WO2023133733A1

WO2023133733A1 - Display device

Info

Publication number: WO2023133733A1
Application number: PCT/CN2022/071641
Authority: WO
Inventors: Tatsuya Nakatsuji
Original assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd.
Priority date: 2022-01-12
Filing date: 2022-01-12
Publication date: 2023-07-20
Also published as: CN118742842A

Abstract

A display device includes an image display element(20,20a to 20d), a light guide plate(10,10a to 10d), a concave mirror(30,30a to 30d), and two or more semi-transparent mirrors(41,41a to 41d;42,42a to 42d;43,43a,43c,43d). The image display element(20,20a to 20d) is configured to emit light rays at a predetermined directivity angle(θ). The light guide plate(10,10a to 10d) includes an incident surface(11,11a to 11d) on which the light rays emitted from the image display element (20,20a to 20d) are incident, a reflecting surface(12,12a to 12d) configured to reflect the light rays injected from the incident surface(11,11a to 11d), and an outgoing surface(13,13a to 13d) facing the reflecting surface(12,12a to 12d) to emit the light rays to an outside. The concave mirror(30,30a to 30d) is configured to reflect the light rays reflected by the reflecting surface(12,12a to 12d) as parallel light. The two or more semi-transparent mirrors(41,41a to 41d;42,42a to 42d;43,43a,43c,43d) are configured to transmit a part of the parallel light reflected by the concave mirror(30,30a to 30d) and to reflect a remainder of the parallel light to emit the remainder from the light guide plate(10,10a to 10d) to the outside, the semi-transparent mirrors(41,41a to 41d;42,42a to 42d;43,43a,43c,43d) being arranged side by side in a traveling direction of the parallel light inside the light guide plate(10,10a to 10d). The concave mirror(30,30a to 30d) reflects the light rays reflected by the reflecting surface(12,12a to 12d) to be incident on a semi-transparent mirror(41,41a to 41d) closest to the concave mirror(30,30a to 30d) among the two or more semi-transparent mirrors(41,41a to 41d;42,42a to 42d;43,43a,43c,43d).

Description

DISPLAY DEVICE

TECHNICAL FIELD

The present invention relates to a display device.

BACKGROUND

In recent years, there have been developed augmented reality (AR) glasses that are a display device configured to superimpose and display a virtual reality image as a virtual image on an actual world by wearing a glasses-type device on eyes. In general, AR glasses are configured to include an image display element (display) configured to emit image light, a collimating optical system configured to convert the image light into parallel light (collimated light) , and a light guide plate configured to repeatedly guide the total reflection of the parallel light. Then, as a structure that takes out the light rays guided inside the light guide plate to the outside to emit them toward human eyes, so as to expand an eye box in a light guide direction of the light rays. Herein, the eye box means a positional range of human eyes in which a virtual image consisting of the light rays emitted from the light guide plate can be correctly observed as an image. There is a problem that the structure requires a collimating optical system and thus it is difficult to downsize AR glasses.

SUMMARY

[Problem to be Solved by the Invention]

Because the structure requires a collimating optical system and thus it is difficult to downsize AR glasses.

The present invention has been made in view of the above-described problem, and an object of the present invention is to provide a display device that can expand an eye box and suppress the size.

[Means for Solving Problem]

To solve the problem described above and achieve the object, a display device according to one embodiment includes an image display element, a light guide plate, a concave mirror, and two or more semi-transparent mirrors. The image display element is configured to emit light rays at a predetermined directivity angle. The light guide plate includes an incident surface on which the light rays emitted from the image display element are incident, a reflecting surface configured to reflect the light rays injected from the incident surface, and an outgoing surface facing the reflecting surface to emit the light rays to an outside. The concave mirror is configured to reflect the light rays reflected by the reflecting surface as parallel light. The two or more semi-transparent mirrors are configured to transmit a part of the parallel light reflected by the concave mirror and to reflect a remainder of the parallel light to emit the remainder from the light guide plate to the outside, the semi-transparent mirrors being arranged side by side in a traveling direction of the parallel light inside the light guide plate. The concave mirror reflects the light rays reflected by the reflecting surface to be incident on a semi-transparent mirror closest to the concave mirror among the two or more semi-transparent mirrors.

[Effect of the Invention]

According to the present invention, it is possible to suppress the disappearance of light rays to be guided, expand the eye box, and suppress the size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a general configuration of conventional AR glasses;

FIG. 2 is a diagram illustrating an example of a configuration of AR glasses according to an embodiment;

FIG. 3 is a diagram explaining behavior of light rays in the AR glasses according to the embodiment;

FIG. 4 is a diagram three-dimensionally illustrating behavior of light rays in the AR glasses according to the embodiment;

FIG. 5 is a diagram explaining that the AR glasses can be worn while wearing glasses according to the embodiment;

FIG. 6 is a diagram explaining a configuration and a ray movement of semi-transparent mirrors and λ/4 of the AR glasses according to the embodiment;

FIG. 7 is a diagram illustrating a configuration of AR glasses according to Example 1;

FIG. 8 is a diagram illustrating distortion aberration of the AR glasses according to Example 1;

FIG. 9 is a diagram illustrating a configuration of AR glasses according to Example 2;

FIG. 10 is a diagram illustrating distortion aberration of the AR glasses according to Example 2;

FIG. 11 is a diagram illustrating a configuration of AR glasses according to Example 3;

FIG. 12 is a diagram illustrating distortion aberration of the AR glasses according to Example 3;

FIG. 13 is a diagram illustrating a configuration of AR glasses according to Example 4;

FIG. 14 is a diagram illustrating distortion aberration of the AR glasses according to Example 4;

FIG. 15 is a diagram illustrating an eye box of the AR glasses according to Example 4; and

FIG. 16 is a diagram illustrating an example of a configuration that two or more AR glasses are arranged to expand a viewing angle according to Example 4.

DETAILED DESCRIPTION

Hereinafter, an embodiment of a display device according to the present invention will be described in detail with reference to the accompanying drawings. Moreover, the present invention is not limited to the following embodiment, and components in the following embodiment include ones easily conceived by those skilled in the art, substantially the same ones, and so-called equivalents. Furthermore, various omissions, substitutions, changes, and combinations of the components can be made without departing from the spirit of the following embodiment.

(Configuration of Conventional AR glasses)

FIG. 1 is a diagram illustrating an example of a general configuration of conventional AR glasses 500. A configuration of the conventional general AR glasses 500 will be described with reference to FIG. 1.

As illustrated in FIG. 1, the AR glasses 500 includes a light guide plate 100, an image display element 200, a collimating optical system 201, and semi-transparent mirrors 401 to 404.

The image display element 200 is a device configured to emit image light (hereinafter, may be simply referred to as light rays) of an image that is the basis of a virtual image to be displayed through the collimating optical system 201 and the light guide plate 100. The image display element 200 may employ various display elements such as an organic light emitting diode (OLED) and a liquid crystal display device, for example. It should be noted that the image display element 200 may employ, if it can display information such as an image, a digital mirror device (DMD) , which is a microelectromechanical systems (MEMS) device in which many micro mirror surfaces (micro-mirrors) are arranged on a plane, a liquid crystal on silicon (LCOS) , a laser display module that is obtained by combining a laser light source and MEMS to be able to display images by scanning and projecting, or the like, for example.

The collimating optical system 201 is an optical system that includes one or more optical lenses, diaphragms, and the like and is configured to convert an angle of image light emitted from the image display element 200 into a direction according to each pixel of the image display element 200 and to convert the image light into parallel light.

The light guide plate 100 is a light guide configured to guide light rays converted into parallel light by the collimating optical system 201 to emit them toward eyes E of a user. The light guide plate 100 includes an incident surface 101 and an outgoing surface 103.

The incident surface 101 is a surface on which the light rays converted into parallel light by the collimating optical system 201 are incident. The incident surface 101 is formed to be a surface inclined by a predetermined angle with respect to a surface perpendicular to the outgoing surface 103 in order to inject the light rays converted into parallel light by the collimating optical system 201 to guide them into the light guide plate 100. The light rays that are image light injected from the incident surface 101 are guided inside the light guide plate 100 and reach the semi-transparent mirrors 401 to 404 while repeating total reflection on the outgoing surface 103 and a surface facing the outgoing surface 103.

The outgoing surface 103 is a surface through which the light rays guided inside the light guide plate 100 are emitted toward the eyes E of the user by reflection on the semi-transparent mirrors 401 to 404.

The semi-transparent mirrors 401 to 404 are optical members configured to transmit some of the light rays guided inside the light guide plate 100 and to reflect a remainder. Moreover, the semi-transparent mirrors 401 to 404 are arranged side by side in the light guide direction of the light rays inside the light guide plate 100 so that their reflecting surfaces have a predetermined angle (e.g., 45°) with respect to the outgoing surface 103. Moreover, in sequence from one close to the incident surface 101, the semi-transparent mirrors are the semi-transparent mirror 401, the semi-transparent mirror 402, the semi-transparent mirror 403, and the semi-transparent mirror 404. As described above, by arranging the plurality of semi-transparent mirrors like the semi-transparent mirrors 401 to 404, an eye box EB10 is expanded in the light guide direction (left-right direction in FIG. 1) of the light rays. It should be noted that the eye box EB10 can be expanded as well even if a diffractive optical element (DOE) , a holographic optical element (HOE) , or the like is applied instead of the semi-transparent mirrors 401 to 404.

However, the configuration of the AR glasses 500 described above has a problem that the collimating optical system 201 configured to make image light emitted from the image display element 200 parallel light is required and thus the overall size of the AR glasses 500 becomes large and the weight increases. Moreover, the configuration also has a problem that, because the light rays incident on the light guide plate 100 are guided by repeating the total reflection inside the light guide plate 100, the total reflection is not performed at an accurate angle due to the scattering etc. of the light rays if the surface accuracy of the light guide plate 100 is bad and thus more errors occur that much as the number of total reflections is larger so as not to be able to correctly recognize an image. In the following embodiment, a configuration of AR glasses solving these problems will be described in detail.

(Configuration of AR glasses according to Embodiment)

FIG. 2 is a diagram illustrating an example of a configuration of AR glasses 1 according to an embodiment. A configuration of the AR glasses 1 according to the present embodiment will be described with reference to FIG. 2.

As illustrated in FIG. 2, the AR glasses 1 according to the present embodiment includes a light guide plate 10, an image display element 20, a concave mirror 30, a semi-transparent mirrors 41 (first semi-transparent mirror) , a semi-transparent mirror 42 (second semi-transparent mirror) , and a semi-transparent mirror 43 (third semi-transparent mirror) .

The light guide plate 10 is a light guide configured to guide image light (hereinafter, may be simply referred to as light rays) , which is emitted from the image display element 20 and is incident on the light guide plate 10, and to emit the light rays toward eyes of a user. The light guide plate 10 includes an incident surface 11, a reflecting surface 12, and an outgoing surface 13.

The incident surface 11 is a surface on which the image light emitted from the image display element 20 is incident. The incident surface 11 is formed to be a surface inclined by a predetermined angle (e.g., 70°) with respect to the outgoing surface 13 (or the reflecting surface 12) , in order to cause light rays that are the image light emitted from the image display element 20 to be incident thereon and to guide them inside the light guide plate 10. The image light injected from the incident surface 11 heads for the reflecting surface 12.

The reflecting surface 12 is a surface that totally reflects the light rays injected from the incident surface 11. The reflecting surface 12 is a surface that faces the outgoing surface 13 located at the eye side of the user. In other words, the reflecting surface 12 is located on the opposite side of the position of the eyes of the user who wears the AR glasses 1 with reference to the outgoing surface 13. The light rays totally reflected by the reflecting surface 12 heads for the concave mirror 30.

The outgoing surface 13 is a surface that emits the light rays toward the eyes of the user after the light rays guided inside the light guide plate 10 are reflected by the semi-transparent mirrors 41 to 43.

The image display element 20 is a device configured to emit image light of an image that is the basis of a virtual image to be displayed through the light guide plate 10. The image display element 20 may employ various display elements such as an organic light emitting diode (OLED) and a liquid crystal display device, for example. It should be noted that the image display element 20 may employ, if it can display information such as an image, DMD, which is a MEMS device in which many micro mirror surfaces (micro-mirrors) are arranged on a plane, LCOS, a laser display module, or the like, for example. As illustrated in FIG. 2, the image display element 20 is arranged so that an outgoing surface (display surface) of image light departs from the incident surface 11 by a predetermined distance and becomes parallel to the incident surface 11. It should be noted that the image display element 20 may shift R (red) , G (green) , and B (blue) images on the outgoing surface (display surface) to emit each image light so as to correct color separation by a prism effect due to the light guide plate 10. In particular, when the light guide plate 10 is made of materials whose Abbe number is low and dispersibility is high, there is an effect of suppressing the color separation of a virtual image.

The concave mirror 30 is formed inside the light guide plate 10 and has an action concentrating the light rays totally reflected by the reflecting surface 12. The reflecting surface of the concave mirror 30 is an aspheric surface that has a shape represented by the following Equation (1) , for example.

Herein, the meanings of characters in Equation (1) are as follows.

z: a sag amount with respect to a direction parallel to an optical axis of the concave mirror 30;

c: a curvature at a surface vertex;

k: a conic coefficient;

A, B, C, D, E, F, G, H, J: deformation coefficients of fourth, sixth, eighth, tenth, twelfth, 14th, 16th, 18th, and 20th (e.g., A=B=C=D=E=F=G=H=J=0 in case of pure conic surface) ; and

r:a distance (expressed by the following Equation (2) ) in a radial direction.

The light rays reflected by the concave mirror 30 are concentrated to be parallel light. Herein, the image light emitted from a specific pixel of the image display element 20 becomes light rays having a predetermined directivity angle as described later in FIG. 3. The light rays having the directivity angle are totally reflected by the reflecting surface 12, become parallel light due to a concentrating effect of reflection on the concave mirror 30, and head for the semi-transparent mirror 41 closest to the concave mirror 30. Moreover, the light rays that become parallel light by the concave mirror 30 are emitted from the outgoing surface 13 as parallel light even after being reflected by the semi-transparent mirrors 41 to 43. It should be noted that the parallel light reflected by the concave mirror 30 does not mean only strict parallel light and includes light rays that can be regarded as parallel light.

It should be noted that a direction (i.e., a direction in which the image light emitted from the image display element 20 is guided) from the image display element 20 to the concave mirror 30, and a direction parallel to the reflecting surface 12 and the outgoing surface 13 are a y direction (y-axis) in FIG. 2. The y direction corresponds to an up-down direction. Moreover, a direction orthogonal to the y-axis and orthogonal to the reflecting surface 12 and the outgoing surface 13 is a z direction (z-axis) , and a direction orthogonal to the y-axis and the z-axis and parallel to the reflecting surface 12 and the outgoing surface 13 is an x direction (x-axis) . The z direction corresponds to a depth direction, and the x direction corresponds to a horizontal direction.

The semi-transparent mirrors 41 to 43 are an optical member configured to transmit some of light rays that are parallel light reflected by the concave mirror 30 and to reflect a remainder. Moreover, the semi-transparent mirrors 41 to 43 are arranged side by side in the traveling direction of parallel light reflected by the concave mirror 30 at positions close to the outgoing surface 13 inside the light guide plate 10 so that their reflecting surfaces have a predetermined angle (e.g., 45°) with respect to the outgoing surface 13. In other words, the semi-transparent mirrors 41 to 43 are arranged so that their reflecting surfaces become parallel to each other. Moreover, the semi-transparent mirror 41, the semi-transparent mirror 42, and the semi-transparent mirror 43 are arranged in sequence from one close to the concave mirror 30. In other words, a reflection function by the semi-transparent mirrors 41 to 43 enables to reflect light rays guided inside the light guide plate 10 and reflected by the concave mirror 30 and to emit them from the outgoing surface 13 so as to make the eyes of the user recognize them as a virtual image, and also a transmission function of the semi-transparent mirrors 41 to 43 enables to transmit light of the outside world from the reflecting surface 12 toward the outgoing surface 13 and to make the eyes of the user recognize an actual world so as to realize augmented reality (AR) .

(Behavior of Light rays in AR glasses)

FIG. 3 is a diagram explaining behavior of light rays in the AR glasses according to the embodiment. FIG. 4 is a diagram three-dimensionally illustrating behavior of the light rays in the AR glasses according to the embodiment. FIG. 5 is a diagram explaining that the AR glasses can be worn while wearing glasses according to the embodiment. The behavior of the light rays in the AR glasses 1 according to the present embodiment will be described with reference to FIGS. 3 to 5.

As illustrated in FIG. 3, image light emitted from pixels of the image display element 20 is first injected into the light guide plate 10 from the incident surface 11. Herein, the image light is emitted from the pixels of the image display element 20 in a state where diffusion is suppressed to have a predetermined directivity angle θ.

Herein, the directivity angle is an angle obtained by doubling an angle at a brightness obtained by halving a brightness on the brightest central portion. Commonly, light emitted from a pixel of OLED, a liquid crystal display device, or the like is the diffused light, but the image display element 20 of the AR glasses 1 according to the present embodiment emits image light in a state (semi-collimated state) where diffusion is suppressed to be "directivity angle θ<8°" . A method of suppressing diffusion of light rays emitted from pixels of the image display element 20 includes, for example, a method of concentrating light by providing micro-lenses on the exit sides of R (red) , G (green) , and B (blue) color filters provided at each pixel, a method of physically suppressing diffusion by providing physical partition plates at boundaries between pixels, and the like. As described above, by emitting the image light from pixels of the image display element 20 in a state where diffusion is suppressed to be "directivity angle θ<8°" , the image light can be totally reflected by the intended part of the reflecting surface 12, and collision of the light rays against an end 43EG close to the reflecting surface 12 of the semi-transparent mirror 43 located closest to the incident surface 11 can be avoided to suppress the occurrence of loss of the light rays.

Then, the light rays (image light) injected into the light guide plate 10 from the incident surface 11 head for the reflecting surface 12 and are totally reflected by the reflecting surface 12. The light rays totally reflected by the reflecting surface 12 head for the concave mirror 30. Herein, because the directivity angle θ of the image light emitted from the image display element 20 is suppressed to be small and thus the light rays totally reflected by the reflecting surface 12 head for the concave mirror 30 in a state where the width of a light beam becomes narrow, collision against an end 41EG close to the reflecting surface 12 of the semi-transparent mirror 41 located closest to the concave mirror 30 can be avoided. As a result, it is possible to suppress the occurrence of loss of the light rays.

Until the bundle of the light rays injected from the incident surface 11 is guided up to the concave mirror 30, the number of total reflections is only once of the total reflection on the reflecting surface 12. As a result, it is possible to suppress the occurrence of loss of the light rays due to the scattering etc. of the light rays caused by the repetition of total reflection and to suppress the accumulation of errors of a reflection angle caused by the repetition of total reflection. In other words, there is a problem that the total reflection is not performed at an accurate angle due to the scattering etc. of the light rays if the surface accuracy of the light guide plate is bad and thus more errors occur that much as the number of total reflections is larger so as not to be able to correctly recognize an image, but the problem can be solved in the present embodiment because the total reflection is performed only once.

Then, the light rays totally reflected by the reflecting surface 12 become parallel light by a concentrating action described above when being reflected by the concave mirror 30. In other words, because the concentrating action (conversion to parallel light) of the collimating optical system included in the conventional AR glasses (e.g., the AR glasses 500 illustrated in FIG. 1) can be replace by a concentrating action by reflection on the concave mirror 30, the AR glasses 1 according to the present embodiment does not require the collimating optical system. In other words, the AR glasses 1 have a configuration that the image display element 20 is arranged outside of the light guide plate 10. As a result, it is possible to reduce the overall size of the AR glasses 1 and to reduce weight.

Then, light rays that become parallel light by reflection on the concave mirror 30 directly reach the semi-transparent mirror 41. Among the light rays incident on the semi-transparent mirror 41, some are reflected and head for the outgoing surface 103, and a remainder passes through the semi-transparent mirror 41 and heads for the semi-transparent mirror 42. Among the light rays incident on the semi-transparent mirror 42, some are reflected and head for the outgoing surface 103, and a remainder passes through the semi-transparent mirror 42 and heads for the semi-transparent mirror 43. By properties of a quarter-wave plate and a polarized dielectric multilayer film to be described later, the light rays incident on the semi-transparent mirror 43 are reflected by the semi-transparent mirror 43 and head for the outgoing surface 103, and the transmission of the semi-transparent mirror 43 is suppressed. As described above, because the light rays reflected by the concave mirror 30 head for the semi-transparent mirror 41 and the light rays passing through all the semi-transparent mirrors 41 to 43 are suppressed, it is possible to suppress the occurrence of loss of the light rays.

Then, the light rays reflected by the semi-transparent mirrors 41 to 43 are emitted from the outgoing surface 13 toward the eyes E of the user. Moreover, because the light rays become parallel light by reflection on the concave mirror 30, the light rays to be reflected by the semi-transparent mirrors 41 to 43 become also parallel light. It should be noted that parallel light reflected by the semi-transparent mirrors 41 to 43 does not mean only strict parallel light and includes light rays that can be regarded as parallel light.

As described above, because a plurality of semi-transparent mirrors such as the semi-transparent mirrors 41 to 43 are arranged side by side in the y direction, an eye box EB formed by the AR glasses 1 can be expanded in the y direction as illustrated in FIG. 3. Herein, a perspective view of the AR glasses 1 is illustrated in FIG. 4. Because the eye box EB is also expanded in the z direction that is the depth direction and an exit pupil is expanded by the expansion of the eye box EB in the y direction, a degree of freedom of a position of an eye point EPT indicating the position of the eyes E of the user is improved. Moreover, because the AR glasses do not have a configuration that light rays are emitted to the outside by a pin mirror, it is possible to suppress the disappearance of light rays. It should be noted that the example of the AR glasses 1 illustrated in FIGS. 2 to 4 has a configuration that three semi-transparent mirrors such as the semi-transparent mirrors 41 to 43 are arranged but the present embodiment is not limited to this. The AR glasses may have a configuration that two semi-transparent mirrors are arranged as far as the expansion of the desired eye box EB can be realized.

The AR glasses 1 according to the present embodiment requires to make the eyes E of the user recognize the image light emitted from the image display element 20 as a virtual image and recognize light from the outside world passing through the light guide plate 10 as described above. In other words, commonly, the user who wears glasses cannot remove the glasses to clearly recognize light (image) from the outside world even when the user wears the AR glasses 1 according to the present embodiment to enjoy an AR function. As described above, in the AR glasses 1 according to the present embodiment, the eye box EB is expanded in the y direction by stacking semi-transparent mirrors and the eye box is also expanded in the depth direction (z direction) . Moreover, because the display surface of the image display element 20 has the width of the x direction larger than the width of the z direction and thus the eye box EB is expanded in the x direction, the user can wear the AR glasses 1 in a state where glasses GL are worn as illustrated in FIG. 5.

It should be noted that, in the example illustrated in FIGS. 2 and 3, the reflecting surface 12 is located on the opposite side of the position of the eyes E of the user who wears the AR glasses 1 with reference to the outgoing surface 13, but the present embodiment is not limited to this. For example, the positions of the reflecting surface 12 and the outgoing surface 13 on which the semi-transparent mirrors 41 to 43 are arranged may be reversed so that the outgoing surface 13 is located on the opposite side of the eyes E of the user who wears the AR glasses 1 with reference to the reflecting surface 12. In this case, the image light emitted from the image display element 20 is totally reflected by the reflecting surface 12 located on the eyes E side, and the light rays reflected by the semi-transparent mirrors 41 to 43 arranged on the outgoing surface 13 side pass through the inside of the light guide plate 10 and are emitted from the reflecting surface 12 located on the eyes E side toward the outside (the eyes E) .

(Peripheral Configuration of Semi-transparent mirrors)

FIG. 6 is a diagram explaining a configuration and a ray movement of the semi-transparent mirrors and λ/4 of the AR glasses according to the embodiment. A peripheral configuration of the semi-transparent mirrors 41 to 43 of the AR glasses 1 according to the present embodiment will be described with reference to FIG. 6.

As illustrated in FIG. 6, the AR glasses 1 according to the present embodiment further includes a quarter-wave plate 52a (first quarter-wave plate) , a quarter-wave plate 52b (second quarter-wave plate) , and a quarter-wave plate 53a (third quarter-wave plate) . The quarter-wave plate 52a is arranged on the semi-transparent mirror 41 side of the semi-transparent mirror 42 and is parallel to the surface of the semi-transparent mirrors 42. The quarter-wave plate 52b is arranged on the semi-transparent mirror 43 side of the semi-transparent mirror 42 and is parallel to the surface of the semi-transparent mirror 42. The quarter-wave plate 53a is arranged on the semi-transparent mirror 42 side of the semi-transparent mirror 43 and is parallel to the surface of the semi-transparent mirror 43.

The quarter-

wave plates

52a, 52b, and 53a are phase plates configured to provide a phase difference π/2 (90°) to the transmitted light rays. For example, the quarter-

wave plates

52a, 52b, and 53a convert linearly-polarized light rays into circularly-polarized light rays, and convert circularly-polarized light rays into linearly-polarized light rays. Moreover, the quarter-

wave plates

52a, 52b, and 53a convert the S polarization component of the light rays into clockwise circularly-polarized light rays, and convert the P polarization component of the light rays into counterclockwise circularly-polarized light rays. It should be noted that the quarter-

wave plates

52a, 52b, and 53a are preferably made of inorganic glass material instead of a film material to increase the surface accuracy.

The semi-transparent mirror 41 is provided with an unpolarized dielectric multilayer film (example of unpolarized film) , and transmits some of the incident light rays and reflects a remainder without changing a polarized state of the light rays. The semi-transparent mirrors 42 and 43 are provided with a polarized separation dielectric multilayer film (example of polarized separation film) , and reflect the S polarization component of the incident light rays and transmit the P polarization component. For example, the quarter-

wave plates

52a, 52b, and 53a are made of crystal, and these configurations are established if two pieces of crystal are provided and an unpolarized dielectric multilayer film or a polarized separation dielectric multilayer film is formed on one surface of the crystal.

An operation of light rays in a configuration of the semi-transparent mirrors 41 to 43 and the quarter-

wave plates

52a, 52b, and 53a as described above will be described with reference to FIG. 6. In FIG. 6, FIG. 6 (a) is a diagram explaining behavior of light rays incident on a substantially central portion of the semi-transparent mirror 41 among light rays reflected by the concave mirror 30. FIG. 6 (b) is a diagram explaining behavior of light rays incident on a portion close to the outgoing surface 13 of the semi-transparent mirror 41 among the light rays reflected by the concave mirror 30. FIG. 6 (c) is a diagram explaining behavior of light rays incident on a portion close to the reflecting surface 12 of the semi-transparent mirror 41 among the light rays reflected by the concave mirror 30.

As illustrated in FIG. 6 (a) , among the light rays reflected by the concave mirror 30, some of the light rays incident on the substantially central portion of the semi-transparent mirror 41 are reflected by the semi-transparent mirror 41 and is emitted from the outgoing surface 13 to the outside, and a remainder passes through it and heads for the semi-transparent mirror 42. In this case, the light rays reflected by and transmitted through the semi-transparent mirror 41 are not changed into a polarized state. Moreover, because the light rays transmitted through the semi-transparent mirror 41 pass through the quarter-wave plate 52a but only the phase of the unpolarized light rays is changed, the transmitted light rays are incident on the semi-transparent mirror 42 in the unpolarized state. Among the light rays incident on the semi-transparent mirror 42, light rays of the S polarization component, for example, are reflected by the semi-transparent mirror 42 and again head for the quarter-wave plate 52a, and are converted into, for example, clockwise circularly-polarized light rays by the quarter-wave plate 52a and are emitted from the outgoing surface 13 to the outside. On the other hand, among the light rays incident on the semi-transparent mirror 42, light rays of the P polarization component pass through the semi-transparent mirror 42, are converted into counterclockwise circularly-polarized light rays by the quarter-wave plate 52b, and head for the semi-transparent mirror 43. Then, the counterclockwise circularly-polarized light rays transmitted through the quarter-wave plate 52b are converted by the quarter-wave plate 53a into S-polarized light rays that are linear polarization, and are incident on the semi-transparent mirror 43. Because the S-polarized light rays incident on the semi-transparent mirror 43 do not include the P polarization component, all the S-polarized light rays are reflected by the semi-transparent mirror 43 and again head for the quarter-wave plate 53a, and are converted into the clockwise circularly-polarized light rays by the quarter-wave plate 53a and are emitted from the outgoing surface 13 to the outside.

As illustrated in FIG. 6 (b) , among the light rays reflected by the concave mirror 30, some of light rays incident on a portion close to the outgoing surface 13 of the semi-transparent mirror 41 are reflected by the semi-transparent mirror 41 and are emitted from the outgoing surface 13 to the outside, and a remainder passes through it and heads for the semi-transparent mirror 42. In this case, the light rays reflected by and transmitted through the semi-transparent mirror 41 are not changed into a polarized state. Moreover, because the light rays transmitted through the semi-transparent mirror 41 pass through the quarter-wave plate 52a but only the phase of the unpolarized light rays is changed, the transmitted light rays are incident on the semi-transparent mirror 42 in the unpolarized state. Among the light rays incident on the semi-transparent mirror 42, the light rays of the S polarization component are reflected by the semi-transparent mirror 42 and are emitted from the outgoing surface 13 to the outside. On the other hand, among the light rays incident on the semi-transparent mirror 42, the light rays of the P polarization component pass through the semi-transparent mirror 42, are converted into counterclockwise circularly-polarized light rays by the quarter-wave plate 52b, and head for the semi-transparent mirror 43. Then, the counterclockwise circularly-polarized light rays transmitted through the quarter-wave plate 52b are converted by the quarter-wave plate 53a into the S-polarized light rays that are linear polarization, and are incident on the semi-transparent mirror 43. Because the S-polarized light rays incident on the semi-transparent mirror 43 do not include the P polarization component, all the S-polarized light rays are reflected by the semi-transparent mirror 43 and are emitted from the outgoing surface 13 to the outside.

As illustrated in FIG. 6 (c) , among the light rays reflected by the concave mirror 30, some of light rays incident on a portion close to the reflecting surface 12 of the semi-transparent mirror 41 are reflected by the semi-transparent mirror 41 and are emitted from the outgoing surface 13 to the outside, a remainder passes through it and heads for the semi-transparent mirror 42. In this case, light rays reflected by and transmitted through the semi-transparent mirror 41 are not changed into a polarized state. Moreover, because light rays transmitted through the semi-transparent mirror 41 pass through the quarter-wave plate 52a but only the phase of the unpolarized light rays is changed, the transmitted light rays are incident on the semi-transparent mirror 42 in the unpolarized state. Among the light rays incident on the semi-transparent mirror 42, light rays of the S polarization component are reflected by the semi-transparent mirror 42, again head for the quarter-wave plate 52a, and are converted into clockwise circularly-polarized light rays by the quarter-wave plate 52a. The clockwise circularly-polarized light rays converted by the quarter-wave plate 52a again head for the semi-transparent mirror 41. Some of the clockwise circularly-polarized light rays again incident on the semi-transparent mirror 41 pass through the semi-transparent mirror 41 and are emitted from the outgoing surface 13 to the outside, and a remainder is reflected to be counterclockwise circularly-polarized light rays and heads for the semi-transparent mirror 42. The counterclockwise circularly-polarized light rays reflected by the semi-transparent mirror 41 are converted into S-polarized light rays that are linear polarization by the quarter-wave plate 52a, and are incident on the semi-transparent mirror 42. Because the S-polarized light rays incident on the semi-transparent mirror 42 do not include the P polarization component, all the S-polarized light rays are reflected by the semi-transparent mirror 42 and are emitted from the outgoing surface 13 to the outside.

On the other hand, among the light rays that pass through the semi-transparent mirror 41 and are incident on the semi-transparent mirror 42, the light rays of the P polarization component pass through the semi-transparent mirror 42, are converted into counterclockwise circularly-polarized light rays by the quarter-wave plate 52b, and head for the semi-transparent mirror 43. Then, the counterclockwise circularly-polarized light rays transmitted through the quarter-wave plate 52b are converted into S-polarized light rays that are linear polarization by the quarter-wave plate 53a, and are incident on the semi-transparent mirror 43. Because the S-polarized light rays incident on the semi-transparent mirror 43 do not include the P polarization component, all the S-polarized light rays are reflected by the semi-transparent mirror 43, again head for the quarter-wave plate 53a, are converted into clockwise circularly-polarized light rays by the quarter-wave plate 53a, and again head for the semi-transparent mirror 42. The clockwise circularly-polarized light rays that again head for the semi-transparent mirror 42 are converted into P-polarized light rays by the quarter-wave plate 52b, and are incident on the semi- transparent mirror 42. Because the P-polarized light rays incident on the semi-transparent mirror 42 do not include the S polarization component, all the P-polarized light rays pass through the semi-transparent mirror 42, are converted into counterclockwise circularly-polarized light rays by the quarter-wave plate 52a, and are emitted from the outgoing surface 13 to the outside.

As described above, according to the configuration of the semi-transparent mirrors 41 to 43 and the quarter-

wave plates

52a, 52b, and 53a, the light rays reflected by the concave mirror 30 are reflected by any of the semi-transparent mirrors 41 to 43 to be emitted from the outgoing surface 13, and do not pass through the semi-transparent mirror 43. Therefore, because light rays transmitted through the semi-transparent mirror 43 are suppressed, it is possible to suppress the occurrence of loss of the light rays.

As described above, the AR glasses 1 according to the present embodiment includes: the image display element 20 configured to emit light rays at the predetermined directivity angle θfrom pixels; the light guide plate 10 including the incident surface 11 on which the light rays emitted from the image display element 20 are incident, the reflecting surface 12 configured to totally reflect a bundle of the light rays injected from the incident surface 11 only once, and the outgoing surface 13 facing the reflecting surface 12 to emit the light rays to the outside; the concave mirror 30 configured to reflect the light rays totally reflected by the reflecting surface 12 as parallel light; and the semi-transparent mirrors 41 to 43 configured to transmit a part of parallel light reflected by the concave mirror 30 and to reflect a remainder of the parallel light to emit the remainder from the outgoing surface 13 to the outside, the semi-transparent mirrors being arranged side by side in the traveling direction of the parallel light inside the light guide plate 10. The concave mirror 30 reflects the light rays totally reflected by the reflecting surface 12 to be incident on the semi-transparent mirror 41 closest to the concave mirror 30 among the semi-transparent mirrors 41 to 43. As described above, because the number of total reflections is only once of the total reflection on the reflecting surface 12 until the bundle of the light rays injected from the incident surface 11 is guided up to the concave mirror 30, it is possible to suppress the occurrence of loss of light rays due to the scattering etc. of the light rays caused by the repetition of the total reflection and to suppress the accumulation of errors of a reflection angle caused by the repetition of the total reflection. Moreover, because the semi-transparent mirrors 41 to 43 arranged side by side in the traveling direction of the parallel light inside the light guide plate 10 are included, the eye box can be expanded. Furthermore, because the AR glasses 1 do not include a collimating optical system included in the conventional AR glasses but include the concave mirror 30 to replace a function of the collimating optical system, it is possible to reduce the overall size of the AR glasses 1 and to reduce weight. Therefore, according to the configuration of the AR glasses 1 of the present embodiment, it is possible to suppress the disappearance of light rays to be guided, to expand the eye box, and to suppress the size.

Moreover, the AR glasses 1 according to the present embodiment has the directivity angle θless than 8°. As described above, by emitting image light from pixels of the image display element 20 in a state where diffusion is suppressed, it is possible to totally reflect the image light on the intended part of the reflecting surface 12 and thus to suppress the occurrence of loss of the light rays.

Moreover, in the AR glasses 1 according to the present embodiment, the semi-transparent mirrors 41 to 43 are arranged on the outgoing surface 13 side inside the light guide plate 10, the image display element 20 emits light rays toward the reflecting surface 12 so as not to collide against the end 43EG close to the reflecting surface 12 of the semi-transparent mirror 43 closest to the incident surface 11 among the semi-transparent mirrors 41 to 43, and the reflecting surface 12 totally reflects the light rays so as not to collide against the end 41EG close to the reflecting surface 12 of the semi-transparent mirror 41 closest to the concave mirror 30 among the semi-transparent mirrors 41 to 43. As a result, it is possible to suppress the occurrence of loss of the light rays.

Moreover, in the AR glasses 1 according to the present embodiment, among the semi-transparent mirrors 41 to 43, the semi-transparent mirror 41 closest to the concave mirror 30 is provided with an unpolarized dielectric multilayer film, and the semi-transparent mirror 42 arranged next to the semi-transparent mirror 41 and the semi-transparent mirror 43 closest to the incident surface 11 are provided with a polarized separation dielectric multilayer film configured to reflect the S polarization component of the incident light rays and to transmit the P polarization component. The AR glasses 1 further includes the quarter-wave plate 52a arranged on the semi-transparent mirror 41 side of the semi-transparent mirror 42, the quarter-wave plate 52b arranged on the semi-transparent mirror 43 side of the semi-transparent mirror 42, and the quarter-wave plate 53a arranged on the semi-transparent mirror 42 side of the semi-transparent mirror 43. As a result, the light rays reflected by the concave mirror 30 are reflected by any of the semi-transparent mirrors 41 to 43 to be emitted from the outgoing surface 13, and do not pass through the semi-transparent mirror 43. Therefore, because light rays transmitted through the semi-transparent mirror 43 are suppressed, it is possible to suppress the occurrence of loss of the light rays.

Hereinafter, specific examples of the AR glasses 1 will be described by using Example 1 to Example 4.

(Example 1)

FIG. 7 is a diagram illustrating a configuration of AR glasses 1a according to Example 1. FIG. 8 is a diagram illustrating distortion aberration of the AR glasses 1a according to Example 1. The AR glasses 1a according to Example 1 will be described with reference to FIGS. 7 and 8.

The AR glasses 1a illustrated in FIG. 7 indicates a specific example in which various dimensions and angles indicated in the following Table 1 and light guide plate glass material are applied to the AR glasses 1 according to the above embodiment. A light guide plate 10a, an incident surface 11a, a reflecting surface 12a, an outgoing surface 13a, an image display element 20a, a concave mirror 30a, and semi-transparent mirrors 41a to 43a in the AR glasses 1a according to the present example respectively correspond to the light guide plate 10, the incident surface 11, the reflecting surface 12, the outgoing surface 13, the image display element 20, the concave mirror 30, and the semi-transparent mirrors 41 to 43 in the AR glasses 1 according to the above embodiment. Moreover, the concave mirror 30a is an aspherical mirror as described above.

Table 1

Name	Symbol	Value	Unit
Pupil distance	EP	15	mm
Pupil diameter	AP		3	mm
Pupil interval	APD		4	mm
Pupil interval -Pupil diameter	APD-AP	1	mm
Mirror interval	MD		4	mm
Light guide plate thickness	WGD	12.5	mm
Eye box V direction	EBV		11	mm
Eye box H direction	EBH		12	mm
Display surface interval	DD		1	mm
Display element short-side direction	DV	4.84	mm
Display element long-side direction	DH	8.85	mm
Vertical FOV	VFOV	7.5	°
Horizontal FOV	HFOV	13.3	°
Diagonal FOV	DFOV	15.3	°
Display element short-side ejection angle	VDang	4.7	°
Display element size	IMS	0.40	inch
Refractive index	RIX	1.5168	-
Abbe number	AN	64.1673	-

Among ones indicated in Table 1, a pupil distance EP is a distance from the light guide plate 10a (the outgoing surface 13a) to the position (eye point) of the eyes of the user. A pupil diameter AP is a width in the y direction (array direction of the semi-transparent mirrors 41a to 43a) by which one semi-transparent mirror of the semi-transparent mirrors 41a to 43a can be shown as an image. A pupil interval APD is an interval of images to be generated by light rays reflected by the semi-transparent mirrors, that is, an interval in the y direction between the semi-transparent mirrors, and is identical with a mirror interval MD. A difference (APD-AP) between the pupil interval APD and the pupil diameter AP indicates a width in the y direction through which light rays pass at a position of the pupil distance EP. A light guide plate thickness WGD is a thickness of the light guide plate 10a, that is, a distance between the reflecting surface 12a and the outgoing surface 13a. An eye box V direction EBV is a vertical-direction (y direction) width of an eye box formed by the AR glasses 1a. An eye box H direction EBH is a horizontal-direction (x direction) width of the eye box formed by the AR glasses 1a. A display surface interval DD is a distance, from the incident surface 11a, of the display surface (outgoing surface) of the image display element 20a. A display element short-side direction DV is a length in a short-side direction (direction from the reflecting surface 12a to the outgoing surface 13a) of the image display element 20a. A display element long-side direction DH is a length in a long-side direction (horizontal direction, x direction) of the image display element 20a. A vertical FOV (VFOV: Vertical Field Of View) is a vertical-direction (y direction) viewing angle. A horizontal FOV (HFOV: Horizontal Field Of View) is a horizontal-direction (x direction) viewing angle. A diagonal FOV (DFOV: Diagonal Filed Of View) is a viewing angle in a diagonal direction. A display element short-side ejection angle (VDang) is an ejection angle on a YZ plane of image light emitted from pixels of the image display element 20a, and corresponds to the directivity angle θ described above. A display element size IMS is a diagonal-direction length of the image display element 20a. A refractive index RIX is a refractive index of glass materials constituting the light guide plate 10a. An Abbe number AN is an Abbe number of glass materials constituting the light guide plate 10a.

By configuring the AR glasses 1a according to Table 1 described above, it is possible to suppress distortion aberration as illustrated in FIG. 8. It should be noted that the distortion aberration illustrated in FIG. 8 illustrates distortion aberration on a display surface of the image display element 20a when an image is formed by reverse tracing onto the display surface from an exit pupil side. By employing such the configuration, the AR glasses 1a has the same effect as that of the AR glasses 1 according to the above embodiment.

Moreover, because a diameter of a human pupil is about at least 2 [mm] , the user can visually recognize an image with sufficient brightness by setting "the pupil interval APD -the pupil diameter AP" to 1 [mm] or less like Table 1. Moreover, it is desirable that the pupil diameter AP is set to 2 [mm] or more that is the minimum value of the diameter of the human pupil like Table 1.

(Example 2)

FIG. 9 is a diagram illustrating a configuration of AR glasses 1b according to Example 2. FIG. 10 is a diagram illustrating distortion aberration of the AR glasses 1b according to Example 2. The AR glasses 1b according to Example 2 will be described with reference to FIGS. 9 and 10.

The AR glasses 1b illustrated in FIG. 9 indicates a specific example in which various dimensions and angles indicated in the following Table 2 and light guide plate glass material are applied to the AR glasses 1 according to the above embodiment. A light guide plate 10b, an incident surface 11b, a reflecting surface 12b, an outgoing surface 13b, an image display element 20b, and a concave mirror 30b in the AR glasses 1b according to the present example respectively correspond to the light guide plate 10, the incident surface 11, the reflecting surface 12, the outgoing surface 13, the image display element 20, and the concave mirror 30 in the AR glasses 1 according to the above embodiment. Moreover, the AR glasses 1b according to the present example include two semi-transparent mirrors (

semi-transparent mirrors

41b and 42b) , instead of the semi-transparent mirrors 41 to 43 in the AR glasses 1 described above. Moreover, the concave mirror 30b is an aspherical mirror as described above.

Table 2

Name	Symbol	Value	Unit
Pupil distance	EP	15	mm
Pupil vertical	APV	3.5	mm
Pupil horizontal	APH	8	mm
Pupil interval	APD	4.5	mm
Pupil interval -Pupil vertical	APD-APV	1	mm
Mirror interval	MD	4.5	mm
Light guide plate thickness	WGD	13.1	mm
Eye box V direction	EBV	8	mm
Eye box H direction	EBH	8	mm
Display surface interval	DD		1	mm
Display element short-side direction	DV	5.33	mm
Display element long-side direction	DH	10.99	mm
Vertical FOV	VFOV	10.0	°
Horizontal FOV	HFOV	20.0	°
Diagonal FOV	DFOV	22.5	°
Display element short-side ejection angle	VDang	6.6	°
Display element size	IMS	0.48	inch
Refractive index	RIX	1.923	-
Abbe number	AN	20.88	-

The meanings of various dimensions and angles indicated in Table 2 and the light guide plate glass material are similar to those of Table 1 described above, but a pupil vertical APV and a pupil horizontal APH are prescribed in Table 2 instead of the pupil diameter AP of Table 1 and a difference (APD-APV) between the pupil interval APD and the pupil vertical APV is prescribed in Table 2 instead of the difference (APD-AP) between the pupil interval APD and the pupil diameter AP of Table 1. The pupil vertical APV is a width in the y direction (vertical direction, array direction of the

semi-transparent mirrors

41b and 42b) by which one semi-transparent mirror of the

semi-transparent mirrors

41b and 42b can be shown as an image. The pupil horizontal APH is a width in the x direction (horizontal direction) by which one semi-transparent mirror of the

semi-transparent mirrors

41b and 42b can be shown as an image.

By configuring the AR glasses 1b according to Table 2 described above, it is possible to suppress distortion aberration as illustrated in FIG. 10. It should be noted that the distortion aberration illustrated in FIG. 10 illustrates distortion aberration on a display surface of the image display element 20b when an image is formed by reverse tracing onto the display surface from the exit pupil side. By employing such the configuration, the AR glasses 1b has the same effect as that of the AR glasses 1 according to the above embodiment.

Moreover, because the diameter of the human pupil is about at least 2 [mm] , the user can visually recognize an image with sufficient brightness by setting "the pupil interval APD -the pupil vertical APV" to 1 [mm] or less like Table 2. Moreover, it is desirable that the pupil vertical APV is set to 2 [mm] or more that is the minimum value of the diameter of the human pupil like Table 2.

(Example 3)

FIG. 11 is a diagram illustrating a configuration of AR glasses 1c according to Example 3. FIG. 12 is a diagram illustrating distortion aberration of the AR glasses 1c according to Example 3. The AR glasses 1c according to Example 3 will be described with reference to FIGS. 11 and 12.

The AR glasses 1c illustrated in FIG. 11 indicates a specific example in which various dimensions and angles indicated in the following Table 3 and light guide plate glass material are applied to the AR glasses 1 according to the above embodiment. A light guide plate 10c, an incident surface 11c, a reflecting surface 12c, an outgoing surface 13c, an image display element 20c, a concave mirror 30c, and semi-transparent mirrors 41c to 43c in the AR glasses 1c according to the present example respectively correspond to the light guide plate 10, the incident surface 11, the reflecting surface 12, the outgoing surface 13, the image display element 20, the concave mirror 30, and the semi-transparent mirrors 41 to 43 in the AR glasses 1 according to the above embodiment. Moreover, the concave mirror 30c is an aspherical mirror as described above.

Table 3

Name	Symbol	Value	Unit
Pupil distance	EP	15	mm
Pupil vertical	APV	2.5	mm
Pupil horizontal	APH	8	mm
Pupil interval	APD		3	mm
Pupil interval -Pupil vertical	APD-APV	0.5	mm
Mirror interval	MD		3	mm
Light guide plate thickness	WGD	8.8	mm
Eye box V direction	EBV	8.5	mm
Eye box H direction	EBH	8	mm
Display surface interval	DD		1	mm
Display element short-side direction	DV	3.13	mm
Display element long-side direction	DH	12.55	mm
Vertical FOV	VFOV	6.0	°
Horizontal FOV	HFOV	24.0	°
Diagonal FOV	DFOV	24.8	°
Display element short-side ejection angle	VDang	4.8	°
Display element size	IMS	0.51	inch
Refractive index	RIX	1.923	-
Abbe number	AN	20.88	-

The meanings of various dimensions and angles indicated in Table 3 and the light guide plate glass material are similar to those of Table 2 described above.

By configuring the AR glasses 1c according to Table 3 described above, it is possible to suppress distortion aberration as illustrated in FIG. 12. It should be noted that the distortion aberration illustrated in FIG. 12 illustrates distortion aberration on a display surface of the image display element 20c when an image is formed by reverse tracing onto the display surface from the exit pupil side. By employing such the configuration, the AR glasses 1c has the same effect as that of the AR glasses 1 according to the above embodiment.

Moreover, because the diameter of the human pupil is about at least 2 [mm] , the user can visually recognize an image with sufficient brightness by setting "the pupil interval APD -the pupil vertical APV" to 1 [mm] or less like Table 3. Moreover, it is desirable that the pupil vertical APV is set to 2 [mm] or more that is the minimum value of the diameter of the human pupil like Table 3.

(Example 4)

FIG. 13 is a diagram illustrating a configuration of AR glasses 1d according to Example 4. FIG. 14 is a diagram illustrating distortion aberration of the AR glasses 1d according to Example 4. FIG. 15 is a diagram illustrating an eye box of the AR glasses 1d according to Example 4. FIG. 16 is a diagram illustrating an example of a configuration that two or more AR glasses are arranged to expand a viewing angle according to Example 4. The AR glasses 1d according to Example 4 will be described with reference to FIGS. 13 to 16.

The AR glasses 1d illustrated in FIG. 13 indicates a specific example in which various dimensions and angles indicated in the following Table 4 and light guide plate glass material are applied to the AR glasses 1 according to the above embodiment. A light guide plate 10d, an incident surface 11d, a reflecting surface 12d, an outgoing surface 13d, an image display element 20d, a concave mirror 30d, and semi-transparent mirrors 41d to 43d in the AR glasses 1d according to the present example respectively correspond to the light guide plate 10, the incident surface 11, the reflecting surface 12, the outgoing surface 13, the image display element 20, the concave mirror 30, and the semi-transparent mirrors 41 to 43 in the AR glasses 1 according to the above embodiment.

Table 4

Name	Symbol	Value	Unit
Pupil distance	EP		45	mm
Pupil vertical	APV	2.5	mm
Pupil horizontal	APH	8	mm
Pupil interval	APD		3	mm
Pupil interval -Pupil vertical	APD-APV	0.5	mm
Mirror interval	MD		3	mm
Light guide plate thickness	WGD		14	mm
Eye box V direction	EBV	8.5	mm
Eye box H direction	EBH	8	mm
Display surface interval	DD		1	mm
Display element short-side direction	DV	3.79	mm
Display element long-side direction	DH	15.80	mm
Vertical FOV	VFOV	6.0	°
Horizontal FOV	HFOV	24.0	°
Diagonal FOV	DFOV	24.8	°
Display element short-side ejection angle	VDang	3.8	°
Display element size	IMS	0.64	inch
Refractive index	RIX	1.5168	-
Abbe number	AN	64.1673	-

The meanings of various dimensions and angles indicated in Table 4 and the light guide plate glass material are similar to those of Table 2 described above. Moreover, the reflecting surface of the concave mirror 30d is an anamorphic aspheric surface that has a shape represented by the following Equation (3) . Herein, the anamorphic aspheric surface means a symmetric aspheric surface with respect to two axes (X-axis and Y-axis) .

Herein, the meanings of characters in Equation (3) are as follows.

z: a sag amount with respect to a direction parallel to an optical axis of the concave mirror 30d;

CUX, CUY: curvatures of x and y;

KX, KY: conic coefficients of x and y;

AR, BR, CR, DR: rotational symmetries of deformation of fourth, sixth, eighth, and tenth from a conic;

AP, BP, CP, DP: non-rotational symmetries of deformation of fourth, sixth, eighth, and tenth from the conic; and

(Normal aspheric surface in case of CUX=CUY, KX=KY, and AP=BP=CP=DP=0) .

By configuring the AR glasses 1d according to Table 4 described above, it is possible to suppress distortion aberration as illustrated in FIG. 14. It should be noted that the distortion aberration illustrated in FIG. 14 illustrates distortion aberration on a display surface of the image display element 20d when an image is formed by reverse tracing onto the display surface from the exit pupil side. By employing such a configuration, the AR glasses 1d has the same effect as that of the AR glasses 1 according to the above embodiment.

Moreover, because the diameter of the human pupil is about at least 2 [mm] , the user can visually recognize an image with sufficient brightness by setting "the pupil interval APD -the pupil vertical APV" to 1 [mm] or less like Table 4. Moreover, it is desirable that the pupil vertical APV is set to 2 [mm] or more that is the minimum value of the diameter of the human pupil like Table 4.

Moreover, by employing the concave mirror 30d having an anamorphic aspheric surface, an eye box EBd can be further expanded in the z direction than those of Examples 1 to 3 as illustrated in FIG. 15, and the user can recognize an image by using a position distant from the outgoing surface 13d as the eye point EPT. Moreover, by expanding the eye box EBd in the z direction, by using three AR glasses 1d-1 to 1d-3 having the same configuration as that of the AR glasses 1d, their outgoing surfaces are arranged at a tilt and their eye boxes EBd are arranged to overlap at the eye point EPT as illustrated in FIG. 16 to be able to expand a viewing angle in a horizontal direction.

[Explanations of Letters or Numerals]

1, 1a to 1d, 1d-1 to 1d-3 AR glasses

10, 10a to 10d Light guide plate

11, 11a to 11d Incident surface

12, 12a to 12d Reflecting surface

13, 13a to 13d Outgoing surface

20, 20a to 20d Image display element

30, 30a to 30d Concave mirror

41, 41a to 41d Semi-transparent mirror

41EG End

42, 42a to 42d Semi-transparent mirror

43, 43a, 43c, 43d Semi-transparent mirror

43EG End

52a, 52b, 53a Quarter-wave plate

100 Light guide plate

101 Incident surface

103 Outgoing surface

200 Image display element

201 Collimating optical system

401 to 404 Semi-transparent mirror

500 AR glasses

E Eyes

EB, EBd, EB10 Eye box

EPT Eye point

GL Glasses

θ Directivity angle.

Claims

A display device comprising:

an image display element configured to emit light rays at a predetermined directivity angle;

a light guide plate including an incident surface on which the light rays emitted from the image display element are incident, a reflecting surface configured to reflect the light rays injected from the incident surface, and an outgoing surface facing the reflecting surface to emit the light rays to an outside;

a concave mirror configured to reflect the light rays reflected by the reflecting surface as parallel light; and

two or more semi-transparent mirrors configured to transmit a part of the parallel light reflected by the concave mirror and to reflect a remainder of the parallel light to emit the remainder from the light guide plate to the outside, the semi-transparent mirrors being arranged side by side in a traveling direction of the parallel light inside the light guide plate, wherein

the concave mirror reflects the light rays reflected by the reflecting surface to be incident on a semi-transparent mirror closest to the concave mirror among the two or more semi-transparent mirrors.
The display device according to claim 1, wherein the directivity angle is less than 8°.
The display device according to claim 1, wherein

the two or more semi-transparent mirrors are arranged along the outgoing surface side in the light guide plate,

the light rays injected from the incident surface are totally reflected only once by the reflecting surface of light guide plate towards the concave mirror.
The display device according to any one of claims 1 to 3, wherein a number of the semi-transparent mirrors is three.
The display device according to claim 4, wherein

among the three semi-transparent mirrors, a first semi-transparent mirror closest to the concave mirror is provided with an unpolarized film, and each of a second semi-transparent mirror arranged next to the first semi-transparent mirror and a third semi-transparent mirror closest to the incident surface is provided with a polarized separation film configured to reflect an S polarization component of the incident light rays and transmit a P polarization component, and

the display device further comprises a first quarter-wave plate arranged on the first semi-transparent mirror side of the second semi-transparent mirror, a second quarter-wave plate arranged on the third semi-transparent mirror side of the second semi-transparent mirror, and a third quarter-wave plate arranged on the second semi-transparent mirror side of the third semi-transparent mirror.
The display device according to any one of claims 1 to 5, wherein a reflecting surface of the concave mirror includes an aspheric surface.
The display device according to any one of claims 1 to 5, wherein a reflecting surface of the concave mirror includes an anamorphic aspheric surface.
The display device according to any one of claims 1 to 7, wherein a difference between an interval of images generated by light rays reflected by the semi-transparent mirrors and an array-direction width of the semi-transparent mirrors of the images is not more than 1 mm.
The display device according to any one of claims 1 to 8, wherein a width in the traveling direction of an image that can be visually recognize by the parallel light reflected by the semi-transparent mirrors is not less than 2 mm.
The display device according to claim 7, wherein a horizontal-direction viewing angle is able to be widen by arranging a plurality of the display devices so that their outgoing surfaces are inclined to overlap their eye boxes with each other.
The display device according to any one of claims 1 to 10, wherein each of the semi-transparent mirrors is arranged to be 45° with respect to the outgoing surface.
The display device according to any one of claims 1 to 11, wherein the reflecting surface is located on an opposite side of a position of eyes of a human who wears the display device with reference to the outgoing surface.
The display device according to any one of claims 1 to 11, wherein the outgoing surface is located on an opposite side of a position of eyes of a human who wears the display device with respect to the reflecting surface.
The display device according to any one of claims 1 to 13, wherein the image display element corrects color separation by the light guide plate by shifting images of respective colors consisting of pixels of a display surface to emit the light rays of the images of the respective colors.
The display device according to claim 5, wherein the first quarter-wave plate, the second quarter-wave plate, and the third quarter-wave plate are made of inorganic glass material.
The display device according to any one of claims 1 to 15, wherein the image display element faces the incident surface.
The display device according to any one of claims 1 to 16, wherein a display surface of the image display element has a width in a direction orthogonal to a direction from the reflecting surface to the outgoing surface and parallel to the incident surface larger than a width in the direction from the reflecting surface to the outgoing surface.
The display device according to any one of claims 1 to 17, wherein the light rays reflected by the semi-transparent mirrors are parallel light.
The display device according to any one of claims 1 to 18, wherein the parallel light reflected by the concave mirror directly reaches the semi-transparent mirror closest to the concave mirror.
The display device according to any one of claims 1 to 19, wherein the incident surface is formed to be a surface inclined by a predetermined angle with respect to the outgoing surface.