JP4159840B2 - Projection display device, rear projector and multi-vision system - Google Patents

Description

【０１００】
この平凹レンズ６８と平凸レンズ６９とを接合して構成したレンズ素子５５も、実施の形態１で用いられるレンズ素子と同様に、全体として正パワーを有している。このため、実施の形態１と同様に、照明光学系５２の出射瞳５８から出射される光束６０ａ、６０ｂ及び６０ｃは、それぞれ主光線が互いに略並行で、反射型ライトバルブ５６の光軸６５となす角度が約２０度のテレセントリックな照明光となる。また、各光束の広がり角はいずれも略等しくなる。
【０１０１】
また、反射型ライトバルブ５６からの出射光は、正パワーのレンズ素子５５により光束が小さくされながら、投写レンズ５７の入射瞳５９に入射する。投写レンズ５７の入射瞳５９に入射した光は投写レンズ５７によってスクリーンに拡大投影される。
【０１０２】
本実施の形態３においては、接合する２枚のレンズの屈折率差が大きいほど接合面のパワーが大きくなる。しかしながら、屈折率差が大きいほど接合面での界面反射が増大し、実施の形態１で述べたと同様の反射による不要光が接合面で発生する。このため、投写レンズ５７に入射する不要光成分が多いと、投写画像のコントラストが低下してしまう。
【０１０３】
このため、本実施の形態３では、接合面での反射率を低減して不要光の発生を抑制するため、図６（ａ）に示すように、低屈折率材料で構成された平凹レンズ６８の面６８ｂと高屈折率材料で構成された平凸レンズ６９の面６９ａとの間に、平凹レンズ６８の屈折率よりも大きく、平凸レンズ６９の屈折率よりも小さい屈折率を有する膜が介在した態様としている。
【０１０４】
具体的には、平凸レンズ６９の面６９ａに、両者の材料の少なくとも中間の屈折率を有する薄膜７０ｂを蒸着等によって形成し、薄膜７０ｂが形成された平凸レンズ６９と平凹レンズ６８とを、薄膜７０ｂと平凹レンズ６８との中間の屈折率を有する接着材７０ａによって接合している。図６（ａ）に示す薄膜７０ｂの例としては、Ｓｉ０₂膜、Ｔｉ０₂膜等や、これらの積層膜が挙げられる。
【０１０５】
また、本実施の形態３では、図６（ｂ）に示すように、平凹レンズ６８の面６８ｂと平凸レンズ６９の面６９ａとの間に、屈折率が平凹レンズ６８の屈折率から平凸レンズ６９の屈折率まで変化する膜を介在させた態様とすることもできる。
【０１０６】
具体的には、屈折率が１.５〜１.８５まで連続的に変化する薄膜７０ｂを平凸レンズ６９の面６９ａにスパッタリングによって形成し、この平凸レンズ６９と平凹レンズ６８とを、平凹レンズ６８と同等の屈折率をもつ接着剤７０ａ（例えば、チバ・スペシャル・ケミカルズ社製「アラルダイトＡＹ１０３」等）によって接合している。
【０１０７】
図６（ｂ）に示す薄膜７０ｂの例としては、高い屈折率を有する膜と、中間の屈折率を有する膜と、低い屈折率を有する膜との積層膜が挙げられる。高い屈折率を有する膜としては、Ｎｂ₂Ｏ₅膜、Ｓｂ₂Ｏ₅膜、Ｔａ₂Ｏ₅膜等や、これらの積層膜が挙げられる。中間の屈折率を有する膜としては、Ｓｉ０₂膜、Ｔｉ０₂膜等や、これらの積層膜が挙げられる。また、低い屈折率を有する膜としては、ＭｇＦ₂膜、ＬｉＦ膜、ＢａＦ₂膜等や、これらの積層膜が挙げられる。
【０１０８】
このような図６（ａ）及び（ｂ）に示す態様とすることにより、平凹レンズ６８と平凸レンズ６９との接合面での界面反射はほぼ零に抑制することができるで、反射光による不要光の発生を抑制した正パワーのレンズ素子を得ることができる。
【０１０９】
本実施の形態３においても、照明光学系５２の出射瞳５８からの光束６０ａ、６０ｂ及び６０ｃは、凹レンズ６８の面６８ａに入射し、一部は面６８ａで反射する。しかし、面６８ａは凹面であり、光束６０ａ、６０ｂ及び６０ｃの各主光線は互いに平行ではない。従って、面６８ａの曲率半径を適切に設定することにより、光束６０ａ、６０ｂ及び６０ｃの面６８ａでの反射光がライトバルブ５６の有効表示領域上に虚像を形成するのを抑制できる。また、反射型ライトバルブ５６からの出射光の光束６１ａ、６１ｂ及び６１ｃが、互いに略平行に出射するためには、面６８ａは凹面であることが必要である。
【０１１０】
ところで、平凹レンズ６８の凹面（面６８ａ）の曲率半径が小さいほど、光束６０ａ、６０ｂ及び６０ｃの反射光に含まれる各種光線の反射角度が大きくなり、反射光の投写レンズ５７に入射する成分は少なくなる。しかし、面６８ａの曲率半径が小さくなると、正パワーのレンズ素子５５全体のパワーを確保するためには、接合面となる面６８ｂ及び面６９ａの曲率半径を小さくするか、平凹レンズ６８と平凸レンズ６９との屈折率差を大きくする必要がある。
【０１１１】
ところが、レンズ間の屈折率差は、実用上世の中に存在する透明ガラス材料を用いた場合は最大０.４５程度であり、それ以上大きくすることはできない。また、接合面となる面６８ｂ及び面６９ａの曲率半径を小さくしようとすると、レンズ加工上、中心厚を厚くする必要があり、投写レンズのバックフォーカスが長くなってしまう。従って、これらの理由から、平凹レンズ６８の凹面（面６８ａ）の曲率半径は、面６８ａにおける反射光が形成する虚像がライトバルブ５６の有効表示領域外に形成される範囲で最大の曲率半径を選択するとよい。
【０１１２】
このように、正パワーのレンズ素子５５として、平凹レンズ６８と平凸レンズ６９との接合レンズを用いれば、不要反射光の入射を抑制しつつ、正パワーのレンズとして適切なパワーを得ることができる。更に、照明光学系５２の出射瞳５８からの光束と、反射型ライトバルブ５６から出射されて投写レンズ５７の入射瞳５９に入射する光束との分離を確実なものとできる。
【０１１３】
また、上記の効果を高める点から、本実施の形態３においては、正パワーのレンズ素子５５として焦点距離が４０ｍｍ〜８０ｍｍ程度のものを用いるのが好ましい。なお、正パワーのレンズ素子５５の焦点距離は、反射型ライトバルブ５６への入射光とそれからの出射光とがなす角度、反射型ライトバルブ５６への入射光のＦナンバ、それからの出射光のＦナンバにあわせて適宜選択できる。
【０１１４】
このように本実施の形態３にかかる投写型表示装置を用いれば、実施の形態１にかかる投写型表示装置よりも、更に不要光成分による投写画像の画質の低下を抑制することができる。また、本実施の形態３においても、実施の形態１と同様に、全反射プリズムを用いることなく正面投写を実現することができる。
【０１１５】
（実施の形態４）
次に、本発明の実施の形態４にかかる投写型表示装置について、図７及び図８を参照しながら説明する。図７は、本発明の実施の形態４にかかる投写型表示装置の構成を示す図である。図８（ａ）は、図７に示す反射型ライトバルブの近傍部分における照明光と投写光の光路を示す図であり、図８（ｂ）は、図７に示す反射型ライトバルブの近傍部分における正パワーのレンズ素子の光学界面での反射光の振る舞いを示す図である。
【０１１６】
なお、本実施の形態４でも、反射型ライトバルブとして、図１７で示したＤＭＤが用いられている。図７および図８は、ＤＭＤを構成する微小ミラーの回転支軸に垂直に切断してなる断面で示されている。また、微小ミラーの可動範囲は±１０度である。
【０１１７】
最初に図７を用いて本実施の形態４における投写型表示装置の構成および動作を説明する。本実施の形態４にかかる投写型表示装置は、以下の点で実施の形態１にかかる投写型表示装置と異なっている。図７に示すように、反射型ライトバルブ７６と正パワーのレンズ素子７５とは互いの光軸（８５、８４）を平行にした状態で、光軸（８５、８４）間に距離ｄ１を設けて配置されている。また、距離ｄ１は、レンズ素子７５の光学界面８８で反射する照明光の不要光成分のうち投写レンズ７７に入射する光が、反射型ライトバルブから出射される変調光の有効光成分と分離されるように設定されている。
【０１１８】
更に、本実施の形態４では、正パワーのレンズ素子７５は、実施の形態１で示したレンズ素子と同様の形状を有しているが、有効径や屈折率の点で異なっている。また、投写レンズ７７のスクリーン側に遮光部７３を有している。
【０１１９】
上記の点以外の点では、本実施の形態４にかかる投写型表示装置は、実施の形態１にかかる投写型表示装置と同様に構成されている。即ち、正パワーのレンズ素子７５の配置は、照明光がレンズ素子７５を通過して反射型ライトバルブ７６を照明するように、又反射型ライトバルブ７６から出射する変調光がレンズ素子７５を通過して投写レンズ７７に入射するように行われている。
【０１２０】
また、光源７１、照明光学系７２、反射型ライトバルブ７６及び投写レンズ７７は、実施の形態１で用いられたものと同様のものである。更に、正パワーのレンズ素子７５と投写レンズ７７とは、互いの光軸（８４、８３）が平行となり、これらが一致するように配置されている。照明光学系７２の出射瞳７８と投写レンズ７７の入射瞳７９とは、正パワーのレンズ素子７５について共役関係にある。なお、図７において、８７は正パワーのレンズ素子７５の焦点面、８６は正パワーのレンズ素子７５の焦点である。
【０１２１】
このような構成により、本実施の形態４にかかる投写型表示装置においても、実施の形態１と同様に、反射型ライトバルブ７６からの出射光が正パワーのレンズ素子７５を通過して投写レンズ７７に入射することにより、反射型ライトバルブ７６上の光学像がスクリーン上に拡大投写される。
【０１２２】
次に、図８を用いて本発明の投写型表示装置の原理を説明する。照明光学系７２の出射瞳７８からは、実施の形態１と同様に、光源７１により集光され、照明光学系７２により均一化および整形された光束が出射する。即ち、図８（ａ）に示すように、照明光学系７２の出射瞳７８からは、反射型ライトバルブ７６の上部を照明する光束８０ａ、反射型ライトバルブ７６の中央部を照明する光束８０ｂ、反射型ライトバルブ７６の下部を照明する光束８０ｃが出射される。
【０１２３】
光束８０ａ、８０ｂ及び８０ｃは、正パワーのレンズ素子７５を通過して反射型ライトバルブ７６へと入射する。このため、出射瞳７８から出射する光線の内、反射型ライトバルブ上部を照明する光束８０ａは、正パワーのレンズ素子７５により屈折し、正パワーのレンズ素子７５に入射する前と比べ、正パワーのレンズ素子７５の光軸８４となす角が小さくなる方向に屈折する。
【０１２４】
一方、反射型ライトバルブ７６の下部を照明する光束８０ｃは、正パワーのレンズ素子７５により、光軸８４とのなす角が大きくなる方向に屈折する。このように、実施の形態１と同様に、正パワーのレンズ素子７５を通過した光束８０ａ、光束８０ｂ及び光束８０ｃはそれぞれ主光線が互いに略並行で、反射型ライトバルブ７６の光軸８５となす角度が約２０度のテレセントリックな照明光となる。また、各光束の広がり角はいずれも略等しくなる。
【０１２５】
このとき、図８（ｂ）に示すように、実施の形態１と同様に、照明光学系７２の出射瞳７８からの光束８０ａ、８０ｂ及び８０ｃの一部は、正パワーのレンズ素子７５の光学界面８８で反射され、光束９０ａ、９０ｂ及び９０ｃが発生し、投写レンズ７７の方向に進行する。これらの光束は、反射型ライトバルブ７６の近傍に虚像８２を形成する不要光である。
【０１２６】
しかしながら、本実施の形態４では、上述したように反射型ライトバルブ７６と正パワーのレンズ素子７５とは、互いの光軸（８５、８４）が距離ｄ１だけ離れるように配置されている。また、距離ｄ１は、上述したように、光学界面８８で発生した光束９０ａ、９０ｂ及び９０ｃのうち投写レンズ７７に入射する光が、反射型ライトバルブ７６から出射される変調光の有効光成分と分離されるように設定されている。
【０１２７】
このため、本実施の形態４によれば、虚像８２は、反射型ライトバルブ７６の有効表示領域以外に形成されることとなり、よって、スクリーンの表示領域上における不要光の発生を抑制できるので、画質の優れた投写画像を得ることができる。
【０１２８】
なお、反射型ライトバルブ７６の光軸８５と正パワーのレンズ素子７５の光軸８４との距離ｄ１の設定においては、反射型ライトバルブ７６の有効表示領域の大きさ、照明光学系７２の出射瞳７８の大きさや形状、虚像８２の強度分布等を加味して行なわれる。
【０１２９】
具体的には、距離ｄ１の設定は、以下のようにして行なうことができる。例えば、反射型ライトバルブ７６が矩形の表示領域を有しており、この矩形のいずれかの辺と平行に距離ｄ１が設けられるのであるならば、距離ｄ１はこの辺の長さの１／４以上、１／２以下とするのが好ましい。この場合、投写レンズ７７の有効像円を著しく大きくすること無く、又光軸を互いにチルトさせること無く、適切なパワーで、照明光学系７２の出射瞳７８からの光束と、反射型ライトバルブ７６から出射されて投写レンズ７７の入射瞳７９に入射する光束との分離を確実なものとしつつ、不要光の発生を抑制できる。
【０１３０】
また、本実施の形態４においては、上述したように、投写レンズ７７のスクリーン側に遮光部７３を有している。このため、投写レンズ７７に入射した不要光を遮光することができる。なお、遮光部７３は、不要光を適切に遮蔽できるのであれば、投写レンズ７７からスクリーンまでの間のいずれに配置してもよい。
図７の例では、不要光は投写レンズ７７から出射する光束のうちの一部であるため、遮光部７３の形状は、不要光の通過する領域のみを遮蔽する形状となっている。但し、遮光部７３の形状は特に限定されるものではなく、例えば、開口部を有した枠状や環状等であっても良い。
【０１３１】
この場合、遮光部７３の開口部は、反射型ライトバルブ７６から出射して投写レンズ７７に入射する光束のうち、本来の映像の表示に必要な有効光束のみが、スクリーン（図示せず）に到達するように設ければ良い。
【０１３２】
また、この場合、遮光部７３を投写レンズ７７のスクリーン側に配置するのであれば、一般にここでの光束はスクリーンの有効表示領域とほぼ相似形であるため、開口部もスクリーンの有効表示領域とほぼ相似形となるように形成するのが好ましい。
【０１３３】
本実施の形態４においては、虚像８２が形成される面と反射型ライトバルブ７６の表示面とが略一致した態様とするのが好ましい。この態様とすれば、表示領域中の虚像８２と重なる領域を最も小さくでき、又正パワーのレンズ素子７５の光軸８４と反射型ライトバルブ７６の光軸８５との距離ｄ１を小さくできる。更に、この態様とすれば、投写レンズ７７の有効像円を小さくできる。
【０１３４】
また、本実施の形態４においては、正パワーのレンズ素子７５として焦点距離が５０ｍｍ〜１２０ｍｍ程度のものを用いるのが好ましい。このような正パワーのレンズ素子７５を用いれば、適切なパワーが得られ、照明光学系７２の出射瞳７８からの光束と反射型ライトバルブ７６から出射して投写レンズ７７の入射瞳７９に入射する光束との分離を確実なものとできるからである。
【０１３５】
なお、正パワーのレンズ素子７５の焦点距離は、反射型ライトバルブ７６への入射光とそれからの出射光とがなす角度、反射型ライトバルブ７６への入射光のＦナンバ、それからの出射光のＦナンバにあわせて適宜選択できる。
【０１３６】
また、本実施の形態４では、上述したように、レンズ素子７５として、実施の形態１で用いられたレンズ素子よりも有効径が大きいレンズ素子が用いられている。これは、距離ｄ１が設定されているため、正パワーのレンズ素子７５における照明光の光束が通過する領域と反射型ライトバルブ７６から出射される光束が通過する領域とを合わせた有効領域が広がるからである。
【０１３７】
ところで、１枚の平凸レンズで正パワーのレンズ素子７５を構成し、有効径を大きくしようとすると、コバ厚を確保するために、厚い中心厚が必要になる。従って、本実施の形態４においても、実施の形態１と同様に、正パワーのレンズ素子７５は屈折率の高い硝材で形成するのが好ましい。具体的には、屈折率が１.７４以上、１．８５以下の材料を用いるのが好ましい。
【０１３８】
このように本実施の形態４にかかる投写型表示装置を用いれば、実施の形態１にかかる投写型表示装置よりも、更に不要光成分による投写画像の画質の低下を抑制することができる。また、本実施の形態４においても、実施の形態１と同様に、全反射プリズムを用いることなく正面投写を実現することができる。
【０１３９】
（実施の形態５）
次に、本発明の実施の形態５にかかる投写型表示装置について、図９及び図１０を参照しながら説明する。図９は、本発明の実施の形態５にかかる投写型表示装置の構成を示す図である。図１０は、図９に示す反射型ライトバルブの近傍部分を拡大して示す図である。なお、本実施の形態５でも、反射型ライトバルブとして、図１７で示したＤＭＤが用いられている。図９及び図１０は、ＤＭＤを構成する微小ミラーの回転支軸に垂直に切断してなる断面で示されている。
【０１４０】
最初に、図９を用いて本実施の形態５にかかる投写型表示装置の構成および動作を説明する。本実施の形態５にかかる投写型表示装置は、以下の点で実施の形態１にかかる投写型表示装置と異なっている。図９に示すように、レンズ素子９５と反射型ライトバルブ９６との光軸方向における距離ｄ２は、レンズ素子９５の光学界面で反射する照明光の不要光成分のうち投写レンズ９７に入射する光が、反射型ライトバルブ９６から出射される変調光の有効光成分と分離されるように設定されている。
【０１４１】
また、本実施の形態５にかかる投写型表示装置は、投写レンズ９７のスクリーン側に遮光部１２０を有している。更に、本実施の形態５にかかる投写型表示装置は、カラーホイール１２１を有しており、照明光学系９２の構成が実施の形態１と異なっている。
【０１４２】
上記の点以外の点では、本実施の形態５にかかる投写型表示装置は、実施の形態１にかかる投写型表示装置と同様に構成されている。即ち、光源９１と、正パワーのレンズ素子９５、反射型ライトバルブ９６及び投写レンズ９７は、実施の形態１で用いられたものと同様のものである。
【０１４３】
また、反射型ライトバルブ９６、投写レンズ９７および正パワーのレンズ素子９５は、実施の形態１と同様に配置されており、互いの光軸（１０５、１０３、１０４）は平行、且つ、一致している。更に、実施の形態１と同様に、照明光学系９２の出射瞳９８と投写レンズ９７の入射瞳９９とは、正パワーのレンズ素子９５について共役関係にある。なお、図９において、１０７は正パワーのレンズ素子９５の焦点面、１０６は正パワーのレンズ素子９５の焦点である。
【０１４４】
本実施の形態５においては、照明光学系９２は、照明光学系９２は、コンデンサレンズ１２２と、第１のレンズアレイ１２３と、第２のレンズアレイ１２４と、リレーレンズ１２５とを順に配置して構成されている。
【０１４５】
本実施の形態５において、カラーホイール１２１は、光源９１からの光が集光する凹面鏡１ｂの第２焦点ｆ２に配置されている。カラーホイール１２１は、円周上にＲ（赤）、Ｇ（緑）、Ｂ（青）の３色のフィルタを順に並べて構成されており、その一部を光が通過する。カラーホイール１２１にはモータなどの原動機（図示せず）が取り付けられており、カラーホイール１２１は軸１２６を中心にして高速で回転するよう構成されている。そのため、通過光は順次Ｒ、Ｇ、Ｂに切り替わる。カラーホイール１２１を通過した光は凹面鏡１ｂの第２焦点ｆ２に焦点を持つコンデンサレンズ１２２により略平行光に変換される。
【０１４６】
変換された略平行光は第１のレンズアレイ１２３に入射する。第１のレンズアレイ１２３は複数の正パワーのレンズ素子で構成されており、この複数の正パワーのレンズ素子はそれぞれ反射型ライトバルブ９６の表示領域の形状に略相似形の開口を有している。また、第２のレンズアレイ１２４も第１のレンズアレイ１２３と同様に複数の正パワーのレンズ素子で構成されている。よって、第１のレンズアレイ１２３に入射した略平行光は、第１のレンズアレイ１２３を構成する複数のレンズ素子によって分割され、該レンズ素子に対応する第２のレンズアレイ１２４を構成する各レンズ素子に発光体像を形成する。
【０１４７】
第２のレンズアレイ１２４を構成する各レンズ素子から出射した光線は、リレーレンズ１２５、反射型ライトバルブ９６近傍の正パワーのレンズ素子９５を順に通過し、反射型ライトバルブ９６を照明する。このとき、第２のレンズアレイ１２４の各レンズ素子から出射した光線は反射型ライトバルブ９６の表示領域で重ね合わされる。なお、照明光学系９２の出射瞳９８は第２のレンズアレイ１２４の略近傍であって、リレーレンズ１２５中にある。
【０１４８】
反射型ライトバルブ９６から出射した光線は、正パワーのレンズ素子９５により収束され、投写レンズ９７の入射瞳９９に入射する。よって、反射型ライトバルブ９６上に形成された光学像は投写レンズ９７によりスクリーンに拡大投写される。
【０１４９】
次に、図１０を用いて、本実施の形態５の不要光成分と有効光成分の分離の原理を説明する。照明光学系９２の出射瞳９８からは、光源９１により集光され、照明光学系９２により均一化および整形された光束が出射し、反射型ライトバルブ９６の上部を照明する光束１００ａ、反射型ライトバルブ９６の中央部を照明する光束１００ｂ、反射型ライトバルブ９６の下部を照明する光束１００ｃが出射される。
【０１５０】
このとき、図１０に示すように、図１０中の照明光学系９２の出射瞳９８からの光束１００ａ、１００ｂ及び１００ｃの一部は、正パワーのレンズ素子９５の光学界面１０２で反射され、光束１１９ａ、１１９ｂ、１１９ｃが発生し、投写レンズ９７の方向に進行する。これらの光束は、反射型ライトバルブ９６の近傍に虚像１１２を形成する不要光である。
【０１５１】
しかしながら、本実施の形態５では、上述したように、レンズ素子９５と反射型ライトバルブ９６との距離ｄ２は、レンズ素子９５の光学界面１０２で発生した光束１１９ａ、１１９ｂ及び１１９ｃのうち投写レンズ９７に入射する光が、反射型ライトバルブ９６から出射される変調光の有効光成分と分離されるように設定されている。このため、スクリーンの表示領域上における不要光の発生を抑制でき、画質の優れた投写画像を得ることができる。
【０１５２】
ここで、距離ｄ２の設定について説明する。距離ｄ２を徐々に大きしていくと、照明光の光束１００ａ、１００ｂ及び光束１００ｃがレンズ素子９５を通過する位置は図中下方向にシフトする。更にこれに伴い、反射光の光束１１９ａ、１１９ｂ及び１１９ｃが正パワーのレンズ素子９５で反射する位置も図中下方向にシフトする。
【０１５３】
この場合、光束１１９ａ、１１９ｂ及び１１９ｃのうち投写レンズ９７に入射する光は、反射型ライトバルブ９６から出射される変調光の有効光成分と徐々に分離され、虚像１１２も、相対的に図中下方向に反射型ライトバルブ９６の光軸１０５から遠ざかるように移動する。
【０１５４】
このことから、距離ｄ２は、虚像１１２が反射型ライトバルブ７６の有効表示領域以外に形成されるように設定するのが好ましく、この場合、上述したスクリーンの表示領域上における不要光の発生をより抑制することができ、より優れた画質の投写画像を得ることができる。
【０１５５】
また、本実施の形態５においても、上述したように、投写レンズ９７のスクリーン側に遮光部１２０を有している。このため、投写レンズ９７に入射した不要光を遮光することができる。遮光部１２０は実施の形態４で示したものと同様のものである。
【０１５６】
本実施の形態５においては、照明光学系９２の出射瞳９８から正パワーのレンズ素子９５までの距離と、正パワーのレンズ素子９５の焦点距離を適切に選択することで、虚像１１２が形成される面と、反射型ライトバルブ９６の表示面とを略一致させることができる。この場合、表示領域中の虚像１１２と重なる領域を最も小さくでき、又正パワーのレンズ素子９５と反射型ライトバルブ９６との距離ｄ２を小さくできるので、投写レンズ９７のバックフォーカスを短縮し、小型化を図ることができる。
【０１５７】
ところで、本実施の形態５においては、距離ｄ２を設定しているため、反射型ライトバルブ９６からの出射光の光束は、実施の形態１に比べて大きくなる。このため、本実施の形態５においても、正パワーのレンズ素子の有効径を大きくするのが好ましい態様である。また、実施の形態４で述べたように、正パワーのレンズ素子９５を１枚の平凸レンズで構成しようとすると、コバ厚を確保するために、厚い中心厚が必要になる。従って、本実施の形態５においても、実施の形態１と同様に、正パワーのレンズ素子９５は屈折率の高い硝材で形成するのが好ましい。具体的には、屈折率が１.７４以上、１．８５以下の材料を用いるのが好ましい。
【０１５８】
このように本実施の形態５にかかる投写型表示装置を用いれば、実施の形態１にかかる投写型表示装置よりも、更に不要光成分による投写画像の画質の低下を抑制することができる。また、本実施の形態５においても、実施の形態１と同様に、全反射プリズムを用いることなく正面投写を実現することができる。
【０１５９】
（実施の形態６）
次に、本発明の実施の形態６にかかる投写型表示装置について、図１１〜図１３を参照しながら説明する。図１１は、本発明の実施の形態６にかかる投写型表示装置の構成を示す図である。図１２は、図１１に示す投写型表示装置を構成する投写レンズの入射瞳を示している。なお、本実施の形態６でも、反射型ライトバルブとして、図１７で示したＤＭＤが用いられている。図１１は、ＤＭＤを構成する微小ミラーの回転支軸に垂直に切断してなる断面で示されている。
【０１６０】
最初に、図１１を用いて本実施の形態６にかかる投写型表示装置の構成および動作を説明する。図１１に示すように、本実施の形態６にかかる投写型表示装置は、投写レンズ９７のスクリーン側に遮光部１２０が設けられておらず、代わりに絞りが設けられている点で、実施の形態５にかかる投写型表示装置と異なっている。それ以外の点では、本実施の形態６にかかる投写型表示装置は、実施の形態５にかかる投写型表示装置と同様である。なお、図１１において図９と同じ符号が付された部分は、図９で示されたものと同様のものである。
【０１６１】
本実施の形態６にかかる投写型表示装置においては、図１２に示すように投写レンズ９７の入射瞳９９に、投写レンズ９７の光軸１０３に対して偏心した絞り１３８が設けられている。また、後述するように第２の絞り（図示せず）も設けられている。１２７は有効領域である。このため、反射型ライトバルブ９６で反射される照明光のうち光学像を構成するもの（変調光の有効光成分）のみが絞り１３８を通過する。この点について図１３を用いて説明する。
【０１６２】
図１３は、図１１に示す反射型ライトバルブの表示領域の中心部分における光束の振る舞いを示す図である。図１３では、反射型ライトバルブを構成する微小ミラーのうち表示領域の中心にあるもののみが図示されている。また、図１３は、ＤＭＤを構成する微小ミラーの回転支軸に垂直に切断してなる断面で示されている。図１３において、９６ａはＯＮ状態の微小ミラー、９６ｂはＯＦＦ状態の微小ミラーであり、投写レンズ９７については入射瞳９９のみが示されている。
【０１６３】
図１３に示すように、照明光学系の光軸１２８と反射型ライトバルブ９６の光軸１０５（投写レンズ９７の光軸１０３）とがなす角をβ、ＯＮ状態の微小ミラーの法線１２９と反射型ライトバルブ９６の光軸１０５とがなす角をγとする。このとき、反射型ライトバルブ９６がＯＮ状態のときに出射される光束の主光線１３２と反射型ライトバルブ９６の光軸１０５とのなす角αは下記式（２）であらわされる。
α＝β−２γ・・・・・（２）
【０１６４】
一方、反射型ライトバルブ９６がＯｆｆ状態のときに出射される光束１３９の主光線１３３と反射型ライトバルブの光軸１０５（投写レンズ９７の光軸１０３）とがなす角をδとすると、δは下記式（３）であらわされる。このＯＦＦ状態のときに出射される光束は不要光となる。
δ＝４γ＋α・・・・・（３）
【０１６５】
投写画像の画質を向上するためには、不要光が投写レンズ９７の入射瞳９９に入射してレンズの内部に迷光を発生させたり、不要光がスクリーンに到達したりしないようにすることが必要である。従って、上記式（３）より、角度αを０以上とすれば、δが大きくなり、反射型ライトバルブ９６がＯＦＦ状態の時に出射される光束は、角度αが０の時に光束１４０の位置にあったものが光束１３９の位置へとシフトする。よって、主光線１３３は投写レンズの入射瞳９９から遠くなり、上記の不要光が入射瞳９９に入射するのを抑制できる。
【０１６６】
また、反射型ライトバルブ９６がＯＮ状態のときに出射される光束の主光線１３２と反射型ライトバルブの光軸１０５とが一致するとき、即ちαが０度の場合の有効領域は点線で示す１３０である。しかし、主光線１３２が傾くと（α>０）と有効領域は図中上方向にシフトし、この場合の有効領域は図１２でも示した１２７となる。よって、本実施の態様においては、投写レンズの入射瞳９９のうち、有効領域１２７以外の領域は、不要光が通過しないよう絞り１３８を設けて遮光している。
【０１６７】
また、反射型ライトバルブの表面に設けられた透明基板で反射される光も不要光となるが、この不要光の主光線１３４と反射型ライトバルブの光軸１０５（投写レンズ９７の光軸１０３）とがなす角もβとなる。よって、角度αを０度以上とすることで、この不要光の主光線１３４と反射型ライトバルブの光軸１０５（投写レンズ９７の光軸１０３）とがなす角βも大きくなり、この不要光が投写レンズの入射瞳９９に入射するのも抑制できる。
【０１６８】
ところで、反射型ライトバルブ９６の表示領域（図示せず）には、微少ミラー、駆動用信号線及び画素電極等で構成された画素が周期的に形成されている。投写画像の高精細化が進むにつれ、反射型ライトバルブ９６上の有効画素数も増大する。このため、反射型ライトバルブ９６のサイズが大型化しない限り、反射型ライトバルブ９６上の画素（微小ミラー）の大きさは小さくなり、画素のピッチも小さくなる。
【０１６９】
また、一般に、反射型ライトバルブのサイズを小さくすることで、反射型ライトバルブ及びそれを用いた光学系のコストを低減することができるので、反射型ライトバルブは小型化するのが好ましいと言える。従って、画素の大きさ及びピッチは今後より小さくなる可能性が高いと考えられる。
【０１７０】
ここで、図１７に示すような反射型ライトバルブのような周期的な構造を有する物体に光が入射した場合を考える。一般に、微細な周期構造をもつ物体に光が入射すると、周期構造をもつ物体は回折格子として機能し、０次光、１次光、２次光、・・・の回折光が発生する。回折格子が反射面で形成される場合には、反射光が回折光になる。回折光は次数に合わせて離散的に強度分布を持って発生し、各次数の回折光は下記式（４）を満たす。なお、下記式（４）において、θは入射光が光軸となす角、θ´は出射光が光軸となす角、ｎは整数で回折次数、λは波長、ｄ３は周期構造のピッチを示す。
（ｎλ）／ｄ３＝ｓｉｎθ−ｓｉｎθ´・・・・・（４）
【０１７１】
従って、図１７に示すような反射型ライトバルブでは、反射型ライトバルブの透明基板で反射されて発生する不要光は、主光線１３４を中心として軸１３５ａ及び１３５ｂの方向に角度θ１の広がり角を有する光束１３６として出射されると共に、上記した微細な周期構造によって発生する回折光としても出射される。この回折光のうち、０次光の外側に発生する１次光の光束は、光束１３６の最外周に位置する軸１３５ａ及び１３５ｂに対し、離散的に出射するが、重畳されて、θ1よりおおきな広がり角を有する光束１３７として出射する。
【０１７２】
ところで、上記の回折光において強度の最も強い光は、１次の回折光である。１次の回折光は、入射光に対し、下記式（５）で表される角度φの広がり角を持って出射される。
ｓｉｎφ＝λ／ｄ・・・・・（５）
【０１７３】
従って、透明基板で反射されて発生する光束１３７は、上記式（５）より、光束１３６の広がり角θ１を含む角度（θ１＋φ）の角度で出射する。
【０１７４】
一方、図１３から分かるように、βは下記式（６）の関係も満たす。なお、θ1は上述したように反射型ライトバルブ９６で反射されて投写レンズに入射する光の広がり角である。
β＝２θ1＋α・・・・・（６）
【０１７５】
従って、図１３に示すように、反射型ライトバルブ９６から出射される変調光の有効光成分（ＯＮ光）の一部が不要光の光束１３７と重なってしまい、不要光の光束１３７の一部が有効領域１２７を通過してしまう。このため、本実施の形態６においては、図１３に示すように第２の絞り１３１を設けて有効領域１２７の一部を遮光し、光束１３７の一部が通過しない構成としている。また、第２の絞り１３１は、その最も光軸１０５側の端部と微小ミラー９６ａとを結ぶ線の光軸１０５に対する角度が（θ３−φ）又は（θ１＋α−φ）となるように、光束１３７の外形に沿って形成するのが好ましい。
【０１７６】
また、本実施の形態６においては、入射瞳９９は図１３で示すように有効領域１２７を包含する必要がある。よって、投写レンズのＦナンバＦ１は、下記式（１）を満たすものであるのが好ましい。
Ｆ１=１／（２ｓｉｎ（θ１十α））・・・・・（１）
【０１７７】
例えば、反射型ライトバルブの画素ピッチが１４μｍ程度である場合、１次回折光は光束１３６に対して約２.４度（φ＝２.４度）広がり角を大きくした範囲で発生する。従って、投写レンズの有効入射瞳（有効領域１２７）は光軸１０３に対して２.４度より大きい角度（α）で偏心させるのが好ましい。また、この場合、微小ミラー（９６ａ、９６ｂ）の傾き角が±１０度であるとすると、投写レンズのＦナンバＦ１は、偏芯の無い場合の約３に対し、上記式（１）より約２.４となる。
【０１７８】
このように本実施の形態６にかかる投写型表示装置においては、投写レンズの入射瞳９９に偏心した絞り１３８と第２の絞り１３１とを設け、反射型ライトバルブからの画像を構成する光束がこれらの絞りを通過するように構成されている。即ち、本実施の形態６においては、反射型ライトバルブがＯＮ状態のときに出射される光束の主光線１３２と反射型ライトバルブの光軸１０５とのなす角αは０度より大きく設定されている。
【０１７９】
よって、本実施の形態６にかかる投写型表示装置を用いれば、Ｏｆｆ光や透明基板で反射された光等の不要光が投写レンズの入射瞳９９に入射するのを抑制でき、投写画像の画質の向上を図ることができる。なお、本実施の形態では絞り１３８は円形を呈しているが、本実施の形態においてはこれに限定されるものではなく、例えば楕円形を呈するものであっても良い。
【０１８０】
このように本実施の形態６にかかる投写型表示装置を用いれば、実施の形態１にかかる投写型表示装置よりも、更に不要光成分による投写画像の画質の低下を抑制することができる。また、本実施の形態６においても、実施の形態１と同様に、全反射プリズムを用いることなく正面投写を実現することができる。
【０１８１】
また、このように投写レンズには偏心した絞り１３８や第２の絞り１３１が設けられているため、絞りが設けられているレンズまたはレンズ群を回転させ、この回転によって前後に焦点調整を行うのは好ましくない。従って、本実施の形態６においては、投写レンズの焦点調整手段としては、レンズ群を回転させることなく光軸方向への移動のみによって焦点調整を行うものが好ましく、特には投写レンズを構成するレンズ群のうち前群のみを移動させて焦点調整を行うものが好ましい。
【０１８２】
具体的には、前進ヘリコイドを用いた焦点調整手段が挙げられる。なお、偏芯した絞りが設けられていないレンズ群のみを回転させて焦点調整を行うのであれば、このような焦点調整手段を用いるのも好ましい態様である。
【０１８３】
また、本実施の形態６においても、実施の形態５と同様に、正パワーのレンズ素子９５は、屈折率の高い硝材で構成しているのが好ましい。具体的には、屈折率が１.７４以上、１．８５以下の材料を用いるのが好ましい。
【０１８４】
（実施の形態７）
次に本発明の実施の形態７にかかる投写型表示装置について、図１４を参照しながら説明する。図１４は、本発明の実施の形態７にかかる投写型表示装置の構成を示す図である。なお、本実施の形態７でも、反射型ライトバルブとして、図１７で示したＤＭＤが用いられている。図１４はＤＭＤを構成する微小ミラーの回転軸に垂直に切断してなる断面で示されている。
【０１８５】
図１４に示すように、本実施の形態７にかかる投写型表示装置は、照明光学系の１４２の構成が異なる以外は、実施の形態６と同様に構成されている。即ち、光源１４１と、正パワーのレンズ素子１４５反射型ライトバルブ１４６及び投写レンズ１４７は実施の形態６と同様のものであり、これらは実施の形態６と同様に配置されている。
【０１８６】
本実施の形態７においては、照明光学系１４２は、コンデンサレンズ１６０と、光束を分割するレンズアレイ１６４と、複数の光ファイバー１６６を束ねて構成されたライトガイド１６５と、リレーレンズ１６７とを順に配置して構成されている。
【０１８７】
このため、カラーホイール１２１を通過し、コンデンサレンズ１６０によって変換された略平行光は、レンズアレイ１６４を通過して、ライトガイド１６５を構成する各光ファイバー１６６に入射する。各光ファイバー１６６に入射した光は、ファイバー内部で反射を繰り返した後、出射する。
【０１８８】
ところで、実施の形態１〜実施の形態５に示す投写型表示装置では、照明光学系の各要素（例えば照明光学系２のリレーレンズ系４など）は照明光学系の光軸に垂直である。しかし、照明光学系は、その光軸が、正パワーのレンズの光軸及び反射型ライトバルブの光軸に対し傾斜するように配置されている。このため、「シャインプルーフの定理」から反射型ライトバルブ上に到達する照明光の形状が菱形や台形等の矩形を傾けた形状となる可能性がある。この場合、反射型ライトバルブから出射する光は図中上から下に向けて光束密度が高くなり、光束分布が不均一となる。
【０１８９】
さらに、反射型ライトバルブ１４６から出射された光の光束１５１ａ、１５１ｂ及び１５１ｃが正パワーのレンズ素子１４５を通過すると、これらには屈折が発生するが、屈折方向および屈折力は反射型ライトバルブ１４６の表示領域のどの部分で反射されたかによって異なる。このため、投写レンズ１４７の入射瞳１４９においても図中上から下に向けて光束密度が高くなり、光束分布が不均一となる可能性がある。
【０１９０】
このような光束分布の不均一が生じると、照明光学系１４２の出射瞳１４８における一部の領域と投写レンズ１４７の入射瞳１４９における一部の領域とは、正パワーのレンズについて、共役関係が保てなくなり、投写画像の明るさが不均一となる可能性がある。
【０１９１】
このため、本実施の形態７においては、上述したように、ライトガイド１６５を用いて照明光学系１４２を構成している。ライトガイド１６５は複数の光ファイバー１６６を束ねて構成され、照明光学系１４２の出射瞳１４８は２次元状に配置された複数の光ファイバー１６６の出射光で構成される。よって、照明光学系１４２の出射瞳１４８は複数の部分瞳要素を有することとなり、出射瞳１４８の形状は複数の部分瞳要素の結合した面形状となる。なお、本実施の形態においてこの面は自由曲面であっても良い。
【０１９２】
更に、図１４に示すように複数の光ファイバー１６６はライトガイド１６５の入射面１６５ａにおいて均等に配列され、出射面１６５ｂにおいて不均等に配列されている。図１４の例では、出射面１６５ｂにおいて光ファイバー１６６の密度は図中上から下に向けて低くなっている。このため照明光学系１４２から出射する照明光の光束分布は、出射された時点では不均一であるが、反射型ライトバルブで反射されたときに均一となる。即ち、「シャインプルーフの定理」から反射型ライトバルブ１４６上に到達する照明光の形状が矩形を傾けた形状となるのが抑制される。
【０１９３】
よって、投写レンズ１４７の入射瞳１４９の全域又は略全域と照明光学系１４２の出射瞳１４８の全域又は略全域とは良好な共役関係を満たすようになり、照明光学系１４２の出射瞳１４８から出射する照明光は、投写光学系１４７の入射瞳１４９を最大限通過する。
【０１９４】
本実施の形態７では、投写レンズ１４７の入射瞳１４９と照明光学系１４２の出射瞳１４８とは正パワーのレンズ素子１４５について共役関係にあるよう配置されている。従って、「シャインプルーフの定理」より、照明光学系１４２の出射瞳１４８の光束分布を適切に制御することで、投写レンズ１４７の入射瞳１４９上の光束分布を均一にすることができ、均一な明るさの投写画像を得ることができる。
【０１９５】
なお、本実施の形態では、照明光学系１４２は、ライトガイド１６５を用いた態様に限定されるものではない。照明光学系１４２は、ライトガイド１６５の代わりに、複数の正パワーのレンズ素子で構成されたレンズアレイが複数枚配置された構成であっても良い。この構成では、レンズアレイを構成する正パワーのレンズ素子として焦点距離がそれぞれ異なるものを用いることで、照明光学系から出射する照明光の光束分布を適切に制御できる。よって、この態様においても反射型ライトバルブで反射された照明光の光束分布を均一なものとすることができる。また、本実施の形態７で示した照明光学系１４２は、他の実施の形態にかかる投写型表示装置の照明光学系として用いることもできる。
【０１９６】
また、本実施の形態７においても、投写レンズ１４７に実施の形態６で示した構成と同様の絞り（図１３中に示す絞り１３８及び第２の絞り１３１）が設けられている。このため、照明光学系１４２は、反射型ライトバルブ１４６で反射される照明光のうち光学像を構成するものが、これら絞りを通過するように配置する必要がある。またこの場合、投写レンズのＦナンバは実施の形態６と同様に上記式（１）を満たしているのが好ましい。
【０１９７】
また、本実施の形態７においても、実施の形態５と同様に、正パワーのレンズ素子１４５は、屈折率の高い硝材で形成するのが好ましい。具体的には、屈折率が１.７４以上、１．８５以下の材料を用いるのが好ましい。
【０１９８】
本発明の投写型表示装置においては、反射型ライトバルブを複数枚用いることもできる。なお、この場合は、各反射型ライトバルブに単色光を入射させるための色分離光学系と、各反射型ライトバルブから出射する光を合成する色合成光学系とを設ける必要がある。
【０１９９】
また、本発明の投写型表示装置においては、反射型ライトバルブの各画素を構成する微小ミラーの可動範囲は±１０度に限定されるものではない。本発明においては、微小ミラーの可動範囲は、使用される反射型ライトバルブの特性に応じ、最適な光出力と高いコントラストが得られるように設定すれば良い。
【０２００】
更に、本発明の投写型表示装置においては、反射型ライトバルブの各画素は稼動する微小ミラーで構成された態様に限定されるものではない。本発明の投写型表示装置においては、反射型ライトバルブは、光の入射方向と出射方向が異なるものであって、出射方向を制御できるものであれば良い。
【０２０１】
（実施の形態８）
図１５は、本発明のリアプロジェクタの一例を示す構成図である。図１５に示すように、リアプロジェックタは、実施の形態１から実施の形態７のいずれかに示した投写型表示装置１７０と、投写型表示装置１７０から投写された光を反射するミラー１７１と、ミラー１７１で反射された光を透過散乱させて表示するスクリーン１７２と、これらを収容する筐体１７３とで構成される。
【０２０２】
このように、図１５に示すリアプロジェクタでは、実施の形態１から実施の形態７のいずれかで示した投写型表示装置を用いるため、小型化及び低コスト化を図ることができ、又画質の良好な投写画像を表示することができる。
【０２０３】
（実施の形態９）
図１６は、本発明のマルチビジョンシステムの一例を示す構成図である。図１６に示すように、マルチビジョンシステムは、複数の投写システムと、映像信号分割回路１８９とを有している。各投写システムは、実施の形態１から実施の形態７のいずれかで示した投写型表示装置（１８０〜１８２）と、透過型スクリーン（１８３〜１８５）と、筐体（１８６〜１８８）とで構成されている。
【０２０４】
映像信号分割回路１８９は、画面を複数の領域に分割し、各領域の映像信号を加工して、各投写システムを構成する投写型表示装置１８０、１８１及び１８２に供給する。このため、投写型表示装置１８０、１８１及び１８２から投写されるそれぞれの映像は、それぞれに対応する透過型スクリーン１８３、１８４及び１８５に結像され、全体として１枚の画像を構成する。このように本実施の形態のマルチビジョンシステムによれば、大画面でありながら、奥行きの短いコンパクトなセットが実現できる。
【０２０５】
また、透過型スクリーン１８３〜１８５のうちの２つで全体として一つの画像を表示し、残りの一つに別の画像を表示しても良い。また、視覚効果を得るために、各透過型スクリーンに同じ画像を表示しても良い。更に、多様な情報を１度に提供するため、各透過型スクリーンに別々のコンテンツを表示するようにして良い。
【０２０６】
投写型表示装置１８０、１８１及び１８２は、各筐体内に取り付けられたセンサにより、点灯開始時の光出力及び色再現性に応じて、映像分割回路１８９によって分配された信号の輝度や色度、彩度等の色情報を加工する態様としても良い。この場合、投写型表示装置１８０、１８１及び投写型表示装置１８２から別々に投写される画像であっても、一つの画面として均一性の高い表示が実現できる。
【０２０７】
【発明の効果】
以上説明したように、本発明によれば、反射型ライトバルブ表示領域の近傍に正パワーのレンズ素子を配置し、照明光学系の出射瞳の虚像を有効表示領域内に形成しないようにすることができる。このため、テレセントリックな光学系においても、投写レンズの入射瞳、照明光学系の出射瞳の有効系を小さくすることができ、入射光と出射光の光路をコンパクトな構成で分離できる。このため、従来使用されていた全反射プリズムスプリッタ等の照明光と投影光とを分離する手段が不用となる。よって、コストダウンを図りつつ、テレセントリックな光学系での正面投写が可能となり、投写面内における画質の均質化を実現できる。
【０２０８】
即ち、本発明の投写型表示装置によれば、反射型ライトバルブを用いた、コンパクトで、且つ、高画質の表示光学系を実現する事ができると言える。また、本発明にかかる投写型表示装置は正面投写による均質な画像を確保することができる。更に、プリズムを用いないため、低価格化を図ると同時に、明るくコントラストの良い高画質を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態１にかかる投写型表示装置の構成を示す図である。
【図２】図２（ａ）は、図１に示す反射型ライトバルブの近傍部分における照明光と投写光の光路を示す図であり、図２（ｂ）は、図１に示す反射型ライトバルブの近傍部分における正パワーのレンズ素子の光学界面での反射光の振る舞いを示す図である。
【図３】本発明の実施の形態２にかかる投写型表示装置の構成を示す図である。
【図４】図３に示す正パワーのレンズ素子の表面を拡大して示す図である。
【図５】本発明の実施の形態３にかかる投写型表示装置の構成を示す図である。
【図６】図５に示す正パワーのレンズ素子を拡大して示す断面図である。
【図７】本発明の実施の形態４にかかる投写型表示装置の構成を示す図である。
【図８】図８（ａ）は、図７に示す反射型ライトバルブの近傍部分における照明光と投写光の光路を示す図であり、図８（ｂ）は、図７に示す反射型ライトバルブの近傍部分における正パワーのレンズ素子の光学界面での反射光の振る舞いを示す図である。
【図９】本発明の実施の形態５にかかる投写型表示装置の構成を示す図である。
【図１０】図９に示す反射型ライトバルブの近傍部分を拡大して示す図である。
【図１１】本発明の実施の形態６にかかる投写型表示装置の構成を示す図である。
【図１２】図１１に示す投写型表示装置を構成する投写レンズの入射瞳を示している。
【図１３】図１１に示す反射型ライトバルブの表示領域の中心部分における光束の振る舞いを示す図である。
【図１４】本発明の実施の形態７にかかる投写型表示装置の構成を示す図である。
【図１５】本発明のリアプロジェクタの一例を示す構成図である。
【図１６】本発明のマルチビジョンシステムの一例を示す構成図である。
【図１７】従来からのＤＭＤの各画素を構成する微小ミラーの動作状態を示す図である。
【図１８】従来のＤＭＤを用いた投写型表示装置の概略構成を示す図である。
【図１９】図１８に示すＤＭＤの近傍部分を拡大して示す図である。
【図２０】従来の投写レンズを非テレセントリック系とした投写型表示装置の概略構成を示す図である。
【図２１】図２０に示す反射型ライトバルブの近傍部分を拡大して示す図である。
【符号の説明】
１、３１、５１、７１、９１、１４１ 光源
１ａ ランプ
１ｂ 凹面鏡
２、３２、５２、７２、９２、１４２ 照明光学系
３ ロッドレンズ
４ リレーレンズ系
５、３５、５５、７５、９５、１４５ 正パワーのレンズ素子
６、３６、５６、７６、９６、１４６ 反射型ライトバルブ
７、３７、５７、７７、９７、１４７ 投写レンズ
８、３８、５８、７８、９８、１４８ 照明光学系の出射瞳
９、３９、５９、７９、９９、１４９ 投写レンズの入射瞳９
１０ａ〜１０ｃ、４０ａ〜４０ｃ、６０ａ〜６０ｃ、８０ａ〜８０ｃ、１００ａ〜１００ｃ、１５０ａ〜１５０ｃ 照明光の光束
１１ａ〜１１ｃ、４１ａ〜４１ｃ、６１ａ〜６１ｃ、１０１ａ〜１０１ｃ、１５１ａ〜１５１ｃ 反射型ライトバルブからの出射光の光束
１３、４３、６３、８３、１０３、１５３ 投写レンズの光軸
１４、４４、６４、８４、１０４、１５４ 正パワーのレンズ素子の光軸
１５、４５、６５、８５、１０５、１５５ 反射型ライトバルブの光軸
１６、４６、６６、８６、１０６、１５６ 正パワーのレンズ素子の焦点
１７、４７、６７、８７、１０７、１５７ 正パワーのレンズ素子の焦点面
１８ ロッドレンズの入射面
１９ ロッドレンズの出射面
２０ａ、８８、１０２ 光学界面（凸面）
２０ｂ、８９ 光学界面（凸面）
２１ａ〜２１ｃ、９０ａ〜９０ｃ、１１９ａ〜１１９ｃ 光学界面における反射光の光束
２２、８２、１１２ 虚像
４２ 突起
６８ 平凹レンズ
６８ａ、６８ｂ 平凹レンズの面
６９ 平凸レンズ
６９ａ、６９ｂ 平凸レンズの面
７０ａ 接着剤
７０ｂ 薄膜
９６ａ ＯＮ状態の微小ミラー
９６ｂ Ｏｆｆ状態の微小ミラー
１２０ 遮光部
１２１ カラーホイール
１２２ コンデンサレンズ
１２３ 第１のレンズアレイ
１２４ 第２のレンズアレイ
１２５ リレーレンズ
１２６ 軸
１２７ 有効領域
１２９ ＯＮ状態の微小ミラーの法線
１３０ αが０度の場合の有効領域
１３１ 第２の絞り
１３２ 反射型ライトバルブがＯｎ状態のときに出射される光束の主光線
１３３ 反射型ライトバルブがＯｆｆ状態のときに出射される光束の主光線
１３４ 不要光の主光線
１３５ 軸
１３６ 不要光の光束
１３７ 回折光の光束
１３８ 絞り
１３９ 反射型ライトバルブがＯＦＦ状態のときに出射される光束
１６０ コンデンサレンズ
１６４ 光束を分割するレンズアレイ
１６５ ライトガイド
１６５ａ ライトガイドの入射面
１６５ｂ ライトガイドの出射面
１６６ 光ファイバー
１６７ リレーレンズ
１７０、１８０〜１８２ 投写型表示装置
１７１ ミラー
１７２、１８３〜１８５ スクリーン
１７３、１８６〜１８８ 筐体
１８９ 映像信号分割回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection display device, a rear projector using the same, and a multivision system.
[0002]
[Prior art]
As a method for obtaining a large screen image, a method of forming an optical image corresponding to an image signal on a reflective light valve, irradiating the optical image with light, and enlarging and projecting the image on a screen by a projection lens has been well known. ing. If a reflection type light distribution correction element that forms an optical image by controlling the traveling direction of light according to a video signal is used as this reflection type light valve, a projected image with higher light utilization efficiency and high brightness can be obtained. Can be displayed.
[0003]
A DMD (Digital Micro Mirror Device) has attracted attention as a reflective light valve. The DMD is formed by two-dimensionally arranging a plurality of minute reflecting mirrors (hereinafter referred to as “minute mirrors”) on a silicon substrate, and each minute mirror constitutes a pixel. Each micromirror is configured to move like a seesaw within a range of ± 10 degrees by two rotational support shafts provided diagonally at diagonal positions of pixels. For example, the state where the micromirror is tilted by +10 degrees is ON, and the state where the micromirror is tilted by 10 degrees is OFF. The DMD forms an optical image by controlling the light emission direction by tilting each micromirror by +10 degrees or −10 degrees according to the video signal.
[0004]
FIG. 17 is a diagram illustrating an operation state of a micromirror that constitutes each pixel of a conventional DMD. This figure is shown in a cross section cut perpendicularly to the rotation support shaft of each micromirror of the DMD, and the counterclockwise direction is the positive rotation direction of the micromirror. In FIG. 17, reference numerals 191 to 196 denote minute mirrors, which constitute each pixel. Reference numeral 197 denotes a part of the projection lens.
[0005]
In the example of FIG. 17, the micro mirror 191, the micro mirror 193, and the micro mirror 196 are inclined +10 degrees (counterclockwise) with respect to the reference surface 190 of the reflective light valve (DMD), and are in the ON state. For this reason, incident light 198 reflected by the micromirror 191, micromirror 193, and micromirror 196 enters the projection lens 197.
[0006]
On the other hand, the minute mirror 192, the minute mirror 194, and the minute mirror 195 are inclined by −10 degrees (clockwise) with respect to the reference surface 190 of the reflective light valve, and are in the OFF state. For this reason, incident light 198 reflected by the minute mirror 192, minute mirror 194, and minute mirror 195 does not enter the projection lens 197. Such a DMD has characteristics such as that it can use natural light, has a high light utilization rate, and has a high response speed compared to a liquid crystal panel using polarized light.
[0007]
A configuration example is shown in Patent Document 1 as an optical system of a projection display device using a DMD as a reflective light valve. FIG. 18 is a diagram showing a schematic configuration of a projection display device using a conventional DMD. FIG. 19 is an enlarged view showing the vicinity of the DMD shown in FIG. 18 and 19 show cross sections obtained by cutting perpendicularly to the rotation support shaft of each micromirror of the DMD.
[0008]
First, a description will be given with reference to FIG. The light source 201 includes a concave mirror 201b and a lamp 201a. The concave mirror 201b is an elliptical mirror, and is formed by vapor-depositing an optical multilayer film that transmits infrared light but reflects visible light on the inner surface of a glass substrate. The lamp 201a is arranged so that the center of the light emitter is positioned at the first focal point (not shown) of the concave mirror 201b.
[0009]
The light emitted from the lamp 201a is reflected by the concave mirror 201b, travels to the second focal point (not shown) of the concave mirror 201b, and forms a light emitter image at the second focal point. Further, the light passing through the second focal point sequentially passes through the lens arrays 202a and 202b and is divided into a plurality of light beams, and then enters the relay lens 203 and is superimposed. The lens arrays 202a and 202b are composed of a plurality of positive power lens elements.
[0010]
The light emitted from the relay lens 203 is reflected by the total reflection mirror 204 and enters the total reflection prism 208 through the field lens 205. The total reflection prism 208 is composed of two single prisms 208a and 208b arranged via an air layer 209. Reference numeral 207 denotes a projection lens.
[0011]
Next, a description will be given with reference to FIG. Incident light 209a to 209c incident on the total reflection prism 208 is totally reflected at the interface between the single prism 208b and the air layer 209 and proceeds toward the reflective light valve 206. The reflection type light valve 206 controls the traveling direction of light according to the video signal to form an optical image.
[0012]
Reflected light 210a to 210c from the reflective light valve 206 is emitted as a light beam having a principal ray perpendicular to the display area of the reflective light valve 206, and is reflected at the interface between the single prism 208b or 208a and the air layer 209. Without passing through the total reflection prism 208, the light enters the projection lens 207 (see FIG. 18). As a result, the optical image on the reflective light valve 206 is enlarged and projected on the screen by the projection lens 207.
[0013]
As described above, when the projection display device shown in FIGS. 18 and 19 is used, the optical path of the illumination light and the optical path of the projection light can be prevented from overlapping, and the image quality of the projected image can be improved. In addition, an increase in the size of the projection lens can be suppressed.
[0014]
However, the projection type display apparatus shown in FIGS. 18 and 19 requires the total reflection prism 208 to separate the illumination light and the projection light, resulting in an increase in cost after all. . Further, since the total reflection prism 208 includes a minute air layer inside, the resolution characteristic of the projection lens 207 is greatly influenced by the tolerance.
[0015]
In order to solve this problem, Patent Document 2 discloses a configuration in which the projection lens is a non-telecentric system and illumination is generated accordingly.
[0016]
FIG. 20 is a diagram showing a schematic configuration of a projection display apparatus in which a conventional projection lens is a non-telecentric system. FIG. 21 is an enlarged view showing the vicinity of the reflective light valve shown in FIG. 20 and 21, DMD is used as the reflective light valve. 20 and 21 are shown in a cross section cut perpendicularly to the rotation support shaft of each micromirror of the DMD.
[0017]
As shown in FIG. 20, the light source 211 includes a lamp 211a and a concave mirror 211b in the same manner as the light source shown in FIG. The lamp 211a and the concave mirror 211b are the same as the lamp 201a and the concave mirror 201b shown in FIG. The lamp 211a is also arranged so that the center of the light emitter is located at the first focal point f1 of the concave mirror 211b. Similarly to the example of FIG. 18, the light emitted from the lamp 211a is reflected by the concave mirror 211b and forms a light emitter image at the second focal point f2. The light that has passed through the second focal point f2 enters the rod lens 212 and is made uniform. The illumination light made uniform by the rod lens 212 passes through the relay lens 213.
[0018]
As shown in FIG. 21, the illumination light that has passed through the relay lens 213 passes through the exit pupil 217 of the illumination optical system and enters the reflective light valve 214 at a predetermined incident angle. The reflective light valve 214 controls the light traveling direction according to the video signal to form an optical image. Incident light 215a to 215c to the reflective light valve 214 is reflected at a predetermined angle, and the reflected light 216a to 216b is incident on an entrance pupil 218 of the projection lens.
[0019]
20 and 21, a non-telecentric projection lens is used as the projection lens 219. Therefore, the optical image formed by the reflective light valve 214 can be enlarged and projected on the screen without using a total reflection prism. Therefore, according to the projection display apparatus shown in FIGS. 20 and 21, it is considered that the cost can be reduced as compared with the projection display apparatus shown in FIG.
[0020]
By the way, the reflection type light valve 214 is configured so that the normal direction of the reflection surface of the micromirror is constant over the entire display area. Therefore, in the configuration of the projection display device shown in FIGS. If the optical axis of the reflective light valve 214 and the optical axis of the projection lens are substantially coincident, the optical paths of the incident light 215a to 215c and the reflected light 216a to 216c will overlap. For this reason, as shown in FIGS. 20 and 21, the optical axis of the projection lens 219 is offset with respect to the optical axis of the reflective light valve 214 to separate the incident light 215a to 215c and the reflected light 216a to 216c. ing.
[0021]
However, in the projection display apparatus shown in FIG. 20 and FIG. 21, the projection lens 219 projects in a state where its optical axis is shifted from the optical axis of the reflective light valve 214. In order to obtain a good image with illumination, it is necessary to enlarge the effective display area. As a result, the projection display apparatus shown in FIGS. 20 and 21 has a problem that the optical system becomes large and the cost increases. There is also a problem that front projection is not possible.
[0022]
Further, Patent Document 3 discloses a projection display device in which a condenser lens that constitutes a part of a projection lens is disposed immediately before a display area of a reflective light valve. In this projection display device, the illumination light is refracted by the condenser lens and enters the reflection type light valve, and the outgoing light from the reflection type light valve is also refracted by the condenser lens and enters the projection lens. Further, this lens is arranged with its optical axis decentered with respect to the optical axis of the projection lens.
[0023]
For this reason, the incident angle of the incident light to the reflective light valve and the outgoing angle of the outgoing light from the reflective light valve vary depending on the position of the display area of the reflective light valve. The change is asymmetric with respect to the optical axis of the reflective light valve or the optical axis of the projection lens.
[0024]
Therefore, even the projection display device described in Patent Document 3 can suppress the overlap of the optical path of the incident light to the reflective light valve and the optical path of the outgoing light from the reflective light valve. Further, since it is not necessary to use a prism, the apparatus can be reduced in size.
[0025]
However, in the projection display device described in Patent Document 3, the condenser lens arranged just before the display area of the reflective light valve is decentered, and this condenser lens constitutes a part of the projection lens. . For this reason, it is considered difficult to obtain an image in which the aberration balance is symmetric about the optical axis, and when the aberration balance is to be corrected, it is necessary to increase the number of projection lenses. It becomes complicated.
[0026]
Furthermore, in the projection display device described in Patent Document 3, in order to obtain a good resolution, the reflection type light valve is inclined from 2 to 8 degrees with respect to the optical axis of the projection lens. However, according to the “Scheinproof theorem”, it is considered that the projection image of the reflective light valve is also inclined with respect to the optical axis of the projection lens. For this reason, when the display area of the reflective light valve is rectangular, the projection image on the plane perpendicular to the optical axis has a trapezoidal shape, and it can be said that it is difficult to obtain a good display image. Note that the Scheinproof theorem means that when an object is inclined with respect to the optical axis, the image is inclined in the opposite direction, and these inclination angles can be defined with respect to each other.
[0027]
Also, Patent Document 4 discloses a projection display device having a configuration in which a positive lens is disposed immediately in front of a display area of a reflective light valve, as in Patent Document 3. Also in this projection display apparatus, since the illumination light from the illumination optical system passes through the positive lens, the reflection type light valve is illuminated after being refracted. The light emitted from the light valve is refracted by the positive lens and then enters the projection lens.
[0028]
However, in the projection display device described in Patent Document 4, a part of the effective area of the positive lens is used for transmitting illumination light, and the remaining area is used for transmitting reflected light from the reflective light valve. The optical axis of the positive lens is arranged to be largely shifted from the optical axis of the projection lens main group.
[0029]
For this reason, also in the projection display device described in Patent Document 4, it is possible to suppress the optical paths of the incident light to the reflective light valve and the light emitted from the reflective light valve from overlapping, and these optical paths can be separated. . Further, since it is not necessary to use a prism, it is considered that the apparatus can be miniaturized.
[0030]
[Patent Document 1]
WO98-29773
[Patent Document 2]
JP 2000-98272 A
[Patent Document 3]
Japanese Patent Laid-Open No. 11-249069
[Patent Document 4]
JP 2000-39585 A
[0031]
[Problems to be solved by the invention]
However, even in the projection display device disclosed in Patent Document 4, the reflection type light valve is arranged so that the optical axis thereof has an accuracy of 5 degrees to 15 degrees with respect to the optical axis of the projection lens main group. . Therefore, the optical axis of the projected image and the optical axis of the light valve are not parallel to the optical axis of the projection lens.
[0032]
For this reason, even in the projection display device disclosed in Patent Document 4, as in the projection display device disclosed in Patent Document 3, it is considered that the projected image is tilted and trapezoidal by the “Scheinproof Theorem”. It can be said that it is difficult to obtain a good image.
[0033]
Further, the positive lens disposed immediately before the display area of the reflective light valve is disposed such that its optical axis forms an angle with respect to the optical axis of the light valve. Furthermore, it is necessary to arrange an eccentric lens in the projection lens. For this reason, even in the projection display device disclosed in Patent Document 4, it is difficult to obtain an image having an aberration balance symmetrical about the optical axis, as in the projection display device disclosed in Patent Document 3. It is done. Further, when trying to correct the aberration balance, it is necessary to increase the number of lenses of the projection lens, which complicates the projection lens. Further, in this case, if the positive lens is composed of a biconvex lens, there is a problem that the center thickness of the lens is increased, and if it is composed of a meniscus lens, there is a problem that it is difficult to ensure sufficient power.
[0034]
Furthermore, in the projection display device disclosed in Patent Document 4, part of the illumination light incident on the positive lens is reflected at the interface between the positive lens and the air layer due to the difference in refractive index. Further, as the positive lens, a lens having convex surfaces on both sides, or a lens having a convex surface on the projection lens side and a concave surface on the reflective light valve side is used.
[0035]
For this reason, the reflected light reflected at this interface is reflected in the direction of the main group of the projection lens and reaches the screen. The reflected light reflected at this interface is stray light that is constantly generated regardless of the video signal input to the reflective light valve, causing a decrease in contrast in the projected image and the generation of ghost images. Will drop significantly.
[0036]
By the way, in general, an antireflection film having practically sufficient performance reflects at least about 0.5% of incident light and transmits at most about 99.5%. For this reason, the surface of the positive lens is Ti0. ₂ Film, Si0 ₂ It is considered that the reflected light can be reduced by forming a normal level antireflection film formed by laminating films and the like. However, only the formation of an antireflection film composed of such a multilayer film has a limit in reducing reflected light as described above, and thus there is a limit in improving the image quality of a projected image. In addition, it is only necessary to form an antireflection film that transmits 100% of incident light, but at present, it is practically impossible to form such an antireflection film.
[0037]
The object of the present invention is to solve the above-mentioned problems, suppress the overlap between the optical path of incident light and the optical path of outgoing light in the reflective light valve, and further suppress unnecessary reflected light from entering the projection lens at the lens interface. Thus, it is an object of the present invention to provide a projection display apparatus that can obtain a small, high-quality projected image, a rear projector and a multi-vision system using the same.
[0038]
[Means for Solving the Problems]
In order to achieve the above object, a projection display apparatus according to the present invention includes an illumination optical system that collects light emitted from a light source to form illumination light, and modulated light that reflects the illumination light to form an optical image. A reflective light valve that emits, a projection lens that projects an optical image formed by the reflective light valve, and a positive power lens element, the reflective light valve having a plurality of pixels, The modulated light is emitted by controlling the reflection direction of the illumination light for each of a plurality of pixels, the lens element is composed of a single plano-convex lens, the reflective light valve and the projection The modulation in which the illumination light passes through the lens element to illuminate the reflective light valve and emits from the reflective light valve with a convex surface facing the projection lens between the lens and the lens. Is arranged so as to pass through the lens element and enter the projection lens, and the reflective light valve, the projection lens, and the lens element are arranged so that their optical axes are parallel to each other and coincide with each other. The lens element and the reflective light valve are: The illumination light Of the lens element Convex Reflected by optical interface Was Of unwanted light components Direction of travel Effective light component of the modulated light Direction of travel And separation Thus, a virtual image formed by the unnecessary light component is formed outside the effective display area of the reflective light valve. As described above, they are arranged at a predetermined distance in the optical axis direction of each other.
[0045]
In the present invention Throw In a copying display Before The projection lens preferably has a stop decentered with respect to its optical axis, and the illumination optical system is preferably arranged so that the modulated light passes through the stop. In this case, it is preferable that the decentering direction of the stop is a direction away from the optical axis of the illumination optical system, and the projection lens has means for performing focus adjustment only by movement in the optical axis direction. . In this case, the F number of the projection lens is F1, the divergence angle of light that is emitted from the illumination optical system, reflected by the reflection type light valve and incident on the projection lens is θ1, and the display of the reflection type light valve It is preferable that the following expression (1) is satisfied, where α is an angle formed between the principal ray emitted from the center of the region and the optical axis of the projection lens.
F1 = 1 / (2 sin (θ1 + α)) (1)
[0046]
The present invention also relates to Throw In the transfer type display device, the illumination optical system has an exit pupil formed by a plurality of partial pupil elements so that the luminous flux distribution of the illumination light is uniform when reflected by the reflective light valve. It is preferable that it is comprised.
[0047]
Further, according to the present invention, Throw In the projection display device, the exit pupil of the illumination optical system and the entrance pupil of the projection lens are substantially conjugate with respect to the lens element, and the reflective light out of the light flux passing through the exit pupil of the illumination optical system. It is preferable that 80% or more of the light beam reflected by the display area of the bulb passes through the lens element and enters the effective area of the entrance pupil of the projection lens.
[0048]
In order to achieve the above object, a rear projector according to the present invention Writing At least a projection display device according to the present invention, a mirror that reflects the light projected from the projection display device, and a screen that transmits and scatters the light reflected by the mirror. Features.
[0049]
In order to achieve the above object, a multivision system according to the present invention includes a plurality of projection systems and a video signal dividing circuit, and each of the plurality of projection systems includes Writing The projection display device according to the present invention, a transmissive screen that projects light projected from the projection display device, and a casing that houses the projection display device. The dividing circuit divides the screen into a plurality of areas, processes the video signal of each area, and supplies the processed signals to each of the projection display devices constituting the projection system.
[0050]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
The projection display apparatus according to the first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a configuration of a projection display apparatus according to Embodiment 1 of the present invention. 2A is a diagram showing the optical paths of illumination light and projection light in the vicinity of the reflective light valve shown in FIG. 1, and FIG. 2B is the vicinity of the reflective light valve shown in FIG. It is a figure which shows the behavior of the reflected light in the optical interface of a positive power lens element.
[0051]
In the first embodiment, the DMD shown in FIG. 17 is used as the reflective light valve. FIGS. 1 and 2 are cross-sectional views cut perpendicularly to the rotation support shaft of the micromirrors constituting the DMD. The movable range of the micromirror is ± 10 degrees.
[0052]
First, the configuration and operation of the projection display apparatus according to the first embodiment will be described with reference to FIG. As shown in FIG. 1, the projection display apparatus according to the present embodiment includes a light source 1, an illumination optical system 2 that collects light emitted from the light source 1 to form illumination light, and reflects the illumination light. A reflective light valve (spatial light modulation element) 6 that emits modulated light that forms an optical image, a projection optical system 7 that projects an optical image formed by the reflective light valve 6, and a positive power lens element 5 are provided. Have at least.
[0053]
As shown in FIG. 1, the positive power lens element 5 is composed of a single plano-convex lens, and a convex surface is directed to the projection lens 7 between the reflective light valve 6 and the projection lens 7. Arranged in a state. Further, the arrangement of the positive power lens element 5 is such that the illumination light passes through the lens element 5 and illuminates the reflective light valve 6, and the modulated light emitted from the reflective light valve 6 passes through the lens element 5. Thus, the light is incident on the projection lens 7.
[0054]
In the first embodiment, the light source 1 includes a lamp 1a and a concave mirror 1b, and is the same as the light source 201 shown in FIG. Therefore, the light emitted from the lamp 1a is reflected by the concave mirror 1b, and forms a light emitter image at the second focal point f2 of the concave mirror 1b.
[0055]
The illumination optical system 2 includes a rod lens 3 and a relay lens system 4. The second focal point f2 of the concave mirror 1b substantially coincides with the incident surface 18 of the rod lens 3. The light incident on the rod lens 3 repeats multiple reflections on the inner surface of the rod lens 3. For this reason, the light flux having unevenness in the amount of light on the incident surface 18 of the rod lens 3 is made uniform on the exit surface 19 of the rod lens 3.
[0056]
The light emitted from the rod lens 3 enters the relay lens system 4 and is emitted from the relay lens system 4 to the reflective light valve 6. The light emitted from the relay lens system 4 passes through the positive power lens element 5 and illuminates the reflective light valve 6.
[0057]
As a result, the light emitted from the reflective light valve 6 passes through the positive power lens element 5 and enters the projection optical system 7, and the optical image on the reflective light valve 6 is enlarged and projected on the screen. Note that the exit surface 19 of the rod lens 3 and the display area of the reflective light valve 6 have a conjugate relationship in an optical system formed by combining the relay lens system 4 and the positive power lens element 5.
[0058]
Next, the principle of the projection display device of the present invention will be described with reference to FIG. As described in the description of FIG. 1, a light beam condensed by the light source 1 and uniformed and shaped by the illumination optical system 2 is emitted from the exit pupil 8 of the illumination optical system 2. That is, as shown in FIGS. 2A and 2B, from the exit pupil 8 of the illumination optical system 2, a light beam 10a that illuminates the upper part of the reflective light valve 6 and the central part of the reflective light valve 6 are illuminated. The light beam 10b that illuminates the lower part of the reflective light valve 6 is emitted.
[0059]
In the present specification, “upper part”, “central part”, and “lower part” indicate positional relationships in the drawing. In FIGS. 2A and 2B, the light beams 10 a to 10 c are the upper light beam that is emitted from the upper end of the exit pupil 8, the principal ray that is emitted from the center of the exit pupil 8, and the lower beam that is emitted from the lower end of the exit pupil 8. Only representative rays such as rays are shown.
[0060]
The light beams 10 a, 10 b and 10 c pass through the positive power lens element 5 and enter the reflective light valve 6. For this reason, the light beam 10a that illuminates the upper part of the reflection type light valve out of the light rays emitted from the exit pupil 8 is refracted by the positive power lens element 5 and has a positive power compared with that before entering the positive power lens element 5. The lens element 5 is refracted in a direction in which the angle formed with the optical axis 14 becomes smaller.
[0061]
On the other hand, the light beam 10c that illuminates the lower portion of the reflective light valve 6 is refracted by the positive power lens element 5 in a direction in which the angle formed with the optical axis 14 increases. Therefore, the luminous fluxes 10a, 10b, and 10c that have passed through the positive power lens element 5 are telecentric illumination light in which the principal rays are substantially parallel to each other and the angle formed with the optical axis 15 of the reflective light valve 6 is approximately 20 degrees. The display area of the reflective light valve 6 is illuminated uniformly. In addition, the spread angles of the light beams are substantially equal.
[0062]
In addition, each micromirror of the reflection type light valve 6 is configured to tilt 10 degrees counterclockwise with respect to a plane perpendicular to the optical axis 14 of the positive power lens element 5 in the ON state. Therefore, since the illumination light is telecentric, the principal rays of the light beams 11a, 11b, and 11c of the emitted light from the reflective light valve 6 are in any of the display areas of the reflective light valve 6 when the micromirror is in the ON state. Is substantially parallel to the optical axis 15 of the reflective light valve 6 and is telecentric.
[0063]
All of the luminous fluxes 11a, 11b and 11c of the outgoing light from the reflective light valve 6 pass through the positive power lens element 5 and enter the entrance pupil 9 of the projection optical system 7. The light incident on the entrance pupil 9 of the projection optical system 7 is enlarged and projected on the screen by the projection optical system.
[0064]
Here, as shown in FIG. 2B, the light beam 10a, the light beam 10b, and the light beam 10c pass through the positive power lens element 5 and enter the reflective light valve 6, but the optical interface of the lens element 5 ( Part of the convex surface 20a is reflected to form a light beam 21a, a light beam 21b, and a light beam 21c. The reflected light from the optical interface 20a forms a virtual image 22 in the vicinity of the light valve display area and becomes an unnecessary light component. Furthermore, it is considered that a part of this unnecessary light component enters the entrance pupil 9 of the projection lens 7 and reaches the screen.
[0065]
On the other hand, the optical interface 20b of the positive power lens element 5 is a flat surface having no power. Therefore, when the light beams 10a, 10b and 10c emitted from the exit pupil 8 of the illumination optical system 2 pass through the optical interface 20b whose optical axis is parallel to the reflective light valve 6, the optical interface 20b and the air layer Refracts according to the Snell's law according to the difference in refractive index.
[0066]
In this case, reflection occurs at the optical interface 20b as well as the optical interface 20a. However, since the optical interface 20b is a plane, the reflected light has the same incident angle as the incident light with respect to the normal of the interface. Output at an angle. Furthermore, since the light beams 10a, 10b, and 10c emitted from the exit pupil 8 of the illumination optical system 2 become substantially telecentric at the optical interface 20b, the light flux reflected and generated at the optical interface 20b is also substantially telecentric.
[0067]
For this reason, the spread angles of the respective light fluxes of the reflected light are the same, and the angles formed by the principal rays of the respective light fluxes of the reflected light and the normal line of the interface are all the same, and the principal rays are substantially parallel. As a result, since the virtual image due to the reflected light at the optical interface 20b is formed at a position very far from the light valve, even if a part of the reflected light at the optical interface 20b is incident on the projection lens 7, the light flux concentrates the screen. It can be said that no ghost image is formed or displayed above.
[0068]
By the way, an aspect in which the convex surface (optical interface 20a) of the positive power lens element 5 is directed to the reflective light valve 6 side, or a lens having both convex surfaces as a positive power lens element as in a conventional projection display device is used. Conceivable embodiments are possible. However, in such an embodiment, the luminous fluxes 10a, 10b and 10c of the illumination light incident on the reflective light valve 6 become telecentric after passing through the positive power lens element.
[0069]
That is, in the above aspect, the principal rays of the luminous fluxes 10a, 10b, and 10c of the illumination light are not substantially parallel to each other at any optical interface in the positive power lens element 5, and the reflected light at these optical interfaces is A virtual image is formed in the vicinity of the reflective light valve. For this reason, in the above aspect, compared to the first embodiment, there are more unnecessary light components incident on the projection lens 7, and as a result, a ghost or the like is generated on the projection image, and the image quality of the projection image is greatly deteriorated. I can say that.
[0070]
Thus, in the projection display apparatus according to the first embodiment, one plano-convex lens is used as the positive power lens element 5, and the positive power lens element 5 has a convex surface (optical interface 20a). Is placed between the reflective light valve 6 and the projection lens 7 with the projection facing the projection lens 7. For this reason, if the projection display apparatus according to the first embodiment is used, it is possible to suppress deterioration of the image quality of the projection image due to unnecessary light components incident on the projection lens 7 as compared with the conventional projection display apparatus. it can.
[0071]
Further, since the positive power lens element 5 is arranged in this manner, the light beams 10a, 10b and 10c incident from the direction inclined with respect to the optical axis 14 of the positive power lens element 5 are relatively well balanced. Refractive power will work. Therefore, the luminous flux does not concentrate on a part of the display area of the reflective light valve 6, and the occurrence of uneven brightness can be suppressed.
[0072]
In the projection display device according to the first embodiment, it is preferable that an antireflection film is formed on the optical interface (convex surface) 20a of the positive power lens element 5 by applying an ultra-low reflection coating or the like. is there. By setting it as such an aspect, generation | occurrence | production of the reflected light in the optical interface 20a can be suppressed more, and since the unnecessary light component which reaches | attains on a screen can be made small, the favorable image which a contrast does not fall more can be obtained. . As an antireflection film, for example, Ti0 ₂ , Si0 ₂ Transparent optical thin films such as these, and laminated films of these.
[0073]
In addition, since the projection display apparatus according to the first embodiment uses the positive power lens element 5, even if a telecentric optical system is used as the projection lens 7, the entrance pupil 9 and the illumination of the projection optical system 7 are illuminated. The exit pupil 8 of the optical system 2 can be reduced. Furthermore, the optical path of the incident light from the illumination optical system 2 and the optical path of the outgoing light from the reflective light valve can be separated without using a prism. For this reason, according to the projection type display apparatus concerning this Embodiment 1, size reduction of an apparatus can be achieved and front projection can further be realized.
[0074]
Further, as shown in FIGS. 1 and 2A, in the projection display device according to the first embodiment, the optical axis 15 of the reflective light valve 6, the optical axis 13 of the projection optical system 7, and the positive power. The optical axes 14 of the lens elements 5 are parallel to each other, and they coincide with each other. For this reason, there is no decentered element in the projection optical system, and the aberration of the projected image can be corrected satisfactorily.
[0075]
In this specification, “optical axis is parallel” includes a case where there is an allowable range of error. Similarly, “matching optical axes” includes not only a case where the optical axes are completely matched but also a case where there is an allowable range of error.
[0076]
Since the optical axes 13 to 15 are parallel to each other and coincide with each other, the chief rays of the light beams 11a, 11b, and 11c of the light emitted from the reflective light valve 6 pass through the focal point 16 of the positive power lens element 5. It will be. Further, as shown in FIGS. 1 and 2A, the exit pupil 8 of the illumination optical system 2 and the entrance pupil 9 of the projection lens 7 are in a conjugate relationship with respect to the positive power lens element 5, and the positive power lens. The focal plane 17 of the element 5 and the entrance pupil 9 of the projection lens 7 coincide.
[0077]
For this reason, in the projection display apparatus according to the present embodiment, it is possible to prevent the projection lens 7 from passing the ambient light without passing, and the projection image can obtain the maximum brightness. The distance d from the apex of the optical interface 20a (convex surface) of the positive power lens element 5 to the entrance pupil 9 of the projection lens 7 is substantially the same as the back focus of the positive power lens element 5.
[0078]
The exit pupil 8 of the illumination optical system 2 and the entrance pupil 9 of the projection optical system 7 are in a conjugate relationship with respect to the positive power lens element 5, and the “conjugate relationship” here is shown in FIGS. 1 and 2. As shown, it is not only the case where the entrance pupil 9 of the projection lens 7 coincides with the focal plane 16 of the positive power lens element 5. This also means a case where the entrance pupil 9 is imaged at the position of the exit pupil 8 of the illumination optical system 2 by the imaging system composed of the positive power lens element 5 and the reflective light valve 6. Specifically, 80% or more of the light beam reflected by the reflective light valve 6 out of the light beam passing through the exit pupil 8 of the illumination optical system 2 passes through the lens element 5 and is effective in the entrance pupil 9 of the projection lens 7. If it is incident on the region, it can be said that it is in the “conjugate relationship”.
[0079]
As shown in FIGS. 1 and 2A, in the first embodiment, the illumination optical system 2 is arranged so that the exit pupil 8 is in the vicinity of the focal plane 17 of the lens element 5 having positive power. Has been. By disposing the illumination optical system 2 in this way, the illumination light incident on the reflective light valve 6 can be easily telecentric, and the loss of the illumination light can be further suppressed.
[0080]
In the present embodiment, it is preferable to use a positive power lens element 5 having a focal length of about 40 mm to 80 mm. If such a positive power lens element 5 is used, an appropriate power can be obtained, and the light beam from the exit pupil 8 of the illumination optical system 2 and the reflective light valve 6 are emitted to the entrance pupil 9 of the projection optical system 7. This is because separation from the incident light beam can be ensured. The focal length of the positive power lens element 5 is the angle between the incident light to the reflective light valve 6 and the outgoing light from the reflective light valve 6, the F number of the incident light to the reflective light valve 6, It can be appropriately selected according to the F number of the light emitted from the reflective light valve 6.
[0081]
By the way, as described above, when the reflection type light valve 6 is in the ON state, the light (ON light) reflected by the reflection type light valve 6 enters the projection lens 7, but when it is in the OFF state, the reflected light (ON light) OFF light) is emitted in a direction of 140 degrees (clockwise) with respect to the optical axis 15. Similarly, the OFF light is incident on the positive power lens element 5, but is different from the entrance pupil 9 of the projection lens 7 although it is close to the focal plane 17 of the positive power lens element 5 because the emission direction is different from the ON light. Concentrate at the position. For this reason, by adopting a configuration in which a stop is provided close to the final surface of the projection lens 7, the incidence of unnecessary light can be suppressed as much as possible.
[0082]
In the first embodiment, the positive power lens element 5 is preferably formed of a glass material having a high refractive index. In this case, the center thickness of the positive power lens element 5 can be reduced, and the projection display device can be further downsized. Further, even if the radius of curvature of the convex surface of the lens element is increased, incident light can be refracted with a strong power, so that it is possible to suppress unnecessary light components due to reflected light from reaching the screen. Specifically, it is preferable to use a material having a refractive index of 1.74 or more and 1.85 or less. With such a material, it is possible to obtain sufficient performance while suppressing the glass material cost.
[0083]
(Embodiment 2)
Next, a projection display apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 3 is a diagram showing the configuration of the projection display apparatus according to the second embodiment of the present invention. 4 is an enlarged view showing the surface of the positive power lens element shown in FIG. Also in the second embodiment, the DMD shown in FIG. 17 is used as the reflective light valve. FIG. 3 shows a cross-section obtained by cutting perpendicularly to the rotation support shaft of a micromirror constituting the DMD.
[0084]
As shown in FIG. 3, the projection display apparatus according to the second embodiment is configured in the same manner as the projection display apparatus according to the first embodiment, except that the positive power lens element 35 is different. That is, the light source 31, the illumination optical system 32, the reflective light valve 36, and the projection lens 37 are the same as those used in the first embodiment.
[0085]
In the second embodiment, the light source 31, the illumination optical system 32, the positive power lens element 35, the reflective light valve 36, and the projection lens 37 are arranged in the same manner as in the first embodiment. Also in the second embodiment, the reflection type light valve 36, the projection lens 37, and the positive power lens element 35 are arranged so that their optical axes (45, 43, 44) are parallel to each other and coincide with each other. Yes. In FIG. 3, reference numeral 38 denotes an exit pupil of the illumination optical system 32, 39 denotes an entrance pupil of the projection lens 37, 47 denotes a focal plane of the positive power lens element 35, and 46 denotes a focal point of the positive power lens element 35. Reference numerals 40a to 40c denote luminous fluxes of illumination light, and reference numerals 41a to 41c denote luminous fluxes of outgoing light from the reflective light valve 36.
[0086]
As shown in FIG. 3, in the second embodiment, unlike the first embodiment, the positive power lens element 35 is composed of a biconvex lens. Further, as shown in FIG. 4, a plurality of minute protrusions 42 are formed on both surfaces of the positive power lens element 35 by a fine processing technique.
[0087]
The pitch p1 of the protrusions 42 is set to ½ or less of the visible band wavelength (illumination light wavelength), preferably 150 nm to 250 nm. In addition, the height h1 of the protrusions 42 is set to be 1 time or more, preferably 3 times or more of the pitch p1, and specifically, 300 nm to 750 nm.
[0088]
In the example of FIG. 4, the protrusion 42 is formed in a conical shape, and the area of the axial cross section gradually increases from the tip toward the bottom, but the present invention is not limited to this. . The protrusion 42 may be formed in a column shape, and the cross section of the protrusion 42 may be a polygon other than a circle.
[0089]
For this reason, in the second embodiment, the lens surface on which the plurality of minute protrusions 42 are formed is in contact with the air layer, and enters the positive power lens element 35 as described in the following reference. The light behaves as if the refractive index is continuously changed by the plurality of minute protrusions 42. In this case, the light incident on the positive power lens element is incident on the lens element without being reflected by the lens surface as shown in FIG. Therefore, according to the projection display apparatus according to the second embodiment, the unnecessary light component incident on the projection lens 37 can be made zero.
[References]
Hiroshi TOYOTA, Koji TAKAHARA, Masato OKANO, Tsutom YOTSUYA and Hisao KIKUTA “FabricatiOn of MicrocOne Array for AntireflectiOn Structured Surface Using Metal Dotted Pattern”, Jpn. J. Appl. Phyn. Vol. 40 (2001) pp. 1747-1749
[0090]
As a result, the light beams 40a, 40b and 40c from the illumination optical system 32 reach the reflection type light valve 36 without being reflected by each optical interface of the positive power lens element 35, and illuminate the optical image. The light emitted from the reflective light valve 36 is converged by the positive power lens element 35 and enters the entrance pupil 39 of the projection lens 37. Therefore, the optical image formed on the reflective light valve 36 is enlarged and projected onto the screen by the projection lens 37.
[0091]
In the second embodiment, as in the first embodiment, a plano-convex lens can be used as the positive power lens element 35, and the convex surface can be disposed toward the projection lens 37. In this case, a plurality of minute protrusions may be provided only on the convex surface. In addition, as a method of forming a plurality of minute protrusions, a method of forming together with the entire lens using a mold having a plurality of minute recesses on the molding surface, or a lens of a lens not provided with a plurality of minute protrusions Examples include a method of forming a surface by etching.
[0092]
As described above, when the projection display apparatus according to the second embodiment is used, it is possible to further suppress the deterioration of the image quality of the projected image due to the unnecessary light component, as compared with the projection display apparatus according to the first embodiment. Also in the second embodiment, similarly to the first embodiment, front projection can be realized without using a total reflection prism.
[0093]
Also in the second embodiment, as in the first embodiment, the positive power lens element 35 is preferably formed of a glass material having a high refractive index. Specifically, it is preferable to use a material having a refractive index of 1.74 or more and 1.85 or less.
[0094]
(Embodiment 3)
Next, a projection display apparatus according to Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 5 is a diagram showing the configuration of the projection display apparatus according to the third embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view of the positive power lens element shown in FIG. In the third embodiment, the DMD shown in FIG. 17 is used as the reflective light valve. FIG. 5 shows a cross-section obtained by cutting perpendicularly to the rotation support shaft of a micromirror constituting the DMD.
[0095]
As shown in FIG. 5, the projection display apparatus according to the third embodiment is also configured in the same manner as the projection display apparatus according to the first embodiment, except that the positive power lens element 55 is different. That is, the light source 51, the illumination optical system 52, the reflective light valve 56, and the projection lens 57 are the same as those used in the first embodiment.
[0096]
In the third embodiment, the light source 51, the illumination optical system 52, the positive power lens element 55, the reflective light valve 56, and the projection lens 57 are arranged in the same manner as in the first embodiment. Also in the third embodiment, the reflection type light valve 56, the projection lens 57, and the positive power lens element 55 are arranged such that their optical axes (65, 63, 64) are parallel and coincide with each other. Yes. In FIG. 5, 58 is the exit pupil of the illumination optical system 52, 67 is the focal plane of the positive power lens element 55, and 66 is the focal point of the positive power lens element 5. Reference numerals 60 a to 60 c denote luminous fluxes of illumination light, and 61 a to 61 c denote luminous fluxes of outgoing light from the reflective light valve 56.
[0097]
As shown in FIGS. 5 and 6, in the third embodiment, the positive power lens element 55 is configured by joining a plano-concave lens 68 and a plano-convex lens 69 unlike the first embodiment. . Further, the refractive index of the plano-convex lens 69 is larger than the refractive index of the plano-concave lens 68.
[0098]
Specifically, as shown in Table 1 below, the plano-concave lens 68 is formed using a material having a relatively low refractive index, such as glass material A and glass material B, for example. On the other hand, as shown in Table 1 below, the plano-convex lens 69 is formed using a glass material having a relatively high refractive index, such as a glass material C and a glass material D. In Table 1, “nd” represents the refractive index of the glass materials A to D, and “νd” represents the dispersion of the glass materials A to D.
[0099]
[Table 1]

[0100]
The lens element 55 formed by joining the plano-concave lens 68 and the plano-convex lens 69 also has a positive power as a whole, like the lens element used in the first embodiment. For this reason, as in the first embodiment, the light beams 60a, 60b and 60c emitted from the exit pupil 58 of the illumination optical system 52 have principal rays substantially parallel to each other, and the optical axis 65 of the reflective light valve 56. Telecentric illumination light having an angle of about 20 degrees is formed. In addition, the spread angles of the light beams are substantially equal.
[0101]
The light emitted from the reflective light valve 56 enters the entrance pupil 59 of the projection lens 57 while the luminous flux is reduced by the positive power lens element 55. The light incident on the entrance pupil 59 of the projection lens 57 is enlarged and projected on the screen by the projection lens 57.
[0102]
In Embodiment 3, the power of the cemented surface increases as the difference in refractive index between the two lenses to be cemented increases. However, the larger the refractive index difference, the greater the interface reflection at the joint surface, and unnecessary light due to reflection similar to that described in the first embodiment is generated at the joint surface. For this reason, when there are many unnecessary light components which inject into the projection lens 57, the contrast of a projection image will fall.
[0103]
For this reason, in Embodiment 3, in order to reduce the reflectance at the cemented surface and suppress the generation of unnecessary light, as shown in FIG. 6A, a plano-concave lens 68 made of a low refractive index material. A film having a refractive index larger than the refractive index of the plano-concave lens 68 and smaller than the refractive index of the plano-convex lens 69 is interposed between the surface 68b of the plano-convex lens 69 made of a high refractive index material. It is an aspect.
[0104]
Specifically, a thin film 70b having a refractive index at least intermediate between both materials is formed on the surface 69a of the plano-convex lens 69 by vapor deposition or the like, and the plano-convex lens 69 and the plano-concave lens 68 on which the thin film 70b is formed are converted into a thin film. 70b and the plano-concave lens 68 are joined by an adhesive 70a having an intermediate refractive index. As an example of the thin film 70b shown in FIG. ₂ Film, Ti0 ₂ A film etc. and these laminated films are mentioned.
[0105]
In the third embodiment, as shown in FIG. 6B, the refractive index between the surface 68b of the plano-concave lens 68 and the surface 69a of the plano-convex lens 69 is changed from the refractive index of the plano-concave lens 68 to the plano-convex lens 69. It is also possible to adopt a mode in which a film that changes up to the refractive index is interposed.
[0106]
Specifically, a thin film 70b having a refractive index continuously changing from 1.5 to 1.85 is formed on the surface 69a of the plano-convex lens 69 by sputtering, and the plano-convex lens 69 and the plano-concave lens 68 are connected to the plano-concave lens 68. Are bonded by an adhesive 70a having a refractive index equivalent to (for example, “Araldite AY103” manufactured by Ciba Special Chemicals).
[0107]
An example of the thin film 70b shown in FIG. 6B is a stacked film of a film having a high refractive index, a film having an intermediate refractive index, and a film having a low refractive index. As a film having a high refractive index, Nb ₂ O _Five Membrane, Sb ₂ O _Five Film, Ta ₂ O _Five A film etc. and these laminated films are mentioned. As a film having an intermediate refractive index, SiO ₂ Film, Ti0 ₂ A film etc. and these laminated films are mentioned. As a film having a low refractive index, MgF ₂ Film, LiF film, BaF ₂ A film etc. and these laminated films are mentioned.
[0108]
By adopting such an embodiment shown in FIGS. 6A and 6B, interface reflection at the joint surface between the plano-concave lens 68 and the plano-convex lens 69 can be suppressed to almost zero, which is unnecessary due to reflected light. A positive power lens element in which generation of light is suppressed can be obtained.
[0109]
Also in the third embodiment, the light beams 60a, 60b and 60c from the exit pupil 58 of the illumination optical system 52 are incident on the surface 68a of the concave lens 68, and a part thereof is reflected by the surface 68a. However, the surface 68a is a concave surface, and the principal rays of the light beams 60a, 60b, and 60c are not parallel to each other. Therefore, by appropriately setting the radius of curvature of the surface 68a, it is possible to suppress the reflected light from the surface 68a of the light beams 60a, 60b and 60c from forming a virtual image on the effective display area of the light valve 56. Further, in order for the light beams 61a, 61b, and 61c of the light emitted from the reflective light valve 56 to be emitted substantially parallel to each other, the surface 68a needs to be concave.
[0110]
By the way, the smaller the radius of curvature of the concave surface (surface 68a) of the plano-concave lens 68, the larger the reflection angle of various rays contained in the reflected light of the light beams 60a, 60b and 60c, and the component of the reflected light incident on the projection lens 57 is Less. However, when the radius of curvature of the surface 68a is reduced, in order to ensure the power of the entire positive power lens element 55, the radius of curvature of the surfaces 68b and 69a to be the cemented surfaces is reduced, or the plano-concave lens 68 and the plano-convex lens. It is necessary to increase the difference in refractive index from 69.
[0111]
However, the difference in refractive index between lenses is about 0.45 at the maximum when a transparent glass material that is practically used is used, and cannot be increased any more. Further, if it is attempted to reduce the curvature radii of the surfaces 68b and 69a serving as the joint surfaces, it is necessary to increase the center thickness for lens processing, and the back focus of the projection lens becomes long. Therefore, for these reasons, the radius of curvature of the concave surface (surface 68a) of the plano-concave lens 68 has the maximum curvature radius in the range where the virtual image formed by the reflected light on the surface 68a is formed outside the effective display area of the light valve 56. It is good to choose.
[0112]
Thus, if a cemented lens of the plano-concave lens 68 and the plano-convex lens 69 is used as the positive power lens element 55, it is possible to obtain an appropriate power as a positive power lens while suppressing the incidence of unnecessary reflected light. . Furthermore, separation of the light beam from the exit pupil 58 of the illumination optical system 52 and the light beam emitted from the reflective light valve 56 and incident on the entrance pupil 59 of the projection lens 57 can be ensured.
[0113]
Further, from the viewpoint of enhancing the above effect, in the third embodiment, it is preferable to use a positive power lens element 55 having a focal length of about 40 mm to 80 mm. The focal length of the positive power lens element 55 is determined by the angle formed between the incident light to the reflective light valve 56 and the outgoing light therefrom, the F number of the incident light to the reflective light valve 56, and the outgoing light therefrom. It can be selected appropriately according to the F number.
[0114]
As described above, when the projection display apparatus according to the third embodiment is used, it is possible to further suppress the deterioration of the image quality of the projection image due to the unnecessary light component, as compared with the projection display apparatus according to the first embodiment. Also in the third embodiment, similarly to the first embodiment, front projection can be realized without using a total reflection prism.
[0115]
(Embodiment 4)
Next, a projection display apparatus according to Embodiment 4 of the present invention will be described with reference to FIGS. FIG. 7 is a diagram showing the configuration of the projection display apparatus according to the fourth embodiment of the present invention. FIG. 8A is a diagram showing the optical path of illumination light and projection light in the vicinity of the reflective light valve shown in FIG. 7, and FIG. 8B is the vicinity of the reflective light valve shown in FIG. It is a figure which shows the behavior of the reflected light in the optical interface of a positive power lens element.
[0116]
In the fourth embodiment, the DMD shown in FIG. 17 is used as the reflective light valve. FIG. 7 and FIG. 8 are shown in a cross section cut perpendicularly to the rotation support shaft of the micromirror constituting the DMD. The movable range of the micromirror is ± 10 degrees.
[0117]
First, the configuration and operation of the projection display apparatus according to the fourth embodiment will be described with reference to FIG. The projection display apparatus according to the fourth embodiment is different from the projection display apparatus according to the first embodiment in the following points. As shown in FIG. 7, the reflective light valve 76 and the positive power lens element 75 are provided with a distance d1 between the optical axes (85, 84) in a state where the optical axes (85, 84) are parallel to each other. Are arranged. Further, the distance d1 is such that the light incident on the projection lens 77 out of the unnecessary light component of the illumination light reflected by the optical interface 88 of the lens element 75 is separated from the effective light component of the modulated light emitted from the reflective light valve. Is set to
[0118]
Furthermore, in the fourth embodiment, the positive power lens element 75 has the same shape as the lens element shown in the first embodiment, but is different in terms of effective diameter and refractive index. In addition, a light shielding portion 73 is provided on the screen side of the projection lens 77.
[0119]
Except for the points described above, the projection display apparatus according to the fourth embodiment is configured in the same manner as the projection display apparatus according to the first embodiment. In other words, the arrangement of the positive power lens element 75 is such that the illumination light passes through the lens element 75 and illuminates the reflective light valve 76, and the modulated light emitted from the reflective light valve 76 passes through the lens element 75. Thus, the light is incident on the projection lens 77.
[0120]
The light source 71, the illumination optical system 72, the reflective light valve 76, and the projection lens 77 are the same as those used in the first embodiment. Further, the positive power lens element 75 and the projection lens 77 are arranged so that their optical axes (84, 83) are parallel to each other. The exit pupil 78 of the illumination optical system 72 and the entrance pupil 79 of the projection lens 77 have a conjugate relationship with respect to the positive power lens element 75. In FIG. 7, reference numeral 87 denotes a focal plane of the positive power lens element 75, and reference numeral 86 denotes a focal point of the positive power lens element 75.
[0121]
With such a configuration, in the projection display apparatus according to the fourth embodiment, similarly to the first embodiment, the light emitted from the reflective light valve 76 passes through the lens element 75 having a positive power and is a projection lens. By being incident on 77, the optical image on the reflective light valve 76 is enlarged and projected on the screen.
[0122]
Next, the principle of the projection display device of the present invention will be described with reference to FIG. From the exit pupil 78 of the illumination optical system 72, similarly to the first embodiment, a light beam condensed by the light source 71 and uniformed and shaped by the illumination optical system 72 is emitted. That is, as shown in FIG. 8A, from the exit pupil 78 of the illumination optical system 72, a light beam 80a that illuminates the upper part of the reflective light valve 76, a light beam 80b that illuminates the central part of the reflective light valve 76, A light beam 80c that illuminates the lower portion of the reflective light valve 76 is emitted.
[0123]
The light beams 80 a, 80 b, and 80 c pass through the positive power lens element 75 and enter the reflective light valve 76. For this reason, among the light beams emitted from the exit pupil 78, the light beam 80a that illuminates the upper part of the reflection type light valve is refracted by the positive power lens element 75 and has a positive power compared with that before entering the positive power lens element 75. The lens element 75 is refracted in a direction in which the angle formed with the optical axis 84 becomes smaller.
[0124]
On the other hand, the light beam 80c that illuminates the lower portion of the reflective light valve 76 is refracted by the positive power lens element 75 in a direction in which the angle formed with the optical axis 84 increases. In this manner, as in the first embodiment, the principal rays of the light beam 80a, the light beam 80b, and the light beam 80c that have passed through the positive power lens element 75 are substantially parallel to each other and form the optical axis 85 of the reflective light valve 76. Telecentric illumination light having an angle of about 20 degrees is obtained. In addition, the spread angles of the light beams are substantially equal.
[0125]
At this time, as shown in FIG. 8 (b), as in the first embodiment, a part of the light beams 80a, 80b and 80c from the exit pupil 78 of the illumination optical system 72 is the optical power of the lens element 75 of positive power. Reflected by the interface 88, light beams 90a, 90b, and 90c are generated and travel in the direction of the projection lens 77. These light beams are unnecessary light that forms a virtual image 82 in the vicinity of the reflective light valve 76.
[0126]
However, in the fourth embodiment, as described above, the reflection type light valve 76 and the positive power lens element 75 are arranged such that their optical axes (85, 84) are separated by a distance d1. Further, as described above, the distance d1 is the effective light component of the modulated light emitted from the reflective light valve 76 when the light incident on the projection lens 77 out of the light beams 90a, 90b and 90c generated at the optical interface 88. It is set to be separated.
[0127]
For this reason, according to the fourth embodiment, the virtual image 82 is formed outside the effective display area of the reflective light valve 76, and therefore, generation of unnecessary light on the display area of the screen can be suppressed. A projected image with excellent image quality can be obtained.
[0128]
In setting the distance d1 between the optical axis 85 of the reflective light valve 76 and the optical axis 84 of the positive power lens element 75, the size of the effective display area of the reflective light valve 76 and the emission of the illumination optical system 72 are set. This is performed in consideration of the size and shape of the pupil 78, the intensity distribution of the virtual image 82, and the like.
[0129]
Specifically, the distance d1 can be set as follows. For example, if the reflective light valve 76 has a rectangular display area and a distance d1 is provided in parallel with any side of the rectangle, the distance d1 is not less than 1/4 of the length of the side. , 1/2 or less is preferable. In this case, the light beam from the exit pupil 78 of the illumination optical system 72 and the reflective light valve 76 can be obtained with appropriate power without significantly increasing the effective image circle of the projection lens 77 and without tilting the optical axes. The generation of unnecessary light can be suppressed while ensuring separation from the light flux emitted from the light and entering the entrance pupil 79 of the projection lens 77.
[0130]
Further, in the fourth embodiment, as described above, the light shielding portion 73 is provided on the screen side of the projection lens 77. For this reason, unnecessary light incident on the projection lens 77 can be shielded. The light shielding unit 73 may be disposed anywhere between the projection lens 77 and the screen as long as unnecessary light can be shielded appropriately.
In the example of FIG. 7, the unnecessary light is a part of the light flux emitted from the projection lens 77, and thus the shape of the light shielding portion 73 is a shape that shields only the region through which the unnecessary light passes. However, the shape of the light shielding portion 73 is not particularly limited, and may be, for example, a frame shape having an opening or an annular shape.
[0131]
In this case, only the effective light beam necessary for displaying the original image out of the light beam emitted from the reflection type light valve 76 and incident on the projection lens 77 is transmitted to the screen (not shown). What is necessary is just to provide so that it may reach | attain.
[0132]
In this case, if the light-shielding portion 73 is disposed on the screen side of the projection lens 77, the light flux here is generally similar to the effective display area of the screen, so the opening is also the effective display area of the screen. It is preferable to form it so as to have a substantially similar shape.
[0133]
In the fourth embodiment, it is preferable that the surface on which the virtual image 82 is formed and the display surface of the reflective light valve 76 are substantially matched. According to this aspect, the area overlapping the virtual image 82 in the display area can be minimized, and the distance d1 between the optical axis 84 of the positive power lens element 75 and the optical axis 85 of the reflective light valve 76 can be reduced. Further, with this aspect, the effective image circle of the projection lens 77 can be reduced.
[0134]
In the fourth embodiment, it is preferable to use a positive power lens element 75 having a focal length of about 50 mm to 120 mm. If such a positive power lens element 75 is used, appropriate power can be obtained, and the light beam from the exit pupil 78 of the illumination optical system 72 and the reflection type light valve 76 are incident on the entrance pupil 79 of the projection lens 77. This is because separation from the luminous flux to be performed can be ensured.
[0135]
The focal length of the positive power lens element 75 is determined by the angle formed between the light incident on the reflective light valve 76 and the light emitted therefrom, the F number of the light incident on the reflective light valve 76, and the light emitted therefrom. It can be selected appropriately according to the F number.
[0136]
In the fourth embodiment, as described above, a lens element having a larger effective diameter than the lens element used in the first embodiment is used as the lens element 75. This is because the distance d1 is set, so that the effective area is increased by combining the area through which the luminous flux of the positive power lens element 75 passes and the area through which the luminous flux emitted from the reflective light valve 76 passes. Because.
[0137]
By the way, if the positive power lens element 75 is constituted by one plano-convex lens and an effective diameter is to be increased, a thick center thickness is required to secure the edge thickness. Therefore, also in the fourth embodiment, as in the first embodiment, the positive power lens element 75 is preferably formed of a glass material having a high refractive index. Specifically, it is preferable to use a material having a refractive index of 1.74 or more and 1.85 or less.
[0138]
As described above, when the projection display apparatus according to the fourth embodiment is used, it is possible to further suppress the deterioration of the image quality of the projected image due to the unnecessary light component, compared with the projection display apparatus according to the first embodiment. Also in the fourth embodiment, similarly to the first embodiment, front projection can be realized without using a total reflection prism.
[0139]
(Embodiment 5)
Next, a projection display apparatus according to Embodiment 5 of the present invention will be described with reference to FIGS. FIG. 9 is a diagram showing the configuration of the projection display apparatus according to the fifth embodiment of the present invention. FIG. 10 is an enlarged view of the vicinity of the reflective light valve shown in FIG. In the fifth embodiment, the DMD shown in FIG. 17 is used as the reflective light valve. 9 and 10 are cross-sectional views obtained by cutting perpendicularly to the rotation support shaft of the micromirror that constitutes the DMD.
[0140]
First, the configuration and operation of the projection display apparatus according to the fifth embodiment will be described with reference to FIG. The projection display apparatus according to the fifth embodiment is different from the projection display apparatus according to the first embodiment in the following points. As shown in FIG. 9, the distance d2 between the lens element 95 and the reflective light valve 96 in the optical axis direction is the light incident on the projection lens 97 among the unnecessary light components of the illumination light reflected by the optical interface of the lens element 95. Is set to be separated from the effective light component of the modulated light emitted from the reflective light valve 96.
[0141]
In addition, the projection display apparatus according to the fifth embodiment includes a light shielding unit 120 on the screen side of the projection lens 97. Further, the projection display apparatus according to the fifth embodiment includes a color wheel 121, and the configuration of the illumination optical system 92 is different from that of the first embodiment.
[0142]
Except for the points described above, the projection display apparatus according to the fifth embodiment is configured in the same manner as the projection display apparatus according to the first embodiment. That is, the light source 91, the positive power lens element 95, the reflective light valve 96, and the projection lens 97 are the same as those used in the first embodiment.
[0143]
The reflective light valve 96, the projection lens 97, and the positive power lens element 95 are arranged in the same manner as in the first embodiment, and their optical axes (105, 103, 104) are parallel and coincident with each other. ing. Further, as in the first embodiment, the exit pupil 98 of the illumination optical system 92 and the entrance pupil 99 of the projection lens 97 have a conjugate relationship with respect to the positive power lens element 95. In FIG. 9, 107 is a focal plane of the positive power lens element 95, and 106 is a focal point of the positive power lens element 95.
[0144]
In the fifth embodiment, the illumination optical system 92 includes a condenser lens 122, a first lens array 123, a second lens array 124, and a relay lens 125 in this order. It is configured.
[0145]
In the fifth embodiment, the color wheel 121 is disposed at the second focal point f2 of the concave mirror 1b on which the light from the light source 91 is collected. The color wheel 121 is configured by arranging filters of three colors of R (red), G (green), and B (blue) in order on the circumference, and light passes through a part thereof. A motor (not shown) such as a motor is attached to the color wheel 121, and the color wheel 121 is configured to rotate at a high speed around a shaft 126. Therefore, the passing light is sequentially switched to R, G, and B. The light that has passed through the color wheel 121 is converted into substantially parallel light by the condenser lens 122 having a focal point at the second focal point f2 of the concave mirror 1b.
[0146]
The converted substantially parallel light is incident on the first lens array 123. The first lens array 123 is composed of a plurality of positive power lens elements, and each of the plurality of positive power lens elements has an opening substantially similar to the shape of the display area of the reflective light valve 96. Yes. Similarly to the first lens array 123, the second lens array 124 is composed of a plurality of positive power lens elements. Therefore, the substantially parallel light incident on the first lens array 123 is divided by a plurality of lens elements constituting the first lens array 123, and each lens constituting the second lens array 124 corresponding to the lens element. A light emitter image is formed on the device.
[0147]
Light rays emitted from the lens elements constituting the second lens array 124 sequentially pass through the relay lens 125 and the positive power lens element 95 in the vicinity of the reflective light valve 96 to illuminate the reflective light valve 96. At this time, the light beams emitted from the lens elements of the second lens array 124 are superimposed on the display area of the reflective light valve 96. The exit pupil 98 of the illumination optical system 92 is in the vicinity of the second lens array 124 and in the relay lens 125.
[0148]
Light rays emitted from the reflective light valve 96 are converged by the positive power lens element 95 and enter the entrance pupil 99 of the projection lens 97. Therefore, the optical image formed on the reflective light valve 96 is enlarged and projected on the screen by the projection lens 97.
[0149]
Next, the principle of separation of the unnecessary light component and the effective light component according to the fifth embodiment will be described with reference to FIG. From the exit pupil 98 of the illumination optical system 92, a light beam condensed by the light source 91 and made uniform and shaped by the illumination optical system 92 is emitted, and a light beam 100 a that illuminates the upper part of the reflective light valve 96, a reflective light A light beam 100 b that illuminates the central portion of the bulb 96 and a light beam 100 c that illuminates the lower portion of the reflective light valve 96 are emitted.
[0150]
At this time, as shown in FIG. 10, some of the light beams 100a, 100b and 100c from the exit pupil 98 of the illumination optical system 92 in FIG. 10 are reflected by the optical interface 102 of the positive power lens element 95, 119a, 119b, and 119c are generated and travel in the direction of the projection lens 97. These light beams are unnecessary light that forms a virtual image 112 in the vicinity of the reflective light valve 96.
[0151]
However, in the fifth embodiment, as described above, the distance d2 between the lens element 95 and the reflective light valve 96 is the projection lens 97 among the light beams 119a, 119b and 119c generated at the optical interface 102 of the lens element 95. Is set so as to be separated from the effective light component of the modulated light emitted from the reflective light valve 96. For this reason, generation | occurrence | production of the unnecessary light on the display area of a screen can be suppressed, and the projection image excellent in the image quality can be obtained.
[0152]
Here, the setting of the distance d2 will be described. As the distance d2 is gradually increased, the positions at which the luminous fluxes 100a and 100b and the luminous flux 100c of the illumination light pass through the lens element 95 are shifted downward in the drawing. Accordingly, the positions at which the reflected light beams 119a, 119b, and 119c are reflected by the positive power lens element 95 are also shifted downward in the figure.
[0153]
In this case, of the light beams 119a, 119b, and 119c, the light incident on the projection lens 97 is gradually separated from the effective light component of the modulated light emitted from the reflective light valve 96, and the virtual image 112 is also relatively illustrated. It moves downward to move away from the optical axis 105 of the reflective light valve 96.
[0154]
For this reason, the distance d2 is preferably set so that the virtual image 112 is formed outside the effective display area of the reflective light valve 76. In this case, the generation of unnecessary light on the display area of the screen described above is further reduced. Therefore, it is possible to obtain a projected image with better image quality.
[0155]
Also in the fifth embodiment, as described above, the light shielding portion 120 is provided on the screen side of the projection lens 97. For this reason, unnecessary light incident on the projection lens 97 can be shielded. The light shielding unit 120 is the same as that shown in the fourth embodiment.
[0156]
In the fifth embodiment, the virtual image 112 is formed by appropriately selecting the distance from the exit pupil 98 of the illumination optical system 92 to the positive power lens element 95 and the focal length of the positive power lens element 95. And the display surface of the reflective light valve 96 can be made substantially coincident with each other. In this case, the area overlapping the virtual image 112 in the display area can be minimized, and the distance d2 between the positive power lens element 95 and the reflective light valve 96 can be reduced, so that the back focus of the projection lens 97 can be shortened and the size can be reduced. Can be achieved.
[0157]
Incidentally, in the fifth embodiment, since the distance d2 is set, the luminous flux of the emitted light from the reflective light valve 96 becomes larger than that in the first embodiment. For this reason, also in the fifth embodiment, it is preferable to increase the effective diameter of the positive power lens element. Further, as described in the fourth embodiment, when the positive power lens element 95 is configured by a single plano-convex lens, a thick center thickness is required to secure the edge thickness. Accordingly, also in the fifth embodiment, as in the first embodiment, the positive power lens element 95 is preferably formed of a glass material having a high refractive index. Specifically, it is preferable to use a material having a refractive index of 1.74 or more and 1.85 or less.
[0158]
As described above, when the projection display apparatus according to the fifth embodiment is used, it is possible to further suppress the deterioration of the image quality of the projected image due to the unnecessary light component, as compared with the projection display apparatus according to the first embodiment. Also in the fifth embodiment, similarly to the first embodiment, front projection can be realized without using a total reflection prism.
[0159]
(Embodiment 6)
Next, a projection display apparatus according to Embodiment 6 of the present invention will be described with reference to FIGS. FIG. 11 is a diagram showing a configuration of a projection display apparatus according to Embodiment 6 of the present invention. FIG. 12 shows the entrance pupil of the projection lens constituting the projection display device shown in FIG. Also in the sixth embodiment, the DMD shown in FIG. 17 is used as the reflective light valve. FIG. 11 shows a cross section obtained by cutting perpendicularly to the rotation support shaft of the micromirror that constitutes the DMD.
[0160]
First, the configuration and operation of the projection display apparatus according to the sixth embodiment will be described with reference to FIG. As shown in FIG. 11, the projection display apparatus according to the sixth embodiment is different from the projection lens 97 in that the light shielding unit 120 is not provided on the screen side and a diaphragm is provided instead. This is different from the projection display apparatus according to the fifth embodiment. In other respects, the projection display apparatus according to the sixth embodiment is the same as the projection display apparatus according to the fifth embodiment. In FIG. 11, the same reference numerals as those in FIG. 9 are the same as those shown in FIG. 9.
[0161]
In the projection display apparatus according to the sixth embodiment, as shown in FIG. 12, the entrance pupil 99 of the projection lens 97 is provided with a stop 138 that is eccentric with respect to the optical axis 103 of the projection lens 97. In addition, a second diaphragm (not shown) is also provided as will be described later. Reference numeral 127 denotes an effective area. For this reason, only the illumination light reflected by the reflective light valve 96 that constitutes an optical image (the effective light component of the modulated light) passes through the aperture 138. This point will be described with reference to FIG.
[0162]
FIG. 13 is a diagram showing the behavior of the light flux in the central portion of the display area of the reflective light valve shown in FIG. In FIG. 13, only the one located at the center of the display area among the micromirrors constituting the reflective light valve is shown. FIG. 13 shows a cross section obtained by cutting perpendicularly to the rotation support shaft of the micromirror that constitutes the DMD. In FIG. 13, 96 a is a micro mirror in the ON state, 96 b is a micro mirror in the OFF state, and only the entrance pupil 99 is shown for the projection lens 97.
[0163]
As shown in FIG. 13, the angle formed by the optical axis 128 of the illumination optical system and the optical axis 105 of the reflective light valve 96 (the optical axis 103 of the projection lens 97) is β, and the normal 129 of the micromirror in the ON state An angle formed by the optical axis 105 of the reflective light valve 96 is denoted by γ. At this time, the angle α formed between the principal ray 132 of the light beam emitted when the reflective light valve 96 is in the ON state and the optical axis 105 of the reflective light valve 96 is expressed by the following equation (2).
α = β-2γ (2)
[0164]
On the other hand, if the angle formed by the principal ray 133 of the light beam 139 emitted when the reflective light valve 96 is in the OFF state and the optical axis 105 of the reflective light valve (the optical axis 103 of the projection lens 97) is δ, δ Is represented by the following formula (3). The light beam emitted in this OFF state becomes unnecessary light.
δ = 4γ + α (3)
[0165]
In order to improve the image quality of the projected image, it is necessary that unnecessary light does not enter the entrance pupil 99 of the projection lens 97 to generate stray light inside the lens, or prevent unnecessary light from reaching the screen. It is. Therefore, from the above equation (3), if the angle α is 0 or more, δ increases, and the light beam emitted when the reflective light valve 96 is in the OFF state is at the position of the light beam 140 when the angle α is 0. What is present is shifted to the position of the light beam 139. Therefore, the principal ray 133 is far from the entrance pupil 99 of the projection lens, and the above-described unnecessary light can be prevented from entering the entrance pupil 99.
[0166]
In addition, the effective area when the principal ray 132 of the light beam emitted when the reflective light valve 96 is in the ON state and the optical axis 105 of the reflective light valve coincide, that is, when α is 0 degrees, is indicated by a dotted line. 130. However, when the chief ray 132 tilts (α> 0), the effective area shifts upward in the figure, and the effective area in this case becomes 127 shown in FIG. Therefore, in this embodiment, the area other than the effective area 127 in the entrance pupil 99 of the projection lens is shielded by providing a stop 138 so that unnecessary light does not pass through.
[0167]
Further, the light reflected by the transparent substrate provided on the surface of the reflective light valve also becomes unnecessary light. The principal ray 134 of the unnecessary light and the optical axis 105 of the reflective light valve (the optical axis 103 of the projection lens 97). ) Is also β. Therefore, by setting the angle α to 0 degree or more, the angle β formed by the principal ray 134 of the unnecessary light and the optical axis 105 of the reflection type light valve (the optical axis 103 of the projection lens 97) is also increased. Can be prevented from entering the entrance pupil 99 of the projection lens.
[0168]
By the way, in the display area (not shown) of the reflective light valve 96, pixels composed of minute mirrors, driving signal lines, pixel electrodes and the like are periodically formed. As the definition of the projected image increases, the number of effective pixels on the reflective light valve 96 also increases. For this reason, unless the size of the reflective light valve 96 is increased, the size of the pixels (micromirrors) on the reflective light valve 96 is reduced, and the pitch of the pixels is also reduced.
[0169]
In general, it is preferable to reduce the size of the reflective light valve because the size of the reflective light valve can be reduced to reduce the cost of the reflective light valve and the optical system using the reflective light valve. . Therefore, it is considered that the size and pitch of the pixel are likely to be smaller in the future.
[0170]
Here, consider a case where light is incident on an object having a periodic structure such as a reflective light valve as shown in FIG. In general, when light is incident on an object having a fine periodic structure, the object having a periodic structure functions as a diffraction grating, and diffracted light of zero-order light, first-order light, second-order light,. When the diffraction grating is formed by a reflecting surface, the reflected light becomes diffracted light. Diffracted light is generated with an intensity distribution discretely according to the order, and the diffracted light of each order satisfies the following formula (4). In the following equation (4), θ is the angle formed by the incident light with the optical axis, θ ′ is the angle formed by the emitted light with the optical axis, n is an integer and the diffraction order, λ is the wavelength, and d3 is the pitch of the periodic structure. Show.
(Nλ) / d3 = sin θ−sin θ ′ (4)
[0171]
Therefore, in the reflection type light valve as shown in FIG. 17, unnecessary light generated by being reflected by the transparent substrate of the reflection type light valve has a spread angle of an angle θ1 in the directions of the axes 135a and 135b with the principal ray 134 as the center. In addition to being emitted as a light beam 136 having the same, it is also emitted as diffracted light generated by the fine periodic structure described above. Of the diffracted light, the primary light beam generated outside the zero-order light is discretely emitted to the axes 135a and 135b located on the outermost periphery of the light beam 136, but is superimposed and is larger than θ1. The light beam 137 having a divergence angle is emitted.
[0172]
By the way, the light having the highest intensity in the diffracted light is the first-order diffracted light. The first-order diffracted light is emitted with a spread angle of an angle φ represented by the following formula (5) with respect to the incident light.
sinφ = λ / d (5)
[0173]
Therefore, the light beam 137 generated by being reflected by the transparent substrate is emitted at an angle (θ1 + φ) including the divergence angle θ1 of the light beam 136 from the above equation (5).
[0174]
On the other hand, as can be seen from FIG. 13, β also satisfies the relationship of the following formula (6). Note that θ1 is the divergence angle of the light reflected by the reflective light valve 96 and incident on the projection lens as described above.
β = 2θ1 + α (6)
[0175]
Therefore, as shown in FIG. 13, a part of the effective light component (ON light) of the modulated light emitted from the reflective light valve 96 overlaps with the unnecessary light beam 137, and a part of the unnecessary light beam 137. Will pass through the effective area 127. For this reason, in the sixth embodiment, as shown in FIG. 13, a second diaphragm 131 is provided to shield a part of the effective area 127 and prevent a part of the light beam 137 from passing therethrough. The second diaphragm 131 has a luminous flux such that the angle of the line connecting the end closest to the optical axis 105 and the micromirror 96a to the optical axis 105 is (θ3-φ) or (θ1 + α-φ). It is preferable to form along the outer shape of 137.
[0176]
In the sixth embodiment, the entrance pupil 99 needs to include an effective area 127 as shown in FIG. Therefore, it is preferable that the F number F1 of the projection lens satisfies the following formula (1).
F1 = 1 / (2 sin (θ1 + α)) (1)
[0177]
For example, when the pixel pitch of the reflective light valve is about 14 μm, the first-order diffracted light is generated in a range where the spread angle is increased by about 2.4 degrees (φ = 2.4 degrees) with respect to the light beam 136. Accordingly, the effective entrance pupil (effective region 127) of the projection lens is preferably decentered at an angle (α) greater than 2.4 degrees with respect to the optical axis 103. In this case, if the tilt angle of the micromirrors (96a, 96b) is ± 10 degrees, the F number F1 of the projection lens is about 3 from the above formula (1), compared to about 3 when there is no eccentricity. 2.4.
[0178]
As described above, in the projection display apparatus according to the sixth embodiment, the diaphragm 138 and the second diaphragm 131 which are decentered at the entrance pupil 99 of the projection lens are provided, and the light beam constituting the image from the reflective light valve is provided. It is configured to pass through these apertures. That is, in the sixth embodiment, the angle α formed between the principal ray 132 of the light beam emitted when the reflective light valve is in the ON state and the optical axis 105 of the reflective light valve is set to be larger than 0 degree. Yes.
[0179]
Therefore, if the projection display apparatus according to the sixth embodiment is used, it is possible to suppress unnecessary light such as off light or light reflected by the transparent substrate from entering the entrance pupil 99 of the projection lens, and the image quality of the projected image Can be improved. In the present embodiment, the diaphragm 138 has a circular shape, but the present embodiment is not limited to this, and may have, for example, an elliptical shape.
[0180]
As described above, when the projection display apparatus according to the sixth embodiment is used, it is possible to further suppress the deterioration of the image quality of the projection image due to the unnecessary light component, as compared with the projection display apparatus according to the first embodiment. Also in the sixth embodiment, similarly to the first embodiment, front projection can be realized without using a total reflection prism.
[0181]
Further, since the projection lens is provided with the eccentric diaphragm 138 and the second diaphragm 131 in this way, the lens or the lens group provided with the diaphragm is rotated, and focus adjustment is performed forward and backward by this rotation. Is not preferred. Therefore, in the sixth embodiment, as the focus adjustment means of the projection lens, it is preferable to perform focus adjustment only by moving in the optical axis direction without rotating the lens group, and in particular, a lens constituting the projection lens. It is preferable to adjust the focus by moving only the front group of the group.
[0182]
Specifically, focus adjustment means using a forward helicoid can be mentioned. It should be noted that if focus adjustment is performed by rotating only a lens group that is not provided with an eccentric stop, it is also a preferable aspect to use such a focus adjustment means.
[0183]
Also in the sixth embodiment, as in the fifth embodiment, the positive power lens element 95 is preferably made of a glass material having a high refractive index. Specifically, it is preferable to use a material having a refractive index of 1.74 or more and 1.85 or less.
[0184]
(Embodiment 7)
Next, a projection display apparatus according to Embodiment 7 of the present invention will be described with reference to FIG. FIG. 14 is a diagram showing the configuration of the projection display apparatus according to the seventh embodiment of the present invention. In the seventh embodiment, the DMD shown in FIG. 17 is used as the reflective light valve. FIG. 14 is a cross-sectional view obtained by cutting perpendicularly to the rotation axis of a micromirror constituting the DMD.
[0185]
As shown in FIG. 14, the projection display apparatus according to the seventh embodiment is configured in the same manner as in the sixth embodiment except that the configuration of the illumination optical system 142 is different. That is, the light source 141, the positive power lens element 145, the reflective light valve 146, and the projection lens 147 are the same as those in the sixth embodiment, and these are arranged in the same manner as in the sixth embodiment.
[0186]
In the seventh embodiment, the illumination optical system 142 sequentially arranges a condenser lens 160, a lens array 164 that splits a light beam, a light guide 165 configured by bundling a plurality of optical fibers 166, and a relay lens 167. Configured.
[0187]
For this reason, the substantially parallel light passing through the color wheel 121 and converted by the condenser lens 160 passes through the lens array 164 and enters each optical fiber 166 constituting the light guide 165. The light incident on each optical fiber 166 is emitted after being repeatedly reflected inside the fiber.
[0188]
By the way, in the projection display apparatus shown in Embodiments 1 to 5, each element of the illumination optical system (for example, the relay lens system 4 of the illumination optical system 2) is perpendicular to the optical axis of the illumination optical system. However, the illumination optical system is arranged such that its optical axis is inclined with respect to the optical axis of the positive power lens and the optical axis of the reflective light valve. For this reason, from the “Scheinproof theorem”, the shape of the illumination light reaching the reflective light valve may be a shape in which a rectangle such as a rhombus or a trapezoid is inclined. In this case, the light emitted from the reflective light valve has a higher light flux density from the top to the bottom in the figure, and the light flux distribution is non-uniform.
[0189]
Further, when the light beams 151a, 151b, and 151c of the light emitted from the reflective light valve 146 pass through the positive power lens element 145, they are refracted, but the refraction direction and refractive power are the reflective light valve 146. Depending on which part of the display area is reflected. For this reason, also in the entrance pupil 149 of the projection lens 147, the light flux density increases from the top to the bottom in the figure, and the light flux distribution may become non-uniform.
[0190]
When such a non-uniform light flux distribution occurs, a part of the region in the exit pupil 148 of the illumination optical system 142 and a part of the region in the entrance pupil 149 of the projection lens 147 have a conjugate relationship with respect to the positive power lens. There is a possibility that the brightness of the projected image becomes non-uniform.
[0191]
For this reason, in the seventh embodiment, as described above, the illumination optical system 142 is configured using the light guide 165. The light guide 165 is configured by bundling a plurality of optical fibers 166, and the exit pupil 148 of the illumination optical system 142 is configured by the output light of the plurality of optical fibers 166 arranged two-dimensionally. Therefore, the exit pupil 148 of the illumination optical system 142 has a plurality of partial pupil elements, and the shape of the exit pupil 148 is a surface shape in which the plurality of partial pupil elements are combined. In the present embodiment, this surface may be a free-form surface.
[0192]
Furthermore, as shown in FIG. 14, the plurality of optical fibers 166 are arranged uniformly on the incident surface 165a of the light guide 165, and unevenly arranged on the exit surface 165b. In the example of FIG. 14, the density of the optical fiber 166 decreases from the upper side to the lower side in the drawing at the emission surface 165b. For this reason, the luminous flux distribution of the illumination light emitted from the illumination optical system 142 is not uniform at the time of emission, but becomes uniform when reflected by the reflective light valve. That is, from the “Scheinproof theorem”, the shape of the illumination light reaching the reflective light valve 146 is prevented from being a shape in which a rectangle is inclined.
[0193]
Accordingly, the entire or substantially entire area of the entrance pupil 149 of the projection lens 147 and the entire or approximately entire area of the exit pupil 148 of the illumination optical system 142 satisfy a good conjugate relationship, and the exit pupil 148 of the illumination optical system 142 exits. The illumination light to be transmitted passes through the entrance pupil 149 of the projection optical system 147 as much as possible.
[0194]
In the seventh embodiment, the entrance pupil 149 of the projection lens 147 and the exit pupil 148 of the illumination optical system 142 are arranged in a conjugate relationship with respect to the positive power lens element 145. Therefore, by appropriately controlling the light flux distribution of the exit pupil 148 of the illumination optical system 142 from the “Scheinproof theorem”, the light flux distribution on the entrance pupil 149 of the projection lens 147 can be made uniform, and the uniform A projected image with brightness can be obtained.
[0195]
In the present embodiment, the illumination optical system 142 is not limited to the mode using the light guide 165. The illumination optical system 142 may have a configuration in which a plurality of lens arrays including a plurality of positive power lens elements are arranged instead of the light guide 165. In this configuration, the luminous flux distribution of the illumination light emitted from the illumination optical system can be appropriately controlled by using different positive power lens elements constituting the lens array. Therefore, also in this aspect, the luminous flux distribution of the illumination light reflected by the reflective light valve can be made uniform. The illumination optical system 142 shown in the seventh embodiment can also be used as an illumination optical system of a projection display device according to another embodiment.
[0196]
Also in the seventh embodiment, the projection lens 147 is provided with the same diaphragm (the diaphragm 138 and the second diaphragm 131 shown in FIG. 13) as the configuration shown in the sixth embodiment. Therefore, the illumination optical system 142 needs to be arranged so that the illumination light reflected by the reflective light valve 146 constitutes an optical image passes through these stops. In this case, it is preferable that the F number of the projection lens satisfies the above formula (1) as in the sixth embodiment.
[0197]
Also in the seventh embodiment, as in the fifth embodiment, the positive power lens element 145 is preferably formed of a glass material having a high refractive index. Specifically, it is preferable to use a material having a refractive index of 1.74 or more and 1.85 or less.
[0198]
In the projection display device of the present invention, a plurality of reflection type light valves can be used. In this case, it is necessary to provide a color separation optical system for allowing monochromatic light to enter each reflective light valve and a color combining optical system for combining light emitted from each reflective light valve.
[0199]
Further, in the projection display device of the present invention, the movable range of the micro mirrors constituting each pixel of the reflective light valve is not limited to ± 10 degrees. In the present invention, the movable range of the micromirror may be set so as to obtain an optimum light output and high contrast according to the characteristics of the reflective light valve used.
[0200]
Furthermore, in the projection display device of the present invention, each pixel of the reflection type light valve is not limited to an aspect constituted by a working fine mirror. In the projection display device of the present invention, the reflection type light valve may be any one that has a different incident direction and an outgoing direction of light and can control the outgoing direction.
[0201]
(Embodiment 8)
FIG. 15 is a configuration diagram showing an example of the rear projector of the present invention. As shown in FIG. 15, the rear projector includes a projection display device 170 described in any of Embodiments 1 to 7, and a mirror 171 that reflects light projected from the projection display device 170. The screen 172 that transmits and scatters the light reflected by the mirror 171 and displays the screen 172, and the housing 173 that accommodates the screen 172.
[0202]
As described above, in the rear projector shown in FIG. 15, since the projection display device shown in any of Embodiments 1 to 7 is used, size reduction and cost reduction can be achieved, and image quality can be reduced. A good projected image can be displayed.
[0203]
(Embodiment 9)
FIG. 16 is a block diagram showing an example of the multivision system of the present invention. As shown in FIG. 16, the multivision system includes a plurality of projection systems and a video signal dividing circuit 189. Each projection system includes the projection display device (180 to 182), the transmission screen (183 to 185), and the housing (186 to 188) described in any of the first to seventh embodiments. It is configured.
[0204]
The video signal dividing circuit 189 divides the screen into a plurality of areas, processes the video signal in each area, and supplies the processed video signals to the projection display devices 180, 181 and 182 constituting each projection system. Therefore, the respective images projected from the projection display devices 180, 181, and 182 are imaged on the corresponding transmission screens 183, 184, and 185, respectively, and constitute one image as a whole. As described above, according to the multivision system of the present embodiment, a compact set with a short depth and a large screen can be realized.
[0205]
Alternatively, two of the transmission screens 183 to 185 may display one image as a whole, and another image may be displayed on the remaining one. In order to obtain a visual effect, the same image may be displayed on each transmissive screen. Furthermore, in order to provide various information at a time, different contents may be displayed on each transmissive screen.
[0206]
The projection display devices 180, 181, and 182 have the brightness and chromaticity of the signal distributed by the video dividing circuit 189 in accordance with the light output and color reproducibility at the start of lighting by sensors attached in the respective cases. It is good also as a mode which processes color information, such as saturation. In this case, even with images projected separately from the projection display devices 180 and 181 and the projection display device 182, a highly uniform display can be realized as one screen.
[0207]
【The invention's effect】
As described above, according to the present invention, a positive power lens element is arranged in the vicinity of the reflective light valve display area so that a virtual image of the exit pupil of the illumination optical system is not formed in the effective display area. Can do. Therefore, even in a telecentric optical system, the effective system of the entrance pupil of the projection lens and the exit pupil of the illumination optical system can be reduced, and the optical paths of the incident light and the outgoing light can be separated with a compact configuration. For this reason, conventionally used means for separating the illumination light and the projection light, such as a total reflection prism splitter, becomes unnecessary. Accordingly, it is possible to perform front projection with a telecentric optical system while reducing the cost, and it is possible to achieve uniform image quality within the projection plane.
[0208]
That is, according to the projection display device of the present invention, it can be said that a compact and high-quality display optical system using a reflective light valve can be realized. Further, the projection display device according to the present invention can ensure a homogeneous image by front projection. Furthermore, since a prism is not used, it is possible to reduce the price and at the same time obtain a high-quality image with high contrast.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a projection display apparatus according to a first embodiment of the present invention.
2A is a diagram showing the optical paths of illumination light and projection light in the vicinity of the reflective light valve shown in FIG. 1, and FIG. 2B is a diagram showing the reflective light shown in FIG. It is a figure which shows the behavior of the reflected light in the optical interface of the lens element of positive power in the vicinity part of a valve | bulb.
FIG. 3 is a diagram showing a configuration of a projection display apparatus according to a second embodiment of the present invention.
4 is an enlarged view of the surface of the positive power lens element shown in FIG. 3; FIG.
FIG. 5 is a diagram showing a configuration of a projection display apparatus according to a third embodiment of the present invention.
6 is an enlarged cross-sectional view of the positive power lens element shown in FIG. 5;
FIG. 7 is a diagram showing a configuration of a projection display apparatus according to a fourth embodiment of the present invention.
8A is a diagram showing the optical paths of illumination light and projection light in the vicinity of the reflective light valve shown in FIG. 7, and FIG. 8B is a diagram showing the reflective light shown in FIG. It is a figure which shows the behavior of the reflected light in the optical interface of the lens element of positive power in the vicinity part of a valve | bulb.
FIG. 9 is a diagram showing a configuration of a projection display apparatus according to a fifth embodiment of the present invention.
10 is an enlarged view of the vicinity of the reflective light valve shown in FIG.
FIG. 11 is a diagram showing a configuration of a projection display apparatus according to a sixth embodiment of the present invention.
12 shows an entrance pupil of a projection lens constituting the projection display apparatus shown in FIG.
13 is a diagram showing the behavior of a light beam in the central portion of the display area of the reflective light valve shown in FIG.
FIG. 14 is a diagram showing a configuration of a projection display apparatus according to a seventh embodiment of the present invention.
FIG. 15 is a configuration diagram showing an example of a rear projector according to the invention.
FIG. 16 is a block diagram showing an example of a multivision system of the present invention.
FIG. 17 is a diagram showing an operating state of a micromirror that constitutes each pixel of a conventional DMD.
FIG. 18 is a diagram showing a schematic configuration of a projection display apparatus using a conventional DMD.
19 is an enlarged view of the vicinity of the DMD shown in FIG.
FIG. 20 is a diagram illustrating a schematic configuration of a projection display apparatus in which a conventional projection lens is a non-telecentric system.
FIG. 21 is an enlarged view of the vicinity of the reflective light valve shown in FIG.
[Explanation of symbols]
1, 31, 51, 71, 91, 141 Light source
1a lamp
1b Concave mirror
2, 32, 52, 72, 92, 142 Illumination optical system
3 Rod lens
4 Relay lens system
5, 35, 55, 75, 95, 145 Positive power lens elements
6, 36, 56, 76, 96, 146 Reflective light valve
7, 37, 57, 77, 97, 147 Projection lens
8, 38, 58, 78, 98, 148 Exit pupil of illumination optical system
9, 39, 59, 79, 99, 149 Projection lens entrance pupil 9
10a-10c, 40a-40c, 60a-60c, 80a-80c, 100a-100c, 150a-150c Luminous flux of illumination light
11a-11c, 41a-41c, 61a-61c, 101a-101c, 151a-151c Luminous flux of light emitted from the reflective light valve
13, 43, 63, 83, 103, 153 Optical axis of projection lens
14, 44, 64, 84, 104, 154 Optical axis of positive power lens element
15, 45, 65, 85, 105, 155 Optical axis of reflective light valve
16, 46, 66, 86, 106, 156 Focus of positive power lens element
17, 47, 67, 87, 107, 157 Focal plane of positive power lens element
18 Incident surface of rod lens
19 Outgoing surface of rod lens
20a, 88, 102 Optical interface (convex surface)
20b, 89 Optical interface (convex surface)
21a-21c, 90a-90c, 119a-119c Luminous flux of reflected light at the optical interface
22, 82, 112 Virtual image
42 Protrusions
68 Plano-concave lens
68a, 68b Plano-concave lens surface
69 Plano-convex lens
69a, 69b Plano-convex lens surfaces
70a Adhesive
70b thin film
96a micro mirror in ON state
96b Off-state micromirror
120 Shading part
121 color wheel
122 condenser lens
123 First lens array
124 second lens array
125 relay lens
126 axes
127 Effective area
129 Normal of micro mirror in ON state
130 Effective area when α is 0 degree
131 Second aperture
132 Principal ray of luminous flux emitted when the reflective light valve is in the On state
133 Principal ray of luminous flux emitted when the reflective light valve is in the OFF state
134 Principal ray of unwanted light
135 axes
136 Light flux of unnecessary light
137 Light flux of diffracted light
138 Aperture
139 Light flux emitted when the reflective light valve is OFF
160 condenser lens
164 Lens array for splitting the luminous flux
165 Light Guide
165a Light guide incident surface
165b Light guide exit surface
166 optical fiber
167 Relay lens
170, 180-182 Projection display device
171 Mirror
172, 183-185 screen
173, 186 to 188 housing
189 Video signal dividing circuit

Claims (9)

An illumination optical system that collects light emitted from a light source to form illumination light, a reflective light valve that reflects the illumination light and emits modulated light that forms an optical image, and the reflective light valve are formed. A projection lens for projecting an optical image and a positive power lens element;
The reflective light valve has a plurality of pixels, and is configured to emit the modulated light by controlling a reflection direction of the illumination light for each of the plurality of pixels.
The lens element is composed of one plano-convex lens, and the illumination light passes through the lens element with a convex surface facing the projection lens between the reflective light valve and the projection lens. Illuminating the reflective light valve, and the modulated light emitted from the reflective light valve is arranged to pass through the lens element and enter the projection lens,
The reflective light valve, the projection lens, and the lens element are arranged so that their optical axes are parallel and coincide with each other,
The lens element and the reflective light valve separate the traveling direction of the unnecessary light component of the illumination light reflected by the convex optical interface of the lens element from the traveling direction of the effective light component of the modulated light , in so that the virtual image formed by the unnecessary light component is formed on the non-effective display region of the reflection type light valve, a projection, characterized in that it is arranged at a predetermined distance from each other in the optical axis direction Display device.   The projection display device according to claim 1, wherein the projection lens has a diaphragm decentered with respect to an optical axis thereof, and the illumination optical system is arranged so that the modulated light passes through the diaphragm.   The projection display device according to claim 2, wherein an eccentric direction of the diaphragm is a direction away from an optical axis of the illumination optical system.   The projection display device according to claim 2, wherein the projection lens includes means for adjusting a focus only by movement in the optical axis direction. F1 of the projection lens is F1, emitted from the illumination optical system, the spread angle of light reflected by the reflective light valve and incident on the projection lens is θ1, and emitted from the center of the display area of the reflective light valve. The projection display apparatus according to claim 2, wherein the following formula (1) is satisfied, where α is an angle formed between a principal ray to be emitted and an optical axis of the projection lens.
F1 = 1 / (2 sin (θ1 + α)) (1)   The illumination optical system has an exit pupil formed by a plurality of partial pupil elements, and is configured to be uniform when a luminous flux distribution of the illumination light is reflected by the reflective light valve. The projection display device according to any one of 1 to 5. The exit pupil of the illumination optical system and the entrance pupil of the projection lens are substantially conjugate with respect to the lens element,
More than 80% of the light beam reflected by the display area of the reflective light valve out of the light beam passing through the exit pupil of the illumination optical system passes through the lens element and enters the effective area of the entrance pupil of the projection lens. The projection display device according to claim 1.   A projection display device according to any one of claims 1 to 7, a mirror that reflects light projected from the projection display device, and a screen that displays the light reflected by the mirror through transmission and scattering. And at least a rear projector. A plurality of projection systems and a video signal dividing circuit;
Each of the plurality of projection systems includes a projection display device according to any one of claims 1 to 7, a transmissive screen that projects light projected from the projection display device, and the projection display device. It consists of a housing that houses it,
The multi-vision system, wherein the video signal dividing circuit divides a screen into a plurality of areas, processes the video signal of each area, and supplies the processed video signals to each of the projection display devices constituting the projection system.

Images