JPH01155526A - Method for detecting tracking shift of optical spot on optical information recording medium - Google Patents
Method for detecting tracking shift of optical spot on optical information recording mediumInfo
- Publication number
- JPH01155526A JPH01155526A JP31348987A JP31348987A JPH01155526A JP H01155526 A JPH01155526 A JP H01155526A JP 31348987 A JP31348987 A JP 31348987A JP 31348987 A JP31348987 A JP 31348987A JP H01155526 A JPH01155526 A JP H01155526A
- Authority
- JP
- Japan
- Prior art keywords
- track
- recording medium
- information recording
- optical information
- light
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title description 7
- 238000001514 detection method Methods 0.000 claims 1
- 230000004075 alteration Effects 0.000 abstract 1
- 230000001678 irradiating effect Effects 0.000 abstract 1
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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- Optical Recording Or Reproduction (AREA)
Abstract
Description
【発明の詳細な説明】
（技術分野）
本発明は光ディスクなどの光情報記録媒体上の光スポッ
トのトラックずれ検出方法に関する。DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for detecting track deviation of a light spot on an optical information recording medium such as an optical disk.
（従来技術）
第３図は光デイスク装置等において光ディスク等の光情
報記録媒体上の光スポットのトラックずれを検出するた
めの光学系の一例を示す。(Prior Art) FIG. 3 shows an example of an optical system for detecting a track deviation of a light spot on an optical information recording medium such as an optical disk in an optical disk device or the like.
半導体レーザ１から出射されたレーザ光２はコリメータ
レンズ３により平行光となって偏光プリズム４．１／４
波長板５．集光レンズ６を通って光情報記録媒体７に集
光照射され、その反射光は集光レンズ６．１／４波長板
５．偏光プリズム４を通って２分割受光素子８で受光さ
れる。光情報記録媒体７は透明基板９と光吸収反射性記
録膜１０から構成され、トラックずれを検出するための
案内溝１１が形成されている。案内溝１０の深さがλ／
８（λは上記レーザ光の波長）付近であれば光情報記録
媒体７からの反射光の遠視野にＩδかれている２分割受
光素子８の各受光部８ａ、８ｂの出力信号Ａ、Ｂの差Ａ
−Ｂを第４図に示すように減算器１２で求めることによ
ってトラックずれ信号Ａ−Ｂが得られる。２分割受光素
子８の受光部８ａ、８ｂを分割する分割線１４は光軸１
３を通りかつ案内溝１１と平行になるように配置されて
いる。A laser beam 2 emitted from a semiconductor laser 1 is converted into parallel light by a collimator lens 3, and then passes through a polarizing prism 4.1/4.
Wave plate 5. The light is condensed and irradiated onto the optical information recording medium 7 through the condenser lens 6, and the reflected light is passed through the condenser lens 6.1/4 wavelength plate 5. The light passes through the polarizing prism 4 and is received by the two-split light receiving element 8 . The optical information recording medium 7 is composed of a transparent substrate 9 and a light absorbing reflective recording film 10, and is provided with a guide groove 11 for detecting track deviation. The depth of the guide groove 10 is λ/
8 (λ is the wavelength of the laser beam), the output signals A and B of the light receiving sections 8a and 8b of the two-split light receiving element 8, which are located in the far field of the reflected light from the optical information recording medium 7, are Difference A
-B is obtained by the subtracter 12 as shown in FIG. 4, thereby obtaining the track deviation signal A-B. A dividing line 14 that divides the light receiving sections 8a and 8b of the two-split light receiving element 8 is along the optical axis 1.
3 and parallel to the guide groove 11.
このような光情報記録媒体上の光スポラ１−のトラック
ずれ検出方法はプッシュプル方法として周知である。This method of detecting track deviation of the optical spoiler 1- on the optical information recording medium is well known as a push-pull method.
一般にトラックサーボ系は一ヒ記トラックずれ信号Ａ−
Ｂにより集光レンズ６を図示しないアクチュエータで案
内溝１１．光軸１３に垂直な方向に動かすことにより光
情報記録媒体７上の集光スポットをトラック１５に合わ
せるようにトラック制御（トラッキング）を行う。Generally, the track servo system uses the following track deviation signal A-
B, the condenser lens 6 is moved into the guide groove 11 by an actuator (not shown). Track control (tracking) is performed so that the focused spot on the optical information recording medium 7 is aligned with the track 15 by moving it in a direction perpendicular to the optical axis 13 .
しかし上記プッシュプル方法では光情報記録媒体７上の
トラック１５は第５１４に示すように未記録のトラック
１５ａ、凹凸ピット１６の存在するトラック１５ｂ、記
録穴ピット１７の存在するトラック１５ｃが混在してい
てレーザ光が矢印１８の方向に入射及び反射をするので
、トラック１５上のピットがある部分から反射光が２分
割受光素子８まで達しなくてトラックずれ信号がこのピ
ットのある部分で弱くなり、これは未記録トラック１５
ａに対するトラックずれ信号の約１７２になる。However, in the push-pull method described above, the tracks 15 on the optical information recording medium 7 include an unrecorded track 15a, a track 15b with uneven pits 16, and a track 15c with recording hole pits 17, as shown in No. 514. Since the laser beam is incident and reflected in the direction of the arrow 18, the reflected light does not reach the two-split light receiving element 8 from the part where the pit is located on the track 15, and the track deviation signal becomes weak at the part where the pit is located. This is unrecorded track 15
The track deviation signal for a is about 172.
このためトラックサーボ系のサーボ利得が減少し、光情
報記録媒体７上の集光スポットのトラックに対するずれ
を十分に小さくできないという欠点があった。As a result, the servo gain of the track servo system decreases, and there is a drawback that the deviation of the focused spot on the optical information recording medium 7 from the track cannot be made sufficiently small.
（目 的）
本発明は上記欠点を改善し、光情報記録媒体上のピット
が存在しているトラックに対するトラックずれ信号のレ
ベル低下を防止してトラッキングの安定性の向上を計る
ことができる光情報記録媒体上の光スポットのトラック
ずれ検出方法を提供することを目的とする。(Objective) The present invention improves the above-mentioned drawbacks, and provides an optical information recording medium capable of improving tracking stability by preventing a drop in the level of a track deviation signal for a track where a pit exists on an optical information recording medium. An object of the present invention is to provide a method for detecting track deviation of a light spot on a recording medium.
（構 成）
本発明は案内溝を有する光情報記録媒体に集光スポット
を照射し、その反射光の遠視野の位置に、光軸を通りか
つ上記案内溝と平行な分割線を有する２分割受光素子を
設けてこの２分割受光素子により上記反射光を受光し、
上記２分割受光素子の各受光部の出力信号Ａ、Ｂから
Ａ −Ｂ ＋ ｋ （ａ −ｂ ）
ｋ：定数
ａ ： Ｉ ｄＡ／ｄ ｔ ｌ
ｂ ： ｜ｄＢ／ｄｔ ｌ
ｄ／ｄｔ：時間微分
なるトラックずれ信号を得ることを特徴としている。(Structure) The present invention irradiates an optical information recording medium having a guide groove with a condensed light spot, and divides the reflected light into two parts having a dividing line passing through the optical axis and parallel to the guide groove at the far field position of the reflected light. A light receiving element is provided, and the reflected light is received by the two-split light receiving element,
From the output signals A and B of each light receiving part of the above-mentioned two-split light receiving element, A - B + k (a - b) k: constant a: I dA/d t l b: | dB/dt l d/dt: time differential It is characterized in that it obtains a track deviation signal.
第１図は本発明の実施例で用いた回路の一例を示す。こ
の実施例は上記第３１・４の光学系で２分割受光素子８
の各受光部８ａ、８ｂから得られる信号、を第１図の回
路で処理してトラックずれ信号を得る。FIG. 1 shows an example of a circuit used in an embodiment of the present invention. In this embodiment, the 31st and 4th optical system has a two-split light receiving element 8.
The signals obtained from each of the light receiving sections 8a and 8b are processed by the circuit shown in FIG. 1 to obtain a track deviation signal.
減算器１９は上記２分割受光素子８の各受光部８ａ、８
ｂから得られる信号Δ、Ｂの差をとることにより２分割
受光索子８の各受光部８ａ、８ｂの出力信号Ａ、Ｂの差
Ａ−１３を算出する。また２分割受光素子８の各受光部
８ａ、８ｂから得られる信号Ａ、Ｂはそれぞれ微分ｊ！
Ｉｆ ２０ Ｈ２１により微分されてｄＡ／ｄｔ、ｄＢ
／ｄｔとなり、更に絶対値回路２２．２３により整流さ
れてｌｄＡ／ｄｔ ｌ 、ｌｄＢ／ｄｔｌとなった後に
、減算器２４により差がとられてｌｄＡ、／ｄｔ Ｉ
−ＪｄＢ／ｄｔ ｌなる信号が得られる。この信号は増
幅器２５により増幅されることにより利得が設定され、
加算器２６により減算器１９の出力信号と加算されてＡ
−Ｂ＋ｋ（ｌｄＡ／ｄｔ ｌ −１ｄＢ／ｄｔ ｌ）な
るトラックずれ信号ＴＥが得られる。ここにｋは定数で
あり、トラックずれ信号ＴＥの未記録トラック１５ａと
、ピットの存在するトラック１５ｂ、１５ｃとに対する
各利得が同一になるように増幅器２５の利得が調整され
る。また絶対値回路２２．２３は全波整流器又は半波整
流器を用いることができる。The subtracter 19 corresponds to each light receiving section 8a, 8 of the two-divided light receiving element 8.
The difference A-13 between the output signals A and B of the light receiving portions 8a and 8b of the two-split light receiving cable 8 is calculated by taking the difference between the signals Δ and B obtained from the signal Δ. Further, the signals A and B obtained from the respective light receiving sections 8a and 8b of the two-split light receiving element 8 are respectively differentiated by j!
Differentiated by If 20 H21 dA/dt, dB
/dt, which is further rectified by the absolute value circuit 22.23 to become ldA/dt l and ldB/dtl, and then the difference is taken by the subtracter 24 and becomes ldA, /dt I
A signal of -JdB/dtl is obtained. This signal is amplified by the amplifier 25 to set the gain.
The adder 26 adds the output signal of the subtracter 19 to A.
A track deviation signal TE of -B+k (ldA/dt l -1 dB/dt l) is obtained. Here, k is a constant, and the gain of the amplifier 25 is adjusted so that the gains of the track deviation signal TE for the unrecorded track 15a and the tracks 15b and 15c in which pits are present are the same. Furthermore, the absolute value circuits 22 and 23 can use full-wave rectifiers or half-wave rectifiers.
次にこの実施例を第２図により信号レベルの面から更に
詳しく説明する。Next, this embodiment will be explained in more detail in terms of signal levels with reference to FIG.
第２図において横軸は時間を示し、縦軸は光情報記録媒
体７とその上に集光レンズ６により集光されたレーザ光
のスポットが相対的に等速度で動いている時に２分割受
光素子８により検出される光量のレベル（２分割受光素
子８の出力信号レベル）と、その処理波形を示している
。第２図（１）は２分割受光素子８におけろ受光部８ａ
によって検出される受光量（受光部８ａの出力信号Ａ）
であり、トラック上の未記録部Ｌ ａｎｄに対しては一
定であるが、トラック上のピットがある部分Ｄ ａｔａ
に対してはパルス的に低下する。第２図（２）は２分割
受光素子８における受光部８ｂによって検出される受光
量（受光部８ｂの出力信号Ｂ）である。In Fig. 2, the horizontal axis indicates time, and the vertical axis indicates two-split light reception when the optical information recording medium 7 and the laser beam spot focused by the condensing lens 6 move at a relatively constant speed. The level of the amount of light detected by the element 8 (output signal level of the two-split light receiving element 8) and its processed waveform are shown. FIG. 2 (1) shows the light receiving section 8a in the two-split light receiving element 8.
The amount of light received (output signal A of the light receiving section 8a) detected by
is constant for the unrecorded part L and on the track, but the part D at which there is a pit on the track
It decreases in a pulse-like manner. FIG. 2(2) shows the amount of light detected by the light receiving section 8b in the two-split light receiving element 8 (output signal B of the light receiving section 8b).
第２図（３）は減算器１９の出力信号であって従来のト
ラックずれ信号と同様であり、トラック上の未記録部Ｌ
ａｎｄに対する部分よりもトラック上のピットがある
部分に対する部分の方が信号レベルが小さくなる。第２
図（４）（５）はＡ、Ｂの微分器２０．２１による各微
分波形であり、その振幅値は元の波形の振幅値に比例し
て大きくなる。これらの微分波形の差をとるためにこれ
らの微分波形の絶対値を絶対値回路２２．２３で演算し
てその差を減算器２４で演算すると、第２図（６）に示
すようなｌ ｄＡ／ｄ ｔ Ｉ −１ｄＢ ／Ｌ＋ ｔ
ｌなる信号が得られる。この信号は直流分しか持たず
、トラック上の未記録部Ｌ ａｎｄでは得られなくてト
ラック上のピットがある部分Ｄ ａｔａでのみ得られる
トラックずれ信号であり、Ａ−Ｂなるトラックずれ信号
に増幅器２５及び加算器２６により適当な量だけ加算し
てＡ−Ｂ＋ｋ（｜ｄＡ／ｄｔ ｌ −１ｄＢ／ｄｔ１）
とすることによりトラック上の未記録部と記録部（穴ピ
ット記録部、凹凸ピット記録部の両方）で利得変動の少
ないトラックずれ信号が得られる。FIG. 2(3) is the output signal of the subtracter 19, which is similar to the conventional track deviation signal, and is the unrecorded area L on the track.
The signal level is lower in the portion corresponding to the pit on the track than in the portion corresponding to and. Second
Figures (4) and (5) show differential waveforms obtained by the differentiators 20 and 21 of A and B, and their amplitude values increase in proportion to the amplitude values of the original waveforms. In order to obtain the difference between these differential waveforms, the absolute values of these differential waveforms are computed by the absolute value circuits 22 and 23, and the difference is computed by the subtracter 24, resulting in l dA as shown in FIG. 2 (6). /d t I -1dB /L+ t
A signal of l is obtained. This signal has only a DC component, and is a track deviation signal that cannot be obtained in the unrecorded part L and on the track, but can only be obtained in the part Data on the track where there are pits. 25 and adder 26 to add an appropriate amount to A-B+k (|dA/dt l -1 dB/dt1)
By doing so, it is possible to obtain a track deviation signal with little gain variation in the unrecorded portion and the recorded portion (both the hole pit recording portion and the uneven pit recording portion) on the track.
（効 果）
以上のように本発明によれば案内溝を有する光情報記録
媒体に集光スポットを照射し、その反射光の遠視野の位
置に、光軸を通りかつ上記案内溝と平行な分割線を有す
る２分割受光素子を設けてこの２分割受光素子により上
記反射光を受光し、上記２分割受光素子の各受光部の出
力信号Ａ、 Ｂから
Ａ−Ｂ＋ｋ（ａ−ｂ）
ｋ：定数
ａ ： ｌｄＡ／ｄｔ ｌ
ｂ ： ｌｄＢ／ｄｔ ｌ
ｄ／ｄｔ：時間微分
なるトラックずれ信号を得るので、光情報記録媒体上の
ピットが存在しているトラックに対するトラックずれ信
号のレベル低下を防止できてトラック上の未記録部と記
録部でトラックずれ信号の利得変動が少なくなり、トラ
ック上の記録部に対するトラックサーボ系の利得不足に
よるトラッキング誤差が少なくなってトラッキングの安
定性の向上を計ることができ、信頼性が向上する。(Effects) As described above, according to the present invention, a condensed light spot is irradiated onto an optical information recording medium having a guide groove, and the far field position of the reflected light is placed along the optical axis and parallel to the guide groove. A two-split light-receiving element having a dividing line is provided, and the two-segment light-receiving element receives the reflected light, and the output signals A and B of each light-receiving part of the two-segment light-receiving element are A-B+k (a-b) k: Constant a: ldA/dt lb: ldB/dt ld/dt: Since a time-differentiated track deviation signal is obtained, it is possible to prevent a drop in the level of the track deviation signal for a track where a pit exists on the optical information recording medium. This reduces the gain fluctuation of the track deviation signal between the unrecorded area and the recorded area on the track, and reduces the tracking error due to insufficient gain of the track servo system for the recorded area on the track, improving tracking stability. and improve reliability.
【図面の簡単な説明】
第１図は本発明の実施例で用いた回路を示すブロック図
、第２図は同実施例のタイミングチャート、第３図はト
ラックずれ検出用光学系の一例を示す図、第４図は従来
のプッシュプル方法で用いた回路を示すブロック図、第
５図は光情報記録媒体の一例の一部を示す斜視図である
。
１９．２４・・・減算器、２０．２１・・・微分器。
２２．２３・・・絶対値回路、２５・・・増幅器、２６
・・・加算器。
くＱ ：＾
＾ ＾ Ａ Σ−′：′
Ｊ ｔ′） −ｆ Ｏ。
ｗ ｗ 、
。[Brief Description of the Drawings] Fig. 1 is a block diagram showing a circuit used in an embodiment of the present invention, Fig. 2 is a timing chart of the same embodiment, and Fig. 3 shows an example of an optical system for detecting track deviation. 4 is a block diagram showing a circuit used in the conventional push-pull method, and FIG. 5 is a perspective view showing a part of an example of an optical information recording medium. 19.24...Subtractor, 20.21...Differentiator. 22.23...Absolute value circuit, 25...Amplifier, 26
...adder. KuQ: ＾
^ ^ A Σ−′:′
J t′) −f O. lol,
.
Claims (1)
、その反射光の遠視野の位置に、光軸を通りかつ上記案
内溝と平行な分割線を有する２分割受光素子を設けてこ
の２分割受光素子により上記反射光を受光し、上記２分
割受光素子の各受光部の出力信号Ａ、ＢからＡ−Ｂ＋ｋ
（ａ−ｂ） ｋ：定数 ａ：｜ｄＡ／ｄｔ｜ ｂ：｜ｄＢ／ｄｔ｜ ｄ／ｄｔ：時間微分 なるトラックずれ信号を得ることを特徴とする光情報記
録媒体上の光スポットのトラックずれ検出方法。[Claims] A condensed light spot is irradiated onto an optical information recording medium having a guide groove, and the reflected light has a dividing line in the far field that passes through the optical axis and is parallel to the guide groove. A device is provided, and the reflected light is received by the two-split light receiving element, and the output signals A and B of each light receiving section of the two-split light receiving element are A-B+k.
(a-b) k: constant a: |dA/dt| b: |dB/dt| d/dt: track deviation of a light spot on an optical information recording medium characterized by obtaining a time-differentiated track deviation signal Detection method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31348987A JPH01155526A (en) | 1987-12-11 | 1987-12-11 | Method for detecting tracking shift of optical spot on optical information recording medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31348987A JPH01155526A (en) | 1987-12-11 | 1987-12-11 | Method for detecting tracking shift of optical spot on optical information recording medium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01155526A true JPH01155526A (en) | 1989-06-19 |
Family
ID=18041929
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP31348987A Pending JPH01155526A (en) | 1987-12-11 | 1987-12-11 | Method for detecting tracking shift of optical spot on optical information recording medium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01155526A (en) |
-
1987
- 1987-12-11 JP JP31348987A patent/JPH01155526A/en active Pending
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