Surface-divided polarization conversion member and display device

Abstract

To provide a surface-divided polarization conversion member capable of generating two images at different virtual image distances from one display panel, and a display device using the surface-divided polarization conversion member.SOLUTION: A surface-divided polarization conversion member has, in a plan view, a first transmissive portion that transmits polarized light for a first image and a second transmissive portion that transmits polarized light for a second image. The second transmissive portion causes a phase difference different by λ / 2 from that caused by the first transmissive portion.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The following disclosure relates to a surface division polarization conversion member and a display device using the surface division polarization conversion member. [Background technology]

[0002] In recent years, attention has been focused on a three-dimensional virtual space called the Metaverse, and the market for VR-HMDs is expected to expand as a tool (product) for accessing the Metaverse. However, VR-HMDs cause a phenomenon called VR sickness (or 3D sickness), which is an obstacle to long-term use and the spread of the VR market.

[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 Patent Document 1 above is capable of displaying 3D images with the naked eye, but requires high-speed driving, which can lead to flicker and blurred images (also called "video") caused by high-speed driving, and can also lead to expensive systems and large housings. It is also known that the VR sickness occurs because the distance of the virtual image cannot be changed. For this reason, it is required to make the distance of the virtual image variable, mainly in HMDs (for VR), and the use of liquid crystal lenses has been considered. However, the conventional method using liquid crystal lenses moves an entire screen back and forth, and it is difficult to move only a part of the screen.

[0006] The present invention has been made in consideration of the above-mentioned current situation, and aims to provide a surface-division polarization conversion element that can generate two images with different virtual image distances from a single display panel, and a display device that uses the surface-division polarization conversion element. [Means for solving the problem]

[0007] (1) One embodiment of the present invention is a surface-dividing polarization conversion member that, in a planar view, has a first transmitting section that transmits polarized light for a first image and a second transmitting section that transmits polarized light for a second image, and the second transmitting section generates a phase difference that is different by λ / 2 compared to the first transmitting section.

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

[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 transmission section is a surface-dividing polarization conversion member that, in a cross-sectional view, comprises a pair of substrates and a liquid crystal layer disposed between the pair of substrates, and the phase difference is variable in response to a voltage applied to the liquid crystal layer.

[0011] (5) In addition, one embodiment of the present invention is a display device comprising: a display panel that outputs polarized light for a first and second image; a surface-division polarization conversion element as described above in (1), (2), (3) or (4) that is arranged at a position where the polarized light is incident; and an optical element that is arranged at a position where the polarized light that has passed through the surface-division polarization conversion element is incident, wherein the optical element differentiates a virtual image distance of a first image generated from a first polarized light that has passed through the first transmitting portion from a virtual image distance of a second image generated from a second polarized light that has passed through the second transmitting portion.

[0012] (6) Furthermore, in one embodiment of the present invention, in addition to the configuration of (5) 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 does not act as a lens for the second polarized light, or acts as a lens having a second focal length.

[0013] (7) Moreover, in addition to the configuration of (6) above, an embodiment of the present invention is a display device, wherein the liquid crystal lens is a refractive lens, a gradient index lens or a diffractive lens.

[0014] (8) Moreover, in one embodiment of the present invention, in addition to the configuration as described above in (6), the liquid crystal lens is a Pancharatnam-Berry phase lens.

[0015] (9) Moreover, in addition to the configuration of (6) above, another embodiment of the present invention is a display device, wherein the liquid crystal lens has a liquid crystal layer, and a focal length is variable in response to a voltage applied to the liquid crystal layer.

[0016] (10) Moreover, an embodiment of the present invention is a display device further comprising a lens other than a liquid crystal lens in addition to the configuration of (5), (6), (7), (8) or (9) above.

[0017] (11) Furthermore, an embodiment of the present invention is a display device comprising, in addition to the configuration of (6), (7), (8), (9) or (10) above, a combination of another surface division polarization conversion member and another liquid crystal lens.

[0018] (12) Furthermore, one embodiment of the present invention is a display device that, in addition to the configuration of (5), (6), (7), (8), (9), (10) or (11) above, performs a first image correction process on an overlapping area between the first image and the second image.

[0019] (13) Moreover, in one embodiment of the present invention, in addition to the configuration of (12) above, the first image correction process is a process of displaying the overlapping region in black.

[0020] (14) Furthermore, in one embodiment of the present invention, in addition to the configuration of (12) above, the first image correction process reduces the luminance of the overlapping area for at least one of the first image and the second image.

[0021] (15) Furthermore, in one embodiment of the present invention, in addition to the configuration of (12), (13) or (14) above, the first image correction process includes a process of determining the overlap area based on an amount of overlap between the first image and the second image detected based on eye tracking.

[0022] (16) Furthermore, in an embodiment of the present invention, in addition to the configuration of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14) or (15) above, a guest-host liquid crystal layer is provided between the surface-division polarization conversion member and the optical element, and the guest-host liquid crystal layer contains a light-absorbing material as a guest material and a liquid crystal as a host material.

[0023] (17) Furthermore, an embodiment of the present invention is a display device having the configuration of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15) or (16) above, further comprising: a second image correction process for a boundary area between the first image and the second image.

[0024] (18) Furthermore, in one embodiment of the present invention, in addition to the configuration of (17) above, the second image correction process is a display device that overlays the first image and the second image by time-division display.

[0025] (19) Furthermore, an embodiment of the present invention is a display device that is a VR display device or a 3D display device in addition to the configuration of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), (17), or (18) above.

[0026] (20) Furthermore, an embodiment of the present invention is a display device that is a head-mounted display device in addition to the configuration of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), (17), (18), or (19) above. Effect of the Invention

[0027] According to the present invention, it is possible to provide a surface-division polarization conversion element capable of generating two images with different virtual image distances from a single display panel, and a display device using the surface-division polarization conversion element. [Brief description of the drawings]

[0028] [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 illustrating a schematic configuration of a display device according to a first embodiment. [Figure 7] 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 8] 8 is a diagram for explaining the operation of the refractive lens in the direction A shown in FIG. 7, 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 9] 8 is a diagram for explaining the operation of the refractive lens in the direction B shown in FIG. 7, 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] FIG. 1 is a top view illustrating the configuration of a Pancharatnam-Berry phase lens. [Figure 11] This is a diagram explaining the function of the Pancharatnam-Berry phase lens. [Figure 12] FIG. 2 is a side view showing an example of a specific configuration of the display device according to the first embodiment. [Figure 13] FIG. 13 is a bird's-eye view of the display device shown in FIG. [Figure 14] 2 is an enlarged cross-sectional view of a surface-dividing polarization conversion member according to the first embodiment. FIG. [Figure 15] 4 is a side view showing another example of a specific configuration of the display device according to the first embodiment. FIG. [Figure 16] FIG. 11 is a side view illustrating a schematic configuration of a display device according to a second embodiment. [Figure 17] FIG. 11 is a side view illustrating a schematic configuration of a display device according to a third embodiment. [Figure 18] 11A and 11B are diagrams for explaining how pixels at the boundary appear when a surface division polarization conversion member is disposed away from the display surface. [Figure 19] 1A and 1B are diagrams for explaining the principle of video overlap and gap generation. [Figure 20] FIG. 1 is a side view illustrating a schematic configuration of a display device in which overlapping virtual images occurs. [Figure 21] FIG. 11 is a front view showing an example of a display surface when virtual images overlap. [Figure 22] FIG. 11 is a front view showing an example of an image when virtual images overlap. [Figure 23] 11A and 11B are diagrams illustrating a first correction for overlapping of virtual image planes, showing original images. [Figure 24] 11A and 11B are diagrams illustrating a first correction for overlapping of virtual image planes, showing enlarged images. [Diagram 25] 13 is a diagram illustrating a second correction for overlapping of virtual image planes, showing an original image. FIG. [Figure 26] 13A and 13B are diagrams illustrating a second correction for overlapping of virtual image planes, showing enlarged images. [Figure 27] 13A and 13B are diagrams illustrating a third correction for overlapping of virtual image planes. [Figure 28] 1 is a flowchart showing an example of image correction when eye-tracking technology is used. [Figure 29] Figure 1 illustrates the first correction when using eye-tracking technology and shows the original image. [Diagram 30] Figure 1 illustrates the first correction when using eye-tracking technology and shows an enlarged image. [Diagram 31] 1 is a diagram illustrating the principle of how gaps between virtual images occur, showing original images. [Diagram 32] 1A and 1B are diagrams illustrating the principle of how gaps between virtual images occur, showing enlarged images. [Diagram 33] FIG. 13 is a diagram illustrating a time-division display. [Diagram 34] 1A and 1B are diagrams illustrating the relationship between the focal length of a lens and a virtual image. [Diagram 35] FIG. 11 is a side view diagrammatically illustrating the configuration of a display device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] 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.

[0030] The surface-splitting polarization conversion member of the present invention is installed in a display device and can generate two images with different virtual image distances from one display panel. Examples of the types of display devices include a VR display device that displays content corresponding to VR (virtual reality) technology and a 3D display device that displays three-dimensional images, and among them, a head-mounted display device (HMD) is preferable. A 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 corresponding to VR (virtual reality) technology. Examples of the configuration of an HMD include 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.

[0031] By using the surface-splitting polarization conversion member of the present invention to generate two images with different virtual image distances, it is possible to reduce the burden on the user (observer) when viewing a display device and to improve the sense of immersion in the content.

[0032] 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 a normal direction to the display surface of the display 11, a solid arrow indicates a path of light that displays a real image from the display surface of the display 11 to the eyes of the user U, and a dotted arrow indicates a path of light that displays a virtual image from the display surface of the display 11 to 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."

[0033] 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, the image R for the right eye and the image L for the left eye are displayed separately, so that the user U is made to visually recognize that the image I1 is at the position where the 3D image is to be displayed. 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, the conventional VR is different 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 toward the image I1 is not consistent with the focus adjustment. It is considered that VR sickness occurs due to the difference between the focus adjustment distance (the distance between the image R for the right eye and the image L for the left eye) D1 and 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.

[0034] 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 the image I1, the 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 the image I1 and the position of the image I2, it is necessary to switch both the liquid crystal lens and the image, and the blur is expressed by the image, so 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, which allows for smooth switching of the viewpoint and provides a good sense of immersion. Therefore, in the present invention, two virtual image planes (two images with different virtual image distances) are generated.

[0035] <Embodiment 1> Fig. 6 is a side view showing a schematic configuration of the display device according to embodiment 1. The display device in Fig. 6 includes, in order from the user U side, 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. 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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, and is, 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.

[0040] 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.

[0041] 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.

[0042] The refractive lens will be described with reference to Figs. 7 to 9. Fig. 7 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. 8 is a diagram for explaining the operation of the refractive lens in the direction A shown in Fig. 7, 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. 9 is a diagram for explaining the operation of the refractive lens in the direction B shown in Fig. 7, 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. The arrows in Figs. 8 and 9 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. 8 and 9), and when a voltage is applied, the liquid crystal 54a is oriented vertically (upper diagrams in Figs. 8 and 9). 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. 8, 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. 9, in the direction B, no refraction difference occurs whether or not a voltage is applied, and the lens function is never generated.

[0043] 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.

[0044] FIG. 10 is a top view for explaining the configuration of a Pancharatnam Berry phase lens, and FIG. 11 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. 10 causes diffraction, resulting in a lens function. In FIG. 11, the optical path of the right-handed circularly polarized RCP output from the Pancharatnam Berry phase lens PBL is shown by a solid line, 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. The Pancharatnam Berry phase lens PBL in FIG. 11 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.

[0045] Fig. 12 is a side view showing an example of a specific configuration of the display device according to the first embodiment, Fig. 13 is a bird's-eye view of the display device shown in Fig. 12, and Fig. 14 is an enlarged cross-sectional view of a surface-splitting polarization conversion member according to the first embodiment. The display device shown in Fig. 12 is a 3D display, in which a display 11 is disposed at a viewing distance of about 500 mm, and a liquid crystal lens 50 is disposed at a position 100 mm away from the display 11. The liquid crystal lens 50 is a refractive lens, and its focal length is about 100 mm. The viewing distance is about 500 mm because a person needs to view a medium-sized display (up to about 20 inches) from a distance of about 500 mm.

[0046] A surface-splitting polarization conversion member (liquid crystal panel) 20 capable of switching between the presence and absence of a phase difference of λ / 2 (i.e., 275 nm for 550 nm light) is disposed on the screen of the display 11. 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-splitting polarization conversion member 20 may be configured by stacking two layers of liquid crystal panels in order to reduce wavelength dependency.

[0047] As shown in Fig. 14, 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. 14, 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).

[0048] 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).

[0049] 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. As explained in FIG. 8, the focal length of the liquid crystal lens 50 is maximum when the voltage is off.

[0050] Fig. 15 is a side view showing another example of a specific configuration of the display device according to the first embodiment. The display device shown in Fig. 15 is a 3D display, and the liquid crystal lens 50 is a Pancharatnam-Berry phase lens (PB lens). The PB lens is a lens that can switch the strength of refraction by the lens (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 alignment pitch of the liquid crystal.

[0051] The PB lens switches between concave and convex lenses depending on whether the circularly polarized light is right or left, so that two virtual images V can be created, one in front of the display 11 and one behind it. When using the PB lens, a circular polarizing plate combining, for example, a polarizing plate 13 and a λ / 4 plate 15 is provided to circularly polarize the light emitted from the display 11. By placing a surface-splitting polarization conversion member 20, which can switch circularly polarized light into the opposite circularly polarized light, on top of the circular polarizing plate, it is possible to switch between left and right circularly polarized light. The surface-splitting polarization conversion member 20 allows switching between two virtual image surfaces, so that two surfaces at different distances can be viewed simultaneously by surface splitting, allowing a display with depth (3D display) to be viewed, enhancing the sense of immersion in VR and enabling smooth switching of viewpoints.

[0052] <Embodiment 2> 16 is a side view showing a schematic configuration of a display device according to embodiment 2. The display device according to this embodiment includes a lens other than a liquid crystal lens. Specifically, a physical lens 40 with a focal length of 100 mm and a liquid crystal lens 50 with a focal length of 100 mm are arranged in close proximity to each other or bonded together, and it is assumed that the liquid crystal lens 50 is placed 50 mm away from the display 11 and observed from a viewing distance of about 65 mm like VR. In the case of VR, the user cannot focus unless the screen is enlarged by a certain amount (for example, about 10 times) using a lens. Therefore, since there is a direction in which the liquid crystal lens 50 does not function as a lens, a physical lens (normal lens) 40 is used in combination. As in the first embodiment, a surface division polarization conversion member (liquid crystal panel) 20 is disposed on the screen of the display 11. The liquid crystal mode of the liquid crystal panel and the driving conditions of the liquid crystal lens are the same as those in the first embodiment. The difference from embodiment 1 is that since the physical lens 40 is also used, even in a direction in which the liquid crystal lens 50 does not act as a lens, the image is magnified by the physical lens 40, and a virtual image rather than a real image is seen. In the second embodiment as well, the surface-division polarization conversion member 20 can switch between two virtual image planes, so that two planes at different distances can be viewed simultaneously by surface division, allowing a display with depth (3D display) to be viewed, enhancing the sense of immersion in VR and enabling smooth switching of viewpoints. Instead of the physical lens 40, a Fresnel lens or a diffractive lens may be used as another lens.

[0053] <Embodiment 3> 17 is a side view showing a schematic configuration of a display device according to embodiment 3. The display devices according to embodiments 1 and 2 use one set of a surface division polarization conversion member and a liquid crystal lens, whereas the display device according to embodiment 3 includes 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 division 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. As shown in Fig. 18, when the surface division polarization conversion member 20 is moved away from the display surface, 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.

[0054] <Embodiment 4> The two virtual image planes generated using the surface-splitting polarization conversion component may appear to overlap at the boundary between them or may have areas with no image depending on the position of the user's eyes and the depth of the virtual image (distance from the user). This occurs because the magnification ratios of the two virtual image planes are different and the position of the eyes moves. FIG. 19 is a diagram for explaining the principle of overlapping and gap generation of images. As shown in FIG. 19, when the eyes of the user U are positioned on the normal line of the lens center, in an ideal state where there is no distortion in the optical system, there is no overlap between the virtual image V1 and the virtual image V2. However, in reality, the position of the eyes may be slightly shifted from the normal line of the lens center when the HMD housing is worn. Due to this shift, the virtual image V1 and the virtual image V2 may appear to overlap, or a gap without an image may occur between the virtual image V1 and the virtual image V2. When the eyes of the user U are closer to the edge of the virtual image than the expected position, the lower part of the virtual image V1 that should be visible cannot be seen (there is no image, and it appears black). When the eyes are farther from the edge of the virtual image than the expected position, the lower part of the virtual image V1 that should not be visible appears to overlap. Note that the shift of the virtual image has no effect on the rotational movement of the eyeball. This is the same as when the dotted part of the virtual image V1 behind the virtual image V2 is not newly visible even if the eyeball is rotated.

[0055] FIG. 20 is a side view showing a schematic configuration of a display device in which virtual images overlap, FIG. 21 is a front view showing an example of a display surface when virtual images overlap, and FIG. 22 is a front view showing an example of an image when virtual images overlap. As shown in FIG. 21, in the original image on the display surface, an image A1 is displayed in an area where the phase difference of the surface division polarization conversion member 20 is zero, and an image B1 is displayed in an area where the phase difference of the surface division polarization conversion member 20 is λ / 2, and the images A1 and B1 are the same size. On the other hand, in the image (enlarged image) obtained by being emitted from the display surface and passing through the surface division polarization conversion member 20, as shown in FIG. 22, the image A1 is displayed as a near virtual image A2, and the image B1 is enlarged and displayed as a far virtual image B2, and the virtual image A2 and the virtual image B2 overlap. The portion AB where the virtual images overlap appears bright because the amount of light is simply added. Normally, the far virtual image B2 is hidden by the near virtual image A2, and such a display creates an uncomfortable feeling, except in some cases where it is acceptable as a production effect. Also, the amount of overlap depends on the position of the eyes, and is not affected much by the movement (rotation) of the eyeballs, but it is affected greatly if the eye position shifts (the amount of overlap shifts).

[0056] In this embodiment, an image correction process (first image correction process) may be performed on an overlapping area (overlap of virtual image planes) between the first image and the second image. Examples of the first image correction process include the following.

[0057] (1) First image correction process The first image correction process includes a process (first correction) in which the overlapping area (the portion where the virtual images overlap) is displayed in black, as shown in the original image in Fig. 23 and the enlarged image in Fig. 24. In this case, image overlap can be fundamentally prevented.

[0058] The first image correction process includes a process (second correction) for reducing the luminance of the overlapping region of at least one of the first image and the second image, as shown in the original image in Fig. 25 and the enlarged image in Fig. 26. Specifically, a luminance gradient may be provided in the overlapping region. Although Fig. 25 shows the image simply in terms of luminance, the image may be weighted by making the luminance of the image in the foreground closer to the original luminance and the image in the background darker than the original luminance.

[0059] The first image correction process may be a third correction, in which a guest-host liquid crystal layer 70 is disposed between the surface division polarization conversion member 20 and the liquid crystal lens 50, as shown in FIG. 27. The guest-host liquid crystal layer 70 is preferably disposed near the liquid crystal lens 50, and more preferably adjacent to the liquid crystal lens 50. The guest-host liquid crystal layer 70 includes a light absorbing material as a guest material and a liquid crystal as a host material, and examples of the guest material include a light absorbing material having a single axis and a liquid crystal material having a vertical alignment type liquid crystal. If such a guest-host liquid crystal layer 70 is disposed, the light is not absorbed when the voltage is off, and only one polarized component is absorbed when the voltage is on. As shown in FIG. 27, if the guest-host liquid crystal layer 70 is disposed in the area where the virtual images V overlap, so that only the polarized light that displays the distant view (distant virtual image) is absorbed, only the light that displays the near view (near virtual image) can be seen. The position of the guest-host liquid crystal layer 70 may be adjusted by using eye tracking, which will be described later.

[0060] The first image correction process may include a process of determining the overlapping area based on the amount of overlap between the first image and the second image detected based on eye tracking. As described above, the overlapping position shifts depending on the position of the user's eyes, so by using eye tracking technology, it is possible to appropriately correct the image in real time. By using eye tracking technology in combination with the first measure and / or the second measure, it is possible to more effectively prevent the discomfort of the display caused by the overlapping of virtual images. Specifically, the position of the user's eyes is identified by eye tracking technology, and the luminance gradient in the second measure is constantly corrected according to the result. In addition, if the image that becomes the distant view (distant virtual image) in the overlapping part of the virtual images is made black, the perspective will naturally appear to be lined up in front and back without overlapping when enlarged.

[0061] FIG. 28 is a flow chart showing an example of image correction when eye tracking technology is used. As shown in FIG. 28, first, an image of the periphery of the user's eye is captured by an imaging means such as a camera (step S11). Next, three-dimensional coordinates (x, y, z) relating to the position of the eye are calculated from the obtained image information of the periphery of the eye (step S12). The three-dimensional coordinates need only specify the position of the eyeball, and do not need to include information regarding the rotation of the eyeball. Based on the three-dimensional coordinates relating to the position of the eye, a region where a gap occurs between virtual images and a region where an overlap occurs between virtual images are calculated (step S13). If an overlap occurs between virtual images based on the calculation result, the first, second, or third correction described above is performed (step S14A). By using such eye tracking technology, it is possible to accurately specify a region where an overlap occurs between virtual images, as shown in the original image in FIG. 29 and the enlarged image in FIG. 30, and perform image correction processing according to the specified region. Furthermore, if a gap occurs between virtual images, a second image correction processing described later is performed (step S14B).

[0062] In this embodiment, an image correction process (second image correction process) may be performed on a boundary region (a gap between virtual images) between the first image and the second image.

[0063] (2) Second Image Correction Process The second image correction process may be a process of displaying the boundary area between the first image and the second image in a time-division manner. Fig. 31 is a diagram for explaining the principle of the occurrence of a gap between virtual images, showing an original image. Fig. 32 is a diagram for explaining the principle of the occurrence of a gap between virtual images, showing an enlarged image. Fig. 33 is a diagram for explaining the time-division display. Due to a shift in the position of the user's eyes or distortion of the optical system, images A and B, which are displayed without gaps in the original image as shown in FIG. 31, may have gaps (black areas) in the enlarged image (image as seen by a person) as shown in FIG. 32. Note that in FIG. 32, there are also areas where images A and B overlap. To address the gaps and overlaps, a correction process may be performed to superimpose images A and B by time-division display. In this case, the position and size of images A and / or B may be adjusted. By displaying at least the boundary area between images A and B in a time-division manner, it is possible to prevent the occurrence of areas in the enlarged image where no display is present (appearing black). Time-division display is performed by simultaneously switching the display and the surface-division polarization conversion member. It is not necessary to display the areas other than the boundary area in a time-division manner, but in that case, it is desirable to adjust the brightness so that it does not differ. In other words, if the area where image A and image B overlap in Fig. 33 were to be switched on and lit for 1 / 2 the time of the original frame, the brightness would be halved. Therefore, it is desirable to double the brightness of only this part, or to halve the brightness of the surrounding area.

[0064] In addition, as shown in Fig. 34, in terms of simple lens geometric optics, as the focal length becomes shorter (i.e., the lens power becomes stronger), the virtual image V becomes farther away and larger. Therefore, in the case of Fig. 32, the virtual image V of image A is closer, and the virtual image V of image B is farther away.

[0065] <Embodiment 5> 35 is a side view showing a schematic configuration of a display device according to embodiment 5. In the above-mentioned embodiment, a voltage-variable liquid crystal lens is used, but a static (non-variable) liquid crystal lens 50 may be used using a UV-curable liquid crystal material. In this embodiment, 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 using the surface division polarization conversion member 20. It can be manufactured inexpensively, and the liquid crystal lens 50 does not require electrical wiring, which has the advantage of being concentrated on the display 11 side, making it applicable to VR and the like.

[0066] According to the surface division polarization conversion member of the present invention, two images with different virtual image distances can be generated, which can reduce the burden on the user (observer) when viewing the display device and improve the immersive feeling in the content. As a specific application example, in the case of a VR display device, a close view (nearby virtual image) and a distant view (distant virtual image) can be displayed as VR. [Explanation of symbols]

[0067] 10: Display panel 11: Display 13: Polarizing plate 15:λ / 4 plate 20: 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 70: Guest-host liquid crystal layer A, A1, B, B1: Images A2, B2: Virtual image AB: The area where the virtual images overlap D1: Focus adjustment distance D2: Convergence distance I1, I2: Video I2a: Blurred image R: Right eye image 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

Claims

1. a first transmitting portion that transmits polarized light for a first image and a second transmitting portion that transmits polarized light for a second image in a plan view; A surface division polarization conversion member, wherein the second transmission portion generates a phase difference different by λ / 2 from that of the first transmission 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 surface division polarization conversion member according to claim 1 .

3. The surface division polarization conversion member according to claim 2 , wherein the conversion portion 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 surface division polarization conversion member according to claim 1 .

5. a display panel that outputs polarized light for the first and second images; The surface division polarization conversion member according to claim 1 , which is disposed at a position where the polarized light is incident; an optical element disposed at a position where the polarized light transmitted through the surface division polarization conversion member is incident, A display device in which 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.

6. 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 display device according to claim 5.

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

8. The display device according to claim 6 , wherein the liquid crystal lens is a Pancharatnam-Berry phase lens.

9. 7. The display device according to claim 6, wherein the liquid crystal lens has a liquid crystal layer, and a focal length thereof is variable in response to a voltage applied to the liquid crystal layer.

10. The display device according to claim 5 , further comprising a lens other than the liquid crystal lens.

11. The display device according to claim 6 , further comprising a combination of another surface division polarization conversion member and another liquid crystal lens.

12. The display device according to claim 5 , wherein a first image correction process is performed on an overlapping area between the first image and the second image.

13. The display device according to claim 12 , wherein the first image correction process displays the overlapping area in black.

14. The display device according to claim 12 , wherein the first image correction process reduces luminance of the overlapping region of at least one of the first image and the second image.

15. 13. The display device according to claim 12, wherein the first image correction process includes a process for determining the overlap area based on an amount of overlap between the first image and the second image detected based on eye tracking.

16. Further, a guest-host liquid crystal layer is provided between the surface division polarization conversion member and the optical element, 6. The display device according to claim 5, wherein the guest-host liquid crystal layer contains a light absorbing material as a guest material and a liquid crystal as a host material.

17. The display device according to claim 5 , further comprising a second image correction process for a boundary area between the first image and the second image.

18. 18. The display device according to claim 17, wherein the second image correction process superimposes the first image and the second image by time-division display.

19. 6. The display device of claim 5, which is a VR display device or a 3D display device.

20. 6. The display device according to claim 5, which is a head-mounted display device.

Images