JP4372891B2 - Video display device - Google Patents

Description

ここで、（ａ）式の第１項は球面項、第２項は自由曲面項である。
【０１２２】
球面項中、
ｃ：頂点の曲率
ｋ：コーニック定数（円錐定数）
ｒ＝√（Ｘ² ＋Ｙ² ）
である。
【０１２３】
自由曲面項は、

ただし、Ｃ_j （ｊは２以上の整数）は係数である。
【０１２４】
上記自由曲面は、一般的には、Ｘ−Ｚ面、Ｙ−Ｚ面共に対称面を持つことはないが、本発明ではＸの奇数次項を全て０にすることによって、Ｙ−Ｚ面と平行な対称面が１つだけ存在する自由曲面となる。例えば、上記定義式（ａ）においては、Ｃ₂ 、Ｃ₅ 、Ｃ₇ 、Ｃ₉ 、Ｃ₁₂、Ｃ₁₄、Ｃ₁₆、Ｃ₁₈、Ｃ₂₀、Ｃ₂₃、Ｃ₂₅、Ｃ₂₇、Ｃ₂₉、Ｃ₃₁、Ｃ₃₃、Ｃ₃₅・・・の各項の係数を０にすることによって可能である。この場合、両眼視用ＨＭＤの左眼用光学系と右眼用光学系を共通化することができ、製作性が良い。
【０１２５】
また、Ｙの奇数次項を全て０にすることによって、Ｘ−Ｚ面と平行な対称面が１つだけ存在する自由曲面となる。例えば、上記定義式においては、Ｃ₃ 、Ｃ₅ 、Ｃ₈ 、Ｃ₁₀、Ｃ₁₂、Ｃ₁₄、Ｃ₁₇、Ｃ₁₉、Ｃ₂₁、Ｃ₂₃、Ｃ₂₅、Ｃ₂₇、Ｃ₃₀、Ｃ₃₂、Ｃ₃₄、Ｃ₃₆・・・の各項の係数を０にすることによって可能である。
【０１２６】
上記対称面の何れか一方を対称面としその対称面方向に偏心させることで、偏心により発生する非回転対称な収差を効果的に補正しながら同時に製作性も向上させることができる。
【０１２７】
本発明の第３６の映像表示装置は、第１、７〜１６の映像表示装置において、投影光学系が回折作用を持つ面を備えていることを特徴とするものである。
【０１２８】
この映像表示装置は後記の実施例６〜８が対応する。
【０１２９】
この映像表示装置の作用効果を以下に説明する。ＤＯＥ（回折光学素子）はスペースをとることなく各種の収差補正を行うことができるので、光学系の小型化に有効である。特に、ＤＯＥを使用せずに色収差を制御する場合は、複数の硝材から構成される複数の光学素子により補正を行う必要があるので、以下のようにいくつかの問題が生ずる：
問題▲１▼ 投影光学系を複数の部材に分割できる構成にする必要があるので、光学系設計上の制約条件となり、小型な光学系の設計を困難にする，
問題▲２▼ 効果的に色収差の補正を行うにはガラス材料を使用する必要があるので、光学系の重量が増加する。この重量の増加は、光学系を小型軽量にする必要があるＨＭＤ光学系の場合に、特に問題となる。
【０１３０】
単色の映像表示素子を使用する光学系の場合は、ＤＯＥで発生する色収差は全く関係ないので、ＤＯＥにより発生する色収差を気にすることなく効果的に収差補正を行うことができる。また、反射作用を主体とした光学系の場合、色収差はほとんど発生しない。
【０１３１】
しかし、白色映像表示素子を使用する場合や、図４のような構成によりダイクロイックミラー８で赤色、緑色、青色の複数波長のカラー映像表示素子の画素Ｒ，Ｇ，Ｂを合成する場合（図４は逆光線追跡の図）、投影光学系の軸上の色収差、倍率の色収差を共に良好に補正しておくことが好ましい。この場合、ＤＯＥで色収差の補正を行うのが、光学系の小型化の点で最も好ましい。
【０１３２】
また、図５のような構成により赤色、緑色、青色の複数波長のカラー映像表示素子の画素Ｒ，Ｇ，Ｂを合成する場合、逆光線追跡で、投影光学系の光軸方向の結像位置が波長により異なるようにしておくのが好ましい。この場合、ＤＯＥで色収差の制御をするのが、光学系の小型化の点で最も好ましい。
【０１３３】
また、図６のような構成により赤色、緑色、青色の複数波長のカラー映像表示素子の画素Ｒ，Ｇ，Ｂを合成する場合、逆光線追跡で、光軸と垂直な面内で投影光学系の結像位置が波長により異なる必要がある。この場合、ＤＯＥで軸上の色収差の補正と倍率の色収差の制御をするのが、光学系の小型化の点で最も好ましい。
【０１３４】
本発明の第３７の映像表示装置は、第３６の映像表示装置において、投影光学系の透過面の表面が透過型のＤＯＥを兼ねるか、あるいは、投影光学系の反射面の表面が反射型のＤＯＥを兼ねるか、あるいは、走査手段のミラー反射面が反射型のＤＯＥを兼ねるというように投影光学系あるいは走査手段の表面がＤＯＥを兼ねることを特徴とするものである。
【０１３５】
この映像表示装置は後記の実施例７、８が対応する。
【０１３６】
この映像表示装置の作用効果を以下に説明する。新たな光学素子を追加する必要がないので、部品点数の増加に伴う光学系の大型化やコストアップがない。また、位置合わせ調整作業を複雑にすることもない。
【０１３７】
また、特開平１０−２０２２６号に開示されているようなフォトリソグラフィー工程でスキャナを作製するいわゆるマイクロマシンミラーを使用する場合、スキャンミラー作製時にスキャンミラー表面のＤＯＥも作製することができ、ＤＯＥの製作コストの増加が少ない。また、本発明の光学系をＨＭＤ光学系として利用し、シースルー機能やスーパーインポーズ機能を付加する場合、走査手段は外界光を妨げない位置にあるので、外界光に対してはＤＯＥが作用をせず外界光を明瞭に観察することができる。
【０１３８】
本発明の第３８の映像表示装置は、第３６の映像表示装置において、プリズム部材と走査手段の間にＤＯＥ作用を持つ面を追加して、色収差の制御をすることを特徴とするものである。
【０１３９】
この映像表示装置は後記の実施例６が対応する。
【０１４０】
この映像表示装置の作用効果を以下に説明する。映像表示素子、投影光学系、スキャナで構成する光学系全体の突出量を増加させることなく、色収差等を制御する機能を付加することができる。これは、特にＨＭＤ光学系の場合に有効である。また、スキャンミラー法線に対するスキャンミラーへの入射光の入射角が小さく、スキャンミラーによる偏向角が小さい場合、同じＤＯＥをスキャンミラーへ入射する光路とスキャンミラーから反射する光路の両方で使用することができ、効果的である。また、本発明の光学系をＨＭＤ光学系として利用し、シースルー機能やスーパーインポーズ機能を付加する場合、走査手段は外界光を妨げない位置にあるので、外界光に対してＤＯＥが作用を持たない構成とするのが容易になるので、外界光を明瞭に観察することができる。
【０１４１】
本発明の第３９の映像表示装置は、第３８の映像表示装置において、プリズム部材と走査手段の間に配置した透過型ＤＯＥにより、プリズム部材射出後に走査手段に入射する光路と、走査手段射出後にプリズム部材に入射する光路の両方の光路で回折作用を受けることを特徴とするものである。
【０１４２】
この映像表示装置は後記の実施例６が対応する。
【０１４３】
この映像表示装置の作用効果を以下に説明する。走査手段へ入射する光路と走査手段から反射する光路の両方でＤＯＥの作用を受ければ、ＤＯＥのピッチを大きくすることができ製作性が向上する。このような配置をした多くの場合、走査手段へ入射する光線がＤＯＥに入射する位置と走査手段から反射する光線がＤＯＥに入射する位置は異なる。この場合、１つのＤＯＥで複数の作用を与えることができ効果的である。
【０１４４】
本発明の第４０の映像表示装置は、第３８の映像表示装置において、ＤＯＥがスキャナと一体に保持されていることを特徴とするものである。
【０１４５】
この映像表示装置は後記の実施例６が対応する。
【０１４６】
この映像表示装置の作用効果を以下に説明する。ＤＯＥとスキャナと一体にしておけば、映像表示素子、投影光学系、スキャナ等を保持する機械的構成を単純にすることができる。また、フォトリソグラフィー工程でスキャナを作製するいわゆるマイクロマシンミラーを使用する場合、スキャンミラー面の保護のために何らかの保護部材でスキャンミラー面を覆うことが望ましい。スキャンミラー面を覆う保護部材としてＤＯＥを利用すれば、部品点数を削減することができる。また、高速スキャナとするためにスキャナを真空パッケージあるいは減圧パッケージとする場合、ＤＯＥを密封部材と利用することができ、部品点数を削減することができる。
【０１４７】
本発明の第４１の映像表示装置は、第１、７〜１６の映像表示装置において、走査手段と投影光学系により形成される像の歪みを打ち消すような映像を映像表示素子に表示することを特徴とするものである。
【０１４８】
この映像表示装置は後記の実施例１〜１１が対応する。ただし、実施例３〜１１は、電気的像歪み補正をしてもしなくともどちらでも使用できる。
【０１４９】
この映像表示装置の作用効果を以下に説明する。１次元走査の場合はＸ方向に走査し、２次元走査の場合はスキャナのＹ方向の傾角を徐々に変化させながらＸ方向の走査を繰り返し２次元画像を形成するとする。図７にＢで示すように、走査により形成される像が、非直線で非等間隔であるとする。このとき、図７にＡで示すように、走査手段と投影光学系により形成される像のディストーションを打ち消すような映像を映像表示素子に表示すれば、走査手段と投影光学系により形成される像は、図７にＣで示すように、直線で等間隔となる。このような処理をすれば、投影光学系でディストーションを制御する必要がなくなるので、投影光学系の負担が減り投影光学系の設計が楽になる。その結果、光学系をより小型化しやすくなる。
【０１５０】
本発明の第４２の映像表示装置は、第４１の映像表示装置において、電気的像歪み補正が、等速走査性の補正であることを特徴とするものである。
【０１５１】
この映像表示装置は後記の実施例３〜１１が対応する。ただし、実施例３〜１１は、この補正をしてもしなくてもどちらでも使用できる。
【０１５２】
この映像表示装置の作用効果を以下に説明する。走査手段＋投影光学系による走査像が直線走査されるのが非等速走査で、図８の実線の像が形成されるとする。この場合、各像位置の相対的スキャン速度の逆数が、その位置の相対的な映像表示間隔となるような映像を映像表示素子に表示すれば、形成される像は図８の破線の直線走査・等速走査の像である。この場合、各画素の映像表示時間は一定のまま、画素と画素の映像表示間隔を変化させてもよいし、例えば映像表示時間＝映像表示間隔となるように、各画素の映像表示時間を変化させてもよい。後者の場合、眼の感度を考慮し、画素毎に映像表示素子に表示する映像の強度を変えるとよい。
【０１５３】
図７の直線走査性と等速走査性の両方の補正に比べ、等速走査性の補正は、処理すべきデータ数が減るので、高解像走査・高速走査時のリアルタイム処理に対応しやすい。したがって、直線走査性と等速走査性の両方の補正を行う場合に比べ、高解像・高速走査ができる。
【０１５４】
本発明の第４３の映像表示装置は、第１、７〜１６の映像表示装置において、走査手段が２次元走査をすることを特徴とするものである。
【０１５５】
この映像表示装置は後記の実施例１〜１１が対応する。
【０１５６】
この映像表示装置の作用効果を以下に説明する。図９に示すように、紙面内方向を走査する１次元走査手段４’と紙面と垂直方向を走査する１次元走査手段４”という２つの１次元走査手段を利用する場合は、この２つの走査手段を共役にする光学系９が必要があるので、光学系が大型化する。２次元走査手段を利用すれば、図１、図２に示すように、光学系を小型化することができる。これは、本発明をＨＭＤ光学系として利用する場合に、特に有効である。
【０１５７】
本発明の第４４の映像表示装置は、第１、７〜１６の映像表示装置において、走査手段の法線に対する軸上主光線の入射角θｓが次式を満足することを特徴とするものである。
【０１５８】
｜θｓ｜≦６０° ・・・（６）
この映像表示装置は後記の実施例１〜１１が対応する。
【０１５９】
この映像表示装置の作用効果を以下に説明する。同じ光束径でも、走査手段に対する軸上主光線の入射角が大きくなると、走査ミラーの面積が大きくなり、高速走査が難しくなる。よって、条件式（６）を満足することが望ましい。
【０１６０】
本発明の第４５の映像表示装置は、第４４の映像表示装置において、走査手段に対する軸上主光線の入射角が次式を満足することを特徴とするものである。
【０１６１】
１０°≦｜θｓ｜≦４５° ・・・（６−１）
この映像表示装置は後記の実施例１〜１１が対応する。
【０１６２】
この映像表示装置の作用効果を以下に説明する。上限の４５°を越えると、走査ミラーを反射した光の偏向度が大きくなりすぎ、光学系も大型化する。よって、条件式の上限を満足することが望ましい。また、走査手段の走査ミラーに対する軸上主光線の入射角が小さすぎると、走査ミラーに入射する光路と走査ミラーを反射する光路の差が小さく、走査ミラーに入射させる光学系と走査ミラーで反射後の光学系の構成が難しくなる。よって、条件式の下限の１０°を満足することが望ましい。
【０１６３】
本発明の第４６の映像表示装置は、第１、７〜１６の映像表示装置において、往復走査をすることを特徴とするものである。
【０１６４】
この映像表示装置は後記の実施例１〜１１が対応する。
【０１６５】
この映像表示装置の作用効果を以下に説明する。往路だけの走査ではなく、往路と復路の両方を利用する往復走査は、走査手段の走査周波数を半分にすることができるので、高速走査をすることができる。
【０１６６】
本発明の第４７の映像表示装置は、第１、７〜１６の映像表示装置において、走査手段は走査方向に正弦波状に振動する走査手段であることを特徴とするものである。
【０１６７】
この映像表示装置は後記の実施例１〜１１が対応する。
【０１６８】
この映像表示装置の作用効果を以下に説明する。高速走査をするための走査手段は共振ミラーのように正弦波状に振動する。この走査手段を使用することで高速走査に対応できる。
【０１６９】
本発明の第４８の映像表示装置は、第４７の映像表示装置において、正弦波状に振動する走査手段の振幅の９５％以下を映像表示に利用することを特徴とするものである。
【０１７０】
この映像表示装置は電気的像歪み補正を行わない場合として後記の実施例３〜１１が対応する。ただし、電気的像歪み補正を行う場合、実施例１〜１１は９５％以上の振幅に対して使用できる。
【０１７１】
この映像表示装置の作用効果を以下に説明する。正弦波状に振動するスキャンミラーに対して、電気的像歪み補正なしに等速走査するには、投影光学系を走査方向に関してｆアークサインθレンズにする必要がある。１次元ｆアークサインθレンズに必要なディストーションを、図１０に示す。図１０は横軸にスキャンミラーから投影光学系への規格化した入射角を取り、縦軸にディストーションを取っている。図１０から次のことが分かる。
【０１７２】
▲１▼スキャンミラーの振幅φ₀ が±５°、±１０°、±１５°程度の場合、光学系で＋４０％以上という非常に大きなディストーションを発生させる必要があり、設計が困難である。
【０１７３】
▲２▼φ₀ が、±５°、±１０°、・・±２５°と増えるにつれ、発生させるプラスのディストーションの量が減る。したがって、φ₀ が大きいと、発生させるディストーションの量が少なくて済むので、この意味では投影光学系の設計がしやすい。一方、φ₀ が大きいと、広角なリレー光学系の設計を行うことになるので、設計が困難である。
【０１７４】
▲３▼ある特定のφ₀ の場合、画面周辺で必要なディストーションの量が急に増加する。
【０１７５】
したがって、▲１▼、▲２▼より、振幅φ₀ が小さくても大きくても、投影光学系の設計が困難であることが分かる。特に、ＨＭＤ光学系は、光学系を小型にするために使用できる光学作用面が限定されるので、正弦波の振幅を全て利用したｆアークサインθレンズの設計は困難である。
【０１７６】
そこで、▲３▼より、スキャンミラーの振れ角の正弦波の中、線形性が比較的良い部分のみで映像表示をすれば、ディストーションの制御が楽になるので、投影光学系の設計が容易になる。
【０１７７】
すなわち、図１１に示すように、振幅φ₀ ／ｋで正弦波状に振動するスキャンミラーの振幅のｋ×１００％、すなわち、±φ₀ の範囲のスキャンミラーの振れ角を映像表示に使用するとき、スキャンミラーの振れ角をφとする。この場合の各画角におけるφ／φ₀ の関係は図１２に示すようになる。
【０１７８】
図１２より、ｋ＝０．９５以下の場合、すなわち、正弦波の振幅の９５％以下を利用すると、φ／φ₀ の線形性が良くなり、ｆアークサインθレンズにするためのディストーションの制御が楽になることが分かる。
【０１７９】
また、正弦波状に振動するミラーの振幅全てを利用して映像表示を行うと、走査速度の速い画面中央部分と走査速度の遅い画面周辺部分の走査速度の差が大きくなりすぎる。その結果、電気的像歪み補正を行う場合でも精度良く補正を行うことができなくなる。
【０１８０】
以上の理由より、正弦波状に振動する走査手段の振幅の９５％以下を映像表示に利用することが望ましい。
【０１８１】
本発明の第４９の映像表示装置は、第４８の映像表示装置において、正弦波状に振動する走査手段の振幅の９０％以下を映像表示に利用することを特徴とするものである。
【０１８２】
この映像表示装置は後記の実施例３〜１１が対応する。
【０１８３】
この映像表示装置の作用効果を以下に説明する。映像表示に利用する走査手段の振幅の割合を９０％にすると、さらに線形性が良くなり、ｆアークサインθレンズの設計が非常に楽になる。また、映像表示にブランキング期間を設ける場合、正弦波状に振動するミラーの振幅の９０％程度を利用すればよい。
【０１８４】
本発明の第５０の映像表示装置は、第１、７〜１６の映像表示装置において、主走査方向の走査を繰り返し２次元像を形成するとき、主走査方向は正弦波状に振動する走査ミラーで、副走査方向は振れ角がリニアに変化する走査ミラーであることを特徴とするものである。
【０１８５】
この映像表示装置は後記の実施例９が対応する。
【０１８６】
この映像表示装置の作用効果を以下に説明する。ポリゴンミラーや三角波状に振動するミラーは、スキャンミラーの傾角がリニアに変化する。このようなスキャンミラーを使用して電気的像歪み補正なしに等速走査するには、投影光学系をｆθレンズにする必要がある。１次元ｆθレンズのディストーション特性を図１３に示す。画角が小さい場合はｔａｎθ≒θであることから、ミラー振れ角φ₀ が±２０°以下の場合、同じミラー振れ角に対して、ｆθレンズで発生させるべきマイナスのディストーションの量は、ｆアークサインθレンズのプラスのディストーションの量より少ない。すなわち、特にφ₀ が小さい場合、ｆアークサインθレンズよりもｆθレンズの方が設計が容易である。
【０１８７】
一方、垂直方向のスキャナ傾角を徐々に変化させながら水平走査を繰り返して２次元の像を形成する場合、主走査方向である水平方向は高速走査が必要であるが、副走査方向の垂直方向の走査はそれほど高速の走査ではない。
【０１８８】
したがって、主走査方向（水平方向）は正弦波状に振動するミラーで、副走査方向（垂直方向）は振れ角がリニアに変化するミラーを使用すれば、高速走査時に電気的像歪み補正なしに等速走査をするための投影光学系の設計が容易になる。この場合、投影光学系は、映像表示に利用するミラー振れ角に対して、主走査方向（水平方向）はｆアークサインθレンズ特性を持ち、副走査方向（垂直方向）はｆθレンズ特性を持つことが望ましい。
【０１８９】
本発明の第５１の映像表示装置は、第１、７〜１６の映像表示装置において、主走査方向も副走査方向も正弦波状に振動するミラーであることを特徴とするものである。
【０１９０】
この映像表示装置は後記の実施例１０が対応する。
【０１９１】
この映像表示装置の作用効果を以下に説明する。非常に高速で走査する場合には、主走査方向（水平方向）も主走査方向と垂直な副走査方向（垂直方向）も共振ミラーのように正弦波状に振動する走査手段を使用する必要がある。この走査手段を使用することで高速走査に対応できる。この場合、投影光学系は、映像表示に利用するミラー振れ角に対して、主走査方向（水平方向）も副走査方向（垂直方向）もｆアークサインθレンズ特性を持つことが望ましい。
【０１９２】
本発明の第５２の映像表示装置は、第１、７〜１６の映像表示装置において、走査手段がフォトリソグラフィーの工程を利用して製作したマイクロマシンミラーであることを特徴とするものである。
【０１９３】
この映像表示装置は後記の実施例１〜１１が対応する。
【０１９４】
この映像表示装置の作用効果を以下に説明する。特開平１０−２０２２６号に開示されているようなマイクロマシンミラーの場合、走査手段が非常に小型にできる。これは、特に、本発明の映像表示装置をＨＭＤとして利用する場合に、有効である。
【０１９５】
また、例えば、静電駆動方式のマイクロマシンミラーの場合、バックライトと透過型ＬＣＤ（液晶表示装置）を利用したＨＭＤよりも低消費電力化できる。これは、バッテリー駆動する携帯用のＨＭＤや携帯用のプロジェクタ等の場合に有効である。
【０１９６】
本発明の第５３の映像表示装置は、第１、７〜１６の映像表示装置において、逆光線追跡で、走査手段から映像表示素子に至る光学系が、少なくとも２面の光学作用を有する面で構成され、この光学系を走査手段側と映像表示素子側に２分割する場合、走査手段側でプラスの球面収差を発生させ、映像表示素子側でマイナスの球面収差を発生させるようになっていることを特徴とするものである。
【０１９７】
この映像表示装置は後記の実施例８、９が対応する。
【０１９８】
この映像表示装置の作用効果を以下に説明する。図１４に示すように、映像表示素子６の法線から離れるにつれて、映像表示素子６を発する光の強度が弱くなるとする。このようなむらを持つ映像表示素子６からの光を単に収束しただけでは、瞳面での強度むらとなり結像性能上好ましくない。また、本発明の光学系をＨＭＤ光学系として利用する場合、瞳面での強度むらがあると、ＨＭＤに対する眼球の位置合わせ誤差で明るさが低下するし、虚像１０の軸外観察時の明るさ低下にもなり好ましくない。
【０１９９】
そこで、図１５（ａ）、（ｂ）に示すように、逆光線追跡で、スキャナ４から映像表示素子６に至る光学系５を、少なくとも２面の光学作用を有する面で構成し、この光学系５のスキャナ側光学系Ｌ２でプラスの球面収差を発生させ、この光学系５の映像表示素子側光学系Ｌ１でマイナスの球面収差を発生させれば、強度むらのある光源に対して射出瞳面（スキャナ面）での強度むらを補正することができる。スキャナ４から映像表示素子６に至る光学系は、入射瞳からスキャナ４までの光学系に比べると画角が小さいので、このような球面収差の補正を最も効果的に行うことができる。なお、図１５（ａ）は光学系５を映像表示素子６側から正パワーの光学系Ｌ１と正パワーの光学系Ｌ２で構成する場合であり、図１５（ｂ）は正パワーの光学系Ｌ１と負パワーの光学系Ｌ２で構成する場合である。
【０２００】
本発明の第５４の映像表示装置は、第１、７〜１６の映像表示装置において、走査方向の面内（２次元走査の場合は、主走査方向と副走査方向のそれぞれの面内）で、
３×Ｇ＞ｆ・tan ２φ／ｄ＞Ｇ／２ ・・・（７）
を満足することを特徴とするものである。ここで、
Ｇ：走査方向画素数
ｆ：映像表示素子から走査手段に至る集光光学系の走査方向面内での焦点距離φ：映像表示に利用する走査手段の走査方向の片側振れ角
（±φの範囲の走査手段振れ角を映像表示に利用する）
ｄ：走査方向の映像表示素子の大きさの半分
ただし、逆光線追跡において次式で定義されるｆを走査手段から映像表示素子に至る集光光学系の焦点距離とする。
【０２０１】
ｆ＝Ｙ／β tan２φ
ここで、Ｙは走査方向における中間像の大きさの半分、βは走査方向における映像表示素子から中間像に至る光学系の倍率である。
【０２０２】
なお、本発明の映像表示装置の光学系は、軸上主光線に対して偏心して配置されている面を含む偏心光学系なので、通常の近軸光線追跡では正確な焦点距離を求めることができない。そこで、集光光学系の焦点距離を上記のように定義する。
【０２０３】
この映像表示装置は後記の実施例１〜１１が対応する。
【０２０４】
この映像表示装置の作用効果を以下に説明する。光学系を図１６のように構成するとする。順追跡で、映像表示素子６からの光を集光レンズ５で平行化し、スキャナ４でスキャンした光をリレーレンズ３で中間像７として形成後、接眼レンズ２で瞳１（ＨＭＤ光学系の場合は、観察者の瞳孔又は回旋中心）に導くとする。このとき、接眼レンズ２からｆ３の位置でかつリレーレンズ３からｆ２の位置に中間像７を形成し、リレーレンズ３からｆ２の位置でかつ集光レンズ５からｆ１の位置に走査手段４を配置し、集光レンズ５からｆ１の位置に映像表示素子６を配置するとする。
【０２０５】
また、映像表示素子６に図１７（ａ）又は図１７（ｂ）のような映像を表示し、走査方向に走査方向画素数分の映像表示素子６の像を形成するとする。
【０２０６】
このとき、光学系の構成が不適切であると、次のような不具合が生ずる。例えば、映像表示素子６の大きさが大きすぎたり、光学系の倍率が大きすぎると、図１８のように形成した映像表示素子６の像１１（仮想的な画素）が大きく重なり合い、良好な像として観察することができなくなる。また、別の例として、映像表示素子６の大きさが小さすぎたり、光学系の倍率が小さすぎたり、映像表示素子６に表示する映像の間隔が大きすぎたりすると、図１９のように形成した映像表示素子６の像１１（仮想的な画素）が離れすぎ、ここの場合も、良好な像として観察することができなくなる。
【０２０７】
そこで、観察しやすい良好な像を形成するには、以下に説明するように、映像表示素子６の大きさ、投影光学系の構成、映像表示素子６に表示する映像の間隔を適切に設定する必要がある。
【０２０８】
中間像７における、画素間隔＝ｋ・画素大きさ、とすると、
走査方向の画素数Ｇ≒中間像の大きさ／仮想画素間隔
＝（中間像の大きさ／中間像での映像表示素子の像の大きさ）／ｋ
＝ｆ・tan ２φ／（ｄ・ｋ）
となる。良好な像として観察するには、２＞ｋ＞１に設定するのが好ましい。
【０２０９】
したがって、図１６の光学系で、２＞ｋ＞１とするには、次式を満足する必要がある。
【０２１０】
２・Ｇ＞ｆ・tan ２φ／ｄ＞Ｇ
この条件を満たせば、図１８や図１９のような不具合なく、良好な像として観察することができる。
【０２１１】
以上の説明は、図１６のように、接眼レンズ２からｆ３の位置でかつリレーレンズ３からｆ２の位置に中間像７を形成し、リレーレンズ３からｆ２の位置でかつ集光レンズ５からｆ１の位置に走査手段４を配置し、集光レンズ５からｆ１の位置に映像表示素子６を配置した場合の結果である。実際には、光学系の小型化のため等に中間像７やスキャナ４や映像表示素子６の位置を図１６の位置からずらしたり、電気的像歪み補正なしに等速走査をするために光学系でディストーションを発生させたりする。したがって、この点を考慮すると、以下の条件式を満足することが望ましい。
【０２１２】
３×Ｇ＞ｆ・tan ２φ／ｄ＞Ｇ／２ ・・・（７）
なお、上記条件式を満たすように、映像表示素子６に遮蔽マスクをしてもよい。
【０２１３】
本発明の第５５の映像表示装置は、映像表示素子に表示された映像を虚像として形成し観察者眼球に導く第１〜５４の映像表示装置と、この映像表示装置を観察者顔面前方に保持する支持部とを備えて構成されたことを特徴とするものである。
【０２１４】
この映像表示装置は後記の実施例１〜１０が対応する。
【０２１５】
この映像表示装置の作用効果を以下に説明する。映像表示素子としてＬＣＤを用いたＨＭＤは、偏光フィルタとカラーフィルタを使用するので、光源光の利用効率が悪い。本発明の光学系の場合、光源光の利用効率が大きく向上する。また、走査手段として、例えば静電駆動方式のマイクロマシンミラーを使用すれば、低消費電力化できるので、携帯用のＨＭＤとして最適である。
【０２１６】
本発明の第５６の映像表示装置は、第５５の映像表示装置において、映像表示装置を観察者の左右の眼に対応してそれぞれ１つずつ配置していることを特徴とするものである。
【０２１７】
この映像表示装置は後記の実施例１〜１０が対応する。
【０２１８】
この映像表示装置の作用効果を以下に説明すると、左右に視差のある映像を表示するようにすれば、立体視が可能となる。
【０２１９】
本発明の第５７の映像表示装置は、映像表示素子に表示された映像を実像として表示する第１〜５４の映像表示装置を備えて構成されたことを特徴とするプロジェクタ、レーザビームプリンタあるいはバーコードリーダである。
【０２２０】
この映像表示装置は後記の実施例１１が対応する。
【０２２１】
この映像表示装置の作用効果を以下に説明すると、映像表示素子としてＬＣＤを用いたプロジェクタは、偏光フィルタとカラーフィルタを使用するので、光源光の利用効率が悪い。本発明の光学系の場合、光源光の利用効率が大きく向上する。また、本発明の光学系は、上述したように、投影光学系にビーム整形機能を持たせることができるので、ＬＤを光源とする光学系のビーム整形用の光学素子を削減することができる。
【０２２２】
【発明の実施の形態】
以下に、本発明の映像表示装置の実施例１から実施例１１について図面を参照して説明する。
【０２２３】
各実施例の逆光線追跡での構成パラメータは後記するが、その各実施例の構成パラメータにおいては、図２０に示すように、逆光線追跡で、軸上主光線（観察者視軸）２２を、光学系の射出瞳（逆光線追跡では入射瞳：観察者の瞳孔あるいは回旋中心位置）２１の中心を通り、スキャンミラー２３を経て映像表示素子２４中心に至る光線で定義する。そして、瞳２１の中心を偏心光学面の原点として、軸上主光線２２に沿う方向をＺ軸方向とし、瞳２１から光学系の第１面３１に向かう方向をＺ軸正方向とし、このＺ軸と映像表示素子２４中心を含む平面をＹ−Ｚ平面とし、原点を通りＹ−Ｚ平面に直交し、紙面の手前から裏面側に向かう方向をＸ軸正方向とし、Ｘ軸、Ｚ軸と右手直交座標系を構成する軸をＹ軸とする。図２０には、この座標系を図示してある。その他の実施例を示す図２１〜図３２については、この座標系の図示は省く。
【０２２４】
実施例１〜１１では、このＹ−Ｚ平面内で各面の偏心を行っており、また、各回転非対称自由曲面の唯一の対称面をＹ−Ｚ面としている。
【０２２５】
偏心面については、上記座標系の原点から、その面の面頂位置の偏心量（Ｘ軸方向、Ｙ軸方向、Ｚ軸方向をそれぞれＸ，Ｙ，Ｚ）と、その面の中心軸（自由曲面については、前記（ａ）式のＺ軸）のＸ軸、Ｙ軸、Ｚ軸それぞれを中心とする傾き角（それぞれα，β，γ（°））とが与えられている。なお、その場合、αとβの正はそれぞれの軸の正方向に対して反時計回りを、γの正はＺ軸の正方向に対して時計回りを意味する。
【０２２６】
また、各実施例の光学系を構成する光学作用面の中、特定の面（仮想面を含む。）とそれに続く面が共軸光学系を構成する場合に、面間隔が与えられており、その他、媒質の屈折率、アッベ数が慣用法に従って与えられている。
【０２２７】
また、本発明で用いられる自由曲面の面の形状は前記（ａ）式により定義し、その定義式のＺ軸が自由曲面の軸となる。
【０２２８】
また、ＤＯＥについては、設計法としてSweatt法（超高屈折率法）を使用し（W.C.Sweatt,^Mathematical equivalence between a holographic optical element and an ultra-high index lens",J.Opt.Soc.Am,Vol.69,No.3(1979) ）、基準波長＝５８７．５６ｎｍ（ｄ線）とし、その基準波長における超高屈折率レンズの屈折率＝１００１、アッベ数＝−３．４５とした。
【０２２９】
なお、データの記載されていない自由曲面に関する項は０である。屈折率については、ｄ線（波長５８７．５６ｎｍ）に対するものを表記してある。長さの単位はｍｍである。
【０２３０】
また、自由曲面の他の定義式として、以下の（ｂ）式で与えられるＺｅｒｎｉｋｅ多項式がある。この面の形状は以下の式により定義する。その定義式のＺ軸がＺｅｒｎｉｋｅ多項式の軸となる。回転非対称面の定義は、Ｘ−Ｙ面に対するＺの軸の高さの極座標で定義され、ＡはＸ−Ｙ面内のＺ軸からの距離、ＲはＺ軸回りの方位角で、Ｚ軸から測った回転角で表せられる。
【０２３１】

なお、Ｘ軸方向に対称な光学系として設計するには、Ｄ₄ ，Ｄ₅ ，Ｄ₆ 、Ｄ₁₀０，Ｄ₁₁，Ｄ₁₂，Ｄ₁₃，Ｄ₁₄，Ｄ₂₀，Ｄ₂₁，Ｄ₂₂…を利用する。
【０２３２】
その他の面の例として、次の定義式（ｃ）があげられる。
【０２３３】
Ｚ＝ΣΣＣ_nmＸＹ
例として、ｋ＝７（７次項）を考えると、展開したとき、以下の式で表せる。
【０２３４】

なお、本発明の実施例では、前記（ａ）式を用いた自由曲面で面形状が表現されているが、上記（ｂ）式、（ｃ）式を用いても同様の作用効果を得られるのは言うまでもない。
【０２３５】
以下の実施例１から実施例１１の全てにおいて、仕様は、水平画角３０°、垂直画角２２．７°、逆光線追跡における入射瞳径４ｍｍである。そして、実施例１〜１０が虚像を形成するＨＭＤ用光学系、実施例１１がプロジェクタ、レーザビームプリンタ、バーコードリーダ等の実像形成用光学系である。
【０２３６】
（実施例１）
この実施例は、ＨＭＤ用光学系で、観察者眼球の１ｍ先に映像表示素子２４の虚像を形成するとき、映像信号に応じて映像表示光を強度変調する。そして、この映像表示光に同期して、スキャナのＹ方向の傾角を徐々に変化させながらＸ方向のスキャンを繰り返すことで、２次元の虚像を形成する。
【０２３７】
図２０は、この実施例の光学系を観察者の横から見た図（Ｙ−Ｚ平面図）である。瞳２１に観察者眼球の瞳孔又は回旋中心を位置させて表示された映像を観察する。図１の配置の上下方向を逆方向に配置してもよい。また、これを観察者の上側から見た図（Ｘ−Ｚ平面図）となるように配置してもよい。これは以下の全ての実施例について言えるが、以下の実施例ではいちいち説明しない。また、以下の光路図では、全て分かりやすいように、スキャナ２３の大きさを必要以上に大きく描いてある。
【０２３８】
この実施例のアイリリーフは３１ｍｍであり、映像表示素子２４として、ＬＥＤ、ＬＤ等が使用できる。また、ポリゴンミラー、ガルバノミラー等を走査手段２３として使用することができる。特開平１０−２０２２６号に開示されているようなフォトリソグラフィー工程を利用して製作したいわゆるマイクロマシンスキャナは、小型、低消費電力等の利点を持つので、ＨＭＤ用としては最適である。この場合、往路だけの走査でも、往復走査でもどちらでもよい。
【０２３９】
この実施例の光学系の構成は、１個の偏心プリズム３０で投影光学系を構成している。この偏心プリズム３０は第１面３１から第５面３５の５面からなり、逆光線追跡で、瞳２１→第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成する。中間像からの光を、第３反射面３３と第２透過面３４で平行光に近づけ、スキャナ２３に導く。スキャナ２３の反射光をプリズム３０に設けた第４反射面３５で収束光として映像表示素子２４に導く。
【０２４０】
なお、第１反射面３２とシースループリズム２５との接合面にＨＭ膜を形成し、シースループリズム２５の瞳２１とは反対側に液晶シャッタ等の外界光の透過率を切り換える手段を配置すれば、スーパーインポーズ機能やシースルー機能が付加できる。ここで、シースループリズム２５とは、投影光学系（プリズム）３０とシースループリズムの合成パワーが外界光に対して略０となる光学素子のことである。
【０２４１】
この実施例においては、スキャナ２３と偏心プリズム３０により形成される像の歪みを打ち消すような映像を映像表示素子２４に表示して、２次元的電気的像歪み補正を行う。
【０２４２】
この実施例の変形として、図２１に示すように、偏心プリズム３０を第１プリズム３０₁ と第２プリズム３０₂ で構成してもよい。その場合には、逆光線追跡で、瞳２１→第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、第３透過面３６→第４透過面３７を経て第２プリズム３０₂ 内に中間像を形成する。中間像からの光を、第３反射面３３と第２透過面３４で平行光に近づけ、スキャナ２３に導く。スキャナ２３の反射光を第２プリズム３０₂ に設けた第４反射面３５で収束光として映像表示素子２４に導く。
【０２４３】
なお、以上及び以下の全ての実施例は、分かりやすいように、視軸を水平方向に統一しているが、観察しやすいように視軸を下向き１０°等に変更してもよい。
【０２４４】
この実施例１の利点は、投影光学系３０で４回反射、スキャナ２３で１回反射の計５回反射しているので、折り畳みの効果で光学系の小型化ができている。また、投影光学系３０を反射作用を主体に構成しているので、色収差の発生が少ない。
【０２４５】
また、逆光線追跡で、接眼光学系から中間像へ入射する主光線は、軸上主光線２２に対して１８．８°以下の収束光として入射している。そのため、接眼光学系から走査手段２３までの光束の有効径が小さくでき、光学系が小型化できている。
【０２４６】
また、プリズム部材１個で投影光学系が構成できているので、先行例に比べて大幅に部品点数を削減している。
【０２４７】
また、走査手段２３と映像表示素子２４を投影光学系３０の上に配置しているので、重量バランスが良い。
【０２４８】
また、第２透過面３４と第４反射面３５は異なる光学作用を持つが、見かけ上連続性の良い面の構成となっている。よって、プリズム部材３０を成形で製作する際に、１つの型でこの２面に対応でき、製作性が良い構成となっている。
【０２４９】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±１４．４°、Ｙ方向のスキャナミラー２３の振れ角φｙ＝±７．６８°であり、よって、φｘ／θｘ＝１４．４／１５＝０．９６、φｙ／θｙ＝７．６８／１１．３６＝０．６８となる。
【０２５０】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝３３．３°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２４．９°である。
【０２５１】
（実施例２）
この実施例は、図２２に示すように、逆光線追跡で、スキャナ２３から映像表示素子２４間の構成が実施例１とは異なる。
【０２５２】
すなわち、この実施例の偏心プリズム３０は第１面３１から第４面３４、第５面３８、第６面３９の６面からなり、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成する。中間像からの光を、第３反射面３３と第２透過面３４で平行光に近づけ、スキャナ２３に導く。スキャナ２３の反射光をプリズム３０に設けた第３透過面３８→第４透過面３９を経てプリズム３０を横断して収束光として映像表示素子２４に導く。
【０２５３】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±８．３０°、Ｙ方向のミラー振れ角φｙ＝±１１．２°であり、よって、φｘ／θｘ＝０．５５、φｙ／θｙ＝０．９９となる。
【０２５４】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝２９．６°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２８．５°である。
【０２５５】
（実施例３）
この実施例は、図２３に示すように、投影光学系を構成する１個の偏心プリズム３０は第１面３１から第３面３３、第４面４０、第５面４１の５面からなり、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成し、中間像→第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第３透過面３３（＝第３反射面＝第２透過面）→第５反射面４１→第４透過面３３（＝第３透過面＝第３反射面＝第２透過面）を経てプリズム３０を横断して収束光として映像表示素子２４に導く。この場合、第２反射面３１と第３反射面３３は全反射である。
【０２５６】
この実施例の構成においては、兼用面が２個所３１、３３あるので、構成する光学作用面が削減されている。この２面で６面の作用をしている。
【０２５７】
また、接眼光学系とリレー光学系を対称な構成としているので、それぞれの発生収差がキャンセルされ、全体の収差が良好に補正されている。また、特に、ディストーションが良好に補正されている。２次元走査を行った場合、逆光線追跡で、映像表示素子２４における各主光線の結像位置のずれは、Ｘ方向（主走査方向）、Ｙ方向（副走査方向）共、５μｍ以下である。これは、順光線追跡において、Ｘ方向（主走査方向）のディストーションが０．３％以下、Ｙ方向（副走査方向）のディストーションが０．５％以下であることを意味する。その結果、電気的像歪み補正なしに２次元的直線走査を行うことができる。
【０２５８】
また、正弦波状に振動するミラー２３の振幅の５５％に対してｆアークサインθレンズ特性を持たせている。そのため、正弦波状に振動するスキャンミラー２３を使用する場合、振幅の５５％を使用すれば、電気的像歪み補正なしに直線走査、等速走査を行うことができ、高速走査に対応できる。
【０２５９】
この場合に、Ｘ方向のミラー振れ角φｘ＝±１３．４°、Ｙ方向のミラー振れ角φｙ＝±１３．８°の振幅の５５％が映像表示に必要なＸ方向のミラー振れ角、φｘ＝±７．３６°、Ｙ方向のミラー振れ角φｙ＝±７．６０°となる。
【０２６０】
また、等速走査性の補正を行えば、正弦波状に振動するミラー２３の振幅全部を利用することもできるし、ミラー振れ角がリニアに変化するミラー２３を利用することもできる。
【０２６１】
また、以下の実施例でいくつか説明するように、Ｘ方向（主走査方向）、Ｙ方向（副走査方向）共、ディストーション特性をｆθ特性に変更するのは可能である。
【０２６２】
また、映像表示素子２４の大きさが４〜５μｍ角の場合、順光線追跡で形成される像において、仮想的な画素が密着した状態に近くなる。そのため、映像が観察しやすい。
【０２６３】
また、逆光線追跡で、スキャナ２３の後をプリズム３０への入射、プリズム３０からの射出という構成にしており、映像表示素子光のビーム整形が可能である。したがって、ＬＤのように楕円状の断面形状を持つ映像表示素子２４を効率良く使用することができる。本実施例の場合、映像表示素子側のＮＡ（開口数）は、ＮＡｘ＝０．３２、ＮＡｙ＝０．２３で、横長断面を持つ映像表示素子光に対するビーム整形を行っている。
【０２６４】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±７．３６°、Ｙ方向のミラー振れ角φｙ＝±７．６０°であり、よって、φｘ／θｘ＝０．４９、φｙ／θｙ＝０．６７となる。
【０２６５】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝１８．７°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２３．４°である。
【０２６６】
（実施例４）
この実施例は実施例３と同様であり、図２４に示すように、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成し、中間像→第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第３透過面３３（＝第３反射面＝第２透過面）→第５反射面４１→第４透過面３３（＝第３透過面＝第３反射面＝第２透過面）を経てプリズム３０を横断して収束光として映像表示素子２４に導く。この場合、第２反射面３１と第３反射面３３は全反射である。
【０２６７】
この実施例は、順光線追跡における瞳倍率を大きくすることで、実施例３の映像表示素子２４から中間像までを小型化したものであり、スキャナ２３の前方への突出量が減っている。
【０２６８】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±８．７３°、Ｙ方向のミラー振れ角φｙ＝±９．８３°であり、よって、φｘ／θｘ＝０．５８、φｙ／θｙ＝０．８７となる。
【０２６９】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝２３．７°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２５．５°である。
【０２７０】
（実施例５）
この実施例は実施例３の映像表示素子２４直前の第４透過面を別の面４２にした例であり、図２５に示すように、投影光学系を構成する１個の偏心プリズム３０は第１面３１から第３面３３、第４面４０、第５面４１、第６面４２の６面からなり、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成し、中間像→第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第３透過面３３（＝第３反射面＝第２透過面）→第５反射面４１→第４透過面４２を経てプリズム３０を横断して収束光として映像表示素子２４に導く。この場合、第２反射面３１と第３反射面３３は全反射である。
【０２７１】
この実施例において、２次元走査を行った場合、逆光線追跡で、映像表示素子２４における各主光線の結像位置のずれは、Ｘ方向（主走査方向）、Ｙ方向（副走査方向）共、３．３μｍ以下であるので、２次元的に良好な直線走査性を持つ。
【０２７２】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±７．７３°、Ｙ方向のミラー振れ角φｙ＝±９．７３°であり、よって、φｘ／θｘ＝０．５２、φｙ／θｙ＝０．８６となる。
【０２７３】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝２０．０°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０．２３°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２３．７°である。
（実施例５−１）
この実施例は実施例５と同様であり、図２６に示すように、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成し、中間像→第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第３透過面３３（＝第３反射面＝第２透過面）→第５反射面４１→第４透過面４２を経てプリズム３０を横断して収束光として映像表示素子２４に導く。
【０２７４】
この実施例は、実施例５の映像表示素子２４直前の第４透過面４２を第１反射面３２に近づけたものである。
【０２７５】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±７．８３°、Ｙ方向のミラー振れ角φｙ＝±１１．２°であり、よって、φｘ／θｘ＝０．５２、φｙ／θｙ＝０．９９となる。
【０２７６】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝２１．２°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０．２６°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２２．８°である。
【０２７７】
（実施例６）
この実施例は実施例５と同様の６面からなる偏心プリズム３０の第２透過面３３とスキャナ２３の間にＤＯＥ４４を追加した例であり、図２７に示すように、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射→中間像→第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経て、入射側に回折面４３を設けたＤＯＥ４４を介してスキャナ２３に導く。スキャナ２３の反射光をＤＯＥ４４を逆に介して第３透過面３３（＝第３反射面＝第２透過面）→第５反射面４１→第４透過面４２を経てプリズム３０を横断して収束光として映像表示素子２４に導く。このように、逆光線追跡で、スキャナ２３へ入射するときとスキャナ２３から反射するときの両方で、ＤＯＥ４４の作用を受けるようにしている。
【０２７８】
図２７に図示しているように、ＤＯＥ４４をスキャナ２３の保護部材や密封部材として使用するなど、スキャナ２３と一体化することができる。ここでは、ＤＯＥの回折面４３を平行平面基板のプリズム３０側に配置したが、プリズム３０とは反対側（スキャナ側）の基板面に配置すれば、回折面４３を汚れから保護することができる。
【０２７９】
この実施例では、簡単のためにＤＯＥ４４は投影光学系３０で発生する色収差を補正しているが、図４〜図６等を用いて説明したように、ＤＯＥにより投影光学系全体の特定の色収差を発生させるようにしてもよい。これは、以下のＤＯＥを使用したすべての実施例でも同様である。
【０２８０】
この実施例においては、２次元走査を行った場合、逆光線追跡で、映像表示素子２４における各主光線の結像位置のずれは、Ｘ方向（主走査方向）、Ｙ方向（副走査方向）共、１．６μｍ以下であるので、２次元的に良好な直線走査性を持っている。また、逆光線追跡における射出瞳（スキャナ）位置での瞳収差は、０．１５ｍｍ以下と良好である。
【０２８１】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±６．２５°、Ｙ方向のミラー振れ角φｙ＝±１２．４°であり、よって、φｘ／θｘ＝０．４２、φｙ／θｙ＝１．０９となる。
【０２８２】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝１９．５°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０．０６°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２３．６°である。
【０２８３】
（実施例７）
この実施例は、図２８に示すように、実施例５、実施例５−１と同様の６面からなる偏心プリズム３０の第４透過面４２に透過型のＤＯＥの回折面４３を設けた例である。すなわち、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成し、中間像→第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第３透過面３３（＝第３反射面＝第２透過面）→第５反射面４１で反射させ、第４透過面４２の回折面４３を経てプリズム３０を横断して収束光として映像表示素子２４に導く。
【０２８４】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±７．６３°、Ｙ方向のミラー振れ角φｙ＝±９．７２°であり、よって、φｘ／θｘ＝０．５１、φｙ／θｙ＝０．８６となる。
【０２８５】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝２０．６°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２３．６°である。
【０２８６】
（実施例８）
この実施例は、図２９に示すように、実施例５、実施例５−１と同様の６面からなる偏心プリズム３０の第５反射面４１に反射型のＤＯＥの回折面４５を設けた例である。すなわち、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成し、中間像→第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第３透過面３３（＝第３反射面＝第２透過面）でプリズム３０内に導入し、第５反射面４１の回折面４５で回折反射させ、第４透過面４２を経てプリズム３０を横断して収束光として映像表示素子２４に導く。
【０２８７】
この実施例においては、図１５（ａ）の構成で、法線から離れると強度が弱くなる映像表示素子２４の配光特性の補正を行っている。
【０２８８】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±８．５０°、Ｙ方向のミラー振れ角φｙ＝±１３．３°であり、よって、φｘ／θｘ＝０．５７、φｙ／θｙ＝１．１７となる。
【０２８９】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝２１．１°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２２．９°である。
【０２９０】
（実施例９）
この実施例は、図３０に示すように、実施例５、実施例５−１と同様の偏心プリズム３０を第１プリズム３０₁ と第２プリズム３０₂ に分割した例であり、第１プリズム３０₁ は第１面３１、第２面３２、第３面４６の３面からなり、第２プリズム３０₂ は第１面４７、第２面４８、第３面４９、第４面５０、第５面５１の５面からなり、逆光線追跡で、瞳２１→第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、第２透過面４６→第３透過面４７を経て第２プリズム３０₂ 中に中間像を形成し、中間像→第３反射面４８で全反射→第４反射面４９→第４透過面４８（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第５透過面４８（＝第３反射面＝第４透過面）→第５反射面５０で反射させ、第６透過面５１を経て第２プリズム３０₂ を横断して収束光として映像表示素子２４に導く。
【０２９１】
この実施例においては、２次元走査を行った場合、逆光線追跡で、映像表示素子２４における各主光線の結像位置のずれは、Ｘ方向（主走査方向）、Ｙ方向（副走査方向）共、３μｍ以下であるので、２次元的に良好な直線走査性を持つ。したがって、電気的像歪み補正なしに２次元的直線走査を行うことができる。
【０２９２】
また、主走査方向（Ｘ方向）は、正弦波状に振動するミラー振れ角の振幅の約９０％に対してｆアークサインθレンズ特性を持たせている。また、副走査方向（Ｙ方向）は、ｆθレンズ特性を持たせている。よって、副走査方向（Ｙ方向）より高周波数が必要な主走査方向（Ｘ方向）は正弦波状に振動し、低周波数の副走査方向（Ｙ方向）はスキャンミラー振れ角がリニアに変化するスキャンミラーを使用する場合、Ｘ方向の正弦波状に振動するミラー振れ角の振幅の９０％を使用すれば、電気的像歪み補正なしに２次元的な直線走査、等速走査を行うことができる。そのため、高速走査に対応できる。なお、Ｘ方向のミラー振れ角φｘ＝±１９．１°のスキャナ２３の振幅の９０％（φｘ＝±１７．２°）を映像表示に利用する。このように、Ｘ方向の振幅の約９０％が利用できるので、非常に効率が良い。
【０２９３】
なお、等速走査性の補正を行えば、正弦波状に振動するミラーの振幅全部を利用することもできるし、ミラー振れ角がリニアに変化するミラーを利用することもできる。
【０２９４】
この実施例においては、図１５（ａ）の構成で、法線から離れると強度が弱くなる映像表示素子２４の配光特性の補正を行っている。
【０２９５】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±１７．２°、Ｙ方向のミラー振れ角φｙ＝±７．９８°であり、よって、φｘ／θｘ＝１．１５、φｙ／θｙ＝０．７０となる。
【０２９６】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝１８．４°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２５．８°である。
【０２９７】
（実施例１０）
この実施例は実施例９と同様の構成で、実施例９の副走査方向（Ｙ方向）のディストーション特性を変えた例であり、図３１に示すように、逆光線追跡で、瞳２１→第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、第２透過面４６→第３透過面４７を経て第２プリズム３０₂ 中に中間像を形成し、中間像→第３反射面４８で全反射→第４反射面４９→第４透過面４８（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第５透過面４８（＝第３反射面＝第４透過面）→第５反射面５０で反射させ、第６透過面５１を経て第２プリズム３０₂ を横断して収束光として映像表示素子２４に導く。
【０２９８】
この実施例においては、主走査方向（Ｘ方向）、副走査方向（Ｙ方向）共に、正弦波状に振動するミラー振れ角の振幅の約８０％に対してｆアークサインθレンズ特性を持たせている。したがって、高速走査するために、主走査方向（Ｘ方向）、副走査方向（Ｙ方向）共に正弦波状に振動するスキャンミラーを使用する場合でも、正弦波状に振動するミラー振れ角の振幅の約８０％を使用すれば、電気的像歪み補正なしに２次元的な直線走査、等速走査を行うことができる。そのため、高速走査に対応できる。なお、Ｘ方向のミラー振れ角φｘ＝±１８．１°、Ｙ方向のミラー振れ角φｙ＝±１４．３°、のスキャナの振幅の８０％（φｘ＝±１４．５°、φｙ＝±１１．４°を映像表示に利用する。
【０２９９】
また、等速走査性の補正を行えば、正弦波状に振動するミラーの振幅全部を利用することもできるし、ミラー振れ角がリニアに変化するミラーを利用することもできる。
【０３００】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±１４．５°、Ｙ方向のミラー振れ角φｙ＝±１１．４°であり、よって、φｘ／θｘ＝０．９７、φｙ／θｙ＝１．００となる。
【０３０１】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝１７．６°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２５．７°である。
【０３０２】
（実施例１１）
この実施例は、前記のように、プロジェクタ、レーザビームプリンタ、バーコードリーダ等の実像形成用光学系であり、図３２に示すように、投影光学系を構成する１個の偏心プリズム３０は第１面３１から第３面３３、第４面４０、第５面４１、第６面４２の６面からなり、逆光線追跡で、瞳２１→プリズム３０の第１透過面３１（＝第２反射面）→第１反射面３２→第２反射面３１（＝第１透過面）で全反射させ、プリズム３０内に中間像を形成し、第３反射面３３で全反射→第４反射面４０→第２透過面３３（＝第３反射面）を経てスキャナ２３に導く。スキャナ２３の反射光を第３透過面３３（＝第３反射面＝第２透過面）→第５反射面４１→第４透過面４２を経てプリズム３０を横断して収束光として映像表示素子２４に導く。
【０３０３】
この実施例においては、瞳１から１ｍの位置に実像を形成している。なお、瞳１とプリズム３０の間隔＝３．６ｍｍである。
【０３０４】
映像表示素子としてＬＣＤを用いたプロジェクタは、偏光フィルタとカラーフィルタを使用するので、光源光の利用率が悪い。本発明の光学系の場合は、光源光の利用効率が大きく向上する。
【０３０５】
なお、画角、Ｆナンバー、映像表示素子光の結像位置を変更し、レーザビームプリンタ用、バーコードリーダ用等、他の用途の光学系として利用することもできる。レーザビームプリンタ用等は画角が大きくなるので、ｆアークサインθレンズとするためのディストーションの制御量が減りｆアークサインθレンズの設計がしやすくなる。
【０３０６】
この実施例の映像表示に必要なＸ方向のミラー振れ角φｘ＝±１８．２°、Ｙ方向のミラー振れ角φｙ＝φｙ＝±１０．３°であり、よって、φｘ／θｘ＝１．２１、φｙ／θｙ＝０．９１となる。
【０３０７】
また、逆光線追跡で、スキャナ２３の基準面に対する軸上主光線２２の入射角θｓ＝２２．１°、第１透過面３１への軸上主光線２２の入射角θ1 ＝０．８１°、第１反射面３２への軸上主光線２２の入射角θ2 ＝２０．８°である。
【０３０８】
以下に上記実施例１〜１１の構成パラメータを示す。これら表中の“ＦＦＳ”は自由曲面、“ＲＳ”は反射面、“ＳＭ”はスキャンミラー、“ＩＤ”は映像表示素子、“ＤＯＥ”は回折面を示す。

【０３０９】

【０３１０】

【０３１１】

【０３１２】

【０３１３】

【０３１４】

【０３１５】

【０３１６】

【０３１７】

【０３１８】

【０３１９】

【０３２０】
以上、本発明の映像表示装置を実施例に基づいて説明してきたが、本発明はこれらの実施例に限定されず数々の変形が可能である。
【０３２１】
以上の本発明の映像表示装置は例えば次のように構成することができる：
〔１〕 映像を表示する映像表示素子と、前記映像表示素子を発する光を走査する走査手段と、前記映像表示素子によって形成され前記走査手段により走査された映像を投影する投影光学系とからなる映像表示装置において、
前記投影光学系が、１より大きな屈折率の媒質で構成されたプリズム部材を少なくとも１個有し、
前記プリズム部材は、光束をプリズム部材に入射させる透過面と、光束をプリズム部材内で反射させる反射面、光束をプリズムから射出する透過面の少なくとも３面を有しており、前記投影光学系が含む前記プリズム部材での反射回数の合計が３回以上で、前記プリズム部材の反射面の少なくとも１面が光学的パワーを有し、光軸に対して偏心しており、
逆光線追跡で、瞳と像面である映像表示素子の間に前記投影光学系と前記走査手段が配置され、瞳からの光線は少なくとも前記プリズム部材を経て前記走査手段に至ることを特徴とする映像表示装置。
【０３２２】
〔２〕 前記投影光学系が含む前記プリズム部材での反射回数の合計が４回以上であることを特徴とする上記１記載の映像表示装置。
【０３２３】
〔３〕 前記投影光学系の反射面が光学的パワーを有することを特徴とする上記１記載の映像表示装置。
【０３２４】
〔４〕 前記投影光学系が、反射面の少なくとも１面と透過面の少なくとも１面が同一面にて形成された透過と反射の兼用面を備えていることを特徴とする上記１記載の映像表示装置。
【０３２５】
〔５〕 少なくとも１つのプリズム部材が、瞳から前記映像表示素子に向かう逆光線追跡で、少なくとも、前記プリズム部材へ入射する第１透過面、光学的パワーを有し光軸に対して偏心した第１反射面、第２反射面、前記プリズム部材から射出する第２透過面を含み、少なくとも前記第１透過面と前記第２反射面が同一の兼用面であることを特徴とする上記４記載の映像表示装置。
【０３２６】
〔６〕 逆光線追跡で、前記第２反射面における反射が全反射であることを特徴とする上記５記載の映像表示装置。
【０３２７】
〔７〕 前記投影光学系が、瞳から前記映像表示素子に向かう逆光線追跡で、少なくとも、前記プリズム部材へ入射する第１透過面、光学的パワーを有し光軸に対して偏心した第１反射面、第２反射面、第３反射面、前記プリズム部材から射出して走査手段に至る第２透過面を含み、前記第１透過面と前記第２反射面が同一の兼用面であり、前記第２反射面と前記第３反射面の間に中間像を形成することを特徴とする上記１記載の映像表示装置。
【０３２８】
〔８〕 前記投影光学系が、瞳から前記映像表示素子に向かう逆光線追跡で、前記走査手段で反射した後、前記プリズム部材の前記第４反射面を経て前記映像表示素子に結像することを特徴とする上記７記載の映像表示装置。
【０３２９】
〔９〕 前記投影光学系が、瞳から前記映像表示素子に向かう逆光線追跡で、前記走査手段で反射した後、少なくとも、第３透過面、第４透過面を経て前記映像表示素子に結像することを特徴とする上記７記載の映像表示装置。
【０３３０】
〔１０〕 前記投影光学系が、第１プリズム部材と第２プリズム部材を含み、瞳から前記映像表示素子に向かう逆光線追跡で、
前記第１プリズム部材が、前記第１プリズム部材へ入射する第１透過面、光学的パワーを有し光軸に対して偏心した第１反射面、第２反射面、前記第１プリズム部材からの射出面を含み、
前記第２プリズム部材が、前記第２プリズム部材への入射面、第３反射面、前記第２プリズム部材から射出して前記走査手段に至る第２透過面、を含み、
前記第１透過面と前記第２反射面が同一面であり、
前記第２反射面と前記第３反射面の間に中間像を形成することを特徴とする上記７記載の映像表示装置。
【０３３１】
〔１１〕 前記第２反射面での反射が全反射であることを特徴とする上記７〜１０の何れか１項記載の映像表示装置。
【０３３２】
〔１２〕 前記投影光学系が、瞳から前記映像表示素子に向かう逆光線追跡で、少なくとも、前記プリズム部材へ入射する第１透過面、光学的パワーを有し光軸に対して偏心した第１反射面、第２反射面、第３反射面、第４反射面、前記プリズム部材から射出して前記走査手段に至る第２透過面を含み、前記第１透過面と前記第２反射面、前記第３反射面と前記第２透過面が同一面であり、前記第２反射面と前記第４反射面の間に中間像を形成することを特徴とする上記１記載の映像表示装置。
【０３３３】
〔１３〕 前記投影光学系が、瞳から前記映像表示素子に向かう逆光線追跡で、前記走査手段で反射した後、少なくとも前記プリズム部材へ入射する第３透過面、第５反射面、前記プリズム部材を射出する第４透過面を経て前記映像表示素子に結像し、前記第３反射面と前記第２透過面と前記第３透過面が同一面であることを特徴とする上記１２記載の映像表示装置。
【０３３４】
〔１４〕 前記投影光学系が、瞳から前記映像表示素子に向かう逆光線追跡で、前記走査手段で反射した後、少なくとも前記プリズム部材へ入射する第３透過面、第５反射面、前記プリズム部材を射出する第４透過面を経て前記映像表示素子に結像し、前記第３反射面と前記第２透過面と前記第３透過面と前記第４透過面が同一面であることを特徴とする上記１３記載の映像表示装置。
【０３３５】
〔１５〕 前記投影光学系が、第１プリズム部材と第２プリズム部材を含み、瞳から前記映像表示素子に向かう逆光線追跡で、
前記第１プリズム部材が、前記第１プリズム部材へ入射する第１透過面、光学的パワーを有し光軸に対して偏心した第１反射面、第２反射面、前記第１プリズム部材から射出する第２透過面を含み、
前記第２プリズム部材が、前記第２プリズム部材へ入射する第３透過面、第３反射面、第４反射面、前記第２プリズム部材から射出して前記走査手段に至る第４透過面、前記走査手段から前記第２プリズム部材に入射する第５透過面、第５反射面、前記第２プリズム部材から射出して前記映像表示素子に至る第６透過面を含むことを特徴とする上記１２記載の映像表示装置。
【０３３６】
〔１６〕 前記投影光学系が、瞳から前記映像表示素子に向かう逆光線追跡で、入射瞳と前記走査手段が略共役な位置関係にあり、前記投影光学系内で一度中間結像し、入射瞳から中間像までの光学系と、中間像から前記走査手段までの光学系が中間像に対して対称な構成となっていることを特徴とする上記１記載の映像表示装置。
【０３３７】
〔１７〕 前記投影光学系が、映像表示素子光を集光光学系で略コリメートし、瞳と略共役な位置の前記走査手段に導き、前記走査手段で走査した光をリレー光学系で中間像として結像し、中間像を接眼光学系で瞳に導く構成で、
逆光線追跡で、前記投影光学系が、入射瞳と前記走査手段の間に少なくとも３面の光学的パワーを持つ反射面を有し、
逆光線追跡で、前記接眼光学系が少なくとも２面の反射面を有し、前記リレー光学系が少なくとも１面の反射面を有し、入射瞳からの光に対する２回目の反射面と、前記走査手段の手前の最後の反射面の間に中間像を形成することを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３３８】
〔１８〕 前記投影光学系が、逆光線追跡で、瞳からの光を中間像として形成する前記接眼光学系が少なくとも２面の反射面を有し、中間像からの光を前記走査手段に導く前記リレー光学系が少なくとも２面の反射面を有することを特徴とする上記１７記載の映像表示装置。
【０３３９】
〔１９〕 逆光線追跡で、入射瞳から前記投影光学系に入射した光は、一度中間像として結像した後に、入射瞳と略共役な位置の前記走査手段を経て前記映像表示素子に結像し、前記走査手段の走査方向における入射瞳から前記投影光学系に入射する半画角θと、前記走査手段の走査方向における映像表示に必要な前記走査手段の片側振れ角φが次式を満たすことを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３４０】
０．１≦φ／θ≦１．８ ・・・（１）
〔２０〕 次式を満たすことを特徴とする上記１９記載の映像表示装置。
【０３４１】
０．２５≦φ／θ≦１．７ ・・・（１−１）
〔２１〕 逆光線追跡において、入射瞳から入射した光線が中間像を形成する際に、入射瞳から中間像に入射する主光線が収束状態であることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３４２】
〔２２〕 前記投影光学系が、前記プリズム部材を１個含むことを特徴とする上記１記載の映像表示装置。
【０３４３】
〔２３〕 前記投影光学系が、前記プリズム部材を少なくとも２個含み、
１≧ｙ' ／ｙ＞０．７ ・・・（２）
を満たすことを特徴とする上記１、１０、１５、１６の何れか１項記載の映像表示装置。ここで、ｙは光学系における中間像高、ｙ' は２つのプリズム部材が対向する面における最軸外光束の主光線高である。
【０３４４】
〔２４〕 前記投影光学系が、前記プリズム部材を２個含み、逆光線追跡で、瞳から第１プリズム部材と第２プリズム部材を経て前記映像表示素子に至るとき、前記第２プリズム部材内に中間像を形成していることを特徴とする上記２３記載の映像表示装置。
【０３４５】
〔２５〕 前記プリズム部材の屈折率が１より大きな媒質のｄ線（５８７．５６ｎｍ）での屈折率をＮd とするとき、
２．０＞Ｎd ＞１．４ ・・・（３）
ことを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３４６】
〔２６〕 前記プリズム部材が、光学プラスチックであることを特徴とする上記２５記載の映像表示装置。
【０３４７】
〔２７〕 逆光線追跡における前記第１透過面が、第１反射面に対して凸面を向けていることを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。
【０３４８】
〔２８〕 逆光線追跡における前記第１反射面が、正のパワーを有するように前記第１透過面側に凹面を向けた形状に構成されていることを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。
【０３４９】
〔２９〕 逆光線追跡で、軸上主光線の前記第１透過面への入射角θ1 が、
２０＞θ1 ＞−３０ 〔°〕 ・・・（４）
を満たすことを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。ただし、入射角θ1 は法線に対して反時計回りが正とする。
【０３５０】
〔３０〕 逆光線追跡で、軸上主光線の前記第１反射面への入射角θ2 が、
４０＞θ2 ＞５ 〔°〕 ・・・（５）
を満たすことを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。ただし、入射角θ1 は法線に対して反時計回りが正とする。
【０３５１】
〔３１〕 前記第１透過面と前記第２反射面との兼用面が、光学的パワーを与えかつ偏心収差を補正する非回転対称な面形状に形成されていることを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。
【０３５２】
〔３２〕 前記第１反射面が、光学的パワーを与えかつ偏心収差を補正する非回転対称な面形状に形成されていることを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。
【０３５３】
〔３３〕 逆光線追跡において、前記走査手段の直前の反射面が、光学的パワーを与えかつ偏心収差を補正する非回転対称な面形状に形成されていることを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。
【０３５４】
〔３４〕 逆光線追跡において、前記走査手段の直後の反射面が、光学的パワーを与えかつ偏心収差を補正する非回転対称な面形状に形成されていることを特徴とする上記５、７〜１６の何れか１項記載の映像表示装置。
【０３５５】
〔３５〕 前記回転非対称な面形状が、対称面を１面のみ有する自由曲面形状にて構成されていることを特徴とする上記３１〜３４の何れか１項記載の映像表示装置。
【０３５６】
〔３６〕 前記投影光学系が回折作用を持つ面を備えていることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３５７】
〔３７〕 前記投影光学系の透過面の表面が透過型のＤＯＥを兼ねるか、あるいは、前記投影光学系の反射面の表面が反射型のＤＯＥを兼ねるか、あるいは、前記走査手段のミラー反射面が反射型のＤＯＥを兼ねるというように前記投影光学系あるいは前記走査手段の表面がＤＯＥを兼ねることを特徴とする上記３６記載の映像表示装置。
【０３５８】
〔３８〕 前記プリズム部材と前記走査手段の間にＤＯＥ作用を持つ面を追加して、色収差の制御をすることを特徴とする上記３６記載の映像表示装置。
【０３５９】
〔３９〕 前記プリズム部材と前記走査手段の間に配置した透過型ＤＯＥにより、前記プリズム部材射出後に走査手段に入射する光路と、前記走査手段射出後に前記プリズム部材に入射する光路の両方の光路で回折作用を受けることを特徴とする上記３８記載の映像表示装置。
【０３６０】
〔４０〕 前記ＤＯＥがスキャナと一体に保持されていることを特徴とする上記３８記載の映像表示装置。
【０３６１】
〔４１〕 前記走査手段と前記投影光学系により形成される像の歪みを打ち消すような映像を前記映像表示素子に表示することを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３６２】
〔４２〕 前記電気的像歪み補正が、等速走査性の補正であることを特徴とする上記４１記載の映像表示装置。
【０３６３】
〔４３〕 前記走査手段が２次元走査をすることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３６４】
〔４４〕 前記走査手段の法線に対する軸上主光線の入射角θｓが次式を満足することを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３６５】
｜θｓ｜≦６０° ・・・（６）
〔４５〕 前記走査手段に対する軸上主光線の入射角が次式を満足することを特徴とする上記４４記載の映像表示装置。
【０３６６】
１０°≦｜θｓ｜≦４５° ・・・（６−１）
〔４６〕 往復走査をすることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３６７】
〔４７〕 前記走査手段は走査方向に正弦波状に振動する走査手段であることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３６８】
〔４８〕 正弦波状に振動する前記走査手段の振幅の９５％以下を映像表示に利用することを特徴とする上記４７記載の映像表示装置。
【０３６９】
〔４９〕 正弦波状に振動する前記走査手段の振幅の９０％以下を映像表示に利用することを特徴とする上記４８記載の映像表示装置。
【０３７０】
〔５０〕 主走査方向の走査を繰り返し２次元像を形成するとき、主走査方向は正弦波状に振動する走査ミラーで、副走査方向は振れ角がリニアに変化する走査ミラーであることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３７１】
〔５１〕 主走査方向も副走査方向も正弦波状に振動するミラーであることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３７２】
〔５２〕 前記走査手段がフォトリソグラフィーの工程を利用して製作したマイクロマシンミラーであることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３７３】
〔５３〕 逆光線追跡で、前記走査手段から前記映像表示素子に至る光学系が、少なくとも２面の光学作用を有する面で構成され、この光学系を走査手段側と映像表示素子側に２分割する場合、走査手段側でプラスの球面収差を発生させ、映像表示素子側でマイナスの球面収差を発生させるようになっていることを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。
【０３７４】
〔５４〕 走査方向の面内（２次元走査の場合は、主走査方向と副走査方向のそれぞれの面内）で、
３×Ｇ＞ｆ・tan ２φ／ｄ＞Ｇ／２ ・・・（７）
を満足することを特徴とする上記１、７〜１６の何れか１項記載の映像表示装置。ここで、
Ｇ：走査方向画素数
ｆ：映像表示素子から走査手段に至る集光光学系の走査方向面内での焦点距離
φ：映像表示に利用する走査手段の走査方向の片側振れ角
（±φの走査手段振れ角を映像表示に利用する）
ｄ：走査方向の映像表示素子の大きさの半分
ただし、逆光線追跡において次式で定義されるｆを走査手段から映像表示素子に至る集光光学系の焦点距離とする。
【０３７５】
ｆ＝Ｙ／β tan２φ
ここで、Ｙは走査方向における中間像の大きさの半分、βは走査方向における映像表示素子から中間像に至る光学系の倍率である。
【０３７６】
〔５５〕 前記映像表示素子に表示された映像を虚像として形成し観察者眼球に導く上記１〜５４の何れか１項記載の映像表示装置と、この映像表示装置を観察者顔面前方に保持する支持部とを備えて構成されたことを特徴とする頭部装着式映像表示装置。
【０３７７】
〔５６〕 前記映像表示装置を観察者の左右の眼に対応してそれぞれ１つずつ配置していることを特徴とする上記５５記載の頭部装着式映像表示装置。
【０３７８】
〔５７〕 前記映像表示素子に表示された映像を実像として表示する上記１〜５４の何れか１項記載の映像表示装置を備えて構成されたことを特徴とするプロジェクタ、レーザビームプリンタあるいはバーコードリーダ。
【０３７９】
【発明の効果】
以上の説明から明らかなように、本発明の映像表示装置によると、反射作用を主体としたプリズム部材を用いて走査型映像表示装置の光学系を構成することにより、部品点数の削減と小型化を達成することができる。
【図面の簡単な説明】
【図１】本発明に基づく映像表示装置の光学系の構成を模式的に示す図である。
【図２】走査手段をミラーで構成する場合の図１と同様な図である。
【図３】逆光線追跡で中間像に入射する主光線を収束状態にする場合の図１と同様な図である。
【図４】映像表示素子の可能な１つの配置を示す図である。
【図５】映像表示素子の可能な別のの配置を示す図である。
【図６】映像表示素子の可能な別のの配置を示す図である。
【図７】直線走査性と等速走査性の両方の電気的像歪み補正を説明するための図である。
【図８】等速走査性の電気的像歪み補正を説明するための図である。
【図９】１次元スキャナを２個使用する場合の図１と同様な図である。
【図１０】１次元ｆアークサインレンズのディストーションを示す図である。
【図１１】スキャンミラーの振幅を制限して映像表示する場合を説明するための図である。
【図１２】正弦波の振幅の制限とミラー傾角の線形性の関係を示す図である。
【図１３】１次元ｆθレンズのディストーションを示す図である。
【図１４】映像表示素子の配光特性による映像表示装置の光学系の不具合を説明するための図である。
【図１５】スキャナから映像表示素子に至る光学系の配置によって映像表示素子の配光特性を補正できることを説明するための図である。
【図１６】適切な画素間隔に関する説明図である。
【図１７】映像表示素子に表示する映像信号を示す図である。
【図１８】不適切な画素間隔による１つの不具合を説明するための図である。
【図１９】不適切な画素間隔による別の不具合を説明するための図である。
【図２０】本発明の実施例１の光学系の光路図である。
【図２１】実施例１の変形の光学系の光路図である。
【図２２】本発明の実施例２の光学系の光路図である。
【図２３】本発明の実施例３の光学系の光路図である。
【図２４】本発明の実施例４の光学系の光路図である。
【図２５】本発明の実施例５の光学系の光路図である。
【図２６】本発明の実施例５−１の光学系の光路図である。
【図２７】本発明の実施例６の光学系の光路図である。
【図２８】本発明の実施例７の光学系の光路図である。
【図２９】本発明の実施例８の光学系の光路図である。
【図３０】本発明の実施例９の光学系の光路図である。
【図３１】本発明の実施例１０の光学系の光路図である。
【図３２】本発明の実施例１１の光学系の光路図である。
【図３３】従来の走査型ＨＭＤの構成を示す図である。
【図３４】従来の別の走査型ＨＭＤの構成を示す図である。
【符号の説明】
１…瞳
２…接眼光学系（接眼レンズ）
３…リレー光学系（リレーレンズ）
４…走査手段
４’、４”…１次元スキャンミラー（１次元走査手段）
５…集光光学系（集光レンズ）
６…映像表示素子
７…中間像
８…ダイクロイックミラー
９…２つの走査手段と共役にする光学系
１０…虚像
１１…映像表示素子の像
２１…射出瞳（逆光線追跡の入射瞳）
２２…軸上主光線（観察者視軸）
２３…キャンミラー
２４…映像表示素子
２５…シースループリズム
３０…偏心プリズム
３０₁ …第１プリズム
３０₂ …第２プリズム
３１…第１面
３２…第２面
３３…第３面
３４…第４面
３５…第５面
３６…第３透過面
３７…第４透過面
３８…第５面
３９…第６面
４０…第４面
４１…第５面
４２…第４透過面
４３…回折面
４４…ＤＯＥ
４５…回折面
４６…第３面
４７…第１面
４８…第２面
４９…第３面
５０…第４面
５１…第５面
Ｌ１…映像表示素子側光学系
Ｌ２…スキャナ側光学系[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a video display device, and more particularly, to a head or face-mounted video display device that can be held on the head or face of an observer.
[0002]
[Prior art]
Among the scanning-type image display devices, there are the following conventional techniques of a scanning-type head-mounted image display device (so-called HMD).
[0003]
Prior Art 1 (Japanese Patent Laid-Open No. 8-54578): As shown in FIG. 33, a light beam from a laser is modulated by an A-O modulator, and the modulated light is converted in a one-dimensional direction by a polygon scanning device (polygon mirror). It is scanned and incident on the incident end of the optical fiber ribbon through two relay mirrors. When the one-dimensional scanned image is emitted from the outgoing end, the outgoing end of the optical fiber ribbon is vibrated to form a two-dimensional scanned image. Then, the scanned image is projected into the observer's eyeball through the projection optical system and the concave mirror, thereby displaying an image.
[0004]
Prior Art 2 (Japanese Patent Laid-Open No. 9-5903): As shown in FIG. 34, the luminous flux from the LED array is scanned in a direction perpendicular to the arrangement direction of the LED array by the rotary reflecting mirror (polygon mirror) through the objective lens, In addition, it is divided into left and right observation optical paths, an intermediate real image is formed through a fixed reflecting mirror, and a scanning image is projected onto the left and right eyeballs of the observer by an eyepiece, thereby displaying an image on both eyes.
[0005]
[Problems to be solved by the invention]
However, in the case of the prior art 1 shown in FIG. 33, the optical system has one concave mirror + 5 lenses after the optical fiber ribbon (projection optical system) + one optical fiber ribbon + two relay mirrors + one polygon mirror + A total of 12 or more optical components, one lens (relay lens) and one light source (laser), are required.
[0006]
In the case of the prior art 2 shown in FIG. 34, a total of 8 optical components of 1 light source, 5 lenses, 1 mirror, and 1 polygon mirror are required for one eye. A total of 11 optical components are required: 1 light source + 7 lenses + 2 mirrors + 1 polygon mirror.
[0007]
As described above, in the prior art, since the number of parts constituting the optical system is very large, the position adjustment of each part is difficult.
[0008]
In addition, since the entire optical system composed of a video display element, a lens, a scan mirror, and the like is large, it is inappropriate as an HMD optical system to be mounted on the face.
[0009]
The present invention has been made to solve such problems of the prior art, and an object of the present invention is to provide an optical system for a small scanning image display apparatus constituted by a small number of optical elements. .
[0010]
[Means for Solving the Problems]
The first image display device of the present invention that achieves the above object includes an image display element that displays an image, a scanning unit that scans light emitted from the image display element, and a scanning unit that is formed by the image display element. In an image display device comprising a projection optical system that projects a scanned image,
The projection optical system has at least one prism member made of a medium having a refractive index larger than 1,
The prism member has at least three surfaces: a transmission surface that makes a light beam incident on the prism member, a reflection surface that reflects the light beam within the prism member, and a transmission surface that emits the light beam from the prism. The total number of reflections by the prism member is 3 times or more, and at least one of the reflection surfaces of the prism member has optical power and is decentered with respect to the optical axis,
In the backward ray tracing, the projection optical system and the scanning unit are arranged between a pupil and an image display element that is an image plane, and light rays from the pupil reach the scanning unit through at least the prism member. It is.
[0011]
When there are a plurality of prism members, the total number of reflections is 3 or more, and each prism member does not reflect three or more times.
[0012]
Examples 1 to 11 described later correspond to this video display device.
[0013]
The effects of this video display device will be described below. The optical system can be miniaturized by the effect of folding by three or more reflections. In addition, since the reflecting surface having optical power and decentered from the optical axis has a lens function and a mirror function, the number of parts constituting the optical system can be reduced. Here, the optical axis is defined by a light beam that passes through the center of the exit pupil, passes through the scanning means, and reaches the center of the image display element. The same applies to other embodiments.
[0014]
In this case, if the reflecting surface having optical power and decentered with respect to the optical axis is configured as one surface of the prism member, the light beam from the pupil is refracted by the transmitting surface. On the other hand, the incident ray height of off-axis rays after the reflecting surface decentered can be set low. Therefore, the optical system can be reduced in size and a larger angle of view can be realized. In addition, since the height of the dependent light beam of the off-axis light beam is reduced, the occurrence of coma aberration and the like can be suppressed.
[0015]
In general, the reflecting surface must be controlled more strictly than the refracting surface, so that the assembly adjustment work becomes difficult. However, if the reflecting surface is configured as one surface of the prism member, the adjustment work of the reflecting surface can be reduced.
[0016]
The second video display device of the present invention is characterized in that, in the first video display device, the total number of reflections by the prism member included in the projection optical system is four or more. When there are a plurality of prism members, the total number of reflections is 4 or more, and each prism member does not reflect four or more times.
[0017]
Examples 1 and 3 to 11 described later correspond to this video display device.
[0018]
The effects of this video display device will be described below. By setting the number of reflections to 4 or more, the effect of downsizing the optical system by folding can be further increased, and aberration correction is also preferable.
[0019]
According to a third image display device of the present invention, in the first image display device, the reflecting surface of the projection optical system has optical power.
[0020]
Examples 1 to 11 described later correspond to this video display device.
[0021]
The effects of this video display device will be described below. If there are three or more reflecting surfaces having both lens action and mirror action, the effect of downsizing the optical system is further increased. Further, since the main power of the projection optical system is given to the reflection action, the occurrence of chromatic aberration in the projection optical system is reduced.
[0022]
According to a fourth image display device of the present invention, in the first image display device, the projection optical system is a combination of transmission and reflection in which at least one of the reflection surfaces and at least one of the transmission surfaces are formed on the same surface. It is characterized by having a surface.
[0023]
Examples 1 to 11 described later correspond to this video display device.
[0024]
The effects of this video display device will be described below. Since the two actions of transmission and reflection are performed on the same surface, the number of surfaces constituting the optical system can be reduced, and the optical system can be made simple and small.
[0025]
According to a fifth image display device of the present invention, in the fourth image display device, at least one prism member is at least a first transmission surface that is incident on the prism member by back ray tracing from the pupil toward the image display element. The first reflecting surface, the second reflecting surface, and the second transmitting surface exiting from the prism member, and at least the first transmitting surface and the second reflecting surface are the same combined surface. It is characterized by being.
[0026]
Examples 1 to 11 described later correspond to this video display device.
[0027]
The effects of this video display device will be described below. When the first transmission surface and the second reflection surface are configured as different surfaces, the following problems occur. That is, in order to configure the first transmission surface and the second reflection surface as separate surfaces, the second reflection surface needs to be formed at a different position away from the first transmission surface. For this reason, it is necessary to increase the space | interval of a 1st reflective surface and a 2nd reflective surface, or to enlarge the reflection angle in a 1st reflective surface. As a result, the optical system becomes large, or a large decentration aberration that cannot be corrected by other surfaces occurs on the first reflecting surface. This problem can be solved by using the first transmission surface and the second reflection surface as a dual-purpose surface.
[0028]
According to a sixth image display device of the present invention, in the fifth image display device, the reflection at the second reflection surface is total reflection in reverse ray tracing.
[0029]
Examples 1 to 11 described later correspond to this video display device.
[0030]
The effects of this video display device will be described below. If the reflection on the second reflecting surface is performed not by total reflection but by reflection from the reflection film, the following problems occur. That is, since the first transmission surface and the second reflection surface are dual-purpose surfaces, it is necessary to form a reflection film for the second reflection surface at another position away from the transmission region for the first transmission surface. For this reason, it is necessary to increase the space | interval of a 1st reflective surface and a 2nd reflective surface, or to enlarge the reflection angle in a 1st reflective surface. As a result, the optical system becomes large, or a large decentration aberration that cannot be corrected by other surfaces occurs on the first reflecting surface. By making the reflection on the second reflecting surface total reflection, this problem can be solved. Further, it is not necessary to produce a reflective film, and the cost can be reduced.
[0031]
According to a seventh image display device of the present invention, in the first image display device, the projection optical system includes at least a first transmission surface incident on the prism member by the backward ray tracing from the pupil toward the image display element, and an optical power. A first reflecting surface, a second reflecting surface, a third reflecting surface, and a second transmitting surface that exits from the prism member and reaches the scanning means, and includes the first transmitting surface and the second reflecting surface. The surfaces are the same combined surfaces, and an intermediate image is formed between the second reflecting surface and the third reflecting surface.
[0032]
This video display apparatus corresponds to Examples 1-2 described later.
[0033]
The effects of this video display device will be described below. An optical system for forming light from the pupil as an intermediate image by an optical action of at least three of the first transmission surface, the first reflection surface, and the second reflection surface is configured, and the third reflection surface and the second transmission surface Since the optical system for guiding the intermediate image to the scanning means is configured by the optical action of at least two surfaces, aberration correction of each optical system can be performed satisfactorily. In addition, since the first transmission surface and the second reflection surface are dual-purpose surfaces, an optical system that forms light from the pupil as an intermediate image and an optical system that guides the intermediate image to the scanning means can be configured with at least four surfaces. it can. Since there are few surfaces which comprise an optical system, an optical system can be reduced in size. Further, since the number of molds for manufacturing the optical system by molding is small, the manufacturing cost is reduced. In addition, since the optical system from the pupil to the scanning means by the back ray tracing is mainly composed of the reflection action, the occurrence of chromatic aberration is small.
[0034]
According to an eighth image display device of the present invention, in the seventh image display device, the projection optical system reflects the light beam by the scanning means in the backward ray tracing from the pupil toward the image display element, and then the fourth reflection surface of the prism member is changed. Then, an image is formed on the image display element.
[0035]
This video display apparatus corresponds to Example 1 described later.
[0036]
The effects of this video display device will be described below. Since the projection optical system that forms an image on the image display element by the reverse ray tracing is configured mainly by the reflection action, the occurrence of chromatic aberration is small. In addition, the projection optical system can be downsized due to the folding effect of at least four reflections. Further, when forming the transmission surface in front of the scanning means and the reflection surface after the scanning means on the prism member by reverse ray tracing, they can be formed in one mold. In addition, since the scanning unit and the image display element can be arranged at close positions, the protrusion amount of the optical system is reduced. When the optical system of the present invention is used as an HMD optical system, the scanning means and the image display element can be arranged on the prism member, so that the weight balance of the entire optical system is improved.
[0037]
According to a ninth image display device of the present invention, in the seventh image display device, after the projection optical system is reflected by the scanning means in the backward ray tracing from the pupil toward the image display element, at least the third transmission surface, The image is formed on the image display element through the four transmission surfaces.
[0038]
This video display apparatus corresponds to Example 2 described later.
[0039]
The effects of this video display device will be described below. Since the distance between the scanning means and the image display element can be secured, the divergence angle of the light beam necessary for the image display element can be reduced. In addition, since the optical system from the scanning unit to the image display element can be configured to have at least two surfaces, the light distribution characteristic of the image display element light can be corrected.
[0040]
According to a tenth image display device of the present invention, in the seventh image display device, the projection optical system includes a first prism member and a second prism member, and performs reverse ray tracing from the pupil toward the image display element.
The first prism member includes a first transmission surface incident on the first prism member, a first reflection surface having optical power and decentered with respect to the optical axis, a second reflection surface, and an exit surface from the first prism member. Including
The second prism member includes an incident surface to the second prism member, a third reflecting surface, and a second transmitting surface that exits from the second prism member and reaches the scanning unit,
The first transmission surface and the second reflection surface are the same surface;
An intermediate image is formed between the second reflecting surface and the third reflecting surface.
[0041]
This video display apparatus corresponds to Example 1 described later.
[0042]
The effects of this video display device will be described below. Distortion and pupil aberration can be controlled efficiently on the exit surface of the first prism member and the entrance surface to the second prism member that are close to the intermediate image, improving linear scanning performance and constant speed scanning performance. Can be made.
[0043]
The eleventh video display apparatus of the present invention is characterized in that, in the seventh to tenth video display apparatuses, the reflection at the second reflecting surface is total reflection.
[0044]
This video display apparatus corresponds to Examples 1-2 described later.
[0045]
The effect of this video display device is the same as that of the sixth video display device.
[0046]
According to a twelfth image display device of the present invention, in the first image display device, the projection optical system is at least a first transmission surface incident on the prism member by an inverse ray tracing from the pupil toward the image display element, and an optical power. A first reflecting surface, a second reflecting surface, a third reflecting surface, a fourth reflecting surface, and a second transmitting surface that exits from the prism member and reaches the scanning means. The surface and the second reflection surface, the third reflection surface and the second transmission surface are the same surface, and an intermediate image is formed between the second reflection surface and the fourth reflection surface.
[0047]
Examples 3 to 11 described later correspond to this video display device.
[0048]
The effects of this video display device will be described below. Since it is mainly composed of a reflecting action, the occurrence of chromatic aberration is small. In addition, an optical system that forms an image of light from the pupil as an intermediate image on at least three of the first transmission surface, the first reflection surface, and the second reflection surface is provided at least on the fourth reflection surface and the second transmission surface. Since the optical system that guides the intermediate image to the scanning unit with two or more surfaces is configured, aberration correction can be performed satisfactorily. Further, since the two locations of the first transmission surface and the second reflection surface, and the third reflection surface and the second transmission surface are dual-purpose surfaces, at least four surfaces can be provided with six optical functions. Since there are few surfaces which comprise an optical system, an optical system can be reduced in size. Further, since the number of molds required for manufacturing by molding is small, the manufacturing cost is reduced. Further, since the light is reflected at least four times, the optical system can be miniaturized due to the folding effect.
[0049]
According to a thirteenth image display device of the present invention, in the twelfth image display device, the projection optical system is reflected by the scanning means by back ray tracing from the pupil toward the image display element, and then enters at least the prism member. The image is formed on the image display element through the transmission surface, the fifth reflection surface, and the fourth transmission surface that exits the prism member, and the third reflection surface, the second transmission surface, and the third transmission surface are the same surface. To do.
[0050]
Examples 3 to 11 described later correspond to this video display device.
[0051]
The effects of this video display device will be described below. Since the two locations of the first transmission surface and the second reflection surface, and the third reflection surface, the second transmission surface, and the third transmission surface are dual-purpose surfaces, at least six surfaces can be provided with nine optical functions. Since there are few surfaces which comprise an optical system, an optical system can be reduced in size. Further, since the number of molds required for manufacturing by molding is small, the manufacturing cost is reduced. In addition, since the optical system from the scanning means to the image display element can be configured to have at least two surfaces, the light distribution characteristic of the image display element light can be corrected.
[0052]
According to a fourteenth image display device of the present invention, in the thirteenth image display device, the projection optical system is incident on at least a prism member after being reflected by the scanning means in reverse ray tracing from the pupil toward the image display element. The image is formed on the image display element through the transmission surface, the fifth reflection surface, and the fourth transmission surface that exits the prism member, and the third reflection surface, the second transmission surface, the third transmission surface, and the fourth transmission surface are the same surface. It is characterized by being.
[0053]
This video display apparatus corresponds to Examples 3 and 4 described later.
[0054]
The effects of this video display device will be described below. Since the two locations of the first transmission surface and the second reflection surface, the third reflection surface, the second transmission surface, the third transmission surface and the fourth transmission surface are shared surfaces, at least five surfaces are provided with nine optical functions. be able to. Since there are few surfaces which comprise an optical system, an optical system can be reduced in size. Further, since the number of molds required for manufacturing by molding is small, the manufacturing cost is reduced.
[0055]
According to a fifteenth image display device of the present invention, in the twelfth image display device, the projection optical system includes a first prism member and a second prism member, and the ray tracing is performed from the pupil toward the image display element.
The first prism member has a first transmission surface incident on the first prism member, a first reflection surface having optical power and decentered with respect to the optical axis, a second reflection surface, and a second light exiting from the first prism member. Including a transmission surface,
The second prism member is incident on the second prism member, the third transmission surface, the third reflection surface, the fourth reflection surface, the fourth transmission surface that exits from the second prism member and reaches the scanning means, and the second from the scanning means. It includes a fifth transmission surface that enters the prism member, a fifth reflection surface, and a sixth transmission surface that exits from the second prism member and reaches the image display element.
[0056]
This video display apparatus corresponds to Examples 9 and 10 described later.
[0057]
The effects of this video display device will be described below. Since the second transmission surface, which is the exit surface of the first prism member, and the third transmission surface, which is the incidence surface of the second prism member, can be arranged near the intermediate image, distortion and pupil aberration can be controlled efficiently. Linear scanability and constant speed scanability can be improved.
[0058]
According to a sixteenth image display apparatus of the present invention, in the first image display apparatus, the projection optical system is reverse ray tracing from the pupil toward the image display element, and the entrance pupil and the scanning means are in a substantially conjugate positional relationship, and the projection An intermediate image is formed once in the optical system, and the optical system from the entrance pupil to the intermediate image and the optical system from the intermediate image to the scanning means are symmetric with respect to the intermediate image. is there. In this case, the symmetrical structure with respect to the intermediate image means that the bending optical path is point-symmetric or plane-symmetric with respect to the intermediate image, and that the power distribution (positive or negative) is symmetric with respect to the intermediate image. Point.
[0059]
Examples 3 to 11 described later correspond to this video display device.
[0060]
The effects of this video display device will be described below. As shown in FIG. 1, the projection optical system includes an eyepiece optical system 2 and a relay optical system 3. Since the scanning means 4 is in the vicinity of the pupil position, the light projected on the pupil 1 is not scattered by forward tracking, and the size of the scanning means 4 can be reduced. Since FIG. 1 is a conceptual diagram for explanation, the case of a transmissive scanning unit such as an acousto-optic deflector AOD is explained for easy explanation. Moreover, this figure is explanatory drawing in the case of using a two-dimensional scanning means.
[0061]
In the configuration of FIG. 1, the optical system (eyepiece optical system 2) from the pupil 1 to the intermediate image 7 and the optical system (relay optical system 3) from the intermediate image 7 to the scanning unit 4 are symmetric in reverse ray tracing. Since aberrations occurring in the respective optical systems cancel each other, the aberrations of the entire projection optical system can be effectively corrected.
[0062]
According to a seventeenth image display device of the present invention, in the first, seventh to sixteenth image display devices, the projection optical system substantially collimates the image display element light by the condensing optical system, and scans a position substantially conjugate with the pupil. The light that is scanned by the scanning means is formed as an intermediate image by the relay optical system, and the intermediate image is guided to the pupil by the eyepiece optical system.
In reverse ray tracing, the projection optical system has a reflecting surface having at least three optical powers between the entrance pupil and the scanning means;
In reverse ray tracing, the eyepiece optical system has at least two reflecting surfaces, the relay optical system has at least one reflecting surface, a second reflecting surface for light from the entrance pupil, and a scanning device in front of the scanning means. An intermediate image is formed between the last reflecting surfaces.
[0063]
Examples 1 to 11 described later correspond to this video display device.
[0064]
The effects of this video display device will be described below. In FIG. 1, the eyepiece optical system 2 receives an optical action of at least three surfaces to form an intermediate image by reverse ray tracing for aberration correction, and the relay optical system 3 receives a convergence action by the optical action of at least two surfaces to the scanning means. It is desirable to be guided. By adopting the configuration of the seventeenth image display device, the eyepiece optical system 2 can perform at least three total optical actions including at least the action of the transmission refractive surface and the reflecting face having at least two optical powers by back ray tracing. Has a surface. The relay optical system 3 has at least two reflecting surfaces having at least one optical power and at least one refracting / transmitting surface action, that is, a total of two optical action surfaces. Therefore, it is preferable for aberration correction.
[0065]
According to an eighteenth image display device of the present invention, in the seventeenth image display device, the projection optical system has a ray tracing and the eyepiece optical system that forms light from the pupil as an intermediate image has at least two reflecting surfaces. The relay optical system for guiding the light from the intermediate image to the scanning means has at least two reflecting surfaces.
[0066]
Examples 3 to 11 described later correspond to this video display device.
[0067]
The effects of this video display device will be described below. In order to completely correct the decentration aberration, the eyepiece optical system for forming light from the pupil as an intermediate image has at least two reflecting surfaces, and at least two relay optical systems for guiding the light from the intermediate image to the scanning means. It is desirable to have a reflective surface. This is particularly important for controlling distortion and performing linear scanning / constant scanning without electrical image distortion correction.
[0068]
According to a nineteenth image display apparatus of the present invention, in the first and seventh to sixteenth image display apparatuses, the light incident on the projection optical system from the entrance pupil is formed as an intermediate image by back ray tracing, and then formed as an intermediate image. The image is formed on the image display element through the scanning means at a position substantially conjugate with the half angle of view θ incident on the projection optical system from the entrance pupil in the scanning direction of the scanning means, and is necessary for video display in the scanning direction of the scanning means. The one-side deflection angle φ of the scanning means satisfies the following expression.
[0069]
0.1 ≦ φ / θ ≦ 1.8 (1)
Here, the scanning means does not necessarily swing ± φ. When video display is performed using a part of the deflection angle of the scanning means, ± φ is used for video display. Examples 1 to 11 described later correspond to this video display device.
[0070]
The effects of this video display device will be described below. Assume that the optical system is configured as shown in FIG. Consider the optimal pupil magnification = exit pupil diameter / incidence pupil diameter in such an optical system. In the case of FIG. 1, the scanner effective diameter is equal to the pupil diameter except for the influence of pupil aberration. However, the reflection type scanning means 4 such as a polygon mirror or a galvanometer mirror generally has an area of the mirror because the optical axis (axial principal ray) and the reference reflecting surface form an angle as shown in FIG. In the case of the decentered optical system, the pupil is also decentered, so it is difficult to define the pupil diameter. Therefore, the ratio of the half field angle 2φ incident on the scanning means 4 from the relay optical system 3 and the half field angle θ incident on the eyepiece optical system 2 from the pupil 1 by reverse tracking is considered as an approximate pupil magnification.
[0071]
In the case of one-dimensional scanning, as shown in FIGS. 1 and 2, θ and φ in the plane to be scanned are considered. In the case of two-dimensional scanning, θ and φ are considered in two planes perpendicular to the main scanning direction and the sub-scanning direction.
[0072]
If the upper limit of 1.8 in equation (1) is exceeded, the angle of incidence from the scanning means to the relay optical system becomes too large, and it becomes difficult to correct aberrations in the relay optical system or the like. When the lower limit of 0.1 is exceeded, it is necessary to increase the focal length of the relay optical system in order to obtain the same intermediate image size, which makes it difficult to reduce the size of the optical system.
[0073]
According to a twentieth video display apparatus of the present invention, the nineteenth video display apparatus satisfies the following expression.
[0074]
0.25 ≦ φ / θ ≦ 1.7 (1-1)
Examples 1 to 11 described later correspond to this video display device.
[0075]
The effects of this video display device will be described below. In the optical systems of FIGS. 1 and 2, in forward tracking, a negative distortion occurs in the relay optical system, and a positive distortion occurs in the eyepiece optical system. When a mirror that vibrates in a sine wave is used as a scanning means, in order to scan at a constant speed without correcting electrical image distortion, it is necessary to generate a positive distortion in the projection optical system to obtain an f arc sine θ lens. (When 2φ is about 20 ° or less). When φ is large, negative distortion generated in the relay optical system increases, and it becomes difficult to design an f arc sine θ lens that generates positive distortion in the entire projection optical system. Therefore, it is desirable to satisfy the upper limit 1.7 of the conditional expression. Further, in order to reduce the size of the optical system for HMD attached to the face, it is desirable to satisfy the lower limit of 0.25.
[0076]
The twenty-first video display apparatus of the present invention is the first, seventh to sixteenth video display apparatuses, and in reverse ray tracing, when a light beam incident from the entrance pupil forms an intermediate image, the light enters the intermediate image from the entrance pupil. The chief ray is in a convergent state.
[0077]
This video display apparatus corresponds to Examples 1 to 10 described later.
[0078]
The effects of this video display device will be described below. As shown in FIG. 3, when the principal ray incident on the intermediate image 7 is converged in the backward ray tracing, the effective diameter of the light flux from the eyepiece 2 to the scanning means 4 through the intermediate image 7 and the relay lens 3 is calculated. Can be small. Further, since the principal ray incident on the relay lens 3 from the intermediate image 7 is in a convergent state, the distance between the relay lens 3 and the scanning means 4 can be reduced. Therefore, the optical system can be reduced in size.
[0079]
Here, in the case of the decentered optical system, since the intermediate image is generally inclined with respect to the axial principal ray, the degree of convergence cannot be defined by the incident angle of the principal ray with respect to the intermediate image. Therefore, it is limited by the difference between the incident angle of the principal ray of each light beam and the incident angle of the axial principal ray. In this case, in reverse ray tracing, it is desirable that the difference between the incident angle at which the light beam incident from the entrance pupil enters the intermediate image and the incident angle of the axial light beam is within 20 °. In reverse ray tracing, if the light enters the intermediate image from the eyepiece at a large angle of 20 ° or more, it becomes difficult to correct the aberration of the relay optical system. Therefore, it is desirable to satisfy this condition.
[0080]
According to a twenty-second image display apparatus of the present invention, in the first image display apparatus, the projection optical system includes one prism member.
[0081]
This video display device corresponds to Examples 1 to 8 and 11 described later.
[0082]
The effects of this video display device will be described below. If the projection optical system can be constituted by one prism member, the number of parts and the position adjustment work of the optical system are reduced, so that the cost is reduced and it is easy to secure the performance at the time of manufacture.
[0083]
According to a twenty-third image display device of the present invention, in the first, tenth, fifteenth, and sixteenth image display devices, the projection optical system includes at least two prism members,
1 ≧ y ′ / y> 0.7 (2)
It is characterized by satisfying. Here, y is the intermediate image height in the optical system, and y ′ is the principal ray height of the most off-axis light beam on the surface where the two prism members face each other.
[0084]
This video display apparatus corresponds to Examples 1 and 9 to 10 described later.
[0085]
The effects of this video display device will be described below. The above conditional expression means that the prism member is divided into two prism members near the intermediate image. In the vicinity of the intermediate image, the light beam is thin and the position of the light beam at each angle of view is different. If the optical system is divided into two prism members at this location, distortion and pupil aberration can be effectively corrected by the surface of the two prism members with respect to the intermediate image. In particular, when the optical system is an fθ lens or an f arc sine θ lens in order to perform linear scanning or constant speed scanning without electrical image distortion correction, it is important to correct distortion on this surface. When dividing into two prisms in the vicinity of the intermediate image, if an optical element having a pupil magnifying function such as a diffuser is placed at the position of the intermediate image, forward tracking can be applied to a small pupil diameter from the image display element to the intermediate image. Since the optical system only needs to be configured, the optical system can be easily designed.
[0086]
According to a twenty-fourth image display apparatus of the present invention, in the twenty-third image display apparatus, the projection optical system includes two prism members, and the image is transmitted from the pupil through the first prism member and the second prism member by reverse ray tracing. When reaching the display element, an intermediate image is formed in the second prism member.
[0087]
This video display apparatus corresponds to Examples 1 and 9 to 10 described later.
[0088]
The effects of this video display device will be described below. If an attempt is made to secure the distance between the pupil and the projection optical system by back ray tracing, it is necessary to increase the focal length of the eyepiece optical system to some extent, so that the distance between the eyepiece optical system and the intermediate image is required to some extent. In this case, in order to reduce the size of the entire projection optical system, it is necessary to form an intermediate image in the second prism. This point is particularly important when the optical system of the present invention is used as an HMD optical system because it is necessary to ensure eye relief.
[0089]
The twenty-fifth image display apparatus of the present invention is the first, seventh to sixteenth image display apparatuses, wherein the refractive index at the d-line (587.56 nm) of the medium having a refractive index of the prism member larger than 1 is Nd. ,
2.0>Nd> 1.4 (3)
It is characterized by this.
[0090]
Examples 1 to 11 described later correspond to this video display device.
[0091]
The effects of this video display device will be described below. The prism member is preferably formed of optical glass or optical plastic having high transparency and less workability problems. If this condition is not met, the transparency of the medium will be low and the processability will also be poor.
[0092]
According to a twenty-sixth video display apparatus of the present invention, in the twenty-fifth video display apparatus, the prism member is an optical plastic.
[0093]
Examples 1 to 11 described later correspond to this video display device.
[0094]
The effects of this video display device will be described below. If the prism member is made of optical plastic, cost and weight can be reduced. In this case, it is desirable to use a low hygroscopic material such as amorphous polyolefin because there is little change in imaging performance with respect to changes in humidity.
[0095]
According to a twenty-seventh image display apparatus of the present invention, in the fifth and seventh to sixteenth image display apparatuses, the first transmission surface in the reverse ray tracing has a convex surface facing the first reflection surface. It is.
[0096]
Examples 1 to 11 described later correspond to this video display device.
[0097]
The effects of this video display device will be described below. When the first transmission surface is negative power with the convex surface facing the first reflection surface side, the first reflection surface is internally reflected by the second reflection surface (the surface that also serves as the first transmission surface) after being reflected by the first reflection surface. It is possible to correct coma and curvature of field that occur on the reflecting surface. In addition, when internal reflection is performed on the second reflection surface (a surface that also serves as the first transmission surface) after reflection on the first reflection surface, the internal reflection is easily converted into total reflection.
[0098]
According to a twenty-eighth image display device of the present invention, in the fifth and seventh to sixteenth image display devices, the first reflecting surface in the reverse ray tracing has a concave surface directed toward the first transmitting surface so as to have a positive power. It is comprised by these.
[0099]
Examples 1 to 11 described later correspond to this video display device.
[0100]
The effects of this video display device will be described below. In the backward ray tracing, the divergent state of the principal ray incident in a divergent state from the pupil to the prism member can be reduced by the positive power of the first reflecting surface. Therefore, the diameter of the light beam after the first reflecting surface can be reduced and the optical system can be downsized.
[0101]
The twenty-ninth image display apparatus of the present invention is the fifth, seventh to sixteenth image display apparatus, wherein the incident angle θ1 of the axial principal ray with respect to the first transmission surface is determined by reverse ray tracing.
20>θ1> −30 [°] (4)
It is characterized by satisfying. However, the incident angle θ1 is positive counterclockwise with respect to the normal line.
[0102]
Examples 1 to 11 described later correspond to this video display device.
[0103]
The effects of this video display device will be described below. If the lower limit of −30 ° of this conditional expression is exceeded, the chromatic aberration of magnification occurring on the first transmission surface will increase. If the upper limit of 20 ° is exceeded, after the reflection at the first reflection surface, the second reflection surface (a surface that also serves as the first transmission surface) is totally reflected, so the inclination angle of the first reflection surface needs to be very large. And a large aberration occurs.
[0104]
The thirtieth image display apparatus of the present invention is the fifth, seventh to sixteenth image display apparatus, wherein the incident angle θ2 of the axial principal ray on the first reflecting surface is determined by reverse ray tracing.
40>θ2> 5 [°] (5)
It is characterized by satisfying. However, the incident angle θ1 is positive counterclockwise with respect to the normal line.
[0105]
Examples 1 to 11 described later correspond to this video display device.
[0106]
The effects of this video display device will be described below. If the upper limit of 40 ° in this conditional expression is exceeded, the amount of protrusion of the first reflecting surface becomes large, and the distance to the reflecting position on the second reflecting surface becomes large, so that the optical system becomes large. Further, since decentration aberrations (particularly coma aberration due to decentration) that cannot be corrected by other surfaces occur, the upper limit may not be exceeded in order to correct aberrations occurring on the second reflecting surface with a small number of surfaces. desirable. If the lower limit of 5 ° is exceeded, the reflected light from the first reflecting surface returns to the pupil direction, and the optical system cannot be constructed.
[0107]
According to a thirty-first image display apparatus of the present invention, in the fifth and seventh to sixteenth image display apparatuses, the combined surface of the first transmission surface and the second reflection surface provides optical power and corrects decentration aberrations. It is formed in a rotationally symmetric surface shape.
[0108]
Examples 1 to 11 described later correspond to this video display device.
[0109]
The effects of this video display device will be described below. In an optical system using a surface that is decentered with respect to the axial principal ray, the incident angle with respect to the decentered surface is slanted, so that coma aberration, astigmatism, etc. due to decentering also occur. This decentration aberration, particularly astigmatism, can be effectively corrected by the non-rotation symmetric surface. Further, by using a rotationally asymmetric surface, it becomes easy to realize the f arc sine θ lens in both the main scanning direction and the sub-scanning direction.
[0110]
According to a thirty-second image display device of the present invention, in the fifth and seventh to sixteenth image display devices, the first reflecting surface is formed in a non-rotationally symmetric surface shape that gives optical power and corrects decentration aberrations. It is characterized by being.
[0111]
Examples 1 to 11 described later correspond to this video display device.
[0112]
The effects of this video display device will be described below. In an optical system using a surface that is decentered with respect to the axial principal ray, the incident angle with respect to the decentered surface is slanted, so that coma aberration, astigmatism, etc. due to decentering also occur. This non-rotationally symmetric surface can effectively correct this decentration aberration, particularly astigmatism.
[0113]
The thirty-third image display apparatus of the present invention is the fifth, seventh to sixteenth image display apparatus, wherein the reflection surface immediately before the scanning means provides optical power and corrects decentration aberration in reverse ray tracing. It is characterized by being formed into a flat surface shape.
[0114]
Examples 1 to 11 described later correspond to this video display device.
[0115]
The effects of this video display device will be described below. In order to obtain the configuration as shown in FIG. 1 with a small number of optical action surfaces, it is preferable to give the main optical power of the relay optical system to the reflection surface immediately before the scanner by back ray tracing. Since this surface is generally decentered with respect to the axial principal ray in order to allow the light beam to enter the scanner at an appropriate angle, coma aberration, astigmatism, and the like due to the decentration occur even with the axial ray. This non-rotationally symmetric surface can effectively correct this decentration aberration, particularly astigmatism.
[0116]
According to a thirty-fourth image display apparatus of the present invention, in the fifth and seventh to sixteenth image display apparatuses, in reverse ray tracing, the reflection surface immediately after the scanning means provides optical power and corrects decentration aberrations. It is characterized by being formed into a flat surface shape.
[0117]
Examples 1 to 11 described later correspond to this video display device.
[0118]
The effects of this video display device will be described below. In order to achieve the configuration as shown in FIG. 1 with a small number of optical action surfaces, it is preferable to give the main optical power of the condensing optical system to the reflection surface immediately after the scanner by backward ray tracing. In general, this surface is decentered with respect to the axial principal ray due to the configuration of the optical system in a small size. Therefore, coma aberration, astigmatism, and the like due to the decentration occur even with the axial ray. This non-rotationally symmetric surface can effectively correct this decentration aberration, particularly astigmatism. In addition, when an image display element that emits light having an elliptical cross-sectional shape, such as an LD, is used, beam shaping can be performed, so that the utilization efficiency of the image display element light is improved.
A thirty-fifth image display device according to the present invention is characterized in that, in the thirty-first to thirty-fourth image display devices, the rotationally asymmetric surface shape is a free-form surface shape having only one symmetric surface. It is.
[0119]
Examples 1 to 11 described later correspond to this video display device.
[0120]
The effects of this video display device will be described below. The free-form surface used in the present invention is defined by the following formula (a). Note that the Z axis of the defining formula is the axis of the free-form surface.
[0121]

Here, the first term of the equation (a) is a spherical term, and the second term is a free-form surface term.
[0122]
In the spherical term,
c: vertex curvature
k: Conic constant (conical constant)
r = √ (X ² + Y ² )
It is.
[0123]
The free-form surface term is

However, C _j (J is an integer of 2 or more) is a coefficient.
[0124]
In general, the free-form surface does not have a symmetric surface in both the XZ plane and the YZ plane. However, in the present invention, by setting all odd-order terms of X to 0, the free-form surface is parallel to the YZ plane. This is a free-form surface with only one symmetrical plane. For example, in the above definition (a), C ₂ , C _Five , C ₇ , C ₉ , C ₁₂ , C ₁₄ , C ₁₆ , C ₁₈ , C ₂₀ , C _{twenty three} , C _{twenty five} , C ₂₇ , C ₂₉ , C ₃₁ , C ₃₃ , C ₃₅ It is possible by setting the coefficient of each term of. In this case, the left-eye optical system and the right-eye optical system of the binocular vision HMD can be shared, and the manufacturability is good.
[0125]
Further, by setting all odd-numbered terms of Y to 0, a free-form surface having only one symmetry plane parallel to the XZ plane is obtained. For example, in the above definition formula, C _Three , C _Five , C ₈ , C _Ten , C ₁₂ , C ₁₄ , C ₁₇ , C ₁₉ , C _{twenty one} , C _{twenty three} , C _{twenty five} , C ₂₇ , C ₃₀ , C ₃₂ , C ₃₄ , C ₃₆ It is possible by setting the coefficient of each term of.
[0126]
By making any one of the symmetric surfaces as a symmetric surface and decentering in the direction of the symmetric surface, it is possible to effectively correct non-rotationally symmetric aberration caused by the decentering and improve the manufacturability at the same time.
[0127]
A thirty-sixth image display apparatus according to the present invention is characterized in that, in the first and seventh to sixteenth image display apparatuses, the projection optical system includes a surface having a diffractive action.
[0128]
Examples 6 to 8 described later correspond to this video display device.
[0129]
The effects of this video display device will be described below. Since DOE (diffractive optical element) can correct various aberrations without taking up space, it is effective for downsizing the optical system. In particular, when chromatic aberration is controlled without using DOE, it is necessary to perform correction using a plurality of optical elements composed of a plurality of glass materials, and thus several problems arise as follows:
Problem (1) Since the projection optical system needs to be configured so as to be divided into a plurality of members, it becomes a constraint on the optical system design and makes it difficult to design a small optical system.
Problem (2) Since it is necessary to use a glass material in order to effectively correct chromatic aberration, the weight of the optical system increases. This increase in weight becomes a problem particularly in the case of an HMD optical system that requires the optical system to be small and light.
[0130]
In the case of an optical system using a monochromatic image display element, the chromatic aberration generated by the DOE is completely unrelated, so that the aberration can be effectively corrected without worrying about the chromatic aberration generated by the DOE. Further, in the case of an optical system mainly composed of a reflecting action, chromatic aberration hardly occurs.
[0131]
However, when a white image display element is used, or when the pixels R, G, and B of the color image display elements having a plurality of wavelengths of red, green, and blue are synthesized by the dichroic mirror 8 with the configuration shown in FIG. 4 (FIG. 4). Is a diagram of reverse ray tracing), it is preferable that both the axial chromatic aberration of the projection optical system and the chromatic aberration of magnification are corrected well. In this case, it is most preferable to correct chromatic aberration by DOE from the viewpoint of miniaturization of the optical system.
[0132]
Further, when the pixels R, G, and B of the color image display elements having a plurality of wavelengths of red, green, and blue are synthesized with the configuration as shown in FIG. 5, the imaging position in the optical axis direction of the projection optical system is determined by reverse ray tracing. It is preferable to make it different depending on the wavelength. In this case, it is most preferable to control the chromatic aberration by DOE from the viewpoint of miniaturization of the optical system.
[0133]
Further, when the pixels R, G, and B of the color image display elements having a plurality of wavelengths of red, green, and blue are synthesized with the configuration as shown in FIG. 6, the projection optical system is arranged in a plane perpendicular to the optical axis by reverse ray tracing. The imaging position needs to be different depending on the wavelength. In this case, correction of axial chromatic aberration and control of chromatic aberration of magnification are most preferable in terms of miniaturization of the optical system by DOE.
[0134]
In a thirty-seventh image display apparatus according to the present invention, in the thirty-sixth image display apparatus, the surface of the projection surface of the projection optical system also serves as a transmission type DOE, or the surface of the reflection surface of the projection optical system is a reflection type. The projection optical system or the surface of the scanning means also serves as the DOE such that the DOE also serves as the DOE, or the mirror reflection surface of the scanning means serves as the reflective DOE.
[0135]
This video display apparatus corresponds to Examples 7 and 8 described later.
[0136]
The effects of this video display device will be described below. Since it is not necessary to add a new optical element, there is no increase in the size and cost of the optical system due to an increase in the number of parts. Further, the alignment adjustment work is not complicated.
[0137]
In addition, when using a so-called micromachine mirror for manufacturing a scanner in a photolithography process as disclosed in JP-A-10-20226, a DOE on the surface of the scan mirror can also be manufactured at the time of manufacturing the scan mirror. There is little increase in cost. In addition, when the optical system of the present invention is used as an HMD optical system and a see-through function or a superimpose function is added, the scanning means is in a position that does not block the external light, so that the DOE acts on the external light. Without being able to observe the ambient light clearly.
[0138]
A thirty-eight video display apparatus according to the present invention is characterized in that in the thirty-sixth video display apparatus, a chromatic aberration is controlled by adding a surface having a DOE action between the prism member and the scanning means. .
[0139]
This video display apparatus corresponds to Example 6 described later.
[0140]
The effects of this video display device will be described below. A function of controlling chromatic aberration and the like can be added without increasing the amount of protrusion of the entire optical system composed of the image display element, the projection optical system, and the scanner. This is particularly effective in the case of an HMD optical system. Also, when the incident angle of incident light to the scan mirror with respect to the scan mirror normal is small and the deflection angle by the scan mirror is small, the same DOE should be used for both the optical path incident on the scan mirror and the optical path reflected from the scan mirror. Can be effective. In addition, when the optical system of the present invention is used as an HMD optical system and a see-through function or a superimpose function is added, the scanning means is in a position that does not interfere with the external light, so that the DOE has an effect on the external light. Since it becomes easy to set it as the structure which does not have, it can observe external light clearly.
[0141]
The thirty-ninth video display apparatus of the present invention is the thirty-eight video display apparatus according to the thirty-eighth video display apparatus, by a transmission type DOE disposed between the prism member and the scanning means, It is characterized in that it is diffracted in both the optical paths incident on the prism member.
[0142]
This video display apparatus corresponds to Example 6 described later.
[0143]
The effects of this video display device will be described below. If the DOE action is applied to both the light path incident on the scanning means and the light path reflected from the scanning means, the pitch of the DOE can be increased and the manufacturability is improved. In many cases with such an arrangement, the position where the light beam incident on the scanning means enters the DOE and the position where the light beam reflected from the scanning means enters the DOE are different. In this case, a plurality of actions can be given by one DOE, which is effective.
[0144]
The 40th video display apparatus of the present invention is the 38th video display apparatus characterized in that the DOE is held integrally with the scanner.
[0145]
This video display apparatus corresponds to Example 6 described later.
[0146]
The effects of this video display device will be described below. If the DOE and the scanner are integrated, the mechanical configuration for holding the image display element, the projection optical system, the scanner, and the like can be simplified. In addition, when using a so-called micromachine mirror for manufacturing a scanner in a photolithography process, it is desirable to cover the scan mirror surface with some kind of protective member in order to protect the scan mirror surface. If DOE is used as a protective member that covers the scan mirror surface, the number of parts can be reduced. Further, when the scanner is a vacuum package or a decompression package in order to obtain a high-speed scanner, the DOE can be used as a sealing member, and the number of parts can be reduced.
[0147]
The forty-first image display device of the present invention is the first, seventh to sixteenth image display devices, wherein an image that cancels distortion of an image formed by the scanning means and the projection optical system is displayed on the image display element. It is a feature.
[0148]
Examples 1 to 11 described later correspond to this video display device. However, Examples 3 to 11 can be used with or without electrical image distortion correction.
[0149]
The effects of this video display device will be described below. In the case of one-dimensional scanning, scanning is performed in the X direction, and in the case of two-dimensional scanning, scanning in the X direction is repeated while gradually changing the tilt angle in the Y direction of the scanner to form a two-dimensional image. As shown by B in FIG. 7, it is assumed that images formed by scanning are non-linear and non-equally spaced. At this time, as shown by A in FIG. 7, if an image that cancels the distortion of the image formed by the scanning unit and the projection optical system is displayed on the image display element, the image formed by the scanning unit and the projection optical system. Are equally spaced on a straight line as indicated by C in FIG. Such a process eliminates the need to control distortion with the projection optical system, thereby reducing the burden on the projection optical system and facilitating the design of the projection optical system. As a result, it becomes easier to miniaturize the optical system.
[0150]
The forty-second video display apparatus of the present invention is characterized in that, in the forty-first video display apparatus, the electrical image distortion correction is a constant-speed scanning correction.
[0151]
Examples 3 to 11 described later correspond to this video display device. However, Examples 3 to 11 can be used with or without this correction.
[0152]
The effects of this video display device will be described below. It is assumed that the scanning image by the scanning means + projection optical system is linearly scanned by non-constant scanning, and the solid line image in FIG. 8 is formed. In this case, if an image is displayed on the image display element so that the reciprocal of the relative scanning speed of each image position is the relative image display interval at that position, the image formed is linearly scanned by the broken line in FIG. -An image of constant speed scanning. In this case, the video display interval of each pixel may be changed while the video display time of each pixel remains constant. For example, the video display time of each pixel is changed so that the video display time = the video display interval. You may let them. In the latter case, the intensity of the image displayed on the image display element may be changed for each pixel in consideration of eye sensitivity.
[0153]
Compared to the correction of both the linear scanning property and the constant velocity scanning property in FIG. 7, the constant velocity scanning property correction reduces the number of data to be processed, so that it is easy to deal with real-time processing during high resolution scanning and high speed scanning. . Therefore, high resolution and high speed scanning can be performed as compared with the case where both the linear scanning property and the constant velocity scanning property are corrected.
[0154]
A forty-third image display apparatus of the present invention is characterized in that, in the first and seventh to sixteenth image display apparatuses, the scanning means performs two-dimensional scanning.
[0155]
Examples 1 to 11 described later correspond to this video display device.
[0156]
The effects of this video display device will be described below. As shown in FIG. 9, when using two one-dimensional scanning means, ie, a one-dimensional scanning means 4 'for scanning the direction in the plane of the paper and a one-dimensional scanning means 4 "for scanning the direction perpendicular to the plane of the paper, these two scannings are used. Since the optical system 9 for conjugating the means is necessary, the optical system is enlarged, and if the two-dimensional scanning means is used, the optical system can be reduced in size as shown in FIGS. This is particularly effective when the present invention is used as an HMD optical system.
[0157]
The forty-fourth image display apparatus of the present invention is characterized in that, in the first and seventh to sixteenth image display apparatuses, the incident angle θs of the axial principal ray with respect to the normal line of the scanning means satisfies the following expression. is there.
[0158]
| Θs | ≦ 60 ° (6)
Examples 1 to 11 described later correspond to this video display device.
[0159]
The effects of this video display device will be described below. Even when the beam diameter is the same, if the incident angle of the axial principal ray with respect to the scanning means increases, the area of the scanning mirror increases and high-speed scanning becomes difficult. Therefore, it is desirable to satisfy conditional expression (6).
[0160]
The 45th video display apparatus of the present invention is characterized in that, in the 44th video display apparatus, the incident angle of the axial principal ray with respect to the scanning means satisfies the following expression.
[0161]
10 ° ≦ | θs | ≦ 45 ° (6-1)
Examples 1 to 11 described later correspond to this video display device.
[0162]
The effects of this video display device will be described below. If the upper limit of 45 ° is exceeded, the degree of deflection of the light reflected from the scanning mirror becomes too large, and the optical system is also enlarged. Therefore, it is desirable to satisfy the upper limit of the conditional expression. In addition, if the incident angle of the axial principal ray with respect to the scanning mirror of the scanning means is too small, the difference between the optical path incident on the scanning mirror and the optical path reflecting the scanning mirror is small and reflected by the optical system incident on the scanning mirror and the scanning mirror. The configuration of the later optical system becomes difficult. Therefore, it is desirable to satisfy the lower limit of 10 ° of the conditional expression.
[0163]
A forty-sixth video display apparatus according to the present invention is characterized in that the first and seventh to sixteenth video display apparatuses perform reciprocal scanning.
[0164]
Examples 1 to 11 described later correspond to this video display device.
[0165]
The effects of this video display device will be described below. In the reciprocating scanning using both the forward path and the backward path instead of the forward path scanning, the scanning frequency of the scanning unit can be halved, so that high speed scanning can be performed.
[0166]
The 47th video display device of the present invention is characterized in that, in the 1st and 7th to 16th video display devices, the scanning means is a scanning means which vibrates in a sine wave shape in the scanning direction.
[0167]
Examples 1 to 11 described later correspond to this video display device.
[0168]
The effects of this video display device will be described below. The scanning means for performing high-speed scanning vibrates in a sine wave shape like a resonant mirror. By using this scanning means, it is possible to cope with high-speed scanning.
[0169]
The forty-eighth video display apparatus of the present invention is characterized in that, in the forty-seventh video display apparatus, 95% or less of the amplitude of the scanning means which vibrates in a sine wave form is used for video display.
[0170]
This video display apparatus corresponds to Examples 3 to 11 described later as cases where electrical image distortion correction is not performed. However, when performing electrical image distortion correction, Examples 1 to 11 can be used for an amplitude of 95% or more.
[0171]
The effects of this video display device will be described below. In order to scan the scan mirror oscillating in a sine wave at a constant speed without correcting the electric image distortion, the projection optical system needs to be an f arc sine θ lens in the scanning direction. FIG. 10 shows the distortion required for the one-dimensional f arc sine θ lens. In FIG. 10, the horizontal axis represents the normalized incident angle from the scan mirror to the projection optical system, and the vertical axis represents distortion. The following can be seen from FIG.
[0172]
(1) Scanning mirror amplitude φ ₀ Is about ± 5 °, ± 10 °, ± 15 °, it is necessary to generate a very large distortion of + 40% or more in the optical system, which makes designing difficult.
[0173]
▲ 2 ▼ φ ₀ However, as it increases to ± 5 °, ± 10 °,... ± 25 °, the amount of positive distortion generated decreases. Therefore, φ ₀ If is large, the amount of distortion to be generated is small, and in this sense, the projection optical system can be easily designed. On the other hand, φ ₀ Is large, it is difficult to design a wide-angle relay optical system.
[0174]
(3) A certain φ ₀ In this case, the amount of distortion required around the screen suddenly increases.
[0175]
Therefore, from (1) and (2), the amplitude φ ₀ It can be seen that it is difficult to design the projection optical system regardless of whether it is small or large. In particular, in the HMD optical system, since the optical working surface that can be used to reduce the size of the optical system is limited, it is difficult to design an f arc sine θ lens that uses all the amplitude of the sine wave.
[0176]
Therefore, from (3), it is easier to control the projection optical system because it is easier to control the distortion if the image is displayed only in the sine wave of the deflection angle of the scan mirror with only a relatively good linearity. .
[0177]
That is, as shown in FIG. ₀ K × 100% of the amplitude of the scan mirror oscillating sinusoidally at / k, ie ± φ ₀ When the deflection angle of the scan mirror in the range is used for image display, the deflection angle of the scan mirror is φ. Φ / φ at each angle of view in this case ₀ The relationship is as shown in FIG.
[0178]
From FIG. 12, when k = 0.95 or less, that is, when 95% or less of the amplitude of the sine wave is used, φ / φ ₀ It can be seen that the linearity is improved, and the distortion control for making the f arc sine θ lens becomes easier.
[0179]
Further, if video display is performed using all the amplitudes of the mirrors that vibrate sinusoidally, the difference in scanning speed between the center portion of the screen having a high scanning speed and the peripheral portion of the screen having a low scanning speed becomes too large. As a result, even when electrical image distortion correction is performed, the correction cannot be performed with high accuracy.
[0180]
For these reasons, it is desirable to use 95% or less of the amplitude of the scanning means that vibrates sinusoidally for video display.
[0181]
The forty-eighth video display apparatus of the present invention is characterized in that, in the forty-eighth video display apparatus, 90% or less of the amplitude of the scanning means that vibrates sinusoidally is used for video display.
[0182]
Examples 3 to 11 described later correspond to this video display device.
[0183]
The effects of this video display device will be described below. When the ratio of the amplitude of the scanning means used for image display is 90%, the linearity is further improved, and the design of the f arc sine θ lens becomes very easy. When a blanking period is provided for video display, about 90% of the amplitude of the mirror that vibrates in a sine wave shape may be used.
[0184]
The 50th video display device of the present invention is a scanning mirror which vibrates in a sinusoidal shape in the main scanning direction when a two-dimensional image is formed by repeating scanning in the main scanning direction in the first, 7-16 video display devices. The sub-scanning direction is a scanning mirror whose deflection angle changes linearly.
[0185]
This video display apparatus corresponds to Example 9 described later.
[0186]
The effects of this video display device will be described below. In a polygon mirror or a mirror that vibrates like a triangular wave, the tilt angle of the scan mirror changes linearly. In order to scan at a constant speed without correcting electric image distortion using such a scan mirror, the projection optical system needs to be an fθ lens. FIG. 13 shows the distortion characteristics of the one-dimensional fθ lens. When the angle of view is small, tan θ≈θ, so the mirror deflection angle φ ₀ Is less than ± 20 °, for the same mirror deflection angle, the amount of negative distortion to be generated by the fθ lens is smaller than the amount of positive distortion of the f arc sine θ lens. That is, in particular φ ₀ Is smaller, the fθ lens is easier to design than the f arc sine θ lens.
[0187]
On the other hand, when forming a two-dimensional image by repeating horizontal scanning while gradually changing the scanner inclination angle in the vertical direction, high-speed scanning is required in the horizontal direction, which is the main scanning direction, but in the vertical direction in the sub-scanning direction. The scan is not so fast.
[0188]
Therefore, if a mirror that vibrates sinusoidally in the main scanning direction (horizontal direction) and a mirror that changes linearly in the sub-scanning direction (vertical direction) is used, there is no electrical image distortion correction during high-speed scanning. Design of a projection optical system for fast scanning is facilitated. In this case, the projection optical system has an f arc sine θ lens characteristic in the main scanning direction (horizontal direction) and an fθ lens characteristic in the sub scanning direction (vertical direction) with respect to the mirror deflection angle used for image display. It is desirable.
[0189]
The fifty-first video display apparatus of the present invention is characterized in that, in the first, seventh to sixteenth video display apparatuses, the mirror vibrates in a sine wave shape in both the main scanning direction and the sub-scanning direction.
[0190]
This video display apparatus corresponds to Example 10 described later.
[0191]
The effects of this video display device will be described below. When scanning at a very high speed, it is necessary to use a scanning means that vibrates sinusoidally like a resonance mirror in both the main scanning direction (horizontal direction) and the sub-scanning direction (vertical direction) perpendicular to the main scanning direction. . By using this scanning means, it is possible to cope with high-speed scanning. In this case, it is desirable that the projection optical system has f arc sine θ lens characteristics in both the main scanning direction (horizontal direction) and the sub-scanning direction (vertical direction) with respect to the mirror deflection angle used for image display.
[0192]
A fifty-second video display apparatus according to the present invention is characterized in that, in the first, seventh to sixteenth video display apparatuses, the scanning means is a micromachine mirror manufactured by using a photolithography process.
[0193]
Examples 1 to 11 described later correspond to this video display device.
[0194]
The effects of this video display device will be described below. In the case of a micromachine mirror as disclosed in JP-A-10-20226, the scanning means can be made very small. This is particularly effective when the video display device of the present invention is used as an HMD.
[0195]
Further, for example, in the case of an electrostatic drive type micromachine mirror, power consumption can be reduced as compared with an HMD using a backlight and a transmissive LCD (liquid crystal display device). This is effective in the case of a portable HMD driven by a battery, a portable projector, or the like.
[0196]
The fifty-third image display device of the present invention is the first, seventh to sixteenth image display devices, wherein the optical system from the scanning means to the image display element by back ray tracing is composed of at least two surfaces having optical action. When this optical system is divided into two parts on the scanning means side and the image display element side, positive spherical aberration is generated on the scanning means side, and negative spherical aberration is generated on the image display element side. It is characterized by.
[0197]
This video display apparatus corresponds to Examples 8 and 9 described later.
[0198]
The effects of this video display device will be described below. As shown in FIG. 14, it is assumed that the intensity of light emitted from the video display element 6 decreases as the distance from the normal line of the video display element 6 increases. If the light from the image display element 6 having such unevenness is simply converged, the intensity on the pupil plane is uneven, which is not preferable in terms of imaging performance. When the optical system of the present invention is used as an HMD optical system, if there is uneven intensity on the pupil plane, the brightness decreases due to an alignment error of the eyeball with respect to the HMD, and the brightness during off-axis observation of the virtual image 10 It is also not preferable because it reduces the thickness.
[0199]
Therefore, as shown in FIGS. 15A and 15B, the optical system 5 from the scanner 4 to the image display element 6 by back ray tracing is configured with at least two surfaces having optical action, and this optical system. If a positive spherical aberration is generated by the scanner-side optical system L2 of FIG. 5 and a negative spherical aberration is generated by the image display element-side optical system L1 of the optical system 5, an exit pupil plane is obtained for a light source with uneven intensity. The intensity unevenness on the (scanner surface) can be corrected. Since the optical system from the scanner 4 to the image display element 6 has a smaller angle of view than the optical system from the entrance pupil to the scanner 4, such spherical aberration can be corrected most effectively. FIG. 15A shows a case where the optical system 5 is constituted by a positive power optical system L1 and a positive power optical system L2 from the image display element 6 side, and FIG. 15B shows a positive power optical system L1. And a negative power optical system L2.
[0200]
The fifty-fourth image display apparatus of the present invention is the first or seventh to sixteenth image display apparatus, in the plane in the scanning direction (in the case of two-dimensional scanning, in the respective planes in the main scanning direction and the sub-scanning direction). ,
3 × G> f · tan 2φ / d> G / 2 (7)
It is characterized by satisfying. here,
G: Number of pixels in the scanning direction
f: Focal length φ in the scanning direction plane of the condensing optical system from the image display element to the scanning means φ: One-side deflection angle in the scanning direction of the scanning means used for image display
(Scanning device deflection angle in the range of ± φ is used for video display)
d: Half the size of the image display element in the scanning direction
However, f defined by the following equation in the backward ray tracing is the focal length of the condensing optical system from the scanning means to the image display element.
[0201]
f = Y / β tan2φ
Here, Y is half the size of the intermediate image in the scanning direction, and β is the magnification of the optical system from the video display element to the intermediate image in the scanning direction.
[0202]
Note that the optical system of the image display device of the present invention is a decentered optical system including a surface that is decentered with respect to the axial principal ray, and therefore an accurate focal length cannot be obtained by normal paraxial ray tracing. . Therefore, the focal length of the condensing optical system is defined as described above.
[0203]
Examples 1 to 11 described later correspond to this video display device.
[0204]
The effects of this video display device will be described below. Assume that the optical system is configured as shown in FIG. In order tracking, the light from the image display element 6 is collimated by the condensing lens 5, the light scanned by the scanner 4 is formed as an intermediate image 7 by the relay lens 3, and then the pupil 1 (in the case of the HMD optical system) by the eyepiece 2. To the observer's pupil or center of rotation. At this time, the intermediate image 7 is formed at the position of the eyepiece lens 2 to f3 and at the position of the relay lens 3 to f2, and the scanning means 4 is disposed at the position of the relay lens 3 to f2 and at the position of the condenser lens 5 to f1. Then, it is assumed that the video display element 6 is arranged at a position f1 from the condenser lens 5.
[0205]
Further, it is assumed that an image as shown in FIG. 17A or FIG. 17B is displayed on the image display element 6 and an image of the image display element 6 corresponding to the number of pixels in the scanning direction is formed in the scanning direction.
[0206]
At this time, if the configuration of the optical system is inappropriate, the following problems occur. For example, if the size of the image display element 6 is too large or the magnification of the optical system is too large, the image 11 (virtual pixels) of the image display element 6 formed as shown in FIG. Can not be observed as. As another example, when the size of the image display element 6 is too small, the magnification of the optical system is too small, or the interval between images displayed on the image display element 6 is too large, the image display element 6 is formed as shown in FIG. The image 11 (virtual pixel) of the image display element 6 is too far away, and also in this case, it cannot be observed as a good image.
[0207]
Therefore, in order to form a good image that is easy to observe, as described below, the size of the image display element 6, the configuration of the projection optical system, and the interval between images displayed on the image display element 6 are set appropriately. There is a need.
[0208]
If the pixel interval in the intermediate image 7 is k · pixel size,
Number of pixels in the scanning direction G≈intermediate image size / virtual pixel spacing
= (Size of intermediate image / size of image of image display element in intermediate image) / k
= F · tan 2φ / (d · k)
It becomes. In order to observe as a good image, it is preferable to set 2>k> 1.
[0209]
Therefore, in order to satisfy 2>k> 1, it is necessary to satisfy the following expression in the optical system of FIG.
[0210]
2 ・ G> f ・ tan 2φ / d> G
If this condition is satisfied, the image can be observed as a good image without problems as shown in FIGS.
[0211]
In the above description, as shown in FIG. 16, the intermediate image 7 is formed at the position from the eyepiece lens 2 to f3 and at the position from the relay lens 3 to f2, and from the relay lens 3 to the position f2 and from the condenser lens 5 to f1. This is a result when the scanning unit 4 is arranged at the position of, and the image display element 6 is arranged at the position of f1 from the condenser lens 5. Actually, in order to reduce the size of the optical system or the like, the intermediate image 7, the position of the scanner 4 or the image display element 6 is shifted from the position shown in FIG. 16, or optical scanning is performed to perform constant speed scanning without correcting electric image distortion. Cause distortion in the system. Therefore, considering this point, it is desirable to satisfy the following conditional expression.
[0212]
3 × G> f · tan 2φ / d> G / 2 (7)
The image display element 6 may be shielded so as to satisfy the above conditional expression.
[0213]
The 55th video display device of the present invention comprises the 1st to 54th video display devices that form the video displayed on the video display element as a virtual image and guide it to the observer's eyeball, and hold this video display device in front of the viewer's face. And a support portion that is configured to be configured.
[0214]
This video display apparatus corresponds to Examples 1 to 10 described later.
[0215]
The effects of this video display device will be described below. An HMD using an LCD as an image display element uses a polarizing filter and a color filter, so that the utilization efficiency of light source light is poor. In the case of the optical system of the present invention, the light source light utilization efficiency is greatly improved. Further, for example, if an electrostatic drive type micromachine mirror is used as the scanning means, the power consumption can be reduced, so that it is optimal as a portable HMD.
[0216]
The fifty-sixth video display device of the present invention is characterized in that, in the fifty-fifth video display device, one video display device is arranged corresponding to each of the left and right eyes of the observer.
[0217]
This video display apparatus corresponds to Examples 1 to 10 described later.
[0218]
The operation and effect of this video display apparatus will be described below. If an image with parallax is displayed on the left and right, stereoscopic viewing is possible.
[0219]
According to a 57th aspect of the present invention, there is provided a projector, a laser beam printer or a bar, comprising the 1st to 54th video display devices for displaying the video displayed on the video display element as a real image. It is a code reader.
[0220]
This video display apparatus corresponds to Example 11 described later.
[0221]
The operation and effect of this video display device will be described below. Since a projector using an LCD as a video display element uses a polarizing filter and a color filter, the utilization efficiency of light source light is poor. In the case of the optical system of the present invention, the light source light utilization efficiency is greatly improved. Further, as described above, the optical system of the present invention can have a beam shaping function in the projection optical system, so that the number of optical elements for beam shaping in an optical system using an LD as a light source can be reduced.
[0222]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments 1 to 11 of the video display device of the present invention will be described below with reference to the drawings.
[0223]
The configuration parameters for back ray tracing of each embodiment will be described later. In the configuration parameters of each embodiment, as shown in FIG. 20, the axial principal ray (observer visual axis) 22 is optically converted by back ray tracing. It is defined as a ray that passes through the center of the exit pupil (incidence pupil: observer's pupil or rotation center position in reverse ray tracing) 21, passes through the scan mirror 23, and reaches the center of the image display element 24. The center of the pupil 21 is the origin of the decentered optical surface, the direction along the axial principal ray 22 is the Z-axis direction, and the direction from the pupil 21 toward the first surface 31 of the optical system is the Z-axis positive direction. A plane including the axis and the center of the image display element 24 is defined as a YZ plane, a direction passing through the origin and orthogonal to the YZ plane, and a direction from the front side of the paper toward the back side is defined as an X axis positive direction. The axis constituting the right-handed orthogonal coordinate system is taken as the Y axis. FIG. 20 shows this coordinate system. The coordinate system is not shown in FIGS. 21 to 32 showing other embodiments.
[0224]
In Examples 1 to 11, each surface is decentered in this YZ plane, and the only symmetric surface of each rotationally asymmetric free-form surface is the YZ plane.
[0225]
For the eccentric surface, from the origin of the above coordinate system, the amount of eccentricity of the surface top position of the surface (X-axis direction, Y-axis direction, and Z-axis direction are X, Y, Z, respectively) and the center axis of the surface (free With respect to the curved surface, inclination angles (α, β, γ (°), respectively) about the X axis, the Y axis, and the Z axis of the equation (a) are given. In this case, positive α and β mean counterclockwise rotation with respect to the positive direction of each axis, and positive γ means clockwise rotation with respect to the positive direction of the Z axis.
[0226]
In addition, when a specific surface (including a virtual surface) and a subsequent surface among the optical action surfaces constituting the optical system of each embodiment constitute a coaxial optical system, a surface interval is given, In addition, the refractive index and Abbe number of the medium are given according to conventional methods.
[0227]
Further, the shape of the surface of the free curved surface used in the present invention is defined by the equation (a), and the Z axis of the defining equation becomes the axis of the free curved surface.
[0228]
For DOE, we use the Sweet method (WCSweatt, ^ Mathematical equivalence between a holographic optical element and an ultra-high index lens ", J.Opt.Soc.Am, Vol. 69, No. 3 (1979)), the reference wavelength = 587.56 nm (d line), the refractive index of the ultrahigh refractive index lens at that reference wavelength = 1001, and the Abbe number = −3.45.
[0229]
In addition, the term regarding the free-form surface for which no data is described is zero. The refractive index is shown for d-line (wavelength 587.56 nm). The unit of length is mm.
[0230]
Another defining equation for free-form surfaces is the Zernike polynomial given by the following equation (b). The shape of this surface is defined by the following equation. The Z axis of the defining formula becomes the axis of the Zernike polynomial. The definition of the rotationally asymmetric surface is defined by polar coordinates of the height of the Z axis with respect to the XY plane, A is the distance from the Z axis in the XY plane, R is the azimuth around the Z axis, and Z axis It is expressed by the rotation angle measured from.
[0231]

To design an optical system that is symmetric in the X-axis direction, D _Four , D _Five , D ₆ , D _Ten 0, D ₁₁ , D ₁₂ , D ₁₃ , D ₁₄ , D ₂₀ , D _{twenty one} , D _{twenty two} Use….
[0232]
The following definition formula (c) can be given as an example of other aspects.
[0233]
Z = ΣΣC _nm XY
As an example, when k = 7 (seventh order term) is considered, when expanded, it can be expressed by the following expression.
[0234]

In the embodiment of the present invention, the surface shape is expressed by a free-form surface using the equation (a). However, similar effects can be obtained by using the equations (b) and (c). Needless to say.
[0235]
In all of Examples 1 to 11 below, the specifications are a horizontal field angle of 30 °, a vertical field angle of 22.7 °, and an entrance pupil diameter of 4 mm in back ray tracing. Examples 1 to 10 are HMD optical systems that form virtual images, and Example 11 is a real image forming optical system such as a projector, a laser beam printer, or a barcode reader.
[0236]
Example 1
This embodiment is an HMD optical system that modulates the intensity of video display light according to a video signal when a virtual image of the video display element 24 is formed 1 m ahead of the observer's eyeball. A two-dimensional virtual image is formed by repeating scanning in the X direction while gradually changing the tilt angle in the Y direction of the scanner in synchronization with the video display light.
[0237]
FIG. 20 is a view (YZ plan view) of the optical system of this embodiment viewed from the side of the observer. The displayed image is observed with the pupil or the center of rotation of the observer's eyeball positioned at the pupil 21. You may arrange | position the up-down direction of arrangement | positioning of FIG. 1 to a reverse direction. Moreover, you may arrange | position so that this may become the figure (XZ top view) seen from the observer upper side. This is true for all of the following examples, which are not described in detail in the following examples. In the following optical path diagrams, the size of the scanner 23 is drawn larger than necessary for easy understanding.
[0238]
The eye relief of this embodiment is 31 mm, and an LED, LD, or the like can be used as the image display element 24. In addition, a polygon mirror, a galvanometer mirror, or the like can be used as the scanning unit 23. A so-called micromachine scanner manufactured using a photolithography process as disclosed in Japanese Patent Laid-Open No. 10-20226 has advantages such as small size and low power consumption, and is optimal for use in an HMD. In this case, either forward path scanning or reciprocal scanning may be used.
[0239]
In the configuration of the optical system of this embodiment, a single decentered prism 30 constitutes a projection optical system. The decentered prism 30 is composed of five surfaces from the first surface 31 to the fifth surface 35, and by reverse ray tracing, pupil 21 → first transmission surface 31 (= second reflection surface) → first reflection surface 32 → second reflection surface. 31 (= first transmission surface) is totally reflected, and an intermediate image is formed in the prism 30. The light from the intermediate image is brought close to parallel light by the third reflection surface 33 and the second transmission surface 34 and guided to the scanner 23. The reflected light of the scanner 23 is guided to the image display element 24 as convergent light by the fourth reflecting surface 35 provided on the prism 30.
[0240]
If a HM film is formed on the joint surface between the first reflecting surface 32 and the see-through prism 25 and a means for switching the transmittance of external light such as a liquid crystal shutter is disposed on the opposite side of the pupil 21 of the see-through prism 25, Superimpose function and see-through function can be added. Here, the see-through prism 25 is an optical element in which the combined power of the projection optical system (prism) 30 and the see-through prism is substantially zero with respect to external light.
[0241]
In this embodiment, an image that cancels the distortion of the image formed by the scanner 23 and the eccentric prism 30 is displayed on the video display element 24, and two-dimensional electrical image distortion correction is performed.
[0242]
As a modification of this embodiment, as shown in FIG. ₁ And the second prism 30 ₂ You may comprise. In that case, by the backward ray tracing, the pupil 21 → the first transmission surface 31 (= second reflection surface) → the first reflection surface 32 → the second reflection surface 31 (= first transmission surface) is totally reflected, and the third The second prism 30 passes through the transmission surface 36 → the fourth transmission surface 37. ₂ An intermediate image is formed inside. The light from the intermediate image is brought close to parallel light by the third reflection surface 33 and the second transmission surface 34 and guided to the scanner 23. The reflected light of the scanner 23 is converted into the second prism 30. ₂ Is led to the image display element 24 as convergent light.
[0243]
In all the embodiments described above and below, the visual axis is unified in the horizontal direction for easy understanding, but the visual axis may be changed to 10 ° downward for easy observation.
[0244]
The advantage of the first embodiment is that the projection optical system 30 reflects the light four times and the scanner 23 reflects the light five times in total, so that the optical system can be downsized due to the folding effect. Further, since the projection optical system 30 is mainly composed of a reflecting action, the occurrence of chromatic aberration is small.
[0245]
Further, the principal ray incident on the intermediate image from the eyepiece optical system in the reverse ray tracing is incident as a convergent light of 18.8 ° or less with respect to the axial principal ray 22. Therefore, the effective diameter of the light beam from the eyepiece optical system to the scanning means 23 can be reduced, and the optical system can be miniaturized.
[0246]
Further, since the projection optical system can be constituted by one prism member, the number of parts is greatly reduced as compared with the previous example.
[0247]
Further, since the scanning unit 23 and the image display element 24 are disposed on the projection optical system 30, the weight balance is good.
[0248]
In addition, the second transmission surface 34 and the fourth reflection surface 35 have different optical functions, but have a configuration with apparently good continuity. Therefore, when the prism member 30 is manufactured by molding, it is possible to deal with these two surfaces with one mold, and the manufacturability is good.
[0249]
The X-direction mirror deflection angle φx = ± 14.4 ° and the Y-direction scanner mirror 23 deflection angle φy = ± 7.68 ° required for video display in this embodiment, so that φx / θx = 14. 4/15 = 0.96 and φy / θy = 7.68 / 11.36 = 0.68.
[0250]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 is 33.3 °, the incident angle θ1 of the axial principal ray 22 to the first transmission surface 31 is 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 24.9 °.
[0251]
(Example 2)
In this embodiment, as shown in FIG. 22, the configuration between the scanner 23 and the image display element 24 is different from that of the first embodiment in back ray tracing.
[0252]
That is, the decentered prism 30 of this embodiment is composed of six surfaces including a first surface 31 to a fourth surface 34, a fifth surface 38, and a sixth surface 39, and the first transmission surface 31 of the pupil 21 → the prism 30 by back ray tracing. (= Second reflecting surface) → first reflecting surface 32 → second reflecting surface 31 (= first transmitting surface) is totally reflected to form an intermediate image in the prism 30. The light from the intermediate image is brought close to parallel light by the third reflection surface 33 and the second transmission surface 34 and guided to the scanner 23. The reflected light of the scanner 23 passes through the third transmission surface 38 provided on the prism 30 → the fourth transmission surface 39 and crosses the prism 30 and is guided to the image display element 24 as convergent light.
[0253]
The mirror deflection angle in the X direction φx = ± 8.30 ° and the mirror deflection angle in the Y direction φy = ± 11.2 ° necessary for video display in this embodiment, so φx / θx = 0.55, φy /Θy=0.99.
[0254]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference surface of the scanner 23 is 29.6 °, the incident angle θ1 of the axial principal ray 22 to the first transmission surface 31 is 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 28.5 °.
[0255]
(Example 3)
In this embodiment, as shown in FIG. 23, one decentered prism 30 constituting the projection optical system is composed of five surfaces including a first surface 31 to a third surface 33, a fourth surface 40, and a fifth surface 41. By reverse ray tracing, total reflection is performed by the pupil 21 → the first transmission surface 31 (= second reflection surface) of the prism 30 → the first reflection surface 32 → the second reflection surface 31 (= first transmission surface) and enters the prism 30. An intermediate image is formed and guided to the scanner 23 through the intermediate image → the third reflection surface 33 and the total reflection → the fourth reflection surface 40 → the second transmission surface 33 (= third reflection surface). The reflected light of the scanner 23 is transmitted through the third transmission surface 33 (= third reflection surface = second transmission surface) → the fifth reflection surface 41 → the fourth transmission surface 33 (= third transmission surface = third reflection surface = second transmission). Through the prism) and is guided to the image display element 24 as convergent light. In this case, the second reflecting surface 31 and the third reflecting surface 33 are totally reflected.
[0256]
In the configuration of this embodiment, since the dual-purpose surfaces 31 and 33 are provided, the optical action surfaces to be configured are reduced. These two surfaces act as six surfaces.
[0257]
Further, since the eyepiece optical system and the relay optical system are symmetrical, each generated aberration is canceled and the entire aberration is corrected well. In particular, the distortion is corrected well. When two-dimensional scanning is performed, the deviation of the imaging position of each principal ray on the image display element 24 by back ray tracing is 5 μm or less in both the X direction (main scanning direction) and the Y direction (sub-scanning direction). This means that in forward ray tracing, distortion in the X direction (main scanning direction) is 0.3% or less, and distortion in the Y direction (sub scanning direction) is 0.5% or less. As a result, two-dimensional linear scanning can be performed without correcting electrical image distortion.
[0258]
Further, 55% of the amplitude of the mirror 23 oscillating in a sine wave form is given an f arc sine θ lens characteristic. Therefore, when using the scan mirror 23 oscillating sinusoidally, if 55% of the amplitude is used, linear scanning and constant speed scanning can be performed without correcting electric image distortion, and high-speed scanning can be handled.
[0259]
In this case, the mirror deflection angle φx = ± 13.4 ° in the X direction and 55% of the amplitude of the mirror deflection angle φy = ± 13.8 ° in the Y direction is the mirror deflection angle in the X direction necessary for video display, φx = ± 7.36 °, mirror deflection angle in the Y direction φy = ± 7.60 °.
[0260]
In addition, if the constant speed scanning property is corrected, it is possible to use the entire amplitude of the mirror 23 oscillating in a sine wave shape, or it is possible to use the mirror 23 whose mirror deflection angle changes linearly.
[0261]
Further, as described in some embodiments below, it is possible to change the distortion characteristic to the fθ characteristic in both the X direction (main scanning direction) and the Y direction (sub scanning direction).
[0262]
When the size of the image display element 24 is 4 to 5 μm square, the image formed by the forward ray tracing is close to a state in which virtual pixels are in close contact with each other. Therefore, it is easy to observe the video.
[0263]
In addition, the back of the scanner 23 is configured to be incident on the prism 30 and exited from the prism 30 by reverse ray tracing, and beam shaping of the image display element light is possible. Therefore, the image display element 24 having an elliptical cross-sectional shape like an LD can be used efficiently. In this embodiment, the NA (numerical aperture) on the image display element side is NAx = 0.32 and NAy = 0.23, and beam shaping is performed on image display element light having a horizontally long cross section.
[0264]
The mirror deflection angle in the X direction φx = ± 7.36 ° and the mirror deflection angle in the Y direction φy = ± 7.60 ° necessary for video display of this embodiment, so that φx / θx = 0.49, φy /Θy=0.67.
[0265]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 = 18.7 °, the incident angle θ1 of the axial principal ray 22 with respect to the first transmission surface 31 = 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 23.4 °.
[0266]
(Example 4)
This embodiment is the same as the third embodiment, and as shown in FIG. 24, in the backward ray tracing, the first transmission surface 31 (= second reflection surface) of the pupil 21 → the prism 30 → the first reflection surface 32 → the second. The reflection surface 31 (= first transmission surface) is totally reflected to form an intermediate image in the prism 30, and the intermediate image → the third reflection surface 33 is totally reflected → the fourth reflection surface 40 → the second transmission surface 33 (= The light is guided to the scanner 23 through the third reflecting surface. The reflected light of the scanner 23 is transmitted through the third transmission surface 33 (= third reflection surface = second transmission surface) → the fifth reflection surface 41 → the fourth transmission surface 33 (= third transmission surface = third reflection surface = second transmission). Through the prism) and is guided to the image display element 24 as convergent light. In this case, the second reflecting surface 31 and the third reflecting surface 33 are totally reflected.
[0267]
In this embodiment, the pupil magnification in forward ray tracking is increased to reduce the size from the video display element 24 to the intermediate image in the third embodiment, and the amount of forward projection of the scanner 23 is reduced.
[0268]
The mirror deflection angle φx = ± 8.73 ° in the X direction and the mirror deflection angle φy = ± 9.83 ° in the Y direction necessary for video display of this embodiment, so φx / θx = 0.58, φy /Θy=0.87.
[0269]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 is 23.7 °, the incident angle θ1 of the axial principal ray 22 to the first transmission surface 31 is 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 25.5 °.
[0270]
(Example 5)
This embodiment is an example in which the fourth transmission surface immediately before the image display element 24 of the third embodiment is replaced with another surface 42. As shown in FIG. 25, one decentered prism 30 constituting the projection optical system is the first one. The first surface 31 to the third surface 33, the fourth surface 40, the fifth surface 41, and the sixth surface 42, and the first transmission surface 31 (= second reflection surface) of the pupil 21 → prism 30 by back ray tracing. ) → first reflection surface 32 → second reflection surface 31 (= first transmission surface) to totally reflect to form an intermediate image in the prism 30, intermediate image → third reflection surface 33 to total reflection → fourth reflection The light is guided to the scanner 23 through the surface 40 → the second transmission surface 33 (= third reflection surface). The reflected light of the scanner 23 passes through the third transmitting surface 33 (= third reflecting surface = second transmitting surface) → the fifth reflecting surface 41 → the fourth transmitting surface 42 and crosses the prism 30 to be converged light. Lead to. In this case, the second reflecting surface 31 and the third reflecting surface 33 are totally reflected.
[0271]
In this embodiment, when two-dimensional scanning is performed, the shift of the imaging position of each principal ray on the image display element 24 in the backward ray tracing is caused in both the X direction (main scanning direction) and the Y direction (sub-scanning direction). Since it is 3.3 μm or less, it has a two-dimensionally good linear scanning property.
[0272]
The mirror deflection angle φx = ± 7.73 ° in the X direction and the mirror deflection angle φy = ± 9.73 ° in the Y direction necessary for video display in this embodiment, so φx / θx = 0.52, φy /Θy=0.86.
[0273]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 is 20.0 °, the incident angle θ1 of the axial principal ray 22 on the first transmission surface 31 is 0.23 °, The incident angle θ2 of the axial principal ray 22 on one reflecting surface 32 is 23.7 °.
(Example 5-1)
This embodiment is the same as the fifth embodiment, and as shown in FIG. 26, in the reverse ray tracing, the first transmission surface 31 (= second reflection surface) of the pupil 21 → the prism 30 → the first reflection surface 32 → the second. The reflection surface 31 (= first transmission surface) is totally reflected to form an intermediate image in the prism 30, and the intermediate image → the third reflection surface 33 is totally reflected → the fourth reflection surface 40 → the second transmission surface 33 (= The light is guided to the scanner 23 through the third reflecting surface. The reflected light of the scanner 23 passes through the third transmitting surface 33 (= third reflecting surface = second transmitting surface) → the fifth reflecting surface 41 → the fourth transmitting surface 42 and crosses the prism 30 to be converged light. Lead to.
[0274]
In this embodiment, the fourth transmission surface 42 immediately before the image display element 24 of the fifth embodiment is brought close to the first reflection surface 32.
[0275]
The X-direction mirror deflection angle φx = ± 7.83 ° and the Y-direction mirror deflection angle φy = ± 11.2 ° required for the image display of this embodiment, so that φx / θx = 0.52, φy /Θy=0.99.
[0276]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 = 21.2 °, the incident angle θ1 of the axial principal ray 22 with respect to the first transmission surface 31 = 0.26 °, The incident angle θ2 of the axial principal ray 22 on one reflecting surface 32 is 22.8 °.
[0277]
(Example 6)
This embodiment is an example in which a DOE 44 is added between the second transmission surface 33 of the decentered prism 30 having the same six surfaces as in the fifth embodiment and the scanner 23. As shown in FIG. → first transmission surface 31 of prism 30 (= second reflection surface) → first reflection surface 32 → total reflection at second reflection surface 31 (= first transmission surface) → intermediate image → total reflection at third reflection surface 33 → 4th reflective surface 40 → 2nd transmissive surface 33 (= 3rd reflective surface) is guided to the scanner 23 via a DOE 44 provided with a diffractive surface 43 on the incident side. The reflected light of the scanner 23 is converged across the prism 30 via the third transmission surface 33 (= third reflection surface = second transmission surface) → the fifth reflection surface 41 → the fourth transmission surface 42 through the DOE 44 in reverse. The light is guided to the image display element 24 as light. As described above, in the backward ray tracing, the action of the DOE 44 is received both when entering the scanner 23 and when reflecting from the scanner 23.
[0278]
As shown in FIG. 27, the DOE 44 can be integrated with the scanner 23, for example, as a protective member or a sealing member of the scanner 23. Here, the diffractive surface 43 of the DOE is disposed on the prism 30 side of the parallel plane substrate. However, if the diffractive surface 43 is disposed on the substrate surface opposite to the prism 30 (scanner side), the diffractive surface 43 can be protected from contamination. .
[0279]
In this embodiment, the DOE 44 corrects chromatic aberration generated in the projection optical system 30 for the sake of simplicity. However, as described with reference to FIGS. May be generated. This is the same in all examples using the following DOE.
[0280]
In this embodiment, when two-dimensional scanning is performed, the shift of the imaging position of each principal ray on the image display element 24 by back ray tracing is the same in both the X direction (main scanning direction) and the Y direction (sub-scanning direction). 1.6 μm or less, it has a two-dimensionally good linear scanning property. Further, the pupil aberration at the exit pupil (scanner) position in the backward ray tracing is as good as 0.15 mm or less.
[0281]
The X-direction mirror deflection angle φx = ± 6.25 ° and the Y-direction mirror deflection angle φy = ± 12.4 ° necessary for video display in this embodiment, so that φx / θx = 0.42, φy. /Θy=1.09.
[0282]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 = 19.5 °, the incident angle θ1 of the axial principal ray 22 with respect to the first transmission surface 31 = 0.06 °, The incident angle θ2 of the axial principal ray 22 on one reflecting surface 32 is 23.6 °.
[0283]
(Example 7)
In this embodiment, as shown in FIG. 28, a transmissive DOE diffraction surface 43 is provided on the fourth transmission surface 42 of the decentered prism 30 having the same six surfaces as the fifth and fifth examples. It is. That is, by the backward ray tracing, total reflection is performed by the pupil 21 → the first transmission surface 31 (= second reflection surface) of the prism 30 → the first reflection surface 32 → second reflection surface 31 (= first transmission surface), and the prism 30. An intermediate image is formed therein, and is guided to the scanner 23 through the intermediate image → the third reflection surface 33 through the total reflection → the fourth reflection surface 40 → the second transmission surface 33 (= third reflection surface). The reflected light of the scanner 23 is reflected by the third transmission surface 33 (= third reflection surface = second transmission surface) → the fifth reflection surface 41, passes through the diffraction surface 43 of the fourth transmission surface 42, and crosses the prism 30. It is guided to the image display element 24 as convergent light.
[0284]
The mirror deflection angle in the X direction φx = ± 7.63 ° and the mirror deflection angle in the Y direction φy = ± 9.72 ° necessary for video display of this embodiment, so φx / θx = 0.51, φy /Θy=0.86.
[0285]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 is 20.6 °, the incident angle θ1 of the axial principal ray 22 to the first transmission surface 31 is 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 23.6 °.
[0286]
(Example 8)
In this embodiment, as shown in FIG. 29, a reflective DOE diffractive surface 45 is provided on the fifth reflecting surface 41 of the decentered prism 30 having the same six surfaces as in the fifth and fifth embodiments. It is. That is, by the backward ray tracing, total reflection is performed by the pupil 21 → the first transmission surface 31 (= second reflection surface) of the prism 30 → the first reflection surface 32 → second reflection surface 31 (= first transmission surface), and the prism 30. An intermediate image is formed therein, and is guided to the scanner 23 through the intermediate image → the third reflection surface 33 through the total reflection → the fourth reflection surface 40 → the second transmission surface 33 (= third reflection surface). The reflected light of the scanner 23 is introduced into the prism 30 by the third transmission surface 33 (= third reflection surface = second transmission surface), diffracted and reflected by the diffraction surface 45 of the fifth reflection surface 41, and the fourth transmission surface 42. Then, the light passes through the prism 30 and is guided to the image display element 24 as convergent light.
[0287]
In this embodiment, with the configuration of FIG. 15A, the light distribution characteristic of the image display element 24 whose intensity decreases as it moves away from the normal is corrected.
[0288]
The X-direction mirror deflection angle φx = ± 8.50 ° and the Y-direction mirror deflection angle φy = ± 13.3 ° necessary for the image display of this embodiment, so that φx / θx = 0.57, φy /Θy=1.17.
[0289]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 is 21.1 °, the incident angle θ1 of the axial principal ray 22 to the first transmission surface 31 is 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 22.9 °.
[0290]
Example 9
In this embodiment, as shown in FIG. 30, the decentered prism 30 similar to the fifth embodiment and the embodiment 5-1 is replaced with the first prism 30. ₁ And the second prism 30 ₂ In this example, the first prism 30 is divided. ₁ Consists of three surfaces, a first surface 31, a second surface 32, and a third surface 46, and the second prism 30. ₂ Is composed of five surfaces including a first surface 47, a second surface 48, a third surface 49, a fourth surface 50, and a fifth surface 51, and by reverse ray tracing, the pupil 21 → the first transmission surface 31 (= second reflection surface). → Total reflection at the first reflection surface 32 → the second reflection surface 31 (= first transmission surface), and the second prism 30 through the second transmission surface 46 → the third transmission surface 47. ₂ An intermediate image is formed therein, and is guided to the scanner 23 through the intermediate image → the third reflection surface 48 through the total reflection → the fourth reflection surface 49 → the fourth transmission surface 48 (= the third reflection surface). The reflected light of the scanner 23 is reflected by the fifth transmission surface 48 (= third reflection surface = fourth transmission surface) → the fifth reflection surface 50, passes through the sixth transmission surface 51, and the second prism 30. ₂ Is guided to the image display element 24 as convergent light.
[0291]
In this embodiment, when two-dimensional scanning is performed, the shift of the imaging position of each principal ray on the image display element 24 by back ray tracing is the same in both the X direction (main scanning direction) and the Y direction (sub-scanning direction). Since it is 3 μm or less, it has a two-dimensionally good linear scanning property. Therefore, two-dimensional linear scanning can be performed without correcting electrical image distortion.
[0292]
Further, in the main scanning direction (X direction), the f arc sine θ lens characteristic is given to about 90% of the amplitude of the mirror deflection angle that vibrates in a sine wave shape. The sub-scanning direction (Y direction) has fθ lens characteristics. Therefore, the main scanning direction (X direction) that requires a higher frequency than the sub-scanning direction (Y direction) vibrates in a sine wave shape, and the scan mirror deflection angle changes linearly in the low-frequency sub-scanning direction (Y direction). When using a mirror, if 90% of the amplitude of the mirror deflection angle that vibrates in a sine wave shape in the X direction is used, two-dimensional linear scanning and constant speed scanning can be performed without electrical image distortion correction. Therefore, it can cope with high-speed scanning. Note that 90% (φx = ± 17.2 °) of the amplitude of the scanner 23 with the mirror deflection angle φx = ± 19.1 ° in the X direction is used for video display. Thus, since about 90% of the amplitude in the X direction can be used, it is very efficient.
[0293]
If the constant speed scanning property is corrected, it is possible to use the entire amplitude of the mirror that vibrates in a sine wave shape, or it is possible to use a mirror whose mirror deflection angle changes linearly.
[0294]
In this embodiment, with the configuration of FIG. 15A, the light distribution characteristic of the image display element 24 whose intensity decreases as it moves away from the normal is corrected.
[0295]
The X-direction mirror deflection angle φx = ± 17.2 ° and the Y-direction mirror deflection angle φy = ± 7.98 ° required for video display of this embodiment, so that φx / θx = 1.15, φy. /Θy=0.70.
[0296]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 = 18.4 °, the incident angle θ1 of the axial principal ray 22 to the first transmission surface 31 = 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 25.8 °.
[0297]
(Example 10)
This embodiment has the same configuration as that of the ninth embodiment, and is an example in which the distortion characteristic in the sub-scanning direction (Y direction) of the ninth embodiment is changed. As shown in FIG. The second prism passes through the second transmission surface 46 → the third transmission surface 47 and is totally reflected by the transmission surface 31 (= second reflection surface) → the first reflection surface 32 → the second reflection surface 31 (= first transmission surface). 30 ₂ An intermediate image is formed therein, and is guided to the scanner 23 through the intermediate image → the third reflection surface 48 through the total reflection → the fourth reflection surface 49 → the fourth transmission surface 48 (= the third reflection surface). The reflected light of the scanner 23 is reflected by the fifth transmission surface 48 (= third reflection surface = fourth transmission surface) → the fifth reflection surface 50, passes through the sixth transmission surface 51, and the second prism 30. ₂ Is guided to the image display element 24 as convergent light.
[0298]
In this embodiment, both the main scanning direction (X direction) and the sub-scanning direction (Y direction) have the f arc sine θ lens characteristic for about 80% of the amplitude of the mirror deflection angle that vibrates sinusoidally. Yes. Therefore, even when a scan mirror that vibrates sinusoidally in both the main scanning direction (X direction) and the sub-scanning direction (Y direction) is used for high-speed scanning, the amplitude of the mirror deflection angle that vibrates sinusoidally is about 80. If% is used, two-dimensional linear scanning and constant speed scanning can be performed without correcting electric image distortion. Therefore, it can cope with high-speed scanning. It should be noted that 80% of the amplitude of the scanner with the mirror deflection angle φx = ± 18.1 ° in the X direction and the mirror deflection angle φy = ± 14.3 ° in the Y direction (φx = ± 14.5 °, φy = ± 11). .4 ° is used for video display.
[0299]
In addition, if the constant speed scanning property is corrected, it is possible to use the entire amplitude of the mirror that vibrates sinusoidally, or it is possible to use a mirror in which the mirror deflection angle changes linearly.
[0300]
The X-direction mirror deflection angle φx = ± 14.5 ° and the Y-direction mirror deflection angle φy = ± 11.4 ° necessary for the image display of this embodiment, so that φx / θx = 0.97, φy. /Θy=1.00.
[0301]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 = 17.6 °, the incident angle θ1 of the axial principal ray 22 with respect to the first transmission surface 31 = 0 °, and the first reflection. The incident angle θ2 of the axial principal ray 22 on the surface 32 is 25.7 °.
[0302]
Example 11
This embodiment is a real image forming optical system such as a projector, a laser beam printer, a barcode reader, etc. as described above. As shown in FIG. 32, one eccentric prism 30 constituting the projection optical system is a first decentering prism 30. The first surface 31 to the third surface 33, the fourth surface 40, the fifth surface 41, and the sixth surface 42, and the first transmission surface 31 (= second reflection surface) of the pupil 21 → prism 30 by back ray tracing. ) → first reflection surface 32 → total reflection on the second reflection surface 31 (= first transmission surface) to form an intermediate image in the prism 30, and total reflection on the third reflection surface 33 → fourth reflection surface 40 → The light is guided to the scanner 23 through the second transmission surface 33 (= third reflection surface). The reflected light of the scanner 23 passes through the third transmitting surface 33 (= third reflecting surface = second transmitting surface) → the fifth reflecting surface 41 → the fourth transmitting surface 42 and crosses the prism 30 to be converged light. Lead to.
[0303]
In this embodiment, a real image is formed at a position 1 m from the pupil 1. Note that the distance between the pupil 1 and the prism 30 is 3.6 mm.
[0304]
A projector using an LCD as an image display element uses a polarizing filter and a color filter, so that the utilization rate of light source light is poor. In the case of the optical system of the present invention, the utilization efficiency of the light source light is greatly improved.
[0305]
Note that the angle of view, the F number, and the imaging position of the image display element light can be changed and used as an optical system for other purposes such as a laser beam printer and a barcode reader. For a laser beam printer or the like, since the angle of view is large, the amount of distortion control for making the f arc sine θ lens is reduced, and the design of the f arc sine θ lens is facilitated.
[0306]
The X-direction mirror deflection angle φx = ± 18.2 ° and the Y-direction mirror deflection angle φy = φy = ± 10.3 ° necessary for video display of this embodiment, and therefore φx / θx = 1.21. Φy / θy = 0.91.
[0307]
Further, in the reverse ray tracing, the incident angle θs of the axial principal ray 22 with respect to the reference plane of the scanner 23 = 22.1 °, the incident angle θ1 of the axial principal ray 22 with respect to the first transmission surface 31 = 0.81 °, The incident angle θ2 of the axial principal ray 22 on one reflecting surface 32 is 20.8 °.
[0308]
The configuration parameters of Examples 1 to 11 are shown below. In these tables, “FFS” indicates a free-form surface, “RS” indicates a reflecting surface, “SM” indicates a scan mirror, “ID” indicates an image display element, and “DOE” indicates a diffraction surface.

[0309]

[0310]

[0311]

[0312]

[0313]

[0314]

[0315]

[0316]

[0317]

[0318]

[0319]

[0320]
As described above, the video display device of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible.
[0321]
The video display device of the present invention described above can be configured as follows, for example:
[1] An image display element that displays an image, a scanning unit that scans light emitted from the image display element, and a projection optical system that projects the image formed by the image display element and scanned by the scanning unit. In the video display device,
The projection optical system has at least one prism member made of a medium having a refractive index larger than 1,
The prism member has at least three surfaces: a transmission surface that makes a light beam incident on the prism member, a reflection surface that reflects the light beam within the prism member, and a transmission surface that emits the light beam from the prism. The total number of reflections by the prism member is 3 times or more, and at least one of the reflection surfaces of the prism member has optical power and is decentered with respect to the optical axis,
In the backward ray tracing, the projection optical system and the scanning unit are arranged between a pupil and an image display element that is an image plane, and light from the pupil reaches the scanning unit through at least the prism member. Display device.
[0322]
[2] The image display apparatus as described in [1] above, wherein the total number of reflections on the prism member included in the projection optical system is four or more.
[0323]
[3] The video display apparatus as described in 1 above, wherein the reflecting surface of the projection optical system has optical power.
[0324]
[4] The image according to [1], wherein the projection optical system includes a combined transmission and reflection surface in which at least one of the reflection surfaces and at least one of the transmission surfaces are the same surface. Display device.
[0325]
[5] At least one prism member has at least a first transmission surface that is incident on the prism member and is decentered with respect to the optical axis by back ray tracing from the pupil toward the image display element. 5. The image according to claim 4, further comprising a reflection surface, a second reflection surface, and a second transmission surface that exits from the prism member, wherein at least the first transmission surface and the second reflection surface are the same dual-purpose surface. Display device.
[0326]
[6] The video display device as described in [5] above, wherein the reflection at the second reflecting surface is total reflection in backward ray tracing.
[0327]
[7] The projection optical system is a reverse ray tracing from the pupil toward the image display element, and at least a first transmission surface incident on the prism member, a first reflection having an optical power and decentered with respect to the optical axis. A second transmission surface that exits from the prism member and reaches the scanning means, and the first transmission surface and the second reflection surface are the same dual-purpose surface, 2. The video display device according to 1 above, wherein an intermediate image is formed between the second reflecting surface and the third reflecting surface.
[0328]
[8] The projection optical system, after being reflected by the scanning means by backward ray tracing from the pupil to the image display element, forms an image on the image display element through the fourth reflecting surface of the prism member. 8. The video display device as described in 7 above.
[0329]
[9] The projection optical system performs reverse ray tracing from the pupil toward the image display element, reflects the light by the scanning unit, and then forms an image on the image display element through at least the third transmission surface and the fourth transmission surface. 8. The video display device as described in 7 above.
[0330]
[10] The projection optical system includes a first prism member and a second prism member, and by tracing back rays from a pupil toward the image display element,
The first prism member includes a first transmission surface that is incident on the first prism member, a first reflection surface that has optical power and is decentered with respect to the optical axis, a second reflection surface, and the first prism member. Including the injection surface,
The second prism member includes an entrance surface to the second prism member, a third reflection surface, and a second transmission surface that exits from the second prism member and reaches the scanning unit;
The first transmission surface and the second reflection surface are the same surface;
8. The video display device according to claim 7, wherein an intermediate image is formed between the second reflecting surface and the third reflecting surface.
[0331]
[11] The video display device as described in any one of 7 to 10 above, wherein the reflection at the second reflecting surface is total reflection.
[0332]
[12] The projection optical system is a reverse ray tracing from the pupil toward the image display element, and at least a first transmission surface incident on the prism member, a first reflection having optical power and decentering with respect to the optical axis. A second transmission surface that exits from the prism member and reaches the scanning means, and includes the first transmission surface, the second reflection surface, and the second reflection surface. 3. The video display device according to claim 1, wherein the three reflection surfaces and the second transmission surface are the same surface, and an intermediate image is formed between the second reflection surface and the fourth reflection surface.
[0333]
[13] The projection optical system includes at least a third transmission surface, a fifth reflection surface, and the prism member that are incident on the prism member after being reflected by the scanning unit in back ray tracing from the pupil toward the image display element. 13. The image display according to claim 12, wherein an image is formed on the image display element through a fourth transmitting surface that exits, and the third reflecting surface, the second transmitting surface, and the third transmitting surface are the same surface. apparatus.
[0334]
[14] The projection optical system includes at least a third transmission surface, a fifth reflection surface, and the prism member incident on the prism member after being reflected by the scanning unit in reverse ray tracing from the pupil toward the image display element. An image is formed on the image display element through a fourth transmission surface that exits, and the third reflection surface, the second transmission surface, the third transmission surface, and the fourth transmission surface are the same surface. 14. The video display device as described in 13 above.
[0335]
[15] The projection optical system includes a first prism member and a second prism member, and by tracing back rays from a pupil toward the image display element,
The first prism member has a first transmission surface incident on the first prism member, a first reflection surface having optical power and decentered with respect to the optical axis, a second reflection surface, and exiting from the first prism member. Including a second transmissive surface,
The second prism member is incident on the second prism member; a third transmission surface; a third reflection surface; a fourth reflection surface; a fourth transmission surface that exits from the second prism member and reaches the scanning means; 13. The fifth transmission surface according to claim 12, further comprising a fifth transmission surface that enters the second prism member from a scanning unit, a fifth reflection surface, and a sixth transmission surface that exits from the second prism member and reaches the image display element. Video display device.
[0336]
[16] The projection optical system performs reverse ray tracing from the pupil toward the image display element, and the entrance pupil and the scanning means are in a substantially conjugate positional relationship, and once forms an intermediate image in the projection optical system, and the entrance pupil 2. The video display device according to claim 1, wherein the optical system from the intermediate image to the intermediate image and the optical system from the intermediate image to the scanning means are symmetrical with respect to the intermediate image.
[0337]
[17] The projection optical system substantially collimates the image display element light by the condensing optical system, guides the light to the scanning means at a position substantially conjugate with the pupil, and outputs the light scanned by the scanning means to the intermediate image by the relay optical system. And the intermediate image is guided to the pupil by the eyepiece optical system.
In reverse ray tracing, the projection optical system has a reflecting surface having at least three optical powers between the entrance pupil and the scanning means;
In reverse ray tracing, the eyepiece optical system has at least two reflecting surfaces, the relay optical system has at least one reflecting surface, a second reflecting surface for light from an entrance pupil, and the scanning means 17. The video display device according to any one of the above items 1 and 7 to 16, wherein an intermediate image is formed between the last reflecting surface before the first layer.
[0338]
[18] The projection optical system forms the light from the pupil as an intermediate image by reverse ray tracing, and the eyepiece optical system has at least two reflecting surfaces, and guides the light from the intermediate image to the scanning unit. 18. The video display device as described in 17 above, wherein the relay optical system has at least two reflecting surfaces.
[0339]
[19] In the backward ray tracing, the light incident on the projection optical system from the entrance pupil is once formed as an intermediate image and then formed on the image display element through the scanning means at a position substantially conjugate with the entrance pupil. The half angle of view θ incident on the projection optical system from the entrance pupil in the scanning direction of the scanning unit and the one-side deflection angle φ of the scanning unit necessary for image display in the scanning direction of the scanning unit satisfy the following expression: 17. The video display device according to any one of the above items 1 and 7 to 16.
[0340]
0.1 ≦ φ / θ ≦ 1.8 (1)
[20] The video display device as described in 19 above, wherein the following formula is satisfied.
[0341]
0.25 ≦ φ / θ ≦ 1.7 (1-1)
[21] In any one of the above items 1 and 7 to 16, the principal ray incident on the intermediate image from the entrance pupil is in a convergent state when the ray incident from the entrance pupil forms an intermediate image in the reverse ray tracing. The video display device according to claim 1.
[0342]
[22] The image display apparatus as described in [1] above, wherein the projection optical system includes one prism member.
[0343]
[23] The projection optical system includes at least two prism members,
1 ≧ y ′ / y> 0.7 (2)
17. The video display device as set forth in any one of 1, 10, 15, and 16, wherein: Here, y is the intermediate image height in the optical system, and y ′ is the principal ray height of the most off-axis light beam on the surface where the two prism members face each other.
[0344]
[24] The projection optical system includes the two prism members. When the projection optical system reaches the image display element from the pupil through the first prism member and the second prism member by back ray tracing, the projection optical system is intermediate in the second prism member. 24. The video display device as described in 23 above, wherein an image is formed.
[0345]
[25] When the refractive index at the d-line (587.56 nm) of the medium having a refractive index of the prism member larger than 1 is Nd,
2.0>Nd> 1.4 (3)
17. The video display device as set forth in any one of the above items 1 and 7 to 16.
[0346]
[26] The video display device as described in 25 above, wherein the prism member is an optical plastic.
[0347]
[27] The video display device as set forth in any one of [5] and [7] to [16], wherein the first transmission surface in reverse ray tracing has a convex surface facing the first reflection surface.
[0348]
[28] Any one of the above items 5 and 7-16, wherein the first reflecting surface in the backward ray tracing is configured to have a concave surface facing the first transmitting surface side so as to have a positive power. The video display device according to claim 1.
[0349]
[29] In reverse ray tracing, the incident angle θ1 of the axial principal ray on the first transmission surface is
20>θ1> −30 [°] (4)
The video display device as set forth in any one of 5, 7 to 16, wherein: However, the incident angle θ1 is positive counterclockwise with respect to the normal line.
[0350]
[30] In the reverse ray tracing, the incident angle θ2 of the axial principal ray to the first reflecting surface is
40>θ2> 5 [°] (5)
The video display device as set forth in any one of 5, 7 to 16, wherein: However, the incident angle θ1 is positive counterclockwise with respect to the normal line.
[0351]
[31] The above-mentioned 5, wherein the combined surface of the first transmission surface and the second reflection surface is formed in a non-rotationally symmetric surface shape that gives optical power and corrects decentration aberrations. The video display device according to any one of 7 to 16.
[0352]
[32] The said 1st reflective surface is formed in the non-rotationally symmetric surface shape which gives optical power and correct | amends eccentric aberration, The said any one of said 5 and 7-16 characterized by the above-mentioned. Video display device.
[0353]
[33] In the reverse ray tracing, the reflecting surface immediately before the scanning unit is formed in a non-rotationally symmetric surface shape that gives optical power and corrects decentration aberrations. The video display device according to any one of the above.
[0354]
[34] In the reverse ray tracing, the reflection surface immediately after the scanning unit is formed in a non-rotationally symmetric surface shape that gives optical power and corrects decentration aberrations. The video display device according to any one of the above.
[0355]
[35] The video display device as described in any one of 31 to 34, wherein the rotationally asymmetric surface shape is a free-form surface shape having only one plane of symmetry.
[0356]
[36] The image display device as set forth in any one of [1] and [7] to [16], wherein the projection optical system includes a surface having a diffractive action.
[0357]
[37] The surface of the transmissive surface of the projection optical system also serves as a transmissive DOE, the surface of the reflective surface of the projection optical system also serves as a reflective DOE, or the mirror reflective surface of the scanning unit 37. The video display device as set forth in 36, wherein the projection optical system or the surface of the scanning means also serves as a DOE, such that the screen also serves as a reflection type DOE.
[0358]
[38] The video display apparatus as set forth in 36, wherein a chromatic aberration is controlled by adding a surface having a DOE action between the prism member and the scanning means.
[0359]
[39] By a transmission type DOE disposed between the prism member and the scanning unit, both an optical path incident on the scanning unit after exiting the prism member and an optical path incident on the prism member after exiting the scanning unit 40. The video display device as set forth in 38, wherein the video display device is subjected to a diffraction action.
[0360]
[40] The video display device as set forth in 38, wherein the DOE is held integrally with a scanner.
[0361]
[41] The image according to any one of [1] and [7] to [16], wherein an image that cancels distortion of an image formed by the scanning unit and the projection optical system is displayed on the image display element. Display device.
[0362]
[42] The video display device as described in 41 above, wherein the electrical image distortion correction is correction of constant speed scanning.
[0363]
[43] The video display device as set forth in any one of [1] and [7] to [16], wherein the scanning means performs two-dimensional scanning.
[0364]
[44] The image display apparatus as set forth in any one of [1] and [7] to [16], wherein an incident angle θs of the axial principal ray with respect to the normal line of the scanning unit satisfies the following expression.
[0365]
| Θs | ≦ 60 ° (6)
[45] The image display device as described in 44 above, wherein the incident angle of the axial principal ray with respect to the scanning means satisfies the following expression.
[0366]
10 ° ≦ | θs | ≦ 45 ° (6-1)
[46] The image display device as set forth in any one of [1] and [7] to [16], wherein reciprocal scanning is performed.
[0367]
[47] The video display device as set forth in any one of [1], [7] to [16], wherein the scanning means is a scanning means that vibrates in a sine wave shape in the scanning direction.
[0368]
[48] The video display device as described in 47 above, wherein 95% or less of the amplitude of the scanning means which vibrates sinusoidally is used for video display.
[0369]
[49] The video display device as described in 48 above, wherein 90% or less of the amplitude of the scanning means which vibrates sinusoidally is used for video display.
[0370]
[50] When a two-dimensional image is formed by repeating scanning in the main scanning direction, the main scanning direction is a scanning mirror that vibrates in a sine wave shape, and the sub-scanning direction is a scanning mirror in which the deflection angle changes linearly. 17. The video display device according to any one of 1, 7 to 16.
[0371]
[51] The image display device as set forth in any one of [1] and [7] to [16], wherein the image display device is a mirror that vibrates sinusoidally in both the main scanning direction and the sub-scanning direction.
[0372]
[52] The image display device as described in any one of [1] to [7], wherein the scanning unit is a micromachine mirror manufactured by using a photolithography process.
[0373]
[53] In reverse ray tracing, an optical system from the scanning means to the image display element is composed of at least two surfaces having optical action, and this optical system is divided into two parts, the scanning means side and the image display element side. The image according to any one of 1 and 7 to 16, wherein a positive spherical aberration is generated on the scanning means side and a negative spherical aberration is generated on the image display element side. Display device.
[0374]
[54] In a plane in the scanning direction (in the case of two-dimensional scanning, in each plane in the main scanning direction and the sub-scanning direction),
3 × G> f · tan 2φ / d> G / 2 (7)
17. The video display device according to any one of the above items 1 and 7 to 16, wherein: here,
G: Number of pixels in the scanning direction
f: Focal length in the scanning direction plane of the condensing optical system from the image display element to the scanning means
φ: One-side deflection angle in the scanning direction of the scanning means used for image display
(± φ scanning means deflection angle is used for video display)
d: Half the size of the image display element in the scanning direction
However, f defined by the following equation in the backward ray tracing is the focal length of the condensing optical system from the scanning means to the image display element.
[0375]
f = Y / β tan2φ
Here, Y is half the size of the intermediate image in the scanning direction, and β is the magnification of the optical system from the video display element to the intermediate image in the scanning direction.
[0376]
[55] The video display device according to any one of 1 to 54 above, wherein the video displayed on the video display element is formed as a virtual image and guided to the observer's eyeball, and the video display device is held in front of the viewer's face. A head-mounted image display device comprising a support portion.
[0377]
[56] The head-mounted image display device as described in 55 above, wherein one image display device is arranged corresponding to each of the left and right eyes of the observer.
[0378]
[57] A projector, a laser beam printer, or a bar code comprising the video display device as described in any one of 1 to 54 above, which displays the video displayed on the video display element as a real image. leader.
[0379]
【The invention's effect】
As is apparent from the above description, according to the image display device of the present invention, the optical system of the scanning image display device is configured by using the prism member mainly having a reflection action, thereby reducing the number of parts and reducing the size. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of an optical system of an image display device according to the present invention.
FIG. 2 is a view similar to FIG. 1 when the scanning means is constituted by a mirror.
FIG. 3 is a view similar to FIG. 1 in the case where a principal ray incident on an intermediate image is brought into a converged state by reverse ray tracing.
FIG. 4 is a diagram showing one possible arrangement of video display elements.
FIG. 5 is a diagram showing another possible arrangement of video display elements.
FIG. 6 is a diagram showing another possible arrangement of video display elements.
FIG. 7 is a diagram for explaining electrical image distortion correction for both linear scanning performance and constant velocity scanning performance.
FIG. 8 is a diagram for explaining electrical image distortion correction with constant speed scanning;
FIG. 9 is a diagram similar to FIG. 1 when two one-dimensional scanners are used.
FIG. 10 is a diagram showing distortion of a one-dimensional f arc sine lens.
FIG. 11 is a diagram for explaining a case where an image is displayed with the amplitude of a scan mirror being limited.
FIG. 12 is a diagram showing the relationship between the limit of the amplitude of a sine wave and the linearity of the mirror tilt angle.
FIG. 13 is a diagram showing distortion of a one-dimensional fθ lens.
FIG. 14 is a diagram for explaining a defect in the optical system of the video display device due to the light distribution characteristic of the video display element.
FIG. 15 is a diagram for explaining that the light distribution characteristic of the video display element can be corrected by the arrangement of the optical system from the scanner to the video display element.
FIG. 16 is an explanatory diagram regarding an appropriate pixel interval;
FIG. 17 is a diagram showing a video signal to be displayed on the video display element.
FIG. 18 is a diagram for explaining one problem caused by an inappropriate pixel interval;
FIG. 19 is a diagram for explaining another problem caused by an inappropriate pixel interval.
FIG. 20 is an optical path diagram of the optical system according to Example 1 of the present invention.
21 is an optical path diagram of a modified optical system according to Example 1. FIG.
FIG. 22 is an optical path diagram of the optical system according to Example 2 of the present invention.
FIG. 23 is an optical path diagram of the optical system according to Example 3 of the present invention.
FIG. 24 is an optical path diagram of the optical system according to Example 4 of the present invention.
FIG. 25 is an optical path diagram of the optical system according to Example 5 of the present invention.
FIG. 26 is an optical path diagram of the optical system according to Example 5-1 of the present invention.
FIG. 27 is an optical path diagram of the optical system according to Example 6 of the present invention.
FIG. 28 is an optical path diagram of the optical system according to Example 7 of the present invention.
FIG. 29 is an optical path diagram of the optical system according to Example 8 of the present invention.
FIG. 30 is an optical path diagram of the optical system according to Example 9 of the present invention.
FIG. 31 is an optical path diagram of the optical system according to Example 10 of the present invention.
FIG. 32 is an optical path diagram of the optical system according to Example 11 of the present invention.
FIG. 33 is a diagram showing a configuration of a conventional scanning HMD.
FIG. 34 is a diagram showing a configuration of another conventional scanning HMD.
[Explanation of symbols]
1 ... Hitomi
2. Eyepiece optical system (eyepiece lens)
3. Relay optical system (relay lens)
4. Scanning means
4 ', 4 "... one-dimensional scanning mirror (one-dimensional scanning means)
5 ... Condensing optical system (condensing lens)
6 ... Video display element
7 ... Intermediate image
8 ... Dichroic mirror
9: Optical system conjugate with two scanning means
10 ... Virtual image
11. Image of image display element
21 ... Ejection pupil (incident pupil for back ray tracing)
22 ... Axial chief ray (observer visual axis)
23 ... Can Mirror
24. Image display element
25. See-through prism
30 ... Eccentric prism
30 ₁ ... 1st prism
30 ₂ ... second prism
31 ... first side
32. Second side
33 ... Third surface
34 ... Fourth side
35 ... Fifth side
36: Third transmission surface
37 ... Fourth transmission surface
38 ... Fifth side
39 ... Sixth surface
40 ... Fourth side
41 ... Fifth side
42. Fourth transmission surface
43 ... Diffraction surface
44 ... DOE
45 ... Diffraction surface
46 ... Third surface
47 ... first side
48 ... Second side
49 ... Third surface
50 ... Fourth side
51. Fifth side
L1: Image display element side optical system
L2 ... Scanner side optical system

Claims (4)

And the image display device that emits light for displaying an image in response to video signals, scanning means for scanning the light emitting of the image display device, the image obtained by scanning the light by the pre-Symbol scanning means In a video display device comprising a projection optical system that projects
The projection optical system is an eccentric prism composed of one or two prism members made of a medium having a refractive index greater than 1 .
The eccentric prisms has a transmission surface for entering the light from said scanning means, a reflective surface for reflecting the light in the prism member, a transmitting surface for emitting the light to the exit pupil, of the at least three sides has, and is intended to reflect three times or more the light in total, at least one surface of the reflective surface has an optical power, and the image display device via the street scanning means the center of the exit pupil Eccentric with respect to the optical axis defined by the ray that reaches the center ,
The scanning optical system is arranged between the exit pupil and the image display element, and in addition, the scanning unit so as to be in a conjugate position with the exit pupil,
In the backward ray tracing directed from the exit pupil to the image display device, light from the exit pupil incident on at least the decentered prism, after once focused as an intermediate image, optimum Ri to said scanning means, said image display device As it forms an image,
An image display apparatus , wherein a half field angle θ incident on the projection optical system from the exit pupil in the scanning direction of the scanning unit and a one-side deflection angle φ in the scanning direction of the scanning unit satisfy the following expression .
0.1 ≦ φ / θ ≦ 1.8 (1) Possessed by the projection optical system, at least one surface of at least one surface and the transmission surface of the reflective surface, one according to claim 1, characterized in that it is formed by a surface which is defined by the same function Video display device. In the backward ray tracing directed from the exit pupil to the image display device, light from the exit pupil, at least, a first transmitting surface that enters the decentered prism has an optical power, and passes through the center of the exit pupil the first reflecting surface which is eccentric with respect to the optical axis defined by the light beam reaches the image display device around through the scanning means, the second reflecting surface, a third reflecting surface, the fourth reflective surface, and emits the eccentric prisms or al together leading to the scanning means through the second transmitting surface, it is one surface on which the second reflecting surface and the first transmitting surface, the second transmitting surface and the third reflecting surface is defined by the same function 2. The video display device according to claim 1 , wherein light rays traveling from the exit pupil toward the video display element form an intermediate image between the second reflective surface and the fourth reflective surface. An image display element that emits light for displaying an image in accordance with an image signal, a scanning unit that scans the light emitted from the image display element, and an image obtained by scanning the light by the scanning unit In a video display device comprising a projection optical system
The projection optical system is an eccentric prism composed of one or two prism members made of a medium having a refractive index larger than 1.
The eccentric prism has at least three surfaces: a transmission surface on which the light from the scanning unit is incident, a reflection surface that reflects the light into the prism member, and a transmission surface that emits the light to the exit pupil. And the light is reflected three times or more in total, and at least one of the reflecting surfaces has optical power, passes through the center of the exit pupil, passes through the scanning means, and passes through the center of the image display element. Is decentered with respect to the optical axis defined by the light beam leading to
The eccentric prism and the scanning unit are disposed between the exit pupil and the image display element,
In the backward ray tracing from the exit pupil to the image display element, the ray from the exit pupil has at least a first transmission surface incident on the decentered prism, optical power, and passes through the center of the exit pupil. A first reflecting surface, a second reflecting surface, a third reflecting surface, a fourth reflecting surface, and a second light exiting from the decentered prism, which are decentered with respect to the optical axis defined by the light beam reaching the center of the image display element through the scanning means. The first transmission surface and the second reflection surface, the third reflection surface and the second transmission surface are one surface defined by the same function while reaching the scanning means through the transmission surface, The light beam traveling from the exit pupil toward the image display element forms an intermediate image between the second reflection surface and the fourth reflection surface.

Images