JP2001060329A - Damping structure of objective lens supporting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a damping structure of an objective lens supporting device capable of effectively absorbing vibration energy concerning the pitching of a movable part having an objective lens and stably projecting an optical beam spot on an information recording surface of a recording medium. SOLUTION: In an objective lens supporting device which hangs displacably and supports a movable part having an objective lens 5 through a plurality of elastic supporting members 3 with respect to a supporting member 9 fixed to a base 1a, the base 1a and the supporting member 9 are separately formed and at the same time, at least in a part of them they are mutually connected through a buffer member 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a compact disc (CD) and a digital versatile disc (DVD).
In an optical head that records and reproduces information on a recording medium such as an optical disc such as an optical disc and a magneto-optical disc such as a mini disc (MD), in order to drive the objective lens in a desired direction, The present invention relates to a vibration damping structure in an objective lens supporting device that supports an objective lens so as to be displaceable.

[0002]

2. Description of the Related Art As a conventional objective lens driving device having an objective lens supporting device, for example, FIGS.
There is something like that shown in FIG. 11 is a perspective view of the entire apparatus, FIG. 12 is an exploded perspective view of a main part of the apparatus, and FIG. 13 is an exploded perspective view showing an arrangement relationship between a drive coil and a permanent magnet. This objective lens driving device is a so-called four-wire supporting type moving coil system. A movable portion including a lens holder 4 that supports an objective lens 5 is suspended and supported by a support member 9. The support member 9 is provided with a connection hole 16 penetrating in the Z-axis direction. For example, as shown in FIG.
Are fitted in the connection holes 16, and are connected to the base 1a by press-fitting, bonding, or tightening with a set screw 14 as shown.

A connection board 1b is provided on a side surface of the support member 9, and the connection board 1b is paired with each other in the Y-axis direction and extends in the X-axis direction adjacent to the Z-axis direction. Be
2 pairs of elastic support members 3 made of alloy, Cu-P alloy, etc.
Are connected at predetermined connection points D spaced apart from each other, for example, so as to be located at the vertices of a rectangle. A lens holder 4 is fixed in the vicinity of the other ends of the four elastic support members 3 so that the objective lens 5 held by the lens holder 4 is moved to an information pit row (track) of a disc-shaped recording medium (not shown). For example, a tracking (Y-axis) direction parallel to the radial direction,
An objective lens supporting device is configured to be suspended and supported so as to be displaceable in a focus (Z-axis) direction substantially parallel to the optical axis of the objective lens 5.

In order to drive the lens holder 4 in the Y-axis direction and the Z-axis direction, for example,
A magnetic yoke 8a made of e, Ni, Co, an alloy containing them, or ferrite is provided. The magnetic yoke 8a is provided with two legs that stand apart in the tangential (X-axis) direction and stand in the Z-axis direction, and a return path portion 8 that connects one end of these legs in the Z-axis direction to each other.
and r. The magnetic yoke 8a is disposed, for example, with Nd-Fe-B such that both legs penetrate into the opening 4a of the lens holder 4 and different magnetic poles face the inner surfaces of the legs via a gap G. Two driving permanent magnets 2a and 2b made of an alloy or the like are provided respectively. Further, the other ends of the two legs of the magnetic yoke 8a are connected to each other via a magnetic cover 8b having a substantially I-shape, and the magnetic yoke 8a, the magnetic cover 8b, and the driving permanent magnets 2a and 2b are used. A magnetic circuit having a closed magnetic path passing through the gap G and the return path portion 8r and a closed magnetic path passing through the gap G and the magnetic cover 8b are formed.

Further, the lens holder 4 has two openings 4a for driving the objective lens 5 in the tracking direction to position the optical axis of the objective lens 5 on the center line of a desired track of the recording medium. Tracking coil 6,
By driving the objective lens 5 in the focus direction, the objective lens 5
And a focusing coil 7 for focusing on the information pit surface.

The focusing coil 7 is provided around a bobbin 11 made of resin or the like so as to be wound around an axis in the Z-axis direction. Two tracking coils 6 are wound around the bobbin 11 respectively around an axis in the X-axis direction. It is provided outside the focusing coil 7 by turning.

The bobbin 11 on which the two tracking coils 6 and the focusing coil 7 are mounted has a conductor portion extending on one side of the focusing coil 7 in the Y-axis direction and a Z-axis portion adjacent to the two tracking coils 6. The wire portion extending in the direction is fitted and fixed in the opening 4a of the lens holder 4 so as to be positioned in the gap G of the magnetic circuit, and the tracking coil 6 and the focusing coil 7 and the magnetic circuit constitute driving means. ing.

According to such a configuration, when the focusing coil 7 is energized, the current flowing through the focusing coil 7 in the Y-axis direction and the driving permanent magnets 2a, 2b
Generates an electromagnetic force in the Z-axis direction in the focusing coil 7 by the interaction with the magnetic flux in the X-axis direction, thereby causing the lens holder 4 and thus the objective lens 5 to move substantially perpendicularly to the recording surface of the recording medium (not shown). To be displaced in parallel with the optical axis direction.

Similarly, when the tracking coil 6 is energized, the interaction between the current flowing in the tracking coil 6 in the Z-axis direction and the magnetic flux in the X-axis direction by the driving permanent magnets 2a and 2b causes the tracking coil 6 to interact. An electromagnetic force in the Y-axis direction is generated at 6 so that the lens holder 4 and thus the objective lens 5 are displaced in the Y-axis direction, that is, in the direction crossing the tracks of the recording medium (not shown).

In the objective lens driving device described above, the movable portion having the objective lens 5 is displaceably suspended and supported by the objective lens supporting device having the four linear elastic support members 3. For example, unlike a shaft sliding type objective lens supporting device which is another typical supporting structure, friction with the shaft portion does not occur when a movable portion including a lens holder or the like is displaced, and smooth and high resolution is achieved. Driving becomes possible.

However, the movable portion suspended and supported by the four elastic support members 3 corresponds to the sliding beam that generates an S-shaped flexure and generates lateral vibration, and the tip-added mass fixed to the tip of the sliding beam. Is configured as a linear vibration in the Y-axis direction, the Z-axis direction or the YZ composite direction, and a torsional vibration around the axis in the X-axis direction. For example, the structure is easy to resonate in a band of several tens Hz.

For this reason, in an objective lens supporting apparatus having such a suspension supporting structure, a damper is usually provided at both ends in the Y-axis direction of the supporting member 9 so as to surround two elastic supporting members 3 adjacent in the Z-axis direction. Cases 9a are respectively formed, and the connection substrate 1 is provided on the side surface of the support member 9 having the damper cases 9a.
b, the connecting board 1b is fixed to the supporting member 9, and the cushioning member 10 is provided inside the damper case 9a.
To absorb the above-mentioned vibration energy.

That is, in the damper case 9a, a buffer member 10 having a large loss elastic modulus, such as silicon gel, is placed.
By injecting and filling so as to wrap the elastic support member 3 extending in the X-axis direction, the vibration energy due to the flexural resonance of the elastic support member 3 is absorbed by the shear deformation of the cushioning member 10 and converted into heat. Intense resonance movement is suppressed.

[0014]

However, when the focusing coil 7 is driven, for example, not only the vibration of the elastic support member 3 as described above, but also the support member fixed to the connection pin 13 as shown in FIG. 9 is also elastically deformed, so that the support member 9 is, for example, several hundred Hz to several kHz.
Resonance is likely to occur in the z band, causing rotational vibration around the Y axis of the objective lens 5, that is, pitching.
Therefore, for example, when the objective lens 5 is driven in the Z-axis direction at an acceleration including a frequency band component corresponding to the resonance frequency of the pitching, a rotational moment is generated around the Y-axis in the objective lens 5, and the optical axis rotates. Therefore, the operation becomes unstable.

However, the cushioning member 10 filled in the above-described damper case 9a is unlikely to cause effective shear deformation even when the support member 9 is elastically deformed, so that vibration energy accompanying such pitching is efficiently absorbed. Can not do. For this reason, the size and density of the spot irradiated on the information recording surface of the recording medium fluctuate due to the vibration displacement of the focal position of the recording and / or reproducing light beam due to these vibrations. There is a problem that the recording cannot be performed, the return light from the recording medium becomes unstable, the drive control ability is reduced, the reproduction signal is jittered, the S / N is reduced, and the performance of the optical head is impaired. Was.

An object of the present invention is to provide a vibration damping structure capable of solving the above-mentioned problems of the prior art, and to provide a support that contributes to rotational vibration (pitting) of the objective lens around the Y axis. An object of the present invention is to provide a vibration damping structure of an objective lens support device that can suppress the resonance of members and stably irradiate a light beam spot on an information recording surface of a recording medium.

[0017]

Means for Solving the Problems As a result of diligent research to achieve the above-mentioned object, the inventors have developed the present invention having the following contents as a summary. That is, according to the first aspect of the present invention, the movable portion having the objective lens is moved in the Y-axis direction and the Z-axis direction through an elastic support member extending in the X-axis direction.
In an objective lens supporting apparatus including a support member for suspending and supporting an axially movable member and a base to which the support member is connected, the base and the support member are formed separately, and both of them are at least. It is characterized in that some of them are connected to each other via a buffer member. According to the first aspect of the present invention, the buffer member interposed between the base and the support member can efficiently absorb the vibration energy caused by pitching, and suppresses the resonance of the support member, thereby reducing the recording medium. Is stably irradiated with the light beam spot.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. In the embodiment described below, the same members as those of the conventional example are denoted by the same reference numerals, and their arrangement and orientation are uniformly shown based on the same coordinate system as the conventional example. Also, some of the members that overlap with the conventional example are omitted.

The objective lens driving device using the objective lens supporting device according to the present invention is a so-called four-wire supporting type moving coil system, and the movable portion including the lens holder 4 for supporting the objective lens 5 is a supporting member. 9 for suspension. A connection hole 16 penetrating along the Z-axis direction is formed in the support member 9, and a connection pin 13 erected in the Z-axis direction on the base 1a is fitted into the connection hole 16.
The base 1a is connected to the base 1a by press-fitting, bonding, or by tightening with a set screw 14 as illustrated.

A counterbore 17 is formed at the upper end and the lower end of the opening of the connection hole 16 of the support member 9 at positions corresponding to the upper end and the lower end of the connection pin 13, that is, the counterbore 17 is formed. Drilled with a large hole diameter. In the counterbore 17, for example, a viscoelastic resin such as silicon gel or Mn-Cu
-Based alloy, an annular cushioning member 12 formed of a vibration-damping material such as a lead-based alloy is mounted, as shown in FIG.
The connection pin 13 is fitted and fixed together with the support member 9. Thus, connection between the base 1a side and the support member 9 side via the buffer member 12 is realized. In this case, the fitting margin may be appropriately set and press-fitted, or may be bonded with an adhesive or by melting, or may be tightened with a set screw 14 as shown in FIG. Good.

A connection board 1b is provided on a side surface of the support member 9. The connection board 1b is paired in the Y-axis direction and extends in the X-axis direction adjacent to the Z-axis direction. C
One end of each of the two pairs of linear elastic support members 3 made of a u-Be alloy, a Cu-P alloy, or the like is connected at a predetermined connection point D spaced apart so as to be located at, for example, a vertex of a rectangle. Have been.

A lens holder 4 is fixed in the vicinity of the other ends of the four elastic support members 3 so that the objective lens 5 held by the lens holder 4 can be moved to an information pit row on a disk-shaped recording medium (not shown). (Track), for example, a tracking (Y-axis) direction parallel to the radial direction, and a focus (Z-axis) substantially parallel to the optical axis of the objective lens 5.
And an objective lens supporting device that is suspended and supported so as to be displaceable in both directions.

In order to drive the lens holder 4 in the Y-axis direction and the Z-axis direction, for example,
A magnetic yoke 8a made of e, Ni, Co, an alloy containing them, or ferrite is provided. The magnetic yoke 8a includes two legs that stand apart in the tangential (X-axis) direction and stand in the Z-axis direction, and a return path portion 8 that connects one end of these legs in the Z-axis direction to each other.
and r.

The magnetic yoke 8a is disposed such that both legs penetrate into the opening 4a of the lens holder 4, and different magnetic poles face the inner surfaces of the legs via a gap G.
For example, two drive permanent magnets 2 made of an Nd-Fe-B alloy or the like
a and 2b are provided respectively.

Further, the other ends of the two legs of the magnetic yoke 8a have a substantially I-shaped magnetic cover (not shown).
The magnetic yoke 8a, the magnetic cover, and the driving permanent magnets 2a and 2b form an air gap G.
A magnetic circuit having a closed magnetic path passing through the return path portion 8r and a closed magnetic path passing through the gap G and the magnetic cover is formed.

Further, the lens holder 4 has two openings 4a for driving the objective lens 5 in the tracking direction to position the optical axis of the objective lens 5 on the center line of a desired track of the recording medium. And a focusing coil (not shown) for driving the objective lens 5 in the focusing direction to focus the objective lens 5 on the information pit surface.

The focusing coil is wound around a bobbin 11 made of resin or the like around the axis in the Z-axis direction. Two tracking coils are wound around the bobbin 11 around the axis in the X-axis direction. Provided outside the focusing coil 7.

A bobbin 11 on which the two tracking coils and the focusing coil are mounted includes a conducting wire portion extending on the side of the focusing coil in the Y-axis direction.
Adjacent to the two tracking coils, a conductor extending in the Z-axis direction is fitted and fixed to the opening 4a of the lens holder 4 so as to be located in the gap G of the magnetic circuit, and the tracking coil and the focusing coil And the magnetic circuit constitute the driving means.

According to such a configuration, when the focusing coil is energized, the interaction between the current flowing through the focusing coil in the Y-axis direction and the magnetic flux in the X-axis direction by the driving permanent magnets 2a and 2b causes the interaction. When an electromagnetic force in the Z-axis direction is generated in the focusing coil, the lens holder 4 and, consequently, the objective lens 5 are displaced in the Z-axis direction, that is, in the optical axis direction substantially perpendicular to the recording surface of the recording medium. .

Similarly, when the tracking coil is energized, an interaction between a current flowing through the tracking coil in the Z-axis direction and a magnetic flux in the X-axis direction by the driving permanent magnets 2a and 2b causes the tracking coil to have a Y-axis. When an electromagnetic force is generated in the axial direction, the lens holder 4 and, consequently, the objective lens 5 are displaced in the Y-axis direction, that is, in the direction crossing the track of the recording medium.

Thus, when the support member 9 attempts to start elastic deformation in the frequency band near the resonance point when driven in the focusing direction, the vibration energy is efficiently absorbed by the buffer member 12, so that the resonance Is suppressed. For this reason, the rotational vibration of the objective lens 5 around the Y axis, that is, the pitching phenomenon can be avoided. As a result, the objective lens 5 does not easily rotate around the Y axis, and the direction of the optical axis does not change, so that a stable operation can be performed.

Therefore, the fluctuation of the focal position of the recording and / or reproducing light beam is suppressed, and the size and density of the spot irradiated on the information recording surface of the recording medium are stabilized. Is maintained, and it is possible to avoid a reduction in drive control capability, a generation of a jitter in a reproduction signal, a reduction in S / N, and the like.

FIG. 3 shows a modification of the above-described first embodiment. The difference from this embodiment is that the support member 9 is directly connected to the connection pin 13 on a part of the inner wall of the connection hole 16. And the buffer member 12 is disposed in the connection hole 16. That is, the connection hole 16 of the support member 9
The lower end has a hole diameter substantially equal to that of the connection pin 13, and the upper end is formed in a liquid retaining portion 18 having a large hole diameter,
The support member 9 has a connection pin 13 at the lower end of the connection hole 16.
And a buffer member made of a viscoelastic resin such as silicone gel.
12 are filled.

With this configuration, when the support member 9 attempts to start elastic deformation in the frequency band near the resonance point when driven in the focusing direction, the vibration energy is efficiently absorbed by the buffer member 12. Therefore, the growth of resonance is suppressed. Therefore, the objective lens
The rotational vibration around the Y-axis, ie, the pitching phenomenon, can be avoided, and the direction of the optical axis does not change, so that a stable operation can be performed.

FIG. 4 shows another modification of the first embodiment. The difference from the first embodiment is that the connection pin 13 itself also serves as the buffer member 12. That is, base 1
In a, a connection pin 13 made of a damping material such as a Mn-Cu alloy or a lead alloy is extended in the Z-axis direction and has a hole diameter substantially equal to that of the connection pin 13. The hole 16 is fitted. Therefore, the base 1a and the support member 9 are connected via the connection pin 13 also serving as a buffer member. Also in this case, the fitting margin may be appropriately set and press-fitted, or may be bonded.

According to such a configuration, when the support member 9 attempts to start elastic deformation in the frequency band near the resonance point when driven in the focusing direction, the vibration energy is applied to the connection pin 13 which also serves as a buffer member. Since it is efficiently absorbed, resonance can be effectively suppressed. Therefore, the rotational vibration around the Y axis of the objective lens 5, that is, the pitching phenomenon can be avoided, and the direction of the optical axis does not change, so that a stable operation can be performed.

FIGS. 5 and 6 show an exploded perspective view and a sectional view of a second embodiment of the present invention.
In this embodiment, the connection between the base 1a and the support member 9 is performed by connection pins as in the first embodiment, but the form and arrangement of the buffer member are different from those of the first embodiment. I have. In this case, the cushioning member 22 is formed of a viscoelastic resin such as silicon gel, a Mn-Cu-based alloy, or a vibration-damping material such as a lead-based alloy into a rectangular sheet shape.
They are disposed between the base 1a and the lower surface of the support member 9 and between the upper surface of the support member 9 and the restraint plate 15, respectively.

That is, the sheet-like cushioning member 22 has an opening 22a corresponding to the position of the connection pin 13, and the restraining plate 15 has an opening 15a corresponding to the position of the connection pin 13. The connection pin 13 formed in the base 1a is inserted through the opening 22a and the connection hole 16 of the support member 9 and is fitted to the opening 15a formed in the restraint plate 15 while being restrained by the set screw 14. When the plate 15 is pressed toward the base 1a, the connection between the support member 9 and the base 1a is established.

According to such a configuration, when the support member 9 attempts to start elastic deformation in the frequency band near the resonance point when driven in the focusing direction, the vibration energy is efficiently absorbed by the buffer member 22. Therefore, resonance can be effectively suppressed. Therefore, objective lens 5
Can be avoided around the Y axis. Therefore, since the objective lens 5 is less likely to rotate around the Y axis, a stable operation in which the fluctuation of the direction of the optical axis is suppressed is possible.

FIGS. 7 and 8 show an exploded perspective view and a sectional view of a third embodiment of the present invention.
In this embodiment, the connection between the base 1a and the support member 9 is made not by the connection pins but by a rectangular connection plate 19 having a surface standing upright from the base 1a and having a surface extending in the X-axis direction. A viscoelastic resin such as silicon gel or Mn is provided between the connection plate 19 and the side surface of the support member 9 in the X-axis direction.
A cushioning member made of a damping material such as a Cu-based alloy or a lead-based alloy and formed in a sheet shape having substantially the same size as the connection plate 19;
32 are interposed.

In this case, the connection between the base 1a and the support member 9 is made from the outside of the support member 9 while the buffer member 32 is sandwiched between the connection plate 19 and the side surface of the support member 9 in the X-axis direction. This is done by a set screw 14 suitably screwed into the base 1a. That is, the base 1a and the support member 9 are fixed to each other by an appropriate tightening force of the set screw 14 and an adhesive force of the buffer member 32.

According to such a configuration, when the support member 9 attempts to start elastic deformation in the frequency band near the resonance point when driven in the focusing direction, the vibration energy is efficiently absorbed by the buffer member 32. Therefore, resonance can be effectively suppressed. Therefore, objective lens 5
Can be avoided around the Y axis. Therefore, since the objective lens 5 is less likely to rotate around the Y axis, a stable operation in which the fluctuation of the direction of the optical axis is suppressed is possible.

FIGS. 9 and 10 show an exploded perspective view and a sectional view of a fourth embodiment of the present invention.
In this embodiment, the connection between the base 1a and the support member 9 is performed by a pair of rectangular connection plates 29 which are erected from the base 1a and have a surface extending in the Y-axis direction. A ring-shaped member made of a viscoelastic resin such as silicon gel, a Mn-Cu-based alloy, a lead-based alloy, or the like is provided between the support member 9 and a side surface of the support member 9 in the Y-axis direction. A buffer member 42 is provided.

In this case, the ring-shaped buffer member 42 is sandwiched between the inner side surface of the support member 9 in the Y-axis direction and the side surface of the connecting plate 29 in the Y-axis direction. Connection hole 36 drilled in the Y-axis direction from outside of 9
Tightening force on the connection plate 29 by the set screw 14 inserted into the
The base 1a and the support member 9 are fixed to each other by the adhesive force of the buffer member.

Thus, when the support member 9 attempts to start elastic deformation in the frequency band near the resonance point when driven in the focusing direction, the vibration energy is efficiently absorbed by the buffer member 42, and the growth of resonance occurs. Is suppressed. Therefore, the rotational vibration around the Y axis of the objective lens 5, that is, the pitching phenomenon can be avoided. Therefore, the objective lens 5 does not easily rotate around the Y axis, and the direction of the optical axis does not change, so that a stable operation can be performed.

In the above description of the objective lens supporting device, an example is shown in which the present invention is applied to a moving coil type objective lens driving device. Instead of this, the driving method is such that a driving permanent magnet is provided on the movable side. A moving magnet type objective lens driving device may be used.

[0047]

According to the present invention, a support member for displaceably supporting a movable member having an objective lens via a plurality of elastic support members and a base for fixing the support member are separately formed. At the same time, at least some of them are connected to each other via the buffer member, so that the vibration energy is efficiently absorbed by the buffer member, the growth of resonance is suppressed, and the objective lens rotates around the Y axis. And the direction of the optical axis does not fluctuate, so that stable operation is possible.

Accordingly, the fluctuation of the focal position of the recording and / or reproducing light beam is suppressed, and the size and density of the spot irradiated on the information recording surface of the recording medium are stabilized. Is maintained, and it is possible to avoid a reduction in drive control capability, a generation of a jitter in a reproduction signal, a reduction in S / N, and the like.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a main part showing a first embodiment of the present invention.

FIG. 2 is a schematic side view showing a cross section of a main part of the first embodiment of the present invention.

FIG. 3 is a schematic side view showing a main part of a modification of the first embodiment in cross section.

FIG. 4 is a schematic side view showing a cross section of a main part of another modification of the first embodiment.

FIG. 5 is an exploded perspective view of a main part showing a second embodiment of the present invention.

FIG. 6 is a schematic side view showing a main part of the second embodiment in cross section.

FIG. 7 is an exploded perspective view of a main part showing a third embodiment of the present invention.

FIG. 8 is a schematic side view showing a main part of the third embodiment.

FIG. 9 is an exploded perspective view of a main part showing a fourth embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view showing a main part of the fourth embodiment.

FIG. 11 is a perspective view showing a conventional objective lens support device.

FIG. 12 is an exploded perspective view of the conventional example.

FIG. 13 is an exploded perspective view showing an arrangement of a drive coil and a permanent magnet according to a conventional example.

FIG. 14 is a diagram for explaining the operation of the conventional example.

[Explanation of symbols]

 Reference Signs List 1 base 2a, 2b permanent magnet 3 elastic support member 4 lens holder 5 objective lens 6 tracking coil 7 focusing coil 8a magnetic yoke 9 support member 9a damper case 10 buffer member 11 bobbin 12, 22, 32, 42 buffer member 13 connection pin 14 Set screw 15 Restraint plate 16 Connection hole 17 Counterbore 18 Liquid retaining part 19, 29 Connection plate 23 Connection pin also serving as buffer member

Claims (1)

[Claims] 1. A support member for suspending and supporting a movable portion having an objective lens in a Y-axis direction and a Z-axis direction via an elastic support member extending in the X-axis direction, and the support member is connected. In the objective lens support device including the base, the base and the support member are formed separately from each other, and at least a part of them is connected to each other via a buffer member. Characteristic damping structure of the objective lens support device.