Surface-split polarized light conversion member and display device

Abstract

Provided are: a surface-divided polarized light conversion member capable of generating two images having different virtual image distances from one display panel; and a display device using the surface-divided polarized light conversion member. In plan view, the plane-splitting polarization conversion member is provided with: a first transmission unit that transmits polarized light for a first image; and a second transmissive section that transmits polarized light for a second image, the second transmissive section generating a phase difference that differs by [lambda] / 2 from the first transmissive section.

Description

Technical Field

[0001] The following disclosure relates to a plane-dividing polarization conversion member and a display device using the plane-dividing polarization conversion member. Background Art

[0002] In recent years, the three-dimensional virtual space called Metaverse has attracted much attention, and the market for VR-HMD is expected to expand as a tool (product) for accessing Metaverse. On the other hand, VR-HMD has a phenomenon called VR motion sickness (or 3D motion sickness), which has become an obstacle to long-term use and the popularization of VR market.

[0003] As an existing technology related to three-dimensional display, for example, patent document 1 discloses a three-dimensional display method, which generates a two-dimensional image obtained by projecting a display object from the line of sight of an observer relative to a plurality of display surfaces arranged at different depth positions when observed from an observer, and displays the generated two-dimensional image on any two of the plurality of display surfaces respectively, so that the brightness of the displayed two-dimensional image varies independently on any two of the plurality of display surfaces to generate a three-dimensional stereoscopic image, and uses a polarization-type multi-focal optical system to image display light of the two-dimensional image on any two of the plurality of display surfaces, and controls the polarization direction of the display light so that the brightness of the two-dimensional image imaged on any two of the plurality of display surfaces varies independently. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2002-156603 Summary of the invention Technical Problems to be Solved by the Invention

[0005] Although the prior art described in Patent Document 1 can perform three-dimensional display using naked eyes, it requires high-speed driving, which results in flickering and unclear images (also called "videos") caused by high-speed driving, and the system tends to become expensive and the housing tends to become large. In addition, it is known that the VR motion sickness described above is caused by the inability to move the distance of the virtual image. Therefore, mainly in HMD (for VR), it is required to make the distance of the virtual image variable, and the use of liquid crystal lenses is being studied. However, the conventional method of using liquid crystal lenses is a method of moving the entire screen forward and backward, and it is difficult to move only a part of the screen.

[0006] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a plane-dividing polarization conversion member capable of generating two images having different virtual image distances from one display panel, and a display device using the plane-dividing polarization conversion member. Technical solutions for solving technical problems

[0007] (1) A plane-split polarization conversion component according to one embodiment of the present invention comprises, when viewed from above, 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, the second transmission portion generating a phase difference of λ / 2 compared with the first transmission portion.

[0008] (2) In addition, in the surface-split polarization conversion component of one embodiment of the present invention, based on the structure of (1) above, the first transmission part is a non-conversion part that transmits the polarized light for the first image without converting the polarization state, and the second transmission part is a conversion part that causes the polarized light for the second image to produce a phase difference of λ / 2 and convert the polarization state.

[0009] (3) In addition, in a plane-divided polarization conversion member according to an embodiment of the present invention, in addition to the configuration of (2) above, the conversion section includes a resin layer having a λ / 2 phase difference.

[0010] (4) In addition, in an embodiment of the present invention, based on the structure of (1), (2) or (3) above, the second transmission part has a pair of substrates and a liquid crystal layer arranged between the pair of substrates when observed in cross section, and the phase difference can be changed according to the voltage applied to the liquid crystal layer.

[0011] (5) In addition, a display device according to one embodiment of the present invention includes: a display panel that emits polarized light for first and second images; a plane-split polarization conversion component according to the configuration of (1), (2), (3) or (4) above, which 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 plane-split polarization conversion component is incident, the optical element making a virtual image distance of a first image generated from the first polarized light that has passed through the first transmission portion different from a virtual image distance of a second image generated from the second polarized light that has passed through the second transmission portion.

[0012] (6) In addition, in a display device according to one embodiment of the present invention, based on the structure 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) In addition, in a display device according to one embodiment of the present invention, in addition to the configuration of (6) above, the liquid crystal lens is a refractive lens, a distributed refractive index lens, or a diffractive lens.

[0014] (8) In addition, in a display device according to an embodiment of the present invention, in addition to the configuration of (6) above, the liquid crystal lens is a Pancharatnam-Berry phase lens.

[0015] (9) In a display device according to one embodiment of the present invention, in addition to the configuration of (6), the liquid crystal lens includes a liquid crystal layer, and the focal length can be changed according to a voltage applied to the liquid crystal layer.

[0016] (10) In addition, a display device according to one embodiment of the present invention further includes a lens other than a liquid crystal lens in addition to the configuration of (5), (6), (7), (8) or (9) described above.

[0017] (11) In addition, a display device according to one embodiment of the present invention further has a combination of other plane-split polarization conversion components and other liquid crystal lenses based on the above-mentioned structure (6), (7), (8), (9) or (10).

[0018] (12) In addition, a display device according to one embodiment of the present invention performs a first image correction process on the overlapping area of ​​the first image and the second image based on the configuration of (5), (6), (7), (8), (9), (10) or (11) above.

[0019] (13) In addition, in a display device according to an embodiment of the present invention, in addition to the configuration described above or in (12), in the first image correction processing, the overlapping area is displayed in black.

[0020] (14) In addition, in a display device according to an embodiment of the present invention, based on the configuration of (12) above, in the first image correction processing, the brightness of the overlapping area of ​​at least one of the first image and the second image is reduced.

[0021] (15) In addition, in a display device according to one embodiment of the present invention, based on the configuration of (12), (13) or (14) above, the first image correction processing includes the following processing: determining the overlapping area based on the amount of overlap between the first image and the second image detected based on eye tracking.

[0022] (16) In addition, a display device according to one embodiment of the present invention, based on the structure of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14) or (15) above, also has a guest-host liquid crystal layer between the plane-split polarization light conversion component and the optical element, wherein the guest-host liquid crystal layer contains a light-absorbing material as a guest material and contains liquid crystal as a host material.

[0023] (17) In addition, a display device according to one embodiment of the present invention performs a second image correction process on the boundary area between the first image and the second image based on the configuration of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15) or (16) described above.

[0024] (18) In addition, in a display device according to an embodiment of the present invention, in addition to the configuration of (17) above, in the second image correction processing, the first image and the second image are overlapped by time-sharing display.

[0025] (19) In addition, a display device according to one embodiment of the present invention is a VR display device or a 3D display device based on the structure of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), (17) or (18) above.

[0026] (20) In addition, a display device according to one embodiment of the present invention is a head-mounted display device based on the structure of (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16) (17), (18) or (19) above. Beneficial Effects

[0027] According to the present invention, it is possible to provide a plane division polarization conversion member capable of generating two images having different virtual image distances from one display panel, and a display device using the plane division polarization conversion member. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A diagram for explaining the display principle of a virtual image in a display device. Figure 2 This is a diagram illustrating the display principle of conventional VR. Figure 3 It is a diagram that illustrates how people see real objects. Figure 4 It is a diagram for explaining a display state when there is only one virtual image plane. Figure 5 It is a diagram for explaining a display state when there are two virtual image planes. Figure 6 It is a side view schematically showing the configuration of the display device according to the first embodiment. Figure 7 The diagrams are for explaining the structure of a refractive lens using a resin, wherein the upper diagram is a cross-sectional view and the lower diagram is a plan view. Figure 8 Yes Description Figure 7 The diagram shows the operation of the refractive lens in orientation A. The upper diagram shows when a voltage is applied to the liquid crystal layer, and the lower diagram shows when no voltage is applied to the liquid crystal layer. Fig. 9 Yes Description Figure 7 The diagram shows the operation of the refractive lens in orientation B. The upper diagram shows when a voltage is applied to the liquid crystal layer, and the lower diagram shows when no voltage is applied to the liquid crystal layer. Fig.10 It is a top view illustrating the structure of the Pancharatnam-Berry phase lens. Fig.11 It is a diagram for explaining the function of the Pancharatnam-Berry phase lens. Fig.12 It is a side view showing an example of a specific configuration of the display device according to the first embodiment. Fig.13 yes Fig.12 A bird's eye view of the display device is shown. Fig.14 It is an enlarged cross-sectional view of the plane-divided polarization conversion member according to the first embodiment. Fig.15 It is a side view showing another example of the specific configuration of the display device according to the first embodiment. Fig.16 It is a side view schematically showing the configuration of a display device according to the second embodiment. Fig.17 It is a side view schematically showing the configuration of a display device according to the third embodiment. Fig.18 This is a diagram for explaining a method of observing pixels at a boundary portion when a plane-divided polarization conversion member is arranged to be separated from a display surface. Fig.19 This is a diagram for explaining the principle of overlapping and gap generation of images. Fig. 20 It is a side view schematically showing the structure of a display device in which virtual images are superimposed. Fig.21 This is a front view showing an example of a display surface when virtual images are superimposed. Fig. 22 This is a front view showing an example of an image when virtual image superposition occurs. Fig.23 This is a diagram for explaining the first correction for superposition of virtual image surfaces, and shows an original image. Fig.24 It is a diagram for explaining the first correction of superposition on the virtual image surface, and shows an enlarged image. Fig.25 It is a diagram for explaining the second correction of superposition of the virtual image plane, and shows the original image. Fig.26It is a diagram for explaining the second correction of superposition of the virtual image plane, and shows an enlarged image. Fig. 27 It is a diagram for explaining the third correction of superposition of the virtual image surface. Fig.28 is a flowchart showing an example of image correction when using eye tracking technology. Fig.29 This is a diagram for explaining the first correction when the eye tracking technology is used, and shows an original image. Fig.30 This is a diagram for explaining the first correction when the eye tracking technology is used, and shows an enlarged image. Fig.31 This is a diagram for explaining the principle of generating a gap between virtual images, and shows an original image. Fig.32 This is a diagram for explaining the principle of generating a gap between virtual images, and shows an enlarged image. Fig.33 It is a diagram illustrating time-sharing display. Fig.34 This is a diagram illustrating the relationship between the focal length of a lens and a virtual image. Fig.35 It is a side view schematically showing the structure of a display device according to the fifth embodiment. DETAILED DESCRIPTION

[0029] Hereinafter, the embodiments of the present invention will be described. The present invention is not limited to the contents described in the following embodiments, and design changes can be appropriately made within the scope of the configuration of the present invention. In addition, in the following description, for the same parts or parts with the same functions, the same figure numerals are appropriately used between different drawings, and the repeated descriptions are appropriately omitted. The various modes of the present invention can also be appropriately combined within the scope of not departing from the gist of the present invention.

[0030] The surface split polarization conversion component of the present invention is arranged in a display device, and can generate two images with different virtual image distances from one display panel. As the type of display device, for example, a VR display device that displays content corresponding to VR (virtual reality) technology, a 3D display device that displays three-dimensional images, etc. can be listed, among which a head-mounted display device (HMD) is preferred. A head-mounted display device (HMD) is a display device that can be worn on the head, for example, having a goggles shape that can be worn on the head, and a display such as a liquid crystal display is arranged in front of the user's eyes when worn. Such an HMD is suitable for viewing and listening to content corresponding to VR (virtual reality) technology. As the structure of the HMD, for example, the following structure can be listed: having a support portion for wearing on the user's head and a display having a liquid crystal module, and the above-mentioned display is arranged in front of the user's eyes when worn.

[0031] By using the plane-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 the audio-visual display device and improve the immersion in the content.

[0032] Figure 1 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 normal direction relative to the display surface of the display 11, a solid arrow indicates the 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 the path of light that displays a virtual image from the display surface of the display 11 to the eyes of the user U. Figure 1 The display device includes a liquid crystal lens 50 with adjustable focal length, a lens (physical lens) 40 with fixed focal length, a polarizing plate 13, and a display 11 in order from the user U side. The distance from the liquid crystal lens 50 to the display 11 is short in a head mounted display device (HMD) or the like, so the user U visually recognizes a virtual image V behind the display 11. Here, if the focal length of the liquid crystal lens 50 is changed, the position of the virtual image V moves forward and backward relative to the user U. Whether the virtual image V moves intermittently or continuously depends on the method of the liquid crystal lens 50. However, in Figure 1 In the display device, the virtual image V at a specific timing is always formed at a specific distance. In other words, the virtual image V is displayed in one plane. Hereinafter, the plane displaying the virtual image V is also referred to as a "virtual image plane".

[0033] Next, the problems when using virtual images for display will be described based on a VR display device as a typical example of a display device that displays virtual images. VR motion sickness is known as the above problem, and its occurrence mechanism is as follows. Figure 2 This is a diagram illustrating the display principle of existing VR. Figure 2 As shown, in VR display, by separately displaying the image R for the right eye and the image L for the left eye, the user U visually recognizes that the image I1 exists at the position where the user wants to project the 3D image. Figure 3 It is a diagram that illustrates the state of a person viewing a real object. Figure 2 and Figure 3 By comparison, it can be seen that the difference between existing VR and the state of people viewing real objects is that the movement (convergence) of rotating the right eye RE and the left eye LE toward the image I1 and the focus adjustment are inconsistent. It is believed that VR motion sickness is caused by 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 based on the gaze point of both eyes. This is caused by the fact that the image R for the right eye and the image L for the left eye are virtual images, and the virtual image plane (the distance of the virtual image) cannot move. Here, if the virtual image plane can be moved using a liquid crystal lens that can adjust the focal length, it can be achieved. Figure 3 state, which can prevent VR motion sickness.

[0034] On the other hand, when displaying stereoscopic images (3D images) through VR, it is difficult to completely eliminate the discomfort compared to the state in which people see real objects by simply moving the virtual image using a liquid crystal lens that can adjust the focal length. Figure 4 is a diagram for explaining a display state when there is only one virtual image plane. Figure 5 2 is a diagram illustrating the display state when there are two virtual image planes. When there is only one virtual image plane, how to express the object in the peripheral vision becomes a problem. Specifically, Figure 4 As shown, when the focus is on the position of image I1, the image I2 of the object at a closer position should be seen blurred. If there is only one virtual image plane, two blurred images I2a for the right eye and the left eye are displayed on the same virtual image plane. By making it look like there is a blurred image I2, it can be perceived as peripheral vision. However, when switching the viewpoint to the position of image I1 and the position of image I2, it is necessary to switch both the liquid crystal lens and the image. Since the blur is expressed by the image, it is difficult to completely eliminate the discomfort. In contrast, Figure 5 As shown, if there are two virtual image planes, there is no need to switch the liquid crystal lens and the image when the viewpoint is switched, so smooth viewpoint switching can be performed to obtain a good sense of immersion. Therefore, in the present invention, two virtual image planes (two images with different virtual image distances) are generated.

[0035] <First Embodiment> Figure 6 It is a side view schematically showing the structure of the display device according to the first embodiment. Figure 6 The display device includes, in order from the user U side: a liquid crystal lens (optical element) 50 capable of adjusting the focal length, a surface split polarization conversion component 20, a polarizing plate 13, and a display 11. The display panel 10 composed of the combination of the display 11 and the polarizing plate 13 emits polarized light. When one of two images with different virtual image distances is defined as a "first image" and the other image is defined as a "second image", the display panel emits polarized light for the first image and the second image, respectively. The polarized light for the first and second images passes through the surface split polarization conversion component 20 and is incident on the liquid crystal lens 50 capable of adjusting the focal length.

[0036] As the display 11, for example, a self-luminous display such as a liquid crystal display (LCD) or an organic EL display (OLED) can be cited. As the polarizing plate 13, a linear polarizer is used that transmits polarized light vibrating in a certain direction (a first polarized light component) and absorbs or reflects polarized light vibrating in a direction orthogonal to the polarized light (a second polarized light component).

[0037] The above-mentioned plane-divided polarization conversion member 20 has 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 in a plan view. The second transmission portion is a region that generates a phase difference of λ / 2 compared with the first transmission portion, and the polarized light for the first image is transmitted through the first transmission portion, and the polarized light for the second image is transmitted through the second transmission portion, so that the polarized light for the first image and the polarized light for the second image can generate a phase difference of λ / 2. Figure 6 The display device can make the virtual image distances of two images different by utilizing the phase difference of λ / 2. Here, "generating a phase difference of λ / 2" means giving a phase difference equivalent to 1 / 2 of the wavelength to the transmitted light, for example, giving a phase difference of 200nm or more and 350nm or less to the light of wavelength 550nm. In the present embodiment, the above-mentioned surface-divided polarization conversion component 20 is a non-conversion part 22 that allows the first transmission part to transmit the polarized light for the first image without converting the polarization state, and the second transmission part is a conversion part 21 that converts the polarization state by generating a phase difference of λ / 2 for the polarized light for the second image. Here, "not converting the polarization state" means, for example, that the phase difference with respect to the light of wavelength 550nm is less than 10nm.

[0038] As the plane-divided polarization conversion member 20, a member that can variably form two or more portions whose phase difference is different from each other by λ / 2 in a plane parallel to the display surface of the display 11 can be used, and for example, a liquid crystal panel can be used. That is, in the plane-divided polarization conversion member 20, when viewed in cross section, the conversion section (second transmission section) 21 includes a pair of substrates and a liquid crystal layer disposed between the pair of substrates, and the phase difference can also be changed by applying a voltage to the liquid crystal layer. In the mode of variably forming two or more portions whose phase difference is different from each other by λ / 2, 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 on / off in time. Specifically, by applying a voltage to the liquid crystal layer, the portion that is the conversion section 21 at a certain time becomes the non-conversion section 22, and the portion that is the non-conversion section 22 at a certain time becomes the conversion section 21. Therefore, it is preferable that the entire plane-divided polarization conversion member 20 is a liquid crystal panel.

[0039] As the above-mentioned plane-divided polarization conversion member 20, a member that stably has two or more parts with phase differences that differ from each other by λ / 2 in a plane parallel to the display surface of the display 11 can be used. For example, a member that is plane-divided in such a manner that the above-mentioned non-conversion part 22 is a transparent member and the above-mentioned conversion part 21 is a λ / 2 plate can be used. The λ / 2 plate is a member that gives a phase difference equivalent to 1 / 2 of the wavelength of visible light, for example, a member that gives a phase difference of 200nm to 350nm to light with a wavelength of 550nm. When the λ / 2 plate is used, the arrangement of the above-mentioned conversion part (second transmission part) 21 and the above-mentioned non-conversion part (first transmission part) 22 in the plane is not switched (ON / OFF). The above-mentioned surface-divided component can be produced, for example, by the following method: after affixing a resin film having a λ / 2 phase difference to the entire surface of a supporting component such as a glass substrate, the resin film is patterned in such a manner that the resin film is arranged on the above-mentioned conversion portion 21 to form a resin layer. Alternatively, it can also be produced by a method of forming a resin layer by affixing a resin film having a λ / 2 phase difference only in the region of the supporting component corresponding to the conversion portion 21. In addition, instead of using a resin film having a λ / 2 phase difference to form a resin layer on a supporting component, for example, an alignment film can be formed on the supporting component, a layer composed of a photopolymerizable liquid crystal material is formed on the alignment film, and the photopolymerizable liquid crystal material is solidified to form a resin layer.

[0040] At the position where the polarized light passing through the plane-split polarization conversion member 20 is incident, an optical element is arranged so that the virtual image distance of the first image generated from the first polarized light passing through the non-conversion portion (first transmission portion) 22 and the virtual image distance of the second image generated from the second polarized light passing through the conversion portion (second transmission portion) 21 are different. As such an optical element, in the present embodiment, a liquid crystal lens 50 capable of adjusting the focal length is provided. The liquid crystal lens 50 acts as a lens having 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 having 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 passing through the non-conversion portion 22 will observe a virtual image V, and the second polarized light switched to polarized light by the conversion portion 21, whose vibration direction is orthogonal by 90 degrees, will observe a real image (display screen of the display panel) because the liquid crystal lens 50 does not act. Thus, two virtual image distances (including a case where one of them becomes a real image) can be realized using one display panel, and smooth viewpoint switching including the above-mentioned peripheral vision can be realized.

[0041] The type of the above-mentioned liquid crystal lens 50 is not particularly limited, and examples thereof include a refractive lens, a refractive index distribution type (GRIN) lens, a diffractive lens, and the like. In addition, the above-mentioned refractive index distribution type (GRIN) lens is a lens that bends light by the orientation of liquid crystal. These liquid crystal lenses generally act as lenses for linear polarization in one vibration direction, but have no lens effect on linear polarization in another vibration direction. In addition, when the liquid crystal material is a solidified 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 changed. Regarding the method of controlling the focal length, the refractive lens can be controlled by voltage, the refractive index distribution type lens can be controlled by both voltage and period, and the diffractive lens can be controlled by period. As the above-mentioned liquid crystal lens, it is preferred to have a liquid crystal layer and a lens whose focal length can be changed according to the voltage applied to the above-mentioned liquid crystal layer.

[0042] Reference Figures 7 to 9 The above-mentioned refractive lens will be described. Figure 7 The diagrams are 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 plan view. Figure 8 Yes Description Figure 7 The diagrams showing the operation of the refractive lens in orientation A show that the upper diagram shows when a voltage is applied to the liquid crystal layer, and the lower diagram shows when no voltage is applied to the liquid crystal layer. Fig. 9 Yes Description Figure 7 The diagrams showing the operation of the refractive lens in orientation B show that the upper diagram shows when a voltage is applied to the liquid crystal layer, and the lower diagram shows when no voltage is applied to the liquid crystal layer. Figure 8 and Fig. 9 The arrows in FIG. 1 represent the paths 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, an electrode 53, and a glass substrate 51 are stacked. For example, when the liquid crystal layer 54 uses positive liquid crystal 54a (the major axis of the refractive index ellipsoid of the liquid crystal is along the electric field), when no voltage is applied, the liquid crystal 54a is horizontally oriented ( Figure 8 and Fig. 9 ), when voltage is applied, the liquid crystal 54a is vertically oriented ( Figure 8 and Fig. 9 ). The combination of the refractive indexes of the resin and the liquid crystal 54a constituting the Fresnel lens 52 is not limited. For example, the refractive index of the resin is about 1.5, and the ne (refractive index on the long axis side) and no (refractive index on the short axis side) of the liquid crystal 54a are 1.8 and 1.5, respectively. Figure 8 As shown, in orientation A, when no voltage is applied, there is a refractive difference, so the light is bent, and when a voltage is applied, the refractive difference disappears, so the light is not bent. Fig. 9 As shown, in the orientation B, no refractive difference occurs when no voltage is applied or when a voltage is applied, and the lens function is never generated.

[0043] The above-mentioned liquid crystal lens 50 can also be a Pancharatnam-Berry Phase lens. The Pancharatnam-Berry Phase lens is a liquid crystal lens that switches divergence and convergence according to the direction of circularly polarized light (for example, refer to U.S. Patent No. 10379419). For example, it functions as a lens that switches the focal length to f and -f using left circularly polarized light and right circularly polarized light. The focal length f only needs to be (Active), and in principle it can be controlled periodically. In this embodiment, by adding a fixed lens with a focal length of f, the switching distance of the focal length can be adjusted. Therefore, for example, if a fixed lens with a focal length of f is added, the focal length can be switched between f / 2 and 0. In addition, circularly polarized light can be achieved by adding a λ / 4 plate to linearly polarized light. Therefore, by adjusting the intensity of the separately provided lens with a configuration that is almost the same as that of linearly polarized light, almost the same effect can be achieved.

[0044] Fig.10 A top view illustrating the construction of a Pancharatnam-Berry phase lens. Fig.11 This 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 Fig.10 The periodic orientation of the liquid crystal 54a shown produces diffraction, thereby achieving a lens function. Fig.11 middle, Fig.11 The solid line in the figure represents the optical path of the right circularly polarized light RCP emitted from the Pancharatnam-Berry phase lens PBL. Fig.11 The dotted line in FIG. 5 represents the optical path of the left circularly polarized light LCP emitted from the Pancharatnam-Berry phase lens PBL. Fig.11 The Pancharatnam-Berry phase lens PBL shows an example in which when the incident circularly polarized light is right circularly polarized light RCP, it converges, and when it is left circularly polarized light LCP, it diverges, and the direction of the circularly polarized light at the time of emission becomes the opposite direction. In this way, the Pancharatnam-Berry phase lens can switch the divergence and focusing of the 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 yes Fig.12 A bird's eye view of the display device shown, Fig.14 It is an enlarged cross-sectional view of the plane-divided polarization conversion member according to the first embodiment. Fig.12The display device shown is a 3D display, and a display 11 is arranged at a viewing distance of about 500 mm, and a liquid crystal lens 50 is arranged 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 the distance required for a person to observe a medium-sized (~20-inch) display is about 500 mm.

[0046] On the screen of the display 11, a plane-divided polarization conversion component (liquid crystal panel) 20 is provided, which can switch the phase difference of λ / 2 (i.e., 275nm relative to 550nm light). As the liquid crystal mode of the liquid crystal panel, the TN mode, VA mode, ECB mode, IPS mode, FFS mode and other modes generally used in liquid crystal panels can be applied. If the VA mode is taken as an example, it can be configured so that the voltage is disconnected and no phase difference is generated, and the voltage is turned on and a phase difference of λ / 2 is generated. In addition, in order to reduce the wavelength dependence, the plane-divided polarization conversion component 20 can also be configured such that two layers of liquid crystal panels are stacked.

[0047] like Fig.14 As shown, the plane-divided polarization conversion component (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 by a pair of substrates 25. The number of regions of the liquid crystal panel constituting the plane-divided polarization conversion component 20 can be the same as the number of pixels of the display 11 arranged in an overlapping manner, or it can be less than the number of pixels of the display 11. Fig.14 In the figure, regarding the VA mode liquid crystal panel, the voltage-on state is shown at the top, and the voltage-off state is shown at the bottom. The linearly polarized light emitted from the display 11 does not change its phase in the plane-divided polarization conversion component 20 in the voltage-off state, and therefore is transmitted in the state of linearly polarized light. Although the orientation of the liquid crystal lens 50 is not limited, the case where the liquid crystal lens 50 is configured so as not to function as a lens is described here. In this case, the transmitted light directly reaches the human eye from the display, so the screen of the display 11 is directly seen (real image is seen).

[0048] On the other hand, when the voltage of the plane-divided polarization conversion component 20 is turned on, the light emitted from the display 11 becomes linear polarization light rotated 90 degrees. In this way, when the linear polarization light passes through, the liquid crystal lens 50 functions as a lens. Since the display 11 is placed at a distance equal to the focal length of the liquid crystal lens 50, it becomes approximately parallel light through the lens action and reaches the eyes of the user U. Therefore, the user U sees that the display 11 is approximately at infinity (can see a virtual image). In this way, since the real image and the virtual image can be switched by the plane splitting polarization conversion member 20, two virtual image planes at different distances can be simultaneously observed by plane splitting, and a display with depth (3D display) can be seen. For example, only the display area of ​​the character to be the foreground can be set as the non-conversion section 22 (the area with zero phase difference), and the background area to be the background can be set as the conversion section 21 (the area with λ / 2 phase difference).

[0049] In the above configuration, for simplicity, the display 11 is placed at the focal length so that the virtual image is infinitely far away. However, by changing the focal length of the liquid crystal lens 50 or the distance from the liquid crystal lens 50 to the display 11, the virtual image can be arranged at any location. The focal length of the liquid crystal lens 50 can be adjusted by voltage, so by increasing the voltage applied to the liquid crystal lens 50, the virtual image distance can also be moved from infinitely far to near. Figure 8 As described in , the focal length of the liquid crystal lens 50 is maximum when the voltage is off.

[0050] Fig.15 It is a side view showing another example of the specific configuration of the display device according to the first embodiment. Fig.15 The display device shown 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 refraction strength of the lens (convex-concave lens), and in principle can be actively switched on and off. That is, if the orientation pitch of the liquid crystal is adjusted, the strength of the lens can be adjusted.

[0051] The PB lens switches the concave-convex lens by the left and right circularly polarized light, and thus can produce two virtual images V in front of and behind the display 11. When the PB lens is used, in order to make the light emitted from the display 11 circularly polarized light, for example, a circular polarization plate composed of a combination of a polarization plate 13 and a λ / 4 plate 15 is provided. By placing a plane-divided polarization conversion component 20 capable of switching circularly polarized light to opposite circularly polarized light on the circular polarization plate, the left and right circularly polarized light can be switched. Since the two virtual image planes can be switched by the plane-splitting polarization conversion component 20, two planes at different distances in the plane division can be observed at the same time, and a display with depth (3D display) can be seen. As VR, the immersion is improved and smooth viewpoint switching can be performed.

[0052] <Second Embodiment> Fig.161 is a side view schematically showing the structure of the display device of the second embodiment. The display device of this embodiment has other lenses besides the liquid crystal lens. Specifically, it is assumed that the physical lens 40 with a focal length of 100 mm and the liquid crystal lens 50 with a focal length of 100 mm are arranged close to or attached to each other, and the liquid crystal lens 50 is 50 mm away from the display 11, and the viewing distance is about 65 mm to VR. In the case of VR, if the screen is not magnified by a certain amount (for example, about 10 times) without using a lens, the user cannot focus. Therefore, there is an orientation where the liquid crystal lens 50 does not function as a lens, so a physical lens (normal lens) 40 is used in combination. As in the first embodiment, a plane-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. Different from the first embodiment, since the physical lens 40 is used in combination, even in an orientation that does not function as a lens in the liquid crystal lens 50, since it is enlarged in the physical lens 40, a real image is not visible but a virtual image is visible. In the second embodiment, the two virtual image planes can also be switched by the surface-splitting polarization conversion component 20, so that two planes with different distances in the surface division can be observed at the same time, and a display with depth (3D display) can be observed. As a VR, the immersion feeling is improved and smooth viewpoint switching can be performed. In addition, as other lenses, a Fresnel lens or a diffraction lens may be used instead of the physical lens 40 .

[0053] <Third Embodiment> Fig.17 : is a side view schematically showing the structure of the display device of the third embodiment. The display devices of the first embodiment and the second embodiment use a set of plane-split polarization conversion components and liquid crystal lenses, but the display device of the third embodiment has multiple sets of plane-split polarization conversion components 20 and liquid crystal lenses 50. By using multiple sets (N sets), 2N virtual image surfaces can be generated. However, driving, image processing described later, etc. become complicated. In principle, the plane-divided polarization conversion component 20 is preferably close to the display surface. This is because the boundary surface of the virtual image V is accurately defined on the display image. Fig.18 As shown, if the plane-divided polarization conversion member 20 is separated from the display surface, pixels at the boundary may be included in any of the two virtual image planes. This problem at the boundary can be solved by using image processing described later. In this way, if a combination of multiple surface-split polarization light conversion components 20 and liquid crystal lenses 50 is used, 2N virtual image planes can be switched, 2N planes at different distances due to surface division can be seen at the same time, a display with depth (3D display) can be viewed, and as a VR, the sense of immersion is improved and smooth viewpoint switching can be performed.

[0054] <Fourth Embodiment> Depending on the position of the user's eyes and the depth of the virtual image (distance from the user), the two virtual image planes generated by the plane-splitting polarization conversion component may overlap and be visible at their boundaries, or may have areas without images. This is caused by the difference in magnification of the two virtual image planes and the movement of the eye position. Fig.19 This is a diagram that explains the principle of image overlap and gap generation. Fig.19 As shown, in the case where the user U's eye is located on the normal line of the lens center, in an ideal state where the optical system is not distorted, the virtual image V1 and the virtual image V2 do not overlap. However, in reality, when wearing the HMD shell, the position of the eye may slightly deviate from the normal line of the lens center. Due to this deviation, the virtual image V1 and the virtual image V2 are visible to overlap, or a gap without an image is generated between the virtual image V1 and the virtual image V2. In the case where the user U's eye is closer to the end of the virtual image than the assumed position, the lower part of the virtual image V1 that should be seen cannot be seen (there is no image and it looks black). In the case where the eye is farther away from the end of the virtual image than the assumed position, the lower part of the virtual image V1 that should not be seen appears to overlap. In addition, the offset of the virtual image has no effect on the movement of the eyeball rotation. This is the same as the case where the dotted part of the virtual image V1 located behind the virtual image V2 cannot be seen even if the eyeball is rotated.

[0055] Fig. 20 is a side view schematically showing the structure of a display device in which virtual images are superimposed. Fig.21 is a front view showing an example of a display surface when virtual images overlap. Fig. 22 This is a front view showing an example of an image when virtual images overlap. Fig.21 As shown, in the original image on the display surface, image A1 is displayed in the area where the phase difference of the plane-divided polarization conversion component 20 is zero, and image B1 is displayed in the area where the phase difference of the plane-divided polarization conversion component 20 is λ / 2, and image A1 and image B1 are of the same size. On the other hand, in the image (enlarged image) obtained by emitting from the display surface and passing through the plane-divided polarization conversion component 20, as shown in FIG. Fig. 22As shown, the image A1 is displayed as a virtual image A2 at a close distance, and the image B1 is displayed as a virtual image B2 at a further distance and amplified, and the virtual images A2 and B2 overlap. Since the portion AB where the virtual images overlap simply adds the light, it appears bright. Usually, the virtual image B2 at the far side is hidden in the virtual image A2 at the near side, so such a display creates a sense of incongruity except for some cases that are permitted as a performance. In addition, the amount of overlap corresponds to the position of the eye and is hardly affected by the movement (rotation) of the eyeball, but if the position of the eye is offset, the impact is greater (overlap amount offset).

[0056] In the present embodiment, an image correction process (first image correction process) may be performed on the overlapping region (overlap of virtual image planes) of the first image and the second image. The first image correction process may include the following image correction processes.

[0057] (1) First Image Correction Process As the first image correction process described above, Fig.23 The original image and Fig.24 As shown in the enlarged image of , the processing (first correction) of making the overlapping area (the part where the virtual image overlaps) black can be cited. In this case, the overlapping of images is fundamentally prevented.

[0058] As the first image correction process described above, Fig.25 The original image and Fig.26 As shown in the enlarged image of , the processing (second correction) of reducing the brightness of the overlapping area for at least one of the first image and the second image can be cited. Specifically, setting a brightness gradient in the overlapping area can be cited. Fig.25 Although it is simply expressed in terms of brightness, in the case of images, weighting may be performed so that the brightness of an image approaching the front is closer to the original brightness, and an image going to the back may be darker than the original brightness.

[0059] As the first image correction process described above, Fig. 27 As shown, a guest-host liquid crystal layer 70 (third correction) may be arranged between the plane-split polarized light conversion component 20 and the liquid crystal lens 50. The guest-host liquid crystal layer 70 is preferably arranged near the liquid crystal lens 50, and more preferably adjacent to the liquid crystal lens 50. The guest-host liquid crystal layer 70 uses a material that includes a light-absorbing material as a guest material and a liquid crystal as a host material. For example, a material in which the guest material is a uniaxial light-absorbing material and the liquid crystal of the host material is a vertically oriented liquid crystal. If such a guest-host liquid crystal layer 70 is arranged, it is possible to absorb no light when the voltage is off and absorb only one polarized component when the voltage is on. As Fig. 27As shown, if the guest-host liquid crystal layer 70 is arranged in a manner to absorb only polarized light showing a distant scene (distant virtual image) in the region where the virtual image V overlaps, only light showing a near scene (near virtual image) can be seen. The position of the guest-host liquid crystal layer 70 can also be adjusted by eye tracking as described later.

[0060] The first image correction process may also include a process for 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, since the overlapping position deviates according to the position of the user's eyes, the image can be properly corrected in real time by using eye tracking technology. If tracking technology is used in combination with the first countermeasure and / or the second countermeasure, the sense of incongruity of the display caused by the overlap of virtual images can be more effectively prevented. Specifically, the position of the user's eyes is determined by eye tracking technology, and the brightness tilt in the second countermeasure is always corrected based on the result. In addition, if the image of the distant view (distant virtual image) is made black in the part where the virtual images overlap, there will be no overlap when zoomed in, and the distance will be naturally arranged in front of and inside.

[0061] Fig.28 FIG. 1 is a flowchart showing an example of image correction using eye tracking technology. Fig.28 As shown, first, the peripheral part of the user's eye is photographed by a photographing unit such as a camera (step S11). Then, based on the photographing information of the peripheral part of the eye obtained, the three-dimensional coordinates (x, y, z) related to the position of the eye are calculated (step S12). The three-dimensional coordinates only need to determine the position of the eyeball, and may not include information related to the rotation of the eyeball. Based on the three-dimensional coordinates related to the position of the eye, the area where gaps between virtual images are generated and the area where repetitions between virtual images are generated are calculated (step S13). Based on the calculation results, when repetitions between virtual images occur, the above-mentioned first, second or third correction is performed (step S14A). If such eye tracking technology is used, as shown Fig.29 The original image and Fig.30 As shown in the enlarged image of , the area where the virtual images overlap can be accurately determined, and the image correction processing is performed based on the determined area. In addition, when a gap occurs between the virtual images, the second image correction processing (step S14B) described later is performed.

[0062] In the present embodiment, the image correction process (second image correction process) may be performed on the boundary region (the 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 correction process for a boundary area between the first image and the second image displayed in a time-sharing manner. Fig.31This is a diagram for explaining the principle of generating a gap between virtual images, and shows an original image. Fig.32 This is a diagram for explaining the principle of generating a gap between virtual images, and shows an enlarged image. Fig.33 It is a diagram illustrating time-sharing display. Due to the positional deviation of the user's eyes or the distortion of the optical system, such as Fig.32 As shown, Fig.31 In the original image, the image A and the image B that are displayed without gaps may have gaps (black areas) in the enlarged image (the image when viewed from a human perspective). Fig.32 In the display, there is also an area where image A and image B overlap. As a countermeasure for gaps and overlaps, a correction process can be performed to overlap image A and image B through time-sharing display. At this time, the position and size of image A and / or image B can also be adjusted. By time-sharing displaying at least the boundary area of ​​image A and image B, it is possible to prevent the generation of an area that is not displayed (appears to be black) in the enlarged image. Time-sharing display is performed by simultaneously switching the display and the surface-divided polarization conversion component. Time-division display is not necessary except for the positions corresponding to the boundary areas, but in this case, it is preferable to adjust so that the brightness does not differ. Fig.33 In the example, if the area where image A and image B overlap is switched to 1 / 2 hour of the original frame and lit, the brightness becomes half. Therefore, it is desired to increase the brightness of only this part by 2 times, or reduce the brightness of the surrounding area to half.

[0064] In addition, if Fig.34 As shown, if we consider simple lens geometry, if the focal length becomes shorter (that is, the lens power becomes stronger), the virtual image V becomes farther and larger. Fig.32 In this case, the virtual image V of image A is closer, and the virtual image V of image B is farther.

[0065] <Fifth Embodiment> Fig.35 : is a side view schematically showing the structure of the display device of the fifth embodiment. In the above embodiment, a voltage-variable liquid crystal lens is used, but a static (unchangeable) liquid crystal lens 50 can also 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 the two virtual images (including the shell of the real image) V can be switched by the plane-divided polarization conversion component 20. It can be manufactured inexpensively, and the liquid crystal lens 50 does not require electrical wiring, and has the advantage of concentrating the electrical wiring on the display 11 side, and can be applied to VR, etc.

[0066] According to the surface split polarization conversion component of the present invention, two images with different virtual image distances can be generated, thereby reducing the burden on the user (observer) when viewing the display device and improving the immersion in the content. As a specific application example, in the case of a VR display device, a near view (virtual image nearby) and a distant view (virtual image far away) can be displayed as VR. Description of Reference Numerals

[0067] 10: Display Panel 11: Display 13: Polarizing plate 15:λ / 4 plate 20: Plane-divided polarization conversion component 21: Conversion Department 22: Non-conversion part 25:Substrate 26: Liquid crystal layer 26a:LCD 40: Lens (physical lens) 50: Liquid crystal lens 51: Glass substrate 52: Fresnel lens 53: Electrode 54: Liquid crystal layer 54a:LCD 70: Guest-host liquid crystal layer A, A1, B, B1: Image A2, B2: Virtual image B: The part where the virtual image overlaps D1: Focus adjustment distance D2: Convergence distance I1, I2: Image I2a: Blurred Image R: Image for the right eye RCP: Right Circular Polarization RE:Right eye L: Image for the left eye LCP: Left Circularly Polarized Light LE: Left Eye U: User (Observer) V, V1, V2: Virtual image

Claims

1. A surface split polarization conversion component, It is characterized in that When viewed from above, it has: 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, The second transmission portion generates a phase difference of λ / 2 compared with the first transmission portion.

2. The plane-divided polarization conversion component according to claim 1, It is characterized in that The first transmission part is a non-conversion part that transmits the polarized light for the first image without converting the polarization state. The second transmission section is a conversion section that generates a phase difference of λ / 2 in the polarized light for the second image and converts the polarization state.

3. The plane-divided polarization conversion component according to claim 2, It is characterized in that The conversion portion includes a resin layer having a λ / 2 phase difference.

4. The plane-divided polarization conversion component according to claim 1, It is characterized in that When viewed in cross section, the second transmission portion includes a pair of substrates and a liquid crystal layer disposed between the pair of substrates. The phase difference can be changed according to the voltage applied to the liquid crystal layer.

5. A display device comprising: A display panel that emits polarized light for the first and second images; The plane-divided polarization conversion component according to claim 1, which is arranged at a position where the polarized light is incident; and an optical element disposed at a position where the polarized light that has passed through the plane-divided polarization conversion member is incident, The optical element makes a virtual image distance of a first image generated from first polarized light transmitted through the first transmission portion different from a virtual image distance of a second image generated from second polarized light transmitted through the second transmission portion.

6. The display device according to claim 5, It is characterized in that The optical element is a liquid crystal lens, The liquid crystal lens functions as a lens having a first focal length for the first polarized light, and does not function as a lens for the second polarized light, or functions as a lens having a second focal length.

7. The display device according to claim 6, It is characterized in that The liquid crystal lens is a refractive lens, a distributed refractive index lens or a diffractive lens.

8. The display device according to claim 6, It is characterized in that The liquid crystal lens is a Pancharatnam-Berry phase lens.

9. The display device according to claim 6, It is characterized in that The liquid crystal lens includes a liquid crystal layer, and the focal length can be changed according to a voltage applied to the liquid crystal layer.

10. The display device according to claim 5, It is characterized in that There are also lenses other than liquid crystal lenses.

11. The display device according to claim 6, It is characterized in that There are also combinations of other plane-divided polarization conversion components and other liquid crystal lenses.

12. The display device according to claim 5, It is characterized in that A first image correction process is performed on an overlapping area of ​​the first image and the second image.

13. The display device according to claim 12, It is characterized in that In the first image correction process, the overlapping area is displayed in black.

14. The display device according to claim 12, It is characterized in that In the first image correction process, brightness of the overlapping area is reduced in at least one of the first image and the second image.

15. The display device according to claim 12, It is characterized in that The first image correction process includes the following processes: The overlapping area is determined according to an overlap amount between the first image and the second image detected based on eye tracking.

16. The display device according to claim 5, It is characterized in that A guest-host liquid crystal layer is further provided between the plane-divided polarization conversion component and the optical element. The guest-host liquid crystal layer contains a light absorbing material as a guest material and contains liquid crystal as a host material.

17. The display device according to claim 5, It is characterized in that A second image correction process is performed on a boundary area between the first image and the second image.

18. The display device according to claim 17, It is characterized in that In the second image correction process, the first image and the second image are overlapped by time-division display.

19. The display device according to claim 5, It is characterized in that The display device is a VR display device or a 3D display device.

20. The display device according to claim 5, It is characterized in that The display device is a head-mounted display device.

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