JPH0812726B2 - Optical pick-up device - Google Patents
Optical pick-up deviceInfo
- Publication number
- JPH0812726B2 JPH0812726B2 JP58209069A JP20906983A JPH0812726B2 JP H0812726 B2 JPH0812726 B2 JP H0812726B2 JP 58209069 A JP58209069 A JP 58209069A JP 20906983 A JP20906983 A JP 20906983A JP H0812726 B2 JPH0812726 B2 JP H0812726B2
- Authority
- JP
- Japan
- Prior art keywords
- semiconductor laser
- optical
- light
- optical disk
- noise
- 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.)
- Expired - Lifetime
Links
Classifications
-
- 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
- G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Head (AREA)
- Semiconductor Lasers (AREA)
Description
【発明の詳細な説明】 〔発明の利用分野〕 本発明はパルス発振する半導体レーザの光デイスク用
ピツク・アツプへの利用に関する。Description: FIELD OF THE INVENTION The present invention relates to the use of a pulsed semiconductor laser for picking up an optical disk.
従来の高周波電流を重畳した半導体レーザを用いた光
ピツク・アツプ装置においては、半導体レーザと光デイ
スクの光路長に関する明確な指針がなく、特定の条件下
で雑音が増大するといつた欠点があつた。In the conventional optical pick-up device using a semiconductor laser with superposed high frequency current, there is no clear guideline regarding the optical path length of the semiconductor laser and the optical disk, and there is a drawback when the noise increases under certain conditions. .
本発明の目的は、パルス発振する半導体レーザを用い
て、低雑音の光デイスク読み出し装置を提供することに
ある。An object of the present invention is to provide a low-noise optical disk reading device using a pulsed semiconductor laser.
半導体レーザに信号周波数より高い周波数の高周波電
流を重畳し、半導体レーザをパルス発振させることによ
り、雑音を抑圧できることが考えられている。ところ
が、このように高周波電流を重畳して半導体レーザを動
作させた場合、半導体レーザと反射体の距離が特定の光
路長となつた場合に雑音が増加する。そして、このよう
に雑音が増加するのは、反射による戻り光がレーザ発振
の開始時に存在する場合であることが明らかとなつた。
したがつて、本発明では、上述の目的を達成するため発
振周期および発振パルス幅および半導体レーザと反射体
の距離を適当な関係が成立するようにし、反射による戻
り光が半導体レーザの発振開始時に重ならないようにし
たことを特徴とする。It is considered that noise can be suppressed by superimposing a high-frequency current having a frequency higher than the signal frequency on the semiconductor laser and causing the semiconductor laser to perform pulse oscillation. However, when the semiconductor laser is operated by superposing the high frequency current in this way, noise increases when the distance between the semiconductor laser and the reflector reaches a specific optical path length. Then, it was revealed that such increase in noise occurs when the return light due to reflection exists at the start of laser oscillation.
Therefore, in the present invention, in order to achieve the above object, the oscillation period, the oscillation pulse width, and the distance between the semiconductor laser and the reflector are made to have an appropriate relationship, and the return light due to the reflection is generated at the start of oscillation of the semiconductor laser. The feature is that they do not overlap.
本発明の一実施例を第１図に示す。第１図は光ピツク
アツプ装置において、半導体レーザと光デイスクの間の
光学系の構成例を示している。１は半導体レーザ、２は
レーザ光を平行光に集束するための集光レンズ、３は光
デイスクからの信号光を受光器に導くためのビーム・ス
プリツター、４は光デイスクからの信号光を受光するた
めの受光器、５は平行光を光デイスク上に集束させるた
めの集束レンズ、６は光デイスクを示す。本実施例にお
いて、半導体レーザは600MHzの高周波電流がしきい値を
切れ込む様に重畳され、第２図に示す光出力波形で発振
している。すなわち、発振時間Ta＝0.87ns、非発振時間
Tb＝0.8ns、周期1.67nsの周期でパルス状に発振してい
る。このとき、１の半導体レーザと６の光デイスクの光
路長Ｌは４〜12cmに設定している。この時の光路長Ｌは
明らかに（ｎ−１）・（Ta＋Tb）・ｃ2L（ｎ−１）
（Ta＋Tb）・ｃ＋Tb・ｃを満たしている。ただし、ｃは
真空中の光速、ｎは本実施例においては１である。この
場合、半導体レーザの出力は3mWで、その相対雑音強度
は測定周波数5MHzで２〜３×10-14Hz-1である。One embodiment of the present invention is shown in FIG. FIG. 1 shows a structural example of an optical system between a semiconductor laser and an optical disk in an optical pickup device. Reference numeral 1 is a semiconductor laser, 2 is a condenser lens for focusing the laser light into parallel light, 3 is a beam splitter for guiding the signal light from the optical disc to a photodetector, and 4 is a signal light from the optical disc. A light receiver 5 for focusing light is a focusing lens for focusing parallel light on the optical disk, and a reference numeral 6 is an optical disk. In this embodiment, the semiconductor laser is superposed so that a high frequency current of 600 MHz cuts the threshold value and oscillates with the optical output waveform shown in FIG. That is, the oscillation time T a = 0.87ns, non-oscillating period
It oscillates like a pulse with a period of T b = 0.8ns and a period of 1.67ns. At this time, the optical path length L of the semiconductor laser 1 and the optical disk 6 is set to 4 to 12 cm. The optical path length L at this time is obviously (n-1) ・ (T a + T b ) ・ c2L (n-1)
(T a + T b ) · c + T b · c is satisfied. However, c is the speed of light in a vacuum, and n is 1 in this embodiment. In this case, the output of the semiconductor laser is 3 mW and its relative noise intensity is 2-3 × 10 −14 Hz −1 at the measurement frequency of 5 MHz.
これに対して、半導体レーザと光デイスクの光路長Ｌ
を５〜27cmの間で変化させた場合の相対雑音強度の変化
を第３図に示す。本実施例におけるＬ12cmの場合に
は、雑音は２〜３×10-14Hz-1に安定している。また、
Ｌ25cmでも同様である。これは、本発明において、ｎ
＝２とした時に（ｎ−１）・（Ta＋Tb）・ｃ2L（ｎ
−１）（Ta＋Tb）・ｃ＋Tb・ｃを満たすためである。こ
れに対し、本発明により規定される光路長Ｌに含まれな
い光路長Ｌ、すなわち12cm＜Ｌ＜25cmの範囲では雑音が
増加している。Ｌ＝23cmで５×10-13Hz-1に対してい
る。したがつて、本実施例の構成を用いることにより、
最悪の場合に較べ10dB以上雑音を抑圧できる。On the other hand, the optical path length L of the semiconductor laser and the optical disk
FIG. 3 shows the change in relative noise intensity when V is varied between 5 and 27 cm. In the case of L12 cm in this embodiment, the noise is stable at 2-3 × 10 −14 Hz −1 . Also,
The same applies to L25 cm. In the present invention, this is
= 2 and the when (n-1) · (T a + T b) · c2L (n
This is because −1) (T a + T b ) · c + T b · c is satisfied. On the other hand, noise increases in the optical path length L not included in the optical path length L defined by the present invention, that is, in the range of 12 cm <L <25 cm. At L = 23 cm, it is against 5 × 10 -13 Hz -1 . Therefore, by using the configuration of this embodiment,
Noise can be suppressed by 10 dB or more compared to the worst case.
また、本発明は、第３図に示すように、ｎ＝１以外の
場合、すなわち任意の自然数ｎに対しても有効である。Further, as shown in FIG. 3, the present invention is also effective when n = 1, that is, for any natural number n.
本発明により、高周波でパルス発振する半導体レーザ
と半導体レーザおよび光デイスクの距離を規定すること
により、半導体レーザの雑音を最悪の場合に較べ10dB以
上低減化することができる。According to the present invention, by defining the distance between the semiconductor laser that oscillates at high frequency and the semiconductor laser and the optical disk, the noise of the semiconductor laser can be reduced by 10 dB or more as compared with the worst case.
なお、本発明において、半導体レーザに重畳する高周
波の周波数は500MHz〜4GHzの範囲内で有効である。In the present invention, the frequency of the high frequency superimposed on the semiconductor laser is effective within the range of 500 MHz to 4 GHz.
第１図は本発明の実施例である半導体レーザと光デイス
クの間の光学系の構成を示す図、第２図は、第１図に示
した半導体レーザの発振状態、すなわち光出力と時間の
関係を示す図、第３図は、第１図において半導体レーザ
と光デイスクの光路長を変化させた場合の、半導体レー
ザの雑音強度の変化を示す図である。 １…半導体レーザ、６…光デイスク。FIG. 1 is a diagram showing a configuration of an optical system between a semiconductor laser and an optical disk according to an embodiment of the present invention, and FIG. 2 is an oscillation state of the semiconductor laser shown in FIG. 1, that is, optical output and time. FIG. 3 is a diagram showing the relationship, and FIG. 3 is a diagram showing changes in the noise intensity of the semiconductor laser when the optical path lengths of the semiconductor laser and the optical disk in FIG. 1 are changed. 1 ... Semiconductor laser, 6 ... Optical disk.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 山口 憲 東京都国分寺市東恋ヶ窪１丁目280番地 株式会社日立製作所中央研究所内 (56)参考文献 特開 昭59−175045（ＪＰ，Ａ) ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ken Yamaguchi 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-59-175045 (JP, A)
Claims (1)
半導体レーザから出射されるレーザ光を光ディスク上に
照射し、該光ディスクからの信号光を上記照射光の上記
光ディスクからの反射光として取り出し、これを受光器
で受光する光ピック・アップ装置において、上記照射光
の上記光ディスクからの反射光が上記半導体レーザから
出射されるレーザ光の発振開始時を除いた発振している
間の出力波形に重なるように上記半導体レーザと上記光
ディスクとの距離を設定したことを特徴とする光ピック
・アップ装置。1. A laser beam emitted from a semiconductor laser driven to periodically oscillate is irradiated onto an optical disc, and signal light from the optical disc is extracted as reflected light of the emitted light from the optical disc. , In an optical pick-up device that receives this with a light receiver, the output waveform of the irradiation light while the reflected light from the optical disk is oscillating except when the oscillation of the laser light emitted from the semiconductor laser is started The optical pick-up device is characterized in that the distance between the semiconductor laser and the optical disk is set so as to overlap with.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58209069A JPH0812726B2 (en) | 1983-11-09 | 1983-11-09 | Optical pick-up device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58209069A JPH0812726B2 (en) | 1983-11-09 | 1983-11-09 | Optical pick-up device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60101735A JPS60101735A (en) | 1985-06-05 |
| JPH0812726B2 true JPH0812726B2 (en) | 1996-02-07 |
Family
ID=16566732
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP58209069A Expired - Lifetime JPH0812726B2 (en) | 1983-11-09 | 1983-11-09 | Optical pick-up device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0812726B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5034942A (en) * | 1987-07-29 | 1991-07-23 | Hitachi, Ltd. | System having a function of reproducing optical information |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59175045A (en) * | 1983-03-23 | 1984-10-03 | Hitachi Ltd | optical system |
-
1983
- 1983-11-09 JP JP58209069A patent/JPH0812726B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60101735A (en) | 1985-06-05 |
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