JP2000180783A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bright image display device which is made in small in size and light in weight, while keeping high optical performance by using an eccentric prism performing internal reflection and a reflection type image display element, such as a reflection type LCD(liquid crystal display element) and a DMD(digital micro device). SOLUTION: This device is provided with a light source 8, a reflection type image display element 7 and an ocular optical system for guiding a display image to an eyeball position 1. In this case, the ocular optical system is provided with a prism member 10, and the member 10 consists of a 4th surface 6 making light incident from the element 7, a 3rd surface 5 for reflecting the incident light from the 4th surface 6, a 1st surface 3 for totally reflecting the reflected light by the 3rd surface 5, and a 2nd surface 4 for reflecting the reflected light by the 1st surface 3, giving optical power to luminous flux, compensating eccentric aberration and having rotationally asymmetric curved surface shape, and is constituted so that the reflected light by the 2nd surface 4 is emitted from the 1st surface 3 to the outside of the prism. The light source 8 is arranged to illuminate the element 7 with an illuminating light through the 3rd surface 5.

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.

Under such circumstances, in Japanese Patent Application Laid-Open Nos. Hei 7-333551 and Hei 8-234137, eyepiece optics for guiding a display image of an image display element comprising a liquid crystal display element (hereinafter, referred to as LCD) to an observer's eyeball. The system is constituted by a decentered optical system composed of a medium having a refractive index larger than 1 and surrounded by three optical surfaces, and a light beam from the liquid crystal display element is made to enter the decentered optical system from the third surface. Inside, the light is totally reflected by the first surface, then internally reflected by the second surface of the concave mirror, and is then emitted out of the decentered optical system via the first surface to form an intermediate image on the display image of the image display device. There has been proposed one that leads the eyeball to the observer's eyeball without any problem.

In this case, the decentered optical system has three optical surfaces, and the number of reflections inside the decentered 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. By the way, JP-A-7-33
No. 3551 and JP-A-8-234137,
The LCD (Liquid Crystal Display) constituting the image display device is planned to be of a transmissive type, but a device using a reflective LCD as the image display device of the face-mounted image display device is also proposed in JP-A-7-72446. Have been. FIG. 15 is a view showing the optical system of the image display device, and the lamp light source 5
5 is collimated by a collimating optical system 56, and a part of the light (S-polarized light) is
7 illuminates the reflective LCD 58 from the front. The display image reflected and modulated by the reflective LCD 58 is projected onto a screen 52 by a projection optical system 59, and the projected image is magnified and observed by an observer through an eyepiece optical system 53.

As a reflection type image display device, an image display device called a DMD (digital micro device) has been proposed in addition to the reflection type LCD. This has a configuration as shown in FIG. That is, FIG.
As shown in FIG. 6A, a plane is shown, and as shown in FIG. 16B, the configuration of each element is such that micromirrors 60 corresponding to each pixel are two-dimensionally arranged. By tilting the mirror 60 ′, light incident on the mirror 60 ′ from a certain direction is reflected in a direction different from that of the mirror that is not tilted, so that a two-dimensional image is displayed. A hinge 6 is provided by a support post 62 erected on the substrate 61 at a pair of diagonal corners.
3 and the substrate 6 on the rear side of the mirror 60
By applying a voltage to one of the pair of electrodes 64 provided on the mirror 1, the mirror 60 can be rotated about the diagonal line between the hinges 63 by electrostatic force (IEEE S).
vector Vol. 30, no. 11, pp. 2
7-31).

[0006]

When an eccentric optical system is used as an optical system of an image display device, the entire device can be configured to be small and lightweight while maintaining high optical performance (angle of view, resolution, etc.), and a bright image display can be achieved. There is an advantage that the device becomes possible. However, as the image display element used with the decentered optical system, only a transmission type LCD has been conventionally planned. Therefore, Japanese Patent Application Laid-Open Nos. Hei 7-333551 and Hei 8-2341 are disclosed.
Each of the decentered optical systems shown in No. 37 was configured only as a telecentric optical system having an entrance pupil at infinity.

A transmission type LCD as an image display device
However, since the aperture ratio of the pixels is lower than that of the reflection type LCD, and the black matrix portion between the pixels becomes conspicuous, it is necessary to use a low-pass filter or the like to make it inconspicuous. On the other hand, the reflection type LCD can increase the aperture ratio of the pixel, and the above problem is small. However, as shown in JP-A-7-72446, an optical system without eccentricity is used. In the case of magnifying observation using, it is necessary to illuminate through an optical element such as a light beam splitter, especially when used for a head or face-mounted image display device, contrary to the demand for miniaturization and weight reduction However, there is a problem that a display image becomes dark.

The present invention has been made in view of such a situation in the prior art, and an object of the present invention is to provide a high optical system using an eccentric prism that internally reflects light and a reflective image display device such as a reflective LCD or DMD. An object of the present invention is to provide a small, lightweight, and bright image display device having performance.

[0009]

According to the present invention, there is provided an image display apparatus, comprising: an illumination light source; an image display element; and an eyepiece optical system for guiding an image formed by the image display element to an observer's eyeball position. Wherein the eyepiece optical system has a prism member sandwiching a medium having a refractive index greater than 1 and the prism member transmits image light emitted from the image display element into the prism. A fourth surface for incidence, and a third surface for reflecting a light beam incident from the fourth surface.
A first surface for totally reflecting the light beam reflected by the third surface
And a second surface formed into a rotationally asymmetric curved surface shape that reflects the light beam reflected by the first surface, applies optical power to the light beam, and corrects eccentric aberration. The reflected light is emitted from the first surface to the outside of the prism; the image display element is configured by a reflective image display element that displays an image by reflected light; and the illumination light source is the prism member. The third of
The image display device is characterized by being arranged so that illumination light can be illuminated on the image display element via a surface.

According to another aspect of the present invention, there is provided an image display apparatus comprising: an illumination light source; an image display element; and an eyepiece optical system for guiding an image formed by the image display element to an observer's eyeball position. The eyepiece optical system has a prism member sandwiching a medium having a refractive index larger than 1, the prism member has a fourth surface that causes image light emitted from the image display element to enter the prism, and A third surface for reflecting the light beam incident from the fourth surface, a first surface for totally reflecting the light beam reflected on the third surface, and an optical device for reflecting the light beam reflected on the first surface and optically converting the light beam; A second surface formed into a rotationally asymmetric curved surface shape that gives power and corrects eccentric aberration, and is configured to emit a light beam reflected by the second surface out of the prism from the first surface; The image display element But is constituted by a reflection type image display device for displaying an image by reflected light, it said third surface of said prism member is characterized in that it is formed by the half-mirror surface which is a half mirror coating.

Still another image display apparatus according to the present invention is an image display apparatus having an illumination light source, an image display element, and an eyepiece optical system for guiding an image formed by the image display element to an observer's eyeball position. The eyepiece optical system comprises:
A prism member sandwiching a medium having a refractive index greater than 1; wherein the prism member has a fourth surface on which image light emitted from the image display element enters the prism;
A third surface for reflecting the light beam incident from the surface, a first surface for totally reflecting the light beam reflected on the third surface, and reflecting the light beam reflected on the first surface and applying optical power to the light beam. And a second surface formed in a rotationally asymmetric curved surface shape for giving the eccentric aberration and correcting the eccentric aberration, wherein the light beam reflected by the second surface is emitted from the first surface to the outside of the prism, and the image is formed. The display element is constituted by a reflection type image display element for displaying an image by reflected light, wherein the third surface of the prism member is formed by a total reflection surface, and a light beam incident from the fourth surface is subjected to total reflection. It is characterized by being configured to reflect light.

Hereinafter, the reason and operation of the above-described configuration in the present invention will be described. In the present invention, in an image display device having an illumination light source, an image display element, and an eyepiece optical system that guides an image formed by the image display element to an observer's eyeball position, the eyepiece optical system has a refractive index. 1
A prism member sandwiching a larger medium, the prism member reflecting a fourth surface on which image light emitted from the image display element enters the prism, and reflecting a light beam incident from the fourth surface. A third surface, a first surface that totally reflects the light beam reflected by the third surface, and a rotation that reflects the light beam reflected by the first surface, applies optical power to the light beam, and corrects eccentric aberration. A second surface formed into an asymmetric curved surface shape, and configured to emit the light beam reflected by the second surface from the first surface to outside the prism;
Since the image display element is constituted by a reflection type image display element for displaying an image by reflected light, the reflection type L
Using a CD or the like and a prism member having three reflecting surfaces, a small, lightweight, and bright image display device having high optical performance can be achieved.

As described above, the prism member (eccentric optical system) constituting the eyepiece optical system has four surfaces, and the space formed by the four surfaces has a refractive index of one.
It is filled with a larger medium and faces the first surface, which is a refraction surface and an internal reflection surface, in the order in which light rays pass according to the reverse ray tracing from the observer's eyeball to the image display element, and faces the first surface. A second surface that is a reflecting surface that is eccentric or inclined with respect to the axis, a third surface that is a reflecting surface adjacent to the second surface, and a refracting surface closest to the image display element; The number of reflections from the observer's eyeball to the image display element is set to three, and the light beam emitted from the image display element is set to 3 in the eyepiece optical system.
By reflecting the light twice, the effect of folding the light rays is enormous, the thickness of the eyepiece optical system is minimized, the size and weight are reduced, and the wide exit pupil diameter and wide observation angle of view provide a clear observation image. Can be provided to the observer.

Since the eyepiece optical system is composed of four surfaces, transmission and reflection are performed on the same surface only on the first surface, and other reflection and refraction operations are performed on independent surfaces. Can correct aberrations with each other, which is very advantageous in correcting aberrations.

On the other hand, even when the image display element is arranged above or to the side of the observer, the image display element is positioned obliquely in front of the adjacent fourth surface, so that the entire apparatus is small in size for observation. Is arranged so as not to interfere with the user. In addition, the surface that reflects toward the observer on the opposite side of the observer face is 2
Therefore, it is possible to take the direction of the optical path after each reflection in a preferred direction without depending on the curvature of each surface. Therefore, it is possible to configure the optical system compactly and set the image display element in a favorable direction without interfering with the observer's face.

By arranging the illumination light source so that the illumination light can be illuminated on the image display element through the third surface of the prism member, the optical system of the image display device including the illumination system can be made compact. It will enable you to achieve it.

In this case, in addition to the effect that a bright, small and lightweight image display device can be achieved by using a reflection type image display device such as a reflection type LCD, the illumination is performed when the third surface is coated with reflection. If the third surface is a half mirror surface or a total reflection surface, the opening for light incidence can be illuminated through the third reflection surface as it is, so that it is possible to illuminate the opening from between the reflection type image display element and the fourth surface. The distance between the reflection type image display device and the fourth surface can be reduced, and the size can be reduced. In the case where the illumination light is to be incident from the first surface side, an optical path for illumination is required between the face or head of the observer and the prism member. This requires consideration and is practically difficult. Note that a mirror may be provided between the light source and the third surface.

Further, by forming the third surface (third reflecting surface) of the prism member with a half mirror surface coated with a half mirror, the illumination light is guided to an image display device such as a reflection type LCD. The reflected light from an image display device such as a reflection type LCD can also be guided to the observer's eyeball.
By reducing the angle reflected by the reflecting surface, the occurrence of decentering aberration can be suppressed.

Also in this case, a bright, compact and lightweight image display device can be achieved by using a reflection type image display device such as a reflection type LCD. In addition, since a folded optical path of three reflections is used, if the third surface is a reflective surface, the reflective image display element will be blocked by the reflective surface, causing a sense of obstruction to the observer. Therefore, by applying a half mirror coat to the third surface, external light can be made to enter through the third surface and the outside can be seen through the first surface even slightly, so that the feeling of blockage can be reduced.

Also, a mirror or a half mirror is not used on the third surface (third reflecting surface), and light from an image display element such as a reflection type LCD is totally reflected, so that a half mirror or the like is used. As compared with the case, the utilization efficiency of the illumination light can be improved, and a bright image can be formed.

In this case, a bright, small and lightweight image display device can be achieved by using a reflection type image display device such as a reflection type LCD, and in addition to the effect, a half mirror coat is applied to the third surface. Also, loss of light amount from the reflective image display element and light amount from the outside can be eliminated, and a brighter image can be formed.

Here, the merits of forming the eyepiece optical system with an internally reflecting prism member will be described. A refractive optical element such as a lens can be given power only by giving a curvature to its boundary surface. Therefore, when a light beam is refracted at the boundary surface of the lens, chromatic aberration due to the chromatic dispersion characteristics of the refractive optical element is inevitably generated.
As a result, another refractive optical element is generally added for the purpose of correcting chromatic aberration.

On the other hand, a reflective optical element such as a mirror or a prism does not generate chromatic aberration in principle even if its reflecting surface has power, and another optical element is used only for the purpose of correcting chromatic aberration. No need to add. Therefore, in the optical system using the reflective optical element, the number of constituent optical elements can be reduced from the viewpoint of chromatic aberration correction, as compared with the optical system using the refractive optical element.

At the same time, since the reflection optical system using the reflection optical element folds the optical path, the size of the optical system itself can be reduced as compared with the refractive optical system.

Further, since the reflection surface has higher sensitivity to eccentricity error than the refraction surface, high accuracy is required for assembly adjustment.
However, among the reflective optical elements, since the relative positional relationship between the surfaces of the prisms is fixed, the eccentricity may be controlled as a single prism, and unnecessary assembly accuracy and adjustment man-hours are unnecessary.

Further, the prism has an entrance surface, an exit surface, and a reflection surface, which are refraction surfaces, and has a greater degree of freedom for aberration correction than a mirror having only a reflection surface. In particular, by allowing the reflection surface to share most of the desired power and reducing the power of the entrance surface and the exit surface, which are refraction surfaces, the degree of freedom in correcting aberrations is larger than that of a mirror, while maintaining the degree of freedom for aberrations. Compared with such a refractive optical element, the occurrence of chromatic aberration can be extremely reduced. Further, since the inside of the prism is filled with a transparent body having a higher refractive index than air, the optical path length can be made longer than that of air. Thinning and miniaturization are possible.

The eyepiece optical system is required to have good imaging performance not only at the center but also at the periphery. Therefore,
In the present invention, as described above, by using one prism member, the fourth surface for causing the image light emitted from the image display element to enter the prism, and the third surface for reflecting the light beam incident from the fourth surface. Surface, a first surface that totally reflects the light beam reflected by the third surface, and a rotationally asymmetric that reflects the light beam reflected by the first surface, applies optical power to the light beam, and corrects eccentric aberration. A second surface formed into a curved surface, and a light beam reflected by the second surface is emitted from the first surface to the outside of the prism, so that not only the center but also off-axis aberrations are satisfactorily corrected. Is possible.

By adopting such a basic structure, the number of constituent optical elements is smaller than that of a refractive optical system or a rotationally symmetric relay optical system and an optical system using an eccentric prism, and the performance from the center to the periphery is excellent. It is possible to obtain a small-sized image display device.

Here, in the reverse ray tracing, when a light beam passing through the center of the pupil and reaching the center of the display surface of the image display element is defined as an axial principal ray, at least one reflecting surface of the prism member is defined as an axial principal ray. If the optical axis is not decentered, the incident ray and the reflected ray of the axial chief ray take the same optical path, and the axial chief ray is blocked in the optical system. As a result, an image is formed only with the light flux whose central portion is shielded,
The center is darkened, or the image is not formed at the center at all.

Further, it is naturally possible to decenter the powered reflecting surface with respect to the axial principal ray. When the reflecting surface with power is decentered with respect to the axial chief ray,
It is preferable that at least one of the surfaces constituting the prism member is a rotationally asymmetric surface. Among them, it is particularly preferable to make the first reflection surface (second surface) a rotationally asymmetric surface for aberration correction.

The reason will be described in detail below. First, a coordinate system to be used and a rotationally asymmetric surface will be described. An optical axis defined by a straight line until the on-axis principal ray intersects the first surface of the optical system is defined as a Z axis, and is orthogonal to the Z axis and within an eccentric plane of each surface constituting the imaging optical system. Is defined as the Y axis,
An axis orthogonal to the optical axis and orthogonal to the Y axis is defined as an X axis. The ray tracing direction will be described with the reverse ray tracing from the pupil to the image display element as described above.

In general, 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 surfaces, so that the aberration is reduced as a whole. Configuration.

On the other hand, in order to favorably correct aberrations with a small number of surfaces, a rotationally symmetric aspherical surface or the like is used. This is to reduce various aberrations generated on the spherical surface. However, in a decentered optical system, it is impossible to correct rotationally asymmetric aberration generated by decentering by a rotationally symmetric optical system. The rotationally asymmetric aberrations caused by this eccentricity include distortion, field curvature, astigmatism and coma which also occur on the axis.

First, the rotationally asymmetric field curvature will be described. For example, light rays incident on a concave mirror decentered from an object point at infinity are reflected and imaged on the concave mirror, but after the light rays hit the concave mirror, the rear focal length to the image plane is
When the image field side is air, the radius of curvature becomes half of the radius of curvature of the portion hit by the light beam. Then, as shown in FIG. 12, an image plane inclined with respect to the axial principal ray is formed. As described above, it is impossible to correct rotationally asymmetric curvature of field with a rotationally symmetric optical system.

In order to correct the tilted curvature of field by the concave mirror M itself, which is the source, the concave mirror M is constituted by a rotationally asymmetric surface. In this example, the curvature is strong in the positive Y-axis direction ( If the refractive power is increased) and the curvature is decreased (the refractive power is decreased) in the negative direction of the Y axis, the correction can be made. In addition, by arranging a rotationally asymmetric surface having the same effect as the above configuration in the optical system separately from the concave mirror M, a flat image surface can be obtained with a small number of components. In addition, the rotationally asymmetric surface is preferably a rotationally asymmetric surface shape having no rotationally symmetric axis both inside and outside the surface, which is preferable in terms of increasing the degree of freedom and correcting aberrations.

Next, rotationally asymmetric astigmatism will be described. As described above, the eccentrically arranged concave mirror M
In this case, astigmatism as shown in FIG. 13 also occurs for axial rays. 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. 14 also occurs for axial rays. 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.

In the image forming optical system according to the present invention, it is also possible that at least one surface having the above-mentioned reflecting action is decentered with respect to the axial principal ray, and has a rotationally asymmetric surface shape having power. With such a configuration, it becomes possible to correct the eccentric aberration caused by giving power to the reflecting surface by the surface itself, and by relaxing the power of the refracting surface of the prism, the occurrence of chromatic aberration itself can be reduced. Can be smaller.

The rotationally asymmetric surface used in the present invention is preferably a plane-symmetric free-form surface having only one plane of symmetry. Here, the free-form surface used in the present invention is:
It is defined by the following equation (a). Note that the Z axis of the definition formula is the axis of the free-form surface.

[0040] 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 generally includes an XZ plane,
Although neither YZ plane has a plane of symmetry, in the present invention, X
By setting all the odd-order terms to 0, a free-form surface having only one symmetry plane parallel to the YZ plane is obtained. 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 ₃₁ , C ₃₃ , C ₃₅ ...

By setting all odd-numbered 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 ...

One of the directions of the symmetry plane is a symmetry plane, and the eccentricity in the direction corresponding thereto, for example, the eccentricity direction of the optical system with respect to the symmetry plane parallel to the YZ plane is in the Y-axis direction. By making the eccentric direction of the optical system the X-axis direction with respect to the symmetric plane parallel to the XZ plane, it is possible to effectively correct rotationally asymmetric aberrations caused by the eccentricity while improving the productivity. Becomes possible.

Further, the above-mentioned definition formula (a) is shown as one example as described above, and the present invention uses a rotationally asymmetric surface having only one symmetric surface to produce a rotation generated by eccentricity. It is characterized by correcting asymmetric aberrations and at the same time improving productivity, and it goes without saying that the same effect can be obtained for any other definitional expressions.

Now, the cross section (YZ plane) where the axial principal ray of the third surface of the prism member of the present invention is folded as described above.
Inside and in a cross section perpendicular to the cross section (XZ plane) are formed by curved surfaces with the concave surface facing the pupil side, and in the cross section where the axial principal ray of the first surface is folded and its Both surface shapes in a cross section perpendicular to the cross section are formed by curved surfaces with the concave surface facing the pupil side, so that distortion of a light beam incident from the outside passing through the third surface and the first surface is reduced. It is desirable (see Examples 1 and 2 described later).

When the third surface and the first surface are configured as described above,
The third surface and the first surface are curved surfaces with the concave surface facing the same pupil side,
When the outside world is viewed through the third and first planes, the distortion of the outside world image is reduced as much as possible, resulting in a desirable arrangement.

When the third surface is formed by a half mirror surface coated with a half mirror, the illumination light source illuminates the image display element with the illumination light through the third surface coated with the half mirror. It is desirable to make the arrangement possible.

When the third surface is a total reflection surface,
It is desirable that the illumination light source be arranged so that the illumination light can be illuminated to the image display element via the third surface formed by the total reflection surface.

Regarding surface shapes other than the second surface, the first surface
The light beam can be formed into a rotationally asymmetric curved surface shape that gives optical power to the light beam and corrects eccentric aberration.

Further, the third surface can be formed into a rotationally asymmetric curved surface shape that gives optical power to the light beam and corrects eccentric aberration.

Further, the fourth surface can be formed into a rotationally asymmetric curved surface shape that gives optical power to the light beam and corrects eccentric aberration. It is effective to take such a surface shape on the refraction surface in order to correct aberrations caused by eccentricity.

Further, it is desirable that the rotationally asymmetric curved surface has a free-form surface having only one symmetrical surface.

In this case, it is desirable that the only plane of symmetry be configured so as to coincide with the cross section where the axial chief ray is folded.

The most effective arrangement of the illumination light source is such that a light beam enters from the third surface and passes through the fourth surface to irradiate the reflective image display device with illumination light. .

Further, in the present invention, the difference between the incident angle of the illumination light from the illumination light source to the reflection type image display device and the exit angle of the reflected principal ray from the reflection type image display device is within ± 10%. It is desirable to configure the illumination light source, the reflection type image display element, and the eyepiece optical system so that they are substantially equal. Within this range, bright display is possible.

Further, between the illumination light source and the prism member,
It is desirable to arrange a numerical aperture reducing member so as to prevent generation of a ghost image.

By the way, the angle formed by the axial principal ray from the center of the display surface of the reflection type image display device and the normal line of the display device surface is θ.
It is important to satisfy the following condition: θ <60 ° (1) If the upper limit of 60 ° of this condition is exceeded, when a reflective image display element having a poor viewing angle characteristic is used, problems such as a decrease in contrast occur, and a clear observation image cannot be displayed.

More preferably, it is important to satisfy the following condition: θ <40 ° (1-1) The meaning of the upper limit of this condition is the same as above.

More desirably, it is important to satisfy the following condition: θ <25 ° (1-2) The meaning of the upper limit of this condition is the same as above.

Next, assuming that the optical path length from the position of the light source for illumination to the reflective image display element is OP, it is important to satisfy the following condition: 1 mm <OP <60 mm (2) If the upper limit of this condition is exceeded, that is, 60 mm, the entire observation optical system including the illumination system becomes too large, and its attractiveness as a head or face-mounted image display device is diminished. If the lower limit of 1 mm is exceeded, the power of the third reflecting surface and the exit surface (fourth surface) becomes too strong, and the imaging performance on the image display surface and the pupil aberration at the light source position become too large.

More preferably, it is important to satisfy the following condition: 5 mm <OP <40 mm (2-1) The meaning of the upper and lower limits of this condition is the same as above.

More preferably, it is important to satisfy the following condition: 10 mm <OP <20 mm (2-1) The meaning of the upper and lower limits of this condition is the same as above.

[0065]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, specific numerical embodiments 1 and 2 of the present invention will be described. In the configuration parameters of each embodiment described later, as shown in FIG. 1, the center of the exit pupil 1 of the decentered prism (prism member) 10 constituting the eyepiece optical system is defined as the origin of the optical system by the backward ray tracing. 2 is defined as an axial principal ray passing through the center (origin) of the exit pupil 1 and reaching the center of the image plane (image display element) 7, and the direction proceeding from the exit pupil 1 along the optical axis 2 is defined as a Z-axis direction. A direction in a plane orthogonal to the Z axis and passing through the center of the exit pupil 1 and where the light beam is bent by the eccentric prism 10 is orthogonal to the Y axis direction, the Y axis and the Z axis, and a direction passing through the center of the exit pupil 1 is the X axis direction. Where the direction from the exit pupil 1 toward the eccentric prism 10 is the positive direction of the Z axis,
The direction from the optical axis 2 to the image plane (image display element) 7 is defined as the positive direction of the Y axis, and the direction forming the right-handed system with the Y axis, the Z axis is defined as the positive direction of the X axis. The ray tracing is performed by the eccentric prism 1
0 is the direction of incidence on the eccentric prism 10 from the exit pupil 1 side.

For a surface having decentering, the amount of decentering in the X-axis direction, Y-axis direction, and Z-axis direction from the center of the exit pupil 1 which is the origin of the decentered prism 10 at the top of the surface. And the inclination angles (α, β, γ (°), respectively) of the central axis of the surface (for the free-form surface, the Z-axis of the above-described equation (a)) around the X-axis, Y-axis, and Z-axis And is given. 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 shape of the surface of the free-form surface used in the present invention is defined by the above equation (a), and the Z axis of the definition expression is the axis of the free-form surface.

The term relating to a free-form surface on which no data is described is zero. The refractive index for d-line (wavelength 587.56 nm) is shown. The unit of the length is mm.

Another defining equation of the free-form surface is a Zernike polynomial given by the following equation (b).
The shape of this surface is defined by the following equation. The Z axis of the defining equation is the axis of the Zernike polynomial. The definition of the rotationally asymmetric surface is defined by polar coordinates of the height of the Z axis with respect to the XY plane, A is the distance from the Z axis in the XY plane, R is the azimuth around the Z axis, and the Z axis It can be expressed by the rotation angle measured from.

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) ····· ··· (b) In addition, to design an optical system symmetric with respect to the X-axis direction, D
_{4, D 5, D 6,} D 10 0, D 11, D 12, D 13, D 14, D
_20, D _21, D ₂₂ ... to use.

As another example, the following definition formula (d)
Is raised. Z = ΣΣC _nm XY As an example, when k = 7 (seventh-order term) is considered, when expanded, it can be expressed by the following equation. _{Z = C 2 + C 3 y} + C 4 | x | + C 5 y 2 + C 6 y | x | + C 7 x 2 + C 8 y 3 + C 9 y 2 | x | + C 10 yx 2 + C 11 | x 3 | + C 12 y 4 ^{_{+ C 13 y 3 | x |}} + C 14 y 2 x 2 + C 15 y | x 3 | + C 16 x 4 + C 17 y 5 + C 18 y 4 | x | + C 19 y 3 x 2 + C 20 y 2 | x 3 | + C ^{_{21 yx 4 + C 22 | x}} 5 | + C 23 y 6 + C 24 y 5 | x | + C 25 y 4 x 2 + C 26 y 3 | x 3 | + C 27 y 2 x 4 + C 28 y | x 5 | + C 29 x ^{_{6 + C 30 y 7 + C}} 31 y 6 | x | + C 32 y 5 x 2 + C 33 y 4 | x 3 | + C 34 y 3 x 4 + C 35 y 2 | x 5 | + C 36 yx 6 + C 37 | x 7 | (C) In the embodiment of the present invention, the surface shape is expressed by a free-form surface using the above equation (a).
It goes without saying that the same operation and effect can be obtained by using the expression (c).

In both of the first and second embodiments, the horizontal angle of view is 25 ° and the value of 0.1 mm is satisfied.
A 47-inch reflective LCD is assumed, and free-form surfaces are used for all the optical surfaces 3 to 6.

FIGS. 1 and 2 are sectional views taken along the line YX of the first and second embodiments including the optical axis. Examples 1 and 2 are all 4
Optical surfaces 3 to 6, and four optical surfaces 3 to 6
Are filled with a transparent medium having a refractive index of greater than 1 and, in the backward ray tracing, a ray traveling along the optical axis 2 through the exit pupil 1 first enters the first surface 3 having a transmitting action and a reflecting action. Then, the light enters the eccentric prism 10, and the incident light is reflected in the direction approaching the exit pupil 1 by the second surface 4, which is a reflecting surface having only a reflection function on the side farther from the exit pupil 1,
The light is reflected again on the surface 3 in a direction away from the exit pupil 1, and the reflected light is reflected on the third surface 5, which is a reflecting surface, and then passes through the fourth surface 6 having only a transmitting function, and is located on the image plane. The light reaches the display surface of the disposed reflective LCD 7, and is specularly reflected by the display surface, enters the eccentric prism 10 from the fourth surface 6, traverses the eccentric prism 10, and is opposite to the fourth surface 6. The light exits the decentered prism 10 from the third surface 5 and reaches a surface light source 8 disposed in front of the third surface 5.

The third reflecting surface of the first embodiment, ie, the third reflecting surface
When a half mirror is used for the surface 5 and it is used as an eyepiece optical system, the light from the light source 8 actually enters the eccentric prism 10 via the half mirror surface 5, exits from the fourth surface 6 and is reflected. Since the display light emitted from the reflective LCD 7 is refracted on the fourth surface 6 and enters the eccentric prism 10 and is reflected on the third surface 5 of the half mirror surface, the light amount decreases. Inevitable. However, since the third surface 5 is a semi-transmissive surface, an observer whose eye pupil is located at the position of the exit pupil 1 can observe the outside world through the first surface 3 and the third surface 5 which is a semi-transmissive surface. can do. In the first embodiment, the focal length in the X direction is 21.23 mm, the focal length in the Y direction is 20.95 mm, and the pupil diameter of the exit pupil 1 is φ4.0 m.
m. It should be noted that θ in the above conditional expression (1) is 14.61.
°, OP in the conditional expression (2) is 16.64 mm.

In the case of the second embodiment, the third surface 5, which is the third reflecting surface, is not subjected to the processing such as a mirror or a half mirror, and the light from the light source 8 is not reflected on the transmitting surface in this case. The light enters the eccentric prism 10 via the third surface 5 and exits from the fourth surface 6 to illuminate the reflective LCD 7. The display light from the reflective LCD 7 is now refracted by the fourth surface 6 and enters the eccentric prism 10. Then, the light is reflected by the third surface 5 of the total reflection surface and guided to the second reflection surface 3 side.
Since the third surface 5 is a transmission surface, an observer whose pupil of the eyeball is located at the position of the exit pupil 1 can receive the first surface 3 and the third surface 5 of the transmission surface as in the first embodiment. You can observe the outside world through. The focal length in the X direction of the second embodiment is 20.
70 mm, the focal length in the Y direction is 19.57 mm,
The pupil diameter of the exit pupil 1 is φ4.0 mm. In the conditional expression (1), θ = 21.10 °, and in the conditional expression (2), OP = 1
4.02 mm. The configuration parameters of the first and second embodiments are shown below. “FFS” in these tables indicates a free-form surface.

Example 1 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface ∞ -1000.00 1 ∞ (aperture surface) 2 FFS Eccentricity (1) 1.4922 57.5 3 FFS Eccentricity (2) 1.4922 57.5 4 FFS Eccentricity (1) 1.4922 57.5 5 FFS eccentricity (3) 1.4922 57.5 6 FFS eccentricity (4) Image plane 偏 eccentricity (5) 8 FFS eccentricity (4) 1.4922 57.5 9 FFS eccentricity (3) Light source ∞ eccentricity (5) FFS C ₄ -1.0834 × ^{_{10 -2 C 6 -6.7379 × 10 -3}} C 8 -3.5545 × 10 -5 C 10 -2.7545 × 10 -4 C 11 -4.4022 × 10 -6 C 13 -4.9598 × 10 -6 C 15 -7.6607 × 10 - ⁶ FFS C ₄ -1.2408 × 10 ^-2 C ₆ -9.9412 × 10 ^-3 C ₈ 2.2186 × 10 ^-5 C ₁₀ -9.9422 × 10 ^-5 C ₁₁ -1.7014 × 10 ^-6 C ₁₃ -4.9304 × 10 ^-6 C ₁₅ -5.0716 × 10 ^-7 FFS C ₄ -4.9692 × 10 ^-3 C ₆ -7.0595 × 10 ^-3 C ₈ 1.0765 × 10 ^-4 C ₁₀ -2.7022 × 10 ^-4 C ₁₁ -7.2416 × 10 ^-6 C ₁₃ 3.8668 × 10 ^-6 C ₁₅ -1.2518 × 10 ^-5 FFS C ₄ 3.0038 × 10 ^-2 C ₆ 9.9082 × 10 ^-3 C ₈ 6.1877 × 10 ^-4 C ₁₀ -2.0735 × 10 ^-3 C ₁₁ -7.3847 × 10 ^-5 C ₁₃ -1 .2648 × 10 ^-4 C ₁₅ -1.5965 × 10 ^-4 Eccentricity (1) X 0.00 Y 6.84 Z 28.31 α 3.62 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.00 Z 35.35 α -22.10 β 0.00 γ 0.00 Eccentricity (3 ) X 0.00 Y 16.91 Z 36.33 α 14.49 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 20.08 Z 28.65 α -14.84 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 21.10 Z 26.59 α -11.64 β 0.00 γ 0.00.

Example 2 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface ∞-1000.00 1 ∞ (aperture surface) 2 FFS Eccentricity (1) 1.4922 57.5 3 FFS Eccentricity (2) 1.4922 57.5 4 FFS Eccentricity (1) 1.4922 57.5 5 FFS eccentricity (3) 1.4922 57.5 6 FFS eccentricity (4) Image plane ∞ eccentricity (5) 8 FFS eccentricity (4) 1.4922 57.5 9 FFS eccentricity (3) Light source ∞ eccentricity (5) FFS C ₄ -7.6310 × ^{_{10 -3 C 6 -4.3408 × 10 -3}} C 8 -1.6615 × 10 -4 C 10 -3.9070 × 10 -5 C 11 -8.2054 × 10 -6 C 13 -1.0462 × 10 -5 C 15 -1.1448 × 10 - ⁶ FFS C ₄ -1.1352 × 10 ^-2 C ₆ -9.2838 × 10 ^-3 C ₈ -4.0158 × 10 ^-5 C ₁₀ -1.5803 × 10 ^-5 C ₁₁ -2.1193 × 10 ^-6 C ₁₃ -3.3963 × 10 ^-6 C ₁₅ -9.7900 × 10 ^-7 FFS C ₄ -2.2140 × 10 ^-3 C ₆ -5.1886 × 10 ^-3 C ₈ 3.0644 × 10 ^-5 C ₁₀ -7.6091 × 10 ^-5 C ₁₁ -1.6505 × 10 ^-5 C ₁₃ -1.2417 × 10 ^-5 C ₁₅ -3.4074 × 10 ^-6 FFS C ₄ 3.8743 × 10 ^-2 C ₆ 1.7912 × 10 ^-2 C ₈ 5.6708 × 10 ^-4 C ₁₀ -1.1830 × 10 ^-3 C ₁₁ -1.2023 × 10 ^-4 C ₁₃ -2.8052 × 10 ^-4 C ₁₅ -2.8715 × 10 ^-4 Eccentricity (1) X 0.00 Y 6.80 Z 28.18 α 3.15 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.00 Z 33.59 α -25.76 β 0.00 γ 0.00 Eccentricity (3 ) X 0.00 Y 18.84 Z 35.76 α 8.59 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 24.19 Z 29.53 α -30.35 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 25.84 Z 27.93 α -24.72 β 0.00 γ 0.00
.

As in the above embodiment, the light from the light source 8 enters the eccentric prism 10 via the third surface 5 and
When illuminating the reflective LCD 7 out of the surface 6, the region where the illumination light passes through the third surface 5 and the region where the display light from the reflective LCD 7 is reflected by the third surface 5 are defined in the third surface 5. It is also possible to configure so that separate areas are arranged in parallel. In that case, only the reflection area of the third surface 5 needs to be mirror-coated or half-mirror-coated.

Further, in the above embodiment, it is assumed that the reflection type LCD 7 is used as the reflection type image display element. Instead, a DMD (digital micro device) shown in FIG. 16 is used. Of course, it is good.

Although the numerical values of the optical system are omitted, the illumination light source 8
3, the illumination light from the light source 8 is decentered from the first surface 3 on the side of the exit pupil 1 in front of the first surface 3 and close to the fourth surface 6, as shown in FIG. So that the light enters the prism 10 and exits from the third surface 5 across the eccentric prism 10, that is, the illumination light from the light source 8 passes through the eccentric prism 10 from the exit pupil 1 side to the opposite side,
The illumination light that has exited from the third surface 5 is directed toward the reflective LCD 7 by the concave mirror 11 and re-enters the inside of the eccentric prism 10 from the vicinity of the intersection of the third surface 5 with the fourth surface 6. So that it crosses and exits from the fourth surface 6,
The display surface of the reflective LCD 7 may be illuminated.

In each of the above embodiments, the reflection type LCD 7 is used for the non-telecentric eccentric prism with the entrance pupil having a finite distance. However, a two-dimensional screen is provided as follows. It is also possible to use an image display element that is not used.

For example, the reflection type LCD 7 of the image display device shown in FIG. 2 is replaced with a mere plane mirror or scattering surface 9 and the image display element 24 which forms a two-dimensional image by scanning the light source 8 is provided. The image display device shown in FIG.

At this time, if the configuration is mainly for one-dimensional scanning, for example, as shown in FIG.
Reference numeral 5 denotes a polygon mirror 26, and an image display element 24 includes a one-dimensional image display element (one in which display pixels such as liquid crystal display pixels and LEDs are arranged one-dimensionally) 27 and a collimator lens 28 that converts light into a parallel light flux. Can be configured. Here, the position of the entrance pupil of the eccentric prism 10 is arranged so as to substantially coincide with the reflection surface formed on the rotating polygonal surface of the polygon mirror 26, and the luminous flux is directed in a direction orthogonal to the pixel array of the one-dimensional image display element 27. It is configured to form a two-dimensional image by scanning.

If the configuration is based on two-dimensional scanning, for example, as shown in FIG. 6, the one-dimensional image display element 27 is configured as a pixel light source 29 for displaying one pixel.
This can be realized by arranging a galvano mirror 30 having a scanning function in a direction orthogonal to the scanning direction of the polygon mirror 26. The galvanometer mirror 30 may have a scanning function, and may be constituted by a polygon mirror or the like.

In the above embodiment, among the light beams emitted from the optical elements such as the light source 8, the reflection type LCD 7, the polygon mirror 26 and the plane mirror 9, those having a large numerical aperture other than the effective light beam forming the entrance pupil. However, in order to prevent a ghost image generated by being guided to the observer's eye via the eccentric prism 10, a numerical aperture reducing element for limiting the numerical aperture of a light beam is arranged in an optical path formed by each of these elements. Is desirable. In particular, it is more effective to arrange the numerical aperture reducing element in the optical path between each of the above elements and the eccentric prism 10. Examples of the numerical aperture reducing element include a louver optical element 16a and an optical fiber plate 16b described below.

FIG. 7 shows an example of the louver optical element 16a.
(A) and FIG. 7 (b). Louver optical element 16a
In this example, a fine light-shielding wall 18 is periodically sandwiched in a transparent film 17, and light outside a certain incident angle range is absorbed by the light-shielding wall 18 and cannot be emitted. Also, by changing the angle of the light shielding wall 18,
The angle of incidence of the maximum transmission can be varied. FIG. 7 (a),
FIGS. 8A and 8B show the transmittance distribution of the louver optical element 16a when a light beam enters from the direction of the arrow in FIG.
Shown in

When such a louver optical element 16a is inserted, for example, between the light source 8 and the third surface 5 in FIG. 1, the light from the light source 8 has its numerical aperture limited by the louver optical element 16a. And is directed toward the eccentric prism 10. Here, assuming that the size of the numerical aperture for generating a ghost image is caused by a light beam larger than the incident angle α, the light beam having a transmittance distribution equal to or larger than the critical incident angle α as shown in FIG. The use of the louver optical element 16a that is configured not to transmit light can prevent the generation of a ghost image.

Further, in the eccentric prism 10 as in each of the above-described embodiments, each optical working surface is not in a coaxial system, and the shape of the surface itself may be formed to be rotationally asymmetric. A large number of light beams may not exist symmetrically about the incident angle 0 as shown in FIG. Therefore, in such a case, as shown in FIG. 8B, the fine light shielding wall 18 in the transparent film 17 is controlled so as to control the transmittance of the light flux centered on the light flux incident at a predetermined angle. It is desirable to use the louver optical element 16a arranged at an angle.

Instead of the louver optical element 16a, an optical fiber plate 16b in which optical fibers are bundled and cut into a plate shape can be used. FIG. 9 shows an example of the structure of the optical fiber plate 16b. As shown in the enlarged view of the figure, the optical fiber plate 16b includes a core glass 19a, a clad glass 19b surrounding the core glass 19a, and an absorbing member 20 coated on the outer periphery thereof.
The optical fiber is formed by bundling a large number of optical fibers having a predetermined numerical aperture into honey, and a light beam having a numerical aperture or more determined by the numerical aperture of the optical fiber passes through the optical fiber wall and is absorbed by the absorbing member 20. Has the same function as the louver optical element 16a.

Now, even if one set of the image display device described above is prepared and configured to be mounted on one eye, such a pair is prepared as a pair of left and right, and they are separated 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. 10 shows a state where the camera is mounted on one eye (in this case, the camera is mounted on the left eye), and FIG. 11 shows a state where the camera is mounted on both eyes. FIG.
In FIG. 11, reference numeral 31 denotes a display device main body. In FIG. 10, a support member is held in front of the left eye of the observer's face, and in FIG. 11, it is held in front of both eyes of the observer's face. Is fixed through the head. One end of the support member is joined to the display device main body 31, the left and right front frames 32 extending from the temple of the observer to the upper part of the ear, and the other end of the front frame 32 is joined to the side of the observer. From the left and right rear frames 33 extending across the head (in the case of FIG. 10), or further, one end of each of them is joined one by one so as to be sandwiched between the other ends of the left and right rear frames 33 and observed. (In the case of FIG. 11).

A rear plate 35 made of an elastic body and formed of, for example, a metal plate spring is joined to the front frame 32 near the junction with the rear frame 33. The rear plate 35 is joined so that the rear cover 36, which carries one wing of the support member, is positioned behind the ear at the portion where the back cover of the observer is attached to the neck of the observer and can be supported (see FIG. 11). 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 transmitted from the display device main body 31 through the top frame 34 (in the case of FIG. 11), the rear frame 33, the front frame 32, and the rear plate 35. Rear plate 3
5 or the rear cover 36 projects outward from the rear end. The cable 41 is connected to the video playback device 40.
It is connected to the. In the figure, reference numeral 40a denotes a switch and a volume adjusting unit of the video reproducing device 40.

The cable 41 may be jacked at the end so that it can be attached to an existing video deck or the like. Furthermore, it is connected to a tuner for TV radio wave reception,
It may be used for viewing, or may be connected to a computer to receive computer graphics images, message images from the computer, and the like. 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] In an image display device including an illumination light source, an image display element, and an eyepiece optical system that guides an image formed by the image display element to an observer's eyeball position, the eyepiece optical system has a refractive index of 1 or more. A prism member sandwiching a large medium, the prism member having a fourth surface for causing image light emitted from the image display element to enter the prism, and a fourth surface for reflecting a light beam incident from the fourth surface. Three surfaces, a first surface that totally reflects the light beam reflected by the third surface, and a rotational asymmetry that reflects the light beam reflected by the first surface, applies optical power to the light beam, and corrects eccentric aberration And a second surface formed in a curved surface shape, and configured to emit a light beam reflected by the second surface from the first surface to outside the prism, and the image display element forms an image by reflected light. Reflective type to display An image display device comprising an image display element, wherein the illumination light source is arranged to be able to illuminate the image display element with illumination light via the third surface of the prism member.

[2] In an image display apparatus having an illumination light source, an image display element, and an eyepiece optical system for guiding an image formed by the image display element to an observer's eyeball position, the eyepiece optical system has a refractive index. Has a prism member sandwiching a medium larger than 1; the prism member converts a fourth surface on which image light emitted from the image display element enters the prism; and a light beam incident from the fourth surface. Third to reflect
A first surface for totally reflecting the light beam reflected by the third surface
And a second surface formed into a rotationally asymmetric curved surface shape that reflects the light beam reflected by the first surface, applies optical power to the light beam, and corrects eccentric aberration. The reflected light beam is emitted from the first surface to the outside of the prism, the image display device is configured by a reflective image display device that displays an image by reflected light, and the third surface of the prism member is Is formed by a half mirror surface coated with a half mirror.

[3] In an image display apparatus having an illumination light source, an image display element, and an eyepiece optical system for guiding an image formed by the image display element to an observer's eyeball position, the eyepiece optical system has a refractive index. Has a prism member sandwiching a medium larger than 1; the prism member converts a fourth surface on which image light emitted from the image display element enters the prism; and a light beam incident from the fourth surface. Third to reflect
A first surface for totally reflecting the light beam reflected by the third surface
And a second surface formed into a rotationally asymmetric curved surface shape that reflects the light beam reflected by the first surface, applies optical power to the light beam, and corrects eccentric aberration. The reflected light beam is emitted from the first surface to the outside of the prism, the image display device is configured by a reflective image display device that displays an image by reflected light, and the third surface of the prism member is Is formed by a total reflection surface, and is configured to reflect a light beam incident from the fourth surface by a total reflection effect.

[4] Both the surface shape in the cross section where the axial principal ray of the third surface is folded and in the cross section perpendicular to the cross section are formed by a curved surface with the concave surface facing the pupil side. Both surface shapes in a cross section where the axial principal ray of the first surface is folded and in a cross section perpendicular to the cross section are formed by curved surfaces with the concave surface facing the pupil side, and the third surface and the first surface are formed. 4. The image display device according to the above item 2 or 3, wherein the distortion of a light beam incident from the outside world is reduced.

[5] The image display device according to the above item 2, wherein the illumination light source is arranged so as to be able to illuminate the image display element with the illumination light via the third surface coated with the half mirror. .

[6] The illumination light source according to the above item 3, wherein the illumination light source is arranged so as to illuminate the image display element with illumination light via a third surface formed by the total reflection surface. Image display device.

[7] The image display device as described in any one of [1] to [6] above, wherein the illumination light source is disposed on the opposite side of the third surface from the prism medium.

[8] The method according to any one of the above items 1 to 7, wherein the first surface is formed in a rotationally asymmetric curved surface shape for giving optical power to a light beam and correcting eccentric aberration. Image display device.

[0103]

[9] The image display according to any one of [1] to [8], wherein the third surface is formed into a rotationally asymmetric curved surface shape that applies optical power to the light beam and corrects eccentric aberration. apparatus.

[10] The fourth surface according to any one of the above items 1 to 9, wherein the fourth surface is formed in a rotationally asymmetric curved surface shape for giving optical power to a light beam and correcting eccentric aberration. Image display device.

[11] The rotationally asymmetric curved surface shape is
11. The image display device according to any one of 1 to 10, wherein the image display device is configured in a free-form surface shape having only one symmetric surface.

[12] The image display apparatus according to the above item 11, wherein the only plane of symmetry is configured to coincide with a cross section where the axial chief ray is folded.

[13] The illumination light source is characterized in that a light beam is incident from the third surface and transmitted through the fourth surface to irradiate the reflective image display element with illumination light. 7. The image display device according to the above 1, 5 or 6, wherein

[14] The difference between the angle of incidence of the illumination light from the illumination light source on the reflective image display device and the angle of emergence of the reflected chief ray from the reflective image display device is ± 10%. The image display device according to any one of claims 1 to 13, wherein the illumination light source, the reflection-type image display element, and the eyepiece optical system are configured to be substantially equal.

[15] Any of the above-mentioned items 1 to 14, wherein a numerical aperture reducing member is arranged between the illumination light source and the prism member so as to prevent generation of a ghost image. 2. The image display device according to claim 1.

[16] Assuming that the angle formed by the axial principal ray from the center of the display surface of the reflective image display element and the normal to the display element surface is θ, θ <60 ° (1) The image display device according to any one of the above items 1 to 15, which satisfies the following.

[17] When the optical path length from the position of the illumination light source to the reflective image display element is defined as OP, the following condition is satisfied: 1 mm <OP <60 mm (2) 17. The image display device according to any one of items 1 to 16.

[18] The image display device comprises a right-eye illumination light source, a left-eye illumination light source, a right-eye image display element, a left-eye image display element, a right-eye ocular optical system, and a left-eye image display element. 18. The image display device according to any one of 1 to 17, wherein the image display device includes an eyepiece optical system.

[19] The image display device according to any one of the above items 1 to 18, wherein the image display device is provided with support means for supporting an observer's head so as to be located in front of the observer's face. 2. The image display device according to claim 1.

[0114]

As is apparent from the above description, according to the present invention, the eyepiece optical system comprises four decentered prisms having three internal reflections, and the image display device displays an image by reflected light of illumination light. Illuminating light is radiated to the reflective image display element through a specific reflective surface of the eccentric prism, so that a reflective LCD or the like and the eccentric prism can be used while having high optical performance. A small, light, and bright image display device can be achieved. In addition, by making the specific reflecting surface a half mirror coating or a total reflecting surface, it is possible to simultaneously observe the outside world.

[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 modification of FIG. 2;

FIG. 4 is a cross-sectional view illustrating another embodiment in which an image display element is configured using a scanning member.

FIG. 5 is a diagram showing an example in which the scanning member of FIG. 4 is configured for one-dimensional scanning.

FIG. 6 is a diagram showing an example in which the scanning member of FIG. 4 is configured for two-dimensional scanning.

FIG. 7 is a diagram showing a louver optical element.

FIG. 8 is a diagram illustrating a transmittance distribution of the louver optical element of FIG. 7;

FIG. 9 is a view showing an optical fiber plate.

FIG. 10 is a diagram illustrating a state in which the image display device of the present invention is configured to be mounted on one eye.

FIG. 11 is a diagram illustrating a state in which the image display device of the present invention is configured to be mounted on both eyes.

FIG. 12 is a diagram for explaining field curvature generated by a concave mirror having an eccentric arrangement.

FIG. 13 is a diagram for explaining astigmatism generated by a concave mirror having an eccentric arrangement.

FIG. 14 is a diagram for explaining on-axis coma generated by a concave mirror having an eccentric arrangement.

FIG. 15 is a diagram showing an optical system of an image display device using a conventional reflective LCD.

FIG. 16 is a diagram illustrating a configuration of a known DMD.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exit pupil 2 ... Optical axis 3 ... 1st surface 4 ... 2nd surface 5 ... 3rd surface 6 ... 4th surface 7 ... Image plane (reflection type LCD) 8 ... Light source 9 ... Plane mirror or scattering surface 10 ... Eccentricity Prism (prism member) 11 ... Concave mirror 16a ... Louver optical element 16b ... Optical fiber plate 17 ... Transparent film 18 ... Light shielding wall 19a ... Core glass 19b ... Clad glass 20 ... Absorptive member 24 ... Image display element 25 ... Scan member 26 ... Polygon mirror 27 ... one-dimensional image display element 28 ... collimator lens 29 ... pixel light source 30 ... galvanometer mirror 31 ... display device main body 32 ... front frame 33 ... rear frame 34 ... crown frame 35 ... rear plate 36 ... rear cover 39 ... speaker 41 ... cable 40: video playback device 40a: volume adjusting unit M: concave mirror

Claims (3)

[Claims] 1. An image display apparatus comprising: an illumination light source; an image display element; and an eyepiece optical system that guides an image formed by the image display element to an observer's eyeball position, wherein the eyepiece optical system has a refractive index. A prism member sandwiching a medium larger than 1; the prism member reflecting a fourth surface on which image light emitted from the image display element enters the prism, and reflecting a light beam incident from the fourth surface; A third surface to be reflected, a first surface that totally reflects the light beam reflected by the third surface, and a light beam that reflects the light beam reflected by the first surface while giving optical power to the light beam and correcting eccentric aberration. A second surface formed into a rotationally asymmetric curved surface shape, and configured to emit a light beam reflected by the second surface from the first surface to the outside of the prism. Display image Reflective by the image display device is configured, the illumination source, an image display apparatus characterized by being illuminable arranging the illumination light through said third surface of said prism member to the image display device. 2. An image display apparatus comprising: an illumination light source; an image display element; and an eyepiece optical system that guides an image formed by the image display element to an observer's eyeball position, wherein the eyepiece optical system has a refractive index. A prism member sandwiching a medium larger than 1; the prism member reflecting a fourth surface on which image light emitted from the image display element enters the prism, and reflecting a light beam incident from the fourth surface; A third surface to be reflected, a first surface that totally reflects the light beam reflected by the third surface, and a light beam that reflects the light beam reflected by the first surface while giving optical power to the light beam and correcting eccentric aberration. A second surface formed into a rotationally asymmetric curved surface shape, and configured to emit a light beam reflected by the second surface from the first surface to the outside of the prism. Display image Reflective by the image display device is configured, an image display apparatus, wherein said third surface of said prism member is formed by the half-mirror surface which is a half mirror coating. 3. An image display device comprising: an illumination light source; an image display element; and an eyepiece optical system that guides an image formed by the image display element to a position of an observer's eyeball, wherein the eyepiece optical system has a refractive index. A prism member sandwiching a medium larger than 1; the prism member reflecting a fourth surface on which image light emitted from the image display element enters the prism, and reflecting a light beam incident from the fourth surface; A third surface to be reflected, a first surface that totally reflects the light beam reflected by the third surface, and a light beam that reflects the light beam reflected by the first surface while giving optical power to the light beam and correcting eccentric aberration. A second surface formed into a rotationally asymmetric curved surface shape, and configured to emit a light beam reflected by the second surface from the first surface to the outside of the prism. Display image It is configured by a reflection type image display element, wherein the third surface of the prism member is formed by a total reflection surface, and is configured to reflect a light beam incident from the fourth surface by a total reflection action. Image display device.