JPH10198993A - Actuator, and optical pickup using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly attenuate the free vibration of a movable part to be generated at the time of changing over objective lenses by generating vibrations of opposite phases in a direction opposite to the vibration direction of the movable part at weights with the intertial force from the movable part to absorb vibration energies to be transmitted with beam shaped members which are of hightly damping and supporting the weights. SOLUTION: Vibration absorbing units 23, 24 consisting of beam shaped members 21 and weights 22 are provided at the outer side face of the sleeve 12 of a movable part 13 and are constituted to be vibratable in the gap of the inside of the cylindrical movable part 13. When the movable part generates a free vibration right after the changeover operation of objective lenses, the vibration absorbing units 23, 24 transmit intertial forces to the weights 22 through beam shaped members 21 with the reaction of the free vibration and the weights 22 are excited in a direction opposite to the vibration direction of the movable part 13. Thus, the movable part 13 and the weights 22 generate vibrations whose phases are opposite each other and the beam shaped members 21 formed with a highly damping material absorb vibration energies which are mutually transmitted to rapidly attenuate the free vibration of the movable part 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video disk (DVD), a DVD-ROM, a CD (compact disk), a CD-ROM, a magneto-optical disk, a phase-change optical disk, and an optical card. The present invention relates to an optical pickup used in an optical information processing device that at least reproduces information recorded on an optical information recording medium having a recording track for recording, and an actuator used in the optical pickup.

[0002]

2. Description of the Related Art In the field of optical disks exemplified by CDs, CD-ROMs, magneto-optical disks, etc., it is necessary to record information at a high density such as a DVD or a DVD-ROM in order to further increase the density. The development of an optical disk capable of recording and the development of an optical disk device for recording and reproducing information on and from this optical disk are being carried out.

In such a situation, an optical disk (for example, a CD), which has been widely used in the past,
An optical disc (eg, DVD) having a higher density recording track capable of recording a larger amount of information
An optical disk device has been proposed which enables a single optical disk device to handle a plurality of types of optical disks having recording tracks on which information is recorded.

[0004] Hereinafter, an example of such an optical disk device that can handle two types of optical disks, DVD and CD, will be described.
In this DVD / CD dual-purpose optical disk device, the DV
It is necessary to make the light beams irradiating D and CD into an optimum focusing state for each type of optical disk, and control is performed so as to be a light beam corresponding to the type of optical disk to be handled.

[0005] For example, two types of objective lenses having an aperture ratio that provides an optimum convergence state for each optical disk, and, among these two types of objective lenses, switching to an objective lens of a type corresponding to the type of optical disk to be handled. Is used in a DVD / CD optical disc device. By controlling this actuator, the light beam is controlled so as to correspond to the type of the optical disk to be handled.

FIG. 9 shows an actuator provided with an objective lens for DVD and an objective lens for CD as such an actuator and capable of switching between these two types of objective lenses. (For example, Japanese Patent Application No. 7-2931)
This actuator has a cylindrical movable part 13 having two types of objective lenses 1 and 2 and a cylindrical fixed part having a shaft 8 fitted to a sleeve 12 provided on the movable part 13. 14. With this configuration,
The movable portion 13 is movable with respect to the fixed portion 14 in the axial direction of the shaft 8 and is rotatable about the shaft 8 as a center axis.

[0007] The movable section 1 is fixed to the fixed section 14.
By using an operation in which the movable section 13 rotates about the shaft 8 with respect to the fixed section 14 among the operations that the 3 can take, the objective lens can be switched. That is, the position of the two types of objective lenses 1 and 2 provided on the movable unit 13 is changed with respect to the fixed unit 14 by rotating the movable unit 13 with respect to the fixed unit 14 about the shaft 8 as a center axis. It is possible to select a desired objective lens from the objective lenses 1 and 2 and insert it into the optical path of the light beam.

FIG. 10 shows an actuator in which the movable part 13 and the fixed part 14 are disassembled. A first drive coil pair 4 and a second drive coil pair 5 are provided on the outer surface of the movable portion 13 symmetrically with respect to the sleeve 12, respectively. A predetermined current is passed through each of the drive coils as needed, and a magnetic field is generated around the drive coils. On the other hand, a focusing magnet pair 6 and a tracking magnet pair 7 are provided on the inner surface of the fixed portion 14 at positions facing the respective drive coils, respectively, symmetrically with respect to the shaft 8.

The focus magnet pair 6 generates a magnetic interaction with a magnetic field generated around a drive coil pair provided opposite to the focus magnet pair 6 among the drive coil pairs 4 and 5 described above. In this case, the objective lenses 1 and 2 are movable in the optical axis direction, that is, the movable portion 13 is
Is magnetized so that it can move in the axial direction of

Also, a tracking magnet pair 7
When a magnetic interaction occurs between a magnetic field generated around a drive coil pair provided opposite to the tracking magnet pair 7 among the drive coil pairs 4 and 5, the objective lens 1 and the 2 is magnetized so as to be movable in a direction perpendicular to the optical axis, that is, the movable part 13 is rotatable about the shaft 8 with respect to the fixed part 14. The switching operation of the objective lenses 1 and 2 is performed by applying a kick pulse to a drive coil pair provided opposite to the tracking magnet pair 7.

Further, the movable portion 13 has a position of each drive coil described above, that is, a focusing magnet pair 6.
The magnetic piece 10 is provided at a position facing each magnet of the tracking magnet pair 7. Each of the magnetic pieces 10 forms a magnetic spring by being paired with each of the magnets described above.

FIG. 11 shows the positional relationship between each magnet constituting the magnetic spring and the magnetic piece. A magnetic attractive force acts between the focusing magnet pair 6 and the magnetic piece 10 and between the tracking magnet pair 7 and the magnetic piece 10 constituting the magnetic spring. Accordingly, when the movable portion 13 provided with the magnetic piece 10 is displaced with respect to the fixed portion 14 provided with the focusing magnet pair 6 and the tracking magnet pair 7, the movable portion 13 A restoring force for restoring the movable portion 13 to a predetermined position can be given, and the movable portion 13 can be positioned at the predetermined position in a floating state.

[0013]

However, in the conventional actuator having such a structure and the optical pickup using this actuator, the movable portion 13 is positioned by the magnetic spring as described above. Damping to the vibration of the movable part 13, that is, damping was very poor.

For example, immediately after the switching operation of the objective lens, the movable portion 13 largely vibrates freely, and along with this vibration, a large vibration also occurs in the objective lens, and it takes a long time for the vibration to attenuate and converge. Was done. Since the next operation cannot be started until this vibration converges, there are disadvantages that the time required for the objective lens to access a position from which data can be read becomes longer and the stability of the servo system deteriorates. Was.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described problems, and has been made in a case where an objective lens switching operation is performed in an actuator having a plurality of objective lenses and an optical pickup using such an actuator. It is an object of the present invention to quickly attenuate free vibrations generated in the movable part and the objective lens.

[0016]

SUMMARY OF THE INVENTION In order to achieve the above object, an actuator of the present invention and an optical pickup using the actuator emit light beams to a plurality of types of optical disks having recording tracks on which information is recorded. A plurality of objective lenses for focused irradiation; a movable section for switching the plurality of objective lenses in accordance with the optical disk to be focused and irradiated with the light beam; and a movable section including the movable section in a direction orthogonal to the direction of the recording track and the movable section. A fixed portion for supporting the objective lens in a movable state in the optical axis direction of the light beam, and a driving force for driving the objective lens in the orthogonal direction and the optical axis direction, the movable portion and the fixed portion Driving means generated between them, switching means for switching an objective lens according to the optical disk on which the light beam is focused and irradiated, and this switching means A vibrating system having a longitudinal direction in a direction orthogonal to the switching direction of the objective lens by the elastic member, one end of which is provided in the movable portion, and the other end of which is provided with the elastic member. And a weight having a predetermined mass whose resonance frequency substantially coincides with the resonance frequency of the vibration system of the movable part.

The actuator of the present invention having such a configuration and the optical pickup using the actuator attenuate the vibration generated in the movable portion as described below. When the switching operation of the objective lens is performed by the switching means described above, immediately after this switching operation, free vibration is generated in the movable portion under the influence of the vibration at the time of switching the objective lens. Under the reaction of the free vibration, the inertial force is transmitted to the weight provided at the other end of the elastic member via the elastic member having one end provided to the movable portion. Here, since the resonance frequency of the vibration system composed of the elastic member and the weight and the resonance frequency of the vibration system of the movable portion are substantially matched, the weight is moved by the inertial force transmitted from the movable portion. The vibration is applied in the direction opposite to the vibration direction. That is, the movable portion and the weight generate vibrations having phases opposite to each other. This allows the elastic members having good damping properties to absorb the vibration energy transmitted to each other, thereby rapidly damping the free vibration of the movable part.

[0018]

FIG. 1 shows an actuator according to a first embodiment of the present invention. This actuator is partially cut away so that the internal structure of the movable section 13 can be understood. FIG. 2 shows a case where the movable portion 13 is viewed from the back side of the state shown in FIG. Also, in the components of the actuator according to the embodiment of the present invention described below, FIGS.
The same reference numerals are given to components corresponding to those of the conventional actuator shown in FIG.

The actuator according to the first embodiment of the present invention comprises a movable section 13, a fixed section 14, and vibration absorbers 23 and 24. The movable part 13 and the fixed part 14 are connected to each other by the sleeve 12 provided on the movable part 13 and the shaft 8 provided on the fixed part 14 being fitted to each other.
3 is configured to be axially slidable with respect to the fixed portion 14, that is, to be rotatable around the shaft 8 and to be slidable in the axial direction of the shaft 8.

The movable portion 13 includes a lens holder 3 having a substantially cylindrical shape, a DVD objective lens 1, a CD objective lens 2, a first drive coil pair 4, a second drive coil pair 5, and a magnetic material. It comprises a piece 10 and a sleeve 12.

The DVD objective lens 1 is a light irradiating means capable of converging and irradiating a light beam on a DVD of an optical disk under conditions that are optimal for reproducing an information signal. Have conditions. The CD objective lens 2 is a light irradiating means capable of converging and irradiating a light beam on a CD of an optical disk under conditions that are optimal for reproducing an information signal. The two different types of objective lenses 1 and 2 are provided at a portion corresponding to the bottom surface on one side of the cylindrical shape. At this time, the objective lenses 1 and 2 are provided so as to have respective optical axis centers at positions equidistant from the center axis of the cylindrical shape, that is, the center of the substantially circular bottom surface.

Each of the first drive coil pair 4 and the second drive coil pair 5 is composed of two electromagnetic coils, and is supplied with a predetermined current to be connected to a later-described focus magnet pair 6 or tracking magnet pair 7. A magnetic field that gives a magnetic interaction is generated in the surroundings. By controlling the magnetic field, operation control of the movable unit 13 with respect to the fixed unit 14, that is, focus control, tracking control, and objective lens switching control are performed.

The two drive coil pairs 4 and 5 are arranged at equal intervals on a curved surface portion corresponding to the cylindrical outer surface. That is, the respective drive coil pairs are arranged axially symmetrically with respect to the central axis of the movable portion 13 (an axis passing through the center of the bottom surface and perpendicular to the bottom surface). The other drive coil pair is arranged at a position rotated by 90 degrees from the position at which the other drive coil pair is arranged.

The magnetic material pieces 10 are provided as magnetic material pieces having substantially the same size at the positions of the respective drive coils of the first drive coil pair 4 and the second drive coil pair 5 described above. . The positions where the respective magnetic material pieces 10 are provided are positions facing the respective magnets of the focusing magnet pair 6 and the tracking magnet pair 7. Each magnetic piece 10
A magnetic spring is formed in pair with each of the above magnets. That is, when the movable part 13 is displaced with respect to the fixed part 14 due to the magnetic attraction force acting between the magnet constituting the magnetic spring and the magnetic piece,
A restoring force for restoring the movable portion 13 to a predetermined position of the fixed portion 14 can be given, and the movable portion 13 can be positioned at the predetermined position in a floating state.

The sleeve 12 is a bearing member made of resin or the like having a hollow substantially tubular shape, and is for inserting and fitting the shaft 8 into the hollow portion so that the movable portion 13 can slide on the shaft. is there. One end of the sleeve 12 is provided on the bottom surface in a state where the center axis of the sleeve 12 coincides with the movable portion 13 and the outer surface of the sleeve 12 faces the inner surface of the movable portion 13. In the first embodiment of the present invention, the outer surface of the sleeve 12 is
4 are provided.

The fixing portion 14 is provided with a shaft 8, a focusing magnet pair 6, and a tracking magnet pair 7 on a substantially cylindrical yoke 9 having a closed bottom surface on one side.
And The movable part 13 is inserted into the cylindrical shape of the fixed part 14 from the opening in the fixed part 14 in a state where the shaft 8 is fitted to the sleeve 12 provided on the movable part 13, and the movable part 13 is connected to the shaft 8. It is rotatable as a central axis and slidable in the axial direction of the shaft 8. As a result, the fixed section 14 moves the objective section 1 in a state in which the objective lens 1 can be moved in a direction orthogonal to the track direction of the optical disc and in the optical axis direction of the light beam.
I support.

The yoke 9 is a substantially cylindrical member having a closed bottom surface on one side as described above. The yoke 9 is provided with a light beam transmission port 11 for transmitting a light beam and guiding the light beam to the objective lenses 1 and 2.

The shaft 8 is a rod-shaped shaft member having one end provided on a closed bottom surface portion of the fixed portion 14. At this time, the shaft 8 is provided at the center of the substantially circular closed bottom portion and in a vertical positional relationship with the bottom portion.

The focusing magnet pair 6 is a magnetic material such as a magnet provided as a pair at a position facing the one of the driving coil pairs 4 and 5 on the inner surface of the fixed portion 14. is there. When a magnetic interaction occurs with a magnetic field generated around a drive coil pair provided opposite to the focusing magnet pair 6, the focus control direction of the light beam with respect to the optical disk, that is, the optical axis of the light beam The focusing magnet pair 6 is magnetized so that the objective lenses 1 and 2 can move in the directions, and the movable portion 13 is configured to be movable in the axial direction of the shaft 8 with respect to the fixed portion 14.

The tracking magnet pair 7 faces a drive coil pair other than the drive coil pair provided at a position facing the focus magnet pair 6 among the drive coil pairs 4 and 5 on the inner surface of the fixed portion 14. It is a magnetic body such as a magnet provided as a pair at a position. When a magnetic interaction occurs with a magnetic field generated around a drive coil pair provided opposite to the tracking magnet pair 7, the magnetic interaction occurs in the tracking control direction of the light beam with respect to the optical disk, that is, with respect to the optical axis. The tracking magnet pair 7 is magnetized so that the objective lenses 1 and 2 can move in a direction perpendicular to the vertical direction, and the movable portion 13 is configured to be rotatable about the shaft 8 with respect to the fixed portion 14. I have.

The vibration absorbers 23 and 24 are constituted by providing a dynamic vibration absorber-like member on the movable part 13. For example, a dynamic vibration absorber-like member including a beam-like member 21 and a weight 22 is provided on the outer surface of the sleeve 12 in the movable portion 13, and the vibration is absorbed so as to be able to vibrate in an internal gap of the movable portion 13 having a substantially cylindrical shape. The devices 23 and 24 are constituted. By providing the vibration absorbers 23 and 24 inside the movable portion 13, it becomes possible to add a new vibration damping function to the actuator while maintaining the same size as the conventional one,
Further miniaturization of the actuator is possible.

The beam-shaped member 21 is a beam-shaped elastic member made of a material having a good damping property, for example, an elastic body such as silicone rubber, and one end is provided on the outer surface of the sleeve 12 in the movable portion 13. A weight 22 is provided at the other end. The beam-shaped member 21 has a longitudinal direction in a direction perpendicular to the center axis of the sleeve 12, that is, in a direction perpendicular to the tracking control direction and perpendicular to the focus control direction. It can vibrate in the vibration direction of the generated free vibration.

The weight 22 is a weight having a predetermined mass, and is provided at one end of the beam-shaped member 21. The mass of the weight 22 depends on the resonance frequency of the vibration system by the vibration absorbers 23 and 24 including the weight 22 and the beam-shaped member 21 and the resonance frequency of the vibration system by the movable unit 13 provided with the vibration absorbers 23 and 24. , So that
A predetermined value is set.

The weight 22, which is a component of the vibration absorbers 23 and 24 in the first embodiment of the present invention, is opposite to the center axis of the sleeve 12 on the side where the objective lenses 1 and 2 are provided. , That is, at a predetermined position that balances the center of gravity of the movable part 13, and has a mass such that the position of the center of gravity of the movable part 13 is held on the central axis of the movable part 13 described above. The movable part 13
Also used as a counterweight to balance the center of gravity. The weight 22 also functions as a counterweight, and the vibration absorber 23 and the vibration absorber 23 are provided in the internal gap of the movable portion 13 without disturbing the wiring of a flexible cable (not shown) for supplying current to the drive coil pairs 4 and 5. In the first embodiment of the present invention, two vibration absorbers 23 and 24
Is provided. By dividing the vibration absorber into two vibration absorbers 23 and 24, a flexible cable can be wired in a space 25 formed between the vibration absorber 23 and the vibration absorber 24.

In the first embodiment of the present invention having such a configuration, vibrations generated in the movable portion 13 are attenuated by the vibration absorbers 23 and 24 as described below. The vibration absorbers 23 and 24 according to the first embodiment of the present invention are configured such that when the movable portion 13 generates free vibration immediately after the objective lens switching operation, the inertia is applied to the weight 22 via the beam member 21 by the reaction of the free vibration. The force is transmitted, and the weight 22 is vibrated in a direction opposite to the vibration direction of the movable portion 13 by the inertial force. As a result, the movable portion 13 and the weight 22 generate vibrations having phases opposite to each other, and the vibration energy transmitted to each other in the beam-shaped member 21 made of a material having a good damping property is absorbed. Rapidly decays.

FIG. 3 shows a model diagram of a vibration damping mechanism by the vibration absorbers 23 and 24 according to the first embodiment of the present invention. The system 1 corresponds to a vibration system by the movable unit 13 and includes a spring K
And the dynamic element of the mass point M. The spring constant of the spring K has a value corresponding to the elasticity of the magnetic spring when the movable portion 13 freely vibrates. Further, the mass of the mass point M corresponds to the mass of the movable portion 13.

The system 2 corresponds to a vibration system by a combined vibration absorber composed of the vibration absorbers 23 and 24, and includes a spring k,
It is composed of a mass point m and a dynamic element of the damping material c. The spring constant of the spring k is the beam-like member 2 in the synthesized vibration absorber.
It has a value corresponding to the elasticity according to 1. The mass of the mass m is
This corresponds to the mass of the weight 22 in the combined vibration absorber. Further, the damping property of the damping material c corresponds to the damping property of the beam-shaped member 21 in the combined vibration absorber.

The vibration system shown in the model diagram of such a vibration damping mechanism is known as a dynamic vibration absorber, and it is possible to attenuate the vibration of the movable portion 13 by applying this to the present invention. That is, the movable part 1 indicated by the system 1
By substantially matching the resonance frequency of the vibration system by the vibration system 3 with the resonance frequency of the vibration system by the vibration absorbers 23 and 24 represented by the system 2, the vibration generated in the movable unit 13 can be attenuated by the vibration absorbers 23 and 24. It becomes possible.

As described above, the actuator according to the first embodiment of the present invention can quickly attenuate the free vibration of the movable portion 13 generated immediately after the objective lens is switched by the action of the vibration absorbers 23 and 24. . Also,
The vibration damping function can be added with the same size as the conventional one, and the weight 22 can also be used as the counterweight without hindering the wiring of the flexible cable.

FIG. 4 is a view showing a movable portion of an actuator according to another embodiment of the present invention, as viewed from the same direction as in FIG. FIG. 4A shows a movable portion of the actuator according to the second embodiment of the present invention. In the movable portion 13, the objective lenses 1 and 2 are
Only one vibration absorber 44 is provided on the outer surface of the sleeve 12 on the side where is provided.

The vibration absorber 44 has the same shape and shape as the beam member 21 and the weight 22 in the first embodiment of the present invention.
A beam member 41 and a weight 42 are made of the same material, and the direction orthogonal to the central axis of the sleeve 12 is
One end of the beam-shaped member 41 is provided on the outer surface of the sleeve 12 so as to be in the longitudinal direction of the sleeve 12, and a weight 42 is provided at the other end. It is configured to be. As in the case of the first embodiment of the present invention, by providing the vibration absorber 44 inside the movable portion 13, the vibration damping function can be added to the actuator while maintaining the same size as the conventional one, and It is possible to cope with miniaturization.

The beam-shaped member 41 is a beam-shaped elastic member made of a material having a good damping property, for example, an elastic body such as silicone rubber, and one end is provided on the outer surface of the sleeve 12 in the movable portion 13. A weight 22 is provided at the other end. The beam-shaped member 41 has a longitudinal direction in a direction orthogonal to the central axis of the sleeve 12 and can vibrate in a vibration direction of free vibration generated in the movable portion 13.

The weight 42 is a weight having a predetermined mass, and is provided at one end of the beam-shaped member 41. The mass of the weight 42 depends on the resonance frequency of the vibration system of the vibration absorber 44 including the weight 42 and the beam-shaped member 41 and the vibration frequency of the vibration absorber 4.
The predetermined value is set so that the resonance frequency of the vibration system of the movable unit 13 provided with the reference numeral 4 substantially coincides with the resonance frequency.

In the second embodiment of the present invention having such a configuration, the vibration generated in the movable portion 13 is attenuated by the vibration absorber 44 as described below. As in the case of the first embodiment of the present invention, in the second embodiment of the present invention, when the movable portion 13 generates free vibration immediately after the objective lens switching operation, the beam-like member is reacted by the free vibration. The inertia force is transmitted to the weight 42 via 41, and the weight 42 is vibrated in the direction opposite to the vibration direction of the movable portion 13 by the inertia force. Thereby, the movable part 1
3 and the weight 42 generate vibrations having phases opposite to each other, and the beam-like member 41 made of a material having a good damping property absorbs the vibration energy transmitted to each other, and the free vibration of the movable portion 13 is rapidly attenuated. .

As described above, the actuator according to the second embodiment of the present invention, as in the case of the first embodiment of the present invention, absorbs the free vibration of the movable section 13 that occurs immediately after the switching of the objective lens. By the action of 44, it is possible to rapidly attenuate.

Unlike the vibration absorbers 23 and 24 according to the first embodiment of the present invention, in the vibration absorber 44 according to the second embodiment of the present invention, the weight 42 which is a component of the vibration absorber 44 is a counterweight. Is not shared. Therefore, in the second embodiment of the present invention, the weight and the arrangement position of the weight 42 are not limited as much as in the first embodiment, so that the second embodiment is easier than in the first embodiment. The vibration absorber 44 can be provided in the movable part 13. Although not shown, a counterweight for balancing the center of gravity of the movable portion 13 is provided separately from the weight 42.

FIG. 4B shows a movable portion of the actuator according to the third embodiment of the present invention. In the movable section 13 in the third embodiment, only one vibration absorber 45 is provided on the outer surface of the sleeve 12 on the opposite side of the center axis of the sleeve 12 from the objective lenses 1 and 2.

The vibration absorber 45 is made of a beam-like member 4 made of the same material as the beam-like member 21 in the first embodiment of the present invention.
6 and 47, and a weight 48 having the same material and shape as the weight 22. One end of each of the beam members 46 and 47 is provided on the outer surface of the sleeve 12, and the other end of the beam members 46 and 47 is common to the other ends of the beam members 46 and 47. By providing the weights 48, the shape is formed in which a space 49 is provided between the beam-shaped members 46 and 47. This space 4
Reference numeral 9 is used for wiring a flexible cable (not shown). Further, the vibration absorber 45 can vibrate in an internal gap of the movable portion 13 having a substantially cylindrical shape. By providing the vibration absorber 45 inside the movable portion 13, the vibration damping function can be provided to the actuator while maintaining the same size as the conventional one. It can be added and can be adapted to miniaturization of the actuator.

The beam-shaped members 46 and 47 are beam-shaped elastic members made of an elastic material such as silicone rubber having a good damping property.
One end is provided on the outer surface of the second and a weight 48 is provided on the other end. The beam members 46 and 47 are
2 has a longitudinal direction in the direction orthogonal to the central axis of the sleeve 12 in the vicinity of one end provided therein.
It can vibrate in the vibration direction of the free vibration generated in the movable portion 13.

The weight 48 is a weight having a predetermined mass, and is provided at one end of the beam members 46 and 47. The mass of the weight 48 is determined by the resonance frequency of the vibration system by the vibration absorber 45 including the weight 48 and the beam-shaped members 46 and 47, and the resonance frequency of the vibration system by the movable unit 13 provided with the vibration absorber 45. A predetermined value is set so as to have a substantially matching relationship.

In the third embodiment of the present invention having such a configuration, the vibration generated in the movable portion 13 is attenuated by the vibration absorber 45 as described below. As in the case of the first embodiment of the present invention, in the third embodiment of the present invention, when the movable portion 13 generates free vibration immediately after the objective lens switching operation, the beam-like member is reacted by the free vibration. The inertia force is transmitted to the weight 48 via 46 and 47, and the inertia force causes the weight 48 to move the movable portion 13
The vibration is applied in the direction opposite to the vibration direction. As a result, the movable portion 13 and the weight 48 generate vibrations having phases opposite to each other, and the beam-shaped members 46 and 4 made of a material having a good damping property.
7, the vibration energy transmitted to each other is absorbed, and the free vibration of the movable portion 13 is rapidly attenuated.

The weight 48, which is a component of the vibration absorber 45 in the third embodiment of the present invention, is
The movable unit 13 is provided at a position opposite to the side on which the objective lenses 1 and 2 are provided with respect to the center axis of the movable unit 2, that is, at a predetermined position that balances the center of gravity of the movable unit 13. Also used as a counterweight to balance the center of gravity. The third embodiment of the present invention is designed such that the weight 48 also functions as a counterweight and that the vibration absorber 45 is provided in the internal gap of the movable portion 13 without disturbing the wiring of a flexible cable (not shown). The space 49 is formed in the vibration absorber 45 according to the embodiment.

As described above, the actuator according to the third embodiment of the present invention, as in the case of the first embodiment of the present invention, absorbs the free vibration of the movable portion 13 that occurs immediately after the switching of the objective lens. It is possible to rapidly attenuate by the action of 45. Further, the vibration damping function can be added with the same size as the conventional one, and the weight 48 can also be used as the counterweight without disturbing the wiring of the flexible cable.

Next, the focus control operation, the tracking control operation, and the objective lens switching operation in the actuator according to the first to third embodiments of the present invention will be described.

FIG. 5 shows the drive coil pairs 4 and 5 and the magnet pair 6 for explaining the focus control operation and the tracking control operation in the actuator of the present invention.
7 and 7 are shown.

The focus control is performed by using the focus magnet pair 6 magnetized in the axial direction of the shaft 8 and using the first drive coil pair 4 or the second drive coil pair 4 in a positional relationship facing the focus magnet pair 6. This is performed by passing a predetermined weak current through any one of the driving coil pairs 5.

In FIG. 5, the first drive coil pair 4
Is located at a position facing the focusing magnet pair 6. The weak current is applied to the first drive coil pair 4 to cause an interaction with the magnetic field generated by the focusing magnet pair 6, thereby causing the first drive coil pair 4 to move in the axial direction of the shaft 8, that is, in the first drive coil pair 4. A force is generated in the direction shown by arrow Z. The generated force causes the movable portion 13 provided with the first drive coil pair 4 to move in the axial direction of the shaft 8 with respect to the fixed portion 14 provided with the focusing magnet pair 6.

By controlling the movement amount and the movement direction, the movement amount and the movement direction of the objective lenses 1 and 2 provided on the movable portion 13 with respect to the fixed portion 14 are controlled. Focus control of the light beam being focused and irradiated is performed. The vibration absorbers 23, 24, 44, and 45 according to the embodiment of the present invention.
Are provided in the gap inside the movable portion 13,
This does not hinder the focus control operation.

The tracking control is performed by using a tracking magnet pair 7 magnetized in a direction perpendicular to the axial direction of the shaft 8 and using a first drive having a positional relationship facing the tracking magnet pair 7. This is performed by passing a predetermined weak current through either the coil pair 4 or the second drive coil pair 5.

In FIG. 5, the second drive coil pair 5
Is located at a position facing the tracking magnet pair 7. The weak current is applied to the second drive coil pair 5 to cause an interaction with the magnetic field generated by the tracking magnet pair 7, so that the second drive coil pair 5 has an axial direction Z of the shaft 8. Generates force in a perpendicular direction. Due to the generated force, the fixed portion 1 provided with the tracking magnet pair 7 is provided.
4, the movable part 13 provided with the second drive coil pair 5 is moved in a direction about the shaft 8 as a central axis, that is,
Rotate in the direction shown by arrow M.

By controlling the amount and direction of the rotation, the amount and direction of movement of the objective lenses 1 and 2 provided on the movable portion 13 with respect to the fixed portion 14 are controlled. The tracking control of the light beam focused and irradiated is performed. The vibration absorbers 23, 24, 44, and 45 according to the embodiment of the present invention.
Are provided in the gap inside the movable portion 13,
It does not hinder the tracking control operation.

An actuator that performs such a control operation installs one of the objective lenses 1 and 2 provided on the movable portion 13 in the optical path of the light beam by utilizing the above-described tracking control operation. Thus, the switching operation of the objective lens can be performed.

FIG. 6 shows the positional relationship between the drive coil pairs 4 and 5 and the magnet pairs 6 and 7 to explain the switching operation of the objective lens in the actuator of the present invention. FIG. 7 shows the time change of the current flowing through the drive coil during the objective lens switching operation.

For example, when the objective lens 2 is arranged in the optical path of the light beam irradiated on the optical disk, the second driving coil pair 5 is opposed to the tracking magnet pair 7 and the focusing magnet pair 6 It is assumed that the first drive coil pair 4 is opposed. FIG. 6A shows the positional relationship between each magnet pair and the drive coil pair at this time.

Here, at time t1 shown in FIG. 7, a current having a predetermined value in the direction indicated by the arrow i in FIG. 6 is supplied to the second drive coil pair 5 arranged opposite to the tracking magnet pair 7. Is done. Then, the second drive coil pair 5 interacts with the magnetic field generated by the tracking magnet pair 7 in the portions 5A and 5B having a positional relationship parallel to the axial direction z of the shaft 8, thereby generating an arrow. It receives the force indicated by f. In response to this force, a force is generated in the second drive coil pair 5 in the direction indicated by arrow m, and the movable unit 13 provided with the second drive coil pair 5
Start rotation in the direction indicated by.

The rotation of the movable portion 13 moves the second drive coil pair 5 with respect to the tracking magnet pair 7. At time t2 during this movement, a portion 5B of the second drive coil pair faces the S pole of the tracking magnet pair 7. At this time point t2, the current supplied to the second drive coil pair 5 is reversed to the opposite polarity as shown in FIG. FIG. 6 shows the positional relationship between each magnet pair and the drive coil pair at this time.
(B).

By the polarity reversal of the current, an arrow which moves the second drive coil pair 5 away from the tracking magnet pair 7 between a portion 5 B of the second drive coil pair 5 and the S pole of the tracking magnet pair 7. f
A force is generated in the direction indicated by. Under this force, the second drive coil pair 5 further moves toward the focusing magnet pair 6. As a result, the movable unit 13 continues to rotate in the direction indicated by the arrow m with respect to the fixed unit 14.
FIG. 6C shows the positional relationship between each magnet pair and the drive coil pair at this time.

At time t3 during the rotation, the current supply to the second drive coil pair 5 is stopped, but after time t3, the rotation of the movable portion 13 is continued by the inertial force. Due to this rotation, the second drive coil pair 5 facing the tracking magnet pair 7 is arranged at a position facing the focusing magnet pair 6 and the first driving coil pair facing the focusing magnet pair 6. When the position 4 is located at a position facing the tracking magnet pair 7, the rotation of the movable portion 13 with respect to the fixed portion 14 is stopped by the action of the magnetic spring between the magnetic piece 10 and each magnet pair. Is done. FIG. 6 shows the positional relationship between each magnet pair and the drive coil pair at this time.
(D). When such a positional relationship is established, the objective lens 1 is provided on the movable part 13 so that the objective lens 1 is arranged in place of the objective lens 2 in the optical path of the light beam irradiated on the optical disc. It is assumed that

In this way, the movable part 13 is
, The objective lens 1 is disposed in the optical path of the light beam instead of the objective lens 2, and the objective lens is switched. In addition, along with the switching of the objective lens, the combination of each drive coil pair 4 and 5 and the magnet pair 6 and 7 facing the drive coil pair is also switched. Note that all of the vibration absorbers 23, 24, 44, and 45 in the embodiment of the present invention are provided in the gaps inside the movable unit 13, and do not hinder the objective lens switching operation.

If the objective lens 1 is arranged in the optical path of the light beam, the first driving coil pair 4 faces the tracking magnet pair 7, and the second driving coil pair 5 faces the focusing magnet pair 6. In this state, the tracking magnet pair 7 related to the objective lens switching operation is in a positional relationship facing the first drive coil pair 4 as described above. Therefore, in such a state of the positional relationship, the objective lens 1
When the operation of switching the objective lens from the first lens to the second objective lens is performed, the switching operation of the objective lens is performed in the same manner as described above by supplying a current with a predetermined value and polarity to the first drive coil pair 4.

As described above, the actuator of the present invention
As described above, it is possible to attenuate the free vibration generated at the time of switching the objective lens generated in the movable portion 13, and
The rotation and sliding of the movable unit 13 with respect to the fixed unit 14 and the operation of switching the objective lens can be executed without any trouble.

Next, an optical pickup using the actuator according to the first to third embodiments of the present invention will be described. FIG. 8 shows a cross section of the actuator according to the first to third embodiments of the present invention, an optical system using the optical frame 15, and an electrical connection relationship with the signal processing unit 81 and the actuator driver 82.

The optical frame 15 includes a laser diode 31, a collimator lens 32, beam splitters 33 and 34, detection lenses 35 and 36, and a photodetector 3.
7 and 38 are provided.

In the optical frame 15, a divergent light beam is generated from the laser diode 31 which is the source of the light beam. The generated light beam is converted into parallel light by the collimator lens 32, and then supplied to the above-described actuator. In this actuator, the supplied light beam is focused by the objective lens 1 or 2 and irradiates the optical disk 39.

As an objective lens for focusing a light beam,
When the optical disk 39 irradiated with the light beam is a DVD, the DVD objective lens 1 is switched, and when the optical disk 39 irradiated with the light beam is a CD, the CD objective lens 2 is switched by an objective lens switching operation described later. And
A light beam is selectively supplied from the optical frame 15 to irradiate the optical disc 39.

The reflected light from the optical disk 39 generated by irradiating the optical disk 39 with the light beam is returned to the optical frame 15 after being made parallel by the objective lens 1 or 2. The light beam returned to the optical frame 15 enters the beam splitters 33 and 34. Each of the beam splitters 33 and 34 separates the incident light beam into two light beams traveling in different directions.

One light beam split by the beam splitter 33 enters the beam splitter 34, and the other light beam enters the detection lens 35. Detection lens 21
Focuses the incident light beam and forms a photodetector 3
Irradiate 7. The photodetector 37 converts a light signal of the light beam into an electric signal in a light detection unit arranged in a predetermined shape, thereby controlling a focus control state of the light beam applied to the optical disc 39 and the optical disc 3.
9 is detected. This electrical signal
The signal is transmitted to the signal processing unit 81 of the optical disk device.

One of the light beams split by the beam splitter 34 enters a detection lens 36. Detection lens 3
Reference numeral 6 focuses the incident light beam and irradiates the photodetector 38 with the light. The photodetector 38 converts a light signal of the light beam into an electric signal by a light detection unit arranged in a predetermined shape, thereby controlling a tracking control state of the light beam applied to the optical disc 39 and information recorded on the optical disc 39. Detect signal. This electric signal is transmitted to the signal processing unit 81 of the optical disk device.

The signal processing unit 81 of the optical disk device receives the electric signals transmitted from the photodetectors 37 and 38, and controls the focus control state and the tracking control state of the light beam applied to the optical disk 39, and the switching state of the objective lens. By transmitting a control signal to the actuator driver 82 so as to irradiate the optical disk 39 with the light beam in a predetermined state, the drive control of the objective lenses 1 and 2 in the actuator and the optical disk device mounted on the optical disk device are detected. The switching control of the objective lens corresponding to the type of the optical disc 39 is performed.

The actuator driver 82 receives the control signal transmitted from the signal processing section 81, and supplies a predetermined electric signal based on the control content represented by the control signal to a predetermined portion of the actuator, thereby causing the actuator to operate. Focusing of objective lenses 1 and 2
Driving in the tracking direction and switching of the objective lens corresponding to the type of the optical disk 39 mounted on the optical disk device are performed.

The optical pickup according to the embodiment of the present invention having the above-described structure is provided with the movable unit 1 by the actuator according to the first to third embodiments of the present invention.
Since the vibration of No. 3 is attenuated, it is possible to quickly shift to the next operation after the objective lens switching operation, and it is possible to perform stable light beam irradiation with little influence of the vibration from the movable unit 13.

Although the actuator according to the embodiment of the present invention has two different types of objective lenses 1 and 2 in the movable portion 13, the number and type of objective lenses provided in the movable portion 13 are not limited to this. It is not something that is
When the present invention is applied to an actuator having only one type of objective lens, stable light beam irradiation with less influence of vibration can be realized.
When the present invention is applied to an actuator having more than one type of objective lens, the transition to the next operation after the objective lens switching operation can be performed quickly and stable light beam irradiation with less influence of vibration is performed. It is possible. Alternatively, the optical frame 15 may be a small-sized optical frame, and may be configured to be included in the actuator according to the embodiment of the present invention, which includes a movable portion, a fixed portion, and a vibration absorber.

[0083]

As described above, the actuator according to the present invention and the optical pickup using this actuator can quickly attenuate the free vibration of the movable portion that occurs immediately after the switching of the objective lens. Since the transition to the next operation after the operation can be performed quickly, the time required for the objective lens to access the position where data can be read can be reduced, and stable servo system operation can be obtained. It is.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view showing an actuator according to a first embodiment of the present invention.

FIG. 2 is a view showing a movable portion of the actuator according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a vibration system of the actuator according to the first embodiment of the present invention.

FIG. 4 is a view showing a movable portion of an actuator according to another embodiment of the present invention.

FIG. 5 is a diagram showing a positional relationship between a drive coil pair and a magnet pair of the actuator according to the embodiment of the present invention.

FIG. 6 is a view for explaining an objective lens switching operation of the actuator according to the embodiment of the present invention.

FIG. 7 is a diagram showing a time waveform of a current supplied during an objective lens switching operation of the actuator according to the embodiment of the present invention.

FIG. 8 is a view showing the relationship between an optical pickup using an actuator according to an embodiment of the present invention and the surroundings.

FIG. 9 is a perspective view showing a conventional actuator.

FIG. 10 is an exploded view showing a conventional actuator.

FIG. 11 is a view showing a positional relationship between a magnet pair and a magnetic piece in a conventional actuator.

[Explanation of symbols]

 1, 2 Light irradiation means (objective lens) 4, 5 Driving coil pair 6 Focusing magnet pair 7 Tracking magnet pair 8 Shaft 10 Magnetic piece 12 Sleeve 13 Movable part 14 Fixed part 15 Optical frame 21 Elastic member (beam member) 22 Weight (weight) 23, 24 Vibration absorber 31 Supply means (laser diode) 37, 38 Detection means (photodetector) 39 Optical information recording medium (optical disc) 81 Signal processing unit 82 Actuator driver

Claims (8)

[Claims] 1. A plurality of light irradiating means for focusing and irradiating a plurality of types of optical information recording media having recording tracks on which information is recorded, with a plurality of light irradiating means; A movable portion provided switchably in accordance with the type of the optical information recording medium to be focused and irradiated, and the movable portion is provided in the direction perpendicular to the track direction of the optical information recording medium and in the optical axis direction of the light beam. A fixing unit that supports the light irradiation unit in a movable state, and a driving unit that generates a driving force for moving the objective lens in the orthogonal direction and the optical axis direction between the movable unit and the fixing unit. Switching means for switching the light irradiating means in accordance with the type of the optical information recording medium on which the light beam is focused and radiated; and a longitudinal direction in a direction orthogonal to the switching direction of the light irradiating means by the switching means. An elastic member having one end provided on the movable portion; and a resonance frequency of a vibration system constituted by the elastic member provided on the other end of the elastic member, and the elastic member. And a weight having a predetermined mass that substantially matches the relationship. 2. A plurality of objective lenses for focusing and irradiating a plurality of types of optical disks having recording tracks on which information is recorded, and a plurality of types of optical disks for focusing and irradiating the plurality of objective lenses with the light beams. A movable portion provided so as to be switchable in accordance with the following: a fixed portion supporting the movable portion in a state in which the objective lens is movable in a direction perpendicular to the direction of the recording track and in an optical axis direction of the light beam; Driving means for generating a driving force for driving the objective lens in the direction and the optical axis direction, between the movable part and the fixed part, and an objective lens according to a type of an optical disc for converging and irradiating the light beam. Switching means for switching, an elastic portion having a longitudinal direction in a direction orthogonal to a switching direction of the objective lens by the switching means, one end of which is provided in the movable portion And a weight provided at the other end of the elastic member and having a predetermined mass such that a resonance frequency of a vibration system constituted by the elastic member substantially matches a resonance frequency of the vibration system by the movable portion. An actuator comprising: 3. A plurality of objective lenses for converging and irradiating a plurality of types of optical discs having recording tracks on which information for recording information signals is recorded with a light beam; The plurality of objective lenses are provided in a state where each objective lens has an optical axis center at a position equidistant from the central axis, and has a central axis substantially coincident with the central axis, and is provided on an inner surface of the substantially cylindrical shape. A movable portion provided with a substantially tubular bearing member having an opposed outer surface, and a shaft member fitted in the bearing member so as to be slidable with the bearing member are provided. A fixed member that supports the movable portion in a state in which it can slide in the rotation direction and the axial direction of the shaft member, and enables the objective lens to move in a direction orthogonal to the recording track direction and in the optical axis direction of the light beam. Part and the straight Driving means for generating a driving force for driving the objective lens in the intersection direction and the optical axis direction, between the movable portion and the fixed portion, and, depending on the type of an optical disc that focuses and irradiates the light beam, Switching means for switching the objective lens by sliding the movable portion in the rotation direction; and a longitudinal direction in a direction orthogonal to the rotation direction in which the switching of the objective lens is performed by the switching means; An elastic member provided on the outer surface of the bearing member, and a resonance frequency of a vibration system provided at the other end of the elastic member is substantially equal to a resonance frequency of the vibration system by the movable portion. And a weight having a predetermined mass that is in a matching relationship. 4. A plurality of objective lenses for converging and irradiating a plurality of types of optical discs having recording tracks on which information is recorded with a light beam, a substantially cylindrical shape, and equidistant from a center axis of the substantially cylindrical shape. The plurality of objective lenses are provided in a state where each objective lens has an optical axis center at a position, and has a central axis substantially coinciding with the central axis, and has an outer surface facing an inner surface of the substantially cylindrical shape. A movable portion provided with a substantially cylindrical bearing member in a state where the shaft member is provided, and a shaft member fitted with the bearing member so as to be slidable with the shaft member, and a rotation direction and a shaft centered on the shaft member. A fixed portion that supports the movable portion so as to be slidable in the axial direction of the member, and that enables the objective lens to move in a direction perpendicular to the direction of the recording track and in an optical axis direction of the light beam; Direction and the optical axis A driving unit for generating a driving force for driving the objective lens in the direction between the movable unit and the fixed unit; and rotating the movable unit according to a type of an optical disc that focuses and irradiates the light beam. A switching means for switching the objective lens by sliding in the direction, a longitudinal direction in a direction orthogonal to the rotation direction in which the switching of the objective lens is performed by the switching means, one end of which is outside the bearing member. An elastic member provided on the side surface, and a resonance frequency of a vibration system provided at the other end of the elastic member and constituted by the elastic member substantially coincides with a resonance frequency of the vibration system by the movable portion. And a weight having a predetermined mass that holds the position of the center of gravity of the movable portion on the central axis. 5. A plurality of light irradiating means for converging and irradiating a plurality of types of optical information recording media having a recording track on which information is recorded with a light beam, and selectively irradiating the plurality of light irradiating means. A supply unit that supplies a light beam, a movable unit that switches the plurality of light irradiation units in accordance with the type of an optical information recording medium that converges and irradiates the light beam, A fixing unit that supports the light irradiation unit in a movable state in a direction orthogonal to the track direction of the information recording medium and in an optical axis direction of the light beam; and the light irradiation unit in the orthogonal direction and the optical axis direction. A driving unit for generating a driving force for driving between the movable unit and the fixed unit, and detecting an information signal recorded on the optical information recording medium from a light beam reflected by the optical information recording medium Detecting means, switching means for switching the light irradiating means in accordance with the type of optical information recording medium for converging and irradiating the light beam, and a longitudinal direction in a direction orthogonal to the switching direction of the light irradiating means by the switching means. An elastic member having one end provided on the movable portion; and a resonance frequency of a vibration system constituted by the elastic member provided on the other end of the elastic member, and the elastic member. An optical pickup comprising: a weight having a predetermined mass, which has a relationship substantially corresponding to: 6. A plurality of objective lenses for converging and irradiating a plurality of types of optical discs having recording tracks on which information is recorded with a light beam, and a supply for selectively supplying a light beam to the plurality of objective lenses. Means, a movable section for switching the plurality of objective lenses in accordance with the type of an optical disc for converging and irradiating the light beam, and a light beam of the light beam in a direction orthogonal to the direction of the recording track. A fixed portion that supports the objective lens in a movable state in the axial direction, and a driving force for driving the objective lens in the orthogonal direction and the optical axis direction is generated between the movable portion and the fixed portion. Driving means, detecting means for detecting an information signal recorded on the optical disc from a light beam reflected by the optical disc, and optical disc for converging and irradiating the light beam Switching means for switching the objective lens according to the type of: an elastic member having a longitudinal direction in a direction orthogonal to the switching direction of the objective lens by the switching means, one end of which is provided on the movable portion; A weight provided at the other end of the member and having a predetermined mass such that a resonance frequency of a vibration system constituted by the elastic member substantially matches a resonance frequency of the vibration system by the movable portion. An optical pickup characterized by the following. 7. A plurality of objective lenses for converging and irradiating a plurality of types of optical discs having recording tracks on which information is recorded with a light beam, and a supply for selectively supplying the plurality of objective lenses with a light beam. A plurality of objective lenses having a substantially cylindrical shape, and each objective lens having an optical axis center at a position equidistant from the central axis of the substantially cylindrical shape, and being substantially coincident with the central axis. A movable portion having a substantially cylindrical bearing member having an outer surface facing the substantially cylindrical inner surface, and a movable member fitted with the bearing member so as to be able to slide with the bearing member. A shaft member is provided, and the movable member is pivotally supported in a state of being slidable in the rotation direction about the shaft member and in the axial direction of the shaft member, and in a direction perpendicular to the direction of the recording track and the light. Beam optical axis direction A driving unit that generates the driving force for driving the objective lens in the orthogonal direction and the optical axis direction between the movable unit and the fixing unit; Detecting means for detecting an information signal recorded on the optical disc from a light beam reflected by the optical disc; and sliding the movable portion in the rotating direction according to the type of the optical disc for converging and irradiating the light beam. A switching means for switching the objective lens by the switching means; a longitudinal direction in a direction orthogonal to the rotating direction in which the switching of the objective lens is performed by the switching means, and one end provided on an outer surface of the bearing member. A member and the other end of the elastic member, the resonance frequency of a vibration system constituted by the elastic member substantially coincides with the resonance frequency of the vibration system by the movable part. An optical pickup comprising: a weight having a predetermined mass. 8. A plurality of objective lenses for focusing and irradiating a plurality of types of optical discs having recording tracks on which information is recorded with a light beam, and a supply for selectively supplying the plurality of objective lenses with a light beam. A plurality of objective lenses having a substantially cylindrical shape, and each objective lens having an optical axis center at a position equidistant from the central axis of the substantially cylindrical shape, and being substantially coincident with the central axis. A movable portion having a substantially cylindrical bearing member having an outer surface facing the substantially cylindrical inner surface, and a movable member fitted with the bearing member so as to be able to slide with the bearing member. A shaft member is provided, and the movable portion is pivotally supported in a state of being slidable in the rotation direction around the shaft member and in the axial direction of the shaft member. Beam optical axis direction A driving unit that generates the driving force for driving the objective lens in the orthogonal direction and the optical axis direction between the movable unit and the fixing unit; Detecting means for detecting an information signal recorded on the optical disc from a light beam reflected by the optical disc; and sliding the movable portion in the rotating direction according to the type of the optical disc for converging and irradiating the light beam. A switching means for switching the objective lens by the switching means; a longitudinal direction in a direction orthogonal to the rotating direction in which the switching of the objective lens is performed by the switching means, and one end provided on an outer surface of the bearing member. A member and the other end of the elastic member, the resonance frequency of a vibration system constituted by the elastic member substantially coincides with the resonance frequency of the vibration system by the movable part. And a weight having a predetermined mass.