JP2629838B2 - Optical head - Google Patents
Optical headInfo
- Publication number
- JP2629838B2 JP2629838B2 JP63138700A JP13870088A JP2629838B2 JP 2629838 B2 JP2629838 B2 JP 2629838B2 JP 63138700 A JP63138700 A JP 63138700A JP 13870088 A JP13870088 A JP 13870088A JP 2629838 B2 JP2629838 B2 JP 2629838B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- optical
- recording medium
- waveguide
- refractive index
- 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 - Fee Related
Links
Landscapes
- Optical Head (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は、光記録再生装置における光学ヘッド、更に
詳細には屈折率分布光カプラを用いた光学ヘッドに関す
るものである。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head in an optical recording / reproducing apparatus, and more particularly, to an optical head using a gradient index optical coupler.
［従来技術］ 従来、この種の光学ヘッドは、第８図に示すように、
半導体レーザ81、コリメータレンズ82、偏光ビームスプ
リッタ83、λ/4板84、対物レンズ85、及び該対物レンズ
を駆動しフォーカシング、トラッキングを行うための図
示されないアクチュエータ、シリンドカルレンズ86、四
分割フォトダイオード等の受光素子87等から構成されて
いる。半導体レーザ81より出射されたレーザ光は、コリ
メータレンズ82で平行光となり偏光ビームスプリッタ83
を透過し、λ/4板84で直線偏光から円偏光となる。さら
に対物レンズ85によりディスク88の記録面上に集光され
る。ディスク88からの反射光は、λ/4板84で再び直線偏
光となる。この反射光の偏光方向は入射光と直交するた
め偏光ビームスプリッタ83で反射されシリンドリカルレ
ンズ86で集光され四分割フォトダイオードで受光され
る。例えばフォーカシングは、シリンドリカルレンズ86
による非点収差法により得られるエラー信号により対物
レンズ85を上下させることにより行われ、また、トラッ
キングは、プッシュプル法により対物レンズ85をディス
ク面方向に移動させることにより行われる。また、アク
セスは、光学ヘッド全体を動かすことにより行う。[Prior Art] Conventionally, this type of optical head has a structure as shown in FIG.
Semiconductor laser 81, collimator lens 82, polarizing beam splitter 83, λ / 4 plate 84, objective lens 85, actuator (not shown) for driving and focusing and tracking the objective lens, cylindrical lens 86, quadrant photo It comprises a light receiving element 87 such as a diode. The laser light emitted from the semiconductor laser 81 is converted into parallel light by a collimator lens 82 and a polarization beam splitter 83
And the light is converted from linearly polarized light to circularly polarized light by the λ / 4 plate 84. Further, the light is focused on the recording surface of the disk 88 by the objective lens 85. The light reflected from the disk 88 is again linearly polarized by the λ / 4 plate 84. Since the polarization direction of the reflected light is orthogonal to the incident light, it is reflected by the polarization beam splitter 83, collected by the cylindrical lens 86, and received by the four-division photodiode. For example, focusing uses a cylindrical lens 86
The tracking is performed by moving the objective lens 85 in the disk surface direction by a push-pull method by moving the objective lens 85 up and down by an error signal obtained by the astigmatism method. Access is performed by moving the entire optical head.
［発明が解決しようとする課題］ しかしながら、このような従来の光学ヘッドでは、固
定ディスク等と比べてアクセス速度が遅い。また、組み
立ての際、部品が多いため、各光学部品の光軸調整がめ
んどうであり、時間がかかる。さらに、各光学部品はガ
ラス等で作られており、大きく重いため、光学ヘッド全
体が大型で重くなる等の問題点があった。[Problems to be Solved by the Invention] However, such a conventional optical head has a slower access speed than a fixed disk or the like. Also, when assembling, since there are many components, the optical axis adjustment of each optical component is troublesome and time-consuming. Furthermore, since each optical component is made of glass or the like and is large and heavy, there is a problem that the entire optical head is large and heavy.
本発明は、上述した問題点を解決するためになされた
ものであり、その目的とするところは、高速アクセスが
可能であり、光軸調整箇所の少い信頼性の高い光学ヘッ
ドを提供することにある。また、光学ヘッドの小型軽量
化を図らんとするものである。The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a highly reliable optical head that can perform high-speed access and has few optical axis adjustment portions. It is in. It is another object of the present invention to reduce the size and weight of the optical head.
［課題を解決するための手段］ この目的を達成するために本発明の光学ヘッドは、光
記録媒体面に近接状態で対向配置され、該媒体面を平行
移動するスライダーに、該記録媒体面の情報を読み取る
ための光を発する光源と、該光源からの光を記録媒体面
に伝送する導波路と、その導波路の記録媒体面側に設け
られ、伝送された光を記録媒体面に集束させるため屈折
率分布が光源からの光の伝送方向に沿って非直線的に変
化する光カプラとからなる光導波器と、該記録媒体面に
集束された光の反射光を受光する光検知器とが備えられ
ている。[Means for Solving the Problems] To achieve this object, an optical head according to the present invention is provided so as to be opposed to an optical recording medium surface in a state of being close to the optical recording medium surface, and has a slider that translates in parallel with the medium surface. A light source that emits light for reading information, a waveguide that transmits light from the light source to the recording medium surface, and a waveguide that is provided on the recording medium surface side of the waveguide and focuses the transmitted light on the recording medium surface An optical waveguide consisting of an optical coupler whose refractive index distribution changes nonlinearly along the transmission direction of light from the light source, and a photodetector that receives the reflected light of the light focused on the recording medium surface Is provided.
［作用］ 上記の構成の本発明の光学ヘッドは、光源からの光は
光導波器の導波路内を伝送され、導波路の記録媒体面側
に設けられた光カプラの非直線的な屈折率分布により記
録媒体面に集束される。記録媒体面からの反射光は、光
検知器により受光される。[Operation] In the optical head of the present invention having the above structure, light from a light source is transmitted through the waveguide of the optical waveguide, and the nonlinear refractive index of the optical coupler provided on the recording medium surface side of the waveguide. The light is focused on the recording medium surface by the distribution. Light reflected from the recording medium surface is received by a photodetector.
［実施例］ 以下、本発明を具体化した一実施例を図面を参照して
説明する。[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.
第１図は本発明の光学ヘッドの一実施例を示す概略構
成図である。半導体レーザ等の光源１から出射したレー
ザ光は、屈折率分布光カプラ２により光導波路３に結合
され、さらに集光作用を有する屈折率分布光カプラ４に
より出射され、記録媒体５上に集光される。屈折率分布
光カプラ４によりレーザ光は、基板６側に出射されるた
め、出射方向は光導波路３中の光の伝搬方向とある角度
をなす。光導波路３、屈折率光カプラ２、４は、高速で
回転する記録媒体５に対し、常に一定の間隔で近接浮上
するスライダ７に固定されている。このスライダ７の空
気浮上作用は、通常の磁気ディスクに用いられる浮動ヘ
ッドスライダの同一である。このため、屈折率分布光カ
プラの集光点が常に記録面上にくるためフォーカシング
が常に行われる。記録媒体５からの反射光は、光検出器
８で受光され、情報信号及びトラッキング信号が得られ
る。FIG. 1 is a schematic configuration diagram showing an embodiment of the optical head of the present invention. Laser light emitted from a light source 1 such as a semiconductor laser is coupled to an optical waveguide 3 by a refractive index distribution optical coupler 2, further emitted by a refractive index distribution optical coupler 4 having a condensing function, and condensed on a recording medium 5. Is done. Since the laser light is emitted toward the substrate 6 by the refractive index distribution optical coupler 4, the emission direction forms an angle with the light propagation direction in the optical waveguide 3. The optical waveguide 3 and the refractive index optical couplers 2 and 4 are fixed to a slider 7 which always floats at a constant interval to the recording medium 5 rotating at a high speed. The air floating action of the slider 7 is the same as that of a floating head slider used for a normal magnetic disk. For this reason, focusing is always performed because the focal point of the refractive index distribution optical coupler is always on the recording surface. The reflected light from the recording medium 5 is received by the photodetector 8, and an information signal and a tracking signal are obtained.
光導波路及び屈折率分布光カプラは例えば第２図のよ
うにLiNbO3等の結晶基板21上に形成されたTi22を熱拡散
することにより作製される。Tiの膜厚分布は第２図のよ
うに光導波路３の部分では均一であるが、屈折率分布光
カプラ部では、図のように膜厚が非直線的に減少する。
このような膜厚分布をもつTiを拡散したときの屈折率分
布は第３図のようになる。すなわちTiを拡散することに
よりLiNbO3の屈折率が増加し、その屈折率の増加の割合
はTi膜厚に依存する。従って光導波路３の両端の屈折率
分布光カプラ2,4の屈折率は第３図のように変化し、こ
の屈折率の変化は、直線的ではなく例えば伝搬距離の平
方根にほぼ比例している。例えばこの屈折率分布カプラ
４を光が図中左から右へ進行する場合、導波光の感じる
等価屈折率が徐々に小さくなるため、光が徐々に基板に
広がり、カットオフ近傍で基板に放射される。このと
き、屈折率分布は、直線的でないため、放射された光
は、集光される。逆に集光点から屈折率分布光カプラに
発せられた光は効率よく導波路に結合される。このた
め、屈折率分布光カプラ２により半導体レーザ１から発
せられた光は効率よく導波路３に結合される。また、屈
折率分布光カプラ４から出射された光は、スライダ７の
空気浮上作用により常に記録媒体面上に集光されるため
高密度記録が可能となる。Optical waveguides and the refractive index distribution optical coupler is fabricated by thermal diffusion Ti22 formed on crystal substrate 21, such as a LiNbO 3 as Figure 2, for example. Although the film thickness distribution of Ti is uniform in the portion of the optical waveguide 3 as shown in FIG. 2, the film thickness in the refractive index distribution optical coupler portion decreases non-linearly as shown in the figure.
FIG. 3 shows the refractive index distribution when Ti having such a film thickness distribution is diffused. That is, by diffusing Ti, the refractive index of LiNbO 3 increases, and the rate of increase in the refractive index depends on the Ti film thickness. Therefore, the refractive indexes of the refractive index distribution optical couplers 2 and 4 at both ends of the optical waveguide 3 change as shown in FIG. 3, and the change in the refractive index is not linear but is substantially proportional to, for example, the square root of the propagation distance. . For example, when light travels from the left to the right in the figure through the refractive index distribution coupler 4, the equivalent refractive index felt by the guided light gradually decreases, so that the light gradually spreads over the substrate and is emitted to the substrate near the cutoff. You. At this time, since the refractive index distribution is not linear, the emitted light is collected. Conversely, light emitted from the focal point to the gradient index optical coupler is efficiently coupled to the waveguide. Therefore, light emitted from the semiconductor laser 1 by the refractive index distribution optical coupler 2 is efficiently coupled to the waveguide 3. Further, the light emitted from the refractive index distribution optical coupler 4 is always focused on the recording medium surface by the air floating action of the slider 7, so that high density recording is possible.
第４図に示すように屈折率分布光カプラ４から出射さ
れたレーザ光41はトラッキング用案内溝42の設けられた
記録媒体５上に集光照射され、記録媒体からの反射光は
案内溝42によって回折されるため、二分割フォトダイオ
ード８で受光することによりプッシュプル法によりトラ
ッキングを行うことができる。すなわち、二分割フォト
ダイオード８の差動出力よりトラッキングエラー信号が
得られる。また、二分割フォトダイオード８の和信号に
より情報信号が得られる。As shown in FIG. 4, the laser beam 41 emitted from the gradient index optical coupler 4 is focused and irradiated on the recording medium 5 provided with the tracking guide groove 42, and the reflected light from the recording medium is Therefore, tracking can be performed by the push-pull method by receiving light with the two-segment photodiode 8. That is, a tracking error signal is obtained from the differential output of the two-part photodiode 8. Further, an information signal is obtained from the sum signal of the two-part photodiode 8.
基板６は、記録媒体に対し必ずしも垂直に保持する必
要はなく例えば第５図のように出射光が記録媒体面上に
垂直となるように配置してもよい。このとき、光導波路
を第６図のように例えば３分岐導波路61とし、中央に半
導体レーザ等の光源１、その両側に受光素子62を配置し
てもよい。この時、記録媒体からの反射光は、案内溝に
よる回折のため中央部の光強度は小さく、その両側の光
強度が大きくなるため、３分岐導波路の両側の分岐導波
路に多くの部分が伝送され受光素子62で検出される。そ
の差動出力によりトラッキングエラー信号、和出力によ
り情報信号が得られる。The substrate 6 does not necessarily need to be held perpendicular to the recording medium, and may be arranged, for example, such that the emitted light is perpendicular to the surface of the recording medium as shown in FIG. At this time, the optical waveguide may be, for example, a three-branch waveguide 61 as shown in FIG. 6, the light source 1 such as a semiconductor laser may be disposed at the center, and the light receiving elements 62 may be disposed on both sides thereof. At this time, the reflected light from the recording medium is diffracted by the guide groove, so that the light intensity at the center is small and the light intensity on both sides is large. The transmitted light is detected by the light receiving element 62. A tracking error signal is obtained by the differential output, and an information signal is obtained by the sum output.
尚、導波路61と光源１の間に光アイソレーダを挿入
し、記録媒体からの反射光が光源に戻らないようにして
もよい。Note that an optical isolator may be inserted between the waveguide 61 and the light source 1 so that the reflected light from the recording medium does not return to the light source.
また、第７図のように３つの導波路71,72,73を用い、
それらの出力を受光素子74,75,76で検出する。この時、
両側の導波路72,73からの出射光のスポットが、情報を
再生しているトラックの両側のトラックにそれぞれ半分
ずつ照射されるいわゆる３ビーム法によるトラッキング
を行うことができる。Also, as shown in FIG. 7, three waveguides 71, 72 and 73 are used,
These outputs are detected by the light receiving elements 74, 75, and 76. At this time,
Tracking can be performed by a so-called three-beam method in which the spots of the light emitted from the waveguides 72 and 73 on both sides are respectively radiated to the tracks on both sides of the track from which information is reproduced, respectively.
スライダと光導波路は、異なった材料でもよいし、ス
ライダをLiNbO3、ガラス等で作製し、その表面に直接導
波路を作製してもよい。また、屈折率分布光カプラの屈
折率分布の形状については特に限定しない。光源から光
導波路への光の入射方法についても限定しない。例え
ば、光導波路端面への直接結合あるいは、光ファイバ等
で接続してもよい。The slider and the optical waveguide may be made of different materials, or the slider may be made of LiNbO 3 , glass or the like, and the waveguide may be made directly on the surface. The shape of the refractive index distribution of the refractive index distribution optical coupler is not particularly limited. There is no limitation on the method of making light incident on the optical waveguide from the light source. For example, it may be directly coupled to the end face of the optical waveguide, or may be connected by an optical fiber or the like.
［発明の効果］ 以上詳述したことから明らかなように、本発明の光学
ヘッドによれば、光源からの光は光導波器の導波路内を
伝送され、導波路の記録媒体面側に設けられた光カプラ
の非直線的な屈折率分布により記録媒体面に集束され、
記録媒体面からの反射光は光検知器により受光される。
このため、高解像度が実現される。この光源と光導波器
と光検出器とがスライダーに設けられているため、前記
従来の光学ヘッドに比べて部品点数が少なく軽量である
ので固定ディスク並の高速アクセスが可能である。ま
た、光軸調整箇所も少なくでき信頼性も高めることがで
きるという大変実用的な効果を奏する。[Effects of the Invention] As is clear from the above, according to the optical head of the present invention, light from a light source is transmitted through the waveguide of the optical waveguide and provided on the recording medium surface side of the waveguide. Focused on the recording medium surface by the non-linear refractive index distribution of the optical coupler,
Light reflected from the recording medium surface is received by a photodetector.
Therefore, high resolution is realized. Since the light source, the optical waveguide, and the photodetector are provided on the slider, the number of components is smaller and the weight is smaller than that of the conventional optical head, so that high-speed access is possible as with a fixed disk. Also, there is an extremely practical effect that the number of optical axis adjustment portions can be reduced and the reliability can be improved.
第１図から第７図までは本発明を具体化した実施例を示
すもので、第１図は本発明の実施例である光学ヘッドを
示す構成図、第２図は光学ヘッドに用いられる導波路及
び屈折率分布光カプラを作製するための拡散前のTiの膜
厚分布を示す図、第３図は導波路及び屈折率分布光カプ
ラの屈折率分布を示す図、第４図は本光学ヘッドによる
再生の説明図、第５図は本発明の変形例を示す図、第６
図は本発明の変形例における導波路の１例を示す図、第
７図は本発明の変形例を示す図、第８図は従来の光学ヘ
ッドの構成例を示す図である。 図中、１は半導体レーザ、2,4は屈折率分布光カプラ、
３は導波路、５は記録媒体、６は基板、７はスライダ、
８は光検出器である。FIGS. 1 to 7 show an embodiment embodying the present invention. FIG. 1 is a block diagram showing an optical head according to an embodiment of the present invention, and FIG. FIG. 3 is a diagram showing a film thickness distribution of Ti before diffusion for producing a waveguide and a gradient index optical coupler, FIG. 3 is a diagram showing a refractive index distribution of a waveguide and a gradient index optical coupler, and FIG. FIG. 5 is an explanatory diagram of reproduction by a head, FIG. 5 is a diagram showing a modification of the present invention, and FIG.
FIG. 1 is a diagram showing an example of a waveguide according to a modification of the present invention, FIG. 7 is a diagram showing a modification of the present invention, and FIG. 8 is a diagram showing a configuration example of a conventional optical head. In the figure, 1 is a semiconductor laser, 2 and 4 are graded index optical couplers,
3 is a waveguide, 5 is a recording medium, 6 is a substrate, 7 is a slider,
8 is a photodetector.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 別所 芳則 愛知県名古屋市瑞穂区堀田通９丁目35番 地 ブラザー工業株式会社内 審査官 山田 洋一 (56)参考文献 特開 平１−271931（ＪＰ，Ａ) 特開 平１−279432（ＪＰ，Ａ) ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshinori Bessho 9-35, Horitadori, Mizuho-ku, Nagoya-shi, Aichi Examiner at Brother Industries, Ltd. Yoichi Yamada (56) References A) JP-A-1-279432 (JP, A)
Claims (1)
該媒体面を平行移動するスライダーに、 該記録媒体面の情報を読み取るための光を発する光源
と、 該光源からの光を記録媒体面に伝送する導波路と、その
導波路の記録媒体面側に設けられ、伝送された光を記録
媒体面に集束させるため屈折率分布が光源からの光の伝
送方向に沿って非直線的に変化する光カプラとからなる
光導波器と、 該記録媒体面に集束された光の反射光を受光する光検知
器とが備えられている光学ヘッド。1. An optical recording medium, comprising:
A light source that emits light for reading information on the recording medium surface, a waveguide that transmits light from the light source to the recording medium surface, and a recording medium surface side of the waveguide. An optical waveguide comprising: an optical coupler having a refractive index distribution that changes nonlinearly along a transmission direction of light from a light source in order to focus transmitted light on a recording medium surface; And an optical detector for receiving reflected light of the light focused on the optical head.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63138700A JP2629838B2 (en) | 1988-06-06 | 1988-06-06 | Optical head |
| US07/262,693 US4865407A (en) | 1987-10-22 | 1988-10-26 | Optical waveguide element, method of making the same and optical coupler employing optical waveguide element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63138700A JP2629838B2 (en) | 1988-06-06 | 1988-06-06 | Optical head |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01307934A JPH01307934A (en) | 1989-12-12 |
| JP2629838B2 true JP2629838B2 (en) | 1997-07-16 |
Family
ID=15228084
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63138700A Expired - Fee Related JP2629838B2 (en) | 1987-10-22 | 1988-06-06 | Optical head |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2629838B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6181673B1 (en) * | 1996-07-30 | 2001-01-30 | Read-Rite Corporation | Slider design |
| JP4146017B2 (en) * | 1998-03-24 | 2008-09-03 | セイコーインスツル株式会社 | Near-field optical head |
| JP4109744B2 (en) * | 1998-03-24 | 2008-07-02 | セイコーインスツル株式会社 | Near-field optical head |
| JP4498429B2 (en) * | 2008-03-19 | 2010-07-07 | セイコーインスツル株式会社 | Near-field optical head |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01271931A (en) * | 1988-04-22 | 1989-10-31 | Sony Corp | Optical reproducing head |
| JPH01279432A (en) * | 1988-04-30 | 1989-11-09 | Nippon Telegr & Teleph Corp <Ntt> | Optical head |
-
1988
- 1988-06-06 JP JP63138700A patent/JP2629838B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01307934A (en) | 1989-12-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Ura et al. | An integrated-optic disk pickup device | |
| EP0306342B1 (en) | Optical information processing apparatus | |
| JP2736894B2 (en) | Optical pickup, optical disk device and rotary encoder including the same | |
| US4876680A (en) | Monolithic optical pick-up using an optical waveguide | |
| JPH0554184B2 (en) | ||
| US5835472A (en) | Optical pickup device with substantially mutually orthogonal reflection surfaces | |
| JPH07192280A (en) | Near-field optical scan recording and reproducing device | |
| US5249167A (en) | Optical pickup apparatus which includes a plate-like element for splitting a returning light beam into different light beams having different focussing point | |
| EP0581597B1 (en) | An optical information reproducing device | |
| JP2629838B2 (en) | Optical head | |
| EP0469552A2 (en) | Optical pickup device | |
| JPS6047239A (en) | Optical head device | |
| US20020122374A1 (en) | Optical recording medium, optical information processing apparatus and optical recording and reproducing method | |
| JPH0793797A (en) | Optical head and disk device using the same | |
| JP2629812B2 (en) | Optical playback pickup | |
| JPH10269614A (en) | Polarization proximity field light detecting head and optical information recording and reproducing device using the same | |
| JPS6288150A (en) | Pickup for optical disk | |
| JP2825873B2 (en) | Optical waveguide | |
| JP2513237B2 (en) | Optical head device | |
| JPH0219537B2 (en) | ||
| Nishihara et al. | Integrated-optic disc pickups | |
| KR850000649Y1 (en) | Forcus detecting device | |
| JPH07169090A (en) | Optical information parallel recorder/reproducer | |
| JPH04265539A (en) | Optical waveguide recording medium | |
| Minami et al. | OPTICAL WAVEGUIDE DEVICE FOR A MAGNETO-OPTICAL DISK HEAD |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |