JPH0620290A - Objective driver - Google Patents

Abstract

PURPOSE:To obtain an objective lens driver having no possibility of breakage by fixing a diamagnetic material to a holder and disposing in a field produced by a coil thereby offsetting attraction force. CONSTITUTION:When current is fed to a coil 5, a yoke 4 becomes an electromagnet having polarity in Z direction. In a field produced by the coil 5 and a yoke 6, a diamagnetic material 3 exhibits reverse polarity because of Meissner effect of superconducting material and repelling force is produced against the yoke 6. The repelling force moves a movable section in Z direction to deform a wire 8 resiliently and thereby the movable section moves substantially in parallel with Z direction up to an equilibrium position. When current flow through the coil 5 is altered, repelling force varies to cause variation in the moving amount of the movable section. Upon interruption of current flow through the coil 5, the wire 8 is recovered from resilient deformation and the movable body returns to original position. Since the diamagnetic material 3 exhibits magnetism only under magnetic field, it is not attracted to a ferromagnetic component such as the yoke 4. Consquently, a magnet is not attracted to a magnetic member during assemblage and an objective lens driver is protected against breakage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for recording / reproducing information on / from a disc-shaped recording medium, and more particularly to an objective lens driving device therefor.

[0002]

2. Description of the Related Art In general, currently used optical disk reproducing apparatuses rotate a disk at a predetermined number of revolutions and focus laser light emitted from a laser diode on the disk by an objective lens. The fluctuation of the reflected light from the disc is converted into an electric signal by a photo detector, and the information recorded on the disc is reproduced. At this time, an objective lens driving device is required to move the objective lens in accordance with the movement of the disc in order to always focus the laser light on the disc.

A conventional objective lens driving device will be described below. FIG. 6 is a sectional view of a conventional objective lens driving device,
FIG. 7 is a perspective view thereof. 6 and 7, the objective lens 11 and the two magnets 13 magnetized in the Y direction are bonded to the holder 12 to form a movable part. Both ends of the four spring wires 18 are fixed to the holder 12 and the fixed member 17, and the movable portion is movably supported in the Z direction with respect to the fixed member 17 by elastic deformation of the wires 18. A coil 15 is wound around each of the two yokes 14 fixed to the base 16. The fixing member 17 is fixed to the base 16 to complete the objective lens driving device.

In FIG. 6, a magnetic circuit is constituted by a yoke 14 and a base 16 made of a ferromagnetic material and a magnet 13 magnetized in the Y direction so as to face each other with different polarities, and a magnetic field shown by an arrow 19 is generated. To do. Since the coil 15 is wound so that the current flows in the X direction in the magnetic field, a force is generated between the magnet 13 and the coil 15 by the magnetic field in the magnetic circuit when the current is passed through the coil 15. This force becomes a force for moving the magnet 13 in the Z direction, the wire 18 is elastically deformed, and the movable portion moves substantially parallel to the Z direction.

[0005]

However, in the above-mentioned conventional configuration, when the objective lens driving device is assembled, particularly when the fixed member having the movable portion attached by the four wires is attached to the base, the magnet is used as the yoke or the yoke. The wire may be plastically deformed by being attracted to another ferromagnetic material component such as the base, or the movable part may collide with another component and damage the holder or the like.

In addition, when the coil is not energized, the movable portion can freely move within the deformation range of the wire by external vibration, so that it may hit the base or the yoke. If a large vibration is applied from the outside, the movable part may strongly collide with other parts such as the base and be damaged.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an objective lens driving device that is free from damage.

[0008]

In order to solve the above problems, an objective lens driving device of a first invention is a holder to which an optical system including an objective lens is attached, a fixing member,
A support member that connects the holder and the fixed member and movably supports the holder with respect to the fixed member, a coil attached to the fixed member, and a holder attached and placed in a magnetic field generated by the coil. It is made of diamagnetic material.

In the objective lens driving device of the second invention, the holder to which the optical system including the objective lens is attached, the magnet attached to the holder, the fixing member, and the holder and the fixing member are connected to each other. And a supporting member that movably supports the holder with respect to the fixing member, a yoke attached to the fixing member, and a coil wound around the yoke.

[0010]

According to the first aspect of the present invention, since the driving force is generated by the diamagnetic material, the attraction force is not generated unlike the one using the magnet. Further, according to the second aspect of the present invention, the movement of the holder is fixed by the attractive force of the magnet and the yoke when the coil is not energized.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An objective lens driving device according to an embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 3 are sectional views of an objective lens driving device showing a first embodiment of the present invention, and FIG. 2 is a perspective view thereof. The objective lens 1 and two diamagnetic bodies 3 made of a superconducting material are bonded to the holder 2 to form a movable part. A coil 5 is wound around each of two yokes 4 made of a ferromagnetic material so as to be perpendicular to the Z axis, and is fixed to a base 6. Both ends of the four spring wires 8 are attached so as to connect the holder 2 and the fixing member 7, respectively, and the elastic deformation of the wire 18 allows the movable portion to move in the Z direction with respect to the fixing member 17. It is supported.

In FIG. 1, when a current is passed through the coil 5, the yoke 4 becomes an electromagnet having a polarity in the Z direction. Coil 5,
In the magnetic field generated by the yoke 6, the diamagnetic body 3 exhibits opposite magnetism due to the Meissner effect of the superconducting material, and a repulsive force is generated between the diamagnetic body 3 and the yoke 6. This repulsive force moves the movable part to Z
The wire 8 is elastically deformed and the movable part moves substantially parallel to the Z direction. Repulsive force due to magnetic field and wire 8
The movable part moves to a position where the elastic forces of the two are balanced, and the state shown in FIG. 3 is obtained. By changing the current to coil 5,
The strength of the magnetic field generated by the coil 5 changes, the repulsive force with the diamagnetic body 3 changes, and the amount of movement of the movable part in the Z direction changes. When the current to the coil 5 is stopped, the elastic deformation of the wire 8 returns and the state shown in FIG. 1 is restored. Since the diamagnetic material 3 does not exhibit magnetism unless it is in a magnetic field, it is not attracted to a ferromagnetic material such as a yoke.

FIG. 4 is a sectional view of an objective lens driving device showing a second embodiment of the present invention, and FIG. 5 is a perspective view thereof. The objective lens 1 and the magnet 9 magnetized in the Z direction are bonded to the holder 2 to form a movable portion. Each of the two yokes 4 made of a ferromagnetic material fixed to the base 6 has a Z
The coil 5 is wound so as to be perpendicular to the axis. Four wires 8 having a spring property are attached so as to connect the fixing member 7 fixed to the base 6 and the holder 2,
The movable portion is movably supported in the Z direction with respect to the fixed member 7 by the elastic deformation of the wire 18. These configurations are the first
This is equivalent to the one described in the embodiment.

FIG. 4 shows a non-operating state, that is, a state in which the coil 5 is not energized. At this time, the magnet 9 is attracted to the yoke 4,
The movement of the movable part is fixed. During operation, a current is passed through the coil 5, and the yoke 4 becomes an electromagnet having a polarity in the Z direction. When a current is passed so that the surface of the yoke 4 facing the magnet 9 has the same pole as the magnet 9, a repulsive force is generated during this. When the current is increased and the repulsive force becomes larger than the attractive force of the magnet 9 and the yoke 4, the movable part moves in the Z direction. As in the case of the first embodiment described with reference to FIG. 3, the repulsive force between the electromagnet of the yoke 4 and the magnet 9 is changed by changing the current to control the amount of movement of the movable part in the Z direction. You can
When the current is stopped, the repulsive force disappears, and the magnet 9 is attracted to the yoke 4 again, and the state shown in FIG. 4 is obtained.

[0016]

As described above, according to the first aspect of the present invention, since the diamagnetic material is used for driving, the attractive force by the magnet is not generated. There is no risk that the wire will be plastically deformed by the material parts and that the movable part will collide with other parts to damage the holder or the like. In addition, the magnetizing process is not required because magnetizing is not required.

In the second aspect of the invention, since the movable part is fixed by the attractive force of the magnet and the yoke when the coil is not energized, the device can be operated even if external vibration is applied during transportation of the device. There is no risk of damage.

[Brief description of drawings]

FIG. 1 is a sectional view of an objective lens driving device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the objective lens driving device according to the first embodiment of the present invention.

FIG. 3 is a sectional view of an objective lens driving device according to a first embodiment of the present invention.

FIG. 4 is a sectional view of an objective lens driving device according to a second embodiment of the present invention.

FIG. 5 is a perspective view of an objective lens driving device according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a conventional objective lens driving device.

FIG. 7 is a perspective view of a conventional objective lens driving device.

[Explanation of symbols]

 1 Objective Lens 2 Holder 3 Diamagnetic Material 4 Yoke 5 Coil 6 Base 7 Fixing Member 8 Wire 9 Magnet

Claims (2)

[Claims] 1. A holder to which an optical system including an objective lens is attached, a fixing member, a supporting member connecting the holder and the fixing member, and movably supporting the holder with respect to the fixing member. And an objective lens driving device made of a diamagnetic material attached to the holder and attached to the holder and arranged in a magnetic field generated by the coil. 2. A holder to which an optical system including an objective lens is attached, and a magnet attached to the holder,
A fixed member, a support member that connects the holder and the fixed member, and movably supports the holder with respect to the fixed member, a yoke attached to the fixed member, and a yoke wound around the yoke. An objective lens driving device comprising a coil, wherein the holder is fixed so as not to move with respect to the fixing member by an attractive force of the magnet and the yoke when the coil is not energized.