JP3658528B2 - 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 disk device.
[0002]
[Prior art]
As an example of an objective lens driving device used in an optical disk device, for example, those described in Japanese Utility Model Laid-Open No. 6-52014 and Japanese Patent Laid-Open No. 6-4885 are known.
[0003]
7 and 8 show the configuration of the basic objective lens driving device. FIG. 7 is a schematic configuration diagram of a conventional objective lens driving device. Two rectangular tube-like focusing coils 6 are joined, and the joined two focusing coils 6 are arranged on the side surface of the lens holder 5 that holds the objective lens 4. Further, one angular flat tracking coil 7 is attached to the joint between the two focusing coils 6.
[0004]
One end of the yoke 1 is placed in the hollow portion of the four focusing coils 6, and magnets 11 and 12 magnetized in the thickness direction are fixed to the other end portion of the yoke 1. Further, the focusing coil 6 and the tracking coil 7 are arranged in the magnetic gap between the yoke 1 and the magnets 11 and 12 in the hollow portion of the focusing coil 6. The magnets 11 and 12 are arranged so that the directions of the magnetic fields are reversed at the two joints between the tracking coil 7 and the pair of focusing coils 6.
[0005]
With such a configuration, driving force in the focusing direction and tracking direction can be obtained, and furthermore, rotational driving force in the optical disc radial direction and optical disc tangential direction can be obtained by adjusting the current direction of the focusing coil 6 as appropriate. It becomes.
[0006]
FIG. 8 is an exploded perspective view of a main part of a conventional objective lens driving device. The lens holder 5 that holds the objective lens 4 has focusing coils 6a and 6b wound in a rectangular cylinder before and after the tracking direction indicated by the arrow T, and is symmetrical with respect to the optical disc tangential direction with the objective lens 4 as the center. The ring-shaped tracking coils 7 a and 7 b are provided at various positions and are floatingly supported by four elastic support members 9, and the elastic support members 9 are fixed to a fixing portion 8.
[0007]
On the other hand, the yoke 1 has a substantially U-shaped cross section when viewed from the front-rear direction of the tracking direction T, and the inner surfaces of the upright portions 1b and 1c that stand up from the opposite edges of the base portion 1a are paired with each other. Magnets 11 and 12 are provided. The magnets 11 and 12 are composed of front portions 11a and 12a in the tracking direction T and rear portions 11b and 12b. The magnets 11 and 12 are magnetized so that their polar directions are opposite to each other. They are the same polarity.
[0008]
Further, the magnets 11 and 12 are provided with upright portions 1d and 1e as extensions of the yoke 1, respectively. The upright portions 1 d and 1 e are loosely inserted into the central through holes 6 c and 6 d of the focusing coils 6 a and 6 b in the lens holder 5.
[0009]
As described above, the magnet provided on the yoke is composed of two parts magnetized in different directions, and the parts facing each other are arranged so as to have the same polarity. By interposing the extending portion of the yoke that constitutes the magnetic circuit together with the magnet, the magnetic flux density can be increased, and the entire apparatus can be reduced in size and weight.
[0010]
Further, since the tracking coil can be used effectively, a desired driving force can be obtained with a small device, and the optical head can be reduced in size and weight.
[0011]
[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. The 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 4. Therefore, in general, the light beam wavelength λ is reduced, and the numerical aperture (NA) of the objective lens 4 is set to a value larger than that of the conventional lens so that the light beam is narrowed down to cope with higher recording density. Has become the mainstream.
[0012]
However, while the NA of the objective lens 4 can be increased, the light beam can be narrowed down more, while the optical characteristic deterioration due to the tilt between the optical disc and the objective lens 4 is significant. Therefore, it is necessary to suppress the tilt angle between the optical disk and the objective lens 4 within a certain value by some means. According to the prior art, by properly controlling the current of the four focusing coils 6 shown in FIG. 7, it is possible to suppress the relative tilt angle between the optical disk and the objective lens 4 within a predetermined value.
[0013]
However, in the case of the configuration of the objective lens driving device according to the prior art of FIG. 7 , it is necessary to arrange two focusing coils 6 in the radial direction of the optical disk, and the assembling work into the lens holder 5 becomes complicated. Further, when the rotational driving force in the optical disc radial direction and the optical disc tangential direction is obtained by appropriately adjusting the current directions of the four focusing coils 6, the focusing driving force and the rotational driving force are generated by the same coil. This makes it difficult to generate the necessary focusing driving force and rotational driving force at the same time.
[0014]
Further, in the case of the configuration of the objective lens driving device according to the prior art of FIG. 8, the magnetic flux acting on the focusing coil 6 deviates from the driving center in the focusing coil 6 due to the tracking operation of the movable part. _A rotational force (R _A ) in the radial direction (radial direction) is generated. Further, in the tracking coil 7 as well, due to the focusing operation of the movable part, the balance of the rotational force balanced by the line elements in the upper half and the lower half of the tracking coil 7 in the optical axis direction is lost, and is generated in the focusing coil 6. A rotational force (R _T ) in the same direction as the rotational force to be generated is generated.
[0015]
Due to the rotational force generated by the focusing coil 6 and the tracking coil 7 as described above, the movable part is greatly inclined during operation. Due to the influence of the tilt, there is a problem that it becomes difficult to accurately write information on the optical disc or to read information more accurately than the optical disc.
[0016]
The present invention has been made in order to solve the above-described problems. An objective lens driving device capable of stably writing to and reading from an optical disk while maintaining the relative angle between the objective lens and the optical disk always constant, and the same An object of the present invention is to realize an optical disk apparatus using the above.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, the first means of the present invention includes an objective lens for condensing a light beam on an optical disc,
A focusing coil for generating a force for driving the objective lens in the optical axis direction;
A tracking coil for generating a force for driving the objective lens in a direction perpendicular to the optical axis;
A tilt coil for tilting the objective lens in a radial direction of the optical disc;
A lens holder for holding the objective lens;
A magnet that generates magnetic flux for the focusing coil, tracking coil, and tilting coil;
A plurality of elastic support members having one end fixed to a movable portion including the objective lens, a lens holder, a focusing coil, a tracking coil, and a tilting coil and elastically supporting the movable portion;
A fixing portion to which the other end of the elastic support member is fixed,
The focusing coil and the tilting coil are arranged vertically on the same axis, and the focusing coil and the tilting coil are integrated and arranged on both sides in the radial direction of the optical disc with the objective lens as the center. .
[0025]
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. characterized in that it is a device.
[0026]
With the above configuration, it is possible to generate independent and efficient driving force by separate coils, such as focusing coil for focusing driving force and tilting coil for rotational driving force, and tilting easily with focusing coil The coil can be incorporated into the lens holder. In addition, even during operation, the inclination of the movable part is kept within an allowable value, and further, the movable part can be tilted and driven so that the relative angle between the objective lens and the optical disk is always kept constant, and writing to a stable optical disk, An objective lens driving device capable of reading from an optical disk is realized.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a first embodiment of the objective lens driving device according to the present invention will be described. 1, FIG. 2 and FIG. 3 are a top view showing a first embodiment according to the present invention, an optical disc radial direction cross-sectional view (AA cross-sectional view of FIG. 1), and an optical disc tangential direction cross-sectional view ( It is BB sectional drawing of FIG.
[0028]
In FIGS. 1, 2, and 3, the objective lens 4 is disposed on the upper surface of the lens holder 5. A set of focusing coils 6 are arranged symmetrically with respect to the approximate center of the objective lens 4 on the side surface in the radial direction of the optical disk of the lens holder 5, and further 1 symmetric with respect to the approximate center of the objective lens 4 in the tangential direction of the optical disk. A set of tracking coils 7 is arranged. Further, a tilting coil 13 having a winding axis substantially coaxially with the focusing coil 6 is disposed adjacent to the lower portion of the focusing coil 6.
[0029]
In this way, by adopting a structure in which the focusing coil 6 and the tilting coil 13 are adjacent to each other, the focusing coil 6 and the tilting coil 13 can be integrated and then incorporated into the lens holder 5. Compared with the operation of incorporating the coils into the lens holder 5, the assembly workability is better. Thus, the movable part is comprised from the objective lens 4, the lens holder 5, the focusing coil 6, the tracking coil 7, the tilting coil 13, and the like.
[0030]
On the other hand, the yoke 1 is provided with four raised portions 1b, 1c, 1g, and 1f so as to surround the four sides of the movable portion, and magnets 11, 12, 2, and 3 are arranged respectively. Of the four magnets, the two magnets 11 and 12 arranged in the tangential direction of the optical disk are magnetized so as to have different polarities in the same plane. Further, the yoke 1 is provided with rising portions 1d and 1e at positions facing the magnets 2 and 3, respectively.
[0031]
The movable portion is supported by six conductive elastic support members 9, one end being fixed to the movable portion and the other end being fixed to the fixed portion 8. The conductive elastic support member 9 is electrically connected to the focusing coil 6, the tracking coil 7, and the tilting coil 13 disposed in the movable part, and the conductive elastic support member 9 is fixed from the fixed part 8. The current can be supplied to the focusing coil 6, the tracking coil 7, and the tilting coil 13 via.
[0032]
FIG. 9 and FIG. 10 are conceptual diagrams for explaining the rotational force in the radial direction of the optical disc during the operation in the first embodiment of the present invention. FIG. 9 shows a case where the magnet center and the driving force center in the focusing direction and the tracking direction ideally match. In this case, as illustrated, the resultant force of F _A1 and F _A2 substantially coincides with the support center of the movable portion, and the resultant force of F _T1 and F _T2 also coincides. Further, since F _T3 , F _T4 , F _T5 , and F _T6 cancel each other, the forces generated in each part are balanced, and no rotational force in the optical disc radial direction is generated.
[0033]
FIG. 10 shows the rotational force in the radial direction of the optical disc when the focusing operation and the tracking operation are performed simultaneously. In the tracking operation, since the magnetic flux distribution from the magnet does not change, F _A2 > F _A1 and a rotational force (R _A1 ) is generated around the support center of the movable part. In addition, due to the focusing operation, the balance of F _T3 , F _T4 , F _T5 , and F _T6 , which had been balanced so far, is lost, and F _T5 > F _T6 , F _T3 ≈F _T4 ≈0. (R _T ) is generated around the support center of the movable part. Since R _A1 and R _T are rotational forces in the same direction, the objective lens 4 is greatly inclined.
[0034]
However, according to the present invention, the driving force generated by the current flowing through the magnets 2 and 3 and the focusing coil 6 by the tracking operation satisfies F _A3 > F _A4 and generates a rotational force (R _A2 ). Since this rotational force (R _A2 ) is generated in the opposite direction to the rotational forces R _T and R _A1 ,
R _T + R _A1 = R _A2
By appropriately adjusting the size, magnetic force and the like of the magnets 2 and 3 so as to satisfy the above condition, it is possible to reduce the inclination of the movable portion during operation.
[0035]
Although not shown, the optical disc system equipped with the objective lens driving device includes a tilt drive circuit that calculates a jitter amount from a signal read from the optical disc and generates a tilt drive signal so as to reduce the jitter amount. Thus, it is possible to supply an appropriate tilting current to the tilting coil 13 by a signal from the tilting drive circuit and tilt the movable part, and this tilting operation makes the relative angle between the optical disc and the objective lens 4 constant. It is possible to keep.
[0038]
4 , 5 , and 6 are a top view showing a second embodiment according to the present invention, a cross-sectional view of an optical disc in the radial direction (cross-sectional view of AA in FIG. 4 ), and a cross-sectional view of the relevant portion in the optical disc tangential direction ( it is a B-B sectional view of FIG. 4).
[0039]
A characteristic point of the second embodiment is that there are divided positioning portions 1h, 1i at the center of the rising portions 1b, 1c provided on the yoke 1, and four magnets 11a, 11b, 12a in the optical disk tangential direction. , 12b are arranged. The arrangement is the same as that of the first or second embodiment except for the arrangement of the divided positioning portions 1h and 1i and the magnets 11a, 11b, 12a and 12b, and the same effect can be obtained. Needless to say.
[0040]
【The invention's effect】
In the present invention, as described above, the winding axes of the focusing coil and the tilting coil are arranged substantially coaxially, so that it can be easily incorporated into the lens holder. Further, since the focusing coil and the tilting coil are independent from each other, it is possible to simultaneously generate the necessary focusing driving force or tilting driving force. Furthermore, the rotational force in the radial direction of the optical disc generated by the tracking coil during the focusing operation and the tracking operation, and the rotational force in the radial direction of the optical disc generated by the magnetic flux generated from the magnet and the current flowing through the focusing coil are arranged in the radial direction of the optical disc. By canceling with the rotational force in the radial direction of the optical disc generated by the magnetic flux generated from the magnet and the current flowing through the focusing coil, there is an effect that a stable operation can be realized.
[0041]
As a result, it is possible to tilt the objective lens in the radial direction of the optical disc while controlling the focusing control and tracking control, and to control it to the optimum tilt. There is an effect.
[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 in the radial direction of the optical disc, showing a first embodiment of the objective lens driving device according to the present invention.
FIG. 3 is a cross-sectional view of an essential part of the optical disk tangent direction showing a first embodiment of the objective lens driving device according to the present invention;
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 in the radial direction of the optical disc, showing a second embodiment of the objective lens driving device according to the present invention.
FIG. 6 is a cross-sectional view of an essential part of an optical disk tangent line showing a second embodiment of the objective lens driving device according to the present invention.
FIG. 7 is a top view of a conventional objective lens driving device.
FIG. 8 is an exploded perspective view of an essential part of a conventional objective lens driving device.
FIG. 9 is a conceptual diagram illustrating optical disk radial direction rotational force in the first embodiment of the objective lens driving device according to the present invention;
FIG. 10 is a conceptual diagram illustrating optical disk radial direction rotational force in the first embodiment of the objective lens driving device according to the present invention;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Yoke 2, 3 Magnet 4 Objective lens 5 Lens holder 6 Focusing coil 7 Tracking coil 8 Fixed part 9 Elastic support member 11, 12 Magnet 13 Tilt coil

Claims (2)

An objective lens for focusing the light beam on the optical disc;
A focusing coil for generating a force for driving the objective lens in the optical axis direction;
A tracking coil that generates a force for driving the objective lens in a direction perpendicular to the optical axis;
A tilt coil for tilting the objective lens in a radial direction of the optical disc;
A lens holder for holding the objective lens;
A magnet that generates magnetic flux for the focusing coil, tracking coil, and tilting coil;
A plurality of elastic support members having one end fixed to a movable part including the objective lens, a lens holder, a focusing coil, a tracking coil, and a tilt coil and elastically supporting the movable part;
A fixing portion to which the other end of the elastic support member is fixed,
The focusing coil and the tilting coil are arranged vertically on the same axis, and the focusing coil and the tilting coil are integrated and arranged on both sides in the radial direction of the optical disc with the objective lens as the center. Objective lens drive. 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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