JPS63266644A - Objective lens supporting device - Google Patents

Abstract

PURPOSE:To support a moving part without inclination by supporting the moving part including an objective lens movably and displacably to a fixed part with a wire to form a bent part arranged in a point symmetry to the gravity center of the moving part. CONSTITUTION:A moving part 20 is supported by a wire 10, and both side surfaces at the remotest position from the gravity center of the moving part 20 are supported at the section of the fixed part so that the rigidity can be made largest to the rotation of the moving part 20. Thus, by supporting both remotest side surface from the moving part 20, the rotation of the moving part 20 can be suppressed. For the wire 10, the rigidity is comparatively small in a Z shaft direction and an X shaft direction and it is comparatively large in a Y shaft direction, and therefore, the moving part 20 can be displaced with the Z shaft direction and the X shaft direction as the focusing direction and the tracking direction. A supporting member is of an S-shape, arranged so as to come to be a point symmetry to the gravity center of the moving part 20, and the wire 10 is linked by an attenuating material 11 between adjoining lines in the part bent to 180 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an objective lens support device for an optical pickup.

(Prior Art) In a device that uses a laser beam to record and reproduce information on an optical recording medium in the form of a disk or a card, the laser beam is focused by an objective lens onto an information bit string, or so-called track, on a rotating disk or reciprocating card. It is necessary to irradiate the laser beam with high precision. In general, a bit string on the surface of a recording medium that rotates or reciprocates, the position of the pit string constantly fluctuates in the direction perpendicular to the direction of the pit string and in the tracking direction due to surface runout or eccentricity of the recording medium, and its size changes. is very large compared to the recording density. In order for the laser beam to track this pit row, it is necessary to move the laser beam in the focus direction and in a direction perpendicular to the track and perform tracking control. There are several mechanisms for moving the laser beam, but the most commonly used method is to drive the objective lens two-dimensionally in parallel. For example, in the conventional example shown in FIG. 5, four parallel metal wires 16 covered with attenuating materials are used for objective lenses l and 1! A magnetic drive coil 3.4 is supported, and the elastic deformation of this metal wire 16 allows the objective lens 1 to be moved in parallel in two directions.

An optical pickup having a mechanism like the one shown in FIG. 3 is usually used with a mechanism that moves the entire pickup largely in the track direction in order to read information at any position on the recording medium that cannot be reached by just moving the objective lens l. Recording and reproducing apparatuses such as optical disk players equipped with optical pickups are required to have optical pickups that are as small and lightweight as possible for miniaturization and high-speed information retrieval. However, in the conventional system shown in FIG. 5, if the structure is further reduced, the movable range required for the objective lens 1 is smaller than that of the metal 11i! If the length of the metal wire 16 is not sufficient, the deformation of the metal wire 16 due to the displacement of the movable part will become large, and there is a possibility that the metal wire 16 will deviate from the linear range as a spring. Furthermore, the positional accuracy of the metal wires 16 is required to be higher as the length becomes shorter in order to maintain parallelism between the metal wires. This becomes an extremely large obstacle to miniaturization and productivity improvement.

Four parallel straight lines (metal wire 1
When the movable part is supported in step 6), the degree of freedom around the X-axis in the coordinate system shown in the figure is restricted by the expansion and contraction rigidity of the metal wire 16. Although this is an advantageous mechanism for moving the movable part in parallel in a low frequency range, mechanically the natural vibration in the rotation mode around the X axis exists in a relatively high frequency vibration range. It is difficult to suppress this resonance phenomenon even with the damping material provided to the four metal wires 16, and unless the center of gravity is completely driven, the excitation frequency is the most inconvenient in the control system. Sub-resonance occurs in the area, making it impossible to realize a stable control system. In addition, complete center-of-gravity drive requires accurate weight balance of the movable parts and accurate positioning of the drive coil, which greatly impairs productivity.

(Problem to be solved by the invention) In this way, in the conventional = *≠ movable part supported by four parallel metal wires, the length of the metal wires has become shorter due to the construction of a shed. Problems arose, such as deviations from the linear range and difficulty in managing the parallelism of the four lines.

The present invention has been made in view of the above circumstances, and its purpose is to provide an objective lens support device which is a support member of a shed and which does not tilt the movable part and has less distortion of each part of the support member. be.

[Structure of the invention]

(Means for Solving the Problems) The objective lens support device of the present invention has a movable part including an objective lens with a curve υ that is arranged point-symmetrically with respect to the center of gravity of the movable part.
It is movably supported on a fixed part by a wire in which a portion is formed.

(Function) In the case of a device using such a supporting member, even if the wire is made smaller and shorter, sufficient linear deformation can be performed because of the bending portion, and the wire is less distorted. In addition, since it has a curved part, the wire has a relatively large spring constant in the longitudinal direction, and can be deformed in a direction perpendicular to this (focus direction, tracking direction) with a smaller spring constant than in the above direction. .

In addition, since the wire is arranged symmetrically with respect to the center of gravity), the rotation of each part of the wire due to the bending moment of the wire becomes zero at the support point of the movable part, regardless of whether it is displaced in the focus or tracking direction, and the movable part is tilted. Parallel movement is possible without any movement.

(Example) The present invention will be described in detail below with reference to FIGS. 1 to 4.

FIG. 1 is a perspective view of a first embodiment of the present invention, and FIG. 2 is an exploded perspective view. In FIGS. 1 and 2, the objective lens 1 is driven translationally in the Z direction and the X direction of the coordinate axes shown in the figures.

The objective lens 1, counterweight 2, focus coil 3, and tracking coil 4 are integrated, and the focus coil 3 is wound around the original axis of the objective lens Io.
The upper and lower focus coil end plates 5 are connected to the objective lens 1 and the counterweight 2 and fixed by adhesive, thereby forming a movable part 20. The four tracking coils 4 are attached to the side surface of the focus coil 3 in a direction whose winding axis is perpendicular to the optical axis of the objective lens 1, and the combined driving force is applied to the movable part 2.
It is attached to drive the center of gravity of 0. These movable parts 20 include the center ball 12 of the magnetic circuit 2) on the fixed side in the focus coil 3, and the magnetic circuit 2) formed by the permanent magnet 7, the meter 8, and the center ball 12 on the fixed side. Focus coil 3 in the gap
and a portion of the tracking coil 4 is configured to enter therein. The movable part 20 integrated with this adhesive configuration is
Although supported by the wire 10 of the invention, the movable part 20
The movable part 2
Both sides located farthest from the zero center of gravity are supported between the fixed part. By supporting both side surfaces farthest from the movable part 20 in this manner, rotation of the movable part 20 can be suppressed.

This wire 10 has relatively low rigidity in two directions along the coordinate axes in the figure, and in the X direction, but relatively high rigidity in the Y direction. Therefore, it becomes possible to displace the movable portion 20 with the Z-axis direction and the X-axis direction serving as the seven orcasing directions and the tracking direction, respectively. The support member has an S-shape and is arranged point-symmetrically with respect to the center of gravity of the movable part 20. As shown in the figure, this wire 10 is bent at 180 degrees and a damping material 11 is inserted between adjacent wires.
It is connected by . Note that the damping material 11 may be made of silicone rubber or silicone gel packed in a small case and attached. In addition, any other material may be used as long as it can provide appropriate attenuation. The damping materials 11 are also arranged at positions symmetrical to each other with respect to the center of gravity, and a suitable balance is obtained.

FIG. 3 shows how the wire 10 is deformed. Since the wire 10 has a symmetrical shape with respect to the position of the movable part 20 shown by the broken line, no inclination occurs even when the wire 10 is displaced in two directions.

In addition, in the conventional example shown in FIG. 6, a damping material is provided around the metal 916 in order to suppress the secondary resonance and the vibration at the main resonance to a certain amount, and to quickly perform the objective lens control retraction operation. However, due to the distortion of the damping material caused by the bending of the metal wire 16, a sufficient damping effect cannot be obtained unless the diameter of the damping material is large in the method shown in the figure. Damping materials generally have spring properties in addition to viscosity, and if an excessive amount of damping material is used, the spring rigidity of the support system will also increase.

The mounting position of the damping material of the present invention is A shown in FIG.

This is position B. The amount of change in the distance between the lines of the A and B portions due to the displacement of the movable part 20 is several tenths of the displacement position of the movable part 20. According to the experiments conducted by the present inventors,
If the damping material is attached to a location where the movable part 20 is displaced at a rate of 15% to 35 inches, an appropriate strain will be applied to the damping material, resulting in an excellent damping effect.

FIG. 4 shows a second embodiment of the invention. In the first embodiment, the linear wire 10 is bent in a plane parallel to the optical axis, but in the second embodiment, it is bent in a plane perpendicular to the optical axis. Even with such a shape, the same function can be obtained if the arrangement is point symmetrical with respect to the center of gravity of the movable horsetail. Further, with such an arrangement, it is possible to reduce the support spring constant in the seven focusing directions in which the amount of movement of the objective lens 1 is large compared to the tracking direction, and it is possible to obtain even better performance than in the first embodiment.

By forming the bent portion in the wire 10 in this way, even when the optical head is miniaturized and the support member is shortened, it is possible to cause the support member to undergo linear deformation within the range of displacement, thereby reducing distortion of the support member. becomes less.

In addition, the degree of freedom around the X-ray in the figure can be obtained to some extent by forming the curved part, and the natural frequency of the rotational mode around the X-ray can be lowered to a frequency range that does not adversely affect the servo control system, making it stable. A control system can be realized.

Note that the shape of the wire 10 is not limited to the above-mentioned embodiment, and may be a tri-shaped support member 10 or a corrugated wire lO as shown in FIGS. 5(a) and 5(b). It is sufficient if they are arranged symmetrically with respect to the center of gravity.

Further, since the wire serves as a lead wire, there is no need to take out a lead wire from the movable part, and vibration characteristics are excellent.

As described above, the present invention can be modified in various ways without departing from its gist.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to obtain an objective lens support device that reduces distortion of the support member and does not cause tilting of the objective lens even when downsized.

[Brief explanation of drawings]

1 is a perspective view of the first embodiment of the present invention, FIG. 2 is an exploded perspective view of the first embodiment of the present invention, FIG. 3 is a modified view of the supporting member of the present invention, and FIG. 4 is a perspective view of the first embodiment of the present invention. FIG. 5 is a side view showing a modified example of the present invention, and FIG. 6 is a perspective view showing a conventional example. 1...Objective lens 3...Focusing coil 4...Tracking coil 5...End plate 6...Side plate 7... ... Permanent magnet 8 ... Yoke 9 ... Fixed plate A 10 ... Wire 11 ... Damping material 12 ... Center ball 13 ...Fixed plate B 20...Movable part

Claims (5)

[Claims] (1) a driving means for moving and displacing an objective lens and a movable part including the objective lens relative to a fixed part consisting of a base at least in the optical axis direction of the objective lens or in a direction perpendicular to the optical axis direction; An objective lens support device, comprising: a wire that movably supports the movable part on the fixed part and has a bent part arranged point-symmetrically with respect to the center of gravity of the movable part. (2) A damping material is provided around the support member in point symmetry with respect to the center of gravity of the movable part.
The objective lens support device described in . (3) The damping material is provided at a location that is displaced at a rate of 15% to 35% of the amount of displacement of the movable part when the support member is displaced. Objective lens support device. (4) The objective lens support device according to claim 1, wherein the side surface of the movable part furthest from the center of gravity of the movable part is supported by the fixed part by the support member. (5) The objective lens support device according to claim 1, wherein the support member has a bent portion in a plane perpendicular to the optical axis of the objective lens.