JPH0424488Y2 - - 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 reproduce information by optical means, a beam spot emitted through an optical system is directed onto a row of information pits formed on the disc surface, and the reflected light is used to collect information. I'm starting to read it. 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, eccentricity, rotational irregularities, etc. of the disk. This control is performed in advance with respect to the focal deviation of the beam spot, that is, the deviation in the direction perpendicular to the disk surface (focus direction), the positional deviation from the information pit row, that is, the deviation in the radial direction of the disk (radial direction), and the information pit row. Alternatively, a subsequent time shift, that is, a shift in the tangential direction (jitter direction) of the information pit row, is detected, and the beam spot accurately follows the information pit row using the error signal.

Conventionally, this beam spot tracking control has been performed using the fifth beam spot.
As shown in the figure, the beam F emitted through the optical system is reflected by two galvano mirrors 1 and 2,
It has a structure that irradiates the disk surface through the objective lens 3, and by controlling the operation of the objective lens 3 in the focus direction, the deviation in the focus direction is corrected, and one galvano mirror 1 is moved in the radial direction.
In some cases, the other galvanometer mirror 2 is controlled to operate in the jitter direction, and the angle of reflection of the beam F is slightly changed to correct the deviation in the radial jitter direction.

Problems to be Solved by the Invention However, in conventional galvano-mirror 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 a control mechanism for operating these two galvano mirrors in the radial direction and jitter direction, respectively, and a control mechanism for operating the objective lens in the focus direction are independent. Therefore, the structure of the actuator becomes complicated and large. In addition, it is difficult to maintain the galvanometer mirror in a neutral state, making assembly difficult. For this reason, it has been impossible to reduce the size and weight of the optical pickup.

This idea was made in consideration of the above points,
The objective lens can be moved in parallel independently in three orthogonal axes directions, and the support springs of the jitter control system are configured with stepped parallel plate springs, thereby making it possible to control the rolling of the lens holder (lens). and a second lens located on the optical axis of the lens.
To reduce the weight of the actuator by using a substantially frame-shaped relay frame, and to improve the responsiveness of the servo.

Means for Solving the Problems In order to achieve the above objectives, this invention has one end of a pair of leaf springs attached to a pair of support columns erected from one longitudinal end of the substantially rectangular actuator base surface. The base is attached in a V-shape that narrows in one direction in the longitudinal direction, a first relay frame is supported on the other end of this leaf spring, and one end of a pair of parallel leaf springs is attached above and below the first relay frame in the longitudinal direction of the base. a substantially frame-shaped second relay frame is cantilever-supported at the other end of the parallel plate spring;
A pair of leaf springs are attached perpendicularly to the base surface and parallel to each other at different levels to the side edges of the second relay frame in a diagonal direction between the side where the parallel leaf springs are attached and the opposite side. The upper end of the spring supports a lens holder with an objective lens attached.
A focus control coil is provided on the second frame, a radial control coil and a jitter control coil are provided on the lens holder, and these three types of coils are attached to the focus, radial, and
Intervened in the air gap of the magnetic circuit for jitter control and combined them together. The pair of parallel springs constitutes a support spring for the focus control system, the eight-shaped plate spring constitutes a support spring for the radial control system, and the uneven parallel plate springs constitute a jitter control system. The lens holder is supported on the support spring of the system. Further, the second relay frame is arranged on the lens optical axis so that the center of its diagonal line substantially coincides with the lens optical axis.

Function According to the objective lens actuator of the present invention having the above configuration, the objective lens includes a plate spring attached in a V-shape on the actuator base surface and a parallel plate spring attached horizontally to the base surface. , is supported in a floating state by uneven parallel plate springs installed perpendicular to the base surface, and the focus, radial, and jitter directions are perpendicular to each other by elastic deformation of each plate spring.
It is provided so as to be movable in the axial direction. This orthogonal 3
Movement control in the axial direction is performed by passing current through each control coil interposed in the air gap of each control magnetic circuit. In this way, the objective lens can be moved independently and parallel to each of the three orthogonal axes directions.

During focus servo, the objective lens is deformed in parallel to the focus direction by deformation of the parallel leaf spring. Further, during radial servo, the objective lens is displaced in parallel to the tracking direction due to the deformation of the V-shaped leaf spring. Furthermore, due to the deformation of the uneven parallel plate spring, the jitter direction is translated in the positive direction of the jitter axis using its support base end as a fulcrum. Since the support springs of the jitter control system are comprised of stepped parallel plate springs, rolling occurring in the lens holder is suppressed during jitter correction. In addition, the second relay frame placed on the optical axis is composed of a substantially frame-shaped body, and the center of its diagonal line substantially coincides with the lens optical axis, reducing the actual movable weight and reducing the weight of the actuator. becomes possible. This improves the responsiveness of the servo.

Embodiments The embodiments of this invention will be described below in Figures 1 to 4 of the drawings.
This will be explained in detail with reference to the drawings.

1 and 2 show an optical pickup according to the present invention, in which an actuator base 10 is provided on a box in which an optical system (not shown) is installed.

The actuator base 10 has a substantially rectangular shape, and its base surface is formed with steps in the longitudinal direction. A passage for an optical axis F is opened in a lower base surface of the base 10. The direction passing through the center of this opening and perpendicular to the 10th surface of the base is the focus direction, that is, the direction perpendicular to the disk surface.
The short direction of the base 10 perpendicular to the optical axis F is the radial direction, that is, the radial direction of the disk D, and the optical axis F
The longitudinal direction of the base 10, which is orthogonal to this, is the jitter direction, that is, the tangential direction to the circumferential direction of the disk D.

The optical pickup main body is slidably mounted on two shafts arranged in parallel, and the optical axis F is reciprocated in the radial direction within the range from the outermost circumference to the innermost circumference of the information pit row of the disk D. be done.

A pair of support columns 11, 11 are erected on a higher base surface of the actuator base 10. A pair of leaf springs 12, 12 are attached to the supports 11, 11 at one end such that their center lines are horizontal to the base surface and their plate surfaces are perpendicular to the base surface. The leaf springs 12, 12 extend in a direction opposite to the optical axis F, and are attached in a V-shape in which the other end is slightly narrower than the attachment end. This leaf spring 12,
The other ends of the relay frames 12 are attached to the sides of the first relay frame 13, respectively. First relay frame 1
A pair of leaf springs 14, 14 are attached to the top and bottom of 3, parallel to each other and horizontally to the base surface, with one end thereof being attached. The other ends of the parallel plate springs 14, 14 extend in the optical axis direction, and the second relay frame 1
5 is supported on a cantilever. Second relay frame 1
5 is formed into a substantially frame shape, and the center of its diagonal line substantially coincides with the optical axis F. A pair of leaf springs 1 are provided at one F end of the second relay frame 15 in the diagonal direction between the mounting side of the parallel leaf springs 14, 14 and the opposite side.
6 and 16 are attached with their lower ends parallel to each other and perpendicular to the base surface. A lens holder 1 is attached to the upper end of these uneven parallel plate springs 16, 16.
7 is supported. An objective lens 18 is mounted on this lens holder 17 with the optical axis F as the center.

As described above, the objective lens 18 is supported in a floating state on the surface of the base 10 so as to be movable in parallel in the three orthogonal axial directions of the focus, radial, and jitter directions by the elastic deformation of each leaf spring.

A focus control coil 20 wound into a cylindrical shape centered on the optical axis F is attached to the lower part of the second relay frame 15. Lens holder 1
A radial control coil 21 wound into a rectangular cylindrical shape is attached to the side surface of the coil 7 perpendicular to the radial direction. Further, a jitter control coil 22 having the same shape as the coil 21 is attached to the side surface perpendicular to the jitter direction.

On the other hand, a focus control magnetic circuit 23 having a substantially annular shape centered on the optical axis F is disposed at the periphery of the opening in the base surface of the actuator base 10, which is located one step lower. The magnetic circuit 23 includes a magnetic body 231 which is annular and has a cylindrical rising edge on its inner circumferential edge, an annular permanent magnet 232 attached to the outer circumferential edge of this magnetic body 231, and a magnetic body 232 on the upper surface of this permanent magnet 232. It is formed by an attached annular magnetic body 232. An annular gap 234 is formed between the outer circumferential surface of the cylindrical part of the magnetic body 231 of this magnetic circuit 23 and the annular inner circumferential surface of the magnetic body 233, and the focus control coil 20 is interposed in this gap 234. There is.

A mounting wall 24 is attached to one side of the outer peripheral edge of the upper surface of the magnetic body 233 of the magnetic circuit 23 . The mounting wall 24 has a curved shape along the mounting portion on the magnetic body 233, and its both ends are provided to face the radial jitter control coils 21 and 22, respectively. This mounting wall 24
A radial control magnetic circuit 25 and a jitter control magnetic circuit 26 are respectively attached to the upper part of the coils 21 and 22 at positions spaced apart from each other by 90 degrees. Both magnetic circuits 25, 26 have the same shape, and a pair of permanent magnets 252, 252, 26 are attached to both side ends of T-shaped magnetic bodies 251, 261.
2, 262 are attached in the direction of the central protrusion, and a pair of magnetic bodies 253, 253, 263, 263 are further attached, forming a substantially E-shape. A gap 254, 254 is formed between the central protrusion of the magnetic body 251 of the radial control magnetic circuit 25 and the pair of magnetic bodies 253, 253.
Both side portions of the radial control coil 21 are interposed in the radial control coil 54, respectively. Similarly, the jitter control coil 22 is interposed in the gaps 264, 264 of the jitter control magnetic circuit 26.

A box provided below the actuator base 10 is equipped with an optical system (not shown).
A laser beam emitted from a semiconductor laser provided at one end of this optical system passes through the optical system, and a beam spot is irradiated onto the information pit row of the disk D through the objective lens 18, and the reflected light is used to read and read information. Error detection is performed in the focus, radial, and jitter directions. As a result of this error detection, current is applied to each of the control coils described above, and the objective lens 18 is driven in parallel in each direction.

In addition, in the actuator with the above configuration,
In particular, the lens holder 1 with the objective lens 18 attached
7, uneven parallel plate springs 16, 16, second relay frame 15, parallel plate springs 14, 14, first relay frame 13, plate springs 12, 12 provided in a V-shape
Each of the coils 20, 21, and 22 is attached by adhesive, and the assembly is lightweight.
In addition, unnecessary parts of the lens holder 17, first and second frames 13, 15, etc. are cut off to the extent that their strength is not compromised, thereby reducing the weight of the movable parts and making them well-balanced in the direction of each center axis. There is.

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

For example, when the pit surface of the disk D shifts in the focus direction, that is, when the beam spot shifts out of focus, a focus error signal is detected. As a result of this error detection, a required current is passed through the focus control coil 20 in a required direction. Then, a force acting upward or downward is generated on the coil 20 interposed in the magnetic circuit 23, and the third
As shown in the figure, the parallel plate springs 14, 14 are elastically deformed to move the second relay frame 15 upward or downward in parallel. At the same time, the lens holder 17 supported by the uneven parallel plate springs 16, 16
moves, and the objective lens 18 is moved parallel to the focus direction. When the current flowing through the coil 20 is stopped, the objective lens 18 is returned to its original supported state by the elastic restoring force of the parallel leaf springs 14, 14. In this way, the objective lens 18 is controlled to move up and down depending on the direction and strength of the current flowing through the coil 20, and follows the information pit row on the disk so that the beam spot does not shift in the focus direction.

Next, when the information pit row shifts from the beam spot, that is, when a shift occurs in the radial direction, a radial error signal is detected. This error signal causes a required current in a required direction to flow through the radial control coil 21. Then, a force acting in one or the other radial direction is generated in the coil 21 inserted in the magnetic circuit 25, and as shown in FIG. 4, the lens holder 17 tends to be moved in the radial direction. Then,
The plate springs 12, 12 provided in a V-shape are elastically deformed to move the lens holder 17 horizontally to the base surface, and at the same time move the objective lens 18 substantially parallel to the radial direction. Next, when the current flowing through the coil 21 is stopped, the objective lens 18
The elastic restoring force returns the support to its original state.
In this way, the movement of the objective lens 18 in the disk radial direction is controlled by the direction and strength of the current flowing through the coil 21, and the information pit row is controlled so that the beam spot does not deviate from the information pit row in the radial direction. follow.

Next, when a time lag occurs in which the information pit precedes or lags behind the beam spot, that is, when there is a shift in the jitter direction, a jitter error signal is detected. This error signal causes a required current in a required direction to flow through the jitter control coil 22. Then, a force is generated in the coil 22 inserted in the magnetic circuit 26 in one direction or the other in the radial direction, and as shown in FIG. is moved in the jitter direction, and at the same time, the objective lens 18 is moved in parallel. Next, coil 2
When the current flowing through the lens 2 is stopped, the objective lens 18 returns to its original supported state by the elastic restoring force of the stepped parallel plate springs 16, 16. In this way, the coil 22
The movement of the objective lens 18 in the jitter direction is controlled by the direction and strength of the current flowing through the beam spot, and the beam spot follows the information pit row on the disk without shifting in the jitter direction.

As described above, the objective lens 18 focuses
The beam spots are controlled to move separately and independently in the radial and jitter directions, so that the beam spot accurately follows the information pit row.

Effects of the Invention As explained above, according to the actuator of the optical pickup according to the present invention, the objective lens can be moved independently and parallel to the three orthogonal axes of focus, radial, and jitter.

In particular, according to the present invention, since the support springs of the jitter control system are composed of uneven parallel plate springs, it is possible to suppress the rolling that occurs in the lens holder during jitter correction, and to perform jitter correction with high precision. be able to. In addition, the second relay frame placed on the optical axis is approximately frame-shaped, and its diagonal center is approximately aligned with the lens optical axis, reducing the actual movable weight of the actuator and making the actuator lighter. can. As a result, servo responsiveness can be improved.

[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 movement of the objective lens in the focus direction and jitter direction, and Fig. 4 is a radial direction thereof. FIG. 5 is a schematic perspective view showing a conventional example. 10... Actuator base, 11, 11...
...Strut, 12, 12... (for radial direction) plate spring, 13... First relay frame, 14, 14...
...(For focus direction) Parallel plate spring, 15... Second relay frame, 16, 16... (For jitter direction) Different level parallel plate spring, 17... Lens holder,
18...Objective lens, 20...Focus control coil, 21...Radial control coil, 22...
... Coil for jitter control, 23... Magnetic circuit for focus control, 24... Mounting wall, 25... Magnetic circuit for radial control, 26... Magnetic circuit for jitter control, F... Optical axis.

Claims (1)

[Scope of utility model registration request] One end of a pair of leaf springs is attached to a pair of pillars erected from one end in the longitudinal direction on the substantially rectangular actuator base surface, respectively, in a figure eight shape that narrows in one direction in the longitudinal direction of the base, and the other end of the leaf spring is A first relay frame is supported at the top and bottom of the first relay frame, one end of a pair of parallel plate springs is attached extending in the other direction in the longitudinal direction of the base, and a substantially frame-shaped plate is attached to the other end of the parallel plate spring. The second relay frame is supported on a cantilever so that its diagonal center substantially coincides with the lens optical axis, and the side of the second relay frame on which the parallel leaf spring is attached is connected to the opposite side. A pair of leaf springs are attached to the side edges in the diagonal direction perpendicularly to the base surface and parallel to each other, and a lens holder with an objective lens attached is supported on the upper end of the leaf spring, and the pair of parallel leaf springs is a focus support spring, the eight-shaped plate spring is a radial support spring, the stepped parallel plate spring constitutes a support spring for a jitter control system, and the base surface side of the second relay frame is A radial control coil and a jitter control coil are provided in the lens holder, and each of these three types of coils is interposed in a gap between a focus, radial, and jitter control magnetic circuit mounted on a base surface. Actuator for light pickup.