JPH0721898B2 - Magneto-optical recording / reproducing method - Google Patents
Magneto-optical recording / reproducing methodInfo
- Publication number
- JPH0721898B2 JPH0721898B2 JP13316184A JP13316184A JPH0721898B2 JP H0721898 B2 JPH0721898 B2 JP H0721898B2 JP 13316184 A JP13316184 A JP 13316184A JP 13316184 A JP13316184 A JP 13316184A JP H0721898 B2 JPH0721898 B2 JP H0721898B2
- Authority
- JP
- Japan
- Prior art keywords
- recording
- magnetic field
- magnetization
- magneto
- light
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
- G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
- G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
- G11B11/10532—Heads
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
- G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
- G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
Description
【発明の詳細な説明】 〔発明の利用分野〕 本発明は、光磁気デイスクフアイル装置に係り、特に情
報の再生時に、記録媒体上に照射できる再生光パワーを
増大させ、大きな信号光量を得るのに好適な光磁気デイ
スク装置に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk file device, and particularly, at the time of reproducing information, increases the reproducing light power that can be irradiated onto a recording medium to obtain a large amount of signal light. The present invention relates to a suitable magneto-optical disk device.
情報の記録時に磁化反転領域の不必要な広がりを制限す
るために磁化反転制限磁界を印加する方式が、例えば特
公昭58−16276号公報に提案されている。この方式は、
記録時の光ビーム照射と外部磁場印加に関するものであ
り、再生時についての外部磁場印加までは配慮されてい
ない。For example, Japanese Patent Publication No. 58-16276 proposes a method of applying a magnetization reversal limiting magnetic field in order to limit the undesired expansion of the magnetization reversal region during recording of information. This method
This relates to the irradiation of the light beam and the application of the external magnetic field during recording, and no consideration is given to the application of the external magnetic field during reproduction.
本発明の目的は、磁気光学効果を利用して情報の再生を
行なう光磁気デイスク装置において、記録時に形成され
た磁化ドメイン周囲からの反磁場を、外部から印加する
弱い消去方向の磁場によつて相殺し、再生時に照射する
光パワーに対する該磁化ドメインの熱磁気的安定性を向
上させ、記録媒体からの反射光量の増加を図ることによ
り、SN比の高い再生信号を得る光磁気デイスク装置を提
供することにある。An object of the present invention is, in a magneto-optical disk device for reproducing information by utilizing a magneto-optical effect, a demagnetizing field from around a magnetization domain formed at the time of recording by a weak erasing direction magnetic field applied from the outside. Provided is a magneto-optical disk device that offsets and improves the thermomagnetic stability of the magnetized domain against the optical power emitted during reproduction and increases the amount of light reflected from the recording medium to obtain a reproduction signal with a high SN ratio. To do.
〔発明の概要〕 上記の目的を達成するために、本発明では情報の再生を
行なう際に弱い消去磁場を記録媒体に印加しておくこと
を特徴とする。記録時に作成された磁化ドメインの磁化
方向は、未記録部の磁化方向とは逆方向であるため、未
記録部からの反磁場の作用により、再生光が照射される
部分の磁化ドメイン周囲は、記録方向の磁場が発生する
ため、再生光パワーの増大に伴ない記録状態が乱されて
しまう危険性が高くなる。再生光パワーを増大させるこ
とは、反射光量の直接的な増加となるため、再生信号の
信号対雑音比（SN比）を向上させるには、少しでも大き
な再生光パワーの照射が有利となる。すなわち記録媒体
からの反射光量の縁対的な増加は、信号検出系の持つ雑
音レベルの影響を少なくする効果となり、等価的に雑音
レベルを低減させることになる。再生光パワーを増大さ
せるほど、磁化ドメインの熱的安定性は低下する。そこ
で磁気的な安定性を向上させる必要がある。未記録部か
らの反磁場は記録磁場方向として働く。本発明では再生
時にも消去磁場を印加し、磁化ドメインの反磁場を相殺
する。これにより、外部から全く磁場を印加せずに再生
するときよりも、大きな再生光パワーの照射を可能に
し、本発明の目的である再生信号のSN比の向上が達成で
きる。SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is characterized in that a weak erasing magnetic field is applied to a recording medium when information is reproduced. Since the magnetization direction of the magnetization domain created at the time of recording is the opposite direction to the magnetization direction of the unrecorded portion, due to the action of the demagnetizing field from the unrecorded portion, the periphery of the magnetization domain of the portion irradiated with the reproduction light Since a magnetic field in the recording direction is generated, there is a high risk that the recording state will be disturbed as the reproduction light power increases. Increasing the reproduction light power directly increases the amount of reflected light, and therefore, in order to improve the signal-to-noise ratio (SN ratio) of the reproduction signal, irradiation of the reproduction light power as large as possible is advantageous. That is, a marginal increase in the amount of light reflected from the recording medium has the effect of reducing the effect of the noise level of the signal detection system, and equivalently reduces the noise level. As the reproducing light power is increased, the thermal stability of the magnetized domain decreases. Therefore, it is necessary to improve magnetic stability. The demagnetizing field from the unrecorded portion acts as the recording magnetic field direction. In the present invention, an erasing magnetic field is applied even during reproduction to cancel the demagnetizing field of the magnetization domain. As a result, it is possible to irradiate a larger reproduction light power than when reproducing without applying a magnetic field from the outside, and it is possible to achieve the improvement of the SN ratio of the reproduction signal, which is the object of the present invention.
以下、本発明の一実施例を第１図，第２図および第３図
により説明する。An embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 3.
第１図は、本発明の光磁気デイスク装置の一実施例を示
したものである。図において１は光磁気デイスクであ
り、垂直磁化膜（記録媒体）２が作成されている。デイ
スク１は、回転モータ３により回転している。記録膜２
への情報の記録，消去，再生は以下のように行なわれ
る。FIG. 1 shows an embodiment of the magneto-optical disk device of the present invention. In the figure, reference numeral 1 is a magneto-optical disk, on which a perpendicularly magnetized film (recording medium) 2 is formed. The disk 1 is rotated by a rotary motor 3. Recording film 2
Recording, erasing, and reproducing of information on / from are performed as follows.
半導体レーザ４から出射した光はカツプリングレンズ５
により平行光束に変換され、偏光プリズム６を透過した
後、対物レンズ７で記録膜２上に微小スポツトとして集
光される。対物レンズ７は、デイスク１の上下振れに追
従して移動させるためのボイスコイル８に取付けられて
いる。情報を記録する場合は、記録すべき情報信号で半
導体レーザ４の駆動電流を変調し、記録膜２の温度を記
録パルスで局所的に上昇させる。記録膜２の温度が或る
温度、例えばキユリー温度あるいは保償点温度以上にな
るとその部分の磁化が失なわれるので、その時、電磁コ
イル９により、記録膜２の未記録部の磁化とは逆方向の
磁場を印加すれば、光照射された部分だけが、周囲とは
逆向きの磁化を持つ、いわゆる磁化ドメインが形成され
る。情報を消去するには、光照射と同時に、記録時とは
逆方向の磁場を電磁コイル９で発生させることにより、
磁化ドメインの磁化を元に戻せばよい。情報の再生は、
記録膜２の磁化方向に対応して、入射光の偏光方向がわ
ずかに回転する効果を利用して行なう。この効果は、磁
化光学効果と呼ばれているものであり、カー効果はその
一つである。記録膜２からの反射光は、対物レンズ７を
通り、偏光プリズム６で反射され、検光子10に導びかれ
る。検光子は、或る特定の偏光成分だけを透過させる性
質を持つので磁化ドメインの有無に対応する偏光面の回
転は、光量の変化に変換される。光量の変化は、光検出
器12で検知され、電気信号に変換される。ここで11は、
光検出器12へ信号光を集光させるためのレンズである。
電気信号に変換された後、増幅器13で増幅され、再生信
号となる。The light emitted from the semiconductor laser 4 is coupled to the coupling lens 5
Is converted into a parallel light flux by the laser beam and transmitted through the polarization prism 6, and then is condensed by the objective lens 7 as a minute spot on the recording film 2. The objective lens 7 is attached to a voice coil 8 for moving the disk 1 following up-and-down shake of the disk 1. When recording information, the drive current of the semiconductor laser 4 is modulated by the information signal to be recorded, and the temperature of the recording film 2 is locally raised by the recording pulse. When the temperature of the recording film 2 reaches a certain temperature, for example, the Curie temperature or the compensation point temperature, the magnetization of that portion is lost. At that time, the electromagnetic coil 9 reverses the magnetization of the unrecorded portion of the recording film 2. When a magnetic field in the direction is applied, a so-called magnetization domain is formed in which only the light-irradiated portion has a magnetization in the opposite direction to the surroundings. To erase information, a magnetic field in the opposite direction to that at the time of recording is generated by the electromagnetic coil 9 at the same time as light irradiation,
It suffices to return the magnetization of the magnetization domain to the original. Information reproduction is
This is performed by utilizing the effect that the polarization direction of the incident light slightly rotates corresponding to the magnetization direction of the recording film 2. This effect is called the magnetization optical effect, and the Kerr effect is one of them. The reflected light from the recording film 2 passes through the objective lens 7, is reflected by the polarization prism 6, and is guided to the analyzer 10. Since the analyzer has a property of transmitting only a specific polarization component, the rotation of the polarization plane corresponding to the presence or absence of the magnetization domain is converted into the change of the light quantity. The change in the amount of light is detected by the photodetector 12 and converted into an electric signal. Where 11 is
A lens for focusing the signal light on the photodetector 12.
After being converted into an electric signal, it is amplified by the amplifier 13 and becomes a reproduction signal.
次に、記録膜２の磁化方向、および反磁場について説明
する。第２図は、記録膜２の磁化方向が記録に伴なつて
反転する様子と、その時、周囲の磁化によつて発生する
反磁場の様子を模式的に示したものである。（ａ）は、
未記録状態の記録膜２の磁化方向を矢線で示したもので
ある。ここに光パルスの照射と同時に、記録膜２の磁化
方向とは逆向きの記録磁場を印加する。すると（ｂ）で
示したように、その部分だけが周囲とは逆向きの磁化を
持つようになる。これが磁化ドメイン21である。磁化ド
メイン21の形成に伴ない、周囲からは、矢線22で示した
ように反磁場が発生する。この反磁場の方向は、記録磁
場と同一方向として磁化ドメイン21に作用する。したが
って記録膜２に照射する再生光パワーを上げていくと磁
化ドメイン21、およびその周囲の磁化が乱されてしまう
ことになる。そこで（ｃ）に示したような弱消去磁場を
印加すれば、反磁場を相殺することができる。これによ
り、再生光パワーを若干増大させても、記録状態の熱磁
気的な安定性は確保されることになる。再生光パワーを
増大させることは、反射光量の増加になるため、再生信
号の絶対レベルの増加により、光検出器12、増幅器13の
持つ雑音レベルを等価的に低減させることができる。Next, the magnetization direction of the recording film 2 and the demagnetizing field will be described. FIG. 2 schematically shows a state in which the magnetization direction of the recording film 2 is reversed with recording and a state of a demagnetizing field generated by the surrounding magnetization at that time. (A) is
The magnetization direction of the unrecorded recording film 2 is shown by the arrow. Simultaneously with the irradiation of the optical pulse, a recording magnetic field opposite to the magnetization direction of the recording film 2 is applied. Then, as shown in (b), only that portion has the opposite magnetization to the surroundings. This is the magnetization domain 21. With the formation of the magnetization domain 21, a demagnetizing field is generated from the surroundings as shown by the arrow line 22. The direction of this demagnetizing field acts on the magnetization domain 21 in the same direction as the recording magnetic field. Therefore, when the reproducing light power with which the recording film 2 is irradiated is increased, the magnetization of the magnetization domain 21 and its surroundings will be disturbed. Therefore, the demagnetizing field can be canceled by applying a weak erasing magnetic field as shown in (c). As a result, the thermomagnetic stability of the recorded state can be ensured even if the reproduction light power is slightly increased. Increasing the reproduction light power increases the amount of reflected light, so that the noise level of the photodetector 12 and the amplifier 13 can be reduced equivalently by increasing the absolute level of the reproduction signal.
第３図は、横軸に再生光パワーの強度をとり、縦軸に外
部印加磁場の強度をとつたグラフである。第３図では、
印加磁場強度零を中心として、上方向に消去磁場、下方
向に記録磁場の方向をとつている。情報の記録，消去を
行なうには、光パルス照射による熱と、外部からの磁場
とを同時に記録膜２に印加するが、反磁場の発生を考慮
すると記録・消去の可能領域，不能領域は、外部磁場が
零の軸を対称に分布するのではなく、反磁場に相当する
磁場強度の分だけ消去磁場方向にシフトする。いま、外
部から全く磁場を印加しない場合に記録状態が乱されな
い限界の再生光パワーをP1とする。ここで反磁場を打ち
消すために、反磁場と同じ大きさで、方向は逆の磁場Ec
を印加する。この磁場Ecは、記録膜２上に形成された磁
化ドメイン21にとつては、見かけの磁場を零にする効果
になるので、記録状態を乱さずに照射できる再生光パワ
ーはP2まで増大することになる。結局P1とP2の差の分だ
け記録膜２へ照射できる光パワーを増やすことが可能に
なつたわけである。数値例を挙げると、記録あるいは消
去時に印加する外部磁場が200Oe（エルステツド）必要
で、記録膜面上で5mWの光パルスの照射により記録，消
去が達成される材料に対して、数十Oe（エルステツド）
の消去磁場をEcとして印加することにより、約2mWの再
生光パワー照射まで記録状態が安定であつた。無磁場再
生時の最大許容再生光パワーに対して、少なくとも十数
％の許容再生光パワーの増大を図ることができた。この
効果は、反射率の低い多層膜構造の光磁気デイスクで特
に有効である。反射光量の低下を極力抑止し、しかも力
−回転角増大の効果を反映できる。FIG. 3 is a graph in which the horizontal axis represents the reproducing light power intensity and the vertical axis represents the intensity of the externally applied magnetic field. In Figure 3,
The erase magnetic field is upward and the recording magnetic field is downward with the applied magnetic field strength of zero. In order to record and erase information, heat due to light pulse irradiation and a magnetic field from the outside are applied to the recording film 2 at the same time. Considering the generation of a demagnetizing field, the recordable and erasable areas are: The external magnetic field is not symmetrically distributed about the axis of zero, but is shifted in the direction of the erasing magnetic field by the magnetic field strength corresponding to the demagnetizing field. Now, let P 1 be the limit of the reproducing light power that does not disturb the recording state when no magnetic field is applied from the outside. Here, in order to cancel the demagnetizing field, a magnetic field Ec with the same magnitude as the demagnetizing field but the opposite direction is obtained.
Is applied. This magnetic field Ec has the effect of reducing the apparent magnetic field to zero for the magnetization domain 21 formed on the recording film 2, so that the reproducing light power that can be applied without disturbing the recording state increases to P 2 . It will be. Eventually, the optical power that can be applied to the recording film 2 can be increased by the difference between P 1 and P 2 . To give a numerical example, an external magnetic field applied at the time of recording or erasing needs to be 200 Oe (elsted), and several tens of Oe ( Elsted)
By applying the erasing magnetic field of Ec as Ec, the recording state was stable until the reproducing light power irradiation of about 2 mW. It was possible to increase the permissible reproducing light power by at least 10% with respect to the maximum permissible reproducing light power during the non-magnetic field reproduction. This effect is particularly effective in a magneto-optical disk having a multilayer film structure having a low reflectance. It is possible to suppress the decrease in the amount of reflected light as much as possible and to reflect the effect of increasing the force-rotation angle.
以上、本発明の実施例につき述べたが、本発明は、第１
図に示した装置構成のみに限定されるものではなく、例
えば外部磁場を対物レンズ７側から印加しても良く、さ
らに記録膜２の磁化方向はどちら向きであつても、第２
図で示した磁場関係が満足されるならば、差支えない。The embodiments of the present invention have been described above.
The present invention is not limited to the device configuration shown in the figure. For example, an external magnetic field may be applied from the objective lens 7 side, and the magnetization direction of the recording film 2 may be either the second direction or the second direction.
It does not matter if the magnetic field relationships shown in the figure are satisfied.
〔発明の効果〕 本発明によれば、光磁気デイスクに情報を再生する際に
も、弱い消去方向の磁場を印加することにより、磁化ド
メインに対する周囲の反磁場を相殺し、記録状態を乱す
ことなく記録膜上に照射できる光パワーの増大を図るこ
とができる。これにより再生信号光量を増大させること
ができるので再生信号のSN比を高める効果がある。EFFECTS OF THE INVENTION According to the present invention, even when information is reproduced on a magneto-optical disk, a weak magnetic field in the erasing direction is applied to cancel the demagnetizing field around the magnetization domain and disturb the recording state. It is possible to increase the optical power that can be irradiated onto the recording film without the need. As a result, the reproduction signal light amount can be increased, which has the effect of increasing the SN ratio of the reproduction signal.
第１図は本発明の光磁気デイスク装置の構成図、第２図
は、記録膜の磁化方向を示す断面図、第３図は、記録・
消去状態と、光パワーおよび外部磁場との関係を示すグ
ラフである。 １……光磁気デイスク、２……記録膜、４……半導体レ
ーザ、10……検光子、21……磁化ドメイン、22……反磁
場。FIG. 1 is a block diagram of a magneto-optical disk device of the present invention, FIG. 2 is a sectional view showing the magnetization direction of a recording film, and FIG.
It is a graph which shows the relationship between an erased state, optical power, and an external magnetic field. 1 ... Magneto-optical disk, 2 ... Recording film, 4 ... Semiconductor laser, 10 ... Analyzer, 21 ... Magnetization domain, 22 ... Demagnetizing field.
Claims (1)
行ない、磁気光学効果を利用して情報の再生を行なう光
磁気記録再生方法において、再生時に消去方向の外部磁
場を印加し、記録媒体上に形成された磁化ドメイン周囲
の反磁場を相殺することを特徴とする光磁気記録再生方
法。1. A magneto-optical recording / reproducing method for recording and erasing information by utilizing a thermomagnetic effect and reproducing information by utilizing a magneto-optical effect, wherein an external magnetic field in the erasing direction is applied during reproduction, A magneto-optical recording / reproducing method characterized by canceling a demagnetizing field around a magnetization domain formed on a recording medium.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13316184A JPH0721898B2 (en) | 1984-06-29 | 1984-06-29 | Magneto-optical recording / reproducing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13316184A JPH0721898B2 (en) | 1984-06-29 | 1984-06-29 | Magneto-optical recording / reproducing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6113461A JPS6113461A (en) | 1986-01-21 |
| JPH0721898B2 true JPH0721898B2 (en) | 1995-03-08 |
Family
ID=15098113
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13316184A Expired - Lifetime JPH0721898B2 (en) | 1984-06-29 | 1984-06-29 | Magneto-optical recording / reproducing method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0721898B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2576106B2 (en) * | 1987-01-26 | 1997-01-29 | ソニー株式会社 | Magneto-optical recording / reproducing device |
| JP2573281B2 (en) * | 1988-02-05 | 1997-01-22 | 株式会社東芝 | Magneto-optical disk playback method |
| JPH04167244A (en) * | 1990-10-30 | 1992-06-15 | Matsushita Electric Ind Co Ltd | Recording, reproducing and erasing method for magneto-optical recording medium and apparatus for the same |
-
1984
- 1984-06-29 JP JP13316184A patent/JPH0721898B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6113461A (en) | 1986-01-21 |
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