention.

FIG. 8 is a side view of FIG. 7.

9 is a shape diagram of a magnetic material attached to the lens holder in FIG.

FIG. 10 is a side view of a permanent magnet rotating mechanism according to the present invention.

FIG. 11 is a side view showing another embodiment of the permanent magnet rotating mechanism according to the present invention.

FIG. 12 is a side view showing another embodiment of the gravity compensation mechanism in the present invention.

FIG. 13 is a top view showing another embodiment of the gravity compensation mechanism of the present invention.

FIG. 14 is a side view showing an embodiment of still another gravity compensation mechanism in the present invention.

FIG. 15 is a perspective view of an example of a conventional objective lens driving device.

[Explanation of symbols]

1-objective lens, 2-lens holder, 3-elastic support member, 4-focus coil, 5-tracking coil,
6-permanent magnet, 7-outer yoke, 8-inner yoke, 9-magnetic circuit fixing member, 10-support shaft, 11-bearing, 12-magnetic material, 13-permanent magnet, 14-elastic support member Fixed part, 15
-Disc-shaped information recording medium, 16-spindle motor,
17-carriage case, 18-bias magnet, 19-
Carriage case drive coil, 20-base, 21-
Yoke, 22-Permanent magnet, 23-Guide bearing, 2
4-guide rail, 25-laser passage hole, 26-semiconductor laser, 27-fixed optical system, 28-rise prism, 2
9-holes provided in the wall of the carriage case, 30-permanent magnet guide mechanism, 31-grooves provided in the guide mechanism, 32
-Distance adjusting member, 33-non-magnetic plastic plate,
34-Holder for positioning rotation stop of permanent magnet, 35-Magnetic material holding permanent magnet, 36-Center of rotation of permanent magnet,
37-magnetic material, 38-iron core, 39-coil, 40-electric contact, 41-conductive plate positioning member, 42-conductive plate, 43-AC power supply, 44-elastic support member 4
5, fixing member 45, elastic support member 46, elastic support member 40c moving member, 47-holder for holding fixing member 44c, 48-nonmagnetic plastic plate for fixing fixing member 44 to holder 47.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masamichi Ito, 502 Jinritsucho, Tsuchiura-shi, Ibaraki, Hiritsu Seisakusho Co., Ltd.Mechanical Research Laboratory (72) Inventor, Atsushi Ichikawa 2880, Kozu, Odawara-shi, Kanagawa Hitachi Storage Co., Ltd. System Division

Claims (5)

[Claims] 1. A base provided with a support shaft, a lens holder mounted so as to be vertically and rotationally movable with respect to the support shaft to hold an objective lens, and the lens holder from a fixing member on the outside thereof. At least two elastic supporting members that elastically support the lens holder and the lens movable portion composed of the elastic supporting member are vertically and rotationally driven on the upper surface of the lens holder symmetrically with respect to the support shaft. A focus coil provided, a tracking coil provided symmetrically with respect to the support shaft on a vertical surface of the upper surface of the lens holder, and a permanent magnet and a yoke provided under the lens movable portion. In an objective lens driving device equipped with a magnetic circuit, the objective lens is installed so that it coincides with the direction of gravity and the objective lens is located below the support shaft. When the magnetic material on the lens holder side, an objective lens driving device comprising a structure fitted with a permanent magnet or an electromagnet so as to face the magnetic material to the outer fixed part of the lens movable portion. 2. The objective lens driving device according to claim 1, further comprising a mechanism for adjusting a distance between the pole of the permanent magnet and the magnetic material. 3. The pole of the permanent magnet with respect to the magnetic material,
2. The objective lens driving device according to claim 1, further comprising a permanent magnet rotating mechanism that is oriented horizontally and vertically. 4. A magnetic material is attached to the lens holder side, and an electromagnet is attached to an outer fixed portion of the lens movable portion so as to face the magnetic material, and a sensor capable of detecting contact between the support shaft and the bearing is provided. The objective lens driving device according to claim 1, wherein 5. The objective lens driving device according to claim 1, further comprising a mechanism capable of moving the elastic supporting member in an axial direction.