JPH03156703A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To suppress the fluctuation in the recording state due to the reduction in the impressed magnetic field caused by a change in the inductance of a magnetic head by controlling the capacitance of the variable capacitor provided in an L-C resonator. CONSTITUTION:An optical head 1 and a magnetic disk 3 are placed opposite to each other with a magneto-optical recording medium 2 inbetween and an exciting coil of the magnetic head 3 and a capacitor form an LC resonator. A sinusoidal wave generating means 5 generates an AC magnetic field whose frequency is fR into the magnetic head 3 and a laser beam with a recording intensity radiates from an optical head 1 while a magnetic field is impressed in the recording direction synchronously with the AC magnetic field. An impressed magnetic field sensing means provided to the optical head receiving the transmitted laser beam with respect to the magneto-optical recording medium 2 consists of an air-core pickup coil 6 and a pickup circuit 7 converting an induced electromotive force from the pickup coil 6 into a voltage. A control means 8 applies feedback control to the capacitance of a varactor capacitor 4 by using the signal. Thus, the fluctuation of the impressed magnetic field is suppressed and the recording state is made stable.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a magneto-optical recording and reproducing device that utilizes the magneto-optic effect, and in particular, to a magneto-optical recording and reproducing device that uses a magnetic head with a resonant frequency of an L-C resonator. This invention relates to a magneto-optical recording and reproducing device that generates an alternating current electric field by manually generating a sine wave.

(Prior Art) This type of magneto-optical recording/reproducing device now uses an override method that allows new data to be directly overwritten on the magneto-optical recording medium without erasing old data. , the transfer sheet has been improved. As one such new method, the proposed method modulates the magnetic field applied to the magneto-optical recording medium. When performing this magnetic field modulation recording, if a coil with large inductance is used on the magnetic head side, high-speed modulation becomes impossible.
On the contrary, there is a problem that the transfer sheet becomes lower. Therefore, a magnetic head with small inductance is usually used.

FIG. 5 schematically shows a magneto-optical recording and reproducing apparatus using such a magnetic field modulation method. Here, a laser beam with a constant recording intensity is irradiated from an optical head 51 onto a magneto-optical recording medium 52, and the optical head 51 is controlled by a focal position control device so that the laser beam is focused on the recording medium 52. Focusing is done at 50. On the other hand, a magnetic head 53 disposed opposite the optical head 51 with the recording medium 52 interposed therebetween is controlled by a magnetic head drive circuit 59. While the recording medium 52 is irradiated with a laser beam of recording intensity from the optical head 51, the magnetic head 53 is modulated and driven by the magnetic head drive circuit 59, and information is recorded on the recording medium using the modulated magnetic field generated thereby. It will be done.

However, in this case, the magnetic head 53 is attached to the air slider 54.
Therefore, it is necessary to maintain a small distance from the recording medium 52, and the magnetic head 53 needs to be driven in a rectangular wave according to the recorded data, resulting in a problem that the magnetic head drive circuit becomes complicated.

As a means to solve this problem, an overridable magneto-optical recording/reproducing device using an LC resonator has been proposed, as described in, for example, Japanese Patent Application Laid-Open No. 2002-120003.

FIG. 6 schematically shows such a magneto-optical recording and reproducing apparatus. Here, the laser beam emitted from the optical head 61 is focused on the recording medium 62, raising the temperature of the irradiation position.

On the other hand, a magnetic head 63 facing the optical head 61 with the recording medium 62 in between constitutes an LC resonator with its coil and a capacitor 64. Then, the oscillator 65 generates a sine wave of the resonant frequency f7 of the L-C resonator.
By inputting it to the -C resonator, an alternating current magnetic field modulated by the above-mentioned sine wave is obtained in the magnetic head 63. As a result, as shown in Figure 2, a laser beam is irradiated at recording intensity in synchronization with a magnetic field modulated by a sine wave, and for a time when a sufficient magnetic field is applied in the direction to be recorded. , data can be recorded on a recording medium.

Such a configuration can be overridden with a simpler configuration than the above-mentioned magneto-optical recording/reproducing device which requires rectangular wave driving.

(Problem to be Solved by the Invention) However, in the above-mentioned magneto-optical recording and reproducing device, as the position of the recording medium changes due to surface runout, the generated magnetic field changes, the recording conditions change, and the error rate increases. There is a problem. In other words, the recording medium is generally made of a magnetic material, and the distance between the magnetic head and the recording medium is shortened to obtain the necessary magnetic field strength even if the inductance is small. Even a slight change in distance changes the inductance of the magnetic head,
The resonant frequency changes, degrading the efficiency of the L-C resonator,
This causes a decrease in the generated magnetic field.

(Object of the Invention) The present invention has been made based on the above circumstances, and includes a variable resonator provided in the L-C resonator so that the applied magnetic field is detected on the optical head side and the amplitude of the output is constant. It is an object of the present invention to provide a magneto-optical recording/reproducing device in which the capacitance of a capacitive capacitor is controlled to suppress fluctuations in the recording state due to a decrease in the applied magnetic field due to changes in the inductance of a magnetic head.

(Means for Solving the Problems) Therefore, in the present invention, an optical head and a magnetic head are opposed to each other with a magneto-optical recording medium in between, and an LC resonator is formed by an excitation coil and a capacitor of the magnetic head. and the number of resonant periods f8 of the L-C resonator is set by the sine wave generating means.
A sine wave having a frequency of In a magneto-optical recording and reproducing device in which an optical head emits a laser beam of recording intensity, an applied magnetic field detection means is provided in a portion of the optical head that transmits the laser beam to a magneto-optical recording medium, and the capacitor is variable. The variable capacitor is configured with a capacitance capacitor, and includes control means for feedback controlling the capacitance of the variable capacitor according to the output of the applied magnetic field detection means so that the amplitude of the output of the applied magnetic field detection means is constant.

(Function) Therefore, since fluctuations in the applied magnetic field due to changes in the inductance of the magnetic head are suppressed, the recording state can be stabilized and the error rate can be reduced.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIGS. 1 to 4. In FIG. 1, reference numeral 1 denotes an optical head, and a laser beam emitted from the optical head 1 is focused on a magneto-optical recording medium 2 to increase the temperature of the irradiation position.

On the other hand, a magnetic head 3 is installed at a position facing the optical head 1 with the recording medium 2 in between. The excitation coil of this magnetic head 3 and the variable capacitor 4 are L −
It constitutes a C resonator. Then, the sine waves of the resonant frequencies f and l of this LC resonator are supplied to the LC# oscillator by the oscillator 5 as a sine wave generating means. This allows the magnetic head 3 to obtain a magnetic field modulated by a sine wave.

Further, on the optical head 1 side, an applied magnetic field detection means is provided in a portion through which the laser beam is transmitted.

In this embodiment, this applied magnetic field detection means is composed of an air-core pickup coil 6 surrounding a portion through which the laser beam is transmitted, and a pickup circuit 7 as a conversion circuit that converts the induced electromotive force from the pickup coil 6 into a voltage. It is configured. The signal from the applied magnetic field detection means is input to the feedback control means 8 manually. The feedback control means 8 controls the capacitance of the variable capacitor 4 according to the output of the applied magnetic field detection means so that the amplitude of the output of the applied magnetic field detection means is constant.

In such a configuration, as shown in Figure 2, data is recorded by irradiating a laser beam at recording intensity only during a period when a sufficient magnetic field is applied in synchronization with the generated magnetic field and in the direction to be recorded. However, in the control means 8, the third
As shown in the figure, the output from the pickup circuit 7 is input to the envelope detection circuit 9 to detect the envelope and extract the amplitude fluctuation of the modulated magnetic field. Since the capacitor capacitance is controlled by input, the efficiency of the LC resonator is controlled. FIG. 4 shows the flow of signals in the control means 8.

In this way, it is possible to suppress deterioration of the efficiency of the LC resonator due to changes in the inductance of the magnetic head 3, and to suppress and stabilize fluctuations in the generated magnetic field.

(Effects of the Invention) The present invention has been described in detail above, and the applied magnetic field detection means is provided on the optical head side, and the capacitance of the variable capacitor of the L-C# oscillator is By performing feedback control, it is possible to suppress fluctuations in the applied magnetic field due to changes in the inductance of the magnetic head, stabilize the recording state, and reduce the error rate.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a magneto-optical recording/reproducing device showing an embodiment of the present invention, FIG. 2 is a time chart showing the recording process by this device, and FIG. 3 is a block diagram showing the configuration of the control means in FIG. 1. 4 are graphs showing signals of this control means, and FIGS. 5 and 6 are schematic diagrams of conventional magneto-optical recording and reproducing apparatuses, respectively. DESCRIPTION OF SYMBOLS 1...Optical head 2...Recording medium 3...Magnetic head 4...Variable capacitor 5...Sine wave oscillator 6...Pickup coil 7...Pickup circuit 8...Control means 9...Envelope detection circuit

Claims (2)

[Claims] (1) An optical head and a magnetic head are opposed to each other with a magneto-optical recording medium in between, an excitation coil and a capacitor of the magnetic head constitute an L-C resonator, and the L-C resonance is generated by a sine wave generating means. A sine wave having a frequency of the resonant period f_R of the device is input to the LC resonator, an alternating magnetic field of the frequency f_R is generated in the magnetic head, and a magnetic field is applied in synchronization with the alternating magnetic field and in the recording direction. In the magneto-optical recording and reproducing apparatus, the optical head irradiates a laser beam of recording intensity for a period of time, and an applied magnetic field detecting means is provided in a portion of the optical head that transmits the laser beam to the magneto-optical recording medium. In addition, the capacitor is configured with a variable capacitor, and control means performs feedback control on the capacitance of the variable capacitor according to the output of the applied magnetic field detection means so that the amplitude of the output of the applied magnetic field detection means is constant. A magneto-optical recording and reproducing device comprising: (2) The magneto-optical recording and reproducing apparatus according to claim 1, wherein the applied magnetic field detection means comprises an air-core coil and a conversion circuit that converts an electromotive force induced from the air-core coil into a voltage.