JP4040116B2 - Disk device, data transmission device and DC level measuring circuit - Google Patents

Description

の関係式で表される値ＡＳをアシンメトリーと呼び、以下、データ長により直流レベルが変化している程度をこのアシンメトリーＡＳで表す。従ってデータ長により直流レベルが変化していない場合、アシンメトリーＡＳは５０〔％〕になる。
【００５２】
このため直流レベル測定回路１４は、この再生信号ＭＯをエンベロ−プ検波回路２２に入力し、ここで再生信号ＭＯをエンベロープ検波する。すなわちエンベロープ検波回路２２は、図８に示すように、再生信号ＭＯの上側エンベロープ検出結果ＥＵと下側エンベロープ検出結果ＥＬを得、これら上側エンベロープ検出結果ＥＵ及び下側エンベロープ検出結果ＥＬを基準レベル生成回路２３に出力する。
【００５３】
ここでこの基準レベル生成回路２３は、抵抗値の等しい抵抗を、この実施例では８本直列接続して形成され、この直列回路の両端にそれぞれ上側エンベロープ検出結果ＥＵと下側エンベロープ検出結果ＥＬとを入力し、各抵抗の接続中点を選択回路２４の各接点に接続する。これにより直流レベル測定回路１４は、上側エンベロープ検出結果ＥＵと下側エンベロープ検出結果ＥＬとで決まる信号レベルを８本の抵抗で分圧し、その結果得られる分圧電圧Ｂ０〜Ｂ６を選択回路２４に出力する。
【００５４】
選択回路２４は、この分圧電圧Ｂ０〜Ｂ６を順次所定周期で選択し、その選択出力を比較回路２５の非反転入力端に出力する。この比較回路２５は、ヒステリシス特性を有し、反転入力端に再生信号ＭＯを入力するようになされている。これにより比較回路２５は、選択された分圧電圧Ｂ０〜Ｂ６を基準にして再生信号ＭＯを２値化し、その２値化結果をカウンタ２６に出力する。
【００５５】
カウンタ２６は、ゲート信号発生回路２７から出力されるリセット信号ＲＴによりリセットされた後、ゲート信号ＧＴを基準にして、比較回路２５の出力信号について、その信号レベルの立ち上がりをカウントし、このカウント値ＣＴを出力する。
【００５６】
この一連の処理につき光磁気ディスク装置１においては、試し書き領域に規定のシリアルデータＤ２を繰り返し記録し、さらにゲート信号発生回路２７からこのシリアルデータＤ２の繰り返し周期に同期した周期でリセット信号ＲＴ及びゲート信号ＧＴが出力されることにより、カウンタ２６は、書き込み領域に試し書きした再生信号ＭＯの繰り返し周期でこのカウント動作を繰り返し、選択回路２４は、この繰り返し周期に同期して順次接点を切り換える。
【００５７】
この場合図８に示すように、選択回路２４において分圧電圧Ｂ１が選択された場合と分圧電圧Ｂ２が選択された場合とでは、再生信号ＭＯの信号レベルが分圧電圧Ｂ２の信号レベルを横切る回数の方が多いことにより、カウンタ２６のカウント値においては、分圧電圧Ｂ２が選択された場合の方がカウント値ＣＴが多くなる。また、この場合再生信号ＭＯを２値化するしきい値としては、カウント値ＣＴの多い分圧電圧Ｂ２の方が適切と判断することができる。
【００５８】
これにより図９に示すように、カウンタ２６を介して得られるカウント値ＣＴは、再生信号ＭＯのアシンメトリーＡＳが５０〔％〕のとき、上側エンベロープ検出結果ＥＵと下側エンベロープ検出結果ＥＬとの中間の信号レベルでなる分圧電圧Ｂ３を選択した場合にカウント値ＣＴが最も大きくなり、比較回路２５の比較基準がこの分圧電圧Ｂ３から遠ざかるとその分値も小さくなる。
【００５９】
また再生信号ＭＯのアシンメトリーＡＳが５０〔％〕からずれているとき、その分分圧電圧Ｂ３から変位した分圧電圧を選択したとき、カウント値ＣＴが最も大きくなり、この分圧電圧から比較基準が遠ざかるとその分値も小さくなる。従ってカウント値ＣＴが最も大きくなる分圧電圧を検出して再生信号ＭＯのアシンメトリーＡＳを検出することができる。
【００６０】
従ってこの種のデータ伝送装置において、この検出したアシンメトリーＡＳに基づいて、データ発生源の条件、伝送系２０の条件、再生時のしきい値等を調整して最適な伝送条件を選択し、これにより直流成分を含むような変調方式を選択した場合でも、再生信号を正しく２値化することができる。
【００６１】
このため光磁気ディスク装置１において、システム制御回路は、このカウンタ２６のカウント値ＣＴを順次取り込んだ後、このカウント値ＣＴが最も立ち上がる分圧電圧Ｂ０〜Ｂ６を検出する。このときシステム制御回路は、図９について上述したカウント値ＣＴを曲線近似して最大値を検出し、これにより離散的な分圧電圧Ｂ０〜Ｂ６に対して、高い精度でアシンメトリーＡＳを検出する。
【００６２】
さらにシステム制御回路は、書き込み領域で検出されたこのアシンメトリーＡＳに基づいて、書き込み用の光量及びレーザービームを書き込み用の光量に立ち上げる期間を算定し、これによりアシンメトリーＡＳがほぼ５０〔％〕になる書き込みの条件を算出する。続いてシステム制御回路は、記録データ処理回路１１及び駆動回路１２に制御コマンドを送出し、これにより続くデータ記録時、算定した条件によりシリアルデータＤ２を光磁気ディスク２に記録する。
【００６３】
これにより光磁気ディスク装置１においては、データ長に応じて直流レベルが変動する伝送系を介してシリアルデータＤ２を再生する場合でも、この直流レベルが最適に保持される条件でシリアルデータＤ２を記録することができ、直流成分を含むような変調方式を選択した場合でも、記録再生系を最適化して再生信号を正しく２値化することができる。
【００６４】
これに対して再生時、光磁気ディスク装置１においては、同様にしてデータの再生に先立って、直流レベル測定回路１４において、再生に供するデータを用いてアシンメトリーＡＳを検出する。さらに光磁気ディスク装置１において、システム制御回路は、このアシンメトリーＡＳの検出結果に基づいて前処理回路５に制御コマンドを発行し、アシンメトリーＡＳが５０〔％〕に近づくように、フィルタリング特性を切り換え、又は比較回路１３のしきい値を最適化する。
【００６５】
すなわち、この種の光磁気ディスク装置においては、光磁気ディスク２を交換する場合があり、この光磁気ディスク装置１で記録したデータを他の光磁気ディスク装置で再生する場合がある。この場合、この実施例のように、直流レベル測定回路１４の測定結果に基づいて書き込み条件を最適化すれば、他の光磁気ディスク装置で再生する場合でも、記録再生系全体として伝送特性を最適化して再生信号ＭＯを正しく２値化することができる。
【００６６】
またこれとは逆に、他の光磁気ディスク装置で記録した光磁気ディスク２をこの実施例に係る光磁気ディスク装置１で再生する場合もあり、この場合、この実施例のようにフィルタリング特性又はしきい値ＳＬを設定することにより、記録系又は再生系全体として伝送特性を最適化して再生信号ＭＯを正しく２値化することができる。
【００６７】
これにより光磁気ディスク装置１は、この光磁気ディスク装置１でデータを記録再生する場合だけでなく、他の光磁気ディスク装置で記録した光磁気ディスク２を再生する場合、さらにはこの光磁気ディスク装置１で記録した光磁気ディスク２を他の光磁気ディスク装置で再生する場合でも、伝送系を最適化して確実に記録したデータを再生できるようになされている。
【００６８】
以上の構成において、外部機器から書き込みのコマンドが入力されると、光磁気ディスク装置１は、光ピックアップ３を試し書き領域に移動させて試し書きし、これにより書き込みの光量が設定される。このとき光磁気ディスク装置１は、規定のデータを規定の条件で繰り返し記録した後、記録したデータを再生し、この再生結果により書き込み条件を選定し、記録再生系を最適化する。
【００６９】
すなわち再生信号ＭＯは、直流レベル測定回路１４において、上側エンベロープ及び下側エンベロープが検出され、基準レベル生成回路２３によりこの上側エンベロープ検出結果ＥＵ及び下側エンベロープ検出結果ＥＬ間の分圧電圧Ｂ０〜Ｂ６が生成される。さらに各分圧電圧Ｂ０〜Ｂ６と再生信号ＭＯとの比較結果がカウンタ２６でカウントされ、このカウント結果によりアシンメトリーＡＳが検出される。
【００７０】
さらにこのアシンメトリーＡＳにより、アシンメトリーＡＳが５０〔％〕になるように、書き込みの光量と、レーザービームを書き込み時の光量に立ち上げる期間とが補正され、最適な書き込み条件に記録再生系が最適化される。
【００７１】
これに対して入出力回路１０を介して外部機器から入力されるデータＤＡＴＡは、記録データ処理回路１１において、所定のブロック単位で誤り訂正符号が附加された後、１−１６変調を受け、シンク、リシンク等のデータが附加されてシリアルデータＤ２に変換される。このシリアルデータＤ２は、駆動回路１２に出力され、これによりこのシリアルデータＤ２の論理レベルに応じてレーザービームの光量が読み出し時の光量から試し書きにより設定された書き込み用の光量に、試し書きにより設定された立ち上がり期間を単位にして間欠的に切り換わり、光磁気ディスク２に順次記録データに対応したピットが形成される。
【００７２】
これに対して外部機器から読み出しのコマンドが入力されると、光ピックアップ３から出力される再生信号ＭＯは、比較回路１３において、しきい値ＳＬを基準にして２値化されて２値化データＤ３が生成され、この２値化データＤ３が、再生データ処理回路１５において、復号された後、誤り訂正処理され、入出力回路１０を介して外部機器に出力される。
【００７３】
この２値化の際、再生信号ＭＯは、直流レベル測定回路１４において、同様にしてアシンメトリーＡＳが検出され、このアシンメトリーＡＳが５０〔％〕になるように、フィルタリング特性が設定され、又は２値化の際のしきい値ＳＬが設定される。
【００７４】
以上の構成によれば、上側エンベロープ及び下側エンベロープを基準にして基準レベル生成回路２３により生成された分圧電圧Ｂ０〜Ｂ６と、再生信号ＭＯとの比較結果をカウンタ２６でカウントし、このカウント結果によりアシンメトリーＡＳを検出することにより、データ長により直流レベルが変化する場合についてもアシンメトリーＡＳを検出することができる。
【００７５】
これによりこの検出したアシンメトリーＡＳを基準にして記録系を最適化し、また再生系を最適化することにより、再生信号ＭＯを正しく２値化データに変換することができる。かくするにつき、記録再生系の周波数帯域を有効に利用して従来に比して記録密度を向上することができる。
【００７６】
（２）他の実施例
なお上述の実施例においては、選択回路２４の接点を順次切り換えてカウント結果を得ることにより、再生信号ＭＯに対してしきい値の信号レベルを順次切り換えて得られるカウント結果を検出する場合について述べたが、本発明はこれに限らず、分圧電圧Ｂ０〜Ｂ６に対応して複数系統の比較回路及びカウンタを配置し、これによりしきい値の信号レベルを切り換えて得られるカウント結果を同時に検出してもよい。
【００７７】
このようにすれば、リアルタイムでアシンメトリーを検出することができることにより、このアシンメトリー検出結果に基づいてリアルタイムでフィルタリング特性又は２値化のしきい値を切り換えることができ、さらに一段と正確に再生信号ＭＯを２値化することができる。
【００７８】
また上述の実施例においては、１−１６変調方式を適用した場合について述べたが、本発明はこれに限らず、種々の変調方式を選択した場合に広く適用することができ、さらには直流成分を伴なわない変調方式を選択した場合にも適用することができる。
【００７９】
さらに上述の実施例においては、本発明を光磁気ディスク装置に適用した場合について述べたが、本発明はこれに限らず、ライトワンス型の光ディスク装置等、種々の光ディスク装置に、さらにはハードディスク装置等の磁気記録再生装置、光ファイバーを用いた光通信装置等のデータ伝送装置に広く適用することができる。
【００８０】
すなわち図１０に示すように、ハードディスク装置等の磁気記録再生装置では、この種の光磁気ディスク装置と同様に、書き込みデータを変調して記録データＲＥＣ（図１０（Ａ））に変換し、この記録データＲＥＣに応じて磁気ヘッドに記録電流を供給する。これにより磁気記録再生装置では、磁気ヘッドの走査軌跡上に順次走査軌跡の方向に連続する磁化領域を形成し（図１０（Ｂ））、書き込みデータをハードディスク等の磁気記録媒体に記録する。
【００８１】
これに対して再生時、磁気記録再生装置は、この磁気ヘッドの走査軌跡を再生ヘッドでトレースし、これにより磁化領域の境界で正及び負に信号レベルがパルス状に立ち上がる再生信号ＰＢを検出し（図１０（Ｃ））、０レベルを間に挟んだ２つのしきい値を基準にしてこの再生信号ＰＢを１、０、−１と判断することにより、再生信号ＰＢを２値化する。従って図１０については、再生信号が０レベルに保持されている状態が論理０、再生信号が１又は−１に変化する状態が論理１を表すことになる。
【００８２】
従って磁気記録再生装置においても、記録密度を向上して符号間干渉が発生すると、結局データ長に応じて、例えばこの論理１に保持されるべき再生信号ＰＢの信号レベルが変化することになる。これによりこの種の磁気記録再生装置に、図１について上述した直流レベル測定回路を適用してアシンメトリーを検出し、このアシンメトリー検出結果に基づいて記録再生系を最適化して再生信号ＰＢを正しく２値化することができる。具体的には、アシンメトリー検出結果に基づいて、記録電流を補正し、また再生信号ＰＢの周波数特性を補正し、さらには再生信号ＰＢを２値化するしきい値を補正して、再生信号ＰＢを正しく２値化することができる。
【００８３】
これに対して光ファイバーを用いた光通信装置においては、図１１に示すように、同様に、書き込みデータを変調して伝送データＤ４（図１１（Ａ））を生成し、この伝送データＤ４に応じてレーザーダイオードを駆動してレーザービームを出射する。これにより光通信装置においては、伝送距離が充分に適切な距離に保持されている場合、伝送データＤ４の論理レベルに対応して、ほぼ０レベルの光量から立ち上がるレーザービーム（図１１（Ｂ））を受光することができ、この受光結果を２値化して伝送データＤ４を再生することができる。
【００８４】
ところが光ファイバーでレーザービームを伝送する場合、光の分散を避けることが困難なことにより、伝送距離が長くなると、光量の立ち上がり及び立ち下がりがなだらかになり（図１１（Ｃ））、ついには振幅方向及び位相方向の双方について、アイパターンの開口が小さくなる。すなわちこの場合、振幅余裕及び位相余裕が伝送距離に応じて低下するようになる（図１１（Ｄ））。
【００８５】
このような特徴を有する光通信装置において、伝送速度を向上することにより符号間干渉が発生すると、結局データ長に応じて、例えばこの論理０に保持されるべきレーザービームの光量が伝送対象側において変化することになる。これによりこの種の光通信装置において、図１について上述した直流レベル測定回路を適用してアシンメトリーを検出し、このアシンメトリー検出結果に基づいて伝送系を最適化して伝送されたデータを正しく再生することができる。具体的には、アシンメトリー検出結果に基づいて、レーザービームの光量を補正し、またレーザービームの照射期間を補正し、さらには受光結果の周波数特性、受光結果を２値化するしきい値を補正して、正しく２値化することができる。
【００８６】
【発明の効果】
上述のように本発明によれば、データ長に応じて直流レベルが変化する場合でも、この直流レベルを検出することができ、またこの検出結果に基づいて記録再生系を最適化するとができ、これにより伝送されたデータを正しく再生することができる。
【図面の簡単な説明】
【図１】本発明の一実施例による光磁気ディスク装置の直流レベル測定回路を示すブロック図である。
【図２】図１の光磁気ディスク装置を示すブロック図である。
【図３】図２の光磁気ディスク装置の動作の説明に供する信号波形図である。
【図４】図２の光磁気ディスク装置において、記録再生系の周波数帯域が充分な場合の再生信号を示す信号波形図である。
【図５】図２の光磁気ディスク装置の実際の周波数特性を示す特性曲線図である。
【図６】図２の光磁気ディスク装置の実際の再生信号を示す信号波形図である。
【図７】アシンメトリーの説明に供する信号波形図である。
【図８】図１の直流レベル測定回路の動作の説明に供する信号波形図である。
【図９】図１の直流レベル測定回路の測定結果を示す特性曲線図である。
【図１０】本発明を磁気記録再生装置に適用した実施例の説明に供する信号波形図である。
【図１１】本発明を光通信装置に適用した実施例の説明に供する信号波形図である。
【符号の説明】
１ 光磁気ディスク装置
２ 光磁気ディスク
３ 光ピックアップ
１３、２５ 比較回路
１４ 直流レベル測定回路
２０ 伝送系
２１ データ発生源
２２ エンベロープ検波回路
２３ 基準レベル生成回路
２６ カウンタ[0001]
[Industrial application fields]
The present invention relates to a disk device, a data transmission device, and a DC level measurement circuit, and can be applied to, for example, a magneto-optical disk device.
[0002]
[Prior art]
Conventionally, a magneto-optical disk device comprising a data transmission device effectively avoids intersymbol interference between successive data, and by selecting recording conditions, the DC level of the reproduction signal is held at a constant value, Thus, the recorded data is surely reproduced.
[0003]
That is, in this type of magneto-optical disk apparatus, the magneto-optical disk has an information recording surface formed by forming a perpendicular magnetization film made of a magnetic film on a predetermined disk-shaped substrate by applying a technique such as sputtering. Further, a protective film is disposed on the information recording surface.
[0004]
With respect to this magneto-optical disk, the magneto-optical disk device intermittently raises the amount of laser beam during recording and irradiates the information recording surface of the magneto-optical disk, and a predetermined modulation magnetic field is applied to the irradiation position of this laser beam. Apply. Thus, the magneto-optical disk apparatus records desired data by applying a thermomagnetic recording method.
[0005]
On the other hand, at the time of reproduction, the magneto-optical disk device irradiates the magneto-optical disk with a linearly polarized laser beam and detects a change in the polarization plane of the return light. The recorded data is reproduced by detecting a reproduction signal whose level changes and binarizing the reproduction signal with a predetermined threshold value. As a result, the magneto-optical disk device reproduces the data recorded on the magneto-optical disk using the magnetic Kerr effect.
[0006]
Therefore, if the DC level of the reproduction signal fluctuates in the magneto-optical disk device, it becomes difficult to correctly binarize the reproduction signal, and eventually it becomes difficult to correctly reproduce the recorded data.
[0007]
For this reason, in the magneto-optical disk apparatus, write data is recorded after being modulated by a predetermined modulation method during recording, and decoding processing corresponding to this modulation method is executed during reproduction. That is, in this modulation processing, after adding an error correction code or the like to write data input from a host computer or the like, the period of logic “H” level is equal to the period of logic “L” level, ie, modulation. For example, EFM (Eight to Fourteen Modulation) modulation is performed on the write data so that the DC level becomes 0 level in the subsequent data string.
[0008]
As a result, the magneto-optical disk device keeps the DC level of the reproduction signal at a constant value during reproduction when the recording data is recorded under the correct conditions.
[0009]
Further, in the magneto-optical disk device, the DC level of the reproduction signal is maintained at a constant value even when the data length of the recording data changes by performing trial writing using the trial writing area formed on the magneto-optical disk in advance. Adjust the light quantity of the laser beam.
[0010]
In other words, in a magneto-optical disk device, by irradiating a laser beam, the temperature of the laser beam irradiation position is raised to be equal to or higher than the Curie temperature of the perpendicular magnetization film, and then the locally heated perpendicular magnetization film becomes a modulated magnetic field during cooling. The recording data is recorded by forming continuous pits with the polarity of the recording data.
[0011]
Therefore, in this type of magneto-optical disk apparatus, the laser beam depends on the Curie temperature of the magnetic material forming the perpendicular magnetization film, the thermal conductivity of the components of the magneto-optical disk, etc. (that is, the sensitivity of the magneto-optical disk). There is a feature that the size of pits to be formed changes depending on the amount of light for writing, the ambient temperature, and the like.
[0012]
In other words, when the ambient temperature is high when the laser beam is irradiated, or when the magneto-optical disk is highly sensitive, the temperature at the laser beam irradiation position quickly rises to the Curie temperature, thereby increasing the amount of laser beam light. Large pits are formed as compared with the case. On the other hand, when the ambient temperature is low, the temperature rise at the laser beam irradiation position is slow, and a small pit is formed as compared with the period in which the light amount of the laser beam is raised.
[0013]
When the size of the pits formed in this way changes, the DC level of the reproduction signal changes according to the data length of the recording data even when the recording data DC level is held at 0 level. . For this reason, the magneto-optical disk apparatus detects an optimum recording condition based on the reproduction result of the trial-written data, and irradiates a laser beam under the recording condition.
[0014]
As a result, in the conventional magneto-optical disk apparatus, the reproduction signal is binarized with a constant threshold value so that the recorded data can be reliably reproduced.
[0015]
[Problems to be solved by the invention]
By the way, if a modulation method that positively uses intersymbol interference is applied as this modulation method, for example, 1-16 modulation method, which is one of the variable length coding methods, the recordable frequency of the spectral magnetic disk is applied. It is considered that the bandwidth can be fully utilized and the recording density of the magneto-optical disk can be improved.
[0016]
However, when the frequency band that can be recorded on the magneto-optical disk is sufficiently utilized by positively utilizing the intersymbol interference in this way, the transmission system of the magneto-optical disk apparatus has a band with a frequency characteristic other than a certain band. Recording and reproduction is performed, and the DC level of the reproduction signal changes according to the data length of the recording data. In this case, in the conventional magneto-optical disk apparatus, it becomes difficult to binarize the reproduction signal correctly by binarizing the reproduction signal whose DC level changes with a certain threshold value.
[0017]
The present invention has been made in consideration of the above points, and intends to propose a disk device, a data transmission device, and a DC level measurement circuit capable of correctly binarizing a reproduction signal even when the DC component fluctuates. Is.
[0018]
[Means for Solving the Problems]
  In order to solve such a problem, in the present invention, an envelope detection circuit for detecting an upper envelope and a lower envelope of an input signal by detecting an input signal input via a transmission system, and an upper envelope and a lower envelope are provided. A threshold setting circuit for setting a threshold value for changing the signal level following the signal levels of the upper envelope and the lower envelope as a reference;A comparison circuit that outputs a comparison result between the threshold value and the input signal, and counts the comparison result.An input signal that is input via the transmission system according to the count result obtained by switching the threshold signal level.Measure DC level ofTo do.
[0019]
  In the second invention, an envelope detection circuit for detecting an upper envelope and a lower envelope of the input signal by detecting an input signal input via the transmission system, and an upper envelope and a lower envelope as a reference. A threshold value setting circuit for setting a threshold value for changing the signal level following the signal levels of the upper envelope and the lower envelope;A comparison circuit that outputs a comparison result between the threshold value and the input signal, and counts the comparison result.With a counter that outputs the count result, and by the count result obtained by switching the signal level of the threshold,Optimize transmission systemTo do.
[0020]
  In the third invention,An envelope detection circuit that detects an input signal input via a transmission system and detects an upper envelope and a lower envelope of the input signal, and an upper envelope and a lower envelope based on the upper envelope and the lower envelope. A threshold value setting circuit that sets a threshold value that changes the signal level following the signal level, a comparison circuit that outputs a comparison result between the threshold value and the input signal, and counts the comparison result. And a signal processing circuit for converting an input signal into serial data, and the signal processing circuit is optimized based on the count result obtained by switching the threshold signal level.
[0021]
  Furthermore, in the fourth invention, an envelope detection circuit for detecting an upper envelope and a lower envelope of the reproduction signal by detecting the reproduction signal obtained by reproducing the disc-shaped recording medium, and using the upper envelope and the lower envelope as a reference A threshold setting circuit for setting a threshold value for changing the signal level following the signal levels of the upper envelope and the lower envelope, and a comparison circuit for outputting a comparison result between the threshold value and the reproduction signal The counter includes a counter that counts the comparison result and outputs the count result, and measures the DC level of the reproduction signal based on the count result obtained by switching the threshold signal level.
[0022]
  In particular, the recording system or reproducing system of the disk-shaped recording medium is optimized by correcting the light amount and / or irradiation time of the light beam irradiated to the disk-shaped recording medium based on the measurement result of the direct current level.
[0023]
  A filter circuit that corrects the frequency characteristics of the reproduction signal; and a signal processing circuit that converts the reproduction signal into serial data by obtaining a comparison result between the reproduction signal and a predetermined binarization level. Based on the DC level measurement results, the frequency characteristics and / or binarization level of the filter circuitto correct.
[0024]
[Action]
  Detects the upper and lower envelopes of the input signal, sets a threshold value that changes the signal level following the signal level of the upper and lower envelopes, and switches the signal level of this threshold value.By counting the comparison result between the obtained threshold value and the input signal, even if the DC level of the input signal fluctuates due to the data length of the input signal, the threshold signal level is maintained at the optimum value for the input signal. When this is done, the count result with the highest count value can be obtained, whereby the direct current level can be easily measured from the count result with the highest count value.
[0025]
Therefore, the same configuration can be applied to the data transmission apparatus to optimize the transmission system of the data transmission apparatus.
[0026]
The signal processing circuit that converts the input signal into serial data can also be optimized.
[0027]
  further,It can also be applied to a disk device to measure the DC level of a reproduction signal. Therefore, in this manner, in the disk device, the light amount and / or irradiation time of the light beam irradiated to the disk-shaped recording medium is corrected.Thus, the recording system or the reproduction system can be optimized. Further, a filter circuit that corrects the frequency characteristics of the reproduction signal and a signal processing circuit that converts the reproduction signal into serial data by obtaining a comparison result between the reproduction signal and a predetermined binarization level are also disclosed. The frequency characteristic and / or the binarization level of the signal can be corrected and optimized.
[0030]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
[0031]
(1) First embodiment
In FIG. 2, reference numeral 1 denotes a magneto-optical disk device as a whole, which records data DATA input from an external device such as a computer on the magneto-optical disk 2, and further reads out the data DATA recorded on the magneto-optical disk 2. Output to an external device.
[0032]
Here, the magneto-optical disk 2 is formed by forming a perpendicular magnetization film on a predetermined disk-shaped substrate and further arranging a plastic protective film. Further, the magneto-optical disk 2 has a so-called pre-groove formed of a guide groove for the laser beam formed in a spiral shape so that tracking control can be performed by this pre-groove, and spindle control is performed by detecting meandering of the pre-groove. Furthermore, position information of the laser beam irradiation position can be detected.
[0033]
That is, in the magneto-optical disk apparatus 1, the optical pickup 3 condenses the laser beam emitted from the laser diode on the information recording surface of the magneto-optical disk 2 by the built-in objective lens 4, and further obtains it from the magneto-optical disk 2. The returned light is condensed by the objective lens 4 and received by the built-in photodetector. Here, the photodetector is formed by dividing the light receiving surface in, for example, the radial direction and the circumferential direction of the magneto-optical disk 2 and outputs an output signal of each divided light receiving surface.
[0034]
The preprocessing circuit 5 performs current-voltage conversion processing on the output signals of the respective light receiving surfaces, and then performs addition / subtraction processing, thereby generating a tracking error signal TE, a focus error signal FE, and the like, and further changes the polarization plane of the return light. A reproduction signal MO is generated by detection. Further, the preprocessing circuit 5 performs a filtering process on the reproduction signal MO, thereby correcting the frequency characteristic of the reproduction signal MO and outputting it.
[0035]
The servo circuit 6 moves the objective lens 4 up and down and left and right based on the focus error signal FE and the tracking error signal TE, thereby performing tracking control and focus control, and also driving the spindle motor 7 to drive the magneto-optical disk 2. Is driven at a constant linear velocity.
[0036]
When a write command is input from the host computer with the tracking control, the focus control and the spindle control in this way, the magneto-optical disk device 1 moves the optical pickup 3 to the magneto-optical disk 2 prior to data recording. The test light is moved to the test writing area, and the light quantity of the laser beam is intermittently raised from the reading light quantity to the specified light quantity in this test writing area, and a predetermined modulation magnetic field is applied. Record the specified data under conditions.
[0037]
Subsequently, the magneto-optical disk apparatus 1 proceeds to a reproducing operation to detect a change in the signal level of the reproducing signal MO and detect an optimum writing condition. These series of processes are executed by controlling the overall operation by the system control circuit, and the system control circuit selects the optimum write light amount based on the measurement result of the DC level measurement circuit 14 described later. It is executed by.
[0038]
When the write condition is selected in the trial writing area in this way, the magneto-optical disk device 1 records the subsequently input data DATA on the magneto-optical disk 2. That is, in the magneto-optical disk apparatus 1, the input / output circuit 10 forms an interface circuit and a data buffer circuit with an external device, and inputs / outputs commands such as writing, reading, and interrupt to / from the external device. Further, data DATA to be written and data DATA to be read are input / output.
[0039]
The recording data processing circuit 11 adds an error correction code to data DATA output from the input / output circuit 10 in a predetermined block unit at the time of writing, and then 1-16 modulation method which is one of variable length coding methods Thus, the data DATA is converted into recording data, and data such as sync, resync, and address are added to the recording data and output.
[0040]
The drive circuit 12 drives the laser diode of the optical pickup 3 according to the serial data D2 output from the recording data processing circuit 11, and the amount of laser beam is changed during the period when the logic level of the serial data D2 is rising. The amount of light is increased from the amount of light at the time of reading to the amount of light at writing. Accordingly, the magneto-optical disk device 1 sequentially forms pits on the magneto-optical disk 2 in accordance with the serial data D2, and records data DATA input from the external device on the magneto-optical disk 2.
[0041]
On the other hand, when a read command is input from an external device, the magneto-optical disk device 1 reads data specified by this command from the magneto-optical disk 2 and outputs it. That is, in the magneto-optical disk device 1, the comparison circuit 13 inputs the reproduction signal MO to the non-inverting input terminal, and inputs the threshold value SL set by the system control circuit to the inverting input terminal. The reproduction signal MO is converted into binary data D3 and output.
[0042]
The reproduction data processing circuit 15 decodes the data DATA from the binarized data D3 and outputs it to the input / output circuit 10. At this time, the reproduction data processing circuit 15 detects the sync and resync of the binarized data D3 and executes processing such as error correction in units of blocks and decodes them, thereby validating the bit error of the read data DATA. To avoid. Furthermore, the reproduction data processing circuit 15 temporarily stores the binarized data D3 in a built-in FIFO (First In First Out) memory circuit for processing such as error correction, and synchronizes with the predetermined internal clock. Is output to the input / output circuit 10 at the timing.
[0043]
Thus, in the magneto-optical disk apparatus 1, by applying the 1-16 modulation method, the frequency band of the magneto-optical disk 2 can be effectively used by actively utilizing the intersymbol interference, and accordingly, the conventional one. The recording density can be improved as compared with the magneto-optical disk apparatus.
[0044]
Here, the DC level measuring circuit 14 is formed as shown in FIG. In FIG. 1, the magneto-optical disk device 1 is grasped as a data transmission device, and a signal processing circuit from the input / output circuit 10 to the drive circuit 12 is represented by a data generation source 21. A recording / reproducing system including a recording medium up to the processing circuit 5 is represented by a transmission system 20.
[0045]
Here, in this type of data transmission system, the serial data D2 generated by the data generation source 21 is transmitted through the transmission system 20, and the signal waveform of the serial data D2 to be transmitted changes according to the transmission characteristics of the transmission system 20. Then, the reproduced signal MO is input to the receiving side.
[0046]
In such a data transmission system, for example, as shown in FIG. 3, when serial data D2 whose logic level is inverted in a period 8T, 2T, 2T, 8T with respect to the basic period T is repeatedly transmitted, this period 8T and When the transmission system 20 has the same amplitude characteristic with respect to the data length of 2T, that is, the frequency band of the transmission system 20 is sufficient for the frequency band having the periods 8T and 2T as a basic period. In this case, a reproduction signal MO as shown in FIG. 4 can be obtained.
[0047]
Here, when the amplitude of the reproduction signal MO is observed with reference to the signal level L1 that is ½ of the maximum amplitude of the reproduction signal MO, in the portion of the data length of the period 8T, the signal level L1 reaches the maximum value. The signal level a1 and the signal level b1 from the signal level L1 to the minimum value b1 are held at the same signal level. In the data length portion of the period 2T, the signal level a2 from the signal level L1 to the maximum value and the signal level b2 from the signal level L1 to the minimum value are held at the same signal level.
[0048]
As a result, when the frequency band of the transmission system 20 is sufficient, the signal level L1 ½ of the maximum amplitude is set as a threshold value and the reproduction signal MO is binarized, whereby the transmitted serial data D2 is It can be binarized correctly.
[0049]
On the other hand, as shown in FIG. 5, when the amplitude characteristics of the transmission system 20 are different with respect to the data lengths of the periods 8T and 2T, that is, in the frequency band having the periods 8T and 2T as a basic period. When the characteristics are changed, a reproduction signal MO whose DC level changes according to the data length is obtained as shown in FIG. That is, in this case, since the amplitude characteristic of the data length of the period 2T deteriorates compared to the data length of the period 8T, the signal level of the reproduction signal MO rises to the maximum amplitude in the part of the period 8T, and then the period 2T The fall of the signal level becomes small at the portion, and the signal level rises to the maximum amplitude at the portion of the subsequent period 2T.
[0050]
Thus, the intermediate value level L2 between the maximum value and the minimum value in the portion of the period 8T (that is, the signal level at which the signal levels a3 and b3 are equal in FIG. 6) and the intermediate value between the maximum value and the minimum value in the portion of the period 2T. The signal level becomes different from the value level L3 (that is, the signal level where the signal levels a4 and b4 become equal in FIG. 6). If the MO is binarized, the serial data D2 cannot be reproduced correctly.
[0051]
As shown in FIG. 7, the signal levels A and B between the signal levels L2 and L3 and the minimum value of the reproduction signal MO are expressed by the following equations.
[Expression 1]

The value AS represented by the relational expression is called asymmetry, and the degree to which the direct current level changes depending on the data length is represented by this asymmetry AS. Therefore, when the DC level does not change due to the data length, the asymmetry AS is 50 [%].
[0052]
For this reason, the DC level measuring circuit 14 inputs the reproduction signal MO to the envelope detection circuit 22 and envelope-detects the reproduction signal MO here. That is, as shown in FIG. 8, the envelope detection circuit 22 obtains an upper envelope detection result EU and a lower envelope detection result EL of the reproduction signal MO, and generates a reference level for the upper envelope detection result EU and the lower envelope detection result EL. Output to the circuit 23.
[0053]
Here, the reference level generation circuit 23 is formed by connecting eight resistors having the same resistance value in series in this embodiment, and the upper envelope detection result EU and the lower envelope detection result EL are respectively connected to both ends of the series circuit. , And the connection midpoint of each resistor is connected to each contact of the selection circuit 24. As a result, the DC level measurement circuit 14 divides the signal level determined by the upper envelope detection result EU and the lower envelope detection result EL by eight resistors, and the divided voltages B0 to B6 obtained as a result are supplied to the selection circuit 24. Output.
[0054]
The selection circuit 24 sequentially selects the divided voltages B0 to B6 in a predetermined cycle, and outputs the selection output to the non-inverting input terminal of the comparison circuit 25. The comparison circuit 25 has a hysteresis characteristic and is adapted to input the reproduction signal MO to the inverting input terminal. Thus, the comparison circuit 25 binarizes the reproduction signal MO with reference to the selected divided voltages B0 to B6, and outputs the binarization result to the counter 26.
[0055]
After being reset by the reset signal RT output from the gate signal generation circuit 27, the counter 26 counts the rise of the signal level of the output signal of the comparison circuit 25 with reference to the gate signal GT. CT is output.
[0056]
In this series of processes, the magneto-optical disk apparatus 1 repeatedly records the specified serial data D2 in the test writing area, and further, the gate signal generating circuit 27 resets the reset signal RT and the reset signal RT in a cycle synchronized with the repetition cycle of the serial data D2. When the gate signal GT is output, the counter 26 repeats this counting operation in the repetition cycle of the reproduction signal MO trial-written in the writing area, and the selection circuit 24 sequentially switches the contacts in synchronization with this repetition cycle.
[0057]
In this case, as shown in FIG. 8, when the divided voltage B1 is selected in the selection circuit 24 and when the divided voltage B2 is selected, the signal level of the reproduction signal MO becomes the signal level of the divided voltage B2. Since the number of times of crossing is larger, the count value CT of the count value of the counter 26 is greater when the divided voltage B2 is selected. In this case, it is possible to determine that the divided voltage B2 having a large count value CT is more appropriate as a threshold value for binarizing the reproduction signal MO.
[0058]
As a result, as shown in FIG. 9, the count value CT obtained via the counter 26 is an intermediate value between the upper envelope detection result EU and the lower envelope detection result EL when the asymmetry AS of the reproduction signal MO is 50 [%]. When the divided voltage B3 having the signal level is selected, the count value CT becomes the largest, and when the comparison reference of the comparison circuit 25 moves away from the divided voltage B3, the divided value becomes smaller.
[0059]
Further, when the asymmetry AS of the reproduction signal MO is deviated from 50 [%], when the divided voltage displaced from the divided voltage B3 is selected, the count value CT becomes the largest, and the reference value is compared with this divided voltage. As the distance increases, the value decreases accordingly. Therefore, it is possible to detect the asymmetry AS of the reproduction signal MO by detecting the divided voltage at which the count value CT becomes the largest.
[0060]
Therefore, in this type of data transmission apparatus, based on the detected asymmetry AS, the conditions of the data generation source, the conditions of the transmission system 20, the threshold value at the time of reproduction, etc. are adjusted, and the optimum transmission conditions are selected. Thus, even when a modulation method including a DC component is selected, the reproduction signal can be correctly binarized.
[0061]
For this reason, in the magneto-optical disk apparatus 1, the system control circuit detects the divided voltages B0 to B6 at which the count value CT rises most after sequentially taking the count value CT of the counter 26. At this time, the system control circuit approximates the count value CT described above with reference to FIG. 9 to detect the maximum value, and thereby detects the asymmetry AS with high accuracy for the discrete divided voltages B0 to B6.
[0062]
  Further, the system control circuit determines a period for raising the write light amount and the laser beam to the write light amount based on the asymmetry AS detected in the write area.Calculating the write condition that the asymmetry AS is almost 50%To do. Subsequently, the system control circuit sends a control command to the recording data processing circuit 11 and the driving circuit 12, and records serial data D2 on the magneto-optical disk 2 according to the calculated condition at the time of subsequent data recording.
[0063]
Thereby, in the magneto-optical disk device 1, even when the serial data D2 is reproduced through the transmission system in which the DC level varies according to the data length, the serial data D2 is recorded under the condition that the DC level is optimally maintained. Even when a modulation method including a direct current component is selected, the recording / reproducing system can be optimized and the reproduced signal can be binarized correctly.
[0064]
  On the other hand, at the time of reproduction, the magneto-optical disk apparatus 1 detects the asymmetry AS using the data provided for reproduction in the DC level measuring circuit 14 in the same manner prior to data reproduction. Further, in the magneto-optical disk apparatus 1, the system control circuit issues a control command to the preprocessing circuit 5 based on the detection result of the asymmetry AS so that the asymmetry AS approaches 50 [%].Switch filtering characteristics, orThe threshold value of the comparison circuit 13 is optimized.
[0065]
That is, in this type of magneto-optical disk device, the magneto-optical disk 2 may be replaced, and data recorded by this magneto-optical disk device 1 may be reproduced by another magneto-optical disk device. In this case, if the write condition is optimized based on the measurement result of the DC level measuring circuit 14 as in this embodiment, the transmission characteristics are optimized as a whole recording / reproducing system even when reproducing with another magneto-optical disk apparatus. Thus, the reproduction signal MO can be correctly binarized.
[0066]
  On the contrary, the magneto-optical disk 2 recorded by another magneto-optical disk apparatus may be reproduced by the magneto-optical disk apparatus 1 according to this embodiment. In this case, as in this embodiment,Filtering characteristics orBy setting the threshold SL,Recording system or playback systemAs a whole, the transmission characteristics can be optimized and the reproduction signal MO can be binarized correctly.
[0067]
As a result, the magneto-optical disk apparatus 1 not only records and reproduces data with the magneto-optical disk apparatus 1, but also reproduces the magneto-optical disk 2 recorded with another magneto-optical disk apparatus. Even when the magneto-optical disk 2 recorded by the apparatus 1 is reproduced by another magneto-optical disk apparatus, the recorded data can be reliably reproduced by optimizing the transmission system.
[0068]
In the above configuration, when a write command is input from an external device, the magneto-optical disk device 1 moves the optical pickup 3 to the test write area and performs test write, thereby setting the write light quantity. At this time, the magneto-optical disk device 1 repeatedly records the specified data under the specified condition, reproduces the recorded data, selects the write condition according to the reproduction result, and optimizes the recording / reproducing system.
[0069]
That is, the DC level measurement circuit 14 detects the upper envelope and the lower envelope of the reproduction signal MO, and the reference level generation circuit 23 divides the divided voltages B0 to B6 between the upper envelope detection result EU and the lower envelope detection result EL. Is generated. Further, the comparison result between the divided voltages B0 to B6 and the reproduction signal MO is counted by the counter 26, and the asymmetry AS is detected based on the count result.
[0070]
Furthermore, with this asymmetry AS, the amount of light written and the period during which the laser beam is raised to the amount of light at the time of writing are corrected so that the asymmetry AS becomes 50%, and the recording / reproducing system is optimized to the optimum writing conditions. Is done.
[0071]
On the other hand, data DATA input from an external device via the input / output circuit 10 is subjected to 1-16 modulation in the recording data processing circuit 11 after an error correction code is added in a predetermined block unit, Data such as resync is added and converted to serial data D2. The serial data D2 is output to the drive circuit 12, whereby the light quantity of the laser beam is changed from the light quantity at the time of reading to the light quantity for writing set by the trial writing in accordance with the logic level of the serial data D2. Switching is performed intermittently in units of the set rising period, and pits corresponding to the recording data are sequentially formed on the magneto-optical disk 2.
[0072]
On the other hand, when a read command is input from an external device, the reproduction signal MO output from the optical pickup 3 is binarized by the comparison circuit 13 with reference to the threshold value SL and binarized data. D3 is generated, and the binarized data D3 is decoded in the reproduction data processing circuit 15 and then subjected to error correction processing and output to the external device via the input / output circuit 10.
[0073]
  At the time of the binarization, the reproduction signal MO is detected by the DC level measuring circuit 14 in the same manner, and the asymmetry AS is 50%.Filtering characteristics are set, orA threshold value SL for binarization is set.
[0074]
According to the above configuration, the counter 26 counts the comparison result between the divided voltages B0 to B6 generated by the reference level generation circuit 23 with respect to the upper envelope and the lower envelope and the reproduction signal MO. By detecting the asymmetry AS based on the result, the asymmetry AS can be detected even when the DC level changes depending on the data length.
[0075]
As a result, by optimizing the recording system based on the detected asymmetry AS and optimizing the reproduction system, the reproduction signal MO can be correctly converted into binary data. Accordingly, the recording density can be improved as compared with the conventional case by effectively using the frequency band of the recording / reproducing system.
[0076]
(2) Other embodiments
In the above-described embodiment, a case is described in which the count result obtained by sequentially switching the threshold signal level with respect to the reproduction signal MO is detected by sequentially switching the contacts of the selection circuit 24 to obtain the count result. However, the present invention is not limited to this, and a plurality of comparison circuits and counters are arranged corresponding to the divided voltages B0 to B6, thereby simultaneously detecting the count result obtained by switching the threshold signal level. May be.
[0077]
  In this way, it is possible to detect asymmetry in real time, and in real time based on this asymmetry detection result.Filtering characteristics orThe threshold value for binarization can be switched, and the reproduction signal MO can be binarized more accurately.
[0078]
  In the above-described embodiments, the case where the 1-16 modulation method is applied has been described. However, the present invention is not limited to this, and can be widely applied when various modulation methods are selected. The present invention can also be applied to a case where a modulation scheme without accompanying is selected.
[0079]
Furthermore, in the above-described embodiments, the case where the present invention is applied to a magneto-optical disk device has been described. However, the present invention is not limited to this, and various optical disk devices such as a write-once optical disk device, and further a hard disk device. The present invention can be widely applied to a data transmission apparatus such as a magnetic recording / reproducing apparatus such as an optical communication apparatus using an optical fiber.
[0080]
That is, as shown in FIG. 10, in a magnetic recording / reproducing apparatus such as a hard disk device, like this type of magneto-optical disk device, the write data is modulated and converted into record data REC (FIG. 10A). A recording current is supplied to the magnetic head according to the recording data REC. As a result, the magnetic recording / reproducing apparatus sequentially forms a magnetization region in the direction of the scanning locus on the scanning locus of the magnetic head (FIG. 10B), and records the write data on a magnetic recording medium such as a hard disk.
[0081]
On the other hand, at the time of reproduction, the magnetic recording / reproducing apparatus traces the scanning trajectory of the magnetic head with the reproducing head, thereby detecting the reproduction signal PB in which the signal level rises in a positive and negative manner at the boundary of the magnetization region. (FIG. 10 (C)), the reproduction signal PB is binarized by determining the reproduction signal PB as 1, 0, −1 with reference to two threshold values sandwiching the 0 level therebetween. ThereforeFIG.For, the state where the reproduction signal is held at 0 level represents logic 0, and the state where the reproduction signal changes to 1 or -1 represents logic 1.
[0082]
Therefore, in the magnetic recording / reproducing apparatus, when the recording density is improved and the intersymbol interference occurs, the signal level of the reproduced signal PB to be held in the logic 1 changes, for example, according to the data length. As a result, the asymmetry is detected by applying the DC level measurement circuit described above with reference to FIG. 1 to this type of magnetic recording / reproducing apparatus, and the recording / reproducing system is optimized based on the asymmetry detection result so that the reproduced signal PB is correctly binary. Can be Specifically, based on the asymmetry detection result, the recording current is corrected, the frequency characteristic of the reproduction signal PB is corrected, and further, the threshold value for binarizing the reproduction signal PB is corrected, and the reproduction signal PB is corrected. Can be binarized correctly.
[0083]
On the other hand, in an optical communication device using an optical fiber, as shown in FIG. 11, similarly, write data is modulated to generate transmission data D4 (FIG. 11A), and in accordance with the transmission data D4. The laser diode is driven to emit a laser beam. As a result, in the optical communication apparatus, when the transmission distance is kept at an appropriate distance, the laser beam rises from the light amount of almost 0 level corresponding to the logical level of the transmission data D4 (FIG. 11B). The transmission data D4 can be reproduced by binarizing the light reception result.
[0084]
However, when a laser beam is transmitted through an optical fiber, it is difficult to avoid dispersion of light, and as the transmission distance increases, the rise and fall of the light amount become gentle (FIG. 11C), and finally the amplitude direction And the opening of the eye pattern is small for both the phase direction. That is, in this case, the amplitude margin and the phase margin are reduced according to the transmission distance (FIG. 11D).
[0085]
In the optical communication apparatus having such a feature, when intersymbol interference occurs by improving the transmission speed, the light amount of the laser beam to be held at the logical 0 is, for example, on the transmission target side according to the data length. Will change. Thus, in this type of optical communication apparatus, the asymmetry is detected by applying the DC level measurement circuit described above with reference to FIG. 1, and the transmission system is optimized based on the asymmetry detection result to correctly reproduce the transmitted data. Can do. Specifically, based on the asymmetry detection result, the laser beam light amount is corrected, the laser beam irradiation period is corrected, and the frequency characteristics of the light reception result and the threshold value for binarizing the light reception result are also corrected. Thus, it can be correctly binarized.
[0086]
【The invention's effect】
As described above, according to the present invention, even when the DC level changes according to the data length, the DC level can be detected, and the recording / reproducing system can be optimized based on the detection result. As a result, the transmitted data can be correctly reproduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a DC level measuring circuit of a magneto-optical disk apparatus according to an embodiment of the present invention.
2 is a block diagram showing the magneto-optical disk device of FIG. 1. FIG.
FIG. 3 is a signal waveform diagram for explaining the operation of the magneto-optical disk apparatus of FIG. 2;
4 is a signal waveform diagram showing a reproduction signal when the frequency band of the recording / reproducing system is sufficient in the magneto-optical disk apparatus of FIG. 2. FIG.
5 is a characteristic curve diagram showing actual frequency characteristics of the magneto-optical disk apparatus of FIG. 2; FIG.
6 is a signal waveform diagram showing an actual reproduction signal of the magneto-optical disk apparatus of FIG. 2. FIG.
FIG. 7 is a signal waveform diagram for explaining asymmetry.
FIG. 8 is a signal waveform diagram for explaining the operation of the DC level measurement circuit of FIG. 1;
9 is a characteristic curve diagram showing a measurement result of the DC level measurement circuit of FIG. 1. FIG.
FIG. 10 is a signal waveform diagram for explaining an embodiment in which the present invention is applied to a magnetic recording / reproducing apparatus.
FIG. 11 is a signal waveform diagram for explaining an embodiment in which the present invention is applied to an optical communication apparatus.
[Explanation of symbols]
1 Magneto-optical disk unit
2 Magneto-optical disk
3 Optical pickup
13,25  Comparison circuit
14 DC level measurement circuit
20 Transmission system
21 Data source
22 Envelope detection circuit
23 Reference level generation circuit
26 counter

Claims (6)

An envelope detection circuit for detecting an upper envelope and a lower envelope of the input signal by performing envelope detection on an input signal input via a transmission system;
A threshold setting circuit for setting a threshold value at which the signal level changes following the signal level of the upper envelope and the lower envelope with reference to the upper envelope and the lower envelope;
A comparison circuit that outputs a comparison result between the threshold value and the input signal;
A counter for counting the comparison results and outputting the count results;
A direct current level measuring circuit for measuring a direct current level of the input signal inputted through the transmission system based on the count result obtained by switching the signal level of the threshold value. An envelope detection circuit for detecting an upper envelope and a lower envelope of the input signal by performing envelope detection on an input signal input via a transmission system;
A threshold setting circuit for setting a threshold value at which the signal level changes following the signal level of the upper envelope and the lower envelope with reference to the upper envelope and the lower envelope;
A comparison circuit that outputs a comparison result between the threshold value and the input signal;
A counter for counting the comparison results and outputting the count results;
A data transmission apparatus, wherein the transmission system is optimized based on the count result obtained by switching the threshold signal level. An envelope detection circuit for detecting an upper envelope and a lower envelope of the input signal by performing envelope detection on an input signal input via a transmission system;
A threshold value setting circuit for setting a threshold value at which a signal level changes following the signal levels of the upper envelope and the lower envelope with reference to the upper envelope and the lower envelope;
A comparison circuit that outputs a comparison result between the threshold value and the input signal;
A counter that counts the comparison result and outputs the count result;
A signal processing circuit for converting the input signal into serial data;
The signal processing circuit is optimized based on the count result obtained by switching the signal level of the threshold value.
A data transmission apparatus characterized by that. In a disk device for recording desired recording data sequentially on a disk-shaped recording medium and further reproducing the data recorded on the disk-shaped recording medium,
An envelope detection circuit for detecting an envelope of the reproduction signal and detecting an upper envelope and a lower envelope of the reproduction signal for a reproduction signal obtained by reproducing the disc-shaped recording medium ;
A threshold setting circuit for setting a threshold value at which the signal level changes following the signal level of the upper envelope and the lower envelope with reference to the upper envelope and the lower envelope;
A comparison circuit for outputting a comparison result between the threshold value and the reproduction signal;
A counter for counting the comparison results and outputting the count results;
A disk device characterized in that a DC level of the reproduction signal is measured based on the count result obtained by switching the signal level of the threshold value. The recording system or reproducing system of the disk-shaped recording medium is optimized by correcting the light amount and / or irradiation time of the light beam irradiated on the disk-shaped recording medium based on the measurement result of the DC level. The disk device according to claim 4 . A filter circuit for correcting frequency characteristics of the reproduction signal;
A signal processing circuit for converting the reproduction signal into serial data by obtaining a comparison result between the reproduction signal and a predetermined binarization level;
6. The disk device according to claim 4 , wherein the frequency characteristic and / or the binarization level of the filter circuit is corrected based on the measurement result of the direct current level .

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