JP2004029099A

JP2004029099A - Image observation device

Info

Publication number: JP2004029099A
Application number: JP2002181300A
Authority: JP
Inventors: Junko Kuramochi; 倉持　純子
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2002-06-21
Filing date: 2002-06-21
Publication date: 2004-01-29

Abstract

<P>PROBLEM TO BE SOLVED: To observe a light beam from one image display element with both eyes by guiding it to an optical system for a left eye and an optical system for a right eye in an HMD for observing a video in a state where it is attached to an observer's head or face. <P>SOLUTION: An angle α formed by a reference axis light beam with the normal of the image display element and an angle β formed by the reference axis light beam with the normal of an exit pupil satisfy [¾α¾≠0, ¾β¾≠ 0]. When the length of perpendiculars drawn from the centers of the exit pupils of two observation optical systems to the normal cross section of the center of the image display element is defined as EW, it satisfies [27≤EW≤35]. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、観察者が両眼で画像を観察する画像表示装置に関するものである。
【０００２】
【従来の技術】
図５に、従来までの画像表示装置の外観図を示す。観察者は図５に示すように、画像表示装置７０１を観察者の頭部、あるいは顔面に装着し、映像・音声を楽しみ、高い没人感が得られるようになっている。
【０００３】
図６は、画像表示装置を形成する単眼用観察光学系の基準軸光線Ａを含む垂直な断面図である。ここで、基準軸光線ＡはＬＣＤ等の画像表示素子３１中心と観察者の眼球３５の中心を結んだ光線とする。３２は前記ＬＣＤ３１を照明するためのバックライト、３４は光学素子である。
【０００４】
ＬＣＤ３１に表示された画像は、光学素子３４を介して拡大され、観察者はその拡大画像を光学素子３４の背面に見ることができる。
【０００５】
以上単眼用観察光学系に関して説明を行ったが両眼で観察する画像表示装置では、２つの単眼用観察光学系を左右眼の前に配置し同一部材で保持したものである。
【０００６】
【発明が解決しようとする課題】
上記従来例では、ＬＣＤ及び、結像プリズムを各２個用いることから、装置の小型化・軽量化の上で限界があった。上記問題点に鑑み、特開平０７−２８７１８８のような一つ画像表示素子の画像を両眼に導く光学系が提案されている。しかしながら、画像表示素子から左右眼への光路が複雑であり、装置の大型化が問題であった。
【０００７】
【課題を解決するための手段】
本発明の画像観察装置は特許請求の範囲のように構成することで、１つの画像表示素子で両眼で画像観察することが可能となり、大幅な小型化、及び軽量化が実現できる。
【０００８】
【発明の実施の形態】
（第１の実施例）
図１は本発明の第一の実施例を説明する画像表示装置の断面図である。
【０００９】
図１において１は２次元映像を表示するための素子であるＬＣＤ，２はＬＣＤ１を照明するためのバックライトである。３はＬＣＤ１に表示された映像を観察者右眼球に導く右眼用観察光学系を形成している光学プリズム、４はＬＣＤ１に表示された映像を観察者左眼球に導く左眼用観察光学系を形成している光学プリズムである。５は右眼用観察光学系の一部である補助レンズであり、左眼用観察光学系の一部である補助レンズと同一部品で構成されている。
【００１０】
図２は図１の観察光学系をさらに詳しく説明するために右眼用観察光学系のみの拡大図である。
【００１１】
図中ＡはＬＣＤの中心と観察者の眼球中心（観察光学系の射出瞳）を結んだ光線であり、以下基準軸光線と呼ぶ。光学プリズム３は透過面３ｃ，全反射面及び透過面３ａ、ＡＬ蒸着が施された反射面３ｂからなり、屈折率が１より大きい媒質を挟んで一体成形されたプラスチック素子である。３ａ，３ｂ，３ｃの少なくとも１つは各面内及び面外共に回転対称軸を有せず、しかも、対称面を１つのみ有する面対称自由曲面からなる。補助レンズ５は透過面５ａ，透過面５ｂからなり、屈折率が１より大きい媒質を挟んで一体成形されたプラスチック素子である。本実施例においては光学プリズム３と補助レンズ５は互いに異なる波長分散を有し、観察光学系が有する色収差を押さえる効果をもつものである。
【００１２】
本実施例の光学的作用について説明する。ＬＣＤ１で表示した画像から射出する光束はまず光学作用面５ｂ、５ａ、３ｃを透過して光学作用面３ａへ向かい、この面３ａで全反射して光学作用面３ｂへ向かい、この面３ｂで反射して収束光となり、再び光学作用面３ａへ向かい、今度はこの面３ａを透過して画像の虚像を形成すると共に観察者の眼球表面ｓに達して観察者に虚像を視認させる。ここでは観察者の眼球表面ｓと観察光学系の射出瞳は一致している。
【００１３】
本実施例の光学系は偏心面で構成しているので、光学系の形状を表す為に絶対座標系とローカル座標系を設定する。絶対座標系の原点は観察者の望ましき瞳孔位置Ｓの中心Ｏに設定し、Ｚ軸は点Ｏを通り瞳孔面に垂直な直線であり、前記平面上にある。Ｙ軸は原点Ｏを通り前記平面上でＺ軸に対して反時計回りに９０°の角度をなす直線である。Ｘ軸は原点Ｏを通り、Ｙ，Ｚ軸に対して直交する直線である。
【００１４】
ローカル座標の原点Ｏｉは絶対座標（Ｓｘｉ，ＳＹｉ，ＳＺｉ）で各面毎に設定する。ローカル座標のｚ軸はＹＺ平面内で原点Ｏｉを通り、絶対座標系のＺ軸と角度Ａｉをなす直線である。ｙ軸は原点Ｏｉを通りｚ軸に対して反時計回りに９０°の角度をなす直線である。ｘ軸は原点Ｏｉを通り、ｙ軸及びｚ軸に直交する直線である。
【００１５】
各面の形状はローカル座標で表す。本発明の各実施例において光学作用面の形状は、円錐係数で定義される円錐関数にゼルニケ多項式による非球面項を有する形状をしており、以下に示す関数により表す。
【００１６】
【数１】

【００１７】
ここにｃは曲率であり、ｃ＝１／ｒ、ただしｒは各面の基本曲率半径である。又、ｋは各面の円錐係数、ｃｊは各面におけるｊ番目のゼルニケ多項式の非球面係数である。本実施例の光学データを表１に示す。
【００１８】
本実施例では光学プリズム３のプラスチック材料の屈折率ｎｄは１．５７，補助レンズ５のプラスチック材料の屈折率ｎｄは１．４９とする。
【００１９】
本実施例において、基準軸光線と画像表示素子法線とが互いの交点で成す角αは４２．７°である。射出瞳中心から観察像面（画像表示素子を光学手段を介して拡大した像面であり、像中心の合焦点を含む面とする）に下した垂線の長さＬは２０００ｍｍ、射出瞳中心から、該画像表示素子中心を通りかつ該画像表示素子入射面と該基準軸光線を含む面に垂直な面（以下、左右観察光学系対称面）に下ろした垂線の長さＥＷは３２．５ｍｍ，射出瞳面上で基準軸光線と射出瞳法線との成す角βは０．９°である。
【００２０】
本実施例のように｜α｜≠０を満たす場合、液晶の任意の点からの左右の観察光学系に向かう光線は液晶出射時から分離されており、従来例（特開平０７−２８７１８８）のような｜α｜＝０の装置と比較してハーフミラーやダイクロフィルター等の光束分離手段を別途設ける必要がない。またβは輻輳角ｔａｎ^−１（ＥＷ／Ｌ）に等しく設定されているため、観察像面において輻輳ずれのない正常な両眼視が可能となる。
【００２１】
本実施例のように構成することで、１つの画像表示素子からの画像を両眼で観察することが可能となり、小型でかつ軽量な画像表示装置の提供が実現できる。
【００２２】
また、本実施例の観察光学系は２回の反射面を有することから観察者眼球と画像表示素子は観察光学系を挟んで逆側に配置しているため観察者の鼻と画像表示素子との干渉の心配のない構成となっており、装置外装設計等の自由度が高くできる。
【００２３】
（第２実施例）
図３は本発明の第二実施例を説明する画像表示装置の断面図である。本実施例においては第一実施例の補助レンズ５の光学作用面５ａを回折素子で構成したものである。ただし、回折素子を形成する基板面はＸトロイダル非球面（ｘｚ面内では非球面、ｙｚ面内では円）としている。
【００２４】
本実施例の光学データを表２に示す。ただし、回折素子は波面位相差量を下記のようなＸＹ多項式で表している。
【００２５】
ＣＩ　Ｘ
Ｃ２　Ｙ
Ｃ３　Ｘ^２
Ｃ４　ＸＹ
Ｃ５　Ｙ^２
本実施例では光学プリズム３のプラスチック材料の屈折率ｎｄは１．５７，補助レンズ５のプラスチック材料の屈折率ｎｄは１．５７、α＝２．８°、β＝０．９°、ＥＷ＝３２．５ｍｍとする。
【００２６】
実施例のように構成することで第一実施例同様の効果が得られる。
【００２７】
（第３実施例）
４は本発明の第三実施例を説明する画像表示装置の断面図である。本実施例においては第一実施例の補助レンズ５の光学作用面５ａを光学素子と張り合わせて構成したものである。
【００２８】
本実施例の光学データを表３に示す。
【００２９】
本実施例では光学プリズム３のプラスチック材料の屈折率ｎｄは１．５７，補助レンズ５のプラスチック材料の屈折率ｎｄは１．４９、α＝５６．０°、β＝０．９°、ＥＷ＝３２．５ｍｍとする。
【００３０】
本実施例のように構成することで第一実施例同様の効果が得られる。
【００３１】
以上説明した実施例では全て右眼用の観察光学系に関して説明したが、左眼用の観察光学素子は，該左右観察光学系対称面に対して折り返したものであり、説明を省略する。また、上記実施例では画像表示素子としてＬＣＤとしたが、それに限るものではない。また、上記実施例ではバックライトに関する詳細な記載はないが、白色蛍光等やＬＥＤ等が望ましい。
【００３２】
【表１】

【００３３】
【表２】

【００３４】
【表３】

【００３５】
【発明の効果】
本発明によれば以上のように、上記実施例のように構成することで小型で軽量な画像表示装置の実現することが可能となる。
【図面の簡単な説明】
【図１】本発明の第一の実施例を説明する画像表示装置の断面図
【図２】本発明の第一の実施例を説明する画像表示装置の断面図
【図３】本発明の第二の実施例を説明する画像表示装置の断面図
【図４】本発明の第三の実施例を説明する画像表示装置の断面図
【図５】従来の画像表示装置の断面図
【図６】従来の画像表示装置の断面図
【符号の説明】
１．ＬＣＤ
２．バックライト
３．光学プリズム
４．光学プリズム
５．補助レンズ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image display device in which an observer observes an image with both eyes.
[0002]
[Prior art]
FIG. 5 shows an external view of a conventional image display device. As shown in FIG. 5, the observer wears the image display device 701 on the observer's head or face, enjoys video and audio, and obtains a high feeling of murder.
[0003]
FIG. 6 is a vertical cross-sectional view including the reference axis ray A of the monocular observation optical system forming the image display device. Here, the reference axis ray A is a ray connecting the center of the image display element 31 such as an LCD and the center of the eyeball 35 of the observer. 32 is a backlight for illuminating the

LCD

31, and 34 is an optical element.
[0004]
The image displayed on the LCD 31 is enlarged via the optical element 34, and the observer can see the enlarged image on the back of the optical element 34.
[0005]
The monocular observation optical system has been described above, but in an image display apparatus for observation with both eyes, two monocular observation optical systems are arranged in front of the left and right eyes and held by the same member.
[0006]
[Problems to be solved by the invention]
In the above conventional example, since two LCDs and two imaging prisms are used, there is a limit in reducing the size and weight of the device. In view of the above problems, there has been proposed an optical system for guiding an image of one image display element to both eyes as disclosed in JP-A-07-287188. However, the optical path from the image display element to the left and right eyes is complicated, and there has been a problem in that the size of the device has been increased.
[0007]
[Means for Solving the Problems]
By configuring the image observation device according to the present invention as described in the claims, it is possible to observe images with both eyes with one image display element, and it is possible to realize a significant reduction in size and weight.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
(First embodiment)
FIG. 1 is a sectional view of an image display device for explaining a first embodiment of the present invention.
[0009]
In FIG. 1, reference numeral 1 denotes an LCD which is an element for displaying a two-dimensional image, and reference numeral 2 denotes a backlight for illuminating the LCD 1. Reference numeral 3 denotes an optical prism that forms an observation optical system for the right eye that guides the image displayed on the LCD 1 to the observer's right eyeball. Reference numeral 4 denotes an observation optical system for the left eye that guides the image displayed on the LCD1 to the observer's left eyeball. Is an optical prism that forms Reference numeral 5 denotes an auxiliary lens which is a part of the observation optical system for the right eye, and is formed of the same components as the auxiliary lens which is a part of the observation optical system for the left eye.
[0010]
FIG. 2 is an enlarged view of only the observation optical system for the right eye in order to explain the observation optical system of FIG. 1 in more detail.
[0011]
A in the figure is a light beam connecting the center of the LCD and the center of the eyeball of the observer (the exit pupil of the observation optical system), and is hereinafter referred to as a reference axis light beam. The optical prism 3 is a plastic element composed of a transmission surface 3c, a total reflection surface and a transmission surface 3a, and a reflection surface 3b on which an AL deposition is performed, and is integrally molded with a medium having a refractive index larger than 1. At least one of 3a, 3b and 3c does not have a rotationally symmetric axis both in-plane and out-of-plane, and is a plane-symmetric free-form surface having only one plane of symmetry. The auxiliary lens 5 is a plastic element that includes a transmission surface 5a and a transmission surface 5b, and is integrally formed with a medium having a refractive index greater than 1 interposed therebetween. In this embodiment, the optical prism 3 and the auxiliary lens 5 have different wavelength dispersions from each other, and have an effect of suppressing chromatic aberration of the observation optical system.
[0012]
The optical function of this embodiment will be described. The luminous flux emitted from the image displayed on the LCD 1 first passes through the optical working surfaces 5b, 5a, and 3c and goes to the optical working surface 3a, and is totally reflected by the surface 3a and goes to the optical working surface 3b, and is reflected by this surface 3b. Then, the light becomes convergent light, and goes again to the optical action surface 3a. This time, the light passes through this surface 3a to form a virtual image of an image, and reaches the eyeball surface s of the observer to make the observer visually recognize the virtual image. Here, the surface s of the eyeball of the observer and the exit pupil of the observation optical system match.
[0013]
Since the optical system according to the present embodiment is formed of an eccentric surface, an absolute coordinate system and a local coordinate system are set to represent the shape of the optical system. The origin of the absolute coordinate system is set at the center O of the desired pupil position S of the observer, and the Z axis is a straight line passing through the point O and perpendicular to the pupil plane, and is on the plane. The Y axis is a straight line passing through the origin O and forming an angle of 90 ° counterclockwise with respect to the Z axis on the plane. The X axis is a straight line passing through the origin O and orthogonal to the Y and Z axes.
[0014]
The origin Oi of the local coordinates is set for each surface in absolute coordinates (Sxi, SYi, SZi). The z axis of the local coordinate is a straight line passing through the origin Oi in the YZ plane and forming an angle Ai with the Z axis of the absolute coordinate system. The y-axis is a straight line passing through the origin Oi and forming an angle of 90 ° counterclockwise with respect to the z-axis. The x-axis is a straight line passing through the origin Oi and orthogonal to the y-axis and the z-axis.
[0015]
The shape of each surface is represented by local coordinates. In each embodiment of the present invention, the shape of the optical working surface has a shape having an aspherical term based on a Zernike polynomial in a conical function defined by a conical coefficient, and is represented by the following function.
[0016]
(Equation 1)

[0017]
Here, c is the curvature, and c = 1 / r, where r is the basic radius of curvature of each surface. Further, k is a conic coefficient of each surface, and cj is an aspherical coefficient of a j-th Zernike polynomial in each surface. Table 1 shows the optical data of this example.
[0018]
In this embodiment, the refractive index nd of the plastic material of the optical prism 3 is 1.57, and the refractive index nd of the plastic material of the auxiliary lens 5 is 1.49.
[0019]
In the present embodiment, the angle α formed by the intersection of the reference axis ray and the image display element normal is 42.7 °. The length L of a perpendicular line extending from the center of the exit pupil to the observation image plane (an image plane obtained by enlarging the image display element via optical means and including the focal point of the image center) is 2000 mm, and the length L is 2000 mm from the center of the exit pupil. The length EW of a perpendicular line passing through the center of the image display element and perpendicular to a plane including the plane of incidence of the image display element and the plane of the reference axis (hereinafter referred to as a symmetrical plane of the left and right observation optical system) is 32.5 mm. The angle β formed between the reference axis ray and the normal to the exit pupil on the exit pupil plane is 0.9 °.
[0020]
When | α | ≠ 0 is satisfied as in the present embodiment, the light rays traveling from the arbitrary point of the liquid crystal to the left and right observation optical systems are separated from the liquid crystal emission time, which is the same as the conventional example (Japanese Patent Laid-Open No. 07-287188). It is not necessary to separately provide a light beam separating means such as a half mirror or a dichroic filter as compared with the apparatus of | α | = 0. Since β is set equal to the convergence angle tan ⁻¹ (EW / L), normal binocular viewing without convergence shift on the observation image plane is possible.
[0021]
With the configuration as in this embodiment, it is possible to observe an image from one image display element with both eyes, and it is possible to provide a small and lightweight image display device.
[0022]
Further, since the observation optical system of the present embodiment has two reflection surfaces, the observer's eyeball and the image display device are arranged on opposite sides of the observation optical system. The configuration is free from the possibility of interference, and the degree of freedom in designing the exterior of the device can be increased.
[0023]
(Second embodiment)
FIG. 3 is a sectional view of an image display device for explaining a second embodiment of the present invention. In the present embodiment, the optical working surface 5a of the auxiliary lens 5 of the first embodiment is constituted by a diffraction element. However, the substrate surface on which the diffraction element is formed is an X toroidal aspherical surface (aspherical surface in the xz plane and a circle in the yz plane).
[0024]
Table 2 shows optical data of this example. However, in the diffraction element, the wavefront phase difference amount is represented by the following XY polynomial.
[0025]
CI X
C2 Y
C3 X ²
C4 XY
C5 Y ²
In this embodiment, the refractive index nd of the plastic material of the optical prism 3 is 1.57, the refractive index nd of the plastic material of the auxiliary lens 5 is 1.57, α = 2.8 °, β = 0.9 °, and EW = 32.5 mm.
[0026]
With the configuration as in the embodiment, the same effect as in the first embodiment can be obtained.
[0027]
(Third embodiment)
FIG. 4 is a sectional view of an image display device for explaining a third embodiment of the present invention. In this embodiment, the optical working surface 5a of the auxiliary lens 5 of the first embodiment is bonded to an optical element.
[0028]
Table 3 shows the optical data of this example.
[0029]
In this embodiment, the refractive index nd of the plastic material of the optical prism 3 is 1.57, the refractive index nd of the plastic material of the auxiliary lens 5 is 1.49, α = 56.0 °, β = 0.9 °, EW = 32.5 mm.
[0030]
With the configuration as in the present embodiment, the same effect as in the first embodiment can be obtained.
[0031]
In all the embodiments described above, the observation optical system for the right eye has been described. However, the observation optical element for the left eye is folded back with respect to the plane of symmetry of the left and right observation optical systems, and the description is omitted. Further, in the above embodiment, the LCD is used as the image display element, but the present invention is not limited to this. Although there is no detailed description of the backlight in the above embodiment, white fluorescent light or LED or the like is preferable.
[0032]
[Table 1]

[0033]
[Table 2]

[0034]
[Table 3]

[0035]
【The invention's effect】
According to the present invention, as described above, by configuring as in the above embodiment, it is possible to realize a small and lightweight image display device.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an image display device illustrating a first embodiment of the present invention. FIG. 2 is a cross-sectional view of an image display device illustrating a first embodiment of the present invention. FIG. 4 is a cross-sectional view of an image display device illustrating a second embodiment. FIG. 4 is a cross-sectional view of an image display device illustrating a third embodiment of the present invention. FIG. 5 is a cross-sectional view of a conventional image display device. Sectional view of conventional image display device [Explanation of reference numerals]
1. LCD
2. Backlight 3. Optical prism4. Optical prism5. Auxiliary lens

Claims

In an image observation apparatus having an observation optical system for guiding an image formed on one image display element to an eyeball of an observer,
When a ray connecting the center of the exit pupil of the observation optical system and the center of the image display element is used as a reference axis ray,
An angle α formed at the intersection of the reference axis ray and the normal of the image display element and an angle β formed at the intersection of the reference axis ray and the exit pupil normal satisfy the following equation: | α | ≠ 0 (1)
| Β | ≠ 0 (2)
The two observation optical systems are symmetrically disposed on a right side (hereinafter, a left and right observation optical system symmetry plane) passing through the center of the image display element and perpendicular to the plane of incidence of the image display element and the plane including the reference axis ray. An image observation device, characterized in that:

2. The image observation apparatus according to claim 1, wherein the following equation is satisfied, where EW is the length of a perpendicular that is symmetrically lowered from the center of the exit pupils of the two observation optical systems to the left and right observation optical systems.
27 ≦ EW ≦ 35 (3)

3. The image observation apparatus according to claim 1, wherein at least one optical working surface of the two observation optical systems is formed in common.

4. The image observation apparatus according to claim 1, wherein at least one optical part of the two observation optical systems is formed integrally.

5. The image observation apparatus according to claim 1, wherein the observation optical system includes a concave reflecting surface.

5. The image observation apparatus according to claim 1, wherein said observation optical system includes an eccentric concave reflection surface.

7. The image observation apparatus according to claim 1, wherein the observation optical system includes an eccentric concave reflection surface and a total reflection surface, and at least one of these optical working surfaces is a free-form surface. .

8. The observation optical system according to claim 1, wherein the observation optical system includes an eccentric concave reflection surface, a total reflection surface, and four transmission surfaces, and at least one of these optical operation surfaces is a free-form surface. Item image observation device.

An optical part 1 composed of an eccentric concave reflecting surface, a total reflection surface, and two transmitting surfaces and filled with a medium having a refractive index of 1 or more, and an optical part 2 composed of two transmitting surfaces filled with a medium having a refractive index of 1 or more. 9. The image observation apparatus according to claim 8, wherein:

10. The image observation apparatus according to claim 1, wherein at least one of the optically active surfaces of the observation optical system is a diffraction element.

10. The image observation apparatus according to claim 9, wherein said optical part 1 and said optical part 2 have different wavelength dispersions.