JP2006179085A - Actuator of optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve tracking sensitivity of an actuator of an optical pickup by improving simply constitution of a wasteful electromagnetic circuit or the like and generating effectively electromagnetic force in a tracking coil. <P>SOLUTION: In an actuator of an optical pickup, permanent magnets 5 of a plate type are fixed to each opposing plane of a pair of back yokes 4 opposing to a direction being orthogonal to a tracking direction on an act base, two tracking coils 7 are fixed to each plane opposing to the permanent magnet 5 of a focus coil 6 wound on an outer peripheral plane of an objective lens holder 2 between the opposing permanent magnets 5, a plate body 8 of which the cross section is a U type is stuck to the back of the back yoke 4 of the actuator provided with a pair of inner yokes 3 opposing to a tracking direction holding an optical axis of a lens 1 between them in the objective lens holder 2, an end part 8a of the U type is positioned to the vicinity of an ineffective side 7b, a part of magnetic flux of the permanent magnets 5 proceeding to the inner yoke 3 piercing an effective side 7a is made to pierce also the ineffective side 7b of the tracking coil 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an optical pickup for writing information to and reading information from an optical disk, and more specifically, in the configuration, an objective lens holder having an objective lens as an optical element has a focus direction (vertical direction) and a tracking direction orthogonal to each other. The present invention relates to the improvement of the structure for increasing the sensitivity of the tracking operation of the actuator driven in the (horizontal direction).

In the optical pickup actuator, as described above, the objective lens holder having the objective lens is driven in the focus direction and the tracking direction. However, in order to read and write information accurately, the objective lens holder is focused by the objective lens. It is necessary to accurately position the light spot on the signal track of the optical recording medium.

For this reason, various proposals have been made to increase the drive sensitivity of the objective lens holder as an actuator of the optical pickup for the purpose of improving the recording density and the access speed. ).

An example of the basic configuration of such an actuator is shown in an exploded perspective view in FIG. In this actuator, the following various components are assembled on an act base 10 as a base, and mounted on a base 20 of an optical pickup. An optical system for reading and writing information is provided.

The optical system includes a light source 11 such as a laser diode, a collimator lens 12 that passes light emitted from the light source 11 to make it parallel light, and focuses the parallel light that has passed through the collimator lens 12 to irradiate the optical disk. The objective lens 1 described above and the objective lens holder 2 that holds the objective lens 1 and is movable in the focus direction and the tracking direction are provided.

Usually, in the optical system, the light source 11 and the collimator lens 12 are mounted on a base 20 of an optical pickup, and mounted on the act base 10 is an objective lens holder 2 having the objective lens 1. It is.

On this act base 10, in addition to the objective lens holder 2, the objective lens holder 2
A moving mechanism that moves the lens in the focus direction and tracking direction is installed. The moving mechanism is driven by an electromagnetic circuit, and a tilt yoke 3 and a back yoke 4 rise from the surface of the act base 10.

The tilt yoke 3 faces the tracking direction corresponding to the x-axis direction in the figure, and the tilt coil 3c is wound around each. The tilt yoke 3 is also called an inner yoke.

Further, on the act base 10, the tilt yoke 3 is sandwiched in a direction (y-axis direction in the figure) perpendicular to the facing direction (tracking direction) of the tilt yoke 3.
A pair of back yokes 4 are arranged to face each other. A rectangular parallelepiped permanent magnet 5 which is paired with each other is bonded to the opposing surface of each back yoke 4 with an adhesive. The objective lens holder 2 is disposed between the opposing permanent magnets 5.

The objective lens holder 2 has a portion that is one step higher than both sides at the center in the longitudinal direction of the rectangular parallelepiped,
That portion is a lens holding portion 1 a that holds the objective lens 1. The objective lens 1 is attached to the upper surface of the lens holding portion 1a.

Both sides of the lens holding portion 1a are rectangular frames 1b. When the objective lens holder 2 is arranged at a predetermined position on the act base 10, the tilt yoke (inner yoke) 3 rises inside the frame 1b. It has become a form.

A focusing coil 6 is wound around the lens holding portion 1 a of the objective lens holder 2 and the peripheral surfaces of the frames 1 b on both sides, and a tracking coil 7 having a rectangular coil surface is fixed to the outer peripheral surface of the focusing coil 6. The In addition, what attached | subjected the code | symbol w is the objective-lens holder 2
Is a suspension wire that supports The above is the configuration of the actuator.

Next, an electromagnetic circuit for moving the objective lens holder 2 of the actuator having the above-described component configuration in the tracking direction will be described. FIG. 3 shows an actuator part extracted from the configuration of the optical pickup shown in the above exploded perspective view, and its assembled view is shown in a plan view in (a) and in a side view in (b).

As shown in (a), a pair of back yokes 4 face each other with the objective lens holder 2 sandwiched in the vertical direction in the figure. A permanent magnet 5 is attached to each of the opposing surfaces of the back yoke 4. The left-right direction in the figure is the tracking direction.

A focus coil 6 is wound around the outer peripheral surface of the objective lens holder 2, and a tracking coil 7 is fixed to each of two surfaces facing the permanent magnet 5 of the focus coil 6 with an adhesive. There are four tracking coils 7 in total.

The tracking coil 7 is fixed at a symmetrical position with the vertical center axis of the rectangular surface of the focus coil 6 as the symmetry axis. In each tracking coil 7, one of the vertical sides is the surface of the focus coil 6. It is attached so that it protrudes from the outside. The protruding side is shaped so as not to face the permanent magnet 5 in a direction orthogonal to the tracking direction.

As described above, the center of the objective lens holder 2 is the lens holding portion 1a, and the objective lens 1 is attached to the upper surface thereof via the attachment plate 1p. The upper end of the tilting yoke 3 rising from the act base 10 is peeping into the rectangular frame 1b adjacent to the lens holder 2 on both sides. The above is the configuration of the actuator.

Next, the operation of the electromagnetic circuit of the actuator will be described with reference to FIG. FIG.
In order to show the operation of the electromagnetic circuit, only the minimum necessary components are extracted from the plan view shown in FIG. 3A and schematically shown. In the figure, thick arrows indicate lines of magnetic force.

As shown in FIG. 4, in each of the four tracking coils 7, the effective side for generating an electromagnetic force that receives a magnetic force line generated from the permanent magnet 5 and that is used for the tracking operation is only the reference numeral 7 a. As described above, the position of the side facing the effective side 7a protrudes outside the focus coil 6 and does not face the magnet surface, that is, the position where the magnetic field lines do not reach, and the tracking. The invalid side 7b does not generate the electromagnetic force responsible for the operation.

In addition, a pair of sides facing vertically (in a direction perpendicular to the paper surface), each part of which faces the magnet surface and receives magnetic lines of force generated from the magnet 5, and electromagnetic waves generated thereby. The force is upward on the upper side (from the back of the page to the front) and downward on the lower side (
The forces of the same magnitude act in the direction from the front to the back of the page to balance them, and do not act in the tracking direction (horizontal direction, left-right direction in the figure).
JP 2004-139680 A (FIGS. 5 and 6)

The above is the configuration of the conventional electromagnetic circuit and the state of the action of the electromagnetic force below. In each tracking coil 7 of the actuator having the above-described configuration, the effective side 7a on which the electromagnetic force acts in the tracking direction has four sides. Only one side. That is, all four tracking coils 7
As for the effective side 7a, only four sides can generate electromagnetic force in the tracking direction.
It is. This is really inefficient.

Accordingly, an object of the present invention is to improve the tracking sensitivity of the actuator of the optical pickup by adding a simple configuration to the above-mentioned wasteful electromagnetic circuit and effectively generating an electromagnetic force in the tracking coil. There is to plan.

In order to achieve the above object, according to the present invention, a pair of back yokes whose plate surfaces are opposed to each other in a direction orthogonal to the tracking direction are erected on the act base, and the back yokes are formed in plate-like shapes on the mutually opposing surfaces. The permanent magnet is fixed, and the objective lens holder with the objective lens is installed between the opposing permanent magnets so as to be movable in the focus direction and the tracking direction, and the configuration of the electromagnetic circuit that drives the movement As an element, in addition to the back yoke and the permanent magnet, a focus coil wound around the optical axis of the objective lens on the outer peripheral surface of the objective lens holder, and two surfaces facing the permanent magnet of the focus coil Each of which has two tracking coils fixed symmetrically with respect to the vertical center axis of the surface, and sandwiches the optical axis of the objective lens in the objective lens holder. A pair of tilt yokes that are disposed on the actuator base so as to face the racking direction, the actuator of the optical pickup that includes a wound tilting coils therewith,
Extending portions from both side edges of the back yoke toward the ineffective side of the tracking coil are provided, and a part of the component of the permanent magnet's magnetic field lines passing through the effective side of the tracking coil toward the tilt yoke is the tracking. The ineffective side of the coil was penetrated.

Since the present invention is configured as described above, the force in the same direction as the electromagnetic force (Lorentz force) acting on the effective side of the tracking coil also acts on the invalid side, and only the force acting on the effective side is used for the tracking operation. Compared with a conventional actuator that has been used as a driving force, the tracking sensitivity is significantly improved.

This improvement in tracking sensitivity means that, for example, a DVD recorder, which is one of optical disk devices, is an example of speeding up the dubbing when performing a dubbing between a hard disk and an optical disk built into the DVD recorder. The result will be realized.

Embodiments of the present invention will be described below. FIG. 1 is a schematic view of the main component of the present invention, in which only the minimum components are extracted in order to briefly explain the operation. (A) is a top view, (b) is a side view. Hereinafter, an embodiment of the present invention will be described with reference to FIG. Constituent elements that are the same as conventional ones are given the same reference numerals, and descriptions thereof are omitted.

FIG. 1 shows only the magnet 5, tracking coil 7 and inner yoke (tilting yoke) 3 extracted from the actuator as shown in FIG. 4 of the prior art. Only the portion of the back yoke 4 on the back surface of the magnet 5. The direction of the current flowing through each tracking coil 7 is as shown in the figure.

As shown in FIG. 1, in the actuator of this embodiment, a plate body 8 having a U-shaped cross section is fixed to the back surface of both back yokes 4 with an adhesive. The U-shaped end portion 8 a of the plate body 8 reaches almost the position near the coil surface of the tracking coil 7.

Since this plate 8 is fixed to the back yoke 4, it has a function of a yoke, and the back yoke 4 is fixed to the S pole side of the permanent magnet 5, and the polarity of the fixed surface of the plate 8 is N. Therefore, the polarity of the U-shaped end portion 8a of the plate body 8 is S. In other words, the yoke having the polarity S exists in the vicinity of the invalid side 7 b of the tracking coil 7. The above is the configuration that forms the basis of the actuator of the embodiment for explaining the main point of the present invention. Next, the operation (operation) will be described with reference to FIG.

As described above, since the U-shaped end portion 8a of the plate body 8 having the polarity of S exists in the vicinity of the invalid side 7b of the tracking coil 7, the tracking coil 7 is effectively generated from the permanent magnet 5. A part of the magnetic field lines that penetrate the side 7a and go toward the inner yoke 3 are directed toward the U-shaped end portion 8a of the plate body 8. A tracking coil 7 is provided in the vicinity of the U-shaped end portion 8a of the plate body 8.
Since the invalid side 7b is located, a part of the magnetic lines of force penetrates the invalid side 7b from the bottom to the top of the page.

At that time, as shown in the figure, the current flowing through the invalid side 7b is directed from the front to the back of the page, so that the electromagnetic force (Lorentz force) acting on the invalid side 7b acts from right to left in the figure. To do. This direction is the same as the electromagnetic force acting on the effective side 7 a of the same tracking coil 7.

Such a relationship is the same in the other three tracking coils 7, and in the four tracking coils 7, the forces acting on the effective side 7a and the ineffective side 7b facing each other are all directed from the right to the left in the figure. . Further, even when the current directions are switched to be reversed, the forces acting on the effective side 7a and the invalid side 7b of the four tracking coils 7 are all directed from the left to the right in the drawing.

Thus, in the actuator of this embodiment, the magnetic lines of force generated from the permanent magnet 5 can be used effectively, and electromagnetic force in the same direction as the effective side 7a is also generated on the ineffective side 7b that has not been applied with a magnetic line of force conventionally. Therefore, the movement in the tracking direction is performed quickly, and the tracking sensitivity is remarkably improved.

In this embodiment, the extending portion from the back yoke 4 which is the main component of the present invention is formed by bonding the back yoke 4 which is originally a separate body and the plate body 8 having a U-shaped cross section with an adhesive. However, it is not necessary to form these separately, and an integrated shape may be manufactured when designing and manufacturing a new one.

The actuator of the present invention can be widely applied to an optical pickup and an optical disk apparatus in which the optical pickup is mounted.

These are the structures which show the gist of the present invention in a schematic plan view (a) and a side view (b). FIG. 3 is an exploded perspective view showing basic components of the pickup. Fig. 2A shows a conventional pickup assembled in a plan view, and Fig. 2B shows a side view. These are figures which show the effect | action of the pickup of the prior art example shown in FIG.

Explanation of symbols

3 Inner yoke (tilting yoke)
4 Back yoke 5 Permanent magnet 7 Tracking coil 7a Effective side 7b Invalid side 8 U-shaped plate (extension part)

Claims (3)

A pair of back yokes whose plate surfaces are opposed to each other in a direction perpendicular to the tracking direction are erected on the act base, and plate-like permanent magnets are fixed to the mutually opposing surfaces of the back yoke. An objective lens holder having an objective lens is installed between the permanent magnets so as to be movable in the focus direction and the tracking direction. In addition to the back yoke and the permanent magnet, the electromagnetic circuit is configured to drive the movement. The focus coil wound around the optical axis of the objective lens on the outer peripheral surface of the objective lens holder, and the two surfaces facing the permanent magnet of the focus coil are each provided with a vertical central axis of the surface. Two tracking coils that are fixed symmetrically, and an actuator that faces the tracking direction across the optical axis of the objective lens in the objective lens holder. A pair of tilt yokes that are disposed on the scan, the actuator of the optical pickup that includes a wound tilting coils therewith,
Extending portions from both side edges of the back yoke toward the ineffective side of the tracking coil are provided, and a part of the component of the permanent magnet's magnetic field lines passing through the effective side of the tracking coil toward the tilt yoke is the tracking. An optical pickup actuator characterized by passing through the ineffective side of the coil.   An optical pickup comprising the actuator according to claim 1.   An optical disc apparatus comprising the optical pickup according to claim 2.

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