JPS62129946A - Actuator for optical head - Google Patents

Abstract

PURPOSE:To simplify the structure of an actuator for an optical head and to obtain the actuator which is easy to assemble and reduced in size by supporting a bobbin where an objective is mounted symmetrically and elastically from both sides by a curved leaf spring. CONSTITUTION:This device has the bobbin 28 which holds the objective 34, a focusing coil 30 provided on the flank of the bobbin 28, a tracking coil 32 fitted on the bobbin flank overlapping with the coil 30, and a magnetic circuit which applies a command magnetic field to both coils 30 and 32. This bobbin 28 is supported movably in a focusing and a tracking direction by the curved lead spring 36 provided between both mutually opposite flanks which are not inserted into a magnetic gap and a base member 20. Thus, the bobbin 28 is supported symmetrically and elastically by the curved lead spring 36, so the structure is simple and the size is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical system in which a bobbin carrying an objective lens is movably supported in a focusing direction and a tracking direction by curved plate springs provided with opposing U-mouths. Concerning actuators for henodes.

U Prior Art] In an optical disc system that reads information on an optical disc or writes information on an optical disc, optics uses a semiconductor laser as a reading or writing stylus.

is used. In this type of optical system, a laser beam is focused by an objective lens and irradiated onto the bit part on the disc, but the diameter of the light spot that irradiates the pit part is about 1 μm. fi+I? so that fi+I connects the point correctly at a predetermined position on the signal surface of the optical disc. n
There is a need to.

For this reason, the objective lens must be configured to be movably supported and driven in at least two directions, the focusing direction and the tracking direction, and various support and drive structures have been used in the past. . At present, the force that drives this type of objective lens is generally an electromagnetic force generated by the interaction between a current flowing through a coil and a magnetic field.

A typical example of the support structure for the objective lens is a spring type.

For example, a structure is adopted in which a bobbin on which an objective lens is mounted is supported by a plurality of elastic arms (for example, an elastic linear member such as a wire covered with rubber). A predetermined coil is wound around the bobbin, and by applying an electromagnetic force due to the coil current and an external magnetic field, it is possible to drive the bobbin in the force nosing direction and the tracking direction perpendicular thereto.

[Problems to be Solved by the Invention] However, in this method of supporting the bobbin on which the objective lens is mounted in a cantilevered manner with an elastic arm, it is difficult to provide appropriate elasticity.
Moreover, in order to prevent the actuator from tilting with respect to the disk surface, the elastic arm must be made long, which is a major constraint in reducing the size of the actuator.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved actuator for an optical head that overcomes the drawbacks of the prior art as described above, has a simple structure, is easy to assemble, and is suitable for miniaturization.

[Means for Solving the Problems] The present invention, which can achieve the above-mentioned objects, has a structure in which a bobbin on which an objective lens is mounted faces each other (supported by curved plate springs arranged). It is an actuator for

The bobbin includes a focusing coil provided on its side and a tracking coil attached to overlap the focusing coil, and is inserted into the gap of the magnetic circuit.

[Operation] The bobbin supported from both sides by curved leaf springs is movable in the four force sowing direction and the tracking direction.

The interaction between the magnetic field generated in the magnetic gap by the magnetic circuit and the current flowing through the focusing coil drives the bobbin in the focus song direction, and the interaction between said magnetic field and the current flowing through the tracking coil drives the bobbin. Driven in the tracking direction.

[Embodiment] FIG. 1 is an exploded perspective view showing an embodiment of an actuator for an optical head according to the present invention, and FIG. 2 is a schematic diagram without showing the support structure of the bobbin. Two magnetic circuits are assembled using the base member 20. These magnetic circuits are composed of a U-shaped yoke 22 provided on the side of the base member 20, and a permanent magnet 24 attached to the inner surface of one of the yoke 22, symmetrically provided.

The opposing side walls of the two bobbins are then inserted into the gear knobs of two sets of magnetic circuits, respectively.

The bobbin 28 has a focusing coil 3 on its outer surface.
0 is provided, and two tracking coils 32 are attached to each of the magnetic gap portions so as to overlap thereon. The tracking coil 32 is wound into a substantially rectangular shape and is mounted symmetrically with respect to the center within the magnetic gap. A lens holder 35 that holds an objective lens 34 is mounted on the upper surface of the bobbin 28 .

The present invention is significantly different from the prior art in the support structure of the bobbin 28. In the present invention, a curved leaf spring 36 having a C-shaped cross section is provided between the base member 20 and both opposing sides of the bobbin 28 (the one not located in the n air gap).
It is mounted symmetrically so as to bulge outward, and is supported movably in the four force sowing direction F and the tiger and king direction T due to its elasticity. An example of the shape of the part during movement is shown by imaginary lines in FIG. In addition, a plurality of steel balls 29 are embedded in the recessed outer surface of the bobbin 28 and are in constant sliding contact with the yoke 22.
The magnetic gear knob is designed not to move in the longitudinal direction.

The permanent magnet 24 attached to the yoke 22 is
As shown in the figure, it may have a very simple shape such as a rectangular parallelepiped. So like rare earth magnets? ! It is possible to use very strong stone, which is difficult to process, for rough shapes, and this, combined with the pure ML support structure using curved leaf springs, has the advantage of making the device more compact. .

The actuator thus configured operates as follows. The magnetic circuit with the bobbin installed is S as shown in FIG. The force nosing coil 30 is wound around the central axis of the bobbin 28 in an I-roidal shape, so when a current is passed through it, as in the case of a normal voice coil, it interacts with an external magnetic field. An upward or downward force acts. Since the bobbin 28 is supported by curved leaf springs 36 on both sides, it can be displaced in the force nosing direction by receiving the electromagnetic driving force thereof.

Since the tracking coil 32 has a structure in which rectangular pattern-wound coils are attached symmetrically, the interaction between the current flowing through the wire portion orthogonal to the focusing coil 30 and the external magnetic field causes the magnetic field to move in the direction of the front and back of the paper in FIG. The power of works. The current flowing through the wire component of the tiger 7 king coil 32 that is wound in the same direction as the force nosing coil 30 is exactly opposite in the upper and lower parts and cancels each other out, so no driving force is generated in the four force nosing direction. .

Since the bobbin 28 is thus movable in the force nosing direction and the tracking direction, the objective lens 34 can be positioned by controlling the currents flowing through the two types of coils. At this time, as is clear from FIG. 2, since the objective lens 34 is supported symmetrically from both sides by the curved leaf spring 36, it always maintains a substantially parallel state to the base member 20 when driven. Continue to do so.

Note that the shape of the curved leaf spring is not limited to that shown in FIG. For example, it may be an arcuate leaf spring as shown in FIG. 4A, an arcuate leaf spring with a flat portion as shown in FIG. 4B, or an elliptical leaf spring as shown in FIG. 4C.

Although a preferred embodiment of the present invention has been described in detail above, it goes without saying that the present invention is not limited to only such a configuration. It goes without saying that the shape of each yoke, the shape of the base member, the shape of the bobbin, etc. can be changed as appropriate. There is one curved plate blade on each side,
A plurality of them may be provided on each side. In the above embodiment, the tracking coil is pasted on the outside of the four-force socing coil, but it is also possible to have a configuration in which the tracking coil is pasted on the side wall of the bobbin and the focusing coil is wound on top of it. be. The permanent magnets constituting the magnetic circuit may be attached to the inner yoke side.

[Effects of the Invention] As described above, the present invention has a configuration in which the bobbin on which the objective lens is mounted is symmetrically and elastically supported from both sides by curved leaf springs, so the structure is extremely simple and assembly is easy, resulting in a significant cost reduction. It also has the effect of being easily miniaturized since a long elastic arm is not required.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view showing one embodiment of the actuator for an optical gutter according to the present invention, Fig. 2 is a schematic diagram showing its bobbin support structure, Fig. 3 is an explanatory diagram of its magnetic circuit, and Fig. 4 A, B, and C are explanatory diagrams showing other examples of curved leaf springs, respectively. 20...Base member, 22...Yoke, 24...
Perpetual N stone, 28...Bobbin, 30...Four force nosing coil, 32...Tracking coil, 34...
・Objective lens, 36...curved leaf spring. Patent applicant: Fuji Electrochemical Co., Ltd. Representative: Minoru Shigeru Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A bobbin that holds an objective lens, a focusing coil provided on the side surface of the bobbin, a tracking coil attached to the side surface of the bobbin so as to overlap with the focusing coil, and a magnetic circuit that applies a common magnetic field to both coils. In the device, the bobbin is supported so as to be movable in the focusing direction and the tracking direction by a curved leaf spring provided between the base member and both opposite side surfaces of the bobbin that are not inserted into the magnetic gap. An actuator for optical heads featuring: