JP3482393B2 - Video display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video display device,
In particular, the present invention relates to a small-sized head- or face-mounted image display device that holds an image on the user's head or face and projects an image on the eyeball.

[0002]

2. Description of the Related Art In recent years, a helmet-type or goggle-type image display device held on the head or face has been developed for virtual reality or for the purpose of personally enjoying a large-screen image.

For example, in Japanese Unexamined Patent Publication No. 3-191389, as shown in FIG. 9A, a liquid crystal display element (LCD) 1 which is an image display element for displaying an image and an image light flux formed by the LCD 1 are provided. In order to guide it to the observer's eyeball 5, a half mirror 2 that is inclined at the intersection of the optical axis of the LCD 1 and the observer's visual axis, and has a positive power and is opposed to the LCD 1 via the half mirror 2. There is disclosed a method that comprises a magnifying reflecting mirror 3 and downsizes an optical system while maintaining a good imaging performance. Also, US Pat.
In No. 269,476, as shown in FIG. 9B, a prism beam splitter 4 is used instead of the half mirror 2.

[0004]

In such an optical system, if an attempt is made to widen the angle of view of an observed image, a) the projection optical system becomes large. b) The distance between the projection optical system and the LCD becomes short. c) The distance between the projection optical system and the eyeball becomes short. And so on.

In this case, the following problems occur. When the projection optical system becomes large, the burden on the user becomes large when the image display device is mounted on the head or face. The diopter of the observed image can be adjusted by moving the LCD in the optical axis direction.
When the distance D becomes shorter, when the LCD is moved in the direction of approaching the magnifying reflection mirror, the half mirror or the prism beam splitter interferes with the LCD, and the diopter adjustment range becomes narrow. When the distance between the projection optical system and the eyeball (working distance: WD) becomes short, it is not possible to observe with the glasses on, and it is necessary to greatly adjust the diopter every time the user changes. Also, if the WD is short, the projection optical system and the LCD interfere with the face.

The present invention has been made in view of the above problems of the prior art, and its object is to be small and lightweight.
It is an object of the present invention to provide an image display device that can be easily adjusted in diopter and that can be worn on the head or face while wearing glasses.

[0007]

SUMMARY OF THE INVENTION An image display device of the present invention that achieves the above object comprises an image display element for displaying an image,
In an image display device having an observation optical system for guiding the image light flux formed by the image display element to an eyeball of an observer, the observation optical system has at least a concave shape that gives positive power to the image light flux. A reflective curved surface, and a transflective working surface having both a transmissive surface function of transmitting the image light flux and a reflective surface function of reflecting the image light flux, wherein the concave reflective curved surface and the transmissive reflective working surface are: The concave reflection curved surface is directed to the concave surface toward the transmission reflection surface side, and the optical path between the concave reflection curved surface and the transflective action is folded back to form a reciprocal optical path, An angle formed by an extension line of the optical axis emitted from the image display element and a normal line of the transmission / reflection action surface at a point where the extension line of the optical axis contacts the transmission / reflection action surface is smaller than π / 4. Which is characterized by That.

In this case, it is preferable that the observing optical system has a prism member in which at least a concave curved surface and a transmissive / reflective surface are filled with a prism medium.

The prism member of the observation optical system has an incident surface for allowing the image light flux to enter the prism member in the optical path of the image light flux emitted from the image display element to reach the concave reflection curved surface. Is preferably arranged.

The observation optical system has at least a prism member, and the prism member included in the observation optical system is
In the optical path until the image light flux emitted from the image display element reaches the concave reflection curved surface, it is configured by arranging an incident surface for the image light flux to enter the prism member, and the incident surface of the prism member is It is desirable that the surface shape is an aspherical shape that gives power to the light flux.

Further, it is desirable that the image display element is arranged so that the surface from which the image light flux is emitted is directed toward the observer's eyeball side.

Further, the angle θ formed by the extension line of the optical axis emitted from the image display element and the normal line of the transmission / reflection action surface at the point where the extension line of the optical axis contacts the transmission / reflection action surface is the vertical direction. Is 2φ and the refractive index of the medium of the prism member is n, then π / 4−φ ′ / 2 ≦ θ <π / 4 (4) where φ ′ = sin ⁻¹ (sinφ / N) It is desirable to satisfy (5).

[0013]

In the present invention, the angle formed by the extension line of the optical axis emitted from the image display element and the normal line of the transmission / reflection action surface at the point where the extension line of the optical axis contacts the transmission / reflection action surface is π. Since it is set to be smaller than / 4, the area of the transmissive / reflective working surface can be reduced, the distance between the projection optical system and the image display element can be shortened, the diopter adjustment range can be increased, and The distance between the system and the eyeball (working distance) becomes shorter, and it is possible to observe while wearing glasses.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of the image display device of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a basic form of an image display apparatus according to the present invention, which is an LCD 1 for displaying an image and an LCD.
In order to guide the image light flux formed by 1 to the observer's eyeball 5, the half mirror 2 tilted at the intersection of the optical axis of the LCD 1 and the observer's visual axis and the half mirror 2 having a positive power are provided. A magnifying mirror 3 arranged to face the LCD 1 through
And the half mirror 2 is arranged such that the angle θ between the normal line of the half mirror 2 and the optical axis of the LCD 1 is smaller than π / 4.

FIG. 2 shows a developed view of the optical system which is the basis of the present invention. The image displayed on the LCDa is magnified and projected onto the eyeball located at the eye point d by the optical element b having a positive power. A half mirror c is arranged between the optical element b and the eye point d.

The focal length f of the optical element b is determined from the size of the image displayed on the LCDa and the angle of view of the observed image.

The element b having a refractive power is a single concave mirror.
In this case, the distance l between LCDa and concave mirror b ₁And concave mirror b and
Distance l of point d₂Is uniquely determined. Optical system layout
On the table, the concave mirror b and the half mirror c have the degree of freedom.
Distance l_{twenty one}And the optical axis of LCDa and the normal of half mirror c
It is the angle formed by. In the present invention, the half mirror c
Improvement of the above-mentioned problems (1) by optimizing the angle
Is possible. Hereinafter, with reference to FIG. 3 to FIG.
Academic system size, distance between projection optical system and LCD, projection optical system
These are explained in terms of eyeball distance.

First, the size of the projection optical system will be described. FIG. 3 shows a half mirror c arranged for the light flux reflected by the concave mirror b. Regarding the area of the half mirror c, keeping the area of the half mirror c small leads to downsizing and weight reduction of the entire projection optical system. The size of the half mirror c must be at least larger than the cross section of the plane of the light flux reflected by the concave mirror b on which the half mirror c is arranged. That is, the normal of the half mirror c and LC
The smaller the angle θ formed by Da with the optical axis, the smaller the size of the half mirror c.

Regarding the size of the prism in the case where the half mirror c is formed of a prism beam splitter, the size of the prism is from the end surface u of the half mirror c closer to the LCDa to the LCDa.
Let v be the intersection point of the perpendicular line drawn to the optical axis of the LCDa and the optical axis of the LCDa, the smaller the angle θ between the normal line of the half mirror c and the optical axis of the LCDa, the weaker the inclination of the half mirror c,
The distance between the concave mirror b and the point v becomes shorter. This is especially true
When the half mirror c is composed of a prism beam splitter, the effect is large, and the smaller the distance between the concave mirror b and the point v, the smaller the volume of the prism.

Next, the distance between the projection optical system and the LCD will be described. The end surface u of the half mirror c on the side closer to the LCDa
Let v be the intersection point of the perpendicular line drawn from the LCD to the optical axis of the LCDa and the optical axis of the LCDa, and the normal line of the half mirror c and the LCDa.
The smaller the angle θ between the concave mirror b and the point v is, the longer the distance between the LCDa and the prism can be, and when the diopter is adjusted by moving the LCDa, the diopter adjustment range is growing.

Next, the distance between the projection optical system and the eyeball will be described. FIG. 4 shows a sectional view of the optical system in a plane including the optical axis x of the LCD and the center of the eyeball. When the point where the optical axis x of the LCD and the concave mirror b intersect is e, and the half mirror c is arranged so that the curve where the concave mirror b and the half mirror c do not block the light flux, the method of the optical axis x of the LCDa and the half mirror c is arranged. The intersection point of the half mirror c and the concave mirror b on the plane including the line is p, LCD
The optical axis x of the LCD and the half mirror c, and the optical axis x of the LCD.
And the normal line of the half mirror c is θ, and L is on the concave mirror b.
A point symmetric to the point p with respect to the optical axis x of the CD is q, an optical axis (visual axis) formed by the light rays from the concave mirror b being reflected by the half mirror c, and the optical axis is lowered from the point q onto the optical axis. Let s be the intersection with the vertical line. WD = l ₂ − (ef + fs) (1), where ef is the distance between the concave mirror b and the half mirror c and fs is the distance between the half mirror c and the point s. Therefore, (ef + fs) When is minimized,
WD is maximum.

When the intersection p of the concave mirror b and the half mirror c is fixed, (ef + fs) becomes a function of only the angle θ, which is g (θ) = ef + fs (2).

The distance between points p and q is 2k, and the optical axis x of the LCD is x.
Let e ′ be the intersection with the perpendicular drawn from the points p and q.

The distance between the points e to e'is a constant when the curvature of the concave mirror b and the position of the point p are fixed, and when this is t, g (θ) = k (tan θ + 1 / sin2θ + tan θcos2θ−cos2θ / tan 2θ) + t (3)

FIG. 5 is a graph showing the relationship between the above g (θ) and θ. g (θ) has a maximum value at θ = π / 4 (45 °), monotonically increases at θ <π / 4, and monotonically decreases at θ> π / 4. However, in the case of θ> π / 4, the LCDa is in the direction of approaching the face, which is not desirable.

From this, it is possible to increase WD by reducing the angle θ formed by the optical axis x of the LCD and the normal line of the half mirror c.

From the above, as the angle of the half mirror c is made smaller than π / 4, the size of the projection optical system becomes smaller, and the distance WD between the eyeball and the projection optical system and the distance between the LCD and the projection optical system become smaller. You can keep it for a long time.

However, when the angle formed by the normal of the half mirror c to the optical axis of the LCDa is made smaller than π / 4, among the light rays emitted from the LCDa and reflected by the concave mirror b and the half mirror c, The light ray that enters the eyeball from the bottom is
It becomes orthogonal to the optical axis x of the LCD.
When the angle formed by the normal to the half mirror c with respect to the optical axis x of the half mirror c is reduced, the edge of the concave mirror b on the opposite side of the optical axis x of the LCD at the intersection of the half mirror c and the concave mirror b becomes half mirror c. It will kick the ray that is reflected by and enters the eyeball.

Specifically, when the vertical angle of view is 2φ and the refractive index of the prism medium when the half mirror c is a prism is n, the optical axis x of the LCD and the half mirror c
It is desirable to set the angle θ formed by the normal line to π / 4−φ ′ / 2 ≦ θ <π / 4 (4). However, φ ′ = sin ⁻¹ (sin φ / n) (5)

When the medium of the prism is air (half mirror), the equation (4) becomes π / 4-φ / 2 ≦ θ <π / 4 (6).

In the above equation (4) or equation (6), the closer the value of θ is to the left side, the greater the above effect.

When a surface having a positive power for miniaturizing the optical system is inserted between the eyeball and the half mirror c, a value slightly larger than the left side of the equations (4) and (6) is optimal. Value exists.

Next, an embodiment of the image display device of the present invention will be described in comparison with a conventional example.

FIG. 6A shows a sectional view of the optical system of the first embodiment of the present invention, and FIG. 6B shows a sectional view of the optical system of the first conventional example corresponding thereto. In the figure, E is the observer's pupil position,
1 is an LCD, 2 is a half mirror, 3 is a concave mirror, L
The angle formed by the optical axis of the CD 1 and the normal line of the half mirror 2 is 38.5 degrees in the case of the first embodiment and 45 in the case of the first conventional example.
It is degree. Although these numerical data will be described later, the angle of view is 35 × 26 degrees, and the LCD size is 26.0 × 1.
It is equal to 9.1 mm, and the concave mirror 3 and the concave mirror 3 from the LCD 1
To pupil position E are equal.

In the present embodiment, the angle formed by the optical axis of the LCD 1 and the normal line of the half mirror 2 is 38.5 degrees, so that the distance from the end face of the optical system to the eyeball is 16.5 m in the conventional example.
From m to 17.5 mm, LCD from half mirror 2 end face
The distance to 1 can be extended from the conventional 14 mm to 19 mm. Further, the area of the half mirror 2 can be reduced by 7.5% as compared with the conventional example.

FIG. 7A shows a sectional view of the optical system of the second embodiment of the present invention, and FIG. 7B shows a sectional view of the optical system of the second conventional example corresponding thereto. In the figure, E is the observer's pupil position,
1 is an LCD, 4 is a prism beam splitter, 2 is a half mirror surface of the prism beam splitter 4, 3 is a concave mirror, 6 is a surface of the prism beam splitter 4 facing the LCD 1, and 7 is a surface of the prism beam splitter 4 facing the eye. The angle formed by the optical axis of the LCD 1 and the normal line of the half mirror surface 2 is 40.5 degrees in the second embodiment and 45 degrees in the second conventional example. Although these numerical data will be described later, the angle of view is equal to 37 × 27.6 degrees, and the LCD size is equal to 26.0 × 19.1 mm.

In this embodiment, the half mirror is a prism beam splitter, whereby the spread of the light flux can be suppressed and the angle of view can be widened. In this embodiment, the angle formed by the optical axis of the LCD 1 and the normal line of the half mirror surface 2 is set to 40.5 degrees, so that the distance from the prism end surface 7 to the eyeball is 19.0 mm to 1 in the conventional example.
The distance from the prism end surface 6 to the LCD 1 can be extended to 9.2 mm from 22.5 mm in the conventional example to 24.9 mm. In addition, the volume of the prism is 12 compared with the conventional example.
% Can be reduced.

FIG. 8A shows a sectional view of the optical system of the third embodiment of the present invention, and FIG. 8B shows a sectional view of the optical system of the third conventional example corresponding thereto. In the figure, E is the observer's pupil position,
1 is an LCD, 4 is a prism beam splitter, 2 is a half mirror surface of the prism beam splitter 4, 3 is a concave mirror, 6 is a surface of the prism beam splitter 4 facing the LCD 1, and 7 is a surface of the prism beam splitter 4 facing the eye. , 8 is a concave lens, 9 is a convex lens, LCD
The angle formed by the optical axis of 1 and the normal of the half mirror surface 2 is the third
In the case of the embodiment, it is 41 degrees, and in the case of the second conventional example, it is 45 degrees. These numerical data will be described later, but the angle of view is 4
4 × 33.2 degrees, LCD size is 26.0 × 1
Equal to 9.1 mm.

In this embodiment, the surface 7 on the eyeball side of the prism of the second embodiment has a convex power to suppress the spread of the light beam in the prism to further widen the angle. In the conventional example, the distance from the LCD 1 to the prism is short,
In the diopter adjustment by moving the LCD 1, the adjustment range is narrow when the diopter is corrected in the negative direction (the image position is moved closer). In this embodiment, the angle between the optical axis of the LCD 1 and the normal to the half mirror surface 2 is 41 degrees, so that the distance from the top of the prism end face 6 to the LCD 1 is 5.55 mm to 7 mm in the conventional example. It can be extended to 0.00 mm. As a result, the diopter correction is performed to the negative side by 1.3 /
It can be extended by m. Further, the distance from the prism end face 7 to the eyeball is set to 20.0 m from the conventional example of 19.3 mm.
can be extended to m. Further, the volume of the prism can be reduced by 10% as compared with the conventional example.

Numerical data of the reverse tracking of each of the above-mentioned embodiments and the conventional example will be shown below, but all these data are shown in the order of the reverse tracking from the pupil E to the image display element 1, and all the embodiments are shown. , R ₀ is the pupil E, d ₀ is the working distance (WD), r ₁ , r ₂ ... Is the radius of curvature of each lens surface or reflecting surface, and d ₁ , d ₂ ... Is the distance between the surfaces. , N _d1 and n _d2
... d-line refractive index of each glass material, ν _d1, ν _d2 ... represents the Abbe number of each glass material, r ₂₀ represents a video display device 1. Moreover, the aspherical shape is expressed by z = ch ² / {1+ ^{[1-c 2 (K + 1} ) h 2 ] ^{1/2} + Ah 4 + Bh 6} + Ch 8 + Dh 10 ··· (7). However, z: deviation from a tangent plane in contact with the lens on the optical axis (sag value) c: paraxial curvature h: distance from the optical axis K: conical constant A: fourth-order aspherical coefficient B: sixth-order aspherical coefficient C : 8th-order aspherical surface coefficient D: 10th-order aspherical surface coefficient.

First Embodiment r ₀ = ∞ (E) d ₀ = 35.300000 r ₁ = ∞ (2) d ₁ = -14.172190 (θ = 38.500000 °) r ₂ = 85.48059 (3) d ₂ = 43.835912 r ₂₀ = ∞ (1) First conventional example r ₀ = ∞ (E) d ₀ = 32.000000 r ₁ = ∞ (2) d ₁ = -17.472190 (θ = 45.000000 °) r ₂ = 85.48059 (3) d ₂ = 43.835912 r ₂₀ = ∞ (1).

Second embodiment r ₀ = ∞ (E) d ₀ = 19.200000 r ₁ = ∞ (7) d ₁ = 16.200000 n _d1 = 1.516330ν _d1 = 64.1 r ₂ = ∞ (2) d ₂ = -13.339170 n _d2 = 1.516330ν _d2 = 64.1 (θ = 40.500000 °) r ₃ = 123.40676 (3) d ₃ = 24.500000 n _d3 = 1.516330ν _d3 = 64.1 r ₄ = ∞ (6) d ₄ = 24.846988 r ₂₀ = ∞ (1) Second conventional example r ₀ = ∞ (E) d ₀ = 19.000000 r ₁ = ∞ (7) d ₁ = 14.500000 nd ₁ = 1.516330ν _d1 = 64.1 r ₂ = ∞ (2) d ₂ = -15.339170 nd ₂ = 1.516330 ν _d2 = 64.1 (θ = 45.000000 °) r ₃ = 123.40638 (3) d ₃ = 28.000000 n _d3 = 1.516330 ν _d3 = 64.1 r ₄ = ∞ (6) d ₄ = 22.542094 r ₂₀ = ∞ (1).

Third Embodiment r ₀ = ∞ (E) d ₀ = 20.000000 r ₁ = 79.40268 (7) d ₁ = 17.000000 n _d1 = 1.516330ν _d1 = 64.1 r ₂ = ∞ (2) d ₂ = -15.000000 n _d2 = 1.516330ν _d2 = 64.1 (θ = 41.000000 °) r ₃ = 55.04852 d ₂ = -0.500000 r ₄ = 140.20084 (8) d ₂ = -1.500000 n _d3 = 1.805177ν _d3 = 25.4 r ₅ = 9305.57882 (9) d ₂ = -2.600000 n _d4 = 1.516330ν _d4 = 64.1 r ₆ = 144.37844 (3) d ₃ = 2.600000 n _d5 = 1.516330ν _d5 = 64.1 r ₇ = 9305.57882 d ₂ = 1.500000 n _d6 = 1.805177ν _d6 = 25.4 r ₈ = 140.20084 d ₂ = 0.500000 r ₈ = 55.04852 d ₃ = 26.000000 n _d7 = 1.516330ν _d7 = 64.1 r ₁₀ = ∞ (6) d ₄ = 7.000000 (aspherical surface) r ₂₀ = ∞ (1) Aspherical surface coefficient 10th surface k = -1.000000 A = 0.187498 × 10 ^-4 B = C = D = 0 3rd conventional example r ₀ = ∞ (E) d ₀ = 19.340000 r ₁ = 91.35114 (7) d ₁ = 16.000000 n _d1 = 1.516330ν _d1 = 64.1 r ₂ = ∞ (2) d ₂ = -17.000000 nd ₂ = 1.51 6330ν _d2 = 64.1 (θ = 45.000000 °) r ₃ = 50.81031 d ₂ = -0.500000 r ₄ = 140.90134 (8) d ₂ = -1.500000 n _d3 = 1.805177ν _d3 = 25.4 r ₅ = 9305.57882 (9) d ₂ =- 2.600000 n _d4 = 1.516330ν _d4 = 64.1 r ₆ = 151.92998 (3) d ₃ = 2.600000 n _d5 = 1.516330ν _d5 = 64.1 r ₇ = 9305.57882 d ₂ = 1.500000 n _d6 = 1.805177ν _d6 = 25.4 r ₈ = 140.90134 d ₂ = 0.500000 r ₈ = 50.81031 d ₃ = 29.000000 n _d7 = 1.516330ν _d7 = 64.1 r ₁₀ = ∞ (6) d ₄ = 5.550034 (aspherical surface) r ₂₀ = ∞ (1) 10th surface of aspherical surface k = -1.000000 A = 0.252379 × 10 ^-4 B = C = D = 0.

Although the video display device of the present invention has been described above based on some embodiments, the present invention is not limited to these embodiments and various modifications can be made.

[0046]

As is apparent from the above description, according to the image display device of the present invention, the extension line of the optical axis emitted from the image display element and the point where the extension line of the optical axis is in contact with the transmissive / reflecting surface. Since the angle formed by the normal line of the transmissive / reflective working surface at is less than π / 4, the area of the transflective working surface can be reduced, and the distance between the projection optical system and the image display element can be reduced. The distance becomes shorter, the diopter adjustment range becomes wider, and the distance (working distance) between the projection optical system and the eyeball becomes shorter, so that it is possible to observe while wearing glasses.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic form of an image display device according to the present invention.

FIG. 2 is a development view of an optical system that is the basis of the present invention.

FIG. 3 is a diagram showing a half mirror arranged for a light flux reflected by a concave mirror.

FIG. 4 is a sectional view of an optical system on a plane including the optical axis of the LCD and the center of the eyeball.

FIG. 5 is a diagram showing a relationship between g (θ) and θ.

FIG. 6 is a sectional view of the optical system of the first example and the optical system of the first conventional example corresponding thereto.

FIG. 7 is a cross-sectional view of an optical system of a second example and an optical system of a first conventional example corresponding thereto.

FIG. 8 is a cross-sectional view of an optical system of a third example and an optical system of a first conventional example corresponding thereto.

FIG. 9 is a cross-sectional view showing a configuration of a conventional image display element.

[Explanation of symbols]

LCD: Liquid crystal display element a ... LCD b ... Optical element with positive power (concave mirror) c ... Half mirror d ... eye point x ... LCD optical axis E ... Observer pupil position 1 ... LCD 2 ... Half mirror (half mirror surface) 3 ... Magnifying mirror 4 ... Prism beam splitter 5 ... Eyeball of observer 6 ... Surface of prism beam splitter facing LCD 7 ... Surface of prism beam splitter facing the eye 8 ... concave lens 9 ... Convex lens

Continuation of front page (51) Int.Cl. ⁷ Identification code FI H04N 5/64 511 H04N 5/64 511A

Claims (6)

(57) [Claims] 1. An image display device having an image display element for displaying an image and an observation optical system for guiding an image light flux formed by the image display element to an eyeball of an observer, wherein the observation optical system comprises: At least, the it has a concave reflection curved surface to provide a positive power in the image beam, and a transparent reflecting action surface that combines both the reflecting surface action of reflection and transmission surface acts to transmit the image beam, before Symbol The concave reflection curved surface and the transflective action surface, the concave reflection curved surface facing the concave surface toward the transmission reflection surface side, and the optical path between the concave reflection curved surface and the transflective action. It is configured to be folded back to form a reciprocal optical path, and the extension line of the optical axis emitted from the image display element and the transmission reflection at the point where the extension line of the optical axis contacts the transmission reflection action surface. The normal of the working surface An image display device having a corner angle smaller than π / 4. 2. The observation optical system comprises a prism member in which a prism medium is filled at least between the concave reflection curved surface and the transmissive / reflecting surface. The image display device according to item 1. 3. The prism member of the observing optical system has the image light beam incident on the prism member in an optical path until the image light beam emitted from the image display element reaches the concave reflection curved surface. The image display device according to claim 2, wherein an incident surface for light is arranged. 4. The observation optical system has at least a prism member, and the prism member of the observation optical system has an optical path through which an image light flux emitted from the image display element reaches the concave reflection curved surface. An incident surface for allowing the image light flux to enter the prism member is disposed therein, and the incident surface of the prism member has an aspherical surface shape that gives power to the light flux. The video display device according to claim 1, wherein 5. The image display device according to claim 1, wherein the image display element is arranged such that a surface from which the image light flux is emitted is directed toward the observer's eyeball side. 6. An angle formed by an extension line of the optical axis emitted from the image display element and a normal line of the transmission / reflection action surface at a point where the extension line of the optical axis is in contact with the transmission / reflection action surface. θ
However, when the vertical angle of view is 2φ and the refractive index of the medium of the prism member is n, then π / 4−φ ′ / 2 ≦ θ <π / 4 (4) where φ ′ = The image display device according to claim 2, wherein sin ⁻¹ (sin φ / n) (5) is satisfied.