Program, display device, head-up display device, vehicle, and display method

Abstract

Provided are a program, a display device, a head-up display device, a vehicle, and a display method with which it is possible for any deterioration in visibility associated with a double image to be easily suppressed. This program causes a control unit that controls a display device for displaying an image serving as an original of a virtual image V to execute a step for adding gradation parts to a main body image part composed of characters or the like as an image and displaying the gradation parts. Gradation parts M1-Mn are displayed as the virtual image V so that, between a main image Vm corresponding to the main body image part and a double image Vd appearing at a position shifted from the main image Vm, the luminance decreases with increasing proximity to the double image Vd from the main image Vm. The luminance of the gradation parts M1-Mn is set so that the expression "y = n·R(x / m)" and the expression "0 < x < m" are satisfied. y is the luminance, x is the positional coordinates, n is the luminance of the main image Vm, R is the ratio of the luminance of the double image Vd to that of the main image Vm, and m is the distance between the main image Vm and the double image Vd of the main image Vm.

Description

Program, display device, head-up display device, vehicle, and display method

[0001] The present disclosure relates to a program, a display device, a head-up display device, a vehicle, and a display method.

[0002] Patent Document 1 discloses a technique for reducing double images in virtual images displayed by a head-up display device, in which the interlayer film of laminated glass onto which light from the head-up display device is projected is made wedge-shaped in cross section.

[0003] Japanese Patent Application Laid-Open No. 2011-207645

[0004] The configuration of Patent Document 1 is not a simple technique for reducing double images, but rather there is a demand for a simpler method for suppressing the decrease in visibility that accompanies double images.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a program, a display device, a head-up display device, a vehicle, and a display method that can easily suppress the reduction in visibility associated with double images.

[0006] In order to achieve the above object, a program according to a first aspect of the present disclosure causes a computer that controls a display device that displays an image that is the basis of a virtual image that appears by projecting display light onto a projection target to execute a step of displaying a main image portion consisting of characters, figures or symbols as the image with a gradation portion added, the gradation portion being displayed as the virtual image between a main image corresponding to the main image portion and a double image that appears at a position shifted from the main image such that the luminance decreases as the main image approaches the double image, and the luminance of the gradation portion is set to satisfy the following (Equation 1) and (Equation 2): y=n・R （ｘ／ｍ） ... (Equation 1) 0 < x < m ... (Equation 2) y: Brightness x: Position coordinate where the direction from the main image towards the double image is positive n: Brightness of the main image R: Ratio of brightness of the double image to the main image m: Distance between the main image and the double image of the main image

[0007] In order to achieve the above object, a display device according to a second aspect of the present disclosure includes a display unit that displays an image that is the basis of a virtual image that appears by projecting display light onto a projection member, the display unit displays the image by adding a gradation portion to a main image portion consisting of characters, figures or symbols, the gradation portion is displayed as the virtual image between a main image corresponding to the main image portion and a double image that appears at a position shifted from the main image so that the luminance decreases as the distance from the main image approaches the double image, and the luminance of the gradation portion is set to a luminance that satisfies the above (Equation 1) and (Equation 2).

[0008] In order to achieve the above object, a head-up display device according to a third aspect of the present disclosure includes: a storage unit that stores the program; a display device that emits the display light; and a control unit that controls the display device by executing the program.

[0009] In order to achieve the above object, a vehicle according to a fourth aspect of the present disclosure is equipped with the head-up display device.

[0010] In order to achieve the above object, a display method according to a fifth aspect of the present disclosure is a display method for displaying an image that is the basis of a virtual image that appears by projecting display light onto a projection member, and includes a step of displaying the image by adding a gradation portion to a main image portion consisting of characters, figures, or symbols, and the gradation portion is displayed as the virtual image between a main image corresponding to the main image portion and a double image that appears at a position shifted from the main image, so that the luminance decreases as the distance from the main image approaches the double image, and the luminance of the gradation portion is set to a luminance that satisfies the above (Equation 1) and (Equation 2).

[0011] According to the present disclosure, it is possible to easily suppress the decrease in visibility caused by double images.

[0012] FIG. 1 is a schematic diagram of a vehicle equipped with a head-up display device according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram of a head-up display device according to an embodiment of the present disclosure. FIG. 3 is a flowchart of image display processing according to an embodiment of the present disclosure. FIG. 4 is a diagram of display content displayed on an image display surface. FIG. 5 is a diagram of a main image and its duplicated image. FIG. 6 is a diagram of display content according to an embodiment of the present disclosure. FIG. 7 is a diagram of virtual image display content according to an embodiment of the present disclosure. FIG. 8 is a graph showing the luminance gradation of virtual image display content according to an embodiment of the present disclosure. FIG. 9 is a table showing the luminance gradation of virtual image display content according to an embodiment of the present disclosure. FIG. 10 is a graph showing the luminance gradation of virtual image display content according to a modified example. FIG. 11 is a table showing the luminance gradation of virtual image display content according to a modified example. FIG. 12 is a schematic diagram showing a virtual image displayable area according to a modified example.

[0013] An embodiment of a program, a display device, a head-up display device, a vehicle, and a display method according to an embodiment of the present disclosure will be described with reference to the drawings. As shown in FIG. 1 , a head-up display device 100 is installed in a dashboard of a vehicle 200. The head-up display device 100 emits display light L representing an image toward a windshield 201, which is the front glass of the vehicle 200. The display light L is reflected by the windshield 201 and reaches a viewer 1 (mainly the driver of the vehicle 200). As a result, a virtual image V is displayed so as to be visible to the viewer 1. The virtual image V includes virtual image display content Vc (see FIG. 7 ) indicating vehicle information. In this example, the virtual image display content Vc is vehicle speed information composed of numbers and Roman letters.

[0014] The windshield 201 is a transparent member with a substantially uniform thickness, and is made of, for example, laminated glass. The windshield 201 has a curvature in the height direction and the width direction of the vehicle. This curvature varies depending on the position on the windshield 201, and the windshield 201 is formed as a free-form surface. The thickness and curvature of the windshield 201 vary depending on the vehicle model.

[0015] As shown enlarged in the upper left of Fig. 1 , the windshield 201 includes an outer glass 205, an interlayer film 206, and an inner glass 207. The outer glass 205, the interlayer film 206, and the inner glass 207 are laminated together. The outer glass 205 is located on the outer side of the vehicle cabin, and the inner glass 207 is located on the inner side of the vehicle cabin. The interlayer film 206 is made of a resin sheet and is located between the outer glass 205 and the inner glass 207. The outer glass 205, the interlayer film 206, and the inner glass 207 each have a uniform thickness.

[0016] As shown in FIG. 2 , the head-up display device 100 includes a display device 10 , a concave mirror 30 , a housing 60 , and a control unit 70 .

[0017] The display device 10 emits display light L. The display device 10 includes an illumination unit 12 that emits illumination light and a display unit 13 that receives the illumination light and emits the display light L. The illumination unit 12 includes a plurality of light-emitting diodes (LEDs) as light sources. The display unit 13 has an image display surface 11 that displays an image G, and emits display light L corresponding to the image G from the image display surface 11. The display unit 13 is a thin-film transistor (TFT) liquid crystal display panel controlled by a control unit 70. Note that the display device 10 is not limited to a configuration including a liquid crystal display panel, and may also be a configuration including an organic electroluminescence (EL) display or a digital micro mirror device (DMD). Furthermore, the display device 10 may be a scanning display device that displays an image by scanning laser light from a light source onto a screen using a micro electro mechanical systems (MEMS) mirror.

[0018] The concave mirror 30 reflects the display light L from the display device 10 toward the windshield 201 while magnifying the light.

[0019] The housing 60 is made of non-transparent resin or metal and has a hollow, approximately rectangular parallelepiped shape. Each component of the head-up display device 100 is housed inside the housing 60. An opening 61 is formed in the housing 60 at a position facing the windshield 201. The housing 60 includes a curved plate-shaped window 50 that closes the opening 61. The window 50 is made of a translucent resin such as acrylic, through which the display light L passes.

[0020] The control unit 70 controls the display device 10. The control unit 70 includes an image processing unit 71 consisting of a CPU (Central Processing Unit) and a GDC (Graphic Display Controller), and a storage unit 72 consisting of a ROM (Read Only Memory) or the like. The storage unit 72 stores original image data and a program PG that defines the operation procedure of the control unit 70. The image processing unit 71 generates an image G from the original image data stored in the storage unit 72 in accordance with the program PG, and displays the generated image G on the image display surface 11. The image processing unit 71 includes, as functional blocks, a displacement acquisition unit 71a and a gradation setting unit 71b.

[0021] The image generation process executed by the image processing unit 71 will be described with reference to the flowchart of FIG. 3 . The displacement acquisition unit 71a acquires the double image displacement amount m and the displacement direction D between the main image Vm and the double image Vd (step S101). Here, the main image Vm and the double image Vd will be described. When display content G1 displaying vehicle information in text as image G is displayed as shown in FIG. 4 , a double image Vd of the main image Vm appears as the virtual image V in addition to the main image Vm corresponding to the display content G1, as shown in FIG. 5 . The main image Vm is an image displayed by reflecting display light L on the surface (inside the vehicle) of the windshield 201. The double image Vd is an image displayed by reflecting display light L on the back surface (outside the vehicle) of the windshield 201. The double image Vd has the same shape as the main image Vm, is shifted in the displacement direction D from the main image Vm by the double image displacement amount m, and has lower brightness than the main image Vm. The double image Vd is not included in the image G displayed on the image display surface 11, but appears as a virtual image V. In other words, the display content G1, which is part of the image G, appears as the main image Vm and its double image Vd, depending on whether the surface on the windshield 201 that reflects the display light L containing the display content G1 is the front or back surface.

[0022] The double image shift amount m is the distance between the main image Vm and the double image Vd as seen by the viewer 1. In this example, the double image shift amount m is expressed as the number of pixel widths, with the width of one pixel of image G being the smallest unit. Note that the double image shift amount m is not limited to a distance, and may also be expressed as an angle, for example, the angle (degree) formed by a line segment from the viewpoint position to a predetermined position on the main image Vm and a line segment from the viewpoint position to a predetermined position on the double image Vd. In this example, the shift direction D is an upper right diagonal direction. The shift direction D varies depending on the curvature of the windshield 201 at the position where the display light L reaches. The shift direction D is not limited to this example, and may also be an upper left diagonal direction or an upward direction.

[0023] The double image shift amount m and shift direction D are obtained by experiment or simulation and stored in advance in the storage unit 72. In this experiment or simulation, for example, the double image shift amount m and shift direction D between the main image Vm and the double image Vd when the virtual image V is viewed from the center position of the eyebox are measured, and the measured double image shift amount m and shift direction D are stored in the storage unit 72. Note that the display content without a gradation portion shown in Figures 4 and 5 is shown for the purpose of explaining the main image Vm and the double image Vd, and in this embodiment, display content with a gradation portion is displayed. A specific description will be given below.

[0024] 3, the gradation setting unit 71b then processes the original image data so as to set multiple gradation areas L1-Ln between the main image Vm and the double image Vd based on the acquired double image shift amount m and shift direction D (step S102).Then, the image processing unit 71 displays an image G including display content G1 based on the processed original image data (step S103), and the image generation process ends.

[0025] As shown in FIG. 6, the display content G1 on the image display surface 11 includes a main image portion Am and multiple gradation portions L1-Ln (n is any natural number). The main image portion Am is the same as the display content G1 described above (see FIG. 4). Each gradation portion L1-Ln has the same shape as the main image portion Am and is shifted at an interval K equal to the shift direction D. The interval K is calculated by dividing the distance ΔL on the image display surface 11, which corresponds to the amount of double image shift m, by the total number of the main image portion Am and the gradation portions L1-Ln. In this example, the distance ΔL is 10 pixel widths, and the total number is 10, so the interval K is 1 pixel width. In this example, the main image portion Am and the gradation portions M1-Mn are each arranged with no gap between them, one pixel apart, in the shift direction D.

[0026] The brightness of each gradation section L1 to Ln is set higher the closer it is to the main image section Am. In other words, the brightness magnitude relationship is set as follows: brightness of gradation section L1 > brightness of gradation section L2 ... > brightness of gradation section Ln. The brightness of each gradation section L1 to Ln is set uniformly. The method for setting the brightness of the main image section Am and the gradation sections L1 to Ln will be described later.

[0027] As shown in FIG. 7 , the gradation portions L1 to Ln displayed in the image G are included in the virtual image display content Vc as gradation portions M1 to Mn (n is any natural number). The gradation portions M1 to Mn are arranged at equal intervals between the main image Vm and the double image Vd. The gradation portions M1 to Mn enable the main image Vm and the double image Vd to be displayed in a connected manner, making the difference in brightness between the main image Vm and the double image Vd less noticeable. This prevents a decrease in visibility of the virtual image display content Vc due to the double image Vd. The double image Vd is a double image of the main image Vm, but double images Vd1 to Vdn of the gradation portions M1 to Mn also appear. Therefore, the virtual image display content Vc includes the gradation portions M1 to Mn and their double images Vd1 to Vdn in addition to the main image Vm and its double image Vd. Double image Vd1 is a double image of gradation portion M1, double image Vd2 is a double image of gradation portion M2, and double image Vdn is a double image of gradation portion Mn. Double images Vd1 to Vdn are positioned to be aligned in the deviation direction D from double image Vd, and like gradation portions M1 to Mn, are arranged at equal intervals in the deviation direction D. Main image Vm and gradation portions M1 to Mn are aligned so as not to overlap with double images Vd and Vd1 to Vdn and without any gaps.

[0028] The brightness of the main image Vm, gradation portions M1 to Mn, and double images Vd, Vd1 to Vdn as the virtual image display content Vc is set so that the brightness of the main image Vm is the maximum brightness and decreases as the distance from the main image Vm in the shift direction D increases.

[0029] The following describes the brightness settings for the main image Vm and each of the gradation portions M1 to Mn. The brightness settings for the main image Vm as the virtual image V and each of the gradation portions M1 to Mn are performed by the designer through the brightness settings for the main image portion Am as the image G and the gradation portions L1 to Ln.

[0030] The luminance of the main image Vm and the gradation portions M1 to Mn is set to satisfy the following (Equation 1) and (Equation 2): y=n·R （ｘ／ｍ） ... (Equation 1) 0 < x < m ... (Equation 2) y: Brightness of the main image Vm or gradation portions M1 to Mn x: Position coordinate where the direction from the main image Vm toward the double image Vd is positive n: Brightness of the main image Vm R: Ratio of brightness of the double image Vd to the main image Vm m: Double image deviation amount, which is the distance between the main image Vm and the double image Vd

[0031] 7 to 9, the position coordinate x advances by one pixel width in the deviation direction D as it increases by 1, and is expressed as a natural number with decimal points rounded down. The main image Vm is displayed in the range where the position coordinate x is 0. A gradation section M1 is displayed in the range where the position coordinate x is 1, a gradation section M2 is displayed in the range where the position coordinate x is 2, and similarly, gradation sections M3 to Mn are displayed in the range where the position coordinate x is 3 to 9, respectively. In the above (Equation 1) and (Equation 2), the maximum value of the position coordinate x is set to the double image deviation amount m, which in this example is a distance equivalent to the width of 10 pixels.

[0032] The ratio R of the brightness of the double image Vd to the main image Vm is the reflectance of the light that generates the double image Vd to the reflectance of the light that generates the main image Vm. In other words, the ratio R is the ratio of "windshield inner surface transmittance × windshield outer surface reflectance × windshield inner surface transmittance" to "windshield inner surface reflectance." The double image shift amount m is expressed by the number of pixel widths or angles, as described above.

[0033] The graph in FIG. 8 and the table in FIG. 9 show the luminance changes of the main image Vm and the gradation portions M1-Mn that satisfy the above-mentioned (Equation 1) and (Equation 2), and also show the luminance of the double images Vd, Vd1-Vdn that are determined in response to this luminance change. In this example, the luminance n of the main image Vm is not a specific luminance value, but is set to 100% as the maximum luminance. The luminances of the gradation portions M1-Mn and the double images Vd, Vd1-Vdn are set to less than 100%. The luminance of the double images Vd, Vd1-Vdn is obtained by multiplying the luminance of the main image Vm and the gradation portions M1-Mn by the above-mentioned ratio R (0.4 in this example). Also, as mentioned above, the amount of double image misalignment m is equivalent to a 10-pixel width. Therefore, the character width of the virtual image display content Vc is a total of 20 pixels, consisting of the 10 pixel width of the main image Vm and the gradation portions M1 to Mn and the 10 pixel width of the double images Vd, Vd1 to Vdn. In this example, as shown in Figures 8 and 9, the brightness gradation of the main image Vm, the gradation portions M1 to Mn, and the double images Vd, Vd1 to Vdn can be smoothly changed in the deviation direction D. This improves the visibility of the virtual image display content Vc.

[0034] Next, the procedure for deriving the above formula (1) will be explained. Generally, the brightness of the double image occurs at a certain ratio (for example, the above-mentioned ratio R) to the brightness of the main image. From this point of view, the inventors of the present application came up with the idea that, as an ideal formula, when the pixel position is x and the brightness is y, with A, B, and C as unknowns, this should be expressed by the following formula (3), which is a general exponential function: y = A B （Ｃ・ｘ） ...(Equation 3) Therefore, in order to find the unknowns A, B, and C in the above (Equation 3), the following conditions 1 to 3 were set.

[0035] (Condition 1) At the y-intercept, the luminance value is the luminance n of the main image. That is, when x = 0, y = n. Substituting x = 0 and y = n into the above (Equation 3), we get the following: A·B （Ｃ・０） =n A=n

[0036] (Condition 2) The brightness of the double image Vd at a position shifted from the main image Vm by the amount of double image shift m is as follows: Brightness of double image Vd = n R In other words, when x = m, y = n R. Substituting y = n R, A = n, and x = m into the above (Equation 3), the following is obtained: n B （Ｃ・ｍ） = n R B （Ｃ・ｍ） =R

[0037] (Condition 3) B （Ｃ・ｍ） The simplest values ​​that satisfy A = R are C = 1 / m and B = R. Therefore, by substituting A = n, B = R, and C = 1 / m into the above (Equation 3), the above (Equation 1) can be derived.

[0038] (Effects) According to the embodiment described above, the following effects are achieved. (1) The program PG causes the control unit 70, which is an example of a computer that controls the display device 10 that displays the image G that is the basis of the virtual image V that appears by projecting the display light L onto the windshield 201, which is an example of a projection target, to execute step S103, which displays the image G by adding gradation portions L1 to Ln to a main image portion Am consisting of characters, figures, or symbols. The gradation portions M1 to Mn are displayed as the virtual image V between the main image Vm corresponding to the main image portion Am and the double image Vd that appears at a position shifted from the main image Vm, so that the brightness decreases as the distance from the main image Vm to the double image Vd increases. The brightness of the gradation portions M1 to Mn is set to satisfy the following (Equation 4) and (Equation 5): y=n·R （ｘ／ｍ）... (Equation 4) 0 < x < m ... (Equation 5) y: Brightness x: Position coordinate where the direction from the main image Vm to the double image Vd is positive n: Brightness of the main image Vm R: Ratio of the brightness of the double image Vd to the main image Vm m: Distance between the main image Vm and the double image Vd of the main image Vm With this configuration, the brightness y of the gradation portions M1 to Mn and the double images Vd1 to Vdn is set to gradually decrease as the position coordinate x increases. This makes it possible to easily suppress the decrease in visibility associated with the double image Vd. In particular, when the projected member is the windshield 201 mounted on the vehicle 200, the thickness of the windshield 201 makes it easy for double images to occur. Therefore, it is beneficial to suppress the decrease in visibility associated with the double image Vd using the above configuration.

[0039] (2) The luminance of the main image Vm and the gradation portions M1 to Mn decreases at a constant rate as the position coordinate x increases. This configuration improves the visibility of the virtual image display content Vc, which includes the main image Vm and its double image Vd.

[0040] (3) The display device 10 includes a display unit 13 that displays an image G, which is the basis of a virtual image V that appears when display light L is projected onto a windshield 201, which is an example of a projection target. The display unit 13 displays the image G by adding gradation portions L1 to Ln to a main image portion Am consisting of characters, figures, or symbols. The gradation portions M1 to Mn are displayed as the virtual image V between a main image Vm corresponding to the main image portion Am and a double image Vd that appears at a position offset from the main image Vm, with the luminance decreasing as the distance from the main image Vm approaches the double image Vd. The luminance of the gradation portions M1 to Mn is set to satisfy the above-described (Equation 4) and (Equation 5). This configuration allows the display device 10 to easily suppress a decrease in visibility associated with the double image Vd.

[0041] (4) The head-up display device 100 includes a storage unit 72 that stores a program PG, a display device 10 that emits display light L, and a control unit 70 that controls the display device 10 by executing the program PG. Furthermore, the windshield 201 is a transparent member with a substantially uniform thickness, and reflects the display light L at a reflection angle toward the viewer 1. This substantially uniform thickness includes, for example, a thickness of the windshield 201 that is within an error range, for example, within a few percent (e.g., within ±1% to ±3%). This configuration allows the head-up display device 100 to easily suppress a decrease in visibility due to the double image Vd. Furthermore, the windshield 201 only needs to have a substantially uniform thickness.

[0042] (5) The head-up display device 100 is mounted on the vehicle 200. With this configuration, in the vehicle 200, it is possible to easily suppress a decrease in visibility due to the double image Vd.

[0043] (6) A display method for displaying an image G that is the basis of a virtual image V that appears by projecting display light L onto a windshield 201, which is an example of a projection target, includes step S103, in which a main image portion Am consisting of a character, figure, or symbol is displayed as image G with gradation portions L1 to Ln added. The gradation portions M1 to Mn are displayed as the virtual image V between a main image Vm corresponding to the main image portion Am and a double image Vd that appears at a position offset from the main image Vm, with the luminance decreasing as the distance from the main image Vm approaches the double image Vd. The luminance of the gradation portions M1 to Mn is set to satisfy the above-described (Equation 4) and (Equation 5). According to this configuration, by displaying the gradation portions M1 to Mn between the main image Vm and the double image Vd, it is possible to easily suppress the decrease in visibility that accompanies the double image Vd.

[0044] The present disclosure is not limited to the above-described embodiments and drawings. Modifications (including deletion of components) may be made as appropriate within the scope of the present disclosure. An example of such a modification is described below.

[0045] (Variant) In the above embodiment, the brightness of the main image Vm and the gradation portions M1 to Mn are exemplified as absolute values, but these brightnesses may also be set in association with the hue, saturation, or RGB values ​​other than brightness among the HSL values.

[0046] In the above embodiment, the character width (one pixel width) of the main image Vm in the shift direction D was the same as the width (one pixel width) of each gradation section M1 to Mn, but the character width of the main image Vm in the shift direction D may be larger than the width of each gradation section M1 to Mn, for example, set to multiple pixel widths.

[0047] In the above embodiment, if the brightness of the virtual image display content Vc is insufficient, the brightness of the virtual image display content Vc may be improved by maintaining the brightness of the main image Vm and the gradation portions M1 to Mn by a specified distance (e.g., the width of multiple pixels) in the deviation direction D. Specifically, in the graph of FIG. 8 , the brightness y when the position coordinate x is 1 is maintained at the brightness y when the position coordinate x is 0 (the brightness of the main image Vm), the brightness y when the position coordinate x is 3 is maintained at the brightness y when the position coordinate x is 2, and similarly, the brightness y when the position coordinate x is an odd number is maintained at the brightness y of the immediately preceding even number. This allows the brightness gradation of the main image Vm and the double images Vd, Vd1 to Vdn to be smoothly changed while improving the brightness of the entire virtual image display content Vc.

[0048] In the above embodiment, the luminance gradation of the main image Vm and the gradation portions M1 to Mn that satisfy the above formulas (1) and (2) is determined based on parameters such as the ratio R generated in the Gatley (central light) of the display light L. However, in reality, the above parameters change depending on the position at which the display light L is irradiated on the windshield 201, and the amount of double image disparity m also changes. Focusing on this point, the luminance gradation of the main image Vm and the gradation portions M1 to Mn may be changed depending on the display position of the virtual image V within the displayable area. Due to the structure of the windshield 201, the amount of double image disparity m increases as the irradiation position on the windshield 201 moves toward the upper outside of the vehicle (the upper right side in a right-hand drive vehicle, and the upper left side in a left-hand drive vehicle). Conversely, the amount of double image disparity m decreases as the irradiation position on the windshield 201 moves toward the lower inside of the vehicle (the lower left side in a right-hand drive vehicle, and the lower right side in a left-hand drive vehicle). As shown in FIG. 12 , the image processing unit 71 displays two virtual image display contents Vc1 and Vc2 at different positions within the virtual image displayable area Ar. The virtual image display content Vc1 is located higher and outside the vehicle than the virtual image display content Vc2, and although not shown in the figure, the virtual image display content Vc1 has a larger double image displacement amount m than the virtual image display content Vc2. The image processing unit 71 displays the virtual image V with a brightness gradation that corresponds to the double image displacement amount m, which differs between the two virtual image display contents Vc1 and Vc2. This makes it possible to display the virtual image display contents Vc1 and Vc2 with high visibility, regardless of their display positions within the virtual image displayable area Ar. For example, the double image displacement amount m for the virtual image display content Vc1 is 10 pixel widths, and the double image displacement amount m for the virtual image display content Vc2 is 7 pixel widths. For the virtual image display content Vc1, the image processing unit 71 displays the virtual image display content Vc1 with a character width of 20 pixels in total, consisting of 10 pixel widths for the main image Vm and gradation portions M1 to Mn and 10 pixel widths for the double images Vd, Vd1 to Vdn, with the brightness gradation shown in Figures 8 and 9 above.On the other hand, the image processing unit 71 displays the virtual image display content Vc2 with a luminance gradation that satisfies the above-described (Equation 1) and (Equation 2) shown in Figures 10 and 11, with the character width of the virtual image display content Vc2 being 14 pixels in total, consisting of the 7 pixel width of the main image Vm and the gradation portions M1 to Mn and the 7 pixel width of the double images Vd, Vd1 to Vdn. The amount of change in the luminance gradation in the virtual image display content Vc2 is steeper than the amount of change in the luminance gradation in the virtual image display content Vc1.

[0049] In the above embodiment, the concave mirror 30 is configured to be non-rotatable, but this is not limiting. The head-up display device 100 may also include a mirror drive unit that rotates the concave mirror 30 about a rotation axis extending in the vehicle width direction. The position of the display light L irradiated onto the windshield 201 changes in the vertical direction depending on the rotation angle of the concave mirror 30. The control unit 70 may rotate the concave mirror 30 via the mirror drive unit to display the virtual image V with a brightness gradation that satisfies the above-described (Equation 1) and (Equation 2) by increasing the double image displacement amount m as the position of the display light L irradiated onto the windshield 201 becomes higher.

[0050] The head-up display device 100 may also include a viewpoint position detection unit that detects the viewpoint position of the viewer 1. The viewpoint position detection unit may be configured with, for example, a camera. The control unit 70 may display the virtual image V with a brightness gradation that satisfies the above-described (Equation 1) and (Equation 2) by increasing the double image displacement amount m as the viewpoint position becomes higher according to the detection result of the viewpoint position detection unit.

[0051] In the above embodiment, the virtual image display content Vc is composed of characters including numbers and Roman letters, but may also include symbols or graphics. That is, the virtual image display content Vc may include one or more of letters, graphics, and symbols.

[0052] In the above embodiment, the deviation acquisition unit 71a may receive image data from a camera that captured the virtual image V and acquire the double image deviation amount m and deviation direction D. Also, in the above embodiment, the gradation setting unit 71b processes the original image data so as to set multiple gradation portions L1 to Ln between the main image Vm and the double image Vd based on the acquired double image deviation amount m and deviation direction D, but multiple gradation portions L1 to Ln may be set in advance in the original image data. In this case, the deviation acquisition unit 71a is omitted.

[0053] In the above embodiment, the head-up display device 100 may include a folding mirror that reflects the display light L from the display device 10 toward the concave mirror 30. The folding mirror is a plane mirror or a concave mirror.

[0054] In the above embodiment, the head-up display device 100 is mounted on the vehicle 200, but it may be mounted on a vehicle other than the vehicle 200, such as an airplane or a ship, or may not even be mounted on a vehicle. In addition, the projection target member is not limited to the windshield 201, and may be a dedicated combiner.

[0055] In the above embodiment, the intermediate film 206 of the windshield 201 is formed to have a substantially constant thickness, but this is not limited thereto, and it may be formed to have a wedge shape in cross section, as in Patent Document 1.

[0056] DESCRIPTION OF SYMBOLS 1 Viewer 10 Display device 11 Image display surface 12 Illumination unit 13 Display unit 30 Concave mirror 50 Window unit 60 Housing 61 Opening 70 Control unit 71 Image processing unit 71a Misalignment acquisition unit 71b Gradation setting unit 72 Memory unit 100 Head-up display device 200 Vehicle 201 Windshield 205 Outer glass 206 Interlayer 207 Inner glass D Misalignment direction G Image G1 Display content K Spacing L Display light ΔL Distance L1-Ln, M1-Mn Gradation unit V Virtual image Vm Main image Vc, Vc1, Vc2 Virtual image display content PG Program m Double image misalignment amount n Brightness of main image y Brightness Am Main image unit Vd, Vd1-Vdn Double image x position coordinate Ar Virtual image displayable area

Claims

1. A program that causes a computer that controls a display device that displays an image that is the basis of a virtual image that appears by projecting display light onto a projection target to execute a step of displaying a main image portion consisting of a character, figure or symbol as the image with a gradation portion added, the gradation portion being displayed as the virtual image between a main image corresponding to the main image portion and a double image that appears at a position shifted from the main image such that the luminance decreases as the main image approaches the double image, and the luminance of the gradation portion is set to satisfy the following (Equation 1) and (Equation 2): y = n R （ｘ／ｍ） ... (Formula 1) 0 < x < m ... (Formula 2) y: Brightness x: Position coordinates where the direction from the main image to the double image is positive n: Brightness of the main image R: Ratio of brightness of the double image to the main image m: Distance between the main image and the double image of the main image 2. The program according to claim 1, wherein the luminance of the main image and the gradation portion decreases at a constant rate as the position coordinate x increases.

3. The program according to claim 1, wherein the projected member is a windshield mounted on a vehicle.

4. A display device comprising a display unit that displays an image that is the basis of a virtual image that appears by projecting display light onto a projection target, the display unit displays the image by adding a gradation portion to a main image portion consisting of characters, figures or symbols, the gradation portion is displayed as the virtual image between a main image corresponding to the main image portion and a double image that appears at a position shifted from the main image such that the luminance decreases as the main image approaches the double image, and the luminance of the gradation portion is set to satisfy the following (Equation 1) and (Equation 2). y = n R （ｘ／ｍ） ... (Formula 1) 0 < x < m ... (Formula 2) y: Brightness x: Position coordinates where the direction from the main image to the double image is positive n: Brightness of the main image R: Ratio of brightness of the double image to the main image m: Distance between the main image and the double image of the main image 5. A head-up display device comprising: a memory unit that stores the program according to any one of claims 1 to 3; a display device that emits the display light; and a control unit that controls the display device by executing the program.

6. The head-up display device according to claim 5, wherein the projected member is a transparent member having a substantially constant thickness, and reflects the display light at a reflection angle toward a viewer.

7. A vehicle equipped with the head-up display device according to claim 5.

8. A display method for displaying an image that is the basis of a virtual image that appears by projecting display light onto a projection member, comprising a step of displaying a main image portion consisting of a character, figure or symbol as the image with a gradation portion added thereto, the gradation portion being displayed as the virtual image between a main image corresponding to the main image portion and a double image that appears at a position shifted from the main image such that the luminance decreases as the main image approaches the double image, and the luminance of the gradation portion is set to a luminance that satisfies the following (Equation 1) and (Equation 2): y = n R （ｘ／ｍ） ... (Formula 1) 0 < x < m ... (Formula 2) y: Brightness x: Position coordinates where the direction from the main image to the double image is positive n: Brightness of the main image R: Ratio of brightness of the double image to the main image m: Distance between the main image and the double image of the main image

Images