JP2000227574A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a clear and high-resolution picture display device that color correction ability is added by using a diffraction optical element for a relay optical system and made compact by reducing the number of lenses. SOLUTION: This picture display device is provided with a picture display element 3 and an observation optical system forming an exit pupil 2 for observing an observation picture displayed at the element 3 and having positive refractive power as a whole. Then, the observation optical system is provided with the relay optical system forming the observation picture as the intermediate picture 7 and an eyepiece optical system forming the pupil 2 in order to guide the picture 7 to an observer. The relay optical system is constituted of an axially symmetric lens group 4 and the diffraction optical element 8 is arranged in the group 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] 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 In recent years, image display apparatuses, particularly, head or face-mounted image display apparatuses have been actively developed for the purpose of individuals enjoying large-screen images.

Conventionally, as a head-mounted image display device, an image on an image display element such as a liquid crystal display (LCD) or a CRT is formed once in the air by a relay optical system, and further transmitted from a semi-transmissive mirror and a concave mirror. There is known an eyepiece optical system that guides the eyeball of an observer (Japanese Patent Laid-Open No. 7-151993). There is also known an eyepiece optical system that uses a decentered concave mirror as an eyepiece optical system and arranges a diffractive optical element (DOE) in a relay optical system that relays an image on an image display element to the concave mirror (US Pat. Nos. 436,763 and 5,526,183).

[0004]

However, when the former eyepiece optical system is composed of a semi-transmissive mirror and a concave mirror, the chromatic aberration, especially the chromatic aberration of magnification, is not sufficiently corrected and is clear and has high resolution. No indication was obtained.

In the latter case of using a concave mirror having an eccentric arrangement, the power of the concave mirror between the intermediate image and the exit pupil is weak, and if the power is to be increased, the deterioration of the aberration becomes conspicuous due to the eccentric arrangement. Therefore, the whole is large and heavy, and is not suitable for a head mounted image display device.

By the way, an image display device having an optical system which forms a primary image using the above-described relay optical system and guides the primary image to an eyeball by an eyepiece optical system comprising a semi-transmissive mirror and a concave mirror. Are superior to the image display device without the relay optical system in the following points. The aberration generated in the eyepiece optical system can be corrected by the relay optical system. By enlarging a small LCD to an intermediate image plane by the relay optical system, it becomes equivalent to an apparently large LCD panel used in an eyepiece optical system including a transflective mirror and a concave mirror. Thus, a wide viewing angle can be obtained even with a small LCD. If an image display device is to be constructed using only an eyepiece optical system consisting of a semi-transmissive mirror and a concave mirror without using a relay optical system, in order to achieve a wide viewing angle of view, the focal length of the concave mirror should be shortened and the magnification increased. It is necessary to raise the power, but if the power of the concave mirror is made too strong, the aberration is worsened.

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 provide an image display device comprising a relay optical system for forming an intermediate image of an image display element and an eyepiece optical system. An object of the present invention is to provide a relay optical system with a small number of lenses by adding a color correction capability to a relay optical system portion by using a diffractive optical element to further reduce the size of the relay optical system and to realize a clear and high-resolution image display device. .

[0008]

In order to achieve the above object, an image display apparatus according to the present invention has an image display element and an exit pupil for observing an observation image displayed on the image display element. In an image display device having an observation optical system having a refractive power, the observation optical system includes a relay optical system that forms the observation image as an intermediate image, and an exit pupil for guiding the intermediate image to an observer. An eyepiece optical system to be formed, wherein the relay optical system comprises an axially symmetric lens group, and a diffractive optical element is arranged in the lens group.

Hereinafter, the reason and operation of the above-described configuration in the present invention will be described. In an image display device using an observation optical system including a relay optical system and an eyepiece optical system,
In order to shorten the object-image distance of the relay optical system, it is necessary to use the relay optical system portion near the same magnification and increase the power thereof. However, if the power of the relay optical system is excessively increased, aberrations occurring on each surface increase, which causes deterioration of optical performance. Conventionally, when a relay optical system having such a strong power is used, it has been necessary to further increase the number of lenses of the relay optical system in order to disperse the strong power of each surface.

However, according to the present invention, an aspherical surface is used as a part of the lens surface in the relay optical system, and a diffractive optical element (DOE) surface is used on the aspherical surface to add chromatic aberration correction capability. Thus, a compact relay optical system can be configured with a small number of lenses.

Conventionally, it is desirable to use an optical system including a DOE as an optical system for photographing on a photographic film using a white continuous spectrum, because of the wavelength dependence of the diffraction efficiency of light on the DOE surface. However, when used for applications such as the head-mounted image display device of the present invention, the wavelength and wavelength width of the illumination light of the LCD used as the image display element are set to LE.
D and the like can be used by limiting it, so that the DOE can be used without causing an adverse effect due to the wavelength dependence.

Further, in the image display device of the present invention, the eyepiece optical system comprises a semi-transmissive mirror and a concave mirror as in the embodiment described later, and the display light beam from the relay optical system is reflected by the semi-transmissive mirror. The reflected light is then reflected by a concave mirror and transmitted through the latter half of the transmission mirror to reach the observation image eyeball.

Alternatively, the display light beam from the relay optical system may be transmitted through the semi-transmissive mirror, then reflected by the concave mirror, and then reflected by the latter-half mirror to reach the observation image eyeball.

In either case, the semi-transmissive mirror and the concave mirror can be formed as an integral prism.

Further, as in the embodiment described later, the display light beam from the relay optical system is reflected by the semi-transmissive mirror, then reflected by the concave mirror, transmitted through the latter-half transparent mirror, and reaches the observation image eyeball. In this case, when the concave mirror is configured as a semi-transmissive front mirror or a semi-transmissive rear mirror of a transparent substrate having the same front and back surfaces, not only the observation image displayed on the image display device, but also the external image is not distorted. See through can be.

Further, as the eyepiece optical system, as will be described later, an incident surface on which the display light beam from the relay optical system enters the prism, at least one reflecting surface for reflecting the light beam in the prism, and An exit surface for emitting the reflected light beam outside the prism and entering the observation image eyeball; at least one reflecting surface has a curved surface shape that gives power to the light beam, and the curved surface shape corrects aberrations caused by eccentricity An eccentric prism having a rotationally asymmetric surface shape can be used. Such rotationally asymmetric surface shapes include the following free-form surfaces.

Further, in the image display device of the present invention, D
Instead of the OE, a hologram optical element having the same function may be used.

As the concave mirror, an axisymmetric spherical mirror,
Not only an aspherical mirror but also a free-form concave mirror can be used.

Here, the free-form surface referred to in the present invention will be described. The free-form surface is defined by the following equation (a). Note that the Z axis of the definition formula is the axis of the free-form surface.

[0020] Here, the first term of the equation (a) is a spherical term, and the second term is a free-form surface term.

In the spherical term, c: curvature of the vertex k: conic constant (conical constant) r = √ (X ² + Y ² ).

The free-form surface term is Here, C _j (j is an integer of 2 or more) is a coefficient.

The free-form surface is generally an XZ surface,
Neither YZ plane has a symmetry plane, but by setting all odd-order terms of X to 0, a free-form surface having only one symmetry plane parallel to the YZ plane exists. For example, in the above definition formula (a), C ₂ , C ₅ , C ₇ , C ₉ , C ₁₂ ,
_{C 14, C 16, C 18} , C 20, C 23, C 25, C 27, C 29, C
It is possible to set the coefficients of the terms ₃₁ , C ₃₃ , C ₃₅ ... To 0.

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 above definition formula, C ₃ ,
_{C 5, C 8, C 10} , C 12, C 14, C 17, C 19, C 21, C
₂₃ , C ₂₅ , C ₂₇ , C ₃₀ , C ₃₂ , C ₃₄ , C ₃₆ ...

The above-mentioned definition formula (a) is shown as one example. By using a rotationally asymmetric surface having only one plane of symmetry, rotationally asymmetric aberrations caused by eccentricity are corrected and simultaneously manufactured. It is a feature of the present invention that the property is also improved, and it goes without saying that the same effect can be obtained for any other defining formula.

By the way, in the image display apparatus of the present invention, when the power of the DOE in the relay optical system is Pdoe, the following condition is satisfied: 0.0001 <Pdoe <0.0200 [1 / mm] (1) It is important to be satisfied. This condition is D
This is a condition for defining the power of the OE and the correction amount of the chromatic aberration. If the upper limit of 0.0200 mm ^-1 is exceeded, the power of the DOE becomes too strong, and the chromatic aberration generated by this DOE becomes too large. This makes it difficult to correct chromatic aberration generated on the DOE surface on another surface. If the lower limit of 0.0001 mm ^-1 is exceeded, the power of the DOE surface becomes too weak, and the chromatic aberration generated on this DOE surface becomes too small. This makes it difficult to cancel chromatic aberration occurring on a surface other than the DOE on the DOE surface.

More desirably, it is important to satisfy the following condition: 0.0010 <Pdoe <0.0100 [1 / mm] (2) The meanings of the upper and lower limits of the conditional expression are the same as those of the conditional expression (1).

More preferably, it is important to satisfy the following condition: 0.0020 <Pdoe <0.0080 [1 / mm] (3) The meanings of the upper and lower limits of the conditional expression are the same as those of the conditional expression (1).

When the maximum height of the axial chief ray in the relay optical system is h, and the height of the lens surface constituting the relay optical system at the position where the axial chief ray passes is H, 0 .8h ≦ H ≦ h (4) It is desirable to dispose the DOE on the lens surface that satisfies (4). This condition is a conditional expression for favorably correcting both the on-axis light beam and the off-axis light beam by the DOE so that the on-axis light beam and the off-axis light beam pass through separate independent areas on the DOE surface. Exceeds 0.8h, it becomes difficult to independently correct aberrations of both the on-axis light beam and the off-axis light beam by the DOE. There is no surface exceeding the upper limit h.

[0030]

Next, specific numerical examples 1 to 3 of the present invention will be described. In the configuration parameters of each embodiment described later, as shown in FIG. 1, in the reverse ray tracing, the axial principal ray 1 passes through the center of the exit pupil 2 of the observation optical system and passes through the center of the image plane (image display element) 3. Defined by the rays that reach. The intersection of the surface on the side facing the exit pupil 2 of the transflective mirror 5 of the eyepiece optical system and the incident axial principal ray 1 and the surface of the transflective mirror 5 of the eyepiece optical system facing the exit pupil 2 Pass through the intersection of the semi-transmissive reflection surface 5 'on the opposite side and the axial principal ray 1 reflected from the surface, and take virtual planes perpendicular to the axial principal ray 1, respectively. The intersection of each virtual plane is defined as the origin of the eccentric optical surface from the optical surface passing through the intersection to the next virtual surface (the image plane for the last virtual surface), and the direction along the principal ray 1 on the axis is the Z axis. Direction, the direction along the traveling direction of the axial principal ray 1 is defined as a positive Z-axis direction, a plane including the Z-axis and the image plane center is defined as a YZ plane, and passes through the origin and is orthogonal to the YZ plane; The direction from the front side of the paper to the back side is defined as the X-axis positive direction, and X
The axis that forms the right-handed rectangular coordinate system with the axis, the Z axis, and the Y axis is defined as the Y axis.
FIG. 1 illustrates a coordinate system related to a first virtual plane defined at an intersection of each virtual plane and a surface of the semi-transmission mirror 5 on the side facing the exit pupil 2. In FIGS. 2 and 3 showing the second and third embodiments, respectively, these virtual planes and coordinate systems are not shown. In the first to third embodiments, each surface is decentered in the YZ plane.

With respect to the eccentric surface, the amount of eccentricity (X, Y, and Z in the X-axis direction, Y-axis direction, and Z-axis direction) at the top of the surface from the origin of the corresponding coordinate system, X of the central axis (for the aspheric surface, the Z axis of the following equation (b))
The tilt angles (α, β, γ (°), respectively) about the axis, the Y axis, and the Z axis are given. In this case, the positive α and β mean counterclockwise with respect to the positive direction of each axis, and the positive γ means clockwise with respect to the positive direction of the Z axis.

In a case where a specific surface (including a virtual surface) and a surface following the specific surface (including a virtual surface) among the optical working surfaces constituting the optical system of each embodiment constitute a coaxial optical system, a surface interval is given. In addition, the refractive index and Abbe number of the medium are given according to a conventional method.

As for the diffractive optical element (DOE), for example, “Small Optical Elements for Optical System Designers”, Chapters 6 and 7 (published by Optronics) and “SPI
E, Vol. 126, p. 46-53 (1977), etc., where the Abbe number ν in the visible region is −3.453 and the partial dispersion ratio θ _{g, F is} 0.03, and the interval between the diffraction gratings can be freely changed. Therefore, it can be treated equivalent to an arbitrary aspheric lens surface. In the following, “SPIE” 126th
Vol., P. 46-53 (1977).
ltra-high index method "is used.

In each surface, the rotationally symmetric aspherical shape has a paraxial radius of curvature, R, on coordinates defining the surface.
K is the conic coefficient, A, B, C, D and E are the fourth order and 6 respectively.
, 8th, 10th, and 12th order aspherical coefficients, h is h ² = X
When ² + Y ^2, aspheric expression are as follows. Z = (h ² / R) / [1+ ｛1− (1 + K) (h ² / R ² )｝ ^1/2 ] + Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ + Eh ¹² (b) The coordinate system of each of the above expressions representing the surface shape is a coordinate system in which the origin is the top of each surface and the Z axis is the center axis of each surface.

In the configuration parameters to be described later, the value of a parameter whose value is not described is zero. The refractive index of the medium between the surfaces is d-line (wavelength 587.56 n
m). The unit of the length is mm.
FIG.
3 to FIG. The first to third embodiments all assume a 0.47 inch LCD with a horizontal angle of view of 25 °, and the concave mirror 6 assumes a spherical mirror in all embodiments.

As shown in FIGS. 1 to 3, the image display devices of the first to third embodiments have a lens system 4 constituting a relay optical system, a semi-transmissive mirror 5 and a concave mirror 6 constituting an eyepiece optical system, respectively. The display light from the image display device arranged on the image plane 3 forms an intermediate image 7 through a lens system 4 which is a relay optical system, and a pupil is formed on a semi-transmissive reflection surface 5 ′ of a rear half transmission mirror 5. , And then reflected by the concave mirror 6, transmitted through the latter half of the transmissive reflection surface 5 ′, and reaches the observation image eyeball located at the exit pupil 2. Note that part or all of the intermediate image 7 may be formed in an eyepiece optical system including the semi-transmissive mirror 5 and the concave mirror 6 (FIG. 1).

The lens system 4 of the relay optical system according to the first embodiment is composed of two groups and three lenses, and the last lens (lens closest to the image plane 3) in reverse ray tracing is aspherical on both surfaces.
DOE 8 is added on the aspherical surface on the image plane 3 side. The focal length of the entire system is −21.54 mm, and the pupil diameter is φ4.0 mm.
It is.

The lens system 4 of the relay optical system of the second embodiment
The final lens is a double-sided aspherical surface, and a DOE 8 is added on the aspherical surface on the image plane 3 side.
The focal length of the entire system is −21.54 mm, and the pupil diameter is φ4.0.
mm.

The lens system 4 of the relay optical system according to the third embodiment is composed of a single lens having two aspheric surfaces, and a DOE 8 is added on the aspheric surface on the image plane 3 side. The focal length of the whole system is-
22.08 mm, and the pupil diameter is φ4.0 mm.

In these embodiments, the external mirror can be seen through by using the concave mirror 6 as a transflective surface. The configuration parameters of the first to third embodiments are shown below. In these tables, "ASS" indicates an aspheric surface, "HRP" indicates a virtual surface, "RS" indicates a reflection surface, and "DOE" indicates a DOE surface.

Example 1 Surface number Curvature radius Surface distance Eccentricity Refractive index Abbe number Object surface ∞ -1000.00 1 瞳 (pupil surface) 37.00 2 ∞ (HRP1) 3 ∞ Eccentricity (1) 1.4922 57.5 4 ∞ Eccentricity (2) 5- 43.61 (RS) Eccentricity (3) 6 ∞ (RS) Eccentricity (2) 7 ∞ (HRP2) 26.56 Eccentricity (4) 8 15.10 5.50 1.7725 49.6 9 -14.12 2.00 1.6278 33.9 10 46.85 1.94 11 ASS 4.00 1.4922 57.5 12 ASS 0.00 1001.0682 -3.5 13 ASS (DOE) 20.00 Image plane ∞ ASS R 48.48 K -1.8639 × 10 ⁺² A 2.2821 × 10 ^-4 B -1.4999 × 10 ^-5 C 2.0397 × 10 ^-7 D -1.4370 × 10 ^-9 E 3.9855 × 10 ^-13 ASS R -19.23 K 3.4556 × 10 ^-3 A 3.9899 × 10 ^-5 B -1.1655 × 10 ^-6 C 3.0263 × 10 ^-8 D -3.8587 × 10 ^-10 E 1.8990 × 10 ^-12 ASS R -19.23 K 1.0327 × 10 ^-2 A 4.0145 × 10 ^-5 B -1.1679 × 10 ^-6 C 3.0260 × 10 ^-8 D -3.8509 × 10 ^-10 E 1.8923 × 10 ^-12 Eccentricity (1) X 0.00 Y 0.00 Z 0.00 α 45.00 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.49 Z 1.63 α 45.00 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.49 Z 19.63 α 0.00 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 0.49 Z 1.63 α 90.00 β 0.00 γ 0.00.

Example 2 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface ∞ -1000.00 1 ∞ (pupil surface) 37.00 2 ∞ (HRP1) 3 ∞ Eccentricity (1) 1.4922 57.5 4 ∞ Eccentricity (2) 5- 47.65 (RS) Eccentricity (3) 6 ∞ (RS) Eccentricity (2) 7 ∞ (HRP2) 18.34 Eccentricity (4) 8 -24.49 3.00 1.7364 52.1 9 -14.36 10.56 10 -41.11 3.80 1.6968 55.5 11 -13.21 0.30 12 ASS 4.00 1.4922 57.5 13 ASS 0.00 1001.0682 -3.5 14 ASS (DOE) 20.00 Image plane ∞ ASS R 276.75 K -1.2099 × 10 ⁺⁵ A 1.0789 × 10 ^-4 B -8.9827 × 10 ^-6 C 3.1269 × 10 ^-7 D -7.0912 × ^{10 -9 E 6.7463 × 10 -11 ASS} R -16.14 K 4.0164 × 10 -3 A 3.9909 × 10 -5 B -1.1672 × 10 -6 C 3.0265 × 10 -8 D -3.8544 × 10 -10 E 1.8925 × 10 - ¹² ASS R -16.14 K 1.0520 × 10 ^-2 A 4.0114 × 10 ^-5 B -1.1662 × 10 ^-6 C 3.0254 × 10 ^-8 D -3.8569 × 10 ^-10 E 1.8991 × 10 ^-12 Eccentricity (1) X 0.00 Y 0.00 Z 0.00 α 45.00 β 0.00 γ 0.00 Eccentricity (2) X 0.0 0 Y 0.49 Z 1.63 α 45.00 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.49 Z 19.63 α 0.00 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 0.49 Z 1.63 α 90.00 β 0.00 γ 0.00.

Example 3 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100 -1000.00 1 ∞ (pupil surface) 37.00 2 ∞ (HRP1) 3 ∞ Eccentricity (1) 1.4922 57.5 4 ∞ Eccentricity (2) 5- 67.52 (RS) Eccentricity (3) 6 mm (RS) Eccentricity (2) 7 mm (HRP2) 84.71 Eccentricity (4) 8 ASS 6.00 1.4922 57.5 9 ASS 0.00 1001.0682 -3.5 10 ASS (DOE) 45.00 Image plane ∞ ASS R 39.91 K -8.2060 × 10 ⁺¹ A 2.5883 × 10 ^-4 B -1.0108 × 10 ^-5 C 2.9058 × 10 ^-7 D -4.6989 × 10 ^-9 E 3.1275 × 10 ^-11 ASS R -23.32 K 6.9913 × 10 ^-4 A 3.9925 × 10 ^-5 B -1.1657 × 10 ^-6 C 3.0231 × 10 ^-8 D -3.8498 × 10 ^-10 E 1.8923 × 10 ^-12 ASS R -23.32 K 1.2606 × 10 ^-2 A 4.0081 × 10 ^-5 B -1.1676 × 10 ^-6 C 3.0293 × 10 ^-8 D -3.8594 × 10 ^-10 E 1.8983 × 10 ^-12 Eccentricity (1) X 0.00 Y 0.00 Z 0.00 α 45.00 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.49 Z 1.63 α 45.00 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.49 Z 19.63 α 0.00 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 0.49 Z 1.63 α 90.00 β 0.00 γ 0.00.

Next, a lateral aberration diagram of the first embodiment is shown in FIG. In this transverse aberration diagram, the numbers shown in parentheses represent (horizontal (X direction) angle of view, vertical (Y direction) angle of view),
The lateral aberration at the angle of view is shown.

Next, the values relating to the conditional expressions (1) and (4) in the first to third embodiments are as follows. (1) (4) Example 1 0.0078 1.0h Example 2 0.0047 1.0h Example 3 0.0030 1.0h.

As the eyepiece optical system of the above embodiment, an optical system consisting of a semi-transmissive mirror 5 and a concave mirror 6 arranged obliquely with respect to the optical axis is used. Instead, an eccentric prism optical system is used. Is also good. 5 to 15 show examples. In addition,
In each case, the intermediate image 7 is formed on the image plane 36, and the pupil 31 corresponds to the exit pupil 2 (FIGS. 1 to 3).

In the case of FIG. 5, the prism P has a first surface 32,
The light from the image surface 36 is refracted by the third surface 34 and enters the prism P, is internally reflected by the second surface 33, and enters the first surface 32. The light is refracted and enters the pupil 31 to form a virtual image of the image plane 36 at a distance.

In the case of FIG. 6, the prism P has a first surface 32,
The light from the image surface 36 is refracted by the third surface 34, enters the prism P, is totally reflected by the first surface 32, and is internally reflected by the second surface 33. Then, the light enters the first surface 32 again, is now refracted and enters the pupil 31, and forms a virtual image of the image plane 36 at a distance.

In the case of FIG. 7, the prism P has a first surface 32,
The light from the image surface 36 is refracted by the second surface 33, enters the prism P, is internally reflected by the third surface 34, and is incident again on the second surface 33. This time, the light is totally reflected, enters the first surface 32, is refracted, enters the pupil 31, and forms a virtual image of the image plane 36 at a distance.

In the case of FIG. 8, the prism P has a first surface 32,
The image plane 3 includes a second surface 33, a third surface 34, and a fourth surface 35.
The light from No. 6 is refracted on the fourth surface 35 and enters the prism P, is internally reflected on the third surface 34, is internally reflected on the second surface 33, and its reflected light path is an incident light path on the third surface 34. Crosses with
The light enters the first surface 32, is refracted, enters the pupil 31, and forms a virtual image of the image plane 36 at a distance.

In the case of FIG. 9, the prism P has a first surface 32,
The light from the image surface 36 is refracted by the second surface 33 and enters the prism P, is totally reflected by the first surface 32, and is internally reflected by the third surface 34. Then, the light enters the second surface 33 again and is totally reflected this time. The light again enters the first surface 32 and is now refracted to enter the pupil 31.
6 is formed.

In the case of FIG. 10, the prism P is the first surface 3
2, the second surface 33, the third surface 33, and the fourth surface 35. The light from the image surface 36 is refracted by the fourth surface 35, enters the prism P, and is internally reflected by the third surface 34; The light is internally reflected by the second surface 33 so as to form a Z-shaped optical path, is incident on the first surface 32, is refracted, is incident on the pupil 31, and forms a virtual image of the image plane 36 at a distance.

In the case of FIG. 11, the prism P is the first surface 3
2, the second surface 33, the third surface 34, and the fourth surface 35. Light from the image surface 36 is refracted on the third surface 34, enters the prism P, and is internally reflected on the fourth surface 35, The light enters the third surface 34 again, is now totally reflected, is incident on the second surface 33, is internally reflected, is incident on the first surface 32, is refracted, is incident on the pupil 31, and is far away from the image surface 36. Form a virtual image.

In the case of FIG. 12, the prism P is
2, the second surface 33, the third surface 34, and the fourth surface 35. The light from the image surface 36 is refracted by the fourth surface 35, enters the prism P, is internally reflected by the second surface 33, Incident on the third surface 34 and internally reflected, and again incident on the second surface 33 and internally reflected,
The light enters the first surface 32, is refracted, enters the pupil 31, and forms a virtual image of the image plane 36 at a distance.

In the case of FIG. 13, the prism P is the first surface 3
2, the second surface 33, the third surface 34, and the fourth surface 35, and the light from the image surface 36 is refracted by the second surface 33, enters the prism P, and is internally reflected by the fourth surface 35, The light enters the second surface 33 again and is totally reflected this time, is incident on the third surface 34 and is internally reflected, and is again incident on the second surface 33 and is also totally reflected again.
The light enters the first surface 32, is refracted, enters the pupil 31, and forms a virtual image of the image plane 36 at a distance.

In the case of FIG. 14, the prism P is the first surface 3
2, the second surface 33 and the third surface 34, and the light from the image surface 36 is refracted by the third surface 34 and is incident on the prism P.
The light is totally reflected on the surface 32, again enters the third surface 34, is now totally reflected, is again incident on the first surface 32, is totally reflected, is internally reflected on the second surface 33, and is again reflected on the first surface 32. And then refracted and enter the pupil 31 to form a virtual image of the image plane 36 at a distance.

In the case of FIG. 15, the prism P is the first surface 3
2, the second surface 33 and the third surface 34, and the light from the image surface 36 is refracted by the first surface 32 and is incident on the prism P.
The light is internally reflected at the surface 34, is again incident on the first surface 32, and is totally reflected again, is again incident on the third surface 34, is internally reflected, is again incident on the first surface 32, and is also totally reflected again. , Second side 3
The light is internally reflected at 3, enters the first surface 32 four times, is refracted and enters the pupil 31, and forms a virtual image of the image plane 36 at a distance.

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. 16 shows a state in which the image display device is mounted on the observer's head when the image display apparatus is configured to be mounted on one eye (in this case, mounted on the left eye). FIG. 17 shows similar states. FIG. 18 shows a cross-sectional view thereof. The observation optical system according to the present invention is used as shown in the cross section of FIG.
Display device main unit 4 including a light source 11 for illuminating the display device
1 in front of the left eye of the observer's face in the case of FIG.
In the case of FIG. 17, two supporting members are fixed via the head so as to be separately held in front of both eyes of the observer's face. Note that, in order to protect the exit surface facing the exit pupil 2 of the eyepiece optical system, a cover member 12 is arranged between the exit pupil 2 and the exit surface as shown in FIG. As the cover member 12, any of a plane-parallel plate, a positive lens, and a negative lens may be used. In the case of FIG. 18, the concave mirror 6 is interposed between the semi-transmissive mirror 5 and the lens system 4 of the relay optical system.
And the optical system is arranged such that only the semi-transmissive mirror 5 is located in front of the observer's visual axis. A liquid crystal shutter 13 is provided for the operation.

As a support member of the display device main body 41,
Left and right front frames 42 each having one end joined to the display device main body 41 and extending from the temple of the observer to the upper part of the ear.
And the left and right rear frames 43 joined to the other end of the front frame 42 and extending across the temporal region of the observer (in the case of FIG. 16).
And a top frame 44 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. 17).

A rear plate 45 made of an elastic material and formed of, for example, a metal plate spring is joined to the front frame 42 near the joint with the rear frame 43. The rear plate 45 is joined so that the rear cover 46, which carries one wing of the support member, is located behind the ear at the portion where the back of the observer is attached to the neck of the observer and can be supported (see FIG. 17). Case). A speaker 49 is mounted in the rear plate 45 or the rear cover 46 at a position corresponding to the ear of the observer.

A cable 51 for transmitting video / audio signals and the like from the outside is transmitted from the display device main body 41 to the top frame 44 (in the case of FIG. 17), the rear frame 43, the front frame 42, and the rear plate 45. Rear plate 4
5 or the rear cover 46 protrudes outside from the rear end. The cable 51 is connected to the video playback device 50.
It is connected to the. In the figure, reference numeral 50a denotes a switch and a volume adjusting unit of the video reproducing device 50.

It is to be noted that the cable 51 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. Further, in order to reject an obstructive code, an antenna may be connected to receive an external signal by radio wave.

The above-described image display device of the present invention can be configured, for example, as follows. [1] An image display apparatus comprising: an image display element; and an observation optical system having an overall positive refractive power that forms an exit pupil for observing an observation image displayed on the image display element. The system has a relay optical system that forms the observation image as an intermediate image, and an eyepiece optical system that forms an exit pupil to guide the intermediate image to an observer, wherein the relay optical system is an axially symmetric lens. An image display device comprising a group, wherein a diffractive optical element is arranged in the lens group.

[2] The image display device as described in [1], wherein the diffractive optical element is arranged on any aspherical surface in the lens group.

[3] The image display device according to the above [1] or [2], wherein the intermediate image is formed between the relay optical system and the eyepiece optical system.

[4] The eyepiece optical system is composed of a semi-transmissive mirror and a concave mirror, and the display light beam from the relay optical system is reflected by the semi-transmissive mirror, and then reflected by the concave mirror. 4. The image display device according to any one of the above items 1 to 3, wherein the image display device is configured to be arranged so as to be transmitted to reach an observation image eyeball.

[5] The eyepiece optical system is composed of a semi-transmissive mirror and a concave mirror, and the display light beam from the relay optical system is transmitted through the semi-transmissive mirror, then reflected by the concave mirror, and then the semi-transmissive mirror 4. The image display device according to any one of the above items 1 to 3, wherein the image display device is configured to be arranged so as to be reflected by the light source and reach the observation image eyeball.

[6] The image display apparatus according to the above item 4 or 5, wherein the semi-transmissive mirror and the concave mirror are configured as an integral prism.

[7] The image display device according to the above item 4, wherein the concave mirror is configured as a semi-transmissive front-surface mirror or a semi-transmissive rear-surface mirror of a transparent substrate having the same front and back surfaces.

[8] The entrance surface where the eyepiece optical system enters the display light beam from the relay optical system into the prism,
At least one reflecting surface for reflecting the light beam inside the prism, and an emitting surface for emitting the light beam out of the prism and entering the observation image eyeball, wherein the at least one reflecting surface gives power to the light beam 4. The eccentric prism according to any one of the items 1 to 3, wherein the eccentric prism has a curved surface shape, and the curved surface shape is constituted by a rotationally asymmetric surface shape that corrects aberrations generated by eccentricity. The image display device as described in the above.

[0072]

[9] When the power of the diffractive optical element in the relay optical system is Pdoe, the following condition is satisfied: 0.0001 <Pdoe <0.0200 [1 / mm] (1) 9. The image display device according to any one of items 1 to 8.

[0073]

As is apparent from the above description, according to the present invention, a diffractive optical element is provided on a relay optical system portion of an image display device comprising a relay optical system for forming an intermediate image of an image display device and an eyepiece optical system. Is used, a relay optical system can be configured with a small number of lenses despite having excellent color correction ability, and a compact, clear and high-resolution image display device can be obtained.

[Brief description of the drawings]

FIG. 1 is an optical path diagram of an image display device according to a first embodiment of the present invention.

FIG. 2 is an optical path diagram of an image display device according to a second embodiment of the present invention.

FIG. 3 is an optical path diagram of an image display device according to a third embodiment of the present invention.

FIG. 4 is a lateral aberration diagram of the first embodiment.

FIG. 5 is a diagram showing a modification of the eyepiece optical system of the image display device of the present invention.

FIG. 6 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 7 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 8 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 9 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 10 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 11 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 12 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 13 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 14 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 15 is a diagram showing another modification of the eyepiece optical system of the image display device of the present invention.

FIG. 16 is a diagram showing a state in which the head-mounted image display device for single-eye mounting according to the present invention is mounted on the observer's head.

FIG. 17 is a diagram illustrating a state in which the head-mounted binocular image display device according to the present invention is mounted on the observer's head.

FIG. 18 is a sectional view of FIGS. 16 and 17;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... On-axis principal ray 2 ... Exit pupil 3 ... Image plane (image display element) 4 ... Lens system 5 ... Semi-transmissive mirror 5 '... Semi-transmissive reflective surface 6 ... Concave mirror 7 ... Intermediate image 8 ... DOE (Diffractive optical element) Reference Signs List 10 LCD 11 Illumination light source 12 Cover member 13 Liquid crystal shutter 32 First surface 33 Second surface 34 Third surface 35 Fourth surface 36 Image surface 41 Display body 42 Front frame 43 ... Rear frame 44 ... Parietal frame 45 ... Rear plate 46 ... Rear cover 49 ... Speaker 50 ... Video playback device 50a ... Volume adjustment unit 51 ... Cable P ... Eccentric prism

Claims (3)

[Claims] 1. An image display device comprising: an image display element; and an observation optical system having an overall positive refractive power and forming an exit pupil for observing an observation image displayed on the image display element, An observation optical system has a relay optical system that forms the observation image as an intermediate image, and an eyepiece optical system that forms an exit pupil to guide the intermediate image to an observer, wherein the relay optical system is axially symmetric. An image display device comprising: a lens group; and a diffractive optical element arranged in the lens group. 2. The image display device according to claim 1, wherein the intermediate image is formed between the relay optical system and the eyepiece optical system. 3. The eyepiece optical system comprises a semi-transmissive mirror and a concave mirror, and a display light beam from the relay optical system passes through the semi-transmissive mirror, is reflected by the concave mirror, and then reflected by the semi-transmissive mirror. The image display device according to claim 1, wherein the image display device is configured to be arranged so as to be reflected and reach an observation image eyeball.