JP3686887B2 - Illumination optical system and enlarged projection display device - Google Patents

Description

【００１９】
ρ²＝ｘ²＋ｙ² （２）
ｃ＝１／ｒ （３）
ここで、α_i（ｉ＝１、２、・・・、８）は補正係数、ｋは円錐係数、ｒは反射面の曲率半径である。
【００２０】
上記の拡大投写型ディスプレイ装置において、照明光学系に反射鏡やプリズム等で代表される光路変換素子を備えると拡大投写型ディスプレイ装置の奥行きを小さくできる利点がある。
【００２１】
（作用・原理）
一般に、図１、図２、図３のように主光線８が角度θを持つことで、画像形成素子６への入射光束８ａの主光線８も所定の角度を持つ。特に画像形成素子６にＤＭＤを使用した場合には、図１に示すように、入射光束８ａの主光線８は所定の角度が２方向にわたって大きく傾く。
【００２２】
図７は通常の結像光学系（レンズ系４０）を用いて斜め方向から輝度ムラ低減素子の出射面像を画像形成素子面に導く様子を示す概略図である。図８は図７における照射面での照射状態、即ち、照度分布を示す図で、画像形成素子６の周囲に描かれた等高線のような曲線は等照度曲線である。図７に図示したように、大きく傾いた方向から画像形成素子６に主光線８が入射するとき、輝度ムラ低減素子の出射面３ｂでは光学系の光軸と光線の交点までが等しい出射面３ｂ上の点Ａ、Ｂでも、照射面上では光軸と照射面上の交点の距離Ａ’、Ｂ’が大きく異なってしまう。このようにして発生する倍率の差がキーストーン歪と呼ばれる収差である。この収差が発生すると、照射領域６０と画像形成素子６とが相似形にならず、図８のように照射領域（図８における等照度曲線で囲まれた領域）６０が歪み、光利用効率が低下する。そのため、本発明は照明光学系にアフォーカル光学系を用いてこのキーストーン歪収差を補正し、光利用効率を向上させている。
【００２３】
アフォーカル光学系がキーストーン歪収差を補正できる理由を図９を使用して説明する。
【００２４】
図９は、キーストーン歪補正の基本的な考え方を示す概略図である。図９の光学系では図７で説明した照明光学系（光源と輝度ムラ低減素子は図示省略。輝度ムラ低減素子の出射面３ｂとレンズ系４０のみが描いてある）と照射領域６０との間に、新たに正のパワーを有する光学系（屈折型光学素子）４１を配置している。このとき、正のパワーを有する光学系４１を、主光線８と照射領域６０とのなす角が一定となるように配置すれば、前述の距離Ａ’、Ｂ’を、概略等しくすることができる。
【００２５】
このように、正のパワーを有する光学系４１を配置することによって、キーストーン歪を効果的に補正することができる。正のパワーを有する光学系４１を配置した照明光学系は、前述のように照射領域６０に配置される画像形成素子６へ入射する主光線８と画像形成素子６の法線とのなす角が一定となる。そのため、画像形成素子６の全面にわたって同一方向から入射する光線を投写光学系（図示省略）の方向に出射することができ、特定の方向からのみ光線を受けるような投写光学系により、効率よく光を投写画面、所謂、スクリーン（図示省略）に導くことができる。さらに、平面及び正のパワーを持つ光学系を反射型光学素子とすることによって、光学系全体の占有スペースを小さくできる。しかし単純に屈折型光学素子の替わりに反射型光学素子を配置するだけでは、図１０に示す如く新たな歪みが発生するので工夫を要する。
【００２６】
図１０で示すように、正のパワーを持つ光学系を反射型光学素子４２で構成すると、反射型光学素子４２への入射光線と、画像形成素子６からの出射光線との干渉が起こらないように反射型光学素子４２を配置しなければならない。これは光軸に対して反射型光学素子４２を傾けて配置することを意味する。そのため出射面３ｂで光学系光軸から等距離にある２つの点Ａ、Ｂに対応する主光線は異なる入射高さで反射光学素子４２に入射する。そのため、照射領域６０と光学系光軸との交点から出射面３ｂ上の２点Ａ、Ｂから光学系を通過した照射領域６０上の２点までの距離Ａ’、Ｂ’は異なってしまう。このことが新たな歪みである。
【００２７】
正のパワーを有する光学系を傾けたことに起因する歪を、以下に示す２つの構成を単独あるいは組合せて補正する。第１の構成は、図１１のように、照明光学系のレンズ系４０を複数の互いに回転偏心しているレンズ郡で構成する方法である。このレンズ郡は１枚で回転偏心していてもよい。一部のレンズ郡を正のパワーを持つ光学系４１への主光線入射高がそろうように回転偏心させることで歪を補正できる。
【００２８】
第２の構成は、出射面３ｂをレンズ系４０の光軸に対して正のパワーを持つ光学系と同一の方向に傾ける構成である。このように構成することによって、正のパワーを持つ光学系への入射高さを補正することができ、歪が補正される。さらに、図１１の如く、出射面３ｂからレンズ系に主光線を略平行に入射させる構成を採用すると、照明光学系の構成を簡単にすることができるとともに、フォーカスがさらに向上し照射領域６０とそうでない領域との区別がはっきりする（図４、図５の構成参照）。
【００２９】
上述の説明から本発明の照明光学系は、画像形成素子形状に略相似な照明領域を得ることが可能になるが、ＤＭＤや正反射型の画像形成素子を用いる場合、画像形成素子への入射光と出射光の光路が重なりあうため、光路上に置かれる投写光学系と照明光学系を構成する光学素子が干渉することは明らかである。そのため画像形成素子からの出射光の主光線に所定の角度θ（画像形成素子の法線との成す角）を持たせ、投写光学系を角度つきテレセントリック光学系で構成し、光量ロスを招かないようにするのが望ましい。本発明ではこの角θをθ≧５°として干渉を防止している。
【００３０】
【発明の実施の形態】
（第１の実施の形態）
本発明の照明光学系の一実施形態を図４に示す。図４は画像形成素子６をＤＭＤとして、拡大投写型ディスプレイ装置の照明光学系に本発明の照明光学系を適用した側面図である。拡大投写型ディスプレイ装置は、図４に示す如く、画像形成素子６を照明する照明光学系と、画像形成素子６と、画像形成素子６からの光束をスクリーン（図示省略）に投写する投写レンズ（投写光学系）７とから構成されている。
【００３１】
照明光学系は、光源１と、この光源１からの光束を集光して仮想的な２次光源を作る集光ミラー２と、２次光源の位置に入射端面３ａが位置するように配置されて２次光源からの光束の輝度分布を均一化して出射面３ｂから出射するライトトンネル３（輝度ムラ低減素子）と、ライトトンネル３からの出射光束を画像形成素子６であるＤＭＤに導くアフォーカル光学系とで構成されている。
【００３２】
ライトトンネル３は、画像形成素子形状が四角形なので照明領域が四角になるよう中空四角柱形状のものを用いた。ライトトンネル３の内壁は反射面になっており、ライトトンネル３に入射した光線は内部で数回繰り返し反射・進行することによってライトトンネル出射端での輝度ムラが低減する。ライトトンネル３の替わりに角柱状や円柱状、棒状のレンズ、所謂、ロッドレンズを用いてもライトトンネルと同様の効果が得られる。なお、ライトトンネルやロッドレンズの輪郭形状は画像形成素子形状に合わせればよい。
【００３３】
アフォーカル光学系は第１〜第３のレンズ４ａ〜４ｃと反射ミラー５とから成り、ライトトンネル３の出射面３ｂを物体面としている。反射ミラー５は平面鏡であり、光路を変更するだけの機能しか持たず、アフォーカル光学系に必須の要素ではないから無くてもよい。本実施形態では光路を折り返して装置を小型にする目的で第２のレンズ４ｂと第３のレンズ４ｃの間に設けた。アフォーカル光学系の照射面（像面）には画像形成素子６としてＤＭＤが配置される。
【００３４】
アフォーカル光学系を構成する３つのレンズのうち、第１のレンズ４ａは平凸レンズとし、平面側をライトトンネル３に面するようにして、光源１とライトトンネル３の中心を結ぶ光軸Ｏから上下方向にシフトして第１のレンズ４ａの中心を光軸Ｏ上からずらして配置してある。第２のレンズ４ｂも平凸レンズとし、光軸Ｏから上下左右にシフトすると共に回転偏心させて配置している。第３のレンズ４ｃは凸レンズを使用し、ＤＭＤの中心点の法線から、シフトし回転偏心して設置され、反射ミラー５からの光束をＤＭＤに照射するようになっている。ＤＭＤはアフォーカル光学系の照射面の位置に配置されている。なお、画像形成素子６のＤＭＤ、投写光学系の投写レンズ７は公知のものを用いたので説明は省略する。
【００３５】
図４の構成によれば、光源１より出射された光束は、集光ミラー２に反射して仮想的な２次光源を作る。仮想的な２次光源より出射した光束は、仮想的な２次光源位置に入射端面３ａを配置したライトトンネル３に入射する。ライトトンネル３に入射した光束は、ライトトンネル３の内部で複数回反射を繰り返してライトトンネル３から出射し、第１〜第３のレンズ４ａ〜４ｃを有するアフォーカル光学系に入射する。アフォーカル光学系を通過して出射した光束の主光線は平行になって、アフォーカル光学系の照射面、即ち、画像形成素子６のＤＭＤに至る。ＤＭＤに入射した光束はＤＭＤで反射され、投写レンズ７を経てスクリーン（図示省略）に投写される。このとき、ＤＭＤから投写レンズ７に向かう光束の主光線と照射面の法線との角度を７．７８°に設定してある。
【００３６】
図４に示した照明光学系の各光学素子の具体的な構成をＤＭＤも含めて表１及び図６（ａ）〜（ｃ）に示す。ここで、表１は各光学素子の具体的な位置、向きを数値で表している。図６（ａ）〜（ｃ）は各光学素子の配置を模式的に示す図で、図６（ａ）は上面図、図６（ｂ）は側面図、図６（ｃ）は正面図を示している。
【００３７】
【表１】

【００３８】
表１の面属性欄における面番号１の「出射面」とは輝度ムラ低減素子（この実施形態ではライトトンネル３）の光線出口面（図４、図６における出射面３ｂ）のことである。このライトトンネル３の出射面３ｂの中心点を原初期原点とし、この原点を通り出射面３ｂに垂直な軸をｚ軸、光線が光源１からライトトンネル３に向かう方向をｚ軸の「＋」方向とし、出射面３ｂをｘ−ｙ平面、ｚ軸に直交し、且つ、互いに直交する軸をそれぞれｘ軸、ｙ軸（図４において紙面に垂直な軸がｘ軸、紙面上の軸がｙ軸）とする座標系を初期の座標系（図６参照）とし、面番号順に相対的に次の原点、即ち、光学素子の面の中心座標位置を「座標変換」で表してある。座標系は右手座標系であり、表中のシフト量、回転量における「＋」、「−」の符号は図６（ａ）〜（ｃ）の表示に従う。
【００３９】
表中、面番号「２」〜「４」は第１のレンズ４ａ、面番号「５」〜「１０」は第２のレンズ４ｂ、面番号「１１」〜「１７」は反射ミラー５、面番号「１８」〜「２６」は第３のレンズ４ｃ、面番号「２７」〜「３４」はＤＭＤの各配置位置と向き及び形状をそれぞれ表している。なお、面番号「３２」、「３３」の「平面」は、ＤＭＤ表面に設けたカバーガラスを意味している。
【００４０】
「面間距離」はその面番号の面から次の面までのｚ軸方向の距離（単位はｍｍ）を表している。言い換えれば、面番号の面から次の面まで座標系をｚ軸方向の平行移動した（或いは平行移動させる）距離である。例えば、面番号「１」の面間距離はこの面番号の面（出射面３ｂ）から面番号「３」の平面までのｚ軸に沿った平行移動距離、面番号「３」の面間距離は面番号「３」の平面から面番号「４」の球面までのｚ軸に沿った平行移動距離、面番号「４」の面間距離は面番号「４」の球面から面番号「９」の平面までのｚ軸に沿った平行移動距離を表している。以下の面間距離についても同様である。
【００４１】
シフト量の欄における「ｘ軸方向」、「ｙ軸方向」は光学素子の面の座標原点が、その面の前の面番号で決まった原点の位置からのｘ軸方向、ｙ軸方向へのシフト量（単位はｍｍ）を示している。例えば、第１のレンズ４ａの例では、面番号「１」における出射面の面間距離が５．３ｍｍで、面番号「２」における座標変換のシフト量がｘ軸方向で−２．１８ｍｍ、ｙ軸方向で０．８６ｍｍであるから、ライトトンネル３の出射面３ｂの中心を座標原点とし、出射面３ｂに垂直な軸をｚ軸、出射面３ｂをｘ−ｙ平面、水平方向をｘ軸、垂直方向をｙ軸とした座標系において、出射面３ｂからｚ軸方向に５．３ｍｍ、ｘ軸方向に−２．１８ｍｍ、ｙ軸方向に０．８６ｍｍの位置に第１のレンズ４ａの光線入力面、即ち、面番号「３」の平面の中心があることを表している。また、面番号「３」の面属性が平面、平面の面間距離が１０ｍｍ、面番号４の面属性が球面で、球面の曲率半径が−１２ｍｍであるから、第１のレンズは平凸レンズで、光線入射側の面すなわちライトトンネル３に面した面が平面（面番号の若い方の面を光線入射側としている）、光線出射側が凸面で、平面（面番号「３」）と球面（面番号「４」）の中心間の距離が１０ｍｍであることを表している。
【００４２】
尚、曲率半径を「−」で表記してあるのは、面の属性が座標変換なので、曲率半径自体の定義がないため、「−」で表記してある。仮想面については全て「−」と表記するのが正しい。
【００４３】
回転量欄の「ｘ軸中心」、「ｙ軸中心」、「ｚ軸中心」はそれぞれ光学素子を回転させる時の回転軸を意味している。例えば面番号「１」の場合、ｘ軸中心とｙ軸中心が０、ｚ軸中心が２１．４°であるから、出射面、即ち、ライトトンネル３をｚ軸を回転軸として図６（ｃ）の正面図において反時計回りに２１．４°回転していることを示している。
【００４４】
座標変換は面番号の若い順に、（１）ｚ軸上平行移動（面間距離の移動）、（２）ｘ軸上平行移動（ｘシフト量）、（３）ｙ軸上平行移動（ｙシフト量）（４）ｚ軸中心の回転、（５）ｙ軸中心の回転、（６）ｘ軸中心の回転、の順序で行われる。
【００４５】
この座標変換によれば第２のレンズ４ｂの例では（面番号「５」〜「１０」）、面番号「４」の球面（第１のレンズ４ａの光線出射面）における面間距離が１８ｍｍ、面番号「５」の座標変換におけるシフト量がｘ軸方向が１．３ｍｍ、ｙ軸方向が−０．６ｍｍ、面番号「６」のシフト量がｘ軸方向が０．５ｍｍ、ｙ軸方向が−１ｍｍなので、面番号「９」における平面（第２のレンズ４ｂの光線入力面）の中心（座標原点）は、球面（面番号「４」）の座標系（面番号「１」〜「３」における座標変換を経た後の座標系。座標原点は球面の中心にあり、ｚ軸は球面に垂直。）の原点（球面（面番号「４」））からｚ軸上を１８ｍｍ移動し、ｘ軸方向に１．３ｍｍ、ｙ軸方向に−０．６ｍｍ（面番号「５」）移動した点からさらに、ｘ軸方向に０．５ｍｍ、ｙ軸方向に−１ｍｍ移動（面番号「６」）した位置にある。また、面番号「７」、「８」の座標変換における回転量がｙ軸中心で−５．２°、ｘ軸中心で１１．７°であるから、球面（面番号「４」）の座標系を上記平面（面番号「９」）の座標原点の位置まで原点を平行移動して出来た座標系をｙ軸を回転の中心軸として−５．２°回転し（面番号「７」）、さらにｘ軸を回転の中心軸として１１．７°回転（面番号「８」）した座標系が平面（面番号「９」）の座標系となる。この座標系のｘ−ｙ平面が面番号「９」の平面となり、初期の座標系に対する平面（面番号「９」）の中心位置と傾きが定まる。面番号「１０」の球面（光線出射面）の中心（曲率の中心ではない）は、平面（面番号「９」）における面間距離が１０ｍｍなので、平面（面番号「９」）の座標系においてｚ軸方向に座標原点（平面（面番号「９」）の中心）から１０ｍｍの位置になる。なお、平面（面番号「９」）の座標系のｚ軸が第２のレンズ４ｂの光軸になる。
【００４６】
平面（面番号「９」）の座標系をｚ軸に沿って１０ｍｍ平行移動し、球面（面番号「１０」）の中心に座標原点を移した座標系（球面（面番号「１０」）の座標系）が、次の光学素子、この実施形態では反射ミラー５の位置と向き、即ち、反射ミラー５の座標系を決めるために座標変換を行う出発の座標系となる。
【００４７】
反射ミラー５（面番号「１１」〜「１７」）の例では、面番号「１０」の球面（第２のレンズ４ｂの光線出射面）における面間距離が０ｍｍ、面番号「１１」の座標変換における回転量がｘ軸中心で−１１．７°、面番号「１２」の座標変換における回転量がｙ軸中心で５．２°、面番号「１３」の座標変換におけるシフト量がｘ軸方向が−０．５ｍｍ、ｙ軸方向が１ｍｍなので、取敢ずｚ軸方向の座標原点の移動は行わず、先ず、球面（面番号「１０」）の座標系において、ｘ軸を回転の中心軸として−１１．７°回転し（面番号「１１」）、ｙ軸を回転の中心軸として５．２°回転する（面番号「１２」）。この回転操作の座標変換により得られた座標系の各座標軸は初期の座標系の対応する各座標軸に平行な座標系になる。この後、この座標系（面番号「１１」、「１２」の回転操作により座標変換した座標系）において、座標原点（球面（面番号「１０」の中心にある）をｘ軸方向に−０．５ｍｍ、ｙ軸方向に１ｍｍ（面番号「１３」）平行移動して出来た座標系を仮想面（面番号「１７」）の座標系とし、この座標系のｘ−ｙ平面を仮想面（面番号「１７」）に設定する。座標原点は仮想面（面番号「１７」）の中心となる。
【００４８】
仮想面（面番号「１７」）における面間距離が４０ｍｍ、面番号「１５」の座標変換における回転量がｙ軸中心で−３４°、面番号「１６」の座標変換における回転量がｘ軸中心で１５°であるから、仮想面の座標系において、座標原点をｚ軸上で４０ｍｍ移動して座標系を平行移動した後、座標軸をｙ軸を回転中心軸として−３４°、ｘ軸を回転中心軸として１５°順次回転して得られた座標系が反射ミラー５の座標系となる。この座標系のｘ−ｙ平面が反射ミラー５の反射面、座標原点が反射ミラー５の中心であり、反射ミラー５の位置と向きが定まる。
【００４９】
以上、第２のレンズ４ｂと反射ミラー５を例に、表１の座標変換について説明したが、他の光学素子の面についても表１の表記に従って上記と同様にして座標変換すればよい。
【００５０】
本実施形態で得られた画像形成素子上の照明状態を図１２、図１３（ａ）（図１２と同一の図である）に示す。また、画像形成素子上の照度分布を図１３（ｂ）に示す。図１２に示すように、画像形成素子サイス゛と照射領域６０をほぼ同一にすることができ、歪みのない均一な照度分布が得られた。なお、図１２、図１３（ａ）における画像形成素子周辺の曲線は等照度曲線を示している。
【００５１】
図１３（ｂ）は、画像形成素子上における図１３（ａ）で示すＡ−Ａ、Ｂ−Ｂ上の照度分布を示す図である。図中、縦軸は照度、横軸は画像形成素子上の位置を示し、曲線１３ａはＡ−Ａ上の照度分布を示す曲線、曲線１３ｂはＢ−Ｂ上の照度分布を示す曲線である。図１３（ｂ）によれば、画像形成素子は均一な照度で照明されていることが分かる。
【００５２】
（第２の実施の形態）
本発明の照明光学系の第２の実施形態を図５に示す。図５は画像形成素子６をＤＭＤとして、拡大投写型ディスプレイ装置の照明光学系に本発明の照明光学系を適用した側面図である。拡大投写型ディスプレイ装置は、図５に示す如く、画像形成素子６を照明する照明光学系と、画像形成素子６と、画像形成素子６からの光束をスクリーン（図示省略）に投写する投写レンズ７、所謂、屈折型結像光学系の投写光学系とから成る。照明光学系は、光源１と、この光源１からの光束を集光して仮想的な２次光源を作る集光ミラー２と、仮想的な２次光源の位置に入射面３ａが位置するように配置されて仮想的な２次光源からの光束の輝度分布を均一化して出射面３ｂから出射するライトトンネル３（輝度ムラ低減素子）と、ライトトンネル３からの出射光束を画像形成素子６であるＤＭＤに導くアフォーカル光学系とで構成されている。
【００５３】
照明光学系に用いたアフォーカル光学系は、図５に示すように、第１のレンズ４ａと第２のレンズ４ｂの２つの屈折型光学素子および反射ミラー５で構成している。反射ミラー５は第１の実施形態の場合と同様、平面鏡であり、光路を変更するだけの機能しか持たず、アフォーカル光学系に必須の要素ではないから無くてもよい。本実施形態では光路を折り返して装置を小型にする目的で第１のレンズ４ａと第５のレンズ４ｂの間に設けた。アフォーカル光学系の照射面には画像形成素子６としてＤＭＤが配置される。この実施形態においては、θは７．８°であり、画像形成素子上の照明状態は図１４のように、画像形成素子サイス゛と照射領域をほぼ同一にすることができ、歪みのない均一な照度分布が得られた。なお、図１４における画像形成素子周辺の曲線は等照度曲線を示している。
【００５４】
図５に示した照明光学系の各光学素子の具体的な構成はＤＭＤも含めて表２に示す。
【００５５】
【表２】

【００５６】
表２の面属性欄における面番号１の「出射面」は、第１実施形態の場合と同様、輝度ムラ低減素子（ライトトンネル３）の光線出口面（出射面３ｂ）のことである。また、このライトトンネル３の出射面３ｂの中心点を原初期原点として初期の座標系を設定するのも第１実施形態の場合と同様である。
【００５７】
表中、面番号「２」〜「４」は第１のレンズ４ａ、面番号「５」〜「８」は反射ミラー５、面番号「９」〜「１７」は第２のレンズ４ｂ、面番号「１８」〜「２５」はＤＭＤの各配置位置と向き及び形状をそれぞれ表している。なお、面番号「２３」、「２４」の平面は、ＤＭＤ表面に設けたカバーガラスを意味している。
【００５８】
（第３の実施の形態）
本発明の照明光学系を用いた拡大投写型ディスプレイ装置の第３の実施形態を図１５に示す。本実施形態は、アフォーカル光学系に１枚の正のパワーを持つ反射ミラーを用いた構成例である。この拡大投写型ディスプレイ装置は、図１５に示す如く、画像形成素子６を照明する照明光学系と、画像形成素子６と、画像形成素子６からの光束をスクリーン（図示省略）に投写する投写レンズ７とから成る。照明光学系は、光源１と、この光源１からの光束を集光して仮想的な２次光源を作る集光ミラー２と、仮想的な２次光源の位置に入射面３ａが位置するように配置されて仮想的な２次光源からの光束の輝度分布を均一化して出射面３ｂから出射するライトトンネル３（輝度ムラ低減素子）と、ライトトンネル３からの出射光束を画像形成素子６であるＤＭＤに導くアフォーカル光学系とで構成されている。
【００５９】
照明光学系に用いたアフォーカル光学系は、図１５に示すように、第１のレンズ４ａと第２のレンズ４ｂの２つの屈折型光学素子および正のパワーを持つ反射ミラー４ｄと光路折り曲げ用の反射ミラー５で構成している。反射ミラー５は凸面鏡を用いた。アフォーカル光学系の照射面には画像形成素子６としてＤＭＤが配置される。この実施形態においては、θは７．８°であり、画像形成素子上の照明状態は図１６のように、画像形成素子サイス゛と照射領域をほぼ同一にすることができ、歪みのない均一な照度分布が得られた。なお、図１６における画像形成素子周辺の曲線は等照度曲線を示している。なる。
【００６０】
図１５に示した照明光学系の各光学素子の具体的な構成をＤＭＤも含めて表３に示す。
【００６１】
【表３】

【００６２】
表３の面属性欄における面番号１の「出射面」は、第１実施形態の場合と同様、輝度ムラ低減素子（ライトトンネル３）の光線出口面（出射面３ｂ）のことである。また、このライトトンネル３の出射面３ｂの中心点を原初期原点として初期の座標系を設定するのも第１実施形態の場合と同様である。
【００６３】
表中、面番号「２」〜「４」は第１のレンズ４ａ、面番号「５」〜「９」は第２のレンズ４ｂ、面番号「１０」〜「１５」は反射ミラー５、面番号「１６」〜「２３」は正のパワーを持つ反射光学素子４ｄ、面番号「２４」〜「３１」はＤＭＤの各配置位置と向き及び形状をそれぞれ表している。なお、面番号「２９」、「３０」の平面は、ＤＭＤ表面に設けたカバーガラスを意味している。
【００６４】
（第４の実施の形態）
本実施の形態は、照明光学系に非球面光学素子を含む拡大投写型ディスプレイ装置の例である。この拡大投写型ディスプレイ装置は、画像形成素子を照明する照明光学系と、画像形成素子と、画像形成素子からの光束をスクリーンに投写する投写レンズとから成るのは上記３つの実施形態と同じである。本実施形態の拡大投写型ディスプレイ装置は、図１５において、反射ミラー５を非球面反射ミラーに替えた構成になっていて、この他は第３実施形態と同じ構成である。この装置における照明光学系の各光学素子の具体的な構成をＤＭＤも含めて表４に示す。画像形成素子上の照明状態は図１７のようになった。
【００６５】
【表４】

【００６６】
尚、表４における面番号１６のシリンダーとはかまぼこ形状のことで、面番号１６の面はｙ−ｚ平面（面番号１６の面の座標系）に平行な任意の面で切った断面が非球面を表す式を満足しているということである。また、非球面とは通常の非球面の式（上記「課題を解決するための手段」の欄に記載の式（１）〜（３））で表記される面のことである。
【００６７】
表の見方は上記３つの実施形態と同じである。表中、面番号「２」〜「４」は第１のレンズ４ａ、面番号「５」〜「９」は第２のレンズ４ｂ、面番号「１０」〜「１６」は非球面反射ミラー、面番号「１６」〜「２５」は正のパワーを持つ反射光学素子４ｄ、面番号「２６」〜「３３」はＤＭＤの各配置位置と向き及び形状をそれぞれ表している。なお、面番号「３１」、「３２」の平面は、ＤＭＤ表面に設けたカバーガラスを意味している。
【００６８】
この実施形態では反射ミラーを非球面光学素子としたが、反射ミラーに限らず、非球面光学素子に非球面レンズを用いてもよい。
【００６９】
（第５の実施の形態）
本実施の形態は、投写光学系に工夫を加えて投写画像の照度ムラを低減した拡大投写型ディスプレイ装置の例である。
【００７０】
拡大投写型ディスプレイ装置は、画像形成素子を照明する照明光学系と、画像形成素子と、画像形成素子からの光束をスクリーンに投写する投写光学系とから成るのは上記の実施形態と同じである。照明光学系が、光源と、この光源からの光束を集光して仮想的な２次光源を作る集光ミラー仮想的な２次光源の位置に入射端面が位置するように配置されて仮想的な２次光源からの光束の輝度分布を均一化して出射面から出射するライトトンネル（輝度ムラ低減素子）と、ライトトンネルからの出射光束を画像形成素子であるＤＭＤに導くアフォーカル光学系とで構成されているのも上記４つの実施形態と同じである。本実施形態においては、図４に示す構成の照明光学系、即ち、第１の実施形態と同じ照明光学系を用いた。
【００７１】
投写光学系はテレセントリックな屈折型結像光学系（投写レンズ）を用い、この屈折型結像光学系中に用いられている絞りの中心を、屈折型結像光学系の光軸（図１８のＬ１）から偏心（図１８中、偏心量ｈ）させた構成になっている。かかる構成によって、投写画像の照度ムラが低減され、高輝度の投写画像が得られる。この投写光学系の具体例を図１８に示す。
【００７２】
図１８に示すように、投写レンズは、スクリーン側から順に第１レンズ群Ｇ１〜第４レンズ群Ｇ４から成る計１４枚のレンズと平行平面ガラスＧ５とから構成されている。第２レンズ群Ｇ２と第３レンズ群Ｇ３の間に絞りＳが設けられている。この絞りの中心は投写レンズの光軸Ｌ１からｈだけ偏心している。投写レンズを構成するレンズ群Ｇ１〜Ｇ４における各レンズのデータは表５に示す通りである。
【００７３】
【表５】

【００７４】
なお、表中では、最もスクリーンに近い屈折面から順に面番号ｉを付しており、ｄ線（波長５８７．６ｎｍ）に対する屈折率が示された番号の屈折面とその次の屈折面とによって１つの光学要素が構成される。面間隔ｄ（単位ｍｍ）は対応する番号の屈折面と次の屈折面とのレンズ厚み若しくは空気間隔を示している。なお、最終面の面間隔は平行平面ガラスから画像形成素子までの距離である。
【００７５】
第１レンズ群Ｇ１は、スクリーン側に凸面を向けた凸メニスカスレンズＧ１１、画像形成素子側に凹面を向けた凹メニスカスレンズＧ１２、凹レンズＧ１３の計３枚のレンズで構成されている。第２レンズ群Ｇ２は、画像形成素子側に凸面を向けた凸メニスカスレンズＧ２１とスクリーン側に凹面を向けた凹メニスカスレンズＧ２２の接合レンズと、凸レンズＧ２３とで構成されている。第３レンズ群Ｇ３は、凹レンズＧ３１と凸レンズＧ３２の接合レンズで構成されている。第４レンズ群Ｇ４は、凹レンズＧ４１、画像形成素子側に凸面を向けた凸メニスカスレンズＧ４２、凹レンズＧ４３と凸レンズＧ４４の接合レンズ、画像形成素子側に凸面を向けた凸メニスカスレンズＧ４５と凸レンズＧ４６で構成されている。凹レンズＧ４３と凸レンズＧ４４の接合レンズはその凹面をスクリーン側に向けて配置されている。
【００７６】
投写レンズは、フォーカス時に面番号６における面間隔ｄ６が変化して第１レンズ群Ｇ１が光軸Ｌ１に沿ってスクリーン側と画像形成素子側とに進退する。第１レンズ群Ｇ１以外の他のレンズ群Ｇ２〜Ｇ４は固定されている。変倍時においては、面番号１１、１５における面間隔ｄ１１、ｄ１５が変化して第２レンズ群Ｇ２、絞りＳ１、第３レンズ群Ｇ３が光軸Ｌ１に沿って移動する。絞りＳは光軸Ｌ１に対して垂直方向に偏心しており、絞りＳの開口中心から光軸Ｌ１までの距離ｈを絞り偏心量として示している。投写距離を無限遠とした時の広角端、標準、望遠端における全系の焦点距離、ｆナンバー、可変面間隔を表６に示す。
【００７７】
【表６】

【００７８】
投写距離無限遠時のレンズ系全長Ｌ、絞り偏心量ｈ１、各レンズ群Ｇ１〜Ｇ４の焦点距離ｆ１〜ｆ４、広角端における全系の合成焦点距離ｆｗはそれぞれ
Ｌ＝１３９．５ｍｍ
ｈ＝４．５ｍｍ
ｆ１＝−３４．９７ｍｍ
ｆ２＝３７．２４ｍｍ
ｆ３＝１２５．９１ｍｍ
ｆ４＝４９．０３ｍｍ
ｆｗ＝２８．５８ｍｍ
である。
【００７９】
上記第１〜第５の実施形態では投写光学系として投写レンズ（屈折型結像光学系）を用いたが、この投写レンズに替えて１枚或いは複数枚の反射ミラーで構成した反射型結像光学系で投写光学系を構成してもよい。また、上記何れの実施の形態も画像形成素子６にＤＭＤを用いた例であるが、例えば反射型液晶ライトバルブ、透過型液晶ライトバルブ等、ＤＭＤ以外の画像形成素子を用いて拡大投写型ディスプレイ装置を構成しても上記実施形態と同様の効果が得られる。
【００８０】
（第６の実施の形態）
本発明の照明光学系を用いた拡大投写型ディスプレイ装置の第６の実施形態を図１９に示す。本実施形態は、投写光学系に反射型結像光学系を用いた例である。
【００８１】
図１９に示す如く、拡大投写型ディスプレイ装置は、画像形成素子６と、画像形成素子６を照明する照明光学系１１と、画像形成素子６からの出射光束をスクリーン（図示省略）に投写する投写光学系とから成る。画像形成素子６と照明光学系１１は第１の実施形態と同じものを用い、同じ配置になっている。
【００８２】
投写光学系は４枚の反射鏡から成るテレセントリック反射型結像光学系から成る。投写光学系を構成するテレセントリックな反射型結像光学系は、回転対称非球面形状の凹面状反射面を有する第１の反射鏡７ａと、第１の反射鏡からの光束に反射面を向けた回転対称非球面形状の凸面状反射面を有する第２の反射鏡７ｂと、第２の反射鏡からの光束に反射面を向けた回転対称非球面形状の凹面状反射面を有する第３の反射鏡７ｃと、第３の反射鏡からの光束に反射面を向けた回転対称非球面形状の凸面状反射面を有する第４の反射鏡７ｄの４つの反射鏡から構成され、反射鏡７ａ、７ｂ、７ｃ、７ｄで順次反射された光束の光路がジグザグになるように反射鏡が配置されて、第４の反射鏡７ｄで反射された光束が投写スクリーン（図示省略）に拡大投写される構成のテレセントリックな反射型結像光学系である。この反射型結像光学系の結像面にはＤＭＤで構成された反射型の画像形成素子６が配置されている。
【００８３】
反射鏡７ａ〜７ｄの反射面形状（回転対称非球面形状）は、図２０に示すように、光軸をｚ軸、ｚ軸に垂直な平面をｘ−ｙ平面（図中４つの頂点Ａ、Ｂ、Ｃ、Ｄが張る平面）、ｚ軸とｘ−ｙ平面との交点を原点Ｏ、原点Ｏで交わりｘ−ｙ平面上の互いに直交する軸をｘ軸、ｙ軸に座標軸を設定すると、下記の（１）式〜（３）式を満足する形状になっている。

【００８４】
ρ²＝ｘ²＋ｙ² （２）
ｃ＝１／ｒ （３）
ここで、α_i（ｉ＝１、２、・・・、８）は補正係数、ｒは反射面の曲率半径、ｋは円錐係数である。
【００８５】
上記の式を満足する反射面形状を持つ反射鏡はｚ軸が中心を通る曲面α（図２０における点ａ、ｂ、ｃ、ｄが張る曲面）を反射面とした反射鏡でも、或いは、ｚ軸が中心を通らない、所謂オフセット型の曲面β（図２０における点ａ’、ｂ’、ｃ’、ｄ’が張る曲面）を反射面とした反射鏡でもよい。本実施の形態ではオフセット型を採用している。
【００８６】
各反射鏡間の空間的位置関係は、反射面形状を定める各反射鏡の座標系の原点が同一平面上にあるように配置するが、反射面形状とは異なり、単純な関係式で表現するのが難しいので、反射面形状を定める上記の（１）式〜（３）式と画像形成素子６への主光線の入射角、画像形成素子６から出射する光束の開き角や光学系の空間的大きさの制限、反射型結像光学系と組み合わせる画像形成素子６（液晶表示素子やＤＭＤ等）の種類とサイズ、画面投写位置等の設計仕様を基に、公知の光線追跡シミュレーションにより反射面形状と共に反射鏡７ａ〜７ｄの配置位置を決定する。この時、反射型結像光学系の光軸（図２２のＡ−Ａ軸、即ちＺ軸）とスクリーン（図２２参照）到達光線の角度、所謂、半画角が４０°以上９０°未満で、且つ、画像形成素子６から反射型結像光学系（投写光学系）への主光線角度θ（画像形成素子６から出射する主光線と画像形成素子の法線との成す角度（図１参照））を５°以上にする。主光線角度が５°以下の場合、画像形成素子６から反射型結像光学系への光線と照明光学系が干渉して光線のケラレが発生するので、主光線角度θを５°以下とするのは望ましくない。主光線角度θの上限は特にないが、反射型結像光学系を組み込む拡大投写型ディスプレイ装置の大きさによって上限は決まる。反射鏡間の上下方向の間隔が広がりすぎずにコンパクトにおさめ、小型化を図るためには、主光線角度の上限を２０°前後にとどめるのがよい。
【００８７】
光線追跡シミュレーションにより各反射鏡間の空間的位置関係を求める手順は、図２１に示すように、先ず、画角、画面サイズ、光学系の空間的大きさ、画像形成素子の種類と大きさ、画面投写位置等の設計仕様を定める（ステップＳ１）。次いで、設計仕様に基づいて、光学系の種類（テレセントリック系か否かを決める。本発明ではテレセントリック系を選択）、反射鏡数（本実施形態では４枚）、光軸シフト量等、設計構想を決める（ステップＳ２）。ステップＳ１、ステップＳ２の情報を基に、絞り位置、反射鏡の空間的配置の概略（各反射鏡が相互に干渉して反射光線の一部が遮蔽されることがないように配置）、反射鏡の形状決定方程式（本発明は上記（１）式〜（３）式を用いる）、光線追跡に必要な光学系要素の初期値等の初期データを作成する（ステップＳ３）。初期データを基に光線追跡シミュレーションを行い、各反射鏡の大きさ、空間的位置、傾き角度等を決定する。なお、光線追跡シミュレーションに当たっては、公知の方法を用いた。本発明者は市販の光学系設計ソフトウェアを用いて光線追跡シミュレーションを行った。光線追跡シミュレーションにおいては、先ず、光線追跡により（１）式〜（３）式におけるｘ、ｙの取り得る範囲、α_i、ｒ、ｋをはじめとし、各反射鏡の大きさ、空間的位置、傾き角度等を決めるパラメータの値を算出する（ステップＳ４）。このステップＳ４の結果を基にＭＴＦ、公差、湾曲、収差、反射鏡の有効光束マージン等の性能評価を行い（ステップＳ５）、評価結果が設計仕様を満足するまでパラメータの算出・性能評価を繰り返し、反射鏡の形状と空間位置を決定する。
【００８８】
上記の手順に基づいて４枚の各反射面形状を最適化することにより、テレセントリック光学系における広画角化及び小型化に好適な反射鏡形状を得る。得られた結果の一例を図２２及び表７に示す。また、投写光学系を最適化された回転対称非球面形状の反射鏡から成るテレセントリックな反射結像光学系で構成することによって、広い画角が実現され、且つ、各反射鏡の間隔も小さくなり、装置の小型化が可能になる。さらに、反射結像光学系を構成する反射鏡が回転対称非球面形状の場合、加工がしやすく、樹脂化に対応でき、安価な反射型結像光学系に実現が可能となる。
【００８９】
【表７】

【００９０】
図２２は反射鏡の配置を示す概略図、表７は反射鏡及びその配置を示す各パラメータの具体的な数値を示す表である。
【００９１】
図２２において、画像形成素子６と４枚の反射鏡７ａ〜７ｄとから成る光学系の座標系（座標軸を大文字で表す）は画像形成素子６の光軸Ａ−ＡをＺ軸、Ｚ軸に交わり紙面に垂直な軸をＸ軸、Ｚ軸と垂直に交わり紙面に平行な軸（紙面上の軸）をＹ軸とし、図の右方向をＺ軸の正の方向、左方向をＺ軸の負の方向、図の上方をＹ軸の正の方向、図の下方、Ｚ軸より下をＹ軸の負の方向、紙面表面から裏面に向かう方向をＸ軸の正の方向に設定し、紙面がＹ−Ｚ平面になっている。座標原点は何処に設定してもよいが、便宜上Ｚ軸と画像形成素子６の交点を座標原点としている。
【００９２】
表７の「Ｎｏ」は反射鏡７ａ〜７ｄ及び画像形成素子６を識別するための番号を示しており、「０」は画像形成素子６を、「１」は第１の反射鏡７ａを、「２」は第２の反射鏡７ｂを、「３」は第３の反射鏡７ｃを、「４」は第４の反射鏡７ｄを表している。「ｄｊ」は反射鏡間の距離を表しており、画像形成素子の欄、即ち、Ｎｏ．０の欄のｄｊは図２２に示したｄ０を表し、画像形成素子６から第１の反射鏡７ａまでの距離を示している。同様にして、Ｎｏ．１の欄、即ち、第１の反射鏡の欄のｄｊは図２２に示したｄ１を表し、第１の反射鏡７ａから第２の反射鏡７ｂまでの距離を示している。以下、同様である。Ｎｏ．４の欄（第４の反射鏡の欄）のｄｊ、即ち、ｄ４は第４の反射鏡７ｄからスクリーン９までの距離を示している。
【００９３】
図２２、表７における各パラメータ、即ち、反射鏡７ａ〜７ｄの曲率半径ｒ、画像形成素子６と第１の反射鏡７ａとの距離ｄ０、反射鏡間の距離ｄ１〜ｄ３、第４の反射鏡７ｄからスクリーン９までの距離ｄ４、及びＺ軸（画像形成素子の光軸Ａ−Ａ）から反射鏡７ａ〜７ｄの座標原点（反射鏡面形状を定義する座標原点、即ち反射鏡面形状を計算する際の座標の原点）までの距離Ｘ、Ｙの単位は「ｍｍ」である。反射鏡７ａ〜７ｄの回転角ａの単位は「度」で、反射鏡の反射面形状を定義する座標系（座標軸は小文字で表す）の座標軸ｘ、ｙ、ｚが光学系の座標軸Ｘ、Ｙ、Ｚに平行な状態（ｙ軸がＺ軸（光軸Ａ−Ａ）に垂直な状態）を基準にしてｘ軸を回転軸として図中右回り（時計回り）回転を「＋」、左回り（反時計回り）回転を「−」とした。上記以外の各パラメータ（円錐係数ｋ、補正係数α１〜α７）は無名数である。距離ｄｊ（ｊ＝０〜４、即ち、図中のｄ０、ｄ１、ｄ２、ｄ３、ｄ４）は、各反射面形状を定義する座標の原点間を光軸Ａ−Ａ（Ｚ軸）に平行に測った距離、即ち、各反射面形状を定義する各座標の原点のＺ座標間の間隔、Ｘは各反射面形状を定義する座標の原点を光軸Ａ−Ａ（Ｚ軸）からＸ軸方向に光軸Ａ−Ａ（Ｚ軸）に垂直に測った距離、Ｙは各反射鏡面形状を定義する座標の原点を光軸Ａ−Ａ（Ｚ軸）からＹ軸方向に光軸Ａ−Ａ（Ｚ軸）に垂直に測った距離である。図２２の例では、反射鏡はオフセット型としたのでその反射鏡の座標原点は反射鏡の中心からずれた位置にあり、距離ｄｊ（ｊ＝０〜４）は、各反射鏡面形状を定義する各座標の原点の相対的なＺ座標が分かればよい（Ｘ座標とＹ座標は不要）ので、図では各反射鏡面形状を定義する各座標の座標原点のＺ座標の位置は示しているが、Ｘ座標、Ｙ座標の位置は明示していない。反射鏡３ｄは左回転させたものであるが、オフセット型の反射鏡面形状の関係で見かけ上右回転したように描かれている。反射鏡の大きさは任意で、上記の反射鏡位置関係において光線が遮られないように大きさを設定すればよい。
【００９４】
図１９において、光源より発せられた光束は照明光学系１１の照射面（反射型結像光学系の結像面でもある）に配置された画像形成素子６に入射し、画像に応じた光強度分布に空間変調されて反射して反射型結像光学系に入射する。反射型結像光学系に入射した光束は、第１の反射鏡７ａ、第２の反射鏡７ｂ、第３の反射鏡７ｃ、第４の反射鏡７ｄで順次反射・拡大され、第４の反射鏡で反射された光束は投写スクリーン（図示省略）上に拡大投影される。このときの投写画像の投影画角は１４０°以上の広画角であった。
【００９５】
反射型結像光学系はテレセントリックな光学系で、主光線は画像形成素子６の法線に対し図２３に示すように所定の角度θを持つ。光束の主光線８に対する光束の開き角ψ（通常、ＮＡ及びＦＮＯに相当する）を持った光束が画像形成素子６に入射し、反射するときに画像形成素子６の法線に対して主光線が角度θを持つことで照明部の光学部品との干渉をなくし、ケラレ等発生させることなく光学系を構成することが出来る。また照明光学系をアフォーカル光学系にすることにより照射面での歪をなくし、照明効率も向上する。しかも画像形成素子が透過型でも反射型でも同一の反射型結像光学系で拡大投写型ディスプレイ装置等のディスプレイ装置を構成できる。
【００９６】
反射型結像光学系では光束が主光線角度θを持つことにより、一般的には投影画面の下側が狭くなり、上側は広がるといった扇形の歪曲収差が必然的に発生する。しかも広画角化にともなってそれはより顕著となる。本実施形態は回転対称非球面形状を持つ反射鏡４枚の構成で歪曲収差を良好にし、各光学部品が比較的大きくなり、高価になるというテレセントリック光学系の欠点を、回転対称非球面形状の反射鏡を使用することで各反射鏡の加工上の精度を緩和し、比較的大型の反射鏡でもプラスチック化を可能にして反射鏡の樹脂化によりコスト低減を実現した。また、反射面が回転対称非球面形状であるため各反射鏡間隔を１５０ｍｍ以下と小さくでき、装置がコンパクトになった。
【００９７】
拡大投写型ディスプレイ装置に適用した場合はその光源からの熱影響を考慮する必要がある。そのため、特に図１９における反射鏡７ｂにおいては、画像形成素子６の近くに配置されるので熱の影響を受け易いから画像歪を抑制する上でその材質の線膨張係数αを
α＜６×１０^-5
に抑えることが望ましい。
【００９８】
（第７の実施の形態）
本発明の照明光学系を用いてスクリーンと一体化した背面投写型のディスプレイ装置を構成した例を図２４に示す。図２４の背面投写型ディスプレイ装置は、照明光学系１１と、透過型画像形成素子６ａと、反射型結像光学系７０から成る投写光学系と、平面反射鏡１２ａ、１２ｂと、透過型スクリーン９とから構成されている。照明光学系１１と透過型画像形成素子６ａおよび反射型結像光学系７０の第１の反射鏡７ａは一直線上にあり、反射型結像光学系７０の結像面（照明光学系の像面でもある）に透過型画像形成素子６ａが配置されている。照明光学系１１は第１の実施形態のものと同じ照明光学系である。また、投写光学系を構成する反射型結像光学系７０は第６の実施形態のものと同じテレセントリックな反射型結像光学系を用いた。
【００９９】
照明光学系１１の光源より発せられた光束は透過型液晶ライトバルブに代表される透過型画像形成素子６ａに入射する。透過型画像形成素子６ａを透過した光束はその主光線に対する開き角を持ったままテレセントリックな反射型結像光学系７０から成る投写光学系に入射する。反射型結像光学系７０は図１９に示した回転対称非球面形状を持つ４枚の反射鏡７ａ〜７ｄで構成されて、反射型結像光学系７０から出射した光束は、照度が均一で広画角になっている。反射型結像光学系７０を出射した光束は、反射型結像光学系７０の出射側の反射鏡３ｄに対向して反射面を垂直に配置した平面反射鏡１２ａと、平面反射鏡１２ａの上方に反射面を下に向けて反射面を水平に配置（平面反射鏡１２ａに垂直に配置）した平面反射鏡１２ｂとで順次反射し、平面反射鏡１２ａに平行に配置した透過型スクリーン９に拡大投射される。
【０１００】
図２４に示すように、反射型結像光学系７０に対して透過型スクリーン９および平面反射鏡１２ａ、１２ｂを配置すると、空間的に少ないスペースでスクリーン９に拡大投射できる。特に、平面反射鏡１２ｂを画像形成素子６ａの法線に対して平行に配置・構成することにより、透過型スクリーン９を観察する観察者の視界より装置全体を見えなくすることができる。また、照明光学系１１は、図４に示すように、光路折り返し用の反射ミラーを有するものを用いており、ディスプレイ装置の奥行きを小さくできる利点がある。
【０１０１】
上記第６、第７の実施の形態は反射型結像光学系７０の第３の反射鏡７ｃに回転対称非球面形状の凹面鏡を用いた例であるが、第３の反射鏡７ｃを回転対称非球面形状の凸面鏡としても回転対称非球面形状の凹面鏡の場合と同様の効果が得られる。また、第６、第７の実施の形態は投写光学系にテレセントリックな反射結像光学系を用いたが、テレセントリックな反射結像光学系に替えて通常の反射光学系、例えば、極端な例だが、反射鏡１枚、或いは、複数枚で光路を折り返すように構成してもよい。
【０１０２】
【発明の効果】
本発明は、照明光学系に、正のパワーを有する最終段の結像光学素子を含む２以上の光学素子によって構成され、それら２以上の光学素子の少なくとも一つが輝度ムラ低減手段の光軸に対して回転偏心して配置されているアフォーカル光学系を含むことによって、キーストーン歪や、光路折り返し用の反射光学素子を用いたことによる歪の発生を抑制でき、画像形成素子サイズと照射領域をほぼ同一にできた。また、輝度ムラ低減素子の出射面の輝度分布を保ったまま高い照度で均一な照度分布の矩形照射領域を形成でき、光利用効率が向上した。さらに、アフォーカル光学系を構成する光学素子に、光路を折り返す機能とアファーカル光学系を構成する機能とを兼ね備えた１つの反射型光学素子を用いれば、装置全体の小型化が可能になる。
【０１０３】
画像形成素子の任意の点から出射する光束の主光線と、画像形成素子の法線とのなす角度θ（図１、２、３参照）が５°以上となる入射角度で画像形成素子に光を入射させることで、照明光学系と投写光学系の干渉を無くすことができた。
【図面の簡単な説明】
【図１】 ＤＭＤから成る画像形成素子に入・出射する光束及び主光線の様子を示す図。
【図２】 正反射型画像形成素子に入・出射する光束及び主光線の様子を示す図。
【図３】 透過型画像形成素子に入・出射する光束及び主光線の様子を示す図。
【図４】 第１の実施形態の斜視図。
【図５】 第２の実施形態の斜視図。
【図６】 光学素子の配置と座標軸の関係を模式的に示す図。
【図７】 従来の照明光学系により斜め方向から画像形成素子を照射する様子を示す概略図。
【図８】 従来の照明光学系による画像形成素子上の照明状態を示す図。
【図９】 キーストーン歪補正の基本的な考え方を示す概略図。
【図１０】 正のパワーを持つ反射型光学素子を用いた時に歪が発生する様子を示す図。
【図１１】 歪補正の基本的な考え方を示す概略図。
【図１２】 第１の実施形態における画像形成素子上の照明状態を示す図。
【図１３】 第１の実施形態における画像形成素子上の照度分布を示す図。
【図１４】 第２の実施形態における画像形成素子上の照明状態を示す図。
【図１５】 第３の実施形態の斜視図。
【図１６】 第３の実施形態における画像形成素子上の照明状態を示す図。
【図１７】 第４の実施形態における画像形成素子上の照明状態を示す図。
【図１８】 第５の実施形態で用いた投写光学系の概略図。
【図１９】 第６の実施形態の概略図。
【図２０】 第６の実施形態の投写光学系で用いた反射鏡の形状と座標軸との関係を示す図。
【図２１】 反射鏡形状と配置を決定する手順を示す流れ図。
【図２２】 各反射鏡の位置関係及び反射面形状の各パラメータを示す図。
【図２３】 画像形成素子と反射型結像光学系の部分拡大図。
【図２４】 第７の実施形態の概略図。
【符号の説明】
１ 光源
２ 集光ミラー
３ ライトトンネル（輝度ムラ低減素子）
３ａ 入射端面
３ｂ 出射面
４ａ 第１のレンズ
４ｂ 第２のレンズ
４ｃ 第３のレンズ
４ｄ 正のパワーを持つ反射光学素子
４０ レンズ系
４１ 正のパワーを持つ光学系
４２ 正のパワーを持つ反射型光学素子
５ 反射ミラー
６ 画像形成素子
６ａ 透過型画像形成素子
６０ 照射領域
７ 投写レンズ
７ａ 第１の反射鏡（凹面鏡）
７ｂ 第２の反射鏡（凸面鏡）
７ｃ 第３の反射鏡（凹面鏡又は凸面鏡）
７ｄ 第４の反射鏡（凸面鏡）
７０ 反射型結像光学系
８ 主光線
８ａ 入射光束
８ｂ 出射光束
９ スクリーン
１０ 画像形成素子の法線
１１ 照明光学系
１２ａ 平面反射鏡
１２ｂ 平面反射鏡
１３ａ 照度分布を示す曲線
１３ｂ 照度分布を示す曲線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an enlarged projection display apparatus that enlarges and projects an image provided by an image forming element such as a liquid crystal light valve or DMD (Digital Micromirror Device (registered trademark of Texas Instruments)) on a screen. The present invention also relates to an illumination optical system used for an enlarged projection display device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various enlargement projection type display apparatuses that enlarge and project an image provided by an image forming element such as a liquid crystal light valve or DMD onto a screen have been proposed. In recent years, in such an enlarged projection display device, with the improvement in performance, the amount of light flux reaching the screen is small, that is, improvement in light utilization efficiency is required. In particular, the need for an enlarged projection type display device using DMD as an image forming element is increasing.
[0003]
As an illumination optical system for an enlarged projection display device using DMD as an image forming element, a small and highly efficient illumination optical system using a reflective optical element is disclosed in WO98 / 029773. The illumination optical system described in this publication is configured such that light emitted from an arc lamp of a white light source enters a DMD at a high angle through a condenser lens and a spherical mirror.
[0004]
[Problems to be solved by the invention]
However, the illumination optical system described in the above publication does not correct the keystone distortion or the like, and no means is taken to resemble the shape of the irradiation region with the shape of an image forming element such as DMD. For this reason, illumination efficiency is inferior.
[0005]
An object of the present invention is to achieve high efficiency of light utilization by correcting keystone distortion and making the shape of an irradiation region formed by an illumination optical system substantially the same as the shape of an image forming element. In order to achieve further miniaturization as an illumination optical system for image forming elements such as a regular reflection type image forming element (for example, a regular reflection type liquid crystal light valve) and a transmission type image forming element (for example, a transmissive liquid crystal light valve). In addition, the present invention provides an illumination optical system and a projection display device that have high light utilization even when the illumination optical path is folded back with a reflection mirror or the like and the image forming element is illuminated obliquely.
[0006]
[Problems to be solved by the invention]
  The present invention relates to an enlarged projection display device having an image forming element represented by a liquid crystal light valve, DMD, etc.2 includes an illumination optical system that irradiates the image forming element with light emitted from a light source from a direction non-parallel to the normal line of the image forming element, and includes an imaging optical element having positive power at the final stage. With the above optical elementsAn afocal optical system (an afocal system is an optical system in which a parallel light beam becomes a parallel light beam again after passing through a lens system)Furthermore, by arranging at least one of the two or more optical elements to be rotationally decentered with respect to the optical axis of the luminance unevenness reducing means,The light utilization efficiency is improved and the miniaturization is achieved.When the illumination optical system of the present invention is incorporated in an enlarged projection display device, the incident angle between the principal ray of the light beam emitted from an arbitrary point of the image forming element and the normal line of the image forming element is 5 ° or more. Thus, it is desirable that light be incident on the image forming element.
[0007]
  The illumination optical system of the present inventionAn illumination optical system for irradiating the image forming element with light emitted from a light source from a direction non-parallel to the normal of the image forming element,A condensing mirror that condenses light from the light source to form a virtual secondary light source, and an incident end face is disposed at the position where the secondary light source is formed.The aboveLuminance unevenness reducing means for uniforming the luminance distribution of the light from the secondary light source, so-called light tunnel, rod lens, etc. Optical that uniformizes the luminance unevenness on the exit surface by repeatedly reflecting the light beam on the inner surface The output surface of the element and the luminance unevenness reducing means is the object surface,The irradiation surface irradiated with light is the image plane.With afocal opticsThe afocal optical system includes two or more optical elements including a final-stage imaging optical element having a positive power, and at least one of the two or more optical elements includes the luminance unevenness reducing unit. Arranged rotationally decentered with respect to the optical axisIt is an illumination optical system characterized by.
[0008]
The afocal optical system provided between the luminance unevenness reducing element typified by a light tunnel or a rod lens and the image forming element emits from the image forming element 6 as shown in FIGS. The principal ray 8 ("principal ray") of an arbitrary light beam (outgoing light beam 8b) directed to a projection optical system (not shown) typified by is defined as a light beam passing through the center of the light beam from an arbitrary object point, An “optical axis ray” is defined as a ray passing through the center of the light beam passing through the origin of the virtual object plane and the origin of the irradiation surface.) And the normal line 10 of the image forming element 6 is 5 ° or more. is there. Here, FIGS. 1A to 1C (where (a) is a top view, (b) is a front view, and (c) is a side view) show the case where the image forming element 6 is a DMD, The angle θ described above is an angle when projected onto the cross-section in the paper as shown in the side view of FIG. 2 (a) and 2 (b) ((a) is a front view and (b) is a side view), the image forming element 6 is a regular reflection type, and the principal ray 8 and the normal 10 of the outgoing light beam 8b. Is the angle shown in the side view of FIG. 2B, the so-called reflection angle. 3 (a) and 3 (b) ((a) is a front view, (b) is a side view), the image forming element 6 is a transmission type, and the principal ray 8 and the normal line 10 of the outgoing light beam 8b are formed. The angle θ is the angle shown in the side view of FIG. In the figure, reference numeral 8a denotes an incident light beam incident on the image forming element.
[0009]
The second feature of the illumination optical system of the present invention is that each element constituting the afocal optical system is arranged in a three-dimensional space. Taking the case where DMD is used as an image forming element as an example, it is as shown in FIG. FIG. 4 is a side view in which the illumination optical system of the present invention is applied to the illumination optical system of an enlarged projection display device using DMD as the image forming element 6.
[0010]
In FIG. 4, the light tunnel 3 is used as the luminance unevenness reducing element. The light tunnel 3 is arranged so that the incident end face 3a is located at a position of a virtual secondary light source formed by condensing the light beam from the light source 1 by the condenser mirror 2. The afocal optical system arranged on the light exit surface 3 b side of the light tunnel 3 is composed of three lenses 4 a, 4 b, 4 c and a reflection mirror 5. The reflection mirror 5 provided between the second lens 4b and the third lens 4c (first, second, and third lenses in order from the side closest to the light source) is a plane mirror and only changes the optical path. Since it is not an essential element for the focal optical system, it may be omitted. What is necessary is just to provide as needed, when turning an optical path and making an apparatus small.
[0011]
In the three lenses 4a, 4b, and 4c constituting the afocal optical system, the first lens 4a is shifted vertically from the optical axis O that connects the light source 1 and the center of the light tunnel 3 that is a luminance unevenness reducing element. Yes. That is, the center of the first lens 4a is not on the optical axis O. The second lens 4b is shifted vertically and horizontally from the optical axis O and is further rotationally decentered. The optical axis of the second lens 4b is not parallel to the optical axis O. The third lens 4c is parallel to the optical axis of the projection lens and is shifted and decentered from the normal of the center point of the image forming element 6. When the reflection mirror 5 is not provided, they are arranged obliquely downward from the image forming element 6 while ensuring the relative positions of the optical elements as viewed from the image forming element 6.
[0012]
In the illumination optical system of the present invention, the afocal optical system may be composed of at least two refractive optical elements (first lens 4a and second lens 4b) as shown in FIG. This is the same as in FIG. In addition, at least one of the optical elements constituting the afocal optical system may be a reflective optical element having a curved surface. For example, the reflecting mirror 5 in FIGS. 4 and 5 may be a concave mirror. Further, at least one of the optical elements constituting the afocal optical system may be constituted by an aspherical optical element.
[0013]
If at least one of the optical elements constituting the afocal optical system is made of a plastic optical element, the illumination optical system can be constructed easily and inexpensively.
[0014]
As shown in FIGS. 4 and 5, the enlarged projection display device using the illumination optical system is arranged on the illumination optical system and the irradiation surface (image plane) of the afocal optical system constituting the illumination optical system. The image forming element 6 is arranged, and a projection optical system that is arranged on the emission side of the image forming element 6 and projects the light emitted from the image forming element 6 onto the screen. The projection optical system can be constituted by a projection lens 7 which is a refractive imaging optical system, a reflection imaging optical system including one or a plurality of reflecting mirrors, and the like.
[0015]
  Enlarged projection display device using a refraction-type imaging optical system as a projection optical systemsoRefracts and projects onto a screen an illumination optical system having a light source and an afocal optical system, an image forming element disposed on an irradiation surface (image surface) of the illumination optical system, and a light beam emitted from the image forming element At least a telecentric refractive imaging optical system, and the diaphragm of the refractive imaging optical system is disposed at a position decentered from the optical axis of the refractive imaging optical system.It is desirable.
[0016]
When the aperture of the refractive imaging optical system is decentered, the upper and lower rays of light emitted from a specific light spot on the image forming element have their emission directions asymmetric with respect to the projection optical axis, and It is tilted with respect to the projection optical axis. As a result, the light rays emitted from the respective points on the image forming element become parallel, and projection light with no unevenness in brightness can be obtained. As a result, the unevenness in illuminance of the projected image is reduced, and a projected image with high brightness is obtained.
[0017]
  Enlarged projection display device using a reflective imaging optical system as a projection optical systemsoReflects and projects an illumination optical system having a light source and an afocal optical system, an image forming element disposed on an irradiation surface (image surface) of the illumination optical system, and a light beam emitted from the image forming element on a screen A first reflecting mirror having a concave reflecting surface of a rotationally symmetric aspherical shape with a reflecting surface facing the image forming element. A second reflecting mirror having a rotationally symmetric aspherical convex reflecting surface facing the light beam from the first reflecting mirror, and a reflecting surface facing the light beam from the second reflecting mirror A third reflecting mirror having a rotationally symmetric aspherical concave reflecting surface or a rotationally symmetric aspherical convex reflecting surface, and a rotationally symmetric aspherical surface with the reflecting surface facing the light beam from the third reflecting mirror. A fourth reflecting mirror having a convex reflecting surface having a shape; Are al configurationIt is desirable.
[0018]
Specifically, the reflecting surface shape of the reflecting mirror is such that the optical axis of the reflecting mirror is the z axis, the plane perpendicular to the z axis is the xy plane, the intersection of the z axis and the xy plane is the origin O, and the origin When the coordinate axes are set with the axes intersecting at O and perpendicular to each other on the xy plane as the x-axis and the y-axis, the rotationally symmetric aspheric shape represented by the following formulas (1) to (3) is obtained. .

[0019]
ρ²= X²+ Y²          (2)
c = 1 / r (3)
Where α_i(I = 1, 2,..., 8) is a correction coefficient, k is a conical coefficient, and r is a radius of curvature of the reflecting surface.
[0020]
In the above-described enlarged projection display device, when the illumination optical system is provided with an optical path conversion element represented by a reflecting mirror, a prism or the like, there is an advantage that the depth of the enlarged projection display device can be reduced.
[0021]
(Action / Principle)
In general, as shown in FIGS. 1, 2, and 3, the principal ray 8 has an angle θ, so that the principal ray 8 of the incident light beam 8 a to the image forming element 6 also has a predetermined angle. In particular, when a DMD is used for the image forming element 6, as shown in FIG. 1, the principal ray 8 of the incident light beam 8a is largely inclined at a predetermined angle in two directions.
[0022]
FIG. 7 is a schematic diagram showing a state in which the exit surface image of the luminance unevenness reducing element is guided to the image forming element surface from an oblique direction using a normal imaging optical system (lens system 40). FIG. 8 is a diagram showing an irradiation state on the irradiation surface in FIG. 7, that is, an illuminance distribution. Curves such as contour lines drawn around the image forming element 6 are isoilluminance curves. As shown in FIG. 7, when the principal ray 8 is incident on the image forming element 6 from a greatly inclined direction, the emission surface 3 b is equal to the intersection of the optical axis of the optical system and the light beam on the emission surface 3 b of the luminance unevenness reducing element. Even at the upper points A and B, the distances A ′ and B ′ between the optical axis and the intersection point on the irradiation surface are greatly different on the irradiation surface. The difference in magnification that occurs in this way is an aberration called keystone distortion. When this aberration occurs, the irradiation area 60 and the image forming element 6 do not have a similar shape, and the irradiation area (area surrounded by an isoillumination curve in FIG. 8) 60 is distorted as shown in FIG. descend. Therefore, the present invention corrects this keystone distortion by using an afocal optical system as the illumination optical system, and improves the light utilization efficiency.
[0023]
The reason why the afocal optical system can correct the keystone distortion will be described with reference to FIG.
[0024]
FIG. 9 is a schematic diagram showing the basic concept of keystone distortion correction. In the optical system of FIG. 9, the illumination optical system described in FIG. 7 (the light source and the luminance unevenness reducing element are not shown. Only the emission surface 3 b of the luminance unevenness reducing element and the lens system 40 are drawn) and the irradiation region 60. In addition, an optical system (refractive optical element) 41 having a positive power is newly provided. At this time, if the optical system 41 having a positive power is arranged so that the angle between the principal ray 8 and the irradiation region 60 is constant, the above-described distances A ′ and B ′ can be made substantially equal. .
[0025]
Thus, by arranging the optical system 41 having a positive power, the keystone distortion can be effectively corrected. In the illumination optical system in which the optical system 41 having a positive power is arranged, the angle formed between the principal ray 8 incident on the image forming element 6 arranged in the irradiation region 60 and the normal line of the image forming element 6 as described above. It becomes constant. Therefore, light incident from the same direction over the entire surface of the image forming element 6 can be emitted in the direction of the projection optical system (not shown), and light can be efficiently emitted by the projection optical system that receives light only from a specific direction. Can be led to a projection screen, a so-called screen (not shown). Furthermore, the space occupied by the entire optical system can be reduced by using a reflective optical element as the optical system having a flat surface and positive power. However, simply disposing a reflective optical element instead of a refractive optical element causes new distortion as shown in FIG.
[0026]
As shown in FIG. 10, when the optical system having a positive power is configured by the reflective optical element 42, interference between the incident light beam on the reflective optical element 42 and the light beam emitted from the image forming element 6 does not occur. The reflective optical element 42 must be disposed on the surface. This means that the reflective optical element 42 is inclined with respect to the optical axis. Therefore, chief rays corresponding to two points A and B that are equidistant from the optical axis of the optical system on the exit surface 3b are incident on the reflective optical element 42 at different incident heights. Therefore, the distances A ′ and B ′ from the intersection of the irradiation area 60 and the optical axis of the optical system to the two points A and B on the emission surface 3b from the two points on the irradiation area 60 that have passed through the optical system are different. This is a new distortion.
[0027]
The distortion caused by tilting the optical system having positive power is corrected by combining the following two configurations alone or in combination. As shown in FIG. 11, the first configuration is a method in which the lens system 40 of the illumination optical system is configured by a plurality of lens groups that are rotationally decentered from each other. One lens group may be rotationally decentered. Distortion can be corrected by rotating and decentering some lens groups so that the principal ray incident height to the optical system 41 having a positive power is aligned.
[0028]
The second configuration is a configuration in which the emission surface 3b is tilted in the same direction as the optical system having a positive power with respect to the optical axis of the lens system 40. With this configuration, the incident height to the optical system having a positive power can be corrected, and distortion can be corrected. Furthermore, as shown in FIG. 11, when the configuration in which the principal ray is incident on the lens system from the exit surface 3b in a substantially parallel manner is adopted, the configuration of the illumination optical system can be simplified, and the focus is further improved, and the irradiation region 60 and The distinction from other regions is clear (see the configurations in FIGS. 4 and 5).
[0029]
From the above description, the illumination optical system of the present invention can obtain an illumination region substantially similar to the shape of the image forming element. However, when a DMD or a specular reflection type image forming element is used, it is incident on the image forming element. Since the optical paths of the light and the outgoing light overlap, it is clear that the optical elements constituting the illumination optical system interfere with the projection optical system placed on the optical path. Therefore, the principal ray of the light emitted from the image forming element is given a predetermined angle θ (angle formed with the normal of the image forming element), and the projection optical system is configured with an angled telecentric optical system so that no light loss occurs. It is desirable to do so. In the present invention, this angle θ is set to θ ≧ 5 ° to prevent interference.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
One embodiment of the illumination optical system of the present invention is shown in FIG. FIG. 4 is a side view in which the illumination optical system of the present invention is applied to the illumination optical system of the enlargement projection display apparatus with the image forming element 6 as a DMD. As shown in FIG. 4, the magnifying projection display device includes an illumination optical system that illuminates the image forming element 6, an image forming element 6, and a projection lens (not shown) that projects a light beam from the image forming element 6. Projection optical system) 7.
[0031]
The illumination optical system is arranged so that the incident end face 3a is located at the position of the light source 1, the condensing mirror 2 that condenses the light beam from the light source 1 to create a virtual secondary light source, and the secondary light source. The light tunnel 3 (luminance unevenness reducing element) that emits from the exit surface 3b after uniformizing the luminance distribution of the luminous flux from the secondary light source, and the afocal that guides the emitted luminous flux from the light tunnel 3 to the DMD that is the image forming element 6 It consists of an optical system.
[0032]
Since the shape of the image forming element is quadrangular, the light tunnel 3 has a hollow quadrangular prism shape so that the illumination area is square. The inner wall of the light tunnel 3 is a reflection surface, and light rays incident on the light tunnel 3 are repeatedly reflected and propagated several times inside, thereby reducing unevenness in luminance at the light tunnel exit end. The same effect as that of the light tunnel can be obtained by using a prismatic, cylindrical, or rod-shaped lens, so-called rod lens, instead of the light tunnel 3. The contour shape of the light tunnel or rod lens may be matched to the shape of the image forming element.
[0033]
The afocal optical system includes first to third lenses 4 a to 4 c and a reflection mirror 5, and uses the exit surface 3 b of the light tunnel 3 as an object surface. The reflection mirror 5 is a plane mirror, has only a function of changing the optical path, and is not essential for the afocal optical system. In the present embodiment, it is provided between the second lens 4b and the third lens 4c for the purpose of folding the optical path and reducing the size of the apparatus. A DMD is disposed as the image forming element 6 on the irradiation surface (image surface) of the afocal optical system.
[0034]
Of the three lenses constituting the afocal optical system, the first lens 4a is a plano-convex lens, the optical axis O connecting the light source 1 and the center of the light tunnel 3 with the plane side facing the light tunnel 3 The center of the first lens 4a is shifted from the optical axis O by shifting in the vertical direction. The second lens 4b is also a plano-convex lens, which is shifted from the optical axis O up and down and left and right and is eccentrically rotated. The third lens 4c uses a convex lens and is shifted and rotationally decentered from the normal point of the center point of the DMD so as to irradiate the DMD with the light beam from the reflection mirror 5. The DMD is disposed at the position of the irradiation surface of the afocal optical system. Since the DMD of the image forming element 6 and the projection lens 7 of the projection optical system are known ones, description thereof is omitted.
[0035]
According to the configuration of FIG. 4, the light beam emitted from the light source 1 is reflected by the condenser mirror 2 to create a virtual secondary light source. The light beam emitted from the virtual secondary light source enters the light tunnel 3 in which the incident end face 3a is disposed at the virtual secondary light source position. The light beam incident on the light tunnel 3 is repeatedly reflected inside the light tunnel 3 and emitted from the light tunnel 3, and then enters an afocal optical system having the first to third lenses 4 a to 4 c. The principal rays of the light beams that have passed through the afocal optical system become parallel and reach the irradiation surface of the afocal optical system, that is, the DMD of the image forming element 6. The light beam incident on the DMD is reflected by the DMD and projected onto a screen (not shown) through the projection lens 7. At this time, the angle between the principal ray of the light beam traveling from the DMD toward the projection lens 7 and the normal of the irradiated surface is set to 7.78 °.
[0036]
A specific configuration of each optical element of the illumination optical system shown in FIG. 4 is shown in Table 1 and FIGS. 6A to 6C including the DMD. Here, Table 1 shows the specific position and orientation of each optical element by numerical values. 6 (a) to 6 (c) are diagrams schematically showing the arrangement of optical elements. FIG. 6 (a) is a top view, FIG. 6 (b) is a side view, and FIG. 6 (c) is a front view. Show.
[0037]
[Table 1]

[0038]
The “exit surface” of surface number 1 in the surface attribute column of Table 1 is the light exit surface (the output surface 3b in FIGS. 4 and 6) of the luminance unevenness reducing element (in this embodiment, the light tunnel 3). The center point of the exit surface 3b of the light tunnel 3 is the original initial origin, the axis passing through the origin and perpendicular to the exit surface 3b is the z axis, and the direction from the light source 1 to the light tunnel 3 is the “+” of the z axis. Direction, the exit surface 3b is orthogonal to the xy plane, the z-axis is orthogonal, and the mutually orthogonal axes are the x-axis and y-axis (in FIG. 4, the axis perpendicular to the paper surface is the x-axis and the axis on the paper surface is the y-axis. The initial coordinate system (see FIG. 6) is used as the coordinate system (axis), and the next origin, that is, the center coordinate position of the surface of the optical element, is expressed by “coordinate conversion” in the order of the surface numbers. The coordinate system is a right-handed coordinate system, and the signs of “+” and “−” in the shift amount and the rotation amount in the table follow the display of FIGS.
[0039]
In the table, surface numbers “2” to “4” are the first lens 4a, surface numbers “5” to “10” are the second lens 4b, surface numbers “11” to “17” are the reflecting mirror 5, and surface. Numbers “18” to “26” represent the third lens 4c, and surface numbers “27” to “34” represent the positions, orientations, and shapes of the DMDs. The “plane” of the surface numbers “32” and “33” means the cover glass provided on the DMD surface.
[0040]
The “distance between planes” represents the distance (unit: mm) in the z-axis direction from the plane with the plane number to the next plane. In other words, it is a distance obtained by translating (or translating) the coordinate system in the z-axis direction from the surface of the surface number to the next surface. For example, the inter-surface distance of the surface number “1” is the parallel movement distance along the z-axis from the surface of the surface number (the exit surface 3b) to the plane of the surface number “3”, and the inter-surface distance of the surface number “3” Is the translational distance along the z-axis from the plane with surface number “3” to the spherical surface with surface number “4”, and the inter-surface distance with surface number “4” is from the spherical surface with surface number “4” to surface number “9”. Represents the translational distance along the z-axis up to the plane. The same applies to the following inter-surface distances.
[0041]
The “x-axis direction” and “y-axis direction” in the shift amount column indicate that the coordinate origin of the surface of the optical element is in the x-axis direction and y-axis direction from the position of the origin determined by the previous surface number of the surface. The shift amount (unit is mm) is shown. For example, in the example of the first lens 4a, the distance between the exit surfaces at the surface number “1” is 5.3 mm, and the shift amount of the coordinate conversion at the surface number “2” is −2.18 mm in the x-axis direction. Since it is 0.86 mm in the y-axis direction, the center of the exit surface 3b of the light tunnel 3 is the coordinate origin, the axis perpendicular to the exit surface 3b is the z-axis, the exit surface 3b is the xy plane, and the horizontal direction is the x-axis. In the coordinate system in which the vertical direction is the y-axis, the light beam of the first lens 4a from the exit surface 3b is 5.3 mm in the z-axis direction, -2.18 mm in the x-axis direction, and 0.86 mm in the y-axis direction. It represents that there is the center of the input surface, that is, the plane of surface number “3”. Further, since the surface attribute of the surface number “3” is a plane, the distance between the planes is 10 mm, the surface attribute of the surface number 4 is a spherical surface, and the curvature radius of the spherical surface is −12 mm, the first lens is a plano-convex lens. The light incident side surface, that is, the surface facing the light tunnel 3 is a plane (the surface with the smaller surface number is the light incident side), the light output side is a convex surface, and the plane (surface number “3”) and the spherical surface (surface The distance between the centers of the number “4”) is 10 mm.
[0042]
It should be noted that the curvature radius is represented by “−” because the attribute of the surface is coordinate conversion, and there is no definition of the curvature radius itself, so it is represented by “−”. It is correct to indicate “−” for all virtual surfaces.
[0043]
“X-axis center”, “y-axis center”, and “z-axis center” in the rotation amount column mean rotation axes when the optical element is rotated. For example, in the case of the surface number “1”, the x-axis center and the y-axis center are 0, and the z-axis center is 21.4 °, so that the exit surface, that is, the light tunnel 3 is rotated about the z axis as shown in FIG. In the front view of (), it is shown that it is rotated 21.4 ° counterclockwise.
[0044]
The coordinate conversion is performed in ascending order of the surface number: (1) parallel translation on the z-axis (movement of distance between surfaces), (2) parallel translation on the x-axis (x shift amount), and (3) parallel translation on the y-axis (y shift) (4) Rotation about the z-axis, (5) Rotation about the y-axis, and (6) Rotation about the x-axis.
[0045]
According to this coordinate conversion, in the example of the second lens 4b (surface numbers “5” to “10”), the distance between the surfaces of the spherical surface with the surface number “4” (the light emitting surface of the first lens 4a) is 18 mm. The shift amount in the coordinate transformation of the surface number “5” is 1.3 mm in the x-axis direction, the y-axis direction is −0.6 mm, the shift amount of the surface number “6” is 0.5 mm in the x-axis direction, and the y-axis direction. Is −1 mm, the center (coordinate origin) of the plane (ray input surface of the second lens 4b) on the surface number “9” is the coordinate system (surface numbers “1” to “4”) of the spherical surface (surface number “4”). The coordinate system after the coordinate transformation in 3 ”. The coordinate origin is at the center of the sphere, and the z axis is perpendicular to the sphere.” 18 mm on the z axis from the origin (spherical surface (surface number “4”)), From the point moved 1.3 mm in the x-axis direction and -0.6 mm in the y-axis direction (surface number “5”), further in the x-axis direction 0.5 mm, -1 mm movement in the y-axis direction (surface number "6") were in position. Further, since the rotation amount in the coordinate transformation of the surface numbers “7” and “8” is −5.2 ° at the y-axis center and 11.7 ° at the x-axis center, the coordinates of the spherical surface (surface number “4”) The coordinate system formed by translating the origin to the position of the coordinate origin of the plane (surface number “9”) is rotated by −5.2 ° using the y axis as the central axis of rotation (surface number “7”). Further, the coordinate system rotated by 11.7 ° (surface number “8”) with the x axis as the central axis of rotation becomes the coordinate system of the plane (surface number “9”). The xy plane of this coordinate system becomes the plane of the surface number “9”, and the center position and inclination of the plane (surface number “9”) with respect to the initial coordinate system are determined. The center (not the center of curvature) of the spherical surface (light emitting surface) of the surface number “10” is 10 mm in the plane (surface number “9”), and the coordinate system of the plane (surface number “9”) is 10 mm. In the z-axis direction, the position is 10 mm from the coordinate origin (center of the plane (surface number “9”)). Note that the z axis of the plane (surface number “9”) coordinate system is the optical axis of the second lens 4b.
[0046]
A coordinate system (spherical surface (surface number “10”) in which the coordinate origin of the plane (surface number “9”) is translated by 10 mm along the z axis and the coordinate origin is moved to the center of the spherical surface (surface number “10”). The coordinate system is the next optical element, in this embodiment, the position and orientation of the reflecting mirror 5, that is, the starting coordinate system for performing coordinate conversion to determine the coordinate system of the reflecting mirror 5.
[0047]
In the example of the reflection mirror 5 (surface numbers “11” to “17”), the distance between the surfaces on the spherical surface (surface of the second lens 4b) of the surface number “10” is 0 mm, and the coordinates of the surface number “11” are used. The rotation amount in the conversion is −11.7 ° at the center of the x axis, the rotation amount in the coordinate conversion of the surface number “12” is 5.2 ° at the center of the y axis, and the shift amount in the coordinate conversion of the surface number “13” is the x axis. Since the direction is -0.5 mm and the y-axis direction is 1 mm, the coordinate origin in the z-axis direction is not moved. First, in the coordinate system of the spherical surface (surface number “10”), the x-axis is the center of rotation. The axis is rotated by −11.7 ° (surface number “11”), and the y-axis is rotated by 5.2 ° (surface number “12”). Each coordinate axis of the coordinate system obtained by the coordinate conversion of the rotation operation becomes a coordinate system parallel to each corresponding coordinate axis of the initial coordinate system. Thereafter, in this coordinate system (coordinate system obtained by coordinate conversion by rotating the surface numbers “11” and “12”), the coordinate origin (spherical surface (in the center of the surface number “10”)) is set to −0 in the x-axis direction. A coordinate system obtained by parallel translation of 5 mm and 1 mm (surface number “13”) in the y-axis direction is used as a virtual surface (surface number “17”) coordinate system, and the xy plane of this coordinate system is the virtual surface ( Surface number “17”) The coordinate origin is the center of the virtual surface (surface number “17”).
[0048]
The distance between the surfaces of the virtual surface (surface number “17”) is 40 mm, the rotation amount in the coordinate conversion of the surface number “15” is −34 ° at the center of the y axis, and the rotation amount in the coordinate conversion of the surface number “16” is the x axis. Since it is 15 ° at the center, in the coordinate system of the virtual plane, after moving the coordinate origin by 40 mm on the z axis and translating the coordinate system, the coordinate axis is -34 ° with the y axis as the rotation center axis, and the x axis is The coordinate system obtained by sequentially rotating 15 ° as the rotation center axis is the coordinate system of the reflection mirror 5. The xy plane of this coordinate system is the reflecting surface of the reflecting mirror 5, the coordinate origin is the center of the reflecting mirror 5, and the position and orientation of the reflecting mirror 5 are determined.
[0049]
The coordinate conversion of Table 1 has been described above by taking the second lens 4b and the reflection mirror 5 as an example. However, the surface of other optical elements may be converted in the same manner as described above according to the notation of Table 1.
[0050]
Illumination states on the image forming element obtained in this embodiment are shown in FIGS. 12 and 13A (the same view as FIG. 12). Further, the illuminance distribution on the image forming element is shown in FIG. As shown in FIG. 12, the image forming element size and the irradiation region 60 can be made substantially the same, and a uniform illuminance distribution without distortion is obtained. In addition, the curve around the image forming element in FIGS. 12 and 13A shows an isoluminance curve.
[0051]
FIG. 13B is a diagram showing the illuminance distribution on AA and BB shown in FIG. 13A on the image forming element. In the figure, the vertical axis indicates illuminance, the horizontal axis indicates the position on the image forming element, the curve 13a is a curve indicating the illuminance distribution on AA, and the curve 13b is a curve indicating the illuminance distribution on BB. FIG. 13B shows that the image forming element is illuminated with uniform illuminance.
[0052]
(Second Embodiment)
FIG. 5 shows a second embodiment of the illumination optical system of the present invention. FIG. 5 is a side view in which the illumination optical system of the present invention is applied to the illumination optical system of the enlargement projection display apparatus with the image forming element 6 as a DMD. As shown in FIG. 5, the enlargement projection type display device includes an illumination optical system that illuminates the image forming element 6, an image forming element 6, and a projection lens 7 that projects a light beam from the image forming element 6 onto a screen (not shown). The projection optical system of a so-called refractive imaging optical system. The illumination optical system includes a light source 1, a condensing mirror 2 that collects a light beam from the light source 1 to create a virtual secondary light source, and an incident surface 3 a positioned at the position of the virtual secondary light source. The light tunnel 3 (brightness unevenness reducing element) that is emitted from the emission surface 3b after uniformizing the luminance distribution of the luminous flux from the virtual secondary light source and the luminous flux emitted from the light tunnel 3 by the image forming element 6 It consists of an afocal optical system that leads to a certain DMD.
[0053]
As shown in FIG. 5, the afocal optical system used in the illumination optical system includes two refractive optical elements, a first lens 4 a and a second lens 4 b, and the reflection mirror 5. As in the case of the first embodiment, the reflecting mirror 5 is a plane mirror, has only a function of changing the optical path, and may be omitted because it is not an essential element in the afocal optical system. In the present embodiment, it is provided between the first lens 4a and the fifth lens 4b for the purpose of folding the optical path and reducing the size of the apparatus. A DMD is disposed as an image forming element 6 on the irradiation surface of the afocal optical system. In this embodiment, θ is 7.8 °, and the illumination state on the image forming element can be made substantially the same as the image forming element size and the irradiation area as shown in FIG. Illuminance distribution was obtained. In addition, the curve around the image forming element in FIG. 14 shows an isoluminance curve.
[0054]
The specific configuration of each optical element of the illumination optical system shown in FIG. 5 is shown in Table 2 including the DMD.
[0055]
[Table 2]

[0056]
The “exit surface” of surface number 1 in the surface attribute column of Table 2 is the light exit surface (exit surface 3b) of the luminance unevenness reducing element (light tunnel 3), as in the first embodiment. The initial coordinate system is set in the same manner as in the first embodiment with the center point of the exit surface 3b of the light tunnel 3 as the original initial origin.
[0057]
In the table, surface numbers “2” to “4” are the first lens 4a, surface numbers “5” to “8” are the reflecting mirror 5, surface numbers “9” to “17” are the second lens 4b, and surface. Numbers “18” to “25” represent the arrangement positions, orientations, and shapes of DMDs. The planes with the surface numbers “23” and “24” mean the cover glass provided on the surface of the DMD.
[0058]
(Third embodiment)
FIG. 15 shows a third embodiment of an enlargement projection type display device using the illumination optical system of the present invention. The present embodiment is a configuration example in which a single reflection mirror having positive power is used in the afocal optical system. As shown in FIG. 15, the enlargement projection display device includes an illumination optical system that illuminates the image forming element 6, an image forming element 6, and a projection lens that projects a light beam from the image forming element 6 onto a screen (not shown). 7 and. The illumination optical system includes a light source 1, a condensing mirror 2 that collects a light beam from the light source 1 to create a virtual secondary light source, and an incident surface 3 a positioned at the position of the virtual secondary light source. The light tunnel 3 (brightness unevenness reducing element) that is emitted from the emission surface 3b after uniformizing the luminance distribution of the luminous flux from the virtual secondary light source and the luminous flux emitted from the light tunnel 3 by the image forming element 6 It consists of an afocal optical system that leads to a certain DMD.
[0059]
As shown in FIG. 15, the afocal optical system used for the illumination optical system includes two refractive optical elements, a first lens 4a and a second lens 4b, a reflection mirror 4d having a positive power, and an optical path bending unit. The reflecting mirror 5 is used. The reflecting mirror 5 is a convex mirror. A DMD is disposed as an image forming element 6 on the irradiation surface of the afocal optical system. In this embodiment, θ is 7.8 °, and the illumination state on the image forming element can be substantially the same as the image forming element size and the irradiation area as shown in FIG. Illuminance distribution was obtained. Note that the curve around the image forming element in FIG. 16 shows an isoluminance curve. Become.
[0060]
Table 3 shows a specific configuration of each optical element of the illumination optical system shown in FIG. 15 including the DMD.
[0061]
[Table 3]

[0062]
The “exit surface” of surface number 1 in the surface attribute column of Table 3 is the light exit surface (exit surface 3b) of the luminance unevenness reducing element (light tunnel 3), as in the first embodiment. The initial coordinate system is set in the same manner as in the first embodiment with the center point of the exit surface 3b of the light tunnel 3 as the original initial origin.
[0063]
In the table, surface numbers “2” to “4” are the first lens 4a, surface numbers “5” to “9” are the second lens 4b, surface numbers “10” to “15” are the reflecting mirror 5, and surface. The numbers “16” to “23” represent the reflective optical element 4d having a positive power, and the surface numbers “24” to “31” represent the positions, orientations, and shapes of the DMDs. The planes with the surface numbers “29” and “30” mean the cover glass provided on the surface of the DMD.
[0064]
(Fourth embodiment)
The present embodiment is an example of an enlarged projection display device that includes an aspheric optical element in the illumination optical system. This enlargement projection type display apparatus includes the illumination optical system that illuminates the image forming element, the image forming element, and the projection lens that projects the light beam from the image forming element onto the screen, as in the above three embodiments. is there. The enlarged projection display device of this embodiment has a configuration in which the reflection mirror 5 is replaced with an aspherical reflection mirror in FIG. 15, and the other configuration is the same as that of the third embodiment. Table 4 shows the specific configuration of each optical element of the illumination optical system in this apparatus, including the DMD. The illumination state on the image forming element is as shown in FIG.
[0065]
[Table 4]

[0066]
The cylinder of surface number 16 in Table 4 has a semi-cylindrical shape, and the surface of surface number 16 has a non-cross section cut by an arbitrary plane parallel to the yz plane (coordinate system of the surface of surface number 16). That is, the expression representing the spherical surface is satisfied. An aspherical surface is a surface represented by an ordinary aspherical expression (equations (1) to (3) described in the above section “Means for Solving the Problems”).
[0067]
The way of viewing the table is the same as in the above three embodiments. In the table, surface numbers “2” to “4” are the first lens 4a, surface numbers “5” to “9” are the second lens 4b, surface numbers “10” to “16” are aspherical reflecting mirrors, Surface numbers “16” to “25” represent the reflective optical element 4d having a positive power, and surface numbers “26” to “33” represent the positions, orientations, and shapes of the DMDs. The planes with the surface numbers “31” and “32” mean the cover glass provided on the DMD surface.
[0068]
In this embodiment, the reflecting mirror is an aspherical optical element, but the present invention is not limited to the reflecting mirror, and an aspherical lens may be used for the aspherical optical element.
[0069]
(Fifth embodiment)
The present embodiment is an example of an enlarged projection display device in which the projection optical system is devised to reduce unevenness in illuminance of the projected image.
[0070]
The magnifying projection display apparatus is the same as the above-described embodiment, comprising an illumination optical system that illuminates an image forming element, an image forming element, and a projection optical system that projects a light beam from the image forming element onto a screen. . The illumination optical system is arranged so that the incident end face is positioned at the position of the virtual secondary light source, which is a light source and a condensing mirror that condenses the light flux from the light source to create a virtual secondary light source. A light tunnel (luminance unevenness reducing element) that emits light from a secondary light source with a uniform luminance distribution, and an afocal optical system that guides the emitted light beam from the light tunnel to a DMD that is an image forming element. The configuration is the same as that of the above-described four embodiments. In the present embodiment, the illumination optical system having the configuration shown in FIG. 4, that is, the same illumination optical system as that in the first embodiment is used.
[0071]
  The projection optical system uses a telecentric refractive imaging optical system (projection lens), and the center of the diaphragm used in the refractive imaging optical system is set to the optical axis of the refractive imaging optical system (in FIG. 18). L1) is eccentric (the amount of eccentricity h in FIG. 18).With this configuration, unevenness in illuminance of the projected image is reduced, and a projected image with high brightness can be obtained.A specific example of this projection optical system is shown in FIG.
[0072]
As shown in FIG. 18, the projection lens is composed of a total of 14 lenses including a first lens group G1 to a fourth lens group G4 and a plane parallel glass G5 in order from the screen side. A diaphragm S is provided between the second lens group G2 and the third lens group G3. The center of this stop is decentered by h from the optical axis L1 of the projection lens. The data of each lens in the lens groups G1 to G4 constituting the projection lens is as shown in Table 5.
[0073]
[Table 5]

[0074]
In the table, the surface number i is assigned in order from the refracting surface closest to the screen, and the refractive index of the number indicating the refractive index for the d-line (wavelength 587.6 nm) and the next refracting surface. One optical element is constructed. The surface interval d (unit: mm) indicates the lens thickness or the air interval between the corresponding refractive surface and the next refractive surface. The surface interval of the final surface is the distance from the parallel flat glass to the image forming element.
[0075]
The first lens group G1 includes a total of three lenses, a convex meniscus lens G11 having a convex surface facing the screen, a concave meniscus lens G12 having a concave surface facing the image forming element, and a concave lens G13. The second lens group G2 includes a cemented lens of a convex meniscus lens G21 having a convex surface facing the image forming element, a concave meniscus lens G22 having a concave surface facing the screen, and a convex lens G23. The third lens group G3 includes a cemented lens of a concave lens G31 and a convex lens G32. The fourth lens group G4 includes a concave lens G41, a convex meniscus lens G42 having a convex surface facing the image forming element, a cemented lens of the concave lens G43 and the convex lens G44, and a convex meniscus lens G45 and a convex lens G46 having a convex surface facing the image forming element. It is configured. The cemented lens of the concave lens G43 and the convex lens G44 is disposed with its concave surface facing the screen side.
[0076]
In the projection lens, the surface distance d6 at the surface number 6 changes during focusing, and the first lens group G1 moves forward and backward along the optical axis L1 to the screen side and the image forming element side. Other lens groups G2 to G4 other than the first lens group G1 are fixed. At the time of zooming, the surface distances d11 and d15 in the surface numbers 11 and 15 change, and the second lens group G2, the diaphragm S1, and the third lens group G3 move along the optical axis L1. The stop S is decentered in the direction perpendicular to the optical axis L1, and the distance h from the center of the aperture of the stop S to the optical axis L1 is shown as the amount of decentering. Table 6 shows the focal length, f-number, and variable surface distance of the entire system at the wide-angle end, standard, and telephoto end when the projection distance is infinity.
[0077]
[Table 6]

[0078]
The total length L of the lens system when the projection distance is infinite, the diaphragm decentering amount h1, the focal lengths f1 to f4 of the lens groups G1 to G4, and the combined focal length fw of the entire system at the wide-angle end, respectively.
L = 139.5mm
h = 4.5mm
f1 = −34.97 mm
f2 = 37.24mm
f3 = 125.91mm
f4 = 49.03mm
fw = 28.58mm
It is.
[0079]
In the first to fifth embodiments, a projection lens (refractive imaging optical system) is used as the projection optical system. However, instead of this projection lens, a reflective imaging formed by one or a plurality of reflecting mirrors. You may comprise a projection optical system with an optical system. Each of the above embodiments is an example in which a DMD is used for the image forming element 6. For example, an enlarged projection display using an image forming element other than the DMD such as a reflective liquid crystal light valve or a transmissive liquid crystal light valve. Even if the apparatus is configured, the same effect as the above-described embodiment can be obtained.
[0080]
(Sixth embodiment)
FIG. 19 shows a sixth embodiment of the enlargement projection type display apparatus using the illumination optical system of the present invention. The present embodiment is an example in which a reflective imaging optical system is used as a projection optical system.
[0081]
As shown in FIG. 19, the enlarged projection display device projects an image forming element 6, an illumination optical system 11 that illuminates the image forming element 6, and a projection that projects an emitted light beam from the image forming element 6 onto a screen (not shown). It consists of an optical system. The image forming element 6 and the illumination optical system 11 are the same as those in the first embodiment, and have the same arrangement.
[0082]
The projection optical system is a telecentric reflection type imaging optical system composed of four reflecting mirrors. The telecentric reflective imaging optical system that constitutes the projection optical system includes a first reflecting mirror 7a having a rotationally symmetric aspherical concave reflecting surface and a reflecting surface directed to the light beam from the first reflecting mirror. A second reflecting mirror 7b having a rotationally symmetric aspherical convex reflecting surface and a third reflecting mirror having a rotationally symmetric aspherical concave reflecting surface with the reflecting surface facing the light beam from the second reflecting mirror. The mirror 7c is composed of four reflecting mirrors, a fourth reflecting mirror 7d having a rotationally symmetric aspherical convex reflecting surface facing the light flux from the third reflecting mirror, and reflecting mirrors 7a and 7b. , 7c and 7d are arranged so that the optical path of the light beam sequentially reflected in a zigzag manner, and the light beam reflected by the fourth reflecting mirror 7d is enlarged and projected onto a projection screen (not shown). This is a telecentric reflective imaging optical system. A reflective image forming element 6 made of DMD is disposed on the imaging surface of the reflective imaging optical system.
[0083]
As shown in FIG. 20, the reflecting surface shape (rotationally symmetric aspherical shape) of the reflecting mirrors 7a to 7d is such that the optical axis is the z axis, and the plane perpendicular to the z axis is the xy plane (four apexes A, B, C, and D), the intersection of the z axis and the xy plane is the origin O, the axis intersecting at the origin O and the axes orthogonal to each other on the xy plane is set as the x axis, and the coordinate axis is set as the y axis. The shape satisfies the following formulas (1) to (3).

[0084]
ρ²= X²+ Y²          (2)
c = 1 / r (3)
Where α_i(I = 1, 2,..., 8) is a correction coefficient, r is a radius of curvature of the reflecting surface, and k is a cone coefficient.
[0085]
A reflecting mirror having a reflecting surface shape that satisfies the above formula may be a reflecting mirror having a reflecting surface that is a curved surface α (a curved surface extending from points a, b, c, and d in FIG. 20) passing through the center of the z axis, or z A so-called offset-type curved surface β (a curved surface stretched by points a ′, b ′, c ′, and d ′ in FIG. 20) whose axis does not pass through the center may be used. In this embodiment, an offset type is adopted.
[0086]
The spatial positional relationship between the reflecting mirrors is arranged so that the origin of the coordinate system of each reflecting mirror that defines the reflecting surface shape is on the same plane, but unlike the reflecting surface shape, it is expressed by a simple relational expression. Therefore, the above formulas (1) to (3) that define the shape of the reflecting surface, the incident angle of the principal ray to the image forming element 6, the opening angle of the light beam emitted from the image forming element 6, and the space of the optical system Reflection surface by known ray tracing simulation based on design specifications such as limitation of size, design and specifications of image forming element 6 (liquid crystal display element, DMD, etc.) combined with reflective imaging optical system, screen projection position, etc. The arrangement positions of the reflecting mirrors 7a to 7d are determined together with the shape. At this time, the angle between the optical axis of the reflective imaging optical system (A-A axis in FIG. 22, that is, the Z-axis) and the rays reaching the screen (see FIG. 22), the so-called half angle of view is 40 ° or more and less than 90 °. The principal ray angle θ from the image forming element 6 to the reflective imaging optical system (projection optical system) (the angle formed between the principal ray emitted from the image forming element 6 and the normal line of the image forming element (see FIG. 1). )) Is set to 5 ° or more. When the chief ray angle is 5 ° or less, the light ray from the image forming element 6 to the reflective imaging optical system interferes with the illumination optical system, and vignetting of the ray occurs, so the chief ray angle θ is set to 5 ° or less. It is not desirable. There is no particular upper limit for the chief ray angle θ, but the upper limit is determined by the size of the magnifying projection display device incorporating the reflective imaging optical system. In order to achieve compactness without reducing the vertical distance between the reflecting mirrors, and to achieve miniaturization, the upper limit of the chief ray angle should be limited to about 20 °.
[0087]
As shown in FIG. 21, the procedure for obtaining the spatial positional relationship between the reflecting mirrors by the ray tracing simulation is as follows. First, the angle of view, the screen size, the spatial size of the optical system, the type and size of the image forming element, Design specifications such as the screen projection position are determined (step S1). Next, based on the design specifications, the type of optical system (determines whether or not it is a telecentric system. In the present invention, the telecentric system is selected), the number of mirrors (four in this embodiment), the optical axis shift amount, etc. Is determined (step S2). Based on the information of step S1 and step S2, the aperture position, the outline of the spatial arrangement of the reflectors (arranged so that each reflector does not interfere with each other and part of the reflected light is blocked), reflection Initial data such as a mirror shape determination equation (the present invention uses the above formulas (1) to (3)) and initial values of optical system elements necessary for ray tracing are created (step S3). A ray tracing simulation is performed based on the initial data, and the size, spatial position, tilt angle, etc. of each reflector are determined. In the ray tracing simulation, a known method was used. The present inventor performed ray tracing simulation using commercially available optical system design software. In the ray tracing simulation, first, the range of x and y in the equations (1) to (3) by ray tracing, α_i, R, k, and other parameter values that determine the size, spatial position, tilt angle, etc. of each reflector are calculated (step S4). Based on the result of step S4, performance evaluation such as MTF, tolerance, curvature, aberration, effective luminous flux margin of the reflector is performed (step S5), and parameter calculation and performance evaluation are repeated until the evaluation result satisfies the design specification. Determine the shape and spatial position of the reflector.
[0088]
  By optimizing the shape of each of the four reflecting surfaces based on the above procedure, a reflecting mirror shape suitable for widening the angle of view and reducing the size of the telecentric optical system is obtained. An example of the obtained results is shown in FIG.In addition, by constructing the projection optical system with a telecentric reflective imaging optical system consisting of optimized rotationally symmetric aspherical reflecting mirrors, a wide angle of view is realized and the interval between the reflecting mirrors is reduced. The apparatus can be downsized. Further, when the reflecting mirror constituting the reflection imaging optical system has a rotationally symmetric aspherical shape, it can be easily processed, can be made into resin, and can be realized as an inexpensive reflection type imaging optical system.
[0089]
[Table 7]

[0090]
FIG. 22 is a schematic diagram showing the arrangement of the reflecting mirrors, and Table 7 is a table showing specific numerical values of the reflecting mirrors and the respective parameters showing the arrangement thereof.
[0091]
In FIG. 22, an optical system coordinate system (coordinate axes are indicated by capital letters) composed of an image forming element 6 and four reflecting mirrors 7a to 7d has an optical axis AA of the image forming element 6 as a Z axis and a Z axis. The axis perpendicular to the intersecting paper plane is the X axis, the axis perpendicular to the Z axis and parallel to the paper plane (the axis on the paper plane) is the Y axis, the right direction in the figure is the positive direction of the Z axis, and the left direction is the Z axis. Set the negative direction, the upper direction in the figure is the positive direction of the Y axis, the lower side of the figure, the lower direction from the Z axis is the negative direction of the Y axis, and the direction from the front to the back of the page is the positive direction of the X axis. Is the YZ plane. The coordinate origin may be set anywhere, but for convenience, the intersection of the Z axis and the image forming element 6 is used as the coordinate origin.
[0092]
“No” in Table 7 indicates a number for identifying the reflecting mirrors 7a to 7d and the image forming element 6, “0” indicates the image forming element 6, “1” indicates the first reflecting mirror 7a, “2” represents the second reflecting mirror 7b, “3” represents the third reflecting mirror 7c, and “4” represents the fourth reflecting mirror 7d. “Dj” represents the distance between the reflecting mirrors. Dj in the column of 0 represents d0 shown in FIG. 22, and indicates the distance from the image forming element 6 to the first reflecting mirror 7a. Similarly, no. Dj in the first column, i.e., the first reflecting mirror column, represents d1 shown in FIG. 22 and indicates the distance from the first reflecting mirror 7a to the second reflecting mirror 7b. The same applies hereinafter. No. Dj in the column 4 (fourth reflecting mirror column), that is, d4 indicates the distance from the fourth reflecting mirror 7d to the screen 9.
[0093]
22, parameters shown in Table 7, that is, the radius of curvature r of the reflecting mirrors 7a to 7d, the distance d0 between the image forming element 6 and the first reflecting mirror 7a, the distances d1 to d3 between the reflecting mirrors, and the fourth reflection. The coordinate origin of the reflecting mirrors 7a to 7d (the coordinate origin defining the reflecting mirror surface shape, that is, the reflecting mirror surface shape) is calculated from the distance d4 from the mirror 7d to the screen 9 and the Z axis (the optical axis AA of the image forming element). The unit of the distances X and Y to the origin of the coordinates is “mm”. The unit of the rotation angle a of the reflecting mirrors 7a to 7d is “degree”, and the coordinate axes x, y, and z of the coordinate system (the coordinate axes are expressed in lower case letters) that define the reflecting surface shape of the reflecting mirror are the coordinate axes X and Y of the optical system. , Rotating in the clockwise direction (clockwise) in the figure with the x axis as the rotation axis with reference to the state parallel to Z (the y axis is perpendicular to the Z axis (optical axis A-A)). (Counterclockwise) The rotation was set to “−”. Each parameter other than the above (cone coefficient k, correction coefficients α1 to α7) is an unknown number. The distance dj (j = 0 to 4, i.e., d0, d1, d2, d3, d4 in the figure) is parallel to the optical axis AA (Z axis) between the origins of the coordinates that define each reflecting surface shape. Measured distance, that is, the interval between the Z coordinates of the origin of each coordinate defining each reflecting surface shape, X is the origin of the coordinates defining each reflecting surface shape from the optical axis AA (Z axis) to the X axis direction Is a distance measured perpendicular to the optical axis AA (Z axis), Y is the origin of the coordinates defining each reflecting mirror surface shape, and the optical axis AA (Z axis) from the optical axis AA (Z axis) to the Y axis direction. This is the distance measured perpendicular to the (Z-axis). In the example of FIG. 22, since the reflecting mirror is an offset type, the coordinate origin of the reflecting mirror is at a position shifted from the center of the reflecting mirror, and the distance dj (j = 0 to 4) defines each reflecting mirror surface shape. Since it is only necessary to know the relative Z coordinate of the origin of each coordinate (the X coordinate and the Y coordinate are not necessary), the position of the Z coordinate of the coordinate origin of each coordinate defining each reflecting mirror surface shape is shown in the figure, The positions of the X and Y coordinates are not specified. The reflecting mirror 3d is rotated counterclockwise, but is drawn as if it is rotated rightward due to the offset reflecting mirror surface shape. The size of the reflecting mirror is arbitrary, and the size may be set so that light rays are not blocked in the above-described reflecting mirror positional relationship.
[0094]
In FIG. 19, the light beam emitted from the light source is incident on the image forming element 6 disposed on the irradiation surface of the illumination optical system 11 (which is also the imaging surface of the reflective imaging optical system), and the light intensity corresponding to the image. It is spatially modulated into the distribution, reflected, and incident on the reflective imaging optical system. The light beam incident on the reflection type imaging optical system is sequentially reflected and enlarged by the first reflecting mirror 7a, the second reflecting mirror 7b, the third reflecting mirror 7c, and the fourth reflecting mirror 7d, and the fourth reflecting mirror. The light beam reflected by the mirror is enlarged and projected on a projection screen (not shown). At this time, the projection angle of the projected image was a wide angle of view of 140 ° or more.
[0095]
The reflective imaging optical system is a telecentric optical system, and the principal ray has a predetermined angle θ with respect to the normal line of the image forming element 6 as shown in FIG. A light beam having an opening angle ψ (usually corresponding to NA and FNO) of the light beam with respect to the principal ray 8 of the light beam is incident on the image forming element 6 and reflected to the normal line of the image forming element 6 when reflected. Having an angle θ eliminates interference with the optical components of the illumination unit, and an optical system can be configured without causing vignetting. Further, by making the illumination optical system an afocal optical system, distortion on the irradiated surface is eliminated, and illumination efficiency is improved. In addition, a display device such as an enlarged projection display device can be configured with the same reflective imaging optical system regardless of whether the image forming element is a transmissive type or a reflective type.
[0096]
In the reflection-type imaging optical system, since the light beam has a principal ray angle θ, generally, a fan-shaped distortion aberration in which the lower side of the projection screen is narrowed and the upper side is widened inevitably occurs. Moreover, it becomes more noticeable as the angle of view increases. In this embodiment, the configuration of four reflecting mirrors having a rotationally symmetric aspheric shape improves the distortion, and each optical component becomes relatively large and expensive. By using reflectors, the processing accuracy of each reflector was eased, and even relatively large reflectors could be made into plastics, and the cost was reduced by using plastic reflectors. In addition, since the reflecting surface has a rotationally symmetric aspherical shape, the distance between the reflecting mirrors can be reduced to 150 mm or less, and the apparatus becomes compact.
[0097]
When applied to an enlarged projection display device, it is necessary to consider the thermal effect from the light source. For this reason, in particular, the reflecting mirror 7b in FIG. 19 is arranged near the image forming element 6 and is easily affected by heat. Therefore, in order to suppress image distortion, the linear expansion coefficient α of the material is set.
α <6 × 10^-Five
It is desirable to keep it down.
[0098]
(Seventh embodiment)
FIG. 24 shows an example in which a rear projection type display device integrated with a screen using the illumination optical system of the present invention is constructed. The rear projection display device of FIG. 24 includes an illumination optical system 11, a transmissive image forming element 6a, a projection optical system composed of a reflective imaging optical system 70, planar reflecting mirrors 12a and 12b, and a transmissive screen 9. It consists of and. The illumination optical system 11, the transmissive image forming element 6a, and the first reflecting mirror 7a of the reflective imaging optical system 70 are in a straight line, and the imaging surface of the reflective imaging optical system 70 (image surface of the illumination optical system). The transmissive image forming element 6a is also disposed. The illumination optical system 11 is the same illumination optical system as that of the first embodiment. The reflection-type imaging optical system 70 constituting the projection optical system is the same telecentric reflection-type imaging optical system as that of the sixth embodiment.
[0099]
A light beam emitted from the light source of the illumination optical system 11 enters a transmissive image forming element 6a typified by a transmissive liquid crystal light valve. The light beam transmitted through the transmissive image forming element 6a enters a projection optical system including a telecentric reflective imaging optical system 70 while having an opening angle with respect to the principal ray. The reflective imaging optical system 70 is composed of four reflecting mirrors 7a to 7d having the rotationally symmetric aspherical shape shown in FIG. 19, and the luminous flux emitted from the reflective imaging optical system 70 has uniform illuminance. Wide angle of view. The light beam emitted from the reflective imaging optical system 70 is opposed to the reflecting mirror 3d on the emission side of the reflective imaging optical system 70, and has a plane reflecting mirror 12a vertically disposed above the plane reflecting mirror 12a. Are sequentially reflected by a flat reflecting mirror 12b having a reflecting surface horizontally disposed (perpendicular to the flat reflecting mirror 12a), and enlarged to a transmissive screen 9 arranged in parallel to the flat reflecting mirror 12a. Projected.
[0100]
As shown in FIG. 24, when the transmissive screen 9 and the plane reflecting mirrors 12a and 12b are arranged with respect to the reflective imaging optical system 70, the projection can be performed on the screen 9 in a spatially small space. In particular, by arranging and configuring the plane reflecting mirror 12b in parallel to the normal line of the image forming element 6a, the entire apparatus can be made invisible from the view of the observer observing the transmissive screen 9. Further, as shown in FIG. 4, the illumination optical system 11 uses a reflection mirror for reflecting the optical path, which has an advantage that the depth of the display device can be reduced.
[0101]
The sixth and seventh embodiments are examples in which a rotationally symmetric aspherical concave mirror is used as the third reflecting mirror 7c of the reflective imaging optical system 70. However, the third reflecting mirror 7c is rotationally symmetric. An effect similar to that of a rotationally symmetric aspherical concave mirror can be obtained as an aspherical convex mirror. In the sixth and seventh embodiments, a telecentric reflective imaging optical system is used as the projection optical system. However, instead of the telecentric reflective imaging optical system, an ordinary reflective optical system such as an extreme example is used. Alternatively, the optical path may be folded back by using one reflecting mirror or a plurality of reflecting mirrors.
[0102]
【The invention's effect】
  The present invention provides an illumination optical system., Constituted by two or more optical elements including a final-stage imaging optical element having a positive power, and at least one of the two or more optical elements is disposed rotationally decentered with respect to the optical axis of the luminance unevenness reducing means. HaveBy including an afocal optical system, generation of keystone distortion and distortion due to the use of a reflection optical element for turning back an optical path can be suppressed, and the image forming element size and irradiation area can be made substantially the same. In addition, a rectangular irradiation region with a high illuminance and a uniform illuminance distribution can be formed while maintaining the luminance distribution on the emission surface of the luminance unevenness reducing element, and the light utilization efficiency is improved. Furthermore, one reflective optical element that combines the function of folding the optical path and the function of forming the afacial optical system is used for the optical element that forms the afocal optical system.If you haveThe entire device can be downsizedbecome.
[0103]
  The principal ray of the light beam emitted from an arbitrary point of the image forming element and the normal line of the image forming elementAngle θ (see Figures 1, 2, and 3) is 5 ° or moreBy making light incident on the image forming element at an incident angle ofInterference between the illumination optical system and the projection optical system could be eliminated.
[Brief description of the drawings]
FIG. 1 is a diagram showing a state of a light beam entering and exiting an image forming element made of DMD and a principal ray.
FIG. 2 is a view showing a state of a light beam and a chief ray entering / exiting a regular reflection type image forming element.
FIG. 3 is a view showing a state of a light beam entering and exiting a transmissive image forming element and a principal ray.
FIG. 4 is a perspective view of the first embodiment.
FIG. 5 is a perspective view of a second embodiment.
FIG. 6 is a diagram schematically showing the relationship between the arrangement of optical elements and coordinate axes.
FIG. 7 is a schematic diagram showing a state in which an image forming element is irradiated from an oblique direction by a conventional illumination optical system.
FIG. 8 is a diagram showing an illumination state on an image forming element by a conventional illumination optical system.
FIG. 9 is a schematic diagram showing a basic concept of keystone distortion correction.
FIG. 10 is a diagram showing how distortion occurs when a reflective optical element having positive power is used.
FIG. 11 is a schematic diagram showing a basic concept of distortion correction.
FIG. 12 is a view showing an illumination state on the image forming element in the first embodiment.
FIG. 13 is a diagram showing an illuminance distribution on the image forming element in the first embodiment.
FIG. 14 is a diagram showing an illumination state on an image forming element in the second embodiment.
FIG. 15 is a perspective view of a third embodiment.
FIG. 16 is a diagram illustrating an illumination state on an image forming element according to a third embodiment.
FIG. 17 is a view showing an illumination state on an image forming element in a fourth embodiment.
FIG. 18 is a schematic diagram of a projection optical system used in the fifth embodiment.
FIG. 19 is a schematic diagram of a sixth embodiment.
FIG. 20 is a diagram showing the relationship between the shape of a reflecting mirror used in the projection optical system of the sixth embodiment and the coordinate axes.
FIG. 21 is a flowchart showing a procedure for determining a reflector shape and arrangement.
FIG. 22 is a diagram showing the positional relationship of each reflecting mirror and each parameter of the reflecting surface shape.
FIG. 23 is a partially enlarged view of an image forming element and a reflective imaging optical system.
FIG. 24 is a schematic diagram of a seventh embodiment.
[Explanation of symbols]
1 Light source
2 Focusing mirror
3 Light tunnel (luminance unevenness reducing element)
3a Incident end face
3b Outgoing surface
4a First lens
4b Second lens
4c Third lens
4d Reflective optical element with positive power
40 Lens system
41 Optical system with positive power
42 Reflective optical elements with positive power
5 Reflection mirror
6 Image forming elements
6a Transmission type image forming element
60 Irradiation area
7 Projection lens
7a First reflecting mirror (concave mirror)
7b Second reflecting mirror (convex mirror)
7c Third reflecting mirror (concave mirror or convex mirror)
7d Fourth reflector (convex mirror)
70 Reflective imaging optical system
8 chief rays
8a Incident luminous flux
8b Outgoing luminous flux
9 screens
10 Normal of image forming element
11 Illumination optical system
12a Planar reflector
12b Planar reflector
13a Curve showing illuminance distribution
13b Curve showing illuminance distribution

Claims (13)

An illumination optical system that irradiates the image forming element with light emitted from a light source from a direction non-parallel to the normal of the image forming element,
Condensing means for condensing light from the light source;
Luminance unevenness reducing means in which an incident end face is arranged so that light condensed by the light collecting means is incident ;
An afocal optical system that irradiates the image forming element with light emitted from the luminance unevenness reducing unit ;
The afocal optical system is composed of two or more optical elements including a final-stage imaging optical element having a positive power,
An illumination optical system , wherein at least one of the two or more optical elements constituting the afocal optical system is rotationally decentered with respect to the optical axis of the luminance unevenness reducing means . An illumination optical system that irradiates the image forming element with light emitted from a light source from a direction non-parallel to the normal of the image forming element,
A condensing mirror that condenses the light from the light source to form a virtual secondary light source;
Luminance unevenness reducing means in which an incident end face is arranged at a position where the secondary light source is formed, and the luminance distribution of light from the secondary light source is made uniform and emitted,
An afocal optical system having an emission surface of the luminance unevenness reducing unit as an object surface and an irradiation surface irradiated with light from the object surface as an image surface;
The afocal optical system is composed of two or more optical elements including a final-stage imaging optical element having a positive power,
An illumination optical system , wherein at least one of the two or more optical elements constituting the afocal optical system is rotationally decentered with respect to the optical axis of the luminance unevenness reducing means . The afocal optical system includes a first optical element, a second optical element, and a third optical element that are sequentially arranged along an optical path.
3. The illumination optical system according to claim 1, wherein the second optical element and the third optical element are arranged so as to be rotationally decentered with respect to the optical axis of the luminance unevenness reducing unit. . The light is incident on the image forming element at an incident angle at which an angle formed between a principal ray of a light beam emitted from an arbitrary point of the image forming element and a normal line of the image forming element is 5 ° or more. The illumination optical system according to any one of claims 1 to 3. The illumination optical system according to any one of claims 1 to 4, wherein the afocal optical system includes at least two refractive optical elements . The illumination optical system according to any one of claims 1 to 4, wherein the afocal optical system includes at least one refractive optical element and at least one reflective optical element . The illumination optical system according to any one of claims 1 to 6, wherein the afocal optical system includes at least one aspherical optical element . An illumination optical system including an afocal optical system and luminance unevenness reducing means;
An image forming element irradiated with light from a direction non-parallel to the normal by the illumination optical system;
Anda projection shooting optical system for projecting the light beam emitted from the image forming element disposed on the exit side of the image forming device,
The afocal optical system is composed of two or more optical elements including a final-stage imaging optical element having a positive power,
At least one of the two or more optical elements constituting the afocal optical system is arranged to be rotationally decentered with respect to the optical axis of the luminance unevenness reducing means . The afocal optical system includes a first optical element, a second optical element, and a third optical element that are sequentially arranged along an optical path.
9. The enlarged projection display device according to claim 8, wherein the second optical element and the third optical element are arranged to be rotationally decentered with respect to the optical axis of the luminance unevenness reducing means . The illumination optical system irradiates the image forming element with an incident angle at which an angle formed between a principal ray of a light beam emitted from an arbitrary point of the image forming element and a normal line of the image forming element is 5 ° or more. The enlarged projection display device according to claim 8 or 9 . 11. The enlarged projection display device according to claim 8, wherein the afocal optical system includes at least two refractive optical elements . 11. The enlarged projection display device according to claim 8, wherein the afocal optical system includes at least one refractive optical element and at least one reflective optical element . The enlarged projection display device according to any one of claims 8 to 12, wherein the afocal optical system includes at least one aspherical optical element .

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