JPS61941A - Semiconductor laser pickup device - Google Patents
Semiconductor laser pickup deviceInfo
- Publication number
- JPS61941A JPS61941A JP59119835A JP11983584A JPS61941A JP S61941 A JPS61941 A JP S61941A JP 59119835 A JP59119835 A JP 59119835A JP 11983584 A JP11983584 A JP 11983584A JP S61941 A JPS61941 A JP S61941A
- Authority
- JP
- Japan
- Prior art keywords
- semiconductor laser
- disk
- distance
- resonator
- laser
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/13—Optical detectors therefor
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- General Physics & Mathematics (AREA)
- Optical Recording Or Reproduction (AREA)
- Optical Head (AREA)
- Semiconductor Lasers (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は光デイスクメモリ、オーディオ及びビデオディ
スク等の情報読み出しに用いる半導体レーザを光源とす
る光ピックアップ装置に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical pickup device that uses a semiconductor laser as a light source for reading information from optical disk memories, audio and video disks, and the like.
（従来例の構成とその問題点）
半導体レーザの出射光の一部が帰還した状態にあるのを
自己結合半導体レーザと呼び、この自己結合状態におか
れた半導体レーザは自己結合効果（Ｓｃ１．ｆ−Ｃｏｕ
ｐｌｅｄ−ＩＥｆｆｅｃｔｓ）を示す。代表的な自己結
合効果として
■） 発振しきい値が低下する。(Structure of conventional example and its problems) A state in which a part of the emitted light of a semiconductor laser is returned is called a self-coupled semiconductor laser, and a semiconductor laser placed in this self-coupled state has a self-coupling effect (Sc1. f-Cou
pled-IEffects). A typical self-coupling effect is ■) The oscillation threshold decreases.
２）発振波長が長波長側にシフトし、縦モードが多モー
ド化する。2) The oscillation wavelength shifts to the long wavelength side, and the longitudinal mode becomes multimode.
３） レーザダイオードの電極間の抵抗値が減少する。3) The resistance value between the electrodes of the laser diode decreases.
等がある。この効果を利用して半導体レーザを光源兼光
検出器として光ピツクアップを構成することができる。etc. Utilizing this effect, it is possible to construct an optical pickup using a semiconductor laser as both a light source and a photodetector.
このような光ピツクアップを５ＣＯＯＰ （Ｓｃｌｆ−
Ｃｏｕｐｌｅｄ−Ｏｐｔｉｃａｌ−Ｐｉｃｋｕｐ）とい
う。5 COOP (Sclf-
Coupled-Optical-Pickup).
代表的な５ｃｏｏｐ方式には２種類あり、第１図（Ｊｌ
）に示すのは、ディスク１、レンズ２からの帰還光の有
無による出力光の増減を半導体レーザ素ｆ’□ ３の他
の端面に置いた光検出器４で受光する形式のもので、こ
れをＬ−３ＣＯＯＰと呼ぶ。また第１図（ｂ）に示すの
は戻り光によるレーザダイオード３間の抵抗値の減少を
端子電圧の変化として検出する形式のもので、これをＥ
−３ＣＯＯＰという。５ｃｏｏｐの大きな利点は半導体
レーザがそれ自身光検出器を兼ねているところであり、
光ピツクアップの大幅な小型・軽１７１．化を実現でき
る。There are two types of typical 5coop systems, as shown in Figure 1 (Jl
) is a type in which a photodetector 4 placed on the other end face of the semiconductor laser element f'□3 receives the increase or decrease in output light depending on the presence or absence of feedback light from the disk 1 and lens 2. is called L-3COOP. In addition, the one shown in Fig. 1(b) is of the type that detects the decrease in the resistance value between the laser diodes 3 due to the returned light as a change in the terminal voltage, and this is detected as a change in the terminal voltage.
It's called -3COOP. The big advantage of 5coop is that the semiconductor laser itself doubles as a photodetector.
Significantly smaller and lighter optical pickup 171. can be realized.
ところでディスク上に記録されている情報を読み出すに
は半導体レーザ光をディスク」−に常に焦点を結ばせて
いなければならない。ディスクは回転による面振れがあ
るので、フォーカスレンズをサーボ機構により光軸方向
に動かし、自動制御する必要がある。半導体レーザに縦
甲−モードでコヒーレンスの良いレーザを用いると、フ
ォーカスサーボが動作している時は半導体レーザとデ、
ｒスク間の光路長が変化するので戻り光の位相が変化し
、大きな雑音が発生する。By the way, in order to read information recorded on a disk, a semiconductor laser beam must always be focused on the disk. Since the disk has surface runout due to rotation, it is necessary to move the focus lens in the optical axis direction using a servo mechanism for automatic control. If a laser with good coherence is used as the semiconductor laser in the longitudinal instep mode, the semiconductor laser and the laser diode will overlap when the focus servo is operating.
Since the optical path length between the r-screens changes, the phase of the returned light changes, causing large noise.
（発明の目的）
本発明は半導体レーザの自己結合効果を用いて情報を読
み出す方式の光ピツクアップにおいて、戻り光による雑
音を低い値に抑えることを目的とする。(Objective of the Invention) An object of the present invention is to suppress noise caused by returned light to a low value in an optical pickup system that reads information using the self-coupling effect of a semiconductor laser.
（発明の構成）
この目的を達成するために、本発明の半導体レーり１光
ピックアップ装置は、半導体レーザとディスクとの間の
距離が変化しないように半導体レーザとレンズ系が一体
として光軸方向に駆動され、ディスクの変位に追随させ
てフォーカスサーボをかけるようにしている。この構成
によれば半導体レーザ内に戻るレーザ光の位相は常に一
定に保つことができ半導体レーザとディスク間の距離を
最適値に設定することにより読み出した信号の雑音成分
を大幅に減少させることができる。(Structure of the Invention) In order to achieve this object, the semiconductor laser 1 optical pickup device of the present invention has a semiconductor laser and a lens system integrated in the optical axis direction so that the distance between the semiconductor laser and the disk does not change. The focus servo follows the displacement of the disk. With this configuration, the phase of the laser light returning into the semiconductor laser can always be kept constant, and by setting the distance between the semiconductor laser and the disk to an optimal value, it is possible to significantly reduce the noise component of the read signal. can.
（実施例の説明） 以１・本発明の実施例について詳しく説明する。(Explanation of Examples) Below, 1. Examples of the present invention will be described in detail.
半導体レーザ内に戻り光が入っている状況は、レーザ自
身の共振器（共振器長２００〜３００μｍ）とレーザ端
面と外部反射鏡で形成された外部共振器（共振器長数十
ｍ）との複合共振器と見ることができる。この場合外部
共振器長が半導体レーザの実効共振器長（共振滞長×屈
折率（〜３．６））の整数倍になるとレーザ共振器の縦
モード間隔が外部共振器のモード間隔の整数倍と一致し
、わずかな外乱（外部共振器長の微少変動等）によりレ
ーザ光は著しくゆらぎ、雑音が発生する。第２図は外部
共振器長に対する半導体レーザ光の相対雑音強度（ＲＩ
Ｎ （ｄａ／ｕ２））の測定例である。実効共振器長
（この場合的０ 、９ ｒｍ ）を周期として雑音レベ
ルは約１０ｄＢの変動を繰り返している。レーザ光の雑
ｒｆに対応して端子間電圧も著しくゆらぐので、Ｌ−５
ＣＯＯＰ、Ｅ−８ＣＯＯＰいづ１１． ニおイテも読み
出した信号に雑音が乗ることになる。従って半導体レー
ザからディスクまでの距離（外部共振器長）を常に一定
に保ち、実効共振器長の整数倍にならないようにするこ
とにより雑音レベルを顕著に下げることが可能である。The situation in which the returned light enters the semiconductor laser is due to the interaction between the laser's own resonator (resonator length 200 to 300 μm) and the external resonator formed by the laser end facet and external reflector (resonator length several tens of meters). It can be seen as a composite resonator. In this case, if the external cavity length becomes an integer multiple of the effective cavity length of the semiconductor laser (resonance residence length x refractive index (~3.6)), the longitudinal mode spacing of the laser cavity becomes an integer multiple of the mode spacing of the external cavity. The laser beam fluctuates significantly due to a slight disturbance (such as a minute change in the external cavity length), and noise is generated. Figure 2 shows the relative noise intensity (RI
This is an example of measurement of N (da/u2)). The noise level repeatedly fluctuates by about 10 dB at intervals of the effective resonator length (in this case, 0.9 rm). The voltage between the terminals fluctuates significantly in response to the miscellaneous RF of the laser beam, so L-5
COOP, E-8 COOP Izu 11. Noise will also be added to the read signal. Therefore, by always keeping the distance from the semiconductor laser to the disk (external resonator length) constant and preventing it from becoming an integral multiple of the effective resonator length, it is possible to significantly reduce the noise level.
これを実現するために、本発明の実施例では第３図に示
すように半導体レーザ３とフォーカスレンズ２からなる
光ピツクアップを構成する光学系を一体としてアクチュ
エータ５で光軸ｂ°向に駆動する構造となっている。こ
のようにすれば、ディスク１の振れに追随するようにフ
ォーカスサーボを動作させた時に半導体レーザ３とディ
スク１の距離は一定となり、この距離を雑音レベルが最
小となる値に調整しておけばよい。In order to realize this, in the embodiment of the present invention, as shown in FIG. 3, the optical system constituting the optical pickup consisting of the semiconductor laser 3 and the focus lens 2 is integrally driven in the direction of the optical axis b° by the actuator 5. It has a structure. In this way, when the focus servo is operated to follow the deflection of the disk 1, the distance between the semiconductor laser 3 and the disk 1 will be constant, and if this distance is adjusted to a value that minimizes the noise level, good.
（発明の効果）
以上のように本発明の５ｃｏｏｐ方式による半導体レー
ザ光ピックアップ装置では、ディスクに記録されている
情報を読み出す時に、半導体レーザどディスク間の距離
を一定に保つことができ、その距離を半導体レーザの実
効共振器長の整数倍にならないようにすることにより、
レーザ光及び端子電圧に重畳している雑音レベルを下げ
ることができ、その実用的効果は大なるものがある。(Effects of the Invention) As described above, in the semiconductor laser optical pickup device using the 5-coop system of the present invention, when reading information recorded on the disk, the distance between the semiconductor laser and the disk can be kept constant, and the distance between the semiconductor laser and the disk can be kept constant. By making sure that it is not an integral multiple of the effective cavity length of the semiconductor laser,
The noise level superimposed on the laser light and the terminal voltage can be lowered, which has a great practical effect.
第１図（ａ）と（ｂ）は５ｃｏｏｐの光学系を示す図。
第２図は外部共振器長を変化させた時の半導体レーザの
雑音強度を示す図、第３図は本発明によるＳ ｃ； ０
０ Ｐ方式の光ピツクアップの構造図である。
Ｉ ・・・ ディスク、 ２ ・・・ レンズ、 ３
・・・半導体レーザ素子、 ４・・・光検出素子、 ５
・・・アクチュエータ。
特許出願人 松下電器産業株式会社
第１図
（ｂ）
第２図
（ｄＢ／Ｈｚ ）
第３図
一２０′、FIGS. 1(a) and 1(b) are diagrams showing a 5-coop optical system. FIG. 2 is a diagram showing the noise intensity of a semiconductor laser when the external cavity length is changed, and FIG. 3 is a diagram showing the noise intensity of a semiconductor laser according to the present invention.
FIG. 2 is a structural diagram of an 0P type optical pickup. I... Disc, 2... Lens, 3
... Semiconductor laser element, 4... Photodetection element, 5
...actuator. Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1 (b) Figure 2 (dB/Hz) Figure 3 -20',
Claims (1)
せる機構を備え、フォーカスサーボを機能させた時に、
半導体レーザとディスク間の距離が変化しないようにし
たことを特徴とする半導体レーザ光ピックアップ装置。Equipped with a mechanism that moves the semiconductor laser and lens system together in the optical axis direction, when the focus servo is activated,
A semiconductor laser optical pickup device characterized in that the distance between the semiconductor laser and the disk does not change.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59119835A JPS61941A (en) | 1984-06-13 | 1984-06-13 | Semiconductor laser pickup device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59119835A JPS61941A (en) | 1984-06-13 | 1984-06-13 | Semiconductor laser pickup device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS61941A true JPS61941A (en) | 1986-01-06 |
Family
ID=14771431
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59119835A Pending JPS61941A (en) | 1984-06-13 | 1984-06-13 | Semiconductor laser pickup device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61941A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0598592A3 (en) * | 1992-11-17 | 1995-09-27 | Seiko Epson Corp | Laser emission unit, optical head and optical memory device. |
| EP0887898A1 (en) * | 1997-06-26 | 1998-12-30 | Victor Company Of Japan, Ltd. | Semiconductor laser and optical pickup with the same |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS566039B2 (en) * | 1971-12-13 | 1981-02-09 | ||
| JPS57198553A (en) * | 1982-05-24 | 1982-12-06 | Hitachi Ltd | Information processor |
-
1984
- 1984-06-13 JP JP59119835A patent/JPS61941A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS566039B2 (en) * | 1971-12-13 | 1981-02-09 | ||
| JPS57198553A (en) * | 1982-05-24 | 1982-12-06 | Hitachi Ltd | Information processor |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0598592A3 (en) * | 1992-11-17 | 1995-09-27 | Seiko Epson Corp | Laser emission unit, optical head and optical memory device. |
| US5581523A (en) * | 1992-11-17 | 1996-12-03 | Seiko Epson Corporation | Laser emission unit, optical head and optical memory device |
| US5680384A (en) * | 1992-11-17 | 1997-10-21 | Seiko Epson Corporation | Laser emission unit, optical head and optical memory device |
| EP0887898A1 (en) * | 1997-06-26 | 1998-12-30 | Victor Company Of Japan, Ltd. | Semiconductor laser and optical pickup with the same |
| US6122304A (en) * | 1997-06-26 | 2000-09-19 | Victor Company Of Japan, Ltd. | Semiconductor laser and optical pickup with the same |
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