JPH01204232A - Lens actuator - Google Patents

Abstract

PURPOSE:To suppress the inclination in a rolling direction and to allow stable tracking servo and tracking jump operation by arranging the magnetic field of a magnetic circuit to be parallel with the shaft direction of a wire so as not to be drive in the direction of rotation of a condenser lens and its holding body. CONSTITUTION:A condenser lens 1 and a holding body 2 are supported by four wires 3a-3d and permanent magnets 7a and 7b and yokes 8a-8d are arranged so as to face to respective driving coils 5, 6a-6d. Then, the magnetic circuit is formed. The magnetic field of this magnetic circuit is arranged so as to be parallel with the shaft direction of the wires 3a-3d and not to be driven in the direction of rotation of the condenser lens 1 and its holding body 2. Thus, the inclination of the condenser lens 1 and holding body 2 in the rolling direction is suppressed and the stable tracking servo, and tracking jump operation can be executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for recording information on the surface of an information recording medium using an optical method such as an optical information device or a data file device, or for recording information that has already been recorded. The present invention relates to a lens actuator that causes a lens to follow the surface runout of a disk in an optical head for reproducing or erasing, or to follow the surface runout and eccentricity of a disk in an optical head for erasing.

[Conventional technology]

Optical disk memories are capable of high-density recording by recording and reproducing information using laser light focused to about 1 μm. In order to achieve this high recording density, it is necessary for the light focused by the lens to correctly focus on all replaced disks and to trace the grooves of the book without deviating from the grooves. In other words, the lens actuator always maintains this good beam focusing state.
This is an extremely important key component that allows the lens to track the surface runout of the disk and the eccentricity of the recording track with submicron precision.

The objective lens is usually designed as a combination lens that also includes the substrate of the disk or a cover glass, and when the lens is tilted with respect to the disk, this combination shifts, causing aberrations in the focused beam. Currently, the tilt of the lens allowed on the device side is about several minutes. In addition, in order to make the lens follow the surface runout and eccentricity of about 1100Ji with submicron precision,
A servo band of about 1 to 2 kHz is required.

Therefore, a lens actuator for an optical disk memory is required to have wide-band dynamic characteristics and maintain accurate posture of the lens.

Lens actuators are mainly of the two-dimensional driving force type that drives in the focusing direction and the tracking direction, and are roughly classified into sliding type and spring supported type depending on the method of supporting the movable part. However, the sliding type is generally used for CDs due to the mechanical gap between the shaft and the sleeve, but it is not suitable for highly accurate and reliable lens position control as in optical disk memory devices. It is difficult to apply this method to devices that require this. Therefore, a wire-supported lens actuator was developed.

FIG. 2 is a perspective view of an example of a conventional wire-supported lens actuator.

A lens actuator that supports a lens portion with a plurality of wires 3a to 3d has been developed. This has a configuration in which the lens 1 is supported by a plurality of wires of equal length arranged from the body in the jitter direction, so that the lens can be moved in parallel in both the focus and tracking driving directions.

This wire-supported lens actuator has a simple supporting part, so it has straightforward characteristics and is less likely to cause unnecessary resonance, so it can be expected to have a wide band.

Furthermore, it has the advantage of being small, thin, lightweight, and easy to manufacture.

[Problem to be solved by the invention]

However, with this configuration in which the movable part is supported by wire, the restraining force in the rotating direction of the movable part is comparable to the restraining force in the focus and tracking directions, and the rigidity is extremely weak, so it may not vibrate in the rolling direction. Cheap. This movement in the rolling direction causes a problem in that the lens tilts and becomes an unstable factor in tracking servo and track jump operations.

[Means to solve the problem]

The present invention provides a condensing lens for condensing laser light onto the surface of an information recording medium, a holder for holding the condensing lens, a plurality of mutually parallel wires supporting the holder, and the holder. a focusing direction drive coil fixed to the condenser lens to drive the condensing lens in the focus direction, a tracking direction drive coil to drive the condensing lens in the tracking direction, and a magnet arranged to face each of the drive coils to form a magnetic circuit. The lens actuator is characterized in that the condenser lens and its holder are not driven in the rotating direction by arranging the magnetic circuit so that the magnetic field direction is parallel to the axial direction of the wire. shall be. Further, it is characterized in that it is configured so that driving force in the focusing direction and the tracking direction can be obtained by the same magnetic circuit.

〔Example〕

FIGS. 1(a) and 1(b) are a top view and a sectional view taken along the line AA', showing an embodiment of the present invention.

The condenser lens 1 and its holder 2 are connected to four wires 3a~
A focusing coil 5 is supported by the fixed part 4 at d, and also drives the condenser lens 1 and the holder 2 in the focusing direction, and tracking coils 6a to 6a to drive the focusing lens in the tracking direction.
d is fixed to the holder 2. Further, permanent magnets 7a, b and yokes 8a to 8d are arranged to face each of these drive coils to form a magnetic circuit.

When the magnetic circuits are arranged so that the magnetic field direction is perpendicular to the axial direction of the wire as shown in Figure 3(a), if an imbalance occurs in each magnetic circuit, as shown in Figure 3(b).
), the movable part also receives force in the rolling direction.

Therefore, as shown in FIG. 1(a), by arranging the magnetic circuits so that the magnetic field direction is parallel to the axial direction of the wire, the inclination caused by the imbalance of the magnetic field strength of each magnetic circuit can be As shown in FIG. 1(b), this occurs in the pitching direction and does not occur in the rolling direction. Here, the rigidity in the pitching direction is stronger than the rigidity in the rolling direction, and pitching resonance does not appear within the servo band, so it does not pose a problem.

In addition, the rolling phenomenon occurs due to mismatch between the center of gravity of the movable part, the point of application of the driving force, and the center of each wire, so by using a jig during manufacturing to suppress the tilt of the lens, Balance can be maintained and resonance in the rolling direction can be prevented from occurring.

Further, as shown in FIG. 1(a), the focus coil 5
By arranging the tracking coils 6a to 6d, it is possible to obtain driving force in the focusing direction and the tracking direction with the same magnetic circuit.

〔Effect of the invention〕

As described above, according to the present invention, the tilting of the condensing lens and its holder in the rolling direction is suppressed, and stable tracking servo and track access operations are possible. Furthermore, since the same magnetic circuit can drive the lens in the focusing direction and the tracking direction, it is possible to reduce the size and cost of the lens actuator.

[Brief explanation of the drawing]

1(a) and 1(b) are a top view and a sectional view taken along the line AA' of an embodiment of the present invention, FIG. 2 is a perspective view of an example of a conventional wire-supported lens actuator, and FIG. 3(a) ), (b)
2A and 2B are a top view and a sectional view taken along the line B-B' of the wire-supported lens actuator when the wire-supported lens actuator is arranged so that the direction of the magnetic field is in the radial direction. DESCRIPTION OF SYMBOLS 1... Condenser lens, 2... Holder, 3a-d...
Wire, 4... Fixed part, 5... Focus coil,
6a to d...Tracking coil, 7a, b...Permanent magnet, 8a to d...Yoke.

Claims (1)

[Claims] A condenser lens that condenses a laser beam onto the surface of an information recording medium, a holder that holds the condenser lens, a plurality of mutually parallel wires that support this holder, and a plurality of wires that are fixed to the holder. A lens actuator having a focus direction drive coil that drives the condensing lens in the focus direction, a tracking direction drive coil that drives the condenser lens in the tracking direction, and a magnet that is arranged to face each of the drive coils and forms a magnetic circuit, A lens actuator, characterized in that the condenser lens and its holder are not driven in the rotating direction by arranging the magnetic circuit so that the magnetic field direction is parallel to the axial direction of the wire. .