JPH05225587A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To suppress the resonance/antiresonance phenomenon of the yawing mode of tracking servo control and to improve the characteristics of the tracking servo control and focusing servo control. CONSTITUTION:Correcting yoke members 31, 32, 33, 34 are provided on the flanks of permanent magnets 11, 15 of magnetic circuit members 12, 16. As a result, the leaking magnetic fields in the magnetic gap of the magnetic circuit members 12, 16 are decreased and the intensity thereof is suppressed. The resonance/antiresonance phenomenon of the yawing mode is thus suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mounts a focusing drive coil for moving an objective lens in a focusing direction and a tracking drive coil for moving an objective lens in a tracking direction on a lens holder for holding an objective lens. In addition, the present invention relates to an objective lens driving device including a magnetic circuit member that generates a magnetic field in which driving currents flowing through the focusing driving coil and the tracking driving coil are interlinked.

[0002]

2. Description of the Related Art An optical pickup device for recording / reproducing (/ erasing) data on / from an optical disk supports an objective lens for focusing a laser beam, and a moving mechanism for moving the objective lens in a focusing direction and a tracking direction. An objective lens driving device including the above is provided.

14 (a) and 14 (b) show a conventional example of an objective lens moving mechanism.

In the drawing, a focusing coil 3 is wound around an objective lens holder 2 which holds the objective lens 1, and a surface of the focusing coil 3 corresponding to the side surfaces 2a and 2b of the objective lens holder 2 has a flat surface. The tracking coils 4 and 5 and the tracking coils 6 and 7 each formed of a circular coil are bonded and fixed.

The base member 8 includes a magnetic circuit member 12 including an outer yoke member 9, an inner yoke member 10 and a permanent magnet 11, an outer yoke member 13, an inner yoke member 14 and a permanent magnet 15. Magnetic circuit member 16
Are provided, and holes 2c and 2d formed in the objective lens holder 2 are inserted into the inner yoke member 10 and the inner yoke member 14, respectively.

As a result, the focusing coil 3 is inserted into the magnetic gap of the magnetic circuit member 12 and the magnetic gap of the magnetic circuit member 16, and the magnetic circuit member 1 is also inserted.
The tracking coils 4 and 5 are inserted into the magnetic gap of No. 2, and the tracking coils 6 and 7 are inserted into the magnetic gap of the magnetic circuit member 16.

Two sets of parallel leaf springs 1 are attached to the supporting portions 2e, 2f, 2g and 2h provided on the objective lens holder 2.
One end of 7, 18, 19, 20 is fixed.
The other end of each of the parallel leaf springs 17, 18, 19, 20 is attached to a support member 21, which supports the base member 8 and the bearing member 22 fixed to the outer yoke member 9. It is rotatably supported between.

As a result, the objective lens holder 2 is movably supported by the parallel leaf springs 17, 18, 19, 20 with respect to the base member 8 in the focusing direction, and is supported by the base member 8 in the tracking direction. It is rotatably supported.

With the above structure, when a driving current is applied to the focusing coil 3, a current interlinking with the magnetic fields of the magnetic circuit member 12 and the magnetic circuit member 16 acts, so that focusing according to the magnitude and direction of the driving current is performed. The thrust in the direction acts on the objective lens holder 2, and the objective lens holder 2 moves in such a manner that the thrust and the restoring force of the deformation of the parallel leaf springs 17, 18, 19, 20 in the focusing direction balance with each other. The position of the objective lens 1 in the focusing direction is determined.

For example, as shown in FIG. 15, the permanent magnet 1
When the magnetic field of 5 is directed from the upper side of the drawing to the lower side of the drawing, when the driving current Ia is applied to the focusing coil 3, the thrust F1 in the upward focusing direction is generated, and the driving current Ib in the opposite direction is applied to the focusing coil 3. Then, a thrust F2 in the downward focusing direction is generated.

The tracking coils 4, 5, 6, 7
When a drive current is applied to the tracking coil 4, 5, a current interlinking the magnetic field of the magnetic circuit member 12 flows in the tracking coils 4 and 5, and a current interlinking the magnetic field of the magnetic circuit member 16 flows in the tracking coils 6 and 7. The thrust in the tracking direction corresponding to the magnitude and direction of the driving current at that time acts on the objective lens holder, and as a result, the objective lens holder 2 rotates about the rotation center 22a of the support member 21. The position of the lens 1 in the tracking direction is determined.

For example, when a clockwise driving current is applied to the tracking coil 6 and a counterclockwise driving current is applied to the tracking coil 7, the tracking coil 6 has a rightward current Ic and a downward current Ic. The current Id and the leftward current Ie act on the magnetic field of the permanent magnet 15, and for the tracking coil 7, the leftward current If, the downward current Ig, and the rightward current Ih act on the magnetic field of the permanent magnet 15. To work.

Therefore, the currents Id and Ig generate a thrust F3 in the right direction (tracking right direction) in the figure, and the current I
Thrust forces F4 and F5 in the upward focusing direction due to c and Ih
Occurs and thrusts F6 and F7 in the downward focusing direction are generated by the currents Ie and If.

If the thrust F4 and the thrust 6, and the thrusts F5 and F7 are balanced, the objective lens holder 2 does not rotate around the center of gravity G, and the objective lens holder 2 is not rotated.
Moves to the left for Focusing.

Similarly, when a driving current in the opposite direction is applied to the tracking coils 6 and 7, the objective lens holder 2
Moves to the left of tracking. Note that in FIG. 15, the position SP indicates the focal position of the objective lens 1.

By the way, the strength of the magnetic field of the permanent magnet 15 acting at the central position of the magnetic gap of the magnetic circuit member 16 is:
As shown in FIG. 16, the distribution has a uniform value in the portion FFa corresponding to the central position of the permanent magnet 15, and has a distribution that decreases from this portion FFa toward the periphery of the permanent magnet 15. Further, in the areas RA and RB outside the permanent magnet 15,
Leakage magnetic field is generated.

In this way, since the magnetic field strength of the permanent magnet 15 is distributed so as to be maximum in the central portion of the permanent magnet 15 and minimum in the peripheral portion, the following inconvenience occurs.

For example, as shown in FIG. 17, when the objective lens holder 2 is moved in the upward focusing direction, the currents Ie and Ih become stronger than the magnetic field strength acting on the currents Ic and If flowing through the tracking coils 6 and 7. The strength of the acting magnetic field is greater.

Therefore, the thrust F6 becomes larger than the thrust F4, and the thrust F7 becomes larger than the thrust F5. At this time, since the thrust force F3 in the right direction of the tracking is generated by the currents Id and Ig, the objective lens holder 2
Causes a rotational moment that rotates in the counterclockwise direction in the drawing about the center of gravity G, and the focal position SP is displaced in the tracking left direction.

As a result, the tracking coils 6 and 7 are
When a sinusoidal drive current is applied, the displacement of the focus position SP is delayed with respect to the change of the drive current, and as a result, a so-called resonance phenomenon occurs in the tracking servo control system.

On the other hand, as shown in FIG. 17, when the objective lens holder 2 is moved in the upward focusing direction, the currents Ic, If flowing in the tracking coils 6, 7 are changed to currents Ie, Ih rather than the magnetic field strength acting on the currents Ic, If. The strength of the acting magnetic field is smaller.

Therefore, the thrust F6 becomes smaller than the thrust F4, and the thrust F7 becomes smaller than the thrust F5. At this time, since the thrust force F3 in the right direction of the tracking is generated by the currents Id and Ig, the objective lens holder 2
Is applied with a rotational moment that rotates in the clockwise direction in the drawing about the center of gravity G, and the focus position SP is displaced in the tracking left direction.

As a result, the tracking coils 6 and 7 are
When a sinusoidal drive current is applied, the displacement of the focus position SP advances with respect to the change of the drive current, and an anti-resonance phenomenon opposite to the above-mentioned resonance phenomenon occurs.

Such resonance phenomenon and anti-resonance phenomenon are
It occurs in both the magnetic circuit member 16 and the magnetic circuit member 12. It should be noted that these phenomena are called yawing phenomena because they cause the focus position SP to swing in the tracking direction around the center of gravity G of the objective lens holder 2, and are caused by this yawing phenomenon. The anti-resonance phenomenon is called yawing mode resonance.

From the above, when the objective lens holder 2 is displaced in the upward focusing direction, the neutral position, and the downward focusing direction, the tracking servo control of the objective lens 1 is performed as shown in FIGS. 19 (a) and 19 (b), respectively. The frequency / gain characteristics as shown in (c) are shown.

That is, when the objective lens holder 2 is displaced in the upward focusing direction, a resonance point occurs in the frequency / gain characteristic of tracking servo control. Also,
When the objective lens holder 2 is displaced in the downward focusing direction, an anti-resonance point occurs in the frequency / gain characteristic of tracking servo control.

Here, the anti-resonance point is generated in the frequency / gain characteristic of the tracking servo control at the neutral position of FIG. 19B, as shown in FIG. 20, the position of the center of gravity G of the objective lens holder 2. However, this is because the thrust F3 in the tracking direction is displaced downward from the point of action PF, and the focus position SP moves in the same manner as shown in FIG.

Thus, in the conventional device, the permanent magnet 15 and the permanent magnet 1 used in the magnetic circuit member 16 are used.
Due to the resonance phenomenon and the anti-resonance phenomenon caused by the magnetic field strength distribution of No. 1, the characteristics of the tracking servo control system deteriorate.

Further, for the same reason, as shown in FIG. 21, the focus positioning characteristic under the focusing servo control is also non-linear.
The X axis in the figure shows the drive current applied to the focusing coil 3.

Therefore, in order to eliminate such an inconvenience, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 62-285261, in the vicinity of the objective lens driving device,
It has been proposed to arrange a correction magnet to reduce the leakage magnetic field in the vicinity of the focal point of the objective lens.

According to this conventional device, since the leakage magnetic field is reduced, the yawing phenomenon can be suppressed, and the influence of the yawing resonance described above can be suppressed. With that,
The characteristics of focusing servo control can also be improved.

[0032]

However, such a conventional device has the following disadvantages.

That is, since the cost for manufacturing the correction magnet is high, the device cost is high. In addition, since the correction magnet may be attracted to the surrounding member made of a magnetic material or may receive a repulsive force, the work for mounting the correction magnet becomes complicated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an objective lens driving device capable of eliminating the influence of the magnetic field strength distribution of the permanent magnet of the magnetic circuit member.

[0035]

SUMMARY OF THE INVENTION The present invention provides a lens holder for holding an objective lens, a focusing drive coil for moving the objective lens in the focusing direction, and a tracking drive coil for moving the objective lens in the tracking direction. In the objective lens driving device equipped with a magnetic circuit member for generating a magnetic field in which driving currents flowing through the focusing driving coil and the tracking driving coil are interlinked, the side surface of the permanent magnet of the magnetic circuit member is formed of a magnetic material. And a correction yoke member attached to the.

Further, a focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to the lens holder for holding the objective lens. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, The permanent magnet has a through hole formed in the center thereof.

Further, a focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to the lens holder for holding the objective lens. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, The permanent magnet is provided with a recess formed in the center of the surface facing the magnetic gap.

Further, a focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to a lens holder for holding the objective lens. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, A through hole is provided at a substantially central portion of an inner yoke member that is arranged to face the permanent magnet with a magnetic gap therebetween.

Further, a focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to the lens holder for holding the objective lens, and the focusing drive coil is used. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, The inner yoke member is provided with a recess provided substantially in the center of the inner yoke member facing the permanent magnet with a magnetic gap therebetween.

A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to the lens holder for holding the objective lens, and the focusing drive coil is used. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, The outer yoke member attracted to the permanent magnet is provided with a through hole formed substantially in the center thereof.

Further, a focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to a lens holder for holding the objective lens, and the focusing drive coil is used. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, The outer yoke member attracted to the permanent magnet is provided with a concave portion provided at a substantially central portion thereof.

Further, a focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to a lens holder for holding the objective lens. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, the objective lens driving device being provided in a substantially central portion of an outer yoke member attracted to a permanent magnet of the magnetic circuit member It is provided with an arm member that holds down the side surface of the permanent magnet.

Further, a focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to the lens holder for holding the objective lens, and the focusing drive coil is used. And an objective lens drive device including a magnetic circuit member that generates a magnetic field in which a drive current flowing in a tracking drive coil interlinks, a permanent magnet of the magnetic circuit member, an outer yoke member attracted to the permanent magnet, and At least one side surface of the inner yoke member disposed with a magnetic gap separated from the permanent magnet is formed in a concave shape.

A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to the lens holder for holding the objective lens, and the focusing drive coil is used. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, A position adjusting means for adjusting the position of the correction yoke member in the focusing direction is provided. The position adjusting means is made of a non-magnetic material and a biasing member that is fixed to an outer yoke member that attracts the permanent magnet and that biases the correction yoke member in the upward focusing direction. The holding member is screwed to the upper end portion and holds the position of the upper end portion of the correction yoke member.

[0045]

Therefore, the leakage magnetic field of the permanent magnet is reduced by providing the correction yoke member or by shaping the side surface of the permanent magnet, the inner yoke member, or the outer yoke member, so that the objective lens holder is focused. The magnetic field strength acting on the drive coil when moving in the direction becomes substantially uniform, and the yawing phenomenon can be suppressed. Further, by shaping the central portion of the permanent magnet, the outer yoke member, or the inner yoke member, the magnetic field strength at that portion can be reduced, and the magnetic field strength in the magnetic gap can be made substantially flat. The characteristics of focusing servo control and tracking servo control can be further improved. Further, when the position adjusting means of the correction yoke member is provided, it is possible to adjust the improved state of the magnetic field strength distribution, so that it is possible to cope with variations in the characteristics of the device. Also, with the arm member provided on the outer yoke member,
Since the same effect as that of the correction yoke member can be realized, the number of parts can be reduced and the labor of assembling work can be reduced.

[0046]

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

1A and 1B show an objective lens moving mechanism according to an embodiment of the present invention. In the figure, the same parts as those in FIGS. 14A and 14B and the corresponding parts are designated by the same reference numerals.

In the figure, correction yoke members 31 and 32 made of a magnetic material are attached to the side surface of the permanent magnet 11 of the magnetic circuit member 12 at the center position in the focusing direction, and the permanent magnet of the magnetic circuit member 16 is attached. Correction yoke members 33 and 34 made of a magnetic material are attached to the side surface of 15 at the center position in the focusing direction.

Thus, for example, when the intensity distribution of the magnetic field of the permanent magnet 15 acting at the central position of the magnetic gap of the magnetic circuit member 16 is examined, as shown in FIG.
The leakage magnetic fields in the regions RA and RB outside the area 5 have substantially the same strength in the focusing direction, and their magnitude is significantly lower than that of the conventional device.

Therefore, according to the experiments by the present inventors,
When the objective lens holder 2 is displaced in the upward focusing direction, the neutral position, and the downward focusing direction, the tracking servo control of the objective lens 1 is performed as shown in FIG.
It was confirmed that the frequency / gain characteristics shown in (a), (b), and (c) were exhibited.

That is, when the objective lens holder 2 is displaced in the upward focusing direction, neither resonance point nor anti-resonance point occurs in the frequency / gain characteristic of tracking servo control. Further, when the objective lens holder 2 is displaced in the focusing neutral position and in the downward focusing direction, an anti-resonance point is generated in the frequency / gain characteristic of tracking servo control, but compared with the conventional device, the anti-resonance point is different. Gain fluctuations are greatly suppressed.

From the above, by providing the correction yoke members 31, 32, 33 and 34 on the permanent magnets 12 and 15, the resonance of the yawing mode can be greatly suppressed and the tracking servo control characteristics can be greatly improved. can do.

When the positions of the correction yoke members 31, 32, 33, 34 provided on the permanent magnets 12, 15 in the focusing direction are displaced in the focusing upward direction, the objective lens holder 2 is moved in the focusing upward direction, the neutral position, and , The tracking servo control of the objective lens 1 when it is respectively displaced downward is as shown in FIG.
As shown in (b) and (c), yaw mode anti-resonance occurs.

When the positions of the correction yoke members 31, 32, 33, 34 provided on the permanent magnets 12, 15 in the focusing direction are displaced in the downward focusing direction, the objective lens holder 2 is moved in the upward focusing direction, the neutral position, and , The tracking servo control of the objective lens 1 when displaced downwards is as shown in FIG.
As shown in (b) and (c), yawing mode resonance occurs.

In this way, the correction yoke members 31, 3 are
By changing the mounting positions of 2, 33 and 34 in the focusing direction, it is possible to control the occurrence state of the resonance phenomenon in the yawing mode in the tracking servo control.

Therefore, the correction yoke members 31, 32, 3
By providing an adjusting mechanism for the mounting position of the focusing direction of 3, 34, it is possible to suppress the occurrence of yawing due to the variation of the center of gravity of the movable part when the objective lens driving mechanism is assembled.

6 and 7 show the correction yoke member 33,
34 shows an example of the position adjusting mechanism 34.

In the figure, a claw member 36 for pressing the upper end portions of the correction yoke members 33 and 34 is attached to the upper end portion of the outer yoke member 13 with a screw 37, and is provided on the lower side surface of the outer yoke member 13. A torsion coil spring 39 for biasing the correction yoke member 33 in the upward focusing direction is inserted in the pin 38. The correction yoke member 34 is provided on the opposite side surface of the outer yoke member 13.
Although a torsion coil spring for improperly focusing on the direction and a pin for supporting the torsion coil spring are provided, the illustration thereof is omitted.

Therefore, by adjusting the tightening amount of the screw 37, the position of the tip portion of the claw member 36 is determined, and the upper end portions of the correction yoke members 33 and 34 can be positioned by this, so that the focusing direction can be adjusted. It is possible to adjust the positions of the correction yoke members 33 and 34 with respect to.

By the way, in the above-mentioned embodiment, the correction yoke member is attached to the outer yoke member.
The correction yoke member may be integrally provided with the outer yoke member. FIG. 8 shows an outer yoke member according to another embodiment of the present invention.

In the figure, the outer yoke member 13 of the magnetic circuit member 16 is integrally provided with arm members 40 and 41 for pressing the permanent magnet 15 from both sides at the central portion in the focusing direction thereof.

Therefore, the arm members 40 and 41 have the same function as the correction yoke members 33 and 34 in the above-described embodiment, flatten the leakage magnetic field of the permanent magnet 15 as in the above-described embodiment, and Can be reduced.

Also, in this embodiment, the outer yoke member 13
In addition, arm members 40 and 41 for realizing the function of the correction yoke member
Since it is integrally provided, compared to the above-mentioned embodiment,
The number of parts can be reduced, and the work for assembling the objective lens drive mechanism can be reduced.

FIG. 9 shows a main part of a magnetic circuit member according to still another embodiment of the present invention. In the figure, the same parts as those in FIGS. 1A and 1B and the corresponding parts are designated by the same reference numerals.

In the figure, the outer yoke member 13, the inner yoke member 14, and the permanent magnet 15 of the magnetic circuit member 16 are shown.
On each side surface of each of the concave portions 13a, 13b, 1 at a position corresponding to the central portion of the permanent magnet 15 in the focusing direction.
4a, 14b, 15a, 15b (recesses 13b, 15b are not visible) are formed to communicate with each other.

As a result, in the magnetic circuit member 16, the leakage magnetic field of the permanent magnet 15 can be reduced, and the same effect as that of the above-described embodiment can be obtained.

By the way, in each of the above-described embodiments, the strength of the leakage magnetic field among the magnetic fields acted by the permanent magnets 11 and 15 of the magnetic circuit members 12 and 16 is made constant, and at the same time, the magnitude thereof is suppressed. In order to suppress or control the resonance (anti-resonance) phenomenon of the yawing mode in the tracking servo control, as shown in FIG.
It is not possible to suppress the increase of the magnetic field strength at the position corresponding to the central portion of 1,15.

In order to suppress the magnetic field strength at the positions corresponding to the central portions of the permanent magnets 11 and 15 to be small and to make the effective magnetic field strength distribution in the magnetic gaps of the magnetic circuit members 12 and 16 substantially flat, for example, As shown in FIG. 10A, a recess 15d is provided in the center of the surface 15c of the permanent magnet 15 that faces the magnetic gap, or
As shown in FIG. 3B, a through hole 15e is formed in the center of the permanent magnet 15.

As a result, the magnetic field strength at the central portion of the permanent magnet 15 can be made smaller than that at other portions, and as a result, the effective magnetic field strength distribution in the magnetic gap can be made flat.

As a result, the focus positioning characteristic by the focusing servo control becomes almost linear as shown in FIG. 11, and the characteristic of the focusing servo control is improved. Further, similarly, the characteristics of tracking servo control can be improved.

By the way, in the above-described embodiment, the concave portion 15c and the through hole 15d are provided in the central portion of the permanent magnet 15, but, for example, as shown in FIG. A step 14c is provided at a substantially central portion of the member 14 in the focusing direction, or FIG.
As shown in FIG.
Even when 4d is provided, the same effect as that of the above-described embodiment can be obtained.

Further, in this case, the degree of freedom in design is improved and the manufacturing is easy and the apparatus cost can be reduced as compared with the case where the shape of the permanent magnet 15 is adjusted.

Further, as shown in FIG. 13, even when the through hole 13c is provided in the central portion of the outer yoke member 13, the same effect as that of the above-described embodiment can be obtained.

In the present invention, as in the above-described embodiment, the lens holder holding the objective lens, the focusing drive coil for moving the objective lens in the focusing direction, and the objective lens for moving in the tracking direction are used. In addition to the tracking drive coil of, the objective lens drive mechanism provided with a magnetic circuit member that generates a magnetic field in which the drive current flowing through the focusing drive coil and the tracking drive coil intersects The same can be applied.

[0075]

As described above, according to the present invention,
By providing the correction yoke member, or by shaping the side surface of the permanent magnet, the inner yoke member, or the outer yoke member, the leakage magnetic field of the permanent magnet is reduced,
The magnetic field strength acting on the drive coil when the objective lens holder is moved in the focusing direction becomes substantially uniform, and the yawing phenomenon can be suppressed. In addition,
By shaping the central portion of the permanent magnet, the outer yoke member, or the inner yoke member, the magnetic field strength at that portion can be reduced, and the magnetic field strength in the magnetic gap can be made almost flat. Therefore, focusing servo control is possible. Further, the characteristics of tracking servo control can be further improved. Further, when the position adjusting means of the correction yoke member is provided,
Since the improvement state of the magnetic field strength distribution can be adjusted,
It is possible to cope with variations in device characteristics. Also,
Since the arm member provided on the outer yoke member can achieve the same effect as that of the correction yoke member, it is possible to reduce the number of parts and the assembly work.

[Brief description of drawings]

FIG. 1 is a schematic perspective view and a schematic plan view showing an objective lens driving mechanism according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a correction situation of a magnetic field strength distribution by a correction yoke member.

FIG. 3 is a graph showing characteristics when a correction yoke member is attached to a center position of a permanent magnet in a focus direction.

FIG. 4 is a graph showing a characteristic when a correction yoke member is attached to a position above a permanent magnet in a focus direction.

FIG. 5 is a graph showing characteristics when a correction yoke member is attached to a lower position of a permanent magnet in a focus direction.

FIG. 6 is a schematic partial perspective view showing an example of a position adjusting mechanism of a correction yoke member.

FIG. 7 is a schematic partial side view showing an example of a position adjusting mechanism of a correction yoke member.

FIG. 8 is a schematic partial perspective view showing an embodiment in which an arm member is provided on the outer yoke member.

FIG. 9 is a schematic partial perspective view showing a magnetic circuit member according to another embodiment of the present invention.

FIG. 10 is a perspective view showing a permanent magnet according to still another embodiment of the present invention.

11 is a graph showing an example of focusing servo control characteristics when the permanent magnet shown in FIG. 10 is used.

FIG. 12 is a schematic partial perspective view showing an inner yoke member according to still another embodiment of the present invention.

FIG. 13 is a schematic partial perspective view showing an outer yoke member according to another embodiment of the present invention.

14A and 14B are a schematic perspective view and a schematic plan view showing a conventional example of an objective lens driving mechanism.

FIG. 15 is a schematic diagram for explaining the movement principle of the focusing movement mechanism and the tracking movement mechanism.

16 is a schematic diagram for explaining a magnetic field strength distribution of a permanent magnet of the device of FIG.

FIG. 17 is a schematic diagram for explaining a resonance phenomenon in a yawing mode.

FIG. 18 is a schematic diagram for explaining an anti-resonance phenomenon in yawing mode.

FIG. 19 is a graph showing an example of tracking servo control characteristics of a conventional device.

FIG. 20 is a schematic diagram for explaining an anti-resonance phenomenon in a yawing mode based on a change in the position of the center of gravity of a movable portion.

FIG. 21 is a graph diagram for explaining inconvenience of focusing servo control.

[Explanation of symbols]

9,13 Outer yoke member 10,14 Inner yoke member 11,15 Permanent magnet 12,16 Magnetic circuit member 13a, 13b, 14a, 14b, 15a, 15b, 1
5d Recesses 13c, 15e, 14d Through hole 14c Steps 31, 32, 33, 34 Correction yoke member 36 Claw member 37 Screw 38 pin 39 Torsion coil spring 40, 41 Arm member

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuaki Koike 1-3-3 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Akihiko Kudo 1-3-6 Nakamagome, Ota-ku, Tokyo Stocks In Ricoh Company (72) Inventor Kiyoshi Amari 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh (72) Inventor Masaaki Nakatsugawa 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh

Claims (11)

[Claims] 1. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. An objective lens driving device provided with a magnetic circuit member for generating, an objective lens driving device comprising a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member. 2. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. In an objective lens driving device having a magnetic circuit member for generating, a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, and a through hole formed in a central portion of the permanent magnet are provided. An objective lens driving device characterized by being provided. 3. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. In an objective lens driving device having a magnetic circuit member for generating, a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, and a central portion of a surface facing the magnetic gap of the permanent magnet. An objective lens driving device comprising a formed recess. 4. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. In an objective lens driving device provided with a magnetic circuit member for generating, a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, and a permanent magnet opposed to the permanent magnet with a magnetic gap therebetween. An objective lens driving device comprising a through hole formed substantially in the center of an inner yoke member. 5. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. In an objective lens driving device provided with a magnetic circuit member for generating, a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, and a permanent magnet opposed to the permanent magnet with a magnetic gap therebetween. An objective lens driving device comprising a recessed portion provided substantially in the center of an inner yoke member. 6. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. In an objective lens driving device having a magnetic circuit member for generating, a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, and a substantially central portion of an outer yoke member attracted to the permanent magnet. An objective lens driving device comprising a through hole formed in the. 7. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. In an objective lens driving device having a magnetic circuit member for generating, a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, and a substantially central portion of an outer yoke member attracted to the permanent magnet. An objective lens driving device, comprising: a concave portion provided in the. 8. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. The objective lens driving device including the magnetic circuit member for generating includes an arm member that is provided substantially at the center of the outer yoke member attracted to the permanent magnet of the magnetic circuit member and presses the side surface of the permanent magnet. Characteristic objective lens driving device. 9. A lens holder for holding an objective lens,
A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached, and a magnetic field in which the driving current flowing through the focusing drive coil and the tracking drive coil is interlinked. In an objective lens driving device including a magnetic circuit member for generating, a permanent magnet of the magnetic circuit member, an outer yoke member attracted to the permanent magnet, and an inner yoke provided with a magnetic gap from the permanent magnet. An objective lens driving device, wherein at least one side surface of the yoke member is formed in a concave shape. 10. A focusing drive coil for moving the objective lens in the focusing direction and a tracking drive coil for moving the objective lens in the tracking direction are attached to a lens holder for holding the objective lens, and the focusing drive coil is also provided. And an objective lens driving device including a magnetic circuit member that generates a magnetic field in which a driving current flowing in a tracking driving coil is interlocked, and a correction yoke member made of a magnetic material and attached to a side surface of a permanent magnet of the magnetic circuit member, An objective lens drive device comprising position adjusting means for adjusting the position of the correction yoke member in the focusing direction. 11. The position adjusting means is made of a non-magnetic material and an urging member fixed to an outer yoke member attracted to the permanent magnet and urging the correction yoke member in an upward focusing direction. 11. The objective lens driving device according to claim 10, comprising a holding member which is screwed to the upper end of the yoke member and holds the position of the upper end of the correction yoke member.