Indication device

Abstract

To provide a display device which makes it difficult to notice noise on image light output form a hologram element.SOLUTION: A display device 1 is provided, comprising light guide 30 having a first hologram element 41 and a second hologram element 42, and an image light emission unit 50 for outputting image light to the light guide 30. The first hologram element 41 has a plurality of first cells 41a for outputting first image light obtained by diffracting the image light propagating through the light guide 30 toward the second hologram element 42. The second hologram element 42 has a plurality of second cells 42a for outputting second image light obtained by diffracting the first image light propagating through the light guide 30. An arrangement of the plurality of first cells 41a is different from that of the plurality of second cells 42a.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a display device.

Background Art

[0002] As a conventional technique, a light guide plate for a head-up display having a plurality of hologram elements in the light guide plate is known. For example, Patent Document 1 discloses an optical device including a first light guide plate and a second light guide plate, a first deflection unit provided on the first light guide plate, and a second deflection unit provided on the second light guide plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, when manufacturing a large-area deflection unit (hologram element), the hologram element is divided into minute regions and each region is sequentially exposed to obtain a large-area hologram element. Therefore, in the optical device of Patent Document 1, when the hologram element is enlarged, at the boundary line where each region abuts, a phase difference of light and a fluctuation of light intensity occur. When such a hologram element is used, there is a problem that linear noise occurs in the image light emitted from the hologram element.

[0005] Therefore, an object of the present disclosure is to provide a display device capable of making the noise generated in the image light emitted from the hologram element less conspicuous.

Means for Solving the Problems

[0006] A display device according to one aspect of the present disclosure comprises a light guide having a first hologram element and a second hologram element, and an image light emitting unit that emits image light to the light guide, wherein the first hologram element has a plurality of first cells for emitting first image light, obtained by diffracting the image light propagating inside the light guide, toward the second hologram element, and the second hologram element has a plurality of second cells for emitting second image light, obtained by diffracting the first image light propagating inside the light guide, and the arrangement of the plurality of first cells is different from the arrangement of the plurality of second cells. The light guide has a third hologram element, the first hologram element is an incident hologram element to which the image light emitted from the image light emission section is incident, the second hologram element is a folded hologram element that diffracts the first image light emitted from the first hologram element and emits the second image light to the third hologram element, the third hologram element is an output hologram element that diffracts the incident second image light and emits the third image light, and the third hologram element propagates inside the light guide before The hologram element has a plurality of third cells for emitting the third image light obtained by diffracting the second image light, wherein the arrangement of the plurality of first cells, the arrangement of the plurality of second cells, and the arrangement of the plurality of third cells are all different, the size of the plurality of first cells, the size of the plurality of second cells, and the size of the plurality of third cells are all different from each other, and at least one of the first hologram element, the second hologram element, and the third hologram element contains two or more types of cells of different sizes. ru. A display device according to one aspect of the present disclosure comprises a light guide having a first hologram element and a second hologram element, and an image light emitting unit that emits image light to the light guide, wherein the first hologram element has a plurality of first cells for emitting first image light, obtained by diffracting the image light propagating inside the light guide, toward the second hologram element, the second hologram element has a plurality of second cells for emitting second image light, obtained by diffracting the first image light propagating inside the light guide, the arrangement of the plurality of first cells differs from the arrangement of the plurality of second cells, the light guide has a third hologram element, the first hologram element is an incident hologram element to which the image light emitted by the image light emitting unit is incident, and the second hologram element diffracts the first image light emitted by the first hologram element The third hologram element is a folding hologram element that emits the second image light to the third hologram element, and the third hologram element is an output hologram element that diffracts the incident second image light and emits the third image light, and the third hologram element has a plurality of third cells for emitting the third image light obtained by diffracting the second image light propagating inside the light guide, and the arrangement of the plurality of first cells, the arrangement of the plurality of second cells, and the arrangement of the plurality of third cells are all different, the size of the plurality of first cells, the size of the plurality of second cells, and the size of the plurality of third cells are all different from each other, and at least one of the first hologram element, the second hologram element, and the third hologram element contains two or more types of cells with different shapes. [Effects of the Invention]

[0007] The display device described herein makes it possible to reduce the visibility of noise generated in the image light emitted from the hologram element. [Brief explanation of the drawing]

[0008] [Figure 1A] Figure 1A is a schematic diagram showing an example of a vehicle in which the display device according to the embodiment is installed. [Figure 1B] Figure 1B is a schematic diagram showing the display device and vehicle according to the embodiment as viewed from the side. [Figure 2] Figure 2 is a perspective view showing a display device according to an embodiment. [Figure 3] Figure 3 is a diagram showing a display device according to an embodiment. [Figure 4] Figure 4 shows a display device and a hologram element cell according to an embodiment. [Figure 5] Figure 5 shows a cell of another hologram element according to an embodiment. [Figure 6] Figure 6 shows the relationship between the size of the hologram element cell and the virtual image projected onto the light-transmitting material. [Figure 7] Figure 7 shows the virtual image when using the hologram element of the comparative example and the virtual image when using the display device according to the embodiment. [Modes for carrying out the invention]

[0009] The embodiments will be described in detail below with reference to the drawings.

[0010] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, any components in the following embodiments that are not described in an independent claim will be described as optional components.

[0011] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Also, the same component is denoted by the same reference numeral in each figure.

[0012] Furthermore, in the following embodiments, expressions such as rectangular, substantially parallel, and in the X-axis direction are used. For example, rectangular, substantially parallel, and in the X-axis direction not only mean that it is perfectly rectangular, parallel, and in the X-axis direction, but also substantially rectangular, parallel, and in the X-axis direction, that is, including an error of a few percent. Also, rectangular, parallel, and in the X-axis direction means rectangular, substantially parallel, and in the X-axis direction to the extent that the effects of this disclosure can be achieved. The same applies to other expressions using "shape," "subjectively," and "direction."

[0013] (Embodiment) <Structure> First, the configuration of the display device 1 will be described with reference to FIGS. 1A to 3. FIG. 1A is a schematic diagram showing an example of a vehicle 2 in which the display device 1 according to the embodiment is installed. FIG. 1B is a schematic diagram showing the display device 1 and the vehicle 2 as viewed from the side. FIG. 2 is a perspective view showing the display device 1 according to the embodiment. FIG. 3 is a view showing the display device 1 according to the embodiment. (a) of FIG. 3 is a front view of the display device 1, (b) of FIG. 3 is a cross-sectional view of the display device 1 taken along line B-B of (a) of FIG. 3, and (c) of FIG. 3 is a cross-sectional view of the display device 1 taken along line C-C of (a) of FIG. 3.

[0014] As shown in FIGS. 1A and 1B, the display device 1 can cause image light to enter a person's eye by emitting and reflecting the image light from a light reflector. For example, when the display device 1 is used in the vehicle 2, the display device 1 can cause image light to enter a person's eye by reflecting the image light emitted to the front windshield 3 as a light-transmitting member. In this case, by the display device 1 emitting the image light, an image shown in the image light is projected onto the light-transmitting member, and a virtual image corresponding to the image can be displayed on the light-transmitting member. The image light is light showing an image and is light for displaying a virtual image in front of the front windshield 3. The image is a still image or a moving image and is an image showing numbers, characters, figures, and the like.

[0015] As shown in FIGS. 1B and 2, the display device 1 includes an image light emitting unit 50 and a light guide 30.

[0016] The image light emitting unit 50 is an image generation device that emits image light to the light guide 30. By the image light emitting unit 50 emitting image light showing a rectangular image, the image light is projected onto the front windshield 3 through the light guide 30. Thereby, a virtual image is recognized by the user.

[0017] Such an image light emitting unit 50 has a plurality of emitters, a plurality of dichroic mirrors, a condenser lens, a mirror, and an emission surface.

[0018] Each of the plurality of emitters is different from one another and emits a light beam that is light in a predetermined wavelength band. Each of the plurality of dichroic mirrors is disposed on the light beam emitted by the emitter, and can reflect the light beam in the predetermined wavelength band and transmit the light beam in other wavelength bands. The condenser lens is a lens that condenses the light beam emitted through the dichroic mirror onto the plurality of mirrors. The emission surface is a screen such as a microlens array or a liquid crystal display element such as a liquid crystal on silicon (LCOS). When the light beams in a plurality of wavelength bands are irradiated from the mirror side, the transmitted light can be emitted toward the light guide 30 as image light.

[0019] The light guide 30 is a holographic light guide plate that displays the image indicated by the image light to the user. The light guide 30 has light transmissivity and can stretch and emit the image shown in the image light emitted from the image light emitting unit 50 in the X-axis direction and the Y-axis direction. The light guide 30 is disposed so as to face the image light emitting unit 50 and the front window 3.

[0020] The light guide 30 has an incident surface 31a and an emission surface 31b.

[0021] The incident surface 31a is disposed so as to face the emission surface of the image light emitting unit 50. The image light emitted from the emission surface of the image light emitting unit 50 is incident on the incident surface 31a. The incident surface 31a is a part of the back surface of the light guide 30 having a rectangular shape. The back surface is the surface on the opposite side of the emission surface 31b of the light guide 30.

[0022] The emission surface 31b emits the image light that has entered from the incident surface 31a and has propagated inside the light guide 30 toward the front window 3. The emission surface 31b faces the front window 3 and is separated from the front window 3 by a predetermined distance. The emission surface 31b is a part of the surface of the light guide 30.

[0023] As shown in FIGS. 3 and 4, the light guide 30 has a light guide portion 31 having light transmissivity and a plurality of hologram elements 40.

[0024] The light guide section 31 has an incident surface 31a that faces the image light emission section 50. The incident surface 31a is the surface facing the image light emission section 50 and is a part of the back surface of the light guide section 31. The light guide section 31 also has an emission surface 31b that faces the front windshield 3. The emission surface 31b is a part of the surface of the light guide section 31.

[0025] The light guide section 31 is made of a light-transmitting material such as glass and resin.

[0026] Multiple holographic elements 40 are enclosed within the light guide section 31. As shown in Figure 3, the multiple holographic elements 40 are light-transmitting optical elements that diffract and emit light propagating through the light guide section 31. The multiple holographic elements 40 are enclosed within the light guide section 31 in a position substantially parallel to the incident surface 31a and the exit surface 31b of the light guide section 31. The multiple holographic elements 40 are made of a light-transmitting material.

[0027] Such a plurality of holographic elements 40 includes a first holographic element 41, a second holographic element 42, and a third holographic element 43.

[0028] The first hologram element 41 and the second hologram element 42 are arranged side by side along the X-axis. The second hologram element 42 and the third hologram element 43 are arranged side by side along the Y-axis. Furthermore, the first hologram element 41 is positioned such that, when viewed along the Z-axis, it overlaps with the incident surface 31a of the light guide 30 and also overlaps with the emission surface of the image light emission unit 50 located on the Z-minus side of the light guide 30.

[0029] The first hologram element 41 is an incident hologram element to which the image light emitted from the image light emission unit 50 is incident. The first hologram element 41 receives image light that travels along the positive Z-axis direction emitted from the emission surface of the image light emission unit 50, and emits the incident image light toward the second hologram element 42. Specifically, the first hologram element 41 emits first image light (bent light), which is the image light from the image light emission unit 50 that has been deflected from the incident surface 31a, toward the second hologram element 42. More specifically, as the image light incident on the light guide 30 propagates within the light guide 30, the first hologram element 41 deflects the image light by diffraction according to the diffraction efficiency of the first hologram element 41, and emits it as first image light that propagates along the positive X-axis direction. The first image light, deflected by diffraction at the first hologram element 41, is incident on the second hologram element 42.

[0030] The second hologram element 42 is located on the positive X-axis side of the first hologram element 41, on the light-emitting side of the first hologram element 41, and on the positive Y-axis side of the third hologram element 43, on the light-ingress side of the third hologram element 43.

[0031] The second hologram element 42 is elongated along the X-axis and is a folded hologram element that diffracts the first image light emitted from the first hologram element 41 and emits the second image light to the third hologram element 43.

[0032] The first image light emitted from the first hologram element 41 is incident on the second hologram element 42. The second hologram element 42 further deflects the first image light, which has been deflected by diffraction by the first hologram element 41, by diffraction, and emits a deflected second image light (deflected light). Specifically, each time the first image light that has passed through the first hologram element 41 is incident on (transmitted) by the second hologram element 42, the second image light, which has been further deflected by diffraction from the incident first image light, is emitted toward the third hologram element 43. More specifically, as the first image light incident on the second hologram element 42 propagates through the light guide 30 along the positive X-axis direction, the second hologram element 42 further deflects the first image light by diffraction according to the diffraction efficiency of the second hologram element 42. At this time, the second hologram element 42 stretches the image of the first image light along the X-axis direction. As a result, the second hologram element 42 emits the second image light, which has been stretched along the X-axis, along the negative Y-axis direction. The second image light, deflected by diffraction in the second hologram element 42, is incident on the third hologram element 43.

[0033] The third hologram element 43 is located on the negative Y-axis side of the second hologram element 42 and is positioned on the light-emitting side of the second hologram element 42. Furthermore, the third hologram element 43 is positioned so as to overlap with and face the light-emitting surface 31b of the light guide 30.

[0034] The third hologram element 43 is an emission hologram element that has a rectangular shape when viewed along the Z-axis.

[0035] The second image light emitted from the second hologram element 42 is incident on the third hologram element 43. The third hologram element 43 further deflects the second image light, which has been deflected by diffraction by the second hologram element 42, by diffraction, and emits the deflected third image light (deflected light) to the outside of the light guide 30. Specifically, each time the second image light that has passed through the second hologram element 42 is incident on (transmitted) by the third hologram element 43, the third hologram element 43 emits the third image light, which has been further deflected by diffraction by the incident second image light, at a predetermined emission angle. More specifically, as the second image light deflected by diffraction by the second hologram element 42 propagates through the light guide 30 along the negative Y-axis direction, the third hologram element 43 further deflects the second image light by diffraction according to the diffraction efficiency of the third hologram element 43. At this time, the third hologram element 43 further stretches the image of the second image light, which has been stretched along the X-axis, along approximately the Y-axis. As a result, the third hologram element 43 emits the third image light, which has been stretched along the X-axis and approximately the Y-axis, to the outside of the light guide 30 at a predetermined emission angle. In other words, the third hologram element 43 further stretches the second image light emitted by the second hologram element 42 along approximately the Y-axis, thereby emitting the third image light, which has been expanded in the X-axis and Y-axis directions, at a predetermined emission angle. In this embodiment, the third hologram element 43 emits the third image light in the Z-axis positive direction so that it is directed toward the front windshield 3.

[0036] Here, the predetermined emission angle is the emission angle of the third image light emitted from the emission surface of the third hologram element 43, and is the angle of the light emitted with respect to the normal of the emission surface of the third hologram element 43.

[0037] Furthermore, the third hologram element 43 may diverge the emitted third image light so that the emission angles of the third image light differ. When the third hologram element 43 deflects the incident second image light by diffraction, it may make the emission angle different depending on the position (part) on the third hologram element 43. In this way, the third hologram element 43 can make the emission angles of some of the third image light deflected by diffraction differ.

[0038] Next, the specific configurations of the first hologram element 41, the second hologram element 42, and the third hologram element 43 will be described using Figures 4 and 5.

[0039] Figure 4 shows a display device 1 and a cell of a hologram element 40 according to an embodiment. Figure 5 shows a cell of another hologram element according to an embodiment.

[0040] As shown in Figure 4, the first hologram element 41 has a plurality of first cells 41a for diffracting and deflecting the image light propagating inside the light guide 30 and emitting the first image light toward the second hologram element 42. The second hologram element 42 has a plurality of second cells 42a for diffracting and deflecting the first image light propagating inside the light guide 30 and emitting the second image light. The third hologram element 43 has a plurality of third cells 43a for diffracting and deflecting the second image light propagating inside the light guide 30 and emitting the third image light.

[0041] In this embodiment, each of the multiple first cells 41a is the same size and shape, each of the multiple second cells 42a is the same size and shape, and each of the multiple third cells 43a is the same size and shape. Furthermore, the multiple first cells 41a, the multiple second cells 42a, and the multiple third cells 43a are all the same shape. Also, each of the multiple first cells 41a, the multiple second cells 42a, and the multiple third cells 43a is polygonal in shape. Figure 4 illustrates the case where each of the multiple first cells 41a, the multiple second cells 42a, and the multiple third cells 43a is substantially rectangular in shape.

[0042] The arrangement of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a are all different. Alternatively, it may suffice for only two of the three arrangements to be different. A different arrangement means that the arrangement or position of the multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a are different, and that when each hologram element 40 is superimposed, the boundary where two adjacent cells touch is different for each hologram element 40.

[0043] If the arrangement of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a is to be different, the following example can be used.

[0044] For example, the sizes of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a may each be different from one another. Alternatively, it may be sufficient for only two of the three sizes (multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a) to be different.

[0045] For example, the multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a may be progressively larger in size in this order. In other words, the hologram elements closer to the incident side where the image light emitted from the image light emission unit 50 enters may have smaller cell sizes. It is also acceptable for the size of the multiple first cells 41a to be smaller than the size of the multiple second cells 42a, or the size of the multiple third cells 43a, or for the size of the multiple second cells 42a to be smaller than the size of the multiple third cells 43a.

[0046] For example, the length of the first side (h1, w1) in multiple first cells 41a does not have to be an integer multiple of the length of the second side (h2, w2) in multiple second cells 42a corresponding to the first side. Also, the length of the first side (h1, w1) in multiple first cells 41a does not have to be an integer multiple of the length of the third side (h3, w3) in multiple third cells 43a corresponding to the first side. That is, it satisfies h1≠n*h2, h2≠n*h3, h1≠n*h3, w1≠m*w2, w2≠m*w3, and w1≠m*w3, where n and m are natural numbers. Also, the length of the second side (h2, w2) in multiple second cells 42a does not have to be an integer multiple of the length of the third side (h3, w3) in multiple third cells 43a corresponding to the second side. This makes it possible to make the sizes of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a different.

[0047] For example, at least one of the first hologram element 41, the second hologram element 42, and the third hologram element 43 may contain two or more cells of different sizes. A plurality of first cells 41a may contain two or more first cells 41a of different sizes. Similarly, a plurality of second cells 42a may contain two or more second cells 42a of different sizes. Furthermore, a plurality of third cells 43a may contain two or more third cells 43a of different sizes. For example, as shown in Figures 5(a) and 5(b), a hologram element may be constructed by combining a large rectangular cell and a small rectangular cell.

[0048] For example, at least one of the first hologram element 41, the second hologram element 42, and the third hologram element 43 may contain two or more cells of different shapes. That is, multiple first cells 41a may contain two or more first cells 41a of different shapes. Similarly, multiple second cells 42a may contain two or more second cells 42a of different shapes. Furthermore, multiple third cells 43a may contain two or more third cells 43a of different shapes. For example, a hologram element may be constructed by combining square cells and rectangular cells.

[0049] Due to this configuration, the arrangement of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a can be made different. As a result, in the third image light emitted from the emission surface 31b, noise in the first image light generated at the boundary where two adjacent first cells 41a meet, noise in the second image light generated at the boundary where two adjacent second cells 42a meet, and noise in the third image light generated at the boundary where two adjacent third cells 43a meet are less likely to overlap.

[0050] Next, we will explain how virtual images appear using Figures 6 and 7.

[0051] Figure 6 shows the relationship between the cell size of the hologram element and the virtual image projected onto the light-transmitting member. Figure 7 shows the virtual image when using the comparative example hologram element and the virtual image when using the display device 1 according to the embodiment. Figure 7(a) shows how the virtual image projected onto the light-transmitting member appears when using the first hologram element, second hologram element, and third hologram element as comparative examples. Figure 7(b) shows how the virtual image projected onto the light-transmitting member appears when using the first hologram element 41, second hologram element 42, and third hologram element 43 of the display device 1 according to the embodiment.

[0052] As shown in Figures 6(a) and 6(b), it has been found that the appearance of the virtual image projected onto the light-transmitting member differs depending on the size of the cell.

[0053] For example, Figure 6(a) shows an example where a large cell size is used for the hologram element, while Figure 6(b) shows an example where a small cell size is used for the hologram element.

[0054] In the display device using a hologram element composed of multiple cells with a large cell size, as shown in Figure 6(a), when a virtual image is projected onto the light-transmitting member, the black target image and multiple images, which are noises indicated by dot hatching and appear around the target image, are displayed on the light-transmitting member.

[0055] In the display device using a hologram element composed of multiple cells with small cell sizes, as shown in Figure 6(b), when a virtual image is projected onto the light-transmitting member, a black target image and multiple noises, indicated by dot hatching, appear on the light-transmitting member as if they were far away from the target image.

[0056] As you can see, the appearance of noise differs depending on the cell size.

[0057] In Figure 7(a), the cells of the first hologram element, the second hologram element, and the third hologram element are configured to have the same arrangement. In this case, the first image light emitted from the first hologram element shows observation image 1, which consists of the target image 1 and low-luminance noise 1, which is shown as dot hatching. The second image light emitted from the second hologram element shows observation image 2, which consists of the target image 2 and low-luminance noise 2, which is shown as dot hatching. The third image light emitted from the third hologram element shows observation image 3, which consists of the target image 3 and low-luminance noise 3, which is shown as dot hatching. Noises 1 to 3 are formed at the same positions relative to the target images 1 to 3. Therefore, the virtual image projected onto the light-transmitting member shows the target image, which is a superposition of each of the observation images 1 to 3, and noise, which is a superposition of the low-luminance noises 1 to 3, shown as dot hatching. In this case, the noise in the virtual image projected onto the light-transmitting material becomes high-luminosity, making it difficult to distinguish from the target image and potentially impairing the visibility of the target image.

[0058] In Figure 7(b), the arrangement of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a in the first hologram element 41, second hologram element 42, and third hologram element 43 are different, respectively, so that the noise does not overlap. In this case, the first image light emitted from the first hologram element 41 shows an observation image 1, which consists of the target image 1 and low-luminance noise 1, which is shown by dot hatching. The second image light emitted from the second hologram element 42 shows an observation image 2, which consists of the target image 2 and low-luminance noise 2, which is shown by dot hatching. The third image light emitted from the third hologram element 43 shows an observation image 3, which consists of the target image 3 and low-luminance noise 3, which is shown by dot hatching. The noises 1 to 3 are formed at different positions relative to the target images 1 to 3. Therefore, the virtual image projected onto the light-transmitting member shows the target image, which is formed by the superposition of each of the observed images 1 to 3, and the noise 1 to 3 which are arranged separately. In this case, since the noise 1 to 3 of the virtual image projected onto the light-transmitting member hardly overlap, only low-luminance noise 1 to 3 is faintly formed around the target image, allowing the target image to be correctly recognized and minimizing any impairment of its visibility.

[0059] <Effects and Effects> Next, the effects and advantages of the display device 1 in this embodiment will be described.

[0060] As described above, the display device 1 according to this embodiment includes a light guide 30 having a first hologram element 41 and a second hologram element 42, and an image light emission unit 50 that emits image light to the light guide 30. The first hologram element 41 has a plurality of first cells 41a for emitting first image light, which is obtained by diffracting image light propagating inside the light guide 30, toward the second hologram element 42. The second hologram element 42 has a plurality of second cells 42a for emitting second image light, which is obtained by diffracting first image light propagating inside the light guide 30. The arrangement of the plurality of first cells 41a is different from the arrangement of the plurality of second cells 42a.

[0061] Conventionally, because the arrangement of multiple first cells in the first hologram element and the arrangement of multiple second cells in the second hologram element are identical, noise due to phase steps and intensity fluctuations between the image light generated at the boundary where two adjacent first cells meet and the image light generated at the boundary where two adjacent second cells meet can overlap. In this case, when the display device projects the image light onto the display medium, high-luminosity noise may be projected.

[0062] Therefore, according to this embodiment, since the arrangement of the multiple first cells 41a in the first hologram element 41 and the arrangement of the multiple second cells 42a in the second hologram element 42 are different, noise in the first image light generated at the boundary where two adjacent first cells 41a meet and noise in the second image light generated at the boundary where two adjacent second cells 42a meet are less likely to overlap. In other words, noise due to phase steps and intensity fluctuations in the first image light emitted by the first hologram element 41 and the second image light emitted by the second hologram element 42 is less likely to overlap.

[0063] Therefore, the display device 1 can emit image light with noise minimized.

[0064] Furthermore, in the display device 1 according to this embodiment, the sizes of the multiple first cells 41a and the multiple second cells 42a are different from each other.

[0065] According to this, noise in the first image light generated at the boundary where two adjacent first cells 41a constituting the first hologram element 41 meet, and noise in the second image light generated at the boundary where two adjacent second cells 42a constituting the second hologram element 42 meet, become less likely to overlap. Therefore, the display device 1 can emit image light in which the noise is less noticeable.

[0066] Furthermore, in the display device 1 according to this embodiment, the size of the multiple second cells 42a is larger than the size of the multiple first cells 41a.

[0067] According to this, it is possible to suppress an increase in the exposure time when manufacturing the second hologram element 42. In particular, in this embodiment, since the second hologram element 42 is larger than the first hologram element 41, it is possible to suppress an increase in the manufacturing time of the second hologram element 42.

[0068] Furthermore, because the size of the multiple second cells 42a is larger than the size of the multiple first cells 41a, the noise in the first image light and the noise in the second image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0069] Furthermore, in the display device 1 according to this embodiment, each of the multiple first cells 41a is the same size and shape. And each of the multiple second cells 42a is the same size and shape.

[0070] According to this, since each of the multiple first cells 41a constituting the first hologram element 41 can be made to be the same size and shape, the first hologram element 41 can be easily manufactured. Furthermore, since each of the multiple second cells 42a constituting the second hologram element 42 can be made to be the same size and shape, the second hologram element 42 can also be easily manufactured.

[0071] Furthermore, because the sizes of the multiple first cells 41a and the multiple second cells 42a are different, the noise in the first image light and the noise in the second image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0072] Furthermore, in the display device 1 according to this embodiment, each of the multiple first cells 41a and the multiple second cells 42a has a polygonal shape. Also, the multiple first cells 41a and the multiple second cells 42a have the same shape. And the length of the first side of each of the multiple first cells 41a is not an integer multiple of the length of the second side of each of the multiple second cells 42a corresponding to the first side.

[0073] In this way, by ensuring that the length of the first side and the length of the second side are not integer multiples, it is easy to make the arrangement of multiple first cells 41a and multiple second cells 42a different.

[0074] Furthermore, because the arrangement of the multiple first cells 41a and the arrangement of the multiple second cells 42a are different, the noise in the first image light and the noise in the second image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0075] Furthermore, in the display device 1 according to this embodiment, at least one of the first hologram element 41 and the second hologram element 42 includes two or more types of cells of different sizes.

[0076] In this way, by using two or more types of cells of different sizes, the arrangement of multiple first cells 41a and the arrangement of multiple second cells 42a can be easily made different.

[0077] Furthermore, since one or more hologram elements contain two or more types of cells of different sizes, the noise in the first image light and the noise in the second image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0078] Furthermore, in the display device 1 according to this embodiment, at least one of the first hologram element 41 and the second hologram element 42 includes two or more types of cells with different shapes.

[0079] In this way, by using two or more types of cells with different shapes, the arrangement of multiple first cells 41a and the arrangement of multiple second cells 42a can be easily made different.

[0080] Furthermore, since one or more hologram elements contain two or more types of cells with different shapes, the noise in the first image light and the noise in the second image light are less likely to overlap. Therefore, the display device 1 can emit image light in which the noise is less noticeable.

[0081] Furthermore, in the display device 1 according to this embodiment, the light guide 30 has a third hologram element 43. The first hologram element 41 is an incident hologram element to which the image light emitted from the image light emission unit 50 is incident. The second hologram element 42 is a folded hologram element that diffracts the first image light emitted from the first hologram element 41 and emits the second image light to the third hologram element 43. The third hologram element 43 is an output hologram element that diffracts the incident second image light and emits the third image light. The third hologram element 43 also has a plurality of third cells 43a for emitting the third image light obtained by diffracting the second image light propagating inside the light guide 30. The arrangement of the plurality of first cells 41a, the plurality of second cells 42a, and the plurality of third cells 43a are all different.

[0082] According to this, the arrangement of the multiple first cells 41a in the first hologram element 41, the arrangement of the multiple second cells 42a in the second hologram element 42, and the arrangement of the multiple third cells 43a in the third hologram element 43 are different. As a result, noise in the first image light generated at the boundary where two adjacent first cells 41a meet, noise in the second image light generated at the boundary where two adjacent second cells 42a meet, and noise in the third image light generated at the boundary where two adjacent third cells 43a meet are less likely to overlap. In other words, noise due to phase steps and intensity fluctuations in the first image light emitted by the first hologram element 41, the second image light emitted by the second hologram element 42, and the third image light emitted by the third hologram element 43 is less likely to overlap.

[0083] Therefore, the display device 1 can emit image light with noise minimized.

[0084] Furthermore, in the display device 1 according to this embodiment, the sizes of the multiple first cells 41a, the multiple second cells 42a, and the multiple third cells 43a are all different from each other.

[0085] According to this, the noise in the first image light generated at the boundary where two adjacent first cells 41a constituting the first hologram element 41 meet, the noise in the second image light generated at the boundary where two adjacent second cells 42a constituting the second hologram element 42 meet, and the noise in the third image light generated at the boundary where two adjacent third cells 43a constituting the third hologram element 43 meet become less likely to overlap. Therefore, the display device 1 can emit image light in which the noise is less noticeable.

[0086] Furthermore, in the display device 1 according to this embodiment, the multiple first cells 41a, the multiple second cells 42a, and the multiple third cells 43a gradually increase in size in this order.

[0087] According to this, it is possible to suppress an increase in the exposure time when manufacturing the second hologram element 42 and the third hologram element 43. In particular, in this embodiment, since the second hologram element 42 is larger than the first hologram element 41, it is possible to suppress an increase in the manufacturing time of the second hologram element 42, and since the third hologram element 43 is larger than both the second hologram element 42 and the first hologram element 41, it is possible to suppress an increase in the manufacturing time of the third hologram element 43.

[0088] Furthermore, since the noise gradually increases in the order of the multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a, the noise in the first image light, the noise in the second image light, and the noise in the third image light become less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0089] Furthermore, in the display device 1 according to this embodiment, each of the multiple first cells 41a is the same size and shape. Also, each of the multiple second cells 42a is the same size and shape. And each of the multiple third cells 43a is the same size and shape.

[0090] According to this, since each of the multiple first cells 41a constituting the first hologram element 41 can be made to be the same size and shape, the first hologram element 41 can be easily manufactured. Similarly, since each of the multiple second cells 42a constituting the second hologram element 42 can be made to be the same size and shape, the second hologram element 42 can also be easily manufactured. Furthermore, since each of the multiple third cells 43a constituting the third hologram element 43 can be made to be the same size and shape, the third hologram element 43 can also be easily manufactured.

[0091] Furthermore, because the sizes of the multiple first cells 41a, the multiple second cells 42a, and the multiple third cells 43a are different, the noise in the first image light, the noise in the second image light, and the noise in the third image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0092] Furthermore, in the display device 1 according to this embodiment, each of the multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a has a polygonal shape. Also, the multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a have the same shape. In addition, the length of the first side (h1, w1) of the multiple first cells 41a is not an integer multiple of the length of the second side (h2, w2) of the multiple second cells 42a corresponding to the first side. Also, the length of the first side (h1, w1) of the multiple first cells 41a is not an integer multiple of the length of the third side (h3, w3) of the multiple third cells 43a corresponding to the first side. And, the length of the second side (h2, w2) of the multiple second cells 42a is not an integer multiple of the length of the third side (h3, w3) of the multiple third cells 43a corresponding to the second side.

[0093] In this way, by ensuring that the lengths of the first, second, and third sides are not integer multiples, it is easy to make the arrangement of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a different.

[0094] Furthermore, because the arrangement of the multiple first cells 41a, the multiple second cells 42a, and the multiple third cells 43a are different, the noise in the first image light, the noise in the second image light, and the noise in the third image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0095] Furthermore, in the display device 1 according to this embodiment, at least one of the hologram elements among the first hologram element 41, the second hologram element 42, and the third hologram element 43 includes two or more cells of different sizes.

[0096] In this way, by using two or more types of cells of different sizes, the arrangement of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a can be easily made to differ.

[0097] Furthermore, since one or more hologram elements contain two or more types of cells of different sizes, the noise in the first image light, the noise in the second image light, and the noise in the third image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0098] Furthermore, in the display device 1 according to this embodiment, at least one of the first hologram element 41, the second hologram element 42, and the third hologram element 43 includes two or more types of cells with different shapes.

[0099] In this way, by using two or more types of cells with different shapes, the arrangement of multiple first cells 41a, multiple second cells 42a, and multiple third cells 43a can be easily made different.

[0100] Furthermore, since one or more hologram elements contain two or more types of cells with different shapes, the noise in the first image light, the noise in the second image light, and the noise in the third image light are less likely to overlap. As a result, the display device 1 can emit image light in which the noise is less noticeable.

[0101] (Other embodiments, etc.) Although the display device relating to this disclosure has been described above based on the embodiments described above, this disclosure is not limited to these embodiments.

[0102] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of the embodiments without departing from the spirit of this disclosure.

[0103] (Note 1) The features of the display device described based on the above embodiment are shown below.

[0104] <Technology 1> A light guide having a first holographic element and a second holographic element, The light guide body is provided with an image light emitting unit that emits image light, The first hologram element has a plurality of first cells for emitting first image light, obtained by diffracting the image light propagating inside the light guide, toward the second hologram element. The second hologram element has a plurality of second cells for emitting a second image light obtained by diffracting the first image light propagating inside the light guide, The arrangement of the plurality of first cells is different from the arrangement of the plurality of second cells. Display device.

[0105] <Technology 2> The sizes of the plurality of first cells and the plurality of second cells are all different from each other. The display device described in Technology 1.

[0106] <Technology 3> The size of the plurality of second cells is larger than the size of the plurality of first cells. The display device described in Technology 2.

[0107] <Technology 4> Each of the aforementioned plurality of first cells is of the same size and shape. Each of the aforementioned plurality of second cells is of the same size and shape. A display device as described in Technology 2 or 3.

[0108] <Technology 5> Each of the aforementioned plurality of first cells and the plurality of second cells has a polygonal shape. The plurality of first cells and the plurality of second cells have the same shape. The length of the first side in each of the plurality of first cells is not an integer multiple of the length of the second side in each of the plurality of second cells corresponding to the first side. A display device as described in any one of the technologies 2 to 4.

[0109] <Technology 6> At least one of the first holographic element and the second holographic element includes two or more cells of different sizes. A display device as described in any one of the technologies 2 to 5.

[0110] <Technology 7> At least one of the first holographic element and the second holographic element includes two or more types of cells with different shapes. A display device as described in any one of the technologies 2 to 6.

[0111] <Technology 8> The light guide has a third holographic element, The first hologram element is an incident hologram element to which the image light emitted from the image light emission unit is incident. The second hologram element is a folded hologram element that diffracts the first image light emitted by the first hologram element and emits the second image light to the third hologram element. The third hologram element is an output hologram element that diffracts the incident second image light and emits the third image light. The third hologram element has a plurality of third cells for emitting the third image light obtained by diffracting the second image light propagating inside the light guide, The arrangement of the plurality of first cells, the arrangement of the plurality of second cells, and the arrangement of the plurality of third cells are all different. The display device described in Technology 1.

[0112] <Technology 9> The sizes of the plurality of first cells, the plurality of second cells, and the plurality of third cells are all different from each other. The display device described in Technical 8.

[0113] <Technology 10> The aforementioned plurality of first cells, plurality of second cells, and plurality of third cells are arranged in such an order that their size gradually increases. The display device described in Technical 9.

[0114] <Technology 11> Each of the aforementioned plurality of first cells is of the same size and shape. Each of the aforementioned plurality of second cells is of the same size and shape. Each of the aforementioned third cells is of the same size and shape. A display device as described in Technical Reference 9 or 10.

[0115] <Technology 12> Each of the plurality of first cells, the plurality of second cells, and the plurality of third cells has a polygonal shape. The plurality of first cells, the plurality of second cells, and the plurality of third cells are all the same shape. The length of the first side in the plurality of first cells is not an integer multiple of the length of the second side in the plurality of second cells corresponding to the first side. The length of the first side in the plurality of first cells is not an integer multiple of the length of the third side in the plurality of third cells corresponding to the first side. The length of the second side in the plurality of second cells is not an integer multiple of the length of the third side in the plurality of third cells corresponding to the second side. A display device as described in any one of the technologies 9 to 11.

[0116] <Technology 13> At least one of the first holographic element, the second holographic element, and the third holographic element includes two or more cells of different sizes. A display device as described in any one of the technologies 9 to 12.

[0117] <Technology 14> At least one of the first holographic element, the second holographic element, and the third holographic element includes two or more types of cells with different shapes. A display device as described in any one of the technologies 9 to 13. [Industrial applicability]

[0118] This disclosure can be used in display devices such as head-up displays for vehicles. [Explanation of Symbols]

[0119] 1 Display device 30 Light guide 41. First Holographic Element 41a Cell 1 42a Cell 2 42. Second Hologram Element 43. Third Holographic Element 43a Cell 3 50 Image light emission section

Claims

1. A light guide having a first holographic element and a second holographic element, The light guide body is provided with an image light emitting unit that emits image light, The first hologram element has a plurality of first cells for emitting first image light, obtained by diffracting the image light propagating inside the light guide, toward the second hologram element. The second hologram element has a plurality of second cells for emitting second image light obtained by diffracting the first image light propagating inside the light guide, The arrangement of the plurality of first cells differs from the arrangement of the plurality of second cells. The light guide has a third hologram element, The first hologram element is an incident hologram element to which the image light emitted from the image light emission unit is incident. The second hologram element is a folded hologram element that diffracts the first image light emitted by the first hologram element and emits the second image light to the third hologram element. The third hologram element is an output hologram element that diffracts the incident second image light and emits the third image light. The third hologram element has a plurality of third cells for emitting the third image light obtained by diffracting the second image light propagating inside the light guide, The arrangement of the plurality of first cells, the arrangement of the plurality of second cells, and the arrangement of the plurality of third cells are all different. The sizes of the plurality of first cells, the plurality of second cells, and the plurality of third cells are all different from each other. At least one of the first holographic element, the second holographic element, and the third holographic element includes two or more cells of different sizes. Display device.

2. A light guide having a first holographic element and a second holographic element, The light guide body is provided with an image light emitting unit that emits image light, The first hologram element has a plurality of first cells for emitting first image light, obtained by diffracting the image light propagating inside the light guide, toward the second hologram element. The second hologram element has a plurality of second cells for emitting second image light obtained by diffracting the first image light propagating inside the light guide, The arrangement of the plurality of first cells differs from the arrangement of the plurality of second cells. The light guide has a third hologram element, The first hologram element is an incident hologram element to which the image light emitted from the image light emission unit is incident. The second hologram element is a folded hologram element that diffracts the first image light emitted by the first hologram element and emits the second image light to the third hologram element. The third hologram element is an output hologram element that diffracts the incident second image light and emits the third image light. The third hologram element has a plurality of third cells for emitting the third image light obtained by diffracting the second image light propagating inside the light guide, The arrangement of the plurality of first cells, the arrangement of the plurality of second cells, and the arrangement of the plurality of third cells are all different. The sizes of the plurality of first cells, the plurality of second cells, and the plurality of third cells are all different from each other. At least one of the first holographic element, the second holographic element, and the third holographic element includes two or more types of cells with different shapes. Display device.

3. The sizes of the plurality of first cells and the plurality of second cells are all different from each other. The display device according to claim 1 or 2.

4. The size of the plurality of second cells is larger than the size of the plurality of first cells. The display device according to claim 3.

5. Each of the aforementioned plurality of first cells is of the same size and shape. Each of the aforementioned plurality of second cells is of the same size and shape. The display device according to claim 3.

6. Each of the aforementioned plurality of first cells and the plurality of second cells has a polygonal shape. The plurality of first cells and the plurality of second cells have the same shape. The length of the first side in each of the plurality of first cells is not an integer multiple of the length of the second side in each of the plurality of second cells corresponding to the first side. The display device according to claim 3.

7. At least one of the first holographic element and the second holographic element includes two or more types of cells of different sizes. The display device according to claim 3.

8. At least one of the first holographic element and the second holographic element includes two or more types of cells with different shapes. The display device according to claim 3.

9. The aforementioned plurality of first cells, plurality of second cells, and plurality of third cells are arranged in such an order that their size gradually increases. The display device according to claim 1 or 2.

10. Each of the aforementioned plurality of first cells is of the same size and shape. Each of the aforementioned second cells is of the same size and shape. Each of the aforementioned third cells is of the same size and shape. The display device according to claim 1 or 2.

11. Each of the plurality of first cells, the plurality of second cells, and the plurality of third cells has a polygonal shape. The plurality of first cells, the plurality of second cells, and the plurality of third cells are all the same shape. The length of the first side in the plurality of first cells is not an integer multiple of the length of the second side in the plurality of second cells corresponding to the first side. The length of the first side in the plurality of first cells is not an integer multiple of the length of the third side in the plurality of third cells corresponding to the first side. The length of the second side in the plurality of second cells is not an integer multiple of the length of the third side in the plurality of third cells corresponding to the second side. The display device according to claim 1 or 2.

Images