JPH1138351A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bright image display device which is small in size and light in weight and also which is provided with a high optical performance, by making an eccentric prism optical system a distortion image optical system, in the case of using the eccentric prism optical system as an eyepiece optical system. SOLUTION: The device is constituted of an image display element 6, and the eyepiece optical system for guiding the image formed by the element 6 to an observer's eye ball position 1 so that the observer can observe the image as a virtual image without forming an intermediate image. In this case, the eyepiece optical system includes the eccentric prism optical system 7 constituted of three faces 3 to 5 including two eccentric reflection faces, and the image display element 6 is constituted so that the image displayed in the vertical direction on the two-dimensional display screen may be displayed in a more compressed state as compared with the image displayed in the horizontal direction, and the eccentric prism optical system 7 is constituted so that the direction corresponding to the vertical direction of the two-dimensional display screen may be elongated as compared with the direction corresponding to the horizontal direction.

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 small-sized head or face-mounted image display device which can be held on the head or face of an observer.

[0002]

2. Description of the Related Art In recent years, head or face-mounted image display devices have been developed for the purpose of allowing individuals to enjoy large-screen images.

Under such circumstances, Japanese Patent Application Laid-Open No. Hei 7-333551 discloses an eyepiece optical system for guiding a display image of a two-dimensional image display element to an observer's eyeball, in which a refractive index surrounded by three optical surfaces is larger than 1. A decentered prism optical system made of a medium, a light beam from the liquid crystal display element is made to enter the decentered optical system from the third surface, and then totally reflected inside the first surface, and A proposal has been made such that the light is internally reflected on two surfaces and then emitted outside the decentered optical system via the first surface, thereby guiding the display image of the image display element to the observer's eyeball without forming an intermediate image. .

In this case, the eccentric prism optical system has three optical surfaces, and the number of reflections inside the eccentric prism optical system is two. In addition, various types of decentered optical systems having two or four or more surfaces and reflecting at least once inside the optical system have been proposed by the present applicant.

[0005]

When an eccentric prism optical system is used as an optical system of a head- or face-mounted image display device, the entire device can be reduced in size and weight while maintaining high optical performance (angle of view, resolution, etc.). And there is an advantage that a bright image display device can be realized. However, in a conventional image display device using an eccentric prism optical system as an eyepiece optical system, an image compressed on one of the vertical and horizontal sides of a screen of a two-dimensional image display element such as a liquid crystal display element (hereinafter, referred to as an LCD). There is no proposal for displaying the image, expanding the compression on the eyepiece optical system side, and displaying the image at the same magnification in the vertical and horizontal directions. That is, when the conventional eccentric prism optical system is used as an eyepiece optical system of an image display device, no proposal has been made for the eccentric prism optical system to be a distorted image optical system.

The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to replace an eccentric prism optical system with a distorted image optical system in an image display apparatus using the eccentric prism optical system as an eyepiece optical system. Accordingly, an object of the present invention is to provide a bright image display device that is smaller and lighter and has high optical performance.

[0007]

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 one of the at least three surfaces is the image table. An incident surface that allows light from the element to enter the optical system, and another surface is an exit surface that emits light from the image display element from the optical system and projects the observer eyeball at the exit pupil position, The image display element includes a two-dimensional image display screen having a plurality of pixels arranged two-dimensionally, and converts an image displayed in a vertical direction of the two-dimensional image display screen into an image displayed in a horizontal direction. The eccentric prism optical system is configured to expand in a direction corresponding to the vertical direction of the two-dimensional image display screen as compared with a direction corresponding to the horizontal direction. It is characterized by having.

[0008] The reason and operation of the above-described configuration in the present invention will be described below. The basic mode of the image display device of the present invention is such that a vertical section is shown in FIG. 1A and a horizontal section is shown in FIG. That is, the refractive index surrounded by the three optical surfaces 3, 4, 5 is 1
An eccentric prism optical system 7 composed of a larger medium is used as an eyepiece optical system, and an exit pupil 1 of the eccentric prism optical system 7 (which coincides with the pupil position of the observer's eyeball) is located on the first surface 3 of the eccentric prism optical system 7. The image display element 6 such as an LCD (liquid crystal display element) is disposed facing the third surface 5 of the eccentric prism optical system 7. In the reverse ray tracing, 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 via the eccentric prism optical system 7 is defined as an axial principal ray of the eccentric prism optical system 7, and the axial principal ray thereof Is the optical axis 2.

In this image display device, 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 mainly bear the positive power for operating the eyepiece optical system of the eccentric prism optical system 7.

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. 1, a ray passing through the center of the exit pupil 1 and reaching 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 until it 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.
Here, for the time being, the left and right horizontal directions when the observer wears this image display device in front of one eye to magnify and observe the display image on the two-dimensional image display screen of the image display element 6 are X It is assumed that they coincide with the axial direction. In actual use, the X-axis direction of the eccentric prism optical system 7 does not need to coincide with the horizontal direction on the left and right.

Here, in the image display device of the present invention, in order to reduce the size of the image display device, it is considered that the size of the screen of the image display element 6 in the X direction is made smaller than that in the X direction. In conventional eyepiece optical systems such as JP-A-7-333551, since the magnifications of the eyepiece optical systems in the X and Y directions are substantially equal, if the size of only the Y direction of a screen such as an LCD is reduced, the size at the time of observation is reduced. As for the image, only an image having a small angle of view in the Y direction can be observed. Therefore, in the present invention, while using the small eccentric prism optical system 7 as the eyepiece optical system, the size of the image display element 6 such as an LCD in the Y direction is reduced, and the magnification of the eccentric prism optical system 7 in the Y direction is increased. At the same time as increasing the magnification in the X direction, the image in the Y direction is shifted with respect to the X direction so that the display image of the image display element 6 is the reciprocal of the magnification ratio of the eccentric prism optical system 7 in the Y direction with respect to the X direction. It is intended to be compressed and displayed.

Therefore, the combined focal length in the YZ plane with respect to the axial principal ray 2 of the entire decentered prism optical system 7 is fy,
Assuming that the composite focal length in a plane orthogonal to the YZ plane is fx, it is desirable that the following condition is satisfied: 0.1 <fy / fx <0.8 (1).

When the value exceeds the upper limit of 0.8 in the above equation (1),
It is impossible to achieve the object of the present invention of reducing the dimension of the image display element 6 in the Y direction. Accordingly, the eccentric prism optical system 7 is reduced, and a thin head-mounted image display device is provided. You can't do that. If the lower limit of 0.1 of the formula (1) is exceeded, the difference between the powers in the X and Y directions of the entire system becomes too large, astigmatism cannot be corrected completely, and an observation image with high resolution is presented. You can't do that.

Here, the surface shape of the decentered prism optical system 7 will be examined. Generally, in a spherical lens system composed of only spherical lenses, spherical aberration caused by a spherical surface, and aberrations such as coma and field curvature are mutually corrected on several planes, so that the aberration is reduced as a whole. Has become. On the other hand, an aspherical surface or the like is used to satisfactorily correct aberrations with a small number of surfaces. This is to reduce various aberrations generated on the spherical surface. However, in an eccentric optical system such as an eccentric prism optical system, it is impossible to correct rotationally asymmetric aberrations generated by eccentricity by a rotationally symmetric optical system.

When the rotationally symmetric optical system is decentered, rotationally asymmetric aberrations occur, and it is impossible to correct this only with the rotationally symmetric optical system. Rotationally asymmetric aberrations caused by this eccentricity include image distortion, field curvature, and astigmatism and coma which also occur on the axis. FIG. 16 shows the field curvature caused by the eccentrically arranged concave mirror M, FIG. 17 shows the astigmatism caused by the eccentrically arranged concave mirror M,
FIG. 18 is a view showing on-axis coma aberration generated by the concave mirror M arranged eccentrically. In the eccentric prism optical system of the present invention, a rotationally asymmetric surface is arranged in the optical system to correct rotationally asymmetric aberrations caused by the above-described eccentricity, and the rotationally asymmetric aberration is corrected. .

The rotationally asymmetric aberrations generated by the concave mirrors disposed eccentrically include rotationally asymmetric field curvature. For example, a ray incident on a concave mirror decentered from an object point at infinity hits the concave mirror and is reflected and imaged. After the ray hits the concave mirror, the rear focal length to the image plane (reflective LCD 8) is equal to the ray. Half of the radius of curvature. Then, as shown in FIG. 16, an image plane inclined with respect to the axial principal ray is formed. Correction of such rotationally asymmetric field curvature has not been possible with rotationally symmetric optical systems.
In order to correct the tilted curvature of field, the concave mirror M is constituted by a rotationally asymmetric surface. In this example, the curvature is increased (the refractive power is increased) in the positive Y-axis direction (upward in the figure). , Can be corrected by weakening the curvature (reducing the refracting power) in the negative direction (lower direction in the figure) of the Y axis. By arranging it in an optical system separately from M, a flat image surface can be obtained with a small number of components.

Next, rotationally asymmetric astigmatism will be described. As described above, the eccentrically arranged concave mirror M
In this case, astigmatism as shown in FIG. This astigmatism can be corrected by appropriately changing the curvature in the X-axis direction and the curvature in the Y-axis direction of the rotationally asymmetric surface, as described above.

Further, rotationally asymmetric coma will be described. Similarly to the above description, in the concave mirror M arranged eccentrically, coma as shown in FIG. To correct the coma aberration, the inclination of the surface can be changed as the distance from the origin of the X axis of the rotationally asymmetric surface increases, and the inclination of the surface can be appropriately changed depending on the sign of the Y axis.

Further, if the decentered prism optical system is configured to have a bent optical path, it is possible to give power to the reflecting surface, and it is possible to omit the transmission type lens. Further, by bending the optical path, the eccentric prism optical system can be made compact.

Further, the reflection surface can be made to have a high reflectivity by being constituted by a total reflection surface which is arranged obliquely with respect to the light beam so that the light beam enters beyond the critical angle. In addition, it is possible to have both a reflecting action and a transmitting action. Further, it is preferable that the reflection surface is formed of a reflection surface having a metal thin film such as aluminum or silver formed on the surface, or a reflection surface or a semi-transmission reflection surface formed of a dielectric multilayer film. When the metal thin film has a reflecting action, it is possible to easily obtain a high reflectance. In the case of a dielectric reflection film, it is advantageous when a reflection film having low wavelength selectivity and low absorption is formed.

More preferably, when a rotationally asymmetric surface is used as the reflecting surface, no chromatic aberration occurs as compared with the case where the reflecting surface is used. Further, since the light beam can be bent even if the inclination of the surface is small, other aberrations are less likely to occur. That is, when the same refracting power is to be obtained, the occurrence of aberration is smaller on the reflecting surface than on the refracting surface.

Here, the rotationally asymmetric surface includes an anamorphic surface, a trick surface and a free-form surface. The surface shape of the anamorphic surface is represented by the following equation (a). However, Z is the amount of deviation from a plane tangent to the origin of the surface shape, CX X-axis direction curvature, CY is the Y-axis direction curvature, K _x is the X-axis direction conical coefficient, K _y is the Y-axis direction conical coefficient, R _n Is an aspherical term rotationally symmetric component, and _Pn is an aspherical term rotationally asymmetric component.

The surface shape of the trick surface is represented by the following equation (b). Z = −Sign (Rx) ｛(Rx−G (y)) ² −x ² ｝ ^1/2 + Rx (b) where Z is the amount of deviation of the surface shape from the tangent plane to the origin, and Rx is The radius of curvature in the X-axis direction, Sign (Rx) is the sign of the radius of curvature in the X-axis direction, and G (y) is Where CY is the curvature in the Y-axis direction, ak is the conic coefficient, and ac (n) is the aspherical coefficient.

The surface shape of the free-form surface is expressed by the following equation (c). _{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 ····· ··· (c) However, Z is the amount of deviation from a plane tangent to the origin of the surface shape (the m 2 or more integer) C _m is the coefficient .

In the decentered prism optical system according to the present invention, it is desirable that at least one of the deflected reflecting surfaces having a decentered rotationally asymmetric surface is a plane-symmetric free-form surface having only one plane of symmetry. In general, the free-form surface represented by the formula (c) does not have a symmetric surface in both the XZ plane and the YZ plane, but in the present invention, all odd-order terms of x are set to 0. YZ plane (plane in FIG. 1A)
Is a free-form surface having only one symmetry plane parallel to. 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 setting one of the symmetry plane parallel to the YZ plane and the symmetry plane parallel to the XZ plane as the 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.

In general, it is difficult to manufacture an eccentric prism optical system having an eccentric rotationally asymmetric reflecting surface by polishing. Therefore, it is necessary to form one surface at a time by grinding, or to manufacture by plastic injection molding or glass molding. Become. At this time, it is necessary to confirm whether the surface of the decentered prism optical system is formed in a predetermined shape.
In general, a three-dimensional coordinate measuring device is used for measuring such a three-dimensional rotationally asymmetric shape, but the measurement takes too much time.

Therefore, it is more desirable that at least one of the surfaces constituting the decentered prism optical system is constituted by a rotationally symmetric surface comprising a spherical surface or a rotationally symmetric aspherical surface. In Example 1 described later, the first surface 3 is formed in a rotationally symmetric aspherical shape.

Now, in the decentered prism optical system having two or more reflecting surfaces as shown in FIG. 1, the first reflecting surface (second surface 4) is changed to the first reflecting surface and the second reflecting surface by back ray tracing counted from the pupil side.
When the second reflecting surface is used as the second reflecting surface (first surface 3), when a rotationally symmetric surface is used as the second reflecting surface, the ratio of the power Px2 in the X direction and the power Py2 in the Y direction of the first reflecting surface. It is desirable that the absolute value | Py2 / Px2 |

0.1 <| Py2 / Px2 | <4 (2) When the value exceeds the upper limit of 4 in the above expression (2), the power in the Y direction becomes too strong, and the power in the Y direction generated on this surface becomes large. Astigmatism in which the focal position of the light beam is close to that of the decentered prism optical system occurs greatly, and it becomes impossible to correct this on other surfaces. If the lower limit of 0.1 is exceeded, the power in the Y direction becomes too weak, so that the focal position of the light beam in the Y direction generated on this surface becomes far from the decentered prism optical system, and astigmatism increases. It is difficult to make corrections in terms of

More preferably, it is desirable to satisfy the following condition: 0.5 <| Py2 / Px2 | <1.5 (2) '

When a rotationally asymmetric surface is used as the second reflecting surface, the absolute value | Py2 / Px2 | of the ratio of the power Px2 in the X direction and the power Py2 in the Y direction of the first reflecting surface, and the second reflecting surface It is desirable that the absolute value | Py3 / Px3 | of the ratio of the power Px3 in the X direction and the power Py3 in the Y direction satisfy the following condition.

0.1 <| Py2 / Px2 | <4 (3) 0.1 <| Py3 / Px3 | <4 (4) 4 of the upper limit of the above equations (3) and (4) Is exceeded, the power in the Y direction becomes too strong, and astigmatism occurs in which the focal position of the light beam in the Y direction generated on these surfaces is close to the decentered prism optical system, and this is corrected on other surfaces. It becomes impossible. If the lower limit of 0.1 of the above formulas (3) and (4) is exceeded, the power in the Y direction becomes too weak, so that the focal position of the light beam in the Y direction generated on these surfaces is far from the eccentric prism optical system. Astigmatism increases, and it becomes difficult to correct this on other surfaces.

More preferably, it is desirable to satisfy the following condition: 0.1 <| Py2 / Px2 | <1 (3) '0.1 <| Py3 / Px3 | <1 (4)' .

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 of an image display device according to the present invention will be described below. 1 and 2 are cross-sectional views of Examples 1 and 2, respectively. In each figure, (a) shows a YZ section including the optical axis, and (b) shows an XZ section.
In the configuration parameters of these embodiments described later,
As shown in these figures, the pupil 1 of the decentered prism optical system 7
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, and the direction from the pupil 1 to the first surface 3 of the optical system 7 is the Z-axis direction. The direction in the plane orthogonal to the Z axis and passing through the center of the pupil 1 and the light beam is bent by the optical system 7 is defined as the Y axis direction, the direction orthogonal to the Y axis and the Z axis, and the direction passing through the center of the pupil 1 is defined as 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, and the direction that constitutes the Y axis, the Z axis and the right hand system is the X axis. In the positive direction. 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 with eccentricity, the amount of eccentricity in the X-, Y-, and Z-axis directions from the center of the pupil 1 which is the origin of the optical system 7 at the top of the plane ( 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 formula (c).
There is an ike polynomial. The shape of this surface is defined by the following equation (d). 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 −5R ⁴ ) sin (4A) + D ₂₉ R ⁶ sin (6A) (D) In the above description, the plane is symmetric in the X direction. 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 (c), 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 equation (e).

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 | (e) The definition of the rotationally symmetric aspheric surface is given by the following expression (f). The Z axis of this definition expression is the axis of the rotationally symmetric aspherical surface. ^{Z = (y 2 / R)} / [1+ {1- (1 + k) y 2 / R 2} 1/2] ay 4 + by 6 + cy 8 + dy 10 + ··· ··· (f) However, Z is a surface The amount of deviation from the tangent plane to the origin of the shape, y is the distance in the direction perpendicular to Z, R is the paraxial radius of curvature, k
Is the conical coefficient, and a, b, c, and d are the fourth, sixth, and eighth, respectively.
Next, it is the 10th order aspheric coefficient.

In the following configuration parameters, the term relating to the aspherical surface for which no data is described is zero. For the refractive index, d-line (wavelength 587.56 nm)
Are written for The unit of the length is mm.

The image display devices of the first and second embodiments of the present invention
As shown in FIGS. 1 and 2, respectively, the decentered prism optical system 7 constituting the eyepiece optical system of the image display device has three surfaces 3,
4 and 5, the three surfaces 3 to 5 are filled with a transparent medium having a refractive index larger than 1 and a ray bundle emitted from an object (not shown) Along the pupil 1 of the optical system 7, firstly, enters the first surface 3 having a transmitting action and a reflecting action and enters the optical system 7, and the incident light beam has only a reflecting action farther from the pupil 1. The light is reflected by the second surface 4 which is a reflecting surface in a direction approaching the pupil 1, and is again reflected by the first surface 3 in a direction away from the pupil 1, and the reflected light passes through the third surface 5 having only a transmitting action. The transmitted light reaches the image plane 6 and forms 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 the first embodiment, the first surface 3 is a rotationally symmetric aspheric surface defined by the above equation (f), which is decentered with the concave surface facing the pupil 1 side, and the second surface 4 has a concave surface on the pupil 1 side. The third surface 5 is formed of a free-form surface defined by the above-described equation (c), and the third surface 5 is also formed of a free-form surface defined by the above-described equation (c). The screen size of the image display element 6 is 14.4 in the horizontal direction.
mm, vertical direction is 8.3 mm, horizontal angle of view 35 °,
The vertical angle of view is 26.6 ° and the pupil diameter is 4 mm.

In the second embodiment, the first surface 3 is an eccentric free spherical surface defined by the above equation (c), and the second surface 4 is a pupil 1
The third surface 5 is also formed of a free-form surface defined by the above-described equation (c), and is formed of a free-form surface defined by the above-described equation (c), which is eccentric with the concave surface facing the side. The screen size of the image display element 6 is 14.4 mm in the horizontal direction and 8.3 mm in the vertical direction.
35 ° horizontal angle of view, 26.6 ° vertical angle of view, pupil diameter 4
mm. The configuration parameters of the first and second embodiments are shown below.

Example 1 Surface Number Surface Shape Curvature Radius Surface Spacing Eccentricity Refractive Index Abbe Number Object Surface ∞ -1000.00 1 (pupil surface) ∞ 2 Rotationally symmetric aspherical surface [1] Eccentricity (1) 1.5254 56.2 3 Free-form surface [1] Eccentricity (2) 1.5254 56.2 4 Rotationally symmetric aspherical surface [1] Eccentricity (1) 1.5254 56.2 5 Free-form surface [2] Eccentricity (3) Image surface ∞ Eccentricity (4) Free-form surface [1] C ₅ -1.0057 × 10 ^-2 C ₇ -9.7298 × 10 ^-3 C ₈ 4.9 125 × 10 ^-5 C ₁₀ 1.9565 × 10 ^-5 C ₁₂ 1.6240 × 10 ^-6 C ₁₄ -2.7913 × 10 ^-6 C ₁₆ -1.6326 × 10 ^-6 C ₁₇ 1.0651 × 10 ^-7 C ₁₉ 1.1768 × 10 ^-7 C ₂₁ 2.5207 × 10 ^-8 Free-form surface [2] C ₅ -4.1118 × 10 ^-2 C ₇ 7.1840 × 10 ^-3 rotationally symmetric aspheric surface [1] R -131.28 k 0. a -7.5909 × 10 ^-7 b -9.8672 × 10 ^-10 c 6.5038 × 10 ^-12 d -7.6508 × 10 ^-15 Eccentricity (1) x 0.00 y 6.83 z 27.93 α 19.00 β 0.00 γ 0.00 Eccentricity (2) x 0.00 y 0.82 z 38.51 α -12.06 β 0.00 γ 0.00 eccentricity (3) x 0.00y 17.57 z 32.34 α 68.89 β 0.00 γ 0.00 eccentricity (4) x 0.00y 21.81 z 34.14 α 63.01 β 0.00 γ 0.00 fy / fx = 0.768531 Py2 / Px2 = 1.03352.

Example 2 Surface Number Surface Shape Curvature Radius Surface Spacing Eccentricity Refractive Index Abbe Number Object Surface -100 -1000.00 1 (pupil surface) ∞ 2 Free-form surface [1] Eccentricity (1) 3 Free-form surface [2] Eccentricity (2) 1.5254 56.2 4 Free-form surface [1] Eccentricity (1) 1.5254 56.2 5 Free-form surface [3] Eccentricity (3) 1.5254 56.2 Image surface ∞ Eccentricity (4) Free-form surface [1] C ₅ 2.1880 × 10 ^-3 C ₇ -4.9617 × 10 ^-3 C ₈ -7.5862 × 10 ^-5 C ₁₀ -6.5631 × 10 ^-5 C ₁₂ -1.4 470 × 10 ^-6 C ₁₄ 3.4252 × 10 ^-6 C ₁₆ 1.6254 × 10 ^-6 C ₁₇ -4.2434 × 10 ^-8 C ₁₉ 7.2914 × 10 ^-8 C ₂₁ 6.6403 × 10 ^-8 Free-form surface [2] C ₅ -5.1650 × 10 ^-3 C ₇ -1.0005 × 10 ^-2 C ₈ -7.6376 × 10 ^-5 C ₁₀ -8.9825 × 10 ^-6 C ₁₂ 5.9080 × 10 ^-6 C ₁₄ 2.1434 × 10 ^-6 C ₁₆ -9.3569 × 10 ^-7 C ₁₇ -7.2994 × 10 ^-8 C ₁₉ -8.4614 × 10 ^-8 C ₂₁ -9.4008 × 10 ^-9 Free-form surface [3 ] C ₅ -2.8569 × 10 ^-2 C ₇ 3.6733 × 10 ^-3 C ₁₀ -1.2982 × 10 ^-4 C ₁₂ 4.8821 × 10 ^-5 C ₁₄ 6.4196 × 10 ^-6 C ₁₆ -2.2278 × 10 ^-6 C ₁₉ 1.2218 × 10 ^-6 C ₂₁ 5.7026 × 10 ^-7 Eccentricity (1) x 0.00 y 8.90 z 27.54 α 1 1.20 β 0.00 γ 0.00 Eccentricity (2) x 0.00 y 0.78 z 38.43 α-15.84 β 0.00 γ eccentricity (3) x 0.00 y 20.05 z 34.21 α 66.45 β 0.00 γ 0.00 Eccentricity (4) x 0.00 y 22.95 z 36.23 α 48.09 β 0.00 γ 0.00 fy / fx = 0.768535 Py2 / Px2 = 0.51613 Py3 / Px3 = −0.44103.

FIGS. 3 to 5 show lateral aberrations at various angles of view in the first embodiment, and FIG. 9 shows distortions. Also,
FIGS. 6 to 8 show a similar lateral aberration situation in the second embodiment, and FIG. 10 shows a distortion situation. In the figure showing the lateral aberration, the numbers shown in parentheses indicate (horizontal (X direction) view angle, vertical (Y direction) view angle), and show the transverse aberration diagram at the view angle.

In the above description, as shown in FIG. 1, the decentered prism optical system 7 is composed of three optically active surfaces, ie, a first surface 3, a second surface 4, and a third surface 5. 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. 11, 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, and 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, and is incident on the first surface 3 and is refracted. The iris position of the observer's pupil or the center of rotation of the eyeball is projected as the exit pupil 1 into the observer's eyeball.

Further, in the image display device of the present invention,
The eyepiece optical system may include an optical element other than the decentered prism optical system 7. FIG. 12 shows an example. FIG. 12A is a diagram illustrating an example in which a viewing angle (angle of view) magnifying lens 11 is arranged between the first surface 3 of the eccentric prism optical system 7 and the observer's eyeball, and the image of the observed image is shown. In addition to the function of enlarging the angle, the eccentric prism optical system 7 has a function as a cover glass of the first surface 3. FIG.
(B) shows an example in which a field lens 12 is arranged between the third surface 5 of the eccentric prism optical system 7 and the LCD 6 as an image display element so that a bright image on the LCD 6 can be observed. In FIG. 12, an LCD 6 is used as an image display element, and a backlight 10 is provided for illumination. When a reflective LCD is used, the illumination light source is arranged in front of the LCD 6.

Now, even if one set of the image display device as 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 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. 13 shows the arrangement of the image display apparatus main body with respect to one eye of the observer, and FIG. 14 shows a state in which the main body is attached to one eye (in this case, attached to the left eye). The state of the case where both eyes are used is shown.
13 to 15, reference numeral 31 denotes a display device main body, and FIG.
In the case of No. 4, a support member is fixed via the head so as to be held in front of the left eye of the observer's face, and in the case of FIG. 15, it is held in front of both eyes of the observer's face. As the support member,
Left and right front frames 32 each having one end joined to the display device body 31 and extending from the temple of the observer to the upper part of the ear.
And left and right rear frames 33 joined to the other ends of the front frames 32 and extending across the temporal region of the observer (in the case of FIG. 14).
And a top frame 34 that supports the top of the observer by joining the two ends thereof one by one so as to be sandwiched by the other end of 3 (FIG. 15).

In the vicinity of the joint of the front frame 32 and 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 sent 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.

It should be noted that 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. One of the at least three surfaces is an incident surface for causing light from the image display element to enter the optical system, and the other surface emits light from the image display element from the optical system. The image display device includes a two-dimensional image display screen having a plurality of pixels arranged two-dimensionally, and the two-dimensional image. Is configured to display in a compressed form as compared with the image displayed the image displayed on the vertical 示画 plane laterally, said decentered prism optical system, the 2
An image display device characterized in that a direction corresponding to a vertical direction of a two-dimensional image display screen is extended as compared with a direction corresponding to a horizontal direction.

[2] The image display device according to the above [1], wherein a two-dimensional image display screen of the image display element is arranged so as to face an incident surface of the eccentric prism optical system.

[3] In the above [1] or [2],
The expansion ratio of the eccentric prism optical system in the direction corresponding to the vertical direction with respect to the direction corresponding to the horizontal direction of the two-dimensional image display screen is the reciprocal of the vertical compression ratio of the image of the two-dimensional image display screen in the horizontal direction. An image display device, which is configured to be substantially equal to:

[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 axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis, and YZ with respect to the axial chief ray of the entire eccentric prism optical system.
Assuming that the combined focal length in the plane is fy and the combined focal length in the plane orthogonal to the YZ plane is fx, 0.1 <fy / fx <0.8 (1) An image display device characterized by the above-mentioned.

[5] Any one of the above [1] to [4]
In the item, in the backward ray tracing counted from the exit pupil side, 1
When the second reflection surface is a first reflection surface and the second reflection surface is a second reflection surface, the second reflection surface has a rotationally symmetric surface shape, passes through the center of the exit pupil, and passes through the center of the exit pupil. A ray reaching the center of the screen is defined as an axial principal ray, and an optical axis defined by a straight line extending to the first surface of the eccentric prism optical system is defined as a Z axis. The eccentric prism optical system is orthogonal to the Z axis. The axis in the eccentric plane of each surface constituting the axis is defined as the Y axis, the axis orthogonal to the Z axis and the axis orthogonal to the Y axis is defined as the X axis, and the axis in the YZ plane with respect to the on-axis principal ray of the first reflecting surface. Power Py2 in
An image display device characterized by satisfying 0.1 <| Py2 / Px2 | <4 (2), where Px2 is a power in a plane orthogonal to the YZ plane.

[6] Any one of the above [1] to [4]
In the item, in the backward ray tracing counted from the exit pupil side, 1
When the second reflecting surface is the first reflecting surface and the second reflecting surface is the second reflecting surface, the second reflecting surface has a rotationally asymmetric surface shape, passes through the exit pupil center, and A ray reaching the center of the screen is defined as an axial principal ray, and an optical axis defined by a straight line extending to the first surface of the eccentric prism optical system is defined as a Z axis. The eccentric prism optical system is orthogonal to the Z axis. The axis in the eccentric plane of each surface constituting the axis is defined as the Y axis, the axis orthogonal to the Z axis and the axis orthogonal to the Y axis is defined as the X axis, and the axis in the YZ plane with respect to the on-axis principal ray of the first reflecting surface. Power Py2 in
And a power Px2 in a plane orthogonal to the YZ plane,
The power Py3 in the YZ plane for the axial principal ray of the second reflecting surface is defined as the power Py3 in the plane orthogonal to the YZ plane.
When x3, 0.1 <| Py2 / Px2 | <4 (3) An image display device satisfying 0.1 <| Py3 / Px3 | <4 (4).

[7] Any one of the above [1] to [6]
In the paragraph, the decentered prism optical system includes a first surface, a second surface,
Surface, a third surface, and a light beam from the two-dimensional image display screen is made incident from the third surface, and the incident light beam is passed through the inside of the eccentric prism optical system to form the first optical surface. An image display apparatus, wherein the image display device is configured to reflect light on a surface, reflect the reflected light beam on the second surface, and emit the reflected light beam from the first surface.

[8] In the above [7], the eccentric prism optical system reflects the light beam incident from the third surface into an optical path that passes through the eccentric prism optical system and reaches the first surface. An image display device comprising a fourth surface having an action.

[0064]

[9] In the above [8], in the eccentric prism optical system, the second surface is disposed on the side opposite to the exit pupil with respect to the first surface, and the fourth surface is the second surface. An image display device, wherein the image display device is arranged at a position farther from an observer's visual axis with respect to a surface and at a position sandwiching a medium with respect to the third surface.

[10] In the above [7], in the eccentric prism optical system, the third surface interposes a medium so that a light beam from the two-dimensional image display screen is incident on the first surface. The second surface is disposed so as to face the first surface, and the second surface sandwiches a medium so as to reflect the light flux reflected by the first surface so as to be turned back toward the first surface again. An image display device, wherein the image display device is arranged at a position facing the first surface.

[11] The image display device according to any one of [7] to [10], wherein the first surface of the eccentric prism optical system has a rotationally symmetric surface shape.

[12] In any one of the above items [7] to [10], the first surface of the eccentric prism optical system has a rotationally asymmetric surface shape having an eccentric aberration correcting action. Image display device.

[13] In any one of the above items [7] to [12], 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, The optical axis defined by a straight line that intersects the first surface of the system is the Z axis, and the axis orthogonal to the Z axis and the axis in the eccentric plane of each surface constituting the eccentric prism optical system is Y.
Axis, an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis, and the second surface has a power in a YZ plane and a power in a surface orthogonal to the YZ plane. An image display device having different rotationally asymmetric surface shapes.

[14] The image display device according to [13], wherein the rotationally asymmetric surface of the second surface is a plane-symmetric free-form surface having only one symmetry surface.

[15] In any one of the above items [7] to [14], the eyepiece optical system includes a pupil-side optical member closer to the exit pupil than the first surface of the eccentric prism optical system. An image display device comprising:

[16] The image display device according to the above [15], wherein the pupil-side optical member includes a lens having an angle-of-view enlargement function.

[17] In any one of the above items [7] to [14], the eyepiece optical system may include a display-side optical member closer to the image display element than the third surface of the eccentric prism optical system. An image display device comprising:

[18] The image display apparatus according to the above [15], wherein the display-side optical member comprises a field lens.

[19] In any one of the above items [1] to [18], a main body including the image display element and the eyepiece optical system, and a support member for mounting the main body on an observer's face. A head mounted image display device comprising:

[0075]

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 reflecting surfaces, and the image display device is constructed as follows. Display the image compressed in one direction,
Since the eccentric prism optical system is configured to extend the screen in that direction, it is necessary to achieve a bright image display device which is smaller, lighter and has higher optical performance while having high optical performance by eccentric aberration correction. Can be.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of an image display device according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a partial lateral aberration state according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a lateral aberration state of another part of the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a lateral aberration state of another part of the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a partial lateral aberration state according to the second embodiment of the present invention.

FIG. 7 is a diagram illustrating a lateral aberration state of another part of the second embodiment of the present invention.

FIG. 8 is a diagram illustrating a lateral aberration state of another part of the second embodiment of the present invention.

FIG. 9 is a diagram illustrating a distortion state according to the first exemplary embodiment of the present invention.

FIG. 10 is a diagram illustrating a state of distortion according to the second embodiment of the present invention.

FIG. 11 is a diagram illustrating another decentered prism optical system to which the present invention can be applied.

FIG. 12 is a diagram showing an example including optical elements other than the decentered prism optical system as the eyepiece optical system of the present invention.

FIG. 13 is a diagram showing an arrangement of the head-mounted image display device according to the present invention with respect to one eye of an observer.

FIG. 14 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. 15 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. 16 is a diagram for explaining field curvature generated by a concave mirror having an eccentric arrangement.

FIG. 17 is a diagram for explaining astigmatism generated by a concave mirror having an eccentric arrangement.

FIG. 18 is a diagram for explaining on-axis coma generated by a concave mirror having an eccentric arrangement.

[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 ... Chief ray 9 ... 4th surface 10 ... Backlight 11 ... Field of view Angle magnifying lens 12 Field lens 31 Display body 32 Front frame 33 Rear frame 34 Top frame 35 Rear plate 36 Rear cover 39 Speaker 41 Cable 40 Video playback device 40a Volume adjuster M concave mirror

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. One of the at least three surfaces is an incident surface that allows light from the image display element to enter the optical system;
The other surface is an emission surface that emits light from the image display element from an optical system and projects the light into an observer's eyeball at an exit pupil position, and the image display element has a plurality of two-dimensionally arranged pixels. A two-dimensional image display screen having the following configuration: an image displayed in the vertical direction of the two-dimensional image display screen is displayed in a compressed form as compared with an image displayed in the horizontal direction; An image display device, wherein the optical system is configured to extend a direction corresponding to a vertical direction of the two-dimensional image display screen as compared with a direction corresponding to a horizontal direction. 2. The image of the two-dimensional image display screen according to claim 1, wherein an expansion ratio of the eccentric prism optical system in a direction corresponding to a vertical direction with respect to a direction corresponding to a horizontal direction of the two-dimensional image display screen is determined. An image display device, which is configured to be substantially equal to a reciprocal of a compression ratio in a vertical direction with respect to a horizontal direction. 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. The axis is defined as the X axis, and the combined focal length in the YZ plane with respect to the axial principal ray of the entire decentered prism optical system is f.
An image display device characterized by satisfying 0.1 <fy / fx <0.8 (1), where fx is a combined focal length in a plane orthogonal to the y, YZ planes.