JPH07174973A - Visual display device - Google Patents

Abstract

PURPOSE:To obtain a visual display device by which an observed picture can be observed as if being in the distance even in a small space and a wide observa tion viewing angle, especially, >=60 deg. is provided, which is miniaturized and where the joint of the picture is made inconspicuous. CONSTITUTION:This device is provided with at least two semitransmissive curved surfaces 2 and 3 whose concave surface is faces the pupil 1 side where the center of curvature is arranged in the vicinity of the pupil 1 of an observer. The curved surfaces 2 and 3 are provided with two or more ocular optical systems consisting of a homocentric optical system arranged so as to transmits a light beam at least once and reflect the light beam at least once, and, the picture is enlarged and projected in the eyeball of the observer by the respective ocular optical systems so that the viewing angle of respective two-dimensional picture display elements 4 displaying the pictures in different directions may be synthesized, thereby the observed picture is observed in the distance at the wide observation viewing angle in a state where the joint of the two-dimensional picture display element is made inconspicuous in spite of the small-sized device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual display device,
In particular, the present invention relates to a visual display device having a wide angle of view and good resolution.

[0002]

2. Description of the Related Art Generally, as a visual display device for providing a wide viewing angle of view, a device for projecting a movie or TV projection device onto a dome screen to provide a viewing angle of 360 ° (for example, Japanese Laid-Open Patent Publication No. No. 178691) or a device for providing a wide viewing angle by arranging television screens is exhibited and viewed at general theaters and pavilions of exhibitions.

[0003]

However, in the above-mentioned screen projection type visual display device, if the screen is not located sufficiently far away, it is not possible to recognize that a distant image is being observed, and a sense of realism is felt. Absent. The cause is that the image observed by the observer is only displayed on the display surface of the screen or TV screen, and the distance from the observer to the image display surface must be a few meters or more,
The observed image does not seem to be far away. This is because the perspective adjustment function of the human eye works to focus on distant objects and nearby objects, so even when images such as distant scenery are displayed on a nearby display surface. , Because it feels close.

[0004] In order to recognize an observing image at a distance as being distant, it is necessary to increase the distance from the observer to the display surface, resulting in a large observing device.

Further, in the method of arranging large televisions, the joints of each TV screen are conspicuous, and the visual display device also lacks the sense of reality. in this way,
As a visual display device that attaches importance to the presence, it can be easily viewed by individuals or by a few people, and can be easily moved to general households.
There has been no small visual display device that can be loaded on a vehicle or the like.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a small image and a wide observation angle of 60 ° or more that allows an observation image to be observed at a distance even in a small space. It is an object of the present invention to provide a visual display device in which the joints are not conspicuous.

[0007]

The visual display device of the present invention which achieves the above object comprises at least two or more two-dimensional image display elements, and the at least two or more two-dimensional image display elements are different from each other. Direction image is displayed, and a first semi-transmissive reflective surface having a center of curvature substantially on the optical axis and having a concave surface in the direction of the center of curvature, and a center of curvature of the first semi-transmissive reflective surface. And at least two eyepiece optical systems each of which is a concentric optical system having a second semi-transmissive reflective surface having a center of curvature substantially at the same position.

In this case, each concentric optical system has first and second semi-transmissive reflective surfaces having the centers of curvature at substantially the same positions, and the light flux transmitted through the first semi-transmissive reflective surface is The reflected light flux reflected by the second semi-transmissive reflective surface and reflected by the second semi-transmissive reflective surface is reflected by the first semi-transmissive reflective surface, and then the second semi-transmissive reflective surface. It is desirable that the concentric optical system is configured such that the first and second semi-transmissive reflective surfaces are configured to be transmitted through the surface.

Further, it is desirable that the two semi-transmissive reflective surfaces of each concentric optical system are arranged with their concave surfaces facing the observer.

Further, it is desirable to dispose a blocking means composed of a polarization optical element in order to block a light ray which is transmitted without being reflected by the two semi-transmissive reflecting surfaces of each concentric optical system.

When the radii of curvature of the first and second semi-transmissive reflecting surfaces are R ₁ and R ₂ , 0.5 <| R ₁ / R ₂ | <1.8 (2) It is desirable to satisfy the conditions.

Further, the radius of curvature of the first semi-transmissive reflective surface is R ₁ , the distance from the pupil to the first semi-transmissive reflective surface near the pupil is D ₁ , and the first semi-transmissive reflective surface and the second semi-transmissive reflective surface. It is desirable that the condition of 0.4 <| (D ₁ + D ₂ ) / R ₂ | <1.7 (3) is satisfied, where D ₂ is the interplanar spacing.

[0013]

The reason and operation of adopting such a structure in the present invention will be described below. The present invention has been made to solve the above-mentioned problems, and has at least two semi-transmissive curved surfaces with concave surfaces facing the pupil, where the center of curvature is arranged near the pupil, and the at least two semi-transmissive curved surfaces are provided. Each curved surface has at least one light transmission and at least one light transmission.
Separate two-dimensional image display device having at least two eyepiece optical systems composed of concentric optical systems arranged so as to reflect a ray of light, and displaying images in different directions by each concentric optical system. Is projected on the observer's eyeball so as to synthesize the angle of view, and a wide viewing angle of view can be obtained with a small device.
The joint of the three-dimensional image display device is made inconspicuous so that the observation image can be observed at a distance.

The concentric optical system used in the present invention will be described below. In the following, for convenience of explanation, the concentric optical system will be described as an image-forming optical system. However, in the optical system of the present invention, it is assumed that a light ray travels in the opposite direction with the image plane as an object point. It goes without saying that it is used as an eyepiece optical system.

The reason why the concentric optical system produces less aberration is shown in FIG.
Will be described with reference to. FIG. 1 is a diagram for explaining the basic configuration of a concentric optical system used in the present invention and the reason why aberration is small. In FIG. 1, the pupil position is 1, the first semi-transmissive reflecting surface is 2, The semi-transmissive reflective surface 2 is 3, and the image surface is 4. FIG. 1 is an optical path diagram when the center of curvature of the first surface 2 and the center of curvature of the second surface 3 completely coincide with the pupil position 1. What can be seen from this optical path diagram is that the pupil plane 1 and the first
Since the center of curvature of the surface 2 and the center of curvature of the second surface 3 coincide with each other, both the on-axis ray and the off-axis ray are rotationally symmetric with respect to the pupil position 1. This means that astigmatism and coma which are off-axis aberrations do not occur. In addition, since all surfaces having refractive power are reflecting surfaces, chromatic aberration does not occur in principle. Further, when the F number is 2 or less, the occurrence of spherical aberration can be almost ignored, and the optical system is very excellent in terms of aberration.

However, there is a problem in production as it is, it is practically impossible to form such a large spherical body, and the production cost is too high to easily use. Further, the field curvature generated in such a concentric optical system is very large, and it is difficult to use a flat two-dimensional image display device.

The present invention succeeds in favorably correcting the field curvature aberration of the concentric optical system in which the occurrence of aberration is extremely small as described above. As a result, it is possible to use a flat image display element, and the price of the image display element can be reduced.

The field curvature correcting means of the present invention will be invented below. The eyepiece optical system of US Pat. No. 27,356 will be described with reference to FIG. 2 is also an eyepiece optical system, but for convenience of explanation of the present invention, reference numeral 66 is a pupil plane, and 62 is a pupil plane.
Will be described as an image plane and an imaging optical system will be described. In FIG. 2, in order to correct the field curvature generated by the concave mirror 6, the image surface 62
Is curved to correct the field curvature. However, in general, a curved image plane is not suitable for arranging an image display element such as a CRT or LCD. Therefore,
In the present invention, as shown in FIG. 1 described above, the convex mirror 2 corrects the aberration of the field curvature generated by the concave mirror 3.

That is, the Petzval sum PS, which is generally well-known as the amount of field curvature, is expressed by the following equation. PS = Σ (1 / n · f) (1) where n is the refractive index and f is the focal length of the surface. In the case of U.S. Pat. No. Re. 27356, the Petzval sum generated when a light ray is reflected by the concave mirror 6 is not corrected at all because the focal length of the plane mirror 16 is ∞. Therefore, in the present invention, the plane mirror 16 is used as the convex mirror 2, and the Petzval sum generated in the concave mirror 3 can be corrected by the convex mirror 2.

In the optical system represented by the camera reflecting telescope shown in FIG. 3, a concave mirror M is used as a light beam extraction port.
It is necessary to provide an opening at the center of C. In order to reduce the vignetting of light rays at the peripheral field angle that occurs at this aperture, the concave mirror M
It is necessary to arrange the pupil plane around the opening of C. However, even with such an arrangement, the angle of view was limited by the aperture of the concave mirror MC and the aperture of the convex mirror MV, and could only be a few degrees.

In order to solve this problem, the pupil plane 1 should not be located around the concave mirror 3 or the convex mirror 2 or on the image side of the concave mirror 3. That is, it is an important means to arrange the pupil plane 1 in the direction in which the concave mirror 3 has the center of curvature.

Further, in order to perform good aberration correction, it is preferable that the following conditional expressions be satisfied. The following conditional expressions correspond to each aberration, and the angle of view and F
Each conditional expression is independent and has no correlation depending on actual use such as number. It is also necessary to satisfy all the conditional expressions depending on the usage conditions.

First, the relationship between the first surface 2 and the second surface 3 will be described. As described above, the correction of the Petzval sum is particularly important for achieving good aberration correction, and the present invention satisfies the following conditions for the correction of the Petzval sum. This is very important. 0.5 <| R ₁ / R ₂ | <1.8 (2) where R ₁ is the radius of curvature of the first surface 2 and R ₂ is the radius of curvature of the second surface 3.

This conditional expression (2) defines the power distribution of the positive second surface 3 and the negative first surface 2. When the lower limit of 0.5 is exceeded, the first surface 2 And the correction balance of the Petzval sum mainly compensating on the second surface 3 is broken,
A large negative Petzval sum will occur. Further, when the upper limit of 1.8 is exceeded, the Petzval sum is positively large, and it becomes impossible to correct it in other aspects.

Further, in recent years, when it is necessary to deal with high-definition images represented by high-definition TV and the like, better Petzval sum correction is necessary, and it is more important to satisfy the following conditions. Is. 0.7 <| R ₁ / R ₂ | <1.7 (6) Next, the second semi-transmissive reflective surface 3 will be described. Pupil face 1
When the distance from the first surface 2 to the first surface 2 is D ₁ and the surface distance between the first surface 2 and the second surface 3 is D ₂ , it is preferable that 0.4 <| (D ₁ + D ₂ ) / R ₂ It is desirable that the condition | <1.7 (3) is satisfied.

When the lower limit of 0.4 to condition (3) is not reached, the angle of inclination of the chief ray exiting through the second surface 3 becomes large and negative astigmatism and coma occur. Also,
When the upper limit of 1.7 is exceeded, negative astigmatism and coma aberrations are reduced. This cancels out positive astigmatism and coma that occur when the light passes through the first surface 2, so that positive astigmatism and coma are increased in the entire lens system.

It is also important that the second surface 3 is concentric in the present invention. If the radius of curvature of the first surface 2 is R ₁ , the radius of curvature of the second surface 3 is R ₂ , and the spacing between the first surface 2 and the second surface 3 is D ₂ , then 1 <| (| R It is important to satisfy the condition of ₁ | + D ₂ ) / R ₂ | <1.8 (4).

The above condition (4) is a condition for enabling the entire system to correct the occurrence of coma and astigmatism generated on the second surface 3. When the lower limit of 1 is exceeded, perfect concentric optics is achieved. It becomes close to the system, the Petzval sum cannot be corrected, and a large field curvature occurs. On the other hand, when the upper limit of 1.8 is exceeded, the incident angle of the principal ray incident on the second surface 3 becomes large, and the positive coma aberration becomes large. In either case, it becomes impossible to form a clear image even in the periphery.

Further, preferably, the pupil plane 1 to the first plane 2
When the distance to is D ₁ and the radius of curvature of the first surface 2 is R ₁ , it is desirable to satisfy the condition | D ₁ / R ₁ | <1.5 (5).

When the upper limit of 1.5 to condition (5) is exceeded, the incident height of the principal ray incident on the first surface 2 becomes large, and the positive coma and astigmatism increase. Therefore, it becomes impossible to form a clear image even in the periphery.

Next, the surface spacing will be described. When the surface distance between the pupil surface 1 and the first surface 2 is D ₁ and the focal length of the entire system is F, it is important to satisfy the following condition: D ₁ /F<1.6 (7) Is.

The conditional expression (7) is a condition for reducing the coma aberration generated on the first surface 2. The upper limit of 1.
When it exceeds 6, the coma aberration generated on the first surface 2 becomes large, and it becomes impossible to correct it on other surfaces. Further, when the optical system of the present invention is used as an eyepiece optical system, it is important to satisfy the condition of 0.5 <D ₁ / F (8).

In the case of the eyepiece optical system, the above conditional expression (8) is the eyepoint of the eyepiece lens, and when the lower limit of 0.5 is exceeded, the observer's pupil position and the exit pupil position of the eyepiece optical system 1
However, it becomes impossible to observe the entire visual field.

When the surface distance between the first surface 2 and the second surface 3 is D ₂ , it is important that the condition of 0.2 <D ₂ /F<0.7 (9) is satisfied. Becomes This condition is the first
It is necessary to balance the Petzval sum generation on the second surface 3 and the Petzval sum generation on the second surface 3. When the upper limit of 0.7 or the lower limit of 0.2 is exceeded, the balance of the aberrations generated on the first surface 2 and the second surface 3 is lost,
Largely corrected Petzval sum aberrations will occur.

In order to cut the flare light which is transmitted through the first surface 2 and the second surface 3 without being reflected once and reaches the image surface 4, a polarization optical element using polarized light is used. Arrangement is important. For example, a first polarizing plate and a quarter-wave plate are arranged on the pupil 1 side of the first surface 2 to make the incident light circularly polarized light, and the semi-transmissive reflection surfaces of the first surface 2 and the second surface 3 are arranged. Another quarter-wave plate is disposed between the two, and the second polarizing plate having the first polarizing plate and the paranicol polarizing surface after the semi-transmissive reflecting surface of the second surface 3 is disposed. When such a polarization optical element is arranged, the regular light rays that are reflected once by the first surface 2 and the second surface 3, respectively, are reflected by the light rays of 4 times between the first surface 2 and the second surface 3.
It will pass through the quarter-wave plate three times, and the regular light beam will pass through the quarter-wave plate a total of four times.
Therefore, the plane of polarization of the light that has passed through the first polarizing plate does not rotate and passes through the second polarizing plate arranged in the paranicols.
However, the light rays that have passed through the semi-transmissive reflection surface of the first surface 2 without passing through the semi-transmissive reflection surface only pass through the quarter-wave plate twice in total, and the polarization surface is rotated 90 ° and cut by the second polarizing plate. To be done.

As described above, by using the polarization optical element, flare light can be cut. In addition, arrangements of polarization optical elements other than those described above are possible, and only one example is shown here.

[0037]

Embodiments of the visual display device of the present invention and a concentric optical system used as an eyepiece optical system thereof will be described below. First Embodiment FIG. 4A is a horizontal cross-sectional view of the visual display device of the first embodiment of the present invention above the observer's head. In the figure, 1 is an observer observation position, 2 is a first semi-transmissive surface, 3 is a second semi-transmissive surface, 4
Is a two-dimensional image display device surface which is an object in the present invention. In the present embodiment, five planar image display elements 4 and the first
And the second semi-transmissive surfaces 2 and 3, five concentric optical systems are connected together, and as shown in FIG. And a concentric optical system may be arranged.
You may change to the arrangement displayed on about 0 degree. Note that FIG.
In (b), the symbol P indicates a polarization optical element for blocking a light beam that directly reaches the observer 1 without being reflected by the two semi-transmissive surfaces 2 and 3.

Specifically, the focal length F of each concentric optical system is set to 1
m, the radius of curvature of the first semi-transmissive surface 2 is 1228 m
m, the distance between the first semi-transmissive surface 2 and the observer 1 is 597 mm, and the F number is 3,
The exit pupil diameter of 333 mm can be taken, and the observer 1
Even if you move your head, the image will not disappear. Furthermore, for use at home, etc., the focal length F should be 5
If it is set to about 00 mm, the overall size can be small.

Second Embodiment With reference to FIG. 5, one concentric optical system as a second embodiment will be described. In the figure, 1 is an observer pupil surface, 2 is a first semi-transmissive reflective surface, 3 is a second semi-transmissive reflective surface, 4 is a two-dimensional image display element surface, and 5 is a protective glass. Numerical examples are as shown below. Here, nd is the refractive index of the transparent glass at the d-line, and νd is its Abbe number (the same applies hereinafter). In this embodiment, the angle of view is 70 ° and the focal length is F = 10 mm, F
The number is 3.0.

Surface number Curvature radius Surface spacing nd νd 1 Pupil position 1 5.975 2 ∞ 0.337 1.5163 64.1 3 ∞ 1.660 4 -12.2885 0.168 1.5163 64.1 5 -12.2885 3.583 6 -12.5161 0.168 1.5163 64.1 7 -12.5161 (Reflecting surface 3) -0.168 1.5163 64.1 8 -12.5161 -3.583 9 -12.2885 -0.168 1.5163 64.1 10 -12.2885 (Reflecting surface 2) 0.168 1.5163 64.1 11 -12.2885 3.583 12 -12.5161 0.168 1.5163 64.1 13 -12.5161 0.033 14 Display surface 4 Third embodiment A single concentric optical system as a third embodiment will be described with reference to FIG. In the figure, 1 is an observer pupil surface, 2 is a first semi-transmissive reflective surface, 3 is a second semi-transmissive reflective surface, and 4 is a two-dimensional image display element surface. In this embodiment, one meniscus lens L is used, the concave surface thereof is the first semi-transmissive reflective surface 2 and the convex surface thereof is the second semi-transmissive reflective surface 3, and further, an aspherical surface for image distortion correction. The lens LA is arranged on the two-dimensional image display element surface 4 side. Numerical examples are as shown below. In this embodiment, the angle of view is 60 ° and the focal length is F = 1.
0 mm, F number is 2.0.

Surface number Curvature radius Surface spacing nd νd 1 Pupil position 1 11.423 2 -14.4225 4.817 1.5163 64.1 3 -14.9832 (Reflecting surface 3) -4.817 1.5163 64.1 4 -14.4225 (Reflecting surface 2) 4.817 1.5163 64.1 5 -14.9832 0.046 6 12.5539 (Aspherical surface) 0.914 1.5163 64.1 K = 0 A = -0.352385 × 10 ^-3 B = -0.213608 × 10 ^-5 C = 0 7 110.7802 1.857 8 Display surface 4 In the above, the aspherical surface has a conic constant of K and a non-spherical surface. When the spherical coefficients are A, B, and C, it is a rotationally symmetric surface represented by the following formula. However, in the following formula, R is a paraxial radius of curvature, and has a Z axis in the optical axis direction and a Y axis in the direction orthogonal to the optical axis. ^{Z = (Y 2 / R)} / [1+ {1- (1 + K) (Y / R) 2} 1/2] + AY 4 + BY 6 + CY 8 spherical aberration of the embodiment in FIG. 11 (a), astigmatism , A longitudinal aberration diagram showing distortion and a lateral aberration diagram are shown in FIG.

Fourth Embodiment One concentric optical system as a fourth embodiment will be described with reference to FIG. In the figure, 1 is an observer pupil surface, 2 is a first semi-transmissive reflective surface, 3 is a second semi-transmissive reflective surface, and 4 is a two-dimensional image display element surface. In this embodiment, one meniscus lens L is used, its concave surface is the first semi-transmissive reflective surface 2, and its convex surface is the second semi-transmissive reflective surface 3. Numerical examples are as shown below. The angle of view of this embodiment is 45 °,
The focal length is F = 10 mm and the F number is 3.0.

Surface number Radius of curvature Surface spacing nd νd 1 Pupil position 1 13.127 2 -11.2445 5.633 1.5163 64.1 3 -14.0354 (Reflecting surface 3) -5.633 1.5163 64.1 4 -11.2445 (Reflecting surface 2) 5.633 1.5163 64.1 5 -14.0354 0.348 6 Display Surface 4 FIG. 12 shows an aberration diagram similar to that of FIG. 11 of the present embodiment.

Fifth Embodiment One concentric optical system as a fifth embodiment will be described with reference to FIG. This embodiment is similar to the fourth embodiment. Numerical examples are as shown below. The angle of view of this embodiment is 4
At 5 °, focal length is F = 10mm, F number is 3.0
Is.

Surface number Radius of curvature Surface spacing nd νd 1 Pupil position 1 5.805 2 -24.3790 4.437 1.5163 64.1 3 -17.4632 (Reflecting surface 3) -4.437 1.5163 64.1 4 -24.3790 (Reflecting surface 2) 4.437 1.5163 64.1 5 -17.4632 3.193 6 Display Surface 4 FIG. 13 shows an aberration diagram similar to that of FIG. 11 of the present embodiment.

Sixth Embodiment One concentric optical system as a sixth embodiment will be described with reference to FIG. This embodiment is similar to the fourth embodiment. Numerical examples are as shown below. The angle of view of this embodiment is 4
At 5 °, focal length is F = 10mm, F number is 3.0
Is.

Surface number Radius of curvature Surface spacing nd νd 1 Pupil position 1 7.259 2 -27.0911 4.287 1.5163 64.1 3 -18.0607 (Reflecting surface 3) -4.287 1.5163 64.1 4 -27.0911 (Reflecting surface 2) 4.287 1.5163 64.1 5 -18.0607 3.534 6 Display Surface 4 FIG. 14 shows an aberration diagram similar to that of FIG. 11 of the present embodiment.

Seventh Embodiment One concentric optical system as a seventh embodiment will be described with reference to FIG. This embodiment is similar to the fourth embodiment.
Numerical examples are as shown below. In this embodiment, the angle of view is 45 °, the focal length is F = 10 mm, and the F number is 3.
It is 0.

Surface number Radius of curvature Surface spacing nd νd 1 Pupil position 1 9.152 2 -10.2521 5.711 1.5163 64.1 3 -13.6695 (Reflecting surface 3) -5.711 1.5163 64.1 4 -10.2521 (Reflecting surface 2) 5.711 1.5163 64.1 5 -13.6695 0.100 6 Display Surface 4 FIG. 15 shows an aberration diagram similar to that of FIG. 11 of the present embodiment.

The above conditional expressions (2) (= (6)), (3), (4), (5) and (7) of the above second to seventh embodiments.
The values of (= (8)) and (9) are shown in the following table.

[0051]

As is apparent from the above description, according to the present invention, it is possible to provide a visual display device capable of clearly observing a peripheral viewing angle with a wide viewing angle.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the basic configuration of a concentric optical system used in the present invention and the reason why aberration is small.

FIG. 2 is a diagram showing a configuration of one conventional eyepiece optical system.

FIG. 3 is a diagram showing a configuration of an optical system of a conventional single reflecting telescope for a camera.

FIG. 4 is a horizontal and vertical sectional view of the visual display device according to the first embodiment of the present invention.

FIG. 5 is a sectional view of a concentric optical system according to a second example.

FIG. 6 is a sectional view of a concentric optical system according to a third example.

FIG. 7 is a sectional view of a concentric optical system according to a fourth example.

FIG. 8 is a sectional view of a concentric optical system according to a fifth example.

FIG. 9 is a sectional view of a concentric optical system according to a sixth example.

FIG. 10 is a sectional view of a concentric optical system according to a seventh example.

FIG. 11 is a longitudinal aberration diagram (a) and a lateral aberration diagram (b) showing spherical aberration, astigmatism, and distortion of the third example.

FIG. 12 is an aberration diagram similar to FIG. 11 of the fourth example.

FIG. 13 is an aberration diagram similar to FIG. 11 of the fifth example.

FIG. 14 is an aberration diagram similar to FIG. 11 of the sixth example.

FIG. 15 is an aberration diagram similar to FIG. 11 of the seventh example.

[Explanation of symbols]

 1 ... Observer pupil position 2 ... 1st semi-transmissive reflective surface 3 ... 2nd semi-transmissive reflective surface 4 ... Two-dimensional image display element surface 5 ... Protective glass L ... Meniscus lens LA ... Aspherical lens P ... Polarizing optical element

Claims (1)

[Claims] 1. At least two or more two-dimensional image display elements are provided, images of different directions are displayed on the at least two or more two-dimensional image display elements, and a center of curvature is approximately on the optical axis. A first semi-transmissive reflective surface having a concave surface in the direction of the center of curvature, and a second semi-transmissive reflective surface having a center of curvature substantially at the same position as the center of curvature of the first semi-transmissive reflective surface. A visual display device comprising at least two eyepiece optical systems each of which is a concentric optical system having.