JP4325135B2 - Lighting device and projector - Google Patents

Description

【００１６】
以上、構造複屈折体が光の偏光状態によって異なる光学的性質を示すことを述べた。ここで、媒質Ａとして金属や半導体のような光反射体を用いる場合、誘電率を複素数として扱うことで、誘電体に対する有効屈折率を求める場合と同様に扱うことができる。但し、有効屈折率は複素数となる。Effective Medium Theory（例えば、Dominique Lemercier−lalanne:Journal of Modern Optics,1996,vol43,no.10,2063-2085）、より厳密にはRigorous Coupled-Wave Analysis(M.G.Moharam:J.Opt.Soc.Am.A,12(1995)1077 )を用いた数値計算により、媒質Ａとして金属を用いた場合、偏光Ａに対する構造複屈折体の有効屈折率の虚数部が大きな値となり、その結果、入射した偏光Ａは構造複屈折体により反射されることが知られている。一方、偏光Ｂに対する有効屈折率の虚数部は小さい値となり、偏光Ｂは構造複屈折体を透過することが知られている。このように、２種類の媒質で、波長よりも小さい周期構造を形成することにより、構造複屈折体の周期構造が並ぶ方向と平行な方向に振動する偏光を透過させ、周期構造が並ぶ方向と直交する方向に振動する偏光を反射する作用を持たせることができる。
【００１７】
上記の構造複屈折型偏光子は無機材料を用いて形成することができるため、有機フィルムからなる位相差板を用いた従来の偏光変換系に比べてはるかに耐光性や耐熱性に優れており、照明光の強度が高くても安定した偏光変換作用を実現することができる。
【００１８】
以上、直線偏光を透過光と反射光とに分離する反射型偏光子について説明したが、円偏光を分離するものを用いてもよい。すなわち、反射型偏光子として、互いに逆回りの円偏光のうちの一方を透過し、他方を反射する機能を有するものを用いてもよい。ただしその場合、光束分割手段と反射型偏光子との間に１／４波長板を設けることが望ましい。
【００１９】
光源からの光束がそのまま光束分割手段に入射された場合、その光束は不定偏光状態となっている。よって、光束分割手段から射出された不定偏光光束が１／４波長板を透過すると、Ｌ円偏光光束とＲ円偏光光束とに分離される（Ｌ円偏光光束とＲ円偏光光束とは互いに回転方向が逆）。そして、反射型偏光子では、例えばＬ円偏光光束が透過し、Ｒ円偏光光束が反射される。上で説明した直線偏光の場合と同様、反射型偏光子で反射されたＲ円偏光光束は入射側の反射ミラーとの間で反射を繰り返し、１／４波長板を透過したり、光束分割手段の内部を伝搬したりする間に偏光方向が変化し、その一部がＬ円偏光光束となって反射型偏光子を透過する。円偏光の場合も直線偏光の場合と同様のメカニズムによって、偏光のリサイクルが可能であり、一種類の偏光方向を有する光として照明に寄与させることができるため、従来の照明装置に比べて偏光変換効率を高めることができる。
【００２０】
上記円偏光を利用する構成の場合、反射型偏光子の射出側にさらに１／４波長板を設けることが望ましい。
この構成によれば、円偏光光束として反射型偏光子から射出された光が１／４波長板を透過することによって直線偏光に変換されるので、この照明装置を適用するプロジェクタの構成を直線偏光を射出する照明装置の場合と共通にすることができる。
【００２１】
前記光束分割手段の具体的構成としては、棒状の導光体、もしくは内面が反射面とされた管状の導光体、いわゆるロッドレンズを用いることができる。その場合、ロッドレンズの形状としては、射出端面は被照明領域と光学的に共役である（相似形である）必要があるが、入射端面と射出端面とは必ずしも相似形である必要はない。また、入射側から射出側に向けて同一の径を有するものであってもよいが、先細りの形状や先拡がりの形状としてもよい。
先細りの形状や先拡がりの形状とした場合、ロッドレンズへの光の入射角に対して射出角を変化させることができる。それぞれの効果については後述する。
【００２２】
前記光束分割手段の入射端面においては、入射領域の形状を円形とし、円形の入射領域の外側の領域に前記反射ミラーを設けることが望ましい。
通常、光源から射出される光束の強度分布は光軸方向から見て円形となるので、それに合わせて光束分割手段の入射領域の形状も円形とするのが最も損失の少ない効率の良い方法である。ここで、被照明領域が矩形の液晶ライトバルブであれば、光束分割手段の射出端面も矩形となり、さらに入射端面も射出端面と相似形にして矩形とした場合、矩形の入射端面の内部に円形の入射領域が配置されるので、その周辺に反射ミラーを設ける構成とすればよい。
【００２３】
特に光束分割手段の入射端面および射出端面の形状をともに矩形状とした場合、射出端面よりも入射端面の方がより細長の矩形状とすることが望ましい。
例えば射出端面が正方形に近い形状であったとしても、入射端面をより細長の長方形状とすれば、入射領域の面積に対して反射ミラーの設置領域の面積が大きく取れるので、偏光のリサイクル率を向上することができる。
【００２４】
光束分割手段の入射端面内の入射領域の配置については、入射端面の中心に入射領域の中心を合わせる場合の他に、入射端面の中心に対して入射領域の中心を偏心させてもよく、光束分割手段に入射する光束の光軸（光源の光軸）と反射型偏光子の入射端面とが垂直以外の角度をなすようにしてもよい。このような構成は、例えば、光束分割手段の略中心を通るシステム光軸に対して光源の光軸を傾けることで、あるいは、光源の光軸をシステム光軸に対して平行にシフトさせるとともに、光束分割手段の入射端面をシステム光軸に対して垂直以外の角度をなすように傾けて配置するなどすることで実現することができる。特に後者の構成では、光源の光軸とシステム光軸とが平行になるため、光学系を小型化しやすいというメリットがある。
この構成によれば、反射型偏光子からの反射光が、光束分割手段の入射側に設置された反射ミラーで反射される割合が高くなるため、高い偏光変換効率を実現することができる。これについても後で詳述する。
【００２５】
本発明のプロジェクタは、上記本発明の照明装置と、この照明装置から射出される光を変調する光変調手段と、光変調手段により変調された光を投写する投写手段とを備えたことを特徴とする。
この構成によれば、高い偏光変換効率と耐久性を有する照明装置を備えたことにより、高輝度で信頼性の高いプロジェクタを実現することができる。
【００２６】
特に、前記光変調手段が液晶ライトバルブである場合、照明装置の光束分割手段から射出される照明光束の照明角が拡がる方向と液晶ライトバルブの視野角が広い方向とを一致させることが望ましい。
この構成によれば、高いコントラストを得ることができ、表示品位の高いプロジェクタを実現することができる。
【００２７】
【発明の実施の形態】
[第１の実施の形態]
以下、本発明の第１の実施の形態を、図１〜図３を参照して説明する。
図１は本実施の形態の照明装置の概略構成図である。図１中符号２は光源、３は反射ミラー、４はロッドレンズ（光束分割手段）、５は反射型偏光子、６はリレー系、７は液晶ライトバルブ（被照明領域）、である。
【００２８】
本実施の形態の照明装置１は、図１に示すように、メタルハライドランプ等のランプ８とリフレクタ９とを備えた光源２と、ロッドレンズ４と、３枚のレンズ１０，１１，１２を備えたリレー系６とから概略構成されている。
【００２９】
ロッドレンズ４としては、透明な棒状の導光体（例えばガラス棒）、もしくは内面が反射面とされた管状の導光体（例えば、複数の反射ミラーを内側に向けて管状に配置した万華鏡）などが用いられる。本実施の形態の場合、ロッドレンズ４の形状としては、入射側から射出側に向けて断面が同一寸法の四角柱状の導光体が用いられている。入射端面および射出端面の形状は、図１の下側に示すように、被照明領域、すなわち液晶ライトバルブ７と相似形であり、例えば縦横比が３：４の長方形となっている。本実施の形態では入射端面と射出端面の形状がともに液晶ライトバルブ７と相似形であるが、入射端面に関しては必ずしも相似形である必要はない。ロッドレンズ４は、光源２からの入射光を複数の光束に分割する機能を有しており、これにより生じる複数の光源像からの光束をリレー系６などの光伝達手段によって被照明領域で重畳させることにより、液晶ライトバルブ７における照度分布を均一化している。
【００３０】
ロッドレンズ４の入射端面には、中央に円形の開口部３ａ（光入射領域）を有する反射ミラー３が反射面をロッドレンズ４の内側に向けて設置されている。この反射ミラー３の具体的な設置の形態としては、ロッドレンズ４が管状の導光体であれば、例えば中央に開口部を有するミラーをロッドレンズの端部に嵌め込んでもよいし、ロッドレンズ４が棒状の導光体であれば、例えば中央部に光透過部が形成されるようにパターニングされた環状の誘電体ミラーをロッドレンズの端面に直接形成してもよい。いずれにしても、光源２からの光束が入射される光入射領域を除く領域に反射ミラー３が設けられていさえすればよい。また、光源２からの光入射領域の構成は開口部に限らず、例えば光透過性の部材で塞がれた構成であってもよい。
【００３１】
ロッドレンズ４の射出端面には、反射型偏光子５が設置されている。本実施の形態の場合、この反射型偏光子５として、図３に示すような、不定偏光を互いに直交する２種類の直線偏光に分離する構造複屈折型の反射型偏光子が用いられている。この反射型偏光子５は、図３に示すように、アルミニウムなどの光反射性を有する金属からなる多数のリブ１４が入射光の波長よりも小さいピッチでガラス基板１５上に形成されたものである。すなわち、この反射型偏光子５は、異なる屈折率を有するＡｌリブ１４と空気とが入射光の波長よりも小さいピッチで交互にストライプ状に配置されたことで複屈折作用を生じ、偏光子として機能する。この構成により、Ａｌリブ１４が形成された側の面に不定偏光が入射されると、Ａｌリブ１４の延在方向に平行な方向に振動するＳ偏光が反射され、Ａｌリブ１４の延在方向に垂直な方向（Ａｌリブが配列する方向）に振動するＰ偏光が透過する。
【００３２】
なお、この反射型偏光子５の方向に関しては、偏光分離の効率を重視してＡｌリブ１４が形成された側の面（入射面）がロッドレンズ４の内側を向くように設置することが望ましい。ただし、管状の導光体ではなく内部が詰まった棒状のロッドレンズと組み合わせて使用する場合には、ロッドレンズの射出端面とＡｌリブ１４との間にごく僅かな隙間が存在するような状態で両者を配置することが望ましい。あるいは、Ａｌリブ１４が形成された側の面（入射面）が液晶ライトバルブ７（被照明領域）の側を向くように、反射型偏光子５を設置することもできる。その場合には、偏光分離の効率が若干低下する可能性があるが、ロッドレンズに密着させて設置できるため、設置しやすいとともに、内部が詰まった棒状のロッドレンズと組み合わせて使用する場合には、ロッドレンズの射出端面と反射型偏光子５のＡｌリブ１４が存在しない側の面とを密着させて光学的に一体化できるため、界面で生じやすい光損失を低減できるメリットがある。
【００３３】
また本実施の形態の場合、リレー系６として３つのレンズ１０，１１，１２が用いられ、最もロッドレンズ４寄りのレンズ１０が、反射型偏光子５に密着するように設置されているが、リレー系６に用いられるレンズの数やレンズの位置についてはこれに限定されるものではなく、適宜変更が可能である。
【００３４】
次に、上記構成の照明装置１の作用について図２を参照して説明する。
光源２から射出された光束は、図２に示すように、反射ミラー３の開口部３ａを通してロッドレンズ４の内部に入射され、射出側に配置された反射型偏光子５に向けて伝搬される。この時点では光束は不定偏光であるが、反射型偏光子５に光が入射されると、偏光方向によって偏光分離され、図３に示したように、反射型偏光子５のＡｌリブ１４の延在方向に垂直な方向（透過軸方向）のＰ偏光が透過し、Ａｌリブ１４の延在方向に平行な方向のＳ偏光が反射される。反射型偏光子５を透過したＰ偏光はリレー系６を経て液晶ライトバルブ７の照明に寄与する一方、反射型偏光子５で反射されたＳ偏光はロッドレンズ４の内部を逆方向（入射端面側）に伝搬される。
【００３５】
反射型偏光子５で反射されたＳ偏光は、その後ロッドレンズ４の入射端面に到達するが、開口部３ａ以外の領域に反射ミラー３が配置されているため、この反射ミラー３で反射され、再度ロッドレンズ４の射出側へと伝搬される。このように、ロッドレンズ４の射出側に反射型偏光子５、入射側に反射ミラー３が配置されたことによって、反射型偏光子５を透過しないＳ偏光はロッドレンズ４の入射側と射出側を行き来することになるが、Ｓ偏光は常にこの偏光方向を維持しているわけではなく、ロッドレンズ４の内面で反射するときに偏光方向が回転して一部はＰ偏光に変換される。そして、Ｐ偏光の状態で反射型偏光子５に到達すると反射型偏光子５を透過することができ、液晶ライトバルブ７の照明に寄与することができる。
【００３６】
本実施の形態の照明装置１によれば、このようなメカニズムによって最初に反射型偏光子５を透過できなかった偏光もリサイクルが可能であり、照明に寄与させることができるため、従来の照明装置に比べて偏光としての利用効率を高められ、明るい照明装置を実現することができる。また、従来から均一照明系として用いられているロッドレンズ４の射出側に反射型偏光子５、入射側に反射ミラー３を配置するだけで済むので、簡単な構成で偏光変換効率（不定偏光を特定の偏光に変換する効率）の高い照明装置を実現することができる。
【００３７】
また、上記の構造複屈折型の反射型偏光子５はガラス基板、アルミニウムなどの無機材料を用いて形成することができるため、有機フィルムからなる位相差板を用いた従来の偏光変換系に比べてはるかに耐光性や耐熱性に優れており、照明光の強度が高くても安定した偏光変換作用を実現することができる。
【００３８】
［第２の実施の形態］
以下、本発明の第２の実施の形態を、図４を参照して説明する。
本実施の形態の照明装置の基本構成は第１の実施の形態と同様であるが、第１の実施の形態が直線偏光を分離する反射型偏光子を用いたのに対して、本実施の形態では円偏光を分離する反射型偏光子を用いた点が異なっている。よって、本実施の形態では図４を用いてロッドレンズの周辺のみを説明し、光源やリレー系についての説明は省略する。
【００３９】
本実施の形態の照明装置において、ロッドレンズ４の入射側の反射ミラー３の構成は第１の実施の形態と同様であるが、射出側の構成が異なっている。すなわち、図４に示すように、ロッドレンズ４の最も射出側に、互いに逆回りの円偏光のうちの一方（例えばＬ偏光）を透過し、他方（Ｒ偏光）を反射する機能を有する円偏光分離型の反射型偏光子１７が設置されている。この種の反射型偏光子１７としては、例えばコレステリック液晶を用いた偏光子を利用することができる。そして、反射型偏光子１７よりも光源２側に第１の１／４波長板１８が設置され、反射型偏光子１７よりもリレー系６側に第２の１／４波長板１９が設置されている。図４では、説明の都合上、第１の１／４波長板１８、反射型偏光子１７、第２の１／４波長板１９を離間して描いているが、これらは特に離間させる必要はなく、密着させてもかまわない。
【００４０】
本実施の形態の照明装置の作用について説明する。
光源２からの不定偏光光束がロッドレンズ４の内部に入射され、伝搬する点は第１の実施の形態と同様である。この不定偏光光束が第１の１／４波長板１８を透過すると、互いに回転方向が逆のＬ円偏光光束とＲ円偏光光束とに分離される。具体的には、例えば、光源光に含まれる不定偏光光束のうち、図４において紙面に垂直な方向に振動する直線偏光がＲ円偏光光束に変換され、紙面に平行な方向に振動する直線偏光がＬ円偏光光束に変換されることによってこれら偏光が分離される。次に、反射型偏光子１７では、例えばＬ円偏光光束が透過し、Ｒ円偏光光束が反射される。後は第１の実施の形態の直線偏光の場合と同様、反射型偏光子１７で反射されたＲ円偏光光束は入射側の反射ミラー３との間で反射を繰り返し、ロッドレンズ４の内部で反射する間に偏光方向（回転方向）が逆回りに変化し、その一部がＬ円偏光光束となって反射型偏光子１７を透過する。
【００４１】
いずれにしても、ロッドレンズ４の射出側の反射型偏光子１７を射出した時点では全てがＬ円偏光光束となっているので、この偏光を第２の１／４波長板１９を透過させることによって、Ｌ円偏光光束が紙面に平行な方向に振動する直線偏光に変換される。なお、第２の１／４波長板１９の光学軸の配置の仕方によっては、紙面に垂直な方向に振動する直線偏光に変換される。また、第２の１／４波長板１９は必ずしもなくてもよいが、反射型偏光子１７の後段に第２の１／４波長板１９を挿入することによって円偏光が直線偏光に変換されるので、液晶ライトバルブ７を含むプロジェクタ側の構成を変えることなく、本実施の形態の照明装置を使用することができる。
【００４２】
このように、本実施の形態の照明装置においても、最初に反射型偏光子１７を透過できなかった偏光のリサイクルが可能であり、一種類の偏光方向を有する光として照明に寄与させることができるため、従来の照明装置に比べて偏光変換効率を高めることができる、という第１の実施の形態と同様の効果を得ることができる。また、円偏光を分離する反射型偏光子１７としてコレステリック液晶による偏光子を用いたが、コレステリック液晶は光吸収性を持たないため、有機フィルムを用いた従来の装置に比べて耐光性や耐熱性を高めることができる。
【００４３】
［第３の実施の形態］
以下、本発明の第３の実施の形態を、図５、図６を参照して説明する。
本実施の形態の照明装置の基本構成は第１、第２の実施の形態と同様であり、ロッドレンズの構成が異なるのみである。よって、本実施の形態では図５、図６を用いてロッドレンズの構成のみを説明し、その他の構成についての説明は省略する。
【００４４】
上記実施の形態ではロッドレンズの断面形状は入射側から射出側まで一定のものとしたが、本実施の形態では、図５（ａ）のような入射側から射出側に向けて先細りのテーパ形状のロッドレンズ２１、もしくは図５（ｂ）のような入射側から射出側に向けて先拡がりの逆テーパ形状のロッドレンズ２２が用いられる。これらロッドレンズ２１，２２の射出側に反射型偏光子５、入射側に反射ミラー３が設置されるのは第１、第２の実施の形態と同様である。反射型偏光子５としては直線偏光分離型、円偏光分離型のいずれを用いてもよい。
【００４５】
図６（ａ）、（ｂ）は、それぞれ図５（ａ）、（ｂ）のロッドレンズ２１，２２の平面図である。図５（ａ）のような先細りのロッドレンズ２１を用いた場合、図６（ａ）に示すように、ロッドレンズ２１に入射された光が、ロッドレンズ２１の反射面２１ａに対してより深い角度で入射し、反射するため、ロッドレンズ２１への入射角θ₁よりも射出角θ₂は大きく拡がって射出される。これに対して、図５（ｂ）のような先拡がりのロッドレンズ２２を用いた場合、図６（ｂ）に示すように、ロッドレンズ２２に入射された光が、ロッドレンズ２２の反射面２２ａに対してより浅い角度で入射し、反射するため、ロッドレンズ２２への入射角θ₁よりも射出角θ₂は小さく絞られて射出される。なお、本実施の形態のロッドレンズ２１，２２は縦方向、横方向ともにテーパ形状、もしくは逆テーパ形状となっているので、平面視した場合に限らず、側面視した場合にも上記の作用を有している。
【００４６】
このようなロッドレンズ２１，２２を本発明に適用した場合、それぞれ次のような効果が得られる。
図５（ａ）に示す先細りのロッドレンズ２１を用いた場合、射出端面に対して入射端面の面積を広く取れるので、光源２からロッドレンズ２１に入射する光束の断面積に対して反射ミラー３を設置する面積が相対的に大きくなり、偏光変換効率を向上させることができる。これに対して、図５（ｂ）に示す先拡がりのロッドレンズ２２を用いた場合、反射ミラー３の設置面積をあまり広く取れないが、上述したように、ロッドレンズ２２から射出される光の射出角θ₂を絞ることができるため、コントラスト特性が光の入射角依存性を有する液晶ライトバルブ７を用いてプロジェクタを構成した場合には、そのプロジェクタで表示される画像のコントラストを向上させることができる。その理由は、射出角θ₂が小さいと液晶ライトバルブ７に対して小さな角度で入射する光が多くなり、コントラストの低下を防止できるからである。もちろん、ロッドレンズの形状は上記の２種類に限定されず、図５において、例えばｘｚ平面とｙｚ平面とで、各々異なるテーパ形状（含む逆テーパ形状）をなすロッドレンズを用いることもできる。
【００４７】
［第４の実施の形態］
以下、本発明の第４の実施の形態を、図７を参照して説明する。
本実施の形態の照明装置の基本構成は第１〜第３の実施の形態と同様であり、ロッドレンズ入射側の反射ミラーの構成と光源２からロッドレンズへの光の入射の仕方が異なるのみである。よって、本実施の形態では図７を用いてロッドレンズおよび反射ミラーの構成のみを説明し、その他の構成についての説明は省略する。
【００４８】
本実施の形態の場合、被照明領域、すなわち液晶ライトバルブとして第１〜第３の実施の形態よりも横長のもので縦横比が９：１６のものを用いることを想定している。したがって、それに伴い、ロッドレンズ２５の断面形状も縦横比が９：１６の横長の形状となっている。そして、ロッドレンズ２５の射出側の反射型偏光子５の構成は第１〜第３の実施の形態と同様でよいが、ロッドレンズ２５の入射側の反射ミラー２４の構成は第１〜第３の実施の形態と異なっている。すなわち、第１〜第３の実施の形態では円形の光入射領域３ａの中心がロッドレンズ４の入射端面の中心に一致していたのに対し、本実施の形態では光入射領域２４ａの中心がロッドレンズ２５の入射端面の中心から偏心し、ロッドレンズ２５の断面形状の長手方向（図７の上側の図における右方向）にずれている。
【００４９】
さらに第１〜第３の実施の形態の場合、光源２から射出される光束の光源光軸Ｌがシステム光軸Ｍに一致していたが、本実施の形態では、光源２からの光束の光源光軸Ｌが、光入射領域２４ａの中心が偏心した方向に傾いており、光源２からの光が光入射領域２４ａを透過するとロッドレンズ２５の射出端面の略中心の位置で反射型偏光子５により反射され、再度反射ミラー２４に到達する位置関係となっている。
【００５０】
このように、光入射領域２４ａの中心をロッドレンズ２５の入射端面の中心から偏心させ、光源２から射出される光束の光源光軸Ｌをシステム光軸Ｍから傾けたことによって、ロッドレンズ２５内の光束が所定の角度を持って反射型偏光子５に入射されることになり、この光が反射ミラー２４の面積の広い側に向けて反射される割合が多くなるので、反射ミラー２４で反射される割合が大きくなり、偏光変換効率をより高めることができる。
【００５１】
また、第３の実施の形態のように、テーパ形状のロッドレンズを使用することを考えれば、液晶ライトバルブが正方形に近い形状（例えば縦横比が３：４）であったときにロッドレンズの射出端面をその形状に合わせた上で、入射端面の形状のみを変えて入射端面をより横長にする（例えば縦横比が９：１６）構成としてもよい。これにより、液晶ライトバルブが正方形に近い形状であっても偏光のリサイクル率を高めることができ、偏光変換効率を高めることができる。この場合でも、光入射領域の中心をロッドレンズの入射端面の中心から偏心させ、光源光軸Ｌをシステム光軸Ｍから傾ければ、上記と同様の効果を得ることができる。
【００５２】
［第５の実施の形態］
以下、本発明の第５の実施の形態を、図８を参照して説明する。
本実施の形態の照明装置の基本構成は第１〜第３の実施の形態と同様であり、ロッドレンズ入射側の反射ミラーの構成と光源２からロッドレンズへの光の入射の仕方が異なるのみである。よって、本実施の形態では図８を用いてロッドレンズおよび反射ミラーの構成のみを説明し、その他の構成についての説明は省略する。
【００５３】
本実施の形態も第４の実施の形態と同様、光入射領域２９ａの中心がロッドレンズ２８の入射端面の中心から偏心し、図８における上方向にずれている。しかしながら、第４の実施の形態の場合、光源２から射出される光束の光源光軸Ｌをシステム光軸Ｍに対して傾けた構成であったのに対し、本実施の形態の場合、光源光軸Ｌをシステム光軸Ｍに対して平行にシフトさせた構成としている。さらに、ロッドレンズ２８の入射端面がシステム光軸Ｍに対して垂直以外の角度をなすように傾けて配置されている。
【００５４】
本実施の形態の場合、光源光軸Ｌとシステム光軸Ｍとが平行であるが、光源光軸Ｌに対してロッドレンズ２８の入射端面が傾いているため、ロッドレンズ２８に入射する光束が入射時に屈折し、所定の角度を持って反射型偏光子５に入射されることになり、この光が反射ミラー２９の面積の広い側に向けて反射されるので、第４の実施の形態と同様、偏光変換効率をより高めることができる。さらに光源光軸Ｌとシステム光軸Ｍとが平行になるため、光学系を小型化しやすいというメリットもある。
【００５５】
［第６の実施の形態］
以下、本発明の第６の実施の形態を、図９、図１０を参照して説明する。
本実施の形態の照明装置の基本構成は第１〜第５の実施の形態と同様であり、ロッドレンズの構成が異なるのみである。よって、本実施の形態では図９、図１０を用いてロッドレンズの構成、作用のみを説明し、その他の構成についての説明は省略する。
【００５６】
第３の実施の形態のロッドレンズ２１が縦方向、横方向ともに先細りのテーパ形状となっていたのに対し、本実施の形態のロッドレンズ２７は、横方向（Ｘ方向）のみが先細りのテーパ形状となっており、縦方向（Ｙ方向）には細くなっていない。この構成とした場合、第３の実施の形態の項で述べたように、ロッドレンズ２７から射出される光の射出角θ₂が横方向に拡がる一方、縦方向には拡がらないことになる。すなわち、このロッドレンズ２７から射出される光の照明角分布は横長（Ｘ方向に長い）の楕円形状を示すことになる。
【００５７】
ここで、被照明領域である液晶ライトバルブの視野角特性に着目すると、液晶ライトバルブの視野角特性は必ずしも対称性を示さず、例えば明視方向が６時あるいは１２時であるＴＮモードの液晶ライトバルブでは、図１０（ｂ）に示すように、等コントラスト曲線が縦方向に狭く、横方向に拡がった特性を示すことが多い。液晶ライトバルブが図１０（ｂ）のような視野角特性を持っている場合、液晶ライトバルブを照明する光の照明角分布として図１０（ａ）のような特性を持つものを用いると、コントラストの高い部分を利用することになり、高いコントラストを得ることができる。
【００５８】
このような観点から、本実施の形態の照明装置をプロジェクタに適用した場合、図９に示したような横方向のみが先細りのテーパ形状となったロッドレンズ２７を用いたことにより、高いコントラストを維持することができ、表示品位の高いプロジェクタを実現することができる。
【００５９】
［プロジェクタ］
図１１は、本発明の照明装置を備えたプロジェクタの一実施の形態を示す概略構成図である。図中、符号５１０は光源、５３０はロッドレンズ、５３１は反射ミラー、５３２は反射型偏光子、５１３，５１４はダイクロイックミラー（色光分離手段）、５１５，５１６，５１７は反射ミラー、５２２，５２３，５２４は液晶ライトバルブ（光変調手段）、５２５はクロスダイクロイックプリズム（色光合成手段）、５２１は導光光学系、５２６は投写レンズ（投写手段）を示している。
【００６０】
照明装置５４０は光源５１０、ロッドレンズ５３０、反射ミラー５３１、反射型偏光子５３２から構成されている。光源５１０はメタルハライド等のランプ５１１とランプの光を反射するリフレクタ５１２とからなる。また、光源光の照度分布を均一化させるための均一照明系として、ロッドレンズ５３０が用いられており、ロッドレンズ５３０の射出端面に反射型偏光子５３２が、入射端面には光源５１０からの光束が入射する円形状の開口部を備えた反射ミラー５３１が設置されている。ロッドレンズ５３０の射出側には集光レンズ５３５が、また、ダイクロイックミラー５１３，５１４の前後にはリレーレンズ５３６，５３７が、さらに、液晶ライトバルブの入射側および導光光学系５２１の入射側には平行化レンズ５１８Ｒ，５１８Ｇと集光レンズ５１８Ｂが各々配置されており、これらのレンズは、先に第１の実施の形態で説明したリレー系６と同様の機能を担っている。
【００６１】
青色光・緑色光反射のダイクロイックミラー５１３は、光源５１０からの光束のうちの赤色光Ｌ_Rを透過させるとともに、青色光Ｌ_Bと緑色光Ｌ_Gとを反射させる。透過した赤色光Ｌ_Rは反射ミラー５１７で反射されて赤色光用液晶ライトバルブ５２２に入射する。一方、ダイクロイックミラー５１３で反射した色光のうち、緑色光Ｌ_Gは緑色光反射用のダイクロイックミラー５１４によって反射し、緑色光用液晶ライトバルブ５２３に入射する。一方、青色光Ｌ_Bは第２のダイクロイックミラー５１４も透過し、集光レンズ５１８Ｂ、２つの反射ミラー５１５，５１６、リレーレンズ５１９および平行化レンズ５２０を経て、青色光用液晶ライトバルブ５２４に入射する。導光光学系５２１は集光レンズ５１８Ｂと平行化レンズ５２０間の光学的距離を補正し、青色光路の長さを他の色光のそれと合わせることで、照明ムラの発生を低減する機能を担っている。
【００６２】
各液晶ライトバルブ５２２，５２３，５２４によって変調された３つの色光は、クロスダイクロイックプリズム５２５に入射する。このプリズムは４つの直角プリズムが貼り合わされ、その内面に赤色光を反射する誘電体多層膜と青色光を反射する誘電体多層膜とが十字状に形成されている。これらの誘電体多層膜によって３つの色光が合成されてカラー画像を表す光が形成される。合成された光は投写光学系である投写レンズ５２６により投写スクリーン５２７上に投写され、拡大された画像が表示される。
【００６３】
プロジェクタには高輝度の光源が用いられることが多く、従来、耐光性や耐熱性の面で問題があったが、この構成によれば、高い偏光変換効率と耐久性を有する照明装置を備えたことにより、高輝度で信頼性の高いプロジェクタを実現することができる。
【００６４】
なお、本発明の技術範囲は上記実施の形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。例えば上記実施の形態では照明装置の構成として、導光光学系５２１を備えたものを例示したが、この導光光学系５２１は照明装置としては必須の構成要素ではなく、なくてもよい。また、ロッドレンズの入射端面および射出端面の形状、反射型偏光子や反射ミラーの構成等に関する具体的に記載についても上記実施の形態に限ることなく、適宜設計変更が可能である。
【００６５】
【発明の効果】
以上、詳細に説明したように、本発明によれば、反射型偏光子を透過できない偏光のリサイクルが可能であり、照明に寄与させることができるため、従来の照明装置に比べて偏光の利用効率を高められ、明るい照明装置を実現することができる。また、従来から均一照明系として用いられている光束分割手段の射出側に反射型偏光子、入射側に反射ミラーを配置するだけで済むので、簡単な構成で偏光変換効率の高い照明装置を実現することができる。また、特に構造複屈折型の反射型偏光子は無機材料を用いて形成することができるため、有機フィルムからなる位相差板を用いた従来の偏光変換系に比べて耐光性や耐熱性にはるかに優れ、安定した偏光変換作用を実現することができる。そして、このような照明装置を備えたことにより、高輝度で信頼性の高いプロジェクタを実現することができる。
【図面の簡単な説明】
【図１】 本発明の第１の実施形態の照明装置を示す概略構成図である。
【図２】 同、照明装置のロッドレンズ内での偏光変換作用を説明するための図である。
【図３】 同、照明装置に用いる構造複屈折型の反射型偏光子の構成を示す斜視図である。
【図４】 本発明の第２の実施形態の照明装置のロッドレンズ射出側の構成を示す概略構成図である。
【図５】 （ａ）、（ｂ）ともに本発明の第３の実施形態の照明装置のロッドレンズの構成を示す斜視図である。
【図６】 図５の（ａ）、（ｂ）のロッドレンズの作用を説明するための図である。
【図７】 本発明の第４の実施形態の照明装置のロッドレンズの構成を示す斜視図である。
【図８】 本発明の第５の実施形態の照明装置のロッドレンズの構成を示す斜視図である。
【図９】 本発明の第６の実施形態の照明装置のロッドレンズの構成を示す斜視図である。
【図１０】 （ａ）同、ロッドレンズから射出される光の照明角分布、（ｂ）液晶ライトバルブの視野角特性をそれぞれ示す図である。
【図１１】 本発明のプロジェクタの一例を示す概略構成図である。
【図１２】 構造複屈折型偏光子の原理を説明するための図である。
【符号の説明】
１，５４０ 照明装置
２，５１０ 光源
３，２４，２９，５３１ 反射ミラー
３ａ，２４ａ 開口部（光入射領域）
４，２１，２２，２５，２７，２８，５３０ ロッドレンズ（光束分割手段）
５，１７，５３２ 反射型偏光子
７，５２２，５２３，５２４ 液晶ライトバルブ（被照明領域、光変調手段）
１８ 第１の１／４波長板
１９ 第２の１／４波長板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an illuminating device and a projector, and more particularly to a configuration of an illuminating device having excellent polarization conversion efficiency.
[0002]
[Prior art]
In recent years, the development of information devices has been remarkable, and the demand for high-resolution, low power consumption and thin display devices has been increasing, and research and development have been promoted. Among them, the liquid crystal display device is expected as a display device that can electrically control the alignment of liquid crystal molecules to change the optical characteristics and can meet the above-mentioned needs. As one form of such a liquid crystal display device, there is known a projector that enlarges and projects an image emitted from a video source including an optical system using a liquid crystal light valve onto a screen through a projection lens.
[0003]
The projector uses a liquid crystal light valve as a light modulation means. In particular, a TN (Twisted Nematic) type liquid crystal light valve performs display using only polarized light in one direction in principle. About half of the polarized light beam is not used for display. Accordingly, an illumination device for a projector provided with a polarization conversion system for the purpose of making it possible to use light that is not normally used by aligning an indefinitely polarized light beam with polarized light in one direction and improving the light utilization efficiency is disclosed in Japanese Patent Application Laid-Open No. 8-304739. And JP-A-10-232430.
[0004]
Further, in a projector lighting device, a light beam emitted from a light source such as a metal halide lamp generally has a non-uniform illuminance distribution. However, in a lighting area, specifically, a display surface of a rectangular liquid crystal light valve. In order to make the illuminance distribution uniform, one having a uniform illumination system including two fly-eye lenses or a rod-shaped light guide is known.
[0005]
[Problems to be solved by the invention]
For example, as described in the above publication, in a conventional illumination device, a polarization beam splitter (Polarized Beam Splitter, hereinafter abbreviated as PBS) array and an organic film retardation plate are used as a polarization conversion system. In most cases, combinations are used. However, while this system can obtain high polarization conversion efficiency, there is a problem that the structure of the PBS array is complicated and expensive, and the cost of the entire illumination device increases. Furthermore, since a high-luminance light source is used in a projector illumination device, a retardation plate made of an organic film has a problem in terms of light resistance and heat resistance.
[0006]
The present invention has been made to solve the above-described problems, and has an object to provide a lighting device that can obtain high polarization conversion efficiency with a simple configuration and is excellent in light resistance and heat resistance. To do. It is another object of the present invention to provide a projector with high brightness and high reliability by including the above-described illumination device.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an illuminating device of the present invention is an illuminating device including a light source and a light beam dividing unit that divides a light beam from the light source into a plurality of light beams by using reflection. , Luminous flux Transmits a part of the polarized light beam incident on the light beam splitting means from the light source and reflects a part of the polarized light on the exit side of the splitting means. Reflective polarizer is provided The reflecting mirror for reflecting the polarized light reflected by the reflective polarizer is provided on the incident side of the light beam splitting means corresponding to the area other than the light incident area from the light source on the incident end face of the light beam splitting means. It is characterized by.
[0008]
In the illuminating device of the present invention described above, the light emitted from the light source is first incident on the light beam dividing means, divided into a plurality of light beams and emitted from the light beam dividing means. The “beam splitting means” here has a function of splitting a group of incident light fluxes from the light source into a plurality of light fluxes, and the resulting light fluxes from the plurality of light source images are provided in the subsequent stage of the light flux splitting means. It is used for the purpose of making the illuminance distribution uniform in the illuminated area by superimposing with another arranged optical system. In the present invention, since the reflective polarizer is provided on the exit side of the light beam splitting means, when light enters the reflective polarizer from the light beam splitting means, the polarization direction coincides with the transmission axis of the reflective polarizer. Light is transmitted and other light is reflected. The light that has passed through the reflective polarizer contributes to the illumination of the illuminated area, while the light reflected by the reflective polarizer is propagated in the light beam splitting means in the reverse direction (on the incident end face side of the light beam splitting means). .
[0009]
Since the light beam emitted from the light source needs to be incident on the light beam splitting means, a predetermined incident area (light transmission area) is provided on the incident end face. The shape of the incident region substantially matches the cross-sectional shape of the light beam from the light source, and is, for example, a circular shape. In the case of the illumination device of the present invention, since the reflecting mirror is provided corresponding to the region other than the incident region, the incident region out of the polarized light reflected by the reflective polarizer and returning to the incident end surface side in the reverse direction. Polarized light that has entered the other region is reflected by the reflecting mirror and propagates again to the exit side of the beam splitting means. As described above, since the reflective polarizer is arranged on the exit side of the light beam splitting means and the reflection mirror is arranged on the incident side, the polarized light reflected by the reflective polarizer is repeatedly reflected inside the light beam splitting means. However, during the reflection, the polarization direction is not always unchanged, but changes. When the changed polarization direction matches the transmission axis of the reflective polarizer, the light that has been reflected until then can pass through the reflective polarizer and reach the illuminated area, contributing to illumination. can do.
[0010]
According to the illuminating device of the present invention, it is possible to recycle light having a polarization direction that could not be transmitted through the reflective polarizer first by such a mechanism, and to contribute to illumination as light having one kind of polarization direction. Therefore, the polarization conversion efficiency can be increased as compared with the conventional illumination device. Moreover, since only a reflective polarizer is required on the exit side of the conventional beam splitting means and a reflection mirror is required on the incident side, polarization conversion efficiency (efficiency for converting indefinite polarization into specific polarization) can be achieved with a simple configuration. A high illumination device can be realized.
[0011]
As the function of the reflective polarizer, one that transmits one of linearly polarized light orthogonal to each other and reflects the other can be used.
In this case, for example, an X-polarized light beam is transmitted through the reflective polarizer, and a Y-polarized light beam (the polarization directions of the X-polarized light beam and the Y-polarized light beam are orthogonal to each other) is reflected. The Y-polarized light beam reflected by the reflective polarizer is repeatedly reflected from the reflection mirror on the incident side, the polarization direction changes while propagating inside the light beam splitting means, and part of it is converted to an X-polarized light beam. And transmitted through the reflective polarizer. In this manner, polarized light can be recycled and can be contributed to illumination as light having one kind of polarization direction. Therefore, the polarization conversion efficiency can be increased as compared with a conventional illumination device.
[0012]
When linearly polarized light is used, it is desirable to use a structural birefringent polarizer.
A “structurally birefringent polarizer” has a grating portion in which two types of media having different refractive indexes are alternately arranged in a stripe pattern with a period shorter than the wavelength of light. Since the refractive index perceived by light is different from that of the vertical polarization component, a birefringence action occurs and functions as a polarizer. That is, as shown in FIG. 12, in the structure birefringent body 100 having a structure including a plurality of mediums A101 arranged in a stripe pattern at a pitch smaller than the wavelength of incident light, a gap between adjacent media A101 is provided in the gap. The medium B102 having a refractive index different from that of the medium A101 needs to be filled. The medium B102 may be solid, liquid, or gas.
[0013]
In the structural birefringent body 100 having such a structure, the refractive index n of the medium A101. ₁ And refractive index n of medium B102 ₂ Therefore, the effective refractive index differs depending on the polarization direction of the light incident on the structural birefringent body 100. For example, the refractive index n of the medium A101 ₁ Is the refractive index n of the medium B102 ₂ Is larger than the effective refractive index of the polarized light A that vibrates in a direction substantially parallel to the extending direction of each medium A101, the polarized light B that vibrates in a direction substantially perpendicular to the extending direction of each medium A101. Is greater than the effective refractive index.
[0014]
In the case where the medium A and the medium B are made of a dielectric, assuming that the width of the medium A101 is a and the width of the medium B102 is b, of the light incident on the structural birefringent body 100, the effective refractive index Na for the polarization A, the polarization It is known that the effective refractive index Nb for B is expressed by the following equations (1) and (2) (for example, M. Born and E. Wolf: Principles of Optics, 1st ed. (Pergamon Press New York, 1959) p.705-708). As can be seen from the following formulas (1) and (2), the effective refractive index is n by the ratio of the thickness a of the medium A101 and the thickness b of the medium B102. ₁ ~ N ₂ It can be changed within the range.
[0015]
[Expression 1]

[0016]
As described above, it has been described that the structural birefringent body exhibits different optical properties depending on the polarization state of light. Here, when a light reflector such as a metal or a semiconductor is used as the medium A, the dielectric constant is handled as a complex number, so that it can be handled in the same manner as when the effective refractive index for the dielectric is obtained. However, the effective refractive index is a complex number. Effective Medium Theory (eg, Dominique Lemercier-lalanne: Journal of Modern Optics, 1996, vol 43, no. 10, 2063-2085), more strictly Rigorous Coupled-Wave Analysis (MGMoharam: J. Opt. Soc. Am. A , 12 (1995) 1077), when a metal is used as the medium A, the imaginary part of the effective refractive index of the structural birefringent body with respect to the polarized light A becomes a large value. As a result, the incident polarized light A is It is known to be reflected by a structural birefringent body. On the other hand, it is known that the imaginary part of the effective refractive index for the polarized light B has a small value, and the polarized light B is transmitted through the structural birefringent body. In this way, by forming a periodic structure having a wavelength smaller than the wavelength with two types of media, the polarized light oscillating in a direction parallel to the direction in which the periodic structures of the structural birefringence are arranged is transmitted, An action of reflecting polarized light oscillating in an orthogonal direction can be provided.
[0017]
Since the above-mentioned structural birefringent polarizer can be formed using an inorganic material, it has far superior light resistance and heat resistance compared to conventional polarization conversion systems using retardation films made of organic films. Even when the intensity of illumination light is high, a stable polarization conversion action can be realized.
[0018]
The reflective polarizer that separates linearly polarized light into transmitted light and reflected light has been described above. However, a polarizer that separates circularly polarized light may be used. That is, as the reflective polarizer, one having a function of transmitting one of circularly polarized light in the opposite directions and reflecting the other may be used. In that case, however, it is desirable to provide a quarter-wave plate between the beam splitting means and the reflective polarizer.
[0019]
When the light beam from the light source is directly incident on the light beam splitting means, the light beam is in an indefinite polarization state. Therefore, when the indefinitely polarized light beam emitted from the light beam splitting means passes through the quarter wavelength plate, it is separated into an L circularly polarized light beam and an R circularly polarized light beam (the L circularly polarized light beam and the R circularly polarized light beam rotate with each other). Reverse direction). In the reflective polarizer, for example, an L circularly polarized light beam is transmitted and an R circularly polarized light beam is reflected. As in the case of the linearly polarized light described above, the R circularly polarized light beam reflected by the reflective polarizer repeats reflection with the incident-side reflection mirror, passes through the quarter-wave plate, or splits the light beam. The direction of polarization changes while propagating through the light, and part of the light becomes an L circularly polarized light beam that passes through the reflective polarizer. In the case of circularly polarized light, polarized light can be recycled by the same mechanism as in the case of linearly polarized light, and can be contributed to illumination as light having one kind of polarization direction. Efficiency can be increased.
[0020]
In the case of the configuration using the circularly polarized light, it is desirable to further provide a quarter wavelength plate on the exit side of the reflective polarizer.
According to this configuration, the light emitted from the reflective polarizer as a circularly polarized light beam is converted to linearly polarized light by transmitting through the quarter-wave plate. Therefore, the configuration of the projector to which this illumination device is applied is linearly polarized light. It can be made common to the case of a lighting device that emits light.
[0021]
As a specific configuration of the light beam splitting means, a rod-shaped light guide or a tubular light guide whose inner surface is a reflection surface, a so-called rod lens can be used. In this case, as the shape of the rod lens, the exit end surface needs to be optically conjugate (similar) to the illuminated area, but the entrance end surface and the exit end surface do not necessarily have to be similar. Further, they may have the same diameter from the incident side toward the emission side, but may have a tapered shape or a widened shape.
When the shape is tapered or widened, the exit angle can be changed with respect to the incident angle of light to the rod lens. Each effect will be described later.
[0022]
On the incident end face of the light beam splitting means, it is desirable that the shape of the incident region is circular, and the reflection mirror is provided in a region outside the circular incident region.
Normally, the intensity distribution of the light beam emitted from the light source is circular when viewed from the optical axis direction, and accordingly the shape of the incident region of the light beam splitting means is also circular, which is an efficient method with the least loss. . Here, if the illuminated area is a rectangular liquid crystal light valve, the exit end face of the light beam splitting means is also rectangular, and if the entrance end face has a rectangular shape similar to the exit end face, the inside of the rectangular entrance end face is circular. In this case, a reflection mirror may be provided around the incident area.
[0023]
In particular, when the shapes of the incident end face and the exit end face of the light beam splitting means are both rectangular, it is desirable that the entrance end face be a narrower rectangular shape than the exit end face.
For example, even if the exit end face has a shape close to a square, if the entrance end face is made into a more elongated rectangle, the area of the installation area of the reflection mirror can be made larger than the area of the entrance area. Can be improved.
[0024]
Regarding the arrangement of the incident area in the incident end face of the beam splitting means, in addition to the case where the center of the incident area is aligned with the center of the incident end face, the center of the incident area may be decentered with respect to the center of the incident end face. The optical axis of the light beam incident on the dividing means (the optical axis of the light source) and the incident end face of the reflective polarizer may form an angle other than perpendicular. Such a configuration is, for example, by tilting the optical axis of the light source with respect to the system optical axis passing through the approximate center of the beam splitting means, or shifting the optical axis of the light source parallel to the system optical axis, This can be realized by, for example, arranging the incident end face of the light beam splitting unit so as to form an angle other than perpendicular to the system optical axis. In particular, the latter configuration has an advantage that the optical system can be easily miniaturized because the optical axis of the light source and the system optical axis are parallel to each other.
According to this configuration, the ratio that the reflected light from the reflective polarizer is reflected by the reflection mirror installed on the incident side of the light beam splitting means is increased, so that high polarization conversion efficiency can be realized. This will also be described in detail later.
[0025]
A projector according to the present invention includes the illumination device according to the present invention, a light modulation unit that modulates light emitted from the illumination device, and a projection unit that projects light modulated by the light modulation unit. And
According to this configuration, a projector with high luminance and high reliability can be realized by including the illumination device having high polarization conversion efficiency and durability.
[0026]
In particular, when the light modulating means is a liquid crystal light valve, it is desirable that the direction in which the illumination angle of the illumination light beam emitted from the light beam dividing means of the illuminating device expands coincides with the direction in which the viewing angle of the liquid crystal light valve is wide.
According to this configuration, a high contrast can be obtained, and a projector with high display quality can be realized.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
[First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of a lighting apparatus according to the present embodiment. In FIG. 1, reference numeral 2 is a light source, 3 is a reflecting mirror, 4 is a rod lens (light beam splitting means), 5 is a reflective polarizer, 6 is a relay system, and 7 is a liquid crystal light valve (illuminated area).
[0028]
As shown in FIG. 1, the illumination device 1 according to the present embodiment includes a light source 2 including a lamp 8 such as a metal halide lamp and a reflector 9, a rod lens 4, and three lenses 10, 11, and 12. And a relay system 6.
[0029]
As the rod lens 4, a transparent rod-shaped light guide (for example, a glass rod) or a tubular light guide whose inner surface is a reflection surface (for example, a kaleidoscope in which a plurality of reflection mirrors are arranged in a tubular shape facing inward). Etc. are used. In the case of the present embodiment, the rod lens 4 is a rectangular columnar light guide having the same cross section from the incident side to the exit side. As shown in the lower side of FIG. 1, the shapes of the incident end face and the exit end face are similar to the illuminated area, that is, the liquid crystal light valve 7, and are, for example, rectangular with an aspect ratio of 3: 4. In the present embodiment, both the incident end face and the exit end face are similar to the liquid crystal light valve 7, but the incident end face is not necessarily similar. The rod lens 4 has a function of dividing incident light from the light source 2 into a plurality of light beams, and superimposes light beams generated from the plurality of light source images on the illuminated area by a light transmission means such as a relay system 6. By doing so, the illuminance distribution in the liquid crystal light valve 7 is made uniform.
[0030]
On the incident end face of the rod lens 4, the reflection mirror 3 having a circular opening 3 a (light incident area) in the center is installed with the reflection surface facing the inside of the rod lens 4. As a specific form of installation of the reflection mirror 3, if the rod lens 4 is a tubular light guide, for example, a mirror having an opening at the center may be fitted into the end of the rod lens. If 4 is a rod-shaped light guide, for example, an annular dielectric mirror patterned so as to form a light transmission portion at the center may be formed directly on the end surface of the rod lens. In any case, it is only necessary that the reflection mirror 3 is provided in a region other than the light incident region where the light flux from the light source 2 is incident. In addition, the configuration of the light incident region from the light source 2 is not limited to the opening, and may be a configuration closed with a light transmissive member, for example.
[0031]
A reflective polarizer 5 is installed on the exit end face of the rod lens 4. In the case of the present embodiment, a structural birefringent reflective polarizer that separates indefinite polarized light into two types of linearly polarized light orthogonal to each other is used as the reflective polarizer 5 as shown in FIG. . As shown in FIG. 3, the reflective polarizer 5 has a large number of ribs 14 made of a metal having light reflectivity such as aluminum formed on a glass substrate 15 at a pitch smaller than the wavelength of incident light. is there. That is, the reflective polarizer 5 has a birefringence effect because Al ribs 14 having different refractive indexes and air are alternately arranged in a stripe shape at a pitch smaller than the wavelength of incident light. Function. With this configuration, when indefinite polarized light is incident on the surface on which the Al rib 14 is formed, S-polarized light that vibrates in a direction parallel to the extending direction of the Al rib 14 is reflected, and the extending direction of the Al rib 14 is reflected. P-polarized light that vibrates in a direction perpendicular to the direction (the direction in which the Al ribs are arranged) is transmitted.
[0032]
As for the direction of the reflective polarizer 5, it is desirable that the surface (incident surface) on which the Al ribs 14 are formed is oriented so as to face the inside of the rod lens 4 with emphasis on the efficiency of polarization separation. . However, when used in combination with a rod-shaped rod lens with a clogged inside instead of a tubular light guide, a very slight gap exists between the exit end surface of the rod lens and the Al rib 14. It is desirable to arrange both. Alternatively, the reflective polarizer 5 can be installed so that the surface (incident surface) on which the Al ribs 14 are formed faces the liquid crystal light valve 7 (illuminated region). In that case, the efficiency of polarization separation may be slightly reduced, but it can be installed in close contact with the rod lens, so it is easy to install and when used in combination with a rod-shaped rod lens with a clogged inside. Since the exit end surface of the rod lens and the surface of the reflective polarizer 5 on the side where the Al rib 14 is not present can be brought into close contact with each other and optically integrated, there is an advantage that light loss that tends to occur at the interface can be reduced.
[0033]
In the case of the present embodiment, three lenses 10, 11, and 12 are used as the relay system 6, and the lens 10 closest to the rod lens 4 is installed so as to be in close contact with the reflective polarizer 5. The number of lenses used for the relay system 6 and the position of the lenses are not limited to this, and can be changed as appropriate.
[0034]
Next, the operation of the illumination device 1 having the above configuration will be described with reference to FIG.
As shown in FIG. 2, the light beam emitted from the light source 2 enters the inside of the rod lens 4 through the opening 3a of the reflection mirror 3, and propagates toward the reflective polarizer 5 disposed on the emission side. . At this time, the light beam is indefinitely polarized, but when light is incident on the reflective polarizer 5, the light is separated according to the polarization direction, and as shown in FIG. 3, the extension of the Al rib 14 of the reflective polarizer 5. P-polarized light in a direction perpendicular to the current direction (transmission axis direction) is transmitted, and S-polarized light in a direction parallel to the extending direction of the Al rib 14 is reflected. The P-polarized light that has passed through the reflective polarizer 5 contributes to the illumination of the liquid crystal light valve 7 via the relay system 6, while the S-polarized light reflected by the reflective polarizer 5 travels in the reverse direction (incident end face) in the rod lens 4. Side).
[0035]
S-polarized light reflected by the reflective polarizer 5 then reaches the incident end face of the rod lens 4, but is reflected by the reflective mirror 3 because the reflective mirror 3 is disposed in a region other than the opening 3a. It is propagated again to the exit side of the rod lens 4. As described above, the reflective polarizer 5 is disposed on the exit side of the rod lens 4 and the reflection mirror 3 is disposed on the entrance side, so that the S-polarized light that does not pass through the reflective polarizer 5 is incident on the entrance side and the exit side of the rod lens 4. However, the S-polarized light does not always maintain this polarization direction. When the S-polarized light is reflected by the inner surface of the rod lens 4, the polarization direction is rotated and a part thereof is converted to P-polarized light. When the light reaches the reflective polarizer 5 in the P-polarized state, it can pass through the reflective polarizer 5 and contribute to the illumination of the liquid crystal light valve 7.
[0036]
According to the illuminating device 1 of the present embodiment, the polarized light that could not be transmitted through the reflective polarizer 5 first by such a mechanism can be recycled and contribute to illumination. Compared to the above, the use efficiency as polarized light can be improved, and a bright illumination device can be realized. In addition, since it is only necessary to arrange the reflective polarizer 5 on the exit side of the rod lens 4 conventionally used as a uniform illumination system and the reflective mirror 3 on the incident side, the polarization conversion efficiency (undefined polarization) can be achieved with a simple configuration. An illuminating device having a high efficiency of conversion into specific polarized light can be realized.
[0037]
In addition, the structural birefringent reflective polarizer 5 can be formed using an inorganic material such as a glass substrate or aluminum, and therefore, compared to a conventional polarization conversion system using a retardation plate made of an organic film. It is far superior in light resistance and heat resistance, and can realize a stable polarization conversion action even if the intensity of illumination light is high.
[0038]
[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
The basic configuration of the lighting apparatus of the present embodiment is the same as that of the first embodiment, but the first embodiment uses a reflective polarizer that separates linearly polarized light, whereas the present embodiment The form is different in that a reflective polarizer for separating circularly polarized light is used. Therefore, in this embodiment, only the periphery of the rod lens will be described with reference to FIG. 4, and description of the light source and the relay system will be omitted.
[0039]
In the illumination device of the present embodiment, the configuration of the reflection mirror 3 on the incident side of the rod lens 4 is the same as that of the first embodiment, but the configuration on the exit side is different. That is, as shown in FIG. 4, the circularly polarized light having a function of transmitting one of the circularly polarized light in the reverse direction (for example, L-polarized light) and reflecting the other (R-polarized light) on the most exit side of the rod lens 4. A separation-type reflective polarizer 17 is provided. As this type of reflective polarizer 17, for example, a polarizer using cholesteric liquid crystal can be used. A first quarter-wave plate 18 is installed on the light source 2 side of the reflective polarizer 17, and a second quarter-wave plate 19 is installed on the relay system 6 side of the reflective polarizer 17. ing. In FIG. 4, for convenience of explanation, the first quarter-wave plate 18, the reflective polarizer 17, and the second quarter-wave plate 19 are drawn apart from each other. There is no problem even if it is in close contact.
[0040]
The operation of the lighting device of the present embodiment will be described.
The point that the indefinitely polarized light beam from the light source 2 enters the rod lens 4 and propagates is the same as in the first embodiment. When the indefinitely polarized light beam passes through the first quarter-wave plate 18, it is separated into an L circularly polarized light beam and an R circularly polarized light beam whose rotation directions are opposite to each other. Specifically, for example, among the indefinitely polarized light beams included in the light source light, linearly polarized light that vibrates in a direction perpendicular to the paper surface in FIG. 4 is converted into an R circularly polarized light beam, and linearly polarized light that vibrates in a direction parallel to the paper surface. Is converted into an L circularly polarized light beam to separate these polarized lights. Next, in the reflective polarizer 17, for example, an L circularly polarized light beam is transmitted and an R circularly polarized light beam is reflected. After that, as in the case of the linearly polarized light of the first embodiment, the R circularly polarized light beam reflected by the reflective polarizer 17 repeats reflection with the reflection mirror 3 on the incident side, and the inside of the rod lens 4. While the light is reflected, the polarization direction (rotation direction) changes in the reverse direction, and a part thereof becomes an L circularly polarized light beam and passes through the reflective polarizer 17.
[0041]
In any case, since all the L-polarized light beams are emitted when the reflective polarizer 17 on the exit side of the rod lens 4 is emitted, this polarized light is transmitted through the second quarter-wave plate 19. Thus, the L circularly polarized light beam is converted into linearly polarized light that vibrates in a direction parallel to the paper surface. Note that, depending on the arrangement of the optical axes of the second quarter-wave plate 19, the light is converted into linearly polarized light that vibrates in a direction perpendicular to the paper surface. Further, the second quarter-wave plate 19 is not necessarily required, but circularly polarized light is converted into linearly polarized light by inserting the second quarter-wave plate 19 after the reflective polarizer 17. Therefore, the illumination device of the present embodiment can be used without changing the configuration on the projector side including the liquid crystal light valve 7.
[0042]
As described above, also in the illumination device of the present embodiment, it is possible to recycle polarized light that could not be transmitted through the reflective polarizer 17 first, and to contribute to illumination as light having one kind of polarization direction. Therefore, it is possible to obtain the same effect as that of the first embodiment that the polarization conversion efficiency can be increased as compared with the conventional illumination device. Further, although a cholesteric liquid crystal polarizer is used as the reflective polarizer 17 for separating the circularly polarized light, the cholesteric liquid crystal has no light absorptivity, so that it has light resistance and heat resistance as compared with a conventional apparatus using an organic film. Can be increased.
[0043]
[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the illumination device of the present embodiment is the same as that of the first and second embodiments, and only the configuration of the rod lens is different. Therefore, in the present embodiment, only the configuration of the rod lens will be described with reference to FIGS. 5 and 6, and the description of the other configurations will be omitted.
[0044]
In the above embodiment, the cross-sectional shape of the rod lens is constant from the entrance side to the exit side, but in this embodiment, the taper shape is tapered from the entrance side to the exit side as shown in FIG. Rod lens 21 or an inversely tapered rod lens 22 that widens from the incident side to the emission side as shown in FIG. 5B is used. The reflection type polarizer 5 is installed on the exit side of the rod lenses 21 and 22 and the reflection mirror 3 is installed on the entrance side, as in the first and second embodiments. As the reflective polarizer 5, either a linearly polarized light separating type or a circularly polarized light separating type may be used.
[0045]
6 (a) and 6 (b) are plan views of the rod lenses 21 and 22 of FIGS. 5 (a) and 5 (b), respectively. When the taper rod lens 21 as shown in FIG. 5A is used, the light incident on the rod lens 21 is deeper than the reflection surface 21a of the rod lens 21 as shown in FIG. Since it is incident and reflected at an angle, the incident angle θ to the rod lens 21 ₁ Than the exit angle θ ₂ Is greatly expanded and injected. On the other hand, in the case where the splayed rod lens 22 as shown in FIG. 5B is used, the light incident on the rod lens 22 is reflected by the reflecting surface of the rod lens 22 as shown in FIG. The incident angle θ to the rod lens 22 is reflected at a shallower angle with respect to 22a. ₁ Than the exit angle θ ₂ Is squeezed small and injected. Since the rod lenses 21 and 22 of the present embodiment are tapered or reversely tapered in both the vertical direction and the horizontal direction, the above action is not limited to a plan view but also a side view. Have.
[0046]
When such rod lenses 21 and 22 are applied to the present invention, the following effects can be obtained.
When the tapered rod lens 21 shown in FIG. 5A is used, the area of the incident end face can be made larger than the exit end face, and therefore, the reflection mirror 3 with respect to the cross-sectional area of the light beam incident on the rod lens 21 from the light source 2. The area where the light source is installed becomes relatively large, and the polarization conversion efficiency can be improved. On the other hand, when the splayed rod lens 22 shown in FIG. 5B is used, the installation area of the reflection mirror 3 is not so large, but as described above, the light emitted from the rod lens 22 can be reduced. Injection angle θ ₂ Therefore, when the projector is configured by using the liquid crystal light valve 7 whose contrast characteristics are dependent on the incident angle of light, the contrast of an image displayed by the projector can be improved. The reason is that the exit angle θ ₂ This is because if the angle is small, the amount of light incident on the liquid crystal light valve 7 at a small angle increases, and a reduction in contrast can be prevented. Of course, the shape of the rod lens is not limited to the above two types. In FIG. 5, for example, rod lenses having different tapered shapes (including reverse tapered shapes) on the xz plane and the yz plane can also be used.
[0047]
[Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.
The basic configuration of the illuminating device of the present embodiment is the same as that of the first to third embodiments, except that the configuration of the reflecting mirror on the rod lens incident side and the way of incidence of light from the light source 2 to the rod lens are different. It is. Therefore, in this embodiment, only the configuration of the rod lens and the reflection mirror will be described with reference to FIG. 7, and description of the other configurations will be omitted.
[0048]
In the case of the present embodiment, it is assumed that an illuminated area, that is, a liquid crystal light valve, is longer than the first to third embodiments and has an aspect ratio of 9:16. Accordingly, along with this, the cross-sectional shape of the rod lens 25 is also a horizontally long shape with an aspect ratio of 9:16. The configuration of the reflective polarizer 5 on the exit side of the rod lens 25 may be the same as in the first to third embodiments, but the configuration of the reflection mirror 24 on the incident side of the rod lens 25 is the first to third. This is different from the embodiment. That is, in the first to third embodiments, the center of the circular light incident region 3a coincides with the center of the incident end surface of the rod lens 4, whereas in this embodiment, the center of the light incident region 24a is the center. It is eccentric from the center of the incident end face of the rod lens 25 and is shifted in the longitudinal direction of the cross-sectional shape of the rod lens 25 (right direction in the upper diagram of FIG. 7).
[0049]
Furthermore, in the case of the first to third embodiments, the light source optical axis L of the light beam emitted from the light source 2 coincides with the system optical axis M, but in this embodiment, the light source of the light beam from the light source 2 The optical axis L is inclined in the direction in which the center of the light incident area 24a is decentered, and when the light from the light source 2 passes through the light incident area 24a, the reflective polarizer 5 is positioned at the approximate center of the exit end face of the rod lens 25. The positional relationship is such that the light reaches the reflection mirror 24 again.
[0050]
As described above, the center of the light incident area 24a is decentered from the center of the incident end face of the rod lens 25, and the light source optical axis L of the light beam emitted from the light source 2 is tilted from the system optical axis M. Is incident on the reflective polarizer 5 at a predetermined angle, and the proportion of this light reflected toward the wide area of the reflective mirror 24 increases. This increases the rate of polarization conversion and can further increase the polarization conversion efficiency.
[0051]
Further, considering the use of a tapered rod lens as in the third embodiment, when the liquid crystal light valve has a shape close to a square (for example, the aspect ratio is 3: 4), the rod lens The exit end face may be adapted to the shape, and only the shape of the entrance end face may be changed to make the entrance end face more horizontally long (for example, the aspect ratio is 9:16). Thereby, even if a liquid crystal light valve is a shape close | similar to a square, the recycling rate of polarized light can be raised and polarization conversion efficiency can be improved. Even in this case, if the center of the light incident area is decentered from the center of the incident end face of the rod lens and the light source optical axis L is tilted from the system optical axis M, the same effect as described above can be obtained.
[0052]
[Fifth Embodiment]
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG.
The basic configuration of the illuminating device of the present embodiment is the same as that of the first to third embodiments, except that the configuration of the reflecting mirror on the rod lens incident side is different from the way of incidence of light from the light source 2 to the rod lens. It is. Therefore, in this embodiment, only the configuration of the rod lens and the reflection mirror will be described with reference to FIG. 8, and description of the other configurations will be omitted.
[0053]
In the present embodiment as well, the center of the light incident area 29a is decentered from the center of the incident end face of the rod lens 28 and is shifted upward in FIG. 8 as in the fourth embodiment. However, in the case of the fourth embodiment, the light source optical axis L of the light beam emitted from the light source 2 is inclined with respect to the system optical axis M, whereas in the case of the present embodiment, the light source light The axis L is shifted in parallel to the system optical axis M. Further, the incident end face of the rod lens 28 is disposed so as to be inclined with respect to the system optical axis M so as to form an angle other than perpendicular.
[0054]
In the case of the present embodiment, the light source optical axis L and the system optical axis M are parallel, but since the incident end face of the rod lens 28 is inclined with respect to the light source optical axis L, the light flux incident on the rod lens 28 is Since the light is refracted at the time of incidence and is incident on the reflective polarizer 5 at a predetermined angle, and this light is reflected toward the wide area of the reflection mirror 29, the fourth embodiment and Similarly, the polarization conversion efficiency can be further increased. Further, since the light source optical axis L and the system optical axis M are parallel, there is an advantage that the optical system can be easily miniaturized.
[0055]
[Sixth Embodiment]
Hereinafter, a sixth embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the illumination device of the present embodiment is the same as that of the first to fifth embodiments, and only the configuration of the rod lens is different. Therefore, in the present embodiment, only the configuration and operation of the rod lens will be described with reference to FIGS. 9 and 10, and the description of the other configurations will be omitted.
[0056]
The rod lens 21 of the third embodiment has a tapered shape that tapers in both the vertical and horizontal directions, whereas the rod lens 27 of the present embodiment has a taper that tapers only in the horizontal direction (X direction). It has a shape and is not thin in the vertical direction (Y direction). In this configuration, as described in the section of the third embodiment, the emission angle θ of the light emitted from the rod lens 27 ₂ Will spread in the horizontal direction but not in the vertical direction. That is, the illumination angle distribution of the light emitted from the rod lens 27 shows a horizontally long (long in the X direction) elliptical shape.
[0057]
Here, paying attention to the viewing angle characteristics of the liquid crystal light valve that is the illuminated area, the viewing angle characteristics of the liquid crystal light valve do not necessarily show symmetry, for example, a TN mode liquid crystal whose clear viewing direction is 6 o'clock or 12 o'clock. In the light valve, as shown in FIG. 10 (b), the isocontrast curve is often narrow in the vertical direction and wide in the horizontal direction. When the liquid crystal light valve has a viewing angle characteristic as shown in FIG. 10B, if an illumination angle distribution of light that illuminates the liquid crystal light valve has a characteristic as shown in FIG. This means that a high-contrast portion is used and high contrast can be obtained.
[0058]
From this point of view, when the illumination device of the present embodiment is applied to a projector, a high contrast is obtained by using the rod lens 27 having a tapered shape that is tapered only in the lateral direction as shown in FIG. Thus, a projector with high display quality can be realized.
[0059]
[projector]
FIG. 11 is a schematic configuration diagram showing an embodiment of a projector provided with the illumination device of the present invention. In the figure, 510 is a light source, 530 is a rod lens, 531 is a reflective mirror, 532 is a reflective polarizer, 513 and 514 are dichroic mirrors (color light separating means), 515, 516 and 517 are reflective mirrors, 522 and 523, respectively. Reference numeral 524 denotes a liquid crystal light valve (light modulation means), 525 denotes a cross dichroic prism (color light combining means), 521 denotes a light guide optical system, and 526 denotes a projection lens (projection means).
[0060]
The illumination device 540 includes a light source 510, a rod lens 530, a reflection mirror 531, and a reflective polarizer 532. The light source 510 includes a lamp 511 such as a metal halide and a reflector 512 that reflects the light of the lamp. In addition, a rod lens 530 is used as a uniform illumination system for making the illuminance distribution of the light source light uniform, a reflective polarizer 532 is provided on the exit end face of the rod lens 530, and a light flux from the light source 510 is provided on the entrance end face. Is provided with a reflection mirror 531 having a circular opening through which light enters. A condensing lens 535 is provided on the exit side of the rod lens 530, relay lenses 536 and 537 are provided on the front and rear sides of the dichroic mirrors 513 and 514, and further on the incident side of the liquid crystal light valve and the incident side of the light guide optical system 521. The collimating lenses 518R and 518G and the condensing lens 518B are respectively arranged, and these lenses have the same function as the relay system 6 described in the first embodiment.
[0061]
The dichroic mirror 513 for reflecting blue light and green light is a red light L of the light flux from the light source 510. _R And transmits blue light L _B And green light L _G And reflect. Transmitted red light L _R Is reflected by the reflection mirror 517 and enters the liquid crystal light valve 522 for red light. On the other hand, among the colored lights reflected by the dichroic mirror 513, the green light L _G Is reflected by the dichroic mirror 514 for reflecting green light and enters the liquid crystal light valve 523 for green light. On the other hand, blue light L _B Also passes through the second dichroic mirror 514, and enters the liquid crystal light valve 524 for blue light through the condenser lens 518B, the two reflecting mirrors 515, 516, the relay lens 519, and the collimating lens 520. The light guide optical system 521 has a function of correcting the optical distance between the condensing lens 518B and the collimating lens 520, and matching the length of the blue light path with that of other color light, thereby reducing the occurrence of illumination unevenness. Yes.
[0062]
The three color lights modulated by the liquid crystal light valves 522, 523, and 524 are incident on the cross dichroic prism 525. In this prism, four right-angle prisms are bonded, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the projection screen 527 by the projection lens 526 which is a projection optical system, and an enlarged image is displayed.
[0063]
Projectors often use high-intensity light sources, and there have been problems in terms of light resistance and heat resistance, but according to this configuration, an illumination device having high polarization conversion efficiency and durability is provided. As a result, a projector with high brightness and high reliability can be realized.
[0064]
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the configuration of the illumination device is illustrated as including the light guide optical system 521. However, the light guide optical system 521 is not an essential component as the illumination device, and may be omitted. In addition, specific descriptions regarding the shapes of the incident end surface and the exit end surface of the rod lens, the configuration of the reflective polarizer and the reflective mirror, and the like can be changed as appropriate without being limited to the above embodiment.
[0065]
【The invention's effect】
As described above in detail, according to the present invention, polarized light that cannot be transmitted through a reflective polarizer can be recycled and contribute to illumination. Therefore, the use efficiency of polarized light is higher than that of a conventional illumination device. And a bright lighting device can be realized. In addition, it is only necessary to place a reflective polarizer on the exit side and a reflection mirror on the entrance side of the beam splitting means used in the past as a uniform illumination system, so an illumination device with high polarization conversion efficiency can be realized with a simple configuration. can do. In particular, the structural birefringence type reflective polarizer can be formed using an inorganic material, so that it has much higher light resistance and heat resistance than a conventional polarization conversion system using a retardation film made of an organic film. And a stable polarization conversion action can be realized. By providing such an illuminating device, a projector with high brightness and high reliability can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an illumination device according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining the polarization conversion action in the rod lens of the illumination device.
FIG. 3 is a perspective view showing a configuration of a structural birefringence reflective polarizer used in the illumination device.
FIG. 4 is a schematic configuration diagram illustrating a configuration on a rod lens exit side of a lighting apparatus according to a second embodiment of the present invention.
FIGS. 5A and 5B are perspective views illustrating a configuration of a rod lens of an illumination apparatus according to a third embodiment of the present invention.
6 is a diagram for explaining the action of the rod lens of FIGS. 5 (a) and 5 (b). FIG.
FIG. 7 is a perspective view showing a configuration of a rod lens of an illumination device according to a fourth embodiment of the present invention.
FIG. 8 is a perspective view showing a configuration of a rod lens of an illumination apparatus according to a fifth embodiment of the present invention.
FIG. 9 is a perspective view showing a configuration of a rod lens of an illumination apparatus according to a sixth embodiment of the present invention.
10A is a view showing an illumination angle distribution of light emitted from a rod lens, and FIG. 10B is a view showing a viewing angle characteristic of a liquid crystal light valve. FIG.
FIG. 11 is a schematic configuration diagram showing an example of a projector according to the present invention.
FIG. 12 is a diagram for explaining the principle of a structural birefringent polarizer.
[Explanation of symbols]
1,540 lighting device
2,510 light source
3, 24, 29, 531 Reflective mirror
3a, 24a Opening (light incident area)
4, 21, 22, 25, 27, 28, 530 Rod lens (light beam splitting means)
5,17,532 Reflective polarizer
7,522,523,524 Liquid crystal light valve (illuminated area, light modulation means)
18 First quarter wave plate
19 Second quarter wave plate

Claims (13)

An illumination device comprising a light source and a light beam splitting unit that splits and emits a light beam from the light source using a reflection.
A reflective polarizer that transmits a part of the polarized light beam incident on the light beam splitting unit from the light source and reflects a part of the polarized light beam is provided on the exit side of the light beam splitting unit. On the incident side of the means, a reflection mirror that reflects the polarized light reflected by the reflective polarizer is provided corresponding to an area other than the incident area of the light beam from the light source on the incident end face of the light beam dividing means,
The center of the incident area is decentered with respect to the center of the incident end face of the light beam splitting means, and the optical axis of the light flux incident on the light flux splitting means and the incident end face of the reflective polarizer form an angle other than perpendicular. A lighting device characterized by that. An illumination device comprising a light source and a light beam splitting unit that splits and emits a light beam from the light source using a reflection.
A reflective polarizer that transmits a part of the polarized light beam incident on the light beam splitting unit from the light source and reflects a part of the polarized light beam is provided on the exit side of the light beam splitting unit. On the incident side of the means, a reflection mirror that reflects the polarized light reflected by the reflective polarizer is provided corresponding to an area other than the incident area of the light beam from the light source on the incident end face of the light beam dividing means,
The center of the incident region is decentered with respect to the center of the incident end face of the light beam splitting means, and passes through the light source optical axis of the light flux from the light source and substantially the center of the light beam splitting means in the longitudinal direction of the light beam splitting means. An illuminating apparatus characterized in that an extending system optical axis is arranged in parallel, and an incident end face of the light beam splitting means forms an angle other than perpendicular to the system optical axis.   The lighting device according to claim 1, wherein the reflective polarizer has a function of transmitting one of linearly polarized light orthogonal to each other and reflecting the other.   The lighting device according to claim 3, wherein the reflective polarizer is a structural birefringent polarizer.   The reflective polarizer has a function of transmitting one of circularly polarized light in the opposite directions and reflecting the other, and a quarter-wave plate is provided between the light beam splitting means and the reflective polarizer. The illumination device according to claim 1, wherein the illumination device is provided.   The illumination device according to claim 5, further comprising a quarter-wave plate provided on an exit side of the reflective polarizer.   The illumination device according to any one of claims 1 to 6, wherein the light beam splitting unit includes a rod-shaped light guide or a tubular light guide having an inner surface as a reflection surface.   The lighting device according to claim 7, wherein the light guide has a tapered shape from the incident side toward the emission side.   The lighting device according to claim 7, wherein the light guide body has a shape that widens from the incident side toward the emission side.   The shape of the said incident area | region in the incident end surface of the said light beam splitting means is circular, The said reflective mirror is provided in the area | region outside this circular incident area | region. The lighting device described in 1.   11. The incident end face and the exit end face of the light beam splitting means are both rectangular, and the entrance end face is a narrower rectangular shape than the exit end face. The lighting device according to one item.   An illumination device according to any one of claims 1 to 11, a light modulation unit that modulates light emitted from the illumination device, and a projection unit that projects light modulated by the light modulation unit. A projector characterized by that. The light beam splitting means is composed of a rod-shaped light guide or a tubular light guide whose inner surface is a reflection surface, and the light guide is incident only in one direction in a plane perpendicular to the optical axis of the light beam. The taper shape is tapered from the side toward the injection side.
The light modulator comprises a liquid crystal light valve, and the isocontrast curve indicating the viewing angle characteristic of the liquid crystal light valve is narrow in one direction and spread in the other direction, and is emitted from the light beam splitting means of the illumination device. that the illumination angle distribution of the illumination light beam is long elliptical shape in the one direction, characterized in that said equal-contrast curve of the the longitudinal direction of the elliptical shape of the illumination angle distribution liquid crystal light valve were to coincide with the direction of spread The projector according to claim 12.

Images