JP2611053B2 - Objective lens drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device, and more particularly to an objective lens driving device mounted on an optical information recording / reproducing device for controlling the position of a light spot focused on an optical information recording medium. The present invention relates to a lens driving device.

[0002]

2. Description of the Related Art FIGS. 7 to 9 each show a conventional objective lens driving device disclosed in, for example, Japanese Patent Publication No. 63-53618. FIG. 7 shows a conventional objective lens driving device. FIG. 8 is a sectional view taken along the line AA in FIG. 7, and FIG. 9 is a perspective view partially cut away.

In these drawings, reference numeral 1 denotes a base formed of a magnetic material in a disk shape, 2 denotes a hole provided substantially at the center of the base 1, and 3a and 3b denote holes formed on the upper surface of the base 1 with the hole 2 as a center. An inner yoke 4 symmetrically protruding upward is a shaft fixed to the hole 2 by an appropriate means, and a special material such as a fluororesin is coated on an outer peripheral portion to minimize a friction coefficient. Have been.

Reference numeral 5 denotes a flat movable plate made of a non-magnetic material. The movable plate 5 has a bearing cylinder 6 which is fitted to the shaft 4 and constitutes a sliding bearing mechanism at a substantially central portion thereof.

[0005] In order to reduce the frictional force of the sliding bearing mechanism composed of the bearing cylinder 6 and the shaft 4, the inner peripheral surface is finished in a shape with extremely high surface accuracy. Reference numeral 7 denotes a hole provided at one longitudinal end of the movable plate 5, and reference numeral 8 denotes an objective lens whose optical axis is parallel to the axis 4 and fixed to the hole 7.

Reference numeral 9 denotes a counterweight fixed to the movable plate 5 and 10 denotes a movable plate 5 provided concentrically with the shaft 4 in a cylindrical shape.
, A focusing coil 11 wound around the outer peripheral surface of the coil bobbin 10, a pair of tracking coils 12 provided at symmetrical positions on the outer peripheral surface of the coil bobbin 10, and 13a and 13b the coil bobbin 10. The outer yokes 14a and 14b are disposed between the base 1 and the outer yokes 13a and 13b, and the outer yokes 14a and 14b are disposed so as to face the inner yokes 3a and 3b, respectively.
The permanent magnets 15 and 16 are magnetized in the longitudinal direction of the permanent magnets 14a and 1b with respect to the outer yokes 13a and 13b, respectively.
4b, bolts 17a, 17b are movable plates 5
18, a thin support plate provided on the lower surface of both ends in the longitudinal direction of
Is a damper member formed in a ring shape that makes a round around the shaft 4 and is fixed to the support plates 17a and 17b.

[0007] 19a and 19b are fixing mechanisms for fixing the damper 18 to the outer yokes 13a and 13b, 20 is a spacer having a groove P on the upper surface into which a part of the damper 18 is fitted, and 21 is a spacer on the upper surface of the spacer 20. A patch plate to be applied,
Reference numeral 22 denotes a screw for integrally fixing the backing plate 21, the spacer 20, and the damper 18 to the outer yokes 13a, 13b.

Next, the operation of the above configuration will be described. The movable plate 5 is driven in the Y-axis direction in FIG. 9 by the electromagnetic force generated by controlling the energization of the focusing coil 11. At this time, the bearing cylinder 6 provided on the movable plate 5 slides with respect to the shaft 4, thereby performing focusing control. Further, the movable plate 5 is driven around the axis 4 around the Y axis in FIG. 9 by an electromagnetic force generated by controlling the energization of the tracking coil 12. At this time, the bearing cylinder 6 provided on the movable plate 5 rotates with respect to the shaft 4, thereby performing tracking control.

[0009]

However, the conventional objective lens driving device constructed as described above has the following disadvantages. That is, since the sliding bearing mechanism is constituted by the shaft 4 and the bearing cylinder 6 in order to regulate the degree of freedom in performing the focusing control and the tracking control, the damper 18 is arranged around the axis of the bearing 4. Even if they are arranged in a symmetrical shape, sliding friction force is inevitably generated in the sliding bearing mechanism, and as a result, the hysteresis characteristic in the relationship between the quasi-static displacement in the focus direction and the tracking direction and the driving electromagnetic force is reduced. Therefore, it is inevitable that servo pull-in becomes difficult due to variations in parts and crosstalk between the focusing direction and the tracking direction occurs.

Further, since the shaft 4 and the bearing cylinder 6 form a sliding bearing mechanism, it is necessary to make the surface accuracy of the sliding portion extremely high, and special attention should be paid to handling during assembly. This necessitated an obstacle to reducing the price of the device.

The damper 18 is the largest member of the objective lens driving device, and determines the outer diameter of the objective lens driving device, which is an obstacle to downsizing the device. In order to fix the damper 18 to the movable plate 5 and the base 1, support plates 17a, 17b,
Fixing mechanism 19a, 19b, spacer 20, backing plate 21,
A member such as a screw 22 is provided, which also has been an obstacle to miniaturization and cost reduction of the device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and suppresses a hysteresis characteristic in a relationship between a quasi-static displacement in a focusing direction and a tracking direction and a driving electromagnetic force, thereby achieving servo control in servo control. It is an object of the present invention to provide an objective lens driving device that improves the pull-in characteristics and realizes a small size and low price of the objective lens driving device.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, an elastic body (dan) as a support means is provided between a support shaft and a bearing cylinder which constitute a slide bearing mechanism.
And the elastic body includes a support shaft or a bearing cylinder or
Engagement with both of these causes the elastic body itself to focus.
To restrict movement in the tracking or tracking direction.
In this case, a regulating section is provided.

[0014]

According to the first aspect of the present invention, the sliding friction force existing in the sliding bearing mechanism is reduced by the elastic member (the damper).
In addition to being removed by the interposition of ( p) , the surface accuracy of the members constituting the sliding mechanism bearing mechanism can be remarkably reduced. In addition, the size of the elastic body is greatly reduced, and the member that supports and fixes the elastic body becomes unnecessary. Further
In addition, the elastic body includes a support shaft, a bearing cylinder, or both.
Is provided with a restricting part by engagement with
In the overall focusing or tracking direction
Movement can be more strongly regulated, and an elastic track
It is also possible to set the initial angle of the steering direction .

[0015]

【Example】

Embodiment 1 FIG. 1 is a perspective view of an objective lens driving device according to an embodiment of the present invention, partially cut away, and FIG. 2 is a plan view of a main part of the objective lens driving device according to an embodiment of the present invention. 3 is a perspective view cut along the line BB in FIG. 2, and FIG. 4 is a view cut along the line BB in FIG. 2 showing a focusing control operation by the objective lens driving device in one embodiment of the present invention. Note that the same or corresponding parts as in the conventional example are denoted by the same reference numerals as in the conventional example, and description thereof will be omitted.

In FIG. 1, reference numeral 101 denotes an axis, which is fixed to the base 1 so as to form an axis parallel to the optical axis of the objective lens 8. However, the outer peripheral surface of the shaft is not coated with a special material as in the conventional example. Reference numeral 102 denotes a bearing cylinder fixedly provided on the movable plate 5, and the inner peripheral surface of the bearing cylinder is not finished with very high surface accuracy as in the conventional example. Numeral 103 denotes a damper for setting a neutral position in the tracking direction disposed between the shaft 101 and the bearing cylinder 102, the inner peripheral surface of which is fixed to the shaft 101 by frictional force, and the outer peripheral surface of which is a bearing cylinder. 102 is fixed by a frictional force.

Next, the operation of the above configuration will be described with reference to FIGS .
It will be described based on the following. In a normal state, the state is as shown in FIG. 4B, but in order to correct the focus shift of the light spot, a desired current is applied to the focusing coil 11, and the movable plate 5 and, consequently, the objective lens (not shown) are moved by electromagnetic force. 4 (a) or by driving in the direction of arrow C shown in (C), it such to put the control in the focusing direction. Further, in order to correct the track deviation of the light spot, by applying a desired current to the tracking coil 12, about an axis 101, the objective lens 8 (not shown) the movable plate 5 and thus the electromagnetic force, the arrow D shown in FIG. 2 To control the tracking direction of the objective lens.

Embodiment 2 FIG. 5 is a cutaway view of an objective lens driving device according to another embodiment of the present invention. In FIG. It is fixed to the base 1 so as to form a shaft, and has a screw portion 105 at the tip. Reference numeral 106 denotes a nut, which is a screw portion 10 for inhibiting movement of the inner peripheral surface of the damper 103 to focusing.
5 is attached. Reference numerals 107a and 107b denote small projections provided at both ends of the bearing cylinder 102 in the axial direction for holding the outer peripheral surface of the damper 103. In this case, the shaft
Formed on the inner circumference at both ends in the axial direction of the receiving cylinder 102
The small protrusions 107a and 107b press the outer peripheral surface of the damper 103.
By contacting and engaging, a restricting portion is provided on the damper 103.
The damper 103 itself.
Movement in the focusing direction can be more strongly regulated
You.

In the first embodiment of the present invention, the damper 10
If there is concern about the movement of the whole 3 in the focusing direction, for example, the configuration shown in FIG. 5 may be adopted. And the movement of the entire damper 103 in the focal length direction can be more firmly restricted.

Embodiment 3 FIG. 6 is an enlarged plan view of a bearing portion of an objective lens driving device according to another embodiment of the present invention. In FIG.
Is an axis, which is fixed to the base 1 so as to form an axis parallel to the optical axis of the objective lens. The outer peripheral surface of the shaft 108 is combined with a projection Q provided on the inner peripheral surface of the damper 109. A groove R is provided to perform initial positioning of the inner peripheral surface of the damper 109 in the tracking direction, and to regulate relative movement between the outer peripheral surface of the shaft 108 and the inner peripheral surface of the tamper 109 during the tracking control operation. Reference numeral 110 denotes a bearing cylinder fixedly provided on the movable plate 5. The inner peripheral surface of the bearing cylinder 110 has a groove T combined with a projection S provided on the outer peripheral surface of the damper 109. And the damper 109 is initially positioned in the tracking direction, and the relative movement between the inner circumferential surface of the bearing cylinder 110 and the outer circumferential surface of the damper 109 during tracking control is restricted. You
That is, the damper 109 is formed on the outer peripheral surface of the shaft 108.
Groove R and groove T formed on the inner peripheral surface of the bearing cylinder 110
The tracking method of the damper 109 itself by engagement with
The projections Q and S as the regulating parts for regulating the movement in the
It is provided. Therefore, the entire damper 109
To further restrict movement in the tracking direction
Can be set, and the initial angle of the tracking direction can be set.
Can be performed at the same time. In this case, the damper
The reference numeral 109 indicates that the cross-sectional shape is on the axis of the shaft 108 (support shaft).
It is formed so as to be non-rotationally symmetric.

In the first embodiment of the present invention, the damper 10
3 If you are concerned about the rotation of the entire tracking direction,
For example, the configuration as shown in FIG. 6 may be adopted, and the inner peripheral surface and the outer peripheral surface of the damper 109 are respectively formed by the shaft 108 and the bearing cylinder 1.
10 in the tracking direction with respect to the damper 10.
It becomes possible to further firmly restrict the movement of the entire 9 in the tracking direction. It is also possible to set the initial angle of the tracking direction at the same time.

[0022]

As described above, according to the present invention, the Coulomb frictional force existing in the sliding bearing mechanism can be removed, so that the quasi-static displacement in the focusing direction and the tracking direction and the driving electromagnetic force can be eliminated. By suppressing the hysteresis characteristics in the relationship, the pull-in characteristics in servo control can be improved, and the surface accuracy of the components that made up the sliding bearing mechanism can be significantly reduced, resulting in lower cost equipment. Become. Also, elastic body
Since the size of the damper can be greatly reduced and the mounting components can be simplified, the size and cost of the device can be reduced. Also,
A damper made of an elastic material has a support shaft,
Is the focus of the elastic body itself
Restrict movement in the singing or tracking direction
The damper itself.
Movement in the focusing or tracking direction
And the initial angle of the damper tracking direction
It is also possible to set the degree.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an objective lens driving device according to a first embodiment of the present invention, which is partially cut away.

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

FIG. 3 is a sectional view taken along line BB of FIG. 2 of the objective lens driving device according to the first embodiment of the present invention;

FIG. 4 is a view B in FIG. 2 showing a focusing control operation in the objective lens driving device according to the first embodiment of the present invention;
FIG.

FIG. 5 is a cross-sectional view of the objective lens driving device according to a second embodiment of the present invention.

FIG. 6 is an enlarged plan view of a bearing portion of an objective lens driving device according to a third embodiment of the present invention.

FIG. 7 is a plan view of a main part showing a conventional objective lens driving device.

8 is a sectional view taken along line AA in FIG. 7;

FIG. 9 is a perspective view of a main part of the device shown in FIG. 7, which is partially cut off.

[Explanation of symbols]

 5 Movable plate 8 Objective lens 101 Shaft 102 Bearing cylinder 103 Damper 108 Shaft 109 Damper 110 Bearing part

Claims (1)

(57) [Claims] 1. An objective lens for condensing a light beam on an optical information recording medium, and an axis parallel to an optical axis of the objective lens, and disposed at a position separated from the optical axis by a certain distance. and the support shaft and, together with the bearing sleeve portion coaxially with respect to the support shaft, and a movable body that holds the objective lens, a first drive means for the upper Symbol movable body is driven and controlled in the axial direction, In an objective lens driving device provided with a second drive means for rotating the movable body about the support shaft in the plane , the movable body is supported so as to be movable in the axial direction of the support shaft.
Together with the support shaft in a plane orthogonal to the support shaft.
Elastic body as a support means rotatably supporting as a center
Is provided between the support shaft and the bearing cylinder, and the elastic
The main body includes the above-mentioned support shaft, bearing cylinder, or both.
The elastic body itself in the focusing direction
Or a regulation unit to regulate movement in the tracking direction
An objective lens driving device, wherein a composed provided.