Head-up display system

Abstract

This head-up display system comprises a display unit that emits a luminous flux that is visually recognized by an observer as a virtual image, and a light guide body that guides the luminous flux to a translucent member. The light guide body has an incidence surface on which the luminous flux from the display unit is incident, and an emission surface from which the luminous flux is emitted from the light guide body. A luminous flux that is incident on the incidence surface of the light guide body, and the propagation direction of the luminous flux is thereby changed, is reproduced into a plurality of luminous fluxes in the horizontal direction and the vertical direction of the virtual image visually recognized by the observer, and the luminous flux is emitted from the emission surface with a city or region thereby expanded. An A-direction and a B-direction intersect in an XZ plane between a visual recognition region and the translucent member, where the A-direction is the direction indicated by a normal line on the visual recognition region side of the direction normal to the translucent member at the intersection of the translucent member and a Z-axis, and the B-direction is the direction connecting to an emission aperture of the display unit from the center of the visual recognition region of the virtual image.

Description

[Technical Field]

[0001] The present disclosure relates to a head-up display system that displays a virtual image. [Background technology]

[0002] A vehicle information projection system that uses a head-up display device to display augmented reality (AR) information has been disclosed. The head-up display device projects light representing a virtual image onto the windshield of the vehicle, allowing the driver to view the virtual image together with the real view outside the vehicle.

[0003] As a device for displaying a virtual image, Patent Document 1 describes an optical element having a waveguide (light guide) for expanding an exit pupil in two directions. The optical element can expand the exit pupil by utilizing a diffractive optical element. Furthermore, Document 2 describes a head-mounted display that performs augmented reality (AR) display using a volume hologram diffraction grating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 10,429,645 [Patent Document 2] International Publication No. 2018 / 198587 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when implementing a pupil widening hologram used in a head-mounted display in a head-up display, fine processing is required on the light guide, making manufacturing difficult.

[0006] The present disclosure provides a head-up display system that facilitates the manufacturing of light guides. [Means for solving the problem]

[0007] The head-up display system of the present disclosure displays a virtual image superimposed on a real scene visible through a light-transmitting member, and includes a display unit that emits a light beam that is viewed by an observer as a virtual image, and a light guide that guides the light beam to the light-transmitting member. The light guide has an incident surface onto which the light beam from the display unit is incident and an exit surface from which the light beam exits the light guide, and the central ray of the light beam exiting the display unit is incident at an angle with respect to the normal to the incident surface of the light guide. The direction in which the observer views the virtual image from the viewing area of ​​the virtual image is defined as the Z-axis direction, the horizontal direction perpendicular to the Z-axis is defined as the X-axis direction, and the direction perpendicular to the XZ plane formed by the X-axis and Z-axis is defined as the Y-axis direction. The light beam that enters the incident surface of the light guide is redirected within the light guide, and is output from the exit surface so as to expand the viewing area by replicating the light beam into multiple light beams in the horizontal and vertical directions of the virtual image viewed by the observer. The central ray of the light beam emitted from the light guide is inclined with respect to the normal direction to the light output surface of the light guide and is emitted toward the light-transmitting member. The light-transmitting member is inclined with respect to the X-axis in a cross-sectional view of the XZ plane. When the direction of the normal direction of the light-transmitting member at the intersection of the light-transmitting member and the Z-axis, which is the direction toward the visible area, is defined as direction A, and the direction connecting the center of the visible area of ​​the virtual image and the output port of the display unit is defined as direction B, direction A and direction B intersect between the visible area and the light-transmitting member in the XZ plane.

[0008] The present disclosure also provides a head-up display system that displays a virtual image superimposed on a real scene visible through a light-transmitting member, and includes a display unit that emits a light beam that is viewed by an observer as a virtual image, and a light guide that guides the light beam to the light-transmitting member. The light guide has an incident surface on which the light beam from the display unit is incident, a combining region that changes the traveling direction of the light beam incident on the incident surface, a first expansion region that expands the viewing area by replicating the light beam propagated from the combining region into multiple light beams in a first direction, a second expansion region that expands the viewing area by replicating the light beam replicated in the first expansion region into multiple light beams in a second direction intersecting the first direction, and an exit surface from which the light beam replicated in the second expansion region exits. The central ray of the light beam emitted from the display unit is incident at an angle with respect to the normal direction of the incident surface of the light guide. When the direction in which an observer views the virtual image from the viewing region of the virtual image is defined as the Z-axis direction, the horizontal direction perpendicular to the Z-axis is defined as the X-axis direction, and the direction perpendicular to the XZ plane formed by the X-axis and Z-axis is defined as the Y-axis direction, in the light guide, a light beam that enters the coupling region and has its traveling direction changed propagates to the first extended region, where it is replicated in the first direction and propagates to the second extended region, where it is replicated in the second direction and emitted from the exit surface. The central light ray of the light beam that exits the light guide exits toward the light-transmitting member at an angle with respect to the normal direction of the exit surface of the light guide. The exit port of the display unit is located closer to the center line of the vehicle in the vehicle width direction than the exit surface of the light guide. [Effects of the Invention]

[0009] According to the head-up display system of the present disclosure, the light guide can be easily manufactured. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic perspective view showing the configuration of a light guide body. [Figure 2] An explanatory diagram showing the direction of incident light and emitted light to a light guide of a head-mounted display. [Figure 3] FIG. 1 is an explanatory diagram showing the directions of incident light and emitted light to a light guide of a head-up display; [Figure 4]YZ plane cross section of a vehicle equipped with a head-up display system [Figure 5] FIG. 1 is an explanatory diagram showing the optical path of a light beam emitted from a display unit. [Figure 6] FIG. 1 is a perspective view showing the configuration of a light guide body. [Figure 7] An explanatory diagram showing the central optical path of a light beam emitted from a display unit. [Figure 8] An explanatory diagram showing the central optical path of a light beam emitted from a display unit. [Figure 9] FIG. 10 is an explanatory diagram illustrating the order of pupil dilation of the light guide body according to the embodiment. [Figure 10] XZ cross-sectional view of a vehicle equipped with a head-up display system [Figure 11] FIG. 10 is an explanatory diagram illustrating the order of pupil expansion of the light guide body according to the embodiment and the comparative example. [Figure 12] FIG. 10 is an explanatory diagram illustrating the order of pupil expansion of a light guide body according to a modified example of the embodiment and a comparative example. [Figure 13] FIG. 10 is an explanatory diagram showing a modified head-up display system; DETAILED DESCRIPTION OF THE INVENTION

[0011] (Summary of the Disclosure) An overview of the present disclosure will first be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the configuration of a light guide 13. A so-called pupil widening type light guide 13 is used in a head-mounted display (hereinafter referred to as HMD) or the like. The pupil widening type light guide 13 includes a coupling region 21 that receives image light from a display unit 11 and changes the direction of travel of the light, a first widening region 23 that widens in a first direction, and a second widening region 25 that widens in a second direction. The first direction and the second direction may intersect with each other, for example, they may be perpendicular to each other.

[0012] The coupling region 21, the first expansion region 23, and the second expansion region 25 each have a diffraction power for diffracting image light, and an embossed hologram or a volume hologram is formed therein. The embossed hologram is, for example, a diffraction grating. The volume hologram is, for example, an interference pattern formed by a dielectric film. The coupling region 21 changes the traveling direction of the image light incident from the outside so that it heads toward the first expansion region 23 by using the diffraction power.

[0013] The first expansion region 23 has, for example, a diffraction grating element disposed therein, and replicates the incident image light by splitting the incident image light into image light traveling in a first direction using diffraction power and image light traveling to the second expansion region 25. For example, in FIG. 1 , the first expansion region 23 has diffraction grating elements disposed at four points 23p aligned in the direction in which the image light travels after repeated total reflection. The diffraction grating element splits the image light at each point 23p, and causes the split image light to travel to the second expansion region 25. As a result, the incident light beam is expanded by being replicated into four light beams of image light in the first direction.

[0014] The second expansion region 25 includes, for example, a diffraction grating element, which splits the incident image light into image light traveling in the second direction and image light emitted from the second expansion region 25 to the outside by using diffraction power, thereby duplicating the image light. For example, in FIG. 1 , three points 25p are arranged in each row in the direction in which the image light travels through repeated total reflection in the second expansion region 25, for a total of four rows, with a diffraction grating element arranged at each of the twelve points 25p. The image light is split at each point 25p, and the split image light is emitted to the outside. As a result, the incident image light beams in the four rows are each duplicated into three image light beams in the second direction, thereby expanding the image light beam. In this way, the light guide 13 can duplicate twelve image light beams from a single incident image light beam, thereby expanding the viewing area by duplicating the beam into multiple beams in the first and second directions. The observer can visually recognize each of the twelve beams of image light as a virtual image, and the visual recognition area in which the observer can visually recognize the image light can be widened.

[0015] Next, the difference between a pupil widening type HMD and a head-up display (hereinafter referred to as HUD) will be explained with reference to Figures 2 and 3. Figure 2 is an explanatory diagram showing incident light and outgoing light of an HMD. Figure 3 is an explanatory diagram showing incident light and outgoing light of an HUD.

[0016] 2, the light guide 13 in the HMD faces substantially directly toward the viewing area Ac in which the observer can view a virtual image. Image light incident perpendicularly from the display unit 11 is split within the light guide 13, and the split image light is emitted perpendicularly from the exit surface 27 of the light guide 13 toward the viewing area Ac.

[0017] In contrast, as shown in FIG. 3 , in the case of an HUD, image light emitted from the light guide 13 is reflected by, for example, the windshield 5 and enters the viewing area Ac, so that the divided image light is emitted obliquely from the exit surface 27 of the light guide 13. In this case, the inventors have newly discovered that making the image light from the display unit 11 enter the light guide 13 obliquely can facilitate optical design. In this way, the direction of the image emitted from the light guide 13 differs between an HMD and an HUD, and the inventors have newly discovered that utilizing this characteristic can facilitate the manufacture of the HUD. The configuration of the present disclosure will be further described below. The configuration of the present disclosure will be further described below.

[0018] (Embodiment) Hereinafter, an embodiment will be described with reference to Figures 4 to 6. Note that components having the same functions as those described above are given the same reference numerals. Also, the inclination angle of the windshield in the figures is shown for ease of understanding and may differ depending on the figure. [1-1.Configuration] [1-1-1. Overall configuration of head-up display system] A specific embodiment of a head-up display system 1 (hereinafter referred to as HUD system 1) according to the present disclosure will be described. FIG. 4 is a diagram showing a cross section of a vehicle 3 equipped with the HUD system 1 according to the present disclosure. FIG. 5 is an explanatory diagram showing the optical path of a light beam emitted from a display unit. In the embodiment, the HUD system 1 equipped in the vehicle 3 will be described as an example. Hereinafter, directions related to the HUD system 1 will be described based on the X-axis, Y-axis, and Z-axis shown in FIG. 4. The Z-axis direction is the direction in which an observer views the virtual image Iv from a visibility area Ac in which the observer can view the virtual image Iv. The X-axis direction is a horizontal direction perpendicular to the Z-axis. The Y-axis direction is a direction perpendicular to the XZ plane formed by the X-axis and Z-axis. Therefore, the X-axis direction corresponds to the horizontal direction of the vehicle 3, the Y-axis direction corresponds to the vertical direction of the vehicle 3, and the Z-axis direction corresponds to the forward direction of the vehicle 3.

[0019] As shown in FIG. 4, the HUD system 1 is disposed inside a dashboard (not shown) below the windshield 5 of a vehicle 3. An observer D perceives the image projected from the HUD system 1 as a virtual image Iv. In this way, the HUD system 1 displays the virtual image Iv superimposed on the real scene visible through the windshield 5. Because multiple replicated images are projected into the visibility area Ac, the observer can view the hologram displayed as an image within the visibility area Ac even if the observer's eye position is shifted in the Y-axis and X-axis directions. The observer D is a person inside the vehicle 3, which is a moving body, such as the driver.

[0020] The HUD system 1 includes a display unit 11, a light guide 13, and a control unit 15. The display unit 11 displays an image to be displayed as a virtual image Iv. The light guide 13 divides and copies a light beam L1 emitted from the display unit 11, and guides the copied light beam L2 to the windshield 5.

[0021] The display unit 11 displays an image under the control of an external control unit. For example, a backlit liquid crystal display, an organic light-emitting diode, or a plasma display can be used as the display unit 11. Alternatively, the display unit 11 may generate an image using a screen that diffuses or reflects light, a projector, or a scanning laser. The display unit 11 can display image content including various information such as road navigation guidance, the distance to the vehicle ahead, the remaining battery charge, and the current vehicle speed. In this way, the display unit 11 emits a light beam L1 including image content that is visually recognized by the observer D as a virtual image Iv.

[0022] The control unit 15 can be realized by a semiconductor element or the like. The control unit 15 can be configured by, for example, a microcomputer, a CPU, an MPU, a GPU, a DSP, an FPGA, or an ASIC. The control unit 15 realizes predetermined functions by reading data and programs stored in a built-in storage unit (not shown) and performing various arithmetic processing. The control unit 15 also includes a storage device 17.

[0023] The storage device 17 is a storage medium that stores programs and data necessary to realize the functions of the control unit 15. The storage device 17 can be realized, for example, by a hard disk drive (HDD), an SSD, a RAM, a DRAM, a ferroelectric memory, a flash memory, a magnetic disk, or a combination of these. The storage device 17 stores multiple image data representing the virtual image Iv. The control unit 15 determines the virtual image Iv to be displayed based on vehicle-related information acquired from an external source. The control unit 15 reads out the image data of the determined virtual image Iv from the storage device and outputs it to the display unit 11.

[0024] [1-1-2. Light guide] The configuration of the light guide 13 will be described with reference to FIGS. 6 and 9. FIG. 6 is a perspective view showing the configuration of the light guide 13. The light guide 13 has a first main surface 13a and a second main surface 13b. The first main surface 13a and the second main surface 13b are opposite each other. The light guide 13 has an incident surface 20, a coupling region 21, a first extended region 23, a second extended region 25, and an exit surface 27. The incident surface 20, the coupling region 21, the first extended region 23, and the second extended region 25 are included in the second main surface 13b, and the exit surface 27 is included in the first main surface 13a. The exit surface 27 is opposite the second extended region 25. The coupling region 21, the first extended region 23, and the second extended region 25 may be located between the first main surface 13a and the second main surface 13b. The first main surface 13a faces the windshield 5. In this embodiment, the incident surface 20 is included in the coupling region 21, but it may also be included in the first main surface 13a, which is a surface facing the coupling region 21. The exit surface 27 may also be included in the second extended region 25.

[0025] The coupling region 21, the first expansion region 23, and the second expansion region 25 each have a different diffraction power, and each has a diffraction grating or a volume hologram formed therein. The coupling region 21, the first expansion region 23, and the second expansion region 25 each have a different diffraction angle of image light. The light guide 13 is configured to totally reflect the incident light beam inside. In this way, the light guide 13 includes a diffraction grating or a volume hologram that diffracts light in a portion thereof. When the coupling region 21, the first expansion region 23, and the second expansion region 25 include a volume hologram, they become three-dimensional regions.

[0026] The coupling region 21 is a region where the light beam L1 emitted from the display unit 11 enters through the incident surface 20 and changes the traveling direction of the light beam L1. The coupling region 21 has diffractive power, and changes the propagation direction of the incident light beam L1 toward the first extended region 23, thereby coupling the light beam L1 into the first extended region 23. In this embodiment, coupling refers to a state in which the light beam L1 propagates within the light guide 13 under total internal reflection conditions.

[0027] The first extension region 23 expands the light flux L1 in a first direction and outputs the light flux L1 to the second extension region. For example, in the first extension region 23 that expands the light flux L1 in the first direction, the length in the first direction is greater than the length in the second direction. The light guide 13 is disposed so that the horizontal (X-axis) component of the first direction is greater than the Z-axis component. The side 23a of the first extension region 23 on the second extension region side extends along the side 25a of the second extension region 25 on the first extension region side. The light flux L1 propagates from the coupling region 21 in the first direction while repeatedly being totally reflected by the first principal surface 13a and the second principal surface 13b. The light flux L1 is replicated by the diffraction grating of the first extension region 23 formed on the second principal surface 13b and is output to the second extension region.

[0028] The second extension region 25 has a shape optimized in the XZ plane view to reduce distortion of the virtual image of the light beam L2 reflected by the curved surface of the windshield 5. The second extension region 25 is a diffraction region surrounded by four or more straight or curved lines of different angles and lengths. The second extension region 25, for example, expands the light beam L1 in a second direction intersecting the first direction and emits the expanded light beam L2 from the exit surface 27. The light guide 13 is disposed, for example, such that the second direction is the Z-axis direction. The light beam L1 propagating from the first extension region 23 propagates in the second direction while repeatedly being totally reflected by the first principal surface 13a and the second principal surface 13b. The light beam L1 is replicated by the diffraction grating of the second extension region 25 formed on the second principal surface 13b and is then emitted to the outside of the light guide 13 via the exit surface 27.

[0029] Therefore, from the viewpoint of observer D, the light guide 13 expands the light beam L1, which has entered the incident surface 20 and changed its direction of travel, in the horizontal direction (the direction of the X axis) of the virtual image Iv viewed by observer D, and then further expands it in the vertical direction (the direction of the Y axis) of the virtual image Iv, and emits the light beam L2 from the exit surface 27.

[0030] See FIG. 4. The light guide 13 is tilted with respect to the Z axis in a cross-sectional view of a YZ plane formed by the Y axis and the Z axis. The central ray of the light beam L1 emitted from the display unit 11 is incident at an angle with respect to the normal to the incident surface 20 of the coupling region 21 of the light guide 13. The central ray of the light beam L1 emitted from the display unit 11 is incident at an angle with respect to the normal to, for example, the center of the incident surface 20 or the center of gravity. The central ray of the light beam L2 emitted from the light guide 13 is emitted toward the windshield 5 at an angle with respect to the normal to the exit surface 27 of the light guide 13. The central ray of the light beam L2 emitted from the light guide 13 is emitted toward the windshield 5 at an angle with respect to the normal to, for example, the center of the exit surface 27 or the center of gravity.

[0031] Referring to FIG. 7, when the Z axis passes through the viewable region Ac of the virtual image Iv in the direction in which the viewer D views the virtual image, the light guide 13 is disposed below the viewable region Ac of the viewer D. For example, the side of the exit surface 27 of the light guide 13 closer to the viewer D is closer to the Z axis, and the side of the exit surface 27 farther from the viewer D is tilted away from the Z axis in a cross-sectional view in the YZ plane. The distance Lg1 between the side 27a of the exit surface 27 facing the viewer and the Z axis is smaller than the distance Lg2 between the side 27b of the exit surface 27 facing the display unit 11 and the Z axis. By tilting the light guide 13 in this way, sunlight incident on the light guide 13 through the windshield 5 can be reflected toward the windshield 5. As a result, sunlight reflected by the light guide 13 does not reach the viewable region Ac, preventing the viewer D from being dazzled. In addition, by adjusting the inclination angle of the light guide 13, it is possible to prevent sunlight reflected by the light guide 13 from reaching the visible area Ac after being reflected by the windshield 5, and thereby preventing the observer D from being dazzled.

[0032] Furthermore, the light guide 13 is disposed at an angle with respect to the Z axis in a cross-sectional view of the YZ plane relative to the windshield 5, and the light beam emitted from the light guide 13 enters the windshield 5 at an angle with respect to the Z axis in a cross-sectional view of the YZ plane.

[0033] Since the light guide 13 is arranged in this manner, the light beam L1 from the display unit 11 enters the light guide 13 at an angle, is divided and replicated, and the light beam L2 is emitted from the light guide 13 at an angle toward the windshield 5.

[0034] As shown in FIG. 8 , if the angular range in the YZ plane in which the viewer D views the virtual image Iv is +θ to −θ degrees around the Z axis, then either or both of the angular difference α between the incident light and the normal to the coupling region 21 of the light guide 13 and the angular difference β between the emitted light and the normal to the exit surface 27 of the light guide 13 are θ to 90-θ degrees in the YZ plane. If either or both of the angular differences α and β are less than θ degrees in the YZ plane, the likelihood of stray sunlight entering the viewing area Ac increases. If they exceed 90-θ degrees, the viewer D has difficulty viewing the virtual image Iv. Therefore, if either or both of the angular differences α and β are in the angular range of θ to 90-θ degrees in the YZ plane, the incidence of stray sunlight entering the viewing area Ac is reduced, allowing the viewer D to properly view the virtual image Iv. The angle θ is, for example, 2 to 3 degrees.

[0035] In addition, in the YZ plane, the incident angle Φ of the light beam L2 emitted from the light guide 13 to the windshield 5 is 45 degrees or more and 75 degrees or less, and the tilt angle γ of the light guide 13 with respect to the Y axis is larger than the incident angle Φ of the light beam L2 to the windshield 5 and is less than 175 degrees. In Fig. 8, the line indicated by reference numeral 41 is a virtual line translated parallel to the Y axis.

[0036] 10 , in the HUD system 1 of the embodiment, the direction in which the light beam L1 enters the light guide 13 from the display unit 11 and the direction in which the light beam L2 exits from the second extended region 25 to the windshield 5 are aligned along the negative direction of the Z axis. The HUD system 1 of the embodiment is disposed on the left side of the center line 3a in the width direction of the vehicle 3, but may also be disposed on the right side. When the HUD system 1 is disposed on the right side of the center line 3a in the width direction of the vehicle 3, the display unit 11 and the coupling region 21 of the light guide 13 are disposed on the center line 3a side of the vehicle 3 with respect to the first extended region 23 of the light guide 13.

[0037] Furthermore, in the HUD system 1 of the embodiment, the display unit 11, the coupling region 21 of the light guide 13, and the second extended region 25 are arranged in this order in the negative direction of the Z axis. This allows the direction in which the light beam L1 enters the light guide 13 from the display unit 11 and the direction in which the light beam L2 is emitted from the second extended region 25 to the windshield 5 to have components in the same direction, thereby reducing the diffraction power of the second extended region 25. Furthermore, the windshield 5 is tilted with respect to the X axis in a cross-sectional view of the XZ plane.

[0038] Furthermore, when the direction of the normal to the windshield 5 at the intersection of the windshield 5 and the Z axis toward the visible area Ac is defined as direction A, and the direction connecting the center of the visible area Ac of the virtual image Iv to the exit 11a of the display unit 11 is defined as direction B, directions A and B intersect within the XZ plane between the visible area Ac and the windshield 5. Exit 11a is the area through which the luminous flux L1 of the image light is emitted from the display unit 11, or is an aperture stop. The effect of this is described below.

[0039] [1-1-3. Order of pupil dilation] Unlike an HMD, in the HUD system 1, the magnitude of the wave vector of the first expansion region 23 and the second expansion region 25 differs depending on the order of pupil expansion of the image light beam L1 in the light guide 13 arranged as described above. The magnitude of the wave vector also changes depending on the position of the display unit 11. The order of pupil expansion in the embodiment and the comparative example will be described with reference to FIG. 11. FIG. 11 is an explanatory diagram illustrating the order of pupil expansion in the light guides of the embodiment and the comparative example. FIG. 11(a) is an explanatory diagram illustrating the order of pupil expansion in the light guide 13 of the embodiment, and FIG. 11(b) is an explanatory diagram illustrating the wave vector of the light guide 13 of the embodiment. FIG. 11(c) is an explanatory diagram illustrating the order of pupil expansion in the light guide 13B of the comparative example, and FIG. 11(d) is an explanatory diagram illustrating the wave vector of the light guide 13B of the comparative example.

[0040] In the embodiment, the light beam L1 of image light incident on the light guide 13 changes its propagation direction to the first expansion region 23, which expands the pupil in a first direction, by the diffractive element formed in the coupling region 21. Therefore, after being obliquely incident on the coupling region 21, the light beam L1 is affected by the wave vector k1 shown in FIG. 11(b) and then propagates in the direction of the first expansion region 23.

[0041] The light beam L1 propagating toward the first extended region 23 extending in the first direction is split by the diffraction element formed in the first extended region 23 while repeatedly undergoing total reflection into a light beam L1 propagating in the first direction and a light beam L1 that is duplicated and changes its propagation direction toward the second extended region 25. At this time, the duplicated light beam L1 is affected by the wave vector k2 shown in FIG. 11(b) and propagates toward the second extended region 25.

[0042] The light beam L1, whose propagation direction has been changed to the second extended region 25 extending along the negative direction of the Z axis as the second direction, is split by the diffraction element formed in the second extended region 25 into the light beam L1 propagating in the second direction and the light beam L2 that is duplicated and emitted from the second extended region 25 to the outside of the light guide 13 via the exit surface 27. At this time, the duplicated light beam L2 is affected by the wave vector k3 shown in FIG. 11(b) and propagates in the direction of the exit surface 27.

[0043] Because the sum of the wave vectors k1, k2, and k3 is zero, the direction of the light beam L1 entering the light guide 13 and the direction of the light beam L2 exiting the light guide 13 are the same. Expanding the pupil in the first direction and then in the second direction can reduce the magnitude of the wave vector k3 of the second extension region 25. Reducing the magnitude of the wave vector k3 reduces the diffractive power of the second extension region 25, allowing the pitch of the diffraction grating of the second extension region 25 to be increased. For example, the diffraction grating pitch of the coupling region 21 and the first extension region 23 can be approximately 300 nm, while the diffraction grating pitch of the second extension region 25 can be approximately 1 μm. This allows the diffraction grating pitch of the second extension region 25, which has the largest area among the regions where diffractive elements are formed, to be increased, thereby facilitating the processing of the second extension region 25. As a result, the light guide 13 can be manufactured more easily.

[0044] Next, referring to Fig. 11(c), in the comparative example, the light exit 11a of the display unit 11 is disposed further outward from the vehicle 3 than the second extended region 25B of the light guide 13B.

[0045] In the light guide 13B of the comparative example, the luminous flux L1 of the image light incident on the display unit 11 is changed in propagation direction by a diffractive element formed in the coupling region 21B to the first expansion region 23B, which expands the pupil of the virtual image Iv in the horizontal direction. Therefore, after the luminous flux L1 is obliquely incident on the coupling region 21B, it is affected by the wave vector k4 shown in FIG. 11(d) and propagates in the direction of the first expansion region 23B.

[0046] The light beam L1 propagating toward the first extended region 23B is split by the diffraction element formed in the first extended region 23B while repeatedly undergoing total reflection into a light beam L1 propagating in the horizontal direction and a light beam L1 that is duplicated and changes its propagation direction toward the second extended region 25B. At this time, the duplicated light beam L1 is affected by the wave vector k5 shown in FIG. 11(d) and propagates toward the second extended region 25B.

[0047] The light beam L1, whose propagation direction has been changed to the second extended region 25B, is split by the diffraction element formed in the second extended region 25B into a light beam L1 that propagates in the negative direction of the Z axis and a light beam L2 that is duplicated and emitted from the second extended region 25B to the outside of the light guide 13B via the exit surface 27. At this time, the duplicated light beam L2 is affected by the wave vector k6 shown in FIG. 11(d) and propagates in the direction of the exit surface 27.

[0048] 10 , the comparative example is a case where direction A and direction B do not intersect in the XZ plane between the visible area and windshield 5, and output port 11a of display unit 11 is disposed outside second extended region 25B of light guide 13B on vehicle 3, so wave vector k4 of coupling region 21B and wave vector k5 of first extended region 23B are significantly larger than wave vector k1 of coupling region 21 and wave vector k2 of first extended region 23 of the embodiment, respectively. Therefore, the diffraction power of coupling region 21B and first extended region 23B of the comparative example must be larger than that of the embodiment, and the pitch of the diffraction gratings of coupling region 21B and first extended region 23B of the modified example must be shorter. As in the embodiment, when the A direction and the B direction intersect between the viewing area and the windshield 5 in the XZ plane, i.e., when the exit 11a of the display unit 11 is positioned inside the vehicle 3 relative to the second extended area 25 of the light guide 13, the magnitudes of the wave vector k1 of the coupling area 21 and the wave vector k2 of the first extended area 23 can be reduced, the pitch of each diffraction grating can be increased, and processing of the coupling area 21 and the first extended area 23 becomes easier.

[0049] Next, the order of pupil dilation in a modified example of the embodiment will be described with reference to Fig. 12. Fig. 12 is an explanatory diagram illustrating the order of pupil dilation in a light guide of a modified example of the embodiment and a comparative example. Fig. 12(a) is an explanatory diagram illustrating the order of pupil dilation in a light guide 13C of a modified example of the embodiment, and Fig. 12(b) is an explanatory diagram illustrating the wave vector of the light guide 13C of the modified example. Fig. 12(c) is an explanatory diagram illustrating the order of pupil dilation in a light guide 13B of a comparative example, and Fig. 12(d) is an explanatory diagram illustrating the wave vector of the light guide 13B of the comparative example.

[0050] As shown in Fig. 12(a), in the modified light guide 13C, a gap 29 exists between the side 23Ca of the first extended region 23C on the second extended region 25C side and the side 25Ca of the second extended region 25C on the first extended region 23C side. In the modified light guide 13C, a luminous flux L1 of image light incident on the display unit 11 is changed in propagation direction by a diffractive element formed in the coupling region 21C to the first extended region 23C, which expands the pupil of the virtual image Iv in the horizontal direction. Therefore, after being obliquely incident on the incident surface 20, the luminous flux L1 is acted upon by the coupling region 21C with a wave vector k7 shown in Fig. 12(b) and propagates toward the first extended region 23C.

[0051] The light beam L1 propagating toward the horizontally extending first extended region 23C is split by the diffraction element formed in the first extended region 23C while repeatedly undergoing total reflection into a light beam L1 propagating in the horizontal direction and a light beam L1 that is duplicated and changes its propagation direction toward the second extended region 25C. At this time, the duplicated light beam L1 is affected by the wave vector k8 shown in FIG. 12(b) and propagates toward the second extended region 25C.

[0052] The light beam L1, whose propagation direction has been changed to the second extended region 25C extending in the negative direction of the Z axis, is split by the diffraction element formed in the second extended region 25C into a light beam L1 that propagates in the negative direction of the Z axis and a light beam L2 that is duplicated and emitted from the second extended region 25C to the outside of the light guide 13C via the exit surface 27. At this time, the duplicated light beam L2 is affected by the wave vector k9 shown in FIG. 12(b) and propagates in the direction of the exit surface 27.

[0053] If a gap 29 exists between the side 23Ca of the first extension region 23C on the second extension region 25C side and the side 25Ca of the second extension region 25C on the first extension region 23C side as in the modified example, the wave vector k7 of the coupling region 21C and the wave vector k8 of the first extension region 23C are larger than those of the embodiment. Therefore, the diffraction power of the coupling region 21C and the first extension region 23C in the modified example must be larger than that of the embodiment, and the pitch of the diffraction gratings of the coupling region 21C and the first extension region 23C in the modified example must be shorter. As in the embodiment, the side 23a of the first extension region 23 on the second extension region 25 side extends along the side 25a of the second extension region 25 on the first extension region 23 side, thereby reducing the gap between the side 23a of the first extension region 23 on the second extension region 25 side and the side 25a of the second extension region 25 on the first extension region 23 side. This allows the magnitude of the wave vector k1 of the coupling region 21 and the wave vector k2 of the first extension region 23 to be reduced, the pitch of each diffraction grating to be increased, and processing of the coupling region 21 and the first extension region 23 becomes easier.

[0054] The magnitude of the wave vector in the modified example is larger than that of the embodiment, but can be smaller than that of the comparative example. Therefore, the pitch of the diffraction grating in the coupling region 21C and the first extension region 23C can be made longer than that of the light guide 13B in the comparative example.

[0055] 7, the distance on the Z axis from viewing area Ac, which includes the viewing position of observer D, to incident surface 20 is longer than the distance on the Z axis from viewing area Ac to exit surface 27. Here, the distance on the Z axis from viewing area Ac to incident surface 20 is the distance from viewing area Ac to the intersection of a perpendicular line to the Z axis from an arbitrary point on incident surface 20 in the YZ plane with the Z axis. Furthermore, the distance on the Z axis between exit surface 27 and viewing area Ac is the distance from viewing area Ac to the intersection of a perpendicular line to the Z axis from an arbitrary point on exit surface 27 in the YZ plane with the Z axis. This reduces the difference between the angle of incidence of light beam L1 on light guide 13 and the angle of total reflection for guiding the light within light guide 13, thereby increasing the diffraction pitch and improving diffraction efficiency.

[0056] 8 and 10, the light beam emitted from the display unit 11 is emitted toward the quadrant where the viewer D is located, centered on the display unit 11, in either or both of the XZ plane and the YZ plane formed by the X axis and the Z axis. This reduces the difference between the angle of incidence of the light beam L1 on the light guide 13 and the angle of total reflection for guiding the light inside the light guide 13, making it possible to lengthen the diffraction pitch of the second extended region 25 and increase the diffraction efficiency. This also simplifies the manufacture of the light guide 13. In addition, the windshield 5 has a curved surface, and at least a portion of the area where the light beam L2 is incident is tilted in the cross-sectional views of the XZ plane and the YZ plane.

[0057] [1-2. Effects, etc.] The HUD system 1 of the present disclosure is a HUD system 1 that displays a virtual image Iv superimposed on a real scene viewable through a windshield 5. The HUD system 1 includes a display unit 11 that emits a light beam that is viewed by an observer D as a virtual image Iv, and a light guide 13 that guides the light beam to the windshield 5. The light guide 13 has an incident surface 20 onto which the light beam from the display unit 11 is incident, and an exit surface 27 from which the light beam exits the light guide 13. The central ray of the light beam that exits the display unit 11 is incident at an angle with respect to the normal direction to the incident surface 20 of the light guide 13. The direction in which the observer D views the virtual image Iv from a viewable region Ac of the virtual image Iv is defined as the Z-axis direction, the horizontal direction perpendicular to the Z-axis is defined as the X-axis direction, and the direction perpendicular to the XZ plane formed by the X-axis and Z-axis is defined as the Y-axis direction. The light beam incident on the incident surface 20 of the light guide 13 has its direction of travel changed within the light guide 13, and is output from the output surface 27 so as to expand the visible area Ac by replicating the light beam into multiple light beams in the horizontal and vertical directions of the virtual image Iv viewed by the observer D. The central ray of the light beam output from the light guide 13 is output toward the windshield 5 at an angle with respect to the normal direction to the output surface 27 of the light guide 13. The windshield 5 is inclined with respect to the X-axis in a cross-sectional view of the XZ plane. When the direction of the normal to the windshield 5 at the intersection of the windshield 5 and the Z-axis on the side of the visible area Ac is defined as direction A, and the direction connecting the center of the visible area Ac of the virtual image Iv with the output port 11a of the display unit 11 is defined as direction B, direction A and direction B intersect between the visible area Ac and the windshield 5 in the XZ plane.

[0058] In HUD system 1, the light beam from display unit 11 is emitted at an angle to incident surface 20 of light guide 13, and the light beam that has undergone pupil expansion in light guide 13 is emitted at an angle from exit surface 27 toward windshield 5. Since direction A and direction B intersect between visible area Ac and windshield 5 in the XZ plane, the diffraction power of the area of ​​light guide 13 that replicates the light beam can be reduced, making it easier to process light guide 13 and manufacture HUD system 1.

[0059] Furthermore, light guide 13 is disposed below viewable region Ac of observer D, and light guide 13 is inclined in a cross-sectional view in the YZ plane so that the side of exit surface 27 of light guide 13 closer to viewable region Ac is closer to the Z axis than the side farther from viewable region Ac. As a result, light guide 13 is disposed to face windshield 5, and sunlight incident through windshield 5 can be reflected by light guide 13 back toward windshield 5. As a result, sunlight can be prevented from being reflected by light guide 13 and guided to viewable region Ac, preventing observer D from being dazzled by sunlight. Furthermore, adjusting the inclination angle of light guide 13 can prevent sunlight reflected by light guide 13 from reaching viewable region Ac after being reflected by windshield 5, preventing observer D from being dazzled by sunlight.

[0060] The light guide 13 also has a coupling region 21 that changes the direction of a light beam incident on the incident surface 20, a first extension region 23 that expands the light beam whose direction has been changed by the coupling region 21 in a first direction within the light guide 13, and a second extension region 25 that expands the light beam expanded by the first extension region 23 in a second direction intersecting the first direction within the light guide 13. The coupling region 21, the first extension region 23, and the second extension region 25 each have a different diffraction power and diffraction angle. The light beam incident on the second extension region 25 exits from the exit surface 27. This allows the diffraction power of the second extension region 25 to be reduced, making the light guide 13 easier to manufacture.

[0061] The coupling region 21, the first extension region 23, and the second extension region 25 are regions having diffractive structures, and the magnitude of the wave vectors of the respective diffractive structures is different. For example, the wave vector k2 of the first extension region 23 is approximately 1.1 times the wave vector k1 of the coupling region 21, and the wave vector k3 of the second extension region 25 is approximately 0.3 times the wave vector k1. Since the diffraction pitch of the diffractive structure of the second extension region 25 can be made longer, the light guide 13 can be manufactured more easily.

[0062] Furthermore, by projecting the light emitted from the HUD system 1 onto the windshield 5 of the vehicle 3, a virtual image Iv suitable for the observer D driving the vehicle 3 can be displayed.

[0063] (Other embodiments) As described above, the above embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can be applied to embodiments in which appropriate modifications, substitutions, additions, omissions, etc. are made. Therefore, other embodiments will be described below as examples.

[0064] In the above embodiment, the split and replicated light beam L2 is reflected by the windshield 5 to allow the observer D to view the virtual image Iv, but this is not limiting. A combiner may be used instead of the windshield 5, and the split and replicated light beam L2 may be reflected by the combiner to allow the observer D to view the virtual image Iv.

[0065] In the above embodiment, the first direction in which the light beam L1 is expanded in the first expansion region 23 is the horizontal direction, and the second direction in which the light beam L1 is expanded in the second expansion region 25 is the negative direction of the Z axis, but this is not limiting. As shown in Fig. 13, the first direction in which the light beam L1 is expanded in the first expansion region 23 may be the negative direction of the Z axis, and the second direction in which the light beam L1 is expanded in the second expansion region 25 may be the horizontal direction.

[0066] In the above embodiment, the HUD system 1 is described as being applied to a vehicle 3 such as an automobile. However, the object to which the HUD system 1 is applied is not limited to the vehicle 3. The object to which the HUD system 1 is applied may be, for example, a train, a motorcycle, a ship, or an airplane, or may be an amusement machine that does not involve movement. In the case of an amusement machine, the light beam from the display unit 11 is reflected by a transparent curved plate that serves as a translucent member that reflects the light beam emitted from the display unit 11 instead of the windshield 5. Furthermore, the actual scene that the user can view through the transparent curved plate may be an image displayed by another image display device. In other words, a virtual image generated by the HUD system 1 may be superimposed on an image displayed by another image display device. In this manner, any of the windshield 5, a combiner, and a transparent curved plate may be used as the translucent member in the present disclosure.

[0067] (Outline of the embodiment) (1) A head-up display system according to the present disclosure displays a virtual image superimposed on a real scene visible through a light-transmitting member, and includes: a display unit that emits a light beam that is viewed by an observer as a virtual image; and a light guide that guides the light beam to the light-transmitting member. The light guide has an incident surface onto which the light beam from the display unit is incident and an exit surface from which the light beam exits the light guide, and the central ray of the light beam that exits the display unit is incident at an angle with respect to the normal to the incident surface of the light guide. When the direction in which the observer views the virtual image from the viewing area of ​​the virtual image is defined as the Z-axis direction, the horizontal direction perpendicular to the Z-axis is defined as the X-axis direction, and the direction perpendicular to the XZ plane formed by the X-axis and Z-axis is defined as the Y-axis direction, the light beam that enters the incident surface of the light guide is redirected within the light guide, and is output from the exit surface so as to expand the viewing area by replicating the light beam into multiple light beams in the horizontal and vertical directions of the virtual image viewed by the observer. The central ray of the light beam emitted from the light guide is emitted toward the light-transmitting member at an angle with respect to the normal direction to the light-emitting surface of the light guide. The light-transmitting member is inclined with respect to the X-axis in a cross-sectional view of the XZ plane. When the direction of the normal direction of the light-transmitting member at the intersection of the light-transmitting member and the Z-axis, which is the direction toward the visible area, is defined as direction A, and the direction connecting the center of the visible area of ​​the virtual image and the output port of the display unit is defined as direction B, direction A and direction B intersect between the visible area and the light-transmitting member in the XZ plane.

[0068] This allows the diffraction power of the region of the light guide that expands the light beam to be reduced, making it easier to process the diffraction grating or volume hologram in this region of the light guide, and facilitating the manufacture of head-up display systems.

[0069] (2) In the head-up display system of (1), the light guide has a coupling region that changes the traveling direction of a light beam incident on the incident surface, a first expansion region that replicates the light beam whose traveling direction has been changed in the coupling region in a first direction within the light guide, and a second expansion region that replicates the light beam expanded in the first expansion region in a second direction intersecting the first direction within the light guide. The coupling region, the first expansion region, and the second expansion region each have different diffraction powers and diffraction angles, and the light beam expanded in the second expansion region is emitted from the exit surface.

[0070] (3) In the head-up display system of (2), the second extended area is a diffractive area surrounded by four or more straight or curved lines of different angles or lengths.

[0071] (4) In the head-up display system of (2) or (3), the side of the first expansion area on the second expansion area side extends along the side of the second expansion area on the first expansion area side.

[0072] (5) In any one of the head-up display systems (1) to (4), the light guide is inclined with respect to the Z axis in a cross-sectional view of a YZ plane formed by the Y axis and the Z axis, the light guide is arranged at an inclination with respect to the light-transmitting member in a cross-sectional view of the YZ plane, and the light beam emitted from the light guide enters the light-transmitting member at an inclination with respect to the Z axis in a cross-sectional view of the YZ plane.

[0073] (6) In the head-up display system of any one of (1) to (5), the distance on the Z axis from the viewing area to the entrance surface is longer than the distance on the Z axis from the viewing area to the exit surface.

[0074] (7) In any one of the head-up display systems (1) to (6), the light guide is positioned below the viewer's viewing area, and the light guide is inclined in a cross-sectional view in the YZ plane so that the side of the light guide's output surface closer to the viewing area is closer to the Z axis than the side farther from the viewing area.

[0075] (8) In any one of the head-up display systems (1) to (7), in the YZ plane, the incident angle of the light beam emitted from the light guide to the light-transmitting member is 45 degrees or more and 75 degrees or less, and the inclination angle of the light guide to the Y axis is greater than the incident angle of the light beam to the light-transmitting member and less than 175 degrees.

[0076] (9) In any one of the head-up display systems (1) to (8), the light beam emitted from the display unit is emitted in either the XZ plane or the YZ plane, or both, toward the quadrant in which the recognition area is located, centered on the display unit.

[0077] (10) In any one of the head-up display systems (1) to (9), when the angular range in which an observer can see a virtual image in the YZ plane is +θ degrees to -θ degrees around the Z axis, either or both of the angular difference between the incident light entering the incident surface of the light guide and the normal direction to the incident surface of the light guide, and the angular difference between the outgoing light exiting the exit surface of the light guide and the normal direction to the exit surface of the light guide, are θ degrees to 90-θ degrees in the YZ plane.

[0078] (11) In any one of the head-up display systems (1) to (10), the light-transmitting member has a curved surface, and at least a portion of the area where the light beam emitted from the light guide is incident is tilted with respect to the cross-sectional view of the XZ plane and the cross-sectional view of the YZ plane.

[0079] (12) In the head-up display system of (2), at least one of the combined region, the first expansion region, and the second expansion region includes a volume hologram.

[0080] (13) In the head-up display system of (2), the coupling region, the first expansion region, and the second expansion region are regions having diffractive structures, and the magnitudes of the wave vectors of the respective diffractive structures are different.

[0081] (14) In the head-up display system of any one of (1) to (13), the light-transmitting member is a windshield of a moving body. In this way, the head-up display system can be applied as a head-up display system for a moving body.

[0082] (15) A head-up display system according to the present disclosure displays a virtual image superimposed on a real scene visible through a light-transmitting member, and includes: a display unit that emits a light beam that is viewed by an observer as a virtual image; and a light guide that guides the light beam to the light-transmitting member. The light guide has an incident surface on which the light beam from the display unit is incident; a combining region that changes the traveling direction of the light beam incident on the incident surface; a first expansion region that expands the viewing area by replicating the light beam propagated from the combining region into multiple light beams in a first direction; a second expansion region that expands the viewing area by replicating the light beam replicated in the first expansion region into multiple light beams in a second direction intersecting the first direction; and an exit surface from which the light beam replicated in the second expansion region exits. The central ray of the light beam emitted from the display unit is incident at an angle with respect to the normal direction of the incident surface of the light guide. When the direction in which an observer views the virtual image from the viewing region of the virtual image is defined as the Z-axis direction, the horizontal direction perpendicular to the Z-axis is defined as the X-axis direction, and the direction perpendicular to the XZ plane formed by the X-axis and Z-axis is defined as the Y-axis direction, in the light guide, a light beam that enters the coupling region and has its traveling direction changed propagates to the first extended region, where it is replicated in the first direction and propagates to the second extended region, where it is replicated in the second direction and emitted from the exit surface. The central light ray of the light beam that exits the light guide exits toward the light-transmitting member at an angle with respect to the normal direction of the exit surface of the light guide. The exit port of the display unit is located closer to the center line of the vehicle in the vehicle width direction than the exit surface of the light guide. [Industrial Applicability]

[0083] The present disclosure is applicable to a head-up display system that displays a virtual image in front of a translucent member. [Explanation of symbols]

[0084] 1 Head-up display system 3 vehicles 3a center line 5 Windshield 11 Display section 13, 13A Light guide 13a First main surface 13b Second principal surface 15 Control Unit 17 Storage device 20 Entrance plane 21 Combined area 23, 23A First expansion area 23p points 25, 25A Second expansion area 25p points 27 Exit surface Ac Visibility Zone D. Observer IV Virtual Image k1, k2, k3 wave vectors L1, L2 luminous flux α, β angle difference

Claims

1. A head-up display system that displays a virtual image superimposed on a real scene visible through a light-transmitting member, a display unit that emits a light beam that is visually recognized by an observer as the virtual image; a light guide that guides the light beam to the light-transmitting member, the light guide has an incident surface onto which the light flux from the display unit is incident and an exit surface from which the light flux exits the light guide, a central ray of the light flux emitted from the display unit is incident on the light guide body at an angle with respect to a normal direction to the incident surface, When the direction in which the observer views the virtual image from the viewing area of ​​the virtual image is defined as a Z-axis direction, the horizontal direction perpendicular to the Z-axis is defined as an X-axis direction, and the direction perpendicular to the XZ plane formed by the X-axis and the Z-axis is defined as a Y-axis direction, The light beam incident on the incident surface of the light guide is changed in its traveling direction within the light guide, and is emitted from the exit surface so as to expand a viewing area by duplicating the light beam into a plurality of light beams in horizontal and vertical directions of the virtual image viewed by the observer, a central ray of the light flux emitted from the light guide is emitted toward the light-transmitting member at an angle with respect to a normal direction to the light-emitting surface of the light guide, the light-transmitting member is inclined with respect to the X-axis in a cross-sectional view of the XZ plane, When a direction of a normal line of the light-transmitting member at an intersection of the light-transmitting member and the Z axis toward the visible area is defined as direction A, and a direction connecting the center of the visible area of ​​the virtual image and the exit port of the display unit is defined as direction B, The A direction and the B direction intersect between the visible region and the light-transmitting member in the XZ plane. Head-up display system.

2. the light guide includes a coupling region that changes the traveling direction of the light beam incident on the incident surface, a first extension region that replicates the light beam whose traveling direction has been changed in the coupling region in a first direction within the light guide, and a second extension region that replicates the light beam replicated in the first extension region in a second direction intersecting the first direction within the light guide, the coupling region, the first extension region, and the second extension region each have a different diffraction power and a different diffraction angle; The light beam replicated in the second expansion region is emitted from the exit surface. The head-up display system of claim 1 .

3. The second extension region is a diffraction region surrounded by four or more straight lines or curves having different angles or lengths. The head-up display system of claim 2 .

4. a side of the first expansion region on the side of the second expansion region extends along a side of the second expansion region on the side of the first expansion region; The head-up display system according to claim 2 or 3.

5. the light guide is inclined with respect to the Z axis in a cross-sectional view of a YZ plane formed by the Y axis and the Z axis, the light guide is disposed at an angle relative to the light-transmitting member in a cross-sectional view taken along the YZ plane, and the light beam emitted from the light guide is incident on the light-transmitting member at an angle relative to the Z axis in a cross-sectional view taken along the YZ plane. A head-up display system according to any one of claims 1 to 4.

6. a distance on the Z axis from the viewing area to the incident surface is longer than a distance on the Z axis from the viewing area to the exit surface; A head-up display system according to any one of claims 1 to 5.

7. the light guide is disposed below a viewing area of ​​the observer, The light guide is inclined in a cross-sectional view of a YZ plane formed by the Y axis and the Z axis so that a side of the light output surface of the light guide that is closer to the viewing area is closer to the Z axis than a side that is farther from the viewing area. A head-up display system according to any one of claims 1 to 6.

8. an incident angle of the light beam emitted from the light guide with respect to the light-transmitting member in a YZ plane formed by the Y axis and the Z axis is equal to or greater than 45 degrees and equal to or less than 75 degrees; an inclination angle of the light guide with respect to the Y axis is greater than an incident angle of the light beam to the light-transmitting member and is less than 175 degrees; A head-up display system according to any one of claims 1 to 7.

9. The light beam emitted from the display unit is emitted toward a quadrant in which the visible area exists, with the display unit as a center, in either or both of the XZ plane and the YZ plane formed by the Y axis and the Z axis. A head-up display system according to any one of claims 1 to 8.

10. If the angular range in which the observer views the virtual image on the YZ plane formed by the Y axis and the Z axis is +θ degrees to −θ degrees around the Z axis, then: one or both of an angular difference between the incident light incident on the incident surface of the light guide and the normal direction of the incident surface of the light guide and an angular difference between the emitted light emitted from the emission surface of the light guide and the normal direction of the emission surface of the light guide is θ degrees to 90-θ degrees in the YZ plane; A head-up display system according to any one of claims 1 to 9.

11. the light-transmitting member has a curved surface, and a part of an area onto which the light flux emitted from the light guide is incident is inclined with respect to a cross-sectional view of the XZ plane and a cross-sectional view of a YZ plane formed by the Y axis and the Z axis; A head-up display system according to any one of claims 1 to 10.

12. At least one of the coupling region, the first expansion region, and the second expansion region includes a volume hologram. The head-up display system of claim 2 .

13. the coupling region, the first extension region, and the second extension region are regions having diffractive structures, and the magnitudes of the wave vectors of the respective diffractive structures are different. The head-up display system of claim 2 .

14. The light-transmitting member is a windshield of a moving object. A head-up display system according to any one of claims 1 to 13.

15. A head-up display system that displays a virtual image superimposed on a real scene visible through a light-transmitting member, a display unit that emits a light beam that is visually recognized by an observer as the virtual image; a light guide that guides the light beam to the light-transmitting member, the optical element includes an incident surface onto which a light beam from a display unit is incident, a combining region that changes the traveling direction of the light beam incident on the incident surface, a first expansion region that expands a viewing region by duplicating the light beam propagated from the combining region into a plurality of light beams in a first direction, a second expansion region that expands the viewing region by duplicating the light beam duplicated in the first expansion region into a plurality of light beams in a second direction intersecting with the first direction, and an exit surface from which the light beam duplicated in the second expansion region exits, a central ray of the light flux emitted from the display unit is incident on the light guide body at an angle with respect to a normal direction to the incident surface, When the direction in which the observer views the virtual image from the viewing area of ​​the virtual image is defined as a Z-axis direction, the horizontal direction perpendicular to the Z-axis is defined as an X-axis direction, and the direction perpendicular to the XZ plane formed by the X-axis and the Z-axis is defined as a Y-axis direction, In the light guide, the light beam that has entered the coupling region and has its traveling direction changed propagates to the first expansion region, where it replicates the light beam in the first direction and propagates to the second expansion region, and in the second expansion region, it replicates the light beam in the second direction and is emitted from the exit surface, a central ray of the light flux emitted from the light guide is emitted toward the light-transmitting member at an angle with respect to a normal direction of the emission surface of the light guide, an exit port of the display unit is disposed closer to a center line of the vehicle in a vehicle width direction than the exit surface of the light guide body; Head-up display system.

Images