JPH04349223A - Lens actuator - Google Patents

Abstract

PURPOSE:To improve the servo pull-in performance of a lens actuator used for an optical type recording and reproducing device, etc., to record and reproduce the information while an optical beam emitted from a light source is focused onto information recording media. CONSTITUTION:An objective lens holder 43 to hold an objective lens 46 fitted rotatably and elevatably to a supporting shaft 33 is floated and supported by holding magnets 44a and 44b and repulsion magnets 41a and 41b the friction force of the objective lens holder is suppressed and the servo pull-in performance is improved.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a lens actuator used in optical recording and reproducing devices that converge a light beam emitted from a light source such as a semiconductor laser onto an information recording medium to record and reproduce information. be.

0002

2. Description of the Related Art Conventionally, this type of lens actuator has been constructed as shown in FIGS. 5 and 6. That is, a base 1 made of a magnetic metal plate fixed between a light source section and an information recording medium of an optical recording/reproducing device is provided with a through hole 2 through which the light beam of the light source passes, and a hole 2 adjacent to the through hole 2 is provided. A mounting hole 4 for fixing the support shaft 3 is provided at a position, and a light emitting element 20 and a light emitting element 2 are provided on the side opposite to the through hole 2 with respect to the mounting hole 4.
The position detector 22 mounted so that the divided light receiving elements 21 face each other is attached by screws 23a and 23b, and a circle is formed on the straight line orthogonal to the straight line formed by the center of the through hole 2, the mounting hole 4, and the position detector 22. Magnet holding pieces 7a and 7b that hold arc-shaped magnets 6a and 6b protruding in an arc shape are provided so as to face each other, and arc-shaped magnetic path pieces 8a and 7b are provided on the outside of these magnet holding pieces 7a and 7b, respectively. 8b are provided at regular intervals.

A bearing 9 that can rotate and slide vertically is incorporated into the support shaft 3, and an objective lens holder 10 made of a material such as polyphenylene sulfide resin or epoxy resin is fitted into the bearing 9 and fixed thereto. has been done. This objective lens holder 10 is provided with a light beam entrance hole 19 at a position corresponding to the through hole 2 of the base 1, and the objective lens 11 is installed in this light beam entrance hole 19. On the other hand, a balancer 13 is built into the objective lens holder 10 at a position facing the objective lens 11, and a position detection pin 12 is built into the lower part of the balancer 13. Around the objective lens holder 10, a focusing control coil 14 formed in a ring shape and an arcuate tracking control coil 15 coupled to each other on the outer periphery are arranged. , 6b and magnetic path pieces 8a, 8
It is placed in the gap between b. Both coils 14, 15
are wired to a board 5 attached to the balancer 13, and further wired from the board 5 to a board 27 on the base 1 by twisted wires 26a, 26b, 26c, and 26d. and,
The whole is covered with a cover 16, and relief windows 17 and 18 are provided at positions corresponding to the objective lens 11, bearing 9, and balancer 13.
is formed.

[0004] In such a configuration, the focus shift of the light beam with respect to the information recording medium surface and the track groove shift of the light beam with respect to the track groove of the information recording medium surface are detected, and the focusing control coil 14 and the tracking control coil 14 are detected based on the detection signals. A current is applied to the control coil 15, and the objective lens 10 is moved up and down and rotated using the magnetic flux constantly formed by the magnets 6a and 6b and the magnetic path pieces 8a and 8b, thereby changing the position of the objective lens 11. control.

[0005]

However, in the above configuration, friction exists between the support shaft 3 and the bearing 9, and the objective lens 11, the objective lens holder 10, the bearing 9, the focusing control coil 14, and the tracking control coil When the movable part composed of the coil 15, balancer 13, position detection pin 12, and substrate 5 is moved in the focusing direction parallel to the optical axis and kept stationary, the focusing control is the sum of the own weight of the movable part and the force due to the friction. Although it stops at a position where the thrust force generated by applying a current to the focusing coil 14 is balanced, the force due to friction changes rapidly when moving from a stationary state to a moving state, so the movement in the focusing direction is not smooth, and the movement in the focusing direction is not smooth. As a result, there was a problem in that the ability to draw the light beam spot focused by the objective lens 11 into a servo that follows the surface runout and eccentricity of the information recording medium was poor.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a lens actuator that suppresses the frictional force of an objective lens holder against a support shaft and has excellent servo retraction performance.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the lens actuator of the present invention includes an objective lens holder for holding an objective lens that is rotatably and vertically movable with respect to a support shaft. It is characterized by being suspended and supported by magnetic force means.

[0008]

[Function] With the above structure, the objective lens holder can be supported in the focusing direction relative to the support shaft with a small frictional force, and a neutral position in the same direction can be maintained, and the movement in this direction can be made very smooth. can.

As a result, the servo pull-in performance, which indicates the ability to make the light beam spot focused by the objective lens follow the surface runout and eccentricity of the information recording medium, can be improved.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the lens actuator of the present invention will be described below with reference to FIGS. 1 and 2 attached hereto. Figure 1,
In FIG. 2, reference numeral 30 denotes a base made of magnetic metal. A circular recess 31 is formed on the base 30, and a light beam transmitter is formed in a part of the recess 31 for passing the light beam from the light source. A hole 32 is provided. Said recess 3
A mounting hole 34 for fixing a support shaft 33 is provided at the center of the 1, and a light emitting element 35 and a light receiving element 36 are mounted in a recess 31 on the side opposite to the light beam through hole 32 with respect to this mounting hole 34. The position detector 37 mounted so as to face the set screw 3
8a and 38b. Further, arc-shaped magnet holding pieces 39a and 39b are arranged so as to protrude upward within this recess 31 at positions facing each other across a line connecting the center of the light beam through hole 32 and the center of the support shaft 33. Similarly, arc-shaped magnetic path pieces 40a and 40b are formed on the outside of the recess 31 on the outer periphery of the magnet holding pieces 39a and 39b.

A support shaft 33 is fixed to the mounting hole 34 of the base 30, and an annular repulsion magnet 41a is fixed to the base of the support shaft 33. The support shaft 33 has
A bearing 41 that is rotatable relative to the axis of the support shaft and movable up and down is incorporated. A center portion of an objective lens holder 43 made of a substantially annular polyphenylene sulfide resin is coupled to this bearing 42, and an annular holding magnet is further attached to this center portion to vertically hold the objective lens holder 43. 44a and a repulsive magnet 41b are fixed. An objective lens 46 is installed above the light beam entrance hole 45 provided in the objective lens holder 43. This objective lens 46 is located at a position corresponding to the light beam through hole 32.
Further, the balancer 47 is incorporated into the objective lens holder 43 at a position facing the objective lens 46, and the position detection pin 48 provided on the objective lens holder 43 at the lower part of the balancer 47 is connected to the light emitting element 35 of the position detector 37. and light receiving element 3
It is placed in the space between 6. This position detection pin 48
partially blocks the light emitted from the light emitting element 35, thereby obtaining an operating output from the two-divided light receiving element 36 that is proportional to the displacement in the tracking direction. Moreover, magnets 49a and 49b formed in an arc shape are fixed to the outer peripheral surfaces of the magnet holding pieces 39a and 39b.
A gap is formed between the outer peripheral surfaces of 9a and 49b and the magnetic path pieces 40a and 40b.

A focusing control coil 50 wound in a ring shape is fixed to the outer periphery of the objective lens holder 43, and a tracking coil 50 having four coils connected in an arc shape is attached to the outer periphery of the focusing control coil 50. Control coils 51 are coupled at predetermined intervals. These coils 50, 51 are connected to the magnets 49a, 49b.
and the magnetic path pieces 40a, 40b. Both coils 50 and 51 are connected to the substrate 5 on the balancer 47.
2, and further twisted wires 53a, 53b, 53c, 5
3d, it is wired to the substrate 54 on the base 30 and receives a current supply from the outside.

A cover 55 is placed over the entire structure, and a presser magnet 44b is attached at a position corresponding to the upper end of the support shaft 33. On the upper surface of this cover 55, a cover 55 is attached at a position corresponding to the objective lens 46 and the balancer 47. window hole 56,5
7 is formed, and this window hole 56 is a hole for passing the light beam that has passed through the objective lens 46.
7 is a balancer 4 when the objective lens holder 43 moves up and down.
This is for escaping to avoid being hit by a 7 and being restricted.

In the above configuration, a light beam is emitted from the light source, the light beam is focused on the information recording medium surface through the objective lens 43, and the focus shift of the light beam spot and the track groove on the recording medium surface are corrected. A current corresponding to the detected amount is applied to the focusing control coil 50 and the tracking control coil 51 to control the magnets 49a, 49b and the magnetic path pieces 40a, 40b.
Using the magnetic flux of the magnetic circuit formed by the two coils 50 and 51, the objective lens holder 43, which has both coils 50 and 51 fixed to its outer periphery, is rotated or moved up and down with respect to the axis of the support shaft 33, thereby adjusting the focusing direction and tracking. The objective lens is controlled to follow the direction.

In this case, the opposing surfaces of the presser magnet 44a and the repulsive magnet 41b attached to the upper and lower surfaces of the central portion of the objective lens holder 43 and the presser magnet 44b and the repulsive magnet 41a located at opposing positions, respectively, have the same polarity. Therefore, the presser magnets 44a and 44b,
A repulsive force is generated between the repulsive magnets 41a and 41b. Here, since the repulsive force generated between the repulsive magnets 41a and 41b is larger than the repulsive force generated between the presser magnets 44a and 44b, the objective lens holder 43 is connected to the focusing control coil 50. It floats in the focusing direction even when no current is applied. Therefore, the objective lens holder 4 as a movable part
There is always a force to support the weight of the 3rd grade, and the bearing 42 due to its own weight.
The friction between the support shaft 33 and the support shaft 33 is significantly reduced. Therefore, stick slip does not occur and it moves smoothly. Moreover,
Presser magnets 44a and 44b, repulsion magnet 41a
The objective lens holder always operates to maintain a neutral position due to the reaction force generated at 41b and 41b.

As a result, the servo pull-in performance for causing the light beam spot focused by the objective lens to follow the surface runout and eccentricity of the information recording medium is not deteriorated.

Next, the second lens actuator of the present invention
An example will be described using FIG. 3. FIG. 3 is a side sectional view.

Note that the same parts as those in the first embodiment of the present invention are given the same numbers, and the description thereof will be omitted. In the figure, the holding coil 58 is a coil provided at the center of the inner surface of the cover 55 and wound in a direction perpendicular to the axis of the support shaft 33, and the repulsion coil 59 is provided on the upper surface of the mounting hole 34 to which the support shaft 33 is attached. The coil is wound in a direction perpendicular to the axial direction of the support shaft 33.

In this case, the opposing surfaces of the presser magnet 44a and the repulsion magnet 41b attached to the upper and lower surfaces of the central portion of the objective lens holder 43 and the presser coil 58 and the repulsion coil 59 located at opposing positions, respectively, have the same polarity. A constant current is always applied to both the coils 58 and 59 so that. Therefore, the presser magnet 44a and the presser coil 58
, a repulsive force is generated between the repulsive coil 59 and the repulsive magnet 41b. Here, the repulsive force generated between the repulsive coil 59 and the repulsive magnet 41b is stronger than that of the presser magnet 44a.
Since a current is applied to both the coils 58 and 59 so as to be larger than the repulsive force generated between the holding coil 58 and the holding coil 58, the objective lens holder 43 can perform focusing even when no current is applied to the focusing control coil 50. floating in the direction. Therefore, there is always a force supporting the weight of the objective lens holder 43 and the like as a movable part, and the friction between the bearing 42 and the support shaft 33 due to the weight is significantly reduced. For this reason, stick slip does not occur and it moves smoothly. In addition, the movable part always maintains the neutral position due to the reaction force generated between the presser magnet 44a, the presser coil 58, the repulsion coil 59, and the repulsion magnet 41b, and
It is also possible to change the neutral position by varying the current applied to both coils.

As a result, the servo pull-in performance for causing the light beam spot focused by the objective lens to follow the surface runout and eccentricity of the information recording medium is not deteriorated.

Furthermore, the third lens actuator of the present invention
An example will be described using FIG. 4. FIG. 4 is a side sectional view.

[0022] The same parts as in the first embodiment of the present invention are given the same numerals and their explanations will be omitted. In the figure, a magnetic bearing 60 is a bearing made of a magnet magnetized along the axial direction of the support shaft 33.

In this case, this magnetic bearing 60 is
The presser magnet 44a and the repulsion magnet 4 attached to the upper and lower surfaces of the central part of the objective lens holder 43 in the embodiment shown in FIG.
It also serves as 1b. Since the opposing surfaces of the presser magnet 44b and the repulsive magnet 41a, which are located at positions facing the magnetic bearing 60, have the same polarity, a repulsive force is generated between the magnetic bearing 60 and the presser magnet 44b and the repulsive magnet 41a. . Here, the repulsive force generated between the repulsive magnet 41a and the magnetic bearing 60 is stronger than the repulsive force generated between the presser magnet 44a and the magnetic bearing 60.
Since the repulsive force is larger than the repulsive force generated between the two, the objective lens holder 43 floats in the focusing direction even when no current is applied to the focusing control coil 50. Therefore, there is always a force to support the weight of the objective lens holder 43, etc. as a movable part, and the friction between the bearing 42 and the support shaft 33 due to the weight is significantly reduced, allowing smooth movement without any stick slip. Moreover, the reaction force generated at both end faces of the magnetic bearing 60 acts to keep the movable part always in the neutral position.

As a result, the servo pull-in performance for causing the light beam spot focused by the objective lens to follow the surface runout and eccentricity of the information recording medium is not deteriorated.

In each of the above embodiments, a magnetic force is applied to oppose the force that magnetically levitates the objective lens holder 43, so that the objective lens holder 43 is held in a neutral position. However, other mechanical forces such as a spring may be used as the holding force opposing the magnetic levitation force or the levitation force opposing the magnetic holding force.

Further, although the magnet and coil for applying the magnetic pressing force are provided on the cover, they may be provided on a separate fixing member.

[0027]

As described above, in the present invention, the objective lens holder for holding the objective lens, which is rotatably and vertically movably mounted on the support shaft provided on the base, is suspended and supported by magnetic means. The objective lens holder can be supported with a reduced frictional force against the support shaft, and the objective lens holder can be held at a neutral position in the focusing direction, and the movement in this direction can be made very smoothly. It can be done.

As a result, the servo pull-in performance for causing the light beam spot focused by the objective lens to follow the surface runout and eccentricity of the information recording medium can be improved.

[Brief explanation of drawings]

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

FIG. 2 is a side sectional view showing the first embodiment of the lens actuator of the present invention.

FIG. 3 is a side sectional view showing a second embodiment of the lens actuator of the present invention.

FIG. 4 is a side sectional view showing a third embodiment of the lens actuator of the present invention.

[Figure 5] Exploded perspective view showing a conventional lens actuator

[Figure 6] Side sectional view showing a conventional lens actuator

[Explanation of symbols]

30 base 33 Support shaft 37 Position detector 41a, 41b Repulsion magnet 42 Bearing 43 Objective lens holder 44a, 44b Presser foot magnet 46 Objective lens 47 Balancer 48 Position detection pin 49a, 49b magnet 50 Focusing control coil 51 Tracking control coil 55 Cover 58 Presser coil 59 Repulsion coil 60 Magnetic bearing

Claims (5)

[Claims] 1. A base provided with at least a support shaft, an objective lens holder for holding an objective lens mounted rotatably and vertically movable with respect to the support shaft, and a base provided on a side of the objective lens holder. a first magnetic force means provided on the base; and a second magnetic force means provided on the side of the base that generates a magnetic force repelling the first magnetic force means; A lens actuator characterized in that the objective lens holder is magnetically suspended and supported. 2. A base provided with at least a support shaft; an auxiliary base assembled to the base; and a base that is arranged between the base and the auxiliary base and is rotatable and movable up and down with respect to the support shaft. an objective lens holder for holding an objective lens attached to the objective lens holder; a first magnetic force means provided on a surface of the objective lens holder facing the base; and a first magnetic force means facing the first magnetic force means. a second magnetic force means provided on the side of the base and generating a magnetic force repelling the first magnetic force means; and a third magnetic force means provided on the side of the objective lens holder facing the auxiliary base. a magnetic force means; and a fourth magnetic force means, which is provided on the side of the auxiliary base so as to face the third magnetic force means and generates a magnetic force repulsive to the third magnetic force means, , a lens actuator characterized in that the objective lens holder is magnetically suspended and supported at a neutral position between the repulsive force based on the second magnetic force means and the repulsive force based on the third and fourth magnetic force means. 3. A base provided with at least a support shaft, a bearing mounted rotatably and vertically movably on the support shaft, an objective lens holder for holding an objective lens mounted on the bearing, and the support shaft. movable-side permanent magnets attached to the upper and lower surfaces of the surrounding objective lens holder, respectively, and surfaces of both movable-side permanent magnets provided at opposing positions in the axial direction of the support shaft. A lens actuator characterized by being equipped with a permanent magnet having the same polarity. 4. A base provided with at least a support shaft, a bearing mounted rotatably and vertically movably on the support shaft, an objective lens holder for holding an objective lens mounted on the bearing, and the support shaft. A movable permanent magnet is attached to the upper and lower surfaces of the surrounding objective lens holder, and a movable permanent magnet is provided at a position facing the both movable permanent magnets in the axial direction of the support shaft, and is wound in a direction perpendicular to the support shaft. A lens actuator characterized by having a turned coil. 5. A base provided with at least a support shaft; a bearing that is rotatably and vertically movably mounted on the support shaft and includes a permanent magnet magnetized in the axial direction of the support shaft; A lens actuator comprising: an objective lens holder that holds an objective lens; and permanent magnets that are provided at positions facing both end surfaces of the bearing and have the same polarity as both end surfaces of the bearing.