JPH02239449A - Magnetic field modulator - Google Patents

Abstract

PURPOSE:To obtain the same effect, that is obtained at the time of providing a magnetic field generating coil with a mobile part to perform the control, with a low cost by controlling the current of the magnetic field generating coil by the servo error signal of an actuator. CONSTITUTION:The intensity of the magnetic field of a magnetic field modulator is changed with the servo error signal which controls the actuator of a magneto- optical recording device. That is, an objective lens 26 is moved by the focus control as shown by a broken line when a recording medium 20 is moved in the focusing direction by an extent dx. At this time, a magnetic field generating coil 22 is not moved but a current I flowing to the coil 22 is increased to equalize the intensity of the magnetic field in the irradiated spot position. Since this current is increased by the focus servo signal which drives an objective lens unit 24, satisfactory control is performed though a special control means is not provided on the coil 22 side. Thus, the magnetic field in the laser spot position is always uniform, and the same effect that is obtained at the time of providing the magnetic field generating coil with a mobile part to perform the control is obtained with a low cost.

Description

[Detailed Description of the Invention] [Field of Application of Industry-L] The present invention relates to a magnetic field modulator used in a magneto-optical recording device employing a magneto-optical recording method. [Journey's technology] In recent years, magneto-optical disks have been attracting attention as large-capacity recording media.Among them, those with a barite function have an access speed of 11D.
It has become a DM and there are high expectations. The magnetic field modulation method can be roughly divided into two types, and Figure 4 is a schematic diagram showing the principle of the magnetic field modulation method. In the figure, 43 is a film as a thousand stages of magnetic field generation, 45 is a magneto-optical disk, 46 is an objective lens, 40 is a magnetic field modulation signal, and 41
is the ta signal recorded on the disk. Now, let us consider a case where "old 001" is to be recorded as a recording signal on a recording medium. Laser light is irradiated onto the board at a certain constant power. In the area hit by the laser spot, the temperature of the medium decreases to -F. due to the laser beam. The temperature rises to a curvature point, and that part is magnetized in the direction of the externally applied magnetic field. Therefore, if the direction of the externally applied magnetic field 40 is changed according to the digital signal to be recorded, the signal will be recorded in the form 41 of the magnetization direction. Therefore, the magnetic field generator used in this method is &! Modulation is necessary to change the direction of the field, and it must be modulated at the same frequency as the recording edge A, 1%.

Furthermore, due to the demand for faster access speeds, the Mi field generator must be light and compact. On the other hand, if it is light and compact, the magnetic field will naturally be weak, so it is necessary to move it as close to the recording medium as possible so that the strongest magnetic field is applied to the part to be recorded. However, in the conventional example, in order to strengthen the magnetic field applied to the medium. ! Even if we tried to bring the magnetic head as close as possible to the '13J, there was a limit due to the risk of head crash. In addition, if the magnetic field generator is made light 1A in order to speed up the access time, the number of turns must be reduced if it is configured with a two-winding coil, and as a result, there is a problem that the applied magnetic field decreases. .

As a countermeasure, the magnetic field generator is also provided with a movable mechanism in the focus h direction and in the tracking direction, so that the magnetic field can be applied to the area to be recorded as accurately as possible in response to the movement of the optical spot on the recording medium 1-. Although some devices are configured to apply voltage, they have the disadvantage that the structure of the movable mechanism is complicated and costs are high.

[1,000 Steps to Solve the Problems] The purpose of the present invention is to make the magnetic field of the laser spot uniform at all times, and to obtain the same effect as when controlling by providing one moving part in the generating magnetic field coil at a low cost. An object of the present invention is to provide a magnetic field modulation device that can be used.

The purpose of the above is to improve the magnetic field intensity of a magnetic field generating means placed near the medium and modulating the magnetic field according to a recording signal. This is achieved by a magnetic field modulation device that uses various servo error signals to control various actuators of a magneto-optical recording device. A typical example of such a servo error signal is the relative position 1 between the track of the medium 1 and the optical head.
There is a tracking error {jj for detecting 6 and a focus z1 difference signal for detecting the distance between the medium and the head, and by using the focus error signal and at least one tracking error signal 3, the magnetic field generating means A possible configuration is to change the magnetic field strength. Here, the basic idea of the present invention will be explained. Figure 2 (a>.(b) is a diagram for explaining a method of compensating for the decrease in the strength of the applied magnetic field due to a shift in the focus direction. medium, 2
2 is a magnetic field generating coil, 26 is an objective lens, and 24 is an objective lens unit. Now, if the recording medium 20 moves from the position of the solid line to the position of the broken line by dx in the focus direction, the objective lens 26 moves as shown by the broken line due to focus control. Here, it can be seen that in order to maintain the same magnetic field strength at the irradiation spot position without moving the magnetic field generating coil 22, it is sufficient to increase the current 1 flowing through the coil 22. Figure 2(b) is a diagram showing an example of its characteristics. This increase is derived from the focus servo that drives the objective lens unit 24 (of course, it is used in reverse).
Thus, good control can be achieved without providing any special control means on the coil 22 side. This idea is exactly the same in correction of the deviation in the tracking direction. FIGS. 3(a) and 3(b) are diagrams for explaining a method of correcting a decrease in the strength of the applied magnetic field due to a deviation in the tracking direction, respectively.

In these controls, the current flow that corrects the deviation in the focus direction or the tracking direction is determined in advance for each focus direction deviation needle and tracking direction deviation product, and the corresponding servo No. 3 is used to flow a predetermined current. You can configure it like this. In addition, in order to improve the accuracy of correction, it is possible to take into account the case where the two directional deviations mentioned in iii occur at the same time, convert these two servo signals at an appropriate ratio, and control using the converted value. good. According to the present invention, for example, by controlling the current of the winding coil that generates a magnetic field by the servo 1τ of the actuator, the precision of the laser irradiation spot can be achieved even if the actuator has no moving parts. The applied magnetic field near L can be made uniform and a great effect can be obtained.

[Example] Hereinafter, the magnetic field modulator In according to the present invention will be described in detail based on a specific example. FIG. 1 is a block diagram of an embodiment of the present invention.

In the figure, l is a magneto-optical disk as a recording medium,
2 is a spindle motor for rotating the disk;
: 3 is a semiconductor laser as a light source, 4 is a collimator lens that converts the light beam into a row, 5 is a beam splitter that splits the light beam, 6 is an objective lens that focuses the light onto the disc I-E, 7 is a focus direction and an actuator ijJ moving part that controls the tracking direction, 8 a condenser lens that focuses light on a sensor, 9 a servo sensor, and 10 a current-voltage converter (referred to as a 1/V converter). I+ is a focus control circuit, 12 is a tracking control circuit, 13 is a tracking coin driver, l4 is a focus film driver,
15 is an adder. +6 is a magnetic field coil driver. +7 is a magnetic field generating coil. Next, the operation of this embodiment will be explained in order. A magneto-optical disk 1 is rotated at high speed by a spindle motor 2. The laser beam Q4 emitted from the semiconductor laser 3 is made into a skewed beam by the collimator lens 4, passes through the beam splitter 5, is focused to a certain spot diameter by the objective lens 6, and is irradiated onto the disk IF. disk l
The reflected light from follows the opposite optical path. The direction of the beam is changed by the beam splitter 5, and the beam is focused on the servo sensor 9 through the condenser lens 8. I/V photocurrent from servo sensor 9 (4-split sensor)
Converter lO converts it into voltage, and the focus control path 11
Through. An AF servo signal is created. By the ΔF servo {No. 3, a predetermined current flows through the AP coil in the acticoator moving part 7 through the driver 14, and control is performed in the forward direction. Regarding the tracking system, the objective lens 6 is moved by a tracking film via a tracking control circuit 12 and a tracking coil driver 13 to control the tracking direction. now. In this embodiment, there is a winding coil l7 as a magnetic field generator for magnetic field modulation, but after converting the output from the servo sensor 9 into voltages for the focus system and tracking system by the l/v converter 10, The adder 15 adds the mixture at an appropriate mixing ratio. The current of coil I7 is controlled according to the added voltage. Due to such current control, the generated magnetic field changes in accordance with the fluctuations of the light beam spot position 1n and the recording track position m so as to cancel out the fluctuations, so that a uniform magnetic field is always realized. The mixing ratio added by the adder 15 is determined based on the concept described in [Operation]. [Other embodiments
However, the effects of the present invention can be sufficiently obtained even if the control is performed using only signals of either -h. Furthermore, the present invention has the advantage of obtaining not only servo signals for focus direction control and tracking direction control, but also signals that can be corrected to substantially cancel out fluctuations in magnetic field strength due to fluctuations in recording track and laser spot position. Various servo signals can be used as long as they can be used. [Effects of the Invention] As explained below. According to the magnetic field modulator of the present invention.
Servo 2 on the actuator: By controlling the current of the magnetic field generating film using a difference signal, the generated magnetic field changes according to the movement of the actuator, so the magnetic field directly above the laser spot is always uniform, and the magnetic field coil generates a lof. The same effect as -1 control by providing a moving part can be obtained, and it can be realized at a lower cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. Figure 2(a). (b) and Figure 3 (a). (b) is a diagram for explaining the basic idea of the present invention.

Claims (2)

[Claims] (1) A magneto-optical recording medium, an optical head that irradiates the medium with light, a focus signal detection means that detects the distance between the medium and the optical head, and a relative position between the track on the medium and the optical head. a tracking signal detection means arranged near the medium and whose magnetic field is modulated according to the recording signal; and at least one of a signal from the focus signal detection means and a signal from the tracking signal detection means. A magnetic field modulation device comprising: means for changing the magnetic field strength of the magnetic field generating means using a signal. (2) A magnetic field modulation device used in a magneto-optical recording device that employs a magnetic field modulation method, in which the magnetic field intensity of a magnetic field generating means that is placed near the medium and whose magnetic field is modulated according to a recording signal is determined by magneto-optical recording. A magnetic field modulation device characterized in that the magnetic field modulation device is changed using various servo error signals that control various actuators of the device.