JP2004258541A - Reflection type optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type optical system which enables a diaphragm and a member retaining the diaphragm to be arranged therein without hindering a luminous flux and interfering with a reflective surface and, nevertheless, is compact as a whole. <P>SOLUTION: The reflection type optical system has a plurality of the reflective surfaces with a curvature and the diaphragm among the plurality of reflective surfaces and is constituted in such a manner that an incident luminous flux repeats reflection at the plurality of reflective surfaces and is emitted. In the reflection type optical system, when a light ray passing through the center of the diaphragm and attaining the center of the final image forming surface is made to be the central principal light ray, the diaphragm is arranged so that the surface normal is inclined to the central principal light ray, when the reflective surface just front of the diaphragm as a view from the light incident side is SA, the reflective surface just rear of the diaphragm is SB, an angle between the central principal light ray which is made incident on the reflective surface SA and the surface normal of the diaphragm is α1 and an angle between the central principal light ray which is emitted from the reflective surface SB and the surface normal of the diaphragm is α2, the reflection type optical system satisfies the relation (1): -180<α1<180, -180<α2<180. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１１】
ただし、−１８０＜α１＜１８０、−１８０＜α２＜１８０
の条件式を満たすことを特徴としている。
【００１２】
【発明の実施の形態】
［実施形態１］
実施形態の説明に入る前に、実施形態の構成の諸元の表し方及び実施形態全体の共通事項について説明する。
【００１３】
図１１は本発明の光学系の構成データを定義する座標系の説明図である。本発明の実施形態では物体側から絞りの中心を通過し、最終結像面の中心に至る１つの光線（図１１中の一点鎖線で示すもので基準軸光線（または中心主光線とも称す。）に沿ってｉ番目の面を第ｉ面とする。
【００１４】
図１１において第１面Ｒ１は絞り、第２面Ｒ２は第１面と共軸な屈折面、第３面Ｒ３は第２面Ｒ２に対してチルトされた反射面、第４面Ｒ４、第５面Ｒ５は各々の前面に対してシフト、チルトされた反射面、第６面Ｒ６は第５面Ｒ５に対してシフト、チルトされた屈折面である。第２面Ｒ２から第６面Ｒ６までの各々の面はガラス、プラスチック等の媒質で構成される一つの光学素子上に構成されている。
【００１５】
従って、図１１の構成では不図示の物体面から第２面Ｒ２までの媒質は空気、第２面Ｒ２から第６面Ｒ６まではある共通の媒質、第６面Ｒ６から不図示の第７面Ｒ７までの媒質は空気で構成されている。
【００１６】
本発明の光学系はＯｆｆ−Ａｘｉａｌ光学系であるため光学系を構成する各面は共通の光軸を持っていない。そこで本発明の実施形態においては光学系を説明しやすいように物体面と反射型光学系の間に基準となる原点を有する面（基準面）を導入し、その原点からの位置関係で面の配置を説明する。そして本発明の実施形態においては絞りの中心を通り最終結像面の中心とを通る光線（基準軸光線）の経路を光学系の基準軸と定義している。
【００１７】
さらに本実施形態中の基準軸は方向（向き）を持っている。その方向は基準軸光線が結像に際して進行する方向である。原点は基準面における基準軸光線の位置であり、基準面の法線は基準軸光線と一致している。
【００１８】
本発明の実施形態においては光学系の基準となる基準軸を上記の様に設定したが、光学系の基準となる軸の決め方は光学設計上、収差の取り纏め上、若しくは光学系を構成する各面形状を表現する上で都合の良い軸を採用すれば良い。
【００１９】
しかしながら、一般的には像面の中心と、絞り又は入射瞳又は射出瞳又は光学系の第１面の中心若しくは最終面の中心のいずれかを通る光線の経路を光学系の基準となる基準軸に設定する。
【００２０】
つまり、本発明の実施形態においては基準軸は絞り面の光線有効径の中心点を通り、最終結像面の中心へ至る光線（基準軸光線）が各屈折面及び反射面によって屈折・反射する経路を基準軸に設定している。各面の順番は基準軸光線が屈折・反射を受ける順番に設定している。
【００２１】
従って基準軸は設定された各面の順番に沿って屈折若しくは反射の法則に従ってその方向を変化させつつ、最終的に像面の中心に到達する。
【００２２】
本発明の各実施形態の光学系を構成するチルト面は基本的にすべてが同一面内でチルトしている。そこで絶対座標系の各軸を以下のように定める。
【００２３】
Ｚ軸：原点を通り第１面Ｒ１に向かう基準軸
Ｙ軸：原点を通りチルト面内（図１１の紙面内）でＺ軸に対して反時計回りに９０゜をなす直線
Ｘ軸：原点を通りＺ、Ｙ各軸に垂直な直線（図１１の紙面に垂直な直線）
また光学系を構成する第ｉ面の面形状を表わすには、絶対座標系にてその面の形状を表記するより、基準軸と第ｉ面が交差する点を原点とするローカル座標系を設定して、ローカル座標系でその面の面形状を表した方が形状を認識する上で理解し易い為、本発明の構成データを表示する実施形態では第ｉ面の面形状をローカル座標系で表わす。
【００２４】
また第ｉ面のＹＺ面内でのチルト角は絶対座標系のＺ軸に対して反時計回り方向を正とした角度θｉ（単位°）で表す。よって本発明の実施形態では各面のローカル座標の原点は図１１中のＹＺ平面上にある。またＸＺおよびＸＹ面内での面の偏心はない。さらに第ｉ面のローカル座標（ｘ，ｙ，ｚ）のｙ，ｚ軸は絶対座標系（Ｘ，Ｙ，Ｚ）に対してＹＺ面内で角度θｉ傾いており、具体的には以下のように設定する。
【００２５】
ｚ軸：ローカル座標の原点を通り、絶対座標系のＺ方向に対しＹＺ面内におい て反時計方向に角度θｉをなす直線
ｙ軸：ローカル座標の原点を通り、ｚ方向に対しＹＺ面内において反時計方向 に９０゜をなす直線
ｘ軸：ローカル座標の原点を通り、ＹＺ面に対し垂直な直線
また、Ｄｉは第ｉ面と第（ｉ＋１）面のローカル座標の原点間の間隔を表すスカラー量、Ｎｄｉ 、νｄｉは各々第ｉ面と第（ｉ＋１）面間の媒質の屈折率とアッベ数である。また本発明の実施形態では光学系の断面図及び数値データを示す。
【００２６】
球面は以下の式で表される形状である。
【００２７】
【数３】

【００２８】
また本発明の光学系は少なくとも回転非対称な非球面を一面以上有し、その形状は以下の式により表す。
【００２９】
【数４】

【００３０】
上記曲面式はｘに関して偶数次の項のみであるため、上記曲面式により規定される曲面はｙｚ面を対称面とする面対称な形状である。
【００３１】
さらに、
Ｃ０２＝Ｃ２０ Ｃ０４＝Ｃ４０＝Ｃ２２／２ Ｃ０６＝Ｃ６０＝Ｃ２４／３＝Ｃ４２／３
が満たされる場合は回転対称な形状を表す。以上の条件を満たさない場合は非回転対称な形状である。
【００３２】
なお本発明の各実施形態においては垂直半画角ｕＹとは図１１のＹＺ面内において基準面Ｒ１に入射する光束の最大画角、水平半画角ｕＸとはＸＺ面内において基準面Ｒ１に入射する光束の最大画角である。また絞りの直径を絞り径として示している。これは光学系の明るさに関係する。
【００３３】
また各実施形態の横収差図を示す。基準面Ｒ１への水平入射角、垂直入射角が夫々（０，ｕＹ），（０，０），（０，−ｕＹ），（ｕＸ，ｕＹ），（ｕＸ，０），（ｕＸ，−ｕＹ）となる入射角の光束の横収差を示す。横収差図においては、横軸は瞳への入射高さを表し、縦軸は収差量を表している。各実施形態とも基本的に各面がｙｚ面を対称面とする面対称の形状となっている為、横収差図においても垂直画角のプラス、マイナス方向は同一となるので、図の簡略化の為に、マイナス方向の横収差図は省略している。
【００３４】
［実施形態１］
図１は本発明の実施形態１の反射型光学系（反射型光学素子）のＹＺ面内での要部断面図、図２は図１に示した絞り周辺での拡大断面図である。
【００３５】
図１において反射型光学系１は物体（不図示）からの光線の通過順に、反射面Ｒ１、反射面Ｒ２、反射面Ｒ３、反射面Ｒ４、絞りＳＴＯ、反射面Ｒ５の５つの反射面で構成され、物体上の画像を撮像面Ｓ１に結像する機能を有している。
【００３６】
本実施形態は水平画角２９．０８度、垂直画角３８．１９度の撮像装置（撮像光学系）に用いられる反射型光学素子である。
【００３７】
本実施形態の構成データは次のとおりである。
【００３８】
【表１】

【００３９】
【表２】

【００４０】
【表３】

【００４１】
本実施形態の反射型光学系は図１に示すように複数の曲面反射面からなる光学系である。同図において物体（不図示）からの光束は凹面鏡Ｒ１、凸面鏡Ｒ２、凹面鏡Ｒ３、そして凸反射面Ｒ４で次々と反射し、絞りＳＴＯで光束が規制され、凹反射面Ｒ５で反射され、ローパスフィルター、赤外カットフィルターで構成されるフィルターＦを通過し撮像手段としての撮像面Ｓ１上に結像する。
【００４２】
ここで、Ｒ０は基準面である。また絞りＳＴＯは、該絞りＳＴＯの中心を通過し、最終結像面の中心に至る光線を基準軸光線（中心主光線）とするとき、その面法線が基準軸光線に対して傾いて配置されている。尚、絞りＳＴＯの開口径は回転非対称より成っている。
【００４３】
このように絞りＳＴＯの面法線を基準軸光線に対して傾けて配置しているので他の光線をけることなく配置できる。絞りＳＴＯは有限の大きさを持ち、かつ保持しなければ成らないのでそれなりのスペースが必要になる。図１，図２，図３においてＬは絞りＳＴＯを配置するために必要なスペースである。本実施形態では絞りＳＴＯを含む平面内に５ｍｍほど取っている。
【００４４】
図３は反射面Ｒ４と反射面Ｒ５のオフアキシャル角を広げることにより、絞りＳＴＯが配置できるように設計した従来の反射型光学系の要部断面図である。図３における仕様は図１と同じである。図３を見れば分かるように絞りＳＴＯを配置するためのスペースを確保するために光学系が大きくなっているのが分かる。さらに図１と比べオフアキシャル角を大きく取っているので収差補正上よろしくない。
【００４５】
本実施形態の場合、絞りや該絞りの保持部材が光束をけらないように配置しなければならない。ここで問題となる光束は絞り直前の反射面に入射する光束と絞り直後の反射面から射出する光束である。
【００４６】
図１、図２において絞りＳＴＯの直前の反射面Ｒ４に入射する光束の角度は、反射面Ｒ３から反射面Ｒ４に向かう基準軸光線の角度に近く、該絞りＳＴＯ直後の反射面Ｒ５から反射する光束の角度は、該反射面Ｒ５から射出する基準軸光線の角度に近い。よって、反射面Ｒ３から反射面Ｒ４に向かう基準軸光線の角度α１と反射面Ｒ５から射出する基準軸光線の角度α２から絞り面の法線の角度を適切な角度に成るように配置すればよい。単純に考えれば角度α１と角度α２の中間の角度に絞り平面が配置されるようになればよい。しかしながら、実際には、絞り位置や基準軸と光束の角度の違いにより多少のずれが存在する。
【００４７】
そこで本実施形態では光入射側から見て絞りＳＴＯの直前の反射面をＲ４、該絞りＳＴＯの直後の反射面をＲ５とし、該反射面Ｒ４に入射する基準軸光線と該絞りＳＴＯの面法線とのなす角度をα１、該反射面Ｒ５から射出する基準軸光線と該絞りＳＴＯの面法線とのなす角をα２とするとき、
【００４８】
【数５】

【００４９】
ただし、−１８０＜α１＜１８０、−１８０＜α２＜１８０
の条件式（１）を満たすように各要素を設定している。これにより絞りＳＴＯや該絞りＳＴＯを保持する部材が光束を妨げることなく、また反射面と干渉することなく配置することが可能でありながら全体としてコンパクトな反射型光学系を得ている。尚、絞りＳＴＯの面法線の方向、基準軸光線の方向を考慮し、絞りＳＴＯの面法線から反時計回りを正とする。
【００５０】
本実施形態において、各々の角度α１、α２を算出すると夫々
α１＝−８４ 、 α２＝−１０４
よって
│α１＋α２│／２＝９４
となり条件式（１）を満たしている。ちなみに図３の従来の反射型光学系では
α１＝−１００、α２＝−１２０
よって
│α１＋α２│／２＝１１０
となり条件式（１）を満たしていない。
【００５１】
本実施形態の反射型光学系の横収差図を図４に示す。同図に示すように絞りＳＴＯを斜めに配置したとしても、横収差は微少であり、画面中心と画面の角ともにバランス良く収差補正できている。望ましくは、絞りＳＴＯを含む平面内に、該絞りＳＴＯに隣接する反射面が配置されていないほうが良い。即ち絞りＳＴＯを含む平面外に、該絞りＳＴＯに隣接する反射面が配置されている。さらに絞りの前後の反射面の光軸方向のほぼ中央の位置に配置されているほうが光束をよけて配置しやすい。
【００５２】
本実施形態では表面反射面のみで構成されているが、屈折レンズを含んでも良い。また表面反射面のみではなく裏面反射面を含まして構成しても良い。また反射面を５面用いているが、反射面は５面に限らない。また反射面はある平面に対して対称な形状であるが、これに限ったことではない。この反射型光学素子一つで撮像素子として機能するが、この反射型光学素子を少なくとも一つ含み、複数の光学素子で撮像光学系を構成してもよい。また前述した特許文献２〜４のように複数の光学素子の相対位置を変化させて変倍光学系を構成することもできる。また本実施形態では撮像光学系（撮像装置）に反射型光学素子を用いたが、この光学系に限らず、例えば読取光学系（画像読取装置）、物体面上のパターンを感光基板上に縮小露光する露光光学系（露光装置）、そしてプロジェクタ等の投射光学系（投射型表示装置）に用いても良い。
【００５３】
［実施形態２］
図５は本発明の実施形態２の反射型光学系（反射型光学素子）のＹＺ面内での要部断面図、図６は図５に示した絞り周辺での拡大断面図である。図５、図６において図１、図２に示した要素と同一要素には同符番を付している。
【００５４】
図５において反射型光学系２は原稿面Ｏからの光線の通過順に、反射面Ｒ１、反射面Ｒ２、絞りＳＴＯ、反射面Ｒ３、反射面Ｒ４の４つの反射面で構成され、原稿面Ｏ上の画像をラインセンサーＩに結像する機能を有している。
【００５５】
本実施形態においても前述の実施形態１と同様に絞りＳＴＯの中心を通過し、最終結像面の中心に至る光線を基準軸光線（中心主光線）とするとき、該絞りＳＴＯは、その面法線が基準軸光線に対して傾いて配置されている。尚、絞りＳＴＯの開口径は回転非対称より成っている。
【００５６】
本実施形態におけるラインセンサーＩの長手方向の長さは６６．０８ｍｍ、読み取る大きさ幅は主走査方向に３０４．８ｍｍ、副走査方向に±１ｍｍである。本実施形態に用いられる反射型光学系２の構成データを示す。
【００５７】
【表４】

【００５８】
【表５】

【００５９】
【表６】

【００６０】
本実施形態の反射型光学系２は図５に示すように複数の曲面反射面からなる光学系である。同図において原稿面Ｏからの光束は凹面鏡Ｒ１、凹面鏡Ｒ２で次々と反射し、絞りＳＴＯで光束が規制され、凹反射面Ｒ３、凹反射面Ｒ４で次々と反射され、ラインセンサーＩ上に結像する。
【００６１】
ここで原稿面Ｏから反射面Ｒ１に向かう光路と反射面Ｒ２から絞りＳＴＯに向かう光路は交差し、さらに絞りＳＴＯから反射面Ｒ３に向かう光路と反射面Ｒ４からラインセンサーＩに向かう光路は交差している。ここで、Ｒ０は基準面である。また反射面Ｒ１〜反射面Ｒ４は各々光学有効に対して１ｍｍの余裕幅をもち、５ｍｍの厚みを有する。また絞りＳＴＯの面法線は図６に示すように基準軸光線に対して傾いて配置されている。このように配置されているので５ｍｍ厚の反射面に干渉することなく配置することが出来る。
【００６２】
絞りＳＴＯは有限の大きさを持ち、かつ保持しなければ成らないのでそれなりのスペースが必要になる。図５，６，７中のＬは絞りＳＴＯを配置するために必要なスペースである。この例では絞りＳＴＯを含む平面内に５ｍｍほど取っている。
【００６３】
図７は反射面Ｒ２と絞りＳＴＯの間隔、絞りＳＴＯと反射面Ｒ３までの間隔を広げることにより該絞りと反射面が干渉しないように絞りを配置できるように設計した従来の反射型光学系の要部断面図である。図７における仕様は図５と同じである。図７を見れば分かるように絞りＳＴＯを配置するためのスペースを確保するために光学系が大きくなっているのが分かる。
【００６４】
さらに図５の反射型光学系と比べて絞りＳＴＯから反射面Ｒ１までの光路長と、絞りＳＴＯから反射面Ｒ４までの光路長が共に長くなり、反射面Ｒ１と反射面Ｒ４の有効径が共に大きくなってしまう。この実施形態の場合、絞りＳＴＯや該絞りＳＴＯの保持部材が反射面と干渉しないように配置しなければならない。
【００６５】
ここで問題となる反射面は絞りＳＴＯに隣接する反射面Ｒ１と反射面Ｒ４であり、この反射面の厚み方向が問題となる。この方向は一般的に面法線と一致する。このことから反射面Ｒ１の面法線の角度γ１と反射面Ｒ４の面法線の角度γ２から絞り面の法線の角度を適切な角度に成るように配置すればよい。単純に考えれば角度γ１と角度γ２の中間の角度に絞り平面が配置されるようになればよい。しかしながら、実際には、絞り位置や隣接する反射面の位置等により多少のずれが存在する。
【００６６】
そこで本実施形態では図６に示すように絞りＳＴＯに隣接する２つの反射面Ｒ１，Ｒ４における基準軸光線が反射する位置での面法線と該絞りＳＴＯの面法線との為す角度を夫々γ１、γ２とするとき、
【００６７】
【数６】

【００６８】
ただし、−１８０＜γ１＜１８０、−１８０＜γ２＜１８０
の条件式（２）を満たすように各要素を設定している。これにより絞りＳＴＯや該絞りＳＴＯを保持する部材が光束を妨げることなく、また反射面と干渉することなく配置することが可能でありながら全体としてコンパクトな反射型光学系を得ている。尚、絞り、反射面の面法線の方向を考慮し、絞りの面法線から反時計回りを正とする。
【００６９】
本実施形態において、角度γ１、γ２を算出すると夫々
γ１＝８３．９８、γ２＝８１．２１
よって
│γ１＋γ２│／２＝８２．５９５
となり条件式（２）を満たしている。ちなみに図７の従来の反射型光学系では
γ１＝６４．２２、γ２＝６１．４５
よって
│γ１＋γ２│／２＝６２．８３５
となり条件式（２）を満たしていない。
【００７０】
本実施形態の反射型光学系の横収差図を図８に示す。同図に示すように絞りＳＴＯを斜めに配置したとしても、横収差は微少であり、画面中心と画面の角ともにバランス良く収差補正できている。望ましくは、絞りＳＴＯを含む平面内に、該絞りＳＴＯに隣接する反射面が配置されていないほうが良い。即ち絞りＳＴＯを含む平面外に、該絞りＳＴＯに隣接する反射面が配置されている。さらに絞りＳＴＯの前後の反射面の光軸方向のほぼ中央の位置に配置されているほうが光束をよけて配置しやすい。
【００７１】
本実施形態では表面反射面のみで構成されているが、屈折レンズを含んでも良い。また表面反射面のみではなく裏面反射面を含まして構成しても良い。また反射面を４面用いているが、反射面は４面に限らない。また反射面はある平面に対して対称な形状であるが、これに限ったことではない。この反射型光学素子一つで撮像素子として機能するが、この反射型光学素子を少なくとも一つ含み、複数の光学素子で撮像光学系を構成してもよい。また前述した特許文献２〜４のように複数の光学素子の相対位置を変化させて変倍光学系を構成することもできる。また本実施形態では撮像光学系に反射型光学素子を用いたが、この光学系に限らず、例えば後述する読取光学系、露光光学系、そしてプロジェクタ等の投射光学系に用いても良い。
【００７２】
［画像読取装置］
図９は実施形態２の反射型光学系２を用いてカラー画像又はモノクロ画像を読み取る画像読取装置を構成した例である。
【００７３】
図中、Ｌａｍｐは光源、ＣＧは原稿台ガラス、Ｍ１〜Ｍ３は第１〜３反射ミラー，２は反射型光学系、ＩはＣＣＤ等で構成されるラインセンサー、Ｃはキヤリッジ（筐体）である。原稿台ガラスＣＧの上に載置された原稿Ｏを第１〜３反射ミラーＭ１〜Ｍ３を介して反射型光学系２によりラインセンサーＩ上に結像して原稿Ｏの１ラインの画像を読み取ることができる。画像読取装置をコンパクトに構成するために第１〜３反射ミラーＭ１〜Ｍ３により光路を折り畳んでいる。反射型光学系２は表面反射面で構成されるため色収差は発生せず、高角化することが可能になる。よって光学系から原稿までの距離を短縮することになり、キヤリッジ一体型光学系の原稿読取装置を３枚の平面ミラーと反射型光学系から成る少ない光学部品で構成することができる。このキヤリッジ一体型光学系はラインセンサーのライン方向（Ｘ方向）に垂直な方向、すなわち副走査方向に原稿ＯとキヤリッジＣとを相対的に走査することによって、該原稿Ｏ面を２次元的に読み取っている。
【００７４】
［投射型表示装置］
図１０は実施形態１の反射型光学系１を用いて画像表示パネル上の画像をスクリーンに上に投影する投射型表示装置を構成した例である。
【００７５】
図１０においてＬＬはライトバルブ（画像表示パネル）ＬＶ１に光を照明する照明系である。１はライトバルブ（画像表示パネル）ＬＶ１で光変調された光をスクリーンＳに投射するためのオフアキシャル系を利用した実施形態１の構成の反射型光学系である。同図においては実施形態１の反射型光学系１を用いて画像表示パネル上の画像をスクリーンＳに上に投影している。
【００７６】
［本発明の実施態様］
本発明の様々な例と実施形態が示され説明されたが、当業者であれば、本発明の趣旨と範囲は本明細書内の特定の説明と図に限定されるのではなく、本願特許請求の範囲に全て述べられた様々の修正と変更に及ぶことが理解されるであろう。
【００７７】
本発明の実施態様の例を以下に列挙する。
【００７８】
［実施態様１］
曲率を有する複数の反射面と、該複数の反射面の間に絞りを有し、入射光束が該複数の反射面で反射を繰り返して射出するように構成した反射型光学系において、
該絞りの中心を通過し、最終結像面の中心に至る光線を中心主光線とするとき、該絞りは、その面法線が中心主光線に対して傾いて配置されており、光入射側から見て該絞りの直前の反射面をＳＡ、該絞りの直後の反射面をＳＢとし、該反射面ＳＡに入射する中心主光線と該絞りの面法線とのなす角度をα１、該反射面ＳＢから射出する中心主光線と該絞りの面法線とのなす角度をα２とするとき、
【００７９】
【数７】

【００８０】
ただし、−１８０＜α１＜１８０、−１８０＜α２＜１８０
の条件式を満たすことを特徴とする反射型光学系。
【００８１】
［実施態様２］
前記絞りを含む平面外に、該絞りに隣接する反射面が配置されていることを特徴とする請求項１に記載の反射型光学系。
【００８２】
［実施態様３］
前記絞りは、該絞りの前後の反射面の光軸方向のほぼ中央の位置に配置されていることを特徴とする実施態様１又は２に記載の反射型光学系。
【００８３】
［実施態様４］
前記絞りの開口径は回転非対称であることを特徴とする実施態様１、２又は３に記載の反射型光学系。
【００８４】
［実施態様５］
曲率を有する複数の反射面と、該複数の反射面の間に絞りを有し、入射光束が該複数の反射面で反射を繰り返して射出するように構成した反射型光学系において、
該絞りの中心を通過し、最終結像面の中心に至る光線を中心主光線とするとき、該絞りは、その面法線が中心主光線に対して傾いて配置されており、該絞りに隣接する２つの反射面における中心主光線が反射する位置での面法線と該絞りの面法線との為す角度を夫々γ１、γ２とするとき、
【００８５】
【数８】

【００８６】
ただし、−１８０＜γ１＜１８０、−１８０＜γ２＜１８０
の条件式を満たすことを特徴とする反射型光学系。
【００８７】
［実施態様６］
前記絞りを含む平面外に、該絞りに隣接する反射面が配置されていることを特徴とする実施態様５に記載の反射型光学系。
【００８８】
［実施態様７］
前記絞りは、該絞りの前後の反射面の光軸方向のほぼ中央の位置に配置されていることを特徴とする実施態様５又は６に記載の反射型光学系。
【００８９】
［実施態様８］
前記絞りの開口径は回転非対称であることを特徴とする実施態様５、６又は７に記載の反射型光学系。
【００９０】
［実施態様９］
実施態様１乃至８の何れか１項に記載の反射型光学系と、撮像手段とを有し、該撮像手段の撮像面上に物体の像を結像することを特徴とする撮像装置。
【００９１】
［実施態様１０］
実施態様１乃至８の何れか１項に記載の反射型光学系とラインセンサーとを有し、画像情報を該ラインセンサー上に結像させて、該画像情報を読み取ることを特徴とする画像読取装置。
【００９２】
［実施態様１１］
実施態様１乃至８の何れか１項に記載の反射型光学系を用いて、物体面上のパターンを感光基板上に縮小露光することを特徴とする露光装置。
【００９３】
［実施態様１２］
実施態様１乃至８の何れか１項に記載の反射型光学系を用いて、画像表示パネル上の画像をスクリーンに上に投影することを特徴とする投射型表示装置。
【００９４】
【発明の効果】
本発明によれば前述の如く絞りをその面法線が中心主光線に対して傾くように配置し、さらに条件式（１）または条件式（２）を満たすように各要素を設定することにより、絞りや該絞りを保持する部材が光束を妨げることなく、また反射面と干渉することなく配置することが可能でありながら全体としてコンパクトな反射型光学系を達成することができる。
【図面の簡単な説明】
【図１】本発明の実施形態１のＹＺ面内での要部断面図
【図２】本発明の実施形態１の絞り周辺の拡大説明図
【図３】実施形態１に対して絞りを傾けずに配置した光学系の要部断面図
【図４】本発明の実施形態１の横収差図
【図５】本発明の実施形態２のＹＺ面内での要部断面図
【図６】本発明の実施形態２の絞り周辺の拡大説明図
【図７】実施形態２に対して絞りを傾けずに配置した光学系の要部断面図
【図８】本発明の実施形態２の横収差図
【図９】本発明の画像読取装置の要部概略図
【図１０】本発明の投射型表示装置の要部概略図
【図１１】従来の反射型光学系のＹＺ面内での要部断面図
【図１２】従来の反射型光学系のＹＺ面内での要部断面図
【符号の説明】
Ｒｉ，Ｒｍ，ｎ 面
Ｄｉ 基準軸に沿った面間隔
Ｎｄｉ 屈折率
νｄｉ アッベ数
θ 反射面の法線と基準軸のなす角度
１，２ 反射光学系
Ｃ キャリッジ
ＣＧ 原稿台ガラス
Ｆ フィルタ
Ｉ ラインセンサー
Ｌ 絞りを配置するためのスペース
Ｌａｍｐ 照明光源
Ｍ１，Ｍ２，Ｍ３ 反射ミラー
Ｏ 原稿
Ｓｉ 撮像面
ＳＴＯ 絞り[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reflection type optical system, and is particularly suitable for an apparatus such as a video camera, a still video camera, a copying machine, a projector, and an exposure apparatus in which an image of an object plane is formed on a predetermined plane. .
[0002]
[Prior art]
Conventionally, various reflection optical systems using a plurality of reflection surfaces have been proposed (for example, see Patent Document 1). FIG. 12 is a cross-sectional view of a principal part of the reflection optical system of Document 1 in the YZ plane. In Patent Document 1, trapezoidal distortion caused by oblique projection is corrected by using an eccentrically arranged reflecting surface.
[0003]
Generally, the use of a reflective surface can suppress the occurrence of chromatic aberration, and the use of a reflective optical system for a reading lens used in projectors and copiers where chromatic aberration poses a problem. Can be realized.
[0004]
Such a non-coaxial optical system is an off-axial optical system (when considering a reference axis along a ray passing through the image center and the pupil center, a curved surface whose surface normal at the intersection with the reference axis of the constituent surface is not on the reference axis ( This is an optical system defined as an optical system including an off-axial curved surface, and at this time, the reference axis has a bent shape.)
[0005]
In this off-axial optical system, the constituent surface is generally non-coaxial, and there is no vignetting on the reflecting surface. Therefore, it is easy to construct an optical system using the reflecting surface. Also, a variable power optical system using these optical elements and a design method thereof are disclosed (for example, see Patent Documents 2, 3, 4, and 5).
[Patent Document 1]
JP 2001-255462 A
[Patent Document 2]
JP-A-8-292372
[Patent Document 3]
JP-A-9-222561
[Patent Document 4]
JP-A-9-258105
[Patent Document 5]
JP-A-9-5650
[0006]
[Problems to be solved by the invention]
In the reflection type optical system shown in FIG. 12, a stop SS is arranged between the reflection surface R2 and the reflection surface R3. In this embodiment, the stop SS is arranged so that no light beam is emitted by the stop SS. In order to place the stop SS between the reflecting surfaces, it is necessary to pay attention to the following two points.
[0007]
(1) Do not cut off the light beam by the stop member,
(2) that the diaphragm member and the reflecting surface do not interfere;
However, if the optical system must be compact, or if the distance between the reflecting surfaces cannot be kept high due to the optical performance, the reference axis ray (passing from the object side to the center of the stop from the object side, If the aperture is arranged such that the normal direction of the aperture coincides with one light ray (also referred to as a central chief ray) reaching the center of the final image plane, the aperture may not be arranged properly.
[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a reflection type optical system having a compact configuration that enables a diaphragm to be appropriately arranged while maintaining good optical performance.
[0009]
[Means for Solving the Problems]
The reflective optical system of the present invention
A plurality of reflective surfaces having a curvature, a stop between the plurality of reflective surfaces, in a reflective optical system configured so that the incident light flux is repeatedly reflected and emitted by the plurality of reflective surfaces,
When a light ray passing through the center of the stop and reaching the center of the final image forming plane is set as a central chief ray, the stop is arranged so that its surface normal is inclined with respect to the central chief ray, and the light incidence side , The reflection surface immediately before the stop is SA, the reflection surface immediately after the stop is SB, the angle between the central principal ray incident on the reflection surface SA and the surface normal of the stop is α1, and the reflection is When an angle between the central principal ray emitted from the surface SB and the surface normal of the stop is α2,
[0010]
(Equation 2)

[0011]
However, −180 <α1 <180, −180 <α2 <180
Is satisfied.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiment 1]
Before starting the description of the embodiment, a description will be given of a method of expressing the specifications of the configuration of the embodiment and common matters of the entire embodiment.
[0013]
FIG. 11 is an explanatory diagram of a coordinate system that defines the configuration data of the optical system according to the present invention. In the embodiment of the present invention, one light beam that passes from the object side to the center of the stop and reaches the center of the final imaging plane (a reference axis light beam (also indicated by a dashed line in FIG. 11 and also referred to as a central principal ray)). The i-th surface along is defined as the i-th surface.
[0014]
In FIG. 11, a first surface R1 is a stop, a second surface R2 is a refracting surface coaxial with the first surface, a third surface R3 is a reflecting surface tilted with respect to the second surface R2, a fourth surface R4, a fifth surface R5. The surface R5 is a reflecting surface shifted and tilted with respect to each front surface, and the sixth surface R6 is a refracting surface shifted and tilted with respect to the fifth surface R5. Each surface from the second surface R2 to the sixth surface R6 is formed on one optical element made of a medium such as glass or plastic.
[0015]
Therefore, in the configuration of FIG. 11, the medium from the object surface (not shown) to the second surface R2 is air, the common medium from the second surface R2 to the sixth surface R6, and the seventh surface (not shown) from the sixth surface R6. The medium up to R7 is composed of air.
[0016]
Since the optical system of the present invention is an off-axial optical system, each surface constituting the optical system does not have a common optical axis. Therefore, in the embodiment of the present invention, a surface (reference surface) having a reference origin is introduced between the object surface and the reflection type optical system so that the optical system can be easily described. The arrangement will be described. In the embodiment of the present invention, a path of a light ray (reference axis light ray) passing through the center of the stop and passing through the center of the final image plane is defined as a reference axis of the optical system.
[0017]
Further, the reference axis in the present embodiment has a direction (direction). The direction is the direction in which the reference axis ray travels during imaging. The origin is the position of the reference axis ray on the reference plane, and the normal to the reference plane coincides with the reference axis ray.
[0018]
In the embodiment of the present invention, the reference axis serving as the reference of the optical system is set as described above.However, the method of determining the reference axis of the optical system depends on the optical design, the arrangement of aberrations, or each of the constituents of the optical system. An axis convenient for expressing the surface shape may be used.
[0019]
However, in general, the path of a ray passing through the center of the image plane and either the stop, the entrance pupil or the exit pupil, or the center of the first surface or the center of the last surface of the optical system is referred to as a reference axis serving as a reference of the optical system. Set to.
[0020]
That is, in the embodiment of the present invention, the reference axis passes through the center point of the effective beam diameter of the stop surface, and a light ray (reference axis light ray) reaching the center of the final imaging plane is refracted and reflected by each refraction surface and reflection surface. The path is set to the reference axis. The order of each surface is set in the order in which the reference axis rays are refracted and reflected.
[0021]
Therefore, the reference axis finally reaches the center of the image plane while changing its direction along the set order of each surface according to the law of refraction or reflection.
[0022]
All of the tilt surfaces constituting the optical system of each embodiment of the present invention are basically tilted in the same plane. Therefore, each axis of the absolute coordinate system is determined as follows.
[0023]
Z axis: reference axis that passes through the origin and goes to the first surface R1
Y axis: a straight line passing through the origin and forming 90 ° counterclockwise with respect to the Z axis in the tilt plane (in the paper plane of FIG. 11)
X axis: straight line passing through the origin and perpendicular to each of the Z and Y axes (straight line perpendicular to the plane of FIG. 11)
In order to express the surface shape of the i-th surface constituting the optical system, a local coordinate system having an origin at a point where the reference axis intersects the i-th surface is set rather than expressing the shape of the surface in an absolute coordinate system. Then, it is easier to understand the shape of the surface by expressing the surface shape in the local coordinate system, and in the embodiment of displaying the configuration data of the present invention, the surface shape of the i-th surface is expressed in the local coordinate system. Express.
[0024]
The tilt angle of the i-th surface in the YZ plane is represented by an angle θi (unit: °) with the counterclockwise direction being positive with respect to the Z axis of the absolute coordinate system. Therefore, in the embodiment of the present invention, the origin of the local coordinates of each surface is on the YZ plane in FIG. There is no eccentricity of the plane in the XZ and XY planes. Further, the y, z axes of the local coordinates (x, y, z) of the i-th plane are inclined at an angle θi in the YZ plane with respect to the absolute coordinate system (X, Y, Z). Set to.
[0025]
z-axis: A straight line that passes through the origin of local coordinates and makes an angle θi in the YZ plane counterclockwise with respect to the Z direction of the absolute coordinate system.
y-axis: A straight line passing through the origin of local coordinates and making 90 ° counterclockwise in the YZ plane with respect to the z direction
x-axis: straight line passing through the origin of local coordinates and perpendicular to the YZ plane
Di is a scalar quantity representing the distance between the origins of the local coordinates of the i-th surface and the (i + 1) -th surface, and Ndi and νdi are the refractive index and Abbe number of the medium between the i-th surface and the (i + 1) -th surface, respectively. is there. In the embodiments of the present invention, a cross-sectional view of an optical system and numerical data are shown.
[0026]
The spherical surface has a shape represented by the following equation.
[0027]
[Equation 3]

[0028]
Further, the optical system of the present invention has at least one or more rotationally asymmetric aspheric surfaces, and the shape is represented by the following equation.
[0029]
(Equation 4)

[0030]
Since the above-mentioned curved surface expression has only even-order terms with respect to x, the curved surface defined by the above-mentioned curved surface expression has a plane-symmetric shape with the yz plane as a symmetric surface.
[0031]
further,
C02 = C20 C04 = C40 = C22 / 2 C06 = C60 = C24 / 3 = C42 / 3
Is satisfied, a rotationally symmetric shape is represented. If the above conditions are not satisfied, the shape is non-rotationally symmetric.
[0032]
In each embodiment of the present invention, the vertical half angle of view uY is the maximum angle of view of the light beam incident on the reference plane R1 in the YZ plane in FIG. 11, and the horizontal half angle of view uX is the same as the reference plane R1 in the XZ plane. This is the maximum angle of view of the incident light beam. The diameter of the stop is shown as the stop diameter. This is related to the brightness of the optical system.
[0033]
In addition, lateral aberration diagrams of each embodiment are shown. The horizontal angle of incidence and the vertical angle of incidence on the reference plane R1 are (0, uY), (0, 0), (0, -uY), (uX, uY), (uX, 0), (uX, -uY), respectively. 4) shows the lateral aberration of the light beam at the incident angle. In the lateral aberration diagram, the horizontal axis represents the height of incidence on the pupil, and the vertical axis represents the amount of aberration. In each embodiment, since each surface is basically a plane-symmetrical shape with the yz plane as the plane of symmetry, the plus and minus directions of the vertical angle of view are the same even in the lateral aberration diagram. For this reason, a lateral aberration diagram in the minus direction is omitted.
[0034]
[Embodiment 1]
FIG. 1 is a cross-sectional view of a main part of a reflection type optical system (reflection type optical element) according to a first embodiment of the present invention in the YZ plane, and FIG. 2 is an enlarged cross-sectional view around the stop shown in FIG.
[0035]
In FIG. 1, the reflective optical system 1 is composed of five reflective surfaces R1, R2, R3, R4, stop STO, and R5 in the order of passage of light rays from an object (not shown). And has a function of forming an image on the object on the imaging surface S1.
[0036]
This embodiment is a reflective optical element used for an imaging device (imaging optical system) having a horizontal angle of view of 29.08 degrees and a vertical angle of view of 38.19 degrees.
[0037]
The configuration data of the present embodiment is as follows.
[0038]
[Table 1]

[0039]
[Table 2]

[0040]
[Table 3]

[0041]
The reflection type optical system of the present embodiment is an optical system including a plurality of curved reflecting surfaces as shown in FIG. In the figure, a light beam from an object (not shown) is reflected one after another by a concave mirror R1, a convex mirror R2, a concave mirror R3, and a convex reflection surface R4, the light beam is regulated by a stop STO, reflected by a concave reflection surface R5, and a low-pass filter. Passes through a filter F constituted by an infrared cut filter, and forms an image on an imaging surface S1 as an imaging means.
[0042]
Here, R0 is a reference plane. When a light beam passing through the center of the stop STO and reaching the center of the final imaging plane is defined as a reference axis light beam (center principal ray), the stop STO is arranged with its surface normal inclined with respect to the reference axis light beam. Have been. The aperture diameter of the stop STO is rotationally asymmetric.
[0043]
As described above, since the surface normal of the stop STO is arranged to be inclined with respect to the reference axis ray, it can be arranged without cutting other rays. The aperture STO has a finite size and must be held, so that a certain space is required. In FIGS. 1, 2, and 3, L is a space required for disposing the stop STO. In this embodiment, about 5 mm is set in a plane including the stop STO.
[0044]
FIG. 3 is a sectional view of a main part of a conventional reflection type optical system designed so that the stop STO can be arranged by increasing the off-axial angle between the reflection surfaces R4 and R5. The specifications in FIG. 3 are the same as those in FIG. As can be seen from FIG. 3, it can be seen that the optical system is enlarged in order to secure a space for disposing the stop STO. Further, since the off-axial angle is set larger than that in FIG. 1, it is not good for aberration correction.
[0045]
In the case of the present embodiment, the stop and the holding member of the stop must be arranged so as not to block the light beam. Here, the luminous fluxes that are problematic are the luminous flux incident on the reflection surface immediately before the stop and the luminous flux emitted from the reflection surface immediately after the stop.
[0046]
1 and 2, the angle of the light beam incident on the reflecting surface R4 immediately before the stop STO is close to the angle of the reference axis ray from the reflecting surface R3 toward the reflecting surface R4, and is reflected from the reflecting surface R5 immediately after the stop STO. The angle of the light beam is close to the angle of the reference axis light beam emitted from the reflection surface R5. Therefore, the angle α1 of the reference axis ray from the reflecting surface R3 toward the reflecting surface R4 and the angle α2 of the reference axis ray emitted from the reflecting surface R5 may be set so that the angle of the normal to the stop surface becomes an appropriate angle. . To put it simply, the aperture plane may be arranged at an intermediate angle between the angles α1 and α2. However, in practice, there is a slight shift due to the difference in the aperture position and the angle between the reference axis and the light beam.
[0047]
Therefore, in the present embodiment, the reflecting surface immediately before the stop STO is R4 and the reflecting surface immediately after the stop STO is R5 when viewed from the light incident side, and the reference axis ray incident on the reflecting surface R4 and the surface method of the stop STO are used. When the angle between the line and the line is α1, and the angle between the reference axis ray emitted from the reflecting surface R5 and the surface normal of the stop STO is α2,
[0048]
(Equation 5)

[0049]
However, −180 <α1 <180, −180 <α2 <180
Are set so as to satisfy the conditional expression (1). As a result, a compact reflective optical system can be obtained as a whole while the stop STO and the member holding the stop STO can be arranged without obstructing the light beam and without interfering with the reflecting surface. Considering the direction of the surface normal of the stop STO and the direction of the reference axis ray, the counterclockwise direction from the surface normal of the stop STO is defined as positive.
[0050]
In the present embodiment, when the angles α1 and α2 are calculated,
α1 = −84, α2 = −104
Therefore
| Α1 + α2 | / 2 = 94
Which satisfies the conditional expression (1). Incidentally, in the conventional reflection type optical system shown in FIG.
α1 = −100, α2 = −120
Therefore
| Α1 + α2 | / 2 = 110
And does not satisfy the conditional expression (1).
[0051]
FIG. 4 shows a lateral aberration diagram of the reflection type optical system of the present embodiment. As shown in the figure, even if the stop STO is arranged obliquely, the lateral aberration is very small, and the aberration can be corrected in a well-balanced manner both at the center of the screen and at the angle of the screen. Desirably, a reflection surface adjacent to the stop STO is not arranged in a plane including the stop STO. That is, the reflection surface adjacent to the stop STO is arranged outside the plane including the stop STO. Furthermore, it is easier to dispose the luminous flux if it is arranged at a substantially central position in the optical axis direction of the reflection surface before and after the stop.
[0052]
In the present embodiment, only the surface reflection surface is used, but a refraction lens may be included. Further, it may be configured to include not only the front reflecting surface but also the back reflecting surface. Although five reflecting surfaces are used, the number of reflecting surfaces is not limited to five. Further, the reflection surface has a shape symmetrical with respect to a certain plane, but is not limited to this. Although the single reflective optical element functions as an image pickup element, the image pickup optical system may include at least one reflective optical element and a plurality of optical elements. Also, as in Patent Documents 2 to 4 described above, a variable power optical system can be configured by changing the relative positions of a plurality of optical elements. In this embodiment, the reflection type optical element is used for the imaging optical system (imaging device). However, the present invention is not limited to this optical system. For example, a reading optical system (image reading device), a pattern on an object surface is reduced on a photosensitive substrate. It may be used for an exposure optical system (exposure device) for exposure and a projection optical system (projection display device) such as a projector.
[0053]
[Embodiment 2]
FIG. 5 is a cross-sectional view of a principal part of the reflective optical system (reflective optical element) according to the second embodiment of the present invention in the YZ plane. FIG. 6 is an enlarged cross-sectional view around the stop shown in FIG. 5 and 6, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.
[0054]
In FIG. 5, the reflection type optical system 2 includes four reflection surfaces R1, R2, aperture STO, reflection surface R3, and reflection surface R4 in the order of passage of light rays from the document surface O. Is formed on the line sensor I.
[0055]
Also in this embodiment, when a light beam passing through the center of the stop STO and reaching the center of the final imaging plane is set as a reference axis light ray (central chief ray) as in the first embodiment, the stop STO is placed on that surface. The normal is inclined with respect to the reference axis ray. The aperture diameter of the stop STO is rotationally asymmetric.
[0056]
In the present embodiment, the length of the line sensor I in the longitudinal direction is 66.08 mm, and the reading width is 304.8 mm in the main scanning direction and ± 1 mm in the sub scanning direction. 2 shows configuration data of a reflective optical system 2 used in the present embodiment.
[0057]
[Table 4]

[0058]
[Table 5]

[0059]
[Table 6]

[0060]
The reflection type optical system 2 of the present embodiment is an optical system including a plurality of curved reflecting surfaces as shown in FIG. In the figure, the light beam from the document surface O is reflected one after another by the concave mirror R1 and the concave mirror R2, the light beam is regulated by the stop STO, is reflected one after another by the concave reflection surface R3 and the concave reflection surface R4, and forms on the line sensor I. Image.
[0061]
Here, the light path from the document surface O to the reflection surface R1 and the light path from the reflection surface R2 to the stop STO intersect, and the light path from the stop STO to the reflection surface R3 intersects with the light path from the reflection surface R4 to the line sensor I. ing. Here, R0 is a reference plane. Each of the reflecting surfaces R1 to R4 has a margin of 1 mm for the optical effect and has a thickness of 5 mm. The surface normal of the stop STO is inclined with respect to the reference axis ray as shown in FIG. With this arrangement, it can be arranged without interfering with the reflecting surface having a thickness of 5 mm.
[0062]
The aperture STO has a finite size and must be held, so that a certain space is required. L in FIGS. 5, 6, and 7 is a space necessary for disposing the stop STO. In this example, about 5 mm is set in a plane including the stop STO.
[0063]
FIG. 7 shows a conventional reflection type optical system designed so that the stop can be arranged so that the stop and the reflection surface do not interfere by increasing the distance between the reflection surface R2 and the stop STO and the distance between the stop STO and the reflection surface R3. It is principal part sectional drawing. The specifications in FIG. 7 are the same as those in FIG. As can be seen from FIG. 7, it can be seen that the optical system is enlarged in order to secure a space for disposing the stop STO.
[0064]
Further, the optical path length from the stop STO to the reflecting surface R1 and the optical path length from the stop STO to the reflecting surface R4 are both longer than those of the reflective optical system of FIG. 5, so that the effective diameters of the reflecting surface R1 and the reflecting surface R4 are both smaller. It gets bigger. In the case of this embodiment, the stop STO and the holding member of the stop STO must be arranged so as not to interfere with the reflection surface.
[0065]
Here, the reflecting surfaces which are problematic are the reflecting surface R1 and the reflecting surface R4 adjacent to the stop STO, and the thickness direction of the reflecting surface becomes a problem. This direction generally coincides with the surface normal. For this reason, it is sufficient to arrange the normal angle of the stop surface to an appropriate angle from the angle γ1 of the surface normal of the reflecting surface R1 and the angle γ2 of the surface normal of the reflecting surface R4. To put it simply, it is sufficient that the stop plane is arranged at an angle between the angles γ1 and γ2. However, actually, there is a slight shift due to the stop position, the position of the adjacent reflection surface, and the like.
[0066]
Therefore, in the present embodiment, as shown in FIG. 6, the angle between the surface normal at the position where the reference axis ray is reflected on the two reflecting surfaces R1 and R4 adjacent to the stop STO and the surface normal of the stop STO are respectively set. When γ1 and γ2 are used,
[0067]
(Equation 6)

[0068]
However, −180 <γ1 <180, −180 <γ2 <180
Are set so as to satisfy the conditional expression (2). As a result, a compact reflective optical system can be obtained as a whole while the stop STO and the member holding the stop STO can be arranged without obstructing the light beam and without interfering with the reflecting surface. In consideration of the direction of the surface normal of the stop and the reflection surface, the counterclockwise direction from the surface normal of the stop is defined as positive.
[0069]
In the present embodiment, when the angles γ1 and γ2 are calculated,
γ1 = 83.98, γ2 = 81.21
Therefore
| Γ1 + γ2 | /2=82.595
Which satisfies the conditional expression (2). Incidentally, in the conventional reflection type optical system shown in FIG.
γ1 = 64.22, γ2 = 61.45
Therefore
| Γ1 + γ2 | /2=62.835
And does not satisfy the conditional expression (2).
[0070]
FIG. 8 shows a lateral aberration diagram of the reflection type optical system of the present embodiment. As shown in the figure, even if the stop STO is arranged obliquely, the lateral aberration is very small, and the aberration can be corrected in a well-balanced manner both at the center of the screen and at the angle of the screen. Desirably, a reflection surface adjacent to the stop STO is not arranged in a plane including the stop STO. That is, the reflection surface adjacent to the stop STO is arranged outside the plane including the stop STO. Furthermore, it is easier to dispose a light beam if it is disposed at a substantially central position in the optical axis direction of the reflection surface before and after the stop STO.
[0071]
In the present embodiment, only the surface reflection surface is used, but a refraction lens may be included. Further, it may be configured to include not only the front reflecting surface but also the back reflecting surface. Although four reflecting surfaces are used, the number of reflecting surfaces is not limited to four. Further, the reflection surface has a shape symmetrical with respect to a certain plane, but is not limited to this. Although the single reflective optical element functions as an image pickup element, the image pickup optical system may include at least one reflective optical element and a plurality of optical elements. Also, as in Patent Documents 2 to 4 described above, a variable power optical system can be configured by changing the relative positions of a plurality of optical elements. Further, in this embodiment, the reflection type optical element is used for the imaging optical system. However, the present invention is not limited to this optical system, and may be used for a reading optical system, an exposure optical system, and a projection optical system such as a projector, which will be described later.
[0072]
[Image reading device]
FIG. 9 illustrates an example of an image reading apparatus configured to read a color image or a monochrome image using the reflective optical system 2 according to the second exemplary embodiment.
[0073]
In the figure, Lamp is a light source, CG is a platen glass, M1 to M3 are first to third reflection mirrors, 2 is a reflective optical system, I is a line sensor composed of a CCD or the like, and C is a carriage (housing). is there. The original O placed on the original platen glass CG is imaged on the line sensor I by the reflection type optical system 2 via the first to third reflection mirrors M1 to M3 to read one line image of the original O. be able to. In order to make the image reading device compact, the optical path is folded by the first to third reflecting mirrors M1 to M3. Since the reflection type optical system 2 is constituted by a surface reflection surface, chromatic aberration does not occur, and the angle can be increased. Therefore, the distance from the optical system to the document is reduced, and the document reading device of the optical system integrated with the carriage can be constituted by a small number of optical components including three plane mirrors and a reflection type optical system. This carriage-integrated optical system two-dimensionally scans the surface of the original O by scanning the original O and the carriage C relatively in a direction perpendicular to the line direction (X direction) of the line sensor, that is, in the sub-scanning direction. Reading.
[0074]
[Projection display device]
FIG. 10 shows an example in which a projection display apparatus that projects an image on an image display panel onto a screen using the reflective optical system 1 of the first embodiment.
[0075]
In FIG. 10, LL denotes an illumination system for illuminating a light valve (image display panel) LV1 with light. Reference numeral 1 denotes a reflective optical system having a configuration according to the first embodiment using an off-axial system for projecting light modulated by a light valve (image display panel) LV1 onto a screen S. In the figure, an image on an image display panel is projected onto a screen S using the reflection type optical system 1 of the first embodiment.
[0076]
[Embodiments of the present invention]
While various examples and embodiments of the present invention have been shown and described, those skilled in the art will recognize that the spirit and scope of the present invention is not limited to the specific description and figures herein, but rather to It will be appreciated that various modifications and changes are set forth which are all set forth in the following claims.
[0077]
Examples of embodiments of the present invention are listed below.
[0078]
[Embodiment 1]
A plurality of reflective surfaces having a curvature, a stop between the plurality of reflective surfaces, in a reflective optical system configured so that the incident light flux is repeatedly reflected and emitted by the plurality of reflective surfaces,
When a light ray passing through the center of the stop and reaching the center of the final image forming plane is set as a central chief ray, the stop is arranged so that its surface normal is inclined with respect to the central chief ray, and the light incidence side , The reflection surface immediately before the stop is SA, the reflection surface immediately after the stop is SB, the angle between the central principal ray incident on the reflection surface SA and the surface normal of the stop is α1, and the reflection is When an angle between the central principal ray emitted from the surface SB and the surface normal of the stop is α2,
[0079]
(Equation 7)

[0080]
However, −180 <α1 <180, −180 <α2 <180
A reflective optical system that satisfies the following conditional expression:
[0081]
[Embodiment 2]
2. The reflection type optical system according to claim 1, wherein a reflection surface adjacent to the stop is arranged outside a plane including the stop.
[0082]
[Embodiment 3]
3. The reflection type optical system according to claim 1, wherein the stop is disposed at a substantially central position in the optical axis direction of a reflection surface before and after the stop.
[0083]
[Embodiment 4]
4. The reflective optical system according to claim 1, wherein the aperture diameter of the stop is rotationally asymmetric.
[0084]
[Embodiment 5]
A plurality of reflective surfaces having a curvature, a stop between the plurality of reflective surfaces, in a reflective optical system configured so that the incident light flux is repeatedly reflected and emitted by the plurality of reflective surfaces,
When a ray passing through the center of the stop and reaching the center of the final image forming plane is set as a central principal ray, the stop is arranged so that its surface normal is inclined with respect to the central principal ray. When the angles formed by the surface normal and the surface normal of the stop at the position where the central principal ray is reflected on two adjacent reflecting surfaces are γ1 and γ2, respectively,
[0085]
(Equation 8)

[0086]
However, −180 <γ1 <180, −180 <γ2 <180
A reflective optical system that satisfies the following conditional expression:
[0087]
[Embodiment 6]
The reflection type optical system according to embodiment 5, wherein a reflection surface adjacent to the stop is arranged outside a plane including the stop.
[0088]
[Embodiment 7]
7. The reflection type optical system according to claim 5, wherein the stop is arranged at a substantially central position in the optical axis direction of a reflection surface before and after the stop.
[0089]
[Embodiment 8]
8. The reflective optical system according to claim 5, wherein the aperture diameter of the stop is rotationally asymmetric.
[0090]
[Embodiment 9]
An imaging apparatus comprising: the reflection type optical system according to any one of Embodiments 1 to 8; and an imaging unit, and forms an image of an object on an imaging surface of the imaging unit.
[0091]
[Embodiment 10]
An image reading apparatus comprising: the reflective optical system according to any one of Embodiments 1 to 8; and a line sensor, wherein the image information is read by forming an image on the line sensor. apparatus.
[0092]
[Embodiment 11]
An exposure apparatus, wherein a pattern on an object surface is reduced-exposed on a photosensitive substrate using the reflective optical system according to any one of Embodiments 1 to 8.
[0093]
[Embodiment 12]
A projection type display device, wherein an image on an image display panel is projected onto a screen using the reflection type optical system according to any one of the first to eighth embodiments.
[0094]
【The invention's effect】
According to the present invention, as described above, the stop is arranged so that its surface normal is inclined with respect to the central principal ray, and each element is set so as to satisfy conditional expression (1) or conditional expression (2). In addition, a reflective optical system that is compact as a whole can be achieved while the stop and the member holding the stop can be arranged without obstructing the light beam and without interfering with the reflecting surface.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part in a YZ plane according to a first embodiment of the present invention.
FIG. 2 is an enlarged explanatory view around a stop according to the first embodiment of the present invention;
FIG. 3 is a sectional view of a main part of an optical system in which the stop is arranged without tilting with respect to the first embodiment;
FIG. 4 is a lateral aberration diagram according to the first embodiment of the present invention.
FIG. 5 is a cross-sectional view of a main part in a YZ plane according to a second embodiment of the present invention.
FIG. 6 is an enlarged explanatory diagram around a stop according to the second embodiment of the present invention;
FIG. 7 is a sectional view of a main part of an optical system in which the stop is arranged without tilting with respect to the second embodiment.
FIG. 8 is a lateral aberration diagram according to the second embodiment of the present invention.
FIG. 9 is a schematic diagram of a main part of the image reading apparatus of the present invention.
FIG. 10 is a schematic diagram of a main part of a projection display device of the present invention.
FIG. 11 is a sectional view of a principal part of a conventional reflection type optical system in the YZ plane.
FIG. 12 is a sectional view of a main part of a conventional reflection type optical system in a YZ plane.
[Explanation of symbols]
Ri, Rm, n-plane
Di Surface spacing along the reference axis
Ndi refractive index
νdi Abbe number
θ Angle between the normal of the reflecting surface and the reference axis
1,2 reflective optical system
C carriage
CG platen glass
F filter
I line sensor
L Space for arranging the aperture
Lamp Illumination light source
M1, M2, M3 Reflection mirror
O manuscript
Si imaging surface
STO aperture

Claims (1)

A plurality of reflective surfaces having a curvature, a stop between the plurality of reflective surfaces, in a reflective optical system configured so that the incident light flux is repeatedly reflected and emitted by the plurality of reflective surfaces,
When a light ray passing through the center of the stop and reaching the center of the final image forming plane is set as a central chief ray, the stop is arranged so that its surface normal is inclined with respect to the central chief ray, and the light incidence side , The reflection surface immediately before the stop is SA, the reflection surface immediately after the stop is SB, the angle between the central principal ray incident on the reflection surface SA and the surface normal of the stop is α1, and the reflection is When an angle between the central principal ray emitted from the surface SB and the surface normal of the stop is α2,

However, −180 <α1 <180, −180 <α2 <180
A reflective optical system that satisfies the following conditional expression:

Images