JP3110854B2 - Optical system drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system driving apparatus used for an optical information recording / reproducing apparatus for recording and / or reproducing information by using a laser beam or the like.

[0002]

2. Description of the Related Art In an optical information recording / reproducing apparatus, a laser beam for recording or reproduction is projected on a recording medium in an in-focus state via an optical system such as an objective lens in order to record and reproduce accurate information. It is necessary that the spot of the laser beam on the recording medium accurately follow a desired track.

[0003] For this reason, for example, Japanese Unexamined Patent Publication No.
-261827, JP-A-62-161322, JP-A-63-181129 and JP-A-3-181129.
Japanese Patent Application Publication No. 52822 proposes an optical system driving device in which a holder for holding an objective lens is driven in an optical axis direction (focus direction) of the objective lens and in a direction (tracking direction) crossing a track of a recording medium. I have.

[0004]

The above-mentioned JP-A-61-2
In the optical system driving device described in Japanese Patent No. 61827, a holder for holding an objective lens is supported on a base made of a magnetic material so as to be displaceable in a focus direction and a tracking direction via wires. In addition, the holder
As shown in FIG. 11, the focus coil 1 is wound, and two tracking coils 2a and 2b are mounted on one side of the focus coil 1, and a part of one side of the focus coil 1 and the tracking coils 2a and 2b.
Yoke 4 provided integrally with the base on each side 3a, 3b of
The magnetic field is applied by one magnetic circuit having the magnets 5a and 4b and the magnet 5 bonded and fixed to one yoke 4b.

In the optical system driving device shown in FIG.
During the movement in the focus direction (Z direction), the hatched portion 7 of the focus coil 1 located in the magnetic gap 6 between the yoke 4a and the magnet 5 receives a driving force. It is a driving point for focus movement. When moving in the tracking direction (X direction), the tracking coil 2 located in the magnetic gap 6 is moved.
Since each side 3a, 3b in the Z direction of a, 2b receives a driving force, the driving point of each coil 2a, 2b is the center 9a, 9b of the cross section of the side 3a, 3b, and the center 10 of these driving points 9a, 9b. Are the driving points of the tracking movement as a whole.
Therefore, the drive point 8 of the focus movement and the drive point 10 of the tracking movement are displaced in the Y direction (track direction) orthogonal to the X and Z directions.

Here, the center of gravity of the entire movable section including the objective lens and the holder and the driving point 8 of the focus movement are Y.
If the directions do not match, a force is generated to rotate the movable portion around the X-axis during the focus driving, so that the movable portion is displaceably supported by the base 12 via the wire 11 as shown in FIG. Pitching resonance that rotates around the X axis occurs in the movable portion 13. If the center of gravity of the movable part 13 does not coincide with the driving point 10 of the tracking movement in the Y direction, the movable part
As shown in FIG.
As shown in (1), yawing resonance that rotates around the Z axis occurs in the movable portion 13.

However, in the optical system driving device shown in FIG. 11, since the driving point 8 for the focus movement and the driving point 10 for the tracking movement do not coincide in the Y direction, the above two undesired two points. Resonance cannot be prevented at the same time. Since the center of rotation of these resonances is near the center of gravity of the movable section 13, the influence can be reduced by positioning the objective lens near the center of gravity of the movable section 13. Y away from the center of gravity of the movable part 13
Since it is arranged at the end in the direction, it is greatly affected by resonance. Therefore, as shown in FIG. 14A and the Bode diagram showing the tracking characteristics in FIG. 14A and FIG. 14B, resonance appears in a high frequency region in both the focus and the tracking. In the configuration shown in FIG. 11, one of these resonances can be eliminated, but not both, as described above.

On the other hand, Japanese Utility Model Laid-Open No. 62-161322
In the optical system driving device disclosed in Japanese Patent Application Laid-Open Publication No. H10-264, since the focus coil or the tracking coil is provided so that one coil sandwiches the other coil, the driving points of the focus and tracking movements in the Y direction must match. become. Therefore, if these drive points are located near the center of gravity of the movable portion in the Y direction, it is possible to prevent pitching and yawing resonance from occurring at the same time. However, in this conventional example, one coil is sandwiched between the other coils, so that the number of coils required for the other coil is twice as large as the number of ordinary coils, which results in a problem that the assembly is complicated and expensive. There is.

Further, in the optical system driving device disclosed in Japanese Patent Application Laid-Open No. 63-181129, a coil side located outside a magnetic gap of a tracking coil is provided with a magnetic circuit so as not to be involved in the tracking drive. Positioned away from magnets. For this reason, considering only the coil sides involved in the tracking drive,
As in the optical system driving device described in Japanese Patent Application Laid-Open No. 1-261827, there is a problem that resonance occurs in focus and tracking.

Further, in the optical system driving device disclosed in Japanese Utility Model Laid-Open No. 3-52822, the magnetic circuit and the coil are arranged symmetrically with respect to the X axis. As in the optical system driving device disclosed in the publication, the driving points of the focus and tracking movement can be matched. Therefore,
If these drive points are located near the center of gravity of the movable part in the Y direction, it is possible to similarly prevent the occurrence of pitching and yawing resonance at the same time. However, in this conventional example, since the magnetic circuit and the coil are arranged symmetrically with respect to the X axis, there is a problem that the configuration is complicated and large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides an optical system driving device which is excellent in characteristics without resonance, and which is appropriately configured so as to be small and inexpensive. With the goal.

[0012]

In order to achieve the above object, according to a first aspect of the present invention, there is provided a movable member for holding an optical element, a movable member having a focus direction substantially perpendicular to a recording medium surface, and a movable member for holding the optical member. Support means for supporting the movable body so as to be displaceable in a tracking direction intersecting a track; a focus coil and a tracking coil provided on the movable body for driving the movable body in the focus direction and the tracking direction, respectively; An optical system driving apparatus comprising: a magnet that applies a magnetic flux to a tracking coil; and a magnetic circuit having a yoke, wherein a portion of the focus coil crossing the magnetic circuit is formed non-parallel to the tracking direction, and the tracking is performed. Attach the coil to the non-parallel part of the focus coil Te, to match the driving point and the drive point of the tracking movement of the focus movement.

Further, in the second invention, a movable body for holding the optical element, and a support for supporting the movable body so as to be displaceable in a focus direction substantially perpendicular to a recording medium surface and a tracking direction intersecting a track of the recording medium. Means, a focus coil and a tracking coil provided on the movable body for driving the movable body in the focus direction and the tracking direction, respectively, and one magnet having a magnet and a yoke for applying a magnetic flux to the focus coil and the tracking coil. In an optical system driving device including a magnetic circuit, the tracking coil is arranged so that driving forces in the same direction in the tracking direction are generated on opposite coil sides, and a driving point at which the resultant force acts is focused. Match the drive point of the movement.

[0014]

1 to 3 show a first embodiment of the present invention. FIG. 1 is a perspective view, FIG. 2 is an exploded perspective view, and FIG. 3 is a sectional view of a main part. In FIGS. 1 and 2, an opening 21a through which a light beam passes is formed in a base 21 made of a magnetic material, and yokes 22 and 23 are separated on one side in the Y direction with the opening 21a interposed therebetween. And a rising portion 24 is integrally provided on the other side. A magnet 25 is adhered to the yoke 23 on a surface facing the yoke 22, and the yoke 22, the base 21, the yoke 23, and the magnet 25 make the magnet 25 and the yoke 22
To form one magnetic circuit having a magnetic gap 26 therebetween.

A wire receiver 27 is fixed to the rising portion 24 by bonding or the like, and a substrate 28 is fixed to the wire receiver 27. One ends of four wires 29a to 29d extending in the Y direction are soldered to the substrate 28, and the other ends of these wires 29a to 29d are connected to wire bonding portions 31a to 31d (31b in FIG. (Not shown), and the leading ends of the substrates 32 adhered to the holder 30.
a, 32b. The wires 29a to 29
Rubbers 33a to 33d are fixed to one end of d, and these rubbers 33a to 33d are fixed to the wire receiver 27.

An objective lens 34 is fixed to the holder 30 at one end in the Y direction so as to face the opening 21a of the base 21. At the other end, the yokes 22, 23 and the magnet 25 are fixed.
Is formed to form an opening 30a. The focus coil 35 is adhered to the opening 30a through the magnetic gap 26 on the inner surface thereof. The focus coil 35 has a shape in which a portion crossing the magnetic gap 26 has a "-" shape.
A tracking coil 36a, 36b is mounted on each side of the "U" shape so that one of the coil sides in the Z direction is located in the magnetic gap 26. The center of gravity of the movable portion including the holder 30 and the components mounted on the holder 30 is located in the magnetic gap 26 where the above-mentioned "<"-shaped portion of the focus coil 35 is located in the Y direction.

Hereinafter, the operation of this embodiment will be described. In the above configuration, the holder 30 includes the four wires 29a to 29a.
Since it is supported by the base 21 via 9d, it can be moved in the X direction (tracking direction) and the Z direction (focus direction) with respect to the base 21. Therefore, the objective lens 34 held by the holder 30 is also focused and moved. It can move in the tracking direction. A laser beam from an optical unit (not shown) is applied to a recording medium (not shown) through an opening 21a of the base 21 and an objective lens 34,
The reflected light again enters the optical assembly through the objective lens 34 and the opening 21a, and a focus error signal, a tracking error signal, and a recording signal are detected based on the reflected light.

When a focus error signal is detected and a corresponding current is passed through the substrate 28, predetermined two wires (for example, wires 29a and 29b) and the substrate 32a to the focus coil 35, the current and the magnetic gap The holder 30 is driven in the focus direction by the electromagnetic action with the magnetic field at 26. When a tracking error signal is detected and a current corresponding thereto is passed through the substrate 28, the other two wires 29c and 29d, and the substrate 32b to the tracking coils 36a and 36b, the current and the magnetic field in the magnetic gap 26 are reduced. The holder 30 is driven in the tracking direction by the electromagnetic action of. In this way, the focus control and tracking control of the objective lens 34 held by the holder 30 are performed.

Here, the driving points of the focus and tracking movements will be described with reference to FIG. First, with respect to the focus movement, on one side in the X direction bounded by a center line 37 parallel to the Y direction, the focus coil 35 mainly receives a driving force at a hatched portion 38 a located in the magnetic gap 26. The center is the driving point 39a,
The part where the focus coil 35 mainly receives the driving force on the other side in the X direction is the portion 38b, and the center is the driving point 39b. Therefore, the drive point of the entire focus coil 35 is the midpoint 40 between the drive points 39a and 39b.

In the tracking movement, the tracking coils 36a and 36b receive the driving force in the tracking direction at the coil sides 41a and 41b in the Z direction located in the magnetic gap 26, and the center of each of them is the driving point 42a. , 42b. Therefore, the driving point of the tracking movement in the entire tracking coils 36a and 36b is the midpoint 40 between the driving points 42a and 42b, and coincides with the driving point of the focus movement. In addition, since the center of gravity of the entire movable part is located in the magnetic gap 26,
The position of the center of gravity can be easily matched with the drive point of the focus and tracking movement. If a slight shift occurs in the focus and tracking driving points due to the influence of the leakage magnetic flux, the tracking coil 3
It can be adjusted by shifting 6a, 36b at the "-"-shaped portion of the focus coil 35. Therefore, according to this embodiment, as shown in FIG. 4A, a Bode diagram showing the focus characteristic, and FIG. 4B shows a Bode diagram showing the tracking characteristic, respectively, the undesired high frequency band in both focus and tracking. Resonance can be effectively prevented.

5 to 7 show an optical system driving device developed prior to the present invention. FIG. 5 is a perspective view, FIG. 6 is an exploded perspective view, and FIG. 7 is a sectional view of a main part. In this optical system driving device, the focus coil 35 is formed in a rectangular shape, and the tracking coils 36a,
6b, the magnet 25 is adhered to the yoke 22 so as to be positioned outside the focus coil 35, and the other configuration is the same as that of the first embodiment.

Hereinafter, the operation of the optical system driving device will be described with reference to FIG. In this optical system driving device, the coil coil 35a between the magnet 25 and the yoke 23 mainly receives the driving force in the Z direction (focus direction) by the focus coil 35, and the center point is the driving point 45. It is the coil sides 46a to 46d in the Z direction that receive the driving force in the X direction (tracking direction) by the tracking coils 36a and 36b.
6a, Y component of the magnetic flux received by the 46c is _{B 1,} whereby the force _{f 1} is exerted in the X direction. On the other hand, the coil side 46
b, in the Y component of the magnetic flux _{B 2} received by the 46d, but whereby the force _{f 2} acts in the X-direction, the coil side 46b, the direction of the current flowing through the 46d, the coil sides 46a, the direction of the current flowing through the 46c is The direction of the force f ₂ is opposite to the direction of the force f ₁
The direction is reversed. Further, the magnetic flux received by the coil sides 46b and 46d is small due to the magnetic flux flowing around, so that f ₁
> The _{f 2.}

Here, the resultant force f _T of f ₁ and f ₂ has a magnitude of

## EQU1 ## When f _T = 2 (f ₁ −f ₂ ), the position of the point of action 47 is the point of action 4 in the Y direction.
When the distance from 7 to the action point of f ₁ is l ₁ , and the distance from the action point 47 to the action point of f ₂ is l ₂ ,

## EQU2 ## l ₁ : l ₂ = f ₂ : f ₁ Therefore, by arranging the coil sides 46a to 46d of the tracking coils 36a and 36b at appropriate positions in accordance with the strength of the magnetic flux, the drive points 45 and 47 for the focus and tracking movement can be matched. Also, in this case, the center of gravity of the entire movable portion is located in the magnetic gap 26 between the magnet 25 and the yoke 23, so that the position of the center of gravity can be easily matched with the drive point of the focus and tracking movement. ,
As in the first embodiment, it is possible to effectively prevent undesired resonance in high frequencies in both focus and tracking.

FIGS. 8 and 9 show an optical system driving device developed prior to the present invention. FIG. 8 is an exploded perspective view and FIG. 9 is a sectional view of a main part. In this optical system driving apparatus, in the first embodiment, the focus coil 35 is formed in a rectangular shape, the tracking coils 36a and 36b are formed in an L shape, and the portion bent into the L shape is positioned away from the focus coil 35. The other configuration is the same as that of the first embodiment.

In this optical system driving device, the driving point 45 for the focus movement and the driving point 47 for the tracking movement
Is determined in the same manner as in the second embodiment. Here, the coil sides 46b, 46 of the tracking coils 36a, 36b
The force f ₂ acting in the opposite direction acting on d
The dimension is made smaller than the magnet 25, these coil side 46b, can manner well adjusted by reducing the Y component B ₂ of the magnetic flux acting on the 46d, thereby making it possible to match the driving point of the focus and tracking At the same time, it is possible to easily match these driving points with the center of gravity of the entire movable part. Therefore, also in this optical system driving device, undesired resonance in a high frequency band can be effectively prevented in both focusing and tracking, as in the above-described embodiment. Further, in this optical system driving device, since the tracking coils 36a and 36b are mounted outside the focus coil 35, as in the first embodiment, compared with the case where the tracking coils 36a and 36b are mounted inside shown in FIGS. And assembly becomes easy.

FIG. 10 is a sectional view of a main part of a second embodiment of the present invention. This embodiment is different from the optical system driving device shown in FIGS.
6a and 36b are adhered so that their bent portions are aligned with the outer corners of the focus coil 35, and among the coil sides 46a to 46d parallel to the Z direction, the coil sides 46a and 46c are placed in the magnetic gap 26, and the coil sides 46 b and 46 d are located on the side of the focus coil 35 in the Y direction, facing the magnet 25.

In this configuration, the magnetic flux B ₁ is applied to the coil sides 46a and 46c of the tracking coils 36a and 36b.
There acts, coil side 46b, the 46d, in the magnetic flux _{B 1} and opposite, and the magnetic flux _{B 2} acts weaker than the magnetic flux _{B 1.} Here, the current flowing through the coil sides 46a and 46c is:
Coil side 46b, since the direction is opposite to the current flowing through the 46d, the force _{f 1} acting coil side 46a, to 46c,
Coil side 46b, and the force _{f 2} that acts on the 46d, the direction is the same, different sizes _(f 1> _{f 2)} as the result, the force _{f T} is the size,

## EQU3 ## When f _T = 2 (f ₁ + f ₂ ), the position of the action point 47 is the action point 4 in the Y direction.
When the distance from 7 to the action point of f ₁ is l ₁ , and the distance from the action point 47 to the action point of f ₂ is l ₂ ,

## EQU4 ## l ₁ : l ₂ = f ₂ : f ₁

Therefore, also in this embodiment, the positions of the coil sides 46a, 46c in the X direction and the coil sides 4a, 46b of the tracking coils 36a, 36b are changed according to the strength of the magnetic flux.
By appropriately adjusting the Y-direction positions of 6b and 46d, the drive points 45 and 47 for the focus and tracking movement can be matched, and the center of gravity of the entire movable part and the drive point for the focus and tracking movement can be easily adjusted. And the same effects as those of the above-described embodiment and development example can be obtained.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications or changes are possible. For example, the arrangement of the focus coil, tracking coil, magnet, and the like are not limited to the above-described embodiment, and can be changed as appropriate. For example,
In the first embodiment, a magnet may be provided in the yoke 22 so that the focus and tracking coils are sandwiched between the two magnets. When the driving point of the focus movement is deviated from the center of the focus coil in the magnetic gap due to, for example, leakage magnetic flux on the side of the magnet other than the magnetic gap, the driving point of the deviated focus movement is shifted to the driving point of the deviated focus movement. The driving points can also be matched.

[0030]

As described above, according to the present invention, the driving point for the focus movement and the driving point for the tracking movement can be matched with a small and inexpensive configuration using one magnetic circuit. The position of the center of gravity of the movable portion can be easily matched with the point, thereby realizing an optical system driving device having excellent characteristics in which the occurrence of pitching resonance and yawing resonance is effectively prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the same.

FIG. 3 is a sectional view of a main part of the same.

FIG. 4 is a Bode diagram showing a focus characteristic and a tracking characteristic in the first embodiment.

FIG. 5 is a perspective view showing an example of an optical system driving device developed prior to the present invention.

FIG. 6 is an exploded perspective view of the same.

FIG. 7 is a sectional view of an essential part of the same.

FIG. 8 is an exploded perspective view showing another example of the optical system driving device developed prior to the present invention.

FIG. 9 is a sectional view of an essential part of the same.

FIG. 10 is a sectional view of a main part of a second embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a main part of a conventional optical system driving device.

12 is a diagram showing pitching resonance generated in the optical system driving device shown in FIG.

13 is a diagram showing yawing resonance that occurs in the optical system driving device also shown in FIG. 11;

FIG. 14 is a Bode diagram showing focus characteristics and tracking characteristics in the optical system driving device shown in FIG.

[Explanation of symbols]

 Reference Signs List 21 base 22, 23 yoke 24 rising portion 25 magnet 26 magnetic gap 27 wire receiver 28 substrate 29a to 29d wire 30 holder 32a, 32b substrate 33a to 33d rubber 34 objective lens 35 focus coil 36a, 36b tracking coil

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-181129 (JP, A) JP-A-2-56736 (JP, A) Fully open 1987-161322 (JP, U) Really open 1987 158630 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/09 G11B 7/095

Claims (2)

(57) [Claims] 1. A movable body for holding an optical element, supporting means for displaceably supporting the movable body in a focus direction substantially perpendicular to a recording medium surface and a tracking direction intersecting a track of the recording medium, and the movable body. A focus coil and a tracking coil for driving the movable body in the focus direction and the tracking direction, respectively, and one magnetic circuit having a magnet and a yoke that applies a magnetic flux to the focus coil and the tracking coil. In the optical system driving device,
A portion of the focus coil crossing the magnetic circuit is formed non-parallel to the tracking direction, and the tracking coil is mounted on a non-parallel portion of the focus coil, and a driving point for the focus movement and a driving point for the tracking movement And an optical system driving device. 2. A movable body for holding an optical element, supporting means for displaceably supporting the movable body in a focus direction substantially perpendicular to a recording medium surface and a tracking direction intersecting a track of the recording medium, and the movable body. A focus coil and a tracking coil for driving the movable body in the focus direction and the tracking direction, respectively, and one magnetic circuit having a magnet and a yoke for applying a magnetic flux to the focus coil and the tracking coil. In the optical system driving device,
The tracking coil is arranged so that a driving force in the same direction in the tracking direction is generated on the opposite coil side, and a driving point at which the resultant force acts is made to coincide with a driving point of a focus movement. Characteristic optical system driving device.