Head-up display

Abstract

This invention provides a head-up display device. The object of the invention is to suppress the reduction in recognizability in an oblique-image HUD device while displaying an image (orthogonal image) of content that can be recognized upright. The control unit of the head-up display device of this invention performs the following control: in actual space, in a display area (Z1) that is an oblique surface (planar or curved) that is inclined from the side closer to the observer and downward to the side further away and upward relative to the ground or a surface equivalent to the ground, an orthogonal image is displayed as an image that can be recognized upright. The orthogonal image is displayed in the display area (Z1) which has a quadrilateral outline as seen from the observer. The convergence angle difference (θL-θU) between the upper end (PU) and the lower end (PL) of the display area (Z1) is set to be less than at least one predetermined threshold determined according to image recognizability, recognition time, and psychological factors such as disharmony or discomfort (preferably, the convergence angle difference is 0.2°).

Description

Technical Field

[0001] The present invention relates to a head-up display (HUD) device, for example, display light that projects (projects) an image onto the windshield or assembly of a vehicle or other vehicle, and displays a virtual image in front of the driver or other vehicle. Background Technology

[0002] In order to improve the information recognition of observers (drivers, etc.), a scheme is proposed to tilt the virtual image display surface of the HUD device in the depth direction (for example, see Patent Document 1).

[0003] In this type of HUD device (hereinafter, sometimes referred to as an oblique HUD device or tilted HUD device), the recognizability is improved when information images with depth information (such as arrows or maps) are displayed, and information images without depth information (such as upright images of text or numbers) that are not emphasized in a broad sense can also be recognized upright, which is very convenient.

[0004] Furthermore, the term "upright" in the context of upright recognition is used in the following ways: For example, it is inevitable that content represented by text or numbers will be upside down, or that the display surface will be tilted at a large angle, making it either impossible or difficult for a person to recognize.

[0005] Therefore, when displaying text or numbers, HUD devices need to display the content correctly in an upright position so that people can read the information correctly. Such an image (virtual image) is called an upright image (or upright virtual image). Furthermore, upright images are usually displayed facing the observer, and are therefore sometimes called front-facing images.

[0006] Existing technical documents

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-120135 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] The inventors have conducted research on slanted HUD devices and discovered the following new challenges. When an image (virtual image) can be displayed on an slanted surface, as described above, an image (virtual image) with a sense of depth can be displayed. Furthermore, if the slant is perpendicular to the ground to a certain extent (or a surface equivalent to the ground: a corresponding surface), it is also possible to display content consisting of text or numbers, which do not emphasize a sense of depth, as an upright image.

[0011] However, when the slope of the inclined surface is large relative to the ground (its equivalent surface), it becomes a state suitable for displaying depth. But on the other hand, it produces problems such as reduced recognizability of upright images, which makes it difficult for the observer to recognize, or even if they can recognize it, the time required to recognize it becomes longer, or it produces a subjective feeling of discomfort or incongruity.

[0012] When these issues are not obvious, one should be able to correctly identify upright images; in other words, one should be able to recognize normal upright images. Otherwise, one should not be able to judge, identify, or recognize upright images, or it should be difficult to recognize upright images.

[0013] Therefore, in order to properly implement efficient design, calibration, or initialization of HUD devices, it is preferable to set a benchmark index to determine whether a normal upright image can be recognized.

[0014] For example, when displaying an image (virtual image) a few meters in front of a vehicle based on a designated point on the vehicle or the viewpoint of an observer (driver, etc.), consider setting the tilt angle of the display area relative to the ground (equivalent surface) so that it does not become a limitation of a few degrees.

[0015] However, human recognition (recognition sensitivity) sometimes depends on the distance to the image. Sensitivity increases when the image is displayed closer to the viewer and decreases when it is displayed further away. Therefore, in the above-mentioned setting method, the slope (tilt angle) also changes if the distance changes, making it impossible to obtain a uniform benchmark (threshold) and resulting in poor usability.

[0016] Therefore, it is important to obtain an index that can be used uniformly as a benchmark (threshold), and to appropriately set an optimal value for that threshold. If such an index is obtained, it is possible to use it to set the slope of the tilted surface (or display area) that does not affect the reading of the upright image, and it also simplifies design. In prior art, such as Patent Document 1, no research has been conducted on this point, and a suitable index cannot be obtained.

[0017] One of the objectives of this invention is to suppress the reduction in recognizability in an oblique-view HUD device while displaying an image of content that can be recognized in an upright position (upright image).

[0018] Other objects of the present invention will be apparent to those skilled in the art from the following examples and preferred embodiments and drawings.

[0019] Methods for solving problems

[0020] Hereinafter, in order to facilitate understanding of the general outline of the invention, embodiments of the invention are illustrated.

[0021] In the first approach, the head-up display device has:

[0022] Image display unit, which displays images;

[0023] An optical system that projects light from the image displayed on the image display unit onto a projection component, enabling the observer to recognize a virtual image of the image within an imaginary display area in the actual space in front of the observer; and

[0024] The control unit controls the display of the image in the image display unit.

[0025] The direction in the actual space that faces the observer is taken as the forward direction.

[0026] The left and right directions are defined as the line segment perpendicular to the forward direction and connecting the observer's left and right eyes.

[0027] The direction along a line segment orthogonal to the forward direction and the left-right direction is taken as the up-down direction or the height direction.

[0028] Taking the direction of the surface in the actual space that is far from or equivalent to the ground as "up" and the direction that is close to the ground as "down", then...

[0029] The control unit performs the following controls, namely,

[0030] In the actual space, within the display area of ​​the inclined surface (which is a plane or curved surface) that slopes from the side closer to the observer and downwards towards the side farther away, relative to the ground or a surface equivalent to the ground, an upright image, which is an image that can be recognized upright, is displayed.

[0031] The upright image is displayed in a display area that shows a quadrilateral outline as seen from the observer.

[0032] The convergence angle difference between the upper and lower ends of the display area is set to be less than at least one predetermined threshold determined based on at least one of the following: image recognizability, recognition time, and psychological factors such as disharmony or discomfort.

[0033] In the first method, "convergence angle difference" is used (where the tilt distortion angle caused by the convergence angle difference is referred to as "convergence angle difference"). Figure 6 The new indicator (as a threshold benchmark) replaces the angle θd of (C) to determine the tilt of the display area of ​​an upright image, thereby efficiently (or easily) determining or setting the tilt.

[0034] The display area has a quadrilateral outline. The ground side (or the equivalent surface of the ground, such as a road surface) of the display area is designated as the lower end (bottom edge), and the opposite side (the side away from the ground) is designated as the upper end (top edge). Here, for example, a pair of corresponding points are set at the lower end (bottom edge) and the upper end (top edge) respectively (these points can be set at any position, but are preferably, for example, the right or left endpoints of each end (each edge)). This pair of points is designated as the first point and the second point. The convergence angle (the angle formed by the visual axis representing the direction of the line of sight of each eye) when observing the first point from the left and right eyes is designated as the first convergence angle, and the convergence angle when observing the second point is designated as the second convergence angle. The difference between the first and second convergence angles (the difference obtained by subtracting the second convergence angle from the first convergence angle) is designated as the "convergence angle difference". This convergence angle difference can be referred to as the "convergence angle difference between the upper and lower ends of the display area".

[0035] Here, if the display area is erected on the ground (its corresponding surface) at approximately right angles, then when viewed from above, the upper end (top side) and lower end (bottom side) of the quadrilateral overlap, and the first point overlaps with the second point. When the length (height) of the quadrilateral's vertical side is small, the variation in distance between the first and second points and the left and right eyes caused by their height positions can be ignored. In the above case, the first and second convergence angles of the first and second points are the same (approximately the same), and the difference in convergence angle is zero (approximately zero).

[0036] Here, when the display area is tilted relative to the ground (its corresponding surface), and the lower end (bottom side) of the quadrilateral moves towards the observer, a difference arises in the convergence angles of the first and second points. In other words, the first convergence angle is greater than the second convergence angle. Therefore, the difference in convergence angles is α (α is an integer greater than 0).

[0037] As the display area tilts further and the lower end (bottom side) of the quadrilateral moves further toward the observer and gets closer to the observer, the first convergence angle increases further, and therefore the difference between it and the second convergence angle increases. The difference in the convergence angle is β (β is an integer that satisfies α < β).

[0038] In this way, the "convergence angle difference between the upper and lower ends of the display area" becomes an indicator of the tilt degree of the display area relative to the ground (its equivalent surface). Furthermore, since the convergence angle varies depending on the distance from the observer's eye, distance information is included. Thus, the convergence angle difference becomes a comprehensive indicator (threshold) that also includes information about the tilt degree of the display area (or virtual image display surface, etc.) relative to the ground (its equivalent surface) based on distance. Unlike existing technologies, it is not necessary to set the slope with preconditions, such as specifying the tilt angle in degrees at a distance of a few meters.

[0039] Here, the recognizability of upright images varies from person to person and cannot be generalized. However, it is possible to objectively determine whether a normal upright image can be recognized based on at least one of the following: the recognizability of the displayed image, the time required for recognition, and psychological factors such as a sense of incongruity or discomfort. Moreover, in making this determination, a threshold that can be used for the determination can be obtained by using the aforementioned indicators.

[0040] As described above, the convergence angle difference increases as the slope of the display area increases and the first point approaches the observer. Therefore, for example, by using the convergence angle difference near the boundary where the observer can recognize an upright image after fusing (synthesizing) the images from the left and right eyes in their brain as a threshold, and setting each part in the design of a HUD device such that the convergence angle difference is less than this threshold, the observer can recognize an upright image even when it is displayed on an inclined surface. In other words, it can be ensured that the observer's recognizability of the upright image is above a specified level.

[0041] In this way, for example, the design of images (upright images) that can display content that can be recognized upright while suppressing the reduction in recognizability can be made more efficient or easier. In addition, this new index (convergence angle difference or tilt distortion angle caused by convergence angle difference) can also be used for HUD device calibration, HUD device initialization, HUD device function simulation, etc., thereby achieving the effect of improving the efficiency of each process.

[0042] In the second method, which is subordinate to the first method, it can be:

[0043] The display area is divided into a first region capable of displaying all of the virtual images of the tilted image (i.e., the depth image) and the virtual image of the upright image, and a second region for displaying the virtual image of the depth image.

[0044] The convergence angle difference between the upper and lower ends of the display area in the first region is set to be less than the predetermined threshold, and the convergence angle difference between the upper and lower ends of the display area in the second region is set to be greater than the predetermined threshold.

[0045] In the second method, the display area is divided into a first area capable of displaying both a depth image and an upright image, and a second area suitable for displaying the depth image, and the convergence angle difference between the upper and lower ends of the display area in the second area is set to be above the aforementioned predetermined threshold.

[0046] As described above, the threshold is set based on the recognizability of upright images, etc. Above this threshold, the recognizability of upright images decreases and they are unsuitable for displaying upright images. In other words, it can be considered suitable for displaying depth images that are tilted (including images that float in the air, visually extend roughly parallel to or overlap with the road surface). Therefore, for the image (virtual image) displayed in the second area, the convergence angle difference, etc., is set to be above the threshold. Thus, for example, when an upright image is displayed in the first area and a depth image is displayed in the second area, appropriate recognizability of each image can be ensured.

[0047] In the third method, which is subordinate to the first or second method, it can be:

[0048] The specified threshold serves as a normal recognition probability determination threshold for assessing the normal recognition probability of the upright image.

[0049] The convergence angle difference, which is the specified threshold, is set to 0.2°.

[0050] In the third approach, the aforementioned “prescribed threshold” is clearly defined. Specifically, it is specified that, for example, it can be used as a “normal recognition probability determination threshold”, and its preferred value is specified as 0.2°.

[0051] In the fourth method, which belongs to any of the methods from the first to the third, it can be:

[0052] When the viewpoint in the vertical direction (or height direction) observed by the observer is referred to as the vertical viewpoint, the specified threshold for limiting the convergence angle difference applies to the content of upright images with a vertical viewpoint of less than 0.75°.

[0053] In the fourth approach, considering that when the size of the displayed content increases, even if the convergence angle difference is the same, it will make it more difficult for the images of the left and right eyes to be fused in the brain, the above threshold is applied to smaller content with a vertical viewing angle of less than 0.75°, and the convergence angle difference between the upper and lower ends is set to be less than the threshold.

[0054] Furthermore, for upright content larger than this size, from the viewpoint of obstructing the field of view in a HUD device, it is confirmed that the current implementation is not very feasible due to increased interference. Therefore, limiting the displayed content to a size below the specified size is considered to have no particular problems even when the aforementioned threshold is applied.

[0055] Those skilled in the art will readily understand that the exemplary embodiments of the invention can be further modified without departing from the spirit of the invention.

[0056] Brief description of the attached diagram

[0057] Figure 1 Figure (A) is an example of the structure and tilted display area of ​​a HUD device mounted in a vehicle. Figure 1 (B) and (C) represent realization Figure 1 The figure shown in (A) is an example of a method for displaying the area.

[0058] Figure 2 (A) is a diagram showing the main structure of a HUD device mounted in a vehicle and an example of a display in the display area. Figure 2 (B) is a diagram showing an example of a display area consisting of all the first regions of the virtual image capable of displaying depth images and the virtual image of the upright image, and the second region of the virtual image displaying depth images.

[0059] Figure 3 (A) is a diagram representing a tilted surface (tilted display area) with a graphic that displays arrows as a depth image positioned in front, and the state in which an observer observes it with both eyes. Figure 3 (B) is a diagram representing the image seen with the left eye. Figure 3 (C) is a diagram representing the depth image observed by fusing (combining) the images from the left and right eyes. Figure 3 (D) is a diagram representing the image seen with the right eye.

[0060] Figure 4 (A) is a diagram representing the state in which an observer views a tilted surface (tilted display area) that displays a vehicle speedometer as an upright image, with both eyes positioned in front of the viewer. Figure 4 (B) is a diagram representing the image seen with the left eye. Figure 4 (C) is a diagram representing an upright image observed by fusing (combining) the images from the left and right eyes. Figure 4 (D) is a diagram representing the image seen with the right eye.

[0061] Figure 5 (A) is a diagram representing the state of a display area that is roughly perpendicular to the road surface as observed by the observer with both eyes. Figure 5 (B) indicates that the eyes are relative to each other. Figure 5 A diagram showing the convergence angle between the first right endpoint of the upper (top) side of the display area in (A) and the second right endpoint of the lower (bottom) side corresponding to the first right endpoint. Figure 5 (C) is a diagram representing the image formed by fusing (combining) the images from the left and right eyes.

[0062] Figure 6 (A) is a diagram representing the state of a display area tilted at approximately 45° relative to the road surface as observed by an observer with both eyes. Figure 6 (B) indicates that the eyes are relative to each other. Figure 6 A diagram showing the convergence angle between the first right endpoint of the upper (top) side of the display area in (A) and the second right endpoint of the lower (bottom) side corresponding to the first right endpoint. Figure 6 (C) is a diagram representing the image seen with the left eye. Figure 6 (D) is a diagram representing an upright image formed by fusing (combining) the images from the left and right eyes. Figure 6 (E) is a diagram representing the image seen with the right eye.

[0063] Figure 7 (A) is a diagram representing the state of an observer using both eyes to view a display area that is tilted at approximately 30° relative to the road surface. Figure 7 (B) indicates that the eyes are relative to each other. Figure 7 A diagram showing the convergence angle between the first right endpoint of the upper (top) side of the display area in (A) and the second right endpoint of the lower (bottom) side corresponding to the first right endpoint. Figure 7 (C) is a diagram representing the image seen with the left eye. Figure 7 (D) is a diagram representing the visual impairment caused by ghosting or other issues when the images from the left and right eyes are fused (combined). Figure 7 (E) is a diagram representing the image seen with the right eye.

[0064] Figure 8 (A) and (B) are flowcharts illustrating examples of design methods for HUD devices (oblique image plane HUD devices).

[0065] Figure 9 This is a diagram illustrating an example of the structure of the display control unit (control unit) in a HUD device.

[0066] Figure 10 (A) and (B) are other examples of tilted display areas.

[0067] Figure 11 This is a graph showing the experimental results of the percentage of people who answered that they did not feel any discomfort with each convergence angle difference (horizontal axis) (vertical axis). Detailed Implementation

[0068] The preferred embodiments described below are intended to facilitate a quick understanding of the invention. Therefore, those skilled in the art should note that the invention is not unduly limited to the embodiments described below.

[0069] Reference Figure 1 . Figure 1 Figure (A) is an example of the structure and tilted display area of ​​a HUD device mounted in a vehicle. Figure 1 (B) and (C) represent realization Figure 1 The diagram (A) shows an example of a method for displaying the area. Figure 1 In this context, the direction along the front of vehicle 1 (also known as the front-to-back direction) is defined as the Z direction, the direction along the width (lateral width) of vehicle 1 (or the left-to-right direction) is defined as the X direction, and the direction of the height of vehicle 1 or the upward direction (the direction of the line segment perpendicular to the flat road surface 40, away from the ground or its equivalent surface (here, the road surface) 40) is defined as the Y direction.

[0070] Furthermore, in the following description, the term "imaginary display area" (sometimes simply referred to as the display area) set in front of the observer can be interpreted broadly. For example, it can be an imaginary display surface (sometimes also called a virtual image display surface) corresponding to the display surface (display area) of the screen or other display surface displaying the image. In addition, when an image displayed on this imaginary display surface is arranged within an image area of ​​a predetermined shape (e.g., a quadrilateral) of a predetermined size, this image area can also be regarded as a display area (or part of the virtual image display surface). In the following description, based on the above, it will only be referred to as "display area".

[0071] Furthermore, in descriptions of the shape of the display area, terms like "up" and "down" are sometimes used. Here, for ease of explanation, the direction along the line segment (normal) perpendicular to the road surface 40 (which is also the height direction of vehicle 1) will be used as the up / down direction. When the road surface is horizontal, vertical downward is "down," and the opposite direction is "up." This also applies to the descriptions of other accompanying drawings.

[0072] like Figure 1 As shown in (A), the HUD device 100 of this embodiment is mounted inside the front bulkhead 41 of the vehicle (this vehicle) 1. The HUD device 100 can display upright images (images that do not particularly emphasize depth, also called vertical images, such as those composed of numbers, text, etc.) and depth images (also called tilted images or tilted pictures, such as navigation arrows extending along the road surface 40) in a display area PS1 in front of the vehicle 1, which has an area tilted relative to the road surface 40.

[0073] The HUD device 100 includes: a display unit (sometimes also called an image display unit, specifically, for example, a screen) 160, which has a display surface 164 for displaying images; an optical system 120, which includes an optical component that projects a display light K for displaying images onto a windshield as a projection component (reflective light-transmitting component) 2; and a projection unit (image projection unit) 150. The optical component 120 has a curved mirror (also called a concave mirror or magnifying mirror) 170, which has a reflective surface 179. The reflective surface 179 of the curved mirror 170 is not a shape with a uniform radius of curvature. For example, it can be a shape composed of a set of local regions with multiple radii of curvature, for example, it can be designed using a freeform surface design method (or it can be a freeform surface itself). Furthermore, a freeform surface refers to a surface that cannot be represented by a simple mathematical formula, but is expressed by setting several intersection points and curvatures in space and interpolating the intersection points using higher-order equations. The shape of the reflective surface 179 has a considerable influence on the shape of the display area PS1 or the road surface.

[0074] Furthermore, the shape of the display area PS1 is affected not only by the shape of the reflective surface 179 of the curved mirror (concave mirror) 130, but also by the curved shape of the windshield (reflective light-transmitting component 2) and the shape of other optical components (such as correction mirrors) mounted in the optical system 120. Additionally, it is affected by the shape of the display surface 164 of the display unit 160 (generally planar, but may be entirely or partially non-planar) and the arrangement of the display surface 164 relative to the reflective surface 179. However, the curved mirror (concave mirror) 170 is a magnifying reflector, and its influence on the shape of the display area (virtual image display surface) is quite significant. Furthermore, if the shape of the reflective surface 179 of the curved mirror (concave mirror) 170 is different, the actual shape of the display area (virtual image display surface) PS1 changes.

[0075] Furthermore, the display area PS1, which extends integrally from the near end U1 to the far end U3, can be formed by arranging the display surface 164 of the display unit 160 at an angle of less than 90 degrees relative to the optical axis of the optical system (the main optical axis corresponding to the main ray).

[0076] Furthermore, the shape of the curved surface of the display area PS1 can be adjusted by modifying the optical characteristics of the entire area or a portion of the optical system, adjusting the configuration of the optical components and the display surface 164, adjusting the shape of the display surface 164, or combining these adjustments. This allows for diverse adjustments to the shape of the virtual image display surface. Consequently, a display area PS1 having a first area Z1 and a second area Z2 can be realized.

[0077] In other words, the display area PS1 is divided into a first area Z1 that can display both depth images (tilted images) and upright images (standing images), and a second area suitable for displaying depth images (tilted images) (in other words, dedicated to displaying depth images).

[0078] The following will explain this point in detail. For example... Figure 1 As shown on the left and lower left of (B), the overall tilt of the display area (including the virtual image display surface) PS1 is adjusted according to the tilt method and degree of the display surface 164 of the display unit 160. Furthermore, in Figure 1 In example (B), the distortion of the display area (virtual image display surface) of the curved surface of the windshield (reflective light-transmitting component 2) is corrected by the curved shape of the reflective surface 179 of the curved mirror (concave mirror, etc.) 170, resulting in the generation of a flat display area (virtual image display surface) PS1.

[0079] In addition, such as Figure 1 As shown on the right and lower left of (B), by adjusting the positional relationship between the optical component (here, a curved mirror (concave mirror, etc.) 170) and the display surface 164, in other words, by rotating the display surface 164 to make its relative relationship with the optical component (curved mirror 170) different, the degree to which the display area (virtual image display surface) PS1, which is an inclined surface, is farthest from the road surface 40 can be adjusted.

[0080] In addition, such as Figure 1 As shown in (C), the virtual image display distance near the end (near end) U1 of the display area PS1 near the vehicle 1 is changed by adjusting the shape of the reflective surface of the curved mirror (concave mirror, etc.) 170, which is an optical component (or adjusting the shape of the display surface 164 of the display unit 160). This is controlled so that the display area PS1 with an inclined portion is obtained by bending towards the road surface near the near end U1 and standing upright relative to the road surface.

[0081] like Figure 1 As shown on the upper side of (C), the reflective surface 179 of the curved mirror 170 can be divided into three parts: Near (near display area), Center (middle (central) display area), and Far (far display area).

[0082] Here, Near refers to the display light E1 generated corresponding to the near end U1 of the display area PS1 (in Figure 4 In (A) and (B), the part represented by a single-dot dash is Center, which generates the display light E2 (represented by a dashed line) corresponding to the middle part (central part) U2 of the display area PS1, and the part represented by a solid line is Far, which generates the display light E3 (represented by a solid line) corresponding to the far end U3 of the display area PS1.

[0083] exist Figure 1 In (C), the parts for Center and Far are related to Figure 1 The curved mirror (concave mirror, etc.) 170 shown in (B) is the same as the one used when generating the display area PS1 of the plane. However, in Figure 1 In (C), the curvature of the Near portion is set to be greater than that of the other portion. Figure 1 (B) is small. Therefore, the multiplier corresponding to the Near part becomes larger.

[0084] The magnification (denoted as c) of the HUD device 100 can be expressed as c = b / a, where c represents the distance from the display surface 164 of the display unit 160 to the windshield 2 (denoted as a) and the distance from the light reflected from the windshield (reflective light-transmitting component 2) to the image formed at the imaging point via viewpoint A (denoted as b). When the curvature of the Near portion decreases, a decreases, the magnification increases, and the image is formed at a position farther away from the vehicle 1. That is, in Figure 1 In case (C), the virtual image display distance is greater than... Figure 1 The case of (B) is larger.

[0085] Therefore, the proximal end U1 of the display area PS1 is away from the vehicle 1, and the proximal end U1 bends towards the road surface 40 in a downward-facing shape, thus forming the first area Z1. Thus, a display area PS1 having a first area Z1 and a second area Z2 can be obtained.

[0086] Next, refer to Figure 2 . Figure 2 (A) is a diagram showing the main structure of a HUD device mounted in a vehicle and an example of a display in the display area. Figure 2 (B) is a diagram illustrating an example of a display area comprised of all the first regions of the virtual image capable of displaying a depth image and the virtual image of the upright image, and a second region of the virtual image displaying the depth image. Figure 2 In China, targeting and Figure 1 Common parts are marked with the same symbol.

[0087] like Figure 2As shown, the HUD device 100 includes: a display unit (e.g., a light-transmitting screen) 160 having a display surface 164; a reflector 165; and a curved mirror (e.g., a concave mirror with a reflective surface 179, sometimes the reflective surface is also a freeform surface) 170, which is an optical component for projecting display light. The image displayed on the display unit 160 is projected onto the projection area 5 of the windshield 2, which is the projection component, via the reflector 165 and the curved mirror 170. Furthermore, multiple curved mirrors may be provided in the HUD device 100. In addition to the mirror (reflective optical element) of this embodiment, or replacing part (or all) of the mirror (reflective optical element) of this embodiment, a structure including functional optical elements such as lenses, diffractive optical elements, etc., may be adopted.

[0088] A portion of the light from the image display is reflected by the windshield 2 and enters the viewpoint (eye) A of the driver or others located inside (or on) a pre-defined viewpoint area (a three-dimensional structure, depicted as a planar structure for convenience), forming an image in front of the vehicle 1, thereby displaying various images (virtual images) on an imaginary display area (virtual image display surface) PS1. Figure 2 In (A), as an example of the display in the first region Z1 of the display area PS1, the vehicle speed display SP as an upright image (upright virtual image) and the image (virtual image) AW' of the navigation arrow as a depth display are shown. In addition, in the second region Z2, the image (virtual image) AW of the navigation arrow extending from the front side of the vehicle 1 inward along the road surface 40 is shown.

[0089] like Figure 2 As shown in (B), the angle (inclination angle) between the first region Z1 and the road surface 40 is θ1 (0 < θ1 < 90°), and the angle (inclination angle) between the second region Z2 and the road surface 40 is θ2 (0 < θ2 < θ1). Both the first region Z1 and the second region Z2 are inclined regions (or at least regions with inclined portions).

[0090] Next, refer to Figure 3 . Figure 3 (A) is a diagram representing a tilted surface (tilted display area) with a graphic that displays arrows as a depth image positioned in front, and the state in which an observer observes it with both eyes. Figure 3 (B) is a diagram representing the image seen with the left eye. Figure 3 (C) is a diagram representing the depth image observed by fusing (combining) the images from the left and right eyes. Figure 3 (D) is a diagram representing the image seen with the right eye.

[0091] exist Figure 3In (A), the midpoint C0 is drawn at the central position between the left eye A1 and the right eye A2. For convenience, the image obtained by fusing the images observed by the left eye A1 and the right eye A2 in the observer's brain is called the image at the midpoint C0.

[0092] exist Figure 3 In (A), an image (virtual image) AW of a slanted, extended navigation arrow is displayed in the second region Z2 of the display area PS1. Figure 3 When the images A1 and A2 of the left and right eyes shown in (B) and (D) (images with binocular disparity) are fused (synthesized), it is possible to recognize the images. Figure 3 (C) Such a depth-of-field (stereoscopic) image. In other words, by changing the shape of the image caused by the positional shift of the upper and lower ends of the viewing angles of the left and right eyes A1 and A2, the image (virtual image) AW of the arrow is naturally recognized in a way that tilts inward, thereby improving recognizability or distinguishability.

[0093] Next, refer to Figure 4 . Figure 4 (A) is a diagram representing the state in which an observer views a tilted surface (tilted display area) that displays a vehicle speedometer as an upright image, with both eyes positioned in front of the viewer. Figure 4 (B) is a diagram representing the image seen with the left eye. Figure 4 (C) is a diagram representing an upright image observed by fusing (combining) the images from the left and right eyes. Figure 4 (D) is a diagram representing the image seen with the right eye.

[0094] exist Figure 4 In (A), the vehicle speed display SP is shown in the first area Z1 of the display area PS1 (e.g., Figure 4 The image (virtual image) shown as “120km / h” as recorded in (B) etc. The vehicle speed display SP is displayed in the tilted first area Z1 and is displayed as an upright image (upright virtual image) that can be recognized upright.

[0095] If the tilt angle of the first region Z1 relative to the road surface 40 is not so small, and it is made partially upright, it can be discerned as an upright image (information is read as an upright image) without affecting the observer's ability to identify it. In this case, for example, when... Figure 4 When the images A1 and A2 of the left and right eyes shown in (B) and (D) (images with binocular disparity) are fused (synthesized), it is possible to recognize the images. Figure 4 (C) is a vertical display of vehicle speed SP.

[0096] On the other hand, the tilt angle of the first region Z1 relative to the road surface 40 is small, and the observation method for the failure of image fusion (combination) of the images realized by the left and right eyes (when fusion is not performed) varies from person to person. For example, the whole is tilted when observing, or the shape of either eye is changed when observing. In short, the recognizability is reduced and the recognition time is increased. In addition, the subjective (psychological factors) are not grasped positively.

[0097] Next, refer to Figure 5 . Figure 5 (A) is a diagram representing the state of a display area that is roughly perpendicular to the road surface as observed by the observer with both eyes. Figure 5 (B) indicates that the eyes are relative to each other. Figure 5 A diagram showing the convergence angle between the first right endpoint of the upper (top) side of the display area in (A) and the second right endpoint of the lower (bottom) side corresponding to the first right endpoint. Figure 5 (C) is a diagram representing the image formed by fusing (combining) the images from the left and right eyes.

[0098] In the following description, the display area is defined by a specified shape (in this case, a quadrilateral), with the ground (or equivalent surface of the ground, such as a road surface) side of the display area being the lower end (bottom edge) and the opposite side (the side away from the ground) being the upper end (top edge). Furthermore, the term "quadrilateral" to describe the shape of the display area includes, for example, rectangles, squares, trapezoids, parallelograms, etc., and is interpreted broadly.

[0099] exist Figure 5 In (A), a display area (here, the first area Z1) is shown in front of the observer, roughly perpendicular to the road surface 40. The observer observes the image (virtual image) displayed in the first area Z1 using both eyes A1 and A2. Figure 5 As shown in (C), the displayed image (virtual image) is the vehicle speed display SP mentioned above.

[0100] exist Figure 5 In (A), the lower end of the viewing angle (hereinafter sometimes simply referred to as the lower end or lower edge) in the display area (first area Z1) is marked with a symbol indicating PL, and the upper end of the viewing angle (sometimes simply referred to as the upper end or upper edge) is marked with a symbol indicating PU.

[0101] Figure 5 (B) shows that in Figure 5 In (A), the convergence angle caused by the observer's binocular parallax when looking down from above (in the figure, the side in the -Y direction indicated by the arrow).

[0102] In addition, Figure 5In (B), a pair of corresponding points are set on the lower end (bottom) PL and the upper end (top) PU respectively (these points can be set at any position, preferably, for example, the right or left endpoints of each end (side)). Figure 5 In (B), there are two points: the right endpoint R1 at the bottom and the right endpoint R2 at the top. Point R1 is called the first point, and point R2 is called the second point.

[0103] The first convergence angle θL is defined as the angle formed by the visual axes of the lines of sight of each eye A1 and A2 when observing the first point R1. The second convergence angle θU is defined as the angle when observing the second point R2. The difference between the first and second convergence angles θL and θU (the difference obtained by subtracting the second convergence angle θU from the first convergence angle θL) is defined as the "convergence angle difference". This convergence angle difference can be referred to as the "convergence angle difference between the upper (or upper edge) and lower (or lower edge) of the display area".

[0104] exist Figure 5 In the example, since the display area (first area Z1) is erected on the road surface 40 at approximately right angles, when viewed from above as a quadrilateral outline of the display area (first area Z1), the upper end (upper side) PU of the quadrilateral overlaps with the lower end (lower side) PL, and the first point R1 overlaps with the second point R2. Here, when the length of the longitudinal side of the quadrilateral ( Figure 5 (A) represents the length of the line segment in the first region Z1: in other words, when the height of the first region (based on the road surface 40) is small, the distance difference (variation in distance) between the first point R1, the second point R2 and the left and right eyes A1, A2 caused by the difference in height position of the first point R1 and the second point R2 can be ignored. In the above case, the values ​​of the first convergence angle θL and the second convergence angle θU of the first point R1 and the second point R2 are the same (approximately the same), and the difference in convergence angle is zero (approximately zero).

[0105] like Figure 5 As shown in (C), the image formed by fusing (combining) the images from the left and right eyes (the image at the central position C0, or simply the image of C0) is recognized as a vertical image, and there is no problem with the recognizability of the vehicle speed display SP.

[0106] Next, refer to Figure 6 . Figure 6 (A) is a diagram representing the state of a display area tilted at approximately 45° relative to the road surface as observed by an observer with both eyes. Figure 6 (B) indicates that the eyes are relative to each other. Figure 6 A diagram showing the convergence angle between the first right endpoint of the upper (top) side of the display area in (A) and the second right endpoint of the lower (bottom) side corresponding to the first right endpoint. Figure 6(C) is a diagram representing the image seen with the left eye. Figure 6 (D) is a diagram representing an upright image formed by fusing (combining) the images from the left and right eyes. Figure 6 (E) is a diagram representing the image seen with the right eye.

[0107] like Figure 6 As shown in (A), the display area (first area Z1) is tilted at approximately 45° relative to the road surface 40. The lower end (bottom side) of the quadrilateral representing the outline of the first area Z1 is moved towards the observer. Figure 6 In (B), the lower (bottom) PL is closer to the observer than the upper (top) PU. As a result, the values ​​of the first convergence angle θL relative to the first point R1 and the second convergence angle θU relative to the second point R2 differ. In other words, the first convergence angle θL is larger than the second convergence angle θU. Therefore, the difference in convergence angles is α (α is an integer greater than 0).

[0108] Reference Figure 6 (C) and (E). Since the display area Z1 tilts inwards towards the upper part, the burden on the left eye A1 and right eye A2 increases at this point. Furthermore, due to binocular parallax, the quadrilateral in the image observed by the left eye A1 is distorted to the left, and the quadrilateral in the image observed by the right eye A2 is distorted to the right, resulting in a roughly parallelogram shape being perceived. At this point, it is also difficult to discern an upright image (vehicle speed display SP).

[0109] However, the human eye can recognize upright images by correcting for depth and left-right distortions to a certain extent. Figure 6 In the example, it did not exceed the limit of its correction function (recognition function). Therefore, as... Figure 6 As shown in (D), the vehicle speed display SP, which is an upright image, can be identified with roughly the correct accuracy.

[0110] Next, refer to Figure 7 . Figure 7 (A) is a diagram representing the state of an observer using both eyes to view a display area that is tilted at approximately 30° relative to the road surface. Figure 7 (B) indicates that the eyes are relative to each other. Figure 7 A diagram showing the convergence angle between the first right endpoint of the upper (top) side of the display area in (A) and the second right endpoint of the lower (bottom) side corresponding to the first right endpoint. Figure 7 (C) is a diagram representing the image seen with the left eye. Figure 7 (D) is a diagram representing the visual impairment caused by ghosting or other issues when the images from the left and right eyes are fused (combined). Figure 7 (E) is a diagram representing the image seen with the right eye.

[0111] like Figure 7 As shown in (A), the display area (first area Z1) is further inclined relative to the road surface 40. Figure 7 As shown in (B), the lower end (bottom side) PL of the quadrilateral moves further toward the observer. As a result, the first convergence angle θL increases further. Therefore, the difference between the first and second convergence angles θU increases, and the convergence angle difference (θL-θU) is β (β is an integer satisfying α < β).

[0112] exist Figure 7 In some examples, the distortion correction capabilities for depth and lateral movement exceed the limits set by human perception, preventing proper image fusion. Therefore, as... Figure 7 As shown in (C) to (E), the vehicle speed display SP, which is an upright image, cannot be correctly identified. Furthermore, since it is difficult to describe in detail in the accompanying drawings, it is simply referred to as SP in the figures.

[0113] The above, as in Figures 5-7 As explained in the text, "the difference in convergence angle (θL-θU) between the upper (top) and lower (bottom) ends of the display area" can be used as an indicator of the degree of tilt of the display area relative to the ground (its equivalent surface).

[0114] Furthermore, the convergence angles θL and θU vary depending on the distances from the observer's eyes A1 and A2, thus distance information is included. Therefore, the convergence angle difference (θL-θU) becomes a comprehensive indicator (threshold) that also includes information about the tilt of the display area (or virtual image display surface, etc.) relative to the ground (its equivalent surface). Unlike existing technologies, it is not necessary to set the slope with distance as a prerequisite, specifying the tilt angle in degrees at a distance of a few meters. Therefore, by incorporating this indicator into the design of HUD devices, the setting of the display area's slope can be made more efficient (easier).

[0115] Here, the recognizability of an upright image varies from person to person and cannot be generalized. However, it is possible to objectively determine whether a normal upright image can be recognized based on at least one of the following: the recognizability of the displayed image (first factor), the time required for recognition (second factor), and psychological factors such as a sense of disharmony or discomfort (third factor). Moreover, in making this determination, a threshold that can be used for the determination can be obtained by using the aforementioned indicators.

[0116] (Experimental Results)

[0117] With the cooperation of several individuals, the inventors attempted to determine whether an upright image, using the aforementioned convergence angle difference as an indicator, could be correctly identified based on the first to third factors described above. Here, when all three factors are detected as NG (Not Good), the image is considered difficult to identify as a normal upright image; when one or two NG values ​​are detected, the image is considered as a normally recognizable upright image.

[0118] The results show that when the convergence angle difference between the top and bottom of an upright image is 0.182°, it is difficult to identify. When the threshold is on the order of 0.1, 0.182 is rounded to 0.2. Therefore, 0.2° can be extracted as an example of a preferred threshold. Thus, by making the convergence angle difference less than 0.2°, upright images can be identified.

[0119] Specifically, the “prescribed threshold” can be used, for example, as a “normal recognition probability determination threshold”, with an example of a preferred value being 0.2° as described above.

[0120] By utilizing this threshold (index), for example, the design of images (upright images) that can display content that is correctly identified while suppressing the reduction in recognizability can be made more efficient or easier. Additionally, this new index (convergence angle difference or tilt distortion angle caused by convergence angle difference) (refer to...) Figure 6 The angle θd) of (C) can also be used for HUD device calibration, HUD device initialization, HUD device function simulation, etc., thereby achieving the effect of improving the efficiency of each process.

[0121] Additionally, as before Figure 2 As shown in (A), the display area is divided into a first area Z1 capable of displaying both depth images and upright images, and a second area Z2 suitable for displaying depth images. In this case, the convergence angle difference between the upper and lower ends of the display area in the second area Z2 can be set to the aforementioned predetermined threshold (preferably 0.2°) or higher.

[0122] As described above, the threshold is set based on the recognizability of upright images, etc. Above this threshold, the recognizability of upright images decreases and they are unsuitable for displaying upright images. In other words, it can be considered suitable for displaying depth images that are tilted (including images that float in the air, visually extend roughly parallel to or overlap with the road surface). Therefore, for the image (virtual image) displayed in the second region Z2, the convergence angle difference is set to be above the threshold. Thus, for example, when an upright image is displayed in the first region Z1 and a depth image is displayed in the second region Z2, appropriate recognizability of each image can be ensured.

[0123] In addition, when the viewpoint in the vertical direction (or height direction) observed by the observer is called the vertical viewpoint, the limitation of the convergence angle difference of the specified threshold can be applied to the content of upright images with a vertical viewpoint of 0.75° or less.

[0124] In other words, considering that when the size of the displayed content increases, even if the convergence angle difference is the same, it will make it more difficult for the images of the left and right eyes to be fused in the brain, the above threshold is applied to smaller content with a vertical viewing angle of less than 0.75°, and the convergence angle difference between the upper and lower ends is set to be less than the threshold.

[0125] Furthermore, for upright content larger than this size, from the viewpoint of obstructing the field of view in the HUD device 100, it is confirmed that the interference would increase, and the possibility of implementing the current situation cannot be considered high. Therefore, limiting the displayed content to a specified size or smaller is considered to have no particular problem even when the above threshold is applied.

[0126] Next, refer to Figure 8 . Figure 8 (A) and (B) are flowcharts illustrating examples of design methods for HUD devices (oblique image plane HUD devices). Figure 8 In (A), in the oblique image HUD device, each part is designed in such a way that the convergence angle difference between the upper and lower ends of the display area of ​​the information image (upright image) for upright recognition (or the tilt distortion angle caused by the convergence angle difference) is less than at least one predetermined threshold (preferably less than 0.2°) determined based on the image recognizability, the time required for recognition, and psychological factors such as disharmony or discomfort.

[0127] exist Figure 8 In step (B), the display area is divided into a first region capable of displaying both tilted and upright information images (depth images) and a second region capable of displaying tilted information images (depth images) (step S2). Next, preferably, for content with a vertical viewing angle of 0.75° or less, the design ensures that the convergence angle difference between the upper and lower ends of the first region is less than a predetermined threshold (preferably less than 0.2°), and the convergence angle difference between the upper and lower ends of the second region is designed to be greater than or equal to the predetermined threshold (step S3).

[0128] Next, refer to Figure 9 . Figure 9 This is a diagram illustrating an example of the structure of the display control unit (control unit) in a HUD device. Figure 9 The image on the upper side of the middle and Figure 1 (A) is roughly the same. However, in Figure 9 The device includes a line-of-sight detection camera 188 and a viewpoint position detection unit 192.

[0129] The display control unit (control unit) 190 has an input / output (I / O) interface 193 and an image processing unit 194. The image processing unit 194 has an image generation control unit 195, a ROM (with an upright image table 199 and a depth image table 200) 198, a VRAM (with a distortion parameter 196 and a buffer 197 for storing data after distortion processing) 201, and an image generation unit (image drawing unit) 202.

[0130] For the image generation control unit 195, for example, in the previous Figure 2In the example shown in (A), it is possible to implement control over the display positions of items such as the vehicle speed display SP and the arrow display AW' in the first area Z1, and the arrow display AW in the second area Z2. Furthermore, the display control unit (control unit) 190 can also use the aforementioned threshold, for example, during the calibration or initialization of the HUD device 100, to perform control such as setting the display area to an appropriate position.

[0131] Next, refer to Figure 10 . Figure 10 Figures (A) and (B) are other examples illustrating tilted display areas. The device structure itself and... Figure 1 (A) is the same.

[0132] The cross-sectional shape of the display area PS1, viewed from the width direction (left-right direction, X direction) of vehicle 1, is not limited to the previous view. Figure 1 The driver's side, as shown, has a convex shape. The display area PS1 can also be like... Figure 10 As shown in (A), the driver's side is concave. Additionally, the display area PS1 can also be as follows: Figure 10 As shown in (B), it is not curved. These are just examples; one can imagine display areas with various cross-sectional shapes.

[0133] Based on the structure of this embodiment, the effect of improving image recognizability was confirmed in experiments. In this experimental example, subjects were asked to identify virtual images displayed on various head-up displays and to provide sensory evaluations of whether they experienced discomfort. In this experiment, various head-up displays showed upright images with different convergence differences at the top and bottom. Here, all upright images on the various head-up displays were perceived as rectangular in the horizontal direction when viewed from the subject's observation position, and the vertical viewing angle was set to 0.75°.

[0134] Figure 11 This is a graph showing the experimental results of the percentage of people who answered that they did not feel discomfort for each convergence angle difference (horizontal axis) (vertical axis). It can be seen that after recognizing the upright image, as the convergence angle difference between the upper and lower ends decreases, the percentage of people who answered that they did not feel discomfort increases.

[0135] When the convergence angle difference was 0.22 degrees, the percentage of people who answered that they did not feel discomfort was 0%, indicating that all participants reported discomfort. Furthermore, when the convergence angle difference was 0.20 degrees, the percentage of people who answered that they did not feel discomfort was 20%; when the convergence angle difference was 0.17 degrees, the percentage was 40%; when the convergence angle difference was 0.15 degrees, the percentage was 40%; when the convergence angle difference was 0.14 degrees, the percentage was 60%; when the convergence angle difference was 0.12 degrees, the percentage was 80%; when the convergence angle difference was 0.09 degrees, the percentage was 100%; and when the convergence angle difference was 0.06 degrees, the percentage was 100%.

[0136] In the above experimental results, when the convergence difference was 0.22 degrees or more, all respondents reported feeling uncomfortable. When the convergence difference was 0.20 degrees or less, the number of people who reported feeling uncomfortable decreased. It is believed that when identifying an upright image, it is preferable that the convergence angle difference between the upper and lower ends of the upright image is 0.20 degrees or less.

[0137] Furthermore, setting the convergence angle difference to 0.14 degrees or less ensured that more than half of the participants did not experience discomfort. In other words, setting the convergence angle difference to 0.14 degrees or less resulted in a sufficiently high level of discomfort relief after viewing an upright image, which can be considered even better.

[0138] Furthermore, setting the convergence angle difference to 0.09 degrees or less ensures that no discomfort is felt by the entire group. In other words, setting the convergence angle difference to 0.09 degrees or less ensures that no discomfort is felt after recognizing an upright image, which can be considered even better.

[0139] This invention is widely applicable to parallax-type HUD devices that project images with parallax, and HUD devices that use beam reconstruction methods such as biconvex lenses.

[0140] In this specification, the term "vehicle" can be broadly interpreted as any means of transportation. Furthermore, terms related to navigation (such as navigation arrows) can be broadly interpreted, for example, considering navigation information that aids in vehicle navigation, and may also include road signs. Additionally, the term "orthogonal image" can be broadly interpreted as an image viewed directly by the observer, without being limited by its name. Furthermore, HUD devices also include those used as simulators (e.g., aircraft simulators, game simulators, etc.).

[0141] The present invention is not limited to the embodiments described above. Furthermore, those skilled in the art can easily modify the embodiments described above within the scope of the technical solution.

[0142] Symbol Explanation

[0143] 1: Vehicle (this vehicle); 2: Projected component (reflective light-transmitting component, windshield, etc.); 5: Projection area; 40: Road surface; 100: HUD device; 120: Optical system including optical components; 150: Projection unit (image projection unit); 160: Display unit (e.g., liquid crystal display device, screen, etc.); 164: Display surface; 170: Curved mirror (concave mirror, etc.); 179: Reflective surface; 188: Eye-tracking camera; 190: Display control unit (control unit); 192: Viewpoint position detection unit; 1 94: Image processing unit; 195: Image generation control unit; 196: Distortion parameter; 197: Distortion-processed data buffer; 198: ROM; 199: Upright image table; 200: Depth image table; 201: VRAM (Image Processing Storage Device); 202: Image generation unit (Image drawing unit); EB: Viewpoint area; PS1: Display area (Virtual image display surface); Z1: First display area capable of displaying both the upright image and the depth image; Z2: Second display area displaying the depth image.

Claims

1. A head-up display device, characterized in that, have: Image display unit, which displays images; An optical system that projects light from the image displayed by the image display unit onto a projection component, enabling the observer to recognize a virtual image of the image within an imaginary display area in the actual space in front of the observer; as well as The control unit controls the display of the image in the image display unit. The direction in the actual space that faces the observer is taken as the forward direction. The left and right directions are defined as the line segment perpendicular to the forward direction and connecting the observer's left and right eyes. Using the direction of a line segment orthogonal to the forward and left / right directions as the up / down or height direction, the direction of the surface in the actual space furthest from or equivalent to the ground is taken as upward, and the direction approaching is taken as downward. The control unit performs the following controls, namely, In the actual space, within the display area of ​​the inclined surface (which is a plane or curved surface) that slopes from the side closer to the observer and downwards towards the side farther away, relative to the ground or a surface equivalent to the ground, an upright image, which is an image that can be recognized upright, is displayed. The upright image is displayed in a display area that shows a quadrilateral outline as seen from the observer. The convergence angle difference between the upper and lower ends of the display area is set to be less than a predetermined threshold determined based on at least one of the following: image recognizability, recognition time, and psychological factors such as disharmony or discomfort. The convergence angle difference, which is the specified threshold, is set to 0.2°.

2. The head-up display device according to claim 1, characterized in that, The display area is divided into a first region capable of displaying all of the virtual images of the tilted image (i.e., the depth image) and the virtual image of the upright image, and a second region for displaying the virtual image of the depth image. The convergence angle difference between the upper and lower ends of the display area in the first region is set to be less than the predetermined threshold. The convergence angle difference between the upper and lower ends of the display area in the second region is set to be above the specified threshold.

3. The head-up display device according to claim 1 or 2, characterized in that, The specified threshold serves as a normal recognition probability determination threshold for assessing the normal recognition probability of the upright image. The convergence angle difference, which is the specified threshold, is set to 0.2°.

4. The head-up display device according to claim 1, characterized in that, When the viewpoint observed by the observer in the vertical (or height) direction is referred to as the vertical viewpoint, The specified threshold for limiting the convergence angle difference applies to the content of upright images with a vertical viewing angle of less than 0.75°.

Images