JPS6299936A - Photomagnetic type recording and reproducing medium - Google Patents
Photomagnetic type recording and reproducing mediumInfo
- Publication number
- JPS6299936A JPS6299936A JP23763585A JP23763585A JPS6299936A JP S6299936 A JPS6299936 A JP S6299936A JP 23763585 A JP23763585 A JP 23763585A JP 23763585 A JP23763585 A JP 23763585A JP S6299936 A JPS6299936 A JP S6299936A
- Authority
- JP
- Japan
- Prior art keywords
- recording
- reproducing medium
- thin film
- address
- signal
- 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.)
- Pending
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2407—Tracks or pits; Shape, structure or physical properties thereof
- G11B7/24085—Pits
-
- 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
-
- 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
- G11B11/10582—Record carriers characterised by the selection of the material or by the structure or form
Abstract
Description
【発明の詳細な説明】
〔発明の技術分野〕
本発明は、記録・再生可能な光磁気ディスク等の光磁気
型記録再生媒体に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magneto-optical recording/reproducing medium such as a magneto-optical disk capable of recording and reproducing information.
〔発明の技術的背景およびその問題点〕従来より、この
種の光磁気型記録再生媒体として例えば第４図に示すよ
うな光磁気ディスクが知られている。この光磁気ディス
クによれば、中央にターンテーブルにクランプするため
の中心孔２を有した基板１に、例えばアモルファス磁性
薄膜からなり、光・熱・磁気効果により情報を記録・再
生する記録再生媒体薄膜４ （第５図参照）が形成され
ている。[Technical Background of the Invention and Problems Thereof] Conventionally, a magneto-optical disk as shown in FIG. 4, for example, has been known as this type of magneto-optical recording/reproducing medium. According to this magneto-optical disk, a recording/reproducing medium is formed of, for example, an amorphous magnetic thin film on a substrate 1 having a center hole 2 in the center for clamping to a turntable, and records and reproduces information using light, heat, and magnetic effects. A thin film 4 (see FIG. 5) is formed.
記録再生媒体薄膜４が形成された側の基板１の面には記
録領域５とプリアドレス領域６が周方向に交互に形成さ
れていて、該記録領域５にはアドレス情報の無い連続的
グループ（プリグループ）２３のみが光学スポットのト
ランキング用案内トラックとして形成され、また該プリ
アドレス領域６にはプリアドレスビット７が断続的ピッ
ト列として形成されていて予めアドレス情報が記２！さ
れている。Recording areas 5 and pre-address areas 6 are formed alternately in the circumferential direction on the surface of the substrate 1 on the side on which the recording/reproducing medium thin film 4 is formed, and the recording areas 5 include continuous groups ( Only the pre-group (23) is formed as a guide track for trunking the optical spot, and in the pre-address area 6, pre-address bits 7 are formed as intermittent pit rows and address information is recorded in advance. has been done.
しかしながら、上記光磁気ディスクでは、記録領域５と
プリアドレス領域６が交互に形成されていて、プリアド
レス領域６には一定面積を必要とするために記録領域５
の面積が充分に確保できず、このため記憶容量が限られ
、またプリアドレス領域６でなければアドレス情報を読
み取ることができないために検索速度を向上させること
が困難であった。However, in the above magneto-optical disk, the recording area 5 and the pre-address area 6 are formed alternately, and since the pre-address area 6 requires a certain area, the recording area 5
Since a sufficient area could not be ensured, the storage capacity was limited, and address information could only be read from the pre-address area 6, making it difficult to improve the search speed.
本発明の目的は、記録容量の拡大と検索速度の向上を図
ることができる光磁気型記録再生媒体を提供することで
ある。An object of the present invention is to provide a magneto-optical recording and reproducing medium that can increase recording capacity and improve search speed.
本発明は、記録再生媒体薄膜に記録された情報信号と、
プリアドレスビットにより記録されたブリアドレス情報
の検出原理が相違し、プリグループのみからなる記録領
域とブリアドレスピットからなるプリアドレス領域を分
けて設けなくても記録再生媒体薄膜に記録された情報を
読み取ることが可能であることに着目してなされたもの
である。The present invention provides an information signal recorded on a recording/reproducing medium thin film;
The principle of detecting the bria address information recorded by the pre-address bits is different, and the information recorded on the thin film of the recording/reproducing medium can be detected without separately providing a recording area consisting only of pre-groups and a pre-address area consisting of bria address pits. This was done with a focus on being readable.
すなわち、本発明は、光学スポットのトラッキング用室
内トラックを有した基板の該トランキング用案内トラッ
クが形成された面に光・熱・磁気効果により記録・再生
する記録再生媒体薄膜を形成してなる光磁気型記録再生
媒体ににおいて、前記基板の記録再生媒体薄膜が形成さ
れた面全体を記録領域とすると共に、前記案内トラック
に、光・熱・磁気効果により記録再生媒体薄膜に記録さ
れる情報信号と異なる情報信号（アドレス情報信号、デ
ィスク回転サーボのための同期信号、記録領域に記録さ
れる情報信号の同期信号、あるいは該情報信号とは全く
無関係の情ＩＩ信号等）を光強度変調信号として読出し
可能な形態で形成してなることを特徴としている。That is, in the present invention, a recording/reproducing medium thin film for recording and reproducing by optical, thermal, and magnetic effects is formed on the surface of a substrate having an indoor track for tracking an optical spot, on which the guide track for trunking is formed. In a magneto-optical recording and reproducing medium, the entire surface of the substrate on which the recording and reproducing medium thin film is formed is used as a recording area, and information is recorded on the recording and reproducing medium thin film in the guide track by light, heat, and magnetic effects. An information signal different from the signal (address information signal, synchronization signal for disk rotation servo, synchronization signal of the information signal recorded in the recording area, information II signal completely unrelated to the information signal, etc.) is converted into a light intensity modulation signal. It is characterized in that it is formed in a form that can be read as.
以下本発明の一実施例を図面を参照して説明する。 An embodiment of the present invention will be described below with reference to the drawings.
第１図は本発明の光磁気型記録再生媒体をディスク形状
にした例を示している。図中符号１はディスク基板で、
その中央部にターンテーブルにクランプするための中心
孔２が形成されている。FIG. 1 shows an example of the magneto-optical recording/reproducing medium of the present invention in the form of a disk. Reference number 1 in the figure is a disk substrate.
A center hole 2 for clamping to a turntable is formed in the center thereof.
また、ディスク基板１の一方の面には光学的スポットで
あるレーザ光束のトラッキング用案内トラック３と、光
・熱・磁気効果により記録・再生する記録再生媒体薄膜
４が形成されて（第２図参照）、この面全体が記録領域
５になっていると共に、プリアドレス等の領域６になっ
ている。Further, on one surface of the disk substrate 1, there are formed a guide track 3 for tracking the laser beam, which is an optical spot, and a recording/reproducing medium thin film 4 for recording and reproducing information using light, heat, and magnetic effects (see Fig. 2). ), this entire surface serves as a recording area 5, as well as an area 6 for pre-address, etc.
この記録再生媒体薄膜４は、蒸着等の手段により形成さ
れるもので、例えばアモルファス磁性薄膜からなり、光
・熱・磁気効果により情報が記録・再生される。すなわ
ち、レーザ光束により温度上昇させると共に、外部磁場
用コイル２１ （第３図参照）により磁力を変化させる
ことにより、磁化反転させたり、あるいはそのまま磁気
モーメントを保磁させることができ、これを利用して情
報が高密度で記録され、また記録した情報が消去される
。また、情報を記録した記録再生媒体薄膜４にレーザ光
束を照射すると、その反射光が磁気モーメントの方向に
より異なった方向に偏光され、これを利用して情報が再
生される。The recording and reproducing medium thin film 4 is formed by means such as vapor deposition, and is made of, for example, an amorphous magnetic thin film, and information is recorded and reproduced by light, heat, and magnetic effects. In other words, by increasing the temperature with the laser beam and changing the magnetic force with the external magnetic field coil 21 (see Figure 3), the magnetization can be reversed or the magnetic moment can be kept as is. information is recorded at high density, and the recorded information is also erased. Furthermore, when the recording/reproducing medium thin film 4 on which information is recorded is irradiated with a laser beam, the reflected light is polarized in different directions depending on the direction of the magnetic moment, and information is reproduced using this polarization.
トラッキング用案内トラック３には、光強度変調信号と
して読出し可能な凸状のプリアドレスビット７が断続的
に形成されている。このブリアドレスピット７の断続的
ビット列によりアドレス情報信号、ディスク回転サーボ
のための同期信号、記録再生媒体薄膜３に記録される情
報信号の同期信号、あるいは該情報信号とは全く無関係
の情報信号等がディスク基板１に予め記録されている。Convex pre-address bits 7 that can be read out as light intensity modulation signals are intermittently formed on the tracking guide track 3. The intermittent bit string of the Briaddress pit 7 can be used to generate an address information signal, a synchronization signal for disk rotation servo, a synchronization signal for an information signal recorded on the recording/reproducing medium thin film 3, or an information signal completely unrelated to the information signal. is recorded on the disk substrate 1 in advance.
なお、ブリアドレスピット７は凹状でもよく、また記録
再生媒体薄膜４上に保護膜、エンハンス膜等を設けたて
もよく、またディスク基板１を二枚貼り合わせて構成し
てもよい。The bridle pits 7 may be concave, a protective film, an enhancement film, etc. may be provided on the recording/reproducing medium thin film 4, or two disc substrates 1 may be bonded together.
第３図は上記光磁気ディスクを記録・再生する装置であ
る。この装置では、ＬＤドライブ回路８により半導体レ
ーザ９を動作して、該半導体レーザ９からレーザ光束を
出射させ、このレーザ光束をレンズ１０、ハーフミラ−
１１、レンズ１２を介して基板１の記録再生媒体薄膜４
に集束させると、該記録再生媒体薄膜４で反射された反
射レーザ光束がハーフミラ−１１からハーフミラ−１３
に導びかれて該ハーフミラ−１３で二つの反射レーザ光
束に分割される。FIG. 3 shows an apparatus for recording and reproducing the above-mentioned magneto-optical disk. In this device, a semiconductor laser 9 is operated by an LD drive circuit 8 to emit a laser beam from the semiconductor laser 9, and this laser beam is transferred to a lens 10, a half mirror, etc.
11. Recording/reproducing medium thin film 4 on substrate 1 via lens 12
When the laser beam is focused on the recording/reproducing medium thin film 4, the reflected laser beam is reflected from the half mirror 11 to the half mirror 13.
The beam is guided by the half mirror 13 and split into two reflected laser beams.
一方の反射レーザ光束は検光子１４に導かれ、該検光子
１４でカー効果による偏光面回転成分が光強度変調成分
に変換された後、レンズ１５を介して光検出器１６に集
光されて該光検出器１６で電気信号に変換され、アンプ
１７により増幅されて情報信号Ｓ２となる。One reflected laser beam is guided to the analyzer 14, where the polarization plane rotation component due to the Kerr effect is converted into a light intensity modulation component, and then focused on the photodetector 16 via the lens 15. It is converted into an electrical signal by the photodetector 16 and amplified by the amplifier 17 to become an information signal S2.
また、他方の反射レーザ光束はレンズアッセンブリ１８
によりフォーカスエラー検出、トラッキングエラー検出
に適した幾何学的変形を与えられた後、光検出器１９に
集光されて該光検出器１９で電気信号に変換され、アン
プ２０で増幅されてブリアドレスビット７による光変調
成分のみが検出されてフォーカスエラー信号Ｓｆ、トラ
ッキングエラー信号Ｓｔ、アドレス情報Ｓ１となる。こ
のアドレス情報Ｓ１により所望のトラッキング用案内ト
ラック３の位置を検索し、外部磁場用コイル２１との共
動作用により記録再生媒体薄膜４にレーザ光束により熱
を加え、また外部磁場用コイル２１により磁場を加えて
情報を記録、消去、再生する。Further, the other reflected laser beam is transmitted to the lens assembly 18.
After being given geometrical deformation suitable for focus error detection and tracking error detection, the light is focused on a photodetector 19 and converted into an electrical signal by the photodetector 19, which is amplified by an amplifier 20 and sent to the bridle address. Only the light modulation component by bit 7 is detected and becomes the focus error signal Sf, tracking error signal St, and address information S1. The position of the desired tracking guide track 3 is searched using this address information S1, heat is applied to the recording/reproducing medium thin film 4 by a laser beam in cooperation with the external magnetic field coil 21, and the magnetic field is applied by the external magnetic field coil 21. to record, erase, and reproduce information.
情報信号Ｓ２には記録再生媒体薄膜４に記録された磁気
モーメントによる偏光面回転成分のほかにプリアドレス
ビット７による光強度変調成分も含まれているため、例
えばＳ２／５１＝３３なる信号を生成する除算器２２に
よってプリアドレスビット７による光強度変調成分を除
いて、記録再生媒体薄膜４に記録された情報信号３２’
のみを取り出す。なお、情報信号Ｓ２からプリアドレス
ビット７による光強度変調成分を除く手段としては除算
器２２に限定されない。Since the information signal S2 includes a polarization plane rotation component due to the magnetic moment recorded on the recording/reproducing medium thin film 4, as well as a light intensity modulation component due to the pre-address bit 7, a signal such as S2/51=33 is generated, for example. The information signal 32' recorded on the recording/reproducing medium thin film 4 is divided by the divider 22 to remove the light intensity modulation component due to the pre-address bit 7.
Take out only. Note that the means for removing the light intensity modulation component by the pre-address bit 7 from the information signal S2 is not limited to the divider 22.
上記実施例では、ブリアドレス等を記録するのにプリア
ドレスビット７ （位相ビット）を使用した場合を示し
たが、これ以外に例えば反射率変化を与える孔のような
ものでもよい。In the above embodiment, the pre-address bit 7 (phase bit) is used to record the briar address, etc., but it may also be a hole that changes the reflectance.
また、予め記録する情報としてアドレス情報等以外にト
ラッキングのパイロット信号等も考えられる。この場合
には、例えばピット列とピント列との間（ランド部）に
光磁気情報を記録する。Furthermore, in addition to address information and the like, tracking pilot signals and the like may also be considered as information to be recorded in advance. In this case, magneto-optical information is recorded, for example, between the pit row and the focus row (land portion).
また、光磁気型記録再生媒体としてディスク形状のもの
について示したが、例えばシート、ドラム形状にしても
よい。Furthermore, although a disk-shaped magneto-optical recording/reproducing medium is shown, it may be sheet-shaped or drum-shaped, for example.
以上説明したように本発明によれば、基板のｌランキン
グ用案内トラックが形成された面の全体が記録領域とな
っているため、記憶容量を増大することができる。また
、トランキング用案内トランクの全域に、光・熱・磁気
効果により記録再生媒体薄膜に記録される情報信号と異
なる情報信号（アドレス情報信号、ディスク回転サーボ
のための同期信号、記録領域に記録される情報信号の同
期信号あるいは該情報信号とは全く無関係の情報信号等
）を光強度変調信号として読出し可能な形態で形成して
なるので、情報検索速度を向上させることができ、また
Ｃ Ｌ Ｖ （Ｃｏｎｓｔａｎｔ ＬｉｎｅａｒＶｅｌ
ｏｃｉｔｙ）記録再生が容易になり、ジッターの低減化
、記録・消去可能範囲の微細領域化、異種情報の同時読
み取り等が可能となる。As described above, according to the present invention, the entire surface of the substrate on which the l-ranking guide track is formed serves as a recording area, so that the storage capacity can be increased. In addition, information signals (address information signals, synchronization signals for disk rotation servo, etc. for disk rotation servo, recorded in the recording area) that are different from the information signals recorded on the thin film of the recording/reproducing medium are recorded in the entire area of the trunking guide trunk by optical, thermal, and magnetic effects. Since the synchronization signal of the information signal to be used or the information signal completely unrelated to the information signal) is formed in a form that can be read as a light intensity modulation signal, the information retrieval speed can be improved, and the C L V (Constant LinearVel
(ocity) Recording and reproducing becomes easier, jitter can be reduced, recording/erasing range can be made finer, different types of information can be read simultaneously, etc.
第１図は本発明の一実施例を示す斜視図、第２図は一部
切欠して示した部分拡大斜視図、第３図は本発明の光磁
気型記録再生媒体を記録・再生させる装置のブロック図
、第４図は従来の光磁気ディスクの斜視図、第５図は同
部分拡大斜視図である。
１・・・基板（ディスク基板）、３・・・トラッキング
用案内トラック、４・・・記録再生媒体薄膜、５・・・
記録領域、６・・・ブリアドレス等の領域。
特許出願人 パイオニア株式会社
第４図
第５図FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a partially enlarged perspective view with a part cut away, and FIG. 3 is an apparatus for recording and reproducing the magneto-optical recording/reproducing medium of the present invention. 4 is a perspective view of a conventional magneto-optical disk, and FIG. 5 is an enlarged perspective view of the same portion. DESCRIPTION OF SYMBOLS 1... Substrate (disk substrate), 3... Guide track for tracking, 4... Recording/reproducing medium thin film, 5...
Recording area, 6... area for Bri address, etc. Patent applicant: Pioneer Corporation Figure 4 Figure 5
Claims (1)
板の該案内トラックが形成された面に光・熱・磁気効果
により記録・再生する記録再生媒体薄膜を形成してなる
光磁気型記録再生媒体において、前記基板の記録再生媒
体薄膜が形成された面全体を記録領域とすると共に、前
記案内トラックに、光・熱・磁気効果により記録再生媒
体薄膜に記録される情報信号と異なる情報信号を光強度
変調信号として読出し可能な形態で形成してなることを
特徴とする光磁気型記録再生媒体。A magneto-optical recording/reproducing medium comprising a substrate having a guide track for tracking an optical spot, and a recording/reproducing medium thin film for recording/reproducing by optical, thermal, or magnetic effects formed on the surface on which the guide track is formed. The entire surface on which the thin film of the recording and reproducing medium is formed is a recording area, and an information signal different from the information signal recorded on the thin film of the recording and reproducing medium is transmitted to the guide track as a light intensity modulation signal by optical, thermal, and magnetic effects. A magneto-optical recording and reproducing medium characterized in that it is formed in a readable form.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23763585A JPS6299936A (en) | 1985-10-25 | 1985-10-25 | Photomagnetic type recording and reproducing medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23763585A JPS6299936A (en) | 1985-10-25 | 1985-10-25 | Photomagnetic type recording and reproducing medium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS6299936A true JPS6299936A (en) | 1987-05-09 |
Family
ID=17018246
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23763585A Pending JPS6299936A (en) | 1985-10-25 | 1985-10-25 | Photomagnetic type recording and reproducing medium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6299936A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62234250A (en) * | 1986-03-20 | 1987-10-14 | Nec Home Electronics Ltd | Magneto-optical recording and reproducing device |
| JPS62164626U (en) * | 1986-04-07 | 1987-10-19 | ||
| JPH01286154A (en) * | 1988-05-13 | 1989-11-17 | Ricoh Co Ltd | Optical disk substrate |
| JPH03187040A (en) * | 1989-12-11 | 1991-08-15 | Internatl Business Mach Corp <Ibm> | Optomagnetic disc reader, detection of signal recorded on optomagnetic disc and optomagnetic disc |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5977648A (en) * | 1982-10-26 | 1984-05-04 | Sharp Corp | Photomagnetic storage element |
| JPS6018831A (en) * | 1983-07-12 | 1985-01-30 | Canon Inc | Optical recording medium |
-
1985
- 1985-10-25 JP JP23763585A patent/JPS6299936A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5977648A (en) * | 1982-10-26 | 1984-05-04 | Sharp Corp | Photomagnetic storage element |
| JPS6018831A (en) * | 1983-07-12 | 1985-01-30 | Canon Inc | Optical recording medium |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62234250A (en) * | 1986-03-20 | 1987-10-14 | Nec Home Electronics Ltd | Magneto-optical recording and reproducing device |
| JPS62164626U (en) * | 1986-04-07 | 1987-10-19 | ||
| JPH01286154A (en) * | 1988-05-13 | 1989-11-17 | Ricoh Co Ltd | Optical disk substrate |
| JPH03187040A (en) * | 1989-12-11 | 1991-08-15 | Internatl Business Mach Corp <Ibm> | Optomagnetic disc reader, detection of signal recorded on optomagnetic disc and optomagnetic disc |
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