JPH02199603A - Bias magnetic field application device for magneto-optical recorder - Google Patents

Abstract

PURPOSE:To obtain a small sized magneto-optical recorder with less heat and excellent response and its bias magnetic field application device by moving a permanent magnet arranged opposite to a major plane of one major plane of a magneto-optical recording medium in parallel substantially with the major plane. CONSTITUTION:A permanent magnet 20 is arranged to an upper side of a magneto-optical recording disk medium 10 and an objective lens 30 is arranged to a position opposite to the permanent magnet 20 on the lower side. The permanent magnet 20 is arranged while its lengthwise direction is substantially in parallel with the radial direction of the medium 10 so as to cover the entire width of the recording area and the position is regulated by a regulation means so that the permanent magnet 20 is moved in a direction X perpendicular substantially to the radial direction Y of the medium 10. Thus, the permanent magnet 20 is moved in parallel on the major face of the recording medium 10 substantially to switch the polarity of the applied magnetic field. Thus, the profile of the device is made thin, the inversion of the bias magnetic field is quickened and the current consumption is reduced.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to a magneto-optical recording device, and more particularly to a device that applies a bias magnetic field for recording and reproduction using a permanent magnet. [Prior Art] A conventional method for recording, reading, or erasing data on a magneto-optical recording medium such as a magneto-optical disk uses an electromagnet to supply a bias magnetic field during light irradiation. However, the polarity of the bias magnetic field is controlled by reversing the direction of the current flowing through it, or by using a permanent magnet instead of an electromagnet and reversing its mechanical direction. In either method, an electromagnet or permanent magnet of a bias magnetic field applying device is provided on one main surface side of a flat magneto-optical recording medium, and a laser beam for recording or reproduction is provided on the other main surface side. means are provided to converge. As is well known, information is recorded by applying a bias magnetic field and irradiating light. When the temperature of the magnetic material of the magneto-optical recording medium exceeds its Curie point by irradiation with light, the recording medium is locally magnetized to a polarity corresponding to the bias magnetic field. The recorded information is read by illuminating the recording medium with weak light that does not exceed the Curie point and then identifying the polarization direction of the reflected light. The recorded information is also erased by applying a bias magnetic field of a predetermined polarity in the same operation as recording, and setting the i-north polarity of the recording medium in a predetermined direction. [Problems to be Solved by the Invention] In this conventional magneto-optical recording device, a method using an electromagnet is advantageous in that the bias magnetic field can be electrically controlled and there are few mechanically movable parts. However, since the coil is constantly energized, it is necessary to take measures to dissipate heat. Also,
The method of reversing permanent magnets requires a motor for mechanical reversal, so the response speed is slow and the structure becomes taller. Miniaturization and thinning of devices is a trend throughout the electronic technology field, and magneto-optical recording devices are also required to be made smaller and thinner. The present invention overcomes these drawbacks of the prior art. It is an object of the present invention to provide a compact magneto-optical recording device that generates little heat and has good responsiveness, and a bias magnetic field applying device thereof. [Means for Solving the Problems] According to the present invention, there is provided a magneto-optical recording device that records information on a magneto-optical recording medium using light irradiated onto the magneto-optical recording medium and a bias magnetic field applied to the magneto-optical recording medium. The device for applying a bias magnetic field includes a permanent magnet whose N pole and S pole are arranged opposite to the main surface of one main surface of the magneto-optical recording medium, and a permanent magnet connected to the permanent magnet. The moving means moves the permanent magnet substantially parallel to the main surface, and the moving means moves the permanent magnet substantially parallel to the main surface.
Either the north pole or the south pole is selectively placed at a position on the magneto-optical recording medium that is irradiated with light. Also according to the invention. It includes such a bias magnetic field applying device and is disposed on the other main surface side of the magneto-optical recording medium,
A bias field applying device is provided that includes a lens that focuses light on the other principal surface. [Function] According to the present invention, on the side of one main surface of the magneto-optical recording medium, the permanent magnet is moved substantially parallel to the main surface by the moving means.
By making this movement, the magnetic pole of the permanent magnet is selectively arranged with respect to the light irradiation position on the medium. As a result, information is recorded, reproduced, and erased on the magneto-optical recording medium. [Example] Next, an example of the bias magnetic field applying device according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, the bias magnetic field application device of the embodiment in which the present invention is applied to a magneto-optical disk device has a permanent magnet 20. Spring 22, slide cam 24, link 26
and a solenoid 60 are arranged, and an objective lens 30 is arranged on the lower surface side of the medium 10 at a position facing the permanent magnet 20. The permanent magnets 20 are arranged such that their elongated directions are substantially parallel to the radial direction of the medium 10 and cover the entire width of the recording area. As can be seen from, for example, FIG. 2B, its cross section has a generally downward U-shape, and the ends of both arms of the U-shape are magnetized to N and S poles, respectively. The position of the permanent magnet 20 is regulated by a regulating means (not shown) so that it can move in a direction X substantially perpendicular to the radial direction Y of the medium 10. The slide cam 24 is
As shown in the figure, a spring 22 is connected to one end thereof, thereby biasing it in the Y-axis direction. The other end of the slide cam 24 is connected to one end of a link 26 by a pin 32 and a pin slot 33, and the link 26 is rotatable about a fulcrum 34. The other end of the link 2B is coupled to the iron core 38 of the solenoid 60 as shown. The slide cam 24 has two guide holes 40 shaped as shown, which are respectively engaged with two pins 42 fixed to the permanent magnet 20 correspondingly. The objective lens 30 is arranged so that the converged light 44 illuminates a portion of the medium 10 where the magnetic flux density is maximum at a position where information is to be recorded or reproduced. Below the lens 30 in FIG.
A laser light source and/or a light detection mechanism (not shown) for generating the light are provided. The magneto-optical recording medium 10 includes a ferrimagnetic material layer and has an overall circular flat disk shape. Magneto-optical recording combines the thermal effect of light and the characteristics of the ferrimagnetic recording layer of the medium 10 to record information. The effect raises the temperature of the recording layer near the Curie temperature, magnetizes the material layer of the medium lO in the direction of the auxiliary magnetic field, and thereby records rOJ, "l". Data reading uses the Kerr effect, in which the plane of polarization rotates depending on the direction of the magnetic moment when light irradiated onto the medium is reflected. An analyzer (not shown) of a read head (not shown) selects the polarization of the light, and a light receiving element (not shown) detects this as the brightness of the light and converts it into five electric values. In FIG. 2A, when a current flows through the solenoid 60, the iron core 38 is attracted to the solenoid 60, and the link 26 rotates about the rotation center 34 as a fulcrum. Therefore, the swidth cam 24 moves in the -Y direction, and the bin 42 relatively slides along the shape of the guide hole 40. Since the permanent magnet 20 is positionally regulated so as to be movable in the predetermined direction X, the permanent magnet 20 is attracted in the +X direction. Therefore, the permanent magnet 20 is placed on the optical axis 50 (FIG. 2B) of the objective lens 30.
There will be one pole, for example the north pole. In FIG. 3A, when no current is flowing through the solenoid 60, the spring 22 pulls the slide cam 24 in the +Y force direction. Therefore, the permanent magnet 20 moves in the -X direction, and in FIG. 3B, on the optical axis 50, the permanent magnet
In this example, there will be a south pole. To explain in more detail with reference to FIG. 4A, in this embodiment, it is assumed that in an initial state in which no information is written, the medium IO is magnetized upward in the figure. At a position on the medium 10 where information is written, a portion where the magnetic flux density due to the N pole of the permanent magnet 20 is maximum is irradiated with light 44 converged by the objective lens 30. The energy of the irradiated light is converted into thermal energy in the medium 10, and the temperature on the optical axis 50 of the medium 10 rises to around the Curie temperature in a portion where significant information is recorded. The direction of the magnetic moment 52 of that portion 8 is reversed by the magnetic field of the permanent magnet 20, that is, it becomes the direction of the arrow 52a in the figure. In this way, information is "recorded", and bit information "1" or "0" is recorded on the medium 10 depending on the presence or absence or strength of the irradiated light.
is recorded. Here, it is assumed that the upward direction of the magnetic moment 52 is "O" and the downward direction is rlJ. Note that for ease of understanding, recording of "0" has been explained as "erasing," but the term "erasing" means to set the magnetization polarity to a predetermined, for example, initial state, and is also referred to as "demagnetization." are different concepts. Therefore, involuntary data,
For example, it may be interpreted as a record of "0". In FIG. 4B, when the permanent magnet 20 moves in parallel on the medium 10 in the -X direction and the direction of the magnetic field on the optical axis 50 is reversed from the north pole to the south pole, the magnetic moment 52a on the optical axis 50 becomes "0". ”, which means that the information has been “erased”. "Reproduction" of recorded information utilizes the fact that the plane of polarization of light irradiated onto the medium 10 and reflected rotates in accordance with the melting polarity of the recording material layer. In the reproduction mode, the light intensity is lowered so that the temperature of the irradiated part of the medium 10 with the light 44 focused by the objective lens 30 is lower than the Curie temperature. This is because the direction of the magnetic moment 52 is This is to prevent recorded information from being erased if it is reversed by irradiation. The reflected light aperture from the medium 10 whose plane of polarization has been rotated according to the direction of magnetization due to the Kerr effect passes through the analyzer of the read head and is detected by the light receiving element as the brightness and darkness of the light. The detected signals are converted into digital signals and processed into electrical signals such as image signals and character signals. 5 and 6 show another embodiment according to the present invention. The device shown in FIG.
By moving this manually, the slide cam 24 moves on the Y axis, thereby moving the permanent magnet 2G in the
Move in the axial direction. As a result, the state shown in FIG. 0 in which the direction of the magnetic field supplied to the optical axis of the medium 10 is reversed corresponds to FIGS. Since the S pole of the permanent magnet 20 exists at , it is in an erased state. When the lever 81 is operated in the direction of arrow A in the figure, the north pole is located on the optical axis 50, so that the recording state is entered. This corresponds to FIG. 2A and FIG. 2B of the previous embodiment. In this method, since the permanent magnet 20 is moved in parallel, no current is consumed for moving the magnet 20. FIG. 6 shows yet another embodiment of the invention. This includes a permanent magnet 120 in which a large number of N and S poles are alternately magnetized and arranged over the entire width of the recording area of the medium 10 in the radial direction, and one end of the permanent magnet 120 is connected to the iron core 138 of the solenoid 180. There is. The other end of the magnet 120 is a spring 22
The media 10 is spring-biased radially outwardly by the media 10 . When the solenoid 1.10 is turned on and off, the permanent magnet 120 moves on the medium 10 by a distance corresponding to the arrangement pitch of the magnetic poles, and the direction of the magnetic field on the optical axis 50 is reversed. Furthermore, a configuration in which one end of the slide cam 24 shown in FIG. 5 is connected to a driving means (not shown) such as a solenoid 18G shown in FIG. 6 to move the permanent magnet 20 is also an embodiment of the present invention. Furthermore, a step motor with low power consumption can be used as the driving means. Although an embodiment in which the present invention is applied to a magneto-optical disk device has been described, the present invention is not limited to this, and can be effectively applied to other forms of magneto-optical recording, such as a card-shaped magneto-optical recording medium. Needless to say, this is true.

【Effect of the invention】

As described above, according to the present invention, the polarity of the applied magnetic field is switched by moving the permanent magnet that applies the bias magnetic field in the magneto-optical recording device substantially parallel to the main surface of the recording medium. Therefore, the device can be made thinner, the bias magnetic field can be reversed faster, and the current consumption can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of a bias magnetic field applying device according to the present invention. 2A and 2B are a top view and a side view, respectively, showing the state when current is flowing through the solenoid fJO in the embodiment shown in FIG. 1. 3A and 3B are a top view and a side view, respectively, showing the state when no current flows through the solenoid fJO in the same embodiment, and FIGS. 4A and 4B are in honor of the same embodiment. FIGS. 5 and 6m are perspective views showing other embodiments of the present invention. 10°20. 120 22゜24゜26゜30゜34゜80, 180 38, 138 42゜44゜50゜52, 52a 61. , magneto-optical disk medium, permanent magnet, spring, slide cam, link, objective lens, rotation center axis, lensoid, iron core, bin light, optical axis, magnetic moment, lever

Claims (1)

[Claims] 1. A bias magnetic field applying device for a magneto-optical recording device that records information on a magneto-optical recording medium using light irradiated onto the magneto-optical recording medium and a bias magnetic field applied to the magneto-optical recording medium. a permanent magnet having an N pole and an S pole arranged opposite to the main surface of the magneto-optical recording medium; a moving means for moving the permanent magnet substantially parallel to the main surface, the moving means moving the permanent magnet substantially parallel to the main surface, so that the magneto-optical recording medium is irradiated with the light. A bias magnetic field applying device for a magneto-optical recording device, characterized in that either one of the north pole and the south pole is selectively placed at a position. 2. In the bias magnetic field application device according to claim 1,
The moving means includes a slide cam coupled to the permanent magnet, and a drive means coupled to the slide cam and driving the slide cam to move the permanent magnet substantially parallel to the main surface. A bias magnetic field applying device characterized by: 3. In the bias magnetic field application device according to claim 1,
The moving means includes a link member coupled to the permanent magnet, and a solenoid coupled to the link member for driving the link member to move the permanent magnet substantially parallel to the main surface. A bias magnetic field applying device characterized by: 4. In the bias magnetic field applying device according to claim 1,
The bias magnetic field applying device is characterized in that the moving means includes a manual lever that is connected to the permanent magnet and manually moves the permanent magnet substantially parallel to the main surface. 5. A bias magnetic field applying device according to claim 1, further comprising a lens disposed on the other main surface side of the magneto-optical recording medium and converging the light on the other main surface. magneto-optical recording device.