JPH0917006A - Suspension structure of objective lens driving device - Google Patents

Abstract

PURPOSE: To reduce the size and cost of the structure and to enhance its performance by providing the structure with second hinge members between a fixing member and leaf springs. CONSTITUTION: A first hinge member 1 is joined to an objective lens holder not shown in Fig. and consists of a base part 1a and a holder joint part 1b and a hinge 2 composed of a thin part therebetween. The one-side ends of the leaf springs 3a, 3b are coupled to the base part 1a of the hinge member 1 and the other-side ends are coupled to the second hinge members 5a, 5b integrally formed to the fixing member 4 made of a synthetic resin. The second hinge members 5a, 5b are so formed that the parts coupled with the leaf springs 3a and 3b are thick and are made gradually thinner toward the connecting parts to the fixing member 4. As a result, the larger deflection than the deflection of the conventional structure is made possible and the size is made smaller for obtaining the same deflection quantity as heretofore.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension structure of an objective lens driving device for performing tracking control and focusing control of a laser spot in a device for optically writing or reading information on an optical disk.

[0002]

2. Description of the Related Art An optical disk device for optically recording or reproducing an optical disk irradiates a recording spot on the optical disk with a laser spot by an optical pickup. In such an optical pickup, in order to correct the focus shift due to the warp of the optical disc and the tracking shift due to the eccentricity, the optical axis of the optical disc is kept by the objective lens driving device while keeping the optical axis of the objective lens perpendicular to the recording surface of the optical disc. It is necessary to drive in two axes, that is, the direction (focus direction) and the direction orthogonal to the optical axis, that is, the radial direction of the optical disk (tracking direction).

FIG. 4 shows an example of a suspension structure of an objective lens driving device in a conventional optical disk device. In this suspension structure, 1 is a holder-supporting hinge member made of synthetic resin or the like that is joined to an objective lens holder (not shown) that holds the objective lens.
hinge 2 composed of a thin portion between a and the holder joint portion 1b
Are formed. To the base portion 1a of the hinge member 1, one ends of leaf springs 3a and 3b made of metal or the like configured to be movable in the focus direction are coupled, and the leaf springs 3a and 3b.
The other end of is fixed to the fixing member 4.

This suspension structure is a driving means for swinging the objective lens holder in a plane orthogonal to the optical axis,
For example, by a tracking coil (not shown) driven by a tracking error signal, as shown in FIG. 5B, the holder joint 1b can be flexibly moved in the tracking direction by the hinge 2 of the hinge member 1. . On the other hand, the leaf springs 3a and 3b are shown in FIG. 5A in the focusing direction by the driving means for driving the objective lens in the direction parallel to the optical axis, for example, the focusing coil (not shown) driven by the focusing error signal. And the objective lens holder moves according to the hinge member 1. In this case, since both ends of the leaf springs 3a and 3b are coupled to the hinge member 1 and the fixing member 4, respectively, they can be regarded as fixed ends.

[0005]

With the above-mentioned conventional suspension structure of the objective lens driving device, it is difficult to further reduce the size, and in order to reduce the size, the leaf spring must be thin and short. It had a problem of becoming expensive. Further, in the case of the leaf spring, there is a problem that the Q value of the main resonance is high and the leaf spring is not stable when the disc track is accessed. In view of the above problems, it is an object of the present invention to provide a suspension structure for an objective lens driving device, which can be downsized, is inexpensive, and has high performance.

[0006]

The present invention provides a suspension structure of an objective lens driving device for driving an objective lens in a focus direction and a tracking direction in a device for optically writing or reading information on an optical disc, A lens holder that holds the objective lens, a first hinge member that supports the lens holder so as to be swingable in a plane orthogonal to the optical axis, one end of which is coupled to a fixing member, and the other end of which is the first hinge member. In a suspension structure including a leaf spring coupled to a hinge member and movably supporting the lens holder in the optical axis direction, a suspension structure is provided between the fixing member and / or the first hinge member and the leaf spring in the optical axis direction. This is provided with a movable second hinge member.

[0007]

The first hinge member for supporting the objective lens holder is connected to one end of the leaf spring, and the second hinge member is provided between the other end of the leaf spring and the fixing member. Due to the presence of the second hinge member, the leaf spring can be made of an inexpensive material without deteriorating the performance, and an inexpensive objective lens driving device as a whole can be provided. The second hinge member is not limited to being provided between the other end of the leaf spring and the fixing member, but may be provided between the leaf spring and the first hinge member or both of them.

[0008]

1 shows an embodiment of a suspension structure of an objective lens driving device of the present invention. The structure of FIG. 1 differs from the conventional structure of FIG. 4 in that one end of the leaf springs 3a and 3b is joined to the hinge member 1 and the other end is integrally formed with a fixing member 4 made of synthetic resin or the like. Members 5a, 5
Being bonded to b, the other structures are the same. The hinge members 5a and 5b are formed such that the portions where the leaf springs 3a and 3b are joined are made thicker and gradually become thinner toward the connecting portion with the fixing member 4, and the hinges are formed near the connecting portion. Composed.

This suspension structure has a driving means for swinging the objective lens holder in a plane orthogonal to the optical axis around the center of gravity of the holder, for example, a tracking coil (not shown) driven by a tracking error signal. As shown in FIG. 2B, the hinge 2 of the hinge member 1 allows the holder joint portion 1b to be flexibly moved in the tracking direction. On the other hand, the leaf springs 3a and 3b and the hinge members 5a and 5b are moved in the focusing direction by a driving unit that drives the objective lens in a direction parallel to the optical axis, for example, a focusing coil (not shown) driven by a focusing error signal. Bends as shown in FIG. 2A, and the objective lens holder moves according to the hinge member 1. In this case, the deflection of the combination of the leaf springs 3a and 3b and the hinge members 5a and 5b can be regarded as the deflection of one free end in which one end of the leaf springs 3a and 3b coupled to the hinge member 1 is fixed. A larger deflection than that of the conventional structure shown in FIG. 4 is possible.

In the constituent elements of the above embodiment,
Although the leaf springs 3a and 3b are made of metal, and the fixing member 4 and the hinge members 1, 5a, 5b are made of synthetic resin, different materials can be used, and each component is integrally formed. You may. In addition, the second hinge member,
Although it is provided between the other end of the leaf spring and the fixing member in the above embodiment, the present invention is not limited to this, and may be provided between the leaf spring and the first hinge member, or both.

As described above, the suspension structure of the present invention shown in FIG. 1 which can be regarded as a flexure at one free end and the conventional suspension structure of FIG. 4 which can be regarded as a flexure at both ends fixed, are subjected to the same load P respectively. Let us compare and calculate the deflection amounts v1 and v2. In the structure of the present invention shown in FIG. 1, an elastic curve when deflected in the focus direction is shown in FIG. 3A, and the amount of deflection v1 is represented by the following equation (1).

[0012]

[Equation 1]

Here, P is the load, L1 is the distance from the connecting point between the hinge member 1 and the leaf springs 3a and 3b to the connecting point between the fixing member 4 and the hinge members 5a and 5b, E is the Young's modulus, and I is the secondary cross section. It is a moment.

On the other hand, in the conventional structure shown in FIG. 4, the elastic curve when deflected in the focus direction is shown in FIG. 3B, and the amount of deflection v2 is expressed by the following equation (2).

[0015]

(Equation 2)

Here, P is the load, L2 is the distance from the connecting point of the hinge member 1 and the leaf springs 3a and 3b to the connecting point of the fixing member 4 and the hinge leaf springs 3a and 3b, E is the Young's modulus, I
Is the second moment of area. As is clear from the equations (1) and (2), L1 = L in the structures of FIGS.
If 2, it can be seen that v1> v2.

On the other hand, assuming that the leaf springs in the structures of FIGS. 1 and 4 are made of the same material and have the same main resonance f0, f
If 0 is the same, the amount of deflection is also the same, so the following equation (3) holds.

[0018]

(Equation 3)

From the above equation (3), L1 / L2≈0.63
Therefore, in order to obtain the same amount of deflection as the structure of FIG. 4, it can be seen that the length of the bent portion can be increased by 0.63 times, and the structure of FIG. 1 can be made smaller.

[0020]

According to the present invention, since one or both ends of the leaf spring are formed by hinge portions, it is possible to provide an objective lens driving device which is smaller than the conventional one. Also, if both ends of the leaf spring are the same length as the fixed end, the leaf spring can be made thicker, the manufacturing method is simplified, and an inexpensive objective lens driving device can be provided. Further, the Q value of the main resonance can be reduced, the operation at the time of accessing the disk track can be stabilized, and a high-performance objective lens driving device can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a suspension structure of an objective lens driving device of the present invention.

2A is a diagram showing a state where the suspension structure of FIG. 1 is moved in a focus direction, and FIG. 2B is a top view of the suspension structure of FIG.

3A is a diagram showing an elastic curve of the suspension structure of FIG. 1, and FIG. 3B is a diagram showing an elastic curve of the suspension structure of FIG.

FIG. 4 shows a perspective view of a suspension structure of a conventional objective lens driving device.

5A is a diagram showing a state where the suspension structure of FIG. 4 is moved in a focus direction, and FIG. 5B is a top view of the suspension structure of FIG.

[Explanation of symbols]

 1 Hinge member 2 Hinge 3a, 3b Leaf spring 4 Fixing member 5a, 5b Hinge member

Claims (1)

[Claims] 1. A suspension structure of an objective lens driving device for driving an objective lens in a focus direction and a tracking direction in a device for optically writing or reading information on an optical disc, the lens holder holding the objective lens. A first hinge member that swingably supports the lens holder in a plane orthogonal to the optical axis,
In a suspension structure including a leaf spring, one end of which is coupled to a fixing member and the other end of which is coupled to the first hinge member, the leaf spring movably supporting the lens holder in the optical axis direction. A suspension structure for an objective lens driving device, characterized in that a second hinge member movable in the optical axis direction is provided between the first hinge member and the leaf spring.