JPH0424489Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to an actuator for an optical pickup, and particularly to an actuator that servo-controls an objective lens in three orthogonal axes directions.

2. Description of the Related Art In devices such as video disc players and optical disc files that play back information by optical means, a beam spot emitted through an optical system is applied to a row of information pits formed on the disc surface, and the reflected light is used to read information. I'm learning to read. For this reason, the optical pickup must be controlled so that the beam spot accurately follows the information pit array in response to surface runout or eccentricity of the disk, or rotating ram. This control includes the following: deviations in the focus of the spot, that is, deviations in the direction perpendicular to the disk surface (focus direction), deviations in position from the information pit row, that is, deviations in the radial direction of the disk,
Detects the time difference leading or following the information pit row, that is, the shift in the tangential direction (jitter direction) of the information pit row, and uses the error signal to ensure that the beam spot accurately follows the information pit row. It is carried out as follows.

Conventionally, this beam spot tracking control has been carried out by reflecting a beam F emitted through an optical system onto two galvano mirrors 1 and 2 and irradiating it onto the disk surface through an objective lens 3, as shown in FIG. , control the movement of the objective lens 3 in the focus direction to correct the deviation in the focus direction, control the movement of one galvano mirror 1 in the radial direction and the other galvano mirror 2 in the jitter direction, and adjust the reflection angle of the beam F. Radial by making slight changes,
There was a method that corrected the deviation in the jitter direction.

Problems that the invention aims to solve However, in conventional galvano-mirror type optical pickups, the radial and jitter directions are controlled by subtly changing the angle of incidence of the beam on the objective lens by moving the galvano-mirror. Therefore, it was necessary to use a heavy, expensive objective lens with a large effective field of view. Furthermore, two galvano mirrors are required separately from the optical system, and the control mechanism for moving these two galvano mirrors in the radial direction and jitter direction, and the control mechanism for operating the objective lens in the focus direction, are independent. The structure of the actuator was complicated and large. Further, the structure for holding the galvano mirror in the neutral position is complicated and difficult to assemble, making assembly difficult. Therefore, it has not been possible to reduce the size and weight of the optical pickup.

Furthermore, a technique disclosed in Japanese Unexamined Patent Application Publication No. 52-55424 is conventionally known for controlling this type of beam spot in three axes perpendicular to the information pit row of the disk. The lens barrel (lens holder) that holds the lens barrel has a circular tube shape, and the support body that supports the lens barrel has a disk shape,
While arranging these members around the lens axis,
Combinations of control coils and permanent magnets for controlling the beam spot in three axial directions are arranged around the outer periphery and the upper periphery, respectively, and the lens barrel is supported by a plurality of elastic support members via the support body. The overall inertial weight, especially the inertial weight around the lens barrel that is the lens holder, is heavy, and the moment of inertia when controlling movement in three orthogonal axes directions becomes large. There is a problem in terms of responsiveness. In particular, according to the technique disclosed in the publication, the moment of inertia in the jitter direction (direction B in Figures 3 and 5 of the publication) becomes large, so there is a drawback that the responsiveness of control to the jitter direction becomes poor.

This idea was made in consideration of the above points,
The objective lens is structured to be able to move in parallel to the three orthogonal axes, allowing the use of lightweight, inexpensive lenses with a small effective field of view, making the optical pickup smaller and lighter, and reducing the moment of inertia in the three orthogonal axes. The purpose is to reduce this and improve the responsiveness of control in three axial directions.

Means for Solving the Problems In order to achieve the above objectives, this invention supports a frame in a cantilever manner parallel to the base surface at the end of a parallel plate spring supported in a cantilever manner on the actuator base. , a lens holder with an objective lens mounted on three cylindrical springs erected on this frame is supported parallel to the frame surface, with the top of the frame and lens holder facing approximately toward the center of the disk. While forming it into an isosceles triangle shape,
One of the three cylindrical springs is arranged at the top of the isosceles triangle shape, and the other two are arranged at both ends of the base, and are wound cylindrically around the optical axis of the lens of the frame. A focus control coil is attached to the coil, and a focus control magnetic circuit arranged on the base is combined with this coil, and a radial control coil and a jitter control coil are attached to the bottom and side portions of the lens holder. A magnetic circuit for radial control and a magnetic circuit for jitter control disposed above the base are respectively combined with each coil.

Effect When a control current is applied to the focus control coil,
The parallel plate spring is elastically deformed by the magnetic force applied to the coil, and the lens holder and the frame supporting it are controlled to move in the focus direction. This corrects the focus of the beam spot on the disk through the objective lens. Further, when a control current is applied to the radial control coil or the jitter control coil, the lens holder is controlled to move in the tracking direction or the jitter direction by the elastic deformation of the cylindrical spring due to the action of the magnetic force acting on each coil. As a result, the beam spot passing through the objective lens is controlled in the tracking direction or jitter direction with respect to the information pit row of the disk, and the deviation of the beam spot in the tracking direction or jitter direction is corrected.

According to the present invention, the lens holder and frame are formed into a substantially isosceles triangular shape with the top facing toward the center of the disk, and one of the three cylindrical springs supporting the lens holder on the frame is located at the top position, and the other is located at the top position. 2
Since the books are placed at both ends of the base of the equilateral triangle, the overall inertial weight is reduced.
The moment of inertia in the three axes perpendicular to focus, tracking, and jitter is significantly reduced compared to conventional structures. Therefore, the responsiveness of control in the three orthogonal axes directions is improved. In particular, according to the configuration of the present invention, the moment of inertia in the jitter direction is significantly reduced.
The responsiveness of control in the same direction can be improved.

Embodiment Examples of the invention will be described below in Figures 1 to 5 of the drawings.
This will be explained in detail with reference to the drawings.

1 and 2 show an objective lens actuator for an optical pickup according to this invention, in which a box equipped with an optical system is provided below an actuator base 10. FIG. The optical pickup main body is provided so as to be slidable in the radial direction of the disk D, and the beam spot is driven in a reciprocating direction from the outermost circumference to the innermost circumference of the information pit row of the disk D.

A gate-shaped mounting block 11 is formed at one end of the actuator base 10, and one ends of a pair of focus parallel plate springs 12, 12 are mounted on the upper and lower surfaces of the capped portion. The parallel plate springs 12, 12 extend horizontally to the base surface and in the direction of the optical axis F, which is perpendicular to the disk surface. Parallel leaf spring 1
A flat frame 13 is attached horizontally to the base surface at the other ends of 2 and 12 and is supported in a cantilevered manner.

The frame 13 is located in the path of the optical axis F, and the path is open. On the upper surface of the frame 13, three cylindrical springs 14, . . . are erected perpendicularly to the frame surface. Three cylindrical springs 14,...
are arranged at each vertex of an acute isosceles triangle, one of which is located at the top facing towards the zero direction of the disk center, and the other two are located upright at both ends of the bottom. The cylindrical spring 14 has a core made of, for example, a copper wire, and has an elastic layer made of rubber or the like formed around its outer periphery, and supports the lens holder 15 at its upper end. An objective lens 16 is mounted on the lens holder 15 with the optical axis F as the center. The frame 13 and the lens holder 15 have substantially the same planar shape that is slightly larger than the acute isosceles triangle formed by the cylindrical springs 14, . . . , and are lightweight by cutting out unnecessary parts. The weight applied to the springs is evened out. That is, three cylindrical springs 14... and plate springs 12,1
The weight applied to 2 is uniform and the weight is balanced. The tops of the frame 13 and lens holder 15 face toward the disk center 0 direction, and
It corresponds to the cylindrical spring 14 of the book. Further, the bottom portions of the frame 13 and the lens holder 15 are located in a direction substantially perpendicular to the central axis connecting the disk center 0 and the lens optical axis F, and two cylindrical springs 14, 14 are arranged at both ends thereof. ing. As mentioned above,
The objective lens 16 is held vertically above the base in a floating state via a lens holder 15, cylindrical springs 14, . . . , a frame 13, and leaf springs 12, 12.

A focus control coil 20 wound into a cylindrical shape centered on the optical axis F is attached to the lower surface of the frame 13 . On the back side of the lens holder 15, that is, on the bottom of the approximately isosceles triangular lens holder, there is a radial control coil 2 wound into a square cylinder shape.
1 is mounted so that its center line is located on a line connecting the center of the objective lens 16 and the center 0 of the disk D. Furthermore, a jitter control coil 22 having the same shape as the radial control coil 21 is attached to one side of the lens holder 15 . The center line of the jitter control coil 22 is located approximately in the middle of the drive range of the optical pickup, that is, in a neutral state, when the jitter control coil 22 is centered on the center 0 of the disk D and the objective lens 1 is
The coil 22 corresponds to a substantially tangential direction with the middle of the coil 22 as a contact point with respect to the circumference passing through the center of the coil 22 . and,
It is mounted slightly inclined from the center 0 of the disk D with respect to the jitter direction which is orthogonal to the focus direction and the radial direction.

On the other hand, the passage of the optical axis F of the actuator base 10 is opened, and a substantially cylindrical focus control magnetic circuit 23 is provided on the base surface around the opening. This magnetic circuit 23 consists of a magnetic body 231 which is annular and has a cylindrical rising wall on its inner periphery.
, an annular permanent magnet 232 attached to the outer peripheral end, and a magnetic body 23 attached to the upper surface of the annular permanent magnet 232.
It consists of 3. A focus control coil 20 is interposed in an annular gap 234 formed between two magnetic bodies 231 and 233 sandwiching a permanent magnet 232 of this magnetic circuit 23 .

Several pillars 24, . . . are erected on one side of the actuator base 10, and a mounting base 25 is supported at a constant height from the base surface by the pillars 24, . A magnetic circuit 2 for radial control is combined with a radial control coil 21 and a jitter control coil 22 on the upper surface of this mounting base 25, respectively.
6 and a jitter control magnetic circuit 27 are attached. Both magnetic circuits 26, 27 have the same shape, and include T-shaped magnetic bodies 261, 271 and a pair of permanent magnets 26 attached in the direction of protrusions at both ends of the T-shaped magnetic bodies 261, 271.
2, 262, 272, 272, and a pair of magnetic bodies 263, 263, 2 attached to the protrusion direction side.
73 and 273, forming a roughly E-shape. The protrusion of the magnetic body 261 of the magnetic circuit 26 and the left and right magnetic bodies 2
63, 263 and the void 264,2 formed between
Both side portions of the radial control coil 21 are interposed at 64 . Similarly, the air gap 27 of the magnetic circuit 27
A jitter control coil 22 is interposed at 4,274. The magnetic circuit 27 is attached to the mounting base surface with an inclination in the same direction as the inclination direction of the coil 22.

Control currents in each direction are passed through each of the above-mentioned coils 20, 21, and 22. As a result, the objective lens 16 is controlled to move in the focusing, tracking, and jitter directions. That is, an optical system (not shown) including a semiconductor laser is assembled in a box provided below the actuator base 10, and a laser beam emitted from the semiconductor laser is directed to the disk D through the objective lens 16. The information pit row is irradiated. By detecting the reflected light from the pit row with a photodetector, it is possible to read the information signal, focus,
Positional deviations of the beam spot in the tracking and jitter directions are detected, and error detection signals in each direction are extracted based on this detection. Control currents in each direction are applied to the coils 20, 21, and 22, respectively, based on the error detection signals in each direction. The movement of the objective lens 16 in the focusing, tracking, and jitter directions is controlled via the lens holder 15 by the action of the magnetic field acting on each coil 20, 21, and 22.

It should be noted that each component/member of the actuator having the above configuration, particularly the lens holder 15 to which the objective lens 16 is attached, the cylindrical spring 14,..., the frame 13,
Parallel plate springs 12, 12 and each coil 20, 2
1 and 22 are fixed by adhesive to further reduce the weight. .

Next, the movement operation of the objective lens of the actuator with the above configuration will be explained.

First, when the pit surface of the disk D shifts in the focus direction, that is, when a focus shift occurs in the beam spot, a required current is applied to the focus control coil 20 in a required direction by detecting a focus error signal. Then, the magnetic circuit 23
A force acting upward or downward is generated on the coil 20 interposed in the parallel plate spring 1, as shown in FIG.
Along with the parallel elastic deformation of lenses 2 and 12, the lens holder 15 moves in parallel upward or downward together with the frame 13. As a result, the objective lens 16 is controlled to move in the focus direction, and the focus shift is corrected. That is, the beam spot passing through the lens is correctly focused on the pit row of the disk D.

Next, when the beam spot deviates from the position of the information pit in the disk radial direction (tracking direction), a required current is applied to the radial control coil 21 in a required direction by detecting the error signal. Then, a force is generated in the coil 21 inserted in the magnetic circuit 26 in one direction in the disk radial direction, and as shown in FIG. Frame 1 with objective lens 16
3 in the tracking direction. As a result, the objective lens 16 is controlled to move in the tracking direction, the beam spot passing through the lens accurately follows the information pit row on the disk D, and the deviation with respect to the pits in the tracking direction is corrected.

Next, there is a time lag in which the beam spot leads or follows the information pit in the circumferential direction, that is,
If the beam spot shifts in the jitter direction,
A required current is applied in a required direction to the error signal jitter control coil 22. Then, a force is generated on the coil 22 inserted in the magnetic circuit 27 in the direction in which it is attached. At this time, the lens holder 15 is moved in a direction slightly inclined with respect to the jitter direction, as shown in FIG. 5, and is moved in a screw-like manner using the cylindrical spring 14 located at the apex as a substantially fulcrum. During this jitter correction, the two cylindrical springs 14 located at both ends of the base of the isosceles triangle have a small amount of distortion, and the one cylindrical spring 14 located at the top
The amount of strain is large, and the three cylindrical springs 14 are each elastically deformed. However, according to this embodiment, 3
The arrangement of the cylindrical springs 14, the support structure of the lens holder 15 by the springs, and the shape and arrangement of the lens holder 15 are devised and designed as described above, and the radial control magnetic circuit 26 is attached to the lens holder 15. At the base of the isosceles triangle,
The jitter control magnetic circuits 27 are arranged on one side of an isosceles triangle, and the coil centerline direction of the jitter control magnetic circuits 27 is set in the disk radial direction with respect to the disk tangent direction passing through the optical axis F. The lens holder 15 is arranged at an angle, and the arrangement structure with respect to the lens holder 15 is devised and set. Therefore, during focus and radial correction, the weight balance of the lens holder 15 in the optical axis F direction and around the optical axis F can be well balanced, and when jitter correction is performed, the arrangement structure of the two magnetic circuits 26 and 27 and the lens holder 15 are well balanced. Due to the shape and arrangement thereof, a torsional moment acts on the lens holder 15 in the jitter control direction with one cylindrical spring 14 located at the top of the isosceles triangle serving as a substantially fulcrum. As a result, the lens holder 15 has a small amount of distortion in the two cylindrical springs 14, 14 at the bottom, and one cylindrical spring 1 at the top.
4, as shown in FIG. 5, the outer side of the disk in the radial direction is torsionally displaced in the jitter control direction, using the single cylindrical spring 14 located at the top as a fulcrum, as shown in FIG. Lens holder 15
is controlled to move in a jitter direction around one cylindrical spring 14 at the top as a fulcrum, in a direction slightly inclined from the disk tangent direction. That is, the tilt is displaced by a predetermined angle. As a result, the movement of the objective lens 16 is controlled approximately along the circumferential direction of the information pit row, and the beam spot correctly follows the information pit row in the jitter direction.

According to the above embodiment, the frame 13 and the lens holder 15 are formed into a substantially acute isosceles triangular shape with the top facing toward the disk center 0, unnecessary parts are removed to reduce weight, and the cylindrical springs 14... and the plate Since the weight applied to the springs 12, 12 is equalized and the weight is balanced, the moment of inertia in the three orthogonal axes directions, especially in the tracking and jitter directions of the lens holder 15, is reduced, and the control responsiveness in the same direction is reduced. can be improved.

Effects of the Invention As explained above, according to the optical pickup actuator according to the present invention, the moments of inertia in the three orthogonal axes directions of focusing, tracking, and jitter are reduced, and the responsiveness of control in the three axes directions is improved. In particular, according to the present invention, the moment of inertia in the jitter direction is reduced, and the responsiveness of control in the jitter direction can be significantly improved.

In addition, the weight around the lens holder is reduced, which reduces the space it occupies, making it possible to make the optical pickup smaller and lighter.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the optical pickup according to the present invention, Fig. 2 is an exploded perspective view thereof, Fig. 3 is a side view showing the movement of the objective lens in the focus direction, and Fig. 4 is its movement in the radial direction. 5 is a sectional view of the main part showing the movement operation in the jitter direction, and FIG. 6 is a schematic perspective view showing the conventional example. 10... Actuator base, 12, 12...
... Parallel leaf spring, 13 ... Frame, 14, 14,
14... Cylindrical spring, 15... Lens holder, 16
... Objective lens, 20 ... Focus control coil, 21 ... Radial control coil, 22 ... Jitter control coil, 23 ... Focus control magnetic circuit, 24, 24, ... Support column, 25 ... Mounting Base, 26... Radial control magnetic circuit, 27...
...Magnetic circuit for jitter control, F...Optical axis.

Claims (1)

[Scope of utility model registration request] A frame is cantilevered parallel to the base surface at the end of a parallel plate spring for focus direction movement supported in a cantilevered manner on the actuator base, and the top of three cylindrical springs erected on this frame is A lens holder on which an objective lens is mounted is supported parallel to the frame surface, and the frame and lens holder are formed into a substantially isosceles triangular shape with the top facing toward the center of the disk, and the three cylindrical columns One of the springs is disposed at the top of the isosceles triangle, and the other two are disposed at both ends of the base, and the focus control is wound in a cylindrical shape around the optical axis of the lens of the frame. A magnetic circuit for focus control disposed on the base is combined with this coil, and a radial control coil and a jitter control coil are attached to the bottom and one side of the lens holder. An actuator for an optical pickup comprising a combination of a radial control magnetic circuit and a jitter control magnetic circuit disposed above the base on each coil.