Virtual image measurement method and measuring device

Abstract

The present application relates to the field of projection display technology, and in particular to a virtual image measurement method and measuring equipment. The present application performs alignment adjustment between a first alignment symbol projected by a HUD device and a second alignment symbol marked by a calibration plate, and specifically adjusts the position, posture and other spatial states of the calibration plate so that the first alignment symbol and the second alignment symbol are located at the same position in the virtual image space, thereby indirectly measuring the corresponding projection parameters of the HUD device based on the physical operability of the calibration plate. The present application does not need to rely on three-coordinate calibration data for the parameter measurement of the projected virtual image, and the measurement method is simple and the hardware cost is low, and portable and accurate measurement can be achieved.

Description

Technical Field

[0001] The present application relates to the field of projection display technology, and in particular to a virtual image measurement method and measurement equipment. Background Art

[0002] HUD (Head Up Display) is a new way to realize in-vehicle display by using reflection on the vehicle windshield. Specifically, the display light is emitted by the optical machine of the HUD display device, and is projected on the windshield through the corresponding optical lens to produce a corresponding virtual image, which forms an enhanced display effect with the real world outside the windshield. The virtual image projected by the HUD display device includes multiple projection parameters such as virtual image distance (VID) and field of view (FOV). They need to be accurately measured and used as the basis for projection control. However, the current measurement methods for these projection parameters are relatively complicated, with high requirements on the conditions of the measurement site, and the measurement cost is not low. Summary of the invention

[0003] The purpose of the present application is to provide a virtual image measurement method and a measuring device, which solve the technical problems in the prior art that the virtual image parameters of the HUD projection cannot be accurately measured, the measurement environment is complex, and the measurement cost is also high.

[0004] In order to solve the above technical problems, this application adopts the following technical solutions.

[0005] In a first aspect, the present application provides a virtual image measurement method, comprising:

[0006] Controlling the HUD device to be projected onto the transparent surface so as to have a first alignment symbol in a virtual image space in front of the transparent surface;

[0007] A calibration plate is arranged in the virtual image space, wherein a second alignment mark having the same shape as the first alignment mark is arranged on a side of the calibration plate facing the transparent surface, and the spatial state of the calibration plate is adjusted so that at least a part of the second alignment mark overlaps with the first alignment mark;

[0008] The projection parameters of the HUD device are determined according to the spatial state of the calibration plate that is finally adjusted.

[0009] According to the above description, an optional implementation method can reproduce the position of the first alignment symbol projected by the HUD device in the virtual image space through the second alignment symbol on the calibration plate, thereby measuring the projection parameters corresponding to the virtual image surface where the first alignment symbol is located through the calibration plate where the second alignment symbol is located, thereby reducing the difficulty of measurement and the requirements for measuring tools.

[0010] In an optional implementation of the first aspect, the first alignment symbol is a cross-shaped symbol projected at the center of the virtual image surface, and the second alignment symbol is a cross-shaped symbol set at the center of the calibration plate.

[0011] In an optional implementation manner of the first aspect, the first alignment symbol is a cross-shaped symbol projected at the center of the virtual image plane, including:

[0012] The first alignment symbol is displayed correspondingly at the center position of the image source display surface of the HUD device before projection.

[0013] According to the above description, the optional implementation method ensures that the first alignment mark and the second alignment mark are within the normal range of the camera, and the corresponding alignment adjustment is also easier to operate.

[0014] In an optional implementation manner of the first aspect, determining the projection parameters of the HUD device according to the spatial state finally adjusted by the calibration plate includes:

[0015] The projection virtual image distance of the HUD device is determined according to the final adjusted position of the calibration plate.

[0016] According to the above description, the optional implementation method supports determining the distance from the projected virtual image to the human eye in the eye box range according to the location of the calibration plate. The distance measurement is easier to implement and is based on a physical object, so the measurement is more accurate.

[0017] In an optional implementation of the first aspect, determining the projection parameters of the HUD device according to the spatial state finally adjusted by the calibration plate includes:

[0018] Determining the projection lower viewing angle or upper viewing angle of the HUD device according to the vertical flip angle finally adjusted by the calibration plate; and / or

[0019] The projection left viewing angle or right viewing angle of the HUD device is determined according to the horizontal flip angle finally adjusted by the calibration plate.

[0020] According to the above description, an optional implementation can use a calibration plate to reproduce the angle of the entire virtual image plane of the projection, thereby determining the lower viewing angle and the like in combination with the relative position relationship between the calibration plate and the human eye, thereby simplifying the angle measurement.

[0021] In an optional implementation manner of the first aspect, adjusting the spatial state of the calibration plate so that at least a portion of the second aligner overlaps with the first aligner includes:

[0022] The first alignment mark and the second alignment mark are clearly photographed simultaneously by a camera arranged in the eye box range of the HUD device.

[0023] In an optional implementation of the first aspect, the camera is located at a central viewpoint within an eye box range of the HUD device to achieve shooting.

[0024] In an optional implementation of the first aspect, the first aligner and the second aligner are clearly photographed simultaneously by a camera disposed in an eye box range of the HUD device, including:

[0025] The contrast between the first alignment symbol and the second alignment symbol photographed by the camera is greater than a first threshold.

[0026] In an optional implementation of the first aspect, the aperture value of the camera is less than a second threshold.

[0027] According to the above description, an optional implementation method utilizes the depth of field principle of the camera so that the first alignment symbol and the second alignment symbol at the same spatial position appear to have consistent clarity when photographed by the camera, thereby assisting in the judgment of the spatial alignment between the first alignment symbol and the second alignment symbol. The alignment operation can be more accurate based on the automatic judgment of the controller.

[0028] In an optional implementation of the first aspect, the first aligner and the second aligner are clearly photographed simultaneously by a camera disposed in an eye box range of the HUD device, including:

[0029] The camera performs phase focusing when photographing the first aligner and the second aligner.

[0030] According to the above description, an optional implementation method uses the focusing principle under phase difference detection to find the spatial state of the calibration plate that meets the focusing requirements, so that the first alignment symbol and the second alignment symbol are accurately aligned and overlapped, and the adaptability is stronger.

[0031] In an optional implementation manner of the first aspect, adjusting the spatial state of the calibration plate so that at least a portion of the second aligner overlaps with the first aligner includes:

[0032] The first aligner and the second aligner are photographed by a camera disposed in an eye box range of the HUD device, wherein the eye box range includes a first viewpoint position and a second viewpoint position;

[0033] The camera takes photos at least at a first viewpoint and a second viewpoint, respectively, and the overlap distance between the first aligner and the second aligner taken at the first viewpoint and the second viewpoint is smaller than a third threshold.

[0034] According to the above description, an optional implementation can determine whether the first aligner and the second aligner completely overlap in spatial position based on the principle of dynamic parallax, so that the first aligner and the second aligner satisfy a smaller parallax change, that is, they are at the same depth, and the judgment is simpler and more direct.

[0035] In an optional implementation of the first aspect, determining the projected virtual image distance of the HUD device according to the final adjusted position of the calibration plate includes:

[0036] Determining a camera position for photographing the first alignment symbol and the second alignment symbol;

[0037] The virtual image distance is the distance between the calibration plate and the camera.

[0038] According to the above description, the optional implementation mode supports automatically determining the virtual image distance while the camera determines the overlap between the first alignment mark and the second alignment mark, thereby improving the efficiency of measurement.

[0039] In an optional implementation of the first aspect, controlling the HUD device to be projected onto a transparent surface comprises:

[0040] The upper edge and lower edge in the vertical direction and the left edge and right edge in the horizontal direction are displayed on the projected virtual image surface;

[0041] The calibration plate includes a vertical direction measuring tool matched with the virtual image surface, and used for measuring a first distance between the upper edge and the lower edge displayed by the virtual image surface;

[0042] The calibration plate includes a horizontal direction measuring tool matched with the virtual image surface, and used for measuring a second distance between the left edge and the right edge displayed by the virtual image surface;

[0043] Determining the projection parameters of the HUD device according to the spatial state finally adjusted by the calibration plate includes:

[0044] The projection field of view of the HUD device is determined in combination with the first distance and the second distance.

[0045] In an optional implementation of the first aspect, determining the projection field of view angle of the HUD device in combination with the first distance and the second distance includes:

[0046] The vertical field of view angle is calculated according to the following formula:

[0047] α=2arctan(H / (2*VID)),

[0048] Wherein, α is the field of view angle in the vertical direction, VID is the projection virtual image distance of the HUD device, and H is the first distance.

[0049] In an optional implementation of the first aspect, determining the projection field of view angle of the HUD device in combination with the first distance and the second distance includes:

[0050] The horizontal field of view angle is calculated according to the following formula:

[0051] β=2arctan(L / (2*VID)),

[0052] Wherein, β is the field of view angle in the horizontal direction, VID is the projection virtual image distance of the HUD device, and L is the second distance.

[0053] According to the above description, the optional implementation supports automatic calculation of the projection field of view angle of the HUD device, thereby improving the convenience of measurement.

[0054] In an optional implementation of the first aspect, displaying the upper edge and the lower edge in the vertical direction and the left edge and the right edge in the horizontal direction on the projected virtual image plane includes:

[0055] A position symbol marking the edge of a range is displayed on the image source display surface of the HUD device.

[0056] According to the above description, an optional implementation can clearly display the upper edge, lower edge, left edge and right edge on the projected virtual image surface as clear reference objects for aligning the measuring tool, making the measurement of the first distance and the second distance more accurate.

[0057] In a second aspect, the present application provides a measuring device, comprising:

[0058] A HUD device having a transparent surface for projection, wherein the transparent surface is configured to receive reflection of the display light to form a first alignment symbol to be measured in a virtual image space in front of the transparent surface;

[0059] A calibration plate cooperates with the HUD device, the calibration plate supports adjusting the spatial state in the virtual image space, and a second alignment mark aligned with the first alignment mark is arranged on the side of the calibration plate facing the transparent surface, and the first alignment mark and the second alignment mark have the same shape.

[0060] In an optional implementation of the second aspect, the HUD device is integrated with the calibration board.

[0061] According to the above description, an optional implementation method can visualize the position of the virtual image projected by the HUD device through a calibration plate, so that the projection parameters can be measured through a physical measuring tool. The measurement method is more convenient and the cost based on the test tool is lower.

[0062] In an optional implementation of the second aspect, a vertical direction measuring tool and a horizontal direction measuring tool are further provided on a surface of the calibration plate facing the transparent surface;

[0063] The vertical direction measuring tool is provided with a first positioning rod and a second positioning rod movable in the vertical direction, the first positioning rod is used to align with the upper edge of the virtual image surface displayed by the HUD device projection, and the second positioning rod is used to align with the lower edge of the virtual image surface displayed;

[0064] The horizontal direction measuring tool is provided with a third positioning rod and a fourth positioning rod which move in the horizontal direction, the third positioning rod is used to align with the left edge of the virtual image surface display, and the fourth positioning rod is used to align with the right edge of the virtual image surface display.

[0065] In an optional implementation of the second aspect, a distance measuring sensor is disposed between the first positioning rod and the second positioning rod, and a distance measuring sensor is disposed between the third positioning rod and the fourth positioning rod.

[0066] In an optional implementation of the second aspect, the first positioning rod and the second positioning rod are the same positioning rod that is reused, and the third positioning rod and the fourth positioning rod are the same positioning rod that is reused.

[0067] According to the above description, the optional implementation can support automatic measurement of the first distance to the virtual image surface in the vertical direction (the distance between the upper edge and the lower edge) and the second distance in the horizontal direction (the distance between the left edge and the right edge). The structure of the test tool is simple and will not result in a large volume and cost.

[0068] In an optional implementation of the second aspect, the calibration plate supports adjusting the spatial state in the virtual image space, including:

[0069] The calibration plate is provided with a first adjustment structure for driving the calibration plate to realize vertical flipping, a second adjustment structure for driving the calibration plate to realize horizontal flipping, and a guide rail for driving the calibration plate to move between the calibration plate and the transparent surface.

[0070] According to the above description, the optional implementation method supports the adjustment of the spatial state of the calibration plate in any direction, ensuring that the second alignment mark on the calibration plate can be completely aligned with the first alignment mark corresponding to the projected virtual image in space.

[0071] In an optional implementation of the second aspect, the first adjustment structure is provided with an angle sensor to measure a vertical flip angle of the calibration plate, and the second adjustment structure is provided with an angle sensor to measure a horizontal flip angle of the calibration plate.

[0072] According to the above description, the optional implementation supports automatically acquiring the rotation angle of the calibration plate after adjustment, thereby facilitating the calculation of the bottom viewing angle and left viewing angle of the HUD device projection.

[0073] In an optional implementation of the second aspect, the guide rail includes a first guide rail moving in a vertical direction, a second guide rail moving in a horizontal direction, and a third guide rail moving in a depth direction.

[0074] According to the above description, the optional implementation supports movement of the calibration plate in any direction to meet the need of aligning the second aligner toward the first aligner.

[0075] In an optional implementation of the second aspect, a position sensor is provided on the guide rail to measure a specific position of the calibration plate on the guide rail.

[0076] According to the above description, the optional implementation supports automatically acquiring the distance between the calibration plate and the transparent surface. Further, the parameters of the virtual image distance can be accurately determined according to the default human eye position or viewpoint detection system, thereby improving the convenience of measurement.

[0077] Compared with the prior art, the present application performs alignment adjustment between the first alignment symbol projected by the HUD device and the second alignment symbol marked by the calibration plate, and specifically adjusts the position, posture and other spatial states of the calibration plate so that the first alignment symbol and the second alignment symbol are located at the same position in the virtual image space, thereby indirectly measuring the corresponding projection parameters of the HUD device based on the physical operability of the calibration plate. The present application does not need to rely on three-coordinate calibration data for the parameter measurement of the projected virtual image, the measurement method is simple and the hardware cost is low, and portable and accurate measurement can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the description of the technical solution. Obviously, the drawings described below are only some examples recorded in the present application, and a person of ordinary skill in the art can obtain other drawings based on these drawings without creative work.

[0079] Figure 1 Schematic diagram of HUD projection display in some examples of this application.

[0080] Figure 2 Schematic diagram of the cooperation between the HUD device and the calibration plate in some examples of this application.

[0081] Figure 3 Schematic diagram of a HUD display device installed on a vehicle in some examples of this application.

[0082] Figure 4 Schematic diagram of the HUD bench used in experiments in some examples of this application.

[0083] Figure 5 This is a schematic diagram of dynamic parallax captured by a camera in some examples of this application.

[0084] Figure 6 This is a schematic diagram of the measurement tool on the calibration board in some examples of this application.

[0085] Figure 7 This is a schematic diagram of the measurement tool on the calibration board in some examples of this application.

[0086] Figure 8 This is a schematic diagram of the measurement tool on the calibration board in some examples of this application. DETAILED DESCRIPTION

[0087] The present application will be described in detail below in conjunction with the accompanying drawings, but the content of the description is merely some examples recorded in the present application and does not limit the present application. Changes in structure, method, function, etc. made by ordinary technicians in this field based on these examples are included in the protection scope of the present application.

[0088] It should be noted that the same reference numerals or marks may be used in different examples, but these do not represent an absolute connection in structure or function. In addition, the "first", "second", etc. mentioned in each example are only for the convenience of description, and do not represent an absolute distinction in structure or function, nor can they be understood as indicating or implying the relative importance or the number of corresponding objects. Unless otherwise specified, the "at least one" that may be involved in the description refers to one or more, and "more than one" refers to two or more.

[0089] In addition, when expressing a feature, the character " / " can indicate that there is an or relationship between the front and back associated objects. For example, head-up display / head-up display can be expressed as head-up display or head-up display. When expressing an operation, the character " / " can indicate that there is a division relationship between the front and back associated objects. For example, the magnification M=L / P can be expressed as L (virtual image size) divided by P (image source size). Moreover, the "and / or" in different examples is only to describe the association relationship between the front and back associated objects. This association relationship can include three situations. For example, a concave mirror and / or a convex mirror can be expressed as the existence of a concave mirror alone, the existence of a convex mirror alone, and the existence of both a concave mirror and a convex mirror.

[0090] HUD projection display mainly uses the optical reflection principle to reflect the imaging light to be displayed through a transparent surface into the viewer's eyes. The human eye can see the virtual image information in the opposite direction of the light. Correspondingly, the transparent surface can be the windshield of the vehicle, and the windshield can be used as a display screen to display the navigation instructions of the vehicle, the vehicle's driving speed, etc. Figure 1As shown, the HUD display device may include at least an optical machine 1, a first reflector 2, a second reflector 3, etc., wherein the optical machine 1 includes a backlight source and an image source (not shown), the backlight source is used to provide illumination light and adjust the brightness of the illumination light according to control, for example, the backlight source may be an LED (Light Emitting Diode), a laser, etc. Under the illumination light provided by the backlight source, the image source adjusts the corresponding display content according to control and projects the display light from the surface of the image source, for example, the image source may be an LCD (Liquid Crystal Display), a DMD (Digital Micromirror Devices), a MEMS (Micro-Electro-Mechanical System) micromirror, a LCOS (Liquid Crystal on Silicon), etc. The first reflector 2 and the second reflector 3 can project the display light projected by the optical machine 1 onto the windshield 4, so as to customize the optical path in a smaller space and meet different projection display requirements. The first reflector 2 and the second reflector 3 can be set as a concave mirror, a convex mirror, a concave lens, a convex lens, etc. according to the requirements of optical planning, and the surface shape of the lens can adopt a free-form surface. Optionally, at least one of the first reflector 2 and the second reflector 3 can also be adjusted to a certain degree of angle, so as to change the projection position of the display light on the windshield 4 to meet the needs of viewers of different heights. The display light of the optical machine 1 is finally reflected on the windshield 4 of the vehicle to form a virtual image 5. When the human eye 6 observes the virtual image 5 facing the windshield 4, it can feel a certain sense of depth, just like watching a real object at a specific distance outside the windshield. The virtual image 5 can be the navigation instruction content, vehicle speed, etc. as described above. It should be added that, according to the characteristics of different optical machines, the HUD display device can also be provided with a diffuser. In some examples, the HUD display device can also include Fresnel lenses, waveguide optical devices, diffractive optical devices, holographic optical devices, tapered optical fibers, etc.

[0091] As mentioned above, the HUD display device can project on a transparent surface such as a windshield to form a corresponding virtual image surface, wherein the navigation instruction content, vehicle speed and other projection information are all part of the virtual image surface, and the effect of the projection display is determined by the projection parameters corresponding to the virtual image surface. Since the virtual image surface is presented in the form of a virtual image formed by reflection, the human eye will perceive the spatial position directly in front of the vehicle. Here, the space where the perceived virtual image is located can be called the virtual image space, and the distance between the human eye and the virtual image surface is the virtual image distance, and the frame of the virtual image surface can be expressed according to the field of view of the human eye viewing the virtual image surface. It should be noted that the front in this application refers to the direction of the human eye or camera from the inside of the car or within the eye box toward the transparent surface and the virtual image surface. Since the mechanism of the camera viewing the content of the virtual image surface is consistent with that of the human eye, the camera can be used to replace the human eye to capture the specific situation of the virtual image surface when measuring the virtual image. In this example, since the projection is reflected on a transparent surface, the virtual image space where the virtual image plane is located is located on the other side of the human eye or camera relative to the transparent surface. Accordingly, a measuring tool (such as a calibration plate) can be set in the virtual image space to compare the virtual image plane without affecting the setting of the human eye or camera on the other side. In addition, it should be added that the eyebox refers to a conical area between the optical system of the HUD display device and the human eye, and is also the area where the display content meets the optimal optical design indicators. Within the eyebox range, the human eye or camera can see the complete FOV (i.e., the entire image) projected by the HUD. When the human eye or camera exceeds this range, it may present serious image distortion, color errors, or even no content display. The viewpoint position refers to the specific position of the viewer's eye when observing the virtual image within the eyebox range. Since the pupil (generally with a radius of 2 to 4 mm) moves within the eyebox range (generally designed to be 130*50 mm), that is, at different viewpoint positions, different optical transmission paths will be generated. Correspondingly, the entire virtual image plane is a set of display information projected by the HUD display device, which corresponds one-to-one to the display content of the image source display surface in the HUD display device, and the projection parameters of the virtual image plane are related to the optical system parameters in the HUD display device. As mentioned above, the image source is an important component of the optical machine in the HUD display device, and the backlight source provides the brightness of the illumination for it. The content in the virtual image plane can be realized by controlling the content on the image source display surface. In the actual application of HUD, the projection parameters such as the virtual image distance and the field of view of the virtual image plane presented by the HUD display device are of great concern, which determine the projection effect of the HUD display device. However, since the entire virtual image plane is perceived through the conversion of the human eye, it does not actually exist in the actual virtual image space. It is only determined by the equivalent of the reverse extension line of the light transmission. Therefore, it is difficult to use physical equipment to detect it. It is more often determined by simulating the viewing process of the human eye through a camera set within the eye box range, so as to use the mechanism of image analysis to determine it. On the one hand, it has high requirements on the processing algorithm, and on the other hand, the measurement accuracy is not so high.

[0092] In order to better obtain the projection parameters of the HUD display device, a calibration plate can be set near the virtual image space projected by the HUD display device, and the calibration plate can be used to materialize the situation where the virtual image surface is in the virtual image space. Figure 2 As shown, the HUD device (the complete structure is not shown) is matched with the calibration plate 51, and the camera 60 is used to simulate the result of human eyes viewing within the eye box range of the HUD device. In order to improve the flexibility of the test, the HUD device is not limited to the actual product form, such as Figure 3 As shown, the HUD device can be a HUD display device 101 actually installed on the vehicle, which can be projected on the windshield 4 and have an alignment mark outside the windshield 4. A calibration plate is also set in front of the vehicle outside the windshield 4 to measure the projection parameters of the installed HUD device. Figure 3 In the embodiment, the eye box is located at the driving position in the vehicle, and the virtual image space is relatively located outside the vehicle on the other side of the windshield 4. When looking outward from the vehicle toward the windshield 4, the direction is forward, and the calibration plate will also be aligned and adjusted with the virtual image surface outside the vehicle. Figure 4 As shown, the HUD device can also be a pre-tested HUD bench 102. The HUD bench 102 not only integrates a HUD with a specified optical system, but also has the same parameters designed for a specific vehicle model. In addition, the HUD bench is also provided with a windshield 4 with a specific test surface shape, and the glass surface shape can be the surface shape of the glass used on a specific vehicle model. Therefore, it is consistent with the actual vehicle-mounted projection display, and will be projected on the windshield 4 and form a virtual image in front, with the same projection parameters. Figure 4 Taking the placement direction of the HUD device as a reference, the reflective surface is located on the left side of the windshield 4. Correspondingly, the eye box range is on the left side of the windshield 4, and the virtual image space where the virtual image is located is on the right side of the windshield 4. Looking from left to right can be considered as looking forward, and the calibration plate will also be aligned and adjusted with the virtual image surface on the right side of the windshield 4.

[0093] like Figure 2 As shown, for the HUD device, the transparent surface 4 is a component in the HUD device that receives display light to realize reflective imaging, referring to Figure 1, the display light can be emitted by the image source (a part of the optical machine) of the HUD device, wherein the light emission range of the image source display surface determines the display range of the virtual image surface 50. In this example, the camera 60 is set within the eye box range of the HUD device to simulate the process of human eyes viewing the virtual image surface 50. Due to the principle of reflection as a virtual image, the virtual image space and the eye box range are respectively located on both sides of the transparent surface 4. As mentioned above, the direction of the eye box range pointing to the virtual image space is determined to be the front. Accordingly, the position of the virtual image surface 50 can be expressed as being located in front of the transparent surface 4 and having a certain distance from the transparent surface 4, which is determined according to the parameters such as the optical path of the optical system in the HUD device and the focal length of the lens. Once the optical system of the projection is determined, it is fixed and unchanged. The position of the camera 60 can be expressed as being located behind the transparent surface 4, and correspondingly being in the eye box range of the HUD device to achieve shooting of the virtual image surface, and the camera shooting parameters will also be configured specifically. Furthermore, by displaying the first alignment symbol on the image source display surface, the projected first alignment symbol 501 (virtual image), such as a cross symbol, will be displayed on the virtual image surface 50 accordingly. The cross symbol is not easily affected by the projection deviation of the field of view angle and thus misaligned, and is easier to achieve alignment. At the same time, a calibration plate 51 is also set in front of the transparent surface 4, and a second alignment symbol 511 (entity) is set on the side of the calibration plate 51 opposite to the transparent surface 4, so that the camera 60 can capture both the first alignment symbol (virtual image) and the second alignment symbol (entity) when facing the front, thereby determining the overlap between the two. The spatial state of the calibration plate 51 can be adjusted, such as moving to any position in the space and adjusting the posture angle of the calibration plate 51 itself. Correspondingly, the second alignment symbol 511 on the calibration plate 51 will also be adjusted, so as to ensure that it coincides with the first alignment symbol 501 in a specific spatial state, that is, the first alignment symbol 501 and the second alignment symbol 511 are in exactly the same position and angle in the virtual image space, so that the calibration plate 51 will be in a coplanar state with the virtual image surface 50, and the corresponding parameters of the virtual image surface 50 can be achieved by measuring the calibration plate 51, which will be described in detail below. In a preferred example, the first alignment symbol 501 is configured to be displayed at the center position of the image source display surface, and the corresponding first alignment symbol 501 after projection will be displayed at the center position of the virtual image surface 50, and the second alignment symbol 511 matched with it will also be set at the center position of the calibration plate 52, which is convenient for positioning and measuring the calibration plate 52, and the shooting position of the camera is also more suitable.

[0094] exist Figure 2In the example, the direction from the virtual image plane 50 to the camera 60 is defined as the depth direction (z axis). Taking the illustrated direction as a reference, the direction from left to right of the virtual image plane 50 is defined as the horizontal direction (x axis), which can be the width direction parallel to the HUD device placement surface when the camera 60 faces the transparent surface 4, where L is the second distance of the virtual image plane in the horizontal direction, and the direction from bottom to top of the virtual image plane 50 is defined as the vertical direction (y axis), which can be the height direction perpendicular to the HUD device placement surface, where H is the first distance of the virtual image plane in the vertical direction. In this example, the HUD device reflects the display light including the first alignment mark to the inner side behind the transparent surface 4 according to the test requirements, and correspondingly forms a virtual image plane 50 in front of the transparent surface 4. The first alignment mark 501 forming the virtual image is located at the center of the virtual image plane 50. Since the HUD device is already in the test preparation state, the corresponding optical system will not change, so the virtual image plane 50 where the first alignment mark 501 is located has relatively fixed projection parameters, and the virtual image plane 50 can be determined to a certain extent by the first alignment mark 501. If the imaging condition of the virtual image surface 50 in the virtual image space, i.e., the projection parameters of the HUD device, needs to be tested, this can be achieved through the camera 60 behind the transparent surface 4. The camera 60 is within the eye box range of the HUD device and can face the virtual image surface 50 through the transparent surface 4. By adjusting the camera's shooting parameters, the first alignment symbol 501 can be clearly and completely photographed. Correspondingly, the calibration plate 51 is also set in the virtual image space, and the second alignment symbol 511 fixedly set on the calibration plate 51 is also facing the camera 60, so it is also photographed by the camera 60. The camera 60 can send the first alignment symbol 501 and the second alignment symbol 511 photographed at the same time to the controller. The controller can be integrated in the HUD device or the calibration plate, or the camera 60 and the calibration plate 51 can be connected separately. The controller can drive the calibration plate 51 to adjust the spatial state, so that the second alignment symbol 511 will also be adjusted accordingly. The controller implements closed-loop management through the feedback of the camera, so that the second alignment mark 511 is constantly approaching the first alignment mark 501. Specifically, the calibration plate 51 can first realize position movement in the horizontal direction, vertical direction and depth direction, so that the second alignment mark 511 reaches the position near the first alignment mark 501, and then the calibration plate 51 is flipped in the horizontal direction and vertical direction, so that the second alignment mark 511 and the first alignment mark 501 overlap as much as possible. Further, the calibration plate 51 can be fine-tuned in the horizontal direction, vertical direction and depth direction, and the corresponding adjustment can also be switched to realize fine-tuning in a cycle, so as to ensure that the second alignment mark 511 is completely aligned with the first alignment mark 501. In this state, the calibration plate 51 is in the same spatial state as the virtual image plane 50 projected by the HUD device, and the intangible virtual image characteristics of the virtual image plane 50 can be avoided during virtual image measurement, and further, the projection parameters of the HUD device can be determined according to the final adjusted spatial state of the calibration plate 51, and the measurement is more convenient.

[0095] Since the first aligner 501 and the second aligner 511 are of the same shape, when the two overlap, it indicates that the first aligner 501 and the second aligner 511 are respectively in the same position in the virtual image space and maintain the same posture. For example, when the cross intersections of the two overlap, it indicates that the first aligner 501 and the second aligner 511 are in the same position. As described above, the alignment of the first aligner 501 and the second aligner 511 in the virtual image space is not only the alignment in the horizontal and vertical directions, that is, the alignment effect on the two-dimensional plane seen by the camera 60 facing the virtual image surface 50, but also the alignment in the depth direction, so as to ensure that the two completely overlap in space. For the alignment in the horizontal and vertical directions, it is relatively simple, and the alignment can be determined by the two-dimensional overlap degree captured by the camera, such as the overlap spacing between the two is less than a specific threshold. In the depth direction, it is consistent with the camera shooting direction, so it cannot be reflected on the two-dimensional shooting surface. In some examples, the depth principle of the camera can be used to achieve consistency in the depth direction. According to the imaging principle of the camera, the camera will focus on the scene within the shooting range. The light transmission mechanism makes the scene within the depth of field determined by the focus clear, while the scene outside the depth of field is blurred. Therefore, the clarity of the camera can be used to determine which scenes are within the same depth of field. Specifically, the clarity can be judged by the contrast of the first aligner and the second aligner. The higher the contrast, the higher the clarity. The first threshold can be used to determine whether the clarity of the specified area is a scene within the depth of field. If the first aligner and the second aligner are both within the depth of field of the camera, it means that the two are close in the depth direction. At the same time, the depth of field range is related to the aperture value of the camera. The smaller the aperture value, the greater the amount of light entering the aperture, and the smaller the depth of field range. On the contrary, the larger the depth of field range, the smaller the depth of field range can be. Therefore, the aperture value can be made smaller than the second threshold to make the depth of field range as small as possible, so that the accuracy of the alignment of the first aligner and the second aligner in the depth direction can be improved. In some examples, the phase focus function in the camera can be used to determine the depth position of the first alignment symbol and the second alignment symbol, thereby further improving the accuracy of the alignment.

[0096] In some examples, the principle of dynamic parallax can also be combined to determine the difference in depth between the first aligner and the second aligner. The difference in depth between the first aligner and the second aligner is actually reflected in the difference in the distance from the first aligner to the camera (or human eye) and the distance from the second aligner to the camera. Based on the mechanism of linear transmission of light, there will be a difference in parallax between the front and back. Figure 5As shown, if the first aligner and the second aligner have a certain distance in the depth direction, and if the camera in the depth direction shoots the first aligner and the second aligner at different positions of the first viewpoint position and the second viewpoint position, it will be determined that the overlap distance between the two has changed. The distance photographed by the camera at the first viewpoint position is d1, and the distance photographed by the camera at the second viewpoint position is d2. Not only are d1 and d2 different in value, but they are also greater than the third threshold. As the first aligner and the second aligner are continuously aligned in the depth direction, their corresponding d1 and d2 will become smaller. When the two are completely aligned in the depth direction, d1 and d2 will tend to zero. Therefore, it can be determined whether the first aligner and the second aligner are completely overlapped by judging whether d1 and d2 are less than the third threshold.

[0097] Accordingly, the HUD device and the calibration plate can be integrated together for easy control, or they can be arranged together in the form of assembly or the like. When the camera captures the specific alignment status of the first alignment symbol and the second alignment symbol, the calibration plate will adjust the spatial state. Referring to the above example, the second alignment symbol is adjusted to tend to the spatial state of the first alignment symbol. Among them, the calibration plate can specifically include a guide rail for adjusting the position of the second alignment symbol. The guide rail can include a first guide rail, a second guide rail and a third guide rail. The first guide rail is used to drive the calibration plate and the second alignment symbol thereon to move in the vertical direction, that is, to drive the second alignment symbol to adjust up and down to be consistent with the height of the first alignment symbol. The second guide rail is used to drive the calibration plate and the second alignment symbol thereon to move in the horizontal direction, that is, to drive the second alignment symbol to adjust left and right to be consistent with the horizontal position of the first alignment symbol. The third guide rail is used to drive the calibration plate and the second alignment symbol thereon to move in the depth direction, that is, to drive the second alignment symbol to adjust forward and backward to be consistent with the depth position of the first alignment symbol. Optionally, the movement of the calibration plate on the guide rail can be acquired in real time by a position sensor on the guide rail, and the acquired position data can be used as a basis for calculating the projection parameters, which will be described in detail below. Taking into account that the projected virtual image surface is not perfectly in a vertical posture, the calibration plate itself also has a first adjustment structure and a second adjustment structure. The first adjustment structure is used to drive the calibration plate to flip vertically, and the second adjustment structure is used to drive the calibration plate to flip horizontally. In this way, the second alignment symbol can be at any angle in the virtual image space, and finally coincide with the posture of the first alignment symbol. Optionally, the first adjustment structure and the second adjustment structure are respectively provided with angle sensors, referring to Figure 2 The actual vertical flip angle can be obtained in real time through the angle sensor 518, and the actual horizontal flip angle can be obtained in real time through the angle sensor 519.

[0098] In some examples, the camera feeds back the overlap of the captured first alignment symbol and the second alignment symbol to the tester through an output device such as a screen, and the calibration plate can be adjusted manually, or the automated structure in the above example can be used to achieve coarse adjustment, and then the tester can manually fine-tune it. In some examples, when manually adjusting the spatial state of the calibration plate, the tester's eyes can also be located in the position of the camera within the eye box range to observe, and the overlap between the first alignment symbol and the second alignment symbol is judged by the human eye, and the calibration plate is adjusted directly. Accordingly, the final adjusted spatial state of the calibration plate can be measured by the above-mentioned sensor, or it can be physically measured by the tester through tools such as a ruler, which greatly improves the flexibility of the measurement and can adapt to temporary measurement scene requirements in actual applications.

[0099] In some examples, after the calibration plate is adjusted, the second alignment mark on it can represent the projection of the first alignment mark, and the position and posture parameters of the calibration plate can be used to further calculate the projection parameters of the virtual image surface. Specifically, when the final adjusted position of the calibration plate is known, the distance between the calibration plate and the camera or human eye can be determined. The position of the camera can be determined based on the sensor on the camera, or the position of the camera or human eye can be replaced by the default viewpoint position coordinates. The calculated distance between the calibration plate and the camera (refer to Figure 2 The VID in the image can be determined as the projected virtual image distance of the virtual image surface. Preferably, the virtual image distance will also eliminate possible deviations through a certain correction coefficient based on the distance between the two. Furthermore, the lower or upper viewing angle corresponding to the virtual image surface can be determined according to the vertical flip angle finally adjusted by the calibration plate, that is, the up and down orientation, and the left or right viewing angle corresponding to the virtual image surface can be determined according to the horizontal flip angle finally adjusted by the calibration plate, that is, the left and right orientation.

[0100] In some examples, when the second alignment mark coincides with the first alignment mark, the virtual image plane where the first alignment mark is located can be equivalently understood as being projected on the calibration plate, and the entire virtual image plane is like being attached to the calibration plate, so the measurement scale on the calibration plate can be used to directly measure the first distance H of the virtual image plane (refer to Figure 2 The vertical range of the virtual image plane 50), the second distance L (reference Figure 2 The first distance H can be the distance between the upper edge and the lower edge of the virtual image surface, and the second distance L can be the distance between the left edge and the right edge of the virtual image surface, which can be aligned and calculated by measuring the scale. In more examples, in order to clearly project the range of the virtual image surface and find the position of the edge of the virtual image surface on the calibration plate, a position symbol marking the edge of the range can be displayed on the image source display surface of the HUD device, which corresponds to the position symbol located at the upper edge, lower edge, left edge, and right edge of the virtual image surface after projection (refer to Figure 3 The position marks at the upper left corner and lower right corner of the virtual image surface are not limited to this. Since the position marks are displayed at the edge of the virtual image surface, the position marks can be directly aligned with the corresponding positions on the calibration plate, which can improve the accuracy of the measurement. Figure 6 As shown, a measuring tool in the vertical direction and a measuring tool in the horizontal direction are respectively arranged on the calibration plate to facilitate the measurement of the virtual image surface range corresponding to the calibration plate. In this example, the measuring tool in the vertical direction may include a first positioning rod 5121 and a slide rail 5122 distributed in the vertical direction. The first positioning rod 5121 can be adjusted along the slide rail 5122 until it is aligned with the upper edge or the lower edge of the virtual image surface. For example, the first positioning rod 5121 can be adjusted up and down until its body coincides with the position symbol. Optionally, the positioning rod aligned with the upper edge and the positioning rod aligned with the lower edge are not the same positioning rod. Specifically, a second positioning rod adjusted along the slide rail 5122 can also be arranged. The first positioning rod 5121 is responsible for aligning with the upper edge of the virtual image surface, and the second positioning rod is responsible for aligning with the lower edge of the virtual image surface. Furthermore, a distance measurement sensor is arranged between the first positioning rod 5121 and the second positioning rod, so that the first distance H can be acquired in real time. Similarly, the horizontal measuring tool may include a third positioning rod 5123 and a horizontally distributed slide rail 5124. The third positioning rod 5123 may be adjusted along the slide rail 5124 until it is aligned with the left edge or the right edge of the virtual image surface. Optionally, a fourth positioning rod that is adjusted along the slide rail 5124 may be provided. The third positioning rod 5123 is responsible for aligning with the left edge of the virtual image surface, and the fourth positioning rod is responsible for aligning with the right edge of the virtual image surface. Furthermore, a distance measurement sensor is provided between the third positioning rod 5123 and the fourth positioning rod, so that the second distance L can be acquired in real time. Figure 7 As shown, the first positioning rod can be moved to the upper side of the calibration plate, aligned with the upper edge of the virtual image surface, and the H1 corresponding to the position can be recorded. The third positioning rod can be moved to the left side of the calibration plate, aligned with the left edge of the virtual image surface, and the L1 of the position can be recorded. Figure 8 As shown, the first positioning rod is further moved to the lower side of the calibration plate, aligned with the lower edge of the virtual image surface, and H2 corresponding to the position is recorded. The third positioning rod is further moved to the lower side of the calibration plate, aligned with the lower edge of the virtual image surface, and L2 at the position is recorded. Therefore, the first distance H can be the difference between H1 and H2, and the second distance L can be the difference between L1 and L2.

[0101] When the first distance H and the second distance L are obtained, the field of view angle of the virtual image plane can be calculated in combination with the virtual image distance calculated in the above example. Specifically, the vertical field of view angle α of the HUD device is calculated according to the first distance H and the virtual image distance VID:

[0102] α=2arctan(H / (2*VID)),

[0103] Wherein, α is the field of view angle in the vertical direction, VID is the projection virtual image distance of the HUD device, and H is the first distance.

[0104] The horizontal viewing angle β of the HUD device is calculated according to the second distance L and the virtual image distance VID:

[0105] β=2arctan(L / (2*VID)),

[0106] Wherein, β is the field of view in the horizontal direction, VID is the projection virtual image distance of the HUD device, and L is the second distance. In some examples, the first distance H and the second distance L can be automatically obtained by the measuring tool on the calibration plate, and the virtual image distance VID can be automatically determined according to the final adjusted position of the calibration plate in the above example, so the field of view of the HUD device projection can also be calculated in real time, which is more real-time and more convenient to calculate than the complex calculation based on image analysis. In addition, the traditional field of view angle measurement requires that the device must be at the center eye point within the eye box range of the HUD device to measure, while the present application calculates the FOV by measuring the real length and width of the virtual image surface in the virtual image space. The data mainly depends on the spatial state of the calibration plate itself, so the position accuracy requirements for camera shooting are reduced, and it is only required to shoot within the eye box range of the HUD device, without shooting completely at the center eye point, which greatly expands the application scenarios of virtual image measurement and improves actual flexibility. At the same time, the virtual image measurement method of the above example can be separated from the measurement requirements of the three-coordinate calibration rig, and can support the precise measurement of portable field of view angle and virtual image distance.

[0107] In some examples, there may be a controller connected to the projection system, camera, and calibration plate of the HUD device, respectively, and the controller can realize the automation of virtual image measurement. Specifically, the controller controls the projection system to form an alignment symbol to be measured in the specified virtual image space, and the alignment symbol can define the spatial state of the entire virtual image surface of its projection. Then the controller can also control the camera to shoot the projected virtual image surface at a specified position, and constantly judge the relative position change between the virtual image surface and other objects in the virtual image space. In this example, other objects in the virtual image space can be calibration plates adjusted by the controller. The controller can not only control the calibration plate to make fine adjustments in the virtual image space, but also control the calibration plate to flip its own angle, and further adjust the calibration plate continuously through the relative position relationship between the virtual image surface and the calibration plate determined by the camera, and the above examples can be specifically referred to. More importantly, the controller can also obtain the spatial state data of the calibration plate after adjustment in real time, so as to calculate the acquired data and finally output the projection parameters of the HUD device. Therefore, the controller may include a processor, a memory, an input device, and an output device, wherein the input device may include a control button, etc., which can be used to trigger the control and configuration of virtual image measurement. The output device may include a display screen, etc., which can be used to prompt the process of virtual image measurement and output the final test results, etc. Furthermore, the memory stores a computer program running on the processor, and the processor implements the virtual image measurement method of the above example when executing the computer program. In some examples, a computer-readable storage medium stores a computer program, and the computer program implements the virtual image measurement method of the above example when executed by the processor, which can be applied in a HUD device to distribute the program of the virtual image measurement method in the above example, so that the HUD device takes into account the advantages of scene application portability and test optimization iteration.

[0108] In combination with the above examples, the technical solutions involved in the present application can be directly embodied as hardware, a software module executed by a control unit, or a combination of the two, that is, one or more steps and / or one or more step combinations, which can correspond to various software modules of a computer program flow, or to various hardware modules, such as ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or any appropriate combination thereof. For the convenience of description, the above description is divided into various modules and described separately according to their functions. Of course, when implementing the present application, the functions of each module can be implemented in the same or more software and / or hardware.

[0109] Through the description of the above examples, those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the technical solution involved in the present application can be essentially or partly contributed to the prior art in the form of a software product. The software is executed by a microcontroller unit and, depending on the required configuration, may include one or more microcontroller units of any type, including but not limited to a microcontroller unit, a microcontroller, a DSP (Digital Signal Processor) or any combination thereof. The software is stored in a memory, such as a volatile memory (such as a random access memory, etc.), a non-volatile memory (such as a read-only memory, a flash memory, etc.) or any combination thereof.

[0110] In summary, the present application performs alignment adjustment between the first alignment symbol projected by the HUD device and the second alignment symbol marked by the calibration plate, specifically by adjusting the position, posture and other spatial states of the calibration plate so that the first alignment symbol and the second alignment symbol are located at the same position in the virtual image space, thereby indirectly measuring the corresponding projection parameters of the HUD device based on the physical operability of the calibration plate. The present application does not need to rely on three-coordinate calibration data for the parameter measurement of the projected virtual image, the measurement method is simple and the hardware cost is low, and portable and accurate measurement can be achieved.

[0111] It should be understood that although this specification includes some examples, none of these examples contains only one independent technical solution, and this description of the specification is only for the purpose of clarity. A person skilled in the art should take the specification as a whole, and the technical solutions in each example can also be appropriately combined to form other implementation methods that can be understood by a person skilled in the art.

[0112] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. All equivalent implementation methods or modifications that do not deviate from the teachings of the present application should be included in the scope of protection of the present application.

Claims

1. A virtual image measurement method, characterized in that: include: Controlling the HUD device to be projected onto the transparent surface so as to have a first alignment symbol in a virtual image space in front of the transparent surface; A calibration plate is arranged in the virtual image space, wherein a second alignment mark having the same shape as the first alignment mark is arranged on a side of the calibration plate facing the transparent surface, and the spatial state of the calibration plate is adjusted so that at least a part of the second alignment mark overlaps with the first alignment mark; Determining projection parameters of the HUD device according to the spatial state of the calibration plate finally adjusted, wherein a projection lower viewing angle or an upper viewing angle of the HUD device is determined according to the vertical flip angle of the calibration plate finally adjusted; and / or The projection left viewing angle or right viewing angle of the HUD device is determined according to the horizontal flip angle finally adjusted by the calibration plate.

2. The virtual image measurement method according to claim 1, characterized in that: The first alignment symbol is a cross-shaped symbol projected at the center of the virtual image surface, and the second alignment symbol is a cross-shaped symbol set at the center of the calibration plate.

3. The virtual image measurement method according to claim 1, characterized in that: Determining the projection parameters of the HUD device according to the spatial state finally adjusted by the calibration plate includes: The projection virtual image distance of the HUD device is determined according to the final adjusted position of the calibration plate.

4. The virtual image measurement method according to claim 1, characterized in that: The step of adjusting the spatial state of the calibration plate so that at least a portion of the second aligner overlaps with the first aligner comprises: The first aligner and the second aligner are photographed by a camera disposed in an eye box range of the HUD device, wherein the eye box range includes a first viewpoint position and a second viewpoint position; The camera takes photos at least at a first viewpoint and a second viewpoint, respectively, and the overlap distance between the first aligner and the second aligner taken at the first viewpoint and the second viewpoint is smaller than a third threshold.

5. The virtual image measurement method according to claim 1, characterized in that: The step of adjusting the spatial state of the calibration plate so that at least a portion of the second aligner overlaps with the first aligner comprises: The first alignment mark and the second alignment mark are clearly photographed simultaneously by a camera arranged in the eye box range of the HUD device.

6. The virtual image measurement method according to claim 5, characterized in that: The first alignment mark and the second alignment mark are clearly photographed by a camera arranged in the eye box range of the HUD device at the same time, including: The contrast between the first alignment symbol and the second alignment symbol photographed by the camera is greater than a first threshold.

7. The virtual image measurement method according to claim 1, characterized in that: The control HUD device is projected onto a transparent surface and comprises: The upper edge and lower edge in the vertical direction and the left edge and right edge in the horizontal direction are displayed on the projected virtual image surface; The calibration plate includes a vertical direction measuring tool matched with the virtual image surface, and used for measuring a first distance between the upper edge and the lower edge displayed by the virtual image surface; The calibration plate includes a horizontal direction measuring tool matched with the virtual image surface, and used for measuring a second distance between the left edge and the right edge displayed by the virtual image surface; Determining the projection parameters of the HUD device according to the spatial state finally adjusted by the calibration plate includes: The projection field of view of the HUD device is determined in combination with the first distance and the second distance.

8. A measuring device, characterized in that: include: A HUD device having a transparent surface for projection, wherein the transparent surface is configured to receive reflection of the display light to form a first alignment symbol to be measured in a virtual image space in front of the transparent surface; A calibration plate cooperates with the HUD device, the calibration plate supports adjusting the spatial state in the virtual image space, the calibration plate is provided with a first adjustment structure for driving the calibration plate to realize vertical flipping, a second adjustment structure for driving the calibration plate to realize horizontal flipping, and a guide rail for driving the calibration plate to move between the calibration plate and the transparent surface, and a second alignment mark aligned with the first alignment mark is provided on a side of the calibration plate facing the transparent surface, and the first alignment mark and the second alignment mark have the same shape.

9. The measuring device according to claim 8, characterized in that A vertical direction measuring tool and a horizontal direction measuring tool are also provided on the side of the calibration plate facing the transparent surface; The vertical direction measuring tool is provided with a first positioning rod and a second positioning rod movable in the vertical direction, the first positioning rod is used to align with the upper edge of the virtual image surface displayed by the HUD device projection, and the second positioning rod is used to align with the lower edge of the virtual image surface displayed; The horizontal direction measuring tool is provided with a third positioning rod and a fourth positioning rod which move in the horizontal direction, the third positioning rod is used to align with the left edge of the virtual image surface display, and the fourth positioning rod is used to align with the right edge of the virtual image surface display.

10. The measuring device according to claim 8, characterized in that The first adjustment structure is provided with an angle sensor to measure the vertical flip angle of the calibration plate, and the second adjustment structure is provided with an angle sensor to measure the horizontal flip angle of the calibration plate.

Images