JP3870071B2 - Image display device and imaging device - Google Patents

Description

【０１２６】
ＴＹＰの欄でＦＦＳの横に記された数値は、その面の形状が同表の下側に記載された非球面係数ｋおよびｃｉ（ｉ＝２，３，４…）に対応する回転非対称形状であることを示している。
【０１２７】
また、面形状は他の式で定義してもよく、ＴＹＰの項にＸＹＰとあるのは、以下の式に従う回転非対称面である。
【０１２８】
【数２】

【０１２９】
ＴＹＰの欄でＦＦＳ並びにＸＹＰの横に記された数値は、その面の形状が同表の下側に記載された非球面係数ｋおよびｃｉ（ｉ＝１，２，３…）に対応する回転非対称形状であることを示している。
【０１３０】
尚、いずれの場合も表中に示されていないｃｉの項については、その係数の値が０である。
【０１３１】
Ｎｄ，νｄ（但し、表ではｖｄと記す）はそれぞれ、その面以降の媒質のｄ線波長での屈折率とアッベ数を示しており、屈折率Ｎｄの符号の変化はその面で光が反射されることを示している。また、媒質が空気層の場合は、屈折率Ｎｄのみを１．０００として表示し、アッベ数νｄは省略している。以上の表の項目説明は、以降の数値実施例においても同様である。
【０１３２】
【表１】

【０１３３】
表１から分かるように、画像表示面ＳＩからの光は、レンズ２１の面Ｓ１０，Ｓ９を通過して第２の光学素子２に向かう。第２の光学素子２に向かった光は、面Ｓ８から第２の光学素子２に入射し、第２の光学素子２と第１の光学素子１との接合面Ｓ７を透過して第１の光学素子１に入射し、Ｓ６で全反射し、反射膜を施したＳ５で裏面反射して折り返され、Ｓ４で全反射し、Ｓ３で裏面反射し、Ｓ２を透過して第１の光学素子１を射出し、光学系の射出瞳Ｓ１に導かれる。
【０１３４】
本数値実施例１の長さのディメンジョンを有する数値をｍｍとして考えると、射出瞳径φ６ｍｍ、画像表示サイズ１０ｍｍ×７．５ｍｍ程度で水平約５０°，垂直約３９°の画角で画像をｚ軸の正方向無限遠方に表示する表示光学系となる。
【０１３５】
なお、本数値実施例の光学系を撮像光学系に利用してもよい。この場合、ｚ軸負方向無限遠方の物点からの光は、絞りＳ１を通過して第１の光学素子１に導かれ、Ｓ２から第１の光学素子１に入射し、Ｓ３で反射し、Ｓ４で反射し、Ｓ５で折り返し反射し、Ｓ６で反射した後、Ｓ７から射出して第２の光学素子２に導かれる。
【０１３６】
第２の光学素子２に導かれた光は、Ｓ８から第２の光学素子２を射出し、レンズ２１に面Ｓ９から入射し、Ｓ１０から射出して撮像面ＳＩに結像する。
【０１３７】
本数値実施例の構成によれば、小型で広表示画角の表示光学系を達成できる。特に、本数値実施例では、第２の光学素子２と画像表示面ＳＩとの間にレンズ２１を設けてリレー光学系部分の光学的パワーをより多くの光学面で分担し、収差の発生を抑えているため、第１実施形態で示した構成に対して光学性能を高めることができる。
【０１３８】
［数値実施例２］
図９には、図７に示した第４実施形態に類似の構成を有する数値実施例の光路断面図を示している。図中、１１は第１の光学素子であり、３つの光学面を有したプリズム形状の透明体により構成されている。Ｓ２，Ｓ４，Ｓ６，Ｓ８は同一面、Ｓ３，Ｓ９は同一面、Ｓ５，Ｓ７は同一面であり、これら３面はそれぞれ上記第４実施形態において説明した面Ａ，Ｂ，Ｃに相当する。
【０１３９】
１２’は第２の光学素子であり、ここでは第１の光学素子１１の面Ｂ（Ｓ３）と接合された射出面Ｓ９および入射面Ｓ１０を有したレンズ形状に形成されている。さらに、本数値実施例２においては、入射面Ｓ１２と射出面Ｓ１１を有したレンズ２１を有している。面Ａにおいて、折り返し反射面Ｓ６として使用される部位には反射膜が形成されている。ＳＩは画像表示面、Ｓ１は表示光学系の射出瞳Ｓである。
【０１４０】
これらＳ１からＳ１２までの光学面は全て回転非対称面であり、紙面（ｙｚ断面）を唯一の対称面として持つ面対称形状を有する。
【０１４１】
なお、図中のｘ，ｙ，ｚは観察者の視軸方向をｚ軸，紙面内でｚ軸に垂直な方向をｙ軸，紙面に垂直な方向をｘ軸とした座標系定義である。
【０１４２】
本数値実施例２の光学データを表２に示す。
【０１４３】
【表２】

【０１４４】
表２から分かるように、画像表示面ＳＩからの光は、レンズ２１の面Ｓ１２，Ｓ１１を通過して第２の光学素子１２’に向かう。第２の光学素子１２’に向かった光は、面Ｓ１０から第２の光学素子１２’に入射し、第２の光学素子１２’と第１の光学素子１１との接合面Ｓ９より第１の光学素子１１に入射し、Ｓ８で全反射し、反射膜を施したＳ７で裏面反射し、面Ａの反射膜形成部に相当する面Ｓ６にて略垂直反射して折り返され、反射膜を施したＳ５で裏面反射し、Ｓ４で全反射し、Ｓ３で裏面反射されてＳ２から第１の光学素子１１を射出し、光学系の射出瞳Ｓ１に導かれる。
【０１４５】
本数値実施例２の長さのディメンジョンを有する数値をｍｍとして考えると、射出瞳径φ６ｍｍ、画像表示サイズ１０ｍｍ×７．５ｍｍ程度で水平約５０°，垂直約３９°の画角で画像をｚ軸の正方向無限遠方に表示する表示光学系となる。
【０１４６】
なお、本数値実施例の光学系を撮像光学系に利用してもよい。この場合、ｚ軸負方向無限遠方の物点からの光は、絞りＳ１を通過して第１の光学素子１１に導かれ、Ｓ２から第１の光学素子１１に入射して、Ｓ３，Ｓ４，Ｓ５で反射し、Ｓ６で折り返し反射して、Ｓ７，Ｓ８で反射した後、Ｓ９から射出して第２の光学素子１２’に導かれる。
【０１４７】
第２の光学素子１２’に導かれた光は、Ｓ１０から第２の光学素子１２’を射出し、レンズ２１に面Ｓ１１から入射し、Ｓ１２から射出して撮像面ＳＩに結像する。
【０１４８】
本数値実施例の構成によれば、小型で広表示画角の表示光学系を実現することができる。また、本数値実施例でも、数値実施例１と同様に、第２の光学素子１２’と画像表示面ＳＩとの間にレンズ２１を設けてリレー光学系部分の光学的パワーをより多くの光学面で分担し、収差の発生を抑えているため、高い光学性能を得易い。
【０１４９】
また、数値実施例１に比べて、第１の光学素子１１内での往復光路を形成するための反射回数を増やしているため、より光路長を有効に重複させて、長い光路長に対して表示光学系をコンパクト化させることができる。
【０１５０】
［数値実施例３］
図１０には、図７に示した第４実施形態の数値実施例の光路断面図を示している。図中、１１は第１の光学素子であり、３つの光学面を有したプリズム形状の透明体により構成されている。Ｓ２，Ｓ４，Ｓ６，Ｓ８は同一面、Ｓ３，Ｓ９は同一面、Ｓ５，Ｓ７は同一面であり、これら３面はそれぞれ上記第４実施形態において説明した面Ａ，Ｂ，Ｃに相当する。
【０１５１】
１２は第２の光学素子であり、ここでは第１の光学素子１１の面Ｂ（Ｓ３）と接合された射出面Ｓ９、反射面Ｓ１０および入射面Ｓ１１を有したプリズム形状の透明体により形成されている。面Ａの上部と面Ｃには反射膜が形成されている。ＳＩは画像表示面、Ｓ１は表示光学系の射出瞳Ｓである。
【０１５２】
これらＳ１からＳ１１までの光学面は全て回転非対称面であり、紙面（ｙｚ断面）を唯一の対称面として持つ面対称形状を有する。
【０１５３】
なお、図中のｘ，ｙ，ｚは観察者の視軸方向をｚ軸，紙面内でｚ軸に垂直な方向をｙ軸，紙面に垂直な方向をｘ軸とした座標系定義である。
【０１５４】
本数値実施例３の光学データを表３に示す。
【０１５５】
【表３】

【０１５６】
表３から分かるように、画像表示面ＳＩからの光は、面Ｓ１１から第２の光学素子１２に入射し、面Ｓ１０で反射して第２の光学素子１２と第１の光学素子１１との接合面Ｓ９より第１の光学素子１１に入射し、Ｓ８で全反射し、反射膜を施したＳ７で裏面反射し、面Ａの反射膜形成部に相当する面Ｓ６にて略垂直反射して折り返され、反射膜を施したＳ５で裏面反射し、Ｓ４で全反射し、Ｓ３で裏面反射されてＳ２から第１の光学素子１１を射出し、光学系の射出瞳Ｓ１に導かれる。
【０１５７】
本数値実施例の長さのディメンジョンを有する数値をｍｍとして考えると、射出瞳径φ６ｍｍ、画像表示サイズ１０ｍｍ×７．５ｍｍ程度で水平約５０°，垂直約３９°の画角で画像をｚ軸の正方向無限遠方に表示する表示光学系となる。
【０１５８】
なお、本数値実施例の光学系を撮像光学系に利用してもよい。この場合、ｚ軸負方向無限遠方の物点からの光は、絞りＳ１を通過して第１の光学素子１１に導かれ、Ｓ２から第１の光学素子１１に入射して、Ｓ３，Ｓ４，Ｓ５で反射し、Ｓ６で折り返し反射して、Ｓ７，Ｓ８で反射した後、Ｓ９から射出して第２の光学素子１２に導かれる。
【０１５９】
第２の光学素子１２に導かれた光は、Ｓ１０で反射してＳ１１から第２の光学素子１２を射出し、撮像面ＳＩに結像する。
【０１６０】
本数値実施例の構成によれば、小型で広表示画角の表示光学系を実現できる。また、本数値実施例では、第２光学素子１２としてプリズム状の光学素子を用い、裏面反射により光路を折り曲げているため、第２光学素子１２を数値実施例１，２に比べてより薄型化させることができる。
【０１６１】
［数値実施例４］
図１１には、図７に示した第４実施形態に類似の構成を有する数値実施例の光路断面図を示している。図中、１１は第１の光学素子であり、３つの光学面を有したプリズム形状の透明体により構成されている。Ｓ２，Ｓ４，Ｓ６，Ｓ８は同一面、Ｓ３，Ｓ９は同一面、Ｓ５，Ｓ７は同一面であり、これら３面はそれぞれ上記第４実施形態において説明した面Ａ，Ｂ，Ｃに相当する。
【０１６２】
１２”は第２の光学素子であり、ここでは第１の光学素子１１の面Ｂ（Ｓ３）と接合された射出面Ｓ９、反射面Ｓ１１および反射面兼入射面Ｓ１０（Ｓ１２と同一面）を有したプリズム形状の透明体により形成されている。面Ａの上部と面Ｃと面Ｓ１１には反射膜が形成されている。ＳＩは画像表示面、Ｓ１は表示光学系の射出瞳Ｓである。
【０１６３】
これらＳ１からＳ１２までの光学面は全て回転非対称面であり、紙面（ｙｚ断面）を唯一の対称面として持つ面対称形状を有する。
【０１６４】
なお、図中のｘ，ｙ，ｚは観察者の視軸方向をｚ軸，紙面内でｚ軸に垂直な方向をｙ軸，紙面に垂直な方向をｘ軸とした座標系定義である。
【０１６５】
本数値実施例４の光学データを表４に示す。
【０１６６】
【表４】

【０１６７】
表４から分かるように、画像表示面ＳＩからの光は、面Ｓ１２から第２の光学素子１２”に入射し、面Ｓ１１，Ｓ１０で反射して第１の光学素子１１との接合面Ｓ９に向かう。面Ｓ９から第１の光学素子１１に入射した光は、Ｓ８で全反射し、反射膜を施したＳ７で裏面反射し、面Ａの反射膜形成部に相当する面Ｓ６にて略垂直反射して折り返され、反射膜を施したＳ５で裏面反射し、Ｓ４で全反射し、Ｓ３で裏面反射されてＳ２から第１の光学素子１１を射出し、光学系の射出瞳Ｓ１に導かれる。
【０１６８】
本数値実施例の長さのディメンジョンを有する数値をｍｍとして考えると、射出瞳径φ４ｍｍ、画像表示サイズ１０ｍｍ×７．５ｍｍ程度で水平約５０°，垂直約３９°の画角で画像をｚ軸の正方向無限遠方に表示する表示光学系となる。
【０１６９】
なお、本数値実施例の光学系を撮像光学系に利用してもよい。この場合、ｚ軸負方向無限遠方の物点からの光は、絞りＳ１を通過して第１の光学素子１１に導かれ、Ｓ２から第１の光学素子１１に入射して、Ｓ３，Ｓ４，Ｓ５で反射し、Ｓ６で折り返し反射して、Ｓ７，Ｓ８で反射した後、Ｓ９から射出して第２の光学素子１２”に導かれる。
【０１７０】
第２の光学素子１２”に導かれた光は、Ｓ１０，Ｓ１１で反射してＳ１２から第２の光学素子１２”を射出し、撮像面ＳＩに結像する。
【０１７１】
本数値実施例の構成によれば、小型で広表示画角の表示光学系を実現することができる。また、本数値実施例では、第２の光学素子１２”としてプリズム状の光学素子を用い、２回の裏面反射により光路を折り曲げているため、第２の光学素子１２”を数値実施例１，２，３に比べてさらに薄型化させることができる。
【０１７２】
【発明の効果】
以上説明したように、本願第１の発明によれば、第１の光学素子において、第１、第２および第３の面の間で光を略往復させて光路を重複させるようにしているので、小型の光学系でありながらも光路長を長く確保できる。このため、小型の原画を用いつつ広表示画角を達成でき、しかも第２の光学素子を含む表示光学系全体として小型化を図ることができる。
【０１７３】
そして、第１の光学素子の第３の面と第２の光学素子の射出面とを接合しているので、第１および第２の光学素子相互間の位置決めを容易にすることができるとともに、第１の光学素子への光の入射時における収差の発生を抑制することができ、さらには強固な光学系構造とすることができる。したがって、光学性能が高く、耐久性に優れた表示光学系を実現することが可能となる。
【０１７４】
なお、表示光学系（例えば、第１の光学素子）内で光を中間結像させるようにすれば、レイアウトの自由度が増え、原画を大画面表示させることができるとともに、光路長をかなり長くしても表示光学系を小型に構成することができる。
【０１７５】
また、本願第２の発明によれば、第１の光学素子において、第１、第２および第３の面の間で光を略往復させて光路を折り畳むようにしているので、小型の光学系でありながらも光路長を長く確保できる。このため、第２の光学素子を含む撮像光学系全体として小型でありながらも広撮影画角を達成することができる。
【０１７６】
そして、第１の光学素子の第３の面と第２の光学素子の射出面とを接合しているので、第１および第２の光学素子相互間の位置決めを容易にすることができるとともに、第１の光学素子からの光の射出時における収差の発生を抑制することができ、さらには強固な光学系構造とすることができる。したがって、光学性能が高く、耐久性に優れた撮像光学系を実現することができる。
【０１７７】
なお、撮像光学系（例えば、第１の光学素子）内で光を中間結像させるようにすれば、レイアウトの自由度が増え、広画角の被写体像を十分縮小して撮像面に導くことができるとともに、光路長をかなり長くしても撮像光学系を小型に構成することができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態である表示光学系の構成図。
【図２】上記第１実施形態である表示光学系の構成図。
【図３】上記第１実施形態である表示光学系の構成図。
【図４】本発明の第２実施形態である撮像光学系の構成図。
【図５】本発明の第３実施形態である表示光学系（１）の構成図。
【図６】本発明の第３実施形態である表示光学系（２）の構成図。
【図７】上記第４実施形態である表示光学系の構成図。
【図８】本発明の数値実施例１の光学系断面図。
【図９】本発明の数値実施例２の光学系断面図。
【図１０】本発明の数値実施例３の光学系断面図。
【図１１】本発明の数値実施例４の光学系断面図。
【図１２】従来の表示光学系の構成図。
【図１３】従来の表示光学系の構成図。
【符号の説明】
１，１’，１”，１１ 第１の光学素子
２，１２，１２’，１２” 第２の光学素子
３ 画像表示素子
４ 撮像素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display optical system suitable for an image display apparatus such as a head-mounted display or a projector that enlarges an original image displayed on an image display element or the like, and an imaging optical system suitable for an imaging apparatus.
[0002]
[Prior art]
2. Description of the Related Art Head-mounted image display devices (head-mounted displays) that use image display elements such as CRTs and LCDs and display enlarged images displayed on these display elements via an optical system are well known.
[0003]
In the image display device such as the head-mounted display, since these devices are mounted on the head, it is particularly required to reduce the size and weight of the entire device. In consideration of weight balance, appearance, etc., it is preferable that the viewer is thin in the visual axis direction of the observer. Furthermore, in order to give the magnified image to be displayed powerful, a magnified image that is as large as possible is desired.
[0004]
FIG. 12 shows an image display device using a conventional coaxial concave mirror. In this apparatus, a light beam from an image displayed on the display element 101 is reflected by the half mirror 102 and incident on the concave mirror 103, and the light beam reflected by the concave mirror 103 is guided to the eye E of the observer via the half mirror 102. Yes. The image displayed on the display element 101 is formed as a virtual image enlarged by the concave mirror 103. Thereby, the observer can observe the enlarged virtual image of the image displayed on the display element 101.
[0005]
Further, for example, in JP-A-7-333551, JP-A-8-50256, JP-A-8-160340, and JP-A-8-179238, an LCD (liquid crystal) as an image display element for displaying an image is disclosed. ) And a thin prism as an observation optical system, and an image display device in which the entire device is thinned has been proposed.
[0006]
FIG. 13 shows an image display device proposed in Japanese Patent Laid-Open No. 7-333551. In this device, the light emitted from the LCD 111 is incident on the incident surface 113 of the small eccentric prism 112. Then, the light flux is folded between the total reflection surface 114 having the curvature formed on the prism 112 and the reflection surface 115, and then emerges from the eccentric prism 112 through the surface 114 and guided to the eye E of the observer. As a result, a virtual image of the image displayed on the display element (LCD) 111 is formed, and the observer observes this virtual image.
[0007]
The reflecting surface 115 of the decentered prism 112 is composed of a decentered free-form surface composed of decentered non-rotationally symmetric surfaces (surfaces having different optical power depending on the azimuth angle, so-called free-form surfaces).
[0008]
The type of the optical system shown in FIG. 13 has the characteristics that the entire apparatus is thinner and the observation field of view is easier than the type using the conventional coaxial concave mirror shown in FIG. Yes.
[0009]
[Problems to be solved by the invention]
In recent years, LCDs and the like, which are display elements for displaying images, have been improved in definition, and LCDs and the like that have the same number of pixels as the conventional ones but have been reduced in size have been developed. Use of such a miniaturized image display element is advantageous for miniaturization of the apparatus, but it is necessary to increase the magnification of the optical system in order to achieve the same angle of view as in the prior art.
[0010]
In view of such a situation, Japanese Patent Application Laid-Open No. 10-153748 discloses that an eccentric prism and a relay lens system are combined, and an intermediate image is once formed by the relay lens system, and then an image displayed on the display element is viewed by an observer. An optical system leading to the above has been proposed. Thereby, while having the feature of a thin type of the type shown in FIG. 13, the magnification is further improved and a wide angle of view is achieved with respect to the LCD size.
[0011]
Further, as a further improvement in optical performance compared with the optical system proposed in Japanese Patent Laid-Open No. 10-153748, the internal reflection surface of the decentered prism is increased and an intermediate image is formed only by the decentered prism. A type in which the image is guided to an observer, a type in which a second decentered prism is provided in the first decentered prism optical system, and the like are disclosed in JP-A-2000-0666106, JP-A-2000-105338, and JP-A-2000. -131614, JP-A 2000-199853, JP-A 2000-227554, and JP-A 2000-23310.
[0012]
In general, optical systems of the type that once form an intermediate image have a problem that the optical path length becomes long and the apparatus becomes large. However, even in the optical systems proposed in these publications, the transmission and reflection functions are also included. It aims at miniaturization by using a dual-purpose surface that fulfills the above, or by crossing the optical path.
[0013]
SUMMARY OF THE INVENTION An object of the present invention is to provide a small display optical system that can achieve a wide display angle of view while using a small display element, and a small image pickup optical system that can achieve a wide shooting angle of view.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, in the first invention of the present application, Image display element and image display element formed Display optical system that guides the light from the original image to the eyes or projection surface of the observer Image display device having In The display optical system At least a first surface having a reflective action, reflected by the first surface From the original A second surface that reflects light back to the first surface and transmits light from the original to the first surface Do And a first optical element having a third surface that reflects the light reflected back from the second surface to the first surface and guides it to the eyes of the observer or the projection surface, and the light from the original image as described above A second optical element guided to the third surface, and joining the third surface and the emission surface of the second optical element In addition, the first optical element is incident on the first surface again at the reflection angle with respect to the normal at the hit point of the central field angle chief ray first incident on the first surface, and reflected on the second surface again. The reflection angle with respect to the normal at the hit point of the principal ray with the central angle of view is opposite to that of the normal, and an intermediate image of the original image is formed in the first optical element. is doing.
[0015]
That is, in the first optical element, a long optical path length can be accommodated in a small optical system by causing light to reciprocate substantially between the first, second, and third surfaces to substantially overlap the optical path. I can do it. For this reason, the entire display optical system including the second optical element can be reduced in size.
[0016]
Then, by joining the third surface of the first optical element and the emission surface of the second optical element, positioning between the first and second optical elements is facilitated, and the first optical element It is possible to suppress the occurrence of aberration when light is incident on the element, and to realize a display optical system with high optical performance and excellent durability as a robust optical system structure.
[0017]
The first optical element has a reflection angle with respect to the normal at the hit point of the central field angle chief ray first incident on the first surface, is reflected by the second surface, and is incident again on the first surface. The reflection angle with respect to the normal line at the hit point of the central field angle chief ray is configured to have an opposite sign. That is, the light reflected by the first surface is reflected by the second surface so as to return to the reflective region side (the reflective region, the vicinity of the reflective region, or the region near the reflective region) of the first light on the first surface. By effectively overlapping the optical paths, the long optical path length is stored in a small optical system.
[0018]
Also, an intermediate image of the original image is formed in the display optical system (for example, the first optical element). is doing . That is, by using an intermediate imaging type that forms a small real image and enlarges and displays it, the degree of freedom in optical design is increased and the original image can be displayed on a large screen.
[0019]
Further, by decentering the optical surfaces of the first optical element and the second optical element with respect to the light beam reflected on the surfaces, it is possible to further reduce the thickness and to provide the optical surface with a curvature. It is possible to reduce the size by removing unnecessary surfaces in the display optical system. In addition, various aberrations can be corrected satisfactorily by using a rotationally asymmetric surface (free curved surface) as the optical surface. By adopting multiple rotationally asymmetric surfaces (free curved surfaces), the aspect ratio of the original image and the aspect ratio of the displayed image Can be made close to each other, and a high-quality display image can be obtained.
[0020]
This display optical system is a projection-type image display device (projector) that projects an image on a projection surface such as a head-mounted display (HMD) or a screen for an observer to wear on the head and observe an image. It is suitable for an image display device such as
[0021]
In the second invention of the present application, An image sensor; The light from the subject Of the image sensor Imaging optical system leading to the imaging surface Imaging device having In The imaging optical system At least a first surface having a reflective action, reflected by the first surface From the subject From the second surface and the subject that reflects light so that it returns to the first light reflection area side (reflection area, near the reflection area, or near the reflection area) on the first surface The light of On the first side Towards A first optical element having a third surface that reflects and transmits the reflected light returned from the second surface to the first surface to the imaging surface side, and imaging light from the third surface. A second optical element that leads to the first optical element, and joins the third surface and the incident surface of the second optical element In addition, the first optical element is incident on the first surface again at the reflection angle with respect to the normal at the hit point of the central field angle chief ray first incident on the first surface, and reflected on the second surface again. The reflection angle with respect to the normal at the hit point of the principal ray with the central angle of view is opposite to the sign, and an intermediate image of the subject is formed in the first optical element. is doing.
[0022]
That is, in the first optical element, a long optical path length can be accommodated in a small optical system by substantially reciprocating light between the first, second, and third surfaces to substantially overlap the optical path. I am doing so. For this reason, it is possible to achieve downsizing of the entire imaging optical system including the second optical element.
[0023]
Then, by joining the third surface of the first optical element and the emission surface of the second optical element, positioning between the first and second optical elements is facilitated, and the first optical element It is possible to realize an imaging optical system that suppresses the occurrence of aberration when light is emitted from the element and has a high optical performance and excellent durability as a robust optical system structure.
[0024]
In the imaging optical system (for example, the first optical element) An intermediate image of the subject is formed . In other words, by adopting an intermediate imaging type that reduces the intermediate imaging surface of the subject and leads it to the imaging surface, the degree of freedom in layout increases, and a wide-angle subject image can be sufficiently reduced and guided to the imaging surface. In addition, the imaging optical system can be made compact even if the optical path length is considerably increased.
[0025]
Further, by decentering the optical surface constituting the imaging optical system with respect to the light beam reflected on the surface, it is possible to further reduce the thickness, and by providing the optical surface with a curvature, it is unnecessary in the imaging optical system. Therefore, it is possible to reduce the size. Furthermore, by making the optical surface a rotationally asymmetric surface (free curved surface), various aberrations can be corrected satisfactorily. When multiple rotationally asymmetric surfaces (free curved surfaces) are used, the aspect ratio of the subject and the aspect ratio of the captured image can be reduced. It becomes possible to make it close, and it becomes possible to obtain a high-quality captured image.
[0026]
This imaging optical system is suitable for an imaging apparatus such as a digital still camera or a video camera.
[0027]
In the first and second aspects of the invention, it is possible to reduce the light amount loss by totally reflecting light with the optical surface on the optical element.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Prior to describing the embodiment of the present invention, the definitions of the bus bar cross section, the bus bar cross section, the local bus bar cross section, and the local bus bar cross section used in the present embodiment will be described.
[0029]
In the definition of the conventional system that does not correspond to the eccentric system, if the z-axis is the optical axis in each surface vertex coordinate system, the yz section is the conventional generatrix section (meridional section), and the xz section is the child section (sagittal section). Become.
[0030]
Since the optical system of the present embodiment is an eccentric system, a local bus cross section and a local sub cross section corresponding to the eccentric system are newly defined.
[0031]
Central field angle chief ray (in the display optical system, this is a light ray that extends from the center of the effective display area of the image display surface of the display element to the exit pupil center of the display optical system. In the imaging optical system, it passes through the entrance pupil center of the imaging optical system. This is a ray that reaches the center of the effective imaging area of the imaging surface of the image sensor) and the hit point between each surface and the surface containing the incident light and the emitted light of the central field angle chief ray is the local bus cross section and includes the hit point A plane perpendicular to the local bus cross section and parallel to the child cross section (normal child cross section) of each surface vertex coordinate system is defined as a local sub cross section.
[0032]
(First embodiment)
FIG. 1 shows a display optical system according to the first embodiment of the present invention. This display optical system includes a first optical element 1 and a second optical element 2.
[0033]
The first optical element 1 is composed of a prism-like transparent body in which three optical surfaces, surface A, surface B, and surface C, are formed on a medium having a refractive index n1, such as glass or plastic. The second optical element 2 is made of a lens-like transparent body in which two optical surfaces, a surface D and a surface E, are formed on a medium having a refractive index n2. An image display element 3 is a transmissive or reflective LCD or the like.
[0034]
In the first optical element 1, the surface A (first surface) and the surface B (third surface) are both transmissive and reflective surfaces that function as a transmissive surface and a reflective surface, and a surface C (second surface). Is a reflective surface.
[0035]
In the second optical element 2, both the surface D and the surface E are transmission surfaces. In the present embodiment, the surface B of the first optical element 1 and the surface D of the second optical element 2 are joined, and the first optical element 1 and the second optical element 2 are integrated. Yes.
[0036]
A reflective film is formed on the surface C, and a semi-transmissive reflective film (half mirror) is formed on at least one of the surface B and the surface D.
[0037]
The reflective film and the half mirror are preferably made of a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is hardly noticeable, and there is almost no difference in reflectance with respect to light having different deflection directions.
[0038]
Further, a part (upper part) of the surface A acts as a reflective surface by utilizing a reflective film, semi-transmissive reflective film formation, or internal total reflection.
[0039]
With this configuration, the surface B functions as the incident surface and the reflecting surface of the first optical element 1, the surface C functions as the reflecting surface, and the surface A functions as the reflecting surface and the exit surface of the first optical element 1. . Further, the surface E functions as an incident surface of the second optical element 2, and the surface D functions as an exit surface of the second optical element 2.
[0040]
The first Optical element 1 Each of the transparent bodies of the second optical element 2 has a refractive power, and has at least one optical surface having a curvature.
[0041]
Light emitted from the image display surface modulated by the image display element 3 enters the second optical element 2 from the surface E of the second optical element 2, and the surface B which is the incident surface of the first optical element 1. The second optical element 2 is emitted from the joined surface D.
[0042]
The light passes through the surface B, enters the first optical element 1, is reflected by the surface A, and is guided to the surface C. The light reflected by the surface A is reflected by the surface C so as to return to a direction substantially opposite to the incident direction. As a result, the light is returned to the vicinity of the first light reflection region on the surface A, reflected again, reflected by the half mirror joint surface B, then transmitted through the surface A, and emitted from the first optical element 1. The pupil S is reached.
[0043]
In the present embodiment, when an observer places his / her eyes near the position of the exit pupil S, the image is displayed on the image display element 3 by the observer whose direction of incidence on the pupil is the central field angle chief ray. A magnified image of the recorded image is visually recognized.
[0044]
FIG. 1 shows a central field angle principal ray that emerges from the center of the image display surface of the image display element 3 as light emitted from the image display element 3 and reaches the center of the exit pupil S. An optical cross section in the plane formed by the rays is shown.
[0045]
In the first optical element 1, light passes through each surface in the order of surface B → surface A → surface C → surface A → surface B (→ surface A), and the optical path up to that point with reflection on the surface C as a boundary. Follow in reverse.
[0046]
Here, the path from plane B to plane A to plane C is referred to as the forward path, the optical path from plane C to plane A to plane B is referred to as the return path, and the forward path and return path are collectively referred to as the reciprocal optical path. Reflecting light in the reverse direction from the forward path to the return path in order to form such a reciprocating optical path is called a return reflection, and corresponds to a return point between the forward path and the return path, and has a return reflection function. (Here, surface C) is referred to as a folded reflection surface.
[0047]
As described above, the surface C is used as a reflection reflecting surface, and a reciprocating optical path is formed in the first optical element 1 so as to overlap the optical path, and the inside of the first optical element 1 is effectively used to increase the optical path length. On the other hand, the size of the first optical element 1 can be reduced. Thereby, the entire display optical system including the second optical element 2 is downsized.
[0048]
That is, in the present embodiment, the forward path, which is the optical path to reach the folded reflection surface C in the first optical element 1, and the return path, which is the optical path after being reflected by the folded reflection surface C, are surfaces A, The two surfaces of B are shared, and the two surfaces are used in the reverse order for the forward path and the return path to form a round-trip optical path.
[0049]
As described above, even if the optical system has a long optical path length by forming a reciprocating optical path using at least two surfaces before and after the return reflection at the surface C to increase the degree of overlap of the optical paths, Realizes a compact optical system that keeps the overall length of the camera short.
[0050]
2 and FIG. 3 are a diagram showing a maximum field angle chief ray and a marginal ray having a central field angle in the same cross section as FIG. 1 in the present embodiment, respectively.
[0051]
As indicated by the dotted line in FIG. 2, the light (maximum field angle principal ray) that exits the edge of the image display surface of the image display element 3 and reaches the center of the exit pupil S is the same as the center field angle principal ray. The light is guided to the first optical element 1 through the second optical element 2, and passes through the B pupil incidence → A plane reflection → C plane return reflection → A plane reflection → B plane reflection → A plane exit in this order. Led to the center of the.
[0052]
Further, as indicated by a chain line in FIG. 3, a light ray (marginal light ray) that exits from the center of the image display surface of the image display element 3 and reaches both ends of the exit pupil S is also similar to the central field angle principal ray. Second optical element 2 Then, the light is guided to the first optical element 1 and guided to both ends of the exit pupil S through B surface incidence → A surface reflection → C surface folding reflection → A surface reflection → B surface reflection → A surface emission in this order.
[0053]
At this time, marginal rays intersect in the first optical element 1, and an intermediate image of the image displayed on the image display element 3 is formed in the vicinity of the intermediate image plane shown in the drawing.
[0054]
Thus, by forming an intermediate image in the first optical element 1, the second optical element 2 can be made compact without extremely increasing the power of the second optical element 2. It is possible to suppress the generation of extra aberration in the second optical element 2 and to prevent the second optical element 2 from becoming complicated.
[0055]
In FIG. 3, the intermediate image is formed during the reflection from the A surface to the reflected reflection at the C surface, but the position of the intermediate image is not necessarily in this position, and is formed in the first optical element 1. It only has to be done.
[0056]
In this embodiment, the refraction at the surface E of the second optical element 2, the refraction at the surface where the surface D of the second optical element 2 and the surface B of the first optical element 1 are joined, and the surface A A relay optical system is formed by the reflection of. In addition, an eyepiece optical system is formed by folding reflection on the surface C, rereflection on the surface A, reflection on the surface B, and refraction on the surface A.
[0057]
In order to facilitate aberration correction of the eyepiece optical system, the intermediate image plane should be appropriately curved or have astigmatism according to the situation where field curvature or astigmatism occurs in the eyepiece optical system. It may be.
[0058]
The surfaces A and B of the first optical element 1 are inclined with respect to the reflected light beam when the effective light beam finally guided to the exit pupil S is reflected by each surface, and is reflected back. The forward path to the C-plane, that is, the B-plane incidence → A-plane reflection → C-plane optical path and the return path after the C-plane C-plane → A-plane reflection → B-plane reflection → A-plane emission optical path, The first optical element 1 is thinned as a configuration in which both are folded.
[0059]
In the configuration described above, the first optical element 1 preferably includes at least two surfaces including the surface B as curved surfaces. As a result, the number of surfaces that do not contribute to image formation or aberration correction can be reduced, the number of optical surfaces necessary for the entire optical system can be reduced, and an effect of reducing manufacturing costs can be expected.
[0060]
More desirably, the surfaces A, B, and C are each formed of a curved surface, whereby an effect of further reducing the manufacturing cost can be obtained. For the same reason, the optical surfaces D and E of the second optical element 2 are preferably curved surfaces.
[0061]
In the present embodiment, the surface B is a curved surface of at least one surface of the first optical element, and the surface B when acting as the final reflecting surface is a concave mirror having very strong optical power. Furthermore, the surface B is a reflecting surface having a very high degree of eccentricity with respect to the light beam after being reflected back by the surface C.
[0062]
That is, decentration aberrations occur on the concave mirror surface B. Therefore, it is desirable to correct the occurrence of decentration aberrations by using a rotationally asymmetric surface (so-called free-form surface) on at least one surface of the first optical element 1.
[0063]
In particular, since the surface B is a curved surface having a strong optical power with respect to the surface A, it is preferable to suppress the occurrence of decentration aberration by making the surface B a rotationally asymmetric shape. Accordingly, the surface D of the second optical element 2 which is a joint surface with the surface B also has a rotationally asymmetric shape.
[0064]
More preferably, all the three surfaces A, B, and C constituting the first optical element 1 are rotationally asymmetrical, thereby increasing the degree of freedom in correcting decentration aberrations and enabling image display with good image quality. become.
[0065]
More preferably, the surfaces D and E constituting the second optical element 2 are both rotationally asymmetric surfaces.
[0066]
At this time, if each rotationally asymmetric surface has a shape that is plane-symmetric in the direction perpendicular to the plane of paper, with the cross-section of the plane of the drawing as the only plane of symmetry, processing and manufacture can be facilitated as compared to the case where there is no symmetry. Therefore, it is preferable.
[0067]
Further, it is preferable that the reflection on the surface A is the total reflection in the first optical element 1 because the light loss is reduced. Further, at least in the region where the reflected light beam and the emitted light beam are shared by the surface A, if the reflected light beam is totally reflected, the degree of freedom in design is increased compared to the case where all the reflected light beam is totally reflected. The same level of brightness can be secured.
[0068]
At this time, a reflection film is formed in an area where the reflected light beam on the surface A is not totally reflected, but the reflectance decreases as the boundary area between the total reflection part and the reflection part by the reflection film approaches the total reflection part. A smooth gradation reflecting film is preferable because it can suppress the phenomenon in which the boundary area is conspicuous due to the scattering in the boundary area and the difference in reflectance between the total reflection and the reflection by the reflection film.
[0069]
Further, as described above, since the surface B is an eccentric curved surface that is decentered with respect to the central field angle chief ray and has a strong condensing function, even when the surface B is used as a refracting surface, decentration aberrations (rotational asymmetry) are also obtained. Aberrations).
[0070]
For this reason, the first optical element 1 having a refractive index n1 (> 1) and the second optical element 2 having a refractive index n2 (> 1) are bonded to each other at the time of refractive transmission on the surface B (first optical element). It is preferable to have an effect of reducing the occurrence of decentration aberrations (when incident on 1).
[0071]
Specifically, the absolute value | n1-n2 | of the difference between n1 and n2 needs to be set smaller than n1-1 and n2-1. More preferably, by setting n1 = n2, it is possible to prevent the occurrence of decentration aberrations during transmission.
[0072]
In FIG. 1, nE and nB are the normal line at the hit point of the central field angle chief ray of the plane E and the normal line at the hit point of the central field angle chief ray of the plane B, respectively. The incident angle θ2 and the outgoing angle θ2 ′ of the central field angle chief ray on the incident surface E of the second optical element 2 are larger than the incident angle θ1 and the outgoing angle θ1 ′ of the first optical element 1 on the incident surface B. It is preferable to incline the surface E with respect to the surface B (surface D) so that the decentration aberration generated at the time of incidence on the second optical element 2 can be reduced.
[0073]
By configuring the display optical system as described above, it is possible to provide an image display device that displays an image displayed on the image display element 3 as an enlarged image with good optical performance.
[0074]
Further, by forming an image once in the display optical system, the degree of freedom in design is improved, and the display angle of view with respect to the display size of the image display element 3 can be increased (high magnification display). As a result, the optical path length is increased by forming a reciprocating optical path in the first optical element 1 so that the optical path is overlapped to reduce the total length of the first optical element 1 and form a very compact optical system. it can.
[0075]
Further, by joining the first optical element 1 and the second optical element 2, both optical elements 1 and 2 can be easily positioned, and decentration aberrations are generated when incident on the first optical element 1. As a strong optical system structure, it is possible to realize a display optical system with high optical performance and excellent durability.
[0076]
(Second Embodiment)
FIG. 4 shows the configuration of an imaging optical system that is the second embodiment of the present invention. This imaging optical system is composed of a first optical element 1 and a second optical element 2 similar to those in the first embodiment. Reference numeral 4 denotes an image sensor such as a CCD. S is an entrance pupil of the imaging optical system composed of the first optical element 1 and the second optical element 2, and a stop is placed at this position to prevent the incidence of unnecessary light.
[0077]
In the present embodiment, the surface A (first surface) functions as an incident surface and a reflective surface of the first optical element 1, and the surface B (third surface) is a reflective surface and an exit surface of the first optical element 1. The surface C (second surface) acts only as a reflecting surface of the first optical element 1.
[0078]
Further, the surface D functions as an incident surface of the second optical element 2, and the surface E functions as an exit surface of the second optical element 2. Then, the reflecting surface / exit surface B of the first optical element 1 and the incident surface D of the second optical element 2 are joined after a semi-transmissive reflective film (half mirror) is formed on at least one of them. .
[0079]
Light from the subject that has passed through the diaphragm S enters the first optical element 1 from the surface A, is reflected by the surface B, is reflected by the surface A, and is guided to the surface C. Then, the light is reflected back by the surface C, returned to the first light reflection region on the surface A, re-reflected by the surface A, transmitted through the surface B, and emitted from the first optical element 1. Here, the surface A and the surface B are decentered with respect to the light rays constituting the reflected light beam on the respective surfaces.
[0080]
The light emitted from the first optical element 1 passes through the second optical element 2 and reaches the imaging element 4. At this time, light from a desired external environment (subject) is imaged on the imaging surface of the image sensor 4, and thus an external image can be captured.
[0081]
By configuring the imaging optical system as described above, it is possible to provide an imaging apparatus that forms an image of a subject on the imaging element 4 with good optical performance.
[0082]
In addition, by performing intermediate image formation once in the first optical element 1, it is possible to widen the shooting angle of view with respect to the size of the image pickup element 4, and the optical path length is increased accordingly. By forming a reciprocating optical path in one optical system 1, the optical paths are folded so as to overlap each other, and the overall length of the first optical system 1 is kept short, thereby realizing a very compact imaging optical system.
[0083]
Further, by joining the first optical element 1 and the second optical element 2, both the optical elements 1 and 2 can be easily positioned and decentered when light is emitted from the first optical element 1. An imaging optical system that suppresses the generation of aberration and has a high optical performance and excellent durability as a robust optical system structure is realized.
[0084]
In the first and second embodiments described above, the central field angle chief ray (in the display optical system, a ray that extends from the center of the display surface of the image display element to the center of the exit pupil S, and incident in the imaging optical system). Although the reflected reflection on the surface C of the light beam passing through the center of the pupil and reaching the center of the imaging surface of the image sensor is depicted as being substantially vertical reflection, the optical system of the present invention is not limited to this configuration.
[0085]
(Third embodiment)
5 and 6 show a display optical system according to the third embodiment of the present invention. These display optical systems are examples in which first optical elements 1 ′ and 1 ″ different from the first optical element 1 of the first embodiment are used.
[0086]
6 and 7, the first optical element of the first embodiment is that an optical path of B surface incidence → A surface reflection → C surface folding reflection → A surface reflection → B surface reflection → A surface emission is formed. Same as 1.
[0087]
However, in the first optical element 1 ′ in FIG. 5, the central field angle principal ray reflected by the surface A is reflected back at an angle θ by the surface C and is higher than the first reflection point on the surface A. However, it is different from the first embodiment in that it is re-reflected in the region near the first light reflection region.
[0088]
Further, in the first optical element 1 ″ of FIG. 6, the central field angle principal ray reflected on the surface A is reflected back at an angle θ on the surface C and is lower than the first reflection point on the surface A. However, it is different from the first embodiment in that it is re-reflected in the region near the first light reflection region.
[0089]
In this way, the light may be incident / reflected at a predetermined angle θ before and after the folded reflection surface C. However, the angle θ is
| Θ | <30 °
It is preferable to satisfy.
[0090]
Exceeding this condition is not preferable because the first optical system becomes large and it becomes difficult to make the entire display optical system small.
[0091]
In the present embodiment, the display optical system having the first optical system has been described. However, the same idea as in the present embodiment can be applied to the imaging optical system as shown in the second embodiment. That is, the light beam may be incident / reflected at a predetermined angle θ (| θ | <30 °) before and after the return reflection at the return reflection surface C.
[0092]
(Fourth embodiment)
FIG. 7 shows the configuration of a display optical system that is the fourth embodiment of the present invention. This display optical system includes a first optical element 11 and a second optical element 12. An image display element 3 is a transmissive or reflective LCD or the like.
[0093]
Similar to the first optical element 1 of the first embodiment, the first optical element 11 has a prism-like shape in which three optical surfaces A, B and C are formed on a medium having a refractive index n1. The surface A and the surface B are made of a transparent body, and both are a transmissive / reflective surface acting as a transmissive surface and a reflective surface, and the surface C is a reflective surface. However, as will be described in detail later, in the present embodiment, the surface A is a surface having both functions of the first surface and the second surface. Surface B is a third surface as in the first embodiment.
[0094]
Further, a reflective film is formed on the surface C, and a semi-transmissive reflective film is formed on the surface B. In the present embodiment, a reflective film is also formed on part (upper part) of the surface A.
[0095]
On the other hand, the second optical element 12 is composed of a prism-like transparent body in which three optical surfaces of a surface D, a surface E, and a surface F are formed on a medium having a refractive index n2, and both the surface D and the surface E are transmission surfaces. The surface F is a surface acting as a reflecting surface. A reflective film is formed on the surface F.
[0096]
In the present embodiment, the surface E functions as the incident surface of the second optical element 12, the surface F functions as the reflecting surface of the second optical element 12, and the surface D functions as the exit surface of the second optical element 12. Further, the surface B functions as an incident surface and a reflection surface of the first optical element 11, the surface C functions as a reflection surface, and the surface A functions as a reflection surface and an emission surface of the first optical element 11.
[0097]
The light emitted after being modulated by the image display element 3 is incident on the second optical element 12 from the surface E, reflected by the surface F, and then emitted from the surface D joined to the surface B of the first optical element. Guided to the first optical element 11.
[0098]
The light passes through the surface B, enters the first optical element 11, is reflected by the surface A, is reflected by the surface C, and is guided to the upper part of the surface A. The light guided to the surface A is reflected almost perpendicularly on the surface A (folded reflection: second reflection) so as to return in a route reverse to the route that has been traced in the first optical element 11 so far. The light is reflected again by the surface C, returned to the first light reflection region on the surface A, re-reflected (third reflection), further reflected by the surface B, transmitted through the surface A, and emitted from the first optical element 11. Then, the exit pupil S is reached.
[0099]
When the observer puts his eyes near the position of the exit pupil S, an enlarged image of the image displayed on the image display element 3 can be visually recognized.
[0100]
In FIG. 7, as an example of light emitted from the image display element 3, a central field angle chief ray that emerges from the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown. An optical cross-section formed by the field angle chief ray is shown.
[0101]
Of the three reflections on the surface A, at least the first and third reflections, the reflection on the surface B, and the reflection on the surface C, each of these surfaces emits the image display element 3 and the exit pupil S. It acts as a decentered reflecting surface that is decentered with respect to an arbitrary light beam that forms an effective light beam reaching the above. Thereby, the optical path is changed to the first optical element. 11 The first optical element 11 has a thin configuration.
[0102]
In the present embodiment, the light passes through the first optical element 11 from the surface B (transmission) → surface A (reflection) → surface C (reflection) → surface A (folded reflection) → surface C (re-reflection) → surface. It passes through each surface in the order of A (re-reflection) → surface B (reflection) (→ surface A (transmission)), and the optical path up to that point reaches the final reflection surface B with the return reflection at the surface A as a boundary. Follow in reverse.
[0103]
That is, in the present embodiment, the optical path up to the return reflection surface A in the first optical element 11 and the optical path after being reflected by the return reflection surface A are the three surfaces A, B, and C. A round trip optical path is formed by overlapping in reverse order on the surface.
[0104]
Thus, the total length of the first optical element is obtained by forming a reciprocating optical path using three surfaces before and after reflection on the return reflection surface A, and further increasing the degree of overlap of the optical paths compared to the first embodiment. It is possible to realize a compact optical system in which
[0105]
In the present embodiment, the reflecting surface F is provided in the second optical element 12. As a result, the degree of freedom in forming the optical path is improved, the entire optical system is further reduced in thickness with respect to the first embodiment, and the optical working surface is increased so as to share the respective surfaces in the second optical element 12. Aberration power is weakened and aberrations are suppressed.
[0106]
Also in the present embodiment, by forming an intermediate image in the first optical element 11, it is possible to suppress the occurrence of extra aberrations. The intermediate image may be formed so as to be appropriately curved or have an astigmatic difference depending on the situation where field curvature or astigmatism occurs in the eyepiece optical system.
[0107]
In addition, by forming at least the surfaces B and C of the first optical element 11 as curved surfaces, the number of surfaces that do not contribute to image formation or aberration correction is reduced, and the number of surfaces necessary for the optical system is reduced.
[0108]
Furthermore, by configuring the surfaces A, B, and C as curved surfaces, it is possible to obtain an optical element that further eliminates the surface that does not contribute to image formation or aberration correction, and thus, an effect of cost reduction can be expected. For the same reason, the optical surfaces D, E, and F of the second optical element 12 are preferably curved surfaces.
[0109]
In addition, it is preferable to suppress the occurrence of decentration aberration by making the surface B a rotationally asymmetric shape. Therefore, the surface D which is a joint surface with the surface B also has a rotationally asymmetric shape.
[0110]
More preferably, all of the three surfaces A, B, and C constituting the first optical element 11 have a rotationally asymmetric shape, thereby increasing the degree of freedom in correcting decentration aberrations and enabling image display with good image quality. become.
[0111]
More preferably, the surfaces D, E, and F constituting the second optical element 12 are also rotationally asymmetric. At this time, if each rotationally asymmetric surface has a shape that is plane-symmetrical in the direction perpendicular to the plane of paper, with the cross-section of the plane of the figure as the only plane of symmetry, processing and production can be facilitated as compared to the case without symmetry. ,preferable.
Further, regarding the reflection other than the reflected reflection on the surface A, it is preferable that the reflection on the surface A is the total reflection in the first optical element 11 because the loss of light amount is reduced. Further, at least in a region where the reflected light beam and the emitted light beam are shared by the surface A (lower part of the surface A), if the reflected light beam is totally reflected, all the reflected light beams other than the reflected reflection on the surface A are totally reflected. Compared to the case, it is possible to secure the same level of brightness while increasing the degree of design freedom.
Further, as in the third embodiment, the light beam may be incident / reflected at a predetermined angle θ before and after the folded surface A. However, the angle θ is
| Θ | <30 °
It is preferable to satisfy. If this condition is not satisfied, the size of the first optical element 11 is increased, and it is difficult to reduce the size of the entire display optical system.
By configuring the display optical system as described above, it is possible to provide an image display device that displays an image displayed on the image display element 3 as an enlarged image with good optical performance.
[0112]
Further, by forming an image once in the display optical system, it is possible to widen the display angle of view (high magnification presentation) with respect to the display size of the image display element 3, and to increase the long optical path length to the first By forming a reciprocating optical path in the optical element 11, the optical path is overlapped, so that the total length of the first optical element 11 is kept short, and a very compact optical system is configured.
[0113]
Note that the optical system described in the present embodiment can be used as an imaging optical system by arranging an imaging element instead of an image display element with the optical path reversed.
[0114]
Further, the number, shape, and combination of the first optical element and the second optical element shown in each embodiment described above are not particularly limited to these.
[0115]
Furthermore, in all the embodiments described above, when an arbitrary ray of the light beam passing through the first optical system is traced, the ray is reflected on the first (first) reflection and the second on the first surface. Reflection takes an optical path that reflects with one reflection angle as a reference and the other with an opposite reflection angle.
[0116]
Specifically, for example, in the paper surface of FIG. 1, the reflection angle in the first reflection (A surface reflection) is a positive sign (when the reflected light exists in the counterclockwise direction in the paper surface with respect to the surface normal). If there is an optical path, the reflection angle in the second reflection (A-side re-reflection) has a negative sign (when the reflected light is present in the clockwise direction in the drawing with respect to the surface normal).
[0117]
By taking such an optical path, the light beam reciprocates substantially between the first surface and the second surface, so that the space in the first optical system. The It can be used effectively to increase the optical path length. In addition, a small optical system can be realized even if the optical path length is long.
[0118]
Hereinafter, numerical examples of the above embodiments will be described.
[0119]
[Numerical Example 1]
FIG. 8 shows an optical path cross-sectional view of a numerical example having a configuration similar to that of the first embodiment shown in FIG. In the figure, reference numeral 1 denotes a first optical element constituting a display optical system, which is constituted by a prism-shaped transparent body having three optical surfaces. S2, S4, and S6 are the same surface, and S3 and S7 are the same surface. These two surfaces and S5 correspond to the surfaces A, B, and C described in the first embodiment, respectively.
[0120]
Reference numeral 2 denotes a second optical element, which is formed in a lens shape having an exit surface S7 and an entrance surface S8 joined to the surface B (S3) of the first optical element 1. Further, the numerical value example 1 includes a lens (third optical element) 21 having an entrance surface S10 and an exit surface S9. SI is an image display surface, and S1 is an exit pupil S of the display optical system.
[0121]
All of the optical surfaces from S1 to S10 are rotationally asymmetric surfaces, and have a plane-symmetrical shape having the paper surface (yz cross section) as the only symmetrical surface.
[0122]
In the figure, x, y, and z are coordinate system definitions in which the visual axis direction of the observer is the z axis, the direction perpendicular to the z axis in the paper is the y axis, and the direction perpendicular to the paper is the x axis.
[0123]
The optical data of this numerical example 1 is shown in Table 1. The leftmost item SURF in the optical data of Table 1 indicates the surface number. X, Y, Z, and A are coordinate systems in which the center of the first surface S1 is the origin (0, 0, 0), and the y-axis and z-axis shown in the figure and the x-axis toward the back of the page. Are the position (x, y, z) of the surface vertex of each surface and the rotation angle a (unit: degree) about the x axis with the counterclockwise direction as the positive direction on the drawing.
[0124]
R is a radius of curvature. The term TYP represents the type of surface shape, SPH is a spherical surface, and FFS is a rotationally asymmetric surface according to the following equation.
[0125]
[Expression 1]

[0126]
The numerical value written next to FFS in the column of TYP is the rotationally asymmetric shape whose surface shape corresponds to the aspheric coefficient k and ci (i = 2, 3, 4...) Described in the lower side of the table. It is shown that.
[0127]
Further, the surface shape may be defined by another equation, and what is represented by XYP in the term of TYP is a rotationally asymmetric surface according to the following equation.
[0128]
[Expression 2]

[0129]
The numerical values written next to FFS and XYP in the column of TYP are the rotations corresponding to the aspherical coefficients k and ci (i = 1, 2, 3...) Whose surface shape is listed on the lower side of the table. It shows an asymmetric shape.
[0130]
In any case, the value of the coefficient is 0 for the term ci that is not shown in the table.
[0131]
Nd and νd (indicated by vd in the table) indicate the refractive index and Abbe number at the d-line wavelength of the medium after that surface, respectively. Nd The change in the sign indicates that light is reflected on the surface. When the medium is an air layer, only the refractive index Nd is displayed as 1.000, and the Abbe number νd is omitted. The item descriptions in the above table are the same in the following numerical examples.
[0132]
[Table 1]

[0133]
As can be seen from Table 1, the light from the image display surface SI passes through the surfaces S10 and S9 of the lens 21 and travels toward the second optical element 2. The light traveling toward the second optical element 2 enters the second optical element 2 from the surface S8, passes through the bonding surface S7 between the second optical element 2 and the first optical element 1, and passes through the first optical element 2. The light enters the optical element 1, is totally reflected at S 6, is reflected by the back surface at S 5 with a reflection film, is folded back, is totally reflected at S 4, is reflected at the back side at S 3, is transmitted through S 2, and is transmitted through the first optical element 1. Is guided to the exit pupil S1 of the optical system.
[0134]
Considering a numerical value having a length dimension of the numerical value example 1 as mm, the image is z with an exit pupil diameter of 6 mm, an image display size of about 10 mm × 7.5 mm, and an angle of view of about 50 ° horizontally and about 39 ° vertically. This is a display optical system that displays the image at infinity in the positive direction of the axis.
[0135]
Note that the optical system of the present numerical example may be used as an imaging optical system. In this case, light from an object point at infinity in the negative z-axis direction is guided to the first optical element 1 through the diaphragm S1, is incident on the first optical element 1 from S2, and is reflected by S3. Reflected in S4, reflected back in S5, reflected in S6, and then emitted from S7 and guided to the second optical element 2.
[0136]
The light guided to the second optical element 2 exits the second optical element 2 from S8, enters the lens 21 from the surface S9, exits from S10, and forms an image on the imaging surface SI.
[0137]
According to the configuration of this numerical example, it is possible to achieve a display optical system that is small and has a wide display angle of view. In particular, in this numerical example, a lens 21 is provided between the second optical element 2 and the image display surface SI to share the optical power of the relay optical system portion with more optical surfaces, thereby generating aberrations. Therefore, the optical performance can be improved with respect to the configuration shown in the first embodiment.
[0138]
[Numerical Example 2]
FIG. 9 shows an optical path cross-sectional view of a numerical example having a configuration similar to that of the fourth embodiment shown in FIG. In the figure, reference numeral 11 denotes a first optical element, which is composed of a prism-shaped transparent body having three optical surfaces. S2, S4, S6, and S8 are the same surface, S3 and S9 are the same surface, and S5 and S7 are the same surface. These three surfaces correspond to the surfaces A, B, and C described in the fourth embodiment, respectively.
[0139]
Reference numeral 12 ′ denotes a second optical element, which is formed in a lens shape having an exit surface S9 and an entrance surface S10 joined to the surface B (S3) of the first optical element 11. Further, the numerical value example 2 includes a lens 21 having an entrance surface S12 and an exit surface S11. In the surface A, a reflective film is formed on a portion used as the folded reflection surface S6. SI is an image display surface, and S1 is an exit pupil S of the display optical system.
[0140]
These optical surfaces from S1 to S12 are all rotationally asymmetric surfaces, and have a plane-symmetrical shape having the paper plane (yz cross section) as the only plane of symmetry.
[0141]
In the figure, x, y, and z are coordinate system definitions in which the visual axis direction of the observer is the z axis, the direction perpendicular to the z axis in the paper is the y axis, and the direction perpendicular to the paper is the x axis.
[0142]
Table 2 shows the optical data of this numerical example 2.
[0143]
[Table 2]

[0144]
As can be seen from Table 2, the light from the image display surface SI passes through the surfaces S12 and S11 of the lens 21 and travels toward the second optical element 12 ′. The light traveling toward the second optical element 12 ′ is incident on the second optical element 12 ′ from the surface S10, and the first optical element 12 ′ is joined to the first optical element 11 from the joint surface S9 between the second optical element 12 ′ and the first optical element 11. The light enters the optical element 11, is totally reflected in S8, is reflected on the back surface in S7 having a reflective film, and is substantially vertically reflected on the surface S6 corresponding to the reflective film forming portion of the surface A and is folded back. The back reflection is performed at S5, the total reflection is performed at S4, the back reflection is performed at S3, the first optical element 11 is emitted from S2, and is guided to the exit pupil S1 of the optical system.
[0145]
Considering a numerical value having a length dimension of the numerical value example 2 as mm, the image is z with an exit pupil diameter of 6 mm, an image display size of about 10 mm × 7.5 mm, and an angle of view of about 50 ° horizontally and about 39 ° vertically. This is a display optical system that displays the image at infinity in the positive direction of the axis.
[0146]
Note that the optical system of the present numerical example may be used as an imaging optical system. In this case, light from an object point at infinity in the z-axis negative direction passes through the diaphragm S1, is guided to the first optical element 11, is incident on the first optical element 11 from S2, and S3, S4, Reflected in S5, reflected back in S6, reflected in S7 and S8, then emitted from S9 and guided to the second optical element 12 ′.
[0147]
The light guided to the second optical element 12 ′ exits the second optical element 12 ′ from S10, enters the lens 21 from the surface S11, exits from S12, and forms an image on the imaging surface SI.
[0148]
According to the configuration of the present numerical example, a compact display optical system having a wide display angle of view can be realized. Also in the present numerical example, as in the numerical example 1, the lens 21 is provided between the second optical element 12 ′ and the image display surface SI, so that the optical power of the relay optical system portion is increased. It is easy to obtain high optical performance because it is shared by the surface and the occurrence of aberration is suppressed.
[0149]
In addition, since the number of reflections for forming a round-trip optical path in the first optical element 11 is increased as compared with Numerical Example 1, the optical path lengths are effectively overlapped to increase the optical path length. The display optical system can be made compact.
[0150]
[Numerical Example 3]
FIG. 10 shows an optical path cross-sectional view of a numerical example of the fourth embodiment shown in FIG. In the figure, reference numeral 11 denotes a first optical element, which is composed of a prism-shaped transparent body having three optical surfaces. S2, S4, S6, and S8 are the same surface, S3 and S9 are the same surface, and S5 and S7 are the same surface. These three surfaces correspond to the surfaces A, B, and C described in the fourth embodiment, respectively.
[0151]
Reference numeral 12 denotes a second optical element, which is formed of a prism-shaped transparent body having an exit surface S9, a reflection surface S10, and an entrance surface S11 joined to the surface B (S3) of the first optical element 11. ing. Reflective films are formed on the upper surface A and the surface C. SI is an image display surface, and S1 is an exit pupil S of the display optical system.
[0152]
All of the optical surfaces from S1 to S11 are rotationally asymmetric surfaces, and have a plane-symmetrical shape having the paper surface (yz cross section) as the only symmetrical surface.
[0153]
In the figure, x, y, and z are coordinate system definitions in which the visual axis direction of the observer is the z axis, the direction perpendicular to the z axis in the paper is the y axis, and the direction perpendicular to the paper is the x axis.
[0154]
Table 3 shows the optical data of this numerical example 3.
[0155]
[Table 3]

[0156]
As can be seen from Table 3, the light from the image display surface SI enters the second optical element 12 from the surface S11, is reflected by the surface S10, and is reflected between the second optical element 12 and the first optical element 11. The light enters the first optical element 11 from the joint surface S9, is totally reflected at S8, is reflected at the back surface at S7 with a reflective film, and is reflected substantially vertically at the surface S6 corresponding to the reflective film forming portion of the surface A. The back surface is reflected at S5 where the reflection film is applied, is totally reflected at S4, is back-reflected at S3, exits the first optical element 11 from S2, and is guided to the exit pupil S1 of the optical system.
[0157]
Assuming that the numerical value having the length dimension of this numerical example is mm, the image is displayed on the z-axis with an exit pupil diameter of 6 mm, an image display size of about 10 mm × 7.5 mm, and a horizontal angle of about 50 ° and a vertical angle of about 39 °. The display optical system displays the image in the positive direction at infinity.
[0158]
Note that the optical system of the present numerical example may be used as an imaging optical system. In this case, light from an object point at infinity in the z-axis negative direction passes through the diaphragm S1, is guided to the first optical element 11, is incident on the first optical element 11 from S2, and S3, S4, Reflected in S5, reflected back in S6, reflected in S7 and S8, then emitted from S9 and guided to the second optical element 12.
[0159]
The light guided to the second optical element 12 is reflected at S10, exits the second optical element 12 from S11, and forms an image on the imaging surface SI.
[0160]
According to the configuration of the present numerical example, a compact display optical system having a wide display angle of view can be realized. Further, in this numerical example, a prism-shaped optical element is used as the second optical element 12, and the optical path is bent by back surface reflection. Therefore, the second optical element 12 is made thinner than the numerical examples 1 and 2. Can be made.
[0161]
[Numerical Example 4]
FIG. 11 shows an optical path cross-sectional view of a numerical example having a configuration similar to that of the fourth embodiment shown in FIG. In the figure, reference numeral 11 denotes a first optical element, which is composed of a prism-shaped transparent body having three optical surfaces. S2, S4, S6, and S8 are the same surface, S3 and S9 are the same surface, and S5 and S7 are the same surface. These three surfaces correspond to the surfaces A, B, and C described in the fourth embodiment, respectively.
[0162]
Reference numeral 12 ″ denotes a second optical element. Here, an emission surface S9, a reflection surface S11, and a reflection / incidence surface S10 (the same surface as S12) joined to the surface B (S3) of the first optical element 11 are provided. The reflective film is formed on the upper surface of the surface A, the surface C, and the surface S11, SI is an image display surface, and S1 is an exit pupil S of the display optical system. .
[0163]
These optical surfaces from S1 to S12 are all rotationally asymmetric surfaces, and have a plane-symmetrical shape having the paper plane (yz cross section) as the only plane of symmetry.
[0164]
In the figure, x, y, and z are coordinate system definitions in which the visual axis direction of the observer is the z axis, the direction perpendicular to the z axis in the paper is the y axis, and the direction perpendicular to the paper is the x axis.
[0165]
Table 4 shows the optical data of this numerical example 4.
[0166]
[Table 4]

[0167]
As can be seen from Table 4, the light from the image display surface SI enters the second optical element 12 ″ from the surface S12, is reflected by the surfaces S11 and S10, and is incident on the bonding surface S9 with the first optical element 11. The light incident on the first optical element 11 from the surface S9 is totally reflected at S8, reflected at the back surface at S7 having a reflective film, and substantially vertical at the surface S6 corresponding to the reflective film forming portion of the surface A. Reflected and folded, the back surface is reflected at S5 to which a reflective film is applied, is totally reflected at S4, is back-reflected at S3, exits the first optical element 11 from S2, and is guided to the exit pupil S1 of the optical system. .
[0168]
Assuming that the numerical value having the length dimension of this numerical example is mm, the image is displayed on the z-axis with an exit pupil diameter of 4 mm and an image display size of about 10 mm × 7.5 mm and a horizontal angle of about 50 ° and a vertical angle of about 39 °. The display optical system displays the image in the positive direction at infinity.
[0169]
Note that the optical system of the present numerical example may be used as an imaging optical system. In this case, light from an object point at infinity in the z-axis negative direction passes through the diaphragm S1, is guided to the first optical element 11, is incident on the first optical element 11 from S2, and S3, S4, Reflected in S5, reflected back in S6, reflected in S7 and S8, then emitted from S9 and guided to the second optical element 12 ″.
[0170]
The light guided to the second optical element 12 ″ is reflected by S10 and S11, exits the second optical element 12 ″ from S12, and forms an image on the imaging surface SI.
[0171]
According to the configuration of the present numerical example, a compact display optical system having a wide display angle of view can be realized. In this numerical example, a prism-shaped optical element is used as the second optical element 12 ″, and the optical path is bent by two back surface reflections. Compared with 2 and 3, it can be made thinner.
[0172]
【The invention's effect】
As described above, according to the first invention of the present application, in the first optical element, the light is substantially reciprocated between the first, second and third surfaces so that the optical paths overlap. Even though it is a small optical system, a long optical path length can be secured. Therefore, a wide display angle of view can be achieved while using a small original image, and the entire display optical system including the second optical element can be miniaturized.
[0173]
Since the third surface of the first optical element and the exit surface of the second optical element are joined, the positioning between the first and second optical elements can be facilitated, Occurrence of aberrations when light enters the first optical element can be suppressed, and a robust optical system structure can be obtained. Therefore, a display optical system having high optical performance and excellent durability can be realized.
[0174]
If light is intermediately imaged in the display optical system (for example, the first optical element), the degree of freedom in layout is increased, the original image can be displayed on a large screen, and the optical path length is considerably increased. Even so, the display optical system can be made compact.
[0175]
According to the second invention of the present application, in the first optical element, the optical path is folded back and forth between the first, second and third surfaces so that the optical path is folded. However, a long optical path length can be secured. For this reason, it is possible to achieve a wide shooting angle of view while being small as an entire imaging optical system including the second optical element.
[0176]
Since the third surface of the first optical element and the exit surface of the second optical element are joined, the positioning between the first and second optical elements can be facilitated, Occurrence of aberrations at the time of light emission from the first optical element can be suppressed, and further a strong optical system structure can be obtained. Therefore, an imaging optical system with high optical performance and excellent durability can be realized.
[0177]
If intermediate imaging of light is performed in the imaging optical system (for example, the first optical element), the degree of freedom of layout increases, and a wide-angle subject image is sufficiently reduced and guided to the imaging surface. In addition, the imaging optical system can be made compact even if the optical path length is considerably increased.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a display optical system according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a display optical system according to the first embodiment.
FIG. 3 is a configuration diagram of a display optical system according to the first embodiment.
FIG. 4 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention.
FIG. 5 is a configuration diagram of a display optical system (1) according to a third embodiment of the present invention.
FIG. 6 is a configuration diagram of a display optical system (2) according to a third embodiment of the present invention.
FIG. 7 is a configuration diagram of a display optical system according to the fourth embodiment.
FIG. 8 is a sectional view of an optical system according to Numerical Example 1 of the present invention.
FIG. 9 is a sectional view of an optical system according to Numerical Example 2 of the present invention.
FIG. 10 is a sectional view of an optical system according to Numerical Example 3 of the present invention.
FIG. 11 is a sectional view of an optical system according to Numerical Example 4 of the present invention.
FIG. 12 is a configuration diagram of a conventional display optical system.
FIG. 13 is a configuration diagram of a conventional display optical system.
[Explanation of symbols]
1, 1 ', 1 ", 11 1st optical element
2, 12, 12 ', 12 "second optical element
3 Image display element
4 Image sensor

Claims (10)

An image display device, an image display device having a viewer's eyes or the display optical system for guiding the projection surface light from the original to which the image display element is formed,
The display optical system includes:
A first surface having at least a reflective action, towards the light from the original reflected by the first surface from the second surface and the original reflected back to the first surface to the first surface a first optical element having a third surface that leads to the eye or the projection surface of the viewer by reflecting light reflected back to the first surface from the second surface while transmitting the light,
A second optical element for guiding light from the original image to the third surface;
It said third surface and the second and the exit surface of the optical element is joined Rutotomoni,
The first optical element has a reflection angle with respect to a normal at a hit point of a central field angle chief ray first incident on the first surface, and is reflected by the second surface and reappears on the first surface. The reflection angle with respect to the normal at the hit point of the incident central field angle chief ray is configured to have an opposite sign,
An image display apparatus , wherein an intermediate image of the original image is formed in the first optical element . The first optical element reflects light incident through the third surface at the first surface, reflects at the second surface, reflects at the first surface, and The image display device according to claim 1, wherein the image display device reflects the light on a third surface, transmits the first surface, and guides it to an observer's eye or a projection surface. The first optical element reflects light incident through the third surface at the first surface, reflects at the second surface, reflects at the first surface, and Reflecting on the second surface, reflecting on the first surface, reflecting on the third surface, transmitting through the first surface, and leading to the observer's eye or projection surface The image display device according to claim 1. The image display apparatus according to claim 1, wherein at least one of the first to third surfaces is decentered with respect to a light beam reflected by the surface. The image display apparatus according to claim 1, wherein at least one of the first to third surfaces has a curvature. The image display device according to claim 1, wherein at least one of the first to third surfaces is a rotationally asymmetric surface. The image display apparatus according to claim 1, wherein the light is totally reflected by any one of the optical surfaces formed on the first optical element. The image display apparatus according to claim 1, wherein an optical surface of the second optical element is a rotationally asymmetric surface. The image display apparatus according to claim 1, wherein the first and second optical elements are formed of materials having the same refractive index. An imaging element, an imaging apparatus having an imaging optical system for guiding light to the imaging surface of the imaging element from the object,
The imaging optical system is
At least a first having a reflecting action of the surface, a second that reflects the light from the object reflected by the first surface back to the first surface plane and the light of the first from the subject A first optical element having a third surface that reflects toward the surface and transmits light reflected from the second surface back to the first surface to the imaging surface;
A second optical element for guiding the light emitted from the third surface to the imaging surface;
It said third surface and the second and the incident surface of the optical element is bonded Rutotomoni,
The first optical element has a reflection angle with respect to a normal at a hit point of a central field angle chief ray first incident on the first surface, and is reflected by the second surface and reappears on the first surface. The reflection angle with respect to the normal at the hit point of the incident central field angle chief ray is configured to have an opposite sign,
An image pickup apparatus , wherein an intermediate image of the subject is formed in the first optical element .

Images