JP3658526B2 - Objective lens driving device and optical disk device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an objective lens driving device used in an optical disc apparatus, and more particularly to an elastic support member that elastically supports a movable portion including an objective lens, a drive coil, a lens holder, and the like.
[0002]
[Prior art]
As an example of an objective lens driving device used in an optical disk device, for example, those described in JP-A-6-251405 and JP-A-6-139600 are known.
[0003]
FIG. 7 to FIG. 9 show the configuration of a basic objective lens driving device, FIG. 7 is a cross-sectional view of the conventional objective lens driving device in the optical disk tangential direction, and FIG. 8 is a side view of the objective lens driving device. FIG. 9 is a cross-sectional view of the objective lens driving device in the radial direction of the optical disc.
[0004]
The objective lens 1 is disposed on the upper surface of the lens holder 2, the focusing coil 3 is wound around the side surface of the lens holder 2, and the tracking coil 4 and the objective lens 1 are tilted and driven in the optical disk radial direction on the side surface of the lens holder 2. The coil 9 is affixed.
[0005]
The four parallel linear elastic support members 8 have one end fixed to the lens holder 2 and the other end fixed to the fixing portion, and the lens holder 2 supporting the objective lens 1 moves in the focusing direction and the tracking direction. It is elastically supported so that it can be tilted in the radial direction of the optical disk.
[0006]
A magnetic circuit composed of a yoke 5 and a magnet 6 is disposed at a fixed portion where one end of the elastic support member 8 is fixed, and the drive current flowing through the focusing coil 3, the tracking coil 4 and the tilt coil 9 is the magnetic current. It arrange | positions so that it may act on the magnetic flux generated from a circuit. An inclination detector 7 for detecting the inclination of the optical disc is disposed on the upper surface of the lens holder 2 that supports the objective lens 1.
[0007]
At the time of focusing control, current is appropriately supplied to the focusing coil 3 in response to surface wobbling of the optical disk recording surface to operate the objective lens 1 in the optical axis direction so that the light beam spot follows the optical disk recording surface. Can do. At the time of tracking control, current is appropriately supplied to the tracking coil 4 corresponding to the eccentricity and meandering of the track of the optical disk, the objective lens 1 is moved in the direction perpendicular to the optical axis, and the spot of the light beam is tracked on the optical disk. It can be made to follow up. With respect to the tilt of the optical disk, a current is appropriately supplied to the tilt coil 9 based on the signal from the tilt detector 7 to drive the objective lens 1 to tilt according to the tilt of the optical disk.
[0008]
[Problems to be solved by the invention]
In recent years, higher recording density has been promoted in optical disc apparatuses. One method for realizing high recording density is a method of narrowing the light beam to reduce the spot diameter on the recording surface of the optical disk. This spot diameter is proportional to (λ / NA) where λ is the wavelength of the light beam and NA is the numerical aperture of the objective lens 1.
[0009]
For this reason, generally, a method for narrowing the light beam by reducing the wavelength λ of the light beam and setting the numerical aperture (NA) of the objective lens 1 to a value larger than the conventional one, and corresponding to a higher recording density. Has become the mainstream. By increasing the NA of the objective lens 1, the light beam can be narrowed down more finely, but the optical characteristics are significantly degraded due to the tilt between the optical disk and the objective lens 1. Therefore, it is necessary to suppress the tilt angle between the optical disk and the objective lens 1 within a certain value by some means.
[0010]
This objective lens driving device detects the relative tilt angle between the optical disk and the objective lens 1 by the tilt detector 7 and supplies a current to the tilt coil 9 based on the detected tilt angle, whereby the relative tilt between the objective lens 1 and the optical disk is detected. It was configured to keep the angle constant.
[0011]
However, in the conventionally proposed invention, no consideration is given to the means for energizing the current supplied to each drive coil. In general, there are only four elastic support members 8 made of a conductive member, and currents can be supplied by the elastic support members 8 to a maximum of two drive coils. If a current is supplied to the focusing coil 3 and the tracking coil 4 via the elastic support member 8, the tilting coil 9 needs a lead wire dedicated to the tilting coil 9 as disclosed in JP-A-6-139600. It becomes. However, this lead wire is not suitable for a high-precision objective lens driving device that performs tilt control in the radial direction of the optical disk because the assembly workability is poor and the adverse effect on the operation tilt characteristics of the objective lens 1 is large. .
[0012]
As described above, in the conventional objective lens driving device, the means for supplying current to each driving coil is not taken into consideration, so that a lead wire or the like is required in addition to the four conductive elastic support members, and the assembly workability is poor. There is a drawback that stable operating characteristics cannot be obtained.
[0013]
The present invention has been made in order to solve the above-described problems, and a tiltable objective lens driving device capable of obtaining a stable operating characteristic by supplying a current to each driving coil with a conductive elastic support member and using the same. The purpose is to realize the optical disc apparatus .
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the first means of the present invention comprises an objective lens for condensing a light beam on an optical disc,
A first drive coil for driving the objective lens in the optical axis direction;
A second drive coil for driving the objective lens in a direction perpendicular to its optical axis;
A tilt drive coil that tilts and drives the objective lens in the radial direction of the optical disc;
A lens holder for holding the objective lens;
A magnet for generating a magnetic flux for the first and second drive coils and the tilt drive coil;
One end is fixed to the movable part including the objective lens, the lens holder, the first and second drive coils, and the tilting drive coil to elastically support the movable part, and the first and second drive coils and the tilting drive coil 6 conductive elastic support members each supplying current,
A fixing portion for fixing the other end of the elastic support member ,
The six conductive elastic support members are arranged on the optical disc side with respect to the substantially center of the objective lens of the movable part in the optical axis direction, and two on the opposite side of the optical disc, respectively.
Of the four arranged on the optical disc side, the rigidity in the axial direction of two elastic support members is made smaller than the rigidity in the axial direction of the other four elastic support members .
[0020]
According to a second means of the present invention, there is provided an optical disk apparatus comprising an objective lens driving apparatus for driving an objective lens for condensing a light beam on the optical disk, wherein the objective lens driving apparatus is the objective lens driving apparatus according to claim 1. It is a device.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1, 2, and 3 are a top view illustrating a first embodiment of an objective lens driving device according to the present invention, a cross-sectional view of a main part in a tangential direction of an optical disk (cross-sectional view taken along line AA in FIG. 1), and an optical disk radius. It is principal part sectional drawing (BB sectional drawing of FIG. 1) of a direction.
[0024]
In these drawings, the objective lens 1 is disposed on the upper surface of the lens holder 2, and a focusing coil 3 is wound around the outer periphery of the lens holder 2 with the objective lens 1 as a substantially center of winding. Tilt coils 9 are arranged on both sides of the focusing coil 3 in the radial direction of the optical disc. A tracking coil 4 is disposed outside the focusing coil 3 in the optical disc tangential direction so as to be placed on the lens holder 2.
[0025]
The objective part 1, the lens holder 2, the focusing coil 3, the tracking coil 4, the tilting coil 9, and the like constitute a movable part. The movable portion is supported by six elastic support members 8, and one end of the elastic support member 8 is fixed to the movable portion and the other end is fixed to the fixed portion. The elastic support member 8 is made of a conductive material such as beryllium copper or phosphor bronze, and is electrically connected to the focusing coil 3, the tracking coil 4, and the tilting coil 9 disposed in the movable part, respectively, and a fixed part. Current can be supplied to the focusing coil 3, the tracking coil 4, and the tilting coil 9 via the conductive elastic support member 8.
[0026]
As shown in FIGS. 1 and 3, four elastic support members 8 are provided on the optical disc side (8a, 8b, 8c, 8d) and two on the opposite side of the optical disc in the optical axis direction of the objective lens 1. (8e, 8f) are arranged. Two of the elastic support members (8a, 8b) arranged on the optical disc side can be arranged and positioned from the optical disc side in a V-shaped groove provided in the lens holder 2 and the fixing portion.
[0027]
By bending the tip of the elastic support members 8a, 8b on the lens holder 2 side into an L shape, it is possible to connect with each coil at a position away from the other four (8c, 8d, 8e, 8f), The assembly workability is improved.
[0028]
As shown in FIG. 1, the elastic support members 8a and 8b are provided with a torsion spring-like portion to reduce the axial rigidity, thereby reducing the adverse effect of excessive restraint by the six elastic support members 8. Stable operating characteristics can be obtained.
[0029]
A magnetic circuit composed of a yoke 5 and a magnet 6 is disposed on a fixed portion where one end of the elastic support member 8 is fixed. Two sets of magnetic circuits composed of magnets 6a and 6b and a yoke 5 are arranged so as to sandwich the outer periphery of the tracking coil 4 and the focusing coil 3 in the tangential direction of the optical disk. The active line portion is located.
[0030]
Two magnets 6c and 6d are disposed on the outer peripheral portion of the movable portion in the radial direction of the optical disk for tilt driving, and tilt driving force is generated by the action of the magnetic flux generated from the magnets 6c and 6d and the current flowing through the tilt coil 9. Is configured to do.
[0031]
Although not shown, the tilting operation of the objective lens 1 is provided with a tilting drive circuit that calculates a jitter amount from a signal read from the optical disk and generates a tilting drive signal so as to reduce this jitter amount. A suitable driving current is supplied to the tilting coil 9 by the above signal, and the objective lens 1 is tilted.
[0032]
Next, the operation of the objective lens driving device will be described.
A focusing error signal is optically generated by an optical pickup with respect to the upper and lower surface vibrations of the optical disk, and an appropriate drive current is supplied from the focusing drive circuit to the focusing coil 3 via the conductive elastic support member 8 in accordance with this signal. Focusing control is performed so that the light spot of the light beam supplied and condensed by the objective lens 1 is always positioned on the recording surface of the optical disk.
[0033]
A tracking error signal is optically generated by the optical pickup even for the meandering / eccentricity of the track, and an appropriate drive current is supplied from the tracking drive circuit to the tracking coil 4 via the conductive elastic support member 8 in accordance with this signal. Tracking control is performed so that the light spot of the light beam is always positioned on the track of the optical disk. In this way, focusing control and tracking control are performed, and a signal can be read from the optical disc.
[0034]
The signal read from the optical disk includes a time-axis direction error (jitter) whose magnitude depends mainly on the relative tilt angle between the optical disk and the objective lens 1. Therefore, the amount of jitter can be reduced by tilting the objective lens 1 appropriately according to the tilt of the optical disk. Conversely, the amount of jitter contained in this read signal is calculated, a tilt drive signal for the objective lens 1 is created so that the jitter amount is minimized, and an appropriate tilt drive current is applied to the tilt coil 9 in accordance with this tilt drive signal. Is supplied via the conductive elastic support member 8, tilt control (tilt control) of the objective lens 1 can be performed.
[0035]
However, the elastic support member 8 disposed for energizing the tilting coil 9 is excessively constrained in the sense of constraining the movable part, so that a stable operation of the movable part is ensured unless high mounting accuracy is realized. Can not. Accordingly, in the present invention, axial rigidity is provided by providing a torsion spring-like or coil spring-like part on a part of the fifth and sixth elastic support members (8a, 8b) so that the influence of excessive restraint can be reduced even with low mounting accuracy. This makes it possible to operate the movable part stably.
[0036]
4, 5, and 6 are a top view illustrating a second embodiment of the objective lens driving device according to the present invention, a cross-sectional view of a main part in a tangential direction of the optical disk (cross-sectional view taken along line AA in FIG. 4), and a radius of the optical disk. It is principal part sectional drawing (BB sectional drawing of FIG. 4) of a direction.
[0037]
What is characteristic in this embodiment is that the distance (effective length) between the fixed position on the movable part side of the elastic support members 8a and 8b and the fixed position on the fixed part side is different from the other four. . With this configuration, the elastic support members 8a and 8b can be connected to the coils at positions apart from the other four, thereby improving the assembly workability.
[0038]
However, when the movable portion functions as a parallel link mechanism using the elastic support members 8c, 8d, 8e, and 8f as arms, two of the elastic support members 8 (8a and 8b) are replaced with the other four (8c , 8d, 8e, 8f) and the effective length are different, it is difficult to ensure a stable operation of the movable part.
[0039]
Therefore, even if the effective lengths of the six elastic support members 8 are different by providing a coil spring-like portion in a part of the elastic support members 8a and 8b and reducing the axial rigidity of the elastic support members 8a and 8b, Stable movement of the movable part is possible.
[0040]
In FIG. 6, the six elastic support members 8 a to 8 f are arranged so as to substantially coincide on the same circumference with the center of gravity of the movable portion or the support center position of the six elastic support members 8 a to 8 f as the center. Has been. As a result, the movable portion tilts around the position of the center of gravity or the support center position, and stable tilting operation characteristics can be obtained.
[0041]
【The invention's effect】
In the present invention, as described above, the movable portion on which the objective lens is arranged is supported by six conductive elastic support members, and the focusing coil, tracking coil, and tilt coil are electrically connected to the conductive elastic support members. In addition, since each drive current can be appropriately supplied to each coil via this elastic support member, there is no need for power supply parts such as lead wires that cause variations in operating characteristics, and stable operation is achieved. Characteristics are obtained.
[0042]
As a result, it is possible to tilt the objective lens in the radial direction of the optical disc while operating focusing control and tracking control, and to control the tilt to the optimum, and to read and write accurate signals with low jitter from the optical disc. Become.
[Brief description of the drawings]
FIG. 1 is a top structural view showing a first embodiment of an objective lens driving device according to the present invention;
FIG. 2 is a cross-sectional view of the main part of the objective lens driving device in the tangential direction of the optical disc.
FIG. 3 is a cross-sectional view of a main part in the radial direction of the optical disk of the objective lens driving device.
FIG. 4 is a top structural view showing a second embodiment of the objective lens driving device according to the present invention;
FIG. 5 is a cross-sectional view of the main part of the objective lens driving device in the tangential direction of the optical disc.
FIG. 6 is a cross-sectional view of the main part of the objective lens driving device in the radial direction of the optical disc.
FIG. 7 is a sectional view of a conventional objective lens driving device in a direction tangent to an optical disc.
FIG. 8 is a side view of the objective lens driving device.
FIG. 9 is a sectional view of the objective lens driving device in the radial direction of the optical disc.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3 Focusing coil 4 Tracking coil 5 Yoke 6 Magnet 8, 8a-8f Elastic support member 9 Tilt coil

Claims (2)

An objective lens for focusing the light beam on the optical disc;
A first drive coil for driving the objective lens in the optical axis direction;
A second drive coil for driving the objective lens in a direction perpendicular to its optical axis;
A tilt drive coil that tilts and drives the objective lens in the radial direction of the optical disc;
A lens holder for holding the objective lens;
A magnet for generating a magnetic flux for the first and second drive coils and the tilt drive coil;
One end is fixed to the movable part including the objective lens, the lens holder, the first and second drive coils, and the tilting drive coil to elastically support the movable part, and the first and second drive coils and the tilting drive coil 6 conductive elastic support members each supplying current,
A fixing portion for fixing the other end of the elastic support member ,
The six conductive elastic support members are arranged on the optical disc side with respect to the substantially center of the objective lens of the movable part in the optical axis direction, and two on the opposite side of the optical disc, respectively.
An objective lens driving device characterized in that two of the four elastic support members arranged on the optical disc side have an axial rigidity smaller than that of the other four elastic support members. . 2. An optical disc device comprising an objective lens driving device for driving an objective lens for condensing a light beam on the optical disc, wherein the objective lens driving device is the objective lens driving device according to claim 1. apparatus.

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