JP3821998B2 - Objective lens driving device, optical pickup and optical disk drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an objective lens driving device including a driving motor for moving an objective lens in an optical pickup in a focusing direction and a tracking direction., Optical pickup, and optical disk driveAbout.
[0002]
[Prior art]
A conventional example of an objective lens driving device of this type of optical disk drive, that is, an actuator will be described with reference to FIG. This example is a conventional example including a driving motor using one cylindrical coil as a focus driving coil and two flat coils as track driving coils. First, the objective lens holding member 2 that holds the objective lens 1 is elastically supported by the four wire springs 4 drawn from the fixing member 3. A cylindrical focus driving coil 5 and two flat track driving coils 6 are wound around the objective lens holding member 2 in directions orthogonal to each other. The wire spring 4 is pulled out from the substrate 7 and is electrically connected to the focus driving coil 5 and the track driving coil 6 by the soldering portions 8 at the distal end and the proximal end, respectively, and has a function as a conducting wire. . A magnet 10 supported by the yoke 9 with the objective lens holding member 2 interposed therebetween is disposed with the magnetic poles facing each other. The magnet 10 is fixed to the yoke 9 through a gap so that the magnetic flux passes through the drive portions of the focus driving coil 5 and the track driving coil 6.
[0003]
In such a configuration, by supplying a control current to the focus driving coil 5 and the track driving coil 6, the objective lens holding member 2 moves to move the objective lens 1 in the focusing direction (Z direction) and the tracking direction (Y Direction).
[0004]
[Problems to be solved by the invention]
In the case of an objective lens driving device having a driving motor having the configuration shown in FIG. 12, in principle, a large moment is generated in the focus driving coil 5 during focusing and tracking movement, so that the objective lens 1 tilts greatly. End up.
[0005]
The principle of the tilt generation will be described with reference to FIGS. FIG. 13 is a schematic plan view showing an extracted drive motor portion, and FIG. 13 is a schematic front view thereof. In the case of performing the focusing operation without performing the tracking operation, the center of the focus driving force generation portion coincides with the center of the four wire springs 4 (support center), and no moment is generated (FIG. 13A Neutral position shown in)). However, when the focusing operation is performed while the tracking operation is being performed, the center of the focus driving force generation portion and the center of the four wire springs 4 (support center) as shown in FIGS. Deviation occurs. That is, the center of the driving force generation portion does not move while substantially coincident with the center of the magnet 10, whereas the support center moves together with the movable portion, so that a deviation corresponding to the tracking operation occurs. A large tilt occurs due to the moment caused by this deviation.
[0006]
The relationship between the deviation amount and the tilt amount is as shown in FIG. 15, for example. In the illustrated example, the tracking movement amount is set to 0.3 mm. Since the conventional objective lens driving device as shown in FIG. 11 generates such a large tilt in principle, it is suitable for an objective lens driving device equipped with a high NA objective lens such as a DVD (Digital Versatile or Video Disk). Absent. In recent years, due to the necessity of high-density recording in optical disks, the demand for tilt has become stricter as the NA of the objective lens increases in order to reduce the spot, and the conventional drive motor as shown in FIG. In the objective lens driving device having the configuration, the tilt when the objective lens is focused and tracked is a big problem.
[0007]
That is, with respect to a conventional optical disk such as a CD, the laser wavelength used in the optical pickup is around 780 nm, the track pitch is about 1.6 μm, and the recording density on the optical disk is relatively low. A product with a tolerance level of the optical tilt of the pickup, especially the objective lens, and if the accuracy of each part is kept within the processing accuracy, the tilt of the optical pickup is not a problem as a total accuracy after assembly. It becomes. However, in recent years, high-density optical discs such as DVDs with increased recording density are in practical use, and the laser wavelength used in the optical pickup has become a short wavelength of 650 nm in response to the higher density. The pitch is also narrowed to about 0.74 μm, and strict standard conditions are required. Corresponding to this, severe conditions are imposed such that the tilt of the optical pickup, particularly the objective lens, must be suppressed to about half that of the conventional CD.
[0008]
  Therefore, the present invention provides an objective lens driving device capable of significantly suppressing tilts associated with focusing and tracking operations to the extent that standard conditions imposed on, for example, DVDs can be satisfied., Optical pickup, and optical disk driveThe purpose is to provide.
[0009]
  Further, the present invention provides an objective lens driving device capable of performing stable focusing and tracking operations by reducing a driving force change during focusing and tracking movement, that is, a gain change., Optical pickup, and optical disk driveThe purpose is to provide.
[0010]
[Means for Solving the Problems]
  According to the first aspect of the present invention, the surface is divided into four regions in a cross shape, and is perpendicular to the surface including the focusing direction and the tracking direction, and is magnetized in a direction opposite to the adjacent region to have a predetermined thickness. A driving magnet fixed to a yoke having a magnetic field, and two magnets positioned on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction. A focus driving coil, and two track driving coils provided on both sides of the magnetization boundary line in the tracking direction near the surface of the driving magnet and straddling the magnetization boundary line in the focusing direction, respectively , A driving motor is provided on one or both sides of the objective lens, and the center in the tracking direction of each of the two focus driving coils is divided into four parts of the driving magnet. Located outside the geometric center position of the tracking direction of each areaAnd coincide with the peak of the magnetic flux density distributionIt is characterized by.
[0013]
Accordingly, by arranging the center of the tracking direction of each of the two focus driving coils outside the geometric center position in the tracking direction of each of the four divided areas of the driving magnet, the magnetic field in the tracking direction is arranged. The center of the distribution is matched, the driving force fluctuations of the two focus driving coils during tracking operation are equal, the absolute value of the moment generated around the axis in the jitter direction can be reduced, and during tracking operation The fluctuation of the focus driving force can be reduced.
[0016]
  According to the second aspect of the present invention, the surface is divided into four regions in a cross shape, and is perpendicular to the surface including the focusing direction and the tracking direction, and is magnetized in a direction opposite to the adjacent region to have a predetermined thickness. A driving magnet fixed to a yoke having a magnetic field, and two magnets positioned on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction. A focus driving coil, and two track driving coils provided on both sides of the magnetization boundary line in the tracking direction near the surface of the driving magnet and straddling the magnetization boundary line in the focusing direction, respectively The driving motor is formed on one or both sides of the objective lens, and the center of each of the two track driving coils in the focusing direction is divided into four parts of the driving magnet. Located outside the geometric center position of the focusing direction of each areaAnd coincide with the peak of the magnetic flux density distributionIt is characterized by.
[0017]
Therefore, the magnetic field in the focusing direction can be obtained by disposing the center in the focusing direction of each of the two track driving coils outside the geometric center position in the focusing direction of each of the four divided areas of the driving magnet. The center of distribution is matched, the driving force fluctuations of the two focus drive coils during focusing operation are equalized, the absolute value of the moment generated around the axis in the jitter direction can be reduced, and during focusing operation The fluctuation of the track driving force can be reduced.
[0032]
  According to a third aspect of the present invention, the surface is divided into four regions in a cross shape, and is perpendicular to the plane including the focusing direction and the tracking direction, and is magnetized in a direction opposite to the adjacent region to have a predetermined thickness. A driving magnet fixed to a yoke having a magnetic field, and two magnets positioned on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction. A focus driving coil, and two track driving coils provided on both sides of the magnetization boundary line in the tracking direction near the surface of the driving magnet and straddling the magnetization boundary line in the focusing direction, respectively , A driving motor comprising one or both sides of the objective lens,
  The center of the focus driving force generating portion having two each of the two focus driving coils is positioned outside the geometric center position in the focusing direction of each of the four divided areas of the driving magnet.And coincide with the peak of the magnetic flux density distributionIt is characterized by.
[0033]
Therefore, the center of the focus driving force generating portion having two of each of the two focus driving coils is arranged outside the geometric center position in the focusing direction of each of the four divided areas of the driving magnet. Thus, by making the centers of the magnetic field distributions in the focusing direction coincide with each other, fluctuations in the focus driving force during the focusing operation can be reduced, and the focusing operation can be performed stably.
[0036]
  According to a fourth aspect of the present invention, the surface is divided into four regions in a cross shape and is magnetized in a direction perpendicular to the adjacent region and perpendicular to the surface including the focusing direction and the tracking direction, and has a predetermined thickness. A driving magnet fixed to a yoke having a magnetic field, and two magnets positioned on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction. A focus driving coil, and two track driving coils provided on both sides of the magnetization boundary line in the tracking direction near the surface of the driving magnet and straddling the magnetization boundary line in the focusing direction, respectively , A driving motor comprising one or both sides of the objective lens,
  The center of the track driving force generating portion having two of each of the two track driving coils is located outside the geometric center position in the tracking direction of each of the four divided areas of the driving magnet.And coincide with the peak of the magnetic flux density distributionIt is characterized by.
[0037]
  Accordingly, the center of the track driving force generating portion having two of each of the two track driving coils is arranged outside the geometric center position in the tracking direction of each of the four divided areas of the driving magnet. Thus, by matching the centers of the magnetic field distributions in the tracking direction, fluctuations in the track driving force during the tracking operation can be reduced and the tracking operation can be performed stably.
An optical pickup according to a fifth aspect of the invention includes the objective lens driving device according to any one of the first to fourth aspects.
An optical disk drive according to a sixth aspect of the invention has the optical pickup according to the fifth aspect.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS.
[0039]
The present embodiment is based on a proposed example of an objective lens driving device according to Japanese Patent Application No. 10-24387 that can suppress the occurrence of tilt for the purpose of improving the conventional example as shown in FIG. Prior to the description of the present embodiment, the configuration of this proposed example and the problems to be improved will be described with reference to FIGS. 16A is a plan view seen from the Y direction showing the focusing direction, FIG. 16B is a longitudinal side view seen from the Z direction showing the tracking direction, and FIG. 17 is an exploded perspective view of the drive motor portion. 18 (a) to (c) are a front view, a plan view, and a side view of the drive motor portion.
[0040]
First, the objective lens holding member 12 that holds the objective lens 11 is elastically supported by the four wire springs 14 drawn from the stem 13. The distal end portion of the objective lens holding member 12 is in an open state, and the objective lens 11 is fixed to the open portion. A single drive coil assembly 15 is laminated and fixed on the objective lens holding member 12 so as to be positioned on one side of the objective lens 11. Further, the rising prism 17 is provided on a plate material integral with the stem 13 so that the optical axis 16 to the objective lens 11 is directly given from the tip side through the rising prism 17.
[0041]
Next, two sets of yokes 18 and 19 are arranged so as to face each of the drive coil assemblies 15 with an appropriate gap therebetween in the axial direction of the wire spring 14 of the objective lens holding member 12 so as to sandwich the drive coil assembly 15. The driving magnets 20 and 21 are provided on a plate material integral with the stem 13. These drive magnets 20 and 21 have a square shape, and are magnetized by being divided into four at the boundary of the cross-shaped magnetization boundary lines a and b, as shown in FIG. In addition, it is magnetized in a direction perpendicular to a plane including the focusing direction and the tracking direction and opposite to the adjacent region. The drive coil assembly 15 described above is constituted by a combination of two focus drive coils 22 and track drive coils 23 each. The focus driving coil 22 is formed of a planar coil, and is provided on both sides of the magnetization boundary line a in the focusing direction of the drive magnets 20 and 21, and the magnetization boundary line b in the tracking direction is set on each side. The objective lens holding member 12 is mounted across the bridge. On the other hand, the track driving coil 23 is formed of a planar coil, and is provided on both sides of the magnetization boundary line b in the tracking direction of the drive magnets 20 and 21, each of which is a magnetization boundary line in the focusing direction. The objective lens holding member 12 is mounted across a. At this time, the drive magnets 20 and 21 are arranged so that the magnetization directions of the portions facing each other with the focus drive coil 22 and the track drive coil 23 in between coincide with each other. In this way, one drive motor 24 is constituted by the focus drive coil 22, the track drive coil 23, and the drive magnets 20, 21. Reference numeral 25 denotes a medium (optical disk).
[0042]
In such a configuration, when the focus driving coil 22 or the track driving coil 23 is energized, a driving force is generated between the driving magnets 20 and 21, and the objective lens holding member 12 is moved. 11 is moved in the focusing direction or the tracking direction. In addition, the objective lens 11 is tilted with respect to the disk recording surface of the medium 25 by supplying power independently to the two focus driving coils 22, and the tilting amount of the light spot with respect to the disk recording surface is adjusted. You can also. In addition, the objective lens 11 is tilted with respect to the disk recording surface of the medium 25 by independently supplying power to the two track driving coils 23, and the tilting amount of the light spot with respect to the disk recording surface is adjusted. You can also. Further, in the example shown in FIG. 16, the objective lens 11 is provided with only one driving motor 24 on one side, so that it is possible to cope with high acceleration by reducing the weight.
[0043]
In the objective lens driving device according to the proposed example of Japanese Patent Application No. 10-24387, the deviation between the center of the focus driving force and the support center of the four wire springs 14 during tracking movement is as much as in the conventional example shown in FIG. Since it is not large, it is possible to reduce the occurrence of tilt. This is because, as can be seen from the size relationship shown in FIG. 18 and the like, the driving magnets 18 and 19 are larger than the thrust generating portions of the coils 22 and 23, and therefore the center of the focus driving force is the movable part during tracking movement. Since it moves almost together with (focus drive coil 22), the positional relationship with the support center of the four wire springs 14 that also move together with the movable part can be maintained. Generation can be reduced.
[0044]
However, even with the objective lens driving apparatus according to the proposed example of Japanese Patent Application No. 10-24387, the tilt still occurs. FIG. 19 is a graph showing the amount of tilt generated due to the focusing movement when the tracking movement amount is 0.3 mm, 0 mm, and −0.3 mm in the example proposed in Japanese Patent Application No. 10-24387. The factors that cause this tilt are as follows.
[0045]
a. Due to the tracking movement, the magnitudes of the driving forces of the two focus driving coils 22 that are paired differ, so that a moment is generated and tilted. Similarly, due to the focusing movement, the magnitude of the driving force of the two paired track driving coils 23 is different, so that a moment is generated and tilted.
[0046]
b. Magnetic field distribution exists due to the magnetic circuit of the yokes 18 and 19 and the drive magnets 20 and 21, but the center of the focus drive force moves completely together with the center of the movable part (focus drive coil 22) during tracking movement. Does not generate a moment and tilts. Similarly, since the center of the track driving force does not move completely together with the center of the movable portion (track driving coil 23) during the focusing movement, a moment is generated and tilted.
[0047]
Next, the present embodiment based on the example proposed in Japanese Patent Application No. 10-24387 will be described. The same parts as those shown in FIGS. 16 to 18 are denoted by the same reference numerals, and description thereof will be omitted (the same applies to the following embodiments). 1A is a plan view seen from the Y direction showing the focusing direction, FIG. 1B is a longitudinal side view seen from the Z direction showing the tracking direction, and FIG. 2 is an explanatory view of the drive motor configuration. (A) is a horizontal sectional view of the coil viewed from the focusing direction, (b) is a characteristic diagram showing the magnetic field distribution in the tracking direction, (c) is a front view showing the positional relationship between the coil and the driving magnet, (d). Is a characteristic diagram showing the magnetic field distribution in the focusing direction, (e) is a longitudinal side view of the coil viewed from the tracking direction, and FIG. 3 is a plan view showing the shape and arrangement relationship of the coils.
[0048]
In the objective lens driving device of the present embodiment, the components thereof are the same as those in the proposed example of Japanese Patent Application No. 10-24387 shown in FIG. Specifically, the moments generated in the focus driving coil 22 and the track driving coil 23 by appropriately devising the shapes and arrangement relationships of the driving magnets 20, 21 and the focus driving coil 22 and the track driving coil 23. And gain fluctuations are reduced.
[0049]
First, a magnetic field distribution (magnetic flux density distribution) generated in a plane on which the coils 22 and 23 are arranged by a magnetic circuit formed by the yoke 18 and the driving magnet 20 (same for the yoke 19 and the driving magnet 21 side) is as follows. The tracking direction is as shown in FIG. 2 (b), and the focusing direction is as shown in FIG. 2 (d). That is, these magnetic flux density distribution peaks (distribution centers) are apparent from the comparison of the positional relationship with FIG. 2C because the magnetic field directions of the adjacent regions in the driving magnet 20 are opposite. In addition, all of the regions divided into four are located outside the geometric center.
[0050]
In accordance with the deviation of the peak (center) position of such a magnetic field distribution, in this embodiment, two focus drive coils 22 are located at the peak position of the magnetic flux density distribution in the tracking direction as shown in FIG. Similarly, two track driving coils 23 are arranged at the peak position of the magnetic flux density distribution in the focusing direction as shown in FIG. 2D, as shown in FIG. 2D. Are arranged so that the center in the focusing direction is located (see FIG. 2E). In other words, the center in the tracking direction of the focus driving coil 22 is set to a position outside the geometric center position in the tracking direction of the four divided regions, and the center in the focusing direction of the track driving coil 23 is It is set at a position outside the geometrical center position in the focusing direction of the four divided areas. However, these coils 22 and 23 are both of a size that can be accommodated within the projected area of the drive magnets 20 and 21.
[0051]
According to such a configuration, first, two focus drivings are performed at the time of tracking movement by arranging the two focus driving coils 22 so that the centers in the tracking direction are positioned at the peak position of the magnetic flux density distribution in the tracking direction. The focus driving force of the working coil 22 varies by almost the same amount. Therefore, the absolute value of the moment generated due to the difference in driving force between the two focus driving coils 22 can be kept small, and the objective lens 11 is not easily tilted.
[0052]
Similarly, by arranging the two track driving coils 23 so that the centers of the two track driving coils 23 are positioned at the peak position of the magnetic flux density distribution in the focusing direction, the track driving force of the two track driving coils 23 is obtained during the focusing movement. Fluctuates by almost the same amount. Therefore, the absolute value of the moment generated by the difference in driving force between the two track driving coils 23 can be suppressed to a small value, and the tilt of the objective lens 11 is hardly caused.
[0053]
In this way, according to the present embodiment, it is possible to greatly reduce the tilt of the objective lens 11 with a simple configuration simply by devising the arrangement of the coils 22 and 23. It becomes an objective lens driving device that can cope. Further, the gain fluctuations associated with the focusing drive and the tracking drive can be reduced depending on the positions of the coils 22 and 23 as described above. In the present embodiment, however, the shape and arrangement of the coils 22 and 23 are further improved. Has been. This point will be described with reference to FIG.
[0054]
First, the focus drive coil 22 side will be described. The two focus driving coils 22 each have two focus driving force generation portions (portions where the coil wire material is orthogonal to the focusing direction), but the focus driving force generation portions have center positions in the focusing direction. As shown in FIG. 3, the track driving coil 23 matches the center position in the focusing direction (therefore, according to FIGS. 2C to 2E, the peak position of the magnetic flux density distribution in the focusing direction). The length of the focus driving coil 22 in the focusing direction is set. In other words, the center of the focus driving force generation portion of the focus driving coil 22 is set to a position outside the geometric center position in the focusing direction of the divided area. As a result, during focusing movement, it is possible to minimize the gain fluctuations at the four focus driving force generation portions, and a stable focusing operation is possible.
[0055]
Next, the track driving coil 23 side will be described. Similarly, in this case, the two track driving coils 23 each have two track driving force generation portions (portion where the coil wire is orthogonal to the tracking direction), but these track driving force generations are generated. As shown in FIG. 3, the center position in the tracking direction of the portion is the center position in the focusing direction of the focus driving coil 22 (therefore, according to FIGS. 2A to 2C, the peak of the magnetic flux density distribution in the tracking direction. The length in the tracking direction of the track driving coil 23 is set so as to coincide with the (position). In other words, the center of the track driving force generation portion of the track driving coil 23 is set to a position outside the geometric center position in the tracking direction of the four divided areas. As a result, during tracking movement, it is possible to minimize the gain fluctuations at the four portions where the track driving force is generated, and a stable tracking operation is possible.
[0056]
A second embodiment of the present invention will be described with reference to FIGS. 4A and 4B are explanatory diagrams of the drive motor configuration, where FIG. 4A is a horizontal sectional view of the coil viewed from the focusing direction, FIG. 4B is a characteristic diagram showing the magnetic field distribution in the tracking direction, and FIG. FIG. 5D is a characteristic view showing the magnetic field distribution in the focusing direction, FIG. 5E is a longitudinal side view of the coil viewed from the tracking direction, and FIG. 5 shows the shape and arrangement of the coil. FIG. 6 is a graph showing the relationship between the movable range and the tilt amount distribution.
[0057]
The objective lens driving device according to the present embodiment basically conforms to the objective lens driving device according to the first embodiment. In particular, the projection area on the moving plane is smaller than the focus driving coil 22 than the focus driving coil 22. By devising such that 23 becomes smaller, the moment by the focus driving coil 22 and the track driving coil 23 is offset, and the tilt of the objective lens 11 is reduced.
[0058]
First, in the above-mentioned proposed example of Japanese Patent Application No. 10-24387 and the objective lens driving device according to the first embodiment, the generated moment of the focus driving coil 22 is opposite to the generated moment of the track driving coil 23. appear. The absolute value of the moment generated by the focus driving coil 22 is greatly influenced by the magnetic field distribution in the tracking direction, and increases as the coil is positioned at the end of the magnetic field distribution. Similarly, the absolute value of the moment generated by the track driving coil 23 is greatly influenced by the magnetic field distribution in the focusing direction, and increases as the coil is positioned at the end of the magnetic field distribution.
[0059]
Here, in the objective lens driving device for CD and DVD, the movable range of the objective lens 11 is about ± 0.6 to 0.8 mm in the focusing direction and about ± 0.25 to 0.35 mm in the tracking direction. When configured as in the first embodiment described above, in both directions, the moment of the track driving coil 23 is greater than the moment of the focus driving coil 22 at the time of maximum movement, and tilt occurs.
[0060]
That is, as in the first embodiment, the focus driving coil 22 and the track driving coil 23 have exactly the same shape, and the lengths of the focusing magnets 20 and 21 in the focusing direction and the tracking direction are equal and square. If formed, the absolute value of the moment generated in the track driving coil 23 is generated in the focus driving coil 22 at the end of the movable range (because the focus moving range is larger than the track moving range). Since it becomes larger than the absolute value of the moment, a certain amount of tilt is generated when the movable part moves.
[0061]
For this reason, in the present embodiment, first, the outer shape of the drive magnets 20 and 21 is not square, but as shown in FIG. 4C, the outer shape is longer in the focusing direction than in the tracking direction. Has been. Also, as shown in FIGS. 4A and 4E, the track driving coil 23 is thicker in the jitter direction than the focus driving coil 22 (d_T> D_FIn addition, the coil wire is made of a wire that is thinner in the track driving coil 23 than in the focus driving coil 22.
[0062]
In this way, the track driving coil 23 is formed thicker in the jitter direction than the focus driving coil 22 and the coil wire material is thin, so that the track driving coil 23 is made of the coil of the coil than the focus driving coil 22. The projected area is small. Further, the outer shape of the drive magnets 20 and 21 is formed longer in the focusing direction than in the tracking direction. By configuring the drive motor 24 in this way, the absolute values of the moment generated in the focus drive coil 22 and the moment generated in the track drive coil 23 are substantially equal, and the tilt of the objective lens 11 is prevented from occurring. Can be suppressed.
[0063]
Here, in the present embodiment, for example, the absolute values of the moments of the focus driving coil 22 and the track driving coil 23 are designed to be equal at the maximum position in the movable range in the focusing direction and the tracking direction ( (See FIG. 6 (a)). According to the relationship between the position of the movable part and the tilt amount shown in FIG. 6A, it can be seen that the tilt is reduced because the moment is canceled at the maximum movement position of the movable part. According to this, when there is a tilt due to focusing movement when there is no tracking due to other factors, even if the moment is not canceled halfway, the entire tilt is not adversely affected (FIG. 6 ( b)).
[0064]
Alternatively, the tilt is not limited to the maximum position of the movable range, and for example, the tilt may be designed to be small at a portion near the middle of the frequently used movable range (see FIG. 6C). When the tilt due to focusing when tracking is not performed after adjustment or the like is eliminated in advance, this design reduces the overall tilt.
[0065]
In these embodiments, the example of the objective lens driving device provided with only one driving motor 24 located on one side of the objective lens 11 has been described. However, as shown in FIGS. A configuration may be adopted in which two drive motors 24 are provided on both sides of the objective lens 11 (the illustrated example shows an application example of the first embodiment as an example). Here, the modification shown in FIGS. 9 and 10 shows an example in which the yoke 19 and the drive magnet 21 on one side of the drive motor 24 are omitted from the modification shown in FIGS.
[0066]
Note that these modifications are applied to an optical system that includes the movable deflection mirror 31 and eliminates the optical axis deviation. The objective lens holding member 12 has a space 32 that is open at one end. An opening 34 is formed in a support wall 33 on one side of the space 32, and the objective lens 11 is fixed to the opening 34. Has been. Further, side walls 35 acting as a substrate are formed on both sides of the space portion 32 of the objective lens holding member 12, and the drive coil assemblies 15 are laminated and fixed to the outer surfaces of these side walls 35. Further, a notch (not shown) for passing the optical axis 16 is formed on one side surface of the space portion 32 of the objective lens holding member 12, and movable deflection is made inside the space portion 32 so as to face the notch. A mirror 31 is provided. Further, in these modifications, the wire spring 14 is offset in the tangential direction from the object farther from the objective lens 11 on the side where the light beam is incident, as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-221276. It is considered not to block the luminous flux. Further, a rising prism 17 that guides the optical axis 16 reflected by the movable deflection mirror 31 to the objective lens 11 is disposed in the space portion 32.
[0067]
In addition, regarding the driving magnet 20 used in these embodiments, it is technically difficult to magnetize each region by dividing it into four crosses in an integrated configuration. For example, as shown in FIG. 11A, the drive magnet 20 is configured by combining four magnets 41 each having a predetermined polarity with one pole as shown in FIG. Alternatively, as shown in FIG. 11 (b), the driving magnet 20 may be configured by combining two magnets 42 each having two poles each having a predetermined polarity (driving). The same applies to the magnet 21 for use).
[0068]
【The invention's effect】
  According to invention of Claim 1,The center of the tracking direction of each of the two focus driving coils is arranged outside the geometric center position in the tracking direction of each of the four divided areas of the driving magnet, thereby reducing the magnetic field distribution in the tracking direction. The center is matched, the driving force fluctuations of the two focus drive coils during tracking operation are equal, the absolute value of the moment generated around the axis in the jitter direction can be reduced, and the focus during tracking operation The fluctuation of the driving force can be reduced.
[0071]
  Claim 2According to the invention, the center in the focusing direction of each of the two track driving coils is arranged outside the geometric center position in the focusing direction of each of the four divided areas of the driving magnet, The center of the magnetic field distribution in the focusing direction is matched, the driving force fluctuations of the two focus driving coils during the focusing operation are made equal, the absolute value of the moment generated around the axis in the jitter direction can be reduced, and In addition, the fluctuation of the track driving force during the focusing operation can be reduced.
[0079]
  Claim 3According to the invention, the center of the focus driving force generating portion having two each of the two focus driving coils is outside the geometric center position in the focusing direction of each of the four divided regions of the driving magnet. By arranging them at the center, the center of the magnetic field distribution in the focusing direction is made coincident, so that the fluctuation of the focus driving force during the focusing operation can be reduced and the focusing operation can be performed stably.
[0081]
  Claim 4According to the invention, the center of the track driving force generating portion having two each of the two track driving coils is outside the geometric center position in the tracking direction of each of the four divided areas of the driving magnet. By arranging them at the same position, the center of the magnetic field distribution in the tracking direction is made coincident, so that the fluctuation of the track driving force during the tracking operation can be reduced and the tracking operation can be performed stably.
[Brief description of the drawings]
1A and 1B show an objective lens driving device according to a first embodiment of the present invention, in which FIG. 1A is a plan view seen from a Y direction indicating a focusing direction, and FIG. 1B is a view seen from a Z direction indicating a tracking direction; It is a vertical side view.
FIGS. 2A and 2B are explanatory views showing a configuration of a driving motor, where FIG. 2A is a horizontal sectional view of the coil viewed from the focusing direction, FIG. 2B is a characteristic diagram showing magnetic field distribution in the tracking direction, and FIG. FIG. 4D is a front view showing the arrangement relationship with the driving magnet, FIG. 4D is a characteristic diagram showing the magnetic field distribution in the focusing direction, and FIG. 3E is a longitudinal side view of the coil viewed from the tracking direction.
FIG. 3 is a plan view showing the shape and arrangement relationship of coils.
FIGS. 4A and 4B are explanatory views showing a drive motor configuration according to a second embodiment of the present invention, in which FIG. 4A is a horizontal sectional view of a coil viewed from the focusing direction, and FIG. 4B is a magnetic field distribution in the tracking direction; (C) is a front view showing the positional relationship between the coil and the drive magnet, (d) is a characteristic diagram showing the magnetic field distribution in the focusing direction, and (e) is a longitudinal side view of the coil viewed from the tracking direction. It is.
FIG. 5 is a plan view showing the shape and arrangement relationship of coils.
FIG. 6 is a graph showing a relationship between a movable range and a tilt amount distribution.
7A and 7B show an objective lens driving device according to a first modified example, in which FIG. 7A is a plan view viewed from a focusing direction, and FIG. 7B is a longitudinal side view viewed from a tracking direction.
FIG. 8 is an exploded perspective view showing a configuration of a drive motor.
9A and 9B show an objective lens driving device according to a second modification, wherein FIG. 9A is a plan view seen from the focusing direction, and FIG. 9B is a longitudinal side view seen from the tracking direction.
FIG. 10 is an exploded perspective view showing a configuration of a drive motor.
FIG. 11 is an exploded perspective view showing a modification of the drive magnet.
FIG. 12 is a perspective view showing a conventional example.
FIG. 13 is a schematic plan view for explaining the presence / absence of a shift during a focusing movement accompanying the presence / absence of a track movement.
FIG. 14 is a schematic front view showing the cause of tilt based on the deviation of the center of the focus driving coil from the center of the movable part.
FIG. 15 is a graph showing characteristics of the occurrence of tilt.
16A and 16B show an objective lens driving device according to the proposed example of Japanese Patent Application No. 10-24387, where FIG. 16A is a plan view seen from the Y direction indicating the focusing direction, and FIG. 16B is a view seen from the Z direction indicating the tracking direction. It is a vertical side view.
FIG. 17 is an exploded perspective view showing a drive motor portion.
18A and 18B show a drive motor portion, in which FIG. 18A is a coil plan view, FIG. 18B is a front view, and FIG. 18C is a coil side view.
FIG. 19 is a graph showing characteristics of tilt generation according to the proposed example of Japanese Patent Application No. 10-24387.
[Explanation of symbols]
11 Objective lens
18, 19 York
20, 21 Driving magnet
22 Focus drive coil
23 Track drive coil
24 Drive motor
a, b Magnetization boundary line

Claims (6)

The surface is divided into four regions in a cross shape and is fixed to a yoke having a predetermined thickness by being magnetized in a direction perpendicular to the surface including the focusing direction and the tracking direction and in the direction opposite to the adjacent region. A drive magnet, two focus drive coils provided on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction, and the drive An objective is a driving motor comprising two track driving coils located on both sides of the magnetization boundary line in the tracking direction in the vicinity of the surface of the magnet for use and straddling the magnetization boundary line in the focusing direction. Provided on one or both sides of the lens,
The center in the tracking direction of each of the two focus driving coils is located outside the geometric center position in the tracking direction of each of the four divided areas of the driving magnet , and at the peak of the magnetic flux density distribution. An objective lens driving device characterized by matching . The surface is divided into four regions in a cross shape and is fixed to a yoke having a predetermined thickness by being magnetized in a direction perpendicular to the surface including the focusing direction and the tracking direction and in the direction opposite to the adjacent region. A drive magnet, two focus drive coils provided on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction, and the drive An objective is a driving motor comprising two track driving coils located on both sides of the magnetization boundary line in the tracking direction in the vicinity of the surface of the magnet for use and straddling the magnetization boundary line in the focusing direction. Provided on one or both sides of the lens,
The center in the focusing direction of each of the two track driving coils is located outside the geometric center position in the focusing direction of each of the four divided areas of the driving magnet , and at the peak of the magnetic flux density distribution. An objective lens driving device characterized by matching . The surface is divided into four regions in a cross shape and is fixed to a yoke having a predetermined thickness by being magnetized in a direction perpendicular to the surface including the focusing direction and the tracking direction and in the direction opposite to the adjacent region. A drive magnet, two focus drive coils provided on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction, and the drive An objective is a driving motor comprising two track driving coils located on both sides of the magnetization boundary line in the tracking direction in the vicinity of the surface of the magnet for use and straddling the magnetization boundary line in the focusing direction. Provided on one or both sides of the lens,
The center of the focus driving force generating portion having two each of the two focus driving coils is located outside the geometric center position in the focusing direction of each of the four divided areas of the driving magnet , and An objective lens driving device characterized by being coincident with a peak of a magnetic flux density distribution . The surface is divided into four regions in a cross shape and is fixed to a yoke having a predetermined thickness by being magnetized in a direction perpendicular to the surface including the focusing direction and the tracking direction and in the direction opposite to the adjacent region. A drive magnet, two focus drive coils provided on both sides of a focusing boundary in the focusing direction near the surface of the driving magnet and straddling the magnetization boundary in the tracking direction, and the drive An objective is a driving motor comprising two track driving coils located on both sides of the magnetization boundary line in the tracking direction in the vicinity of the surface of the magnet for use and straddling the magnetization boundary line in the focusing direction. Provided on one or both sides of the lens,
The center of the track driving force generating portion having two of each of the two track driving coils is located outside the geometric center position in the tracking direction of each of the four divided areas of the driving magnet , and An objective lens driving device characterized by being coincident with a peak of a magnetic flux density distribution .   An optical pickup comprising the objective lens driving device according to claim 1.   An optical disk drive comprising the optical pickup according to claim 5.

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