JPH03245338A - Magneto-optical disk device - Google Patents

Abstract

PURPOSE:To maintain the specified distance of a magnetic head for magnetic field modulation from a electrode medium with simple constitution by detecting the moving distance in the focusing direction of an objective lens and moving the magnetic head for magnetic field modulation in the same direction by as much as the same distance as the detected moving distance of the lens. CONSTITUTION:Electrodes 26a, 26b constituting an electrostatic capacity type displacement sensor 26 are mounted to the respective opposite points of a yoke 25 for focusing driving and a movable body 16. A magnetic head servo circuit 29 compares the electrostatic capacity thereof with the electrostatic capacity between two electrodes 12a and 12b of an electrostatic capacity type displace ment sensor 12 on a magnetic head 3 side and passes an electric current to a coil 3b of the magnetic head 3 in such a manner that both capacities coincide with each other, thereby moving the magnetic head 3 in the same direction by as much as the moving distance in the focusing direction of the objective lens 19. The distance between the magnetic head 3 and the recording medium 1b is maintained always constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic field modulation type magneto-optical disk device, and more particularly to means for controlling the distance of a magnetic field modulation head to a recording medium.

[Prior Art] A magneto-optical disk device using a magnetic field modulation method is equipped with a magnetic field modulating magnetic head that changes the direction of an external magnetic field applied to a recording medium according to data to be recorded, and an optical head that applies an optical beam to the recording medium using an optical head. At the same time, signals are recorded by applying an external magnetic field to the recording medium using the magnetic field modulation head in a direction corresponding to recording data.

The magnetic head for magnetic field modulation in a conventional magnetic field modulation type magneto-optical disk device is naturally movable in the radial direction of the disk, but is fixedly provided in the direction perpendicular to the disk surface.

[Problems to be Solved by the Invention] The magnetic head for magnetic field modulation needs to apply a high frequency and strong perpendicular magnetic field to the recording medium, but it is difficult to apply such a strong magnetic field from a position away from the recording medium. Although it is difficult to do so, the distance between the magnetic head for magnetic field modulation and the recording medium is generally made as small as possible. however,
Since the disk has surface runout, in a configuration in which the magnetic head for magnetic field modulation is fixedly provided as in the conventional device described above, the distance between the magnetic head and the recording medium varies, so the magnetic field strength applied to the recording medium changes. There is a problem in that the reliability of signal recording decreases. In addition, since it is necessary to provide a large magnetic field strength corresponding to when the surface runout is large,
A large current must be passed through the magnetic head for magnetic field modulation.

In addition, as a countermeasure to the above problem, there is a method of using a flying head, which is commonly used for magnetic disks, but it is difficult to make the disk medium replaceable, and the surface run-out occurs because the substrate is made of plastic. There have been problems such as difficulty in realizing this method using media with poor mechanical properties.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and has a simple configuration that allows the distance of the magnetic head for magnetic field modulation to the recording medium to be kept constant, and enables highly reliable signal recording. The purpose is to provide a magneto-optical disk device.

[Means for Solving the Problems] - The present invention for solving the problems described above provides a magnetic field modulation system comprising an optical head that irradiates a recording medium with a light beam and a magnetic field modulation magnetic head that applies an external magnetic field to the recording medium. In this type of magneto-optical disk device, a lens movement distance sensor is provided on the objective lens actuator of the optical head and detects the movement distance of the objective lens in the focusing direction, and the magnetic field modulation magnetic head is controlled by the lens movement distance sensor. The present invention is characterized by comprising a magnetic field modulation magnetic head position control means for moving the detected lens movement distance by the same distance in the same direction.

[Operation] In the above configuration, the distance of the objective lens to the recording medium is controlled to be constant by focusing control of the objective lens actuator, so the magnetic field modulation head moves in the same direction by the same distance as the moving distance of the objective lens. Thus, like the objective lens, it is kept at a constant distance from the recording medium.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 1 denotes a magneto-optical disk (hereinafter simply referred to as a disk) in which a recording medium 1b is provided on one side of a transparent substrate lEt.
1-) One objective lens of the objective lens actuator 2 of the optical head that irradiates the recording section with a light beam and the recording medium 1
A magnetic field modulating magnetic head (hereinafter abbreviated as magnetic head) 3 that applies an external magnetic field to the recording section b is provided so as to be movable in the disk radial direction in a j-system between constantly opposing positions.

The magnetic head 3 is constructed by winding a coil 3b around a yoke 3a, and is supported by a magnetic head holder 4 via a spiral plate spring 5 so as to be elastically movable up and down. FIG. 2 shows the shape of the spiral leaf spring 5 viewed from above. The magnetic helad holder 4 is fixed to a frame 6, and the frame 6 is sent in the disk radial direction by the illustrated feeding drive mechanism so as to always face the objective lens actuator 2 of the optical head. A connecting member 7 is vertically provided on the upper surface of the magnetic head 3.
This connecting member 7 penetrates upward from a hole 4a made in the magnetic head holder 4, and a magnetic head driving coil 8 is provided on the upper part. A magnet 9 and a yoke 10 are attached to the frame 6 and constitute a magnetic circuit that crosses the drive coil 8.

Further, a protrusion 1] is attached to the magnetic head 3, and two electrodes 12a and 12b constituting a capacitive displacement sensor 12 are attached to locations where the magnetic head holder 4 and this protrusion 11 face each other. It is being

To explain the objective lens actuator 2 of the optical head, a cylindrical outer gauge 14 is provided with upper and lower spiral plate springs 15 having the same shape as the spiral plate spring 5 shown in FIG.
The cylindrical movable body 16 moves up and down through the arrow F in the focusing direction. The lens boulder 18 is supported so as to be elastically movable in the left and right directions in FIG. One objective lens is attached to this lens bolder 18. The lens holder 18 is provided with a tracking coil 20 that protrudes outward from an opening formed in the movable body 16. Outside game 1
Magnets 1 to 21 and a yoke 22 forming a magnetic circuit that crosses the tracking coil 20 are attached to the yoke 4 .

Further, a focusing coil 23 is provided at the lower part of the movable body 16, and a magnet 24 and a yoke 2 form a magnetic circuit that crosses this focusing coil 23.
5 has been removed and 1” has been removed.

The objective lens actuator 2 of the optical spatula is the above-mentioned horizontal or conventional general type, but in the present invention,
A capacitive displacement sensor 2 is provided at each of the locations where the focusing drive yoke 25 and the movable body 16 face each other.
Electrodes 26a and 26b constituting 6 are attached. A C/V conversion circuit 27 converts the capacitance between these two electrodes 26a and 26b into voltage, and a low-pass filter (
LPF) 28, and two magnetic head servo circuits that perform control to maintain a constant distance of the magnetic head 3 with respect to the recording medium 1b based on the output of the LPF 28. Also, two electrodes 12a of the capacitive displacement sensor 12 on the side of the magnetic head 3.

121] is a similar C/V conversion circuit 30 and LPF 31
It is connected to the two magnetic helad servo circuits via.

The two magnetic herad servo circuits in this embodiment are the electrodes 26a on the objective lens actuator 2 side.

The capacitance between 26b and the electrodes 12a and 1 on the magnetic head 3 side
A control method is adopted in which a current is passed through the coil 3b of the magnetic head 3 so that the capacitance between the coils 2b and 2b matches. In this case, the two capacitors 12.degree. 26 are made to have the same characteristics.

Next, the operation will be explained.

The original operation of the optical head 2 and the original operation of the magnetic head 3 are common and will not be explained here, but on the objective lens actuator 2 side, one objective lens, a parallel plate spring 17, and a movable body 16 are operated by a focusing servo. When the two electrodes 26a of the capacitive displacement sensor 26 move together in the focusing direction (arrow F direction), the two electrodes 26a,
The distance between 26b changes and its capacitance changes. The capacitance between the electrodes 26 a and 26 b is converted into voltage by the C/V conversion circuit 27 and inputted to two magnetic head servo circuits via the LPF 28 . Compare the capacitance between the two electrodes 12a and 12b of the capacitive displacement sensor 12, and apply a current to the coil 3b of the magnetic head 3 so that the capacitances match.
As a result, the magnetic head 3 is moved in the same direction by the same distance as the moving distance of one objective lens in the focusing direction.

In this way, the distance between the magnetic head 3 and the recording medium 1b is always kept constant.

In the embodiment, the mechanism for moving the magnetic head 3 up and down is a structure in which the magnetic head is supported by a spring and driven up and down by electromagnetic force acting on a drive coil placed in a magnetic field = 8-. However, this is not necessarily the case. but not limited to. In short, it is sufficient if the magnetic head can be moved in the vertical direction.

Furthermore, as a means for moving the magnetic head by the same distance as the objective lens, a capacitance type displacement sensor is used on the magnetic head side as well, but various other methods can be adopted for this as well.

Further, the lens movement distance sensor itself that detects the movement distance of the objective lens in the focusing direction is not limited to a capacitance displacement sensor, and for example, an optical type or other type can be adopted.

[Effects of the Invention] Since the present invention is configured as described above, it has the following effects.

Since the distance between the magnetic field modulating magnetic head and the recording medium is always kept small and constant, reliable and good signal recording is performed. Further, there is no need to flow an unnecessarily large current to the magnetic head for magnetic field modulation.

In addition, since the position control means for the magnetic head for magnetic field modulation is configured to detect the movement of the objective lens in the focusing direction in the objective lens actuator, the configuration is different from that in which the moving distance of the magnetic head for magnetic field modulation is directly detected. is extremely easy.

Furthermore, if a capacitance displacement sensor is used as the lens movement distance sensor as in claim 2, it is extremely suitable to be provided in the objective lens actuator, and the mechanism for detecting the movement distance of the objective lens is extremely simple. It's over.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an optical head and a magnetic field modulating magnetic head of a magneto-optical disk device showing one embodiment of the present invention;
The figure is a sectional view taken along the line ■-■ in FIG. 3... Magnetic head for magnetic field modulation, 4... Magnetic head holder, 5... Spiral plate spring, 7... Connecting member, 8
...Magnetic head drive coil, 9...Magnet,
10-... Yoke, 12... Capacitive displacement sensor,
12a 12b...electrode, 16...movable body/movable part>, 23...focusing coil, 24...magnet, 25...yoke (fixed part), 26...capacitive displacement sensor, 26a, 26b...electrodes, two...
・Magnetic head servo circuit.

Claims (2)

[Claims] (1) In a magnetic field modulation type magneto-optical disk device equipped with an optical head that irradiates a light beam onto a recording medium and a magnetic field modulation head that applies an external magnetic field to the recording medium, the objective lens actuator of the optical head is provided with: a lens movement distance sensor that detects the movement distance of the objective lens in the focusing direction; and a magnetic field modulation that moves the magnetic field modulation magnetic head in the same direction by the same distance as the lens movement distance detected by the lens movement distance sensor. 1. A magneto-optical disk device comprising a magnetic head position control means. (2) The lens movement distance sensor is a capacitive displacement sensor configured by providing electrodes at mutually opposing positions of a movable part and a fixed part in the objective lens actuator. The magneto-optical disk device described above.