JPH0676396A - Magneto-optical recording / reproducing device - Google Patents

Abstract

(57) [Summary] [Object] To provide a magneto-optical recording / reproducing device capable of preventing a focus error by suppressing vibration of a disk surface during sliding. [Structure] A magnetic head 3 is arranged above and an optical pickup 4 is arranged below, with a magneto-optical disk 2 in between. The magnetic head 3 is arranged so as to contact and slide on the upper surface of the magneto-optical disk 2, and the magnetic head 3 and the optical pickup 4 are integrally configured by a U-shaped arm 9. The optical pickup 4 is servo-controlled so as to follow the surface of the disc 2. The ratio of the mass m (g) of the magnetic head 3 to the servo gain Gservo of the optical pickup 4 satisfies the following formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing apparatus which contacts and slides on a magneto-optical recording medium to perform magneto-optical recording and reproduction.

[0002]

2. Description of the Related Art One of so-called writable optical disks capable of writing, erasing and reading information by using a light beam is called a magneto-optical disk.

As shown in FIG. 11, the magneto-optical disk 21 is provided with a magneto-optical recording layer 23 made of a perpendicular magnetization film on a transparent substrate 22 with a SiN protective film 28 interposed therebetween. A reflection film 24 made of a metal thin film, for example, an Al thin film, is laminated on the SiN protective film 28 and further,
A protective film 2 made of an ultraviolet curable resin or the like is formed on the reflective film 24.
5 is formed.

Magnetic recording methods such as a magnetic field modulation method and an optical modulation method are known as recording methods for a magneto-optical disk.

The magnetic field modulation method enables so-called overwriting in which a new signal is overwritten on an old signal. In this magnetic field modulation type magneto-optical recording, as shown in FIG. 12, an optical pickup that irradiates a laser beam 26 on one side (the substrate 22 side) with a magneto-optical disk 21 having a magneto-optical recording layer made of a perpendicularly magnetized film is sandwiched. On the other side (protective film 25 side), a magnetic field generating means that moves in synchronization with the laser spot, that is, a magnetic head 27 having a magnetic core 27a around which a coil 29 is wound is provided, and the direction of the current flowing through the coil 29 is changed. To change the magnetic field direction.

The magneto-optical disk 21 is rotated at a predetermined rotation speed with the central portion as the center of rotation. A magnetic field corresponding to the recording signal is formed near the laser spot 26a, so that the desired rewrite portion 21A of the disk 21 is heated to a Curie temperature or higher by the laser spot 26a and demagnetized, and then moved from the laser spot 26a to the Curie. When the temperature drops below the temperature, recording is performed by magnetizing in the magnetic field direction.

[0007]

The present applicant has previously developed a microminiature digital recording / reproducing apparatus capable of digital recording / reproducing with a microminiature magneto-optical disk. This recording / reproducing apparatus adopts a magnetic field modulation type magneto-optical recording system to enable overwriting.

By the way, since the conventional magneto-optical disk performs non-contact recording as described above, the magnetic head 27 for magneto-optical recording is generated at the time of rotation while the disk 21 is rotated at a predetermined distance d ₀ from the disk 21. The electromagnetic servo mechanism is attached so as to follow the surface runout (due to the inclination of the disk 21, the uneven thickness, etc.). For this reason,
In a recording / reproducing apparatus that employs a non-contact method with respect to a magneto-optical disk, there are limits to reduction of power consumption, downsizing of equipment (in particular, reduction of thickness of equipment), and the like.

Therefore, if the magnetic head is brought into contact-sliding contact with the magneto-optical disk, the magnetic head need only be supported simply, and the conventional electromagnetic servo mechanism which takes up a large volume can be omitted. This is advantageous for reducing the power consumption of the playback device and downsizing the device.

However, when such a contact system is adopted, the following problems occur. That is, in the manufacturing process of the magneto-optical disk, a protrusion having a height of about 10 μm is formed on the surface of the protective film of the upper layer during the formation process. Therefore, the collision between the protrusion and the slider causes the magneto-optical disc to vibrate. As a result, there is a possibility that a focus error of the optical pickup may occur at the outer peripheral portion of the disc, especially during reproduction.

The present invention has been made in view of the above points, and an object of the present invention is to provide a magneto-optical recording / reproducing apparatus capable of suppressing a vibration of a disk surface during sliding to prevent a focus error. It is in.

[0012]

According to the present invention, as shown in FIG. 1, for example, a sliding magnetic field modulation head 3 which slides in contact with one surface of a disk 2 as a recording medium, and the disk 2 described above.
In a magneto-optical recording / reproducing apparatus having an optical head 4 disposed on the other surface side of which is servo-controlled for the distance from the disk 2, the mass of the sliding magnetic field modulation head 3 including a sliding portion and a magnetic head element ( g) and the servo gain ratio at 350 Hz It is what

[0013]

Now, referring to FIG. 10, the vibration amplitude of the disk 2 surface caused by the collision between the projection on the disk 2 surface and the sliding magnetic field modulation head 3 will be briefly derived. in this case,
Since the vibration of the surface of the disk 2 is larger at the outer peripheral portion where the equivalent mass appears smaller, it will be discussed at the outermost periphery.

When the existence of the clamp hole located at the center of the disk 2 is negligible with respect to the mass M of the disk 2 and the disk 2 is regarded as a circular flat plate having a radius R, its diameter axis is the rotation axis. Its moment of inertia I is Also, the rotational equation of motion is Becomes Here, from torque = R × F and angular velocity ω = R × v, That is, the equivalent mass Mi of the disc 2 is M / 4.

A parabolic projection 2 as shown in FIG. 10B.
0 and the time from the start of collision of the sliding magnetic field modulation head 3 to the apex thereof is Δt, the mass m of the sliding magnetic field modulation head 3 (the mass of the core, the bobbin and the coil after the time Δt). (Including) and the disc 2 have a conservation of momentum, and thus mv = MiV (1). However, v and V are respectively the velocity in the normal direction of the sliding magnetic field modulation head 3 and the displacement velocity of the disk 2 at the apex of the protrusion 20. _Assuming that the motion from the start of the collision to standing on the top of the protrusion 20 is a uniform acceleration motion, the acceleration α _M acting on the disk 2 is The displacement amount h _d of the disk 2 at the apex of the protrusion 20 is Similarly, the displacement amount h _h of the sliding magnetic field modulation head 3 is Since the sum of both displacements is equal to the height h of the protrusion 20, When the displacement velocity of the disk 2 is calculated from the equations (1) and (5),

According to the energy conservation law, the deformation of the disk 2 has the maximum amplitude when all the kinetic energy at the time Δt is converted into elastic energy due to the deflection of the disk 2. That is, Δt is in the shape of the protrusion 20 shown in FIG. 10B, When the disk 2 is displaced, the optical head, that is, the optical detector tries to follow the displacement by the focus servo mechanism, and its tracking error X _E is expressed as follows. The optical detector causes a read error when the tracking error X _E exceeds the depth of focus Df, that is, when X _E ≧ Df _OP (11) is satisfied. Therefore, the mass m of the sliding magnetic field modulation head 3 required to prevent a read error is obtained as follows. Each value of the equation (12) is determined as follows. ω _D ; observed resonant frequency of the main disk 700π
/ S (350 Hz) h / a; as the upper limit value observed on the disc, h = 0.01 mm, a = 0.1 mm Mi; the mass M of the disc is 4.4 g on a polycarbonate substrate having a diameter of 65 mm, and thus Mi = M /4=1.1 g v _o ; Determined by the CD format, maximum 1.4 m / s Gservo; Servo gain is 0 dB at 1 kHz as a typical value of a CD system, and frequency characteristic is -12 dB.
Therefore, when ω _D = 700π / s, 8.16 times (= 18 dB) Df _OP ; the depth of focus of the objective lens is 2 μm _PP , and therefore 1 μm _OP . Therefore, when the equation (12) is transformed and the above values are substituted, Therefore, when the ratio of the mass m of the sliding magnetic field modulation head 3 to the servo gain Gservo satisfies the expression (13), the vibration of the disk 2 is suppressed and the focus error due to it is not generated. On the other hand, the lower limit of the value of m / Gservo is
Due to the limit of the mass m of the sliding magnetic field modulation head 3 in the device configuration, it becomes 4 × 10 ⁻³ .

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of this embodiment. As shown in the figure, in this embodiment, a magneto-optical disk 2 driven by a magnet chuck type motor 1 is used.
A magnetic head 3 is arranged above and an optical pickup 4 is arranged below so as to sandwich a (disc). The magnetic head 3 is arranged so as to come into contact with and slide on the surface of the disk 2, and the magnetic head 3 and the optical pickup 4 are integrally configured by a U-shaped arm 9.

FIG. 2 schematically shows the structure of the magnetic head 3 of this embodiment. The magnetic head 3 of this embodiment is of the magnetic field modulation type, and has an E-shaped ferrite core 5.
And the coil 6 wound around the bobbin 6a constitute a magnetic circuit for magnetic field modulation. Then, the assembly of the ferrite core 5 and the coil 6 is made up of the core support plate 7 with an adhesive.
Fixed to. The core support plate 7 is fixed to the slider body 8 by engagement of the claw portions 8a provided on the slider body 8 and the notches 7a formed at the two corners of the core support plate 7. In this case, as shown in FIG. 2B, the winding 6b of the coil 6 is guided to the solder land 10 provided on the upper surface of the arm 9 via the tube portion 8b formed on the upper portion of the slider body 8. Get burned.

In the magnetic head 3, the tube portion 8b of the slider body 8 is connected to the slider support hole 9a of the arm 9 via the coil spring 10.
The stopper ring 11 is fixed to the arm 9 by passing the stopper ring 11 to the tip of the tube portion 8b. The arm 9 has a hole 9b for fixing a head body (not shown).
Is provided.

A sliding surface 7c that slides on the disk 2 is formed on the lower surface of the core supporting plate 7. A small amount of lubricant is dripped on the inner surface of the slider support hole 9a so that the magnetic head 3 moves smoothly. The coil spring 1
The spring constant of 0 is 19.6 mN / mm, and it is assumed that the disk is pressed in by 1 mm and used from the state of being in contact with the surface of the disk 2.

FIG. 3 shows the outer shape of the ferrite core 5. As shown in the figure, the ferrite core 5 is
Length a = 3.4 mm, width b = 0.8 mm, height c = 1.
6 mm, the height of the core part is d = 1.1 mm, the thickness of the central core is 1 = 0.6 mm, and the distance between the two end cores is f = 2.6.
mm.

As shown in FIG. 4, the shape of the sliding surface 7c is such that both the inflow end 7d and the outflow end 7e have a radius of 0.4 mm, and the sliding portion 7f has a thickness t of 0.
It is 8 mm and the length L is 3.8 mm.

A winding 6b having a diameter of 80 μm is wound around the bobbin 6a 33 times, so that the distance from the recording medium is 100 μ.
8000 due to 0.3A _OP current in case of m
A magnetic field of A / m is applied to the recording medium. In this case, the mass of 40 to 70 can be obtained by changing the thickness of only the sliding portion 7f of the core supporting plate 7 with the slider body 8 being common.
The magnetic head 3 of mg is obtained, and the slider body 8 and the core support plate 7 are both increased in size to obtain 100 to 150
mg of magnetic head 3 is obtained. Even when the mass of the magnetic head 3 is changed, the shape of the sliding surface 7c remains the same. By the way, the mass of the magnetic head 3 is minimum (40 mg).
If, the mass of each part is 12 for the ferrite core 5.
mg, the coil 6 is 12 mg, the slider body 8 is 8 mg, and the core support plate 7 is 8 mg.

FIG. 5 shows the structure of the focus servo mechanism of the optical pickup 4 of this embodiment. As shown in the figure, the optical pickup 4 includes a focus error signal detector 1 that detects a focus shift and converts the focus error signal into an error signal.
2, the focus error signal detector 12 is connected to
It is connected to a drive amplifier 14 for driving the focus coil 13 of the optical pickup 4. With this configuration, the optical pickup 4 moves up and down following the surface wobbling of the disk 2.

FIG. 6 is a graph showing the servo gain characteristics of the focus servo mechanism of this embodiment. As shown in the figure, the cross frequency fc of the servo system of this embodiment is 1 kHz.
Then, the frequency characteristic is −12 dB / oct. Therefore,
At 350 Hz, which is the resonance frequency of the disk 2 described later, a servo gain of 18 dB is obtained. Here, the servo gain means a ratio between the focus shift amount detected by the optical pickup 4 and the amount to be tracked and corrected by the output of the focus coil 13.

Next, using a system as shown in FIG. 7, the relationship between the mass of the magnetic head 3 and the displacement of the surface of the disk 2 at the time of collision with a protrusion was analyzed. In this system, the displacement of the disc 2 is measured by a laser type displacement gauge 15 arranged above the disc 2. This laser displacement meter 1
5 is an FFT through a high pass filter (HPF) 16.
It is connected to the analyzer 17 and the oscilloscope 18. With this configuration, the output signal from the laser displacement meter 15 is subjected to the high-pass filter 16 to remove the surface fluctuation component of the disk 2, and the FFT analyzer 17 performs the frequency analysis and the oscilloscope 18 to perform the amplitude analysis. went. As a result, a diameter of 65 mm,
It was found that the main vibration frequency of the disk 2 using a polycarbonate substrate having a thickness of 1.2 mm was approximately 350 Hz.

On the other hand, 30.5 mm from the center of the disk 2
A sample having a protrusion of 10 μm at the position of is prepared, and the mass of the magnetic head 3 is 40 mg, 50 mg, 70 mg, 1
The vibration of the surface of the disk 2 when the protrusions of the respective magnetic heads 3 collide with each other was observed using the above system instead of 00 mg and 150 mg. The result is shown in FIG. As can be seen from FIG. 8, as the mass of the magnetic head 3 increases, the vibration on the surface of the disk 2 tends to increase linearly.

At the position 30.5 mm from the center, 10
A magnetic head 3 having a mass of 40 mg to 150 mg described above, using a pre-mastered disk having protrusions of μm.
The relationship between the block error rate, that is, the read error and the mass of the magnetic head 3 when the signal was reproduced by the above was analyzed using the system described above. The result is shown in FIG.

It is said that the limit block error rate as a device for audio reproduction is 220. The servo gain of the focus servo mechanism of this embodiment is 350H as described above.
Since it is 18 dB in z, as can be understood from FIG.
If the mass of the magnetic head 3 is about 70 mg or less, the condition for a hi-fi sound reproducing device is satisfied. Then, in this case, all satisfy 4 × 10 ⁻³ <[mass (g) of magnetic head 3] / [servo gain] ≦ 9 × 10 ⁻³ .

As shown in FIG. 9, if the value of the servo gain of the focus servo mechanism can be set to, for example, 24 dB, the above condition is satisfied until the mass of the magnetic head 3 reaches about 150 mg.

[0031]

As described above, according to the present invention, the ratio of the mass (g) of the sliding magnetic field modulation head to the servo gain at 350 Hz is calculated. Therefore, it is possible to prevent a focus error when the sliding magnetic field modulation head collides with the projection on the disk surface, and it is possible to perform stable recording and reproduction.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a magneto-optical recording / reproducing apparatus according to the present invention.

FIG. 2 is an exploded perspective view and a front view showing the configuration of the magnetic head of the embodiment.

3A and 3B are a plan view and a front view of a ferrite core of the same example.

FIG. 4 is an explanatory diagram showing a shape of a sliding portion of the magnetic head of the embodiment.

FIG. 5 is a block diagram showing a configuration of a focus servo mechanism of the embodiment.

FIG. 6 is a graph showing a servo gain characteristic of the focus servo mechanism of the example.

FIG. 7 is an explanatory diagram showing a system for analyzing a disc surface displacement during sliding.

FIG. 8 is a graph showing the relationship between the mass of the magnetic head and the displacement of the disk.

FIG. 9 is a graph showing the relationship between the mass of the magnetic head and the block error rate.

FIG. 10 is an explanatory diagram schematically showing a disk surface displacement during sliding.

FIG. 11 is a cross-sectional view showing the structure of a magneto-optical disk.

FIG. 12 is an explanatory diagram of a magnetic field modulation method.

[Explanation of symbols]

 2 Magneto-optical disk 3 Magnetic head 4 Optical pickup

Claims (1)

[Claims] 1. A sliding magnetic field modulation head that comes into contact with and slides on one surface of a disk as a recording medium, and an optical head disposed on the other surface of the disk and servo-controlled for the distance to the disk. In the magneto-optical recording / reproducing apparatus having the above, the ratio of the mass (g) of the sliding magnetic field modulation head including the sliding portion and the magnetic head element to the servo gain at 350 Hz is A magneto-optical recording / reproducing apparatus characterized in that