JP3943450B2 - Optical deflection apparatus, optical deflection method, and image display apparatus - Google Patents

Description

【００５８】
同様に、図４(ｂ)に示すように、電極４間に印加する電圧方向を反転させて、紙面表側から紙面奥側へ向かう電界を発生させた場合、液晶分子５ａの自発分極が正ならば、液晶ダイレクタが図４中右下方向に傾斜する液晶分子５ａの数が増加し、液晶層としての平均的な光学軸も図４中下側に角度θで傾斜する。ここに、液晶層５は、角度θで傾斜する複屈折板として機能する。
【００５９】
この状態で、図４中左側から異常光として入射した直線偏光は、図４(ｂ)中Ｂに示す光路をとり、入射光の入射位置に対して下側に平行シフトされる。
【００６０】
光偏向素子１では、このように電界方向を反転させることにより、２Ｓ分の光偏向量(シフト量)を得ることができる。
【００６１】
ところで、液晶分子５ａが反転して再配向した後の安定状態について図２ないし図４を参照して説明したが、液晶分子５ａの配向状態は、液晶分子５ａの配向方向が反転する過程で大きく乱れる。この液晶分子５ａの配向状態の乱れにより、配向状態の乱れによる過渡的な光の散乱現象が観測される過渡光散乱が発生する。
【００６２】
ここで、過渡光散乱について図５を参照して説明する。図５は、図２と同様に、光偏向素子内の液晶分子の傾斜状態を示した模式図である。キラルスメクチックＣ相の螺旋構造が解ける閾値電界以上では、図５(ａ)に示すように、液晶分子５ａは均一に配向している。
【００６３】
この状態から液晶の応答時間よりも短時間で印加電界を反転させると、液晶分子５ａはコーン状の仮想面Ｃ内に沿って反転し始める(図２および図３参照)。このとき、液晶層５では、図５(ｂ)に示すように、液晶分子５ａが右回りに回転する領域Ｒと、液晶分子５ａが左回りに回転し始める領域Ｌとが発生すると推測される。上述した過渡光散乱は、この回転方向の異なるドメイン間の界面Ｓで強く生じると考えられる。
【００６４】
この過渡光散乱は、図５(ｃ)に示すように、図５(ａ)に対する液晶分子５ａの反転が終了し、液晶分子５ａが均一に傾斜した状態に再配向すると消滅する。
【００６５】
すなわち、上記の過渡光散乱を低減させるためには、電界方向の反転により液晶層５内の少なくとも一部の液晶分子５ａがスメクチック層内でコーン状の仮想面Ｃ内を回転運動して配向方向を反転する際に、図５(ｄ)に示すように、反転する各液晶分子５ａの回転方向を同一方向に制御することが効果的であると推測される。
【００６６】
本実施の形態では、垂直配向膜６に対して、図６中矢印ｆで示す方向、すなわち、電界方向に略平行に設定したラビング処理を施すことにより、液晶層５自体の配向方向に指向性を与え、液晶分子５ａの回転方向を同一方向に制御するようにした。ここに、ラビング処理された垂直配向膜６によって回転方向制御手段が実現されている。
【００６７】
これにより、液晶分子５ａの回転開始に際して、液晶分子５ａがラビング方向に回転し始める確率が高くなり、液晶分子５ａの回転方向を制御することができる。なお、ラビング方向は、光偏向方向、すなわち、定常状態での光学軸の傾斜方向と異なればよく、図６に示すような基板面に略垂直方向に限定されるものではない。
【００６８】
本実施の形態のように、垂直配向膜６にラビング処理を施すことにより液晶層５自体の配向方向に指向性を与えて液晶分子５ａの回転方向を同一方向に制御する方法では、安定な傾斜方向が一方向のみに設定されるので、液晶分子５ａの反転時の回転運動は、常に安定な傾斜方向を経由する往復運動となる。
【００６９】
なお、本実施の形態では、電極４の配置位置と液晶層５に対する電圧の印加状態を改良して液晶分子５ａの配向状態を制御可能としたものであるが、透明な基板３、垂直配向膜６、液晶層５、スペーサーおよび電極４(本実施の形態では金属シート部材により兼用)は、従来の光偏向素子と同様の構成を用いることができる。
【００７０】
次に、本発明の第二の実施の形態について図７を参照して説明する。本実施の形態では、液晶層５中にポリマーネットワークを形成することにより液晶層５自体の配向方向に指向性を与え、液晶分子５ａの回転方向を同一方向に制御するようにした。
【００７１】
図７(ａ)は、本実施の形態の光偏向素子を示す水平断面図である。本実施の形態の光偏向素子は、図２に示すように、液晶層５中に含有されたポリマー鎖８によってポリマーネットワークが形成されている。液晶層５中におけるポリマーネットワークは、紫外線や熱などにより反応する重合性モノマーやプレポリマーを液晶中に添加しておき、液晶層５に水平電界を印加して液晶分子５ａを均一に傾斜させた状態で重合性モノマーの重合反応を行わせることにより形成する。重合性モノマーやプレポリマーの重合反応に際しては、一時的に外部電極などを設置するなどして、通常動作時の電界方向と異なる方向に電界を発生させることで、液晶分子５ａの安定な傾斜方向を、光偏向方向と異なる方向に設定する。これにより、液晶層５中に指向性を有するポリマーネットワークが形成され、ポリマースタビライズ液晶層を形成することができる。
【００７２】
本実施の形態のポリマー鎖８は、液晶層５中にモノマーやプレポリマーを含有させた状態で液晶層５に対して一時的に外部電界を発生させることで、液晶層５中における液晶分子５ａが図７(ａ)中右側に傾斜した状態でモノマーやプレポリマーを重合させることにより形成されている。なお、図７(ａ)に示す状態は、ポリマー鎖８を形成した後の液晶層５に対して、図７(ａ)中左方向に電界が発生している状態を示す。
【００７３】
ポリマー鎖８を形成するモノマーやプレポリマーは、光(紫外線)重合性であっても熱重合(硬化)性であってもよいが、例えば、光重合性のモノマーやプレポリマーを用いてポリマー鎖を形成する場合には、図７(ａ)中左右方向の直線偏光を照射しても良い。
【００７４】
このような光偏向素子７の電極４間に電圧を印加して液晶層５中に電界を発生させると、液晶層５中の液晶分子５ａは、図７(ｂ)に示すように、垂直配向状態をとる。このとき、ポリマー鎖８は、図７(ｂ)に示すように、垂直配向状態にある液晶分子５ａの長軸方向に対して斜めに伸びた状態になっていると推測される。
【００７５】
ここで、垂直配向状態にある液晶分子５ａの長軸方向に対してポリマー鎖８が斜めに伸びた状態であっても、ポリマー鎖５による配向規制力に比べて、電極４間に電圧を印加して液晶層５中に発生させた電界による駆動力の方が十分に大きい場合、液晶分子５ａは(ｂ)のようにポリマー鎖の影響を受けずに(ａ)のように配向する。
【００７６】
一方、電界方向の切換えに際して、液晶層５中に発生する電界の影響が小さくなると、ポリマー鎖８による配向規制力が強くなる。そして、液晶層５中に発生する電界の影響よりもポリマー鎖８による配向規制力が強くなった瞬間、液晶分子５ａは、図７(ｃ)に示すように、ポリマー鎖８によって図７(ｃ)中左方向に回転する。回転方向を制御することができる。すなわち、液晶層５中にポリマーネットワークを形成することにより、液晶分子５ａの回転し易さに非対称性が生じるため、液晶分子５ａが回転し始める方向を同一方向に制御することができる。ここに、ポリマーネットワークによって回転方向制御手段が実現されている。
【００７７】
なお、ポリマーネットワークは、主鎖や側鎖に液晶性の構造を有するポリマー鎖８によって形成しても良い。
【００７８】
液晶層中にポリマーネットワークを形成する方法では、ポリマーの添加量や材質を最適化することで、光偏向方向がずれてしまうことや応答時間が長くなるという副作用を低減することができる。
【００７９】
本実施の形態のように、液晶層５中にポリマースタビライズを形成することにより液晶層５自体の配向方向に指向性を与えて液晶分子５ａの回転方向を同一方向に制御する方法では、安定な傾斜方向が一方向のみに設定されるので、液晶分子５ａの反転時の回転運動は、常に安定な傾斜方向を経由する往復運動となる。
【００８０】
次に、本発明の第三の実施の形態について図７および図８を参照して説明する。
本実施の形態では、液晶分子５ａの反転時に、通常の電界方向に直交した電界成分を与えることにより、液晶分子５ａの回転方向を同一方向に制御するものである。
【００８１】
図８は、本実施の形態の光偏向装置の光偏向素子を示す斜視図である。本実施の形態の光偏向装置の光偏向素子１０は、第一の実施の形態の光偏向素子１とほぼ同様の構成を有しており、第一の実施の形態の光偏向素子１の垂直配向膜６へのラビング処理に代えて、電極４間に発生する電界方向に対して直交する方向に電界を発生させる一対の直交電極１１によって形成される直交電極対を備えている。直交電極１１は、電極４側の端部が、それぞれ電極４から離間するように配置されている。
【００８２】
また、本実施の形態の光偏向装置は、液晶層５近傍に配置された直交電極１１と、直交電極１１間に電圧を印加する図示しない第二の電源とを備えている。第二の電源は、電界方向の反転に際して、電源２によって電極４間に印加する電圧方向を反転させる直前に動作を開始し、動作を開始してから液晶分子５ａの応答時間が経過する以前に動作を終了するように図示しない制御系によって駆動制御される。
【００８３】
電極４間に発生させる電界方向を反転する直前に直交電極対に電圧を印加することにより、液晶層５中には、図９(ａ)中斜め下向きの矢印ｅｆで示す電界が発生するので、液晶分子５ａは反時計回りに回転し始める。
【００８４】
この状態で電極４間に印加する電圧方向を反転させて電極４間に発生する電界方向を反転させると、液晶分子５ａは反時計回りに回転し続けて反転する。
【００８５】
ここに、直交電界を発生させてから基板面の法線方向および光偏向方向に略直交する方向に発生させる電界方向を反転させることで、電界方向の反転による液晶分子５ａの反転が開始する時点で、液晶分子５ａに対して回転方向を揃えるような電界を作用させて、確実に液晶分子の回転方向を揃えることができる。ここに、回転方向制御手段が実現されている。
【００８６】
これによって、液晶配向方向の反転に伴って発生する過渡散乱を防止して透過率や光利用効率の向上を図るとともに、実効的な切り換え時間を短くして光偏向方向の切り換えの高速化を図ることができる。
【００８７】
また、本実施の形態では、光偏向素子１０における有効領域外に設けた一対の直交電極１１によって直交電界を発生させているため、比較的簡単な構成で、過渡散乱現象を低減し、透過率や光利用効率の向上を図ることができる。
【００８８】
本実施の形態によれば、基板面の法線方向および光偏向方向に直交する電界成分の向きや大きさや印加タイミングを制御することにより、液晶分子５ａの回転方向を確実に同一方向に制御することができる。
【００８９】
また、本実施の形態によれば、液晶分子５ａの回転運動を往復運動のように制御することも、一方向へ連続して回転運動するように制御することもできる。
【００９０】
ところで、直交電極１１間に電圧を印加し続けると、この直交電界の作用によって、図９(ｂ)中斜め下向きの矢印ｅｆで示すように、電極４間に発生する電界が基板面に直交する方向からずれた状態となる。これにより、液晶分子の傾斜方向が、本来目的とする角度に対して僅かにズレてしまい、光偏向方向も僅かにズレてしまう。
【００９１】
本実施の形態では、第二の電源による電圧の印加を開始してから液晶分子５ａの応答時間が経過する以前に動作を終了するので、液晶分子５ａの配向方向の反転が終了する時点においては、光偏向位置を変化させてしまう要因となる直交電界が発生していない。
【００９２】
ここに、電界方向の反転によって開始される液晶分子５ａの配向方向の反転が終了する以前に、直交電界の発生を終了させることで、一旦同一方向に回転運動を開始すれば不要となる直交電界の発生を速やかに終了させ、光偏向位置を正確に制御して、光偏向位置の精度が良い光偏向装置を提供することができる。
【００９３】
加えて、直交電極１１の配設位置は、光偏向素子１０の有効領域外であって、かつ液晶層５の近傍であるとともに、電極対に対して過剰に接近しない位置であることが好ましい。本実施の形態では、光偏向素子１０における光偏向に関わる部分を有効領域とする。電極４と直交電極１１とが接近している場合、電極４間に電位差を発生させても、直交電極１１が等電位になってしまうので、直交電極１１の近傍では所望の電位差すなわち電界分布を得ることが困難になる。
【００９４】
これに対し、本実施の形態では、直交電極１１の電極４側の端部を、それぞれ電極４から離間させて配置しているため、直交電極１１の近傍においても目的とする方向に電界を発生させることができる。
【００９５】
なお、本実施の形態では、一対の直交電極１１としたが、これに限るものではなく、例えば、図１０に示すように、分割された複数対の直交電極１１としてもよい。
【００９６】
また、本実施の形態では、基板３の面方向に沿って液晶層５を介して対向する一対の直交電極１１としたが、これに限るものではなく、例えば、図１１に示すように、一対の基板３および液晶層５を介して基板３の面方向に対して斜め方向に設けるようにしてもよい。これによって、直交電極１１に電圧を印加すると図１１中矢印ｔで示すように、基板面の法線方向および光偏向方向に直交し、基板３の面方向に対して斜め方向に作用する電界が発生する。電極４と直交電極１１との間に基板３などを挟んでそれぞれの距離を離すことで、直交電極１１に電界を印加しない状態、すなわち、液晶分子５ａの回転が終了した後の液晶層５内水平方向の電界分布に対する直交電極１１の影響を少なくすることができる。
【００９７】
上述したように、直交電極を分割したり、直交電極１１間に基板３などの誘電体を挟んだりすることで、直交電極１１による等電位部が広がることを防止できる。
【００９８】
加えて、本実施の形態では、一対の電極４によって基板面の法線方向および光偏向方向に直交する電界を発生させるようにしたが、例えば、図１２に示すように、基板面の法線方向および光偏向方向に直交する電界を発生させる光偏向用の電極が透明ライン電極群４ｘからなる場合、両基板３の透明ライン電極群４ｘの上に誘電体層１３を形成し、この誘電体層１３で直交電極１１を挟むように形成する。この構成とすることにより、透明ライン電極群４ｘによる電界と直交電極１１による電界との相互作用を低減することができる。
【００９９】
次に、本発明の第四の実施の形態について図１３を参照して説明する。本実施の形態は、２系統での光偏向が可能な光偏向装置への適用例を示す。
【０１００】
図１３(ａ)は本実施の形態の光偏向装置を示す斜視図であり、図１３(ｂ)はその分解斜視図である。本実施の形態の光偏向装置は、図１に示す光偏向素子１と同様の構成を有する２つの光偏向素子２０(２０ａ，２０ｂ)と、２つの光偏向素子２０間に設けられて入射光の偏光面を略直角に回転させる偏向面回転手段としての偏光面回転板２１と、を備えている。
【０１０１】
偏光面回転板２１としては、例えば、半波長板や電極を持たないツイストネマチック液晶セル、ツイストネマチック液晶を固定化したフィルムなどを用いることができる。
【０１０２】
光偏向装置における２つの光偏向素子２０ａ，２０ｂは、偏光面回転板２１を介して、光偏向素子(第一の光偏光手段)２０ａが有する液晶層(第一の液晶層)５Ａの法線方向と光偏向素子(第二の光偏光手段)２０ｂが有する液晶層(第二の液晶層)５Ｂの法線方向とが略一致するように配置されている。また、光偏向装置における２つの光偏向素子２０ａ，２０ｂは、光偏向素子２０ａが有する電極４ａ間に発生する電界方向と、光偏向素子２０ｂが有する電極４ｂ間に発生する電界方向とが略直交するように配置されている。
【０１０３】
光偏向素子２０ａ，２０ｂが有する各電極対４ａ，４ｂには、これらの電極対４ａ，４ｂに電圧を印加する図示しない電源が接続されている。本実施の形態では、対をなす電極４ａおよび４ｂのうちの一方電極４ａ，４ｂが、矩形波交流電源に接続されている。電源は、図示しない制御系によって駆動制御され、電極４ａ間に発生させる電界方向の反転タイミングに対して、電極４ｂ間に発生させる電界方向の反転タイミングが異なるように、各電極対４ａ，４ｂに対する電圧印加のタイミングを制御する。ここに、図示しない電源および電極４ａおよび４ｂによって第一の電界発生手段および第二の電界発生手段が実現されている。本実施の形態では、図１４に示すタイミングとなるように、各電極対４ａ，４ｂに対する電圧印加のタイミングを制御する。すなわち、電極４ａに印加する電圧の極性と電極４ｂに印加する電圧の極性とが完全に反転することのないように、電極４ａに印加する電圧と電極４ｂに印加する電圧とが同一極性となるようにタイミング設定されている。本実施の形態では、電極４ａに印加する電圧の極性の反転周期に対して、電極４ｂに印加する電圧の極性の反転周期が１／４周期ずれるように設定されている。ここに、タイミング調整手段が実現される。
【０１０４】
なお、図１４に示すようなパターンで電圧を印加する場合、印加電圧値や基板３の厚さなどは、一方の光偏向素子２０ａまたは２０ｂで発生する電界が他方の光偏向素子２０ｂまたは２０ａの偏向方向に影響が少ないように設定されている。
【０１０５】
このような構成において、電極４ａ，４ｂ間に発生させる基板面法線方向および光偏向方向に略直交する方向に発生させる電界方向をそれぞれ反転させることにより、各液晶層５Ａ，５Ｂにおける液晶分子５ａの配向方向が反転し、液晶層５の層法線方向に対する光学軸の傾斜方向がそれぞれ切り換わる。
【０１０６】
このとき、光偏向素子２０ａ，２０ｂ間に配設された偏光面回転板２１によって、光偏向素子２０ａからの出射光の偏光面が略直角に回転されて光偏向素子２０ｂに入射するため、光偏向装置への入射光に対する出射光路を、紙面水平方向(図１３中Ｙ方向)および紙面垂直方向(図１３中Ｘ方向)の２系統で切り換えることができる。これにより、例えば、光偏向装置の光偏向素子２０ｂから出射される光をスクリーン２２等に照射する場合、Ｘ方向への２方向とＹ方向への２方向との組み合わせることにより、図１５(ａ)ないし(ｄ)に示すように、照明領域Ｐが略四角形の四隅を順次移動して回転するように光路をシフトすることができる。
【０１０７】
また、本実施の形態では、偏光面回転板２１を介して２つの光偏向素子２０ａ，２０ｂを近接して配設するとともに各電極対に対する電圧印加のタイミングを図１４に示すように制御することにより、２つの光偏向素子２０ａ，２０ｂの位置関係を利用して、新たな電極対を設けること無く、一方の電極４ａまたは４ｂ間に発生する電界方向を他方の電極４ｂまたは４ａ間に発生する電界方向に直交する電界として作用させることができ、一方の電極４ａまたは４ｂ間に発生する電界によって、他方の電極４ｂまたは４ａ間に発生する電界方向の反転による回転運動する各液晶分子５ａの回転方向を同一方向に制御して、液晶分子５ａの回転方向を揃えることができる。ここに、回転方向制御手段が実現されている。
【０１０８】
これによって、２系統での光偏向が可能な光偏向装置で、専用の電極を設けることなく、電界方向の切り換えに際して回転する液晶分子５ａの回転方向の違いによるドメインの発生を防止して、液晶分子５ａの反転運動に伴って発生する過渡散乱現象を最小限に抑え、透過率や光利用効率の低減を防止することができる。
【０１０９】
次に、本発明の第五の実施の形態について図１６を参照して説明する。本実施の形態は、第四の実施の形態と比較して、２つの電極対に印加する電圧の波形が異なっており、一方の光偏向素子における電界方向の反転タイミングに合わせて、他方の光偏向素子からの漏れ電界を積極的に利用する。
【０１１０】
本実施の形態では、図１６に示すように、一方の光偏向素子２０ａまたは２０ｂの電界反転時刻の前後の期間のみ、他方の光偏向素子２０ｂまたは２０ａの印加電圧値を一時的に大きくした電圧を印加する。
【０１１１】
このような波形の電圧を印加することにより、一方の光偏向素子２０ａまたは２０ｂにおける電界方向の反転に際して発生する漏れ電界を大きくし、他方の光偏向素子２０ｂまたは２０ａに対して光偏向方向に垂直な電界成分を効果的に作用させることができる。
【０１１２】
なお、図１６に示すように、一時的に高くする電圧値や、一時的に高くする電圧の印加時間などは、液晶材料や基板厚みなどの素子構成に応じて最適化する。
【０１１３】
本発明の第六の実施の形態について図１７を参照して説明する。本実施の形態は、画像表示装置への適用例を示す。
【０１１４】
図１７は、本実施の形態の画像表示装置を示す概略図である。本実施の形態の画像表示装置３０は、図１７に示すように、光を照射する照明手段としての光源３１を備えている。本実施の形態の光源３１は、ＬＥＤランプを二次元アレイ状に配列した構成を有している。
【０１１５】
この光源３１からスクリーン３２に向けて発せられる光の光路上には、光の進行方向に沿って順に配設された拡散板３３、コンデンサレンズ３４、画像表示素子としての透過型液晶パネル３５、画像パターンを観察するための光学装置としての投射レンズ３６が設けられている。光源３１から出射する光のＯＮ／ＯＦＦは、光源ドライブ部３７によって駆動制御される。透過型液晶パネル３５は、表示駆動手段としての液晶ドライブ部３８によって駆動制御され、光源３１から出射する光を画像情報にしたがって制御可能な複数の画素が二次元的に配列された構成を有している。本実施の形態の透過型液晶パネル３５は光源３１からの照明光を空間光変調し、液晶ドライブ部３８は画像フィールドを時間的に分割した複数のサブフィールド単位で透過型液晶パネル３５を駆動する。
【０１１６】
透過型液晶パネル３５と投射レンズ３６との間の光路上には、ピクセルシフト素子として機能する光偏向装置３９が介在されている。光偏向装置３９は、上述したいずれの実施の形態の光偏向装置を用いてもよい。本実施の形態の光偏向装置３９は、第六の実施の形態の光偏向装置と同様の構成を有する。光偏向装置３９は、偏向ドライブ部４０に接続されており、透過型液晶パネル３５を介して出射される画像光路を偏向する。偏向ドライブ部４０は、透過型液晶パネル３５を介して出射される画像光路をサブフィールド毎に偏向するように光偏向装置３９を駆動制御する。本実施の形態では、光偏向装置３９によるシフト量が、透過型液晶パネル３５における画素ピッチの１／２に設定されている。
【０１１７】
このような構成において、光源ドライブ部３７で制御されて光源３１から放出された照明光は、拡散板３３により均一化された照明光となり、コンデンサレンズ３４を介して透過型液晶パネル３５をクリティカル照明する。透過型液晶パネル３５は、液晶ドライブ部３８によって駆動制御されて、光源３１からの照明光をサブフィールド単位で空間光変調する。
【０１１８】
透過型液晶パネル３５で空間光変調された照明光は、画像光として光偏向装置３９に入射する。光偏向装置３９は、偏向ドライブ部４０によって駆動制御されて、スクリーン３２に投射される画像光が画素の配列方向に任意の距離だけシフトされるように、画像光を偏向させる。偏向された画像光は、投射レンズ３６で拡大されスクリーン３２上に投射される。
【０１１９】
本実施の形態の光偏向装置３９は、上述の実施の形態で説明したように、投射光路をＸ方向とＹ方向との２系統で偏向させることができるため、透過型液晶パネル３５によるサブフィールド単位での空間光変調タイミングと、照明領域Ｐが略四角形の四隅(図１５(ａ)ないし(ｄ)参照)を順次移動して回転するように光路をシフトさせるタイミングとを同期させることで、スクリーン３２上に表示される表示画像の画素数を見掛け上４倍に増倍することができる。これによって、透過型液晶パネル３５の画素数を実際に像倍することなく高精細な画像を表示することができる。
【０１２０】
ここで、本実施の形態では、光偏向装置３９を用いることにより、光の利用効率を向上させることができるので、光源３１の負荷を増加することなく明るく高品質の画像を提供できる。
【０１２１】
また、本実施の形態では、光偏向装置３９を用いることにより、光偏向装置３９における光偏向位置を、電極４ａ，４ｂ間に発生させる電界方向および電界強度を調整することで制御することができるので、適切なピクセルシフト量を保持し、良好な画像を得ることができる。
【０１２２】
特に、本実施の形態では、光偏向装置３９を用いることにより、光偏向動作の切り換え時に発生する過渡光散乱を低減できるので、透過率やＭＴＦの低下を抑制することができる。このように、偏向方向の切り換えに際して過渡光散乱を抑制することにより、従来は散乱していた光を画像光として表示に利用できる時間を長くすることができ、これによっても光の利用効率を向上させることができる。
【０１２３】
【実施例】
次に、本発明の実施例について説明する。実施例では、以下に説明するような光偏向素子を作製し、作製した光偏向素子の光学軸を観察し、過渡光散乱を測定し、高速度カメラによる光路シフト現象を観察した。
【０１２４】
(光偏向素子の作製)
まず、光偏向素子１０の作製について説明する。実施例として、厚さ０．６μｍの垂直(ホメオトロピック)配向膜を形成した厚さ１ｍｍのガラス基板の表面に、厚さ６０μｍ、幅０．５ｍｍ、長さ１２ｍｍのアルミ電極シートをスペーサー兼電極として設け、有効領域が約１ｃｍ幅となるように平行に配置することで電極対４を形成し、この電極対４と同様なアルミ電極シートを第一の電極対に直交するよう２ｃｍ間隔で配置して直交電極対１１を形成して、図１６に示すような電極配置を有するセルを作製した。
【０１２５】
このセルを約９０度に加熱した状態で、基板３間の空間に強誘電性液晶(チッソ製ＣＳ１０２９：複屈折Δｎ＝０．１６、チルト角θ＝２５度、自発分極Ｐｓ＝−４０ｎＣ／ｃｍ^２)を毛管法にて注入し、冷却後に接着剤で封止することで、液晶層５の厚さ６０μｍ、有効面積１ｃｍ角の光偏向素子１０を作製した。
【０１２６】
この光偏向素子１０の電極対４および直交電極対１１にパルスジェネレータと高速アンプとからなる電源５０，５１を接続し、光偏向装置５２を得た。
【０１２７】
(光学軸の観察)
次に、光学軸の観察について説明する。無電界の状態で、この光偏向素子１０の有効領域内の液晶層のコノスコープ像を観察したところ、十字と円環の画像が中心部に観察された。これにより、無電界下では光学軸が液晶層５に垂直であることを確認できる。この状態では液晶分子５ａのチルト方向が基板３面に垂直方向に対して回転する螺旋構造をとっており、平均的な光学軸は螺旋軸の方向である基板３面に垂直な方向に観察される。
【０１２８】
続いて、電源５０から電極対４に±２０００Ｖ、１Ｈｚの矩形波電圧を印加した。このとき、コノスコープ像の十字と円環の位置が上下方向に１Ｈｚで往復シフトした。公知の技術であるため説明を省略するが、顕微鏡の対物レンズのＮＡ値と液晶の屈折率と十字位置のシフト量とから光学軸の傾斜角度を計算すると、約２５度であることが判る。これにより、光学軸の傾斜角度が、該液晶材料固有のチルト角θと一致していることが確かめられた。液晶分子５ａの螺旋構造は、電極４間に２００Ｖ／ｍｍ程度の電界強度を発生させることにより解けて液晶分子５ａが一様な方向に配向し、液晶層５の光学軸の方向が±２５度で切り換え可能であった。
【０１２９】
(過渡光散乱の測定)
次に、過渡光散乱の測定について説明する。図１７に示す測定装置６０を用いて、図１６の光偏向素子１０の過渡光散乱の時間の強度を測定した。測定装置６０は、Ｈｅ−Ｎｅレーザを出射する図示しない光源と、光源から出射されるＨｅ−Ｎｅレーザの偏光面を回転する偏光面回転板６１と、レーザ光の偏光面を回転するクロスニコルの偏光板６２と、クロスニコルの偏光板６２から出射される光の強度と時間とを検出するフォトディテクタ６３とを有している。測定に際しては、偏光面回転板６１とクロスニコルの偏光板６２との間に図１６に示す光偏向素子１０をセットする。図１６に示す光偏向素子１０は、光偏向素子１０による偏向方向が入射光の偏光方向と一致するようにセットされる。
【０１３０】
測定装置６０では、光源から出射されるレーザ光を偏光面回転板６１を通して光偏向素子１０に入射させると、光偏向素子１０が有する液晶層５内の液晶分子５ａが均一に配向している状態では、光路シフト現象は生じるが偏光面の回転や乱れは生じないため、クロスニコルの偏光板６２を透過する光はない。すなわち、フォトディテクタ６３によって検出される光はない。
【０１３１】
一方、光偏向素子１０が有する液晶層５中に過渡光散乱が発生している状態では、液晶分子５ａの配向方向が乱れているため偏光面が乱れる。このため、偏光面が回転された光が発生し、クロスニコルの偏光板６２を漏れて出てくる光が生じる。この漏れて出てきた光の強度と時間とが、フォトディテクタ６３によって検出され、過渡光散乱の強度や時間が測定することができる。
【０１３２】
上述した測定装置６０を用いて、電源５０から電極対４に±２０００Ｖ，１００Ｈｚの矩形波電圧を印加し、この矩形波電圧の極性の切り換え時刻から±０.２５ｍｓｅｃの期間に同期して電源５１から直交電極対１１に＋４０００Ｖ，パルス幅０.５ｍｓｅｃのパルス状電圧を印加しながら漏れて出てきた光の強度と時間とを測定したところ、過渡光散乱による漏れ光の検出電圧は０.１ｍＶ、漏れ光の検出時間は１ｍｓｅｃであった。
【０１３３】
(高速度カメラによる光路シフト現象の観察)
次に、高速度カメラによる光路シフト現象の観察について説明する。開口部が４μｍ角の図示しないマスクパターンを裏面から照明し、マスクパターンを透過する透過光を図１６に示す光偏向素子１０を通して観察した。このとき、電源５０から電極対４に電圧を印加することで光偏向素子１０を動作させることでマスクパターンの位置がシフトしたように観察されるので、このシフトの様子を顕微鏡付き高速度カメラで観察することで、光路シフト量とその応答時間を測定した。
【０１３４】
具体的に、電源５０から電極対４に±２０００Ｖ，１００Ｈｚの矩形波電圧を印加し、この矩形波電圧の極性の切り換え時刻から±０.２５ｍｓｅｃの期間に同期して、電源５１から直交電極対１１に＋４０００Ｖ，パルス幅０.５ｍｓｅｃのパルス状電圧を印加しながら、高速度カメラによる観察(時間分解能４０５００フレーム／秒)を行ったところ、シフト量は９μｍ、その移動に要する応答時間は１ｍｓｅｃであった。このとき、開口部を透過して観察される開口パターンＨ(図２０参照)の移動の様子は、僅かに円弧を描くように比較的はっきりと移動していることが観察された。これは、液晶分子５ａが反転するときの回転方向が揃っていること表していると考えられる。
【０１３５】
また、１ｍｓｅｃという応答時間は、僅かな過渡光散乱時間と同一であり、液晶分子５ａの反転時に不必要配向乱れが発生していないと考えられる。したがって、過渡光散乱の少ない光偏向装置が得られたことが判る。
【０１３６】
続いて、上述した実施例に対する比較例について説明する。比較例は、直交電極対１１および電源５１を設置しない以外は、図１６に示す光偏向装置５２の光偏向素子１０とほぼ同様の構成を有する光偏向素子６５を備える光偏向装置を用いた。比較例では、電極対４の印加電圧パターンも実施例と同様にした。
【０１３７】
このような光偏向装置を用いて、図１９に示す測定装置６０を用いて測定を行ったところ、過渡光散乱による漏れ光の検出電圧は０.５ｍＶ、漏れ光の検出時間は２ｍｓｅｃであり、過渡光散乱が顕著に発生していることが判った。
【０１３８】
また、実施例と同様に、高速度カメラによる開口部を透過して観察される開口パターンＨのシフト状態を測定したところ、シフト量は９μｍ、その移動に要する応答時間は１ｍｓｅｃであり、上記実施例と同一であることが判った。しかしながら、開口部を透過して観察される開口パターンＨの移動の様子は、比較的不鮮明であり、ボヤッと広がるような開口パターンＨが観察された。また、移動が終了した後の画像も僅かにぼやけていることが観察された。これは、液晶分子５ａが反転するときの回転方向が不均一であり、大多数の液晶分子５ａが反転し終わった後も、配向が乱れていることを示唆している。
【０１３９】
【発明の効果】
請求項１記載の発明の光偏向装置によれば、基板面の法線方向および光偏向方向に略直交する方向に発生させる電界方向を反転させることにより、スメクチック相を形成する強誘電性液晶分子をスメクチック層内でコーン状の仮想面内を回転運動させて配向方向を反転させ、液晶層の層法線方向に対する光学軸の傾斜方向を切り換えて、入射光に対する出射光路を切り換えるとともに、電界方向の反転により液晶層内の少なくとも一部の液晶分子の配向方向がスメクチック層内でコーン状の仮想面内を回転運動して反転する際に、回転運動する各液晶分子の回転方向を同一方向に制御して、液晶分子の回転方向を揃えることで、回転方向の違いによるドメインの発生を防止して、液晶分子の反転運動に伴って発生する液晶配向状態の乱れ、すなわち、過渡散乱現象を最小限に抑えることができるので、透過率や光利用効率の低減を防止することができる。
【０１４０】
請求項２記載の発明によれば、請求項１記載の光偏向装置において、強誘電性液晶分子がコーン状の仮想面内を回転運動して反転する際に、基板面の法線方向および光偏向方向に略直交する方向に直交する一方向に発生させた直交電界によって、回転運動する各液晶分子の回転方向を同一方向に制御することができ、液晶配向方向の反転に伴って発生する過渡散乱現象を実用上確実に低減して、透過率や光利用効率の向上を図ることができる。
【０１４１】
請求項３記載の発明によれば、請求項２記載の光偏向装置において、入射光に対する出射光路の切り換えに関わる有効領域となる液晶層の近傍に直交電極対を設けることで、電界発生手段が発生させる電界方向に直交する一方向の直交電界を比較的簡単な構成で発生させることができるので、比較的簡単な構成で、液晶配向方向の反転に伴って発生する過渡散乱現象を低減し、透過率や光利用効率の良い光偏向装置を提供する。
【０１４２】
請求項４記載の発明によれば、請求項３記載の光偏向装置において、直交電界を発生させてから基板面の法線方向および光偏向方向に略直交する方向に電界方向を反転させ、液晶分子の反転が開始する時点で液晶分子に対して回転方向を揃えるような電界を作用させて確実に液晶分子の回転方向を揃えることにより、過渡散乱を防止して透過率や光利用効率の向上を図るとともに、実効的な切り換え時間を短くして光偏向方向の切り換えの高速化を図ることができる。また、電界方向の反転によって開始される液晶分子の配向方向の反転が終了する以前に、直交電界の発生を終了させることで、一旦同一方向に回転運動を開始すれば不要となる直交電界の発生を速やかに終了させ、光偏向位置を正確に制御して、光偏向位置の精度が良い光偏向装置を提供することができる。
【０１４３】
請求項５記載の発明の光偏向装置によれば、第一または第二の光偏向手段からの出射光の偏光面を略直角に回転して第二または第一の光偏向手段に入射させる偏向面回転手段を第一および第二の光偏向手段の近傍に設けることで、光学軸の傾斜方向を２系統に切り換えるとともに、第一、第二の電界反転手段によって発生させる電界方向の位置関係を利用して、第一の電界反転手段による電界方向の反転タイミングに対する第二の電界反転手段による電界方向の反転タイミングを異ならせることで、第一、第二の液晶層に対して第一、第二の電界発生手段が発生させる電界方向に直交する一方向の電界を偏向面回転手段を介して作用させることで、新たな電極対を設けることなく、第一、第二の液晶層内で回転運動する各液晶分子の回転方向を同一方向に制御して液晶分子の回転方向を揃え、回転方向の違いによるドメインの発生を防止して、液晶分子の反転運動に伴って発生する過渡散乱現象を最小限に抑えて、透過率や光利用効率の低減を防止することができる。
【０１４４】
請求項６記載の発明の光偏向方法によれば、電界方向の反転によりスメクチック相を形成する強誘電性液晶分子がスメクチック層内でコーン状の仮想面内で回転運動して配向方向を反転させる際に、回転運動する各液晶分子の回転方向を同一方向に制御して液晶分子の回転方向を揃えることで、回転方向の違いによるドメインの発生を防止して、液晶分子の反転運動に伴って発生する過渡散乱現象を最小限に抑え、透過率や光利用効率の低減を防止することができる。
【０１４５】
請求項７記載の発明によれば、請求項６記載の光偏向方法において、強誘電性液晶分子がコーン状の仮想面内を回転運動して配向方向が反転する際に、基板面の法線方向および光偏向方向と略直交する方向に発生させる電界方向に直交する電界を発生させることにより、回転運動する各液晶分子の回転方向を実際上確実に同一方向に制御して、液晶配向方向の反転に伴って発生する過渡散乱現象を実用上確実に低減して、透過率や光利用効率の向上を図ることができる。
【０１４６】
請求項８記載の発明の画像表示装置によれば、画像フィールドを時間的に分割した複数のサブフィールド単位で画像表示素子が表示する画像を照明手段によって照明することにより各画素から出射される出射光の光路を、光偏向装置によってサブフィールド毎に偏向することで、光学装置によって観察される画像パターンを実際の画素数よりも見掛け上増倍して表示画像を高精細化するとともに、請求項１ないし５のいずれか一に記載の光偏向装置を用いることで、過渡散乱現象が低減され、透過率やＭＴＦの低下を抑制し、表示に利用できる時間を長くして光利用効率の高い画像表示装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の第一の実施の形態の光偏向装置を示す斜視図である。
【図２】光偏向素子の液晶層における電界方向と液晶分子の傾斜方向との関係を示す模式図である。
【図３】液晶層における液晶分子の状態を説明する斜視図である。
【図４】液晶分子の一端が仮想的なコーン状の面内を回転運動する様子を二次元的に説明する模式図である。
【図５】光偏向素子内の液晶分子の傾斜状態を示した模式図である。
【図６】垂直配向膜のラビング方向を説明する水平断面図である。
【図７】 (ａ)は本発明の第二の実施の形態の光偏向素子を示す水平断面図、(ｂ)，(ｃ)はその縦断面図である。
【図８】本発明の第三の実施の形態の光偏向装置の光偏向素子を示す斜視図である。
【図９】光偏向素子の液晶層における電界方向と液晶分子の傾斜方向との関係を示す模式図である。
【図１０】別の実施の形態の光偏向素子の液晶層における電界方向と液晶分子の傾斜方向との関係を示す模式図である。
【図１１】また、別の実施の形態の光偏向装置の光偏向素子を示す斜視図である。
【図１２】さらに、別の実施の形態の光偏向装置の光偏向素子を示す斜視図である。
【図１３】本発明の第四の実施の形態の光偏向装置を示し、(ａ)はその斜視図であり、(ｂ)はその分解斜視図である。
【図１４】各電極対に対する電圧印加のタイミングを説明するタイミングチャートである。
【図１５】光偏向動作により観察される照明領域の移動状態を示す説明図である。
【図１６】本発明の第五の実施の形態の光偏向素子の光偏光素子が備える各電極対に対する電圧印加のタイミングを説明するタイミングチャートである。
【図１７】本発明の第六の実施の形態の画像表示装置を示す概略図である。
【図１８】実施例の光偏向素子を説明する説明図である。
【図１９】測定装置を示す概略図である。
【図２０】開口パターンの移動状態を示す説明図である。
【符号の説明】
２ 電界反転手段
３ 基板
５ 液晶層
５ａ 第一の液晶層
５ｂ 第二の液晶層
１１ 直交電極対
２０ａ 第一の光偏向手段
２０ｂ 第二の光偏向手段
２１ 偏光面回転手段
３０ 画像表示装置
３１ 照明手段
３５ 画像表示素子
３６ 光学装置
３９ 光偏向装置
４０ 表示駆動手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflection apparatus, an optical deflection method, and an image display apparatus.
[0002]
[Definition]
In this specification, the “light deflecting element” means that the optical path of light is deflected by an external electric signal, that is, the outgoing light is shifted in parallel with respect to the incident light, or is rotated with a certain angle, Alternatively, it means an optical element capable of switching the optical path by combining both. In this description, the magnitude of the shift with respect to the optical path deflection due to the parallel shift is referred to as “shift amount”, and the amount of rotation with respect to the optical path deflection due to rotation as the “rotation angle”. The “light deflecting device” means a device that includes such a light deflecting element and deflects the optical path of light.
[0003]
In addition, the “pixel shift element” is an image display element in which a plurality of pixels that can control light according to image information is two-dimensionally arranged, a light source that illuminates the image display element, and an image displayed on the image display element An optical member for observing the image pattern, and a light deflecting means for deflecting an optical path between the image display element and the optical member for each of a plurality of subfields obtained by temporally dividing the image field. An optical deflecting unit in an image display device that displays an image pattern in which the display position is shifted in accordance with the deflection of the optical path for each subfield, thereby increasing the apparent number of pixels of the image display element. means. Therefore, basically, it can be said that the light deflection element and the light deflection device defined above can be applied as the light deflection means.
[0004]
[Prior art]
Conventionally, KH has been used as an optical element as a light deflection element. ₂ PO ₄ (KDP), NH ₄ H ₂ PO ₄ (ADP), LiNbO ₃ , LiTaO ₃ , GaAs, CdTe, and other materials having a large primary electro-optic effect (Pockels effect), KTN, SrTiO ₃ , CS ₂ Electro-optical devices using materials with large secondary electro-optic effect such as nitrobenzene, glass, silica, TeO ₂ Acousto-optic devices using materials such as these are known (for example, Shoji Aoki; “Optoelectronic Device”, Shosodo).
In general, in order to obtain a sufficiently large amount of light deflection, it is necessary to take a long optical path length, and the application is limited because the material is expensive.
[0005]
On the other hand, various types of optical elements, which are light deflecting elements using a liquid crystal material, have been proposed, and several examples thereof are as follows.
[0006]
For example, according to the technique disclosed in Japanese Patent Laid-Open No. 6-18940, a light beam shifter composed of an artificial birefringent plate has been proposed for the purpose of reducing the light loss of the optical space switch. Specifically, two wedge-shaped transparent substrates are arranged in opposite directions, and a light beam shifter having a liquid crystal layer sandwiched between the transparent substrates, and the light beam shifter is connected to the rear surface of a matrix type deflection control element. A light beam shifter has been proposed. In addition, two wedge-shaped transparent substrates are arranged in opposite directions, and a matrix drive is possible between the transparent substrates, and a light beam shifter sandwiching a liquid crystal layer that shifts the incident light beam by a half cell. An optical beam shifter has been proposed in which a half-cell is shifted and connected in multiple stages.
[0007]
Further, according to the technique disclosed in Japanese Patent Laid-Open No. 9-133904, a large deflection can be obtained, the deflection efficiency is high, and the deflection angle and the deflection distance can be arbitrarily set. A switch has been proposed. Specifically, two transparent substrates are arranged opposite to each other at a predetermined interval, a vertical alignment process is performed on the opposed surfaces, smectic A phase liquid crystal is sealed between the transparent substrates, and the substrate is perpendicular to the transparent substrate. The liquid crystal element includes a driving device in which an electrode pair is arranged so that an alternating electric field can be applied in parallel with the smectic layer and an alternating electric field is applied to the electrode pair. In other words, the electroclinic effect of the smectic A phase liquid crystal is used, and the refraction angle and the direction of displacement of the polarized light incident on the liquid crystal layer can be changed by birefringence due to the tilt of the liquid crystal molecules.
[0008]
In the technique disclosed in the former JP-A-6-18940, nematic liquid crystal is used as the liquid crystal material, so it is difficult to increase the response speed to sub-milliseconds. Cannot be used.
[0009]
In the latter technique disclosed in JP-A-9-133904, a smectic A-phase liquid crystal is used. However, since the smectic A-phase does not have spontaneous polarization, high-speed operation cannot be expected.
[0010]
Next, several techniques that have been conventionally proposed for the pixel shift element will be described. As a technique using a pixel shift element, for example, as disclosed in Japanese Patent No. 2939826, in a projection display apparatus that projects an image displayed on a display element on a screen by a projection optical system, the display is performed. Means for shifting a projection image comprising at least one optical element capable of rotating the polarization direction of transmitted light in the middle of an optical path from the element to the screen and at least one transparent element having a birefringence effect; There is a projection display device comprising means for effectively reducing the aperture ratio of the display element and discretely projecting the projection area of each pixel of the display element on the screen.
[0011]
In the technique disclosed in the publication, at least one optical element (referred to as an optical rotatory element) capable of rotating the polarization direction and at least one transparent element (referred to as a birefringent element) having a birefringence effect are provided. The pixel shift is performed by the projected image shift means (pixel shift means), but as a problem, since the optical rotation element and the birefringence element are used in combination, the light quantity loss is large, the pixel depending on the wavelength of light The shift amount fluctuates and the resolution tends to decrease, and optical noise such as ghost due to leaked light tends to occur at a position outside the pixel shift where an image is not originally formed due to a mismatch in optical characteristics between the optical rotation element and the birefringence element, It is mentioned that the cost for elementization is large. In particular, the KH as described above for the birefringent element ₂ PO ₄ (KDP), NH ₄ H ₂ PO ₄ (ADP), LiNbO ₃ , LiTaO ₃ This is remarkable when a material having a large primary electro-optic effect (Pockels effect) such as, GaAs, CdTe is used.
[0012]
In the projector disclosed in Japanese Patent Application Laid-Open No. 5-313116, the control circuit samples the image to be originally displayed stored in the image storage circuit into the pixel selection circuit in a checkered pattern, and sequentially performs the spatial light modulator. In addition, the control circuit controls the panel rocking mechanism in response to the display and moves the adjacent pixel pitch distance of the spatial light modulator by an integer by one to display the original image. The power image is reproduced by temporal synthesis. As a result, an image can be displayed with a resolution that is an integral multiple of the pixels of the spatial light modulator, and a projector can be constructed at low cost by using a spatial light modulator with coarse pixels and a simple optical system.
[0013]
However, the technique disclosed in the publication describes a pixel shift method in which the image display element itself is swung at a high speed by a distance smaller than the pixel pitch. In this method, the optical system is fixed. Therefore, although various aberrations are not generated, the image display element itself needs to be translated accurately and at high speed, so that the accuracy and durability of the movable part is required, and vibration and sound become a problem.
[0014]
Further, according to the technique disclosed in Japanese Patent Application Laid-Open No. 6-324320, in order to improve the resolution of a display image apparently without increasing the number of pixels of an image display device such as an LCD, Each of the plurality of pixels arranged in the direction emits light according to the display pixel pattern, thereby changing the optical path for each field between the image display device on which the image is displayed and the observer or the screen. An optical member is arranged, and for each field, a display pixel pattern in a state where the display position is shifted in accordance with the change of the optical path is displayed on the image display device. Here, the optical path is changed by causing the portions having different refractive indexes to appear alternately in the optical path between the image display device and the observer or the screen for each field of the image information. It is.
[0015]
In the technique disclosed in the publication, as a means for changing the optical path, a combination mechanism of an electro-optic element and a birefringent material, a lens shift mechanism, a vari-angle prism, a rotating mirror, a rotating glass, and the like are described. In addition to a system that combines elements and birefringent elements, a system that switches optical paths by displacing (translating, tilting) optical elements such as lenses, reflectors, and birefringent plates using voice coils, piezoelectric elements, etc. has been proposed. However, in this method, the configuration is complicated to drive the optical element, and the cost is increased.
[0016]
Further, according to the technique disclosed in Japanese Patent Application Laid-Open No. 10-133135, the rotating machine element can be eliminated, the entire size can be reduced, the accuracy and the resolution can be increased, and the influence of external vibration can be obtained. Difficult light beam deflecting devices have been proposed. Specifically, a translucent piezoelectric element disposed on the light beam traveling path, a transparent electrode provided on the surface of the piezoelectric element, and a light beam incident surface and a light beam emitting surface of the piezoelectric element. Voltage applying means for applying a voltage to the piezoelectric element through the electrode in order to change the optical path length between them and deflect the optical axis of the light beam.
[0017]
In the technique disclosed in this publication, a method is proposed in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes, and the thickness is changed by applying a voltage to shift the optical path. There are the same problems as in the case of the above-mentioned Japanese Patent Laid-Open No. 6-324320, such as requiring an element and increasing the device cost.
[0018]
By the way, Japanese Patent Application Laid-Open No. 2001-264821 discloses a technique for preventing domain generation by providing an electric field component orthogonal to the electric field switching direction although having a different purpose. According to the technique disclosed in the publication, a liquid crystal device having a homeotropic alignment in a neutral electric field state and an electrode pair for applying an electric field in a direction substantially parallel to the substrate are used to change the alignment direction of the liquid crystal molecules. Change the face. The number of electrode pairs can be increased to increase the uniformity of the electric field at the location where the light passes through the liquid crystal device.
[0019]
[Problems to be solved by the invention]
According to the applicant of the present invention, a pair of transparent substrates, a liquid crystal composed of a chiral smectic C phase having a homeotropic orientation filled between the substrates, and at least one set of electric fields that cause an electric field to act on the liquid crystal 5. An optical deflecting element including an applying unit has been filed. By using a liquid crystal composed of a chiral smectic C phase, the cost increases due to the complicated structure, the size of the device, the loss of light amount, and the generation of optical noise are improved compared to the conventional optical deflection element. be able to. In addition, according to the proposal, compared with the conventional optical deflecting element, it is possible to improve the dullness of the response of the liquid crystal when using the conventional smectic A liquid crystal or nematic liquid crystal, and to enable high-speed response. It can be.
[0020]
By the way, in the liquid crystal layer of the optical deflection element described above, when an electric field is applied in a direction perpendicular to the spiral axis of the chiral smectic C phase, that is, in the horizontal direction of the smectic layer, the liquid crystal molecules rotate in a conical virtual plane within the smectic layer. It is considered to exercise. At this time, the ratio of the liquid crystal molecules aligned in the same direction changes according to the characteristics such as the helical pitch and spontaneous polarization of the liquid crystal layer, and the inclination direction of the optical axis of the liquid crystal layer corresponding to the average alignment direction of the liquid crystal molecules is Change. When a sufficiently large electric field is applied, the orientation directions of the liquid crystal molecules in each smectic layer are aligned, and the spiral is unwound. When the electric field direction is reversed, the tilt direction of the optical axis of the liquid crystal layer is also reversed, so that it functions as a dynamic birefringent plate and is applied to an optical deflector or the like.
[0021]
However, when the liquid crystal molecules are inverted due to the inversion of the electric field direction, a transient light scattering phenomenon due to the disorder of the alignment state is observed. This is called the Transient-scattering mode (TSM) type electro-optic effect, and the detailed cause of the occurrence is not clear, but the difference in the rotation direction within the cone-shaped virtual plane when the liquid crystal molecules are inverted. It is considered that a domain is generated by this, and light scattering occurs at the domain interface. Conventionally, it has also been proposed to apply a change in the transparent state and the light scattering state to a display device using a light deflection element that generates such transient light scattering.
[0022]
This transient light scattering does not become a uniform domain when the inversion of liquid crystal molecules is completely completed, but is inappropriate for application as a light deflection apparatus that requires a small light scattering intensity and a short scattering time.
[0023]
An object of the present invention is to suppress the transient scattering phenomenon that occurs with the inversion motion of liquid crystal molecules.
[0024]
An object of the present invention is to prevent a reduction in transmittance and light utilization efficiency.
[0025]
[Means for Solving the Problems]
The optical deflecting device according to the first aspect of the present invention includes a transparent pair of substrates, a liquid crystal layer capable of forming a chiral smectic C phase having a homeotropic orientation filled between the substrates, and a normal direction of the substrate surface And an electric field generating means for generating an electric field in a direction substantially perpendicular to the light deflection direction, an electric field inverting means for inverting the electric field direction generated by the electric field generating means, and a reversal of the electric field direction by the electric field inverting means in the smectic layer. A rotation direction control means for controlling the rotation direction of at least some of the liquid crystal molecules in the liquid crystal layer that rotates in a cone-like virtual plane to reverse the alignment direction in the same direction.
[0026]
Therefore, the ferroelectric liquid crystal molecules forming the smectic C phase are transformed into the smectic layer by inverting the electric field direction generated by the electric field generating means in the direction substantially orthogonal to the normal direction of the substrate surface and the light deflection direction. The orientation direction is reversed by rotating in the cone-shaped virtual plane, and the tilt direction of the optical axis with respect to the normal direction of the liquid crystal layer is switched, so that the outgoing optical path for the incident light is switched. Here, when the orientation direction of at least a part of the liquid crystal molecules in the liquid crystal layer is reversed by rotating in the conical virtual plane in the smectic layer due to the reversal of the electric field direction, the rotation direction is controlled by the rotation direction control means. By controlling the rotation direction of each liquid crystal molecule to be the same direction and aligning the rotation direction of the liquid crystal molecules, it is possible to prevent the occurrence of domains due to the difference in the rotation direction.
[0027]
According to a second aspect of the present invention, in the optical deflection apparatus according to the first aspect, the rotation direction control means is an orthogonal electric field orthogonal to the electric field direction generated by the electric field generation means when the electric field direction is reversed by the electric field inversion means. Is generated.
[0028]
Therefore, when the ferroelectric liquid crystal molecules are rotated in the cone-shaped virtual plane and reversed, an electric field is generated by the rotation direction control means in one direction orthogonal to the electric field direction generated by the electric field generation means. In practice, the rotation direction of each of the rotating liquid crystal molecules can be controlled in the same direction by the electric field generated by the rotation direction control means.
[0029]
According to a third aspect of the present invention, in the optical deflecting device according to the second aspect, the rotation direction control means is arranged in the vicinity of the liquid crystal layer to generate the orthogonal electric field, and a voltage is applied to the orthogonal electrode pair. And an orthogonal voltage applying means for applying.
[0030]
Therefore, by providing a pair of orthogonal electrodes in the vicinity of the liquid crystal layer, which is an effective area for switching the outgoing optical path for incident light, a perpendicular electric field in one direction perpendicular to the direction of the electric field generated by the electric field generating means is relatively simple. Can be generated in the configuration.
[0031]
According to a fourth aspect of the present invention, in the optical deflecting device according to the third aspect, the rotation direction control means generates the orthogonal electric field by the orthogonal voltage application means immediately before reversal of the electric field direction by the electric field inversion means, Before the reversal of the alignment direction of the liquid crystal molecules due to the reversal of the electric field direction, the generation of the orthogonal electric field by the orthogonal voltage applying means is terminated.
[0032]
Therefore, by generating an orthogonal electric field by the orthogonal voltage application means and then reversing the electric field direction by the electric field inversion means, an electric field that aligns the rotation direction is applied to the liquid crystal molecules when the inversion of the liquid crystal molecules starts. The rotation direction of the liquid crystal molecules is surely aligned, and the generation of the orthogonal electric field by the orthogonal voltage applying means is terminated before the reversal of the alignment direction of the liquid crystal molecules started by the reversal of the electric field direction is completed. If the rotational motion is started in the direction, the generation of the unnecessary orthogonal electric field can be quickly terminated.
[0033]
An optical deflecting device according to a fifth aspect of the present invention includes a transparent pair of substrates, a first liquid crystal layer capable of forming a chiral smectic C phase having a homeotropic alignment filled between the substrates, and the substrate surface. A first electric field generating means for generating an electric field in a direction substantially perpendicular to the normal direction and the light deflection direction; and a first electric field inversion means for reversing the electric field direction generated by the first electric field generating means. The first light deflecting means, a pair of transparent substrates, and a chiral smectic C phase filled between the substrates to form a homeotropic alignment can be formed and substantially coincide with the normal direction of the first liquid crystal layer. A second liquid crystal layer having a normal direction, and a second electric field that generates an electric field in a direction substantially perpendicular to the normal direction of the substrate surface, the light deflection direction, and the electric field direction generated by the first electric field generating means. Generating means and said second A second electric field reversing means for reversing the direction of the electric field generated by the electric field generating means, and a second light deflecting means disposed in the vicinity of the first light polarizing means; A polarization plane rotating means disposed between the two light deflecting means and rotating the polarization plane of the incident light to the second polarizing means substantially at right angles to the light emitted from the first light deflecting means; Timing adjusting means for making the inversion timing of the electric field direction by the second electric field inversion means different from the inversion timing of the electric field direction by the first electric field inversion means.
[0034]
Therefore, the first and second electric field generating means generate the first and second electric field inversions in the first and second liquid crystal in the direction of the electric field generated in the direction substantially perpendicular to the normal direction of the substrate surface and the light deflection direction. By reversing each by means, the orientation directions of the liquid crystal molecules in the first and second liquid crystals are reversed, and the tilt direction of the optical axis with respect to the normal direction of the liquid crystal layer is switched. Since the polarization plane rotating means is disposed between the first and second light deflecting devices, the plane of polarization of the light emitted from the first or second light deflecting means is substantially perpendicular by the polarization plane rotating means. Since it is rotated and incident on the second or first light deflecting means, the outgoing optical path for the incident light to the light deflecting device can be switched to two systems. Since both the first and second optical deflecting devices are disposed in the vicinity of the deflection surface rotating means, the electric field generated by the second electric field inversion means with respect to the inversion timing in the electric field direction by the first electric field inversion means. By changing the direction inversion timing according to the timing adjustment means, the electric field in one direction orthogonal to the electric field direction generated by the first and second electric field generation means is rotated on the deflection surface with respect to the first and second liquid crystal layers. It can act via means.
[0035]
According to a sixth aspect of the present invention, there is provided a light deflection method in which linearly polarized light is incident on a liquid crystal layer capable of forming a chiral smectic C phase having a homeotropic alignment filled between transparent substrates, and a normal direction of the substrate surface. And an optical deflection method for switching a deflection direction of outgoing light with respect to incident light by inverting an electric field direction generated in a direction substantially orthogonal to the light deflection direction, wherein at least some liquid crystal molecules in the liquid crystal layer are However, when the orientation direction is reversed by rotating in a conical imaginary plane within the smectic layer, the rotation direction of each liquid crystal molecule to be reversed is controlled in the same direction.
[0036]
Therefore, when the orientation direction of the ferroelectric liquid crystal molecules forming the smectic phase by the reversal of the electric field direction is reversed by rotating in the conical virtual plane within the smectic layer, the rotation direction of each liquid crystal molecule that rotates. Are controlled in the same direction, and the rotation direction of the liquid crystal molecules is aligned, so that the occurrence of domains due to the difference in the rotation direction can be prevented.
[0037]
According to a seventh aspect of the present invention, in the optical deflection method according to the sixth aspect, by generating an electric field orthogonal to a normal direction of the substrate surface and an electric field direction generated in a direction substantially orthogonal to the optical deflection direction, The rotation direction of the liquid crystal molecules was controlled in the same direction.
[0038]
Therefore, when the ferroelectric liquid crystal molecules rotate and rotate in a cone-shaped virtual plane, an electric field perpendicular to the normal direction of the substrate surface and the direction perpendicular to the light deflection direction is generated. By doing so, it is possible to control the rotational direction of each of the rotating liquid crystal molecules in the same direction with certainty in practice.
[0039]
An image display device according to an eighth aspect of the present invention is an image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, illumination means for illuminating the image display element, and the image An optical device for observing an image pattern displayed on the display element; display drive means for driving the image display element in units of a plurality of subfields obtained by temporally dividing the image field; and each pixel of the image display element The light deflection apparatus according to any one of claims 1 to 5, wherein the light path of the emitted light is deflected for each of the subfields.
[0040]
Therefore, the optical path of the emitted light emitted from each pixel by illuminating the image displayed by the image display element in units of a plurality of subfields obtained by dividing the image field by the illuminating means is set for each subfield by the light deflecting device. The image pattern observed by the optical device is apparently multiplied from the actual number of pixels. Moreover, by using the optical deflecting device according to any one of claims 1 to 5, the transient scattering phenomenon is reduced, and the decrease in transmittance and MTF is suppressed.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. This embodiment shows an application example to an optical deflection apparatus.
[0042]
FIG. 1 is a longitudinal sectional view showing an optical deflecting device of the present embodiment. The optical deflection apparatus of the present embodiment includes an optical deflection element 1 and a power source 2 (see FIG. 2) that applies a voltage to an electrode pair 4 (described later) included in the optical deflection element 1. The power source 2 is driven and controlled by a control system (not shown) to apply an AC voltage having a rectangular wave shape in which the application direction is switched periodically so that the electric field direction is switched in accordance with the target light deflection direction. To do. Here, an electric field generating means is realized by the electrode pair 4 and the power source 2. Moreover, the electric field inversion means is realized by the power source 2.
[0043]
The light deflection element 1 includes a pair of transparent substrates 3 arranged to face each other. As the transparent substrate 3, glass, quartz, plastic or the like can be used, and a transparent material having no birefringence is preferable. The thickness of the substrate 3 is set within a range of several tens of μm to several mm.
[0044]
A metal sheet member 4 is provided between the pair of substrates 3 to share a spacer that defines the distance between the pair of substrates 3 and a pair of electrodes that generate an electric field in a liquid crystal layer described later. In the present embodiment, an electrode pair is realized by the pair of metal sheet members 4. Hereinafter, the metal sheet member is referred to as an electrode or an electrode pair, and a reference numeral 4 is given for explanation. As the spacer, a sheet member having a thickness of about several μm to several mm, or a particle having a particle size of about several μm to several mm is used. The spacer is preferably provided outside the effective area of the device. As the electrode, it is possible to use a metal such as aluminum, copper, or chromium, a transparent electrode such as ITO, etc. In order to apply a uniform horizontal electric field in the liquid crystal layer 5 described later, the thickness of the liquid crystal layer 5 It is preferable to use a metal sheet having the same thickness as the above. The electrode 4 is provided outside the effective area which is an area related to the light deflection operation by the liquid crystal.
[0045]
In the present embodiment, as a more preferred embodiment, the spacer and the electrode are shared by the metal sheet member, so that the number of parts can be reduced and the manufacturing can be facilitated.
[0046]
A liquid crystal layer 5 is provided at a position between the pair of substrates 3 and between the electrodes 4. As the liquid crystal layer 5, a liquid crystal capable of forming a smectic C phase is used.
When a voltage is applied between the electrodes 4 by the power supply, an electric field is generated in the horizontal direction of the liquid crystal layer 5.
[0047]
Further, vertical alignment films 6 for vertically aligning (homeotropic alignment) the liquid crystal molecules 5a (see FIG. 2) with respect to the surface of the substrate 3 are provided on the mutually opposing surfaces (inner side surfaces) of the pair of substrates 3, respectively. Yes. The vertical alignment film 6 is not particularly limited as long as it is a material that homeotropically aligns the liquid crystal molecules 5a with respect to the surface of the substrate 3. For example, a vertical alignment agent or silane coupling used for a general liquid crystal display is used. Agent, SiO ₂ A vapor deposition film or the like can be used.
[0048]
The “vertical alignment (homeotropic alignment)” in the present invention is not limited to the state in which the liquid crystal molecules 5a are aligned strictly perpendicular to the substrate surface of the substrate 3, and the liquid crystal molecules 5a are aligned with respect to the substrate surface. It includes an alignment state tilted to several tens of degrees.
[0049]
Here, the liquid crystal layer 5 capable of forming a smectic C phase will be described in detail. A “smectic liquid crystal” is a liquid crystal layer in which the major axis direction of liquid crystal molecules is arranged in a layered manner (smectic layer). With respect to such a liquid crystal, a liquid crystal in which the normal direction of the layer (layer normal direction) and the major axis direction of the liquid crystal molecules coincide with each other is referred to as “smectic A phase”, and a liquid crystal that does not coincide with the normal direction is referred to as “ It is called “smectic C phase”. A ferroelectric liquid crystal composed of a smectic C phase generally has a so-called helical structure in which a liquid crystal director direction is helically rotated for each smectic layer in a state where an external electric field does not work, and is called a “chiral smectic C phase”. In addition, the chiral smectic C reciprocal ferroelectric liquid crystal faces the direction in which the liquid crystal directors face each other. Since the liquid crystal composed of these chiral smectic C phases has an asymmetric carbon in the molecular structure and is spontaneously polarized by this, the liquid crystal molecules are rearranged in a direction determined by the spontaneous polarization Ps and the external electric field E. Optical properties are controlled.
[0050]
In the present embodiment, the light deflection element 1 will be described by taking a ferroelectric liquid crystal as an example of the liquid crystal layer 5. However, the present invention is not limited to this, and the liquid crystal layer 5 can be similarly used in the case of an antiferroelectric liquid crystal. .
[0051]
The chiral smectic C phase has an extremely fast response compared to the smectic A phase and nematic liquid crystal, and is characterized in that switching in sub ms is possible. In particular, since the liquid crystal director direction is uniquely determined with respect to the electric field direction, control of the director direction is easier and easier to handle than a liquid crystal composed of a smectic A phase.
[0052]
The liquid crystal layer composed of smectic C phase forming homeotopic alignment has a more restrictive action from the substrate than the liquid crystal director when compared to the homogeneous alignment (the liquid crystal director is aligned parallel to the substrate surface). It is difficult to receive, and it is easy to control the direction of light deflection by adjusting the direction of the external electric field, and has the advantage that the required electric field is low. Further, when the liquid crystal directors are homogeneously oriented, the liquid crystal directors strongly depend not only on the direction of the electric field but also on the substrate surface, so that more positional accuracy is required for the installation of the light deflection element. Conversely, in the case of homeotopic orientation as in the present embodiment, the setting margin of the optical deflection element 1 increases with respect to optical deflection. In making use of these features, it is not necessary to strictly orient the spiral axis perpendicular to the substrate surface, and it may be inclined to some extent. It suffices if the liquid crystal director can face in two directions without receiving the regulating force from the substrate.
[0053]
Here, the operation principle of the optical deflection element 1 will be described with reference to FIGS. FIG. 2 is a schematic diagram showing the relationship between the electric field direction in the liquid crystal layer 5 of the optical deflection element 1 and the tilt direction of the liquid crystal molecules 5a. In FIG. 2, the side where the width of the liquid crystal molecules 5a is drawn is inclined to the front (front) side of the paper, and the side where the width is drawn is inclined to the back (back) side of the paper. The relationship between the electric field direction and the tilt direction of the liquid crystal molecules in the case of is shown. In FIG. 2, the spontaneous polarization direction of the liquid crystal molecules 5a is indicated by an arrow Ps (PS in FIG. 2).
[0054]
When the direction of the electric field is reversed from the state shown in FIGS. 2A and 3A, the direction of the tilt angle of the liquid crystal molecules 5a that are substantially vertically aligned as shown in FIGS. 2B and 3B. Is reversed. Here, when the direction of the tilt angle is reversed, as shown in FIG. 3A, one end of the liquid crystal molecule 5a is considered to rotate in a virtual cone-shaped surface (virtual cone surface) C. .
[0055]
Here, FIG. 4 is a schematic diagram for two-dimensionally explaining how one end of the liquid crystal molecule 5a rotates in a virtual cone-shaped plane C. In FIG. 4, it is assumed that a voltage is applied in the front and back direction of the paper and that an electric field acts in the front and back direction of the paper. Further, it is assumed that the incident light incident on the light deflection element 1 is linearly polarized light. In FIG. 4, the vertical alignment film 6, the metal sheet member that also serves as the spacer and the electrode will be omitted. As shown in FIG. 4A, when an electric field is generated between the electrodes 4 from the back side to the front side of the paper, if the spontaneous polarization of the liquid crystal molecules 5a is positive, the liquid crystal director tilts in the upper right direction in FIG. Since the number of the liquid crystal molecules 5a increases, the average optical axis as the liquid crystal layer 5 is also inclined in the upper right direction in FIG. Here, the liquid crystal layer 5 functions as a birefringent plate.
[0056]
Above the threshold electric field at which the helical structure of the chiral smectic C phase can be solved, all the liquid crystal directors exhibit a tilt angle θ as shown in FIG. When an electric field from the back side to the near side is generated, the birefringent plate has an optical axis inclined upward at an angle θ. In this state, the linearly polarized light that has entered as extraordinary light from the left side in FIG. 4 takes the optical path indicated by A in FIG. 4A, and is parallel shifted upward with respect to the incident position of the incident light.
[0057]
Here, when the refractive index in the major axis direction of the liquid crystal molecules 5a is ne, the refractive index in the minor axis direction is no, and the thickness (gap) of the liquid crystal layer 5 is d, the exit position of the emitted light with respect to the incident position of the incident light. The shift amount S, which is a shift amount, is expressed by the following equation (see, for example, “Crystal Optics” Applied Physics Society, Optical Society, p198).

[0058]
Similarly, as shown in FIG. 4B, when the direction of the voltage applied between the electrodes 4 is reversed to generate an electric field from the front side to the back side of the paper, the spontaneous polarization of the liquid crystal molecules 5a is positive. For example, the number of liquid crystal molecules 5a in which the liquid crystal director tilts in the lower right direction in FIG. 4 increases, and the average optical axis as the liquid crystal layer tilts at an angle θ in the lower side in FIG. Here, the liquid crystal layer 5 functions as a birefringent plate inclined at an angle θ.
[0059]
In this state, the linearly polarized light that is incident as extraordinary light from the left side in FIG. 4 takes the optical path indicated by B in FIG. 4B and is parallel-shifted downward relative to the incident position of the incident light.
[0060]
In the optical deflection element 1, the amount of light deflection (shift amount) for 2S can be obtained by reversing the electric field direction in this way.
[0061]
Incidentally, the stable state after the liquid crystal molecules 5a are reversed and re-oriented has been described with reference to FIGS. 2 to 4. However, the alignment state of the liquid crystal molecules 5a is greatly increased in the process of reversing the alignment direction of the liquid crystal molecules 5a. Disturbed. Due to the disorder of the alignment state of the liquid crystal molecules 5a, transient light scattering in which a transient light scattering phenomenon due to the disorder of the alignment state is observed occurs.
[0062]
Here, the transient light scattering will be described with reference to FIG. FIG. 5 is a schematic diagram showing the tilted state of the liquid crystal molecules in the optical deflection element, as in FIG. Above the threshold electric field at which the helical structure of the chiral smectic C phase can be solved, the liquid crystal molecules 5a are uniformly oriented as shown in FIG.
[0063]
When the applied electric field is reversed from this state in a shorter time than the response time of the liquid crystal, the liquid crystal molecules 5a start to be reversed along the cone-like virtual plane C (see FIGS. 2 and 3). At this time, in the liquid crystal layer 5, as shown in FIG. 5B, it is estimated that a region R in which the liquid crystal molecules 5a rotate clockwise and a region L in which the liquid crystal molecules 5a begin to rotate counterclockwise are generated. . The above-mentioned transient light scattering is considered to occur strongly at the interface S between domains having different rotation directions.
[0064]
As shown in FIG. 5 (c), the transient light scattering disappears when the inversion of the liquid crystal molecules 5a with respect to FIG. 5 (a) is completed and the liquid crystal molecules 5a are reoriented to a uniformly inclined state.
[0065]
That is, in order to reduce the above-mentioned transient light scattering, at least a part of the liquid crystal molecules 5a in the liquid crystal layer 5 is rotated in the cone-like virtual plane C in the smectic layer by reversal of the electric field direction. As shown in FIG. 5D, it is presumed that it is effective to control the rotation direction of each liquid crystal molecule 5a to be inverted in the same direction.
[0066]
In the present embodiment, the vertical alignment film 6 is rubbed in the direction indicated by the arrow f in FIG. 6, that is, the rubbing process set substantially parallel to the electric field direction, thereby directing the alignment direction of the liquid crystal layer 5 itself. And the rotation direction of the liquid crystal molecules 5a is controlled in the same direction. Here, the rotation direction control means is realized by the rubbing-processed vertical alignment film 6.
[0067]
Thereby, when the rotation of the liquid crystal molecules 5a starts, the probability that the liquid crystal molecules 5a start to rotate in the rubbing direction is increased, and the rotation direction of the liquid crystal molecules 5a can be controlled. The rubbing direction only needs to be different from the light deflection direction, that is, the inclination direction of the optical axis in a steady state, and is not limited to a direction substantially perpendicular to the substrate surface as shown in FIG.
[0068]
In the method of controlling the rotation direction of the liquid crystal molecules 5a in the same direction by giving the directivity to the alignment direction of the liquid crystal layer 5 by performing a rubbing process on the vertical alignment film 6 as in the present embodiment, a stable tilt Since the direction is set to only one direction, the rotational motion at the time of inversion of the liquid crystal molecules 5a is always a reciprocating motion via a stable tilt direction.
[0069]
In the present embodiment, the arrangement position of the electrodes 4 and the voltage application state to the liquid crystal layer 5 are improved so that the alignment state of the liquid crystal molecules 5a can be controlled. 6. The liquid crystal layer 5, the spacer, and the electrode 4 (also used in this embodiment by a metal sheet member) can have the same configuration as that of a conventional light deflection element.
[0070]
Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, by forming a polymer network in the liquid crystal layer 5, directivity is given to the alignment direction of the liquid crystal layer 5 itself, and the rotation direction of the liquid crystal molecules 5a is controlled in the same direction.
[0071]
FIG. 7A is a horizontal cross-sectional view showing the light deflection element of the present embodiment. As shown in FIG. 2, in the light deflecting element of the present embodiment, a polymer network is formed by the polymer chains 8 contained in the liquid crystal layer 5. The polymer network in the liquid crystal layer 5 is prepared by adding a polymerizable monomer or prepolymer that reacts by ultraviolet rays or heat to the liquid crystal, and applying a horizontal electric field to the liquid crystal layer 5 to uniformly tilt the liquid crystal molecules 5a. It forms by making the polymerization reaction of a polymerizable monomer in a state. In the polymerization reaction of the polymerizable monomer or prepolymer, a stable tilt direction of the liquid crystal molecules 5a is generated by generating an electric field in a direction different from the electric field direction during normal operation by temporarily setting an external electrode or the like. Is set in a direction different from the light deflection direction. Thereby, a polymer network having directivity is formed in the liquid crystal layer 5, and a polymer stabilized liquid crystal layer can be formed.
[0072]
The polymer chain 8 according to the present embodiment generates a liquid crystal molecule 5a in the liquid crystal layer 5 by temporarily generating an external electric field with respect to the liquid crystal layer 5 in a state where the liquid crystal layer 5 contains a monomer or a prepolymer. Is formed by polymerizing a monomer or a prepolymer in a state inclined to the right side in FIG. 7A shows a state in which an electric field is generated in the left direction in FIG. 7A with respect to the liquid crystal layer 5 after the polymer chain 8 is formed.
[0073]
The monomer or prepolymer that forms the polymer chain 8 may be photopolymerizable (ultraviolet) or thermally polymerized (cured). For example, a polymer chain using a photopolymerizable monomer or prepolymer may be used. May be irradiated with linearly polarized light in the left-right direction in FIG.
[0074]
When a voltage is applied between the electrodes 4 of the light deflection element 7 to generate an electric field in the liquid crystal layer 5, the liquid crystal molecules 5a in the liquid crystal layer 5 are aligned vertically as shown in FIG. Take a state. At this time, as shown in FIG. 7B, the polymer chain 8 is presumed to be in an obliquely extended state with respect to the major axis direction of the liquid crystal molecules 5a in the vertically aligned state.
[0075]
Here, even when the polymer chain 8 is obliquely extended with respect to the major axis direction of the liquid crystal molecules 5a in the vertical alignment state, a voltage is applied between the electrodes 4 as compared with the alignment regulating force by the polymer chain 5. When the driving force by the electric field generated in the liquid crystal layer 5 is sufficiently larger, the liquid crystal molecules 5a are aligned as shown in (a) without being affected by the polymer chain as shown in (b).
[0076]
On the other hand, when the electric field direction is switched, if the influence of the electric field generated in the liquid crystal layer 5 becomes small, the alignment regulating force by the polymer chain 8 becomes strong. Then, at the moment when the alignment regulating force by the polymer chain 8 becomes stronger than the influence of the electric field generated in the liquid crystal layer 5, the liquid crystal molecule 5a is shown in FIG. 7 (c) by the polymer chain 8 as shown in FIG. ) Rotate in the middle left direction. The direction of rotation can be controlled. That is, by forming a polymer network in the liquid crystal layer 5, asymmetry occurs in the ease of rotation of the liquid crystal molecules 5a, so that the direction in which the liquid crystal molecules 5a start to rotate can be controlled in the same direction. Here, the rotation direction control means is realized by the polymer network.
[0077]
The polymer network may be formed by polymer chains 8 having a liquid crystalline structure in the main chain or side chain.
[0078]
In the method of forming a polymer network in the liquid crystal layer, it is possible to reduce the side effect of deviating the light deflection direction and increasing the response time by optimizing the addition amount and material of the polymer.
[0079]
In the method of controlling the rotation direction of the liquid crystal molecules 5a in the same direction by giving directivity to the alignment direction of the liquid crystal layer 5 by forming polymer stabilization in the liquid crystal layer 5 as in the present embodiment, the method is stable. Since the tilt direction is set to only one direction, the rotational motion at the time of inversion of the liquid crystal molecules 5a is always a reciprocating motion via a stable tilt direction.
[0080]
Next, a third embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, the rotation direction of the liquid crystal molecules 5a is controlled in the same direction by applying an electric field component orthogonal to the normal electric field direction when the liquid crystal molecules 5a are inverted.
[0081]
FIG. 8 is a perspective view showing an optical deflection element of the optical deflection apparatus of the present embodiment. The light deflection element 10 of the light deflection apparatus according to the present embodiment has substantially the same configuration as the light deflection element 1 according to the first embodiment, and is perpendicular to the light deflection element 1 according to the first embodiment. Instead of the rubbing process for the alignment film 6, an orthogonal electrode pair formed by a pair of orthogonal electrodes 11 that generate an electric field in a direction orthogonal to the direction of the electric field generated between the electrodes 4 is provided. The orthogonal electrode 11 is disposed so that the end portion on the electrode 4 side is separated from the electrode 4.
[0082]
In addition, the optical deflecting device of the present embodiment includes an orthogonal electrode 11 disposed in the vicinity of the liquid crystal layer 5 and a second power source (not shown) that applies a voltage between the orthogonal electrodes 11. The second power supply starts the operation immediately before reversing the voltage direction applied between the electrodes 4 by the power supply 2 when the electric field direction is reversed, and before the response time of the liquid crystal molecules 5a elapses after the operation is started. Drive control is performed by a control system (not shown) so as to end the operation.
[0083]
By applying a voltage to the orthogonal electrode pair immediately before reversing the direction of the electric field generated between the electrodes 4, an electric field indicated by an obliquely downward arrow ef in FIG. 9 (a) is generated in the liquid crystal layer 5. The liquid crystal molecules 5a begin to rotate counterclockwise.
[0084]
In this state, when the direction of the voltage applied between the electrodes 4 is reversed to reverse the direction of the electric field generated between the electrodes 4, the liquid crystal molecules 5a continue to rotate counterclockwise and are reversed.
[0085]
Here, by reversing the electric field direction generated in the direction substantially perpendicular to the normal direction of the substrate surface and the light deflection direction after generating the orthogonal electric field, the inversion of the liquid crystal molecules 5a due to the inversion of the electric field direction starts. Thus, the rotation direction of the liquid crystal molecules can be reliably aligned by applying an electric field that aligns the rotation direction to the liquid crystal molecules 5a. Here, the rotation direction control means is realized.
[0086]
This prevents transient scattering caused by the reversal of the liquid crystal alignment direction and improves the transmittance and light utilization efficiency, and shortens the effective switching time and speeds up the switching of the light deflection direction. be able to.
[0087]
In the present embodiment, since the orthogonal electric field is generated by the pair of orthogonal electrodes 11 provided outside the effective region of the optical deflection element 10, the transient scattering phenomenon is reduced with a relatively simple configuration, and the transmittance. And improvement of light utilization efficiency.
[0088]
According to the present embodiment, by controlling the direction and magnitude of the electric field component orthogonal to the normal direction of the substrate surface and the light deflection direction and the application timing, the rotation direction of the liquid crystal molecules 5a is reliably controlled in the same direction. be able to.
[0089]
Further, according to the present embodiment, the rotational movement of the liquid crystal molecules 5a can be controlled like a reciprocating movement, or can be controlled so as to continuously rotate in one direction.
[0090]
By the way, when the voltage is continuously applied between the orthogonal electrodes 11, the electric field generated between the electrodes 4 is orthogonal to the substrate surface due to the action of the orthogonal electric field, as indicated by the obliquely downward arrow ef in FIG. 9B. It is in a state shifted from the direction. As a result, the tilt direction of the liquid crystal molecules is slightly shifted from the originally intended angle, and the light deflection direction is also slightly shifted.
[0091]
In the present embodiment, since the operation is finished before the response time of the liquid crystal molecules 5a has elapsed since the start of voltage application by the second power supply, at the time when the reversal of the alignment direction of the liquid crystal molecules 5a is finished. The orthogonal electric field that causes the light deflection position to change is not generated.
[0092]
Here, before the reversal of the alignment direction of the liquid crystal molecules 5a started by the reversal of the electric field direction is terminated, the generation of the orthogonal electric field is terminated, so that the orthogonal electric field which becomes unnecessary once the rotational motion is started in the same direction. Can be promptly terminated, and the optical deflection position can be accurately controlled to provide an optical deflection apparatus with high accuracy of the optical deflection position.
[0093]
In addition, the arrangement position of the orthogonal electrode 11 is preferably outside the effective area of the light deflecting element 10 and in the vicinity of the liquid crystal layer 5 and at a position not excessively approaching the electrode pair. In the present embodiment, a portion related to light deflection in the light deflection element 10 is defined as an effective area. When the electrode 4 and the orthogonal electrode 11 are close to each other, even if a potential difference is generated between the electrodes 4, the orthogonal electrode 11 becomes equipotential. Therefore, a desired potential difference, that is, an electric field distribution is generated in the vicinity of the orthogonal electrode 11. It becomes difficult to obtain.
[0094]
On the other hand, in the present embodiment, since the end portions of the orthogonal electrode 11 on the electrode 4 side are arranged away from the electrodes 4, an electric field is generated in the target direction even in the vicinity of the orthogonal electrode 11. Can be made.
[0095]
In the present embodiment, the pair of orthogonal electrodes 11 is used. However, the present invention is not limited to this. For example, as shown in FIG. 10, a plurality of divided orthogonal electrodes 11 may be used.
[0096]
Further, in the present embodiment, the pair of orthogonal electrodes 11 facing each other through the liquid crystal layer 5 along the surface direction of the substrate 3 is used. However, the present invention is not limited to this. For example, as shown in FIG. The substrate 3 and the liquid crystal layer 5 may be provided in an oblique direction with respect to the surface direction of the substrate 3. As a result, when a voltage is applied to the orthogonal electrode 11, an electric field acting perpendicularly to the normal direction of the substrate surface and the light deflection direction and acting obliquely with respect to the surface direction of the substrate 3, as indicated by an arrow t in FIG. appear. A state in which an electric field is not applied to the orthogonal electrode 11 by separating the substrate 3 and the like between the electrode 4 and the orthogonal electrode 11, that is, in the liquid crystal layer 5 after the rotation of the liquid crystal molecules 5 a is completed. The influence of the orthogonal electrode 11 on the electric field distribution in the horizontal direction can be reduced.
[0097]
As described above, by dividing the orthogonal electrodes or sandwiching a dielectric such as the substrate 3 between the orthogonal electrodes 11, it is possible to prevent the equipotential portion due to the orthogonal electrodes 11 from spreading.
[0098]
In addition, in this embodiment, an electric field orthogonal to the normal direction of the substrate surface and the optical deflection direction is generated by the pair of electrodes 4. For example, as shown in FIG. When the light deflection electrode for generating an electric field perpendicular to the direction and the light deflection direction is composed of the transparent line electrode group 4x, a dielectric layer 13 is formed on the transparent line electrode group 4x of both substrates 3, and this dielectric The layer 13 is formed so as to sandwich the orthogonal electrode 11 therebetween. With this configuration, the interaction between the electric field generated by the transparent line electrode group 4x and the electric field generated by the orthogonal electrode 11 can be reduced.
[0099]
Next, a fourth embodiment of the present invention will be described with reference to FIG. This embodiment shows an application example to an optical deflection apparatus capable of deflecting light in two systems.
[0100]
FIG. 13A is a perspective view showing the optical deflecting device of this embodiment, and FIG. 13B is an exploded perspective view thereof. The optical deflection apparatus of the present embodiment is provided between two optical deflection elements 20 (20a, 20b) having the same configuration as the optical deflection element 1 shown in FIG. And a polarization plane rotating plate 21 as a deflection plane rotating means for rotating the polarization plane of the lens at a substantially right angle.
[0101]
As the polarization plane rotating plate 21, for example, a half-wave plate, a twisted nematic liquid crystal cell having no electrode, a film in which twisted nematic liquid crystal is fixed, or the like can be used.
[0102]
The two light deflecting elements 20a and 20b in the light deflecting device are normal to the liquid crystal layer (first liquid crystal layer) 5A of the light deflecting element (first light polarizing means) 20a via the polarization plane rotating plate 21. The direction and the normal direction of the liquid crystal layer (second liquid crystal layer) 5B of the light deflecting element (second light polarization means) 20b are arranged so as to substantially coincide with each other. Further, in the two optical deflection elements 20a and 20b in the optical deflection apparatus, the direction of the electric field generated between the electrodes 4a of the optical deflection element 20a and the direction of the electric field generated between the electrodes 4b of the optical deflection element 20b are substantially orthogonal. Are arranged to be.
[0103]
A power supply (not shown) for applying a voltage to the electrode pairs 4a and 4b is connected to the electrode pairs 4a and 4b of the light deflection elements 20a and 20b. In the present embodiment, one electrode 4a, 4b of the pair of electrodes 4a, 4b is connected to a rectangular wave AC power source. The power source is driven and controlled by a control system (not shown), and the inversion timing of the electric field direction generated between the electrodes 4b is different from the inversion timing of the electric field direction generated between the electrodes 4a. Control the timing of voltage application. Here, a first electric field generating means and a second electric field generating means are realized by a power source and electrodes 4a and 4b (not shown). In the present embodiment, the timing of voltage application to the electrode pairs 4a and 4b is controlled so as to be the timing shown in FIG. That is, the voltage applied to the electrode 4a and the voltage applied to the electrode 4b have the same polarity so that the polarity of the voltage applied to the electrode 4a and the polarity of the voltage applied to the electrode 4b are not completely reversed. The timing is set as follows. In the present embodiment, the polarity inversion period of the voltage applied to the electrode 4b is set to be shifted by ¼ period with respect to the inversion period of the polarity of the voltage applied to the electrode 4a. Here, the timing adjusting means is realized.
[0104]
When a voltage is applied in a pattern as shown in FIG. 14, the applied voltage value, the thickness of the substrate 3, and the like are such that the electric field generated in one optical deflection element 20a or 20b is the same as that of the other optical deflection element 20b or 20a. It is set so that there is little influence on the deflection direction.
[0105]
In such a configuration, the liquid crystal molecules 5a in the respective liquid crystal layers 5A and 5B are inverted by reversing the electric field directions generated in the direction substantially orthogonal to the substrate surface normal direction and the light deflection direction generated between the electrodes 4a and 4b. The orientation direction of the liquid crystal layer 5 is inverted, and the inclination direction of the optical axis with respect to the normal direction of the liquid crystal layer 5 is switched.
[0106]
At this time, the polarization plane of the light emitted from the light deflection element 20a is rotated substantially at right angles by the polarization plane rotating plate 21 disposed between the light deflection elements 20a and 20b and is incident on the light deflection element 20b. The outgoing optical path for the incident light to the deflecting device can be switched between two systems, the horizontal direction (Y direction in FIG. 13) and the vertical direction (X direction in FIG. 13). Thereby, for example, when the light emitted from the light deflecting element 20b of the light deflecting device is irradiated onto the screen 22 or the like, by combining two directions in the X direction and two directions in the Y direction, FIG. As shown in (d) to (d), the light path can be shifted so that the illumination area P sequentially moves and rotates around the four corners of the substantially square shape.
[0107]
Further, in the present embodiment, the two light deflection elements 20a and 20b are disposed close to each other via the polarization plane rotating plate 21, and the timing of voltage application to each electrode pair is controlled as shown in FIG. By using the positional relationship between the two light deflection elements 20a and 20b, an electric field direction generated between one electrode 4a or 4b is generated between the other electrode 4b or 4a without providing a new electrode pair. Rotation of each liquid crystal molecule 5a that can act as an electric field orthogonal to the electric field direction and that rotates by the inversion of the electric field direction generated between the other electrode 4b or 4a by the electric field generated between the one electrode 4a or 4b. The direction of the liquid crystal molecules 5a can be aligned by controlling the direction to be the same direction. Here, the rotation direction control means is realized.
[0108]
As a result, an optical deflecting device capable of deflecting light in two systems, without providing a dedicated electrode, prevents the occurrence of domains due to the difference in the rotation direction of the liquid crystal molecules 5a that rotate when the electric field direction is switched. It is possible to minimize the transient scattering phenomenon that occurs with the inversion motion of the molecule 5a, and to prevent the transmittance and the light utilization efficiency from being reduced.
[0109]
Next, a fifth embodiment of the present invention will be described with reference to FIG. Compared with the fourth embodiment, the present embodiment differs in the waveform of the voltage applied to the two electrode pairs, and the other light is synchronized with the inversion timing of the electric field direction in one optical deflection element. The leakage electric field from the deflecting element is actively used.
[0110]
In this embodiment, as shown in FIG. 16, the voltage obtained by temporarily increasing the applied voltage value of the other optical deflection element 20b or 20a only during the period before and after the electric field inversion time of one optical deflection element 20a or 20b. Is applied.
[0111]
By applying a voltage having such a waveform, a leakage electric field generated upon reversal of the electric field direction in one of the optical deflection elements 20a or 20b is increased, and is perpendicular to the optical deflection direction with respect to the other optical deflection element 20b or 20a. It is possible to effectively act on the electric field component.
[0112]
As shown in FIG. 16, the voltage value to be temporarily increased, the application time of the voltage to be temporarily increased, and the like are optimized according to the element configuration such as the liquid crystal material and the substrate thickness.
[0113]
A sixth embodiment of the present invention will be described with reference to FIG. This embodiment shows an application example to an image display device.
[0114]
FIG. 17 is a schematic diagram showing an image display apparatus according to the present embodiment. As shown in FIG. 17, the image display device 30 of the present embodiment includes a light source 31 as an illumination unit that emits light. The light source 31 of the present embodiment has a configuration in which LED lamps are arranged in a two-dimensional array.
[0115]
On the optical path of light emitted from the light source 31 toward the screen 32, a diffusion plate 33, a condenser lens 34, a transmissive liquid crystal panel 35 as an image display element, an image display element, and an image display element are disposed in order along the light traveling direction. A projection lens 36 as an optical device for observing the pattern is provided. ON / OFF of the light emitted from the light source 31 is controlled by the light source drive unit 37. The transmissive liquid crystal panel 35 is driven and controlled by a liquid crystal drive unit 38 as display driving means, and has a configuration in which a plurality of pixels that can control light emitted from the light source 31 according to image information are two-dimensionally arranged. ing. The transmissive liquid crystal panel 35 of the present embodiment spatially modulates the illumination light from the light source 31, and the liquid crystal drive unit 38 drives the transmissive liquid crystal panel 35 in units of a plurality of subfields obtained by temporally dividing the image field. .
[0116]
On the optical path between the transmissive liquid crystal panel 35 and the projection lens 36, an optical deflection device 39 that functions as a pixel shift element is interposed. As the optical deflecting device 39, the optical deflecting device of any of the above-described embodiments may be used. The light deflecting device 39 of the present embodiment has the same configuration as the light deflecting device of the sixth embodiment. The optical deflection device 39 is connected to the deflection drive unit 40 and deflects an image optical path emitted through the transmissive liquid crystal panel 35. The deflection drive unit 40 drives and controls the optical deflection device 39 so as to deflect the image optical path emitted through the transmissive liquid crystal panel 35 for each subfield. In the present embodiment, the shift amount by the light deflecting device 39 is set to ½ of the pixel pitch in the transmissive liquid crystal panel 35.
[0117]
In such a configuration, the illumination light that is controlled by the light source drive unit 37 and emitted from the light source 31 becomes illumination light that is made uniform by the diffusion plate 33, and the transmissive liquid crystal panel 35 is critically illuminated via the condenser lens 34. To do. The transmissive liquid crystal panel 35 is driven and controlled by the liquid crystal drive unit 38 to spatially modulate the illumination light from the light source 31 in units of subfields.
[0118]
The illumination light that has been spatially light modulated by the transmissive liquid crystal panel 35 enters the light deflecting device 39 as image light. The light deflection device 39 is driven and controlled by the deflection drive unit 40 to deflect the image light so that the image light projected on the screen 32 is shifted by an arbitrary distance in the pixel arrangement direction. The deflected image light is magnified by the projection lens 36 and projected onto the screen 32.
[0119]
As described in the above embodiment, the light deflecting device 39 according to the present embodiment can deflect the projection light path in two systems of the X direction and the Y direction. By synchronizing the spatial light modulation timing in units with the timing of shifting the optical path so that the illumination area P sequentially moves and rotates around the four corners of the substantially rectangular shape (see FIGS. 15A to 15D), The number of pixels of the display image displayed on the screen 32 can be apparently multiplied by four times. As a result, a high-definition image can be displayed without actually multiplying the number of pixels of the transmissive liquid crystal panel 35.
[0120]
Here, in the present embodiment, since the light utilization efficiency can be improved by using the light deflecting device 39, a bright and high-quality image can be provided without increasing the load on the light source 31.
[0121]
In the present embodiment, by using the optical deflecting device 39, the optical deflection position in the optical deflecting device 39 can be controlled by adjusting the electric field direction and electric field strength generated between the electrodes 4a and 4b. Therefore, an appropriate pixel shift amount can be maintained and a good image can be obtained.
[0122]
In particular, in the present embodiment, the use of the optical deflection device 39 can reduce transient light scattering that occurs at the time of switching the optical deflection operation, so that a decrease in transmittance and MTF can be suppressed. In this way, by suppressing transient light scattering when switching the deflection direction, it is possible to lengthen the time during which scattered light can be used for display as image light, thereby improving the light utilization efficiency. Can be made.
[0123]
【Example】
Next, examples of the present invention will be described. In the example, an optical deflection element as described below was manufactured, the optical axis of the manufactured optical deflection element was observed, transient light scattering was measured, and the optical path shift phenomenon was observed with a high-speed camera.
[0124]
(Preparation of optical deflection element)
First, the fabrication of the light deflection element 10 will be described. As an example, an aluminum electrode sheet having a thickness of 60 μm, a width of 0.5 mm, and a length of 12 mm is formed on a surface of a 1 mm thick glass substrate on which a 0.6 μm thick vertical (homeotropic) alignment film is formed. The electrode pairs 4 are formed by arranging them in parallel so that the effective area is about 1 cm wide, and aluminum electrode sheets similar to the electrode pairs 4 are arranged at intervals of 2 cm so as to be orthogonal to the first electrode pairs. Thus, the orthogonal electrode pair 11 was formed to produce a cell having an electrode arrangement as shown in FIG.
[0125]
In a state where the cell is heated to about 90 degrees, a ferroelectric liquid crystal (Chisso CS1029: birefringence Δn = 0.16, tilt angle θ = 25 degrees, spontaneous polarization Ps = −40 nC / cm ² ) Was injected by a capillary method and sealed with an adhesive after cooling, thereby producing a light deflection element 10 having a liquid crystal layer 5 thickness of 60 μm and an effective area of 1 cm square.
[0126]
Power sources 50 and 51 including a pulse generator and a high-speed amplifier were connected to the electrode pair 4 and the orthogonal electrode pair 11 of the optical deflection element 10 to obtain an optical deflection device 52.
[0127]
(Observation of optical axis)
Next, observation of the optical axis will be described. When a conoscopic image of the liquid crystal layer in the effective region of the light deflection element 10 was observed in the absence of an electric field, a cross and a ring image were observed at the center. Thereby, it can be confirmed that the optical axis is perpendicular to the liquid crystal layer 5 under no electric field. In this state, the liquid crystal molecules 5a have a spiral structure in which the tilt direction of the liquid crystal molecules 5a rotates with respect to the direction perpendicular to the surface of the substrate 3, and the average optical axis is observed in the direction perpendicular to the surface of the substrate 3 that is the direction of the spiral axis. The
[0128]
Subsequently, a rectangular wave voltage of ± 2000 V and 1 Hz was applied from the power source 50 to the electrode pair 4. At this time, the positions of the cross and the ring of the conoscopic image were reciprocally shifted in the vertical direction at 1 Hz. Although the description is omitted because it is a known technique, it can be seen that the tilt angle of the optical axis is calculated to be about 25 degrees from the NA value of the objective lens of the microscope, the refractive index of the liquid crystal, and the shift amount of the cross position. This confirmed that the tilt angle of the optical axis coincided with the tilt angle θ inherent to the liquid crystal material. The spiral structure of the liquid crystal molecules 5a can be solved by generating an electric field strength of about 200 V / mm between the electrodes 4 so that the liquid crystal molecules 5a are aligned in a uniform direction, and the direction of the optical axis of the liquid crystal layer 5 is ± 25 degrees. It was possible to switch with.
[0129]
(Measurement of transient light scattering)
Next, measurement of transient light scattering will be described. Using the measuring device 60 shown in FIG. 17, the intensity of the transient light scattering time of the light deflection element 10 of FIG. 16 was measured. The measuring device 60 includes a light source (not shown) that emits a He—Ne laser, a polarization plane rotating plate 61 that rotates the polarization plane of the He—Ne laser emitted from the light source, and a crossed Nicols that rotates the polarization plane of the laser light. A polarizing plate 62 and a photodetector 63 for detecting the intensity and time of light emitted from the crossed Nicols polarizing plate 62 are provided. In the measurement, the light deflection element 10 shown in FIG. 16 is set between the polarization plane rotating plate 61 and the crossed Nicols polarizing plate 62. The optical deflection element 10 shown in FIG. 16 is set so that the deflection direction by the optical deflection element 10 matches the polarization direction of the incident light.
[0130]
In the measuring apparatus 60, when laser light emitted from the light source is incident on the light deflection element 10 through the polarization plane rotating plate 61, the liquid crystal molecules 5a in the liquid crystal layer 5 of the light deflection element 10 are uniformly aligned. Then, although the optical path shift phenomenon occurs, there is no rotation or disturbance of the polarization plane, and therefore no light passes through the crossed Nicols polarizing plate 62. That is, no light is detected by the photodetector 63.
[0131]
On the other hand, in the state where transient light scattering occurs in the liquid crystal layer 5 of the light deflection element 10, the polarization plane is disturbed because the orientation direction of the liquid crystal molecules 5a is disturbed. For this reason, light whose polarization plane is rotated is generated, and light that leaks out of the crossed Nicols polarizing plate 62 is generated. The intensity and time of the leaked light are detected by the photodetector 63, and the intensity and time of transient light scattering can be measured.
[0132]
Using the measuring device 60 described above, a rectangular wave voltage of ± 2000 V and 100 Hz is applied from the power source 50 to the electrode pair 4, and the power source 51 is synchronized with a period of ± 0.25 msec from the switching time of the polarity of the rectangular wave voltage. When the intensity and time of the leaked light were measured while applying a pulse voltage of +4000 V and a pulse width of 0.5 msec to the orthogonal electrode pair 11, the detection voltage of leaked light due to transient light scattering was 0.1 mV. The detection time for leaking light was 1 msec.
[0133]
(Observation of optical path shift phenomenon with high-speed camera)
Next, observation of the optical path shift phenomenon with a high-speed camera will be described. A mask pattern (not shown) having an opening of 4 μm square was illuminated from the back surface, and the transmitted light transmitted through the mask pattern was observed through the light deflection element 10 shown in FIG. At this time, it is observed that the position of the mask pattern is shifted by operating the optical deflection element 10 by applying a voltage from the power source 50 to the electrode pair 4, and this shift state is observed with a high-speed camera with a microscope. By observing, the optical path shift amount and its response time were measured.
[0134]
Specifically, a rectangular wave voltage of ± 2000 V and 100 Hz is applied from the power source 50 to the electrode pair 4, and the orthogonal electrode pair is supplied from the power source 51 in synchronization with a period of ± 0.25 msec from the switching time of the polarity of the rectangular wave voltage. Observation with a high-speed camera (time resolution of 40500 frames / second) while applying a pulse voltage of +4000 V and pulse width of 0.5 msec to No. 11, the shift amount is 9 μm, and the response time required for the movement is 1 msec. there were. At this time, it was observed that the movement of the opening pattern H (see FIG. 20) observed through the opening moves relatively clearly so as to draw a slight arc. This is considered to represent that the rotation directions when the liquid crystal molecules 5a are inverted are aligned.
[0135]
Further, the response time of 1 msec is the same as the slight transient light scattering time, and it is considered that unnecessary alignment disorder does not occur when the liquid crystal molecules 5a are inverted. Therefore, it can be seen that an optical deflecting device with little transient light scattering was obtained.
[0136]
Subsequently, a comparative example for the above-described embodiment will be described. In the comparative example, an optical deflection apparatus provided with an optical deflection element 65 having substantially the same configuration as the optical deflection element 10 of the optical deflection apparatus 52 shown in FIG. 16 except that the orthogonal electrode pair 11 and the power source 51 are not installed. In the comparative example, the applied voltage pattern of the electrode pair 4 was also the same as in the example.
[0137]
When measurement was performed using such an optical deflector using the measuring device 60 shown in FIG. 19, the leakage light detection voltage due to transient light scattering was 0.5 mV, and the leakage light detection time was 2 msec. It was found that transient light scattering occurred remarkably.
[0138]
Similarly to the embodiment, when the shift state of the opening pattern H observed through the opening by the high-speed camera was measured, the shift amount was 9 μm and the response time required for the movement was 1 msec. It was found to be identical to the example. However, the movement of the opening pattern H observed through the opening is relatively unclear, and an opening pattern H that spreads out is observed. It was also observed that the image after the movement was slightly blurred. This suggests that the rotation direction when the liquid crystal molecules 5a are inverted is non-uniform, and the alignment is disturbed even after the majority of the liquid crystal molecules 5a have been inverted.
[0139]
【The invention's effect】
According to the optical deflecting device of the first aspect of the present invention, the ferroelectric liquid crystal molecules that form the smectic phase by reversing the electric field direction generated in the direction normal to the substrate surface and in the direction substantially orthogonal to the optical deflection direction. Is rotated in a conical imaginary plane in the smectic layer to reverse the orientation direction, and the tilt direction of the optical axis with respect to the normal direction of the liquid crystal layer is switched to switch the outgoing optical path for the incident light, and the electric field When the orientation direction of at least some liquid crystal molecules in the liquid crystal layer is reversed in the smectic layer by rotating in the cone-like virtual plane, the rotation direction of each of the rotating liquid crystal molecules is the same direction. By aligning the rotation direction of the liquid crystal molecules to prevent the occurrence of domains due to the difference in the rotation direction, the disorder of the liquid crystal alignment state caused by the inversion movement of the liquid crystal molecules KazuSatoshi, since the transient scattering phenomenon can be minimized, it is possible to prevent the reduction of transmittance and light utilization efficiency.
[0140]
According to a second aspect of the present invention, in the optical deflecting device according to the first aspect, when the ferroelectric liquid crystal molecules are rotated and reversed in a cone-like virtual plane, the normal direction of the substrate surface and the light The orthogonal electric field generated in one direction orthogonal to the direction substantially perpendicular to the deflection direction can control the rotational direction of each rotating liquid crystal molecule to be the same direction, and a transient generated as the liquid crystal alignment direction is reversed. The scattering phenomenon can be reliably reduced practically and the transmittance and light utilization efficiency can be improved.
[0141]
According to a third aspect of the present invention, in the optical deflection apparatus according to the second aspect, the electric field generating means is provided by providing the orthogonal electrode pair in the vicinity of the liquid crystal layer serving as an effective region related to switching of the outgoing optical path with respect to the incident light. Since the orthogonal electric field in one direction perpendicular to the direction of the electric field generated can be generated with a relatively simple configuration, the transient scattering phenomenon that occurs with the reversal of the liquid crystal alignment direction can be reduced with a relatively simple configuration. An optical deflecting device with good transmittance and light utilization efficiency is provided.
[0142]
According to a fourth aspect of the present invention, in the optical deflecting device according to the third aspect, after an orthogonal electric field is generated, the electric field direction is reversed in a direction substantially perpendicular to the normal direction of the substrate surface and the optical deflection direction. By applying an electric field that aligns the rotation direction to the liquid crystal molecules when the inversion of the molecules starts, the rotation direction of the liquid crystal molecules is reliably aligned to prevent transient scattering and improve transmittance and light utilization efficiency. In addition, the effective switching time can be shortened to increase the switching speed of the light deflection direction. In addition, by terminating the generation of the orthogonal electric field before the reversal of the orientation direction of the liquid crystal molecules started by the reversal of the electric field direction, the generation of the orthogonal electric field that becomes unnecessary once the rotational motion is started in the same direction. Can be promptly terminated, and the optical deflection position can be accurately controlled to provide an optical deflection apparatus with high accuracy of the optical deflection position.
[0143]
According to the light deflecting device of the fifth aspect of the present invention, the deflection of rotating the polarization plane of the light emitted from the first or second light deflecting means substantially at a right angle and making it incident on the second or first light deflecting means. By providing the surface rotation means in the vicinity of the first and second light deflection means, the inclination direction of the optical axis is switched to two systems, and the positional relationship between the electric field directions generated by the first and second electric field inversion means is changed. The first and second liquid crystal layers are made different from each other by making the electric field direction inversion timing by the second electric field inversion means different from the electric field direction inversion timing by the first electric field inversion means. By rotating the electric field in one direction perpendicular to the electric field direction generated by the second electric field generating means via the deflecting surface rotating means, it rotates in the first and second liquid crystal layers without providing a new electrode pair. Direction of rotation of each moving liquid crystal molecule Control the same direction to align the rotation direction of the liquid crystal molecules, prevent the occurrence of domains due to the difference in the rotation direction, minimize the transient scattering phenomenon caused by the inversion movement of the liquid crystal molecules, Reduction of light utilization efficiency can be prevented.
[0144]
According to the light deflection method of the invention described in claim 6, ferroelectric liquid crystal molecules forming a smectic phase by reversal of the electric field direction rotate in a conical imaginary plane within the smectic layer to reverse the alignment direction. In this case, the rotation direction of each rotating liquid crystal molecule is controlled in the same direction to align the rotating direction of the liquid crystal molecules, thereby preventing the occurrence of domains due to the difference in the rotating direction and accompanying the inversion movement of the liquid crystal molecules. It is possible to minimize the transient scattering phenomenon that occurs, and to prevent a reduction in transmittance and light utilization efficiency.
[0145]
According to a seventh aspect of the invention, in the light deflection method according to the sixth aspect, when the ferroelectric liquid crystal molecules rotate in the cone-shaped virtual plane and the orientation direction is reversed, the normal line of the substrate surface is obtained. By generating an electric field perpendicular to the direction of the electric field and the direction of light deflection substantially perpendicular to the light deflection direction, the rotational direction of each of the rotating liquid crystal molecules is practically controlled in the same direction, and the liquid crystal alignment direction The transient scattering phenomenon that occurs with the inversion can be reliably reduced practically, and the transmittance and light utilization efficiency can be improved.
[0146]
According to the image display device of the present invention, the image displayed by the image display element is illuminated by the illuminating means in units of a plurality of subfields obtained by temporally dividing the image field. Claims: The optical path of the incident light is deflected for each subfield by the optical deflecting device, so that the image pattern observed by the optical device is apparently increased from the actual number of pixels, and the display image is highly defined. By using the light deflecting device according to any one of 1 to 5, the transient scattering phenomenon is reduced, the decrease in transmittance and MTF is suppressed, and the time that can be used for display is lengthened to increase the light utilization efficiency. A display device can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an optical deflecting device according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a relationship between an electric field direction in a liquid crystal layer of an optical deflection element and a tilt direction of liquid crystal molecules.
FIG. 3 is a perspective view illustrating a state of liquid crystal molecules in a liquid crystal layer.
FIG. 4 is a schematic diagram for two-dimensionally explaining how one end of a liquid crystal molecule rotates in a virtual cone-shaped plane.
FIG. 5 is a schematic diagram showing a tilted state of liquid crystal molecules in the light deflection element.
FIG. 6 is a horizontal sectional view for explaining a rubbing direction of a vertical alignment film.
7A is a horizontal sectional view showing an optical deflector according to a second embodiment of the present invention, and FIGS. 7B and 7C are longitudinal sectional views thereof.
FIG. 8 is a perspective view showing an optical deflection element of an optical deflection apparatus according to a third embodiment of the present invention.
FIG. 9 is a schematic diagram showing a relationship between an electric field direction in a liquid crystal layer of an optical deflection element and a tilt direction of liquid crystal molecules.
FIG. 10 is a schematic diagram showing a relationship between an electric field direction and a liquid crystal molecule tilt direction in a liquid crystal layer of an optical deflection element according to another embodiment.
FIG. 11 is a perspective view showing an optical deflection element of an optical deflection apparatus according to another embodiment.
FIG. 12 is a perspective view showing an optical deflection element of an optical deflection apparatus according to another embodiment.
FIGS. 13A and 13B show an optical deflector according to a fourth embodiment of the present invention, in which FIG. 13A is a perspective view thereof, and FIG. 13B is an exploded perspective view thereof.
FIG. 14 is a timing chart illustrating the timing of voltage application to each electrode pair.
FIG. 15 is an explanatory diagram showing a movement state of an illumination area observed by a light deflection operation.
FIG. 16 is a timing chart illustrating the timing of voltage application to each electrode pair included in the light polarization element of the light deflection element according to the fifth embodiment of the invention.
FIG. 17 is a schematic view showing an image display apparatus according to a sixth embodiment of the present invention.
FIG. 18 is an explanatory diagram illustrating an optical deflecting element of an example.
FIG. 19 is a schematic view showing a measuring apparatus.
FIG. 20 is an explanatory diagram showing a movement state of the opening pattern.
[Explanation of symbols]
2 Electric field inversion means
3 Substrate
5 Liquid crystal layer
5a First liquid crystal layer
5b Second liquid crystal layer
11 Orthogonal electrode pair
20a First light deflecting means
20b Second light deflecting means
21 Polarization plane rotating means
30 Image display device
31 Illumination means
35 Image display element
36 Optical devices
39 Optical deflection device
40 Display drive means

Claims (8)

A pair of transparent substrates;
A liquid crystal layer capable of forming a chiral smectic C phase having a homeotropic alignment filled between the substrates;
An electric field generating means for generating an electric field in a direction substantially perpendicular to the normal direction and the light deflection direction of the substrate surface;
Electric field reversing means for reversing the electric field direction generated by the electric field generating means;
Rotation for controlling the rotation direction of at least some liquid crystal molecules in the liquid crystal layer to rotate in the cone-like virtual plane in the smectic layer and reverse the alignment direction by reversing the electric field direction by the electric field inverting means. Direction control means;
An optical deflection apparatus comprising: 2. The optical deflection apparatus according to claim 1, wherein the rotation direction control means generates an orthogonal electric field orthogonal to the electric field direction generated by the electric field generation means when the electric field direction is inverted by the electric field inversion means. 3. The optical deflecting device according to claim 2, wherein the rotation direction control unit includes an orthogonal electrode pair that is disposed in the vicinity of the liquid crystal layer and generates the orthogonal electric field, and an orthogonal voltage application unit that applies a voltage to the orthogonal electrode pair. . The rotation direction control means generates the orthogonal electric field by the orthogonal voltage application means immediately before the electric field direction is inverted by the electric field inversion means, and before the reversal of the alignment direction of the liquid crystal molecules by the inversion of the electric field direction is completed. The optical deflection apparatus according to claim 3, wherein the generation of the orthogonal electric field by the orthogonal voltage applying unit is terminated. A pair of transparent substrates, a first liquid crystal layer capable of forming a chiral smectic C phase filled between the substrates and forming a homeotropic alignment, and a direction substantially orthogonal to the normal direction and the light deflection direction of the substrate surface A first light deflecting means comprising: a first electric field generating means for generating an electric field; and a first electric field inverting means for inverting the electric field direction generated by the first electric field generating means;
A pair of transparent substrates and a second liquid crystal that can be formed between the substrates and can form a chiral smectic C phase having homeotropic alignment and has a normal direction substantially coincident with the normal direction of the first liquid crystal layer A second electric field generating means for generating an electric field in a direction substantially perpendicular to the normal direction of the substrate surface, the light deflection direction, and the electric field direction generated by the first electric field generating means, and the second electric field A second electric field inverting means for inverting the electric field direction generated by the generating means, and a second light deflecting means disposed in the vicinity of the first light polarizing means,
Polarized light that is disposed between the first and second light deflecting means and rotates the plane of polarization of incident light to the second polarizing means approximately at right angles to the light emitted from the first light deflecting means. Surface rotation means;
Timing adjustment means for making the inversion timing of the electric field direction by the second electric field inversion means different from the inversion timing of the electric field direction by the first electric field inversion means,
An optical deflection apparatus comprising: Linearly polarized light is incident on a liquid crystal layer capable of forming a homeotropically aligned chiral smectic C phase filled between transparent substrates, and is generated in a direction substantially perpendicular to the normal direction of the substrate surface and the light deflection direction. In the light deflection method for switching the deflection direction of the outgoing light with respect to the incident light by reversing the electric field direction,
When at least some of the liquid crystal molecules in the liquid crystal layer rotate in a cone-like virtual plane in the smectic layer by reversing the direction of the electric field to reverse the alignment direction, the rotation direction of each liquid crystal molecule to be reversed is the same direction. An optical deflection method characterized in that the control is performed. The rotation direction of the liquid crystal molecules is controlled in the same direction by generating an electric field orthogonal to an electric field direction generated in a direction substantially orthogonal to the normal direction of the substrate surface and the light deflection direction. The light deflection method according to claim 6. An image display element in which a plurality of pixels capable of controlling light according to image information are arranged two-dimensionally;
Illuminating means for illuminating the image display element;
An optical device for observing an image pattern displayed by the image display element;
Display driving means for driving the image display element in units of a plurality of subfields obtained by temporally dividing an image field;
The light deflecting device according to any one of claims 1 to 5, wherein an optical path of light emitted from each pixel of the image display element is deflected for each subfield;
An image display device comprising:

Images