JP2940649B2 - Magnetic field generator for magneto-optical recording - 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 generator for magneto-optical recording which enables a recording signal to be overwritten by applying a modulating magnetic field to a magneto-optical recording medium.

[0002]

2. Description of the Related Art Magneto-optical recording methods are roughly classified into two types, an optical modulation method and a magnetic field modulation method. In the light modulation method, a beam whose emission level changes according to a recording signal is irradiated from an optical head in a state in which a constant bias magnetic field having a different polarity from that at the time of erasing is applied to a recording medium.
When the light emission level is high, the temperature of the recording film at the irradiation spot is raised to the Curie temperature or higher, and when the temperature is lowered, the recording film is magnetized in the direction of the bias magnetic field.

On the other hand, in the magnetic field modulation system, a light beam having a constant intensity is constantly irradiated, and the direction of a bias magnetic field is controlled in accordance with a recording signal. Ii) Erasing and recording can be performed simultaneously, that is, overwriting (overwriting) can be performed.

FIG. 5 shows a conventional example of a magneto-optical recording apparatus of a magnetic field modulation system. That is, a constant laser beam irradiated from the semiconductor laser 38 onto the perpendicular magnetic film 34 of the magneto-optical disk 36 is condensed via the lens 37, and the temperature of the perpendicular magnetic film 34 is passed through the disk substrate 35 to the magnetic film. 34, the magnetic field generated by the magnetic head 31 is modulated via a magnetic field modulation circuit 33 in accordance with a recording signal, and a magnetic pattern corresponding to a change in the magnetic field is left on the magnetic film 34 to thereby obtain information. It is for recording.

When recording is performed by such a magnetic field modulation method, the magnetic field required for reversing the magnetization of the perpendicular magnetization film 34 depends on the film characteristics, but generally requires a large magnetic field of several hundred Oe or more. . Further, in order to take advantage of the non-contact recording of the magneto-optical recording, the magnetic head 1 needs to be separated from the magneto-optical disk 36 by several hundreds μm or more. Magnetomotive force is required. Further, in order to perform high-density recording, it is necessary to sufficiently increase the rise time of the magnetic field generated by the head.

In order to satisfy such a condition, it is necessary to generate a magnetic flux which changes at a high speed in accordance with a recording signal inside a core around which an exciting coil of a magnetic head is wound. Therefore, as means for instantly applying a high voltage to both ends of the coil with low power consumption, auxiliary coils 40 and 4 as shown in FIG.
Magnetic head drive circuit using a back electromotive voltage of 1
-94406) has been devised. This magnetic head drive circuit includes auxiliary coils 40 and 41 having an inductance sufficiently larger than the inductance of the head coil 42, and switches the switching elements 43 and 44 on and off alternately.
F, the sum of the back electromotive voltage generated in the auxiliary coils 40 and 41 and the voltage Vc of the DC power
2 to generate magnetic flux that changes at high speed in the head using a low-voltage power supply.

However, in this drive circuit, due to the action of the back electromotive force generated in the head coil 42, the exciting current is not constant, and fluctuates greatly when a steady magnetic field is generated. Also, in high-density recording, the pulse width of the recording signal becomes shorter, so that the time for releasing the energy stored in the auxiliary coils 40 and 41 becomes shorter, the current that can be passed to the head becomes smaller, and the stored energy becomes smaller. Become. For this reason,
In high-density recording, there is a problem that the magnetic field generated by the head is reduced.

In order to solve the above-mentioned problem of the driving circuit, the present applicant has disclosed in Japanese Patent Application No. 2-116114.
A resonance type magnetic head drive circuit has been proposed. This head drive circuit 49 is shown in FIG. As shown in FIG. 7, the head drive circuit 49 includes the head coil 42 and the auxiliary coil 4.
7 excluding 7.

In FIG. 7, a head coil 42 is a coil of a magnetic head for modulating a magnetic field, and has an inductance L. The head coil 42 has a capacitor 46 connected in series.
Are connected, and the capacitance is C. Capacitor 4
6 and the head coil 42 form a series resonance circuit. This resonance circuit is connected to a DC power supply 45 via a first switching element 43.

An auxiliary coil 47 is connected in parallel to both ends of the capacitor 46 of the series resonance circuit. The auxiliary coil 47 has an inductance Le larger than the inductance L of the head coil 42. Are connected to a DC power supply 45 via a second switching element 44.

Here, each of the switching elements 43, 44
For example, the recording signal RS is applied directly and via the inverter 48, and accordingly, the recording signal RS is alternately turned on and off in response to the recording signal RS.
3 is OFF and the second switching element 44 is ON, the auxiliary coil 47 is connected to the DC power supply 45, and the auxiliary coil 47 has an auxiliary coil exciting current i of と し て · Le.
Energy corresponding to i · i is accumulated.

Further, the second switching element 44 is turned off.
The back electromotive voltage generated at both ends of the auxiliary coil 47 is sometimes given to the capacitor 46 of the series resonance circuit by the energy stored in the auxiliary coil 47, and at the same time, the first switching element 4
Since 3 is ON, a resonance current flows through the magnetic head coil 42 under the resonance condition of the series resonance circuit.

According to this prior art, the back electromotive voltage generated by the auxiliary coil 47 is applied to the resonance capacitor 46, and the magnetic field generating head coil 4 constituting the head under the resonance condition.
When the back electromotive voltage is large by flowing the resonance current to 2,
High voltage is applied to the head even if the power supply voltage Vc is low
In addition, if the series resonance condition is satisfied, the current flowing through the head will not depend on the inductance of the head,
The head changes quickly because it is determined only by the loss resistance of the circuit.
This allows a large current to flow, thereby enabling high-density magnetic field modulation recording with low power consumption.

However, in the drive circuit using the back electromotive force of the auxiliary coil in the prior art shown in FIGS. 6 and 7, in order to make the inductance of the auxiliary coil equal to or more than that of the head, many coils are wound or the core is wound. Therefore, an auxiliary coil having a size equal to or larger than that of the magnetic head having a large cross-sectional area is required, and there is a problem that the space occupied by the auxiliary coil in the drive circuit becomes large.

Further, in order to reduce the core loss of the auxiliary coil, it is necessary to form the core with a magnetic material having the same high frequency characteristics as the magnetic head. Has the problem that the cost is as high as that of the magnetic head. In order to solve the problem of the drive circuit using the back electromotive voltage of the auxiliary coil as described above, the present applicant has a feature in Japanese Patent Application No. 2-289586 that the auxiliary coil and the magnetic head are formed on the same core. Has been proposed. This magnetic field generator is shown in FIG.

In FIG. 8, a magnetic head 51 includes a main magnetic pole portion 52, a main magnetic pole exciting coil 53 wound therearound, a drive circuit auxiliary inductor portion 54, and an auxiliary coil 55 wound therearound.
And a portion 56 connecting the core of the main magnetic pole portion 52 and the core of the auxiliary inductor portion 54. Auxiliary inductor part 5
4 is set to be larger than the inductance L20 of the main pole exciting coil 53.

Here, 52, 54, and 56 are integral cores, and the tip of the main magnetic pole portion 52 faces the optical pickup 57 via the magneto-optical disk 6 as a magneto-optical recording medium. Here, the coil 53 wound around the main magnetic pole portion 52 corresponds to the head coil 42 of the drive circuit shown in FIGS. 6 and 7, and the auxiliary coil 55 wound around the auxiliary inductor portion 54
Are the auxiliary coils 40, 4 of the drive circuit shown in FIGS.
1,47.

According to the magnetic head 51, the first coil 5 is provided as a magnetic head coil on the same core of the magnetic head.
3 and a space for winding the second coil 55 as an auxiliary coil, the auxiliary coil of the magnetic head drive circuit can be integrated with the magnetic head. Therefore, there is no need to provide the auxiliary coil in the space of the drive circuit. The size and cost of the entire circuit can be reduced.

Further, the material of the magnetic head core has high magnetic characteristics in high-frequency excitation, for example, high permeability and saturation magnetic flux density in high-frequency magnetic fields, and small iron loss. Therefore, the auxiliary coil of the drive circuit excited at the same frequency is used. And a small, low-loss auxiliary coil can be formed on the head core.

On the other hand, as a conventional example of the optical modulation system, there is Japanese Patent Application Laid-Open No. 2-54453. In this conventional example, a pair of bias coils are arranged so as to sandwich a disk, and these are connected by an iron-based substrate to also serve as a yoke for a magnetic circuit. On this substrate, I
C, resistors, etc. are mounted.

[0021]

In a magnetic field generator in which a magnetic head core and an auxiliary coil core of a drive circuit are integrated as shown in FIG. 8, the magnetic field generator and the drive circuit for driving the magnetic field device are close to each other. In this case, electromagnetic radiation noise accompanying high-frequency excitation from the magnetic head and the auxiliary coil is mixed into the drive circuit, and is similar to the recording signal flowing from the drive circuit to the connection line that supplies the excitation current to the magnetic head and the auxiliary coil. There has been a problem that electromagnetic radiation noise from a connection line due to a high-frequency large current causes noise in a circuit portion in the magneto-optical recording device, thereby hindering circuit operation.

When an electromagnetic shield is to be applied to the connection line or the drive circuit in order to prevent the electromagnetic radiation noise generated from the connection line or the drive circuit itself, the magnetic head and the auxiliary coil are connected to the drive circuit. If it is separated, the surface area of the shield cover increases, the space and cost for the shield increase, the noise source is concentrated in a small space, and the effective noise reduction measure by one point ground cannot be implemented. Met.

Further, in the case where the frequency of the drive circuit is increased to increase the recording density, if the lines connecting the magnetic head coil and the auxiliary coil and the drive circuit excluding the auxiliary coil are long,
As the connection line becomes longer, the parasitic inductance and the parasitic capacitance of the connection line increase, and there is a problem that high-frequency operation of the drive circuit becomes difficult.

On the other hand, in the light modulation system, the intensity of light is modulated by a recording signal, and the bias magnetic field may be a DC magnetic field having a constant intensity. Electromagnetic radiation noise due to the bias magnetic field hardly causes a problem. For example, in the conventional example of Japanese Patent Application Laid-Open No. 2-54453, a pair of coils is connected by a substrate also serving as a yoke. However, electromagnetic radiation noise constituting a magnetic head driving circuit when performing magnetic field modulation recording is used. It does not prevent.

The present invention has been made in view of the above points, and reduces electromagnetic radiation noise from a magnetic head main magnetic coil and an auxiliary coil to a drive circuit, which is a problem when performing recording in a magnetic field modulation system. And measures against electromagnetic radiation noise from the magnetic head, auxiliary coil and drive circuit to peripheral circuits
It is an object of the present invention to provide a magnetic field generator for magneto-optical recording, which can be realized effectively in a small space and at low cost, and which enables high-frequency operation of a drive circuit and facilitates high-density recording.

[0026]

According to the present invention, there is provided a first core having one end facing a magneto-optical recording medium, a first coil for exciting the first core with a recording signal, and a first coil. A second core different from the core, a second coil wound around the second core, a back core magnetically coupled to the first core, and a voltage generated in the second coil. In a magnetic field generating apparatus for magneto-optical recording comprising a drive circuit for flowing a current through the first coil by utilizing the drive circuit, the drive circuit includes at least one of the first coil and the second coil; The first coil and the second coil of the magnetic field generating device are integrally formed in the vicinity of each other with the back core interposed therebetween.
The electromagnetic radiation noise from the coil to the drive circuit is reduced, and the electromagnetic radiation noise countermeasures from the magnetic field generator to the peripheral circuits can be effectively realized in a small space and at low cost. And high-density recording can be easily performed.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a magneto-optical recording / reproducing apparatus including a magnetic field generator according to a first embodiment of the present invention. The magneto-optical recording / reproducing apparatus 1 shown in FIG. 1 has a magnetic field generating device 3 of the first embodiment facing one surface of a magneto-optical disk 2 as a magneto-optical recording medium which is rotated by a spindle motor (not shown).
The optical pickup 4 is arranged to face the other surface of the magneto-optical disk (also simply referred to as a disk) 2, and the beam from the optical pickup 4 is irradiated on the recording film 2 b via the substrate 2 a. On the other hand, the magnetic field generated by the magnetic field generator 3 is applied.

The optical pickup 4 is mounted on a carriage 5 and, for example, a VCM 6 as pickup moving means.
Thus, the disk 2 can be moved in the radial direction of the disk 2, that is, in the direction T crossing the track, and an arbitrary track can be accessed. The magnetic field generator 3 is also moved in the direction T by means (not shown) in conjunction with the movement of the optical pickup 4.

A laser beam from a laser diode 7 constituting the optical pickup 4 is shaped into a parallel beam by a collimator lens 8 and then is incident on a beam splitter 9. The beam transmitted through the beam splitter 9 is 1 /
The azimuth of the polarization direction is set by the two-wavelength plate 10, condensed by the objective lens 11, and irradiated on the recording film 2 b of the disk 2 with linearly polarized light to form a beam spot.

The beam reflected by the disk 2 is condensed by the objective lens 11, passes through the half-wave plate 10, and is further partially reflected by the beam splitter 9.
Are divided into transmitted light and reflected light by the beam splitter 12. The reflected light passes through a critical angle prism 13 and is received by a light detector 14 for generating a control signal.

On the other hand, the transmitted light passes through an analyzer 15 and is received by a light detector 16 for generating a reproduction signal. The outputs of the optical detectors 4 and 16 are input to, for example, a signal processing unit 17 arranged on the carriage 5 and are subjected to signal processing to generate a track error signal TE, a focus error signal FE, and a magneto-optical reproduction signal RF during reproduction. I do. The track error signal TE and the focus error signal FE are used for track servo and focus servo, respectively.

The laser diode 7 emits light at a low level and a constant light emission intensity during reproduction. At the time of recording, light is emitted with a large light emission intensity at a constant level, and the portion of the recording film 2b irradiated with this beam is heated to a Curie temperature or higher. At the time of this recording, the magnetic field generator 3 of the first embodiment applies a magnetic field corresponding to the recording signal RS to the portion of the recording film 2b irradiated with the beam.

The magnetic field generator 3 includes a first core 18 for applying a recording magnetic field to the disk 2 and a first core 18.
The first coil 1 for exciting the first coil according to the recording signal RS
9, a second core 20 different from the first core, a second coil 21 for exciting the second core 20, and magnetically coupled with the first core 18 and the second core 20. Back core 22 and a drive circuit 23 for driving the first and second coils 19 and 21.
The second coil 21 and the driving circuit 23 and the first core 18
The first coil 19 and the first coil 19 are integrally disposed close to the front and back with a back core 22 therebetween.

When the drive circuit 23 has the structure of the drive circuit 49 shown in FIG. 7, for example, a permanent magnet or the like is formed near the first core 18 and the first coil 19 constituting the magnetic head 24. A bias magnetic field generating means is provided. The bias magnetic field generating means generates a constant bias magnetic field in a direction opposite to the direction of the magnetic field generated by the magnetic head 24. A magnetic field generator base 25 is attached to the opposite side of the drive circuit 23 to which the back core 22 is attached, and the optical pickup 4 is moved by moving means such as a VCM.
Are driven in conjunction with the VCM 6 that moves.

The back core 22 is made of a magnetic material having the same high-frequency characteristics as the first core 18, such as ferrite, sendust, or an amorphous alloy. Therefore, if a material having a high magnetic permeability and a high saturation magnetic flux density at high frequency excitation and a relatively high conductivity is used as the magnetic material of the back core 22, the first coil 19
A high-frequency exciting current corresponding to the recording signal, thereby magnetically and electrically shielding high-frequency electromagnetic radiation noise generated by the first core 18 and the first coil 19 from the drive circuit 23. And the drive circuit 23 can be operated stably.

Further, in this embodiment, since the first coil 19 and the drive circuit 23 are arranged close to each other, the connection line through which the excitation current flows from the drive circuit 23 to the first coil 19 is shortened. And minimizes electromagnetic radiation noise caused by the high-frequency excitation current flowing through the connection line, which is caused by the long connection line, and reduces noise induction to the drive circuit 23 and other peripheral circuits inside and outside the device. Therefore, the malfunction of the peripheral circuit is prevented, and a stable circuit operation is enabled. (In FIG. 1, the connection line for connecting the first coil 19 to the drive circuit 23 bypasses the back core 22. In practice, a small through-hole is formed in the back core 22 and the first through-hole is formed through the through-hole.
Drive circuit 23 disposed close to the back side of the coil 19 of FIG.
Can be connected with short connection lines).

Further, since the parasitic inductance and the parasitic capacitance of the connection line, which become larger as the connection line becomes longer, are reduced, the frequency of the drive circuit can be easily increased, and a recording magnetic field generator capable of coping with high-density recording can be realized.

Further, the integration of the magnetic head 24 composed of the first core 18 and the first coil 19 and the drive circuit 23 facilitates miniaturization and weight reduction of the magneto-optical recording apparatus 1. In addition, the signal processing unit 17 is
Are disposed on the opposite side of the second core 20 and the second coil 21 with respect to the second core 20 and the second coil 21, so that a short connection (not shown) connected to the second core 20 and the second coil 21 (and the driving circuit 23 (Wire) can be less affected by electromagnetic radiation noise. Further, the magnetic head 24 is
As a result, the generation of electromagnetic radiation noise can be reduced, so that the noise given to the signal processing unit 17 disposed separately can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG. The configuration of the magnetic field generator 3 of the second embodiment shown in FIG. 2 is basically the same as that of the first embodiment, except that the first core 18 and the first coil 19, and the second core 20 and The second coil 21 includes the drive circuit 23 and the back core 2.
2 and the extended portion 22a in which the end of the back core 22 is extended toward the rear surface (upward in FIG. 2), and accommodates the drive circuit 23. It differs from the first embodiment in that it is formed in a box shape and covers the drive circuit 23 (except for the surface in contact with the magnetic field generator base 25).

That is, in the second embodiment, similarly to the first core 18 and the first coil 19, the second core 20 and the second
Of the back core 2 with respect to the drive circuit 23
By separating the drive circuit 22 between the first and second embodiments, the electromagnetic induction noise to the drive circuit 22 can be reduced as compared with the first embodiment. Also, a back core 2 having an electromagnetic noise shielding effect
2 is formed so as to surround the drive circuit 22 by extending
By joining to the magnetic field generator base 25 having an electromagnetic noise shielding effect, the lead shielding effect of the back core 22 can be further increased.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a sectional view of a magnetic field generator of the third embodiment, and FIG. 4 is a perspective view of a flexible printed circuit board of the magnetic field generator of the third embodiment.

In FIG. 3, the configuration of the magnetic field generator 3 is as follows.
Basically the same as the second embodiment, but the first coil 1
9, the second coil 21 and the drive circuit are configured on the same printed circuit board 28, and a shield cover 29 covering the drive circuit 23 is provided.

That is, as shown in FIG. 4, the printed circuit board 28 is composed of a thin first (excitation) coil 19, a second coil 21, and a drive circuit lead portion formed of copper on a flexible substrate that can be bent. It is formed of a conductor such as aluminum and has a drive circuit chip component 30 mounted thereon. The first core 18 formed on the back core 22 is provided at the center of the first coil 19 and the second coil 21. And the insertion hole for the second core 20, the central portion is bent and the back core 2 is bent.
The magnetic field generator can be easily formed simply by bonding to the back core 22 so as to sandwich the two. In addition, the shield cover 2
Reference numeral 9 denotes a conductor having high conductivity and is set to a material having high magnetic permeability. For example, the surface of a material having high magnetic permeability may be coated with a metal having high conductivity.

Accordingly, in the third embodiment, since the drive circuit 23, the first coil 19, and the second coil 21 are integrally formed on the printed circuit board 28, the step of winding the coil is not required, so that mass production is possible. In addition, the magnetic field generator 3 can be manufactured at low cost, and the size of the coil and the circuit can be easily reduced. In addition, since the connection lead wire between the coil and the circuit can be designed to be the shortest, it is easy to increase the frequency of the drive circuit 23.

Further, by providing an electromagnetic shield cover 29 so as to cover the drive circuit 23 and connecting it to the back core 22, the electromagnetic shielding effect of the back core 22 can be further increased. In addition, if this cover is made of a material with good electromagnetic shielding properties and good thermal conductivity, such as iron, the heat dissipation fins of the drive circuit parts and the shield cover are thermally joined to form a heat dissipation component. Function can be provided.

The circuit configuration of the driving circuit 23 is not limited to the one shown in FIG.
For example, a driving circuit proposed by the present applicant such as No. 5754 can be used. Further, in addition to the two cores and the coil, a magnetic field generating device having a core and a coil for generating a DC bias magnetic field may be provided.

[0047]

As described above, according to the present invention, at least one of the first coil for exciting the core for applying the recording magnetic field to the magneto-optical recording medium and the second coil for generating the voltage is used. , A driving circuit for the first and second coils, and a back core having an electromagnetic shielding effect formed integrally with each other with a back core interposed therebetween. Also, by separating and shielding the electromagnetic radiation noise source of the connecting wire between the two coils and the drive circuit from the circuit, it is possible to reduce the noise mixing into the drive circuit. In addition, by concentrating noise sources in a small space and magnetically and electrically shielding the entire magnetic field generator from peripheral circuits, measures against electromagnetic radiation noise can be effectively realized in a small space and at low cost. Also, the size and weight of the magnetic field application device including the drive circuit can be easily reduced. Furthermore, according to the present invention, the connecting wires between the first and second coils and the driving circuit are shortened, the parasitic inductance and the parasitic capacitance of the connecting wires are reduced, and the high frequency operation of the driving circuit is facilitated. A magnetic field generator suitable for high-density recording can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magneto-optical recording / reproducing apparatus including a magnetic field generator according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a magnetic field generator according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing the configuration of a magnetic field generator according to a third embodiment of the present invention.

FIG. 4 is a perspective view showing a flexible printed circuit board of the magnetic field generator of the third embodiment.

FIG. 5 is a configuration diagram of a conventional magnetic field modulation type magneto-optical recording and reproducing apparatus.

FIG. 6 is a circuit diagram showing a configuration of a conventional magnetic head drive circuit of a magnetic field modulation system.

FIG. 7 is a circuit diagram showing a configuration of a magnetic head drive circuit of a prior art by the present applicant.

FIG. 8 is a diagram showing a schematic configuration of a magneto-optical recording / reproducing apparatus according to a prior art by the present applicant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magneto-optical recording / reproducing apparatus 2 ... Magneto-optical disk 3 ... Magnetic field generator 4 ... Optical pickup 6 ... VCM 7 ... Laser diode 11 ... Objective lens 14, 16 ... Optical detector 17 ... Signal processing unit 18 ... First core 19 ... first coil 20 ... second core 21 ... second coil 22 ... back core 23 ... drive circuit 24 ... magnetic head 25 ... base

Claims (2)

(57) [Claims] 1. A first core having one end facing a magneto-optical recording medium, a first coil for exciting the first core with a recording signal, and a second core different from the first core. , The second
A second coil wound around the first core, a back core magnetically coupled to the first core, and a current flowing through the first coil using a voltage generated in the second coil. The magnetic field generation device for magneto-optical recording of the magnetic field modulation system, comprising: a driving circuit, wherein the driving circuit includes at least one of the first coil and the second coil and the back core interposed therebetween. A magnetic field generating apparatus for magneto-optical recording, wherein the magnetic field generating apparatus is configured to be adjacent to and integrated with the magnetic field. 2. The apparatus according to claim 1, wherein the first coil wound around the first core and a drive circuit component including the second coil are formed on the same printed circuit board.
The magnetic field generator for magneto-optical recording according to claim 1.