JP3787399B2

JP3787399B2 - Observation optical system

Info

Publication number: JP3787399B2
Application number: JP33031296A
Authority: JP
Inventors: 和隆猪口
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1996-11-25
Filing date: 1996-11-25
Publication date: 2006-06-21
Anticipated expiration: 2016-11-25
Also published as: JPH10153748A

Description

【０００１】
【発明の属する技術分野】
本発明は観察光学系に関し、特にメガネ型ディスプレイ、ヘッドマウントディスプレイ等の名称で呼ばれる頭部装着型の画像表示装置に好適なものである。
【０００２】
【従来の技術】
従来より、CRT や液晶表示装置（LCD)等の表示手段を観察者の頭部近傍に配置し、CRT 及びLCD が表示する像を観察できるようにした画像表示装置が提案されている。
【０００３】
例えば米国特許4,081,209 号明細書、米国特許4,969,724 号明細書、特開昭58-78116号公報、特開平2-297516号公報、特開平3-101709号公報等にかかる表示装置が開示されている。
【０００４】
特開平3-101709号公報では、表示手段に表示した原画像を一旦中間像として再結像させ、観察者は光学系によってこの中間像を観察する所謂実像タイプの比較的見易い画像表示装置を開示している。
【０００５】
一方、米国特許4,081,209 号明細書、米国特許4,969,724 号明細書、特開昭58-78116号公報、特開平2-297516号公報では、見易さの点では若干劣るが、小型化を図る上では有利な、光学系の途中で中間像を形成しない虚像観察タイプの画像表示装置を開示している。
【０００６】
【発明が解決しようとする課題】
特開平3-101709号公報に開示されている画像表示装置では、再結像させるための光学レンズを用いているために装置が大型化する問題がある。
【０００７】
また、米国特許4,081,209 号明細書、米国特許4,969,724 号明細書、特開昭58-78116号公報、特開平2-297516号公報に開示されている画像表示装置では、確かに実像タイプに比べ小型化を図れるとはいえ、まだまだ十分小型とは言えなかった。
【０００８】
これらの中で、特開昭58-78116号公報に開示されているものは比較的小型であるが、観察者の眼の光軸方向の厚みはまだ厚い。又、観察される像に光学的歪み、非点収差、コマ収差等の発生することが記載されている。
【０００９】
本発明は、実像タイプでありながら、前後方向に極めて薄型で、小型・広視野角の観察光学系の提供を目的とする。
【００１０】
更に、表示手段及びリレー光学系を画像表示装置の支持部より上に配置し、光学素子を該支持部より下に配置することで重量バランスの良い画像表示装置を構成できる観察光学系の提供を目的とする。
【００１１】
【課題を解決するための手段】
請求項１の発明の観察光学系は、表示手段に表示する原画像からの光束を、光学系を介して該光学系に対して予め決められた射出瞳に導光し、該射出瞳の位置に観察者の瞳を略位置させて該観察者に該原画像の拡大虚像を視認せしめる観察光学系において、該観察光学系は、屈折面として作用する第１の面、反射面として作用する第２の面、全反射面及び屈折面として作用する第３の面の少なくとも３つの光学作用面を有する光学素子と、前記表示手段と前記光学素子の間に配置された集光レンズを有し、前記原画像からの光束は、前記集光レンズを介して前記第１の面より前記光学素子に入射し、前記第２の面での反射と前記第３の面での全反射とを経た後、前記第３の面より前記光学素子を射出すると共に、前記光学素子内に前記原画像の中間像が実像として形成され、前記表示手段の表示面の中心から射出して前記射出瞳の中心を通る光線を基準光線とした場合に、前記光学素子は、該基準光線が２回反射する面を有し、この面は、この面での１回目の前記原画像からの光束の反射部位と２回目の前記原画像からの光束の反射部位との少なくとも一部分が重なっており、且つ該基準光線に対して偏心した曲面であることを特徴としている。
請求項２の発明は、請求項１の発明において、前記集光レンズは、前記基準光線に対して偏心して配置される曲面を有していることを特徴としている。
請求項３の発明は、請求項２の発明において、前記集光レンズで前記基準光線に対して偏心して配置される曲面は透過面であることを特徴としている。
請求項４の発明は、請求項１、２又は３の発明において、前記集光レンズは、前記原画像からの光束を集光して前記光学素子に入射させることを特徴としている。
請求項５の発明は、請求項１乃至４のいずれか１項の発明において、前記中間像は、前記光学素子を構成する光学面間で反射される光束上に形成され、且つ該中間像を形成した光束が前記光学素子を構成する光学面間で再度反射された後に該中間像を横切ることを特徴としている。
請求項６の発明は、請求項１乃至５のいずれか１項の発明において、前記原画像からの光束は前記第１の面を透過して前記光学素子へ入射し、次いで前記第２の面により反射して前記第３の面へ向かい、該第３の面により全反射して該第２の面へ向かい、該第２の面により再度反射して該第３の面へ向かい、該第３の面を透過して該光学素子を出射して前記射出瞳に導光され、αを前記基準光線が前記第３の面で屈折する際の入射点における面法線に対する該基準光線の傾き角、βを該基準光線が前記第２の面において２回目の反射をする際の入射点における面法線に対する該基準光線の傾き角とした場合、
以下の条件式：
３０゜≦２β＋α≦９０゜
−１０゜≦α≦３０゜
を満足することを特徴としている。
請求項７の発明は、請求項１乃至６のいずれか１項の発明において、前記原画像からの光束は前記第１の面を透過して前記光学素子へ入射し、次いで前記第２の面により反射して前記第３の面へ向かい、該第３の面により全反射して該第２の面へ向かい、該第２の面により再度反射して該第３の面へ向かい、該第３の面を透過して該光学素子を出射して前記射出瞳に導光され、ｒｃを前記基準光線が前記第２の面において１回目の反射をする際の入射点における前記第２の面の垂直断面の曲率半径、ｒａを前記基準光線が前記第２の面において２回目の反射をする際の入射点における前記第２の面の垂直断面の曲率半径として、以下の条件式：
０＜｜ｒａ／ｒｃ｜＜１．５
を満足することを特徴としている。
請求項８の発明の画像表示装置は、請求項１乃至７に記載の観察光学系と、該観察光学系を観察者の頭部に装着するための支持部を有する画像表示装置であって、該観察光学系のリレー光学系が該支持部の上方であって、該観察光学系の光学素子が該支持部の下方になるように観察者の頭部に装着されることを特徴としている。
請求項９の発明の画像表示装置は、請求項１乃至７に記載の観察光学系を観察者の左右の眼に対応して夫々一つずつ配置したことを特徴としている。
【００１２】
【発明の実施の形態】
図１は本発明の実施形態１の基本構成図である。図は垂直断面図である。図中１は原画像を表示する表示手段で，例えば公知の液晶表示素子(LCD) やCRT 等で構成する。２は光学素子であり、第１の面A 、第２の面B 、第３の面C の３つの光学作用面を有している。このうち、第１の面A は屈折面である。第２の面B は表面に反射膜を付けており、反射面として作用する。第３の面C は全反射面及び屈折面として作用する。３は集光レンズ（リレー光学系）である。４は観察光学系の射出瞳である。９は観察光学系を収納している筐体の壁であり、画像からの表示光束が射出する略長方形の覗窓ｗを設けている。w₀は覗窓ｗの中心である。観察者は射出瞳４の位置に瞳を位置させて覗窓ｗを通して原画像の虚像を観察する。なお、光学素子２、集光レンズ３及び覗窓ｗ等は観察光学系の一要素を構成している。
【００１３】
本実施形態の作用を説明する。表示手段１に表示する画像からの光束はまず集光レンズ３で屈折作用を受けて集光した後、光学素子３の第１の面A に向かい、この面を屈折して光学素子２の中にはいり、第２の面B へ向かう。光束は第２の面B により反射されて第３の面C に向かい、第３の面C により全反射されて再び第２の面B に向かう。光束は第２の面B により再び反射されて再び第３の面C に向かい、今度は第３の面C を屈折・透過して覗窓ｗを通過して射出瞳４に向かう。表示手段１の表示面上の各点からの光束は射出瞳４に集まる。そして、各光束はこの射出瞳４の位置にある観察者の瞳へ入射する。この時、射出光束は遠方に原画像の虚像を形成しているので観察者はこの射出瞳４の位置に瞳をおけばこの虚像を観察することができる。
【００１４】
このとき、表示手段１からの光束が、光学素子２の第２の面B による１回目の反射から第３の面C に向かう際に一旦中間像を結像しており、光束が第３の面C で全反射して第２の面B に向かう際に上記の中間結像面８を横切るよう構成している。
【００１５】
本実施形態では、屈折面として作用する第１の面A 、光束を２回反射する面として作用する第２の面B 、全反射面及び屈折面として作用する第３の面C の少なくとも３つの光学作用面を有する光学素子を観察光学系中に設けることにより、原画像上の各点からの光束が、第１の面A から入射して、第２の面B での１回目の反射から第３の面C へ向かう光束群を横切る様に実像を形成することにより、第３の面C における全反射の条件を満足しつつ、第２の面B のパワーを従来よりも強くすることが可能となるため、観察光学系の薄型化を可能にするものである。
【００１６】
又、本実施形態は前記光学素子以外に集光レンズ（リレー光学系）を有し、原画像からの光束を該集光レンズにより集光させて該光学素子へ入射するよう構成することにより、該光学素子の入射面の有効径を小さくしている。
【００１７】
又、本実施形態は特に前記光学素子中の第２の面Ｂにおける１回目の反射部位と２回目の反射部位とを少なくとも一部分共通にすることにより即ち一部分が重なるようにして全長を制限し、更に軽量な観察光学系としている。
【００１８】
以下，垂直断面方向における構成をもとに本実施形態をより詳しく説明する。本発明の観察光学系は通常の光学系にある光軸が無い。そこで本発明の観察光学系では”基準光線”を設定して構成を明確にする。本発明で言う基準光線とは、表示手段１の表示面の中心から射出して射出瞳４の中心を通る光線である。なお、本実施形態の場合この基準光線は視窓ｗの中心w₀ も通っている。
【００１９】
図２は本発明の観察光学系の基準光線と各面との関係の説明図である。この基準光線が光学素子２で反射・全反射・屈折を行う際の各面の入射点をそれぞれ図のようにa,b,c,d とし、基準光線が第３の面C を屈折する際の入射点d における面法線dd₁ に対する屈折基準光線の傾き角をαとする。又、基準光線が第２の面B において２回目の反射をする際の入射点a における面法線に対する反射基準光線の傾き角をβとする。又、基準光線が第２の面B において１回目の反射をする際の入射点c における面法線に対する反射基準光線の傾き角をγとする。
【００２０】
本実施形態においては、上記αとβとが以下の条件式
30゜≦ 2β＋α≦90゜ (条件式1)
を満たすように設定している。（条件式1)の下限値は第３の面C での全反射の条件に関するものであり，下限を越えると第３の面C で全反射させることが非常に困難となる。また，上限を越えると基準光線に対して下側の視野画角の光束で光量不足を生じ易くなり、性能が低下する。
【００２１】
更に，このとき上記αを
−10゜≦α≦30゜ (条件式2)
と設定することが好ましい。 (条件式2)の下限を越えると光学素子２の第３の面C に垂直な方向の厚みが増し重量が増加するので好ましくない。また，上限を越えると第３の面C で全反射させることが難しくなる。
【００２２】
また，基準光線が第２の面B において１回目の反射をする際の入射点c における垂直断面（紙面内）の曲率半径をr_c、基準光線が第２の面B において２回目の反射をする際の入射点a における垂直断面（紙面内）の曲率半径をr_aとするとき，これらを
0 ＜｜r_a/r_c|＜1.5 (条件式3)
を満足するように設定することが望ましい。 (条件式3)の条件を越えると光学素子２の第３の面C に平行な方向の長さが増し，全体の重量増を招くため好ましくない。特に（条件式3）の下限を越えると光学素子２をコンパクトに保ちつつ、十分な瞳径を確保するのが困難になる。また、（条件式3）の上限を越えると光学素子２をコンパクトに保ちつつ、広画角を確保するのが困難になる。
【００２３】
尚、本実施形態では上記の様に基準光線に対して光学素子２の第３の面C 、第２の面B を偏心配置させているため、これらにより生じる偏心収差を補正するために、光学素子２の第１の面A 及び集光レンズ３を偏心配置させることが望ましい。
【００２４】
図３は本発明の観察光学系を用いた画像表示装置の概略配置図である。図中31は本発明の観察光学系を観察者の頭部に装着するための支持部で、例えばベルトと光学系保持部を支持するための支持部材により構成されている。32は光学系２を保持する保持部（筐体）、34は表示手段１の表示部の駆動を行う回路部、33は集光レンズ３並びに表示手段１、回路部34を保持する保持部である。図３に示す様に、本発明の観察光学系を支持部31を介して観察者の頭部に装着する際、観察光学系の光学素子２の保持部32を支持部31より下方に、集光レンズ３及び表示手段等の保持部33を上方に配置することにより、重量バランスの良い画像表示装置を構成することが可能である。即ち、観察光学系が該光学素子２以外に集光レンズ（リレー光学系）３を有し、該集光レンズ３と該光学素子２とを支持部に対して上下に配置することにより重量バランスの良い観察光学系が得られる。
【００２５】
以下に本発明にかかる３つの数値実施例の構成データを示す。
【００２６】
尚、構成データ中、R は面の曲率半径、D は面間隔、N は媒質の屈折率、νは媒質のアッベ数であり、θは前面の光軸に対する面の光軸の傾き、YDは光軸に対する垂直方向の面の移動量、ZDは光軸方向の面の移動量を示す。
【００２７】
また、ASP と示された面は以下の式で表される非球面であり、記載のない係数は 0である。
【００２８】

として：
【００２９】
【数１】

なお、各数値実施例の厚さを示す為に、図２の点a において法線dd₁ に平行に測ったプリズムの厚みをDa、点c において法線dd₁ に平行に測ったプリズムの厚みをDcとしてその数値を示す。
［数値実施例１］
図４は数値実施例１の垂直方向の断面図である。その構成データを以下に示す。
【００３０】

垂直方向視野画角±23.4゜
α:-5.40゜、β:25.46゜
2β＋α＝45.52 ゜
r_a 86.011mm
r_c 173.836mm
｜r_a/r_c| = 0.495
Da=11.77mm、Dc=21.28mm
［数値実施例２］
図５は数値実施例２の垂直方向の断面図である。その構成データを以下に示す。
【００３１】

垂直方向視野画角±23.4゜
α:20.00゜、β:20.84゜
2β＋α＝61.68 ゜
r_a= 86.619mm
r_c=166.355mm
｜r_a/r_c|= 0.521
Da=13.68mm、Dc=19.84mm
［数値実施例３］
図６は数値実施例３の垂直方向の断面図である。その構成データを以下に示す。
【００３２】

垂直方向視野画角±23.4゜
α:27.07゜、β:22.15゜
2β＋α＝71.37 ゜
r_a= 90.584mm
r_c= 68.158mm
｜r_a/r_c|= 1.329
Da=10.56mm、Dc=15.02mm
以上のように、本発明の各数値実施例は原画像からの光束を光学素子を介して観察者の眼球の位置する射出瞳に導く観察光学系において，屈折面として作用する第１の面A 、光束を２回反射する面として作用する第２の面B 、全反射面及び屈折面として作用する第３の面C の少なくとも３つの光学作用面を有する光学素子を観察光学系中に設けることにより、原画像上の各点からの光束が、第１の面A から入射して、第２の面B での１回目の反射から第３の面C へ向かう光束群を横切る様に中間結像面を形成することにより、垂直方向画角±20゜程度の広視野画角で、薄型で軽量な観察光学系となっている。
【００３３】
更に、該観察光学系は前記光学素子以外に集光レンズ（リレー光学系）を有し、該集光レンズと該光学素子とを支持部に対して上下に配置することにより重量バランスの良い画像表示装置を構成できる。
【００３４】
更に、上記の各数値実施例のいずれか１つの観察光学系を観察者の左右の眼に対応して夫々一つずつ配置して画像表示装置を構成すれば、軽量で使用感の良い画像表示装置が得られ、更に左右の表示手段に表示する原画像を左右の視差画像とすれば軽量な立体画像表示装置が得られる。
【００３５】
【発明の効果】
本発明は以上の構成により、実像タイプでありながら、前後方向に極めて薄型で、小型・広視野角の観察光学系を達成する。
【００３６】
更に、表示手段及びリレー光学系を画像表示装置の支持部より上に配置し、光学素子を該支持部より下に配置することで重量バランスの良い画像表示装置を構成できる観察光学系を達成する。
【図面の簡単な説明】
【図１】本発明の観察光学系の実施形態１の基本構成図
【図２】本発明の観察光学系の基準光線と各面との関係の説明図
【図３】本発明の観察光学系を用いた画像表示装置の概略配置図
【図４】本発明の数値実施例１の垂直方向断面図
【図５】本発明の数値実施例２の垂直方向断面図
【図６】本発明の数値実施例３の垂直方向断面図
【符号の説明】
１・・・表示手段
２・・・光学素子
３・・・集光レンズ（リレー光学系）
４・・・射出瞳（観察者の瞳が位置する）
Ａ・・・第１の面
Ｂ・・・第２の面
Ｃ・・・第３の面
８・・・中間結像面
９・・・筐体の壁
ｗ・・・覗窓
ｗ₀ ・・覗窓の中心
31・・・支持部
32・・・保持部
33・・・保持部
34・・・回路部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an observation optical system, and is particularly suitable for a head-mounted image display device called by a name such as a glasses-type display or a head-mounted display.
[0002]
[Prior art]
Conventionally, an image display device has been proposed in which display means such as a CRT and a liquid crystal display (LCD) are arranged in the vicinity of the observer's head so that images displayed on the CRT and LCD can be observed.
[0003]
For example, display devices according to U.S. Pat. No. 4,081,209, U.S. Pat. No. 4,969,724, JP-A-58-78116, JP-A-2-97516, JP-A-3-101709, and the like are disclosed.
[0004]
Japanese Patent Laid-Open No. 3-101709 discloses a so-called real image type image display device that is relatively easy to see, in which an original image displayed on a display means is re-imaged as an intermediate image, and an observer observes this intermediate image with an optical system. is doing.
[0005]
On the other hand, in U.S. Pat.No. 4,081,209, U.S. Pat.No. 4,969,724, JP-A-58-78116, and JP-A-2-2751616, although it is slightly inferior in viewability, An advantageous virtual image observation type image display device that does not form an intermediate image in the middle of an optical system is disclosed.
[0006]
[Problems to be solved by the invention]
In the image display device disclosed in Japanese Patent Laid-Open No. 3-101709, there is a problem that the size of the device is increased because an optical lens for re-imaging is used.
[0007]
In addition, the image display devices disclosed in U.S. Pat.No. 4,081,209, U.S. Pat.No. 4,969,724, Japanese Patent Laid-Open No. 58-78116, and Japanese Patent Laid-Open No. 2-227516 are certainly smaller than the real image type. However, it was still not small enough.
[0008]
Among these, those disclosed in Japanese Patent Application Laid-Open No. 58-78116 are relatively small, but the thickness of the observer's eyes in the optical axis direction is still thick. Further, it is described that optical distortion, astigmatism, coma and the like occur in an observed image.
[0009]
An object of the present invention is to provide an observation optical system that is a real image type but is extremely thin in the front-rear direction, and has a small size and a wide viewing angle.
[0010]
Furthermore, it is possible to provide an observation optical system that can constitute an image display device having a good weight balance by disposing the display means and the relay optical system above the support portion of the image display device and disposing the optical element below the support portion. Objective.
[0011]
[Means for Solving the Problems]
The observation optical system according to the first aspect of the present invention guides the light beam from the original image displayed on the display means to the exit pupil predetermined for the optical system via the optical system, and the position of the exit pupil. In the observation optical system in which the observer's pupil is substantially positioned to allow the observer to visually recognize the magnified virtual image of the original image, the observation optical system is a first surface that acts as a refractive surface and a first surface that acts as a reflective surface. An optical element having at least three optical action surfaces of a second surface, a total reflection surface and a third surface acting as a refracting surface, and a condensing lens disposed between the display means and the optical element, The light beam from the original image is incident on the optical element from the first surface via the condenser lens, passes through the reflection on the second surface and the total reflection on the third surface. The optical element is emitted from the third surface, and the original image is placed in the optical element. When the intermediate image is formed as a real image and a light beam that exits from the center of the display surface of the display unit and passes through the center of the exit pupil is used as a reference light beam, the optical element reflects the reference light beam twice. This surface is such that at least a part of the reflected portion of the light beam from the first original image on this surface overlaps with the reflected portion of the light beam from the second original image, and the reference light beam It is characterized by a curved surface decentered with respect to.
The invention of claim 2 is characterized in that, in the invention of claim 1, the condensing lens has a curved surface arranged eccentrically with respect to the reference beam.
According to a third aspect of the present invention, in the second aspect of the present invention, the curved surface arranged eccentrically with respect to the reference beam in the condenser lens is a transmission surface.
According to a fourth aspect of the present invention, in the first, second, or third aspect of the invention, the condensing lens condenses the light flux from the original image and makes it incident on the optical element.
The invention of claim 5 is the invention of any one of claims 1 to 4, wherein the intermediate image is formed on a light beam reflected between optical surfaces constituting the optical element, and the intermediate image is The formed light beam crosses the intermediate image after being reflected again between the optical surfaces constituting the optical element.
According to a sixth aspect of the present invention, in the first aspect of the present invention, the light beam from the original image passes through the first surface and enters the optical element, and then the second surface. Reflected by the third surface, totally reflected by the third surface and directed to the second surface, reflected again by the second surface and directed to the third surface, 3 is transmitted through the surface 3, exits the optical element, is guided to the exit pupil, and α is the inclination of the reference ray with respect to the surface normal at the incident point when the reference ray is refracted by the third surface. When the angle, β is the inclination angle of the reference ray with respect to the surface normal at the incident point when the reference ray is reflected for the second time on the second surface,
The following conditional expression:
30 ° ≦ 2β + α ≦ 90 ° −10 ° ≦ α ≦ 30 ° is satisfied.
According to a seventh aspect of the present invention, in the first aspect of the present invention, the light beam from the original image passes through the first surface and enters the optical element, and then the second surface. Reflected by the third surface, totally reflected by the third surface and directed to the second surface, reflected again by the second surface and directed to the third surface, The second surface at the incident point when the reference light beam is reflected on the second surface for the first time by being transmitted through the surface 3 and exiting the optical element and guided to the exit pupil. As a curvature radius of the vertical cross section of the second surface, and ra as a radius of curvature of the vertical cross section of the second surface at the incident point when the reference ray is reflected for the second time on the second surface, the following conditional expression:
0 <| ra / rc | <1.5
It is characterized by satisfying.
An image display device according to an eighth aspect of the present invention is an image display device comprising: the observation optical system according to any one of the first to seventh aspects; and a support unit for mounting the observation optical system on an observer's head, The observation optical system is mounted on the observer's head so that the relay optical system is above the support and the optical element of the observation optical system is below the support.
An image display apparatus according to a ninth aspect of the invention is characterized in that the observation optical systems according to the first to seventh aspects are arranged one by one in correspondence with the left and right eyes of the observer.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a basic configuration diagram of Embodiment 1 of the present invention. The figure is a vertical sectional view. In the figure, reference numeral 1 denotes a display means for displaying an original image, which is composed of, for example, a known liquid crystal display element (LCD) or CRT. Reference numeral 2 denotes an optical element, which has three optical action surfaces, a first surface A, a second surface B, and a third surface C. Of these, the first surface A is a refractive surface. The second surface B has a reflective film on the surface and acts as a reflective surface. The third surface C acts as a total reflection surface and a refractive surface. Reference numeral 3 denotes a condenser lens (relay optical system). Reference numeral 4 denotes an exit pupil of the observation optical system. Reference numeral 9 denotes a wall of a housing that houses the observation optical system, and is provided with a substantially rectangular viewing window w through which a display light beam from the image is emitted. w ₀ is the center of the viewing window w. The observer locates the pupil at the position of the exit pupil 4 and observes the virtual image of the original image through the viewing window w. The optical element 2, the condensing lens 3, the viewing window w, and the like constitute an element of the observation optical system.
[0013]
The operation of this embodiment will be described. A light beam from an image displayed on the display means 1 is first refracted by the condensing lens 3 to be condensed and then directed toward the first surface A of the optical element 3, and this surface is refracted to be inside the optical element 2. Enter and head to the second side B. The light beam is reflected by the second surface B and travels toward the third surface C, and is totally reflected by the third surface C and travels again to the second surface B. The light beam is reflected again by the second surface B and travels again toward the third surface C. This time, the light beam is refracted and transmitted through the third surface C, passes through the viewing window w, and travels toward the exit pupil 4. The light flux from each point on the display surface of the display means 1 gathers at the exit pupil 4. Each light beam enters the observer's pupil at the position of the exit pupil 4. At this time, since the emitted light beam forms a virtual image of the original image in the distance, the observer can observe this virtual image by placing the pupil at the position of the exit pupil 4.
[0014]
At this time, when the light beam from the display means 1 goes from the first reflection by the second surface B of the optical element 2 to the third surface C, an intermediate image is once formed, and the light beam is the third light beam. When the light is totally reflected by the surface C and travels toward the second surface B, the intermediate imaging surface 8 is traversed.
[0015]
In the present embodiment, at least three of the first surface A that acts as a refractive surface, the second surface B that acts as a surface that reflects the light beam twice, the total reflection surface, and the third surface C that acts as a refractive surface. By providing an optical element having an optical action surface in the observation optical system, a light beam from each point on the original image is incident from the first surface A 1 and is reflected from the first reflection on the second surface B 2. By forming a real image so as to cross the light flux group toward the third surface C, it is possible to make the power of the second surface B stronger than before while satisfying the condition of total reflection on the third surface C 1. Therefore, the observation optical system can be thinned.
[0016]
In addition, the present embodiment has a condensing lens (relay optical system) in addition to the optical element, and the light beam from the original image is condensed by the condensing lens so as to be incident on the optical element. The effective diameter of the incident surface of the optical element is reduced.
[0017]
In addition, this embodiment limits the overall length by making at least a part of the first reflection part and the second reflection part in the second surface B in the optical element in particular, that is, the parts overlap each other . Furthermore, a light observation optical system is provided.
[0018]
Hereinafter, the present embodiment will be described in more detail based on the configuration in the vertical sectional direction. The observation optical system of the present invention does not have an optical axis as in a normal optical system. Therefore, in the observation optical system of the present invention, the “reference beam” is set to clarify the configuration. The reference light beam referred to in the present invention is a light beam that exits from the center of the display surface of the display unit 1 and passes through the center of the exit pupil 4. In the case of this embodiment, this reference ray also passes through the center w _{0 of the} viewing window w.
[0019]
FIG. 2 is an explanatory diagram of the relationship between the reference light beam and each surface of the observation optical system of the present invention. When the reference ray is reflected, totally reflected, or refracted by the optical element 2, the incident points of the respective surfaces are a, b, c, d as shown in the figure, and the reference ray is refracted on the third surface C. Let α be the inclination angle of the refraction reference ray with respect to the surface normal dd _{1 at} the incident point d. Further, the inclination angle of the reflected reference ray with respect to the surface normal at the incident point a when the reference ray is reflected for the second time on the second surface B is β. Further, the inclination angle of the reflected reference light beam with respect to the surface normal at the incident point c when the reference light beam is reflected for the first time on the second surface B is γ.
[0020]
In the present embodiment, α and β are the following conditional expressions:
30 ° ≦ 2β + α ≦ 90 ° (Condition 1)
It is set to satisfy. The lower limit value of (Condition 1) relates to the condition of total reflection on the third surface C. If the lower limit is exceeded, it is very difficult to cause total reflection on the third surface C. On the other hand, if the upper limit is exceeded, the light flux with a lower field angle of view with respect to the reference light beam tends to be insufficient, and the performance deteriorates.
[0021]
Furthermore, at this time, α is −10 ° ≦ α ≦ 30 ° (Condition 2)
Is preferably set. Exceeding the lower limit of (Condition 2) is not preferable because the thickness in the direction perpendicular to the third surface C of the optical element 2 increases and the weight increases. If the upper limit is exceeded, it is difficult to totally reflect the third surface C.
[0022]
Also, the radius of curvature of the vertical section (in the paper) at the incident point c when the reference ray is reflected on the second surface B for the first time is r _c , and the reference ray is reflected on the second surface B for the second time. when the radius of curvature of the vertical cross-section (in the plane) at an incident point a when a r _a, these
0 <| r _a / r _c | <1.5 (conditional expression 3)
It is desirable to set so as to satisfy If the condition of (Condition 3) is exceeded, the length in the direction parallel to the third surface C of the optical element 2 will increase, leading to an increase in the overall weight, which is not preferable. In particular, if the lower limit of (conditional expression 3) is exceeded, it will be difficult to ensure a sufficient pupil diameter while keeping the optical element 2 compact. If the upper limit of (Condition 3) is exceeded, it will be difficult to ensure a wide angle of view while keeping the optical element 2 compact.
[0023]
In the present embodiment, since the third surface C 2 and the second surface B 2 of the optical element 2 are decentered with respect to the reference beam as described above, the optical aberration is corrected in order to correct the decentration aberration caused by them. It is desirable that the first surface A of the element 2 and the condenser lens 3 are arranged eccentrically.
[0024]
FIG. 3 is a schematic layout diagram of an image display apparatus using the observation optical system of the present invention. In the figure, reference numeral 31 denotes a support part for mounting the observation optical system of the present invention on the observer's head, and is composed of a support member for supporting, for example, a belt and an optical system holding part. Reference numeral 32 denotes a holding unit (housing) that holds the

optical system

2, 34 denotes a circuit unit that drives the display unit of the

display unit

1, and 33 denotes a holding unit that holds the condenser lens 3, the display unit 1, and the circuit unit 34. is there. As shown in FIG. 3, when the observation optical system of the present invention is mounted on the observer's head via the support portion 31, the holding portion 32 of the optical element 2 of the observation optical system is gathered below the support portion 31. By disposing the optical lens 3 and the holding unit 33 such as a display unit on the upper side, it is possible to configure an image display device with a good weight balance. In other words, the observation optical system has a condensing lens (relay optical system) 3 in addition to the optical element 2, and the weight balance is achieved by arranging the condensing lens 3 and the optical element 2 above and below the support portion. A good observation optical system.
[0025]
The configuration data of three numerical examples according to the present invention will be shown below.
[0026]
In the configuration data, R is the radius of curvature of the surface, D is the surface spacing, N is the refractive index of the medium, ν is the Abbe number of the medium, θ is the inclination of the optical axis of the surface with respect to the optical axis of the front surface, and YD is The amount of movement of the surface in the direction perpendicular to the optical axis, ZD, indicates the amount of movement of the surface in the direction of the optical axis.
[0027]
The surface indicated as ASP is an aspherical surface expressed by the following formula, and the coefficient not described is 0.
[0028]

As:
[0029]
[Expression 1]

Incidentally, in order to show the thickness of each numerical example, the thickness of the prism measured parallel to the normal dd ₁ the thickness of the prism measured parallel to the normal dd ₁ in a point of FIG. 2 Da, at a point c The value is shown as Dc.
[Numerical Example 1]
4 is a vertical sectional view of Numerical Example 1. FIG. The configuration data is shown below.
[0030]

Vertical field of view ± 23.4 ° α: -5.40 °, β: 25.46 °
2β + α = 45.52 ゜
r _a 86.011mm
r _c 173.836mm
│r _a / r _c | = 0.495
Da = 11.77mm, Dc = 21.28mm
[Numerical Example 2]
FIG. 5 is a vertical sectional view of Numerical Example 2. The configuration data is shown below.
[0031]

Vertical field angle of view ± 23.4 ° α: 20.00 °, β: 20.84 °
2β + α = 61.68 °
r _a = 86.619mm
r _c = 166.355mm
| R _a / r _c | = 0.521
Da = 13.68mm, Dc = 19.84mm
[Numerical Example 3]
FIG. 6 is a cross-sectional view of Numerical Example 3 in the vertical direction. The configuration data is shown below.
[0032]

Vertical field of view ± 23.4 ° α: 27.07 °, β: 22.15 °
2β + α = 71.37 ゜
r _a = 90.584mm
r _c = 68.158mm
| R _a / r _c | = 1.329
Da = 10.56mm, Dc = 15.02mm
As described above, in each numerical example of the present invention, the first surface A that acts as a refractive surface in the observation optical system that guides the light beam from the original image to the exit pupil where the eyeball of the observer is positioned through the optical element. An observation optical system is provided with an optical element having at least three optical action surfaces: a second surface B that acts as a surface that reflects the light beam twice, a third surface C that acts as a total reflection surface and a refracting surface. As a result, the intermediate beam is formed so that the light flux from each point on the original image enters from the first surface A and crosses the light flux group from the first reflection on the second surface B toward the third surface C. By forming the image plane, the observation optical system is thin and lightweight with a wide field angle of view of about ± 20 ° in the vertical direction.
[0033]
Further, the observation optical system has a condensing lens (relay optical system) in addition to the optical element, and an image with a good weight balance is provided by arranging the condensing lens and the optical element above and below the support portion. A display device can be configured.
[0034]
Furthermore, if an image display device is configured by arranging any one observation optical system in each of the numerical examples described above corresponding to the left and right eyes of the observer, the image display is light and easy to use. If the original image displayed on the left and right display means is the left and right parallax images, a lightweight stereoscopic image display device can be obtained.
[0035]
【The invention's effect】
With the above configuration, the present invention achieves an observation optical system that is a real image type, is extremely thin in the front-rear direction, and has a small size and a wide viewing angle.
[0036]
Furthermore, an observation optical system capable of constructing an image display device having a good weight balance by arranging the display means and the relay optical system above the support portion of the image display device and arranging the optical element below the support portion is achieved. .
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of Embodiment 1 of an observation optical system of the present invention. FIG. 2 is an explanatory diagram of the relationship between a reference light beam and each surface of the observation optical system of the present invention. FIG. 4 is a vertical sectional view of Numerical Example 1 of the present invention. FIG. 5 is a vertical sectional view of Numerical Example 2 of the present invention. Vertical sectional view of Example 3 [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Display means 2 ... Optical element 3 ... Condensing lens (relay optical system)
4 ... Exit pupil (the observer's pupil is located)
A ... first surface B ... second surface C ... third surface 8 ... intermediate imaging surface 9 ... wall of the housing w ... view window w ₀ .. The center of the sight window
31 ... Supporting part
32 ・・・ Holding part
33 ・・・ Holding part
34 ・・・ Circuit part

Claims

The light beam from the original image displayed on the display means is guided to the exit pupil predetermined for the optical system via the optical system, and the observer's pupil is substantially positioned at the position of the exit pupil. In an observation optical system that allows an observer to view an enlarged virtual image of the original image,
The observation optical system has an optical element having at least three optical action surfaces: a first surface acting as a refracting surface, a second surface acting as a reflecting surface, a total reflection surface, and a third surface acting as a refracting surface. When it has placed a condensing lens between the display means and the optical element,
The light beam from the original image is incident on the optical element from the first surface via the condenser lens, passes through the reflection on the second surface and the total reflection on the third surface. The optical element is emitted from the third surface , and an intermediate image of the original image is formed as a real image in the optical element .
When a light beam that exits from the center of the display surface of the display means and passes through the center of the exit pupil is used as a reference light beam, the optical element has a surface on which the reference light beam is reflected twice . at least partially overlaps the reflecting part of the light beam from the reflective portion and the second of the original image of the light beam from the first of the original image in this plane, is in and curved surface decentered with respect to the reference ray An observation optical system characterized by that.

The observation optical system according to claim 1, wherein the condensing lens has a curved surface arranged eccentrically with respect to the reference light beam.

The observation optical system according to claim 2, wherein the curved surface that is decentered with respect to the reference beam by the condenser lens is a transmission surface.

The observation optical system according to claim 1, wherein the condensing lens collects a light beam from the original image and makes it incident on the optical element.

The intermediate image is formed on a light beam reflected between optical surfaces constituting the optical element, and the light beam forming the intermediate image is reflected again between optical surfaces constituting the optical element. The observation optical system according to any one of claims 1 to 4, wherein the observation optical system traverses an image.

The light flux from the original image is transmitted through the first surface and incident on the optical element, and then directed reflected by said second surface to the third surface, and total reflected by the third surface Te directed to said second side, and again reflected by the second surface directed to said third surface, is guided in the third the exit pupil is transmitted through the surface and exit the optical element ,
α is the inclination angle of the reference ray with respect to the surface normal at the incident point when the reference ray is refracted by the third surface , and β is the second reflection of the reference ray on the second surface . When the inclination angle of the reference ray with respect to the surface normal at the incident point,
The following conditional expression:
Any one of the observation optical system of claims 1 to 5, characterized by satisfying 30 ° ≦ 2β + α ≦ 90 ° -10 ° ≦ alpha ≦ 30゜Wo.

The light flux from the original image is transmitted through the first surface and incident on the optical element, and then directed reflected by said second surface to the third surface, and total reflected by the third surface Te directed to said second side, and again reflected by the second surface directed to said third surface, is guided in the third the exit pupil is transmitted through the surface and exit the optical element ,
rc is the radius of curvature of the vertical cross section of the second surface at the point of incidence when the reference beam is reflected for the first time on the second surface , and ra is the second time the reference beam is reflected on the second surface . As the radius of curvature of the vertical cross section of the second surface at the incident point at the time of reflection, the following conditional expression:
0 <| ra / rc | <1.5
The observation optical system according to any one of claims 1 to 6 , wherein:

8. An image display device comprising: the observation optical system according to claim 1 ; and a support unit for mounting the observation optical system on an observer's head, wherein the relay optical system of the observation optical system supports the support. An image display device is mounted on the observer's head so that the optical element of the observation optical system is below the support and below the support.

8. An image display device, wherein the observation optical systems according to claim 1 are arranged one by one corresponding to the left and right eyes of the observer.