Display device and light guide element

Abstract

To inhibit decrease in visibility of an image.SOLUTION: A display device according to one embodiment comprises: a transparent substrate including a first principal surface and a second principal surface facing the first principal surface; a display element configured to emit display light toward the transparent substrate; an optical path adjustment element arranged on the second principal surface facing the display element; a first optical element overlapping the optical path adjustment element and diffracting the display light transmitting through the transparent substrate and the optical path adjustment element so as to be totally reflected in the transparent substrate; and a second optical element arranged on the second principal surface and diffracting the display light propagating in the transparent substrate so as to be emitted from the first principal surface. The optical path adjustment element is configured to be able to adjust an optical path of the display light in order to change the emission position of the display light.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a display device and a light guide element.

Background Art

[0002] In recent years, various head-mounted displays using a holographic optical element (hereinafter sometimes simply referred to as HOE) that diffracts display light from a display element and a light guide member have been studied. In one example, a technique of providing a holographic diffraction optical element on each surface of a light guide member is known. The HOE disposed on one surface of the light guide member diffracts the display light so as to be totally reflected by the light guide member, and the HOE disposed on the other surface of the light guide member diffracts the display light propagating inside the light guide member so as to be emitted to the outside. In such a head-mounted display, when the observation region where an image is displayed is narrow, the position of the user's eyes and the observation region are likely to be inconsistent. In this case, the visibility of the image for the user is reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the embodiment is to provide a display device and a light guide element capable of suppressing a decrease in visibility of an image.

Means for Solving the Problems

[0005] According to one embodiment, a display device is A transparent substrate having a first main surface and a second main surface facing the first main surface, a display element configured to emit display light toward the transparent substrate, an optical path adjustment element disposed on the second main surface facing the display element, a first optical element that overlaps the optical path adjustment element and diffracts the display light transmitted through the transparent substrate and the optical path adjustment element so as to totally reflect the display light inside the transparent substrate, and a second optical element disposed on the second main surface and diffracting the display light propagated inside the transparent substrate so as to emit the display light from the first main surface, wherein the optical path adjustment element is configured to be able to adjust the optical path of the display light in order to change the emission position of the display light.

[0006] According to one embodiment, the display device is A transparent substrate having a first main surface and a second main surface facing the first main surface, a display element configured to emit display light toward the transparent substrate, an optical path adjustment element disposed on the first main surface between the transparent substrate and the display element, a first optical element disposed on the second main surface facing the optical path adjustment element and diffracting the display light transmitted through the transparent substrate so as to totally reflect the display light inside the transparent substrate, and a second optical element disposed on the second main surface and diffracting the display light propagated inside the transparent substrate so as to emit the display light from the first main surface, wherein the optical path adjustment element is configured to be able to adjust the optical path of the display light in order to change the emission position of the display light.

[0007] According to one embodiment, the light guide element is A transparent substrate having a first main surface and a second main surface facing the first main surface, an optical path adjustment element disposed on the second main surface, a first optical element that overlaps the optical path adjustment element and diffracts the light transmitted through the transparent substrate and the optical path adjustment element so as to totally reflect the light inside the transparent substrate, and a second optical element disposed on the second main surface and diffracting the light propagated inside the transparent substrate so as to emit the light from the first main surface, wherein the optical path adjustment element is configured to be able to adjust the optical path of the incident light in order to change the emission position of the light.

[0008] According to one embodiment, the light guide element is A transparent substrate having a first main surface and a second main surface facing the first main surface, an optical path adjustment element disposed on the first main surface, and a first optical element disposed on the second main surface facing the optical path adjustment element and configured to diffract light transmitted through the transparent substrate so as to totally reflect the light inside the transparent substrate, and a second optical element disposed on the second main surface and configured to diffract light propagated inside the transparent substrate so as to emit the light from the first main surface, wherein the optical path adjustment element is configured to be able to adjust the optical path of incident light in order to change the light emission position.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Best Mode for Carrying Out the Invention

[0010] Hereinafter, this embodiment will be described with reference to the drawings. Note that the disclosure is merely an example, and those that can be easily conceived by those skilled in the art for appropriate modifications while maintaining the gist of the invention are naturally included in the scope of the present invention. Also, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. Further, in this specification and each drawing, components that exhibit the same or similar functions as those described above with respect to the already presented drawings may be assigned the same reference numerals, and detailed descriptions that overlap may be appropriately omitted.

[0011] In this specification, "light" includes visible light and invisible light. For example, the lower limit wavelength of the visible light region is 350 nm or more and 400 nm or less, and the upper limit wavelength of the visible light region is 700 nm or more and 830 nm or less. Visible light includes a first component (blue component) in a first wavelength band (for example, 400 nm to 500 nm), a second component (green component) in a second wavelength band (for example, 500 nm to 600 nm), and a third component (red component) in a third wavelength band (for example, 600 nm to 700 nm). Invisible light includes ultraviolet rays in a wavelength band shorter than the first wavelength band and infrared rays in a wavelength band longer than the third wavelength band. In this specification, "transparent" preferably means colorless and transparent. However, "transparent" may be translucent or colored transparent.

[0012] FIG. 1 is a cross-sectional view showing a configuration example of a display device DSP according to this embodiment.

[0013] The display device DSP includes a light guide element LG and a display module DM. The display device DSP is held by frames 31 and 32. The light guide element LG includes a transparent substrate 1, a first optical element 11, a second optical element 12, and an optical path adjustment element AD. The display module DM includes a display element 2 and an optical system 3.

[0014] The transparent substrate 1 is constituted by, for example, a transparent glass plate or a transparent synthetic resin plate. The transparent substrate 1 may be constituted by, for example, a flexible transparent synthetic resin plate. The transparent substrate 1 can take any shape. For example, the transparent substrate 1 may be curved. The transparent substrate 1 is formed in a flat plate shape and has a first main surface 1A and a second main surface 1B facing the first main surface 1A. The first main surface 1A and the second main surface 1B are parallel to each other.

[0015] The optical path adjustment element AD is disposed on the second main surface 1B facing the display element 2, although its details will be described later. The first optical element 11 overlaps the optical path adjustment element AD. The optical path adjustment element AD is located between the transparent substrate 1 and the first optical element 11. In one example, the optical path adjustment element AD is adhered to the transparent substrate 1, and the first optical element 11 is adhered to the optical path adjustment element AD.

[0016] The second optical element 12 is disposed on the second main surface 1B facing the user's eye E and is adhered to the transparent substrate 1. The first optical element 11 and the second optical element 12 are diffraction elements that diffract incident light at a predetermined diffraction angle. In one example, they are holographic optical elements (HOEs). Each of the first optical element 11 and the second optical element 12 is, for example, a multilayer film in which a HOE that diffracts blue components, a HOE that diffracts green components, and a HOE that diffracts red components are laminated. However, when only light of a specific wavelength is diffracted, each of the first optical element 11 and the second optical element 12 may be a single-layer film. Note that the first optical element 11 and the second optical element 12 may be diffraction gratings or mirrors.

[0017] The display element 2 is configured to emit display light DL toward the transparent substrate 1. The display element 2 is disposed on the side facing the first main surface 1A of the transparent substrate 1. That is, in the illustrated example, the display element 2 is located on the side opposite to the optical path adjustment element AD and the first optical element 11 with the transparent substrate 1 interposed therebetween. Such a display element 2 may be, for example, a display element including a self-luminous element such as an organic electroluminescence element or a light-emitting diode, or may be a display element combining an optical switch such as a liquid crystal panel and an illumination device.

[0018] The optical system 3 is disposed between the display element 2 and the transparent substrate 1. Such an optical system 3 includes at least one lens and is configured to collimate the divergent display light DL emitted from the display element 2.

[0019] The frame 31 houses the display module DM and has an opening 31A facing the eye E. The frame 32 sandwiches the light guide element LG between itself and the frame 31 and has an opening 32A overlapping the opening 31A. The second optical element 12 is located in the opening 32A. In the illustrated example, the area of the second optical element 12 is smaller than the area of the opening 32A. Note that the second optical element 12 may be disposed over the entire area of the opening 32A.

[0020] In such a display device DSP, the display light DL emitted from the display element 2 is collimated by the optical system 3 and then enters the transparent substrate 1 almost perpendicularly. The display light DL transmitted through the transparent substrate 1 is diffracted by the first optical element 11 after passing through the optical path adjustment element AD. At this time, the first optical element 11 diffracts the display light DL transmitted through the transparent substrate 1 and the optical path adjustment element AD so as to totally reflect it inside the transparent substrate 1. As a result, the display light DL is propagated inside the transparent substrate 1 while being totally reflected at the first main surface 1A and the second main surface 1B, and is diffracted by the second optical element 12. At this time, the second optical element 12 diffracts the display light DL so as to emit it almost perpendicularly from the first main surface 1A. That is, the display light DL incident on the transparent substrate 1 and the display light DL emitted from the transparent substrate 1 are substantially parallel to each other. Thereby, the user can visually recognize the image displayed by the display element 2 in the observation region where the second optical element 12 is disposed among the openings 32A and 32B. Further, when the back of the display device DSP is open, the user can observe the background through the display device DSP.

[0021] Such a display device DSP can be applied to a glasses-type or goggle-type head-mounted display, and can be used for applications that provide virtual reality, augmented reality, etc. to the user.

[0022] The optical path adjustment element AD of the present embodiment is configured to be able to adjust the optical path of the display light DL in order to change the emission position of the display light DL. This will be described below.

[0023] FIG. 2 is a diagram for explaining the definition of the light guiding length L.

[0024] The optical path adjustment element AD has a thickness D. The first optical element 11 diffracts the display light DL, which is the incident light, at a diffraction angle θ. At this time, the distance from the position where the display light DL is incident on the first main surface 1A to the position where the display light DL, which is the diffracted light diffracted by the first optical element 11, is first totally reflected at the first main surface 1A is defined as the light guiding length L.

[0025] FIG. 3 is a diagram for explaining the operation of the optical path adjustment element AD.

[0026] The example shown in FIG. 3 corresponds to the case where the thickness D1 of the optical path adjustment element AD is greater than the initial thickness. At this time, assuming that the diffraction angle of the display light DL in the first optical element 11 is constant, the optical path length of the diffracted light in the optical path adjustment element AD is extended. That is, when the optical path adjustment element AD has a thickness D1, a longer light guiding length L1 can be obtained than when the optical path adjustment element AD has the initial thickness. And the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P1 on the left side of the figure (the side away from the first optical element 11) compared to the case where the optical path adjustment element AD has the initial thickness.

[0027] FIG. 4 is a diagram for explaining the operation of the optical path adjustment element AD.

[0028] The example shown in FIG. 4 corresponds to the case where the thickness D2 of the optical path adjustment element AD is smaller than the initial thickness. At this time, assuming that the diffraction angle of the display light DL in the first optical element 11 is constant, the optical path length of the diffracted light in the optical path adjustment element AD is shortened. That is, when the optical path adjustment element AD has a thickness D2, a shorter light guiding length L2 can be obtained than when the optical path adjustment element AD has the initial thickness. And the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P2 on the right side of the figure (the side close to the first optical element 11) compared to the case where the optical path adjustment element AD has the initial thickness.

[0029] In this way, by adjusting the thickness of the optical path adjustment element AD in the range from the thickness D1 shown in FIG. 3 to the thickness D2 shown in FIG. 4, the emission position of the display light DL can be adjusted in the range from the position P1 shown in FIG. 3 to the position P2 shown in FIG. 4. That is, by adjusting the thickness of the optical path adjustment element AD, the observation region of the image can be freely shifted.

[0030] The display device DSP of this embodiment is assumed to be used by a plurality of users whose eye E positions are different from each other. For example, when an adult uses the display device DSP and when a child uses the display device DSP, the positions of their respective eyes E are different. In such a case, by adjusting the thickness of the optical path adjustment element AD, the display light DL can be emitted to an optimal location corresponding to the position of the user's eye E. Therefore, it is possible to suppress a decrease in the visibility of the image without giving discomfort to the user.

[0031] Next, some configuration examples for adjusting the thickness of the optical path adjustment element AD will be described.

[0032] FIG. 5 is a cross-sectional view showing a configuration example of the optical path adjustment element AD applicable to the display device DSP shown in FIG. 1.

[0033] The optical path adjustment element AD includes an elastic layer 21 disposed between the transparent substrate 1 and the first optical element 11, and a variable mechanism 24 for varying the thickness of the elastic layer 21. In the illustrated example, the elastic layer 21 is sandwiched between a support 22 and a support 23. Both the support 22 and the support 23 are transparent glass plates or transparent synthetic resin plates. The support 22 is adhered to the transparent substrate 1. The support 23 is adhered to the first optical element 11. The variable mechanism 24 is disposed between the frame 31 and the first optical element 11 and is configured to be stretchable along the normal direction of the frame 31. The variable mechanism 24 may be manually operated or controlled by an electric signal. The distance between the frame 31 and the transparent substrate 1 is invariant.

[0034] FIG. 6 is a diagram for explaining the state of the optical path adjustment element AD.

[0035] In the example shown in FIG. 6, the elastic layer 21 is formed of a transparent resin. Examples of suitable materials for forming the elastic layer 21 include silicone resin and ethylene propylene resin (EPDM).

[0036] The cross-sectional view shown in the center of the figure shows the initial state of the optical path adjustment element AD. At this time, the optical path adjustment element AD has a thickness D0.

[0037] The cross-sectional view shown on the left side of the figure shows a state in which the variable mechanism 24 has shrunk toward the frame 31 and the elastic layer 21 has extended in the thickness direction (or the normal direction of the frame 31) compared to the initial state. At this time, the optical path adjustment element AD has a thickness D1 greater than the thickness D0. As described above, when the optical path adjustment element AD is in the extended state, as described with reference to FIG. 3, the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P1 on the left side of the figure compared to the initial state.

[0038] The cross-sectional view shown on the right side of the figure shows a state in which the variable mechanism 24 has extended toward the first optical element 11 and the elastic layer 21 has shrunk in the thickness direction compared to the initial state. At this time, the optical path adjustment element AD has a thickness D2 smaller than the thickness D0. As described above, when the optical path adjustment element AD is in the shrunk state, as described with reference to FIG. 4, the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P2 on the right side of the figure compared to the initial state.

[0039] FIG. 7 is a diagram for explaining the state of the optical path adjustment element AD.

[0040] In the example shown in FIG. 7, the elastic layer 21 is formed of a transparent liquid. Examples of suitable materials for forming the elastic layer 21 include water, silicone oil, an aqueous solution of hydroxypropyl cellulose, and an aqueous solution of polyvinyl alcohol. When the elastic layer 21 is a liquid, the elastic layer 21 is sealed with a sealing film 25. The sealing film 25 is formed of a material having elasticity.

[0041] The cross-sectional view shown in the center of the figure shows the initial state of the optical path adjustment element AD. At this time, the optical path adjustment element AD has a thickness D0.

[0042] The cross-sectional view shown on the left side of the figure shows a state in which the variable mechanism 24 is contracted toward the frame 31 and the elastic layer 21 is extended in the thickness direction as compared with the initial state. At this time, the optical path adjustment element AD has a thickness D1 that is larger than the thickness D0. Thus, in the state where the optical path adjustment element AD is extended, as described with reference to FIG. 3, the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P1 on the left side of the figure as compared with the initial state.

[0043] The cross-sectional view shown on the right side of the figure shows a state in which the variable mechanism 24 is extended toward the first optical element 11 and the elastic layer 21 is contracted in the thickness direction as compared with the initial state. At this time, the optical path adjustment element AD has a thickness D2 that is smaller than the thickness D0. Thus, in the state where the optical path adjustment element AD is contracted, as described with reference to FIG. 4, the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P2 on the right side of the figure as compared with the initial state.

[0044] The method for changing the emission position of the display light DL is realized by adjusting the thickness of the optical path adjustment element AD in the configuration example described with reference to FIGS. 5 to 7, but is not limited thereto. The emission position of the display light DL may be changed by refracting the display light DL passing through the optical path adjustment element AD.

[0045] Hereinafter, some configuration examples for refracting the display light DL inside the optical path adjustment element AD will be described.

[0046] FIG. 8 is a cross-sectional view showing another configuration example of the optical path adjustment element AD applicable to the display device DSP shown in FIG. 1.

[0047] The optical path adjustment element AD includes a first liquid crystal cell C1 between the transparent substrate 1 and the first optical element 11. The first liquid crystal cell C1 includes a first substrate SUB1, a second substrate SUB2, and a first liquid crystal layer LC1. The first substrate SUB1 is adhered to the second main surface 1B of the transparent substrate 1. The second substrate SUB2 faces the first substrate SUB1. The first liquid crystal layer LC1 is held between the first substrate SUB1 and the second substrate SUB2 and is sealed by a seal SE1. Such a first liquid crystal cell C1 is driven by a driver DR, and the refractive index distribution of the first liquid crystal layer LC1 is controlled. The first optical element 11 is adhered to the second substrate SUB2.

[0048] FIG. 9 is a cross-sectional view showing another configuration example of the optical path adjustment element AD applicable to the display device DSP shown in FIG. 1.

[0049] The optical path adjustment element AD includes a first liquid crystal cell C1 and a second liquid crystal cell C2 between the transparent substrate 1 and the first optical element 11. The configuration of the first liquid crystal cell C1 is as described with reference to FIG. 8, and the description thereof is omitted.

[0050] The second liquid crystal cell C2 includes a third substrate SUB3, a fourth substrate SUB4, and a second liquid crystal layer LC2. The third substrate SUB3 is adhered to the second substrate SUB2. The fourth substrate SUB4 faces the third substrate SUB3. The second liquid crystal layer LC2 is held between the third substrate SUB3 and the fourth substrate SUB4 and is sealed by a seal SE2. Such a first liquid crystal cell C1 and second liquid crystal cell C2 are driven by a driver DR, and the refractive index distributions of the first liquid crystal layer LC1 and the second liquid crystal layer LC2 are respectively controlled. The first optical element 11 is adhered to the fourth substrate SUB4.

[0051] As shown in FIGS. 8 and 9, the optical path adjustment element AD includes at least one liquid crystal cell, and may be configured by laminating three or more liquid crystal cells.

[0052] FIG. 10 is a diagram for explaining the operation of the optical path adjustment element AD including a liquid crystal cell.

[0053] In the optical path adjustment element AD, when the refractive index distribution of the liquid crystal cell is in the initial state, the display light DL passes through the path OP0 indicated by the solid line in the optical path adjustment element AD and is totally reflected by the first main surface 1A of the transparent substrate 1. At this time, the light guiding length L0 is obtained. And the emission position of the display light DL diffracted by the second optical element 12 becomes the position P0.

[0054] In the optical path adjustment element AD, when the refractive index distribution of the liquid crystal cell is in a state different from the initial state, the display light DL is refracted in the optical path adjustment element AD, passes through a path different from the path OP0, and is totally reflected by the first main surface 1A of the transparent substrate 1.

[0055] When the display light DL passes through the path OP1 indicated by the dashed-dotted line, the optical path length of the diffracted light in the optical path adjustment element AD is extended compared to the initial state. At this time, a light guiding length L1 longer than the light guiding length L0 is obtained. And the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P1 on the left side of the figure (the side away from the first optical element 11) compared to the position P0 in the initial state.

[0056] When the display light DL passes through the path OP2 indicated by the double-dashed-dotted line, the optical path length of the diffracted light in the optical path adjustment element AD is shortened compared to the initial state. At this time, a light guiding length L2 shorter than the light guiding length L0 is obtained. And the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P2 on the right side of the figure (the side close to the first optical element 11) compared to the position P0 in the initial state.

[0057] In this way, by controlling the refractive index distribution of the liquid crystal cell constituting the optical path adjustment element AD, the emission position of the display light DL can be adjusted within the range from the position P1 to the position P2. That is, by adjusting the refractive index distribution, the observation region of the image can be freely shifted.

[0058] Even in such a configuration example, the same effects as those described above can be obtained.

[0059] FIG. 11 is a cross-sectional view showing another configuration example of the display device DSP.

[0060] The configuration example shown in FIG. 11 is different from the configuration example shown in FIG. 1 in that the optical path adjustment element AD is located between the display element 2 or the display module DM and the transparent substrate 1 and is disposed on the first main surface 1A of the transparent substrate 1. The first optical element 11 is disposed on the second main surface 1B facing the optical path adjustment element AD. The second optical element 12 is disposed on the second main surface 1B facing the user's eye E. In one example, the first optical element 11, the second optical element 12, and the optical path adjustment element AD are all adhered to the transparent substrate 1.

[0061] FIG. 12 is a cross-sectional view showing a configuration example of the optical path adjustment element AD applicable to the display device DSP shown in FIG. 11.

[0062] The optical path adjustment element AD includes a first liquid crystal cell C1 between the display element 2 and the transparent substrate 1. The first liquid crystal cell C1 includes a first substrate SUB1, a second substrate SUB2, and a first liquid crystal layer LC1. The first substrate SUB1 is adhered to the first main surface 1A of the transparent substrate 1. The second substrate SUB2 faces the first substrate SUB1. The first liquid crystal layer LC1 is held between the first substrate SUB1 and the second substrate SUB2 and is sealed by a seal SE1. Such a first liquid crystal cell C1 is driven by a driver DR, and the refractive index distribution of the first liquid crystal layer LC1 is controlled.

[0063] FIG. 13 is a cross-sectional view showing another configuration example of the optical path adjustment element AD applicable to the display device DSP shown in FIG. 11.

[0064] The optical path adjustment element AD includes a first liquid crystal cell C1 and a second liquid crystal cell C2 between the display element 2 and the transparent substrate 1. The configuration of the first liquid crystal cell C1 is as described with reference to FIG. 12, and the description thereof is omitted.

[0065] The second liquid crystal cell C2 includes a third substrate SUB3, a fourth substrate SUB4, and a second liquid crystal layer LC2. The third substrate SUB3 is adhered to the second substrate SUB2. The fourth substrate SUB4 faces the third substrate SUB3. The second liquid crystal layer LC2 is held between the third substrate SUB3 and the fourth substrate SUB4 and is sealed by a seal SE2. Such a first liquid crystal cell C1 and a second liquid crystal cell C2 are driven by a driver DR, and the refractive index distributions of the first liquid crystal layer LC1 and the second liquid crystal layer LC2 are respectively controlled.

[0066] As shown in FIGS. 12 and 13, the optical path adjusting element AD includes at least one liquid crystal cell, and may be configured by laminating three or more liquid crystal cells.

[0067] FIG. 14 is a diagram for explaining the operation of the optical path adjusting element AD provided with a liquid crystal cell.

[0068] In the optical path adjusting element AD, when the refractive index distribution of the liquid crystal cell is in the initial state, the display light DL travels substantially straight in the optical path adjusting element AD, is diffracted at a diffraction angle θ0 in the first optical element 11 after passing through the transparent substrate 1, and the diffracted light is totally reflected at the first main surface 1A. At this time, a light guiding length L0 is obtained, and the emission position of the display light DL diffracted by the second optical element 12 becomes the position P0.

[0069] FIG. 15 is a diagram for explaining the operation of the optical path adjusting element AD provided with a liquid crystal cell.

[0070] In the optical path adjustment element AD, the refractive index distribution of the liquid crystal cell is in a state different from the initial state. In the example shown in FIG. 15, the display light DL is refracted in the optical path adjustment element AD, bends to the right side of the figure, and after passing through the transparent substrate 1, it is diffracted at the diffraction angle θ1 in the first optical element 11. The diffraction angle θ1 is smaller than the diffraction angle θo (θ1 < θo). The diffracted light is totally reflected at the first main surface 1A of the transparent substrate 1. At this time, a light guiding length L1 shorter than the light guiding length L0 is obtained. Then, the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P1 on the right side of the figure (the side closer to the first optical element 11) compared to the position P0 in the initial state.

[0071] FIG. 16 is a diagram for explaining the operation of the optical path adjustment element AD provided with a liquid crystal cell.

[0072] In the optical path adjustment element AD, the refractive index distribution of the liquid crystal cell is in a state different from the initial state. In the example shown in FIG. 16, the display light DL is refracted in the optical path adjustment element AD, bends to the left side of the figure, and after passing through the transparent substrate 1, it is diffracted at the diffraction angle θ2 in the first optical element 11. The diffraction angle θ2 is larger than the diffraction angle θo (θo < θ2). The diffracted light is totally reflected at the first main surface 1A of the transparent substrate 1. At this time, a light guiding length L2 longer than the light guiding length L0 is obtained. Then, the emission position of the display light DL diffracted by the second optical element 12 shifts to the position P2 on the left side of the figure (the side away from the first optical element 11) compared to the position P0 in the initial state.

[0073] In this way, by controlling the refractive index distribution of the liquid crystal cell constituting the optical path adjustment element AD, the emission position of the display light DL can be adjusted within the range from the position P1 to the position P2. That is, by adjusting the refractive index distribution, the observation region of the image can be freely shifted.

[0074] Even in such a configuration example, the same effects as those described above can be obtained.

[0075] Next, some configuration examples for controlling the refractive index distribution of the optical path adjustment element AD will be described.

[0076] FIG. 17 is a cross-sectional view showing a configuration example of the optical path adjustment element AD.

[0077] The configuration example shown in FIG. 17 is applicable to the optical path adjustment element AD shown in FIGS. 8 and 12. The first liquid crystal cell C1 constituting the optical path adjustment element AD includes a first substrate SUB1, a second substrate SUB2, and a first liquid crystal layer LC1.

[0078] The first substrate SUB1 includes a transparent first insulating substrate IS1, a first transparent electrode TE1, and a first horizontal alignment film AL1 that covers the first transparent electrode TE1. The first insulating substrate IS1 is adhered to the first main surface 1A or the second main surface 1B of the transparent substrate 1. The first transparent electrode TE1 is a single electrode disposed on substantially the entire surface of the first insulating substrate IS1. The alignment treatment direction D1 of the first horizontal alignment film AL1 is, for example, a direction from left to right in the figure.

[0079] The second substrate SUB2 includes a transparent second insulating substrate IS2, a second transparent electrode TE2, and a first vertical alignment film AL2 that covers the second transparent electrode TE2. The second transparent electrode TE2 is a single electrode disposed on substantially the entire surface of the second insulating substrate IS2. The driver DR controls the applied voltages of the first transparent electrode TE1 and the second transparent electrode TE2.

[0080] A state in which no voltage is applied to the first transparent electrode TE1 and the second transparent electrode TE2, that is, a state in which no electric field is formed in the first liquid crystal layer LC1, is referred to as an off state (OFF). Also, a state in which a voltage is applied to the first transparent electrode TE1 and the second transparent electrode TE2, that is, a state in which an electric field is formed in the first liquid crystal layer LC1, is referred to as an on state (ON).

[0081] The first liquid crystal layer LC1 is held between the first substrate SUB1 and the second substrate SUB2 and is in contact with the first horizontal alignment film AL1 and the first vertical alignment film AL2. The liquid crystal molecules LM1 contained in the first liquid crystal layer LC1 are hybrid-aligned in the off state. That is, the liquid crystal molecules LM1 located in the vicinity of the first horizontal alignment film AL1 are aligned almost horizontally along the main surface of the first insulating substrate IS1. Also, the liquid crystal molecules LM1 located in the vicinity of the first vertical alignment film AL2 are aligned almost vertically along the normal line of the second insulating substrate IS2.

[0082] Such a first liquid crystal layer LC1 may be a positive type in which the major axis of the liquid crystal molecules LM1 is aligned along the electric field with respect to the vertical electric field between the first transparent electrode TE1 and the second transparent electrode TE2, or may be a negative type in which the major axis of the liquid crystal molecules LM1 is aligned crossing the electric field.

[0083] Note that the alignment film of the first substrate SUB1 may be the first vertical alignment film, and the alignment film of the second substrate SUB2 may be the first horizontal alignment film.

[0084] FIG. 18 is a diagram for explaining the relationship between the refractive index distribution of the first liquid crystal cell C1 shown in FIG. 17 and the display light DL.

[0085] In the example shown in FIG. 18, the first liquid crystal layer LC1 is of the positive type.

[0086] The left side of the figure shows the case where the first liquid crystal cell C1 is in the off state (OFF), and the liquid crystal molecules LM1 are hybrid-aligned in the first liquid crystal layer LC1. The display light DL passes through while being affected by the non-uniform refractive index distribution in the first liquid crystal cell C1. As a result, the display light DL is refracted and bends to the left side of the figure.

[0087] The right side of the figure shows the case where the first liquid crystal cell C1 is in the on state (ON), and the liquid crystal molecules LM1 are almost uniformly vertically aligned in the first liquid crystal layer LC1. The display light DL passes through while being affected by the almost uniform refractive index distribution in the first liquid crystal cell C1. As a result, the display light DL travels straight with almost no refraction.

[0088] FIG. 19 is a diagram for explaining another relationship between the refractive index distribution of the first liquid crystal cell C1 shown in FIG. 17 and the display light DL.

[0089] In the example shown in FIG. 19, the first liquid crystal layer LC1 is of the negative type.

[0090] The left side of the figure shows the case where the first liquid crystal cell C1 is in the off state (OFF), and the liquid crystal molecules LM1 are hybrid-aligned in the first liquid crystal layer LC1. At this time, the display light DL refracts in the same manner as in the off state shown in FIG. 18 and bends to the left side of the figure.

[0091] The right side of the figure shows the case where the first liquid crystal cell C1 is in the on state (ON), and the liquid crystal molecules LM1 are almost uniformly horizontally aligned in the first liquid crystal layer LC1. The display light DL passes while being affected by the almost uniform refractive index distribution in the first liquid crystal cell C1. As a result, the display light DL travels straight with almost no refraction.

[0092] As shown in FIGS. 18 and 19, when the first liquid crystal cell C1 is in the off state, the display light DL bends to the left, and for example, the display light DL is emitted at the position P2 as shown in FIG. 16. Also, when the first liquid crystal cell C1 is in the on state, the display light DL travels straight, and for example, the display light DL is emitted at the position P0 as shown in FIG. 14.

[0093] Therefore, by controlling the refractive index distribution of the first liquid crystal layer LC1, the emission position of the display light DL can be adjusted within the range from the position P0 to the position P2.

[0094] FIG. 20 is a cross-sectional view showing another configuration example of the optical path adjustment element AD.

[0095] The configuration example shown in FIG. 20 is applicable to the optical path adjustment element AD shown in FIGS. 9 and 13. The first liquid crystal cell C1 that constitutes the optical path adjustment element AD includes a first substrate SUB1, a second substrate SUB2, and a first liquid crystal layer LC1. The configuration of the first liquid crystal cell C1 is as described with reference to FIG. 17, and the description thereof is omitted.

[0096] The second liquid crystal cell C2 that constitutes the optical path adjustment element AD includes a third substrate SUB3, a fourth substrate SUB4, and a second liquid crystal layer LC2.

[0097] The third substrate SUB3 includes a transparent third insulating substrate IS3, a third transparent electrode TE3, and a second horizontal alignment film AL3 that covers the third transparent electrode TE3. The third insulating substrate IS3 is adhered to the second insulating substrate IS2. The third transparent electrode TE3 is a single electrode disposed on substantially the entire surface of the third insulating substrate IS3. The alignment treatment direction D2 of the second horizontal alignment film AL3 is parallel to the alignment treatment direction D1 and is in the opposite direction to the alignment treatment direction D1 (the direction from right to left in the figure).

[0098] The fourth substrate SUB4 includes a transparent fourth insulating substrate IS4, a fourth transparent electrode TE4, and a second vertical alignment film AL4 that covers the fourth transparent electrode TE4. The fourth transparent electrode TE4 is a single electrode disposed on substantially the entire surface of the fourth insulating substrate IS4. The driver DR controls the applied voltages of the third transparent electrode TE3 and the fourth transparent electrode TE4.

[0099] A state in which no voltage is applied to the third transparent electrode TE3 and the fourth transparent electrode TE4, that is, a state in which no electric field is formed in the second liquid crystal layer LC2, is referred to as an off state (OFF). Also, a state in which a voltage is applied to the third transparent electrode TE3 and the fourth transparent electrode TE4, that is, a state in which an electric field is formed in the second liquid crystal layer LC2, is referred to as an on state (ON).

[0100] The second liquid crystal layer LC2 is held between the third substrate SUB3 and the fourth substrate SUB4 and is in contact with the second horizontal alignment film AL3 and the second vertical alignment film AL4. The liquid crystal molecules LM2 contained in the second liquid crystal layer LC2 are hybrid-aligned in the off state. That is, the liquid crystal molecules LM2 located in the vicinity of the second horizontal alignment film AL3 are aligned almost horizontally along the main surface of the third insulating substrate IS3. Also, the liquid crystal molecules LM2 located in the vicinity of the second vertical alignment film AL4 are aligned almost vertically along the normal line of the fourth insulating substrate IS4.

[0101] Such a second liquid crystal layer LC2 may be a positive type in which the major axis of the liquid crystal molecules LM2 is aligned along the electric field with respect to the vertical electric field between the third transparent electrode TE3 and the fourth transparent electrode TE4, or may be a negative type in which the major axis of the liquid crystal molecules LM2 is aligned crossing the electric field.

[0102] Note that the alignment film of the third substrate SUB3 may be the second vertical alignment film, and the alignment film of the fourth substrate SUB4 may be the second horizontal alignment film.

[0103] FIG. 21 is a diagram for explaining the relationship between the refractive index distributions of the first liquid crystal cell C1 and the second liquid crystal cell C2 shown in FIG. 20 and the display light DL.

[0104] In the example shown in FIG. 21, both the first liquid crystal layer LC1 and the second liquid crystal layer LC2 are of the positive type.

[0105] The center of the figure shows the case where the first liquid crystal cell C1 and the second liquid crystal cell C2 are in the on state (ON). In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are aligned almost uniformly vertically. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are aligned almost uniformly vertically. The display light DL travels straight through the first liquid crystal cell C1 with almost no refraction and then travels straight through the second liquid crystal cell C2 with almost no refraction. For this reason, the display light DL is emitted, for example, at the position P0 as shown in FIG. 14.

[0106] On the left side of the figure, it shows the case where the first liquid crystal cell C1 is in the ON state and the second liquid crystal cell C2 is in the OFF state. In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are almost uniformly vertically aligned. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are in a hybrid alignment. The display light DL travels straight through the first liquid crystal cell C1 with little refraction and then refracts in the second liquid crystal cell C2 and bends to the left side of the figure. Therefore, the display light DL is emitted at position P2 as shown in, for example, Figure 16.

[0107] On the right side of the figure, it shows the case where the first liquid crystal cell C1 is in the OFF state and the second liquid crystal cell C2 is in the ON state. In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are in a hybrid alignment. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are almost uniformly vertically aligned. The display light DL refracts in the first liquid crystal cell C1, bends to the right side of the figure, and hardly refracts in the second liquid crystal cell C2. As a result, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 bends to the right side of the figure. Therefore, the display light DL is emitted at position P1 as shown in, for example, Figure 15.

[0108] Therefore, by controlling the refractive index distributions of the first liquid crystal layer LC1 and the second liquid crystal layer LC2, the emission position of the display light DL can be adjusted within the range from position P1 to position P2.

[0109] Figure 22 is a diagram for explaining another relationship between the refractive index distributions of the first liquid crystal cell C1 and the second liquid crystal cell C2 shown in Figure 20 and the display light DL.

[0110] In the example shown in Figure 22, both the first liquid crystal layer LC1 and the second liquid crystal layer LC2 are of the positive type.

[0111] The center of the figure shows the case where the first liquid crystal cell C1 and the second liquid crystal cell C2 are in the off state (OFF). In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are in a hybrid alignment. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are in a hybrid alignment. The display light DL is refracted in the first liquid crystal cell C1 and bends to the right. Also, the display light DL is refracted in the second liquid crystal cell C2 and bends to the left. As a result, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 travels almost straight. For this reason, the display light DL is emitted at the position P0 as shown in, for example, FIG. 14.

[0112] The left side of the figure shows the case where the first liquid crystal cell C1 is in the on state (ON) and the second liquid crystal cell C2 is in the off state (OFF). In this case, similar to the example shown on the left side of FIG. 21, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 bends to the left. For this reason, the display light DL is emitted at the position P2 as shown in, for example, FIG. 16.

[0113] The right side of the figure shows the case where the first liquid crystal cell C1 is in the off state (OFF) and the second liquid crystal cell C2 is in the on state (ON). In this case, similar to the example shown on the right side of FIG. 21, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 bends to the right. For this reason, the display light DL is emitted at the position P1 as shown in, for example, FIG. 15.

[0114] Therefore, by controlling the refractive index distribution of the first liquid crystal layer LC1 and the second liquid crystal layer LC2, the emission position of the display light DL can be adjusted within the range from the position P1 to the position P2.

[0115] FIG. 23 is a diagram for explaining another relationship between the refractive index distribution of the first liquid crystal cell C1 and the second liquid crystal cell C2 shown in FIG. 20 and the display light DL.

[0116] In the example shown in FIG. 23, both the first liquid crystal layer LC1 and the second liquid crystal layer LC2 are of the negative type.

[0117] The center of the figure shows the case where the first liquid crystal cell C1 and the second liquid crystal cell C2 are in the ON state. In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are almost uniformly horizontally aligned. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are almost uniformly horizontally aligned. The display light DL travels straight through the first liquid crystal cell C1 with almost no refraction and then travels straight through the second liquid crystal cell C2 with almost no refraction. Therefore, the display light DL is emitted at the position P0 as shown in, for example, FIG. 14.

[0118] The left side of the figure shows the case where the first liquid crystal cell C1 is in the ON state and the second liquid crystal cell C2 is in the OFF state. In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are almost uniformly horizontally aligned. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are in a hybrid alignment. The display light DL travels straight through the first liquid crystal cell C1 with almost no refraction and then refracts in the second liquid crystal cell C2 and bends to the left side of the figure. Therefore, the display light DL is emitted at the position P2 as shown in, for example, FIG. 16.

[0119] The right side of the figure shows the case where the first liquid crystal cell C1 is in the OFF state and the second liquid crystal cell C2 is in the ON state. In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are in a hybrid alignment. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are almost uniformly horizontally aligned. The display light DL refracts in the first liquid crystal cell C1, bends to the right side of the figure, and hardly refracts in the second liquid crystal cell C2. As a result, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 bends to the right side of the figure. Therefore, the display light DL is emitted at the position P1 as shown in, for example, FIG. 15.

[0120] Therefore, by controlling the refractive index distribution of the first liquid crystal layer LC1 and the second liquid crystal layer LC2, the emission position of the display light DL can be adjusted within the range from the position P1 to the position P2.

[0121] FIG. 24 is a diagram for explaining another relationship between the refractive index distributions of the first liquid crystal cell C1 and the second liquid crystal cell C2 shown in FIG. 20 and the display light DL.

[0122] In the example shown in FIG. 24, both the first liquid crystal layer LC1 and the second liquid crystal layer LC2 are of the negative type.

[0123] The center of the figure shows the case where the first liquid crystal cell C1 and the second liquid crystal cell C2 are in the off state (OFF). In the first liquid crystal layer LC1, the liquid crystal molecules LM1 are hybrid-aligned. Also, in the second liquid crystal layer LC2, the liquid crystal molecules LM2 are hybrid-aligned. The display light DL is refracted in the first liquid crystal cell C1 and bends to the right. Also, the display light DL is refracted in the second liquid crystal cell C2 and bends to the left. As a result, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 travels almost straight. For this reason, the display light DL is emitted at the position P0 as shown in FIG. 14, for example.

[0124] The left side of the figure shows the case where the first liquid crystal cell C1 is in the on state (ON) and the second liquid crystal cell C2 is in the off state (OFF). In this case, similar to the example shown on the left side of FIG. 23, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 bends to the left. For this reason, the display light DL is emitted at the position P2 as shown in FIG. 16, for example.

[0125] The right side of the figure shows the case where the first liquid crystal cell C1 is in the off state (OFF) and the second liquid crystal cell C2 is in the on state (ON). In this case, similar to the example shown on the right side of FIG. 23, the display light DL that has passed through the first liquid crystal cell C1 and the second liquid crystal cell C2 bends to the right. For this reason, the display light DL is emitted at the position P1 as shown in FIG. 15, for example.

[0126] Therefore, by controlling the refractive index distributions of the first liquid crystal layer LC1 and the second liquid crystal layer LC2, the emission position of the display light DL can be adjusted within the range from the position P1 to the position P2. In addition, when the optical path adjustment element AD is configured by stacking a plurality of liquid crystal cells, a liquid crystal cell including a negative-type liquid crystal layer and a liquid crystal cell including a positive-type liquid crystal layer may be combined.

[0127] FIG. 25 is a diagram for explaining an application example of the display device DSP.

[0128] FIG. 25 shows a pair of glasses-type head-mounted display 100. The head-mounted display 100 includes display devices DSP at positions corresponding to the user's right and left eyes, respectively, and also includes an eye tracking mechanism ET that tracks the positions of the right and left eyes. The eye tracking mechanism ET is configured to output a signal corresponding to the eye position to the driver DR. The driver DR drives at least one of the first liquid crystal cell C1 and the second liquid crystal cell C2 as described above. That is, the driver DR controls the applied voltages of the first transparent electrode, the second transparent electrode, the third transparent electrode, and the fourth transparent electrode, and controls the refractive index distribution of the first liquid crystal layer LC1 and the refractive index distribution of the second liquid crystal layer LC2. Thereby, an image can be displayed corresponding to the position of the user's eyes.

[0129] As described above, according to the present embodiment, it is possible to provide a display device and a light guide element capable of suppressing a decrease in the visibility of an image.

[0130] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0131] DSP... Display device LG... Light guide element 1... Transparent substrate 1A... First main surface 1B... Second main surface 2… denotes an element 3… optical system 11… first optical element 12… second optical element 21… elastic layer 24… variable mechanism 25… sealing film 31… frame 31A… opening 32… frame 32A… opening AD… optical path adjustment element AL1… first horizontal alignment film D1… alignment processing direction AL2… first vertical alignment film AL3… second horizontal alignment film D2… alignment processing direction AL4… second vertical alignment film C1… first liquid crystal cell LC1… first liquid crystal layer LM1… liquid crystal molecules C2… second liquid crystal cell LC2… second liquid crystal layer LM2… liquid crystal molecules SUB1… first substrate TE1… first transparent electrode SUB2… second substrate TE2… second transparent electrode SUB3… third substrate TE3… third transparent electrode SUB4… fourth substrate TE4… fourth transparent electrode

Claims

1. A transparent substrate having a first main surface and a second main surface facing the first main surface; A display element configured to emit display light toward the transparent substrate; An optical path adjustment element disposed on the second main surface facing the display element; A first optical element that overlaps the optical path adjustment element and diffracts the display light transmitted through the transparent substrate and the optical path adjustment element so as to totally reflect the display light inside the transparent substrate; A second optical element disposed on the second main surface and diffracting the display light propagated inside the transparent substrate so as to emit the display light from the first main surface, comprising: The optical path adjustment element is configured to be able to adjust the optical path of the display light in order to change the emission position of the display light.

2. The optical path adjustment element includes an elastic layer disposed between the transparent substrate and the first optical element, and a variable mechanism for varying the thickness of the elastic layer. The display device according to claim 1.

3. The elastic layer is formed of a transparent resin. The display device according to claim 2.

4. The elastic layer is formed of a transparent liquid. The display device according to claim 2.

5. A transparent substrate having a first main surface and a second main surface facing the first main surface; A display element configured to emit display light toward the transparent substrate; An optical path adjustment element disposed on the first main surface between the transparent substrate and the display element; A first optical element disposed on the second main surface facing the optical path adjustment element and diffracting the display light transmitted through the transparent substrate so as to totally reflect the display light inside the transparent substrate; A second optical element disposed on the second main surface and diffracting the display light propagated inside the transparent substrate so as to emit the display light from the first main surface, comprising: The optical path adjustment element is configured to be able to adjust the optical path of the display light in order to change the emission position of the display light.

6. The optical path adjustment element includes at least one liquid crystal cell. The display device according to claim 1 or 5.

7. The optical path adjustment element is a first liquid crystal cell, A first substrate including a first transparent electrode and a first horizontal alignment film covering the first transparent electrode; A second substrate including a second transparent electrode and a first vertical alignment film covering the second transparent electrode; A first liquid crystal layer held between the first substrate and the second substrate and including hybrid-aligned liquid crystal molecules in a state where no voltage is applied to the first transparent electrode and the second transparent electrode. The display device according to claim 6.

8. The optical path adjustment element further includes, as a second liquid crystal cell overlapping the first liquid crystal cell, a third substrate including a third transparent electrode and a second horizontal alignment film covering the third transparent electrode, a fourth substrate including a fourth transparent electrode and a second vertical alignment film covering the fourth transparent electrode, and a second liquid crystal layer held between the third substrate and the fourth substrate and including liquid crystal molecules hybrid-aligned in a state where no voltage is applied to the third transparent electrode and the fourth transparent electrode. The display device according to claim 7.

9. The alignment treatment directions of the first horizontal alignment film and the second horizontal alignment film are parallel to each other and opposite to each other. The display device according to claim 8.

10. A transparent substrate having a first main surface and a second main surface facing the first main surface, an optical path adjustment element disposed on the second main surface, a first optical element that overlaps the optical path adjustment element and diffracts light transmitted through the transparent substrate and the optical path adjustment element so as to totally reflect the light inside the transparent substrate, and a second optical element disposed on the second main surface and diffracting light propagated inside the transparent substrate so as to emit the light from the first main surface. The optical path adjustment element is a light guiding element configured to be able to adjust the optical path of incident light in order to change the light emission position.

11. The optical path adjustment element includes an elastic layer disposed between the transparent substrate and the first optical element, and a variable mechanism for varying the thickness of the elastic layer. The light guiding element according to claim 10.

12. The elastic layer is formed of a transparent resin. The light guiding element according to claim 11.

13. The elastic layer is formed of a transparent liquid. The light guiding element according to claim 11.

14. A transparent substrate having a first main surface and a second main surface facing the first main surface, an optical path adjustment element disposed on the first main surface, a first optical element disposed on the second main surface facing the optical path adjustment element and diffracting light transmitted through the transparent substrate so as to totally reflect the light inside the transparent substrate, and a second optical element disposed on the second main surface and diffracting light propagated inside the transparent substrate so as to emit the light from the first main surface. The optical path adjustment element is a light guiding element configured to be able to adjust the optical path of incident light in order to change the light emission position.

15. The optical path adjustment element includes at least one liquid crystal cell. The light guiding element according to claim 10 or 14.

16. The light guiding element according to claim 10 or 14.

16. The optical path adjustment element is a first liquid crystal cell, a first substrate including a first transparent electrode and a first horizontal alignment film covering the first transparent electrode, a second substrate including a second transparent electrode and a first vertical alignment film covering the second transparent electrode, and a first liquid crystal layer held between the first substrate and the second substrate and including hybrid-aligned liquid crystal molecules in a state where no voltage is applied to the first transparent electrode and the second transparent electrode. The light guide element according to claim 15.

17. The optical path adjustment element further includes, as a second liquid crystal cell overlapping the first liquid crystal cell, a third substrate including a third transparent electrode and a second horizontal alignment film covering the third transparent electrode, a fourth substrate including a fourth transparent electrode and a second vertical alignment film covering the fourth transparent electrode, and a second liquid crystal layer held between the third substrate and the fourth substrate and including hybrid-aligned liquid crystal molecules in a state where no voltage is applied to the third transparent electrode and the fourth transparent electrode. The light guide element according to claim 16.

18. The alignment treatment directions of the first horizontal alignment film and the second horizontal alignment film are parallel to each other and opposite to each other. The light guide element according to claim 17.

Images