Ghost Measurement Method for Head-Up Display

Abstract

The embodiment of the present application relates to the field of display technology and provides a method for measuring ghost images of a head-up display. The method includes obtaining a virtual image screen of the head-up display when the projection distance is D, where the virtual image screen includes a plurality of virtual images arranged in an array and a plurality of ghost images arranged in an array, and each virtual image has a corresponding ghost image; calculating the distance S between each virtual image and its corresponding ghost image, and calculating the percentage of the brightness A2 of each virtual image and the brightness A1 of its corresponding ghost image; and determining whether all the virtual images and their corresponding ghost images in the virtual image screen satisfy: A2 / A1×100% < 50% and S ≤ 2×D×tan(MAR / 2), where MAR is the minimum resolvable angle; if all are satisfied, it is determined that the ghost images of the head-up display meet the condition that they are indistinguishable to the human eye; otherwise, it is determined that the ghost images of the head-up display do not meet the condition that they are indistinguishable to the human eye.

Description

Technical Field

[0001] This application relates to the field of display technology, and more particularly, to a method for measuring virtual images of a head-up display. Background Art

[0002] Currently, the front-loaded head-up display (HUD) is a virtual image display system for driving information installed in a vehicle. Due to the requirements of the HUD for the screen and projection distance, corresponding detection requirements have emerged. Currently, the measurement methods mainly refer to those of flat panel displays, but there is no industry-recognized measurement device for measuring image quality. Therefore, during the development of HUD products, the corresponding image quality detection has become a top priority.

[0003] Since the windshield of a vehicle is laminated glass, the light path of the image will be reflected simultaneously on the two opposite surfaces of the laminated double glass when passing through the double glass. When there is a deviation in the wedge angle of the windshield, or when the surface shapes of the inner and outer surfaces of the windshield deviate too much from the ideal due to the manufacturing process of the windshield, it will cause the first reflected light and the second reflected light to enter the observer's eyes after being reflected by the inner and outer glasses, and the light traveling routes cannot perfectly coincide, resulting in the observer feeling that the image has ghosting. The measurement and determination methods of ghosting in the field of virtual image projection have always been a problem to be solved urgently. Summary of the Invention

[0004] This application provides a method for measuring ghosting of a head-up display on the one hand. The method for measuring ghosting of the head-up display includes:

[0005] Obtain a virtual image screen of the head-up display when the projection distance is D. The virtual image screen includes a plurality of virtual images arranged in an array and a plurality of ghosts arranged in an array. Each virtual image has a corresponding ghost;

[0006] Calculate the distance S between each virtual image and its corresponding ghost, and calculate the percentage of the brightness A2 of each virtual image and the brightness A1 of its corresponding ghost; and

[0007] Determine whether all the virtual images and their corresponding ghosts in the virtual image screen satisfy: A2 / A1×100% < 50% and S ≤ 2×D×tan(MAR / 2), where MAR is the minimum resolvable angle; if all are satisfied, it is determined that the ghosting of the head-up display meets the condition that it is indistinguishable to the human eye; otherwise, it is determined that the ghosting of the head-up display does not meet the condition that it is indistinguishable to the human eye.

[0008] The above-mentioned ghosting measurement method for the head-up display determines the ghosting degree of each virtual image by detecting whether the distances between all virtual images and their corresponding ghosts in the virtual image screen meet a specific value and whether the brightness ratios between all virtual images and their corresponding ghosts meet a specific value. Among them, if all virtual images and their ghosts meet the above two formulas, it indicates that the detection points with the most serious ghosting degree all meet the above two formulas at the same time. Therefore, it can be determined that the ghosting of the head-up display meets the condition that it is indistinguishable to the human eye, that is, the optical characteristics of the head-up display in terms of ghosting measurement meet the quality requirements. Otherwise, it means that the optical quality of the head-up display in terms of ghosting measurement does not meet the requirements. In this way, the problem of measuring the ghosting amount in the projected virtual image of the front-loaded head-up display is solved. Description of the Drawings

[0009] Figure 1 It is a schematic diagram of the light paths of the virtual image and the ghosting perceived by the observer when the windshield of the vehicle does not have a wedge angle.

[0010] Figure 2 It is a schematic diagram of the light paths of the virtual image and the ghosting perceived by the observer when the windshield of the vehicle has a wedge angle.

[0011] Figure 3 and Figure 4 They are respectively schematic diagrams of the structures of the head-up display and the windshield at different viewing angles after being placed on the measuring device.

[0012] Figure 5 It is a schematic diagram of the virtual image screen in the ghosting measurement method of the head-up display according to an embodiment of the present application.

[0013] Figure 6 It is a schematic diagram of the virtual image screen in the ghosting measurement method of the head-up display according to another embodiment of the present application.

[0014] Figure 7 It is a schematic diagram of the virtual image screen in the ghosting measurement method of the head-up display according to still another embodiment of the present application.

[0015] Main Element Symbol Description:

[0016] Windshields 10, 10a, 10b

[0017] Inner layer glass 11

[0018] Adhesive layer 12

[0019] Outer layer glass 13

[0020] Measuring device 100

[0021] Head-up display 20

[0022] Moving component 30

[0023] Wedge angle α

[0024] Eye E

[0025] First reflected light L1

[0026] Second reflected light L2

[0027] Virtual image screen P

[0028] First direction D1

[0029] Second direction D2 Detailed implementation manner

[0030] As Figure 1 shown, the windshield 10a of the vehicle is laminated glass. The windshield 10a includes an inner layer of glass 11, an outer layer of glass 13, and an adhesive layer 12 sandwiched between the inner layer of glass 11 and the outer layer of glass 13 to bond the two. In the windshield 10a, the opposite surfaces of the inner layer of glass 11 and the outer layer of glass 13 are substantially parallel. There is no wedge angle between the inner layer of glass 11 and the outer layer of glass 13. When the light of the image from a head-up display (not shown in the figure) passes through the windshield 10a, it will be reflected simultaneously on the surface of the inner layer of glass 11 and the surface of the outer layer of glass 13. When the manufacturing process of the windshield 10a causes the surface profiles of the inner and outer surfaces of the windshield to deviate too much from the ideal values, when the first reflected light L1 and the second reflected light L2 enter the observer's eye E after being reflected by the inner and outer glasses, the light traveling routes cannot perfectly coincide, resulting in the observer feeling that the image has a ghost image. Similarly, as Figure 2 shown, the windshield 10b of the vehicle is laminated glass, and there is a wedge angle α between the inner layer of glass 11 and the outer layer of glass 13. When there is a deviation in the wedge angle α of the windshield 10b, or when the surface profiles of the inner and outer surfaces of the windshield 10b deviate too much from the ideal values, when the first reflected light L1 and the second reflected light L2 enter the observer's eye E after being reflected by the inner and outer glasses, the light traveling routes also cannot perfectly coincide, resulting in the observer feeling that the image has a ghost image. Therefore, in the application field of virtual image projection, the measurement and determination method of ghost images has always been an urgent problem to be solved.

[0031] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0032] The embodiments of the present application provide a method for measuring ghost images of a head-up display, which includes the following steps.

[0033] Step S1: Obtain the virtual image screen of the head-up display at a projection distance of D. The virtual image screen includes a plurality of virtual images arranged in an array and a plurality of ghost images arranged in an array. Each virtual image has a corresponding ghost image.

[0034] Specifically, in step S1, as Figure 3 and Figure 4 shown, place the head-up display 20 to be measured and the windshield 10 on the measuring device 100. The measuring device 100 includes a camera, an imaging colorimeter, and a control and analysis device (such as a computer) electrically connected to the camera and the imaging colorimeter. The camera is, for example, one of a CCD (Charge Coupled Device) camera and a CMOS (Complementary Metal Oxide Semiconductor) camera. Among them, the head-up display 20 can be lit according to the instructions of the control and analysis device and project a test screen onto the windshield 10. The measuring device 100, for example, includes a moving component 30 to adjust the relative positions of the windshield 10 and the camera so that the projection distance of the head-up display is D. Then, obtain the virtual image screen of the head-up display at a projection distance of D through the camera. Among them, in step S1, the relative positions and relative tilting angles of the head-up display and the windshield can be adjusted according to the actual structure of the vehicle model to simulate the actual use environment of the head-up display and conduct tests on the head-up display in this environment.

[0035] Specifically, as Figure 5 shown, the virtual image screen P includes a plurality of virtual images V11 to VMN arranged in an array and a plurality of ghost images G11 to GMN arranged in an array. The patterns of each virtual image are the same and are all dots. Each virtual image has a corresponding ghost image. The ghost image of each virtual image is located on the right side of it along the first direction D1. The pattern of each ghost image is also a dot. The plurality of virtual images are arranged in multiple columns along the first direction D1 and in multiple rows along the second direction D2. The second direction D2 is perpendicular to the first direction D1. It is defined that along the first direction D1, the multiple virtual images in the first row are V11, V12,..., V1N in sequence, the multiple virtual images in the second row are V21, V22,..., V2N in sequence, and so on. The multiple virtual images in the Mth row are VM1, VM2,..., VMN in sequence; it is defined that along the first direction D1, the multiple ghost images in the first row are G11, G12,..., G1N in sequence, the multiple ghost images in the second row are G21, G22,..., G2N in sequence, and so on. The multiple ghost images in the Mth row are GM1, GM2,..., GMN in sequence. G11 is the ghost image of V11, G12 is the ghost image of V12, and so on. GMN is the ghost image of VMN. M is an integer greater than or equal to 1, and N is an integer greater than or equal to 1. M can be the same as N or different.

[0036] In some embodiments, multiple virtual images are arranged in an odd number of rows and / or an odd number of columns. That is, M is odd and / or N is odd. The center of the array formed by the multiple virtual images coincides with the center of the virtual image screen P. In this way, it is beneficial to determine the center point to align the center of the image with the center of the measuring instrument (such as an imaging colorimeter).

[0037] In some embodiments, step S1 further includes obtaining the brightness of each virtual image and its corresponding ghost image through an imaging colorimeter.

[0038] Step S2: Calculate the distance S between each virtual image and its corresponding ghost image, and calculate the percentage of the brightness A2 of each virtual image and the brightness A1 of its corresponding ghost image.

[0039] Specifically, in step S2, taking the center of the virtual image screen P as the coordinate origin, obtain the coordinates of each virtual image. By analyzing the virtual image screen P, obtain the coordinates of the ghost image corresponding to each virtual image. Then, by comparing the coordinates of each virtual image and the coordinates of its corresponding ghost image, obtain the distance S between each virtual image and its corresponding ghost image. When there are M×N virtual images in the virtual image screen P, analyze each virtual image and its ghost image to obtain the distances S between M×N virtual images and their corresponding ghost images.

[0040] Wherein, the distance S between each virtual image and its corresponding ghost image is the distance from the center point of the virtual image to the center point of the corresponding ghost image. For example, Figure 5 in the illustrated embodiment, both the virtual image and its ghost image are dots, and the distance S is the distance between the center of the circle of the virtual image and the center of the circle of its ghost image. In other embodiments, the pattern of each virtual image in the virtual image screen P is not limited to a dot. For example, in Figure 6 the illustrated embodiment, the pattern of the virtual image is a rectangle, then the distance S is the distance between the center of the rectangle of the virtual image and the center of its ghost image. Another example, Figure 7 in the illustrated embodiment, the pattern of the virtual image is a crosshair, and the distance S is the distance between the center of the crosshair of the virtual image and the center of its ghost image. It can be understood that when the pattern of the virtual image is a regular and symmetric figure, it is beneficial to measure the distance between the virtual image and its ghost image. In other embodiments, the figure of the virtual image is not limited to Figures 5 to 7 shown.

[0041] Step S3: Determine whether all the virtual images and their corresponding ghost images in the virtual image screen satisfy: A2 / A1×100% < 50% (hereinafter referred to as formula one) and S ≤ 2×D×tan(MAR / 2) (hereinafter referred to as formula two), where MAR is the minimum resolvable angle; if all are satisfied, it is determined that the ghost image of the head-up display meets the condition that it is indistinguishable to the human eye; otherwise, it is determined that the ghost image of the head-up display does not meet the condition that it is indistinguishable to the human eye.

[0042] In step S2 and step S3, analysis can be performed by controlling the algorithm in the analysis device.

[0043] Specifically, there are two reasons why a ghost image can be perceived: one is that the deviation distance between the center position of the ghost image and the center of the main image exceeds 2×D×tan(MAR / 2); the other is that the image brightness of the ghost image and the image brightness of the main image have a difference so small that the image of the ghost image can be perceived, that is, A2 / A1×100% is greater than or equal to 50%. Therefore, if the ghost image is not to cause a visual impact, both formula one and formula two need to be satisfied simultaneously.

[0044] Among them, for humans, the normal visual acuity in vision is the resolution ability of one arc minute. That is, MAR = 1 arcmin = 1 / 60°. If the distance between the center of the projected test point and the center of the point of its ghost image and the apex angle θ of the isosceles triangle formed by the projection distance of the head-up display is not greater than the visual acuity of the human eye, then the ghost image meets at least one condition of not being perceivable by the human eye (or rather, the ghost image meets at least one condition of being indistinguishable by the human eye).

[0045] According to Figure 5 the geometric relationship in, θ = 2×tan -1 (S / 2D); if θ ≤ MAR, then the ghost image meets at least one condition of not being perceivable by the human eye. That is, S ≤ 2×D×tan(MAR / 2) = 2×D×tan(0.017° / 2).

[0046] The method for measuring the ghost image of the head-up display according to the embodiment of the present application determines the degree of ghosting of each virtual image by detecting whether the distances between all virtual images in the virtual image screen P and their corresponding ghost images meet specific values and whether the brightness ratios between all virtual images and their corresponding ghost images meet specific values. Among them, if all virtual images and their ghost images meet the above two formulas, it indicates that the detection points with the most serious ghosting degree all meet the above two formulas at the same time. Therefore, it can be determined that the ghost image of the head-up display meets the condition of being indistinguishable by the human eye, that is, the optical characteristics of the head-up display in terms of ghost image measurement meet the quality requirements. Otherwise, it means that the optical quality of the head-up display in terms of ghost image measurement does not meet the requirements. In this way, the problem of measuring the ghost image in the projected virtual image of the front-loading head-up display is solved.

[0047] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for measuring ghost images of a head-up display, characterized in that, Including: Obtain the virtual image screen of the head-up display when the projection distance is D. The virtual image screen includes a plurality of virtual images arranged in an array and a plurality of ghost images arranged in an array. Each of the virtual images has a corresponding ghost image; Calculate the distance S between each virtual image and its corresponding ghost image, and calculate the percentage of the brightness A2 of each virtual image and the brightness A1 of its corresponding ghost image; And Determine whether, in the virtual image screen, all of the virtual images and their corresponding ghost images satisfy: A2 / A1×100% < 50% and S ≤ 2×D×tan(MAR / 2), where MAR is the minimum resolvable angle; if all are satisfied, it is determined that the ghost images of the head-up display meet the condition of being indistinguishable by the human eye; otherwise, it is determined that the ghost images of the head-up display do not meet the condition of being indistinguishable by the human eye.

2. The ghosting measurement method of the head-up display according to claim 1, wherein, The center of the array formed by the plurality of virtual images coincides with the center of the virtual image screen.

3. The ghosting measurement method of the head-up display according to claim 2, characterized in that, The step of calculating the distance S between each virtual image and its corresponding ghost image includes: Taking the center of the virtual image screen as the coordinate origin, obtain the coordinates of each virtual image; Through the analysis of the virtual image screen, obtain the coordinates of the ghost image corresponding to each virtual image; and By comparing the coordinates of each virtual image and the coordinates of its corresponding ghost image, obtain the distance S between each virtual image and its corresponding ghost image.

4. The ghosting measurement method of the head-up display according to claim 1, characterized in that, The plurality of virtual images are arranged in an odd number of rows.

5. The ghosting measurement method of the head-up display according to claim 1, characterized in that, The plurality of virtual images are arranged in an odd number of columns.

6. The method for measuring ghost images of a head-up display according to claim 1, wherein, The pattern of each virtual image in the virtual image screen is the same, and the pattern of the virtual image is one of a dot, a rectangle, and a crosshair.

7. The method for measuring ghosting of a head-up display according to any one of claims 1 to 6, characterized in that, The MAR is 1 / 60°.

8. The ghosting measurement method of the head-up display according to any one of claims 1 to 6, characterized in that Obtaining the virtual image screen includes setting the head-up display and a windshield on a measuring device, and causing the head-up display to project the virtual image screen onto the windshield.

9. The method for measuring ghosting of a head-up display according to claim 8, wherein, The measuring device includes a camera and an imaging colorimeter; obtaining the virtual image screen includes using the camera to collect the virtual image screen and using the imaging colorimeter to obtain the brightness of the ghost image.

10. The method for measuring ghost images of the head-up display according to claim 9, characterized in that, The method for measuring the ghost images of the head-up display further includes adjusting the relative positions of the windshield and the camera so that the projection distance of the head-up display is D.

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