JPH0422403Y2 - - Google Patents

Description

[Detailed explanation of the idea] Industrial applications The present invention relates to a magneto-optical recording device.

BACKGROUND ART AND PROBLEMS Recording on a magneto-optical recording medium having a perpendicularly magnetized film, such as a magneto-optical disk, is performed by irradiating the perpendicularly magnetized film with a laser beam whose intensity is modulated according to the information signal to be recorded. That is, as shown in FIG. 1, before recording, the perpendicular magnetization film 1 formed on a substrate (not shown) of glass, acrylic, etc.
The magnetization is perpendicular to the film surface, that is, one direction in the film thickness direction. And this magnetized film 1
When the laser beam LB is irradiated as shown in FIG. 2, the magnetization direction of the portion of the magnetized film 1 that is hit by the laser beam LB spot is reversed, and a cylindrical magnetic domain, that is, a magnetic bubble is formed. Information is recorded. In this case, in order to ensure the formation of magnetic bubbles whose magnetization direction is reversed, a recording bias magnetic field is usually applied in the opposite direction to the magnetization direction in the unrecorded state.
H _W is applied to the magnetized film 1 .

On the other hand, when erasing or rewriting information on the magnetized film 1 on which the magnetic bubbles 2 are formed in this manner, it is necessary to erase the magnetic bubbles 2 as explained in FIG. Therefore, as shown in FIG. 3, an erasing magnetic field H _E in the same direction as the magnetization direction in the unrecorded state is applied to the magnetized film 1, and the laser beam LB is irradiated to reverse the magnetization direction. The magnetization direction of the magnetic bubble 2 is returned to the forward direction to erase it.

In this way, when recording and erasing information,
External magnetic fields H _W and H _E whose directions of magnetic fields are opposite to each other
must be applied to a magneto-optical recording medium, such as a magneto-optical disk. For example, the recording bias magnetic field H _W is
For example, the erasing magnetic field H _E is about 300Oe to 500Oe.
1000Oe or more is desired.

Therefore, the present applicant has solved the above-mentioned problems by using permanent magnets, and has developed a magneto-optical recording device that uses a simple mechanism to reliably apply a stable recording magnetic field and erase magnetic field to a magneto-optical recording medium. The device has already been proposed.

First, the previously proposed magneto-optical recording device (hereinafter referred to as the "proposed device") will be described with reference to FIGS. 4 to 6.

FIG. 4 shows the configuration of the previously proposed device. In FIG. 4, reference numeral 3 denotes a magneto-optical recording medium, for example a magneto-optical disk, in which a perpendicular magnetization film 1 is formed on a non-magnetic substrate 4 made of glass, acrylic or the like. It is formed by depositing. This disk 3 is rotated around its central axis 0-0' by a rotational drive means (not shown). An optical head 5 performs optical recording and erasing on the magnetized film 1, and in some cases also performs reproduction. This optical head 5 is
The disk 3 is moved in the direction of arrow a, that is, in the radial direction of the disk 3, by a linear drive means (not shown).

Furthermore, a magnet device 6 including a permanent magnet is provided opposite the optical head 5 with the disk 3 in between. This magnet device 6 has a recording magnet section 6W that applies a recording bias magnetic field H _W to the magnetized film 1, and an erasing magnet section 6E that provides an erasing magnetic field H _E to the magnetized film 1.

Further, this magnet device 6 is configured to be able to rotate around a rotation axis 7 along the surface direction of the disk 3,
At least two rotational positions are performed: one in which the recording magnet section 6W faces the disk 3 as shown in FIG. 5, and the other in which the erasing magnet section 6E faces the disc 3 as shown in FIG. It is configured such that it can assume a rotating position (first and second rotational positions).

Further, both magnet parts 6W and 6E apply uniform magnetic fields H _W and H _E to the laser beam irradiation part, respectively, over the entire scanning width of the laser beam by the optical head 5 along the radial direction of the disk 3. It is made to extend along the radial direction of the disk 3 so that it can do so. These magnet parts 6W and 6E are arranged at an angular interval of 180° with respect to the rotating shaft 7, and the magnetized films 1 and 6E are arranged so that the respective end faces facing the disk 3 have different polarities. N, S in the thickness direction
It is magnetized. In addition, each of these magnet parts 6W
and 6E can be configured as one, or
They can also be configured separately. The polarity of these magnet parts 6W and 6E is such that the magnetic field is in the opposite direction for the magnet part 6W and in the opposite direction for the magnet part 6E, depending on the magnetization direction of the magnetized film 1 of the disk 3 explained in FIG. The direction is selected.

The magnet device 6 is provided with a stopper 8 as shown in FIGS. 5 and 6, and this stopper 8 is in the above-mentioned first and second rotational positions when the fixed part 9W,
9E, so that the magnet parts 6W and 6E face the magnetized film 1 at each rotational position.

Further, the magnet parts 6W and 6E are eccentrically arranged with different distances γ _w and γ _E from the rotation axis 7, and the magnet parts 6W and 6E are arranged eccentrically with different distances γ w and γ E from the rotation axis 7, and the magnet parts 6W and 6E are arranged eccentrically with different distances γ w and γ E from the rotation axis 7. The distances d _w and d _E between the magnet portion 6W and the erasing magnet portion 6E from the magnetized film 1 are respectively
The strengths of the magnetic fields applied to the magnetized film 1 are different so that d _w > d _E (for example, 4 to 5 mm and 2 to 3 mm, respectively), and the magnetic field during erasing is larger than the magnetic field during recording. It is done like this.

The magnet device 6 is rotatably connected to a rotary drive section such as a motor that is switched in conjunction with a recording, erasing, and even reproducing mode switching operation section of the magneto-optical recording device, so that the magnet device 6 can switch between recording and reproducing modes. The rotating shaft 7 is automatically rotated in response to the switching of the erase mode, and the rotating shaft 7 is switched to the first and second rotating positions, respectively, in a short time of, for example, about 20 mS.

In recording and playback (erase confirmation) mode,
The recording magnet section 6W is brought to the side facing the disk 3, a bias magnetic field _HW in the opposite direction to the magnetization direction is applied to the magnetized film 1, and magnetic bubbles are formed by heating by laser beam irradiation. , that is, the signal is recorded.

In the erasing mode, the erasing magnet section 6E is brought to the side facing the disk 3, and the magnetized film 1
An erasing magnetic field H _E is applied in the forward direction to the magnetization direction (in the opposite direction to the magnetic bubble), and the magnetic bubble is erased by heating by laser beam irradiation.

However, in such previously proposed devices, in order to apply a bias magnetic field to the magneto-optical recording medium, a magnet device including a strong permanent magnet must be provided and this must be instantaneously rotated during recording and erasing. The disadvantages are that the device becomes large, its structure becomes complicated, and the price increases.

In addition, as a bias magnetic field generating means, one using an electromagnet has been proposed, but this also increases the size of the device, complicates the configuration, increases the price, generates heat, and reduces power consumption. The disadvantage is that it leads to increase in size.

Purpose of the invention In view of these points, the present invention aims to propose a magneto-optical recording device that can be downsized, has a simple configuration, and is inexpensive.

Summary of the invention A magneto-optical recording device according to the invention includes an optical head having an electromagnetic actuator for driving an objective lens that drives an objective lens at least in the direction of the optical axis of the objective lens, and an optical head with a magneto-optical recording medium in between. The optical head irradiates the magneto-optical recording medium with light, and the bias magnetic field generated by the bias magnetic field generating means and leakage magnetic flux from the electromagnetically driven actuator are provided. Accordingly, information signals are recorded and erased on the magneto-optical recording medium.

According to the present invention, it is possible to obtain a magneto-optical recording device that can be miniaturized, has a simple configuration, and is inexpensive.

Then, the leakage magnetic flux from the permanent magnet of the electromagnetic actuator that drives the objective lens of the optical head is used in conjunction with the bias magnetic field from the bias magnetic field generating means to record an information signal on the magneto-optical recording medium or to record the recorded information signal. Since the erasing operation is performed, a sufficient bias magnetic field can be applied to the magneto-optical recording medium, and information signals will not be left unerased, and stable information signals can be recorded. can.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. In the drawings from FIG. 7 onwards, parts corresponding to those in FIGS. Some explanations will be omitted.

First, the structure of an example of an optical head will be explained with reference to FIG. Optical head 5 is disk 3
It is located on the magnetized film 1 side. Reference numeral 11 denotes a housing, in which an optical system 14 described below and an electromagnetic actuator 12 for driving an objective lens 13 of the optical system 14 are built-in.

First, the optical system 14 will be explained. An objective lens 13 is attached to the cylindrical body 15. This cylindrical body 15 is connected to the housing 1 through a plurality of springs 16.
It is attached to the opening 11a of 1. Reference numeral 17 denotes a semiconductor laser light source (laser diode), and the laser light from this enters the objective lens 15 through a collimator lens 18 - a polarizing beam splitter 19 - a quarter-wave plate 20, and the output focused light is used to magnetize the disk 3. The membrane 1 is irradiated. Semiconductor laser light source 1
The drive current 7 is modulated by the recording signal during recording, and is kept constant during erasing. The reflected light from the magnetized film 1 enters the polarizing beam splitter 19 through the objective lens 13-1/4 wavelength plate 20, the optical path is deflected by 90 degrees by the reflecting surface, and the output light is transmitted to the imaging lens 21- The light enters a four-split photodetector 23 through a semi-cylindrical lens 22 . A focus error signal is obtained from this photodetector 23.

Next, the electromagnetically driven actuator 12 will be explained. A cylindrical bobbin 2 integrated with the cylindrical body 15
4 is provided, and a coil 25 is wound around this.
26 is an annular permanent magnet, which is magnetized in N and S directions in the thickness direction. An annular yoke 27 and a flanged cylindrical yoke 28 are provided to sandwich the magnet 26 above and below, and a bobbin 24 on which a coil 25 is wound is placed in a cylindrical gap formed between these yokes 27 and 28. made to be located. Then, the focus error signal obtained from the photodetector 23 is supplied to a servo circuit (not shown), and its output is supplied to the coil 25, so that the objective lens 13 is moved along the optical axis according to the focus error signal. Perform focus servo by moving back and forth in the direction.

Note that an electromagnetically driven actuator (including a permanent magnet) for tracking is provided separately, and a tracking error signal from the photodetector 23 is supplied to this actuator via a servo circuit to perform tracking servo. You can also do that. Incidentally, the optical head 5 can also be used as a reproducing head.

Therefore, most of the magnetic flux from the permanent magnet 26 passes through the yokes 27 and 28 and the gap between them;
A part of the magnetic flux from the permanent magnet 26 passes approximately perpendicularly to the magnetized film 1 of the disk 3, and this constitutes part (or all) of the bias magnetic field during recording and erasing.

In the embodiment shown in FIG. 8, a magnet device 6 similar to that shown in FIG. Keep the distances approximately equal. When erasing, the erasing magnet section 6
A bias magnetic field obtained by adding the magnetic flux from E and the magnetic flux from the optical head (recording/erasing optical head) 5 on the side of the magnetized film 1 is applied to the magnetized film 1. Furthermore, during recording, the bias magnetic field obtained by subtracting the magnetic flux from the optical head 5 from the magnetic flux from the recording magnet section 6W (the magnetic flux in the opposite direction to the magnetic flux from the erasing magnet section 6E) A magnetic field opposite to and weaker than the bias magnetic field is applied to the magnetized film 1.

In the embodiment shown in FIG. 9, separate optical heads 5W and 5E are provided for recording and erasing, and the permanent magnets 26 of the electromagnetically driven actuator 12 are magnetized in opposite directions in the thickness direction. . and,
The magnetic fluxes from the recording and erasing magnet sections 6W and 6E and the magnetic fluxes from the recording and erasing optical heads 5W and 5E are added to each other to create biases for recording and erasing in opposite directions. A magnetic field is obtained and applied to the magnetized film 1. In this case, if the magnetic fluxes from the optical heads 5W, 5E are approximately the same, and the magnetomotive forces of both magnet parts 6W, 6E are the same, then the erasing magnet part 6E is more sensitive to the disk 3 than the recording magnet part 6W.
Keep it close to. Note that 30 is a spindle for rotating the disk 3, and is rotationally driven by a motor (not shown).

In the case of FIG. 9, if a sufficient bias magnetic field can be obtained only from the optical heads 5W and 5E, the magnet sections 6W and 6E can be omitted.

In the embodiment of FIG. 10, the magnetized film 1 of the disk 3
and optical head (optical head for recording/erasing) 5
In this case, an electromagnetic coil (electromagnet) is provided between the two, a direct current is applied to it from a direct current power source 33, and a changeover switch 34 is used to switch the direction of the current flow between recording and erasing. During erasing, a bias magnetic field obtained by adding the magnetic flux from the erasing electromagnetic coil 32 and the magnetic flux from the optical head 5 is applied to the magnetized film 1. Further, during recording, a bias magnetic field obtained by subtracting the magnetic flux from the optical head 5 from the magnetic flux from the electromagnetic coil 32 is applied to the magnetized film 1.

In FIG. 10, a core can be inserted into the electromagnetic coil 32, but in that case, a cylindrical core is used to ensure an optical path between the optical head 5 and the magnetized film 1. . Further, the electromagnetic coil 32 may be provided on the substrate 4 side of the disk 3.

In the embodiments shown in FIGS. 8 and 9, the magnet device 6 can be made compact, and in the latter case in particular, there is no need to rotate the magnet device 6. In the embodiment shown in FIG. 10, the current flowing through the electromagnetic coil 32 can be reduced, and the amount of heat generated can be reduced.

According to the present invention, it is possible to obtain a magneto-optical recording device that can be miniaturized, has a simple configuration, and is inexpensive.

Effects of the Invention According to the present invention, it is possible to obtain a magneto-optical recording device that can be miniaturized, has a simple configuration, and is inexpensive.

Then, the leakage magnetic flux from the permanent magnet of the electromagnetic actuator that drives the objective lens of the optical head is used in conjunction with the bias magnetic field from the bias magnetic field generating means to record an information signal on the magneto-optical recording medium or to record the recorded information signal. Since the erasing operation is performed, a sufficient bias magnetic field can be applied to the magneto-optical recording medium, and information signals will not be left unerased, and stable information signals can be generated.

[Brief explanation of the drawing]

Figures 1 to 3 are pattern diagrams showing the magnetization states of the magnetized film in the unrecorded, recorded, and erased states.
6 to 6 are cross-sectional views of the previously proposed magneto-optical recording device and its operating state, and FIG. 7 is an example of an optical head used in an embodiment of the magneto-optical recording device according to the present invention. The sectional views and FIGS. 8 to 10 are layout diagrams showing each embodiment of the present invention. 1 is a magnetized film, 3 is a magneto-optical recording medium (disk),
4 is a non-magnetic substrate; 5, 5W, and 5E are optical heads; 6 is a magnet device; 6W, 6E are recording and erasing magnet sections thereof; 12 is an electromagnetic actuator;
13 is an objective lens, 14 is an optical system, and 26 is a permanent magnet of the actuator 12.

Claims (1)

[Claims for Utility Model Registration] An optical head having an electromagnetic actuator for driving an objective lens that drives the objective lens at least in the direction of the optical axis of the objective lens, and facing the optical head with a magneto-optical recording medium in between. a bias magnetic field generating means disposed such that the optical head irradiates the magneto-optical recording medium with light, and a bias magnetic field from the bias magnetic field generating means and leakage magnetic flux from the electromagnetically driven actuator. A magneto-optical recording device that records and erases information signals on a magneto-optical recording medium.