JP3397256B2 - 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,
A half mirror obliquely arranged at the intersection of the optical axis of the image display element and the visual axis of the observer for guiding the image light flux formed by the image display element to the eyeball of the observer, and having a positive power. In an image display device comprising a magnifying mirror arranged to face the image display element via the half mirror, an angle formed by a normal line of the half mirror and an optical axis of the image display element is π / 4. It is characterized by being smaller.

In this case, the angle θ formed by the normal line of the half mirror and the optical axis of the image display element is π / 4−φ / 2 ≦ θ <π / 4 when the vertical angle of view is 2φ. It is desirable to satisfy (6).

Another image display device of the present invention is an image display device for displaying an image and a light beam of the image display device for guiding an image light flux formed by the image display device to an eyeball of an observer. Axis and a prism beam splitter having a half mirror surface inclined at the intersection of the observer's visual axis, and a magnifying mirror having a positive power and facing the image display element via the half mirror surface. And an optical axis of the image display element forms an angle of π /
It is characterized by being smaller than 4.

In this case, the angle θ formed by the normal line of the half mirror surface and the optical axis of the image display device is 2φ in the vertical direction.
When the refractive index of the medium of the prism is n, then π / 4−φ ′ / 2 ≦ θ <π / 4 (4) where φ ′ = sin ⁻¹ (sin φ / n) It is desirable to satisfy (5).

[0011]

In the present invention, the angle formed by the normal line of the half mirror or the half mirror surface and the optical axis of the image display element is π / 4.
Since it is set smaller, the area of the half mirror or the volume of the prism beam splitter can be reduced, the distance between the projection optical system and the image display element is shortened, and the diopter adjustment range is increased. The distance (working distance) between the projection optical system and the eyeball becomes short, and it is possible to observe while wearing glasses.

[0012]

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 device according to the present invention. An LCD 1 for displaying an image and an optical axis of the LCD 1 and an observer for guiding an image light flux formed by the LCD 1 to an eyeball 5 of the observer. A half mirror 2 that is inclined at the intersection of the visual axes of
It comprises a magnifying reflecting mirror 3 having a positive power and opposed to the LCD 1 through a half mirror 2, and an angle θ formed by a normal line of the half mirror 2 and an optical axis of the LCD 1 is smaller than π / 4. Thus, the half mirror 2 is arranged.

FIG. 2 shows a development view of an 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 display image size of the LCDa and the angle of view of the observed image. When the element b having refractive power is a single concave mirror, the distance l ₁ between the LCDa and the concave mirror b and the distance l ₂ between the concave mirror b and the eye point d.
Is uniquely determined. The degree of freedom in the arrangement of the optical system is that the distance l ₂₁ between the concave mirror b and the half mirror c and the LCDa
Is an angle formed by the optical axis of and the normal line of the half mirror c. In the present invention, by optimizing the angle of the half mirror c, it becomes possible to improve the above-mentioned problems (1) to (3). Hereinafter, these will be described in terms of the size of the projection optical system, the distance between the projection optical system and the LCD, and the distance between the projection optical system and the eyeball with reference to FIGS.

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 when the half mirror c is formed of a prism beam splitter, LCDa from the end surface u of the half mirror c closer to 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) is a function of the angle θ only, and this is given by 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 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 decreasing the angle θ formed by the optical axis x of the LCD and the normal line of the half mirror c.

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

However, when the angle formed by the normal line 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 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 is inserted between the eyeball and the half mirror c to reduce the size of the optical system, the optimum value is a little larger than the left side of the equations (4) and (6). 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 LCD, 2 is a half mirror, 3 is a concave mirror, and the angle formed by the optical axis of LCD 1 and the normal to half mirror 2 is 38 in the case of the first embodiment. .5
And 45 degrees in the case of the first conventional example. Although these numerical data will be described later, the angle of view is 35 × 26 degrees, LCD
The size is equal to 26.0 x 19.1 mm, and LC
Distances from D1 to concave mirror 3 and from concave mirror 3 to pupil position E are equal.

In this embodiment, the angle between the optical axis of the LCD 1 and the normal line of the half mirror 2 is set to 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, since the half mirror is a prism beam splitter, 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 line of 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 in the conventional example to 7 mm. 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-described 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 = 1.516 330ν _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 based on some embodiments, the present invention is not limited to these embodiments and various modifications can be made.

[0041]

As is apparent from the above description, according to the image display device of the present invention, the angle formed by the normal line of the half mirror or the half mirror surface and the optical axis of the image display element is set to be smaller than π / 4. Therefore, the area of the half mirror or the volume of the prism beam splitter can be reduced, the distance between the projection optical system and the image display element is shortened, and the diopter adjustment range is increased. The eyeball distance (working distance) becomes shorter, and 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

Claims (4)

(57) [Claims] 1. An image display element for displaying an image, and an intersection of an optical axis of the image display element and a visual axis of the observer for guiding an image light flux formed by the image display element to an eyeball of the observer. An image display device comprising an inclined half mirror and a magnifying mirror which has a positive power and is opposed to the image display element via the half mirror, wherein a normal line of the half mirror and the An image display device characterized in that an angle formed by an optical axis of the image display element is smaller than π / 4. 2. The angle θ formed by the normal line of the half mirror and the optical axis of the image display element is π / 4−φ / 2 ≦ θ <π / when the vertical angle of view is 2φ. 4. The image display device according to claim 1, characterized in that (4) is satisfied. 3. An image display element for displaying an image and an intersection of an optical axis of the image display element and a visual axis of the observer for guiding an image light flux formed by the image display element to an eyeball of the observer. An image display device comprising: a prism beam splitter having an inclined half mirror surface; and a magnifying mirror having a positive power and facing the image display element via the half mirror surface. An image display device, wherein an angle formed by a normal line of the half mirror surface and an optical axis of the image display element is smaller than π / 4. 4. The angle θ formed by the normal line of the half mirror surface and the optical axis of the image display element has a vertical field angle of 2φ,
When the refractive index of the medium of the prism is n, then π / 4−φ ′ / 2 ≦ θ <π / 4 (4) where φ ′ = sin ⁻¹ (sin φ / n) The image display device according to claim 3, wherein the condition (5) is satisfied.