JPH1138352A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized image display device which affords a clear observation image with less distortion also at a wide viewing angle and which is especially suitable to a head-mount type or face mask type image display device. SOLUTION: The device is constituted of an image display element 6 and an eyepiece optical system for guiding an image formed by the image display element 6 to an observer's eye ball position 1 without forming an intermediate image so that the image may be observed as a virtual image. In this case, the eyepiece optical system is constituted of an eccentric prism optical system constituted of three faces 3 to 5 including two eccentric reflection faces, and at least one of the reflection faces is constituted of a rotation asymmetrical free-curved face provided with one symmetrical face, and also, the eyepiece optical system is constituted so that a chief ray 8 emitted from each point of the image display screen of the image display element 6 may be diverged and made incident on the eccentric prism optical system 7, so that the small- sized, light-weight image display device whose viewing angle is wide and which is provided with a high optical performance is obtained by introducing the aberration correction by eccentricity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, and more particularly to a head or face-mounted image display device capable of being held on the head or face of an observer.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 3-101709 discloses a conventional head or face-mounted image display apparatus. This image display device transmits a display image of an image display element as an aerial image by a relay optical system composed of a positive lens, and enlarges this aerial image by an eyepiece optical system composed of a concave reflecting mirror to enter an observer's eyeball. It is to project.

Another conventional type is disclosed in US Pat. No. 4,669,810. This apparatus forms an intermediate image from a CRT image via a relay optical system, and projects the intermediate image on an observer's eye by a combiner having a reflective holographic element and a hologram surface.

Another conventional image display device is disclosed in Japanese Patent Application Laid-Open No. 62-214782. In this device, an image display element is magnified by an eyepiece so that it can be directly observed.

Further, another conventional image display device is disclosed in US Pat. No. 4,026,641. In this device, an image of an image display device is transmitted to a curved object surface by a transmission device, and the object surface is projected onto the air by a toric reflection surface.

Another conventional image display device is disclosed in US Pat. No. Re. 27,356.
This apparatus is an eyepiece optical system that projects an object plane onto an exit pupil by using a transflective concave mirror and a transflective plane mirror.

In addition, US Pat. No. 4,322,135
No. 4,969,724; European Patent No. 0,724;
Nos. 583 and 116A2, JP-A-7-333551 and JP-A-8-313829 are also known.

[0008]

However, in these prior arts, since the reflecting surface and the transmitting surface constituting the optical system are composed of a spherical surface, a rotationally symmetric aspherical surface, a toric surface, an anamorphic surface and the like, a wide area is required. It has been difficult to satisfactorily correct ray aberration and distortion simultaneously at the angle of view.

If the aberration of the observed image is corrected well and the distortion is not corrected properly, the observed image is distorted and observed by the observer. , Can not be fused,
When a graphic or the like is displayed, the graphic or the like is distorted and observed, and a correct shape cannot be recognized.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a small-sized head or face type, which can provide a clear and less distorted observation image even at a wide angle of view. An object of the present invention is to provide an image display device suitable for an image display device.

[0011]

According to the present invention, there is provided an image display apparatus, comprising: an image display element; and an intermediate image at an observer's eyeball position so that an image formed by the image display element can be observed as a virtual image. And an eyepiece optical system including an eccentric prism optical system that guides without forming an image, wherein the eccentric prism optical system has at least one of reflection and transmission of light emitted from the image display element. At least three surfaces are arranged eccentrically to each other, the space between the at least three surfaces is filled with a transparent medium having a refractive index of 1.3 or more, and internal reflection is performed at least twice inside the optical system. At least two of the at least three surfaces are formed of reflective surfaces, and the at least two reflective surfaces are At least two reflecting surfaces are arranged at positions where the reflected light does not intersect inside the optical system, and at least one of the reflecting surfaces has an in-plane and out-of-plane shape. Neither of them has an axis of rotational symmetry, and it is a plane-symmetric free-form surface having only one plane of symmetry, and exits from each point of the image display surface of the image display element and is the center of the exit pupil at the eyeball position of the observer. , While being incident on the decentered prism optical system while diverging.

Hereinafter, the reason and operation of the above-described configuration in the present invention will be described. The basic configuration of the image display device of the present invention is, as shown in the optical path diagram of FIG. 10, an eccentric prism optical system 7 composed of a medium having a refractive index larger than 1 and surrounded by three optical surfaces 3, 4, and 5. Is used as an eyepiece optical system, the exit pupil 1 of the eccentric prism optical system 7 (which coincides with the pupil position of the observer's eyeball) faces the first surface 3 of the eccentric prism optical system 7, and the LCD ( The image display element 6 such as a liquid crystal display element is a third eccentric prism optical system 7.
It is arranged facing the surface 5. Then, in the reverse ray tracing, a ray reaching the center of the screen of the image display element 6 through the decentered prism optical system 7 through the center of the exit pupil 1 is defined as an axial principal ray of the decentered prism optical system 7, and the axial principal ray thereof Is the optical axis 2.

In this image display device, the display light from the image display element 6 enters the eccentric prism optical system 7 through the third surface 5 of the transmission surface facing the image display element 6, and is incident on the exit pupil 1. Reflected by the total reflection inside the first surface 3,
Next, the light enters the second surface 4 located on the side opposite to the exit pupil 1 side with respect to the first surface 3 and is reflected inside the surface, and the reflected light is now smaller than the critical angle on the first surface 3 Incident at an angle, transmitted through the first surface 3, exits from the eccentric prism optical system 7, enters the observer's pupil at the exit pupil 1 without forming an intermediate image, and is incident on the observer's retina. A display image. Then, at least two reflecting surfaces are eccentric with respect to the optical axis 2.

Here, any or all of the reflecting surfaces 3 and 4 constituting the eccentric prism optical system 7 are mainly responsible for the positive power for performing the function of the eyepiece optical system of the eccentric prism optical system 7, and the reflection of the positive power is carried out. It is desirable that at least one of the surfaces has a plane-symmetric free-form surface shape having only one plane of symmetry in order to correct aberration based on eccentricity of the surface.
Hereinafter, this point will be described.

First, a coordinate system used in the following description will be described. Note that ray tracing is considered as reverse tracing in which light from a distant object point passes through the exit pupil 1 and forms an image on the screen of the image display element 6 unless otherwise specified.
As shown in FIG. 10, a ray that passes through the center of the exit pupil 1 and reaches the center of the screen of the image display element 6 is defined as an axial principal ray, and is represented by a straight line that intersects the first surface 3 of the eccentric prism optical system 7. An optical axis to be defined is defined as a Z axis, an axis orthogonal to the Z axis and within an eccentric plane of each surface constituting the eyepiece optical system is defined as a Y axis, and an axis orthogonal to the Z axis and orthogonal to the Y axis. Is the X axis.

In general, an aspherical surface or the like is used to satisfactorily correct aberrations with a small number of surfaces. In general, a spherical lens system is configured to correct aberrations such as spherical aberration, coma, and field curvature occurring on a spherical surface on other surfaces.
Therefore, an aspherical surface is used to reduce various aberrations generated on the spherical surface. This is to reduce the occurrence of various aberrations generated on one surface, reduce the number of surfaces on which aberration correction is performed, and reduce the total number of constituent surfaces.

However, in an eccentrically arranged optical system such as the eccentric prism optical system 7 used in the image display device of the present invention, an aberration occurs due to eccentricity which cannot be corrected by a conventional rotationally symmetric aspherical surface. Aberrations caused by eccentricity include coma, astigmatism, image distortion, field curvature, and the like.
In the prior art, there is an example in which a toric surface or an anamorphic surface is used to correct these aberrations.
The emphasis has been placed on astigmatism caused by eccentricity, and there has been no one that has a wide angle of view, a small size, and sufficient aberration correction up to image distortion.

In order to simultaneously and satisfactorily correct the above-mentioned aberration, the present invention does not have a rotationally symmetric axis both in-plane and out-of-plane.
Moreover, a feature is that a plane-symmetric free-form surface having only one symmetric surface is used.

Here, the free-form surface of the present invention is defined by the following equation. _{Z = C 2 + C 3 y} + C 4 x + C 5 y 2 + C 6 yx + C 7 x 2 + C 8 y 3 + C 9 y 2 x + C 10 yx 2 + C 11 x 3 + C 12 y 4 + C 13 y 3 x + C 14 y 2 x 2 + C ^{_{15 yx 3 + C 16 x 4}} + C 17 y 5 + C 18 y 4 x + C 19 y 3 x 2 + C 20 y 2 x 3 + C 21 yx 4 + C 22 x 5 + C 23 y 6 + C 24 y 5 x + C 25 y 4 x 2 + C ^{_{26 y 3 x 3 + C 27}} y 2 x 4 + C 28 yx 5 + C 29 x 6 + C 30 y 7 + C 31 y 6 x + C 32 y 5 x 2 + C 33 y 4 x 3 + C 34 y 3 x 4 + C 35 y 2 x ^{_{5 + C 36 yx 6 + C}} 37 x 7 ····· ···· (a) although, Z is the amount of deviation from a plane tangent to the origin of the surface shape, C _m (m is an integer of 2 or more) is a factor is there.

In the decentered prism optical system of the present invention,
The aberration correction effect is further improved by using a plane-symmetric free-form surface having only one symmetric surface as at least one of the reflecting surfaces having an eccentric rotationally asymmetric surface shape. The free-form surface represented by the above formula (a) generally includes an XZ plane,
Although neither YZ plane has a plane of symmetry, in the present invention, x
By setting all the odd-order terms to 0, a free-form surface having only one symmetric plane parallel to the YZ plane (the plane in FIG. 10) is obtained. For example, in the above definition formula (a), C ₄ ,
_{C 6, C 9, C 11} , C 13, C 15, C 18, C 20, C 22, C
₂₄ , C ₂₆ , C ₂₈ , C ₃₁ , C ₃₃ , C ₃₅ , C ₃₇ ,...

By setting all odd-order terms of y to 0, a free-form surface having only one symmetry plane parallel to the XZ plane is obtained. For example, in the definition formula (a),
C ₃ , C ₆ , C ₈ , C ₁₀ , C ₁₃ , C ₁₅ , C ₁₇ , C ₁₉ , C
_{21, C 24, C 26,} C 28, C 30, C 32, C 34, C 36, ··
It is possible by setting the coefficient of each term of 0 to 0, and it is possible to improve the manufacturability by having the above-mentioned plane of symmetry.

By making one of the symmetry plane parallel to the YZ plane and the symmetry plane parallel to the XZ plane a symmetry plane,
It is possible to effectively correct rotationally asymmetric aberrations caused by eccentricity. The above definition formula is shown as one example, and it goes without saying that the same effect can be obtained for any other definition formula.

By using such a free-form surface as at least one reflecting surface having a reflecting action, an inclined eccentric surface, for example, a second surface of an embodiment to be described later, has an eccentric direction of the Y-axis as described above. The direction of the line of sight of the observer's eye is the Z axis,
Assuming that the axis orthogonal to the axis and the Z axis is the X axis, the inclination in the Y direction at any position on the X axis can be arbitrarily given. This can be corrected by the image distortion generated by the concave mirror arranged eccentrically, in particular, the image distortion generated by changing the image height in the X-axis direction and occurring in the Y-axis direction. That is, as a result,
It is possible to satisfactorily correct the image distortion observed when the horizontal line is bowed.

Next, the trapezoidal distortion generated by the concave mirror arranged eccentrically will be described. This image distortion will be described with reference to the reverse tracking from the observer's eyeball. Light rays having a spread in the X-axis direction emitted from the eyeball are reflected by the eccentrically arranged second surface, but are reflected by the Y surface of the second surface. Due to the difference in the optical path length between the light beam in the positive axis direction and the light beam in the negative Y axis direction, the light beam is reflected by the second surface after the spread in the X axis direction is greatly different. Therefore, the size of the image in the positive Y-axis direction and the size of the image in the negative Y-axis direction are differently formed, and as a result, the observed image has trapezoidal distortion.

This distortion can be corrected by using a free-form surface. This is because the free-form surface has an odd-order term of Y and an even-order term of X whose curvature can be arbitrarily changed in the X-axis direction depending on the sign of the Y-axis, as is clear from the definition equation (a). is there.

Next, rotationally symmetric image distortion will be described. As in the eccentric prism optical system of the present invention, for example, in an optical system having a pupil at a position away from the concave surface of the second surface and having a wide angle of view, a pincushion-type rotation is used in the reverse ray tracing from the pupil surface side. A large symmetric image distortion occurs. The occurrence of such image distortion can be suppressed by changing the inclination of the surface around the reflection surface.

Further, astigmatism can be achieved by appropriately changing the difference between the second derivative in the X-axis direction and the second derivative in the Y-axis direction.

In addition, coma can be corrected by arbitrarily giving the inclination of the arbitrary point on the X axis in the Y direction in the same way as the bow-shaped image distortion.

More preferably, in consideration of the manufacturability of optical parts, it is desirable that the free-form surface be minimized.
Therefore, it is possible to increase the productivity by setting one reflecting surface of at least three surfaces, for example, the second surface as the above-mentioned free-form surface and the other surface as a flat surface, a spherical surface, or an eccentric rotationally symmetric surface. .

Since the second surface, which is the reflecting surface facing the exit pupil of the eyepiece optical system, has a stronger reflective refracting power than the other surfaces,
A free-form surface is effective for suppressing the occurrence of aberration.

Also, coma aberration can be suppressed by forming the refracting surface and the reflecting surface facing the exit pupil of the eyepiece optical system as free-form surfaces. this is,
This is because, when the first surface acts as a reflection surface, the first surface is arranged to be largely inclined with respect to the axial principal ray.

Further, by making the third surface a free-form surface, the occurrence of image distortion can be corrected. this is,
This is because the third surface is arranged close to the image forming position, so that a good result can be obtained for correcting image distortion without deteriorating other aberrations.

It is needless to say that each aberration can be further corrected by making the two surfaces free-form surfaces. For example, when the second surface and the third surface are free-form surfaces, the first surface can be a flat surface, and the manufacturability of the optical element constituting the eyepiece optical system can be improved. Further, the first surface can be configured as a spherical surface or a rotationally symmetric aspherical surface.

The reflecting surfaces having a reflecting action in the present invention include all reflecting faces having a reflecting action such as a total reflecting face, a mirror coat face, and a semi-transmissive reflecting face.

As shown in FIG. 10, in the image display apparatus of the present invention, the principal ray 8 which exits from each point on the image display surface of the image display element 6 and reaches the center of the exit pupil 1 diverges. It is configured to enter the decentered prism optical system 7. That is, the entrance pupil position of the eccentric prism optical system 7 (the position conjugate with the exit pupil 1 with respect to the eccentric prism optical system 7), which is the point P where the principal ray 8 extends to the opposite side and intersects, is behind the image display element 6. The eccentric prism optical system 7 is configured to be located at a finite distance.

When the principal ray 8 emitted from the image display element 6 is made to enter while diverging, the size of the image display element 6 itself can be reduced, and accordingly, the eccentric prism optical system 7 is also provided. The image display device can be configured to be smaller, and the entire image display device can be made smaller and have a wider angle of view.

In the above coordinate system, it is desirable from the viewpoint of aberration correction that the reflecting surface of the decentered prism optical system satisfies one of the following conditions (1) and (2). 1 <| Py2 / Py | <5 (1) 0.2 <| Py3 / Py | <0.8 (2) However, Py2 and Py3 are the first reflection surfaces in reverse ray tracing, respectively. (The second surface 4), the reflection refractive power in the YZ plane of the area where the axial principal ray of the second reflection surface (the first surface 3) is reflected, and Py is the entire system of the decentered prism optical system in reverse ray tracing Is the refracting power in the YZ plane for the on-axis principal ray.

When the value exceeds the upper limit of 5 in the expression (1), the image position cannot be moved out of the eccentric prism optical system, and the image display element cannot be arranged. When the value exceeds the upper limit of 0.8 in the expression (2), the second reflecting surface has too much negative power, and the curvature of field convex on the pupil side generated on the first reflecting surface is excessively corrected. A concave field curvature occurs on the pupil side. When the lower limit of 1 in the expression (1) is exceeded, the second reflecting surface has too strong a positive power this time, and there is no surface which cancels out the convex curvature of field on the pupil side generated by the first reflecting surface. As a result, a convex curvature of field is strongly generated on the pupil side. (2)
If the lower limit of 0.8 of the expression is exceeded, the ability of the second reflecting surface to correct the field curvature is reduced, and the field curvature generated on the first reflecting surface remains. Furthermore, (1), (2)
If both of the expressions exceed the upper limits, the powers of the first reflecting surface and the second reflecting surface become too strong, so that other aberrations cannot be completely corrected, which is not preferable for aberration correction. If the lower limits of both formulas are exceeded, the size of the optical system increases. In addition,
It is desirable that both of the expressions (1) and (2) be satisfied at the same time.

In order to further reduce the size of the decentered prism optical system, 1.4 <| Py2 / Py | <3 (1) '0.2 <| Py3 / Py | <0.5. It is preferable to satisfy the condition (2) ′. In this case, in any case, when the upper limit is exceeded, the curvature of field is excessively corrected, and other aberrations cannot be completely corrected. If the lower limit is exceeded, the size of the optical system cannot be reduced.

It is desirable that the reflecting surface of the decentered prism optical system further satisfies one of the following conditions (3) and (4). 1 <| Px2 / Px | <5 (3) 0.2 <| Px3 / Px | <3 (4) where Px2 and Px3 are the first reflecting surfaces (the The second surface 4), the reflection refractive power in the plane perpendicular to the YZ plane of the area where the axial principal ray of the second reflection surface (the first surface 3) is reflected, and Px is an eccentric prism optical system for reverse ray tracing It is the refracting power in the plane perpendicular to the YZ plane for the axial principal ray of the whole system.

If the upper limits of (3) and (4) are exceeded, the powers of the first reflecting surface and the second reflecting surface become too strong.
The field curvature is excessively corrected, and other aberrations cannot be completely corrected, which is not preferable for aberration correction. If the lower limits of both formulas are exceeded, the size of the optical system increases.

To further reduce the size of the decentered prism optical system, 1 <| Px2 / Px | <2.5 (3) '0.2 <| Px3 / Px | <1.5 It is preferable to satisfy the condition (4) ′. In this case, in any case, when the upper limit is exceeded, the curvature of field is excessively corrected, and other aberrations cannot be completely corrected. If the lower limit is exceeded, the size of the optical system cannot be reduced.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image display device according to the present invention will be described below. In the configuration parameters of this embodiment, which will be described later, the center of the pupil 1 of the decentered prism optical system 7 is optically adjusted as shown in the YZ section in FIG. 1A and the XZ section in FIG. As the origin of the system, the optical axis 2 is defined by a ray passing from the center of the distant object to the center (origin) of the pupil 1, the direction from the pupil 1 toward the first surface 3 of the optical system 7 is the Z-axis direction, and this Z-axis Are orthogonal to the pupil 1 and pass through the center of the pupil 1, and the light beam is
The direction in the plane bent by Y axis direction, Y axis,
The direction orthogonal to the Z axis and passing through the center of the pupil 1 is the X axis direction, the direction from the pupil 1 toward the optical system 7 is the positive direction of the Z axis, the direction from the optical axis 2 to the image plane 6 is the positive direction of the Y axis, The direction forming the right-handed system with these Y axis and Z axis is defined as the positive direction of the X axis. In addition,
The ray tracing is a reverse ray tracing that enters the optical system 7 from the object side of the optical system 7 on the pupil 1 side.

Then, for a plane having eccentricity, the amount of eccentricity in the X-axis direction, Y-axis direction, and Z-axis direction from the center of the pupil 1 which is the origin of the optical system 7 at the top of the surface ( X, y, z), and the inclination angles (°) (°, respectively) of the center axis of the surface (for a free-form surface, the Z axis in equation (a)) around the X, Y, and Z axes, respectively. , Β, γ). In this case, the positive α and β mean counterclockwise in the positive direction of each axis, and the positive γ means clockwise in the positive direction of the Z axis. In addition, the radius of curvature of the spherical surface, the spacing between the surfaces, the refractive index of the medium, and the Abbe number are given according to conventional methods.

The formula for defining a free-form surface is given by the above equation (a).
There is an ike polynomial. The shape of this surface is defined by the following equation (b). The Z axis of the defining equation is the axis of the Zernike polynomial. X = R × cos (A) Y = R × sin (A) Z = D ₂ + D ₃ R cos (A) + D ₄ R sin (A) + D ₅ R ² cos (2A) + D ₆ (R ² -1) + D ₇ ^{R 2 sin (2A) + D} 8 R 3 cos (3A) + D 9 (3R 3 -2R) cos (A) + D 10 (3R 3 -2R) sin (A) + D 11 R 3 sin (3A) + D 12 R 4 _{cos (4A) + D 13 (} 4R 4 -3R 2) cos (2A) + D 14 (6R 4 -6R 2 +1) + D 15 (4R 4 -3R 2) sin (2A) + D 16 R 4 sin (4A) + D 17 ^{R 5 cos (5A) + D} 18 (5R 5 -4R 3) cos (3A) + D 19 (10R 5 -12R 3 + 3R) cos (A) + D 20 (10R 5 -12R 3 + 3R) sin (A) + D 21 ( ^{5R 5 -4R 3) sin (3A} ) + D 22 R 5 sin (5A) + D 23 R 6 cos (6A) + D 24 (6R 6 -5R 4) cos (4A) + D 25 (15R 6 -20R 4 + 6R 2) _{cos (2A) + D 26 (} 20R 6 -30R 4 + 12R 2 -1) + D 27 (15R 6 -20R 4 + 6R 2) sin (2A) + D 28 (6R 6 - ^{R 4) sin (4A) +} D 29 R 6 sin (6A) ····· ··· (b) In addition, expressed in X direction symmetric surface above. Here, D _m (m is an integer of 2 or more) is a coefficient.

As another expression example of a surface that can be used in the present invention, as in the case of the expression (a), k is a surface symmetrical in the X direction.
In the case of expressing a surface where = 7, it can be expanded as in the following expression (c).

Z = C ₂ + C ₃ Y + C ₄ | X | + C ₅ Y ² + C ₆ Y | X | + C ₇ X ² + C ₈ Y ³ + C ₉ Y ² | X | + C ₁₀ YX ² + C ₁₁ | X ³ | + C ₁₂ Y ⁴ + C ₁₃ Y ³ | X | + C ₁₄ Y ² X ² + C ₁₅ Y | X ³ | + C ₁₆ X ⁴ + C ₁₇ Y ⁵ + C ₁₈ Y ⁴ | X | + C ₁₉ Y ³ X ² + C ₂₀ Y ² | X ^{_{3 | + C 21 YX 4 +}} C 22 | X 5 | + C 23 Y 6 + C 24 Y 5 | X | + C 25 Y 4 X 2 + C 26 Y 3 | X 3 | + C 27 Y 2 X 4 + C 28 Y | X 5 | ^{_{+ C 29 X 6 + C 30}} Y 7 + C 31 Y 6 | X | + C 32 Y 5 X 2 + C 33 Y 4 | X 3 | + C 34 Y 3 X 4 + C 35 Y 2 | X 5 | + C 36 YX 6 + C 37 | X ⁷ | (c) In the following configuration parameters, the term relating to the aspherical surface for which no data is described is zero. The refractive index for d-line (wavelength 587.56 nm) is shown. The unit of the length is mm.

FIG. 1 shows an YZ section (a) and an XZ section (b) including the optical axis 2 of the image display device according to one embodiment of the present invention. The decentered prism optical system 7 constituting the eyepiece optical system of the image display device includes three surfaces 3, 4, 5, and 3
The space between the three surfaces 3 to 5 is filled with a transparent medium having a refractive index larger than 1, and in backward ray tracing, a light beam emitted from an object (not shown) first passes through the pupil 1 of the optical system 7 along the optical axis 2. The light passes through, enters the first surface 3 having a transmission function and a reflection function, enters the optical system 7, and the incident light is reflected by the second surface 4 which is a reflection surface having a reflection function only on the side farther from the pupil 1. 1 is reflected in a direction approaching the pupil 1 this time, and is reflected again in a direction away from the pupil 1 on the first surface 3, and the reflected light passes through a third surface 5 having only a transmitting action and reaches an image plane 6, Form an image.
Actually, the image display element is arranged at the position of the image plane 6, and the light beam advances in the reverse order to the above, and the display image of the image display element 6 is displayed in the eyeball of the observer through the observer's pupil at the pupil 1 position. It is enlarged and projected.

In this embodiment, the first surface 3 and the second surface 4 are composed of free-form surfaces defined by the above-mentioned equation (a), which are decentered with the concave surface facing the pupil 1 side. (A) defined by a free-form surface. Further, the image display element 6
Has a horizontal dimension of 11.2 mm and a vertical direction of 8.3 mm, a horizontal angle of view of 35 °, and a vertical angle of view of 26.6.
°, pupil diameter 4 mm. The configuration parameters of the above embodiment are shown below.

Surface number Surface shape Radius of curvature Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ -1000.00 1 (pupil surface) ∞ 2 Free-form surface [1] Eccentricity (1) 1.5254 56.2 3 Free-form surface [2] Eccentricity (2) 1.5254 56.2 4 free-form surface [1] eccentricity (1) 1.5254 56.2 5 free curved [3] eccentricity (3) image surface ∞ eccentricity (4) the free-form surface _{[1] C 5 -2.1693 × 10} -3 C 7 -8.1988 × 10 - ³ C ₈ -1.7175 × 10 ^-4 C ₁₀ -5.5459 × 10 ^-4 C ₁₂ -8.8529 × 10 ^-6 C ₁₄ -1.7316 × 10 ^-5 C ₁₆ -1.5602 × 10 ^-6 C ₁₇ -1.0807 × 10 ^-7 C ₁₉ -3.2639 × 10 ^-7 C ₂₁ -4.4367 × 10 ^-8 Free-form surface [2] C ₅ -9.3708 × 10 ^-3 C ₇ -1.2274 × 10 ^-2 C ₈ -6.1321 × 10 ^-5 C ₁₀ -1.1820 × 10 ^-4 C ₁₂ -1.3873 × 10 ^-6 C ₁₄ 8.1930 × 10 ^-7 C ₁₆ -1.0808 × 10 ^-6 C ₁₇ 1.7748 × 10 ^-7 C ₁₉ -9.9319 × 10 ^-8 C ₂₁ -1.5314 × 10 ^-7 Free-form surface [3] C ₅ -2.2380 × 10 ^-2 C ₇ -2.6346 × 10 ^-2 C ₁₀ -8.2832 × 10 ^-5 C ₁₂ -1.8592 × 10 ^-4 C ₁₄ 1.7372 × 10 ^-4 C ₁₆ 3.9752 × 10 ^-5 C ₁₉ -2.6887 × 10 ^-6 C ₂₁ 8.9660 × 10 ^-7 Eccentricity (1) x 0.00 y 9.83 z 27.87 α 2.70 β 0.00 γ 0.00 Eccentricity (2) x 0.00 y 0.07 z 36.33 α -24.29 β 0.00 γ 0.00 Eccentricity (3) x 0.00 y 17.36 z 33.25 α 56.53 β 0.00 γ 0.00 Eccentricity (4) x 0.00 y 19.53 z 34.86 α 47.90 β 0.00 γ 0.00 Py2 / Py = 1.53059 Py3 / Py = −0.35432 Px2 / Px = 2.02894 Px3 / Px = 1.35529.

FIGS. 2 to 4 show lateral aberrations at various angles of view in the above embodiment, and FIG. 5 shows distortions. In FIGS. 2 to 4 showing the lateral aberration, the numbers shown in parentheses indicate (horizontal (X direction) angle of view, vertical (Y direction) angle of view), and show lateral aberration diagrams at the angle of view.

In the above description, as shown in FIG. 1, the decentered prism optical system 7 is composed of three optical working surfaces of a first surface 3, a second surface 4, and a third surface 5, and The light beam emitted from the display element 6 is refracted on the third surface 5 and enters the eccentric prism optical system 7, internally reflected on the first surface 3, reflected on the second surface 4, and again on the first surface 3. Has been presumed to be an optical system which is incident on the observer, is refracted, and is projected into the eyeball of the observer as the exit pupil 1 at the iris position of the observer's pupil or the center of rotation of the eyeball. The present invention is not limited to the prism optical system 7, but can be applied to an eccentric prism optical system 7 having four or more optically active surfaces as illustrated in FIG. In the case of FIG. 6, the decentered prism optical system 7 is composed of four optical working surfaces of a first surface 3, a second surface 4, a third surface 5, and a fourth surface 9,
The light beam emitted from the image display element 6 is refracted on the third surface 5 and is incident on the decentered prism optical system 7, is internally reflected on the fourth surface 9, is incident on the second surface 4 and is internally reflected. The light enters the one surface 3 and is refracted, and is projected into the eyeball of the observer as the exit pupil 1 at the iris position of the observer's pupil or the center of rotation of the eyeball.

Now, even if one set of the image display device described above is prepared and configured to be mounted on one eye, such a pair is prepared as a pair of left and right, and they are separated from each other by an eye distance. By supporting, it may be configured for binocular wear. In this way, it can be configured as a stationary or portable image display device that can be observed with one eye or both eyes.

FIG. 7 shows the arrangement of the image display apparatus main body with respect to one eye of the observer, in which the image display apparatus is configured to be attached to one eye (in this case, attached to the left eye), and FIG. The state of the case where both eyes are used is shown. FIG.
In FIG. 9, reference numeral 31 denotes a display device main body. In FIG. 8, a supporting member is held in front of the left eye of the observer's face, and in FIG. 9, it is held in front of both eyes of the observer's face. Is fixed through the head. As the supporting members, left and right front frames 32 each having one end joined to the display device main body 31 and extending from the temple of the observer to the upper part of the ear, and a front frame 3
2 and the left and right rear frames 33 extending across the temporal region of the observer from the left and right rear frames 33 (in the case of FIG. 8), or further sandwiched between the other ends of the left and right rear frames 33. As shown in FIG. 9, the both ends are joined one by one, and the top frame 34 supports the top of the observer.

In the vicinity of the joint of the front frame 32 with the rear frame 33, a rear plate 35 made of an elastic body and made of, for example, a metal plate spring is joined. The rear plate 35 is joined so that the rear cover 36, which carries one wing of the support member, is supported by being positioned behind the ear at a portion where the back of the observer is attached to the neck of the observer (see FIG. 9). Case). A speaker 39 is mounted in the rear plate 35 or the rear cover 36 at a position corresponding to the ear of the observer.

A cable 41 for transmitting video / audio signals and the like from the outside is provided from the display device main body 31 to the top frame 34 (in the case of FIG. 9), the rear frame 33, and the front frame 3.
2. Rear plate 35 through the inside of rear plate 35
Alternatively, it protrudes outside from the rear end of the rear cover 36. The cable 41 is connected to the video playback device 40. In the figure, reference numeral 40a denotes a switch and a volume adjusting unit of the video reproducing device 40.

The cable 41 may be jacked at the end so that it can be attached to an existing video deck or the like. Furthermore, it is connected to a tuner for TV radio wave reception,
It may be used for viewing, or may be connected to a computer to receive computer graphics images, message images from the computer, and the like. In addition, an antenna may be connected to receive an external signal by radio wave in order to reject an obstructive code.

The above-described image display device of the present invention can be configured, for example, as follows. [1] An image display device, and an eyepiece optical system including an eccentric prism optical system that guides an image formed by the image display device at an observer's eyeball position without forming an intermediate image so that the image can be observed as a virtual image. In the image display device,
In the decentered prism optical system, at least three surfaces having at least one of a function of reflecting and transmitting light emitted from the image display element are arranged eccentrically, and a refractive index between the at least three surfaces is 1. At least two of the at least three surfaces are formed of surfaces having a reflective action so as to be filled with three or more transparent media and to perform internal reflection at least twice inside the optical system. The at least two reflecting surfaces are arranged at positions where the light beams reflected by the at least two reflecting surfaces do not intersect inside the optical system, and at least one of the reflecting surfaces is provided. The surface shape of the surface does not have an axis of rotational symmetry both inside and outside the surface, and is formed of a plane-symmetric free-form surface having only one symmetry surface,
The image display device is configured so that a chief ray exiting from each point of an image display surface of the image display element and reaching the center of an exit pupil at an observer's eyeball position enters the eccentric prism optical system while diverging. Characteristic image display device.

[2] In the above item [1], a ray passing through the center of the exit pupil and reaching the center of the screen of the image display element is defined as an axial principal ray until the ray intersects the first surface of the eccentric prism optical system. The optical axis defined by the straight line of
When an axis orthogonal to the Z axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as an Y axis, and an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis, Condition (2)
An image display device characterized by satisfying the following. 0.2 <| Py3 / Py | <0.8 (2) where Py3 is Y− of the area where the on-axis principal ray of the second reflecting surface of the decentered prism optical system is reflected in the reverse ray tracing. The reflected refractive power in the Z plane, Py, is the refractive power in the YZ plane with respect to the axial principal ray of the entire decentered prism optical system in the reverse ray tracing.

[3] An image display device according to [2], wherein 0.2 <| Py3 / Py | <0.5 (2) 'is satisfied.

[4] Any one of the above [1] to [3]
In the item, a ray passing through the center of the exit pupil and reaching the center of the screen of the image display element is defined as an axial principal ray, and an optical axis defined by a straight line that intersects the first surface of the decentered prism optical system is defined as Z axis, an axis in the eccentric plane of each surface constituting the eccentric prism optical system orthogonal to the Z axis and the Y axis,
An image display device characterized by satisfying the following condition (1) when an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis. 1 <| Py2 / Py | <5 (1) where Py2 is in the YZ plane of the area where the axial principal ray of the first reflecting surface of the decentered prism optical system is reflected in the reverse ray tracing. The reflection refractive power Py is the refractive power in the YZ plane with respect to the axial principal ray of the entire decentered prism optical system in the reverse ray tracing.

[5] An image display apparatus according to the above [4], wherein 1.4 <| Py2 / Py | <3 (1) 'is satisfied.

[6] Any one of the above [1] to [5]
In the item, a ray passing through the center of the exit pupil and reaching the center of the screen of the image display element is defined as an axial principal ray, and an optical axis defined by a straight line that intersects the first surface of the decentered prism optical system is defined as Z axis, an axis in the eccentric plane of each surface constituting the eccentric prism optical system orthogonal to the Z axis and the Y axis,
An image display device characterized by satisfying the following conditions (3) and (4) when an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis. 1 <| Px2 / Px | <5 (3) 0.2 <| Px3 / Px | <3 (4) where Px2 and Px3 are the first reflecting surface and the 2 Y- of the area where the axial principal ray of the reflecting surface is reflected
Px is the refractive power in the plane perpendicular to the YZ plane with respect to the axial principal ray of the entire decentered prism optical system in the reverse ray tracing.

[7] Any one of the above [1] to [6]
In the above paragraph, the decentered prism optical system comprises three optically active surfaces, a light beam enters from a first surface by back ray tracing, the incident light beam is reflected by a second surface, and a light beam reflected by the second surface Are reflected by the first surface, and the first surface, the second surface, and the third surface are arranged such that the light beam reflected by the first surface passes through the optical system and exits from the third surface. An image display device, wherein are arranged.

[8] In the above item [7], the first surface is formed such that the transmission function and the reflection function thereof overlap in at least a part of the area within the effective plane.
An image display device, wherein at least a reflection action in a region where the transmission action and the reflection action in the effective surface of the first surface overlap with each other is based on a total reflection action.

[0066]

As is apparent from the above description, according to the present invention, the eyepiece optical system is composed of an eccentric prism optical system composed of three or more surfaces including at least two decentered reflective surfaces, At least one surface is formed of a rotationally asymmetric free-form surface having only one symmetric surface, and a principal ray emitted from each point of the image display surface of the image display element is incident on the eccentric prism optical system while diverging. Therefore, it is possible to achieve a small and lightweight image display device having a wide angle of view while having high optical performance due to eccentric aberration correction.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image display device according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a partial lateral aberration state according to an embodiment of the present invention.

FIG. 3 is a diagram showing a lateral aberration state of another part of one embodiment of the present invention.

FIG. 4 is a diagram showing a lateral aberration situation of another part of the embodiment of the present invention.

FIG. 5 is a diagram showing a state of distortion aberration according to an example of the present invention.

FIG. 6 is a diagram illustrating another decentered prism optical system to which the present invention can be applied.

FIG. 7 is a diagram showing an arrangement of a head-mounted image display device according to the present invention with respect to one eye of an observer.

FIG. 8 is a diagram illustrating a state in which the head-mounted image display device according to the present invention is configured to be mounted on one eye.

FIG. 9 is a diagram illustrating a state in which the head-mounted image display device according to the present invention is configured to be worn on both eyes.

FIG. 10 is an optical path diagram showing a basic form picture of the image display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exit pupil 2 ... Optical axis 3 ... 1st surface 4 ... 2nd surface 5 ... 3rd surface 6 ... Image display element 7 ... Eccentric prism optical system 8 ... Principal ray 9 ... 4th surface 31 ... Display device main body 32 ... front frame 33 ... rear frame 34 ... crown frame 35 ... rear plate 36 ... rear cover 39 ... speaker 41 ... cable 40 ... video playback device 40a ... volume adjustment unit

Claims (3)

[Claims] 1. An eyepiece optical system including an image display element and an eccentric prism optical system for guiding an image formed by the image display element to an observer's eyeball position without forming an intermediate image so that the image can be observed as a virtual image. In the image display device having the above, the eccentric prism optical system is configured such that at least three surfaces having at least one action of reflection and transmission of light emitted from the image display element are arranged eccentrically to each other, and The space is filled with a transparent medium having a refractive index of 1.3 or more, and at least two of the at least three surfaces have a reflecting action so as to perform internal reflection at least twice inside the optical system. And at a position where the rays reflected by the at least two reflective surfaces do not intersect within the optical system. At least two surfaces having a reflecting action are arranged, and the surface shape of at least one of the reflecting surfaces does not have an axis of rotational symmetry both in-plane and out-of-plane, and has only one symmetric surface. A chief ray which is composed of a plane-symmetric free-form surface and has a principal ray reaching from the point on the image display surface of the image display element and reaching the center of the exit pupil at the position of the observer's eyeball diverges and enters the decentered prism optical system. An image display device characterized by being configured as described above. 2. A straight line extending through the center of the exit pupil and reaching the center of the screen of the image display element as an axial principal ray and intersecting the first surface of the eccentric prism optical system according to claim 1. The optical axis defined by Z axis, the axis orthogonal to the Z axis and the axis in the eccentric plane of each surface constituting the eccentric prism optical system is the Y axis, the axis orthogonal to the Z axis and orthogonal to the Y axis. An image display device characterized by satisfying the following condition (2) when defined as an X axis. 0.2 <| Py3 / Py | <0.8 (2) where Py3 is Y− of the area where the on-axis principal ray of the second reflecting surface of the decentered prism optical system is reflected in the reverse ray tracing. The reflected refractive power in the Z plane, Py, is the refractive power in the YZ plane with respect to the axial principal ray of the entire decentered prism optical system in the reverse ray tracing. 3. The eccentric prism optical system according to claim 1, wherein a ray passing through the center of the exit pupil and reaching the center of the screen of the image display element is defined as an axial principal ray and intersects the first surface of the eccentric prism optical system. The optical axis defined by the straight line is the Z axis, the axis in the eccentric plane of each surface constituting the eccentric prism optical system is orthogonal to the Z axis, and the axis in the eccentric plane is orthogonal to the Z axis and orthogonal to the Y axis. An image display device characterized by satisfying the following condition (1) when an axis is defined as an X axis. 1 <| Py2 / Py | <5 (1) where Py2 is in the YZ plane of the area where the axial principal ray of the first reflecting surface of the decentered prism optical system is reflected in the reverse ray tracing. The reflection refractive power Py is the refractive power in the YZ plane with respect to the axial principal ray of the entire decentered prism optical system in the reverse ray tracing.