JP2004286767A - Projection display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection display device which can display an image of high contrast in spite of easy manufacturing. <P>SOLUTION: The projection display device is constituted so as to separate the light from a light source 1 by a color separation prism 20 to three primary color lights, to illuminate three reflection spatial optical modulation elements 24, 25 and 26 respectively through polarization beam splitters 16, 17 and 18 by the three primary color lights and to put together and project the reflected lights from the three elements 24, 25 and 26 by a color combination prism 20. The so-called "Phillips prism" is used as the prism 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００８７】
そこで、例えば、各フィールドレンズ２２と各偏向プリズム１３，１４，１５との間に位相差板（１／２波長板）２１を挿入することによって、偏光方向を９０°回転させれば、色分解プリズム１０のダイクロイック膜１１，１２へ入射するＳ偏光（信号光）は、色合成プリズム２０のダイクロイック膜２７，２８に対してもＳ偏光となる（〔表１〕の「偏光ビームスプリッタ（ＰＢＳ）と色分解プリズムの間に１／２波長板がある場合」の欄）。
【００８８】
すなわち、位相差板（１／２波長板）２１を上述の位置に挿入することにより、色分解プリズム１０及び色合成プリズム２０において、同一の偏光方向（Ｓ偏光）を基準としたダイクロイック膜の設計ができる。そして、これら全てのダイクロイック膜１１，１２、２７，２８を同時に成膜することとすれば、波長特性（分光特性）などの特性が一致したダイクロイック膜が得られ、色分解及び色合成におけるスペクトル損失を最小限に抑えることができる。
【００８９】
同様に、各偏光ビームスプリッタ１５，１６，１７と色合成プリズム２０との間に、位相差板（１／２波長板）を挿入し、色分解プリズム１０と色合成プリズム２０とで、ともにＰ偏光を基準として設計されたダイクロイック膜を用いることもできる（〔表１〕の「偏光ビームスプリッタ（ＰＢＳ）と色合成プリズムの間に１／２波長板がある場合」の欄）。
【００９０】
この場合においても、全てのダイクロイック膜１１，１２、２７，２８を同時に成膜して特性が一致したダイクロイック膜を得ることができ、色分解及び色合成におけるスペクトル損失を最小限に抑えることができる。
【００９１】
図６は、各偏光ビームスプリッタ１６，１７，１８に入射する光を偏光ビームスプリッタ内の入射面に対するＰ偏光とし、この反射面（ＰＢＳ面）を透過した光を受光する位置に各反射型空間光変調素子２４，２５，２６を配置した構成（「Ｐ配置」という。）を示す斜視図である。
【００９２】
この場合においては、各偏光ビームスプリッタ１６，１７，１８への入射光の偏光方向は、上述した「Ｓ配置」と異なり、偏光ビームスプリッタ１６，１７，１８の反射面に対するＰ偏光である。そして、色分解プリズム１０のダイクロイック膜１１，１２における入射面と偏光ビームスプリッタ１６，１７，１８の入射面とが互いに直交していることから、偏光ビームスプリッタ１６，１７，１８に対するＰ偏光は、色分解プリズム１０のダイクロイック膜１１，１２に対しては、Ｓ偏光となる。また、各偏光ビームスプリッタ１５，１６，１７から出射されるＳ偏光に対応する偏光は、色合成プリズム２０のダイクロイック膜２７，２８に対してはＰ偏光となるようになっている。
【００９３】
したがって、色分解プリズム１０においては各ダイクロイック膜１１，１２をＳ偏光用に設計し、色合成プリズム２０においては各ダイクロイック膜２７，２８をＰ偏光用に設計する必要がある。
【００９４】
この場合の色分解プリズム１０及び色合成プリズム２０のダイクロイック膜に対する偏光状態をまとめると、以下の〔表２〕のようになる（「１／２波長板無し」の欄）。
【００９５】
【表２】

【００９６】
そこで、例えば、各フィールドレンズ２２と各偏向プリズム１３，１４，１５との間に位相差板（１／２波長板）を挿入することによって、偏光方向を９０°回転させれば、色分解プリズム１０のダイクロイック膜１１，１２に対するＰ偏光に対応する光は、色合成プリズム２０のダイクロイック膜２７，２８に対してもＰ偏光となる（〔表２〕の「偏光ビームスプリッタ（ＰＢＳ）と色分解プリズムの間に１／２波長板がある場合」の欄）。
【００９７】
すなわち、位相差板（１／２波長板）２１を上述の位置に挿入することにより、色分解プリズム１０及び色合成プリズム２０において、同一の偏光方向（Ｐ偏光）を基準としたダイクロイック膜の設計ができる。そして、これら全てのダイクロイック膜１１，１２、２７，２８を同時に成膜することとすれば、波長特性（分光特性）などの特性が一致したダイクロイック膜が得られ、色分解及び色合成におけるスペクトル損失を最小限に抑えることができる。
【００９８】
同様に、各偏光ビームスプリッタ１５，１６，１７と色合成プリズム２０との間に、位相差板（１／２波長板）を挿入し、色分解プリズム１０と色合成プリズム２０とで、ともにＳ偏光を基準として設計されたダイクロイック膜を用いることもできる（〔表２〕の「偏光ビームスプリッタ（ＰＢＳ）と色合成プリズムの間に１／２波長板がある場合」の欄）。
【００９９】
この場合においても、全てのダイクロイック膜１１，１２、２７，２８を同時に成膜して特性が一致したダイクロイック膜を得ることができ、色分解及び色合成におけるスペクトル損失を最小限に抑えることができる。
【０１００】
次に、この投射型表示装置においては、各偏向プリズム１３，１４，１５を、各偏光ビームスプリッタ１５，１６，１７に接離する方向に移動調整することにより、各反射型光変調素子２４，２５，２６上における照明領域の位置を微調整することができる。
【０１０１】
一方、図７は、偏向プリズム１３，１４，１５に代えて、平面鏡、または、曲面鏡３０を用いた構成を示す斜視図である。
【０１０２】
この投射型表示装置においては、偏向プリズム１３，１４，１５に代えて、平面鏡、または、曲面鏡３０を用いることができ、この場合には、この平面鏡、または、曲面鏡３０を、図７中の矢印で示すように、各偏光ビームスプリッタ１５，１６，１７に接離する方向、あるいは、平面鏡、または、曲面鏡３０の反射面に沿う２方向に移動させることにより、各反射型光変調素子２４，２５，２６上における照明領域の位置を微調整することができる。
【０１０３】
図８は、フィールドレンズ２２を光軸に対して直交する２方向に移動調整するための構成を示す斜視図である。
【０１０４】
この投射型表示装置においては、フィールドレンズ２２を光軸に対して直交する２方向に移動調整することにより、各反射型光変調素子２４，２５，２６上における照明領域の位置を微調整することができる。この場合には、フィールドレンズ２２を支持する支持枠３１を固定枠３２に対して移動可能に取り付けておき、この固定枠３２に対して、２方向の押しネジ３３，３４により、支持枠３１を移動させることにより、フィールドレンズ２２の光軸に対する直交２方向についての移動調整を行うことができる。
【０１０５】
なお、押しネジ３３，３４に代えて、圧電素子を使用することとしてもよい。
【０１０６】
上述のような投射型表示装置において、色分解プリズム１０及び色合成プリズム２０をなす材質（硝材）としては、いわゆる「ＢＫ−７」が一般的に使用されるが、これに限られるものではない。また、上述した、色分解プリズム１０及び色合成プリズム２０の形状、例えば、頂角α１，α２の角度等は、特に限定されるものではない。
【０１０７】
さらに、上述の実施の形態においては、ロッドインテグレータ３を照明系に使用しているが、これには限られず、例えば、フライアイインテグレータを照明系に用いても良い。
【０１０８】
上述のように、本実施の形態の投射型表示装置においては、クロスダイクロイックプリズムを用いた場合のように投射画像中にダイクロイック膜の交差部の影や不要な輝線などの発生がなく、いわゆる「レジずれ」もない。また、他の色用の反射型光変調素子ヘの漏れ光が少なく、ゴーストの発生が防止された良好なコントラストの画像を表示することができる。
【０１０９】
さらに、ダイクロイック膜に対する光の入射角度が小さく、色合成時の光利用効率を高くすることができる。また、各色毎に最適な特性の偏光ビームスプリッタを使用でき、各色ごとに最適な狭帯域カラーフィルタを使用することができるため、高いコントラストの画像表示を容易に実現できる。
【０１１０】
また、この投射型表示装置においては、３つの反射型光変調素子が表示する像が互いに反転したり鏡像関係になることがないので、反射型光変調素子に起因する面内むら（反射率むら等）がある場合であっても、３色を合成したときに色むら等の発生がない。すなわち、この投射型表示装置の色分解プリズムにおいては、緑色光は反射されずに透過し、赤色光及び青色光はそれぞれ２回反射されるため、照明光像が反転しない正立像となる。そのため、各反射型光変調素子の物理方向に対して緑色光、赤色光及び青色光の全てが同じ照明光となり、照明ムラが色むらの原因となることがない。
【０１１１】
そして、この投射型表示装置においては、色分解プリズム及び色合成プリズムの設計、製造が容易である。
【０１１２】
図９は、第２の実施の形態の投射型表示装置の構成を示す斜視図である。
【０１１３】
第２の実施の形態の投射型表示装置は、第１の実施の形態における偏光ビームスプリッタ１６，１７，１８の代わりに、金属偏光板（Ｗｉｒｅ Ｇｒｉｄ Ｐｏｌａｒｉｚｅｒ）を使用するものである。
【０１１４】
図９においては、第１の実施の形態の図６における、フィールドレンズ２２以降のＰＢＳ部、合成プリズム２０における偏光ビームスプリッタ（ＰＢＳ）１６，１７，１８を金属偏光板に置き換えた実施の形態を示している。光源１からフィールドレンズ２２（必要に応じて１／２波長板２１）に至る光源系・色分解系の光学系は共通であるため、図上では省略している。
【０１１５】
金属偏光板は金属グリッド偏光板あるいはグリッド偏光子とも称され、特開昭４９−９０１４９号公報、米国特許第４２８９３８１号、米国特許第４５１４４７９号、特開昭５８−４２００３号公報に見られる様に、１９７０年代から開発されてきたものである。
【０１１６】
具体的に説明すると、分解されて３原色となった光がそれぞれＰＢＳ用金属偏光板４３，４４，４５を透過して、反射型光変調素子２４，２５，２６に照射する。反射型光変調素子２４，２５，２６に印加された画像情報に応じて変調された反射光はＰＢＳ用金属偏光板４３，４４，４５にて反射し、「フィリップスプリズム」と称される色合成プリズム２０に入射されて３色合成される。
【０１１７】
従来のガラス製ＰＢＳ１６，１７，１８は、光学的にはガラスの直方体であるので、上述のＳ配置・Ｐ配置のいずれの配置を取っても、光学的な収差は基本的に同等である。一方、ＰＢＳ用金属偏光板４３，４４，４５は、ガラス板上に金属製の格子を設けた構造で、平行平面板であるから、ガラス製ＰＢＳ１６，１７，１８の代わりに用いる場合、反射型光変調素子２４，２５，２６の出射光の光路にガラスが透過で入ると非点収差等の原因となり、画面の解像度が極端に劣化する。そのため、図６と同様にＰ配置としている。
【０１１８】
また、ＰＢＳ用金属偏光板４３，４４，４５の格子面と逆側ガラス面で反射があると、その面でも反射をしてしまい、その結果として、画面が２重像となるという不具合が発生する。よって、本実施の形態においては、ＰＢＳ用金属偏光板４３，４４，４５の金属偏光板の格子面と逆側のガラス面には反射防止（ＡＲ）コートを設けることが必要である。ＡＲコートの反射率は、そのチャンネルの色の帯域を含む帯域において、約１％以下であることが望ましい。帯域は、例えば、青チャンネルに於いては、４２０〜５００ｎｍ、緑チャンネルに於いては、５００〜５８０ｎｍ、赤チャンネルに於いては、５８０ｎｍ〜６８０ｎｍである。更に、上記帯域において、０．５％以下であれば更に良い。
【０１１９】
金属偏光板によるプリポラライザー４０，４１，４２はＰＢＳ用金属偏光板４３，４４，４５に前置されて透過光の偏光度を向上させるものである。なお、便宜上、図中にはプリポラライザー４２のみが示されている。
【０１２０】
ポストポラライザー４６，４７，４８はＰＢＳ用金属偏光板４３，４４，４５に後置され、反射型光変調素子２４，２５，２６で変調されない反射光のうちＰＢＳ用金属偏光板４３，４４，４５で透過されずに反射してしまった光（ＰＢＳ用金属偏光板４３，４４，４５に対してＰ偏光）を阻止してコントラストをより向上させるために用いられる。
【０１２１】
図１０は、本発明に係る第３の実施の形態の投射型表示装置の構成を示す斜視図である。
【０１２２】
図１０（ａ）は第３の実施の形態の投射型表示装置の全体の構成を示す図であり、図１０（ｂ）は第３の実施の形態の投射型表示装置におけるポストポラライザー４６，４７，４８の光軸に対する位置関係を説明するための斜視図である。
【０１２３】
第３の実施の形態における第２の実施の形態との相違点は、光軸に対してポストポラライザー４６，４７，４８が所定角度傾斜していることである。すなわち、光軸とポストポラライザー４６，４７，４８の主面の法線が所定角度を有している。
【０１２４】
これは、ポストポラライザー４６，４７，４８で反射した反射型光変調素子２４，２５，２６で再度反射し、さらにＰＢＳ用金属偏光板４３，４４，４５で反射して投射レンズの入射瞳に入射することによって、ゴーストが発生することを防止するものである。
【０１２５】
図１０（ｂ）は、収差補正のための４枚一組のプレートを示す図である。
【０１２６】
これらのプレートは、金属偏光板又は単なる透明なガラス板等からなり、光軸に対して所定角度αを有するプレート７１、プレート７１を光軸に垂直な面について鏡映対称に配置したプレート７２、プレート７１，７２を光軸について９０°回転したプレート７３，７４から構成される。
【０１２７】
第３の実施の形態のポストポラライザー４６，４７，４８は、光軸に対して例えばプレート７１に相当する位置に配置したものである。
【０１２８】
ポストポラライザー４６，４７，４８の光軸に対する傾斜角度は、上記趣旨により簡単に作図から求めることができる。具体的には、反射型光変調素子２４，２５，２６から反射する光のコーンアングル（円錐角）（すなわち、結像に寄与する光の最大広がり角度と光軸とのなす角である）をα度とした場合に、ポストポラライザー４６，４７，４８の傾斜角度をα度とすると、任意の角度で反射型光変調素子２４，２５，２６から反射した光がポストポラライザー４６，４７，４８及びＰＢＳ用金属偏光板４３，４４，４５で反射して反射型光変調素子２４，２５，２６に戻る角度がα度となる。言い換えると、ポストポラライザー４６，４７，４８の傾斜角度をα度以上に設定すれば反射型光変調素子２４，２５，２６での再反射光はコーンアングル以上の角度の付いた光線となり、投射レンズの入射瞳に入射しなくなるため、スクリーンに到達せず、よってゴーストを確実に防止することができる。
【０１２９】
前記コーンアングルは、投射レンズのＦナンバーと対応する。具体的設計に応じて、Ｆナンバー（すなわち、コーンアングル）は変わるが、一般的にはＦナンバーは２．８〜４．０である。
【０１３０】
ここで、Ｆナンバー４にて約７．２度、Ｆナンバー２．８にて約１０．３度、Ｆナンバー２にて約１４．５度であるため、望ましい傾斜角度としては、５〜１５度である。
【０１３１】
図１１は、本発明に係る第４の実施の形態の投射型表示装置の構成を示す斜視図である。
【０１３２】
本実施の形態は、第３の実施の形態の投射型装置において、ポストポラライザー４６，４７，４８とフィリップスプリズム２０の間にシリンドリカルレンズ４９，５０，５１が設置されていることが特徴である。これは、ポストポラライザー４６，４７，４８が傾斜していることによる収差を補正するものである。
【０１３３】
なお、シリンドリカルレンズ４９，５０，５１の代替として、前記図１０（ｂ）に示した４枚一組の収差補正機能付きのプレートセット７１，７２，７３，７４で置き換えることもできる。この４枚のプレート７１，７２，７３，７４の内の１枚をポストポラライザー４６，４７，４８とすることにより、ポストポラライザー４６，４７，４８とシリンドリカルレンズ４９，５０，５１の機能の代替とすることができる。
【０１３４】
図１２は、第２乃至第４の実施の投射型表示装置におけるＰＢＳ用金属偏光板４３，４４，４５とポストポラライザー４６，４７，４８の実装方法を示す斜視図である。
【０１３５】
これらの実施の形態においては、色合成プリズム２０の上面にアルミナ系セラミック５２による共通のベース５２を設けている。
【０１３６】
ホルダー５３Ａ、５３Ｂ、５３Ｃは、ＰＢＳ用金属偏光板４３，４４，４５とポストポラライザー４６，４７，４８を固定するとともに、ＰＢＳ用金属偏光板４３，４４，４５とポストポラライザー４６，４７，４８と反射型光変調素子２４，２５，２６によってそれらの内側の空間を密閉構造とするためのものである。ＰＢＳ用金属偏光板４３，４４，４５及びポストポラライザー４６，４７，４８の金属格子（グリッド）側は密閉空間側になるように設置する。このようにしたことによって、金属格子面が密閉に保持され、金属格子が他者と接触することによるダメージ、各種原因によるコンタミネーション等の不具合を効果的に防止することができる。
【０１３７】
ホルダー５３Ａ、５３Ｂ、５３Ｃは、ベース５２に固定されている状態とし、そのホルダー５３Ａ、５３Ｂ、５３Ｃに反射型光変調素子２４，２５，２６をレジストレーション調整されても良いし、反射型光変調素子２４，２５，２６とともに固定されたユニット状態でレジストレーション調整されても良い。
【０１３８】
金属偏光板は金属格子の作用により、偏光作用を発揮するのであるが、金属偏光板に入射する光の幾分かは金属格子により吸収されるため、金属偏光板は温度上昇する。よって、金属偏光板は、その信頼性確保の観点及び、温度変化により金属偏光板の平面度が劣化すると、結像性能が劣化するという問題点除去の観点から、適切に冷却される必要がある。しかしながら、金属偏光板の金属格子側は結像光学系を構成しているため、直接冷却すると上記弊害があるため、密閉された金属偏光板をその基板側から空冷することが必要となる。
【０１３９】
前記図１２は、ＰＢＳ用金属偏光板４３，４４，４５のシロッコファン５４Ａ、５４Ｂ、５４Ｃも示している。これらのシロッコファン５４Ａ、５４Ｂ、５４Ｃは、ＰＢＳ用金属偏光板４３，４４，４５の非金属格子面を冷却する。
【０１４０】
当、シロッコファン５４Ａ、５４Ｂ、５４Ｃでなく軸流ファンであっても良く、シロッコファン５４Ａ、５４Ｂ、５４Ｃからの風を適切な導風路を経て冷却されても良い。またプリポラライザー４０，４１，４２や、ポストポラライザー４６，４７，４８も適切に冷却することが望ましい。直接図示していないが、ポストポラライザー４６，４７，４８は、ホルダー５３Ａ、５３Ｂ、５３Ｃと色合成プリズム２０の隙間への送風により、プリポラライザー４０，４１，４２はそれらの周りの空間への送風により冷却が達成されている。
【０１４１】
以上の構成により、ガラス製ＰＢＳ１６，１７，１８の代わりに、金属偏光板（Ｗｉｒｅ Ｇｒｉｄ Ｐｏｌａｒｉｚｅｒ）を使用した投射型表示装置を実現することができ、光学系の軽量化、ガラスの複屈折による影響を除去することによるコントラスト向上に資することができる。
【０１４２】
以上の金属偏光板を使用したプリポラライザー−ＰＢＳ−ポストポラライザーの構成は、従来のクロスダイクロイックプリズムを使用したシステムにおいても当然に適用することが可能である。
【０１４３】
以下では、金属偏光板をクロスダイクロイックプリズムを備える投射型表示装置に適用した実施の形態を示す。
【０１４４】
なお、クロスダイクロイックプリズムの従来例としては、特開２００１−３９８１９８号公報が挙げられる。この従来例は、従来のクロスダイクロイックプリズムを使用したシステムであり、ガラス製ＰＢＳをプリポラライザー、及びＰＢＳとして使用し、補助的に金属偏光板のプリポラライザーを追加挿入したものである。
【０１４５】
前記従来例においてもプリＰＢＳガラスの複屈折による影響を除去することによるコントラスト向上に資することができた。しかしながら、コントラルト向上等の画質要求は強く、更なる改善が望まれていた。
【０１４６】
図１３〜図１５はクロスダイクロイックプリズムを使用した合成ブロックを有する、第５乃至第７の実施の形態の投射型表示装置の構成を示す図である。なお、図中のようにＸ、Ｙ、Ｚ軸を定義する。
【０１４７】
図１３は、本発明に係る第５の実施の形態の投射型表示装置の構成を示す図である。第５の実施の形態の投射型表示装置は、図９に示した第２の実施の形態の投射型表示装置に対応している。
【０１４８】
ランプならびに放物面鏡等の凹面鏡から構成される光源１から射出された略平行光束の光源光（白色光）１ａは折り曲げミラー（コールドミラー）６５を経て水平方向に所定の角度例えば略９０°に折り曲げられて偏光変換装置６０に入射して偏光変換を受ける。
【０１４９】
ここで、偏光変換装置６０は複数のフライアイレンズ６１ａを有する第１のレンズ板６１と複数のフライアイレンズ６２ａを有する第２のレンズ板６２とからなるフライアイインテグレータと、偏光ビームスプリッタをアレイ状に形成した偏光ビームスプリッタアレイ６３と、所定位置に形成した１／２波長位相板６４とから構成される。
【０１５０】
上記の偏光変換装置６０から射出された光は大部分がＳ偏光であるが、一部Ｐ偏光が混じっている。偏光変換装置６０を射出した光はコンデンサーレンズ５９を経てＢ（青）光反射ダイクロイックミラー５７と、Ｒ（赤）光とＧ（緑）光を反射するダイクロイックミラー５８とを互いに直交するようにＸ型に配置したクロスダイクロイックミラー５６に入射され、入射光軸に直交し互いに反対方向に進行するＢ光（図中右方へ進行）と、Ｒ光、Ｇ光（図中左方へ進行）とに色分解する。
【０１５１】
前記色分解されたＢ光はミラー５５にて反射され、フィールドレンズ５３Ｂを経てプリポララリザー４１を透過してＰＢＳ用金属偏光板４５に入射される。ミラー５５は、コールドミラーでも良く、金属偏光板であっても良い。
【０１５２】
一方、前記色分解されたＧ光、Ｒ光はミラー５６にて反射されてＧ光反射ダイクロイックミラー５４に入射される。ここで、反射するＧ光（図中右方へ進行）と、透過するＲ光（図中上方へ進行）とに色分解され、それぞれフィールドレンズ５３Ｇ，５３Ｒを経て、プリポラライザー４２，４０を経て、それぞれのＰＢＳ用金属偏光板４３，４４に入射される。
【０１５３】
本実施の形態においても、ＰＢＳ用金属偏光板４３，４４，４５は図６と同様にＰ配置としている。
【０１５４】
金属偏光板によるプリポラライザー４０，４１，４２はＰＢＳ用金属偏光板４３，４４，４５に前置されて透過光の偏光度を向上させるものである。金属偏光板によるポストポラライザー４６，４７、４８は、ＰＢＳ用金属偏光板４３，４４，４５に後置され、反射型光変調素子８３，８４，８５で変調されない反射光がＰＢＳ用金属偏光板４３，４４，４５で透過されずに反射してしまった光（金属偏光板に対してＰ偏光）を阻止してコントラストをより向上させるために用いられる。
【０１５５】
反射型光変調素子８３，８４，８５でそれぞれ変調されたＲ光、Ｇ光、Ｂ光は、それぞれポストポラライザー４７，４６，４５を介してクロスダイクロイックプリズム８１で合成され、投射レンズ８２方向に射出される。
【０１５６】
図１４は、本発明に係る第６の実施の形態の投射型表示装置の構成を示す図である。図１４（ａ）は第６の実施の形態の投射型表示装置の全体の構成を示す図であり、図１４（ｂ）は第６の実施の形態の金属偏光板によるポストポラライザー４４，４５，４６の光軸に対する位置関係を説明するための図である。
【０１５７】
第６の実施の形態の投射型表示装置は、図１０に示した第２の実施の形態の投射型表示装置に対応している。
【０１５８】
第１３に示した第５の実施の形態との相違点は、ポストポラライザー４６，４７，４８が光軸に対して所定角度傾斜していることである。これは、ポストポラライザーで反射した光が反射型光変調素子８３，８４，８５で再度反射し、さらに金属偏光板４３，４４，４５で反射して投射レンズ８２の入射瞳に入射することによって、ゴーストが発生することを防止するものである。
【０１５９】
図１４（ｂ）は、収差補正のための４枚１組のプレートを示す図である。
【０１６０】
これらのプレートは、光軸に対して所定角度αを有するプレート７１、プレート７１を光軸に垂直な面について鏡映対称に配置したプレート７２、プレート７１，７２を光軸について９０°回転したプレート７３，７４から構成される。
【０１６１】
本実施の形態のポストポラライザー４６，４７，４８は、光軸に対して例えばプレート７１に相当する位置に配置したものである。
【０１６２】
ポストポラライザー４３，４４，４５の傾斜角度は、上記趣旨により簡単に作図から求めることができる。具体的には、反射型光変調素子８３，８４，８５から反射する光のコーンアングル（円錐角）（すなわち、結像に寄与する光の最大広がり角度と光軸とのなす角である）をα度とした場合に、ポストポラライザー４３，４４，４５の傾斜角度をα度とすると、任意の角度で反射型光変調素子８３，８４，８５から反射した光がポストポラライザー４３，４４，４５及びＰＢＳ用金属偏光板４３，４４，４５で反射して反射型光変調素子８３，８４，８５に戻る角度がα度となる。言い換えると、ポストポラライザー４３，４４，４５の傾斜角度をα度以上に設定すれば反射型光変調素子８３，８４，８５での再反射光はコーンアングル以上の角度の付いた光線となり、投射レンズの入射瞳に入射しなくなるため、スクリーンに到達せず、よってゴーストを確実に防止することができる。
【０１６３】
前記コーンアングルは、投射レンズのＦナンバーと対応する。具体的設計に応じて、Ｆナンバー（すなわち、コーンアングル）は変わるが、一般的にはＦナンバーは２．８〜４．０である。
【０１６４】
ここで、Ｆナンバー４にて約７．２度、Ｆナンバー２．８にて約１０．３度、Ｆナンバー２にて約４．５度であるため、望ましい傾斜角度としては、５〜１５度である。
【０１６５】
図１５は、本発明に係る第７の実施の形態の投射型表示装置の構成を示す図である。第７の実施の形態の投射型表示装置は、図１１に示した第４の実施の形態の投射型表示装置に対応している。
【０１６６】
第７の実施の形態においては、ポストポラライザー４６，４７，４８とクロスダイクロイックプリズム８１の間にシリンドリカルレンズ４９，５０，５１が設置されていることが特徴である。これは、ポストポラライザー４６，４７，４８が傾斜していることによる収差を補正するものである。
【０１６７】
前記図１４（ｂ）は、シリンドリカルレンズ４９，５０，５１の代替としての機能を有する収差補正のための４枚１組のプレートを示す図である。
【０１６８】
これらのプレートは、光軸に対して所定角度αを有するプレート７１、プレート７１を光軸に垂直な面について鏡映対称に配置したプレート７２、プレート７１，７２を光軸について９０°回転したプレート７３，７４から構成される。
【０１６９】
本実施の形態のポストポラライザー４６，４７，４８は、光軸に対して例えばプレート７１に相当する位置に配置したものである。
【０１７０】
この４枚のプレート７１，７２，７３，７４の内の１枚をポストポラライザーと兼用することにより、ポストポラライザー４６，４７，４８とシリンドリカルレンズ４９，５０，５１の機能の代替とすることができる。
【０１７１】
図１３〜図１５において、ＰＢＳ用金属偏光板４３，４４，４５とポストポラライザー４６，４７，４８の実装方法を以下で説明する。クロスダイクロイックプリズム８１と３色用のＰＢＳ用金属偏光板４３，４４，４５等を含む部分の上下面にアルミナ系セラミックによる共通のベース５２を設ける。
【０１７２】
ＰＢＳ用金属偏光板４３，４４，４５とポストポラライザー４６，４７，４８と反射型光変調素子８３，８４，８５により囲まれる空間は密閉構造とする密閉構造にする方法としては、これら３種類の部材の間をゴム等の可撓性部材で密閉する方法がある。このようにしたことによって、金属格子面が密閉に保持され、金属格子が他者と接触することによるダメージ、各種原因によるコンタミネーション等の不具合を効果的に防止することができる。
【０１７３】
金属偏光板は金属格子の作用により、偏光作用を発揮するのであるが、金属偏光板に入射する光の幾分かは金属格子により吸収されるため、金属偏光板は温度上昇する。よって、金属偏光板は、その信頼性確保の観点及び、温度変化により金属偏光板の平面度が劣化すると、結像性能が劣化するという問題点除去の観点から、適切に冷却される必要がある。しかしながら、金属偏光板の金属格子側は結像光学系を構成しているため、直接冷却すると上記弊害があるため、密閉された金属偏光板をその基板側から空冷することが必要となる。図１２〜図１５では、図中の空気流８７に示すように図示しない冷却手段によってＰＢＳ用金属偏光板４３，４４，４５の非金属格子面は冷却されている。前記冷却手段としては、シロッコファン、軸流ファンが選択できる。またプリポラライザー４０，４１，４２や、ポストポラライザー４６，４７，４８も適切に冷却することが望ましい。
【０１７４】
以上の第５乃至第７の実施の形態で示したように、クロスダイクロイックプリズム８１を使用した投射型表示装置においても、ガラス製偏光ビームスプリッタの代わりに、金属偏光板（Ｗｉｒｅ Ｇｒｉｄ Ｐｏｌａｒｉｚｅｒ）を使用することができ、光学系の軽量化、ガラスの複屈折による影響を除去することによるコントラスト向上に資することができる。
【０１７５】
【発明の効果】
本発明は、製造が容易であり、画像のぼけやゴーストがなく、高いコントラストの画像を表示できるようになされた投射型表示装置を提供することができるものである。
【図面の簡単な説明】
【図１】第１の実施の形態の投射型表示装置の構成を示す斜視図である。
【図２】前記投射型表示装置における色分解プリズムの形状を示す側面図である。
【図３】前記投射型表示装置における色合成プリズムの周辺の構成を示す側面図である。
【図４】前記投射型表示装置における色分解プリズム及び色合成プリズムの周辺の構成を示す斜視図である。
【図５】前記投射型表示装置における色分解プリズム、色合成プリズム及び反射型光変調素子の構成を示す斜視図である。
【図６】前記投射型表示装置において各偏光ビームスプリッタに入射する光を偏光ビームスプリッタ内の反射面に対するＰ偏光としこの反射面を透過した光を受光する位置に各反射型空間光変調素子を配置した構成を示す斜視図である。
【図７】前記投射型表示装置において偏向プリズムに代えて、平面鏡、または、曲面鏡を用いた構成を示す斜視図である。
【図８】前記投射型表示装置においてフィールドレンズを光軸に対して直交する２方向に移動調整するための構成を示す斜視図である。
【図９】第２の実施の形態の投射型表示装置の構成を示す斜視図である。
【図１０】第３の実施の形態の投射型表示装置の構成を示す斜視図である。
【図１１】第４の実施の形態の投射型表示装置の構成を示す斜視図である。
【図１２】第２乃至第４の実施の形態の実装方法を示す斜視図である。
【図１３】第５の実施の形態の投射型表示装置の構成を示す斜視図である。
【図１４】第６の実施の形態の投射型表示装置の構成を示す図である。
【図１５】第７の実施の形態の投射型表示装置の構成を示す図である。
【図１６】いわゆる「クロスダイクロイックプリズム」を用いた光学系を備えた従来の投射型表示装置の構成を示す斜視図である。
【図１７】画面対応部分に接合部を有さないプリズムを使用した従来の投影型表示装置の構成を示す側面図である。
【図１８】従来の「３個以上のプリズムにより構成される色合成光学素子」の構成を示す側面図である。
【符号の説明】
１ 光源
３ ロッドインテグレータ
５，６，８ リレーレンズ
７ Ｐ−Ｓ合成素子
１０ 色分解プリズム
１３，１４，１５ 偏向プリズム
１６，１７，１８ 偏光ビームスプリッタ
２０ 色合成プリズム
４０，４１，４２…プリポラライザー
４３，４４，４５…ＰＢＳ用金属偏光板
４６，４７，４８ ポストポラライザー
５３Ｂ，５３Ｇ，５３Ｒ…フィールドレンズ
５４ Ｇ光反射ダイクロイックミラー
５６，５７，５８ クロスダイクロイックミラー
５９ コンデンサレンズ
６０ 偏光変換装置
６５ コールドミラー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a projection display device that illuminates a spatial light modulator with primary color light that has passed through a color separation optical system, combines the primary color light that has passed through the spatial light modulator with a color combining prism, and projects the image to display an image. .
[0002]
[Prior art]
Conventionally, a so-called “reflection type liquid crystal light valve” is provided as a reflection type spatial light modulation element, and the image is displayed by enlarging and projecting light spatially modulated by the reflection type spatial light modulation element onto a screen. There has been proposed a projection type display device.
[0003]
In this projection display device, white light from a light source is color-separated into red (R), green (G), and blue (B) primary color lights. Each of the modulation elements is illuminated. Each reflective spatial light modulator modulates and reflects the primary color illumination light according to the red, green, and blue components of the display image. Then, by combining the reflected lights from the respective reflective spatial light modulators and projecting them on a screen, a color image is displayed on the screen.
[0004]
As an optical system constituting such a projection display device, there is an optical system using a so-called “cross dichroic prism” as a color combining optical component.
[0005]
FIG. 16 is a perspective view showing the configuration of a conventional projection display device including an optical system using a so-called “cross dichroic prism”.
[0006]
In this projection display device, white light emitted horizontally from a light source 101 is incident on a first dichroic mirror 106 via a collimator lens 102, first and second integrators 103 and 104, and a cold mirror 105. You. The first dichroic mirror 106 transmits the magenta light (R + B) as it is, reflects the green light (G), and deflects it by 90 °. The green light (G) reflected by the first dichroic mirror 106 is incident on a reflecting mirror 107G arranged at an angle of 45 ° with respect to the optical axis, and is vertically reflected by the reflecting mirror 107G. The light is deflected by 90 ° in the direction, and is incident on the condenser lens 111G.
[0007]
On the other hand, the magenta light (R + B) transmitted through the first dichroic mirror 106 is incident on a second dichroic mirror 108 which is arranged at an angle of 45 ° with respect to the optical axis. The second dichroic mirror 108 transmits the red light (R) as it is, reflects the blue light (B), and deflects it by 90 °. The blue light (B) reflected by the second dichroic mirror 108 is deflected 90 degrees in the vertical direction and is incident on the condenser lens 111B.
[0008]
Then, the red light (R) transmitted through the second dichroic mirror 108 is guided to a plurality of mirrors (not shown), deflected 90 degrees in the vertical direction, and made incident on the condenser lens 111R.
[0009]
The white light emitted by the light source 101 is thus separated into three primary color lights.
[0010]
The green light (G) incident on the condenser lens 111G illuminates the green reflective spatial light modulator 114G via the first and second green light polarizing beam splitters 112G and 113G. The reflective spatial light modulator 114G modulates and reflects the illumination light according to the green component of the display image.
[0011]
The blue light (B) incident on the condenser lens 111B illuminates the blue reflective spatial light modulator 114B via the first and second blue light polarizing beam splitters 112B and 113B. The reflective spatial light modulator 114B modulates and reflects the illumination light according to the blue component of the display image.
[0012]
Further, the red light (R) incident on the condenser lens 111R illuminates the red reflective spatial light modulator 114R via the first and second red light polarizing beam splitters 112R and 113R. The reflective spatial light modulator 114R modulates and reflects the illumination light according to the red component of the display image.
[0013]
The second polarizing beam splitters 113G, 113B, and 113R for the respective colors respectively transmit the modulated light from the reflective spatial light modulators 114G, 114B, and 114R and emit the modulated light to the cross dichroic prism 115-3. It is made to face the entrance surface of the surface.
[0014]
The cross dichroic prism 115 combines the reflected light from each of the reflective spatial light modulators 114G, 114B, 114R and makes the reflected light enter the projection lens 116. That is, the cross dichroic prism 115 has a dichroic film surface perpendicular to each other. Modulated light from the green reflective spatial light modulator 114G passes through these dichroic film surfaces and exits from the exit surface of the cross dichroic prism 115. The modulated light from the blue reflective spatial light modulator 114B is reflected by one dichroic film surface and emitted from the exit surface of the cross dichroic prism 115. The modulated light from the red reflective spatial light modulator 114R is reflected by the other dichroic film surface and emitted from the exit surface of the cross dichroic prism 115.
[0015]
The light emitted from the exit surface of the cross dichroic prism 115 is incident on a projection lens 116, and is projected on a screen (not shown) by the projection lens 116, thereby displaying a color image on the screen.
[0016]
In this projection type display device, a “color separation / light guide optical system” from the light source 101 to each gyroic mirror is installed at the lower stage, and “modulation / color” from each beam splitter to the projection lens via the cross dichroic prism. The composition / projection optical system "is installed in the upper stage.
[0017]
Such a configuration allows the routing of the optical path in the `` color separation / light guide optical system '' to be contained in a rectangular area occupied in the horizontal plane by the `` modulation / color synthesis / projection optical system ''. The device configuration can be reduced in size.
[0018]
[Patent Document 1]
JP-A-11-64796
[Patent Document 2]
JP 2001-290010 A
[Patent Document 3]
JP-A-2002-55210
[Patent Document 4]
JP-A-2002-55305
[0019]
[Problems to be solved by the invention]
By the way, in the projection type display device as described above, the "cross dichroic prism" as a color combining optical component is formed so that the angles of the apex angles of four right-angle prisms are formed accurately, and each surface is polished with high precision Otherwise, the dichroic film surfaces crossing each other will bend at the position of the apex angle of the right-angle prism.
[0020]
If the dichroic film surface is bent in this way, the projected image on the screen becomes a double image, and there is a problem that the resolution of the image is significantly deteriorated.
[0021]
Also, in order to keep the resolution on the screen good, when joining the four right-angle prisms, it is necessary to join them with high precision so that no step is formed on the joining surface. Therefore, joining of the four right-angle prisms in manufacturing the “cross dichroic prism” is a difficult task.
[0022]
Furthermore, the right angle ridge of the right-angle prism does not allow defects such as so-called pills and chips, and if the width of the ridge is wide, the portion where the dichroic film surface intersects is projected on the screen as a vertical streak. There was also a problem.
[0023]
As described above, in the conventional cross dichroic prism, it is extremely difficult to process and join the prisms, and it takes a lot of time and cost to manufacture.
[0024]
In order to solve such a problem, it is effective to use a prism having no joint in a portion corresponding to the screen of the prism. As such an example, there is a technique described in Japanese Patent No. 2505758.
[0025]
FIG. 17 is a side view showing a configuration of a projection display device using a prism having no joint at a portion corresponding to a screen described in Japanese Patent No. 2505758.
[0026]
That is, as shown in FIG. 17, the projection display device uses a color separation prism (so-called “Philips prism”) used in a so-called “three-panel video camera”.
[0027]
In this display device, a light beam emitted from the light source 101 is converted into a parallel light beam by the collimator lens 102 and is incident on the polarization beam splitter 117. In the polarization beam splitter 117, only the S-polarized light component on the reflection surface inclined with respect to the incident light beam is reflected and enters the color separation prism 118.
[0028]
In the color separation prism 118, the light beam incident from the incident surface 118B of the first triangular prism 118A is incident on the first dichroic film 118C on the back surface of the first triangular prism 118A, and the first dichroic film In the film 118C, cyan light (R + G) is transmitted and blue light (B) is reflected.
[0029]
The blue light (B) is totally internally reflected by the incident surface 118B of the first triangular prism 118A, passes through the blue color filter 119, and is incident on the reflection type light modulation element 122 for blue. The light modulated and reflected by the blue reflective light modulation element 122 is totally internally reflected by the incident surface 118B of the first triangular prism 118A, is reflected by the first dichroic film 118C, and is polarized by the polarization beam splitter 117. Return to
[0030]
The cyan light (R + G) transmitted through the first dichroic film 118C is incident on the second triangular prism 118D, and is incident on the second dichroic film 118E on the rear surface of the second triangular prism 118D. In the dichroic film 118E, green light (G) is transmitted and red light (R) is reflected.
[0031]
The red light (R) is totally internally reflected by the incident surface of the second triangular prism 118D, and enters the red reflective light modulation element 123 via the red color filter 120. The light modulated and reflected by the red reflective light modulation element 123 is totally internally reflected by the incident surface of the second triangular prism 118D, is reflected by the second dichroic film 118E, and is reflected by the first triangular prism 118D. The light passes through 118A and returns to the polarizing beam splitter 117. Note that an air space exists between the first triangular prism 118A and the second triangular prism 118D.
[0032]
The green light (G) transmitted through the second dichroic film 118E is incident on the third prism 118F, transmitted through the third prism 118F, passes through the green color filter 121, and passes through the reflective light modulator for green. It is incident on the reference numeral 124. The light modulated and reflected by the green reflective light modulation element 124 passes through the third prism 118F, the second triangular prism 118D, and the first triangular prism 118A, and returns to the polarization beam splitter 117.
[0033]
In the polarization beam splitter 117, only the component modulated by each reflection type light modulation element passes through the reflection surface, enters the projection lens 116, and is projected on the screen 128 by the projection lens 116.
[0034]
The reflection type light modulation elements 122, 123, and 124 are driven by the corresponding drive circuits 125, 126, and 127, respectively.
[0035]
However, in a conventional projection display device using a so-called "Philips prism", a color separation prism 118 exists between the polarization beam splitter 117 and each of the reflection type light modulation elements 122, 123, and 124. In addition, since one polarizing beam splitter 117 is used as a polarizing element, there is a problem that the contrast of a displayed image is reduced.
[0036]
Accordingly, an object of the present invention is to provide a projection-type display device that can display a high-contrast image while being easy to manufacture.
[0037]
[Means for Solving the Problems]
In order to solve the above-described problems, a projection display device according to the present invention includes a white light source and a color that receives light from the white light source and separates the white light into first to third primary color lights. Separation optical system, three polarization beam splitters into which the respective primary color lights separated by the color separation optical system are respectively incident, and arranged corresponding to the respective polarization beam splitters. Combining three reflective spatial light modulators that polarize and reflect according to each primary color component of the display image and the primary color light that has passed through the three reflective spatial light modulators and the three polarization beam splitters A color combining prism, and a projection optical system that projects the light combined by the color combining prism, wherein the color combining prism has a first surface that vertically enters the first primary color light, 1st to 1st And a second surface on which a first dichroic film is formed, which reflects the first primary color light and transmits the second and third primary color lights, A third surface from which primary color light is emitted perpendicularly, wherein the first primary color light is incident on the first surface, is totally reflected by the third surface, and is reflected by the second surface. A first prism that reflects and exits from the third surface, wherein the second and third primary color lights are incident on the second surface and exit from the third surface; A fourth surface on which primary color light is vertically incident, and a second dichroic film that reflects the second primary color light out of the second and third primary color lights and transmits the third primary color light And a sixth surface parallel to the second surface of the first prism through an air layer, from which the second and third primary color lights are emitted. The second primary color light is incident on the fourth surface, totally reflected on the sixth surface, reflected on the fifth surface, emitted from the sixth surface, and exited from the third surface. Is incident on the fifth surface and exits from the sixth surface, a seventh surface on which the third primary light is incident perpendicularly, and the third primary color A fifth surface of the second prism from which light is emitted, and an eighth surface bonded with an optical adhesive to the fifth surface of the second prism, wherein the third primary color light is incident on the seventh surface. , And a third prism emitted from the eighth surface.
[0038]
In this projection type image display device, since the optical components are not interposed between each polarization beam splitter and each reflection light modulation element as in the related art, the light modulated by each reflection type light modulation element disturbs the vibration surface. There is no danger that the light enters the polarization beam splitter as it is. Therefore, in this projection type image display device, it is possible to prevent the contrast of the displayed image from being lowered, and the assembly is easy.
[0039]
The color separation optical system reflects the first primary color light out of the first to third primary color lights, and a third surface on which the first to third primary color lights are vertically incident, and A second surface on which a first dichroic film is formed, the second surface transmitting the second and third primary color lights; and a first surface for vertically emitting the first primary color light, Are incident on the third surface, are reflected on the second surface, are totally reflected on the third surface, are emitted from the first surface, and are the second and third primary colors. Light is incident on the third surface and is incident on a first prism that exits from the second surface, and on a second surface of the first prism where the second and third primary colors are incident. A sixth surface that faces in parallel via an air layer, and a second surface that reflects the second primary light and transmits the third primary light among the second and third primary light. Dichroic A fifth surface on which a black film is formed, and a fourth surface for vertically emitting the second primary color light, wherein the second primary color light is incident on the sixth surface. The third primary color light is reflected on the fifth surface, totally reflected on the sixth surface, emitted from the fourth surface, and incident on the sixth surface, A second prism emitted from a surface, an eighth surface, to which the third primary color light is incident, bonded to a fifth surface of the second prism with an optical adhesive, and the third primary color A third surface from which light exits vertically, and wherein the third primary color light is incident on the eighth surface, and comprises a third prism that exits from the seventh surface. A color separation prism is desirable.
[0040]
It is desirable that the color separation prism has substantially the same shape as the color synthesis prism.
[0041]
Each primary color light that has passed through the color separation prism is deflected by 90 ° by a deflecting prism to form a light beam whose traveling direction is parallel to each other, is incident on a corresponding polarizing beam splitter, and is reflected on a reflecting film surface of the polarizing beam splitter. It is desirable that the light be S-polarized light or P-polarized light.
[0042]
In addition, the light incident on each polarization beam splitter and the light that has been modulated or not modulated by the reflection type spatial light modulator corresponding to the polarization beam splitter and has passed through the polarization beam splitter have mutually traveling directions. It is desirable that they are orthogonal.
[0043]
In this case, there is no possibility that the polarized light passing through the color separation prism and the color synthesis prism is largely rotated on its vibration surface. Therefore, in this projection type image display device, it is possible to prevent a decrease in contrast of a display image, and it is easy to assemble.
[0044]
The color separation prism and the color synthesis prism in the present invention are disclosed in JP-A-2001-290010, JP-A-2002-55210, and JP-A-2002-55305. Color combining optical element ". In the optical elements described in these publications, there is no air layer for total reflection in the two dichroic films D1 and D2 as shown in FIG. On the other hand, in the present invention, as shown in FIG. 2, there is an air layer in the portion of the dichroic film for “to totally reflect the second primary color light in the prism”. Miniaturization has been achieved.
[0045]
It is desirable to arrange a half-wave plate on an optical path from the color separation prism to each of the polarization beam splitters, or on an optical path from each of the polarization beam splitters to the color combining prism.
[0046]
It is desirable that the light incident on each polarizing beam splitter be S-polarized light or P-polarized light with respect to the reflection film surface of the polarizing beam splitter by the half-wave plate.
[0047]
It is desirable to arrange a field lens between the decomposing prism and the polarizing beam splitter, and adjust the position of light incident on the reflective spatial light modulator by displacing the field lens in a direction perpendicular to the principal ray. .
[0048]
It is desirable to arrange a steering prism between the color separation prism and the polarization beam splitter, and adjust the illumination distribution to the reflection type spatial modulation element by displacing the steering prism in a direction perpendicular to the principal ray.
[0049]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0050]
FIG. 1 is a perspective view illustrating the configuration of the projection display device according to the first embodiment.
[0051]
In this projection display device, a light beam emitted from the light source 1 is transmitted through the UV / IR filter 2 to remove ultraviolet rays and infrared rays, and is condensed and incident on the incident end face of the rod integrator 3. The light source 1 includes a discharge lamp that emits white light and the like, and a concave reflecting mirror (a spheroidal mirror or a parabolic mirror).
[0052]
In the rod integrator 3, the incident light repeats total internal reflection on the side surface of the rod, makes the illuminance uniform, and is emitted from the emission end face as light having a uniform spatial distribution.
[0053]
Light emitted from the rod integrator 3 is incident on a deflection mirror (steering mirror) 9 via a collimator lens 4, relay lenses 5 and 6, a PS synthesizing element 7, and a condenser lens 8. The PS combining element 7 is an element for aligning light from a light source to linearly polarized light in a certain direction, and has a structure in which a plurality of polarizing beam splitters and a half-wave plate are arranged in a plane.
[0054]
The light incident on the deflecting mirror 9 is deflected by 90 ° in the optical path by the deflecting mirror 9. As the deflecting mirror 9, a cold mirror can be used in addition to the aluminum reflecting mirror and the silver mirror. The cold mirror is a mirror configured by laminating dielectric layers, and has a property of transmitting ultraviolet light and infrared light and reflecting only visible light. The light reflected by the deflecting mirror 9 enters the color separation prism 10.
[0055]
Note that the optical axis from the light source 1 toward the polarizing mirror 9 is the Z axis, the optical axis of the light reflected by the polarizing mirror 9 is the Y axis, and the XYZ coordinate axis is the X axis, which is orthogonal to the Z axis and the Y axis. Set.
[0056]
FIG. 2 is a side view showing the shape of the color separation prism 10.
[0057]
The color separation prism 10 includes three glass blocks of first and second triangular prisms 10A and 10B and a third prism (quadrangular prism) 10C.
[0058]
The color separation prism 10 is a so-called “Philips prism”, and is a three-block color separation prism utilizing selective reflection of a color by a dichroic film and total reflection by a prism surface. The first dichroic film 11 that reflects blue light (B) is provided on the back surface of the first triangular prism 10A. The blue light (B) reflected by the first dichroic film 11 is totally internally reflected by the incident surface of the first triangular prism 10A. In the first triangular prism 10A, the apex angle (α1) of the prism is selected so that the blue light (B) is totally internally reflected, and the exit surface (XY plane) of the blue light (B) is light. A prism shape that is perpendicular to the axis (Z direction) is adopted.
[0059]
The second dichroic film 12 that reflects the red light (R) is provided on the back surface of the second triangular prism 10B, and the red light (R) reflected by the second dichroic film 12 is The inner surface is totally reflected at the incident surface of the second triangular prism 10B. In the second triangular prism 10B, the apex angle (α2) of the prism is selected so that the red light (R) is totally internally reflected, and the exit surface of the red light (R) is positioned with respect to the optical axis. The shape of the prism is a right angle. The first and second triangular prisms 10A and 10B are used to use the incident surface of the second triangular prism 10B as a total reflection surface, so that the back surface of the first triangular prism 10A and the second triangular prism 10B are used. It is assembled so that a very narrow air layer is maintained between the light emitting surface and the light incident surface.
[0060]
Then, the green light (G) transmitted through the second dichroic film 12 is transmitted through the third prism 10C and emitted. The third prism 10C has a prism shape such that the emission surface of green light (G) is perpendicular to the optical axis.
[0061]
In this projection display device, the light beam incident on the color separation prism 10 is incident on the incident surface of the first triangular prism 10 and is incident on the first dichroic film 11 on the back surface of the first triangular prism 10A. Then, the first dichroic film 11 transmits the cyan light (R + G) and reflects the blue light (B). The blue light (B) is totally internally reflected by the incident surface of the first triangular prism 10A, and is emitted from the side surface of the first triangular prism 10A.
[0062]
The cyan light (R + G) transmitted through the first dichroic film 11 is incident on the second triangular prism 10B, and is incident on the second dichroic film 12 on the back surface of the second triangular prism 10B. In the dichroic film 12, green light (G) is transmitted and red light (R) is reflected. The red light (R) is totally internally reflected by the incident surface of the second triangular prism 10B and is emitted from the side surface of the second triangular prism 10B.
[0063]
The green light (G) transmitted through the second dichroic film 12 enters the third prism 10C, passes through the third prism 10C, and is emitted from the back surface of the third triangular prism 10C. .
[0064]
The three primary color lights separated in this way enter the deflecting prisms 13, 14, and 15, respectively, are deflected by 90 degrees in the optical path, and travel in directions parallel to each other (Z direction). That is, the three primary color lights separated by color are respectively perpendicular to the incident direction (Y direction) of the light from the light source to the color separation prism 10 and the emission direction (in the XY plane) of each primary color light from the color separation prism 10. Proceed in different directions.
[0065]
That is, as shown in FIG. 1, a blue deflecting prism 13 is provided on the side surface of the first triangular prism 10A from which the blue light (B) is emitted. A red deflecting prism 14 is provided on the side surface of the second triangular prism 10B from which the red light (R) is emitted. A green deflecting prism 15 is provided on the back surface of the third triangular prism 10C from which the green light (G) is emitted.
[0066]
These deflecting prisms 13, 14, 15 are so-called right angle prisms.
[0067]
FIG. 3 is a side view showing a configuration around the color combining prism 20 in the projection display device according to the present invention.
[0068]
The three primary color lights emitted from the deflecting prisms 13, 14, 15 and traveling in directions parallel to each other enter the polarizing beam splitters 16, 17, 18, respectively. These polarization beam splitters 16, 17, 18 are attached via a spacer 19 to a color combining prism 20 configured similarly to the color separation prism 10. The color synthesizing prism 20 has a substantially mirror-symmetrical shape with respect to the color separation prism 10. That is, the color synthesizing prism 20 has a configuration similar to a so-called “Philips prism”, and includes three first prisms 20A and 20B and a third prism (square prism) 20C. Is a three-block color synthesizing prism having the above glass block and first and second dichroic films.
[0069]
FIG. 4 is a perspective view showing a configuration around the color separation prism 10 and the color synthesis prism 20 in the projection display device according to the present invention.
[0070]
Between each of the deflecting prisms 13, 14, 15 and each of the polarizing beam splitters 16, 17, 18, a phase difference plate (1/2 wavelength plate) 21, a field lens 22, and a polarizing plate 23 are arranged, respectively. . The field lens 22, together with the relay lenses 5 and 6 and the condenser lens 8, forms an image of the light from the exit end face of the rod integrator 3 on an image plane of a reflective spatial light modulator described later. In addition, the phase difference plate (1/2 wavelength plate) 21 and the polarizing plate 23 are installed as needed.
[0071]
FIG. 5 is a perspective view showing a configuration of the color separation prism 10, the color synthesis prism 20, and the reflection type light modulation elements 24, 25, 26 in the projection display device according to the present invention.
[0072]
The light that has entered the polarization beam splitters 16, 17, and 18 is S-polarized with respect to the incident surfaces in the polarization beam splitters 16, 17, and 18. Therefore, this incident light is reflected by the PBS film surface, deflected by 90 °, and emitted from the polarization beam splitters 16, 17, and 18. The light emitted in this manner is incident on the reflection type light modulation elements 24, 25, 26 for the respective primary colors provided corresponding to the polarization beam splitters 16, 17, 18.
[0073]
The P-polarized light component of the light incident on the polarization beam splitters 16, 17, 18 does not reach the reflection type light modulation elements 24, 25, 26 because it passes through the reflection surface.
[0074]
Each of the reflective light modulating elements 24, 25, and 26 is driven by a corresponding drive circuit (not shown), and the blue reflective light modulating element 24 performs spatial light modulation (polarization modulation) based on a blue component of a display image. The reflection-type light modulation element 25 for red performs spatial light modulation (polarization modulation) based on the red component of the display image, and the reflection-type light modulation element 26 for green performs spatial light modulation (polarization modulation) based on the green component of the display image. Polarization modulation).
[0075]
The blue light (B) incident on the blue reflection type light modulation element 24 is modulated and reflected by the blue reflection type light modulation element 24, and the modulated P-polarized component is converted into the polarization beam splitter 16. And enters from the side surface of the first triangular prism 20A of the color combining prism 20.
[0076]
The blue light (B) incident on the first triangular prism 20A of the color synthesizing prism 20 is totally internally reflected by the exit surface of the first triangular prism 20A, is reflected by the first dichroic film 27, and The light is emitted from the emission surface of one triangular prism 20A.
[0077]
Also, the red light (R) incident on the red reflective light modulation element 25 is modulated and reflected by the red reflective light modulation element 25, and the modulated P-polarized light is converted into a polarized light beam. The light passes through the splitter 17 and enters from the side surface of the second triangular prism 20B of the color combining prism 20.
[0078]
The red light (R) incident on the second triangular prism 20B of the color synthesizing prism 20 is totally internally reflected by the exit surface of the second triangular prism 20B, reflected by the second dichroic film 28, and The light is emitted from the emission surface of the second triangular prism 20B, passes through the first triangular prism 20A, and is emitted from the emission surface of the first triangular prism 20A.
[0079]
The green light (G) that has entered the green reflective light modulating element 26 is modulated and reflected by the green reflective light modulating element 26, and the modulated P-polarized light is converted into a polarized light beam. The light passes through the splitter 18 and enters from the back surface of the third prism 20C of the color combining prism 20.
[0080]
The green light (G) incident on the third prism 20C of the color combining prism 20 transmits through the third prism 20C, transmits through the second triangular prism 20B, and further transmits the first triangular prism 20A. The light is transmitted and exits from the exit surface of the first triangular prism 20A.
[0081]
In this manner, the primary color lights that have entered the color combining prism 20 are combined and emitted from the color combining block 20. Then, as shown in FIG. 1, the light is incident on a projection lens 29 which is a projection optical system, and is projected on a screen (not shown) by the projection lens 29.
[0082]
In this projection type display device, the physical directions of the reflection type light modulation elements 24, 25, 26, that is, the relative positions of the reflection type light modulation elements 24, 25, 26 with respect to the image projected on the screen, all match. ing. Therefore, the discrimination direction, the element drive direction, and the like are all the same, and the difference in characteristics caused by the difference in the element drive direction does not appear on the screen, and the resolution and shading can be improved.
[0083]
In this projection display device, the S-polarized light (polarized light in the X direction) incident on each of the polarization beam splitters 16, 17, 18 becomes P-polarized light with respect to the dichroic films 11, 12 of the color separation prism 10. The P-polarized light (polarized light in the Y direction) as the signal light emitted from each of the polarization beam splitters 15, 16, and 17 becomes S-polarized light with respect to the dichroic films 27 and 28 of the color combining prism 20.
[0084]
Therefore, in the color separation prism 10, each dichroic film 11, 12 must be designed for P-polarized light, and in the color combining prism 20, each dichroic film 27, 28 needs to be designed for S-polarized light.
[0085]
Here, such an arrangement in which the S-polarized light is incident on each of the polarization beam splitters 16, 17, 18 will be referred to as an "S arrangement". In this case, the polarization states of the color separation prism 10 and the color synthesis prism 20 with respect to the dichroic film are summarized in Table 1 below (the column of "No half-wave plate").
[0086]
[Table 1]

[0087]
Therefore, for example, by inserting a phase difference plate (１ ／ wavelength plate) 21 between each field lens 22 and each of the deflecting prisms 13, 14, and 15 to rotate the polarization direction by 90 °, color separation becomes possible. The S-polarized light (signal light) incident on the dichroic films 11 and 12 of the prism 10 also becomes S-polarized light with respect to the dichroic films 27 and 28 of the color combining prism 20 (see “Polarization beam splitter (PBS)” in Table 1). And １ ／ wavelength plate between the color separation prism ”)).
[0088]
That is, by inserting the phase difference plate (（wavelength plate) 21 at the above-described position, the dichroic film is designed in the color separation prism 10 and the color synthesis prism 20 based on the same polarization direction (S polarization). Can be. If all these dichroic films 11, 12, 27, and 28 are formed simultaneously, a dichroic film having characteristics such as wavelength characteristics (spectral characteristics) can be obtained, and spectral loss in color separation and color synthesis can be obtained. Can be minimized.
[0089]
Similarly, a phase difference plate (1/2 wavelength plate) is inserted between each of the polarization beam splitters 15, 16, 17 and the color combining prism 20, and both the color separating prism 10 and the color combining prism 20 have P It is also possible to use a dichroic film designed on the basis of polarized light (in the case of [Table 1], "In the case where there is a half-wave plate between the polarizing beam splitter (PBS) and the color combining prism").
[0090]
Also in this case, all the dichroic films 11, 12, 27, and 28 can be simultaneously formed to obtain a dichroic film having the same characteristics, and the spectral loss in color separation and color synthesis can be minimized. .
[0091]
FIG. 6 shows that the light incident on each of the polarization beam splitters 16, 17, and 18 is P-polarized light with respect to the incident surface in the polarization beam splitter, and each reflection type space is located at a position where the light transmitted through this reflection surface (PBS surface) is received. FIG. 3 is a perspective view showing a configuration in which light modulation elements 24, 25, and 26 are arranged (referred to as “P arrangement”).
[0092]
In this case, the polarization direction of the light incident on each of the polarization beam splitters 16, 17, and 18 is P-polarized light with respect to the reflection surfaces of the polarization beam splitters 16, 17, and 18, unlike the above-described “S arrangement”. Since the incidence planes of the dichroic films 11 and 12 of the color separation prism 10 and the incidence planes of the polarization beam splitters 16, 17 and 18 are orthogonal to each other, the P-polarized light for the polarization beam splitters 16, 17 and 18 is The dichroic films 11 and 12 of the color separation prism 10 become S-polarized light. Further, the polarized light corresponding to the S-polarized light emitted from each of the polarizing beam splitters 15, 16, 17 is configured to be P-polarized light with respect to the dichroic films 27, 28 of the color combining prism 20.
[0093]
Therefore, in the color separation prism 10, each dichroic film 11, 12 must be designed for S-polarized light, and in the color combining prism 20, each dichroic film 27, 28 needs to be designed for P-polarized light.
[0094]
The polarization states of the color separation prism 10 and the color synthesis prism 20 with respect to the dichroic film in this case are summarized in the following Table 2 (the column of "No half-wave plate").
[0095]
[Table 2]

[0096]
Therefore, for example, by inserting a phase difference plate (half-wave plate) between each field lens 22 and each of the deflecting prisms 13, 14, 15 to rotate the polarization direction by 90 °, the color separation prism can be obtained. The light corresponding to the P-polarized light with respect to the dichroic films 11 and 12 of FIG. 10 also becomes the P-polarized light with respect to the dichroic films 27 and 28 of the color synthesizing prism 20 (see Table 2). Column with a half-wave plate between the prisms).
[0097]
That is, by inserting the phase difference plate (（wavelength plate) 21 at the above-described position, the dichroic film is designed in the color separation prism 10 and the color synthesis prism 20 based on the same polarization direction (P polarization). Can be. If all these dichroic films 11, 12, 27, and 28 are formed simultaneously, a dichroic film having characteristics such as wavelength characteristics (spectral characteristics) can be obtained, and spectral loss in color separation and color synthesis can be obtained. Can be minimized.
[0098]
Similarly, a phase difference plate (half-wave plate) is inserted between each of the polarization beam splitters 15, 16, 17 and the color combining prism 20, and both the color separating prism 10 and the color combining prism 20 perform S A dichroic film designed on the basis of polarized light can also be used (in the case of [Table 2] in the case of "1/2 wavelength plate between polarizing beam splitter (PBS) and color combining prism").
[0099]
Also in this case, all the dichroic films 11, 12, 27, and 28 can be simultaneously formed to obtain a dichroic film having the same characteristics, and the spectral loss in color separation and color synthesis can be minimized. .
[0100]
Next, in this projection type display device, each of the deflecting prisms 13, 14, 15 is moved and adjusted in a direction of coming and coming from each of the polarizing beam splitters 15, 16, 17 so that each of the reflective light modulating elements 24, The position of the illuminated area on 25 and 26 can be finely adjusted.
[0101]
On the other hand, FIG. 7 is a perspective view showing a configuration using a plane mirror or a curved mirror 30 instead of the deflecting prisms 13, 14, 15.
[0102]
In this projection type display device, a flat mirror or a curved mirror 30 can be used instead of the deflecting prisms 13, 14, 15; in this case, the flat mirror or the curved mirror 30 is replaced with the one shown in FIG. As shown by arrows, each reflection type light modulation element is moved in the direction of coming and going to or from each of the polarization beam splitters 15, 16 and 17 or in two directions along the reflection surface of the plane mirror or the curved mirror 30. The position of the illumination area on 24, 25, 26 can be finely adjusted.
[0103]
FIG. 8 is a perspective view showing a configuration for moving and adjusting the field lens 22 in two directions orthogonal to the optical axis.
[0104]
In this projection display device, the position of the illumination area on each of the reflective light modulation elements 24, 25, and 26 is finely adjusted by moving and adjusting the field lens 22 in two directions orthogonal to the optical axis. Can be. In this case, a support frame 31 for supporting the field lens 22 is movably attached to a fixed frame 32, and the support frame 31 is attached to the fixed frame 32 by two-direction push screws 33 and 34. By moving, the movement adjustment in two directions orthogonal to the optical axis of the field lens 22 can be performed.
[0105]
Note that a piezoelectric element may be used instead of the push screws 33 and 34.
[0106]
In the above-described projection type display device, a so-called “BK-7” is generally used as a material (glass material) forming the color separation prism 10 and the color synthesis prism 20, but is not limited thereto. . Further, the shapes of the color separation prism 10 and the color synthesis prism 20 described above, for example, the angles of the apex angles α1 and α2 are not particularly limited.
[0107]
Further, in the above-described embodiment, the rod integrator 3 is used for the illumination system. However, the present invention is not limited to this. For example, a fly-eye integrator may be used for the illumination system.
[0108]
As described above, in the projection display device of the present embodiment, there is no occurrence of shadows or unnecessary bright lines at intersections of dichroic films in a projected image as in the case of using a cross dichroic prism, and the so-called “ There are no cashiers. Further, it is possible to display an image with good contrast in which light leakage to the reflection type light modulation element for other colors is small and generation of ghost is prevented.
[0109]
Further, the angle of incidence of light on the dichroic film is small, and the light use efficiency during color synthesis can be increased. In addition, a polarizing beam splitter having optimal characteristics can be used for each color, and an optimal narrow band color filter can be used for each color, so that a high-contrast image display can be easily realized.
[0110]
Further, in this projection display device, since the images displayed by the three reflection-type light modulation elements do not invert or mirror each other, the in-plane unevenness (reflectance unevenness) caused by the reflection-type light modulation elements. Etc.), there is no color unevenness when three colors are combined. That is, in the color separation prism of the projection display device, the green light is transmitted without being reflected, and the red light and the blue light are respectively reflected twice, so that the illumination light image is an erect image that is not inverted. Therefore, green light, red light, and blue light all become the same illumination light in the physical direction of each reflective light modulation element, and illumination unevenness does not cause color unevenness.
[0111]
In this projection display device, the design and manufacture of the color separation prism and the color synthesis prism are easy.
[0112]
FIG. 9 is a perspective view illustrating a configuration of a projection display device according to the second embodiment.
[0113]
The projection display device of the second embodiment uses a metal polarizing plate (Wire Grid Polarizer) instead of the polarization beam splitters 16, 17, and 18 in the first embodiment.
[0114]
FIG. 9 shows an embodiment in which the polarizing beam splitters (PBS) 16, 17, and 18 in the PBS section and the synthetic prism 20 in the first embodiment shown in FIG. 6 in FIG. 6 are replaced with metal polarizing plates. Is shown. The optical system of the light source system and the color separation system from the light source 1 to the field lens 22 (the half-wave plate 21 if necessary) are common, and are not shown in the drawing.
[0115]
Metal polarizers are also referred to as metal grid polarizers or grid polarizers, as shown in JP-A-49-90149, U.S. Pat. No. 4,289,381, U.S. Pat. No. 4,514,479, and JP-A-58-42003. , Developed since the 1970s.
[0116]
More specifically, the light that has been decomposed into three primary colors passes through the PBS metal polarizers 43, 44, and 45 and irradiates the reflective light modulation elements 24, 25, and 26, respectively. The reflected light modulated according to the image information applied to the reflection type light modulation elements 24, 25, and 26 is reflected by the PBS metal polarizing plates 43, 44, and 45, and is referred to as a "Philips prism". The light enters the prism 20 and is synthesized in three colors.
[0117]
Since the conventional glass PBSs 16, 17, and 18 are optically a rectangular parallelepiped of glass, optical aberrations are basically the same regardless of the above-described S arrangement or P arrangement. On the other hand, the PBS metal polarizing plates 43, 44, and 45 have a structure in which a metal lattice is provided on a glass plate and are parallel flat plates. If glass enters the optical path of the light emitted from the light modulation elements 24, 25, and 26 by transmission, it causes astigmatism and the like, and the resolution of the screen is extremely deteriorated. For this reason, a P arrangement is used as in FIG.
[0118]
Also, if there is reflection on the glass surface opposite to the grating surface of the metal polarizing plates 43, 44, 45 for PBS, the light is also reflected on that surface, resulting in a problem that the screen becomes a double image. I do. Therefore, in the present embodiment, it is necessary to provide an antireflection (AR) coating on the glass surface of the PBS metal polarizing plates 43, 44, and 45 opposite to the lattice surface of the metal polarizing plates. It is desirable that the reflectance of the AR coat is about 1% or less in a band including the color band of the channel. The band is, for example, 420 to 500 nm for the blue channel, 500 to 580 nm for the green channel, and 580 nm to 680 nm for the red channel. Furthermore, in the above-mentioned band, it is even better if it is 0.5% or less.
[0119]
The prepolarizers 40, 41, and 42 made of metal polarizing plates are provided in front of the metal polarizing plates 43, 44, and 45 for PBS to improve the degree of polarization of transmitted light. For the sake of convenience, only the prepolarizer 42 is shown in the figure.
[0120]
The post polarizers 46, 47, and 48 are disposed after the PBS metal polarizers 43, 44, and 45, and the PBS metal polarizers 43, 44, and 45 of the reflected light that is not modulated by the reflective light modulators 24, 25, and 26. The light is used to block the light (P-polarized light with respect to the PBS metal polarizers 43, 44, and 45) that has been reflected without being transmitted, thereby further improving the contrast.
[0121]
FIG. 10 is a perspective view showing the configuration of the projection display device according to the third embodiment of the present invention.
[0122]
FIG. 10A is a diagram showing the overall configuration of a projection display device according to the third embodiment, and FIG. 10B is a diagram illustrating post-polarizers 46 and 47 in the projection display device according to the third embodiment. And FIG. 48 are perspective views for explaining a positional relationship with respect to an optical axis.
[0123]
The difference between the third embodiment and the second embodiment is that the post polarizers 46, 47 and 48 are inclined at a predetermined angle with respect to the optical axis. That is, the optical axis and the normal to the main surface of the post polarizers 46, 47, and 48 have a predetermined angle.
[0124]
This is reflected again by the reflection type light modulating elements 24, 25, 26 reflected by the post polarizers 46, 47, 48, further reflected by the PBS metal polarizing plates 43, 44, 45 and incident on the entrance pupil of the projection lens. This prevents the occurrence of ghost.
[0125]
FIG. 10B is a diagram showing a set of four plates for aberration correction.
[0126]
These plates are made of a metal polarizing plate or a mere transparent glass plate, and have a predetermined angle α with respect to the optical axis, a plate 71, a plate 72 in which the plates 71 are arranged mirror-symmetrically with respect to a plane perpendicular to the optical axis, The plates 71 and 72 are composed of plates 73 and 74 rotated by 90 ° about the optical axis.
[0127]
The post polarizers 46, 47, and 48 of the third embodiment are arranged at positions corresponding to, for example, the plate 71 with respect to the optical axis.
[0128]
The inclination angles of the post polarizers 46, 47, and 48 with respect to the optical axis can be easily obtained from the drawing according to the above-mentioned purpose. Specifically, the cone angle (cone angle) of the light reflected from the reflection type light modulation elements 24, 25, and 26 (that is, the angle between the maximum spread angle of light contributing to image formation and the optical axis) is determined. If the inclination angle of the post-polarizers 46, 47, 48 is α-degree in the case of α degrees, the light reflected from the reflection type light modulation elements 24, 25, 26 at an arbitrary angle will be reflected by the post-polarizers 46, 47, 48 and The angle at which the light is reflected by the PBS metal polarizing plates 43, 44, and 45 and returns to the reflection type light modulation elements 24, 25, and 26 is α degrees. In other words, if the inclination angles of the post-polarizers 46, 47, 48 are set to α degrees or more, the re-reflected light from the reflection type light modulation elements 24, 25, 26 becomes a light beam having an angle greater than the cone angle, and the projection lens Does not reach the entrance pupil, and does not reach the screen, so that ghost can be reliably prevented.
[0129]
The cone angle corresponds to the F-number of the projection lens. The F-number (i.e., cone angle) varies depending on the specific design, but generally the F-number is 2.8 to 4.0.
[0130]
Here, since the F number is about 7.2 degrees, the F number 2.8 is about 10.3 degrees, and the F number 2 is about 14.5 degrees, the preferable inclination angle is 5 to 15 degrees. Degrees.
[0131]
FIG. 11 is a perspective view illustrating a configuration of a projection display device according to a fourth embodiment of the present invention.
[0132]
This embodiment is characterized in that cylindrical lenses 49, 50, 51 are provided between the post-polarizers 46, 47, 48 and the Philips prism 20 in the projection type device of the third embodiment. This corrects the aberration due to the inclination of the post polarizers 46, 47, 48.
[0133]
Note that, as an alternative to the cylindrical lenses 49, 50, and 51, plate sets 71, 72, 73, and 74 each having a function of correcting aberration shown in FIG. By using one of the four plates 71, 72, 73, 74 as the post polarizers 46, 47, 48, the functions of the post polarizers 46, 47, 48 and the cylindrical lenses 49, 50, 51 can be replaced. can do.
[0134]
FIG. 12 is a perspective view showing a mounting method of the PBS metal polarizers 43, 44, 45 and the post polarizers 46, 47, 48 in the projection display devices of the second to fourth embodiments.
[0135]
In these embodiments, a common base 52 made of alumina ceramic 52 is provided on the upper surface of the color combining prism 20.
[0136]
The holders 53A, 53B, and 53C fix the PBS metal polarizers 43, 44, and 45 and the post polarizers 46, 47, and 48, and the PBS metal polarizers 43, 44, and 45 and the post polarizers 46, 47, and 48. The reflection type light modulation elements 24, 25, and 26 are used to make the space inside them a closed structure. The metal polarizers 43, 44, 45 for PBS and the metal grid (grid) sides of the post polarizers 46, 47, 48 are installed so as to be in the closed space side. By doing so, the metal grid surface is kept hermetically sealed, and damages due to the metal grid contacting with others, and problems such as contamination due to various causes can be effectively prevented.
[0137]
The holders 53A, 53B, and 53C may be fixed to the base 52, and the registration of the reflection type light modulation elements 24, 25, and 26 may be performed on the holders 53A, 53B, and 53C. The registration may be adjusted in a unit state fixed together with the elements 24, 25, and 26.
[0138]
The metal polarizing plate exerts a polarizing action by the action of the metal grating. However, since some of the light incident on the metal polarizing plate is absorbed by the metal grating, the temperature of the metal polarizing plate rises. Therefore, the metal polarizing plate needs to be appropriately cooled from the viewpoint of securing its reliability and from the viewpoint of eliminating the problem that the imaging performance is deteriorated when the flatness of the metal polarizing plate is deteriorated due to a temperature change. . However, since the metal grating side of the metal polarizing plate constitutes an imaging optical system, direct cooling has the above-mentioned adverse effects. Therefore, it is necessary to air-cool the sealed metal polarizing plate from the substrate side.
[0139]
FIG. 12 also shows sirocco fans 54A, 54B, and 54C of the PBS metal polarizing plates 43, 44, and 45. These sirocco fans 54A, 54B, 54C cool the non-metal grid surfaces of the PBS metal polarizers 43, 44, 45.
[0140]
The sirocco fans 54A, 54B, and 54C may be axial fans instead of the sirocco fans 54A, 54B, and 54C, and the air from the sirocco fans 54A, 54B, and 54C may be cooled through an appropriate air guide path. It is also desirable that the pre-polarizers 40, 41, 42 and the post-polarizers 46, 47, 48 be appropriately cooled. Although not shown directly, the post-polarizers 46, 47, and 48 blow air to the gaps between the holders 53A, 53B, and 53C and the color combining prism 20, and the pre-polarizers 40, 41, and 42 blow air to the space around them. To achieve cooling.
[0141]
With the above configuration, it is possible to realize a projection type display device using a metal polarizing plate (Wire Grid Polarizer) instead of the glass PBSs 16, 17, and 18, and to reduce the weight of the optical system and the effects of glass birefringence. Is removed, thereby improving the contrast.
[0142]
The configuration of the pre-polarizer-PBS-post-polarizer using the metal polarizing plate described above can be naturally applied to a system using a conventional cross dichroic prism.
[0143]
Hereinafter, an embodiment in which a metal polarizing plate is applied to a projection display device including a cross dichroic prism will be described.
[0144]
In addition, as a conventional example of the cross dichroic prism, JP-A-2001-398198 is cited. This conventional example is a system using a conventional cross dichroic prism, in which a glass PBS is used as a prepolarizer and a PBS, and a metal polarizer prepolarizer is additionally inserted.
[0145]
Also in the above conventional example, it was possible to contribute to the improvement of the contrast by removing the influence of the birefringence of the pre-PBS glass. However, there is a strong demand for image quality such as improvement in contrast, and further improvement has been desired.
[0146]
FIG. 13 to FIG. 15 are diagrams showing the configurations of the projection display devices according to the fifth to seventh embodiments each having a synthesis block using a cross dichroic prism. The X, Y, and Z axes are defined as shown in the figure.
[0147]
FIG. 13 is a diagram illustrating a configuration of a projection display device according to a fifth embodiment of the present invention. The projection type display device according to the fifth embodiment corresponds to the projection type display device according to the second embodiment shown in FIG.
[0148]
Light source light (white light) 1a of a substantially parallel light flux emitted from a light source 1 composed of a lamp and a concave mirror such as a parabolic mirror passes through a bending mirror (cold mirror) 65 and has a predetermined horizontal angle, for example, approximately 90 °. And enters the polarization conversion device 60 to undergo polarization conversion.
[0149]
Here, the polarization conversion device 60 is an array of a fly-eye integrator and a polarization beam splitter each including a first lens plate 61 having a plurality of fly-eye lenses 61a and a second lens plate 62 having a plurality of fly-eye lenses 62a. And a half-wave phase plate 64 formed at a predetermined position.
[0150]
The light emitted from the polarization conversion device 60 is mostly S-polarized light, but partially P-polarized light. The light emitted from the polarization conversion device 60 passes through a condenser lens 59 and is then X-coupled to a B (blue) light reflecting dichroic mirror 57 and a dichroic mirror 58 that reflects R (red) light and G (green) light so as to be orthogonal to each other. B light (propagating to the right in the figure), which is incident on the cross dichroic mirror 56 arranged in the mold and travels in opposite directions perpendicular to the incident optical axis, R light, and G light (progressing to the left in the figure) Color separation.
[0151]
The color-separated B light is reflected by a mirror 55, passes through a prepolarizer 41 via a field lens 53B, and is incident on a PBS metal polarizing plate 45. The mirror 55 may be a cold mirror or a metal polarizing plate.
[0152]
On the other hand, the color-separated G light and R light are reflected by a mirror 56 and are incident on a G light reflecting dichroic mirror 54. Here, the color is separated into a reflected G light (traveling rightward in the figure) and a transmitted R light (traveling upward in the figure), passes through field lenses 53G and 53R, and passes through prepolarizers 42 and 40, respectively. Are incident on the respective PBS metal polarizing plates 43 and 44.
[0153]
Also in the present embodiment, the metal polarizing plates 43, 44, and 45 for PBS are arranged in a P arrangement as in FIG.
[0154]
The prepolarizers 40, 41, and 42 made of metal polarizing plates are provided in front of the metal polarizing plates 43, 44, and 45 for PBS to improve the degree of polarization of transmitted light. The post-polarizers 46, 47, and 48 made of a metal polarizing plate are disposed after the PBS metal polarizing plates 43, 44, and 45, and the reflected light that is not modulated by the reflection-type light modulators 83, 84, and 85 is reflected by the PBS metal polarizing plate 43. , 44, 45 are used to block the light that has not been transmitted and reflected (P-polarized light with respect to the metal polarizing plate) to further improve the contrast.
[0155]
The R light, G light, and B light modulated by the reflection-type light modulation elements 83, 84, and 85 are combined by the cross dichroic prism 81 via post-polarizers 47, 46, and 45, respectively, and emitted toward the projection lens 82. Is done.
[0156]
FIG. 14 is a diagram illustrating a configuration of a projection display device according to a sixth embodiment of the present invention. FIG. 14A is a diagram illustrating the overall configuration of a projection display device according to the sixth embodiment, and FIG. 14B is a diagram illustrating post-polarizers 44, 45, and 45 using a metal polarizing plate according to the sixth embodiment. It is a figure for explaining the positional relationship with respect to the optical axis of 46.
[0157]
The projection display device according to the sixth embodiment corresponds to the projection display device according to the second embodiment shown in FIG.
[0158]
The difference from the fifth embodiment shown in the thirteenth embodiment is that the post polarizers 46, 47 and 48 are inclined at a predetermined angle with respect to the optical axis. This is because the light reflected by the post polarizer is reflected again by the reflection type light modulation elements 83, 84, 85, further reflected by the metal polarizing plates 43, 44, 45, and is incident on the entrance pupil of the projection lens 82. This is to prevent ghosts from occurring.
[0159]
FIG. 14B is a diagram showing a set of four plates for aberration correction.
[0160]
These plates include a plate 71 having a predetermined angle α with respect to the optical axis, a plate 72 in which the plate 71 is arranged mirror-symmetrically with respect to a plane perpendicular to the optical axis, and a plate obtained by rotating the plates 71 and 72 by 90 ° about the optical axis. 73 and 74.
[0161]
The post polarizers 46, 47, 48 of the present embodiment are arranged at positions corresponding to, for example, the plate 71 with respect to the optical axis.
[0162]
The inclination angles of the post polarizers 43, 44, and 45 can be easily obtained from the drawing according to the above-described purpose. Specifically, the cone angle (cone angle) of light reflected from the reflection type light modulation elements 83, 84, 85 (that is, the angle between the maximum spread angle of light contributing to image formation and the optical axis) is determined. If the inclination angle of the post-polarizers 43, 44, 45 is α-degree in the case of α degrees, light reflected from the reflection-type light modulation elements 83, 84, 85 at an arbitrary angle will be reflected by the post-polarizers 43, 44, 45 and The angle at which the light is reflected by the PBS metal polarizing plates 43, 44, and 45 and returns to the reflection type light modulation elements 83, 84, 85 is α degrees. In other words, if the inclination angles of the post-polarizers 43, 44, 45 are set to α degrees or more, the re-reflected light from the reflection-type light modulation elements 83, 84, 85 becomes light rays having an angle greater than the cone angle, and the projection lens Does not reach the entrance pupil, and does not reach the screen, so that ghost can be reliably prevented.
[0163]
The cone angle corresponds to the F-number of the projection lens. The F-number (i.e., cone angle) varies depending on the specific design, but generally the F-number is 2.8 to 4.0.
[0164]
Here, since the F number is about 7.2 degrees, the F number 2.8 is about 10.3 degrees, and the F number 2 is about 4.5 degrees, the preferable inclination angle is 5 to 15 degrees. Degrees.
[0165]
FIG. 15 is a diagram illustrating a configuration of a projection display device according to a seventh embodiment of the present invention. The projection display device according to the seventh embodiment corresponds to the projection display device according to the fourth embodiment shown in FIG.
[0166]
The seventh embodiment is characterized in that cylindrical lenses 49, 50, 51 are provided between the post polarizers 46, 47, 48 and the cross dichroic prism 81. This corrects the aberration due to the inclination of the post polarizers 46, 47, 48.
[0167]
FIG. 14B is a diagram showing a set of four plates for aberration correction having a function as an alternative to the cylindrical lenses 49, 50, and 51.
[0168]
These plates include a plate 71 having a predetermined angle α with respect to the optical axis, a plate 72 in which the plate 71 is arranged mirror-symmetrically with respect to a plane perpendicular to the optical axis, and a plate obtained by rotating the plates 71 and 72 by 90 ° about the optical axis. 73 and 74.
[0169]
The post polarizers 46, 47, 48 of the present embodiment are arranged at positions corresponding to, for example, the plate 71 with respect to the optical axis.
[0170]
By using one of the four plates 71, 72, 73, 74 as a post-polarizer, the functions of the post-polarizers 46, 47, 48 and the cylindrical lenses 49, 50, 51 can be substituted. .
[0171]
13 to 15, a mounting method of the PBS metal polarizers 43, 44, 45 and the post polarizers 46, 47, 48 will be described below. A common base 52 made of alumina-based ceramic is provided on the upper and lower surfaces of a portion including the cross dichroic prism 81 and the three-color PBS metal polarizing plates 43, 44, and 45.
[0172]
The space surrounded by the metal polarizing plates 43, 44, 45 for PBS, the post polarizers 46, 47, 48, and the reflection type light modulation elements 83, 84, 85 is made a closed structure. There is a method of sealing between members with a flexible member such as rubber. By doing so, the metal grid surface is kept hermetically sealed, and damages due to the metal grid contacting with others, and problems such as contamination due to various causes can be effectively prevented.
[0173]
The metal polarizing plate exerts a polarizing action by the action of the metal grating. However, since some of the light incident on the metal polarizing plate is absorbed by the metal grating, the temperature of the metal polarizing plate rises. Therefore, the metal polarizing plate needs to be appropriately cooled from the viewpoint of securing its reliability and from the viewpoint of eliminating the problem that the imaging performance is deteriorated when the flatness of the metal polarizing plate is deteriorated due to a temperature change. . However, since the metal grating side of the metal polarizing plate constitutes an imaging optical system, direct cooling has the above-mentioned adverse effects. Therefore, it is necessary to air-cool the sealed metal polarizing plate from the substrate side. In FIGS. 12 to 15, the non-metal lattice surfaces of the PBS metal polarizing plates 43, 44, and 45 are cooled by cooling means (not shown) as indicated by an air flow 87 in the drawings. As the cooling means, a sirocco fan or an axial fan can be selected. It is also desirable that the pre-polarizers 40, 41, 42 and the post-polarizers 46, 47, 48 be appropriately cooled.
[0174]
As described in the fifth to seventh embodiments, in a projection display device using the cross dichroic prism 81, a metal polarizing plate (Wire Grid Polarizer) is used instead of a glass polarizing beam splitter. This can contribute to a reduction in the weight of the optical system and an improvement in contrast by removing the influence of the birefringence of the glass.
[0175]
【The invention's effect】
An object of the present invention is to provide a projection display device which can be easily manufactured, has no image blur or ghost, and can display a high-contrast image.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating a configuration of a projection display device according to a first embodiment.
FIG. 2 is a side view showing a shape of a color separation prism in the projection display device.
FIG. 3 is a side view showing a configuration around a color combining prism in the projection display device.
FIG. 4 is a perspective view showing a configuration around a color separation prism and a color synthesis prism in the projection display device.
FIG. 5 is a perspective view showing a configuration of a color separation prism, a color synthesis prism, and a reflection type light modulation element in the projection type display device.
FIG. 6 is a view showing a configuration in which light incident on each polarization beam splitter in the projection type display device is P-polarized light with respect to a reflection surface in the polarization beam splitter, and each reflection type spatial light modulator is provided at a position where light transmitted through the reflection surface is received. FIG. 3 is a perspective view showing a configuration in which the components are arranged.
FIG. 7 is a perspective view showing a configuration in which a plane mirror or a curved mirror is used instead of the deflecting prism in the projection display device.
FIG. 8 is a perspective view showing a configuration for moving and adjusting a field lens in two directions orthogonal to an optical axis in the projection display device.
FIG. 9 is a perspective view illustrating a configuration of a projection display device according to a second embodiment.
FIG. 10 is a perspective view illustrating a configuration of a projection display device according to a third embodiment.
FIG. 11 is a perspective view illustrating a configuration of a projection display device according to a fourth embodiment.
FIG. 12 is a perspective view illustrating a mounting method according to the second to fourth embodiments.
FIG. 13 is a perspective view illustrating a configuration of a projection display apparatus according to a fifth embodiment.
FIG. 14 is a diagram illustrating a configuration of a projection display device according to a sixth embodiment.
FIG. 15 is a diagram illustrating a configuration of a projection display device according to a seventh embodiment.
FIG. 16 is a perspective view showing a configuration of a conventional projection display device provided with an optical system using a so-called “cross dichroic prism”.
FIG. 17 is a side view showing a configuration of a conventional projection display device using a prism having no joint at a screen corresponding portion.
FIG. 18 is a side view showing a configuration of a conventional “color combining optical element composed of three or more prisms”.
[Explanation of symbols]
1 light source
3 Rod integrator
5,6,8 relay lens
7 PS composite element
10 color separation prism
13,14,15 Deflection prism
16,17,18 Polarizing beam splitter
20 color synthesis prism
40, 41, 42 ... pre-polarizer
43,44,45 ... Metal polarizing plate for PBS
46, 47, 48 Post polarizer
53B, 53G, 53R: Field lens
54 G light reflection dichroic mirror
56,57,58 Cross dichroic mirror
59 Condenser lens
60 Polarization converter
65 cold mirror

Claims (5)

A white light source,
A color separation optical system that receives light from the white light source and separates the white light into first to third primary color lights;
Three polarizing beam splitters into which respective primary color lights separated by the color separation optical system are respectively incident;
Three reflective spatial light modulators arranged corresponding to the respective polarizing beam splitters, and polarization-modulating and reflecting light passing through the polarizing beam splitter according to each primary color component of a display image;
A color combining prism that combines the primary color lights that have passed through the three reflective spatial light modulators and the three polarization beam splitters;
A projection optical system that projects the light combined in the color combining prism,
The color combining prism,
A first surface on which the first primary color light is perpendicularly incident, and the first to third primary color lights, which reflect the first primary color light and transmit the second and third primary color lights. A second surface on which a first dichroic film is formed, and a third surface on which the first to third primary color lights are emitted perpendicularly. The first primary color light is 1, the light is totally reflected on the third surface, reflected on the second surface, emitted from the third surface, and the second and third primary color lights are reflected on the second surface. A first prism incident on a surface and exiting from the third surface;
A fourth surface on which the second primary color light is perpendicularly incident, and a second surface that reflects the second primary color light and transmits the third primary color light among the second and third primary color lights. A fifth surface on which the second dichroic film is formed, and a sixth surface in parallel with the second surface of the first prism, through which the second and third primary colors of light are emitted, via an air layer. And the second primary color light is incident on the fourth surface, is totally reflected on the sixth surface, is reflected on the fifth surface, and is emitted from the sixth surface. And the third primary color light is incident on the fifth surface, and is emitted from the sixth surface, a second prism; and a seventh surface on which the third primary color light is vertically incident; An eighth surface, from which the third primary color light is emitted, bonded to a fifth surface of the second prism with an optical adhesive; Enter the face And a third prism that emits light and emits from the eighth surface. The color separation optical system,
A third surface on which the first to third primary color lights are vertically incident, and the first primary color light of the first to third primary color lights is reflected, and second and third primary color lights are reflected. And a second surface on which the first dichroic film is formed, and a first surface for vertically emitting the first primary color light, wherein the first primary color light is 3, the light is reflected by the second surface, is totally reflected by the third surface, emerges from the first surface, and the second and third primary color lights are A first prism that is incident on a surface and exits from the second surface;
A sixth surface, on which the second and third primary color lights are incident, which is opposed to the second surface of the first prism in parallel with an air layer interposed therebetween, among the second and third primary color lights; A fifth surface on which a second dichroic film is formed, which reflects the second primary color light and transmits the third primary color light, and a fourth surface which vertically emits the second primary color light And the second primary color light is incident on the sixth surface, is reflected on the fifth surface, is totally reflected on the sixth surface, and is emitted from the fourth surface. A second prism that is incident on the sixth surface and exits from the fifth surface;
An eighth surface, on which the third primary color light is incident, bonded to a fifth surface of the second prism with an optical adhesive, and a seventh surface, from which the third primary color light is emitted perpendicularly Wherein the third primary color light is a color separation prism composed of a third prism that enters the eighth surface and exits from the seventh surface. The projection display device according to claim 1. 3. The projection according to claim 2, wherein a half-wave plate is arranged on an optical path from the color separation prism to each of the polarization beam splitters, or on an optical path from each of the polarization beam splitters to the color synthesis prism. Type display device. A field lens is arranged between the decomposing prism and the polarizing beam splitter, and the position of light incident on the reflective spatial light modulator is adjusted by displacing the field lens in a direction perpendicular to the principal ray. 4. The projection display device according to claim 2, wherein: A steering prism is arranged between the color separation prism and the polarization beam splitter, and the illumination distribution to the reflective spatial light modulator is adjusted by displacing the steering prism in a direction perpendicular to the principal ray. The projection type display device according to claim 2 or 3, wherein:

Images