JP2003016674A - Optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator that facilitates high-density recording ultimately by reducing tilt incident to tracking displacement. SOLUTION: The device is composed of an objective lens 11 for converging a laser beam that is not shown; a lens holder 12 for holding this objective lens 11, focus driving coils 22a, 22b and two track driving coils 23a, 23b; yokes 18, 19 forming a magnetic circuit; magnets 20, 21 formed in a manner holding these coils in-between; an elastic supporting member 14 for supporting the lens holder 12; a stem 13 for fixing the entirety of the objective lens driving device; a rising mirror 17 for refracting the laser beam from the objective lens 11; and a base 15.

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 of an optical disk drive device, and more specifically,
The present invention relates to an objective lens driving device that reduces tilt caused by tracking displacement.

[0002]

2. Description of the Related Art FIGS.
It is a figure explaining the structure of the motor of 37922 publication, and the mechanism of tilt moment generation accompanying tracking displacement. First, the magnetic circuit will be described. FIG. 16 is a schematic cross-sectional view of the magnetic circuit of the objective lens driving device described in Japanese Patent Laid-Open No. 2000-137922, taken along a plane orthogonal to the jitter direction. In this figure, the magnet 20 has magnetizing boundaries 20a and 20b and is magnetized in four divisions. And, it is magnetized in the opposite direction to the adjacent regions. For example, it is assumed that the order is N, S, N, S clockwise. In a magnetic circuit made up of two such magnets, the magnetic flux density near the center of the magnetic circuit is as shown in FIG. 16 (a) for the tracking direction and as shown in FIG. 16 (c) for the focusing direction. Next, the driving force generating coil will be described. In the motor described in Japanese Patent Application Laid-Open No. 2000-137922, the focusing drive coils 22a and 22b and the tracking drive coils 23a and 23b each have two coils each, for a total of four coils.
One coil is used. By supplying a current to this coil, a driving force is generated according to Fleming's law. Note that the driving force is actually generated in FIG.
It is a portion shown in (b). As the magnetic flux density in this portion is larger, a larger driving force can be obtained with the same current.

Next, the operation of this motor is shown in FIG.
Will be explained. FIG. 18B is a sectional view of the motor taken along a plane orthogonal to the focusing direction. FIG.
FIG. 18A is a diagram schematically showing the magnetic flux density distribution of this magnetic circuit, and FIGS. 18B and 18C show how the lens holder is moved in the tracking direction and driven in the focusing direction. Shows. In this case, the driving force generated in the two coils is proportional to the areas of 40a and 40b in FIG. 18A when the currents flowing in the two coils are equal. When the magnetic flux density distribution is symmetrical with respect to the magnetized boundaries 20a and 21a as shown in this figure, the forces generated by the two coils are equal and tilt does not occur. However, as shown in FIG. 19A, when the magnetic flux density distribution is asymmetric with respect to the magnetization boundaries 20a and 21a, the forces generated in the two coils are different.
Since the areas of a and 40b do not become the same, as a result, moment and eventually tilt occur. Here, the configuration of a general magnetic circuit will be described with reference to FIG. FIG. 20A is a sectional view of the magnetic circuit taken along a plane orthogonal to the tracking direction. In this figure, the yokes 15, 18, and 19 are made of a soft magnetic material such as a zinc steel plate, and the magnetic circuit has a U-shape. In such a magnetic circuit, a U for mounting the objective lens driving device is provided on the side far from the information recording medium (not shown).
In many cases, the V-shaped bottom portion 15 is formed. In this magnetic circuit, the U-shaped bottom portion 15 affects the distribution of the magnetic force lines 30, and as a result, the magnetic flux density distribution in the magnetic circuit is different from the magnetization boundary in the focusing direction in FIG.
The distribution is asymmetrical. When the tracking operation is performed in this state, a tilt moment is generated because the forces generated in the two tracking coils are not equal.

[0004]

As described above,
The conventional objective lens driving device has the following problems. 1) As shown in FIG. 19A, when the magnetic flux density distribution is asymmetric with respect to the magnetization boundaries 20a and 21a, the forces generated in the two coils are different 40a and 40b.
Since the areas are not the same, a moment and eventually a tilt are generated. 2) As shown in FIG. 20 (a), the U-shaped bottom portion 15 affects the distribution of the magnetic force lines 30, and as a result, the magnetic flux density distribution in the magnetic circuit is different from the magnetization boundary in the focus direction. The distribution becomes asymmetric as shown in FIG. When the tracking operation is performed in this state, a tilt moment is generated because the forces generated in the two tracking coils are not equal. SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an actuator that can reduce tilt caused by tracking displacement and can finally perform high-density recording.

[0005]

In order to solve the above-mentioned problems, the present invention provides an objective for holding a plurality of focus drive coils and track drive coils facing an magnet and an objective lens. In an optical disk drive device provided with a lens holding member and driving the objective lens holding member by energizing each of the coils, an optical disc drive device is provided, with respect to a center point between the plurality of track driving coils. The objective lens holding member is set such that the suspension center points of the objective lens holding member are located at different positions. It is characterized in that the suspension center point of the objective lens holding member is shifted with respect to the center point of the track driving coil. Other configurations are the same as the conventional configurations. By setting the deviation between the suspension center point and the center point of the track drive coil such that no moment is generated by the resultant force of the two track drive coils, the track drive coil close to the recording medium and Even though the forces generated in the distant track drive coils are different, a moment is not generated around the suspension center point, so that the occurrence of tilt can be prevented. According to this invention, it is possible to suppress the tilt associated with tracking drive without adding any new component.
Further, in the invention of claim 2, the suspension center point of the objective lens holding member is set to a position where a moment is not generated by the force generated by the two track driving coils, which is an effective means of the present invention. is there. The moment is generated in the vector direction when a plurality of different forces are applied around a certain fulcrum. As a method of preventing the moment, there is a method of applying the same force or a method of canceling the vector. Even if the coils have the same number of turns, there is an error, and even if they are the same, if an error occurs in the current value flowing in that coil, the strength of the magnetic field is
It is uniquely determined by the product of the number of turns and the current. Therefore,
As a practical solution, it is realistic to apply force in the direction of canceling the latter vector. According to such a technical means, since the suspension center point is set to a position where no moment is generated, it is possible to suppress the tilt associated with the tracking drive without adding any new component by adjusting only.

According to a third aspect of the present invention, there is provided an objective lens holding member for holding a plurality of focus driving coils and track driving coils facing the magnet and the objective lens, and by energizing each of the coils, the objective lens holding member is provided. In an optical disk drive device provided with an objective lens driving device for driving an objective lens holding member, a plurality of elastic supporting members for supporting the objective lens holding member are provided, and the elastic supporting member is provided near a recording medium. The elastic moments of the elastic support members provided at positions far from the recording medium are different. It is characterized in that the center of suspension is changed without shifting the attaching position of the wire by making the second elastic moments of area different between the two elastic supporting members near the recording medium and the two elastic supporting members far from the recording medium. For example, the suspension center can be moved toward the recording medium by thickening the supporting elastic body on the side closer to the recording medium. According to this invention, it is possible to change the center of suspension in the focusing direction without newly manufacturing an assembling jig or the like, and to suppress the tilt associated with tracking drive without adding any new parts. Becomes In addition, claim 4
According to another aspect of the invention, the elastic moment of the elastic supporting member provided at a position close to the recording medium and the elastic moment of the elastic supporting member provided at a position far from the recording medium is such that the focus driving coil drives the objective lens holding member. Is the same value, and different values are used when the track driving coil drives the objective lens holding member, which is an effective means of the present invention. For example, only two wires close to the recording medium have an elliptical cross section, and two wires far from the recording medium have a circular cross section. By appropriately setting this elliptical shape, the spring elasticity coefficients of the four wires are made equal in the focus direction, and the cross sections of two elastic support members near the recording medium and two elastic support members far from the recording medium in the tracking direction. It is possible to make the second moment different. According to such a technical means, since the four spring elastic coefficients in the focusing direction can be made equal, the tilt of the lens in the jitter direction can be suppressed by the focus driving. Further, by making the second moment of area of the elastic support member near and far of the recording medium different, it is possible to suppress the tilt accompanying the tracking drive without adding any new component.

Further, the invention of claim 5 is also effective in that the elastic support member provided at a position close to the recording medium and the elastic support member provided at a position far from the recording medium have different sectional shapes. It is a means. In order to change the spring elastic coefficient of the wire, there are a method of changing the material and a method of changing the sectional shape of the same material. To increase the spring elastic modulus by the latter method, the cross section should be made thicker or elliptical to change the orientation. According to this technical means, the second moment is different only by changing the cross-sectional shape of the wire, and it is possible to easily suppress the tilt accompanying the tracking drive. The invention of claim 6 is
It is also an effective means of the present invention that the distance between the mounting positions of the elastic supporting members provided near the recording medium is different between the objective lens holding member side and the fixed portion side. Of the four wires supporting the objective lens holding member, two wires close to the recording medium were tilted to change the apparent spring elastic coefficient in the tracking direction of the tilted wires to shift the suspension center. It is characterized by By obliquely supporting the support elastic body on the side closer to the recording medium, the apparent spring elastic coefficient in the tracking direction can be improved and the suspension center can be moved in the direction of the recording medium. According to such a technical means, it is possible to suppress the tilt associated with the tracking drive without adding any new component. Further, by using the present invention, the torsional rigidity of the objective lens with respect to the inclination in the tracking direction (radial tilt) can be improved, and the tilt can be suppressed against disturbance or the like. The invention of claim 7 is
An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing the magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In an optical disk drive device provided with a drive device, the magnetic flux density of the magnet is formed to have different values in a portion near the recording medium and a portion far from the recording medium. Magnetic field strength (H)
Can be expressed as H = B / μ ₀ −M (1) where (B) is the magnetic flux density, (μ ₀ ) is the magnetic permeability, and (M) is the magnetization vector. From the equation, it can be seen that the strength of the magnetic field is proportional to the magnetic flux density. Therefore, if the magnetic flux density of the magnet near the recording medium and the magnetic flux density of the magnet far away from the recording medium are set to different values, naturally the magnetic field is higher between the magnet with the higher magnetic flux density and the magnet with the lower magnetic flux density according to equation (1). The moments can be eliminated if they have different strengths and are configured to cancel each other out. According to this invention, since the moments can be canceled out by changing the magnetic flux density of the magnet, it is possible to suppress the tilt associated with the tracking drive without changing the external configuration.

Further, the invention of claim 8 is also an effective means of increasing the magnetic flux density of the magnet corresponding to the track driving coil located far from the recording medium. Of the four magnetized areas that make up the magnetic circuit,
It is characterized in that the magnetic flux densities in the two regions far from the recording medium are made higher than those in the two regions near the recording medium. With such a structure, the driving forces generated in the two track driving coils can be equalized. Further, since the magnetic flux density distribution with respect to the focusing direction can be made symmetrical, tangential tilt associated with the focusing operation does not occur. According to such a technical means, it is possible to suppress the tilt associated with the tracking drive without adding any new component. Further, the invention of claim 9 is an effective means of the present invention, wherein the magnetizing amount of the magnet corresponding to the track driving coil located at a position far from the recording medium is increased. It is characterized in that, out of the four magnetized regions forming the magnetic circuit, the magnetized amounts of the magnets in the two farther regions are larger than those in the two regions closer to the recording medium. According to such a technical means, among the four magnetized regions forming the magnetic circuit,
Since the magnetic flux densities in the two areas far from the recording medium can be made higher than those in the two areas close to the recording medium, it is possible to obtain the same effect as that of the invention described in claims 7 and 8.

The invention of claim 10 is also an effective means of the present invention, wherein the material of the magnet corresponding to the track driving coil located far from the recording medium is a material having a large residual magnetic flux density. is there. Compose a magnetic circuit 4
One of the magnetized areas is characterized by using a magnet material having a large residual magnetic flux density as the magnet material in the two areas farther from the two areas closer to the information recording medium. For example, it is possible to use a ferrite magnet on the side closer to the information recording medium and a rare earth magnet on the side farther from the information recording medium. According to this technical means, the magnetic flux density can be made higher in the two farther areas than in the two areas near the information recording medium among the four magnetized areas forming the magnetic circuit. It is possible to obtain the same effect as that of the described invention. In the eleventh aspect of the present invention, providing a sub-yoke on the magnet close to the recording medium is also an effective means of the present invention. As described in the conventional example, the yoke of the magnet may affect the surrounding magnetic field and disturb the magnetic distribution. Therefore, by providing a sub-yoke on the side closer to the recording medium, the magnetic flux is similarly attracted not only to the yoke formed on the side far from the information recording medium but also to the sub-yoke attached to the information recording medium side. By doing so, the magnetic flux density can be made symmetrical with respect to the magnetized boundary. With such a structure, the driving forces generated in the two track driving coils can be equalized. Further, since the magnetic flux density distribution with respect to the focusing direction can be made symmetrical, tangential tilt associated with the focusing operation does not occur. According to such a technical means, it becomes possible to suppress the tilt accompanying the tracking drive by adding a simple component. In addition, since the upper part of the yoke is connected, unnecessary resonance of the yoke can be suppressed when disturbance acts, and stable reading / writing and unpleasant resonance can be suppressed.

According to a twelfth aspect of the present invention, an objective lens holding member for holding a plurality of focus driving coils and track driving coils facing the magnet and the objective lens is provided, and by energizing each coil, In an optical disk drive device equipped with an objective lens driving device for driving an objective lens holding member, the material of the yoke bottom of the magnet is formed of a non-magnetic material or is covered with a non-magnetic material. It is characterized in that the yoke bottom is not affected by the magnetic flux in the magnetic circuit by forming the yoke bottom with a non-magnetic material or covering it with a non-magnetic material. With such a structure, the driving forces generated in the two tracking coils can be equalized. Further, since the magnetic flux density distribution with respect to the focusing direction can be made symmetrical, tangential tilt associated with the focusing operation does not occur. According to this invention, it is possible to suppress the tilt associated with tracking drive without adding any new component. According to a thirteenth aspect of the present invention, an objective lens holding member for holding a plurality of focus driving coils and track driving coils facing the magnet and the objective lens is provided, and the objective lens holding member is held by energizing each coil. In an optical disk drive device provided with an objective lens drive device for driving a member, the yoke bottom part of the magnet is separated from the magnetic circuit. It is characterized in that the bottom of the yoke is sufficiently distant from the magnetic circuit so that the magnetic flux in the magnetic circuit is not affected by the bottom of the yoke. According to this invention, an effect equivalent to that of the invention of claim 12 can be obtained. By using the present invention, it is possible to suppress the tilt associated with tracking drive without adding any new component. In the invention of claim 14, the yoke of the magnet is formed integrally with the holding member of the objective lens driving device, which is an effective means of the present invention. By integrating the yoke with the carriage in the pickup of the optical disk drive, the bottom of the yoke is sufficiently distant from the magnetic circuit, and the magnetic flux in the magnetic circuit is not affected by the bottom of the yoke. According to this technical means, it is possible to obtain the same effect as that of the invention of claim 12. Further, it is possible to suppress the tilt associated with the tracking drive while reducing the number of parts, and it is possible to reduce the thickness by reducing the number of yokes.

According to a fifteenth aspect of the present invention, an objective lens holding member for holding a plurality of focus driving coils and track driving coils facing the magnet and the objective lens is provided, and by energizing each of the coils, the objective lens holding member is provided. In an optical disc drive device equipped with an objective lens driving device for driving an objective lens holding member, a gap distance of a magnetic circuit is different between a portion near a recording medium and a portion far from the recording medium. The magnetic circuit is configured so that the gap of the magnetic circuit is not constant in the focusing direction. For example, by widening the gap of the magnetic circuit closer to the recording medium, the same effect as the reduction of the magnetic flux density due to the bottom of the yoke can be realized on the side closer to the recording medium. According to this invention, claim 1
The same effect as that of the invention described in 2 can be obtained. Also,
It is possible to suppress the tilt caused by the tracking drive without adding any new component. According to a sixteenth aspect of the present invention, an objective lens holding member that holds a plurality of focus driving coils and track driving coils facing the magnet and an objective lens is provided, and the objective lens holding member is held by energizing each coil. In an optical disk drive device including an objective lens drive device configured to drive a member, the number of windings of the plurality of track drive coils is different between a coil near the recording medium and a coil far from the recording medium. It is characterized in that the number of turns of the two track driving coils is made different between the coil near the information recording medium and the coil far from the information recording medium. As described above, the strength of the magnetic field is proportional to the number of turns of the coil. Therefore, by appropriately setting the number of turns, it becomes possible to equalize the driving forces generated by the two tracking coils and cancel the asymmetry of the magnetic flux density. According to this invention, claim 1
The same effect as that of the invention described in 2 can be obtained. Also,
It is possible to suppress the tilt associated with the tracking drive without adding any new component, and it is possible to improve the driving force per unit current by increasing the number of turns.

According to a seventeenth aspect of the present invention, an objective lens holding member for holding a plurality of focus driving coils and track driving coils facing the magnet and the objective lens is provided, and by energizing each of the coils, the objective lens holding member is provided. In an optical disk drive device equipped with an objective lens driving device for driving an objective lens holding member, the plurality of track driving coils have different outer shapes depending on whether they are close to the information recording medium or far from the coil. In order to cancel the asymmetry of the magnetic flux density, the outer shapes of the two track driving coils are made different between the coil close to the information recording medium and the coil far from the information recording medium, so that the driving forces generated by the two track driving coils are equalized. It is characterized by doing.
For example, by enlarging the track drive coil on the side far from the recording medium affected by the bottom of the yoke, even if the same current is applied to the two drive coils, the asymmetry of the magnetic flux density is canceled and the two drive coils are driven. It is possible to equalize the driving force generated in the coil for use and suppress the occurrence of tilt. According to this invention, an effect equivalent to that of the invention of claim 12 can be obtained. Further, it becomes possible to suppress the tilt caused by the tracking drive without adding any new component. The invention of claim 18 is
It is also an effective means of the present invention to provide an optical pickup for performing focus servo or tracking servo by the objective lens driving device. In the optical disk recording / reproducing apparatus, the operation of focusing (focusing) the laser beam on the recording surface of the optical disk and further searching for a desired track (seek operation) is the most important operation. An optical pickup equipped with an objective lens driving device driven by a control signal from a servo circuit performs these operations. It is a necessary and absolute condition that the objective lens holding member that holds the objective lens used in this objective lens driving device is parallel to the recording surface of the optical disc. According to this technical means, it is possible to mount the objective lens driving device on which the countermeasure for preventing the tilt has been taken in the optical pickup, and it is possible to stably perform the focus servo or the tracking servo. In the nineteenth aspect of the present invention, it is also an effective means of the present invention to reproduce the information recorded on the optical disc or record the information by the optical pickup. The part that affects the performance of the optical disk drive is
This is the performance of the optical pickup. It is no exaggeration to say that the performance of the optical pickup is determined by the performance of the objective lens driving device mounted therein. In other words, the recording density to be recorded on the optical disc is determined by the performance of the objective lens driving device. According to such technical means, it is possible to mount an optical pickup having a tilt prevention measure,
An optical disk drive device capable of high density recording can be provided.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings. However, the constituent elements, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely explanatory examples, not the gist of limiting the scope of the present invention thereto, unless specifically stated. .. First, before describing the embodiments of the present invention, a conventional objective lens driving device will be described to clarify the difference from the present invention. FIG. 2 is a cross-sectional view of the objective lens driving device described in Japanese Patent Laid-Open No. 2000-137922. The configuration of this objective lens driving device is such that the objective lens 11 that condenses a laser beam (not shown), the lens holder 1 that holds the objective lens 11, the focus driving coils 22a and 22b, and the two track driving coils 23a and 23b.
2, yokes 18 and 19 that form a magnetic circuit, and magnets 20 and 21 that sandwich the coil.
An elastic support member 14 that supports the lens holder 12, a stem 13 that fixes the entire objective lens driving device, and a raising mirror 17 that refracts the laser beam from the objective lens 11.
And a base 15.

Next, the operation of the objective lens driving device will be described. It is characterized by using the drive magnets 20 and 21 magnetized by being divided into four cross-shaped regions, two focus drive coils 22a and 22b, and two track drive coils 23a and 23b. .
In this motor, when the distribution of the magnetic flux density is symmetrical with respect to the magnetizing boundary line (the magnet boundary line when a magnetic circuit is composed of a plurality of magnets), the current flowing through the two driving coils By making them equal, the driving forces generated there can be made equal. However, since the yoke bottom portion 15 exists near the lower part of the magnetic circuit and the yoke does not exist above the magnetic circuit, the magnetizing boundary line (the magnet boundary line when a plurality of magnets form a magnetic circuit) in the focusing direction. ), The magnetic flux density distribution was asymmetric. As a result, when the track drive is performed with the tracking drive coil at the position shown in FIG. 3B, the driving force proportional to the hatched area of FIG. It will occur in the coil. Since the magnetic flux density distribution is asymmetric with respect to the magnetization boundary, the forces fa and fb generated in the upper and lower track drive coils are different. As a result, Fig. 3 (a)
As described above, when the center T of the track coil and the center S of suspension are aligned, the forces fa and fb generated by the two track driving coils are effective only by the track driving force F with respect to the objective lens holder. Instead, a moment M was generated, and as a result, tilt was generated.

FIG. 1 is a sectional view of an objective lens driving device according to the first embodiment of the present invention. The same components are given the same reference numerals, and a duplicate description will be omitted. As shown in FIG. 1, the suspension center S is displaced from the tracking coil center T. Other configurations are the same as those in FIG. By setting the displacement between the center S of the suspension and the center T of the tracking coil so that no moment is generated by the resultant force of the forces fa and fb generated by the two tracking coils, the information recording medium is recorded in the same manner as in the case of FIG. Even though the forces generated in the near track driving coil and the far track driving coil are different, FIG.
Since no moment is generated around the center of suspension as in (a), tilt is not generated. By doing this,
It is possible to suppress the tilt associated with the tracking drive without adding any new component.

FIG. 5 is a sectional view of the objective lens driving device according to the second embodiment of the present invention. As shown in FIG. 5A, two elastic support members 14a close to the information recording medium,
It is characterized in that the center of suspension is changed without shifting the attaching position of the wire by changing the second moments of area of the two distant elastic support members 14b. For example, as shown in FIG. 5B, the suspension center can be moved toward the information recording medium by thickening the support elastic body 14a on the side closer to the information recording medium in FIG. 5A. According to the present invention, it is possible to change the center of suspension in the focusing direction without newly manufacturing an assembling jig or the like, and to suppress the tilt associated with tracking drive without adding any new parts. Becomes Also,
FIG.5 (c) is sectional drawing of the support elastic body of the 3rd Embodiment of this invention. As shown in the figure, for example, only two wires 14a close to the information recording medium have an elliptical cross section, and two wires 14b far from the information recording medium have a circular cross section. By properly setting this elliptical shape, the spring elasticity coefficients of the four wires are made equal in the focus direction, and the two elastic support members 1 close to the information recording medium in the tracking direction.
4a and the two elastic support members 14b far from each other can have different moments of inertia in area. In FIG. 5B, the spring stiffness in the focusing direction is different between the support elastic body 14a closer to the information recording medium and the support elastic body 14b farther from the information recording medium. In this state, a tangential tilt will occur during focusing movement. However, FIG. 5 (c)
According to the method, the spring elasticity coefficient in the focusing direction can be made equal to all four, so that the tilt of the lens in the jitter direction can be suppressed by the focus driving. As a result, it becomes possible to suppress the tilt associated with the tracking drive without adding any new component.

FIG. 6 is a sectional view of the objective lens driving device according to the fourth embodiment of the present invention. As shown in the figure, with respect to the four wires supporting the lens holder 12, two wires 14a close to the information recording medium are obliquely supported, so that the apparent spring elasticity coefficient of the obliquely supported wires in the tracking direction is increased. Is changed to shift the center of suspension. Support elastic body 1 on the side closer to the information recording medium
It is possible to improve the apparent spring elastic coefficient in the tracking direction and move the suspension center S toward the information recording medium by tilting and supporting 4a. As a result, it becomes possible to suppress the tilt associated with the tracking drive without adding any new component. Further, by using the present invention, the torsional rigidity of the objective lens with respect to the inclination in the tracking direction (hereinafter referred to as radial tilt) can be improved, and the tilt can be suppressed against disturbance or the like.

FIG. 7 is a sectional view of a magnet of an objective lens driving device according to the fifth embodiment of the present invention. Among the four magnetized areas forming the magnetic circuit, the magnetic flux density is higher in the two areas farther from the two areas closer to the information recording medium. With such a configuration, the driving force fa generated in the two tracking coils,
fb can be made equal. Further, since the magnetic flux density distribution with respect to the focusing direction can be made symmetrical, tangential tilt associated with the focusing operation does not occur. By using the present invention, it is possible to suppress the tilt associated with tracking drive without adding any new component. Further, in the sixth embodiment of the present invention, of the four magnetized areas forming the magnetic circuit, the magnetized amounts of the magnets in the two farther areas are larger than those in the two areas closer to the information recording medium. It is characterized by With such a configuration, the magnetic flux density can be made higher in two regions farther from the two regions closer to the information recording medium than the four magnetic regions constituting the magnetic circuit. It is possible to obtain the same effect as the form. In addition, in the seventh embodiment of the present invention, of the four magnetized areas forming the magnetic circuit, the magnet material in the far two areas has a large residual magnetic flux density as compared with the two areas near the information recording medium. It is characterized by using a material. For example, it is possible to use a ferrite magnet on the side closer to the information recording medium and a rare earth magnet on the side farther from the information recording medium. With such a configuration, the magnetic flux density can be made higher in two regions farther from the two regions closer to the information recording medium than the four magnetic regions constituting the magnetic circuit. It is possible to obtain the same effect as the invention of the embodiment.

FIG. 8 is a sectional view of the magnet of the objective lens driving device according to the eighth embodiment of the present invention. By providing the sub-yoke 30 on the side closer to the information recording medium, not only the yoke 15 in which the magnetic flux is formed on the side far from the information recording medium, but also the sub-yoke 3 attached to the information recording medium side.
Since the magnetic flux is similarly drawn to 0, the magnetic flux density can be made symmetrical with respect to the magnetization boundary. With such a configuration, the driving forces fa and fb generated in the two tracking coils shown in FIGS. 3 and 4 can be equalized. Further, since the magnetic flux density distribution with respect to the focusing direction can be made symmetrical, tangential tilt associated with the focusing operation does not occur. By using the present invention, it is possible to suppress tilt due to tracking drive by adding a simple component. Further, since the upper part of the yoke is connected, unnecessary resonance of the yoke can be suppressed at the time of disturbance action and the like, and stable reading / writing and suppression of unpleasant resonance sound can be suppressed. The sub-yoke can be formed as a separate component, but can also be formed by bending a conventional yoke.

FIG. 9 is a sectional view of a magnet of an objective lens driving device according to a ninth embodiment of the present invention. By forming the yoke bottom portion 15 with a non-magnetic material or by covering it with a non-magnetic material, the yoke bottom portion 1 with respect to the magnetic flux in the magnetic circuit
5 is not affected. With such a configuration, the driving forces fa and fb generated in the two tracking coils shown in FIGS. 3 and 4 can be equalized. Further, since the magnetic flux density distribution with respect to the focusing direction can be made symmetrical, tangential tilt associated with the focusing operation does not occur. By using the present invention, it is possible to suppress the tilt associated with tracking drive without adding any new component.

FIG. 10 is a sectional view of a magnet of an objective lens driving device according to the tenth embodiment of the present invention. It is characterized in that the yoke bottom portion 15 is sufficiently distant from the magnetic circuit so that the magnetic flux in the magnetic circuit is not affected by the yoke bottom portion 15. With such a configuration, it is possible to obtain the same effects as the invention of the ninth embodiment. Further, by using the present invention, it becomes possible to suppress the tilt accompanying the tracking drive without adding any new component.

FIG. 11 is a sectional view of the objective lens driving device of the eleventh embodiment of the present invention. By integrating the yoke 15 with the carriage in the pickup of the optical disk drive, the bottom of the yoke is sufficiently separated from the magnetic circuit, and the magnetic flux in the magnetic circuit is not affected by the bottom of the yoke. With such a configuration, it is possible to obtain the same effects as the invention of the ninth embodiment. By using the present invention, it is possible to suppress the tilt associated with tracking drive while reducing the number of parts. Further, it is possible to reduce the thickness by reducing the number of yokes.

FIG. 12 is a sectional view of a magnet of an objective lens driving device according to the twelfth embodiment of the present invention. The magnetic circuit is configured so that the gap of the magnetic circuit is not constant in the focusing direction. For example, as shown in the figure, by widening the gap G of the magnetic circuit closer to the information recording medium, the same effect as the reduction of the magnetic flux density due to the bottom of the yoke can be realized on the side closer to the information recording medium. With this configuration,
An effect equivalent to that of the invention of the ninth embodiment can be obtained. By using the present invention, it is possible to suppress the tilt associated with tracking drive without adding any new component. The thirteenth embodiment of the present invention is characterized in that the number of turns of the two track driving coils is made different between the coil near the information recording medium and the coil far from the information recording medium. By setting this winding number appropriately, 2
It is possible to equalize the driving forces generated by the two track driving coils and cancel the asymmetry of the magnetic flux density. With such a configuration, it is possible to obtain the same effects as the invention of the ninth embodiment. Further, by using the present invention, it becomes possible to suppress the tilt accompanying the tracking drive without adding any new component. Furthermore, the driving force per unit current can be improved by increasing the number of turns.

FIG. 13 is a top view of the track driving coil of the objective lens driving device according to the fourteenth embodiment of the present invention. By canceling the asymmetry of the magnetic flux density, the outer shapes of the two track driving coils 23c and 23d are made different between the coil close to the information recording medium and the coil far from the information recording medium. Are equal to each other. Since the shapes of the two track driving coils are the same in FIGS. 3 and 4, the areas of the magnetic flux densities serving as the driving forces of the two coils (see FIG. 3C) are different. However, even if the same current is passed through the two drive coils by increasing the size of the track drive coil 23d far from the information recording medium affected by the bottom of the yoke, the asymmetry of the magnetic flux density is canceled and Equalize the driving forces fc and fd generated in the two driving coils,
It is possible to suppress the occurrence of tilt. Therefore, the ninth
It is possible to obtain the same effect as the invention of the embodiment. Further, by using the present invention, it becomes possible to suppress the tilt accompanying the tracking drive without adding any new component.

FIG. 14 is a block diagram of the optical pickup of the objective lens driving device of the fifteenth embodiment of the present invention. The light beam (linearly polarized light) emitted from the semiconductor laser 100 as divergent light is collimated by the coupling lens 200 and is incident on the polarization beam splitter 300. The beam splitter 300 has a function of transmitting or reflecting light on the bonding surface depending on the polarization direction of the light. The incident light is parallel light, and since it oscillates in parallel to the incident surface of the beam splitter 300, it is transmitted. The transmitted light beam changes its direction by the rising mirror 400 and then enters the quarter-wave plate 500. The quarter-wave plate 500 converts linearly polarized light into circularly polarized light. After that, the light beam passes through the objective lens 6
Incident on 00. The light incident on the objective lens 600 is condensed on the recording surface of the optical disc 700. The light reflected from the recording surface is again converted into the objective lens 600 and the quarter-wave plate 50.
It is incident on 0. At this time, the circularly polarized light is converted again to the linearly polarized light, but the phase of the light which first enters the quarter-wave plate 500 is shifted by 90 degrees, and the light vibrates vertically. This light is reflected by the beam splitter 300 in a direction perpendicular to the incident direction. Then, after being condensed by the condenser lens 800, the light is received by the light receiving element 900. Then, the amount of light received by the light receiving element 900 is converted into an electric signal, and the information recorded on the optical disc 700 is reproduced. Further, the light receiving element 900 is divided, and a tracking error signal and a focus error signal are generated according to the amount of light received by each of the divided light receiving elements. Then, based on these signals, the tracking coil 100
0 or a current is passed through the focusing coil 1100 to perform tracking servo or focusing servo. Although not shown, the objective lens 600, the tracking coil 1000, and the focusing coil 1100 are mounted on the objective lens driving device described in the first to fourteenth embodiments.

FIG. 15 is a block diagram showing the arrangement of an optical disk drive device according to the 16th embodiment of the present invention.
In the present embodiment, a recording / playback type optical disc drive will be described, but the present invention is not limited to this.
For example, it may be a reproduction type optical disk drive in which the recording compensation in FIG. 15 is omitted. An audio circuit, an image compression / expansion circuit, or an interface for connection with a computer is connected to the signal input / output depending on the purpose of using the signal. The recording compensation includes a circuit such as laser modulation by a recording signal, and the RF signal processing includes a circuit such as waveform shaping of a read signal. The servo detects an error component from the read signal and feeds it back to the optical pickup or the disk motor to control the rotation of the focus servo, tracking servo and spindle motor. First, in the information reproducing operation, the information signal recorded on the optical disc 54 is read by the optical pickup 53, and the signal is input to the RF signal processing circuit 52. The RF signal processing circuit 52 shapes the waveform of the input signal, and then inputs the signal to the demodulation circuit 50. After demodulation, the signal is output to a host computer or the like (not shown). Further, in the information recording operation, when a signal to be recorded is first input, the signal modulation circuit 50 modulates the signal into a signal that is easily recorded on the optical disc 54. The next modulated signal is the recording compensation circuit 5
1 is input to the optical pickup 53, laser modulation is performed, and a laser drive current corresponding to a signal is passed to the optical pickup 53. In general, the current passed when recording information is larger than when reproducing information. And
Information recording is performed by emitting a semiconductor laser based on an input signal and irradiating the recording surface of the optical disc 54 with the laser from the optical pickup 53. During this operation, servo control is always performed. In the present invention, the above operation is performed using the optical pickup described in the fifteenth embodiment.

[0027]

According to the present invention as described above, according to the first aspect, it is possible to suppress the tilt caused by the tracking drive without adding any new parts. According to the second aspect of the present invention, the center point of suspension is set at a position where no moment is generated. Therefore, it is possible to suppress the tilt associated with the tracking drive without adding any new component only by adjustment. According to the third aspect, the suspension center can be changed in the focusing direction without newly producing an assembling jig or the like, and the tilt accompanying the tracking drive can be suppressed without adding any new component. Become. According to the fourth aspect, since the four spring elastic coefficients in the focusing direction can be made equal, the tilt of the lens in the jitter direction is suppressed by the focus driving. Further, by making the second moment of area of the elastic support member near and far of the recording medium different, it is possible to suppress the tilt accompanying the tracking drive without adding any new component. According to the fifth aspect, the second moment is different only by changing the cross-sectional shape of the wire, and it is possible to easily suppress the tilt accompanying the tracking drive.

According to the sixth aspect, it is possible to suppress the tilt associated with the tracking drive without adding any new component. Further, by using the present invention, the torsional rigidity of the objective lens with respect to the inclination in the tracking direction (radial tilt) can be improved, and the tilt can be suppressed against disturbance or the like. According to the seventh aspect, since the moments can be canceled out by changing the magnetic flux density of the magnet, it is possible to suppress the tilt associated with the tracking drive without changing the external configuration. According to the eighth aspect, it is possible to suppress the tilt associated with the tracking drive without adding any new component. According to a ninth aspect of the present invention, the magnetic flux density can be increased in two regions farther from the four magnetized regions forming the magnetic circuit than in the two regions closer to the recording medium. It is possible to obtain the same effect as the invention. According to a tenth aspect of the present invention, the magnetic flux density can be made higher in the two farthest areas compared to the two areas closer to the information recording medium among the four magnetized areas forming the magnetic circuit.
It is possible to obtain the same effect as the invention described in item 8. According to the eleventh aspect, it becomes possible to suppress the tilt accompanying the tracking drive by adding a simple component. Also,
By connecting the upper part of the yoke, unnecessary read / write of the yoke is suppressed when disturbance acts and stable reading / writing,
Unpleasant resonance can be suppressed. Claim 12
It is possible to suppress the tilt caused by the tracking drive without adding any new component. Claim 13
Can obtain an effect equivalent to that of the invention of claim 12. By using the present invention, it is possible to suppress the tilt associated with tracking drive without adding any new component. According to claim 14, it is possible to obtain the same effect as that of the invention according to claim 12. Further, it is possible to suppress the tilt associated with the tracking drive while reducing the number of parts, and it is possible to reduce the thickness by reducing the number of yokes.

According to the fifteenth aspect, it is possible to obtain the same effect as the invention according to the twelfth aspect. Further, it becomes possible to suppress the tilt caused by the tracking drive without adding any new component. According to claim 16, it is possible to obtain the same effect as that of the invention according to claim 12. Further, it is possible to suppress the tilt associated with the tracking drive without adding any new component, and it is possible to improve the driving force per unit current by increasing the number of turns. The seventeenth aspect can obtain an effect equivalent to that of the twelfth aspect of the invention. Further, it becomes possible to suppress the tilt caused by the tracking drive without adding any new component. According to the eighteenth aspect, the objective lens driving device provided with measures for preventing tilt can be mounted on the optical pickup, and the focus servo or the tracking servo can be stably performed. Claim 19
It is possible to provide an optical pickup device capable of high-density recording by mounting an optical pickup having a tilt prevention measure.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a conventional objective lens driving device that is referred to in order to explain the present invention.

FIG. 3 is a diagram for explaining a mechanism of generating a moment M.

FIG. 4 is a diagram for explaining a mechanism for canceling a moment M of the present invention.

FIG. 5 is a sectional view of an objective lens driving device according to a second embodiment of the present invention.

FIG. 6 is a measurement sectional view of an objective lens driving device according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a magnet of an objective lens driving device according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view of a magnet of an objective lens driving device according to an eighth embodiment of the present invention.

FIG. 9 is a sectional view of a magnet of an objective lens driving device according to a ninth embodiment of the present invention.

FIG. 10 is a sectional view of a magnet of an objective lens driving device according to a tenth embodiment of the present invention.

FIG. 11 is a sectional view of an objective lens driving device according to an eleventh embodiment of the present invention.

FIG. 12 is a sectional view of a magnet of an objective lens driving device according to a twelfth embodiment of the present invention.

FIG. 13 is a top view of a track driving coil of an objective lens driving device according to a fourteenth embodiment of the present invention.

FIG. 14 is a configuration diagram of an optical pickup of an objective lens driving device according to a fifteenth embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration of an optical disc drive device according to a sixteenth embodiment of the present invention.

FIG. 16 is a schematic cross-sectional view of the magnetic circuit of the objective lens driving device of the conventional example taken along a plane orthogonal to the jitter direction.

FIG. 17 is a diagram for explaining a portion where a driving force is actually generated in the conventional example.

FIG. 18 is a sectional view of a motor according to a conventional example, which is taken along a plane orthogonal to the focusing direction.

FIG. 19 is a diagram illustrating a mechanism of tilt moment generation associated with tracking displacement in a conventional example.

FIG. 20 is a diagram showing a configuration of a general magnetic circuit of a conventional example.

[Explanation of symbols] 11 Objective lens 12 lens holder 13 Stem (actuator fixing part) 14 Elastic support material 15 base 17 Launch mirror 18, 19 York 20, 21 magnet 20a, 20b Magnetization boundary of the magnet 20 21a, 21b Magnetization boundary of the magnet 21 22a, 22b Focus coil 23a, 23b track coil Suspension center Center of T track coil Driving force generated by fa 23a Driving force generated by fb 23b F The resultant force of the driving force generated by the two driving coils

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D118 AA02 AA12 AA13 BA01 CD04                       EA02 EB11 ED07 FA23 FB03

Claims (19)

[Claims] 1. An objective lens holding member for holding a plurality of focus driving coils facing a magnet and a track driving coil and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In the optical disk drive apparatus including the objective lens driving device configured to perform the objective lens holding device, the objective lens holding member is arranged such that the suspension center point of the objective lens holding member is different from the center point between the plurality of track driving coils. An optical disk drive device in which members are set. 2. The optical disk drive apparatus according to claim 1, wherein the suspension center point of the objective lens holding member is set at a position where a moment is not generated by a force generated by the plurality of track driving coils. . 3. An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing a magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In the optical disk drive device including the objective lens driving device as described above, a plurality of elastic supporting members for supporting the objective lens holding member are provided, and the elastic supporting member provided at a position close to the recording medium and the position far from the recording medium are provided. An optical disk drive device characterized in that the elastic moments of the elastic support members are different. 4. The focus driving coil drives the objective lens holding member by the elastic moment of the elastic supporting member provided at a position near the recording medium and the elastic moment of the elastic supporting member provided at a position far from the recording medium. 4. The optical disk drive device according to claim 3, wherein the values are the same in the case, and the values are different when the track driving coil drives the objective lens holding member. 5. The sectional shape of the elastic support member provided at a position close to the recording medium and the elastic support member provided at a position far from the recording medium are different from each other.
4. The optical disk drive device described in 4. 6. The optical disk according to claim 3, wherein the elastic support member provided at a position close to the recording medium has a different mounting position between the objective lens holding member side and the fixed portion side. Drive device. 7. An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing a magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In an optical disk drive device including the objective lens driving device as described above, the magnetic flux density of the magnet is formed to have different values in a portion near a recording medium and a portion far from the recording medium. 8. The optical disk drive device according to claim 7, wherein the magnetic flux density of the magnet corresponding to the track driving coil located far from the recording medium is increased. 9. The optical disk drive device according to claim 7, wherein the magnetizing amount of the magnet corresponding to the track driving coil located far from the recording medium is increased. 10. The material of the magnet corresponding to the track driving coil at a position far from the recording medium is made of a material having a high residual magnetic flux density.
The optical disk drive device described. 11. The optical disk drive device according to claim 7, wherein a sub-yoke is provided on the magnet close to the recording medium. 12. An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing a magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In the optical disk drive device including the objective lens driving device configured as described above, the yoke bottom portion of the magnet is formed of a non-magnetic material,
Alternatively, an optical disk drive device characterized by being covered with a non-magnetic material. 13. An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing a magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. An optical disk drive device including the objective lens driving device as described above, wherein the yoke bottom portion of the magnet is separated from a magnetic circuit. 14. The optical disk drive device according to claim 13, wherein the yoke of the magnet is formed integrally with a holding member of the objective lens driving device. 15. An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing a magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In the optical disk drive device including the objective lens driving device as described above, an optical disk drive device is characterized in that a gap distance of a magnetic circuit is different between a portion near a recording medium and a portion far from the recording medium. 16. An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing a magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In the optical disc drive device including the objective lens drive device as described above, the number of turns of the plurality of track drive coils is different between the coil near the recording medium and the coil far from the recording medium. Drive device. 17. An objective lens holding member for holding a plurality of focus driving coils and track driving coils facing a magnet and an objective lens is provided, and the objective lens holding member is driven by energizing each coil. In the optical disk drive device including the objective lens driving device as described above, the outer shapes of the plurality of track driving coils are different between a coil located near the information recording medium and a coil located far from the information recording medium. Drive device. 18. The optical disk drive device according to claim 1, further comprising an optical pickup that performs a focus servo or a tracking servo by the objective lens driving device. 19. The optical disk drive device according to claim 18, wherein information recorded on an optical disk is reproduced or information is recorded by the optical pickup.