JP2749877B2 - Information recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording apparatus for recording information on a magnetic recording medium using the interaction between light and magnetism.

[Conventional technology]

Examples of such devices include a magneto-optical disk device. Magneto-optical disk devices have attracted attention because of their large storage capacity and the ability to erase and rewrite. In addition, studies are being made on overwriting (overwriting) to further increase the data transfer speed and studies to increase the storage capacity.

The overwriting method is a magnetic field modulation method in which an external magnetic field is modulated according to recording information while irradiating a constant laser power and applied to a medium, thereby inverting the magnetization of a recording layer to form a bit, and a constant magnetic field modulation method. Optical modulation that modulates the binary laser power corresponding to recording and erasing according to recording information while applying an external magnetic field, and irradiates the medium, thereby inverting the magnetization of the recording layer to form pits. There is a method.

However, in the above-described magnetic field modulation method, it is difficult to modulate a large magnetic field at a high speed and apply it to the medium because the distance between the magnetic head and the recording layer is large. Further, in principle, the pits formed have an arrowhead shape, which causes a problem of edge variation and unerased portions, and it has been difficult to record the pit length.

Even with the optical modulation method, there were problems of unerased data and a decrease in the C / N ratio, and it was also difficult to record the pit length. Also, control of the semiconductor laser is complicated because it requires three levels of power of recording, erasing, and reproducing.

Meanwhile, IBM Technical Disclosure Bulletin Vol.6, No.17 D
ecember 1973, P2365 ~ 2366, using a two-layer iron oxide-based disk with different coercive force, first record the track of the conventional pattern by the conventional magnetic transducer in the storage transmission layer of low coercive force, A method has been proposed in which a narrow portion thereof is recorded by a conventional thermomagneck transfer process using a laser light source for a main storage layer having a high coercive force. In this method, information is read out by transferring information from the main storage layer to the storage transmission layer and using a conventional magnetic transducer.

Also, in Japanese Patent Application Laid-Open No. 63-276731, a disc having a two-layer structure of a Co-Cr alloy thin film and a Tb-Fe thin film is described.
It has been proposed to record information with a magnetic head and transfer the information with an optical head, and to reproduce information with an optical head.

By using such a method, unerased portions are reduced, and pit length recording is facilitated.

[Problems to be solved by the invention]

On the other hand, in a general information recording apparatus, tracking control is performed. However, in the above-mentioned Japanese Patent Application Laid-Open No. 63-276731, it is described that the tracking control becomes unnecessary by increasing the width of the magnetic head.

However, if you increase the width of the magnetic head,
Not only does this hinder the miniaturization of the device, it also increases power consumption. Conversely, if the width of the magnetic head is reduced, there is a problem that the scanning position on the medium between the magnetic head and the optical head will be different when a large track error occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an information recording apparatus capable of solving the above-mentioned problems of the prior art and reliably recording information without increasing the size of a magnetic head.

[Means for solving the problem]

The object of the present invention is to provide a magnetic head for applying a magnetic field modulated according to information to a magnetic recording medium having a track, an optical head for irradiating a light beam focused on a track of the medium, the magnetic head, A coarse actuator for integrally moving the optical head in the cross-track direction, means for detecting a track error signal of the light beam using the light beam, and irradiation of the light beam mounted on the optical head in the cross-track direction A fine actuator for finely adjusting the position; and a means for extracting a low frequency component of the track error signal. The fine actuator is driven based on the track error signal, and the fine tracking control of the light beam is performed. Driving the coarse actuator based on a low-frequency component of a track error signal; Is achieved by performing the coarse tracking control described above.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the information recording apparatus of the present invention. In FIG. 1, 1 is a perpendicular magnetic head, 2
Denotes an optical head, 3 denotes a magneto-optical disk, 4 denotes a substrate, 5 denotes a protection and interference layer, 6 denotes a recording magnetic layer, 7 denotes a recording auxiliary magnetic layer, and 8 denotes a protective layer. FIG. 2 shows the coercive force characteristics of these magnetic layers with respect to temperature. Curve 9 is
The characteristics of the recording assisting magnetic layer 7 are shown. That is, the recording auxiliary magnetic layer 7 has a small coercive force H _C1 at room temperature and has a high Curie temperature T _C1 . On the other hand, a curve 10 shows the characteristics of the recording magnetic layer 6, in which the coercive force H _C2 at room temperature is larger than that of the recording auxiliary layer 7, and the Curie temperature T _{C2 is} lower.
It has. Further, T _comp of the curve 9 indicates the magnetic layer 7
Is the compensation point temperature.

The magneto-optical disk 3 has a track extending in the direction of arrow A in FIG. This track is constituted by a groove or a pre-pit for sampling servo formed on the substrate 4 in advance. And the magneto-optical disk 3
Is similarly moved in the direction of arrow A by means not shown.

The optical head 2 incorporates a semiconductor laser as a light source. This semiconductor laser is controlled by the laser drive circuit 11 so as to emit light beams having different intensities during recording and during reproduction. The light beam emitted from the semiconductor laser is condensed into a spot by the objective lens 28, and is irradiated on the magnetic layer of the disk 3 from the substrate 4 side. The spot diameter on the magnetic layer is about 0.5 to 1 μm.

The light beam reflected by the disk 3 again passes through the objective lens 28, and is photoelectrically converted by a photodetector (not shown) in the optical head 2. Then, the servo error detection circuit 12 obtains a focus error signal and a track error signal from the photoelectric signal. As a method of detecting these error signals, for example, a known method described in Japanese Patent Publication No. Sho 62-56578 can be used. The error signal is
The signal is input to an AF (auto-focusing) and AT (auto-tracking) servo circuit 22 of the optical head, and a control signal is created and sent to the optical head. In accordance with this control signal, the optical head 2 moves the objective lens 28 in the direction of the optical axis and in the direction perpendicular to the optical axis (direction B) by a lens actuator (not shown) to perform AF and AT.

On the other hand, the perpendicular magnetic head 1 is provided on the side opposite to the optical head 2 with respect to the disk 3, and scans a position on the track on which the light spot scanning is performed, slightly ahead of the light spot. The distance between these heads must be at least as long as the range affected by heat by the light spot and the range affected by the magnetic field by the perpendicular magnetic head do not overlap.

In this embodiment, the magnetic head 1 and the optical head 2 are integrally held by the same support 21. And
The support 21 can be moved by a linear motor (not shown) in a direction crossing the track (direction B), and constitutes a coarse tracking mechanism.

As described above, the focus error signal and the track error signal detected by the servo error detection circuit 12
-The signal is input to the precision AT servo circuit 22, and the objective lens 28 is moved by the lens actuator in the optical axis direction and the direction perpendicular to the optical axis (B
Direction), AF and AT are performed. On the other hand, the track error signal output from the servo error detection circuit 12 is also input to the coarse AT servo circuit 23, and drives the aforementioned linear motor in accordance with this signal,
Is moved to perform coarse tracking.

As described above, in this embodiment, rough tracking control for a desired track is performed by integrally moving the magnetic head and the optical head according to the track error signal. At the same time, the lens actuator mounted on the optical head is driven according to the track error signal, and precise tracking control is performed so that the light spot accurately follows the desired track.

Further, in the present embodiment, a low-pass filter may be provided between the servo error detection circuit 12 and the coarse AT servo circuit, and the support portion 21 may be driven using only the low frequency component of the track error signal.

Information is recorded by sending the information signal 9 to the magnetic head 1 after an error correction code is added by the modulation circuit 10 and applying a magnetic field modulated according to this signal to the disk 3 from the magnetic head 1. Done. The recording process will be described in detail with reference to FIGS.

3A and 4A are schematic sectional views of a magneto-optical disk, and FIG. 3B is a plan view.

In FIG. 3 (a), first, the magnetic field is modulated according to the recorded information using the perpendicular magnetic head 1. At this time, the maximum magnitude of the magnetic field on the magnetic layer is the maximum value of the recording auxiliary magnetic layer (hereinafter, referred to as an auxiliary layer) 7 and the recording magnetic layer (hereinafter, referred to as a recording layer) 6 at room temperature. Each coercive force H _C1
If, when to take a suitable value between H _C2, in accordance with the modulation of the magnetic field, up to the auxiliary layer 7, due to the downward difference, pits are formed as a vertical magnetic domain sequence. However, in the recording layer 6, since the intensity of the applied magnetic field is equal to or less than the coercive force, the recording layer 6 is not affected and the previous state is maintained.

The length of the pit by the perpendicular magnetic head in the direction parallel to the track can be on the order of submicron,
The linear density can be higher than that of a conventional pit recorded by an optical head. The width in the direction perpendicular to the track is set to several to several tens of tracks, so that the tracking accuracy required for the perpendicular magnetic head can be eased. This makes it possible to perform tracking of the magnetic head using only the low-frequency component of the track error signal obtained by the optical head as described above.

In FIG. 3B, reference numerals 19a to 19e denote tracks, respectively, and the width thereof is 1 to 2 μm. The pits recorded by the perpendicular magnetic head have a magnetic domain row indicated by a solid line. Now, assuming that the track to be recorded is 19c, the magnetic domain sequence extends over several to several tens of tracks around 19c,
Overwritten on previous data.

After recording the magnetic domain row with the perpendicular magnetic head 1 in this manner,
As shown in FIG. 4, the spot 20 of the optical head 2 scans on a desired track 19c. The rising temperature of the magnetic layer at this time is determined by the respective Curie temperatures of the auxiliary layer 7 and the recording layer 6.
The laser drive circuit 11 controls the light intensity according to the number of rotations of the disk so that the temperature becomes appropriate between T _C1 and T _C2 . Then, in the desired track 19c of the recording layer 6 heated to the Curie temperature T _C2 or more by the light spot 20, magnetization disappears, and thus the previously recorded information is erased.
Then, when the light spot passes and the heat falls below the Curie temperature T _C2 , magnetization corresponding to the magnetization of the auxiliary layer 7 appears. That is, in the hatched area of the recording layer 6 in FIG.
The magnetic domain sequence corresponding to the magnetic domain sequence of the auxiliary layer 7 is transferred and information is written.

Here, as described above, the auxiliary layer 7 has a compensation point at room temperature or higher, and has a large coercive force at the temperature during transfer, so that stable transfer is performed.

The final pit shape recorded in this way is approximately square. The length of the pit in the direction parallel to the track has a submicron size determined by the perpendicular magnetic head, and the width in the direction perpendicular to the track is about 0.5 to 1 μm determined by the light spot of the optical head.

On the other hand, information is reproduced by scanning a desired track with the light spot of the optical head. On this occasion,
The intensity of the light spot is controlled by the laser drive circuit 11 so that the temperature of the magnetic layer does not become higher than the Curie point temperature T _C2 of the second layer. The reflected light of this light spot is modulated into a polarization state by a magneto-optical effect such as a Kerr effect, a Faraday effect, and a circular dichroism effect, and is converted into a change in intensity by an analyzing means. Received. The output of this photodetector is sent to the information reproducing circuit 15 shown in FIG. 1, and a reproduced signal 16 is output.

Also shown in Figure 2, the temperature of the intersection point of curves 17 and 18 T _W0
Then, the temperature of the magnetic layer at the time of recording is set between T _W0 and T _C1 ,
The temperature of the magnetic layer during reproduction may be set to _TW0 or lower.

The power of the semiconductor laser for recording / reproducing in this method may be binary.

The recording on the auxiliary layer by the magnetic head may be overwritten as described above, or the same magnetic head or the second magnetic head may be used after transferring by a light spot in order to take the effect of unerasing. The data may be erased by the head.

5 and 6 show other examples of the configuration of the magneto-optical disk used in the present invention, respectively, and FIG. 7 shows the characteristics of the coercive force of each layer with respect to the temperature in these disks.

FIG. 5 shows an arrangement in which an exchange force adjusting layer 24 is arranged between the auxiliary layer 7 and the main recording layer 6 of the configuration of the magneto-optical disk shown in FIG. The coercivity H _C3 and the Curie temperature T _C3 of this layer at room temperature are
The characteristic is as shown by a curve 26 in FIG. This layer
At room temperature, it is magnetized in the in-plane direction, and when the temperature rises by the power of the light spot at the time of recording, the auxiliary layer 7 has the same perpendicular magnetization as the direction of magnetization or disappears.
Then, it functions to weaken the exchange coupling force between the auxiliary layer 7 and the main recording layer 6 at room temperature. Therefore, the strength of the magnetic field during recording can be further reduced to the _HC1 side.

In FIG. 6, a reproducing layer 25 is further provided between the recording layer 6 and the protection / interference layer 5 having the structure shown in FIG. As described above, the Kerr rotation angle due to the Kerr effect during reproduction is larger in the magnetic layer having a higher Curie temperature. Therefore, the coercive force H _C4 and the Curie temperature T _C4 of the reproducing layer 25 have characteristics as shown by a curve 27 in FIG. This reproduction layer 25
At a temperature increased by the power of the light spot during reproduction, a perpendicular magnetization corresponding to the magnetization of the pits of the recording layer 6 appears due to the exchange coupling force with the recording layer 6. Since the reflection of light at the time of reproduction is almost influenced by the reproduction layer 25, the Kerr rotation angle is larger than that at the time of reflection at the recording layer 6.

Up to here, as shown in FIG. 2, the characteristics of the auxiliary layer 7 and the recording layer 6 have a compensation point at room temperature or higher (curve 9), and the recording layer 6 has no compensation point (curve 10). Although the case has been described, the configuration shown in FIG. 5 or FIG. 6 may have the characteristics shown in FIG. 8 to FIG. Here, FIGS. 8, 9 and 10 show the auxiliary layer 7 respectively.
Although neither (curve 9 ') nor the main recording layer 6 (curve 10) has a compensation point, the auxiliary layer 7 (curve 9') has no compensation point, but the recording layer 6 (curve 10 ') has a compensation point. The figure also shows that both the auxiliary layer 7 (curve 9) and the recording layer 6 (curve 10 ') have compensation points.

As a specific material for each layer of the magnetic layer group, an amorphous alloy made of a combination of at least one of a transition metal and a rare earth metal can be used. For example, as a transition metal,
Mainly Fe, Co, Ni, and rare earth metals are mainly Gd, Tb, Dy, Ho, N
There are d and Sm. Typical combinations are TbFeCo, GdTbF
e, GdFeCo, GdTbFeCo, GdDyFeCo and the like.

The material of the auxiliary layer is Co-Cr, Ba-Ferrite, MnB.
i system, iron oxide system, Co-doped iron oxide system, CrO ₂ system, Ni-Co system, Fe
A magnetic material such as -Ni-Co or a Heusler alloy such as PtMnSb may be used.

In addition, the auxiliary layer 7 may be a magnetic layer having in-plane magnetization as shown in FIG. In this case, an in-plane magnetic head is used for recording.

The substrate 4 is a glass material or a plastic material such as polycarbonate (PC) or polymethyl methacrylate (PMMA), and may be thick and hard, or thin and flexible.

The present invention can be applied to various applications in addition to the embodiments described above. For example, although a magneto-optical disk has been described in the embodiments, a card-shaped or tape-shaped medium may be used.

Further, the present invention is not limited to the apparatus using the process as in the embodiment, but may use another process (for example, the above-described magnetic field modulation method) as long as the apparatus performs recording by cooperation of a magnetic head and an optical head. Even if there is, all can be applied.

〔The invention's effect〕

As described above, according to the present invention, in a device for recording information using a magnetic head and an optical head, tracking control of the magnetic head is performed using a low frequency component of a track error signal detected by the optical head. So
It is possible to reliably record information without increasing the width of the magnetic head. Therefore, according to the present invention, it is possible to easily reduce the size and cost of the device and to prevent power from being wasted.

[Brief description of the drawings]

1 is a schematic diagram for explaining an embodiment of the present invention, FIG. 2 is a diagram showing characteristics of a magneto-optical disk used in the present invention, and FIGS. 3 and 4 are recording and transfer processes according to the present invention, respectively. FIGS. 5 and 6 are schematic sectional views showing other examples of the configuration of a magneto-optical disk used in the present invention. FIGS. 7 to 10 are magneto-optical disks used in the present invention, respectively. FIG. 11 is a view showing characteristics of a disk. FIG. 11 is a schematic view showing a state of magnetization when an in-plane magnetic film is used as an auxiliary layer. 1 ... Magnetic head 2 ... Optical head 3 ... Magneto-optical disk 12 ... Servo error detection circuit 14 ... AT servo circuit of magnetic head 22 ... AF / AT servo circuit of optical head 28 ... Objective lens

Claims (1)

(57) [Claims] A magnetic head for applying a magnetic field modulated according to information to a magnetic recording medium having a track; an optical head for irradiating a focused light beam on a track of the medium;
A coarse actuator for integrally moving the magnetic head and the optical head in the cross-track direction, means for detecting a track error signal of the light beam using the light beam, and a track for the light beam mounted on the optical head A fine actuator for finely adjusting the irradiation position in the transverse direction; and a means for extracting a low frequency component of the track error signal, wherein the fine actuator is driven based on the track error signal, and fine tracking control of the light beam is performed. And a coarse tracking control of the magnetic head and the optical head by driving the coarse actuator based on a low frequency component of the track error signal.