JP4021697B2 - Optical path deflecting element, optical path deflecting device, image display apparatus, and optical path deflecting element driving method - Google Patents

Description

の式で表される（例えば、「結晶光学」応用物理学会、光学懇話会編、p198参照）。
【００８４】
同様に、図３（ｂ）のように電極への印加電圧を反転して紙面奥側へ向けた電界が印加された場合、液晶分子９の自発分極Ｐｓが正ならば液晶ダイレクタは図右下がりに傾斜し、光学軸が下側に角度θで傾斜した複屈折板として機能する。異常光として左側から入射した直線偏光は下側に平行シフトする。電界方向の反転によって、２Ｓ分の光路偏向量が得られる。
【００８５】
このような光路偏向方式では、一対の電極に対応した一方向のみの光路偏向動作しか行うことができない。例えば、Ｘ方向とＹ方向との２方向への偏向動作を行う場合には、少なくもと２つの光路偏向素子１′が必要であり、基板の数が増えることによる透過率の低下や解像度の低下が懸念される。
【００８６】
そこで、本実施の形態では、基板２，３、配向膜４，５、液晶層８、電極７などは上述の図１と同様なものを用いることができるが、電極の形状、数、配置並びに電圧印加方法などに特徴がある。図４を参照して本実施の形態の光路偏向素子１の構成例について説明する。
【００８７】
まず、本実施の形態では、後述する画像表示装置等への適用を想定し、液晶層８を通る光路の有効領域１１が例えば矩形状に設定された光路偏向素子１への適用例を示し、基板２，３等も有効領域１１よりも一回り大きな矩形形状のものが用いられている。もっとも、基板２，３の形状が有効領域１１の形状と同じである必要はない。また、このような液晶層８の有効領域１１を取り囲むように直交する２方向（Ｘ，Ｙ方向とする）の相対向する位置には２組（＝４個）の電極群１２，１２′、１３，１３′が配設されている。各電極群１２，１２′、１３，１３′は、有効領域１１の各辺に沿って各々形成されたもので、何れも当該有効領域１１を取り囲む方向（辺に沿う方向）にｎ個に分割された複数の分割電極により構成されている。即ち、電極群１２は、分割電極Ｘ１，Ｘ２，…，Ｘｎより構成され、同様に、電極群１２′は分割電極Ｘ′１，Ｘ′２，…，Ｘ′ｎ、電極群１３は分割電極Ｙ１，Ｙ２，…，Ｙｎ、電極群１３′は分割電極Ｙ′１，Ｙ′２，…，Ｙ′ｎにより構成されている。
【００８８】
このような構成の光路偏向素子１に対して、外部からの電気的な操作により、各電極群１２，１２′，１３，１３′内の個々の分割電極には、独立かつ択一的に、略一定な単一極性電位、接地電位或いは段階的に変化する電位となるような電圧印加が可能とされている。
【００８９】
いま、一例として、図５に例示するように、目的とする偏向方向に応じて電極群１２の分割電極Ｘ１〜Ｘｎの全てに印加する電圧が単一極性電圧Ｖ１（一定値）に設定された場合、相対向して組をなす電極群１２′の分割電極Ｘ'１〜Ｘ'ｎの全ても略一定電圧値に設定される。ここでは分割電極Ｘ'１〜Ｘ'ｎの電位はゼロボルト（接地）に設定される。このようにＹ方向に対向してＸ方向に組をなす電極群１２，１２′間への電位差Ｖ１の電圧印加により、図５中に矢印で示すように、液晶層８には光路に直交する方向の偏向用の電界が作用することになる。このような偏向用の電界を作用させるための電圧印加が偏向用電圧印加手段（ここでは、図示せず）により行われる。この場合の動作原理は、分割電極構造の場合であっても、図２により説明した場合と基本的には同様である。このようなＸ方向に組をなす２つの電極群１２，１２′間に電位差によって電界が発生するが、電極群１２，１２′の間隔が比較的広い場合には均一な電界を形成することは困難になる。特に、電極群１３，１３′がＹ方向に沿って連続した１枚電極の場合には、有効領域１１に臨んでいる当該１枚電極の全長に亘って（１辺相当の長さに亘って）等電位となってしまうため、偏向用の電界の両側付近に対してその均一性を乱してしまうこととなり、有効領域１１全域に亘って均一な電界が得られなくなってしまう。
【００９０】
そこで、本実施の形態では、目的とする偏向方向に応じて選択的に一方の組の相対向する電極群、例えば１２，１２′間に電圧を印加して液晶層８に光路に直交する方向の偏向用の電界を作用させる偏向時には、他方の組の電極群、例えば１３，１３′により強制的に偏向用の電界方向の電位勾配を持たせることを基本とする。その一例として、例えば、図５中に示すように、他方の組の電極群、例えば１３，１３′内の各分割電極Ｙ１〜Ｙｎ及びＹ'１〜Ｙ'ｎに対して図中、上側から段階的に電圧値がＶ１からゼロに変化するような段階的に電圧値が変化する電圧を印加することで、有効領域１１の周囲及び内部に強制的に所望の電位分布を形成させるものである。このような電圧印加は、補助電圧印加手段（ここでは、図示せず）により行われる。
【００９１】
ここで、より詳細には、有限の幅を持った各分割電極近傍では電位は一定となり分割電極間のみ電界が発生するため、電極群１３，１３′の分割電極Ｙ１〜Ｙｎ及びＹ'１〜Ｙ'ｎの近傍では図５中に示すように階段状の電位分布が形成されてしまう。しかし、電極群１３，１３′からある程度の距離が離れた有効領域１１内ではこのような階段状の電位分布が鈍り、縦方向（Ｙ方向）に略均一な電界が形成される。また、電極群１２，１２′の各分割電極Ｘ１〜Ｘｎ及びＸ'１〜Ｘ'ｎでは略均一な電圧が印加されているが、各分割電極間では周囲の電位の影響を受けて僅かに電位変化が生じるため、厳密には図５中に示すように僅かに不均一な電位分布となる。しかし、電極群１２，１２′からある程度の距離が離れた有効領域１１内では電位分布が鈍り、横方向の電界は発生しない。従って、有効領域１１内にはその全域に亘って図中下方向に均一な電界が発生する。ここで、図２の場合と同様に液晶分子９の傾斜状態をモデル的に図示すると、図５中、左側に光学軸が傾斜した状態となる（自発分極Ｐｓが正の場合）。
【００９２】
図５に示す状態は、一例を示すものであり、図５に示す例に加えて、２組（４つ）の電極群１２，１２′，１３，１３′への電圧印加状態を３種類切換えることで、図６（ａ）〜（ｃ）に示すように光学軸の傾斜方向、従って、光路偏向素子１による光路偏向方向を上下左右（±Ｘ，±Ｙ方向）の４方向に切換えることができる。
【００９３】
即ち、図６（ａ）は組をなす電極群１３，１３′については偏向用電圧印加手段により電極群１３の分割電極Ｙ１〜Ｙｎの全てに単一極性電圧Ｖ１（一定値）、電極群１３′の分割電極Ｙ′１〜Ｙ′ｎの全てにゼロボルト（接地）を印加し、他方の組をなす電極群１２，１２′については補助電圧印加手段により各分割電極Ｘ１〜Ｘｎ及びＸ'１〜Ｘ'ｎに対して図中、左側から段階的に電圧値がＶ１からゼロに変化するような段階的に電圧値が変化する電圧を印加した場合を示す。これにより、図６中、光学軸が下側に傾斜した状態となる（自発分極Ｐｓが正の場合）。
【００９４】
図６（ｂ）は組をなす電極群１２，１２′については偏向用電圧印加手段により電極群１２′の分割電極Ｘ′１〜Ｘ′ｎの全てに単一極性電圧Ｖ１（一定値）、電極群１２の分割電極Ｘ１〜Ｘｎの全てにゼロボルト（接地）を印加し、他方の組をなす電極群１３，１３′については補助電圧印加手段により各分割電極Ｙ１〜Ｙｎ及びＹ'１〜Ｙ'ｎに対して図中、下側から段階的に電圧値がＶ１からゼロに変化するような段階的に電圧値が変化する電圧を印加した場合を示す。これにより、図６中、光学軸が右側に傾斜した状態となる（自発分極Ｐｓが正の場合）。
【００９５】
図６（ｃ）は組をなす電極群１３，１３′については偏向用電圧印加手段により電極群１３′の分割電極Ｙ′１〜Ｙ′ｎの全てに単一極性電圧Ｖ１（一定値）、電極群１３の分割電極Ｙ１〜Ｙｎの全てにゼロボルト（接地）を印加し、他方の組をなす電極群１２，１２′については補助電圧印加手段により各分割電極Ｘ１〜Ｘｎ及びＸ'１〜Ｘ'ｎに対して図中、右側から段階的に電圧値がＶ１からゼロに変化するような段階的に電圧値が変化する電圧を印加した場合を示す。これにより、図６中、光学軸が上側に傾斜した状態となる（自発分極Ｐｓが正の場合）。
【００９６】
つまり、どの組の電極群間に偏向用の電圧を印加させるかは、目的とする偏向方向に応じて選択的かつ択一的なものであり、この結果に応じて他方の組の電極群に対する段階的な電圧印加も設定される。
【００９７】
なお、特に図示しないが、各電極群１２，１２′，１３，１３′が本実施の形態のような分割電極構成の場合、偏向用の電界を形成するための電圧が印加されない方の他方の組の電極群に関しては、各分割電極に段階的に変化する電圧を印加せずに、フロート状態に浮かすだけでもよい。この場合でも、各電極群が連続した１枚電極ではなく、有効領域１１に沿って複数の分割電極に分割されているので、このような分割電極が有効領域１１に臨んでいても当該他方の組の電極群により強制的に偏向用の電界方向の電位勾配を階段状に持たせることができ、有効領域１１内の電界の均一化を図れる。これによれば、補助電圧印加手段を要せず、比較的簡単に実現可能となる。
【００９８】
本発明の第二の実施の形態を図７及び図８に基づいて説明する。第一の実施の形態で示した部分と同一部分は同一符号を用いて示し、説明も省略する（以降の各実施の形態でも同様とする）。
【００９９】
本実施の形態の光路偏向素子２１では、図５に示したような光路偏向素子１の構成に加えて、各電極群１２，１２′，１３，１３′の各分割抵抗間に同一抵抗値の抵抗Ｒが設けられ、これらの抵抗Ｒを直列に接続した直列抵抗群２２，２２′，２３，２３′が設けられている。即ち、ｎ個の分割電極からなる各電極群１２，１２′，１３，１３′に対応させて、各直列抵抗群２２，２２′，２３，２３′は、（ｎ−１）個の抵抗Ｒを直列に接続した構成とされている。各直列抵抗群２２，２２′，２３，２３′の両端の端子間には電圧印加回路２４，２４′，２５，２５′が接続されている。このような光路偏向素子２１及び電圧印加回路２４，２４′，２５，２５′により光路偏向装置２６が構成されている。
【０１００】
ここに、何れの電圧印加回路２４，２４′，２５，２５′も同じ回路構成であって、偏向用電圧印加手段と補助電圧印加手段との機能を併せ持ち、電気的な切換えにより何れか一方の手段の機能を択一的に発揮するように構成されている。
【０１０１】
例えば、一例として電圧印加回路２５の構成例を説明する。まず、電極群１３（直列抵抗群２３）の両端の端子Ｔ１，Ｔ２間に交流電圧を印加するには、一端を接地し他端に正負極性の電圧を印加する方式が一般的であるが、本実施の形態では、図５（図６（ａ），（ｃ））で説明したように、偏向用電圧印加手段として機能させ電極群１３（直列抵抗群２３）の両端の端子Ｔ１，Ｔ２間に同一の電位Ｖ１又は０Ｖを与える必要があり、一般的な交流電源では対応できない。そこで、本実施の形態では、電圧印加回路２５は電圧Ｖ１の直流電源２７と４つのスイッチＳＷ１〜ＳＷ４との組合せ回路として構成され、スイッチＳＷ１〜ＳＷ４の開閉の組合せにより、端子Ｔ１，Ｔ２に電圧Ｖ１の印加と接地とを独立して切換え制御できるように構成されている。即ち、スイッチＳＷ１は端子Ｔ１に電圧Ｖ１を印加させるか否かを切換え、スイッチＳＷ２は端子Ｔ１を接地に接続するか否かを切換え、スイッチＳ３は端子Ｔ２に電圧Ｖ１を印加させるか否かを切換え、スイッチＳＷ４は端子Ｔ２を接地に接続するか否かを切換えるものである。これにより、スイッチＳＷ１，ＳＷ３が共に閉じられた時、又は、スイッチＳＷ２，ＳＷ４が共に閉じられた時には、当該電圧印加回路２５は偏向用電圧印加手段として機能し、スイッチＳＷ１，Ｓ４が共に閉じられ、又は、スイッチＳＷ３，Ｓ２が共に閉じられた時には、当該電圧印加回路２５は補助電圧印加手段として機能することとなる。
【０１０２】
ちなみに、図７に示す例では、スイッチＳＷ１，ＳＷ４が共に閉じられており、電圧印加回路２５は補助電圧印加手段として機能する場合を示している（図５に示した場合に類似する）。これにより、直列抵抗群２３の両端間に電圧Ｖ１を印加すれば、この電圧Ｖ１が（ｎ−１）個の抵抗Ｒにより分圧されるので、そのまま各分割電極Ｙ１〜Ｙｎに対して段階的に変化する電圧を印加することができる。この結果、各分割電極Ｙ１〜Ｙｎに対して個別に独立して電圧値の異なる電源を接続して段階的に変化する電圧を印加する構成に比べて、回路構成が簡単で済み、低コストにて実現可能となる。
【０１０３】
つまり、本実施の形態の光路偏向素子２１の場合、目的とする偏向方向に応じて選択的に一方の組の相対向する電極群間に電圧印加回路により電圧Ｖ１を印加して液晶層８に光路に直交する方向の偏向用の電界を作用させる偏向用電圧印加ステップと、この偏向用電圧印加ステップの電圧印加による偏向時に、他方の組の電極群の直列抵抗群の両端間に電圧印加回路により電圧Ｖ１を印加して強制的に偏向用の電界方向の電位勾配を持たせる補助電圧印加ステップとを実行させることにより、偏向方向が何れの方向であっても、有効領域１１全域について均一な電界を形成することができ、有効領域１１全域について均一な光路偏向が可能となる。
【０１０４】
ところで、電圧印加回路２５中に設けるスイッチＳＷ１〜ＳＷ４としては、耐電圧が高く、高速動作が可能なものを用いることが好ましい。その具体例を挙げると、例えば、図８に示すようにスイッチＳＷ１〜ＳＷ４をフォトカプラＰＣ１〜ＰＣ４により構成すればよい。
【０１０５】
本発明の第三の実施の形態を図９に基づいて説明する。本実施の形態は、前述した第二の実施の形態を改良したもので、光路偏向素子２１に関しては、隣接する電極群(直列抵抗群)の端部同士が電気的に接続されている。即ち、直列抵抗群２２，２３の端部同士、直列抵抗群２３，２２′の端部同士、直列抵抗群２２′，２３′の端部同士、直列抵抗群２３′，２２の端部同士が各々接続部２８ａ〜２８ｄとして電気的に接続されている。これらの接続部２８ａ〜２８ｄに対しては、電圧Ｖ１なる単一極性電位と接地とで切換え自在とされている。具体的には、図７中に示した電圧印加回路２４，２４′が省略され、電圧印加回路２５，２５′のみとされている（逆に、電圧印加回路２５，２５′を省略し、電圧印加回路２４，２４′のみとしてもよい）。電圧印加回路２５，２５′自体の構成は図７の場合と同様である。
【０１０６】
この結果、電圧印加回路２５，２５′は、電極群１２，１２′（直列抵抗群２２，２２′）に対して偏向用電圧印加手段として機能する時には、電極群１３，１３′（直列抵抗群２３，２３′）に対しては補助電圧印加手段として機能し、逆に、電極群１３，１３′（直列抵抗群２３，２３′）に対して偏向用電圧印加手段として機能する時には、電極群１２，１２′（直列抵抗群２２，２２′）に対しては補助電圧印加手段として機能するものであり、２つの電極群に対して兼用されることとなる。
【０１０７】
即ち、図７に示した構成例では、各電極群１２，１２′，１３，１３′毎に４つの電圧印加回路２４，２４′，２５，２５′を設けたが、図５に示した原理のように電界を印加する場合は、光路偏向素子２１の４隅の電位を独立に設定できれば良いので、図９に示すように、隣接する電極群の端部の電極間を各々接続部２８ａ〜２８ｄとして電気的に接続することで、電源回路の数を２組に減らすことができる。また、図９では直流電源２７と４つのスイッチＳＷ１〜ＳＷ４からなる回路を一つの電圧印加回路２５，２５′としているが、これらの電圧印加回路２５，２５′に関して直流電源２７を共用し、４つのスイッチＳＷ１〜ＳＷ４部分のみを別個に２組設ける構成としてもよい。これによれば、より一層電源を減らすことができる。
【０１０８】
本発明の第四の実施の形態を図１０に基づいて説明する。前述したように、各電極群１２，１２′，１３，１３′を複数の分割電極により構成する場合、有効領域１１内の電位分布の均一性を向上させるためには、各分割電極の電極幅は極力狭くて電極数は極力多いことが好ましい。しかし、光路偏向素子１又は２１の構成を簡略化して低コスト化を実現するためは、分割電極の数を減らす必要がある。分割電極の数を減らすと、分割電極間の位置での電位低下が現れるが、対向する分割電極の位置が全く一致している場合には分割電極間の位置同士も重なるため、電界の均一性の低下が顕著となる。そこで、本実施の形態では、図１０に示すように、相対向して組をなす電極群１２，１２′内、電極群１３，１３′内の個々の分割電極が互いにずれた交互の位置に配置させるようにしたものである。
【０１０９】
このような構成によれば、分割電極間の位置が対向する分割電極の位置に対応することとなり、電位低下の影響が小さくなり、有効領域１１内の電界の均一性が向上する。
【０１１０】
本発明の第五の実施の形態を図１１に基づいて説明する。前述したように、各電極群１２，１２′，１３，１３′を複数の分割電極により構成する場合、有効領域１１内の電位分布の均一性を向上させるためには、各分割電極の電極幅は極力狭くて電極数及び抵抗Ｒの数は極力多いことが好ましい。
【０１１１】
本実施の形態の光路偏向素子３１では、このような点を考慮し、理想的に電極幅を極限まで狭くし、抵抗数を無限大に増やすために、有効領域１１を取り囲む方向に各々連続させた抵抗体電極３２により各電極群１２，１２′，１３，１３′を構成したものである。各抵抗体電極３２の両端には電圧印加用の電極３３が各々設けられている。つまり、各電極群を抵抗体として連続的に形成したものである。
【０１１２】
抵抗体電極３２としては、カーボンブラック、酸化スズ系、酸化インジウム系などの導電性粉末の樹脂分散膜やＩＴＯ膜を用いることができる。本実施の形態の抵抗体層の機能は、有効領域１１の周囲に沿って所望の電位勾配を形成させるためのものであり、通電した時の発熱量が小さい条件で使用することが好ましい。
【０１１３】
有効領域１１に沿った位置に抵抗体電極３２を設けているので、抵抗体電極３２の両端部に電極３３を通じて電圧を印加して通電することで、抵抗体電極３２が電極群として機能し、抵抗体電極３２近傍の液晶層８内（有効領域１１）に図１１中に示すような連続的な電位勾配を形成することができる。この連続的な電位勾配により有効領域１１には均一な電界分布が得られる。
【０１１４】
つまり、本実施の形態の光路偏向素子３１によれば、目的とする偏向方向に応じて選択的に一方の組の相対向する電極群間に電圧Ｖ１を印加して液晶層８に光路に直交する方向の偏向用の電界を作用させる偏向用電圧印加ステップと、この偏向用電圧印加ステップの電圧印加による偏向時に、他方の組の電極群の抵抗体電極３２の両端間に電圧Ｖ１を印加して強制的に偏向用の電界方向の連続的な電位勾配を持たせる補助電圧印加ステップとを実行させるだけで、偏向方向が何れの方向であっても、有効領域１１全域について均一な電界を形成することができ、有効領域１１全域について均一な光路偏向が可能となる。
【０１１５】
本発明の第六の実施の形態を図１２に基づいて説明する。
【０１１６】
前述した各実施の形態では、有効領域１１周囲の電極群１２，１２′，１３，１３′に電位分布を与えることで有効領域１１内の電位分布を制御しているが、有効面積が大きくなると電極群１２，１２′，１３，１３′からの距離が離れた位置での制御性が悪くなり電界の均一性が低下する。
【０１１７】
そこで、本実施の形態の光路偏向素子４１は、図１２に示すように、基板２，３と垂直配向膜４，５との間に透明抵抗体層４２，４３を全面的に設け、各電極群１２，１２′，１３，１３′と透明抵抗体層４２，４３とを電気的に接続した構成とされている。なお、透明抵抗体層４２，４３は何れか一方のみでもよい。
【０１１８】
透明抵抗体層４２，４３としては、酸化スズ系、酸化インジウム系などの導電性粉末の樹脂分散膜やＩＴＯ膜を用いることができる。本実施の形態の透明抵抗体層４２，４３の機能は、有効領域１１内部の基板面に沿って所望の電位勾配を形成させるためのものであり、通電した時の発熱量が小さい条件で使用することが好ましい。ここで、透明抵抗体層４２，４３の表面抵抗をＲｓ［Ω／□］、電極群間の距離をａ［ｃｍ］、電極群の長さをｂ［ｃｍ］とすると、透明抵抗体層４２，４３全体の抵抗Ｒ［Ω］はＲ＝ａ／ｂ×Ｒｓになる。このような透明抵抗体層４２，４３にＥ［Ｖ］の電圧を印加すると、Ｅ^２／Ｒの電力Ｐ［Ｗ］を消費する。電流Ｉ［Ａ］は、Ｉ＝Ｅ／Ｒで求められる。透明抵抗体層４２，４３の面積はａ×ｂだからＰ／（ａ×ｂ）で得られる単位面積当たりの消費電力Ｐｄ［Ｗ／ｃｍ^２］は、温度上昇を予測するための特性値となる。本実施の形態では、１ｃｍ当たり数百ボルトから数キロボルトの電位差を印加するため、発熱を抑えるためには抵抗値を大きくする必要がある。単位面積当たり消費電力が０．０１Ｗ／ｃｍ^２程度ならば、温度上昇は１０℃以下程度に抑えられる。
【０１１９】
例えば、素子の面積を３ｃｍ×４ｃｍとし、表面抵抗値Ｒｓ＝１×１０^８Ω／□、電極群間の距離を３ｃｍ、電極群の長さを４ｃｍとした時、透明抵抗体層４２，４３の抵抗値は１．３３×１０^８Ωになる。この距離３ｃｍの間に３０００Ｖの電圧を印加すると２２．５μＡの電流が流れる。この時、全体で約０．０７Ｗ、単位面積当たり約０．００６Ｗ／ｃｍ^２の電力を消費する。この程度ならば発熱は実用上問題ない。従って、表面抵抗値が１×１０^８Ω／□程度以上の高抵抗の透明抵抗体層４２，４３を用いることが好ましい。これに対応した体積抵抗値を考える場合、透明抵抗体層４２，４３の膜厚が０．１μｍの時は１０^３Ωｃｍ以上、膜厚が１μｍの時は１０^４Ωｃｍ以上、膜厚が１０μｍの時は１０^５Ωｃｍ以上であることが好ましい。このような高抵抗値の透明抵抗体層４２，４３としては、帯電防止塗料などと同様の材料を用いることができる。この時、透明抵抗体層４２，４３の時定数はマイクロ秒以下であり、数百マイクロ秒周期で電圧を切換えるような用途では実用上問題ない値である。
【０１２０】
このように透明抵抗体層４２，４３の周囲に電極群１２，１２′，１３，１３′を接続して通電することで、透明抵抗体層４２，４３の表面近傍の液晶層８内（有効領域１１）に連続的な電位勾配を形成することができ、有効面積が比較的広い場合でも、比較的簡単な構成で有効領域１１内の液晶層８の水平方向に均一な電界分布を与えることができる。
【０１２１】
本発明の第七の実施の形態を図１３ないし図１５に基づいて説明する。本実施の形態は、より実際的な光路偏向装置５１の構成例を示すもので、光路偏向素子５２の入射面側に電気的操作によって直線偏光の偏光方向を回転変更可能な偏光方向切換素子（偏光方向切換手段）５３を付加したものである。ここに、光路偏向素子５２としては、前述した各実施の形態における光路偏向素子（電圧印加回路を含めて）の何れであってもよい。また、液晶層８における液晶の自発分極Ｐｓ及び偏向用の電界の作用により定まる液晶分子９の配向を電圧印加回路による電圧Ｖ１の印加により所定の方向に揃う状態で、一方の基板面から他方の基板面に向かって液晶分子９を投影した場合に他方の基板上に投影された液晶分子９における長軸方向が、この偏光方向切換素子５３により切換え制御される偏光方向と同一方向となるように、電圧印加回路による電圧Ｖ１の印加が同期して制御される。なお、液晶分子９の投影された長軸方向とは、投影光学軸方向である。図１４には一方の基板３（図示せず）から他方の基板２に投影された液晶分子９の方向（Ｃダイレクタ）９ｂを示す。各液晶分子９が均一な方向に配向している場合、投影光学軸方向はＣダイレクタ方向９ｂと一致する。
【０１２２】
例えば、入射光が水平方向の直線偏光の場合、図１３（ａ）では偏光方向切換素子５３は偏光方向を維持するように動作させ、光路偏向素子５２の有効領域１１には下向きの電界が作用するように電圧が印加されている。液晶の自発分極Ｐｓが正の場合、光学軸は図の左側に傾斜する。この時、偏光方向切換素子５３を出た偏光方向と光学軸の傾斜方向（液晶分子９を投影した場合に他方の基板上に投影された液晶分子９における長軸方向）とが一致しているので、光路が左側にシフトした状態となる。この時のシフト量は上述の（１）式で求められる。
【０１２３】
次に、図１３（ｂ）では偏光方向切換素子５３を偏光方向が９０度回転するように動作を切換えると同時に、光路偏向素子５２の有効領域１１には右向きの電界が作用する電圧を印加するように電圧印加回路の動作を切換える。液晶の自発分極Ｐｓが正の場合、光学軸は図の下側に傾斜する。この時、偏光方向切換素子５３を出た偏光方向と光学軸の傾斜方向（液晶分子９を投影した場合に他方の基板上に投影された液晶分子９における長軸方向）とが一致しているので、光路が下側にシフトした状態となる。同様にして、偏光方向切換素子５３による直線偏光の偏光方向及び光路偏向素子５２に対する電界の作用方向を図１３（ｃ），（ｄ）の状態に切換えることで、光路をＸ，Ｙの２方向（±４方向）に平行シフトさせることができる。
【０１２４】
このように、直線偏光の偏光方向を切換える偏光方向切換素子５３を光路偏向素子５２の入射側に備えることにより、２つの素子５２，５３による構成により直交するＸ，Ｙ２方向（±４方向）の偏向方向が設定できる。即ち、従来のように、Ｘ方向光路偏向素子と偏光面回転素子とＹ方向光路偏向素子との３つの素子の組合せ構成に比べて、素子の数が少なく構成要素の界面の数が少ないので、光透過率の低下やＭＴＦの低下が少ない光路偏向装置５１が得られる。
【０１２５】
偏光方向切換素子５３としては、磁場により直線偏光の偏光面が回転するファラデー回転素子や、図１５に示すようなツイスト構造を有する液晶セル５４を用いることができる。この液晶セル５４では、２枚の基板５５，５６の配向処理方向が直交に配置されており、液晶セル５４に電界が印加されていない状態ではツイストネマチック液晶層の液晶分子５７は厚み方向に９０度ねじれて配向している。入射基板５５側の液晶配向方向に平行な直線偏光を入射すると、液晶分子５７のねじれに沿って偏光面が回転して出射する。液晶セル５４の厚み方向に電界を印加すると、液晶分子５７が基板面に垂直に配向して入射光に対して等方的になり、偏光面は回転せずに出射する。特にツイスト構造を有する液晶セル５４は、波長による偏光面回転角のバラツキを比較的小さく設定可能であるため、多波長よりなる光を扱う場合に好適である。
【０１２６】
本発明の第八の実施の形態を図１６に基づいて説明する。本実施の形態は、例えば図１３に示した偏光方向切換素子５３として、電界の作用により液晶分子の配向方向が制御可能な表面安定型強誘電性液晶素子５８を用いるようにしたものである。表面安定型強誘電性液晶素子５８は、特に図示しないが、一対の基板と透明電極と水平配向膜と基板間のスペーサとキラルスメクチックＣ相を形成可能な液晶とにより構成されている。液晶層の厚みをキラルスメクチックＣ相の螺旋ピッチ以下に設定すると、螺旋が解けて表面安定型の配向状態となる。
【０１２７】
図１６に表面安定型強誘電性液晶素子５８の配向状態の模式図を示す。紙面垂直方向の電界の向きを切換えると、強誘電性液晶分子５９に固有のチルト角をθとした場合、コーン角２θだけ配向方向が切換わる。ここで、図１６（ａ）に示すように入射光の偏光方向と強誘電性液晶分子５９の配向方向とが一致している状態では、偏光方向は回転せずそのまま出射する。一方、図１６（ｂ）に示すように電界を反転させて強誘電性液晶分子５９を２θ傾斜した状態に切換えると、液晶層が半波長板として機能し、偏光面が４θだけ回転して出射される。ここでは、偏光面を９０度回転させるために、入射光の偏光方向に対して強誘電性液晶分子５９の配向方向が平行状態と約４５度傾斜した状態に切換えられるように配向処理方向及び液晶材料（チルト角θ＝２２．５°）を設定することが好ましいが、実用上問題ない範囲であれば、この角度に限定されない。セル厚みは入射光の波長と強誘電性液晶分子５９の複屈折に応じて適宜設定される。
【０１２８】
このような表面安定型強誘電性液晶素子５８を用いた場合、高速に偏光方向の切換えが可能な偏光方向切換素子５３が得られ、全体として高速応答の光路偏向装置５１が得られる。
【０１２９】
本発明の第九の実施の形態を図１７に基づいて説明する。本実施の形態は、前述した第七又は第八の実施の形態の光路偏向装置５１に関して、より実際的に構成したものである。即ち、前述の第七又は第八の実施の形態では、偏光方向切換素子５３に入射する光が直線偏光であることを前提に説明したが、無偏光の光を入射した場合、出射光には偏向を受けない成分を含むため、光路偏向の有無に対するコントラストが低下してしまう。
【０１３０】
そこで、本実施の形態の光路偏向装置５１では、図１６のように光路偏向素子５２（偏光方向切換素子５３）への入射光の偏光方向を光路の偏向方向（±４方向のうちの何れか一つの方向）と一致させる偏光方向制御手段６０を設けたものである。偏光方向制御手段６０としては、ヨウ素系偏光板、染料系偏光板、ワイヤグリッド偏光板などの直線偏光板を用いることができる。また、入射光が円偏光の場合や偏光方向が所望の方向と異なっている場合には、１／４波長板や１／２波長板などの位相差板を用いる。直線偏光板と位相差板とを組合せても良い。位相差板としては水晶や雲母をガラス板で挟んだものや液晶性ポリマフィルムを用いることができる。
【０１３１】
入射光が無偏光或いは円偏光の場合でも、液晶分子９の傾斜による光路偏向作用を受けない光成分をカットするので、確実に光路偏向による光スイッチングを行うことができる。
【０１３２】
本発明の第十の実施の形態を図１８に基づいて説明する。本実施の形態は、画像表示装置への適用例を示す。図１８において、７１はＬＥＤランプを２次元アレイ状に配列した照明装置用の光源であり、この光源７１からスクリーン７２に向けて発せられる光の進行方向には拡散板７３、コンデンサレンズ７４、画像表示素子としての透過型液晶パネル７５、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７６が順に配設されている。７７は光源７１に対する光源ドライブ部、７８は透過型液晶パネル７５に対する表示駆動手段としての液晶ドライブ部である。
【０１３３】
ここに、透過型液晶パネル７５と投射レンズ７６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路偏向装置７９が介在されている。この光路偏向装置７９は、前述した各実施の形態で説明したような構成からなるものであり、その光路偏向素子の有効領域は透過型液晶パネル７５に対応するように設定されている。この光路偏向装置７９には電圧印加回路及びこの電圧印加回路中のスイッチ等を開閉制御する機能を果たすドライブ制御部８０が接続されている。
【０１３４】
光源ドライブ部７７で制御されて光源７１から放出された照明光は、拡散板７３により均一化された照明光となり、コンデンサレンズ７４により液晶ドライブ部７８で照明光源と同期して制御されて透過型液晶パネル７５をクリティカル照明する。この透過型液晶パネル７５で空間光変調された照明光は、画像光として光路偏向装置７９の有効領域に入射し、この光路偏向装置７９によって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。この光は投射レンズ７６で拡大されスクリーン７２上に投射される。
【０１３５】
ここに、光路偏向装置７９により投射光路をＸＹ２方向の４位置にシフトさせるタイミングと、シフト位置に対応した４つのサブフィールド画像を透過型液晶パネル７５に順次表示させるタイミングとを同期させることで、見掛け上４倍に画素数が増倍した高精細な画像を表示することができる。この場合、光路偏向装置７９によるシフト量は透過型液晶パネル７５の画素ピッチの１／２に設定される。この際、光路偏向装置７９として、前述した各実施の形態のような光偏向装置を用いているので、光の利用効率を向上させ、光源の負荷を増加することなく観察者に対してより明るく高品質の画像を提供できる。光路偏向位置制御を、当該光路偏向素子における組をなす電極群による電界印加方向及び電界強度により行うことで、適切なピクセルシフト量が保持され良好な画像を得ることができる。特に、本発明の光路偏向素子ないしは光路偏向装置は少ない部品構成でＸＹ２方向（±４方向）へのシフトが可能であるため、素子全体の透過率が高く、ＭＴＦの劣化も少ないため、高効率で高解像度の表示画像が得られる。また、有効領域全域に亘って均一な電界が形成されるので、この電界の作用による偏向動作も有効領域全域、即ち、透過型液晶パネル７５により空間光変調される画像全体について均一に行わせることができ、より高精細な画像表示に寄与する。
【０１３６】
【実施例】
［実施例１］
(光路偏向素子及び装置の作製)
大きさ３ｃｍ×４ｃｍ、厚さ１ｍｍのガラス基板の表面に厚み０．０６μｍの垂直（ホメオトロピック）配向膜を形成した。厚み６０μｍ、幅０．５ｍｍ、長さ１〜２ｃｍのアルミニウム電極シートをスペーサ兼電極とし、有効領域が約１ｃｍ角となるように、その周囲の各辺に０．５ｍｍ間隔で１０本ずつ配置し、２枚の基板間に挟み込んで、図４に示した場合と類似の電極群配置のセルを作製した。セルを約９０℃に加熱した状態で、基板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°、自発分極Ｐｓ＝−４０ｎＣ／ｃｍ^２）を毛管法にて注入した。冷却後、接着剤で封止し、液晶厚み６０μｍ、有効面積１ｃｍ角の光路偏向素子を作製した。各辺のアルミニウム電極群の分割電極間に対して図９に示したように２００ｋΩの抵抗Ｒで接続し、図８に示したようなフォトカプラを用いた電圧印加回路に接続した。
【０１３７】
(光学軸の観察)
無電界の状態で、この光路偏向素子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、十字形と円環の画像が中心部に観察された。従って、無電界下では光学軸が液晶層に垂直であることを確認できた。この状態では液晶分子のチルト方向が基板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面に垂直な方向として観察される。
【０１３８】
次に、直流電源Ｖ１の出力を２０００Ｖに設定し、パルスジェネレータからフォトカプラの駆動信号を発生させ、図５で説明したように素子の４隅の内の上側左右２箇所に２０００Ｖが印加され、下側左右２箇所が接地される状態とした。同様にコノスコープ像を観察すると十字と円環の位置が右側にシフトした。これは本実施例では用いた強誘電性液晶の自発分極Ｐｓが負であるため、図５の場合とは反対側に光学軸が傾斜していることを示している。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から光学軸の傾斜角度を計算すると約２５°となり、この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。従って、２００Ｖ／ｍｍ程度の電界強度では螺旋構造が解けて一様な方向に液晶分子が配向した状態であると考えられる。
【０１３９】
同様にして４隅に印加する電圧のパターンを変化させたところ、コノスコープ像の十字と円環の位置も対応して上下左右に移動し、光学軸がＸＹ２方向の４位置に傾斜可能であることが確認できた。有効面積内の数箇所について同様な観察を行ったところ、位置によって光学軸の傾斜方向と傾斜角度に１０％以内のバラツキがあったが、実用上問題ないレベルと判断した。
【０１４０】
従って、単一セルで２方向（±４方向）以上への光学軸の偏向が可能な光路偏向素子及び光路偏向装置が得られた。
【０１４１】
［実施例２］
(光路偏向素子及び装置の作製)
大きさ３ｃｍ×４ｃｍ、厚さ１ｍｍのガラス基板の表面に厚さ１μｍの透明導電性塗料を塗布した。透明導電性塗料には、１次粒径が０．０１μｍ以下の酸化スズ系粉末をポリエステル樹脂に分散したものを用いた。分散濃度や塗布後の乾燥条件を調整し、表面抵抗値が１×１０^８Ωとなるように設定した。この透明導電性膜の可視光透過率は９０％以上であった。この表面に厚み０．０６μｍの垂直（ホメオトロピック）配向膜を形成した。その後、基板端部の配向膜を除去し、透明導電性膜が表面に出ている部分を形成した。厚み６０μｍ、幅０．５ｍｍ、長さ０．５〜１ｃｍのアルミニウム電極シートをスペーサ兼電極とし、有効領域が約２ｃｍ角となるように、その周囲の各辺に０．５ｍｍ間隔で２０本ずつ配置し、２枚の基板間に挟み込んで、図１２に示した場合と類似の電極群配置のセルを作製した。セルを約９０℃に加熱した状態で、基板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°、自発分極Ｐｓ＝−４０ｎＣ／ｃｍ^２）を毛管法にて注入した。冷却後、接着剤で封止し、液晶厚み６０μｍ、有効面積２ｃｍ角の光路偏向素子を作製した。各辺のアルミニウム電極群を２００ｋΩの抵抗で接続し、図８に示したようなフォトカプラを用いた電圧印加回路に接続した。
【０１４２】
(光学軸の観察)
直流電源Ｖ１の出力を４０００Ｖに変更した以外は実施例１と同様にして光学軸の傾斜状態を観察した。コノスコープ像の十字と円環の位置も対応して上下左右に移動し、光学軸がＸＹ２方向の４位置に傾斜可能であることが確認できた。また、有効面積内の数箇所について同様な観察を行ったところ、位置によって光学軸の傾斜方向と傾斜角度に５％以内のバラツキがあったが、実用上問題ないレベルと判断した。有効領域の面積が大きいにも関わらず、面内での光学軸傾斜方向の均一性が向上していることが確かめられた。
【０１４３】
［実施例３］
(偏光方向切換素子の作製)
大きさ３ｃｍ×４ｃｍ、厚さ１ｍｍのＩＴＯ付きガラス基板のＩＴＯ面に厚み０．１μｍの絶縁膜と厚み０．０６μｍの水平（ホモジニアス）配向膜を形成した。配向膜をラビング処理後、２枚の基板間に直径１．７μｍの球形スペーサを１００個／ｍｍ^２の密度で散布し、有効領域が２ｃｍ角のセルを作製した。セルを約９０℃に加熱した状態で、基板間の空間に上記と同様の強誘電性液晶（チッソ製ＣＳ１０２９）を毛管法にて注入した。冷却後、接着剤で封止し偏光面回転素子を作製した。２枚の基板のＩＴＯ電極間に±１０Ｖが印加可能な電源を接続した。直交した偏光板の間で液晶分子の配向方向の切換え状態を観察したところ、電界の反転により基板に平行配向した液晶分子の配向方向が約５０°傾斜し、この液晶材料固有のチルト角の２倍のコーン角２θと一致していることが確かめられた。偏光面を９０°回転させるためにはコーン角が４５°あることが理想であるが、５０°でも実用上問題ないと判断した。また、電界反転時の配向方向の切換え時間は１０Ｖ印加時に０．１２ｍｓｅｃであり、高速応答であることが確かめられた。
【０１４４】
(光路偏向動作の確認)
このような偏光方向切換素子と光路偏向素子とを図１３に示したような配置関係で貼り合わせて、光路偏向装置を作製した。この際、偏光方向切換素子の液晶配向方向の一方と、光路偏向素子の電界印加方向の一方とが一致するように配置した。光路偏向素子の入射面側に開口部５μｍ角、ピッチ２０μｍのマスクパターンを設け、このマスクパターンを通して直線偏光で照明した。直線偏光の向きは、偏光面回転素子の液晶配向方向の一方と同一となるように設定した。実施例１と同様に光路偏向素子への電圧印加パターンを切換えると同時に、偏光方向切換素子への電圧極性を切換えながら、マスクパターンを透過した光を光路偏向素子の有効領域を通して顕微鏡で観察した。
【０１４５】
電圧印加パターンは図１３（ａ）から図１３（ｄ）のように１秒毎に順次切換えた。素子中央部では開口パターンが上下左右の方向に約９μｍのシフト量で揺動して観察された。マスクパターンや光路偏向素子、顕微鏡は機械的に静止しているので、電気光学的にＸＹ２方向への光路シフトが可能であることが確認できた。また、高速度カメラを用いて開口パターンが移動する様子を観察して応答時間を測定したところ、０．４ｍｓであった。強誘電性液晶材料を用いているため充分速い応答速度が得られることが確かめられた。
【０１４６】
［実施例４］
図１８に示したような画像表示装置を作製した。画像表示素子として対角０．９インチＸＧＡ（１０２４×７６８ドット）のポリシリコンＴＦＴ液晶パネルを用いた。画素ピッチは縦横ともに約１８μｍである。画素の開口率は約５０％である。また、画像表示素子の光源側にマイクロレンズアレイを設けて照明光の集光率を高める構成とした。本実施例では、光源としてＲＧＢ３色のＬＥＤ光源を用い、上記の１枚の液晶パネルに照射する光の色を高速に切換えてカラー表示を行う、いわゆるフィールドシーケンシャル方式を採用している。本実施例では、画像表示のフレーム周波数が３０Ｈｚ、ピクセルシフトによる４倍の画素増倍のためのサブフィールド周波数が４倍の１２０Ｈｚとした。１つのサブフレーム内をさらに３色分に分割するため、各色に対応した画像を３６０Ｈｚで切換える。液晶パネルの各色の画像の表示タイミングに合わせて、対応した色のＬＥＤ光源をＯＮ／ＯＦＦすることで、観察者にはフルカラー画像が見える。
【０１４７】
光路偏向素子の構成は実施例３と同様であるが、液晶パネルを出射した光の偏光方向が偏光方向切換素子の液晶配向方向の一方と同一となるように設置した。また、光路偏向素子への入射光の偏光度を確実にするために、光路偏向素子の入射面側に直線偏光板を設けた。
【０１４８】
パルスジェネレータによってフォトカプラのスイッチングタイミングを制御して、電圧印加パターンが図１３（ａ）から図１３（ｄ）のように８．３ｍｓｅｃ毎に順次切換えるように設定した。光路シフト位置の切換えタイミングに同期して、画像表示素子に表示するサブフィールド画像を１２０Ｈｚで書き換えることで、縦横２方向に見掛け上の画素数が４倍に増倍した高精細画像が表示できた。光路偏向素子の切換え時間は約０．４ｍｓｅｃであり、充分な光利用効率が得られた。また、フリッカーなどは観測されなかった。また、スクリーン面にＣＣＤを配置して、ＣＣＤ上に画像を結像させて画素の形状を観察した。ここで、２画素周期のライン／スペース画像（１画素幅の白表示ラインと１画素幅の黒表示ラインが交互に並んだ画像）を表示し、白部の輝度をＩｍａｘ、黒部の輝度をＩｍｉｎとして、コントラスト・トランスファー・ファンクション(ＣＴＦ)＝（Ｉｍａｘ−Ｉｍｉｎ）／（Ｉｍａｘ−Ｉｍｉｎ）を求めた。一般に光学素子の変調伝達関数（ＭＴＦ）の値が小さいと画素の形状が鈍って、隣接した表示画素部と非表示画素部の輝度コントラストが低下し、ＣＴＦ値が小さくなる。本実施例ではＣＴＦ値は０．８であり、画素形状が比較的シャープな高精細画像が表示できることが確かめられた。
【０１４９】
【発明の効果】
請求項１記載の発明によれば、基本的に、ホメオトロピック配向をなすキラルスメクチックＣ相の強誘電性又は反強誘電性の液晶層に対してこの液晶層を通る光路に直交する方向の偏向用の電界を作用させることにより、液晶分子の傾斜角度や傾斜方向が変化して平均的な光学軸の傾斜方向を制御することができ、この際、液晶層を通る光路の有効領域を取り囲むように直交する２方向の相対向する位置に各々配設された２組の電極群を用意しておき、目的とする偏向方向に応じてこの偏向用の電界を作用させる電極群の組を選択的に切換えることにより、電気的な操作により直交する２方向に偏向方向を切換えることができ、また、このような偏向用電圧印加手段の電圧印加による偏向時に、他方の組の電極群に関しては、強制的に偏向用の電界方向の電位勾配を持たせることにより、偏向用の電界がこれらの他方の組の電極群により乱されることがなくなり、よって、有効領域全体に亘って均一な電界を形成することができる。
【０１５０】
請求項２記載の発明によれば、請求項１記載の発明を実現する上で、各電極群を複数の分割電極からなる分割構造とし、偏向用電圧印加手段の電圧印加による偏向時に、他方の組の電極群内の個々の分割電極に対して段階的に電圧値が変化する電圧を印加するようにしたので、当該他方の組の電極群により強制的に偏向用の電界方向の電位勾配を持たせることができ、比較的簡単に実現することができる。
【０１５１】
請求項３記載の発明によれば、請求項１記載の発明を実現する上で、各電極群を複数の分割電極からなる分割構造とし、かつ、電極群毎に各々隣接する分割電極間に設けられた抵抗を直列に接続した直列抵抗群を備える構成とし、偏向用電圧印加手段の電圧印加による偏向時に、他方の組の電極群の直列抵抗群の両端間に電圧を印加するようにしたので、直列抵抗群の各抵抗により抵抗分割されて段階的に変化する電圧を各分割電極に印加させることができ、当該他方の組の電極群により強制的に偏向用の電界方向の電位勾配を持たせることができ、簡単かつ低コストにて実現することができる。
【０１５２】
請求項４記載の発明によれば、請求項２又は３記載の光路偏向装置において、対向する分割電極の位置を互いにずらして交互の位置となるように配置させたので、分割電極間の位置が対向する電極群の分割電極に対応することとなり、電位低下の影響が小さくなり、電界の均一性を向上させることができる。
【０１５３】
請求項５記載の発明によれば、請求項１記載の発明を実現する上で、電極群として有効領域に沿った位置に抵抗体電極を設けるようにしたので、抵抗体電極の両端間に電圧を印加して通電するだけで、抵抗体電極近傍の液晶層内に連続的な電位勾配を形成することができ、このような連続的な電位勾配により、より均一な電界分布を得ることができる。
【０１５４】
請求項６記載の発明によれば、請求項２ないし５記載の発明を実現する上で、隣接する電極群の端部同士を電気的に接続し、その接続部の電位を接地と単一極性電位とで切換え自在としたので、偏向用電圧印加手段用の電源と補助電圧印加手段用の電源とを共用させることができ、低コストにて実現することができる。
【０１５５】
請求項７記載の発明によれば、請求項１ないし６記載の発明に加えて、有効領域全面に透明抵抗体層を設けて電極群と接続したので、組をなす電極群から比較的離れた有効領域にも効果的に電位分布を形成することができ、よって、有効領域が比較的大きな場合でも、比較的均一な電界を形成することができる。
【０１５６】
請求項８記載の発明によれば、請求項１記載の発明を実現する上で、各電極群を複数の分割電極からなる分割構造とし、偏向用電圧印加手段の電圧印加による偏向時に、他方の組の電極群内の個々の分割電極をフロート状態とするだけで、当該他方の組の電極群により強制的に偏向用の電界方向の電位勾配を持たせることができ、補助電圧印加手段を要せず、比較的簡単に実現することができる。
【０１５７】
請求項９記載の発明によれば、請求項１ないし８記載の発明に加えて、直線偏光の偏光方向を切換える偏光方向切換手段を入射側に備えるので、２つの素子構成により直交する２方向の偏向方向が設定できる。即ち、従来のように、Ｘ方向光路偏向素子と偏光面回転素子とＹ方向光路偏向素子との３つの素子の組合せ構成に比べて、素子の数が少なく構成要素の界面の数が少ないので、光透過率の低下やＭＴＦの低下が少ない光路偏向装置を提供することができる。
【０１５８】
請求項１０記載の発明によれば、請求項９記載の光路偏向装置を実現する上で、偏光方向切換手段として電界の作用により液晶分子の配向方向が制御可能な表面安定型強誘電性液晶素子を用いたので、この表面安定型強誘電性液晶素子の液晶分子の屈折率、電界印加時の配向方向、液晶層の厚みなどを半波長板としての最適条件に設定することで、高速に偏光面の回転が可能な偏光方向切換手段を得ることができ、全体として高速応答の光路偏向装置を提供することができる。
【０１５９】
請求項１１記載の発明によれば、請求項９又は１０記載の光路偏向装置を実現する上で、偏光方向切換手段に入射する入射光の偏光方向を光路の偏向方向に一致させる偏光方向制御手段を備え、光学軸の傾斜方向に平行な直線偏光の光のみを入射させるようにしたので、入射光が無偏光の光であっても光路偏向されないノイズ光の透過を防止し、ノイズの少ない確実な光路偏向を実現することができる。
【０１６０】
請求項１２記載の発明の画像表示装置によれば、いわゆるピクセルシフトデバイスとして請求項１ないし１１の何れか一記載の直交する２方向に光路偏向可能な光路偏向装置を用いたので、投射光路をサブフィールド画像に対応して高速に偏向させることができ、見掛け上、高精細な画像表示が可能となり、また、当該光路偏向装置の構成要素が少ない上に、有効領域全域に亘って均一な偏向用の電界が形成されるので、基板界面などが少なく、透過率やＭＴＦの低下が少なくできる上に、均一な画素シフトが可能となり、従って、より光利用効率が高く、より高精細な表示画像を得ることができる。
【０１６１】
請求項１３記載の発明の光路偏向素子によれば、基本的に、ホメオトロピック配向をなすキラルスメクチックＣ相の強誘電性又は反強誘電性の液晶層に対して、液晶層を通る光路の有効領域を取り囲むように相対向する位置に配設させた電極群の組に外部からの電気的な操作により電圧を印加して、この液晶層を通る光路に直交する方向の偏向用の電界を作用させることにより、液晶分子の傾斜角度や傾斜方向が変化して平均的な光学軸の傾斜方向を制御することができ、この際、組をなす電極群として、液晶層を通る光路の有効領域を取り囲むように直交する２方向の相対向する位置に各々配設された２組の電極群を用意しておき、目的とする偏向方向に応じてこの偏向用の電界を作用させる電極群の組を選択的に切換えるようにすれば、電気的な操作により直交する２方向に偏向方向を切換えることができ、また、各電極群を複数の分割電極からなる分割構造とし、偏向用電圧印加手段の電圧印加による偏向時に、他方の組の電極群に関しては、個々の分割電極に対して段階的に電圧値が変化する電圧を印加する等の操作により、当該他方の組の電極群により強制的に偏向用の電界方向の電位勾配を持たせることにより、偏向用の電界がこれらの他方の組の電極群により乱されることがなくなり、よって、有効領域全体に亘って均一な電界を形成させることができる。
【０１６２】
請求項１４記載の発明によれば、請求項１３記載の発明を実現する上で、分割電極構造の各電極群に加えて、電極群毎に各々隣接する分割電極間に設けられた抵抗を直列に接続した直列抵抗群を備える構成としたので、一方の組の電極群に対する電圧印加による偏向時に、他方の組の電極群の直列抵抗群の両端間に電圧を印加するだけで、直列抵抗群の各抵抗により抵抗分割されて段階的に変化する電圧を各分割電極に印加させることができ、当該他方の組の電極群により強制的に偏向用の電界方向の電位勾配を持たせることができ、簡単かつ低コストにて実現することができる。
【０１６３】
請求項１５記載の発明によれば、請求項１３又は１４記載の光路偏向素子を実現する上で、対向する分割電極の位置を互いにずらして交互の位置に配置させたので、分割電極間の位置が対向する電極群の分割電極に対応することとなり、電位低下の影響が小さくなり、電界の均一性を向上させることができる。
【０１６４】
請求項１６記載の発明の光路偏向素子によれば、基本的には請求項１３記載の発明の光路偏向素子と同様な効果が得られるが、電極群として有効領域に沿った位置に抵抗体電極を設けたので、外部からの電気的な操作として、一方の組の電極群間に電界を作用させる電圧を印加させるとともに、他方の組の電極群に関しては、抵抗体電極の両端間に電圧を印加して通電するだけで、抵抗体電極近傍の液晶層内に連続的な電位勾配を形成することができ、このような連続的な電位勾配により、より均一な電界分布が得られるようにすることができる。
【０１６５】
請求項１７記載の発明によれば、請求項１３ないし１６記載の発明を実現する上で、隣接する電極群の端部同士を電気的に接続したので、外部からの電気的な操作により、この接続部の電位を接地と単一極性電位とで切換え自在とすることにより、偏向用電圧印加手段用の電源と補助電圧印加手段用の電源とを共用させることができ、低コストにて光路偏向装置を実現することができる。
【０１６６】
請求項１８記載の発明によれば、請求項１３ないし１７記載の発明に加えて、有効領域全面に透明抵抗体層を設けて電極群と接続したので、外部からの電気的な操作による電圧印加時に、組をなす電極群から比較的離れた有効領域にも効果的に電位分布を形成することができ、よって、有効領域が比較的大きな場合でも、比較的均一な電界を形成することができる。
【０１６７】
請求項１９記載の発明の光路偏向素子の駆動方法によれば、有効領域全域について直交する２方向についての光路偏向を実現する上で、液晶層を通る光路の有効領域を取り囲むように直交する２方向の相対向する位置に２組の電極群を配設するが、これらの各電極群を複数の分割電極からなる分割構造とし、かつ、電極群毎に各々隣接する分割電極間に設けられた抵抗を直列に接続した直列抵抗群を備える構成とし、目的とする偏向方向に応じて選択的に一方の組の相対向する電極群間に電圧を印加して液晶層に前記光路に直交する方向の偏向用の電界を作用させる偏向時に、他方の組の電極群の直列抵抗群の両端間に電圧を印加するだけで、直列抵抗群の各抵抗により抵抗分割されて段階的に変化する電圧を各分割電極に印加させることができ、当該他方の組の電極群により強制的に偏向用の電界方向の電位勾配を持たせることができ、偏向方向が何れの方向であっても、有効領域全域について均一な電界を形成することができ、有効領域全域について均一な光路偏向が可能となる。
【０１６８】
請求項２０記載の発明の光路偏向素子の駆動方法によれば、有効領域全域について直交する２方向についての光路偏向を実現する上で、液晶層を通る光路の有効領域を取り囲むように直交する２方向の相対向する位置に２組の電極群を配設するが、これらの各電極群を有効領域を取り囲む方向に連続した抵抗体電極により構成し、目的とする偏向方向に応じて選択的に一方の組の相対向する電極群間に電圧を印加して液晶層に前記光路に直交する方向の偏向用の電界を作用させる偏向時に、他方の組の電極群の抵抗体電極の両端間に電圧を印加して通電するだけで、抵抗体電極近傍の液晶層内に連続的な電位勾配を形成することができ、このような連続的な電位勾配により、より均一な電界分布が得られるようにすることができ、偏向方向が何れの方向であっても、有効領域全域について均一な電界を形成することができ、有効領域全域について均一な光路偏向が可能となる。
【図面の簡単な説明】
【図１】前提となる光路偏向素子を示す断面構成図である。
【図２】その電界方向と液晶配向方向との関係を示す模式図である。
【図３】光路偏向動作の原理を説明するための模式図である。
【図４】本発明の第一の実施の形態の光路偏向素子の電極群の構成例を示し、（ａ）は平面図、（ｂ）はその側面図である。
【図５】その電圧印加状態と液晶分子傾斜方向との関係を示す概念図である。
【図６】電界方向を切換えた場合の様子を示す概念図である。
【図７】本発明の第二の実施の形態の光路偏向装置の構成例を示す平面図である。
【図８】その電圧印加回路の構成例を示す回路図である。
【図９】本発明の第三の実施の形態の光路偏向装置の構成例を示す平面図である。
【図１０】本発明の第四の実施の形態の光路偏向素子の構成例を示す平面図である。
【図１１】本発明の第五の実施の形態の光路偏向装置の構成例を示す平面図である。
【図１２】本発明の第六の実施の形態の光路偏向装置の構成例を示し、（ａ）は平面図、（ｂ）はその縦断側面図である。
【図１３】本発明の第七の実施の形態の光路偏向装置の構成例を示す斜視図である。
【図１４】液晶分子の長軸方向の投影部分を説明するための斜視図である。
【図１５】偏光方向切換素子の構成例を示す側面図である。
【図１６】本発明の第八の実施の形態の偏光方向切換素子の動作を説明するための正面図である。
【図１７】本発明の第九の実施の形態の光路偏向装置の構成例を示す斜視図である。
【図１８】本発明の第十の実施の形態の画像表示装置の構成例を示す側面図である。
【符号の説明】
１ 光路偏向素子
２，３ 基板
４，５ 配向膜
８ 液晶層
９ 液晶分子
１１ 有効領域
１２，１２′ 電極群の組
１３，１３′ 電極群の組
２１ 光路偏向素子
２２，２２′，２３，２３′ 直列抵抗群
２４，２４′，２５，２５′ 偏向用電圧印加手段、補助電圧印加手段
２６ 光路偏向装置
２８ａ〜２８ｄ 接続部
３１ 光路偏向素子
３２ 抵抗体電極
４１ 光路偏向素子
４２，４３ 透明抵抗体層
５１ 光路偏向装置
５２ 光路偏向素子
５３ 偏光方向切換手段
５８ 表面安定型強誘電性液晶素子
６０ 偏光方向制御手段
７１ 照明装置
７５ 画像表示素子
７６ 光学装置
７８ 表示駆動手段
７９ 光路偏向装置
Ｘ１〜Ｘｎ，Ｘ′１〜Ｘ′ｎ，Ｙ１〜Ｙｎ，Ｙ′１〜Ｙ′ｎ 分割電極
Ｒ 抵抗[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical path deflecting element, an optical path deflecting device, an image display apparatus, and an optical path deflecting element driving method.
[0002]
[Prior art]
As an optical element that becomes an optical path deflecting element, conventionally, KH₂PO₄(KDP), NH₄H₂PO₄(ADP), LiNbO₃, LiTaO₃, GaAs, CdTe, and other materials having a large primary electro-optic effect (Pockels effect), KTN, SrTiO₃, CS₂Electro-optical devices using materials with large secondary electro-optic effect such as nitrobenzene, glass, silica, TeO₂Acoustooptic devices using materials such as these are known (for example, Shoji Aoki; “Optoelectronic Device”, Shosodo). In these cases, generally, in order to obtain a sufficiently large amount of light deflection, it is necessary to take a long optical path length, and the use is limited because the material is expensive.
[0003]
On the other hand, various types of optical elements that are optical path deflecting elements using a liquid crystal material have been proposed, and several examples thereof are as follows.
[0004]
For example, according to Japanese Patent Laid-Open No. 6-18940, a light beam shifter made of an artificial birefringent plate is proposed for the purpose of reducing the light loss of the optical space switch. Specifically, a light beam shifter in which two wedge-shaped transparent substrates are arranged in opposite directions, a liquid crystal layer is sandwiched between the transparent substrates, and the light beam shifter is connected to the rear surface of the matrix-type deflection control element. A beam shifter has been proposed. At the same time, two wedge-shaped transparent substrates are arranged in opposite directions, and a matrix drive is possible between the transparent substrates. There has been proposed a light beam shifter in which multiple stages are shifted by half a cell.
[0005]
Japanese Patent Laid-Open No. 9-133904 proposes an optical deflection switch that can obtain a large deflection, has a high deflection efficiency, and can arbitrarily set a deflection angle and a deflection distance. Yes. Specifically, two transparent substrates are arranged opposite to each other at a predetermined interval, a vertical alignment process is performed on the opposed surfaces, and a smectic A phase ferroelectric liquid crystal is sealed between the transparent substrates. The liquid crystal element includes a driving device that is vertically aligned with respect to the electrode pair, the electrode pair is arranged so that an AC electric field can be applied in parallel with the smectic layer, and the AC electric field is applied to the electrode pair. In other words, the refraction angle and the direction of displacement of the polarized light incident on the liquid crystal layer can be changed by the birefringence due to the inclination of the liquid crystal molecules by using the electroclinic effect of the smectic A phase ferroelectric liquid crystal.
[0006]
In the former Japanese Patent Application Laid-Open No. 6-18940, nematic liquid crystal is used as the liquid crystal material, so it is difficult to increase the response speed to sub ms. Can not.
[0007]
In the latter example of JP-A-9-133904, a smectic A-phase ferroelectric liquid crystal is used. However, since the smectic A-phase does not have spontaneous polarization, high-speed operation cannot be expected.
[0008]
Next, several techniques that have been conventionally proposed for the pixel shift element will be described.
[0009]
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, transmitted light is transmitted in the middle of an optical path from the display element to the screen. Means for shifting a projection image having at least one optical element capable of rotating the polarization direction of the light and at least one transparent element having a birefringence effect, and effectively reducing the aperture ratio of the display element And a means for discretely projecting the projection area of each pixel of the display element on the screen.
[0010]
In the example of the publication, at least one optical element (optical rotator) capable of rotating the polarization direction and at least one transparent element (birefringent element) having a birefringence effect are projected image shift means ( The pixel shift is performed by the pixel shift means). However, since the optical rotation element and the birefringence element are used in combination, the loss of light amount is large and the pixel shift amount fluctuates depending on the wavelength of light, resulting in a decrease in resolution Optical noise such as ghost due to leaked light is likely to occur outside the pixel shift where the image is not originally formed due to mismatch of optical characteristics between the optical rotator and the birefringent element, and the cost for elementization is high. It can be mentioned. In particular, the KH as described above for the birefringent element₂PO₄(KDP), NH₄H₂PO₄(ADP), LiNbO₃, LiTaO₃This is remarkable when a material having a large primary electro-optic effect (Pockels effect) such as, GaAs, CdTe is used.
[0011]
In the projector disclosed in Japanese Patent Application Laid-Open No. 5-313116, the image to be originally displayed stored in the image storage circuit is sampled in a checkered pattern in the pixel selection circuit by the control circuit and sequentially displayed on the spatial light modulator. Then, the control circuit controls the panel rocking mechanism in correspondence with the display and moves the adjacent pixel pitch distance of the spatial light modulator by an integer by one. 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.
[0012]
However, the example of 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, and various aberrations are thus eliminated. Although the occurrence is small, since the image display element itself needs to be translated accurately and at high speed, the accuracy and durability of the movable part is required, and vibration and sound become a problem.
[0013]
Further, according to Japanese Patent 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, they are arranged in the vertical and horizontal directions. Each of the plurality of pixels emits light according to the display pixel pattern, and an optical member that changes the optical path for each field is disposed between the image display device on which the image is displayed and the observer or the screen. In addition, for each field, a display pixel pattern whose 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.
[0014]
In this example, 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 as means for changing the optical path. In addition to the method of combining refractive elements, a method of switching the optical path by displacing (translating, tilting) optical elements such as lenses, reflectors, birefringent plates, etc. by a voice coil, piezoelectric element, etc. has been proposed. In this method, the configuration is complicated to drive the optical element, and the cost is increased.
[0015]
Further, according to Japanese Patent Laid-Open No. 10-133135, a light beam deflecting device that can eliminate the need for a rotating machine element, can achieve overall downsizing, high accuracy and high resolution, and is hardly affected by external vibrations. Has been proposed. Specifically, a translucent piezoelectric element disposed on the traveling path of the light beam, a transparent electrode provided on the surface of the piezoelectric element, a light beam incident surface A and a light beam emitting surface B 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 and the electrode to deflect the optical axis of the light beam.
[0016]
In the example of the publication, a method is proposed in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes and a thickness is changed by applying a voltage to shift the optical path. However, a relatively large transparent piezoelectric element is required. However, there is a problem similar to the case of the above-mentioned Japanese Patent Laid-Open No. 6-324320, such as an increase in apparatus cost.
[0017]
[Problems to be solved by the invention]
When the problems of the conventional technology described above are arranged, the problem with the conventional pixel shift element is that
(1) High cost due to the complicated structure, large equipment, light loss, ghost and other optical noise or resolution reduction
(2) Problems with position accuracy, durability, vibration and sound, especially in the case of configurations with moving parts
(3) Response speed in nematic liquid crystal
It is.
[0018]
Regarding the response speed of (3), the speed of light deflection required for pixel shift in the image display device can be estimated as follows. Image field (time t_Field) In terms of time, and the optical path between the image display element and the optical member is deflected for each of n subfields to determine the pixel shift shift positions at n locations. Time t_SFIs
t_SF= T_Field/ N
It is represented by This time t_SFThe light is deflected during the period of time t_shiftAnd this t_shiftSince the display cannot be performed during this period, the light use efficiency is reduced by an amount corresponding to this period.
[0019]
The light utilization efficiency E is expressed by the following formula.
E = (t_SF−t_shift) / T_SF
[0020]
If the pixel shift position n is n = 4, the image field t_FieldIn order to ensure the light use efficiency E of 90% or more when is 16.7 ms,
0.9 <(16.7 / 4-t_shift) / (16.7 / 4)
t_shift<0.42 (ms)
Therefore, it is necessary to perform light deflection in 0.42 ms. Since a normal nematic liquid crystal has a response speed of several ms or more, it cannot be used as an optical element for high-speed pixel shift as shown here.
[0021]
In Japanese Patent Application Laid-Open No. 6-18940, nematic liquid crystal is used as the liquid crystal material, so it is difficult to increase the response speed to sub ms, and it cannot be used for pixel shift. On the other hand, the response speed of a ferroelectric liquid crystal composed of a chiral smectic C phase can be sufficiently set to 0.42 ms or less.
[0022]
In Japanese Patent Laid-Open No. 9-133904, a smectic A-phase ferroelectric liquid crystal is used. However, since the smectic A-phase does not have spontaneous polarization, high-speed operation as seen in the chiral smectic C-phase cannot be expected. .
[0023]
Considering these points, the problems in the conventional optical path deflecting element, that is, the high cost, the large size of the apparatus, the light loss and the optical noise due to the complicated configuration, are improved, the configuration is simple and the size is small. There is a need for a proposal of an optical path deflecting element or an optical deflecting device that can reduce the amount of light, optical noise, and resolution, and can reduce the cost.
[0024]
Therefore, according to the present applicant, a pair of transparent substrates, a liquid crystal composed of a chiral smectic C phase having a homeotropic orientation filled between the substrates, and an electric field applied to the liquid crystal 1 A configuration example including a set of electric field applying means more than a set has been proposed. According to this proposed example, since liquid crystal composed of a chiral smectic C phase is used, the cost is increased due to the complicated structure compared to the conventional optical path deflecting element, the size of the apparatus is increased, the amount of light is lost, and the optical Noise can be improved, and dullness of response in conventional smectic A liquid crystal or nematic liquid crystal can be improved, and high-speed response is possible.
[0025]
However, since the smectic C-phase ferroelectric liquid crystal layer is used as a birefringent plate in the optical path deflecting element according to this proposed example, the direction of optical path deflection is determined by the tilt direction of the optical axis tilt angle of the liquid crystal layer. Since one optical path deflecting element can only perform an optical path deflecting operation in one direction, in order to perform an optical path deflecting operation in two directions, two optical path deflecting elements and a linear polarization direction between them are set to the deflecting direction. A polarization direction switching element to be matched is required. Since it is composed of three optical elements, there are problems that the number of substrates and interfaces increases, and the transmittance and MTF of the entire optical element decrease.
[0026]
In this respect, for example, two electrode pairs are provided at two orthogonal positions so as to surround the effective area of the optical path passing through the liquid crystal layer, and a voltage is selected between one pair of electrode pairs according to the direction to be deflected. It is conceivable that deflection in two directions (± 4 directions) is selectively performed by applying an electric field for deflection in a direction perpendicular to the optical path to the liquid crystal layer.
[0027]
Here, the two pairs of electrodes cause a deflection electric field to act on a common effective region by applying a voltage alternatively according to the deflection direction. It is set as the structure which has compatibility. Specifically, it can be said that it is common to provide a strip-shaped electrode having a length corresponding to one side on each side of the effective area set in a substantially rectangular shape. As a result, when a voltage for applying an electric field for deflection is applied between one pair of electrode pairs, each electrode of the other pair of electrode pairs facing the effective region extends over its entire length ( Since it is equipotential (over a length corresponding to one side), the uniformity of the deflection electric field is disturbed near both sides, and a uniform electric field is obtained over the entire effective area. It will not be possible. If a uniform electric field cannot be obtained over the entire effective region, uniform deflection characteristics (uniformity in the deflection direction) cannot be obtained over the entire effective region.
[0028]
The present invention relates to an optical path deflecting element and an optical path capable of uniformly forming an electric field for deflection in a target effective area under a configuration in which the deflection direction can be switched in two orthogonal directions by an electric operation from the outside. It is an object of the present invention to provide a deflection apparatus and a method for driving an optical path deflection element.
[0029]
It is an object of the present invention to provide an optical path deflecting element, an optical path deflecting device, and an optical path deflecting element driving method that can easily form a uniform electric field.
[0030]
It is an object of the present invention to provide an optical path deflecting element and an optical path deflecting device that can realize uniform electric field formation at low cost.
[0031]
An object of the present invention is to provide an optical path deflecting element and an optical path deflecting device capable of improving the uniformity of the electric field formed.
[0032]
An object of the present invention is to provide an optical path deflecting element and an optical path deflecting device capable of realizing formation of a uniform electric field even when the effective area is wide.
[0033]
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical path deflecting device that can prevent transmission of noise light that is not optically deflected and that can reliably perform optical path deflection with little noise.
[0034]
The present invention uses an optical path deflecting device in which a deflection electric field is uniformly formed and exhibits uniform deflection characteristics over the entire effective region, thereby enabling high-speed response, high light utilization efficiency, and higher definition images. An object of the present invention is to provide a pixel shift image display device capable of display.
[0035]
[Means for Solving the Problems]
An optical path deflecting device according to a first aspect of the present invention includes a pair of transparent substrates with opposed intervals regulated, a vertical alignment film provided on the inner surface side of the substrate, and the vertical alignment film interposed between the substrates. A liquid crystal layer composed of a chiral smectic C phase that is filled and homeotropically aligned by the vertical alignment film, and is disposed at opposite positions in two orthogonal directions so as to surround an effective region of an optical path passing through the liquid crystal layer. In addition, a voltage is selectively applied between the two electrode groups and one electrode group opposite to each other according to a target deflection direction to deflect the liquid crystal layer in a direction perpendicular to the optical path. A deflecting voltage applying means for applying an electric field, and forcing a voltage gradient in the direction of the deflecting electric field by the other group of electrodes when deflecting by applying a voltage from the deflecting voltage applying means. I did it.
[0036]
Therefore, by applying an electric field for deflection in the direction perpendicular to the optical path passing through the liquid crystal layer of the chiral smectic C phase having homeotropic orientation to the ferroelectric or antiferroelectric liquid crystal layer, The inclination direction of the average optical axis can be controlled by changing the inclination angle and the inclination direction. At this time, two sets of electrode groups respectively prepared at positions opposite to each other in two orthogonal directions so as to surround an effective area of the optical path passing through the liquid crystal layer are prepared. By selectively switching the set of electrode groups that act on the deflection electric field, the deflection direction can be switched in two orthogonal directions by electrical operation. At the time of deflection by voltage application of such a deflection voltage application means, the other set of electrode groups is forced to have a potential gradient in the direction of the deflection electric field, so that the deflection electric field is It is not disturbed by the set of electrodes, and a uniform electric field is formed over the entire effective area.
[0037]
According to a second aspect of the present invention, in the optical path deflecting device according to the first aspect, each of the electrode groups includes a plurality of divided electrodes divided in a direction surrounding the effective region, and the voltage of the deflection voltage applying unit is When deflecting by application, the other group of electrodes is forced to have a potential gradient in the direction of the electric field for deflection, and the voltage is applied stepwise to each divided electrode in the other group of electrodes. Auxiliary voltage applying means for applying a voltage whose value changes is provided.
[0038]
Therefore, in realizing the invention according to claim 1, each electrode group is divided into a plurality of divided electrodes, and each of the electrodes in the other set of electrode groups is deflected by voltage application by the deflection voltage applying means. By applying a voltage whose voltage value changes stepwise to the divided electrodes, the other set of electrodes can forcibly have a potential gradient in the direction of the electric field for deflection, relatively easily. It becomes feasible.
[0039]
According to a third aspect of the present invention, in the optical path deflecting device according to the first aspect, each of the electrode groups includes a plurality of divided electrodes divided in a direction surrounding the effective area, and is adjacent to each of the electrode groups. A series resistor group in which resistors provided between the divided electrodes are connected in series, and the other set of electrodes forcibly deflects the electric potential in the direction of the electric field when deflecting by applying the voltage of the deflecting voltage applying unit. Auxiliary voltage applying means for applying a voltage across the series resistance group of the other set of electrode groups so as to have a gradient.
[0040]
Therefore, in realizing the invention according to claim 1, each electrode group is divided into a plurality of divided electrodes, and resistors provided between adjacent divided electrodes are connected in series for each electrode group. It is configured to have a series resistance group, and at the time of deflection by voltage application of the voltage application means for deflection, only voltage is applied across the series resistance group of the other set of electrode groups, and resistance is divided by each resistance of the series resistance group Thus, a voltage that changes stepwise can be applied to each divided electrode, and the other set of electrodes can forcibly have a potential gradient in the direction of the electric field for deflection. Can be realized.
[0041]
According to a fourth aspect of the present invention, in the optical path deflecting device according to the second or third aspect, the plurality of divided electrodes are arranged so that their positions are shifted from each other between the electrode groups forming a set.
[0042]
Therefore, in order to improve the uniformity of the potential distribution in the effective region, it is preferable that the electrode width of the divided electrodes is narrow and the number of electrodes is large. However, the device configuration is simplified and the cost is reduced. Therefore, it is necessary to reduce the number of divided electrodes. When the number of divided electrodes is reduced, a potential drop appears at the position between the divided electrodes.However, if the positions of the divided electrodes that form a pair match each other, the divided electrodes also overlap each other. The decrease is remarkable. In this regard, in the present invention, the positions of the opposed divided electrodes are shifted from each other and arranged at alternate positions, so that the positions between the divided electrodes correspond to the divided electrodes of the opposed electrode group, and thus the influence of the potential drop is small. Thus, the uniformity of the electric field is improved.
[0043]
According to a fifth aspect of the present invention, in the optical path deflecting device according to the first aspect, each of the electrode groups includes a resistor electrode continuous in a direction surrounding the effective region, and is based on voltage application of the deflection voltage applying means. Auxiliary voltage for applying a voltage across the resistor electrodes of the other electrode group so that the other electrode group of the other group forcibly has a potential gradient in the direction of the electric field for deflection during deflection. Application means are provided.
[0044]
Therefore, in realizing the invention according to claim 1, by providing a resistor electrode at a position along the effective region as an electrode group, a resistance is simply applied by applying a voltage between both ends of the resistor electrode. A continuous potential gradient can be formed in the liquid crystal layer in the vicinity of the body electrode, and such a continuous potential gradient can provide a more uniform electric field distribution.
[0045]
According to a sixth aspect of the present invention, in the optical path deflecting device according to any one of the second to fifth aspects, the end portions of the adjacent electrode groups are electrically connected to each other, and the potential of the connection portion between the end portions is single. Switching between unipolar potential and ground is possible.
[0046]
Therefore, in realizing the inventions according to claims 2 to 5, the ends of adjacent electrode groups are electrically connected to each other, and the potential of the connecting portion can be switched between ground and a single polarity potential. Thus, the power supply for the deflection voltage application means and the power supply for the auxiliary voltage application means can be shared, and can be realized at low cost.
[0047]
A seventh aspect of the invention is the optical path deflecting device according to any one of the first to sixth aspects, further comprising a transparent resistor layer provided on at least one of the substrates and electrically connected to the electrode group. .
[0048]
Therefore, in addition to the inventions of claims 1 to 6, since the transparent resistor layer is provided over the entire effective area and connected to the electrode group, it is effective also in the effective area relatively far from the electrode group forming the set. Therefore, even when the effective area is relatively large, a relatively uniform electric field can be formed.
[0049]
According to an eighth aspect of the present invention, in the optical path deflecting device according to the first aspect, each of the electrode groups includes a plurality of divided electrodes divided in a direction surrounding the effective region, and the voltage of the deflection voltage applying unit is At the time of deflection by application, the other divided electrodes in the other set of electrode groups are floated so as to force the other set of electrode groups to have a potential gradient in the direction of the electric field for deflection.
[0050]
Therefore, in realizing the invention according to claim 1, each electrode group is divided into a plurality of divided electrodes, and each of the electrodes in the other set of electrode groups is deflected by voltage application by the deflection voltage applying means. By simply bringing the divided electrode into a floating state, the other electrode group can forcibly give a potential gradient in the direction of the electric field for deflection, and does not require an auxiliary voltage application means and is realized relatively easily. It becomes possible.
[0051]
According to a ninth aspect of the present invention, in the optical path deflecting device according to any one of the first to eighth aspects, the liquid crystal layer includes a polarization direction switching unit that is disposed on a light incident side and switches a polarization direction of linearly polarized light. In the state where the orientation of the liquid crystal molecules determined by the spontaneous polarization of the liquid crystal and the action of the electric field for deflection is aligned in a predetermined direction by the application of a voltage by the deflection voltage applying means, the surface is directed from one substrate surface to the other substrate surface. When the liquid crystal molecules are projected, the major axis direction of the liquid crystal molecules projected onto the other substrate is the same direction as the polarization direction by the polarization direction switching means. The voltage application was controlled.
[0052]
Accordingly, in addition to the first to eighth aspects of the invention, by providing a polarization direction switching means for switching the polarization direction of linearly polarized light on the incident side, two orthogonal deflection directions can be set by the two element configurations. That is, since the number of elements is small and the number of interfaces of the constituent elements is small compared to the conventional combination of the three elements of the X direction optical path deflecting element, the polarization plane rotating element, and the Y direction optical path deflecting element, An optical path deflecting device with little reduction in light transmittance and MTF can be obtained.
[0053]
According to a tenth aspect of the present invention, in the optical path deflecting device according to the ninth aspect, the polarization direction switching means is a surface stable ferroelectric liquid crystal element capable of controlling an alignment direction of liquid crystal molecules by the action of an electric field.
[0054]
Therefore, in realizing the optical path deflecting device according to claim 9, a surface stable ferroelectric liquid crystal element capable of controlling the orientation direction of liquid crystal molecules by the action of an electric field is used as the polarization direction switching means. Polarization direction switching means capable of rotating the polarization plane at high speed by setting the refractive index of the liquid crystal molecules of the dielectric liquid crystal element, the orientation direction when an electric field is applied, the thickness of the liquid crystal layer, etc. to the optimum conditions as a half-wave plate As a whole, a high-speed response optical path deflecting device can be provided.
[0055]
The eleventh aspect of the present invention is the optical path deflecting device according to the ninth or tenth aspect, wherein the polarization direction control means makes the polarization direction of the incident light incident on the polarization direction switching means coincide with one of the deflection directions of the optical path. Is provided.
[0056]
Accordingly, in order to realize the optical path deflecting device according to claim 9 or 10, the optical system includes a polarization direction control means for matching the polarization direction of the incident light incident on the polarization direction switching means with the deflection direction of the optical path, and the tilt direction of the optical axis. Since only linearly polarized light that is parallel to the light is incident, even if the incident light is non-polarized light, transmission of noise light that is not deflected is prevented, and reliable optical path deflection with less noise can be realized.
[0057]
An image display device according to a twelfth 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, an illumination device that illuminates the image display element, and the image display element An optical device for observing the image pattern displayed on the display, display driving means formed of a plurality of subfields obtained by temporally dividing the image field, and an effective area corresponding to the image display element, The optical path deflecting device according to claim 1, wherein the optical path of light emitted from the pixel is deflected for each subfield.
[0058]
Accordingly, since the optical path deflecting device capable of deflecting the optical path in two orthogonal directions according to any one of claims 1 to 11 is used as a so-called pixel shift device, the projection optical path is deflected at high speed corresponding to the subfield image. It is possible to display a high-definition image apparently. In addition, since there are few components of the optical path deflecting device and a uniform deflection electric field is formed over the entire effective region, there are few substrate interfaces and the like, and the reduction in transmittance and MTF can be reduced. A uniform pixel shift is possible. Therefore, a higher-definition display image with higher light utilization efficiency can be obtained.
[0059]
According to a thirteenth aspect of the present invention, there is provided an optical path deflecting element comprising: a pair of transparent substrates whose opposing intervals are regulated; a vertical alignment film provided on an inner surface side of the substrate; and the vertical alignment film between the substrates. A liquid crystal layer composed of a chiral smectic C phase that is filled and homeotropically aligned by the vertical alignment film, and is disposed at opposite positions in two orthogonal directions so as to surround an effective region of an optical path passing through the liquid crystal layer. And two sets of electrode groups each having a plurality of divided electrodes divided in a direction surrounding the effective area.
[0060]
Accordingly, a group of electrodes arranged at opposite positions so as to surround an effective region of an optical path passing through the liquid crystal layer with respect to a chiral smectic C phase ferroelectric or antiferroelectric liquid crystal layer having homeotropic alignment. By applying a voltage to the pair by an electric operation from the outside and applying a deflection electric field in a direction perpendicular to the optical path passing through the liquid crystal layer, the tilt angle and tilt direction of the liquid crystal molecules change. The inclination direction of the average optical axis can be controlled. At this time, as a pair of electrode groups, two sets of electrode groups respectively arranged at opposite positions in two orthogonal directions so as to surround an effective area of the optical path passing through the liquid crystal layer are prepared. By selectively switching the set of electrode groups that act on the deflection electric field according to the deflection direction to be performed, the deflection direction can be switched to two orthogonal directions by electrical operation. Each electrode group has a divided structure composed of a plurality of divided electrodes, and the voltage value of the other set of electrode groups is stepwise with respect to the individual divided electrodes at the time of deflection by voltage application of the deflection voltage applying means. By applying a changing voltage or the like to force the other set of electrodes to have a potential gradient in the direction of the deflecting electric field, the deflecting electric field is applied to the other set of electrodes. It is not disturbed, so that a uniform electric field can be formed over the entire effective area.
[0061]
The invention according to a fourteenth aspect is the optical path deflecting element according to the thirteenth aspect, further comprising a series resistance group in which resistors provided between adjacent divided electrodes are connected in series for each of the electrode groups.
[0062]
Accordingly, in order to realize the invention according to claim 13, in addition to each electrode group of the divided electrode structure, a series resistance group is provided in which resistors provided between adjacent divided electrodes are connected in series for each electrode group. With this configuration, when a voltage is applied to one set of electrode groups, the voltage is applied between both ends of the series resistance group of the other set of electrode groups, and resistance is divided by each resistance of the series resistance group. Can be applied to each divided electrode, and the other set of electrodes can force a potential gradient in the direction of the electric field for deflection. It becomes feasible.
[0063]
According to a fifteenth aspect of the present invention, in the optical path deflecting element according to the thirteenth or fourteenth aspect, the plurality of divided electrodes are arranged so that their positions are deviated from each other between the electrode groups forming a set.
[0064]
Therefore, in realizing the optical path deflecting element according to claim 13 or 14, in order to improve the uniformity of the potential distribution in the effective region, the electrode width of the divided electrodes is narrow and the number of electrodes is large. Although it is preferable, it is necessary to reduce the number of divided electrodes in order to reduce the cost by simplifying the configuration of the element. When the number of divided electrodes is reduced, a potential drop appears at the position between the divided electrodes.However, if the positions of the divided electrodes that form a pair match each other, the divided electrodes also overlap each other. The decrease is remarkable. In this regard, in the present invention, the positions of the opposed divided electrodes are shifted from each other and arranged at alternate positions, so that the positions between the divided electrodes correspond to the divided electrodes of the opposed electrode group, and the effect of potential drop And the uniformity of the electric field can be improved.
[0065]
An optical path deflecting element according to a sixteenth aspect of the present invention is directed to a pair of transparent substrates with opposed spacings, a vertical alignment film provided on the inner surface side of the substrate, and the vertical alignment film between the substrates. A liquid crystal layer composed of a chiral smectic C phase that is filled and homeotropically aligned by the vertical alignment film, and is disposed at opposite positions in two orthogonal directions so as to surround an effective region of an optical path passing through the liquid crystal layer. And two sets of electrode groups each having a resistor electrode continuous in a direction surrounding the effective area.
[0066]
Therefore, this is basically the same as the optical path deflecting element of the invention described in claim 13, but by providing a resistor electrode at a position along the effective area as an electrode group, A liquid crystal layer in the vicinity of the resistor electrode is applied by applying a voltage between both ends of the resistor electrode and applying a voltage to the other electrode group. A continuous electric potential gradient can be formed within the electric field, and such a continuous electric potential gradient can provide a more uniform electric field distribution.
[0067]
According to a seventeenth aspect of the present invention, in the optical path deflecting element according to any one of the thirteenth to sixteenth aspects, the ends of the adjacent electrode groups are electrically connected.
[0068]
Therefore, in realizing the inventions according to claims 13 to 16, since the ends of the adjacent electrode groups are electrically connected to each other, the potential of this connection is grounded by an external operation. And a single polarity potential, the power supply for the deflection voltage applying means and the power supply for the auxiliary voltage applying means can be shared, and an optical path deflecting device can be realized at low cost.
[0069]
The invention according to claim 18 is the optical path deflecting element according to any one of claims 13 to 17, further comprising a transparent resistor layer provided on at least one of the substrates and electrically connected to the electrode group. .
[0070]
Therefore, in addition to the inventions of claims 13 to 17, since the transparent resistor layer is provided on the entire effective area and connected to the electrode group, a set is formed when voltage is applied by an external electric operation. A potential distribution can be effectively formed even in an effective region relatively far from the electrode group. Therefore, even when the effective region is relatively large, a relatively uniform electric field can be formed.
[0071]
A driving method of an optical path deflecting element according to claim 19 is the following: a pair of transparent substrates whose opposing intervals are regulated, a vertical alignment film provided on the inner surface side of the substrate, and the vertical alignment film between the substrates And a liquid crystal layer composed of a chiral smectic C phase that is homeotropically aligned by the vertical alignment film, and two orthogonal directions opposite to each other so as to surround an effective region of an optical path passing through the liquid crystal layer. A series of two sets of electrode groups each having a plurality of divided electrodes divided in a direction surrounding the effective area, and resistors provided between adjacent divided electrodes for each of the electrode groups connected in series And a resistor group, and selectively applying a voltage between the opposing electrode groups of one set according to a target deflection direction to orthogonally cross the optical path of the liquid crystal layer. Direction deflection And applying a voltage across the series resistance group of the electrode group of the other group at the time of deflection by voltage application in the deflection voltage application step for applying the electric field of And an auxiliary voltage applying step for providing a potential gradient in the electric field direction for deflection.
[0072]
Therefore, in order to realize optical path deflection in two directions orthogonal to the entire effective area, two sets of electrode groups are arranged at opposite positions in two orthogonal directions so as to surround the effective area of the optical path passing through the liquid crystal layer. However, each of these electrode groups has a divided structure composed of a plurality of divided electrodes, and each electrode group has a series resistance group in which resistors provided between adjacent divided electrodes are connected in series. A voltage is selectively applied between one set of opposing electrode groups according to the deflection direction to cause a deflection electric field to act on the liquid crystal layer in a direction perpendicular to the optical path. By simply applying a voltage between both ends of the series resistance group of the electrode group, it is possible to cause each divided electrode to be applied with a voltage that is resistance-divided by each resistance of the series resistance group and changes stepwise. Forcibly deflected by electrode group Can have the electric field direction of the potential gradient, be any deflection direction, can form a uniform electric field on the effectiveness entire region, it is possible to uniform the optical path deflecting the effectiveness entire region.
[0073]
The method of driving an optical path deflecting element according to claim 20 includes a pair of transparent substrates, the opposed distance of which is regulated, a vertical alignment film provided on the inner surface side of the substrate, and the vertical alignment film between the substrates. And a liquid crystal layer composed of a chiral smectic C phase that is homeotropically aligned by the vertical alignment film, and two orthogonal directions opposite to each other so as to surround an effective region of an optical path passing through the liquid crystal layer. Two sets of electrode groups each having a resistor electrode continuous in a direction surrounding the effective area, and selectively selecting one set according to a target deflection direction. By applying a voltage between the electrode groups facing each other to apply a deflection electric field to the liquid crystal layer in a direction perpendicular to the optical path, and applying the voltage in the deflection voltage application step When direction, and a supplementary voltage application step to give the electric field direction of the potential gradient for forcibly the deflection by applying a voltage across the resistor electrode of the electrode group of the other set.
[0074]
Therefore, in order to realize optical path deflection in two directions orthogonal to the entire effective area, two sets of electrode groups are arranged at opposite positions in two orthogonal directions so as to surround the effective area of the optical path passing through the liquid crystal layer. However, each of these electrode groups is composed of resistor electrodes that are continuous in the direction surrounding the effective region, and a voltage is selectively applied between one set of opposing electrode groups according to the target deflection direction. When a deflection electric field is applied to the liquid crystal layer in a direction perpendicular to the optical path, a voltage is applied between both ends of the resistor electrodes of the other set of electrode groups, and only the current is applied. A continuous potential gradient can be formed in the liquid crystal layer, and a more uniform electric field distribution can be obtained by such a continuous potential gradient. Even throughout the effective area It is possible to form an electric field, it is possible to uniform the optical path deflecting the effectiveness entire region.
[0075]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS.
First, a premise configuration and operation of the optical path deflecting element used in the present embodiment will be described with reference to FIGS.
[0076]
FIG. 1 shows a cross-sectional configuration example of a premise optical path deflecting element 1 ′. In this optical path deflecting element 1 ', a pair of transparent substrates 2 and 3 are provided so as to face each other. As the transparent substrates 2 and 3, glass, quartz, plastic, or the like can be used, but a transparent material having no birefringence is preferable. The thickness of the substrates 2 and 3 is several tens of μm to several mm. Vertical alignment films 4 and 5 are formed on the inner side surfaces of the substrates 2 and 3. The vertical alignment films 4 and 5 are not particularly limited as long as they are materials that vertically align liquid crystal molecules (homeotropic alignment) with respect to the surfaces of the substrates 2 and 3, but vertical alignment agents for liquid crystal displays, silane coupling agents, SiO 2₂A vapor deposition film or the like can be used. The “vertical alignment (homeotropic alignment)” referred to in the present invention includes not only a state in which liquid crystal molecules are aligned perpendicularly to the substrate surface but also an alignment state in which the liquid crystal molecules are tilted to several tens of degrees.
[0077]
A spacer 6 for restricting the facing distance between the substrates 2 and 3 is provided, and an electrode 7 and a liquid crystal layer 8 are formed between the substrates 2 and 3. As the spacer 6 that regulates the facing distance between the substrates 2 and 3, and thus the thickness of the liquid crystal layer 8, a sheet member having a thickness of about several μm to several mm or particles having the same particle diameter is used. The optical path deflecting element 1 ′ is preferably provided outside the effective area. As the electrode 7, a metal such as aluminum, copper, or chromium, or a transparent electrode such as ITO is used. In order to apply a uniform horizontal electric field in the liquid crystal layer 8, the thickness is about the same as the thickness of the liquid crystal layer 8. It is preferable to use a metal sheet having the above, and it is provided outside the effective area of the optical path deflecting element 1 '. In FIG. 1, as a more preferable example, the spacer 6 and the metal sheet member are common and serve as an electrode spacer, and the thickness of the liquid crystal layer 8 is defined by the thickness of the metal sheet member. As the liquid crystal layer 8, a liquid crystal capable of forming a chiral smectic C phase is used. By applying a voltage between the electrodes 7, an electric field is applied in the horizontal direction of the liquid crystal layer 8.
[0078]
Here, the liquid crystal layer 8 capable of forming a smectic C phase will be described in detail. A “smectic liquid crystal” is a liquid crystal layer in which the long axis directions of liquid crystal molecules are arranged in layers. With respect to such a liquid crystal, a liquid crystal in which the normal direction of the liquid crystal 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 spiral structure in which the liquid crystal director direction is spirally rotated for each layer in the 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. In the present embodiment and the like, the liquid crystal layer 8 will be described by taking a ferroelectric liquid crystal as an example, but the light deflection element 1 will be described. However, the liquid crystal layer 8 can be similarly used in the case of an antiferroelectric liquid crystal.
[0079]
The chiral smectic C phase has an extremely high speed 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.
[0080]
The liquid crystal layer 8 composed of smectic C phase forming homeotopic alignment is more restrictive in terms of the operation of the liquid crystal director than the case where the liquid crystal director is in the homogeneous alignment (the liquid crystal director is aligned parallel to the substrate surface). It is easy to control the deflection direction of the optical path 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 aligned, the liquid crystal directors strongly depend not only on the electric field direction but also on the substrate surface, so that more positional accuracy is required for the installation of the optical path deflecting element. On the contrary, in the homeotopic orientation as in the present embodiment, the setting margin of the optical path deflecting element 1 ′ increases with respect to the optical deflection. In making use of these features, it is not necessary that the spiral axis be strictly oriented perpendicular to the substrate surface, and it may be tilted to some extent. It suffices if the liquid crystal director can face two directions without receiving the regulating force from the substrates 2 and 3.
[0081]
The operation principle of such an optical path deflecting element 1 ′, which is also applied to the optical path deflecting element of the present embodiment, will be described with reference to FIG. FIG. 2 schematically shows the relationship between the electric field direction and the tilt direction of the liquid crystal molecules 9 in the configuration shown in FIG. The side where the width of the liquid crystal molecules 9 shown in a wedge shape is drawn wide is inclined to the upper side (front side) of the paper, and the side where the width is drawn is inclined to the lower side (back side) of the paper. In addition, the spontaneous polarization Ps of the liquid crystal is indicated by an arrow. When the direction of the electric field is reversed, the direction of the tilt angle of the substantially vertically aligned liquid crystal molecules 9 is reversed. Here, the relationship between the electric field application direction from the rectangular voltage power supply 10 and the tilt direction of the liquid crystal molecules 9 in the case where the spontaneous polarization Ps is positive is illustrated.
[0082]
FIG. 3 schematically shows the alignment state of the liquid crystal molecules 9 in order to explain the principle of the optical path deflection operation, and the vertical alignment films 4 and 5, the spacer 6 and the electrode 7 are omitted. In FIG. 3, for the sake of convenience, a voltage is applied in the front and back direction of the paper, and the electric field acts in the front and back direction of the paper. The electric field direction is switched by the rectangular voltage power source 10 (see FIG. 2) corresponding to the target light deflection direction. Further, the incident light with respect to the optical path deflecting element 1 'is linearly polarized light.
[0083]
When an electric field from the back side to the near side is applied as shown in FIG. 3A, if the spontaneous polarization Ps of the liquid crystal molecules 9 is positive, the number of molecules in which the liquid crystal director is inclined to the right increases. The average optical axis as the liquid crystal layer 8 is also tilted upward in the figure and functions as a birefringent plate. 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 and become birefringent plates with the optical axis inclined upward at an angle θ. Linearly polarized light incident from the left side as extraordinary light is shifted in parallel upward. Here, when the refractive index in the major axis direction of the liquid crystal molecules 9 is ne, the refractive index in the minor axis direction is no, and the thickness (gap) of the liquid crystal layer 8 is d, the shift amount S is

(See, for example, “Crystal Optics” Applied Physics Society, Optical Society, p198).
[0084]
Similarly, as shown in FIG. 3B, when an electric field directed to the back side of the paper is applied by reversing the voltage applied to the electrodes, the liquid crystal director is lowered to the right if the spontaneous polarization Ps of the liquid crystal molecules 9 is positive. And the optical axis functions as a birefringent plate inclined downward at an angle θ. Linearly polarized light incident from the left side as extraordinary light is shifted in parallel downward. By reversing the electric field direction, an optical path deflection amount of 2S is obtained.
[0085]
In such an optical path deflection system, only an optical path deflection operation corresponding to a pair of electrodes can be performed. For example, in the case of performing a deflection operation in two directions of the X direction and the Y direction, at least two optical path deflecting elements 1 ′ are necessary, and a decrease in transmittance or resolution due to an increase in the number of substrates. There is concern about the decline.
[0086]
Therefore, in the present embodiment, the substrates 2, 3, the alignment films 4, 5, the liquid crystal layer 8, the electrode 7 and the like can be the same as those shown in FIG. It is characterized by a voltage application method. A configuration example of the optical path deflection element 1 of the present embodiment will be described with reference to FIG.
[0087]
First, in the present embodiment, an application example to the optical path deflecting element 1 in which the effective area 11 of the optical path passing through the liquid crystal layer 8 is set in, for example, a rectangular shape is shown assuming application to an image display device and the like which will be described later. The substrates 2, 3, etc. also have rectangular shapes that are slightly larger than the effective area 11. However, the shapes of the substrates 2 and 3 do not have to be the same as the shape of the effective region 11. In addition, two sets (= 4) of electrode groups 12, 12 ′, 2 ′ (= 4) are opposed to each other in two orthogonal directions (X and Y directions) so as to surround the effective region 11 of the liquid crystal layer 8. 13, 13 'are arranged. Each electrode group 12, 12 ′, 13, 13 ′ is formed along each side of the effective area 11, and is divided into n pieces in a direction (direction along the side) surrounding the effective area 11. The plurality of divided electrodes are formed. That is, the electrode group 12 is composed of divided electrodes X1, X2,..., Xn. Similarly, the electrode group 12 ′ is divided electrodes X′1, X′2,. Y1, Y2,..., Yn, and the electrode group 13 'are composed of divided electrodes Y'1, Y'2,.
[0088]
With respect to the optical path deflecting element 1 having such a configuration, the individual divided electrodes in each of the electrode groups 12, 12 ′, 13, and 13 ′ can be independently and alternatively provided by electrical operation from the outside. It is possible to apply a voltage that has a substantially constant single polarity potential, a ground potential, or a potential that changes stepwise.
[0089]
As an example, as illustrated in FIG. 5, the voltage applied to all of the divided electrodes X1 to Xn of the electrode group 12 is set to a single polarity voltage V1 (a constant value) according to the target deflection direction. In this case, all of the divided electrodes X′1 to X′n of the electrode group 12 ′ that are opposed to each other are set to a substantially constant voltage value. Here, the potentials of the divided electrodes X′1 to X′n are set to zero volts (ground). Thus, by applying the voltage of the potential difference V1 between the electrode groups 12 and 12 'that are paired in the X direction so as to face each other in the Y direction, the liquid crystal layer 8 is orthogonal to the optical path as indicated by an arrow in FIG. An electric field for deflecting the direction acts. Voltage application for applying such a deflection electric field is performed by a deflection voltage application means (not shown here). The operation principle in this case is basically the same as that described with reference to FIG. An electric field is generated due to a potential difference between the two electrode groups 12 and 12 'paired in the X direction. However, when the distance between the electrode groups 12 and 12' is relatively wide, a uniform electric field is not formed. It becomes difficult. In particular, in the case where the electrode groups 13 and 13 ′ are one electrode continuous along the Y direction, the entire length of the one electrode facing the effective region 11 (over a length corresponding to one side). Since the potential becomes equipotential, the uniformity is disturbed with respect to the vicinity of both sides of the deflection electric field, and a uniform electric field cannot be obtained over the entire effective region 11.
[0090]
Therefore, in the present embodiment, a voltage is selectively applied between one set of opposed electrode groups, for example, 12 and 12 ', according to the target deflection direction, and the liquid crystal layer 8 is orthogonal to the optical path. When the deflection electric field is applied, the other electrode group, for example, 13, 13 'is forcibly provided with a potential gradient in the direction of the electric field for deflection. As an example, for example, as shown in FIG. 5, the other electrode group, for example, each of divided electrodes Y1 to Yn and Y′1 to Y′n in 13, 13 ′ is shown from the upper side in the figure. By applying a voltage whose voltage value changes stepwise such that the voltage value changes from V1 to zero stepwise, a desired potential distribution is forcibly formed around and inside the effective region 11. . Such voltage application is performed by auxiliary voltage application means (not shown here).
[0091]
More specifically, since the potential is constant in the vicinity of each divided electrode having a finite width and an electric field is generated only between the divided electrodes, the divided electrodes Y1 to Yn and Y′1 to Y′1 of the electrode groups 13 and 13 ′ are generated. In the vicinity of Y′n, a step-like potential distribution is formed as shown in FIG. However, such a stepwise potential distribution is dull in the effective region 11 at a certain distance from the electrode groups 13 and 13 ', and a substantially uniform electric field is formed in the vertical direction (Y direction). In addition, a substantially uniform voltage is applied to each of the divided electrodes X1 to Xn and X′1 to X′n of the electrode groups 12 and 12 ′, but is slightly affected by the surrounding potential between the divided electrodes. Since the potential change occurs, strictly, the potential distribution is slightly nonuniform as shown in FIG. However, the potential distribution is dull in the effective region 11 that is a certain distance away from the electrode groups 12 and 12 ', and no horizontal electric field is generated. Therefore, a uniform electric field is generated in the effective region 11 in the downward direction in the figure over the entire region. Here, when the tilt state of the liquid crystal molecules 9 is modeled as in the case of FIG. 2, the optical axis is tilted to the left in FIG. 5 (when the spontaneous polarization Ps is positive).
[0092]
The state shown in FIG. 5 shows an example. In addition to the example shown in FIG. 5, three types of voltage application states to two sets (four) of electrode groups 12, 12 ', 13, and 13' are switched. Thus, as shown in FIGS. 6A to 6C, the inclination direction of the optical axis, and thus the optical path deflection direction by the optical path deflecting element 1, can be switched to four directions, up, down, left and right (± X, ± Y directions). it can.
[0093]
That is, FIG. 6A shows that the electrode groups 13 and 13 'forming a pair have a single polarity voltage V1 (a constant value) applied to all of the divided electrodes Y1 to Yn of the electrode group 13 by the deflection voltage applying means. 'Is applied to all of the divided electrodes Y'1 to Y'n, and the other electrode group 12, 12' is applied to the divided electrodes X1 to Xn and X'1 by the auxiliary voltage applying means. In the figure, a case where a voltage whose voltage value changes stepwise from V1 to zero is applied to ˜X′n is shown. Thereby, in FIG. 6, the optical axis is inclined downward (when the spontaneous polarization Ps is positive).
[0094]
In FIG. 6B, for the electrode groups 12 and 12 'forming a pair, a single polarity voltage V1 (constant value) is applied to all of the divided electrodes X'1 to X'n of the electrode group 12' by the deflection voltage applying means. Zero volts (ground) is applied to all the divided electrodes X1 to Xn of the electrode group 12, and the divided electrodes Y1 to Yn and Y′1 to Y ′ are applied to the other electrode groups 13 and 13 ′ by the auxiliary voltage applying means. The case where a voltage whose voltage value changes stepwise such that the voltage value changes from V1 to zero stepwise from the lower side is shown in FIG. Thereby, in FIG. 6, the optical axis is inclined to the right (when the spontaneous polarization Ps is positive).
[0095]
FIG. 6 (c) shows a group of electrode groups 13, 13 'with a single polarity voltage V1 (constant value) applied to all of the divided electrodes Y'1-Y'n of the electrode group 13' by the deflection voltage applying means. Zero volts (ground) is applied to all of the divided electrodes Y1 to Yn of the electrode group 13, and the divided electrodes X1 to Xn and X'1 to X 'are applied to the other electrode group 12, 12' by the auxiliary voltage applying means. The case where a voltage whose voltage value changes step by step such that the voltage value changes from V1 to zero stepwise from the right side is shown in FIG. Thereby, in FIG. 6, the optical axis is inclined upward (when the spontaneous polarization Ps is positive).
[0096]
That is, the deflection voltage applied between which set of electrode groups is selective and alternative depending on the target deflection direction. Depending on this result, the other set of electrode groups Stepwise voltage application is also set.
[0097]
Although not particularly illustrated, when each of the electrode groups 12, 12 ', 13, 13' has a divided electrode configuration as in the present embodiment, the other of the electrodes to which a voltage for forming an electric field for deflection is not applied is applied. With respect to the set of electrode groups, a voltage that changes stepwise may not be applied to each divided electrode, but may be floated. Even in this case, each electrode group is not a continuous single electrode, but is divided into a plurality of divided electrodes along the effective region 11, so even if such a divided electrode faces the effective region 11, A potential gradient in the direction of the electric field for deflection can be forcibly given in a staircase pattern by the set of electrode groups, and the electric field in the effective region 11 can be made uniform. According to this, the auxiliary voltage applying means is not required, and it can be realized relatively easily.
[0098]
A second embodiment of the present invention will be described with reference to FIGS. The same parts as those shown in the first embodiment are denoted by the same reference numerals, and description thereof is also omitted (the same applies to the following embodiments).
[0099]
In the optical path deflecting element 21 of the present embodiment, in addition to the configuration of the optical path deflecting element 1 as shown in FIG. 5, the same resistance value is provided between the divided resistors of the electrode groups 12, 12 ', 13, 13'. A resistor R is provided, and series resistor groups 22, 22 ', 23, and 23' are provided in which these resistors R are connected in series. That is, in correspondence with each electrode group 12, 12 ', 13, 13' composed of n divided electrodes, each series resistance group 22, 22 ', 23, 23' has (n-1) resistors R. Are connected in series. Voltage application circuits 24, 24 ', 25, 25' are connected between terminals at both ends of each series resistance group 22, 22 ', 23, 23'. Such an optical path deflecting element 21 and voltage application circuits 24, 24 ', 25, 25' constitute an optical path deflecting device 26.
[0100]
Here, any of the voltage application circuits 24, 24 ', 25, and 25' has the same circuit configuration, and has both functions of the deflection voltage application means and the auxiliary voltage application means. It is comprised so that the function of a means may be exhibited alternatively.
[0101]
For example, a configuration example of the voltage application circuit 25 will be described as an example. First, in order to apply an alternating voltage between the terminals T1 and T2 at both ends of the electrode group 13 (series resistance group 23), a method in which one end is grounded and a positive / negative voltage is applied to the other end is common. In the present embodiment, as described with reference to FIG. 5 (FIGS. 6A and 6C), it functions as a deflection voltage applying unit and is connected between terminals T1 and T2 at both ends of the electrode group 13 (series resistance group 23). Need to be given the same potential V1 or 0V, which cannot be handled by a general AC power supply. Therefore, in the present embodiment, the voltage application circuit 25 is configured as a combination circuit of the DC power source 27 having the voltage V1 and the four switches SW1 to SW4, and the voltage applied to the terminals T1 and T2 by the combination of opening and closing the switches SW1 to SW4. V1 application and grounding can be independently switched and controlled. That is, the switch SW1 switches whether to apply the voltage V1 to the terminal T1, the switch SW2 switches whether to connect the terminal T1 to the ground, and the switch S3 determines whether to apply the voltage V1 to the terminal T2. The switch SW4 switches whether to connect the terminal T2 to the ground. As a result, when both the switches SW1 and SW3 are closed, or when both the switches SW2 and SW4 are closed, the voltage application circuit 25 functions as a deflection voltage application unit, and both the switches SW1 and S4 are closed. Alternatively, when the switches SW3 and S2 are both closed, the voltage application circuit 25 functions as auxiliary voltage application means.
[0102]
Incidentally, in the example shown in FIG. 7, the switches SW1 and SW4 are both closed, and the voltage application circuit 25 functions as auxiliary voltage application means (similar to the case shown in FIG. 5). Thus, if the voltage V1 is applied across the series resistor group 23, the voltage V1 is divided by the (n-1) resistors R, so that the divided electrodes Y1 to Yn are stepped as they are. A voltage that changes can be applied. As a result, the circuit configuration is simpler and lower in cost than the configuration in which power supplies having different voltage values are individually connected to the divided electrodes Y1 to Yn and a voltage that changes stepwise is applied. Can be realized.
[0103]
In other words, in the case of the optical path deflecting element 21 of the present embodiment, the voltage V1 is selectively applied to the liquid crystal layer 8 by the voltage applying circuit between one set of opposing electrode groups according to the target deflection direction. A voltage application circuit between the ends of the series resistance group of the other electrode group during deflection by applying a deflection voltage application step in which a deflection electric field in a direction orthogonal to the optical path is applied, and voltage application in this deflection voltage application step By applying the voltage V1 and forcing the auxiliary voltage application step for forcing a potential gradient in the direction of the electric field for deflection, the entire effective area 11 is uniform regardless of the direction of deflection. An electric field can be formed, and a uniform optical path deflection is possible over the entire effective region 11.
[0104]
By the way, as the switches SW1 to SW4 provided in the voltage application circuit 25, it is preferable to use a switch having a high withstand voltage and capable of high speed operation. As a specific example, for example, as shown in FIG. 8, the switches SW1 to SW4 may be configured by photocouplers PC1 to PC4.
[0105]
A third embodiment of the present invention will be described with reference to FIG. The present embodiment is an improvement of the second embodiment described above. With respect to the optical path deflecting element 21, the ends of adjacent electrode groups (series resistance groups) are electrically connected. That is, the ends of the series resistance groups 22 and 23, the ends of the series resistance groups 23 and 22 ', the ends of the series resistance groups 22' and 23 ', and the ends of the series resistance groups 23' and 22 are connected. These are electrically connected as connecting portions 28a to 28d, respectively. These connection portions 28a to 28d can be switched between a single polarity potential of voltage V1 and ground. Specifically, the voltage application circuits 24 and 24 'shown in FIG. 7 are omitted, and only the voltage application circuits 25 and 25' are provided (reversely, the voltage application circuits 25 and 25 'are omitted and the voltage application circuits 25 and 25' are omitted. Only the application circuits 24 and 24 'may be used). The configuration of the voltage application circuits 25 and 25 'itself is the same as in the case of FIG.
[0106]
As a result, when the voltage application circuits 25 and 25 ′ function as deflection voltage application means for the electrode groups 12 and 12 ′ (series resistance groups 22 and 22 ′), the electrode groups 13 and 13 ′ (series resistance group) 23, 23 ') functions as auxiliary voltage application means, and conversely, when it functions as deflection voltage application means for the electrode groups 13, 13' (series resistance groups 23, 23 '), the electrode group 12 and 12 '(series resistance groups 22 and 22') function as auxiliary voltage applying means, and are also used as two electrode groups.
[0107]
That is, in the configuration example shown in FIG. 7, four voltage application circuits 24, 24 ', 25, and 25' are provided for each of the electrode groups 12, 12 ', 13, and 13', but the principle shown in FIG. When the electric field is applied as in FIG. 9, it is sufficient that the potentials at the four corners of the optical path deflecting element 21 can be set independently. Therefore, as shown in FIG. By electrically connecting as 28d, the number of power supply circuits can be reduced to two sets. Further, in FIG. 9, the circuit composed of the DC power supply 27 and the four switches SW1 to SW4 is used as one voltage application circuit 25, 25 ', but the DC power supply 27 is shared with respect to these voltage application circuits 25, 25'. Only two switches SW1 to SW4 may be separately provided. According to this, the power source can be further reduced.
[0108]
A fourth embodiment of the present invention will be described with reference to FIG. As described above, when each electrode group 12, 12 ′, 13, 13 ′ is composed of a plurality of divided electrodes, in order to improve the uniformity of the potential distribution in the effective region 11, the electrode width of each divided electrode is used. Is as narrow as possible and the number of electrodes is preferably as large as possible. However, in order to reduce the cost by simplifying the configuration of the optical path deflecting element 1 or 21, it is necessary to reduce the number of divided electrodes. When the number of divided electrodes is reduced, a potential drop at the position between the divided electrodes appears. However, if the positions of the opposed divided electrodes are exactly the same, the positions between the divided electrodes also overlap each other. The reduction of the becomes remarkable. Therefore, in the present embodiment, as shown in FIG. 10, the electrode groups 12, 12 'that form a pair opposite to each other, and the individual divided electrodes in the electrode groups 13, 13' are at alternate positions shifted from each other. It is intended to be arranged.
[0109]
According to such a configuration, the position between the divided electrodes corresponds to the position of the opposed divided electrodes, the influence of the potential decrease is reduced, and the uniformity of the electric field in the effective region 11 is improved.
[0110]
A fifth embodiment of the present invention will be described with reference to FIG. As described above, when each electrode group 12, 12 ′, 13, 13 ′ is composed of a plurality of divided electrodes, in order to improve the uniformity of the potential distribution in the effective region 11, the electrode width of each divided electrode is used. Is as narrow as possible, and the number of electrodes and the number of resistors R are preferably as large as possible.
[0111]
In the optical path deflecting element 31 of the present embodiment, in consideration of such points, in order to ideally narrow the electrode width to the limit and increase the number of resistances to infinity, the optical path deflecting element 31 is continuously arranged in the direction surrounding the effective region 11. The electrode groups 12, 12 ', 13, 13' are constituted by the resistor electrodes 32. A voltage application electrode 33 is provided at each end of each resistor electrode 32. That is, each electrode group is continuously formed as a resistor.
[0112]
As the resistor electrode 32, a resin dispersion film or an ITO film of conductive powder such as carbon black, tin oxide, or indium oxide can be used. The function of the resistor layer of the present embodiment is to form a desired potential gradient along the periphery of the effective region 11 and is preferably used under the condition that the amount of heat generated when energized is small.
[0113]
Since the resistor electrode 32 is provided at a position along the effective region 11, the resistor electrode 32 functions as an electrode group by applying a voltage to the both ends of the resistor electrode 32 through the electrode 33 and energizing the resistor electrode 32. A continuous potential gradient as shown in FIG. 11 can be formed in the liquid crystal layer 8 (effective region 11) in the vicinity of the resistor electrode 32. Due to this continuous potential gradient, a uniform electric field distribution is obtained in the effective region 11.
[0114]
In other words, according to the optical path deflecting element 31 of the present embodiment, the voltage V1 is selectively applied between one set of opposing electrode groups according to the target deflection direction, and the liquid crystal layer 8 is orthogonal to the optical path. A voltage V1 is applied between both ends of the resistor electrode 32 of the other electrode group at the time of deflection by voltage application in the deflection voltage application step in which an electric field for deflection in the direction to be applied is applied. By simply executing the auxiliary voltage application step of forcing a continuous potential gradient in the direction of the electric field for deflection, a uniform electric field is formed over the entire effective region 11 regardless of the direction of deflection. Thus, uniform optical path deflection is possible for the entire effective area 11.
[0115]
A sixth embodiment of the present invention will be described with reference to FIG.
[0116]
In each of the above-described embodiments, the potential distribution in the effective region 11 is controlled by applying a potential distribution to the electrode groups 12, 12 ', 13, and 13' around the effective region 11. However, when the effective area increases. The controllability at a position away from the electrode groups 12, 12 ', 13, 13' is deteriorated, and the uniformity of the electric field is lowered.
[0117]
Therefore, as shown in FIG. 12, the optical path deflecting element 41 according to the present embodiment is provided with transparent resistor layers 42 and 43 over the entire surface between the substrates 2 and 3 and the vertical alignment films 4 and 5. The groups 12, 12 ', 13, 13' and the transparent resistor layers 42, 43 are electrically connected. Note that only one of the transparent resistor layers 42 and 43 may be provided.
[0118]
As the transparent resistor layers 42 and 43, a resin dispersion film or an ITO film of conductive powder such as tin oxide or indium oxide can be used. The functions of the transparent resistor layers 42 and 43 of the present embodiment are for forming a desired potential gradient along the substrate surface inside the effective region 11, and are used under the condition that the amount of heat generated when energized is small. It is preferable to do. Here, when the surface resistance of the transparent resistor layers 42 and 43 is Rs [Ω / □], the distance between the electrode groups is a [cm], and the length of the electrode groups is b [cm], the transparent resistor layer 42 , 43 as a whole, the resistance R [Ω] is R = a / b × Rs. When a voltage of E [V] is applied to such transparent resistor layers 42 and 43, E²/ R power P [W] is consumed. The current I [A] is obtained by I = E / R. Since the area of the transparent resistor layers 42 and 43 is a × b, the power consumption Pd [W / cm per unit area obtained by P / (a × b)]²] Is a characteristic value for predicting a temperature rise. In this embodiment, since a potential difference of several hundred volts to several kilovolts is applied per 1 cm, it is necessary to increase the resistance value in order to suppress heat generation. Power consumption per unit area is 0.01 W / cm²If so, the temperature rise is suppressed to about 10 ° C. or less.
[0119]
For example, the area of the element is 3 cm × 4 cm, and the surface resistance value Rs = 1 × 10.⁸When the distance between the electrode groups is 3 cm and the length of the electrode groups is 4 cm, the resistance values of the transparent resistor layers 42 and 43 are 1.33 × 10 6.⁸It becomes Ω. When a voltage of 3000 V is applied during this distance of 3 cm, a current of 22.5 μA flows. At this time, about 0.07 W as a whole, about 0.006 W / cm per unit area²Consume power. At this level, heat generation is not a problem in practice. Therefore, the surface resistance value is 1 × 10⁸It is preferable to use transparent resistor layers 42 and 43 having a high resistance of about Ω / □ or more. When considering the volume resistance value corresponding to this, when the film thickness of the transparent resistor layers 42 and 43 is 0.1 μm, 10³10 when Ωcm or more and film thickness is 1 μm⁴10 when the thickness is 10 μm or more.⁵It is preferable that it is Ωcm or more. As the high resistance transparent resistor layers 42 and 43, the same material as the antistatic paint can be used. At this time, the time constants of the transparent resistor layers 42 and 43 are not more than microseconds, which is a value that causes no practical problem in applications in which the voltage is switched at a cycle of several hundred microseconds.
[0120]
Thus, by connecting the electrode groups 12, 12 ', 13, 13' around the transparent resistor layers 42, 43 and energizing them, the liquid crystal layer 8 near the surface of the transparent resistor layers 42, 43 (effective) A continuous potential gradient can be formed in the region 11), and even when the effective area is relatively wide, a uniform electric field distribution can be provided in the horizontal direction of the liquid crystal layer 8 in the effective region 11 with a relatively simple configuration. Can do.
[0121]
A seventh embodiment of the present invention will be described with reference to FIGS. The present embodiment shows a more practical configuration example of the optical path deflecting device 51. A polarization direction switching element (which can rotate and change the polarization direction of linearly polarized light by electrical operation on the incident surface side of the optical path deflecting element 52). (Polarization direction switching means) 53 is added. Here, the optical path deflecting element 52 may be any of the optical path deflecting elements (including the voltage application circuit) in each of the above-described embodiments. Further, in the state where the orientation of the liquid crystal molecules 9 determined by the action of the spontaneous polarization Ps of the liquid crystal in the liquid crystal layer 8 and the electric field for deflection is aligned in a predetermined direction by the application of the voltage V1 by the voltage application circuit, When the liquid crystal molecules 9 are projected toward the substrate surface, the major axis direction of the liquid crystal molecules 9 projected on the other substrate is the same as the polarization direction switched and controlled by the polarization direction switching element 53. The application of the voltage V1 by the voltage application circuit is controlled synchronously. The projected major axis direction of the liquid crystal molecules 9 is the projection optical axis direction. FIG. 14 shows the direction (C director) 9b of the liquid crystal molecules 9 projected from one substrate 3 (not shown) to the other substrate 2. When the liquid crystal molecules 9 are aligned in a uniform direction, the projection optical axis direction coincides with the C director direction 9b.
[0122]
For example, when the incident light is linearly polarized light in the horizontal direction, in FIG. 13A, the polarization direction switching element 53 is operated so as to maintain the polarization direction, and a downward electric field acts on the effective region 11 of the optical path deflecting element 52. A voltage is applied so as to When the spontaneous polarization Ps of the liquid crystal is positive, the optical axis is inclined to the left side of the figure. At this time, the polarization direction exiting the polarization direction switching element 53 coincides with the inclination direction of the optical axis (the major axis direction in the liquid crystal molecules 9 projected on the other substrate when the liquid crystal molecules 9 are projected). Therefore, the optical path is shifted to the left side. The shift amount at this time is obtained by the above-described equation (1).
[0123]
Next, in FIG. 13B, the operation of the polarization direction switching element 53 is switched so that the polarization direction is rotated by 90 degrees, and at the same time, a voltage in which a rightward electric field acts is applied to the effective region 11 of the optical path deflection element 52. Thus, the operation of the voltage application circuit is switched. When the spontaneous polarization Ps of the liquid crystal is positive, the optical axis is inclined downward in the figure. At this time, the polarization direction exiting the polarization direction switching element 53 coincides with the inclination direction of the optical axis (the major axis direction in the liquid crystal molecules 9 projected on the other substrate when the liquid crystal molecules 9 are projected). Therefore, the optical path is shifted downward. Similarly, by switching the polarization direction of linearly polarized light by the polarization direction switching element 53 and the action direction of the electric field on the optical path deflecting element 52 to the states of FIGS. 13C and 13D, the optical path is changed to the two directions X and Y. It is possible to shift in parallel in (± 4 directions).
[0124]
Thus, by providing the polarization direction switching element 53 that switches the polarization direction of linearly polarized light on the incident side of the optical path deflecting element 52, the X and Y2 directions (± 4 directions) orthogonal to each other by the configuration of the two elements 52 and 53 are provided. The deflection direction can be set. That is, since the number of elements is small and the number of interfaces of the constituent elements is small compared to the conventional combination of the three elements of the X direction optical path deflecting element, the polarization plane rotating element, and the Y direction optical path deflecting element, An optical path deflecting device 51 with little reduction in light transmittance and MTF is obtained.
[0125]
As the polarization direction switching element 53, a Faraday rotation element in which the polarization plane of linearly polarized light is rotated by a magnetic field, or a liquid crystal cell 54 having a twist structure as shown in FIG. In this liquid crystal cell 54, the alignment treatment directions of the two substrates 55 and 56 are arranged orthogonally, and the liquid crystal molecules 57 of the twisted nematic liquid crystal layer are 90 in the thickness direction when no electric field is applied to the liquid crystal cell 54. It is twisted and oriented. When linearly polarized light parallel to the liquid crystal alignment direction on the incident substrate 55 side is incident, the polarization plane rotates along the twist of the liquid crystal molecules 57 and is emitted. When an electric field is applied in the thickness direction of the liquid crystal cell 54, the liquid crystal molecules 57 are oriented perpendicular to the substrate surface and become isotropic with respect to the incident light, and the polarization plane is emitted without rotating. In particular, the liquid crystal cell 54 having a twisted structure can be set with a relatively small variation in the rotation angle of the polarization plane depending on the wavelength, and thus is suitable for handling light having multiple wavelengths.
[0126]
An eighth embodiment of the present invention will be described with reference to FIG. In the present embodiment, for example, as the polarization direction switching element 53 shown in FIG. 13, a surface stable ferroelectric liquid crystal element 58 capable of controlling the alignment direction of liquid crystal molecules by the action of an electric field is used. Although not particularly shown, the surface stable ferroelectric liquid crystal element 58 includes a pair of substrates, a transparent electrode, a horizontal alignment film, a spacer between the substrates, and a liquid crystal capable of forming a chiral smectic C phase. When the thickness of the liquid crystal layer is set to be equal to or less than the spiral pitch of the chiral smectic C phase, the spiral is unwound and a surface stable alignment state is obtained.
[0127]
FIG. 16 shows a schematic diagram of the alignment state of the surface stable ferroelectric liquid crystal element 58. When the direction of the electric field in the direction perpendicular to the paper surface is switched, the orientation direction is switched by the cone angle 2θ when the tilt angle inherent to the ferroelectric liquid crystal molecules 59 is θ. Here, as shown in FIG. 16A, when the polarization direction of the incident light and the alignment direction of the ferroelectric liquid crystal molecules 59 coincide with each other, the polarization direction does not rotate and is emitted as it is. On the other hand, as shown in FIG. 16B, when the electric field is inverted to switch the ferroelectric liquid crystal molecules 59 to a state inclined by 2θ, the liquid crystal layer functions as a half-wave plate, and the polarization plane rotates by 4θ and is emitted. Is done. Here, in order to rotate the polarization plane by 90 degrees, the alignment treatment direction and the liquid crystal are changed so that the alignment direction of the ferroelectric liquid crystal molecules 59 is switched from the parallel state to the state inclined by about 45 degrees with respect to the polarization direction of the incident light. The material (tilt angle θ = 22.5 °) is preferably set, but is not limited to this angle as long as there is no practical problem. The cell thickness is appropriately set according to the wavelength of incident light and the birefringence of the ferroelectric liquid crystal molecules 59.
[0128]
When such a surface stable ferroelectric liquid crystal element 58 is used, the polarization direction switching element 53 capable of switching the polarization direction at high speed is obtained, and the optical path deflecting device 51 with high speed response as a whole is obtained.
[0129]
A ninth embodiment of the present invention will be described with reference to FIG. This embodiment is configured more practically with respect to the optical path deflecting device 51 of the seventh or eighth embodiment described above. That is, in the seventh or eighth embodiment described above, it has been described on the assumption that the light incident on the polarization direction switching element 53 is linearly polarized light. However, when unpolarized light is incident, Since the component which does not receive a deflection is included, the contrast with respect to the presence or absence of the optical path deflection is lowered.
[0130]
Therefore, in the optical path deflecting device 51 of this embodiment, as shown in FIG. 16, the polarization direction of the incident light to the optical path deflecting element 52 (polarization direction switching element 53) is set to any one of the deflection directions (± 4 directions) of the optical path. One direction) is provided with a polarization direction control means 60. As the polarization direction control means 60, a linear polarizing plate such as an iodine polarizing plate, a dye polarizing plate, or a wire grid polarizing plate can be used. When the incident light is circularly polarized or the polarization direction is different from the desired direction, a retardation plate such as a quarter wavelength plate or a half wavelength plate is used. You may combine a linearly-polarizing plate and a phase difference plate. As the retardation plate, a crystal plate or mica sandwiched between glass plates or a liquid crystal polymer film can be used.
[0131]
Even when the incident light is non-polarized light or circularly polarized light, the light component that is not subjected to the optical path deflection action due to the tilt of the liquid crystal molecules 9 is cut, so that optical switching by the optical path deflection can be performed reliably.
[0132]
A tenth embodiment of the present invention will be described with reference to FIG. This embodiment shows an application example to an image display device. In FIG. 18, reference numeral 71 denotes a light source for an illuminating device in which LED lamps are arranged in a two-dimensional array. In the traveling direction of light emitted from the light source 71 toward the screen 72, a diffusion plate 73, a condenser lens 74, an image A transmissive liquid crystal panel 75 as a display element and a projection lens 76 as an optical device for observing the image pattern are sequentially arranged. Reference numeral 77 denotes a light source drive unit for the light source 71, and 78 denotes a liquid crystal drive unit as display drive means for the transmissive liquid crystal panel 75.
[0133]
Here, an optical path deflecting device 79 functioning as a pixel shift element is interposed on the optical path between the transmissive liquid crystal panel 75 and the projection lens 76. The optical path deflecting device 79 is configured as described in the above embodiments, and the effective area of the optical path deflecting element is set to correspond to the transmissive liquid crystal panel 75. The optical path deflector 79 is connected to a drive control unit 80 that performs a function of controlling opening and closing of a voltage application circuit and a switch in the voltage application circuit.
[0134]
The illumination light that is controlled by the light source drive unit 77 and emitted from the light source 71 becomes illumination light that is made uniform by the diffusion plate 73, and is controlled by the condenser lens 74 in synchronization with the illumination light source by the liquid crystal drive unit 78. The liquid crystal panel 75 is critically illuminated. The illumination light spatially modulated by the transmissive liquid crystal panel 75 enters the effective area of the optical path deflecting device 79 as image light, and the optical path deflecting device 79 shifts the image light by an arbitrary distance in the pixel arrangement direction. The This light is magnified by the projection lens 76 and projected onto the screen 72.
[0135]
Here, the timing at which the optical path deflecting device 79 shifts the projection optical path to the four positions in the XY2 direction and the timing at which the four subfield images corresponding to the shift positions are sequentially displayed on the transmissive liquid crystal panel 75 are synchronized. It is possible to display a high-definition image having the number of pixels multiplied by about 4 times. In this case, the shift amount by the optical path deflecting device 79 is set to ½ of the pixel pitch of the transmissive liquid crystal panel 75. At this time, since the optical deflector as in each of the above-described embodiments is used as the optical path deflector 79, the light utilization efficiency is improved, and the viewer is brighter without increasing the load on the light source. High quality images can be provided. By performing the optical path deflection position control based on the electric field application direction and the electric field intensity by the electrode group forming a pair in the optical path deflection element, an appropriate pixel shift amount can be maintained and a good image can be obtained. In particular, since the optical path deflecting element or the optical path deflecting device of the present invention can be shifted in the XY2 direction (± 4 directions) with a small number of components, the entire element has a high transmittance and the MTF is hardly deteriorated, so that it is highly efficient. A high-resolution display image can be obtained. In addition, since a uniform electric field is formed over the entire effective area, the deflection operation by the action of this electric field is also performed uniformly over the entire effective area, that is, the entire image spatially modulated by the transmissive liquid crystal panel 75. This contributes to higher-definition image display.
[0136]
【Example】
[Example 1]
(Production of optical path deflecting element and device)
A vertical (homeotropic) alignment film having a thickness of 0.06 μm was formed on the surface of a glass substrate having a size of 3 cm × 4 cm and a thickness of 1 mm. An aluminum electrode sheet having a thickness of 60 μm, a width of 0.5 mm, and a length of 1 to 2 cm is used as a spacer electrode, and 10 pieces are arranged at intervals of 0.5 mm on each side so that the effective area is about 1 cm square. A cell having an electrode group arrangement similar to the case shown in FIG. 4 was produced by sandwiching between two substrates. With the cell heated to about 90 ° C., a ferroelectric liquid crystal (Chisso CS1029: birefringence Δn = 0.16, tilt angle θ = 25 °, spontaneous polarization Ps = −40 nC / cm²) Was injected by capillary method. After cooling, it was sealed with an adhesive to produce an optical path deflecting element having a liquid crystal thickness of 60 μm and an effective area of 1 cm square. As shown in FIG. 9, the divided electrodes of the aluminum electrode group on each side were connected with a resistance R of 200 kΩ, and connected to a voltage application circuit using a photocoupler as shown in FIG.
[0137]
(Observation of optical axis)
When a conoscopic image of the liquid crystal layer in the effective region of the optical path deflecting element was observed in the absence of an electric field, a cross-shaped and circular image was observed at the center. Therefore, it was confirmed that the optical axis was perpendicular to the liquid crystal layer under no electric field. In this state, the liquid crystal molecules have a spiral structure in which the tilt direction of the liquid crystal molecules rotates with respect to the direction perpendicular to the substrate surface, and the average optical axis is observed as a direction perpendicular to the substrate surface that is the direction of the spiral axis.
[0138]
Next, the output of the DC power source V1 is set to 2000V, a photocoupler drive signal is generated from the pulse generator, and 2000V is applied to the upper left and right two of the four corners of the element as described in FIG. The lower left and right two places were grounded. Similarly, when the conoscopic image was observed, the positions of the cross and the ring shifted to the right. This indicates that since the spontaneous polarization Ps of the ferroelectric liquid crystal used in this example is negative, the optical axis is inclined on the opposite side to the case of FIG. When the tilt angle of the optical axis is calculated 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, it is about 25 °, which is confirmed to coincide with the tilt angle θ inherent to this liquid crystal material. . Therefore, it can be considered that the electric field strength of about 200 V / mm is a state in which the liquid crystal molecules are aligned in a uniform direction after the helical structure is dissolved.
[0139]
Similarly, when the pattern of the voltage applied to the four corners is changed, the positions of the cross and the ring of the conoscopic image also move up, down, left, and right, and the optical axis can be tilted to four positions in the XY2 direction. I was able to confirm. When similar observations were made at several locations within the effective area, there was variation within 10% in the tilt direction and tilt angle of the optical axis depending on the position, but it was determined that there was no practical problem.
[0140]
Therefore, an optical path deflecting element and an optical path deflecting device capable of deflecting the optical axis in two directions (± 4 directions) or more in a single cell are obtained.
[0141]
[Example 2]
(Production of optical path deflecting element and device)
A transparent conductive paint having a thickness of 1 μm was applied to the surface of a glass substrate having a size of 3 cm × 4 cm and a thickness of 1 mm. As the transparent conductive paint, a tin oxide powder having a primary particle size of 0.01 μm or less dispersed in a polyester resin was used. Adjusting the dispersion concentration and drying conditions after coating, the surface resistance is 1 × 10⁸It was set to be Ω. The visible light transmittance of this transparent conductive film was 90% or more. A vertical (homeotropic) alignment film having a thickness of 0.06 μm was formed on this surface. Thereafter, the alignment film at the edge of the substrate was removed to form a portion where the transparent conductive film was exposed on the surface. An aluminum electrode sheet having a thickness of 60 μm, a width of 0.5 mm, and a length of 0.5 to 1 cm is used as a spacer electrode, and 20 pieces are provided at intervals of 0.5 mm on each side so that the effective area is about 2 cm square. Arranged and sandwiched between two substrates, a cell having an electrode group arrangement similar to that shown in FIG. 12 was produced. With the cell heated to about 90 ° C., a ferroelectric liquid crystal (Chisso CS1029: birefringence Δn = 0.16, tilt angle θ = 25 °, spontaneous polarization Ps = −40 nC / cm²) Was injected by capillary method. After cooling, it was sealed with an adhesive to produce an optical path deflecting element having a liquid crystal thickness of 60 μm and an effective area of 2 cm square. The aluminum electrode groups on each side were connected with a resistance of 200 kΩ and connected to a voltage application circuit using a photocoupler as shown in FIG.
[0142]
(Observation of optical axis)
The inclination state of the optical axis was observed in the same manner as in Example 1 except that the output of the DC power supply V1 was changed to 4000V. The positions of the cross and the ring of the conoscopic image also moved up and down and left and right, and it was confirmed that the optical axis can be tilted to four positions in the XY2 direction. Similar observations were made at several locations within the effective area, and there were variations within 5% in the tilt direction and tilt angle of the optical axis depending on the position, but it was determined that there was no practical problem. In spite of the large effective area, it was confirmed that the uniformity of the optical axis tilt direction in the surface was improved.
[0143]
[Example 3]
(Preparation of polarization direction switching element)
An insulating film having a thickness of 0.1 μm and a horizontal (homogeneous) alignment film having a thickness of 0.06 μm were formed on the ITO surface of a glass substrate with ITO having a size of 3 cm × 4 cm and a thickness of 1 mm. After the alignment film is rubbed, 100 spherical spacers with a diameter of 1.7 μm between the two substrates / mm²A cell having an effective area of 2 cm square was produced. While the cell was heated to about 90 ° C., a ferroelectric liquid crystal (CS1029 manufactured by Chisso) similar to the above was injected into the space between the substrates by the capillary method. After cooling, it was sealed with an adhesive to produce a polarization plane rotating element. A power supply capable of applying ± 10 V was connected between the ITO electrodes of the two substrates. When the switching state of the alignment direction of the liquid crystal molecules was observed between the orthogonal polarizing plates, the alignment direction of the liquid crystal molecules aligned in parallel with the substrate was tilted by about 50 ° by the inversion of the electric field, which was twice the tilt angle inherent to this liquid crystal material. It was confirmed that it coincided with the cone angle 2θ. In order to rotate the polarization plane by 90 °, it is ideal that the cone angle is 45 °, but it was judged that there is no practical problem even at 50 °. Further, the switching time of the orientation direction at the time of electric field inversion was 0.12 msec when 10 V was applied, and it was confirmed that the response was fast.
[0144]
(Confirmation of optical path deflection operation)
Such a polarization direction switching element and an optical path deflecting element were bonded together in an arrangement relationship as shown in FIG. 13 to produce an optical path deflecting device. At this time, one of the liquid crystal alignment directions of the polarization direction switching element and one of the electric field application directions of the optical path deflecting element were arranged to coincide with each other. A mask pattern having openings of 5 μm square and a pitch of 20 μm was provided on the incident surface side of the optical path deflecting element, and illumination was performed with linearly polarized light through this mask pattern. The direction of linearly polarized light was set to be the same as one of the liquid crystal alignment directions of the polarization plane rotating element. Similarly to Example 1, the voltage application pattern to the optical path deflecting element was switched, and at the same time, the light transmitted through the mask pattern was observed with a microscope through the effective area of the optical path deflecting element while switching the voltage polarity to the polarization direction switching element.
[0145]
The voltage application pattern was sequentially switched every second as shown in FIGS. 13 (a) to 13 (d). In the central part of the element, the opening pattern was observed to swing in the vertical and horizontal directions with a shift amount of about 9 μm. Since the mask pattern, the optical path deflecting element, and the microscope are mechanically stationary, it has been confirmed that the optical path can be shifted electro-optically in the XY2 direction. Further, when the response time was measured by observing the movement of the aperture pattern using a high-speed camera, it was 0.4 ms. It was confirmed that a sufficiently fast response speed can be obtained because the ferroelectric liquid crystal material is used.
[0146]
[Example 4]
An image display device as shown in FIG. 18 was produced. A 0.9-inch diagonal XGA (1024 × 768 dots) polysilicon TFT liquid crystal panel was used as the image display element. The pixel pitch is about 18 μm both vertically and horizontally. The aperture ratio of the pixel is about 50%. Further, a microlens array is provided on the light source side of the image display element to increase the collection rate of illumination light. In this embodiment, a so-called field sequential method is employed in which RGB three-color LED light sources are used as the light source, and color display is performed by switching the color of light applied to the one liquid crystal panel at a high speed. In this embodiment, the frame frequency of image display is 30 Hz, and the subfield frequency for pixel multiplication by 4 times by pixel shift is 120 Hz, which is 4 times. In order to further divide one subframe into three colors, an image corresponding to each color is switched at 360 Hz. A full color image can be seen by an observer by turning ON / OFF the LED light source of the corresponding color in accordance with the display timing of each color image on the liquid crystal panel.
[0147]
The configuration of the optical path deflecting element is the same as that of Example 3, but the polarizing direction of the light emitted from the liquid crystal panel was set to be the same as one of the liquid crystal alignment directions of the polarization direction switching element. Further, in order to ensure the degree of polarization of incident light to the optical path deflecting element, a linear polarizing plate is provided on the incident surface side of the optical path deflecting element.
[0148]
The switching timing of the photocoupler was controlled by a pulse generator, and the voltage application pattern was set to be sequentially switched every 8.3 msec as shown in FIGS. 13 (a) to 13 (d). In synchronization with the switching timing of the optical path shift position, by rewriting the subfield image displayed on the image display device at 120 Hz, a high-definition image in which the apparent number of pixels was doubled in the vertical and horizontal directions could be displayed. . The switching time of the optical path deflecting element was about 0.4 msec, and sufficient light utilization efficiency was obtained. Also, no flicker was observed. Also, a CCD was placed on the screen surface, an image was formed on the CCD, and the shape of the pixel was observed. Here, a line / space image having a period of two pixels (an image in which a white display line having a width of one pixel and a black display line having a width of one pixel are alternately arranged) is displayed, the luminance of the white portion is Imax, and the luminance of the black portion is Imin As a result, the contrast transfer function (CTF) = (Imax−Imin) / (Imax−Imin) was obtained. In general, when the value of the modulation transfer function (MTF) of the optical element is small, the shape of the pixel is dull, the luminance contrast between the adjacent display pixel portion and the non-display pixel portion is lowered, and the CTF value is reduced. In this example, the CTF value was 0.8, and it was confirmed that a high-definition image having a relatively sharp pixel shape can be displayed.
[0149]
【The invention's effect】
According to the first aspect of the invention, basically, a chiral smectic C phase ferroelectric or antiferroelectric liquid crystal layer having homeotropic alignment is deflected in a direction perpendicular to the optical path passing through the liquid crystal layer. By applying an electric field, the tilt angle and the tilt direction of the liquid crystal molecules can be changed to control the tilt direction of the average optical axis. In this case, the effective area of the optical path passing through the liquid crystal layer is surrounded. Two sets of electrode groups respectively prepared at positions opposite to each other in two directions orthogonal to each other are prepared, and a set of electrode groups for applying an electric field for deflection is selectively selected according to a target deflection direction. By switching to, the deflection direction can be switched to two orthogonal directions by electrical operation, and the other set of electrodes is forced when deflecting by voltage application of such a deflection voltage application means. For deflection By having an electric field direction of the potential gradient, the electric field for deflection no longer be disturbed by these other set of electrodes, thus, it is possible to form a uniform electric field across the active area.
[0150]
According to the second aspect of the present invention, in order to realize the first aspect of the invention, each electrode group has a divided structure composed of a plurality of divided electrodes. Since a voltage whose voltage value changes stepwise is applied to each divided electrode in the set of electrode groups, the potential gradient in the direction of the electric field for deflection is forcibly applied by the other set of electrode groups. And can be realized relatively easily.
[0151]
According to the invention described in claim 3, in order to realize the invention described in claim 1, each electrode group is divided into a plurality of divided electrodes, and each electrode group is provided between adjacent divided electrodes. Since a series resistance group in which the resistances are connected in series is provided, a voltage is applied across the series resistance group of the other electrode group during deflection by voltage application of the deflection voltage applying means. The voltage divided by the resistors of the series resistor group and gradually changing can be applied to each divided electrode, and the other electrode group forcibly has a potential gradient in the electric field direction for deflection. Can be realized easily and at low cost.
[0152]
According to the fourth aspect of the invention, in the optical path deflecting device according to the second or third aspect, the positions of the divided electrodes facing each other are shifted from each other so as to be alternately positioned. It corresponds to the divided electrode of the opposing electrode group, and the influence of the potential drop is reduced, and the uniformity of the electric field can be improved.
[0153]
According to the fifth aspect of the present invention, since the resistor electrode is provided at a position along the effective region as the electrode group in realizing the invention of the first aspect, the voltage between the both ends of the resistor electrode is set. A continuous potential gradient can be formed in the liquid crystal layer in the vicinity of the resistor electrode simply by applying a current to the resistor electrode, and a more uniform electric field distribution can be obtained by such a continuous potential gradient. .
[0154]
According to the invention described in claim 6, in realizing the inventions described in claims 2 to 5, the ends of the adjacent electrode groups are electrically connected to each other, and the potential of the connection is set to the ground and the single polarity. Since switching is possible depending on the potential, the power supply for the deflection voltage application means and the power supply for the auxiliary voltage application means can be shared, and can be realized at low cost.
[0155]
According to the seventh aspect of the invention, in addition to the first to sixth aspects of the invention, since the transparent resistor layer is provided on the entire effective area and connected to the electrode group, it is relatively far from the electrode group forming the set. A potential distribution can be effectively formed also in the effective region, so that a relatively uniform electric field can be formed even when the effective region is relatively large.
[0156]
According to the invention described in claim 8, in order to realize the invention described in claim 1, each electrode group has a divided structure composed of a plurality of divided electrodes, and the other of the electrodes is subjected to deflection by voltage application of the deflection voltage applying means. By simply bringing the individual divided electrodes in a group of electrodes into a floating state, the other group of electrodes can force a potential gradient in the direction of the electric field for deflection, requiring auxiliary voltage application means. And can be realized relatively easily.
[0157]
According to the ninth aspect of the invention, in addition to the first to eighth aspects of the invention, the polarization direction switching means for switching the polarization direction of the linearly polarized light is provided on the incident side. The deflection direction can be set. That is, since the number of elements is small and the number of interfaces of the constituent elements is small compared to the conventional combination of the three elements of the X direction optical path deflecting element, the polarization plane rotating element, and the Y direction optical path deflecting element, It is possible to provide an optical path deflecting device with little reduction in light transmittance and MTF.
[0158]
According to the tenth aspect of the present invention, in order to realize the optical path deflecting device according to the ninth aspect, the surface stable ferroelectric liquid crystal element capable of controlling the alignment direction of liquid crystal molecules by the action of an electric field as a polarization direction switching means. Therefore, by setting the refractive index of the liquid crystal molecules of this surface-stable ferroelectric liquid crystal element, the orientation direction when an electric field is applied, the thickness of the liquid crystal layer, etc. to the optimum conditions as a half-wave plate, high-speed polarization is possible. A polarization direction switching unit capable of rotating the surface can be obtained, and an optical path deflecting device with high-speed response as a whole can be provided.
[0159]
According to the eleventh aspect of the invention, in realizing the optical path deflecting device according to the ninth or tenth aspect, the polarization direction control means for matching the polarization direction of the incident light incident on the polarization direction switching means with the deflection direction of the optical path. Because only linearly polarized light parallel to the tilt direction of the optical axis is made incident, even if the incident light is unpolarized light, transmission of noise light that is not deflected in the optical path is prevented, and there is less noise. Can be realized.
[0160]
According to the image display device of the twelfth aspect of the present invention, since the optical path deflecting device capable of deflecting the optical path in two orthogonal directions according to any one of the first to eleventh aspects is used as a so-called pixel shift device, the projection optical path is changed. It can be deflected at high speed corresponding to the sub-field image, and apparently high-definition image display is possible. In addition, the number of components of the optical path deflecting device is small, and uniform deflection is made over the entire effective area. Since the electric field for use is formed, the interface of the substrate is small, the transmittance and the MTF can be reduced, and the uniform pixel shift is possible. Therefore, the light utilization efficiency is higher and the display image is higher in definition. Can be obtained.
[0161]
According to the optical path deflecting element of the thirteenth aspect of the invention, basically, the optical path passing through the liquid crystal layer is effective against the chiral smectic C phase ferroelectric or antiferroelectric liquid crystal layer having homeotropic alignment. A voltage is applied by electric operation from the outside to a set of electrodes arranged opposite to each other so as to surround the region, and an electric field for deflection in a direction orthogonal to the optical path passing through the liquid crystal layer is applied. By changing the tilt angle and the tilt direction of the liquid crystal molecules, the tilt direction of the average optical axis can be controlled. At this time, the effective area of the optical path passing through the liquid crystal layer is set as a group of electrodes. Prepare two sets of electrode groups respectively arranged at opposite positions in two orthogonal directions so as to surround them, and set a set of electrode groups that act on the deflection electric field according to the target deflection direction. If you switch selectively, The deflection direction can be switched to two orthogonal directions by a pneumatic operation, and each electrode group has a divided structure composed of a plurality of divided electrodes. With respect to the electrode group, the other set of electrode groups forcibly has a potential gradient in the electric field direction for deflection by applying a voltage whose voltage value changes stepwise to each divided electrode. By doing so, the deflection electric field is not disturbed by the other set of electrodes, so that a uniform electric field can be formed over the entire effective region.
[0162]
According to the invention of claim 14, in order to realize the invention of claim 13, in addition to each electrode group of the divided electrode structure, a resistance provided between adjacent divided electrodes for each electrode group is connected in series. The series resistance group is configured to include a series resistance group connected to the other electrode group, so that, when the voltage is applied to one set of electrode groups, the voltage is applied between both ends of the series resistance group of the other set of electrode groups. A voltage that is divided by the resistance of each of the resistors and changes stepwise can be applied to each divided electrode, and the other electrode group can forcibly have a potential gradient in the direction of the electric field for deflection. It can be realized easily and at low cost.
[0163]
According to the fifteenth aspect of the invention, the optical path deflecting element according to the thirteenth or fourteenth aspect is realized, and the positions of the opposed divided electrodes are shifted from each other and arranged at alternate positions. Corresponds to the divided electrode of the opposing electrode group, the influence of the potential drop is reduced, and the uniformity of the electric field can be improved.
[0164]
According to the optical path deflecting element of the invention of the sixteenth aspect, basically the same effect as that of the optical path deflecting element of the thirteenth aspect of the invention can be obtained, but the resistor electrode is arranged at a position along the effective region as an electrode group. Therefore, as an electrical operation from the outside, a voltage for applying an electric field is applied between one set of electrode groups, and a voltage is applied across the resistor electrodes with respect to the other set of electrode groups. By simply applying and energizing, a continuous potential gradient can be formed in the liquid crystal layer in the vicinity of the resistor electrode, and a more uniform electric field distribution can be obtained by such a continuous potential gradient. be able to.
[0165]
According to the invention of claim 17, since the ends of the adjacent electrode groups are electrically connected to realize the inventions of claims 13 to 16, this can be achieved by an electrical operation from the outside. By making the connection potential switchable between ground and single polarity potential, the power supply for the deflection voltage application means and the power supply for the auxiliary voltage application means can be shared, and the optical path deflection can be performed at low cost. An apparatus can be realized.
[0166]
According to the invention described in claim 18, in addition to the invention described in claims 13-17, the transparent resistor layer is provided on the entire effective region and connected to the electrode group, so that voltage application by an external electric operation is performed. Sometimes a potential distribution can be effectively formed even in an effective region that is relatively far from the pair of electrodes, so that a relatively uniform electric field can be formed even when the effective region is relatively large. .
[0167]
According to the driving method of the optical path deflecting element of the nineteenth aspect of the invention, in order to realize optical path deflection in two directions orthogonal to each other over the entire effective area, 2 orthogonal to surround the effective area of the optical path passing through the liquid crystal layer. Two sets of electrode groups are arranged at opposite positions in the direction. Each of these electrode groups has a divided structure composed of a plurality of divided electrodes, and each electrode group is provided between adjacent divided electrodes. A configuration including a series resistance group in which resistors are connected in series, and a voltage is selectively applied between one set of opposing electrode groups in accordance with a target deflection direction, and the liquid crystal layer is perpendicular to the optical path. When the deflection electric field is applied, only the voltage is applied across the series resistance group of the other set of electrode groups, and the voltage that changes stepwise is divided by each resistance of the series resistance group. Applying to each divided electrode The other set of electrodes can force a potential gradient in the direction of the electric field for deflection, and form a uniform electric field over the entire effective region regardless of the direction of deflection. Thus, the optical path can be deflected uniformly over the entire effective area.
[0168]
According to the driving method of the optical path deflecting element of the twentieth aspect of the invention, in realizing the optical path deflection in two directions orthogonal to the entire effective area, 2 orthogonal to surround the effective area of the optical path passing through the liquid crystal layer. Two sets of electrode groups are arranged at opposite positions in the direction, and each of these electrode groups is constituted by a resistor electrode continuous in a direction surrounding the effective region, and selectively according to the target deflection direction. During deflection in which a voltage is applied between one pair of opposing electrode groups to cause a deflection electric field to act on the liquid crystal layer in a direction perpendicular to the optical path, between the ends of the resistor electrodes of the other group of electrode groups By simply applying a voltage and energizing, a continuous potential gradient can be formed in the liquid crystal layer near the resistor electrode, and such a continuous potential gradient can provide a more uniform electric field distribution. The deflection direction can be Even the direction of the Le, it is possible to form a uniform electric field on the effectiveness entire region, it is possible to uniform the optical path deflecting the effectiveness entire region.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram showing an optical path deflection element as a premise.
FIG. 2 is a schematic diagram showing the relationship between the electric field direction and the liquid crystal alignment direction.
FIG. 3 is a schematic diagram for explaining the principle of an optical path deflection operation.
FIGS. 4A and 4B show a configuration example of an electrode group of the optical path deflecting element according to the first embodiment of the present invention, where FIG. 4A is a plan view and FIG. 4B is a side view thereof.
FIG. 5 is a conceptual diagram showing the relationship between the voltage application state and the liquid crystal molecule tilt direction.
FIG. 6 is a conceptual diagram showing a state when the electric field direction is switched.
FIG. 7 is a plan view showing a configuration example of an optical path deflecting device according to a second embodiment of the present invention.
FIG. 8 is a circuit diagram showing a configuration example of the voltage application circuit.
FIG. 9 is a plan view showing a configuration example of an optical path deflecting device according to a third embodiment of the present invention.
FIG. 10 is a plan view showing a configuration example of an optical path deflecting element according to a fourth embodiment of the present invention.
FIG. 11 is a plan view showing a configuration example of an optical path deflecting device according to a fifth embodiment of the present invention.
FIGS. 12A and 12B show a configuration example of an optical path deflecting device according to a sixth embodiment of the present invention, where FIG. 12A is a plan view and FIG. 12B is a longitudinal side view thereof.
FIG. 13 is a perspective view showing a configuration example of an optical path deflecting device according to a seventh embodiment of the present invention.
FIG. 14 is a perspective view for explaining a projected portion of liquid crystal molecules in a major axis direction.
FIG. 15 is a side view showing a configuration example of a polarization direction switching element.
FIG. 16 is a front view for explaining the operation of the polarization direction switching element according to the eighth embodiment of the present invention;
FIG. 17 is a perspective view showing a configuration example of an optical path deflecting device according to a ninth embodiment of the present invention.
FIG. 18 is a side view showing a configuration example of an image display apparatus according to a tenth embodiment of the present invention.
[Explanation of symbols]
1 Optical path deflection element
2, 3 substrate
4,5 Alignment film
8 Liquid crystal layer
9 Liquid crystal molecules
11 Effective area
12, 12 'set of electrode groups
13, 13 'set of electrodes
21 Optical path deflecting element
22, 22 ', 23, 23' Series resistance group
24, 24 ', 25, 25' Deflection voltage application means, auxiliary voltage application means
26 Optical path deflecting device
28a-28d connection part
31 Optical path deflecting element
32 resistor electrode
41 Optical path deflecting element
42, 43 Transparent resistor layer
51 Optical path deflecting device
52 Optical path deflecting element
53 Polarization direction switching means
58 Surface Stabilized Ferroelectric Liquid Crystal Device
60 Polarization direction control means
71 Lighting equipment
75 Image display element
76 Optical devices
78 Display drive means
79 Optical path deflecting device
X1-Xn, X'1-X'n, Y1-Yn, Y'1-Y'n Split electrode
R resistance

Claims (20)

A pair of transparent substrates with opposed spacings restricted;
A vertical alignment film provided on the inner surface side of the substrate;
A liquid crystal layer composed of a chiral smectic C phase filled between the substrates via the vertical alignment film and homeotropically aligned by the vertical alignment film;
Two sets of electrodes each disposed at opposite positions in two orthogonal directions so as to surround an effective area of an optical path passing through the liquid crystal layer;
Applying a voltage between one set of opposing electrode groups selectively according to a target deflection direction, and applying a deflection voltage application to the liquid crystal layer in a direction perpendicular to the optical path Means,
With
An optical path deflecting device in which a potential gradient in the direction of the electric field for deflection is forcibly given by the other group of electrodes during deflection by voltage application of the deflection voltage applying means. Each of the electrode groups comprises a plurality of divided electrodes divided in a direction surrounding the effective area,
In the deflection by the voltage application of the deflection voltage applying means, the other group of the electrode groups forcibly has a potential gradient in the direction of the electric field for the deflection. 2. The optical path deflecting device according to claim 1, further comprising auxiliary voltage applying means for applying a voltage whose voltage value changes stepwise to the electrode. Each of the electrode groups comprises a plurality of divided electrodes divided in a direction surrounding the effective area,
A series resistor group in which resistors provided between adjacent divided electrodes for each electrode group are connected in series;
The series resistor group of the other set of electrode groups so as to force the other set of electrodes to have a potential gradient in the direction of the electric field for deflection during deflection by voltage application of the deflection voltage applying means. Auxiliary voltage applying means for applying a voltage between both ends of
The optical path deflecting device according to claim 1. 4. The optical path deflecting device according to claim 2, wherein the plurality of divided electrodes are arranged so as to be displaced from each other between the electrode groups forming a set. Each of the electrode groups comprises a resistor electrode continuous in a direction surrounding the effective area,
The resistor electrode of the other set of electrode groups is forced to have a potential gradient in the direction of the electric field for deflection by the other set of electrodes during deflection by voltage application of the deflection voltage applying means. The optical path deflecting device according to claim 1, further comprising auxiliary voltage applying means for applying a voltage between both ends of the optical path. The optical path deflection according to any one of claims 2 to 5, wherein ends of the adjacent electrode groups are electrically connected, and a potential of a connection between the ends can be switched between a single polarity potential and a ground. apparatus. 7. The optical path deflecting device according to claim 1, further comprising a transparent resistor layer provided on at least one of the substrates and electrically connected to the electrode group. Each of the electrode groups comprises a plurality of divided electrodes divided in a direction surrounding the effective area,
In the deflection by the voltage application of the deflection voltage applying means, the other group of the electrode groups forcibly has a potential gradient in the direction of the electric field for the deflection. 2. The optical path deflecting device according to claim 1, wherein the electrode is in a float state. A polarization direction switching means disposed on the light incident side to switch the polarization direction of linearly polarized light;
In a state where the orientation of liquid crystal molecules determined by the spontaneous polarization of the liquid crystal in the liquid crystal layer and the action of the electric field for deflection is aligned in a predetermined direction by application of a voltage by the deflection voltage applying means, from one substrate surface to the other substrate When the liquid crystal molecules are projected toward the surface, the deflection voltage is set such that the major axis direction of the liquid crystal molecules projected on the other substrate is the same as the polarization direction by the polarization direction switching means. 9. The optical path deflecting device according to claim 1, wherein voltage application by the applying means is controlled. 10. The optical path deflecting device according to claim 9, wherein the polarization direction switching means is a surface stable ferroelectric liquid crystal element capable of controlling an orientation direction of liquid crystal molecules by the action of an electric field. 11. The optical path deflecting device according to claim 9, further comprising a polarization direction control unit configured to match a polarization direction of incident light incident on the polarization direction switching unit with any one of the deflection directions of the optical path. An image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged;
An illumination device for illuminating the image display element;
An optical device for observing an image pattern displayed on the image display element;
Display driving means for forming an image field by a plurality of subfields divided in time, and
The optical path deflecting device according to any one of claims 1 to 11, wherein an effective area is set corresponding to the image display element, and the optical path of the emitted light from each pixel is deflected for each of the subfields.
An image display device comprising: A pair of transparent substrates with opposed spacings restricted;
A vertical alignment film provided on the inner surface side of the substrate;
A liquid crystal layer composed of a chiral smectic C phase filled between the substrates via the vertical alignment film and homeotropically aligned by the vertical alignment film;
Two sets of electrodes each having a plurality of divided electrodes that are respectively arranged at mutually opposing positions in two orthogonal directions so as to surround the effective region of the optical path passing through the liquid crystal layer and divided in the direction surrounding the effective region When,
An optical path deflection element comprising: The optical path deflecting element according to claim 13, further comprising a series resistor group in which resistors provided between adjacent divided electrodes are connected in series for each of the electrode groups. The optical path deflecting element according to claim 13 or 14, wherein a plurality of divided electrodes each divided are disposed so as to be displaced from each other between pairs of electrode groups. A pair of transparent substrates with opposed spacings restricted;
A vertical alignment film provided on the inner surface side of the substrate;
A liquid crystal layer composed of a chiral smectic C phase filled between the substrates via the vertical alignment film and homeotropically aligned by the vertical alignment film;
Two sets of electrode groups each having a resistor electrode that is disposed at opposite positions in two orthogonal directions so as to surround an effective area of an optical path passing through the liquid crystal layer, and that is continuous in a direction surrounding the effective area;
An optical path deflection element comprising: The optical path deflecting element according to any one of claims 13 to 16, wherein ends of the adjacent electrode groups are electrically connected to each other. The optical path deflecting element according to any one of claims 13 to 17, further comprising a transparent resistor layer provided on at least one of the substrates and electrically connected to the electrode group. A pair of transparent substrates with opposed spaces regulated, a vertical alignment film provided on the inner surface of the substrate, and the vertical alignment film are filled between the substrates, and homeotropic alignment is performed by the vertical alignment film. A liquid crystal layer composed of a chiral smectic C phase, and a plurality of divided liquid crystal layers disposed in opposing directions in two orthogonal directions so as to surround an effective region of an optical path passing through the liquid crystal layer, and divided in a direction surrounding the effective region For an optical path deflection element comprising two sets of electrode groups each having a plurality of divided electrodes and a series resistance group in which resistors provided between adjacent divided electrodes for each of the electrode groups are connected in series.
Applying a voltage between one set of opposing electrode groups selectively according to a target deflection direction, and applying a deflection voltage application to the liquid crystal layer in a direction perpendicular to the optical path Steps,
Auxiliary for forcing a potential gradient in the direction of the electric field for deflection by applying a voltage across the series resistance group of the other electrode group during the deflection by voltage application in the deflection voltage application step. Voltage application step;
A method for driving an optical path deflecting element. A pair of transparent substrates with opposed spacings, a vertical alignment film provided on the inner surface side of the substrate, and the substrate are filled via the vertical alignment film, and homeotropic alignment is performed by the vertical alignment film. A liquid crystal layer composed of a chiral smectic C phase, and a resistor continuously disposed in two orthogonal directions so as to surround an effective region of an optical path passing through the liquid crystal layer, and in a direction surrounding the effective region An optical path deflecting element comprising two sets of electrodes each having an electrode,
Applying a voltage between one set of opposing electrode groups selectively according to a target deflection direction, and applying a deflection voltage application to the liquid crystal layer in a direction perpendicular to the optical path Steps,
Auxiliary forcing a potential gradient in the direction of the electric field for deflection by applying a voltage across the resistor electrodes of the other group of electrodes during deflection by voltage application in the deflection voltage application step. Voltage application step;
A method for driving an optical path deflecting element.

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