JPS59221836A - Actuator of optical pickup - Google Patents

Abstract

PURPOSE:To make an optical pickup thin and to make it small-sized and lightweight by setting radial and focus controlling coils, which are orthogonal to each other, on an object lens holder as one body. CONSTITUTION:A torsion flat spring 12 is provided in the center of the base end side in the lengthwise direction of a base plate 11 provided on an optical base 110, and a pair of the first flat springs 13 and 13 are provided in both sides of the other end in the lengthwise direction of the plate 11 symmetrically with respect to the center line in the lengthwise direction of the base 110. One end of a frame 15 is supported on the torsion flat spring 12 as a cantilever, and both sides of the end part extended in the lengthwise direction of the frame 15 are supported on the first flat springs 13 and 13, and a pair of the second flat springs 17 and 17 for focus supporting are attached to the base end part of the frame 15 as cantilevers, and an object lens holder 21 where focus and radial controlling coils 22 and 23 are set is supported on the end part, which is extended in parallel with the base surface along the lengthwise direction of the base, of springs 17 as a cantilever.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field This invention relates to an optical pickup applied to an optical player, etc., and more specifically, the present invention relates to an optical pickup applied to an optical player, etc., and more specifically, by moving an objective lens, the position of a beam spot from a light source is adjusted between the focus axis and the radial axis. The present invention relates to an objective lens actuator for biaxial control for direct firing.

Background technology] In an optical amplifier applied to optical players such as compact disc players, minute bits on the disc are focused to a minute beam spot of about 1 μm. In order to read the disc, it is necessary to accurately control the spot position by following the disc's surface runout and eccentricity.

This control detects the focus deviation of the spot or the position deviation from the bit string (trunk), and uses the error signal to move the objective lens in two orthogonal directions: the focus axis (Z-axis) or the radial axis (X-axis). This is done by letting Therefore, an objective lens actuator for controlling the movement of the objective lens in two axial directions is essential.

This actuator has conventionally been constructed as shown in FIGS. 1, 2, and 3.

In the figure, a cylindrical storage tube 1 is arranged along the vertical direction parallel to the Z-axis, and an objective I is placed inside the storage tube 1 at the top.
A lens barrel 3 with a lens 2 attached thereto is fitted coaxially. A focus drive section F is provided on the circumference of the lower end side of the storage cylinder 1. The lens barrel 3 is elastically supported by a pair of elastic supports 4, 4 attached above and below the drive unit F so as to be movable in the X-axis direction.

As shown in FIG. 2, the focus drive unit F includes a tube flange-shaped magnetic material IF, an annular permanent magnet 2F installed along the periphery of the base Mlj of the magnetic material IJ, and a top surface periphery of the permanent magnet 2F. An annular magnetic body 3F fixed integrally along
A magnetic circuit consisting of: and a magnetic circuit protruding from the outer periphery of the lens barrel 8 and interposed in the air gap 4F formed between the magnetic body IF of the magnetic circuit, the water-immersed magnet zF, and the magnetic body 3F. It is constituted by an annular coil 5F provided.

The magnetic circuit is fixed to the inner circumference of the storage cylinder l.

The objective lens 2 is attached to the inner circumference near the upper end of the storage tube 1 on the radial axis (
A pair of radial drive parts R and R that control in the X-axis direction are 1
They are arranged at intervals of 80°. As shown in FIG. 3, the radial drive unit R consists of a magnetic body A, a pair of permanent magnets B, 13 provided on both sides of one end of the magnetic body A, and a pair of permanent magnets B, Magnetic material A on each N pole side
A pair of mouth-shaped bodies 0. It is composed of a magnetic circuit formed in an E shape by C and a rectangular coil E combined with this magnetic circuit.

The magnetic circuit is fixed to the inner circumference of the storage cylinder 1.

Moreover, the coil E is installed along the outer periphery so as to surround the peaked body A, and is interposed between the magnetic bodies A and 0 in the gap d formed between the magnetic bodies A and C. The cast is as follows. The coil E is fixed to the outer periphery of the lens barrel 3.

The lens barrel 3 is moved in parallel in the X-axis direction by elastic supports 4, 4, and is also tilted in the X-axis direction within a predetermined angle range. Thereby, the objective lens 2 is moved and adjusted in each axis direction.

However, in the conventional actuator structure as described above, the focus drive section F and the radial drive section R must be arranged in series in two stages, upper and lower, along the focus axis (Z-axis) with an interval between them. Additionally, along with this, the storage tube 1 and lens tube 3 must be elongated (extended) in the direction of the disk D along the focus axis. In addition, a fairly large drive system for each axis is arranged around the outer periphery of the lens barrel 3, and this is housed in the housing barrel 1 as a whole. The lens barrel 3 must be supported by the provided elastic support 4 which has a considerably large diameter.Therefore, the outer diameter of the housing barrel 1 must be increased and its external shape must be made considerably large. As the size of the optical pink-up increased, so did the number of heavy electrical appliances.As a result, the problem arose that it was impossible to make the optical pink-up smaller, lighter, and thinner.

(Since the outer diameter of the storage tube 1 becomes larger, the direction from the center of the objective lens to the center of the disc of the optical pickup housing,
In other words, the distance 1t to the end face on the side of the spindle motor for driving the disk had to be considerably shortened. However, when an actuator having the structure described above is applied to a compact disc player, the following problems occur.

The innermost diameter of the compact disc is 46%.

Therefore, if the distance from the center of the objective lens to the end face of the optical pick-up housing is R, the diameter φ of the spindle motor is expressed as φ=46-2R.

Incidentally, the larger the housing diameter of the spindle motor, the cheaper it can be. Therefore, it is most desirable for cost-effective VC to use a motor with as large a housing diameter as possible. However, in the conventional actuator structure, due to the large distance mentioned above, the above formula φ-4
6-2R becomes larger and smaller. Therefore, it was necessary to use an expensive motor with a small housing diameter φ and a large motor shaft length.

In addition, since the objective lens 2 is extended one degree in the radial-pongee (X-axis) direction for tracking, the center of the lens may be tilted more than the allowable limit with respect to the optical axis, resulting in comatic aberration. However, if you try to use a lens that allows this, it will be quite expensive.

Moreover, since the lens barrel is supported only by a pair of upper and lower elastic supports and is moved in both the X-axis and Z-axis directions, the degree of independence between each axis is low, and secondary resonance may occur due to mutual interference. 62.

DISCLOSURE OF THE INVENTION This invention has been made to solve the above-mentioned conventional problems, and its purpose is to make the objective lens actuator smaller and thinner, thereby making the optical pick amplifier smaller, lighter, and thinner. At the same time, the distance between the center of the objective lens and the end face of the big upper housing can be shortened, and a spindle motor with a larger housing diameter can be used.

1-This objective can be achieved by configuring as follows.

That is, in the present invention, a torsion plate spring is provided on the longitudinal proximal end of the base plate installed on the optical base, and a longitudinal core and a line are provided on both sides of the other end of the plate in the longitudinal direction. A pair of conduit 10 leaf springs are provided so as to be symmetrical to each other, one end of the frame is cantilever-supported by the torsion leaf spring, and both ends of the frame extending along the longitudinal direction are supported by the torsion leaf spring. A pair of second leaf springs for focus support are supported by the first leaf springs and attached to the base end of the frame in a cantilevered manner, and the second leaf springs are mounted along the longitudinal direction of the base of the second leaf springs. Focus on the end extending parallel to the base surface.

The feature is that the objective lens holder to which the radial valley control coil is attached is supported in a cantilevered manner.

According to this invention, the frame and the second leaf spring extend parallel to the base surface along the receiver direction of the optical base, and the objective lens holder is attached to the second leaf spring extending parallel to the base surface.
Since the actuator is cantilevered at g, the maximum height of the actuator from the optical base can be set to a height approximately corresponding to the mounting height of the objective lens holder. Moreover, the objective lens holder can be placed closer to the base surface. Therefore, the height of the actuator from the base surface is significantly lower than that of the conventional actuator, and the actuator can be made into a public book type. Therefore, the optical pick amplifier can be made thinner, smaller and lighter.

In history, optical pick atupno uzing. The surface facing the disk drive spindle motor can be brought close to the end surface of the objective lens holder so that it is substantially flush with the end surface of the objective lens holder.

Therefore, the distance R from the inside of the lens to the end face of the housing can be significantly shortened compared to the conventional case. Therefore, the housing diameter of the spindle motor (φ-46-2R
), making it possible to use an inexpensive motor with a large housing and diameter. In addition, since the spring system supporting each axis is formed by a plate spring with grooves, the shape is simple, and manufacturing is easy and inexpensive. Therefore, the manufacturing cost of the optical pickup can be reduced.

Moreover, the frame is extended in the direction of the receiver of the optical base so as to cancel the moment in the focus axis direction (moving force of the objective lens x length of the second leaf spring) applied to the second leaf spring. , which is supported at three points on a radial torsion leaf spring and a first leaf spring. Moreover, the second leaf spring has a flat-rte spring shape. Therefore, when the objective lens moves in the direction of the focus axis, the lens holder moves in parallel without tilting, and the collimator lens is not tilted beyond the allowable range from the collimator optical axis.Therefore, coma aberration occurs. (It can be made into a structure, and the problems caused by this can be suppressed and alleviated.)

Furthermore, the degree of independence between each axis is high, and the occurrence of secondary eyelids due to mutual interference can be suppressed as much as possible.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings from FIG. 4 onwards.

4 to 47 show an optical pickup to which the present invention is applied, in which a base plate 11 is mounted on a base 110 of an optical pickup housing (hereinafter simply referred to as a housing) 10 that houses an optical system. The base 110
It is installed along the longitudinal direction (direction perpendicular to Xfill) and fixed with screws. A torsion plate spring 12 is formed upright at the center of the base end side in the longitudinal direction of the base plate 11 so as to be perpendicular to the longitudinal direction and parallel to the X axis. Both ends of the base plate 11 extending along the longitudinal direction protrude laterally in a substantially T-shape, and at the protruding ends,! The leaf spring 13.18 of 7!1 is along the longitudinal center line L+
(located on the optical axis of the optical system), and are formed in a pair to stand up and be symmetrical to each other. The first leaf spring 13.13 is inclined at a predetermined angle θ toward the direction of the torsion leaf spring 12 with respect to the longitudinal center L1. This reduces the amount of twisting of the torsion plate spring 12 during radial movement, which will be described later, and allows for smooth operation. Furthermore, by tilting around 1 in this manner, it is possible to suppress the occurrence of secondary resonance. The torsion leaf spring 12 and the first leaf springs 18, 1.8 form a three-point support leaf spring system in the radial direction, and the base end of the frame 140 is cantilevered by the desk torsion leaf spring 12. Frame 14 is gl,! :It is made by combining frames 15 and 16 of g2 into one body. A base end portion 151 of the first frame 15 is bent into an L shape from above toward the rear. Both sides of the other end in the longitudinal direction extend laterally in a substantially T-shape, and the extension...
A pair of support legs 152, 152 having a shape are formed to protrude. Long hole 15 along the longitudinal direction of the first frame 15
3 is set.℃・ru. On the other hand, the base end group 161 of the second frame 160 is bent into an L shape with the lower part facing rearward. A long hole 162 communicating with the long hole 153 is provided in the second frame 16 along the longitudinal direction. Both f1/
- The members 15 and 16 are fixed together by adhesive or the like. The long holes 153 and 162 are used to reduce the amount of frame to be taken, and at the same time are used as operation holes when the base grating 11 is fixed to the optical base. Then, the base end portion 151 of the first frame 15 is attached to the torsion plate spring 12 in a cantilevered manner. The frame 14 has a first leaf spring 1.3.1 parallel to the base 110 along the longitudinal direction of the base 110.
3, and support leg portions 152, 152 provided at the extending ends thereof are elastically supported by the first leaf springs 13°13. The support leg portion 152 is inclined at a predetermined angle toward the center of the base end with respect to the longitudinal center line so as to correspond to the inclination of the first leaf springs ia and la.

The frame 14 includes a torsion leaf spring 12 and a first leaf spring 13.
13, it is supported at three points along the radial axis (X axis).

One end of a pair of second leaf springs 17, 17 is attached in a cantilever manner to the ground surface of the base end 151 of the first frame 15 and to the lower surface of the base end 161 of the second frame 160. The second leaf spring 17.17 is a parallel leaf spring, and the other end extends along the longitudinal direction to the base [parallel to Mj and extends a required length toward the center of the objective lens so as to sandwich the frame 14 from above and below. An objective lens holder 21 having an objective lens 20 attached to its end is supported in a cantilevered manner. Second
The plane of the leaf spring 17.17 is perpendicular to the focus axis (two axes), and the longitudinal direction thereof is perpendicular to the radial axis (X axis). The 20th leaf spring 17 is formed into a substantially U-shape with a bifurcated end.

The lens holder 21 is formed into a substantially rectangular block shape, and has a circular hole 211 in the center of which the objective lens 20 is attached. It is perforated. A pair of coil support pieces 212 and 212 are provided protruding from both side walls of the lens holder 210 along the longitudinal direction. Spring mounting pieces 213, 213 are formed protruding from the upper and lower parts 13 of the coil support piece 212, and second leaf springs 17, 17 are mounted on the upper and lower surfaces of these mounting pieces 213, 213. .

A rectangular focus control coil 22 is installed along the outer peripheral wall of the lens holder 21 including the coil support pieces 212, 212.
It is provided circumferentially so as to be perpendicular to the focus axis (Z-axis). A gap G is provided between the coil 22 and the front two rivers perpendicular to both side walls of the lens holder 21 .

G is formed.

A pair of left and right rectangular radial control coils 23.28 are arranged along the upper and lower surfaces and both sides and sides of the coil support piece 212.212.
is fitted around the focus control coil 22 and is disposed perpendicular thereto. The coil 23 is connected to the radial axis (X
IIIll). According to this, both coils 22 and 23 can be placed on the same horizontal plane, and
Both coils can be accommodated within the range of -thickness between the upper and lower surfaces of the lens holder 21. Therefore, the actuator can be made into a [υy type].

On the other hand, the lower base ll behind Ail of the 1/lens holder 21
A pair of magnetic circuits 30 and 31 are arranged on the base 110 at a predetermined interval in the longitudinal direction of the base 110, and on the radial axis (
1qlI). Magnetic circuit 30.3
1, when the focus control coil 22 or the radial control coil 23 is energized, the lens holder 21 is moved in a required direction via the coil 22 or 23 depending on its direction and size. That is, magnetic circuit 30.31
is used for focus drive, radial, and actual operation.

Magnetic circuit 80.81 is radial 1! L-shaped first magnetic body 30 installed on the base 110 along l1il
1, all, and this first magnetic body 801. ．． 311
A channel-shaped second magnetic body 8 fixed to the outer wall of the
02.812 and the second magnetic body 302.312
It consists of rectangular block-shaped permanent magnets 808 and 813 attached along the longitudinal direction to the inner wall of the magnet.

first magnetic body 301, 31.1 and permanent magnet 303,
Gaps 304 and 314 are formed between the two.

A pair of notches 305, 815, which are deeper than the distance between the radial control coils 23, are formed at both ends of the first magnetic bodies 301, 3], 1 at a predetermined distance from above and below.

Projected pieces 306, 816 are formed between the notches 305, 305 and 315, 315, respectively. Further, a pair of right and left suspensions (317, 317) are provided below the notch 315 of the first magnetic body 311, through which the second leaf spring 17 of the upper and lower pair is inserted. .

The 1/lens holder 21 is interposed between the first magnetic bodies 301 and 811.

Then, the radial axis (X
The part along the axis) is the first magnetic body 301 and the permanent magnet 303 of the magnetic circuit 30 and the first magnetic body 31 of the magnetic circuit 31.
1 and a permanent magnet 313. In addition, the portions of the radial control coil 23 along the focus #=(2 axes) are notches 305° 305 and 315, 315.
They are interposed between the first magnetic body 301 and the permanent magnet 303 and between the first magnetic body 311 and the permanent magnet 313 so as to surround the protruding pieces 806 and 316, respectively.

Next, the operation of the actuator of the above embodiment will be explained.

First, when the laser beam from the optical system is incident on the disk surface without any focal deviation of the spot or one line deviation from the track, the focus error signal and radial error signal are zero, and each control signal is No current flows through the coils 22, 23, and the objective lens holder 21 is held in a stationary position.

Here, the error signal is extracted by the following procedure.

In FIG. 7, the laser light emitted from the semiconductor laser 41 of the optical system 40 first passes through the polarizing beam splitter 42 along a predetermined optical path L2, and then is made into a parallel beam by the collimating lens 43 at 90° from wave plate 44
The light is guided to the objective lens 20 through the deflection mirror 45. The light is then narrowed down to a diameter of about 1 μm and irradiated onto the disk D in the form of a minute spot. The light reflected from the disk D is returned along the optical path L2 in the reverse order to the polarizing beam splinter 42, where it is deflected 90' and then
The light is guided through a light shielding plate (not shown) to a four-split optical sensor, where the light is received and detected. An error signal is extracted based on this detection signal.

On the other hand, when a focus shift occurs in the beam spot, a focus error signal is generated according to the amount and direction of the shift, and a current flows through the focus control coil 22 according to the error signal. The direction of this current and the direction of magnetic flux generated in the magnetic circuits ao and ai are perpendicular to each other. Therefore, according to Fleming's law, the focus control coil 22 receives an upward or downward force along the Z-axis. coil 22
When the spring 17 receives a force, the second leaf spring 17
．． 17 is elastically displaced with its base end as a fulcrum, for example, as shown by the imaginary line in FIG. Then, the lens holder 21 moves integrally with the coil 22 by a required amount along the Z-axis as shown by an arrow 100. In this case, as mentioned above, frame 1
4 is the focus axis (Z
Since the lens holder 21 is arranged so as to cancel the moment in the Z-axis direction, the lens holder 21 does not tilt (moves in parallel in the Z-axis direction).As a result, the objective lens 20 is focused as shown by the imaginary line in figure g7. The movement is controlled by a required amount in the axial direction. Therefore, the focal shift of the beam spot is corrected. The direction and amount of movement of the objective lens 20 are determined by the direction and magnitude of the current flowing through the focus control coil 22.

Next, when a track deviation occurs in the beam spot, a radial error signal is generated according to the amount and direction of the deviation, and a current flows through the radial control coil 23 according to the error signal. Since the direction of this current and the direction of the magnetic flux generated in the magnetic circuits ao and ai are perpendicular to each other, the radial control coils 23 and 28 receive force in one direction or the other along the X axis according to Fleming's left hand rule. . When the coil 23 receives a force, the torsion leaf spring 12, which is a three-point support leaf spring that supports the 1-nome 14, twists as shown by the arrow 101 in FIG. As a result, the first leaf spring 13.
13 are displaced parallel to each other in the tangential direction of the circumference of the torsion leaf spring 12 with the lower end as a fulcrum. Note that this tangential direction is set along the radial axis.

Then, the frame 14 is rotated by a required amount in the radial axis direction using the second leaf springs 17, 17 and supported by the torsion leaf spring 12 as a fulcrum, as shown by the arrow 102 in FIG. As a result, the lens holder 21 moves in the direction of the arrow 102 together with the objective lens 20 to the stored position. As a result, the position of the beam spot is controlled and track deviation is corrected. The amount and direction of movement of the objective lens 20 in the radial direction are determined by the direction and magnitude of the direct current flowing through the radial control coil 23.

6. In the first row of implementation, the frame 14 is divided into the first and second frames 1,5,16 and these are combined into one, but it was decided to make this an integral structure from the beginning. It's okay. Furthermore, the base plate and frame are not limited to those shown in the embodiments, and may have various shapes. Further, in the embodiment, the first leaf springs 13.13 are tilted at an angle of θ, but the drawing leaf springs 13.13 may be arranged parallel to each other.

[Brief explanation of the drawing]

FIG. 1 is a sectional perspective view of a conventional actuator, FIG. 2 is a partial sectional view thereof, FIG. 3 is a partial perspective view thereof, FIG. 4 is an exploded perspective view of an actuator according to the present invention, and FIG. 5 is an assembly thereof. 6 is a plan view of the present actuator, and FIG. 7 is a side sectional view. 10・・・・・・・・・Housing. 110...Base. 11...Base plate. 12・・・・・・・・・Torsional leaf spring. 13.13...First leaf spring. 17.17...Second leaf spring. 20・・・・・・・・・・・・Objective lens. 21・・・・・・・・・・・・Lens holder. 22・・・・・・・・・ Focus control coil. 23・・・・・・・・・ Radial control coil. 152.152...Support leg. θ・・・・・・・Inclination angle of the first leaf spring. Figure 2 Figure 3

Claims (3)

[Claims] (1) An actuator for an optical pickup that controls the movement of an objective lens in two axial directions for direct firing, in which a base plate installed on an optical base is provided with a leaf spring at the center of the proximal end in the longitudinal direction; A pair of first leaf springs are provided on both sides of the other end of the plate so as to be symmetrical with respect to the longitudinal center line of the base, and the base end of the frame is cantilever supported by the torsion leaf springs marked hjJ. At the same time, both ends of the frame extending along the longitudinal direction of the base are supported by leaf springs of +j1J, respectively, and a pair of second focusing supports are attached to the four ends of the frame. ``One piece of leaf spring''? The objective lens holder is mounted on one end of the second leaf spring extending parallel to the base surface along the longitudinal direction of the head, and the objective lens holder is supported on one side.
An optical pink-up actuator characterized in that a radial and no-occurrence control coil that intersects with each other is integrally attached to an object lens holder. (2) A pair of support legs are formed protruding from both sides of the other end of the frame L/-, and the support legs are supported by the first plate spring. Actuator for optical pick amplifier. (3) The optical pink-up actuator according to claim 1, wherein the first leaf spring is angled at a predetermined angle in the direction of the torsional leaf spring with respect to the longitudinal center line.