Head-up display

Abstract

This invention provides a head-up display that can display projected images according to the observer's height while suppressing the need for larger mirrors. [Solution] The head-up display 1 is a head-up display 1 that forms a virtual image by projecting display light onto a display medium, and comprises a display element 21 from which display light that becomes a projected image on the display medium when an image is displayed, and a mirror 30 that guides the display light emitted from the display element 21 onto the display medium, thereby forming a virtual image on the opposite side of the viewer from the display medium, and the display element 21 displays the image in such a way that the position of the center point of the image corresponding to the center point of the virtual image moves.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a head-up display mounted on, for example, a vehicle or the like. BACKGROUND ART

[0002] Conventionally, a display device that is a head-up display mounted on, for example, a vehicle or the like has been proposed (see Patent Document 1). The display device of Patent Document 1 includes: a display unit that emits light constituting an image; a reflection unit that reflects the light emitted from the display unit toward an eye point of an occupant of the vehicle; and a position variable unit that makes a light emission position of the display unit variable according to the position of the eye point, such that light incident on a fixed position of the reflection unit is reflected toward the position of the eye point that varies within an eye range. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2024-155802 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In the conventional display device of Patent Document 1, the display position can be shifted by rotating the main mirror mounted on the head-up display. Therefore, the projected image can be displayed according to the height of the observer.

[0005] However, in the conventional art, since a mechanism for rotating the main mirror is mounted, the main mirror is also likely to vibrate due to vibration of the vehicle. In this case, the projected image is blurred, and the virtual image that is the projected image becomes difficult to see. If the main mirror is fixed to the housing and the main mirror is enlarged, the projected image can be displayed according to the height of the observer, but there is a problem that the main mirror becomes larger in size.

[0006] Therefore, the present disclosure aims to provide a head-up display that can display a projected image according to the observer's height while suppressing the need to enlarge the mirror. [Means for solving the problem]

[0007] A head-up display according to one aspect of the present disclosure is a head-up display that forms a virtual image by projecting display light onto a display medium, comprising: a display element that emits display light which becomes a projected image on the display medium by displaying an image; and a mirror that guides the display light emitted from the display element onto the display medium so as to form the virtual image on the opposite side of the display medium from the observer, wherein the display element displays the image such that the position of the center point of the image corresponding to the center point of the virtual image is moved. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, a head-up display can be used to display a projected image according to the observer's height while suppressing the need for a larger mirror. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view showing a head-up display according to an embodiment mounted in a vehicle. [Figure 2] Figure 2 is a cross-sectional view showing the windshield and head-up display. [Figure 3] Figure 3 is a cross-sectional view showing the windshield and the head-up display when the mirror is only the primary mirror. [Figure 4] Figure 4 shows the relationship between the display surface of the display element and the virtual image projected onto the windshield. [Figure 5A] Figure 5A shows the difference between the case where the direction of the display light emitted by the image generation unit is not changed and the case where the direction of the display light emitted by the image generation unit is changed. [Figure 5B]Figure 5B shows the relationship between the display surface of the display element and the virtual image projected onto the windshield. [Figure 6A] Figure 6A shows the relationship between the virtual image, the principal axis, and the eyebox. [Figure 6B] Figure 6B shows the relationship between viewing distance and the size of the primary mirror. [Figure 7] Figure 7 shows the virtual image projected onto the windshield when the orientation of the optical axis of the display light emitted by the image generation unit and the position of the image displayed by the display element are changed. [Figure 8] Figure 8 is an explanatory diagram regarding back reflection. [Figure 9] Figure 9 shows the simulation results illustrating the luminous flux of the display light. [Figure 10] Figure 10 is an explanatory diagram regarding the optical performance of the secondary mirror. [Figure 11] Figure 11 shows the amount of virtual image blur when the primary mirror is semi-fixed and the amount of virtual image blur when the primary mirror is fixed. [Figure 12] Figure 12 is an explanatory diagram illustrating the blurring of virtual images. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the drawings.

[0011] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions of components, and connection configurations shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, any components in the following embodiments that are not described in an independent claim will be described as optional components.

[0012] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Also, the same component is denoted by the same reference numeral in each figure.

[0013] Further, in the following embodiments, in Figure 2, the front side of the vehicle is defined as the forward direction, the right side when viewed along the front of the vehicle is defined as the rightward direction, and the direction perpendicular to the forward direction and the rightward direction, with the vertically upward direction defined as the upward direction. The directions in Figure 2 are also applied to the drawings from Figure 3 onwards. In the following embodiments, the front-rear direction is synonymous with the full length direction of the vehicle, and the left-right direction is synonymous with the width direction of the vehicle.

[0014] Further, in the following embodiments, expressions such as rectangular shape and upward direction are used. For example, the terms rectangular shape and upward direction not only mean a perfect rectangle and a perfectly upward direction, but also mean a substantially rectangular shape and a substantially upward direction, that is, including an error of about several percent. In addition, the rectangular shape and upward direction mean a rectangle and an upward direction within the range where the effects of the present disclosure can be achieved. The same applies to other expressions using "shape" and "direction".

[0015] (Embodiment) <Configuration and Functions> Hereinafter, the configuration and functions of the head-up display 1 according to the embodiment will be described with reference to Figures 1 to 3.

[0016] Figure 1 is a perspective view showing the head-up display 1 according to the embodiment mounted on a vehicle. Figure 2 is a cross-sectional view showing a windshield 3 and the head-up display 1. Figure 3 is a cross-sectional view showing the windshield 3 and the head-up display 1 in a case where a mirror 30 consists only of a main mirror 31.

[0017] As shown in Figure 1, the head-up display 1 is mounted on a vehicle 2, projects an image onto a display medium capable of transmitting and reflecting display light, and can form a virtual image on the side opposite to the observer with respect to the display medium.

[0018] For example, the head-up display 1 can display a virtual image represented by the display light to an observer, such as the driver, by reflecting the display light representing the projected image emitted from the image generation unit 20 onto a display medium such as the windshield 3 or a translucent combiner. In other words, the head-up display 1 can display the projected image indicated by the display light on the windshield 3 by projecting the display light emitted from the image generation unit 20 in front of the windshield 3. As a result, the projected image projected onto the windshield 3 of the vehicle 2 is visible to the observer. Figures 1 and onward of this embodiment illustrate the case in which the head-up display 1 projects image light onto the windshield 3.

[0019] Here, the display light is light that represents a projected image including numbers, letters, and figures, and is displayed as a virtual image in front of the windshield 3. The projected image can be a still image or a moving image, and is an image of numbers, letters, and figures.

[0020] As shown in Figure 2, the head-up display 1 comprises a housing 10, an image generation unit 20, one or more mirrors 30, and a cover 40.

[0021] The housing 10 is a housing that accommodates the image generation unit 20 and one or more mirrors 30. The housing 10 constitutes the outer shell of the head-up display 1. The housing 10 is fixed to the vehicle 2 either when mounted on the dashboard 5 or when mounted on a bracket located on the vehicle reinforcement. The housing 10 is made of resin material or metal material.

[0022] An opening for positioning the cover 40 is formed on the upper side of the housing 10. Display light consisting of the projected image generated by the image generation unit 20 passes through the opening.

[0023] The image generation unit 20 generates a projected image and outputs display light that represents the generated projected image so that the projected image is displayed on the windshield 3. Specifically, the image generation unit 20 emits display light from the display element 21. The display light emitted from the display element 21 of the image generation unit 20 is reflected by one or more mirrors 30, passes through the opening, enters the cover 40, passes through the cover 40, and is then emitted from the head-up display 1 to be projected onto the windshield 3. In other words, the image generation unit 20 can project a projected image onto the windshield 3 by emitting display light. The reflection of the display light from the windshield 3 allows the observer to perceive a virtual image. The image generation unit 20 is, for example, a liquid crystal display device having a liquid crystal display or the like.

[0024] The image generation unit 20 includes a display element 21, a container 22, a light-emitting module 23, and a focusing lens 24.

[0025] The display element 21 is a liquid crystal display element such as a liquid crystal display. However, the display element 21 may also be a device other than a liquid crystal display, such as an organic light-emitting diode (electroluminescent diode).

[0026] The display element 21 can display an image. In this case, the display element 21 emits light from its back surface when light from the light-emitting module 23 is shone on it, and display light that forms the projected image is emitted. Specifically, the display element 21 emits display light from its emitter surface that shows a projected image including numbers, characters, and figures, in response to control instructions from the ECU (Electronic Control Unit) mounted in the vehicle 2. The display element 21 is driven by DC power obtained from the power supply unit inside the vehicle 2.

[0027] The container 22 is a housing that contains the display element 21, the light-emitting module 23, and the light-gathering lens 24. The container 22 is located on the bottom plate of the housing 10.

[0028] The light-emitting module 23 has multiple light sources and a substrate on which the multiple light sources are mounted. Each of the multiple light sources is mounted on the substrate. The substrate is held so as to irradiate light from the back of the display element 21 toward the display element 21 via a focusing lens 24. Each of the multiple light sources is composed of, for example, a light-emitting diode. For example, each of the multiple light sources is driven by DC power obtained from a power supply unit in the vehicle 2.

[0029] The focusing lens 24 is positioned on the side of the light emission direction of each of the multiple light sources and is located in the optical path between each of the multiple light sources and the display element 21. The focusing lens 24 has multiple lenses that correspond one-to-one with the multiple light sources. Each of the multiple lenses can emit light emitted from each of the multiple light sources toward the display element 21.

[0030] As shown in Figure 3, one or more mirrors 30 may include only a primary mirror 31.

[0031] The primary mirror 31 may reflect the display light emitted by the image generation unit 20 toward the cover 40. In other words, the primary mirror 31 can form a virtual image on the opposite side of the windshield 3 from the observer by guiding the display light, which becomes the projected image emitted by the image generation unit 20, toward the windshield 3.

[0032] The primary mirror 31 is pivotable so as not to affect the observer's eyebox. For example, when the observer does not see the virtual image, such as when the vehicle is parked, the primary mirror 31 may be rotated to avoid adverse effects from sunlight. The primary mirror 31 and the image generation unit 20 may be arranged in the housing 10 so as to face each other at a predetermined distance apart. The primary mirror 31 is positioned in the housing 10 in an upright position along the vertical direction.

[0033] Specifically, the primary mirror 31 may be positioned on the front side of the housing 10 so as to face the output surface of the image generation unit 20, which is located on the rear side of the housing 10. In other words, the primary mirror 31 may be positioned parallel to the image generation unit 20 along the front-to-back direction. The primary mirror 31 may be a concave mirror having a free-form surface.

[0034] Furthermore, in this embodiment, the primary mirror 31 may be a rectangular mirror that is elongated in the left-right direction. The shape of the primary mirror 31 is not particularly limited and may be polygonal or circular.

[0035] As shown in Figure 2, one or more mirrors 30 may include a primary mirror 31 and a secondary mirror 32.

[0036] The secondary mirror 32 may reflect the display light emitted by the image generation unit 20 toward the primary mirror 31. Alternatively, the primary mirror 31 may reflect the display light emitted by the image generation unit 20, which has been reflected by the secondary mirror 32, toward the cover 40. In other words, the primary mirror 31 can form a virtual image on the side opposite the observer relative to the windshield 3 by guiding the display light, which becomes the projected image emitted by the image generation unit 20, toward the windshield 3.

[0037] The primary mirror 31 and the secondary mirror 32 are pivotable so as not to affect the observer's eyebox. The primary mirror 31 and the secondary mirror 32 may be arranged in the housing 10 so as to face each other at a predetermined distance apart.

[0038] Specifically, the secondary mirror 32 may be positioned on the rear side of the housing 10 so as to face the primary mirror 31 and the output surface (display element 21) of the image generation unit 20, which is located on the rear side of the housing 10. The primary mirror 31 and the secondary mirror 32 may be positioned between the image generation unit 20 and the aperture. The primary mirror 31 may face the secondary mirror 32 and be positioned further forward than the secondary mirror 32. In other words, the primary mirror 31 may be positioned parallel to the secondary mirror 32 along the front-to-back direction. The secondary mirror 32 is positioned in the housing 10 in an upright position along the vertical direction.

[0039] The secondary mirror 32 may be a concave mirror or a convex mirror. The primary mirror 31 may be a concave mirror having a free-form surface.

[0040] The secondary mirror 32 may have a convex curve in the direction corresponding to the left-right direction of the virtual image, and a convex curve in the direction corresponding to the up-down direction of the virtual image. In other words, the secondary mirror 32 may be convexly curved toward the front when viewed from the left-right direction, and convexly curved toward the front when viewed from the up-down direction.

[0041] Furthermore, the secondary mirror 32 may be curved in a convex or concave shape in the direction corresponding to the left-right direction of the virtual image, and curved in a concave shape in the direction corresponding to the up-down direction of the virtual image. In other words, the secondary mirror 32 may be curved in a concave shape toward the front when viewed from the left-right direction, and curved in a convex or concave shape toward the front when viewed from the up-down direction.

[0042] Furthermore, in this embodiment, the primary mirror 31 and the secondary mirror 32 may each be rectangular mirrors that are elongated in the left-right direction. The shapes of the primary mirror 31 and the secondary mirror 32 are not particularly limited and may be polygonal or circular.

[0043] In this embodiment, if the head-up display 1 comprises a primary mirror 31 and a secondary mirror 32, the display element 21 may be positioned within the combined focal length of the primary mirror 31 and the secondary mirror 32 from the principal point position. The principal point position is a reference point in the head-up display 1 when considered as a single imaging optical system consisting of at least the primary mirror 31 and the secondary mirror 32, and functions as the base point for the display light. The imaging optical system may further include a display medium. By adjusting the combined focal length of the primary mirror 31 and the secondary mirror 32, a virtual image can be displayed in front of the windshield 3.

[0044] Furthermore, in the head-up display 1 of this embodiment, the distance of the central optical path from the display element 21 to the windshield 3 may be set to be shorter than the distance from the observer to the virtual image. In this case, the virtual image can be displayed at an appropriate position. Also, by setting the position of the virtual image to a distance that is natural for the observer, eye strain can be reduced and the movement of the gaze can be minimized. The central optical path is the optical path connecting the center of the image shown by the display light and the center of the virtual image.

[0045] Furthermore, in the head-up display 1 of this embodiment, the first horizontal ratio (ratio in the left-right direction) indicated by the aspect ratio of the virtual image is smaller than the second horizontal ratio (ratio in the X-axis direction, described later) indicated by the aspect ratio of the display element 21. Also, the first vertical ratio (ratio in the up-down direction) indicated by the aspect ratio of the virtual image is larger than the second vertical ratio (width in the Y-axis direction, described later) indicated by the aspect ratio of the display element 21. In other words, when a is the horizontal size in the X-axis direction of the display surface 21a of the display element 21 corresponding to the left-right direction of the virtual image, b is the vertical size in the Y-axis direction of the display surface 21a corresponding to the up-down direction of the virtual image, A is the size in the left-right direction of the virtual image, and B is the size in the up-down direction of the virtual image, the relationship a / b ≥ A / B exists.

[0046] In this case, the focal length of the imaging optical system corresponding to the left-right direction of the virtual image is made longer than the focal length of the imaging optical system corresponding to the up-down direction of the virtual image. The focal length here may be the focal length when the primary mirror 31, secondary mirror 32, and windshield 3 are considered as a single imaging optical system, or the focal length when the primary mirror 31 and secondary mirror 32 are considered as a single imaging optical system. Furthermore, if the secondary mirror 32 is planar, or if only the primary mirror 31 is used without the secondary mirror 32, the focal length may be the focal length of the primary mirror 31 alone.

[0047] The distance of the central optical path from the principal point to the display element 21 is set to be shorter than the distance of the central optical path from the principal point to the windshield 3. In this case, by positioning the display element 21 close to the principal point, the viewing distance can be extended, allowing the observer to instantly focus on the displayed virtual image even when shifting their gaze from the foreground to the virtual image, thus contributing to the safety and security of the vehicle.

[0048] Next, the configuration and functions of the head-up display 1 will be explained in more detail with reference to Figure 4.

[0049] Figure 4 shows the relationship between the display surface 21a of the display element 21 and the virtual image projected onto the windshield 3. In Figure 4, the image is shown as viewed from the light source side of the display element 21. Figure 4(a) shows the correspondence between the observer's height and the position of the image displayed on the display element 21. Figure 4(b) shows the correspondence between the image displayed on the display element 21 in Figure 4(a) and the virtual image projected onto the windshield 3.

[0050] Figure 4 illustrates images shown with solid lines for an observer of the first height (Middle), dashed lines for an observer of the second height (Taller), and dashed lines for an observer of the third height (Shorter). In Figure 4, the positive X-axis corresponds to the rightward direction of the virtual image, the negative X-axis corresponds to the leftward direction of the virtual image, the positive Y-axis corresponds to the downward direction of the virtual image, and the negative Y-axis corresponds to the upward direction of the virtual image. Figure 4 is merely an example, and the correspondence between the left-right direction of the virtual image and the XY direction of the image is not necessarily limited to Figure 4.

[0051] In this embodiment, the observer's height was described using three categories, but this is merely an example. For example, the display element 21 may be configured to divide the observer's height into two categories, or into four or more categories.

[0052] As shown in Figure 4(a), the display element 21 of this embodiment is configured to move the displayed image by moving the position of the center point of the image corresponding to the center point of the virtual image. For example, the display element 21 can move the position of the image along the Y-axis so as to project display light onto the observer's eye box according to the observer's height.

[0053] The display surface 21a of the display element 21 can be defined by the X-axis and the Y-axis, as shown in Figure 4(a). As described above, the X-axis corresponds to the left-right direction of the virtual image when the virtual image is projected onto the windshield 3. The Y-axis corresponds to the up-down direction of the virtual image when the virtual image is projected onto the windshield 3.

[0054] Figure 4(a) illustrates three center points. The center point closest to the positive Y-axis corresponds to the second height, the center point closest to the negative Y-axis corresponds to the third height, and the center point located between these two corresponds to the first height.

[0055] For example, the display element 21 can move the position of the center point of the image in a second direction that intersects the first direction. In other words, the display element 21 can move the position of the center point of the image displayed on the display surface 21a in the positive Y-axis direction or in the negative Y-axis direction. The Y-axis direction is an example of a second direction.

[0056] For example, as shown in Figures 4(a) and 4(b), when the display element 21 aligns the center point of the image indicated by the dashed line displayed on the display surface 21a with the center point of the display surface 21a, the display light of the image is incident on the first position W1 of the windshield 3, and a virtual image is displayed at the position corresponding to the first position W1. In this way, the display element 21 can adjust the position of the image to be displayed so that the display light illuminates the central part of the primary mirror 31 relative to the eye box of an observer of first height.

[0057] For example, if the display element 21 moves the center point of the image indicated by the solid line displayed on the display surface 21a in the positive Y-axis direction, the display light of the image will be incident on a second position W2 above the first position W1 on the windshield 3, and a virtual image will be displayed at the position corresponding to the second position W2. In this way, the display element 21 can adjust the position of the displayed image so that the display light illuminates the central part of the primary mirror 31 relative to the eye box of a second-height observer.

[0058] For example, if the display element 21 moves the center point of the image indicated by the dashed line displayed on the display surface 21a downward relative to the center point of the display surface 21a, the display light of the image will be incident on a third position W3 below the first position W1 on the windshield 3, and a virtual image will be displayed at the position corresponding to the third position W3. In this way, the display element 21 can adjust the position of the displayed image so that the display light illuminates the central part of the primary mirror 31 relative to the eye box of an observer of third height.

[0059] This makes it possible to suppress an increase in the vertical size of the primary mirror 31.

[0060] In the above description, we explained the case in which the position of the image displayed by the display element 21 is moved along the Y-axis. However, in this embodiment, the position of the image displayed by the display element 21 may also be moved along the X-axis. In other words, the display element 21 may change the position of the image it displays on the display surface 21a.

[0061] The display element 21 can move the position of the center point of the image in a first direction. In other words, the display element 21 can move the position of the center point of the image displayed on the display surface 21a in the positive X-axis direction or the negative X-axis direction. The X-axis direction is an example of the first direction.

[0062] For example, in this embodiment, as shown in Figures 5A and 5B, the direction of the emitted display light may be adjusted by shifting the display position of the image in the X-axis direction.

[0063] Figure 5A shows the difference between the case where the direction of the display light emitted by the conventional image generation unit is not changed and the case where the direction of the display light emitted by the image generation unit 20 is changed. The direction of the display light is indicated by the arrow in Figure 5A. Figure 5B shows the relationship between the display surface 21a of the display element 21 and the virtual image projected onto the windshield 3. Figure 5B(a) shows the correspondence between the observer's height and the position of the image displayed on the display element 21. Figure 5B(b) shows the correspondence between the image displayed on the display element 21 in Figure 5B(a) and the virtual image projected onto the windshield 3.

[0064] Figure 5B illustrates the images shown by solid lines for an observer of the first height (Middle), dashed lines for an observer of the second height (Taller), and dashed lines for an observer of the third height (Shorter). In Figure 5B, the positive X-axis corresponds to the left direction of the virtual image, the negative X-axis corresponds to the right direction of the virtual image, the positive Y-axis corresponds to the downward direction of the virtual image, and the negative Y-axis corresponds to the upward direction of the virtual image. Figure 5B is merely an example, and the correspondence between the left-right direction of the virtual image and the X and Y directions of the image is not necessarily limited to Figure 5B.

[0065] Figure 5A(a) shows a conventional technology where the direction of the display light is not adjusted. In this case, the direction of the display light emitted from the image generation unit 20 to the primary mirror 31 is different for the first height (Middle), the second height (Taller), and the third height (Shorter) observers. However, in Figure 5A(a), when a virtual image is displayed on the windshield, the position of the virtual image is shifted laterally due to the difference in the observer's height. In this case, with an AR (Augmented Reality) head-up display that superimposes the foreground and the display of the head-up display 1, a lateral shift occurs due to the difference in height.

[0066] On the other hand, Figure 5A(b) shows this embodiment, where the direction of the display light is adjusted.

[0067] In this case, as shown in Figure 5A(b) and Figure 5B(a), the position of the display light incident on the primary mirror 31 can be changed by moving the position of the image displayed on the display surface 21a along the X and Y axes. In other words, by changing the display position, the position of the display light incident on the primary mirror 31 can be moved vertically or horizontally. For example, the central optical path of the display light emitted from the display element 21 can be moved along the vertical direction of the primary mirror 31, which corresponds to the vertical direction of the virtual image, and can be moved along the horizontal direction of the primary mirror 31, which corresponds to the left-right direction of the virtual image. Therefore, the position of the display light incident on the windshield 3 can be changed vertically.

[0068] For example, as shown in Figures 5B(a) and (b), when the display element 21 aligns the center point of the image indicated by the dashed line displayed on the display surface 21a with the center point of the display surface 21a, the display light of the image is incident on the first position W1 of the windshield 3, and a virtual image is displayed at the position corresponding to the first position W1. In this way, the display element 21 can adjust the position of the image to be displayed so that the display light illuminates the central part of the primary mirror 31 relative to the eye box of an observer of first height.

[0069] For example, if the display element 21 moves the center point of the image indicated by the solid line displayed on the display surface 21a in the positive Y-axis direction, the display light of the image will be incident on a second position W2 above the first position W1 on the windshield 3, and a virtual image will be displayed at the position corresponding to the second position W2. In this way, the display element 21 can adjust the position of the displayed image so that the display light illuminates the central part of the primary mirror 31 relative to the eye box of a second-height observer.

[0070] For example, if the display element 21 moves the center point of the image indicated by the dashed line displayed on the display surface 21a downward relative to the center point of the display surface 21a, the display light of the image will be incident on a third position W3 below the first position W1 on the windshield 3, and a virtual image will be displayed at the position corresponding to the third position W3. In this way, the display element 21 can adjust the position of the displayed image so that the display light illuminates the central part of the primary mirror 31 relative to the eye box of an observer of third height.

[0071] In this case, by moving the position of the image displayed on the display surface 21a along the X-axis, the position of the display light incident on the primary mirror 31 can be changed horizontally, thereby changing the position of the projected image of the display light incident on the windshield 3. Also, by moving the position of the image displayed on the display surface 21a along the Y-axis, the position of the display light incident on the primary mirror 31 can be changed vertically, thereby changing the position of the projected image of the display light incident on the windshield 3.

[0072] This makes it possible to suppress the increase in size of the primary mirror 31 in the left-right direction.

[0073] Here, referring to Figures 6A and 6B, we present the results of a geometric calculation of how much the central optical path of the virtual image moves around the eyebox.

[0074] Figure 6A shows the relationship between the virtual image, the principal axis, and the eyebox. Figure 6B shows the relationship between the viewing distance and the size of the primary mirror 31.

[0075] In Figure 6A, since the power (refractive force) of windshield 3 is small, for simplicity, we treat the power of windshield 3 as zero and assume that the primary mirror position and the position of windshield 3 are equal.

[0076] First, let φ be the angle between the virtual image and the edge of the eyebox, relative to a straight line V1 parallel to the front-to-back direction, let x be the size of the eyebox from the line V1 to the top edge of the eyebox, let d be the distance from the position of the primary mirror 31 on the line V1 to the line V2, let L be the distance from the intersection point P of a line drawn from the eyebox perpendicular to the line V1 to the virtual image, and let K be the distance from the intersection point P to the windshield 3. Distance d is the distance from the line V1 to the center point of the projected image when the display light is projected onto the highest point of the windshield 3. Distance L is the viewing distance from the eyebox to the virtual image. Distance K is the central optical path length of the display light from the eyebox to the point corresponding to the primary mirror 31 (in other words, the windshield 3).

[0077] in this case, tanφ = X / L tanφ = d / (LK) It is possible to derive this.

[0078] The two equations derived above are: x / L = d / (LK) And further d = x / L*(LK) And further d = x(1-K / L) This is the result.

[0079] For example, in the head-up display 1, since it is configured to project an enlarged image onto the display medium, it is conceivable that the amount of movement in the projected image projected onto the windshield 3 will be greater than the distance d.

[0080] Therefore, if we let D be the amount of movement of the center point of the projected image projected onto the windshield 3, D > x(1-K / L) (Equation 1) That's all you need to do.

[0081] This relationship also holds true at the periphery of the virtual image, so the magnification amount D of the primary mirror 31 for projecting display light onto the observer's eye box can be treated as D. Therefore, in the head-up display 1, the magnification amount D of the primary mirror 31 for illuminating display light onto the eye box must satisfy equation (1), where x is the size of the eye box, L is the distance, and K is the distance.

[0082] Furthermore, the value obtained by dividing the display range L in the direction on the display surface 21a corresponding to the vertical direction of the virtual image by the amount of movement D of the center of the image along the direction on the display surface 21a corresponding to the amount of vertical movement in the virtual image may be 100 or less. The "direction on the display surface 21a corresponding to the vertical direction of the virtual image" and the "direction on the display surface 21a corresponding to the amount of vertical movement in the virtual image" are the Y-axis direction. The display range L of the display element 21 means the width along the Y-axis direction on the display surface 21a.

[0083] Regarding viewing distance, as shown in Figure 6B, when the viewing distance is increased while keeping the eyebox size constant, there is a tendency for the size of the primary mirror 31 to increase by the amount the viewing distance increases. For example, if the virtual image is at a distance of 2.0m from the eyebox, the size of the primary mirror 31 will be as shown by the hatched area. However, if the virtual image is at a distance of 2.2m from the eyebox, the size of the primary mirror 31 will increase by the amount shown by the solid line in the dashed circle. Therefore, when considering the size of the primary mirror 31, it is necessary to consider the viewing distance.

[0084] In the above description, we explained the case in which the image displayed by the display element 21 is moved along the X and Y axes. However, in this embodiment, as shown in Figure 7, in addition to changing the position of the image, it may also be possible to change the direction of the optical axis of the display light emitted by the image generation unit 20. The optical axis is the direction of emission of the main light emitted by the image generation unit 20.

[0085] Figure 7 shows the virtual image projected onto the windshield 3 when the orientation of the optical axis of the display light emitted by the image generation unit 20 and the position of the image displayed by the display element 21 are changed.

[0086] For example, the display element 21 aligns the center point of the image indicated by the dashed line displayed on the display surface 21a with the center point of the display surface 21a, and the display element 21 emits display light so that the central optical path of the display light intersects with the central part of the primary mirror 31. In this case, as shown in Figure 7, the display light is reflected by the central part of the primary mirror 31 and incident on the first position W1 of the windshield 3, so a virtual image is displayed at the position corresponding to the first position W1. In this way, the display element 21 can adjust the position of the image to be displayed so that the display light illuminates the central part of the primary mirror 31 with respect to the eye box of an observer of first height.

[0087] For example, the display element 21 moves the center point of the image indicated by the dashed line displayed on the display surface 21a upward relative to the center point of the display surface 21a, and the display element 21 emits display light so that the central optical path of the display light intersects with the lower part of the primary mirror 31. In this case, the display light is reflected by the lower part of the primary mirror 31 and incident on the second position W2 of the windshield 3, so a virtual image is displayed at the position corresponding to the second position W2. In this way, the display element 21 can adjust the position of the displayed image so that the display light illuminates the lower part of the primary mirror 31 with respect to the eye box of a second-height observer.

[0088] For example, the display element 21 moves the center point of the displayed image, indicated by a solid line on the display surface 21a, downward relative to the center point of the display surface 21a, and emits display light so that it intersects with the upper portion of the primary mirror 31 in the display light. In this case, the display light is reflected by the lower portion of the primary mirror 31 and incident on the third position W3 of the windshield 3, so a virtual image is displayed at the position corresponding to the third position W3. In this way, the display element 21 can adjust the position of the displayed image so that the display light illuminates the lower portion of the primary mirror 31 with respect to the eye box of a third-height observer.

[0089] Furthermore, by shifting the position of the central optical path on the primary mirror 31 in the vertical direction, the display surface 21a in the Y-axis direction on the display element 21 can be miniaturized. In this embodiment, since this miniaturized display element 21 can be used, the increase in manufacturing costs can be suppressed.

[0090] In this embodiment, the head-up display 1 incorporates measures to mitigate back reflection, as shown in Figure 8.

[0091] Figure 8 is an explanatory diagram regarding back reflection. Figure 8(a) shows a head-up display without measures to prevent back reflection. Figure 8(b) shows a head-up display 1 with measures to prevent back reflection, which is an embodiment of this design.

[0092] As shown in Figure 8(a), the normal of the display element to the display surface on which the image is displayed is approximately parallel to the optical axis of the display light emitted from the display element. Therefore, when ambient light enters the head-up display and enters the image generation unit via one or more mirrors, the display element can reflect the ambient light in a direction nonparallel to the line of incidence. As a result, the ambient light reflected by the display element enters the observer's eyes via one or more mirrors and the windshield.

[0093] On the other hand, in this embodiment as shown in Figure 8(b), the normal to the display surface 21a on which the display element 21 displays an image is inclined with respect to the optical axis of the display light emitted from the display element 21. Therefore, the normal to the display surface 21a is inclined with respect to the ambient light incident on the display element 21. In other words, the display element 21 is arranged such that the normal to the display surface 21a and the incident line of ambient light incident on the display element 21 are non-parallel.

[0094] Therefore, even if ambient light enters the head-up display 1 and then enters the image generation unit 20 via one or more mirrors 30, the display element 21 can reflect the ambient light in a direction nonparallel to the line of incidence. This suppresses back reflection, which occurs when ambient light reflected by the display element 21 enters the observer's eyes via one or more mirrors 30 and the windshield 3.

[0095] <Simulation Results> Next, referring to Figure 9, we will explain the simulation results showing the luminous beam of the display light from the display element 21 to the eye box.

[0096] Figure 9 shows the simulation results illustrating the luminous flux of the display light.

[0097] Figure 9(a) shows a conventional head-up display having a primary mirror and a secondary mirror. The primary mirror in Figure 9(a) has a rotating tilt function.

[0098] Figure 9(b) shows a head-up display 1 of this embodiment having a primary mirror 31 and a secondary mirror 32. In Figure 9(b), the primary mirror 31 is fixed to the housing and does not rotate.

[0099] Figure 9(c) shows a conventional head-up display with a primary mirror. The primary mirror in Figure 9(c) has a rotating tilt function.

[0100] Figure 9(d) shows the head-up display 1 of this embodiment, which has a primary mirror 31. The primary mirror 31 in Figure 9(d) is fixed to the housing and does not rotate.

[0101] As shown in Figures 9(b) and 9(d), in the head-up display 1 of this embodiment, the width of the light beam of display light from the display element 21 to the sub-mirror 32 is larger than the width of the light beam of display light from the display element to the sub-mirror in the conventional head-up display shown in Figures 9(a) and 9(c). This is thought to be because, in this embodiment, the image moves on the display surface 21a of the display element 21.

[0102] However, in this embodiment, since the primary mirror 31 is fixed to the housing, the primary mirror 31 is less prone to vibration compared to the primary mirror 31 of the conventional head-up display 1. As a result, the projected image on the windshield 3 is less prone to blurring, and the virtual image is also less prone to blurring.

[0103] As shown in Figure 9(b), the head-up display 1 having a primary mirror 31 and a secondary mirror 32 has superior optical performance, such as distortion, compared to the head-up display 1 in Figure 9(d) which has only one primary mirror 31.

[0104] As shown in Figure 9(d), the head-up display 1 having a primary mirror 31 can be made smaller than the head-up display 1 having a primary mirror 31 and a secondary mirror 32.

[0105] Next, with reference to Figure 10, the optical performance of the secondary mirror 32 mounted on the head-up display 1 will be explained.

[0106] Figure 10 is an explanatory diagram regarding the optical performance of the secondary mirror 32. Figure 10 illustrates four patterns d1 to d4 for the secondary mirror 32.

[0107] When the reflective surface of the secondary mirror 32 is defined in the horizontal and vertical directions, the horizontal direction is along the X-axis direction of the display surface 21a, and the vertical direction is along the Y-axis direction.

[0108] In this case, patterns d1 and d2 used a secondary mirror 32 in which the shape in the direction corresponding to the vertical direction of the virtual image (the vertical direction of the secondary mirror 32) is curved in a convex shape, and the shape in the direction corresponding to the left-right direction of the virtual image (the horizontal direction of the secondary mirror 32) is curved in a convex shape. Pattern d3 used a secondary mirror 32 in which the shape in the vertical direction is curved in a convex shape, and the shape in the horizontal direction is curved in a concave shape. Pattern d4 used a secondary mirror 32 in which the shape in the vertical direction is curved in a concave shape, and the shape in the horizontal direction is curved in a concave shape.

[0109] Each of patterns d1 to d4 corresponds to the optical performance, size, configuration diagram, FOV (deg.), viewing distance (mm), LCD width x height (mm), LCD-secondary mirror 32 (mm), and secondary mirror 32-primary mirror 31 (mm).

[0110] In pattern d1, the X direction is concave (positive), the Y direction is concave (positive), and the size of the secondary mirror 32 is maximized. The optical performance was good when the configuration shown in Figure 10 was as follows: FOV (deg.) 7×3, viewing distance (mm) 7000, LCD (width × height: mm) 53.15×38.22, LCD-secondary mirror 32 (mm) 124.67, and secondary mirror 32-primary mirror 31 (mm) 195.35.

[0111] In pattern d2, the X direction is concave (positive), the Y direction is concave (positive), and the size of the secondary mirror 32 is medium. In the configuration shown in Figure 10, with an FOV (deg.) of 7 × 3, a viewing distance (mm) of 7000, an LCD (width × height: mm) of 50.85 × 38.39, an LCD-secondary mirror 32 (mm) of 210.87, and a secondary mirror 32-primary mirror 31 (mm) of 125.00, the optical performance was slightly better.

[0112] In pattern d3, the X direction is convex (negative), the Y direction is concave (positive), and the size of the secondary mirror 32 is small. In the configuration shown in Figure 10, with an FOV (deg.) of 7 × 3, a viewing distance (mm) of 7000, an LCD (width × height: mm) of 61.07 × 37.44, an LCD-secondary mirror 32 (mm) of 160.00, and a secondary mirror 32-primary mirror 31 (mm) of 130.00, the optical performance was normal.

[0113] In pattern d4, the X direction is convex (negative), the Y direction is convex (negative), and the size of the secondary mirror 32 is (small). In the configuration shown in Figure 10, with an FOV (deg.) of 7 × 3, a viewing distance (mm) of 7000, an LCD (width × height: mm) of 57.24 × 53.08, an LCD-secondary mirror 32 (mm) of 157.43, and a secondary mirror 32-primary mirror 31 (mm) of 113.00, the optical performance was slightly better.

[0114] Note that (positive) and (negative) indicate refractive power, with (positive) indicating convergence and (negative) indicating divergence.

[0115] In this embodiment, a secondary mirror 32 that is curved concavely in the lateral direction and convexly in the vertical direction is not used. This is because shortening the focal length in the Y-axis direction reduces the vertical size of the display element, resulting in insufficient optical path length in the vertical direction. This would cause the mirror to obstruct the optical path, resulting in a missing eye box. If the optical path length were extended as a countermeasure, the vertical direction of the secondary mirror 32 would become concave.

[0116] Furthermore, in this embodiment, in order to suppress the usable area in the Y-axis direction of the display element 21, it is preferable that the focal length in the X direction > the focal length in the Y direction.

[0117] Next, with reference to Figures 11 and 12, we will explain the blurring of the virtual image displayed by the head-up display 1.

[0118] Figure 11 shows the amount of virtual image blur when the primary mirror is semi-fixed and when the primary mirror 31 is fixed. Figure 12 is an explanatory diagram showing the virtual image blur.

[0119] Figure 11 shows the case when a conventional head-up display 1, which has a semi-fixed primary mirror that can rotate, is vibrated in the front-to-back direction and when it is vibrated in the up-and-down direction.

[0120] Figure 11 shows the head-up display 1 of this embodiment when the primary mirror 31 is fixed and does not require oscillation, and when it is vibrated in the front-to-back direction and in the up-and-down direction.

[0121] In Figure 11, the horizontal axis represents frequency, and the vertical axis represents the angle of the virtual image displacement.

[0122] In the conventional technology shown in Figure 11, vibrations below 100 Hz are dominant. In this case, for example, as shown in Figure 11, in the conventional head-up display 1 with the primary mirror semi-fixed, the primary mirror 31 vibrates as much as the amount of vibration β, causing the virtual image to appear blurred.

[0123] However, in Figure 11 of this embodiment, there were almost no vibrations below 100 Hz, and the frequency components of vibrations above 100 Hz were dominant. In this case, for example, as shown in Figure 11, this embodiment can suppress display blurring due to vehicle vibration, making it difficult to see blurred virtual images.

[0124] <Effects and Effects> Next, the effects and advantages of the head-up display 1 in this embodiment will be described.

[0125] The head-up display 1 of Technology 1 in this embodiment is a head-up display 1 that forms a virtual image by projecting display light onto a display medium, and comprises a display element 21 from which display light that becomes a projected image on the display medium when an image is displayed, and a mirror 30 that guides the display light emitted from the display element 21 onto the display medium, thereby forming a virtual image on the opposite side of the viewer relative to the display medium, and the display element 21 displays the image in such a way that the position of the center point of the image corresponding to the center point of the virtual image moves.

[0126] However, according to this disclosure, since the display element 21 displays the image by moving the position of the center point of the image corresponding to the center point of the virtual image, the projected image can be displayed according to the observer's height without increasing the size of the mirror 30.

[0127] Therefore, this head-up display 1 allows for the display of projected images according to the observer's height while suppressing the need to enlarge the mirror 30.

[0128] In particular, since this embodiment does not involve rotating the mirror 30, it is possible to suppress the generation of abnormal noise caused by a motor used to rotate the mirror 30, as is the case with conventional technology.

[0129] In the head-up display 1 of Technology 2 in this embodiment, the mirror 30 includes a primary mirror 31 and a secondary mirror 32, and the display element 21 is positioned within the range of the combined focal length of the primary mirror 31 and the secondary mirror 32 from the principal point position consisting of at least the primary mirror 31 and the secondary mirror 32.

[0130] According to this, by adjusting the combined focal length of the primary mirror 31 and the secondary mirror 32, a virtual image can be displayed in front of the windshield 3. Therefore, the driver, who is the observer, can see the virtual image while keeping their gaze focused on the traffic environment. This minimizes the amount of eye movement the driver has to make, and is expected to reduce distraction while driving.

[0131] In the head-up display 1 of Technology 3 in this embodiment, the distance of the central optical path from the display element 21 to the windshield 3 is shorter than the distance from the observer to the virtual image.

[0132] This allows for the display of a virtual image in an appropriate position, causing the observer to focus on that virtual image. Furthermore, by setting the virtual image at a natural distance for the observer, eye strain is reduced, and the amount of eye movement required from the driver (who is the observer) is minimized. This allows the driver to easily see the virtual image even while driving.

[0133] In the head-up display 1 of Technology 4 in this embodiment, when the horizontal size in the X-axis direction of the display surface 21a of the display element 21 corresponding to the left-right direction of the virtual image is a, the vertical size in the Y-axis direction of the display surface 21a corresponding to the up-down direction of the virtual image is b, the size in the left-right direction of the virtual image is A, and the size in the up-down direction of the virtual image is B, the relationship a / b ≥ A / B exists.

[0134] According to this, the size of the display element 21 can be reduced, thereby suppressing the increase in manufacturing costs of the head-up display 1.

[0135] In the head-up display 1 of technology 5 in this embodiment, the focal length of the imaging optical system corresponding to the left-right direction of the virtual image is longer than the focal length of the imaging optical system corresponding to the up-down direction of the virtual image.

[0136] According to this, the size of the display element 21 can be reduced, thereby suppressing the increase in manufacturing costs of the head-up display 1.

[0137] In the head-up display 1 of technology 6 in this embodiment, the distance of the central optical path from the principal point position to the display element 21 is shorter than the distance of the central optical path from the principal point position to the display medium.

[0138] According to the head-up display 1 of this embodiment, telecentricity can be improved, and a decrease in contrast of the display element 21 can be suppressed, as can brightness unevenness caused by the backlight of the image generation unit 20.

[0139] In the head-up display 1 of Technology 7 in this embodiment, the normal to the display surface 21a on which the display element 21 displays an image is inclined with respect to the optical axis of the display light emitted from the display element 21.

[0140] According to this, even if ambient light enters the head-up display 1 and then enters the image generation unit 20 via one or more mirrors 30, the display element 21 can reflect the ambient light in a direction nonparallel to the line of incidence, as shown in Figure 8(b). This suppresses back reflection, as shown in Figure 8(b), where the ambient light reflected by the display element 21 enters the observer's eyes via one or more mirrors 30 and the windshield 3.

[0141] In the head-up display 1 of technology 8 in this embodiment, the magnification amount D of the mirror 30 for projecting display light onto the observer's eye box satisfies equation (1), where x is the size of the eye box, L is the viewing distance from the eye box to the virtual image, and K is the central optical path length from the observer to the point corresponding to the mirror 30. D>x(1-K / L) Formula (1) According to this, even if the position of the image displayed on the display surface 21a is moved along the X-axis, the display light emitted from the display element 21 will still be incident on the central portion of the primary mirror 31 at the same position. When moved in this way, the angle of incidence to the primary mirror 31 will differ, and the angle of reflection reflected by the primary mirror 31 will also differ. Therefore, the position of the display light incident on the windshield 3 can be changed in the vertical direction. This makes it possible to suppress an increase in the size of the primary mirror 31 in the horizontal direction.

[0142] In the head-up display 1 of technology 9 in this embodiment, the central optical path of the display light emitted from the display element 21 moves along the direction of the mirror 30, which corresponds to the vertical direction of the virtual image.

[0143] According to this, the position of the display light incident on the windshield 3 can be changed in the vertical direction.

[0144] In the head-up display 1 of technology 10 in this embodiment, the display element 21 can move the position of the center point of the image in a first direction.

[0145] According to this, the position of the display light incident on the windshield 3 can be changed in the vertical direction (first direction).

[0146] In the head-up display 1 of technology 11 in this embodiment, the display element 21 can move the position of the center point of the image in a second direction that intersects with the first direction.

[0147] According to this, the position of the display light incident on the windshield 3 can be changed in the vertical direction (first direction).

[0148] In the head-up display 1 of technology 12 in this embodiment, the display element 21 moves the position of the center point of the image so as to project display light onto the observer's eye box according to the observer's height.

[0149] According to this, even if the observer's height changes, the virtual image can be displayed at a position appropriate to the observer's height. Therefore, by setting the position of the virtual image at a natural distance for the observer, eye strain can be reduced and eye movement can be minimized.

[0150] In the head-up display 1 of technology 13 in this embodiment, the mirror 30 is a concave mirror.

[0151] According to this method, the virtual image can be enlarged by adjusting its focal length or by focusing the display light. This allows the image displayed by the display element 21 to be displayed larger and easier to see within the field of view.

[0152] In the head-up display 1 of technology 14 in this embodiment, the mirror 30 consists only of a primary mirror 31.

[0153] This approach can help prevent the casing from becoming too large.

[0154] In the head-up display 1 of technology 15 in this embodiment, the mirror 30 includes a primary mirror 31 and a secondary mirror 32, the secondary mirror 32 being a free-form surface.

[0155] According to this, optical distortion can be corrected by the secondary mirror 32.

[0156] In the head-up display 1 of technology 16 in this embodiment, the mirror 30 includes a primary mirror 31 and a secondary mirror 32, the secondary mirror 32 being planar.

[0157] According to this, by reflecting the light rays with the secondary mirror 32, it is possible to increase the flexibility of the head-up display layout, such as avoiding vehicle components such as meters. In addition, by using a cold mirror for the secondary mirror 32, it is possible to prevent the temperature of the display elements from rising due to sunlight irradiation.

[0158] In the head-up display 1 of technology 17 in this embodiment, the secondary mirror 32 has a shape that is convex in the direction corresponding to the left-right direction of the virtual image, and a shape that is convex in the direction corresponding to the up-down direction of the virtual image, and the secondary mirror 32 has a shape that is convex or concave in the direction corresponding to the left-right direction of the virtual image, and a shape that is concave in the direction corresponding to the up-down direction of the virtual image.

[0159] According to this, the head-up display 1 has excellent optical performance, including distortion control.

[0160] In the head-up display 1 of technology 18 in this embodiment, the secondary mirror 32 is curved in a convex shape in the direction corresponding to the left-right direction of the virtual image, and curved in a convex or concave shape in the direction corresponding to the up-down direction of the virtual image.

[0161] According to this, the optical performance, such as distortion, of the head-up display 1 is superior.

[0162] In the head-up display 1 of technology 19 in this embodiment, the observer's height includes a first height, a second height that is taller than the first height, and a third height that is shorter than the first height. The mirror 30 is positioned in an upright position along the vertical direction. The display element 21 adjusts the position of the center point of the displayed image so that the display light illuminates the central part of the mirror 30 for the eye box of an observer of the first height, the position of the center point of the displayed image so that the display light illuminates the upper part of the mirror 30 for the eye box of an observer of the second height, and the position of the center point of the displayed image so that the display light illuminates the lower part of the mirror 30 for the eye box of an observer of the third height.

[0163] According to this, the optical performance, such as distortion, of the head-up display 1 is superior.

[0164] In the head-up display 1 of technology 20 in this embodiment, the value obtained by dividing the display range L on the display surface 21a of the display element 21 corresponding to the vertical direction of the virtual image by the amount of movement D of the center of the image along the direction on the display surface 21a corresponding to the amount of vertical movement of the virtual image is 100 or less.

[0165] According to this, the amount of image movement on the display surface 21a can be increased to compensate for differences in the driver's height.

[0166] In the head-up display 1 of technology 21 in this embodiment, the mirror 30 is pivotable so as not to affect the observer's eye box.

[0167] According to this, the mirror 30 can be fixed to the housing, thus suppressing display blur caused by vehicle vibrations.

[0168] (Other variations, etc.) Although the present disclosure has been described above based on embodiments, the present disclosure is not limited to the embodiments described above.

[0169] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of the embodiments without departing from the spirit of this disclosure. [Industrial applicability]

[0170] The head-up display of this disclosure can be used in moving objects such as vehicles. [Explanation of symbols]

[0171] 1. Head-up display 3. Windshield (Display medium) 21 Display elements 21a Display surface 30 Mirror 31 Primary mirror 32 Secondary mirror

Claims

1. A head-up display that forms a virtual image by projecting display light onto a display medium, A display element that emits the display light which becomes a projected image on the display medium by displaying an image, The system includes a mirror that guides the display light emitted from the display element to the display medium, thereby forming a virtual image on the opposite side of the display medium from the observer, The display element displays the image by moving the position of the center point of the image, which corresponds to the center point of the virtual image. Head-up display.

2. The aforementioned mirror includes a primary mirror and a secondary mirror. The display element is positioned within a range from the principal point position, which consists of at least the primary mirror and the secondary mirror, to the combined focal length of the primary mirror and the secondary mirror. The head-up display according to claim 1.

3. The distance of the central optical path from the display element to the display medium is shorter than the distance from the observer to the virtual image. The head-up display according to claim 1 or 2.

4. When a is the horizontal size in the X-axis direction on the display surface of the display element corresponding to the left-right direction of the virtual image, b is the vertical size in the Y-axis direction on the display surface corresponding to the up-down direction of the virtual image, A is the size in the left-right direction of the virtual image, and B is the size in the up-down direction of the virtual image, then the relationship a / b ≥ A / B exists. The head-up display according to claim 1 or 2.

5. The focal length of the imaging optical system, consisting of the mirror and the display medium, corresponding to the left-right direction of the virtual image, is longer than the focal length of the imaging optical system corresponding to the up-down direction of the virtual image. The head-up display according to claim 4.

6. The distance of the central optical path from the principal point to the display element is shorter than the distance of the central optical path from the principal point to the display medium. The head-up display according to claim 2.

7. The normal vector of the display element to the display surface on which the image is displayed is inclined with respect to the optical axis of the display light emitted from the display element. The head-up display according to claim 1 or 2.

8. The magnification amount D of the mirror for projecting the display light onto the observer's eye box satisfies equation (1), where x is the size of the eye box, L is the viewing distance from the eye box to the virtual image, and K is the central optical path length from the observer to the point corresponding to the mirror. D>x(1-K / L) Formula (1) The head-up display according to claim 1 or 2.

9. The central optical path of the display light emitted from the display element moves along the direction of the mirror, which corresponds to the vertical direction of the virtual image. The head-up display according to claim 1 or 2.

10. The display element can move the position of the center point of the image in a first direction. The head-up display according to claim 1 or 2.

11. The display element can move the position of the center point of the image in a second direction that intersects with the first direction. The head-up display according to claim 1 or 2.

12. The display element moves the position of the center point of the image so as to project the display light onto the observer's eye box according to the observer's height. The head-up display according to claim 1 or 2.

13. The aforementioned mirror is a concave mirror. The head-up display according to claim 1 or 2.

14. The aforementioned mirror consists only of the primary mirror. The head-up display according to claim 13.

15. The aforementioned mirror includes a primary mirror and a secondary mirror. The aforementioned secondary mirror is a free-form surface. The head-up display according to claim 13.

16. The aforementioned mirror includes a primary mirror and a secondary mirror. The secondary mirror is flat. The head-up display according to claim 13.

17. The secondary mirror has a shape that is convex in the direction corresponding to the left-right direction of the virtual image, and a shape that is convex in the direction corresponding to the up-down direction of the virtual image. The secondary mirror has a shape that is convex or concave in the direction corresponding to the left-right direction of the virtual image, and a shape that is concave in the direction corresponding to the up-down direction of the virtual image. The head-up display according to claim 15.

18. The secondary mirror has a shape that is convex in the direction corresponding to the left-right direction of the virtual image, and a shape that is convex or concave in the direction corresponding to the up-down direction of the virtual image. The head-up display according to claim 15.

19. The observer's height includes a first height, a second height that is taller than the first height, and a third height that is shorter than the first height. The aforementioned mirror is positioned in an upright position along the vertical direction. The aforementioned display element is The position of the center point of the image to be displayed is adjusted so that the display light is projected onto the central portion of the mirror relative to the eye box of the observer of the first height, The position of the center point of the image to be displayed is adjusted so that the display light is projected onto the upper portion of the mirror relative to the eye box of the observer of the second height. Adjust the position of the center point of the image to be displayed so that the display light illuminates the lower part of the mirror with respect to the eye box of the observer of the third height. The head-up display according to claim 14.

20. The value obtained by dividing the display range L on the display surface of the display element corresponding to the vertical direction of the virtual image by the amount of movement D of the center of the image along the direction on the display surface corresponding to the amount of vertical movement of the virtual image is 100 or less. The head-up display according to claim 1 or 2.

21. The mirror is pivotable so as not to affect the observer's eyebox. The head-up display according to claim 1 or 2.

Images