JP2000123382A - Actuator for objective lens - Google Patents

Abstract

(57) [Problem] To minimize the inclination of an optical axis generated when an actuator is driven, even if there are variations in dimensions of individual actuator components and variations in assembly accuracy. A yoke (8) and a sub-base (6) supporting a magnet (9) are superimposed on a back surface of a base (5) elastically supporting an actuator movable part (2) holding an objective lens (1). The screw through hole 5c of the base is formed in a long hole shape long in the tracking direction, and the sub base is moved with respect to the base in accordance with the tilt amount of the optical axis of the objective lens in the disk radial direction when driven only in the focusing direction. The base and the sub-base are integrated by connecting the four corners with screws 9 at the four corners. [Effect] It is possible to eliminate the adverse effect on the reading and writing of information due to the inclination of the optical axis of the objective lens without extremely increasing the dimensional accuracy and assembly accuracy of the actuator components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator for an objective lens used in an optical disk device or the like.

[0002] The present invention relates to an adjustment mechanism for a magnetic circuit that suppresses a tilt of a lens optical axis generated when an actuator is driven.

[0003]

2. Description of the Related Art Conventionally, in an actuator for an objective lens used in an optical disk device or the like, a device disclosed in Japanese Patent Application Laid-Open No. 7-240031, for example, is disclosed in Japanese Patent Application Laid-Open No. 7-240031. is there. According to this, it is shown that the moment about the center of gravity axis, which is generated when the actuator is simultaneously driven in the focusing and tracking directions, is canceled by generating a reverse moment by devising the driving means. I have.

[0004]

When the actuator is designed, the position where the drive center point is generated when the actuator is normally driven only in the focusing direction is set so as to be located on the center of gravity (center of gravity) axis of the movable portion. Therefore, it is considered that when only the focusing direction is driven, no unnecessary moment theoretically occurs, and the inclination of the optical axis of the objective lens does not occur. In addition, in order to realize this major design premise, efforts are being made to increase the dimensional accuracy and assembly accuracy of the actuator components as much as possible. It is necessary to guarantee a small amount of tilt (tilt) of the lens optical axis which is allowed for reading / writing of an actual optical disk, for example, ± 10 minutes or less in a DVD-RAM or the like.

However, at the time of actual manufacturing, variations in dimensions of individual parts and variations in assembly accuracy always occur. Especially for magnets that are magnetic field generating means,
Considering mass productivity, some dimensional tolerances (eg ±
50 .mu.m) must be allowed, and the present design premise cannot be easily achieved. Therefore, when driving only in the focusing direction, the tilt of the optical axis of the objective lens occurs.When driving in the focusing and tracking directions simultaneously, the tilt of the optical axis is superimposed depending on the stroke position. There was a risk of adverse effects.

[0006]

In order to solve the above-mentioned problems, even if there are variations in the dimensions of individual actuator components and variations in assembly accuracy, the inclination of the optical axis generated when the actuator is driven is minimized. In order to realize the suppression, in the present invention, the actuator movable unit holding the objective lens and integrating the focusing and tracking coils, and moving the actuator movable unit in each of the focusing and tracking directions A base that freely supports via elastic support means, and a sub-base on which a magnet and a yoke are fixed, wherein the base and the sub-base are relatively movable and the relative movement amount is adjusted. After that, they are combined with each other by fixing means and integrated.

Accordingly, the base and the sub-base are relatively moved in accordance with the inclination amount of the optical axis of the objective lens, so that the displacement of the center of gravity of the movable portion with respect to the drive center point in the focusing direction is eliminated. Can be.

In addition, since the moving direction is substantially parallel to at least one of the tracking direction and the focusing direction, the adjustment can be easily performed.

[0009]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view showing a main part of an actuator for an objective lens to which the present invention is applied. The actuator for an objective lens is used in an optical disk device or the like. FIG. 2 is a plan view of the objective lens actuator, and FIG. 3 is a fragmentary side view of the actuator.

As shown in FIGS. 1 to 3, the objective lens actuator includes an actuator movable section 2 for holding an objective lens 1 at one end and an objective lens 1 for driving the objective lens 1 in each of focusing and tracking directions. A focusing coil 3 and a tracking coil 4 fixed to the movable part 2 and a base 5 for elastically supporting the movable part 2
And a sub-base 6 having a magnetic field generating means and attached so as to be superimposed on the back surface of the base 5.

A fixed block 5a is provided on the base 5 in an upright state, and a pair of left and right wire-shaped springs 7 as elastic support means extend parallel to the upper surface of the base 5 on the fixed block 5a. Have been to be. The extending ends of the pair of left and right wire-shaped springs 7 are connected to the intermediate portions of the left and right walls of the movable portion 2, and thus the movable portion 2 is mounted on the base so that it can move in parallel in the focusing and tracking directions. 5 (fixed block 5a).

The sub-base 6 has a U-shaped yoke 8 which is cut and raised so as to pass through the center of the movable part 2 from an opening 5b opened in the center of the base 5 in a state of being superposed on the base 5. The yoke 8 is set upright.
A pair of symmetrical magnets 9 are fixed to the opposing inner surfaces. These yoke 8 and magnet 9 constitute a magnetic field generating means. 2 and 3
As shown in FIG. 2, in the assembled state, the short-circuit magnetic plate 11 is attached between both ends of the yoke 8.

A hole capable of receiving the yoke 8 and the magnet 9 in a penetrating state is provided in an intermediate portion of the movable portion 2, and the focusing coil 3 and the tracking coil 4 are provided in the hole. The focusing coil 3 is formed in a rectangular shape, and is fixed to a part of the inner surface of the hole so that one of the yoke 8 and the magnet 9 can pass therethrough in the assembled state of FIGS. 2 and 3. A rectangular tracking coil 4 is fixed to a part of the outer peripheral surface of 3.

The tracking direction in the present actuator is the arrow X direction shown in FIG. 1, and the focusing direction is the arrow Z direction shown in FIG.

The base 5 and the sub-base 6 are superimposed on each other, are joined at four corners by screws 10, and are integrated with each other. In addition, base 5
The base 5 is provided with a guide slot 11 extending in the tracking direction X so that the sub-base 6 and the sub base 6 can move relative to each other only in parallel with the tracking direction X when the actuator is mounted.
A pair of pins 12 that can be inserted into the sub-base 6 project from the sub-base 6 so that the pins 12 are received in the guide slots 11 in a state where the base 5 and the sub-base 6 are overlapped with each other. The guide slot 11 and the pair of pins 12 are provided near both longitudinal edges of the base 5 and the sub-base 6, respectively, and the slot width of the guide slot 11 and the outer diameter of the pin 12 are adjusted so that the pin 12 can move. By making them approximately the same, it is possible to move only in the tracking direction X with the highest possible accuracy.

In the objective lens actuator configured as described above, when the objective lens 1 (movable part 2) is driven only in the focusing direction Z, the drive center point is the center of gravity (center of gravity) of the movable part 2 Although the designs are made to match each other, some deviation occurs between the drive center point and the center of gravity because dimensional variations of individual components and variations in assembly accuracy are included.

Here, the sub-base 6 (yoke 8 and magnet 9) is moved in accordance with the amount of inclination of the optical axis of the objective lens 1 in the radial direction of the disc (arrow X in FIG. 2) when driven only in the focusing direction. The base 5 is moved in the tracking direction X. For example, as shown by the solid line in FIG. 4, when the optical axis is inclined with respect to the Z-axis in the designed focusing direction (θ in FIG. 4), the sub-base 6 is moved relative to the base 5 in the direction of arrow A shown in FIG. Move.

As a result, the drive center point in the focusing direction Z moves on the axis of the center of gravity of the movable part 2, so that it is possible to cancel the amount of deviation due to the dimensional variation of each component and the variation in assembly accuracy. . That is, by adjusting the amount of movement of the sub-base 6 with respect to the base 5,
The inclination amount θ of the optical axis can be substantially eliminated. When the adjustment is completed, the sub base 6 and the base 5 are screwed into the screw holes 6a of the sub base 6 by screwing the screws 10 inserted into the screw through holes 5c provided in the base 5 as in the present embodiment. Or fixed by bonding or soldering.

In the above adjustment, for example, the base 5 is fixed to the fixed base, the sub-base 6 is fixed to the movable base, and the movable base is guided in only one direction (tracking direction) with respect to the fixed base, and is minute. The adjustment can be made by using an adjustment jig which can be moved. In the above embodiment, the guide slot 1 for restricting the movement between the base 5 and the sub-base 6 is provided.
1 and the pin 12 are provided, but the guide slot 11 and the pin 1
Even if the base 2 and the sub-base 6 are not provided, the base 5 and the sub-base 6 may be integrated by screwing the fixed base and the movable base in a fixed state after the adjustment.

FIG. 6 shows data showing the effect of this embodiment. 6, the tilt amount (tilt angle θ) of the optical axis of the objective lens 1 in the radial direction X of the disc is defined as the X axis in the figure, the stroke amount in the focusing direction Z is defined as the Y axis in the figure, 6 is plotted in units of 10 μm between −40 μm and 40 μm relative to the tracking direction X. As shown in the figure, even if the tilt amount of the optical axis is tilted about ± 3 minutes, ± 40 μm
It can be seen that the tilt amount can be substantially eliminated by adjusting the relative movement amount between the base 5 and the sub-base 6 to -40 μm to 40 μm because the distance falls within the relative movement range of m. Naturally, it is easy to further increase the adjustment allowance.

FIG. 7 shows the inclination distribution of the optical axis of the objective lens before and after using this adjustment method. FIG. 7A shows the ratio of the optical axis tilt amount before adjustment based on the present invention, and FIG. 7B shows the corresponding figure after adjustment. As shown in the figure, the optical axis tilt amount can be effectively suppressed.

Next, another embodiment according to the present invention will be described below with reference to FIG. 8 corresponding to FIG. 2 and FIG. 9 corresponding to FIG. In the drawings, the same parts as those in the illustrated example are denoted by the same reference numerals, and detailed description thereof will be omitted.

The configuration of the objective lens actuator shown in FIGS. 8 and 9 is the same as that of the above-described embodiment.
The pin 12 is formed in the focusing direction Z to a length corresponding to the adjustment allowance. Adjustment, for example, fixing the base 5,
The sub-base 6 is moved by an adjustment jig that can move only in the focusing direction Z and the tracking direction X. The sub-base 6 is moved in the focusing direction Z and the tracking direction X with respect to the base 5 in accordance with the tilt amount of the optical axis of the objective lens 1 in the disk radial direction X when driven only in the focusing direction Z. This makes it possible to substantially eliminate the amount of tilt by adjustment, as in the above embodiment. When the adjustment is completed, the sub-base 6 and the base 5 are bonded with an adhesive W or soldered with a solder W to integrate them.

As described above, by moving and adjusting only the focusing direction Z and the tracking direction X, the focusing coil 3 and the tracking coil 4 are adjusted.
In contrast, the adjustment is easy because the magnetic pole surface of the magnet 9 can move while always maintaining a constant distance. Further, since the point of application of the driving force is determined only by the relative movement amount, automation of assembly is facilitated and mass productivity can be improved.

[0026]

As described above, according to the present invention, the base and the sub-base are relatively moved in accordance with the amount of inclination of the optical axis of the objective lens, and the displacement of the center of gravity of the movable portion with respect to the driving center point in the focusing direction is caused. Since the base and sub-base are integrated after the adjustment to eliminate the error, the reading and writing of information due to the tilt of the optical axis of the objective lens is not affected without extremely increasing the dimensional accuracy and assembly accuracy of the actuator components. Can be provided at a low cost. The adjustment can be easily performed by making the moving direction substantially parallel to at least one of the tracking direction and the focusing direction.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a main part showing an objective lens actuator to which the present invention is applied.

FIG. 2 is a plan view of an actuator for an objective lens.

FIG. 3 is a side view of a cutaway side of a main part as viewed from the direction of arrow III in FIG. 2;

FIG. 4 is an explanatory diagram showing the inclination of the optical axis of the objective lens.

FIG. 5 is a view corresponding to FIG. 2, showing an adjustment procedure based on the present invention.

FIG. 6 is a diagram illustrating a relationship between a relative movement amount of a base and a sub-base and an optical axis tilt amount.

7A is a diagram illustrating a ratio of an optical axis tilt amount before being adjusted based on the present invention, and FIG. 7B is a diagram illustrating an improvement effect adjusted based on the present invention.

FIG. 8 is a view showing another embodiment and corresponding to FIG. 2;

FIG. 9 is a view showing another embodiment and corresponding to FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Moving part 3 Focusing coil 4 Tracking coil 5 Base, 5a Fixed block, 5b opening, 5c
Screw through hole 6 Sub-base, 6a Screw hole 7 Wire spring 8 Yoke 9 Magnet 10 Screw 11 Guide slot 12 Pin

Claims (2)

[Claims] 1. An actuator movable unit which holds an objective lens and integrates focusing and tracking coils, and supports the actuator movable unit via elastic support means so as to be movable in each of the focusing and tracking directions. A base and a sub-base on which a magnet and a yoke are fixed, wherein the base and the sub-base are coupled to each other by fixing means after being movable relative to each other and after adjusting the amount of relative movement. An actuator for an objective lens, which is integrated. 2. The objective lens actuator according to claim 1, wherein the moving direction is substantially parallel to at least one of the tracking direction and the focusing direction.