Head-mounted display

Abstract

To provide a head-mounted display capable of switching between light field and binocular methods.SOLUTION: A head-mounted display 1 comprises: a 3D / 2D switching display section 20 switching, with an optical element capable of switchably enabling or disenabling the lens functions of a lens array, between displaying a three-dimensional image by the light field method using an element image group and displaying a two-dimensional image by the binocular method using parallax image; a focal position variable enlarged part 30 changing a focal position of the lens back and forth by the light field method and binocular method to enlarge an image displayed by the 3D / 2D switching display 20; and a control section 40 controlling the lens array functions of the optical element in the 3D / 2D switching display section 20 to be enabled or disenabled.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present invention relates to a head mounted display. [Background technology]

[0002] In recent years, the use of virtual reality (VR) and augmented reality (AR) has been expanding in various fields such as education, medicine, and entertainment. Head mounted displays (HMDs) are used as display devices for VR and AR. In recent years, development of high-definition, wide-field-of-view devices has been progressing so that users of head mounted displays can feel highly immersive and present in virtual spaces.

[0003] A typical head mounted display is composed of a display and an eyepiece, and allows the user to view a virtual image displayed at a depth of about 1m to 2m from the user. This head mounted display also allows the user to feel a sense of three-dimensionality by displaying images with left and right parallax on the display. The head mounted display also allows the user to view content that displays 360-degree images (two-dimensional images) or 3D objects (three-dimensional images) by displaying images on the display that correspond to the direction of the head based on posture information from the mounted tracking sensor.

[0004] Problems with head-mounted displays include visual fatigue and discomfort when used for long periods of time. It is said that the cause of this is that the position where the eyes focus due to the focus adjustment function does not match the position where the gaze directions of both eyes intersect due to the convergence function. In particular, when viewing a 3D object, the content is displayed at a close depth of within 1m from the user, so the difference between the position where the eyes focus due to the focus adjustment function (about 1m to 2m from the user) and the position where the gaze directions of both eyes intersect due to the convergence function (within 1m from the user) becomes large, which significantly affects visual fatigue and discomfort. It is expected that this problem can be improved by using a light field method that virtually reproduces the light rays of a 3D object.

[0005] Patent Document 1 and Non-Patent Document 1 disclose a head mounted display 9 as shown in FIG. 15. The head mounted display 9 is compatible with the light field method and includes a display 90, a lens array 91, and an eyepiece 93. In this head mounted display 9, when an elemental image group EP in which elemental images ep are arranged is displayed on the display 90, an intermediate image M is formed between the lens array 91 in which lenses 92 corresponding to the elemental images ep are arranged, and the eyepiece 93. Then, in the head mounted display 9, a three-dimensional image T (virtual image) in which the intermediate image M is enlarged can be reproduced through the eyepiece 93. At this time, a point X of the three-dimensional image T is focused on one point on the retina 102 by the crystalline lens 101 as a light ray incident on the eyeball 100. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-073988 A [Non-patent literature]

[0007] [Non-Patent Document 1] H. Huang and H. Hua, "High-performance integral-imaging-based light field augmented reality display using freeform optics," Opt. Express, 26, 17578-17590 (2018). Summary of the Invention [Problem to be solved by the invention]

[0008] A light field head mounted display creates a 3D image using light rays from multiple pixels, so a large number of pixels are required to create a 3D image. As a result, light field head mounted displays have the problem of lower resolution and viewing angle compared to conventional twin-eye 2D images. Therefore, an object of the present invention is to provide a head-mounted display that can switch the display method between a light field method and a twin-eye method depending on whether a three-dimensional image or a two-dimensional image is viewed. [Means for solving the problem]

[0009] In order to solve the above problems, the head-mounted display of the present invention is a head-mounted display that is worn on a person's head to display images, and is configured to include a 3D2D switching display unit, a variable focus position magnification unit, and a control unit.

[0010] In such a configuration, the head mounted display switches between displaying a 3D image using a group of elemental images by a light field method and displaying a 2D image using parallax images by a twin-eye method by an optical element that can switch between enabling and disabling the lens function of the lens array by a 3D2D switching display unit. This switching is performed by a control unit. The head mounted display then uses a variable focal position enlargement unit to switch the focal position of the lenses back and forth between the light field method and the twin-eye method, thereby enlarging the image displayed by the 3D2D switching display unit.

[0011] This allows the head mounted display to switch between displaying a 3D image using the light field method and displaying a 2D image using the twin-eye method under the control of the control unit. In addition, the head mounted display allows the user to view a 3D object, which is a 3D image, and a 360-degree image, which is a 2D image, at different virtual image plane positions, respectively, using the variable focal position magnification unit. Effect of the Invention

[0012] According to the present invention, the display method can be switched between the light field method and the twin-lens method. [Brief description of the drawings]

[0013] [Figure 1] 1 is an external view of a head mounted display according to an embodiment of the present invention. [Figure 2A] FIG. 1 is a diagram showing the configuration of a head mounted display (light field type) according to a first embodiment of the present invention, where (a) is a side view and (b) is a top view. [Figure 2B] FIG. 1 is a configuration diagram (twin-eye type) of a head-mounted display according to a first embodiment of the present invention, where (a) is a side view and (b) is a top view. [Diagram 3] FIG. 2 is an explanatory diagram for explaining an example of three-dimensional image formation in a light field method in the head mounted display according to the first embodiment of the present invention. [Figure 4] FIG. 2 is an explanatory diagram for explaining an example of two-dimensional image formation in a twin-eye system in the head mounted display according to the first embodiment of the present invention. [Figure 5A] 2A to 2C are explanatory diagrams for explaining transition of the polarization state of the head mounted display according to the first embodiment of the present invention. [Figure 5B] 1A to 1C are explanatory diagrams for explaining modifications associated with the polarization state of the head mounted display according to the first embodiment of the present invention. [Figure 5C] 1A to 1C are explanatory diagrams for explaining modifications associated with the polarization state of the head mounted display according to the first embodiment of the present invention. [Figure 6A] 11A and 11B are diagrams illustrating the configuration of a head mounted display according to a second embodiment of the present invention (light field type), where (a) is a side view and (b) is a top view. [Figure 6B] 11A and 11B are diagrams illustrating the configuration of a head mounted display (twin-eye type) according to a second embodiment of the present invention, in which (a) is a side view and (b) is a top view. [Figure 7] FIG. 11 is an explanatory diagram for explaining an example of two-dimensional image formation in a twin-eye system in a head mounted display according to a second embodiment of the present invention. [Figure 8A] 11 is an explanatory diagram for explaining the transition of the polarization state of a head mounted display according to a second embodiment of the present invention. FIG. [Figure 8B] 11A to 11C are explanatory diagrams for explaining modified examples associated with the polarization state of the head mounted display according to the second embodiment of the present invention. [Figure 8C] 11A to 11C are explanatory diagrams for explaining modified examples associated with the polarization state of the head mounted display according to the second embodiment of the present invention. [Figure 9A] 11A and 11B are diagrams illustrating the configuration of a head mounted display according to a third embodiment of the present invention (light field type), in which (a) is a side view and (b) is a top view. [Figure 9B] 11A and 11B are diagrams showing the configuration of a head mounted display (twin-eye type) according to a third embodiment of the present invention, in which (a) is a plan view when a two-dimensional image is displayed, and (b) is a top view. [Figure 10A] 11 is an explanatory diagram for explaining an effect of the lens array switching unit functioning as a lens; FIG. [Figure 10B] 11 is an explanatory diagram for explaining the effect of the lens array switching portion functioning as a transparent flat plate. FIG. [Figure 11]FIG. 11 is an explanatory diagram for explaining an example of three-dimensional image formation in a light field method in a head mounted display according to a third embodiment of the present invention. [Figure 12] FIG. 11 is an explanatory diagram for explaining an example of two-dimensional image formation in a twin-eye system in a head mounted display according to a third embodiment of the present invention. [Figure 13A] 13 is an explanatory diagram for explaining the transition of the polarization state when a three-dimensional image is displayed in the head mounted display according to the third embodiment of the present invention. FIG. [Figure 13B] 13 is an explanatory diagram for explaining the transition of the polarization state when a two-dimensional image is displayed in the head mounted display according to the third embodiment of the present invention. FIG. [Figure 14A] 13A to 13C are explanatory diagrams for explaining modified examples associated with the polarization state of the head mounted display according to the third embodiment of the present invention. [Figure 14B] 13A to 13C are explanatory diagrams for explaining modified examples associated with the polarization state of the head mounted display according to the third embodiment of the present invention. [Figure 15] FIG. 1 is an explanatory diagram for explaining formation of a three-dimensional image in a light field method in a conventional head mounted display. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First Embodiment The configuration of a head mounted display 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1, 2A, and 2B. Fig. 1 is a diagram showing a state in which a user wears a head mounted display 1. The state shown in Fig. 1 is the same when a head mounted display described in other embodiments is worn.

[0015] 2A and 2B are configuration diagrams showing the head mounted display 1 according to the first embodiment of the present invention with a housing thereof seen through, where (a) is a side view and (b) is a top view. 2A shows a state in which the head mounted display 1 displays a three-dimensional image (hereinafter, referred to as a 3D image), and FIG 2B shows a state in which the head mounted display 1 displays a two-dimensional image (hereinafter, referred to as a 2D image).

[0016] The head mounted display 1 is a display device for virtual reality (VR) that is worn on the user's head H. The head mounted display 1 has a goggle-shaped housing with a built-in display 21 (described later) and the like, and has a function of switching between displaying a 3D image using a light field method and displaying a 2D image using a twin-eye method. The 3D image is an image that allows a user wearing the head mounted display 1 to visually recognize a 3D object. The 2D image is an image that allows a user wearing the head mounted display 1 to visually recognize a 360-degree image by looking around the surroundings. The head mounted display 1 is attached to the head H by a wearing band 2. As shown in Fig. 1, the head mounted display 1 may also include a speaker 3 and may be configured to play back audio from the speaker 3 in conjunction with the displayed image.

[0017] The head mounted display 1 includes a tracking sensor 10, a 3D / 2D switching display unit 20, a variable focal position magnification unit 30, and a control unit 40. The head mounted display 1 has two sets (B, C, D, D, E ... L ,B R ) Prepare. Here, the three-dimensional space is a coordinate system with the left-right direction (horizontal direction) corresponding to the eyeballs 100L and 100R as the x-axis, the up-down direction (vertical direction) as the y-axis, and the depth direction as the z-axis. In the depth direction, the direction in which the eyeball 100 is located is defined as the front (near side), and the opposite direction is defined as the rear (deep side).

[0018] The tracking sensor 10 is a sensor that acquires head movement information of a user wearing the head mounted display 1. The head movement information consists of rotational movement information and translational movement information. For example, the rotational movement information is information acquired from an acceleration sensor, a gyro sensor, a geomagnetic sensor, etc. The translational movement information is information calculated based on depth information estimated by extracting feature points from images captured by a stereo camera.

[0019] That is, the tracking sensor 10 is composed of a group of multiple sensors such as an acceleration sensor, a gyro sensor, a geomagnetic sensor, a stereo camera, etc. The head movement information acquired by the tracking sensor 10 may be only rotational movement information. In that case, the image displayed on the head mounted display 1 corresponds to the rotational movement of the user's head H, but does not correspond to the translational movement. The tracking sensor 10 outputs the acquired head movement information to a server (not shown) that provides images via communication such as WiFi.

[0020] The 3D2D switching display unit 20 switches between displaying a 3D image using a group of elemental images based on the light field method and displaying a 2D image using parallax images based on the twin-eye method, using an optical element that can switch the lens function of a lens array between enabled and disabled. The 3D / 2D switching display unit 20 includes a display 21, a polarizer 22, and a lens array switching element .

[0021] The display 21 displays images (a group of elemental images or parallax images) input from a server (not shown) in accordance with head movement information acquired by the tracking sensor 10. When a 3D image is displayed on the head mounted display 1, the display 21 displays an element image group EP in which element images ep are arranged two-dimensionally, as shown in Fig. 2A. The element images ep are images of parts of the 3D image from different viewpoints. When a 2D image is displayed on the head mounted display 1, the display 21 displays a parallax image PV as shown in Fig. 2B. The parallax image PV is an image seen from left and right viewpoint positions corresponding to the depth of the video. In addition, for ease of understanding, the elemental image group EP and the parallax image PV are illustrated as having a thickness, but in reality, they are images displayed on the display 21 and do not have a thickness.

[0022] The display 21 can be configured with a direct-view display (organic EL display, liquid crystal display) such as a liquid crystal panel or an organic EL (Electronic Luminescent) panel in which pixels are arranged two-dimensionally (x-axis direction, y-axis direction). Here, a case will be described in which the display 21 is an organic EL display that emits randomly polarized or circularly polarized light. Although the display 21 is configured by two separate displays for the left eye 100L and the right eye 100R, it may be configured by one display with the display area divided for each of the left and right eyes.

[0023] The polarizer 22 is disposed in front of the display 21 and transmits, among the light emitted from the display 21, light that is linearly polarized in a specific direction. Here, the polarizer 22 irradiates the lens array switching element 23 with vertically polarized light as linearly polarized light in a specific direction, out of the light emitted from the display 21 . In this embodiment, the polarizer 22 is configured with two pieces, one for the left eye 100L and one for the right eye 100R. However, they may be configured with one piece and used commonly for both eyes.

[0024] The lens array switching element 23 is an optical element that is disposed in front of the polarizer 22 and can electrically switch between enabling and disabling a lens function. The lens array switching element 23 is, for example, a liquid crystal lens array or a liquid lens array. Liquid crystal lens arrays and liquid lens arrays are common. For example, liquid crystal lens arrays are disclosed in the following References 1 and 2, and liquid lens arrays are disclosed in the following Reference 3.

[0025] (References) Reference 1: https: / / opg.optica.org / oe / fulltext.cfm?uri=oe-30-16-28941&id=481183 Reference 2: https: / / opg.optica.org / oe / fulltext.cfm?uri=oe-21-22-26520&id=270379 Reference 3: https: / / opg.optica.org / ao / abstract.cfm?uri=ao-54-10-2565

[0026] Lens array switching element 23 switches between having and not having a lens function through voltage control (ON / OFF control) by control unit 40. When lens array switching element 23 is OFF, it functions as a transparent plate that allows light to pass directly, and when it is ON, it functions as a lens array. When the lens array switching element 23 functions as a lens array, the element lenses 23e are formed to correspond to the element images ep. That is, when the lens array switching element 23 functions as a lens array, the element lenses 23e are arranged two-dimensionally (x-axis direction, y-axis direction). The shape of the element lenses 23e is, for example, a square, a rectangle, a circle, or the like.

[0027] The lens array switching element 23 is disposed so that the distance from the display 21 is shorter than the focal length of the element lenses 23e. Note that there are lens array switching elements 23 that have polarization dependency and those that do not have polarization dependency. When using a lens array switching element 23 that has polarization dependency, the lens array switching element 23 is arranged in a direction that passes light that is linearly polarized in a specific direction when the irradiated light is linearly polarized in that direction. The lens array switching element 23 irradiates the linearly polarized light (here, vertically polarized light) emitted from the polarizer 22 onto the eyepiece lens 31. Here, the lens array switching element 23 is configured with two elements, one for the left eyeball 100L and one for the right eyeball 100R, but it may be configured with one element that is shared for both eyes.

[0028] The variable focal position enlargement unit 30 changes the focal position of the image displayed by the 3D2D switching display unit 20 and enlarges it. Here, the head mounted display 1 is configured separately into a first housing 1a and a second housing 1b, and the focal position is changed by moving the second housing 1b, to which an eyepiece lens 31 is fixed, in the forward and backward directions relative to the first housing 1a. The first housing 1a is provided with a tracking sensor 10, a 3D2D switching display unit 20, and a control unit 40, which are fixed thereto. The variable focal position magnifying section 30 includes an eyepiece lens 31 and a position switching mechanism 32 .

[0029] The eyepiece lens 31 magnifies the image formed by the display 21 and the lens array switching element 23. For example, the eyepiece lens 31 is a plano-convex lens or a biconvex lens. The type of the eyepiece lens 31 that can be used includes a spherical lens, an aspherical lens, a Fresnel lens, etc.

[0030] When the elemental image group EP is displayed on the display 21, the eyepiece lens 31 magnifies the intermediate image that is reproduced by the display 21 and the lens array switching element 23 and formed behind the display 21, allowing the user to view the enlarged 3D image (virtual image). Furthermore, when the parallax image PV is displayed on the display 21, the eyepiece lens 31 enlarges the parallax image and allows the user to visually recognize a 2D image (virtual image) formed on the back side of the display 21 by the enlarged parallax image. When a 2D image is displayed, the eyepiece lens 31 is moved forward (closer) by a position switching mechanism 32, which will be described later, and positioned further forward than when a 3D image is displayed.

[0031] The position switching mechanism 32 switches the position of the eyepiece 31 between when a 3D image is displayed and when a 2D image is displayed. The position switching mechanism 32 includes a first recess 32a and a second recess 32b on the top, bottom, left and right sides of the first housing 1a, and includes protrusions 32c on the top, bottom, left and right sides of the second housing 1b.

[0032] The first recess 32a and the second recess 32b are for connecting the first housing 1a to the second housing 1b. The first recess 32a and the second recess 32b are formed to be spaced apart by a predetermined distance that changes the focal length of the eyepiece lens 31 between when displaying a 3D image and when displaying a 2D image.

[0033] The protrusion 32c connects the second housing 1b to the first housing 1a. The protrusion 32c is fitted into the first recess 32a or the second recess 32b, whereby the first housing 1a and the second housing 1b are connected to each other and configured as a single head mounted display 1. When a 3D image is to be displayed on the head mounted display 1, as shown in FIG. 2A, the user pushes the second housing 1b toward the rear side, thereby fitting the convex portion 32c into the first concave portion 32a. On the other hand, when a 2D image is to be displayed on the head mounted display 1, as shown in FIG. 2B, the user pulls out the second housing 1b towards the user, thereby fitting the convex portion 32c into the second concave portion 32b.

[0034] This allows the variable focal position magnification section 30 to switch the focal position of the eyepiece 31 in the forward and backward directions when switching between displaying a 3D image and a 2D image. The relationship between the head mounted display 1 and each image when displaying a 3D image in the light field method and when displaying a 2D image in the twin-eye method will be described later (FIGS. 3 and 4).

[0035] The control unit 40 controls the lens array switching element 23 when switching between displaying a 3D image and a 2D image. When an instruction to display a 3D image is received from an external instruction such as a switch or an external signal, the control unit 40 controls the voltage applied to the lens array switching element 23 so that the lens array switching element 23 functions as a lens array. Furthermore, when an external instruction is given to display a 2D image, the control unit 40 controls the voltage applied to the lens array switching element 23 so that the lens array switching element 23 functions as a transparent flat plate. With the above-described configuration, the head mounted display 1 can switch the display method between the light field method and the twin-eye method.

[0036] (3D image formation using the light field method) Next, the formation of a 3D image in the light field type of the head mounted display 1 will be described with reference to Fig. 3. This corresponds to the configuration for displaying a 3D image described in Fig. 2A. Note that the polarizer 22 is not shown. The head mounted display 1 has a distance a between the display 21 and the lens array switching element 23, which is set to a focal length f of the lens array switching element 23 (element lens 23e). array As a result, an intermediate image M formed by the display 21 and the lens array switching element 23 is formed behind the display 21 as a virtual image. Here, if the distance between the lens array switching element 23 and the intermediate image surface SM is b, the distance between the display 21 and the lens array switching element 23 and the focal length f of the lens array switching element 23 are array The relationship between them is shown in the following formula (1).

[0037]

number

[0038] In this way, the head mounted display 1 forms an intermediate image (virtual image) M behind the display 21, so that the distance between the lens array switching element 23 and the eyepiece lens 31 can be shortened, making the device thinner (smaller). In addition, the distance between the lens array switching element 23 and the eyepiece 31 is c, and the focal length of the eyepiece 31 is f eye In this case, the head mounted display 1 defines the distance b+c between the intermediate image plane SM and the eyepiece lens 31 as f eye Make it shorter than. As a result, a 3D image T formed by the intermediate image M and the eyepiece lens 31 is formed as a virtual image behind the intermediate image M. At this time, a virtual image plane ST, which is a conjugate plane of the display 21, is formed behind the intermediate image plane SM.

[0039] Here, if the distance between the eyepiece 31 and the virtual image plane ST is d, the distance b+c between the intermediate image plane SM and the eyepiece 31 and the focal length f of the eyepiece 31 are eye The relationship between them is shown in the following formula (2).

[0040]

number

[0041] Generally, in the light field method, 3D objects are often displayed at a short distance of less than 1 m from the user, and therefore the virtual image surface ST is often also placed within 1 m from the user.

[0042] (2D image formation in twin-lens system) Next, the formation of a 2D image in the twin-eye type of the head mounted display 1 will be described with reference to Fig. 4. This corresponds to the configuration for displaying a 2D image described in Fig. 2B. Note that the polarizer 22 is not shown. When switching from the light field system to the twin-eye system, the head mounted display 1 turns off the lens function of the lens array switching element 23 (transparent flat plate) and moves the eyepiece lens 31 to the front side. The head mounted display 1 is configured such that the distance g between the display 21 and the eyepiece 31 is equal to the focal length f eyeAs a result, a virtual image T of the parallax image PV displayed on the display 21 is formed behind the display 21.

[0043] Here, if the distance between the eyepiece 31 and the virtual image surface ST is d', the distance between the display 21 and the eyepiece 31 is g, and the focal length of the eyepiece 31 is f eye The relationship between them is shown in the following formula (3).

[0044]

number

[0045] Generally, in the twin-eye system, the virtual image of the display 21 is often placed at a depth of about 1 to 2 m away from the user. When switching from the light field system to the twin-eye system, the head mounted display 1 moves the eyepiece lens 31 in a direction away from the display 21 by gac.

[0046] (Example) Here, a description will be given of an embodiment of the head mounted display 1. Of course, this is just an example, and the present invention is not limited to this embodiment. In this embodiment, the head mounted display 1 is configured as shown in the following table (see Figs. 3 and 4).

[0047] [Table 1]

[0048] In this way, when switching the display method of the head mounted display 1 from the light field method to the twin eye method, it is sufficient to move the eyepiece lens 31 in a direction away from the display 21 by g(95.2)-a(9.34)-c(66.15) ≒ 19.7 millimeters. In other words, in this case, by setting the distance between the first recess 32a and the second recess 32b of the position switching mechanism 32 to 19.7 millimeters, the head mounted display 1 can shift the focal position of the eyepiece lens 31 between the light field method and the twin eye method, thereby switching between displaying 3D images and 2D images.

[0049] (Deformation due to polarization) The above describes the head mounted display 1 according to the first embodiment, but it is also possible to omit the polarizer 22 depending on the polarization of the light emitted from the display 21 used and the polarization dependency of the lens array switching element 23 used.

[0050] Here, modified examples associated with polarization will be described with reference to Figures 5A to 5C. Note that, although Figures 5A to 5C show an example in which the display 21 displays a group of elemental images, the same applies to the case in which parallax images are displayed. FIG. 5A shows a configuration including the polarizer 22 described in FIG. 2A. That is, FIG. 5A shows a case where an organic EL display that emits randomly polarized or circularly polarized light is used as the display 21. In this case, the polarizer 22 causes the emitted light from the display 21 to be linearly polarized in a specific direction (here, vertically polarized light) and to be irradiated onto the lens array switching element 23. When there is polarization dependency, the lens array switching element 23 is arranged in a direction that passes polarized light (vertically polarized light) that is passed by the polarizer 22. When there is no polarization dependency, the lens array switching element 23 is a flat plate that passes linearly polarized light, so there is no need to be aware of the direction in the arrangement. As a result, the lens array switching element 23 irradiates the polarized light (vertically polarized light) that is passed by the polarizer 22 onto the eyepiece lens 31. The eyepiece lens 31 passes the vertically polarized light as is.

[0051] FIG. 5B shows a case where a liquid crystal display that emits linearly polarized light (here, vertically polarized light) is used as the display 21. In this case, it is possible to omit the polarizer 22. Then, the light emitted from the display 21 is irradiated onto the lens array switching element 23 without changing the polarization state. The polarization after the lens array switching element 23 is the same as in FIG. 5A. Although the light after polarizer 22 in FIG. 5A or the light emitted from display 21 in FIG. 5B is vertically polarized, it may be horizontally polarized.

[0052] FIG. 5C shows a case where an organic EL display with randomly polarized emitted light is used as the display 21, and a lens array switching element 23 that has no polarization dependency is used. In this case, the polarizer 22 can be omitted. The light emitted from the display 21 is irradiated to the lens array switching element 23 as randomly polarized light without changing its polarization state. Here, since the lens array switching element 23 does not have polarization dependency, the light irradiated to the lens array switching element 23 is irradiated to the eyepiece 31 without changing its polarization state. The eyepiece 31 passes the randomly polarized light as it is. Note that Figure 5C shows an example in which the light emitted from display 21 is randomly polarized, but if the lens array switching element 23 has no polarization dependency, the polarizer 22 can be omitted regardless of the polarized light (circularly polarized, linearly polarized).

[0053] <Second embodiment> Next, a configuration of a head mounted display 1B according to a second embodiment of the present invention will be described with reference to FIGS. 6A and 6B. 6A and 6B are configuration diagrams showing a head mounted display 1B according to a second embodiment of the present invention with a housing thereof seen through, where (a) is a side view and (b) is a top view. Fig. 6A shows a state in which the head mounted display 1B displays a 3D image, and Fig. 6B shows a state in which the head mounted display 1B displays a 2D image.

[0054] The head mounted display 1B includes a tracking sensor 10, a 3D2D switching display unit 20, a focal position variable magnification unit 30B, and a control unit 40B. The configuration other than the focal position variable magnification section 30B and the control section 40B is the same as that of the head mounted display 1 according to the first embodiment, and therefore the description thereof will be omitted.

[0055] The variable focus position magnifying section 30B changes the focal position to magnify the 3D image or 2D image formed on the 3D2D switching display section 20. This variable focus position magnifying section 30B can be composed of a variable focus lens 31B.

[0056] The variable-focus lens 31B is an optical element that is disposed in front of the 3D2D switching display unit 20 and can electrically switch the focal length. For example, the variable-focus lens 31B can be a liquid crystal lens, a liquid lens, a polymer lens, or the like. Note that there are variable-focus lenses 31B that have polarization dependency and those that do not have polarization dependency. When using a variable-focus lens 31B that has polarization dependency, the variable-focus lens 31B is arranged in a direction that passes light that is linearly polarized in a specific direction when the light to be irradiated is linearly polarized light in that direction.

[0057] When the elemental image group EP is displayed on the display 21, the variable focus lens 31B magnifies the intermediate image that is reproduced by the display 21 and the lens array switching element 23 and formed behind the display 21, allowing the user to view the enlarged 3D image (virtual image). Furthermore, when the parallax image PV is displayed on the display 21, the variable-focus lens 31B enlarges the parallax image and allows the user to visually recognize a 2D image (virtual image) formed on the back side of the display 21 by the enlarged parallax image. When a 2D image is displayed, the focal length of this variable-focus lens 31B is controlled so that the focal position moves forward (toward the viewer) compared to when a 3D image is displayed.

[0058] The relationship between the head mounted display 1B and a virtual image when displaying a 3D image in the light field system is the same as that of the head mounted display 1 described with reference to FIG. The relationship between the head mounted display 1B and a 2D image when displaying a 2D image in the twin-eye system will be described later (FIG. 7).

[0059] The control unit 40B controls the lens array switching element 23 and the variable-focus lens 31B when switching between displaying a 3D image and a 2D image. When the control unit 40B is instructed to display a 3D image by an external instruction such as a switch or an external signal, the control unit 40B controls the voltage applied to the lens array switching element 23 so that the lens array switching element 23 functions as a lens array. Furthermore, the control unit 40B controls the voltage applied to the variable-focus lens 31B so that the focal length of the variable-focus lens 31B becomes a predetermined distance for displaying a 3D image.

[0060] Furthermore, when an external instruction is given to display a 2D image, the control unit 40B controls the voltage applied to the lens array switching element 23 so that the lens array switching element 23 functions as a transparent plate. Furthermore, the control unit 40B controls the voltage applied to the variable-focus lens 31B so that the focal length of the variable-focus lens 31B becomes a predetermined distance for displaying a 2D image.

[0061] (2D image formation in twin-lens system) Next, the formation of a 2D image in the twin-eye system of the head mounted display 1B will be described with reference to FIG. . When switching from the light field system to the twin-eye system, the head mounted display 1B turns off the lens function of the lens array switching element 23 (transparent flat plate) and makes the focal length of the variable-focus lens 31B shorter than that of the light field system. Here, if the distance between the variable-focus lens 31B and the virtual image surface ST is d', the distance between the display 21 and the variable-focus lens 31B is a+c (the same as in FIG. 3), and the focal length f' of the variable-focus lens 31B iseye The relationship between them is shown in the following formula (4).

[0062]

number

[0063] In addition, the distance a+c between the display 21 and the variable-focus lens 31B is known, and when it is desired to set the distance d′ between the variable-focus lens 31B and the virtual image surface ST to a certain value, the focal length f′ of the variable-focus lens 31B is eye can be determined by the following equation (5).

[0064]

number

[0065] When switching from the light field system to the twin-eye system, the head mounted display 1B changes the focal length of the variable-focus lens 31B to the focal length f eye From the focal length f' for the twin-lens system eye Switch to.

[0066] (Example) Here, an embodiment of the head mounted display 1B will be described. Of course, this is just an example, and the present invention is not limited to this embodiment. In this embodiment, the head mounted display 1B is configured as shown in the following table (see FIG. 7). The symbols for the light field method are the same as those in FIG. 3. However, the eyepiece lens 31 in FIG. 3 is a variable focus lens 31B.

[0067] [Table 2]

[0068] In this way, when the display method of the head mounted display 1B is switched from the light field method to the twin-eye method, the focal length of the variable-focus lens 31B is changed from 100 mm to 78.5 mm.

[0069] (Deformation due to polarization) The above describes the head mounted display 1B according to the second embodiment. However, depending on the polarization of the light emitted from the display 21 used and the polarization dependency of the lens array switching element 23 and the variable focus lens 31B used, it is also possible to omit the polarizer 22.

[0070] Here, modified examples associated with polarization will be described with reference to Figures 8A to 8C. Note that, although Figures 8A to 8C show an example in which the display 21 displays a group of elemental images, the same applies to the case in which parallax images are displayed. FIG. 8A shows a configuration including the polarizer 22 described in FIG. 6A. That is, FIG. 8A shows a case where an organic EL display that emits randomly polarized or circularly polarized light is used as the display 21. In this case, the polarizer 22 causes the emitted light from the display 21 to be linearly polarized in a specific direction (here, vertically polarized light) and to be irradiated onto the lens array switching element 23.

[0071] When there is polarization dependency, the lens array switching element 23 is arranged in a direction that passes polarized light (vertically polarized light) that is passed by the polarizer 22. When there is no polarization dependency, the lens array switching element 23 is a flat plate that passes linearly polarized light, so there is no need to be aware of the direction in the arrangement. As a result, the lens array switching element 23 irradiates the polarized light (vertically polarized light) that the polarizer 22 passes through, onto the variable-focus lens 31B.

[0072] When there is polarization dependency, the variable-focus lens 31B is arranged in a direction that passes polarized light (vertically polarized light) that is passed by the lens array switching element 23. When there is no polarization dependency, the variable-focus lens 31B is a lens that passes linearly polarized light, so there is no need to be aware of the direction in the arrangement. Variable-focus lens 31B passes the vertically polarized light as is.

[0073] FIG. 8B shows a case where a liquid crystal display that emits linearly polarized light (here, vertically polarized light) is used as the display 21. In this case, it is possible to omit the polarizer 22. Then, the light emitted from the display 21 is irradiated onto the lens array switching element 23 without changing the polarization state. The polarization after the lens array switching element 23 is the same as in FIG. 8A. Although the light after polarizer 22 in FIG. 8A or the light emitted from display 21 in FIG. 8B is vertically polarized, it may be horizontally polarized.

[0074] FIG. 8C shows a case where an organic EL display with randomly polarized emitted light is used as the display 21, and lens array switching element 23 and variable focal length lens 31B that do not have polarization dependency are used. In this case, the polarizer 22 can be omitted. The light emitted from the display 21 is irradiated to the lens array switching element 23 as randomly polarized light without changing its polarization state. Here, since the lens array switching element 23 does not have polarization dependency, the light irradiated to the lens array switching element 23 is irradiated to the variable-focus lens 31B without changing its polarization state. Here, the variable-focus lens 31B has no polarization dependency and therefore passes the randomly polarized light as it is.

[0075] Note that Figure 8C shows an example in which the light emitted from display 21 is randomly polarized, but if the lens array switching element 23 and variable-focus lens 31B have no polarization dependency, the polarizer 22 can be omitted regardless of the polarized light (circularly polarized, linearly polarized).

[0076] <Third embodiment> Next, a configuration of a head mounted display 1C according to a third embodiment of the present invention will be described with reference to FIGS. 9A and 9B. 9A and 9B are configuration diagrams showing a head mounted display 1C according to a third embodiment of the present invention with a housing thereof seen through, where (a) is a side view and (b) is a top view. Fig. 9A shows a state in which the head mounted display 1C displays a 3D image, and Fig. 9B shows a state in which the head mounted display 1C displays a 2D image.

[0077] The head mounted display 1C includes a tracking sensor 10, a 3D / 2D switching display section 20C, a variable focal position magnifying section 30B, and a control section 40C. The tracking sensor 10 has the same configuration as the head mounted display 1, 1B according to the first and second embodiments, and the focal position variable magnification unit 30B has the same configuration as the head mounted display 1B according to the second embodiment, so their explanations are omitted.

[0078] The 3D2D switching display unit 20C uses an optical element that can enable or disable the lens function of a lens array to switch between displaying a 3D image using a group of elemental images based on a light field method and displaying a 2D image using parallax images based on a twin-eye method. The 3D / 2D switching display unit 20C includes a display 21, a polarization switching unit 22C, and a lens array switching unit 23C. The display 21 has the same configuration as the head mounted displays 1 and 1B according to the first and second embodiments.

[0079] The polarization switching section 22C is provided with a polarizer 220 and a polarization switching element 221, and passes light that is linearly polarized in a specific direction. The polarizer 220 is disposed in front of the display 21, and passes light that is linearly polarized in a specific direction among the light emitted from the display 21. The polarizer 220 can be the same as the polarizer 22 used in the head mounted displays 1 and 1B.

[0080] The polarization switching element 221 is disposed in front of the polarizer 220, and electrically switches between one polarization state and the other polarization state. For example, a liquid crystal element such as a ferroelectric liquid crystal or an OCB (Optically Compensated Bend) liquid crystal having a fast response speed can be used for the polarization switching element 221. The polarization switching element 221 may be disposed at a predetermined interval (for example, about several mm) from the polarizer 220, or may be disposed closely to the polarizer 220. The polarization switching element 221 switches between one polarization state and the other polarization state through voltage control (ON / OFF control) by the control unit 40C. Here, when the polarization switching element 221 is OFF, it passes vertically polarized light (one polarization state) as it is, and when it is ON, it switches to a state where it converts vertically polarized light into horizontally polarized light (the other polarization state). The polarization switching element 221 irradiates the transmitted or converted light to the lens array switching section 23C.

[0081] The lens array switching unit 23C is disposed in front of the polarization switching element 221, and electrically switches between the presence and absence of a lens function. The lens array switching unit 23C includes a polarization diffraction lens array 230 and a lens array 231.

[0082] The polarized diffraction lens array 230 is disposed in front of the polarization switching element 221, and diffracts incident light according to the polarization state of light irradiated from the polarization switching element 221. The polarized diffraction lens array 230 may be disposed at a predetermined interval (for example, about several mm) from the polarization switching element 221, or may be disposed closely to the polarization switching element 221. In addition, the polarized diffraction lens array 230 is configured by arranging polarized diffraction lenses 230e on a two-dimensional plane when viewed from the front. The lens pitch of the polarized diffraction lens array 230 is the same as the pitch of the lens array 231 described below.

[0083] When horizontally polarized light is incident on the incident surface of the polarizing diffractive lens 230e, the traveling direction of the light is considered to be positive and the polarizing diffractive lens 230e has a positive focal length (f diff ) (convex lens). When light polarized perpendicularly to the incident surface is incident on the polarizing diffractive lens 230e, the direction of travel of the light is considered positive and the lens has a negative focal length (-f diff The polarizing diffractive lens 230e functions as a lens (concave lens) having a focal length of 100 nm to 150 nm. The absolute value of the focal length of the polarizing diffractive lens 230e is the same as the focal length of the lens array 231 described later.

[0084] The lens array 231 is disposed in front of the polarizing diffraction lens array 230, and has element lenses 231e arranged in correspondence with the element images ep. That is, the lens array 231 has element lenses 231e arranged two-dimensionally (x-axis direction, y-axis direction).

[0085] The element lenses 231e are minute plano-convex or biconvex lenses. The shape of the element lenses 231e is, for example, a square, a rectangle, a circle, etc. The type of the element lenses 231e that can be used includes a spherical lens, an aspherical lens, a Fresnel lens, etc. The lens array 231 is preferably disposed in close proximity to the polarizing diffractive lens array 230 . The lens array 231 of the lens array switching unit 23C is disposed so that the distance from the display 21 is shorter than the composite focal length made up of the positive focal length of the polarizing diffractive lens 230e and the focal length of the element lens 231e.

[0086] Here, the operation of the lens array switching unit 23C will be described with reference to FIGS. 10A and 10B. Fig. 10A shows a state in which horizontally polarized light is incident on lens array switching unit 23C, and Fig. 10B shows a state in which vertically polarized light is incident on lens array switching unit 23C. As shown in FIG. 10A, when horizontally polarized light is incident, the polarizing diffractive lens 230e of the polarizing diffractive lens array 230 has a positive focal length (f diff ), so horizontally polarized light acts as a lens with a positive focal length (f diff When the light passes through the element lens 231e of the lens array 231 having a focal length (f diff / 2) In other words, the polarizing diffractive lens array 230 and the lens array 231 can be regarded as one lens array having a composite focal length.

[0087] As shown in FIG. 10B, when vertically polarized light is incident, the polarizing diffractive lens 230e of the polarizing diffractive lens array 230 has a negative focal length (−f diff ), so that vertically polarized light has a positive focal length (f diff When the light passes through element lenses 231e of lens array 231 having the condensing function, the light passes through as is without being condensed. In other words, polarizing diffraction lens array 230 and lens array 231 can be regarded as transparent flat plates. Returning to FIGS. 9A and 9B, the configuration of the head mounted display 1C will be further described. The lens array switching unit 23C irradiates the light emitted from the lens array 231 to the variable-focus lens 31B.

[0088] The control unit 40C controls the polarization switching element 221 and the variable-focus lens 31B when switching between displaying a 3D image and a 2D image. When the control unit 40C is instructed to display a 3D image by an external instruction such as a switch or an external signal, the control unit 40C controls the voltage applied to the polarization switching element 221 so as to change the vertically polarized light to horizontally polarized light. Furthermore, the control unit 40C controls the voltage applied to the variable-focus lens 31B so that the focal length of the variable-focus lens 31B becomes a predetermined distance for displaying a 3D image.

[0089] Furthermore, when an external instruction is given to display a 2D image, the control unit 40C controls the voltage applied to the polarization switching element 221 so as to pass vertically polarized light as it is. Furthermore, the control unit 40C controls the voltage applied to the variable-focus lens 31B so that the focal length of the variable-focus lens 31B becomes a predetermined distance for displaying a 2D image.

[0090] (Transition of polarization state) Here, with reference to FIGS. 13A and 13B, a description will be given of the transition of the polarization state of the light emitted by the display 21 due to the optical element group when the head mounted display 1C displays a 3D image and when it displays a 2D image. FIG. 13A shows the transition of the polarization state when a 3D image is displayed, and FIG. 13B shows the transition of the polarization state when a 2D image is displayed.

[0091] 13A, when a 3D image is displayed, the light emitted from the display 21 (organic EL display) is converted by the polarizer 220 into linearly polarized light in a specific direction (here, vertically polarized light) and is irradiated onto the polarization switching element 221. At this time, the polarization switching element 221 is turned ON. As a result, the vertically polarized light is converted by the polarization switching element 221 into horizontally polarized light, and is irradiated onto the polarization diffraction lens array 230. After this, the light transitions as horizontally polarized light. The polarizing diffractive lens array 230 then has a positive focal length (f diff ) and functions as a lens (convex lens) with a positive focal length (f diffA 3D image is reproduced by the lens array 231 having a variable-focus lens 31B, and the 3D image is enlarged by the variable-focus lens 31B. This allows the user to view the enlarged 3D image.

[0092] 13B, when a 2D image is displayed, the light emitted from the display 21 (organic EL display) is converted by the polarizer 220 into linearly polarized light in a specific direction (here, vertically polarized light) and is irradiated onto the polarization switching element 221. At this time, the polarization switching element 221 is turned OFF. As a result, the vertically polarized light passes through the polarization switching element 221 while remaining vertically polarized, and is irradiated onto the polarization diffraction lens array 230. After this, the light transitions as vertically polarized light. The polarizing diffractive lens array 230 then has a negative focal length (−f diff ) and acts as a lens (concave lens) with a positive focal length (f diff The lens array 231 having the variable-focus lens 31B functions as a transparent flat plate to display a 2D image, and the 2D image is magnified by the variable-focus lens 31B. This allows the user to view the magnified 2D image.

[0093] (Example) Here, an embodiment of the head mounted display 1C will be described. Of course, this is just an example, and the present invention is not limited to this embodiment. In this embodiment, the head mounted display 1C is configured as shown in the following table (see FIGS. 11 and 12).

[0094] [Table 3]

[0095] (Deformation due to polarization) Although the head mounted display 1C according to the third embodiment has been described above, it is possible to omit the polarizer 22 depending on the polarization of the emitted light of the display 21 used. Fig. 14 and Fig. 14B show a case where a liquid crystal display that emits linearly polarized light (here, vertically polarized light) is used as the display 21. FIG. 14A shows the case where a 3D image is displayed, and FIG. 13B shows the case where a 2D image is displayed.

[0096] As shown in Fig. 14A, when a 3D image is displayed, the light emitted from the display 21 (liquid crystal display) remains linearly polarized (vertically polarized) and is irradiated onto the polarization switching element 221. At this time, the polarization switching element 221 is turned ON. As a result, the vertically polarized light is converted into horizontally polarized light by the polarization switching element 221, and is irradiated onto the polarization diffraction lens array 230. After this, the transition is the same as that described in Fig. 13A.

[0097] As shown in Fig. 14B, when a 2D image is displayed, the light emitted from the display 21 (liquid crystal display) is irradiated to the polarization switching element 221 while remaining linearly polarized (vertically polarized). At this time, the polarization switching element 221 is turned OFF. As a result, the vertically polarized light is irradiated to the polarization diffraction lens array 230 while remaining vertically polarized through the polarization switching element 221. After this, the transition is the same as that described in Fig. 13B. In this way, when a liquid crystal display that emits linearly polarized light is used as the display 21, the polarizer 220 can be omitted from the configuration.

[0098] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and also includes design modifications and the like within the scope of the present invention that do not depart from the gist of the present invention. For example, in the above embodiment, the head mounted displays 1, 1B, and 1C are described as display devices for VR, but they may be display devices for AR. For example, a head mounted display for AR may be configured to include a half mirror in front of the eyepiece lens 31 of the head mounted display 1 and the variable focus lens 31B of the head mounted displays 1B and 1C, so that light emitted through the eyepiece lens 31 and the variable focus lens 31B is reflected by the half mirror to reach both eyes, and light from the foreground passes through the half mirror to reach both eyes. This makes it possible for AR head-mounted displays to display 3D objects (3D images) using the light field method as well as high-resolution, wide-field 360-degree video (2D images). [Explanation of symbols]

[0099] 1,1B,1C Head-mounted display 10 Tracking Sensor 20,20C 3D2D switching display section 21 Display 22 Polarizer 22C Polarization switching unit 220 Polarizer 221 Polarization switching element 23 Lens array switching element 23C Lens array switching section 230 Polarized Diffractive Lens Array 231 Lens Array 30, 30B Variable focus magnification unit 31,31B Eyepiece 32 Position switching mechanism 40, 40B, 40C Control section EP Element Images ep element image PV parallax image

Claims

1. A head-mounted display that is worn on a person's head to display images, a 3D2D switching display unit that switches between displaying a 3D image using a group of elemental images by a light field method and displaying a 2D image using parallax images by a twin-lens method by using an optical element that can switch between enabling and disabling the lens function of the lens array; a focal position variable enlargement unit that switches a focal position of a lens back and forth between the light field method and the twin-lens method to enlarge an image displayed by the 3D2D switching display unit; A control unit that controls the function of the lens array of the optical element to be enabled or disabled; A head mounted display comprising:

2. The 3D2D switching display unit is a display for displaying the elemental image group or the parallax image; and A lens array switching element is an optical element that is arranged in front of the display and can switch the lens function between enabled and disabled; The head mounted display according to claim 1 ,

3. The light emitted from the display is randomly polarized or circularly polarized, and the lens array switching element has polarization dependency, A polarizer is further provided between the display and the lens array switching element to convert the emitted light into linearly polarized light, The head mounted display according to claim 2 , wherein the lens array switching element is disposed so as to pass the linearly polarized light.

4. The light emitted from the display is linearly polarized light, and the lens array switching element has polarization dependency, The head mounted display according to claim 2 , wherein the lens array switching element is disposed so as to pass the linearly polarized light.

5. The 3D2D switching display unit is a display that outputs randomly polarized light or circularly polarized light and displays the elemental image group or the parallax image; a polarizer that transmits only light of a specific polarization among the light emitted from the display; a polarization switching element that switches the light passing through the polarizer between one polarization state and the other polarization state; a polarized diffractive lens array having a positive or negative focal length with respect to a traveling direction of light depending on the one polarization state and the other polarization state switched by the polarization switching element; a lens array having the same positive focal length as the polarizing diffractive lens array with respect to the traveling direction of the light; The head mounted display according to claim 1 ,

6. The 3D2D switching display unit is a display that uses linearly polarized light as output light and displays the elemental image group or the parallax image; a polarization switching element for switching the output light of the display between one polarization state and another polarization state; a polarized diffractive lens array having a positive or negative focal length with respect to a traveling direction of light depending on the one polarization state and the other polarization state switched by the polarization switching element; a lens array having the same positive focal length as the polarizing diffractive lens array with respect to the traveling direction of the light; The head mounted display according to claim 1 ,

7. The focal position variable magnification unit is an eyepiece lens that magnifies the image displayed by the 3D2D switching display unit; a position switching mechanism for switching the position of the eyepiece lens back and forth; The head mounted display according to claim 1 ,

8. The focal position variable magnification unit is a variable-focus lens that changes the focal length, The head mounted display according to claim 1 , wherein the control unit further controls a focal length of the variable focus lens so that the focal length of the two-lens system is shorter than that of the light field system.

Images