JP3734647B2 - Optical information recording device - Google Patents

Description

【００８７】
Ｐｅ＋αレベルによるレーザ発光とＰｅ−αレベルによるレーザ発光は、ＤＡＣ９０３へのＰｅ−αレベル設定が間に合うなら連続した１４Ｔスペースデータ出力時に行なってもよいが、通常Ｐｅレベル発光による１４Ｔスペース記録を間に挟んでもよい。
その場合でも、正しい微分効率ηを算出するためにはなるべく短い時間間隔で両レベルによる発光を行なうことが必要である。
【００８８】
ところで、微分効率ηを算出する際に通常イレースレベル（Ｐｅ）を±αする理由は、イレースレベルで許容されるパワーレンジを有効に利用するためである。
そして、相変化型メディアの場合、イレースレベルの適正範囲が概ね決まっており、例えば、あるメディア種類では３ｍＷ≦Ｐｅ≦８ｍＷの範囲が望ましいとされている。
【００８９】
その適正範囲よりも高パワーで記録すると、オーバーライト特性の劣化や膜破壊が生じ、適正範囲より低パワーで記録するとオーバーライト特性の劣化や消し残りが生じる。
【００９０】
通常、相変化型メディアへの適正なイレースパワー（Ｐｅ）は試し書きによって決定されるが、その値は適正範囲の中心あたりに決定されることが多い。
また、微分効率ηを算出する際には、２点のパワーレベル差はなるべく離れていた方が算出誤差が少なくなる。
【００９１】
そこで、この実施形態の光情報記録再生装置では、通常イレースレベルを中心にレベル増加／減少させた２点のパワーで発光させることによって、オーバーライト特性劣化や消し残りを生じない範囲で、なお且つ算出誤差を少なくして微分効率ηを算出することができる。
【００９２】
この実施形態でのαの具体的な値の例として、適正イレースレベル範囲が３ｍＷ≦Ｐｅ≦８ｍＷ，Ｐｅ＝６ｍＷとした場合、α＝１．５ｍＷとする。
【００９３】
このようにして、この実施形態の光情報記録再生装置は、イレースレベルのレーザパワーを複数レベルに切り替えて発光させ、複数のイレースレベルの発光パワーと各々のレーザ駆動電流値からレーザの微分効率を算出し、算出された微分効率をもとにボトムレベル及び／或いはピークレベルのレーザパワーを決定するので、記録データの欠損を招かず、且つ低帯域の回路構成で正確にボトムレベル，イレースレベル，及びピークレベルのパワー制御を行なうことができる。
【００９４】
また、イレースレベル電流重畳手段として複数の電流源を具備し、複数の電流源を適宜切り替えることによって複数のイレースレベルで発光を行なえるようにしたので、記録データの欠損を招かず、且つ低帯域の回路構成で正確にボトムレベル，イレースレベル，及びピークレベルのパワー制御を行なうことができる。
【００９５】
さらに、イレースレベルのレーザパワーを切り替える期間は、記録情報が所定長以上のイレース情報（スペースデータ）出力期間であるようにしたので、イレースレベルは速やかに通常レベルに復帰し、再生時ジッタ劣化への影響を防ぐことができる。
【００９６】
また、微分効率を求める際には、通常記録動作時のイレースレベルパワー（Ｐｅ）から所定分増加させたパワー（Ｐｅ＋α）と通常記録動作時のイレースレベルパワー（Ｐｅ）から所定分減少せたパワー（Ｐｅ−α）の２箇所のイレースレベルの発光パワーと各々のレーザ駆動電流から、微分効率を算出するようにしたので、適正イレースレベル範囲を有効に利用することができる。
【００９７】
さらに、通常記録動作時のイレースレベルパワーを所定分増加又は減少させたレベル（Ｐｅ+α）と（Ｐｅ−α）は、記録媒体の適正イレースレベルの範囲内であるようにしたので、オーバーライト特性劣化や消し残しを生じないように記録することができる。
【００９８】
次に、この発明の他の実施形態について説明する。
上述した微分効率算出シーケンスでは、通常イレースレベルＰｅをα分増加／減少させた２点のパワーで発光を行なって微分効率ηの算出を行なった。
【００９９】
これは、通常イレースレベルＰｅが適正イレースパワー範囲の中央近辺に設定された場合に有効であり、試し書きの結果、最適イレースレベル（通常イレースレベル）が適正範囲の上限／下限のどちらかに偏ってしまった場合には適用できない。
【０１００】
そこで、通常イレースレベルと適正レベルの上限値或いは下限値とのレベル差が所定値以下であった場合は、通常イレースレベルと所定レベルβを増加／減少させたパワーとの２点でパワーを測定し、微分効率ηを算出するようにするとよい。
【０１０１】
この場合、上記ＣＰＵ１，イレースレベル用電流駆動装置９等が、記録媒体の適正イレースレベル電流の上限値と通常記録動作時のイレースレベル電流とのレベル差が所定値以下のとき、複数個のイレースレベル電流源によって通常記録動作時のイレースレベル電流と通常記録動作時のイレースレベル電流から所定分減少させたイレースレベル電流とに切り替え、記録媒体の適正イレースレベル電流の下限値と通常記録動作時のイレースレベル電流とのレベル差が所定値以下のとき、複数個のイレースレベル電流源によって通常記録動作時のイレースレベル電流と通常記録動作時のイレースレベル電流から所定分増加させたイレースレベル電流とに切り替える手段の機能を果たす。
【０１０２】
次に、図５の（ｂ）と（ｃ）、図１０に基づいてこの発明の一実施形態の光情報記録再生装置における他の微分効率算出シーケンスについて説明する。
この微分効率算出シーケンスを開始する際、図５の（ｂ）に示すように、通常イレースレベルＰｅと適正イレースレベルの下限とのレベル差がｄ以下であった場合、ＣＰＵ１はＤＡＣ９０３に対してイレースレベルを所定レベル増加させたＰｅ＋βになるように設定する。
【０１０３】
そして、上述の微分効率算出シーケンスと同様にして、ＣＰＵ１が記録情報として１４Ｔスペースデータが出力される際にイレースレベル切り替え信号１１５を切り替えることにより、ＬＤ２は１４Ｔ期間のみＰｅ＋βのイレースレベルで発光する（図１０の状態遷移（２））。
【０１０４】
ＣＰＵ１は、イレースパワーサンプル信号１１４として取得したＰｅ＋βレベルのパワーと、通常ＡＰＣ制御時に取得した通常イレースレベルＰｅとの２レベルのパワーと、それぞれのＬＤ駆動電流Ｉｅ′，Ｉｅ″とを基にして微分効率ηを算出する。
【０１０５】
ここで、上述の微分効率算出シーケンスにおけるパワー増減分αとβとの関係を次の数７の（１０）の式で表すことができ、この（１０）式によって得られたパワー増減分βを用いることによって、この場合の微分効率ηも（９）の式と同様にして算出することができる。
【０１０６】
【数７】
β＝２×α…（１０）
【０１０７】
また、図５の（ｃ）に示すように、通常イレースレベルＰｅと適正イレースレベルの上限とのレベル差がｄ以下であった場合も同様にして、通常イレースレベルＰｅと所定レベル減少させたＰｅ−βとの２点のレベルでサンプリングを行なって微分効率ηを算出する。
【０１０８】
したがって、通常イレースレベルが適正イレースレベルの下限／上限近傍に設定されていたとしても、得られる微分効率算出誤差を少なくすることができる。
【０１０９】
このようにして、この実施形態の光情報記録再生装置では、微分効率を求める際に、通常記録動作時のイレースレベルパワー（Ｐｅ）と記録媒体の適正イレースレベルの上限値とのレベル差が所定値以下である場合は通常記録動作時のイレースレベルパワー（Ｐｅ）とそのＰｅから所定分減少させたパワー（Ｐｅ−β）の２箇所のイレースレベルの発光パワーと各々のレーザ駆動電流から微分効率を算出し、通常記録動作時のイレースレベルパワー（Ｐｅ）と適正イレースレベルの下限値とのレベル差が所定値以下である場合は、通常記録動作時のイレースレベルパワー（Ｐｅ）とそのＰｅから所定分増加させたパワー（Ｐｅ＋β）の２箇所のイレースレベルの発光パワーと各々のレーザ駆動電流から微分効率を算出するようにしたので、通常イレースレベルが適正イレースレベルの下限／上限近傍に設定されていたとしても微分効率算出誤差を少なくすることができる。
【０１１０】
なお、上述の如く述べてきた各実施形態においては、イレースレベルの電流駆動装置として２個の電流源で構成した場合の例を述べてきたが、この電流源の個数は本願各請求項をなんら制約するものではなく、３個以上の電流源で構成しても上述と同じようにして実施することができる。
【０１１１】
【発明の効果】
以上説明してきたように、この発明の光情報記録再生装置によれば、相変化型メディアに対する情報の記録時、検出帯域の限られた出射光量検出器を使用しても正確にピークパワー，イレースパワー，及びボトムパワーを正確に制御し、なお且つ記録マークが欠損しないように記録することができる。
【図面の簡単な説明】
【図１】この発明の一実施形態である光情報記録再生装置の主要部の構成を示すブロック図である。
【図２】図１に示したイレースレベル用電流駆動装置９の内部構成を示すブロック図である。
【図３】図１に示した光情報記録再生装置における情報記録時のマルチパルスの一例を示す波形図である。
【図４】図１に示した光情報記録再生装置の微分効率算出シーケンスにおける各部の出力信号の一例を示す波形図である。
【図５】同じく図１に示した光情報記録再生装置の微分効率算出シーケンスにおける各部の出力信号の一例を示す波形図である。
【図６】図１に示した光情報記録再生装置の各部における情報記録時の出力信号の一例を示す波形図である。
【図７】図１に示した光情報記録再生装置で算出される微分効率の説明に供する線図である。
【図８】図１に示した光情報記録再生装置で算出される微分効率の説明に供する他の線図である。
【図９】図１に示した光情報記録再生装置で算出される微分効率の変動の説明に供する他の線図である。
【図１０】図１に示した光情報記録再生装置の他の微分効率算出シーケンス時の各部における出力信号の一例を示す波形図である。
【図１１】従来の光情報記録再生装置における記録ストラテジの説明に供する波形図である。
【符号の説明】
１：ＣＰＵ ２：レーザダイオード（ＬＤ）
３：モニタＰＤ ４：ＬＤ駆動装置
５：Ｉ／Ｖ変換回路 ６：サンプルホールド回路
７：Ａ／Ｄコンバータ ８：ボトムレベル用電流源
９：イレースレベル用電流駆動装置
１０：ピークレベル用電流源
９０２，９０３：Ｄ／Ａコンバータ（ＤＡＣ）
９０４：スイッチ
１０１：ボトムパワーイネーブル信号
１０２：イレースパワーイネーブル信号
１０３：ピークパワーイネーブル信号
１０４：ボトムレベル制御信号
１０５：通常イレースレベル制御信号
１０６：η算出時イレースレベル制御信号
１０７：ピークレベル制御信号
１０８：ボトムレベル駆動電流
１０９：イレースレベル重畳電流
１１０：ピークレベル重畳電流
１１１：イレースパワーサンプルタイミング信号
１１２：モニタ（ＰＤ出力）電流
１１３：パワーモニタ信号
１１４：イレースパワーサンプル信号
１１５：イレースレベル切り替え信号[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical information recording apparatus that records information by irradiating a laser beam from a semiconductor laser light source onto a recording medium such as an optical disk.
[0002]
[Prior art]
With the spread of multimedia in recent years, reproduction-only media (recording media) such as music CDs, CD-ROMs and DVD-ROMs, CD drives for reproducing information recorded on such reproduction-only media, CD- Optical information reproducing apparatuses such as a ROM drive and a DVD-ROM drive have been put into practical use.
[0003]
In addition to write-once optical disks that use dye media and rewritable MO disks that use magneto-optical (MO) media, phase change media are also attracting attention. An optical information recording / reproducing apparatus to be used has been put into practical use.
[0004]
In particular, phase change media typified by rewritable DVD media are attracting much attention as next-generation multimedia recording media and large-capacity storage media.
[0005]
In such phase change media, information is recorded by reversibly changing the recording material on the recording surface between a crystalline phase and an amorphous phase.
[0006]
Unlike magneto-optical media such as MO media, phase-change media do not require an external magnetic field, and can record and reproduce information using only laser light from a semiconductor laser light source (LD). Overwriting recording is possible in which recording and erasing are performed at once by laser light.
[0007]
As a general recording waveform for recording information on the phase change type medium as described above, for example, there is a single pulse semiconductor laser emission waveform generated based on an 8-16 modulation code or the like. In single-pulse recording, the recording mark is distorted like a tear due to animal heat, or the cooling rate is insufficient, resulting in insufficient formation of the amorphous phase, resulting in a low reflection recording mark for laser light. There was a problem that a problem such as not occurring occurred.
[0008]
Therefore, in a new method of recording information on the phase change type media, the phase change type media is marked by a laser beam having a multi-pulse waveform using multiple recording powers as shown in FIG. By forming the above, the occurrence of the above-described problems is prevented.
[0009]
As shown in FIG. 3 (c), the mark portion of the multi-pulse waveform has a leading heating pulse “A” for sufficiently preheating the recording film of the phase-change-type media to the melting point or higher, and a plurality of subsequent heating pulses. And a continuous cooling pulse “C” between the leading heating pulse “A” and the continuous heating pulse “B”.
[0010]
The emission power (peak power: peak level current) of the top heating pulse “A” and continuous heating pulse “B” is “Pw”, and the emission power (bottom power: bottom level current) of the continuous cooling pulse “C” is If “Pb” is assumed and the light emission power (read power) at the time of reading is “Pr”, the respective light emission powers are set so that the arithmetic expression shown in Equation 1 is established.
[0011]
[Expression 1]
Pw> Pb≈Pr (1)
[0012]
Further, as shown in FIG. 3C, the space portion of the multi-pulse waveform is composed of an erase pulse “D”, and the light emission power (erase power: erase level current) “Pe” is the peak power “Pw”. And the bottom power “Pb” are set such that the relationship shown in Equation 2 is established.
[0013]
[Expression 2]
Pw>Pe> Pb (2)
[0014]
In this way, by making the recording waveform a multi-pulse light emission waveform, the mark portion of the phase change type media is heated by the head heating pulse “A”, the continuous heating pulse “B”, and the continuous cooling pulse “C”. An amorphous phase is formed under the rapid cooling condition, and a crystal phase is formed in the space portion under a slow cooling condition only by heating with the erase pulse “D”, so that a sufficient reflectance difference can be obtained between the amorphous phase and the crystalline phase. become.
[0015]
Next, when recording on the phase change medium, it is necessary to correctly control the recording light emission power.
[0016]
In the semiconductor laser light source (LD), the “driving current-light emission power characteristic” easily fluctuates due to self-heating or the like, and therefore, APC control (Automatic Power Control) is generally performed as means for stabilizing the light emission power. .
[0017]
In this APC control, a part of the emitted light (LD emitted light) from the LD is made incident on the photodetector (PD), and the LD is driven using a monitor current generated in proportion to the emitted light power (LD emitted power) of the LD. The current (LD drive current) is controlled.
[0018]
In this APC control, when only information reproduction is considered, a high-frequency current is generally superimposed on the LD drive current to suppress noise, but since it is a constant current in terms of DC, a relatively low-band feedback is achieved. APC control can be easily realized by configuring a loop.
[0019]
In addition, when APC control is performed during recording, the recording power changes at a high speed in order to form marks and spaces, and thus it is necessary to devise the control.
[0020]
For example, in a CD-type or DVD-type media, if a low-band feedback loop is configured using the fact that the DSV (Digital Sum Value) of recorded data becomes zero, the recording power can be reduced with a simple configuration as in the case of playback. Although it can be controlled, the exact power cannot be controlled.
[0021]
Therefore, for example, when recording on a CD-R (dye-based) medium with an LD waveform having a strategy as shown in FIG. 11C, for example, the longest data length of 11T is used. When the mark or space data is recorded, if the emission power is sampled / held at each mark / space, the control bandwidth can be several MHz even when the disk rotation speed is about 4 times faster. Accurate recording power can be controlled with a relatively inexpensive configuration.
[0022]
In the case of DVD media, it is desirable to perform multi-pulse light emission as described above. However, in order to detect peak level power, a simple sample / hold circuit requires a very high control band in the light receiving system and subsequent circuits, which is not practical.
[0023]
Therefore, if the sample and hold is performed when the long space data is output, the erase power can be detected.
[0024]
In order to control the bottom power or peak power, the differential efficiency characteristic of the semiconductor laser is calculated in advance before starting recording, and the current calculated from the differential efficiency is added / subtracted to the current for driving the erase power. There is a method of making the drive current of peak power.
[0025]
However, the above method is based on the premise that the differential efficiency of the semiconductor laser does not vary, and there is a problem that an error occurs in the current that drives the peak power if the differential efficiency varies.
[0026]
As means for solving such a problem, conventionally, the peak power is accurately detected by emitting light in a non-pulse state, and the peak power detected by emitting light in a non-pulse state, and There has been a laser power control device (for example, see Japanese Patent Laid-Open No. 9-171631) of an optical disk drive device that corrects bottom power based on erase power detected at the time of space output.
[0027]
For the phase change media as described above, it is necessary to keep the three points of peak power, erase power, and bottom power at optimum power in order to obtain an optical waveform with good jitter characteristics during playback. There is.
[0028]
Therefore, according to the laser power control device of the conventional optical disk drive device as described above, the peak power and the space power can be accurately detected, and the bottom power can be corrected based on these two powers. .
[0029]
[Problems to be solved by the invention]
However, the laser power control device of the conventional optical disk drive device as described above is in a non-pulse state when applied to the peak power control of the recording strategy of the phase change media such as DVD as shown in FIG. There was a problem in that the recording mark was not formed well by the continuous heating, and the recording mark was lost.
[0030]
The present invention has been made to solve the above-described problems. When recording information on a phase change type medium, a semiconductor laser light source can be accurately used even when an emitted light amount detector having a limited detection band is used. An object of the present invention is to accurately control the peak power, erase power, and bottom power of the recording medium, and to enable recording so that the recording mark is not lost.
[0031]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention causes a semiconductor laser light source to emit laser light pulses according to a predetermined light emission rule, and irradiates the laser light to irradiate the laser light on a recording medium based on a predetermined recording modulation method. An optical information recording apparatus for recording information formed by a light emission pulse having a positive integer multiple of one or more of: a bottom level current applying means for applying a bottom level current to the semiconductor laser light source; and the bottom level current Erase level current superimposing means for superimposing an erase level current on, a peak level current superimposing means for superimposing a peak level current on the bottom level current, and the erase level current superimposing means, During the long space data output period when the information to be recorded on the recording medium is a predetermined length or more There is erase level current switching means for switching the erase level current to a plurality of levels, and the semiconductor laser light source emits light based on an applied current in which each erase level current switched by the erase level current switching means is superimposed during a recording operation. The light emission power of each laser beam is detected, and the differential efficiency of the semiconductor laser light source is calculated based on each light emission power and each applied current that caused each light emission power, and based on the differential efficiency The bottom level current or the peak level current at the time of recording is switched during the recording operation.
[0032]
Further, in the optical information recording apparatus as described above, the erase level current switching means has a plurality of erase level current sources, and a plurality of levels of erase level currents are selected by appropriately selecting each of the erase level current sources. It is good to be a means for switching.
[0034]
Further, in the optical information recording apparatus as described above, the erase level current switching means may be configured to increase the erase level current increased by a predetermined amount from the erase level current during the normal recording operation by the plurality of erase level current sources and the normal recording. It is preferable to have means for switching from an erase level current during operation to an erase level current reduced by a predetermined amount.
[0035]
Further, in the optical information recording apparatus as described above, the erase level current switching means has a predetermined value based on the erase level current increased by a predetermined amount from the erase level current during the normal recording operation and the erase level current during the normal recording operation. It is preferable to provide means for setting both erase level currents of the erase level currents reduced by the same amount within the range of the appropriate erase level current of the recording medium.
[0036]
Furthermore, in the optical information recording apparatus as described above, the erase level current switching means has a level difference between the upper limit value of the appropriate erase level current of the recording medium and the erase level current during the normal recording operation equal to or less than a predetermined value. The plurality of erase level current sources to switch between an erase level current during the normal recording operation and an erase level current reduced by a predetermined amount from the erase level current during the normal recording operation, and an appropriate erase level for the recording medium. When the level difference between the lower limit value of the current and the erase level current during the normal recording operation is equal to or less than a predetermined value, the erase level current during the normal recording operation and the erase during the normal recording operation are caused by the plurality of erase level current sources. A means for switching to an erase level current increased by a predetermined amount from the level current is provided. When may.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
In this embodiment, an optical information recording / reproducing apparatus for recording (overwriting) DVD format code data on a phase change type medium (for example, a phase change type disc) and reproducing the recorded data is shown. The method will be described when mark edge (pulse width modulation: PWM) recording is performed using an 8-16 modulation code as a data modulation method.
[0038]
FIG. 1 is a block diagram showing a functional configuration of a main part of an optical information recording / reproducing apparatus according to an embodiment of the present invention.
In this optical information recording / reproducing apparatus, a semiconductor laser light source emits multi-pulse light to a phase change type medium (not shown) such as a DVD disk as a recording medium and irradiates the laser beam to the recording surface of the phase change type medium. This is an apparatus for recording information by forming a recording mark. Hereinafter, only information recording related to the present invention will be described, and description of processing and functional units will be omitted for reproduction.
[0039]
In this optical information recording / reproducing apparatus, during information recording, a peak power (Pw) that is a peak level current for forming a mark with multi-pulses, a bottom power (Pb) that is a bottom level current, and an erase for forming a space. Three types of recording power, ie, erase power (Pe), which is a level current, are required.
[0040]
First, the APC control operation during normal recording in the optical information recording / reproducing apparatus will be described.
[0041]
This optical information recording / reproducing apparatus is provided with a bottom level current source 8, an erase level current driver 9, and a peak level control signal 104, a normal erase level control signal 105, and a peak level control signal 107 output from the CPU 1, respectively. The output current of the level current source 10 is set.
[0042]
Specifically, the bottom level current source 8 and the peak level current source 10 are DACs, and a bottom level drive current (bottom level current), which is an analog signal, based on LD drive current information digitally set by the CPU 1. ) 108 and a peak level superimposed current (peak level current) 110 are output.
The erase level current driver 9 switches and outputs a plurality of levels of erase level superimposed currents (erase level currents) 109 according to the configuration described later.
[0043]
The LD driving device 4 emits light of the bottom power (Pb), erase power (Pe), and peak power (Pw) of the LD 2 according to the bottom level driving current 108, the erase level superimposed current 109, and the peak level superimposed current 110, respectively. Determine the level.
[0044]
Further, the CPU 1 converts the information to be recorded into an 8-16 modulation signal as shown in FIG. 3B, further generates a multi-pulse waveform as shown in FIG. 3C, and according to the waveform. Thus, the bottom power enable signal 101, the erase power enable signal 102, and the peak power enable signal 103 are supplied to the LD driving device 4, respectively.
[0045]
The LD driving device 4 applies the bottom level driving current 108 to the LD 2 when the bottom power enable signal 101 is at the high level “H”, and the bottom level driving current 108 when the erase power enable signal 102 is at the high level “H”. The erase level superimposed current 109 is added to and applied to the LD 2. When the peak power enable signal 103 is at the high level “H”, the peak level superimposed current 110 is added to the bottom level drive current 108 and applied to the LD 2 to drive the current. Supply.
[0046]
As shown in FIGS. 6B to 6D, the bottom power enable signal 101 is set to the high level “H” during the recording period.
When the light is emitted at the erase level, the erase power enable signal 102 is also set to the high level “H” at the same time, and the LD drive device 4 adds the bottom level drive current 108 and the erase level superimposed current 109 to obtain the drive current of LD2.
[0047]
When light is emitted at the peak level, the peak power enable signal 103 is set to the high level “H”, and the LD driving device 4 adds the bottom level driving current 108 and the peak level superimposed current 110 to obtain the driving current of the LD 2.
[0048]
When a driving current is supplied from the LD driving device 4 to the LD 2, a laser beam is emitted from the LD 2 to irradiate a phase change medium (not shown) to record and reproduce information on the recording surface.
At that time, part of the emitted light is incident on the monitor PD 3, and a monitor current 112 proportional to the light emission power is output to the I / V conversion circuit 5.
[0049]
Then, APC control is performed by using the power monitor current 112 that has been subjected to current-voltage conversion by the I / V conversion circuit 5.
[0050]
The power monitor signal 113 is sampled / held by the sample and hold circuit 6 during a period when the erase power sample timing signal 111 output from the CPU 1 is at a high level “H” when long space data is output (for example, 14T space data). Then, it is digitized by the A / D converter 7 and outputted to the CPU 1 as the erase power sample signal 114 (see FIG. 6).
[0051]
The CPU 1 compares the erase power sample signal 114 with a reference value and corrects the value of the normal erase level control signal 105 so that the erase power (Pe) becomes an appropriate value.
[0052]
Further, the bottom power and the peak power are corrected by calculating a drive current from the corrected erase power and the differential efficiency η (differential efficiency value) described later.
The differential efficiency η is a value defined as the slope ΔP / ΔI of the LD drive current-light emission power characteristic, as shown by a diagram in FIG.
[0053]
If the LD drive currents corresponding to the bottom power (Pb), erase power (Pe), and peak power (Pw) are Ib, Ie, and Iw, respectively, the bottom power (Pb) and peak power (Pw) are the following numbers. 3 (3) and (4).
[0054]
[Equation 3]
Pb = Pe−η × (Ie−Ib) (3)
Pw = Pe + η × (Iw−Ie) (4)
[0055]
Based on the above formulas (3) and (4), the bottom power drive current (Ib) and the peak power drive current (Iw) can be calculated from the following formulas (5) and (6).
[0056]
[Expression 4]
Ib = Ie− (Pe−Pb) / η (5)
Iw = Ie + (Pw−Pe) / η (6)
[0057]
In this way, the CPU 1 calculates the bottom power drive current (Ib) and the peak power drive current (Iw) and causes the bottom level current source 8 and the peak level current source 10 to output the respective drive currents. Take control.
[0058]
As described above, since the erase level and the peak level LD drive current are obtained by adding the current to the bottom level drive current 108, if the erase level superimposed current 109 is ΔIe and the peak level superimposed current 110 is ΔIw, The drive current (applied current obtained by adding the erase level superimposed current 109) Ie and the peak level drive current (applied current obtained by adding the peak level superimposed current 110) Iw are respectively expressed by the following equations (7) and (8). Can be expressed as
[0059]
[Equation 5]
Ie = Ib + ΔIe (7)
Iw = Ib + ΔIw (8)
[0060]
The time interval for performing this normal APC control is set to be relatively shorter than the time interval of the differential efficiency calculation sequence described below.
For example, the erase level is sampled when 14T space, which is the longest data length of the 8-16 recording modulation system, is output.
[0061]
Further, since the 14T data length in the DVD standard is a SYNC code, when the space power sampling period is set to 14T space data output, sampling / holding is performed approximately once every two SYNC frames (1488T). .
[0062]
Since 14T mark or 14T space is selected for 14T data according to the rule in order to set DSV to zero “0”, 14T space is not necessarily output once in 2SYNC, but in this embodiment, for convenience, It is assumed that 14T marks / 14T spaces appear alternately.
[0063]
In this manner, this optical information recording / reproducing apparatus calculates the power of the bottom level and the peak level based on the erase level sampled at the time of outputting the long space data and the differential efficiency obtained in advance, so that the low band circuit configuration However, it is possible to perform power correction for the bottom level and the peak level during information recording.
[0064]
As shown in FIG. 9, if the differential efficiency η fluctuates during the recording operation, an error occurs in the calculation of the bottom power driving current Ib and the peak power driving current Iw, and the correction of the bottom power and the peak power is accurate. It becomes impossible to go to.
[0065]
Therefore, as a method for recalculating the differential efficiency η during the recording operation, the light emission power is sampled at two points of the erase level and the peak level as in the conventional technique described above (see, for example, Japanese Patent Laid-Open No. 9-171631). However, according to such a method, there is a problem that the data of the mark portion in a non-pulse state is lost.
[0066]
Therefore, in the optical information recording / reproducing apparatus of this embodiment, the erase level current is appropriately switched to a plurality of levels, and the light emission power based on the plurality of erase level currents is sampled and held to calculate the differential efficiency η.
[0067]
That is, this optical information recording / reproducing apparatus causes a semiconductor laser light source to emit laser light pulses according to a predetermined light emission rule, and irradiates the laser light to irradiate the laser beam onto a recording medium based on a predetermined recording modulation system ( It is an apparatus for recording information formed by a light emission pulse having a predetermined multiple of T) (n: a positive integer of 1 or more).
[0068]
The LD driving device 4 and the bottom level current source 8 function as a bottom level current applying means for applying a bottom level current to the semiconductor laser light source.
The LD driving device 4 and the erase level current driving device 9 serve as erase level current superimposing means for superimposing the erase level current on the bottom level current. The LD driving device 4 and the peak level current source 10 function as peak level current superimposing means for superimposing the peak level current on the bottom level current.
[0069]
Further, the erase level current driver 9 functions as an erase level current switching means for switching the erase level current to a plurality of levels.
[0070]
The CPU 1, the erase level current driver 9 and the like are During recording operation The light emission power of each laser beam when the semiconductor laser light source emits light is detected based on the applied current superimposed with each erase level current switched by the erase level current switching means, and the respective light emission power and each light emission power are detected. The differential efficiency of the semiconductor laser light source is calculated based on each applied current generated, and the bottom level current or peak level current during recording is calculated based on the differential efficiency. Switch during recording Serves as a means.
[0071]
The DACs 902 and 903 correspond to a plurality of erase level current sources, and the CPU 1 and the switch 904 have a function of switching a plurality of levels of erase level currents by appropriately selecting each of the erase level current sources. Fulfill.
[0072]
Further, the CPU 1 or the like serves as a means for causing the erase level current switching period of a plurality of levels to correspond to an erase information output period of space data or the like whose information recorded on the recording medium has a predetermined length or more.
[0073]
Further, the CPU 1 or the like uses the plurality of erase level current sources to increase the erase level current by a predetermined amount from the erase level current during the normal recording operation and the erase level current decreased by a predetermined amount from the erase level current during the normal recording operation. It functions as a means to switch between.
[0074]
Further, the CPU 1 and the like record both erase level currents, the erase level current increased by a predetermined amount from the erase level current during the normal recording operation and the erase level current decreased by a predetermined amount from the erase level current during the normal recording operation. Serves as a means for bringing the medium within the proper erase level current range.
[0075]
Next, a differential efficiency calculation sequence according to the present invention in the optical information recording / reproducing apparatus of this embodiment will be described based on FIGS. 2, 4, and 5A. As shown in FIG. 2, the erase level current driver 9 includes two D / A converters (DACs) 902 and 903 and a switch 904, and a DAC (902 or 903) selected by the switch 904. , Erase level superimposed currents are respectively output.
[0076]
The DAC 902 is set so that the erase level becomes the normal erase level (Pe) by the normal erase level control signal 105 from the CPU 1, and the erase level switching from the CPU 1 is performed when the LD 2 is emitting the normal erase level. The switch 904 is set to the high level “H” side by the signal 115.
[0077]
The CPU 1 starts the differential efficiency calculation sequence at a frequency lower than the normal APC control interval (the frequency is determined experimentally because the optimum value is determined by the temporal variation of the differential efficiency of the LD 2).
[0078]
First, the CPU 1 sets the DAC 903 so that the LD 2 emits light at the level of Pe + α by the erase level control signal 106 when the differential efficiency η is calculated (see state transition (2) in FIG. 4).
[0079]
In the sequence state, when 14T space data is output as recording information, the CPU 1 sets the erase level switching signal 115 to the low level “L” so that the erase level superimposed current becomes the DAC 903 output.
Then, LD2 emits light at the erase level of Pe + α only for the 14T period.
[0080]
The power at this level is sampled as an erase power sample signal 114 and output to the CPU 1. The CPU 1 obtains a sample value in distinction from the erase level normally sampled during APC.
[0081]
After outputting the 14T space data, the CPU 1 immediately returns the erase level switching signal 115 to the high level “H”, so that the subsequent erase level emission is restored to the normal erase power (Pe) level (FIG. 4). (See state transition (3)).
[0082]
The power of the erase level and peak level is set to an optimum value by trial writing or the like so as to suppress the jitter at the time of reproduction, but the light emission of the erase level different from the normal erase power (Pe) level continues to be emitted for a long time. There is a concern about the reduction of jitter.
Therefore, if the erase level is quickly returned to the normal erase power (Pe) level, the influence on the jitter can be almost ignored.
[0083]
Next, the CPU 1 sets the DAC 903 so that the LD 2 emits light at the Pe-α level (state transition (4) in FIG. 4).
In this sequence state, when 14T space data is output as recording information, the CPU 1 sets the erase level switching signal 115 to L so that the erase level superimposed current becomes the DAC 903 output.
[0084]
Then, LD2 emits light at the erase level of Pe-α only for the 14T period.
As with the Pe + α level output, the power at this level is sampled and output to the CPU 1.
[0085]
The CPU 1 calculates the differential efficiency η based on the following equation (9) based on the obtained two-level light emission power (Pe + α, Pe−α) and the respective LD drive currents Ie ′, Ie ″. Calculate (see FIG. 8).
[0086]
[Formula 6]

[0087]
Laser light emission by the Pe + α level and laser light emission by the Pe-α level may be performed at the time of continuous 14T space data output if the Pe-α level setting to the DAC 903 is in time. You may pinch it.
Even in that case, in order to calculate the correct differential efficiency η, it is necessary to emit light at both levels at a time interval as short as possible.
[0088]
By the way, the reason why the normal erase level (Pe) is ± α when calculating the differential efficiency η is to effectively use the power range permitted by the erase level.
In the case of phase change media, the appropriate range of the erase level is generally determined. For example, in a certain media type, a range of 3 mW ≦ Pe ≦ 8 mW is desirable.
[0089]
When recording at a power higher than the appropriate range, the overwrite characteristics are deteriorated and the film is broken. When recording is performed at a power lower than the appropriate range, the overwrite characteristics are deteriorated and unerased.
[0090]
Normally, the appropriate erase power (Pe) for the phase change media is determined by trial writing, but the value is often determined around the center of the appropriate range.
Further, when the differential efficiency η is calculated, the calculation error decreases when the power level difference between the two points is as far as possible.
[0091]
Therefore, in the optical information recording / reproducing apparatus of this embodiment, light is emitted at two points of power that are increased / decreased around the normal erase level, so that overwriting characteristic deterioration and unerased residue do not occur. The differential efficiency η can be calculated with less calculation error.
[0092]
As an example of a specific value of α in this embodiment, when the proper erase level range is 3 mW ≦ Pe ≦ 8 mW and Pe = 6 mW, α = 1.5 mW.
[0093]
In this manner, the optical information recording / reproducing apparatus of this embodiment switches the erase level laser power to a plurality of levels to emit light, and obtains the differential efficiency of the laser from the plurality of erase level emission powers and the respective laser drive current values. Since the bottom level and / or peak level laser power is determined based on the calculated differential efficiency, recording data is not lost, and the bottom level, erase level, And peak level power control.
[0094]
In addition, a plurality of current sources are provided as erase level current superimposing means, and light emission can be performed at a plurality of erase levels by appropriately switching the plurality of current sources. With this circuit configuration, power control at the bottom level, erase level, and peak level can be performed accurately.
[0095]
Furthermore, the period during which the laser power of the erase level is switched is an erase information (space data) output period in which the recorded information is longer than a predetermined length, so that the erase level quickly returns to the normal level and jitter during reproduction deteriorates. Can prevent the influence.
[0096]
When obtaining the differential efficiency, the power (Pe + α) increased by a predetermined amount from the erase level power (Pe) during the normal recording operation and the power decreased by a predetermined amount from the erase level power (Pe) during the normal recording operation. Since the differential efficiency is calculated from the emission power of the two erase levels (Pe−α) and the respective laser drive currents, the appropriate erase level range can be used effectively.
[0097]
Further, the levels (Pe + α) and (Pe−α), which are increased or decreased by a predetermined amount during the normal recording operation, are within the range of the appropriate erase level of the recording medium. It is possible to record so as not to cause characteristic deterioration and unerased.
[0098]
Next, another embodiment of the present invention will be described.
In the differential efficiency calculation sequence described above, the differential efficiency η is calculated by emitting light at two points of power obtained by increasing / decreasing the normal erase level Pe by α.
[0099]
This is effective when the normal erase level Pe is set near the center of the proper erase power range. As a result of trial writing, the optimum erase level (normal erase level) is biased to either the upper limit or the lower limit of the appropriate range. It is not applicable when it has been.
[0100]
Therefore, if the level difference between the normal erase level and the upper limit or lower limit of the appropriate level is less than or equal to a predetermined value, the power is measured at two points: the normal erase level and the power obtained by increasing / decreasing the predetermined level β. Then, it is preferable to calculate the differential efficiency η.
[0101]
In this case, when the level difference between the upper limit value of the appropriate erase level current of the recording medium and the erase level current during the normal recording operation is equal to or less than a predetermined value, the CPU 1, the erase level current driver 9 and the like The level current source switches between the erase level current during the normal recording operation and the erase level current reduced by a predetermined amount from the erase level current during the normal recording operation, and the lower limit of the appropriate erase level current of the recording medium and the normal recording operation When the level difference from the erase level current is less than or equal to a predetermined value, the erase level current is increased by a predetermined amount from the erase level current during normal recording operation and the erase level current during normal recording operation by a plurality of erase level current sources. Acts as a means of switching.
[0102]
Next, another differential efficiency calculation sequence in the optical information recording / reproducing apparatus according to the embodiment of the present invention will be described with reference to FIGS. 5B and 5C and FIG.
When starting the differential efficiency calculation sequence, as shown in FIG. 5B, when the level difference between the normal erase level Pe and the lower limit of the appropriate erase level is equal to or less than d, the CPU 1 erases the DAC 903. The level is set to Pe + β increased by a predetermined level.
[0103]
Similarly to the above-described differential efficiency calculation sequence, the CPU 1 switches the erase level switching signal 115 when 14T space data is output as recording information, so that the LD 2 emits light at the erase level of Pe + β only during the 14T period ( State transition (2) in FIG.
[0104]
The CPU 1 uses the power of the Pe + β level acquired as the erase power sample signal 114, the power of the two levels of the normal erase level Pe acquired during the normal APC control, and the respective LD drive currents Ie ′ and Ie ″. The differential efficiency η is calculated.
[0105]
Here, the relationship between the power increase / decrease α and β in the above-described differential efficiency calculation sequence can be expressed by the following equation (10) (10), and the power increase / decrease β obtained by the equation (10) is expressed as follows. By using this, the differential efficiency η in this case can be calculated in the same manner as the equation (9).
[0106]
[Expression 7]
β = 2 × α (10)
[0107]
Further, as shown in FIG. 5C, when the level difference between the normal erase level Pe and the upper limit of the appropriate erase level is equal to or less than d, the normal erase level Pe and Pe decreased by a predetermined level are similarly applied. Sampling is performed at the two levels of -β to calculate the differential efficiency η.
[0108]
Therefore, even if the normal erase level is set near the lower limit / upper limit of the proper erase level, the obtained differential efficiency calculation error can be reduced.
[0109]
Thus, in the optical information recording / reproducing apparatus of this embodiment, when the differential efficiency is obtained, the level difference between the erase level power (Pe) during the normal recording operation and the upper limit value of the appropriate erase level of the recording medium is predetermined. If the value is equal to or less than the value, the differential efficiency is calculated from the emission power at two erase levels, ie, the erase level power (Pe) during normal recording operation and the power (Pe-β) reduced by a predetermined amount from the Pe, and the respective laser drive currents. If the level difference between the erase level power (Pe) during the normal recording operation and the lower limit value of the appropriate erase level is equal to or less than a predetermined value, the erase level power (Pe) during the normal recording operation and the Pe Since the differential efficiency is calculated from the emission power of two erase levels of the power (Pe + β) increased by a predetermined amount and the respective laser drive currents, Even if the erase level is set near the lower limit / upper limit of the appropriate erase level, the differential efficiency calculation error can be reduced.
[0110]
In each of the embodiments described above, an example in which two current sources are used as the erase level current driving device has been described. However, the number of current sources is not limited to each claim of the present application. The present invention is not limited, and even if it is constituted by three or more current sources, it can be carried out in the same manner as described above.
[0111]
【The invention's effect】
As described above, according to the optical information recording / reproducing apparatus of the present invention, when information is recorded on the phase change type medium, the peak power and erase can be accurately detected even when the output light quantity detector with a limited detection band is used. The power and bottom power can be accurately controlled, and recording can be performed so that the recording mark is not lost.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a main part of an optical information recording / reproducing apparatus according to an embodiment of the present invention.
2 is a block diagram showing an internal configuration of an erase level current driver 9 shown in FIG. 1; FIG.
3 is a waveform diagram showing an example of a multi-pulse at the time of information recording in the optical information recording / reproducing apparatus shown in FIG. 1. FIG.
4 is a waveform diagram showing an example of an output signal of each part in the differential efficiency calculation sequence of the optical information recording / reproducing apparatus shown in FIG. 1. FIG.
5 is a waveform diagram showing an example of an output signal of each part in the differential efficiency calculation sequence of the optical information recording / reproducing apparatus shown in FIG.
6 is a waveform diagram showing an example of an output signal at the time of information recording in each part of the optical information recording / reproducing apparatus shown in FIG. 1. FIG.
7 is a diagram for explaining differential efficiency calculated by the optical information recording / reproducing apparatus shown in FIG. 1; FIG.
8 is another diagram for explaining the differential efficiency calculated by the optical information recording / reproducing apparatus shown in FIG. 1. FIG.
FIG. 9 is another diagram for explaining the variation in differential efficiency calculated by the optical information recording / reproducing apparatus shown in FIG. 1;
10 is a waveform diagram showing an example of an output signal in each part in another differential efficiency calculation sequence of the optical information recording / reproducing apparatus shown in FIG.
FIG. 11 is a waveform diagram for explaining a recording strategy in a conventional optical information recording / reproducing apparatus.
[Explanation of symbols]
1: CPU 2: Laser diode (LD)
3: Monitor PD 4: LD drive device
5: I / V conversion circuit 6: Sample hold circuit
7: A / D converter 8: Current source for bottom level
9: Erase level current drive
10: Current source for peak level
902, 903: D / A converter (DAC)
904: Switch
101: Bottom power enable signal
102: Erase power enable signal
103: Peak power enable signal
104: Bottom level control signal
105: Normal erase level control signal
106: Erase level control signal for η calculation
107: Peak level control signal
108: Bottom level drive current
109: Erase level superimposed current
110: Peak level superimposed current
111: Erase power sample timing signal
112: Monitor (PD output) current
113: Power monitor signal
114: Erase power sample signal
115: Erase level switching signal

Claims (5)

A semiconductor laser light source is caused to emit a pulse of laser light according to a predetermined light emission rule, and the laser light is irradiated to emit light having a positive integer multiple of one or more of a channel clock period based on a predetermined recording modulation method on a recording medium. An optical information recording device for recording information formed by pulses,
Bottom level current application means for applying a bottom level current to the semiconductor laser light source;
Erase level current superimposing means for superimposing an erase level current on the bottom level current;
Peak level current superimposing means for superimposing a peak level current on the bottom level current;
The erase level current superimposing means has erase level current switching means for switching the erase level current to a plurality of levels during a long space data output period in which information to be recorded on the recording medium is a predetermined length or longer ,
Detecting the emission power of each laser beam when the semiconductor laser light source emits light based on the applied current superimposed with each erase level current switched by the erase level current switching means during the recording operation, The differential efficiency of the semiconductor laser light source is calculated based on the applied currents that cause the respective emission powers, and the bottom level current or the peak level current during recording is recorded during the recording operation based on the differential efficiency. An optical information recording apparatus characterized by switching. The optical information recording apparatus according to claim 1,
The optical information recording characterized in that the erase level current switching means has a plurality of erase level current sources, and switches between the plurality of levels of erase level currents by appropriately selecting each of the erase level current sources. apparatus. The optical information recording apparatus according to claim 2 Symbol placement,
The erase level current switching means reduces the erase level current increased by a predetermined amount from the erase level current during the normal recording operation and the erase level current during the normal recording operation by a predetermined amount by the plurality of erase level current sources. An optical information recording apparatus comprising means for switching to an erase level current. The optical information recording apparatus according to claim 3 ,
Both erase level currents of the erase level current increased by a predetermined amount from the erase level current during the normal recording operation and the erase level current decreased by a predetermined amount from the erase level current during the normal recording operation. The optical information recording apparatus further comprises means for setting the value within a range of an appropriate erase level current of the recording medium. The optical information recording apparatus according to claim 2,
When the level difference between the upper limit value of the appropriate erase level current of the recording medium and the erase level current during normal recording operation is equal to or less than a predetermined value, the erase level current switching means Switching between the erase level current during the recording operation and the erase level current reduced by a predetermined amount from the erase level current during the normal recording operation, and the lower limit value of the appropriate erase level current of the recording medium and the erase level current during the normal recording operation When the level difference is less than or equal to a predetermined value, the erase level current during the normal recording operation and the erase level current increased by a predetermined amount from the erase level current during the normal recording operation by the plurality of erase level current sources An optical information recording apparatus having a switching means.

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