JPS6366747A - Magneto-optical recorder - Google Patents

Abstract

PURPOSE:To reduce the output load of an auxiliary magnetic field generation means and to efficiently switch an auxiliary magnetic field intensity by making the permanent magnet of an objective lens driving means generate the magnetic field in the same direction to the magnetic field impressed from the auxiliary magnetic field generation means at the time of deleting information in the light beam projected part of a magneto-optical recording medium. CONSTITUTION:A magneto-optical recorder has a driving means which includes the objective lens 5 focusing the light beam on the magneto-optical recording medium 1, the permanent magnet 9 and a coil 11 and drives the objective lens 5, at least, in one direction, and the magnet field generation means 6 which impresses the auxiliary magnetic field on the medium in the respective directions which are different at the time of recording information and at the time of deleting information and the permanent magnet 9 of the drive means is allowed to generate the magnetic field which has the same direction as the magnetic field impressed from the magnetic field generation means 6 at the time of deleting information in the light beam projected part of the medium 1. Thus the output load of the auxiliary magnetic field generation means 6 can be reduced and auxiliary magnetic field intensity can be efficiently switched at the time of recording information and at the time of deleting information.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to recording information on a magneto-optical recording medium by irradiating the medium with a light beam while applying an auxiliary magnetic field, and recording information on the medium. The present invention relates to a magneto-optical recording device for erasing data.

[Prior art]

2. Description of the Related Art In recent years, research has been actively conducted on optical information recording devices that record information on a recording medium using a light beam as large-capacity memories used in information devices. In particular, a magneto-optical recording device using a magneto-optical recording medium as a recording medium is attracting attention as a device capable of erasing and rewriting information. The configuration and operation of such a conventional magneto-optical recording device will be explained below.

FIG. 4(A) to FIG. 4(D) are schematic diagrams showing an example of the configuration of a conventional magneto-optical recording device. In the figure, 1 indicates a magneto-optical recording medium, which is constructed by laminating a recording layer 3 and a protective layer 2 made of a magnetic film having an axis of easy magnetization in a direction perpendicular to the film surface on a transparent substrate 4. . Further, 5 is an objective lens, and 6 is an electromagnet consisting of a coil 7 and a yoke 8. As shown in FIG. 4(A), the recording layer 3 has its magnetization direction aligned in one direction in advance by a strong magnet or the like.

When recording information, as shown in FIG. 4(B), a light beam 16 emitted from a light source (not shown) such as a semiconductor laser and modulated according to the information is directed onto the recording layer 3 by the objective lens 5 with a diameter of about 1 μm. The light is focused into a minute spot, and its energy heats the recording layer 3 to nearly one Curie temperature, almost demagnetizing the irradiated area. And electromagnet 6
When an auxiliary magnetic field is applied to this irradiated area in the opposite direction to the direction in which it was previously magnetized, the direction of magnetization is reversed by the action of this auxiliary magnetic field and the leakage magnetic field from the surrounding recording layer.
A signal pit array is formed on the medium as a magnetization pattern.

Next, when reproducing the information recorded in this way, as shown in FIG. 4(C), an unmodulated light beam weaker than that during recording is irradiated without applying an auxiliary magnetic field. Then, the aforementioned signal pit string is optically read using the magnetic Kerr effect or Faraday effect, in which the polarization direction of the reflected or transmitted beam changes depending on the difference in the magnetization direction.

In order to erase the recorded information, as shown in FIG. 4(D), a strong unmodulated light beam is irradiated to the medium while applying a direct current bias magnetic field in the opposite direction to that during recording using the electromagnet 6. This is done by aligning the aforementioned signal pit rows in the magnetization direction before recording.

Incidentally, the strength of the auxiliary magnetic field required during recording and erasing varies depending on the material of the medium and the laser power, but is generally stronger during erasing than during recording. The reason for this is that during recording, the leakage magnetic field from the surrounding recording layer helps to reverse the magnetization of the light beam irradiated area, as explained with reference to FIG. 4(B). Furthermore, applying a magnetic field stronger than necessary during recording is undesirable because it leads to instability of the boundaries of signal pits. Therefore, in a magneto-optical recording device, it is necessary to switch the polarity and intensity of the auxiliary 6H field between recording and reproduction.

However, in the conventional magneto-optical recording device as shown in Fig. 4, when reducing the strength of the magnetic field, a portion of the current flowing through the electric coil is converted into thermal energy using a resistor, etc. This caused the internal temperature to rise and wasted a lot of energy. Furthermore, if a permanent magnet is used instead of an electromagnet, the problem of temperature rise as described above does not occur, but since the strength of the magnetic field generated by the magnet is constant, it is difficult to control the strength of the auxiliary magnetic field. .

On the other hand, in order to accurately focus a light beam on a predetermined position on a magneto-optical recording medium, a normal magneto-optical recording device moves the objective lens in the direction of the optical axis (focusing direction) and in the direction perpendicular to the optical axis (tracking direction). ).

Most of such drive means include a permanent magnet and a coil, and are configured to drive the objective lens by electromagnetic force. Although this permanent magnet generates a fairly strong magnetic field, it has conventionally been used for no purpose other than driving an objective lens.

(Summary of the Invention) An object of the present invention is to provide a magneto-optical recording device that can reduce the output load of an auxiliary magnetic field generating means and can efficiently switch the auxiliary magnetic field strength between recording and erasing information. It's about doing.

The above-mentioned objects of the present invention include: an objective lens that focuses a light beam on a magneto-optical recording medium; a driving means that includes a permanent magnet and a coil and drives the objective lens in at least one direction; In a magneto-optical recording device, the permanent magnet of the driving means is applied to a portion of the medium irradiated with a light beam, and the magnetic field generating means applies an auxiliary magnetic field in a different direction when erasing information. This is achieved by configuring the device to generate a magnetic field in the same direction as the magnetic field applied from the source.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1(A) and FIG. 1(B) are schematic configuration diagrams showing one embodiment of a magneto-optical recording device based on the present invention, and also show the state of magnetic lines of force during erasing and recording, respectively. be. In the figure, reference numeral 1 denotes a magneto-optical recording medium, in which a recording layer 3 and a protective layer 2 are formed of a magnetic film that has an axis of easy magnetization perpendicular to the film surface and is magnetized in one direction in advance on a transparent substrate 4. It consists of Reference numeral 5 denotes an objective lens that focuses a light beam 16 emitted from a light source (not shown) such as a semiconductor laser onto the recording layer 3. This objective lens 5 has a bobbin 10
The actuator is fixed to the bobbin 10, a coil 11 wound around the bobbin 10, and an actuator magnet 9 that generates a magnetic field that crosses the coil 11. ing.

A focus error signal detected by a well-known method is input to the coil 11, and the objective lens 5 is adjusted according to this signal.
So-called automatic focus control (hereinafter referred to as AF) is performed, in which the light beam 16 is always accurately focused on the recording layer 3 by driving the light beam 16 in the optical axis direction.

The actuator magnet 9 is composed of a permanent magnet and a yoke, and has two magnets on the side facing the magneto-optical recording medium 1.
It has a U-shaped cross section with two protrusions.

Furthermore, among these protruding parts, the protruding part on the side closer to the objective lens 5 becomes the S pole, and a magnetic field that helps erase information is applied to the irradiated part of the recording layer 3 with the light beam 16, that is, the recording layer 3 is magnetized in advance. The magnetic field is configured to apply a magnetic field in the same direction as the magnetic field.

Further, on the opposite side of the magneto-optical recording medium 1 from the objective lens 5, an electromagnet 6 consisting of a coil 7 and a yoke 8 is provided. The electromagnet 6 applies an auxiliary magnetic field in different directions to the recording layer 3 when recording and erasing information by switching the current flowing through the coil 7.

When recording information, the electromagnet 6 generates a magnetic field in the opposite direction to the magnetization direction of the recording layer 3, as shown in FIG. 1(B).

That is, a current is passed through the coil 7 so that the center portion of the yoke 8 facing the light beam irradiation portion becomes the south pole. In this case, the magnetic field generated by the electromagnet 6 needs to be stronger than the magnetic field generated by the actuator magnet 9 in the light beam irradiated portion of the recording layer 3. By doing this, an auxiliary magnetic field with a strength equal to the magnetic field generated by the electromagnet 6 minus the magnetic field generated by the actuator magnet 9 is applied to the recording layer 3 in a direction that helps recording (if the recording layer 3 is not magnetized in advance). applied in the opposite direction). In this state, a light beam 16 modulated according to recorded information is focused on the recording layer 3 by the objective lens 5, and the magnetization direction of the irradiated portion is reversed to form a signal bit string.

Next, when erasing information, the electromagnet 6 generates a magnetic field in the same direction as the direction in which the recording layer 3 was previously magnetized, as shown in FIG. 1(A). That is, the direction of the current flowing through the coil 7 is reversed so that the yoke 8 faces the light beam irradiation part.
so that the center part becomes the north pole. Then, the magnetic field generated from the electromagnet 6 and the El field generated from the actuator magnet 9 are added, and an auxiliary magnetic field stronger than that during recording is applied to the recording layer 3 in a direction that aids erasing (if the recording layer 3 is not magnetized in advance). applied in the same direction as the original direction). in this case,
Since the electromagnet 6 and the actuator magnet 9 are located opposite each other with the magneto-optical recording medium 1 in between, the lines of magnetic force have a large component in the direction perpendicular to the film surface of the recording layer 3, and the auxiliary magnetic field is efficiently applied to the light beam irradiated area. I can concentrate on things. In this state,
An unmodulated light beam 16 is applied to the recording layer 3 by an objective lens 5.
The magnetization direction of the already recorded signal pit row is
Information is erased by adjusting the state to the state before recording.

As a specific example, the recording layer 3 is made of GdTbF with a thickness of 1000 nm.
A magneto-optical recording device was constructed using a four-element eCo amorphous magnetic thin film with a recording/erasing linear velocity of Ion/sec, a signal bit diameter of 1 μm, a recording laser power of 5 mW, and an erasing laser power of 6 mW. The strength of the necessary auxiliary magnetic field is determined by
+2000e (Oersted) when recording, -5 when erasing
00e (however, the sign indicates the direction of the magnetic field).

Here, if a 3500G (Gauss) magnet is used on the surface close to the recording layer as the actuator magnet, and the surface is arranged so that the distance from the recording layer is 5 mm, the recording layer 3 will have an approximately -1500G A magnetic field was obtained. During recording, +35 in the recording layer from the electromagnet 6
Generate a magnetic field with a strength of 00e, subtract +2000e
A recording beam was irradiated while applying a magnetic field to record information. Furthermore, during erasing, a current in the opposite direction was passed through the coil 7 to generate a magnetic field with an intensity of -35008 in the recording layer. Then, a magnetic field of 15,000 e was applied to the recording layer in combination with the magnetic field from the actuator magnet 9, and the recorded information could be erased without leaving any unerased information by irradiation with the erasing beam.

In this embodiment, since the leakage magnetic field from the actuator magnet to the medium is used as part of the auxiliary magnetic field, the electromagnet serving as the auxiliary magnetic field generating means can have a small output, and the electric power consumption can be reduced. Less is needed. In addition, it is only necessary to change the direction of the current flowing through the coil of this electromagnet between recording and erasing, and there is no need to throttle the output with a resistor, etc., so the amount of heat generated inside the device is small, and the amount of heat generated inside the device is small. It is possible to suppress the rise in temperature.

FIG. 2 is a schematic configuration diagram showing another embodiment of the magneto-optical recording device based on the present invention. In the figure, the same members as in FIG. 1 are given the same reference numerals, and detailed explanations will be omitted. This example protects the actuator from dust, etc.
A cover 13 made of a ferromagnetic material (for example, an iron plate) is added. In this embodiment, the lines of magnetic force emitted from the electromagnet 6 can easily pass through the cover 13 as shown in the figure.
The component of the auxiliary magnetic field in the direction perpendicular to the film surface of the recording layer 3 increases, and the magnetic field strength in the recording layer 3 increases by about 50 to 700 e.

FIG. 3 is a schematic diagram showing still another embodiment of the magneto-optical recording device according to the present invention. In the figure, the same members as in FIG. 2 are given the same reference numerals, and detailed explanations will be omitted. In this embodiment, the electromagnet 6 of the device shown in the second figure is replaced with a permanent magnet 14. Here, the permanent magnet 14 generates a stronger magnetic field than the permanent magnet 9 at the position of the recording layer.

When erasing information, as shown in the figure, the N pole of the permanent magnet 14 is directed toward the recording layer 3 side, a magnetic field is generated in the same direction as the permanent magnet 9, and a strong auxiliary magnetic field is applied to the recording layer 3. Also,
During recording, the permanent magnet 14 is rotated about the shaft 15 by a motor or the like (not shown) so that the south pole faces the recording medium 1.

Then, an auxiliary magnetic field having an intensity equal to the magnetic field produced by the permanent magnet 14 minus the magnetic field produced by the permanent magnet 9 is applied to the recording layer 3 in a direction opposite to that during erasing.

In this embodiment, since no electromagnet is used, the power consumption of the device can be reduced.

Furthermore, with a simple mechanism that only rotates a magnet, the strength of the auxiliary magnetic field during recording and erasing can be made different. Furthermore, since the leakage magnetic field from the actuator magnet is used as part of the auxiliary magnetic field, the permanent magnet of the magnetic field generating means can be made smaller and the time required to switch the magnetic poles by rotation can be shortened.

The present invention can be applied in various ways in addition to the embodiments described above. For example, although an example of an actuator used for AF is shown in the embodiment, it is also possible to move the objective lens in a direction perpendicular to the optical axis and use the magnet of the actuator that performs tracking control as the source of the auxiliary magnetic field. Further, the present invention can also be applied to a magnet used as a means for driving the entire optical head including the light source and the like together with the objective lens. Furthermore, the shapes of the electromagnets and permanent magnets are not limited to those shown in the embodiments, and can be modified in various ways.

[Effect of the Invention] As explained above, the present invention provides a conventional optical 6U optical recording device in which the permanent magnet of the objective lens driving means applies an auxiliary magnetic field to the light beam irradiated portion of the magneto-optical recording medium when erasing information. Since it is configured to generate a magnetic field in the same direction as the magnetic field applied from the generating means, the output load on the auxiliary magnetic field generating means is reduced, and the auxiliary magnetic field strength can be efficiently adjusted when recording and erasing information. It is now possible to switch.

[Brief explanation of drawings]

FIGS. 1(A) and 1(B) are schematic configuration diagrams showing one embodiment of the present invention, and FIGS. 2 and 3 are schematic configuration diagrams showing other embodiments of the present invention, respectively. Figure 4 (A) to Figure 4 (
D) is a schematic configuration diagram illustrating the operation of each conventional magneto-optical recording device. t ------- L-1 magneto-optical recording medium 5 ---
---------One objective lens 6-----------Electromagnet 7.11----Coil

Claims (1)

[Claims] (1) an objective lens that focuses a light beam on a magneto-optical recording medium; a driving means that includes a permanent magnet and a coil and drives the objective lens in at least one direction; A magneto-optical recording device comprising magnetic field generating means for applying auxiliary magnetic fields in different directions, wherein the permanent magnet of the driving means receives a magnetic field from the magnetic field generating means when erasing information in a portion of the medium irradiated with a light beam. A magneto-optical recording device characterized in that it is configured to generate a magnetic field in the same direction as the magnetic field.