Display device and display method
By generating images with gaps on a transmissive-reflective unit using two windshield surfaces, the system addresses high costs and discomfort from double images in head-up displays, improving visibility and reducing brightness differences.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KOITO MFG CO LTD
- Filing Date
- 2024-12-23
- Publication Date
- 2026-07-03
Smart Images
Figure 2026111033000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a display device and a display method.
Background Art
[0002] Patent Document 1 describes forming a wedge-shaped intermediate film between two sheets of glass of a front glass (windshield) in order to suppress double vision in the display of a head-up display (HUD).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the case of the configuration of Patent Document 1, an expensive front glass is required, so the cost of the display system increases.
[0005] An object of the present invention is to suppress the discomfort of double images while suppressing costs.
Means for Solving the Problems
[0006] One aspect of the present invention for achieving the above object is an image generation unit that generates an image, an optical system that projects the image as image light onto a transmissive-reflective unit, a control unit that causes the image generation unit to generate the image and displays a virtual image of the image, <The image generation unit generates a corrected image with gaps, the first virtual image of the corrected image is displayed by reflection from the first surface of the transmission reflection unit, and the second virtual image of the corrected image is displayed by reflection from a second surface of the transmission reflection unit that is different from the first surface. The second virtual image is displayed in the gap in the first virtual image, and the first virtual image is displayed in the gap in the second virtual image. This is an image display device characterized by the following features.
[0007] Further issues disclosed in this application, and methods for solving them, will be made clear in the section on embodiments for carrying out the invention and in the drawings. [Effects of the Invention]
[0008] According to the present invention, it is possible to suppress the discomfort caused by double images while keeping costs down. [Brief explanation of the drawing]
[0009] [Figure 1] Figure 1 is an explanatory diagram of the overall configuration of the display system 100. [Figure 2] Figure 2 is an explanatory diagram illustrating how light incident on the windshield 50 is reflected. [Figure 3] Figure 3 is an explanatory diagram of the corrected image. [Figure 4] Figure 4 is an explanatory diagram of the first virtual image 60A, the second virtual image 60B, and the composite virtual image 60AB of the corrected image. [Figure 5] Figure 5 is a flowchart of the correction process performed by the vehicle-side control unit 10 and the HUD-side control unit 26. [Figure 6] Figures 6A to 6C are explanatory diagrams of the images shown in the image data. [Figure 7] Figure 7 is a graph of the luminance ratio with respect to the angle of incidence. [Figure 8] Figure 8 is an explanatory diagram of another method for suppressing brightness differences. [Figure 9] Figure 9 is an explanatory diagram illustrating the positional relationship between the first eye box 70A and the second eye box 70B. [Figure 10] FIG. 10 is an explanatory diagram of the positional relationship between the driver's eyes (pupils) and the eyepieces (first eyepiece 70A and second eyepiece 70B). [Figure 11] FIG. 11 shows the area ratio of the aperture with respect to the adjustment amount p. [Figure 12] FIG. 12A is an explanatory diagram of a corrected image of the first modification. FIG. 12B is an explanatory diagram of a composite virtual image 60AB of the first modification. [Figure 13] FIG. 13A is an explanatory diagram of a corrected image of the second modification. FIG. 13B is an explanatory diagram of a composite virtual image 60AB of the second modification. [Figure 14] FIG. 14 is a flowchart of the correction process of the modification using the first modification and the second modification. [Figure 15] FIG. 15 is an explanatory diagram of a double image (composite virtual image 60AB) of the comparative example. [Figure 16] FIG. 16 is an explanatory diagram of the contrast in the double image (composite virtual image 60AB) of the comparative example.
MODE FOR CARRYING OUT THE INVENTION
[0010] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following description, the same or similar configurations may be denoted by common reference numerals and redundant descriptions may be omitted.
[0011] ===EMBODIMENT=== <OVERALL CONFIGURATION> FIG. 1 is an explanatory diagram of the overall configuration of the display system 100.
[0012] The display system 100 is a system (image display device) that displays an image (virtual image) by a head-up display (hereinafter referred to as "HUD"). The display system 100 includes a vehicle-side control unit 10 and a HUD 20.
[0013] The vehicle-side control unit 10 performs various vehicle controls and transmits various signals to the HUD 20. The vehicle-side control unit 10 is composed of at least one ECU (Electronic Control Unit). The vehicle-side control unit 10 transmits image data and control data to the HUD 20. The vehicle-side control unit 10 is composed of a computer equipped with an arithmetic processing unit and a memory device (not shown). The arithmetic processing unit is composed of a CPU, MPU, GPU, etc. The memory device is composed of ROM, RAM, etc.
[0014] The vehicle-side control unit 10 has a correction processing unit 10A. The correction processing unit 10A corrects the image to be displayed on the HUD 20. The correction processing unit 10A is realized by the arithmetic processing unit executing a correction processing program stored in the memory device. The processing performed by the correction processing unit 10A will be described later. In addition, the correction processing unit 10A is set with shift direction data and shift amount data (see Figure 1). The shift direction data and shift amount data will be described later.
[0015] The HUD20 is a display device mounted in a vehicle that displays a virtual image 60 (60A, 60B, 60AB) in front of the vehicle. The HUD20 is a so-called head-up display. The HUD20 comprises an image generation unit 22, an optical system 24, and a HUD-side control unit 26.
[0016] The image generation unit 22 generates an image to be projected onto the windshield 50 (front glass). The image generation unit 22 in the figure comprises a display unit 22A and a backlight 22B. Here, the image generation unit 22 is composed of a liquid crystal display. The display unit 22A displays an image according to the image data. Here, the display unit 22A is composed of a liquid crystal panel. The backlight 22B illuminates the back of the display unit 22A (liquid crystal panel) with light. The backlight 22B is composed of, for example, an LED or a light guide plate. Note that the image generation unit 22 is not limited to a liquid crystal display, and may be composed of, for example, an organic EL display device, a micro-LED display device, or a projector device using a laser light source.
[0017] The optical system 24 projects the image generated by the image generation unit 22 onto the windshield 50 (windshield) as image light. The optical system 24 is composed of one or more optical elements. The optical elements that make up the optical system 24 are, for example, lenses, mirrors, and prisms. The optical system 24 is configured so that a virtual image 60 (60A, 60B, 60AB) is displayed to the driver. The windshield 50 transmits light from outside the vehicle while reflecting the image light from the optical system 24. The windshield 50 functions as a transmission-reflecting part (a so-called half-mirror). The driver sees the background visible through the windshield 50 superimposed with the virtual image 60 (spatial image) seen due to the reflection of image light by the windshield 50.
[0018] The HUD-side control unit 26 controls the image generation unit 22. The HUD-side control unit 26 outputs image data to the display unit 22A of the image generation unit 22 and controls the image to be displayed on the display unit 22A. The HUD-side control unit 26 also outputs a drive signal to the backlight 22B of the image generation unit 22 and controls the ON / OFF status and brightness of the backlight 22B. The HUD-side control unit 26 controls the display unit 22A and backlight 22B of the image generation unit 22 based on the image data and control data received from the vehicle-side control unit 10.
[0019] The HUD-side control unit 26 is composed of a computer equipped with an arithmetic processing unit and a memory device (not shown). The arithmetic processing unit consists of a CPU, MPU, GPU, etc. The memory device consists of ROM, RAM, etc. The various processes performed by the HUD-side control unit 26 are realized by the arithmetic processing unit executing a program stored in the memory device.
[0020] The HUD 20 in the diagram has a motor 28, and the HUD-side control unit 26 controls the motor 28. The motor 28 is a drive source that outputs driving force to move the mirror of the optical system 24. The driving force of the motor 28 moves the mirror of the optical system 24, and the display position of the virtual image is adjusted. The HUD-side control unit 26 controls the display position of the virtual image by moving the mirror of the optical system 24 by outputting a drive signal to the motor 28. The mirror of the optical system 24, which is moved by the motor 28, becomes an adjustment unit that adjusts the position of the virtual image. Note that the HUD 20 does not necessarily have to be equipped with a motor 28 for moving the mirror.
[0021] <About double images> Figure 2 is an explanatory diagram showing how light incident on the windshield 50 is reflected. Figure 1 shows two virtual images 60 (60A, 60B) that are visible to the driver.
[0022] As shown in Figure 2, the light incident from the image generation unit 22 (image light) is reflected by the reflective surface 50A on the interior side of the windshield 50. In the following explanation, the reflective surface 50A on the interior side of the windshield 50 (the driver's side) will be referred to as the "first surface" or "surface." The reflection of light by the surface 50A of the windshield 50 will be referred to as the "first reflection" or "surface reflection," and the light reflected by the surface 50A of the windshield 50 (image light) will be referred to as the "first reflected light" or "surface reflected light."
[0023] Furthermore, of the light (image light) incident from the image generation unit 22, the light that passes through the surface 50A of the windshield 50 is reflected by a surface other than the first surface of the windshield 50. Figure 2 shows how the light that passes through the surface 50A of the windshield 50 is reflected by the reflective surface 50B on the outside of the vehicle. In the following explanation, the reflective surface other than the first surface of the windshield 50 will be referred to as the "second surface". Note that the second surface includes not only the back surface 50B of the windshield 50 (the surface opposite to the surface 50A) as shown in Figure 2, but also the second glass surface when the windshield 50 is composed of two panes of glass (laminated glass). The reflection of light by the second surface is called "second reflection", and the light (image light) reflected by the second surface is called "second reflected light". Furthermore, as shown in Figure 2, when the second surface is the back surface 50B of the windshield 50, the second reflection is called "back surface reflection," and the second reflected light is called "back surface reflected light."
[0024] As shown in Figure 2, the first reflected light reaches the driver's eye from position P1 on the windshield 50, while the second reflected light reaches the driver's eye from a different position P2. As a result, the driver sees two virtual images 60 (60A, 60B) at different positions. In the following explanation, the virtual image 60A displayed by the first reflection (surface reflection) will be called the "first virtual image" or "normal image," and the virtual image 60B displayed by the second reflection (in this case, back reflection) will be called the "second virtual image." Furthermore, the virtual image 60AB formed by the first virtual image 60A and the second virtual image 60B (the virtual image 60AB where the first virtual image 60A and the second virtual image 60B overlap) will be called the "composite virtual image" or "double image." Note that position P2 may shift not only upward relative to position P1, but also horizontally depending on the shape of the windshield 50 and the angle of incidence of light. However, for the sake of simplification, the following explanation will describe the case where the second virtual image 60B is displayed shifted upward relative to the first virtual image 60A.
[0025] The direction in which the second virtual image 60B is shifted relative to the first virtual image 60A varies depending on the vehicle model, or even within the same vehicle model, depending on individual vehicle differences. In the following explanation, the direction in which the second virtual image 60B is shifted relative to the first virtual image 60A will be referred to as the "shift direction." The correction processing unit 10A of the vehicle-side control unit 10 has data indicating the shift direction (shift direction data) for vehicles equipped with the HUD 20 stored in advance. Furthermore, the amount of shift of the second virtual image 60B relative to the first virtual image 60A also differs depending on the vehicle model, or even within the same vehicle model, depending on individual vehicle differences. In the following explanation, the amount of shift of the second virtual image 60B relative to the first virtual image 60A will be referred to as the "shift amount." The correction processing unit 10A of the vehicle-side control unit 10 has data (shift amount data) indicating the shift amount in a vehicle equipped with the HUD 20 stored in advance.
[0026] <Comparative Example> Figure 15 is an explanatory diagram of the double image (composite virtual image 60AB) of the comparative example. Figure 16 is an explanatory diagram of the contrast in the double image (composite virtual image 60AB) of the comparative example. In the comparative example, the HUD 20 displays the image "0 (zero)" directly on the image generation unit 22. As shown in Figure 15, the second virtual image 60B is displayed shifted relative to the first virtual image 60A, resulting in a double image in the comparative example that can cause discomfort to the driver. Furthermore, as shown in Figure 16, the brightness is higher in the overlapping area of the first virtual image 60A and the second virtual image 60B (the blacked-out area in Figure 16), and the brightness difference between this area and the non-overlapping area (the hatched area in Figure 16; the upper and lower edge areas) is large, making the double image (composite virtual image 60AB) in the comparative example more likely to cause discomfort to the driver.
[0027] <About corrected images and composite virtual images> Figure 3 is an explanatory diagram of the corrected image. Here, as with the comparative example, we will explain the case where the image "0 (zero)" is displayed.
[0028] As shown in Figure 3, the HUD-side control unit 26 (and the vehicle-side control unit 10) causes the image generation unit 22 to generate images with gaps between them. The width of the gap (length of the gap in the shift direction) L1 is approximately equivalent to the shift amount Ls (the amount by which the second virtual image 60B is shifted relative to the first virtual image 60A). Note that the width of the gap L1 does not necessarily have to match the shift amount Ls. Also, the spacing between gaps (spacing in the shift direction of the gaps; gap pitch) L2 is equivalent to twice the shift amount Ls.
[0029] The image generation unit 22 generates the corrected image shown in Figure 3 and projects the image light of the corrected image onto the windshield 50. Figure 4 is an explanatory diagram of the first virtual image 60A, the second virtual image 60B, and the composite virtual image 60AB of the corrected image.
[0030] The second virtual image 60B (see upper right diagram in Figure 4) is displayed shifted by a shift amount Ls in the shift direction (a predetermined direction; in this case, upward) relative to the first virtual image 60A (see upper left diagram in Figure 4). The driver will see a composite virtual image 60AB (see lower diagram in Figure 4) which is formed by the overlapping and synthesis of the first virtual image 60A and the second virtual image 60B. In the composite virtual image 60AB seen by the driver, the second virtual image 60B (more specifically, the image between the gaps of the second virtual image 60B) is displayed in the gaps of the first virtual image 60A, and the first virtual image 60A (more specifically, the image between the gaps of the first virtual image 60A) is displayed in the gaps of the second virtual image 60B. In other words, the first virtual image 60A and the second virtual image 60B overlap in a way that complements each other's gaps. As a result, a composite virtual image 60AB is displayed, which is constructed to form a single image "0 (zero)," thus reducing the sense of discomfort experienced by the driver. Furthermore, by creating a gap in the corrected image, the overlapping area of the first virtual image 60A and the second virtual image 60B can be suppressed, thus preventing the continuous vertical movement of high-brightness areas (the black areas in the composite virtual image 60AB in Figure 16), as seen in the comparative example. This makes the brightness differences within the composite virtual image 60AB less noticeable, further reducing the sense of discomfort experienced by the driver.
[0031] <Correction process> Figure 5 is a flowchart of the correction processing performed by the vehicle-side control unit 10 and the HUD-side control unit 26. Processes S001 to S003 in the figure are performed by the correction processing unit 10A of the vehicle-side control unit 10. Process S004 in the figure is performed by both the vehicle-side control unit 10 and the HUD-side control unit 26. Figures 6A to 6C are explanatory diagrams of the images shown in the image data.
[0032] The vehicle-side control unit 10 (correction processing unit 10A) acquires initial image data (S001). The initial image data is data that indicates the image to be displayed on the HUD 20, and it is data that indicates the image before correction. Figure 6A is an explanatory diagram of the image indicated by the initial image data. Here, the image indicated by the initial image data (initial image) is an image that indicates "0 (zero)".
[0033] Next, the vehicle-side control unit 10 (correction processing unit 10A) performs preprocessing on the initial image data (S002). Preprocessing is performed before the subsequent decimation process. Here, the vehicle-side control unit 10 performs resolution conversion processing as preprocessing. Resolution conversion processing is a process that converts the resolution of the image data, or in other words, a process that converts the size of the pixels that make up the image shown by the image data. Figure 6B is an explanatory diagram of the image shown by the image data after resolution conversion. Based on the shift amount data (see Figure 1), the correction processing unit 10A converts the resolution of the initial image data so that the size of the pixels becomes the shift amount Ls.
[0034] Furthermore, the resolution conversion process causes the size of the pixels (the length of one side of a pixel) that make up the initial image to become the shift amount Ls. Therefore, the resolution conversion process makes the length of vertically continuous lines in the initial image an integer multiple of the shift amount Ls. Also, the resolution conversion process corrects lines that are thinner than the shift amount Ls in the initial image to lines with a width equivalent to one pixel, corresponding to the shift amount Ls. In other words, the resolution conversion process causes thin lines to be thickened and expanded. If thin horizontal lines (thin lines perpendicular to the shift direction) were displayed as they were, there is a risk that two separate thin lines would appear in the composite virtual image 60AB. However, by expanding the thin lines to make them thicker, the lines of the first virtual image 60A and the lines of the second virtual image 60B can be brought closer together, thus preventing the driver from seeing two separate thin lines.
[0035] Next, the vehicle-side control unit 10 (correction processing unit 10A) performs a decimation process (S003). Decimation is a process that creates gaps (blanks) in the image represented by the image data. In the decimation process, the grayscale values of the pixels that make up the image are converted to the grayscale values of the blank spaces.
[0036] Figure 6C is an explanatory diagram of the image shown by the image data after decimation processing. Based on the shift direction data (see Figure 1), the vehicle-side control unit 10 identifies regions in the image data (image data after resolution conversion processing) where the pixels constituting the image are continuous along the shift direction, and leaves every other pixel blank along the shift direction in the multiple pixels that make up that region. In the case of image "0 (zero)", there are regions on both the left and right sides of the image where pixels are continuous along the vertical direction, so the vehicle-side control unit 10 will create every other pixel blank in each region. Decimation processing generates image data showing a corrected image with gaps (corrected image data). According to this decimation processing, the width L1 of the gaps in the corrected image shown by the corrected image data becomes the shift amount Ls. Also, according to this decimation processing, the gap interval L2 in the corrected image shown by the corrected image data becomes twice the shift amount Ls.
[0037] Next, the corrected image data is output to the image generation unit 22 (S004). First, the vehicle-side control unit 10 (correction processing unit 10A) transmits the corrected image data to the HUD-side control unit 26. Then, the HUD-side control unit 26 controls the image generation unit 22 based on the corrected image data received from the vehicle-side control unit 10, causing the image generation unit 22 to generate the corrected image indicated by the corrected image data. As a result, the image generation unit 22 generates the corrected image shown in Figure 3, and the composite virtual image 60AB (first virtual image 60A and second virtual image 60B) shown in Figure 4 is displayed.
[0038] In the above description, the vehicle-side control unit 10 generates image data for the correction image (S001-S003), and the vehicle-side control unit 10 and the HUD-side control unit 26 cause the image generation unit 22 to generate the correction image (S004). Therefore, in this case, the vehicle-side control unit 10 and the HUD-side control unit 26 constitute a control unit that causes the image generation unit 22 to generate a correction image with gaps. However, the HUD-side control unit 26 may also be configured as a control unit that causes the image generation unit 22 to generate a correction image with gaps, by having the correction processing unit 10A of the vehicle-side control unit 10 perform the function of the correction processing unit 10A.
[0039] Furthermore, if the correction processing unit 10A can generate image data showing a corrected image with gaps, it may perform a correction process different from the one shown in Figure 5. For example, if the gap width L1 is different from the shift amount Ls, as in the corrected image described later, the correction processing unit 10A will perform a correction process different from the one shown in Figure 5.
[0040] <About brightness difference> The brightness of the second virtual image 60B, formed by reflection from the back surface of the windshield, is dimmer than the brightness of the first virtual image 60A, formed by reflection from the front surface. This creates a brightness difference between the first virtual image 60A and the second virtual image 60B. Generally, humans are said to be able to distinguish between two virtual images when the brightness ratio is less than 0.8. Therefore, if the ratio of the brightness of the first virtual image 60A to the brightness of the second virtual image 60B is less than 0.8, the driver will be able to distinguish between the first virtual image 60A and the second virtual image 60B that constitute the composite virtual image 60AB, which may cause discomfort to the driver when they see the composite virtual image 60AB. On the other hand, if the ratio of the brightness of the first virtual image 60A to the brightness of the second virtual image 60B is 0.8 or higher, the driver will have difficulty distinguishing between the first virtual image 60A and the second virtual image 60B that constitute the composite virtual image 60AB, thus reducing the discomfort caused to the driver. Therefore, it is desirable that the first virtual image 60A and the second virtual image 60B are displayed such that the ratio of the brightness of the first virtual image 60A to the brightness of the second virtual image 60B is 0.8 or higher.
[0041] Figure 7 is a graph of the luminance ratio against the angle of incidence. The horizontal axis of the graph represents the angle of incidence θ. The angle of incidence θ is the angle between the incident light (image light) from HUD20 and the normal to the surface 50A of the windshield 50 (see Figure 2). The vertical axis of the graph represents the luminance ratio R. When the luminance of the first virtual image 60A is I1 and the luminance of the second virtual image 60B is I2, the luminance ratio R is R = I2 / I1.
[0042] As shown in Figure 7, the luminance ratio R increases as the incident angle θ decreases. Also, as shown in Figure 7, when the incident angle θ is 50 degrees or less, the luminance ratio R becomes 0.8 or more. For this reason, it is desirable that the optical system 24 be configured to project image light onto the windshield 50 such that the incident angle θ is 50 degrees or more. This results in a ratio of 0.8 or more between the luminance of the first virtual image 60A and the luminance of the second virtual image 60B, making it difficult for the driver to distinguish between the first virtual image 60A and the second virtual image 60B, thereby reducing the discomfort caused to the driver.
[0043] Furthermore, the ratio of the brightness of the first virtual image 60A to the brightness of the second virtual image 60B may be less than 0.8. Even in such a case, when the image generation unit 22 generates a corrected image with a gap and displays the first virtual image 60A and the second virtual image 60B, the overlapping area of the first virtual image 60A and the second virtual image 60B can be suppressed compared to when an image without a gap is displayed as is. Therefore, the difference in brightness between the area where the first virtual image 60A and the second virtual image 60B overlap and have high brightness, and the second virtual image 60B which has relatively low brightness, can be made less noticeable, thereby reducing the discomfort caused to the driver.
[0044] Figure 8 is an explanatory diagram of another method for suppressing brightness differences. Figure 8 shows a first eyebox 70A and a second eyebox 70B. The first eyebox 70A is the range in which the driver can see the first virtual image 60A. The second eyebox 70B is the range in which the driver can see the second virtual image 60B. The display system 100 in the figure is equipped with an eye-tracking system 41 that tracks the position of the driver's eyes (pupils). The eye-tracking system 41 outputs information about the position of the driver's eyes (pupils) to the vehicle-side control unit 10. The vehicle-side control unit 10 obtains information about the position of the driver's eyes (pupils) from the eye-tracking system 41 and controls the motor 28 based on the position of the driver's eyes to move the mirror of the optical system 24 and adjust the positions of the first eyebox 70A and the second eyebox 70B.
[0045] Figure 9 is an explanatory diagram illustrating the positional relationship between the first eyebox 70A and the second eyebox 70B. As shown in the figure, the positions of the first eyebox 70A and the second eyebox 70B are offset from each other.
[0046] Figure 10 is an explanatory diagram illustrating the positional relationship between the driver's eyes and the eye boxes (first eye box 70A and second eye box 70B). The solid lines in the diagram indicate the positions of the eye boxes (first eye box 70A and second eye box 70B) before adjustment. Before adjustment, the entire area of the driver's eye (pupil) is within the range of the first eye box 70A, and the entire area of the driver's eye is within the range of the second eye box 70A. In this case, it is not possible to suppress the brightness difference between the first virtual image 60A and the second virtual image 60B. The dotted lines in the diagram indicate the positions of the eye boxes (first eye box 70A and second eye box 70B) after adjustment. By adjusting the position of the eye boxes, a portion of the driver's eye (pupil) is outside the range of the first eye box 70A. On the other hand, even after adjustment, the entire range of the driver's eye remains within the range of the second eye box 70A. This allows the driver to perceive the first virtual image 60A with reduced brightness while maintaining the brightness of the second virtual image 60B.
[0047] Figure 11 shows the area ratio of the aperture to the adjustment amount p. The area ratio represents the proportion of the driver's eye (pupil) area within the eye box to the actual area of the driver's eye (pupil). The closer the area ratio is to 1, the less the light is restricted, and the higher the brightness of the virtual image is perceived. The smaller the area ratio, the more the light is restricted, and the lower the brightness of the virtual image is perceived. The black circles in the figure show the relationship between the adjustment amount p and the area ratio in the first eye box 70A. The white circles in the figure show the relationship between the adjustment amount p and the area ratio in the second eye box 70B.
[0048] For example, the adjustment amount is p A In this case, the area ratio is about 0.7 compared to before adjustment, and the light constituting the first virtual image 60A is focused, so the brightness of the first virtual image 60A will decrease compared to before adjustment. On the other hand, the amount of adjustment is p A In this case, the area ratio is approximately 1, and the light constituting the second virtual image 60B is hardly focused, so the brightness of the second virtual image 60B hardly changes from before the adjustment. For this reason, the brightness of the first virtual image 60A can be reduced without changing the brightness of the second virtual image 60B.
[0049] As described above, the luminance of the second virtual image 60B formed by the rear surface reflection of the windshield 50 is darker than the luminance of the first virtual image 60A formed by the front surface reflection. Under such circumstances, as shown in FIG. 11, by narrowing the light that constitutes the first virtual image 60A more than the light that constitutes the second virtual image 60B, the luminance difference between the first virtual image 60A and the second virtual image 60B can be suppressed. That is, under such circumstances, by making all areas of the driver's eye (pupil) fall within the range of the second eye box 70A while making some areas of the driver's eye (pupil) fall outside the range of the first eye box 70A, the luminance difference between the first virtual image 60A and the second virtual image 60B can be suppressed.
[0050] The vehicle-side control unit 10 acquires information on the position of the driver's eye (pupil) from the gaze tracking system 41, and based on the position of the driver's eye (pupil), controls the motor 28 so as to be at a position corresponding to the adjustment amount p in FIG. 11. In other words, as shown in FIG. 10, while making some areas of the driver's eye (pupil) fall outside the range of the first eye box 70A, all areas of the driver's eye (pupil) are made to fall within the range of the second eye box 70A, and the mirror of the optical system 24 is moved to adjust the position of the eye box with respect to the driver's eye. Thereby, the luminance difference between the first virtual image 60A and the second virtual image 60B can be suppressed. A As shown in FIG. 10, while making some areas of the driver's eye (pupil) fall outside the range of the first eye box 70A, all areas of the driver's eye (pupil) are made to fall within the range of the second eye box 70A, and the mirror of the optical system 24 is moved to adjust the position of the eye box with respect to the driver's eye. Thereby, the luminance difference between the first virtual image 60A and the second virtual image 60B can be suppressed.
[0051] <Modification Example> FIG. 12A is an explanatory diagram of a corrected image of the first modification example. FIG. 12B is an explanatory diagram of the composite virtual image 60AB of the first modification example. Note that FIG. 12B shows an enlarged view of a portion where the first virtual image 60A and the second virtual image 6OB are adjacent (the joint between the first virtual image 60A and the second virtual image 60B).
[0052] As shown in FIG. 12A, also in the first modification example, the gap interval L2 is set to twice the shift amount Ls. In the first modification example, the gap width L1 is set to be smaller than the shift amount Ls (L1 < Ls). The correction processing unit 10A of the first modification example generates image data showing the corrected image shown in FIG. 12A and outputs it to the image generation unit 22.
[0053] As shown in Figure 12B, in the first modified example, the second virtual image 60B (more specifically, the image between the gaps of the second virtual image 60B) is displayed in the gaps of the first virtual image 60A, and the first virtual image 60A (more specifically, the image between the gaps of the first virtual image 60A) is displayed in the gaps of the second virtual image 60B. In other words, in the first modified example, the first virtual image 60A and the second virtual image 60B overlap in a way that complements each other's gaps, so that the composite virtual image 60AB is displayed to form a single image "0 (zero)", thereby reducing the sense of discomfort given to the driver.
[0054] Furthermore, as shown in Figure 12B, in the first modified example, the portion (edge) adjacent to the gap in the first virtual image 60A and the portion (edge) adjacent to the gap in the second virtual image 60B partially overlap. In other words, in the first modified example, the portions adjacent to the gaps in the first virtual image 60A and the second virtual image 60B overlap. As a result, in the first modified example, the formation of a gap in the composite virtual image 60AB can be suppressed.
[0055] Incidentally, if a gap is formed in the composite virtual image 60AB under conditions where the background is dark, the difference between the brightness of the image (first virtual image 60A or second virtual image 60B) and the brightness of the gap (background brightness) becomes large, making it easier for the driver to recognize the gap and potentially causing discomfort to the driver. On the other hand, under conditions where the background is dark, the brightness of the composite virtual image 60AB (first virtual image 60A or second virtual image 60B) relative to the background is high, so even if a part of the first virtual image 60A and the second virtual image 60B overlap, the high brightness in that overlapping region becomes less noticeable. In other words, under conditions where the background is dark, the formation of a gap in the composite virtual image 60AB is unacceptable, but the overlap of a part of the first virtual image 60A and the second virtual image 60B is more acceptable. Therefore, the first modified example is particularly effective under conditions where the background is dark.
[0056] Figure 13A is an explanatory diagram of the corrected image of the second modified example. Figure 13B is an explanatory diagram of the composite virtual image 60AB of the second modified example. Figure 13B also shows an enlarged view of the area where the first virtual image 60A and the second virtual image 60B are adjacent.
[0057] As shown in Figure 13A, in the second modified example, the gap spacing L2 is set to twice the shift amount Ls. On the other hand, in the second modified example, the gap width L1 is set to be larger than the shift amount Ls (L1 > Ls). The correction processing unit 10A in the second modified example generates image data showing the corrected image shown in Figure 13A and outputs it to the image generation unit 22.
[0058] As shown in Figure 13B, in the second modified example, the second virtual image 60B (more specifically, the image between the gaps of the second virtual image 60B) is displayed in the gaps of the first virtual image 60A, and the first virtual image 60A (more specifically, the image between the gaps of the first virtual image 60A) is displayed in the gaps of the second virtual image 60B. In other words, in the second modified example, the first virtual image 60A and the second virtual image 60B overlap in a way that complements each other's gaps, so that the composite virtual image 60AB is displayed to form a single image "0 (zero)", thereby reducing the sense of discomfort given to the driver.
[0059] Furthermore, as shown in Figure 13B, in the second modified example, the portion (edge) adjacent to the gap in the first virtual image 60A and the portion (edge) adjacent to the gap in the second virtual image 60B are separated. In other words, in the second modified example, the portions adjacent to the gaps in the first virtual image 60A and the second virtual image 60B are separated from each other. As a result, in the second modified example, the formation of a gap in the composite virtual image 60AB can be suppressed.
[0060] Incidentally, if a portion of the first virtual image 60A and the second virtual image 60B overlap under bright background conditions, the brightness of the composite virtual image 60AB (either the first virtual image 60A or the second virtual image 60B) relative to the background is low, making the high brightness in the overlapping region more noticeable. On the other hand, under bright background conditions, even if a gap is formed in the composite virtual image 60AB, the difference between the brightness of the image (first virtual image 60A or the second virtual image 60B) and the brightness of the gap (background brightness) is small, making the gap in the composite virtual image 60AB less noticeable. In other words, under bright background conditions, partial overlap between the first virtual image 60A and the second virtual image 60B is unacceptable, but the formation of a gap in the composite virtual image 60AB is more acceptable. Therefore, the second modification is particularly effective under bright background conditions.
[0061] Figure 14 is a flowchart of the correction process for a modified example using the first and second modified examples. The processes S101 to S102 in the figure are for determining the gap width L1 of the corrected image (see Figures 3, 12A, and 13A), and are performed by the correction processing unit 10A of the vehicle-side control unit 10. The processes S001' to S003' in the figure are also performed by the correction processing unit 10A of the vehicle-side control unit 10. Furthermore, the process S004' in the figure is performed by both the vehicle-side control unit 10 and the HUD-side control unit 26.
[0062] First, the vehicle-side control unit 10 (correction processing unit 10A) acquires information regarding the brightness of the background (brightness information) (S101). Here, the brightness information is the output of the sensor 40 (see Figure 1) that detects the brightness around the car. However, the brightness information is not limited to the information indicated by the sensor 40 that detects the brightness around the car; for example, it could be time information to distinguish between daytime and nighttime, or information on whether the headlights are on or off.
[0063] Next, the vehicle-side control unit 10 (correction processing unit 10A) determines the gap width L1 of the corrected image based on the brightness information acquired in S101 (S102). Based on the brightness information, the vehicle-side control unit 10 sets the gap width L1 to be larger the darker the background. For example, based on the brightness information, the vehicle-side control unit 10 sets the gap width L1 to be larger than the shift amount Ls when it is dark, and sets the gap width L1 to be smaller than the shift amount Ls when it is bright. This sets a gap width L1 that is appropriate for the brightness of the background.
[0064] Next, the vehicle-side control unit 10 (correction processing unit 10A) acquires initial image data (S001'). This process is the same as S001 in the correction process described above (see Figure 5).
[0065] Next, the vehicle-side control unit 10 (correction processing unit 10A) performs preprocessing on the initial image data (S002'). As a preprocessing step in the modified example, lines with a width thinner than the shift amount Ls in the initial image are corrected to lines with a width equivalent to the shift amount Ls. By expanding the thin lines to make them thicker, the lines of the first virtual image 60A and the lines of the second virtual image 60B can be brought closer together, thus preventing the driver from seeing two separate thin lines.
[0066] Next, the vehicle-side control unit 10 (correction processing unit 10A) performs a decimation process (S003'). In the modified decimation process, first, the vehicle-side control unit 10 identifies a region in which the pixels constituting the image are continuous along the shift direction, based on the shift direction data. Then, for multiple pixels constituting the identified region, the vehicle-side control unit 10 makes pixels with a width L1 blank at intervals L2 (twice the shift amount Ls) according to the shift amount data. In the modified example as well, the decimation process generates image data showing a corrected image with gaps (corrected image data). In the modified decimation process, the width L1 of the gaps in the corrected image shown by the corrected image data is the width set according to the brightness, and the interval L2 of the gaps in the corrected image shown by the corrected image data is an interval equivalent to twice the shift amount Ls (see Figures 3, 12A, and 13A).
[0067] Next, the corrected image data is output to the image generation unit 22 (S004). This process is the same as S004 in the correction process described above (see Figure 5). This allows the image generation unit 22 to generate a corrected image with a gap width L1 suitable for the brightness of the background.
[0068] <Summary> The above-described display device (display system 100) comprises an image generation unit 22, an optical system 24, and a control unit (vehicle-side control unit 10 and HUD-side control unit 26). The control unit causes the image generation unit 22 to generate a corrected image with gaps (see Figures 3, 12A, and 13A), and displays a first virtual image 60A of the corrected image by reflection from the surface 50A (first surface) of the windshield 50 (transmissive reflective part), and displays a second virtual image 60B of the corrected image by reflection from the back surface 50B (second surface) of the windshield 50. As shown in the lower part of Figure 4, and in Figures 12B and 13B, the control unit displays the second virtual image 60B in the gaps in the first virtual image 60A, and displays the first virtual image 60A in the gaps in the second virtual image 60B. As a result, the first virtual image 60A and the second virtual image 60B overlap in a way that complements the gap between them, and a composite virtual image 60AB is displayed, which is formed by combining them to form a single image, thus reducing the discomfort caused to the driver. According to this embodiment, it is not necessary to use an expensive windshield with a wedge-shaped interlayer between two panes of glass, thus reducing the discomfort caused to the driver while keeping costs down.
[0069] In the display system 100 described above, the control unit is composed of a vehicle-side control unit 10 and a HUD-side control unit 26. However, the control unit may be composed solely of the HUD-side control unit 26, provided that the HUD-side control unit 26 also performs the function of the correction processing unit 10A of the vehicle-side control unit 10. In this case, the display system 100, which includes the image generation unit 22, the optical system 24, and the control unit, will be composed solely of the HUD 20. Furthermore, in the above explanation, the second virtual image 60B is displayed by reflection from the back surface 50B of the windshield 50 (back surface reflection), as shown in Figure 2. However, the second virtual image 60B is not limited to a virtual image displayed by back surface reflection of the windshield 50. For example, if the windshield 50 is composed of two panes of glass (laminated glass), the second virtual image 60B may be a virtual image displayed by reflection from the second glass surface.
[0070] In the display system 100 described above, gaps are formed between pixels aligned in the shift direction (a predetermined direction). As a result, the first virtual image 60A and the second virtual image 60B appear alternately in the shift direction, thereby forming a continuous image in the shift direction. In the above description, the shift direction was the vertical direction, but the shift direction may also be a direction that has a horizontal component.
[0071] Furthermore, in the display system 100 described above, the control unit (vehicle-side control unit 10) identifies a region in which the pixels constituting the initial image are continuous in the shift direction (a predetermined direction), and generates a corrected image by downsampling the pixels in that region (see S003 in Figure 5 and S003' in Figure 14). This makes it possible to generate image data (corrected image data) that shows a corrected image with gaps. However, it is sufficient if the corrected image with gaps can be displayed on the image generation unit 22 even without such downsampling processing.
[0072] Furthermore, in the display system 100 described above, the control unit (vehicle-side control unit 10) performs an expansion process to thicken the thin lines in the initial image. This suppresses the appearance of two separate thin lines in the composite virtual image 60AB.
[0073] It is desirable that the ratio R (=I2 / I1) of the luminance I1 of the first virtual image 60A to the luminance I2 of the second virtual image 60B be 0.8 or greater. Furthermore, it is desirable that the optical system 24 be configured such that the incident angle θ (see Figure 2; the angle at which the image light is incident relative to the normal of the transmission and reflection section) is 50 degrees or greater. This makes it difficult for the driver to distinguish between the first virtual image 60A and the second virtual image 60B, thereby reducing the discomfort caused to the driver.
[0074] The optical system 24 has a mirror (adjustment unit) that adjusts the position for displaying the virtual image. The control unit (vehicle-side control unit 10 and HUD-side control unit 26) acquires the driver's eye position information from the eye-tracking system 41 and controls the mirror of the optical system 24 based on the driver's eye position so that the light constituting the first virtual image 60A is more focused than the light constituting the second virtual image 60B. This makes it possible to suppress the brightness difference between the first virtual image 60A and the second virtual image 60B.
[0075] As shown in Figures 12A and 12B, it is desirable that the first virtual image 60A and the second virtual image 60B are displayed such that adjacent parts of the gap between them overlap. This reduces the discomfort caused to the driver in situations where the background is dark. It is also desirable that the first virtual image 60A and the second virtual image 60B are displayed such that adjacent parts of the gap between them are separated. This reduces the discomfort caused to the driver in situations where the background is bright. Furthermore, as shown in Figure 14, it is desirable that the control unit acquires information about the brightness of the background and, when the background is dark, reduces the gap in the corrected image compared to when the background is bright. This allows the image generation unit 22 to generate a corrected image with a gap width L1 suitable for the brightness of the background, thereby reducing the discomfort caused to the driver.
[0076] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments and includes various modifications. Furthermore, the above embodiments are described in detail to explain the configuration in an easy-to-understand manner and are not necessarily limited to those having all the configurations described. In addition, some of the configurations of the above embodiments can be added to, deleted from, or replaced with other configurations. [Explanation of Symbols]
[0077] 10 Vehicle-side control unit, 10A Correction processing unit, 20 HUD, 22 Image generation unit, 22A Display unit, 22B Backlight, 24 Optical system, 26 HUD side control unit, 28 Motor, 40 sensors, 41 eye-tracking systems, 50 Windshield (transmitting and reflecting part), 50A front side (first side), 50B back side (second side), 60 virtual image, 60A first virtual image, 60B second virtual image, 60AB composite virtual image, 70A First eyebox, 70B Second eyebox, 100 Display Systems
Claims
1. An image generation unit that generates images, An optical system that projects the aforementioned image as image light onto a transmission / reflection surface, A control unit that causes the image generation unit to generate the image and displays a virtual image of the image, Equipped with, The control unit, The image generation unit generates a corrected image with gaps, the first virtual image of the corrected image is displayed by reflection from the first surface of the transmission reflection unit, and the second virtual image of the corrected image is displayed by reflection from a second surface of the transmission reflection unit that is different from the first surface. The second virtual image is displayed in the gap in the first virtual image, and the first virtual image is displayed in the gap in the second virtual image. An image display device characterized by the following features.
2. An image display device according to claim 1, The aforementioned gap is formed between pixels aligned in a predetermined direction, characterized in that it is an image display device.
3. An image display device according to claim 1 or 2, The control unit, Get the initial image, A region is identified in which the pixels constituting the initial image are continuous in a predetermined direction. An image display device characterized by generating the corrected image by downsampling pixels in the aforementioned region.
4. An image display device according to claim 3, The control unit is characterized by performing an expansion process to thicken the thin lines in the initial image.
5. An image display device according to claim 1, An image display device characterized in that the ratio of the brightness of the first virtual image to the brightness of the second virtual image is 0.8 or more.
6. An image display device according to claim 1, The optical system is characterized by projecting the image light onto the transmission and reflection portion such that the angle with respect to the normal of the transmission and reflection portion is 50 degrees or more.
7. An image display device according to claim 1, The optical system has an adjustment unit for adjusting the position of the eye box. The control unit, Obtain information about the driver's eye position, An image display device characterized by controlling the adjustment unit based on the position of the eye such that the light constituting the first virtual image is more focused than the light constituting the second virtual image.
8. An image display device according to claim 1, An image display device characterized in that the first virtual image and the second virtual image are displayed such that the portions adjacent to the gap between the first virtual image and the second virtual image overlap.
9. An image display device according to claim 1, An image display device characterized in that the first virtual image and the second virtual image are displayed such that the parts adjacent to the gap between the first virtual image and the second virtual image are separated from each other.
10. An image display device according to claim 1, The control unit, Obtain information about the brightness of the background, When the background is dark, the gap in the corrected image is reduced compared to when the background is bright. An image display device characterized by the following features.
11. To generate a corrected image with gaps, Projecting the image light of the corrected image onto the transmission and reflection portion, The first virtual image of the corrected image is displayed by reflection from the first surface of the transmission and reflection portion. The second virtual image of the corrected image is displayed by reflection from a second surface different from the first surface of the aforementioned transmission and reflection portion, and Display the second virtual image in the gap in the first virtual image, and display the first virtual image in the gap in the second virtual image. An image display method characterized by performing the following.