JPH0739097Y2 - Magnetic head servo device in magneto-optical recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention drives a magnetic head used in a magneto-optical disk recording device in the direction near and far with respect to the recording surface of the optical disk, so that the magnetic head is kept constant from the optical disk. The present invention relates to a magnetic head servo device that holds a magnetic head servo device at a distance position.

SUMMARY OF THE INVENTION The present invention relates to a magnetic head servo device for driving and displacing a magnetic head in a perspective direction with respect to a recording surface of a magneto-optical disk, and a capacitance detection electrode attached to the magnetic head and a magneto-optical disk. A magnetic head servo device that detects a change in the relative distance between the magnetic head and the magneto-optical disk based on a change in electrostatic capacitance between the magnetic head and the magneto-optical disk, and drives and displaces the magnetic head according to the change in electrostatic capacitance. In this configuration, the area information of the magneto-optical disk, particularly on the recording surface, is supplied as a bias signal to the servo circuit, and the relative distance between the magnetic head and the magneto-optical disk is controlled more accurately.

[Conventional technology]

Generally, in a magneto-optical disk recording apparatus, an optical head and a magnetic head are arranged so as to face each other in a non-contact manner with a magneto-optical disk interposed therebetween, and in a magnetic field modulation method, a magnetic field corresponding to a recording signal is applied to the magnetic head. Is applied to the magneto-optical disk from above, and the same area is heated by a laser beam from an optical head to perform a recording operation. At this time, the focus information of the laser beam is obtained by using the reflected light from the recording surface of the magneto-optical disk that irradiates the laser beam, and the focus is controlled so as to form a predetermined beam spot on the recording surface of the magneto-optical disk. There is.

For this reason, the optical head maintains a constant relative distance to the magneto-optical disk even if the magneto-optical disk has surface deviation or thickness variation, or the position of the magneto-optical disk changes due to tilting of the disk table. It does not come in contact with the magneto-optical disk when it leans.

However, since the magnetic head does not have a simple means for detecting the relative distance to the magneto-optical disk, when the position of the magneto-optical disk fluctuates for the reason described above, the magneto-optical disk is prevented from coming into contact with the magneto-optical disk. Many are located at a distance from.

However, when the magnetic head is arranged at a position away from the magneto-optical disk, a strong magnetic field must be generated from the magnetic head in order to apply a predetermined recording magnetic field to the recording surface of the magneto-optical disk, resulting in a large power consumption. There are drawbacks.

Also, if the magnetic head is too far away from the magneto-optical disk, the magnetic field applied to the recording surface of the magneto-optical disk will be insufficient, which not only causes an increase in error rate and a decrease in C / N, but also in the worst case. May become unrecordable.

Therefore, in order to solve such a problem, the present applicant has, for example, attached an electrode to the magnetic head so as to face the magneto-optical disk, and change the capacitance between the magneto-optical disk and the electrode. It was proposed that the change in the relative distance between the magnetic head and the magneto-optical disk be detected by, and that the detection output be used to keep the relative distance between the magneto-optical disk and the magnetic head constant. (Japanese Patent Application No. 1-214138) Hereinafter, a position control device for a magnetic head disclosed in the above prior art will be described in detail with reference to FIG.

A magnetic head 2 and an optical head 3 that are opposed to the magneto-optical disk 1 in a non-contact manner with the magneto-optical disk 1 whose rotation is controlled by a spindle motor M are provided. The magnetic head 2 is provided to a recording coil 4 for recording. A recording magnetic field according to the current is applied to the recording surface 5 of the magneto-optical disk 1.

Further, the optical head 3 irradiates the recording surface 5 of the magneto-optical disk 1 with a laser beam output from a built-in laser diode.

Information is recorded on the recording surface 5 by the recording magnetic field and the laser beam. Here, the magnetic head 2 and the optical head 3 are attached to a slider (not shown), and both are simultaneously driven in the radial direction of the magneto-optical disk 1 (direction of arrow X). Further, the head 2 and the optical head 3 are respectively displaceable in the perspective direction (arrow Y direction) with respect to the recording surface 5 of the magneto-optical disk 1, and the optical head 3 is controlled in the arrow Y direction by the focus servo. ing.

A capacitance detection electrode 6 is attached to the magnetic head position control device so as to face the magneto-optical disk 1.
The capacitance detecting electrode 6 is displaced together with the magnetic head 2 in the arrow Y direction. Therefore, a capacitance c corresponding to the relative distance d between the capacitance detection electrode 6 and the magneto-optical disc 1 is generated between the capacitance detection electrode 6 and the magneto-optical disc 1. Therefore, by detecting the change in the capacitance c, the change in the relative distance between the magneto-optical disk 1 and the magnetic head 2 can be detected.

FIG. 4 shows a specific example of the capacitance detecting electrode 6. In the magnetic head 2, a cylindrical magnetic yoke 21 is projected from the center of the inner wall of a core 20 having a U-shaped cross section. The recording coil 4 is wound around the peripheral wall of the.

The capacitance detection electrode 6 is fixed to the U-shaped ends of the core 20 by adhesion or the like in a state where the tip of the magnetic yoke 21 penetrates the through hole. The magnetic head 2 is attached so that the tip of the magnetic yoke 21 and the capacitance detection electrode 6 face the magneto-optical disk 1.

The capacitance detection electrode 6 is connected to the oscillation circuit 7 as shown in FIG. The oscillation circuit 7 changes its oscillation frequency according to the change in the capacitance detected by the capacitance detecting electrode 6, and is constructed as shown in FIG. 5, for example.

That is, the oscillation circuit 7 is an LC oscillation circuit in which the coil 42 and the capacitors 43 and 44 are connected to both ends of the amplifier 41. Of these, the capacitor 43 is the capacitance detection electrode 6 and the magneto-optical disk 1.
The capacity c between and is shown. Therefore, in the oscillation circuit 7, the oscillation frequency changes according to the change in the capacitance of the capacitor 43, that is, the change in the capacitance c between the capacitance detecting electrode 6 and the magneto-optical disk 1.

Further, by setting the Q of the oscillation circuit 7 high,
The disturbance of the electromagnetic field from the magnetic head 3 is made less likely to occur, and the control operation can be stabilized.

The oscillation output from the oscillation circuit 7 is sent to a phase locked loop (PLL) type phase detection circuit 8.

The PLL type phase detection circuit 8 comprises a phase difference detection circuit 10, a voltage controlled oscillator 11, a low pass filter (LPF) 13, etc., and an oscillation output from the oscillation circuit 7 is passed through a frequency divider 9 to a phase difference detection circuit. The oscillation output of the voltage controlled oscillator 11 is supplied to the phase difference detection circuit 10 via the frequency divider 12.
The detected output is given to 10 and is fed back to the voltage controlled oscillator 11 via the LPF 13.

The voltage controlled oscillator 11 has an oscillation characteristic similar to the oscillation characteristic of the oscillation circuit 7, and for example, the one shown in FIG. 6 is used. That is, in the voltage controlled oscillator 11, the coil 52 and the capacitors 53 and 54 are connected to both ends of the amplifier 51 similarly to the oscillation circuit 7, and one end of the capacitor 53 is connected to the negative power source −B via the variable capacitance diode 55. It is connected. In this voltage controlled oscillator 11, the detection output given from the phase difference detection circuit 10 is supplied to the connection point between the capacitor 53 and the variable capacitance diode 55 via the LPF 13, and the capacitance of the variable capacitance diode 55 is supplied according to this detection output. Changes. Therefore, in the voltage controlled oscillator 11, the frequency of the oscillation output taken out from the amplifier 51 via the buffer amplifier 56 changes according to the detection output.

This oscillation output is compared in phase with the oscillation output supplied to the phase difference detection circuit 10 via the frequency dividing circuit 12. Then, when a phase difference occurs in these oscillation outputs, according to the phase difference,
The oscillation phase of the voltage controlled oscillator 11 is feedback-controlled so that the phase difference is reduced. Further, the detection output output from the phase detection circuit 10 of the PLL type phase detection circuit 8 is output as a detection output via the LPF 13.

That is, the PLL type phase detection circuit 8 outputs a detection output corresponding to a change in the relative distance d between the capacitance detecting electrode 6 and the magneto-optical disk 1, that is, a change in the relative distance between the magnetic head 2 and the magneto-optical disk 1. can get. This detection output is sent to the phase compensating circuit 14 for phase compensation, and is supplied from the phase compensating circuit 14 to the drive circuit 15.

The drive circuit 15 uses the detected output as a control signal to cause the magnetic head 2 to detect the capacitance detection electrode 6 by electromagnetic means, for example.
At the same time, it is driven and displaced in the perspective direction to keep the relative distance between the magnetic head 2 and the magneto-optical disk 1 constant.

As described above, in the magnetic head position control device according to the prior invention, the PLL phase detection circuit 8 including the voltage controlled oscillator 11 having the oscillation characteristic close to the oscillation characteristic of the oscillation circuit 7 transmits the control signal of the drive circuit 15 to the control signal. Is forming. Therefore, for example, an error due to the temperature characteristics of the circuit elements such as the coils 42 and 53 and an error due to the non-linear characteristics of the voltage controlled oscillator 11 can be canceled out, and accurate control can be realized.

[Problems to be solved by the invention]

However, since the magnetic head position control device described above performs position servo only by the capacitance detection electrode 6 and the electrostatic capacitance C formed on the recording surface (deposition surface) of the magneto-optical disk 1, When the dimensions and the area of the recording surface change, there is a problem that it is not possible to control so as to always provide an optimum magnetic gap.

That is, the electrostatic capacitance C actually changes due to the stray capacitance C _O between the turntable and the reflection surface (aluminum foil) formed on the recording surface of the optical disc when the magneto-optical disc 1 is mounted on the turntable. The stray capacitance C _O changes the oscillation frequency of the oscillation circuit 7.

Since the stray capacitance C _O greatly changes depending on the external dimensions of the magneto-optical disk 1 mounted on the turntable, particularly the area of the metal deposition surface forming the recording surface of the magneto-optical disk 1, the position servo of the magnetic head as described above is performed. In the apparatus, there is a problem that the relative distance d slightly changes depending on the size of the magneto-optical disk, and the optimum magnetic gap cannot always be set.

[Means for solving problems]

The present invention has been made in consideration of such problems,
In a magnetic head, a capacity detecting means for detecting a capacity between the magnetic head and the magneto-optical disk, and a servo circuit of the magnetic head for controlling an actuator of the magnetic head based on a signal output from the capacity detecting means, Information corresponding to the outer shape or recording area of the mounted magneto-optical disk is configured to be able to be supplied to the servo circuit as a bias voltage, and the stray capacitance generated when the magneto-optical disk is mounted in the magneto-optical recording device is The target servo value of the head is not changed.

[Action]

The area of the metal deposition surface (aluminum foil) formed on the recording surface of the magneto-optical disk is the external dimension of the disk or the area of the recording surface that changes the value of the stray capacitance that occurs when this magneto-optical disk is mounted on the turntable. By selecting a preset bias signal according to the information and adding it to the control signal of the servo circuit, it is possible to prevent the magnetic gap from fluctuating significantly due to stray capacitance, and to always provide an optimum recording magnetic field to the disc. Will be able to.

〔Example〕

FIG. 1 is a block diagram of a magnetic head servo device in a magneto-optical recording device according to an embodiment of the present invention. The same parts as those in FIG. 3 are designated by the same symbols.

That is, 1 is a magneto-optical disk, 2 is a magnetic head arranged facing this magneto-optical disk, and 3 is an optical head.

The output of the capacitance detecting electrode 6 that moves up and down together with the magnetic head 2 is supplied to a C / V converter 21 that converts the capacitance value into a signal voltage. The C / V converter 21 is composed of the PLL type phase detection circuit 8 as shown in FIG. 3, but may be a circuit of another conversion system.

Reference numeral 22 denotes a disc information detection unit for detecting the outer dimensions of the magneto-optical disc 1 or the area information data of the recording surface on which the metal foil is vapor-deposited from the reproduction data output from the optical head 3. Further, 23 is a D / V that selects and outputs a predetermined bias signal from the signal data of the disc information detection unit 22.
The output of the D / V converter 23 and the output of the C / V converter 21 are combined by an adder 24 to form a control signal for the magnetic head 2. The disc information detection unit 22 detects, for example, data (recording area information) regarding the disc outer shape or inner diameter recorded in the lead-in area of the magneto-optical disc 1, and this data is processed in advance as pit information on the disc. It is what

In addition, the D / V converter 23 uses the data to determine the magnetic head 2
A predetermined bias signal is supplied to the servo circuit.

As shown in FIG. 2, when the outer diameter φ of the magneto-optical disk 1 is large, generally the stray capacitance between the magneto-optical disk 1 and the installation is large.
C _O increases, and the capacitance value input to the magnetic head 2 increases. Therefore, the servo circuit of the magnetic head 2 is controlled so that the gap (magnetic gap) between the magnetic head 2 and the magneto-optical disk 1 becomes large. Then, when the magnetic head 2 is separated from the magneto-optical disk 1, the strength of the applied magnetic field becomes weak.

Therefore, in this case, the magnetic head 2 is prevented from being separated from the magneto-optical disk 1 by superimposing and supplying a bias signal from the D / V converter 23 to the servo circuit so as to reduce the control amount.

When the installed magneto-optical disk 1 is a disk having a small diameter, the stray capacitance C _O becomes small, the magnetic head 2 is controlled in the opposite direction to the case described above, and the magnetic gap GAP is controlled so as to be narrowed. It When the magneto-optical disk 1 and the magnetic head 2 come close to each other by a predetermined distance or more, when the strong shock is applied to the magneto-optical recording device, the magnetic head 2 collides with the recording surface of the magneto-optical disk 1 and the recording surface of the magneto-optical disk 1 is collided. It is not preferable because it may cause damage.

However, in the case of the present invention, when a small-diameter disc is mounted, the disc information detection unit 22 first reads the data indicating that it is a small-diameter disc, and an appropriate bias signal for this disc is D / V converted. Since the servo signal is supplied from the section 23 to the servo circuit, the position of the magnetic head 2 is controlled so as to form the magnetic gap that prevents the above-mentioned obstacle.

As described above, the servo circuit for controlling the position of the magnetic head of the present invention outputs from the D / V converter 23 in consideration of the influence of the stray capacitance C _O generated by the mounted magneto-optical disk 1. Since the value of the bias signal is automatically changed, the magnetic head can be controlled so that the magneto-optical disk 1 set in the magneto-optical recording device always has an optimum magnetic gap.

In order to identify the loaded magneto-optical disc, the data regarding the outer shape or inner diameter of the disc is input in advance in the lead interior of the disc, but this is adopted in the conventional multi-disc player. As described above, a disk size detection unit 25 for detecting the outer dimensions of the magneto-optical disk set by using a photo sensor is provided, and the optimum magnetic gap for the set disk is set from the disk size detection unit 25. Select the bias signal as obtained and add it as shown by the dotted line.
May be supplied to.

The bias signal supplied to the servo circuit is C / V directly.
It is also possible to input to the conversion unit 21.

[Effect of device]

As described above, in the magneto-optical recording apparatus of the present invention, the servo circuit for controlling the position of the magnetic head is applied with a predetermined bias signal which is different depending on the mounted magneto-optical disk, and the magneto-optical disk of the mounted magneto-optical disk is controlled. The effect of stray capacitance that fluctuates depending on the metal deposition surface is compensated, so servo can always be applied to give a proper magnetic gap to the magnetic head, and highly accurate data recording can be performed. There is.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the influence of stray capacitance, FIG. 3 is a block diagram of a magnetic head controller showing prior art, and FIG. FIG. 5 is a perspective view showing a specific example, and FIG. 5 is a circuit diagram showing an example of an oscillation circuit. FIG. 6 is a circuit diagram showing an example of the voltage controlled oscillator. In the figure, 1 is a magneto-optical disk, 2 is a magnetic head, 3 is an optical head, 4 is a coil, 6 is a capacitance detection electrode, 7 is an oscillation circuit,
8 is a PLL type phase detection circuit, 14 is a phase compensation circuit, 15 is a drive circuit, 21 is a C / V conversion unit, 22 is a disk information detection unit, and 23 is D /
The V converter is shown.

Claims (1)

[Scope of utility model registration request] 1. A magnetic head arranged to face a magneto-optical disk, a capacity detecting means for detecting an electrostatic capacity between the magnetic head and the magneto-optical disk, and a signal obtained from the capacity detecting means. In a magnetic head servo device including an actuator for controlling a relative distance between the magnetic head and the magneto-optical disk based on, the outer diameter information of the magneto-optical disk or the area information of the recording surface of the magneto-optical disk A means for detecting at least one by means of information or a sensor recorded in advance on the magneto-optical disk, and a displacement signal for correcting a control error due to a change in stray capacitance caused by a change in the outer diameter or area of the magneto-optical disk, A magneto-optical recording apparatus having a servo circuit which gives the actuator based on the detected outer diameter information or area information. The magnetic head servo device definitive.