JPS62239326A - Optical memory device - Google Patents

Abstract

PURPOSE:To rewrite the contents of an optical memory at a high speed without deteriorating the heat stability by adding a means to a conventional optical memory device to cause the magnetic flux change. CONSTITUTION:An optical disk device 10 records, reproduces and erases the information or data via an optical head 40 which is controlled by a signal processor 150. Here a magnetic flux generator 20 is added to the optical disk 10 for generation of a magnetic field. As a result, an eddy current is produced within the disk 10 and therefore the disk 10 is heated. Then the information or data recorded to the disk 10 are erased when the temperature of a recording medium of the disk 10 reaches an erasing level. The generator 20 also contributes to improvement of the recording sensitivity. That is, the heating load of the head 40 is reduced as long as the heating temperature is kept under the erasion level when the recording medium is heated by the eddy current. Furthermore, the time needed to reach a recording temperature is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of changing the contents of an optical memory, and particularly to a recording/erasing method of an optical memory suitable for changing a large amount of information.

[Conventional technology]

Devices that use laser light focused on the submicron order to record information at high density on a recording medium and play it back can record large amounts of information such as video and audio, and will be useful in the future information society. It is expected that it will become an indispensable device. For example, "Nikkei Electronics" is used for such optical recording and reproducing devices.
(1984, 3.26) is an optical disk device. There are three types of optical disk devices: (1) read-only type, (2) write-once type, and (3) rewritable type, and read-only type and write-once type have almost reached the stage of practical use.

On the other hand, there is still no established method for rewritable formats.
Research and development of rewritable optical disks using magneto-optical materials, phase change materials, etc. is actively underway. Magneto-optical disks and optical disks using phase-change materials that are currently being researched all use a method of erasing data using laser light. However, in the case of magneto-optical disks, it is necessary to reverse the magnetic field during erasing, so it is not suitable for so-called sequential erasing recording, in which recording is performed while erasing.On the other hand, in the case of optical discs that utilize phase change, recording sensitivity is generally low. Since the erasing sensitivity is lower, a method of irradiating an elongated elliptical beam for erasing is used.

[Problem that the invention seeks to solve]

However, even when producing a long elliptical beam, the ratio of the major axis to the minor axis is limited to about 10:1, and materials that can erase data with an elliptical beam of about 10:1 have poor thermal stability. There was a problem in that a good one could not be erased with an elliptical beam of about 10:1.

An object of the present invention is to provide a method for rewriting the contents of a memory at high speed without impairing thermal stability.

[Means for solving problems]

The above object can be achieved by adding means for generating magnetic flux changes to a conventional optical memory device.

[Operation] Conventional rewritable optical discs employ a method of applying thermal energy to the medium using laser light. This method is based on the principle that light energy enters the medium, causing molecules to vibrate and heat up.

On the other hand, in the present invention, what happens when a change in magnetic flux is applied to a conductor?
This method utilizes the fact that a kttt flow occurs and heat is generated due to this eddy current loss. This makes it possible to heat a wide range that could not be achieved with conventional light sources such as lasers, and allows even low-power lasers to heat the disk, allowing recording and
It is possible to speed up erasing.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.
r! ! 1, 10 is an optical memory medium and a substrate.

It consists of records, materials, and a protective film. The recording material used here is preferably a conductor, but in the case of an insulator, a conductor may be attached close to the recording material as shown in Figure 16. Figure 16 (a) shows a good conductor. (b) is an example in which a good conductor is attached to the substrate side. Figures 15 and 16 show the minimum required film configuration to carry out the present invention, and when used as an optical disk, other groove-forming films and optical 2 Important elements in the present invention are 11! Absorption membranes etc. are often added. At least one layer of i contains a good conductor film.

In FIG. 15, 20 indicates a magnetic flux generation source.

For convenience of explanation below, it is assumed that a magnetic field is generated from the substrate toward the protective film by the magnetic flux generation source. FIG. 17(a) shows VtTe at this time as viewed from the magnetic flux generation source 20 side. When the disk 10 rotates clockwise in this state, the magnetic flux passing through the conductor changes, so an eddy current (2) is generated. This eddy current eventually becomes Joule heat and increases the temperature of the recording medium.

Further, FIG. 17(b) shows the occurrence of leakage current I when the power source of the magnetic flux generation source 20 is set to AC and the magnetic flux intensity is changed.

Next, a recording medium in which the good conductor shown in FIG. 15 is not added will be described. The inventors have applied for patent application No. 59-42070.
In Japanese Patent Application No. 59-430611, a novel optical recording alloy medium is disclosed. This optical recording alloy is
It has two crystal structures at room temperature. That is, the 18th
As shown in the figure, the crystal structure is different depending on whether the medium is raised to a transformation temperature of 01 or higher and rapidly cooled and when it is held between the transformation temperature θ2 and OL. Because it has two different crystal structures at room temperature, it has physical properties such as spectral reflectance of electromagnetic waves such as laser light, electrical resistivity, refractive index, polarization rate, and transmittance.
Alternatively, since the electrical characteristics also differ, information can be recorded using changes in these characteristics. This optical recording alloy is
Even when the phase changes between two different crystal structures, the resistivity hardly changes and both exhibit good conductor characteristics. In this way, when both states are good conductors, eddy currents are generated in the recording material, so it can be seen that a simple film structure as shown in FIG. 15 is sufficient.

On the other hand, Mr. S. R. Opsinski's Special Publication 1972-268
When a crystal-amorphous phase change recording medium, typified by the recording material disclosed in Japanese Patent No. 97, becomes amorphous, it becomes an insulating state that hardly conducts electricity. Therefore, even if a change in magnetic flux is applied to this amorphous material, no eddy current is generated. When using a recording medium that does not generate eddy currents or generates only a small amount of eddy current, it is necessary to add a good conductor film close to the recording medium, as shown in FIG. 16.

Next, a specific magnetic flux generation method will be explained.

The magnetic flux generator 20 in FIG. 19 includes a coil 22.degree. switch 24. ffi source26. It is composed of a variable resistor 28. When switch 24 is turned on, current flows through coil 22 and magnetic flux 1-1 is generated. If the positions of the magnetic flux generator 20 and the disk 10 change relative to each other, the disk 1
Eddy currents occur on the zero conductor. Moreover, if the tii source 26 is an alternating current, the magnetic flux H changes with time, and an eddy current as shown in FIG. 17(b) is generated on the conductor. Further, the variable resistor 28 is used to control the strength of the magnetic flux H, and can be adjusted according to the sensitivity of the recording medium.

FIG. 1 is a diagram showing the configuration of an optical disk device suitable for implementing the present invention, in which an optical disk 10 is rotated by a motor 30. As shown in FIG. Currently, optical disk devices have been developed that use a constant rotational speed force type and a constant peripheral speed force type type, but either of these may be used here. In a normal optical disk device with such a configuration, information or data is recorded, reproduced, and erased by the optical head 40 controlled by the signal processor 150, but the present system is further characterized by magnetic flux generation. This is because a container 20 is added. That is, as explained with reference to FIG. 19, a magnetic field is generated by the magnetic flux generator 20, an eddy current is generated within the optical disk 10, and the disk is heated.

In this way, the recording medium in the disk is heated to an erase temperature of 02
When this point is reached, the information or data recorded on the disc will be erased. Further, this magnetic flux generating device 20 can also be used to improve recording sensitivity. That is,
When heating the recording medium with eddy current, if the recording medium is heated to less than the erase temperature 02, the burden of heating on the optical head 40 will be reduced.
The time required to reach the recording temperature θ1 is also shortened. Although the magnetic flux generator 20 and the head 40 are located on the opposite side in FIG. 4, it is of course possible to install them on the same side. In addition, as shown in FIG. 2(a), there is an override recording system that records while erasing by arranging the positional relationship between the eddy current generating part and the optical laser spot as shown in the figure with respect to the rotational direction of the disk. can be realized. In other words, as shown in Fig. 2(b), although the temperature rises due to eddy current, the amount of eddy current generation is controlled so that the time over O2 is slightly less than the time required for erasure. Therefore, when the laser is not irradiated, the temperature is α
It descends like a line, and when irradiated, it can maintain its temperature like beta rays, making it possible to erase it.

In addition, the intensity of the laser can be further increased like a gamma ray to reach a recording temperature of 01 for recording. In this way, the feature of this system is that recording and erasing can be performed only by laser intensity modulation.

Next, FIG. 3 shows the control system of the magnetic flux generator 20.

This will be explained using FIG. The control system is a track address control system 50. 30, 70 and a magnetic flux intensity control system 80.The track address is generated by driving the actuator 50 according to a command from the address control section 70.The actuator 5o can be made using a voice coil, a gear, or the like. or.

Actual address 62 is detected by sensor 60 and used for feedback control. The actual track address may be the address 62 recorded on the disk 1o as shown in Figure 4, or may be recorded on a fixed part of the '1ift, for example on the stationary side of the voice coil. Also good. Further, when used for purposes that do not require accurate address control, address feedback control is not necessary, and in this case, 60 may be omitted.

Furthermore, when the disk is rotated at a constant rotational speed, the sensitivity differs between the inner and outer circumferences of the disk. Therefore, it is desirable to control the magnetic flux intensity according to the 1 to 1000000 address.

Block 80 performs this control function. Since the sensitivity is approximately proportional to the circumferential speed, the magnetic flux can be controlled based on this circumferential speed. Specifically, the variable resistor 28 in FIG. Alternatively, by changing the size of the power source 26, the coil 2
2 changes, and the magnetic flux strength H can be changed.

FIG. 5 shows another embodiment. Although FIG. 3 shows an example in which the magnetic flux generator 20 is smaller than the recording area of the disk, FIG. 5 shows an example in which the magnetic flux generator 20 is larger.

In principle, all the information on a disk can be erased by rotating the disk once.

As shown in FIG. 6, the actual optical disc 10 is composed of a large number of blocks. In other words, there is a block address 62 in the circumferential direction, and the blocks are 16a, i, 16b,
They are assigned as i+z, -. Further, the block is composed of a plurality of tracks 17, as shown in FIG. From this, when applying the present invention, it is also possible to divide the inside of the disk into a plurality of blocks and apply magnetic flux to each block to erase information.

FIG. 8 shows an example in which blocks 16a and 16b are arranged concentrically. In such a case, if an insulator is added between the concentrically divided blocks, local heating is possible without worrying about eddy currents flowing in the radial direction. In addition, the insulator reduces the outflow of heat in the radial direction, increasing thermal efficiency.

FIG. 9 shows an embodiment in which data is erased while checking the status. In the figure, an optical head 40 monitors the reflectance of the optical disk and feeds back one reflectance to the track address control section 70.

The track address control unit 70 instructs the actuators 50 and 40 with addresses so that the reflectance falls within an appropriate value.The reflectance monitor unit 40 monitors one reflectance and monitors a plurality of reflectances. There may be cases where it is monitored.

10 and 11 show the method of the optical head 40 and the algorithm of the address control section 70 when monitoring one reflectance.

In FIG. 10, 100 is the optical system of the optical head,
The optical system is basically the same as that used in playback-only optical discs such as compact discs, so the explanation will be omitted.

The light detected by the six-segment sensor of the optical head optical system 100 is amplified by the amplifier 42, and becomes the single-unit intensity of the light, an autofocus signal, and a tracking error signal.

Of these, the total intensity of light is used to estimate the reflectance (
Block 44), feedback to the track address control. Also, the autofocus signal.

The light is led to an autofocus controller 46 and used to control the objective lens of the optical head optical system. Further, the tracking error signal is guided to the tracking control section 48, used for correcting the signal from the track address control section 70, and finally sent to the tracking mirror of the optical head optical system 100 or the two-dimensional objective. used for track direction control. FIG. 11 shows a control method for 1 to rack addresses when the reflectance is fed back. first,
First, in block 44, the estimated reflectance is read out and checked to see if it falls within a predetermined value. If it is there, it is assumed that the deletion is complete.

The address is updated to move the coil 20 and optical system 100 to the next track address, and the process ends. On the other hand, if the 1 reflectance is not within the predetermined value, the purpose of lowering the disk speed is to allow enough time for erasing, and raising the temperature of the substrate will have the same effect. Instead of an instruction to decrease the disk speed, an instruction to increase the magnetic flux strength may be given.

Fig. 12 shows a track address control method when a plurality of reflectance monitors are installed according to another embodiment of the present invention. Fig. 12U7A(a) shows the relative positional relationship of the reflectance monitors. Therefore, it is desirable that the monitoring spot be installed at the rear with respect to the moving direction of the memory such as the disk. FIG. 12(b) shows an example of the algorithm of the track address control unit when two reflectances are monitored.
First, the monitor position for 0 reflectance B where reflectance A and B are read out is assumed to be behind the 0 reflectance.The first step is to check whether 1 reflectance A is within the specified value. The fact that A is within the specified value indicates that erasing has already been completed at the position of A, so the memory movement speed can be further increased.
When the reflectance B is not within the specified value, the reflectance B is further checked.

The fact that this reflectance B is within the specified value means that A
This indicates that erasing was completed between and B, which means that the speed of movement of the disk and the strength of the magnetic flux were appropriate.

Therefore, in this case, you only need to update the track address, and if 1 reflectance B is not within the specified value, it indicates that erasing is not completed, so change the disk movement speed. Either lower it or increase the magnetic flux strength.

You need to try erasing again.

FIG. 13 shows an embodiment in which a temperature sensor 90 is provided. The temperature detected by this temperature sensor 90 is used for controlling the magnetic flux intensity. FIG. 14 shows the control algorithm. It is desirable to install the temperature sensor at the end of the eddy current generation section in the direction of memory movement, as shown in FIG. 14(a). This is because the temperature of the tail is the highest and it is necessary to control this temperature so that it does not reach the recorded temperature. Of course, it is also possible to monitor and use the temperature of other parts as a substitute.

FIG. 14(b) shows an example of a control algorithm. The temperature detected by the detector is compared with a set value (a value slightly lower than the recorded temperature), and calculations such as proportional and integral control are performed. Magnetic flux strength is determined.

As mentioned above, the method of heating by applying magnetic flux to generate eddy current can heat a wider area compared to the conventional method of spot heating by focusing laser light.
Suitable for fast and bulk deletion. On the other hand, if there is a large amount of leakage magnetic flux, the heating effect cannot be obtained.

Based on this, a magnetic pole configuration suitable for efficient generation of eddy current will be described below. For this purpose, it is preferable to arrange the magnetic poles N and S on the same surface of the optical disk. FIG. 20 shows an example of this arrangement.

In FIG. 20, magnetic head 2. When a switch (not shown) is turned on, a current flows through the coil 26 and a magnetic flux φ is generated. The important factor here is that at least one layer of the film contains a good conductor film.

The optical recording alloy described above is a good conductor. If the power source 28 of this magnetic head is an AC power source, the magnetic flux φ becomes an alternating magnetic field,
Eddy currents are generated in the recording material 14, which is a conductor of the disk 10. Here, the core 24 faces the core 22 with the disk 10 in between, and forms a magnetic circuit through which the magnetic flux generated from the core 22 passes. The disk 10 includes a substrate 12 and a recording material 14. The basic structure is a protective film 15, and the thickness of the substrate 12 is usually 1.2-.

The thickness of this substrate (glass) is set so that the diameter of the laser spot on the glass surface is a few square centimeters in order to reduce the influence of dust etc. on the disk surface, and the laser spot diameter is focused on the film surface of the recording material 14 to a spot diameter of about 1 μrnφ. It is standardly determined to have high energy density. This substrate thickness provides a magnetic resistance similar to that of an air gap, so the recording material 14
If the poles N and S of the core 22 are brought closer to each other in order to increase the magnetic flux v14 degrees in the recording material 14. Magnetic flux density decreases and efficiency decreases. In other words, it is better to reduce the distance between magnetic poles N and S to the extent that there is less leakage magnetic flux, but if it becomes smaller than the substrate thickness, the current that actually flows through the conductor of the disk will decrease by 11% for a given ampere turn. do. When this distance Q is increased, the magnetic circuit between the magnetic poles N and S becomes 1
The air gap that forms the area becomes larger, and the magnetic flux density in the recording film decreases. Therefore, when the core 24 is provided, the magnetic resistance is lowered, and most of the magnetic flux generated from the magnetic head passes through the core 24, and therefore passes through the section @Pa14.

When the magnetic flux φ is an alternating magnetic field, eddy currents are generated in a direction that prevents changes in the magnetic flux, and Joule heat is generated. Magnetic flux φ
Even if is a DC magnetic field, if the disk rotates, @Membrane 1
Eddy currents occur because the magnetic flux of 4 changes. Here, the case of an alternating magnetic field will be explained. The plan view of FIG. 20(a) and FIG. 20(b) show the eddy current flowing through the recording film 14. The eddy current flows in the above-mentioned direction around the magnetic hole N and the magnetic pole S, and the current density is low around the magnetic poles and high between the magnetic poles, and the generated energy density is high between the magnetic poles. Therefore, the temperature of the recording film 14 between the magnetic poles can be increased.

〔Effect of the invention〕

According to the present invention, since the disk can be preheated over a wide range, it is possible to speed up recording and erasing.

[Brief explanation of drawings]

Figure 1 is an equipment configuration diagram of one embodiment of the present invention, and Figure 2 is a diagram of the equipment configuration of an embodiment of the present invention.
Supplementary explanatory diagram of the embodiment shown in the figure, FIG. 3 is a device configuration diagram of the second embodiment of the present invention, FIG. 4 is an example of a track address on a disk, and FIG. 5 is a diagram of the third embodiment of the present invention. 6 is an explanatory diagram of a disk suitable for carrying out the present invention, FIG. 7 is a partially enlarged view of the disk, FIG. 8 is an example of another disk, and FIG. 9 is a fourth embodiment of the present invention. FIG. 10 is a configuration diagram of the embodiment. FIG. 11 is a detailed diagram of FIG. 9, FIG. 12 is a configuration diagram of the fifth embodiment of the present invention, FIGS. 13 and 14 are diagrams of other embodiments including humidity detection, and FIG. 15 is a diagram of the present invention. A block diagram showing the concept of the invention, Fig. 16 is a configuration diagram of an optical memory medium, Fig. 17 is a diagram of the principle of eddy current generation, Fig. 18 is a time chart showing the recording and erasing method, and Fig. 19 is a diagram of magnetic flux generation. Principle diagram, No. 20
The figure shows a magnetic pole structure suitable for the present invention.

Claims (1)

[Claims] 1. In an optical memory device whose optical characteristics change due to heating of the medium, the device has a means for generating a change in magnetic flux, heats the memory medium by induced current loss generated by the change in magnetic flux, and changes the contents of the memory. optical memory device. 2. An optical memory device whose optical characteristics change due to heating of a medium, characterized by comprising a wide area heating means such as an induced current due to a change in magnetic flux and a minute part heating means such as a laser. 3. An optical memory device whose optical characteristics change due to heating of the medium, characterized in that an N magnetic pole and an S magnetic pole are arranged on the same surface of the optical memory medium.