JPH07169124A - Magneto-optical recording and reproducing device and magneto-optical recording disk - Google Patents

Abstract

PURPOSE:To perform data recording, reproducing and transfer at a high speed by placing multi-beams in the radial direction of a recording disk in parallel and simultaneously performing information recording and reproducing for every beam. CONSTITUTION:Serial digital signal strings are divided for every plural bits by a multiplexer 2 and they pass respective modulating circuits 3, enter plural independent recording and reproducing readers 4, pass a first polarizing beam splitter 5, is converged by an objective lens 6, reach a magneto-optical disk 7 and recorded as pit strings. In order to reproduce the signals, a laser power, which is smaller than the power used in the recording, is continuously applied and the reflected beams from the disk are divided into incident and reflected light beams by the splitter 5. Then, a second polarizing splitter 8 separates the direction of magnetization, leads to signal detection photodiodes 9 and differences are taken. On the other hand, prepits, in which guide grooves and position information are beforehand included, are placed on the disk 7 and a lens 6 is controlled by the tracking and the focusing.

Description

Detailed Description of the Invention

[0001]

This invention relates to document files, images,
The present invention relates to a magneto-optical recording disk on which information such as code data is optically recorded with high density, and a magneto-optical recording / reproducing device.

[0002]

2. Description of the Related Art In the prior art, as shown in FIG. 6, in a magneto-optical disk device capable of recording / reproducing / erasing,
The light returned to the disk 44 by driving one laser 41 and irradiating the disk 44 is a polarization beam splitter 45.
It is separated into a servo signal used for beam focus control and a reproduction signal used for reading recorded information. In addition,
In the figure, 39 is a recording signal, 40 is a modulation circuit, and 42 is
Is a polarization beam splitter, 43 is an objective lens, 46 is a polarization beam splitter, 47 is a signal detection photodiode, 48 is a reproduction signal, 49 is a servo address signal detection photodiode, 50 is a focus drive circuit, 51 is a tracking drive circuit, 52 Is an actuator.

In this magneto-optical recording / reproducing apparatus, the data transfer rate is determined by the size of the recording bit and the linear velocity of the laser spot passing through the bit.

The size of the recording bit depends on the spot size of the writing laser. In the conventional technology, the semiconductor laser used in the magneto-optical recording / reproducing apparatus is 780-780.
It is about 830 nm, and the spot size in this wavelength range does not become 1 μm or less due to optical restrictions. The size of the bit to be actually recorded is about 0.8 μm at the shortest in consideration of the thermal conductivity of the recording film.

The linear velocity of the laser spot depends on the number of rotations of the recording disk. Restrictions due to the mechanical characteristics of the substrate material of the recording disk (The acceleration component of the displacement of the laser spot due to the minute irregularities of the rotating disk has a great influence on the focus control of the pickup, but this acceleration is the number of rotations of the substrate. The spindle motor for rotating a board used in small and inexpensive office equipment is at most 3
It is about 600 rpm.

Under the above conditions, for example, an IS with a diameter of 86 mm
Format of a magneto-optical recording disk compliant with O standard (division into 25 sectors within one rotation track, 51 sectors per sector)
2 bytes, 25 × 512 = 12.8 × 10 ³ bytes)
Then rotate at 3600 rpm (rotation frequency 60 Hz)
The data transfer rate is only about 2.8 × 10 ³ × 60 = 786 × 10 ³ bytes / s, and the number of fixed type magnetic recording devices (so-called hard disks) is MB / s (× 10 ⁶ bytes / s).
It falls short of s).

[0007]

In order to improve the current data transfer rate, it is conceivable to first reduce the write bit size in the above situation. Generally, it is necessary to reduce the spot size of the laser as a means for reducing the bit size. Therefore, a method using a short wavelength laser has been proposed. However, it can be accommodated in a compact size as an information recording device, for example, 400 nm to 500 n.
The emergence of a semiconductor laser having a wavelength of m will be extremely difficult in the future due to problems such as high output for magneto-optical use, stability at room temperature, device life, and manufacturing cost.

Further, as a means for increasing the data transfer speed, there is a method of increasing the number of rotations of the recording disk, but as described above, there are large technical restrictions on both the recording disk side and the spindle motor side. Is desired.

[0009]

In order to solve the above-mentioned problems, a magneto-optical recording disk and a recording / reproducing apparatus according to the present invention are provided with a plurality of recording / reproducing lasers arranged side by side in the radial direction of the recording disk. By independently driving each, several bits are simultaneously recorded / reproduced to achieve high-speed writing and reading, and the data transfer rate, which is a problem of the prior art, is improved.

[0010]

The signal written by the plural collocated lasers is recorded along the tracking guide groove formed on the recording disk side. The guide grooves are set at a pitch such that all the laser spots juxtaposed in the radial direction of the recording disk can be accommodated. One or two of the juxtaposed laser spots are on this guide groove for extracting the tracking servo signal. Be served. In addition, address information for sector management of recording data, clock signals for synchronizing signals, etc. are formed beforehand in the form of concave and convex pits along the guide groove on the recording disk, and the collocated laser is used. Apply one spot to this. At the time of recording / reproducing, multiple laser spots share their respective roles to extract the tracking control signal, read the address, extract the clock, write several bits in parallel, or read the information. To transfer data to.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the embodiments shown in the drawings. Although the 8-bit parallel processing is used in the embodiment, the present invention is not limited to this.
FIG. 1 is a schematic diagram of a recording / reproducing apparatus which constitutes the present invention. 2 is a diagram showing the structure of a recording / reproducing laser section of this apparatus, FIG. 3 is a diagram showing the structure of the laser, FIG. 4 is a diagram showing the structure of a signal detecting section, and FIG. 5 is a magneto-optical disk. It is a figure showing the state where the laser spot is irradiated on.

In FIG. 1, a serial digital signal sequence (recording signal 1) is divided into 8 bits by a multiplexer 2, passes through a modulation circuit 3, respectively, enters into 8 independent recording / reproducing lasers 4, and is pulsed. Eight laser beams pass through the first polarization beam splitter 5, are condensed by the objective lens 6, reach the magneto-optical disk 7, and are recorded as a pit train. Recording is a perpendicular magnetic recording system using so-called external magnetic field application / thermomagnetic writing.

For signal reproduction, laser power smaller than that at the time of recording is continuously irradiated, and reflected light from the disc (shown by a broken line arrow in the figure) is first converted into incident light and reflected light by the first polarization beam splitter 5. The beam emitted from the laser is a linearly polarized light having a polarization plane of an electric field parallel to the paper surface. The beam reflected from the disk is shifted by a half wavelength and returns as a linearly polarized light perpendicular to the paper surface. If only the linearly polarized light parallel to the paper surface is transmitted, the reflected light does not return to the laser but goes to the detector side.) Then, the direction of the magnetization of the recording bit is recorded on the recording film by the second polarization beam splitter 8. This is performed by separating the upward or downward direction to the signal detection photodiode 9 and taking the differential. The principle of reproduction utilizes the magnetic Kerr effect.
That is, the Kerr rotation angle of the plane of polarization is proportional to the magnetization of the magnetic recording film, and the rotation direction is right rotation when the incident light direction and the magnetization direction are the same, and left rotation when the magnetization direction is opposite.
Now, the reflected light extracted as the linearly polarized light has a difference in the vector component of the linearly polarized light due to the difference in the magnetization direction of the recording film, and is divided into lights having different intensities by the second polarization beam splitter 8. It enters the signal detecting photodiode 9 and is converted into an electric signal to become a reproduction signal 10 (for example, a low level output is set to "0" and a high level is set to "1" to be digitized). Taking the differential of this electric signal means to further increase the signal strength.

On the other hand, in order to accurately trace the position of the signal in which the spot of the laser beam is recorded, the magneto-optical disk 7 is previously provided with guide grooves and irregularities called pre-pits containing position information in the circumferential direction of the disk. It has been applied (details are shown in Fig. 5). With this trace (tracking),
Laser spot is correctly focused (focusing)
It is necessary to control the objective lens 6 so that

In the present invention, a light source is separately prepared to obtain this control signal (servo signal). The continuous light emitted from the laser 12 by the laser drive signal 11 for the servo address signal is different from the light of the recording / reproducing laser 4,
It is set so as to be linearly polarized light perpendicular to the paper surface, and enters the second polarization beam splitter 8. Since the second polarization beam splitter 8 passes only polarized light horizontal to the paper surface, this light is totally reflected and further reflected by the first polarization beam splitter 5 to enter the magneto-optical disk 7. The reflected light from the magneto-optical disk 7 is also shifted by half a wavelength to become horizontal linearly polarized light, passes through the first polarization beam splitter 5, and enters the servo / address signal detecting photodiode 13. The servo / address signal detecting photodiode 13 is composed of four-divided photodiodes 20 (FIG. 2). When the laser spot is not focused on the surface of the magneto-optical disk 7, the image formation on the four-divided photodiodes is not circular but elliptical. By utilizing the fact that the difference between the outputs of the four photodiodes becomes zero, the focus driving circuit 14 is actuated, the actuator 15 is operated, and the objective lens 6 is moved vertically with respect to the magneto-optical disk (astigmatism). Control called the aberration method).

Further, in order to prevent the laser spot from coming off from the guide groove 35 (FIG. 5) of the magneto-optical disk 7, the output of the corresponding four-divided photodiode 20 is symmetrical so that this spot is symmetrical with respect to the guide groove 35. The tracking drive circuit 16 is operated from the combination to move the objective lens in the radial direction as well (Push-pull control method).
The address signal 17 is obtained as the total output of this 4-division photodiode.

FIG. 2 shows the arrangement of a recording / reproducing laser and a servo / address signal detecting photodiode. Two combinations of 4-beam lasers 18 and 19 and 4 in the center
It consists of a split photodiode 20.

FIG. 3 shows the structure of a 4-beam laser.

In the figure, an n-GaAlAs clad layer 22 and p-GaAlAs are provided on an n-GaAs substrate 21.
A clad layer 23 is provided and separated by a GaAlAs active layer 24, followed by an n-GaAs current blocking layer 25, p-.
The GaAs cap layer 26 is laminated, and the n-electrode 27, p
-A heat sink (SiC) sandwiched between electrodes 28
It is composed of 29. Although the laser light 30 is emitted from the end face of the element, four separate lasers can be driven by the separation grooves 31.

FIG. 4 shows the arrangement of the signal detecting photodiode and the servo / address signal reproducing laser. It comprises eight signal detecting photodiodes 32 and a servo / address signal reproducing laser 33.

FIG. 5 shows a laser spot arrangement on the magneto-optical disk substrate.

A guide groove 35 and a prepit portion 36 for a bit-shaped address signal are formed in advance on the magneto-optical disk 34. Laser spot for reproducing servo / address signal 3
7 is focused on this pre-pit portion, and the recording / reproducing laser spot 38 is recorded / reproduced in parallel in 8-bit units under the control of the servo / address signal reproducing laser spot 37.

Although not shown in detail, the structure of the magneto-optical disk 34 is shown below.

A dielectric film made of oxides or nitrides of Si, Al, etc., Fe, Co is formed on a substrate made of glass or synthetic resin such as polycarbonate, polyester, etc. which has sufficient transparency for the recording / reproducing laser wavelength. A recording film layer dielectric film made of an alloy of a transition metal such as Al and a rare earth element such as Tb, Gd, Dy, and a reflective film layer made of Al, Ni, Cr, or the like are formed by a vacuum deposition method or a sputtering method. . The laser is incident from this substrate side, and the dielectric film brings about the so-called Kerr rotation angle enhancing effect (increase in reproduction signal amplitude) due to protection of the recording film and multiple reflection of reproduction light.

[0025]

INDUSTRIAL APPLICABILITY As described above, the magneto-optical recording / reproducing apparatus and the recording disk according to the present invention enable high-speed recording / reproducing by using the multi-beam, and shorten the wavelength of the laser and the recording signal. Increasing the recording density or increasing the number of rotations of the recording disk by using a special modulation / demodulation method (for example, partial response-Vidabi decoding applied in communication technology) or a method that miniaturizes the laser spot through a special slit. The effect is very large compared to the above. For example, as shown in the embodiment, the 8-bit parallel processing can surely achieve the 8-times speed, but there is no specific means for increasing the linear recording density by 8-times.

Further, increasing the number of rotations of the recording disk eight times (current maximum speed 3600 rpm × 8 = 28800 rpm) is not suitable for compact information equipment due to problems such as bearings.

With respect to the manufacturing method of the recording disk, not only the almost same process can be followed, but also the guide groove pitch is 8 times that of the conventional one (currently 1.6 μm × 8 = 12.8 μm), the manufacturing risk can be reduced, and the high speed is inexpensive Can provide discs.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a recording / reproducing apparatus that constitutes the present invention.

FIG. 2 is a diagram showing a configuration of a recording / reproducing laser section of the apparatus.

FIG. 3 is a diagram showing a laser structure of the laser unit.

FIG. 4 is a diagram showing a configuration of a signal detection unit of the same device.

FIG. 5 is a view showing a state in which a magneto-optical disk is irradiated with a laser spot in the same device.

FIG. 6 is a schematic diagram of a conventional recording / reproducing apparatus.

[Explanation of symbols]

 4 Recording / reproducing laser 7 Magneto-optical disk 9 Signal detecting photodiode 12 Servo address signal reproducing laser 13 Servo address signal detecting photodiode 35 Guide groove 36 Prepit portion of address signal

Claims (5)

[Claims] 1. A magneto-optical recording / reproducing apparatus for recording / reproducing information on / from a rotating recording disk using an optical pickup and a magnetic field generator, wherein a laser is used as a light source of the optical pickup in a radial direction of the recording disk. A magneto-optical recording / reproducing apparatus characterized in that a plurality of beams are arranged in parallel to form a multi-beam, and information is recorded / reproduced simultaneously for each laser beam. 2. The laser is a multi-beam type in which one chip is divided and can be independently controlled. A servo signal detecting photodiode is installed between the multi-beam lasers, and the reproducing signal detecting photodiode is the multi-beam laser. Arrangement corresponding to each of the reflected light from the beam laser,
The magneto-optical recording / reproducing apparatus according to claim 1, wherein a servo control laser is installed between the photodiodes, and the recording / reproducing laser and the servo signal detecting laser are separated from the photodiode. . 3. A recording disk mounted on the magneto-optical recording / reproducing apparatus according to claim 1, wherein guide grooves for recording / reproducing information along a rotation direction are concentric circles in the circumferential direction of the disk. Formed in a circular or spiral shape, the guide groove is used to detect the reflected light of the servo signal laser to perform tracking control, and the recording / reproducing laser spots arranged in parallel within the pitch of the guide groove. A magneto-optical recording disk characterized by having a side-by-side configuration. 4. The recording disk according to claim 3, wherein, in addition to the guide groove, a clock signal for synchronizing addresses and signals for sector management of recording information is formed in advance as uneven pits. A magneto-optical recording disk characterized by being formed. 5. The concavo-convex pit row is provided in parallel with the guide groove, and the address and the synchronizing signal are extracted by also serving as a laser spot for servo control. The magneto-optical recording disk according to claim 4.