JP3778966B2

JP3778966B2 - Full color image display device

Info

Publication number: JP3778966B2
Application number: JP19506195A
Authority: JP
Inventors: 敏貴戸田; 進高橋
Original assignee: Toppan Inc
Current assignee: Toppan Inc
Priority date: 1995-07-31
Filing date: 1995-07-31
Publication date: 2006-05-24
Anticipated expiration: 2015-07-31
Also published as: JPH0943594A

Description

【０００１】
【発明の属する技術分野】
本発明は、白色光源からの光を三原色成分に分光する回折格子を用いた表示装置に係り、特に、フルカラー画像を表示する際に、光の利用効率を改善でき、好ましくは立体像の表示も可能なフルカラー画像表示装置に関する。
【０００２】
【従来の技術】
フルカラー画像を液晶パネルで表示する場合には各画素毎にＲ，Ｇ，Ｂ三原色の色成分が割り当てられる。液晶ディスプレイではバックライトの全面積のうち液晶パネル上に存在する画素の開口面積の分だけ光源光が画素表示に利用されることになる。従って、この開口面積が広いことが望ましい。また、観察者が移動してもカラー画像の明るさや色調が変化しないことが望ましい。然し乍ら、従来技術の場合、特に、ＴＦＴ液晶パネルの場合にはバックライトの全面積のうち１／４程度しか画素開口が存在しない。更に、この１／４の開口面積をＲ，Ｇ，Ｂの３つの画素に分けることが必要になり、１つの色に対しては全面積の１／１２しか入射光が利用されないことになる。ところで、従来のフルカラー画像表示装置では、各画素に対応してＲ，Ｇ，Ｂの着色セルを設けたカラーフィルタを使用していた。然し乍ら、カラーフィルタを介在させると白色光源光が大量に着色セルで吸収されるため、バックライトの利用効率が悪かった。この点を改善するため、予め白色光をＲ，Ｇ，Ｂ成分に分光してカラーフィルタの対応する着色セルに導く回折格子アレイを採用した技術が、例えば特開平６−２２２３６１号公報に開示されている。然し乍ら、回折格子アレイを用いると、Ｒ，Ｇ，Ｂ各成分の出射角度範囲に相異が生じるため、観察者の位置に依存して画像の明度や色調が変化する。
【０００３】
【発明が解決しようとする課題】
前記したように液晶ディスプレイの場合には１つの色について使用し得る開口面積は全面積の１／１２程度であり極めて小さい。この開口面積を広げることは一般に難しいため、光の集光性を向上させ光の拡散を防止することが必要になる。また、基本的にカラーフィルタは光源光を吸収するため、利用効率を改善するためにはこれを必要としない構造が望まれる。更に、前記のように観察者の位置により画像の明るさが顕著に変ることは製品価値を低下させるため解決すべき課題となる。
【０００４】
本発明は、以上の問題点を解決するもので、光の利用効率を向上し、明るい画像の観察ができると共に色ずれがなく、観察位置による明るさの変化が少なく、且つ好ましくは両眼視差を利用して立体像の表示が可能になるフルカラー画像表示装置を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は、以上の目的を達成するために、入射する光を赤色（Ｒ），緑色（Ｇ），青色（Ｂ）の各波長分布の光に分散し、更に分散した光を観察者に対し少なくとも垂直方向に収束する機能を有する第１の回折格子を複数配置した第１の回折格子アレイと、前記第１の回折格子から出射したＲ，Ｇ，Ｂの各波長分布の光を、波長ごとの分光時の出射角度の違いを補償するように、夫々ほぼ同様な出射角度範囲で回折する機能を有する第２の回折格子からなる第２の回折格子アレイと、前記第１の回折格子アレイから出射したＲ，Ｇ，Ｂの各波長分布の光が前記第２の回折格子に入射する前もしくは後に配設され、前記各波長分布の光の透過強度を変調する空間光変調器とを設けてなるフルカラー画像表示装置を構成するものである。更に具体的に、前記第１の回折格子は、観察者に対し水平方向の出射方向分布を決定すべく水平方向に光を収束する機能を有するものからなり、前記第２の回折格子は水平方向に光をそのまま透過することを特徴とする。また、前記第１の回折格子は水平方向に光をそのまま透過するものからなり、前記第２の回折格子は、観察者に対し水平方向の出射方向分布を決定すべく水平方向に光を収束又は発散する機能を有することを特徴とする。また、前記第１の回折格子アレイと前記第２の回折格子アレイとの間でＲ，Ｇ，Ｂの各波長分布の光の収束位置付近に、前記波長分布の光のうちの夫々予め決められた波長成分の光を透過し、それ以外の波長成分を空間的に遮断する遮光板を設けることを特徴とする。また、Ｒ，Ｇ，Ｂに対応した着色セルを備え、夫々予め決められた波長成分のみを透過する機能を有するカラーフィルタを前記空間光変調器の前もしくは後に配置し、前記Ｒ，Ｇ，Ｂの各波長分布の光を夫々対応する着色セルに通すフルカラー画像表示装置を特徴とする。更に、前記第１の回折格子は、連続的に傾きが変化する曲線を基本要素とし、各要素間の間隔を少しずつ変化させながら前記基本要素を垂直方向に沿って並べたものからなり、前記曲線上の各点での傾きは、水平方向の収束，発散の角度範囲から決められ、前記間隔は、垂直方向の収束，発散の角度範囲から決められることを特徴とする。また、前記第２の回折格子アレイは、直線を基本要素とする均一な回路格子で覆われることを特徴とする。更に、前記第１の回折格子アレイは、複数種類の第１の回折格子を組み合わせたものを要素グループとしてこれを複数並べたものからなり、前記要素グループ内の各第１の回折格子は、水平方向に互いに隣接した角度範囲に光を回折し、垂直方向には同じ角度範囲に光を回折して水平方向に視差を有する立体像を表示可能にするフルカラー画像表示装置を特徴とするものである。また、前記第１の回折格子アレイを構成する第１の回折格子は、水平な直線を基本要素とし、各要素間の間隔が垂直方向に少しずつ変化するものであることを特徴とする。更に、前記第２の回折格子アレイを構成する第２の回折格子は、連続的に傾きが変化する曲線を基本要素とし、該基本要素を垂直方向に並べたものからなり、前記曲線上の各点の傾きは水平方向の収束，発散の角度範囲から決められるものであることを特徴とする。また、前記第２の回折格子アレイは、複数種類の前記第２の回折格子を組み合わせたものを要素グループとしてこれを複数並べたものからなり、前記要素グループ内の各第２の回折格子は、水平方向に互いに隣接した角度範囲に光を回折し、垂直方向には同じ角度範囲に光を回折して水平方向に視差を有する立体像を表示可能にするフルカラー画像表示装置を特徴とするものである。
【０００６】
本発明によれば、前段の第１の回折格子アレイで白色光をＲ，Ｇ，Ｂ各成分に分光し、且つ集光している。集光した各色成分は夫々対応する空間光変調器の画素に導かれる。このため、原理的にカラーフィルタは不要であり、且つ光の利用効率が高い。また、後段の第２の回折格子アレイによりＲ，Ｇ，Ｂ各成分の出射角度範囲を互いに等しくなるように補正しているので、視角依存性がなくなる。更に、垂直方向だけでなく水平方向に対しても出射角度範囲を制御可能とし、好ましくは両眼視差を利用して立体表示を実現している。以上の構成により、光の利用効率が向上し、明るい画像が得られ、立体像の表示が可能になり、観察位置による明るさの変化が少なくなる効果が得られる。
【０００７】
【発明の実施の形態】
以下、本発明に係るフルカラー画像表示装置を図面を参照にして詳述する。図１は本発明のフルカラー画像表示装置の基本的な構成を示すものである。図１および図２に示すように、フルカラー画像表示装置は光源５からの白色光等の入射光４をＲ，Ｇ，Ｂ各色の波長分布の光に分散，集光する第１の回折格子１と、各波長分布の光を同様な出射角度範囲で回折する第２の回折格子２と、第２の回折格子２からの光の透過強度を変調してカラー画像を表示する空間光変調器３等から構成される。空間光変調器３は例えばアクティブマトリックス型の液晶パネルからなる。観察者６は観察範囲７内でカラー画像を観察する。なお、第１の回折格子１および第２の回折格子２は複数配置され第１の回折格子アレイ１Ａおよび第２の回折格子アレイ２Ａ（図２）を形成する。
【０００８】
第１の回折格子１は入射光４をＲ，Ｇ，Ｂの各波長分布の光に分散し、更に、互いに分散した光を少なくとも垂直方向に収束する機能を有する。これに対し、第２の回折格子２は、互いに異なる発散角で入射したＲ，Ｇ，Ｂの各波長分布の光を補償的に回折して出射角度範囲を互いに一致させる。このとき一般的に回折格子の回折角度βは入射光の入射角α，波長λおよび格子間隔ｄ（空間周波数の逆数）との関係において次式が成立する。
ｍλ＝ｄ（ｓｉｎα−ｓｉｎβ）
ここでｍは回折次数であり通常は＋１もしくは−１のみを考えればよい。即ち、回折格子の形状をブレーズド型等にすることにより＋１次もしくは−１次の回折光の回折効率を非常に高くすることができる。このため＋１次もしくは−１次の回折光のみを考えればよい。以上の式から垂直方向について考えると第１の回折格子１によって波長ごとに回折角度が変るが、各波長に対して第２の回折格子２の回折角度が一定でも第１の回折格子での分散の角度を補償するように機能できることがわかる。従って、第２の回折格子２においてＲ，Ｇ，Ｂ用の回折格子を共通のものとしてよく、作製が非常に容易になる。
【０００９】
回折光８は前記したように少なくとも垂直方向に収束するが水平方向に対しては図３又は図１１に示す２通りの場合が採用される。図３は水平方向についても回折する場合を示すもので入射光４は第１の回折格子１でＲ，Ｇ，Ｂの各波長分布ともほぼ同じ角度で水平方向に回折する回折光９となる。この場合、図示のように第２の回折格子２では影響を受けずにそのまま透過し空間光変調器３に入射される。これは、第１の回折格子１の空間周波数が垂直方向に高く水平方向に低い場合に容易に実現できる。以上のように、図３の例では第１の回折格子１に水平方向の回折作用を付加して水平方向の観察範囲７を規制している。図１１の場合は、入射光４は水平方向に関してはそのまま第１の回折格子１を通過する透過光１０となる。第２の回折格子２で水平方向に所定の出射角度範囲で広げられて空間光変調器３に入射する。即ち、図３の例とは逆に、図１１の例では第２の回折格子２に水平方向の回折作用を付加している。勿論、場合によってはいずれの回折格子にも水平方向の回折作用を付加しなくてもよい。一般に、ディスプレイでは水平方向の視角範囲に較べて垂直方向の視角範囲を最適に制御することが重要である。即ち、水平方向に広い視角範囲を得たい場合には水平方向に散乱の効果を有するパネルをディスプレイ前面に取り付けるなどの容易な方法がある。
【００１０】
再び図１に戻って第２の回折格子２は第１の回折格子１からのＲ，Ｇ，Ｂの各波長分布の回折光８を垂直方向に関しほぼ同一の出射角度範囲の回折光Ｂ，Ｇ，Ｒとして回折する機能を有するものからなる。
【００１１】
以上のように垂直方向および水平方向に回折された各波長分布ごとの光は観察範囲７内にのみ回折される。これにより観察者６は観察範囲７内においては均一な明るさのカラー画像を観察することができる。
【００１２】
空間光変調器３は第２の回折格子２の前又は後に配設されるもので（図示では第２の回折格子２の後に配置されている）各波長分布の光の透過強度を変調するものであり例えば液晶パネルに相当するものである。
【００１３】
図４は第１の回折格子１と第２の回折格子２との間に遮光板１１を介設した例を示す。遮光板はＲ，Ｇ，Ｂの各波長分布の光の垂直方向における収束位置付近に配置され、前記波長分布の光のうちの夫々予め決められた波長成分を透過し、それ以外の波長成分の光を空間的に遮断するものである。第１の回折格子１からの回折光８の例えばＲとＧとの間には中間色が連続的に介在するため光をＲ，Ｇ，Ｂに分散したとしても他の波長成分が混在して第２の回折格子２側に入射される。遮光板１１は第２の回折格子２に入射する波長成分を空間的に選択することができ、Ｒ，Ｇ，Ｂの各波長成分を最適化することが可能である。従って、必要な光に関する損失はなく、観察される画像の彩度を高くすることができる。図５は遮光板１１の一例を示すものである。遮光板１１はＲ，Ｇ，Ｂに対応して水平方向に長い長方形の３個の開口部１２を有しそれを囲んで遮光部１３が形成される。開口部１２が長孔状に形成されているのは一般的に水平方向と垂直方向の収束位置が異なるためである。なお、遮光板１１を介設することによりカラーフィルタが不要となる。
【００１４】
図６はカラーフィルタ１４を補助的に配置した場合を示す。カラーフィルタ１４はＲ，Ｇ，Ｂに対応した着色セルを備え、夫々予め決められた波長成分のみを透過する機能を有し、Ｒ，Ｇ，Ｂの各波長分布の光を夫々対応する着色セルに通す。この場合には、遮光板１１（図４，図５）を用いた場合と同様にＲ，Ｇ，Ｂの各波長成分を最適化でき、彩度の高い画像を表示することができる。しかし、カラーフィルタ１４はその内部に光を吸収する度合が遮光板１１よりも大きく若干光の利用効率は下る。しかし、遮光板１１に較べて配置に関する位置精度が要求されないので組み込みが容易にできる。なお、図６では空間光変調器３の後側に配置されているが、その前側に配置してもよい。
【００１５】
図７（ａ）は第１の回折格子アレイ１Ａの一例を示す。第１の回折格子アレイ１Ａは図７（ｂ）に示す第１の回折格子１を縦横に多数個配設したものからなる。第１の回折格子１は連続的に傾きが変化する曲線１５を基本要素とし、各要素内の間隔１６を少しずつ変化させたものからなる。曲線１５上の各点での傾きは水平方向の収束，発散の角度範囲から決められる。また、間隔１６は垂直方向の収束，発散の角度範囲から決められる。図示のように、第１の回折格子アレイは同じパターンの第１の回折格子１を並べるだけでよく、作製も容易である。また、第１の回折格子１はほぼ隙間なく表示部全域に並べることができるため入射する光を効率よく使える利点を有する。
【００１６】
図８は第２の回折格子アレイ２Ａの全体構成と、Ｒ，Ｇ，Ｂに対応した第２の回折格子２（ｂ）のパターンを示す。図示のように、第２の回折格子２は水平な直線を基本要素とし等間隔で配列している。第２の回折格子アレイ２Ａは同形の第２の回折格子２を縦横に並べたものである。図８（ａ）は第２の回折格子２を複数個並べたものから形成されるがパターンが共通のため領域分けは必要でなく一枚ものから形成されてもよく、作製が決めて容易である。この場合には位置合わせの精度を要求されないため作製が容易である。一要素分の３つの回折格子は夫々Ｂ用，Ｇ用，Ｒ用のものからなり、夫々の回折格子の直線間隔は一定である。
【００１７】
図９は第１の回折格子アレイ１Ａの他の例を示す。この第１の回折格子アレイ１Ａは一対の左右対称の回折格子１７，１８を組み合わせてなる要素グループを複数個縦横に配置したものからなる。要素グループの回折格子１７，１８は傾きが徐々に変化する曲線１９からなり、且つ垂直方向の間隔２０は徐々に変化する。この回折格子１７，１８は水平方向に互いに隣接した角度範囲に光を回折し、垂直方向には同じ角度範囲に光を回折し水平方向に視差を有する立体像を表示可能にするものである。前記左側の回折格子１７は正面から左側の決められた角度範囲まで光を広げて回折し、もう一方の右側の回折格子１８は正面から右側の決められた角度範囲まで光を広げて回折する機能を有する。そこで、要素グループの内、回折格子１７に対応する空間光変調器の各画素で３次元物体を左側から見た左画像を表示するようにし、回折格子１８に対応する画素で右側から見た右画像を表示すると本発明の表示装置の正面付近で観察している観察者６の左目に回折格子１７で得られた左画像が観察され、右目に回折格子１８で得られた右画像が夫々独立に観察され両眼視差による立体像が認識できる。
【００１８】
図１０は前記図９における第１の回折格子アレイ１Ａに組み合わされる遮光板２１を示す。回折格子１７，１８に対応し、左右同一形状の一対の遮光板を組み合わせたものからなり、図５と同様に開口部２２と遮光部２３を有する。
【００１９】
図１１乃至図１５に示す実施形態は前記のものと異なり、第１の回折格子１は水平方向の光をそのまま透過させ、第２の回折格子２は観察者に対し、水平方向に光の出射方向分布を決定すべく水平方向に光を回折する機能を有する。この点は先に図１１を参照して説明を行った。なお、この場合も、図４，図６に示した遮光板１１およびカラーフィルタ１４に類するものを使用してもよいが説明を省略する。なお、図１２の遮光板２４がこの場合適用される。遮光板２４は開口部２５，遮光部２６を有するものからなり、開口部２５は図４の遮光板１１の開口部１２に較べて横長に形成される。これは第１の回折格子１が図１１に示すように水平方向の光をそのまま通過光１０として透過させるために広幅に形成する必要があるためである。
【００２０】
図１３は図１１に示した第１の回折格子アレイ１Ａの具体例を示す。第１の回折格子１は水平直線を基本要素とし、水平方向は均一で垂直方向には格子間隔が変化するものからなる。この第１の回折格子アレイ１Ａは以上のパターン構造の第１の回折格子１を縦横に配列したものからなる。同一のパターンの第１の回折格子１を使用できるため作製が容易である。また、ほぼ隙間なく表示部全域に並べることができるため入射する光を効率よく使うことができる。
【００２１】
図１４は図１１に示した第２の回折格子アレイ２Ａの具体例を示す。第２の回折格子２はＲ用回折格子２７，Ｇ用回折格子２８およびＢ用回折格子２９の３つの回折格子を１組としたものからなり、第２の回折格子アレイ２Ａは前記１組の第２の回折格子２を縦横に並べたものからなる。なお、Ｒ用回折格子２７，Ｇ用回折格子２８およびＢ用回折格子２９はすべて同一の形状のものからなる。即ち、Ｒ用回折格子２７は連続的に傾きが変化する曲線３０を基本要素とし、この基本要素を垂直方向に等間隔で並べたものからなる。曲線３０上の各点の傾きは、水平方向の収束，発散の角度範囲から決められるものである。前記したように同一のパターンが使用されるため作製が容易である。以上の本発明の例では同一パターンのものを複数個配列したものからなるが、本発明の表示装置の表示面積が観察可能範囲よりも非常な大きい場合は表示装置の位置に応じて回折格子のパターンを変えた方が光の利用効率などの面で適する場合もある。
【００２２】
図１５は第２の回折格子アレイ２Ａの別の例を示し、立体表示を可能にしている。第２の回折格子２は左右対称の回折格子３１，３２を一つの要素グループとして組み合わせたものを縦横に配列したものからなる。図の左側の回折格子３１は同一パターン形状のＲ用回折格子３３，Ｇ用回折格子３４およびＢ用回折格子３５を縦に並べたものからなり右側の回折格子３２は前記Ｒ用，Ｇ用，Ｂ用回折格子３３，３４，３５と対称なＲ用回折格子３６，Ｇ用回折格子３７およびＢ用回折格子３８を縦に並べたものからなる。各回折格子３３乃至３８は傾きが連続的に変化する曲線３９からなる。曲線３９上の各点の傾きは水平方向の収束，発明の角度範囲から決められる。水平方向に互いに隣接した角度範囲に光を回折するものであり、垂直方向には同じ角度範囲に光を回折する。図１５（ｂ）の要素グループの左側の回折格子３１は正面から左側の決められた角度範囲まで光を広げて回折し、残る右側の回折格子３２は正面から右側の決められた角度範囲まで光を広げて回折する機能を持っている。そこで要素グループの内の回折格子３１に対応する空間光変調器３の各画素で３次元物体を左側から見た左画像を表示するようにし、右側の回折格子３２に対応する空間光変調器３の各画素で右側から見た右画像を表示すると本発明の表示装置の正面付近で観察している観察者６（図２）の左目には左画像が観察され、右目には右画像が夫々独立に観察され、両眼視差による立体像が認識される。
【００２３】
本発明は以上のものに限られるものではなく、以下のようにしてもよい。本実施態様では、第２の回折格子アレイ２Ａの観察者側に空間光変調器３を配置する場合について述べたが、第２の回折格子アレイ２Ａと第１の回折格子アレイ１Ａの間に配置してもよい。また、本実施態様では、第１の回折格子アレイ１Ａと第２の回折格子アレイ２Ａが夫々独立した素子であるように述べたが、１つの透明基材の表裏に夫々の回折格子アレイを形成してもよい。この場合、装置として簡単になるだけでなく、２つの回折格子アレイの相対配置位置が正確にできる。また、本実施態様では、第１の回折格子１からの回折光が一度収束した後、第２の回折格子２に入射する場合について述べたが、ある程度収束していれば、収束中であっても同様の効果が得られる。また、本実施態様では、例えば第１の回折格子１で回折光の出射角度範囲を決める場合について述べたが、第１の回折格子１における収束角度を適当なものとし、第２の回折格子２によって観察範囲に適した出射角度で回折するようにしてもよい。この場合は、第２の回折格子２が比較的複雑になり、第１の回折格子１との位置合わせは正確に行う必要があるが、遮光板１１を挿入する場合に配置が容易になり、Ｒ，Ｇ，Ｂの各波長分布の選択が任意に行える。本実施態様では、例えば第１の回折格子１で回折光の垂直方向の出射角度範囲を決め、第２の回折格子２で水平方向の出射角度範囲を決める場合について述べたが、第１の回折格子１では装置構成上適当な位置に光が収束するようにし、第２の回折格子２において水平方向に加えて垂直方向の出射角度も適切にするような機能を持たせてもよい。この場合、例えば、遮光板１１を挿入する場合に配置が容易になり、Ｒ，Ｇ，Ｂの各波長成分の選択が任意に行える。本実施態様では、２枚の視差画像によって立体像を表示する場合について述べたが、これに限らず、複数枚の視差画像と、同数個の種類の第１の回折格子１又は第２の回折格子２を要素グループとして用意することにより、より自然な立体像が表示できる。このとき、要素グループ内の第１の回折格子１又は第２の回折格子２は夫々隣接する角度範囲に光を回折する機能を持っている必要がある。
【００２４】
【発明の効果】
本発明のフルカラー画像表示装置は、次のような顕著な効果を奏する。
１）本発明の装置は、液晶ディスプレイのようなバックライトを必要とする表示装置において光の利用効率を非常に高くでき明るい像が観察できる。また、色ずれなどが極めて小さくできる効果を有する。
２）本発明の表示装置では、入射光の波長ごとの分光と収束の２つの機能をもつ第１の回折格子により１画素毎に対応したＲ，Ｇ，Ｂの収束光とし、この収束光のうち、Ｒ，Ｇ，Ｂの各波長成分を同一の角度範囲に回折する機能を有する第２の回折格子によりほぼ同じ出射角度範囲を持った光としている。このＲ，Ｇ，Ｂの各波長成分は夫々空間光変調器の各画素により光強度が変調され、原理的にカラーフィルタを用いることなくＲ，Ｇ，Ｂの夫々の光強度により任意の色調を表示することができる。
３）第１の回折格子における収束角度は、基本的に観察者に対する垂直方向の観察範囲によって決められる。一般的には垂直方向の観察範囲は狭くてよいため、回折格子における同方向の収束角度範囲は狭くてよい。第２の回折格子は第１の回折格子による波長ごとの分光時の出射角度の違いを補償するように機能し、従って観察範囲では色ずれなくフルカラー画像が観察できる。一方、観察範囲以外には光が殆ど漏れないため、光の利用効率は非常に高く、明るい画像を観察することができる。
４）第１，第２の回折格子を適切に設計することによって、観察可能範囲内での垂直方向および水平方向における光量分布を均一にできる。従って、観察可能範囲内において観察者はどの位置から見ても等しい明るさの画像を観察できる。
５）第１の回折格子からの光の垂直方向の収束位置付近に予め決められたＲ，Ｇ，Ｂの波長成分を通過するような開口部が設けられた遮光板を配置することにより、必要な波長成分の損失を避けて、且つ観察される色を形成するＲ，Ｇ，Ｂの各色の波長分布を適切に狭くすることができ、従って彩度の高いフルカラー画像を表示することができる。
６）空間光変調器の前、もしくは後に補助的なカラーフィルタを配置して、各色の波長分布を補正しても５）とほぼ同様な効果が得られる。
７）第２の回折格子アレイは全面均一な回折格子とすることも可能であり、この場合、第１の回折格子アレイとの位置合わせなどの必要なく、非常に簡便に実施できる。
８）複数種類の第１の回折格子又は第２の回折格子を要素グループとし、要素グループ内の各回折格子は、観察者に対し、夫々垂直方向には同じ角度範囲に光を回折し、水平方向には夫々隣接する角度範囲に回折する機能を持たせることにより、各回折格子について夫々独立、且つ隣接した観察範囲が設定でき、従って本発明の表示装置は観察する方向により独立して異なる視差画像を表示できるため、両眼視差を利用した立体像の表示が可能になる。
【図面の簡単な説明】
【図１】本発明に係るフルカラー画像表示装置の実施の形態の概要構成を示す断面図。
【図２】本発明のフルカラー画像表示装置の実施の形態の構成と観察者との関係を示す斜視図。
【図３】水平方向の光を収束するように形成される第１の回折格子における水平方向の回折光を示す断面図。
【図４】遮光板を配設した本発明の実施の形態の構成を示す断面図。
【図５】図４における遮光板の平面図。
【図６】補助カラーフィルタを配設した本発明の実施の形態の構成を示す断面図。
【図７】曲線の要素を有する第１の回折格子を複数個配列した本発明の実施の形態の第１の回折格子アレイの平面図。
【図８】同一パターンの直線状の要素回折格子を有する第２の回折格子を複数個配列した本発明の実施の形態の第２の回折格子アレイの平面図。
【図９】立体像を形成するための第１の回折格子アレイを示す平面図。
【図１０】図９における遮光板の平面図。
【図１１】水平方向に光を透過する第１の回折格子および水平方向に回折する第２の回折格子を組み合わせした実施の形態における水平方向の回折光を示す断面図。
【図１２】図１１に示した第１の回折格子を使用する本発明のフルカラー画像表示装置に使用される遮光板の平面図。
【図１３】水平方向に光をそのまま透過する第１の回折格子の構造を示す平面図。
【図１４】水平方向に光を回折する機能と垂直方向に光を同様な出射角度範囲で回折する機能を有する第２の回折格子の平面図。
【図１５】立体像を形成するための第２の回折格子を示す平面図。
【符号の説明】
１第１の回折格子
１Ａ第１の回折格子アレイ
２第２の回折格子
２Ａ第２の回折格子アレイ
３空間光変調器
４入射光
５光源
６観察者
７観察範囲
８回折光
９回折光
１０透過光
１１遮光板
１２開口部
１３遮光部
１４補助カラーフィルタ
１５曲線
１６間隔
１７回折格子
１８回折格子
１９曲線
２０間隔
２１遮光板
２２開口部
２３遮光部
２４遮光板
２５開口部
２６遮光部
２７Ｒ用回折格子
２８Ｇ用回折格子
２９Ｂ用回折格子
３０曲線
３１回折格子
３２回折格子
３３Ｒ用回折格子
３４Ｇ用回折格子
３５Ｂ用回折格子
３６Ｒ用回折格子
３７Ｇ用回折格子
３８Ｂ用回折格子
３９曲線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device using a diffraction grating that splits light from a white light source into three primary color components. In particular, when displaying a full-color image, the light use efficiency can be improved, and preferably a stereoscopic image is also displayed. The present invention relates to a possible full color image display device.
[0002]
[Prior art]
When a full color image is displayed on the liquid crystal panel, R, G, and B primary color components are assigned to each pixel. In the liquid crystal display, light source light is used for pixel display by the opening area of the pixel existing on the liquid crystal panel out of the total area of the backlight. Therefore, it is desirable that this opening area be large. In addition, it is desirable that the brightness and color tone of the color image do not change even when the observer moves. However, in the case of the prior art, particularly in the case of a TFT liquid crystal panel, only about 1/4 of the total area of the backlight exists. Further, it is necessary to divide this 1/4 aperture area into three pixels of R, G, and B, and incident light is used only for 1/12 of the total area for one color. By the way, in the conventional full-color image display device, a color filter provided with R, G, B colored cells corresponding to each pixel is used. However, when a color filter is interposed, a large amount of white light source light is absorbed by the colored cells, so that the use efficiency of the backlight is poor. In order to improve this point, for example, a technique that employs a diffraction grating array that splits white light into R, G, and B components and leads them to the corresponding colored cells of the color filter is disclosed in, for example, Japanese Patent Laid-Open No. 6-222361. ing. However, when the diffraction grating array is used, the light emission angle range of the R, G, and B components is different, so the brightness and color tone of the image change depending on the position of the observer.
[0003]
[Problems to be solved by the invention]
As described above, in the case of a liquid crystal display, the aperture area that can be used for one color is about 1/12 of the total area and is extremely small. Since it is generally difficult to widen the opening area, it is necessary to improve the light condensing property and prevent the light from diffusing. In addition, since the color filter basically absorbs light from the light source, a structure that does not require this is desired to improve the utilization efficiency. Further, as described above, the remarkable change in the brightness of the image depending on the position of the observer is a problem to be solved in order to reduce the product value.
[0004]
The present invention solves the above problems, improves the light utilization efficiency, allows bright images to be observed, has no color shift, has little change in brightness depending on the observation position, and preferably has binocular parallax. An object of the present invention is to provide a full-color image display device that can display a stereoscopic image using
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention disperses incident light into light of each wavelength distribution of red (R), green (G), and blue (B), and further distributes the dispersed light to an observer. A first diffraction grating array in which a plurality of first diffraction gratings having a function of converging at least in a vertical direction are disposed; and light having a wavelength distribution of R, G, and B emitted from the first diffraction grating, To compensate for the difference in the emission angle at the time of spectroscopy for each wavelength, A second diffraction grating array composed of a second diffraction grating having a function of diffracting in substantially the same emission angle range, and light of R, G, and B wavelength distributions emitted from the first diffraction grating array. A full-color image display device is provided which is provided before or after entering the second diffraction grating and provided with a spatial light modulator for modulating the transmission intensity of the light of each wavelength distribution. More specifically, the first diffraction grating has a function of converging light in a horizontal direction so as to determine a horizontal emission direction distribution with respect to an observer, and the second diffraction grating is in a horizontal direction. The light is transmitted as it is. The first diffraction grating is configured to transmit light as it is in the horizontal direction, and the second diffraction grating converges the light in the horizontal direction or determines the horizontal emission direction distribution for the observer. It has a diverging function. Further, between the first diffraction grating array and the second diffraction grating array, each of the light of the wavelength distribution is determined in the vicinity of the convergence position of the light of the wavelength distribution of R, G, B. A light-shielding plate is provided that transmits light having a wavelength component and spatially blocks other wavelength components. In addition, a color cell having colored cells corresponding to R, G, and B and having a function of transmitting only predetermined wavelength components is disposed before or after the spatial light modulator, and the R, G, and B are disposed. A full-color image display device that passes light of each wavelength distribution through a corresponding colored cell. Further, the first diffraction grating comprises a curve whose inclination changes continuously as a basic element, and the basic elements are arranged along the vertical direction while changing the interval between the elements little by little. The inclination at each point on the curve is determined from the angle range of convergence and divergence in the horizontal direction, and the interval is determined from the angle range of convergence and divergence in the vertical direction. Further, the second diffraction grating array is covered with a uniform circuit grating having a straight line as a basic element. Further, the first diffraction grating array is formed by arranging a plurality of combinations of first diffraction gratings as an element group, and each first diffraction grating in the element group is horizontally arranged. A full-color image display device that diffracts light in an angular range adjacent to each other in the direction and diffracts light in the same angular range in the vertical direction to display a stereoscopic image having parallax in the horizontal direction. . Further, the first diffraction grating constituting the first diffraction grating array has a horizontal straight line as a basic element, and an interval between the elements changes little by little in the vertical direction. Further, the second diffraction grating constituting the second diffraction grating array has a curve whose inclination changes continuously as a basic element, and the basic elements are arranged in a vertical direction. The inclination of the point is determined by the angle range of convergence and divergence in the horizontal direction. Further, the second diffraction grating array is composed of a combination of a plurality of types of the second diffraction gratings as an element group, and each second diffraction grating in the element group includes: It is characterized by a full-color image display device that diffracts light in an angular range adjacent to each other in the horizontal direction and diffracts light in the same angular range in the vertical direction to display a stereoscopic image having parallax in the horizontal direction. is there.
[0006]
According to the present invention, white light is split into R, G, and B components and collected by the first diffraction grating array in the previous stage. Each condensed color component is guided to the corresponding pixel of the spatial light modulator. For this reason, in principle, a color filter is unnecessary and the light use efficiency is high. Further, since the emission angle ranges of the R, G, and B components are corrected to be equal to each other by the second diffraction grating array at the subsequent stage, the viewing angle dependency is eliminated. Furthermore, the emission angle range can be controlled not only in the vertical direction but also in the horizontal direction, and preferably stereoscopic display is realized using binocular parallax. With the above configuration, light use efficiency is improved, a bright image can be obtained, a stereoscopic image can be displayed, and an effect of reducing the change in brightness depending on the observation position can be obtained.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a full-color image display device according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a basic configuration of a full-color image display apparatus of the present invention. As shown in FIGS. 1 and 2, the full-color image display device is a first diffraction grating 1 that disperses and condenses incident light 4 such as white light from a light source 5 into light having a wavelength distribution of R, G, and B colors. A second diffraction grating 2 that diffracts light of each wavelength distribution in a similar emission angle range, and a spatial light modulator 3 that displays a color image by modulating the transmission intensity of the light from the second diffraction grating 2 Etc. The spatial light modulator 3 is composed of, for example, an active matrix type liquid crystal panel. The observer 6 observes the color image within the observation range 7. Note that a plurality of first diffraction gratings 1 and second diffraction gratings 2 are arranged to form a first diffraction grating array 1A and a second diffraction grating array 2A (FIG. 2).
[0008]
The first diffraction grating 1 has a function of dispersing incident light 4 into light having respective wavelength distributions of R, G, and B, and further converging the dispersed light at least in the vertical direction. On the other hand, the second diffraction grating 2 diffracts light of R, G, and B wavelength distributions incident at different divergence angles so as to make the emission angle ranges coincide with each other. At this time, in general, the following equation is established in relation to the diffraction angle β of the diffraction grating with respect to the incident angle α of incident light, the wavelength λ, and the grating interval d (reciprocal of the spatial frequency).
mλ = d (sin α−sin β)
Here, m is the diffraction order, and usually only +1 or -1 should be considered. That is, the diffraction efficiency of the + 1st order or -1st order diffracted light can be made extremely high by making the shape of the diffraction grating a blazed type or the like. For this reason, only the + 1st order or −1st order diffracted light need be considered. Considering the vertical direction from the above formula, the diffraction angle changes for each wavelength by the first diffraction grating 1, but even if the diffraction angle of the second diffraction grating 2 is constant for each wavelength, the dispersion in the first diffraction grating It can be seen that it can function to compensate for the angle. Therefore, the R, G, B diffraction gratings may be common in the second diffraction grating 2, and the fabrication becomes very easy.
[0009]
As described above, the diffracted light 8 converges at least in the vertical direction, but the two cases shown in FIG. 3 or FIG. 11 are adopted for the horizontal direction. FIG. 3 shows a case where diffraction is also performed in the horizontal direction. The incident light 4 becomes diffracted light 9 diffracted in the horizontal direction at substantially the same angle in the R, G, B wavelength distribution by the first diffraction grating 1. In this case, as shown in the figure, the second diffraction grating 2 passes through without being affected and enters the spatial light modulator 3. This can be easily realized when the spatial frequency of the first diffraction grating 1 is high in the vertical direction and low in the horizontal direction. As described above, in the example of FIG. 3, the horizontal diffraction range is added to the first diffraction grating 1 to regulate the horizontal observation range 7. In the case of FIG. 11, the incident light 4 becomes the transmitted light 10 that passes through the first diffraction grating 1 as it is in the horizontal direction. The second diffraction grating 2 spreads in the horizontal direction within a predetermined emission angle range and enters the spatial light modulator 3. That is, contrary to the example of FIG. 3, in the example of FIG. 11, a horizontal diffraction action is added to the second diffraction grating 2. Of course, in some cases, it is not necessary to add a horizontal diffraction action to any diffraction grating. Generally, in a display, it is important to optimally control the viewing angle range in the vertical direction compared to the viewing angle range in the horizontal direction. That is, in order to obtain a wide viewing angle range in the horizontal direction, there is an easy method such as attaching a panel having a scattering effect in the horizontal direction to the front surface of the display.
[0010]
Returning to FIG. 1 again, the second diffraction grating 2 diffracts the diffracted light 8 of the R, G, B wavelength distribution from the first diffraction grating 1 in the substantially same emission angle range with respect to the vertical direction. , R have a function of diffracting.
[0011]
As described above, the light of each wavelength distribution diffracted in the vertical direction and the horizontal direction is diffracted only within the observation range 7. Thus, the observer 6 can observe a color image with uniform brightness within the observation range 7.
[0012]
The spatial light modulator 3 is disposed before or after the second diffraction grating 2 (arranged after the second diffraction grating 2 in the figure), and modulates the transmission intensity of light of each wavelength distribution. For example, it corresponds to a liquid crystal panel.
[0013]
FIG. 4 shows an example in which a light shielding plate 11 is interposed between the first diffraction grating 1 and the second diffraction grating 2. The light shielding plate is disposed in the vicinity of the convergence position in the vertical direction of the light of each wavelength distribution of R, G, and B, transmits a predetermined wavelength component of the light of the wavelength distribution, and transmits other wavelength components. It blocks light spatially. For example, intermediate colors are continuously interposed between R and G of the diffracted light 8 from the first diffraction grating 1, so that even if the light is dispersed in R, G, and B, other wavelength components are mixed. 2 is incident on the diffraction grating 2 side. The light shielding plate 11 can spatially select the wavelength components incident on the second diffraction grating 2 and can optimize the wavelength components of R, G, and B. Therefore, there is no loss related to the necessary light, and the saturation of the observed image can be increased. FIG. 5 shows an example of the light shielding plate 11. The light shielding plate 11 has three rectangular rectangular opening portions 12 corresponding to R, G, and B in the horizontal direction, and a light shielding portion 13 is formed surrounding them. The reason why the opening 12 is formed in the shape of a long hole is that the convergence positions in the horizontal direction and the vertical direction are generally different. Note that a color filter is not necessary by providing the light shielding plate 11.
[0014]
FIG. 6 shows a case where the color filter 14 is arranged as an auxiliary. The color filter 14 is provided with colored cells corresponding to R, G, and B, and has a function of transmitting only predetermined wavelength components, respectively, and colored cells corresponding to light of each wavelength distribution of R, G, and B, respectively. Pass through. In this case, similarly to the case where the light shielding plate 11 (FIGS. 4 and 5) is used, R, G, and B wavelength components can be optimized, and an image with high saturation can be displayed. However, the color filter 14 has a higher degree of light absorption than the light shielding plate 11 and slightly reduces the light use efficiency. However, since the positional accuracy regarding arrangement | positioning is not requested | required compared with the light-shielding plate 11, it can integrate easily. In FIG. 6, it is arranged on the rear side of the spatial light modulator 3, but may be arranged on the front side thereof.
[0015]
FIG. 7A shows an example of the first diffraction grating array 1A. The first diffraction grating array 1A includes a plurality of first diffraction gratings 1 shown in FIG. 7B arranged vertically and horizontally. The first diffraction grating 1 has a curve 15 whose slope changes continuously as a basic element, and a gap 16 in each element is changed little by little. The inclination at each point on the curve 15 is determined from the angle range of convergence and divergence in the horizontal direction. The interval 16 is determined from the angle range of convergence and divergence in the vertical direction. As shown in the drawing, the first diffraction grating array only needs to be arranged with the first diffraction gratings 1 having the same pattern, and can be easily manufactured. Further, since the first diffraction grating 1 can be arranged over the entire display portion with almost no gap, there is an advantage that incident light can be used efficiently.
[0016]
FIG. 8 shows the overall configuration of the second diffraction grating array 2A and the pattern of the second diffraction grating 2 (b) corresponding to R, G, and B. As shown in the figure, the second diffraction gratings 2 are arranged at equal intervals with a horizontal straight line as a basic element. The second diffraction grating array 2A is configured by arranging second diffraction gratings 2 having the same shape vertically and horizontally. FIG. 8A is formed by arranging a plurality of second diffraction gratings 2, but since the pattern is common, it is not necessary to divide the region, and it may be formed from a single piece, which is easy to manufacture. is there. In this case, since the positioning accuracy is not required, the fabrication is easy. The three diffraction gratings for one element are for B, G, and R, respectively, and the linear spacing of each diffraction grating is constant.
[0017]
FIG. 9 shows another example of the first diffraction grating array 1A. The first diffraction grating array 1A is formed by arranging a plurality of element groups, each of which is a combination of a pair of symmetrical diffraction gratings 17 and 18, arranged vertically and horizontally. The diffraction gratings 17 and 18 of the element group are composed of a curve 19 whose inclination gradually changes, and the vertical interval 20 gradually changes. The diffraction gratings 17 and 18 diffract light in an angle range adjacent to each other in the horizontal direction, diffract light in the same angle range in the vertical direction, and display a stereoscopic image having parallax in the horizontal direction. The left diffraction grating 17 spreads and diffracts light from the front to a predetermined angle range on the left side, and the other right diffraction grating 18 spreads and diffracts light from the front to the predetermined angle range on the right side. Have Therefore, in the element group, each pixel of the spatial light modulator corresponding to the diffraction grating 17 displays a left image when the three-dimensional object is viewed from the left side, and the pixel corresponding to the diffraction grating 18 is viewed from the right side. When the image is displayed, the left image obtained by the diffraction grating 17 is observed in the left eye of the observer 6 observing near the front of the display device of the present invention, and the right image obtained by the diffraction grating 18 is independently observed in the right eye. The stereoscopic image due to binocular parallax can be recognized.
[0018]
FIG. 10 shows a light shielding plate 21 combined with the first diffraction grating array 1A in FIG. Corresponding to the diffraction gratings 17, 18, it is composed of a combination of a pair of light shielding plates of the same shape on the left and right, and has an opening 22 and a light shielding part 23 as in FIG.
[0019]
The embodiment shown in FIGS. 11 to 15 is different from the above-described embodiment. The first diffraction grating 1 transmits light in the horizontal direction as it is, and the second diffraction grating 2 emits light in the horizontal direction to the observer. It has the function of diffracting light in the horizontal direction to determine the direction distribution. This point was previously described with reference to FIG. In this case as well, those similar to the light shielding plate 11 and the color filter 14 shown in FIGS. 4 and 6 may be used, but the description thereof is omitted. The light shielding plate 24 of FIG. 12 is applied in this case. The light-shielding plate 24 has an opening 25 and a light-shielding portion 26, and the opening 25 is formed in a horizontally longer shape than the opening 12 of the light-shielding plate 11 in FIG. This is because the first diffraction grating 1 needs to be formed wide so that the light in the horizontal direction is transmitted as it is as the passing light 10 as shown in FIG.
[0020]
FIG. 13 shows a specific example of the first diffraction grating array 1A shown in FIG. The first diffraction grating 1 has a horizontal straight line as a basic element, and is composed of a uniform horizontal direction and a change in the grating interval in the vertical direction. The first diffraction grating array 1A is formed by arranging the first diffraction gratings 1 having the above pattern structure vertically and horizontally. Since the first diffraction grating 1 having the same pattern can be used, the fabrication is easy. Further, since the light can be arranged in the entire display portion with almost no gap, incident light can be used efficiently.
[0021]
FIG. 14 shows a specific example of the second diffraction grating array 2A shown in FIG. The second diffraction grating 2 is composed of a set of three diffraction gratings, an R diffraction grating 27, a G diffraction grating 28, and a B diffraction grating 29, and the second diffraction grating array 2A includes the one set. The second diffraction grating 2 is composed of vertical and horizontal lines. The R diffraction grating 27, the G diffraction grating 28, and the B diffraction grating 29 all have the same shape. That is, the R diffraction grating 27 includes a curved line 30 whose inclination changes continuously as a basic element, and the basic elements are arranged in the vertical direction at equal intervals. The slope of each point on the curve 30 is determined from the angle range of convergence and divergence in the horizontal direction. As described above, since the same pattern is used, the fabrication is easy. In the above example of the present invention, a plurality of the same patterns are arranged. However, when the display area of the display device of the present invention is much larger than the observable range, the diffraction grating is arranged according to the position of the display device. In some cases, changing the pattern is more suitable in terms of light utilization efficiency.
[0022]
FIG. 15 shows another example of the second diffraction grating array 2A, which enables stereoscopic display. The second diffraction grating 2 is formed by vertically and horizontally arranging symmetrical diffraction gratings 31 and 32 as one element group. The diffraction grating 31 on the left side of the figure consists of an R diffraction grating 33, a G diffraction grating 34, and a B diffraction grating 35 arranged in the same pattern, and the right diffraction grating 32 is for the R, G, The B diffraction gratings 33, 34, and 35 are symmetric with respect to the R diffraction grating 36, the G diffraction grating 37, and the B diffraction grating 38. Each of the diffraction gratings 33 to 38 includes a curve 39 whose inclination changes continuously. The slope of each point on the curve 39 is determined from the horizontal convergence and the angle range of the invention. Light is diffracted into an angular range adjacent to each other in the horizontal direction, and light is diffracted into the same angular range in the vertical direction. The diffraction grating 31 on the left side of the element group in FIG. 15B spreads and diffracts the light from the front to the determined angle range from the left side, and the remaining right diffraction grating 32 emits light from the front to the determined angle range on the right side. It has the function of spreading and diffracting. Therefore, a left image of a three-dimensional object viewed from the left side is displayed at each pixel of the spatial light modulator 3 corresponding to the diffraction grating 31 in the element group, and the spatial light modulator 3 corresponding to the right diffraction grating 32 is displayed. When the right image viewed from the right side is displayed by each of the pixels, the left image is observed in the left eye of the observer 6 (FIG. 2) observing near the front of the display device of the present invention, and the right image is observed in the right eye. Observed independently, a stereoscopic image due to binocular parallax is recognized.
[0023]
The present invention is not limited to the above, and may be as follows. In the present embodiment, the case where the spatial light modulator 3 is disposed on the observer side of the second diffraction grating array 2A has been described. However, the spatial light modulator 3 is disposed between the second diffraction grating array 2A and the first diffraction grating array 1A. May be. In the present embodiment, the first diffraction grating array 1A and the second diffraction grating array 2A are described as being independent elements, but each diffraction grating array is formed on the front and back of one transparent substrate. May be. In this case, not only the apparatus becomes simple, but also the relative arrangement position of the two diffraction grating arrays can be made accurately. In the present embodiment, the case where the diffracted light from the first diffraction grating 1 is once converged and then incident on the second diffraction grating 2 has been described. The same effect can be obtained. Further, in this embodiment, for example, the case where the first diffraction grating 1 determines the emission angle range of the diffracted light has been described. However, the convergence angle in the first diffraction grating 1 is set to an appropriate value, and the second diffraction grating 2 is used. May be diffracted at an emission angle suitable for the observation range. In this case, the second diffraction grating 2 becomes relatively complicated, and alignment with the first diffraction grating 1 needs to be performed accurately. However, when the light shielding plate 11 is inserted, the arrangement becomes easy. R, G, B wavelength distribution can be arbitrarily selected. In the present embodiment, for example, the case where the first diffraction grating 1 determines the vertical emission angle range of the diffracted light and the second diffraction grating 2 determines the horizontal emission angle range has been described. The grating 1 may have a function of converging light at an appropriate position in the apparatus configuration, and the second diffraction grating 2 having a function of making the emission angle in the vertical direction appropriate in addition to the horizontal direction. In this case, for example, when the light shielding plate 11 is inserted, the arrangement becomes easy, and the selection of R, G, and B wavelength components can be performed arbitrarily. In this embodiment, the case where a stereoscopic image is displayed by two parallax images has been described. However, the present invention is not limited to this, and a plurality of parallax images and the same number of types of first diffraction gratings 1 or second diffraction images. By preparing the lattice 2 as an element group, a more natural stereoscopic image can be displayed. At this time, the first diffraction grating 1 or the second diffraction grating 2 in the element group needs to have a function of diffracting light into adjacent angular ranges.
[0024]
【The invention's effect】
The full-color image display device of the present invention has the following remarkable effects.
1) The device of the present invention can make the light use efficiency very high and can observe a bright image in a display device such as a liquid crystal display that requires a backlight. In addition, the color misregistration can be extremely reduced.
2) In the display device of the present invention, R, G, B converged light corresponding to each pixel is obtained by the first diffraction grating having two functions of spectrum and convergence for each wavelength of incident light. Of these, the second diffraction grating having a function of diffracting each wavelength component of R, G, B into the same angle range is used as light having substantially the same emission angle range. The light intensity of each wavelength component of R, G, and B is modulated by each pixel of the spatial light modulator, and in principle, an arbitrary color tone is obtained by the light intensity of R, G, and B without using a color filter. Can be displayed.
3) The convergence angle in the first diffraction grating is basically determined by the observation range perpendicular to the observer. In general, since the observation range in the vertical direction may be narrow, the convergence angle range in the same direction in the diffraction grating may be narrow. The second diffraction grating functions to compensate for the difference in emission angle at the time of spectral separation by the first diffraction grating, so that a full color image can be observed without color shift in the observation range. On the other hand, since light hardly leaks outside the observation range, the light use efficiency is very high, and a bright image can be observed.
4) By appropriately designing the first and second diffraction gratings, the light quantity distribution in the vertical and horizontal directions within the observable range can be made uniform. Therefore, the observer can observe an image having the same brightness from any position within the observable range.
5) Necessary by arranging a light-shielding plate provided with an opening that passes predetermined wavelength components of R, G, B in the vicinity of the vertical convergence position of the light from the first diffraction grating. Therefore, the wavelength distribution of each of the R, G, and B colors forming the observed color can be appropriately narrowed, so that a full color image with high saturation can be displayed.
6) Even if an auxiliary color filter is arranged before or after the spatial light modulator to correct the wavelength distribution of each color, the same effect as 5) can be obtained.
7) The second diffraction grating array may be a uniform diffraction grating on the entire surface, and in this case, alignment with the first diffraction grating array is not necessary, and the second diffraction grating array can be implemented very simply.
8) A plurality of types of first diffraction gratings or second diffraction gratings are used as element groups, and each diffraction grating in the element group diffracts light into the same angle range in the vertical direction with respect to the observer, and By giving the function of diffracting to adjacent angular ranges in each direction, it is possible to set independent and adjacent observation ranges for each diffraction grating, and therefore the display device of the present invention has different parallaxes independently depending on the observation direction. Since an image can be displayed, a stereoscopic image using binocular parallax can be displayed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of an embodiment of a full-color image display device according to the present invention.
FIG. 2 is a perspective view showing the relationship between the configuration of an embodiment of a full-color image display device of the present invention and an observer.
FIG. 3 is a cross-sectional view showing the diffracted light in the horizontal direction in the first diffraction grating formed so as to converge the light in the horizontal direction.
FIG. 4 is a cross-sectional view showing a configuration of an embodiment of the present invention in which a light shielding plate is provided.
5 is a plan view of the light shielding plate in FIG. 4. FIG.
FIG. 6 is a cross-sectional view showing a configuration of an embodiment of the present invention in which an auxiliary color filter is provided.
FIG. 7 is a plan view of a first diffraction grating array according to an embodiment of the present invention in which a plurality of first diffraction gratings having curved elements are arranged.
FIG. 8 is a plan view of a second diffraction grating array according to an embodiment of the present invention in which a plurality of second diffraction gratings having linear element diffraction gratings of the same pattern are arranged.
FIG. 9 is a plan view showing a first diffraction grating array for forming a stereoscopic image.
10 is a plan view of the light shielding plate in FIG. 9. FIG.
FIG. 11 is a cross-sectional view showing the diffracted light in the horizontal direction in the embodiment in which the first diffraction grating that transmits light in the horizontal direction and the second diffraction grating that diffracts in the horizontal direction are combined.
12 is a plan view of a light shielding plate used in the full color image display device of the present invention using the first diffraction grating shown in FIG. 11. FIG.
FIG. 13 is a plan view showing the structure of a first diffraction grating that transmits light as it is in the horizontal direction.
FIG. 14 is a plan view of a second diffraction grating having a function of diffracting light in the horizontal direction and a function of diffracting light in the vertical direction in the same emission angle range.
FIG. 15 is a plan view showing a second diffraction grating for forming a stereoscopic image.
[Explanation of symbols]
1 First diffraction grating
1A First diffraction grating array
2 Second diffraction grating
2A Second diffraction grating array
3 Spatial light modulator
4 Incident light
5 Light source
6 observers
7 Observation range
8 Diffracted light
9 Diffracted light
10 Transmitted light
11 Shading plate
12 opening
13 Shading part
14 Auxiliary color filter
15 Curve
16 intervals
17 Diffraction grating
18 Diffraction grating
19 Curve
20 intervals
21 Shading plate
22 opening
23 Shading part
24 Shading plate
25 opening
26 Shading part
27 R diffraction grating
28 G diffraction grating
29 B diffraction grating
30 curves
31 Diffraction grating
32 diffraction grating
33 R diffraction grating
34 G diffraction grating
35 B diffraction grating
36 R diffraction grating
37 G diffraction grating
38 B diffraction grating
39 Curve

Claims

First diffraction having a function of dispersing incident light into light having a wavelength distribution of red (R), green (G), and blue (B), and further converging the dispersed light at least in the vertical direction with respect to the observer. The first diffraction grating array in which a plurality of gratings are arranged and the light of each wavelength distribution of R, G, B emitted from the first diffraction grating are compensated for the difference in emission angle at the time of spectroscopy for each wavelength. , A second diffraction grating array composed of a second diffraction grating having a function of diffracting in substantially the same emission angle range, and light of R, G, B wavelength distribution emitted from the first diffraction grating array. Is provided before or after entering the second diffraction grating, and is provided with a spatial light modulator for modulating the transmission intensity of the light of each wavelength distribution.

The first diffraction grating has a function of converging light in the horizontal direction so as to determine a horizontal emission direction distribution with respect to the observer, and the second diffraction grating transmits light in the horizontal direction as it is. The full-color image display device according to claim 1.

The first diffraction grating transmits light in the horizontal direction as it is, and the second diffraction grating converges or diverges light in the horizontal direction so as to determine the horizontal emission direction distribution for the observer. 2. The full-color image display device according to claim 1, which has a function.

Predetermined wavelengths of the light of the wavelength distribution near the convergence position of the light of the wavelength distribution of R, G, B between the first diffraction grating array and the second diffraction grating array. 4. The full-color image display device according to claim 1, further comprising a light-shielding plate that transmits components and spatially blocks other wavelength components.

A color cell corresponding to R, G, B is provided, and a color filter having a function of transmitting only predetermined wavelength components is disposed before or after the spatial light modulator, and each of the R, G, B 4. The full-color image display device according to claim 1, wherein light having a wavelength distribution is allowed to pass through a corresponding colored cell.

The first diffraction grating comprises a curve whose slope changes continuously as a basic element, and the basic elements are arranged along the vertical direction while gradually changing the interval between the elements. The slope at each point is determined from the angular range of convergence and divergence in the horizontal direction, and the interval is determined from the angular range of convergence and divergence in the vertical direction. Any full-color image display device.

7. The full color image display device according to claim 1, wherein the second diffraction grating array is covered with a uniform circuit grating having a straight line as a basic element.

The first diffraction grating array is composed of a combination of a plurality of types of first diffraction gratings arranged as an element group, and each first diffraction grating in the element group is arranged in a horizontal direction. The light is diffracted in an angular range adjacent to each other, and the light is diffracted in the same angular range in the vertical direction so that a stereoscopic image having parallax in the horizontal direction can be displayed. 6 or 7 full-color image display device.

6. The first diffraction grating constituting the first diffraction grating array has a horizontal straight line as a basic element, and an interval between each element changes little by little in the vertical direction. A full color image display device.

The second diffraction grating constituting the second diffraction grating array has a curve whose slope changes continuously as a basic element, and the basic elements are arranged in a vertical direction. The full-color image display device according to any one of claims 1, 3, 4, 5, and 9, wherein the inclination is determined from an angular range of convergence and divergence in the horizontal direction.

The second diffraction grating array is formed by arranging a plurality of combinations of the second diffraction gratings as element groups, and each second diffraction grating in the element group has a horizontal direction. And diffracting light in an angular range adjacent to each other and diffracting light in the same angular range in the vertical direction so that a stereoscopic image having parallax in the horizontal direction can be displayed. The full-color image display device according to any one of 10.