Head-up display for displaying graphics on a vehicle's windshield

Abstract

Head-up display (10) for displaying graphics on a windshield (12) of a vehicle (14), the head-up display (10) comprising: a graphics projection module (22) for generating one or more graphic images (42) on the windshield (12) of the vehicle (14); a forward-facing camera (24) that collects image data representative of a view of the vehicle's (14's) surroundings (34) visible through the windshield (12); an ambient light sensor (28) that detects a degree of ambient light in the area (34) surrounding the vehicle (14);and one or more controllers (20) in electronic communication with the graphic projection module (22), with the forward-facing camera (24) and with the ambient light sensor (28), wherein the one or more controllers (20) are configured to execute instructions to: monitor the image data from the forward-facing camera (24) until determining, based on the image data, that an object (40) of interest is visible through the windshield (12); in response to determining that the object (40) of interest is visible through the windshield (12), determine one or more graphic images (42) to be displayed on the windshield (12) to draw a user's attention to the object (40) of interest; determine the degree of ambient light in the vicinity (34) of the vehicle (14) based on an ambient light signal received from the ambient light sensor (28);and to adjust the saturation level of one or more colors of the one or more graphic images (42) generated by the graphic projection module (22) on the basis of the ambient light present in the environment (34); wherein adjusting the saturation level of the one or more colors of the one or more graphic images (42) includes increasing the saturation level when the level of ambient light decreases and decreasing the saturation level when the level of ambient light increases.

Description

The present disclosure relates to a head-up display for a vehicle that takes into account the color vision deficiencies of a user. A head-up display (HUD) projects information such as vehicle speed and navigation instructions directly onto the windshield of a vehicle in the driver's front field of vision. The head-up display thus provides the driver with information without requiring them to take their eyes off the road. For example, the head-up display can project graphics onto the windshield containing information such as vehicle speed and navigation instructions. The three main types of color vision deficiency are protanomaly, i.e., an abnormal response of the L-cones in the retina to long-wavelength light; deuteranomaly, i.e., an abnormal response of the M-cones in the retina to medium-wavelength light; and tritanomaly, i.e., an abnormal response of the S-cones in the retina to short-wavelength light. A color space chromaticity diagram, such as the 1931 color space chromaticity diagram of the International Commission on Illumination (CIE), depicts the human eye's response to physical colors, or wavelengths, in the electromagnetic visible light spectrum. A person with color vision deficiency may be unable to distinguish between colors located along color confusion lines in a color space chromaticity diagram. These color confusion lines are mapped for the different types of color vision deficiency (i.e., protanomaly, deuteranomaly, and tritanomaly).Color confusion lines of the same luminance converge to a single intersection point, known as a punctual point, which corresponds to the specific type of color vision deficiency. At the same luminance, individuals with a particular color vision deficiency are unable to distinguish colors that lie on the same color confusion line of the corresponding color space chromaticity diagram. It should be recognized that it can be difficult for the human eye to distinguish between different colors in dim ambient light, even for people with normal color vision. This is because the human eye uses scotopic vision in dim light, where the cone cells are less sensitive to color discrimination. Consequently, the difficulties experienced by people with color vision deficiencies when trying to differentiate certain colors can be particularly pronounced in dim light. Although current head-up displays fulfill their purpose, there is therefore a need for an improved head-up display that accommodates people with color vision deficiencies. DE 11 2019 002 489 T5 describes a display control component for a vehicle. The display control component includes an overlap detection component, which, in a case where a first overlay image is displayed over a first object and a second object is detected as an overlapping object, determines whether an overlap occurs between the overlay images, etc., and a visibility control component, which reduces the visibility of the first overlay image, which overlays the first object, compared to the visibility of the second overlay image, which overlays the second object, when the overlap occurs. US 2015 / 0348477A1 describes a display device for a vehicle. The display device comprises an image display panel in which pixels are arranged in a two-dimensional matrix, each pixel comprising a first subpixel for displaying a first color, a second subpixel for displaying a second color, a third subpixel for displaying a third color, and a fourth subpixel for displaying a fourth color; and a signal processing unit that converts input values ​​from input signals into extended values ​​in an extended color space to generate output signals and outputs the generated output signals to the image display panel. The signal processing unit modifies the output signals for the first through fourth subpixels based at least on the saturation of the input signals. The object of the invention can be considered to be to provide an improved heap-up display to accommodate people with color vision deficiencies. According to the invention, a head-up display for projecting graphics onto a vehicle's windshield is described. The head-up display comprises a graphics projection module for generating one or more graphic images onto the vehicle's windshield, a forward-facing camera that collects image data representative of the vehicle's surroundings as seen through the windshield, an ambient light sensor that detects the level of ambient light in the vehicle's environment, and one or more controllers. The one or more controllers communicate electronically with the graphics projection module, the forward-facing camera, and the ambient light sensor.The one or more controllers are configured to execute instructions to monitor the image data from the forward-facing camera until they determine, based on the image data, that an object of interest is visible through the windshield. In response to this determination, the one or more controllers are configured to determine one or more graphic images to be displayed on the windshield to draw a user's attention to the object of interest. The one or more controllers are also configured to determine the level of ambient light in the vehicle's surroundings based on an ambient light signal received from the ambient light sensor.The one or more controllers are configured to adjust the saturation level of one or more colors of the one or more graphic images generated by the graphics projection module based on the ambient light present in the environment. In one embodiment, the one or more controllers are configured to execute instructions to direct the graphics projection module to generate one or more graphic images with an adjusted saturation level on the windshield. According to the invention, adjusting the saturation level of one or more colors of one or more graphic images includes increasing the saturation level when the level of ambient light decreases, and decreasing the saturation level when the level of ambient light increases. In another embodiment, the ambient light sensor is configured to detect three discrete levels of ambient light, including a high level of light representing full daylight conditions, a medium level of light representing overcast conditions, and a low level of light representing twilight conditions. In another embodiment, the high light level corresponds to a saturation level of sixty percent, the medium light level corresponds to a saturation level of seventy percent, and the low light level corresponds to a saturation level of eighty percent. In another embodiment, the saturation values ​​are increased by five percent for persons who are at least forty years old. In another embodiment, the images generated by the graphics projection module contain two or more colors. In another embodiment, the one or more controllers are configured to execute instructions to compare color and luminance information corresponding to the two or more colors of the one or more graphic images generated by the graphics projection module against a potentially confusing color combination. Upon determining that the potentially confusing color combination exists, the one or more controllers map the color coordinates corresponding to the two or more colors to a color space chromaticity diagram as a first color and a second color. In another embodiment, the one or more controllers are configured to execute instructions to calculate a correlation coefficient between the first color and the second color and a punctual point that is part of the color space chromaticity diagram, and to compare the correlation coefficient with a threshold, where values ​​greater than the threshold indicate that the first color and the second color are a potentially confusing color pair. In another embodiment, the one or more controllers are configured to execute instructions to calculate a Delta-E value between the first color and the second color in response to the determination that the correlation coefficient is greater than the threshold, and to compare the Delta-E value with a Delta-E threshold. In another embodiment, the one or more controllers are configured to execute instructions to adjust the saturation and luminance levels of the first and / or second color in response to the determination that the Delta-E value is below the Delta-E threshold, and to instruct the graphics projection module to produce one or more graphic images with increased Delta-E values ​​on the windshield. In another embodiment, the forward-facing camera is configured to capture uncalibrated color and luminance information of the vehicle's surroundings. In another embodiment, the one or more controllers are configured to execute instructions to convert the uncalibrated color and luminance information from the forward-facing camera into calibrated color and luminance information based on values ​​stored in one or more lookup tables. In another embodiment, the one or more controllers are configured to execute instructions to compare the calibrated color and luminance information corresponding to a specific object located in the vehicle's environment with color and luminance information corresponding to two or more colors of the one or more graphic images generated by the graphics projection module, in order to determine a potentially confusing color combination. In another embodiment, in response to the determination that a potentially confusing color combination exists, the one or more controllers are configured to map the calibrated color and luminance information corresponding to the specific object and the color coordinates of one of the two or more colors of the one or more graphic images onto a color space chromaticity diagram as a third color and a fourth color. In another embodiment, the one or more controllers are configured to execute instructions to calculate a correlation coefficient between the third color and the fourth color and a punctual point that is part of the color space chromaticity diagram. The one or more controllers are configured to compare the correlation coefficient to a threshold value, where a value greater than the threshold indicates that the third and fourth colors are a potentially confusing color pair. In response to determining that the correlation coefficient is greater than the threshold, the one or more controllers are configured to calculate a delta-E value between the third and fourth colors. The one or more controllers are then configured to compare the delta-E value to a delta-E threshold value. In one embodiment, in response to the determination that the Delta-E value is less than the Delta-E threshold, a saturation level and a luminance level of the fourth color corresponding to one or more graphic images are adjusted to increase the Delta-E value above the Delta-E threshold, and the graphic projection module is instructed to produce the one or more graphic images with increased Delta-E values ​​on the windshield. In one application, a method for displaying graphics on a vehicle's windshield using the head-up display according to the invention is described. The method comprises monitoring image data from a forward-facing camera by one or more controllers until, based on the image data, it is determined that an object of interest is visible through the windshield, wherein the image data represents a view of the vehicle's surroundings visible through the windshield. In response to the determination that the object in question is visible through the windshield, the method includes determining one or more graphic images to be displayed on the windshield in order to draw a user's attention to the object in question.The method comprises determining the level of ambient light in the vehicle's surroundings based on an ambient light signal received by an ambient light sensor in electronic communication with one or more controllers. Finally, the method comprises adjusting the saturation level of one or more colors of the one or more graphics generated by a graphics projection module based on the ambient light present in the environment. The drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way. Fig. 1 is a schematic diagram of a vehicle containing the disclosed head-up display system for displaying graphic images on a windshield; Fig. 2 is an interior view of the windshield while the head-up display system generates a graphic image to highlight an object of interest, which is a road sign; Fig. 3 is an alternative interior view of the windshield while the head-up display system generates a plurality of graphic images to highlight an object of interest, which is a road vehicle; Fig. 4 shows a first color and a second color, which are depicted in an exemplary color space chromaticity diagram; Fig. 5 shows a third and a fourth color, which are depicted in the color space chromaticity diagram; Fig.Figure 6 is a process flow diagram illustrating a method for adjusting the color vision deficiency of a vehicle user by the head-up display shown in Figure 1 based on ambient light levels; and Figure 7 is a process flow diagram illustrating a method for taking into account the color vision deficiency of the vehicle user by adjusting the saturation and luminance levels of the colors produced by the head-up display. Figure 1 shows an exemplary head-up display 10 for generating graphics on the windshield 12 of a vehicle 14. As explained below, the head-up display 10 adjusts the saturation of a single color and / or the luminance of colors that are part of the graphics generated on the windshield 12 of the vehicle 14 to compensate for color vision deficiencies of a user of the vehicle 14. The user is an occupant of the vehicle 14 and can be a driver or passenger. The vehicle 14 can be any type of vehicle, such as a sedan, truck, sport utility vehicle, van, or motorhome. The head-up display 10 comprises one or more controllers 20 that communicate electronically with a graphics projection module 22, a forward-facing camera 24, a tristimulus colorimeter 26, and an ambient light sensor 28. The graphics projection module 22 is configured to generate images on the windshield 12 of the vehicle 14 and includes a projection device that generates an excitation light for projecting images. The forward-facing camera 24 captures periodic or sequential images representing a view of the vehicle 14's surroundings 34 as seen through the windshield 12. In one embodiment, the forward-facing camera 24 is a digital camera with a photosensor array 30 and a red, green, and blue (RGB) filter 32 positioned above the photosensor array 30, wherein the forward-facing camera 24 captures uncalibrated color and luminance information of the vehicle 14's surroundings 34.The uncalibrated color and luminance information captured by the forward-facing camera 24 includes, in particular, an uncalibrated luminance value L and uncalibrated color coordinates x and y based on the color space chromaticity diagram of the International Lighting Commission (CIE) 1931. The tristimulus colorimeter 26 is any device for acquiring color and luminance information of the environment 34 of the vehicle 14, which is visible through the windshield 12 of the vehicle 14. In one embodiment, the tristimulus colorimeter 26 is a spectroradiometer. The tristimulus colorimeter 26 acquires color and luminance information of the environment 34 of the vehicle 14 (i.e., L, x, y), wherein the color and luminance information acquired by the tristimulus colorimeter 26 is used to calibrate the uncalibrated color and luminance information received by the forward-facing camera 24. In particular, the one or more controllers 20 store one or more transformation matrices or lookup tables 38 that correlate the uncalibrated color and luminance information from the forward-facing camera 24 with the color and luminance information of the tristimulus colorimeter 26 in memory.The one or more controllers 20 convert the uncalibrated color and luminance information from the forward-facing camera 24 into calibrated color and luminance information based on values ​​stored in the one or more lookup tables 38. In some embodiments, the tristimulus colorimeter 26 is installed in the vehicle 14 during the calibration process of the forward-facing camera 24 and removed after the calibration is complete. The ambient light sensor 28 is a photodetector configured to detect the intensity of ambient light in the vicinity 34 of the vehicle 14. In a non-limiting embodiment, the ambient light sensor 28 detects three discrete levels of ambient light: a high level, a medium level, and a low level. The high level corresponds to full daylight, the medium level to overcast skies, and the low level to twilight. Although three levels of ambient light are described, fewer or more levels can, of course, be defined. Once the forward-facing camera 24 is calibrated, it can also provide luminance information for each object in the vicinity 34. Fig. 2 is a front view of the windshield 12 in which an object 40 of interest located in the environment 34 surrounding the vehicle 14 is highlighted by one or more graphic images 42 generated on the windshield 12 by the graphic projection module 22 of the head-up display 10 (Fig. 1). In the example shown in Fig. 2, the object 40 of interest is a road sign, and the one or more graphic images 42 comprise an octagon drawn around the road sign. However, it should be noted that Fig. 2 is merely illustrative and the disclosure is not limited to specific objects 40 of interest or graphic images 42. As explained below, the head-up display 10 adjusts the saturation level of one or more colors of the one or more graphic images 42 generated by the graphic projection module 22 based on the ambient light sensor 28 (in Fig. 1).(1 shown) the detected ambient light level. Adjusting the saturation level changes the saturation intensity of one or more colors generated by the graphics projection module 22. With reference to Figures 1 and 2, the one or more controllers 20 monitor image data representing the view of the vehicle 14's surroundings 34, visible through the vehicle 14's windshield 12 from the forward-facing camera 24. The one or more controllers 20 monitor the image data until they determine, based on the image data, that the object 40 in question is located within an area 50 encompassing the windshield 12. Although a stop sign is depicted, it should be understood that Figure 2 is for illustrative purposes only, and the object 40 of interest is any object located in the vehicle 14's surroundings 34 that has the potential for color and luminance values ​​that may be indistinguishable from other objects located in the surroundings 34. The head-up display 10 alerts the user to the object 40 of interest, which may include objects such as... B.This may include a child on a bicycle, another vehicle, weather conditions, road conditions, obstacles, pedestrians, emergency vehicles, points of interest, road signs, billboards, and destinations. In response to the determination that the object 40 of interest is visible through the windshield 12, the one or more controls 20 then determine the one or more graphic images 42 to be displayed on the windshield 12, the graphic image 42 drawing the user's attention to the object 40 of interest. The graphic image 42 can be any type of graphic that highlights the object 40 of interest and draws the user's attention. Although an octagon is shown in Fig. 2, the graphic image 42 can be any type of graphic, such as circles or boxes surrounding an object of interest, arrows, warning symbols, text, numbers, colors, lines, indicators, and logos. The graphic image 42 contains one or more colors. In the example of Fig. 2, the graphic image 42 contains the color red. The one or more controllers 20 then determine the level of ambient light in the environment 34 of the vehicle 14 based on an ambient light signal received from the ambient light sensor 28. The one or more controllers 20 then adjust the saturation level of the one or more colors of the graphic image 42 generated by the graphic projection module 22 based on the ambient light present in the environment 34. Specifically, adjusting the saturation level of the one or more colors of the graphic image 42 involves increasing the saturation level when the level of ambient light decreases and decreasing the saturation level when the level of ambient light increases. In other words, the saturation level increases when there is less ambient light.It is understood that a person's color vision deficiencies may be more pronounced in lower ambient light conditions, and the Head-Up Display 10 takes into account the color vision deficiencies of a user of the vehicle 14 by adjusting the saturation level of one or more colors displayed by the Head-Up Display 10 based on the ambient light conditions. In a non-restrictive embodiment, the high light level corresponds to a saturation level of approximately sixty percent, the medium light level corresponds to a saturation level of approximately seventy percent, and the low light level corresponds to a saturation level of approximately eighty percent. It should be noted that the standard saturation level is sixty percent. In one embodiment, the saturation values ​​can be adjusted according to the user's age, with the saturation values ​​being increased for individuals above a certain age. In one embodiment, the saturation values ​​are increased by approximately five percent for individuals who are at least forty years old. Therefore, the high light level corresponds to a saturation level of approximately sixty-five percent, the medium light level to a saturation level of approximately seventy-five percent, and the low light level to a saturation level of approximately eighty-five percent. Fig. 3 is a front view of the windshield 12, showing an alternative environment 34 around the vehicle 14. In the example shown in Fig. 3, the object 40 of interest is a vehicle, and a plurality of graphic images 42 are generated on the windshield 12 by the graphic projection module 22 of the head-up display 10 (Fig. 1). The plurality of graphic images 42 comprises two or more colors. In the example shown in Fig. 3, the graphic projection module 22 generates a green arrow 42A, a series of blue bars 42B, and a red wall 42C. As explained below, in one embodiment, the head-up display 10 adjusts the saturation and luminance levels of the two or more colors generated by the graphic projection module 22 to avoid color confusion problems for a user with color vision deficiencies. Referring to Figures 1, 3, and 4, the one or more controllers 20 first compare the color and luminance information corresponding to the two or more colors of the plurality of graphic images 42 generated by the graphic projection module 22 for a potentially confusing color combination that might be perceived as such by individuals with color vision deficiencies. It is understood that potentially confusing color combinations could exist between the colors red and green or between the colors blue and yellow. In the example shown in Figure 3, a potentially confusing color combination exists between the green arrow 42A and the red wall 42C. In response to the finding that a potentially confusing color combination exists between the two or more colors of the plurality of graphic images 42 generated by the graphic projection module 22, the one or more controllers 20 determine the color coordinates (i.e.,the x and y values), which correspond to the potentially confusing color combination, are represented in a color space chromaticity diagram 60 as a first color 70 and a second color 72, as shown in Fig. 4. In the embodiment shown in Fig. 4, the color space chromaticity diagram 60 is the CIE 1931 color space chromaticity diagram. However, it should be noted that Fig. 3 is only exemplary and that other types of color space chromaticity diagrams can also be used, such as the CIE 1976 L*a*b* color space chromaticity diagram. In the embodiment shown in Fig. 4, the color space chromaticity diagram 60 is intended for people affected by protanomaly, wherein the color space chromaticity diagram 60 contains a plurality of protane-based color confusion lines 62 that converge to a punctual point 64. In the example shown in Figures 3 and 4, the green arrow 42A is represented as the first color 70 and the red wall 42C as the second color 72 in the color space chromaticity diagram 60. Since the color space chromaticity diagram 60 is intended for people affected by a protanomaly, the blue bars 42B are not represented in the color space chromaticity diagram 60. That is, the first color 70 and the second color 72 represented in the color space chromaticity diagram 60 are known color combinations that have the potential to cause color confusion in people with color vision deficiencies. The one or more controllers 20 then determine a position of the first color 70 and the second color 72 relative to the color confusion lines 62 and the punctuated point 64 on the color space chromaticity diagram 60 in order to identify a potentially confusing color pair. It is understood that colors located on the same color confusion lines 62 can lead to color confusion in people with color vision deficiencies. In the example shown in Fig. 4, the first color 70 and the second color 72 are located on the same color confusion line 62. In one embodiment, the one or more controllers 20 identify a potentially confusing color pair by calculating a correlation coefficient between the first color 70 and the second color 72, which are mapped on the color space chromaticity diagram 60, and the punctuated point 64.In one embodiment, a correlation coefficient greater than 0.7 indicates that the first color 70 and the second color 72 are a potentially confusing color pair. However, it should be understood that the correlation coefficient can be adjusted based on the sensitivity of the head-up display 10. In response to the determination that the first color 70 and the second color 72 are a potentially confusing color pair, one or more controls 20 calculate a Delta-E value between the first color 70 and the second color 72, as depicted in the color space chromaticity diagram 60. The Delta-E value is a measure of the change in visual perception between the first color 70 and the second color 72, as depicted in the color space chromaticity diagram 60. If the Delta-E value is approximately equal to 2, all individuals (with or without color vision deficiency) are unable to distinguish between the first color 70 and the second color 72. A higher Delta-E value indicates a greater color and luminance shift, and a lower Delta-E value indicates a lesser color and luminance shift. In one embodiment, the controls 20 determine that individuals with color vision deficiency are unable to distinguish between the first color 70 and the second color 72 when they determine that the Delta-E value is less than a Delta-E threshold. In one embodiment, the Delta-E threshold is twenty; however, it is understood that the Delta-E threshold can be adjusted based on sensitivity.In response to the finding that individuals with color vision deficiency are unable to distinguish between the first color 70 and the second color 72, one or more controls 20 adjust the saturation of at least one of the primary colors that are part of the first color 70 or the second color 72, and the luminance of at least one of the first color 70 and the second color 72, to increase the Delta-E value above the Delta-E threshold. For example, if the saturation for the color yellow is adjusted, then at least one of the primary colors (i.e., red and green in this example) is adjusted at the subpixel level. The reason for this is that yellow luminance is created by mixing red and green. In this example, the yellow color lies on a yellow-blue color confusion line, and the yellow color is moved away from this line by increasing the red component at the subpixel level. Referring to Figures 1 and 3, in another embodiment, the one or more controllers 20 also identify a potentially confusing color combination between the multitude of graphic images 42 generated by the head-up display 10 and objects 80 located in the vehicle's surroundings 34. In the example shown in Figure 3, the objects 80 are vegetation such as trees and shrubs, which are green. The one or more controllers 20 receive the uncalibrated color and luminance information captured by the forward-facing camera 24. As mentioned earlier, the one or more controllers 20 convert the uncalibrated color and luminance information from the forward-facing camera 24 into calibrated color and luminance information based on values ​​stored in one or more lookup tables 38. The one or more controllers 20 then compare the calibrated color and luminance information for a particular object 80 located in the environment 34 surrounding the vehicle 14 with the color and luminance information corresponding to the colors of the multiple graphic images 42 generated by the graphic projection module 22, in order to determine a potentially confusing color combination that would be perceived by people with color vision deficiencies. In the example shown in Fig. 3, a potentially confusing color combination exists between the red wall 42C and the objects 80, which are vegetation and are green. In response to determining that a potentially confusing color combination exists between the colors of the multiple graphic images 42 generated by the graphic projection module 22 and the objects 80 located in the environment 34, the one or more controllers 20 form the color coordinates (i.e.,the x and y values) corresponding to the specific object 80, and the color of one of the graphic images 42 on the color space chromaticity diagram 60 as a third color 90 and a fourth color 92, as shown in Fig. 5. In the example shown in Fig. 5, the third color 90 corresponds to the objects 80 located in the environment 34, which are vegetation, and the fourth color 92 corresponds to the red wall 42C. As mentioned above, the one or more controllers 20 can then identify a potentially confusing color pair by calculating a correlation coefficient between the third color 90 and the fourth color 92, which are mapped on the color space chromaticity diagram 60, and the punctual point 64. In one embodiment, a correlation coefficient greater than 0.7 indicates that the third color 90 and the fourth color 92 are a potentially confusing color pair; however, it should be noted that the correlation coefficient can be adjusted based on the sensitivity of the head-up display 10. In response to determining that the third color 90 and the fourth color 92 are a potentially confusing color pair, the one or more controllers 20 calculate a Delta-E value between the third color 90 and the fourth color 92, which are mapped on the color space chromaticity diagram 60.The one or more controllers 20 determine that individuals with color vision deficiency are unable to distinguish between the third color 90 and the fourth color 92 when they determine that the Delta-E value is less than a Delta-E threshold. As mentioned above, in one embodiment the Delta-E threshold is twenty, but the value can be adjusted based on sensitivity. In response to determining that individuals with color vision deficiency are unable to distinguish between the third color 90 and the fourth color 92, the one or more controllers 20 adjust the saturation and luminance of the fourth color 92, which corresponds to the red wall 42C shown in Fig. 3, to increase the Delta-E value to above twenty. Fig. 6 is a process flow diagram illustrating an exemplary process 200 for taking into account the color vision deficiencies of a user of the vehicle 14 based on the ambient light conditions. With general reference to Fig. 1, Fig. 2, Fig. 4, and Fig. 6, the process 200 can begin in decision block 202. In decision block 202, the one or more controllers 20 continue to monitor the image data from the forward-facing camera 24 until they determine, based on the image data, that the object 40 of interest (Fig. 2) is visible through the windshield 12. The process 200 can then proceed to block 204. In block 204, in response to the determination that the object 40 of interest is visible through the windshield 12, the one or more controllers 20 determine one or more graphic images 42 (shown in Fig. 2) to be displayed on the windshield 12 in order to draw the user's attention to the object 40 of interest. The procedure 200 can then proceed to block 206. In block 206, the one or more controllers 20 determine the intensity of the ambient light in the vicinity 34 of the vehicle 14 based on the ambient light signal received by the ambient light sensor 28 (shown in Fig. 1). The process 200 can then proceed to block 208. In block 208, the one or more controllers 20 adjust the saturation level of one or more colors of the one or more graphic images 42 generated by the graphics projection module 22 based on the ambient light present in the environment 34. The process 200 can then proceed to decision block 210. If the one or more controllers 20 in decision block 210 determine that a potentially confusing color combination for persons with color vision deficiencies exists between the two or more colors of the one or more graphic images 42 generated by the graphic projection module 22, or between the colors generated by the graphic projection module 22 and the objects 80 located in the environment 34 surrounding the vehicle 14 (Fig. 3), the procedure 200 can be terminated and proceed to decision block 302 of the procedure 300 shown in Fig. 7. However, if the one or more controllers 20 determine that no potentially confusing color combination for persons with color vision deficiencies exists, the procedure 200 can proceed to block 212. In block 212, the one or more controllers 20 instruct the graphics projection module 22 to generate the one or more graphic images 42 with the adjusted saturation level on the windshield 12 of the vehicle 14. The procedure 200 can then be terminated. Fig. 7 is a process flow diagram illustrating a method 300 for accommodating color vision deficiencies of a user of the vehicle 14 by adjusting the saturation and luminance levels of the colors produced by the graphics projection module 22 to avoid color confusion caused by a user with color vision deficiencies. Referring to Figs. 1, 3-5, and 7, the method 300 begins with decision block 302. If, in decision block 302, the one or more graphic images 42 produced by the graphics projection module 22 contain more than one color, the method proceeds to decision block 304. If the one or more graphic images 42 produced by the graphics projection module 22 do not contain more than one color, the method 300 may proceed to block 318. In decision block 304, the one or more controllers 20 compare the color and luminance information corresponding to the two or more colors of the plurality of graphic images 42 (as shown in Fig. 3) generated by the graphic projection module 22 for a potentially confusing color combination that might occur in people with color vision deficiencies. In response to the determination that a potentially confusing color combination exists between the two or more colors of the plurality of graphic images 42 generated by the graphic projection module 22, the procedure 300 proceeds to block 306. In response to the determination that no potentially confusing color combination exists, the procedure 300 may proceed to block 318. In block 306, the one or more controllers 20 assign the color coordinates (i.e., the x and y values) corresponding to the two or more colors in the color space chromaticity diagram 60 as the first color 70 and second color 72 (Fig. 4). The procedure 300 can then proceed to block 308. In block 308, the one or more controllers 20 calculate the correlation coefficient between the first color 70 and the second color 72, which are mapped on the color space chromaticity diagram 60 and the punctual point 64 (Fig. 4). The procedure 300 can then proceed to decision block 310. In decision block 310, the one or more controllers 20 compare the correlation coefficient with a threshold value. In one embodiment, the threshold value is 0.7, where a value greater than the threshold indicates that the first color 70 and the second color 72 are a potentially confusing color pair. In response to determining that the correlation coefficient is greater than the threshold value, the procedure 300 proceeds to block 312. If the correlation coefficient is less than the threshold value, the procedure 300 proceeds to block 318. In block 312, in response to the determination that the first color 70 and the second color 72 constitute a potentially confusing color pair, the one or more controllers 20 calculate the Delta-E value between the first color 70 and the second color 72, which are represented in the color space chromaticity diagram 60. The procedure 300 can then proceed to decision block 314. In decision block 314, the Delta-E value is compared to a Delta-E threshold. In response to the determination that the Delta-E value is less than the Delta-E threshold, one or more controls 20 determine that individuals with color vision deficiency are unable to distinguish between the first color 70 and the second color 72, and procedure 300 proceeds to block 316. Otherwise, procedure 300 proceeds to block 318. In Block 316, in response to the finding that individuals with color vision deficiency are unable to distinguish between the first color 70 and the second color 72, one or more controls 20 adjust the saturation and luminance levels of at least one of the first color 70 and the second color 72 to increase the Delta-E value above the Delta-E threshold. Procedure 300 can then proceed to Block 318. In block 318, the one or more controllers 20 receive the uncalibrated color and luminance information acquired by the forward-facing camera 24. The process 300 can then proceed to block 320. In block 320, the one or more controllers 20 convert the uncalibrated color and luminance information from the forward-facing camera 24 into calibrated color and luminance information based on values ​​stored in one or more lookup tables 38 (Fig. 1). The process 300 can then proceed to block 322. In block 322, the one or more controllers 20 then compare the calibrated color and luminance information corresponding to a specific object 80 in the environment 34 surrounding the vehicle 14 with the color and luminance information corresponding to the two or more colors of the multitude of graphic images 42 generated by the graphic projection module 22, in order to determine a potentially confusing color combination that might occur in people with color vision deficiencies. The procedure 300 can then proceed to decision block 324. In decision block 324, the procedure can proceed to block 326 if it is determined that a potentially confusing color combination exists between the two or more colors of the multitude of graphic images 42 generated by the graphics projection module 22 and the objects 80 located in the environment 34. Otherwise, the procedure proceeds to block 338. In block 326, the one or more controllers 20 assign the calibrated color coordinates (i.e., the x and y values) corresponding to the specific object 80 and the color coordinates of one of the two or more colors of the multiple graphic images 42 on the color space chromaticity diagram 60 as a third color 90 and a fourth color 92, as shown in Fig. 5. The procedure 300 can then proceed to block 328. In block 328, the one or more controllers 20 calculate a correlation coefficient between the third color 90 and the fourth color 92, which are mapped on the color space chromaticity diagram 60, and the punctual point 64. The procedure 300 can then proceed to decision block 330. In decision block 330, the one or more controllers 20 determine whether the correlation coefficient is greater than a threshold. In one embodiment, the threshold is 0.7, indicating that the third color 90 and the fourth color 92 are a potentially confusing color pair. In response to determining that the correlation coefficient is greater than the threshold, the procedure 300 proceeds to block 332. If the correlation coefficient is less than the threshold, the procedure 300 proceeds to block 338. In block 332, in response to the determination that the third color 90 and the fourth color 92 are a potentially confusing color pair, the one or more controllers 20 calculate the Delta-E value between the third color 90 and the fourth color 92, which are mapped in the color space chromaticity diagram 60. The procedure 300 can then proceed to decision block 334. If the Delta-E value in decision block 334 is greater than the Delta-E threshold, then individuals with color vision deficiency are unable to distinguish between the third color 90 and the fourth color 92, and procedure 300 continues with block 336. Otherwise, procedure 300 continues with block 338. In block 336, in response to the finding that individuals with color vision deficiency are unable to distinguish between the third color 90 and the fourth color 92, the one or more controllers 20 adjust the saturation and luminance of the fourth color 92, which corresponds to the red wall 42C in the graphic shown in Fig. 3, to increase the Delta-E value to over twenty. The one or more controllers 20 then instruct the graphic projection module 22 to generate the one or more graphic images 42 with the increased Delta-E values ​​on the windshield 12. The process 300 can then be terminated. In block 338, the one or more controllers 20 determine that there is no potentially confusing color combination between the colors of the multitude of graphic images 42 generated by the graphics projection module 22 and the objects 80 located in the environment 34, and therefore no further adjustment of the saturation and luminance levels is required. The one or more controllers 20 then instruct the graphics projection module 22 to generate the one or more graphic images 42 with increased Delta-E values ​​on the windshield 12. The procedure 300 can then be terminated. With regard to the figures in question, the head-up display offers various technical effects and advantages. In particular, it is recognized that a person's color vision deficiencies can be pronounced in low ambient light, and the head-up display takes these deficiencies into account by adjusting the saturation of the colors it generates based on the ambient light conditions. Furthermore, the head-up display also identifies potentially confusing color combinations that may exist between the graphics it generates or between objects in the surroundings and the graphics it displays. The head-up display adjusts the saturation and luminance levels accordingly to eliminate these potentially confusing color combinations, thus also accommodating the user's color vision deficiencies.

Claims

Head-up display (10) for displaying graphics on a windshield (12) of a vehicle (14), the head-up display (10) comprising: a graphics projection module (22) for generating one or more graphic images (42) on the windshield (12) of the vehicle (14); a forward-facing camera (24) that collects image data representative of a view of the vehicle's (14's) surroundings (34) visible through the windshield (12); an ambient light sensor (28) that detects a degree of ambient light in the area (34) surrounding the vehicle (14);and one or more controllers (20) in electronic communication with the graphic projection module (22), with the forward-facing camera (24) and with the ambient light sensor (28), wherein the one or more controllers (20) are configured to execute instructions to: monitor the image data from the forward-facing camera (24) until determining, based on the image data, that an object (40) of interest is visible through the windshield (12); in response to determining that the object (40) of interest is visible through the windshield (12), determine one or more graphic images (42) to be displayed on the windshield (12) to draw a user's attention to the object (40) of interest; determine the degree of ambient light in the vicinity (34) of the vehicle (14) based on an ambient light signal received from the ambient light sensor (28);and to adjust the saturation level of one or more colors of the one or more graphic images (42) generated by the graphic projection module (22) on the basis of the ambient light present in the environment (34); wherein adjusting the saturation level of the one or more colors of the one or more graphic images (42) includes increasing the saturation level when the level of ambient light decreases and decreasing the saturation level when the level of ambient light increases. Head-Up-Display (10) according to claim 1, wherein the one or more controllers (20) are configured to execute instructions to: instruct the graphics projection module (22) to generate the one or more graphic images (42) with an adapted saturation level on the windshield (12). Head-Up-Display (10) according to claim 1, wherein the ambient light sensor (28) is configured to detect three discrete levels of ambient light, including a high level of light representing full daylight conditions, a medium level of light representing overcast conditions, and a low level of light representing twilight conditions. Head-Up-Display (10) according to claim 3, wherein the high luminous intensity corresponds to a saturation level of sixty percent, the medium luminous intensity corresponds to a saturation level of seventy percent and the low luminous intensity corresponds to a saturation level of eighty percent. Head-Up-Display (10) according to claim 4, wherein the saturation levels are increased by five percent for persons who are at least forty years old. Head-Up-Display (10) according to claim 1, wherein the one or more graphic images (42) generated by the graphics projection module (22) comprise two or more colors. Head-Up Display (10) according to claim 6, wherein the one or more controllers (20) are configured to execute instructions to: compare color and luminance information corresponding to the two or more colors of the one or more graphic images (42) generated by the graphics projection module (22) against a potentially confusing color combination; and, in response to determining that the potentially confusing color combination exists, map color coordinates corresponding to the two or more colors in a color space chromaticity diagram (60) as a first color (70) and a second color (72). Head-Up Display (10) according to claim 7, wherein the one or more controllers (20) are configured to execute instructions to: calculate a correlation coefficient between the first color (70) and the second color (72) and a punctual point that is part of the color space chromaticity diagram (60); and compare the correlation coefficient with a threshold, wherein values ​​greater than the threshold indicate that the first color (70) and the second color (72) are a potentially confusing color pair. Head-Up Display (10) according to claim 8, wherein the one or more controllers (20) are configured to execute instructions to: calculate a Delta-E value between the first color (70) and the second color (72) in response to determining that the correlation coefficient is greater than the threshold; and compare the Delta-E value with a Delta-E threshold.

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