JP2000241751A - Video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device which is capable of providing good-quality videos in spite of small-sized and lightweight constitution suitable for a use form by arranging a translucent reflection element for separating illumination light and reflected light between a liquid crystal display and a reflection surface having power. SOLUTION: This video display device 1 has a liquid crystal display 11 of a reflection type for displaying videos, a light source section 12 for supplying the illumination light to be imparted to the liquid crystal display 11, the translucent reflection element (PBS mirror) 14 and observation optical systems (prism faces) 17 to 19. The PBS mirror 14 introduces the illumination light form the light source section 12 to the liquid crystal display 11 and introduces the reflected light of the liquid crystal display 11 to a direction different from a direction heading to the light source section 12. The prism faces 17 to 19 include at least one reflection surface having optical power and introduce the reflected light of the liquid crystal display 11 introduced by the PBS mirror 14 to the observer's eyes, thereby providing the observer with the virtual image of the video displayed on the liquid crystal display 11.

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 which is used by being arranged in front of an observer's eyes, and more particularly to an image display device which displays an image by a reflection type liquid crystal display.

[0002]

2. Description of the Related Art There is an image display device which is mounted on a head or held by a hand and used in front of an observer.
It is often used as a means for providing virtual reality with a sense of realism, or as a finder incorporated in a shooting device such as a video camera. Such a video display device,
The light of the displayed image is guided to the eyes of the observer via the observation optical system, and the image is provided to the observer as an enlarged virtual image.

[0003] It is desirable that an image provided to an observer is bright and has high definition, and particularly when providing virtual reality, a wide field of view is desired. On the other hand, it is strongly demanded that the device be small and lightweight due to the usage form of being attached to the head or holding by hand. A liquid crystal display is one of the display elements that can satisfy such requirements, and most of the video display devices used in front of the eyes adopt the liquid crystal display.

A liquid crystal display has a large number of two-dimensionally arranged pixels, and converts polarization of given illumination light in each pixel to bring about a change in intensity distribution of polarized light in the converted light. Modulates light. The polarization conversion of each pixel is individually controlled according to the video signal, and the degree of polarization conversion differs for each pixel. As a result, there is a difference in the amount of polarized light after conversion between pixels, and an image or video having a difference in luminance is provided by guiding the polarized light having the difference in amount to the eyes.

[0005] Liquid crystal displays are roughly classified into a transmission type in which illumination light is applied from the side opposite to the observation side and a reflection type in which illumination light is applied from the same side as the observation side. Reflective LCDs have various advantages over transmissive LCDs. Circuit parts such as TFTs that control each pixel of the liquid crystal display need a certain size, but in a transmissive liquid crystal display, these circuit parts cause the aperture of each pixel to be small. In the reflection type liquid crystal display, since the circuit portion can be disposed on the surface opposite to the observation side, a decrease in the aperture ratio due to the circuit portion is reduced and a bright image can be obtained.

The difference in the aperture ratio between the transmissive liquid crystal display and the reflective liquid crystal display becomes more remarkable as the size of the pixel becomes smaller. Therefore, when the same number of pixels and the same brightness are used, the reflection type liquid crystal display can be formed smaller. On the other hand, when the size of the display is the same, the reflection type liquid crystal display can have a larger number of pixels and can provide an image with higher definition.

In a reflection type liquid crystal display, it is possible in principle to make a liquid crystal layer for performing polarization conversion thinner than a transmission type liquid crystal display. Therefore, the reflection type liquid crystal display can switch the display more quickly.

The use of a reflection type liquid crystal display having such features greatly contributes to achieving a bright and high-definition image required for a video display device used in front of the eyes. In addition, since the size of the display device is reduced, the observation optical system can be reduced, and the device can be easily reduced in size.

The observation optical system that guides light from the display element to the eyes of the observer can be provided to the observer without deteriorating the quality of the displayed image, and is small and lightweight suitable for use. It is desirable that From this viewpoint, it has been proposed to provide a reflection surface having optical power in the observation optical system.

[0010] Unlike a refraction surface in which the refraction angle depends on the wavelength, the reflection surface has no wavelength dependence in the reflection angle and does not generate chromatic aberration. Also, while having a positive power to converge light, the Petzval value becomes negative, which contributes to the improvement of the overall Petzval sum, and provides an image excellent in flatness with almost no image field distortion even in the periphery. it can. In addition, since the optical paths of the incident light and the reflected light partially overlap, the optical path length can be easily increased.
Therefore, in an observation optical system having a reflecting surface having optical power, it is possible to increase the magnification and increase the field of view while avoiding a decrease in image quality, while being small in size.

A head-mounted display device (HMD) provided with a reflecting surface having such features in an observation optical system is disclosed in
-90270, 8-313829, 7-17500
No. 9.

[0012]

As described above, it is necessary to apply illumination light to the reflection type liquid crystal display from the observation side, and the optical paths of the illumination light and the reflected light overlap. Therefore, it is necessary to separate the unmodulated illumination light from the light source from the reflected light from the modulated liquid crystal display. However, in the HMDs of the above publications, illumination light and modulated light cannot be separated, and a reflection type liquid crystal display device cannot be used as a display element. For this reason, a transmissive liquid crystal display device having somewhat inferior performance is employed, and there is a limit in improving the quality of an image provided to an observer even though an observation optical system having a reflection surface is used.

On the other hand, an HMD using a reflection type liquid crystal display has been proposed. The configuration is shown in FIG. In this HMD, a reflection type liquid crystal display 91 and a light source unit 92 for illuminating the same are provided.
A polarization separation (PBS) mirror 93 that transmits one of the two polarization components whose polarization planes are perpendicular to each other and reflects the other is disposed between the two, and the liquid crystal display 9 reflected by the PBS mirror 93.
An eyepiece lens 94 is arranged as an observation optical system on the optical path of the reflected light from 1. The reflected light from the liquid crystal display 91 is P
The illumination light from the light source unit 92 is separated by the BS mirror 93 and guided to the pupil EP of the observer by the eyepiece 94.

In this HMD, high quality images can be displayed by the reflection type liquid crystal display 91. However, since the observation optical system is constituted only by the refraction surface, if the magnification is increased, the quality of the image provided to the observer is easily deteriorated, and it is difficult to widen the visual field. The eyepiece 94 constituting the observation optical system is designed so as to make the best use of the characteristics of the reflection type liquid crystal display 91 having excellent definition. However, there is a limit to this, especially under conditions where the size is limited. Then, it is difficult to design an eyepiece that can make full use of the features of the reflective liquid crystal display.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to realize a video display device which can provide a higher quality video while having a small and lightweight configuration suitable for a use form. I do.

[0016]

In order to achieve the above object, according to the present invention, an image is displayed on an image display device which is arranged in front of the observer and provides a virtual image of the displayed image to the observer. A reflection type liquid crystal display, a light source unit that supplies illumination light to be given to the liquid crystal display, and a direction in which the illumination light from the light source unit is guided to the liquid crystal display and the reflected light of the liquid crystal display is directed toward the light source unit A semi-transmissive reflective element for guiding in different directions,
Includes at least one reflective surface having optical power, guides reflected light of a liquid crystal display guided by a semi-transmissive reflective element to an observer's eyes, and observes a virtual image of an image displayed on the liquid crystal display And an observation optical system provided to the user.

This image display device displays an image using a reflection type liquid crystal display having many of the above-mentioned features, and can display a high-quality image. In addition, the observation optical system includes a reflection surface having optical power and can be provided to an observer without deteriorating the quality of a displayed image. Since the illuminating light and the reflected light are separated by the semi-transmissive reflecting element, the illuminating light is not guided to the observer's eyes, and no ghost occurs. Therefore, it is possible to provide a bright, high-definition, and clear image. In addition, since the translucent reflective element that separates illumination light and reflected light is placed between the liquid crystal display and the reflective surface having power, the principal point of the observation optical system may be far away from the observer's eyes. Is prevented, and the eye point can be easily secured.

The reflecting surface included in the observation optical system is preferably a concave reflecting surface having a positive power. This reflective surface magnifies the image displayed on the liquid crystal display and guides it to the eyes. Even if the magnification is increased, no image surface distortion occurs. Therefore, it is possible to easily increase the viewing angle of the image without deteriorating the quality of the image to be provided.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the video display device of the present invention will be described with reference to the drawings. In FIG.
1 shows a configuration of an optical system of a video display device 1 according to a first embodiment. The image display device 1 includes a reflective liquid crystal display 11,
The light source unit 12 includes a PBS mirror 14 and a prism 16.

The light source unit 12 includes a plurality of lamps 12a and a light guide plate 12b arranged in a straight line.
To provide illumination light for illuminating the. The lamp 12a emits light whose polarization plane is disordered. The light guide plate 12b is formed by arranging a large number of columnar minute triangular prisms in a plane, receives linear light from the lamp 12a from the side, and reflects the light by each prism to form a display surface of the liquid crystal display 11. A light beam having a diameter that can illuminate the whole is used.

The PBS mirror 14 reflects the light from the light guide plate 12b and guides the light to the liquid crystal display 11, and transmits the light representing the image contained in the reflected light from the liquid crystal display 11 and guides the light to the prism 16. The PBS mirror 14 is set to transmit a polarized light component incident as P-polarized light and reflect light incident as S-polarized light. Of the light from the light guide plate 12b, only the polarization component that becomes S-polarized light with respect to the PBS mirror 14 is reflected and guided to the liquid crystal display 11, and
The light that becomes P-polarized light passes through the BS mirror 14 and is discarded.

The liquid crystal display 11 reflects the applied illumination light and modulates the illumination light according to the displayed image to rotate a part of the reflected light by 90 °. In the image display device 1, the driving of the liquid crystal display 11 is controlled so that the polarization component whose polarization plane is rotated by 90 ° becomes light representing an image. Therefore, light representing an image contained in the reflected light of the liquid crystal display 11 becomes P-polarized light with respect to the PBS mirror 14 and transmits through the PBS mirror 14. The light included in the reflected light of the liquid crystal display 11 whose polarization plane has not rotated remains S-polarized light with respect to the PBS mirror 14, is reflected and discarded.

The prism 16 is made of polymethyl methacrylate (PMMA). The prism 16 guides reflected light from the liquid crystal display 11 provided via the PBS mirror 14 to the pupil EP of the observer, and has surfaces 17, 18, and 19 as surfaces involved in this. The surface 17 is a flat surface and is set so as to transmit all the light from the PBS mirror 14. The surface 18 is also a flat surface, but the light transmitted through the surface 17 is set so as to enter beyond the critical angle, and the light transmitted through the surface 17 is totally reflected by the surface 18.

The surface 19 is a convex surface of an anamorphic aspheric surface which is non-rotationally symmetric with respect to the optical axis. The surface 19 is provided with a total reflection film, and the surface 19 functions as a concave mirror having a positive power with respect to light from the surface 18 side.
The surface 19 is set so as to reflect the light totally reflected by the surface 18 and re-enter the surface 18 at an incident angle smaller than the critical angle. Therefore, light incident on the surface 19 is reflected at a reflection angle different from the incident angle, passes through the surface 18, and
The light enters the pupil EP of the observer while converging.

The observer can touch the liquid crystal display 11 through the surface 19.
Of the displayed image is observed by observing the display surface of. Three faces 17, 18 of prism 16
And 19 form an observation optical system for guiding the reflected light of the liquid crystal display 11 separated from the illumination light to the pupil EP and providing a virtual image of the displayed image to the observer. The surface 18 is a selective reflection surface that transmits or reflects light according to the incident direction.

The image display apparatus 1 having the above-described configuration can be provided as an HMD or a hand-held binoculars type apparatus provided with two sets, or incorporated in a photographing device such as a video camera for converting a photographed image into an electric signal. It can also be used as a finder. As described above, the image display apparatus 1 employs the observation optical system of the non-coaxial optical system, and thereby, the apparatus is small in the direction of the line of sight of the observer, that is, a thin apparatus.

FIG. 2 shows the configuration of the optical system of the video display device 2 according to the second embodiment. The image display device 2 includes a reflective liquid crystal display 21, a light source unit 22, a condenser lens 23,
And a prism 26. A light source unit 22 that emits illumination light to be supplied to the liquid crystal display 21;
The reflector 22b reflects the light emitted from the lamp 22a. The condenser lens 23 has two convex surfaces 24 and 25
And guides the illumination light from the light source unit 22 to the liquid crystal display 21 as substantially parallel light.

The prism 26 is made of PMMA, and has three surfaces 27, 28 and 29 involved in the propagation of light.
The surface 27 is a concave surface of an anamorphic aspheric surface, and is a PBS mirror that transmits P-polarized light and reflects S-polarized light. Of the light having a disordered polarization plane from the light source unit 22, PB
The polarization component that becomes P-polarized light with respect to the S mirror 27 is transmitted and discarded, and the polarization component that becomes S-polarized light with respect to the PBS mirror 27 is reflected and guided to the condenser lens 23. Although the light from the light source unit 22 is a divergent light beam, the light is made closer to a parallel light beam by the PBS mirror 27 having a concave surface, is converted into a substantially parallel light beam by the condenser lens, and enters the liquid crystal display 21.

In the image display device 2, the liquid crystal display 2
1 is controlled such that light whose polarization plane is rotated by 90 ° becomes light representing an image. The reflected light from the liquid crystal display 21 passes through the condenser lens 23 and enters the PBS mirror 27 again. Of these, light representing an image is P-polarized light with respect to the PBS mirror 27 and passes through the PBS mirror 27 toward the surface 28. The light whose polarization plane has not rotated even after the modulation remains S-polarized light with respect to the PBS mirror 27, is reflected and discarded.

Surface 28 is also an anamorphic aspheric concave surface. The surface 28 is set so that the reflected light of the liquid crystal display 21 transmitted through the PBS mirror 27 is incident beyond the critical angle, and the light transmitted through the PBS mirror 27 is totally reflected by the surface 28.

Surface 29 is an anamorphic aspheric convex surface. On the surface 29, a reflective film of total reflection is formed,
The surface 29 acts as a concave mirror having a positive power with respect to the light from the surface 28 side. The surface 29 reflects the light totally reflected by the surface 28 so that the surface 28 has an incident angle smaller than the critical angle.
Is set to be incident again. The light incident on the surface 29 is reflected at a reflection angle different from the incident angle, and
And enters the pupil EP of the observer while converging.

In the image display device 2, the surface (PBS mirror) 27 provided on the prism 26 serves as a semi-transmissive reflective element for separating illumination light and light reflected from the liquid crystal display 21. Also, the three surfaces 27, 28 and 29 of the prism 26
The reflected light after the separation is guided to the pupil EP, and an observation optical system that provides a virtual image of the displayed image to the observer is configured. The surface 27 also serves as a semi-transmissive reflective element for separation and a part of the observation optical system.

In the image display device 2, the condenser lens 2
3, the light source unit 22 is disposed at a position substantially conjugate with the pupil EP. For this reason, the video display device 1 of the first embodiment
The light guide plate 12b, which was necessary for the above, is not required, and the light source section 22 only needs to include a lamp 22a which is a point light source and a reflector 22b.

Tables 1 and 2 show specific set values of the optical system of the video display device 2.

[0035]

[Table 1]

[0036]

[Table 2]

In Table 1, parameters relating to the anamorphic aspherical surface are defined by the sag in the Z-axis direction defined by Equation 1 when the origin is the intersection of each surface and its optical axis and the optical axis is the Z-axis. Z is defined (unit: mm). RDX
Is the radius of curvature in the X-axis direction.

Z = (CUX · X ² + CUY · Y ² ) / [1+ ｛1− (1 + KX) · CUX ² · X ² − (1 + KY) · CUY ² · Y ² ｝ ^1/2 ] + AR · ｛(1 −AP) · X ² + (1 + AP) · Y ² ｝ ² + BR · ｛(1-BP) · X ² + (1 + BP) · Y ² ｝ ³ + CR · ｛(1-CP) · X ² + (1 + CP) · Y ^{2 4} + DR · ｛(1-DP) · X ² + (1 + DP) · Y ² ｝ ⁵ ... Here, CUX and CUY are the reciprocals of the radii of curvature in the X-axis direction and the Y-axis direction. is there.

Table 2 shows the relative positional relationship between the surfaces. Here, the center of the pupil EP is the origin, and the axis perpendicular to the pupil plane (first plane) is the Z axis. XS
C, YSC, ZSC are X, the intersection of each surface and its optical axis.
Represents Y, Z coordinates (unit: mm), ASC, BSC, CS
C represents a rotation angle (unit ゜) of each plane from the pupil plane with respect to the X axis, the Y axis, and the Z axis.

FIG. 3 shows the configuration of the optical system of the video display device 3 according to the third embodiment. The image display device 3 includes a reflective liquid crystal display 31, a light source unit 32, a condenser lens 33,
A prism 36 and a prism 41 are provided. The light source unit 32 includes a lamp 32a that emits illumination light to be supplied to the liquid crystal display 31, a reflector 32b that reflects the light emitted by the lamp 32a, and a stop 32c that regulates a light beam diameter.
It is arranged close to the prism 36. The condenser lens 33 has two convex surfaces 34 and 35 and guides the illumination light from the light source 32 to the liquid crystal display 31 as substantially parallel light.

The prism 36 is formed by joining two prisms 36a and 36b made of PMMA. Prisms 36a, 3
6b is a curved surface, transmits P-polarized light, and
It is a PBS mirror that reflects polarized light. Prism 3
6 has three surfaces 3 involved in light propagation in addition to the surface 37.
8, 39, and 40. Surface 38 is a flat surface and surface 40 is a convex surface. The surface 39 is a convex surface of an anamorphic aspherical surface, and has a total reflection reflective film. Therefore, the surface 39 acts as a concave mirror having a positive power with respect to the light from the surface 38 side.

The prism 41 is also made of PMMA. The prism 41 has a flat surface 42 and a convex surface 43, and is arranged with the surface 42 facing a part of the surface 38 of the prism 36b. Surface 38 and surface 42 are parallel. A minute gap of several tens μm or less is formed between the surfaces 38 and 42, and the surfaces 38 and 42 form a TIR (total internal reflection) surface.

The illumination light from the light source 32 is transmitted to the PBS mirror 3
7, the polarized light component that becomes the P-polarized light with respect to the PBS mirror 37 is transmitted and discarded, and the polarized light component that becomes the S-polarized light with respect to the PBS mirror 37 is reflected and passes through the surface 40 to the condenser lens 33. Be guided. The light from the light source 32 is a divergent light beam, but the concave PBS mirror 37
The light is made closer to a parallel light beam by the convex surface 40 and is made into a substantially parallel light beam by the condenser lens 33 to enter the liquid crystal display 31.

In the image display device 3, the liquid crystal display 3
1 is controlled such that light whose polarization plane is rotated by 90 ° becomes light representing an image. The reflected light from the liquid crystal display 31 passes through the condenser lens 33 and the surface 40 and enters the PBS mirror 37 again. Of these, the light that represents the image is PBS
The light is P-polarized light with respect to the mirror 37, and passes through the PBS mirror 37 toward the surface 38. The light whose polarization plane has not rotated even after the modulation remains S-polarized with respect to the PBS mirror 37, is reflected and discarded.

The surface 38 is set so that the reflected light of the liquid crystal display 31 transmitted through the PBS mirror 37 is incident beyond the critical angle, and the light transmitted through the PBS mirror 37 is
Is totally reflected. As described above, the prism 41 faces a part of the surface 38, but since air is interposed between the surface 38 and the surface 42, the light from the PBS mirror 37 is
Is totally reflected at any part of the body.

The surface 39 is set so that the light totally reflected by the surface 38 is reflected and re-enters the surface 38 at an incident angle smaller than the critical angle. Light incident on the surface 39 is reflected at a reflection angle different from the incident angle, passes through the surface 38 while converging, and further passes through the surface 42. This light passes through the surface 43 acting as a convex lens, and enters the pupil EP of the observer while converging further.

In the image display device 3, the surface (PBS mirror) 37 provided on the prism 36 serves as a semi-transmissive reflective element for separating illumination light and light reflected from the liquid crystal display 31. Further, the two surfaces 38 and 39 of the prism 36 and the surface 43 of the prism 41 form an observation optical system that guides the reflected light after separation to the pupil EP and provides a virtual image of the displayed image to the observer. The light source unit 32 is located at a position substantially conjugate with the pupil EP.

Tables 3 and 4 show specific set values of the optical system of the image display device 3.

[0049]

[Table 3]

[0050]

[Table 4]

The parameters relating to the anamorphic aspherical surface in Table 3 define the above-described equation (1). Table 4
The parameters in the table are as described above. In Table 3, the parameters relating to the rotationally symmetric aspherical surface define the sag Z in the Z-axis direction defined by Expression 2 when the intersection point between each surface and its optical axis is the origin and the optical axis is the Z-axis. (Unit: mm).

Z = c · h ² / [1+ ｛1− (1 + K) · c ² · h ² ｝ ^1/2 ] + A · h ⁴ + B · h ⁶ + Ch · ⁸ + D · h ¹⁰ Equation 2 Here, h = (X ² + Y ² ) ^1/2 and c is the reciprocal of the radius of curvature.

The image display device 3 has the surface 42 and the surface 38 constitutes a TIR surface, so that all the light transmitted through the surface 38 can go straight. Therefore, in order for the light totally reflected by the surface 38 to re-enter the surface 38 at less than the critical angle,
Can be reduced. As a result, the amount of eccentricity of the concave mirror 39 is reduced, and the occurrence of eccentric aberration is suppressed.

In addition, by providing the convex lens surface 43 in addition to the concave mirror 39, the power for converging the reflected light from the liquid crystal display 31 is dispersed between them. Therefore, the curvature of the concave mirror surface 39 can be reduced, and the occurrence of decentering aberration can be further suppressed.

The surface 43 having positive power is the pupil EP
Because it is located near, it is easy to secure an eye point.

FIG. 4 shows the configuration of the optical system of the video display device 4 according to the fourth embodiment. The image display device 4 includes a reflective liquid crystal display 51, a light source 52, a condenser lens 53,
A PBS mirror 54 and a pancake type optical element 56 are provided. The PBS mirror 54 transmits P-polarized light and
The liquid crystal display 51 is set to reflect polarized light.
Is controlled so that light whose polarization plane is rotated by 90 ° becomes light representing an image.

The component of the illumination light from the light source 52 that becomes S-polarized light with respect to the PBS mirror 54 is reflected and guided to the condenser lens 53. The condenser lens 53 is
This light is incident on the liquid crystal display 51 as a substantially parallel light beam. The light modulated and reflected by the liquid crystal display 51 is
The light passes through the condenser lens 53 and enters the PBS mirror 54. Of these, only the polarization component representing an image passes through the PBS mirror 54 and enters the optical element 56.

Surface 5 of optical element 56 on PBS mirror 54 side
Reference numeral 7 denotes a convex surface, which is a half mirror. The other surface 58 of the optical element 56 is concave, has a cholesteric liquid crystal layer, and serves as a selective reflection surface. Optical element 5
Half of the light incident on 6 passes through surface 57 and enters surface 58 while converging slightly. This light is reflected by the surface 58 and re-enters the surface 57, and half is reflected. The light reflected by the surface 57 passes through the surface 58 while being further converged, and enters the pupil EP of the observer.

In the image display device 4, the observation optical system is composed of two surfaces 57 and 58, of which the surface 57 is a concave mirror having a positive power. Although having such an extremely simple configuration, the image display device 4 can provide a clear image with high brightness, high definition, and a wide field of view to the observer.

[0060]

According to the image display device of the present invention, a bright and high-definition image is displayed by a reflection type liquid crystal display, and an image displayed by an observation optical system including a reflection surface having optical power. The reflected light from the liquid crystal display can be guided to the observer's eyes while maintaining the quality of the image. Also, the illumination light and the reflected light are separated by a semi-transmissive reflective element,
The occurrence of ghost due to the mixing of the illumination light into the reflected light is also prevented. Therefore, an excellent quality image can be provided to the observer.

In a configuration in which the reflecting surface included in the observation optical system is a concave reflecting surface having a positive power, the image plane is not distorted even if the magnification of the reflecting surface is increased, so that the quality is excellent and the visual field is excellent. It is possible to provide a wide image.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical system of a video display device according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration of an optical system of a video display device according to a second embodiment.

FIG. 3 is a diagram illustrating a configuration of an optical system of a video display device according to a third embodiment.

FIG. 4 is a diagram illustrating a configuration of an optical system of a video display device according to a fourth embodiment.

FIG. 5 is a diagram showing a configuration of an optical system of a conventional video display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image display apparatus 11 Reflective liquid crystal display 12 Light source part 14 PBS mirror (semi-transmissive reflective element) 16 Prism 17 Prism surface (observation optical system) 18 Prism surface (observation optical system) 19 Prism surface (concave mirror, observation optics) 2) Image display device 21 Reflective liquid crystal display 22 Light source unit 23 Condenser lens 24 Condenser lens surface 25 Condenser lens surface 26 Prism 27 Prism surface (PBS mirror, semi-transmissive reflective element, observation optical system) 28 Prism surface (Observation) Optical system) 29 Prism surface (concave mirror, observation optical system) 3 Image display device 31 Reflective liquid crystal display 32 Light source unit 33 Condenser lens 34 Condenser lens surface 35 Condenser lens surface 36 Prism 37 Prism junction surface (PBS mirror, semi-transmission) Reflective element) 38 Prism surface (observation light) System) 39 prism surface (concave mirror, observation optical system) 40 prism surface 41 prism 42 prism surface 43 prism surface (observation optical system) 4 image display device 51 reflective liquid crystal display 52 light source unit 53 condenser lens 54 PBS mirror (half) Transmissive reflective element) 56 Pancake optical element 57 Optical element surface (concave mirror, observation optical system) 58 Optical element surface (observation optical system) EP Pupil

Claims (2)

[Claims] 1. An image display device arranged in front of an observer's eyes to provide a virtual image of a displayed image to an observer, a reflective liquid crystal display for displaying an image, and illumination light applied to the liquid crystal display And a semi-transmissive reflective element that guides illumination light from the light source unit to the liquid crystal display and guides reflected light from the liquid crystal display in a direction different from the direction toward the light source unit. An image displayed on the liquid crystal display, comprising at least one reflection surface having optical power, and guiding reflected light of the liquid crystal display guided by the semi-transmissive reflection element to an observer's eye; And an observation optical system for providing a virtual image of the image to an observer. 2. The image display device according to claim 1, wherein the reflection surface is a concave reflection surface having a positive power.