JP2601809B2 - Objective lens drive - Google Patents

Description

The present invention relates to an objective lens driving device, and more particularly to a method for supporting a movable body including a lens.

(Prior Art) In an optical reproducing apparatus using a laser beam, a laser beam is focused on a recording medium by a lens or the like to detect a signal.
In order to correctly detect a signal, it is necessary to perform forcing control for focusing the light spot on the information recording medium in accordance with unevenness or vibration of the recording medium and tracking control for causing the light spot to follow a signal track.

In order to perform these controls, an error detection device that detects each error and an actuator that moves the optical system so as to cancel the errors are required.

2. Description of the Related Art Conventionally, the following objective lens driving devices are known.

First, as shown in FIG. 5 to FIG. 7, there is an apparatus which realizes movement of an objective lens in two directions perpendicular to a focus direction and a tracking direction by rotation of a movable body around a principal axis of inertia and parallel movement in a direction of the principal axis of inertia. . That is, a shaft 102 is implanted at the center of the upper surface of a base 101 formed of a magnetic material, and the shaft 102 is fitted to the shaft 102 to form a bearing cylinder 103 constituting a sliding bearing mechanism.
A holding cylinder 104 formed in a cylindrical shape with a bottom is mounted so as to be slidable in the axial direction and rotatable around the axis. The so-called bottom wall 104a of the holding cylinder 104 supports the objective lens 105, and uses the cylinder 104b of the holding cylinder 104 as a coil bobbin. The focusing coil 106 controls the axial position on the outer periphery of the cylinder 104b. And a tracking coil 107 for controlling the position around the axis.

Also, the two inner yokes 108a and 108b are symmetrical about the axis 102 in such a manner that the two inner yokes 108a and 108b are fitted into the cylindrical portion 104b in a non-contact manner at a position facing the inner surface of the bottom wall 104a of the holding cylinder 104 on the upper surface of the base 101. The inner yoke 10 is provided outside the cylindrical portion 104b.
The outer yokes 109 are respectively opposed to the outer surfaces of 8a and 108b.
a, 109b, and these outer yokes 109a, 109b and base 1
A permanent magnet 110 that is magnetized in the axial direction is interposed between the upper surface of 01 and the upper surface of 01. Also, on the upper surface of the base 101 and the holding cylinder 1
A small shaft 111 is erected at a position facing the inner surface of the bottom wall 104a of 04,
A damper member 11 for setting a neutral position in the tracking direction formed between the small shaft 111 and the bearing cylinder 103, for example, made of rubber or the like.
2 is interposed. In addition, 113 in FIG.
And a transmission hole that guides light to the objective lens 105 and light from the objective lens 105.

The objective lens driving device configured as described above uses the electromagnetic force that accompanies the energization control of the focusing coil 106 to
The position of the holding cylinder 104 is changed in the X direction in FIG. 5 by changing the position of 04 in the Y-axis direction in FIG. 5, thereby performing the focusing control, and by the electromagnetic force accompanying the energization control to the tracking coil 107. It is moved so that tracking kick control is performed. These energization controls are performed by a servo system (not shown).

Also, as shown in FIG. 8, the movable body holding the objective lens is directly perpendicular to the focus direction and the tracking direction.
There is also known an objective lens driving device that moves in a direction.
That is, a metal rod fixing plate 212 is provided to protrude upward from the end of the base 211 made of a magnetic material. One end of metal bars 213a, 213b, 213c, 213d parallel to each other in a plane perpendicular to the base 211 is fixed to the metal bar fixing plate 212. Objective lens 214 at the other end of metal rod 213a, 213b, 213c, 213d
Is fixed. Further, a focusing coil 216 and tracking coils 217a and 217b are fixed to the movable body 215.

On the other hand, the base 211 has the focusing coil 216
Inner yokes 218a and 218b protrude so as to be inserted with a certain gap provided inside. The focusing yoke 216 and the tracking coils 217a and 217b are sandwiched between the inner yokes 218a and 218b, and the outer yokes 219a and 219b are located at positions facing the inner yokes 218a and 218b.
Is protruding. Magnets 220a and 220b are fixed to surfaces of the outer yokes 219a and 219b facing the inner yokes 218a and 218b.

The objective lens driving device configured as described above uses the electromagnetic force accompanying the energization control of the focusing coil 216 to move the movable body 2.
8 is moved in the Y direction in FIG. 8, thereby performing focusing control.
The movable body 215 is moved in the X-axis direction in FIG. 5 by the electromagnetic force accompanying the control of energizing b, thereby performing tracking control.

(Problems to be Solved by the Invention) However, the conventional objective lens driving device configured as described above has the following problems.

In other words, in the objective lens driving device shown in FIGS. 5 to 7, the neutral position of the holding cylinder 104 is determined by the damper member 112 and the restoring force in the tracking direction is obtained at the same time. Although the Q value at the main resonance is suppressed to a low value by the internal damping, a material having a large damping rate generally has a problem that the neutral position changes with time because it tends to creep. That is, if a material having a large damping rate is used to improve the control characteristics, the neutral position changes and a predetermined driving range cannot be obtained. On the other hand, if a material that does not change the neutral position is selected, the Q value increases and the control characteristics increase. There was a problem that it became worse.

In the objective lens driving device shown in FIG. 8, when the objective lens is moved in the tracking direction indicated by the X axis in the figure, the point of action of the force generated by the tracking coil is matched with the center of gravity of the movable body. The movable body is moved in parallel. For this reason, when the movable body shifts from the neutral position in the focusing direction, the point of action of the force generated by the tracking coil deviates from the center of gravity of the movable body.
It was to be rotated around the axis indicated by the axis. As a result, the objective lens is tilted, causing an increase in jitter.

In place of the four metal rods, a combination of parallel leaf springs as shown in FIGS. 9 and 10 or a parallel leaf spring and a rotary bearing shown in FIGS. Although the restraining force against the rotational displacement around is strong, when the movable body is shifted from the neutral position in the focusing direction, basically, the force for rotating the movable body about the Z axis acts. As a result, although the amount of tilt in the low frequency region is small, tilt vibration is excited in a frequency region near 1 KHz, and as a result, the control operation is unstable.

The present invention has been made in view of such circumstances,
The purpose is to realize a structure in which the neutral position does not change while holding down the Q value small, and to prevent the balance of force from being lost even in a state shifted in the focus direction or the tracking direction, thereby preventing the lens from tilting, Accordingly, an object of the present invention is to provide an objective lens driving device having a simple configuration, which facilitates a servo pull-in operation at the start of a control operation, and achieves stable control characteristics.

[Structure of the Invention] (Means for Solving the Problems) In the objective lens driving device of the present invention, electric power is supplied to the plurality of coils of a movable body including a plurality of coils and an optical system including at least one objective lens. A movable body that supplies a signal and drives the objective lens in two directions, that is, a radial direction and a vertical direction of the optical recording medium, and moves the objective lens in the radial direction of the optical recording medium to fix the objective lens. In the objective lens driving device realized by rotation about the principal axis of inertia, one end is fixed to the movable body, and has a hinge for obtaining a restoring force against rotation about a central axis coaxial with the principal axis of inertia. A hinge member configured, a parallel leaf spring having one end fixed to the other end of the hinge member and having a supporting and restoring force of the movable body in a vertical direction, and fixing the other end of the parallel leaf spring. And the hinge is arranged inside both fixed ends of the parallel leaf spring, and the rotation center axis of the hinge and one end of the parallel leaf spring are arranged close to each other. Things.

(Function) According to the objective lens driving device of the present invention, the small size and the weight of the movable body can be reduced by arranging the hinge inside the both fixed ends of the leaf spring. Further, by arranging one end of the parallel leaf spring and the rotation center axis of the hinge close to each other, the hinge is arranged inside both the fixed ends of the leaf spring as described above, so that the movable body including the objective lens can be moved. Rolling does not occur for each operation in the radial direction (tracking direction) and the vertical direction (focus direction), thereby improving control characteristics.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a front view of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line CC in FIG. 1, FIG. 3 is an exploded perspective view, and FIG. It is a perspective view showing the whole.

In these figures, 11 is a yoke formed of a magnetic material. The objective lens 13 is fixed to one end 121 of the movable body 12. The hinge member 140 including the hinge 14 having a rotation center axis parallel to the optical axis direction of the objective lens 13 is made of an elastic material, for example, a synthetic resin. This hinge member 140
One end 15 of the movable body 12 is fixed to the other end 122 of the movable body 12 by a fixing means such as press-fitting or bonding. The other end 16 of the hinge member 140 is connected to one end 171a, 171b of two parallel leaf springs 17a, 17b. The other end portions 172a, 172b of the parallel leaf springs 17a, 17b are fitted and fixed to the pins 11a, 11b implanted in the yoke 11 by the fixing member 18.

That is, the hinge member 140 is disposed inside the fixed ends 171a, 171b and 172a, 172b of the parallel leaf springs 17a, 17b, and one end of the parallel leaf spring and the rotation center axis of the hinge (141 in FIG. 1).
Are placed in close proximity.

And, as described above, the inertia main axis of the movable body 12 and the hinge
14 is arranged coaxially, and by arranging the rotation center axis 141 of the hinge 14 and the one ends 171a, 171b of the parallel leaf springs 17a, 17b close to each other, for example, the objective lens drive of the present invention In the optical playback device incorporating the device, it shows high stability characteristics even with vibration due to high-speed access of the optical system including the objective lens and movement in the focus direction,
The range of follow-up control can be greatly expanded.

Further, focusing coils 19a and 19b and tracking coils 20a and 20b are fixed to the movable body 12 at positions symmetrical to each other with respect to the center of inertia of the movable body 12. The inner yoke 11 is inserted into the yoke 11 such that a certain interval is provided inside the focusing coils 19a and 19b.
21a and 21b protrude. And the inner yokes 21a, 21b
Outside yokes 22a and 22b are provided at positions facing the inner yokes 21a and 21b with the focusing coils 19a and 19b and the tracking coils 20a and 20b interposed therebetween.
Magnets 23a and 23b are fixed to surfaces of the outer yokes 22a and 22b facing the inner yokes 21a and 21b.

The external connection of the tracking coils 20a and 20b and the focusing coils 19a and 19b is performed by flexible sheets 24a and 24b.

In the objective lens driving device according to the embodiment of the present invention, the movement of the objective lens in the radial direction of the recording medium is performed with the rotation center axis (141 in FIG. 1) of the hinge as the rotation center. A leaf spring is used. The hinge may be configured as a leaf spring. Further, the hinge having a restoring force against the rotation about the inertia main axis and the parallel leaf spring may be integrally formed by injection molding, whereby the assembling process can be reduced and the cost can be reduced.

[Effects of the Invention] The present invention has the following advantages.

By arranging the hinge inside both fixed ends of the leaf spring, the size and the weight of the movable body can be reduced. Further, by arranging one end of the parallel leaf spring and the rotation center axis of the hinge close to each other, the hinge is arranged inside both the fixed ends of the leaf spring as described above, so that the movable body including the objective lens can be moved. Rolling does not occur for each operation in the radial direction (tracking direction) and the vertical direction (focus direction), thereby improving control characteristics.

[Brief description of the drawings]

1 is a front view of the objective lens driving device of the present invention, FIG. 2 is a sectional view of the objective lens driving device of the present invention, FIG. 3 is an exploded perspective view of the objective lens driving device of the present invention, and FIG. FIG. 5 is a perspective view of an objective lens driving device according to the present invention, FIG. 5 to FIG. 7 are diagrams showing a conventional objective lens driving device, FIG. 8 is a diagram showing another conventional objective lens driving device, FIG. 10 is a diagram showing another conventional objective lens driving device, and FIGS. 11 and 12 are diagrams showing another conventional objective lens driving device.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Koichi Tamai 72 Horikawacho, Saiwai-ku, Kawasaki City Inside Toshiba Horikawacho Plant (72) Inventor Hiroshi Matsuo 72 Horikawacho, Saiwai-ku, Kawasaki City Toshiba Horikawacho Plant (72) Inventor Akihiko Okumura 72 Horikawa-cho, Yuki-ku, Kawasaki-shi Toshiba Electronics Device Engineering Co., Ltd. (72) Inventor Seiichi Takakuwa 72 Horikawa-cho, Yuki-ku, Kawasaki-shi Inside Toshiba Electronics Device Engineering Co., Ltd. ) References JP-A-62-40627 (JP, A)

Claims (1)

(57) [Claims] 1. An electric signal is supplied to said plurality of coils of a movable body having a plurality of coils and an optical system including at least one objective lens, and said objective lens is moved in a radial direction and a vertical direction of an optical recording medium. An objective lens driving device for driving the objective lens in the radial direction of the optical recording medium by rotating the movable body for fixing the objective lens around a principal axis of inertia. A hinge member fixed to the body, for obtaining a restoring force against rotation about a rotation center axis coaxial with the inertia main axis, a hinge member made of an elastic body, and one end fixed to the other end of the hinge member A parallel leaf spring having a supporting and restoring force of the movable body with respect to a vertical direction, and a member for fixing the other end of the parallel leaf spring. An objective lens driving device, which is disposed on the side of the object and the rotation center axis of the hinge and one end of the parallel leaf spring are disposed close to each other.