JPH08106642A - Optical pickup device - Google Patents

Abstract

PURPOSE: To prevent unwanted resonance around an o-axis as a center axis of four supporting members for supporting an objective lens. CONSTITUTION: A lens holder 2 equipped with the objective lens 1 is supported by free end parts of the four supporting members 5a-5d provided on a fixed part 6. These supporting members 5a-5d are provided in two parallel planes vertical to an optical axis, each allotted for one pair of the members respectively, and a space between the two pairs of supporting members is set to be wider on the side of the objective lens than the side of the fixed part 6. When the objective lens is to rotate around the o-axis, the two supporting members opposite to each other with the o-axis between them are acted by force to the compression side, while the other two supporting members the pulling side, and hence the lens holder 2 is prevented from turning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device, and more particularly to an optical pickup device of a type in which an objective lens is supported by four rod-shaped members.

[0002]

2. Description of the Related Art As a driving device of an optical pickup device used for a disc-shaped recording medium such as an optical disc such as a CD or MD or a magneto-optical disc, a rod-shaped body having four objective lenses as shown in FIG. 11 is used. It is well known that a supporting device of a supporting type is adopted. FIG. 14 is a simplified view of the optical pickup device of FIG.

The optical pickup device shown in FIG. 11 is mounted on a feed base (not shown) which is parallel to the information surface of the disk-shaped recording medium and is movable in the radial direction (radial direction, that is, tracking direction). There is. Other optical devices (not shown) are arranged on the feed base.

The objective lens 1 is attached to a lens holder 2. A focus coil 3 is attached to the lens holder 2 so that the objective lens 1 can be moved in the optical axis direction (focusing direction), and a tracking coil 4a is provided so that the objective lens 1 can be moved in a direction perpendicular to the optical axis direction. , 4b are attached. In this example,
The focus coil 3 is arranged on the inner wall of the hole formed in the lens holder 2.

The lens holder 2 is supported by the free ends of the four support members 5a-5d provided on the fixed portion 6. A pair of these support members 5a to 5d are provided in each of two parallel planes perpendicular to the optical axis, and the pair of support members are provided so as to be parallel to each other.

The fixing portion 6 is attached to the base 7. The base 7 is provided with a yoke 8a and a yoke 8b facing each other, and a magnet 9 is attached to one of them.

Each of the support members 5 has elasticity, which allows the lens holder 2 to maintain its posture and move in parallel in the focus direction and the radial direction. FIG.
Figure 13 shows the radial movement of the optical pickup device.
Shows the movement in the focus direction.

With such a structure, the focused light of the objective lens 1 attached to the lens holder 2 can follow the deviation between the information surface of the disk-shaped recording medium and the recording track formed on the surface. become.

[0009]

In such a drive unit for an optical pickup device, oscillation is apt to occur when there is unnecessary resonance within 3 to 5 times the servo control band, in which case control becomes impossible. As a player, a sound break occurs. The oscillation is triggered by surface wobbling or eccentricity of the disk-shaped recording medium, or external vibration.

In this apparatus, a driving force F generated by supplying an electric current to the focus coil 3 and / or the tracking coils 4a and 4b, and a movable portion (objective lens, lens holder, focus coil, tracking coil) supported by a supporting member. It is desirable that the center of gravity G of the coil ...) and the intersection point P that connects the four connection points of each support member and the movable portion be the same. However, these agreements are difficult due to design constraints or manufacturing variations.

As a result, the frequency f0 based on the mass M of the movable part and the spring constant K around the O-axis passing through the approximate center of the movable part and parallel to the support member (in FIG. 14, the relationship between f0 and K and M is shown). It is easy to generate unnecessary resonance alternating around the O-axis. FIG. 17 shows an example of vibration characteristics of this device.

FIG. 15 is a view of the lens holder 2 rotating around the O axis as viewed from the radial direction. As is clear from the figure, the lens holder 2 is closer to the fixed portion 6 side than the position before the rotation. 16 is a view of FIG. 15 as seen from the O-axis side. In each of the four support members 5, the same stress is generated around the O axis.

The present invention has been made to solve the above problems, and an object thereof is to provide an optical pickup device capable of suppressing unnecessary resonance around the O-axis.

[0014]

In order to achieve the above object, the present invention provides four rod-shaped support members for supporting an objective lens in pairs in two parallel planes perpendicular to the focus direction. It is characterized in that it is provided and the distance between the pair of support members is set wider on the objective lens side than on the fixed portion side.

[0015]

When the objective lens tries to rotate around the O-axis, a force acts on the two supporting members facing each other with the O-axis interposed therebetween, and on the pulling side of the other two supporting members. To do.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a schematic plan view of FIG. 1, and FIG. 3 is a schematic front view of FIG. The optical pickup device shown in each figure is mounted on a feed base (not shown) which is parallel to the information recording surface of the disk-shaped recording medium and is movable in the radial direction. The objective lens 1 that focuses the light emitted from the light emitting means in the sending base and irradiates the information surface as spot light is attached to the lens holder 2. A focus coil 3 is attached to the lens holder 2 so that the objective lens can be moved in the optical axis direction. Further, tracking coils 4a and 4b are mounted so that the coils can be moved in a direction perpendicular to the optical axis direction.

The lens holder 2 is supported by the free ends of the four rod-shaped supporting members 5a-5d provided on the fixed portion 6. A pair of these supporting members 5a to 5d are provided in two parallel planes perpendicular to the optical axis, and the distance between the pair of supporting members is set to be wider on the objective lens side than on the fixed portion side. ing. In this example,
The two pairs of support members provided in each surface are arranged in an isosceles triangle shape, and their vertices are on the fixed portion 6 side. The fixed portion 6 is attached to the base 7.
The base 7 is provided with yokes 8a and 8b facing each other, and a magnet 9 is attached to one of them.

Each of the support members 5a-5d has elasticity,
As a result, the lens holder 2 can be moved in parallel in the focus direction while maintaining the optical axis direction of the objective lens 1.
Also in the radial direction, while the optical axis direction of the objective lens 1 is maintained, the movement can be performed by performing an arc motion with the apex side of the angle formed by the two pairs of support members as the center point of rotation.

In order to simplify the description, description will be given below using the objective lens 1, the lens holder 2, the supporting member 5 and the fixing portion 6.

As shown in FIG. 4, in this embodiment, the focus direction (optical axis direction) is moved in the focus direction while maintaining the optical axis direction by the principle of a parallel spring. Regarding the radial direction, as shown in FIG. 5, two pairs of support members are arranged in an isosceles triangle shape, and an arc motion is performed to enable the movement.

The principle by which this embodiment prevents unnecessary resonance (rolling) around the O axis, which is the central axis of the four support members, will be described with reference to FIGS. 6 and 7. The balance between the generation point F of the driving force generated by applying a current to the focus coil and / or the tracking coil, the center of gravity G of the movable portion, and the intersection point P diagonally connecting the four support members 5a to 5d is out of balance. As shown in FIG. 7, it is assumed that the movable portion is tilted around the O axis. At that time, as shown in FIG. 6, the lens holder 2 is made up of the supporting member 5a and the supporting member 5d which face each other with the O-axis interposed therebetween.
And its connection point approach the connection point with the fixed part 6,
Bending and compressive stress are generated in these support members, which prevent the lens holder 2 from approaching the fixing portion 6 and prevent its rotation. On the other hand, in the support members 5b and 5c, the lens holder 2 and its connection point move away from the connection point with the fixed portion 6, so that a tensile stress is generated in those support members and the lens holder 2 is fixed to the fixed portion 6. Cause the approach of.

In this way, opposing forces are generated with respect to the lens holder 2, and the rotation thereof can be remarkably prevented. As a result, good vibration characteristics without unnecessary resonance as shown in FIG. 8 can be obtained.

9 and 10 are schematic plan views showing another embodiment of the present invention. FIG. 9 shows a supporting member 5a and a supporting member 5c.
And the supporting member 5b and the supporting member 5d are connected by the fixing portion 6. FIG. 10 shows that both ends of the support member are parallel to the O-axis to improve the assembling workability. Also with these configurations, it is possible to obtain an optical pickup device having characteristics similar to those of the embodiment shown in FIG.

[0024]

As described above, when the objective lens tries to rotate around the O axis, the two supporting members facing each other with the O axis interposed therebetween are pulled toward the compression side, and the other two supporting members are pulled toward each other. Force acts on each side. In this way, a force that opposes the objective lens is generated, and the rotation thereof can be significantly prevented. As a result, unnecessary resonance around the O axis can be prevented.

Further, since the spacing between the supporting members is narrower on the fixed portion side than on the objective lens side, it is possible to contribute to downsizing of the optical pickup device. That is, because the focus coil 3 and the tracking coil 4 are mounted on the lens holder 2 that supports the objective lens 1, the support member cannot be narrowed on the objective lens side, but there is such a restriction on the fixed side. No, it can be narrowed. This increases the degree of freedom in designing a disc player using the optical pickup device.

[Brief description of drawings]

FIG. 1 is a perspective view of one embodiment of the present invention.

FIG. 2 is a schematic plan view of FIG.

FIG. 3 is a schematic front view of FIG. 1.

FIG. 4 is a schematic front view showing the manner of movement in the focus direction according to the embodiment of the present invention.

FIG. 5 is a schematic plan view showing a state of movement in the radial direction according to the embodiment of the present invention.

FIG. 6 is a schematic plan view showing the manner of rotation around the O-axis according to the embodiment of the present invention.

FIG. 7 is a schematic side view showing the manner of rotation around the O axis according to the embodiment of the present invention.

FIG. 8 is a diagram showing an example of vibration characteristics according to an embodiment of the present invention.

FIG. 9 is a schematic plan view of another embodiment of the present invention.

FIG. 10 is a schematic plan view showing still another embodiment of the present invention.

FIG. 11 is a perspective view of a conventional optical pickup device.

FIG. 12 is a schematic plan view showing how the conventional optical pickup device is moved in the radial direction.

FIG. 13 is a schematic front view showing how the conventional optical pickup device moves in the focus direction.

FIG. 14 is a perspective view showing a schematic structure of a conventional optical pickup device.

FIG. 15 is a schematic plan view showing how the conventional optical pickup device is rotated around the O-axis.

FIG. 16 is a schematic side view showing how the conventional optical pickup device is rotated around the O-axis.

FIG. 17 is a diagram showing an example of vibration characteristics of a conventional optical pickup device.

[Explanation of symbols]

 1 Objective Lens 2 Lens Holder 3 Focus Coil 4a, 4b Tracking Coil 5a, 5b, 5c, 5d Supporting Member 6 Fixing Part 7 Base 8a, 8b Yoke 9 Magnet

Claims (1)

[Claims] 1. An optical pickup device in which an objective lens is supported by four rod-shaped support members so as to be movable in a focus direction and a radial direction with respect to a fixed portion, wherein each support member is 2 perpendicular to the focus direction. An optical pickup device, characterized in that a pair is provided in each of two parallel planes, and a distance between the pair of support members is set to be wider on the objective lens side than on the fixed portion side.