JP2004164710A - Device for driving objective lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a peak on a frequency characteristic of a high order resonance without adding a particular structure to a lens holder with an objective lens mounted thereon. <P>SOLUTION: In a device for driving an objective lens for supporting a lens holder 2 to hold an objective lens 1 by elastic support members 6a-6b fixed to a fixing block 7, the position with an adhesive 10 for adhering the objective lens 1 to the lens holder 2 is coated thereon is set at a place at which variations in the high order resonance is reduced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an objective lens driving device equipped with an objective lens for converging light in an optical recording / reproducing apparatus for recording and reproducing information by irradiating a recording medium with a converged light beam.
[0002]
[Prior art]
In recent years, DVDs and the like that can record information seven times or more on a disk of the same size as a compact disk have appeared. In addition, devices that can record and reproduce information at a speed several tens of times faster than a compact disk have appeared.
A high control band is required for an objective lens driving device used for such a high-density, high-transfer-rate optical recording / reproducing device. At this time, a problem is high-order resonance due to elastic resonance of the movable portion of the objective lens driving device. In order to raise this higher-order resonance frequency to the highest possible frequency,
(1) A method in which the movable part is made of a material having a high Young's modulus and lightness
{Circle around (2)} There is a method of increasing the rigidity of the movable part by making the movable part into a shape without holes, notches, and the like.
It has also been proposed to prevent the vibration of resonance of the lens holder from being transmitted to the objective lens to reduce the influence of resonance on the objective lens.
[0003]
An objective lens driving device in which measures for increasing the higher-order resonance frequency are taken will be described below with reference to the drawings. FIG. 5 is an exploded perspective view of an objective lens driving device configured by employing the above method, and FIG. 6 is a top view thereof. The objective lens 101 is fixed to a lens holder 102 around which a focus coil 103 is wound with an adhesive 110 such as an ultraviolet curing resin. In this prior art example, the application positions of the adhesive are two places passing through a center line parallel to the tracking direction (Y-axis direction). Track coil holders 104 around which a track coil 105 is wound are adhesively fixed to the left and right of the lens holder 102. The movable part 111 is configured as described above. The movable portion 111 has a substantially cubic shape without a cutout or a hole for passing a magnetic circuit, and has a shape with high rigidity.
[0004]
Elastic support members 106a, 106b, 106c, 106d made of a metal elastic material are adhered to the upper and lower portions of the protrusion 104a of the track coil holder 104, respectively. The other ends of the elastic support members 106a, 106b, 106c, 106d are fixed to a fixed block 107.
Magnets 109a and 109b magnetized as shown in the figure are fixed to the yoke 108, respectively. The fixed block 107 is fixed to the yoke 108.
By energizing the focus coil 103 and the track coil 105 via the elastic support members 106a, 106b, 106c, and 106d, an electromagnetic force is generated by the magnetic circuit of the magnets 109a and 109b, and the elastic support members 106a, 106b, 106c, and 106d. Is driven in the illustrated Z direction (focusing direction) and Y direction (tracking direction).
[0005]
As a measure for increasing the higher-order resonance frequency, the length of the side wall of the lens holder on the side through which light passes is shortened and the thickness thereof is increased, and the thickness of the side wall on the opposite side is increased. Increasing the length and reducing the thickness (see, for example, Patent Document 1) is a measure for preventing the resonance of the lens holder from being transmitted to the objective lens. It has been proposed to provide a damping slit extending in a direction orthogonal to the tracking direction and the focusing direction so that a displacement portion due to secondary resonance is located near the center of the damping slit (for example, see Patent Document 2). ing.
[0006]
[Patent Document 1]
JP 2001-216665 A (page 4, right column, FIGS. 2 to 4)
[Patent Document 2]
JP 2000-268383 A (page 6, left column, FIGS. 5 to 7)
[0007]
[Problems to be solved by the invention]
FIG. 7 shows a deformation contour map in the focusing direction of the movable portion 111 at a higher-order resonance frequency when the objective lens driving device shown in FIGS. 5 and 6 is driven in the focusing direction. The deformation near the center of each side is the largest, and the deformation is small on the diagonal line and the lowest at the center point. An adhesive 110 for fixing the objective lens 101 to the lens holder 2 is applied to a place where deformation is large, and fixes the objective lens 1 to the lens holder 102. In such a configuration, the deformation of the lens holder 102 is transmitted to the objective lens 101 as it is, and appears as a large peak in frequency characteristics. There is a problem that a high control band cannot be secured if the frequency characteristic has a large peak.
[0008]
Further, in the above-described Patent Documents 1 and 2, an opening for passing a yoke through the lens holder is provided. In the structure described in Patent Document 2, slits are further formed at two places. Since the rigidity is reduced in the structure having many openings and slits, it is difficult to increase the higher-order resonance frequency. In addition, in any case, in addition to the opening for the yoke, it is necessary to change the shape of the side wall or provide a slit, so that the structure becomes complicated, and a mold for forming the lens holder becomes expensive. There is a problem.
An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a high-order resonance frequency characteristic peak without adding a special structure to a lens holder on which an objective lens is mounted. Is to suppress the effects of
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a movable section on which an objective lens is mounted, support means for supporting the movable section, and a drive system for driving the movable section in a focusing direction and a tracking direction. In a plurality of higher-order resonance frequencies due to elastic resonance of the movable part, at the higher-order resonance frequency having the largest resonance peak, the objective lens is located at a position where deformation at the higher-order resonance frequency is small. An objective lens driving device characterized by being fixed is provided.
Preferably, the objective lens is fixed on a diagonal line of a substantially rectangular upper surface of the movable portion. Preferably, the movable section has a substantially cubic shape without a hole into which a magnetic circuit constituting a drive system for driving the movable section in the focusing direction and the tracking direction is inserted. More preferably, the objective lens is fixed to the movable portion with an adhesive.
[0010]
[Action]
According to the present invention, since the objective lens is fixed at a position where the deformation of the movable portion at the higher-order resonance is small, the deformation of the movable portion at the higher-order resonance is transmitted to the objective lens via a fixing material such as an adhesive. As a result, the peak of resonance in the objective lens can be suppressed low.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an exploded perspective view of one embodiment of the present invention, and FIG. 2 is a top view thereof. In each figure, the Z axis indicates the focusing direction and the Y axis indicates the tracking direction. The objective lens 1 is fixed to a lens holder 2 around which a focus coil 3 is wound with an adhesive 10. The application positions of the adhesive 10 are small places where the deformation of the lens holder 2 is small as shown in the focusing direction deformation contour diagram shown in FIG. 4, that is, four X-shaped positions shown by a dashed line in the figure. In order to observe the state of deformation of the lens holder 2 at such a higher-order resonance frequency, it can be observed by a simulation by FEM analysis or the like, a two-dimensional scanning Doppler displacement meter, or the like.
[0012]
Track coil holders 4 around which a track coil 5 is wound are adhered and fixed to the left and right sides of the lens holder 2, and these constitute a movable portion 11. Here, a straight line parallel to the Z axis passing through the center of gravity of the movable portion 11 coincides with a straight line parallel to the Z axis passing through the center of gravity of the objective lens. The movable portion 11 has a substantially cubic shape without a notch, and has a high rigidity. Plate-like elastic support members 6a, 6b, 6c, and 6d made of a metal elastic material are adhered above and below the protrusion 4a of the track coil holder 4. The other ends of the elastic support members 6a, 6b, 6c, 6d are fixed to a fixed block 7.
When the focus coil 3 and the track coil 5 are energized, an electromagnetic force is generated by the magnetic circuit of the magnets 9a and 9b, and the movable portion 11 supported by the elastic support members 6a, 6b, 6c and 6d moves in the Z direction shown (focusing direction). ), And driven in the Y direction (tracking direction).
[0013]
FIG. 4 shows a deformation contour diagram of the movable portion 11 at a higher-order resonance frequency having the largest resonance peak among a plurality of higher-order resonances caused by elastic resonance of the movable portion when the movable portion 11 is driven in the focusing direction. . The objective lens 1 is fixed to the movable part 11 with an adhesive 10 at a portion where its deformation is small. Therefore, the degree to which the deformation of the movable portion 11 is transmitted to the objective lens 1 can be reduced, and the resonance peak of the objective lens can be reduced.
FIG. 3 shows a frequency characteristic in the focusing direction from 10 kHz to 100 kHz when the movable section 11 is driven in the focusing direction (the measurement point is at the center of the objective lens). In the figure, the solid line shows the case according to the embodiment of the present invention, and the broken line shows the case of the prior art example shown in FIG. As shown in FIG. 3, the peak on the frequency characteristic can be reduced by 10 dB.
[0014]
Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and can be appropriately modified without departing from the gist of the present invention. For example, in the embodiment, the focus coil and the track coil are mounted on the lens holder side, but they may be mounted on the fixed part side and the magnet may be mounted on the lens holder side. Further, in the embodiment, the objective lens is bonded and fixed at four positions, but may be fixed at only two positions on one diagonal line of the lens holder. Further, the objective lens may be fixed to the lens holder by fixing means other than the adhesive.
[0015]
【The invention's effect】
As described above, in the objective lens driving device of the present invention, the position at which the objective lens is fixed to the lens holder is set to a position where the amount of deformation of the lens holder at the higher resonance frequency is small. The degree to which the deformation of the lens holder is transmitted to the objective lens can be reduced without adding a special structure and without using a complicated and expensive mold or the like, thereby reducing the amplitude peak at the higher resonance frequency. be able to.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of an embodiment of the present invention.
FIG. 2 is a top view of one embodiment of the present invention.
FIG. 3 shows a frequency characteristic in a focusing direction of 10 kHz to 100 kHz according to an embodiment of the present invention and a prior art.
FIG. 4 is a contour diagram in the focusing direction at a higher-order resonance frequency of the movable unit according to the embodiment of the present invention.
FIG. 5 is an exploded perspective view of a prior art example of the present invention.
FIG. 6 is a top view of a prior art example of the present invention.
FIG. 7 is a deformation contour diagram in the focusing direction at a higher-order resonance frequency of the movable section according to the prior art example of the present invention.
[Explanation of symbols]
1, 101: Objective lens, 2, 102: Lens holder, 3, 103: Focus coil, 4, 104: Track coil holder, 4a, 104a: Projection, 5, 105: Track coil, 6a, 6b, 6c, 6d , 106a, 106b, 106c, 106d: elastic support member, 7, 107: fixed block, 8, 1081: yoke, 9a, 9b, 109a, 109b: magnet, 10, 110: adhesive, 11, 111: movable part

Claims (8)

A movable section on which an objective lens is mounted; supporting means for supporting the movable section; and a drive system for driving the movable section in a focusing direction and a tracking direction, and a plurality of higher-order resonances caused by elastic resonance of the movable section. An objective lens driving device, wherein the objective lens is fixed to the movable portion at a position where deformation at the higher-order resonance frequency is small at a higher-order resonance frequency having the largest resonance peak among the frequencies. 2. The objective lens driving device according to claim 1, wherein the objective lens is fixed on a diagonal line of a substantially rectangular upper surface of the movable portion. 3. The objective lens driving device according to claim 1, wherein the objective lens is fixed at four points on a diagonal line. The objective lens driving device according to claim 1, wherein the objective lens is adhered to the movable portion with an adhesive. The movable part does not have a hole into which a magnetic circuit forming a drive system for driving the movable part in the focusing direction and the tracking direction is inserted, and has a substantially cubic shape. Item 5. The objective lens driving device according to any one of Items 1 to 4. The objective lens according to any one of claims 1 to 5, wherein a straight line parallel to a focusing direction passing through a center of gravity of the movable portion coincides with a straight line parallel to a focusing direction passing through the center of gravity of the objective lens. Drive. 7. The objective lens driving device according to claim 1, wherein one track coil is fixed to each side surface of the movable portion in the tracking direction. The objective lens driving device according to claim 1, wherein one focus coil is wound around the outer periphery of the movable portion.

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