JP2690771B2 - Lens drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device, and is particularly suitable for enhancing the controllability of a lens for forming a light spot used in an optical head in an optical information recording / reproducing device. Lens driving device.

[Prior Art] FIG. 7 is an exploded perspective view of a conventional lens driving device.
In the figure, (1) is an objective lens for forming a laser beam spot on an optical information recording medium (not shown),
A lens (3) is rotatably and slidably held by a support shaft (5) via a bearing (4) in the center thereof and holds the objective lens (1) at a position eccentric to the support shaft (5). Holder, (2) is objective lens (1) and support shaft (5) on lens holder (3)
Counterweight to balance around,
(6) is a support rubber for elastically holding the lens holder (3), and (7) is a permanent focus control for slidingly driving the lens holder (3) along the support shaft (5) in the direction of arrow A. magnet,
(8a) and (8b) are track control permanent magnets that rotate the lens holder (3) around the support shaft (5) in the direction of arrow B, and (9) is a support shaft (5) and focus control permanent magnet. A focus control yoke for holding (7), (10) is attached to the lens holder (3) and is attached to the focus control permanent magnet (7) along the support shaft (5) on the lens holder (3) by magnetic force. Focusing control coils that give a driving force in the focusing control direction, and as a result, a movement in the focusing control direction to the objective lens (1), (11a) and (11b) are track control permanent magnets (8
A track that gives a rotational force about the support shaft (5) to the lens holder (3) by the magnetic force acting between a) and (8b), and as a result, gives a movement in the track control direction to the objective lens (1). Control coils, (12a) and (12b) are track control yokes for fixing track control permanent magnets (8a) and (8b), and (13a), (13b), (13c), and (13d) are tracks. A support rubber mounting portion for fixing the support rubber (6) holding the lens holder (3) integrally formed on the fixing base (14) together with the control yokes (12a), (12b),
Reference numeral (15) is a hole for guiding the laser light to the objective lens (1) through the fixed base (14).

Next, the operation of the above configuration will be described.

When the objective lens (1) defocuses with respect to an optical recording medium (not shown), a defocusing detecting means (not shown) supplies a control current according to the defocusing amount to the focus control coil (10). It As a result, a magnetic force acts between the focus control coil (10) and the focus control permanent magnet (7), and the lens holder (3) moves along the support shaft (5) in the direction of arrow A, that is, the objective lens ( It is slidably driven in the focus control direction of 1). Then, the focus of the objective lens (1) is optimally controlled.

On the other hand, when the objective lens (1) causes a track shift with respect to the optical recording medium (not shown), the track control coil (11a), track tracking coil (11a),
A control current corresponding to the track deviation amount is supplied to (11b). As a result, track control coils (11a), (11b)
The magnetic force acts between the track control permanent magnets (8a) and (8b) attached to the track control yokes (12a) and (12b), and the lens holder (3) is centered on the support shaft (5). Is driven to rotate in the direction of arrow B. Then, the objective lens (1) is driven in the track control direction to optimally control the track.

The support rubber (6) elastically supports the lens holder (3), and when the focus control coil (10) is de-energized, the lens holder (3) returns to the neutral state in the focus control direction. ·Hold. On the other hand, when the track control coils (11a) and (11b) are de-energized, the lens holder (3) is rotated to return / hold the track control direction to the neutral state.

As described above, a light beam from a light emitting device (not shown) on the hole (15) side, for example, a semiconductor laser, is spot-formed on the optical information recording medium (not shown) through the objective lens (1) whose focus and track are controlled. Then, optical writing or reading of information is performed.

[Problems to be Solved by the Invention] Since the conventional lens driving device is configured as described above, there is a problem that the influence of the structural resonance of the lens holder (3) appears significantly on the objective lens (1). there were. This structural resonance has a characteristic that even if the resonance frequency can be increased by the shape and the material, it cannot be basically avoided in a structure. Moreover, in recent years, the optical head has been required to have a lightweight and thin design, and it is extremely difficult to set the resonance frequency of the movable portion to 10 kHz or more.

In particular, in the actuator structure as shown in FIG. 7,
The structural resonance in which the lowest frequency appears is often the bending first-order mode in the focus control direction as shown by the solid line in the explanatory view of FIG. 8, and the objective lens (1) itself cannot avoid deformation. The focus control direction at the position C (FIG. 8) at the center of the objective lens (1) shown in the resonance characteristic diagram of FIG. 9, that is, arrow A
As can be seen from an example of frequency characteristics during directional driving, the resonance peak amount Q1 was about 20 to 25 dB. When resonance having a large peak amount appears on the objective lens (1), the servo characteristics become remarkably unstable and sometimes oscillation occurs.

The present invention solves the problems of the prior art as described above, reduces the amount of deformation of the objective lens itself due to the structural resonance of the bending control first-order mode of the movable portion, and displaces the objective lens due to the deformation of the movable portion. It is an object of the present invention to obtain a highly reliable lens drive device having excellent servo characteristics, in which the amount of peaks of the gain can be suppressed in the frequency characteristics as a result.

[Means for Solving the Problems] In order to solve the above problems, a lens driving device according to the present invention includes a movable holder that is rotatable about a predetermined axis and is movably held along the axis. On the movable holder, a lens having an optical axis substantially parallel to the axis, the lens being provided at a position decentered from the axis of the movable holder,
A counterweight provided at a position symmetrical to the lens with respect to the axis, first driving means for performing track deviation control by moving the movable holder around the axis, and the movable holder with the axis A second driving means for controlling defocus by moving the movable holder along the axis, and fixing the center of the lens substantially above the node position of the structural resonance of the bending holder in the focus control direction bending primary mode of the movable holder; And a lens mounting means fixed to the.

[Operation] In the above means, the lens driving device of the present invention is apt to appear at a low frequency, and the influence of structural resonance of the sliding direction bending first-order mode, which makes the servo characteristics unstable, is provided by providing the lens attaching means near the resonance node. , Make the lens less susceptible to structural resonances.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is an exploded perspective view of a lens driving device according to an embodiment of the present invention, FIG. 2 is a partial plan view of FIG. 1, and FIG. 3 is a longitudinal sectional view taken along line XX of FIG. , FIG. 4 shows Y- in FIG.
It is a longitudinal cross-sectional view taken on the Y line. In each figure, (3a),
(3b) is precisely positioned and adhered to the node position of the structural resonance of the bending primary mode in the sliding direction of the movable part including the lens holder (3), that is, the focus control direction, and the objective lens (1) is attached and held. This is an objective lens mounting part. The other structure is the same as the conventional structure shown in FIG.

In such a configuration, the basic operation is the same as the configuration in FIG. 7, and by applying a control current to the focus control coil (10), the movable part including the lens holder (3) becomes a support shaft (5). Is driven in the sliding direction, that is, the focus control direction. On the other hand, the track control coils (11a), (11
By applying a control current to b), the lens holder (3) is driven around the support shaft (5) in the rotation direction, that is, the track control direction. Then, as in the conventional case, structural resonance occurs due to the driving of the movable part including the lens holder (3) in the focus control direction, and the structural resonance in the bending first-order mode is likely to occur particularly near a low frequency.

The objective lens mounting portions (3a) and (3b) prevent the influence of this structural resonance from reaching the objective lens (1). Here, the operation of the objective lens attachment portions (3a) and (3b) will be described based on the explanatory view of FIG. 5 and the structural resonance characteristic diagram of FIG. By the way, Figure 5 shows the lens holder (3).
FIG. 6 shows an example of the frequency characteristic in the structural resonance, with the solid resonance showing the state of the structural resonance of the movable part.

Structural resonance of the movable portion as shown in FIG. 5 often has a bending primary mode in the sliding direction, that is, the focus control direction at a low frequency. In this mode, there are two vibration nodes where the displacement due to deformation is zero. In the configuration of the present embodiment, the objective lens mounting portions (3a) and (3b) are so small that the objective lens (1) can be stably mounted at one point of this vibration node.
And the objective lens (1) is attached thereto. Therefore, the displacement due to resonance is small in the vicinity of the center of the objective lens (1), and the amount of deformation of the objective lens (1) itself is small. As shown in FIG. 6, the frequency characteristic in the focus control direction at the point C near the center of the objective lens (1) can suppress the resonance peak amount Q of the bending primary mode to 10 dB or less.

As described above, the objective lens mounting portion (3a) is provided in the vicinity of the node of the structural resonance of the bending first mode on the lens holder (3).
By attaching (3b) and holding the objective lens (1) on it, the structural resonance of the bending primary mode when the movable part including the lens holder (3) is driven in the focus control direction of the objective lens (1). Is suppressed from affecting the objective lens (1), and the controllability of the objective lens (1) is improved.

EFFECTS OF THE INVENTION As described above, according to the present invention, the minute lens mounting portion is provided in the vicinity of the resonance node of the bending mode in the focus control direction of the movable portion to hold the objective lens. The objective lens is less likely to be affected by the deformation of the structural resonance of the bending primary mode of the movable part, so that stable servo characteristics are obtained and controllability is improved.

[Brief description of the drawings]

1 is an exploded perspective view of a lens driving device according to an embodiment of the present invention, FIG. 2 is a partial plan view of FIG. 1, and FIG.
FIG. 4 is a vertical sectional view taken along line XX in FIG. 4, and FIG. 4 is YY in FIG.
5 is a longitudinal sectional view obtained by a line, FIG. 5 is an explanatory view showing a state of structural resonance of a movable part by a solid line, and FIG. 6 is a structural resonance characteristic diagram showing an example of frequency characteristics in the structural resonance in the configuration of FIG. , 7th
FIG. 8 is an exploded perspective view of a conventional lens driving device, and FIG.
FIG. 9 is an explanatory diagram of structural resonance in the configuration shown in FIG. 9, and FIG. 9 is a structural resonance characteristic diagram showing an example of frequency characteristics in structural resonance in the configuration shown in FIG. (1) is an objective lens, (2) is a counterweight,
(3) is a lens holder, (3a) and (3b) are objective lens mounting parts, (4) is a bearing, (5) is a support shaft, (6) is support rubber, (7) is a permanent magnet for focus control, (8a) and (8b) are permanent magnets for track control, (9) is a yoke for focus control,
(10) is a focus control coil, (11a), (11b) is a track control coil, (12a), (12b) is a track control yoke, (13a), (13b), (13c), (13d). Is a support rubber mounting part, (14) is a fixed base, and (15) is a hole. In the drawings, the same reference numerals indicate the same or corresponding parts.

Continuation of front page (56) Reference JP-A 64-52234 (JP, A) JP-A 63-13137 (JP, A) JP-A 61-198441 (JP, A) JP-A 61-198438 (JP , A) Actual development Sho 63-153321 (JP, U)

Claims (1)

(57) [Claims] 1. A movable holder, which is rotatable about a predetermined axis and is movably held along the axis, has an optical axis substantially parallel to the axis, and is eccentric from the axis of the movable holder. A lens provided at a position, a counterweight provided on the movable holder at a position symmetrical to the lens with respect to the axis, and a track shift by moving the movable holder around the axis. First drive means for performing control, second drive means for performing defocus control by moving the movable holder along the axis, and bending center of the lens substantially in the focus control direction of the movable holder. A lens driving device, comprising: a lens mounting means fixed on the movable holder, which is fixed on a node position of structural resonance of a mode.