Head-up display device

Abstract

The purpose of the present invention is to make it possible to display, in an oblique image surface HUD device, an image (erect image) of a content to be viewed in an erect position while suppressing a decrease in visibility.　A control unit of a head-up display device according to the present invention performs control for displaying an erect image that is an image to be viewed in an erect position within a display area (Z1) that is a flat or curved inclined plane inclined from a side that is close to a viewer and a lower side to a side that is far from the viewer and an upper side with respect to a ground surface or a plane (40) corresponding to the ground surface in real space, the erect image is displayed in the display area (Z1) that is a quadrangular outline when viewed from the viewer, a convergence angle difference (θL-θU) between an upper end (PU) and a lower end (PL) of the display area (Z1) is set to less than a predetermined threshold (preferably a convergence angle of 0.2°) determined on the basis of at least one of the visibility of the image, the time required for visual recognition, and a psychological factor such as an uncomfortable feeling or an unpleasant feeling.

Description

[Technical field]

[0001] The present invention relates to a head-up display (HUD) device that projects (projects) display light of an image onto a projection member such as a windshield or combiner of a vehicle, etc., and displays a virtual image in front of a driver, etc. [Background technology]

[0002] 2. Description of the Related Art For the purpose of improving information recognition by a viewer (such as a driver), a head-up display (HUD) device having a virtual image display surface that is tilted in the depth direction has been proposed (see, for example, Patent Document 1).

[0003] This type of HUD device (hereinafter sometimes referred to as an oblique image plane HUD device or an inclined plane HUD device) improves recognition when it presents an information image with depth information (depth images such as arrows and maps), and it is also possible to view information images without depth information (in a broader sense, information images that do not emphasize depth) (upright images such as text and numbers) upright, making it highly convenient.

[0004] In addition, when it is said that something should be viewed upright, "upright" is used in the following sense: For example, content expressed by letters, numbers, etc. cannot be viewed (recognized) by humans or is difficult to view when it is upside down or inverted, or when the display surface is significantly tilted.

[0005] Therefore, when a HUD device displays letters, numbers, etc., it is necessary to display them as content that is correctly upright so that people can read the information correctly. The above-mentioned image (virtual image) is called an upright image (upright virtual image). Note that upright images are often displayed so that the viewer faces them, so they can also be called normal images. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-120135 A Summary of the Invention [Problem to be solved by the invention]

[0007] The inventors have studied oblique image plane HUD devices and have recognized the following new problem: If an image (virtual image) can be displayed on an inclined plane, as described above, it becomes possible to display an image (virtual image) with a sense of depth, and if the inclination is set upright to some extent with respect to the ground (or a surface equivalent to the ground: an equivalent surface), it is also possible to display an upright image of content that includes components such as letters and numbers for which a sense of depth is not important.

[0008] However, if the inclined surface is significantly inclined with respect to the ground (or its equivalent surface), this is suitable for displaying a sense of depth, but on the other hand, problems such as reduced visibility can arise for upright images, making it difficult for the viewer to recognize the image, or even if they are able to recognize it, it can take a long time for them to recognize it, or they may feel subjectively uncomfortable or unnatural.

[0009] If these issues do not become apparent, then an upright image can be correctly recognized, in other words, a normally upright image can be viewed; if not, then an upright image cannot be distinguished, identified, viewed, etc., or it is difficult to view it.

[0010] Therefore, in order to be able to efficiently design a HUD device, properly calibrate a HUD device, or properly initialize a HUD device, it is preferable to provide a reference index for determining whether or not a properly upright image can be recognized.

[0011] For example, when an image (virtual image) is displayed at a certain position in front of a specific point on the vehicle or the viewpoint of the viewer (driver, etc.), it is possible to impose a restriction such that the inclination angle of the display area with respect to the ground (equivalent surface) must not be less than a certain number of degrees.

[0012] However, human visibility (visual sensitivity) depends on the distance to the image. When displayed on the front side, the sensitivity is high, and when displayed on the back side, the sensitivity is relatively low. Therefore, with the above-described setting method, if the distance changes, the inclination (tilt angle) also changes, and a unified standard (threshold) cannot be obtained, resulting in poor usability.

[0013] Therefore, it is important to obtain an index that can be used as a unified standard (threshold) and to appropriately set a preferable value of the threshold. If this index is obtained, it becomes possible to set the inclination of an inclined surface (or display area) so that the reading of the upright image is not hindered by using the index, and the design and the like can be facilitated. In the prior art such as Patent Document 1, this point has not been studied at all, and an appropriate index has not been obtained.

[0014] One object of the present invention is to enable display of an image (upright image) of content that is visually recognized upright while suppressing a decrease in visibility in an oblique image plane HUD device.

[0015] Other objects of the present invention will become apparent to those skilled in the art by referring to the embodiments and best modes exemplified below and the accompanying drawings.

Means for Solving the Problems

[0016] Hereinafter, embodiments according to the present invention will be exemplified in order to easily understand the outline of the present invention.

[0017] In a first aspect, a head-up display device includes an image display unit that displays an image, an optical system that projects light of the image displayed by the image display unit toward a projection member, so that a virtual image of the image is visually recognized by a viewer within a virtual display area in front of the viewer in real space, a control unit that controls display of the image in the image display unit, and has A direction toward the front of the viewer in real space is defined as a forward direction, A direction perpendicular to the forward direction and along a line segment connecting the left and right eyes of the viewer is defined as a left-right direction; A direction along a line perpendicular to the forward direction and the left-right direction is defined as a vertical direction or a height direction, When the direction away from the ground or a surface equivalent to the ground in the real space is defined as the upward direction, and the direction approaching the ground is defined as the downward direction, The control unit is Implementing control to display an upright image, which is an image to be viewed upright, within the display area, which is a flat or curved inclined surface that is inclined from a side closer to the viewer and below the ground or a surface equivalent to the ground, to a side farther from the viewer and above the ground, in the real space; the upright image is displayed in a display area that is a rectangular outline as seen by the viewer, The difference in convergence angle between the upper end and the lower end of the display area is set to be less than a predetermined threshold determined based on at least one of image visibility, the time required for viewing, and psychological factors such as a sense of strangeness or discomfort.

[0018] In the first aspect, the degree of tilt of the display area that allows an upright image to be correctly viewed is determined using a new index (a threshold standard) called the "convergence angle difference (which can be replaced by the tilt distortion angle caused by it (see angle θd in Figure 6(C))")," making it more efficient (or easier) to determine or set the degree of tilt.

[0019] The display area has a rectangular outline, and the ground (or a surface equivalent to the ground: a road surface, etc.) side of the display area is the lower end (lower side), and the opposite side (the side away from the ground) is the upper end (upper side). Here, for example, a pair of points (which can be set at any position, but preferably, for example, the right end point or the left end point of each end (each side)) corresponding to each other are set at each of the lower end (lower side) and the upper end (upper side). The pair of points is set as a first point and a second point, the convergence angle (the angle formed by the visual axis indicating the line of sight of each eye) when the first point is seen from each of the left and right eyes is set as the first convergence angle, the convergence angle when the second point is seen is set as the second convergence angle, and the difference between the first convergence angle and the second convergence angle (the difference obtained by subtracting the second convergence angle from the first convergence angle) is set as the "convergence angle difference". In other words, this convergence angle difference can be called the "convergence angle difference between the upper end and the lower end of the display area".

[0020] Here, if the display area is erected on the ground (or its equivalent surface) at, for example, a substantially right angle, the top end (upper side) and bottom end (lower side) of the rectangle overlap in a plan view of the rectangle from above, and the first point overlaps with the second point. If the length (height) of the vertical side of the rectangle is small, the variation in the distance between the first and second points and the left and right eyes due to the height positions of the first and second points can be ignored. In the above case, the first and second convergence angles for the first and second points are the same (substantially the same), and the convergence angle difference is zero (substantially zero).

[0021] Here, when the display area is inclined with respect to the ground (or its equivalent surface) and the bottom end (bottom side) of the rectangle moves toward the viewer, a difference occurs between the convergence angles of the first and second points. In other words, the first convergence angle becomes larger than the second convergence angle. Therefore, the convergence angle difference is α (α is an integer greater than 0).

[0022] As the display area is further tilted and the bottom end (bottom side) of the rectangle moves further toward the viewer, the first convergence angle increases further, causing a larger difference with the second convergence angle, and the convergence angle difference becomes β (β is an integer that satisfies α<β).

[0023] In this way, the "convergence angle difference between the upper and lower ends of the display area" is an index showing the degree of inclination of the display area with respect to the ground (or its equivalent surface). In addition, since the convergence angle varies depending on the distance from the viewer's eyes, it contains distance information, and therefore the convergence angle difference is a single integrated index (threshold value) that contains information on the degree of inclination of the display area (or virtual image display surface, etc.) with respect to the ground (or its equivalent surface), including distance. There is no need to set the inclination with preconditions such as a certain number of degrees of inclination angle for a certain number of meters of distance, as in the past.

[0024] Here, the visibility of an upright image varies from person to person and cannot be generalized, but it is possible to objectively determine whether or not a properly upright image is visible based on at least one of the visibility of the displayed image, the time required for viewing, and psychological factors such as discomfort or annoyance, etc. In addition, by using the above-mentioned index when making such a judgment, a threshold value that can be used for the judgment can be obtained.

[0025] As described above, the greater the inclination of the display area, the closer the first point is to the viewer, the greater the value of the convergence angle difference. Therefore, for example, the convergence angle difference near the limit at which the viewer can fuse (synthesize) the images of the left and right eyes in the brain and recognize an upright image is set as a threshold, and for example, when designing a HUD device, if each part is set so that the convergence angle difference is less than the threshold, the viewer can recognize the upright image even if it is displayed on an inclined surface. In other words, the visibility of the upright image by the viewer is ensured to be at a predetermined level or higher.

[0026] In this way, for example, the design that enables displaying an image of content to be viewed upright (upright image) while suppressing the decrease in visibility is made more efficient or easier. In addition, this new index (convergence angle difference, or the tilt distortion angle caused by it) can be used for the calibration of the HUD device, the initialization of the HUD device, the simulation of the functions of the HUD device, etc., and the effect of making each process more efficient can be obtained.

[0027] In a second embodiment dependent on the first embodiment, The display area is divided into a first area capable of displaying both a virtual image of a depth image, which is an image viewed at an angle, and a virtual image of the upright image, and a second area 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 may be set to less than the predetermined threshold, and the convergence angle difference between the upper and lower ends of the display area in the second region may be set to greater than or equal to the predetermined threshold.

[0028] In a second aspect, 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 a 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 equal to or greater than the above-mentioned predetermined threshold value.

[0029] As described above, the threshold is set based on the visibility of an upright image, and above that threshold, the visibility of the upright image decreases and it is not suitable for displaying an upright image, but in other words, it is suitable for displaying a depth image expressed at an angle (including an image that gives the visual sensation of floating in the air and extending substantially parallel to the road surface, or superimposed on the road surface). Therefore, for the image (virtual image) displayed in the second area, the convergence angle difference, etc. is set to a threshold or higher. This makes it possible to ensure appropriate visibility of each image, for example, when an upright image is displayed in the first area and a depth image is displayed in the second area.

[0030] In a third aspect dependent on the first or second aspect, The predetermined threshold functions as a normal tone visibility determination threshold for determining the normal tone visibility of the upright image, The convergence angle difference as the predetermined threshold may be set to 0.2°.

[0031] In the third aspect, it is made clear that the above-mentioned "predetermined threshold" can be used, specifically, for example, as a "normal tone visibility determination threshold", and it is made clear that an example of a preferable value thereof is 0.2°.

[0032] In a fourth aspect dependent on any one of the first to third aspects, When the angle of view in the up-down direction (or height direction) as seen by the viewer is referred to as a vertical angle of view, the limitation on the convergence angle difference by the predetermined threshold value may be applied to upright image content with a vertical angle of view of 0.75° or less.

[0033] In the fourth aspect, taking into consideration that as the size of the displayed content increases, even with the same convergence angle difference, it becomes more difficult for the brain to fuse the image for the left eye and the image for the right eye, the above threshold is applied to small content with a vertical angle of 0.75° or less, and the convergence angle difference between the upper and lower ends is set to be less than the threshold.

[0034] In addition, it has been confirmed that upright content larger than this size increases the annoyance of the HUD device in terms of obstructing the view, and the current feasibility of implementing it is not high. Therefore, there is no particular problem in applying the above threshold to display content that is equal to or smaller than a certain size.

[0035] Those skilled in the art will easily understand that the exemplified embodiments according to the present invention can be further modified without departing from the spirit of the present invention. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1(A) is a diagram showing the configuration of a HUD device mounted on a vehicle and an example of an inclined display area, and FIGS. 1(B) and 1(C) are diagrams showing examples of a method for realizing the display area shown in FIG. 1(A). [Diagram 2] FIG. 2(A) is a diagram showing the main configuration of a HUD device mounted on a vehicle and an example of a display in the display area, and FIG. 2(B) is a diagram showing an example of a display area composed of a first area capable of displaying both a virtual image of a depth image and a virtual image of an upright image, and a second area that displays a virtual image of a depth image. [Diagram 3]Figure 3(A) shows an inclined surface (inclined display area) with an arrow shape displayed as a depth image placed in front of the viewer, which is viewed with both eyes; Figure 3(B) shows the image seen by the left eye; Figure 3(C) shows a depth image seen by fusing (synthesizing) the images of the left and right eyes; and Figure 3(D) shows an image seen by the right eye. [Figure 4] Figure 4(A) shows an inclined surface (inclined display area) with a vehicle speed displayed as an upright image placed in front of the viewer, which is viewed with both eyes; Figure 4(B) shows the image seen by the left eye; Figure 4(C) shows an upright image seen by fusing (synthesizing) the images from the left and right eyes; and Figure 4(D) shows the image seen by the right eye. [Diagram 5] Figure 5(A) shows a state in which a viewer is looking with both eyes at a display area that is erected almost perpendicular to the road surface, Figure 5(B) shows the convergence angle of both eyes relative to a first right end point at the upper end (upper edge) of the display area in Figure 5(A) and a second right end point at the lower end (lower edge) corresponding to the first right end point, and Figure 5(C) shows an image obtained by fusion (synthesizing) the images of the left eye and the right eye. [Figure 6] Figure 6(A) shows a state in which a viewer is looking with both eyes at a display area inclined at approximately 45 degrees with respect to the road surface. Figure 6(B) shows the convergence angle of both eyes relative to a first right end point at the upper end (upper edge) of the display area in Figure 6(A) and a second right end point at the lower end (lower edge) corresponding to the first right end point. Figure 6(C) shows an image seen by the left eye. Figure 6(D) shows an upright image formed by fusing (synthesizing) the images of the left and right eyes. Figure 6(E) shows an image seen by the right eye. [Figure 7] Figure 7(A) shows a state in which a viewer is looking with both eyes at a display area inclined at approximately 30° with respect to the road surface; Figure 7(B) shows the convergence angle of both eyes relative to a first right end point at the upper end (upper edge) of the display area in Figure 7(A) and a second right end point at the lower end (lower edge) corresponding to the first right end point; Figure 7(C) shows an image seen with the left eye; Figure 7(D) shows a visual field that is difficult to see due to double vision when the images of the left and right eyes are fused (synthesized); and Figure 7(E) shows an image seen with the right eye. [Figure 8]8(A) and (B) are flowcharts showing an example of a design method for a HUD device (oblique image plane HUD device). [Figure 9] FIG. 2 is a diagram illustrating an example of the configuration of a display control unit (control unit) in the HUD device. [Figure 10] 10A and 10B are diagrams showing other examples of tilted display areas. [Figure 11] FIG. 11 is a graph showing the experimental results, showing the percentage of people who answered that they did not feel discomfort (vertical axis) for each convergence angle difference (horizontal axis). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The best mode described below is used to easily understand the present invention. Therefore, those skilled in the art should be aware that the present invention is not unduly limited by the mode described below.

[0038] Please refer to Fig. 1. Fig. 1(A) is a diagram showing an example of the configuration of a HUD device mounted on a vehicle and an inclined display area, and Fig. 1(B) and (C) are diagrams showing an example of a method for realizing the display area shown in Fig. 1(A). In Fig. 1, the direction along the front of the vehicle 1 (also called the front-rear direction) is the Z direction, the direction along the width (horizontal width) of the vehicle 1 (or the left-right direction) is the X direction, and the height direction or upward direction of the vehicle 1 (the direction of a line segment perpendicular to a flat road surface 40, moving away from the ground or its equivalent surface (here, the road surface) 40) is the Y direction.

[0039] In the following description, the term virtual display area (sometimes simply referred to as display area) provided in front of the viewer or the like can be interpreted in a broad sense. For example, it may be a virtual display surface (sometimes referred to as a virtual image display surface) corresponding to (the display range of) a display surface such as a screen on which an image is displayed, and when an image displayed on the virtual display surface is arranged within an image area of ​​a predetermined size and a predetermined shape (e.g., a rectangle), the image area can be considered as one display area (or a part of the virtual image display surface). In the following description, taking the above into consideration, it will be simply referred to as a "display area".

[0040] In addition, in explaining the shape of the display area, the terms up and down may be used. Here, for convenience of explanation, the direction along the line segment (normal line) perpendicular to the road surface 40 (which is also the height direction of the vehicle 1) is defined as the up-down direction. When the road surface is horizontal, the vertical downward direction is the down direction, and the opposite direction is the up direction. This point can also be applied to the explanation of the other drawings.

[0041] 1(A), a HUD device 100 according to this embodiment is mounted inside a dashboard 41 of a vehicle (host vehicle) 1. The HUD device 100 is capable of displaying, in a display area PS1 having an area inclined with respect to a road surface 40 in front of the vehicle 1, an upright image (an image that does not particularly emphasize depth, also called a standing image, which may be composed of, for example, numbers, letters, etc.) that is viewed upright, and a depth image in which depth is an important element (also called a tilted image or tilted image, for example, a navigation arrow extending along the road surface 40, etc.).

[0042] The HUD device 100 has a display section (sometimes called an image display section, specifically, for example, a screen) 160 having a display surface 164 for displaying an image, an optical system 120 including an optical member for projecting display light K for displaying an image onto a windshield, which is a projection target member (reflective light-transmitting member) 2, and a light projection section (image projection section) 150. The optical member 120 has a curved mirror (also called a concave mirror or a magnifying reflector) 170 having a reflecting surface 179. The reflecting surface 179 of the curved mirror 170 does not have a uniform radius of curvature, but can have a shape consisting of a collection of partial regions having multiple radii of curvature, for example, and can utilize a design method for a free-form surface (it may be the free-form surface itself). A free-form surface is a curved surface that cannot be expressed by a simple mathematical formula, and can be expressed by a high-order equation by setting several intersections and curvatures in space. The curved surface is expressed by interpolating the intersections of the two. The shape of the reflecting surface 179 has a significant effect on the shape of the display area PS1 and its relationship to the road surface.

[0043] The shape of the display area PS1 is influenced by the shape of the reflecting surface 179 of the curved mirror (concave mirror) 130, the curved shape of the windshield (reflective light-transmitting member 2), and the shape of other optical members (e.g., correction mirrors) mounted in the optical system 120. It is also influenced by the shape of the display surface 164 of the display unit 160 (which is generally flat, but may be non-flat in whole or in part) and the arrangement of the display surface 164 relative to the reflecting surface 179. However, the curved mirror (concave mirror) 170 is a magnifying reflecting mirror, and has a significant effect on the shape of the display area (virtual image display surface). If the shape of the reflecting surface 179 of the curved mirror (concave mirror) 170 is different, the shape of the display area (virtual image display surface) PS1 actually changes.

[0044] In addition, the display area PS1 extending integrally from the near end U1 to the far end U3 can be formed by positioning the display surface 164 of the display unit 160 obliquely at an intersection angle of less than 90 degrees with respect to the optical axis of the optical system (the main optical axis corresponding to the principal ray).

[0045] The shape of the curved surface of the display region PS1 may be adjusted by adjusting the optical characteristics of the entire region or a part of the region in the optical system, by adjusting the arrangement of the optical members and the display surface 164, by adjusting the shape of the display surface 164, or by a combination of these. In this way, the shape of the virtual image display surface can be adjusted in various ways. This makes it possible to realize the display region PS1 having the first region Z1 and the second region Z2.

[0046] In other words, the display area PS1 is divided into a first area Z1 capable of displaying both depth images (tilted images) and upright images (standing images), and a second area suitable for displaying depth images (tilted images) (in other words, used exclusively for displaying depth images).

[0047] This point will be described in detail below. As shown on the left and bottom left of Fig. 1(B), the manner and degree of the overall inclination of the display area (including the virtual image display surface) PS1 is adjusted depending on the manner and degree of inclination of the display surface 164 of the display unit 160. In the example of Fig. 1(B), the distortion of the display area (virtual image display surface) caused by the curved surface of the windshield (reflective translucent member 2) is corrected by the curved shape of the reflecting surface 179 of the curved mirror (concave mirror, etc.) 170, and as a result, a flat display area (virtual image display surface) PS1 is generated.

[0048] Furthermore, as shown on the right and lower left of Figure 1(B), by adjusting the positional relationship between the optical member (here, a curved mirror (concave mirror, etc.) 170) and the display surface 164, in other words, for example by rotating the display surface 164 to change the relative relationship with the optical member (curved mirror 170), the degree to which the display area (virtual image display surface) PS1, which is an inclined surface, is separated from the road surface 40 can be adjusted.

[0049] Furthermore, as shown in FIG. 1(C), by adjusting the shape of the reflective surface of the curved mirror (concave mirror, etc.) 170, which is an optical component (or by adjusting the shape of the display surface 164 of the display unit 160), the virtual image display distance near the end (near end) U1 of the display area PS1 closer to the vehicle 1 is changed, so that the area near the near end U1 is bent toward the road surface and controlled to stand upright relative to the road surface (in other words, made vertical), thereby obtaining a display area PS1 having an inclined portion.

[0050] As shown in the upper part of FIG. 1(C), reflecting surface 179 of curved mirror 170 can be divided into three parts (areas): Near (nearby display area), Center (middle (central) display area), and Far (distant display area).

[0051] Here, Near is the part that generates display light E1 (shown by a dotted line in Figures 4(A) and (B)) corresponding to the near end U1 of the display area PS1, Center is the part that generates display light E2 (shown by a dashed line) corresponding to the middle (central) part U2 of the display area PS1, and Far is the part that generates display light E3 (shown by a solid line) corresponding to the far end U3 of the display area PS1.

[0052] In Fig. 1(C), the Center and Far parts are the same as the curved mirror (concave mirror or the like) 170 shown in Fig. 1(B) when generating the planar display area PS1. However, in Fig. 1(C), the curvature of the Near part is set smaller than that in Fig. 1(B). As a result, the magnification corresponding to the Near part becomes larger.

[0053] The magnification (c) of the HUD device 100 can be expressed as c=b / a, where a is the distance from the display surface 164 of the display unit 160 to the windshield 2 and b is the distance from the light reflected by the windshield (reflective light-transmitting member 2) to the imaging point via viewpoint A, but as the curvature of the near portion decreases, a becomes smaller, the magnification increases, and the image is formed at a position farther away from the vehicle 1. That is, in the case of Fig. 1(C), the virtual image display distance is greater than in the case of Fig. 1(B).

[0054] Therefore, the near end U1 of the display area PS1 is pulled away from the vehicle 1, and the near end U1 is curved toward the road surface 40 in a bowed shape, resulting in the formation of the first area Z1. This results in the display area PS1 having the first area Z1 and the second area Z2.

[0055] Next, refer to Fig. 2. Fig. 2(A) is a diagram showing the main configuration of a HUD device mounted on a vehicle and a display example in the display area, and Fig. 2(B) is a diagram showing an example of a display area configured with a first area capable of displaying both a virtual image of a depth image and a virtual image of an upright image, and a second area displaying the virtual image of a depth image. In Fig. 2, parts common to Fig. 1 are given the same reference numerals.

[0056] As shown in FIG. 2, the HUD device 100 has a display unit (e.g., a light-transmitting screen) 160 having a display surface 164, a reflecting mirror 165, and a curved mirror (e.g., a concave mirror having a reflecting surface 179, which may be a free-form surface) 170 as an optical member that projects display light. An image displayed on the display unit 160 is projected onto a projection area 5 of a windshield 2 as a projection target member via the reflecting mirror 165 and the curved mirror 170. Note that the HUD device 100 may be provided with a plurality of curved mirrors. In addition to the mirror (reflective optical element) of this embodiment, or instead of a part (or the whole) of the mirror (reflective optical element) of this embodiment, a configuration including a refractive optical element such as a lens, a functional optical element such as a diffractive optical element, etc. may be adopted.

[0057] A part of the display light of the image is reflected by the windshield 2 and enters the viewpoint (eye) A of the driver or the like located inside (or on) a preset eye box EB (which is three-dimensional but is drawn two-dimensionally for convenience), and is imaged in front of the vehicle 1, thereby displaying various images (virtual images) on a virtual display area (virtual image display surface) PS1. In FIG. 2(A), as display examples in the first area Z1 of the display area PS1, for example, a vehicle speed display SP which is an upright image (upright virtual image) and an image (virtual image) AW' of a navigation arrow which is a depth display are shown. In addition, in the second area Z2, an image (virtual image) AW of a navigation arrow extending from the front side to the back side of the vehicle 1 along the road surface 40 is shown.

[0058] 2(B), the angle (inclination angle) that the first region Z1 makes with the road surface 40 is θ1 (0<θ1<90°), and the angle (inclination angle) that the second region Z2 makes with the road surface 40 is θ2 (0<θ2<θ1). Both the first and second regions Z1 and Z2 are inclined regions (or regions having at least an inclined portion).

[0059] Next, reference is made to Fig. 3. Fig. 3(A) is a diagram showing a state in which an inclined surface (inclined display area) on which an arrow figure is displayed as a depth image is placed in front of the viewer and the viewer views it with both eyes, Fig. 3(B) is a diagram showing the image seen by the left eye, Fig. 3(C) is a diagram showing a depth image seen by fusing (combining) the images of the left and right eyes, and Fig. 3(D) is a diagram showing the image seen by the right eye.

[0060] In Fig. 3(A), a midpoint C0 is drawn at the center between the left eye A1 and the right eye A2. For convenience, the image obtained by fusing the image seen by the left eye A1 and the image seen by the right eye A2 in the viewer's brain can be called the image at the midpoint position C0.

[0061] In Fig. 3(A), an image (virtual image) AW of a navigation arrow extending at an angle is displayed in the second area Z2 of the display area PS1. When the images (images with binocular parallax) of the left and right eyes A1 and A2 shown in Figs. 3(B) and (D) are fused (combined), an image with a sense of depth (three-dimensionality) as shown in Fig. 3(C) is viewed. In other words, due to a change in image shape caused by a positional shift between the upper and lower ends of the angle of view for each of the left and right eyes A1 and A2, the image (virtual image) AW of the arrow is naturally viewed as being inclined toward the back, improving visibility or recognizability.

[0062] Next, reference is made to Fig. 4. Fig. 4(A) is a diagram showing a state in which an inclined surface (inclined display area) on which a vehicle speed display is displayed as an upright image is placed in front of the viewer and the viewer views the inclined surface with both eyes, Fig. 4(B) is a diagram showing the image seen by the left eye, Fig. 4(C) is a diagram showing an upright image seen by fusing (combining) the images of the left and right eyes, and Fig. 4(D) is a diagram showing the image seen by the right eye.

[0063] In Fig. 4(A), an image (virtual image) of a vehicle speed display SP (displaying "120km / h" as shown in Fig. 4(B) etc.) is displayed in a first region Z1 of a display region PS1. This vehicle speed display SP is displayed in the inclined first region Z1, and is displayed as an upright image (upright virtual image) that is visually recognized upright.

[0064] If the inclination angle of the first area Z1 with respect to the road surface 40 is not too small and the area is erected to some extent, the viewer's recognition is not impaired and the viewer can view the image as an upright image (read information as an upright image). In this case, for example, when the images (images with binocular parallax) of the left and right eyes A1 and A2 shown in Fig. 4(B) and (D) are fused (combined), the vehicle speed display SP is viewed as an upright image as shown in Fig. 4(C).

[0065] On the other hand, when the inclination angle of the first region Z1 with respect to the road surface 40 is small and the images fail to be fused (combined) by each of the left and right eyes, the appearance will vary from person to person; for example, the image may appear tilted overall, or the shape of one of the eyes may change. In any case, visibility will decrease, the recognition time will increase, and it will not be perceived favorably subjectively (due to psychological factors).

[0066] Next, reference is made to Fig. 5. Fig. 5(A) is a diagram showing a state in which a viewer is viewing a display area that is erected almost perpendicularly to a road surface with both eyes, Fig. 5(B) is a diagram showing the convergence angle of both eyes with respect to a first right end point of the upper end (upper side) of the display area in Fig. 5(A) and a second right end point of the lower end (lower side) corresponding to the first right end point, and Fig. 5(C) is a diagram showing an image obtained by fusing (combining) the images of the left eye and the right eye.

[0067] In the following description, the display area is assumed to have an outline of a given shape (here, a rectangle), and the ground side (or the surface equivalent to the ground: road surface, etc.) of the display area is assumed to be the bottom end (lower side), and the opposite side (the side away from the ground) is assumed to be the top end (upper side). Note that the "rectangle" indicating the shape of the display area is interpreted in a broad sense to include, for example, a rectangle, a square, a trapezoid, a parallelogram, etc.

[0068] In Fig. 5(A), a display area (here, a first area Z1) is shown that is set up substantially perpendicular to a road surface 40 in front of a viewer. The viewer sees an image (virtual image) displayed in the first area Z1 with both eyes A1 and A2. As shown in Fig. 5(C), the displayed image (virtual image) is the vehicle speed display SP shown above.

[0069] In Figure 5 (A), the lower end of the angle of view in the display area (first area Z1) (hereinafter sometimes simply referred to as the lower end or lower side) is indicated with the symbol PL, and the upper end of the angle of view (hereinafter sometimes simply referred to as the upper end or upper side) is indicated with the symbol PU.

[0070] FIG. 5B shows the convergence angle due to the viewer's binocular disparity in plan view when looking from the top to the bottom (the -Y direction indicated by the arrow in the figure) in FIG. 5A.

[0071] In addition, in Fig. 5(B), a pair of corresponding points (which can be set at any position, but preferably are, for example, the right end point or the left end point of each end (each side)) is set at each of the lower end (lower side) PL and the upper end (upper side) PU. In Fig. 5(B), a right end point R1 of the lower end (lower side) and a right end point R2 of the upper end (upper side) are set. Point R1 is called the first point, and point R2 is called the second point.

[0072] The convergence angle when the first point R1 is viewed from each of the left and right eyes A1 and A2 (the angle formed by the visual axes indicating the line of sight of each eye A1 and A2) is the first convergence angle θL, the convergence angle when the second point R2 is viewed is the second convergence angle θU, and the difference between the first convergence angle θL and the second convergence angle θU (the difference obtained by subtracting the second convergence angle θU from the first convergence angle θL) is the "convergence angle difference." In other words, this convergence angle difference can be called the "convergence angle difference between the upper end (or upper side) and the lower end (or lower side) of the display area."

[0073] In the example of FIG. 5, the display area (first area Z1) is erected at a substantially right angle to the road surface 40, so that in a plan view of the rectangle of the outline of the display area (first area Z1) seen from above, the upper end (upper side) PU of the rectangle overlaps with the lower end (lower side) PL, and the first point R1 overlaps with the second point R2. Here, if the length of the vertical side of the rectangle (the length of the line segment showing the first area Z1 in FIG. 5(A): in other words, the height of the first area based on the road surface 40) is small, the difference in distance (variation in distance) between the first and second points R1 and R2 and the left and right eyes A1 and A2 due to the difference in the height positions of the first and second points R1 and R2 can be ignored. In the above case, the values ​​of the first and second convergence angles θL and θU for the first and second points R1 and R2 are the same (almost the same), and the convergence angle difference is zero (almost zero).

[0074] As shown in FIG. 5(C), the image obtained by fusing (synthesizing) the images from the left and right eyes (the image at the central position C0, abbreviated as the image at C0) is viewed as a vertical image, and there is no problem with the visibility of the vehicle speed display SP.

[0075] Next, reference is made to Fig. 6. Fig. 6(A) is a diagram showing a state in which a viewer is viewing a display area inclined at approximately 45° with respect to the road surface with both eyes, Fig. 6(B) is a diagram showing the convergence angle of both eyes with respect to a first right end point at the upper end (upper side) of the display area in Fig. 6(A) and a second right end point at the lower end (lower side) corresponding to the first right end point, Fig. 6(C) is a diagram showing an image viewed by the left eye, Fig. 6(D) is a diagram showing an upright image obtained by fusing (combining) the images of the left eye and the right eye, and Fig. 6(E) is a diagram showing an image viewed by the right eye.

[0076] As shown in FIG. 6(A), the display area (first area Z1) is arranged at an inclination of approximately 45° with respect to the road surface 40. The lower end (lower side) of the rectangle showing the outline of the first area Z1 moves toward the viewer. In FIG. 6(B), the lower end (lower side) PL is closer to the viewer than the upper end (upper side) PU. As a result, a difference occurs between the values ​​of the first convergence angle θL with respect to the first point R1 and the second convergence angle θU with respect to the second point R2. In other words, the first convergence angle θL is larger than the second convergence angle θU. Therefore, the convergence angle difference is α (α is an integer greater than 0).

[0077] See Figures 6(C) and (E). The display area Z1 is inclined toward the back as it approaches the top, which places a heavy burden on the left eye A1 and the right eye A2. Furthermore, due to binocular parallax, the image seen by the left eye A1 is distorted to the left as a rectangle, and the image seen by the right eye A2 is distorted to the right as a rectangle, resulting in an image that is perceived as a roughly parallelogram shape. This also makes it difficult to view the upright image (vehicle speed display SP).

[0078] However, the human eye can recognize an upright image by correcting the depth and left / right distortion to a certain extent, and the limit of the correction function (recognition function) is not exceeded in the example of Fig. 6. Therefore, as shown in Fig. 6(D), the vehicle speed display SP can be correctly recognized as an upright image.

[0079] Next, reference is made to Fig. 7. Fig. 7(A) is a diagram showing a state in which a viewer is viewing a display area inclined at approximately 30° with respect to the road surface with both eyes, Fig. 7(B) is a diagram showing the convergence angle of both eyes with respect to a first right end point at the upper end (upper side) of the display area in Fig. 7(A) and a second right end point at the lower end (lower side) corresponding to the first right end point, Fig. 7(C) is a diagram showing an image viewed with the left eye, Fig. 7(D) is a diagram showing a visual field that is difficult to view due to double vision when the images of the left eye and the right eye are fused (combined), and Fig. 7(E) is a diagram showing an image viewed with the right eye.

[0080] As shown in FIG. 7(A), the display area (first area Z1) is further inclined with respect to the road surface 40. As shown in FIG. 7(B), the bottom end (bottom side) PL of the rectangle moves further toward the viewer, approaching the viewer. As a result, the first convergence angle θL increases further. Therefore, the difference with the second convergence angle θU becomes larger, and the convergence angle difference (θL-θU) becomes β (β is an integer that satisfies α<β).

[0081] In the example of Fig. 7, the limit of the correction function for the depth and left-right distortion of a person is exceeded, and the image cannot be fused correctly. Therefore, as shown in Fig. 7(C) to (E), the vehicle speed display SP, which is an upright image, cannot be viewed correctly. Note that since it is difficult to draw a specific figure, it is simply written as SP in the figure.

[0082] As explained above in Figures 5 to 7, the "convergence angle difference (θL-θU) between the upper end (upper side) and lower end (lower side) of the display area" can be an indicator of the degree of inclination of the display area with respect to the ground (or its equivalent surface).

[0083] In addition, the convergence angles θL, θU vary depending on the distance from the viewer's eyes A1, A2, and therefore contain distance information. Therefore, the convergence angle difference (θL-θU) is a single integrated index (threshold value) that contains information on the degree of inclination of the display area (or virtual image display surface, etc.) with respect to the ground (or its equivalent surface), including distance. Unlike the conventional method, it is no longer necessary to set the inclination with a prerequisite distance, such as a certain number of degrees of inclination angle for a certain number of meters of distance. Therefore, by introducing this index into the design of the HUD device, the setting of the inclination of the display area becomes more efficient (easier).

[0084] Here, the visibility of an upright image varies from person to person, and cannot be generalized, but it is possible to objectively determine whether or not a properly upright image is visible based on at least one of the visibility of the displayed image (first factor), the time required for viewing (second factor), and psychological factors such as a sense of incongruity or discomfort (third factor).Then, by using the above-mentioned indexes when making this determination, a threshold value that can be used for the determination can be obtained.

[0085] (Experimental Results) The present inventor, with the cooperation of several people, tried to determine whether an upright image can be correctly judged using the convergence angle difference as an index based on each of the first to third factors. Here, when NG is detected in all three factors, it is deemed difficult to view a normal upright image, and when NG is detected in one or two factors, it is deemed possible to view a normal upright image.

[0086] As a result, it was found that when the convergence angle difference between the upper and lower ends of an image viewed upright is 0.182°, it becomes difficult to view. When the threshold is set to the order of 0.1, 0.182 is rounded up to 0.2. Therefore, 0.2° was extracted as an example of a preferable threshold. Therefore, by making the convergence angle difference less than 0.2°, it becomes possible to view an upright image.

[0087] Specifically, this "predetermined threshold" can be used as, for example, a "normal tone visibility determination threshold", and a preferable value thereof is the above-mentioned 0.2°.

[0088] By utilizing this threshold (index), for example, the design that allows the display of an image of content to be viewed upright (erect image) while suppressing the decrease in visibility can be made more efficient or easier. In addition, this new index (convergence angle difference, or the tilt distortion angle caused by it (see angle θd in FIG. 6(C))) can also be used for the calibration of the HUD device, the initialization of the HUD device, and the simulation of the functions of the HUD device, and the like, and has the effect of making each process more efficient.

[0089] Furthermore, as previously shown in FIG. 2(A), when 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, the convergence angle difference between the upper and lower ends of the display area in the second area Z2 is preferably set to be greater than or equal to the above-mentioned predetermined threshold value (preferably 0.2°).

[0090] As described above, the threshold is set based on the visibility of an upright image, and above the threshold, the visibility of the upright image is reduced and it is not suitable for displaying an upright image, but in other words, it is suitable for displaying a depth image expressed at an angle (including an image that gives the visual sensation of floating in the air and extending approximately parallel to the road surface, or superimposed on the road surface). Therefore, for the image (virtual image) displayed in the second area Z2, the convergence angle difference is set to a threshold or more. This makes it possible to ensure appropriate visibility of each image, for example, when an upright image is displayed in the first area Z1 and a depth image is displayed in the second area Z2.

[0091] When the angle of view in the up-down direction (or height direction) as seen by the viewer is referred to as the vertical angle of view, the limitation of the convergence angle difference by a predetermined threshold value may be applied to upright image content with a vertical angle of view of 0.75° or less.

[0092] In other words, as the size of the displayed content increases, it becomes more difficult for the brain to fuse the image for the left eye and the image for the right eye, even with the same convergence angle difference. Therefore, for small content with a vertical angle of 0.75° or less, the above threshold is applied, and the convergence angle difference between the upper and lower ends is set to be less than the threshold.

[0093] Moreover, it has been confirmed that upright content larger than this size increases the annoyance in terms of obstructing the view in the HUD device 100, and the current feasibility of implementing it is not high. Therefore, it is considered that there is no particular problem in applying the above threshold value only to display content that is equal to or smaller than a certain size.

[0094] Next, reference is made to Fig. 8. Fig. 8(A) and (B) are flowcharts showing an example of a design method for a HUD device (oblique image plane HUD device). In Fig. 8(A), in the oblique image plane HUD device, each part is designed so that the convergence angle difference (or the tilt distortion angle caused by it) between the upper and lower ends of the display area of ​​an information image (erect image) to be viewed upright is less than a predetermined threshold (preferably less than 0.2°) determined based on at least one of the visibility of the image, the time required for viewing, and psychological factors such as discomfort or annoyance (step S1).

[0095] 8B, the display area is divided into a first area capable of displaying both an information image (depth image) viewed at an angle and an information image (upright image) viewed upright, and a second area for displaying an information image (depth image) viewed at an angle (step S2). Next, for content with a vertical angle of view of 0.75° or less, the first area is designed so that the difference in convergence angle between the top and bottom ends is less than a predetermined threshold (preferably less than 0.2°), and the difference in convergence angle between the top and bottom ends of the second area is designed to be equal to or greater than the predetermined threshold (step S3).

[0096] Next, reference is made to Fig. 9. Fig. 9 is a diagram showing an example of the configuration of a display control unit (control unit) in a HUD device. The upper diagram of Fig. 9 is almost the same as Fig. 1(A). However, in Fig. 9, a gaze detection camera 188 and a viewpoint position detection unit 192 are provided.

[0097] 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 (having an upright image table 199 and a depth image table 200) 198, a VRAM (having warping parameters 196 and a post-warping data storage buffer 197) 201, and an image generation unit (image rendering unit) 202.

[0098] The image generation control unit 195 can control the display position of the content, for example, in the example shown in Fig. 2(A) above, by arranging 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 perform control such as setting the display area to an appropriate position, for example, by using the above threshold value, for example, during calibration or initialization of the HUD device 100.

[0099] Next, reference is made to Fig. 10. Fig. 10(A) and (B) are diagrams showing another example of an inclined display area. The device configuration itself is the same as that of Fig. 1(A).

[0100] The cross-sectional shape of the display area PS1 as viewed in the width direction (left-right direction, X direction) of the vehicle 1 is not limited to the convex shape on the driver's side shown in FIG. 1 and the like. The display area PS1 may be concave on the driver's side as shown in FIG. 10(A). Also, the display area PS1 does not have to be curved as shown in FIG. 10(B). These are just examples, and display areas with various cross-sectional shapes can be envisioned.

[0101] It has been confirmed through experiments that the configuration of this embodiment has the effect of improving the visibility of images. In this experimental example, a sensory evaluation was carried out in which subjects viewed virtual images displayed by a plurality of types of head-up display devices and responded whether or not they felt discomfort. In this experiment, the plurality of types of head-up display devices each displayed an upright image with a different convergence difference between the upper end and the lower end. Here, in each of the plurality of types of head-up display devices, the upright image has a shape that is viewed as a rectangle in the vertical and horizontal directions when viewed from the observation position of the subject, and the vertical angle of view is set to 0.75°.

[0102] Figure 11 is a graph of the experimental results showing the percentage of people who answered that they did not feel discomfort (vertical axis) for each convergence angle difference (horizontal axis). It can be seen that when viewing an upright image, the percentage of people who answered that they did not feel discomfort increases as the convergence angle difference between the top and bottom ends becomes smaller.

[0103] When the convergence angle difference was 0.22 degrees, the percentage of people who answered that they did not feel uncomfortable was 0%, and all of the subjects answered that they felt uncomfortable. When the convergence angle difference was 0.20 degrees, the percentage of people who answered that they did not feel uncomfortable was 20%, when the convergence angle difference was 0.17 degrees, the percentage of people who answered that they did not feel uncomfortable 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 100%, when the convergence angle difference was 0.09 degrees, and the percentage was 100% when the convergence angle difference was 0.06 degrees.

[0104] In the above experimental results, when the convergence disparity was 0.22 [degrees] or more, all participants reported feeling uncomfortable, and when the convergence disparity was 0.20 [degrees] or less, the number of participants who reported feeling uncomfortable decreased. Therefore, when viewing an upright image, it is considered preferable that the convergence angle difference between the upper and lower ends of the upright image be 0.20 [degrees] or less.

[0105] In addition, it was confirmed that more than half of the subjects did not feel uncomfortable when the convergence angle difference was set to 0.14 degrees or less. In other words, it can be said that setting the convergence angle difference to 0.14 degrees or less is sufficient to prevent discomfort when viewing an upright image, and is therefore more preferable.

[0106] In addition, we were able to confirm that setting the convergence angle difference to 0.09 degrees or less was effective in preventing any discomfort felt by anyone. In other words, setting the convergence angle difference to 0.09 degrees or less is sufficient to prevent any discomfort felt when viewing an upright image, and is therefore more preferable.

[0107] The present invention can be widely applied to parallax type HUD devices that input images with parallax, and light reproduction type HUD devices that use a lenticular lens or the like.

[0108] In this specification, the term "vehicle" may be broadly interpreted as a vehicle. In addition, terms related to navigation (e.g., navigation arrows, etc.) may be broadly interpreted, taking into consideration the viewpoint of navigation information in a broad sense that is useful for driving a vehicle, and may include road signs, etc. In addition, an upright image may be an upright image that a viewer sees facing forward, and may be broadly interpreted without being bound by the name. In addition, the HUD device may include a device used as a simulator (e.g., an aircraft simulator, a simulator as a game device, etc.).

[0109] The present invention is not limited to the above-described exemplary embodiments, and those skilled in the art could easily modify the above-described exemplary embodiments to the extent that they fall within the scope of the claims. [Explanation of symbols]

[0110] 1···vehicle (own vehicle), 2···projected member (reflective translucent member, windshield, etc.), 5···projection area, 40··road surface, 100···HUD device, 120···optical system including optical members, 150···light projecting unit (image projection unit), 160···display unit (e.g., liquid crystal display device or screen), 164···display surface, 170···curved mirror (concave mirror, etc.), 179···reflective surface, 188···gaze detection camera, 190···display control unit (control unit), 192···viewpoint position detection unit, 194···image processing unit, 195···Image generation control unit, 196···Warping parameters, 197···Post-warping data buffer, 198···ROM, 199···Upright image table, 200···Depth image table, 201···VRAM (image processing storage device), 202···Image generation unit (image rendering unit), EB···Eye box, PS1···Display area (virtual image display surface), Z1···First display area capable of displaying both upright images and depth images, Z2···Second display area for displaying depth images.

Claims

1. an image display unit for displaying an image; an optical system that projects light of the image displayed by the image display unit toward a projection target member, thereby allowing the viewer to view a virtual image of the image within a virtual display area in a real space in front of the viewer; A control unit that controls display of the image on the image display unit; having A direction toward the front of the viewer in real space is defined as a forward direction, A direction perpendicular to the forward direction and along a line segment connecting the left and right eyes of the viewer is defined as a left-right direction; When the direction along the line segment perpendicular to the forward direction and the left-right direction is defined as the up-down direction or height direction, the direction away from the ground or a surface equivalent to the ground in the real space is defined as the up direction, and the direction approaching is defined as the down direction, The control unit is Implementing control to display an upright image, which is an image to be viewed upright, within the display area, which is a flat or curved inclined surface that is inclined from a side closer to the viewer and below the ground or a surface equivalent to the ground, to a side farther from the viewer and above the ground, in the real space; the upright image is displayed in a display area that is a rectangular outline as seen by the viewer, a convergence angle difference between an upper end and a lower end of the display area is set to be less than a predetermined threshold value determined based on at least one of image visibility, a time required for viewing, and psychological factors such as a sense of incongruity or discomfort, The predetermined threshold functions as a normal tone visibility determination threshold for determining the normal tone visibility of the upright image, The convergence angle difference as the predetermined threshold is set to 0.2°. A head-up display device comprising:

2. The display area is divided into a first area capable of displaying both a virtual image of a depth image, which is an image viewed at an angle, and a virtual image of the upright image, and a second area displaying the virtual image of the depth image, a convergence angle difference between an upper end and a lower end of the display area in the first area is set to be less than the predetermined threshold value; a convergence angle difference between an upper end and a lower end of the display area in the second area is set to be equal to or greater than the predetermined threshold value; The head-up display device according to claim 1 .

3. When the angle of view in the vertical direction or height direction as seen by the viewer is referred to as a vertical angle of view, The upright image is a content having a vertical angle of 0.75° or less.

3. The head-up display device according to claim 1, wherein the head-up display device is a vehicle-mounted display.

Images