JPH1040560A - Optical head apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a natural frequency of a vibration mode and stabilize a servo system by supporting a movable member holding an optical system by means of deformable supporting members which are not parallel to each other when seen from an orthogonal direction to a direction in which the supporting members extend. SOLUTION: A holder 2 holding an objective lens is held at a fixing member 4 having a thin part via four wires 3 not parallel to each other when seen from a direction in which the wires extend. In the thus-constituted optical head apparatus, the direction in which the wires extend is a Y axis, and a lateral and an up-down directions orthogonal to the Y axis are made an X axis and a Z axis. When a force acts to the wires 3 in the Y-axis direction, a fixed part 4a is shifted in the Y-axis direction because of the thin part of the fixing member, but is hard to shift in the X-axis and Z-axis directions. Therefore, while a natural frequency in a mode of the parallel movement in the X-axis direction as a focusing direction and Z-axis direction as a tracking direction is kept to be 20-40Hz, a natural frequency in a vibration mode of the rotation about the X-axis, Z-axis direction is decreased as compared with a gain intersection frequency of a control servo system controlling a position of the holder, so that the servo system is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an object mounted on an optical pickup used for recording and reproducing information on an optical recording medium such as an optical disk such as a compact disk and a video disk and a magneto-optical disk. The present invention relates to a device for supporting an optical system such as a lens.

[0002]

2. Description of the Related Art Generally, in an optical disk pickup, an objective lens has an optical axis for irradiating an optical disk in a focused state with a recording / reproducing light beam via an objective lens and for following a track of the optical disk. The optical pickup is supported by the optical pickup main body so as to be movable in a focus direction, which is a direction, and a tracking direction orthogonal to the focus direction and orthogonal to the track direction of the optical disk.

[0003] As a supporting device for such an objective lens, for example, a device as disclosed in Japanese Patent Application Laid-Open No. 59-221839 has been proposed. In the objective lens supporting device disclosed in this publication, four elastic wires 3 are arranged in parallel, and the objective lens 1 is held at one end thereof, as shown in FIG. The other end of the wire 3 is fixed to a fixing member 4, and the four wires 3 are fixed.
Are bent in different directions orthogonal to each other, so that the objective lens 1 can be moved in the focus direction and the tracking direction.

[0004]

However, in the objective lens supporting apparatus having the above-mentioned structure, the center of gravity of the movable portion 2 and the center of the driving force applied by the drive control mechanism due to an error in manufacturing or assembling parts. In some cases, the vibrations do not coincide with each other, thereby generating vibrations in a mode in which the movable unit 2 rotates. There are three possible rotation axes in this rotation mode vibration. That is, the first axis is parallel to the track direction, the second axis is parallel to the tracking direction orthogonal to the track direction, and the third axis is parallel to the focus direction. It passes.

If the first axis is the Y axis, the second axis is the X axis, and the third axis is the Z axis, the natural frequency of the vibration mode rotating about the Y axis is the bending rigidity of the wire 3 and the wire rigidity. 3 and is inversely proportional to the square root of the moment of inertia of the movable part 2 about the Y axis. In addition, the natural frequency of the vibration mode that rotates around the X axis and the Z axis is proportional to the elongational rigidity of the wire 3 and the square root of the interval between the wires 3, and the square root of the moment of inertia of the movable part 2 around the X axis and the Z axis. Inversely proportional.

The length, diameter and material of the wire 3 are determined so that the natural frequency of the mode in which the wire 3 moves in the focusing direction and the tracking direction is within a predetermined range. The rigidity cannot be freely selected. In addition, the interval between the wires 3 cannot be too small in order to avoid interference with the driving coil.

For this reason, the natural frequency of the vibration mode rotating around the Y axis is often 40 to 100 Hz, and the natural frequency of the vibration mode rotating around the X axis and the Z axis is often 800 to 5 kHz. However, the gain intersection frequency of the servo system for controlling the position of the objective lens 1 held by the movable section 2 is usually 1-2 kHz, and the frequency of the vibration mode rotating about the X and Z axes is the gain intersection point. Since the value is close to the frequency, the stability of the servo system is hindered.

Japanese Unexamined Patent Application Publication No.
There is a technique disclosed in Japanese Patent Application Laid-Open No. 3-195834. The publication includes an elongated portion extending on a straight line (for example, the connecting portion 43 in FIG. 3 of the publication) and an extending portion non-parallel to the linear direction (for example, the curved portion 44 of FIG. 3 of the publication). Is described as a continuous member, and an integrally-formed leaf spring etched from a thin metal plate is described.

However, in this publication, when the objective lens 1 moves in the focus direction, the curved portion 44 is deformed in the direction in which the support member 7 extends, so that the objective lens 1 is tilted, resulting in accurate recording / reproducing characteristics and stable servo. It has the disadvantage that characteristics cannot be obtained.

Japanese Unexamined Patent Publication (Kokai) No. 61-261827 discloses a plurality of support members (for example, wire 5 in FIG. 4 of the publication).
Are non-parallel when viewed from the focus direction. However, in this publication, the wire 5 is linear and fixed to the base 6 having high rigidity, so that the configuration is very rigid in the extending direction of the wire 5.
Therefore, there is a disadvantage that the frequency of the vibration mode as described above is high and the stability of the servo system is hindered. Also,
The upper and lower wires 5 are arranged in parallel in the X direction, which is a direction substantially perpendicular to the extending direction and the focus direction of the wires 5. In Japanese Patent Application Laid-Open No. 59-218639, a plurality of support members (for example, the support arms 2a and 2b in FIG. 3 of the publication) are configured to be non-parallel when viewed in a direction perpendicular to the extending direction of the support members. . However, this publication also has a configuration in which rigidity is high in the extending direction of the support member. Therefore, when the objective lens is moved in the focus direction, the objective lens tilts in a specific direction. Therefore, there is a major drawback that the objective lens can be tilted only with respect to a disk with a very specific inclination as shown in FIG. Further, since the extending direction of the support member is also limited to the radial direction of the disk, the configuration of the optical head device is limited. This development was made in order to solve the above-mentioned problems in the conventional objective lens holding device, and is configured to reduce the natural frequency of the vibration mode rotating around each axis generated in the movable portion, It is an object of the present invention to provide an optical head device configured to correct a tilt when a movable part moves, and to obtain an accurate recording / reproducing characteristic and a stable servo system.

[0011]

An optical head device according to the present invention connects a fixed member, a movable member holding an optical system, the fixed member and the movable member, and moves the movable member at least in a focus direction. An optical system support device having a plurality of first support members movably supported, the optical system support device including a second support member deformable in a direction substantially orthogonal to the focus direction, wherein the first support member is the first support member. The support member is arranged so as to be non-parallel when viewed from a direction substantially perpendicular to the extending direction of the support member and the focus direction.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view showing an entire configuration of a first embodiment of an optical head device according to the present invention except for a main part, FIG. 2 is a plan view showing a fixing member, and FIG. FIG. 3 is a side view as viewed from the direction of arrow A.
FIG. 9 is a schematic diagram showing a modification in the case of a configuration having wires arranged in parallel with each other, FIG. 10 is a schematic diagram showing a comparative example of FIG. 9, and FIG. FIG. 2 is a schematic diagram illustrating a main part of one embodiment. In the figure, reference numeral 1 denotes an objective lens, and one end of four wires 3 arranged in parallel with each other is fixed to a holder 2 on which the objective lens 1 is mounted. The other end of the wire 3 is fixed to a fixing member 4. The fixing member 4 includes a wire fixing portion 4a disposed at a corner for fixing the other end of the wire 3, an attachment fixing portion 4c disposed at a central portion for fixing the fixing member 4 to a base (not shown), A thin portion 4b having a reduced thickness is provided between the wire fixing portion 4a and the mounting fixing portion 4c, and is integrally formed of a metal such as plastic or stainless steel. In the optical head device according to this embodiment, a coil, a magnet, and the like for driving the holder are arranged, but are not shown because they are not directly related to the present development. In such a configuration, if the longitudinal direction (extending direction) of the wire 3 is the Y axis, the horizontal direction perpendicular to the longitudinal direction of the wire 3 is the X axis, and the vertical direction perpendicular to the longitudinal direction is the Z axis, When a force acts in the Y-axis direction of the wire 3, that is, in the longitudinal direction, the thin portion 4b of the fixing member 4 is easily deformed in the Y-axis direction, and the wire fixing portion 4a is displaced in the Y-axis direction. That is, the rigidity in the Y-axis direction has decreased. On the other hand, since the thin portion 4b of the fixing member 4 is hard to be deformed in the X-axis direction and the Z-axis direction and has high rigidity, the wire fixing portion 4a is in the X-axis and Z-axis directions similarly to the conventional fixing member. It is difficult to displace. Therefore,
The natural frequency of the mode that translates in the Z-axis direction (focusing direction) and the X-axis direction (tracking direction) is set to 20.
The natural frequency of the vibration mode that rotates around the X axis and the Z axis can be reduced to about several tens to 200 Hz while maintaining the frequency at about 40 Hz. This natural frequency is 1 to 2 of the gain intersection frequency of the servo system for controlling the position of the holder.
It is considerably lower than kHz and does not hinder the stability of the servo system. In this embodiment, the fixing member 4 can be constituted by a printed circuit board that also serves as an electric connection member to the wire 3.

In this embodiment, the fixed member 4 is provided with a thin portion deformable in the Y-axis direction.
May be provided at the fixed portion, and in this case, the wire 3 can be easily displaced in the Y-axis direction.

FIG. 9 is a schematic diagram viewed from a direction perpendicular to the direction in which the wires 3 extend in the case of a configuration having four wires 3 arranged in parallel with each other. The broken line shows the state after being deformed by receiving the force F in the Z-axis (+) direction. Now, assuming that the holder 2 moves in the focus direction (Z-axis direction) as shown in the drawing, and assuming that a force F in the Z-axis (+) direction is applied to the holder 2, the Z-axis (+ The force f1 in the Y-axis (-) direction acts on the wire fixing portion 4a-1 disposed on the (-) side, while the wire fixing portion 4a-2 disposed on the Z-axis (-) side A force f2 in the Y-axis (+) direction acts.
As a result, the holder 2 and the wire 3 are respectively 2 ′
And 3 ', the wire fixing portions 4a-1 and 4a-2 of the fixing member 4 in the Z-axis (+) direction and the Z-axis (-) direction are simultaneously moved to the Z-axis (+) side. 1 ′ and 4a-2 ′, respectively, displaces by δ in opposite directions, so that the holder 2 moves around the X axis by △ θ1
Just tilt. When the value of the inclination △ θ1 of the holder 2 is large, coma aberration occurs in the light spot on the optical disk by the objective lens 1 and accurate recording and reproduction cannot be performed.
Servo characteristics for position control are degraded.

To solve this problem, first consider the configuration shown in FIG. That is, the configuration shown in FIG. 10 arranges the wires 3 so as to be non-parallel when viewed from the X-axis direction, and the distance d1 between the fixed ends of the wires 3 on the fixing member 4 side is the distance between the fixed ends on the holder 2 side. It is set larger than d2, and the fixing member 4 is configured not to be deformed in the Y-axis direction. In such a configuration, when the holder 2 and the wire 3 are moved in the Z-axis (+) direction, the holder 2 and the wire 3 are displaced as indicated by broken lines 2 "and 3". It is inclined by △ θ2 in the opposite direction to the case of the configuration shown. Therefore, it is possible to eliminate the inclination of the holder 2 by combining the configuration shown in FIG. 9 with the wire configuration shown in FIG. FIG. 11 is a schematic diagram illustrating a main part of the first embodiment of the present invention configured based on the above concept. That is, in this embodiment, the wire 3 is not viewed from the direction perpendicular to the extending direction of the wire 3 and the focus direction such that the inclination △ θ1 around the Z axis becomes equal to the inclination △ θ2 in the opposite direction. Fixing member 4 arranged in parallel and provided with thin portion 4c
Are fixed to the wire fixing portions 4a-1 and 4a-2, respectively. With this configuration, even when the holder 2 and the wire 3 are moved in the Z-axis direction (focus direction), as shown by 2 "" and 3 "", the wire fixing portions 4a-1 and 4a " No tilt of the holder 2 of -2 occurs, and the coma of the light spot by the objective lens 1 on the optical disk is corrected, so that accurate recording and reproduction can be performed and good servo characteristics are maintained.

FIG. 4 is a plan view showing a modification of the first embodiment, and FIG. 5 is a side view as seen from the direction of arrow A. In this modification, one end of the wire 3 is similarly fixed to the wire fixing portion 4a of the fixing member 4, and the wire fixing portion 4a and the fixing member 4 are fixed to a base (not shown). When a viscoelastic body 5 such as butyl rubber, which can be elastically deformed, acts on the wire 3 in the Y-axis direction instead of the thin portion between the attachment fixing portion 4c,
By easily deforming in the Y-axis direction, the rigidity of the wire 3 in the Y-axis direction is reduced.

In this modification, since the viscoelastic body 5 has good damping characteristics, the natural frequency of the vibration mode rotating around the X axis and the Z axis can be reduced to about several tens to 200 Hz. At the same time, the resonance itself can be reduced.

FIG. 6 is a perspective view showing another modified example of the first embodiment, and FIG. 7 is a view showing a configuration of a wire as a main part thereof. In this modified example, a wire 3 is formed by forming a loop 3a in the middle. When a force is applied in the longitudinal direction of the wire 3, that is, in the Y-axis direction, the force required to change the distance between both ends of the wire 3 becomes equal to the force for expanding and contracting the wire 3 when the loop 3a is not provided. Although it is very large, when a loop 3a is provided in the middle of the wire 3 as in this modification, when a force acts in the longitudinal direction, bending deformation occurs in the loop 3a, and the wire 3 The distance changes easily. Therefore, the rigidity of the wire 3 in the Y-axis direction has decreased.

When the loop 3a is formed in the middle of the wire 3 as described above, it is necessary to bend the wire 3 when a force acts in a direction perpendicular to the longitudinal direction of the wire 3, that is, in the X axis or the Z direction. Power is loop 3
As compared with the case where a is not provided, the length is reduced due to the extension of the entire length of the wire 3. However, the amount of reduction is such that it can be easily canceled by adjusting the overall length or diameter of the wire 3.

In the above modification, a loop 3a is provided as a portion where bending deformation occurs in the middle of the wire 3. However, instead of the loop, a U-shaped bent portion 3 as shown in FIG.
When b is provided, similarly to the case where a force acts in the Y-axis direction,
Bending deformation occurs in the bent portion 3b, so that the distance between both ends of the wire can be easily changed, and the same operation and effect can be obtained. Further, even when the end of the wire 3 is bent into an L-shape and fixed to the fixing member 4, the same function and effect can be obtained.

The present invention is not limited to the above embodiment, but can be modified in many ways, and any structure can be used as long as the means reduces the rigidity in the Y-axis direction. .

In the above embodiment, the supporting device using four wires is shown. However, the present invention is similarly applied to a supporting system using a leaf spring other than a wire, a link supporting system, or the like. be able to. In the above embodiment, the means for reducing the rigidity in the Y-axis direction is provided at one place, but may be provided at a plurality of places such as both ends of the wire. The same effect can be obtained by providing this stiffness reducing means only on some of the wires, without providing them on all of the plurality of wires.

[0023]

As described above with reference to the embodiments, according to the present invention, the fixed member, the movable member holding the optical system, the fixed member and the movable member are connected, and the movable member is connected to the movable member. An optical head device comprising: a plurality of first support members that support a member so as to be movable at least in a focus direction; a second support member that can be deformed substantially in a direction in which the support member extends; Since the support member is arranged so as to be non-parallel when viewed from a direction perpendicular to the direction in which the first support member extends, the natural frequency of the mode of moving parallel to the focus direction is maintained within a predetermined range. Meanwhile, the natural frequency of the vibration mode rotating around a predetermined axis can be reduced, and therefore, the stability of the servo system is not hindered. can get.

Further, the allowable amount of deviation between the center of gravity of the movable member and the center of the driving force, which is a cause of vibration, can be increased, so that the yield of components and the yield of products are improved.
It is possible to reduce the cost.

Further, since the tilt generated when the movable portion is moved in the focus direction is corrected, the light spot on the disk is good, accurate recording and reproduction can be performed, and stable servo characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a first embodiment of an optical head device according to the present invention, except for a main part.

FIG. 2 is a plan view showing the fixing member.

FIG. 3 is a side view of the fixing member.

FIG. 4 is a plan view showing a modification of the first embodiment of the present invention.

FIG. 5 is a side view thereof.

FIG. 6 is a perspective view showing another modification of the first embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of the wire.

FIG. 8 is a view showing a modified example of a wire.

FIG. 9 is a schematic diagram showing a modified embodiment in the case of a configuration including wires arranged in parallel with each other.

FIG. 10 is a schematic diagram showing a comparative example of FIG. 9;

FIG. 11 is a schematic diagram showing a main part of the first embodiment of the present invention.

FIG. 12 is a perspective view showing a configuration example of a conventional optical head device.

[Explanation of symbols]

 1 Objective lens 2 Holder 3 Wire 4 Fixing member 4a Wire fixing portion 4b Thin member 4c Mounting fixing portion 5 Viscoelastic body 3a Loop 3b Shows a U-shaped bent portion.

Claims (2)

[Claims] 1. A plurality of first support members for connecting a fixed member, a movable member holding an optical system, the fixed member and the movable member, and supporting the movable member at least in a focus direction. In the optical head device having
A second support member that is deformable substantially in the direction in which the support member extends, wherein the first support member is non-conductive when viewed from a direction substantially orthogonal to the extension direction of the first support member and the focus direction. An optical head device, which is arranged in parallel. 2. The first support member and the second support member,
The optical head device according to claim 1, wherein the optical head device is formed integrally.