JPH05205274A - Information reproducing method - Google Patents
Information reproducing methodInfo
- Publication number
- JPH05205274A JPH05205274A JP4010762A JP1076292A JPH05205274A JP H05205274 A JPH05205274 A JP H05205274A JP 4010762 A JP4010762 A JP 4010762A JP 1076292 A JP1076292 A JP 1076292A JP H05205274 A JPH05205274 A JP H05205274A
- Authority
- JP
- Japan
- Prior art keywords
- information
- recording
- recording medium
- laser
- laser beam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Optical Recording Or Reproduction (AREA)
- Optical Head (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は光ディスク等の情報記録
媒体にレーザ光を照射して、コンピュータ用のコードデ
ータや画像情報あるいは音楽情報、等の再生を行う情報
の再生方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reproducing information such as code data for computers, image information or music information by irradiating an information recording medium such as an optical disk with a laser beam.
【０００２】[0002]
【従来の技術】レーザ光を用いて情報の再生を行う情報
再生装置には、例えば、光ディスク装置が実用化されて
いる。情報再生装置では、情報記録媒体上の記録マーク
にレーザ光を照射し、反射光または透過光の光量変化や
偏光面の回転を検出してデジタル信号やアナログ信号の
情報に変換する。コンパクトディスクやビデオディス
ク，ＣＤ−ＲＯＭなどの記録マークは、スタンパ法によ
り情報記録媒体上に凹凸としてあらかじめ形成されてい
る。一方、追記型や書き換え型の光ディスクや光カード
では、記録膜の微小領域にレーザ光を照射して光学的に
読み取り可能な記録マークを生じさせる。例えば、レー
ザ光を照射して記録膜に穴を形成するもの（穴あけ記
録）や、磁化の向きを変えるもの（光磁気記録）、結晶
−非晶質の相変化を生じさせるもの（相変化記録）など
が知られている。情報を再生するには、記録マークの位
置（記録マークの有無）を検出する方法と、記録マーク
のエッジ（記録マークの長さや間隔）を検出する方法が
ある。2. Description of the Related Art For example, an optical disk device has been put into practical use as an information reproducing device for reproducing information by using a laser beam. In the information reproducing apparatus, a recording mark on an information recording medium is irradiated with laser light, and a change in the amount of reflected light or transmitted light or rotation of a polarization plane is detected and converted into digital signal or analog signal information. Recording marks such as compact discs, video discs, and CD-ROMs are formed beforehand as irregularities on an information recording medium by a stamper method. On the other hand, in a write-once or rewritable optical disk or optical card, a minute area of a recording film is irradiated with laser light to generate an optically readable recording mark. For example, those that irradiate laser light to form holes in the recording film (drilling recording), those that change the direction of magnetization (magneto-optical recording), those that cause a crystalline-amorphous phase change (phase change recording). ) Is known. To reproduce information, there are a method of detecting the position of the recording mark (presence or absence of the recording mark) and a method of detecting the edge of the recording mark (length and interval of the recording mark).
【０００３】光ディスク等の情報記録媒体で、記録再生
の高速化と、記録密度の高密度化を行うには、できるだ
け小さい記録マークをできるだけ短い間隔で記録し、こ
れを再生する必要がある。しかし、再生の分解能はレー
ザ光の収束直径によって制限されるので、記録マークの
大きさや間隔を再生レーザ光の収束直径の半分以下にす
ると、情報を分離して読み取りが困難になる。従って、
情報の正確な再生を行うには、記録マークの大きさや間
隔をどこまでも小さくすることはできない。ここでレー
ザ光の収束直径Ｗとは、波長λのレーザ光と開口数ＮＡ
の焦点レンズを用いた場合、Ｗ＝０.８２×λ／ＮＡ と
見積もることができる。これはレーザ光の強度が１／ｅ
2 となる直径である。In order to increase the recording / reproducing speed and the recording density on an information recording medium such as an optical disk, it is necessary to record the smallest possible recording marks at the shortest intervals and reproduce the recorded marks. However, since the reproduction resolution is limited by the convergent diameter of the laser beam, if the size or interval of the recording marks is set to be half the convergent diameter of the reproducing laser beam or less, it becomes difficult to separate and read the information. Therefore,
In order to reproduce information accurately, it is impossible to reduce the size and interval of recording marks to any extent. Here, the convergent diameter W of the laser light means the laser light of the wavelength λ and the numerical aperture NA.
When the focusing lens of 1 is used, it can be estimated that W = 0.82 × λ / NA. This is because the laser light intensity is 1 / e
The diameter is 2 .
【０００４】これを解決する方法として、一つの記録マ
ークから三値以上の方法がある。例えば、特開昭60−24
2532号公報には、記録マークの深さに応じて四種類の情
報を再生する方法が記載されている。また、特開昭63−
146224号公報には、あらかじめ再生出力レベルの基準と
なるマークを記録媒体上に設けておき、これと比較する
ことによって、記録マークの再生レベルを正確に多値化
して読み出す方法が記載されている。As a method for solving this, there is a method in which one recording mark has three or more values. For example, JP-A-60-24
Japanese Patent No. 2532 describes a method of reproducing four types of information according to the depth of a recording mark. In addition, JP-A-63-
Japanese Patent Publication No. 146224 describes a method in which a mark serving as a reference of a reproduction output level is provided on a recording medium in advance, and by comparing it with a mark, the reproduction level of the record mark is accurately multivalued and read. ..
【０００５】[0005]
【発明が解決しようとする課題】従来技術では、記録媒
体にわずかな反射率や透過率の変動があると、正確な再
生出力レベルの判定が行えず、多値情報の再生を行うこ
とは困難であった。従って、例えば、従来例で述べたよ
うにあらかじめ再生出力レベルの基準となるマークを記
録媒体上に形成しておく必要があった。In the prior art, if the recording medium has a slight variation in reflectance or transmittance, it is difficult to accurately determine the reproduction output level and it is difficult to reproduce multi-valued information. Met. Therefore, for example, as described in the conventional example, it is necessary to previously form a mark serving as a reference of the reproduction output level on the recording medium.
【０００６】本発明の目的は、構成や製造方法が簡便で
安価な記録媒体を用いても、高密度の情報の再生が可能
な情報の再生方法を提供することにある。An object of the present invention is to provide an information reproducing method capable of reproducing high-density information even if a recording medium having a simple structure and a simple manufacturing method is used.
【０００７】[0007]
【課題を解決するための手段】本発明は、上記目的を達
成するために、以下の手段を用いた。 (1）情報記録媒体にレーザ光を照射することによって情
報の再生を行う方法において、収束直径の異なる複数の
レーザ光を同一の記録面上に照射し、それぞれのレーザ
光の反射光または透過光から得られる再生信号を比較し
て、再生情報のレベル判定を行う。複数のレーザ光は、
情報記録媒体上の同一点に、同時に照射しても良いし、
異なる点に照射しても良い。 (2）(1）の手段において、収束直径の異なる複数のレー
ザ光を照射する手段として、波長の異なる複数のレーザ
光、または開口数の異なる複数の焦点レンズの少なくと
も一方を用いることとした。In order to achieve the above object, the present invention uses the following means. (1) In the method of reproducing information by irradiating an information recording medium with a laser beam, a plurality of laser beams having different convergent diameters are irradiated on the same recording surface, and reflected light or transmitted light of each laser beam is irradiated. The reproduction signals obtained from the above are compared to determine the level of the reproduction information. Multiple laser lights
The same point on the information recording medium may be irradiated at the same time,
You may irradiate at different points. (2) In the means of (1), at least one of a plurality of laser beams having different wavelengths or a plurality of focus lenses having different numerical apertures is used as a means for irradiating a plurality of laser beams having different convergent diameters.
【０００８】波長の異なるレーザ光と開口数の異なる焦
点レンズの両方を組合せて用いる方法は、再生に都合の
良い任意のレーザ光の収束直径を選択することができる
ので、望ましい。また、波長の異なるレーザ光を用いる
方法は、例えば、焦点レンズの数を少なくして光学ヘッ
ドを軽くすることができるので、高速でアクセスを行う
際に望ましい。一方、開口数の異なる焦点レンズを用い
る方法は、例えば、短波長のレーザ光源を用いる際に望
ましい。なぜなら、レーザ光源は一般に、短波長になる
ほど、高価あるいは大型になるからである。The method of using both the laser beams having different wavelengths and the focusing lenses having different numerical apertures in combination is preferable because it is possible to select an arbitrary convergent diameter of the laser beam which is convenient for reproduction. Further, the method of using laser beams having different wavelengths is desirable when performing access at high speed, for example, because the number of focus lenses can be reduced and the optical head can be made lighter. On the other hand, the method of using focusing lenses having different numerical apertures is desirable, for example, when using a laser light source of short wavelength. This is because the laser light source generally becomes more expensive or larger as the wavelength becomes shorter.
【０００９】(3）(1）の手段において、記録マークの大
きさや間隔に対応する三値以上の情報を読みだすことと
した。ここで記録マークの大きさとは、記録マークの面
積，直径、あるいは長さの情報である。(3) In the means of (1), the information of three or more values corresponding to the size and the interval of the recording mark is read out. Here, the size of the recording mark is information on the area, diameter, or length of the recording mark.
【００１０】なお、記録媒体とは、光ディスクや光カー
ドに限らず、レーザ光によって情報の読み取りが可能な
記録媒体であればよい。また、記録マークは、例えば、
位相差型記録マークが望ましい。The recording medium is not limited to an optical disc or an optical card, and any recording medium capable of reading information by laser light may be used. Also, the recording mark is, for example,
A retardation recording mark is desirable.
【００１１】[0011]
【作用】同一の記録マークであっても、照射するレーザ
光の収束直径が異なると、反射光または透過光から得ら
れる再生信号レベルは、レーザ光の収束直径に依存して
異なる。また、再生信号レベルの、記録マーク直径依存
性や記録マーク依存性は、レーザ光の収束直径によって
異なる。従って、収束直径の異なる複数のレーザ光を照
射して、両者の再生信号レベルを比較すれば、記録媒体
に反射率や透過率の変動が存在しても、記録マークの正
確な大きさや間隔の情報を得ることができる。さらに、
用いるレーザ光の収束直径と記録マークの大きさや間隔
の組合せをうまく選ぶことによって、より正確な再生を
行うことが可能となる。Even if the same recording mark is used, if the convergent diameter of the laser light to be irradiated is different, the reproduction signal level obtained from the reflected light or the transmitted light differs depending on the convergent diameter of the laser light. Further, the recording mark diameter dependency and the recording mark dependency of the reproduction signal level differ depending on the converged diameter of the laser light. Therefore, by irradiating a plurality of laser beams having different convergent diameters and comparing the reproduction signal levels of the two laser beams, even if there are variations in the reflectance and the transmittance of the recording medium, the accurate size and spacing of the recording marks can be determined. You can get information. further,
By properly selecting the combination of the convergent diameter of the laser beam to be used and the size and interval of the recording marks, more accurate reproduction can be performed.
【００１２】ここで情報の再生には、収束直径の異なる
レーザ光から得られたそれぞれの再生信号レベルに加え
て、再生信号レベル間の大小の比較結果や、一方を基準
にして他方を引算して得られる値や、割算を行って得ら
れる値などを用いる。Here, in reproducing the information, in addition to the respective reproduction signal levels obtained from the laser beams having different convergent diameters, the comparison result of the magnitudes of the reproduction signal levels or the one is subtracted from the other. The value obtained by doing, or the value obtained by dividing is used.
【００１３】記録マークの大きさや間隔から、多値情報
を読みだすことができるので、記録媒体の高密度化と再
生の高速化を実現できる。Since multi-valued information can be read from the size and interval of the recording marks, it is possible to realize high density recording medium and high speed reproduction.
【００１４】[0014]
【実施例】図１は、波長が５３０ｎｍと６７０ｎｍのレ
ーザ光を照射したときの再生信号強度の記録マーク直径
依存性を示す。再生信号強度は、未記録部分から得られ
る反射率をＲ(０)、記録マークの中心にレーザ光の中心
が一致したとき得られる反射率をＲ(１)とし、（Ｒ(０)
−Ｒ(１)）／Ｒ(０)として定義した。すなわち、信号強
度とは記録マークが存在することによる反射率変化を、
未記録部分の反射率を基準にして表したものである。焦
点レンズの開口数は０.６０ である。記録マークには、
往復でλ／２の位相差を持たせた。図に示すように、５
３０ｎｍと６７０ｎｍのレーザ光で、再生信号強度のマ
ーク直径依存性が異なる。再生信号強度が最大となるマ
ーク直径は、５３０ｎｍでは０.４４μｍ ，６７０ｎｍ
では０.５５μｍである。また、マーク直径０.４８μｍ
で、両者の再生信号強度の大小関係が逆転する。例えば
記録媒体の反射率変化が生じても、再生信号強度の大小
関係は変わらない。EXAMPLE FIG. 1 shows the recording mark diameter dependence of the reproduction signal intensity when laser beams having wavelengths of 530 nm and 670 nm are irradiated. For the reproduction signal intensity, the reflectance obtained from the unrecorded portion is R (0), the reflectance obtained when the center of the laser beam coincides with the center of the recording mark is R (1), and (R (0)
It was defined as -R (1)) / R (0). That is, the signal strength is the reflectance change due to the presence of the recording mark,
This is expressed based on the reflectance of the unrecorded portion. The numerical aperture of the focusing lens is 0.60. The recording marks include
There was a phase difference of λ / 2 in the round trip. As shown in the figure, 5
The laser beam with a wavelength of 30 nm and the laser beam with a wavelength of 670 nm have different mark diameter dependences of the reproduction signal intensity. The mark diameter that maximizes the reproduction signal intensity is 0.44 μm at 530 nm and 670 nm.
Then, it is 0.55 μm. Also, the mark diameter is 0.48 μm
Then, the magnitude relationship between the reproduction signal strengths of the both is reversed. For example, even if the reflectance of the recording medium changes, the magnitude relationship of the reproduction signal strength does not change.
【００１５】図２は、本実施例で用いた光学系と再生信
号処理回路の一部である。レーザ光源１，２からそれぞ
れのレーザ光３，４はハーフミラー５を通過し、焦点レ
ンズ６によって記録媒体７上に集光される。ここで、レ
ーザ光源１，２の波長はそれぞれ５３０ｎｍと６７０ｎ
ｍである。記録媒体からの反射レーザ光は、ハーフミラ
ーで反射され、光検出器８，９に入る。それぞれの光検
出器は８ａと８ｂ、および９ａと９ｂに２分割されてい
る。再生パルス１０，１１，１２，１３は増幅器１４，
１５，１６，１７で増幅されて加算器１８，１９と減算
器２０，２１で信号処理される。ゼロクロス検出器２
２，２３で記録マークの中心にレーザ光の中心が一致し
たことを知ることができるので、このタイミングでサン
プルホールドレベル検出器２４，２５を用いて、再生信
号レベル２６，２７を読み取れば良い。FIG. 2 shows a part of the optical system and the reproduction signal processing circuit used in this embodiment. The respective laser beams 3 and 4 from the laser light sources 1 and 2 pass through the half mirror 5 and are focused on the recording medium 7 by the focusing lens 6. Here, the wavelengths of the laser light sources 1 and 2 are 530 nm and 670 n, respectively.
m. The reflected laser light from the recording medium is reflected by the half mirror and enters the photodetectors 8 and 9. Each photodetector is divided into two, 8a and 8b, and 9a and 9b. The reproduction pulses 10, 11, 12, 13 are transmitted to the amplifier 14,
The signals are amplified by 15, 16 and 17 and processed by adders 18 and 19 and subtractors 20 and 21. Zero cross detector 2
Since it is possible to know that the center of the laser beam coincides with the center of the recording mark in 2 and 23, it is sufficient to read the reproduction signal levels 26 and 27 using the sample and hold level detectors 24 and 25 at this timing.
【００１６】図３は、同図（ａ）のように直径が０.３
８μｍ，０.４４μｍ，０.４８μｍ,０.５２μｍ の記
録マークから読み取った再生信号レベルを示したもので
ある。同図（ｂ）は５３０ｎｍのレーザ光で読み取った
値、同図（ｃ）は６７０ｎｍレーザ光で読み取った値、
同図（ｄ）は（ｂ）−（ｃ）として求めた値である。い
ずれも、未記録部分からの反射光量を１としている。図
に示すように、（ｄ）の再生信号レベルを用いれば、同
図（ａ）の四種類の大きさの記録マークを判別すること
ができる。未記録の場合を‘０’、記録マークの小さい
順に、‘１’，‘２’，‘３’，‘４’とすれば五値の
情報を再生できる。従来の二値記録の場合の、約２.３
倍の高密度化を行うことができた。In FIG. 3, the diameter is 0.3 as shown in FIG.
The reproduced signal levels read from the recording marks of 8 μm, 0.44 μm, 0.48 μm and 0.52 μm are shown. The figure (b) is the value read with a 530 nm laser beam, the figure (c) is the value read with a 670 nm laser beam,
The figure (d) is the value calculated as (b)-(c). In both cases, the amount of reflected light from the unrecorded portion is 1. As shown in the figure, by using the reproduction signal level of (d), it is possible to discriminate the recording marks of four sizes shown in (a) of the figure. Five-valued information can be reproduced by setting "0" when not recorded and "1", "2", "3", and "4" in ascending order of recording marks. About 2.3 in the case of conventional binary recording
The density could be doubled.
【００１７】レーザ光の波長や焦点レンズの開口数の組
合せを増やせば、さらに多値度の高い情報を再生するこ
とが可能である。この場合、レーザ光の収束直径が大き
く異なるように選ぶことが好ましい。例えば、表１に示
すような組合せの中から選択できる。円形の記録マーク
を用いる場合は、記録マークの直径をこの収束直径の
０.３倍から０.９倍の値にするのがよい。By increasing the combination of the wavelength of the laser light and the numerical aperture of the focusing lens, it is possible to reproduce information having a higher degree of multivalue. In this case, it is preferable to select so that the converged diameters of the laser light differ greatly. For example, the combination shown in Table 1 can be selected. When a circular recording mark is used, the diameter of the recording mark is preferably 0.3 to 0.9 times the convergent diameter.
【００１８】[0018]
【表１】 [Table 1]
【００１９】波長が６７０ｎｍの一つのレーザ光源と、
開口数が０.５０，０.５５，0.60の焦点レンズを用いた
場合にも、同様に再生を行うことができた。One laser light source having a wavelength of 670 nm,
Similar reproduction could be performed using the focusing lenses having numerical apertures of 0.50, 0.55, and 0.60.
【００２０】ここでは、円形の記録マークについてだけ
述べたが、長さの異なる記録マークを用いても良い。ま
た、記録マークの間隔にも、情報を持たせることができ
る。Although only circular recording marks have been described here, recording marks having different lengths may be used. Further, it is possible to give information to the intervals between recording marks.
【００２１】[0021]
【発明の効果】本発明によれば、記録マークの大きさや
間隔から多値情報を再生することができるので、光記録
媒体の高密度化と大容量化を行える。また、レーザ光の
走査方向（光ディスクではトラック方向）の密度が上が
るためデータの転送速度が上がる。さらに、あらかじめ
基準マークを形成しておく必要がなく、また、大きさや
間隔の異なる記録マークの形成は従来の光記録媒体を用
いても容易に実現できるので、安価な光記録媒体が使用
できる。According to the present invention, since multi-valued information can be reproduced from the size and interval of recording marks, it is possible to increase the density and capacity of the optical recording medium. In addition, since the density of the laser beam in the scanning direction (track direction in the optical disk) increases, the data transfer rate increases. Further, it is not necessary to form the reference mark in advance, and the formation of recording marks having different sizes and intervals can be easily realized even by using the conventional optical recording medium, so that an inexpensive optical recording medium can be used.
【図１】本発明の一実施例の波長の異なるレーザ光を用
いたときの信号強度の記録マーク直径依存性を示す説明
図。FIG. 1 is an explanatory diagram showing the dependency of signal strength on recording mark diameter when laser lights having different wavelengths are used according to an embodiment of the present invention.
【図２】本実施例で用いた光学系と再生信号処理系の一
部を示す説明図。FIG. 2 is an explanatory diagram showing a part of an optical system and a reproduction signal processing system used in this embodiment.
【図３】直径の異なる記録マークから得られる再生信号
レベルを示す説明図。FIG. 3 is an explanatory diagram showing reproduction signal levels obtained from recording marks having different diameters.
１，２…レーザ光源、３，４…レーザ光、５…ハーフミ
ラー、６…焦点レンズ、７…情報記録媒体、８，９…光
検出器。1, 2 ... Laser light source, 3, 4 ... Laser light, 5 ... Half mirror, 6 ... Focus lens, 7 ... Information recording medium, 8, 9 ... Photodetector.
フロントページの続き (72)発明者 宮内 靖 東京都国分寺市東恋ケ窪１丁目280番地 株式会社日立製作所中央研究所内Front page continuation (72) Inventor Yasushi Miyauchi 1-280 Higashi Koigokubo, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd.
Claims (3)
よって情報の再生を行う情報の再生方法において、収束
直径の異なる複数の前記レーザ光を同一の記録面上に照
射し、それぞれの前記レーザ光の反射光または透過光か
ら得られる再生信号を比較して、再生情報のレベル判定
を行うことを特徴とする情報の再生方法。1. An information reproducing method for reproducing information by irradiating an information recording medium with a laser beam, wherein a plurality of laser beams having different convergent diameters are irradiated on the same recording surface, and each laser beam is irradiated. A method for reproducing information, characterized in that the level of reproduced information is judged by comparing reproduced signals obtained from reflected light or transmitted light.
記レーザ光、または開口数の異なる複数の焦点レンズの
少なくとも一方を用いる情報の再生方法。2. The information reproducing method according to claim 1, wherein at least one of the plurality of laser beams having different wavelengths or the plurality of focusing lenses having different numerical apertures is used.
間隔に対応する三値以上の情報を再生する情報の再生方
法。3. The information reproducing method according to claim 1, wherein information of three or more values corresponding to the size and interval of recording marks is reproduced.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4010762A JPH05205274A (en) | 1992-01-24 | 1992-01-24 | Information reproducing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4010762A JPH05205274A (en) | 1992-01-24 | 1992-01-24 | Information reproducing method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05205274A true JPH05205274A (en) | 1993-08-13 |
Family
ID=11759343
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4010762A Pending JPH05205274A (en) | 1992-01-24 | 1992-01-24 | Information reproducing method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05205274A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000025308A1 (en) * | 1998-10-26 | 2000-05-04 | Mitsubishi Chemical Corporation | Multivalue recording / reproducing method and phase-change multivalue recording medium |
| WO2000034948A1 (en) * | 1998-12-07 | 2000-06-15 | Sony Corporation | Optical recording medium, recorder for optical recording medium, method for recording the same, reproducing device and reproducing method therefor |
-
1992
- 1992-01-24 JP JP4010762A patent/JPH05205274A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000025308A1 (en) * | 1998-10-26 | 2000-05-04 | Mitsubishi Chemical Corporation | Multivalue recording / reproducing method and phase-change multivalue recording medium |
| US6567367B2 (en) | 1998-10-26 | 2003-05-20 | Mitsubishi Chemical Corporation | Multilevel recording and reproduction method and phase change multilevel recording medium |
| WO2000034948A1 (en) * | 1998-12-07 | 2000-06-15 | Sony Corporation | Optical recording medium, recorder for optical recording medium, method for recording the same, reproducing device and reproducing method therefor |
| AU771285B2 (en) * | 1998-12-07 | 2004-03-18 | Sony Corporation | Optical recording medium, recorder for optical recording medium, method for recording the same, reproducing device and reproducing method therefor |
| US7397748B2 (en) | 1998-12-07 | 2008-07-08 | Sony Corporation | Optical recording medium, recording method and apparatus for optical recording medium and reproducing method and apparatus |
| CN100409333C (en) * | 1998-12-07 | 2008-08-06 | 索尼公司 | Optical recording medium, recording apparatus and method for optical recording medium |
| US7539107B2 (en) | 1998-12-07 | 2009-05-26 | Sony Corporation | Optical recording medium, recording method and apparatus for optical recording medium, and reproducing method and apparatus |
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