JPH03152731A - Rotary optical head - Google Patents

Abstract

PURPOSE:To miniaturize a focus magnetic circuit and to increase the torque moving an objective lens in an optical axis direction by magnetizing a magnet in the focus magnetic circuit and a radial magnetic circuit in both the optical axis direction of the objective lens and arranging at least a part of magnets in the radial magnetic circuit in a repulsing relation against the magnet of the focus magnetic circuit. CONSTITUTION:The magnets in a focus magnetic circuit 110 and a radial magnetic circuit 120 are magnetized in the optical axis direction of an objective lens 101, and at least a part of the magnets in the radial magnetic circuit, for example, the magnets opposite to the magnets of the focus magnetic circuit 110 are arranged in a relation repulsing against the magnets of the focus magnetic circuit 110. Thus, the movement of the objective lens 101 in the radial direction is facilitated. Moreover, a magnetic member 131 is arranged between the focus magnetic circuit 110 and the radial magnetic circuit 120 to facilitate similarly the movement of the objective lens in the radial direction. Thus, the optical head is miniaturized and the torque moving the objective lens 101 in the optical direction is increased.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an optical head used in an optical disk device that records/reproduces information using an optical disk (including a magneto-optical disk). In particular, the present invention relates to a rotary optical head that performs an access operation through a rotational operation.

(Prior Art) An optical head used in an optical disk device focuses and irradiates a light beam for recording/reproduction onto a desired track on an optical disk through an objective lens, and also focuses and irradiates a light beam for recording/reproducing onto a desired track on an optical disk. It is detected through an objective lens.

A rotary optical head is known as one type of optical head. This is an optical head that accesses a desired track through rotational movement, and uses a magnetic circuit to move the lens holder that holds the objective lens in the radial direction of the disk and in the focus direction (direction of the optical axis of the objective lens). It is configured so that it can be done.

A magnetic circuit that moves the lens holder in the focus direction is called a focus magnetic circuit, and a magnetic circuit that moves the lens holder in the radial direction is called a radial magnetic circuit.

An example of such a rotary optical head is, for example, Japanese Patent Laid-open No. 6
1-123030.

In this conventional quadrilateral optical head, both the focus magnetic circuit and the radial magnetic circuit are provided in the fixed part. In this case, as the objective lens moves in the radial direction, the focus coil needs to be able to move in the radial direction within the focus magnetic circuit, so the focus magnetic circuit must have a shape that extends in the radial direction.

For this reason, not only does the entire optical head become larger, but
Since only a small proportion of the magnetic flux generated in the focus magnetic circuit is effectively used by interlinking with the focus coil, it is not possible to increase the driving force when moving the objective lens in the focus direction.

(Three problems to be solved by the invention) As mentioned above, in the conventional rotary optical head, the focus magnetic circuit must be shaped to extend in the radial direction, so the entire optical head becomes large, and the focus magnetic circuit There was a problem in that only a small proportion of the magnetic flux generated was effectively used, making it impossible to increase the driving force of the objective lens in the optical axis direction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotary optical head that can reduce the size of the focus magnetic circuit and increase the driving force when moving the objective lens in the optical axis direction.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, in the present invention, a focus magnetic circuit is attached to a rotating body in which an objective lens holding member is attached at a position offset from the center of rotation. A radial magnetic circuit is installed on a fixed base provided on the outside, magnets in the focus magnetic circuit and the radial magnetic circuit are both magnetized in the optical axis direction of the objective lens, and at least some of the magnets in the radial magnetic circuit are magnetized in the direction of the optical axis of the objective lens. 'It is arranged in a mutually repulsive relationship with the magnets in the magnetic circuit.

In addition, in the present invention, as another solution to achieve the above object, a focus magnetic circuit is attached to a rotating body in which the objective lens holding member is attached at a position offset from the center of rotation, and a focus magnetic circuit is attached to a fixed position provided on the outside of the rotating body. A radial magnetic circuit is installed on the base, and a magnetic member is installed between the radial magnetic circuit and the focus magnetic circuit.

This magnetic member is more preferably attached to the radial magnetic circuit via a non-magnetic member.

Furthermore, in the present invention, as another solution to achieve the above object, a focus magnetic circuit is installed on the rotating body, a radial magnetic circuit is installed on a fixed base provided outside the rotating body, and a focus magnetic circuit is installed on the rotating body. The magnet in the magnetic circuit is magnetized in the optical axis direction of the objective lens, and is also magnetized in a position approximately symmetrical to the magnet in the focus magnetic circuit with respect to the rotation center of the rotating body, and opposite to the magnet in the focus magnetic circuit in the direction of the optical axis of the objective lens. A polarized auxiliary magnet is attached.

(Function) As described above, in the present invention, the radial magnetic circuit is installed on the fixed base, but the focus magnetic circuit is installed on the rotating body, so the focus magnetic circuit allows the focus coil to move in the optical axis direction of the objective lens. Any shape is sufficient, and the shape does not need to extend in the radial direction. Therefore, the optical head can be made smaller. In addition, since the flux magnetic circuit only needs to be provided in the movement range of the focus coil in the optical axis direction of the objective lens, the generated magnetic flux effectively acts on the focus coil, resulting in an effect on the coil. The electromagnetic force, that is, the driving force that moves the objective lens in the optical axis direction increases.

On the other hand, if the focus magnetic circuit is provided on the rotating body, the focus magnetic circuit passes near the radial magnetic circuit provided on the fixed base when rotating in the radial direction, so that the magnetic interaction between the focus and radial magnetic circuits increases. Interference must be considered. That is, when an attractive force is exerted between the two magnetic circuits, it becomes difficult for the focus magnetic circuit to move in the radial direction, which impedes the movement of the objective lens in the radial direction.

According to the present invention, the magnets in the focus magnetic circuit and the radial magnetic circuit are demagnetized in the optical axis direction of the objective lens, and at least some of the magnets in the radial magnetic circuit, for example, the magnets on the side opposite to the magnets in the focus magnetic circuit, are focused. By arranging it in a mutually repelling relationship with the magnets in the magnetic circuit, this problem can be solved and the objective lens can be easily moved in the radial direction.

Further, if a magnetic member is disposed between both the focus and radial magnetic circuits, both magnetic circuits are magnetically interrupted, thereby facilitating the movement of the objective lens in the radial direction. If this magnetic member is attached to the radial magnetic circuit via a non-magnetic member, the magnetic flux flowing into the magnetic member from the radial magnetic circuit will be reduced, making it even more effective.

Furthermore, if an auxiliary magnet electromagnetized with a polarity opposite to that of the magnet in the focus magnetic circuit is installed in the optical axis direction of the objective lens at a position almost symmetrical to the magnet in the focus magnetic circuit with respect to the center of rotation of the rotating body, the focus magnetic circuit A moment is generated by the interaction between this auxiliary magnet and the magnets of the radial magnetic circuit, which cancels out the rotational moment caused by the interaction between the respective magnets of the radial magnetic circuit, facilitating the movement of the objective lens in the radial direction. .

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

First Embodiment> FIG. 1 is a perspective view of a rotary optical head according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view, FIG. 3 is a plan view, and FIG.
The figure is a side sectional view.

The objective lens 101 is a lens holder (lens holding member) 1
02, and the lens holder 102 is held by a pair of leaf springs 1.
03 so as to be movable in parallel in the direction of arrow Z, that is, in the direction of the optical axis of the objective lens 101 (also referred to as the focus direction). The other end of the leaf spring 103 is supported by a rotating drum (rotating body) 105 via a leaf spring fixing member 104. The rotating drum 105 is connected to the shaft 1 via a bearing 106.
The shaft 107 is rotatably supported by the shaft 107, and the base end of the shaft 107 is fixed to the fixed base 108 by being press-fitted or in contact with the fixed base 108. Note that the lens holder 102 is arranged at a position offset from the axis 107 that is the center of rotation of the rotating drum 105.

A focus coil 109 is wound around the lens holder 102 (see FIG. 4). This focus coil 1
A focus magnetic circuit 110 is provided on the rotary drum 105 outside the rotary drum 105 . The focus magnetic circuit 110 includes a ring-shaped magnet 111, a ring-shaped yoke 112 disposed on the magnet 111, and surrounding surfaces of the ring-shaped magnet 111 and the yoke 112.
It also includes a plate-like yoke 113 formed to support the bottom surface of the magnet 111 and fixed on the rotating drum 105.

For example, when a current corresponding to the focus error of the objective lens 101 is applied to the focus coil 109, the objective lens 101 moves in the optical axis direction of arrow Z due to the electromagnetic interaction between this current and the magnetic flux generated by the focus magnetic circuit 110. It is moved together with the holder 102 and focus control is performed.

Here, the focus magnetic circuit 110 is attached to the lens holder 10.
Since it is formed so as to surround the focus coil 109 wound around the focus coil 109, it has a very compact shape compared to a conventional rotary optical head in which the focus magnetic circuit is extended in the radial direction. This can greatly contribute to downsizing the entire head.

Moreover, unlike the focus magnetic circuit in a conventional rotary optical head, the focus magnetic circuit 110 uses almost all of the generated magnetic flux effectively by interlinking with the focus coil 109, so that the objective lens can be used despite its small size. The driving force for moving 101 in the optical axis direction can be increased.

On the other hand, a pair of radial coils 114 are fixed to both ends of the rotating drum 105 near the leaf spring fixing member 104 . Further, a pair of radial magnetic circuits 120 are arranged on the fixed base 108 outside the rotating drum 105. The radial magnetic circuit 120 is attached to the fixed base 10
8, plate magnets 121, 122, a center yoke 123, and a back yoke 124. magnet 1
21 and 122 are provided sandwiching a center yoke 123, and a back yoke 124 is provided outside the magnets 121 and 122. The fixed base 108 is attached to the back yoke 12
It also serves as another yoke on the opposite side of 4. Further, the center yoke 123 passes inside the radial coil 114.

When a current is applied to the radial coil 114, due to the electromagnetic interaction between this current and the magnetic flux generated by the radial magnetic circuit 120, the λ·l object lens 101 is generated in the radial direction of the optical disc 200 as shown by the arrow X, that is, in the tracking direction. It is moved together with the lens holder 102, and access and tracking control is performed.

Furthermore, in this embodiment, the focus magnetic circuit 110
The magnet 111 in the radial magnetic circuit 120 and the magnet 121 near the magnet 111 in the radial magnetic circuit 120 are arranged at almost the same position in the Z direction, that is, in the optical axis direction of the objective lens 101 (actually, (They are located very far apart). As shown in FIG. 5, both the magnet 111 and the magnet 121 are magnetized in the Z direction, and the polarity of the magnetization of the magnet 111 and the magnet 121 (
direction) is also the same.

In this way, the distance between the magnetic poles of the magnets 111 and 121 of the same polarity is shorter than the distance between the magnetic poles of different polarities, so a repulsive force is generated between the magnets 111 and 121. . Therefore, the focus magnetic circuit 110 is no longer attracted to the radial magnetic circuit 120, and the movement of the objective lens 101 in the optical axis direction due to the interaction between the focus coil 109 and the focus magnetic circuit 110 is facilitated.

To give a specific numerical example, the force required to rotate the focus magnetic circuit 110 against the radial magnetic circuit 120 when moving the objective lens 101 in the direction of arrow Z (hereinafter referred to as peeling force) is: If the magnets 111 and 121 are arranged in a mutually attracting relationship, the amount is about 20 tr, whereas if the magnets 111 and 121 are arranged in a mutually repelling relationship as in this embodiment, the amount is significantly reduced to about 3 g.

In addition, in the above description, the magnet 1 of the focus magnetic circuit 110
11 is slightly shifted in the optical axis direction with respect to the magnet 121 of the radial magnetic circuit 120, but as shown in FIG. 6(a), the magnet 111 and the magnet 121 are provided at the same position in the optical axis direction, and Similarly, the magnetic poles of both magnets 111 and 121 may be oriented in the same direction.

In addition, as shown in FIG. 6(b), the magnet 111 is connected to the magnet 12.
1 by a distance equal to or more than the thickness of the magnet 111 in the optical axis direction. In this case,
As shown in the figure, by reversing the direction of the magnetic poles of the magnets 111 and 121, a repulsive force is generated between the magnets 111 and 121, and the same effect as described above can be obtained.

Second Embodiment FIGS. 7 and 8 are a perspective view and a plan view of a rotary optical head according to a second embodiment of the present invention. The basic configuration of this embodiment is the same as that of the first embodiment. This embodiment differs from the first embodiment in that a semi-arc-shaped magnetic plate (magnetic member) 131 is provided between the focus magnetic circuit 110 and the radial magnetic circuit 120. The material of the magnetic plate 131 is preferably a ferromagnetic material such as iron.

In this way, both magnetic circuits 110 and 120 are magnetically isolated by the magnetic plate 131. In other words,
The magnetic plate 131 forms a magnetic path that short-circuits leakage magnetic flux from the radial magnetic circuit 120, and has the effect of suppressing the leakage magnetic flux from acting on the focus magnetic circuit 110.

Therefore, according to this embodiment, the magnetic interaction (repulsion) between the respective magnets of both magnetic circuits 110 and 120 is further reduced, and the movement of the objective lens 101 in the radial direction is further facilitated. Incidentally, when the first embodiment and this embodiment are combined, the above-mentioned peeling force is reduced to about 2 g.

Third Embodiment FIGS. 9 and 10 are a perspective view and a plan view of a rotary optical head according to a third embodiment of the present invention. Radial magnetic circuit 1
20, a non-magnetic plate (non-magnetic member) 132 is provided.

The material of the non-magnetic plate 132 may be any non-magnetic material, but resin, aluminum, etc. are suitable.

When the magnetic plate 131 is supported through the non-magnetic plate 132 in this way, the magnetic plate 13] separates from the radial magnetic circuit 120 by the thickness of the non-magnetic plate 132, and thus flows from the radial magnetic circuit 120 into the magnetic plate 131. The magnetic flux is reduced and the magnetic interaction between both magnetic circuits 110, 120 is further reduced. As a result, when this embodiment and the first embodiment are combined, the above-mentioned peeling force can be reduced to about 1 g, and the movement of the objective lens 101 in the radial direction becomes even easier.

Fourth Embodiment FIGS. 11 and 12 are a perspective view and a plan view of a convoluted optical head according to a fourth embodiment of the present invention. In this embodiment, an auxiliary magnet is magnetized at a position substantially symmetrical to the magnet 111 of the focus magnetic circuit 110 with respect to the axis 107, which is the center of rotation of the rotating drum 105, and with a polarity opposite to that of the magnet 111 in the optical axis direction of the objective lens 101. A magnet 140 is attached.

According to this embodiment, the rotational moment generated by the interaction between the magnets of the focus magnetic circuit 110 and the radial magnetic circuit 120 is opposite in direction and has substantially the same magnitude as that of the auxiliary magnet 140 and the radial magnetic circuit 120. occurs due to the interaction of Therefore, due to the rotational moment newly generated by this auxiliary magnet 140,
Rotational moments caused by interaction between the magnets of the focus magnetic circuit 110 and the radial magnetic circuit 120 are canceled out.

As a result, similarly to the first to third embodiments, the objective lens 1
01 can be easily moved in the radial direction.

Note that the present invention is not limited to the above embodiments,
Various modifications can be made without departing from the gist of the invention. For example, the second and third embodiments may be implemented separately from the first embodiment, or the fourth embodiment and the first to third embodiments may be implemented separately.
It is also possible to implement it in combination with any of the third embodiments.

[Effects of the Invention] According to the present invention, the focus magnetic circuit is small,
It is possible to provide a rotary optical head that can downsize the entire head and has a large driving force for moving the objective lens in the optical axis direction.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a first embodiment of the present invention, Fig. 2 is an exploded perspective view of the same embodiment, Fig. 3 is a side view of the same embodiment, and Fig. 4 is a side view of the same embodiment. 5 is a cross-sectional view, and FIG.
The figures also show other examples of the positional relationship and magnetization polarity relationship of the magnets in the focus magnetic circuit and the radial magnetic circuit, FIG. 7 is a perspective view showing the second embodiment of the present invention, and FIG. FIG. 9 is a plan view of the same embodiment, FIG. 9 is a perspective view of the third embodiment of the present invention, FIG. 10 is a plan view of the same embodiment, and FIG. 11 is a perspective view of the fourth embodiment of the present invention. 12 are plan views of the same embodiment. 101... Objective lens 102... Lens holder (lens holding member) 103.
... Leaf spring 104 ... Leaf spring support member 105 ... Rotating drum (rotating body) 106 ... Bearing 107 ... Shaft 108 ... Fixed base 109 ... Focus coil 110 ... Focus magnetism Circuit 111.112...Magnet 113...Yoke 120...Radial magnetic circuit 121.122...Magnet 123.124...Yoke 131...Magnetic plate (magnetic member) 132...Nonmagnetic Plate (non-magnetic member) 140... Auxiliary magnet 200... Optical disk

Claims (4)

[Claims] (1) A rotating body, a lens holding member attached to a position offset from the center of rotation of the rotating body, an objective lens held by the lens holding member, and a lens holding member attached to the lens holding member and holding the objective lens. A focus magnetic circuit consisting of a focus coil that moves in the focus direction, a magnet and a yoke that generate a magnetic flux that interlinks with the focus coil, and a focus magnetic circuit that is attached to the rotary body and rotates the rotary body to move the objective lens to the optical disk. In the rotary optical head, the focus magnetic circuit includes a radial coil that moves in the radial direction of the rotating body, and a radial magnetic circuit that includes a magnet and a yoke that generate magnetic flux that interlinks with the radial coil. Magnetic circuits are respectively provided on identification bases provided outside the rotating body, and magnets in the focus magnetic circuit and the radial magnetic circuit are both magnetized in the optical axis direction of the objective lens, and at least a portion of the radial magnetic circuit is magnetized in the optical axis direction of the objective lens. A rotary optical head characterized in that the magnet is arranged in a mutually repelling relationship with the magnet in the focus magnetic circuit. (2) A rotating body, a lens holding member attached to a position offset from the center of rotation of the rotating body, an objective lens held by the lens holding member, and a lens holding member attached to the lens holding member and holding the objective lens. A focus magnetic circuit consisting of a focus coil that moves in the focus direction, a magnet and a yoke that generate a magnetic flux that interlinks with the focus coil, and a focus magnetic circuit that is attached to the rotary body and rotates the rotary body to move the objective lens to the optical disk. In the rotary optical head, the focus magnetic circuit includes a radial coil that moves in the radial direction of the rotating body, and a radial magnetic circuit that includes a magnet and a yoke that generate magnetic flux that interlinks with the radial coil. A rotary optical head characterized in that magnetic circuits are respectively provided on fixed bases provided on the outside of the rotating body, and further a magnetic member is provided between the focus magnetic circuit and the radial magnetic circuit. (3) Claim 2, wherein the magnetic member is attached to the radial magnetic circuit via a non-magnetic member.
The rotary optical head described. (4) A rotating body, a lens holding member attached to a position offset from the center of rotation of the rotating body, an objective lens held by the lens holding member, and a lens holding member attached to the lens holding member and holding the objective lens. A focus magnetic circuit consisting of a focus coil that moves in the focus direction, a magnet and a yoke that generate a magnetic flux that interlinks with the focus coil, and a focus magnetic circuit that is attached to the rotary body and rotates the rotary body to move the objective lens to the optical disk. In the rotary optical head, the focus magnetic circuit includes a radial coil that moves in the radial direction of the rotating body, and a radial magnetic circuit that includes a magnet and a yoke that generate magnetic flux that interlinks with the radial coil. Magnetic circuits are respectively provided on fixed bases disposed outside the rotating body, and the magnets in the focus magnetic circuit are magnetized in the optical axis direction of the objective lens, and the magnets are magnetized in the direction of the optical axis of the objective lens. A rotary optical head characterized in that an auxiliary magnet is attached at a position substantially symmetrical to the magnet in the focus magnetic circuit in the optical axis direction of the objective lens with the direction of the magnet and the magnetic pole in the focus magnetic circuit being reversed.