JPS62202340A - Objective lens driver - Google Patents

Abstract

PURPOSE:To decrease the kinetic energy supplied to a moving part including an objective lens at a proper speed by providing an accommodating means accommodating a damping member to a part of a wire. CONSTITUTION:In supplying a current to a focus coil 3 or a track coil 4, a magnetic field in the direction of the arrow B by the electromagnetic operation with a magnet and the force in the direction of arrow F is produced. Thus, four wires 40 of a moving part are moved with a deflection in the direction of arrow F by the force of the focus coil 3 in the focusing direction and the track coil 4 in the tracking direction. The movement of the moving part is controlled by silicon rubber gel injected in the accommodation section 42 and the vibration is attenuated when the damping system is resonated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an objective lens driving device for optically reading information by projecting a light spot onto a disk-shaped recording medium, for example in an optical disk device or the like.

[Technical background of the invention and its problems]

In general, in order to read information accurately in this type of optical disk device, focus control is required to control the distance between the objective lens and the information track position to prevent warping or wobbling of the disk, and to control the eccentricity of the information track. In contrast, it is necessary to perform tracking control to follow the objective lens, and for this purpose, an objective lens drive device in the focus direction and the tracking direction is required.

In addition, the objective lens is usually held by a spring, but in the past it was held horizontally without any load being applied, so when it is actually used, it is lowered due to the weight of the objective lens and its holder. 9. Therefore, there is a drawback that torsional resonance is likely to occur. Another method has been considered in which a predetermined bias current is passed through the drive coil in advance and the objective lens is lifted by the action of the bias current, but this method consumes excess power and tends to generate heat. There is.

Therefore, as a conventional example, an objective lens driving device as shown in No. 6@ has been considered. That is, the objective lens (1
) is fixed to the holder (2), and this holder (2)
A focusing direction drive coil (3) (hereinafter referred to as a focus coil) is wound around the holder (2), and two pairs of tracking direction drive coils (4) (hereinafter referred to as a focusing coil) are wound on both sides of the holder (2). , track coils) are glued, and these track coils (4) are connected in one piece.

In addition, (5) is a U-shaped base made of magnetic material,
On the inner wall of this base (5) are two magnets (6a),
(6b) are bonded to face each other to form a magnetic circuit for the focus coil (3) and track coil (4). The objective lens (1) is mounted on a holder (
Two metal wires (7) are inserted into the through holes (not shown) drilled in the convex portions (2a) and (2a) of (2), respectively, and are supported by these four metal wires (7). ing.

Therefore, by passing current through the focus coil (3) and track coil (4), the objective lens (
1) is adapted to move together with the holder (2) in two directions: focusing and tracking.

However, as shown in FIG. 7, in such a device, when a current is applied to the track coil (4) to shift it in the tracking direction, and then the focus coil (3) is driven in the focus direction, the focus coil (3) shifts. A positional shift occurs between the drive center (N) and the center of gravity (G) of the movable part consisting of the objective lens (1), holder (2), focus coil (3), and track coil (4). Therefore 1
A rotational moment (M) is generated around the center of gravity (G), causing the objective lens (1) to tilt together with the holder (2), resulting in comatic aberration, making it impossible to read information accurately. This has the disadvantage that the servo system becomes unstable.

FIGS. 8(a) and 8(b) show an example of an objective lens support device for attenuating kinetic energy applied to a movable part including an objective lens at an appropriate speed. In the figure, the objective lens (1), the focus coil (3), the track coil (4), and the holder (2) are connected to the fixed part (8).
is supported by four parallel metal wires (7). This metal wire (7) also serves as a lead wire (not shown) for the drive coils (3) and (4) and a support spring.
(7) is covered with a rubber tube (9) to add a damping effect.

In such a structure, the damping effect when displaced from the neutral point position shown in FIG. 8(a) to FIG. 8(b) is due to the bending deformation of the metal wire (7). 9)
This is due to the energy consumed in each part of the bending moment distribution (10), which has the same shape as the metal wire (7). However, since the curvature of the bending deformation of the metal wire (7) is minute, the corresponding deformation of each part of the rubber tube (9) is also minute, so the damping effect is not sufficient, and the mass of the support member is increased. However, this method has the disadvantage that it only increases the spring constant of the entire support mechanism.

[Purpose of the invention]

The present invention was made based on the above circumstances, and an object of the present invention is to provide an objective lens driving device that is capable of attenuating kinetic energy given to a movable part including an objective lens at an appropriate speed. .

[Summary of the invention]

In order to achieve the above object, the present invention includes an objective lens for condensing light onto an information storage medium, a holder for holding this objective lens, and a plurality of mutually parallel lenses that are fitted into and supported by this holder. a wire, a focus direction drive coil provided on the outer periphery of the holding body to drive the objective lens in the focus direction, a track direction drive coil to drive the objective lens in the track direction, and a magnetic circuit disposed opposite to these drive coils. In order to damp the vibration of the wire based on the kinetic energy of the drive coil, a housing means for housing a vibration damping member is provided in a part of the wire.

[Embodiments of the invention]

The present invention will be explained below based on an embodiment shown in FIGS. 1 to 5. First, an overview of an objective lens drive device used in an optical disk device will be explained. Now, in order to write or read information, a laser beam is focused on the surface of an information storage medium, and the imaged point is guided to a predetermined position by a spiral groove carved on the information storage medium. . Therefore, writing is performed by melting the thin film on the surface of the storage medium using the heat of the laser beam, forming a bit, and reading is performed by irradiating the storage medium with a laser beam and detecting the reflected light to recognize the presence or absence of a bit. It is done by doing.

To guide the above laser beam to a predetermined position, an optical system detects defocus and track position deviation, and a servo circuit drives an actuator to control the laser beam so that there is no blur in the focus direction or track position misalignment. There is a need to. In order to realize this control, the objective lens driving device is capable of driving the objective lens in two directions: focus and track. That is, as shown in Fig. 3, the objective lens (1), the drive coil in the focus direction (
3) (hereinafter referred to as a focus coil) and a tracking direction drive coil (4) (hereinafter referred to as a track coil) form an integral movable part, and are wires made of non-metallic fibers, such as carbon fibers, arranged in parallel. One end of the wire (40) supported by the wire (40) is fitted into a block (41) mounted on the base (31), and the movable part is connected to the wire (40) from the block (41).
). That is, a accommodating part (42) into which gel silicone rubber (S) is injected is bored in the block (41), and this accommodating part (42)
) into which the end of the wire (40) is inserted.

In addition, as shown in Fig. 1, there is a magnetic material (
For example, a yoke (32a) made of Fe), (32
b).

(32c) is erected and formed integrally, and the inner wall surfaces of the yokes (32a) and (32b) each have one
A pair of magnets I'' (33a) and (33b) are mounted facing each other, while the above-mentioned focus coil (3) and track coil (4) are wound around the outer periphery of the yoke (32c) to form a magnetic circuit. It consists of

Further, (34) is a printed circuit board attached to the outer wall surface of the yoke (32a) set up on the base (31). Lead wires (3L) leading out from both ends and lead wires (4L) leading out from both ends of the track coil (4)
are soldered to each other, and lead wires (35) are further soldered to each of them through the patterned copper foil for electrical connection.

When current is supplied to the focus coil (3) or the track coil (4), the magnet (3)
3), a magnetic field in the direction of arrow B is generated, and a force in the direction of arrow F appears at the position indicated by the dashed-dotted line according to Fleming's left hand rule (see Figures 4(a) and (b)).

Therefore, the movable part is moved by the four wires (40) by the force of the focus coil (3) acting in the focusing direction and the force of the track coil (4) acting in the tracking direction.
exhibits a phenomenon in which they are each curved and moved in the direction indicated by arrow F. At this time, the movement of the movable part is controlled by gel-like silicone rubber (S) injected into the housing part (42), so that vibrations are damped when this vibration system resonates.

Next, in order to attenuate the kinetic energy generated by the focus coil and the track coil in the movable part including the objective lens, an opening of the housing part (42) is introduced as a method of injecting gel-like silicone rubber (S) into the housing part (42). Although it is possible to inject gel-like silicone rubber (S) in the form of droplets from the side, this has the disadvantage that bubbles are likely to be generated and workability is poor. Therefore, in the present invention, a means for injecting gel-like silicone rubber (S) will be explained in detail based on FIG. 5.

In the figure, (41) is a block having an accommodating part (42) in which gel silicone rubber (S) is accommodated and an insertion hole (43) for fixing one end of each of the four wires (40); The seal) is a movable part for inserting and fixing the other end of the wire (40) into a hole (not shown) made in the holder (2) of the objective lens (1). Also, (4
4) is the housing part (4) from the side of the block (41).
2) is an injection hole for gel-like silicone rubber that is penetrated through the side surface, and the size of this injection hole (44) is, for example, that of a syringe (13).
The syringe (13) is set to such an extent that a syringe needle (13a) can be inserted into the syringe (13), and gel-like silicone rubber (S) as a vibration damping member is accommodated in the syringe (13).

Therefore, when injecting the gel silicone rubber (S) into the accommodating part (42) of the block (41), the block (41) should be placed so that the accommodating part (42) faces upward as shown in FIG.
) and place one end of the wire (40) in the housing part (42).
From there, insert it toward the insertion hole (43). On the other hand, the other end of the wire (40) is inserted into a hole in the holder (2) that forms part of the movable part (30) for positioning.

Next, insert the injection needle (13a) of the syringe (13) containing the gel silicone rubber (S) into the injection hole (44) provided on the side surface of the block (41), and
By injecting from the bottom of 2), gel-like silicone rubber (S) can be easily injected.

〔Effect of the invention〕

As explained above, according to the present invention, the objective lens holder is supported by a wire, and the objective lens is provided with a movable part consisting of a drive coil in the focus direction and a drive coil in the track direction that apply driving force to the holder. In this drive device, the kinetic energy of the movable part can be injected into the vibration damping member around the wire at a faster injection speed, and the generation of bubbles can be suppressed and the injection can be performed easily, improving workability. This has the effect that it is possible to improve the

[Brief explanation of drawings]

FIG. 1 is a perspective view of an objective lens driving device showing an embodiment of the present invention, FIG. 2 is a front view of FIG. 1 viewed from the direction indicated by the arrow, and FIG. 3 is a portion showing the main parts of the device Cross-sectional view, Figure 4 (
a) and (b) are explanatory diagrams showing the force generated and the force generated in the wire when current flows through the drive coil in the focus direction and the drive coil in the track direction, respectively.
The figure is a perspective view showing a method of injecting a vibration damping member around a wire made of non-metallic fibers, FIG. 6 is a perspective view of an objective lens drive device showing a conventional example, and FIGS.
b) is a schematic plan view and front view for explaining the cause of the tilting of the objective lens, and FIGS. FIG. 1... Objective lens 2... Holder 3...
Focus coil (drive coil in focus direction) 4.
...Track coil (drive coil in the track direction) 13
...Syringe 13a...Syringe needle S...
・Gel-like silicone rubber (vibration damping member) average...Movable parts 33a, 33b...Magnet 40
・・・Wire 41...Block 42・
... Accommodation part 43 ... Insertion hole 44 ...
injection hole

Claims (3)

[Claims] (1) An objective lens that focuses light on an information storage medium, a holder that holds this objective lens, a plurality of mutually parallel wires that are inserted into and supported by this holder, and an outer periphery of the holder. a focus direction drive coil that is provided to drive the objective lens in the focus direction and a track direction drive coil that drives the objective lens in the track direction; a magnetic circuit that is disposed opposite to these drive coils; and a kinetic energy of the drive coil. 1. An objective lens driving device comprising a housing means for housing a vibration damping member in a part of the wire in order to damp vibrations of the wire. (2) The accommodating means is comprised of a accommodating part provided around the wire and an injection hole drilled in the side surface of the accommodating part through which the vibration damping member can be injected. The objective lens driving device according to item 1. (3) The objective lens driving device according to claim 2, wherein the vibration damping member is made of gel-like silicone rubber.