JP2004233659A - Optical deflection device, optical deflection device, and image display apparatus - Google Patents

Optical deflection device, optical deflection device, and image display apparatus Download PDF

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JP2004233659A
JP2004233659A JP2003022259A JP2003022259A JP2004233659A JP 2004233659 A JP2004233659 A JP 2004233659A JP 2003022259 A JP2003022259 A JP 2003022259A JP 2003022259 A JP2003022259 A JP 2003022259A JP 2004233659 A JP2004233659 A JP 2004233659A
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light
liquid crystal
optical
deflecting
deflection
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JP4194381B2 (en
Inventor
Masanori Kobayashi
正典 小林
Toshiaki Tokita
才明 鴇田
Hiroyuki Sugimoto
浩之 杉本
Yumi Matsuki
ゆみ 松木
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Ricoh Co Ltd
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Ricoh Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical deflection device which can reduce the aberration due to the difference in optical path length, by the constitution in which the deflection directions of the light in the optical detection operation are made symmetrical with respect to the incident optical axis and in which the deflection angles agree. <P>SOLUTION: In the optical deflection device, having a pair of transparent substrates 2 and 3, a liquid crystal layer 4 which is sandwiched between the substrates and which can control the refractive index with respect to the incident light by controlling the alignment by the application of voltage, and a voltage application control means 5 which can apply the voltage to the liquid crystal layer 4, in which at least one substrate 2 of the pair of substrates 2 and 3 is a serrate shape substrate on whose surface at the side of the liquid crystal layer a slant serrate shape part 2a corresponding to the light deflection direction is formed, the light deflection angles which are deflected by the liquid crystal layer 4 so as to be emitted are symmetrical with respect to the incident optical axis. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電気信号によって光の方向を変える光偏向素子及び光偏向装置、及び光偏向素子を利用した画像表示装置に関する。
【０００２】
【従来の技術】
光偏向素子として用いられる光学素子として、従来より、ＫＨ２ＰＯ４（ＫＤＰ），ＮＨ４Ｈ２ＰＯ４（ＡＤＰ），ＬｉＮｂＯ３，ＬｉＴａＯ３，ＧａＡｓ，ＣｄＴｅ等の第１次電気光学効果（ポッケルス効果）の大きな材料や、ＫＴＮ，ＳｒＴｉＯ３，ＣＳ２，ニトロベンゼン等の第２次電気光学効果の大きな材料を用いた電気光学デバイスや、ガラス、シリカ、ＴｅＯ２などの材料を用いた音響光学デバイスが知られている（例えば、非特許文献１参照）。これらは、一般的に、十分大きな光偏向量を得るためには光路長を長く取る必要があり、また、材料が高価であるため用途が制限されている。
【０００３】
一方で、液晶材料を用いた光偏向素子なる光学素子も各種提案されており、その数例を挙げると、以下に示すような提案例がある。
例えば、下記の特許文献１によれば、光空間スイッチの光の損失を低減することを目的に、人工複屈折板からなる光ビームシフタが提案されている。内容的には、２枚のくさび形の透明基板を互いに逆向きに配置し、該透明基板間に液晶層を挟んだ光ビームシフタ、及びマトリクス形偏向制御素子の後面に前記光ビームシフタを接続した光ビームシフタが提案され、併せて、２枚のくさび形の透明基板を互いに逆向きに配置し、該透明基板間にマトリクス駆動が可能で、入射光ビームを半セルシフトする液晶層を挟んだ光ビームシフタを半セルずらして多段接続した光ビームシフタが提案されている。
【０００４】
また、下記の特許文献２によれば、大きな偏向を得ることが可能で、偏向効率が高く、しかも、偏向角と偏向距離とを任意に設定することができる光偏向スイッチが提案されている。具体的には、２枚の透明基板を所定の間隔で対向配置させ、対向させた面に垂直配向処理を施し、透明基板間にスメクチックＡ相の強誘電性液晶を封入し、前記透明基板に対して垂直配向させ、スメクチック層と平行に交流電界を印加できるように電極対を配置し、電極対に交流電界を印加する駆動装置を備えた液晶素子である。即ち、スメクチックＡ相の強誘電性液晶による電傾効果を用い、液晶分子の傾斜による複屈折によって、液晶層に入射する偏光の屈折角と変位する方向を変化できるようにしたものである。
【０００５】
この他に光偏向素子を用いた例では、低電圧で駆動でき２次元化、小型化を目的とした光偏向装置が提案されている（特許文献３参照）。これは一対の透明基板間に複屈折性を有する液晶を保持しており、該透明基板の一方に鋸歯状格子が形成されている。保持されている液晶は鋸歯状格子の刻線方向にホモジニアス配向しており、液晶の長軸あるいは短軸のいずれかの屈折率は鋸歯状格子を形成する材料の屈折率と一致している。入射光は偏向回転装置の制御に応じて偏光方向が９０°回転でき、入射光の偏光状態に応じて出射光の方向を切り替えることが可能なものである。また、似たような構成として、基板の一方の面に鋸歯状格子が形成されている２枚の透明基板を有し、それら鋸歯状格子は各々反対方向を向き、同一形状、同一の屈折率をもっている光偏向装置（特許文献４参照）などがある。
【０００６】
【特許文献１】
特開平６−１８９４０号公報
【特許文献２】
特開平９−１３３９０４号公報
【特許文献３】
特開平５−２０４００１号公報
【特許文献４】
特開平９−１３３９３１号公報
【非特許文献１】
青木昌治編；「オプトエレクトロニックデバイス」、昭晃堂
【０００７】
【発明が解決しようとする課題】
前述の従来技術において、光が偏向する原理としては、主に液晶材料の複屈折性と、入射光に対する基板の傾斜が起因している。
例えば特許文献１に記載の従来技術によれば、傾斜方向が逆向きに配置された２枚のくさび型基板間に液晶材料が封入されており、液晶の配向は基板面に対してホモジニアス配向している。基板間に電圧を印加すると、基板間の液晶の配向（液晶分子のダイレクタ方向）は変化し、その方向は基板面に対してホメオトロピック配向をする。ここで入射光の偏光方向がホモジニアス配向の方向と同一方向である場合、入射光が感じる液晶層の実効的な屈折率は、液晶の配向がホモジニアス配向のときには異常光として感じ、また、液晶の配向がホメオトロピック配向のときには常光として感じる。ここで異常光または常光として感じる屈折率を基板の屈折率と一致させることで、素子への入射光はそのまま直進する光と偏向する光の２通りを選択することが可能となり、光偏向機能が実現される。尚、光偏向機能とは光路の平行シフトを含むものとする。
しかし、上記従来技術では、直進光と偏向光では光路長に差が生じるため、光路長差に起因して光偏向した出射光の収差が大きくなるといった問題がある。また、くさび型の基板を用いた構成では基板厚さを厚くする必要があり、素子全体が大きくなるといった問題もある。
【０００８】
特許文献２に記載の従来技術では、２枚の透明基板を対向配置し、基板間にスメクチックＡ相の強誘電性液晶を基板面に対してホメオトロピック配向させ、スメクチック層と平行に交流電界を印加するといった構成としている。これはスメクチックＡ相の強誘電性液晶による電傾効果を用い、液晶分子の傾斜による複屈折によって液晶層に入射する偏向角を変化することが可能であり、光偏向時の光路長差を小さくすることができる。しかし、電傾効果を得るためにスメクチック層と平行に電界を印加しなければならない。即ち、基板端に電極を設け基板面に対して水平電界を発生させなければならない。このような水平電界ではデバイスの位置により電界強度が異なる。そのため、デバイスの電極近傍と電極間の中間位置においては光偏向量（光路シフト量）が異なり、実用的には信頼性に欠けるといった問題がある。
【０００９】
特許文献３，４に記載の従来技術では、基板表面を鋸歯形状にすることで小型化を実現している。しかし、光偏向機能としては特許文献１と同様であり、直進する光と偏向する光により光偏向するため、出射光を受光する位置までの光路長には大きな差ができてしまい、かつ出射角が異なるため、光偏向動作において出射偏向光は大きな収差を含んでしまうといった問題がある。また、従来の光偏向素子を画像表示装置などに応用する場合、結像位置が異なってしまい表示画像がボケて劣化するという問題がある。
【００１０】
本発明は上記従来技術の問題を解決するためになされたものであり、光偏向動作における光の偏向方向を入射光軸と対称にし、かつ偏向角を一致させるような構成とすることで、光路長差による収差を少なくすることができる光偏向素子を提供することを目的とし、さらには、その光偏向素子を用いた光偏向装置や、画像表示装置を提供することを目的とする。
【００１１】
より具体的には、請求項１〜３に係る発明は、出射偏向光において光路長差のない光偏向素子を提供することを目的とし、請求項４に係る発明は、前記目的に加えて、広波長帯域において出射偏向光の波長依存性が少ない光偏向素子を提供することを目的とし、請求項５，６に係る発明は、前記目的に加えて、出射偏向光において光路長差がなく、かつ偏向角を多値に選択できる光偏向素子を提供することを目的とする。
また、請求項７〜９に係る発明は、前記光偏向素子を用い、収差の少ない高精細画像を表示する画像表示装置を提供することを目的とする。
さらに、請求項１０〜１２に係る発明は、前記光偏向素子を用い、出射光の収差が少なく、入射光軸から任意の位置に光路シフトが可能な光偏向装置を提供することを目的とする。
【００１２】
【課題を解決するための手段】
前述の課題を解決するための手段として、請求項１に係る発明は、一対の透明基板と、該基板間に挟まれ電圧印加によって配向を制御することにより入射光に対する屈折率の制御が可能な液晶層と、該液晶層に電圧を印加することが可能な電圧印加制御手段とを備え、前記一対の基板のうち少なくとも一方の基板は、液晶層側の面に光偏向方向に対応して傾斜している鋸歯形状部を形成してなる鋸歯形状基板である光偏向素子において、前記液晶層で偏向されて出射される光の偏向角が入射光軸に対して対称であることを特徴とするものである。
【００１３】
請求項２に係る発明は、一対の透明基板と、該基板間に挟まれ電圧印加によって配向を制御することにより入射光に対する屈折率の制御が可能な液晶層と、該液晶層に電圧を印加することが可能な電圧印加制御手段とを備え、前記一対の基板のうち少なくとも一方の基板は、液晶層側の面に光偏向方向に対応して傾斜している鋸歯形状部を形成してなる鋸歯形状基板である光偏向素子において、入射光波長における前記鋸歯形状基板の屈折率をｎｇ、液晶駆動（光偏向動作）時に入射光が感じる液晶の実効的な屈折率をｎ１（＝ｎｅ）、ｎ２（＝ｎｏ）（ｎ１＞ｎ２）とするとき、
ｎ１＞ｎｇ＞ｎ２
の関係を満たすことを特徴とするものである。
また、請求項３に係る発明は、請求項２記載の光偏向素子において、入射光波長における前記鋸歯形状基板の屈折率をｎｇ、液晶駆動（光偏向動作）時に入射光が感じる液晶の実効的な屈折率をｎ１（＝ｎｅ）、ｎ２（＝ｎｏ）（ｎ１＞ｎ２）とするとき、
０．９９・［（ｎ１＋ｎ２）／２］＜ｎｇ＜１．０１・［（ｎ１＋ｎ２）／２］
の関係を満たすことを特徴とする。
さらに、請求項４に係る発明は、請求項２または３記載の光偏向素子において、前記鋸歯形状基板のアッベ数が液晶の異常光（ｎ１＝ｎｅ）、常光（ｎ２＝ｎｏ）におけるアッベ数の平均から±１０％以内のズレであることを特徴とするものである。
【００１４】
請求項５に係る発明は、請求項１〜４のいずれか一つに記載の光偏向素子において、前記液晶層がネマチック液晶であることを特徴とするものである。
また、請求項６に係る発明は、請求項５記載の光偏向素子において、前記ネマチック液晶の初期配向方向と入射光の偏光方向が前記鋸歯形状基板の鋸歯刻線方向と一致することを特徴とするものである。
【００１５】
請求項７に係る発明は、画像表示装置であり、少なくとも、画像情報に従って光を制御可能な複数の画素が二次元配列した画像表示素子と、該画像表示素子を照明する光源と、前記画像表示素子に表示した画像パターンを観察するための光学部材と、該光学部材の間の光路を偏向する光偏向素子を有し、該光偏向素子は請求項１〜６のいずれか一つに記載の光偏向素子からなることを特徴とするものである。
また、請求項８に係る発明は、請求項７記載の画像表示装置において、前記光偏向素子は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域を有し、第一の傾斜領域で屈折された光が、一定間隔をおいて設置された第二の傾斜領域に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置された光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子の見かけ上の画素数を増倍して表示することを特徴とするものである。
【００１６】
請求項９に係る発明は、請求項７記載の画像表示装置において、前記光偏向素子は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の傾斜領域を有し、該傾斜領域で屈折された光が偏向光として出射するような光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子の見かけ上の画素数を増倍して表示することを特徴とするものである。
【００１７】
請求項１０に係る発明は、光偏向装置であり、請求項１〜６のいずれかに記載の光偏向素子を複数用い、前記光偏向素子が多段に配置されてなることを特徴とするものである。
また、請求項１１に係る発明は、請求項１０記載の光偏向装置において、前記光偏向素子として、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域を有し、第一の傾斜領域で屈折された光が、一定間隔をおいて設置された第二の傾斜領域に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置され、出射偏向光の偏向角が基板面の法線方向に対して対称であることを特徴とする光偏向素子を複数用い、前記光偏向素子が多段に配置されてなることを特徴とするものである。
さらに請求項１２に係る発明は、請求項１１記載の光偏向装置において、前記光偏向素子は対向して配置された一対の傾斜領域の間に中間基板を有し、多段に配置された複数の光偏向素子の中間基板厚ｄを、それぞれ入射光側から順にｄ１、ｄ２、ｄ３、・・・ とする場合、
ｄｍ＝ｄｍ− １／２ｍ− １ （ｍ＝１，２，３，・・・、但しｄ０＝ｄ１）
の関係を満たすことを特徴とするものである。
【００１８】
【発明の実施の形態】
以下、本発明の構成、動作及び作用に関して詳細に説明する。
まず、光偏向動作原理及び光偏向素子の基本構成について説明する。図１は本発明に係る光偏向素子の基本構成例を示すものであり、この光偏向素子１は、少なくとも一方の基板に鋸歯形状部（傾斜領域）が形成されている一対の透明基板２，３と、一対の基板間に挟まれ電圧印加条件によって配向状態の制御が可能な液晶層４と、液晶層４へ電界を印加する透明電極５と、透明電極５への電圧印加状態を変化させる印加電圧制御手段（図示せず）とを有している。図１の例では、一対の透明基板２，３のうち一方の基板２は、液晶層４側の面に光偏向方向に対応して傾斜している鋸歯形状部（傾斜領域）２ａを形成してなる鋸歯形状基板であり、他方の基板３は対向基板である。鋸歯形状基板２に形成される鋸歯の形状、アレイ数は特に限定しないが、所望の偏向量、偏向方向になるように形成される。前記液晶層４は電圧印加条件によって液晶分子４ａの配向状態が変化するので、電圧印加条件を設定することによって、例えば図２に示すように、液晶分子４ａは２つの配向状態をとり得る。この光偏向素子１における液晶の配向状態の変化を図２により説明する。基本的にはホモジニアス配向されたネマチック液晶を用いる光偏向素子に準ずる構成のものであるが、電圧印加条件によって液晶の配向状態が変化し、それに伴って入射光に対する屈折率が変化するものであればよい。例えば、スメクチックＣ相よりなる強誘電性液晶も同様の構成で用いることができる。
【００１９】
ここで、液晶の初期配向を規制するために、両基板２，３の表面に形成される配向膜（図示せず）に対してラビング処理を行なう（図２では図示していないがラビング方向はＹ軸方向としている）。液晶のダイレクタ方向はラビング処理の方向に依存して強く規制される。このような配向処理用の材料としては、ＴＮ液晶、ＳＴＮ液晶等に用いられるポリイミド等の通常の配向膜が利用できる。配向処理としてはラビング処理や光配向処理を施すことが好ましい。また、液晶の配向は電圧印加条件によって変化するため、一対の透明電極５による電極対が一対の基板２，３の液晶層側表面に電圧印加手段として形成されている。この電極対により、ホモジニアス配向している液晶ダイレクタに直交する方向、即ち、基板面内方向に電界が印加される構成としている。さらには、鋸歯形状基板２側の面が入射光の法線方向に対して傾きψ１をなすように傾斜状態が設定されている。鋸歯形状基板２の作製方法としては、ガラス基板、透明プラスチック基板などをエッチングまたは切削加工して、鋸歯形状部（傾斜領域）２ａを形成するといった方法がある。また、透明プラスチック材料は射出成形により加工するといった方法もある。どのような作製方法においても、鋸歯形状基板２に用いる材料は複屈折性がないものが好ましい。
【００２０】
図２に示すように、液晶ダイレクタは初期配向または電極からの電界方向に対応して２方向に配向される（第１の配向状態及び第２の配向状態）。このような構成の光偏向素子において、液晶の配向を図２に示す通り基板面に対して水平方向と垂直方向に規制することで、入射光を効率良く偏向させることが可能となる。即ち、図２において入射光の直線偏光方向がＹ軸方向になるよう入射光を操作してこの光偏向素子に入射させたとき、基板間に電界が発生しないような状態では液晶ダイレクタは初期配向によりＹ軸方向を向く（第１の配向状態）。
一方、基板面に対して垂直方向に向くように電界を印加するような状態では、液晶ダイレクタは電界方向、即ち初期配向と直交する方向を向く（第２の配向状態）。
【００２１】
このような第１の配向状態（初期配向＝ホモジニアス配向）における液晶の屈折率をｎ１ 、第２の配向状態（電圧印加時の配向＝ホメオトロピック配向）における液晶の屈折率をｎ２ 、液晶を挟持する基板の屈折率をｎｇとする場合、ｎｇ≠ｎ１≠ｎ２であれば入射光は第１の配向状態及び第２の配向状態において界面との屈折率差により偏向される。
【００２２】
このような構成の光偏向素子の特徴は、入射光に対する出射光が液晶ダイレクタの制御によって、回転移動可能な点である。従って、当該光偏向素子と受光部との距離を適切に選ぶことで所望の偏向量を得ることができる。例えば図３に示すように、図１に示した構成の光偏向素子１を２つ用い、このような２つの光偏向素子を光進行方向上に配設させて光偏向デバイスを構成し、配設した素子間の距離Ｘを適切に選ぶことで入射光と出射光を平行に保ったまま必要な偏向量を得ることができる。これによって、偏向量を外部から簡単に調整することができ、利便性に優れた光偏向デバイスを構成することができる。
また、光偏向量が一定であれば、図４に示すように、厚さＬの中間基板６を介して１つの光偏向素子内に２層の液晶層４と２つの対向する鋸歯形状部（傾斜領域）を設けてもよい。
【００２３】
図１に示すような光偏向素子の構成における光の進行方向を求める場合、厳密には、入射光進行方向に対する液晶ダイレクタの方向及び屈折率ｎ１，ｎ２の両者から屈折率楕円体を基に各方向における屈折率が求められ、それを基に光偏向方向が求められる。しかし、ここでは簡単に液晶の配向状態によって屈折率ｎ１と屈折率ｎ２とが切り替わるものと仮定し、図５に示すようにスネルの法則に従うと仮定すれば、光偏向方向（以後、光偏向角と呼ぶ場合もある）を求めることが可能である。
【００２４】
図５において、液晶４の長軸方向の屈折率をｎ１ 、短軸方向の屈折率をｎ２ とし、光進行方向に対して液晶４の手前側界面の法線方向が光偏向方向となす角がψ１（≠０）、後方側界面の法線が入射光方向となす角が０°となるよう基板２，３を配置する。また、液晶と接する光学部材（鋸歯形状基板２）は屈折率ｎｇ のものを選ぶ。ここで、入射光の直線偏光方向が液晶の長軸方向と一致する場合、液晶の屈折率はｎ１ であり、スネルの法則によって手前側液晶界面での界面法線方向からの光偏向角ψ２ は、
ｓｉｎψ２＝（ｎｇ／ｎ１）ｓｉｎψ１
より求まり、また、液晶４を挟んだ対向基板３に入射する光線の対向基板の法線方向からの光偏向角ψ３ は、
ψ３＝ψ１−ψ２
より求まり、対向基板３に入射した光線の基板内での光偏向角ψ４ は、
ｓｉｎψ４＝（ｎ１／ｎｇ）ｓｉｎψ３
より求まる。
【００２５】
また、入射光の直線偏光方向が液晶の短軸方向と一致する場合は液晶の屈折率はｎ２ であり、この場合においても前記と同様にしてスネルの法則から光偏向角が求められる。
【００２６】
ここで、図４に示したように、中間基板６を設けて平行シフトを行なう場合、中間基板６の厚みをＬとすると、シフト量ｘ（μｍ）を得るために必要な厚みＬは、
Ｌ・ｓｉｎψ４＝ｘ（μｍ）
より、
Ｌ＝ｘ／ｓｉｎψ４ （μｍ）
となる。
【００２７】
このようにして、光偏向方向は主に鋸歯形状基板２の鋸歯傾斜角ψ１ と液晶４の屈折率異方性に起因して変化し、光偏向量は受光面までの距離、または液晶層厚さ、基板厚さなどによって調整することが可能である。
【００２８】
光偏向動作原理としては前述した通りであるが、後述のようにしても光偏向機能は得られる。例えば、光偏向素子の鋸歯形状基板２の屈折率ｎｇ が液晶の屈折率に一致する場合、基板と液晶層では屈折率差がないので入射光は基板の傾斜面を感じない。そのため、入射光はスネルの法則には従わずにそのまま直進する。このように基板の屈折率ｎｇ が液晶の長軸方向の屈折率、または短軸方向の屈折率のどちらか一方の屈折率に一致する際の光偏向動作は図６（ここでは、液晶の短軸方向の屈折率＝基板の屈折率としている）のようになる。つまり直進光と偏向光により光偏向機能を実現することもできる。ここで、出射光の光路長は受光面までの距離によって決定されるため、図６では明らかに光路長が異なる。光路長が異なると、それに伴なって結像位置がずれ、出射光は収差を含んでしまう。そこで、図１に示すように光偏向方向を入射光軸に対して対称にすることで、出射光の光路長差を小さくすることができる（請求項１）。
【００２９】
光偏向方向を入射光軸に対して対称にするには、前記鋸歯形状基板２の屈折率をｎｇ 、液晶層４の長軸方向の屈折率をｎ１（＝ｎｅ）、液晶層４の短軸方向の屈折率をｎ２（＝ｎｏ）（ｎ１＞ｎ２）とするとき、各屈折率をｎ１＞ｎｇ＞ｎ２の関係になるように設定すればよい。つまり、鋸歯形状基板２の屈折率、または液晶材料の複屈折率を前記関係になるよう選択することで、光偏向素子１からの出射偏向光は入射光軸に対して対称方向に出射され、設定される受光面位置において偏向光の光路長差をなくすことができる（請求項２）。
【００３０】
また、基板硝材と液晶の複屈折率の関係を、
０．９９・［（ｎ１＋ｎ２）／２］＜ｎｇ＜１．０１・［（ｎ１＋ｎ２）／２］
に設定することで更に精度よく入射光軸に対して対称方向に出射される。その精度は光路長差による影響を受けない程度あればよく、その対称性のズレは偏向角の平均から±１０％以下であることが好ましい。ｎｇとして、
０．９９・［（ｎ１＋ｎ２）／２］＜ｎｇ＜１．０１・［（ｎ１＋ｎ２）／２］
なる関係を満たす硝材を用いることで±１０％以下とすることができ、特にレーザー等の偏向方向制御に適用した場合、ビーム形状の劣化が少なく良好な出射光を得ることが可能となる（後述の実施例２参照）（請求項３）。
【００３１】
一般的に液晶は、可視光の波長範囲で屈折率は波長が短くなるとともに大きくなるという正常分散特性を示す。また、基板として用いることができる光学材料も屈折率の波長分散特性を示し、そのイメージを図７に示す。波長分散を定量的に表すものとしては次式で定義されるアッベ数が一般的に用いられ、図７のようにアッベ数が大きいと分散は小さく、アッベ数が小さいと分散が大きいといった特性となる。
【００３２】
ここで、鋸歯形状基板２の屈折率ｎｇ の波長特性と、液晶の各屈折率ｎ１（＝ｎｅ）、ｎ２（＝ｎｏ）（ｎ１＞ｎ２）の波長特性を、下記の式よりアッベ数として規定する。
νｄ＝（ｎｄ−１）／（ｎｆ−ｎｃ）
尚、ｎｄ、ｎｆ、ｎｃはそれぞれＤ線（５８７．６ｎｍ）、Ｆ線（４８６．１ｎｍ）、Ｃ線（６３６．３ｎｍ）各々の波長における屈折率である。
【００３３】
そこで、鋸歯形状基板のアッベ数を液晶の異常光成分屈折率ｎ１（＝ｎｅ）、常光成分屈折率ｎ２（＝ｎｏ）におけるアッベ数の平均から±１０％以内のズレになるように設定することで、比較的広域の波長帯域において波長依存性を少なくすることができる。基板としてはアッベ数の高い低分散硝材のクラウン（Ｋ）ガラス、逆に数値の低い高分散硝材のフリント（Ｆ）などが使用でき、例えばＢＫ７、Ｂａｋ４、ＬＬＦ１、Ｆ２、ＳＦ８などを用いることができる。また、複屈折性がなく透明であれば、アクリル、ポリカーボネイトなどのプラスチック材料も用いることができる（請求項４）。
【００３４】
液晶の特性としては他にも電圧依存特性などがあり、特にネマチック液晶の場合、電圧と透過率特性にはリニアリティがある。これは液晶のダイレクタ方向が電圧により多値に制御できることを示しており、液晶の実効的な屈折率も多値に制御可能となる。つまり基板と液晶の屈折率の差によって、光偏向方向は可変することができるため、印加する電圧の制御により、出射光の偏向角を多値に選択することが可能になる（請求項５）。
【００３５】
ここで液晶の初期配向の方向について示す。ネマチック液晶の初期配向の方向は、例えば図８に示すように、鋸歯形状の刻線方向と刻線とは異なった方向に分けられる。液晶の初期配向が鋸歯の刻線方向とは異なる方向に配向する場合、刻線部分による配向の乱れが顕著になる。また、液晶は鋸歯の傾斜部分に沿って配向するため、液晶ダイレクタ方向は鋸歯傾斜方向になる。しかし、鋸歯形状の形成されていない基板では、液晶ダイレクタ方向は入射光軸に対して垂直であり、液晶ダイレクタの方向は傾斜方向と垂直方向（入射光軸に対して）の２方向となる。つまり、入射光が感じる液晶の屈折率は傾斜方向と垂直方向の２方向の平均となり、ばらつきが生じる。
【００３６】
そこで、液晶の初期配向の方向を鋸歯形状基板の鋸歯刻線方向と一致するようにし、かつ、入射光の偏光方向を鋸歯形状基板の鋸歯刻線方向と一致させることで、液晶の配向乱れを少なくでき、かつ液晶の異常光成分（液晶の長軸方向の屈折率）に起因する実効的な屈折率のばらつきが少なくできる（請求項６）。
【００３７】
次に、本発明の光偏向素子を用いた画像表示装置について詳細に説明する。図９に画像表示装置の構成例を示す。この画像表示装置は、光源１０、光源駆動手段２０、照明装置１１、画像表示素子１４、表示駆動手段２１、縮小光学素子１５、光偏向素子１６、光偏向電圧制御手段２２、画像表示制御回路１９、投射レンズ１７、スクリーン１８などから成る。光源１０としては、白色あるいは任意の色の光を高速にＯＮ／ＯＦＦできるものならば全て用いることができる。例えば、ＬＥＤランプやレーザー光源、白色のランプ光源にシャッターを組合わせたものなど用いることができる。照明装置１１は光源１０から出た光を均一に画像表示素子１４に照射するものであり、拡散板１２、コンデンサレンズ１３、あるいはフライアイレンズなどから構成される。画像表示素子１４は、入射した均一照明光を空間光変調して出射するもので、透過型液晶ライトバルブ、反射型液晶ライトバルブ、ＤＭＤ（Ｄｉｇｉｔａｌ Ｍｉｃｒｏ−ｍｉｒｒｏｒ Ｄｅｖｉｃｅ）素子などを用いることができる。図９に示す構成例では、光源駆動手段２０で制御されて光源１０から放出された光は、照明装置１１の拡散板１２により均一化された照明光となり、コンデンサレンズ１３により画像表示素子１４をクリティカル照明する。ここでは、画像表示素子１４の一例として透過型液晶ライトバルブを用いている。この液晶ライトバルブで空間光変調された照明光は、画像光として投射レンズ１７で拡大されスクリーン１８に投射される。
【００３８】
縮小光学素子１５はライトバルブの表示画素を縮小するもので、マイクロレンズ、コリメートレンズなどから構成される。その縮小量は画素ピッチの整数分の１であることが好ましい。
ここで、液晶ライトバルブ１４と縮小光学素子１５の後方に配置された光偏向素子１６を電圧制御手段２２により印加電圧を制御することで、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。
【００３９】
光偏向素子１６としては、前述の構成の光偏向素子が用いられる（請求項７）。この光偏向素子１６の配置位置は画像表示素子１４から表示される画素のデフォーカス位置に配置し、表示画像の解像度を劣化させない構成とする。シフト量は縮小量と同様に画素ピッチの整数分の１であることが好ましく、シフト量と縮小量が等しい場合、シフトした画素が重なることはない。そのため、画素シフト効果により解像度を落とすこともない。また、シフト量と縮小量が異なる場合にはシフトした画素は重なる、あるいは画素間が広がるなどして解像度を落とす原因となるが、表示画像に問題がない程度であれば、シフト量と縮小量は等しくなくてもよい。
【００４０】
具体的には、画素の配列方向に対して２倍の画像増倍を行う場合は画素ピッチの１／２にし、３倍の画素増倍を行う場合は画素ピッチの１／３にする。また、光偏向電圧制御手段２２の構成によってシフト量が大きくなる場合には、シフト量、画素縮小量を画素ピッチの「整数倍＋整数分の１」の距離に設定しても良い。いずれの場合も、画素のシフト位置に対応したサブフィールドの画像信号で液晶ライトバルブ１４を駆動すれば、図１０に示すように見かけ上の画素増倍効果が得られ、使用したライトバルブの解像度以上の高精細画像を表示することができる。
【００４１】
図９に示す構成の画像表示装置では、透過型液晶ライトバルブにカラーフィルターを組み合わせた画像表示素子１４を用い、光源１０に白色ランプを用いることによりカラーの画像表示装置とすることができる。また、単板の画像表示素子を時間順次に三原色光で照明するフィールドシーケンシャル方式でもフルカラー画像を表示することができる。この時、白色ランプ光源と回転カラーフィルターを組み合わせて時間順次の三原色光を生成しても良い。
【００４２】
次に図１１に画像表示装置における光偏向素子の配置の概略を示す。光偏向素子１６の鋸歯形状は紙面の上下方向にアレイ状に形成されている。画像表示素子１４を出射した光が紙面の上下方向の直線偏光の場合、光偏向素子１６により画像表示素子１４からの画像の全体を紙面の左右方向に画素シフトさせることができる。
【００４３】
ここで、光偏向素子１６の構成は、例えば図３に示すような２つの光偏向素子１を配設した構成とする。即ち、この例の画像表示装置では、光偏向素子１６は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域（鋸歯形状部）を有し、第一の傾斜領域（第一の光偏向素子の鋸歯形状部）で屈折された光が、一定間隔をおいて設置された第二の傾斜領域（第二の光偏向素子の鋸歯形状部）に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置された光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子１４の見かけ上の画素数を増倍して表示する。この場合、光路シフト量は、図３に示すように光偏向素子１間の距離Ｘによって設定され、画素ピッチの１／２となるように設定する。光偏向動作において光偏向素子１６からの出射光の光路長は常に同じであるため、表示画面の横方向シフトにおいて高精細で収差のない画像表示装置が実現できる（請求項８）。
【００４４】
また、別の例として、光偏向素子１６の構成を図１のような構成とする。即ち、この例の画像表示装置では、光偏向素子１６は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の傾斜領域（鋸歯形状部）を有し、該傾斜領域（鋸歯形状部）で屈折された光が偏向光として出射するような光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子の見かけ上の画素数を増倍して表示する。この場合、光路シフト量は光偏向素子１６からの距離により、画素ピッチの１／２だけシフトする位置に結像位置を設定するように光学系を組む。光偏向動作において、光偏向素子１６からの偏向角は入射光軸に対して対称であるため、出射光の光路長は常に同じである。即ち、前述の素子構成に比べて、比較的簡単な素子構成で表示画面の横方向シフトにおいて高精細で収差のない画像表示装置が実現できる（請求項９）。
【００４５】
次に、本発明の光偏向素子を用いた光偏向装置について詳細に説明する。
本発明の光偏向装置は、前述した構成の光偏向素子を複数用い、前記光偏向素子が多段に配置されてなる構成である（請求項１０）。
より詳しく述べると、本発明の光偏向装置は、光偏向素子として、例えば図３に示すように、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域（鋸歯形状部）を有し、第一の傾斜領域（第一の光偏向素子の鋸歯形状部）で屈折された光が、一定間隔をおいて設置された第二の傾斜領域（第二の光偏向素子の鋸歯形状部）に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置され、出射偏向光の偏向角が基板面の法線方向に対して対称であることを特徴とする光偏向素子を複数用い、前記光偏向素子が多段に配置されてなる構成である（請求項１１）。
【００４６】
さらに具体的に説明すると、本発明の光偏向装置は、図３に示すような２つの光偏向素子１を配設した構成の光偏向素子を複数用い、この複数の光偏向素子▲１▼，▲２▼，▲３▼，・・・を図１２に示すように多段（図１２では３段）に配置し、複数の光偏向素子▲１▼，▲２▼，▲３▼を選択的に駆動することで、入射光は任意の位置へ出力可能になる。例えば、入射光を出力位置［２］に出力する場合、光偏向素子▲１▼をＯＮにし、光偏向素子▲２▼はＯＦＦ、光偏向素子▲３▼をＯＦＦにすることで出力位置［２］に出力することができる（出力位置［２］に出力するために駆動する光偏向素子の選択は他にもある。例えば、光偏向素子▲１▼をＯＦＦにし、光偏向素子▲２▼はＯＦＦ、光偏向素子▲３▼をＯＮなど）。
このようにして複数の光偏向素子▲１▼，▲２▼，▲３▼を選択的に駆動することで、入射光は任意の位置へ出力可能になる。さらにここでは、偏向角が入射光軸に対して対称な光偏向素子を用いることで、出射位置での光の歪み、つまり出射光における収差は少なくできる。
【００４７】
また、光偏向装置の別の例として、図４に示すように、対向して配置された一対の傾斜領域（鋸歯形状部）の間に中間基板６を有する構成の光偏向素子を複数用い、この複数の光偏向素子▲１▼，▲２▼，▲３▼，・・・を図１３に示すように多段（図１３では３段）に配置し、複数の光偏向素子▲１▼，▲２▼，▲３▼，・・・の中間基板厚ｄを、それぞれ入射光側から順にｄ１、ｄ２、ｄ３、・・・とする場合、
ｄｍ＝ｄｍ− １／２ｍ− １（ｍ＝１，２，３，・・・、但しｄ０＝ｄ１）
の関係を満たすことで、図１３に示すように、３段の光偏向素子▲１▼，▲２▼，▲３▼を通過する光路のシフト量は素子を通過する度に半分になる。そのため複数の光偏向素子▲１▼，▲２▼，▲３▼を選択的に駆動することで出射光は等間隔の位置に光路シフトすることができ、出力位置は倍増する（請求項１２）。
【００４８】
【実施例】
次に本発明の具体的な実施例について説明する。
まず、光偏向素子の作製方法について説明する。
大きさ３ｃｍ×４ｃｍ、厚さ１ｍｍのガラス基板（白板）をドライエッチングして、傾き角が約１°、ピッチ１００μｍの鋸歯形状を１ｃｍ×１ｃｍの面積に形成した鋸歯形状基板２を形成した後、鋸歯形状基板２の鋸歯形状面に透明電極５としてＩＴＯを１５００Åの厚さにスパッタした。次にポリイミド配向剤ＡＬ３０４６−Ｒ３１（ＪＳＲ）を約８００Åの厚さに塗布し、その基板表面を、ホモジニアス方向の安定方向が傾斜領域の傾斜方向に垂直な方向になるような条件（鋸歯形状の刻線方向）でラビング法により配向処理を行った。次に平滑な面のＩＴＯ付きガラス基板を対向基板３として、液晶層厚の小さい部分が３μｍになるようにビーズを混入した接着剤を用いて貼り合わせた。その後、２枚の基板間に液晶４を毛管法で注入方向が鋸歯形状に沿うようにして注入し、紫外線（ＵＶ）硬化接着剤により封止をした。このようにして図１に示す構成の光偏向素子１を作製した。
【００４９】
（比較例１）
前記した光偏向素子の作製方法において、液晶として屈折率がｎｅ＝１．７５、ｎｏ＝１．５２であるネマチック液晶（Ｅ７ メルク）を注入した。この素子をサンプル１とする。また、基板の屈折率はｎｇ＝１．５２である。
【００５０】
（実施例１）
前記した光偏向素子の作製方法において、液晶として屈折率がｎｅ＝１．５８、ｎｏ＝１．４８であるネマチック液晶（ＺＬＩ−４７９２ メルク）を注入した。この素子をサンプル２とする。また、基板の屈折率はｎｇ＝１．５２である。
【００５１】
ここで、作製した光偏向素子に電圧を印加して動作させる。印加電圧はファンクションジェネレイターを用いて±１５Ｖの電圧を印加した。入力波形は矩形波とし、電圧値はテスターで確認した。光偏向素子への入射光は約１ｍｍ径の白色レーザー光を用い、波長選択フィルター（５８８ｎｍ）を通過させて入射光の波長を設定した。さらに光偏向素子とレーザー装置の間に偏光板を設置し、直線偏光の方向を鋸歯刻線方向に設定し、鋸歯形状アレイ位置へ入射させた。
【００５２】
このようにして光偏向素子を動作させ、光偏向素子を通過する透過光をＣＣＤカメラにより観察した。ＣＣＤカメラは素子から１ｍ離した距離に設置した。その結果、電圧によって透過光が偏向することが確認できた。この光偏向動作は比較例１に対しても確認することできた。しかし、光偏向時に観察したレーザー光の光偏向光による像は実施例１に比べて比較例１ではボケていた。そこで、光偏向光におけるＣＣＤカメラの位置までの光路長差を計算し、光路長差の計算結果と表示画像の観察結果を下記の表１にまとめたところ、光路長差の大きな比較例１は像がボケていたが、光路長差の少ない実施例１では像がぼけていなかった。
光路長差は液晶の屈折率と基板の屈折率により設定されるため、実施例１のように液晶と基板の屈折率がｎｅ＞ｎｇ＞ｎｏの関係を満たすことで収差のない表示像が得られることが分かる。
【００５３】
【表１】

Figure 2004233659
【００５４】
（実施例２）
前記した光偏向素子の作製方法において、液晶として屈折率がｎｅ＝１．６２、ｎｏ＝１．５０であるネマチック液晶（ＺＬＩ−２４７１ メルク）を注入した。この素子をサンプル３とする。また、基板の屈折率はｎｇ＝１．５２である。
ここで実施例１と同様にして電圧を印加し、素子を駆動させて光偏向動作をＣＣＤカメラにより観察した。その結果、光偏向動作は確認できたが観察像は少しボケていた。
【００５５】
光偏向時の光路長差を計算した結果を実施例１の結果とともに下記の表２に示す。表２から光路長差が大きくなると像がボケるということが分かる。また、光路長差は液晶の屈折率と基板の屈折率により設定されるため、ｎｅ＞ｎｇ＞ｎｏかつ、０．９９・［（ｎ１＋ｎ２）／２］＜ｎｇ＜１．０１・［（ｎ１＋ｎ２）／２］の関係を満たすことで収差のない表示像が得られることが分かる。
【００５６】
【表２】
Figure 2004233659
【００５７】
（実施例３）
実施例１と同様にして作製した光偏向素子（サンプル２）を用いて、駆動する印加電圧を±０〜±１５Ｖと可変にしたところ、印加電圧の大きさによって光偏向量は多値に異なっていた。また、キラルスメクチックＣ相からなる強誘電性液晶（Ｒ５００２ クラリアント）を用いて同様に光偏向素子を作製し、印加電圧を±０〜２０Ｖまで可変に設定したところ、光偏向量は一定の値しかとらなかった。つまり、ネマチック液晶のリニアな電界依存性により、多値の光偏向が可能になることが分かった。
【００５８】
（実施例４）
実施例１の光偏向素子（サンプル２）をモデルとして短波長（Ｆ線）側と長波長（Ｃ線）側における光偏向動作時の光路長差（素子とディテクタの距離は１ｍとした）を計算した。この時の基板の硝材はＬＬＦ１またはＢＫ７とした。下記の表３，４に計算結果および液晶と硝材のＤ線（５８７．６ｎｍ）、Ｃ線（６３６．３ｎｍ）、Ｆ線（４８６．１ｎｍ）に対する屈折率とアッベ数を示す。また、図１４に、液晶（ＺＬＩ−４７９２）の常光、異常光の屈折率（ｎｏ、ｎｅ）及びＬＬＦ１の屈折率の波長特性を示す（図中のａは液晶の常光の屈折率ｎｏ、ｂは液晶の異常光の屈折率ｎｅ、ｃはＬＬＦ１の屈折率である）。
計算結果からＦ線での光路長差とＣ線での光路長差の差（Ｆ線−Ｃ線）は異なっており、ＬＬＦ１の方がその差が小さいためＦ線とＣ線における波長依存性が少ないことが分かる。
【００５９】
ここで、下記の表３に示す液晶（ＺＬＩ−４７９２）のｎｏとｎｅのアッベ数の平均は４２．６となり、この平均から±１０％ズレた範囲は３８．４〜４６．９である。硝材のアッベ数を比較すると、ＬＬＦ１は前記範囲内にあるが、ＢＫ７は範囲外にある。すなわち、硝材のアッベ数が液晶のｎｏとｎｅのアッベ数の平均から±１０％ズレた範囲内にあることで波長依存性は少なくなる。
【００６０】
【表３】
Figure 2004233659
【００６１】
【表４】
Figure 2004233659
【００６２】
（実施例５）
次に図９に示すような構成の画像表示装置を作製した。画像表示素子１４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（液晶ライトバルブ）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１４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。光源１０としては白色ランプを用い、カラーフィルターを各画素表面に設けた透過型液晶ライトバルブ１４により、カラー表示を行なった。また、マイクロレンズ、コリメートレンズを用いて縮小光学素子１５を構成し、液晶ライトバルブ１４の直後に設置して、画素位置との位置合わせを調整した。光偏向素子１６として実施例１で作製した素子を用い、縮小光学素子１５の後に設置した。投射光学系の結像位置はシフト量が９μｍになるように調整した。また、液晶セルの出射側に薄い拡散層を有する拡散板を合わせて、出射面での拡散光を拡大し、表示画像を観察した結果、比較例１の素子を用いた場合の表示画像に比べて、ボケが少なく横方向の画素密度が二倍の高精細な表示画像が得られた。
【００６３】
（実施例６）
次に図３のように、２つの光偏向素子１を用い、傾斜領域面（鋸歯形状部）が互いに対向するように配置した構成の光偏向素子を作製する。そして図３のように構成したペアの光偏向素子を複数用い、図１２に示すように光偏向素子▲１▼，▲２▼，▲３▼を３つ並べて光偏向装置を作製した。この光偏向素子を構成するペアの光偏向素子１は全て実施例１と同様にして作製したものである。各光偏向素子に電圧を印加して駆動するための電源を３台用意し、各ペアの光偏向素子がそれぞれ駆動できるように設置した。ここで、ペアの光偏向素子は同一の電源で駆動するように配線した。
【００６４】
入射光には実施例１と同様のレーザー光を使用し、光を入射する前に各ペアの光偏向素子▲１▼，▲２▼，▲３▼の駆動のＯＮ、ＯＦＦを選択しておく。選択肢としては数通りあるが、ここでは下記の表５のように４通りの選択肢について実験した。その結果、各ペアの光偏向素子の駆動のＯＮ、ＯＦＦを選択することで、任意の出力位置に光を出射することができた。このときの出射光の像をＣＣＤカメラで観察したところ、ビーム形状に歪みはなかった。
【００６５】
【表５】
Figure 2004233659
【００６６】
【発明の効果】
以上説明したように、請求項１に係る発明では、一対の透明基板と、該基板間に挟まれ電圧印加によって配向を制御することにより入射光に対する屈折率の制御が可能な液晶層と、該液晶層に電圧を印加することが可能な電圧印加制御手段とを備え、前記一対の基板のうち少なくとも一方の基板は、液晶層側の面に光偏向方向に対応して傾斜している鋸歯形状部を形成してなる鋸歯形状基板である光偏向素子において、出射偏向光の偏向角が入射光軸に対して対称であるため、設定される受光面位置において偏向光の光路長差をなくすことができる。
【００６７】
請求項２に係る発明では、一対の透明基板と、該基板間に挟まれ電圧印加によって配向を制御することにより入射光に対する屈折率の制御が可能な液晶層と、該液晶層に電圧を印加することが可能な電圧印加制御手段とを備え、前記一対の基板のうち少なくとも一方の基板は、液晶層側の面に光偏向方向に対応して傾斜している鋸歯形状部を形成してなる鋸歯形状基板である光偏向素子において、入射光波長における前記鋸歯形状基板の屈折率をｎｇ、液晶駆動（光偏向動作）時に入射光が感じる液晶の実効的な屈折率をｎ１（＝ｎｅ）、ｎ２（＝ｎｏ）（ｎ１＞ｎ２）とするとき、ｎ１＞ｎｇ＞ｎ２の関係を満たすように各屈折率を設定することで、光偏向素子からの出射偏向光は入射光軸に対して対称方向に出射され、設定される受光面位置において偏向光の光路長差をなくすことができる。
【００６８】
請求項３に係る発明では、請求項２記載の光偏向素子において、入射光波長における前記鋸歯形状基板の屈折率をｎｇ、液晶駆動（光偏向動作）時に入射光が感じる液晶の実効的な屈折率をｎ１（＝ｎｅ）、ｎ２（＝ｎｏ）（ｎ１＞ｎ２）とするとき、
０．９９・［（ｎ１＋ｎ２）／２］＜ｎｇ＜１．０１・［（ｎ１＋ｎ２）／２］
の関係を満たすように各屈折率を設定することで、光偏向素子からの出射偏向光は入射光軸に対して対称方向に出射され、設定される受光面位置において、精度よく偏向光の光路長差をなくすことができる。
【００６９】
請求項４に係る発明では、請求項２または３記載の光偏向素子において、前記鋸歯形状基板のアッベ数が液晶の異常光（ｎ１＝ｎｅ）、常光（ｎ２＝ｎｏ）におけるアッベ数の平均から±１０％以内のズレであることを特徴とし、液晶における屈折率の波長特性と基板における屈折率の波長特性のズレが小さくなるように前記鋸歯形状基板のアッベ数を規定することで、広波長帯域における波長依存性を低減することができる。
【００７０】
請求項５に係る発明では、請求項１〜４のいずれか一つに記載の光偏向素子において、前記液晶層がネマチック液晶であるため、印加電圧によって液晶の実効的な屈折率を段階的に変化させることができる。
また、請求項６に係る発明では、請求項５記載の光偏向素子において、前記ネマチック液晶の初期配向方向と入射光の偏光方向が前記鋸歯形状基板の鋸歯刻線方向と一致するため、液晶の配向は傾斜面の影響を受けずに均一に配向することができる。さらに、入射光の偏光方向を鋸歯形状基板の鋸歯刻線方向と一致させることで、液晶の異常光成分（液晶ダイレクタの長軸）に起因する実効的な屈折率のばらつきを少なくできる。
【００７１】
請求項７に係る発明では、少なくとも、画像情報に従って光を制御可能な複数の画素が二次元配列した画像表示素子と、該画像表示素子を照明する光源と、前記画像表示素子に表示した画像パターンを観察するための光学部材と、該光学部材の間の光路を偏向する光偏向素子を有する画像表示装置であり、光偏向素子は請求項１〜６のいずれか一つに記載の光偏向素子からなることにより、請求項１〜６の効果が得られ、収差の少ない高精細画像を表示する画像表示装置を実現することができる。
【００７２】
請求項８に係る発明では、請求項７記載の画像表示装置において、前記光偏向素子は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域を有し、第一の傾斜領域で屈折された光が、一定間隔をおいて設置された第二の傾斜領域に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置された光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子の見かけ上の画素数を増倍して表示することを特徴とするので、前記光偏向素子の印加電圧を切換えることで光路をシフトすることができる。また、光偏向時の偏向方向は入射光軸に対して対称であるため、出射偏向光の光路長差は小さい。即ち、表示画像の画素数を増倍し、収差の少ない表示画像を得ることができる。
【００７３】
請求項９に係る発明では、請求項７記載の画像表示装置において、前記光偏向素子は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の傾斜領域を有し、該傾斜領域で屈折された光が偏向光として出射するような光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子の見かけ上の画素数を増倍して表示することを特徴とするので、素子構成が簡単な光偏向素子の印加電圧を切換えることで光路をシフトすることができる。また、光偏向時の偏向方向は入射光軸に対して対称であるため、出射偏向光の光路長差は小さい。即ち、表示画像の画素数を増倍し、収差の少ない表示画像を得ることができる。
【００７４】
請求項１０に係る発明では、請求項１〜６のいずれかに記載の光偏向素子を複数用い、前記光偏向素子が多段に配置されてなることを特徴とするので、多段に配置した複数の光偏向素子を選択的に駆動することで、出射光を任意の位置に光路シフトすることが可能となる。
請求項１１に係る発明では、請求項１０記載の光偏向装置において、前記光偏向素子として、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域を有し、第一の傾斜領域で屈折された光が、一定間隔をおいて設置された第二の傾斜領域に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置され、出射偏向光の偏向角が基板面の法線方向に対して対称であることを特徴とする光偏向素子を複数用い、前記光偏向素子が多段に配置されてなることを特徴とするので、多段に配置した複数の光偏向素子を選択的に駆動することで、出射光を任意の位置に光路シフトすることができる。また、出射偏向光の偏向角が入射光軸に対して対称であるため、出射光における収差を少なくすることができる。
【００７５】
請求項１２に係る発明では、請求項１１記載の光偏向装置において、前記光偏向素子は対向して配置された一対の傾斜領域の間に中間基板を有し、多段に配置された複数の光偏向素子の中間基板厚ｄを、それぞれ入射光側から順にｄ１、ｄ２、ｄ３、・・・ とする場合、
ｄｍ＝ｄｍ− １／２ｍ− １ （ｍ＝１，２，３，・・・、但しｄ０＝ｄ１）
の関係を満たすことを特徴とするので、光偏向素子を通過する光路シフト量は素子を通過する度に半分になる。そのため複数の光偏向素子を選択的に駆動することで出射光は等間隔の位置に光路シフトすることができ、出力位置は倍増する。また、出射偏向光の偏向角が入射光軸に対して対称であるため、出射光における収差を少なくすることができる。
【図面の簡単な説明】
【図１】本発明の光偏向素子の基本構成例を示す図である。
【図２】図１に示す光偏向素子の液晶配向状態の変化の説明図である。
【図３】本発明の光偏向素子の別の構成例を示す図である。
【図４】本発明の光偏向素子の別の構成例を示す図である。
【図５】本発明の光偏向素子における偏向理論の説明図である。
【図６】本発明の光偏向素子の別の構成例を示す図である。
【図７】液晶の屈折率及び基板硝材の屈折率の波長特性を示す図である。
【図８】鋸歯形状基板を用いた場合の液晶の初期配向状態の例を示す説明図である。
【図９】本発明に係る画像表示装置の概略構成例を示す図である。
【図１０】光偏向素子を用いた場合の見かけ上の画素倍増の様子を示す図である。
【図１１】画像表示装置における光偏向素子の配置の概略を示す図である。
【図１２】本発明に係る光偏向装置の概略構成例を示す図である。
【図１３】本発明に係る光偏向装置の別の概略構成例を示す図である。
【図１４】液晶（ＺＬＩ−４７９２）の常光、異常光の屈折率（ｎｏ、ｎｅ）及びＬＬＦ１の屈折率の波長特性を示す図である。
【符号の説明】
１：光偏向素子
２：鋸歯形状基板
２ａ：鋸歯形状部（傾斜領域）
３：対向基板
４：液晶層（液晶）
４ａ：液晶分子
５：透明電極
６：中間基板
１０：光源
１１：照明装置
１２：拡散板
１３：コンデンサレンズ
１４：画像表示素子（透過型液晶ライトバルブ）
１５：縮小光学素子
１６：光偏向素子
１７：投射レンズ
１８：スクリーン
２０：光源駆動手段
１９：画像表示制御回路
２１：表示駆動手段
２２：光偏向電圧制御手段
▲１▼，▲２▼，▲３▼：光偏向素子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light deflecting element and a light deflecting device that change the direction of light by an electric signal, and an image display device using the light deflecting element.
[0002]
[Prior art]
Conventionally, KH has been used as an optical element used as a light deflecting element.2PO4(KDP), NH4H2PO4(ADP), LiNbO3, LiTaO3, GaAs, CdTe, etc., materials having a large primary electro-optic effect (Pockels effect), KTN, SrTiO3, CS2Device using a material having a large secondary electro-optic effect, such as glass, silica, TeO2An acousto-optic device using such a material is known (for example, see Non-Patent Document 1). These generally require a long optical path length in order to obtain a sufficiently large light deflection amount, and their use is limited due to the expensive material.
[0003]
On the other hand, various types of optical elements, which are optical deflection elements using a liquid crystal material, have been proposed, and there are the following proposals to name a few.
For example, according to Patent Document 1 below, a light beam shifter including an artificial birefringent plate has been proposed for the purpose of reducing light loss of an optical space switch. In detail, two wedge-shaped transparent substrates are arranged in opposite directions, a light beam shifter having a liquid crystal layer sandwiched between the transparent substrates, and a light in which the light beam shifter is connected to a rear surface of a matrix-type deflection control element. A beam shifter has been proposed. In addition, two wedge-shaped transparent substrates are arranged in opposite directions, and a matrix drive can be performed between the transparent substrates, and a light beam shifter that sandwiches a liquid crystal layer that shifts an incident light beam by half a cell is used. There has been proposed a light beam shifter in which a half cell is shifted and connected in multiple stages.
[0004]
Further, according to Patent Literature 2 below, there is proposed 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. Specifically, two transparent substrates are arranged facing each other at a predetermined interval, the surfaces facing each other are subjected to a vertical alignment treatment, a ferroelectric liquid crystal of a smectic A phase is sealed between the transparent substrates, and the transparent substrate is sealed. The liquid crystal device is provided with a driving device that vertically aligns the electrodes with each other so that an AC electric field can be applied in parallel with the smectic layer, and that applies an AC electric field to the electrode pairs. That is, the refraction angle and the direction of displacement of the polarized light incident on the liquid crystal layer can be changed by the birefringence caused by the tilt of the liquid crystal molecules using the electroclinical effect of the ferroelectric liquid crystal of the smectic A phase.
[0005]
In addition, in an example using an optical deflecting element, an optical deflecting device that can be driven at a low voltage and has a two-dimensional and miniaturized size has been proposed (see Patent Document 3). This holds liquid crystal having birefringence between a pair of transparent substrates, and a sawtooth lattice is formed on one of the transparent substrates. The held liquid crystal is homogeneously oriented in the direction of the sawtooth grating, and the refractive index of either the long axis or the short axis of the liquid crystal matches the refractive index of the material forming the sawtooth grating. The polarization direction of the incident light can be rotated by 90 ° under the control of the deflecting rotation device, and the direction of the outgoing light can be switched according to the polarization state of the incident light. Further, as a similar configuration, there are two transparent substrates having a sawtooth grating formed on one surface of the substrate, and the sawtooth gratings face in opposite directions, have the same shape, and have the same refractive index. (See Patent Document 4).
[0006]
[Patent Document 1]
JP-A-6-18940
[Patent Document 2]
JP-A-9-133904
[Patent Document 3]
JP-A-5-204001
[Patent Document 4]
JP-A-9-133931
[Non-patent document 1]
Shoji Aoki, "Optoelectronic Devices", Shokodo
[0007]
[Problems to be solved by the invention]
In the above-mentioned prior art, the principle of light deflection is mainly due to the birefringence of the liquid crystal material and the inclination of the substrate with respect to incident light.
For example, according to the prior art described in Patent Document 1, a liquid crystal material is sealed between two wedge-shaped substrates arranged in opposite directions of inclination, and the liquid crystal is aligned homogeneously with respect to the substrate surface. ing. When a voltage is applied between the substrates, the orientation of the liquid crystal between the substrates (the director direction of the liquid crystal molecules) changes, and the direction is homeotropically aligned with the substrate surface. Here, when the polarization direction of the incident light is the same direction as the direction of the homogeneous alignment, the effective refractive index of the liquid crystal layer felt by the incident light is perceived as extraordinary light when the orientation of the liquid crystal is homogeneous, and When the orientation is homeotropic orientation, it is perceived as ordinary light. Here, by matching the refractive index that is perceived as extraordinary light or ordinary light with the refractive index of the substrate, it is possible to select two types of light incident on the element: straight traveling light and deflected light. Is achieved. Note that the light deflection function includes a parallel shift of the optical path.
However, in the above-described prior art, there is a problem that a difference occurs in the optical path length between the straight traveling light and the deflected light, so that the aberration of the outgoing light deflected due to the difference in the optical path length increases. Further, in a configuration using a wedge-shaped substrate, it is necessary to increase the thickness of the substrate, and there is also a problem that the entire element becomes large.
[0008]
In the prior art described in Patent Document 2, two transparent substrates are arranged to face each other, a ferroelectric liquid crystal of a smectic A phase is homeotropically aligned with respect to the substrate surface between the substrates, and an AC electric field is applied in parallel with the smectic layer. It is configured to apply voltage. This uses the electroclinical effect of the ferroelectric liquid crystal of the smectic A phase, and can change the deflection angle incident on the liquid crystal layer by birefringence due to the tilt of the liquid crystal molecules, reducing the optical path length difference during light deflection. can do. However, an electric field must be applied in parallel with the smectic layer in order to obtain an electroclinical effect. That is, an electrode must be provided at the edge of the substrate to generate a horizontal electric field with respect to the substrate surface. In such a horizontal electric field, the electric field intensity varies depending on the position of the device. Therefore, the amount of light deflection (the amount of optical path shift) differs between the vicinity of the electrodes of the device and the intermediate position between the electrodes, and there is a problem that the reliability is practically lacking.
[0009]
In the prior arts described in Patent Documents 3 and 4, miniaturization is realized by making the substrate surface into a saw-tooth shape. However, the light deflecting function is the same as that of Patent Document 1, and the light is deflected by the light that goes straight and the light that deflects, so that there is a large difference in the optical path length to the position where the outgoing light is received, and the outgoing angle Therefore, there is a problem that the outgoing deflected light includes a large aberration in the light deflector operation. Further, when the conventional light deflecting element is applied to an image display device or the like, there is a problem that an image forming position is different and a displayed image is blurred and deteriorated.
[0010]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has a configuration in which the light deflecting direction in the light deflecting operation is symmetrical with the incident optical axis and the deflection angles are made to coincide with each other, so that the optical path It is an object of the present invention to provide an optical deflecting element capable of reducing aberration due to a difference in length, and further to provide an optical deflecting device and an image display device using the optical deflecting element.
[0011]
More specifically, the invention according to claims 1 to 3 aims at providing an optical deflecting element having no optical path length difference in the outgoing deflecting light, and the invention according to claim 4 provides, in addition to the above object, It is an object of the present invention to provide an optical deflecting element having less wavelength dependence of outgoing deflected light in a wide wavelength band. In addition to the above objects, the invention according to Claims 5 and 6 has no optical path length difference in outgoing deflected light, It is another object of the present invention to provide an optical deflecting element capable of selecting a multi-valued deflection angle.
Another object of the present invention is to provide an image display device that displays a high-definition image with less aberration using the light deflecting element.
It is a further object of the present invention to provide an optical deflecting device that uses the optical deflecting element, has less aberration of emitted light, and can shift the optical path from the incident optical axis to an arbitrary position. .
[0012]
[Means for Solving the Problems]
As means for solving the above-mentioned problems, the invention according to claim 1 can control the refractive index with respect to incident light by controlling the orientation by applying a voltage between a pair of transparent substrates and the substrates. A liquid crystal layer, and voltage application control means capable of applying a voltage to the liquid crystal layer, wherein at least one of the pair of substrates is tilted on the surface on the liquid crystal layer side in accordance with the light deflection direction. An optical deflecting element which is a saw-tooth-shaped substrate formed by forming a saw-tooth-shaped portion, wherein a deflection angle of light deflected by the liquid crystal layer and emitted is symmetric with respect to an incident optical axis. Things.
[0013]
The invention according to claim 2 provides a pair of transparent substrates, a liquid crystal layer sandwiched between the substrates, a liquid crystal layer capable of controlling the refractive index with respect to incident light by controlling the alignment by applying a voltage, and applying a voltage to the liquid crystal layer. At least one of the pair of substrates is formed with a sawtooth-shaped portion inclined on the surface on the liquid crystal layer side corresponding to the light deflection direction. In the light deflecting element that is a sawtooth-shaped substrate, the refractive index of the sawtooth-shaped substrate at the wavelength of the incident light is ng, the effective refractive index of the liquid crystal sensed by the incident light when driving the liquid crystal (light deflecting operation) is n1 (= ne), When n2 (= no) (n1> n2),
n1> ng> n2
Is satisfied.
According to a third aspect of the present invention, in the optical deflecting element according to the second aspect, the refractive index of the sawtooth-shaped substrate at the wavelength of the incident light is ng, and the effective liquid crystal sensed by the incident light when driving the liquid crystal (light deflecting operation). When the refractive indexes are n1 (= ne) and n2 (= no) (n1> n2),
0.99 · [(n1 + n2) / 2] <ng <1.01 · [(n1 + n2) / 2]
Is satisfied.
Furthermore, the invention according to claim 4 is the optical deflecting element according to claim 2 or 3, wherein the Abbe number of the sawtooth-shaped substrate is an Abbe number of an abnormal light (n1 = ne) and an ordinary light (n2 = no) of the liquid crystal. The deviation is within ± 10% from the average.
[0014]
The invention according to claim 5 is the optical deflection element according to any one of claims 1 to 4, wherein the liquid crystal layer is a nematic liquid crystal.
According to a sixth aspect of the present invention, in the optical deflecting element according to the fifth aspect, the initial alignment direction of the nematic liquid crystal and the polarization direction of the incident light coincide with the sawtooth cutting line direction of the sawtooth-shaped substrate. Is what you do.
[0015]
The invention according to claim 7 is an image display device, wherein at least an image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, a light source illuminating the image display element, and the image display device An optical member for observing an image pattern displayed on the element, and a light deflecting element for deflecting an optical path between the optical members, the light deflecting element according to any one of claims 1 to 6. It is characterized by comprising a light deflection element.
According to an eighth aspect of the present invention, in the image display device according to the seventh aspect, the light deflecting element comprises a pair of inclined planes having a non-parallel substrate spacing and a constant inclination angle ψ with respect to a traveling direction of incident light. Having a region, the light refracted by the first inclined region is incident on a second inclined region provided at a fixed interval, and is refracted again by the second inclined region and emitted as substantially parallel light. As described above, the first inclined region and the second inclined region are constituted by optical deflecting elements arranged to face each other, and an image pattern in a state where the display position is shifted according to the deflection of the optical path for each subfield is displayed. In this case, the display is performed by multiplying the apparent number of pixels of the image display element.
[0016]
According to a ninth aspect of the present invention, in the image display device according to the seventh aspect, the light deflecting element has an inclined region having a non-parallel substrate interval and a constant inclination angle ψ with respect to a traveling direction of incident light. An image deflecting element that emits light refracted by the inclined region as deflecting light, and displays an image pattern in a state where the display position is shifted in accordance with the deflection of the optical path for each subfield, thereby forming an image. It is characterized in that display is performed by multiplying the apparent number of pixels of the display element.
[0017]
A tenth aspect of the present invention is an optical deflecting device, wherein a plurality of the optical deflecting elements according to any one of the first to sixth aspects are used, and the optical deflecting elements are arranged in multiple stages. is there.
According to an eleventh aspect of the present invention, in the optical deflecting device according to the tenth aspect, as the optical deflecting element, a pair of inclined substrates having a non-parallel substrate interval and a constant inclined angle に 対 し て with respect to the traveling direction of the incident light. Having a region, the light refracted by the first inclined region is incident on a second inclined region provided at a fixed interval, and is refracted again by the second inclined region and emitted as substantially parallel light. As described above, the first inclined region and the second inclined region are arranged to face each other, and a plurality of optical deflecting elements are used, wherein the deflection angle of the outgoing deflected light is symmetric with respect to the normal direction of the substrate surface. The light deflection elements are arranged in multiple stages.
According to a twelfth aspect of the present invention, in the optical deflecting device according to the eleventh aspect, the optical deflecting element has an intermediate substrate between a pair of inclined regions arranged opposite to each other, and a plurality of tiers arranged in multiple stages. The intermediate substrate thickness d of the light deflecting element is set to d in order from the incident light side.1, D2, D3, ...
dm= Dm- 1/ 2m- 1  (M = 1, 2, 3,..., Where d0= D1)
Is satisfied.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration, operation, and operation of the present invention will be described in detail.
First, the light deflection operation principle and the basic configuration of the light deflection element will be described. FIG. 1 shows an example of a basic configuration of an optical deflecting element according to the present invention. This optical deflecting element 1 is composed of a pair of transparent substrates 2 and 3 having at least one substrate having a sawtooth-shaped portion (inclined region). 3, a liquid crystal layer 4 sandwiched between a pair of substrates, the alignment state of which can be controlled by a voltage application condition, a transparent electrode 5 for applying an electric field to the liquid crystal layer 4, and a voltage application state for the transparent electrode 5 are changed. And an applied voltage control means (not shown). In the example of FIG. 1, one of the pair of transparent substrates 2 and 3 has a sawtooth-shaped portion (inclined region) 2 a that is inclined in accordance with the light deflection direction on the surface on the liquid crystal layer 4 side. And the other substrate 3 is a counter substrate. Although the shape and the number of arrays of the sawtooth formed on the sawtooth-shaped substrate 2 are not particularly limited, the sawtooth is formed to have a desired deflection amount and deflection direction. Since the alignment state of the liquid crystal molecules 4a changes in the liquid crystal layer 4 depending on the voltage application condition, by setting the voltage application condition, the liquid crystal molecule 4a can take two alignment states, for example, as shown in FIG. The change in the alignment state of the liquid crystal in the light deflecting element 1 will be described with reference to FIG. Basically, the configuration is similar to that of a light deflecting element using a homogeneously aligned nematic liquid crystal.However, if the alignment state of the liquid crystal changes depending on the voltage application condition, the refractive index for incident light changes accordingly. Just fine. For example, a ferroelectric liquid crystal composed of a smectic C phase can be used in the same configuration.
[0019]
Here, in order to regulate the initial alignment of the liquid crystal, a rubbing process is performed on an alignment film (not shown) formed on the surfaces of the substrates 2 and 3 (not shown in FIG. Y-axis direction). The director direction of the liquid crystal is strongly regulated depending on the rubbing direction. As such a material for alignment treatment, a normal alignment film such as polyimide used for TN liquid crystal, STN liquid crystal, or the like can be used. As the alignment treatment, a rubbing treatment or a photo-alignment treatment is preferably performed. Further, since the alignment of the liquid crystal changes depending on the voltage application condition, an electrode pair composed of the pair of transparent electrodes 5 is formed on the liquid crystal layer side surface of the pair of substrates 2 and 3 as a voltage application unit. With this electrode pair, an electric field is applied in a direction orthogonal to the liquid crystal director that is homogeneously aligned, that is, in the in-plane direction of the substrate. Further, the inclined state is set such that the surface on the side of the sawtooth-shaped substrate 2 forms an inclination ψ1 with respect to the normal direction of the incident light. As a method for manufacturing the sawtooth-shaped substrate 2, there is a method of etching or cutting a glass substrate, a transparent plastic substrate, or the like to form a sawtooth-shaped portion (inclined region) 2a. There is also a method of processing a transparent plastic material by injection molding. In any manufacturing method, the material used for the saw-tooth substrate 2 preferably has no birefringence.
[0020]
As shown in FIG. 2, the liquid crystal director is aligned in two directions corresponding to the initial alignment or the direction of the electric field from the electrodes (first alignment state and second alignment state). In the light deflecting element having such a configuration, by regulating the orientation of the liquid crystal in the horizontal and vertical directions with respect to the substrate surface as shown in FIG. 2, it is possible to efficiently deflect incident light. That is, in FIG. 2, when the incident light is manipulated so that the linear polarization direction of the incident light becomes the Y-axis direction and is incident on this light deflecting element, the liquid crystal director is initially aligned in a state where no electric field is generated between the substrates. , Thereby turning in the Y-axis direction (first alignment state).
On the other hand, in a state where an electric field is applied so as to be perpendicular to the substrate surface, the liquid crystal director is oriented in the direction of the electric field, that is, in a direction orthogonal to the initial alignment (second alignment state).
[0021]
The refractive index of the liquid crystal in the first alignment state (initial alignment = homogeneous alignment) is n1, the refractive index of the liquid crystal in the second alignment state (alignment when voltage is applied = homeotropic alignment) is n2, and the liquid crystal is sandwiched. When the refractive index of the substrate to be formed is ng, if ng で あ れ ば n1 ≠ n2, the incident light is deflected by the difference in the refractive index from the interface in the first alignment state and the second alignment state.
[0022]
The feature of the light deflecting element having such a configuration is that the outgoing light with respect to the incident light can be rotationally moved by controlling the liquid crystal director. Therefore, a desired amount of deflection can be obtained by appropriately selecting the distance between the light deflection element and the light receiving section. For example, as shown in FIG. 3, two light deflecting elements 1 having the structure shown in FIG. 1 are used, and such two light deflecting elements are arranged in the light traveling direction to constitute an optical deflecting device. By appropriately selecting the distance X between the provided elements, it is possible to obtain a necessary amount of deflection while keeping the incident light and the emitted light parallel. As a result, the deflection amount can be easily adjusted from the outside, and a highly convenient optical deflection device can be configured.
If the amount of light deflection is constant, as shown in FIG. 4, two liquid crystal layers 4 and two opposing saw-tooth-shaped portions (in one light deflecting element) via an intermediate substrate 6 having a thickness L. (A slope region) may be provided.
[0023]
When determining the traveling direction of light in the configuration of the light deflecting element as shown in FIG. 1, strictly speaking, each of the directions of the liquid crystal director with respect to the traveling direction of the incident light and the refractive indices n1 and n2 is used based on the refractive index ellipsoid. The refractive index in the direction is determined, and the light deflection direction is determined based on the refractive index. However, here, it is simply assumed that the refractive index n1 and the refractive index n2 are switched according to the alignment state of the liquid crystal, and assuming that Snell's law is followed as shown in FIG. May be called).
[0024]
In FIG. 5, the refractive index in the major axis direction of the liquid crystal 4 is n1 and the refractive index in the minor axis direction is n2, and the angle between the normal direction of the front interface of the liquid crystal 4 and the light deflection direction with respect to the light traveling direction.基板 1 (≠ 0), the substrates 2 and 3 are arranged so that the angle between the normal of the rear interface and the incident light direction is 0 °. The optical member (sawtooth substrate 2) in contact with the liquid crystal is selected to have a refractive index of ng. Here, when the linear polarization direction of the incident light coincides with the long axis direction of the liquid crystal, the refractive index of the liquid crystal is n1, and the light deflection angle ψ2 from the interface normal direction at the front liquid crystal interface is determined by Snell's law. ,
sinψ2 = (ng / n1) sinψ1
Further, the light deflection angle ψ3 of the light beam incident on the opposite substrate 3 sandwiching the liquid crystal 4 from the normal direction of the opposite substrate is:
ψ3 = ψ1-ψ2
And the light deflection angle ψ4 of the light beam incident on the opposing substrate 3 within the substrate is:
sinψ4 = (n1 / ng) sinψ3
Find more.
[0025]
When the direction of the linear polarization of the incident light coincides with the direction of the minor axis of the liquid crystal, the refractive index of the liquid crystal is n2. In this case, the light deflection angle is obtained from Snell's law in the same manner as described above.
[0026]
Here, as shown in FIG. 4, when the parallel shift is performed with the intermediate substrate 6 provided, assuming that the thickness of the intermediate substrate 6 is L, the thickness L required to obtain the shift amount x (μm) is
L · sinψ4 = x (μm)
Than,
L = x / sinψ4 (μm)
Becomes
[0027]
In this manner, the light deflection direction changes mainly due to the sawtooth inclination angle ψ1 of the sawtooth-shaped substrate 2 and the refractive index anisotropy of the liquid crystal 4, and the amount of light deflection depends on the distance to the light receiving surface or the liquid crystal layer thickness. It can be adjusted by the thickness of the substrate.
[0028]
Although the principle of the light deflecting operation is as described above, the light deflecting function can be obtained as will be described later. For example, when the refractive index ng of the sawtooth-shaped substrate 2 of the light deflecting element matches the refractive index of the liquid crystal, there is no difference in the refractive index between the substrate and the liquid crystal layer, so that the incident light does not feel the inclined surface of the substrate. Therefore, the incident light goes straight without obeying Snell's law. As described above, the light deflection operation when the refractive index ng of the substrate matches one of the refractive index in the major axis direction and the minor axis direction of the liquid crystal is shown in FIG. (The refractive index in the axial direction is the refractive index of the substrate). That is, the light deflecting function can be realized by the straight light and the deflecting light. Here, since the optical path length of the emitted light is determined by the distance to the light receiving surface, the optical path length is clearly different in FIG. If the optical path lengths are different, the imaging position shifts accordingly, and the emitted light includes aberration. Therefore, as shown in FIG. 1, by making the light deflecting direction symmetrical with respect to the incident optical axis, the difference in the optical path length of the outgoing light can be reduced.
[0029]
To make the light deflection direction symmetric with respect to the incident optical axis, the refractive index of the sawtooth-shaped substrate 2 is ng, the refractive index in the major axis direction of the liquid crystal layer 4 is n1 (= ne), and the minor axis of the liquid crystal layer 4 is When the refractive index in the direction is n2 (= no) (n1> n2), each refractive index may be set so as to satisfy the relationship of n1> ng> n2. That is, by selecting the refractive index of the sawtooth-shaped substrate 2 or the birefringence of the liquid crystal material so as to satisfy the above relationship, the deflecting light emitted from the light deflecting element 1 is emitted in a symmetric direction with respect to the incident optical axis, The difference in the optical path length of the deflecting light can be eliminated at the set light receiving surface position (claim 2).
[0030]
Also, the relationship between the substrate glass material and the birefringence of the liquid crystal,
0.99 · [(n1 + n2) / 2] <ng <1.01 · [(n1 + n2) / 2]
With this setting, the light is emitted more precisely in a symmetric direction with respect to the incident optical axis. It is sufficient that the precision is not affected by the optical path length difference, and the deviation of the symmetry is preferably ± 10% or less from the average of the deflection angles. As ng,
0.99 · [(n1 + n2) / 2] <ng <1.01 · [(n1 + n2) / 2]
By using a glass material that satisfies the following relationship, it can be reduced to ± 10% or less, and in particular, when applied to the control of the deflection direction of a laser or the like, it is possible to obtain good emitted light with little deterioration in the beam shape (described later). Example 2) (Claim 3).
[0031]
Generally, liquid crystals exhibit normal dispersion characteristics in which the refractive index increases with decreasing wavelength in the wavelength range of visible light. Further, an optical material that can be used as a substrate also shows wavelength dispersion characteristics of a refractive index, and an image thereof is shown in FIG. The Abbe number defined by the following equation is generally used to quantitatively express the chromatic dispersion. As shown in FIG. 7, when the Abbe number is large, the dispersion is small, and when the Abbe number is small, the dispersion is large. Become.
[0032]
Here, the wavelength characteristics of the refractive index ng of the sawtooth-shaped substrate 2 and the wavelength characteristics of the respective refractive indexes n1 (= ne) and n2 (= no) (n1> n2) of the liquid crystal are defined as Abbe numbers according to the following equation. I do.
νd = (nd−1) / (nf−nc)
In addition, nd, nf, and nc are the refractive index at each wavelength of D line (587.6 nm), F line (486.1 nm), and C line (636.3 nm).
[0033]
Therefore, the Abbe number of the sawtooth-shaped substrate is set to be within ± 10% of the average of the Abbe numbers of the extraordinary light component refractive index n1 (= ne) and the ordinary light component refractive index n2 (= no) of the liquid crystal. Thus, the wavelength dependency can be reduced in a relatively wide wavelength band. As the substrate, crown (K) glass of a low-dispersion glass material having a high Abbe number and, on the contrary, flint (F) of a high-dispersion glass material having a low numerical value can be used. For example, BK7, Bak4, LLF1, F2, SF8 and the like can be used. it can. Further, plastic materials such as acryl and polycarbonate can be used as long as they have no birefringence and are transparent (claim 4).
[0034]
There are other characteristics of the liquid crystal such as a voltage-dependent characteristic. In particular, in the case of a nematic liquid crystal, the voltage and the transmittance have linearity. This indicates that the director direction of the liquid crystal can be controlled to be multi-valued by the voltage, and the effective refractive index of the liquid crystal can also be controlled to be multi-valued. That is, since the light deflection direction can be changed by the difference in the refractive index between the substrate and the liquid crystal, the deflection angle of the emitted light can be selected to be multi-valued by controlling the applied voltage. .
[0035]
Here, the direction of the initial alignment of the liquid crystal will be described. As shown in FIG. 8, for example, the direction of the initial alignment of the nematic liquid crystal is divided into a sawtooth-shaped notching direction and a direction different from the notching line. When the initial orientation of the liquid crystal is oriented in a direction different from the direction of the sawtooth line, the disorder of the alignment due to the line portion becomes remarkable. In addition, since the liquid crystal is oriented along the sawtooth inclined portion, the liquid crystal director direction is the sawtooth inclined direction. However, in a substrate having no saw-tooth shape, the liquid crystal director direction is perpendicular to the incident optical axis, and the direction of the liquid crystal director is two directions: a tilt direction and a vertical direction (with respect to the incident optical axis). In other words, the refractive index of the liquid crystal sensed by the incident light becomes an average in two directions, that is, the tilt direction and the vertical direction, and a variation occurs.
[0036]
Therefore, by aligning the direction of the initial alignment of the liquid crystal with the sawtooth notching direction of the sawtooth-shaped substrate, and by matching the polarization direction of the incident light with the sawtooth notching direction of the sawtooth-shaped substrate, the alignment disorder of the liquid crystal is reduced. The variation of the effective refractive index due to the extraordinary light component of the liquid crystal (the refractive index in the long axis direction of the liquid crystal) can be reduced (claim 6).
[0037]
Next, an image display device using the light deflection element of the present invention will be described in detail. FIG. 9 shows a configuration example of the image display device. This image display device includes a light source 10, a light source driving unit 20, an illumination device 11, an image display element 14, a display driving unit 21, a reduction optical element 15, a light deflecting element 16, a light deflecting voltage control unit 22, and an image display control circuit 19. , A projection lens 17, a screen 18, and the like. As the light source 10, any light source capable of turning on / off white or arbitrary color light at high speed can be used. For example, an LED lamp, a laser light source, a combination of a white lamp light source and a shutter, or the like can be used. The illumination device 11 uniformly irradiates the light emitted from the light source 10 to the image display element 14, and includes a diffusion plate 12, a condenser lens 13, a fly-eye lens, and the like. The image display device 14 is a device that spatially modulates the incident uniform illumination light and emits the light. A transmissive liquid crystal light valve, a reflective liquid crystal light valve, a DMD (Digital Micro-mirror Device) element, or the like can be used. In the configuration example shown in FIG. 9, light emitted from the light source 10 under the control of the light source driving unit 20 becomes illumination light uniformized by the diffusion plate 12 of the illumination device 11, and the image display element 14 is condensed by the condenser lens 13. Critical lighting. Here, a transmissive liquid crystal light valve is used as an example of the image display element 14. The illumination light spatially modulated by the liquid crystal light valve is enlarged by a projection lens 17 as image light and projected on a screen 18.
[0038]
The reduction optical element 15 reduces a display pixel of the light valve, and includes a micro lens, a collimator lens, and the like. It is preferable that the reduction amount is an integer fraction of the pixel pitch.
Here, by controlling the applied voltage of the light deflecting element 16 disposed behind the liquid crystal light valve 14 and the reducing optical element 15 by the voltage control means 22, the image light is shifted by an arbitrary distance in the pixel arrangement direction. You.
[0039]
As the light deflecting element 16, the light deflecting element having the above-described configuration is used (claim 7). The light deflecting element 16 is arranged at a defocus position of a pixel displayed from the image display element 14 so that the resolution of a displayed image is not deteriorated. The shift amount is preferably an integer fraction of the pixel pitch similarly to the reduction amount. When the shift amount is equal to the reduction amount, the shifted pixels do not overlap. Therefore, the resolution does not decrease due to the pixel shift effect. If the shift amount and the reduction amount are different, the shifted pixels may overlap or the pixels may be widened, causing a drop in resolution. However, if there is no problem in the display image, the shift amount and the reduction amount may be different. Need not be equal.
[0040]
Specifically, in the case where the image multiplication is performed twice in the pixel arrangement direction, the pixel pitch is set to １ ／, and in the case where the pixel multiplication is performed three times, the pixel pitch is set to ３. Further, when the shift amount is increased by the configuration of the light deflection voltage control means 22, the shift amount and the pixel reduction amount may be set to a distance of “integer multiple + 1 / integer” of the pixel pitch. In any case, if the liquid crystal light valve 14 is driven by the image signal of the subfield corresponding to the pixel shift position, an apparent pixel multiplication effect is obtained as shown in FIG. The above high-definition image can be displayed.
[0041]
In the image display device having the configuration shown in FIG. 9, a color image display device can be obtained by using an image display element 14 in which a color filter is combined with a transmission type liquid crystal light valve and using a white lamp as the light source 10. Also, a full-color image can be displayed by a field sequential method in which a single-plate image display element is illuminated with light of three primary colors in time sequence. At this time, time-sequential three primary color lights may be generated by combining a white lamp light source and a rotating color filter.
[0042]
Next, FIG. 11 schematically shows an arrangement of the light deflection elements in the image display device. The sawtooth shape of the light deflecting element 16 is formed in an array in the up and down direction on the paper surface. When the light emitted from the image display element 14 is linearly polarized light in the vertical direction on the paper surface, the light deflecting element 16 can shift the entire image from the image display element 14 in the horizontal direction on the paper surface.
[0043]
Here, the configuration of the light deflector 16 is, for example, a configuration in which two light deflectors 1 are arranged as shown in FIG. That is, in the image display device of this example, the light deflecting element 16 has a pair of inclined regions (sawtooth-shaped portions) in which the substrate interval is non-parallel to the traveling direction of the incident light and the inclination angle ψ is constant, The light refracted in the first inclined region (sawtooth-shaped portion of the first light deflecting element) is transmitted to the second inclined region (sawtooth-shaped portion of the second light deflecting element) provided at a constant interval. An optical deflecting element in which the first inclined region and the second inclined region are arranged to face each other so as to be incident and refracted by the second inclined region again and exit as substantially parallel light, and an optical path for each subfield By displaying an image pattern in which the display position is shifted according to the deflection of the image, the apparent number of pixels of the image display element 14 is multiplied and displayed. In this case, the optical path shift amount is set by the distance X between the light deflecting elements 1 as shown in FIG. 3, and is set to be の of the pixel pitch. Since the optical path length of the light emitted from the light deflecting element 16 in the light deflecting operation is always the same, it is possible to realize an image display device with high definition and no aberration in the lateral shift of the display screen.
[0044]
Further, as another example, the configuration of the light deflecting element 16 is configured as shown in FIG. That is, in the image display device of this example, the light deflecting element 16 has an inclined region (sawtooth-shaped portion) in which the substrate interval is not parallel to the traveling direction of the incident light and the inclination angle ψ is constant. It is composed of a light deflecting element that emits light refracted in a region (sawtooth-shaped portion) as deflecting light, and displays an image pattern in a state where the display position is shifted according to the deflection of the optical path for each subfield. In this case, the display is performed by multiplying the apparent number of pixels of the image display element. In this case, the optical system is constructed so that the optical path shift amount is set to a position shifted by half the pixel pitch according to the distance from the light deflecting element 16. In the light deflecting operation, the deflection angle from the light deflecting element 16 is symmetric with respect to the incident optical axis, so that the optical path length of the outgoing light is always the same. That is, an image display device with high definition and no aberration in the lateral shift of the display screen can be realized with a relatively simple element configuration as compared with the above-described element configuration.
[0045]
Next, an optical deflector using the optical deflector of the present invention will be described in detail.
The light deflecting device of the present invention has a configuration in which a plurality of light deflecting elements having the above-described configuration are used, and the light deflecting elements are arranged in multiple stages.
More specifically, the light deflecting device of the present invention, as an optical deflecting element, for example, as shown in FIG. 3, a pair of inclined planes having a non-parallel substrate spacing and a constant inclination angle ψ with respect to the traveling direction of incident light. A second inclined region (a second sawtooth-shaped portion) that is disposed at regular intervals and is refracted by the first inclined region (the sawtooth-shaped portion of the first optical deflection element). And the first inclined region and the second inclined region are arranged so as to face each other so as to be incident on the sawtooth-shaped portion of the light deflecting element, and to be refracted again by the second inclined region and emitted as substantially parallel light. A plurality of light deflecting elements, wherein the deflection angle of the deflecting light is symmetric with respect to the normal direction of the substrate surface, are used, and the light deflecting elements are arranged in multiple stages.
[0046]
More specifically, the light deflecting device of the present invention uses a plurality of light deflecting elements having a configuration in which two light deflecting elements 1 are arranged as shown in FIG. Are arranged in multiple stages (three stages in FIG. 12) as shown in FIG. 12, and a plurality of light deflecting elements (1), (2), (3) are selectively provided. By driving, the incident light can be output to an arbitrary position. For example, when the incident light is output to the output position [2], the light deflection element (1) is turned on, the light deflection element (2) is turned off, and the light deflection element (3) is turned off. (There is another selection of the optical deflecting element to be driven to output to the output position [2]. For example, the optical deflecting element (1) is turned off, and the optical deflecting element (2) is OFF, light deflection element (3) ON).
By selectively driving the plurality of light deflection elements (1), (2), and (3) in this manner, incident light can be output to an arbitrary position. Further, here, by using an optical deflecting element whose deflection angle is symmetric with respect to the incident optical axis, distortion of light at the emission position, that is, aberration in the emitted light can be reduced.
[0047]
Further, as another example of the optical deflecting device, as shown in FIG. 4, a plurality of optical deflecting elements each having an intermediate substrate 6 between a pair of inclined regions (sawtooth-shaped portions) arranged opposite to each other are used. The plurality of light deflecting elements (1), (2), (3),... Are arranged in multiple stages (three in FIG. 13) as shown in FIG. The intermediate substrate thickness d of 2), 3),...1, D2, D3, ...
dm= Dm- 1/ 2m- 1(M = 1, 2, 3,..., Where d0= D1)
By satisfying the relationship, as shown in FIG. 13, the shift amount of the optical path passing through the three-stage light deflecting elements (1), (2), and (3) is halved every time the light deflecting element passes. Therefore, by selectively driving the plurality of light deflecting elements (1), (2), and (3), the emitted light can be shifted in the optical path to equally spaced positions, and the output position is doubled. .
[0048]
【Example】
Next, specific examples of the present invention will be described.
First, a method for manufacturing an optical deflection element will be described.
After a glass substrate (white plate) having a size of 3 cm × 4 cm and a thickness of 1 mm is dry-etched to form a saw-tooth substrate 2 having a saw-tooth shape having an inclination angle of about 1 ° and a pitch of 100 μm in an area of 1 cm × 1 cm. Then, ITO was sputtered on the sawtooth-shaped surface of the sawtooth-shaped substrate 2 as a transparent electrode 5 to a thickness of 1500 °. Next, a polyimide alignment agent AL3046-R31 (JSR) is applied to a thickness of about 800 °, and the substrate surface is subjected to a condition such that the stable direction in the homogeneous direction is perpendicular to the tilt direction of the tilt region (sawtooth shape). The alignment treatment was performed by a rubbing method in the direction of the marking line). Next, the glass substrate with ITO having a smooth surface was used as the counter substrate 3 and bonded using an adhesive mixed with beads so that the portion where the thickness of the liquid crystal layer was small was 3 μm. Thereafter, the liquid crystal 4 was injected between the two substrates by a capillary method so that the injection direction was along the saw-tooth shape, and sealed with an ultraviolet (UV) curing adhesive. Thus, the light deflecting element 1 having the configuration shown in FIG. 1 was manufactured.
[0049]
(Comparative Example 1)
In the above-described method for manufacturing an optical deflection element, nematic liquid crystal (E7 Merck) having a refractive index of ne = 1.75 and no = 1.52 was injected as a liquid crystal. This element is referred to as Sample 1. The refractive index of the substrate is ng = 1.52.
[0050]
(Example 1)
In the above-described method for manufacturing the light deflection element, nematic liquid crystal (ZLI-4792 Merck) having a refractive index of ne = 1.58 and no = 1.48 was injected as a liquid crystal. This element is referred to as Sample 2. The refractive index of the substrate is ng = 1.52.
[0051]
Here, a voltage is applied to the manufactured light deflection element to operate it. The applied voltage was a voltage of ± 15 V using a function generator. The input waveform was a rectangular wave, and the voltage value was checked with a tester. As the incident light to the light deflecting element, white laser light having a diameter of about 1 mm was used and passed through a wavelength selection filter (588 nm) to set the wavelength of the incident light. Further, a polarizing plate was installed between the light deflecting element and the laser device, the direction of the linearly polarized light was set to the sawtooth cutting line direction, and the light was incident on the sawtooth array position.
[0052]
The light deflecting element was operated in this way, and the transmitted light passing through the light deflecting element was observed with a CCD camera. The CCD camera was installed at a distance of 1 m from the device. As a result, it was confirmed that the transmitted light was deflected by the voltage. This light deflection operation was also confirmed for Comparative Example 1. However, the image due to the light deflection light of the laser light observed at the time of light deflection was blurred in Comparative Example 1 as compared with Example 1. Therefore, the optical path length difference up to the position of the CCD camera in the light deflected light was calculated, and the calculation result of the optical path length difference and the observation result of the displayed image are summarized in Table 1 below. Although the image was blurred, the image was not blurred in Example 1 having a small optical path length difference.
Since the optical path length difference is set by the refractive index of the liquid crystal and the refractive index of the substrate, a display image having no aberration can be obtained by satisfying the relationship of ne> ng> no as in the first embodiment. It is understood that it can be done.
[0053]
[Table 1]
Figure 2004233659
[0054]
(Example 2)
In the above-described method for manufacturing an optical deflection element, nematic liquid crystal (ZLI-2471 Merck) having a refractive index of ne = 1.62 and no = 1.50 was injected as a liquid crystal. This element is referred to as Sample 3. The refractive index of the substrate is ng = 1.52.
Here, a voltage was applied in the same manner as in Example 1, the element was driven, and the light deflection operation was observed with a CCD camera. As a result, the light deflection operation was confirmed, but the observed image was slightly blurred.
[0055]
Table 2 below shows the result of calculating the optical path length difference at the time of light deflection together with the result of Example 1. It can be seen from Table 2 that the image becomes blurred when the optical path length difference increases. Further, since the optical path length difference is set by the refractive index of the liquid crystal and the refractive index of the substrate, ne> ng> no and 0.99 · [(n1 + n2) / 2] <ng <1.01 · [(n1 + n2) / 2], a display image without aberration can be obtained.
[0056]
[Table 2]
Figure 2004233659
[0057]
(Example 3)
When the applied voltage for driving was varied from ± 0 to ± 15 V using the optical deflection element (sample 2) manufactured in the same manner as in Example 1, the amount of optical deflection varied in multiple values depending on the magnitude of the applied voltage. I was In addition, a light deflecting element was similarly manufactured using a ferroelectric liquid crystal (R5002 Clariant) composed of a chiral smectic C phase, and the applied voltage was variably set to ± 0 to 20V. Did not take. That is, it was found that multi-level light deflection was possible due to the linear electric field dependence of the nematic liquid crystal.
[0058]
(Example 4)
Using the optical deflecting element (sample 2) of Example 1 as a model, the optical path length difference (the distance between the element and the detector was 1 m) during the light deflecting operation on the short wavelength (F line) side and the long wavelength (C line) side. Calculated. At this time, the glass material of the substrate was LLF1 or BK7. Tables 3 and 4 below show the calculation results and the refractive indices and Abbe numbers of the liquid crystal and the glass material with respect to the D line (587.6 nm), the C line (636.3 nm), and the F line (486.1 nm). FIG. 14 shows the wavelength characteristics of the refractive index (no, ne) of ordinary light and extraordinary light of the liquid crystal (ZLI-4792) and the refractive index of LLF1 (a in the figure is the refractive index no, b of ordinary liquid crystal. Is the refractive index ne of the extraordinary light of the liquid crystal, and c is the refractive index of LLF1).
From the calculation result, the difference between the optical path length difference at the F line and the optical path length difference at the C line (F line-C line) is different, and the wavelength difference between the F line and the C line is smaller in the LLF1 because the difference is smaller. Is small.
[0059]
Here, the average of the Abbe numbers of no and ne of the liquid crystal (ZLI-4792) shown in Table 3 below is 42.6, and the range deviated from this average by ± 10% is 38.4 to 46.9. Comparing the Abbe numbers of the glass materials, LLF1 is within the above range, but BK7 is outside the range. That is, when the Abbe number of the glass material is within a range of ± 10% from the average of the Abbe numbers of no and ne of the liquid crystal, the wavelength dependency is reduced.
[0060]
[Table 3]
Figure 2004233659
[0061]
[Table 4]
Figure 2004233659
[0062]
(Example 5)
Next, an image display device having a configuration as shown in FIG. 9 was manufactured. As the image display element 14, a 0.9 inch diagonal XGA (1024 × 768 dots) polysilicon TFT liquid crystal panel (liquid crystal light valve) was used. The pixel pitch is about 18 μm both vertically and horizontally. The aperture ratio of the pixel is about 50%. Also, a microlens array is provided on the light source side of the image display element 14 to increase the light collection rate of the illumination light. As a light source 10, a white lamp was used, and color display was performed by a transmissive liquid crystal light valve 14 provided with a color filter on the surface of each pixel. Further, the reduction optical element 15 was configured using a micro lens and a collimating lens, and was installed immediately after the liquid crystal light valve 14 to adjust the alignment with the pixel position. The element manufactured in Example 1 was used as the light deflecting element 16, and was installed after the reduction optical element 15. The imaging position of the projection optical system was adjusted so that the shift amount was 9 μm. In addition, a diffuser having a thin diffusion layer was aligned on the exit side of the liquid crystal cell, the diffused light on the exit surface was enlarged, and the display image was observed. As a result, compared with the display image using the element of Comparative Example 1, As a result, a high-definition display image with less blur and twice the pixel density in the horizontal direction was obtained.
[0063]
(Example 6)
Next, as shown in FIG. 3, an optical deflecting element having a configuration in which two optical deflecting elements 1 are arranged so that inclined surface areas (sawtooth-shaped portions) face each other is manufactured. Then, a plurality of light deflecting elements configured as shown in FIG. 3 were used, and three light deflecting elements (1), (2) and (3) were arranged as shown in FIG. All of the pairs of light deflecting elements 1 constituting this light deflecting element were manufactured in the same manner as in Example 1. Three power supplies for driving each optical deflecting element by applying a voltage were prepared and installed so that each pair of optical deflecting elements could be driven. Here, the pair of light deflection elements were wired so as to be driven by the same power supply.
[0064]
The same laser light as in the first embodiment is used as the incident light, and the ON and OFF of the drive of each pair of light deflection elements (1), (2), and (3) are selected before the light is incident. . Although there are several options, experiments were performed on four options as shown in Table 5 below. As a result, it was possible to emit light to an arbitrary output position by selecting ON or OFF of the drive of each pair of light deflection elements. When the image of the emitted light at this time was observed with a CCD camera, there was no distortion in the beam shape.
[0065]
[Table 5]
Figure 2004233659
[0066]
【The invention's effect】
As described above, in the invention according to claim 1, a pair of transparent substrates, a liquid crystal layer sandwiched between the substrates and capable of controlling the refractive index with respect to incident light by controlling the alignment by applying a voltage, and Voltage application control means capable of applying a voltage to the liquid crystal layer, wherein at least one of the pair of substrates has a saw-tooth shape in which the surface on the liquid crystal layer side is inclined corresponding to the light deflection direction. Since the deflection angle of the outgoing deflected light is symmetrical with respect to the incident optical axis in the optical deflector which is a sawtooth-shaped substrate formed with a portion, eliminating the optical path length difference of the deflected light at the set light receiving surface position Can be.
[0067]
In the invention according to claim 2, a pair of transparent substrates, a liquid crystal layer sandwiched between the substrates and capable of controlling the refractive index with respect to incident light by controlling the alignment by applying a voltage, and applying a voltage to the liquid crystal layer At least one of the pair of substrates is formed with a sawtooth-shaped portion inclined on the surface on the liquid crystal layer side corresponding to the light deflection direction. In the light deflecting element that is a sawtooth-shaped substrate, the refractive index of the sawtooth-shaped substrate at the wavelength of the incident light is ng, the effective refractive index of the liquid crystal sensed by the incident light when driving the liquid crystal (light deflecting operation) is n1 (= ne), When n2 (= no) (n1> n2), by setting each refractive index so as to satisfy the relationship of n1> ng> n2, the deflected light emitted from the light deflecting element is symmetric with respect to the incident optical axis. Light-receiving surface emitted and set in the direction It is possible to eliminate the optical path length difference of the polarized light in the location.
[0068]
According to a third aspect of the present invention, in the optical deflecting element according to the second aspect, the refractive index of the sawtooth-shaped substrate at an incident light wavelength is ng, and the effective refraction of the liquid crystal sensed by the incident light when driving the liquid crystal (light deflecting operation). When the rates are n1 (= ne) and n2 (= no) (n1> n2),
0.99 · [(n1 + n2) / 2] <ng <1.01 · [(n1 + n2) / 2]
By setting the respective refractive indices so as to satisfy the relationship, the deflected light emitted from the light deflecting element is emitted in a symmetrical direction with respect to the incident optical axis, and the optical path of the deflected light is accurately determined at the set light receiving surface position. Long differences can be eliminated.
[0069]
According to a fourth aspect of the present invention, in the optical deflecting element according to the second or third aspect, the Abbe number of the sawtooth-shaped substrate is determined from an average of Abbe numbers of the abnormal light (n1 = ne) and the ordinary light (n2 = no) of the liquid crystal. The deviation is within ± 10%, and by defining the Abbe number of the sawtooth-shaped substrate so as to reduce the deviation between the wavelength characteristic of the refractive index in the liquid crystal and the wavelength characteristic of the refractive index in the substrate, a wide wavelength range is obtained. The wavelength dependence in the band can be reduced.
[0070]
In the invention according to claim 5, in the optical deflecting element according to any one of claims 1 to 4, the liquid crystal layer is a nematic liquid crystal. Can be changed.
In the invention according to claim 6, in the optical deflecting element according to claim 5, the initial alignment direction of the nematic liquid crystal and the polarization direction of the incident light coincide with the sawtooth cutting line direction of the sawtooth-shaped substrate. The orientation can be uniform without being affected by the inclined surface. Furthermore, by making the polarization direction of the incident light coincide with the sawtooth line direction of the sawtooth-shaped substrate, it is possible to reduce the variation in the effective refractive index caused by the extraordinary light component of the liquid crystal (the long axis of the liquid crystal director).
[0071]
In the invention according to claim 7, at least an image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, a light source for illuminating the image display element, and an image pattern displayed on the image display element 7. An image display device comprising: an optical member for observing light; and a light deflecting element for deflecting an optical path between the optical members, wherein the light deflecting element is the light deflecting element according to claim 1. Thus, the effects of claims 1 to 6 can be obtained, and an image display device that displays a high-definition image with little aberration can be realized.
[0072]
According to an eighth aspect of the present invention, in the image display device according to the seventh aspect, the light deflecting element includes a pair of inclined regions having a non-parallel substrate spacing and a constant inclination angle ψ with respect to a traveling direction of incident light. Having, the light refracted by the first inclined region is incident on the second inclined region provided at a fixed interval, and is refracted again by the second inclined region and emitted as substantially parallel light. The first inclined region and the second inclined region are constituted by optical deflecting elements arranged to face each other, and by displaying an image pattern in which the display position is shifted according to the deflection of the optical path for each subfield, Since the display is performed by multiplying the apparent number of pixels of the image display element, the optical path can be shifted by switching the voltage applied to the light deflection element. Further, since the deflection direction at the time of light deflection is symmetric with respect to the incident optical axis, the difference in the optical path length of the outgoing deflected light is small. That is, the number of pixels of the display image can be multiplied, and a display image with less aberration can be obtained.
[0073]
According to a ninth aspect of the present invention, in the image display device according to the seventh aspect, the light deflecting element has an inclined region in which a substrate interval is non-parallel and an inclination angle ψ is constant with respect to a traveling direction of incident light. An image deflecting element that emits the light refracted by the inclined region as deflecting light, and displays an image pattern in a state where the display position is shifted according to the deflection of the optical path for each subfield, thereby forming an image. Since the display is performed by multiplying the apparent number of pixels of the display element, the optical path can be shifted by switching the applied voltage of the light deflection element having a simple element configuration. Further, since the deflection direction at the time of light deflection is symmetric with respect to the incident optical axis, the difference in the optical path length of the outgoing deflected light is small. That is, the number of pixels of the display image can be multiplied, and a display image with less aberration can be obtained.
[0074]
According to a tenth aspect of the present invention, a plurality of light deflecting elements according to any one of the first to sixth aspects are used, and the light deflecting elements are arranged in multiple stages. By selectively driving the light deflecting element, it is possible to shift the emitted light to an arbitrary position.
According to an eleventh aspect of the present invention, in the optical deflecting device according to the tenth aspect, as the optical deflecting element, a pair of inclined regions having a non-parallel substrate spacing and a constant inclination angle ψ with respect to the traveling direction of the incident light. Having, the light refracted by the first inclined region is incident on the second inclined region provided at a fixed interval, and is refracted again by the second inclined region and emitted as substantially parallel light. A plurality of light deflecting elements, wherein the first inclined region and the second inclined region are arranged to face each other, and the deflection angle of the outgoing deflected light is symmetric with respect to the normal direction of the substrate surface. Since the light deflecting elements are arranged in multiple stages, by selectively driving the multiple light deflecting elements arranged in multiple stages, the light path of the emitted light can be shifted to an arbitrary position. Further, since the deflection angle of the outgoing deflected light is symmetric with respect to the incident optical axis, aberration in the outgoing deflected light can be reduced.
[0075]
According to a twelfth aspect of the present invention, in the optical deflecting device according to the eleventh aspect, the light deflecting element has an intermediate substrate between a pair of inclined regions arranged to face each other, and a plurality of lights arranged in multiple stages. The intermediate substrate thickness d of the deflecting element is set to d in order from the incident light side.1, D2, D3, ...
dm= Dm- 1/ 2m- 1  (M = 1, 2, 3,..., Where d0= D1)
Is satisfied, the shift amount of the optical path passing through the light deflecting element is halved every time the light deflecting element is passed. Therefore, by selectively driving the plurality of light deflecting elements, the emitted light can be optical path shifted to equally spaced positions, and the output position is doubled. Further, since the deflection angle of the outgoing deflected light is symmetric with respect to the incident optical axis, aberration in the outgoing deflected light can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a basic configuration of an optical deflection element of the present invention.
FIG. 2 is an explanatory diagram of a change in a liquid crystal alignment state of the light deflecting element shown in FIG.
FIG. 3 is a diagram showing another configuration example of the light deflection element of the present invention.
FIG. 4 is a diagram showing another configuration example of the light deflection element of the present invention.
FIG. 5 is an explanatory diagram of a deflection theory in the optical deflection element of the present invention.
FIG. 6 is a diagram showing another configuration example of the light deflection element of the present invention.
FIG. 7 is a diagram showing wavelength characteristics of a refractive index of a liquid crystal and a refractive index of a glass substrate.
FIG. 8 is an explanatory diagram showing an example of an initial alignment state of liquid crystal when a sawtooth-shaped substrate is used.
FIG. 9 is a diagram showing a schematic configuration example of an image display device according to the present invention.
FIG. 10 is a diagram showing an appearance of apparent pixel doubling when an optical deflecting element is used.
FIG. 11 is a diagram schematically illustrating an arrangement of light deflecting elements in the image display device.
FIG. 12 is a diagram showing a schematic configuration example of a light deflecting device according to the present invention.
FIG. 13 is a diagram showing another schematic configuration example of the light deflecting device according to the present invention.
FIG. 14 is a diagram showing the wavelength characteristics of the refractive index (no, ne) of ordinary light and extraordinary light of the liquid crystal (ZLI-4792) and the refractive index of LLF1.
[Explanation of symbols]
1: Light deflection element
2: sawtooth-shaped substrate
2a: Sawtooth-shaped part (inclined area)
3: Counter substrate
4: Liquid crystal layer (liquid crystal)
4a: liquid crystal molecules
5: Transparent electrode
6: Intermediate board
10: Light source
11: Lighting device
12: Diffusion plate
13: Condenser lens
14: Image display element (transmission type liquid crystal light valve)
15: Reduction optical element
16: Optical deflection element
17: Projection lens
18: Screen
20: Light source driving means
19: Image display control circuit
21: display driving means
22: Light deflection voltage control means
(1), (2), (3): Light deflection element

Claims (12)

一対の透明基板と、該基板間に挟まれ電圧印加によって配向を制御することにより入射光に対する屈折率の制御が可能な液晶層と、該液晶層に電圧を印加することが可能な電圧印加制御手段とを備え、前記一対の基板のうち少なくとも一方の基板は、液晶層側の面に光偏向方向に対応して傾斜している鋸歯形状部を形成してなる鋸歯形状基板である光偏向素子において、
前記液晶層で偏向されて出射される光の偏向角が入射光軸に対して対称であることを特徴とする光偏向素子。A pair of transparent substrates, a liquid crystal layer sandwiched between the substrates and capable of controlling the refractive index with respect to incident light by controlling the alignment by applying a voltage, and a voltage application control capable of applying a voltage to the liquid crystal layer Means, wherein at least one of the pair of substrates is a sawtooth-shaped substrate having a sawtooth-shaped portion formed on a surface on the liquid crystal layer side, the sawtooth-shaped portion being inclined corresponding to the light deflection direction. At
A light deflecting element, wherein a deflection angle of light deflected by the liquid crystal layer and emitted is symmetric with respect to an incident optical axis. 一対の透明基板と、該基板間に挟まれ電圧印加によって配向を制御することにより入射光に対する屈折率の制御が可能な液晶層と、該液晶層に電圧を印加することが可能な電圧印加制御手段とを備え、前記一対の基板のうち少なくとも一方の基板は、液晶層側の面に光偏向方向に対応して傾斜している鋸歯形状部を形成してなる鋸歯形状基板である光偏向素子において、
入射光波長における前記鋸歯形状基板の屈折率をｎｇ、液晶駆動（光偏向動作）時に入射光が感じる液晶の実効的な屈折率をｎ１（＝ｎｅ）、ｎ２（＝ｎｏ）（ｎ１＞ｎ２）とするとき、
ｎ１＞ｎｇ＞ｎ２
の関係を満たすことを特徴とする光偏向素子。A pair of transparent substrates, a liquid crystal layer sandwiched between the substrates and capable of controlling the refractive index with respect to incident light by controlling the alignment by applying a voltage, and a voltage application control capable of applying a voltage to the liquid crystal layer Means, wherein at least one of the pair of substrates is a sawtooth-shaped substrate having a sawtooth-shaped portion formed on a surface on the liquid crystal layer side, the sawtooth-shaped portion being inclined corresponding to the light deflection direction. At
The refractive index of the sawtooth-shaped substrate at the wavelength of the incident light is ng, and the effective refractive index of the liquid crystal felt by the incident light when driving the liquid crystal (light deflecting operation) is n1 (= ne) and n2 (= no) (n1> n2). When
n1>ng> n2
A light deflecting element satisfying the following relationship: 請求項２記載の光偏向素子において、
入射光波長における前記鋸歯形状基板の屈折率をｎｇ、液晶駆動（光偏向動作）時に入射光が感じる液晶の実効的な屈折率をｎ１（＝ｎｅ）、ｎ２（＝ｎｏ）（ｎ１＞ｎ２）とするとき、
０．９９・［（ｎ１＋ｎ２）／２］＜ｎｇ＜１．０１・［（ｎ１＋ｎ２）／２］
の関係を満たすことを特徴とする光偏向素子。The optical deflecting element according to claim 2,
The refractive index of the sawtooth-shaped substrate at the wavelength of the incident light is ng, and the effective refractive index of the liquid crystal felt by the incident light when driving the liquid crystal (light deflecting operation) is n1 (= ne) and n2 (= no) (n1> n2). When
0.99 · [(n1 + n2) / 2] <ng <1.01 · [(n1 + n2) / 2]
A light deflecting element satisfying the following relationship: 請求項２または３記載の光偏向素子において、
前記鋸歯形状基板のアッベ数が液晶の異常光（ｎ１＝ｎｅ）、常光（ｎ２＝ｎｏ）におけるアッベ数の平均から±１０％以内のズレであることを特徴とする光偏向素子。The optical deflecting element according to claim 2 or 3,
An optical deflecting element, wherein the Abbe number of the sawtooth-shaped substrate is within ± 10% of the average of the Abbe numbers of the liquid crystal extraordinary light (n1 = ne) and ordinary light (n2 = no). 請求項１〜４のいずれか一つに記載の光偏向素子において、
前記液晶層がネマチック液晶であることを特徴とする光偏向素子。The optical deflection element according to claim 1, wherein
The light deflecting element, wherein the liquid crystal layer is a nematic liquid crystal. 請求項５記載の光偏向素子において、
前記ネマチック液晶の初期配向方向と入射光の偏光方向が前記鋸歯形状基板の鋸歯刻線方向と一致することを特徴とする光偏向素子。The optical deflection element according to claim 5,
An optical deflecting element, wherein an initial alignment direction of the nematic liquid crystal and a polarization direction of incident light coincide with a sawtooth cutting line direction of the sawtooth-shaped substrate. 少なくとも、画像情報に従って光を制御可能な複数の画素が二次元配列した画像表示素子と、該画像表示素子を照明する光源と、前記画像表示素子に表示した画像パターンを観察するための光学部材と、該光学部材の間の光路を偏向する光偏向素子を有し、該光偏向素子は請求項１〜６のいずれか一つに記載の光偏向素子からなることを特徴とする画像表示装置。At least, an image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, a light source illuminating the image display element, and an optical member for observing an image pattern displayed on the image display element An image display device, comprising: a light deflecting element for deflecting an optical path between the optical members, wherein the light deflecting element comprises the light deflecting element according to claim 1. 請求項７記載の画像表示装置において、
前記光偏向素子は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域を有し、第一の傾斜領域で屈折された光が、一定間隔をおいて設置された第二の傾斜領域に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置された光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子の見かけ上の画素数を増倍して表示することを特徴とする画像表示装置。The image display device according to claim 7,
The light deflecting element has a pair of inclined regions in which the substrate interval is non-parallel and the inclination angle ψ is constant with respect to the traveling direction of the incident light, and the light refracted in the first inclined region has a constant interval. The first inclined region and the second inclined region are arranged to face each other so that the light is incident on the second inclined region provided therein, and is refracted by the second inclined region again and emitted as substantially parallel light. It consists of optical deflecting elements and displays an image pattern whose display position is shifted according to the deflection of the optical path for each subfield, so that the apparent number of pixels of the image display element can be multiplied and displayed. Characteristic image display device. 請求項７記載の画像表示装置において、
前記光偏向素子は、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の傾斜領域を有し、該傾斜領域で屈折された光が偏向光として出射するような光偏向素子からなり、サブフィールド毎の光路の偏向に応じて表示位置がずれている状態の画像パターンを表示することで、画像表示素子の見かけ上の画素数を増倍して表示することを特徴とする画像表示装置。The image display device according to claim 7,
The light deflecting element has an inclined region in which the substrate interval is non-parallel to the traveling direction of the incident light and the inclination angle ψ is constant, and light refracted in the inclined region is emitted as polarized light. It consists of a deflecting element, and displays an image pattern in which the display position is shifted according to the deflection of the optical path for each subfield, so that the apparent number of pixels of the image display element is multiplied and displayed. Image display device. 請求項１〜６のいずれかに記載の光偏向素子を複数用い、前記光偏向素子が多段に配置されてなることを特徴とする光偏向装置。An optical deflecting device comprising a plurality of optical deflecting elements according to any one of claims 1 to 6, wherein the optical deflecting elements are arranged in multiple stages. 請求項１０記載の光偏向装置において、
前記光偏向素子として、入射光の進行方向に対して、基板間隔が非平行で傾斜角度ψが一定の一対の傾斜領域を有し、第一の傾斜領域で屈折された光が、一定間隔をおいて設置された第二の傾斜領域に入射し、第二の傾斜領域で再度屈折されて略平行光として出射するように、第一の傾斜領域と第二傾斜領域が対向して配置され、出射偏向光の偏向角が基板面の法線方向に対して対称であることを特徴とする光偏向素子を複数用い、前記光偏向素子が多段に配置されてなることを特徴とする光偏向装置。The optical deflecting device according to claim 10,
The light deflecting element has a pair of inclined regions in which the distance between the substrates is non-parallel and the inclination angle ψ is constant with respect to the traveling direction of the incident light, and the light refracted in the first inclined region has a constant interval. The first inclined region and the second inclined region are arranged so as to be incident on the second inclined region provided in the first inclined region and to be refracted by the second inclined region again and emitted as substantially parallel light, An optical deflecting device, comprising: a plurality of optical deflecting elements, wherein the deflection angles of the outgoing deflecting light are symmetric with respect to the normal direction of the substrate surface, wherein the optical deflecting elements are arranged in multiple stages. . 請求項１１記載の光偏向装置において、
前記光偏向素子は対向して配置された一対の傾斜領域の間に中間基板を有し、多段に配置された複数の光偏向素子の中間基板厚ｄを、それぞれ入射光側から順にｄ１、ｄ２、ｄ３、・・・ とする場合、
ｄｍ＝ｄｍ− １／２ｍ− １ （ｍ＝１，２，３，・・・、但しｄ０＝ｄ１）
の関係を満たすことを特徴とする光偏向装置。The optical deflecting device according to claim 11,
The light deflecting element has an intermediate substrate between a pair of inclined regions arranged opposite to each other, and the intermediate substrate thickness d of the plurality of light deflecting elements arranged in multiple stages is d 1 in order from the incident light side, When d 2 , d 3 ,...
d m = d m- 1/2 m- 1 (m = 1,2,3, ···, where d 0 = d 1)
A light deflecting device that satisfies the following relationship:
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