JPH06105508B2 - Magneto-optical record erasing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disc file device, and more particularly to a magneto-optical recording / erasing method suitable for enabling overwriting of information.

[Background of the Invention]

Conventionally, as an example of an overwrite system for a magneto-optical disk, Japanese Patent Laid-Open Nos. 58-14304, 58-14307, and
As described in JP-A-58-14308, by using a soft magnetic material having a coercive force of 1 Oe or less as a recording material, irradiation light power and magnetic field strength can be obtained without changing the direction of an external bias magnetic field during recording and erasing. It is a method of recording and erasing by changing the. However, this method imposes a heavy load on the recording material and is inconvenient in that it cannot be used for a magneto-optical disk using a general perpendicular magnetization film.

As another method, it is possible to easily provide two optical heads individually and record on one side and erase on the other side.
In this method, an access system and a signal processing system are separately required for each optical head, so that the device scale becomes large and it cannot be said to be an effective method.

[Object of the Invention]

It is an object of the present invention to record and erase information alternately between a pair of adjacent sectors by a single optical spot and a single optical head having an external magnetic field applying means (electromagnetic coil), thereby overwriting the information. It is to provide a magneto-optical recording / erasing method that can realize writing.

[Outline of the Invention] In order to achieve the above object, the present invention firstly uses a magneto-optical disk in which one track (one round) is divided into an even number of sectors. Secondly, the initial magnetization directions of two adjacent sector areas of the magneto-optical disk are set in advance so as to be opposite to each other. For example, an odd-numbered sector area is magnetized upward, and an even-numbered sector area is magnetized downward, and a DC optical pulse is continuously applied to the disk recording film (perpendicular magnetization film) before the disk is supplied, and the external magnetic field direction is set to the sector. It can be dealt with by alternately inverting according to the number.

To record information on such a magneto-optical disk, the following is done. Now, consider a disk in which upward perpendicular magnetization is set as a magnetization direction in an unrecorded state, and odd-numbered sectors are set to upward magnetization and even-numbered sectors are set to downward magnetization. That is, in this state, the odd-numbered sector areas are in the continuous erasing state, and the even-numbered sector areas are in the continuous DC recording state. Consider a case where information is written in the area of sector number 1. Magneto-optical recording corresponds to inversion of perpendicular magnetization in a direction opposite to that of peripheral magnetization in response to an information signal. Therefore, the information writing to the sector number 1 is performed by setting the direction of the externally applied magnetic field downward and modulating the light pulse in accordance with the signal. At the same time, for the area of the succeeding sector number 2, The erasing operation is executed by reversing the applied magnetic field direction upward and irradiating continuous light in a direct current.

Again, when rewriting to the new information is requested for the pair area of sector numbers 1 and 2, contrary to the above processing,
For the sector number 1 area, the externally applied magnetic field is directed upward, and direct current continuous light is applied to erase the old information. For the sector number 2 area, the externally applied magnetic field is directed downward. Then, the information is recorded by irradiating a light pulse modulated corresponding to the signal.

By performing the above processing alternately, it is not overwriting in a safe sense, but by introducing the concept of the alternate sector, pseudo overwriting can be realized by erasing recording equality.

At present, it is necessary to recognize the state of sector numbers 1 and 2, that is, in which sector information is recorded, and whether the magnetization direction is set upward or downward. In this system, one semiconductor memory module is separately provided for each disk to be used, and the current state of each sector, that is, the magnetization direction information and the recording / erasing state information are always stored. For example, the address of the semiconductor memory is made to correspond to the track number and the sector number, and the memory contents store the magnetization direction information in the first operand and the recording / erasing state information in the second operand. A non-volatile memory is suitable as the memory module. In other words, since it is always used as a pair with the disk, it is necessary that the memory contents are saved even if the memory module is removed from the file device.
This point can be dealt with by having a backup battery or a large-capacity capacitor in the module and charging the module when the module is connected to the file device. Further, a memory module which is not currently used may be stored in the file device itself, and the file device may be constantly charged during storage. Further, if the disk itself is used in the form of being housed in a cartridge, it is also preferable to provide a memory module in the same cartridge.

Further, a directory dedicated to storing the magnetization direction information of each sector is provided in a certain area of the magneto-optical disk, and after the disk is attached to the file device, the contents of the directory are stored in the semiconductor memory at the time of initial startup. The memory is used when writing to a module and executing recording / erasing while using the disk. Then, when the use of the disk is finished and before the disk is removed from the file device, the latest magnetization direction information currently stored in the memory is again set to the latest magnetization direction information.
Rewrite the directory contents of the disk. With this method, it is not necessary to hold the semiconductor memory in pairs with the disk, and there is a merit that it is sufficient to prepare it as a work memory in the file device.

Next, there is a problem of time required for reversing the direction of the externally applied magnetic field, that is, magnetic field switching. One of the features of the magneto-optical disk is non-contact reproduction, in which the optical head can reproduce without contacting the disk surface. In order to make full use of this feature, the electromagnetic coils for applying the external magnetic field must also be installed at a distance that considers the vertical deflection of the disk. It is convenient to previously provide disk information and the like in the form of concave and convex pits at the beginning of each sector of the disk. This region is called the Hedder region, but it is necessary to perform magnetic field reversal while passing through the Hedder region.
By decreasing the time constant of the electromagnetic coil and increasing the coil drive current, it is possible to keep the switching time within the header region passage time. If the electromagnetic coil requires a switching time of one sector, it is preferable to pair every other sector instead of pairing two adjacent sectors. For example, by using sector numbers 1 and 3 as a pair and sector numbers 2 and 4 as a pair, it is possible to cope with the delay in magnetic field switching.

Example of Invention

 Hereinafter, the present invention will be described together with examples.

FIG. 1 is a block diagram showing an example of a magneto-optical disk device embodying the present invention. In the figure, reference numeral 1 is a magneto-optical disk, and a perpendicular magnetization film having a magneto-optical effect is formed on the disk. Recording / erasing / reproducing of magnetization information is performed as follows.

The light emitted from the semiconductor laser 2 is converted into a parallel light flux by the coupling lens 3, is incident on the focusing lens 5 via the polarizing prism 4, and is condensed as a minute spot on the perpendicular magnetization film of the disk 1. When recording information, the drive current of the semiconductor laser 2 is modulated by the information signal to be recorded, and the temperature of the perpendicular magnetization film on the disk 1 is locally raised by the heat of the optical pulse corresponding to the information.
The perpendicular magnetization film has the property of losing its magnetization when the temperature exceeds the Curie temperature. Therefore, when the magnetization of the magnetized film is lost, a magnetic field in the opposite direction to the magnetization of the unrecorded portion is applied from the outside by the electromagnetic coil 6, so that only the light-irradiated portion is magnetized in the opposite direction. , That is, a magnetization domain is formed. In order to erase the already written information, a magnetic field in the direction opposite to the magnetization direction of the recording magnetization domain is applied by the electromagnetic coil 6 at the same time as the light irradiation onto the disk 1.

Information is reproduced by utilizing the magneto-optical effect represented by the Kerr effect. The Kerr effect is an effect in which the polarization planes of incident light slightly rotate in opposite directions corresponding to the upper and lower sides of the magnetization direction of the perpendicular magnetization film. The reflected light from the disk 1 which has caused the rotation of the polarization plane passes through the diaphragm lens 5, is separated by the polarization prism 4, and is guided to the analyzer 7. The analyzer 7 is an optical element that passes only a specific polarization component.
Therefore, due to the Kerr effect, when the light whose polarization plane is rotated corresponding to the magnetization direction of the magnetization domain is incident on the analyzer 7, it is converted into a change in the amount of light. This change in the amount of light is converted into an electric signal by the photodetector 8 and then amplified by the amplifier 9 to a desired level. Since the signal light from the disk 1 contains defects of the disk 1, noise due to dust, etc., and fluctuations of the reproduction light, etc., the level slicing circuit 10 allows only signals having a certain amplitude or more to be output. I am trying to output it. The signal digitized by the level slice circuit 10 is used as a signal processing system and an address decoder.
Guided to 11. The address decoder 11 has a function of decoding a track number and a sector number written in the header section. Therefore, the optical spot can always know the track number and sector number where it is currently located. The address decoder 11 is also used in the write-once type optical disk and is well known, so the detailed description thereof will be omitted. The address information 12 is input to the recording / erasing controller 13. On the other hand, 14 is a semiconductor memory module, and the address bus of the module is a track number of the disk 1,
Corresponds to the sector number. By the command from the controller 13, it is possible to store the magnetization direction information to any address, the recording / erasing state, and rewrite.

The controller 13 also controls the energizing direction of the electromagnetic coil 6 and the driving of the semiconductor laser 2.

Next, a disk form for carrying out the present invention will be described. FIG. 2 shows an example of a disk form. The disk 1 is divided into an even number of sectors, and a header is provided at the beginning of each sector. The header has a sector mark, a self-clock synchronization signal,
The track number and sector number are included. The information in these header areas is recorded by the pits of unevenness information (phase structure). FIG. 3 is a diagram showing the magnetization direction of each sector and the recording / erasing state. 21 to 24 in FIG.
Indicates a header area provided at the head of each sector. The arrows in the data areas 31 to 34 of each sector indicate the magnetization direction of the perpendicular magnetization film. Consider a case where the magnetization direction is set to the state shown in FIG. 3 (a). Further, consider a case where sector numbers 1 and 2 and sector numbers 3 and 4 are paired. Sector number 1 in memory module 14
As the contents of the memory addresses corresponding to and 3, the upward direction of the magnetization direction information and the fact that it is in the erased state are stored.
On the contrary, the contents of the memory addresses corresponding to the sector numbers 2 and 4 are stored such that the magnetization direction is downward and the recording state. Now, let us consider a case where an information recording command is given from the upper CPU to the data area of the pair of sector numbers 1 and 2.

In FIG. 3B, the data area 31 of sector number 1
It can be recognized from the content of the corresponding address of the memory module 14 that the memory cell is upward in the magnetization direction from the erased state. Therefore, in the section of the data area 31, the external magnetic field is directed downward, and at the same time, the light pulse modulated corresponding to the information is irradiated to perform recording. Sector number 2 data area 32
On the contrary, in the section, the direction of the external magnetic field is set to the upward direction, and the erasing is executed by irradiating DC light at the same time. At the same time, the contents of the memory module address corresponding to the sector number 1 are rewritten to the sector number 1 so that the magnetization direction is downward and the recording state is set. Sector number 2
The contents of the memory address corresponding to
Rewrite to the erased state.

Next, consider a case where a rewrite command for new information is given to the pair area of sector numbers 1 and 2. In FIG. 3 (c), contrary to the case of FIG. 3 (b), an upward magnetic field and a DC optical pulse were applied to the data area 31 of sector number 1, and the data was already recorded. Data is erased, and a downward magnetic field and an optical pulse modulated corresponding to new information are applied to the data area 32 of sector number 2 to rewrite information. Also in this case, the contents of the memory module 14 are changed in the same manner as shown in FIG. 3 (b).

To write new information to the same area again,
The processing shown in FIG.

In this embodiment, as shown in FIG. 1, one analyzer converts the rotation of the polarization plane into a change in the amount of light, but there is no particular limitation on the signal detection method. Therefore, the present invention can be implemented by a method of performing differential detection using two analyzers and a method of performing differential detection using a half-wave plate and a polarization beam splitter.

〔The invention's effect〕

According to the present invention, information can be overwritten on a magneto-optical disk with only a single optical head. In the present invention, two sector areas are used as a pair,
By always alternating the recording and erasing states, it is possible to rewrite information in an overwrite manner without waiting for disk rotation. Moreover, since a single optical head is sufficient, the file device can be downsized, and this is an economical method.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a magneto-optical disk device for carrying out the present invention, FIG. 2 is a plan view of a magneto-optical disk divided into sector units, and FIG. 3 is a perpendicular magnetization direction on the disk, irradiation. It is the figure which showed the relationship between an optical pulse and an external magnetic field. 1 ... Magneto-optical disk, 2 ... Semiconductor laser, 6 ... Electromagnetic coil, 7 ... Analyzer, 11 ... Address decoder, 13 ... Controller, 14 ... Memory module, 21-24 ... Header area,
31 to 34 ... Data area.

Claims (6)

[Claims] 1. A magneto-optical recording and erasing method in which information is recorded and erased by a thermomagnetic effect by using a perpendicular magnetization film and information is reproduced by a magneto-optical effect, and a sector structure having an even number of sectors is provided. , And two adjacent sectors as a pair of information recording units, a header area including at least a track number and a sector number is provided in advance at the beginning of the sector with uneven pits, and a portion other than the header area is used as a data area. Using a magneto-optical disk,
At least two sectors in the pair of information recording units have perpendicular magnetization directions opposite to each other, and when one of them is in a recording state, the other is in an erasing state, and a semiconductor memory is provided, and the semiconductor memory has the above-mentioned structure. The perpendicular magnetization direction of the data area of the sector corresponding to the track number and the sector number and whether the data area of the sector is in the recording / erasing state are stored.
A magneto-optical recording and erasing method, characterized in that the state of the sector can be recognized. 2. The magneto-optical recording and erasing method according to claim 1, wherein the magnetization direction of the data area of the odd-numbered sector is set upward and the magnetization direction of the data area of the even-numbered sector is set downward. Incidentally, the fact that the odd-numbered sector is in the erased state and is magnetized upward is stored in the operand part of the address corresponding to the sector of the semiconductor memory, and the even-numbered sector is in the recorded state and magnetized downward. Similarly, when storing information in the semiconductor memory and recording information, a downward external magnetic field is applied to an odd-numbered certain sector area and a laser light pulse modulated corresponding to the information is applied. And irradiating the odd-numbered sector with the external magnetic field directed upward and the laser beam in a direct current direction to the adjacent even-numbered sector. Magneto-optical recording and erasing method characterized by previously rewritten operand in the address corresponding to the coater. 3. A magneto-optical recording and erasing method according to claim 2, wherein when data is rewritten to new information, an upward sector is applied to an odd-numbered sector with downward magnetization in which information is already recorded. Laser light irradiation is performed in a direct current manner with an external magnetic field, and the subsequent upward magnetic even-numbered sector is irradiated with a downward external magnetic field and a laser light pulse modulated corresponding to information. Record erasing method. 4. A magneto-optical recording and erasing method according to claim 1, wherein a series of recording and erasing processes performed on odd-numbered and even-numbered sector areas is an odd number. A magneto-optical recording and erasing method characterized by rewriting information in the same process by reversing the handling of number and even numbers. 5. A magneto-optical recording and erasing method according to claim 1, wherein the semiconductor memory can be attached to and detached from a magneto-optical disk file device in the form of a module. A magneto-optical recording and erasing method characterized by using a nonvolatile random access memory (RAM) and associating one memory module with one magneto-optical disk. 6. A magneto-optical recording and erasing method according to any one of claims 1 to 5, wherein a magnetization direction of each sector region and a recording or erasing state are determined. A directory area for storing is provided in a certain area of the magneto-optical disk, and after the disk is set in a file device, the directory contents at the time of initial startup,
The magnetization direction information of each sector in use of the disk is transferred to the semiconductor memory in the file device, and stored in the semiconductor memory each time, and at the end of use of the disk and before removal from the file device. In addition, a magneto-optical recording and erasing method, characterized in that the directory area of the disk is rewritten with the contents of the semiconductor memory.