JP4086524B2

JP4086524B2 - Illumination system and image reading apparatus having the same

Info

Publication number: JP4086524B2
Application number: JP2002094445A
Authority: JP
Inventors: 貴士須藤
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2002-03-29
Filing date: 2002-03-29
Publication date: 2008-05-14
Anticipated expiration: 2022-03-29
Also published as: JP2003295061A

Description

【０００１】
【発明の属する技術分野】
本発明は照明系及びそれを有する画像読取装置に関し、特に書画カメラなどの上向き原稿の画像を読み取る装置に適用される場合に好適なものである。
【０００２】
【従来の技術】
従来、画像読取装置においては、装置全体を小型化し、均一照明を行なうために様々な照明系が提案されている。特に上向き原稿の画像を読み取る画像読取装置に用いられる照明系の場合、原稿面で反射した画像光が撮影光学系（撮影手段）に至るまでに照明装置によりけられないこと、また光源（発光部）から発せられ原稿面で正反射した光が直接撮影光学系に入射して該撮影光学系に光源像が写りこまない等の条件が必要である。それらの条件を満足した照明系としては、例えば特開平１１−２９５６０３号公報がある。
【０００３】
図１６（Ａ），（Ｂ）は各々同公報で提案されている照明系の要部概略図である。同公報においては図１６（Ａ），（Ｂ）に示すように照明系を長尺状の光源（発光部）１８と母線が光源１８と平行なシリンダ形状の反射鏡１９で構成しており、該反射鏡１９を第１、第２、第３の３つの領域１９ａ，１９ｂ，１９ｃに分けている。そして第１の領域１９ａは反射面を楕円形状に高次の非球面の項を加えた形状とし、光源１８から射出される光を１回反射させて被照明面２０に導き、また第２の領域１９ｂは反射面を円形とし、光源１８から射出される光を光源１８側に向けて反射させ、該反射光を第１の領域１９ａで反射させて被照明面２０に導き、また第３の領域１９ｃは光源１８から射出された光が直接被照明面２０を照明しないように光を遮ることで被照明面２０を比較的均一に斜め方向から照明している。
【０００４】
この従来例においては、１つの光源を用いているが、照明系の小型化のため光源１８として冷陰極管のような外径の小さい光源を用いた場合、明るさが十分ではないという問題点がある。また光源として大光量の熱陰極管を使用する場合には、光源の外径が大きいためそれに比例して反射鏡も大型化し、照明系全体を小型化するにはかなり難しいという問題点もある。
【０００５】
更にこの従来例においては、反射鏡１９の第１の領域１９ａによって該反射鏡１９の近くに一度集光させた後、被照明面を照明しているため、該被照明面の該光源１８から遠い領域が近い領域よりも暗くなるという問題点がある。また反射鏡１９の第２の領域１９ｂにより光源１８から射出される光を該光源１８により集光させているが、該光源１８が有限の大きさを持っているので、例えば光源１８の表面に光が入射した場合、該表面により拡散、吸収されてしまうので透過して第１の領域１９ａに入射する成分がかなり小さくなり、そのため第２の領域１９ｂにより反射される光は効率的には利用できない。
【０００６】
したがって、この従来例では明るさが十分でなく、また被照明面の光源から遠い領域が近い領域よりも暗くなって照度ムラが若干大きいという問題点があった。
【０００７】
【発明が解決しようとする課題】
本発明は比較的簡単な構成でありながら、原稿面をほぼ均一な明るさで効率的に照明することができる照明系及びそれを有する画像読取装置の提供を目的とする。
【０００８】
【課題を解決するための手段】
請求項１の発明の照明系は、
発光部が長尺状の光源と、該光源から射出される光を斜め方向から被照明面に向けて反射する長尺状の反射部材を含む照明光学系を１組以上有する照明系であって、
該反射部材は、母線が該発光部と平行なシリンダ形状、母線と直交する面が楕円形状で、反射面が該被照明面側に向いた第１の反射鏡と、反射面が該被照明面と反対側に向いた第２の反射鏡を有し、
該第１、第２の反射鏡の光の反射率は８０％であり、
該第１、第２の反射鏡は、該母線と直交する面内において、該楕円の２つの焦点のうち該被照明面の中心位置から遠い側の焦点を第１焦点、近い側の焦点を第２焦点とするとき、該第１、第２の反射鏡のそれぞれの第１焦点は近傍に位置しており、
該第１、第２の反射鏡は、それぞれの楕円の長軸が略同一直線上に位置し、該第１、第２の反射鏡の反射面は前記長軸を挟んで互いに向かい合うように位置しており、
該発光部は、該第１、第２の反射鏡の第１焦点の近傍に位置し、
該第１の反射鏡の第２焦点は、該発光部の位置と該被照明面の該発光部から最も遠い位置との中間位置よりも該被照明面側にあり、
該第２の反射鏡は、長軸が該第１の反射鏡の長軸よりも短いことを特徴としている。
【０００９】
請求項２の発明の照明系は、
発光部が長尺状の光源と、該光源から射出される光を斜め方向から被照明面に向けて反射する長尺状の反射部材を含む照明光学系を１組以上有する照明系であって、
該反射部材は、母線が該発光部と平行なシリンダ形状、母線と直交する面内で放物線状で、反射面が該被照明面側に向いた第１の反射鏡と、母線と直交する面内で楕円形状で反射面が該被照明面と反対側に向いた第２の反射鏡を有し、
該第１、第２の反射鏡の光の反射率は８０％であり、
該第１の反射鏡の放物線の軸と、該第２の反射鏡の楕円の長軸が略同一直線上に位置し、該第１の反射鏡と該第２の反射鏡の反射面は該長軸を挟んで互いに向かい合うように位置しており、該第２の反射鏡の２つの焦点のうち該被照明面から遠い側の焦点を第１焦点、近い側の焦点を第２焦点としたとき、該第１の反射鏡の焦点は該第１焦点の近傍に位置し、該発光部は該第１焦点の近傍に位置していることを特徴としている。
【００１０】
請求項３の発明は請求項１又は２の発明において、
前記発光部の長尺方向は前記被照明面と平行な面内に配置されていることを特徴としている。
【００１１】
請求項４の発明は請求項１又は３の発明において、前記母線と直交する面内において、前記第１、第２の反射鏡の長軸は、前記発光部と前記被照明面の該発光部から最も遠い位置を結ぶ直線上にあることを特徴としている。
【００１２】
請求項５の発明は請求項１、３又は４の何れか１項の発明において、前記照明光学系を少なくとも２組有し、前記母線と直交する面内において、該１組の照明光学系に含まれる第１又は第２の反射鏡の長軸が、該照明光学系と隣り合う照明光学系に含まれる第１又は第２の反射鏡の長軸に対して成す角度θが、
０°≦θ≦１０°
を満足することを特徴としている。
【００１３】
請求項６の発明は請求項１乃至５の何れか１項の発明において、
前記母線と直交する面内において、前記発光部から射出された光のうち、前記第１の反射鏡に入射する光は反射面により反射されて前記被照明面の該発光部から遠い領域に導かれ、前記第２の反射鏡に入射する光は反射面により反射されて該第２の反射鏡の第２焦点に集光したあと、該第１の反射鏡により該被照明面の広範囲の領域に導かれ、該第１、第２の反射鏡に入射しない光は直接該被照明面に入射することを特徴としている。
【００１４】
請求項７の発明は請求項５の発明において、
前記少なくとも２組の照明光学系の間には、遮光部材が配置されていることを特徴としている。
【００１５】
請求項８の発明は請求項１乃至７の何れか１項の発明において、
前記光源は、長尺状の冷陰極管、又は熱陰極管、又はＸｅランプ、又は水銀ランプ、又はメタルハライドランプであることを特徴としている。
【００１６】
請求項９の発明の画像読取装置は
請求項１乃至８の何れか１項に記載の照明系と、該照明系からの光により照明された被照明領域の画像を取り込む撮像装置を有することを特徴としている。
【００１７】
【発明の実施の形態】
［実施形態１］
図１は本発明の実施形態１の３灯式照明系を画像読取装置に用いたときの要部概略図である。
【００１８】
同図において１は照明系であり、第１、第２、第３の３組の照明光学系１ａ，１ｂ，１ｃを有している。第１、第２、第３の照明光学系１ａ，１ｂ，１ｃは各々発光部が長尺状の光源２，５，８と、該光源２，５，８から射出される光を斜め方向から被照明面１３に向けて反射する長尺状の第１、第２、第３の３組の反射部材１ａ１，１ｂ１，１ｃ１を有している。第１、第２、第３の反射部材１ａ１，１ｂ１，１ｃ１は、各々母線が発光部と平行なシリンダ形状、母線と直交する面（紙面）が楕円形状で、反射面が被照明面１３側に向いた第１の反射鏡３，６，９と、反射面が被照明面１３と反対側に向いた第２の反射鏡４，７，１０を有している。
【００１９】
尚、第１、第２の反射鏡３，４，６，７，９，１０は、上記の如く反射鏡の母線と垂直な面（紙面）において楕円形状をしており、以下第１、第２の反射鏡３，４，６，７，９，１０を各々第１、第２の楕円鏡３，４，６，７，９，１０と称する。
【００２０】
１１，１２は各々遮光部材であり、第１、第２の反射部材１ａ１，１ｂ１の第２の楕円鏡４、７の反射面の裏側の面に配置されており、第２、第３の照明光学系１ｂ，１ｃの光源（発光部）５，８から射出される光のうち、第２の楕円鏡４、７の裏側の面で反射し、被照明面１３に至る光線をカットして、迷光の発生を防いでいる。１３は被照明面としての原稿面であり、該原稿面１３は図１上の辺が長辺に対応し、紙面に垂直な方向が短辺方向に対応している。１４は平面ミラーであり、原稿面１３で反射された光を撮影光学系１５に向けて反射させている。１５は撮影光学系（撮像装置）であり、照明系１からの光により照明された被照明領域の画像を取り込んでいる。
【００２１】
２１は照明系１から射出される光の原稿面１３による正反射成分が撮影光学系１５に入り、光源像が該撮影光学系１５に写りこむ光源位置の境界線である。同図において境界線２１より原稿面１３側に光源が存在する場合は、撮影光学系１５に光源の像が写りこんでしまい、また境界線２１の原稿面１３から遠い側に光源が存在する場合は光源の像は写りこまない。本実施形態では撮影光学系１５に光源の像が写りこまないよう図１に示すように写りこみ領域から脇にずれた位置に照明系１を配置している。
【００２２】
図２は照明系を構成する３組の照明光学系のうち、１組の照明光学系の要部概略図である。尚、各照明光学系１ａ，１ｂ，１ｃを構成する各々の反射部材１ａ１，１ｂ１，１ｃ１は同じ形状であるので、以下では第１の照明光学系１ａの構成について説明する。図２において図１に示した要素と同一要素には同符番を付している。
【００２３】
同図において第１、第２の楕円鏡３，４は、母線と直交する面内において、楕円の２つの焦点のうち原稿面１３の中心位置１３ｂから遠い側の焦点を第１焦点３ａ，４ａ、近い側の焦点を第２焦点３ｂ，４ｂとするとき、該第１、第２の楕円鏡３，４のそれぞれの第１焦点３ａ，４ａは互いに接近している。
【００２４】
また第１、第２の楕円鏡３，４は、それぞれの長軸３ｃ，４ｃが略同一直線Ｌａ上に位置し、該第１、第２の楕円鏡３，４の反射面３ｄ，４ｄは前記長軸３ｃ，４ｃを挟んで互いに向かい合うように位置している。また発光部２ａは、第１、第２の楕円鏡３，４の第１焦点３ａ，４ａの近傍に位置しており、該発光部２ａの長尺方向は原稿面１３と平行な面内に配置されている。また第１の楕円鏡３の第２焦点３ｂは発光部２ａの位置と原稿面１３の発光部２ａから最も遠い位置１３ａとの中間位置３ｅよりも該原稿面１３側にあり、該第２の楕円鏡４は、長軸４ｃが該第１の楕円鏡３の長軸３ｃよりも短い。
【００２５】
また母線と直交する面内において、第１、第２の楕円鏡３，４の長軸３ｃ，４ｃは発光部２ａと原稿面１３の発光部２ａから最も遠い位置１３ａを結ぶ直線上に位置している。
【００２６】
また第１の楕円鏡３はその第２焦点３ｂが原稿面１３上に近い位置となるように長軸３ｃを大きくした楕円鏡の一部とし、第２の楕円鏡４は第１の楕円鏡３より短い長軸４ｃの楕円鏡とし、該楕円鏡を長軸について半分にした半楕円鏡の発光部２ａから遠い一部の領域を図２に示すように、第１焦点４ａを中心とし、該楕円鏡の長軸４ｃからの成す角度αだけ広げている。
【００２７】
ここで第２の楕円鏡４の間口をなくした場合、すなわち角度αが０のとき、原稿面１３上の発光部２ａに近い領域が暗くなって、原稿面１３上の照度分布を改善することができない。また角度αが大きすぎると原稿面１３の発光部２ａに近い領域が明るくなりすぎて、照度分布を改善することができない。そこで本実施形態ではこの角度αを下記の条件式
１０°≦α≦３０° ‥‥‥（Ａ）
を満たすように設定している。
【００２８】
図３は本発明の実施形態１における照明系の光学作用を説明する説明図であり、光源２、５，８から射出される光を原稿面１３に導く第１、第２の楕円鏡３、４，６，７，９，１０の効果について説明している。図３において図１に示した要素と同一要素には同符番を付している。
【００２９】
同図における第１の照明光学系１ａでは、第１、第２の楕円鏡３，４の第１焦点に配置された光源２（発光部２ａ）から射出される光のうち、一部の光が第１の楕円鏡３の反射面３ｄでの１回反射の後、原稿面１３の光源２から遠い領域に集光され、また一部の光が第２の楕円鏡４の反射面４ｄで反射され第２焦点４ｂに集光した後、第１の楕円鏡３の反射面３ｄで反射されて原稿面１３上の広範囲の領域を斜め方向から照明し、それ以外の光が第１、第２の楕円鏡３，４で反射せず、直接原稿面１３に至り該原稿面１３を斜め方向から照明している。
【００３０】
図４は本発明の実施形態１における楕円鏡の光学作用を説明する説明図であり、光源２から射出される光が第１、第２の楕円鏡３，４で反射される作用を説明している。図４において図２に示した要素と同一要素には同符番を付している。
【００３１】
同図において第１の楕円鏡３は上記の如く反射面３ｄが原稿面（不図示）側に向いており、第２の楕円鏡４は反射面４ｄが原稿面と反対側に向いている。同図において光源２（発光部２ａ）から図面上、上側に射出される光は第１の楕円鏡３の反射面３ｄによって１回反射されて原稿面の光源２から遠い領域に向けて導かれ、図面上、下側に射出される光は第２の楕円鏡４の反射面４ｄによって反射されて該第２の楕円鏡４の第２焦点４ｂ（１６）に集光された後、第１の楕円鏡３の反射面３ｄによって原稿面に向けてほぼ均等な角度で反射される。
【００３２】
図５は本発明の実施形態１における楕円鏡による１回反射光の光路図であり、第１の楕円鏡３の光学作用を説明している。図５において図２に示した要素と同一要素には同符番を付している。
【００３３】
同図において第１の楕円鏡３の長軸は光源２（発光部２ａ）と原稿面１３の光源２から最も遠い位置１３ａを結んだ直線と一致させているので、第１の楕円鏡３の第１焦点に配置した光源２から該第１の楕円鏡３側に射出された光は図５に示すように光源２と原稿面１３の光源２から最も遠い位置１３ａを結んだ直線上で一度集光した後、原稿面１３の光源２から遠い領域を照明している。図５の点線内Ａは、光源２から射出された光が第１の楕円鏡３で反射される光路図の拡大図である。
【００３４】
図６は本発明の実施形態１における楕円鏡による２回反射光の光路図であり、図４で示した第１、第２の楕円鏡３，４の光学作用を説明している。図６において図２に示した要素と同一要素には同符番を付している。
【００３５】
同図において第１の楕円鏡３の第１焦点に配置された光源２（発光部２ａ）から第２の楕円鏡（不図示）側に射出された光は該第２の楕円鏡によって該第２の楕円鏡の第２焦点４ｂに集光されるため、該第２の楕円鏡の第２焦点４ｂに仮想光源１６があるとして、該仮想光源１６から発せられる光の第１の楕円鏡３による反射を考慮すればよい。
【００３６】
図６に示すように仮想光源１６から射出される光は第１の楕円鏡３によって原稿面１３を広範囲にほぼ均等に照明するようにしている。図６の点線内Ａは仮想光源１６から射出された光が第１の楕円鏡３で反射される光路図の拡大図である。
【００３７】
原稿面１３上の照度分布は、図５に示す照明光による照度分布と図６に示す照明光による照度分布を足し合わせ、さらに第１、第２の楕円鏡３，４のいずれにも反射せず直接原稿面１３を照明する直接光による照度分布を足し合わせたものになるので、図５では原稿面１３の光源２から遠い領域を、図６ではそれ以外の領域をほぼ均等に照明し、原稿面１３上の全体を均一に照明するようにしている。
【００３８】
ここで光源２から射出される光を第１の楕円鏡３により光源２から最も遠い領域に集光させるようにしているのは、第１の反射部材１ａ１がなく、光源２だけの状態で原稿面１３を照明する場合、原稿面上のある点の照度は入射角の余弦に比例し、光源からの距離の逆自乗に比例するので、図７に示すように原稿面１３上の照度分布は光源２から遠い領域になるにつれて暗くなるためで、原稿面１３を均一な明るさで照明するには光源２側の光の強度を小さくし、光源２から遠い領域に集光させて明るくさせるためである。尚、図７は楕円鏡がない場合の被照明面上の照度分布図であり、左側が光源２に近い側である。
【００３９】
本実施形態では上記の如く照明光学系を３組有し、母線と直交する面内において、１組の照明光学系に含まれる第１又は第２の楕円鏡の長軸が、該照明光学系と隣り合う照明光学系に含まれる第１又は第２の楕円鏡の長軸に対して成す角度θが、
０°≦θ≦１０° ‥‥‥（１）
を満足するようにしている。これにより照明系全体の小型化を図っている。
【００４０】
尚、本実施形態において第１の楕円鏡３を母線と垂直な面内（紙面内）で反射面３ｄが放物形状と成る放物面より構成しても良い。このとき楕円鏡の第２の焦点に相当する放物面の第２の焦点が長軸３ｃ上の無限遠に位置するものとして取扱えば楕円面と同様に取扱うことができる。
【００４１】
また本実施形態における光源としては、例えば長尺状の冷陰極管、又は熱陰極管、又はＸｅランプ、又は水銀ランプ、又はメタルハライドランプ等が用いられる。
【００４２】
［実施形態２］
図８は本発明の実施形態２の２灯式照明系を画像読取装置に用いたときの要部概略図である。図８において図１に示した要素と同一要素には同符番を付している。
【００４３】
本実施形態において前述の実施形態１と異なる点は照明系１を第１、第２の２組の照明光学系１ａ，１ｂより構成したことである。その他の構成および光学的作用は実施形態１と同様であり、これにより同様な効果を得ている。
【００４４】
即ち、同図において１は照明系であり、第１、第２の２組の照明光学系１ａ，１ｂを有しており、該第１、第２の照明光学系１ａ，１ｂは各々発光部が長尺状の光源２，５と、該光源２，５から射出される光を斜め方向から被照明面１３に向けて反射する長尺状の第１、第２の２組の反射部材１ａ１，１ｂ１を有している。本実施形態における第２の反射部材１ｂ１の第１の楕円鏡６は第１の反射部材１ａ１の第１の楕円鏡３と形状は同じだが、反射領域を狭くして小型にし、該第１の反射部材１ａ１から射出される光が第２の反射部材１ｂ１によりけられないようにしている。
【００４５】
図９は本発明の実施形態２における照明系の光学作用を説明する説明図であり、光源２、５から射出される光を原稿面１３に導く第１、第２の楕円鏡３、４、６、７の効果について説明している。図９において図３に示した要素と同一要素には同符番を付している。
【００４６】
同図における第１の照明光学系１ａでは、第１、第２の楕円鏡３、４の第１焦点に配置された光源２（発光部２ａ）から該第１の楕円鏡３側に射出される光が、該第１の楕円鏡３の反射面３ｄによって原稿面１３の光源２から遠い領域に向けて反射され、該光源２から第２の楕円鏡４側に射出される光が、該第２の楕円鏡４の反射面４ｄによって該第２の楕円鏡４の第２焦点に集光された後、第１の楕円鏡３の反射面３ｄによって原稿面１３に向けてほぼ均等な角度で反射され、それ以外の光が第１、第２の楕円鏡３，４で反射せず、直接原稿面１３に至り、該原稿面１３を斜め方向から照明している。
【００４７】
また本実施形態においては第２の反射部材１ｂ１の第１の楕円鏡６の裏面に遮光部材１７を配置し、該遮光部材１７により光源２から射出された光で該第１の楕円鏡６の裏の面で反射して再び第１、第２の楕円鏡３、４に入射して、原稿面１３を照明してしまう不要な光線をカットしている。
【００４８】
尚、上記各実施形態１,２においては照明系を３組もしくは２組の照明光学系より構成したが、これに限らず、たとえば１組もしくは４組以上の照明光学系で構成しても良い。
【００４９】
［数値実施例］
次に本発明の各実施形態１,２の数値実施例を示す。
【００５０】
図１０は数値実施例の楕円鏡の形状を説明する説明図である。同図においてａは楕円の長軸の半分の長さ、ｂは楕円の短軸の半分の長さ、ｄは楕円の長軸上の第１焦点側の端から間口の端までの長軸方向の長さである。
【００５１】
図１１は数値実施例の楕円鏡の位置を説明する説明図である。同図においてｔ１は原稿面１３から最も遠い側の第１の反射部材１ａ１に含まれる楕円鏡の第１焦点から原稿面１３の光源２（発光部２ａ）から最も遠い位置１３ａまでの距離、ｔ２は原稿面１３から２番目に遠い側の第２の反射部材１ｂ１に含まれる楕円鏡の第１焦点から原稿面１３の光源５から最も遠い位置１３ａまでの距離、ｔ３は原稿面１３に最も近い側の第３の反射部材１ｃ１に含まれる楕円鏡の第１焦点から原稿面１３の光源８から最も遠い位置１３ａまでの距離、θ１は第１の反射部材１ａ１に含まれる楕円鏡の第１焦点と原稿面１３の光源２から最も遠い位置１３ａを結ぶ直線と原稿面１３との成す角度、θ２は第２の反射部材１ｂ１に含まれる楕円鏡の第１焦点と原稿面１３の光源５から最も遠い位置１３ａを結ぶ直線と原稿面１３との成す角度、θ３は第３の反射部材１ｃ１に含まれる楕円鏡の第１焦点と原稿面１３の光源８から最も遠い位置１３ａを結ぶ直線と原稿面１３との成す角度である。
【００５２】
表１、表２はそれぞれ本発明の実施形態１，２における数値実施例である。
【００５３】
図１２は表１で示した本発明の数値実施例１における原稿面上の照度分布を示す図である。同図の横軸は原稿面上の辺の長さを示しており、縦軸は照度の相対値で、同図の曲線は原稿面の中心を通り原稿面の長辺方向の直線上の照度分布を示している。同図の左側が照明系に近い側に対応している。図１３は図１２と同様、表１の数値実施例１の原稿面上の照度分布を示す図である。同図の曲線は原稿面の中心を通り原稿面の短辺方向の直線上の照度分布を示している。図１４は表２で示した本発明の数値実施例２における原稿面上の照度分布を示す図である。同図の横軸は原稿面上の辺の長さを示しており、縦軸は照度の相対値で、同図の曲線は原稿面の中心を通り原稿面の長辺方向の直線上の照度分布を示している。同図の左側が照明系に近い側に対応している。図１５は図１４と同様、表２の数値実施例２の原稿面上の照度分布を示す図である。同図の曲線は原稿面の中心を通り原稿面の短辺方向の直線上の照度分布を示している。図１２から図１５に示すように各数値実施例１，２においては、原稿面をほぼ均一な明るさで効率的に照明していることがわかる。
【００５４】
尚、図１２から図１５までの照度分布図を求める照明計算において、反射面の反射率を８０％として計算している。
【００５５】
このように実施形態１においては上記の如く照明系を構成する各要素を適切に設定し、さらに条件式（１）を満足するように構成することにより、照明系全体の小型化を図っている。また数値実施例１に示すように距離ｔ１を距離ｔ２より短く、該距離ｔ２を距離ｔ３より短く設定することにより、各照明光学系から射出される光が照明光学系の楕円鏡によってけられることなく照明系全体を小型化できる。また斜め方向の一方向から原稿面を照明することによって、照明系を原稿面から脇に寄せた位置に配置することができ、これにより照明系によって画像光がけられることや、照明光の正反射成分の撮影光学系に入射することが回避でき、さらに光源から射出される光を原稿面に向けて均一に照明することができる。尚、実施形態１において第１の楕円鏡の替わりに楕円形状に高次の非球面項を加えた形状より成る反射鏡を用いても良い。
【００５６】
実施形態２においては上記の如く照明系を構成する各要素を適切に設定し、さらに条件式（１）を満足するように構成することにより、照明系全体の小型化を図っている。また数値実施例２に示すように距離ｔ１を距離ｔ２より長くすることにより、照明系全体を小型化できる。また実施形態１と同様に斜め方向の一方向から原稿面を照明することによって、照明系を原稿面から脇に寄せた位置に配置することができ、これにより照明系によって画像光がけられることや、照明光の正反射成分の撮影光学系に入射することが回避でき、さらに光源から射出される光を原稿面に向けて比較的均一に照明することができる。尚、実施形態２において原稿面から遠い側の楕円鏡の替わりに楕円形状に高次の非球面項を加えた形状より成る反射鏡を用いても良い。
【００５７】
また本発明は上記の実施形態１,２の構成の照明系に限らず、放物面鏡と楕円鏡を含む照明光学系を１組以上用いて斜め方向から被照明面を照明する照明系においても、上記の実施形態１,２と同様に各条件を満足させることによって同様な効果を得ることができる。またこのとき放物面鏡の替わりに放物面形状に高次の非球面項を加えた形状より成る反射鏡を用いても良い。
【００５８】
【発明の効果】
本発明によれば前述の如く照明系を構成する各要素を適切に設定することにより、比較的簡単な構成でありながら、原稿面をほぼ均一な明るさで効率的に照明することができ、また斜め方向の一方向から照明しているため、照明系を折りたたみ可能とする携帯型の画像読取装置に用いる場合には特に好適で、該照明系を含む画像読取装置全体の小型化に効果が非常に大きい照明系及びそれを有する画像読取装置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の要部構成図
【図２】本発明の実施形態１の反射鏡の要部構成図
【図３】本発明の実施形態１における照明光学系の光学作用の説明図
【図４】本発明の実施形態１における反射鏡の光学作用の説明図
【図５】本発明の実施形態１における反射鏡による１回反射光の光路図
【図６】本発明の実施形態１における反射鏡による２回反射光の光路図
【図７】反射鏡がない場合の被照明面上の照度分布図
【図８】本発明の実施形態２の要部構成図
【図９】本発明の実施形態２における照明光学系の光学作用の説明図
【図１０】本発明の楕円鏡の形状の説明図
【図１１】本発明の楕円鏡の位置の説明図
【図１２】本発明の数値実施例１の被照明面上の被照明面の中心を通り被照明面の長辺方向の直線上の照度分布図
【図１３】本発明の数値実施例１の被照明面上の被照明面の中心を通り被照明面の短辺方向の直線上の照度分布図
【図１４】本発明の数値実施例２の被照明面上の被照明面の中心を通り被照明面の長辺方向の直線上の照度分布図
【図１５】本発明の数値実施例２の被照明面上の被照明面の中心を通り被照明面の短辺方向の直線上の照度分布図
【図１６】従来の照明系の要部構成図
【符号の説明】
１照明系
１ａ，１ｂ，１ｃ照明光学系
１ａ１，１ｂ１，１ｃ１反射部材
３，６，９第１の楕円鏡
４，７，１０第２の楕円鏡
１１，１２、１７遮光部材
１３原稿面
１４平面ミラー
１５撮影光学系
２１光源位置の境界線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an illumination system and an image reading apparatus having the illumination system, and is particularly suitable when applied to an apparatus for reading an image of an upward document such as a document camera.
[0002]
[Prior art]
Conventionally, in an image reading apparatus, various illumination systems have been proposed in order to reduce the size of the entire apparatus and perform uniform illumination. In particular, in the case of an illumination system used for an image reading apparatus that reads an image of an upward document, image light reflected on the document surface cannot be scattered by the illumination apparatus before reaching the photographing optical system (photographing means), and a light source (light emitting unit). ), And the light regularly reflected on the original surface is directly incident on the photographing optical system, and a light source image is not reflected on the photographing optical system. An illumination system that satisfies these conditions is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-295603.
[0003]
FIGS. 16A and 16B are schematic views of the main part of the illumination system proposed in the publication. In the publication, as shown in FIGS. 16A and 16B, the illumination system is composed of a long light source (light emitting portion) 18 and a cylindrical reflecting mirror 19 whose bus is parallel to the light source 18, The reflecting mirror 19 is divided into three regions 19a, 19b, and 19c of first, second, and third. The first area 19a has an elliptical reflection surface with a higher-order aspherical term added, reflects the light emitted from the light source 18 once, and guides it to the illuminated surface 20. The region 19b has a circular reflecting surface, reflects light emitted from the light source 18 toward the light source 18, reflects the reflected light at the first region 19a, and guides it to the illuminated surface 20. The region 19c illuminates the illuminated surface 20 from the oblique direction relatively uniformly by blocking the light so that the light emitted from the light source 18 does not directly illuminate the illuminated surface 20.
[0004]
In this conventional example, one light source is used. However, when a light source with a small outer diameter such as a cold cathode tube is used as the light source 18 for downsizing the illumination system, the brightness is not sufficient. There is. Further, when a hot cathode tube having a large amount of light is used as a light source, the outer diameter of the light source is large, so that the reflecting mirror is enlarged in proportion to it and it is quite difficult to downsize the entire illumination system.
[0005]
Further, in this conventional example, the first area 19a of the reflecting mirror 19 is once condensed near the reflecting mirror 19, and then the illuminated surface is illuminated. There is a problem that a far region becomes darker than a near region. The light emitted from the light source 18 by the second region 19b of the reflecting mirror 19 is condensed by the light source 18. Since the light source 18 has a finite size, for example, on the surface of the light source 18. When light is incident, it is diffused and absorbed by the surface, so that the component that is transmitted and incident on the first region 19a is considerably reduced. Therefore, the light reflected by the second region 19b is efficiently used. Can not.
[0006]
Therefore, in this conventional example, there is a problem that the brightness is not sufficient, and the area far from the light source on the surface to be illuminated is darker than the near area and the illuminance unevenness is slightly large.
[0007]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide an illumination system capable of efficiently illuminating a document surface with substantially uniform brightness while having a relatively simple configuration, and an image reading apparatus having the illumination system.
[0008]
[Means for Solving the Problems]
The illumination system of the invention of claim 1
An illumination system having at least one set of illumination optical system including a light source having a long light-emitting portion and a long reflecting member that reflects light emitted from the light source toward an illuminated surface from an oblique direction. ,
The reflecting member includes a first reflecting mirror having a cylindrical shape in which a bus line is parallel to the light emitting portion, an elliptical shape in a plane orthogonal to the bus line, and a reflecting surface facing the illuminated surface side, and a reflecting surface in the illuminated surface A second reflector facing away from the surface,
The light reflectance of the first and second reflecting mirrors is 80%,
The first and second reflecting mirrors have a focal point on the side far from the center position of the illuminated surface among the two focal points of the ellipse in a plane orthogonal to the generatrix, and a focal point on the near side. When the second focus is set, the first focus of each of the first and second reflecting mirrors is located in the vicinity,
The first and second reflecting mirrors are positioned so that the major axes of the respective ellipses are substantially on the same straight line, and the reflecting surfaces of the first and second reflecting mirrors face each other across the major axis. And
The light emitting unit is located in the vicinity of the first focal point of the first and second reflecting mirrors,
The second focal point of the first reflecting mirror is on the illuminated surface side with respect to an intermediate position between the position of the light emitting unit and the farthest position of the illuminated surface from the light emitting unit,
The second reflecting mirror is characterized in that the major axis is shorter than the major axis of the first reflecting mirror.
[0009]
The illumination system of the invention of claim 2
An illumination system having at least one set of illumination optical system including a light source having a long light-emitting portion and a long reflecting member that reflects light emitted from the light source toward an illuminated surface from an oblique direction. ,
The reflecting member has a cylindrical shape in which a bus line is parallel to the light emitting portion, a parabolic shape in a plane orthogonal to the bus bar, and a surface in which the reflecting surface faces the illuminated surface, and a surface orthogonal to the bus bar A second reflecting mirror having an elliptical shape and a reflecting surface facing away from the illuminated surface,
The light reflectance of the first and second reflecting mirrors is 80%,
The parabolic axis of the first reflecting mirror and the major axis of the ellipse of the second reflecting mirror are located on substantially the same straight line, and the reflecting surfaces of the first reflecting mirror and the second reflecting mirror are It is located so as to face each other across the long axis, and the focus on the side far from the illuminated surface is the first focus and the focus on the near side is the second focus among the two focal points of the second reflecting mirror. In this case, the focal point of the first reflecting mirror is located in the vicinity of the first focal point, and the light emitting unit is located in the vicinity of the first focal point.
[0010]
The invention of claim 3 is the invention of claim 1 or 2, wherein
The longitudinal direction of the light emitting part is arranged in a plane parallel to the surface to be illuminated.
[0011]
According to a fourth aspect of the present invention, in the first or third aspect of the present invention, in the plane orthogonal to the generatrix, the major axes of the first and second reflecting mirrors are the light emitting portion and the light emitting portion of the illuminated surface. It is characterized by being on a straight line that connects the farthest positions.
[0012]
The invention of claim 5 is the invention of any one of claims 1 , 3 or 4, and has at least two sets of the illumination optical system, and the set of illumination optical systems is within a plane orthogonal to the generatrix. An angle θ formed between the major axis of the first or second reflecting mirror included and the major axis of the first or second reflecting mirror included in the illumination optical system adjacent to the illumination optical system is
0 ° ≦ θ ≦ 10 °
It is characterized by satisfying.
[0013]
The invention of claim 6 is the invention of any one of claims 1 to 5,
Of the light emitted from the light emitting unit within the plane perpendicular to the bus, light incident on the first reflecting mirror is reflected by the reflecting surface and guided to a region far from the light emitting unit on the illuminated surface. Then, the light incident on the second reflecting mirror is reflected by the reflecting surface and condensed on the second focal point of the second reflecting mirror, and then the wide area of the illuminated surface by the first reflecting mirror. Therefore, the light that is not incident on the first and second reflecting mirrors is directly incident on the illuminated surface.
[0014]
The invention of claim 7 is the invention of claim 5,
A light shielding member is arranged between the at least two sets of illumination optical systems.
[0015]
The invention of claim 8 is the invention of any one of claims 1 to 7,
The light source is a long cold cathode tube, a hot cathode tube, an Xe lamp, a mercury lamp, or a metal halide lamp.
[0016]
An image reading apparatus according to a ninth aspect of the invention includes the illumination system according to any one of the first to eighth aspects, and an imaging device that captures an image of an illuminated area illuminated by light from the illumination system. It is a feature.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
FIG. 1 is a schematic view of a main part when the three-lamp illumination system of Embodiment 1 of the present invention is used in an image reading apparatus.
[0018]
In the figure, reference numeral 1 denotes an illumination system, which has first, second, and third sets of illumination optical systems 1a, 1b, and 1c. The first, second, and third illumination optical systems 1a, 1b, and 1c are light sources 2, 5, and 8 each having a long light emitting portion, and light emitted from the light sources 2, 5, and 8 from an oblique direction. There are three long, first, second, and third reflecting members 1a1, 1b1, and 1c1 that reflect toward the surface 13 to be illuminated. Each of the first, second, and third reflecting members 1a1, 1b1, and 1c1 has a cylindrical shape in which the generatrix is parallel to the light emitting portion, an elliptical surface (paper surface) orthogonal to the generatrix, and the reflecting surface is on the illuminated surface 13 side. The first reflecting mirrors 3, 6, 9 facing the light source and the second reflecting mirrors 4, 7, 10 having the reflecting surface facing away from the illuminated surface 13.
[0019]
The first and second reflecting mirrors 3, 4, 6, 7, 9, and 10 have an elliptical shape on the plane (paper surface) perpendicular to the generatrix of the reflecting mirror as described above. The two reflecting mirrors 3, 4, 6, 7, 9, and 10 are referred to as first and second elliptical mirrors 3, 4, 6, 7, 9, and 10, respectively.
[0020]
Reference numerals 11 and 12 denote light shielding members, which are arranged on the back surface of the reflecting surface of the second elliptical mirrors 4 and 7 of the first and second reflecting members 1a1 and 1b1, respectively. Of the light emitted from the light sources (light emitting portions) 5 and 8 of the optical systems 1b and 1c, the light reflected from the back surfaces of the second elliptical mirrors 4 and 7 and cut to the illuminated surface 13, Prevents the generation of stray light. Reference numeral 13 denotes an original surface as an illuminated surface. The original surface 13 corresponds to the long side in FIG. 1, and the direction perpendicular to the paper surface corresponds to the short side direction. A flat mirror 14 reflects light reflected by the document surface 13 toward the photographing optical system 15. Reference numeral 15 denotes a photographing optical system (imaging device), which captures an image of an illuminated area illuminated by light from the illumination system 1.
[0021]
Reference numeral 21 denotes a boundary line of a light source position where a regular reflection component of light emitted from the illumination system 1 by the document surface 13 enters the photographing optical system 15 and a light source image is reflected in the photographing optical system 15. In the figure, when a light source is present on the side of the document surface 13 from the boundary line 21, an image of the light source is reflected in the photographing optical system 15, and a light source is present on the far side from the document surface 13 of the boundary line 21. Does not capture the image of the light source. In the present embodiment, the illumination system 1 is arranged at a position shifted to the side from the reflected area as shown in FIG. 1 so that the image of the light source does not appear in the photographing optical system 15.
[0022]
FIG. 2 is a schematic view of a main part of one set of illumination optical systems among the three sets of illumination optical systems constituting the illumination system. In addition, since each reflection member 1a1, 1b1, 1c1 which comprises each illumination optical system 1a, 1b, 1c is the same shape, the structure of the 1st illumination optical system 1a is demonstrated below. In FIG. 2, the same elements as those shown in FIG.
[0023]
In the figure, the first and second elliptical mirrors 3 and 4 place the focal points on the side far from the center position 13b of the document surface 13 out of the two focal points of the ellipse within the plane orthogonal to the generating line. When the focal points on the near side are the second focal points 3b and 4b, the first focal points 3a and 4a of the first and second elliptical mirrors 3 and 4 are close to each other.
[0024]
The first and second elliptical mirrors 3 and 4 have their major axes 3c and 4c located on substantially the same straight line La, and the reflecting surfaces 3d and 4d of the first and second elliptical mirrors 3 and 4 are They are positioned so as to face each other with the long axes 3c and 4c interposed therebetween. The light emitting unit 2a is located in the vicinity of the first focal points 3a and 4a of the first and second elliptical mirrors 3 and 4, and the longitudinal direction of the light emitting unit 2a is in a plane parallel to the document surface 13. Is arranged. The second focal point 3b of the first elliptical mirror 3 is closer to the original surface 13 than the intermediate position 3e between the position of the light emitting portion 2a and the position 13a farthest from the light emitting portion 2a of the original surface 13, and the second focal point 3b. The major axis 4 c of the elliptical mirror 4 is shorter than the major axis 3 c of the first elliptical mirror 3.
[0025]
In the plane orthogonal to the generatrix, the major axes 3c and 4c of the first and second elliptical mirrors 3 and 4 are located on a straight line connecting the light emitting portion 2a and the position 13a farthest from the light emitting portion 2a of the document surface 13. ing.
[0026]
The first elliptical mirror 3 is a part of an elliptical mirror whose major axis 3c is increased so that the second focal point 3b is close to the original surface 13, and the second elliptical mirror 4 is the first elliptical mirror. 2 is a elliptical mirror having a long axis 4c shorter than 3, and a partial area far from the light emitting portion 2a of the semi-elliptical mirror in which the elliptical mirror is halved about the long axis, as shown in FIG. It is widened by an angle α formed from the major axis 4c of the elliptical mirror.
[0027]
Here, when the opening of the second elliptical mirror 4 is eliminated, that is, when the angle α is 0, the area near the light emitting portion 2a on the document surface 13 becomes dark, and the illuminance distribution on the document surface 13 is improved. I can't. On the other hand, if the angle α is too large, the area near the light emitting portion 2a on the original surface 13 becomes too bright, and the illuminance distribution cannot be improved. Therefore, in the present embodiment, this angle α is set to the following conditional expression 10 ° ≦ α ≦ 30 ° (A)
It is set to satisfy.
[0028]
FIG. 3 is an explanatory diagram for explaining the optical action of the illumination system according to the first embodiment of the present invention. The first and second elliptical mirrors 3 for guiding the light emitted from the light sources 2, 5, 8 to the document surface 13, The effects of 4, 6, 7, 9, 10 are described. In FIG. 3, the same elements as those shown in FIG.
[0029]
In the first illumination optical system 1a in the figure, some of the light emitted from the light source 2 (light emitting unit 2a) disposed at the first focal point of the first and second elliptical mirrors 3 and 4 is used. Is reflected once on the reflecting surface 3d of the first elliptical mirror 3, and then condensed on a region far from the light source 2 on the original surface 13, and part of the light is reflected on the reflecting surface 4d of the second elliptical mirror 4. After being reflected and condensed on the second focal point 4b, it is reflected by the reflecting surface 3d of the first elliptical mirror 3 and illuminates a wide area on the document surface 13 from an oblique direction. The light is not reflected by the elliptical mirrors 3 and 4 but directly reaches the document surface 13 to illuminate the document surface 13 from an oblique direction.
[0030]
FIG. 4 is an explanatory diagram for explaining the optical action of the elliptical mirror according to the first embodiment of the present invention, and explains the action of the light emitted from the light source 2 reflected by the first and second elliptical mirrors 3 and 4. ing. In FIG. 4, the same elements as those shown in FIG.
[0031]
In the figure, the first elliptical mirror 3 has the reflecting surface 3d facing the original surface (not shown) as described above, and the second elliptical mirror 4 has the reflecting surface 4d facing the opposite side of the original surface. In the drawing, light emitted upward from the light source 2 (light emitting portion 2a) in the drawing is reflected once by the reflecting surface 3d of the first elliptical mirror 3 and guided toward a region far from the light source 2 on the original surface. In the drawing, the light emitted downward is reflected by the reflecting surface 4d of the second elliptical mirror 4 and focused on the second focal point 4b (16) of the second elliptical mirror 4, and then the first Are reflected by the reflecting surface 3d of the elliptical mirror 3 toward the document surface at substantially equal angles.
[0032]
FIG. 5 is an optical path diagram of the one-time reflected light by the elliptical mirror according to the first embodiment of the present invention, and illustrates the optical action of the first elliptical mirror 3. In FIG. 5, the same elements as those shown in FIG.
[0033]
In the drawing, the long axis of the first elliptical mirror 3 is aligned with the straight line connecting the light source 2 (light emitting portion 2a) and the position 13a farthest from the light source 2 on the document surface 13, so The light emitted from the light source 2 arranged at the first focal point toward the first elliptical mirror 3 is once on a straight line connecting the light source 2 and the position 13a farthest from the light source 2 of the document surface 13 as shown in FIG. After condensing, an area far from the light source 2 on the document surface 13 is illuminated. A dotted line A in FIG. 5 is an enlarged view of an optical path diagram in which light emitted from the light source 2 is reflected by the first elliptical mirror 3.
[0034]
FIG. 6 is an optical path diagram of the twice reflected light by the elliptical mirror according to the first embodiment of the present invention, and illustrates the optical action of the first and second elliptical mirrors 3 and 4 shown in FIG. In FIG. 6, the same elements as those shown in FIG.
[0035]
In the figure, light emitted from a light source 2 (light emitting portion 2a) disposed at the first focal point of the first elliptical mirror 3 to the second elliptical mirror (not shown) side is transmitted to the second elliptical mirror by the second elliptical mirror. Since the virtual light source 16 is present at the second focal point 4b of the second elliptical mirror because the light is focused on the second focal point 4b of the second elliptical mirror, the first elliptical mirror 3 of the light emitted from the virtual light source 16 is assumed. It is sufficient to consider the reflection due to.
[0036]
As shown in FIG. 6, the light emitted from the virtual light source 16 illuminates the document surface 13 almost uniformly over a wide range by the first elliptical mirror 3. A dotted line A in FIG. 6 is an enlarged view of an optical path diagram in which the light emitted from the virtual light source 16 is reflected by the first elliptical mirror 3.
[0037]
The illuminance distribution on the document surface 13 is the sum of the illuminance distribution due to the illumination light shown in FIG. 5 and the illuminance distribution due to the illumination light shown in FIG. 6, and is reflected on both the first and second elliptical mirrors 3 and 4. Since the illuminance distribution by the direct light directly illuminating the original surface 13 is added, the area far from the light source 2 on the original surface 13 is illuminated in FIG. 5, and the other areas in FIG. The entire document surface 13 is illuminated uniformly.
[0038]
Here, the light emitted from the light source 2 is condensed on the farthest area from the light source 2 by the first elliptical mirror 3 so that the original is not provided with the first reflecting member 1a1 and only the light source 2 is used. When illuminating the surface 13, the illuminance at a certain point on the document surface is proportional to the cosine of the incident angle and proportional to the inverse square of the distance from the light source, so that the illuminance distribution on the document surface 13 is as shown in FIG. Since it becomes darker as it goes farther from the light source 2, in order to illuminate the document surface 13 with uniform brightness, the light intensity on the light source 2 side is reduced, and the light is condensed and brightened in a region far from the light source 2. It is. FIG. 7 is an illuminance distribution diagram on the illuminated surface when there is no elliptical mirror, and the left side is the side close to the light source 2.
[0039]
In the present embodiment, as described above, there are three sets of illumination optical systems, and the long axis of the first or second elliptical mirror included in the set of illumination optical systems is within the plane orthogonal to the generating line. And the angle θ formed with respect to the major axis of the first or second elliptical mirror included in the illumination optical system adjacent to
0 ° ≦ θ ≦ 10 ° (1)
To be satisfied. This reduces the overall size of the illumination system.
[0040]
In the present embodiment, the first elliptical mirror 3 may be composed of a paraboloid in which the reflecting surface 3d has a parabolic shape in a plane perpendicular to the generatrix (in the paper). At this time, if the second focal point of the paraboloid corresponding to the second focal point of the elliptical mirror is handled at an infinite distance on the major axis 3c, it can be handled in the same manner as the elliptical surface.
[0041]
As the light source in the present embodiment, for example, a long cold cathode tube, a hot cathode tube, an Xe lamp, a mercury lamp, a metal halide lamp, or the like is used.
[0042]
[Embodiment 2]
FIG. 8 is a schematic view of the main part when the two-lamp illumination system of Embodiment 2 of the present invention is used in an image reading apparatus. In FIG. 8, the same elements as those shown in FIG.
[0043]
The present embodiment is different from the above-described first embodiment in that the illumination system 1 is composed of first and second sets of illumination optical systems 1a and 1b. Other configurations and optical actions are the same as those of the first embodiment, and the same effects are obtained.
[0044]
That is, in FIG. 1, reference numeral 1 denotes an illumination system, which has first and second two sets of illumination optical systems 1a and 1b, and each of the first and second illumination optical systems 1a and 1b is a light emitting section. Are elongated light sources 2 and 5 and first and second long reflecting members 1a1 that reflect light emitted from the light sources 2 and 5 toward the illuminated surface 13 from an oblique direction. , 1b1. The first ellipsoidal mirror 6 of the second reflecting member 1b1 in the present embodiment is the same as the first ellipsoidal mirror 3 of the first reflecting member 1a1, but the reflecting area is narrowed to make the first ellipsoidal mirror 3 small. The light emitted from the reflecting member 1a1 is prevented from being scattered by the second reflecting member 1b1.
[0045]
FIG. 9 is an explanatory diagram for explaining the optical action of the illumination system according to the second embodiment of the present invention. First and second elliptical mirrors 3, 4, 4 for guiding the light emitted from the light sources 2, 5 to the document surface 13. The effects of 6 and 7 are described. In FIG. 9, the same elements as those shown in FIG.
[0046]
In the 1st illumination optical system 1a in the figure, it inject | emits from the light source 2 (light emission part 2a) arrange | positioned at the 1st focus of the 1st, 2nd elliptical mirrors 3 and 4 to this 1st elliptical mirror 3 side. Is reflected by the reflecting surface 3d of the first elliptical mirror 3 toward a region far from the light source 2 on the document surface 13, and the light emitted from the light source 2 toward the second elliptical mirror 4 is After the light is condensed on the second focal point of the second elliptical mirror 4 by the reflective surface 4d of the second elliptical mirror 4, the angle substantially uniform toward the document surface 13 by the reflective surface 3d of the first elliptical mirror 3 The other light is not reflected by the first and second elliptical mirrors 3 and 4 but directly reaches the document surface 13 to illuminate the document surface 13 from an oblique direction.
[0047]
In the present embodiment, a light shielding member 17 is disposed on the back surface of the first elliptical mirror 6 of the second reflecting member 1 b 1, and the light emitted from the light source 2 by the light shielding member 17 is used for the first elliptical mirror 6. Unnecessary light rays that are reflected by the back surface and enter the first and second elliptical mirrors 3 and 4 again to illuminate the document surface 13 are cut off.
[0048]
In each of the first and second embodiments, the illumination system is configured by three or two sets of illumination optical systems. However, the present invention is not limited to this, and may be configured by, for example, one set or four or more sets of illumination optical systems. .
[0049]
[Numerical examples]
Next, numerical examples of the first and second embodiments of the present invention will be shown.
[0050]
FIG. 10 is an explanatory diagram for explaining the shape of the elliptical mirror of the numerical example. In the figure, a is half the length of the major axis of the ellipse, b is half the length of the minor axis of the ellipse, and d is the major axis direction from the first focal side end to the end of the front opening on the major axis of the ellipse. Is the length of
[0051]
FIG. 11 is an explanatory diagram for explaining the position of the elliptical mirror of the numerical example. In the figure, t1 is the distance from the first focal point of the elliptical mirror included in the first reflecting member 1a1 farthest from the document surface 13 to the position 13a farthest from the light source 2 (light emitting portion 2a) on the document surface 13, t2. Is the distance from the first focal point of the elliptical mirror included in the second reflecting member 1b1 farthest from the document surface 13 to the position 13a farthest from the light source 5 on the document surface 13, and t3 is closest to the document surface 13. The distance from the first focal point of the elliptical mirror included in the third reflecting member 1c1 on the side to the position 13a farthest from the light source 8 on the document surface 13, and θ1 is the first focal point of the elliptical mirror included in the first reflective member 1a1. Is the angle formed between the straight line connecting the position 13a farthest from the light source 2 of the document surface 13 and the document surface 13, and θ2 is the most from the first focal point of the elliptical mirror included in the second reflecting member 1b1 and the light source 5 of the document surface 13. A straight line connecting the distant position 13a and the original The angle θ3 formed with the document surface 13 is an angle formed between the document surface 13 and a straight line connecting the first focal point of the elliptical mirror included in the third reflecting member 1c1 and the position 13a farthest from the light source 8 of the document surface 13. .
[0052]
Tables 1 and 2 are numerical examples in the first and second embodiments of the present invention, respectively.
[0053]
FIG. 12 is a diagram showing the illuminance distribution on the document surface in Numerical Example 1 of the present invention shown in Table 1. The horizontal axis of the figure shows the length of the side on the document surface, the vertical axis is the relative value of the illuminance, and the curve in the figure is the illuminance on the straight line passing through the center of the document surface along the long side of the document surface. Distribution is shown. The left side of the figure corresponds to the side closer to the illumination system. FIG. 13 is a diagram showing the illuminance distribution on the document surface of Numerical Example 1 shown in Table 1 as in FIG. The curve in the figure shows the illuminance distribution on a straight line passing through the center of the document surface in the short side direction of the document surface. FIG. 14 is a diagram showing the illuminance distribution on the document surface in Numerical Example 2 of the present invention shown in Table 2. The horizontal axis of the figure shows the length of the side on the document surface, the vertical axis is the relative value of the illuminance, and the curve in the figure is the illuminance on the straight line passing through the center of the document surface along the long side of the document surface. Distribution is shown. The left side of the figure corresponds to the side closer to the illumination system. FIG. 15 is a diagram showing the illuminance distribution on the document surface in Numerical Example 2 in Table 2 as in FIG. The curve in the figure shows the illuminance distribution on a straight line passing through the center of the document surface in the short side direction of the document surface. As shown in FIGS. 12 to 15, it can be seen that in each of the numerical examples 1 and 2, the document surface is efficiently illuminated with substantially uniform brightness.
[0054]
In the illumination calculation for obtaining the illuminance distribution diagrams from FIG. 12 to FIG. 15, the reflectance of the reflecting surface is calculated as 80%.
[0055]
As described above, in the first embodiment, the elements constituting the illumination system are appropriately set as described above, and further configured to satisfy the conditional expression (1), thereby reducing the size of the entire illumination system. . Also, as shown in Numerical Example 1, by setting the distance t1 to be shorter than the distance t2 and the distance t2 to be shorter than the distance t3, the light emitted from each illumination optical system can be made by the elliptical mirror of the illumination optical system. The entire illumination system can be downsized. Also, by illuminating the document surface from one diagonal direction, it is possible to place the illumination system at a position close to the document surface so that image light can be emitted by the illumination system, and the regular reflection of the illumination light. It is possible to prevent the component from entering the imaging optical system, and it is possible to uniformly illuminate the light emitted from the light source toward the document surface. In the first embodiment, instead of the first elliptical mirror, a reflecting mirror having a shape obtained by adding a higher-order aspheric term to an elliptical shape may be used.
[0056]
In the second embodiment, the elements constituting the illumination system are appropriately set as described above, and further configured to satisfy the conditional expression (1), thereby reducing the size of the entire illumination system. Further, as shown in Numerical Example 2, by making the distance t1 longer than the distance t2, the entire illumination system can be reduced in size. Further, as in the first embodiment, by illuminating the document surface from one oblique direction, the illumination system can be arranged at a position close to the document surface, whereby image light can be emitted by the illumination system. Further, it is possible to avoid the regular reflection component of the illumination light from entering the photographing optical system, and it is possible to illuminate the light emitted from the light source relatively uniformly toward the document surface. In the second embodiment, instead of the elliptical mirror on the side far from the original surface, a reflecting mirror having a shape obtained by adding a higher-order aspheric term to an elliptical shape may be used.
[0057]
Further, the present invention is not limited to the illumination systems having the configurations of the first and second embodiments described above, but in an illumination system that illuminates a surface to be illuminated from an oblique direction using one or more illumination optical systems including a parabolic mirror and an elliptical mirror. In the same manner as in the first and second embodiments, the same effect can be obtained by satisfying each condition. In this case, instead of the parabolic mirror, a reflecting mirror having a shape obtained by adding a higher-order aspheric term to the parabolic shape may be used.
[0058]
【The invention's effect】
According to the present invention, by appropriately setting each element constituting the illumination system as described above, it is possible to efficiently illuminate the document surface with substantially uniform brightness while having a relatively simple configuration. In addition, since the illumination is performed from one oblique direction, it is particularly suitable for use in a portable image reading apparatus in which the illumination system can be folded, and is effective in downsizing the entire image reading apparatus including the illumination system. A very large illumination system and an image reading device having it can be achieved.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram of Embodiment 1 of the present invention. FIG. 2 is a main part configuration diagram of a reflecting mirror of Embodiment 1 of the present invention. FIG. 3 is an optical action of an illumination optical system in Embodiment 1 of the present invention. Explanatory drawing of FIG. 4 Explanatory drawing of the optical action of the reflective mirror in Embodiment 1 of this invention [FIG. 5] The optical path figure of the once reflected light by the reflective mirror in Embodiment 1 of this invention [FIG. FIG. 7 is an illuminance distribution diagram on the surface to be illuminated when there is no reflecting mirror. FIG. 8 is a main part configuration diagram of Embodiment 2 of the present invention. FIG. 10 is an explanatory diagram of the optical action of the illumination optical system in Embodiment 2 of the present invention. FIG. 10 is an explanatory diagram of the shape of the elliptical mirror of the present invention. FIG. 11 is an explanatory diagram of the position of the elliptical mirror of the present invention. Illuminance distribution diagram on a straight line in the long side direction of the illuminated surface passing through the center of the illuminated surface on the illuminated surface in Numerical Example 1 of the invention FIG. 13 is an illuminance distribution diagram on a straight line in the short side direction of the illuminated surface passing through the center of the illuminated surface on the illuminated surface according to Numerical Example 1 of the present invention. Illuminance distribution diagram on a straight line in the long side direction of the illuminated surface passing through the center of the illuminated surface on the illuminated surface. FIG. 15 illustrates passing through the center of the illuminated surface on the illuminated surface according to Numerical Example 2 of the present invention. Illuminance distribution diagram on a straight line in the short side direction of the illumination surface [Fig. 16] Main part configuration diagram of a conventional illumination system [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Illumination system 1a, 1b, 1c Illumination optical system 1a1, 1b1, 1c1 Reflective member 3,6,9 1st elliptical mirror 4,7,10 2nd elliptical mirror 11,12,17 Light shielding member 13 Original surface 14 Plane Mirror 15 Imaging optical system 21 Boundary line of light source position

Claims

An illumination system having at least one set of illumination optical system including a light source having a long light-emitting portion and a long reflecting member that reflects light emitted from the light source toward an illuminated surface from an oblique direction. ,
The reflecting member includes a first reflecting mirror having a cylindrical shape in which a bus line is parallel to the light emitting portion, an elliptical shape in a plane orthogonal to the bus line, and a reflecting surface facing the illuminated surface side, and a reflecting surface in the illuminated surface A second reflector facing away from the surface,
The light reflectance of the first and second reflecting mirrors is 80%,
The first and second reflecting mirrors have a focal point on the side far from the center position of the illuminated surface among the two focal points of the ellipse in a plane orthogonal to the generatrix, and a focal point on the near side. When the second focus is set, the first focus of each of the first and second reflecting mirrors is located in the vicinity,
The first and second reflecting mirrors are positioned so that the major axes of the respective ellipses are substantially on the same straight line, and the reflecting surfaces of the first and second reflecting mirrors face each other across the major axis. And
The light emitting unit is located in the vicinity of the first focal point of the first and second reflecting mirrors,
The second focal point of the first reflecting mirror is on the illuminated surface side with respect to an intermediate position between the position of the light emitting unit and the farthest position of the illuminated surface from the light emitting unit,
The illumination system, wherein the second reflecting mirror has a major axis shorter than a major axis of the first reflecting mirror.

An illumination system having at least one set of illumination optical system including a light source having a long light-emitting portion and a long reflecting member that reflects light emitted from the light source toward an illuminated surface from an oblique direction. ,
The reflecting member has a cylindrical shape in which a bus line is parallel to the light emitting portion, a parabolic shape in a plane orthogonal to the bus bar, and a surface in which the reflecting surface faces the illuminated surface, and a surface orthogonal to the bus bar A second reflecting mirror having an elliptical shape and a reflecting surface facing away from the illuminated surface,
The light reflectance of the first and second reflecting mirrors is 80%,
The parabolic axis of the first reflecting mirror and the major axis of the ellipse of the second reflecting mirror are located on substantially the same straight line, and the reflecting surfaces of the first reflecting mirror and the second reflecting mirror are It is located so as to face each other across the long axis, and the focus on the side far from the illuminated surface is the first focus and the focus on the near side is the second focus among the two focal points of the second reflecting mirror. The illumination system is characterized in that the focal point of the first reflecting mirror is located in the vicinity of the first focal point, and the light emitting unit is located in the vicinity of the first focal point.

The illumination system according to claim 1, wherein a longitudinal direction of the light emitting unit is arranged in a plane parallel to the illuminated surface.

In the plane orthogonal to the generatrix, the major axes of the first and second reflecting mirrors are on a straight line connecting the light emitting portion and a position farthest from the light emitting portion of the illuminated surface. The illumination system according to claim 1 or 3 .

The long axis of the first or second reflecting mirror included in the one set of illumination optical systems is adjacent to the illumination optical system in a plane orthogonal to the generatrix having at least two sets of the illumination optical systems. An angle θ formed with respect to the major axis of the first or second reflecting mirror included in the illumination optical system is
0 ° ≦ θ ≦ 10 °
The illumination system according to any one of claims 1, 3, and 4, wherein:

Of the light emitted from the light emitting unit within the plane perpendicular to the bus, light incident on the first reflecting mirror is reflected by the reflecting surface and guided to a region far from the light emitting unit on the illuminated surface. Then, the light incident on the second reflecting mirror is reflected by the reflecting surface and condensed on the second focal point of the second reflecting mirror, and then the wide area of the illuminated surface by the first reflecting mirror. The illumination system according to any one of claims 1 to 5, wherein light that is guided to the light and does not enter the first and second reflecting mirrors directly enters the surface to be illuminated.

The illumination system according to claim 5, wherein a light blocking member is disposed between the at least two sets of illumination optical systems.

8. The light source according to claim 1, wherein the light source is a long cold cathode tube, a hot cathode tube, an Xe lamp, a mercury lamp, or a metal is a ride lamp. Lighting system.

9. An image reading apparatus comprising: the illumination system according to claim 1; and an imaging device that captures an image of an illumination area illuminated by light from the illumination system.