JPH01290133A - Objective lens actuator for optical pickup - Google Patents

Abstract

PURPOSE:To improve driving efficiency by fixing a focusing coil and a tracking coil on a lens holder neighboring mutually, fixing a magnetic material at a position confronting with both coils in a main body, and magnetizing an N pole and an S pole on specific areas, respectively. CONSTITUTION:The focusing coil 5 and the tracking coil 8 are fixed on the lens holder 2 neighboring mutually, and also, the magnetic material 7 is fixed at the position confronting with both coils 5 and 8 in the main body 3. And the N pole and the S pole are magnetized on two areas confronting with both sides of the focusing coil 5 in a focusing direction on the plane of the magnetic material 7 confronting with both coils 5 and 8, respectively, and also, the N pole and the S pole are magnetized on the two areas confronting with both sides of the tracking coil 8 in a tracking direction, respectively. In such a way, since an electromagnetic force functions on currents on both sides 5a, 5b and 8a, 8b of the focusing coil 5 and the tracking coil 8, the driving efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an objective lens actuator that displaces an objective lens for focusing control and tracking control in an optical pickup of an optical recording/reproducing device.

[Conventional technology]

The objective lens actuator displaces the objective lens in the focusing direction, which is the optical axis direction of the objective lens in the optical pickup, and controls the focusing of the light beam that the optical pickup irradiates onto the recording medium. Also,
This objective lens 7 cue unit displaces the objective lens in a tracking direction that is a direction perpendicular to the track direction on a plane perpendicular to the optical axis direction of the objective lens, and tracks the light beam irradiated onto the recording medium by this optical pickup. Take control.

An example of this conventional objective lens actuator (first conventional example) is shown in FIG.

The objective lens 21 is fixedly supported around the periphery at an eccentric position of the lens holder 22. And this lens holder 22
The objective lens 21
can be moved in the focusing direction and the tracking direction.

Around this lens holder 22, there is an actuator shaft 2.
A focusing coil 25 is wound around 4. Further, from the main body 23, two pairs of yokes 26...
are erected, and focusing magnets 27 are fixed to one of the yokes 26 of each pair. The left and right (tracking direction) both sides of the focusing coil 25 are connected to each pair of corks 26 and 2.
6, focusing magnet 27.2
7, respectively. Therefore, this focusing coil 25
If a current is applied to the focusing magnet 27.27
The lens holder 22 can be slid in the vertical direction on the actuator shaft 24 by the electromagnetic force exerted by the magnetic field on the current flowing on both sides of the focusing coil 250, and the objective lens 21 can be displaced in the focusing direction.

Tracking coils 28 are fixed to both front and rear (track direction) ends of the lens holder 22, respectively. Further, from the main body 23, the yoke 29
29 is provided upright, and tracking magnets 30, 30 are fixed to these yokes 29, 29, respectively. The tracking coils 28, 28 are arranged such that either one of the right or left sides thereof faces the tracking magnets 30, 30, respectively. Therefore, when a current is passed through the tracking coils 28, 28, the magnetic field of the tracking magnets 30, 30 is applied to the lens holder 2 by the electromagnetic force acting on the current flowing to one side of the coil.
2 can be rotated left and right on the actuator shaft 24 to displace the objective lens 21 in the tracking direction.

In addition, another example of the conventional objective lens actuator (second
Conventional example) is shown in FIGS. 5 and 6. For convenience of explanation, components having the same functions as those of the conventional example shown in FIG. 4 are given the same reference numerals.

As shown in FIG. 5, the objective lens 21 is slidably and rotatably attached to the actuator shaft 24, so that the objective lens 21 can be moved in the focusing direction and the tracking direction. The same is true for .

The cylindrical protrusion at the bottom of the lens holder 22 has a focusing coil 2 centered around the actuator shaft 24.
5 is wound. A yoke 26 is arranged around the focusing coil 25 in a ring shape from the main body 23.
is set upright, and a focusing magnet 2 is placed on the inner peripheral surface of this
7 is fixed. Therefore, if current is passed through this focusing coil 25, the focusing magnet 27
Due to the electromagnetic force exerted by the magnetic field on this current, the lens holder 22 can be slid in the vertical direction on the actuator shaft 24, and the objective lens 21 can be displaced in the focusing direction.

Tracking coils 28 are fixed to both front and rear ends of the upper part of the lens holder 22, respectively. Further, yokes 29, 29 are provided upright from the main body 23, and a tracking magnet 3 is attached to each yoke 29, 29.
0 and 30 are fixed respectively. The tracking coils 28, 28 are arranged to face the tracking magnets 30, 30, respectively. However, as shown in FIG. 6, each tracking magnet 30 is magnetized so that the opposing surface of the tracking coil 28 is separated into left and right sides, and an N pole and an S pole appear on each surface. For this reason, each tracking coil 2
Both the left and right sides of 8 face the N pole or the S pole, respectively. Therefore, when a current flows through the tracking coils 28, 28, the various magnetic fields of the tracking magnets 30, 30 cause the lens holder 22 to move toward the actuator shaft 2 by electromagnetic force acting on the current flowing on both sides of the coil.
4, the objective lens 21 can be displaced in the tracking direction.

[Problem to be solved by the invention]

However, in the case of the first conventional example, the magnetic field of the focusing magnets 27, 27 is
5, and the magnetic field of the tracking magnets 30, 30 acts only on the current flowing to one side of the tracking coils 28, 28, resulting in poor drive efficiency. Was.

However, in the case of the second conventional example, the magnetic field of the focusing magnet 27 acts on all the currents flowing through the focusing coil 25, and the magnetic field of the tracking magnets 30, 30 flows on both the left and right sides of the tracking coils 28, 28. Since it acts on the current, the above-mentioned problem of poor drive efficiency can be solved. However, in the case of this second conventional example, as in the case of the first conventional example, separate focusing magnets 27 and tracking magnets 30 must be used to apply magnetic fields to the focusing coil 25 and the tracking coil 28, respectively. Moreover, since these are fixed to the respective yokes 26 and 29, there is a problem in that the workability of assembling becomes poor.

[Means to solve the problem]

In order to solve the above problems, an objective lens actuator for an optical pickup according to the present invention has an optical pink-up objective lens attached to a main body so that a lens holder supporting the objective lens can be displaced in a focusing direction and a tracking direction. In a lens actuator, a focusing coil and a tracking coil are fixed to a lens holder in close proximity to each other, and a magnetic body is fixed at a position facing both coils in the main body, and a magnetic body is fixed on a surface of the magnetic body facing both coils. N-pole or S-pole is magnetized in both regions of the focusing coil facing both sides in the focusing direction, and N-pole or S-pole is magnetized in both regions of the tracking coil facing both sides in the tracking direction. It is characterized by

[For production]

For example, the lens holder is slidably and rotatably attached to a shaft protruding from the main body, or is attached to the main body so as to be swingable in vertical and horizontal directions via an elastic body having a hinge structure. It can be displaced in the focusing direction and the tracking direction. And the objective lens,
Along with this lens holder, the lens can be displaced in the focusing direction and the tracking direction.

When a current is passed through the focusing coil, the currents on both sides of this coil in the focusing direction are in opposite directions. However, each region of the magnetic material surface facing both sides of this coil is magnetized to mutually different north poles or south poles. Therefore, the electromagnetic forces acting on the currents flowing on both sides of the coil due to the N-pole and S-pole magnetic fields are always in the same direction. Therefore, a force acts on the focusing coil in either the focusing direction depending on the polarity of the current.

Furthermore, when a current is passed through the tracking coil, the currents on both sides of the tracking direction are in opposite directions. However, each area of the magnetic material surface facing both sides of this coil is
They are magnetized to mutually different north poles or south poles. Therefore, similarly to the above, the electromagnetic forces acting on the current flowing on both sides of the coil due to the magnetic fields of the north and south poles are always in the same direction. Therefore, a force acts on the focusing coil in one of the tracking directions depending on the polarity of the current.

As a result of the above, by flowing current through the focusing coil and the tracking coil, the lens holder, that is, the objective lens, can be appropriately displaced in the focusing direction and the trunking direction by the electromagnetic force acting on them.

Note that a plurality of pairs of both coils and the magnetic body may be provided in the lens holder.

Further, in the four magnetized regions on the magnetic material surface, the north pole and the south pole are arranged side by side in directions perpendicular to each other, so either the north pole or the Si can be shared. In this case, the sides of both coils facing the shared area need to be arranged adjacent to each other or intersecting with each other.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 to 3.

The objective lens 1 is a lens for condensing a light beam onto a recording medium in an optical pickup.

The lens holder 2 has a disk shape that is long in the front and back (tracking direction), and rectangular long holes 10 are formed along the longitudinal direction on both sides of the lens holder 2 (in the tracking direction). The objective lens l is fixedly supported around the front end of the lens holder 2. Further, the objective lens l is arranged so that its optical axis coincides with the direction perpendicular to the surface of the lens holder 2.

An actuator shaft 4 projects upward from the center of the main body 3 of the objective lens actuator. Further, a hole is bored in the center of the lens holder 2 in parallel to the optical axis direction of the objective lens 1. By fitting this hole into the actuator shaft 4 protruding from the main body 3, the lens holder 2 is attached to the actuator shaft 2.
4 in a slidable and rotatable manner. Therefore, the objective lens l is movable in the focusing direction and the tracking direction with respect to the main body 3 of the objective lens actuator.

A focusing coil 5 and a tracking coil 8 are arranged and fixed on both left and right side surfaces of the lens holder 2, respectively, in a row. However, the focusing coils 5 are wound in the same direction, but the tracking coils 8 are wound in opposite directions.

Further, from both left and right end portions of the main body 3, plate-shaped yokes 6, 6, which are long in the front-back direction, are respectively erected upward. Magnetic plates 7, 7 made of magnetic material are fixed to the inward surfaces of these yokes 6, 6, respectively. Therefore, the focusing coils 5 and the tracking coils 8 fixed to both sides of the lens holder 2 are respectively arranged at positions facing the magnetic plate 7 with a gap 11 in between.

Further, plate-shaped yokes 9, 9, which are long in the front-rear direction, are erected upward from the center portions of both the left and right sides of the main body 3, respectively. These yokes 9, 9 are connected to elongated holes 10, 10 formed on both sides of the lens holder 2.
They fit inside each other. The fit between the elongated holes 1O and 10 and the yokes 9 and 9 is such that the lens holder 2 can sufficiently rotate about the actuator shaft 4 in the tracking direction.

The surface of the one magnetic plate 7 facing the focusing coil 5 and the tracking coil 8 is magnetized as shown in FIG. That is, a region 7a on the facing surface of the magnetic plate 7 facing one side 5a above the focusing coil 5 is magnetized with an S pole. Also, a region 7b opposite to the lower side 5b of this focusing coil 5
The N pole is magnetized. Further, a region 7C facing the front side 8a of the tracking coil 8 is magnetized with an N pole. Further, a region 7d facing the rear side 8b of the tracking coil 8 is magnetized with an S pole. The opposing surface of the other magnetic plate 7 is magnetized symmetrically with this.

In addition, in order to share the north pole of this magnetic plate 7, the region 7b and the region 7C can be made to coincide with each other, as shown in FIG. However, in this case, focusing coil 5
The tracking coil 8 needs to be fixedly arranged on both sides of the lens holder 2 such that one side 5b of the tracking coil 8 intersects one side 8a of the tracking coil 8.

Thereby, the focusing coil 5 and the tracking coil 8 can be respectively arranged in a magnetic circuit formed by each magnetic pole of the magnetic plate 7 through the yokes 6 and 9.

The operation of the objective lens actuator having the above configuration will be explained.

When current is passed through the focusing coil 5, this - side 5a
An electromagnetic force in either the vertical direction acts on the current due to the magnetic field from the S-pole region 7a.

Then, the other side 5b of this focusing coil 5
An electromagnetic force in the same direction as above acts on the current due to the magnetic field from the N-pole region 7b. Therefore, a force acts on the focusing coil 5 in either direction in the focusing direction depending on the polarity of the current.

Furthermore, when a current is passed through the tracking coil 8, an electromagnetic force in either the front or rear direction acts on this negative side 8a due to the magnetic field from the N-pole region 7C. The current on the other side 8b of this tracking coil 8 has a region 7 of si.
An electromagnetic force in the same direction as above acts due to the magnetic field from d. Therefore, a force acts on the tracking coil 8 in either the forward or backward direction depending on the polarity of the current. However, since the left and right tracking coils 8 are wound in opposite directions, this force in the longitudinal direction always acts in opposite directions.

As a result, when a current is applied to the focusing coil 5, the electromagnetic force acting on the focusing coil 5 causes the lens holder 2 to slide along the actuator shaft 4, and the objective lens 1 can be appropriately displaced in the focusing direction. Also, if a current is passed through the tracking coil 8, the electromagnetic force acting on the tracking coil 8 will cause
Forces are applied to move the left and right sides of the lens holder 2 in different directions, front and rear. Then,
Since the lens holder 2 rotates in any direction around the actuator shaft 4, the objective lens 1 can be appropriately displaced in the tracking direction accordingly.

The above operation is the same regardless of whether the magnetic plate 7 is magnetized in either the state shown in FIG. 2 or FIG. 3.

In this way, the objective lens actuator of this example is
By simply arranging one magnetic plate 7 for each of the two pairs of focusing coils 5 and tracking coils 8, the objective lens 1 can be displaced in the focusing direction and the tracking direction. Further, since electromagnetic force acts on the current flowing to both sides 5a, 5b, 8a, and 8b of each focusing coil 5 and tracking coil 8, the driving efficiency is improved.

〔Effect of the invention〕

As described above, the objective lens actuator for an optical pickup according to the present invention includes the following steps: A focusing coil and a tracking coil are fixed to the lens holder in close proximity to each other, and a magnetic body is fixed at a position opposite to both coils in the main body, and focusing of the focusing coil is performed on a surface of the magnetic body facing both coils. Both regions facing both sides of the tracking coil are magnetized with N poles or S poles, and both regions of the tracking coil facing both sides of the tracking direction are magnetized with N poles or S poles, respectively. There is.

As a result, it is sufficient to fix one magnetic body to the main body for one pair of focusing coils and tracking coils. Furthermore, electromagnetic force acts on the focusing coil and the tracking coil on both sides in the focusing direction and the tracking direction, respectively.

Therefore, the objective lens actuator of the present invention has the effect of reducing the number of man-hours required for attaching the magnetic body. Moreover, like the second conventional example, the electromagnetic force is applied to the currents of both coils without waste, thereby improving the driving efficiency.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1(a) is a plan view of an objective lens actuator, and FIG. 1(b) is a plan view of an objective lens actuator, and FIG. ■ Cross-sectional rear view along the line, Figure 2 is a diagram showing an example of arrangement of magnetic plates and coils, Figure 3 is a diagram showing an example of the arrangement of magnetic plates and coils.
The figure shows another example of arrangement of magnetic plates and coils. Fourth
The figures show a conventional example (first conventional example), in which FIG. 4(a) is a plan view of an objective lens actuator, and FIG.
b) is a rear view of the objective lens actuator. Fifth
6 and 6 show another conventional example (second conventional example), in which FIG. 5(a) is a plan view of the objective lens actuator, and FIG. 5(b) is a plan view of the objective lens actuator. FIG. 6 is a cross-sectional rear view taken along the line V-V, and a perspective view showing the arrangement of the tracking magnet and the tracking coil. 1 is an objective lens, 2 is a lens holder, 3 is a main body, 4 is an actuator shaft, 5 is a focusing coil, 7 is a magnetic plate (magnetic material), and 8 is a tracking coil. Patent applicant: Sharp Co., Ltd.
a) 1st square (b) 2nd square a (7 Figure 3 Figure 4 Square (a) 5th square (a) ≦29 Figure 5 (b) Figure 6

Claims (1)

[Claims] 1. In an objective lens actuator of an optical pickup that is attached to a main body so that a lens holder supporting an objective lens can be displaced in a focusing direction and a tracking direction, a focusing coil and a tracking coil are close to each other. and fixed to the lens holder, and a magnetic body is fixed at a position facing both of these coils in the main body,
On the surface of this magnetic material that faces both coils, both regions facing both sides of the focusing coil in the focusing direction are respectively magnetized with N poles or S poles, and both regions of the tracking coil facing both sides of the tracking coil are magnetized. An objective lens actuator for an optical pickup, each of which is magnetized with either a north pole or a south pole.