JPH0927165A - Optical disk recording / reproducing method and optical disk - Google Patents

Abstract

(57) [Abstract] [Problem] Even for overwritable optical discs,
Provided is a recording / reproducing device capable of recording or reproducing even on an optical disc which cannot be overwritten. SOLUTION: An optical disc is irradiated with laser light to reproduce information recorded in a predetermined area, and the optical disc is an overwritable optical disc or an unoverwritable optical disc based on the reproduced information. If it is determined that the optical disc cannot be overwritten, the erasing operation is performed before the information is recorded on the disc, and if it is determined that the optical disc can be overwritten, the recording is performed. The erase operation is not performed before performing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overwritable optical disk and a recording / reproducing apparatus therefor.

[0002]

2. Description of the Related Art Recently, an optical recording / reproducing method satisfying various requirements including high density, large capacity, high access speed, and high recording / reproducing speed, and a recording apparatus, reproducing apparatus and recording medium used therefor. Efforts are being made to develop. Among a wide range of optical recording / reproducing methods, the magneto-optical recording / reproducing method has the unique advantage that information can be recorded and then erased, and that new information can be recorded again and again. For, is full of the greatest charm.

A magneto-optical recording disk (medium) used in this magneto-optical recording / reproducing method has a magnetic film composed of one layer or multiple layers as a layer for recording. The magnetic film is a perpendicular magnetic film (perpendicular film) with high recording density and high signal strength.
magnetic layer or layers) have been developed and are being used. Such a magnetized film is made of, for example, amorphous GdFe or
It is composed of GdCo, GdFeCo, TbFe, TbCo, TbFeCo and the like. The perpendicular magnetic film generally has concentric or spiral tracks, and information is recorded on the tracks.

[Principle of Mark Formation] In the formation of marks, the characteristic of the laser, that is, the excellent coherence in terms of space and time is advantageously used, and it is almost the same as the diffraction limit determined by the wavelength of laser light. The beam is narrowed down to a small spot. The narrowed light is irradiated to the track surface, heats the recording film, and the diameter of the recording film is 1 μm.
Information is recorded by forming marks of m or less. In optical recording, theoretically about 10 ⁸ marks / cm
Recording densities up to ² can be achieved. This is because the laser beam can be concentrated into a spot with a diameter as small as about its wavelength.

In magneto-optical recording, a laser beam (L) is focused on a perpendicularly magnetized film (MO) and heated. Meanwhile, the recording magnetic field (Hb) in the opposite direction to the initialized direction is externally applied to the heated portion.
Then, the coercive force Hc (coers of the locally heated portion)
activity) decreases and becomes smaller than the recording magnetic field (Hb). As a result, the magnetization of that portion is aligned in the direction of the recording magnetic field (Hb). In this way, the oppositely magnetized mark is formed.

[Principle of Reproduction] Light is an electromagnetic wave having an electromagnetic field vector normally diverging in all directions on a plane perpendicular to the optical path. Light is converted to linearly polarized light (LP),
Then, when the perpendicular magnetic film (MO) is irradiated, the light is reflected on the surface thereof or transmitted through the perpendicular magnetic film (MO). At this time, the polarization plane rotates according to the direction of the magnetization M. This rotating phenomenon is called the magnetic Kerr effect or the magnetic Faraday effect.

For example, if the plane of polarization of the reflected light is "A direction"
Rotation of θ K degrees with respect to magnetization causes rotation of −θ K degrees with respect to “inverse A direction” magnetization. Therefore, if the axis of the optical analyzer (polarizer) is set perpendicular to the plane tilted by -θK, the light reflected from the mark (B0) magnetized in the "inverse A direction" will pass through the analyzer. I can't. On the other hand, the mark (B
The light reflected from 1) is multiplied by (sin2θk) ² and passes through the analyzer, where it is captured by the detector (photoelectric conversion means). As a result, the mark (B1) magnetized in the "A direction" appears brighter than the mark (B0) magnetized in the "reverse A direction", and generates a strong electric signal at the detector. Therefore, the electrical signal from this detector is modulated according to the recorded information, so that the information is reproduced.

[Light Intensity Modulation Overwrite] However, in conventional magneto-optical recording, since heat generated by laser light is used for recording, it is necessary to erase the recorded portion once. In magnetic recording, a new signal can be recorded without erasing, that is, so-called overwriting is possible, whereas in magneto-optical recording, there is a drawback that re-recording takes time.

However, if the direction of the recording magnetic field Hb can be freely modulated as required, overwriting is possible. However, it is impossible to modulate the direction of the recording magnetic field Hb at a high speed. For example, the recording magnetic field H
When b is a permanent magnet, it is necessary to mechanically reverse the direction of the magnet, but it is impossible to reverse the magnet at high speed. Even when the recording magnetic field Hb is an electromagnet, it is difficult to modulate the direction of a large-capacity current at such a high speed.

However, the technological progress has been remarkable, and the magneto-optical recording method is capable of overwriting by simply modulating the intensity of the irradiation light beam without modulating the intensity of the recording magnetic field Hb according to the binary information to be recorded. And an overwritable magneto-optical recording medium used therefor and an overwritable recording device also used therein have been invented and applied for a patent. (JP-A-62-175948 = DE3,619,618A1 =
This invention will be described below.

In the basic invention, "a memory layer (hereinafter, M layer) basically consisting of a magnetic thin film capable of perpendicular magnetization and a recording layer (hereinafter W layer) consisting of a magnetic thin film capable of perpendicular magnetization are included, and both layers are exchanged. An overwritable multi-layered magneto-optical recording medium which is coupled and is capable of directing only the magnetization of the W layer to a predetermined direction without changing the magnetization direction of the M layer at room temperature is used.

Then, information is expressed by the direction of magnetization in the M layer and recording is performed. The M layer and W layer are generally composed of an alloy of a rare earth metal and a transition metal. The exchange coupling force acts in the direction of aligning the sublattice magnetizations of the transition metal and the sublattice magnetizations of the rare earth metal. This medium is W
The magnetization direction of the layers can be aligned in one direction. Moreover,
At that time, the magnetization direction of the M layer is not reversed, and further, the magnetization direction of the W layer once aligned in one direction is not reversed even when the exchange coupling force from the M layer is received, and conversely, the magnetization direction of the M layer is reversed. The direction of magnetization is W
It does not reverse even when it receives exchange coupling force from the layers. And W
The layer has a lower coercive force Hc and a higher Curie point T than the M layer.
has c.

According to the recording method of the basic invention, in the recording medium, only the direction of magnetization of the W layer is aligned in one direction by the initialization means before recording. The initialization means may use a magnetic field from the outside, or the medium itself may have the initialization means. Then, the medium is irradiated with the laser beam pulse-modulated according to the binarized information. The intensity of the laser beam has a high level PH and a low level PL. This low level is higher than the reproduction level PR applied to the medium during reproduction. At this time, the recording magnetic field Hb is applied to the medium portion irradiated with the laser beam.

When the initialized medium is irradiated with a laser beam of low level PL, the temperature of the medium rises and M
The coercive force of the layer is very small or extremely zero.
It becomes zero when the temperature of the medium is equal to or higher than the Curie point of the M layer. At this time, the coercive force of the W layer is sufficiently large and is not reversed by the recording magnetic field Hb. Then, since an exchange coupling force acts from the W layer to the M layer, the sub-lattice magnetization of the M layer follows the initialized sub-lattice magnetization of the W layer. When the irradiation of the laser beam is stopped from this state, the temperature of the medium is lowered, but the direction of the sublattice magnetization of the M layer is not changed.

On the other hand, when the laser beam of high level PH is irradiated, the temperature of the medium rises higher than that at the time of irradiation of the PL laser beam, exceeds the Curie point of the M layer, and the coercive force of the M layer becomes zero. The coercive force will be very small or extremely zero. The magnetization of the W layer having a reduced coercive force is reversed by the recording magnetic field Hb. When the irradiation of the laser beam is stopped, the temperature of the medium drops, and when the temperature becomes equal to or lower than the Curie point of the M layer, the magnetization of the M layer appears following the inverted sublattice magnetization of the W layer. Further, even if the medium temperature is lowered, the direction of the sub-lattice magnetization of the M layer does not change. At this time, the direction of the sub-lattice magnetization of the M layer is opposite to that in the case of irradiating the PL level laser beam.

As described above, low level PL and high level P L
By irradiating the laser beam of H 2, the magnetization direction of the M layer is determined without depending on the magnetization direction of the original M layer.
Overwriting is possible because the layers do not have to be erased before re-recording. The medium used in the light modulation overwrite method has a multi-layer structure including an M layer and a W layer. The M layer is a magnetic layer having a large coercive force and a low magnetization reversal temperature at room temperature. The W layer is a magnetic layer having a relatively higher magnetization reversal temperature than the M layer. The M layer and the W layer may themselves be composed of a multilayer film. In some cases, an intermediate layer may be present between the M layer and the W layer. Further, an initialization layer for initializing the W layer may be provided adjacent to the W layer.

[Recording / reproducing apparatus for magneto-optical recording disk] As a recording / reproducing apparatus for an optical disk using a magneto-optical recording / reproducing system, a disk and a recording / reproducing apparatus which cannot be overwritten by optical modulation are currently put into practical use. On the other hand, a disc and a recording / reproducing device which can be overwritten by optical modulation using an exchange coupling film have been put into practical use.

[0018]

Conventionally, in order to record and reproduce an optical disc capable of optical modulation overwrite, a recording / reproduction device dedicated to the optical modulation overwrite has been required. Further, in order to record and reproduce on an optical disc that cannot be overwritten, a non-overwrite-dedicated recording / reproducing device is required. For this reason, when recording and reproducing both an optical modulation overwritable optical disk and an optical overwritable optical disk, there is a problem that two optical disk recording / reproducing devices must be prepared.

It is an object of the present invention to provide a recording / reproducing apparatus capable of recording or reproducing information on an overwritable optical disk or an optical disk which cannot be overwritten.

[0020]

In order to solve the above-mentioned problems, a recording / reproducing method of the present invention irradiates an optical disc with a laser beam to reproduce information recorded in a predetermined area, and from the reproduced information, It is determined whether the optical disc is an overwritable optical disc or a non-overwritable optical disc, and if it is determined that the optical disc is not overwritable, the optical disc is erased before recording information on the disc. When it is determined that the optical disc is an overwritable optical disc, the erasing operation is not performed before recording.

If it is determined that the optical disc cannot be overwritten, the laser light intensity for erasing and the laser light intensity for recording are set, and if it is determined that the optical disc is an overwritable optical disc. The laser light intensity at the time of recording may be set. Further, the recording / reproducing method of the present invention reproduces the information recorded in a predetermined area by irradiating the optical disc with a laser beam, and based on the reproduced information, the optical disc is an optical disc that cannot be overwritten. It is determined whether the optical disc is overwritable and requires an initialization magnet at the time of recording, or whether the optical disc is overwritable and does not require an initialization magnet at the time of recording, and the optical disc cannot be overwritten. If it is determined that the initializing magnet is away from the optical disc, and the erasing operation is performed before the information is recorded on the disc, the optical disc that can be overwritten and needs the initializing magnet at the time of recording. If it is determined that there is an overwrite magnet, the erase magnet is not performed before recording while the initialization magnet is close to the optical disk. If initialization magnet be possible bets during recording is judged to be unnecessary optical disc, a state alienated initialization magnet from the optical disc, and it was decided not to perform erasing operation before performing recording.

The optical disc of the present invention is an optical disc capable of overwriting information by optical modulation, and information indicating that information can be overwritten is recorded on the recording surface. And In addition, the information indicating that the information can be overwritten,
It may be recorded by a magneto-optical signal.

Further, the information indicating that information can be overwritten may be recorded by a change in reflectance. Further, the information indicating that information can be overwritten may be recorded by changing the depth of the pit. Further, the optical disc of the present invention is an optical disc capable of overwriting information by optical modulation, and whether or not a magnet for initializing the recording surface is required before overwriting information is checked. It is assumed that the information shown is recorded on the recording surface.

The information indicating whether or not a magnet for initializing the recording surface is necessary may be recorded by a magneto-optical signal. Further, the information indicating whether or not a magnet for initializing the recording surface is necessary may be recorded by the reflectance change. Further, the information indicating whether or not a magnet for initializing the recording surface is necessary may be recorded by changing the depth of the pit.

[0025]

[Embodiment 1] FIG. 1 is a flowchart showing a start-up operation of an optical disk recording / reproducing apparatus according to this embodiment. FIG.
FIG. 4 is a vertical sectional view showing a state in which the initialization magnet is retracted from the optical disc in the optical disc recording / reproducing apparatus according to the present embodiment.

FIG. 3 is a vertical sectional view showing a state in which the initialization magnet approaches the optical disc in the optical disc recording / reproducing apparatus according to the present embodiment. The optical disc 1 is housed in an optical disc cartridge 2. An insertion slot 13 is provided in the front panel 7 of the housing 9 of the optical disk recording / reproducing apparatus. The insertion port 13 is normally closed by the lever panel 8. By pushing the optical disk cartridge 2 into the insertion slot 13, the lever panel 8 opens inward of the housing 9, and the optical disk cartridge 2 is loaded into the housing 9. Then, the optical pickup 3 moves to the innermost peripheral area of the optical disc 1. FIG. 2 shows this state. Then, the spindle motor 4 starts rotating, and the optical disk 1 also starts rotating accordingly. When the optical disc 1 reaches a predetermined number of rotations, the optical pickup 3 emits laser light (not shown) having a predetermined light intensity. The reflected light reflected by the optical disc 1 is used to perform the focusing operation of the laser light on the surface of the disc medium. Further, a tracking operation for following the track formed on the optical disc is performed.

Further, in this apparatus, the exhaust fan 5 for preventing the temperature inside the housing 9 from rising due to the heat generated from the electric substrate 6 provided with an electric circuit and the like and the heat generating source of the electric substrate 6 and the like. Is provided. FIG. 4 shows the structure of the recording surface of the optical disc for overwrite. A plurality of concentric circular or spiral recording tracks are provided on the recording surface of the overwrite optical disc (the plurality of tracks are not shown in FIG. 4). One track is divided into a plurality of areas called sectors. Each sector is mainly composed of a user data area 21 and an address information area 22. The data used by the user is written in the user data area 21 of each sector.

Information about the disc is written in the innermost track (information area 23) of these recording areas. In FIG. 4, it is pre-recorded in the information area 23 that overwriting by optical modulation is possible by means of pits that change in depth when the optical disc is manufactured. For an overwritable optical disk, information indicating whether an initialization magnet is necessary or not at the time of overwriting recording is also recorded in the information area 23 by pits accompanied by a depth change.

The optical pickup 3 reproduces a pit signal recorded in the information area 23 located in the innermost circumference of the optical disc, which is accompanied by a change in depth. This makes it possible to identify whether the rotating optical disc is an optical disc that can be overwritten or an optical disc that cannot be overwritten. When the optical disc is capable of overwriting at the same time, it is determined whether or not the initialization magnet is necessary during overwriting recording.

When it is determined that the optical disc cannot be overwritten, the initialization magnet 10 is kept in a retracted state from the optical disc until the optical disc is taken out from the optical disc recording / reproducing apparatus (state of FIG. 2). .
Then, when performing the recording operation of the optical disc which cannot be overwritten, it is necessary to perform the erasing operation in advance before the recording operation. On the other hand, when it is determined that the optical disc is an optical disc that can be overwritten and the initialization magnet 10 is an unnecessary optical disc at the time of overwriting, the initialization magnet 10 retains the state retracted from the optical disc. Then, when the recording operation is performed until the optical disk is taken out from the optical disk recording / reproducing apparatus, the recording operation is performed without performing the erasing operation. In addition, when it is determined that the initialization magnet 10 is an overwritable optical disk that requires the initialization magnet 10 during overwriting, the initialization magnet 10 is a motor for moving the initialization magnet to a position where a predetermined magnetic field can be applied to the optical disk. It moves by 11 (state of FIG. 3). Then, the initialization magnet 10 remains at that position until the optical disk is taken out from the optical disk recording / reproducing apparatus. Then, when the recording operation is performed, the recording operation is performed after the optical disk is initialized by the initialization magnet 10.

The operation of the apparatus configured as described above will be described with reference to FIG. First, the optical disk cartridge 2 is inserted (S101). The optical pickup 3 is moved to the inner circumference side of the optical disc 1 (S102). The spindle motor 4 is activated to start the rotation of the optical disc 1 (S
103). When the spindle motor 4 is in steady rotation (S104), laser light is emitted from the optical pickup 3 and is irradiated onto the recording surface of the optical disc 1 (S105).
Focusing pull-in control is performed by the reflected light from the optical disc 1, and focusing control is performed so that the laser beam converges on the recording surface of the optical disc 1 (S10).
6). Further, tracking pull-in control is performed by the reflected light from the optical disc 1, and tracking control is performed so that the irradiation position of the laser beam on the recording surface of the optical disc 1 can follow the track (S107). Then, the irradiation position of the laser light is aligned with the innermost track, and the information area 2
The information recorded in No. 3 is reproduced (S108).

Based on the reproduced information, it is determined whether or not the optical disc is a disc capable of optical modulation overwriting (S1).
09). If the disc cannot be overwritten, the intensity of the laser beam at the time of recording on the optical disc is set to the non-overwrite recording power (S110). Further, the intensity of the laser beam when erasing the information recorded on the optical disc is set to the erasing power for non-overwriting (S11).
1). Then, the optical pickup 3 is moved to the area to be recorded, and the erasing operation is performed (S112). Next, an operation of recording information in the erased area is performed (S113). The information recording operation is completed as described above (S114).

When it is determined that the optical disk is a light modulation overwritable disk, it is further determined from the information reproduced from the information area 23 whether or not the initialization magnet is required at the time of overwriting. Yes (S1
15). If it is determined that the disc does not require the initialization magnet, the initialization magnet 10 remains in the state of being retracted from the optical disc 1. Then, the intensity of the laser beam at the time of recording on the optical disc is set to the recording power for overwriting (S116). Since the erase operation is not necessary, it is not necessary to set the erase power. Then, the optical pickup 3 is moved to the area to be recorded, and the operation of recording information is performed (S117). The information recording operation is completed as described above (S118).

If it is determined that the disk does not require the initialization magnet, the initialization magnet moving motor 11 moves the initialization magnet 10 to bring it closer to the optical disk 1 (S1).
19). In this way, by bringing the initialization magnet 10 closer to the optical disc, the recording surface of the rotating optical disc is initialized, and the state becomes overwritable. Next, the intensity of the laser beam at the time of recording on the optical disc is set to the recording power for overwriting (S120). Since the erase operation is not necessary, it is not necessary to set the erase power.
Then, the optical pickup 3 is moved to the area to be recorded, and the operation of recording information is performed (S121). The information recording operation is completed as described above (S122).

In the present embodiment, information indicating whether overwriting is possible or not, whether the initialization magnet is necessary or not, is recorded in the pit with depth. Although the case has been described, this information may be recorded by a magneto-optical signal or a signal with a change in reflectance. Further, in this embodiment, the case where this information is recorded in the innermost peripheral area of the disc has been described, but it may be recorded in any position of the disc.

[0036]

[Embodiment 2] FIG. 5 is a flow chart showing a start-up operation of an optical disk reproducing apparatus according to the present embodiment. In this embodiment, no initialization magnet is provided in the optical disk recording / reproducing apparatus. This apparatus can record and reproduce an optical disc that cannot be overwritten and an optical disc that can be overwritten and does not require an initialization magnet.
Further, this apparatus can only perform reproduction and cannot perform recording operation on an overwrite optical disc that requires an initialization magnet.

FIG. 6 is a vertical sectional view showing an optical disk recording / reproducing apparatus according to this embodiment. The optical disc 1 is housed in an optical disc cartridge 2. An insertion slot 13 is provided in the front panel 7 of the housing 9 of the optical disk recording / reproducing apparatus. The insertion port 13 is normally closed by the lever panel 8. By pushing the optical disk cartridge 2 into the insertion slot 13,
The lever panel 8 opens inward of the housing 9, and the optical disk cartridge 2 is loaded into the housing 9. Then, the optical pickup 3 moves to the innermost peripheral area of the optical disc 1. FIG. 6 shows this state. Then, the spindle motor 4 starts rotating, and the optical disk 1 also starts rotating accordingly. When the optical disc 1 reaches a predetermined number of rotations, the optical pickup 3 emits laser light (not shown) having a predetermined light intensity. The reflected light reflected by the optical disc 1 is used to perform the focusing operation of the laser light onto the disc medium surface. Further, a tracking operation for following the track formed on the optical disc is performed.

Further, in this apparatus, the exhaust fan 5 for preventing the temperature inside the housing 9 from rising due to the heat generated from the electric substrate 6 provided with an electric circuit and the like and the heat generating source of the electric substrate 6 and the like. Is provided. As described with reference to FIG. 4, in the innermost peripheral area of the overwritable optical disc, information indicating that overwriting is possible by optical modulation is recorded in advance by the pits that change in depth. Similarly, information on whether the disc requires an initialization magnet or not at the time of overwriting recording is also recorded in a pit with a change in depth in the innermost peripheral region of the disc.

The optical pickup 3 reproduces a pit signal in the innermost circumference of the optical disc with a change in depth. This reproduction signal makes it possible to identify whether the currently rotating optical disc is an optical disc that can be overwritten or an optical disc that cannot be overwritten. In the case of an overwritable optical disc, it is possible to identify whether the initialization magnet is necessary or not at the time of overwriting recording. When it is determined that the optical disc cannot be overwritten as a result of the identification, the erasing operation is performed before the recording operation until the optical disc is ejected from the optical disc reproducing apparatus.

When it is determined that the optical disk is an overwritable optical disk that does not require the initialization magnet, the recording operation is performed without performing the erasing operation until the optical disk is ejected. 5, the processing in S201 to S218 is the same as the processing in S101 to S118 in FIG.
On the other hand, if it is determined that the optical disk is an overwritable optical disk that requires the initialization magnet, the recording operation cannot be performed. Therefore, the recording operation is prohibited and only the reproducing operation is performed (S219).

As described above, in the present embodiment, information indicating whether overwriting is possible or not, whether the initialization magnet is necessary or not, is recorded in the pit with depth. However, this information may be recorded by a magneto-optical signal or a signal with a change in reflectance. Further, although the present embodiment has described the case where this information is recorded in the innermost peripheral area, it may be recorded in any position of the optical disc.

As described above, according to the above-described embodiment, by reading the information recorded on the optical disc with the optical pickup, it is determined whether the optical disc is an overwritable optical disc or an unwritable optical disc. It is possible to identify whether an initialization magnet is needed or not. As a result, it becomes possible to record and reproduce an optical disc that can be overwritten and an optical disc that cannot be overwritten by one optical disc recording / reproducing device.

Further, since the optical pickup is used as the identification method, it is not necessary to newly add identification means to the optical disc recording / reproducing apparatus.

[Brief description of drawings]

FIG. 1 is a flow chart of a start-up operation of an optical disc recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the optical disk recording / reproducing apparatus according to the first embodiment of the present invention in a state where the initialization magnet is retracted from the optical disk.

FIG. 3 is a vertical cross-sectional view showing a state in which the initializing magnet approaches the optical disc in the optical disc recording / reproducing apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a recording surface of the optical disc according to the first embodiment of the present invention.

FIG. 5 is a flowchart of a start-up operation of the optical disc recording / reproducing apparatus according to the second embodiment of the present invention.

FIG. 6 is a vertical sectional view of an optical disc recording / reproducing apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 1 ... Optical disc 2 ... Optical disc cartridge 3 ... Optical pickup 4 ... Spindle motor 5 ... Fan 6 ... Electrical board 7 ... Front panel 8 ... Lever panel 9 ... Housing 10 ... Initializing magnet 11 ... Initializing magnet moving motor 12 ... Recording magnet 13 ... Inserting port 21 ... User data area 22 ... Address information area 23 ... Information region

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 11/10 586 9296-5D G11B 11/10 586A 19/02 501 19/02 501A (72) Invention Hiroyuki Matsumoto 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (11)

[Claims] 1. An optical disc is irradiated with a laser beam to reproduce information recorded in a predetermined area, and the optical disc is an overwritable optical disc or an unoverwritable optical disc according to the reproduced information. If it is determined that the optical disc cannot be overwritten, the erase operation is performed before the information is recorded on the disc, and if the optical disc is determined to be the overwritable optical disc, A recording / reproducing method for an optical disc, wherein an erasing operation is not performed before recording. 2. If it is determined that the optical disc cannot be overwritten, the laser light intensity for erasing and the laser light intensity for recording are set, and if it is determined that the optical disc is overwritable. The optical disk recording / reproducing method according to claim 1, wherein the laser light intensity at the time of recording is set. 3. An optical disc is irradiated with a laser beam to reproduce information recorded in a predetermined area, and the optical disc is an overwritable optical disc or an overwritable optical disc according to the reproduced information. Disc is determined whether it is an optical disc that requires an initialization magnet during recording or an optical disc that can be overwritten and does not require an initialization magnet during recording, and if it is determined that the optical disc cannot be overwritten. , It is determined that the initialization magnet is away from the optical disc and the erasing operation is performed before the information is recorded on the disc and the optical disc is overwritable and needs the initialization magnet at the time of recording. If the initializing magnet is close to the optical disc, and the erasing operation is not performed before recording, overwriting is possible. When it is determined that the initialization magnet is an optical disk that does not require the initialization magnet during recording, the recording / reproduction of the optical disk is characterized in that the erasing operation is not performed before the recording while the initialization magnet is kept away from the optical disk. Method. 4. An optical disk capable of overwriting information by optical modulation, wherein information indicating that information can be overwritten is recorded on a recording surface. 5. The optical disc according to claim 4, wherein the information indicating that information can be overwritten is recorded by a magneto-optical signal. 6. The optical disc according to claim 4, wherein the information indicating that information can be overwritten is recorded by a change in reflectance. 7. The optical disc according to claim 4, wherein the information indicating that information can be overwritten is recorded by changing the depth of the pits. 8. An optical disk capable of overwriting information by optical modulation, wherein information indicating whether or not a magnet for initializing a recording surface is required before overwriting information is provided. An optical disc recorded on the recording surface. 9. The optical disk according to claim 8, wherein the information indicating whether or not a magnet for initializing the recording surface is necessary is recorded by a magneto-optical signal. 10. The optical disc according to claim 8, wherein the information indicating whether or not a magnet for initializing the recording surface is necessary is recorded by a change in reflectance. 11. The optical disk according to claim 8, wherein the information indicating whether or not a magnet for initializing the recording surface is necessary is recorded by a change in pit depth.