JPH0792890B2 - Magnetic field application device for recordable optical disk - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field applying device for a recordable optical disc used for recording an information signal on a recordable optical disc such as a magneto-optical disc.

[0002]

2. Description of the Related Art Conventionally, for example, GdCo, FeTe, Gd
By irradiating the recording film of a recording-type optical disk having a recording film made of a thin film such as TbFe with a laser beam, the magnetization formed in the perpendicular direction of the recording film is changed by the Kerr effect. A recording device for recording a predetermined information signal has been proposed.

When writing and / or erasing an information signal on the recording film, it is necessary to apply a magnetic field having a specific polarity to the recording film. Therefore, a recording device that records and / or erases an information signal on such a recordable optical disc includes a magnetic field applying device that applies a magnetic field to the recordable optical disc. That is, as shown in FIG. 6, the optical pickup device 10 is provided on one side of the recording type optical disc 102 on which the recording film 101 is formed.
3 are opposed to each other, and the magnetic field applying device 104 is opposed to the other surface side of the recording type optical disk 102.

The magnetic field applying device 104 has a magnet 105. As shown in FIG. 6, the magnet 105 is rotatably supported by a support shaft 106 so as to face one surface of the recording type optical disk 102 facing the optical pickup device 103 and the other surface thereof. And this magnet 10
In order to control the rotation of No. 5, the first coil 107 is arranged at a position deviated in the circumferential direction of the recording type optical disc 102 from a position facing the other surface of the recording type optical disc 102 via the support shaft 106. And a second coil 108 that surrounds the magnet 105 and that generates a magnetic field orthogonal to the recording film 101. In addition, the first coil 107 and the second coil 108.
Magnetic field detecting means 109 such as a Hall element for detecting the rotational angle position of the magnet 105 is provided at a predetermined position between and.

In a recording apparatus having such a magnetic field applying device 104, as shown in FIG.
In order to write an information signal to a recording type optical disc (orientation disc) in which 01 is magnetized in one direction, the intensity of the laser beam emitted from the optical pickup device 103 to the recording surface 101 is increased and at the same time. A magnetic field in the direction opposite to the magnetization direction of the recording film 101 is applied by the magnet 105. That is, utilizing the fact that the magnetization of the recording film 101 is reversed, the magnet 10
5 is rotationally controlled by the first and second coils 107 and 108 to invert the state in which recording and / or erasing is not performed, and while modulating the laser beam according to a predetermined information signal, The recording type optical disk 10
2 is rotationally driven. Then, the magnetization direction of the recording film 101 is inverted according to the change in the intensity of the laser beam, as shown by the arrow in the section indicated by W _T in FIG. 6, and the information signal is written.

The above first and second coils 107 and 108
As shown in FIG. 6, the rotation control of the magnet 105 is performed by the magnetic field generated by the magnet 105 and the first magnetic flux φ generated by the first and second coils 107 and 108.
_This is done by the interaction with ₁ and the second magnetic flux φ ₂ .

That is, in the state before supplying the drive current to the first and second coils 107 and 108 shown in FIG. 7A, the direction of the magnetic field generated by the magnet 105 is the above-mentioned recording. It is equal to the direction of magnetization of the surface 101. By supplying a drive current in a predetermined direction to the first coil 107, an apparent magnetic pole n ₁ is formed by the _first magnetic flux φ _{1 as} shown in FIG. 7A. When the apparent magnetic pole n ₁ and the S pole of the magnet 105 attract each other,
(B) Rotational force (kick torque) in the direction indicated by the middle arrow k
In response to this, rotation is started as shown in FIG. Then, as shown in FIG. 7C, the magnet 105 continues to rotate due to the apparent magnetic pole n ₁ and the S pole of the magnet 105 attracting each other, and as shown in FIG. To
Even if the S pole of the magnet 105 and the apparent magnetic pole n ₁ come closest to each other, and then the S pole of the magnet 105 and the apparent magnetic pole n ₁ start moving away from each other due to the rotation of the magnet 105,
The magnet 105 continues to rotate due to its inertial force. At this time, the angular position of the magnet 105 is detected by the magnetic field detecting means 109, a predetermined drive current is supplied to the second coil 108, and the second magnetic flux φ ₂ is generated.
The second magnetic flux φ ₂ forms apparent magnetic poles s ₂ and n ₂ as shown in FIG. 7D. Due to these apparent magnetic poles n ₁ , n ₂ and s ₂ , the magnet 105
7D, a stopping force (brake torque) in the direction indicated by the arrow b in FIG. 7D acts, and the magnet 105 starts decelerating. Then, the magnet 105 continues to rotate due to inertia while decelerating, and as shown in (e) of FIG. 7, stops in an inverted state with respect to the beginning of rotation. At this time, the magnetic field detection means 109 detects that the magnet 105 is reversed, and the first and second coils 10 are detected.
The drive current supply to 7, 108 is cut off. The first and second magnetic fluxes φ ₁ and φ ₂ disappear, and the magnet 105
The rotating force and the stopping force for the
5 is kept stopped.

[0008]

In the magnetic field applying device as described above, the magnet 1 is generated by the first magnetic flux φ ₁ formed by the first coil 107.
The turning force and the stopping force applied to 05 vary depending on the angular position of the magnet 105, as shown in FIG.

That is, when the rotation angle of the magnet 105 shown in FIG. 7A is 0 °, the magnet 105 receives a rotational force as shown in FIG. 8A. The magnet 105 starts to rotate by receiving the rotational force, and when the north pole and the south pole of the magnet 105 shown in FIG. 7B have the same distance with respect to the apparent magnetic pole n ₁ . As shown in FIG. 8 [b], the rotational force on the magnet 105 is maximized. The magnet 105 continues to rotate by receiving the rotational force, and when the rotation angle of the magnet 105 shown in (c) of FIG. 7 becomes 90 °, as shown in [c] of FIG. The magnet 105 receives a rotational force. And
The rotation angle of the magnet 105 shown in (d) of FIG.
And the S pole of the magnet 105 exceeds the apparent magnetic pole n.
_In the state closest to ₁ , the rotational force on the magnet 105 becomes zero, as indicated by [d] in FIG.

The magnet 105 continues to rotate further due to its inertial force, and the state shown in FIG.
When the S pole of the magnet 105 moves away from the apparent magnetic pole n ₁ between the state shown by (e) in the middle and the state shown by (e), as shown between [d] and [e] in FIG. Receives a stopping power.

As described above, while the magnet 105 rotates 180 °, the magnet 105 rotates the first magnetic flux φ.
_The force received from ₁ is the rotational force until the magnet 105 rotates beyond 90 °. That is, the magnet 105
The angular range in which the stop force is received is smaller than the angular range in which the rotational force is received. Therefore, with only the first coil 107, there is an imbalance between the rotational force and the stopping force applied to the magnet 105, and the magnet 105 cannot be stopped in the inverted state. As a result, the magnet 105 rotates beyond 180 °, causing a so-called overshoot. When this overshoot occurs, the magnetic field applied to the recording film 101 does not have a predetermined direction and strength, and accurate recording characteristics cannot be guaranteed.

Therefore, due to the second magnetic flux φ ₂ generated by the second coil 108, the S pole of the magnet 105 shown in (d) of FIG. 7 comes closest to the apparent magnetic pole n _1. In this state, a stopping force is applied to the magnet 105 to compensate for the stopping force of the first magnetic flux φ ₁ and the magnet 105 is adjusted to stop in the inverted state. As described above, in order to supply the drive current to the second coil 108 when the magnet 105 reaches the predetermined angular position, the angular position of the magnet 105 is set by the magnetic field detecting means 109. It is necessary to detect and control the supply of the drive current to the second coil 108 based on this detection.

The circuit for controlling the drive current supplied to the second coil 108 includes a circuit for controlling the drive current supplied to the first and second coils 10 when it is detected that the magnet 105 is reversed.
It is necessary to separately provide a circuit for interrupting the drive current supplied to each of 7 and 108, independently. Therefore, the structure of the magnetic field applying device is complicated.

The amount of drive current supplied to the second coil 108 and the angular position of the magnet 105 at which supply is started are determined by the strength of the first magnetic flux φ ₁ and the magnet 10.
It must be determined in consideration of various conditions such as the magnitude of the inertial force of 5 and cannot be easily determined. Therefore, it is difficult to design and manufacture the magnetic field applying device.

Further, a circuit for controlling the amount of drive current supplied to the second coil 108 and the start of supply is required to have high precision, and the manufacture and adjustment of this circuit is a complicated work. .

Therefore, the present invention has been proposed in view of the above-mentioned circumstances and facilitates design, manufacture and adjustment, and stops in a state in which a rotatably supported magnet is accurately inverted. It is an object of the present invention to provide a magnetic field applying device for a recording-type optical disc that is configured as described above.

[0017]

In order to achieve the above-mentioned object, a magnetic field applying device for a recording-type optical disc according to the present invention has an axis facing the recording-type optical disc surface and having an axis parallel to the recording-type optical disc surface. The magnet includes a magnet rotatably supported in the center and first and second coils to which a driving current for controlling the rotation of the magnet is supplied.
Coils are arranged in parallel at the symmetrical positions on the left and right sides of the rotation center axis of the magnet while facing the recording type optical disk surface.

[0018]

In the magnetic field applying apparatus for the recording type optical disk according to the present invention, the driving current is simultaneously supplied to each of the first and second coils, so that the magnet is applied to the magnet while rotating by 180 °. Since the rotational force and the stopping force given by the same become equal, the magnet stops in the inverted state.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. A magnetic field applying device for a recordable optical disc according to the present invention is, for example, a GdC as shown in FIG.
Recording film 1 composed of a thin film of o, FeTe, GdTbFe, etc.
The present invention is applied to a recording-type optical disc apparatus that records and / or erases an information signal with respect to a recording-type optical disc 102 having 01 on one surface.

As shown in FIGS. 1 and 2, the magnetic field applying device for a recording-type optical disk according to the present invention faces one surface of the recording-type optical disk 102 opposite to the one surface on which the recording film 101 is provided. Magnet 1 is disposed. The magnet 1 is supported rotatably around an axis extending in the radial direction of the optical disk 102, which is parallel to the other surface of the recording optical disk 102. Further, the first and second coils 2 and 3 which face the other surface of the recording optical disk 102 and to which a drive current for controlling the rotation of the magnet 1 is supplied.
Is provided. These first and second coils 2 and 3
Are arranged in parallel at symmetrical positions on the left and right sides of the rotation center axis of the magnet 1.

The magnet 1 has the recording type optical disk 1
A rod-shaped magnet having a length extending over the inner and outer circumferences of the No. 02 recording area is used. The magnet 1 is magnetized in a direction from one side to the other side, as shown in FIG. The magnet 1 is extended in the radial direction of the recording-type optical disc 102 by a support mechanism (not shown) so that one side or the other side faces the other side of the recording-type optical disc 102. It is rotatably supported around a support shaft 4 parallel to the other surface.

The first and second coils 2 and 3 are wound in a substantially rectangular shape, and the length in the longitudinal direction thereof is substantially equal to the length of the magnet 1. Each of the first and second coils 2 and 3 is attached to a support plate 5 which is supported in parallel with the other surface of the recording type optical disc 102 via the magnet 1 by a support mechanism (not shown). . The first coil 2 and the second coil 3 are arranged symmetrically in parallel with each other with their longitudinal directions opposed to each other with the support shaft 4 as the center. The first and second coils 2 and 3 are supported so that the direction of the magnetic flux generated when current is supplied to each of them is perpendicular to the recording film 101.

The magnet 1 is provided at a predetermined position on the support plate 5.
A magnetic field detecting means 6 such as a Hall element for detecting the angular position of is provided.

The magnetic field applying device for the recording type optical disk according to the present invention having the above-mentioned structure is an optical device for sandwiching the recording type optical disk 102 in the recording type optical disk device as shown in FIGS. It is arranged so as to face the pickup device 103.

In the recording type optical disc device, when writing an information signal to a recording type optical disc (orientation disc) in which the recording film 101 is magnetized in one direction, the magnet 1 is used for the first and the second recording medium. Second
By controlling the rotation around the support shaft 4 by the coils 2 and 3 of the above, and reversing the state in which writing is not performed, the direction of the magnetic field generated by the magnet 1 is changed.
The direction of magnetization is 01. At this time, the magnetic field strength of the magnet 1 on the recording surface 101 is maximized in the direction opposite to the magnetization direction of the recording film 101, as shown in the section Wr of FIG. Also,
The recording type optical disc 102 is rotationally driven while modulating the laser beam according to a predetermined information signal, as indicated by a section Write in FIG. Then, as indicated by the arrow in the recording film 101 in the section indicated by Wt in FIG. 2, the magnetization direction of the recording surface 101 is reversed according to the change in the intensity of the laser beam, and the writing of the information signal is performed. Done.

When the information signal is not written, the direction of the magnetic field generated by the magnet 1 is the same as the magnetization direction of the recording film 101, as shown in the section indicated by Or in FIG. It is made to become. At this time, the magnetic field strength of the magnet 1 on the recording surface 101 is maximized in the same direction as the magnetization direction of the recording film 101, as shown in the section Or of FIG. In this state, even if the recording type optical disc 102 is rotationally driven,
The magnetization direction of the recording film 101 does not change.

To erase the information signal, the direction of the magnetic field generated by the magnet 1 is as shown by the section Er in FIG. 3D, the recording film 1 before the information signal is written.
01, and the laser beam has a predetermined intensity sufficient for erasing, as shown in the section Erase of FIG. It is performed by rotationally driving.

As described above, when recording and / or erasing the information signal, the magnet 1 is set so that the direction of the magnetic field generated by the magnet 1 becomes a predetermined direction depending on the case. It is necessary to control the rotation. In the magnetic field applying apparatus for the recording type optical disk according to the present invention, a predetermined drive current as shown in FIG. 3A is applied to the first and second coils 2 and 3 by the arrow i in FIG. ₁ or arrow i ₂
As shown in, the rotation of the magnet 1 is controlled by simultaneously supplying the first and second coils 2 and 3 in the same direction in the adjacent portions.

That is, the first and second coils 2,
3 is supplied with a predetermined constant current for a predetermined time as shown in section A of FIG. 3 (a), and a current in the direction indicated by arrow i ₁ in FIG. 4 (a)
As shown in (e) to (e), the rotation is controlled and the motor is stopped in the inverted state.

Before writing the information signal, the magnet 1 is oriented in a predetermined direction, as shown in FIG. Then, in the first and second coils 2 and 3,
When a drive current in the direction indicated by arrow i ₁ in FIG. 1 is supplied,
As shown in FIG. 2, the first and second coils 2 generate first and second magnetic fluxes Φ ₁ and Φ ₂ , respectively. As described above, the first and second magnetic fluxes Φ ₁ and Φ ₂ are combined because the directions in which the drive currents flow are the same in the portions where the first and second coils 2 and 3 are adjacent to each other. The magnetic flux becomes Φ. As shown in FIG. 4A, this magnetic flux Φ forms apparent magnetic poles N ₁ and S ₁ at symmetrically juxtaposed positions about the spindle 4.

The magnet 1 has a rotational force in a direction indicated by an arrow T, as shown in FIG. 4 (a), due to the magnetic force exerted by the N and S poles of the magnet 1 and the apparent magnetic poles N ₁ and S ₁ . Received and started rotating. At this time, the apparent magnetic pole N ₁
When the force exerted on the magnet 1 by the magnet is the driving force F ₁ and the force exerted by the apparent magnetic pole S ₁ on the magnet 1 is the driving force F ₂ , the driving force F ₁ and the driving force F ₂ are shown in FIG. As shown, it changes with the rotation of the magnet 1. A driving force F, which is a resultant force of the driving force F ₁ and the driving force F ₂ , is applied to the magnet 1. The driving force F when the magnet 1 shown in FIG. 4A starts to rotate is a rotational force (kick torque) for rotating the magnet 1 as shown in FIG. 5A. is there.

Due to the rotation of the magnet 1, as shown in FIG. 4B, the N pole of the magnet 1 becomes the apparent magnetic pole S ₁
When the driving force F ₂ becomes closest to
It becomes zero as shown in the middle [b]. At this time, the driving force F ₁ gives a rotational force in the direction of arrow T shown in FIG. 4B to the magnet 1, so that the driving force F is
As shown by [B] in FIG. 5, it is a rotational force. Therefore, the rotation of the magnet 1 is further accelerated.

When the magnet 1 is rotated by 90 ° as shown in FIG. 4 (c), the apparent magnetic pole N ₁ is different from the magnet 1 in FIG. 4 (c). ), A rotational force in the direction of arrow T is exerted. Further, the apparent magnetic pole S ₁ exerts a stopping force (brake torque) on the magnet 1 in the direction of arrow B to stop the rotation of the magnet 1 as shown in FIG. 4C. ing. At this time, since the distance from the N pole of the magnet 1 to the apparent magnetic pole S ₁ is equal to the distance from the S pole of the magnet 1 to the apparent magnetic pole N ₁ , the rotational force and the above The stopping power is the same. That is, the driving force F ₁ and the driving force F ₂ are forces having the same magnitude in opposite directions. Therefore, as shown in FIG. 5C, the driving force F becomes zero. However, at this time, since the magnet 1 has an inertial force, it further continues to rotate. When the magnet 1 rotates over 90 °, the driving force F ₂ becomes larger than the driving force F ₁ as shown between [c] and [d] in FIG. Since F becomes a stopping force, the magnet 1 starts decelerating.

The magnet 1 continues to rotate, and as shown in FIG. 4D, the south pole of the magnet 1 is the apparent magnetic pole N ₁
When the driving force F ₁ is closest to
It becomes zero as shown in the middle [d]. At this time, the driving force F ₂ is a stopping force in the direction indicated by the arrow B in FIG. Therefore, the driving force F is a stopping force, and the magnet 1 is further decelerated.

When the magnet 1 is reversed as shown in FIG. 4E, the magnet 1 is driven by the driving force F shown in the section from [d] to [e] in FIG. It slows down and stops. At this time, the magnetic field detecting means 6 detects that the magnet 1 is reversed, and based on this detection, the supply of the drive current to the first and second coils 2 and 3 is cut off, thereby The magnet 1 is held in a stopped state. The output of the magnetic field detecting means 6 increases with the rotation of the magnet 1 as shown in (c) of FIG. 3, and becomes maximum when the magnet 1 rotates 90 °, and is inverted. Sometimes it becomes zero again.

In the magnetic field applying apparatus for the recording type optical disk according to the present invention, the energy of the rotational force and the energy of the stopping force by the driving force F applied to the magnet 1 while the magnet 1 rotates 180 °. Is equal to.
Therefore, the kinetic energy given by the driving force F by the time the magnet 1 rotates 90 ° is the driving force by the time the magnet 1 reaches the inverted position from the position rotated 90 °. All are destroyed by F. Therefore, the magnet 1 stops in the inverted state, and if the driving force F disappears at this time, the magnet 1 is held in the stopped state.

The first and second coils 2 and 3 are
To the first and second coils 2 and 3 by supplying a drive current as shown in section B of FIG.
_When the current in the direction indicated by ₂ is made to flow, the above magnetic flux Φ
Has the opposite polarity to the state shown in FIG. 4 as described above. At this time, since the magnet 1 is already in the inverted state, the rotation of the magnet 1 by the magnetic flux Φ at this time is the same as the rotation of the magnet 1 described above.
To (e) in FIG.

In the embodiment described above, the first
The second coil 2 and the second coil 3 are attached to the support plate 5 so that the direction of the magnetic flux generated is perpendicular to the other surface of the recording type optical disc 102. However, the first and second coils 2, 3
However, the direction of the magnetic flux generated is the above-mentioned recording type optical disc 1
02 even if it is tilted with respect to the other surface, as long as it is arranged symmetrically with respect to a plane perpendicular to the disk surface of the recording type optical disk 102 including the support shaft 4, The same effect as the example is obtained, and the magnet 1
Stops in the inverted state.

[0039]

As described above, in the magnetic field applying device for the recordable optical disk according to the present invention, the first and second magnetic field applying devices are provided.
By simultaneously supplying equal driving currents to the respective coils, the respective energies of the rotational force and the stopping force applied to the magnet during the rotation of 180 ° are equal.

Therefore, the magnet stops in the inverted state, and so-called overshoot does not occur. Therefore, in the magnetic field applying device for the recordable optical disk according to the present invention, the coil for preventing the overshoot provided in the conventional magnetic field applying device and the circuit for controlling the current supplied to the coil are not provided. It is unnecessary and has a simplified structure.

That is, according to the present invention, since the structure is simplified, the design, manufacturing and adjustment are facilitated, and the rotatably supported magnet is stopped in the state of being correctly inverted. It is possible to provide a magnetic field applying device for a recordable optical disc that guarantees various recording characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a magnetic field applying apparatus for a recording type optical disk according to the present invention and an arrangement state in a recording type optical disk apparatus to which the magnetic field applying apparatus for a recording type optical disk according to the present invention is applied.

FIG. 2 is a side view schematically showing a configuration of a magnetic field applying device for the recording type optical disc and an arrangement state in the recording type optical disc device.

FIG. 3 is a diagram showing the current supplied to the first and second coils of the magnetic field applying device for the recording type optical disc, the output of the magnetic field detecting means, the magnetic field strength applied to the recording type optical disc, and the optics of the recording type optical disc device. FIG. 6 is a waveform diagram showing a change in intensity of a laser beam emitted by a pickup device.

FIG. 4 is a schematic diagram illustrating a rotating state of a magnet of a magnetic field applying device for the recording type optical disc.

FIG. 5 is a graph showing driving force applied to the magnet by the first and second coils.

FIG. 6 is a side view schematically showing a configuration of a magnetic field applying device for a conventional recording type optical disc and an arrangement state in a recording type optical disc device to which the conventional magnetic field applying device for a recording type optical disc is applied.

FIG. 7 is a schematic diagram illustrating a rotating state of a magnet of a magnetic field applying device for a conventional recordable optical disc.

FIG. 8 is a graph showing a driving force applied to a magnet of a magnetic field applying device for a conventional recordable optical disc.

[Explanation of symbols]

 1 Magnet 2 1st Coil 3 2nd Coil 4 Spindle 101 Recording Film 102 Recording Type Optical Disc 103 Optical Pickup Device

Claims (1)

[Claims] 1. A magnet that faces a surface of a recording-type optical disk and is rotatably supported about an axis parallel to the surface of the recording-type optical disk, and a drive current that controls the rotation of the magnet.
And a second coil, wherein the first and second coils are the recording-type optical disc surface.
On the left and right sides of the rotation center axis of the magnet.
Magnetic field applying device for a recording-type optical disc which is arranged in parallel at the symmetrical position of .