JP2001331954A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems that a rolling resonant frequency is also lowered when a yawing resonant frequency of a movable part is lowered in order to stabilize tracking control of an objective lens driving device and a tilt of the objective lens due to resonance occurs. SOLUTION: When the attaching interval of supporting members 6a-6c of the movable part to a lens holder 2 is expressed by A, the attaching interval of the same to a fixing member 5 is expressed by B and the minimum interval is expressed by M, respective intervals are set so as to satisfy M<A<B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device for an apparatus for optically recording or reproducing information on a disk-shaped recording medium.

[0002]

2. Description of the Related Art An objective lens driving device moves an objective lens with respect to the surface of a recording medium (hereinafter, referred to as a disk) in order to correct a focusing deviation due to a vertical movement of a warp of a disk-shaped recording medium or a tracking deviation due to eccentricity. Driving is performed in two axes, a perpendicular optical axis direction and a radial direction parallel to the recording medium surface, to optically record or reproduce.

An example of the above-described conventional objective lens driving device will be described below with reference to the drawings.

FIG. 5 is a perspective view showing the structure of a conventional objective lens driving device. In FIG. 5, reference numeral 52 denotes a lens holder to which the objective lens 51, the focusing coil 53, and the tracking coil 54 are fixed, and constitute a movable unit. The focusing coil 53 has a winding axis in the optical axis direction, and the tracking coil 54 has a winding axis in a direction (peripheral direction) substantially perpendicular to the optical axis and the radial direction. 56a-56
d is a supporting member formed of an elastic body, one end of which is connected to the lens holder 52 and the other end of which is connected to the fixing member 55. Since the lens holder 52 is cantilevered by the support members 56a to 56d, it can freely move within the elastic deformation range of the support members 56a to 56d. 57a and 57b are magnets fixed to the yoke 58a of the base 58. Magnet 5
Reference numerals 7a and 57b are disposed opposite to each other, and a focusing coil 53 and a tracking coil 54 are disposed in a gap between the magnets, and constitute a focusing driving unit and a tracking driving unit, respectively.

The operation of the objective lens driving device configured as described above will be described below.

An operation of driving the objective lens 51 in two directions, the optical axis direction and the radial direction, in order to correct a focusing deviation due to the vertical movement of the warpage of the disk or a tracking deviation due to eccentricity or the like will be described.

In FIG. 5, a magnetic flux in the circumferential direction is generated in the gap between the magnets 57a and 57b, and when a current is applied to the focusing coil 53, a force in the optical axis direction is generated in the focusing coil intersecting the magnetic flux. When the supporting members 56a to 56d bend by the force generated in the focusing coil 53, the movable portion translates substantially in the optical axis direction.

Similarly, when a current is applied to the tracking coil 54, a radial force is generated in the tracking coil 54 crossing the magnetic flux. When the support members 56a to 56d bend by the force generated in the tracking coil 54, the movable portion translates substantially in the radial direction.

[0009]

In order to stably drive the objective lens in the optical axis direction and the radial direction with respect to the driving current supplied to the focusing coil and the tracking coil, the center of gravity of the movable portion, the focus coil and the tracking are used. It is necessary to match the center of the driving force generated by the coil. For example, when the movable portion is driven in the radial direction by the tracking coil, resonance around the circumferential direction (rolling resonance) and resonance around the optical axis direction (yawing resonance) occur due to a shift between the position of the center of gravity and the center of the driving force. When the objective lens driving device is miniaturized, it is difficult to completely match the position of the center of gravity with the center of the driving force due to variations in component accuracy and assembly accuracy.

In an apparatus having a structure in which the position of the center of gravity of the movable portion is separated from the position of the objective lens as shown in FIG. 5, when yawing resonance occurs in the movable portion, the objective lens is swung in a substantially radial direction, so that tracking control becomes unstable. There is a risk of becoming. For this reason, it is necessary to lower the resonance frequency to stabilize the tracking control. For this reason, the bending portions 66a to 6
By lowering the circumferential rigidity of the support member by adding 6d, the frequency of the yawing resonance is reduced.

Further, in order to reduce the diameter of the disk or increase the data transfer rate, it is necessary to increase the rotation speed of the disk. As the number of rotations increases, the rotation cycle becomes shorter. In the conventional support member configuration shown in FIG. 5, when the yawing resonance frequency is lowered, the rolling resonance frequency is also lowered at the same time. If the rolling resonance frequency is low, it approaches the rotation cycle of the disk, and rolling resonance occurs due to the driving force, causing the objective lens to tilt. As a result, an optical aberration occurs in the spot condensed by the objective lens, which causes problems such as deterioration of a data reproduction signal of the disk and inability to correctly record data at the time of recording.

For example, in a small objective lens driving device, tracking control of the yawing resonance frequency is stabilized.
If the support member is configured to have a shape shown in FIG. 5 so as to be about 0 Hz, the rolling resonance frequency will be about 60 Hz. FIG. 6 shows displacement frequency characteristics in the radial direction (tracking control) at this time. In an apparatus using a small-diameter disk, the rotation of the disk increases to about 40 to 50 Hz. At this time, the rolling resonance frequency of the movable part is 80 Hz.
Otherwise, rolling resonance occurs and the objective lens is tilted. Therefore, the conventional configuration has a problem that the objective lens is tilted.

SUMMARY OF THE INVENTION In view of the above problems, the present invention reduces the yaw resonance frequency around the optical axis without lowering the rolling resonance frequency around the circumferential direction of the movable portion, thereby ensuring tracking control stability and preventing the objective lens from tilting. It is an object of the present invention to provide an objective lens driving device capable of achieving both.

[0014]

In order to solve the above-mentioned problems, an objective lens driving apparatus according to the present invention has an optical system including an objective lens for optically recording or reproducing information on a recording medium. A lens holder, one end of which is attached to the lens holder and the other end of which is attached to a fixing member, which movably supports the lens holder in an optical axis direction substantially perpendicular to the recording medium and in a radial direction of the recording medium; It comprises a plurality of elastic support members disposed apart from each other in the axial direction, and driving means for driving the lens holder in the optical axis direction and in the radial direction. The elastic support members are mounted in the lens holder in the radial direction. When the opposite dimension is PA, the opposite dimension attached to the fixing member is PB, and the minimum dimension formed between the opposed support members is PM, PM <PA <PB. .

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a perspective view of an objective lens driving device according to Embodiment 1 of the present invention. FIG.
, 2 is a lens holder to which the objective lens 1, the focusing coil 3, and the tracking coil 4 are fixed,
Construct a movable part. The focusing coil 3 has a winding axis in the optical axis direction, and the tracking coil 4 has a winding axis in a direction (peripheral direction) substantially perpendicular to the optical axis and the radial direction.
Reference numerals 6a to 6d denote supporting members made of a leaf spring-like elastic body formed by punching or the like, which are arranged so as to be substantially parallel to each other. Are combined. The lens holder 2 is a support member 6a
6d, the supporting members 6a to 6d
It can move freely within the elastic deformation range of d. 7a,
Reference numeral 7b denotes a magnet which is fixed to the yoke portion 8a of the base 8. The magnets 7a and 7b are arranged opposite to each other, and the focusing coil 3 and the tracking coil 4 are arranged in the gap between the magnets to form focusing driving means and tracking driving means, respectively. These configurations are the same as those of the conventional objective lens driving device described with reference to FIG.

The operation of the objective lens driving device configured as described above will be described below.

The operation of driving the objective lens 1 in two directions, the optical axis direction and the radial direction, in order to correct the focusing deviation due to the vertical movement of the warpage of the disk and the tracking deviation due to the eccentricity, etc., will be described with reference to FIG. Equivalent to what was described.

FIG. 2 is a plan view of the present invention, showing the shape of the support member. In FIG. 2, the support members 6a to 6d are provided with bent portions. This lowers the yawing resonance frequency and stabilizes the tracking control as in the conventional example. Further, as shown in FIG.
Assuming that the mounting interval of the lens holder 2 is PA and the mounting interval of the fixing member 5 is PB, PA <PB
, Thereby increasing the rolling resonance frequency. Assuming that the minimum width of the mounting interval of the support member is PM, for example, the circumferential dimension of the support member is 9 m.
For a small actuator of about m, if PA = PB, the yawing resonance frequency is about 1.2 kHz to secure the rolling resonance frequency of 90 Hz, which is not enough to stabilize the tracking control. PA> PM
By doing so, the yawing resonance frequency can be reduced to 800 Hz while keeping the rolling frequency at 90 Hz, and the stability of tracking control can be ensured. FIG. 3 shows displacement frequency characteristics in the radial direction (tracking control) at this time.

(Embodiment 2) FIG. 4 is a plan view of an objective lens driving device according to Embodiment 2 of the present invention. FIG.
In (2), the support members 6a to 6d are wire-like elastic bodies having a uniform cross section, and are curved when attached to the lens holder 2 and the fixing member 5. Also in the second embodiment, an effect equivalent to that of the first embodiment is obtained in which the yawing resonance frequency is increased without lowering the rolling resonance frequency, and both the stability of the tracking control and the prevention of the inclination of the objective lens are achieved. Further, since the wire-like elastic body is used for the support member, the effect that the material cost is lower than that of the first embodiment in which the leaf spring is punched is obtained.

[0021]

According to the objective lens driving device of the present invention, the stability of tracking control and the tilt of the objective lens due to rolling resonance can be suppressed, and a small objective lens driving device corresponding to a small-diameter disk or a high transfer rate can be realized. It becomes feasible.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an objective lens driving device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing the objective lens driving device according to the first embodiment of the present invention.

FIG. 3 is a displacement frequency characteristic diagram in the objective lens driving device according to the first embodiment of the present invention.

FIG. 4 is a plan view showing an objective lens driving device according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a conventional objective lens driving device.

FIG. 6 is a displacement frequency characteristic diagram in a conventional objective lens driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3 Focusing coil 4 Tracking coil 5 Fixing member 6a-6d Supporting member 7a, 7b Magnet 8 Base

Claims (3)

[Claims] A lens holder having an optical system including an objective lens for optically recording or reproducing information on a recording medium; one end attached to the lens holder and the other end attached to a fixed member; A lens holder is supported movably in an optical axis direction substantially perpendicular to the recording medium with respect to the fixing member and in a radial direction of the recording medium, and is disposed apart from the radial direction and the optical axis direction. A plurality of elastic support members, and driving means for driving the lens holder in the optical axis direction and the radial direction, wherein the elastic support members are opposed to each other in the radial direction when attached to the lens holder. Is PA, the dimension opposed to the fixing member is PB, and the minimum dimension formed between the opposed elastic support members is PM, PM <PA <PB. An objective lens driving device that. 2. The objective lens driving device according to claim 1, wherein the plurality of elastic body support members are formed of leaf springs having bent portions. 3. The objective lens driving device according to claim 1, wherein the plurality of elastic body support members have a uniform linear cross section and a curved shape.