JPH0433547Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention relates to an objective lens actuator for an optical pickup in an optical disc player.
In particular, it relates to a device for holding an objective lens in a neutral position.

Conventional Technology Optical pickups applied to optical disc players such as compact disc players require movement control of the objective lens in the focusing and tracking directions in order to make the minute beam spot of the semiconductor laser accurately follow the recording track pit row of the disc. A servo actuator is provided.

This objective lens actuator is, for example, the sixth objective lens actuator.
It was configured as shown in the figure. That is, a shaft 3 is erected at the center of a pair of magnetic yokes 2, 2 provided on an actuator base 1, and a substantially rectangular lens holder 4 is rotatably mounted on this shaft 3 in the middle thereof, and is attached vertically. A focus coil 5 is slidably supported on the lens holder 4 and is wound around the rotation center of the lens holder 4 in a cylindrical shape. A radial coil 6 is interposed between the cavities 2a, 2a of the magnet yoke bodies 2, 2. Further, an objective lens 7 is attached to one end of the lens holder 4, and an optical system (not shown) is provided below the objective lens 7 in the optical axis direction. On the other hand, the other end side tail end of the lens holder 4,
Support 8 formed on actuator base 1
A rubber damper 9 is attached to the lens holder 4, and the elastic return force of the damper 9 holds the lens holder 4 at a neutral position with respect to the focus and radial directions. With this configuration, the objective lens 7 is controlled to move in the focus and radial directions, and when the servo is released, it returns to the neutral position in the focus and radial directions.

Problems to be Solved by the Invention As described above, the conventional objective lens actuator that performs servo control in the radial direction, that is, in the tracking direction, by sliding and rotating the objective lens. The objective lens is then returned to the neutral position by the elastic return force of a buffer member such as a rubber damper. As this buffer member, silicon-based rubber, which has excellent thermal properties and durability, is generally used. However, this silicone-based rubber has extremely poor adhesion. For this reason, they are attached using methods such as screwing or caulking using a metal fitting.

However, with conventional structures that use the restoring force of a rubber damper to return and hold the damper to a neutral position, the metal fittings or set screws used to secure the rubber damper may loosen, or the rubber may deteriorate. . As a result, the return force becomes weak or fluctuates. As a result, the return force becomes unstable, resulting in poor servo stability and failure to perform reliable control.

This idea was made in consideration of the above points,
It is an object of the present invention to enable an objective lens to be returned to a neutral position reliably and stably and to be held therein, and to improve the stability of the servo of an objective lens actuator.

Means for Solving the Problems In order to achieve the above objectives, this invention supports a lens holder provided with an objective lens on an actuator base so as to be rotatable along the base surface and slidable up and down. , a focus coil wound around the lens holder in a cylindrical shape around the center of rotation; and a pair of focus coils on each side of the outer circumferential surface of the focus coil on both sides narrowly facing the center of rotation. A set of magnetic circuits consisting of a magnet and a yoke body are installed on both sides of the base narrowly facing each other around the center of rotation, and the circumference of this magnetic circuit is In an objective lens actuator in which both sides of a focus coil and one side of each pair of radial coils on both sides are interposed in the sky in the direction, a coil circle is formed on the outer peripheral surface of both sides of the focus coil. A substantially U-shaped or frame-shaped magnetic field whose one side along the circumferential direction extends from one end of the magnetic circuit to a portion corresponding to the other end of the magnetic circuit, with bent ends corresponding to both ends of the magnetic circuit formed at both ends. The magnetic body was attached so that when one end of the magnetic body and the bent portions at both ends were located within the space of the magnetic circuit, the forces applied to the magnetic body were balanced.

Effect According to the above configuration, when the objective lens actuator is controlled in the focus or radial direction and a current is passed through the focus or radial coil combined with the magnetic circuit, the lens holder slides vertically or the base surface It is rotated in the direction along. Then, the magnetic material provided on the focus coil surface is moved at the same time,
The end of the magnetic material in the direction of movement is removed from the magnetic circuit. When this happens, the balance of attraction between the magnetic body and the magnetic circuit is disrupted, and a force acts to restore the original balanced state. This force causes the lens holder to return to its original neutral position when the control is released.

Embodiments Hereinafter, embodiments of this invention will be described in detail with reference to the drawings.

FIG. 1 shows an objective lens actuator according to the present invention, and FIG. 2 shows its main parts.

A pair of magnet yoke bodies 11, 11 are provided on the actuator base 10, and a shaft 12 is erected at the center thereof. The magnetic yoke body 11 is a first yoke body 11 having an L-shaped cross section.
1, a magnet 112 provided at one end of this,
It is formed by the second yoke body 113 provided on this and the rising inner surface of the first yoke body 111 and the second yoke body 113.
A space 114 is formed between the outer surface of the yoke body 113 and the outer surface of the yoke body 113. Hollows 114, 11 formed in a pair of magnetic yoke bodies 11, 11
4 has a circular shape centered on the axis 12.

The lens holder 13 has a substantially rectangular shape, and its middle portion is attached to the shaft 12. Lens holder 1
3 is provided so as to be rotatable between the pair of magnet yoke bodies 11, 11 about the shaft 12 and to be slidable in the axial direction. A focus coil 14 is attached to the lens holder 13 and is wound into a cylindrical shape around the center of rotation of the lens holder 13. Further, on the outer peripheral surface of the focus coil 14, four radial coils 15, . The focus coil 14 is connected to a pair of magnetic yoke bodies 11, 11 on both sides of the lens holder 13.
4,114, and the radial coils 15,...
, one rising side of each is empty = 11
4,114.

Furthermore, the holes 114, 11 of the magnet yoke bodies 11, 11 on the outer peripheral surface of the focus coil 14 are
A pair of magnetic bodies 16, 16 are attached at positions corresponding to 4. The magnetic body 16 is formed by bending a rod-shaped iron material along the outer circumferential surface of the focus coil 14, and bending both ends of the iron material downward at substantially right angles so as to correspond to both ends of the air 114. The bent ends 161 and 162 at both ends of the magnetic body 16 correspond to both ends of the air 114, respectively, and when the magnetic body is located in the air, the magnetic body 16 bends at both ends 161 and 16.
The lens holder 13 is attracted toward the neutral direction by the magnetic force of the magnet yoke body 11 between the two, and the lens holder 13 is held in the neutral position by the balance of the forces applied to the magnetic body.

The objective lens 1 is attached to one end of the lens holder 13.
7 is installed. A surface of the actuator base 10 corresponding to the optical axis direction of the objective lens 17 is open, and an optical system (not shown) is provided at the bottom of the base 10.

Next, the operation of the apparatus of this embodiment having the above configuration will be explained.

As shown in FIG. 3, the objective lens holder 13
is the magnetic yoke body 11, 11 when not in operation.
Due to the magnetic force, each bent end 1 of the magnetic bodies 16, 16
The magnets 61 and 162 are drawn toward the neutral direction, and the forces acting on the magnetic bodies 16 and 16 are kept balanced. Thereby, the objective lens holder 13 is connected to the line connecting the objective lens 17 and the shaft 12, and the objective lens 17
The line connecting the disk center 0 and the disk center 0 are held perpendicular to each other. When a tracking error signal is detected in this state, the radial coil 15,
A current is passed through... Then, a force is applied to the radial coil 15 in the direction of rotating it around the axis 12, and the objective lens holder 13 is moved as indicated by the arrow
Rotate it in the direction of 00. In this way, the objective lens 17 is controlled to move in the radial direction, that is, the tracking direction.

When the objective lens holder 13 is rotated in one direction in the radial direction, the magnetic bodies 16, 16 are also moved at the same time, and as shown in FIG.
1,161 are removed from the holes 114,114 of the magnetic yoke bodies 11,11. Then, the equilibrium state of the attractive forces applied to the magnetic bodies 16, 16 is disrupted, and an attractive force acts on the magnetic bodies 16, 16 to move the lens holder 13 toward the original neutral position. Then, the current flowing through the radial coils 15, . . . is weakened, and when the force applied to the radial coils 15, . The magnetic bodies 16 rotate until the forces acting on them are balanced. When the current is completely stopped, the forces applied to the magnetic bodies 16, 16 are balanced, and the objective lens 13 is returned to the neutral position.

When a current is applied to the radial coils 15, .
162 is removed from the blanks 114, 114, and a force is exerted to return the objective lens holder 13 to the neutral position, similar to the operation described above. This causes the lens holder 13 to move back to the neutral position.

Furthermore, as shown in FIG. 5, when a current is applied to the focus coil 14 and the objective lens holder is slid in the upward direction to control the focus direction, the curved portions of the magnetic bodies 16, 16, ie, the upper sides is off the sky = 114, 114 upwards,
A force that pulls down the objective lens holder 13 acts. As a result, the lens holder 13 moves back to the neutral position in the focus direction.

Note that various shapes of the magnetic body can be considered, and are not limited to the shapes shown in the examples. For example, various shapes such as a frame shape, a substantially U-shape, etc. can be adopted.

Effects of the invention As explained above, according to the neutral holding device of the objective lens actuator according to the present invention, the focus servo or the tracking servo can be used to adjust the position between the bent ends of the magnetic material or between the both bent ends. When the side part is removed from the magnetic circuit, a magnetic force acts on the magnetic body in the direction of moving the lens holder back to the neutral position, and this magnetic force moves the lens holder back to the neutral position, so it is secure without contact. In addition, a stable return force can be obtained, and it is possible to accurately return to the neutral position and maintain the neutral position. Therefore, stable focus servo and tracking servo can be performed.

In particular, the present application has an extremely simple configuration of just adding a substantially U-shaped or frame-shaped magnetic body to the outer circumferential surface of the focus coil, yet it is capable of reliably returning to the neutral position and reliably returning to the neutral state. This has the effect that it can be retained.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view showing the objective lens actuator according to the present invention, Fig. 2 is an enlarged perspective view of its main parts, Figs. 3 and 4 are plan views showing its operation in the tracking direction, and Fig. 5. 6 is a side sectional view showing the operation in the focus direction, and FIG. 6 is a plan view showing the conventional example. 10... Actuator base, 11, 11...
...Magnetic yoke body, 12...Shaft, 13...
Objective lens holder, 14...focus coil,
15, 15, 15, 15...Radial coil, 1
6, 16...Magnetic material, 17...Objective lens.

Claims (1)

[Scope of utility model registration request] A lens holder with an objective lens mounted on an actuator base is supported so as to be rotatable along the base surface and slidable up and down, and a focus coil is wound around the lens holder in a cylindrical shape around the rotation center. , a pair of rectangular radial coils are installed on each side of the outer peripheral surface of the focus coil at two locations on each side narrowly facing each other with the center of rotation on the base, and the center of rotation on the base is narrowed. A pair of magnetic circuits consisting of a magnet and a yoke body are installed at opposing positions on both sides, and both sides of the focus coil and each pair of radial coils on both sides are installed in the circumferential space of this magnetic circuit. In the objective lens actuator, one side extends from one end of the magnetic circuit to a portion corresponding to the other end of the magnetic circuit, and the objective lens actuator has one side extending from one end of the magnetic circuit to a portion corresponding to the other end on the outer circumferential surface of the both sides of the focus coil. A substantially U-shaped or frame-shaped magnetic body with bent ends corresponding to both ends of the magnetic circuit is attached to the magnetic body, and both bent ends and one side end of the magnetic body are attached to A neutral holding device for an objective lens actuator so that the forces applied to the magnetic body are balanced when the objective lens actuator is positioned in the sky.