JP4208325B2 - Illumination device and photographing device using the same - Google Patents

Description

であらわされるような形状としている。
【００６５】
本実施形態では、射出面から射出する射出角度をβ,第一入射面と第二入射面の境界と光源中心とを結ぶ角度をθ_bdr、必要照射角に応じた比例定数ｈとすると、
β＝ｈ・｛θ−（４５°＋θ_bdr／２）｝
の関係にあるようにしている。
【００６６】
上式（２）の意味するところは、まず射出光軸１Ｚ近傍の角度成分を入射させる入射面１ａから入射した光束は、まず、光源中心から射出光軸に向かう光線は、そのまま光学プリズム１を通過する。
【００６７】
ここを基点として、光源中心からの射出角度θに応じて光学プリズムの射出面１dからある比例定数ｋ倍されて射出面から射出される。ここで、比例定数ｋは０から１までの定数である。
【００６８】
ここで、ｋ＝０は射出光束がすべて射出光軸と平行に変換された最も集光された状態を意味し、ｋ＝１は、光学プリズムへの入射時の角度θと射出時の角度αが等しい角度変換のない形状、すなわち、光学プリズムへの入射出前後で屈折率の影響を受けないそれぞれの面のパワーをキャンセルするような形状、たとえば入射出面をそれぞれ平面とするような形状を意味する。
【００６９】
一方、（５）式は以下のような意味を持っている。まず、光源中心から照射光軸に対して上方に射出した光束が、入射面１ｂから入射した後、全反射面１ｃで反射後、光射出面１ｄから射出される。このとき、光源からの光学プリズム１に入射する射出角度の最も大きい成分、すなわち射出光軸１Ｚに対して垂直方向の成分が照射光軸とほぼ平行の最も光軸の方向に近い成分に変換される。
【００７０】
一方、入射面１ａとの交点に近い部分から入射した光線は、射出光軸１Ｚに対して最も大きな角度βをもって交錯する成分に変換される。この中間の領域は射出角度に比例して上記角度範囲内を徐々に変化する。この場合も上記同様、比例定数ｈは０から１まで変化し、ｈ＝０は射出光すべてが射出光軸と平行に変換されることを意味し最も集光した状態となる。また、ｈ＝１は、入射角の変化量と射出角度の変化量のない面、すなわち、光学プリズム内で集光効果を持たない照射方向のみを変化させることを意味する。すなわち、空気中に置かれた平面鏡のような効果を持たせる面構成である。
【００７１】
次に、上記方法で形成された入射面１ａによる屈折光による配光分布と、入射面１ｂ、全反射面１ｃによる全反射光による配光分布との関係について説明する。上記説明のように、この両者の配光分布はそれぞれの面形状によって独立に制御できる。そして、光源の内径が十分に小さい場合や、光源に対して、光学プリズムが十分に大きいとみなせる場合には、上記方法で、かなり効率よく配光分布の制御が可能となる。
【００７２】
しかし、実際の配光特性を考えてみた場合、光源の有効発光部である内径の大きさは無視できるほどには小さくない場合が多く、この影響が全体の配光特性に与える影響は大きい。特に、光源の近くにある制御面、例えば、光軸近傍の角度成分を入射させる入射面１ａや、全反射面１ｃでも光源に近いプリズム後端部での反射光束は、この光源が有限の大きさを持つことによって配光に一定の広がりを生じるため、この要因をある程度加味して形状設定を行う必要がある。
【００７３】
一方、全反射面１ｃでも射出部に近い成分は光源から遠く離れた位置で射出方向が制御される為、このブレが少なく、かなり効率良く意図する範囲に配光制御することができる。このような特性を考慮しつつ、上記、各入射面、および全反射面の形状を定義する必要がある。
【００７４】
上記理由から各入射面によって制御される配光の特性は各々異なり独立に制御可能であるが、上記実施形態１では、この特性のうち光源の上側に向かった光束は、入射面１ｂに入射後、全反射面１ｃで反射後、射出光軸１Ｚから下側へ必要照射角まで均一に角度変換し、逆に光源の下側に向かった光束は、入射面１ｂ′に入射後、全反射面１ｃ′で反射後、射出光軸１Ｚから上側に必要照射角まで均一に角度変換したものである。
【００７５】
また、射出光軸付近に向かった光束は、上記側方から入射した成分による配光分布とほぼ一致するように入射面１aの形状を設定してある。このように、上記各入射面からの配光分布は特殊な配光分布を必要されるとき以外は、ある程度一致させると小型で効率の良い配光分布に変換することができる。このことから、一般に上記配光特性の実用的な規制方法としては、各入射面での制御角度の最大角を規定する以下の領域内に各値が存在することが望ましい。
【００７６】
入射面１ａで屈折光による最大角度成分；α_max、全反射面１ｃで全反射光による最大射出角度成分；β_maxとしたとき、
０．８≦｜β_max／α_max｜≦１．２ ……（５）
とすることである。
次に、上記入射面の境界面の位置について説明する。上述したように、上記入射面の樹脂材料に対する熱の影響を考慮した上で効率良く、また最小の光学系を形成するための条件としては、第１の入射面１ａと第２の入射面１ｂの交点の座標と光源の中心を結ぶ直線の角度がある一定の範囲内にあることが望ましい。
【００７７】
すなわち、この角度が所定角度より小さいと第１の入射面１ａへの距離が離れ、光源の大きさによる影響を受けにくくなるため屈折による集光効率は上がるが、第２の入射面１ｂへの入射角度が大きくなり入射面での表面反射によるロスが生じやすくなる。
【００７８】
一方、この角度が所定角度より大きいと光源に近い面で制御が必要な第１入射面１aからの入射光束が増え、光源の大きさによっては、十分な集光効果が得られにくい。そこで、上記直線の角度が、以下のような数値範囲に収まることが望ましい。すなわち、上記光学プリズム１の正面に向かった光を屈折のみによって制御する入射面１aと主に光源から斜め前方に射出した光を全反射面１ｃに導く入射面１ｂとの境界線と、光源中心とを結ぶ線分の傾きθ_bdrとすると、
２５°≦θ_bdr≦４５° ……（６）
の範囲にあることが、効率面や集光制御の観点から望ましい。
【００７９】
次に、光学プリズム１の入射面１ｂと全反射面１ｃとの交点の形状について説明する。
【００８０】
本発明の実施形態１では、この交点が直接交わって鋭角を形成するような形状とし、かつ、この交点と光源の中心位置とが前後方向にほぼ一致するように構成されている。
【００８１】
このような構成は、光学プリズムの形状を最小にしつつ配光制御を効率良く行うのに有効な手段である。すなわち、例えば、この入射面１ｂと全反射面１ｃとの間に異なった特性の面、例えば、特開平８−２６２５３７号公報に示されるように光軸に垂直な面を形成するとすると、その面は、光学系としては機能しないばかりでなく、光学プリズムの上下方向また、奥行き方向の大型化につながる。
【００８２】
一方、本実施形態ではこの交点の位置と光源中心の前後方向の位置とを一致させているが、これは、光学系全体を小型化すると共に、効率アップに必要な形状であり、プリズム内での全反射角度との関係、及び光源に応じた反射傘の形状とも密接な関係があり形状を規制しているものである。
【００８３】
すなわち、プリズム内での全反射を入射面１ｂの角度を０°付近に設定し、光学プリズムを樹脂材料とするとその屈折率は１．５前後であり、これより後方までプリズム面の交点を伸ばすと、全反射しきれずにプリズムの後方に射出する成分が生じる。これは、光源の内径が大きいほど生じやすく、光源中心より前方から射出した成分の一部が全反射面１cから抜け出ることになる。
【００８４】
本実施形態ではこの全反射面１ｃの後方に抜け出る光を再度、光学プリズム１内に戻す反射傘３を一部全反射面１ｃの後方まで伸ばした構成をとっている。そして、反射傘として有効に機能する最大の大きさまで反射傘３を伸ばし、あとは光学プリズム１の入射面に入射させるように構成している。
【００８５】
その最適な反射傘の形状とは、光源である閃光放電管２と同心の半円筒状の反射傘を採用し、この反射傘の開口部の前端を光源中心の前後方向とほぼ一致させ、かつ光学プリズムの後端もほぼ光源の中心と一致させることである。
【００８６】
反射傘の形状を光源中心と同心とし、その前端を光源中心と一致させる理由としては、まず、閃光放電管のガラス部分での影響が挙げられる。今回の実施例のような極めて小型の発光光学系においては、光源から後方に向かった光束を反射傘で反射させて、照射方向に向かわせる必要があるが、光学系全体が小型化である為、反射傘での反射光をすべて、閃光放電管の内部を介さずに閃光放電管の外側をまわして配光制御を行う為のスペース的な余裕がない為、閃光放電管のガラス管内に再入射させる光路を利用する必要がある。
【００８７】
このとき、閃光放電管へ再入射した成分は閃光放電管のガラス部での屈折や全反射により影響を受け、光学プリズムへの入射成分にも大きな影響を与える。特にこのガラス厚が厚いほど顕著であり、光源形状と反射傘の形状が適切に対応していないと反射傘からの反射光の分布が必要以上に広がってしまうことになる。
【００８８】
このことから、反射傘を光源形状に対応した円筒状にし、かつ上記閃光放電管の円筒形状のガラス部と同心形状にすると、閃光放電管への再入射時の入射角度が小さくなり、ガラス管表面での表面反射によるロスが少なく、また、再入射後の光束のガラス管内で全反射する成分が少なくなり効率がよい。
【００８９】
特に、光源２に対して隙間が少ないと反射傘３での反射後の角度変化が少なく特に有効である。また、反射傘を、光源中心の位置とほぼ一致する半円筒状にする理由としては、反射傘をこれ以上長くすると反射傘が前まで回り込んでしまい、反射傘内に光がこもるので効率が低下してしまうこと、また、反射傘を光源中心よりも短くしてしまうと、前述のように光学プリズムの後端が後方まで延び、光量ロスとなるばかりでなく、光学系全体が大きくなってしまい好ましい構成とはならない。
【００９０】
次に、実施形態１における光源からの光束の射出角度と光学プリズム１を通過後の射出面１ｄからの射出角度の関係について具体的な数値を用いて説明する。
【００９１】
まず、上記発光の際に生じる熱の影響を考慮し、閃光放電管２（外径φ２．０、内径φ１．３）に対して光学プリズム１の入射面１ａ，１ｂの距離ｄ，ｅをそれぞれ０．５ｍｍ離して配置した。
【００９２】
また、簡単の為、全反射面１ｃに導く上面の入射面１ｂの形状は、射出光軸１Ｚの後方側に広がる傾き１°の平面とした。この値は条件式（１）を満たす範囲内に存在する値である。
【００９３】
また、光源中心部から射出された光束が、各入射面及び全反射面での全反射によって制御され光射出面１dから射出される、配光分布が均一でかつ照射角α_max,β_maxの最大値がそれぞれ２０°となるような形状を例にとって説明する。
【００９４】
すなわち、｜β_max／α_max｜＝１であり条件式（５）の関係を満たしている。まず、この条件で最適化された形状において、入射面１aと入射面１bの境界線と光源中心とを結ぶ線分の傾きθ_bdr、上下方向の集光に寄与する反射傘を含めた深さｆ、上下方向の集光に寄与する上下開口ｇ、はそれぞれ、
θ_bdr＝３７．４４° 、 ｆ＝４．４０ 、 ｇ＝６．７０
であり、傾きθ_bdrは上記（６）式を満たす範囲内にある。また、上記値に示すように従来タイプの閃光発光装置の発光光学系に比べて極めて小型に構成することができる。
【００９５】
また、同図においては、実際の製品を想定して、光学プリズムの前側部分に光学プリズムを外観部に出す為の形状、すなわち光学プリズムの全反射面の延長上に全周にわたる細いリブ１ｅ，１ｅ′が一体的に形成されている。
【００９６】
これは、不図示の外観部材との合わせの形状であり、光学プリズムと外観部品の隙間から不要な内部部品が見えるのを防止すると共に以下の目的で付加したものである。
【００９７】
すなわち、金属でできた反射傘と外装部品として使用される金属カバーとの間、または、光学プリズムと外観部品との隙間の延長上に配された導伝性の物との間で、トリガーリークが発生し発光ができなくなることを未然に防止する為である。
【００９８】
一般に、本発明のような閃光発光装置においては、閃光放電管に高電圧トリガー信号を反射傘に直接与え、この反射傘に接触した放電管のネサコート部を介して発光を開始させているが、本発明のように小型化した光学系ではこの反射傘と金属で成形された外装部品や製品外部の導電性の物との距離が近い為、トリガーリーク現象を起こしやすかった。
【００９９】
上述のように光学プリズムの全反射面延長部にリブ１ｅ、１ｅ′を付加することで縁面距離を伸ばすことができ、上記トリガーリーク現象を未然に防止することができる。
【０１００】
またこれと同時に、外部からのゴミや水滴の侵入の防止、特に水滴は、内部の高圧部品との間での感電の危険性があるが、このような危険性も同時に未然に防止することができる。この付加部分の長さｉ、及び外観開口部の長さｊとすると、
ｉ＝１．０ ｊ＝６．５
であり、外観開口部の長さｊは、上下方向の集光に寄与する上下開口ｇより若干狭くなっている。
【０１０１】
これは、全反射面１ｃ，１ｃ′の先端付近で全反射した成分は射出光軸の方向にかなり大きな角度で交錯する成分であり、このことから外観開口部の長さを狭めることが十分に可能になる。
【０１０２】
また、上記付加部分の先端部には、左右方向の配光制御を行う為の縦プリズムが図３に示すように形成されている。
【０１０３】
一方、同図における光線トレースからも明らかなように、本発明の一つの目的である均一配光特性に関しても十分に特性をみたしていることがわかる。まず、図１に示されるように、光源中心から射出し、射出光軸１Ｚに近い角度で射出した光束は、入射面１ａで屈折制御されるが、この時の変換は、入射角θと光射出面１ｄからの射出角αとの間に（３）式が成り立ち、その時の係数ｋは、
ｋ＝ａ_max／θ_bdr＝２０．０°／３７．４４°＝０．５３４
であるから、一般式は、
α＝０．５３４・θ （ただし−３７．４４°≦θ≦３７．４４°）
で表わされ、光源からの射出成分が射出角度に応じて均等に割り振られ、光学プリズム１の射出面１dから射出していることがわかる。
【０１０４】
一方、図２に示されるように、光源中心Ｏから射出し、射出光軸１Ｚに対して上方に進む光束は、入射面１ｂで屈折後、全反射面１ｃで全反射によって制御されるが、この時の変換は、入射角θと光射出面１ｄからの射出角βとの間に（５）式が成り立ち、その時の係数ｈは、
ｈ＝β_max／（９０°−θ_bdr）＝２０．０°／５２．５６°＝０．３８１
であるから、一般式は、
β＝−０．３８１・｛（９０°＊｜θ｜−θ＊＊２）／θ｝
（ただし３７．４４°≦｜θ｜≦９０°）
で表わされ、光源からの射出成分が射出角度に応じて均等に割り振られ、先に示した射出光軸に近い角度で射出した成分の分布とは異なる密度分布で、均一に光学プリズム１の射出面１ｄから射出していることがわかる。
【０１０５】
一方、図示していないが、閃光放電管２の射出光軸１Ｚの後方に進んだ光束の光路について説明する。射出光軸後方には光源中心Ｏと同心の円筒状の反射傘３があり、また、閃光放電管２のガラス管も光源中心に対して同心形状である為、光源中心から後方に射出した光束はすべてガラス管による屈折の影響を受けずに再度光源中心に戻って来ることになる。
【０１０６】
また、光源中心に戻って来た後の光線の振る舞いについては、図１及び図２に示した光線トレースとほぼ同等の特性を持って照射すべき被写体に均一に照射される。
【０１０７】
また、反射傘３は、光学プリズム１の全反射面１ｃの後方、光源である閃光放電管のほぼ前端まで回り込み、かつその形状は、反射面１ｃとほぼ同一形状としているが、この理由は、閃光放電管の発光部であるガラス管内径部は光源中心から前側にも存在するが、この前側から射出した光束の一部が全反射面１ｃで全すべて全反射しきれずに外部に出てしまうのを防止する為である。
【０１０８】
このように、全反射面とほぼ同一形状とし、全反射面のすぐ後方に配置することにより、全反射面１ｃの効果とほぼ同等となり、必要照射範囲に効率よく均一な分布にすることが可能となる。
【０１０９】
次に、上記定義に基づく光学プリズムの非球面形状の近似値について説明する。まず、入射面１ａの形状は頂点をPとしここを原点とした場合、以下の式でほぼ近似できる。
【０１１０】

また、全反射面１ｃも同様にして近似式で表わすと、原点を光源中心Ｏとすると、

で表される。
【０１１１】
しかし、光源を点光源と仮定すると上記形状に一致させることが望ましいが、実際には光源は閃光放電管の内径部にあたるような有限の大きさを持っているため、ここまで厳密に形状を規制しなくてもほぼ同等の配光特性が得ることができる。
【０１１２】
たとえば、上記形状を近似した単一もしくは複数の円筒面、さらには楕円等の２次曲面を用いても、上記形状で得られる配光特性とほぼ同等の効果が得られる形状が存在する。
【０１１３】
このため、本発明における上記入射面１ａ，１ｂ及び全反射面１ｃの形状は、上記式を厳密に満足する形状に限定するわけではなく、光学プリズムの各面の形状を近似的に満たすような形状を含めて規定するするものとする。
【０１１４】
また、このような近似形状で光学プリズムを形成することによって、実際加工されたものが設計値通りできているかの測定が、面形状が非球面である場合に比べて極めて容易にできる、という利点がある。
【０１１５】
実際、このような近似形状で製作した光学プリズムを用いても上式に示した形状とそれほど大きな配光特性の相違は生じていない。
【０１１６】
次に、上記実施形態１の考え方に基づいて光学プリズムの形状を規制したいくつかの他の実施形態について説明する。
【０１１７】
図７，図８は、本発明の閃光発光装置の実施形態２の要部平面図である。同図は比較的広い照射範囲を均一に照明するための光学系の主要断面図と、この形状における光線トレース図を示したものである。
【０１１８】
同図において、４は光学プリズム、５は反射傘であり、各図は光学系の形状は同一で、光線トレース部のみをそれぞれの入射面４ａと入射面４ｂと別に示している。
【０１１９】
特に、実施形態２は、光源から上下方向に射出した光束を反射させる全反射面４ｃ，４ｃ′の角度が（１）に示す範囲の最小値、また、各入射面で制御される光学プリズムの通過後のそれぞれ射出最大角度の関係を示す（５）式に示す範囲の中心値、さらに、全反射面４ｃ，４ｃ′に入射面４ｂの境界線と光源中心とを結んだ線分と射出光軸となす角度が（６）で示した範囲の中で最大値、すなわち
φ＝０°
｜β_max／α_max｜＝１．０
θ_bdr＝４５°
の状態を示したものである。
【０１２０】
また、光源中心Ｏから照射光軸１Ｚに近い角度成分を入射させる入射面４aは、射出光軸に垂直な平面とし、また、全反射面４ｃは、（５）式を満たし、かつ、光学プリズム４を通過することによって光線の方向のみを変換しての角度分布は変化させないような、すなわち、空気中に置かれた平面鏡のような特性を持たせるような面構成となっている。
【０１２１】
すなわち、（３）式の係数ｋ、（４）式の係数ｈはそれぞれ、以下の値をとったときの形状である。
【０１２２】
ｋ＝１．０ ｈ＝１．０
また、実施形態１と同様、反射傘５は、光源２と同心形状の円筒面５aと、光学プリズム４の全反射面４ｃ，４ｃ′の後方に回り込む曲面形状部５bとによって構成されている。
【０１２３】
上記構成において、各状態の光線の振る舞いについて説明する。まず、図７に示す光源２から入射面４ａに入射した光束は、図示のように入射面４aと射出面４dが共に射出光軸１Ｚに対して垂直なお互い平行な平面である為、光学プリズム４で入射、射出時に屈折はするものの、光線の角度自体は変化していない。
【０１２４】
すなわち、光学プリズム４を通過することによって、厳密には各面での表面反射によって幾分光量ロスは生じるものの、光学プリズム４の通過前後で基本的には集光、拡散の効果はなく、光源２からの配光特性がそのまま照射面上に反映される。
【０１２５】
一方、入射面４ｂ，４ｂ′から入射した光束は、前述のように、全反射面４ｃによって光学プリズム４からの射出後の角度分布は一定で照射方向のみを変えるように変換されている。
【０１２６】
すなわち、光源中心Ｏから光学プリズム４の後方の頂点付近に向かった光束はほぼ射出光軸の方向に変換され、また、入射面４ａとの交点付近に向かった光束は、入射面４ａからの射出光の最大角度と一致し、方向は照射光軸１Ｚに対してちょうど対称形となるような方向に変換されるように構成している。
【０１２７】
また図示はしていないが、光源中心Ｏから射出光軸１Ｚの後方に向かった光束は、光源と同心状に形成されて反射傘５によって、再度光源中心Ｏに戻るように構成されている。この為、光源中心Ｏにもどされた光束は、図７，図８に示すような光線トレースを描いて、均一な配光分布に変換される。
【０１２８】
上記構成の光学系を使用することによって、ほぼ光源中心から射出した光束は、−４５°から４５°にわたる９０°の範囲を均一に照射することができる。また、実際には、光源の発光点は光源中心だけではなく光源の内径全体で発光している。この為、実際の配光特性は、上記範囲より幾分広がることになる。
【０１２９】
また、このように、光源が光学系全体の形状に対して無視できないくらい大きい場合には、ここで設定した光源中心より前側の部分から前方に射出した光束の一部が、全反射面４cで全反射しきれずに光学プリズム４外に射出してしまう成分がありえる。
【０１３０】
この全反射面４ｃからの射出光束を光学プリズム４へ再入射させる為の反射面が、反射傘２の全反射面４ｃの後方に配置した反射面５ｂであり、図示のように全反射面４ｃとほぼ同一形状とし至近位置に配置することによって、全反射面４ｃによる配光分布とほぼ同等の均一な配光特性が得られる。
【０１３１】
上記実施形態２の構成は、光源中心Ｏから射出した光束を均一な配光特性に変換する光学系のうち、特に最小形状を示したものであり、この時の具体的数値を以下に示す。閃光放電管の内径、外径は実施形態１と同様それぞれ、φ１．３、φ２．０とすると、光源と光学プリズムの各入射面までの最短距離をそれぞれｄ，ｅ、また、光学系全体の奥行きｆ、光学プリズムの上下の開口をｇはそれぞれ以下のようである。
【０１３２】
ｄ＝０．３ ｅ＝０．３ ｆ＝３．３ ｇ＝４．７
光学プリズムをこのように光源に対して極めて小型に構成することが可能となる。また、この時の配光特性は均一で、光源中心から３６０°の方向に射出された光束をその約１／４の９０°の角度範囲に狭めることが可能になる。
【０１３３】
次に、本発明の実施形態３について説明する。図９，図１０は、本発明の実施形態３の要部断面図である。実施形態２に対しての変更点は、光源中心Ｏからの光学プリズム６の通過後の射出光束の範囲を約半分に狭めたことである。同図において、６は光学プリズム、７は反射傘であり、各構成要素は実施形態２と同様であり、閃光放電管２に対する反射傘７の関係は、光学プリズム６で制御しきれない光束を効率よく利用するような構成となっている。
【０１３４】
また、入射面６ｂ，６ｂ′の光軸１Ｚに対する角度φ、各入射面で制御後のそれぞれ射出最大角度の関係、さらに、入射面の境界線と光源中心とを結んだ線分と射出光軸となす角度θ_bdrとすると、本実施例はそれぞれ以下の値をとった時の状態を示したものである。
【０１３５】
φ＝０°｜β_max／α_max｜＝１．０ θ_bdr＝３８．７°
一方、本実施形態においても、入射面６ａ，６ｂは、（３）式、（４）式に基づいて形成され、各係数ｋ，ｈは、以下の数値になるように各形状を規制している。
【０１３６】
ｋ＝０．６０ ｈ＝０．４５
また、光学系の全体形状としては、閃光放電管の内径、外径は実施形態１と同様それぞれ、φ１．３、φ２．０とすると、光源と光学プリズム６の各入射面までの最短距離をそれぞれｄ，ｅ、また、光学系全体の奥行きｆ、光学プリズムの上下の開口をｇはそれぞれ以下のようである。
【０１３７】
ｄ＝０．３ ｅ＝０．３ ｆ＝３．９ ｇ＝５．７
このように光学プリズム６の各形状を設定することによって、配光特性は均一で、光源中心から３６０°の方向に射出された光束をその約１／８の４６°の角度範囲に狭めることが可能になる。
【０１３８】
実際には、光源には、ある有限の大きさを持っている為、光源の発光部の大きさに応じて、配光特性も全体に広がることになる。
【０１３９】
次に、本発明の実施形態４について説明する。
【０１４０】
図１１，図１２は、本発明の実施形態４の要部断面図である。実施形態２に対しての変更点は、光源中心Ｏからの光学プリズム８の通過後の射出光束の範囲を極端に狭めたことである。同図において、８は光学プリズム、９は反射傘であり、各構成要素は実施形態２と同様であり、閃光放電管２に対する反射傘９の関係は、光学プリズム８で制御しきれない光束を効率よく利用するような構成となっている。
【０１４１】
また、入射面８ｂ，８ｂ′の角度φ、各入射面で制御後のそれぞれ射出最大角度の関係、さらに、入射面の境界線と光源中心とを結んだ線分と射出光軸となす角度θ_bdrとすると、本実施形態はそれぞれ以下の値をとった時の状態を示したものである。
φ＝０°｜β _max ／α _max ｜＝１．０ θ _bdr ＝３８．６°
【０１４２】
一方、本実施例においても、入射面８ａ，８ｂは、（３）式，（４）式に基づいて形成され、各係数ｋ、ｈは、以下の数値になるように各形状を規制している。
【０１４３】
ｋ＝０．１５ ｈ＝０．０８９
また、光学系の全体形状としては、閃光放電管の内径、外径は実施形態１と同様それぞれ、φ１．３、φ２．０とすると、光源と光学プリズムの各入射面までの最短距離をそれぞれｄ，ｅまた、光学系全体の奥行きｆ、光学プリズムの上下の開口をｇはそれぞれ以下のようである。
【０１４４】
ｄ＝０．３ ｅ＝０．３ ｆ＝４．８ ｇ＝７．１
このように光学プリズムの各形状を設定することによって、配光特性は均一で、光源中心から３６０°の方向に射出された光束をその約１／３６の１０°の角度範囲に狭めることが可能になる。
【０１４５】
実際には、光源には、ある有限の大きさを持っている為、光源の発光部の大きさに応じて、配光特性も全体に広がることになる。
【０１４６】
次に、本発明の実施形態５について説明する。図１３，図１４は、本発明の実施形態５の要部断面図である。図中３１は光学プリズム、３２は閃光放電管、３３は反射傘である。反射傘３３は閃光放電管３２と同心形状の反射部３３ａと、光学プリズム３１の全反射面３１ｃ、３１ｃ′の後方にほぼ光学プリズム３１の形状に近似した形状からなる反射部３３ｂ、３３ｂ′とから構成され、その他の各部の形状は、ほぼ上記実施例と同様で、対応箇所は同一の記号で示している。
【０１４７】
また、図１３と図１４は形状は同一形状であり、図中に示した光線トレース部のみが異なっており、図１３は光軸１Ｚ近傍に進んだ光束を入射させる入射面３１aから入射した成分を、図１４は全反射面３１ｃ、３１ｃ′に導く入射面３１ｂ、３１ｂ′に入射した成分をそれぞれ示している。
【０１４８】
本実施形態は、実施形態１とほぼ同等の配光特性をもたせつつ、全反射面３１ｃ，３１ｃ′の形状を工夫し、均一配光を得られるようにした変形光学系であり、実施形態１で示したような光学プリズム３１の全周に設けたリブ形状や光射出部の段差等は示していない。
【０１４９】
本実施形態の最大の特徴は、光源中心Ｏから射出される成分のうち特に全反射面３１ｃ，３１ｃ′によって制御される成分を、それぞれの全反射面に対して必要最大角から最小角までの範囲に、均一に分配していることである。
【０１５０】
すなわち、全反射面３１ｃと３１ｃ′のそれぞれの面で制御された成分が、光源中心Ｏからの射出角度に対応してある一定の割合で変換され、照射面上で必要とされる最大角度から最小角度に対応する分布に変換されていることである。
【０１５１】
まず、図１３を用いて、光学系の構成を説明する。実施形態１と同様各部の形状を実際の数値で示すと図中ｄ，ｅ，ｆ，ｇ，α_max，θ_bdrはそれぞれ以下の値をとる。
【０１５２】
ｄ＝０．５， ｅ＝０．５ ｆ＝４．６５ ｇ＝７．４８
α_max＝２０° θ_bdr＝３７．４４°
また、この時の光源中心Ｏから射出した主に射出光軸１Ｚに近い成分については、図示のように実施形態１とほぼ同一の分布を示し、光源３２から７４．８８°に広がった光束を、約半分の範囲である４０°の分布に変換することができる。
【０１５３】
実際の配光特性は、実施形態１でも説明したように光源の大きさが有限である為、光源の大きさによって広がるが、上記値を基に光源の大きさの補正を加えることによって必要とされる配光特性が得られる形状に変換することができる。
【０１５４】
次に、本実施形態の最も特徴的な全反射光の配光分布について、図１４を用いて説明する。まず、光源３２の上方に進んだ光束は、実施形態１同様１°の平面で構成された入射面３１ｂ，３１ｂ′を介して入射する。
【０１５５】
この入射面から入射した光束は、全反射面３１ｃ，３１ｃ′に導かれ、光学プリズム３１の後端の反射成分が光源から離れる方向の最大成分に対応し、射出部付近で反射した光束が射出光軸と交わる最大成分に対応するように変換される。
【０１５６】
特に、この時の変換が、射出光軸１Ｚから離れる方向の成分の最大値γ_max、射出光軸と交わる方向の成分の最大値β_maxがそれぞれ以下関係の角度となり、また光源中心からの射出角度に応じて、一定の割合で変換されるように形状を規制し、全体として均一な配光となるような形状を工夫している。
【０１５７】
α_max＝β_max＝γ_max＝２０°
一方、図示していないが、光源中心Ｏから射出光軸１Ｚ後方に向かった光束は、上記実施例同様、後方に配置した反射傘３３が光源３２に対して同心形状に配置されている為、基本的に光源中心の光束は反射後再度光源中心に戻り、光源のガラス管の悪影響を最小限にして、所望の配光特性を得られるような構成を達成することができる。
【０１５８】
また、上記実施形態５の構成では、光源中心Ｏから射出される光束が、それぞれの入射面及び全反射面によってそれぞれ最大角が一致するように規制したが、必ずしも完全に一致させる必要はなく、（５）式で規制される角度、または
０．８≦｜γ_max／α_max｜≦１．２ ……（７）
の範囲にあれば、十分に均一で効率の良い配光特性をえることが可能である。
【０１５９】
このように、照射角度の最大値の範囲をある一定の範囲を持たせている理由として、上述のように光源がある一定の大きさを持っていることに起因している。
【０１６０】
すなわち、光源がある大きさを持っていることによって、全体の配光は広がる方向にブレるが、このブレは、光源から近い位置に光線の射出方向を規制する面が存在するほど大きくなる。すなわち、光源から近い入射面３１ａや、全反射面３１ｃの後方で配光制御される成分は光源の大きさによるブレが生じ易やすく、実際現象では上記規制では配光が広がりやすい成分である。
【０１６１】
一方、光源から遠い位置で制御された、全反射面３１ｃ，３１ｃ′の射出面近傍で反射した成分は光源からの立体角が十分に小さくブレを生じにくい成分であり、光源が大きくても上記全反射面の形状規制によって効率良く必要照射角に変換できる部分である。
【０１６２】
このようなことから、上記広がりやすい成分の最大照射角、例えば、γ_max，α_maxを必要照射角度よりも狭めに設定することで、更に効率の良い角度変換を行うことができる。
【０１６３】
このことを関係式で示すと以下のようになる。
【０１６４】
γ_max≦β_max ， α_max≦β_max
実施形態１と同様、上記光学プリズム３１の各面の形状を上記定義式にのっとって求めた形状の近似式は以下のようである。ただし、入射面３１ａの形状に関しては、ほぼ実施形態１の形状と同一の為省略する。
【０１６５】
全反射面３１ｃを、近似式で表わすと、原点を光源中心Ｏとすると、

で表わされる。
【０１６６】
上記形状は実施形態１同様、厳密に上記近似式に一致させた形状に限定されるわけではなく、上記形状を近似する円筒面形状の組み合わせ等の近似形状でもほぼ同一の効果を得ることができ、光源の大きさに伴う許容範囲として、光学系の全体形状に対する光源の大きさ程度の誤差範囲まで含むものとする。
【０１６７】
また、上記実施例では、上下入射面３１ｂ，３１ｂ′、及び全反射面３１ｃ，３１ｃ′は上下対称形状としているが、特に対称形状に限定されるわけではなく、上下非対称形状としても良い。
【０１６８】
この理由として、例えば、上記閃光発光装置をカメラ等の撮影装置に装着して使用する場合、撮影光軸と照明系の照明光軸が異なる為、被写体面上で視差を生じるが、この場合照明系の照射光軸を被写体の距離に応じてある一定量撮影光軸に傾ける必要がある。
【０１６９】
この場合、上下の照射範囲の分布を上下非対称として対応させた方が上記光学系では有効である。また、上記説明のように、同一全反射面でも光源から離れて位置に存在する面の方が、指向性が高く狭い範囲に効率良く集光制御できる性質を利用して、光源付近に存在する入射面や全反射面は所定量やや狭目に集光させるようにやや集光性を強めて構成することによって、各面での配光分布を一致させ全体の配光特性を均一に、かつ照射範囲外に照射される成分を最小にした効率の良い集光光学系を形成することができる。
【０１７０】
上記説明のように、実施形態１の考え方とは異なる本実施形態のような光学プリズムの各面形状の設定方法でも、光源中心からの射出光束を必要照射範囲に対して均一に配分することができる。上記実施例の形状は上下方向の開口部の高さｇや光学系全体の奥行きｆは大型化するものの以下のような利点がある。
【０１７１】
すなわち、上記説明のように各入射面毎の照射範囲がほぼ一定であり、かつ連続した面形状となっている為、不連続点が生じず、むらのない均一な配光特性が得やすいこと、また、射出光軸中心に向かう成分、すなわち中心光量を規定する成分が、各入射面、全反射面の中心部付近の最も安定した領域を使用して指向させている為、各面の周辺部分で中心方向に指向させる場合に比べて中心光量変化に対する敏感度が低い、すなわち、光学プリズムの加工精度のばらつきや、部品間の寸法精度による位置関係の誤差等のによる部品間のばらつきが生じにくいので、安定して高い中心光量が得られるという点が挙げられる。
【０１７２】
次に、本発明の実施形態６について説明する。図１５，図１６は、本発明の実施形態６の要部断面図である。４１は光学プリズム、４２は閃光放電管、４３は反射傘である。
【０１７３】
反射傘４３は閃光放電管４２と同心形状の反射部４３ａと、光学プリズム４１の全反射面４１ｃ，４１ｃ′の後方にほぼ光学プリズムの形状に近似した形状からなる反射部４３ｂ，４３ｂ′とから構成され、その他の各部の形状は、ほぼ上記実施例と同様で、対応箇所は同一の記号で示している。
【０１７４】
また、図１５と図１６は各構成部品の形状は同一であり、図中に示した光線トレース部のみが異なっており、図１５は光軸近傍に進んだ光束を入射させる入射面４１aから入射した成分を、図１６は全反射面４１ｃ，４１ｃ′に導く入射面４１ｂ，４１ｂ′に入射した成分をそれぞれ示している。
【０１７５】
本実施形態は、実施形態１とほぼ同等の配光特性をもたせつつ、入射面及び全反射面の形状を工夫し均一配光を得られるようにした変形光学系であり、実施形態１で示したような光学プリズム全周に設けたリブ形状や光射出部の段差等は示していない。
【０１７６】
本実施形態の最大の特徴は、光源中心Ｏから射出される成分のうち、射出光軸１Ｚに近い角度成分は必要照射範囲の中心部分に集光させ、光源中心Ｏから照射光軸１Ｚに対し上下方向に照射されたは必要照射角度範囲の周辺部分に照射されるように各面形状を設定したものである。
【０１７７】
特に、光源中心Ｏから照射光軸１Ｚに対し上下方向に照射されたは成分のうち、光源４２に近い側の成分は光学プリズム４１の通過後射出光軸１Ｚから離れる方向に、射出面に近い側で全反射した成分は光学プリズム４１の通過後射出光軸１Ｚに交わる方向に、それぞれ光源からの射出角に応じて射出角度を変換している点である。
【０１７８】
そして、このように構成することによって、上記複数の入射面から入射した光束が合成されて、必要照射範囲に対して均一に照射されることになり、実施形態１及び、実施形態５とほぼ同等の配光特性をえることができる。
【０１７９】
まず、図１５を用いて、光学系の構成を説明する。実施形態１と同様各部の形状を実際の数値で示すと図中ｄ，ｅ，ｆ，ｇ，α_max,θ_bdrはそれぞれ以下の値をとる。
【０１８０】
ｄ＝０．５ ，ｅ＝０．５ ，ｆ＝５．０５ ，ｇ＝７．８７
α_max＝１０° θ_bdr＝３４．６５°
また、この時の光源中心から射出した主に射出光軸１Ｚに近い成分については、図示のようにこの入射面のパワーを強め、実施形態１の半分の約１０°に狭めている。この為、光源中心Ｏからこの入射面４１ａに入射する成分の最大値θ_bdrは３°程度狭くなっている。この為、光源中心から６９．３°に広がった光束を、約１／３の範囲である２０°の分布に変換することができる。
【０１８１】
実際の配光特性は、実施形態１でも説明したように光源の大きさが有限である為、光源の大きさによって広がるが、上記値を基に光源の大きさの補正を加えることによって必要とされる配光特性が得られる形状に変換することができる。
【０１８２】
次に、本実施形態の最も特徴的な全反射光の配光分布について、図１６を用いて説明する。まず、光源の上下方向に進んだ光束は、実施形態１同様１°の平面で構成された入射面４１ｂ，４１ｂ′を介して入射する。
【０１８３】
この入射面から入射した光束は、全反射面４１ｃ，４１ｃ′に導かれ、光学プリズム４１の後端の反射成分が光源から離れる方向の最大成分に対応し、射出部付近で反射した光束が射出光軸１Ｚと交わる最大成分に対応するように変換される。ここまでは、実施形態５と同様である。
【０１８４】
しかし、その照射角度範囲が異なっている。すなわち、この時の変換が、射出光軸から離れる方向の成分の最小値γ_min，最大値γ_maxであり、また射出光軸と交わる方向の成分の最小値β_min、最大値β_maxがそれぞれ図示のようであり、実施形態５では存在した光軸中心付近に向かう成分が抜けていることである。
【０１８５】
実際に本実施例で採用した図中の各パラメータは、以下のような数値設定を行ったものである。
【０１８６】
α_max＝β_min＝γ_min＝１０° ， β_max＝γ_max＝２０°
また、上記区画された成分は、それぞれ各面で光源中心Ｏからの射出角度に応じて一定の割合で変換されるような形状で規制されている為、光源中心Ｏから射出される光束は、全体として中心部と周辺部で重ね合わせが行われ、全照射範囲にわたって均一な配光に制御することができる。
【０１８７】
一方、図示していないが、光源中心Ｏから射出光軸１Ｚの後方に向かった光束は、上記実施例同様、後方に配置した反射傘４３が光源４２に対して同心形状に配置されている為、基本的に光源中心の光束は反射後再度光源中心に戻り、光源のガラス管の悪影響を最小限にして、所望の配光特性を得られるような構成を達成することができる。
【０１８８】
また、上記実施形態６の構成では、光源中心Ｏから射出される光束を、それぞれの入射面に応じて制御し、境界線すなわち図中の光軸から１０°の角度成分で一致させるように構成しているが、必ずしもこの角度で一致するように規制する必要はなく、両者の配光分布を一部重ねあわせたり、光源が有限の大きさを持っていることを考慮して各照射分布を狭めに設定し重ねあわせによって配光ムラが生じないような角度設定に便宜変更してもかまわない。
【０１８９】
実際に有効に機能する重ね合わせ量としては、以下で規定される程度の設定を行うことが望ましい。
【０１９０】
０．８≦｜β_min／α_max｜≦１．２ ……（８）
０．８≦｜γ_min／α_max｜≦１．２ ……（９）
上記説明のように、実施形態１の考え方とは異なる本実施形態のような光学プリズムの各面形状の設定方法でも、光源中心からの射出光束を必要照射範囲に対して均一に配分することができる。
【０１９１】
上記実施例の形状は上下方向の開口部の高さｇや光学系全体の奥行きｆはさらに大型化するものの以下のような利点がある。すなわち、上記説明のように各入射面毎の照射範囲を任意の角度範囲に設定することができる為、照射面上での配光分布を任意の分布に変換できること、例えば、中心光量のみを上昇させたり、周辺の配光を意図的に明るくするなど、照射面上での任意の配光特性をえることができ、その応用範囲は広い。
【０１９２】
上記各実施形態では、全反射面での配光分布特性の制御を照射光軸１Ｚを挟む、上下２種の全反射面で構成した例を示したが、必ずしも分割数はこの２面に限定されるわけではなく異なる特性３面以上の面で構成しても良い。
【０１９３】
例えば、照射光軸近傍の成分を増やす為、全反射面を３分割し、全反射光の一部を射出光軸中心に向かわせるように構成しても良い。このようにすることによって、例えば、中心光量のみが不足した場合、全体配光を大きくいじらずこのポイントのみ集光性を上げられる為、必要配光特性を補正する際に特に有効である。
【０１９４】
一方、逆にこの全反射によって制御される成分を射出光軸から離れる方向または、射出光軸に交わる方向のどちらか１種類のみで構成し、射出光軸近傍に向かった成分との合成で必要照射角範囲をカバーするように構成しても良い。
【０１９５】
このように構成することによって開口部の高さを狭くすることができ、光学系の全体形状をさらに小型化することが可能となる。
【０１９６】
また、上記各実施例では、光学プリズムからの射出角度が、光源中心から射出する角度θに比例するように各入射面、全反射面形状を設定してきたが、必ずしも上記比例関係にあるように変換させるような面形状に限定されるわけではない。
【０１９７】
例えば、プリズム面に入射される際に生じる表面反射によりプリズム面入射出時に光量損失を生じるが、この光量損失をあらかじめ考慮した補正関数で規定した各面構成として定義したり、照明光学系の照射すべき被照射体が平面である場合、周辺部では光源中心から距離が離れる為中心部に対して光量不足となるが、この光量不足を解消するように、あらかじめ、周辺光量を高めるような配光特性が得られるような各面形状を設定を行っても良い。
【０１９８】
さらに、以上の各実施形態では、プリズムの材料として光学樹脂材料、特にアクリル樹脂を想定して説明してきたが、プリズムの材料としては、この材料に限定されるものではなく、ガラス等の透過率の高い材料や、透過率の高い液体を封入したような材料を用いてもよく、上記材料に限定されるものではない。
【０１９９】
【発明の効果】
本発明によれば、本出願人が先に種々と提案した照明装置を更に改良し、撮影装置の照明光学系の全体形状を極端に小型化しつつ、そのときの必要照射範囲の配光特性を均一に保つこと、さらに、光学特性を低下させず、むしろ画角内に照射される有効エネルギを増加させることのできる照明装置及びそれを用いた撮影装置を達成することができる。
【０２００】
又本発明によれば、今までの照明光学系に比べて極端に小型、薄型化、そして軽量化を図ると共に、光源からのエネルギを高い効率で利用し、照射面上で均一な配光特性を保った照明ができるスチルカメラ、ビデオカメラ等に好適な照明装置及びそれを用いた撮影装置を達成することができる。
【０２０１】
この他本発明によれば、照明光学系の集光制御を光学プリズム内で行わせるため、所望の配光特性を持たせた照明光学系を極端に小型化できると共に、そのときの必要照射範囲に対する配光特性を均一に保つことが容易にできる。
【０２０２】
また、光学プリズム内での集光を全反射を利用して行っている為、同一光源に対するエネルギの利用効率が高く、小型しても光学特性を低下させずむしろ画角内に照射される有効エネルギを増加させることが可能になる。
【０２０３】
さらには、光学プリズムの各入射面及び全反射面を本発明の手法によって最適化することにより、必要画角内での照度分布を自由にコントロールすることが可能な照明装置及びそれを用いた撮影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の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図２】本発明の実施形態１の他の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図３】本発明の実施形態１の閃光発光装置を適用したカメラの斜視図
【図４】本発明の実施形態１の閃光発光装置を前方からみた斜視図
【図５】本発明の実施形態１の閃光発光装置を前方からみた分解斜視図
【図６】本発明の実施形態１の閃光発光装置を背面からみた分解者斜視図
【図７】本発明の実施形態２の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図８】本発明の実施形態２の他の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図９】本発明の実施形態３の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図１０】本発明の実施形態３の他の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図１１】本発明の実施形態４の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図１２】本発明の実施形態４の他の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図１３】本発明の実施形態５の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図１４】本発明の実施形態５の他の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図１５】本発明の実施形態６の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【図１６】本発明の実施形態６の他の光線分布を示す閃光発光装置の閃光放電管径方向の縦断面図
【符号の説明】
１，４，６，８、１１，３１，４１ 光学プリズム
２，１２，３２，４２ 閃光放電管（光源手段）
３，５，７，９，３３，４３………反射傘
２１ レリーズボタン
２２ カメラのモード切り替えスイッチ
２３ 液晶表示窓
２４ 測光装置の覗き窓
２５ ファインダー覗き窓
２６ カートリッジ装填蓋
２７ レンズ鏡筒
２８ カメラ本体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an illuminating device and a photographing device using the same, for example, a video camera, a film camera, a digital camera or the like that is attached to a part of a camera body (photographing body) and illuminates in conjunction with a photographing operation of the camera body. This is suitable for efficiently irradiating light (flash) to the subject side and photographing.
[0002]
[Prior art]
2. Description of the Related Art An illumination device used in a conventional photographing apparatus such as a camera is composed of a light source and optical components such as a reflector and a Fresnel lens that guide a light beam emitted from the light source forward (subject side).
[0003]
Among such illuminating devices, various illuminating devices have been conventionally proposed in which light beams emitted in various directions from a light source are efficiently condensed within a necessary irradiation angle of view.
[0004]
In particular, in place of the Fresnel lens that has been placed on the front side (subject side) of the light source in recent years, optical components using total reflection such as prisms and light guides can be placed to improve light collection efficiency and reduce size. What has been proposed has been proposed.
[0005]
For example, as shown in Japanese Patent Application Laid-Open No. 4-138438, the present applicant uses a lens having a positive refractive power for a light beam emitted forward from a light source, and a light beam emitted sideways from the light source to an optical member. The light is collected by a total reflection surface that reflects toward the front, and is emitted from the same exit surface (that is, the light beam that has been split in the optical path at the position of the entrance surface from the light source to the optical member is emitted from the same exit surface). We have proposed an illumination optical system using prisms with high light efficiency.
[0006]
Further, as a proposal for this improvement, in JP-A-8-262537, a prism is arranged in front of the light source, the overall shape of the illumination optical system is reduced, and the exit surface corresponding to the total reflected light of the prism Has been proposed that is inclined with respect to the optical axis.
[0007]
Further, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 8-234277 that a light beam using a light guide is taken into an optical member in the vicinity of the light source, and then total reflection is repeated in the optical member to collect and uniformly distribute the light. We have proposed an illumination optical system that converts light into light and uses less total light loss.
[0008]
[Problems to be solved by the invention]
In recent years, in a photographing apparatus such as a camera, the apparatus itself has been reduced in size and weight, while the photographing lens tends to have a high magnification zoom in order to provide high added value. In general, the photographic lens tends to gradually become darker due to the downsizing and higher magnification of such a photographic device. If you try to shoot under the same brightness conditions as before without using an auxiliary light source, camera shake will occur. In many cases, the photos did not look as expected.
[0009]
In order to compensate for this situation, in general, an imaging device such as a camera has a built-in illumination device (hereinafter referred to as a strobe device) as an auxiliary light source. As a result, the amount of light emission required for one shooting tends to increase. That is, if it is assumed that a strobe light is emitted once every two times in a photographing device such as a normal camera, the energy consumed for this illumination is said to account for 80% of the total consumption of the camera. ing.
[0010]
The increase in the use frequency of the strobe as described above further accelerates the increase in the ratio of power consumption in the strobe unit in the entire apparatus. In addition, since the taking lens is dark, more light is required to shoot subjects at the same distance with the same brightness, but the shape of the lighting device itself has become smaller with the downsizing of the taking device. The challenges imposed on this type of lighting device have become more severe than ever.
From such a background, in Japanese Patent Laid-Open No. 4-138438, a light beam emitted mainly to the side of a light source is incident on the optical member on the front surface of the flash light emitting device, and then totally reflected and collected in a certain direction. Consists of two upper and lower surfaces that illuminate and a surface that has a positive refractive power and condenses separately from the front surface. After condensing light from each surface, the light exits efficiently from the same exit surface to the subject. The illumination optical system of the form to make was proposed.
[0011]
However, this proposal is very effective in improving the illuminance near the center of the subject to be illuminated.
[0012]
Japanese Laid-Open Patent Publication No. 8-262537 discloses a lighting device obtained by improving the previously proposed lighting device. Japanese Patent Application Laid-Open No. 8-234277 discloses a configuration in which light in the longitudinal direction of a light source is obtained by repeating total reflection inside a light guide to form a uniform illumination optical system with little light loss. Yes.
[0013]
The present invention further improves the illuminating device previously proposed by the present applicant and makes the overall shape of the illuminating optical system of the photographing apparatus extremely small while making the light distribution characteristics of the required irradiation range uniform at that time. It is another object of the present invention to provide an illumination device and an imaging device using the illumination device that can maintain, and further increase the effective energy irradiated within the angle of view without degrading the optical characteristics.
[0014]
A further object of the present invention is to achieve extremely small, thin, and light weight compared to the conventional illumination optical system, and use the energy from the light source with high efficiency, and uniform light distribution on the irradiation surface. An object of the present invention is to provide an illumination device suitable for a still camera, a video camera, and the like that can perform illumination with characteristics maintained, and a photographing device using the illumination device.
[0015]
[Means for Solving the Problems]
  The illuminating device of the invention of claim 1 is an illuminating device comprising a light source means and an optical prism for irradiating a light beam from the light source means in an irradiated direction. Among the light beams from the first incident surface on which the light beam emitted near the emission optical axis is incident, the emission surface on which the light beam from the first incident surface is directly incident, and the light beam from the light source means, Each of these surfaces has a second incident surface on which a part of the light beam emitted at a large angle is incident, and a total reflection surface on which the light beam from the second incident surface is inclined and emitted from the emission surface. Has a certain correlation between the angle formed by the light beam emitted from the light source center of the light source means with respect to the emission optical axis and the emission angle with respect to the emission optical axis after passing through the emission surface, Maximum emission angle component α controlled at the first entrance surface_maxAnd the maximum emission angle component β controlled by the second entrance surface and the total reflection surface_maxBetween
      0.8 ≦ | β_max/ Α_max| ≦ 1.2
It is characterized by having a shape that satisfies this relationship.
[0016]
  The illuminating device of the invention of claim 2 is an illuminating device comprising a light source means and an optical prism for irradiating a light beam from the light source means in a direction to be irradiated. Among the light beams from the first incident surface on which the light beam emitted near the emission optical axis is incident, the emission surface on which the light beam from the first incident surface is directly incident, and the light beam from the light source means, Each of these surfaces has a second incident surface on which a part of the light beam emitted at a large angle is incident, and a total reflection surface on which the light beam from the second incident surface is inclined and emitted from the emission surface. Has a certain correlation between the angle formed by the light beam emitted from the light source center of the light source means with respect to the emission optical axis and the emission angle with respect to the emission optical axis after passing through the optical prism, and the first incidence The luminous flux from the surface corresponds to the component near the exit optical axis. Together to correspond to the peripheral portion of the required irradiation range of light beam incident from the second incident surface, the maximum exit angle component α controlled by a first incident surface_maxComponent β intersecting with the exit optical axis among the minimum exit angle components controlled by the second entrance surface and the total reflection surface_min, Component γ in the opposite direction_minBetween
    0.8 ≦ | β_min/ Α_max| ≦ 1.2
    0.8 ≦ | γ_min/ Α_max| ≦ 1.2
It is characterized by having a shape that satisfies the above relationship.
[0017]
  According to a third aspect of the present invention, in the first or second aspect of the present invention, the shape of the first incident surface is such that the angle formed by the light beam from the light source means and the exit optical axis when incident on the first incident surface is θ, Assuming that the exit angle emitted from the exit surface is α and the proportional constant k according to the required irradiation angle, α = k · θ and the shapes of the second entrance surface and the total reflection surface are as follows. When the angle θ formed with the exit optical axis at the time of incidence on the entrance surface, β the exit angle exiting from the exit surface, and a proportional constant h corresponding to the required irradiation angle,
    β = h · (θ−90 °)
It is characterized by having a relationship.
[0018]
  According to a fourth aspect of the present invention, in the first, second, or third aspect of the invention, the shape of the first incident surface is an angle formed by the light beam from the light source means and the exit optical axis when incident on the first incident surface. If θ is an emission angle emitted from the emission surface and α is a proportional constant k corresponding to the required irradiation angle,
    α = k · θ
The shapes of the second incident surface and the total reflection surface are defined as an angle θ formed by the light beam from the light source means and the exit optical axis when incident on the second incident surface, and an exit angle emitted from the exit surface by β, The angle connecting the boundary between the incident surface and the second incident surface and the light source center is θ_bdrIf the proportional constant h is set according to the required irradiation angle,
    β = h · {θ− (45 ° + θ_bdr/ 2)}
It is characterized by having a relationship.
[0019]
  According to a fifth aspect of the present invention, in the first aspect of the present invention, the shape of the first incident surface or the total reflection surface of the optical prism has a correlation with the emission angle from the center of the light source. It is characterized by being formed by a combination of surface shapes that approximate a continuous non-curved surface shape.
[0020]
  A sixth aspect of the present invention is the optical axis according to any one of the first to fifth aspects, wherein the output optical axis is a line connecting the boundary line between the first incident surface and the second incident surface of the optical prism and the light source center. Slope θ with respect to_bdrBut,
    25 ° ≦ θ_bdr≦ 45 °
It is characterized by being in the range of.
[0021]
  The invention of claim 7 is the invention of any one of claims 1 to 6, wherein the total reflection surface of the optical prism extends to a direction substantially coincident with the light source center of the light source means with respect to the emission optical axis direction. It is characterized by.
[0022]
  The invention of claim 8 is the invention of any one of claims 1 to 7, wherein the light source means is a straight tubular flash discharge tube.
[0023]
  The invention of claim 9 is the invention of any one of claims 1 to 8, wherein a reflector that reflects the emitted light beam from the light source means is disposed behind the light source means along the optical axis of the light source means, and The reflector is characterized in that at least a part of a substantially concentric reflecting surface centering on the center of the light source means is formed.
[0024]
  According to a tenth aspect of the present invention, in the invention according to any one of the first to eighth aspects, a reflector that reflects the emitted light beam from the light source means is disposed behind the light source means along the optical axis of the light source means. The reflecting umbrella is characterized by being arranged so as to wrap around at least a part of the total reflection surface of the optical prism.
[0025]
  An imaging device according to an eleventh aspect of the invention includes the illumination device according to any one of the first to tenth aspects.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 of the present invention will be described below with reference to the drawings. 1 and 2 are cross-sectional views of the main part of the first embodiment of the flash light emitting device of the present invention. FIGS. 3 to 6 show the illumination device according to the first embodiment of the present invention, and this example shows the flash light emitting device. 3 is a perspective view of a camera in which the flash light emitting device of the present invention is applied to the camera, FIG. 4 is a perspective view of only the flash light emitting device of FIG. 3 from the front, and FIG. 5 is an exploded view of only the flash light emitting device of FIG. FIG. 6 is an exploded perspective view of the flash light emitting device of FIG. 3 as viewed from the back.
[0032]
1 and 2 show the same shape, and shows what kind of light trajectory is drawn after that when the light beam emitted from the center of the light source enters each incident surface of the optical member. is there.
[0033]
In FIG. 3, reference numeral 11 denotes an optical prism of a flash light emitting device, which corresponds to an exit window from which irradiated light exits. 21 is a release button, 22 is an operation switch for switching various modes of the camera, 23 is a liquid crystal display window for notifying the user of the operation of the camera, and 24 is a viewing window of a photometric device for measuring the brightness of external light ( (Photometric window), 25 is a viewfinder window (observation window), 26 is a cartridge loading lid for loading a cartridge type film, 27 is a lens barrel having a photographing lens, and 28 is a camera body.
[0034]
Since each function except the flash light emitting device is a known technique, detailed description thereof is omitted here. In addition, the mechanical component of this invention is not limited to the above-mentioned structure.
[0035]
In FIG. 4, 15 is a fixing member for attaching the flash light emitting device to the camera, 16 is a lid of the fixing member 15, and 17 is a lead wire attached to a xenon tube or a reflector. 5 and 6 are exploded perspective views for explaining the internal structure of the flash light emitting device 101 shown in FIG. 3, and for the sake of simplification, the lid 16 and the lead wire 17 on the upper surface of FIG. Is not shown.
[0036]
5 and 6, reference numeral 11 denotes an optical prism, which has an optimum shape for simultaneously controlling the upper, lower, left, and right arranged in the emission direction of the flash light emitting device 101 with one member. The optical prism 11 is made of an optical resin material having a high transmittance such as acrylic resin, and includes a prism member for controlling the light distribution characteristics of illumination light from the flash light emitting device.
[0037]
  A prism surface 11d that controls light distribution characteristics in the left-right direction (X direction) is formed on the front surface of the optical prism 11 on the subject side. Further, the light distribution characteristics in the vertical direction (Y direction) are controlled mainly by a front incident surface 11a that makes a light beam emitted in front of the irradiation optical axis incident and converts it into a desired light distribution characteristic by refraction, and mainly irradiation light. An upper incident surface 11b for injecting a component emitted vertically with respect to the axis;UpThis is performed by a total reflection surface 11c that totally reflects a light beam incident from the side incident surface 11b. The shape will be described in detail later.
[0038]
In the figure, 12 is a straight tubular flash discharge tube (xenon tube) that emits flash light, and 13 reflects a component emitted backward from the light emission direction of the light beam emitted from the flash discharge tube 12 in the emission direction. The inner surface is made of a metallic material such as bright aluminum having high reflectivity.
[0039]
Reference numeral 14 denotes an elastic member for pressing the reflector 13 against the flash discharge tube 12 to restrict the position and preventing leakage between the nesa coat portion of the flash discharge tube 12 and the terminal soldering portion.
[0040]
In the above configuration, the camera body 28 is the above-described known technique. For example, when the camera body 28 is set in the “strobe auto mode”, after the release button 21 is pressed by the user, The central processing unit in the camera main body 28 determines whether or not the flash light emitting device 101 emits light based on the brightness of the external light measured by the photometric device and the sensitivity of the loaded film.
[0041]
When the central processing unit determines that “flash light emitting device emits light” under the shooting conditions, the central processing unit outputs a light emission signal, is attached to the reflector, and the flash discharge tube 12 is connected via the trigger lead wire 17. Make it emit light. The emitted light is emitted in the direction opposite to the irradiation optical axis, the light beam emitted through the reflector 13 arranged at the rear, and the light beam emitted in the irradiation direction is directly emitted from the optical prism 11 arranged on the front surface. The light enters the incident surface 11a, is converted into a predetermined light distribution characteristic, and is irradiated on the subject side.
[0042]
At this time, the vertical direction with respect to the subject is controlled by the incident surfaces 11a and 11b and the total reflection surface 11c of the optical prism 11, and the horizontal direction is controlled by the prism surface 11d formed on the subject side. It is changed so as to obtain optical characteristics.
[0043]
In the present embodiment, the shape of the optical prism is appropriately set in order to optimize the light distribution characteristic in the vertical direction (Y direction). Hereinafter, a method for setting the optimum shape of the optical prism 11 will be described in detail with reference to FIGS.
[0044]
1 and 2 are longitudinal sectional views in the radial direction (X direction) of the flash discharge tube 12 of the flash light emitting device 101. Reference numeral 1 denotes an optical prism for controlling the light distribution, which corresponds to the optical prism 11 shown in FIGS.
[0045]
Reference numeral 2 denotes a cylindrical flash discharge tube, and 3 denotes a substantially semi-cylindrical reflector that is concentric with the flash discharge tube. FIGS. 1 and 2 also show the tracking of the representative light beam emitted from the central portion of the inner diameter of the flash discharge tube 3 at the same time. FIG. 1 is close to the emission optical axis (illumination optical axis, optical axis) 1Z. FIG. 2 shows a ray trace of a component whose component is controlled only by refraction by the optical prism 1, and FIG. Is shown.
[0046]
1 and 2, the configuration and shape of all optical systems other than the light beam are the same. Embodiment 1 shown here is characterized in that the opening height in the vertical direction can be minimized while keeping the light distribution characteristic in the vertical direction (Y direction) uniform. Hereinafter, the characteristics of the shape and the behavior of the light beam at that time will be described in detail.
[0047]
First, in FIG. 1, the flash discharge tube 2 shows the inner and outer diameters of a glass tube. In order to improve efficiency, the light emission phenomenon of an actual flash discharge tube of this type of flash light emitting device is often emitted to the full inner diameter, and it is considered that the flash discharge tube emits light almost uniformly over the full inner diameter. There is no problem.
[0048]
However, at the design stage, in order to efficiently control the light emitted from the flash discharge tube (light source) 2, it is ideal that there is a point light source at the center of the light source, rather than considering all the luminous fluxes of this inner diameter at the same time. Assuming that the shape of the optical system is designed and then correction is made in consideration of the fact that the light source has a finite size, it is possible to design efficiently.
[0049]
Based on this idea, the present invention also considers the center of the light emitting part of the light source 2 as a reference value for determining the shape, and sets the shape of each part of the optical prism 1 as follows.
[0050]
First, as the material of the optical prism 1, it is optimal to use an optical resin material such as an acrylic resin from the viewpoint of moldability, cost, and optical characteristics. However, in this type of flash light emitting device, a large amount of heat is generated simultaneously with the generation of light from the light source. It is necessary to select the optical material and set the heat dissipation space in consideration of the heat energy generated in one light emission and the shortest light emission period.
[0051]
At this time, it is the respective incident surfaces of the optical prism that are closest to the light source that are actually most susceptible to heat, and it is necessary to first determine the minimum distance between the light source and the incident surface. In the first embodiment, the minimum distance between the light source and the first incident surface 1a that directly controls the angle component whose exit angle from the light source center is close to the exit optical axis is d, and is separated from the exit optical axis (optical axis) 1Z. The distance between the second incident surface 1b on which the light controlled by the total reflection with the selected angle component is incident and the light source is defined as e, and the interval is regulated.
[0052]
  Next, the total reflection surface 1 of the optical prism 1cThe shape of the second incident surface 1b that guides incident light is determined. In order to minimize the shape of the optical prism, the second incident surface 1b is preferably a plane parallel to the optical axis 1Z.
[0053]
That is, the component of the luminous flux emitted from the light source that travels in a direction different from the exit optical axis is refracted once at the incident surface 1b. The closer the angle of this surface is to the optical axis direction, the greater the refraction effect. This is because the incident light can be guided once away from the optical axis by refraction, and the total length of the optical prism can be kept short.
[0054]
The inclination of the second incident surface 1b with respect to the optical axis 1Z is determined by the molding conditions of the optical prism. The smaller the angle is, the more severe the actual molding conditions are. However, the ideal shape of the maximum angle φ of the incident surface 1b is within the following range regardless of whether the incident surface 1b is flat or curved. It is desirable to do.
[0055]
0 ≦ φ <2 ° …… (1)
Here, the angle φ = 0 indicates that the incident surface 1b is parallel to the optical axis 1Z.
[0056]
The above range is a set value that seems to be severe at first glance, but is a sufficiently possible value because the distance of the second incident surface is short and the surface shape is a smooth surface. By regulating the inclination of the second incident surface 1b as described above, the opening area in the vertical direction is minimized and the efficiency is not reduced.
[0057]
Next, the shape of the incident surface of the first incident surface 1a is determined. In the present embodiment, in order to make the necessary irradiation range uniform light distribution with the minimum shape, the shape of the first incident surface 1a is defined by the following method.
[0058]
In the first embodiment, a shape that gives a certain correlation between the exit angle of the light beam from the center of the light source and the exit angle after passing through the optical prism 1, that is, the exit angle from the light source center O is set. θ and the irradiation angle after exiting from the optical prism 1 controlled by the refractive surface 1a is α,
α = f (θ) (2)
The shape of the incident surface 1a of the optical prism is defined by a continuous aspheric shape represented by
[0059]
In particular, in the present embodiment, the correlation is set so as to have a proportional relationship.
[0060]
That is, if the angle formed with the optical axis 1Z at the time of incidence of the incident surface 1a is θ, the emission angle emitted from the emission surface 1d is α, and the proportionality constant according to the required irradiation angle is k.
α = k · θ (3)
The shape is expressed as
[0061]
On the other hand, the surface shape of the second incident surface 1b and the shape of the total reflection surface 1c are defined by the following method in order to make the necessary irradiation range uniform light distribution with the minimum shape in this embodiment. .
[0062]
In the first embodiment, a shape that gives a certain correlation between the exit angle of the light beam from the center of the light source and the exit angle after passing through the optical prism 1, that is, the exit angle from the center of the light source is θ. When the irradiation angle after emission from the optical prism 1 controlled by the total reflection surface 1c is β,
β = g (θ) (4)
It is formed by the continuous aspherical shape represented by these.
[0063]
In particular, in the present embodiment, the correlation is set so as to be proportional.
[0064]
That is, if the angle θ formed with the optical axis at the time of incidence, β the exit angle exiting from the exit surface 1d, and h the proportionality constant according to the required illumination angle,

The shape is expressed as
[0065]
In this embodiment, β is an exit angle emitted from the exit surface, and θ is an angle connecting the boundary between the first entrance surface and the second entrance surface and the light source center._bdrIf the proportional constant h is set according to the required irradiation angle,
β = h · {θ− (45 ° + θ_bdr/ 2)}
To be in a relationship.
[0066]
The meaning of the above equation (2) is that the light beam incident from the incident surface 1a that makes the angle component near the exit optical axis 1Z incident first, the light beam traveling from the light source center to the exit optical axis passes through the optical prism 1 as it is. pass.
[0067]
With this as the base point, the light is emitted from the exit surface after being multiplied by a proportional constant k from the exit surface 1d of the optical prism in accordance with the exit angle θ from the light source center. Here, the proportionality constant k is a constant from 0 to 1.
[0068]
Here, k = 0 means the most condensed state in which all the emitted light beams are converted in parallel with the emission optical axis, and k = 1 means the angle θ when incident on the optical prism and the angle α when emitted. Means a shape without equal angle conversion, that is, a shape that cancels the power of each surface that is not affected by the refractive index before and after entering and exiting the optical prism, for example, a shape that makes the entrance and exit surfaces flat. To do.
[0069]
On the other hand, equation (5) has the following meaning. First, the light beam emitted upward from the center of the light source with respect to the irradiation optical axis is incident from the incident surface 1b, reflected by the total reflection surface 1c, and then emitted from the light emission surface 1d. At this time, the component having the largest emission angle incident on the optical prism 1 from the light source, that is, the component perpendicular to the emission optical axis 1Z is converted to the component closest to the direction of the optical axis substantially parallel to the irradiation optical axis. The
[0070]
On the other hand, a light beam incident from a portion close to the intersection with the incident surface 1a is converted into a component that intersects with the largest angle β with respect to the emission optical axis 1Z. This intermediate region gradually changes within the angle range in proportion to the injection angle. Also in this case, as described above, the proportionality constant h changes from 0 to 1, and h = 0 means that all the emitted light is converted in parallel with the emitted optical axis, which is the most condensed state. Further, h = 1 means that only the surface without the change amount of the incident angle and the change amount of the exit angle, that is, the irradiation direction having no light condensing effect in the optical prism is changed. That is, it is a surface configuration that provides an effect like a plane mirror placed in the air.
[0071]
Next, the relationship between the light distribution by the refracted light by the incident surface 1a formed by the above method and the light distribution by the total reflected light by the incident surface 1b and the total reflection surface 1c will be described. As described above, the light distributions of the two can be controlled independently by their surface shapes. When the inner diameter of the light source is sufficiently small, or when the optical prism can be considered sufficiently large with respect to the light source, the light distribution distribution can be controlled fairly efficiently by the above method.
[0072]
However, when considering the actual light distribution characteristics, the size of the inner diameter, which is the effective light emitting portion of the light source, is often not small enough to be ignored, and this influence has a large influence on the overall light distribution characteristics. In particular, the reflected light flux at the control surface near the light source, for example, the incident surface 1a on which the angle component near the optical axis is incident, or the prism rear end near the light source even on the total reflection surface 1c, has a finite size. Therefore, it is necessary to set the shape by taking this factor into consideration to some extent.
[0073]
On the other hand, in the total reflection surface 1c, since the emission direction of the component close to the emission part is controlled at a position far away from the light source, the light distribution can be controlled to an intended range considerably efficiently with little blurring. In consideration of such characteristics, it is necessary to define the shapes of the respective incident surfaces and total reflection surfaces.
[0074]
For the above reasons, the characteristics of the light distribution controlled by the respective incident surfaces are different and can be controlled independently. In the first embodiment, the luminous flux directed toward the upper side of the light source among these characteristics is incident on the incident surface 1b. Then, after being reflected by the total reflection surface 1c, the angle is uniformly converted from the exit optical axis 1Z to the required irradiation angle, and the light beam directed to the lower side of the light source is incident on the incidence surface 1b 'and then the total reflection surface. After reflection at 1c ', the angle is uniformly converted from the exit optical axis 1Z to the required irradiation angle on the upper side.
[0075]
Further, the shape of the incident surface 1a is set so that the light beam directed toward the vicinity of the exit optical axis substantially coincides with the light distribution by the component incident from the side. In this way, the light distribution distribution from each incident surface can be converted into a small and efficient light distribution distribution if they are matched to some extent except when a special light distribution is required. Therefore, in general, as a practical method for regulating the light distribution characteristics, it is desirable that each value exists in the following region that defines the maximum control angle at each incident surface.
[0076]
  Maximum angle component due to refracted light at the incident surface 1a; α_max, The maximum emission angle component by the total reflection light on the total reflection surface 1c; β_maxWhen
      0.8 ≦ | β_max/ Α_max| ≦ 1.2 …… (5)
It is to do.
Next, the position of the boundary surface of the incident surface will be described. As described above, the first incident surface 1a and the second incident surface 1b can be used efficiently and in consideration of the influence of heat on the resin material of the incident surface. It is desirable that the angle of the straight line connecting the coordinates of the intersection of the light source and the center of the light source is within a certain range.
[0077]
That is, if this angle is smaller than the predetermined angle, the distance to the first incident surface 1a is increased, and the light collection efficiency is increased because the distance to the first incident surface 1a is less affected by the size of the light source. Incidence angle increases and loss due to surface reflection at the incident surface is likely to occur.
[0078]
  On the other hand, if this angle is larger than the predetermined angle, the incident light flux from the first incident surface 1a that needs to be controlled on the surface close to the light source increases, and it is difficult to obtain a sufficient light collecting effect depending on the size of the light source. Therefore, it is desirable that the angle of the straight line be within the following numerical range. That is, the boundary between the incident surface 1a that controls light directed toward the front of the optical prism 1 only by refraction and the incident surface 1b that mainly guides light emitted obliquely forward from the light source to the total reflection surface 1c, and the light source center The slope of the line connecting_bdrThen,
      25 ° ≦ θ_bdr≦ 45 ° …… (6)
It is desirable from the viewpoint of efficiency and light collection control to be in this range.
[0079]
Next, the shape of the intersection of the incident surface 1b of the optical prism 1 and the total reflection surface 1c will be described.
[0080]
In the first embodiment of the present invention, the intersections are formed so as to form an acute angle by directly intersecting with each other, and the intersections and the center position of the light source are substantially aligned in the front-rear direction.
[0081]
Such a configuration is an effective means for efficiently performing light distribution control while minimizing the shape of the optical prism. That is, for example, when a surface having different characteristics is formed between the incident surface 1b and the total reflection surface 1c, for example, a surface perpendicular to the optical axis as shown in JP-A-8-262537, the surface is formed. Not only does not function as an optical system, but also leads to an increase in the size of the optical prism in the vertical direction and depth direction.
[0082]
On the other hand, in this embodiment, the position of this intersection and the position in the front-rear direction of the center of the light source coincide with each other, but this is a shape necessary for reducing the size of the entire optical system and increasing efficiency, and within the prism. There is a close relationship with the relationship with the total reflection angle and the shape of the reflector according to the light source, and the shape is regulated.
[0083]
That is, when the angle of the incident surface 1b is set to around 0 ° for the total reflection in the prism and the optical prism is made of a resin material, the refractive index is around 1.5, and the intersection of the prism surfaces extends to the rear. As a result, a component that is not completely reflected and exits behind the prism is generated. This is more likely to occur as the inner diameter of the light source is larger, and a part of the component emitted from the front of the light source center escapes from the total reflection surface 1c.
[0084]
In the present embodiment, a configuration is adopted in which the reflector 3 that returns the light that escapes behind the total reflection surface 1c back into the optical prism 1 is partially extended to the back of the total reflection surface 1c. Then, the reflector 3 is extended to the maximum size that effectively functions as a reflector, and then incident on the incident surface of the optical prism 1.
[0085]
The optimum shape of the reflector is a semi-cylindrical reflector that is concentric with the flash discharge tube 2 that is a light source, the front end of the opening of the reflector is substantially aligned with the longitudinal direction of the center of the light source, and The rear end of the optical prism is also substantially coincident with the center of the light source.
[0086]
The reason why the shape of the reflector is concentric with the center of the light source and the front end thereof coincides with the center of the light source is, first, the influence on the glass portion of the flash discharge tube. In the extremely small light emitting optical system as in the present embodiment, it is necessary to reflect the light beam directed backward from the light source by the reflector and direct it in the irradiation direction, but the entire optical system is downsized. Because there is not enough room to control the light distribution by turning the outside of the flash discharge tube without passing through the inside of the flash discharge tube, all the light reflected by the reflector is re-entered in the glass tube of the flash discharge tube. It is necessary to use an incident optical path.
[0087]
At this time, the component re-incident on the flash discharge tube is affected by refraction and total reflection at the glass portion of the flash discharge tube, and has a great influence on the incident component on the optical prism. In particular, the thicker the glass, the more conspicuous. If the shape of the light source and the shape of the reflecting umbrella do not correspond appropriately, the distribution of reflected light from the reflecting umbrella will spread more than necessary.
[0088]
Therefore, if the reflector is made into a cylindrical shape corresponding to the shape of the light source and concentric with the cylindrical glass portion of the flash discharge tube, the incident angle when re-entering the flash discharge tube becomes small, and the glass tube There is little loss due to surface reflection on the surface, and the component that is totally reflected in the glass tube of the light beam after re-incidence is reduced, which is efficient.
[0089]
In particular, if the gap with respect to the light source 2 is small, the angle change after reflection by the reflector 3 is small, which is particularly effective. Also, the reason for making the reflecting umbrella into a semi-cylindrical shape that almost coincides with the position of the light source center is that if the reflecting umbrella is made longer than this, the reflecting umbrella will wrap around to the front, and light will be trapped in the reflecting umbrella, so efficiency is increased. If the reflector is made shorter than the center of the light source, the rear end of the optical prism extends to the rear as described above, resulting in not only a loss of light quantity but also an increase in the entire optical system. Therefore, it is not a preferable configuration.
[0090]
Next, the relationship between the emission angle of the light beam from the light source in Embodiment 1 and the emission angle from the exit surface 1d after passing through the optical prism 1 will be described using specific numerical values.
[0091]
First, in consideration of the influence of heat generated during the light emission, the distances d and e of the incident surfaces 1a and 1b of the optical prism 1 are set to the flash discharge tube 2 (outer diameter φ2.0, inner diameter φ1.3), respectively. They were placed 0.5 mm apart.
[0092]
For simplicity, the shape of the incident surface 1b on the upper surface leading to the total reflection surface 1c is a flat surface with an inclination of 1 ° spreading toward the rear side of the emission optical axis 1Z. This value is a value that exists within a range that satisfies the conditional expression (1).
[0093]
Further, the light beam emitted from the central portion of the light source is controlled by total reflection at each incident surface and total reflection surface and is emitted from the light emission surface 1d, the light distribution is uniform, and the irradiation angle α_max, β_maxA description will be given by taking as an example a shape in which the maximum value of each becomes 20 °.
[0094]
  That is, | β_max/ Α_max| = 1 and the conditional expression (5) Is satisfied. First, in the shape optimized under this condition, the slope θ of the line segment connecting the boundary line between the incident surface 1a and the incident surface 1b and the light source center_bdr, The depth f including the reflector that contributes to the vertical focusing, and the upper and lower openings g that contribute to the vertical focusing, respectively,
      θ_bdr= 37.44 °, f = 4.40, g = 6.70
And the inclination θ_bdrIs the above (6) Is in a range that satisfies the equation. Further, as shown in the above values, it can be made extremely small compared with the light emitting optical system of the conventional type flash light emitting device.
[0095]
Also, in the figure, assuming an actual product, a shape for projecting the optical prism to the external portion on the front side portion of the optical prism, that is, a thin rib 1e extending over the entire circumference on the extension of the total reflection surface of the optical prism, 1e 'is integrally formed.
[0096]
This is a combined shape with an external member (not shown), and is added for the following purpose while preventing unnecessary internal parts from being seen through the gap between the optical prism and the external parts.
[0097]
That is, a trigger leak between a reflector made of metal and a metal cover used as an exterior part, or a conductive object placed on the extension of the gap between the optical prism and the exterior part. This is to prevent the occurrence of light emission and the inability to emit light.
[0098]
In general, in a flash light emitting device such as the present invention, a high voltage trigger signal is directly applied to a flashlight discharge tube to a reflector, and light emission is started via a nesacoat portion of the discharge tube in contact with the reflector. In a miniaturized optical system as in the present invention, a trigger leak phenomenon is likely to occur because the distance between the reflector and a metal-made exterior part or a conductive material outside the product is short.
[0099]
As described above, by adding the ribs 1e and 1e 'to the total reflection surface extension portion of the optical prism, the edge surface distance can be extended, and the trigger leak phenomenon can be prevented in advance.
[0100]
At the same time, the invasion of dust and water droplets from the outside, especially water droplets, has a risk of electric shock with internal high-voltage components, but this risk can be prevented at the same time. it can. Assuming that the length i of this additional portion and the length j of the appearance opening are:
i = 1.0 j = 6.5
The length j of the appearance opening is slightly narrower than the upper and lower openings g that contribute to light collection in the vertical direction.
[0101]
This is because the component totally reflected in the vicinity of the tips of the total reflection surfaces 1c and 1c 'is a component that intersects at a considerably large angle in the direction of the emission optical axis. From this, it is sufficient to reduce the length of the external opening. It becomes possible.
[0102]
Further, a vertical prism for performing light distribution control in the left-right direction is formed at the tip of the additional portion as shown in FIG.
[0103]
On the other hand, as can be seen from the ray trace in the figure, it can be seen that the uniform light distribution characteristic, which is one of the objects of the present invention, is sufficiently satisfactory. First, as shown in FIG. 1, a light beam emitted from the center of the light source and emitted at an angle close to the emission optical axis 1Z is refracted by the incident surface 1a. Equation (3) holds between the exit angle α from the exit surface 1d, and the coefficient k at that time is
k = a_max/ Θ_bdr= 20.0 ° / 37.44 ° = 0.534
Therefore, the general formula is
α = 0.534 · θ (however, −37.44 ° ≦ θ ≦ 37.44 °)
It can be seen that the emission components from the light source are evenly allocated according to the emission angle and are emitted from the emission surface 1d of the optical prism 1.
[0104]
On the other hand, as shown in FIG. 2, the light beam emitted from the light source center O and traveling upward with respect to the emission optical axis 1Z is controlled by total reflection at the total reflection surface 1c after being refracted at the incident surface 1b. In this conversion, the equation (5) is established between the incident angle θ and the exit angle β from the light exit surface 1d, and the coefficient h at that time is
h = β_max/ (90 ° -θ_bdr) = 20.0 ° / 52.56 ° = 0.382
Therefore, the general formula is
β = −0.381 · {(90 ° * | θ | −θ ** 2) / θ}
(However, 37.44 ° ≦ | θ | ≦ 90 °)
The emission components from the light source are uniformly allocated according to the emission angle, and the optical prism 1 is uniformly distributed with a density distribution different from the distribution of the components emitted at an angle close to the emission optical axis shown above. It can be seen that the light is emitted from the exit surface 1d.
[0105]
On the other hand, although not shown, the optical path of the light beam traveling behind the emission optical axis 1Z of the flash discharge tube 2 will be described. Behind the emission optical axis is a cylindrical reflector 3 concentric with the light source center O, and the glass tube of the flash discharge tube 2 is also concentric with the light source center. All return to the center of the light source again without being affected by refraction by the glass tube.
[0106]
Further, regarding the behavior of the light beam after returning to the center of the light source, the subject to be irradiated is irradiated with uniform characteristics having substantially the same characteristics as the ray tracing shown in FIGS.
[0107]
In addition, the reflector 3 wraps behind the total reflection surface 1c of the optical prism 1 to substantially the front end of the flash discharge tube as a light source, and the shape thereof is substantially the same as that of the reflection surface 1c. The inner diameter portion of the glass tube, which is the light emitting portion of the flash discharge tube, also exists on the front side from the center of the light source. This is to prevent this.
[0108]
In this way, by making the shape almost the same as the total reflection surface and disposing it immediately behind the total reflection surface, the effect of the total reflection surface 1c is almost the same, and the distribution can be efficiently and uniformly distributed over the required irradiation range. It becomes.
[0109]
Next, an approximate value of the aspherical shape of the optical prism based on the above definition will be described. First, the shape of the incident surface 1a can be approximately approximated by the following expression when the apex is P and this is the origin.
[0110]

Similarly, when the total reflection surface 1c is also expressed by an approximate expression, if the origin is the light source center O,

It is represented by
[0111]
However, assuming that the light source is a point light source, it is desirable to match the above shape, but in reality the light source has a finite size that corresponds to the inner diameter of the flash discharge tube, so the shape is strictly regulated so far. Even if not, almost the same light distribution characteristics can be obtained.
[0112]
For example, even if a single or a plurality of cylindrical surfaces approximating the above shape or a quadratic curved surface such as an ellipse are used, there is a shape that can obtain substantially the same effect as the light distribution characteristic obtained by the above shape.
[0113]
For this reason, the shapes of the incident surfaces 1a and 1b and the total reflection surface 1c in the present invention are not limited to shapes that strictly satisfy the above-described formula, but approximately satisfy the shapes of the surfaces of the optical prism. It shall be specified including the shape.
[0114]
In addition, by forming an optical prism with such an approximate shape, it is extremely easy to measure whether the actually processed product is as designed, compared to when the surface shape is aspherical. There is.
[0115]
In fact, even when an optical prism manufactured in such an approximate shape is used, the difference between the shape shown in the above formula and the light distribution characteristic is not so great.
[0116]
Next, some other embodiments in which the shape of the optical prism is regulated based on the concept of the first embodiment will be described.
[0117]
7 and 8 are plan views of the essential portions of Embodiment 2 of the flash light emitting device of the present invention. This figure shows a main cross-sectional view of an optical system for uniformly illuminating a relatively wide irradiation range, and a ray tracing diagram in this shape.
[0118]
In the same figure, 4 is an optical prism, 5 is a reflector, and each figure has the same optical system shape, and only the ray tracing portion is shown separately for each of the incident surface 4a and the incident surface 4b.
[0119]
  Particularly, in the second embodiment, the angle of the total reflection surfaces 4c and 4c ′ for reflecting the light beam emitted from the light source in the vertical direction is the minimum value in the range shown in (1), and the optical prism controlled by each incident surface is used. Shows the relationship of each injection maximum angle after passing (5) And the angle between the line segment connecting the boundary line of the incident surface 4b and the light source center to the total reflection surfaces 4c and 4c 'and the exit optical axis (6) Is the maximum value in the range indicated by
      φ = 0 °
      ｜ β_max/ Α_max| = 1.0
      θ_bdr= 45 °
This shows the state.
[0120]
Further, the incident surface 4a on which an angle component close to the irradiation optical axis 1Z is incident from the light source center O is a plane perpendicular to the emission optical axis, and the total reflection surface 4c satisfies the formula (5) and is an optical prism. The surface configuration is such that the angle distribution obtained by changing only the direction of the light beam by passing through 4 does not change, that is, has a characteristic like a plane mirror placed in the air.
[0121]
  That is, the coefficient k in equation (3), (4The coefficient h in the equation (1) is a shape when the following values are taken.
[0122]
k = 1.0 h = 1.0
Similarly to the first embodiment, the reflector 5 is configured by a cylindrical surface 5 a concentric with the light source 2 and a curved surface portion 5 b that goes around the total reflection surfaces 4 c and 4 c ′ of the optical prism 4.
[0123]
In the above configuration, the behavior of light rays in each state will be described. First, the light beam incident on the incident surface 4a from the light source 2 shown in FIG. 7 is an optical prism because the incident surface 4a and the exit surface 4d are both parallel planes perpendicular to the exit optical axis 1Z as shown in the figure. 4 refracts at the time of incidence and emission, but the angle of the light beam itself does not change.
[0124]
That is, passing through the optical prism 4 strictly causes some spectral loss due to surface reflection on each surface, but basically there is no condensing and diffusing effect before and after passing through the optical prism 4, and the light source The light distribution characteristics from 2 are reflected on the irradiation surface as they are.
[0125]
On the other hand, as described above, the light beams incident from the incident surfaces 4b and 4b 'are converted by the total reflection surface 4c so that the angle distribution after emission from the optical prism 4 is constant and only the irradiation direction is changed.
[0126]
That is, the light beam from the light source center O toward the vicinity of the vertex at the back of the optical prism 4 is converted into the direction of the exit optical axis, and the light beam toward the vicinity of the intersection with the incident surface 4a is emitted from the incident surface 4a. It is configured so as to be converted into a direction that coincides with the maximum angle of light and that is symmetric with respect to the irradiation optical axis 1Z.
[0127]
Although not shown in the figure, the light beam directed from the light source center O toward the rear of the emission optical axis 1Z is formed concentrically with the light source and is returned to the light source center O again by the reflector 5. For this reason, the light flux returned to the light source center O is converted into a uniform light distribution by drawing a ray trace as shown in FIGS.
[0128]
By using the optical system having the above-described configuration, the light beam emitted from the center of the light source can be uniformly irradiated in a range of 90 ° ranging from −45 ° to 45 °. Actually, the light emitting point of the light source emits light not only at the center of the light source but also at the entire inner diameter of the light source. For this reason, the actual light distribution characteristic is somewhat wider than the above range.
[0129]
Further, in this way, when the light source is so large that it cannot be ignored with respect to the shape of the entire optical system, a part of the light beam emitted forward from the portion in front of the light source center set here is reflected on the total reflection surface 4c. There may be a component that is not completely reflected and exits the optical prism 4.
[0130]
The reflection surface for re-entering the light beam emitted from the total reflection surface 4c into the optical prism 4 is a reflection surface 5b disposed behind the total reflection surface 4c of the reflector 2, and as shown in the figure, the total reflection surface 4c. And a uniform light distribution characteristic substantially equal to the light distribution by the total reflection surface 4c can be obtained.
[0131]
The configuration of the second embodiment shows a minimum shape among optical systems that convert a light beam emitted from the light source center O into a uniform light distribution characteristic. Specific numerical values at this time are shown below. When the inner diameter and outer diameter of the flash discharge tube are φ1.3 and φ2.0, respectively, as in the first embodiment, the shortest distances between the light source and each incident surface of the optical prism are d and e, respectively, and the entire optical system Depth f and upper and lower openings g of the optical prism are as follows.
[0132]
d = 0.3 e = 0.3 f = 3.3 g = 4.7
Thus, the optical prism can be configured to be extremely small with respect to the light source. In addition, the light distribution characteristic at this time is uniform, and the light beam emitted in the direction of 360 ° from the center of the light source can be narrowed to an angle range of 90 °, which is about ¼.
[0133]
Next, a third embodiment of the present invention will be described. 9 and 10 are cross-sectional views of main parts of Embodiment 3 of the present invention. The change from the second embodiment is that the range of the emitted light beam after passing through the optical prism 6 from the light source center O is narrowed to about half. In the figure, 6 is an optical prism, 7 is a reflector, and each component is the same as in Embodiment 2. The relationship of the reflector 7 with respect to the flash discharge tube 2 is a light beam that cannot be controlled by the optical prism 6. It is configured to be used efficiently.
[0134]
Further, the relationship between the angle φ of the incident surfaces 6b and 6b ′ with respect to the optical axis 1Z, the maximum emission angle after the control on each incident surface, the line segment connecting the boundary line of the incident surface and the light source center, and the emission optical axis. Angle θ_bdrIn this case, the present embodiment shows the state when the following values are taken.
[0135]
      φ = 0 ° | β_max/ Α_max| = 1.0 θ_bdr= 38.7 °
  On the other hand, also in the present embodiment, the incident surfaces 6a and 6b are expressed by Equation (3), (4) And the respective coefficients k and h regulate each shape so as to have the following numerical values.
[0136]
k = 0.60 h = 0.45
Further, as the overall shape of the optical system, if the inner diameter and outer diameter of the flash discharge tube are φ1.3 and φ2.0, respectively, as in the first embodiment, the shortest distance between the light source and each incident surface of the optical prism 6 is as follows. D, e, depth f of the entire optical system, and g above and below the opening of the optical prism are as follows.
[0137]
d = 0.3 e = 0.3 f = 3.9 g = 5.7
By setting each shape of the optical prism 6 in this way, the light distribution characteristic is uniform, and the light beam emitted in the direction of 360 ° from the center of the light source can be narrowed to an angle range of 46 °, which is about 1/8. It becomes possible.
[0138]
Actually, since the light source has a certain finite size, the light distribution characteristic spreads over the whole according to the size of the light emitting portion of the light source.
[0139]
Next, a fourth embodiment of the present invention will be described.
[0140]
11 and 12 are cross-sectional views of main parts of Embodiment 4 of the present invention. A change from the second embodiment is that the range of the emitted light beam after passing through the optical prism 8 from the light source center O is extremely narrowed. In the figure, 8 is an optical prism, 9 is a reflector, and each component is the same as in the second embodiment. The relationship of the reflector 9 with respect to the flash discharge tube 2 is a light flux that cannot be controlled by the optical prism 8. It is configured to be used efficiently.
[0141]
  In addition, the incident surface8b, 8b 'Angle φ, the relationship between the maximum emission angle after control at each entrance plane, and the angle θ between the line segment connecting the boundary line of the entrance plane and the light source center and the exit optical axis_bdrThen, this embodiment shows the state when taking the following values, respectively.
φ = 0 ° | β _max / Α _max | = 1.0 θ _bdr = 38.6 °
[0142]
  On the other hand, also in the present embodiment, the incident surfaces 8a and 8b are represented by the formula (3), (4) And each coefficient k, h regulates each shape so as to have the following numerical values.
[0143]
k = 0.15 h = 0.089
Further, as the overall shape of the optical system, if the inner diameter and outer diameter of the flash discharge tube are φ1.3 and φ2.0, respectively, as in the first embodiment, the shortest distances to the incident surfaces of the light source and the optical prism are respectively set. d, e, the depth f of the entire optical system, and g of the upper and lower openings of the optical prism are as follows.
[0144]
d = 0.3 e = 0.3 f = 4.8 g = 7.1
By setting each shape of the optical prism in this way, the light distribution characteristics are uniform, and the light beam emitted in the direction of 360 ° from the center of the light source can be narrowed to an angular range of 10 ° that is about 1/36 of that. become.
[0145]
Actually, since the light source has a certain finite size, the light distribution characteristic spreads over the whole according to the size of the light emitting portion of the light source.
[0146]
Next, a fifth embodiment of the present invention will be described. 13 and 14 are cross-sectional views of the essential parts of Embodiment 5 of the present invention. In the figure, 31 is an optical prism, 32 is a flash discharge tube, and 33 is a reflector. The reflector 33 includes a reflecting portion 33a concentric with the flash discharge tube 32, and reflecting portions 33b and 33b ′ having shapes approximately similar to the shape of the optical prism 31 behind the total reflecting surfaces 31c and 31c ′ of the optical prism 31. The other parts are substantially the same as those in the above embodiment, and the corresponding parts are indicated by the same symbols.
[0147]
13 and FIG. 14 are the same in shape, and only the ray tracing portion shown in the figure is different. FIG. 13 shows the component incident from the incident surface 31a on which the light beam traveling near the optical axis 1Z is incident. FIG. 14 shows components incident on the incident surfaces 31b and 31b ′ leading to the total reflection surfaces 31c and 31c ′, respectively.
[0148]
This embodiment is a modified optical system in which uniform light distribution can be obtained by devising the shapes of the total reflection surfaces 31c and 31c ′ while providing light distribution characteristics substantially equivalent to those of the first embodiment. The rib shape provided on the entire circumference of the optical prism 31 as shown in FIG.
[0149]
The greatest feature of this embodiment is that the components controlled by the total reflection surfaces 31c and 31c 'among the components emitted from the light source center O are from the necessary maximum angle to the minimum angle with respect to each total reflection surface. The distribution is evenly distributed over the range.
[0150]
That is, the component controlled on each of the total reflection surfaces 31c and 31c ′ is converted at a certain ratio corresponding to the emission angle from the light source center O, and from the maximum angle required on the irradiation surface. It is converted into a distribution corresponding to the minimum angle.
[0151]
First, the configuration of the optical system will be described with reference to FIG. Similarly to the first embodiment, when the shapes of the respective parts are shown by actual numerical values, d, e, f, g, α in the figure._max, Θ_bdrEach takes the following values:
[0152]
d = 0.5, e = 0.5 f = 4.65 g = 7.48
α_max= 20 ° θ_bdr= 37.44 °
Further, the component mainly emitted from the light source center O at this time and mainly close to the emission optical axis 1Z shows almost the same distribution as that of the first embodiment as shown in the figure, and the light beam spreading from the light source 32 to 74.88 ° is shown. , It can be converted to a 40 ° distribution, which is about half the range.
[0153]
The actual light distribution characteristic is widened by the size of the light source because the size of the light source is finite as described in the first embodiment, but is necessary by correcting the size of the light source based on the above values. It can be converted into a shape that provides the light distribution characteristics.
[0154]
Next, the most characteristic light distribution of total reflected light of this embodiment will be described with reference to FIG. First, the light beam that has traveled above the light source 32 is incident through the incident surfaces 31b and 31b ′ configured by a 1 ° plane as in the first embodiment.
[0155]
The light beam incident from the incident surface is guided to the total reflection surfaces 31c and 31c ', and the reflected light component at the rear end of the optical prism 31 corresponds to the maximum component in the direction away from the light source. Conversion is performed so as to correspond to the maximum component that intersects the optical axis.
[0156]
In particular, the conversion at this time is the maximum value γ of the component in the direction away from the emission optical axis 1Z._max, The maximum value β of the component in the direction intersecting the exit optical axis_maxThe angles are related to each other below, and the shape is regulated so as to be converted at a constant rate according to the emission angle from the center of the light source, and the shape is designed so that the light distribution is uniform as a whole.
[0157]
α_max= Β_max= Γ_max= 20 °
On the other hand, although not shown in the drawing, the luminous flux directed from the light source center O to the rear of the emission optical axis 1Z is arranged in a concentric shape with respect to the light source 32 because the reflector 33 disposed at the rear is arranged concentrically with the light source 32, Basically, the light flux at the center of the light source returns to the center of the light source again after being reflected, and it is possible to achieve a configuration in which desired light distribution characteristics can be obtained while minimizing the adverse effects of the glass tube of the light source.
[0158]
  Further, in the configuration of the fifth embodiment, the light beams emitted from the light source center O are regulated so that the maximum angles coincide with each other by the respective incident surfaces and total reflection surfaces. (5) Angle regulated by the formula, or
      0.8 ≦ | γ_max/ Α_max| ≦ 1.2 (7)
In this range, it is possible to obtain sufficiently uniform and efficient light distribution characteristics.
[0159]
As described above, the reason why the range of the maximum value of the irradiation angle has a certain range is that the light source has a certain size as described above.
[0160]
That is, when the light source has a certain size, the overall light distribution blurs in the spreading direction, but this blur becomes larger as there is a surface that regulates the light emission direction at a position closer to the light source. That is, the component whose light distribution is controlled behind the incident surface 31a and the total reflection surface 31c close to the light source is likely to be shaken due to the size of the light source.
[0161]
On the other hand, the component reflected near the exit surface of the total reflection surfaces 31c and 31c ′, which is controlled at a position far from the light source, is a component that has a sufficiently small solid angle from the light source and hardly causes blurring. This is a part that can be efficiently converted to the required irradiation angle by regulating the shape of the total reflection surface.
[0162]
For this reason, the maximum irradiation angle of the component that tends to spread, for example, γ_max, Α_maxIs set to be narrower than the necessary irradiation angle, it is possible to perform more efficient angle conversion.
[0163]
This is represented by the following relational expression.
[0164]
γ_max≦ β_max, Α_max≦ β_max
As in the first embodiment, an approximate expression of the shape obtained by following the above definition formula for the shape of each surface of the optical prism 31 is as follows. However, the shape of the incident surface 31a is omitted because it is substantially the same as the shape of the first embodiment.
[0165]
If the total reflection surface 31c is expressed by an approximate expression, the origin is the light source center O.

It is represented by
[0166]
As in the first embodiment, the shape is not limited to a shape that exactly matches the approximate expression, and almost the same effect can be obtained with an approximate shape such as a combination of cylindrical surface shapes that approximate the shape. The allowable range according to the size of the light source includes an error range of about the size of the light source with respect to the overall shape of the optical system.
[0167]
In the above embodiment, the upper and lower incident surfaces 31b and 31b 'and the total reflection surfaces 31c and 31c' have a vertically symmetrical shape, but are not limited to a symmetrical shape, and may be vertically asymmetrical.
[0168]
The reason for this is that, for example, when the flash light emitting device is used by being mounted on a photographing device such as a camera, the photographing optical axis and the illumination optical axis of the illumination system are different, so that parallax occurs on the subject surface. It is necessary to tilt the irradiation optical axis of the system to a certain amount of photographing optical axis according to the distance of the subject.
[0169]
In this case, it is more effective in the above optical system to correspond to the distribution of the upper and lower irradiation ranges as asymmetrical in the vertical direction. In addition, as described above, even if the same total reflection surface is located away from the light source, the surface is located near the light source by utilizing the property that the directivity is high and the light can be efficiently controlled in a narrow range. The incident surface and the total reflection surface are configured with slightly increased light condensing properties so that the light is condensed in a predetermined amount and narrowly, so that the light distribution distribution on each surface is matched and the overall light distribution characteristics are uniform. An efficient condensing optical system that minimizes the components irradiated outside the irradiation range can be formed.
[0170]
As described above, even with the method for setting the shape of each surface of the optical prism as in the present embodiment, which is different from the concept of the first embodiment, the emitted light beam from the center of the light source can be uniformly distributed over the required irradiation range. it can. The shape of the above embodiment has the following advantages although the height g of the opening in the vertical direction and the depth f of the entire optical system are increased.
[0171]
That is, as described above, the irradiation range for each incident surface is almost constant and has a continuous surface shape, so that there is no discontinuity and it is easy to obtain uniform light distribution characteristics without unevenness. In addition, since the component toward the center of the exit optical axis, that is, the component that defines the central light amount is directed using the most stable region near the center of each incident surface and total reflection surface, the periphery of each surface Compared to directing in the center direction, the sensitivity to changes in the center light intensity is low.In other words, variations in the processing accuracy of the optical prism and variations in the positional relationship due to dimensional accuracy between the components occur. Since it is difficult, a high central light quantity can be obtained stably.
[0172]
Next, a sixth embodiment of the present invention will be described. 15 and 16 are cross-sectional views of the essential parts of Embodiment 6 of the present invention. 41 is an optical prism, 42 is a flash discharge tube, and 43 is a reflector.
[0173]
The reflector 43 includes a reflector 43a concentric with the flash discharge tube 42, and reflectors 43b and 43b 'having a shape approximately similar to the shape of the optical prism behind the total reflection surfaces 41c and 41c' of the optical prism 41. The other parts are configured in the same manner as in the above embodiment, and corresponding parts are indicated by the same symbols.
[0174]
15 and FIG. 16 are the same in the shape of each component, and only the ray tracing portion shown in the figure is different. FIG. 15 is incident from the incident surface 41a on which the light beam traveling near the optical axis is incident. FIG. 16 shows components incident on the incident surfaces 41b and 41b 'leading to the total reflection surfaces 41c and 41c', respectively.
[0175]
The present embodiment is a modified optical system that has a light distribution characteristic substantially the same as that of the first embodiment, and that has a uniform light distribution by devising the shapes of the incident surface and the total reflection surface. The rib shape provided on the entire circumference of the optical prism, the step of the light emitting portion, and the like are not shown.
[0176]
The greatest feature of the present embodiment is that, among the components emitted from the light source center O, the angle component close to the emission optical axis 1Z is condensed on the central portion of the necessary irradiation range, and the light source center O is directed to the irradiation optical axis 1Z. In the vertical direction, each surface shape is set so as to irradiate the peripheral portion of the necessary irradiation angle range.
[0177]
In particular, among the components irradiated vertically from the light source center O to the irradiation optical axis 1Z, the component closer to the light source 42 is close to the exit surface in the direction away from the exit optical axis 1Z after passing through the optical prism 41. The component totally reflected on the side is that the exit angle is converted in the direction intersecting the exit optical axis 1Z after passing through the optical prism 41 according to the exit angle from the light source.
[0178]
And by comprising in this way, the light beam which injected from the said several entrance plane is synthesize | combined, and it will irradiate uniformly with respect to a required irradiation range, and is substantially equivalent to Embodiment 1 and Embodiment 5. The light distribution characteristics can be obtained.
[0179]
First, the configuration of the optical system will be described with reference to FIG. Similarly to the first embodiment, when the shapes of the respective parts are shown by actual numerical values, d, e, f, g, α in the figure._max, θ_bdrEach takes the following values:
[0180]
d = 0.5, e = 0.5, f = 0.05, g = 7.87
α_max= 10 ° θ_bdr= 34.65 °
In addition, for the component mainly emitted from the light source center at this time and mainly close to the emission optical axis 1Z, the power of the incident surface is increased as shown in the figure, and is narrowed to about 10 °, which is half of the first embodiment. Therefore, the maximum value θ of the component incident on the incident surface 41a from the light source center O_bdrIs about 3 ° narrower. For this reason, the light beam that spreads 69.3 ° from the center of the light source can be converted into a 20 ° distribution that is in the range of about 1/3.
[0181]
The actual light distribution characteristic is widened by the size of the light source because the size of the light source is finite as described in the first embodiment, but is necessary by correcting the size of the light source based on the above values. It can be converted into a shape that provides the light distribution characteristics.
[0182]
Next, the most characteristic light distribution of total reflected light of this embodiment will be described with reference to FIG. First, the light beam traveling in the up and down direction of the light source is incident through the incident surfaces 41b and 41b ′ configured by a 1 ° plane as in the first embodiment.
[0183]
The light beam incident from this incident surface is guided to the total reflection surfaces 41c and 41c ', and the reflected light component at the rear end of the optical prism 41 corresponds to the maximum component in the direction away from the light source, and the light beam reflected in the vicinity of the emission part is emitted. Conversion is performed so as to correspond to the maximum component that intersects the optical axis 1Z. The process up to this point is the same as that of the fifth embodiment.
[0184]
However, the irradiation angle range is different. That is, the conversion at this time is the minimum value γ of the component in the direction away from the emission optical axis._min, Maximum value γ_maxAnd the minimum value β of the component in the direction intersecting the exit optical axis_min, Maximum value β_maxThese are as shown in the figure. In the fifth embodiment, the component toward the vicinity of the center of the optical axis is missing.
[0185]
Each parameter in the figure actually employed in the present embodiment is a numerical value set as follows.
[0186]
α_max= Β_min= Γ_min= 10 °, β_max= Γ_max= 20 °
Further, since the divided components are regulated in a shape that is converted at a certain ratio according to the emission angle from the light source center O on each surface, the light beam emitted from the light source center O is As a whole, superposition is performed at the central portion and the peripheral portion, and uniform light distribution can be controlled over the entire irradiation range.
[0187]
On the other hand, although not shown in the drawing, the luminous flux directed from the light source center O to the rear of the emission optical axis 1Z is arranged in a concentric shape with respect to the light source 42, as in the case of the above embodiment. Basically, the light flux at the center of the light source returns to the center of the light source again after being reflected, and it is possible to achieve a configuration in which desired light distribution characteristics can be obtained while minimizing the adverse effect of the glass tube of the light source.
[0188]
Further, in the configuration of the sixth embodiment, the light beam emitted from the light source center O is controlled according to the respective incident surfaces, and is matched with the boundary line, that is, the angle component of 10 ° from the optical axis in the drawing. However, it is not always necessary to regulate to match at this angle, and each irradiation distribution is considered considering that the light distributions of both are partially overlapped or that the light source has a finite size. For convenience, the angle may be set so that unevenness in light distribution does not occur due to the setting being narrow and overlapping.
[0189]
It is desirable to set the amount of superposition that actually functions effectively to the extent specified below.
[0190]
      0.8 ≦ | β_min/ Α_max| ≦ 1.2...... (8)
      0.8 ≦ | γ_min/ Α_max| ≦ 1.2...... (9)
  As described above, even with the method for setting the shape of each surface of the optical prism as in the present embodiment, which is different from the concept of the first embodiment, the emitted light beam from the center of the light source can be uniformly distributed over the required irradiation range. it can.
[0191]
The shape of the above embodiment has the following advantages although the height g of the opening in the vertical direction and the depth f of the entire optical system are further increased in size. That is, as described above, the irradiation range for each incident surface can be set to an arbitrary angle range, so that the light distribution on the irradiation surface can be converted into an arbitrary distribution, for example, only the central light amount is increased. It is possible to obtain arbitrary light distribution characteristics on the irradiated surface, such as making the surrounding light distribution intentionally bright, and its application range is wide.
[0192]
In each of the above-described embodiments, the example in which the control of the light distribution characteristics on the total reflection surface is configured with the two upper and lower total reflection surfaces sandwiching the irradiation optical axis 1Z has been described, but the number of divisions is not necessarily limited to these two surfaces. However, it may be constituted by three or more surfaces having different characteristics.
[0193]
For example, in order to increase the component in the vicinity of the irradiation optical axis, the total reflection surface may be divided into three, and a part of the total reflection light may be directed toward the center of the emission optical axis. By doing so, for example, when only the central light quantity is insufficient, the light collecting property can be increased only at this point without greatly changing the overall light distribution, and this is particularly effective in correcting the necessary light distribution characteristics.
[0194]
On the other hand, the component controlled by this total reflection is composed of only one of the direction away from the emission optical axis or the direction intersecting the emission optical axis, and is necessary for the synthesis with the component toward the vicinity of the emission optical axis. You may comprise so that an irradiation angle range may be covered.
[0195]
With this configuration, the height of the opening can be reduced, and the overall shape of the optical system can be further reduced.
[0196]
In each of the above-described embodiments, the shape of each incident surface and total reflection surface is set so that the emission angle from the optical prism is proportional to the angle θ emitted from the center of the light source. It is not limited to the surface shape to be converted.
[0197]
For example, light loss occurs when the prism surface enters and exits due to surface reflection that occurs when the light is incident on the prism surface. When the object to be irradiated is a flat surface, the peripheral part is far from the center of the light source, so the light quantity is insufficient with respect to the central part. Each surface shape may be set so that optical characteristics can be obtained.
[0198]
Further, in each of the above embodiments, the optical resin material, particularly acrylic resin, has been described as the material of the prism, but the material of the prism is not limited to this material, and the transmittance of glass or the like. A material having a high density or a material in which a liquid having a high transmittance is sealed may be used, and the present invention is not limited to the above materials.
[0199]
【The invention's effect】
According to the present invention, the illumination device previously proposed by the applicant is further improved, and the overall shape of the illumination optical system of the photographing apparatus is extremely reduced, while the light distribution characteristics of the necessary irradiation range at that time are reduced. It is possible to achieve an illuminating device that can be kept uniform, and that can increase the effective energy irradiated within the angle of view, and an imaging device using the same, without deteriorating optical characteristics.
[0200]
In addition, according to the present invention, it is extremely small, thin, and lightweight as compared with the conventional illumination optical system, and the energy from the light source is utilized with high efficiency, and the uniform light distribution characteristic on the irradiation surface. It is possible to achieve an illumination device suitable for a still camera, a video camera, and the like capable of illuminating the image and a photographing device using the illumination device.
[0201]
In addition, according to the present invention, since the condensing control of the illumination optical system is performed in the optical prism, the illumination optical system having a desired light distribution characteristic can be extremely miniaturized, and the necessary irradiation range at that time It is easy to keep the light distribution characteristic for the same.
[0202]
In addition, since the light is condensed in the optical prism using total reflection, the energy use efficiency for the same light source is high, and even if it is compact, the optical characteristics are not deteriorated, but it is effectively irradiated within the angle of view. Energy can be increased.
[0203]
Furthermore, by optimizing each incident surface and total reflection surface of the optical prism by the method of the present invention, an illumination device capable of freely controlling the illuminance distribution within the required angle of view, and photographing using the same An apparatus can be achieved.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view in the radial direction of a flash discharge tube of a flash light emitting device showing a light distribution according to Embodiment 1 of the present invention.
FIG. 2 is a longitudinal cross-sectional view in the flash discharge tube radial direction of the flash light emitting device showing another light distribution according to the first embodiment of the present invention.
FIG. 3 is a perspective view of a camera to which the flash light emitting device according to the first embodiment of the invention is applied.
FIG. 4 is a perspective view of the flash light emitting device according to the first embodiment of the present invention as viewed from the front.
FIG. 5 is an exploded perspective view of the flash light emitting device according to the first embodiment of the present invention as viewed from the front.
FIG. 6 is an exploded perspective view of the flash light emitting device according to the first embodiment of the present invention as viewed from the back side.
FIG. 7 is a longitudinal sectional view in the radial direction of the flash discharge tube of the flash light emitting device showing the light distribution according to the second embodiment of the present invention.
FIG. 8 is a longitudinal sectional view in the radial direction of the flash discharge tube of a flash light emitting device showing another light distribution according to the second embodiment of the present invention.
FIG. 9 is a longitudinal sectional view in the radial direction of the flash discharge tube of the flash light emitting device showing the light distribution according to the third embodiment of the present invention.
FIG. 10 is a longitudinal sectional view in the radial direction of the flash discharge tube of a flash light emitting device showing another light distribution according to the third embodiment of the present invention.
FIG. 11 is a longitudinal sectional view of the flash discharge tube radial direction of the flash light emitting device showing the light distribution according to the fourth embodiment of the present invention.
FIG. 12 is a longitudinal sectional view in the radial direction of the flash discharge tube of the flash light emitting device showing another light distribution according to the fourth embodiment of the present invention.
FIG. 13 is a longitudinal sectional view in the radial direction of the flash discharge tube of the flash light emitting device showing the light distribution according to the fifth embodiment of the present invention.
FIG. 14 is a longitudinal sectional view in the radial direction of the flash discharge tube of a flash light emitting device showing another light distribution according to the fifth embodiment of the present invention.
FIG. 15 is a longitudinal sectional view in the radial direction of the flash discharge tube of the flash light emitting device showing the light distribution according to the sixth embodiment of the present invention.
FIG. 16 is a longitudinal sectional view in the radial direction of the flash discharge tube of a flash light emitting device showing another light distribution according to the sixth embodiment of the present invention.
[Explanation of symbols]
1, 4, 6, 8, 11, 31, 41 Optical prism
2, 12, 32, 42 Flash discharge tube (light source means)
3, 5, 7, 9, 33, 43 ......... Reflective umbrella
21 Release button
22 Camera mode selector switch
23 LCD display window
24 Photometry device viewing window
25 Viewfinder viewing window
26 Cartridge loading lid
27 Lens barrel
28 Camera body

Claims (11)

In an illuminating device having a light source means and an optical prism for irradiating a light beam from the light source means in an irradiation direction, the optical prism emits a light beam emitted in the vicinity of an emission optical axis out of the light beams from the light source means A first incident surface on which the light is incident, an exit surface on which the light beam from the first incident surface is directly incident, and a part of the light beam from the light source means that is emitted at a larger angle than the vicinity of the emission optical axis. A second incident surface for incidence, and a total reflection surface for inclining a light beam from the second incident surface to be emitted from the emission surface, each of these surfaces being emitted from the light source center of the light source means. The maximum emission controlled by the first incident surface while having a certain correlation between the angle formed by the light beam with respect to the emission optical axis and the emission angle with respect to the emission optical axis after passing through the emission surface angle component alpha _max and control of the second incident plane and the total reflection surface _{Β max / α max | | 0.8} ≦ between the maximum exit angle component beta _max was ≦ 1.2
The lighting device is characterized by being configured in a shape that satisfies the above relationship. In an illuminating device having a light source means and an optical prism for irradiating a light beam from the light source means in an irradiation direction, the optical prism emits a light beam emitted in the vicinity of an emission optical axis out of the light beams from the light source means A first incident surface on which the light is incident, an exit surface on which the light beam from the first incident surface is directly incident, and a part of the light beam from the light source means that is emitted at a larger angle than the vicinity of the emission optical axis. A second incident surface for incidence, and a total reflection surface for inclining a light beam from the second incident surface to be emitted from the emission surface, each of these surfaces being emitted from the light source center of the light source means. There is a certain correlation between the angle formed by the light beam with respect to the exit optical axis and the exit angle with respect to the exit optical axis after passing through the optical prism, and the light beam from the first incident surface is placed near the exit optical axis. Light flux incident from the second incident surface corresponding to the component Together to correspond to the peripheral portion of the required irradiation range, component intersecting the exit optical axis of the maximum exit angle component alpha _max and the minimum emission angle component that is controlled by the second incidence surface and the total reflection surface which is controlled by the first incidence plane Between β _min and the component γ _{min in the} opposite direction, 0.8 ≦ | β _min / α _max | ≦ 1.2
0.8 ≦ | γ _min / α _max | ≦ 1.2
A lighting device characterized by having a shape that satisfies the above relationship. The shape of the first incident surface is such that the angle between the light beam from the light source means and the exit optical axis when incident on the first incident surface is θ, the exit angle exiting from the exit surface is α, and the required illumination angle When the proportionality constant k is set, α = k · θ and the shapes of the second incident surface and the total reflection surface are the angle θ formed by the light beam from the light source means and the exit optical axis when incident on the second incident surface, If the injection angle emitted from the emission surface is β and the proportional constant h according to the required irradiation angle,
β = h · (θ−90 °)
The lighting device according to claim 1 or 2 , wherein The shape of the first incident surface is such that the angle between the light beam from the light source means and the exit optical axis when incident on the first incident surface is θ, the exit angle exiting from the exit surface is α, and the required illumination angle If the proportionality constant k is
α = k ・ θ
The shapes of the second incident surface and the total reflection surface are defined as an angle θ formed by the light beam from the light source means and the exit optical axis when incident on the second incident surface, and an exit angle emitted from the exit surface by β, Assuming that the angle connecting the boundary between the incident surface and the second incident surface and the light source center is θ _bdr , and a proportional constant h corresponding to the required irradiation angle,
β = h · {θ− (45 ° + θ _bdr / 2)}
The lighting device according to claim 1, 2, or 3 . The shape of the first incident surface or total reflection surface of the optical prism is formed by a combination of surface shapes approximating a continuous non-curved surface shape having a correlation with an emission angle from the light source center. Item 5. The lighting device according to any one of Items 1 to 4 . The inclination θ _bdr with respect to the emission optical axis of the line segment connecting the boundary line between the first incident surface and the second incident surface of the optical prism and the light source center,
25 ° ≦ θ _bdr ≦ 45 °
The illumination device according to any one of claims 1 to 5 , wherein the illumination device is in the range. The illumination device according to any one of claims 1 to 6 , wherein the total reflection surface of the optical prism extends to a direction substantially coincident with a light source center of the light source means with respect to an emission optical axis direction. It said light source means, the lighting apparatus of claims 1 to 7 any one of which being a flash discharge tube straight tube. A reflector that reflects the light flux emitted from the light source means is disposed behind the light source means along the emission optical axis, and the reflector has at least a substantially concentric reflection surface centered on the center of the light source means. lighting device according to any one of claims 1 to 8, characterized in that it is formed in a part. A reflector umbrella that reflects the light beam emitted from the light source means is disposed behind the light source means along the emission optical axis, and the reflector umbrella wraps around at least a part of the total reflection surface of the optical prism. lighting device according to any one of claims 1 to 8, wherein the arrangement to be configured as. An imaging device comprising the illumination device according to claim 1 .

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