Indication device

Abstract

To provide a display device capable of improving quality of an image projected onto a display medium.SOLUTION: A light guide 30 provided herein comprises a hologram element 40 configured to receive image light emitted by an image light emission unit 50, and a light guide unit 31 containing the hologram element 40. In an intensity distribution of the image light diffracted and output by the hologram element 40, end portions of the intensity distribution have smaller intensity than a middle portion of the intensity distribution.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This disclosure relates to ,table a display device.

Background Art

[0002] As a prior art, 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 having a volume hologram diffraction grating, and a second deflection unit provided on the second light guide plate and having a volume hologram diffraction grating, and emitting light diffracted by the first deflection unit and the second deflection unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional optical device, when light diffracted by a volume hologram diffraction grating propagates, the propagation angle varies according to the viewing angle, and the distance by which the emitted light shifts may vary during one round trip in the thickness direction of the light guide plate. At this time, since part of the light emitted from the light guide plate may overlap or the light may not overlap, when the light emitted by the optical device is projected onto the display medium, bright streaks or dark streaks may occur, degrading the image quality.

[0005] Therefore, in this disclosure, the quality of the image projected onto the display medium can be improved.

Means for Solving the Problems

[0006] A display device according to an aspect of this disclosure is The system comprises a light guide and an image light emission unit that outputs image light to the light guide, and the light guide is The image light emission unit comprises a hologram element into which the emitted image light is incident, and a light guide unit enclosing the hologram element. In the intensity distribution of the image light emitted by the hologram element after diffraction, the intensity is lower at the edges of the intensity distribution than in the middle portion of the distribution. The image light emitting unit emits image light having an intensity distribution in a trapezoidal, triangular, or semicircular shape, corresponding to the diffraction efficiency distribution in the hologram element. . [Effects of the Invention]

[0007] Display of this disclosure Place Therefore, the quality of images projected onto a display medium can be improved. [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 hologram element of a display device according to an embodiment, and the diffraction efficiency of the hologram element. [Figure 5A] Figure 5A shows the state of the first image light emitted from the first hologram element when image light with different angles of view is incident on the first hologram element. [Figure 5B] Figure 5B shows the intensity distribution in the comparative example. [Figure 5C] Figure 5C shows the behavior of the second image light emitted from the second hologram element when image light with a different field of view is incident on the first hologram element. [Figure 6A] Figure 6A shows the behavior of the second image light emitted from the second hologram element when the first image light with a different field of view is incident on the second hologram element. [Figure 6B]Figure 6B shows the state of the third image light emitted from the third hologram element when the first image light with a different field of view is incident on the second hologram element. [Figure 6C] Figure 6C shows the intensity distribution of the third image light emitted from the third hologram element when a second image light with a different field of view is incident on the third hologram element. [Figure 7] Figure 7 shows a display device according to a modified example of 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] In FIG. 1B, the arrangement direction of the second hologram element with respect to the first hologram element is defined as the positive X-axis direction, the arrangement direction of the second hologram element with respect to the third hologram element is defined as the positive Y-axis direction, and the arrangement direction of the first hologram element with respect to the image generation device is defined as the positive Z-axis direction. The correspondence in FIG. 1B may be applied to each figure.

[0014] (Embodiment) <Configuration> First, the configuration of the display device 1 will be described using FIGS. 1A to 3.

[0015] 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 according to the embodiment 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 side view of the display device 1, and (c) of FIG. 3 is a front view of the display device 1.

[0016] 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 a display medium such as the front window 3 as a light transmissive member. In this case, by the display device 1 emitting the image light, an image shown in the image light can be projected onto the light transmissive member, and a virtual image corresponding to the image can be displayed in front of the light transmissive member. The image light is light showing an image and is light for displaying a virtual image in front of the front window 3. The image is a still image or a moving image and is an image showing numbers, characters, figures, etc.

[0017] As shown in FIGS. 1B and 2, the display device 1 includes an image light emitting unit 50 and a light guide 30.

[0018] The image light emission unit 50 is an image generation device that emits image light to the light guide 30. The image light emission unit 50 emits image light that represents a rectangular image, and the image light is projected onto the front windshield 3 via the light guide 30. This allows the user to perceive a virtual image.

[0019] Such an image light emitting unit 50 includes a plurality of emitters, a plurality of dichroic mirrors, a focusing lens, a mirror, and an emission unit.

[0020] Each of the multiple emitters emits a light ray that is different from the others and is in a predetermined wavelength band. Each of the multiple dichroic mirrors is positioned on the light ray emitted by the emitter and can reflect light rays in a predetermined wavelength band and transmit light rays in other wavelength bands. The focusing lens is a lens that focuses the light rays emitted through the dichroic mirrors onto the multiple mirrors. The emission part is a screen such as a microlens array, a liquid crystal display element such as LCOS (Liquid Crystal On Silicon), and by irradiating light rays of multiple wavelength bands from the mirror side, the transmitted light can be emitted towards the light guide 30 as image light.

[0021] The light guide 30 is a hologram light guide plate that displays the image indicated by the image light to the user. The light guide 30 is light-transmitting and can extend the image indicated by the image light emitted by the image light emission unit 50 in the X-axis and Y-axis directions. The light guide 30 is arranged so that one side (emission surface 31b) faces the front windshield 3 and multiple sides (incident surface 31a) face the image light emission unit 50.

[0022] The light guide 30 has an incident surface 31a and an exit surface 31b.

[0023] The incident surface 31a is positioned to face the output surface of the image light output section 50. Image light emitted from the output surface of the image light output section 50 is incident on the incident surface 31a. The incident surface 31a is part of the back surface of the light guide 30. The back surface is the surface opposite to the output surface 31b of the light guide 30.

[0024] The emission surface 31b is the image light incident from the incident surface 31a, which propagates through the inside of the light guide 30 and is emitted toward the front windshield 3. The emission surface 31b faces the front windshield 3 and is positioned at a predetermined distance from the front windshield 3. The emission surface 31b is a part of the surface of the light guide 30.

[0025] As shown in Figures 3 and 4, the light guide 30 has a light-transmitting light guide portion 31 and a plurality of holographic elements 40.

[0026] The light guide section 31 has an incident surface 31a facing the image light emission section 50. The incident surface 31a is a part of the back surface of the light guide section 31. The light guide section 31 also has an emission surface 31b facing the front windshield 3. The emission surface 31b is a part of the front surface of the light guide section 31.

[0027] The light guide section 31 is made of a light-transmitting material such as glass and resin.

[0028] The light guide section 31 contains multiple holographic elements 40. 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 contained within the light guide section 31 so as to be positioned substantially parallel to the incident surface 31a and the outgoing surface 31b of the light guide section 31.

[0029] Such a plurality of hologram elements 40 are made of a light-transmitting material. The plurality of hologram elements 40 includes a first hologram element 41, a second hologram element 42, and a third hologram element 43. In this embodiment, three hologram elements are given as an example of the plurality of hologram elements 40, but the embodiment is not limited to this. For example, the plurality of hologram elements 40 may consist of two. Specifically, the plurality of hologram elements may have at least two of the following: an incident hologram element to which image light is incident, a folded hologram element to which image light is incident, and an output hologram element to which image light is incident.

[0030] 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.

[0031] 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.

[0032] Image light traveling along the positive Z-axis direction, emitted from the emission surface of the image light emission unit 50, is incident on the first hologram element 41. The first hologram element 41 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 propagating along the positive X-axis direction. The first image light deflected by diffraction in the first hologram element 41 is incident on the second hologram element 42.

[0033] 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.

[0034] 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.

[0035] 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 further diffraction, and emits a deflected second image light (deflected light). Specifically, in the second hologram element 42, the first image light that has passed through the first hologram element 41 is incident (transmitted) while repeatedly reflecting off the light guide plate. Each time the first image light is incident on the second hologram element 42, the second hologram element 42 emits a second image light, which has been further deflected by diffraction, 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. 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.

[0036] 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.

[0037] The third hologram element 43 is an emission hologram element that has a rectangular shape when viewed along the Z-axis.

[0038] 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, the second image light that has passed through the second hologram element 42 is incident on (transmitted) to the third hologram element 43. Each time the second image light is incident on 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, which has been 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.

[0039] Here, the predetermined emission angle is the emission angle of the third image light emitted from 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.

[0040] Next, using Figure 4, we will explain the diffraction efficiency and intensity distribution of the image light emitted after diffraction by the hologram element 40.

[0041] Figure 4 shows a hologram element 40 of a display device according to an embodiment, and the diffraction efficiency of the hologram element 40. Figure 4(a) shows a first hologram element 41 and the diffraction efficiency of the first hologram element 41. Figure 4(b) shows a second hologram element 42 and the diffraction efficiency of the second hologram element 42. Figure 4(c) shows a third hologram element 43 and the diffraction efficiency of the third hologram element 43.

[0042] The diffraction efficiency of the hologram element 40 is lower at the edges of the hologram element 40 than at the center of the hologram element 40. Therefore, in the intensity distribution of the image light emitted by the hologram element 40 after diffraction, the intensity distribution is lower at the edges than in the middle. The central part includes the following first central part 41a, second central part 42a, and third central part 43a. The edge part includes the following first edge part 41b, second edge part 42b, and third edge part 43b. The middle part includes the following first middle part, second middle part, and third middle part. The edge part includes the following first edge part, second edge part, and third edge part.

[0043] Specifically, as shown in Figure 4(a), the first hologram element 41 is composed of a first central portion 41a and a pair of first edge portions 41b, which are arranged along the X-axis in the order of one first edge portion 41b, the first central portion 41a, and the other first edge portion 41b. The width a1 is the same as the width of the first hologram element 41 in the X-axis direction. As shown in Figure 3(c) and Figure 4(a), when the first hologram element 41 is viewed along the Y-axis direction, the diffraction efficiency of the first hologram element 41 is lower at the first edge portions 41b than at the first central portion 41a.

[0044] In such a first hologram element 41, as shown in Figure 4(a1), the intensity distribution of the first image light emitted by the first hologram element 41 due to diffraction has a first intermediate portion and a pair of first end portions located on either side of the first intermediate portion. Furthermore, the first intermediate portion of the intensity distribution and the pair of first end portions of the intensity distribution are aligned along a first direction parallel to the direction in which the emitted first image light propagates inside the light guide 31. In the intensity distribution of the first image light emitted by the first hologram element 41 due to diffraction, the intensity distribution of the first end portions is smaller than that of the first intermediate portion. In other words, the first hologram element 41 has a non-uniform intensity distribution and can emit first image light in which the first end portions are smaller than those of the first intermediate portion. The X-axis direction is an example of the first direction.

[0045] Furthermore, as shown in Figure 4(b), the second hologram element 42 is composed of a second central portion 42a and a pair of second edge portions 42b, which are arranged along the Y-axis in the order of one second edge portion 42b, the second central portion 42a, and the other second edge portion 42b. The width a2 is the same as the width of the second hologram element 42 in the Y-axis direction. As shown in Figures 3(b) and 4(b), when the second hologram element 42 is viewed along the X-axis direction, the diffraction efficiency of the second hologram element 42 is lower at the second edge portions 42b than at the second central portion 42a.

[0046] In such a second hologram element 42, as shown in Figure 4(b1), the intensity distribution of the second image light emitted by the second hologram element 42 due to diffraction has a second intermediate portion and a pair of second end portions located on either side of the second intermediate portion. Furthermore, the second intermediate portion of the intensity distribution and the pair of second end portions of the intensity distribution are aligned along a second direction parallel to the direction in which the emitted second image light propagates inside the light guide 31. In addition, in the intensity distribution of the second image light emitted by the second hologram element 42 due to diffraction, the intensity distribution of the second end portions is smaller than that of the second intermediate portion. In other words, the second hologram element 42 has a non-uniform intensity distribution and can emit second image light in which the second end portions are smaller than those of the second intermediate portion. The Y-axis direction is an example of the second direction.

[0047] Furthermore, as shown in Figure 4(c), the third hologram element 43 is composed of a third central portion 43a and a pair of third edge portions 43b, which are arranged along the Y-axis in the order of one third edge portion 43b, the third central portion 43a, and the other third edge portion 43b, and are also arranged along the X-axis. In other words, in the third hologram element 43, the outer edge of the third hologram element 43 may be composed of the third edge portions 43b so as to surround the third central portion 43a. The width a3 is the same as the width of the third hologram element 43 in the Y-axis direction and also the same as the width in the X-axis direction. Note that the width a3 may be the same as the width in the Y-axis direction or the width in the X-axis direction. As shown in Figure 3(a) and Figure 4(c), when the third hologram element 43 is viewed along the X-axis or along the Y-axis, the diffraction efficiency of the third hologram element 43 is lower at the third edge portion 43b of the third hologram element 43 than at the third central portion 43a of the third hologram element 43.

[0048] In such a third hologram element 43, as shown in Figure 4(c1), the intensity distribution of the third image light emitted by the third hologram element 43 due to diffraction has a third intermediate portion of the intensity distribution and a third end portion of the intensity distribution located around the third intermediate portion of the intensity distribution. Furthermore, in the intensity distribution of the third image light emitted by the third hologram element 43 due to diffraction, the intensity distribution of the third end portion is smaller than that of the third intermediate portion. In other words, the third hologram element 43 has a non-uniform intensity distribution and can emit third image light in which the third end portion is smaller than that of the third intermediate portion.

[0049] Furthermore, the intensity distribution of the first image light emitted after diffraction from the first hologram element 41, the intensity distribution of the second image light emitted after diffraction from the second hologram element 42, and the intensity distribution of the third image light emitted after diffraction from the third hologram element 43 are all different.

[0050] Furthermore, at least one of the intensity distributions among the intensity distribution of the first hologram element 41 in the first direction, the intensity distribution of the second hologram element 42 in the second direction, and the intensity distribution of the third hologram element 43 in the first and second directions is trapezoidal, triangular, semicircular, or stepped. In this embodiment, the intensity distributions of the first hologram element 41, the second hologram element 42, and the third hologram element 43 are trapezoidal. In this case, the image light emitting unit 50 may emit image light with an intensity distribution that is trapezoidal, triangular, or semicircular, depending on the diffraction efficiency distribution in the hologram element 40.

[0051] Next, using Figures 5A to 6C, we will explain the intensity distribution of image light emitted from the light guide 30 according to the field of view.

[0052] Figure 5A shows the first image light emitted from the first hologram element 41 when image light with a different field of view is incident on the first hologram element 41. Figure 5B shows the intensity distribution in a comparative example. Figure 5C shows the second image light emitted from the second hologram element 42 when image light with a different field of view is incident on the first hologram element 41. Figure 6A shows the second image light emitted from the second hologram element 42 when first image light with a different field of view is incident on the second hologram element 42. Figure 6B shows the third image light emitted from the third hologram element 43 when first image light with a different field of view is incident on the second hologram element 42. Figure 6C shows the intensity distribution of the third image light emitted from the third hologram element 43 when second image light with a different field of view is incident on the third hologram element 43. Furthermore, Figure 5B(a) shows the case when image light with a field of view of g1 is incident on the incident surface 31a, Figure 5B(b) shows the case when image light with a field of view of g2 is incident on the incident surface 31a, and Figure 5B(c) shows the case when image light with a field of view of g3 is incident on the incident surface 31a. The same applies to Figures 5C, 6B, and Figures 6C(a), (b), and (c).

[0053] As shown in Figure 5A, the image light emitted from the image light emission unit 50 is incident on the incident surface 31a of the light guide 30, but the angle of the image light incident on the incident surface 31a differs depending on the field of view. For example, image light with field of view g1, image light with field of view g2, and image light with field of view g3 are incident on the incident surface 31a.

[0054] As shown in Figure 5B, the comparative example uses a first hologram element, a second hologram element, and a third hologram element with uniform diffraction efficiency. Therefore, the intensity distribution of the first hologram element, the intensity distribution of the second hologram element in the second direction, and the intensity distribution of the third hologram element in both the first and second directions are all rectangular.

[0055] In this case, as shown in Figure 5B(a), when the image light incident on the first hologram element at a field of view g1 is emitted as the third image light from the third hologram element, the intensity distribution shifts, and a gap is formed in the intensity distribution of two adjacent third image beams. As a result, when the third image light is projected onto the front windshield, dark streaks appear in the image.

[0056] Furthermore, as shown in Figure 5B(b), when the image light incident on the first hologram element at a field of view g2 is emitted as the third image light from the third hologram element, no gap is formed in the intensity distribution of the two adjacent third image light beams. Therefore, when the third image light is projected onto the front windshield, the image is clearly visible.

[0057] Furthermore, as shown in Figure 5B(c), when image light incident on the first hologram element at a field of view g1 is emitted as third image light from the third hologram element, the intensity distribution shifts, and parts of the intensity distributions of two adjacent third image lights overlap. As a result, the third image lights reinforce each other as shown by the dashed line, and when the third image light is projected onto the front windshield, bright streaks appear in the image.

[0058] Therefore, in the comparative example, bright and dark streaks appear in the image projected onto the front windshield, resulting in reduced visibility.

[0059] However, in this embodiment, as shown in Figure 5C(a), when image light with field of view g1 is incident on the incident surface 31a, the image light with field of view g1 is incident on the first hologram element 41, deflected by diffraction in the first hologram element 41 to become the first image light with field of view g1, and emitted toward the second hologram element 42.

[0060] As shown in Figures 6A and 6B(a), the first image light with field of view g1 incident on the second hologram element 42 is deflected by diffraction in the second hologram element 42 to become the second image light with field of view g1, which is then emitted toward the third hologram element 43.

[0061] The second image light with field of view g1 that enters the third hologram element 43 is deflected by diffraction within the third hologram element 43 to become the third image light with field of view g1, which is then emitted toward the front windshield 3.

[0062] When the third hologram element 43 is emitted toward the front windshield 3, as shown in Figure 6C(a), the intensity distribution of the third image light at field of view g1 shifts, and the third end portions of the intensity distributions of two adjacent third image lights overlap and reinforce each other as shown by the dashed line. Even in this case, when the third image light is projected onto the front windshield 3, dark streaks in the image are suppressed compared to Figure 5B(a). Therefore, in this embodiment, dark streaks can be made less noticeable.

[0063] Next, as shown in Figure 5C(b), when image light with field of view g2 is incident on the incident surface 31a, the image light with field of view g2 is incident on the first hologram element 41, deflected by diffraction in the first hologram element 41 to become the first image light with field of view g2, and emitted toward the second hologram element 42.

[0064] As shown in Figures 6A and 6B(b), the first image light with a field of view g2 incident on the second hologram element 42 is deflected by diffraction in the second hologram element 42 to become the second image light with a field of view g2, which is then emitted toward the third hologram element 43.

[0065] The second image light with a field of view g2 that enters the third hologram element 43 is deflected by diffraction within the third hologram element 43 to become the third image light with a field of view g2, which is then emitted toward the front windshield 3.

[0066] When the third hologram element 43 is emitted toward the front windshield 3, as shown in Figure 6C(b), the third image light with a field of view g2 has the third end portions of the intensity distributions of two adjacent third image lights overlapping and reinforcing each other as shown by the dashed line. In this case, the image is properly displayed when the third image light is projected onto the front windshield 3.

[0067] Next, as shown in Figure 5C(c), when image light with field of view g3 is incident on the incident surface 31a, the image light with field of view g3 is incident on the first hologram element 41, deflected by diffraction in the first hologram element 41 to become the first image light with field of view g3, and emitted toward the second hologram element 42.

[0068] As shown in Figures 6A and 6B(c), the first image light with field of view g3 incident on the second hologram element 42 is deflected by diffraction in the second hologram element 42 to become the second image light with field of view g3, which is then emitted toward the third hologram element 43.

[0069] The second image light with field of view g3 that enters the third hologram element 43 is deflected by diffraction within the third hologram element 43 to become the third image light with field of view g3, which is then emitted toward the front windshield 3.

[0070] When the third hologram element 43 is emitted toward the front windshield 3, as shown in Figure 6C(c), the intensity distribution of the third image light at field of view g3 shifts, and the third end portions of the intensity distributions of two adjacent third image lights overlap and reinforce each other as shown by the dashed line. In this case, when the third image light is projected onto the front windshield 3, bright streaks in the image are suppressed compared to Figure 5B(c). Therefore, in this embodiment, bright streaks can be made less noticeable.

[0071] <Effects and Effects> Next, the effects of the light guide 30 in this embodiment will be described.

[0072] As described above, the light guide 30 according to this embodiment comprises a hologram element 40 into which the image light emitted from the image light emission unit 50 is incident, and a light guide unit 31 enclosing the hologram element 40. In the intensity distribution of the image light emitted by the hologram element 40 after diffraction, the intensity is lower at the edges of the intensity distribution than in the middle of the intensity distribution.

[0073] For example, because image light is repeatedly incident on the hologram element, the hologram element emits diffracted and deflected image light each time image light is incident on it. As in the comparative example, if the intensity distribution of the image light deflected and deflected by the hologram element is constant (rectangular), as shown in Figure 5B, the diffraction and deflection of the hologram element may cause parts of two adjacent image beams to overlap or not overlap. This can result in noise being generated in the image light emitted by the light guide, such as bright or dark streaks, which reduces visibility.

[0074] However, according to this embodiment, the hologram element 40 has a non-uniform intensity distribution, and in terms of intensity distribution, the edge portion emits image light that is smaller than the middle portion.

[0075] Furthermore, when image light is repeatedly incident on the hologram element 40, even if the hologram element 40 diffracts and parts of two adjacent image beams emitted overlap, the light guide 30 can suppress the degree of bright and dark streaks that occur in the image light emitted, as shown in Figure 6C.

[0076] Furthermore, since it is also possible to incident image light with an intensity distribution smaller at the edges than in the middle portion onto another hologram element 40, even if the image light is repeatedly incident on another hologram element 40 and the diffraction of the other hologram element 40 causes parts of two adjacent image lights to overlap, the degree of bright and dark streaks that occur in the image light emitted by the light guide 30 can be suppressed.

[0077] Therefore, in this embodiment, the quality of the image projected onto the display medium (front window 3) can be improved.

[0078] Furthermore, the display device 1 according to this embodiment includes a light guide 30 and an image light emission unit 50 that outputs image light to the light guide 30.

[0079] This display device 1 also produces the same effects as described above.

[0080] Furthermore, in the light guide 30 according to this embodiment, the hologram element 40 includes a first hologram element 41 to which image light is incident, and a second hologram element 42 to which image light is incident. The intensity distribution of the image light emitted after diffraction from the first hologram element 41 is different from the intensity distribution of the image light emitted after diffraction from the second hologram element 42.

[0081] According to this, it is possible to suppress the overlap between the noise contained in the image light emitted by the first hologram element 41 (first image light) and the noise contained in the image light emitted by the second hologram element 42 (second image light). Since noise generated in the image light emitted from the light guide unit 31 (third image light) can be suppressed, the image quality can be improved.

[0082] Furthermore, in the light guide 30 according to this embodiment, the first hologram element 41 and the second hologram element 42 are any two of the following: an incident hologram element into which image light is incident, a folded hologram element into which image light (first image light) emitted from the incident hologram element is incident, and an exit hologram element into which image light (second image light) emitted from the folded hologram element is incident.

[0083] According to this, it is possible to suppress the overlapping of noise contained in the image light emitted by any two of the incident hologram element, folded hologram element, and output hologram element. Since noise generated in the image light emitted from the light guide unit 31 can be suppressed, the image quality can be improved.

[0084] Furthermore, in the light guide 30 according to this embodiment, the hologram element 40 includes a first hologram element 41 into which image light is incident, a second hologram element 42 into which image light (first image light) emitted from the first hologram element 41 is incident, and a third hologram element 43 into which image light (second image light) emitted from the second hologram element 42 is incident. The intensity distribution of the image light (first image light) emitted after diffraction from the first hologram element 41, the intensity distribution of the image light (second image light) emitted after diffraction from the second hologram element 42, and the intensity distribution of the image light (third image light) emitted after diffraction from the third hologram element 43 are all different.

[0085] According to this, it is possible to suppress the overlap of noise contained in the first image light emitted by the first hologram element 41, the noise contained in the second image light emitted by the second hologram element 42, and the noise contained in the third image light emitted by the third hologram element 43. Since noise generated in the third image light emitted from the light guide unit 31 can be suppressed, the image quality can be improved.

[0086] Furthermore, in the light guide 30 according to this embodiment, the first hologram element 41 is an incident hologram element to which image light is incident. The second hologram element 42 is a folded hologram element to which image light (first image light) emitted from the incident hologram element is incident. The third hologram element 43 is an output hologram element to which image light (second image light) emitted from the folded hologram element is incident.

[0087] According to this, it is possible to suppress the overlapping of noise contained in the image light emitted from each of the incident hologram element, the folded hologram element, and the output hologram element. Since noise generated in the image light emitted from the light guide unit 31 can be suppressed, the image quality can be improved.

[0088] Furthermore, in the light guide 30 according to this embodiment, the intensity distribution of the image light (first image light) emitted after diffraction from the incident hologram element has a first intermediate portion and a pair of first end portions positioned so as to sandwich both sides of the first intermediate portion. The first intermediate portion and the pair of first end portions are aligned along a first direction parallel to the direction in which the emitted image light (first image light) propagates inside the light guide 31. In the intensity distribution of the image light (first image light) emitted after diffraction from the incident hologram element, the intensity distribution of the first end portions is lower than that of the first intermediate portion.

[0089] According to this, the incident hologram element has a non-uniform intensity distribution, and the first end portion can emit image light that is weaker than the first intermediate portion.

[0090] Furthermore, since image light with a non-uniform intensity distribution can be incident on another hologram element 40, even if the image light is repeatedly incident on another hologram element 40 and the diffraction of the other hologram element 40 causes some of the emitted image light from two adjacent images to overlap, the degree of bright and dark streaks in the image light emitted by the light guide 30 can be suppressed.

[0091] Furthermore, in the light guide 30 according to this embodiment, the intensity distribution of the image light (second image light) emitted after diffraction by the folded hologram element has a second intermediate portion and a pair of second end portions located so as to sandwich both sides of the second intermediate portion. The second intermediate portion and the pair of second end portions are aligned along a second direction parallel to the direction in which the emitted image light (second image light) propagates inside the light guide 31. In the intensity distribution of the image light (second image light) emitted after diffraction by the folded hologram element, the intensity distribution of the second end portions is lower than that of the second intermediate portion.

[0092] According to this, when the first image light is reflected by the light guide 31 and repeatedly incident on the folded hologram element, even if a portion of the two adjacent image lights (second image light) emitted by the folded hologram element overlaps due to diffraction, the degree of bright and dark streaks that occur in the image light (third image light) emitted by the light guide 30 can be suppressed.

[0093] Furthermore, since the output hologram element can be irradiated with image light (second image light) whose intensity distribution is smaller at the edges than in the middle, even if the output hologram element is repeatedly irradiated with image light (second image light), and some of the two adjacent image lights (second image light) emitted overlap due to diffraction by the output hologram element, the degree of bright and dark streaks that occur in the image light (second image light) emitted by the light guide 30 can be suppressed.

[0094] Furthermore, in the light guide 30 according to this embodiment, the intensity distribution of the image light emitted by the diffracted output hologram element has a third intermediate portion and a third end portion located so as to surround the third intermediate portion. In the intensity distribution of the image light emitted by the diffracted output hologram element, the intensity distribution of the third end portion is lower than that of the third intermediate portion.

[0095] According to this method, the displayed image does not abruptly end, and the brightness of the displayed image gradually decreases from the third middle portion to the third end portion. As a result, the boundary of the display range limit is less visible, and the quality of the displayed image can be improved.

[0096] Furthermore, in the light guide 30 according to this embodiment, the hologram element 40 includes at least two of the following: an incident hologram element into which image light is incident, a folded hologram element into which image light (first image light) emitted from the incident hologram element is incident, and an exit hologram element into which image light (second image light) emitted from the folded hologram element is incident. In addition, the intensity distribution of the image light (first image light) emitted by the incident hologram element after diffraction has a first intermediate portion and a pair of first end portions located so as to sandwich both sides of the first intermediate portion. Furthermore, the first intermediate portion and the pair of first end portions are aligned along a first direction parallel to the direction in which the emitted image light (first image light) propagates inside the light guide 31. In addition, the intensity distribution of the image light (second image light) emitted by the folded hologram element after diffraction has a second intermediate portion and a pair of second end portions located so as to sandwich both sides of the second intermediate portion. Furthermore, the second intermediate portion and the pair of second end portions are aligned along a second direction parallel to the direction in which the emitted image light (second image light) propagates inside the light guide portion 31. In addition, the intensity distribution of the image light (third image light) emitted after diffraction from the output hologram element has a third intermediate portion and a third end portion that surrounds the third intermediate portion. Furthermore, in the intensity distribution of the image light (first image light) emitted after diffraction from the incident hologram element, the intensity distribution of the first end portion is lower than that of the first intermediate portion. Furthermore, in the intensity distribution of the image light (second image light) emitted after diffraction from the folded hologram element, the intensity distribution of the second end portion is lower than that of the second intermediate portion. Furthermore, in the intensity distribution of the image light (third image light) emitted after diffraction from the output hologram element, the intensity distribution of the third end portion is lower than that of the third intermediate portion.

[0097] According to this, each hologram element 40 has a non-uniform intensity distribution, and the edge portion emits image light with a smaller intensity distribution than the middle portion. Therefore, even if parts of two adjacent image lights overlap, the degree of bright and dark streaks that occur in the image light emitted by the light guide 30 can be suppressed.

[0098] Furthermore, in the light guide 30 according to this embodiment, at least one of the intensity distributions among the intensity distribution of the incident hologram element in the first direction, the intensity distribution of the folded hologram element in the second direction, and the intensity distribution of the output hologram element in the first and second directions is trapezoidal, triangular, semicircular, or stepped.

[0099] According to this, noise generated in the image emitted from the light guide unit 31 and projected onto the display medium can be suppressed, thereby improving the quality of the image.

[0100] Furthermore, in the light guide 30 according to this embodiment, the image light emitting section 50 emits image light with an intensity distribution that is trapezoidal, triangular, or semicircular, depending on the diffraction efficiency distribution in the hologram element 40.

[0101] According to this, noise generated in the image emitted from the light guide unit 31 and projected onto the display medium can be suppressed, thereby improving the quality of the image.

[0102] (Modified example of the embodiment) First, the configuration of the display device 1a in this modified example will be explained using Figure 7.

[0103] Figure 7 shows a modified example of the embodiment, specifically a display device 1a.

[0104] This modified example differs from the embodiment in that it uses two hologram elements 40. Unless otherwise specified, the other components in this modified example are the same as those in the embodiment, and the same reference numerals are used for identical components, and detailed descriptions of the components are omitted.

[0105] The light guide 30a has a light-transmitting light guide portion 31 and a plurality of holographic elements 40.

[0106] Each of the multiple holographic elements 40 has two holographic elements.

[0107] The two hologram elements may be any two of the following: an incident hologram element into which image light is incident; a folded hologram element into which image light emitted from the incident hologram element is incident; and an outgoing hologram element into which image light emitted from the folded hologram element is incident. Thus, the plurality of hologram elements 40 may have at least two of the following: an incident hologram element into which image light is incident; a folded hologram element into which image light is incident; and an outgoing hologram element into which image light is incident.

[0108] The light guide 30a of this embodiment includes, as an example of a plurality of hologram elements 40, an incident hologram element 141 and an exit hologram element 143.

[0109] The incident hologram element 141 and the output hologram element 143 are arranged side by side along the Y-axis. Furthermore, the incident hologram element 141 is positioned so as to overlap with the image light output section 50 when viewed along the X-axis.

[0110] The image light emission unit 50 is positioned at the end face of the light guide 30a so that it can emit light along the elongated incident hologram element 141 in the X-axis direction. The end face of the light guide 30a is the side surface of the light guide 30a and is the incident surface 31a1 of the light guide 30a on the negative X-axis side of the incident hologram element 141.

[0111] Image light traveling along the positive X-axis direction, emitted from the image light emission unit 50, is incident on the incident hologram element 141. The incident hologram element 141 emits the incident image light toward the exit hologram element 143. Specifically, the incident hologram element 141 emits a 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 31a1, toward the exit hologram element 143. More specifically, as the image light incident on the light guide 30a propagates within the light guide 30a, the incident hologram element 141 deflects the image light by diffraction according to the diffraction efficiency of the incident hologram element 141. At this time, the incident hologram element 141 stretches the image of the first image light along the X-axis direction. As a result, the incident hologram element 141 emits the first image light, which has been stretched along the X-axis direction, as first image light that propagates along the negative Y-axis direction. The first image light, deflected by diffraction at the incident hologram element 141, is incident on the exit hologram element 143.

[0112] The first image light emitted from the incident hologram element 141 is incident on the output hologram element 143. The output hologram element 143 further deflects the first image light, which has been deflected by diffraction from the incident hologram element 141, by further diffraction, and emits a deflected third image light (deflected light) to the outside of the light guide 30a. Specifically, the first image light that has been transmitted through the incident hologram element 141 is incident on (transmitted) to the output hologram element 143. Each time the first image light is incident on the output hologram element 143, the output hologram element 143 emits a third image light, which has been further deflected by diffraction from the incident first image light, at a predetermined emission angle. More specifically, as the first image light, which has been deflected by diffraction from the incident hologram element 141, propagates through the light guide 30a along the negative Y-axis direction, the output hologram element 143 further deflects the first image light by diffraction according to the diffraction efficiency of the output hologram element 143. At this time, the output hologram element 143 further stretches the image of the first image light, which has been stretched along the X-axis, along approximately the Y-axis. As a result, the output hologram element 143 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 30a at a predetermined emission angle. In other words, the output hologram element 143 further stretches the first image light emitted by the incident hologram element 141 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 output hologram element 143 emits the third image light in the Z-axis positive direction so that it is directed toward the front windshield 3.

[0113] (Other variations) Although the light guide and display device relating to this disclosure have been described above based on the embodiments described, this disclosure is not limited to these embodiments. Various modifications to the embodiments that a person skilled in the art can conceive of may also be included in the scope of this disclosure, as long as they do not deviate from the spirit of this disclosure.

[0114] Furthermore, this disclosure also includes forms that can be obtained by applying various modifications to the above embodiments that a person skilled in the art could conceive, as well as forms that can be realized by arbitrarily combining the components and functions of the embodiments without departing from the spirit of this disclosure.

[0115] (Note) The following describes the features of the light guide and display device described based on the above embodiment.

[0116] <Technology 1> The image light emitting unit emits image light into a hologram element, It comprises a light guide section containing the aforementioned holographic element, In the intensity distribution of the image light emitted by the hologram element after diffraction, the intensity is lower at the edges of the intensity distribution than in the middle of the distribution. Light guide.

[0117] <Technology 2> The hologram element includes a first hologram element into which image light is incident, and a second hologram element into which image light is incident. The intensity distribution of the image light emitted after diffraction by the first hologram element is different from the intensity distribution of the image light emitted after diffraction by the second hologram element. The light guide described in Technology 1.

[0118] <Technology 3> The first hologram element and the second hologram element are any two of the following: an incident hologram element into which image light is incident; a folded hologram element into which image light emitted from the incident hologram element is incident; and an outgoing hologram element into which image light emitted from the folded hologram element is incident. The light guide described in Technology 2.

[0119] <Technology 4> The hologram element includes a first hologram element into which image light is incident, a second hologram element into which image light emitted from the first hologram element is incident, and a third hologram element into which image light emitted from the second hologram element is incident. The intensity distribution of the image light emitted after diffraction from the first hologram element, the intensity distribution of the image light emitted after diffraction from the second hologram element, and the intensity distribution of the image light emitted after diffraction from the third hologram element are all different. A light guide described in any one of the technologies 1 to 3.

[0120] <Technology 5> The first hologram element is an incident hologram element into which image light is incident, The second hologram element is a folded hologram element into which the image light emitted from the incident hologram element is incident. The third hologram element is an output hologram element into which the image light emitted from the folded hologram element is incident. The light guide described in Technical 4.

[0121] <Technology 6> The intensity distribution of the image light emitted by the incident hologram element after diffraction has a first intermediate portion and a pair of first end portions located so as to sandwich both sides of the first intermediate portion. The first intermediate portion and the pair of first end portions are aligned along a first direction parallel to the direction in which the emitted image light propagates inside the light guide portion. In the intensity distribution of the image light emitted after diffraction by the incident hologram element, the intensity distribution of the first end portion is lower than the intensity distribution of the first intermediate portion. A light guide as described in Technology 3 or 5.

[0122] <Technology 7> The intensity distribution of the image light emitted by the folded hologram element after diffraction has a second intermediate portion and a pair of second end portions located so as to sandwich both sides of the second intermediate portion. The second intermediate portion and the pair of second end portions are aligned along a second direction parallel to the direction in which the emitted image light propagates inside the light guide portion. In the intensity distribution of the image light emitted by the aforementioned folded hologram element after diffraction, the intensity distribution of the second end portion is lower than that of the second intermediate portion. A light guide as described in Technology 3 or 5.

[0123] <Technology 8> The intensity distribution of the image light emitted by the emission hologram element after diffraction has a third intermediate portion and a third end portion located so as to surround the third intermediate portion. In the intensity distribution of the image light emitted by the emission hologram element after diffraction, the intensity distribution of the third end portion is lower than that of the third intermediate portion. A light guide as described in Technology 3 or 5.

[0124] <Technology 9> The hologram element includes at least two of the following: an incident hologram element into which image light is incident, a folded hologram element into which image light is incident, and an output hologram element into which image light is incident. The intensity distribution of the image light emitted by the incident hologram element after diffraction has a first intermediate portion and a pair of first end portions located so as to sandwich both sides of the first intermediate portion. The first intermediate portion and the pair of first end portions are aligned along a first direction parallel to the direction in which the emitted image light propagates inside the light guide portion. The intensity distribution of the image light emitted by the folded hologram element after diffraction has a second intermediate portion and a pair of second end portions located so as to sandwich both sides of the second intermediate portion. The second intermediate portion and the pair of second end portions are aligned along a second direction parallel to the direction in which the emitted image light propagates inside the light guide portion. The intensity distribution of the image light emitted by the emission hologram element after diffraction has a third intermediate portion and a third end portion located so as to surround the third intermediate portion. In the intensity distribution of the image light emitted after diffraction by the incident hologram element, the intensity distribution of the first end portion is lower than that of the first intermediate portion. In the intensity distribution of the image light emitted by the aforementioned folded hologram element after diffraction, the intensity distribution of the second end portion is lower than that of the second intermediate portion. In the intensity distribution of the image light emitted by the emission hologram element after diffraction, the intensity distribution of the third end portion is lower than that of the third intermediate portion. The light guide described in Technology 1.

[0125] <Technology 10> At least one of the intensity distributions among the intensity distribution of the incident hologram element in the first direction, the intensity distribution of the folded hologram element in the second direction, and the intensity distribution of the exit hologram element in the first and second directions is trapezoidal, triangular, semicircular, or stepped. The light guide described in Technical 9.

[0126] <Technology 11> A light guide described in any one of technologies 1 to 10, The light guide body is provided with an image light emission unit that outputs the image light. Display device.

[0127] <Technology 12> The image light emitting unit emits image light having an intensity distribution in a trapezoidal, triangular, or semicircular shape, depending on the diffraction efficiency distribution in the hologram element. A display device as described in Technical 11. [Industrial applicability]

[0128] This disclosure can be used in vehicle head-up display devices, etc. [Explanation of symbols]

[0129] 1, 1a Display device 30, 30a light guide 31 Light guide section 40 hologram elements 41. First Holographic Element 141 Incident Hologram Element 42. Second Hologram Element 43. Third Holographic Element 143 Emission Hologram Element 41a 1st center part 41b First edge 42a 2nd center part 42b Second edge 43a 3rd center 43b Third edge 50 Image light emission section

Claims

1. A light guide and The light guide body is further equipped with an image light emission unit that outputs image light, The light guide body is The image light emitting unit emits image light into a hologram element, It comprises a light guide section containing the aforementioned holographic element, In the intensity distribution of the image light emitted by the hologram element after diffraction, the intensity is lower at the edges of the intensity distribution than at the middle of the distribution. The image light emitting unit emits image light having an intensity distribution in a trapezoidal, triangular, or semicircular shape, depending on the diffraction efficiency distribution in the hologram element. Display device.

2. The hologram element includes a first hologram element into which image light is incident, and a second hologram element into which image light is incident. The intensity distribution of the image light emitted by the first hologram element after diffraction is such that the intermediate portion and the end portion are aligned along the first direction. The intensity distribution of the image light emitted by the second hologram element after diffraction is such that the intermediate portion and the end portion are aligned along a second direction different from the first direction. The display device according to claim 1.

3. The first hologram element and the second hologram element are any two of the following: an incident hologram element into which image light is incident; a folded hologram element into which image light emitted from the incident hologram element is incident; and an outgoing hologram element into which image light emitted from the folded hologram element is incident. The display device according to claim 2.

4. The hologram element includes a first hologram element into which image light is incident, a second hologram element into which image light emitted from the first hologram element is incident, and a third hologram element into which image light emitted from the second hologram element is incident. The intensity distribution of the image light emitted by the first hologram element after diffraction has a first intermediate portion and a first end portion aligned along a first direction. The intensity distribution of the image light emitted by the second hologram element after diffraction has a second intermediate portion and a second end portion aligned along the second direction. The intensity distribution of the image light emitted by the third hologram element after diffraction has a third intermediate portion and a third end portion surrounding the third intermediate portion. The display device according to claim 1.

5. The first hologram element is an incident hologram element into which image light is incident, The second hologram element is a folded hologram element into which the image light emitted from the incident hologram element is incident. The third hologram element is an output hologram element into which the image light emitted from the folded hologram element is incident. The display device according to claim 4.

6. The intensity distribution of the image light emitted by the incident hologram element after diffraction has a first intermediate portion and a pair of first end portions located so as to sandwich both sides of the first intermediate portion. The first intermediate portion and the pair of first end portions are aligned along a first direction parallel to the direction in which the emitted image light propagates inside the light guide portion. In the intensity distribution of the image light emitted after diffraction by the incident hologram element, the intensity distribution of the first end portion is lower than the intensity distribution of the first intermediate portion. The display device according to claim 3 or 5.

7. The intensity distribution of the image light emitted by the folded hologram element after diffraction has a second intermediate portion and a pair of second end portions located so as to sandwich both sides of the second intermediate portion. The second intermediate portion and the pair of second end portions are aligned along the second direction parallel to the direction in which the emitted image light propagates inside the light guide portion. In the intensity distribution of the image light emitted by the aforementioned folded hologram element after diffraction, the intensity distribution of the second end portion is lower than that of the second intermediate portion. The display device according to claim 3 or 5.

8. The intensity distribution of the image light emitted by the emission hologram element after diffraction has a third intermediate portion and a third end portion located so as to surround the third intermediate portion. In the intensity distribution of the image light emitted by the emission hologram element after diffraction, the intensity distribution of the third end portion is lower than that of the third intermediate portion. The display device according to claim 3 or 5.

9. The hologram element includes at least two of the following: an incident hologram element into which image light is incident, a folded hologram element into which image light is incident, and an output hologram element into which image light is incident. The intensity distribution of the image light emitted by the incident hologram element after diffraction has a first intermediate portion and a pair of first end portions located so as to sandwich both sides of the first intermediate portion. The first intermediate portion and the pair of first end portions are aligned along a first direction parallel to the direction in which the emitted image light propagates inside the light guide portion. The intensity distribution of the image light emitted by the folded hologram element after diffraction has a second intermediate portion and a pair of second end portions located so as to sandwich both sides of the second intermediate portion. The second intermediate portion and the pair of second end portions are aligned along a second direction parallel to the direction in which the emitted image light propagates inside the light guide portion. The intensity distribution of the image light emitted by the emission hologram element after diffraction has a third intermediate portion and a third end portion located so as to surround the third intermediate portion. In the intensity distribution of the image light emitted after diffraction by the incident hologram element, the intensity distribution of the first end portion is lower than that of the first intermediate portion. In the intensity distribution of the image light emitted by the aforementioned folded hologram element after diffraction, the intensity distribution of the second end portion is lower than that of the second intermediate portion. In the intensity distribution of the image light emitted by the emission hologram element after diffraction, the intensity distribution of the third end portion is lower than that of the third intermediate portion. The display device according to claim 1.

10. At least one of the intensity distributions among the intensity distribution of the incident hologram element in the first direction, the intensity distribution of the folded hologram element in the second direction, and the intensity distribution of the exit hologram element in the first and second directions is trapezoidal, triangular, semicircular, or stepped. The display device according to claim 9.

Images