Augmented reality display device

Abstract

To provide an augmented reality display device with an enhanced sense of realism of display images.SOLUTION: An augmented reality display device causes a user to visually recognize first and second images at different distances in a state where a real environment can be visually recognized. The augmented reality display device includes: a display panel that emits polarized lights for the first and second images; a surface-divided polarization conversion member arranged at a position where the polarized lights enter; and an optical element and a concave half mirror arranged at a position where the polarized lights transmitted through the surface-divided polarization conversion member enter. The surface-divided polarization conversion member has, in a plan view, a first transmissive portion that transmits the polarized light for the first image and a second transmissive portion that transmits the polarized light for the second image and causes a phase difference different by λ / 2 from that caused by the first transmissive portion. The optical element makes a virtual image distance of the first image generated from the first polarized light transmitted through the first transmissive portion different from a virtual image distance of the second image generated from the second polarized light transmitted through the second transmissive portion.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The following disclosure relates to augmented reality displays. [Background technology]

[0002] In recent years, research and development of augmented reality display devices that display images (also called "video") superimposed on the real world has progressed, and for example, a head-up display that displays an image of information for the driver on the windshield has been proposed. In such augmented reality display devices, three-dimensional images are sometimes used as images superimposed on the real world to improve the sense of realism.

[0003] As an example of prior art related to three-dimensional display, Patent Document 1 discloses a three-dimensional display method in which a two-dimensional image of an object to be displayed is generated by projecting it from the line of sight of an observer onto a plurality of display surfaces arranged at different depth positions as seen by the observer, the generated two-dimensional image is displayed on each of two arbitrary display surfaces among the plurality of display surfaces, and the luminance of the displayed two-dimensional image is changed independently for each of the arbitrary two display surfaces among the plurality of display surfaces to generate a three-dimensional stereoscopic image, characterized in that the display light of the two-dimensional image is focused on any two display surfaces among the plurality of display surfaces by a polarized multifocal optical system, and the polarization direction of the display light is controlled to change independently the luminance of the two-dimensional image focused on any two display surfaces among the plurality of display surfaces. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-156603 A Summary of the Invention [Problem to be solved by the invention]

[0005] The prior art described in the above Patent Document 1 is capable of three-dimensional display with the naked eye, but is not applicable to an augmented reality display device.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide an augmented reality display device with improved realism of displayed images. [Means for solving the problem]

[0007] (1) One embodiment of the present invention is an augmented reality display device that allows a user to view first and second images at different distances while allowing the user to view a real environment. The augmented reality display device includes a display panel that outputs polarized light for the first and second images, a surface-division polarization conversion element that is arranged at a position where the polarized light is incident, and an optical element and a concave half mirror that are arranged at positions where the polarized light that has passed through the surface-division polarization conversion element is incident. In a planar view, the surface-division polarization conversion element has a first transmitting section that transmits polarized light for the first image, and a second transmitting section that transmits polarized light for the second image and generates a phase difference that is λ / 2 different from that of the first transmitting section. The optical element differentiates a virtual image distance of a first image generated from the first polarized light that has passed through the first transmitting section from a virtual image distance of a second image generated from the second polarized light that has passed through the second transmitting section.

[0008] (2) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1) above, the first transmissive section is a non-conversion section that transmits polarized light for a first image without converting the polarization state, and the second transmissive section is a conversion section that converts the polarization state by generating a phase difference of λ / 2 for polarized light for a second image.

[0009] (3) Moreover, in one embodiment of the present invention, in addition to the configuration of (2) above, the conversion section includes a resin layer having a phase difference of λ / 2.

[0010] (4) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), or (3) above, the second transmissive section, in a cross-sectional view, comprises a pair of substrates and a liquid crystal layer disposed between the pair of substrates, and a phase difference is variable in response to a voltage applied to the liquid crystal layer.

[0011] (5) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3) or (4) above, the optical element is a liquid crystal lens, and the liquid crystal lens acts as a lens having a first focal length for the first polarized light, and either does not act as a lens for the second polarized light or acts as a lens having a second focal length.

[0012] (6) Moreover, in one embodiment of the present invention, in addition to the configuration of (5) above, the liquid crystal lens is a refractive lens, a gradient index lens, or a diffractive lens.

[0013] (7) Moreover, in one embodiment of the present invention, in addition to the configuration of (5) above, the liquid crystal lens is a Pancharatnam-Berry phase lens.

[0014] (8) Furthermore, in one embodiment of the present invention, in addition to the configuration of (5) above, the liquid crystal lens has a liquid crystal layer, and the focal length is variable in response to a voltage applied to the liquid crystal layer.

[0015] (9) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7) or (8) above, the augmented reality display device further comprises a polarization selective reflector arranged at a position where the polarized light that has passed through the surface division polarization conversion member is incident.

[0016] (10) Furthermore, an embodiment of the present invention is an augmented reality display device comprising, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8) or (9) above, a combination of another surface division polarization conversion member and another liquid crystal lens.

[0017] (11) Furthermore, one embodiment of the present invention is an augmented reality display device that is a head-mounted display device in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), or (10) above. Effect of the Invention

[0018] According to the present invention, it is possible to provide an augmented reality display device with an improved sense of realism in displayed images. [Brief description of the drawings]

[0019] [Figure 1] 1A and 1B are diagrams illustrating the display principle of a virtual image in a display device. [Diagram 2] FIG. 1 is a diagram illustrating the display principle of conventional VR. [Diagram 3] FIG. 1 is a diagram for explaining how a person sees a real object. [Figure 4] FIG. 13 is a diagram illustrating a display state when there is one virtual image surface. [Diagram 5] FIG. 13 is a diagram illustrating a display state when there are two virtual image surfaces. [Figure 6] 1 is a side view showing a schematic configuration of an augmented reality display device according to a first embodiment. [Figure 7] 2 is an enlarged cross-sectional view of a surface-dividing polarization conversion member according to the first embodiment. FIG. [Figure 8] 1A and 1B are diagrams for explaining the structure of a refractive lens using resin, the upper diagram being a cross-sectional view and the lower diagram being a top view. [Figure 9] 9A and 9B are diagrams for explaining the operation of the refractive lens in the direction A shown in FIG. 8, where the upper diagram shows the state when a voltage is applied to the liquid crystal layer, and the lower diagram shows the state when no voltage is applied to the liquid crystal layer. [Figure 10] 9A and 9B are diagrams for explaining the operation of the refractive lens in the direction B shown in FIG. 8, where the upper diagram shows the state when a voltage is applied to the liquid crystal layer, and the lower diagram shows the state when no voltage is applied to the liquid crystal layer. [Figure 11] FIG. 1 is a top view illustrating the configuration of a Pancharatnam-Berry phase lens. [Figure 12]This is a diagram explaining the function of the Pancharatnam-Berry phase lens. [Figure 13] FIG. 11 is a side view illustrating a schematic configuration of an augmented reality display device according to a second embodiment. [Figure 14] FIG. 11 is a side view illustrating a schematic configuration of an augmented reality display device according to a third embodiment. [Figure 15] 13 is a side view showing another example of the configuration in the vicinity of the concave half mirror in the augmented reality display device according to the third embodiment. FIG. [Figure 16] FIG. 2 is an explanatory diagram showing an example of an image displayed by the augmented reality display device, in which the left side shows an original image and the right side shows an enlarged image. [Figure 17] FIG. 1 is an explanatory diagram showing an example of a state in which a display image of an augmented reality display device installed in an automobile is superimposed on a real environment. [Figure 18] 13 is a plan view showing a schematic configuration of a surface division polarization conversion member included in the augmented reality display device according to the fourth embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiment, and appropriate design changes can be made within the scope of the configuration of the present invention. In the following description, the same reference numerals are appropriately used in common between different drawings for the same parts or parts having similar functions, and repeated explanations thereof will be omitted as appropriate. Each aspect of the present invention may be appropriately combined within the scope of the gist of the present invention.

[0021] The augmented reality display device of the present embodiment allows a user to view first and second images at different distances while being able to view the real environment. The type of the display device is not particularly limited, and may be, for example, an AR (Augmented Reality) display device that displays content compatible with AR technology, or a Head-Up Display (abbreviated as HUD). The type of the display device is not particularly limited, and may be, for example, a head-mounted display device (HMD). The head-mounted display device (HMD) is a display device that can be worn on the head, and has, for example, a goggle shape that can be worn on the head, and a display such as a liquid crystal display is placed in front of the user's eyes when worn. Such an HMD is suitable for viewing content compatible with AR (Augmented Reality) technology. For example, the configuration of the HMD includes a support part for wearing on the user's head and a display equipped with a liquid crystal module, and the display is placed in front of the user's eyes when worn.

[0022] The augmented reality display device of this embodiment is equipped with a surface-splitting polarization conversion member, and can generate two images with different virtual image distances from one display panel. As a specific application example, in the case of an AR display device, a close view (nearby virtual image) and a distant view (distant virtual image) can be added to the real world. This can improve the sense of realism of the displayed image, thereby reducing the burden on the user (observer) when viewing and improving the sense of immersion in the content.

[0023] 1 is a diagram for explaining the display principle of a virtual image in a display device. In the drawings of the present application, a dashed line indicates the direction of the line of sight of a user U, a solid arrow indicates the path of light that displays a real image toward the eyes of the user U, and a dotted arrow indicates the path of light that displays a virtual image toward the eyes of the user U. The display device in FIG. 1 includes, in order from the user U side, a liquid crystal lens 50 with an adjustable focal length, a lens (physical lens) 40 with a fixed focal length, a polarizing plate 13, and a display 11. In a head-mounted display device (HMD) or the like, the distance from the liquid crystal lens 50 to the display 11 is short, so the user U visually recognizes a virtual image V behind the display 11. Here, when the focal length of the liquid crystal lens 50 is changed, the position of the virtual image V moves forward or backward relative to the user U. Whether the virtual image V moves intermittently or continuously depends on the type of the liquid crystal lens 50. However, in the display device in FIG. 1, the virtual image V at a specific timing is always formed at a specific distance. In other words, the virtual image V is displayed within one plane. Hereinafter, the plane on which the virtual image V is displayed is also referred to as the "virtual image plane."

[0024] Next, problems that arise when using virtual images for display will be explained based on a VR display device, which is a typical example of a display device that uses virtual images for display. One of the problems is known as VR sickness, and the mechanism by which it occurs is as follows. FIG. 2 is a diagram for explaining the display principle of conventional VR. As shown in FIG. 2, in VR display, an image R for the right eye and an image L for the left eye are displayed separately, so that the user U is made to visually recognize that an image I1 is at the position where the 3D image is to be projected. FIG. 3 is a diagram for explaining the state in which a person sees a real object. As can be seen from a comparison of FIG. 2 and FIG. 3, conventional VR differs from the state in which a person sees a real object in that the movement (convergence) of rotating the right eye RE and the left eye LE toward the image I1 and the focus adjustment are not consistent. It is believed that VR sickness occurs when the focus adjustment distance (the distance between the image R for the right eye and the image L for the left eye) D1 is different from the distance D2 of the gaze points of both eyes. This occurs because the image R for the right eye and the image L for the left eye are virtual images, and the virtual image surface (the distance of the virtual image) cannot be moved. Here, if the virtual image surface can be moved using a liquid crystal lens or the like with an adjustable focal length, the state of FIG. 3 can be realized, and VR sickness can be prevented.

[0025] On the other hand, when displaying a stereoscopic image (3D image) by VR, it is difficult to completely eliminate the sense of incongruity when compared with the state in which a person sees a real object by simply moving the virtual image using a liquid crystal lens with an adjustable focal length. FIG. 4 is a diagram explaining the display state when there is one virtual image surface, and FIG. 5 is a diagram explaining the display state when there are two virtual image surfaces. When there is only one virtual image surface, the problem is how to express an object in peripheral vision. Specifically, as shown in FIG. 4, when the focus is set on the position of image I1, image I2 of an object located closer should appear blurred. When there is one virtual image surface, two blurred images I2a are displayed for the right eye and the left eye on one virtual image surface, making it appear as if there is a blurred image I2, which makes it feel like peripheral vision. However, when switching the viewpoint between the position of image I1 and the position of image I2, it is necessary to switch both the liquid crystal lens and the image, and the blur is expressed by the image, so that it is difficult to completely eliminate the sense of incongruity. In contrast, as shown in Fig. 5, if there are two virtual image planes, there is no need to switch the liquid crystal lens and the image when switching the viewpoint, so the viewpoint can be switched smoothly and a good sense of immersion can be obtained. Therefore, in the present invention, two virtual image planes (two images with different virtual image distances) are generated.

[0026] <Embodiment 1> 6 is a side view showing a schematic configuration of the augmented reality display device according to the first embodiment. The augmented reality display device according to the first embodiment is an AR display device. The AR display device uses a concave lens (concave half mirror) 60, a light guide plate, and the like to superimpose an image from a display 11 and a real environment, allowing a user U to view the image. The concave half mirror 60 transmits ambient light to the user U side, and reflects image light from the display 11 to the user U side. The AR display device includes, facing the reflecting surface of the concave half mirror 60, a liquid crystal lens (optical element) 50 with an adjustable focal length, a surface division polarization conversion member 20, a polarizing plate 13, and a display 11, in that order.

[0027] A display panel 10 formed by a combination of the display 11 and the polarizing plate 13 emits polarized light. When one of two images having different virtual image distances is defined as a "first image" and the other as a "second image," the display panel emits polarized light for the first and second images, respectively. The polarized light for the first and second images passes through a surface division polarization conversion member 20 and enters a liquid crystal lens 50 with an adjustable focal length.

[0028] Examples of the display 11 include self-luminous displays such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs). The polarizing plate 13 is a linear polarizer that transmits polarized light (first polarized component) that vibrates in one direction and absorbs or reflects polarized light (second polarized component) that vibrates in a direction perpendicular to the first polarized light.

[0029] The surface division polarization conversion member 20 has, in plan view, a first transmission section that transmits polarized light for a first image and a second transmission section that transmits polarized light for a second image. The second transmission section is a region that generates a phase difference different by λ / 2 from the first transmission section, and the polarized light for the first image transmits through the first transmission section and the polarized light for the second image transmits through the second transmission section, so that the polarized light for the first image and the polarized light for the second image can generate a phase difference different by λ / 2. The display device of FIG. 6 can make the virtual image distances of two images different by utilizing a phase difference of λ / 2. Here, "generating a phase difference of λ / 2" means that a phase difference equivalent to 1 / 2 of the wavelength of the transmitted light is given to the transmitted light, and for example, means that a phase difference of 200 nm or more and 350 nm or less is given to light with a wavelength of 550 nm. In this embodiment, the surface division polarization conversion member 20 has a first transmitting section which is a non-conversion section 22 that transmits polarized light for a first image without converting the polarization state, and a second transmitting section which is a conversion section 21 that converts the polarization state by generating a phase difference of λ / 2 for polarized light for a second image. Here, "without converting the polarization state" means, for example, that the phase difference for light with a wavelength of 550 nm is 10 nm or less.

[0030] The surface division polarization conversion member 20 may be one that variably forms two or more parts having a phase difference of λ / 2 different from each other in a plane parallel to the display surface of the display 11, and may be, for example, a liquid crystal panel. That is, in the surface division polarization conversion member 20, the conversion section (second transmission section) 21 may include a pair of substrates and a liquid crystal layer disposed between the pair of substrates in a cross-sectional view, and the phase difference may be variable depending on the voltage applied to the liquid crystal layer. In a form in which two or more parts having a phase difference of λ / 2 different from each other are variably formed, the arrangement of the conversion section (second transmission section) 21 and the non-conversion section (first transmission section) 22 in the plane can be switched over time (ON / OFF). Specifically, by applying a voltage to the liquid crystal layer, what was the conversion section 21 at a certain time becomes the non-conversion section 22, and what was the non-conversion section 22 at a certain time becomes the conversion section 21. Therefore, it is preferable that the entire surface division polarization conversion member 20 is a liquid crystal panel.

[0031] 7 is an enlarged cross-sectional view of the surface division polarization conversion member according to the first embodiment. On the screen of the display 11, a surface division polarization conversion member (liquid crystal panel) 20 capable of switching the presence or absence of a phase difference of λ / 2 (i.e., 275 nm for light of 550 nm) is arranged. As the liquid crystal mode of the liquid crystal panel, modes generally used in liquid crystal panels, such as TN mode, VA mode, ECB mode, IPS mode, and FFS mode, can be applied. Taking the VA mode as an example, a configuration can be adopted in which no phase difference occurs when the voltage is off, and a phase difference of λ / 2 occurs when the voltage is on. Note that the surface division polarization conversion member 20 may be configured by stacking two layers of liquid crystal panels in order to reduce wavelength dependency.

[0032] As shown in Fig. 7, the surface-division polarization conversion member (liquid crystal panel) 20 can drive the liquid crystal 26a in the liquid crystal layer 26 for each region by applying a voltage to the liquid crystal layer 26 sandwiched between a pair of substrates 25. The number of regions of the liquid crystal panel constituting the surface-division polarization conversion member 20 may be the same as the number of pixels of the display 11 arranged to be superimposed, or may be less than the number of pixels of the display 11. In Fig. 7, the voltage-on state is shown at the top and the voltage-off state is shown at the bottom for the VA mode liquid crystal panel. The phase of the linearly polarized light emitted from display 11 does not change when the surface division polarization conversion member 20 is in the voltage-off state, so the linearly polarized light is transmitted as it is. The orientation of liquid crystal lens 50 is not limited, but here we will explain the case where liquid crystal lens 50 is positioned so that it does not act as a lens. In this case, the transmitted light reaches the human eye just as it leaves the display, so the screen of display 11 is seen as it is (a real image is seen).

[0033] On the other hand, when the voltage of the surface division polarization conversion member 20 is turned on, the light emitted from the display 11 becomes linearly polarized light rotated by 90 degrees. Then, the liquid crystal lens 50 acts as a lens when the linearly polarized light passes through. Because the display 11 is placed at a distance equivalent to the focal length of the liquid crystal lens 50, this lens action causes the light to become nearly parallel and reach the eyes of the user U. Therefore, the user U sees the display 11 as if it were almost infinitely far away (a virtual image is seen). In this way, the real image and the virtual image can be switched by the surface division polarization conversion member 20, so that two virtual image planes at different distances can be simultaneously viewed by surface division, and a display with depth (3D display) can be viewed. For example, only the display area of ​​the character to be the foreground may be the non-conversion section 22 (area with zero phase difference), and the background area to be the background may be the conversion section 21 (area with phase difference λ / 2).

[0034] In the above configuration, for simplicity, the display 11 is placed at the focal length and the virtual image is at infinity, but the virtual image can be placed at any location by changing the focal length of the liquid crystal lens 50 or the distance from the liquid crystal lens 50 to the display 11. Since the focal length of the liquid crystal lens 50 can be adjusted by voltage, the virtual image distance can also be moved from infinity to the near side by increasing the voltage applied to the liquid crystal lens 50.

[0035] The surface-divided polarization conversion member 20 may steadily have two or more parts with phase differences of λ / 2 in a plane parallel to the display surface of the display 11, and may be, for example, a surface-divided member in which the non-conversion section 22 is a transparent member and the conversion section 21 is a λ / 2 plate. The λ / 2 plate is a member that imparts a phase difference equivalent to 1 / 2 of the wavelength to visible light, for example, a member that imparts a phase difference of 200 nm or more and 350 nm or less to light with a wavelength of 550 nm. When a λ / 2 plate is used, the arrangement of the conversion section (second transmission section) 21 and the non-conversion section (first transmission section) 22 in the plane is not time-switched (ON / OFF). The surface-divided member can be produced, for example, by a method of attaching a resin film having a phase difference of λ / 2 to the entire surface of a support member such as a glass substrate, and then patterning the resin film so that it is disposed in the conversion unit 21 to form a resin layer. Alternatively, the member may be produced by a method of attaching a resin film having a phase difference of λ / 2 to only the region of the support member corresponding to the conversion unit 21 to form a resin layer. Also, instead of using a resin film having a phase difference of λ / 2, a resin layer having a phase difference of λ / 2 may be formed on the support member. For example, a method may be used in which an alignment film is formed on the support member, a layer made of a photopolymerizable liquid crystal material is formed on the alignment film, and the photopolymerizable liquid crystal material is cured to form a resin layer.

[0036] At the position where the polarized light transmitted through the surface division polarization conversion member 20 is incident, an optical element is disposed that makes the virtual image distance of the first image generated from the first polarized light transmitted through the non-conversion section (first transmission section) 22 different from the virtual image distance of the second image generated from the second polarized light transmitted through the conversion section (second transmission section) 21. As such an optical element, in this embodiment, a liquid crystal lens 50 with an adjustable focal length is provided. The liquid crystal lens 50 acts as a lens with a first focal length for the first polarized light, and does not act as a lens (does not bend light) or acts as a lens with a second focal length for the second polarized light. For example, when the vibration direction of the polarized light emitted from the display panel 10 coincides with the direction in which the liquid crystal lens 50 acts, the first polarized light transmitted through the non-conversion section 22 shows a virtual image V, and the second polarized light in which the vibration direction of the polarized light is switched by the conversion section 21 to be orthogonal by 90 degrees shows a real image (display screen of the display panel) because the liquid crystal lens 50 does not act. This makes it possible to achieve two virtual image distances (including cases where one of them is a real image) using a single display panel, enabling smooth switching of viewpoints, including peripheral vision, as described above. When the liquid crystal lens 50 acts on the ambient light, the magnification differs between the direction in which the lens acts and the direction in which it does not, so two images of different sizes are seen. For this reason, the liquid crystal lens 50 is placed in a position where the ambient light does not pass through, and a concave half mirror 60 is placed on the user U side of the optical path of the liquid crystal lens 50.

[0037] The type of the liquid crystal lens 50 is not particularly limited, and examples thereof include a refractive lens, a gradient index (GRIN) lens, and a diffractive lens. The gradient index (GRIN) lens is a lens that bends light by the orientation of liquid crystal. These liquid crystal lenses generally act as a lens for linearly polarized light in one vibration direction, but do not act as a lens for linearly polarized light in the other vibration direction. In addition, when the liquid crystal material is a hardening type, the focal length of the liquid crystal lens is fixed. On the other hand, when the liquid crystal material is movable, the focal length of the lens can be made variable. Regarding the method of controlling the focal length, a refractive lens can be controlled by voltage, a gradient index lens can be controlled by both voltage and period, and a diffractive lens can be controlled by period. As the liquid crystal lens, one having a liquid crystal layer and having a focal length that can be changed according to the voltage applied to the liquid crystal layer is preferable.

[0038] The refractive lens will be described with reference to Figs. 8 to 10. Fig. 8 is a diagram for explaining the structure of a refractive lens using a resin, with the upper diagram being a cross-sectional view and the lower diagram being a top view. Fig. 9 is a diagram for explaining the operation of the refractive lens in the direction A shown in Fig. 8, with the upper diagram showing when a voltage is applied to the liquid crystal layer and the lower diagram showing when no voltage is applied to the liquid crystal layer. Fig. 10 is a diagram for explaining the operation of the refractive lens in the direction B shown in Fig. 8, with the upper diagram showing when a voltage is applied to the liquid crystal layer and the lower diagram showing when no voltage is applied to the liquid crystal layer. Arrows in Figs. 9 and 10 indicate the path of light passing through the refractive lens. The refractive lens has a structure in which a glass substrate 51, a resin Fresnel lens 52, an electrode 53, a liquid crystal layer 54, another electrode 53, and a glass substrate 51 are laminated. For example, when a positive type liquid crystal 54a (the major axis of the refractive index ellipsoid of the liquid crystal is aligned with the electric field) is used for the liquid crystal layer 54, the liquid crystal 54a is oriented horizontally when no voltage is applied (lower diagrams in Figs. 9 and 10), and when a voltage is applied, the liquid crystal 54a is oriented vertically (upper diagrams in Figs. 9 and 10). The combination of the refractive indexes of the resin and liquid crystal 54a constituting the Fresnel lens 52 is not limited, but for example, the refractive index of the resin is about 1.5, the ne (refractive index on the major axis side) of the liquid crystal 54a is 1.8, and the no (refractive index on the minor axis side) is 1.5. In this case, as shown in Fig. 9, in the direction A, when no voltage is applied, light is bent due to the refraction difference, and when a voltage is applied, the refraction difference disappears, so the light is not bent. On the other hand, as shown in FIG. 10, in the direction B, no refraction difference occurs whether or not a voltage is applied, and the lens function is never generated.

[0039] The liquid crystal lens 50 may be a Pancharatnam-Berry Phase lens. The Pancharatnam-Berry Phase lens is a liquid crystal lens that can switch between divergence and convergence depending on the direction of circularly polarized light (see, for example, U.S. Patent No. 10,379,419). For example, it functions as a lens whose focal length switches between f and -f for left-handed and right-handed circularly polarized light. If the focal length f is active, it can be controlled periodically in principle. In this embodiment, the focal length switching distance can be adjusted by adding a separate fixed lens with a focal length f, so that, for example, the focal length f / 2 and 0 can be switched by adding a fixed lens with a focal length f. In addition, circular polarization can be realized by adding a λ / 4 plate to linear polarization, so that the same effect can be achieved by adjusting the strength of a separate lens in a configuration similar to that of linear polarization.

[0040] FIG. 11 is a top view for explaining the configuration of a Pancharatnam Berry phase lens, and FIG. 12 is a diagram for explaining the function of the Pancharatnam Berry phase lens. The Pancharatnam Berry phase lens uses the Pancharatnam Berry phase (PB orientation), and the periodic orientation of the liquid crystal 54a as shown in FIG. 11 causes diffraction and obtains a lens function. In FIG. 12, the optical path of the right-handed circularly polarized RCP output from the Pancharatnam Berry phase lens PBL is shown by a solid line in FIG. 12, and the optical path of the left-handed circularly polarized LCP output from the Pancharatnam Berry phase lens PBL is shown by a dotted line in FIG. 12. The Pancharatnam Berry phase lens PBL in FIG. 12 shows an example in which the incident circularly polarized light is focused when it is a right-handed circularly polarized RCP, and diverges when it is a left-handed circularly polarized LCP, and the direction of the circularly polarized light at the time of output is reversed. In this way, the Pancharatnam-Berry phase lens can switch between diverging and converging focal point f by switching the direction of the incident circularly polarized light.

[0041] Pancharatnam-Berry phase lens (PB lens) is a lens that can switch the strength of refraction (concave-convex lens), and in principle can be actively switched on and off. In other words, the strength of the lens can be adjusted by adjusting the orientation pitch of the liquid crystal. When using a PB lens, the polarizing plate 13 is, for example, a circular polarizing plate that combines a linear polarizer and a λ / 4 plate to make the light emitted from the display 11 circularly polarized. By placing a surface-splitting polarization conversion member 20 that can switch circularly polarized light to the opposite circularly polarized light on top of the circular polarizing plate, it is possible to switch between left and right circular polarization.

[0042] According to the augmented reality display device of this embodiment, two virtual image planes can be switched using the plane-splitting polarization conversion member 20. This makes it possible to simultaneously view two planes at different distances by plane splitting, and to perform a display with depth (3D display), thereby enhancing the sense of immersion in AR and enabling smooth viewpoint switching.

[0043] <Embodiment 2> FIG. 13 is a side view showing a schematic configuration of an augmented reality display device according to a second embodiment. The augmented reality display device according to the second embodiment is an AR display device equipped with an optical system called a birdbath system. By disposing a polarized light selective reflector 61 between the liquid crystal lens 50 and the concave half mirror 60, the image is less likely to be distorted while ensuring light utilization efficiency. In this configuration, the distance of the virtual image can be switched by the liquid crystal lens 50, but the distance of each virtual image V can also be changed by changing the curvature of the concave half mirror 60 placed in front of the user U and the concave mirror 62 placed below the eyes of the user U. A λ / 4 plate 63 is disposed on the surface of the concave half mirror 60 and the concave mirror 62 facing the polarized light selective reflector 61.

[0044] In the configuration of FIG. 13, it is possible to simultaneously realize two virtual image distances simply by eliminating the liquid crystal lens 50 and varying the curvature of the concave mirror 62.

[0045] <Embodiment 3> The augmented reality display device according to the third embodiment is a head-up display (abbreviated as HUD). A head-up display generally uses a semi-transparent surface (often a spherical surface or a free-form surface similar to the spherical surface) called a windshield or a combiner to superimpose an image from a display and the real environment. 14 is a side view showing a schematic configuration of an augmented reality display device according to embodiment 3, illustrating the configuration of an optical system for a HUD using the windshield of a passenger vehicle. The windshield 80 has a curved surface close to a sphere, and thus has some effect of magnifying the image, but this alone is insufficient, so it is generally provided with a concave mirror 62 on the entrance side, and the combination of these mirrors magnifies the original image. There are several possible locations for placing the liquid crystal lens 50, but because the optical distance is expanded to determine the distance of the virtual image, and because the liquid crystal lens 50 cannot be superimposed on the ambient light (as the ambient light would also be expanded), it is preferable to place the liquid crystal lens 50 between the windshield 80 and the concave mirror 62 or near the concave mirror 62. Also, a liquid crystal lens 50 can be placed in front of the concave mirror 62 to use the liquid crystal lens 50 with approximately double the lens power. In this case, if a refractive liquid crystal lens as shown in Fig. 8 is used, the lens power changes depending on linearly polarized light, so that approximately double the lens power can be obtained as is, but in the case of a PB lens type as shown in Fig. 11, for example, taking into consideration that the direction of circularly polarized light changes, a λ / 4 plate 63 is placed as shown in Fig. 15. Fig. 15 is a side view showing a schematic diagram of another example of the configuration in the vicinity of the concave half mirror in the augmented reality display device according to the third embodiment. With this configuration, by dividing the area into one with a phase difference of λ / 2 and one with a phase difference of zero (if a PB lens is used, the area with a phase difference of λ / 4 and an axis perpendicular to the area with a phase difference of λ / 4), the images appear to float at different distances, as in virtual images V1 and V2, making it possible to use (distinguish) the virtual image distance according to the situation.

[0046] <Embodiment 4> Fig. 16 is an explanatory diagram showing an example of an image displayed by an augmented reality display device, with the left side showing the original image and the right side showing the enlarged image. Fig. 17 is an explanatory diagram showing an example of a state in which a display image of an augmented reality display device installed in a car is superimposed on a real environment. The augmented reality display device has the following display characteristics because it displays an image superimposed on the real environment. (1) As shown in FIG. 16, in a display using an augmented reality display device, the areas where no image is displayed (areas that are displayed in black) tend to be large. (2) As shown in Fig. 17, in the display by the augmented reality display device, the virtual image distance is often closer at the bottom of the screen and farther at the top of the screen, and an image is often superimposed on the real environment. In Fig. 17, an AR image to be superimposed on the real environment is displayed as a back virtual image V3 at the top of the screen. An AR image generated in response to the behavior of the vehicle is displayed as a first foreground virtual image V4 at the center of the screen. An AR image of a meter or the like is displayed as a second foreground virtual image V5 at the bottom of the screen.

[0047] Due to the above characteristics, in the augmented reality display device, it is assumed that the upper side of the screen fixes the virtual image in the back, and the lower side of the screen fixes the virtual image in the front, and the virtual image distance (virtual image position) is switched only in a part of the screen. In this case, by configuring at least a part of the surface division polarization conversion member with a liquid crystal panel to make it possible to switch the virtual image position, and by configuring at least another part with a phase difference plate to shift the phase by λ / 2, it is possible to provide a part where the virtual image distance switches between the back and the front, and a part where the virtual image distance is fixed.

[0048] FIG. 18 is a plan view showing a schematic configuration of a surface division polarization conversion member included in the reality augmented display device according to the fourth embodiment. As shown in FIG. 18, the surface division polarization conversion member 120 has, in a plan view, a first transmission section 121 that transmits polarized light for a first image, a second transmission section 122 that transmits polarized light for a second image, and a third transmission section 123 that transmits polarized light for a third image. The first transmission section 121 is not provided with a retardation plate, the second transmission section 122 is provided with a liquid crystal panel, and the third transmission section 123 is provided with a retardation plate. The configuration of the surface division polarization conversion member 120 in FIG. 18 corresponds to an example of division of a display screen of the reality augmented display device. That is, the first transmission section 121 corresponds to the upper side of the screen where a virtual image is fixed in the back, the second transmission section 122 corresponds to the center of the screen where the virtual image distance (virtual image position) is switched, and the third transmission section 123 corresponds to the lower side of the screen where a virtual image is fixed in the front.

[0049] The third transmission section 123 can be formed inexpensively by bonding a retardation plate. On the other hand, the liquid crystal panel constituting the second transmission section 122 may be enlarged, and the third transmission section 123 may also be constituted by a liquid crystal panel. As the liquid crystal panel, one that utilizes liquid crystal that is horizontally aligned without application of voltage is preferably used. In any case, since the first transmission section 121 does not require the arrangement of a liquid crystal panel or a retardation plate, the surface-splitting polarization conversion member 120 of the fourth embodiment can be manufactured inexpensively compared to a surface-splitting polarization conversion member that can switch the virtual image distance over the entire screen.

[0050] <Variation 1> The augmented reality display devices of the first and second embodiments use one set of a surface division polarization conversion member and a liquid crystal lens, but may have multiple sets of a surface division polarization conversion member 20 and a liquid crystal lens 50. By using multiple sets (N sets), the virtual image surface can be divided into two. N However, this makes the drive and image processing, which will be explained later, more complicated. In principle, it is better for the surface-splitting polarization conversion member 20 to be closer to the display surface. This is because the boundary surface of the virtual image V is precisely defined on the display image. If the surface-splitting polarization conversion member 20 is moved away from the display surface, the pixels at the boundary may be included in both of the two virtual image surfaces. This problem at the boundary can be dealt with by using image processing, etc., which will be described later. In this way, by using multiple sets of the surface division polarization conversion member 20 and the liquid crystal lens 50, N Since the virtual image plane can be switched, two different distances can be obtained by dividing the surface. N It allows users to see multiple surfaces simultaneously and see a display with depth (3D display), which increases the sense of immersion in VR and enables smooth switching of viewpoints.

[0051] <Variation 2> In the above embodiment, a voltage-variable liquid crystal lens is used, but a static (non-variable) liquid crystal lens 50 made of a UV-curable liquid crystal material may also be used. In this case, since a static liquid crystal lens 50 is used, the virtual image V cannot be moved by voltage, but two virtual images (including the case of a real image) V can be switched by the surface-splitting polarization conversion member 20. This has the advantages of being inexpensive to manufacture, and the liquid crystal lens 50 does not require electrical wiring, which is concentrated on the display 11 side. [Explanation of symbols]

[0052] 10: Display panel 11: Display 13: Polarizing plate 20, 120: surface division polarization conversion member 21: Conversion section 22: Non-conversion section 25: Circuit board 26: Liquid crystal layer 26a: Liquid crystal 40: Lens (physical lens) 50: Liquid crystal lens 51: Glass substrate 52: Fresnel lens 53: Electrode 54: Liquid crystal layer 54a: Liquid crystal 60: Concave half mirror 61: Polarized selective reflector 62: Concave mirror 63:λ / 4 plate 64: Mirror 80: Windshield 121: First transmission section 122: Second transmission section 123: Third transmission section D1: Focus adjustment distance D2: Convergence distance I1, I2: 3D images I2a: Blurred image R: Image for the right eye RCP: Right circular polarization RE: Right eye L: Image for the left eye LCP: Left circular polarization LE: Left eye U: User (observer) V, V1, V2: Virtual image V3: Virtual image in the depths V4: First virtual image in front V5: Second foreground virtual image

Claims

1. 1. An augmented reality display device that allows a user to view first and second images at different distances while being able to view a real environment, a display panel that outputs polarized light for the first and second images; a surface division polarization conversion member disposed at a position where the polarized light is incident; an optical element and a concave half mirror arranged at a position where the polarized light transmitted through the surface division polarization conversion member is incident, the surface division polarization conversion member has, in a plan view, a first transmission portion that transmits polarized light for a first image, and a second transmission portion that transmits polarized light for a second image and generates a phase difference that is different by λ / 2 from that of the first transmission portion; An augmented reality display device, wherein the optical element differentiates a virtual image distance of a first image generated from a first polarized light transmitted through the first transparent portion from a virtual image distance of a second image generated from a second polarized light transmitted through the second transparent portion.

2. the first transmission unit is a non-conversion unit that transmits polarized light for a first image without converting the polarization state of the polarized light, The second transmission unit is a conversion unit that converts the polarization state by generating a phase difference of λ / 2 with respect to the polarized light for the second image. The augmented reality display device according to claim 1.

3. The augmented reality display device according to claim 2 , wherein the conversion section includes a resin layer having a phase difference of λ / 2.

4. The second transmission portion includes, in a cross-sectional view, a pair of substrates and a liquid crystal layer disposed between the pair of substrates, The phase difference is variable depending on the voltage applied to the liquid crystal layer. The augmented reality display device according to claim 1.

5. the optical element is a liquid crystal lens, the liquid crystal lens acts as a lens having a first focal length for the first polarized light, and acts as a lens having a second focal length or does not act as a lens for the second polarized light; The augmented reality display device according to claim 1.

6. The augmented reality display device according to claim 5 , wherein the liquid crystal lens is a refractive lens, a gradient index lens or a diffractive lens.

7. The augmented reality display device according to claim 5 , wherein the liquid crystal lens is a Pancharatnam-Berry phase lens.

8. 6. The augmented reality display device according to claim 5, wherein the liquid crystal lens has a liquid crystal layer, and a focal length of the liquid crystal lens is variable in response to a voltage applied to the liquid crystal layer.

9. 2. The augmented reality display device according to claim 1, further comprising a polarization selective reflector disposed at a position where the polarized light transmitted through the surface division polarization conversion member is incident.

10. The augmented reality display device according to claim 1 , further comprising a combination of another surface division polarization conversion member and another liquid crystal lens.

11. 2. The augmented reality display device of claim 1, which is a head-mounted display device.

Images