JPH04186535A - Optical information replay unit - Google Patents

Optical information replay unit

Info

Publication number
JPH04186535A
JPH04186535A JP2319664A JP31966490A JPH04186535A JP H04186535 A JPH04186535 A JP H04186535A JP 2319664 A JP2319664 A JP 2319664A JP 31966490 A JP31966490 A JP 31966490A JP H04186535 A JPH04186535 A JP H04186535A
Authority
JP
Japan
Prior art keywords
frequency
light
laser
path length
recording medium
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
Application number
JP2319664A
Other languages
Japanese (ja)
Inventor
Masaki Kono
正基 河野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Priority to JP2319664A priority Critical patent/JPH04186535A/en
Priority to DE4133772A priority patent/DE4133772A1/en
Priority to NL9101734A priority patent/NL9101734A/en
Publication of JPH04186535A publication Critical patent/JPH04186535A/en
Pending legal-status Critical Current

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
    • G11B7/126—Circuits, methods or arrangements for laser control or stabilisation

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)

Abstract

PURPOSE:To restrain a noise at a relay operation by a method wherein, when a high-frequency current is superposed in order to drive a semiconductor laser with which an information recording medium is irradiated, a specific relationship is established between its frequency and the distance from the light-emitting edge of the laser up to the recording medium. CONSTITUTION:An optical pickup is divided into a fixed unit 7 and a movement unit 8; an AlGaAs semiconductor laser 1 and a collimator lens 2 are installed at the unit 7; a beam splitter 3, an object lens 4, a condensing lens 5 and a photodetector 6 are installed at the unit 8. It is arranged that a formula is established between the following: a frequency (f) (Hz) for a high-frequency current superposed on a DC driving current for the laser 1; and a light-path length L(mm) in terms of the air from the light-emitting edge of the laser 1 up to a recording medium 10. Since the light-path length L is at 50 to 94mm in the case of this example, 650 to 1,100MHz is selected for the frequency (f). Thereby, it is possible to restrain a noise at a replay operation.

Description

【発明の詳細な説明】 （産業上の利用分野） この発明は、光学的情報の再生装置にかかり、特に半導
体レーザを用いた光ディスクの再生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 information reproducing apparatus, and more particularly to an optical disc reproducing apparatus using a semiconductor laser.

〔従来の技術〕[Conventional technology]

従来、例えば第３図に示すような光ディスクの再生装置
か実用されている。すなわち、半導体レーザｌの発光は
、コリメートレンズ２、ビームスプリッタ３及び対物レ
ンズ４を経て光デイスク１０上に焦点を結び、その反射
光は、対物レンズ４、ビームスプリッタ３及び集光レン
ズ５を経て光検出器６に入射して、光デイスク１０上の
記録情報を再生するのであり、上記１〜６によって光学
式ピックアップ９を構成している。Conventionally, for example, an optical disk reproducing apparatus as shown in FIG. 3 has been put into practical use. That is, the light emitted from the semiconductor laser l passes through the collimating lens 2, the beam splitter 3, and the objective lens 4 and is focused on the optical disk 10, and the reflected light passes through the objective lens 4, the beam splitter 3, and the condensing lens 5. The light enters the photodetector 6 and reproduces the recorded information on the optical disk 10, and the above-described elements 1 to 6 constitute an optical pickup 9.

この種の光学式ピックアップては半導体レーザは５ｍＷ
以下ての低出力て使用されるか、光ディスク１０におけ
る反射光の一部か半導体レーザ１に帰還され、これに起
因して半導体レーザに雑音か発生する。よって、この雑
音の発生を抑止するために半導体レーザの直流駆動電流
に５０ＭＨｚ以上の高周波電流を重畳することか、特公
昭５９−９０８６号公報に示されている。For this type of optical pickup, the semiconductor laser is 5mW.
If the optical disk 10 is used at a low output power, a part of the reflected light from the optical disk 10 is fed back to the semiconductor laser 1, and this causes noise in the semiconductor laser. Therefore, in order to suppress the generation of this noise, Japanese Patent Publication No. 59-9086 discloses that a high frequency current of 50 MHz or more is superimposed on the DC drive current of the semiconductor laser.

（発明か解決しようとする課題） 第３図に示すような光学式ピックアップ９は、半導体レ
ーザ１及び光検出器６を含むすべての部品を一体にまと
めているために、小型軽量化が閤約され、情報再生時に
高速て運動させるのに支障を生じていた。(Problem to be solved by the invention) Since the optical pickup 9 as shown in FIG. This made it difficult to move at high speeds when reproducing information.

その対策として、光学式ピックアップを１半導体レーザ
やコリメートレンズなどを含む固定ユニットと、ビーム
スプリッタや光検出器などを含む移動ユニットとに分け
ることにより、移動ユニットを小型軽量化して、高速運
動を容易にすることを試みた。しかし、このようにする
と、半導体レーザの発光面から情報記録媒体までの光路
長か大きく変化するため、レーザの直流駆動電流に高周
波電流を重畳しても光路長か成る値のときにＳ／Ｎ比が
悪化し、かつこのＳ／Ｎ比が悪くなる光路長の値か、直
流駆動電流に重畳する高周波電流の周波数によって変わ
ることか発見された。As a countermeasure, the optical pickup can be divided into a fixed unit that includes a semiconductor laser, collimating lens, etc., and a moving unit that includes a beam splitter, photodetector, etc., thereby making the moving unit smaller and lighter and facilitating high-speed movement. I tried to make it. However, when this is done, the optical path length from the light emitting surface of the semiconductor laser to the information recording medium changes significantly, so even if a high frequency current is superimposed on the laser's DC drive current, the S/N will remain at a value equal to the optical path length. It has been discovered that the value of the optical path length at which the S/N ratio deteriorates depends on the frequency of the high-frequency current superimposed on the DC drive current.

よフて、この発明は、半導体レーザと光ディスクとの間
の光路長との関連のもとに、半導体レーザの駆動電流に
重畳する高周波電流の最適周波数範囲を見出そうとする
ものである。Therefore, the present invention attempts to find the optimum frequency range of the high frequency current to be superimposed on the driving current of the semiconductor laser in relation to the optical path length between the semiconductor laser and the optical disk.

（課題を解決するための手段） この発明も、前記特公昭５９−９０８６号に示された装
置と同様に、半導体レーザの発光を記録媒体上に照射し
、その反射光を光電変換して情報再生信号を得る装置に
おいて、半導体レーザを駆動する直流電流に高周波電流
を重畳するものであるか、その高周波電流の周波数ｆ　
（Ｈｚ）と半導体レーザの発光端面から情報記録媒体ま
での空気中換算光路長Ｌ（ｍ層）との関係を ３．２５ｘ　１０”／　Ｌ≦ｆ≦１０．：ｌｘ　１０１
０／　Ｌに選んだことを特徴とするものである。(Means for Solving the Problems) Similar to the device disclosed in Japanese Patent Publication No. 59-9086, the present invention also irradiates light emitted from a semiconductor laser onto a recording medium, converts the reflected light into electricity, and converts the reflected light into information. In the device for obtaining reproduction signals, whether a high-frequency current is superimposed on the DC current that drives the semiconductor laser, or the frequency f of the high-frequency current is
(Hz) and the in-air equivalent optical path length L (m layer) from the light emitting end surface of the semiconductor laser to the information recording medium is 3.25x 10"/L≦f≦10.: lx 101
It is characterized by being selected as 0/L.

〔作用〕[Effect]

半導体レーザとしてＡｌＧａＡｓレーザを用い、発光出
力か３■Ｗになるように駆動直流を設定し、これに周波
数ｆの高周波を重畳して発光させ、情報記録媒体の代り
に戻り光率７％の反射体を置いた。An AlGaAs laser is used as the semiconductor laser, and the driving DC is set so that the emission output is 3 ■ W. A high frequency wave of frequency f is superimposed on this to emit light, and the reflection with a light rate of 7% is returned instead of the information recording medium. I put my body down.

そして、１０　Ｍｌ（ｚ±１５０ＫＨｚの帯域内に３け
るＳ／Ｎ比と光路長しとの関係を重畳高周波の周波数ｆ
か２５０ＭＨｚ、：１００ＭＨｚ、４００ＭＨｚ、５０
０ＭＨｚ、　６００ＭＨｚ、　７００ＭＨｚ　、　８０
０１１Ｈｚの場合について求めた結果を、それぞれ第４
図（ａ）、　（ｂ）　、（ｃｌ　（ｄＬ　（ｅ）、　（
ｆ）、　（ｇ）に示す。これらの図におけるＳ／Ｎ比か
悪い光路長領域を整理すれば、次の通りである。Then, the relationship between the S/N ratio and the optical path length is superimposed within the band of 10 Ml (z ± 150 KHz) and the high frequency frequency f
or 250MHz, :100MHz, 400MHz, 50
0MHz, 600MHz, 700MHz, 80
The results obtained for the case of 0.011Hz are
Figures (a), (b), (cl (dL (e), (
f) and (g). The optical path length regions with poor S/N ratios in these figures are summarized as follows.

また、上述の重畳高周波の各周波数において。Also, at each frequency of the above-mentioned superimposed high frequency.

２０　ＫＨｚ±１５０　Ｈｚの帯域内におけるＳ／Ｎ比
と光路長りとの関係はそれぞれ第５図（ａ）、（ｂ）ｕ
ｃ）、（ｄ）、（ｅ）、（ｆ）　、　（ｇ）の通りであ
り、これらの図におけるＳ／Ｎ比が悪い光路長領域は次
の通りである。The relationship between the S/N ratio and the optical path length within the band of 20 KHz ± 150 Hz is shown in Figures 5 (a) and (b), respectively.
c), (d), (e), (f), and (g), and the optical path length regions in which the S/N ratio is poor in these figures are as follows.

第１図は、横軸に光路長のｉ！数（１／Ｌ）をとり、縦
軸に上記重畳周波数ｆをとって、その中に第４図におけ
るＳ／Ｎ比不良不良領域線て、第５図におけるＳ／Ｎ比
不良不良領域線て示した図である。この図によると、Ｓ
／Ｎ比不良不良領域すべて ｆ　＝　３．２５ｘ　１０”／　し て表わされる線１１の右側、または ｆ　＝　１０．３ｘ　１０′。／　し て表わされる線１２の左側に分布している。In Figure 1, the horizontal axis represents the optical path length i! The number (1/L) is taken, and the superimposed frequency f is plotted on the vertical axis, and therein, the poor S/N ratio defective area line in FIG. 4 and the poor S/N ratio defective area line in FIG. 5 are plotted. FIG. According to this figure, S
/N ratio defective areas are all distributed on the right side of line 11, expressed as f = 3.25x 10''/, or on the left side of line 12, expressed as f = 10.3x 10'./.

従って、光学式ピックアップが固定ユニットと移動ユニ
ットとに分かれていて、光路長しか大幅に変化しても、
光路長りの変化範囲か線１１と１２の間に納まるように
重畳高周波数を選ぶことにより、情報再生時の雑音を抑
制することかてきる。Therefore, even if the optical pickup is divided into a fixed unit and a moving unit, and only the optical path length changes significantly,
By selecting the superimposed high frequency so that the variation range of the optical path length falls between lines 11 and 12, noise during information reproduction can be suppressed.

また、！ｓ３図に示すような一体型の光学式ピックアッ
プ９においても、組立て誤差や各部品の特性のばらつき
による光路長しの変動か線１１と１２の間に納まるよう
に設計することにより、面倒な光の位相調整を行なうこ
となく、雑音の発生か少ないピックアップを製作するこ
とかできる。Also,! Even in the case of the integrated optical pickup 9 shown in Figure s3, the optical path length variation due to assembly errors and variations in the characteristics of each component is designed so that it falls between lines 11 and 12. It is possible to manufacture a pickup that generates less noise without performing phase adjustment.

（実施例〕 第２図に示すように、光学式ピックアップを固定ユニッ
ト７と移動ユニット８とに分け、固定ユニット７にはＡ
ｌＧａＡｓ半導体レーザ１とコリメートレンズ２を設け
、移動ユニット８にはビームスプリッタ３、対物レンズ
４、集光レンズ５及び光検出器６を設ける。(Example) As shown in FIG. 2, the optical pickup is divided into a fixed unit 7 and a moving unit 8, and the fixed unit 7 has an
A lGaAs semiconductor laser 1 and a collimating lens 2 are provided, and a moving unit 8 is provided with a beam splitter 3, an objective lens 4, a condensing lens 5, and a photodetector 6.

情報記録媒体１０か３．５インチの光ディスクの場合は
、移動ユニット８の移動距離は約４４−■であり、レー
ザ１の発光面から光ディスク１ｏまでの光路長りのうち
、不変部分が約５０１厘になるから、この実施例におけ
る光路長りは約５０ｍｍがら約９４ｍｍの聞出変化する
ことになる。従って、直流駆動電流に重畳する高周波電
流の周波数ｆを６５０Ｍ）ｌｚ以上１１００Ｍ）Ｉｚ以
下に選ぶことにより、第１図から明らかなように情報再
生時の雑音を抑制することかてきる。In the case of an information recording medium 10 or a 3.5-inch optical disc, the movement distance of the moving unit 8 is approximately 44-■, and the unchanging portion of the optical path length from the light emitting surface of the laser 1 to the optical disc 1o is approximately 501. Therefore, the optical path length in this embodiment changes from about 50 mm to about 94 mm. Therefore, by selecting the frequency f of the high frequency current to be superimposed on the DC drive current to be between 650 M) Iz and 1100 M) Iz, noise during information reproduction can be suppressed, as is clear from FIG.

また、第３図に示すような一体型の光学式ピックアップ
で光路長か４５−一の場合は、直流駆動電流を重畳する
高周波電流の周波数ｆを７５０ＭＨｚ以上に選ぶことに
より、組立時の光路長しか設計値から多少外れていても
、第１図から明らかなように情報再生時の雑音を抑制す
ることかてきる。In addition, when the optical path length is 45-1 with an integrated optical pickup as shown in Fig. 3, the optical path length during assembly can be reduced by selecting the frequency f of the high-frequency current that superimposes the DC drive current to 750 MHz or more. However, even if it deviates somewhat from the design value, it is possible to suppress noise during information reproduction, as is clear from FIG.

〔発明の効果〕〔Effect of the invention〕

以上の説明によって明らかなように、この発明によると
きは、光学式ピックアップを固定ユニットと移動ユニッ
トとに分割した場合の光路長の変化の全範囲にわたって
、情報再生時の雑音を抑制てきるのて、光学式ピックア
ップの移動部分の小型軽量化を実現してその高速運動を
可能にすることかてきる。また、一体型の光学式ピック
アップの場合も、製造時の寸法誤差などによる再生時の
雑音を抑制することかてきるAs is clear from the above description, according to the present invention, noise during information reproduction can be suppressed over the entire range of changes in optical path length when an optical pickup is divided into a fixed unit and a moving unit. This makes it possible to make the moving parts of an optical pickup smaller and lighter, thereby enabling its high-speed movement. Also, in the case of an integrated optical pickup, it is possible to suppress noise during playback due to dimensional errors during manufacturing.

【図面の簡単な説明】[Brief explanation of drawings]

第１図はこの発明におけるレーザ駆動電流に重畳する高
周波電流の選択範囲を示す図、第２図はこの発明を実施
した分割型光学式ピックアップの光路図、第３図は従来
の一体型光学式ビツクアップの光路図、第４図は光学式
ピックアップの１０ＭＨｚ±１５０ＫＨｚ帯における光
路長とＳ／Ｎ比の関係を重畳高周波の各周波数ごとに示
す図、第５図は光学式ピックアップの２０　Ｋ）ｌｚ±
１５［ＩＨｚ帯における光路長とＳ／Ｎ比の関係を重畳
高周波の各周波数ごとに示す図である。 １・・・・半導体レーザ、２・・・・コリメートレンズ
、３・・・・ビームスプリッタ２４・・・・対物レンズ
、５・・・・集光レンズ、６・・・・光検呂器、１ｏ・
・・・情報記録媒体。Fig. 1 is a diagram showing the selection range of the high-frequency current to be superimposed on the laser drive current in this invention, Fig. 2 is an optical path diagram of a split-type optical pickup implementing this invention, and Fig. 3 is a conventional integrated optical pickup. Optical path diagram of the pickup. Figure 4 is a diagram showing the relationship between the optical path length and S/N ratio in the 10 MHz ± 150 KHz band of the optical pickup for each frequency of the superimposed high frequency. Figure 5 is the optical path diagram of the optical pickup at 20 KHz. ±
15 is a diagram showing the relationship between the optical path length and the S/N ratio in the IHz band for each frequency of the superimposed high frequency. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Collimating lens, 3... Beam splitter 24... Objective lens, 5... Condensing lens, 6... Optical detector, 1o・
...Information recording medium.

Claims (1)

【特許請求の範囲】[Claims] （１）半導体レーザに高周波電流を重畳した直流駆動電
流を与えてレーザ発光させ、この発光を情報記録媒体に
照射し、その反射光を検出することによって上記媒体に
記録されている情報を再生する装置において、上記レー
ザの発光端面から上記記録媒体までの空気中３．２５×
１０＾１＾０／Ｌ≦ｆ≦１０．３×１０＾１＾０／Ｌに
選んだことを特徴とする光学的情報再生装置。(1) Applying a DC drive current superimposed on a high-frequency current to a semiconductor laser to cause it to emit laser light, irradiating the emitted light onto an information recording medium, and detecting the reflected light to reproduce information recorded on the medium. In the apparatus, the distance from the light emitting end face of the laser to the recording medium is 3.25× in the air.
An optical information reproducing device characterized in that 10^1^0/L≦f≦10.3×10^1^0/L.
JP2319664A 1990-11-20 1990-11-20 Optical information replay unit Pending JPH04186535A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP2319664A JPH04186535A (en) 1990-11-20 1990-11-20 Optical information replay unit
DE4133772A DE4133772A1 (en) 1990-11-20 1991-10-11 Optical disc esp. CD reading unit - applies DC to drive semiconductor laser and modulates by HF current related to formula length of optical air path
NL9101734A NL9101734A (en) 1990-11-20 1991-10-17 SYSTEM FOR RECOVERING OPTICAL INFORMATION.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2319664A JPH04186535A (en) 1990-11-20 1990-11-20 Optical information replay unit

Publications (1)

Publication Number Publication Date
JPH04186535A true JPH04186535A (en) 1992-07-03

Family

ID=18112824

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2319664A Pending JPH04186535A (en) 1990-11-20 1990-11-20 Optical information replay unit

Country Status (3)

Country Link
JP (1) JPH04186535A (en)
DE (1) DE4133772A1 (en)
NL (1) NL9101734A (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5475235A (en) * 1993-08-09 1995-12-12 Wyatt Technoloy Corporation Control of laser light power output for use in light scattering instruments by inducing mode hopping and averaging result

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6035344A (en) * 1983-08-08 1985-02-23 Hitachi Tobu Semiconductor Ltd Light emitting device and optical signal processor using light emitting device

Also Published As

Publication number Publication date
DE4133772A1 (en) 1992-05-21
NL9101734A (en) 1992-06-16

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