Display device

Abstract

A display device (1) includes a light guide (10) that displays an image of light emitted from the light guide (10). The light guide (10) is curved and includes a light guide plate (31) and an optical element (33) that diffracts and emits light propagating in the light guide plate (31). The optical element (33) is disposed in the light guide (10) such that a constant angle (α) is formed with respect to the propagation direction of light propagating in the light guide plate (31) regardless of the position of the optical element (33).

Description

Technical Field

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

[0002] Patent Document 1 discloses a display device comprising: a light source for emitting light; a display element for modulating the light emitted from the light source to display an image; a light guide member having two opposing surfaces, each of which has a parallel flat surface; and a plurality of volume phase holographic diffractive optical elements held at different locations on the flat surface of the light guide member. The light guide member and holographic diffractive optical elements in this display device are flat.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-219106 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In the display device described in Patent Document 1, external light, such as sunlight, can sometimes reflect off the surface of the light guide member and enter the user's eyes, causing glare. Therefore, one approach is to curve the light guide member, for example, to reduce the chance of external light reflected from the light guide member entering the user's eyes. However, a curved light guide member would require the holographic diffractive optical element to be similarly curved, making it difficult to simply manufacture the holographic diffractive optical element.

[0008] Therefore, an object of the present disclosure is to provide a display device capable of suppressing external light from entering the eyes of a user and capable of simply manufacturing an optical element.

[0009] Solutions for solving problems

[0010] A display device involved in one embodiment of the present disclosure includes a light guide, which displays an image of light emitted from the light guide. In the display device, the light guide has a curved shape, and has a light guide plate and an optical element that diffracts and emits light propagating in the light guide plate. The optical element is arranged in the light guide in such a manner that it has a fixed angle with respect to the propagation direction of the light propagating in the light guide plate regardless of the position on the optical element.

[0011] In addition, the specific methods of some of them can also be implemented using systems, methods, integrated circuits, computer programs or computer-readable CD-ROMs and other recording media, and can also be implemented using any combination of systems, methods, integrated circuits, computer programs and recording media.

[0012] Effects of the Invention

[0013] According to the display device of the present disclosure, it is possible to suppress external light from entering the user's eyes, and it is possible to simply manufacture optical elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1A Schematic diagram illustrating a state where the display device and the vehicle are viewed from the lateral direction.

[0015] Figure 1B This is a cross-sectional view of a light guide body of a display device according to a comparative example as viewed from the side.

[0016] Figure 2 This is a cross-sectional view of the light guide of the display device according to Embodiment 1 as viewed from the side.

[0017] Figure 3A This is a cross-sectional view of the display device according to Embodiment 1 as viewed from the horizontal direction.

[0018] Figure 3B This is a schematic diagram illustrating the structure of the image light emitting section of the display device according to the first embodiment.

[0019] Figure 3C This is an exploded perspective view of the display device according to Embodiment 1.

[0020] Figure 4 3 are three views of the display device according to Embodiment 1.

[0021] Figure 5A This is a cross-sectional view of a display device according to Modification 1 of Embodiment 1 as viewed from the horizontal direction.

[0022] Figure 5B This is a cross-sectional view of a display device according to Modification 2 of Embodiment 1 as viewed from the horizontal direction.

[0023] Figure 6 This is a cross-sectional view of the display device according to Embodiment 2 as viewed from the horizontal direction.

[0024] Figure 7A This is a cross-sectional view of a display device according to Modification 1 of Embodiment 2 as viewed from the lateral direction.

[0025] Figure 7B This is a cross-sectional view of a display device according to Modification 2 of Embodiment 2 as viewed from the horizontal direction. DETAILED DESCRIPTION

[0026] The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, configuration positions and connection methods of the components, steps, and the order of the steps shown in the following embodiments are examples, and their purpose is not to limit the present disclosure. In addition, among the components of the following embodiments, the components that are not described in the independent claims are described as arbitrary components. In addition, in all embodiments, the respective contents can also be combined.

[0027] In addition, each figure is a schematic diagram and is not necessarily a strict illustration. In addition, the same reference numerals are used for the same components in each figure. In addition, in the following embodiments, expressions such as "approximately consistent" are used. For example, "approximately consistent" not only means completely consistent, but also means substantially consistent, that is, for example, including an error of a few percent. In addition, "approximately consistent" means consistent within the range that can achieve the effect of the present disclosure. The same applies to other expressions using "approximately".

[0028] Hereinafter, a display system according to one embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0029] (Implementation 1)

[0030] <Summary>

[0031] Figure 1A : is a schematic diagram illustrating a state where the display device and the vehicle 2 are viewed from the lateral direction. Figure 1A The lateral direction in the text is a lateral direction when the direction in which a user such as a driver or a passenger is facing is set to the front, and corresponds to a second direction described later.

[0032] like Figure 1A As shown, the display device is disposed on, for example, the dash panel (also called the instrument panel) of a vehicle 2, such as an automobile. A front window 3 is disposed above the dash panel of vehicle 2. A light guide for the display device is disposed between the dash panel and the front window 3. The front window 3 is an example of a display medium.

[0033] The display device can display an image of the image light to the user by reflecting the image light emitted from the light guide off the front window 3. In other words, the display device projects the image light emitted from the light guide onto the front window 3 to display the image represented by the image light to the user. Image light represents information, including images such as numbers, text, and graphics, and is displayed as a virtual image onto the front window 3. The image is either a still image or a moving image, and is an image of numbers, text, and graphics.

[0034] In the above-mentioned display device, the light guide is flat, and external light such as sunlight may be reflected from the surface of the light guide and enter the user's eyes, causing glare. Therefore, a display device is sought that can prevent external light reflected from the light guide from entering the user's eyes.

[0035] Here, a display device according to a comparative example will be described.

[0036] Figure 1B This is a cross-sectional view of a light guide 110 of a display device 101 according to a comparative example as viewed from the side.

[0037] The light guide 110 of the display device 101 of the comparative example includes a light guide plate 141 and an optical element 143 that diffracts and emits light propagating within the light guide plate 141. When viewed from the side, the light guide 110 has a curved shape. Specifically, the light guide 110 of the comparative example has a light trap shape in which the curvature of the light guide 110 varies depending on the position. This shape causes external light reflected from the surface 110b of the light guide 110 to be directed to a position different from the user's eyes, thereby preventing external light from entering the user's eyes.

[0038] However, when the light guide 110 is curved, the optical element 143 must also be curved. Figure 1B As shown, in the comparative example optical element 143, the angle at which light propagating through the light guide plate 141 enters the optical element 143 varies depending on the position on the optical element 143 (e.g., angles β1 and β2). Therefore, when manufacturing the optical element 143, it is necessary to process the workpiece while simultaneously changing the irradiation position and irradiation angle of the irradiation light beam relative to the workpiece, making it difficult to easily manufacture the optical element 143.

[0039] In contrast, the display device of this embodiment has the following structure in order to suppress external light from entering the user's eyes and to simplify the production of optical elements.

[0040] Figure 2 This is a cross-sectional view of the light guide 10 of the display device 1 according to the first embodiment as viewed from the side.

[0041] like Figure 2 As shown, the display device 1 includes an image light emitting unit 20 and a light guide 10. The light guide 10 includes a light guide plate 31 and an optical element 33 that diffracts light propagating through the light guide plate 31 and emits the diffracted light.

[0042] The light guide 10 is as follows Figure 2In this way, the light guide 10 has a curved shape when viewed from the side, specifically, a circular arc shape in cross section. The optical element 33 is provided in the light guide 10 so that, regardless of the position of the optical element 33, it has a constant angle α with respect to the propagation direction of light propagating in the light guide plate 31 (the direction of the arrow intersecting the optical element 33).

[0043] That is, in the display device 1 of Embodiment 1, the angle α at which light propagating through the light guide plate 31 enters the optical element 33 remains constant regardless of its position on the optical element 33. Consequently, when manufacturing the optical element 33, the irradiation angle of the irradiation light beam relative to the workpiece can be fixed, and the workpiece can be processed while changing the irradiation position of the irradiation light beam. This simplifies the manufacture of the optical element 33.

[0044] The display device 1 of this embodiment includes an image light emitting unit 20 and a light guide 10 including a first light guide 30 and a second light guide 40. Figures 3A to 4 , the image light emitting section 20 , the first light guide 30 , and the second light guide 40 included in the display device 1 of the present embodiment will be described.

[0045] <Image Light Emitter 20>

[0046] Figure 3A This is a cross-sectional view of the display device according to Embodiment 1 as viewed from the horizontal direction.

[0047] The image light emitting unit 20 emits image light representing an image and directs it into the light guide. The image light is reflected by the front window 3, allowing a virtual image to be perceived. The image light emitting unit 20 emits the image light from the emission surface 29. The image light emitted from the emission surface 29 of the image light emitting unit 20 enters and passes through the first light guide 30, then enters and passes through the second light guide 40 before being emitted and projected onto the front window 3.

[0048] Figure 3B This is a schematic diagram illustrating the configuration of the image light emitting section 20 of the display device 1 according to the first embodiment. Figure 3B a illustrates a case where the second reflective mirror 23b is used as a MEMS (Micro Electro Mechanical Systems) reflective mirror in the image light emitting unit 20. Figure 3B Graph b illustrates a case where the second reflection mirror 23 b is used as DLP (Digital Light Processing) in the image light emitting unit 20 .

[0049] like Figure 3BAs shown, the image light emitting unit 20 includes a first emitter 21 a for emitting a first light ray, a second emitter 21 b for emitting a second light ray, a third emitter 21 c for emitting a third light ray, a plurality of dichroic mirrors, a condenser lens 22 , a first reflecting mirror 23 a , a second reflecting mirror 23 b , and an emitting surface portion 29 .

[0050] The wavelengths of the first light, the second light, and the third light are different. For example, the first light, the second light, and the third light are first, second, and third laser beams. In this embodiment, the first light is blue, the second light is green, and the third light is red. Red light refers to light in a wavelength range that can be recognized as red. Green light refers to light in a wavelength range that can be recognized as green. Blue light refers to light in a wavelength range that can be recognized as blue.

[0051] The first emitter 21 a , the second emitter 21 b , and the third emitter 21 c irradiate light toward the plurality of dichroic mirrors in a one-to-one correspondence with the plurality of dichroic mirrors.

[0052] In this embodiment, a case where the first dichroic mirror 24 a , the second dichroic mirror 24 b , and the third dichroic mirror 24 c are used as the plurality of dichroic mirrors will be described.

[0053] The first dichroic mirror 24a is positioned on the first light beam emitted from the first emitter 21a. The first light beam enters the first dichroic mirror 24a via a lens. The first dichroic mirror 24a reflects the first light beam and guides it to the second dichroic mirror 24b. In this embodiment, the first dichroic mirror 24a reflects light beams in the blue wavelength band and transmits light beams in other wavelength bands (e.g., green light beams, red light beams, etc.).

[0054] The second dichroic mirror 24b is arranged on the second light emitted by the second emitter 21b. The second light enters the second dichroic mirror 24b through the lens, and the first light enters the second dichroic mirror 24b from the side of the first dichroic mirror 24a. The second dichroic mirror 24b transmits the first light and guides it to the third dichroic mirror 24c. In addition, the second dichroic mirror 24b reflects the second light and guides it to the third dichroic mirror 24c. In this embodiment, the second dichroic mirror 24b has the function of reflecting light in the green wavelength band and transmitting light in other wavelength bands (for example, blue light, red light, etc.).

[0055] The third dichroic mirror 24c is positioned on the third light beam emitted from the third emitter 21c. The third light beam enters the third dichroic mirror 24c via a lens, and the first and second light beams enter the third dichroic mirror 24c from the side of the second dichroic mirror 24b. The third dichroic mirror 24c transmits the third light beam and guides it to the condenser lens 22. Furthermore, the third dichroic mirror 24c reflects the second and third light beams and guides them to the condenser lens 22. In this embodiment, the third dichroic mirror 24c has the function of reflecting light beams in the green and blue wavelength bands and transmitting light beams in other wavelength bands (e.g., red light beam).

[0056] In addition, you can also Figure 3B As shown in FIG. 2( b ), DLP (Digital Light Processing) is used as the second reflector 23b. In this case, a microlens array 25 may be arranged between the condenser lens 22 and the third dichroic mirror 24c. In addition, a projection lens 26 may be arranged on the optical path between the second reflector 23b and the emission surface 29.

[0057] The condenser lens 22 is a lens that condenses the first light, the second light, and the third light emitted through the third dichroic mirror 24c onto the first reflector 23a. The condenser lens 22 is made of glass, transparent resin, etc. In this embodiment, the condenser lens 22 is a convex lens, but it can also be a concave lens.

[0058] The condenser lens 22 is arranged on the emission direction side of the first light beam, the second light beam, and the third light beam emitted from the third dichroic mirror 24 c .

[0059] The first reflecting mirror 23 a reflects the first light beam, the second light beam, and the third light beam to guide the first light beam, the second light beam, and the third light beam to the second reflecting mirror 23 b .

[0060] The second reflector 23b reflects the first, second, and third rays reflected by the first reflector 23a and directs the first, second, and third rays toward the emission surface 29. The second reflector 23b is, for example, a MEMS mirror and can change the irradiation directions of the first, second, and third rays by rotating.

[0061] The emitting surface portion 29 is a screen such as a microlens array or a liquid crystal display element such as a liquid crystal display (LCD). For example, the emitting surface portion 29 is a translucent or semi-translucent TFT liquid crystal display (TFT).

[0062] The emitting surface 29 is irradiated with the first light, the second light, and the third light from the second reflector 23b side, and the image light is emitted by the light transmitted. The emitting surface 29 is driven together with the first emitter 21a, the second emitter 21b, and the third emitter 21c by the power obtained from the vehicle 2 side. The emitting surface 29 makes the image light appear to be the same as the image light from the vehicle 2. Figure 1A Image light of figures, characters, graphics, etc. corresponding to the control instructions of the control unit of the vehicle 2 is emitted from the emission surface. The emission surface is the surface of the emission surface portion 29 and is the surface facing the first light guide 30.

[0063] The emitting surface portion 29 is supported in the housing with its emitting surface facing the first light guide 30 and its back surface facing the second reflector 23b. Specifically, the emitting surface portion 29 is supported in the housing so that the optical axis of the image light emitted from the emitting surface portion 29 is substantially the same as the optical axis of the image light reflected by the second reflector 23b. The housing houses the first emitter 21a, the second emitter 21b, the third emitter 21c, multiple dichroic mirrors, the condenser lens 22, the first reflector 23a, the second reflector 23b, and the emitting surface portion 29, and is housed in the dash panel of the vehicle 2. Furthermore, in this embodiment, a telecentric lens 28 is disposed on the image light emitting side of the emitting surface portion 29. The emitting surface portion 29 allows the image light to enter the first incident surface 31a via the telecentric lens 28.

[0064] <First Light Guide 30>

[0065] Figure 3C This is an exploded perspective view of the display device 1 according to the first embodiment. Figure 4 3 are three views of the display device 1 according to Embodiment 1. Figure 3C In FIG. 3 , the first incident optical element 32 is shown as a flat shape for easy understanding. Figure 4 The diagram shows a state before the first light guide 30 and the second light guide 40 are formed into an arc shape.

[0066] like Figures 3A to 4 As shown, the first light guide 30 is a light guide 10 that stretches the image represented by the image light emitted by the image light emitting unit 20 in a first direction D1. The first direction D1 is a direction along an arc-shaped curve. A portion of the axis along the first direction D1 is orthogonal to the optical axis of the image light emitted by the image light emitting unit 20.

[0067] The first light guide 30 is a light guide 10 extending along the first direction, and has an arc-shaped cross-section when viewed from the side. The first light guide 30 is fixed to the second light guide 40 so as to overlap with the second light guide 40. The first light guide 30 is arranged so that one end side in the longitudinal direction faces the emission surface 29 of the image light emitting portion 20. The first light guide 30 has a back surface 30a located on the image light emitting portion 20 side, and a front surface 30b located opposite the back surface 30a and on the second light guide 40 side. The thickness of the first light guide 30 is constant, and the radius of curvature of the back surface 30a of the first light guide 30 is larger than the radius of curvature of the front surface 30b. In other words, when viewed from the side, the first light guide 30 is curved convexly relative to the image light emitting portion 20 and concavely relative to the front window 3.

[0068] The first light guide 30 includes a first light guide plate 31, a first incident optical element 32, and a first emitting optical element 33. The first light guide 30 is an example of a light guide, the first light guide plate 31 is an example of a light guide plate, and the first emitting optical element 33 is an example of an optical element.

[0069] The first light guide plate 31 is light-transmissive and has a curved shape extending in a first direction D1 from an incident surface facing the emission surface portion 29 of the image light emitting unit 20. The first light guide plate 31 has an arc-shaped cross-section when viewed from the horizontal direction. The first light guide plate 31 has a first incident surface 31a and a first emission surface 31b.

[0070] The image light emitted from the emission surface section 29 is incident on the first incident surface 31a. The first incident surface 31a faces the emission surface section 29 and is located a predetermined distance away from the emission surface section 29. The first incident surface 31a is a portion of the back surface 30a of the first light guide 30 and is a surface on one end side of the first light guide 30. The light incident on the first incident surface 31a is incident on the first incident optical element 32.

[0071] The first emission surface 31b emits image light emitted from the first emission optical element 33, described later, toward the second light guide 40. The first emission surface 31b is disposed facing the second light guide 40 and in close contact with the second light guide 40. The first emission surface 31b is a portion of the surface 30b of the first light guide 30.

[0072] The first incident optical element 32 and the first emitting optical element 33 are each an arc-shaped light-transmitting diffraction hologram pattern included in the first light guide plate 31. The first incident optical element 32 and the first emitting optical element 33 are arranged side by side along the first direction D1.

[0073] The first incident optical element 32 is included in the first light guide plate 31 so as to face the first incident surface 31a of the first light guide 30. When viewed overlapping the exit surface 29, the first incident optical element 32 has a larger area than the exit surface of the exit surface 29, thereby covering the exit surface. The first incident optical element 32 diffracts the image light incident from the first incident surface 31a, guiding the image light within the first light guide 30 based on the diffraction efficiency, and causing it to enter the first exit optical element 33.

[0074] The first emission optical element 33 has the function of stretching the incident image light in the first direction D1. The first emission optical element 33 is included in the first light guide plate 31 so as to face the first emission surface 31b of the first light guide body 30. Regarding the first emission optical element 33, when viewed in a manner overlapping with the first emission surface 31b, the area of ​​the first emission optical element 33 is smaller than the area of ​​the first emission surface 31b, and is thus covered by the first emission surface 31b. The first emission optical element 33 is arranged at a position closer to the light emission side of the guided image light than the first incident optical element 32. The first emission optical element 33 is arranged along the first emission surface 31b, that is, along the first direction D1. The cross-sectional shape of the first emission optical element 33 when viewed from the horizontal direction is an arc shape, and has the same curvature regardless of the position on the first emission optical element 33.

[0075] The image light diffracted by the first incident optical element 32 is incident on the first emission optical element 33. The first emission optical element 33 is disposed at a fixed angle α with respect to the propagation direction of the light propagating through the first light guide plate 31 (the direction of the arrow intersecting the first emission optical element 33). Angle α is the angle formed between the centerline of the first emission optical element 33 and the axis along the direction of the light propagating through the first light guide plate 31.

[0076] The first emission optical element 33 diffracts a portion of the image light incident on (passing through) the first emission optical element 33 from a predetermined direction, and emits the image light from the first emission surface 31b. The remaining image light not diffracted by the first emission optical element 33 is reflected by the front surface 30b and the back surface 30a, guided within the first light guide 30, and incident on the first emission optical element 33 again. The first emission optical element 33 diffracts a portion of the remaining image light and emits the image light from the first emission surface 31b. The further remaining image light not diffracted by the first emission optical element 33 is reflected by the front surface 30b and the back surface 30a, guided within the first light guide 30, and incident on the first emission optical element 33 again. This cycle of image light incidence, diffraction, emission, and reflection is repeated in the first light guide 30. The diffraction efficiency of the first emission optical element 33 may be set lower the closer it is to the first incident optical element 32 and higher the farther it is from the first incident optical element 32. The image light emitted from the first light guide 30 is incident on the second light guide 40.

[0077] <Second Light Guide 40>

[0078] The second light guide 40 is a light guide 10 that stretches the image represented by the image light emitted from the first light guide 30 in a second direction D2 and emits the image. The second direction D2 is the same as the lateral direction described above. The axis along the second direction D2 is linear and is substantially orthogonal to the axis along the first direction D1 and the optical axis of the image light emitted by the image light emitting unit 20.

[0079] The second light guide 40 is a light guide 10 extending along the first direction D1 and the second direction D2, and has an arc-shaped cross-section when viewed from the horizontal direction. The second light guide 40 fixes the first light guide 30 so as to overlap with the first light guide 30. The second light guide 40 is arranged so that one end side in the longitudinal direction faces the first light guide 30. The second light guide 40 has a back surface 40a located on the side of the first light guide 30 and a front surface 40b located opposite the back surface 40a and on the side of the front window 3. The thickness of the second light guide 40 is fixed, and the radius of curvature of the back surface 40a of the second light guide 40 is larger than the radius of curvature of the surface 40b.

[0080] The second light guide 40 includes a second light guide plate 41, a second incident optical element 42, and a second emitting optical element 43. The second light guide 40 is an example of a light guide, the second light guide plate 41 is an example of a light guide plate, and the second emitting optical element 43 is an example of an optical element.

[0081] The second light guide plate 41 is light-transmissive and extends along the first direction D1 and the second direction D2. The second light guide plate 41 has an arc-shaped cross-section when viewed from the horizontal direction, i.e., the second direction D2. The second light guide plate 41 has a second incident surface 41a and a second exit surface 41b.

[0082] The image light emitted from the first exit surface 31b of the first light guide plate 31 is incident on the second incident surface 41a. The second incident surface 41a faces the first exit surface 31b and is in close contact with the first exit surface 31b. The second incident surface 41a is a portion of the back surface 40a of the second light guide 40 and is a surface on one end side of the second light guide 40.

[0083] The second emission surface 41b emits image light emitted from the second emission optical element 43, described later, toward the front window 3. The second emission surface 41b faces the front window 3 and is a predetermined distance away from the front window 3. The second emission surface 41b is a portion of the surface 40b of the second light guide 40.

[0084] The second incident optical element 42 and the second emitting optical element 43 are arc-shaped light-transmitting diffraction hologram patterns contained in the second light guide plate 41. The second incident optical element 42 and the second emitting optical element 43 are arranged side by side along the second direction D2.

[0085] The second incident optical element 42 is included in the second light guide plate 41 so as to face the second incident surface 41a of the second light guide 40. When viewed overlapping the emission surface portion 29, the area of ​​the second incident optical element 42 is larger than that of the first emission optical element 33 of the first light guide 30, thereby covering the first emission optical element 33. The second incident optical element 42 diffracts the image light emitted from the first emission surface 31b of the first light guide 30, that is, the image light incident from the second incident surface 41a, and guides the image light within the second light guide 40 according to the diffraction efficiency, causing it to enter the second emission optical element 43.

[0086] The second emission optical element 43 has the function of stretching the incident image light in the second direction D2. The second emission optical element 43 is included in the second light guide plate 41 so as to face the second emission surface 41b of the second light guide body 40. Regarding the second emission optical element 43, when viewed overlapping with the second emission surface 41b, the area of ​​the second emission optical element 43 is smaller than the area of ​​the second emission surface 41b, and is thus covered by the second emission surface 41b. The second emission optical element 43 is arranged at a position closer to the light emission side of the guided image light than the second incident optical element 42. The second emission optical element 43 is arranged to extend along the second emission surface 41b, that is, along the first direction D1 and the second direction D2. The cross-sectional shape of the second emission optical element 43 when viewed from the horizontal direction is an arc, and the curvature is the same regardless of the position on the second emission optical element 43.

[0087] Image light diffracted by the second incident optical element 42 and propagating within the second light guide plate 41 is incident on the second exit optical element 43. Whenever the image light enters (passes through) the second exit optical element 43 from a predetermined direction, the second exit optical element 43 further diffracts the image light and causes a portion of the image light to be emitted from the second exit surface 41b via the second light guide plate 41. Specifically, a portion of the image light diffracted by the second exit optical element 43 is emitted from the second exit surface 41b via the second light guide plate 41, and the remaining image light is diffracted by the second exit optical element 43 while being guided by the second light guide 40 and emitted from the second exit surface 41b. In addition, the diffraction efficiency of the second exit optical element 43 can be set to be lower the closer to the second incident optical element 42 and higher the farther from the second incident optical element 42. The image light incident on the second emission optical element 43 is stretched in the second direction D2 and emitted from the second emission surface 41 b .

[0088] like Figure 3A As shown, the emission angles θ1 and θ2 of the light emitted from the second emission optical element 43 differ depending on the emission area of ​​the light on the second emission optical element 43. Each emission angle θ1 and θ2 is an angle based on the normal line (indicated by a double-dashed line) of the surface of the second emission optical element 43. For example, when the second emission optical element 43 is divided into a front area and a rear area from the user's perspective, the emission angle θ2 of the rear area is larger than the emission angle θ1 of the front area. In this display device 1, the light emitted from the second emission optical element 43 toward the front window 3 is approximately parallel regardless of the front area and the rear area. Approximately parallel means that it contains an angular error of, for example, several percent relative to true parallelism.

[0089] <Action>

[0090] In such a display device 1, light emitted from the light source of the image light emitting unit 20 passes through the condenser lens 22 and is irradiated onto the entire back surface of the emitting surface portion 29. Thus, image light including an image is emitted from the emitting surface, which is the front surface of the emitting surface portion 29.

[0091] The image light emitted from the emission surface of the image light emitting unit 20 enters the first incidence surface 31a of the first light guide plate 31, is guided within the first light guide plate 31, and then enters the first incidence optical element 32. The image light entering the first incidence optical element 32 is diffracted by the first incidence optical element 32, guided within the first light guide plate 31, and then enters the first emission optical element 33. The image light entering the first emission optical element 33 is diffracted by the first emission optical element 33. A portion of the image light is guided within the first light guide plate 31 and then emitted from the first emission surface 31b. The remaining portion is guided within the first light guide plate 31 (after being reflected by the front surface 30b and the back surface 30a) and then enters the first emission optical element 33 again. In this way, the image light emitted from the image light emitting unit 20 is stretched in the first direction D1 by the repetition of diffraction by the first emission optical element 33 and the emission of a portion of the image light.

[0092] The image light emitted from the first exit surface 31b of the first light guide 30 enters the second exit surface 41a of the second light guide plate 41, is guided within the second light guide plate 41, and then enters the second exit optical element 42. The image light entering the second exit optical element 42 is diffracted by the second entrance optical element 42, guided within the second light guide plate 41, and then enters the second exit optical element 43. The image light entering the second exit optical element 43 is diffracted by the second exit optical element 43. A portion of the image light is guided within the second light guide plate 41 and then exits from the second exit surface 41b. The remaining portion is guided within the second light guide plate 41 (after being reflected by the front surface 40b and the back surface 40a) and then enters the second exit optical element 43 again. In this way, the image light emitted from the first light guide 30 is stretched in the second direction D2 by the repeated diffraction and emission of a portion of the image light by the second exit optical element 43. That is, the second emission optical element 43 emits image light obtained by enlarging the image represented by the image light emitted by the image light emitting section 20 by stretching the image in the first direction D1 and the second direction D2.

[0093] The image light emitted by the second emission optical element 43 is guided within the second light guide plate 41 and then emitted from the second emission surface 41b of the second light guide plate 41. The image light emitted from the second emission surface 41b of the second light guide plate 41 enters the front window 3, where it is reflected and then directed toward the user of the vehicle 2. The user can thus see the virtual image of the display device 1 superimposed on the scenery ahead, as seen through the front window 3, in the direction of travel of the vehicle 2.

[0094] (Variation 1 of Implementation Example 1)

[0095] A description will be given of a display device 1 according to a first modification of Embodiment 1. In the first modification, an example in which the image light emitting section 20 emits convergent light will be described.

[0096] Figure 5A This is a cross-sectional view of the display device 1 according to the first modification of the first embodiment when viewed from the horizontal direction. Figure 5A Only the image light emitting section 20 and the first light guide 30 are shown.

[0097] The image light emitting portion 20 of the display device 1 of Modification 1 includes a field lens 28a for converging image light. The field lens 28a is a cylindrical lens that converges the image light emitted from the emission surface portion 29 in the first direction D1, i.e., the curved direction of the first light guide 30, without converging it in the second direction D2. The converged light obtained by converging through the field lens 28a is incident on the back surface 30a (the outer surface of the curve) of the first light guide 30, i.e., the first incident surface 31a. The first light guide 30 has a front surface 30b and a back surface 30a, and the curvature radius of the back surface 30a is larger than the curvature radius of the front surface 30b. Light having an equal incident angle relative to the first incident surface 31a is incident on the first incident surface 31a.

[0098] Furthermore, the image light emitting section 20 of Modification 1 outputs image light toward an end portion (first direction D1) along the curved surface of the back surface 30a of the first light guide 30. Specifically, the image light emitting section 20 outputs focused light toward the front end portion of the first light guide 30, of the two ends along the curved surface of the back surface 30a.

[0099] In this modified example, the image light output from the image light emitting unit 20 is convergent light and is incident at a fixed angle relative to the back surface 30a of the first light guide 30. This allows the image light emitted by the image light emitting unit 20 to be incident at a fixed, appropriate angle relative to the first light guide 30, allowing the image light to be emitted from the first light guide 30 in an appropriately shaped manner. This allows the display device 1 to be used to allow the user to view an image of an appropriately shaped image.

[0100] (Variation 2 of Implementation 1)

[0101] A description will be given of a display device 1 according to a second modification of Embodiment 1. Also in the second modification, an example in which the image light emitting section 20 emits convergent light will be described.

[0102] Figure 5B This is a cross-sectional view of a display device 1 according to a second modification of the first embodiment as viewed from the horizontal direction. Figure 5B Only the image light emitting section 20 and the first light guide 30 are shown.

[0103] The image light emitting portion 20 of the display device 1 of Modification 2 includes a field lens 28a for converging the image light. The field lens 28a is a cylindrical lens that converges the image light emitted from the emission surface portion 29 in the first direction D1, i.e., the curved direction of the first light guide 30, without converging the image light in the second direction D2. The converged light obtained by converging through the field lens 28a is incident on the back surface 30a (the outer surface of the curve) of the first light guide 30, i.e., the first incident surface 31a. The first light guide 30 has a front surface 30b and a back surface 30a, and the curvature radius of the back surface 30a is larger than the curvature radius of the front surface 30b. Light having an equal incident angle relative to the first incident surface 31a is incident on the first incident surface 31a.

[0104] Furthermore, the image light emitting section 20 of Modification 2 outputs image light toward an end portion (first direction D1) along the curved surface of the rear surface 30a of the first light guide 30. Specifically, the image light emitting section 20 outputs focused light toward the rear end portion of the first light guide 30, of the two ends along the curved surface of the rear surface 30a.

[0105] In this modified example, the image light output from the image light emitting unit 20 is convergent light and is incident at a fixed angle relative to the back surface 30a of the first light guide 30. This allows the image light emitted by the image light emitting unit 20 to be incident at a fixed, appropriate angle relative to the first light guide 30, allowing the image light to be emitted from the first light guide 30 in an appropriately shaped manner. This allows the display device 1 to be used to allow the user to view an image of an appropriately shaped image.

[0106] (Implementation Method 2)

[0107] The structure of the display device 1a in Embodiment 2 will be described. This embodiment differs from the first input optical element, first output optical element, second input optical element, and second output optical element in Embodiment 1 in that the first input optical element 32a, first output optical element 33a, second input optical element 42a, and second output optical element 43a are reflective optical elements. Unless otherwise specified, the remaining structures in Embodiment 2 are the same as those in Embodiment 1. Identical structures are denoted by the same reference numerals, and detailed descriptions of the structures are omitted.

[0108] Figure 6 This is a cross-sectional view of the display device 1 a according to the second embodiment when viewed from the horizontal direction.

[0109] In this embodiment, the first emission optical element 33a diffracts a portion of the image light incident on the first light guide 30 after being reflected from the surface 30b of the first light guide 30, and emits the diffracted image light from the first emission surface 31b. Furthermore, the first emission optical element 33a directs the remaining undiffracted image light toward the back surface 30a of the first light guide 30. In other words, the first emission optical element 33a is a light-reflecting diffraction hologram pattern contained within the first light guide 30.

[0110] The first light guide 30 of Embodiment 2 has a curved shape when the display device 1a is viewed from the side. Specifically, its cross-section has an arcuate shape. The first emission optical element 33a is disposed within the first light guide 30 such that, regardless of its position on the first emission optical element 33a, it forms a constant angle α with respect to the propagation direction of light propagating within the first light guide plate 31 (the direction of the arrow intersecting the first emission optical element 33a).

[0111] Specifically, in the display device 1a of Embodiment 2, the angle α at which light propagating through the first light guide plate 31 enters the first emission optical element 33a remains constant regardless of its position on the first emission optical element 33a. Consequently, when manufacturing the first emission optical element 33a, the angle of the irradiation beam relative to the workpiece can be fixed, allowing the workpiece to be processed while only the irradiation position of the irradiation beam is changed. This simplifies manufacturing of the first emission optical element 33a.

[0112] In addition, if Figure 6 As shown, the emission angles θ3 and θ4 of light emitted from the second emission optical element 43a vary depending on the light emission area on the second emission optical element 43a. Each emission angle θ3 and θ4 is relative to the normal to the surface of the second emission optical element 43a (indicated by a two-dot chain line). For example, if the second emission optical element 43a is divided into a front area and a rear area from the user's perspective, the emission angle θ4 in the rear area is larger than the emission angle θ3 in the front area. In this display device 1a, light emitted from the second emission optical element 43a toward the front window 3 is substantially parallel, regardless of the front and rear areas.

[0113] (Variation 1 of Implementation 2)

[0114] A display device 1 a according to a first modification of Embodiment 2 will be described. In the first modification of Embodiment 2, an example in which the image light emitting section 20 emits divergent light toward the surface 30 b of the first light guide 30 will be described.

[0115] Figure 7A This is a cross-sectional view of a display device 1 a according to Modification 1 of Embodiment 2 as viewed from the side. Figure 7A Only the image light emitting section 20 and the first light guide 30 are shown.

[0116] The image light emitting portion 20 of the display device 1a of the variant example 1 of the second embodiment includes a field lens 28b for diverging the image light. The field lens 28b is a cylindrical lens that causes the image light emitted from the emission surface portion 29 to diverge in the first direction D1, i.e., the curved direction of the first light guide 30, without diverging in the second direction D2. The divergent light obtained by the divergence by the field lens 28b is incident on the surface 30b (the inner surface of the curve) of the first light guide 30. The first light guide 30 has a surface 30b and a back surface 30a, and the curvature radius of the surface 30b is smaller than the curvature radius of the back surface 30a. Light having an equal incident angle relative to the first incident surface 31a is incident on the first incident surface 31a.

[0117] Furthermore, the image light emitting section 20 of this modified example outputs image light toward an end portion (a first direction D1) along the curved surface of the back surface 30a of the first light guide 30. Specifically, the image light emitting section 20 outputs divergent light toward the front end portion of the first light guide 30, of the two ends along the curved surface of the back surface 30a.

[0118] In this modified example, the image light output from the image light emitting unit 20 is divergent light and is incident at a fixed angle relative to the back surface 30a of the first light guide 30. Consequently, the image light emitted by the image light emitting unit 20 can be incident at a fixed, appropriate angle relative to the first light guide 30, allowing image light of an appropriate shape to be emitted from the first light guide 30. This allows the display device 1a to be used to allow the user to view an image of an appropriate shape.

[0119] (Variation 2 of Implementation 2)

[0120] A display device 1 a according to a second modification of Embodiment 2 will be described. In the second modification of Embodiment 2, an example in which the image light emitting section 20 emits divergent light toward the surface 30 b of the first light guide 30 will be described.

[0121] Figure 7B This is a cross-sectional view of a display device 1 a according to a second modification of the second embodiment when viewed from the horizontal direction. Figure 7B Only the image light emitting section 20 and the first light guide 30 are shown.

[0122] The image light emitting portion 20 of the display device 1a of the second variant of the second embodiment includes a field lens 28b for diverging the image light. The field lens 28b is a cylindrical lens that causes the image light emitted from the emission surface portion 29 to diverge in the first direction D1, i.e., the curved direction of the first light guide 30, without diverging in the second direction D2. The divergent light obtained by the divergence by the field lens 28b is incident on the surface 30b (the inner surface of the curve) of the first light guide 30. The first light guide 30 has a surface 30b and a back surface 30a, and the curvature radius of the surface 30b is smaller than the curvature radius of the back surface 30a. Light having an equal incident angle relative to the first incident surface 31a is incident on the first incident surface 31a.

[0123] The image light emitting section 20 of this modified example outputs image light toward an end portion (a first direction D1) along the curved surface of the back surface 30a of the first light guide 30. Specifically, the image light emitting section 20 outputs divergent light toward the rear end portion of the first light guide 30, of the two ends along the curved surface of the back surface 30a.

[0124] In this modified example, the image light output from the image light emitting unit 20 is divergent light and is incident at a fixed angle relative to the back surface 30a of the first light guide 30. Consequently, the image light emitted by the image light emitting unit 20 can be incident at a fixed, appropriate angle relative to the first light guide 30, allowing image light of an appropriate shape to be emitted from the first light guide 30. This allows the display device 1a to be used to allow the user to view an image of an appropriate shape.

[0125] <Effects>

[0126] Next, the effects of the display device 1 in the above-described embodiment will be described.

[0127] As described above, the display device 1 according to this embodiment includes a light guide and displays an image of light emitted from the light guide. The light guide has a curved shape and includes a light guide plate and an optical element that diffracts and emits light propagating within the light guide plate. The optical element is disposed within the light guide such that, regardless of its position on the optical element, it maintains a constant angle with respect to the propagation direction of light propagating within the light guide plate.

[0128] Because the light guide is curved, any external light reflected from the light guide's surface is directed to a location different from the user's eyes, preventing it from entering the user's eyes. Furthermore, the angle at which light propagating through the light guide plate enters the optical element remains constant regardless of its location on the optical element. Therefore, when manufacturing an optical element, for example, the angle of the irradiation beam relative to the workpiece can be fixed, allowing the workpiece to be processed while changing the irradiation position. This simplifies the manufacture of optical elements.

[0129] Alternatively, the light guide may have an arc-shaped cross section.

[0130] Since the light guide has an arcuate cross-section, any external light reflected from the light guide's surface is directed to a location different from the user's eyes, preventing it from entering the user's eyes. Furthermore, due to the arcuate cross-section of the light guide, the angle at which light propagating within the light guide plate enters the optical element remains constant regardless of its location on the optical element. This allows, for example, the angle of the incident light beam relative to the workpiece to be processed while the workpiece is processed while the beam's location is varied during fabrication. This simplifies the fabrication of optical elements.

[0131] Furthermore, the emission angle of light emitted from the optical element may differ depending on the emission area of ​​the light on the optical element.

[0132] By making the emission angle of light emitted from the optical element different depending on the emission area of ​​the light on the optical element, the light emitted from the optical element can be directed in the same direction. As a result, the image of the display device 1 as a virtual image can be seen superimposed on the forward scenery viewed through the display medium such as the front window 3.

[0133] Alternatively, the light emitted from the optical element may be substantially parallel.

[0134] Thus, by making the light emitted from the optical element substantially parallel, the light emitted from the optical element can be directed in the same direction. Thus, the image of the display device 1 as a virtual image can be seen superimposed on the forward scenery seen through the display medium such as the front window 3.

[0135] Furthermore, the display device 1 may further include an image light emitting unit 20 that outputs image light to a light guide (eg, the first light guide 30 ), and the image light emitting unit 20 may output converged or divergent light as image light.

[0136] This allows, for example, image light emitted by the image light emitting unit 20 to be appropriately incident on the light guide. This allows image light of an appropriate shape to be emitted from the light guide. This allows the user to view an image of an appropriate shape using the display device 1.

[0137] Alternatively, the image light may be incident at a fixed angle on the front surface 30 b or the back surface 30 a of the light guide (for example, the first light guide 30 ).

[0138] By causing the image light to enter the light guide body's front surface 30b or rear surface 30a at a fixed angle, for example, image light of an appropriate shape can be emitted from the light guide body.

[0139] Alternatively, the light guide (eg, the first light guide 30 ) may include a back surface 30 a and a front surface 30 b having a smaller curvature radius than the back surface 30 a , and the image light emitting unit 20 may output divergent light toward the front surface 30 b .

[0140] This allows the image light to enter the surface 30b of the light guide at a constant angle, and allows the image light of an appropriate shape to be emitted from the light guide.

[0141] Alternatively, the light guide (eg, the first light guide 30 ) may include a surface 30 b and a back surface 30 a having a larger curvature radius than the surface 30 b , and the image light emitting unit 20 may output the converged light toward the back surface 30 a .

[0142] This allows the image light to enter the back surface 30a of the light guide at a constant angle, and allows the image light of an appropriate shape to be emitted from the light guide.

[0143] (Other modifications, etc.)

[0144] As mentioned above, the present disclosure has been described based on the first and second embodiments and the first and second modifications of the respective embodiments. However, the present disclosure is not limited to the first and second embodiments and the first and second modifications.

[0145] For example, the processing units included in the display devices according to the above-described embodiments are typically implemented as LSIs, which are integrated circuits. These units may be implemented as separate chips or partially or entirely as a single chip.

[0146] Furthermore, integrated circuit implementation is not limited to LSIs; it can also be achieved using dedicated circuits or general-purpose processors. Alternatively, an FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing or a reconfigurable processor that allows the connections and settings of circuit cells within the LSI to be reconfigured can be used.

[0147] In addition, in each of the above-mentioned embodiments, each component may be formed by dedicated hardware, or may be implemented by executing a software program suitable for each component. Each component may also be implemented by a program execution unit such as a CPU or a processor reading a software program recorded on a recording medium such as a hard disk or semiconductor memory and executing the software program.

[0148] In addition, all the numbers used above are exemplified to specifically describe the present disclosure, and the embodiments and the like of the present disclosure are not limited to the exemplified numbers.

[0149] The division of functional blocks in the block diagram is merely an example. It is also possible to implement multiple functional blocks as one functional block, or to divide one functional block into multiple blocks, or to move some functions to other functional blocks. Furthermore, it is also possible to process the functions of multiple functional blocks having similar functions in parallel or in a time-sharing manner by a single piece of hardware or software.

[0150] In addition, the execution order of each step in the flowchart is exemplified for the purpose of specifically explaining the present disclosure, and may be an order other than the above-described order. In addition, some of the above-described steps may be executed simultaneously (in parallel) with other steps.

[0151] Furthermore, the present disclosure also includes various modifications that can be conceived by those skilled in the art to the embodiments and the like, and arbitrarily combines components and functions in the embodiments and the like without departing from the gist of the present disclosure.

[0152] Industrial applicability

[0153] The present disclosure can be applied to mobile objects such as vehicles, for example.

[0154] Description of Reference Numerals

[0155] 1, 1a: Display device; 10: Light guide; 20: Image light emitting portion; 21a: First emitter; 21b: Second emitter; 21c: Third emitter; 22: Condenser lens; 23a: First reflector; 23b: Second reflector; 24a: First dichroic mirror; 24b: Second dichroic mirror; 24c: Third dichroic mirror; 25: Microlens array; 26: Projection lens; 28: Telecentric lens; 28a, 28b: Field lenses; 29: Emission surface; 30: First light guide (light guide); 30a: Back surface; 30b: Surface; 31: First light guide plate (light guide plate) ; 31a: first incident surface; 31b: first exit surface; 32, 32a: first incident optical element; 33, 33a: first exit optical element (optical element); 40: second light guide (light guide); 40a: back surface; 40b: surface; 41: second light guide plate (light guide plate); 41a: second incident surface; 41b: second exit surface; 42, 42a: second incident optical element; 43, 43a: second exit optical element (optical element); D1: first direction; D2: second direction; α, β1, β2: angles; θ1, θ2, θ3, θ4: exit angles.

Claims

1. A display device comprising a light guide and an image light emitting unit for outputting image light to the light guide, wherein the display device displays an image of light emitted from the light guide, wherein: The light guide has a curved shape and includes a light guide plate and an optical element that diffracts and emits light propagating in the light guide plate. The image light emitting portion has an emitting surface portion, The optical element is disposed within the light guide in such a manner that the optical element has a fixed angle with respect to the propagation direction of light propagating within the light guide plate regardless of any position on the optical element. The light guide has a surface and a back surface having a curvature radius larger than that of the surface. The image light emitting section allows divergent light to be incident on the front surface from the emitting surface portion, or allows convergent light to be incident on the back surface from the emitting surface portion.

2. The display device according to claim 1, wherein The cross-section of the light guide is arc-shaped.

3. The display device according to claim 1 or 2, wherein: An emission angle of light emitted from the optical element varies depending on an emission area of ​​the light on the optical element.

4. The display device according to claim 3, wherein The light emitted from the optical element is substantially parallel.

5. The display device according to claim 1 or 2, wherein: The image light emitting section outputs converged light or divergent light as the image light. The display device according to claim 5 , wherein: The image light is incident at a fixed angle with respect to the front surface or the back surface of the light guide.

Images