JPH10162394A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object lens driving device in which a light spot of an objective lens is not largely displaced even if tilt of an object lens is corrected. SOLUTION: This device has an objective lens 1, an objective lens sustaining member 2, supporting members 7, 8 supporting the sustaining member in a displaceable state, a tilt coil 5 which is fixed to the sustaining member and rotates the sustaining member around a shaft almost intersecting at right angle to the direction of an optical axis of an objective lens, and magnetic field applying means 13, 14 applying magnetic fluxes to the tilt coil. In this case, this device is constituted so that the center of rotation of the objective lens by the tilt coil and the magnetic field applying means almost coincides with a nodal point of the object lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus for optically recording / reproducing information on / from a recording medium, for example, a magneto-optical disk drive, a write-once type disk drive, a phase change type disk drive, and a CD-ROM. The present invention relates to an objective lens driving device in a drive, a DVD drive, and the like.

[0002]

2. Description of the Related Art In an information recording / reproducing apparatus which at least optically reproduces information on a recording medium, an objective lens condenses and irradiates a light beam to form a minute light spot on the recording medium to reproduce an information signal. It is carried out. However, if the optical axis of the objective lens does not irradiate the information recording surface of the recording medium at an appropriate incident angle, optical aberrations occur, crosstalk and jitter increase, and the information signal deteriorates. In addition, when recording information on the information recording surface, if the optical axis of the objective lens is tilted, the information signal to be recorded is degraded, causing a problem that a correct pit mark is not formed.

In order to solve such a problem, there has been proposed an objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 7-65397 (hereinafter referred to as Conventional Example 1). FIG.
1 shows the objective lens driving device disclosed in the prior art 1. Hereinafter, the configuration of the objective lens driving device will be described with reference to FIG.

As shown in FIG. 11, the optical axis direction of the objective lens 51 is Z, the circumferential direction of the optical disk is Y, and the radial direction of the optical disk is X. The objective lens 51 is held by a holder 52. A focus coil 53 is provided on the side of the holder 52.
Is wound horizontally, and the circumferential direction of the holder 52 (Y direction)
Tracking coils 54a to 54d (54d
Are not shown), but the tracking coil 54
Tilt coils 55a to 55d (55d is not shown) are attached to portions located below each of the a to 54d.

[0005] First and second tilt coils 55a, 55b
And the third and fourth tilt coils 55c and 55d are X
They are arranged along the radial direction of the optical disk so as to be symmetrical with the axis. In this case, the tilt coils 55a, 55c
Then, the tilt coils 55b and 55d are arranged along the circumferential direction of the optical disk.

On the upper surface of the holder 52, radial tilt detectors 61a, 61b are arranged along the X direction with the objective lens 51 interposed therebetween.
Is attached. Further, circumferential inclination detectors 61c and 61d are attached along the Y direction with the objective lens 51 interposed therebetween.

One end of each of the four parallel supporting members 56a to 56d is fixed to a side surface of the holder 52, and the other end is fixed to a supporting member fixing portion 58 mounted on a base 57. The supporting members 56a to 56d are arranged such that the holder 52
(Z axis), tracking direction b (X axis), radial inclination c, and circumferential inclination d so as to be finely and tiltably supported in four directions.

A pair of U-shaped yokes 59a, 59b are attached to the base 57 in the Y direction, and magnets 60a, 60b are fixed to the pair of yokes 59a, 59b. The yokes 59a, 59b constitute a magnet applying means together with the magnets 60a, 60b.

The operation of the objective lens driving device thus configured will be further described with reference to FIG. Of the light emitted from the objective lens 51 and condensed on the optical disk D, the diffracted light that does not return to the objective lens 51 is divided into radial tilt detectors 61a and 61b and circumferential tilt detectors 61c and 61c.
The light is received by 61d. FIG. 12A shows a state in which the optical axis of the objective lens 51 is not tilted in the radial direction c with respect to the optical disc D, and the amount of diffracted light received by the radial tilt detectors 61a and 61b is equal. I have. That is, no error signal is generated in this state. On the other hand, FIG.
Indicates a state in which the optical axis of the objective lens 51 is tilted in the radial direction c with respect to the optical disc D, a difference occurs in the amount of light received by the radial tilt detectors 61a and 61b, and an error signal is generated.

That is, the radial tilt detectors 61a and 61b
So that the error signal from the tilt coil 55a becomes zero.
To 55d, the objective lens 51
Can be corrected in the radial direction c.

In the circumferential direction d, similarly to the case of the radial direction c, drive currents for correcting error signals from the circumferential direction tilt detectors 61c and 61d are supplied to the tilt coils 55a to 55d.
, The inclination of the optical axis of the objective lens 51 in the circumferential direction d can be corrected.

[0012]

However, FIG.
Since the objective lens 51 is mounted above the holder 52, the objective lens 51 and the center of gravity of the movable part (comprising the objective lens 51, the holder 52, and the respective drive coils) are in the Z direction. When the objective lens 51 is tilted by the tilt coils 55a to 55d, the objective lens is displaced in the tilted direction, and the light spot is displaced accordingly.

For example, when a drive current in a predetermined direction is applied to the tilt coils 55a to 55d so as to tilt the optical axis of the objective lens 51 around the Y axis, the objective lens 51 tilts around the Y axis and moves in the X direction, The light spot moves in the X direction. This movement of the light spot becomes a disturbance in the X direction, and it is necessary to apply a drive current to the tracking coils 54a to 54d to perform correction. Therefore, the load on the servo in the tracking direction increases, which causes a problem that current consumption increases.

Similarly to the case around the X axis, when the optical axis of the objective lens is tilted around the X axis, the objective lens tilts around the X axis and moves in the Y direction, and the light spot moves in the Y direction. Resulting in. Since a general objective lens driving device in an information recording / reproducing device does not have a driving mechanism for driving the objective lens in the Y direction, the movement of the light spot in the Y direction cannot be corrected. For this reason, jitter occurs, and the reflected light from the recording medium enters the tracking and focusing photodetectors with a shift, resulting in an offset in the tracking error and focusing error signals, thereby preventing accurate servo. .

The present invention has been made in view of such a problem, and an object of the present invention is to provide an objective lens driving device in which the light spot of the objective lens is not largely displaced even when the inclination of the objective lens is corrected. .

[0016]

To achieve the above object, an objective lens driving device according to the present invention comprises an objective lens, a holding member for holding the objective lens, and a support for movably supporting the holding member. A member, a tilt coil fixed to the holding member and rotating the holding member about an axis substantially perpendicular to an optical axis direction of the objective lens, and a magnetic field applying unit for applying a magnetic flux to the tilt coil. In the objective lens driving device, the rotation center of the objective lens by the cooperation of the tilt coil and the magnetic field applying means is configured to substantially coincide with the nodal point of the objective lens.

For this reason, even if the holding member is rotated by the cooperation of the tilt coil and the magnetic field applying means, the holding member is rotated about the nodal point of the objective lens, and the nodal point of the objective lens is rotated. The point is not largely displaced, and the displacement amount of the light spot becomes very small.

More specifically, by configuring the objective lens driving device such that the center of rotation of the objective lens coincides with the center of gravity of the movable portion that rotates around the axis, the movable portion can be driven at a low frequency. Even if it is rotated, the displacement of the light spot becomes very small.

Further, by configuring the objective lens driving device so as to coincide with the center of rotation of the objective lens and the support center supported by the support member, the movable portion can be rotated at a high frequency. Also, the displacement amount of the light spot becomes very small.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an objective lens driving device according to a first embodiment of the present invention will be described with reference to FIGS.

This objective lens driving device is an objective lens driving device in a magneto-optical disk drive that uses a magneto-optical disk as a recording medium and performs recording and reproduction on the magneto-optical recording medium. Of the coordinate axes in the figure, the X direction is the tracking direction (the normal direction of the information track), the Y direction is the tangential direction (the tangential direction of the information track), and the Z direction is the focusing direction (the direction perpendicular to the magneto-optical disk surface, the objective direction). (In the direction of the lens optical axis).

As shown in FIG. 1, the objective lens 1 is fixed to a through hole formed at the center of a holder (holding member) 2. A groove is formed on the upper surface of the holder 2 so as to surround the objective lens 1, and the focusing coil 3 wound around the groove is inserted and fixed. Further, two wound tracking coils 4 are fixed to one side surface of the holder 2 in the Y direction, and two wound tracking coils 4 are similarly fixed to the other side surface. A total of four tilt coils 5 are fixed outside each of the tracking coils 4.

The movable section 20 includes an objective lens 1, a holder 2,
End 9 of focusing coil 3, tracking coil 4, tilt coil 5, and leaf springs 9, 10 on holder 2 side
c, 10c.

Fixed portions 6 and 6 are provided on both sides of the holder 2 in the X direction.
Are formed, and one ends of the support springs 7, 8 are fixed to the fixing portions 6, 6, respectively. As shown in FIG. 2, the supporting spring 7 includes leaf springs (supporting members) 9 and 10 disposed vertically with a gap of about 0.5 to 1.5 mm, and silicon injected into the gap. It is composed of a damping material such as gel. The leaf springs 9 and 10 have end portions 9 at both ends in the Y direction, respectively.
Narrow bending portions 9a and 10a are formed near c and 10c. The bent portions 9a and 10a are formed so as to be slightly shifted in the X direction as shown in FIG. Bent portions 9b and 10b formed by bending one side in the width direction (X direction) at a right angle are formed in an intermediate portion between the two bent portions 9a and 10a. Then, the bent portions 9b and 10b are assembled so as to face each other, and the cross section on the ZX plane is configured to present a horizontally long rectangle as shown in FIG. Note that the support spring 8 is configured in the same manner as the support spring 7, and the description thereof is omitted.

The other ends of the support springs 7 and 8 are fixed to a fixed portion 12 formed to rise from the base 11. 2
The two magnets 13 (magnetic field applying means) are respectively fixed to two yoke portions 14 rising from the base 11 so as to face the tracking coil 4 and the tilt coil 5. The magnet 13 is fixed to the yoke part 14 such that the two magnetic poles of the two magnets 13 facing the tracking coil 4 and the tilt coil 5 have N poles, respectively.

The magnetic flux generating means comprises a magnet 13 and a yoke portion 14. Here, the mutual positional relationship between the focusing coil 3, the tracking coil 4, and the tilt coil 5 and the positional relationship with the magnet 13 will be described in more detail with reference to FIGS.

The focusing coil 3 is fixed to the holder 2 such that the center position in the Z direction coincides with the center position of the magnet 13 in the Z direction. The tracking coil 4 has its center position in the Z direction coincident with the center position of the magnet 13 in the Z direction, and has effective sides (sides adjacent to each other inside the tracking coil) 41a, 42a,
The holder 43 is fixed to the holder 2 so that 43a and 44a are located in the effective magnetic field of the magnet 13. The tilt coil 5 is Z
Each effective side 51a, 52a, 53a on the (+) side
The magnet 54 is fixed to the holder 2 such that the center position of the magnet 54 in the Z direction coincides with the center position of the magnet 13 in the Z direction.

Next, the relationship between the nodal point (hereinafter referred to as NP) of the objective lens and the center of gravity and the support center S of the movable section 20 will be described with reference to FIG. FIG. 5 is a schematic sectional view in which the center of the objective lens 1 in FIG. 1 is cut along the AA plane parallel to the XZ plane, and is viewed from the Y (-) side. Since the objective lens 1 of the present embodiment is an infinite optical system that makes parallel light incident and condenses it on the disk D, the objective lens 1 has a N.D. P coincides with the rear principal point Ho ′, and the rear principal point Ho ′ of the objective lens 1 coincides with the center of gravity G of the movable part 20. Also, on a plane parallel to the YZ plane, the N.V. P and the center of gravity G of the movable part 20 are matched. Then, the N.V. P is the movable part 20
Of the four bending portions 9a and 10a of the support springs 7 and 8 on the holder 2 side, that is, the support center S for rotation about the Y axis. When the rigidities and positions of the four flexures 9a and 10a are not uniform, the support center may deviate from the midpoint of the flexures. The support center S is assumed to be an axis parallel to the direction in which the support springs 7 and 8 extend (Y direction), and the rotation of the movable section 20 when a static torque is applied to the movable section 20 around the axis. The center.

The resonance frequency of the resonance mode in which the movable part 20 rotates around the Y axis is determined by the moment of inertia of the movable part 20 around the Y axis and the torsion constant around the Y axis of the support springs 7 and 8 as supporting members. fr is determined. Movable part 2
When a frequency lower than fr or a static torque around the Y-axis is applied to 0, the movable portion 20 rotates about the support center S substantially. Further, when a torque having a frequency higher than fr is applied to the movable portion 20, the movable portion 20 rotates substantially around the center of gravity of the movable portion 20.

Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 4 schematically shows the focusing coil 3, the tracking coil 4, and the tilt coil 5, and shows a state in which the tilt coil 5 is rotated around the Y axis by applying a predetermined drive current.

The four tilt coils 5 (51, 52, 5)
3, 54), drive currents in the same direction are applied to the tilt coils 51 and 53 provided on the X (+) side, and a drive force in the Z (-) direction is generated on the effective sides 51a and 53a.
Also, tilt coils 52 and 54 provided on the X (-) side
Is applied with a drive current in the opposite direction to the tilt coils 51 and 53, and a drive force in the Z (+) direction is generated on the effective sides 52a and 54a. Therefore, the movable unit 20 is rotated around the Y axis (clockwise as viewed from the Y (-) direction). Naturally, by reversing the direction of the drive current applied to the tilt coil 5, the tilt coil is rotated counterclockwise as viewed from the Y (−) direction.

In this embodiment, the N.V. Since P is coincident with the center of gravity G and the support center S of the movable unit 20, even if the movable unit 20 is rotated around the Y axis by the tilt coil 5, the light spot of the objective lens 1 moves as in the conventional case. Never. The reason will be described in more detail.

FIG. 6A shows that the center of gravity G and the center of support S of the movable part 20 ′ are the N.D. This shows a state where P does not match. When the movable unit 20 'is rotated around the Y axis by θ degrees by the tilt coil 5 (not shown), the movable unit 20' is rotated about its center of gravity G and the support center S, and the N of the objective lens 1 is changed. . P moves by m to the X (-) side. That is, from the center of gravity G of the movable part 20 ′, the N.D. Assuming that the distance to P is 1, the light spot O
Is the moving amount m of the light spot O. The moving amount m of the light spot O becomes larger as the l becomes larger.

On the other hand, in the present embodiment, FIG.
, The center of gravity G and the support center S of the movable section 20 and the N.V. P and the movable part 2
0 is rotated about the Y axis by θ degrees by the tilt coil 5, the movable unit 20 It turns around P. That is, from the center of gravity G of the movable unit 20 to the N.V. Since the distance 1 to P is 0, the moving amount m of the light spot O is m = l · θ = 0. Therefore, even if the objective lens 1 is tilted around the Y axis by the tilt coil 5, the light spot O does not shift in the X direction, and does not cause disturbance in the tracking direction.

In this embodiment, even if the movable section 20 is rotated not only about the Y axis but also about the X axis, the center of gravity G of the movable section 20 and the N.V. Since P coincides, the light spot O does not move.

In this embodiment, the N.V. Since P coincides with the center of gravity G of the movable part 20 and the support center S around the Y axis, a frequency lower than the resonance frequency around the Y axis is generated in the movable part 20, and
Is rotated around the support center S, the N.D. Since the light spot O rotates around P, the movement amount m of the light spot O becomes extremely small.

As described above, according to the present embodiment, the center of gravity G and the support center S of the movable part 20 including the objective lens 1, the holder 2, the focusing coil 3, the tracking coil 4, and the tilt coil 5 are set to the objective. N. of lens 1 P. N. P, the center of rotation when the movable part 20 is rotated by the tilt coil 5 is equal to the N.P. of the objective lens 1. The position becomes P, and the movement of the light spot O by rotating the movable portion 20 by the tilt coil 5 is eliminated.

In the present embodiment, the center of gravity of the movable section 20 and the N.D. Since a weight balancer for adjusting the position of the center of gravity of the movable section 20 is not required to match P, the movable section 20 can be reduced in size and weight.

Further, since the interval between the upper and lower leaf springs 9 and 10 is reduced, the spring constant when rotating the movable portion 20 around the X axis is reduced, and the movable portion 20 is rotated around the X axis with a small current. Can be moved.

In the present embodiment, the movable part 20 is rotated around the X axis and the Y axis. However, the present invention is not limited to only two axes, and the X axis or the Y axis may be used. The present invention can also be applied to an objective lens driving device in which only one of the surroundings is inclined.

In this embodiment, since the infinite optical system is adopted, the N.V. P and back principal point Ho '
, But is not limited to this when a finite optical system or the like is employed. P is shifted from the rear principal point Ho '.

Next, a second embodiment of the present invention will be described with reference to FIGS. This objective lens driving device moves the movable unit 40 in the Z-axis direction and rotates around the Y-axis.

Hereinafter, the configuration of the objective lens driving device of the present embodiment will be described. On both sides in the X direction of the holder (holding member) 22 to which the objective lens 21 is fixed, coils 25 (251 and 252) wound in a prism shape are fixed. The objective lens 21, the holder 22, and the coil 25 constitute a movable section 40. A convex portion 26 is formed on both sides of the holder 22 in the Y direction, and the convex portion 26
Is fitted and fixed in the hole 27g of the prism 27a. The prism 27a constitutes a mounting portion for mounting the holder 22. A thin connecting portion 27c (support member) is formed between the prism 27a and the relay piece 27b, and the prism 27a is connected by the connecting portion 27c. The connecting portion 27c is a support center S of the movable portion 40 around the Y axis, and the holder 22 fixed to the support member 27 is rotated around the Y axis around the connecting portion 27c.

Objective lens 21, holder 22, coil 25
(251, 252) and the prism 27a constitute the movable part 40. The support member 27 has a parallel link shape,
Two relay pieces 27b each having the prism 27a formed thereon, four link parts 27d extending in the X direction from both ends of the two relay pieces 27b, and the base 31 connected to the other ends of the four link parts 27d. And a fixing portion 27e fixed to Between the relay piece 27b and the link member 27d, and the link portion 2
A very thin thin portion hinge portion 27f is formed at the connection portion between 7d and the fixing portion 27e. The support member 27 is integrally formed of a material having a deformable hinge portion 27f, for example, a polyurethane elastomer.

An outer yoke 3 is provided on both sides of the base 31 in the X direction.
1a is formed, and an inner yoke 3
1b is formed. Magnets (magnetic field generating means) 33 are fixed to the surface of the outer yoke 31a facing the inner yoke 31b, and a magnetic gap is formed between the outer yoke 31a and the inner yoke 31b.

The inner side surface of the fixing portion 27e of the support member 27 is fixed to the outer side surface of the outer yoke 31a on the left side of the base 31 in the drawing, and the support member 27 is fixed to the base 31.

The objective lens driving device according to the present embodiment is arranged such that the center of the interval between the two coils 25 on both sides of the holder 22 and the N.D. P, the center of gravity G of the movable part 40, and the connecting part 27c, that is, the support center S are aligned in a straight line.
As shown in FIG. P, the center of gravity G of the movable section 40, and the connecting section 27c are aligned when viewed from the Y direction.

The tracking drive of the objective lens 21 is performed by providing another tracking drive mechanism, for example, a galvanomirror, without driving the objective lens 21.

The operation of the objective lens driving device according to the second embodiment having the above-described configuration will be described below. As shown in FIG. 10, a driving current of a signal obtained by adding a focusing servo signal and a tilt servo signal is applied to the coil 251, and a driving current of a difference signal between the focusing signal and the tilt servo signal is applied to the coil 252.

When the objective lens 21 is displaced to the Z (+) side in the focusing direction, the coils 251 and 252
Then, a drive current of a signal that generates a drive force on the Z (+) side is applied. Both coils 251 and 252 have Z
A driving force to the (+) side is generated, and the movable part 40 is displaced to the Z (+) side. At this time, the hinge portion 27f of the support member 27
Is deformed, and the relay piece 27b of the support member 27, the link 2
The displacement of the movable portion 40 on the Z (+) side is enabled by the displacement of 7d.

When the objective lens 21 is rotated about the Y axis, drive currents in opposite directions are applied to the coils 251 and 252, respectively, so that the drive forces generated by the coils 251 and 252 are opposite to each other in the Z direction. Orient it. A moment about the Y axis centering on the connecting portion 27c is generated in the movable portion 40, and the movable portion 40 is rotated around the Y axis around the connecting portion 27c, that is, the support center S as the connecting portion 27c is deformed. Move.

In the case of the present embodiment, the connecting portion 27c is the support center S only around the Y axis, and the N.C. of the objective lens 21 is placed on the Y axis passing through the connecting portion 27c. Since P and the center of gravity G of the movable part coincide with each other, even if the movable part 40 rotates about the connecting part 27c that is the support center S, the N.P.
The position of P does not shift, and therefore the position of the light spot does not shift.

Further, since the connecting portion 27c is a support member for the rotating shaft around the Y axis of the movable portion, it is clear that the position of the support center S is on the Y axis passing through the connecting portion 27c, and the first embodiment The position of the support center S can be easily known as compared with the position of the support center S and the N.N. P can be matched exactly.

Further, since the rigidity of deformation of the connecting portion 27c other than around the Y axis is very high compared to the rigidity of deformation around the Y axis, the center of gravity G of the movable portion 40 passes through the connecting portion 27c.
Even if it is slightly displaced from the axis, the movable portion 40 is connected to the connecting portion 27c.
, And the allowable range of the dimensional accuracy and the assembling accuracy of the parts is widened.

Further, since the link portion 27d of the support member 27 extends in the X direction in the tracking direction, X generated when the objective lens driving device is accessed at a high speed in the X direction.
Accurate focusing servo and tilt servo can be performed without deformation of the link portion 27d in the X direction with respect to the acceleration in the direction.

It is to be noted that a tilt coil can be added to the present embodiment and tilted around the X axis. For example, by disposing four tilt coils 253 (only two are shown in the figure) as shown in FIG. 7 and generating a force as shown in the figure, the movable part 40 is also rotated around the X axis. be able to.

In each of the above embodiments, the objective lens N.D. P is matched with the center of gravity G of the movable part or the support center S of the support member. However, if the objective lens driving device is configured such that the center of gravity G or the support center S is located inside the objective lens, the objective lens N. P, center of gravity G, support center S
Is about 0 to 2 mm, and the movement amount of the light spot can be made extremely small even if it is considered from the viewpoint of optical accuracy, and the object of the present invention can be sufficiently achieved.

In each of the above-described embodiments, the tilt coil is fixed to the movable portion and the magnet is arranged on the fixed base. However, the so-called moving ink is fixed to the movable portion and the tilt coil is arranged on the base. The object of the present invention can be achieved even with a magnet type objective lens driving device.

In each of the above embodiments, the support member may be a wire or the like. If it is a wire, four wires are preferable. Further, the objective lens is used for forming a light spot on the disc, and if the objective lens can form a light spot on the disc,
It is not limited to the objective lens. For example, it may be a hologram. In addition, the objective lens and the holder are formed as separate members, and the objective lens is fixed to the holder. However, the objective lens and the holder are integrally formed, and the present invention is naturally applicable to a single component.

[0060]

As described above, according to the present invention,
Even if the movable part is rotated by the cooperation of the tilt coil and the magnetic field applying means, the center of rotation of the movable part coincides with the nodal point of the objective lens, so that the nodal point of the objective lens is largely displaced. The light spot from the objective lens is not greatly displaced.

[Brief description of the drawings]

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

FIG. 2 is a ZX cross-sectional view of a support spring 7 of the objective lens driving device according to the first embodiment.

FIGS. 3A and 3B are plan views showing a support spring 7 of the objective lens driving device according to the first embodiment, and FIG. 3A shows a state before the support spring 7 is deformed. State, FIG. 3
(B) is a figure which shows the state in which the support spring 7 was deformed.

FIG. 4 is a perspective view schematically showing a focusing coil, a tracking coil, and a tilt coil of the objective lens driving device according to the first embodiment.

FIG. 5 is a sectional view taken along the line AA in FIG. 1;

6 (a) and 6 (b) are diagrams showing displacement amounts of a light spot when an objective lens is tilted, and FIG. 6 (a) shows a conventional case, and FIG. 6 (b) Shows the case of the first embodiment.

FIG. 7 is an exploded perspective view of an objective lens driving device according to a second embodiment of the present invention.

FIG. 8 is an overall perspective view of an objective lens driving device according to a second embodiment.

FIG. 9 is a side view of the movable portion and its periphery of the objective lens driving device according to the second embodiment as viewed from the Y direction.

FIG. 10 is a block diagram illustrating a drive circuit that drives a coil.

FIG. 11 is an exploded perspective view showing a conventional objective lens driving device.

12A and 12B are explanatory diagrams of the operation of the conventional objective lens driving device. FIG. 12A shows a case where there is no inclination of the beam optical axis.
FIG. 2B is a diagram illustrating a case where the beam optical axis is inclined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Holder 3 Focusing coil 4 (41, 42, 43, 44) Tracking coil 5 (51, 52, 53, 54) Tilt coil 7, 8 Support spring 9, 10 Leaf spring 11 Base 12 Fixed part 13 Magnet 14 Outer yoke 20 movable part

Claims (3)

[Claims] 1. An objective lens, a holding member for holding the objective lens, a support member for supporting the holding member so as to be displaceable, and an optical axis direction of the objective lens fixed to the holding member. An objective lens driving device comprising: a tilt coil that rotates around an axis substantially perpendicular to the tilt coil; and a magnetic field applying unit that applies a magnetic flux to the tilt coil; wherein the objective lens is formed by cooperation of the tilt coil and the magnetic field applying unit. An object lens driving device, wherein the center of rotation of the objective lens is substantially coincident with the nodal point of the objective lens. 2. The objective lens driving device according to claim 1, wherein a center of rotation of the objective lens coincides with a center of gravity of a movable portion that rotates around the axis. 3. The objective lens driving device according to claim 1, wherein a center of rotation of the objective lens coincides with a support center supported by the support member. apparatus.