JP4014722B2 - Variable focus lens, variable focus diffractive optical element, and variable declination prism - Google Patents

Description

とする。なお、ｔの下限値は、図１から明らかなように、ｔ＝Ｄで、Ｄは、上述したように２ｎｍ以上であるので、Ｄ・ｔの下限値は、（２×１０^-3μｍ）² 、すなわち４×１０^-6〔μｍ〕² となる。
【００２７】
なお、物質の光学特性を屈折率で表す近似が成り立つのは、「岩波科学ライブラリー８ 小惑星がやってくる」向井正著,1994,岩波書店発行の第５８頁に記載されているように、Ｄが１０ｎｍ〜５ｎｍより大きい場合である。また、Ｄが５００λを越えると、光の散乱は幾何学的となり、高分子セル１８を構成する高分子と液晶分子１７との界面での光の散乱がフレネルの反射式に従って増大するので、Ｄは、実用的には、
７ｎｍ≦Ｄ≦５００λ （２０）
とする。
【００２８】
図１または図４に示す構成において、上記のｎ_ox，ｎ_oy，ｎ_o ，ｎ_z ，ｎ_e ，ｎ_P ，ff，Ｄ，ｔ，λ，Ｒ₁ ，Ｒ₂ ，ｎ_LC′，ｎ_LC，ｎ_A ，ｎ_B ，ｆ₁ ，ｆ₂ 、および可変焦点レンズ１１の直径φは、具体的には、それぞれ以下の値にする。
ｎ_ox＝ｎ_oy＝ｎ_o ＝１．５
ｎ_z ＝ｎ_e ＝１．７５
ｎ_P ＝１．５４
ff＝０．５
Ｄ＝５０ｎｍ
ｔ＝１２５μｍ
λ＝５００ｎｍ
Ｒ₁ ＝２５ｍｍ
Ｒ₂ ＝∞
ｎ_LC′＝ｎ_LC＝１．５８３３
ｎ_A ＝１．５６１７
ｎ_B ＝１．５２
ｆ₁ ＝４４．５ｍｍ
ｆ₂ ＝４８．０４ｍｍ
φ＝５ｍｍ
【００２９】
この場合、上記（１９）式の右辺は、
λ・45μｍ・(1.585−1.45) ² /( ｎ_u −ｎ_P ) ²
＝500nm ・45μｍ・(0.135) ² /(0.0433) ²
≒２１８７１２nm・μｍ
となる。また、Ｄ・ｔは、

となり、確かに（１９）式を満足する。
【００３０】
また、上記の具体例において、Ｒ₁ ＝Ｒ₂ ＝∞、とすることもできる。この場合は、高分子分散液晶層１４の光路長が、電圧のオン・オフで変わることになるので、可変焦点レンズ１１をレンズ系の光束が平行でない部分に配置して、ピント調整を行うのに用いたり、レンズ系全体の焦点距離等を変えるのに用いることができる。
【００３１】
図５は、図４に示す可変焦点レンズ１１を用いるデジタルカメラ用の撮像光学系の構成を示すものである。この撮像光学系においては、物体（図示せず）の像を、絞り２１、可変焦点レンズ１１およびレンズ２２を介して、例えばＣＣＤよりなる固体撮像素子２３上に結像させる。なお、図５では、液晶分子の図示を省略してある。
【００３２】
かかる撮像光学系によれば、可変抵抗器１９により可変焦点レンズ１１の高分子分散液晶層１４に印加する交流電圧を調整して、可変焦点レンズ１１の焦点距離を変えることより、可変焦点レンズ１１およびレンズ２２を光軸方向に移動させることなく、例えば、無限遠から６００ｍｍまでの物体距離に対して、連続的に合焦させることが可能となる。
【００３３】
図６は、この発明に係る可変焦点レンズを用いる電子内視鏡用の対物光学系の構成を示すものである。この対物光学系では、物体（図示せず）の像を、前方レンズ２５、絞り２６、可変焦点レンズ２７および後方レンズ２８を経て、例えばＣＣＤよりなる固体撮像素子２９上に結像させる。ここで、可変焦点レンズ２７は、高分子分散液晶層１４を挟む一方のレンズ１２ａの内面の曲率半径Ｒ1 を無限大とし、他方のレンズ１２ｂの内面をフレネルレンズ状に形成する他は、図４と同様に構成して、その高分子分散液晶層１４に交流電源１６から可変抵抗器１９およびスイッチ１５を経て交流電圧を印加するようにする。なお、図６では、液晶分子の図示を省略してある。
【００３４】
かかる対物光学系においても、物体距離に応じて可変焦点レンズ２７の高分子分散液晶層１４に印加する交流電圧を調整して、該可変焦点レンズ２７の焦点距離を変えることにより、可変焦点レンズ２７および後方レンズ２８を光軸方向に移動させることなく、ピント調整を行うことが可能となる。
【００３５】
図７は、この発明に係る可変焦点回折光学素子の一例の構成を示すものである。この可変焦点回折光学素子３１は、平行な第１，第２の面３２ａ，３２ｂを有する第１の透明基板３２と、光の波長オーダーの溝深さを有する断面鋸歯波状のリング状回折格子を形成した第３の面３３ａおよび平坦な第４の面３３ｂを有する第２の透明基板３３とを有し、入射光を第１，第２の透明基板３２，３３を経て出射させるものである。第１，第２の透明基板３２，３３間には、図１で説明したと同様に、透明電極１３ａ，１３ｂを介して高分子分散液晶層１４を設け、透明電極１３ａ，１３ｂをスイッチ１５を経て交流電源１６に接続して、高分子分散液晶層１４に交流電界を印加するようにする。
【００３６】
かかる構成において、可変焦点回折光学素子３１に入射する光線は、第３の面３３ａの格子ピッチをｐとし、ｍを整数とすると、
ｐ sinθ＝ｍλ （２１）
を満たす角度θだけ偏向されて出射される。また、溝深さをｈ、透明基板３３の屈折率をｎ₃₃とし、ｋを整数とすると、
ｈ（ｎ_A −ｎ₃₃）＝ｍλ （２２）
ｈ（ｎ_B −ｎ₃₃）＝ｋλ （２３）
を満たせば、波長λで回折効率が１００％となり、フレアの発生を防止することができる。
【００３７】
ここで、上記（２２）および（２３）式の両辺の差を求めると、
ｈ（ｎ_A −ｎ_B ）＝（ｍ−ｋ）λ （２４）
が得られる。したがって、例えば、λ＝５００ｎｍ、ｎ_A ＝１．５５、ｎ_B ＝１．５とすると、
０．０５ｈ＝（ｍ−ｋ）・５００ｎｍ
となり、ｍ＝１，ｋ＝０とすると、
ｈ＝１００００ｎｍ＝１０μｍ
となる。この場合、透明基板３３の屈折率ｎ₃₃は、上記（２２）式から、ｎ₃₃＝１．５であればよい。また、可変焦点回折光学素子３１の周辺部における格子ピッチｐを１０μｍとすると、θ≒２．８７°となり、Ｆナンバーが１０のレンズを得ることができる。
【００３８】
かかる、可変焦点回折光学素子３１は、高分子分散液晶層１４への印加電圧のオン・オフで光路長が変わるので、例えば、レンズ系の光束が平行でない部分に配置して、ピント調整を行うのに用いたり、レンズ系全体の焦点距離等を変えるのに用いることができる。
【００３９】
なお、この実施形態において、上記（２２）〜（２４）式は、実用上、
０．７ｍλ≦ｈ（ｎ_A −ｎ₃₃）≦１．４ｍλ （２５）
０．７ｋλ≦ｈ（ｎ_B −ｎ₃₃）≦１．４ｋλ （２６）
０．７（ｍ−ｋ）λ≦ｈ（ｎ_A −ｎ_B ）≦１．４（ｍ−ｋ）λ （２７）
を満たせば良い。
【００４０】
図８および図９は、可変焦点眼鏡３５を示し、眼鏡レンズとして可変焦点回折光学素子３６を用いたものである。可変焦点回折光学素子３６は、レンズ３７および３８を有し、その入射側のレンズ３７の内面には、図７で説明したと同様の断面鋸歯波状のリング状回折格子を形成する。これらレンズ３７，３８の内面上には、それぞれ透明電極１３ａ，１３ｂを介して配向膜３９ａ，３９ｂを設け、これら配向膜３９ａ，３９ｂ間に、図１で説明したと同様の高分子分散液晶層１４を設ける。また、透明電極１３ａ，１３ｂは、スイッチ１５を介して交流電源１６に接続し、これにより高分子分散液晶層１４に交流電界を印加するようにする。
【００４１】
かかる構成の可変焦点眼鏡３５によれば、スイッチ１５を例えば手動でオン・オフすることにより、図８に示すスイッチ１５をオフにしたときと、図９に示すスイッチ１５をオンにしたときとで、高分子分散液晶層１４の液晶分子１７の配列を変えることができるので、眼鏡レンズ全体の視度を変えることができる。したがって、図１０に示す従来の二重焦点レンズ４１を用いる眼鏡４２のように、視線方向で視度が変わるものに比べて、違和感がなくなる。
【００４２】
図１１は、図８に示す可変焦点眼鏡３５において、例えばフレーム３５ａに物体４５までの距離を測定する測距センサ４６を設け、この測距センサ４６の出力に基づいてスイッチ１５をオン・オフ制御して、自動的に視度調整を行うようにしたものである。
【００４３】
このように、物体距離に基づいて自動的に視度調整するようにすれば、特に、視度調整力の衰えた老人に便利な眼鏡が得られる。
【００４４】
なお、図８および図１１に示した可変焦点眼鏡３５においては、眼鏡レンズ全体を可変焦点回折光学素子３６としたが、眼鏡レンズの一部、例えば図１２に示すように、中心よりやや下側に可変焦点回折光学素子３６を設けるようにしてもよい。また、可変焦点回折光学素子３６に代えて、図１に示した可変焦点レンズ１１や、図６に示した可変焦点レンズ２７を用いることもできる。さらに、図１１では、測距センサ４６の出力に基づいてスイッチ１５を自動的に切り換えるようにしたが、新たにスイッチを設けて、測距センサ４６による自動切り換えと、手動による切り換えとを選択できるようにしたり、測距センサ４６による自動切り換え中に、手動による切り換えに変更できるように構成することもできる。さらにまた、上記の可変焦点眼鏡３５に一体的に補聴器を設けることもできる。
【００４５】
また、図１１に示すように測距センサ４６を設ける場合には、可変焦点回折光学素子３６の高分子分散液晶層１４への印加電圧を段階的または連続的に可変できるようにすると共に、ユーザに応じて測距センサ４６の出力と印加電圧との対応関係をプリセットして、測距センサ４６の出力に基づいて印加電圧を制御するようにすることもできる。このようにすれば、ユーザ毎に物体距離に応じたより正確な視度調整を自動的に行うことができる。
【００４６】
さらに、上記の可変焦点眼鏡３５において、交流電源１６は、電池を電源とするインバータ回路をもって構成することができる。この場合、電池としは、マンガン電池、リチウム電池、太陽電池、充電式電池の一種または複数種を、フレーム３５ａに一体的に、すなわち内蔵したり、別体に設けてコードで接続したり、あるいは内蔵電池と外部電池とを有するようにすることもできる。
【００４７】
また、単に、可変焦点眼鏡を構成する場合には、上述した高分子分散液晶を用いる可変焦点レンズに代えて、ツイストネマティック液晶を用いる可変焦点レンズを用いることもできる。図１３および図１４は、この場合の可変焦点眼鏡５０の構成を示すものであり、可変焦点レンズ５１は、レンズ５２および５３と、これらレンズの内面上にそれぞれ透明電極１３ａ，１３ｂを介して設けた配向膜３９ａ，３９ｂと、これら配向膜間に設けたツイストネマティック液晶層５４とを有して構成し、その透明電極１３ａ，１３ｂを可変抵抗器１９を経て交流電源１６に接続して、ツイストネマティック液晶層５４に交流電界を印加するようにする。
【００４８】
かかる構成において、ツイストネマティック液晶層５４に印加する電圧を高くすると、液晶分子５５は、図１４に示すようにホメオトロピック配向となり、図１３に示す印加電圧が低いツイストネマティック状態の場合に比べて、ツイストネマティック液晶層５４の屈折率は小さくなり、焦点距離が長くなる。
【００４９】
ここで、図１３に示すツイストネマティック状態における液晶分子５５の螺旋ピッチＰは、光の波長λに比べて十分小さくする必要があるので、例えば、
２ｎｍ≦Ｐ≦２λ／３ （２８）
とする。なお、この条件の下限値は、液晶分子の大きさで決まり、上限値は、入射光が自然光の場合に、図１３の状態でツイストネマティック液晶層５４が等方媒質として振る舞うために必要な値であり、この上限値の条件を満たさないと、可変焦点レンズ５１は偏光方向によって焦点距離の異なるレンズとなり、これがため二重像が形成されてぼけた像しか得られなくなる。
【００５０】
図１５（Ａ）は、この発明に係る可変偏角プリズムの構成を示すものである。
この可変偏角プリズム６１は、第１，第２の面６２ａ，６２ｂを有する入射側の第１の透明基板６２と、第３，第４の面６３ａ，６３ｂを有する出射側の平行平板状の第２の透明基板６３とを有する。入射側の透明基板６２の内面（第２の面）６２ｂは、フレネル状に形成し、この透明基板６２と出射側の透明基板６３との間に、図１で説明したと同様に、透明電極１３ａ，１３ｂを介して高分子分散液晶層１４を設ける。透明電極１３ａ，１３ｂは、可変抵抗器１９を経て交流電源１６に接続し、これにより高分子分散液晶層１４に交流電界を印加して、可変偏角プリズム６１を透過する光の偏角を制御するようにする。なお、図１５（Ａ）では、透明基板６２の内面６２ｂをフレネル状に形成したが、例えば、図１５（Ｂ）に示すように、透明基板６２および６３の内面を相対的に傾斜させた傾斜面を有する通常のプリズム状に形成することもできるし、あるいは図７に示した回折格子状に形成することもできる。回折格子状に形成する場合には、上記の（２１）〜（２７）式が同様にあてはまる。
【００５１】
かかる構成の可変偏角プリズム６１は、例えば、ＴＶカメラ、デジタルカメラ、フィルムカメラ、双眼鏡等のブレ防止用として有効に用いることができる。この場合、可変偏角プリズム６１の屈折方向（偏向方向）は、上下方向とするのが望ましいが、さらに性能を向上させるためには、２個の可変偏角プリズム６１を偏向方向を異ならせて、例えば図１６に示すように、上下および左右の直交する方向で屈折角を変えるように配置するのが望ましい。なお、図１５および図１６では、液晶分子の図示を省略してある。
【００５２】
図１７は、この発明に係る可変焦点レンズとしての可変焦点ミラーを示すものである。この可変焦点ミラー６５は、第１，第２の面６６ａ，６６ｂを有する第１の透明基板６６と、第３，第４の面６７ａ，６７ｂを有する第２の透明基板６７とを有する。第１の透明基板６６は、平板状またはレンズ状に形成して、内面（第２の面）６６ｂに透明電極１３ａを設け、第２の透明基板６７は、内面（第３の面）６７ａを凹面状に形成して、該凹面上に反射膜６８を施し、さらにこの反射膜６８上に透明電極１３ｂを設ける。透明電極１３ａ，１３ｂ間には、図１で説明したと同様に、高分子分散液晶層１４を設け、これら透明電極１３ａ，１３ｂをスイッチ１５および可変抵抗器１９を経て交流電源１６に接続して、高分子分散液晶層１４に交流電界を印加するようにする。なお、図１７では、液晶分子の図示を省略してある。
【００５３】
かかる構成によれば、透明基板６６側から入射する光線は、反射膜６８により高分子分散液晶層１４を折り返す光路となるので、高分子分散液晶層１４の作用を２回もたせることができると共に、高分子分散液晶層１４への印加電圧を変えることにより、反射光の焦点位置を変えることができる。この場合、可変焦点ミラー６５に入射した光線は、高分子分散液晶層１４を２回透過するので、高分子分散液晶層１４の厚さの２倍をｔとすれば、上記の各式を同様に用いることができる。なお、透明基板６６または６７の内面を、図７に示したように回折格子状にして、高分子分散液晶層１４の厚さを薄くすることもできる。このようにすれば、散乱光をより少なくできる利点がある。
【００５４】
なお、以上の説明では、液晶の劣化を防止するため、電源として交流電源１６を用いて、液晶に交流電界を印加するようにしたが、直流電源を用いて液晶に直流電界を印加するようにすることもできる。また、液晶分子の方向を変える方法としては、電圧を変化させること以外に、液晶にかける電場の周波数、液晶にかける磁場の強さ・周波数、あるいは液晶の温度等を変化させることによってもよい。
以上に示した実施形態において、高分子分散液晶は液状ではなく固体に近いものもあるので、その場合はレンズ１２ａ，１２ｂの一方、透明基板３２、レンズ３８、レンズ５２，５３の一方、図１５（Ａ）における透明基板６３、図１５（Ｂ）における透明基板６２，６３の一方、透明基板６６，６７の一方はなくてもよい。
【００５５】
次に、レンズの一つである不均質媒質レンズの製造方法について説明する。
不均質媒質レンズとは、レンズの部分ごとの屈折率が異なる媒質でできたレンズのことで、例えば、図２０に示すような半径方向に屈折率が変化するラジアルグラディエントの不均質媒質レンズ７１では、図２１に示すように、分光中心軸（屈折率分布中心軸）である光軸Ｏを中心として、半径ｒが大きくなるに従って屈折率ｎが小さくなっている。なお、光軸に沿った方向では屈折率は変化していない。
【００５６】
このような不均質媒質レンズ７１は、ガラスやプラスチック等の材料を用い、イオン交換法やゾルゲル法等で、その素材が作成される。しかし、図２２に示すように、これらの方法で作成される不均質媒質レンズの素材７２は棒状であるため、最終製品としての不均質媒質レンズ７１を得るためには、切断、研磨、コート等の工程を経る必要がある。
【００５７】
一方、ガラス等よりなる通常の均質レンズを得る場合には、先ず、一枚のレンズの両面を研磨し、次に、二つの球面の中心を結ぶ線（光軸）に対して回転対象となるように外周を削るようにしている。この方法は、一般に広く用いられており、安価にできる利点がある。
【００５８】
しかしながら、不均質媒質レンズの場合には、通常のレンズ加工と異なり、素材７２の分光中心軸がレンズの外周の中心になければならず、また、図２０に示すように、レンズ面７３は分光中心軸と直交しなければならない。このため、上述した通常のレンズの加工法によって製造すると、分光中心軸とレンズ外周の中心とがずれたり、傾いたり、また、レンズ面７３が分光中心軸に対して正確に直交しない場合がある。
【００５９】
以下、このような不具合を解決し得る不均質媒質レンズの製造方法について、図面を参照して説明する。
先ず、レンズ面７３が平面の場合の製造方法の一例について説明する。この場合には、素材７２の中心に分光中心軸があるものと仮定する。この仮定は、イオン交換法、ゾルゲル法等で作られた素材７２では、実際に一致する。先ず、図２３に示すように、分光中心軸が素材７２の中心からずれないように、センターレス７５で素材７２の直径を小さく削る。なお、センターレス７５は、削って小さくなった素材７２ａの外径が必要なレンズの直径となるように、予め２軸の距離を調整しておく。
【００６０】
次に、図２４に示すように、切断機７６で素材７２ａを、研磨しろを加えた必要なレンズ長さに切断する。その後、切断した素材７２ｂを、図２５に示すように、平面上に載置したＶブロック７７のＶ溝の側面に、平面に対して分光中心軸が直交するように接着するか、あるいは、図２６に示すように歯車７８の歯溝の側面に、歯車７８の中心軸と分光中心軸とが平行となるように接着する。
【００６１】
次に、Ｖブロック７７あるいは歯車７８に接着した素材７２ｂを、図２７に示すように平面研削盤８１にセットして、素材７２ｂの一方のレンズ面を、分光中心軸と直交するようにダイヤモンド砥石で削る。その後、図２８に示すように、研磨機８２で、徐々に細かいダイヤモンドペレット８２ａを用いて何段階かの精研削を行ってから、ウレタンシートあるいはピッチ等を用いて、ＣｅＯ₂ と水とで研磨してレンズ面を鏡面状に仕上げる。他方のレンズ面についても、図２５〜図２８に示す工程を行って、同様に、鏡面状に仕上げる。
【００６２】
その後、図２９に示すように、ダライ盤８４等で両レンズ面の面取りを行った後、両レンズ面に反射防止用のマルチコートあるいはＭｇＦ₂ 等の単層コートを施して、両面が平面の不均質媒質レンズを得る。
【００６３】
なお、図２４に示した切断工程で、分光中心軸に対する切断面（レンズ面）の直角度が保たれる場合には、図２５あるいは図２６に示したＶブロック７７あるいは歯車７８に接着することなく、図２７および図２８に示すレンズ面の精研削および研磨を行うようにすることもできる。また、図２８に示す工程で一方のレンズ面の研磨が終了したら、その研磨が終了したレンズ面を、図３０に示すように貼りつけ皿８６に突き当てて貼り、その状態で研磨機８２で精研削および研磨を行うようにしてもよい。このようにすれば、工程が簡単となり、コスト面で有利となる。
【００６４】
さらに、レンズ面７３が平面の場合の他の製造方法においては、図２３で示した外径の研削工程を行うことなく、図２４に示した切断工程を行い、その後、図２５〜図２８に示した工程を両方のレンズ面に対して行う。次に、図３１に示すように、レンズ面の研磨が終了した素材７２ｃをピッチ８８を介してサイダ式芯取り機９０に貼りつける。この貼りつけにあたっては、サイダ式芯取り機９０を回転させたときに素材７２ｃが振れないように、ピックテスタ９１で調べながら、あるいは顕微鏡９２で素材７２ｃの外周を観察しながら行う。この状態で、サイダ式芯取り機９０を回転させながら、砥石９３で素材７２ｃの外周を、仕上がりレンズの外径となるまで研削する。その後、サイダ式芯取り機９０で面取りを行ってから、レンズ面に反射防止コートを施して、レンズ中心と分光中心軸とが一致する不均質媒質レンズを得る。
【００６５】
以上、両面が平面の不均質媒質レンズの製造方法について説明したが、上述した製造方法は、片面が平面の不均質媒質レンズの場合や、仕上がり後に外径を揃える場合にも有効に適用することができる。
【００６６】
次に、レンズ面が半径Ｒの球面の不均質媒質レンズを得る場合の製造方法の一例について説明する。図３２に示すように、先ず、ガラス、金属、樹脂等により半径Ｒの面を持つレンズ面部材９５を作成する。その後、このレンズ面部材９５をサイダ式芯取り機の回転軸に偏芯のないように貼り付けて、回転軸を回転させながら、その中心にダイヤモンド砥石９６を用いて、切断した不均質媒質レンズ素材が入る穴を形成すると共に、外周の芯取りを行う。この穴を形成したレンズ面部材をヤトイと呼ぶことにする。
【００６７】
次に、図３３に示すように、ヤトイ９７の穴に、切断した不均質媒質レンズ素材７２ｄを入れて石膏等で固定し、その状態で、図３４に示すように、研磨機８２でヤトイ９７とともに素材７２ｄを精研削および研磨して、分光中心軸に対して偏芯のない球面を形成する。なお、ヤトイ９７の穴に入れる切断した不均質媒質レンズ素材７２ｃは、予めセンターレスで仕上がりレンズの外径に削っておくこともできる。この場合には、当然のことながら、ヤトイ９７の穴は、仕上がりレンズの外径とほぼ等しい内径とする。
【００６８】
他方の面についても、同様にして球面に形成することができるが、特に、レンズの縁肉（外周面の光軸方向の寸法）が小さい場合には、以下の方法で他方の面を球面に形成することができる。すなわち、図３５に示すように、一方の面を球面に研磨した不均質媒質レンズ素材７２ｅを、その球面側を半径Ｒの凹面を有するヤトイ１０１にピッチ８８を介して貼り付ける。この貼り付けにあたっては、図３１で説明したと同様に、ヤトイ１０１を回転させたときに、素材７２ｅが振れないように、ピックテスタ９１で調べながら、あるいは顕微鏡９２で素材７２ｅの外周を観察しながら行う。ここで、ヤトイ１０１は、後述するカーブジェネレータや芯取り機の回転軸とほぼ同径で、素材７２ｅを貼り付けたまま、カーブジェネレータや芯取り機に取り付けられるようにする。なお、ヤトイ１０１に貼り付ける球面は、最終的に形成する二つの球面のうち、曲率半径の大きい球面とするのが、上記の貼り付け作業を容易に行う点で好ましい。
【００６９】
次に、図３６に示すように、ヤトイ１０１をカーブジェネレータ１０２に取り付けて、素材７２ｅの他方の面（図において、右側の面）を所望の曲率となるように研削する。その後、ヤトイ１０１を芯取り機に取り付けて、素材７２ｅの外周をレンズの仕上がり外径まで研削する。次に、素材７２ｅの他方の面を通常の研磨機で鏡面に研磨してから、両面に必要なコーティングを施して、両面球面の不均質媒質レンズを得る。
【００７０】
なお、芯取り機による素材７２ｅの外周の研削工程は、他方の面の研磨後に行うようにしてもよい。この場合には、図３７に示すように、ベルクランプ芯取り機１０３を用いて、素材７２ｅの外周を研削することもできる。また、他方の面の研磨後に、素材７２ｅの外周を研削する場合には、図３８に示すように、両面研磨した素材７２ｅをピッチ８８を介してヤトイ１０１に貼り付け、ヤトイ１０１を回転させながら砥石で研削することもできる。この場合には、回転振れが生じないように、顕微鏡９２で観察しながら、素材７２ｅをヤトイ１０１に貼り付ける。あるいは、顕微鏡９２を用いず、通常のサイダ式芯取り機で素材７２ｅの球面（図３８において、右側の面）の反射像の振れを観測して、素材７２ｅの外周を研削することもできる。
【００７１】
球面形状の不均質媒質レンズは、上述した製造方法に限らず、特に、レンズの縁肉、すなわちレンズ外周面の光軸方向の寸法が大きい場合には、以下の方法によっても得ることができる。すなわち、図３９に示すように、先ず、切断した素材７２ｂをコレットチャック１０５に取り付け、カーブジェネレータ１０２で一方の面を所望の球面に研削した後、該面を精研削、ピッチ研磨を行って鏡面にする。次に、図４０に示すように、球面を支えるパイプ１０６を有するコレットチャック１０７に、素材７２ｂの他方の面（未研磨面）が外側となるように、該素材７２ｂを取り付けて、同様にして、カーブジェネレータ１０２で他方の面を所望の球面に研削する。なお、パイプ１０６を用いるのは、レンズの縁肉Ｌが所望の値になるようにするため、および素材７２ｂの分光中心軸に対して球面が偏芯しないようにするためである。その後、球面に研削した他方の面に対して、精研削、ピッチ研磨を行って鏡面にする。次に、必要に応じて、上述したいずれかの方法で、素材７２ｂの外径をレンズ仕上がり外径に研削した後、面取り、コーティングを行って、両面球面の不均質媒質レンズを得る。なお、上記の説明では、球面形状の不均質媒質レンズを製造するようにしたが、同様にして、非球面形状の不均質媒質レンズを製造することもできる。
【００７２】
付記項
１．請求項１記載の可変焦点レンズにおいて、該可変焦点レンズは、
第１および第２の面を有し、入射光を前記第１および第２の面を経て透過させる第１の光学部材と、
該第１の光学部材を透過した光を受ける第３の面を有する第２の光学部材と、
前記第１、第２および第３の面の少なくとも一面に形成したレンズ面と、
前記第２および第３の面側にそれぞれ設けた一対の透明電極と、
これら透明電極間に設けた高分子分散液晶層とを有し、
前記一対の透明電極を介して前記高分子分散液晶層に電界を印加することにより、前記第１および第２の光学部材を透過する光、または前記第１の光学部材を透過し、前記第３の面で反射されて再び前記第１の光学部材を透過する光の焦点位置を可変し得るよう構成したことを特徴とする可変焦点レンズ。
２．請求項２記載の可変焦点回折光学素子において、該可変焦点回折光学素子は、
第１および第２の面を有し、入射光を前記第１および第２の面を経て透過させる第１の光学部材と、
第３および第４の面を有し、前記第１の光学部材を透過した光を前記第３および第４の面を経て出射させる第２の光学部材と、
前記第１、第２および第３の面の少なくとも一面に形成した回折面と、
前記第２および第３の面側にそれぞれ設けた透明電極と、
これら透明電極間に設けた高分子分散液晶層とを有し、
前記一対の透明電極を介して前記高分子分散液晶層に電界を印加することにより、前記第１および第２の光学部材を透過する光の焦点位置を可変し得るよう構成したことを特徴とする可変焦点回折光学素子。
３．請求項３記載の可変偏角プリズムにおいて、該可変偏角プリズムは、
第１および第２の面を有し、入射光を前記第１および第２の面を経て透過させる第１の光学部材と、
第３および第４の面を有し、前記第１の光学部材を透過した光を前記第３および第４の面を経て出射させる第２の光学部材と、
前記第１、第２および第３の面の少なくとも一面に形成した傾斜面と、
前記第２および第３の面側にそれぞれ設けた透明電極と、
これら透明電極間に設けた高分子分散液晶層とを有し、
前記一対の透明電極を介して前記高分子分散液晶層に電界を印加することにより、前記第１および第２の光学部材を透過する光の偏角を可変し得るよう構成したことを特徴とする可変偏角プリズム。
４．請求項１，２、付記項１，２のいずれか一項記載の可変焦点レンズまたは可変焦点回折光学素子を有することを特徴とする可変焦点眼鏡。
５．請求項３または付記項３記載の可変偏角プリズムを、偏角方向が異なるように複数個配置したことを特徴とする光偏向装置。
６．請求項１，２，３、付記項１，２，３のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムを有することを特徴とする撮像装置。
７．請求項１，２，３、付記項１，２，３のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムよりなる液晶光学素子において、
前記高分子分散液晶層の体積に占める液晶分子の体積の割合をffとするとき、０．１≦ff≦０．９９９
を満足するよう構成したことを特徴とする液晶光学素子。
８．請求項１，２，３、付記項１，２，３のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムよりなる液晶光学素子において、
4 ×10^-6〔μｍ〕² ≦Ｄ・ｔ≦λ・45μｍ・(1.585−1.45) ² /( ｎ_u −ｎ_P ) ²
を満足することを特徴とする液晶光学素子。
ただし、Ｄ：高分子分散液晶層を構成する液晶分子を含む高分子セルの平均の直径
ｔ：光軸方向における高分子分散液晶層１４の厚さ
λ：使用波長
ｎ_P ：高分子セルを構成する高分子の屈折率
（ｎ_u −ｎ_P ）² ：（ｎ_LC′−ｎ_P ）² と（ｎ_o ′−ｎ_P ）² とのうち大きい方で、
ｎ_LC′：液晶分子の平均屈折率
ｎ_o ′：常光線の平均屈折率
９．請求項１，２，３、付記項１，２，３のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムよりなる液晶光学素子において、
２ｎｍ≦Ｄ≦λ／５
を満足することを特徴とする液晶光学素子。
９’．請求項１，２，３、付記項１，２，３のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムよりなる液晶光学素子において、
２ｎｍ≦Ｄ＜λ
を満足することを特徴とする液晶光学素子。
１０．請求項１，２，３、付記項１，２，３のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムよりなる液晶光学素子において、
０．０１≦｜ｎ_o ′−ｎ_LC′｜≦１０
を満足することを特徴とする液晶光学素子。
１１．請求項１，２，３、付記項１，２，３のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムよりなる液晶光学素子において、
７ｎｍ≦Ｄ≦５００λ
を満足することを特徴とする液晶光学素子。
１２．請求項２、付記項２，７〜１１のいずれか一項記載の可変焦点回折光学素子において、
０．７ｍλ≦ｈ（ｎ_A −ｎ₃₃）≦１．４ｍλ
０．７ｋλ≦ｈ（ｎ_B −ｎ₃₃）≦１．４ｋλ
０．７（ｍ−ｋ）λ≦ｈ（ｎ_A −ｎ_B ）≦１．４（ｍ−ｋ）λ
を満足することを特徴とする可変焦点回折光学素子。
ただし、ｍ，ｋ：整数
ｈ：格子の溝深さ
ｎ_A ：電界を印加しない状態での高分子分散液晶層の屈折率
ｎ_B ：電界を印加した状態での高分子分散液晶層の屈折率
ｎ₃₃：回折格子を形成した透明基板の屈折率
１３．請求項１，２、付記項１，２，７〜１２のいずれか一項記載の可変焦点レンズまたは可変焦点回折光学素子を有することを特徴とする液晶可変焦点眼鏡。
１４．付記項７〜１２いずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムを有することを特徴とする撮像装置。
１５．対向する一対の電極と、これら電極間に設けたツイストネマティック液晶層とを有する眼鏡レンズとしての液晶光学素子を有し、
前記ツイストネマティック液晶層は、ツイストネマティック状態における液晶分子の螺旋ピッチＰが、
２ｎｍ≦Ｐ≦２λ／３
を満足することを特徴とする液晶可変焦点眼鏡。
１６．付記項１記載の可変焦点レンズにおいて、
前記第３の面に反射膜を設けて、入射光線を前記高分子分散液晶層中に折り返して複数回通過させるよう構成したことを特徴とする可変焦点ミラー。
１７．付記項１〜１６のいずれか一項記載の可変焦点レンズ、可変焦点回折光学素子または可変偏角プリズムよりなる液晶光学素子と、該液晶光学素子の前記一対の電極間に電圧を印加する電圧源とを有することを特徴とする液晶光学装置。
１８．付記項１７記載の液晶光学装置において、
前記電圧源は、前記一対の電極間に可変の電圧を印加するよう構成したことを特徴とする液晶光学装置。
１９．不均質媒質レンズを製造するにあたり、
不均質素材の外径をセンターレスを用いてレンズ仕上がり外径に研削する工程を含むことを特徴とする不均質媒質レンズの製造方法。
２０．不均質媒質レンズを製造するにあたり、
ピックテスタまたは顕微鏡を用いて不均質素材の外周の振れを調節して、該不均質素材を芯取り機の回転軸に固定した後、その外径をレンズ仕上がり外径に研削する工程を含むことを特徴とする不均質媒質レンズの製造方法。
２１．不均質媒質レンズを製造するにあたり、
不均質素材に、中心が分光中心軸とほぼ一致するように所望の形状の曲面を形成した後、前記不均質素材の外周をベルクランプまたはサイダ式芯取り機を用いてレンズ仕上がり外径に研削する工程を含むことを特徴とする不均質媒質レンズの製造方法。
２２．不均質媒質レンズを製造するにあたり、
不均質素材を、その研削面方向に対して垂直となるように治具に固定した状態で、前記不均質素材を平面に研削および研磨する工程を含むことを特徴とする不均質媒質レンズの製造方法。
２３．付記項２２記載の不均質媒質レンズの製造方法において、
前記治具として、Ｖブロックまたは歯車を用いることを特徴とする不均質媒質レンズの製造方法。
２４．不均質媒質レンズを製造するにあたり、
外径が製造すべき不均質媒質レンズの外径よりも大きく、かつ所望の形状の曲面を有し、その中心部に不均質素材の直径にほぼ等しい穴を形成したガラス、金属、樹脂等からなるヤトイを用い、該ヤトイの穴に不均質素材を固定して、該不均質素材を前記ヤトイとともに所望の形状の曲面に研削および研磨する工程を含むことを特徴とする不均質媒質レンズの製造方法。
２５．不均質媒質レンズを製造するにあたり、
一方の面を所望の形状の曲面に研削した不均質素材の前記曲面を、逆の形状の曲面を有するヤトイの回転軸に、ピックテスタまたは顕微鏡を用いて外周の振れを調節して固定した後、カーブジェネレータを用いて前記不均質素材の他方の面を所望の形状の曲面に研削する工程を含むことを特徴とする不均質媒質レンズの製造方法。
２６．不均質媒質レンズを製造するにあたり、
不均質素材の両端に、中心が分光中心軸にほぼ一致する所望の形状の曲面をそれぞれ形成した後、該不均質素材をベルクランプ法により芯取りする工程を含むことを特徴とする不均質媒質レンズの製造方法。
２７．不均質媒質レンズを製造するにあたり、
不均質素材の両端に、中心が分光中心軸にほぼ一致する所望の形状の曲面をそれぞれ形成した後、一方の曲面を、それとは逆の形状の曲面を有するヤトイに固定し、他方の曲面による反射像を観測して、サイダ式芯取り機により前記不均質素材を芯取りする工程を含むことを特徴とする不均質媒質レンズの製造方法。
２８．不均質媒質レンズを製造するにあたり、
不均質素材の両端に、中心が分光中心軸にほぼ一致する所望の形状の曲面をそれぞれ形成した後、該不均質素材をサイダ式芯取り機により芯取りする工程を含むことを特徴とする不均質媒質レンズの製造方法。
２９．不均質媒質レンズを製造するにあたり、
不均質素材をコレットチャックにて固定した状態で、カーブジェネレータを用いて一方の面を所望の形状の曲面に研削する工程を含むことを特徴とする不均質媒質レンズの製造方法。
３０．不均質媒質レンズを製造するにあたり、
不均質素材の一方の面を、分光中心軸にほぼ一致する中心を有する所望の形状の曲面に形成した後、該曲面をパイプで支えながら不均質素材をコレットチャックにて固定し、その状態でカーブジェネレータを用いて他方の面を所望の形状の曲面に研削する工程を含むことを特徴とする不均質媒質レンズの製造方法。
３１．付記項１９〜３０のいずれか一項記載の不均質媒質レンズの製造方法において、
前記不均質素材として、該素材の中心軸と分光中心軸とがほぼ一致しているものを用いることを特徴とする不均質媒質レンズの製造方法。
【００７３】
付記項６記載の撮像装置によれば、液晶光学素子の応答が速いので、動画のオートフォーカスが可能になると共に、光量損失が少ないので、暗いところでも撮像できる利点がある。
付記項１９記載の不均質媒質レンズの製造方法によれば、安価な費用で偏芯の少ない不均質媒質レンズを得ることができる。
付記項２０記載の不均質媒質レンズの製造方法によれば、付記項１９記載の製造方法と比較して、より精度の良い不均質媒質レンズを得ることができ、品質管理がし易くなる。
付記項２１記載の不均質媒質レンズの製造方法によれば、所望の形状の曲面を精度良く形成することにより、簡単な加工で偏芯の少ない不均質媒質レンズを得ることができる。
付記項２２記載の不均質媒質レンズの製造方法によれば、面偏芯の少ない不均質媒質レンズを得ることができる。
付記項２４記載の不均質媒質レンズの製造方法によれば、ヤトイさえ精度良く形成すれば、偏芯の少ない不均質媒質レンズを容易に得ることができる。
付記項２５記載の不均質媒質レンズの製造方法によれば、縁肉の小さい不均質媒質レンズでも容易に得ることができる。
付記項２６記載の不均質媒質レンズの製造方法によれば、偏芯の少ない不均質媒質球面レンズを得ることができる。
付記項２７記載の不均質媒質レンズの製造方法によれば、より偏芯の少ない高精度の不均質媒質球面レンズを得ることができる。
付記項２８記載の不均質媒質レンズの製造方法によれば、簡単な加工で、偏芯の少ない高精度の不均質媒質球面レンズを得ることができる。
付記項２９および３０記載の不均質媒質レンズの製造方法によれば、偏芯の少ない不均質媒質球面レンズを簡単に得ることができる。
【００７４】
【発明の効果】
この発明に係る液晶光学素子としての可変焦点レンズ、可変焦点回折光学素子および可変偏角プリズムによれば、高分子分散液晶を用いるようにしたので、例えば電界の印加によって屈折率を迅速に変化させて、その光学特性を変更することができる。したがって、液晶光学素子を介する光線の光路を迅速に変更することができる。また、高分子分散液晶を用いることにより、必ずしも偏光板を必要としないので、光量低減を抑えることができ、したがって、フィルムカメラ、顕微鏡、ＴＶカメラ、双眼鏡、眼鏡、内視鏡、デジタルカメラ、光ピックアップ等の各種の光学機器の焦点調整、ズームレンズ、ぶれ防止用として広く用いることができる。さらに、特に、可変焦点回折光学素子および可変偏角プリズムにおいては、全体を薄くできるので、光散乱も少なくできる。
【図面の簡単な説明】
【図１】この発明に係る可変焦点レンズの原理的構成を示す図である。
【図２】一軸性のネマティック液晶分子の屈折率楕円体を示す図である。
【図３】図１に示す高分子分散液晶層に電界を印加状態を示す図である。
【図４】図１に示す高分子分散液晶層への印加電圧を可変にする場合の一例の構成を示す図である。
【図５】この発明に係る可変焦点レンズを用いるデジタルカメラ用の撮像光学系の一例の構成を示す図である。
【図６】同じく、この発明に係る可変焦点レンズを用いる電子内視鏡用の対物光学系の一例の構成を示す図である。
【図７】この発明に係る可変焦点回折光学素子の一例の構成を示す図である。
【図８】この発明に係る可変焦点回折光学素子を眼鏡レンズとして用いる可変焦点眼鏡を示す図である。
【図９】図８に示す可変焦点回折光学素子に電圧を印加した状態を示す図である。
【図１０】従来の二重焦点レンズを用いる眼鏡を示す図である。
【図１１】図８に示す可変焦点眼鏡の変形例を示す図である。
【図１２】同じく、他の変形例を示す図である。
【図１３】ツイストネマティック液晶を用いる可変焦点レンズを有する可変焦点眼鏡の構成を示す図である。
【図１４】図１３に示すツイストネマティック液晶層への印加電圧を高くしたときの液晶分子の配向状態を示す図である。
【図１５】この発明に係る可変偏角プリズムの二つの例の構成を示す図である。
【図１６】図１５に示す可変偏角プリズムの使用態様を説明するための図である。
【図１７】この発明に係る可変焦点レンズとしての可変焦点ミラーの一例の構成を示す図である。
【図１８】従来の液晶レンズを用いる光学系の構成を示す図である。
【図１９】図１８に示す液晶レンズに電界を印加した状態を示す図である。
【図２０】ラジアルグラディエントの不均質媒質レンズを示す図である。
【図２１】図２０に示す不均質媒質レンズの屈折率分布を示す図である。
【図２２】不均質媒質レンズの素材を示す図である
【図２３】センターレスによる不均質素材の研削工程を説明するための図である。
【図２４】切断機による不均質素材の切断工程を説明するための図である。
【図２５】切断した不均質素材のＶブロックへの接着状態を示す図である。
【図２６】切断した不均質素材の歯車への接着状態を示す図である。
【図２７】平面研削盤による不均質素材の研削工程を説明するための図である。
【図２８】研磨機による不均質素材の精研削、研磨工程を説明するための図である。
【図２９】ダライ盤による不均質素材の面取り工程を説明するための図である。
【図３０】研磨機による不均質素材の精研削、研磨工程の他の例を説明するための図である。
【図３１】サイダ式芯取り機による不均質素材の研削工程を説明するための図である。
【図３２】球面の不均質媒質レンズの製造に用いるヤトイの形成工程を説明するための図である。
【図３３】ヤトイへの不均質素材の取り付け状態を示す図である。
【図３４】研磨機による不均質素材の精研削、研磨工程を説明するための図である。
【図３５】不均質素材のヤトイへの貼り付け工程を説明するための図である。
【図３６】カーブジェネレータによる不均質素材の曲率面研削工程を説明するための図である。
【図３７】ベルクランプ芯取り機による不均質素材の外周の研削工程を説明するための図である。
【図３８】両面研磨後の不均質素材の外周の研削工程を説明するための図である。
【図３９】カーブジェネレータによる不均質素材の一方の面の研削工程を説明するための図である。
【図４０】同じく、カーブジェネレータによる不均質素材の他方の面の研削工程を説明するための図である。
【符号の説明】
８ａ 第１の面
８ｂ 第２の面
９ａ 第３の面
９ｂ 第４の面
１１ 可変焦点レンズ
１２ａ，１２ｂ レンズ
１３ａ，１３ｂ 透明電極
１４ 高分子分散液晶層
１５ スイッチ
１６ 交流電源
１７ 液晶分子
１８ 高分子セル
１９ 可変抵抗器
２１ 絞り
２２ レンズ
２３ 固体撮像素子
２５ 前方レンズ
２６ 絞り
２７ 可変焦点レンズ
２８ 後方レンズ
２９ 固体撮像素子
３１ 可変焦点回折光学素子
３２，３３ 透明基板
３２ａ 第１の面
３２ｂ 第２の面
３３ａ 第３の面
３３ｂ 第４の面
３５ 可変焦点眼鏡
３５ａ フレーム
３６ 可変焦点回折光学素子
３７，３８ レンズ
３９ａ，３９ｂ 配向膜
４５ 物体
４６ 測距センサ
６１ 可変偏角プリズム
６２，６３ 透明基板
６２ａ 第１の面
６２ｂ 第２の面
６３ａ 第３の面
６３ｂ 第４の面
６５ 可変焦点ミラー
６６，６７ 透明基板
６６ａ 第１の面
６６ｂ 第２の面
６７ａ 第３の面
６７ｂ 第４の面
６８ 反射膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable focus lens, a variable focus diffractive optical element, and a variable deflection prism as liquid crystal optical elements.
[0002]
[Prior art]
Conventionally, in constructing a variable focus lens system, when a lens manufactured by polishing glass is used, it is difficult to change the focal length by itself. As in the lens, the focal length of the lens system is changed by moving a part of the lens group in the optical axis direction. However, such a configuration has a drawback that the mechanical structure becomes complicated.
[0003]
As a solution to such a problem, for example, an optical system using a polarizing plate 1 and a liquid crystal lens 2 has been proposed as shown in FIG. Here, the liquid crystal lens 2 has lenses 3a and 3b and a liquid crystal layer 5 provided between these lenses via transparent electrodes 4a and 4b, and an AC power supply via a switch 6 between the transparent electrodes 4a and 4b. 7 is connected, and an electric field is selectively applied to the liquid crystal layer 5 to change its refractive index.
[0004]
In such an optical system, for example, when natural light is incident on the polarizing plate 1, only the predetermined linearly polarized light component passes through the polarizing plate 1 and enters the liquid crystal lens 2. Here, as shown in FIG. 18, in the state where the switch 6 is off and no electric field is applied to the liquid crystal layer 5, the liquid crystal molecules 5a are oriented in the same direction as the incident linearly polarized light. The refractive index increases and the focal length of the liquid crystal lens 2 decreases. On the other hand, as shown in FIG. 19, when the switch 6 is on and an electric field is applied to the liquid crystal layer 5, the liquid crystal molecules 5 a have the major axis parallel to the optical axis. The refractive index is lowered, and the focal length of the liquid crystal lens 2 is increased. As described above, in the optical system shown in FIG. 18, the focal length is made variable by selectively applying an electric field to the liquid crystal lens 2.
[0005]
[Problems to be solved by the invention]
However, in the optical system using the liquid crystal lens 2 shown in FIG. 18, it is necessary to dispose the polarizing plate 1 in front of the liquid crystal lens 2 so that only a predetermined linearly polarized component enters the liquid crystal lens 2. There is a problem in that the light that passes through the polarizing plate 1 and enters the liquid crystal lens 2 is reduced, and the light use efficiency is lowered. In addition, since the light utilization efficiency is low as described above, there is a problem in that applicable products are limited and lack of versatility.
[0006]
The present invention has been made paying attention to the above-mentioned conventional problems, and can improve the light use efficiency, and is a liquid crystal having excellent versatility that is appropriately configured so that it can be effectively applied to various optical products. An object of the present invention is to provide a variable focus lens, a variable focus diffractive optical element, and a variable deflection prism as optical elements.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a variable focus lens, a variable focus diffractive optical element, or a variable declination prism as a liquid crystal optical element using a polymer dispersed liquid crystal,
The liquid crystal optical element includes a first optical member, a second optical member, and a pair of transparent electrodes,
The pair of transparent electrodes are arranged such that one transparent electrode is disposed on the first optical member and the other transparent electrode is disposed on the second optical member between the first optical member and the second optical member. Placed in
A layer of polymer dispersed liquid crystal is disposed between a pair of transparent electrodes,
The following conditions
0.01 ≦ | n _o '-N _LC ′ | ≦ 10
D ・ t ≦ λ ・ 15μm
The liquid crystal optical element characterized by satisfying the above can be provided.
Where n _o ′ Is the average refractive index of ordinary rays, and n _LC 'Is the average refractive index of the liquid crystal molecules, D is the average diameter of the polymer cell containing the liquid crystal molecules constituting the polymer dispersed liquid crystal, t is the thickness of the polymer dispersed liquid crystal layer in the optical axis direction, and λ is the light The wavelength is λ = 500 nm.
[0008]
Further, according to the present invention, a variable focus lens, a variable focus diffractive optical element, or a variable declination prism as a liquid crystal optical element using a polymer dispersed liquid crystal,
The liquid crystal optical element includes a first optical member, a second optical member, and a pair of transparent electrodes,
The pair of transparent electrodes are arranged such that one transparent electrode is disposed on the first optical member and the other transparent electrode is disposed on the second optical member between the first optical member and the second optical member. Placed in
A layer of polymer dispersed liquid crystal is disposed between a pair of transparent electrodes,
The following conditions
7nm ≦ D ≦ 500λ
D ・ t ≦ λ ・ 15μm
The liquid crystal optical element characterized by satisfying the above can be provided.
Where D is the average diameter of the polymer cell containing the liquid crystal molecules constituting the polymer dispersed liquid crystal layer, t is the thickness of the polymer dispersed liquid crystal layer in the optical axis direction, λ is the wavelength of light, and λ = 500 nm It is.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing the basic configuration of a variable focus lens according to the present invention. The variable focus lens 11 includes a first lens 12a having lens surfaces 8a and 8b as first and second surfaces, and a second lens having lens surfaces 9a and 9b as third and fourth surfaces. 12b and a polymer-dispersed liquid crystal layer 14 provided between these lenses via transparent electrodes 13a and 13b, and converges incident light through the first and second lenses 12a and 12b. The transparent electrodes 13a and 13b are connected to an AC power source 16 via a switch 15 so as to selectively apply an AC electric field to the polymer dispersed liquid crystal layer. The polymer-dispersed liquid crystal layer 14 includes a large number of minute polymer cells 18 each having an arbitrary shape such as a sphere or a polyhedron each containing liquid crystal molecules 17, and the volume thereof constitutes the polymer cell 18. To the sum of the volume occupied by the polymer and the liquid crystal molecules 17.
[0011]
Here, when the size of the polymer cell 18 is, for example, a spherical shape, when the average diameter D is λ and the wavelength of light to be used is, for example,
2 nm ≦ D ≦ λ / 5 (1)
And That is, since the size of the liquid crystal molecules 17 is about 2 nm or more, the lower limit value of the average diameter D is 2 nm or more. The upper limit value of D also depends on the thickness t of the polymer dispersed liquid crystal layer 14 in the optical axis direction of the variable focus lens 11, but if it is larger than λ, the refractive index of the polymer and the liquid crystal molecules 17 Due to the difference from the refractive index, light is scattered at the boundary surface of the polymer cell 18 and the polymer-dispersed liquid crystal layer 14 becomes opaque. Therefore, as described later, it is preferably λ / 5 or less. Depending on the optical product in which the variable focus lens is used, high accuracy may not be required, and D may be equal to or less than λ. The transparency of the polymer dispersed liquid crystal layer 14 becomes worse as the thickness t increases.
[0012]
The liquid crystal molecules 17 are, for example, uniaxial nematic liquid crystal molecules. The refractive index ellipsoid of the liquid crystal molecules 17 has a shape as shown in FIG.
n_ox= N_oy= N_o        (2)
It is. Where n_oIndicates the refractive index of ordinary light, n_oxAnd n_oyIndicates the refractive index in the direction perpendicular to each other in the plane including the ordinary ray.
[0013]
Here, as shown in FIG. 1, when the switch 15 is turned off, that is, when an electric field is not applied to the polymer dispersed liquid crystal layer 14, the liquid crystal molecules 17 are directed in various directions. The layer 14 has a high refractive index and becomes a lens having a strong refractive power. On the other hand, as shown in FIG. 3, when the switch 15 is turned on and an AC electric field is applied to the polymer dispersed liquid crystal layer 14, the liquid crystal molecules 17 have a refractive index ellipsoid whose major axis direction is the optical axis of the variable focus lens 11. Therefore, the lens has a low refractive index and a low refractive power.
[0014]
Note that the voltage applied to the polymer-dispersed liquid crystal layer 14 can be changed stepwise or continuously by a variable resistor 19, for example, as shown in FIG. In this way, as the applied voltage increases, the liquid crystal molecules 17 are oriented so that the elliptical long axis gradually becomes parallel to the optical axis of the variable focus lens 11, so that the refractive power is stepwise or continuous. Can be changed to
[0015]
Here, the average refractive index n of the liquid crystal molecules 17 in the state shown in FIG. 1, that is, in the state where no electric field is applied to the polymer-dispersed liquid crystal layer 14._LC′ Represents the refractive index in the major axis direction of the refractive index ellipsoid as shown in FIG._zThen approximately
(N_ox+ N_oy+ N_z) / 3≡n_LC′ (3)
It becomes. Further, the average refractive index n when the above equation (2) is satisfied._LCIs n_zIs the refractive index n of extraordinary rays_eAnd
(2n_o+ N_e) / 3≡n_LC        (4)
Given in. At this time, the refractive index n of the polymer dispersed liquid crystal layer 14_AIs the refractive index of the polymer constituting the polymer cell 18_PAssuming that the volume ratio of the liquid crystal molecules 17 to the volume of the polymer dispersed liquid crystal layer 14 is ff, according to Maxwell Garnet's law,
n_A= Ff · n_LC'+ (1-ff) n_P        (5)
Given in.
[0016]
Therefore, as shown in FIG. 4, the radii of curvature of the inner surfaces of the lenses 12a and 12b, that is, the surfaces on the polymer dispersed liquid crystal layer 14 side are respectively R₁And R₂Then, the focal length f of the variable focus lens 11₁Is
1 / f₁= (N_A-1) (1 / R₁-1 / R₂(6)
Given in. R₁And R₂Is positive when the center of curvature is on the image point side. Further, refraction by the outer surfaces of the lenses 12a and 12b is excluded. That is, the focal length of the lens by only the polymer-dispersed liquid crystal layer 14 is given by equation (6).
[0017]
In addition, the average refractive index of ordinary light,
(N_ox+ N_oy) / 2 = n_o′ (7)
Then, the refractive index n of the polymer dispersed liquid crystal layer 14 in the state shown in FIG. 3, that is, in a state where an electric field is applied to the polymer dispersed liquid crystal layer 14._BIs
n_B= Ff · n_o'+ (1-ff) n_P        (8)
In this case, the focal length f of the lens by only the polymer-dispersed liquid crystal layer 14 is given by₂Is
1 / f₂= (N_B-1) (1 / R₁-1 / R₂(9)
Given in. The focal length when a lower voltage than that in FIG. 3 is applied to the polymer-dispersed liquid crystal layer 14 is the focal length f given by equation (6).₁And the focal length f given by equation (9)₂It becomes a value between.
[0018]
From the above formulas (6) and (9), the change rate of the focal length by the polymer dispersed liquid crystal layer 14 is
| (F₂-F₁) / F₂| = | (N_B-N_A) / (N_B-1) | (10)
Given in. Therefore, to increase this rate of change, | n_B-N_AIt is sufficient to increase |. here,
n_B-N_A= Ff (n_o'-N_LC′) (11)
Therefore, | n_o'-N_LCIf ′ | is increased, the rate of change can be increased. In practice, n_BIs about 1.3 to 2,
0.01 ≦ | n_o'-N_LC′ | ≦ 10 (12)
Then, when ff = 0.5, the focal length by the polymer dispersed liquid crystal layer 14 can be changed by 0.5% or more, so that an effective variable focus lens can be obtained. | N_o'-N_LC'| Cannot exceed 10 due to the limitation of the liquid crystal material.
[0019]
Next, the basis of the upper limit value of the above equation (1) will be described.
`` Solar Energy Materials and Solar Cells '' Vol. 31, Wilson and Eck, 1993, Eleevier Science Publishers Bv, pp. 197-214, `` Transmission variation using scattering / transparent switching films '' shows the size of polymer dispersed liquid crystals. The change in transmittance τ when changed is shown. On page 206 of this document, FIG. 6 shows that the radius of the polymer dispersed liquid crystal is r, t = 300 μm, ff = 0.5, n_P= 1.45, n_LC= 1.585 and λ = 500 nm, the transmittance τ is a theoretical value, r = 5 nm (D = λ / 50, D · t = λ · 6 μm (where D and λ are in nm, below It is also shown that τ≈90% when the same)) and τ≈50% when r = 25 nm (D = λ / 10).
[0020]
Here, for example, assuming that t = 150 μm, assuming that the transmittance τ varies with an exponential function of t, and estimating the transmittance τ when t = 150 μm, r = When 25 nm (D = λ / 10, D · t = λ · 15 μm), τ≈71%. Similarly, when t = 75 μm, τ≈80% when r = 25 nm (D = λ / 10, D · t = λ · 7.5 μm).
[0021]
From these results,
D ・ t ≦ λ ・ 15μm (13)
Then, τ is 70% to 80% or more, and it is sufficiently practical as a lens. Therefore, for example, when t = 75 μm, sufficient transmittance can be obtained with D ≦ λ / 5.
[0022]
The transmittance of the polymer dispersed liquid crystal layer 14 is n_PValue of n_LCThe closer to the value of ′, the better. On the other hand, n_o′ And n_PIf the value becomes different, the transmittance of the polymer dispersed liquid crystal layer 14 becomes worse. The average transmittance of the polymer-dispersed liquid crystal layer 14 between the state of FIG. 1 and the state of FIG.
n_P= (N_o'+ N_LC′) / 2 (14)
When you are satisfied.
[0023]
Here, since the varifocal lens 11 is used as a lens, the transmittance is substantially the same in the state of FIG. 1 and the state of FIG. For this purpose, there are limitations on the material of the polymer constituting the polymer cell 18 and the material of the liquid crystal molecule 17, but practically,
n_o′ ≦ n_P≦ n_LC′ (15)
And it is sufficient.
[0024]
If the above expression (14) is satisfied, the above expression (13) is further relaxed,
D ・ t ≦ λ ・ 60μm (16)
If it is good. This is because, according to Fresnel's reflection law, the reflectance is proportional to the square of the difference in refractive index. Therefore, the reflection of light at the boundary between the polymer constituting the polymer cell 18 and the liquid crystal molecule 17, that is, polymer dispersion This is because the decrease in the transmittance of the liquid crystal layer 14 is approximately proportional to the square of the difference in refractive index between the polymer and the liquid crystal molecules 17.
[0025]
The above is n_o'≒ 1.45, n_LCIt was the case of ′ ≒ 1.585, but more generally formulated,
D ・ t ≦ λ ・ 15μm ・ (1.585 −1.45)²/ (N_u-N_P)²    (17)
If it is. However, (n_u-N_P)²(N_LC'-N_P)²And (n_o'-N_P)²And the larger one.
[0026]
Further, in order to increase the focal length change of the variable focus lens 11, it is better that the value of ff is large. However, when ff = 1, the polymer volume becomes zero and the polymer cell 18 cannot be formed.
0.1 ≦ ff ≦ 0.999 (18)
And On the other hand, as ff becomes smaller, τ improves, so the above equation (17) is preferably

And As is clear from FIG. 1, the lower limit value of t is t = D, and D is 2 nm or more as described above. Therefore, the lower limit value of D · t is (2 × 10^-3μm)²Ie 4 × 10^-6[Μm]²It becomes.
[0027]
The approximation that expresses the optical properties of a substance in terms of refractive index is valid, as described in “Iwanami Science Library 8 Asteroids Come” by Mukai Tadashi, 1994, page 58 of Iwanami Shoten. This is the case when it is larger than 10 nm to 5 nm. When D exceeds 500λ, the light scattering becomes geometric, and the light scattering at the interface between the polymer constituting the polymer cell 18 and the liquid crystal molecules 17 increases according to Fresnel's reflection formula. Is practical
7 nm ≦ D ≦ 500λ (20)
And
[0028]
In the configuration shown in FIG. 1 or FIG._ox, N_oy, N_o, N_z, N_e, N_P, Ff, D, t, λ, R₁, R₂, N_LC', N_LC, N_A, N_B, F₁, F₂Specifically, the diameter φ of the variable focus lens 11 is set to the following values, respectively.
n_ox= N_oy= N_o= 1.5
n_z= N_e= 1.75
n_P= 1.54
ff = 0.5
D = 50 nm
t = 125 μm
λ = 500nm
R₁= 25mm
R₂= ∞
n_LC'= N_LC= 1.5833
n_A= 1.5617
n_B= 1.52
f₁= 44.5mm
f₂= 48.04mm
φ = 5mm
[0029]
In this case, the right side of the equation (19) is
λ ・ 45μm ・ (1.585−1.45)²/ (n_u-N_P)²
= 500nm ・ 45μm ・ (0.135)²/(0.0433)²
≒ 218187nm ・ μm
It becomes. D · t is

This certainly satisfies the equation (19).
[0030]
In the above specific example, R₁= R₂= ∞. In this case, since the optical path length of the polymer-dispersed liquid crystal layer 14 changes depending on whether the voltage is turned on or off, the varifocal lens 11 is arranged in a portion where the light flux of the lens system is not parallel to adjust the focus. Or for changing the focal length of the entire lens system.
[0031]
FIG. 5 shows a configuration of an imaging optical system for a digital camera using the variable focus lens 11 shown in FIG. In this image pickup optical system, an image of an object (not shown) is formed on a solid-state image pickup device 23 made of, for example, a CCD via a diaphragm 21, a variable focus lens 11, and a lens 22. In FIG. 5, the liquid crystal molecules are not shown.
[0032]
According to such an imaging optical system, the variable focus lens 11 is adjusted by changing the focal length of the variable focus lens 11 by adjusting the AC voltage applied to the polymer dispersed liquid crystal layer 14 of the variable focus lens 11 by the variable resistor 19. For example, it is possible to continuously focus on an object distance from infinity to 600 mm without moving the lens 22 in the optical axis direction.
[0033]
FIG. 6 shows a configuration of an objective optical system for an electronic endoscope using the variable focus lens according to the present invention. In this objective optical system, an image of an object (not shown) is formed on a solid-state imaging device 29 made of, for example, a CCD via a front lens 25, a diaphragm 26, a variable focus lens 27, and a rear lens 28. Here, the varifocal lens 27 is configured in such a manner that the radius of curvature R1 of the inner surface of one lens 12a sandwiching the polymer dispersed liquid crystal layer 14 is infinite and the inner surface of the other lens 12b is formed in a Fresnel lens shape. In the same manner, an AC voltage is applied to the polymer dispersed liquid crystal layer 14 from an AC power source 16 via a variable resistor 19 and a switch 15. In FIG. 6, the liquid crystal molecules are not shown.
[0034]
Also in such an objective optical system, by adjusting the AC voltage applied to the polymer-dispersed liquid crystal layer 14 of the variable focus lens 27 according to the object distance and changing the focal length of the variable focus lens 27, the variable focus lens 27 is changed. In addition, it is possible to perform focus adjustment without moving the rear lens 28 in the optical axis direction.
[0035]
FIG. 7 shows a configuration of an example of a variable focus diffractive optical element according to the present invention. The variable focus diffractive optical element 31 includes a first transparent substrate 32 having parallel first and second surfaces 32a and 32b, and a ring-shaped diffraction grating having a sawtooth wave cross section having a groove depth in the order of the wavelength of light. The second transparent substrate 33 having the formed third surface 33a and flat fourth surface 33b is provided, and incident light is emitted through the first and second transparent substrates 32 and 33. As described with reference to FIG. 1, the polymer-dispersed liquid crystal layer 14 is provided between the first and second transparent substrates 32 and 33 via the transparent electrodes 13a and 13b, and the switch 15 is connected to the transparent electrodes 13a and 13b. Then, it is connected to an AC power supply 16 so that an AC electric field is applied to the polymer dispersed liquid crystal layer 14.
[0036]
In such a configuration, when the light beam incident on the variable focus diffractive optical element 31 has the grating pitch of the third surface 33a as p and m is an integer,
p sinθ = mλ (21)
It is deflected by an angle θ that satisfies the condition and emitted. Further, the groove depth is h, and the refractive index of the transparent substrate 33 is n.₃₃And k is an integer,
h (n_A-N₃₃) = Mλ (22)
h (n_B-N₃₃) = Kλ (23)
If the above condition is satisfied, the diffraction efficiency becomes 100% at the wavelength λ, and the occurrence of flare can be prevented.
[0037]
Here, when the difference between both sides of the equations (22) and (23) is obtained,
h (n_A-N_B) = (M−k) λ (24)
Is obtained. Thus, for example, λ = 500 nm, n_A= 1.55, n_B= 1.5
0.05h = (m−k) · 500 nm
When m = 1 and k = 0,
h = 10000 nm = 10 μm
It becomes. In this case, the refractive index n of the transparent substrate 33₃₃From the above equation (22), n₃₃= 1.5 is sufficient. If the grating pitch p at the periphery of the variable focus diffractive optical element 31 is 10 μm, θ≈2.87 °, and a lens with an F number of 10 can be obtained.
[0038]
Since the optical path length of the varifocal diffractive optical element 31 changes depending on whether the voltage applied to the polymer-dispersed liquid crystal layer 14 is turned on or off, for example, the varifocal diffractive optical element 31 is arranged in a portion where the luminous flux of the lens system is not parallel to perform focus adjustment It can be used to change the focal length of the entire lens system.
[0039]
In this embodiment, the above formulas (22) to (24) are practically
0.7 mλ ≦ h (n_A-N₃₃) ≦ 1.4mλ (25)
0.7 kλ ≦ h (n_B-N₃₃) ≦ 1.4kλ (26)
0.7 (m−k) λ ≦ h (n_A-N_B) ≦ 1.4 (m−k) λ (27)
Should be satisfied.
[0040]
FIGS. 8 and 9 show variable-focus eyeglasses 35 using a variable-focus diffractive optical element 36 as a spectacle lens. The varifocal diffractive optical element 36 has lenses 37 and 38, and a ring-shaped diffraction grating having a sawtooth wave section similar to that described in FIG. 7 is formed on the inner surface of the lens 37 on the incident side. Alignment films 39a and 39b are provided on the inner surfaces of the lenses 37 and 38 via transparent electrodes 13a and 13b, respectively. A polymer-dispersed liquid crystal layer similar to that described in FIG. 1 is provided between the alignment films 39a and 39b. 14 is provided. Further, the transparent electrodes 13a and 13b are connected to an AC power source 16 through a switch 15 so that an AC electric field is applied to the polymer dispersed liquid crystal layer.
[0041]
According to the variable focus glasses 35 having such a configuration, when the switch 15 shown in FIG. 8 is turned off by manually turning on / off the switch 15, for example, and when the switch 15 shown in FIG. 9 is turned on. Since the arrangement of the liquid crystal molecules 17 in the polymer dispersed liquid crystal layer 14 can be changed, the diopter of the entire spectacle lens can be changed. Therefore, a sense of incongruity is eliminated as compared with a case where the diopter changes in the line-of-sight direction, such as the glasses 42 using the conventional bifocal lens 41 shown in FIG.
[0042]
FIG. 11 shows a variable focus eyeglass 35 shown in FIG. 8, for example, provided with a distance measuring sensor 46 for measuring the distance to the object 45 on the frame 35a, and the switch 15 is turned on / off based on the output of the distance measuring sensor 46. Thus, diopter adjustment is automatically performed.
[0043]
In this way, if the diopter is automatically adjusted based on the object distance, it is possible to obtain spectacles that are particularly useful for elderly people with diminished diopter adjustment power.
[0044]
8 and 11, the entire spectacle lens is the variable focus diffractive optical element 36, but a part of the spectacle lens, for example, slightly below the center as shown in FIG. Alternatively, the variable focus diffractive optical element 36 may be provided. Further, in place of the variable focus diffractive optical element 36, the variable focus lens 11 shown in FIG. 1 or the variable focus lens 27 shown in FIG. 6 may be used. Further, in FIG. 11, the switch 15 is automatically switched based on the output of the distance measuring sensor 46, but a new switch can be provided to select between automatic switching by the distance measuring sensor 46 and manual switching. It is also possible to configure such that it can be changed to manual switching during automatic switching by the distance measuring sensor 46. Furthermore, a hearing aid can be provided integrally with the variable focus glasses 35 described above.
[0045]
When the distance measuring sensor 46 is provided as shown in FIG. 11, the voltage applied to the polymer dispersed liquid crystal layer 14 of the variable focus diffractive optical element 36 can be varied stepwise or continuously, and the user can Accordingly, the correspondence relationship between the output of the distance measuring sensor 46 and the applied voltage can be preset, and the applied voltage can be controlled based on the output of the distance measuring sensor 46. In this way, more accurate diopter adjustment according to the object distance can be automatically performed for each user.
[0046]
Further, in the variable focus glasses 35 described above, the AC power supply 16 can be configured with an inverter circuit using a battery as a power supply. In this case, as the battery, one or more of a manganese battery, a lithium battery, a solar battery, and a rechargeable battery are integrated into the frame 35a, that is, built in, or provided separately and connected by a cord, or An internal battery and an external battery may be included.
[0047]
Further, when simply configuring variable focus glasses, a variable focus lens using twisted nematic liquid crystal can be used instead of the above-described variable focus lens using polymer dispersed liquid crystal. FIGS. 13 and 14 show the configuration of the varifocal glasses 50 in this case. The varifocal lens 51 is provided on the inner surfaces of the lenses 52 and 53 and transparent electrodes 13a and 13b, respectively. Alignment films 39a and 39b and a twisted nematic liquid crystal layer 54 provided between the alignment films. The transparent electrodes 13a and 13b are connected to the AC power supply 16 via the variable resistor 19, and twisted. An AC electric field is applied to the nematic liquid crystal layer 54.
[0048]
In such a configuration, when the voltage applied to the twisted nematic liquid crystal layer 54 is increased, the liquid crystal molecules 55 are in a homeotropic orientation as shown in FIG. 14, and compared with the twisted nematic state where the applied voltage is low as shown in FIG. The refractive index of the twisted nematic liquid crystal layer 54 becomes smaller and the focal length becomes longer.
[0049]
Here, since the helical pitch P of the liquid crystal molecules 55 in the twisted nematic state shown in FIG. 13 needs to be sufficiently smaller than the wavelength λ of light,
2 nm ≦ P ≦ 2λ / 3 (28)
And The lower limit of this condition is determined by the size of the liquid crystal molecules, and the upper limit is a value necessary for the twisted nematic liquid crystal layer 54 to behave as an isotropic medium in the state of FIG. 13 when the incident light is natural light. If the upper limit condition is not satisfied, the variable focus lens 51 becomes a lens having a different focal length depending on the polarization direction, so that a double image is formed and only a blurred image can be obtained.
[0050]
FIG. 15A shows the configuration of the variable declination prism according to the present invention.
The variable deflection prism 61 has a first transparent substrate 62 on the incident side having first and second surfaces 62a and 62b, and a parallel flat plate shape on the output side having third and fourth surfaces 63a and 63b. And a second transparent substrate 63. The inner surface (second surface) 62b of the incident-side transparent substrate 62 is formed in a Fresnel shape, and a transparent electrode is formed between the transparent substrate 62 and the emitting-side transparent substrate 63 in the same manner as described with reference to FIG. A polymer-dispersed liquid crystal layer 14 is provided via 13a and 13b. The transparent electrodes 13a and 13b are connected to the AC power supply 16 via the variable resistor 19, thereby applying an AC electric field to the polymer dispersed liquid crystal layer 14 to control the deflection angle of the light transmitted through the variable deflection prism 61. To do. In FIG. 15A, the inner surface 62b of the transparent substrate 62 is formed in a Fresnel shape. For example, as shown in FIG. 15B, the inner surfaces of the transparent substrates 62 and 63 are relatively inclined. It can be formed in a normal prism shape having a surface, or can be formed in the diffraction grating shape shown in FIG. In the case of forming a diffraction grating, the above formulas (21) to (27) are similarly applied.
[0051]
The variable deflection prism 61 having such a configuration can be effectively used for preventing blurring of, for example, a TV camera, a digital camera, a film camera, and binoculars. In this case, the refractive direction (deflection direction) of the variable deflection prism 61 is preferably the vertical direction, but in order to further improve the performance, the deflection directions of the two variable deflection prisms 61 are different. For example, as shown in FIG. 16, it is desirable to arrange the refraction angle to change in the vertical and horizontal directions. In FIG. 15 and FIG. 16, the liquid crystal molecules are not shown.
[0052]
FIG. 17 shows a variable focus mirror as a variable focus lens according to the present invention. The variable focus mirror 65 includes a first transparent substrate 66 having first and second surfaces 66a and 66b, and a second transparent substrate 67 having third and fourth surfaces 67a and 67b. The first transparent substrate 66 is formed in a flat plate shape or a lens shape, and the transparent electrode 13a is provided on the inner surface (second surface) 66b. The second transparent substrate 67 has the inner surface (third surface) 67a. A reflective film 68 is formed on the concave surface, and a transparent electrode 13 b is provided on the reflective film 68. As described with reference to FIG. 1, a polymer dispersed liquid crystal layer 14 is provided between the transparent electrodes 13a and 13b, and these transparent electrodes 13a and 13b are connected to an AC power source 16 via a switch 15 and a variable resistor 19. Then, an AC electric field is applied to the polymer dispersed liquid crystal layer 14. In FIG. 17, the liquid crystal molecules are not shown.
[0053]
According to such a configuration, the light incident from the transparent substrate 66 side becomes an optical path for folding the polymer-dispersed liquid crystal layer 14 by the reflective film 68, so that the action of the polymer-dispersed liquid crystal layer 14 can be given twice. By changing the voltage applied to the polymer dispersed liquid crystal layer 14, the focal position of the reflected light can be changed. In this case, the light beam incident on the variable focus mirror 65 is transmitted twice through the polymer-dispersed liquid crystal layer 14, so that the above equations are the same if t is twice the thickness of the polymer-dispersed liquid crystal layer 14. Can be used. In addition, the inner surface of the transparent substrate 66 or 67 may be formed in a diffraction grating shape as shown in FIG. 7 to reduce the thickness of the polymer dispersed liquid crystal layer 14. In this way, there is an advantage that scattered light can be reduced.
[0054]
In the above description, in order to prevent deterioration of the liquid crystal, an AC electric field is applied to the liquid crystal using the AC power source 16 as a power source. However, a DC electric field is applied to the liquid crystal using a DC power source. You can also As a method of changing the direction of the liquid crystal molecules, in addition to changing the voltage, the frequency of the electric field applied to the liquid crystal, the strength / frequency of the magnetic field applied to the liquid crystal, or the temperature of the liquid crystal may be changed.
In the embodiment described above, the polymer-dispersed liquid crystal is not liquid but is almost solid, and in that case, one of the lenses 12a and 12b, one of the transparent substrate 32, the lens 38, and the lenses 52 and 53, FIG. One of the transparent substrates 63 and 67 in FIG. 15B and one of the transparent substrates 66 and 67 in FIG.
[0055]
Next, a method for manufacturing an inhomogeneous medium lens that is one of the lenses will be described.
The inhomogeneous medium lens is a lens made of a medium having a different refractive index for each lens portion. For example, in a radial gradient inhomogeneous medium lens 71 whose refractive index changes in the radial direction as shown in FIG. As shown in FIG. 21, the refractive index n decreases as the radius r increases with the optical axis O being the spectral central axis (refractive index distribution central axis) as the center. Note that the refractive index does not change in the direction along the optical axis.
[0056]
Such a non-homogeneous medium lens 71 is made of a material such as glass or plastic, and is made by an ion exchange method or a sol-gel method. However, as shown in FIG. 22, the material 72 of the inhomogeneous medium lens produced by these methods is in the form of a rod, and in order to obtain the inhomogeneous medium lens 71 as the final product, cutting, polishing, coating, etc. It is necessary to go through this process.
[0057]
On the other hand, in order to obtain a normal homogeneous lens made of glass or the like, first, both surfaces of one lens are polished, and then the object is rotated with respect to a line (optical axis) connecting the centers of two spherical surfaces. So that the outer periphery is shaved. This method is widely used in general and has an advantage of being inexpensive.
[0058]
However, in the case of an inhomogeneous medium lens, unlike the normal lens processing, the spectral center axis of the material 72 must be at the center of the outer periphery of the lens, and as shown in FIG. Must be orthogonal to the central axis. For this reason, when manufactured by the above-described normal lens processing method, the spectral center axis and the center of the lens outer periphery may be shifted or inclined, and the lens surface 73 may not be accurately orthogonal to the spectral center axis. .
[0059]
Hereinafter, a method for manufacturing an inhomogeneous medium lens capable of solving such a problem will be described with reference to the drawings.
First, an example of a manufacturing method when the lens surface 73 is a flat surface will be described. In this case, it is assumed that the center of the material 72 has a spectral center axis. This assumption is actually the same for the material 72 made by an ion exchange method, a sol-gel method or the like. First, as shown in FIG. 23, the diameter of the material 72 is sharpened with a centerless 75 so that the spectral center axis does not deviate from the center of the material 72. In the centerless 75, the biaxial distance is adjusted in advance so that the outer diameter of the material 72a that has been reduced by cutting becomes the required lens diameter.
[0060]
Next, as shown in FIG. 24, the material 72 a is cut into a necessary lens length with a polishing margin added by a cutting machine 76. Thereafter, as shown in FIG. 25, the cut material 72b is adhered to the side surface of the V groove of the V block 77 placed on the plane so that the spectral center axis is orthogonal to the plane, or As shown in FIG. 26, the center axis of the gear 78 and the spectral center axis are bonded to the side surface of the tooth groove of the gear 78 so as to be parallel to each other.
[0061]
Next, the material 72b bonded to the V block 77 or the gear 78 is set on a surface grinder 81 as shown in FIG. 27, and the diamond grindstone is set so that one lens surface of the material 72b is orthogonal to the spectral center axis. Sharpen with. Thereafter, as shown in FIG. 28, the grinding machine 82 gradually performs fine grinding at several stages using fine diamond pellets 82 a, and then uses a urethane sheet or pitch to obtain CeO.₂And polished with water to finish the lens surface mirror-like. For the other lens surface, the steps shown in FIGS. 25 to 28 are performed to finish the lens surface in the same manner.
[0062]
Then, as shown in FIG. 29, after chamfering both lens surfaces with a drape board 84 or the like, both lens surfaces are coated with anti-reflection multi-coat or MgF.₂A single layer coating such as the above is applied to obtain an inhomogeneous medium lens having both surfaces flat.
[0063]
In the cutting step shown in FIG. 24, when the perpendicularity of the cut surface (lens surface) with respect to the spectral center axis is maintained, it is adhered to the V block 77 or the gear 78 shown in FIG. 25 or FIG. Alternatively, the lens surface shown in FIGS. 27 and 28 may be precisely ground and polished. When the polishing of one lens surface is completed in the step shown in FIG. 28, the lens surface that has been polished is abutted against and pasted on the affixing plate 86 as shown in FIG. Fine grinding and polishing may be performed. This simplifies the process and is advantageous in terms of cost.
[0064]
Furthermore, in another manufacturing method in which the lens surface 73 is a flat surface, the cutting step shown in FIG. 24 is performed without performing the outer diameter grinding step shown in FIG. The steps shown are performed on both lens surfaces. Next, as shown in FIG. 31, the material 72 c whose lens surface has been polished is attached to the cider-type centering machine 90 via the pitch 88. This pasting is performed while examining with the pick tester 91 or observing the outer periphery of the material 72c with the microscope 92 so that the material 72c does not shake when the cider type centering machine 90 is rotated. In this state, while rotating the cider-type centering machine 90, the outer periphery of the material 72c is ground with the grindstone 93 until the outer diameter of the finished lens is reached. Then, after chamfering with the cider type centering machine 90, an antireflection coating is applied to the lens surface to obtain an inhomogeneous medium lens in which the lens center and the spectral center axis coincide.
[0065]
The manufacturing method of the inhomogeneous medium lens having a flat surface on both sides has been described above. However, the above-described manufacturing method can be effectively applied to the case of a non-homogeneous medium lens having a flat surface on one side or the case where the outer diameter is made uniform after finishing. Can do.
[0066]
Next, an example of a manufacturing method for obtaining a spherical inhomogeneous medium lens having a radius R of the lens surface will be described. As shown in FIG. 32, first, a lens surface member 95 having a surface having a radius R is made of glass, metal, resin, or the like. Thereafter, the lens surface member 95 is affixed to the rotating shaft of the cider type centering machine so as not to be eccentric, and the rotating heterogeneous medium lens is rotated using the diamond grindstone 96 at the center while rotating the rotating shaft. A hole for entering the material is formed and the outer periphery is centered. The lens surface member in which this hole is formed will be referred to as yatoi.
[0067]
Next, as shown in FIG. 33, the cut heterogeneous medium lens material 72d is put into the hole of the yato 97 and fixed with gypsum or the like, and in this state, as shown in FIG. At the same time, the material 72d is precisely ground and polished to form a spherical surface having no eccentricity with respect to the spectral center axis. Note that the cut heterogeneous medium lens material 72c to be inserted into the hole of the Yatoi 97 can be pre-centered and trimmed to the outer diameter of the finished lens. In this case, as a matter of course, the hole of the Yatoi 97 has an inner diameter substantially equal to the outer diameter of the finished lens.
[0068]
The other surface can be formed into a spherical surface in the same manner, but in particular, when the lens rim (dimension in the optical axis direction of the outer peripheral surface) is small, the other surface is formed into a spherical surface by the following method. Can be formed. That is, as shown in FIG. 35, the inhomogeneous medium lens material 72e having one surface polished to a spherical surface is attached to a Yatoi 101 having a concave surface having a radius R on the spherical surface side via a pitch 88. In this pasting, as described with reference to FIG. 31, while the yatoe 101 is rotated, the material 72e is not shaken while being examined with the pick tester 91 or while the outer periphery of the material 72e is observed with the microscope 92. Do. Here, the yatoy 101 has substantially the same diameter as a rotation shaft of a curve generator or a centering machine, which will be described later, and can be attached to the curve generator or the centering machine with the material 72e attached. In addition, it is preferable that the spherical surface to be pasted on the Yatoi 101 is a spherical surface having a large curvature radius among the two spherical surfaces to be finally formed in terms of facilitating the pasting operation.
[0069]
Next, as shown in FIG. 36, the yatoe 101 is attached to the curve generator 102, and the other surface (the right surface in the figure) of the material 72e is ground so as to have a desired curvature. Thereafter, the Yatoi 101 is attached to the centering machine, and the outer periphery of the material 72e is ground to the finished outer diameter of the lens. Next, the other surface of the material 72e is polished to a mirror surface with a normal polishing machine, and then a necessary coating is applied to both surfaces to obtain a double-sided spherical inhomogeneous medium lens.
[0070]
In addition, you may make it perform the grinding process of the outer periphery of the raw material 72e by a centering machine after grinding | polishing of the other surface. In this case, as shown in FIG. 37, the outer periphery of the material 72e can be ground using a bell clamp centering machine 103. Further, when the outer periphery of the material 72e is ground after the other surface is polished, the double-side polished material 72e is attached to the yatoe 101 via the pitch 88 as shown in FIG. It can also be ground with a grindstone. In this case, the material 72e is attached to the Yatoi 101 while observing with the microscope 92 so as not to cause rotational shake. Alternatively, the outer periphery of the material 72e can be ground by observing the shake of the reflected image of the spherical surface of the material 72e (the surface on the right side in FIG. 38) with a normal cider-type centering machine without using the microscope 92.
[0071]
The spherically shaped inhomogeneous medium lens is not limited to the above-described manufacturing method, and can be obtained by the following method particularly when the edge of the lens, that is, the dimension of the lens outer peripheral surface in the optical axis direction is large. That is, as shown in FIG. 39, first, the cut material 72b is attached to the collet chuck 105, and one surface is ground to a desired spherical surface by the curve generator 102, and then the surface is precisely ground and pitch-polished. To. Next, as shown in FIG. 40, the material 72b is attached to the collet chuck 107 having the pipe 106 supporting the spherical surface so that the other surface (unpolished surface) of the material 72b is on the outside. Then, the other surface is ground to a desired spherical surface by the curve generator 102. The pipe 106 is used so that the lens rim L becomes a desired value and the spherical surface is not decentered with respect to the spectral center axis of the material 72b. Thereafter, the other surface ground to a spherical surface is subjected to fine grinding and pitch polishing to obtain a mirror surface. Next, if necessary, the outer diameter of the material 72b is ground to the finished lens outer diameter by any of the methods described above, and then chamfered and coated to obtain a double-sided spherical inhomogeneous medium lens. In the above description, the spherical inhomogeneous medium lens is manufactured. However, an aspherical inhomogeneous medium lens can be manufactured in the same manner.
[0072]
Additional notes
1. 2. The variable focus lens according to claim 1, wherein the variable focus lens is:
A first optical member having first and second surfaces and transmitting incident light through the first and second surfaces;
A second optical member having a third surface for receiving light transmitted through the first optical member;
A lens surface formed on at least one of the first, second and third surfaces;
A pair of transparent electrodes respectively provided on the second and third surface sides;
A polymer-dispersed liquid crystal layer provided between the transparent electrodes,
By applying an electric field to the polymer-dispersed liquid crystal layer via the pair of transparent electrodes, the light transmitted through the first and second optical members or the first optical member is transmitted, and the third A varifocal lens, wherein the focal position of the light reflected by the surface of the light and transmitted again through the first optical member can be varied.
2. 3. The variable focus diffractive optical element according to claim 2, wherein the variable focus diffractive optical element includes:
A first optical member having first and second surfaces and transmitting incident light through the first and second surfaces;
A second optical member having third and fourth surfaces and emitting light transmitted through the first optical member through the third and fourth surfaces;
A diffractive surface formed on at least one of the first, second and third surfaces;
Transparent electrodes respectively provided on the second and third surface sides;
A polymer-dispersed liquid crystal layer provided between the transparent electrodes,
A focus position of light transmitted through the first and second optical members can be varied by applying an electric field to the polymer dispersed liquid crystal layer through the pair of transparent electrodes. Variable focus diffractive optical element.
3. The variable deflection prism according to claim 3, wherein the variable deflection prism is
A first optical member having first and second surfaces and transmitting incident light through the first and second surfaces;
A second optical member having third and fourth surfaces and emitting light transmitted through the first optical member through the third and fourth surfaces;
An inclined surface formed on at least one of the first, second and third surfaces;
Transparent electrodes respectively provided on the second and third surface sides;
A polymer-dispersed liquid crystal layer provided between the transparent electrodes,
A declination angle of light transmitted through the first and second optical members can be varied by applying an electric field to the polymer dispersed liquid crystal layer through the pair of transparent electrodes. Variable declination prism.
4). A variable-focus eyeglass comprising the variable-focus lens or the variable-focus diffractive optical element according to any one of claims 1 and 2.
5. 4. An optical deflection apparatus comprising a plurality of variable deflection prisms according to claim 3 or appendix 3 so as to have different deflection directions.
6). An imaging apparatus comprising: the variable focus lens according to claim 1, a variable focus diffractive optical element, or a variable declination prism.
7). In the liquid crystal optical element comprising the variable focus lens, the variable focus diffractive optical element or the variable declination prism according to any one of claims 1, 2, 3, and appendices 1, 2, 3,
When the ratio of the volume of liquid crystal molecules to the volume of the polymer dispersed liquid crystal layer is ff, 0.1 ≦ ff ≦ 0.999
A liquid crystal optical element characterized by satisfying the above.
8). In the liquid crystal optical element comprising the variable focus lens, the variable focus diffractive optical element or the variable declination prism according to any one of claims 1, 2, 3, and appendices 1, 2, 3,
4 × 10^-6[Μm]²≦ D ・ t ≦ λ ・ 45μm ・ (1.585−1.45)²/ (n_u-N_P)²
A liquid crystal optical element characterized by satisfying
However, D: Average diameter of polymer cell containing liquid crystal molecules constituting polymer dispersed liquid crystal layer
t: thickness of the polymer-dispersed liquid crystal layer 14 in the optical axis direction
λ: Wavelength used
n_P: Refractive index of polymer constituting polymer cell
(N_u-N_P)²: (N_LC'-N_P)²And (n_o'-N_P)²The larger of
n_LC': Average refractive index of liquid crystal molecules
n_o': Average refractive index of ordinary ray
9. In the liquid crystal optical element comprising the variable focus lens, the variable focus diffractive optical element or the variable declination prism according to any one of claims 1, 2, 3, and appendices 1, 2, 3,
2 nm ≦ D ≦ λ / 5
A liquid crystal optical element characterized by satisfying
9 '. In the liquid crystal optical element comprising the variable focus lens, the variable focus diffractive optical element or the variable declination prism according to any one of claims 1, 2, 3, and appendices 1, 2, 3,
2 nm ≦ D <λ
A liquid crystal optical element characterized by satisfying
10. In the liquid crystal optical element comprising the variable focus lens, the variable focus diffractive optical element or the variable declination prism according to any one of claims 1, 2, 3, and appendices 1, 2, 3,
0.01 ≦ | n_o'-N_LC′ | ≦ 10
A liquid crystal optical element characterized by satisfying
11. In the liquid crystal optical element comprising the variable focus lens, the variable focus diffractive optical element or the variable declination prism according to any one of claims 1, 2, 3, and appendices 1, 2, 3,
7nm ≦ D ≦ 500λ
A liquid crystal optical element characterized by satisfying
12 The varifocal diffractive optical element according to any one of claims 2 and 7, or 7 to 11,
0.7 mλ ≦ h (n_A-N₃₃) ≦ 1.4mλ
0.7 kλ ≦ h (n_B-N₃₃) ≦ 1.4kλ
0.7 (m−k) λ ≦ h (n_A-N_B) ≦ 1.4 (m−k) λ
A varifocal diffractive optical element that satisfies the following.
Where m and k are integers
h: Groove depth of the lattice
n_A: Refractive index of polymer-dispersed liquid crystal layer when no electric field is applied
n_B: Refractive index of polymer-dispersed liquid crystal layer with electric field applied
n₃₃: Refractive index of transparent substrate with diffraction grating
13. A liquid crystal variable focus spectacle having the variable focus lens or the variable focus diffractive optical element according to any one of claims 1 and 2 and appendices 1, 2, and 7-12.
14 An imaging apparatus comprising: the variable focus lens according to any one of appendices 7 to 12, a variable focus diffractive optical element, or a variable deflection prism.
15. A liquid crystal optical element as a spectacle lens having a pair of electrodes facing each other and a twisted nematic liquid crystal layer provided between the electrodes;
The twisted nematic liquid crystal layer has a helical pitch P of liquid crystal molecules in a twisted nematic state.
2 nm ≦ P ≦ 2λ / 3
Liquid crystal variable focus glasses characterized by satisfying
16. In the variable focus lens according to appendix 1,
A varifocal mirror characterized in that a reflective film is provided on the third surface so that incident light is folded back into the polymer-dispersed liquid crystal layer and allowed to pass a plurality of times.
17. Item 17. A liquid crystal optical element comprising the variable focus lens, variable focus diffractive optical element or variable declination prism according to any one of items 1 to 16, and a voltage source for applying a voltage between the pair of electrodes of the liquid crystal optical element. And a liquid crystal optical device.
18. In the liquid crystal optical device according to appendix 17,
The liquid crystal optical device, wherein the voltage source is configured to apply a variable voltage between the pair of electrodes.
19. In manufacturing inhomogeneous medium lenses,
A method for producing a heterogeneous medium lens, comprising a step of grinding an outer diameter of a heterogeneous material to a lens finished outer diameter using a centerless.
20. In manufacturing inhomogeneous medium lenses,
Adjusting the deflection of the outer periphery of the heterogeneous material using a pick tester or a microscope, fixing the heterogeneous material to the rotation shaft of the centering machine, and then grinding the outer diameter to the lens finished outer diameter. A method for producing a heterogeneous medium lens.
21. In manufacturing inhomogeneous medium lenses,
After forming a curved surface with a desired shape on the inhomogeneous material so that the center substantially coincides with the spectral center axis, the outer periphery of the inhomogeneous material is ground to the lens finished outer diameter using a bell clamp or a cider type centering machine. A method for producing a heterogeneous medium lens, comprising the step of:
22. In manufacturing inhomogeneous medium lenses,
Manufacturing a heterogeneous medium lens, comprising a step of grinding and polishing the heterogeneous material into a flat surface in a state in which the heterogeneous material is fixed to a jig so as to be perpendicular to the grinding surface direction. Method.
23. In the method for manufacturing an inhomogeneous medium lens according to Additional Item 22,
A method for manufacturing a heterogeneous medium lens, wherein a V block or a gear is used as the jig.
24. In manufacturing inhomogeneous medium lenses,
Glass, metal, resin, etc. whose outer diameter is larger than the outer diameter of the inhomogeneous medium lens to be manufactured and which has a curved surface of a desired shape and has a hole substantially equal to the diameter of the inhomogeneous material at the center. A heterogeneous medium lens comprising the steps of: fixing a heterogeneous material in a hole of the yatoy, and grinding and polishing the heterogeneous material into a curved surface of a desired shape together with the yatoy Method.
25. In manufacturing inhomogeneous medium lenses,
After fixing the curved surface of the inhomogeneous material obtained by grinding one surface into a curved surface having a desired shape, to the rotation axis of a Yatoi having a curved surface having the opposite shape, by adjusting the deflection of the outer periphery using a pick tester or a microscope, A method of manufacturing an inhomogeneous medium lens, comprising a step of grinding the other surface of the inhomogeneous material into a curved surface having a desired shape using a curve generator.
26. In manufacturing inhomogeneous medium lenses,
A heterogeneous medium comprising a step of forming a curved surface having a desired shape whose center substantially coincides with the spectral center axis at both ends of the heterogeneous material, and then centering the heterogeneous material by a bell clamp method. Lens manufacturing method.
27. In manufacturing inhomogeneous medium lenses,
After forming a curved surface of the desired shape whose center is almost coincident with the spectral center axis at both ends of the heterogeneous material, fix one curved surface to a yatoi having a curved surface of the opposite shape, and use the other curved surface A method for producing a heterogeneous medium lens, comprising the step of observing a reflected image and centering the heterogeneous material with a cider type centering machine.
28. In manufacturing inhomogeneous medium lenses,
A non-uniform material comprising a step of forming a curved surface having a desired shape whose center substantially coincides with the spectral center axis at both ends of the heterogeneous material, and then centering the heterogeneous material with a cider-type centering machine. A method for producing a homogeneous medium lens.
29. In manufacturing inhomogeneous medium lenses,
A method of manufacturing a heterogeneous medium lens, comprising a step of grinding one surface into a curved surface having a desired shape using a curve generator in a state where the heterogeneous material is fixed by a collet chuck.
30. In manufacturing inhomogeneous medium lenses,
After forming one surface of the inhomogeneous material into a curved surface having a desired shape having a center substantially coincident with the spectral center axis, the inhomogeneous material is fixed with a collet chuck while supporting the curved surface with a pipe. A method of manufacturing an inhomogeneous medium lens, comprising a step of grinding the other surface into a curved surface having a desired shape using a curve generator.
31. In the method for producing a heterogeneous medium lens according to any one of appendices 19 to 30,
A method for producing an inhomogeneous medium lens, wherein the inhomogeneous material uses a material in which a central axis of the material and a spectral center axis substantially coincide with each other.
[0073]
According to the image pickup apparatus described in appendix 6, since the response of the liquid crystal optical element is fast, the moving image can be autofocused, and there is an advantage that the image can be picked up even in a dark place because there is little light loss.
According to the method for manufacturing an inhomogeneous medium lens described in appendix 19, an inhomogeneous medium lens with less eccentricity can be obtained at low cost.
According to the method for manufacturing a heterogeneous medium lens described in appendix 20, compared to the manufacturing method described in appendix 19, a more accurate heterogeneous medium lens can be obtained, and quality control is facilitated.
According to the method for manufacturing an inhomogeneous medium lens described in appendix 21, an inhomogeneous medium lens with less eccentricity can be obtained by simple processing by accurately forming a curved surface having a desired shape.
According to the method for manufacturing an inhomogeneous medium lens described in Additional Item 22, an inhomogeneous medium lens with little surface eccentricity can be obtained.
According to the method for manufacturing an inhomogeneous medium lens described in appendix 24, an inhomogeneous medium lens with less eccentricity can be easily obtained as long as Yatoi is formed with high accuracy.
According to the method for manufacturing an inhomogeneous medium lens described in appendix 25, an inhomogeneous medium lens having a small edge can be easily obtained.
According to the method for manufacturing an inhomogeneous medium lens described in appendix 26, an inhomogeneous medium spherical lens with less eccentricity can be obtained.
According to the method for manufacturing an inhomogeneous medium lens described in Additional Item 27, a highly accurate inhomogeneous medium spherical lens with less eccentricity can be obtained.
According to the method for manufacturing an inhomogeneous medium lens described in Additional Item 28, a highly accurate inhomogeneous medium spherical lens with less eccentricity can be obtained by simple processing.
According to the method for manufacturing an inhomogeneous medium lens described in the additional items 29 and 30, an inhomogeneous medium spherical lens with less eccentricity can be easily obtained.
[0074]
【The invention's effect】
  According to the variable focus lens, the variable focus diffractive optical element and the variable declination prism as the liquid crystal optical element according to the present invention, since the polymer dispersed liquid crystal is used,For example, the optical characteristics can be changed by rapidly changing the refractive index by applying an electric field. Therefore, the optical path of the light beam passing through the liquid crystal optical element can be quickly changed.In addition, the use of polymer-dispersed liquid crystal does not necessarily require a polarizing plate, so the amount of light can be reduced. Therefore, a film camera, microscope, TV camera, binoculars, glasses, endoscope, digital camera, optical It can be widely used for focus adjustment of various optical devices such as pickups, zoom lenses, and blur prevention. Further, in particular, the variable focus diffractive optical element and the variable deflection angle prism can be thinned as a whole, so that light scattering can also be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic configuration of a variable focus lens according to the present invention.
FIG. 2 is a diagram showing a refractive index ellipsoid of uniaxial nematic liquid crystal molecules.
3 is a diagram showing a state in which an electric field is applied to the polymer-dispersed liquid crystal layer shown in FIG. 1. FIG.
FIG. 4 is a diagram showing an example of the configuration when the applied voltage to the polymer-dispersed liquid crystal layer shown in FIG. 1 is variable.
FIG. 5 is a diagram showing a configuration of an example of an imaging optical system for a digital camera using the variable focus lens according to the present invention.
FIG. 6 is also a diagram showing a configuration of an example of an objective optical system for an electronic endoscope using the variable focus lens according to the present invention.
FIG. 7 is a diagram showing a configuration of an example of a variable focus diffractive optical element according to the present invention.
FIG. 8 is a diagram showing variable focus glasses using the variable focus diffractive optical element according to the present invention as a spectacle lens.
9 is a diagram showing a state in which a voltage is applied to the variable focus diffractive optical element shown in FIG. 8. FIG.
FIG. 10 is a view showing spectacles using a conventional bifocal lens.
11 is a diagram showing a modification of the variable focus glasses shown in FIG.
FIG. 12 is a diagram similarly showing another modification.
FIG. 13 is a diagram showing a configuration of variable focus glasses having a variable focus lens using twisted nematic liquid crystal.
14 is a diagram showing an alignment state of liquid crystal molecules when a voltage applied to the twisted nematic liquid crystal layer shown in FIG. 13 is increased.
FIGS. 15A and 15B are diagrams showing configurations of two examples of a variable deflection prism according to the present invention. FIGS.
16 is a diagram for explaining a usage mode of the variable deflection prism shown in FIG.
FIG. 17 is a diagram showing a configuration of an example of a variable focus mirror as a variable focus lens according to the present invention.
FIG. 18 is a diagram showing a configuration of an optical system using a conventional liquid crystal lens.
19 is a diagram showing a state in which an electric field is applied to the liquid crystal lens shown in FIG.
FIG. 20 shows a radial gradient inhomogeneous medium lens.
FIG. 21 is a diagram showing a refractive index distribution of the inhomogeneous medium lens shown in FIG. 20;
FIG. 22 is a diagram showing a material of a heterogeneous medium lens.
FIG. 23 is a diagram for explaining a centerless grinding process of a heterogeneous material.
FIG. 24 is a diagram for explaining a cutting process of a heterogeneous material by a cutting machine.
FIG. 25 is a diagram showing a state of adhesion of a cut heterogeneous material to a V block.
FIG. 26 is a diagram showing a state of adhesion of a cut heterogeneous material to a gear.
FIG. 27 is a diagram for explaining a grinding process of a heterogeneous material by a surface grinder.
FIG. 28 is a view for explaining precise grinding and polishing steps of a heterogeneous material by a polishing machine.
FIG. 29 is a diagram for explaining a chamfering process of a heterogeneous material by a drier board.
FIG. 30 is a view for explaining another example of a precision grinding and polishing process of a heterogeneous material by a polishing machine.
FIG. 31 is a diagram for explaining a grinding process of a heterogeneous material by a cider type centering machine.
FIG. 32 is a diagram for explaining a process for forming a yato used for manufacturing a spherical inhomogeneous medium lens;
FIG. 33 is a diagram showing a state in which a heterogeneous material is attached to a yatoy.
FIG. 34 is a view for explaining precise grinding and polishing steps of a heterogeneous material by a polishing machine.
FIG. 35 is a diagram for explaining a process of attaching a heterogeneous material to a yatoy.
FIG. 36 is a diagram for explaining a step of grinding a curved surface of a heterogeneous material by a curve generator.
FIG. 37 is a view for explaining a grinding process of the outer periphery of a heterogeneous material by a bell clamp centering machine.
FIG. 38 is a view for explaining a grinding process of an outer periphery of a heterogeneous material after double-side polishing.
FIG. 39 is a diagram for explaining a grinding process of one surface of a heterogeneous material by a curve generator.
FIG. 40 is also a diagram for explaining a grinding process of the other surface of the heterogeneous material by the curve generator.
[Explanation of symbols]
8a 1st surface
8b Second side
9a Third side
9b 4th surface
11 Variable focus lens
12a, 12b lens
13a, 13b Transparent electrode
14 Polymer dispersed liquid crystal layer
15 switch
16 AC power supply
17 Liquid crystal molecules
18 Polymer cell
19 Variable resistor
21 Aperture
22 lenses
23 Solid-state image sensor
25 Front lens
26 Aperture
27 Variable focus lens
28 Rear lens
29 Solid-state image sensor
31 Variable focus diffractive optical element
32, 33 Transparent substrate
32a first surface
32b Second side
33a Third surface
33b Fourth surface
35 Variable focus glasses
35a frame
36 Variable focus diffractive optical element
37, 38 lenses
39a, 39b Alignment film
45 objects
46 Ranging sensor
61 Variable deflection prism
62, 63 Transparent substrate
62a first surface
62b Second surface
63a Third surface
63b 4th surface
65 Variable focus mirror
66, 67 Transparent substrate
66a first side
66b second side
67a Third surface
67b 4th surface
68 Reflective film

Claims (2)

A variable focus lens, a variable focus diffractive optical element, or a variable declination prism as a liquid crystal optical element using a polymer dispersed liquid crystal,
The liquid crystal optical element includes a first optical member, a second optical member, and a pair of transparent electrodes,
In the pair of transparent electrodes, one transparent electrode is disposed on the first optical member between the first optical member and the second optical member, and the other transparent electrode is the second optical member. Arranged to be placed in
The polymer dispersed liquid crystal layer is disposed between the pair of transparent electrodes,
The following conditions _{0.01 ≦ | n o '-n LC} ' | ≦ 10
D ・ t ≦ λ ・ 15μm
A liquid crystal optical element characterized by satisfying
Where n _o ′ is the average refractive index of ordinary light, n _LC ′ is the average refractive index of the liquid crystal molecules , D is the average diameter of the polymer cell containing the liquid crystal molecules constituting the polymer dispersed liquid crystal, t is the thickness of the polymer dispersed liquid crystal layer in the optical axis direction, λ is the wavelength of light, and λ = 500 nm . A variable focus lens, a variable focus diffractive optical element, or a variable declination prism as a liquid crystal optical element using a polymer dispersed liquid crystal,
The liquid crystal optical element includes a first optical member, a second optical member, and a pair of transparent electrodes,
In the pair of transparent electrodes, one transparent electrode is disposed on the first optical member between the first optical member and the second optical member, and the other transparent electrode is the second optical member. Arranged to be placed in
The polymer dispersed liquid crystal layer is disposed between the pair of transparent electrodes,
The following conditions: 7 nm ≦ D ≦ 500λ
D ・ t ≦ λ ・ 15μm
A liquid crystal optical element characterized by satisfying
However, D is the average diameter of the polymer cell containing the liquid crystal molecules constituting the liquid crystal layer, t is the thickness in the optical axis direction in the liquid crystal layer, lambda is a wavelength of light lambda = 500 nm .

Images