JP3787835B2

JP3787835B2 - Multiple wavelength synthesizer

Info

Publication number: JP3787835B2
Application number: JP2000092537A
Authority: JP
Inventors: 浩松本; 泰二篠田
Original assignee: Miyazaki Epson Corp
Current assignee: Miyazaki Epson Corp
Priority date: 2000-03-29
Filing date: 2000-03-29
Publication date: 2006-06-21
Anticipated expiration: 2020-03-29
Also published as: JP2001283457A

Description

【０００１】
【発明の属する技術分野】
本発明は、概して光学素子に関し、さらに詳細には、波長の異なる２つの光線を１つの光線に合成する素子とこれを用いた光ピックアップに関する。
【０００２】
【従来の技術】
光ディスク装置に用いられる光ピックアップは、種類の異なる光ディスクに対応するため、波長の異なる複数のレーザ光が使用できる構造となっている。
図１０に、異なる波長の光源を２つ使用する光ピックアップの一般的な構成例を示す。図１０において、１は波長６５０ｎｍのＬＤ（レーザダイオード），２は波長７８０ｎｍのＬＤ、３は２波長を合成するダイクロイックプリズムである。
このように構成した２波長の光を合成する光学系において、波長６５０ｎｍのＬＤ１の光は、ほぼ９０％以上がダイクロイックプリズム３を透過する。また、波長７８０ｎｍのＬＤ２の光は、ほぼ９０％以上がダイクロイックプリズム３で９０°反射して、ＬＤ１からの透過光と同じ光路に入る。それぞれの光を同じ方向に反射および透過させる事で２波長を合成する事が一般的であった。
しかしながら、このような従来の方法では、ＬＤの配置が２方向になるため光ピックアップのコンパクト化が困難であった。
【０００３】
【発明が解決しようとする課題】
本発明は上記問題点を解決するためになされたものであり、隣接して配置された複数の光源からの平行な光線を１つに合成する複数波長合成素子を提供することを課題とする。
このような複数波長合成素子を用いたコンパクトな光ピックアップを提供することも別の課題である。
また、複数波長の光を１つの半導体チップで発光出射可能な発光源において、複数波長の光線を１つの光線に合成する機能を持ったデバイスをパッケージの蓋もしくは発光源と一体化する事で、複数波長の光線を１つに合成する機能を持った発光源を提供することを課題とする。
さらに、本発光源を用いたさらにコンパクト且つ低コストの光ピックアップを提供することを課題とする。
【０００４】
【課題を解決するための手段】
上述の課題は、以下の波長の異なる複数のレーザ光線を単一光線にする方法および光学系、光ピックアップ、およびこれらを用いた波長の異なる複数のレーザ光線を用いる装置によって達成される。
請求項１の波長の異なる複数のレーザ光線を単一光線にする方法は、波長の異なる複数のレーザ光線を発する複数の光源を、前記複数のレーザ光線が同一平面上で平行となるように配置するステップと、対向する面に対し４５度の光学軸を有する一軸結晶の板からなる複数波長合成素子を前記光学軸が前記同一平面と平行になるように前記レーザ光線の光路上に前記レーザ光線と直角に配置するステップと、前記レーザ光線の偏波面が前記複数波長合成素子に対して共に異常光線となるように設定するステップと、前記複数波長合成素子に入射した前記レーザ光線が前記複数波長合成素子から同一の光路で出射するように前記複数の光源の間隔を調節するステップとを含むことを特徴とする。
請求項２記載の波長の異なる複数のレーザ光線を単一光線にする光学系は、波長の異なる複数のレーザ光線を同一平面内で平行に発するように配置された複数の光源と、対向する面に対し４５度の光学軸を有する一軸結晶の板からなり且つ前記光学軸が前記同一平面と平行になるように前記レーザ光線の光路上に前記レーザ光線と直角に配置された複数波長合成素子とを備え、前記レーザ光線の偏波面が前記複数波長合成素子に対して共に異常光線となるように設定されており、且つ前記複数の光源の間隔が、前記複数波長合成素子に入射した前記レーザ光線が前記複数波長合成素子から同一の光路で出射するように調節されたことを特徴とする。
請求項３の発明は、請求項２記載の光学系において、前記複数の光源が、前記複数のレーザ光線を単独で発する多波長レーザダイオードであることを特徴とする。
請求項４の発明は、請求項２又は３記載の光学系を備えたことを特徴とする光ピックアップである。
請求項５の発明は、請求項２又は３記載の光学系を備えたことを特徴とする波長の異なる複数のレーザ光線を用いる装置である。
請求項６の発明は、波長の異なる３以上のレーザ光線を発する３以上の光源を、前記３以上のレーザ光線が同一平面上で平行になるように配置するステップと、対向する面に対し４５度の光学軸を有する一軸結晶の板からなる複数波長合成素子を前記光学軸が前記同一平面と平行になるように前記レーザ光線の光路上に前記レーザ光線と直角に配置するステップと、前記レーザ光線の偏波面が前記複数波長合成素子に対して常光線または異常光線となるように設定するステップと、前記複数波長合成素子に入射した前記レーザ光線が前記複数波長合成素子から同一の光路で出射するように前記３以上の光源の間隔を調節するステップとを含むことを特徴とする。
請求項７の発明は、波長の異なる２つのレーザ光線を発する２つの光源を、前記２つのレーザ光線が同一平面上で平行となるように配置するステップと、対向する面に対し角度ψの光学軸を有する一軸結晶の板からなる複数波長合成素子を前記光学軸が前記同一平面と平行になるように前記レーザ光線の光路上に前記レーザ光線と直角に配置するステップと、前記レーザ光線の偏波面が前記複数波長合成素子に対して共に異常光線となるように設定するステップと、前記複数波長合成素子に入射した前記レーザ光線が前記複数波長合成素子から同一の光路で出射するために、前記板の常光線屈折率ｎｏの逆数をａ、異常光線屈折率ｎｅの逆数をｂ、前記板厚をｅ、前記ａ、ｂ、ψとの関係をｃ＝ａ²×ｓｉｎ²ψ十ｂ²×ｃｏｓ²ψとし、前記板の主面に入射する２つのレーザ光線の光線間距離をＳとした際に、
Ｓ＝（ｂ²−ａ²／（２ｃ²））×ｓｉｎ（２ψ）×ｅ
を満足するように前記２つの光源の間隔を調節するステップとを含むことを特徴とする波長の異なる２つのレーザ光線を単一光線にする方法である。
請求項８の発明は、波長の異なる２つのレーザ光線を同一平面内で平行に発するように配置された２つの光源と、対向する面に対し角度ψの光学軸を有する一軸結晶の板からなり且つ前記光学軸が前記同一平面と平行になるように前記レーザ光線の光路上に前記レーザ光線と直角に配置された複数波長合成素子とを備え、前記レーザ光線の偏波面が前記複数波長合成素子に対して共に異常光線となるように設定されており、且つ前記２つの光源の間隔が、前記複数波長合成素子に入射した前記レーザ光線が前記複数波長合成素子から同一の光路で出射するために、前記板の常光線屈折率ｎｏの逆数をａ、異常光線屈折率ｎｅの逆数をｂ、前記板厚をｅ、前記ａ、ｂ、ψとの関係をｃ＝ａ²×ｓｉｎ²ψ十ｂ²×ｃｏｓ²ψとし、前記板の主面に入射する２つのレーザ光線の光線間距離をＳとした際に、
Ｓ＝（ｂ²−ａ²／（２ｃ²））×ｓｉｎ（２ψ）×ｅを満足するように調節されたことを特徴とする波長の異なる２つのレーザ光線を単一光線にする光学系である。
請求項９の発明は、前記２つの光源が、前記２つのレーザ光線を単独で発する多波長レーザダイオードであることを特徴とする。
請求項１０の発明は、請求項８又は９記載の光学系を備えたことを特徴とする光ピックアップである。
請求項１１の発明は、請求項８又は９記載の光学系を備えたことを特徴とする波長の異なる複数のレーザ光線を用いる装置である。
【０００５】
【発明の実施の形態】
以下、本発明の実施の形態例と添付図面により本発明を詳細に説明する。なお、複数の図面に同じ要素を示す場合には同一の参照符号を付ける。図面に描かれた各部の寸法は、分かり易くするために部分的に拡大または縮小することがあるので、縮尺は寸法間で必ずしも一定ではない。
（実施の形態１）図１は、本発明の複数波長合成素子の斜視図である。図１において、本発明の複数波長合成素子１は、複屈折性を有する一軸結晶の材料を光学軸Ａｏが表面と４５°の角度（これは、一般的にサバール板と呼ばれるデバイスと同じ切断角度である）を成すように薄切りにしたものである。複数波長合成素子１の光学軸Ａｏと合成しようとする複数の光線（例えば、Ｌ１とＬ２）との配置は、複数の光線Ｌ１およびＬ２を含む平面と光学軸Ａｏとが平行となるようにする。図２は、発光波長の異なる２つの光源から平行な方向に出射されるそれぞれの光線を図１の本発明の複数波長合成素子１が１つに合成する光学系を示す図である。図２は、図１の複数波長合成素子１をＶの方向から見た図である。図２の光学系１００において、２は波長６５０ｎｍのレーザ光Ｌ１を発するＬＤ（レーザダイオード）、３はＬＤ２と並列に配置され光線Ｌ１と平行な波長７８０ｎｍのレーザ光Ｌ２を発するＬＤである。光線Ｌ１とＬ２との間隔はＳとする。レーザ光源ＬＤ２および３からそれぞれ出射した光線Ｌ１およびＬ２は、複数波長合成素子１に垂直に入射する。この時、ＬＤ２から出射する光線Ｌ１は、複数波長合成素子１に入射したときの常光線Ｌ１ｏと同じ偏波面となるようにする。また、ＬＤ３から出射する光線Ｌ２は、複数波長合成素子１に入射したときの異常光線Ｌ２ｅと同じ偏波面となるようにする。即ち、光線Ｌ２の磁気ベクトルの振動方向が主断面（ＸＹ平面）に平行となり（上下方向の矢印で示す）、光線Ｌ１の磁気ベクトルの振動方向が主断面に垂直となる（中に点を有する小円で示す）ように、ＬＤ１とＬＤ２とを出射光軸を中心として回転させながら調整を行う。
【０００６】
図１および２に示した複数波長合成素子１による２波長の合成においては、次ぎの式が成立する。
Ｓ＝（ｂ²−ａ²／２Ｃ²）sin２ψ・ｅ（１）
ただし、Ｓ：光線間距離
ψ：光学軸と基板法線との角度
ｅ：基板の板厚
ａ＝１／ｎｅｎｅ：異常光線屈折率
ｂ＝１／ｎｏｎｏ：常光線屈折率
ｃ＝ａ²sin²ψ十ｂ²cos²ψ
ここで、材料としてＬＮ（ニオブ酸リチウム）を用いて複数波長合成素子１を構成した場合、波長６５０ｎｍの光線のＬＮに対する常光線屈折率ｎｏは２．２８２、波長７８０ｎｍの光線のＬＮに対する異常光線屈折率ｎｅは２．１７８である。複数波長合成素子１の厚さｅをｅ＝２．１５ｍｍとすると、式（１）から、Ｌ１とＬ２との間隔Ｓは、０．１０ｍｍとなる。したがって、ＬＤ２およびＬＤ３は、それぞれの光線Ｌ１およびＬ２の間隔Ｓが０．１０ｍｍとなるような間隔で配置すればよい。
なお、複数波長合成素子１の材料としては、ＬＮの他に、方解石やルチル（金紅石）も利用可能である。
このように、本発明では、屈折率の波長依存性を用いて複数波長の光を合成する。因みに、光ディスクで使用される波長のＬＮに対する屈折率は、次のとおりである。

【０００７】
（実施の形態２）
図３は、発光波長の異なる３つの光源から平行な方向に出射されるそれぞれの光線を本発明の複数波長合成素子が１つに合成する光学系を示す図である。図３の光学系２００において、１は上述の本発明の複数波長合成素子、２は上述の波長６５０ｎｍのＬＤ、３は上述の波長７８０ｎｍのＬＤ、４は波長４１０ｎｍのＬＤである。即ち、図３の光学系２００は図２の光学系１００に波長４１０ｎｍのＬＤ４を追加したものである。光学系２００の要素１〜３およびこれらの配置は、光学系１００と全く同じである。
ＬＤ４は、ＬＤ１およびＬＤ２と並列に配置され、光線Ｌ１およびＬ２と同一平面上にあり且つ平行な光線Ｌ３を４１０ｎｍの波長で出射する。ＬＤ４から出射した光線Ｌ３も、複数波長合成素子１に垂直に入射する。この時も、前述のようにＬＤ４から出射する光線Ｌ３が複数波長合成素子１に入射したときの異常光線Ｌ３ｅと同じ偏波面となるように、ＬＤ４を出射光軸を中心に回転させて調整する。
この場合も、式（１）が成立するので、ＬＮに対する波長４１０ｎｍの異常光屈折率は２．３１９であるから、光線Ｌ１とＬ３との間隔Ｓ１＋Ｓ２は、式（１）から０．１１ｎｍと計算できる。Ｓ１＝Ｓとすると、Ｓ２＝０．１１０．１０ｎｍである。したがって、ＬＤ３は、光線Ｌ２とＬ３との間隔Ｓ２が０．０１ｎｍとなるように、配置すればよい。
【０００８】
（実施の形態３）
図４は、本発明の複数波長合成素子１を用いた光ピックアップ３００の一実施例の要部を模式的に表した図である。図４（ａ）は、光ピックアップ３００のケース１０の上面を透視した平面図であり、図４（ｂ）は、（ａ）の下方の壁を取り去って描いた側面図である。図４において、要素１〜３は、図１の光学系１００そのものである。この点を除けば、光ピックアップ３００は、複数波長合成素子１からの出射光Ｌの光路上に配置されたハーフミラー５、ハーフミラー５を透過した光の光路に配置された立上げミラー６、立上げミラー６による反射光の光路上に配置されケース１０に取り付けられた対物レンズ７、対物レンズ７を通り光ディスク９０、立上げミラー６およびハーフミラー５でそれぞれ反射された戻り光を検出する光検出器８、およびケース１０を備え、通常の光ピックアップと同じである。
動作としては、波長６５０ｎｍのＬＤ２および７８０ｎｍのＬＤ３からそれぞれ出射された平行な光線は実施の形態１で述べたように複数波長合成素子１に於いて１つの光線Ｌに合成される。以降、光線Ｌは、各要素で周知の光学作用を経て光検出器８で検出される。
光源ＬＤ２およびＬＤ３が並列に配置できることで光学系の幅方向寸法を小さくできるため光ピックアップをコンパクトにすることができる。なお、２つの光源２および３を用いる代わりに、波長の異なる光線を発する１つの光源を用いてもよい。
【０００９】
（実施の形態４）
図５は、波長６５０ｎｍおよび７８０ｎｍのレーザ光を１つの半導体チップで発光出射可能な２波長半導体レーザと本発明の複数波長合成素子１とを一体化した新奇なレーザ光源装置の一実施例を示す、２波長の光路を含む断面図である。図５において、本発明による光源装置４００は、波長６５０ｎｍと波長７８０ｎｍの光を１チップで発光する２波長ＬＤ２３、本発明により複屈折性を用いて２波長を合成する複数波長合成素子１ａ、２波長ＬＤ２３の電極（図示せず）に接続された電極端子１１、複数波長合成素子１ａと電極端子１１とを取り付け固定する絶縁体１２、およびケース１３からなる。
２波長レーザダイオード２３から出射した光線は、本発明の複数波長合成素子１ａに入射する。この時、波長６５０ｎｍのレーザ光線は、複数波長合成素子１ａに入射したときの常光線と同じ偏波面となるようにする。波長７８０ｎｍのレーザ光線は、複数波長合成素子１ａに入射したときの異常光線と同じ偏波面となるようにする。この時、２波長ＬＤ２３から発光出射される２つのレーザ光線の間隔、即ち、ＬＤ２３の発光点の間隔は、式（１）のＳで与えられる。
このように構成することにより、２波長ＬＤ２３から出射した波長６５０ｎｍと波長７８０ｎｍの光は、複数波長合成素子１ａにより１つの光線に合成される。
【００１０】
（実施の形態５）
図６は、本発明により２波長レーザダイオードと本発明の複数波長合成素子とを一体化した新奇なレーザ光源装置の第２の実施例を示す、２波長の光路を含む断面図である。図６の光源装置４００ａは、図５の２波長ＬＤ２３を２波長ＬＤ２３ａで置き換えた点を除けば、図５の光源装置４００と同じである。
図６の光源装置４００ａでは、２波長ＬＤ２３ａから出射される２つの光線Ｌ１およびＬ２を複数波長合成素子１ａ内で異常光線とし、これらの異常光線を複数波長合成素子１ａの出射面で重なり合わせて１つの合成波Ｌにする。このため、発振波長６５０ｎｍおよび７８０ｎｍの２波長ＬＤ２３ａは、平行な各波長のレーザ光線Ｌ１およびＬ２を、複数波長合成素子１ａにそれぞれ入射したときの異常光線と同じ偏波面となるように、出射する。さらに、この時、光線Ｌ１およびＬ２の間隔は、複数波長合成素子１ａに入射した時の異常光線どおしが複数波長合成素子１ａの出射面で一致するように調整する。
この場合、複数波長合成素子１ａから出射する合成光線Ｌと波長６５０ｎｍの光線Ｌ１との距離Ｓ１、および合成光線Ｌと波長７８０ｎｍの光線Ｌ２との距離Ｓ２は、共に式（１）によって計算される。したがって、光線Ｌ１とＬ２との間隔、即ち２波長ＬＤ２３ａの出射点の間隔は、Ｓ１Ｓ２とすればよい。
【００１１】
（実施の形態６）
図７は、図５又は６のレーザ光源装置４００又は４００ａを用いて更に小型化した光ピックアップの要部を模式的に、ケースを透視して、表した平面図である。図７の光ピックアップ５００は、図４の光ピックアップ３００のＬＤ２、ＬＤ３および複数波長合成素子１をレーザ光源装置４００又は４００ａで置き換え、ケース１０をケース１０ａと小型化した点を除けば、光ピックアップ３００と同じである。
このように、本発明の実施の形態６によれば、複数波長の光線を１つに合成する機能を持った光源装置を使用することで、ピックアップをコンパクトにでき、且つコスト削減が可能である。
【００１２】
（変形様態）
図８は、本発明の複数波長合成素子と波長の異なる光源を２つ用いた光ピックアップの他の実施例のケースを透視した平面図である。図８の光ピックアップ３００ａは、複数波長合成素子１を光源１および２とハーフミラー５との間ではなくハーフミラー５と受光素子８との間に配置した点を除けば、図４の光ピックアップ３００と同じである。また、全体の寸法に応じてケースも１０から１０ｂに変更した。
このように、光源を並列に配置できることで光学系の幅方向寸法を小さくでき、且つ受光素子８が１つで済むため光軸調整などが簡単にできる。
図９は、本発明の複数波長合成素子と波長の異なる光線を発する光源を１つ用いた光ピックアップの他の実施例のケースを透視した平面図である。図８の光ピックアップ３００ｂは、２つの光源２および３を波長の異なる光線を発する１つの光源２３で置き換えた点を除けば、図８の光ピックアップ３００ａと同じである。
このように、２つの光源を１つにすることで、さらに部品数を減らすことができる。
以上の説明に於いて、「波長の異なる複数の光線を複数波長合成素子により単一光線に合成する」とは、「波長の異なる複数の光線を複数波長合成素子に入射させて、複数波長合成素子から同一の光路で出射させること」を意味する。したがって、合成という語を用いているが、複数の光源は必ずしも同時に発光する必要はない。複数の何れの光源から出射した光線も、複数波長合成素子から同一の光路で出射すれば、各光源が単独で発光する場合も「合成」の意味に含まれるものとする。
以上は、本発明の説明のために実施の形態の例を掲げたに過ぎない。したがって、本発明の技術思想または原理に沿って上述の実施の形態に種々の変更、修正または追加を行うことは、当業者には容易である。故に、本発明は、以上述べた実施の形態に捕らわれることなく、ただ特許請求の範囲の記載に従って解釈するべきである。
【００１３】
【発明の効果】
以上のように本発明によれば、波長の異なる複数の平行な光線を１つの光線に合成する複数波長合成素子が得られる。この複数波長合成素子を用いることにより、複数波長の光を使用する光ピックアップを小型化することができる。
また、異なる波長の光源と本発明の複数波長合成素子とを組み合わせることにより複数波長の光を合成した単一光線を出射する光源装置を得ることができる。この光源装置を用いることにより、複数波長の光を使用する光ピックアップをさらに小型化することができる。
【図面の簡単な説明】
【図１】本発明の複数波長合成素子の斜視図である。
【図２】発光波長の異なる２つの光源から平行な方向に出射されるそれぞれの光線を図１の複数波長合成素子が１つに合成する光学系を示す図である。
【図３】発光波長の異なる３つの光源から平行な方向に出射されるそれぞれの光線を図１の複数波長合成素子が１つに合成する光学系を示す図である。
【図４】本発明の複数波長合成素子を用いた光ピックアップの一実施例の要部を模式的に表した図である。（ａ）は、ケースを透視した平面図であり、（ｂ）は、（ａ）の下方の壁を取り去って描いた側面図である。
【図５】波長の異なるレーザ光を発光出射する２波長半導体レーザと本発明の複数波長合成素子１とを一体化した新奇なレーザ光源装置の一実施例を示す、２波長の光路を含む断面図である。
【図６】２波長レーザダイオードと本発明の複数波長合成素子とを一体化した新奇なレーザ光源装置の第２の実施例を示す、２波長の光路を含む断面図である。
【図７】図５又は６のレーザ光源装置４００又は４００ａを用いて更に小型化した光ピックアップの要部を模式的に、ケースを透視して、表した平面図である。
【図８】本発明の複数波長合成素子と波長の異なる光源を２つ用いた光ピックアップの他の実施例のケースを透視した平面図である。
【図９】本発明の複数波長合成素子と波長の異なる光線を発する光源を用いた光ピックアップの他の実施例のケースを透視した平面図である。
【図１０】異なる波長の光源を２つ使用する従来の光ピックアップの一般的な構成例を示す図である。
【符号の説明】
１、１ａ：本発明の複数波長合成素子
２〜４：レーザダイオード（ＬＤ）
５：ハーフミラー
６：立上げミラー
７：対物レンズ
８：光センサ
１０：ピックアップのケース
１１：電極端子
１２：絶縁体
１３：光源装置のケース
２３、２３ａ：２波長レーザダイオード
３００、５００：本発明による光ピックアップ
４００：本発明によるレーザ光源装置[0001]
BACKGROUND OF THE INVENTION
The present invention generally relates to an optical element, and more particularly to an element for combining two light beams having different wavelengths into one light beam and an optical pickup using the element.
[0002]
[Prior art]
The optical pickup used in the optical disc apparatus is adapted to use different types of optical discs, so that a plurality of laser beams having different wavelengths can be used.
FIG. 10 shows a general configuration example of an optical pickup using two light sources having different wavelengths. In FIG. 10, 1 is an LD (laser diode) having a wavelength of 650 nm, 2 is an LD having a wavelength of 780 nm, and 3 is a dichroic prism that combines two wavelengths.
In the optical system configured to synthesize light of two wavelengths configured in this way, approximately 90% or more of the light of the LD 1 having a wavelength of 650 nm is transmitted through the dichroic prism 3. Further, almost 90% or more of the light of the LD2 having a wavelength of 780 nm is reflected by 90 ° by the dichroic prism 3 and enters the same optical path as the light transmitted from the LD1. It was common to synthesize two wavelengths by reflecting and transmitting each light in the same direction.
However, in such a conventional method, since the LD is arranged in two directions, it is difficult to make the optical pickup compact.
[0003]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a multi-wavelength synthesizing element that synthesizes parallel light beams from a plurality of adjacent light sources.
It is another problem to provide a compact optical pickup using such a multi-wavelength synthesizing element.
In addition, in a light emitting source capable of emitting and emitting light of a plurality of wavelengths with a single semiconductor chip, by integrating a device having a function of combining light beams of a plurality of wavelengths into one light beam, with a package lid or a light emitting source, It is an object of the present invention to provide a light emitting source having a function of combining light beams of a plurality of wavelengths into one.
It is another object of the present invention to provide a more compact and low-cost optical pickup using the light emission source.
[0004]
[Means for Solving the Problems]
The above-described problems are achieved by the following method and optical system for making a plurality of laser beams having different wavelengths, an optical pickup , and an apparatus using the plurality of laser beams having different wavelengths using them.
The method according to claim 1 , wherein a plurality of laser beams having different wavelengths are converted into a single beam, and a plurality of light sources emitting a plurality of laser beams having different wavelengths are arranged so that the plurality of laser beams are parallel on the same plane. A multi-wavelength synthesizing element comprising a uniaxial crystal plate having an optical axis of 45 degrees with respect to the opposing surface, and the laser beam on the optical path of the laser beam so that the optical axis is parallel to the same plane. And a step of setting the polarization plane of the laser beam to be an extraordinary ray with respect to the multiple wavelength combining element, and the laser beam incident on the multiple wavelength combining element is the multiple wavelength. Adjusting the intervals of the plurality of light sources so that the light is emitted from the combining element through the same optical path.
An optical system for converting a plurality of laser beams having different wavelengths into a single beam according to claim 2 , and a surface facing a plurality of light sources arranged so as to emit a plurality of laser beams having different wavelengths in parallel in the same plane A multi-wavelength combining element that is formed of a uniaxial crystal plate having an optical axis of 45 degrees with respect to the laser beam and is disposed at right angles to the laser beam on the optical path of the laser beam so that the optical axis is parallel to the same plane. The laser beam is set such that the plane of polarization of the laser beam is an extraordinary beam with respect to the plurality of wavelength combining elements, and the interval between the plurality of light sources is incident on the plurality of wavelength combining elements. Is adjusted so as to be emitted from the multi-wavelength combining element in the same optical path.
According to a third aspect of the present invention, in the optical system according to the second aspect , the plurality of light sources are multi-wavelength laser diodes that independently emit the plurality of laser beams.
According to a fourth aspect of the present invention, there is provided an optical pickup comprising the optical system according to the second or third aspect.
According to a fifth aspect of the present invention, there is provided an apparatus using a plurality of laser beams having different wavelengths, comprising the optical system according to the second or third aspect.
According to a sixth aspect of the present invention, there are provided a step of disposing three or more light sources emitting three or more laser beams having different wavelengths so that the three or more laser beams are parallel on the same plane, A step of arranging a multi-wavelength synthesizing element composed of a uniaxial crystal plate having an optical axis of a predetermined degree on the optical path of the laser beam so that the optical axis is parallel to the same plane; A step of setting a polarization plane of the light beam to be an ordinary ray or an extraordinary ray with respect to the multi-wavelength synthesis element; and the laser beam incident on the multi-wavelength synthesis element is emitted from the multi-wavelength synthesis element in the same optical path Adjusting the interval between the three or more light sources.
The invention according to claim 7 is the step of arranging two light sources emitting two laser beams having different wavelengths so that the two laser beams are parallel on the same plane, and an optical device having an angle ψ with respect to the opposing surface. Disposing a multi-wavelength combining element comprising a uniaxial crystal plate having an axis on the optical path of the laser beam at right angles to the laser beam so that the optical axis is parallel to the same plane; A step of setting the wavefront to be an extraordinary ray with respect to the plurality of wavelength combining elements, and the laser beam incident on the plurality of wavelength combining elements to be emitted from the plurality of wavelength combining elements in the same optical path, The reciprocal of the ordinary ray refractive index no of the plate is a, the reciprocal of the extraordinary ray refractive index ne is b, the plate thickness is e, and the relationship between a, b, and ψ is c = a ² × sin ² ψ + b ² × and cos ² [psi, the plate The inter-optical-beam distance of the two laser beams incident on the major surface upon the S,
S = (b ² −a ² / (2c ² )) × sin (2ψ) × e
The two laser beams of different wavelengths, which comprises the step of adjusting the spacing of the two light sources so as to satisfy a method for a single beam.
The invention of claim 8 comprises two light sources arranged so as to emit two laser beams having different wavelengths in parallel in the same plane, and a uniaxial crystal plate having an optical axis at an angle ψ with respect to the opposing surface. And a plurality of wavelength combining elements arranged at right angles to the laser beam on the optical path of the laser beam so that the optical axis is parallel to the same plane, and the plane of polarization of the laser beam is the multiple wavelength combining element Both are set to be extraordinary rays, and the interval between the two light sources is such that the laser beam incident on the multiple wavelength combining device is emitted from the multiple wavelength combining device in the same optical path. The inverse of the ordinary ray refractive index no of the plate is a, the inverse of the extraordinary ray refractive index ne is b, the thickness of the plate is e, and the relationship between a, b, and ψ is c = a ² × sin ² ψ + b and ^² × cos ^{2 ψ,} enter the main surface of the plate The inter-optical-beam distance of the two laser beams upon the S to,
An optical system for converting two laser beams having different wavelengths into a single light beam, which is adjusted to satisfy S = (b ² −a ² / (2c ² )) × sin (2ψ) × e. is there.
The invention of claim 9 is characterized in that the two light sources are multi-wavelength laser diodes emitting the two laser beams independently.
A tenth aspect of the present invention is an optical pickup comprising the optical system according to the eighth or ninth aspect.
An eleventh aspect of the invention is an apparatus using a plurality of laser beams having different wavelengths, comprising the optical system according to the eighth or ninth aspect.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments of the present invention and the accompanying drawings. In addition, when showing the same element in several drawing, the same referential mark is attached | subjected. Since the dimensions of each part depicted in the drawings may be partially enlarged or reduced for easy understanding, the scale is not necessarily constant between the dimensions.
(Embodiment 1) FIG. 1 is a perspective view of a multi-wavelength synthesizing element of the present invention. In FIG. 1, a multi-wavelength synthesizing element 1 according to the present invention is made of a uniaxial crystal material having birefringence and an angle at which the optical axis Ao is 45 ° with the surface (this is the same cutting angle as a device generally called a Savart plate). )). The arrangement of the plurality of light beams (for example, L1 and L2) to be combined with the optical axis Ao of the multiple wavelength combining element 1 is such that the plane including the plurality of light beams L1 and L2 and the optical axis Ao are parallel. . FIG. 2 is a diagram showing an optical system in which light beams emitted in parallel directions from two light sources having different emission wavelengths are combined into one by the multiple wavelength combining element 1 of the present invention shown in FIG. FIG. 2 is a view of the multiple wavelength combining element 1 of FIG. In the optical system 100 of FIG. 2, 2 is an LD (laser diode) that emits a laser beam L1 having a wavelength of 650 nm, and 3 is an LD that is arranged in parallel with the LD2 and emits a laser beam L2 having a wavelength of 780 nm that is parallel to the light beam L1. The interval between the light beams L1 and L2 is S. Light rays L1 and L2 respectively emitted from the laser light sources LD2 and 3 are perpendicularly incident on the multiple wavelength combining element 1. At this time, the light beam L1 emitted from the LD2 has the same polarization plane as the ordinary light beam L1o when entering the multi-wavelength combining element 1. The light beam L2 emitted from the LD 3 has the same polarization plane as that of the extraordinary light beam L2e when entering the multi-wavelength combining element 1. That is, the vibration direction of the magnetic vector of the light beam L 2 is parallel to the main section (XY plane) (indicated by vertical arrows), the point in which the composed (in perpendicular to the vibration direction main section of the magnetic vector of the light beam L 1 As shown by a small circle having a), adjustment is performed while rotating LD1 and LD2 around the output optical axis.
[0006]
In the synthesis of two wavelengths by the multi-wavelength synthesizing element 1 shown in FIGS. 1 and 2, the following equation is established.
S = (b ² −a ² / 2C ² ) sin 2ψ · e (1)
Where S: distance between light beams ψ: angle between optical axis and substrate normal e: substrate thickness a = 1 / ne ne: extraordinary ray refractive index b = 1 / no no: ordinary ray refractive index c = a ² sin ² ψ 10 b ² cos ² ψ
Here, when the multi-wavelength synthesis element 1 is configured using LN (lithium niobate) as a material, the ordinary ray refractive index no with respect to LN of light having a wavelength of 650 nm is 2.282, and an extraordinary ray with respect to LN of light having a wavelength of 780 nm. The refractive index ne is 2.178. Assuming that the thickness e of the multi-wavelength combining element 1 is e = 2.15 mm, the distance S between L1 and L2 is 0.10 mm from the equation (1). Therefore, LD2 and LD3 may be arranged at an interval such that the interval S between the light beams L1 and L2 is 0.10 mm.
As a material for the multi-wavelength synthesizing element 1, calcite and rutile (goldenite) can be used in addition to LN.
Thus, in the present invention, light of a plurality of wavelengths is synthesized using the wavelength dependence of the refractive index. Incidentally, the refractive index with respect to LN of the wavelength used with an optical disk is as follows.

[0007]
(Embodiment 2)
FIG. 3 is a diagram showing an optical system in which the light beams emitted in the parallel direction from three light sources having different emission wavelengths are combined into one by the multiple wavelength combining element of the present invention. In the optical system 200 of FIG. 3, 1 is the above-described multi-wavelength synthesizing element of the present invention, 2 is the LD having the wavelength of 650 nm, 3 is the LD having the wavelength of 780 nm, and 4 is the LD having the wavelength of 410 nm. That is, the optical system 200 of FIG. 3 is obtained by adding an LD 4 having a wavelength of 410 nm to the optical system 100 of FIG. Elements 1 to 3 of the optical system 200 and their arrangement are the same as those of the optical system 100.
LD4 is arranged in parallel with LD1 and LD2, and emits a light ray L3 that is coplanar with and parallel to light rays L1 and L2 at a wavelength of 410 nm. The light beam L3 emitted from the LD 4 also enters the multiple wavelength combining element 1 perpendicularly. Also at this time, as described above, the light beam L3 emitted from the LD4 is adjusted by rotating the LD4 about the outgoing optical axis so that it has the same polarization plane as that of the extraordinary light beam L3e when entering the multiple wavelength combining element 1. .
Also in this case, since the formula (1) is established, the extraordinary refractive index at the wavelength of 410 nm with respect to LN is 2.319, and the distance S1 + S2 between the light beams L1 and L3 is calculated as 0.11 nm from the formula (1). it can. If S1 = S, then S2 = 0.110.10 nm. Therefore, LD3 should just be arrange | positioned so that the space | interval S2 of the light rays L2 and L3 may be set to 0.01 nm.
[0008]
(Embodiment 3)
FIG. 4 is a diagram schematically showing a main part of an embodiment of the optical pickup 300 using the multiple wavelength combining element 1 of the present invention. 4A is a plan view of the optical pickup 300 seen through the top surface of the case 10, and FIG. 4B is a side view of the optical pickup 300 with the lower wall removed. In FIG. 4, elements 1 to 3 are the optical system 100 itself of FIG. 1. Except this point, the optical pickup 300 includes a half mirror 5 disposed on the optical path of the outgoing light L from the multiple wavelength combining element 1, a rising mirror 6 disposed on the optical path of the light transmitted through the half mirror 5, Light for detecting return light reflected on the optical disk 90, the rising mirror 6 and the half mirror 5 through the objective lens 7 and the objective lens 7 which are arranged on the optical path of the reflected light by the rising mirror 6 and attached to the case 10. A detector 8 and a case 10 are provided, which is the same as a normal optical pickup.
In operation, parallel light beams respectively emitted from the LD 2 having a wavelength of 650 nm and the LD 3 having a wavelength of 780 nm are combined into one light beam L in the multi-wavelength combining element 1 as described in the first embodiment. Thereafter, the light beam L is detected by the photodetector 8 through a known optical action in each element.
Since the light sources LD2 and LD3 can be arranged in parallel, the size in the width direction of the optical system can be reduced, so that the optical pickup can be made compact. Instead of using the two light sources 2 and 3, one light source that emits light beams having different wavelengths may be used.
[0009]
(Embodiment 4)
FIG. 5 shows an embodiment of a novel laser light source device in which a two-wavelength semiconductor laser capable of emitting and emitting laser beams having wavelengths of 650 nm and 780 nm with one semiconductor chip and the multiple wavelength combining element 1 of the present invention are integrated. It is sectional drawing containing the optical path of 2 wavelengths. In FIG. 5, a light source device 400 according to the present invention includes a two-wavelength LD 23 that emits light having a wavelength of 650 nm and a wavelength of 780 nm with one chip, and a plurality of wavelength combining elements 1a, 2 that combine two wavelengths using birefringence according to the present invention. It comprises an electrode terminal 11 connected to an electrode (not shown) of wavelength LD 23, an insulator 12 for attaching and fixing the multi-wavelength synthesis element 1 a and the electrode terminal 11, and a case 13.
The light beam emitted from the two-wavelength laser diode 23 is incident on the multiple-wavelength combining element 1a of the present invention. At this time, the laser beam having a wavelength of 650 nm has the same polarization plane as that of the ordinary beam when entering the multi-wavelength combining element 1a. The laser beam having a wavelength of 780 nm is set to have the same polarization plane as the extraordinary beam when entering the multi-wavelength combining element 1a. At this time, the interval between the two laser beams emitted and emitted from the two-wavelength LD 23, that is, the interval between the emission points of the LD 23 is given by S in Expression (1).
With this configuration, light having a wavelength of 650 nm and a wavelength of 780 nm emitted from the two-wavelength LD 23 is combined into one light beam by the multiple wavelength combining element 1a.
[0010]
(Embodiment 5)
FIG. 6 is a cross-sectional view including a two-wavelength optical path showing a second embodiment of a novel laser light source apparatus in which a two-wavelength laser diode and a multi-wavelength combining element of the present invention are integrated according to the present invention. The light source device 400a of FIG. 6 is the same as the light source device 400 of FIG. 5 except that the two-wavelength LD 23 of FIG. 5 is replaced with the two-wavelength LD 23a.
In the light source device 400a of FIG. 6, the two light beams L1 and L2 emitted from the two-wavelength LD 23a are made extraordinary rays in the multiple-wavelength synthesizing device 1a, and these extraordinary rays are overlapped on the emission surface of the multi-wavelength synthesizing device 1a. One synthetic wave L is used. For this reason, the two-wavelength LDs 23a having the oscillation wavelengths of 650 nm and 780 nm emit the parallel laser beams L1 and L2 so as to have the same polarization plane as the extraordinary beam when entering the multi-wavelength combining element 1a, respectively. . Further, at this time, the distance between the light beams L1 and L2 is adjusted so that the extraordinary light beams when they enter the multi-wavelength synthesizing element 1a coincide with each other on the exit surface of the multi-wavelength synthesizing element 1a.
In this case, the distance S1 between the combined light L emitted from the multi-wavelength combining element 1a and the light beam L1 having a wavelength of 650 nm, and the distance S2 between the combined light beam L and the light beam L2 having a wavelength of 780 nm are both calculated by the equation (1). . Therefore, the distance between the light beams L1 and L2, that is, the distance between the emission points of the two-wavelength LD 23a may be S1S2.
[0011]
(Embodiment 6)
FIG. 7 is a plan view schematically showing the main part of an optical pickup further miniaturized using the laser

light source device

400 or 400a of FIG. 5 or 6, seeing through the case. The optical pickup 500 in FIG. 7 is the same as the optical pickup 300 except that the LD 2 and LD 3 and the multiple wavelength combining element 1 of the optical pickup 300 in FIG. 4 are replaced with the laser

light source device

400 or 400a and the case 10 is downsized with the case 10a. 300 is the same.
As described above, according to the sixth embodiment of the present invention, the pickup can be made compact and the cost can be reduced by using the light source device having the function of combining the light beams having a plurality of wavelengths into one. .
[0012]
(Deformation mode)
FIG. 8 is a plan view seen through a case of another embodiment of an optical pickup using two light sources having different wavelengths from the multi-wavelength synthesis element of the present invention. The optical pickup 300a of FIG. 8 is the optical pickup of FIG. 4 except that the multi-wavelength combining element 1 is arranged between the half mirror 5 and the light receiving element 8 instead of between the

light sources

1 and 2 and the half mirror 5. 300 is the same. Also, the case was changed from 10 to 10b according to the overall dimensions.
As described above, since the light sources can be arranged in parallel, the dimension in the width direction of the optical system can be reduced, and since only one light receiving element 8 is required, the optical axis can be easily adjusted.
FIG. 9 is a plan view seen through a case of another embodiment of an optical pickup using one light source that emits light beams having different wavelengths from the multiple wavelength combining element of the present invention. The optical pickup 300b in FIG. 8 is the same as the optical pickup 300a in FIG. 8 except that the two light sources 2 and 3 are replaced with one light source 23 that emits light beams having different wavelengths.
Thus, the number of parts can be further reduced by using two light sources.
In the above description, “combining a plurality of light beams having different wavelengths into a single light beam by a plurality of wavelength combining elements” means “combining a plurality of light beams having different wavelengths into a plurality of wavelength combining elements to combine multiple wavelengths. This means that the light is emitted from the element in the same optical path. Therefore, although the word “synthetic” is used, a plurality of light sources do not necessarily have to emit light simultaneously. The light emitted from any of the plurality of light sources is included in the meaning of “combining” even when each light source emits light alone if it is emitted from the multiple wavelength combining element through the same optical path.
The above is merely an example of an embodiment for explaining the present invention. Accordingly, it is easy for those skilled in the art to make various changes, modifications, or additions to the above-described embodiments in accordance with the technical idea or principle of the present invention. Therefore, the present invention should not be construed as the embodiments described above, but should be construed according to the description of the claims.
[0013]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a multiple wavelength combining element that combines a plurality of parallel light beams having different wavelengths into one light beam. By using this multi-wavelength synthesizing element, an optical pickup using light of a plurality of wavelengths can be reduced in size.
Moreover, the light source device which radiate | emits the single light which synthesize | combined the light of multiple wavelengths can be obtained by combining the light source of a different wavelength and the multiple wavelength synthetic | combination element of this invention. By using this light source device, an optical pickup that uses light of a plurality of wavelengths can be further downsized.
[Brief description of the drawings]
FIG. 1 is a perspective view of a multiple wavelength combining device of the present invention.
FIG. 2 is a diagram showing an optical system in which light beams emitted in parallel directions from two light sources having different emission wavelengths are combined into one by the multiple wavelength combining element in FIG. 1;
3 is a diagram illustrating an optical system in which light beams emitted in parallel directions from three light sources having different emission wavelengths are combined into one by the multiple wavelength combining element in FIG. 1;
FIG. 4 is a diagram schematically showing a main part of an embodiment of an optical pickup using the multiple wavelength combining element of the present invention. (A) is the top view which saw through the case, (b) is the side view drawn by removing the lower wall of (a).
FIG. 5 is a cross-sectional view including a two-wavelength optical path showing an embodiment of a novel laser light source device in which a two-wavelength semiconductor laser that emits and emits laser beams having different wavelengths and a multi-wavelength combining element 1 of the present invention are integrated. FIG.
FIG. 6 is a cross-sectional view including a two-wavelength optical path showing a second embodiment of a novel laser light source device in which a two-wavelength laser diode and a multi-wavelength combining element of the present invention are integrated.
7 is a plan view schematically showing a main part of an optical pickup further miniaturized by using the laser

light source device

400 or 400a of FIG. 5 or 6, seeing through a case. FIG.
FIG. 8 is a plan view seen through a case of another embodiment of an optical pickup using two or more light sources having different wavelengths and a multi-wavelength synthesizing element of the present invention.
FIG. 9 is a plan view seen through a case of another embodiment of an optical pickup using a light source that emits light beams having different wavelengths from the multi-wavelength synthesis element of the present invention.
FIG. 10 is a diagram illustrating a general configuration example of a conventional optical pickup that uses two light sources having different wavelengths.
[Explanation of symbols]
1, 1a: Multiple wavelength combining element 2-4 of the present invention: Laser diode (LD)
5: Half mirror 6: Rising mirror 7: Objective lens 8: Optical sensor 10: Pickup case 11: Electrode terminal 12: Insulator 13: Light

source device case

23, 23a: Two-wavelength laser diode 300, 500: Present invention Optical pickup 400 according to the invention: laser light source device according to the invention

Claims

Arranging a plurality of light sources emitting a plurality of laser beams having different wavelengths such that the plurality of laser beams are parallel on the same plane;
A multi-wavelength synthesizing element composed of a uniaxial crystal plate having an optical axis of 45 degrees with respect to the opposing surface is arranged on the optical path of the laser beam at right angles to the laser beam so that the optical axis is parallel to the same plane. And steps to
Setting the polarization plane of the laser beam to be an extraordinary beam with respect to the multiple wavelength combining element;
Adjusting the intervals of the plurality of light sources so that the laser beams incident on the plurality of wavelength combining elements are emitted from the plurality of wavelength combining elements in the same optical path. How to make a single ray.

A plurality of light sources arranged to emit a plurality of laser beams having different wavelengths in parallel in the same plane;
A plurality of wavelengths made of a uniaxial crystal plate having an optical axis of 45 degrees with respect to the opposing surface, and arranged at right angles to the laser beam on the optical path of the laser beam so that the optical axis is parallel to the same plane A composite element,
The plane of polarization of the laser beam is set to be an extraordinary ray with respect to the plurality of wavelength combining elements, and the intervals between the plurality of light sources are the plurality of laser beams incident on the plurality of wavelength combining elements. An optical system for converting a plurality of laser beams having different wavelengths into a single beam, which is adjusted so as to be emitted from the wavelength synthesis element in the same optical path.

3. The optical system according to claim 2 , wherein the plurality of light sources are multi-wavelength laser diodes that independently emit the plurality of laser beams.

An optical pickup that comprising the claims 2 or 3 optical system according.

A plurality of devices using laser beams of different wavelengths, comprising the claims 2 or 3 optical system according.

Disposing three or more light sources emitting three or more laser beams having different wavelengths so that the three or more laser beams are parallel on the same plane;
A multi-wavelength synthesizing element composed of a uniaxial crystal plate having an optical axis of 45 degrees with respect to the opposing surface is arranged on the optical path of the laser beam at right angles to the laser beam so that the optical axis is parallel to the same plane. And steps to
Setting the polarization plane of the laser beam to be an ordinary ray or an extraordinary ray with respect to the multiple wavelength combining element;
Adjusting the intervals of the three or more light sources so that the laser beams incident on the multiple wavelength combining element are emitted from the multiple wavelength combining element through the same optical path. To make a single laser beam.

Disposing two light sources emitting two laser beams having different wavelengths so that the two laser beams are parallel on the same plane;
A multi-wavelength synthesizing element composed of a uniaxial crystal plate having an optical axis at an angle ψ with respect to the opposing surface is disposed on the optical path of the laser beam at right angles to the laser beam so that the optical axis is parallel to the same plane. And steps to
Setting the polarization plane of the laser beam to be an extraordinary beam with respect to the multiple wavelength combining element;
In order for the laser beam incident on the multiple wavelength combining element to exit from the multiple wavelength combining element in the same optical path,
The reciprocal of the ordinary ray refractive index no of the plate is a, the reciprocal of the extraordinary ray refractive index ne is b, the plate thickness is e, and the relationship between the a, b, and ψ is c = a ² × sin ² ψ + b ² X cos ² ψ
When the distance between the two laser beams incident on the main surface of the plate is S,
S = (b ² −a ² / (2c ² )) × sin (2ψ) × e
Adjusting the distance between the two light sources so as to satisfy the following: a method of making two laser beams having different wavelengths into a single beam.

Two light sources arranged to emit two laser beams having different wavelengths in parallel in the same plane;
A plurality of wavelengths made of a uniaxial crystal plate having an optical axis at an angle ψ with respect to the opposing surface, and arranged at right angles to the laser beam on the optical path of the laser beam so that the optical axis is parallel to the same plane A composite element,
The plane of polarization of the laser beam is set to be an extraordinary ray with respect to the plurality of wavelength combining elements, and the interval between the two light sources is the plurality of laser beams incident on the plurality of wavelength combining elements. In order to emit from the wavelength synthesis element in the same optical path,
The reciprocal of the ordinary ray refractive index no of the plate is a, the reciprocal of the extraordinary ray refractive index ne is b, the plate thickness is e, and the relationship between the a, b, and ψ is c = a ² × sin ² ψ + b ² X cos ² ψ
When the distance between the two laser beams incident on the main surface of the plate is S,
S = (b ² −a ² / (2c ² )) × sin (2ψ) × e
An optical system for making two laser beams having different wavelengths into a single beam, adjusted so as to satisfy

9. The optical system according to claim 8 , wherein the two light sources are multi-wavelength laser diodes that independently emit the two laser beams.

An optical pickup that comprising the claims 8 or 9 optical system according.

Apparatus using two laser beams having different wavelengths, comprising the claims 8 or 9 optical system according.