JP7221161B2 - Head-up display and its calibration method - Google Patents

Description

The present invention relates to a head-up display, and more particularly to adjustment (calibration) of the shape and display position of a virtual image.

Conventionally, information such as vehicle speed and information such as instructions related to car navigation are projected onto a windshield (windshield) or the like to display a virtual image. )It has been known.

As a technique for adjusting the display position of a virtual image displayed on a HUD, Patent Document 1 discloses that "the projection unit emits projection light indicating a display image, and the first reflection unit emits the projection light emitted by the projection unit. toward the second reflecting portion, the second reflecting portion reflects the projected light reflected by the first reflecting portion toward the transmissive screen, and the transmissive screen reflects the projected light reflected by the second reflecting portion By rotating the first reflecting section and the second reflecting section to adjust the angle of the optical axis of the projection light incident on the transmissive screen, the transmitted Adjusting the angle of the image light emitted from the mold screen (abstract excerpt)” configuration is disclosed.

Japanese Patent Application Laid-Open No. 2002-200000 describes a technique for eliminating image distortion of a virtual image, which is described as "an image forming unit and a method for displaying a virtual image in front of a vehicle by reflecting light emitted from the image forming unit on the windshield. and a virtual image optical system including a windshield, the horizontal radius of curvature Rh of the windshield and the vertical radius of curvature Rv of the windshield are different, and the virtual image optical system has at least the radius of curvature of the windshield in the horizontal direction of the vehicle body A concave reflective mirror with a reflective curved surface that offsets the difference between Rh and the vertical radius of curvature Rv (summary excerpt)” is disclosed.

JP 2016-014861 A WO2017/061016

According to Patent Document 1, the viewpoint position of the driver can be detected by viewpoint position detection means such as an infrared camera, and the display position of the projected image on the windshield can be moved according to the detected viewpoint position. However, the left and right radii of curvature are different at the display positions (regions) of the projected image on the windshield. Therefore, even if the display position on the windshield is moved based on the driver's viewpoint position, the shape change depending on the display position on the windshield, more specifically, the horizontal curvature radius and the vertical curvature There is a difference in radius, and distortion occurs in the projected image, for example, image distortion such as a difference in size between the left and right sides of the projected image. .

Regarding this point, in Patent Document 2, a concave surface having a reflective curved surface that offsets the difference between the horizontal curvature radius Rh and the vertical curvature radius Rv of the windshield (corresponding to the "windshield" in Patent Document 1) The above problem is solved by using a reflecting mirror.

In general, the shape of the windshield has a design value according to the vehicle type. The adjustment of the display position of the virtual image in the HUD has conventionally been made based on design values. For example, both Patent Document 1 and Patent Document 2 described above describe the display position of the projected image and image distortion correction without considering variations in the shape inherent to each windshield. This is because the shape of is assumed to be the same for the same vehicle model.

Recently, however, it has become known that the shape of the windshield varies from one vehicle to another, even for vehicles of the same type. Due to this variation in the shape of the windshield, the coordinates on the windshield, for example, the horizontal curvature of a point on the windshield at the same angle and distance from the reference point, with the upper end of the right front pillar as the reference point. and the curvature in the vertical direction are different for each vehicle even for the same vehicle type. Therefore, even if the same projected image is displayed at the same coordinates on the windshield, a new problem has been found that different image distortion occurs for each vehicle, and the problem has not yet been solved.

Accordingly, it is an object of the present invention to provide a head-up display that displays a virtual image to the observer with less positional displacement and less image distortion, while following the observer's viewpoint position and taking into consideration the shape variation inherent to each windshield. With the goal.

In order to achieve the above object, the present invention has the configuration described in the claims. One example is a head-up display mounted on a vehicle, which is a video display device that generates and emits video light including display content to be displayed as a virtual image, and directs the video light to the windshield of the vehicle. a virtual image optical system for projecting a virtual image on the windshield; a viewpoint detection device for detecting a viewpoint of an observer of the virtual image; a main controller for performing image distortion correction of a display position on the windshield of a projected image, which is an image of the display content appearing upon incidence of video light, and the projected image, wherein the main controller controls the vehicle; a projection image correction data storage unit for storing projection image correction data defining a correction amount for offsetting the display position deviation of the projection image and the image distortion of the projection image caused by the shape distortion specific to the windshield mounted on the windshield; wherein the main controller determines a target position on the windshield to which the image light is to be projected in response to data from which the viewpoint detection device detects the viewpoint of the observer, and performs the projection at the target position. correcting the image distortion of the display content using a correction amount for canceling out the image distortion of the image, emitting the image light including the display content corrected for the image distortion from the image display device, and is an angle at which the image light including the display content corrected for the image distortion is reflected toward the target position, using a correction amount that offsets the positional deviation amount of the projection image at the target position. It is characterized by controlling an optical system.

According to the present invention, there is provided a head-up display that displays a virtual image with little positional displacement and image distortion to the observer, while following the observer's viewpoint position and taking into consideration the shape variations inherent in each windshield. be able to. Objects, configurations, and effects other than those described above will be clarified in the following embodiments.

Schematic diagram showing an example of the configuration of the HUD according to the present embodiment Top view of vehicle (passenger car) equipped with HUD Diagram showing the shape of the windshield An exploded perspective view of the rotating mechanism of the concave mirror Schematic diagram showing a mounting example of the mirror driving unit Schematic diagram showing an example of mounting the electric motor and the lower housing Enlarged view of the connecting part between the mirror driving part and the concave mirror Explanatory drawing about adjustment of the display position of the virtual image in HUD Block diagram showing an example of connection between the main controller and various vehicle devices Functional configuration diagram of the main controller Explanatory diagram showing the correspondence relationship between the target position on the HUD and the position of the driver's head Explanatory drawing showing the correspondence relationship between the target position and the depression angle θ in the HUD Diagram showing an example of a windshield shape that deviates from the design center value of the radius of curvature View from the driver's side (inside the car) of the displacement of the projected image on the windshield and the distortion of the projected image. Flowchart for explaining the flow of processing for correcting the display position of the projected image on the windshield and correcting the distortion of the projected image Flowchart showing details of projection image correction data generation processing A diagram showing an example of a grid-shaped reference image A diagram showing an example of a concentric reference image

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In principle, the same reference numerals are given to the same parts in all the drawings for describing the embodiments, and the repeated description thereof will be omitted. On the other hand, parts that have been described with reference numerals in one drawing may be referred to with the same reference numerals, although they are not shown again in the description of other drawings. Further, in the embodiments of the present invention described below, a case where a head-up display (hereinafter referred to as "HUD") is installed in a vehicle such as an automobile will be described as an example. The present invention is applicable to any HUD that eliminates the unique shape variation of each projected member, and is not limited to an automotive HUD. For example, it can be applied to other vehicles such as trains, aircraft, and ships, and may be used for applications other than vehicles, such as simulators.

FIG. 1 is a schematic diagram showing an example of the configuration of a HUD 1 according to this embodiment.

In the HUD 1 of the present embodiment, the image displayed by the image display device 30 arranged in the housing (see FIG. 4) or at a place detachable from the housing is displayed from the virtual image optical system to the windshield of the vehicle 2. Project to 3. The virtual image optical system of this embodiment reflects the image by the concave mirror 52 and projects it toward the windshield 3 via a necessary optical element (here, the free-form surface lens 43).

The image display device 30 may be, for example, an LCD (Liquid Crystal Display) having a backlight, or may be a self-luminous VFD (Vacuum Fluorescent Display) or the like. It may be displayed. Such a screen may be configured by, for example, a microlens array in which microlenses are arranged two-dimensionally.

The concave mirror 52 is composed of, for example, a free-form surface mirror, a mirror having an asymmetrical shape with respect to the optical axis, or the like. More specifically, the shape of the concave mirror 52 is designed to reduce the distortion of the virtual image projected onto the windshield 3 purely optically, that is, without using image processing. In the upper region (that is, the light rays reflected here are reflected below the windshield 3, so the distance to the viewpoint of the driver 5 (corresponding to the "observer" of the virtual image) is relatively short), The radius of curvature is made relatively small so that the enlargement ratio becomes large. On the other hand, in the region below the concave mirror 52 (that is, the light rays reflected here are reflected above the windshield 3, the distance from the viewpoint of the driver 5 is relatively long), the magnification ratio is small. increase the radius of curvature relatively. By arranging the image display device 30 so as to be inclined with respect to the optical axis of the concave mirror 52, the difference in image magnification as described above may be corrected and the distortion that occurs may be reduced.

Image light emitted from the HUD 1 is reflected by the windshield 3 and enters the driver's 5 eyes. The driver 5 visually recognizes the image as a virtual image in front through the transparent windshield 3 by the image light incident on the eyes. According to this configuration, by adjusting the angle of the concave mirror 52, the display position of the virtual image viewed by the driver 5 can be adjusted in the vertical direction by adjusting the position where the image light is projected onto the windshield 3. . The image light includes content to be displayed as a virtual image (display content).

The display content included in the image light appears on the windshield 3 at the position where the image light is projected onto the windshield 3 . In the following description, an image reflected at a point where image light emitted from the HUD 1 is reflected by the windshield 3 is called a "projection image". A projected image may be a still image or a moving image.

The displayed content is not particularly limited, and for example, vehicle information such as vehicle speed, navigation information, and the front and side scenery captured by a camera (monitoring camera, around viewer, etc.) installed inside or outside the vehicle (not shown). In addition, obstacles around the vehicle, such as figures and marks that indicate vehicles traveling in front and pedestrians existing around the vehicle, are extracted from images taken by the camera (not shown) by image processing, etc. can be displayed as appropriate.

Here, the driver 5 can use the windshield as a figure surrounded by a rectangle along the outline of the vehicle running ahead or an ellipse surrounded by the outline of a pedestrian present around the own vehicle. A virtual image that is superimposed on the real scenery that can actually be seen through 3 is called "augmented reality content." A HUD that displays augmented reality content is particularly called an AR-HUD (Augmented Reality-HUD).

AR-HUD needs to superimpose and display augmented reality content on a real landscape while maintaining the corresponding positional relationship. Therefore, when the augmented reality content is displayed shifted from the position where it should be displayed, or when the projection image includes a large image distortion due to the change in the display position of the projection image on the windshield 3, When the driver 5 visually recognizes the augmented reality content on the windshield, it becomes very difficult to see.

Specifically, when an elliptical augmented reality content that should be displayed so as to surround a pedestrian in the vicinity of the own vehicle is displayed with a large deviation from the pedestrian, the driver 5 can ensure that the pedestrian is displayed. The effect of displaying augmented reality content for viewing is lost.

Therefore, in the AR-HUD, compared to a normal HUD (a HUD that does not display AR content), higher accuracy is required for the display position of the AR content, and the As for the projection image, it is desirable to display it in a state in which image distortion is removed as much as possible. In the AR-HUD, main controller 20 analyzes the image of camera 116 (see FIG. 8B) outside the vehicle to determine the presence, type, and position of an object to which augmented reality content is to be added. Then, the optimum display position of the virtual image for adding the virtual image to the object is determined. Then, in order to display the virtual image at the optimum display position of the virtual image, the display position and image distortion caused by the individual shape distortion of the windshield 3 are corrected.

The HUD 1 also includes a main controller 20 that controls the image display device 30 and the concave mirror 52 . The main controller 20 is composed of, for example, an electronic board.

The HUD 1 also includes a viewpoint detection device 6 that captures the movement of the driver's 5 eyes. The viewpoint detection device 6 preferably uses a camera capable of photographing from the infrared range to the visible range. Although the viewpoint detection device 6 is attached to a part of the steering wheel in this example, it may be mounted in another position as long as the viewpoint of the driver 5 can be detected. may be attached to part of the

The HUD 1 also includes a projection image camera 28 that captures a projection image on the windshield. The projection image camera 28 is mainly composed of a camera capable of photographing the visible region. An example in which the projection image camera 28 is installed on the dashboard between the steering wheel and the windshield 3 is shown, but it may be installed at another position as long as it can capture the projection image on the windshield 3. For example, the vehicle 2 may be configured to be installed on the ceiling portion in the vehicle.

In addition, the camera used for the projection image camera 28 is not limited to a camera that captures images only in the visible range, but may be one that has sensitivity in the infrared range or the ultraviolet range. You may make it adjust suitably by doing.

When installing (setting) the HUD 1 on the vehicle, a reference image (hereinafter referred to as a "reference image"), for example, a grid-shaped image or a concentric image is displayed on the windshield 3 as a projection image. A projected image camera 28 captures the projected image. Then, the imaging data of the projected image is output to the main controller 20, and the main controller 20 quantitatively measures the displacement of the projected image displayed on the windshield 3 and the extent to which the projected image is distorted. Execute the processing to be performed.

Here, with reference to FIGS. 2 and 3, the general shape of the windshield (also called windshield) of the vehicle 2 and the shape of the display area on the windshield 3 where the virtual image is displayed by the HUD 1 will be described.

FIG. 2 is a top view of a vehicle 2 (passenger car) on which the HUD 1 is mounted. A windshield 3 is present as a projected member in front of the driver's seat of the vehicle 2 . The angle of inclination of the windshield 3 with respect to the vehicle body (the angle of inclination from the perpendicular to the ground surface of the vehicle body) differs depending on the type of vehicle (1-box type, sedan type, sports type, etc.). 20 to 30 degrees, 30 to 40 degrees for sedan types, and 40 degrees or more for sports types. Also, most of the same vehicle, for example, a one-box type, differs depending on the type of vehicle.

FIG. 3 is a diagram showing the shape of the windshield 3. As shown in FIG. In FIG. 3, the longitudinal direction of the vehicle 2 is the x-axis, the width direction of the vehicle 2 is the y-axis, and the height direction of the vehicle 2 orthogonal to the xy plane is the z-axis. According to the inventors' research, the windshield 3 has a horizontal curvature radius Rh parallel to the ground plane (xy plane) of the vehicle 2 and a vertical direction perpendicular to the horizontal axis (y-axis) ( It was found that, unlike the curvature radius Rv in the z-axis direction), Rh and Rv generally have the relationship of the following formula (1).
Rh>Rv (1)

It was also found that the difference in radius of curvature, that is, Rh with respect to Rv, was often in the range of 1.5 to 2.5 times.

Furthermore, according to the inventors' research, the windshield 3 is originally designed and manufactured using the horizontal radius of curvature Rh and the vertical radius of curvature Rv as parameters so that these values fall within a certain range. However, when measuring one lot (for example, 100 sheets) of the windshield 3, the above parameters, that is, the horizontal curvature radius Rh and the vertical curvature radius Rv are different from the target even if the vehicle type is the same. It was found that there is a variation of ±10% to 15% with respect to the design value of .

Therefore, the shape of the windshield 3 is different for each vehicle even if it is the same vehicle type. It was found that the shape also differs depending on the point). As a result, the shape of the projected image on the windshield 3 is not only a change in projection position, but also a point on the windshield 3 with the same coordinates (a point on the windshield 3 indicated by coordinates (y, z)). However, it was found that the radius of curvature Rh in the horizontal direction and the radius of curvature Rv in the vertical direction were different.

Therefore, in this embodiment, the image distortion caused by the deviation of the radius of curvature unique to each windshield 3 from the original design value is detected from the reference image projected on the windshield 3, and the image distortion is corrected. For this reason, the image input to the image display device 30 is subjected to image processing that imparts a reverse distortion in advance, thereby canceling out the distortion. This specific correction method will be described later.

(Rotating Mechanism of Concave Mirror 52)
The position at which the image light is projected onto the windshield 3 , in other words, the display position of the projected image on the windshield 3 is adjusted by the rotation angle of the mirror surface of the concave mirror 52 . Therefore, the rotating mechanism of the concave mirror 52 will be described with reference to FIGS. 4 to 6. FIG. FIG. 4 is an exploded perspective view of the rotating mechanism of the concave mirror 52. As shown in FIG.

As shown in FIG. 4, the HUD 1 comprises a housing by arranging an upper housing 61 on a lower housing 65 . The image display device 30 is attached to the lower housing 65 . The image display device 30 includes a light source and a display element therein. Further, inside the housing, a free-form surface lens 43 as an optical element necessary for correcting chromatic aberration and displaying a virtual image at a distance, a concave mirror 52 and a mirror driving unit 42 for the concave mirror 52, and a main controller 20 and are accommodated. FIG. 5A is a schematic diagram showing a mounting example of the mirror driver 42. As shown in FIG. FIG. 5B is a schematic diagram showing an attachment example of the electric motor 422 and the lower housing 65. As shown in FIG. FIG. 6 is an enlarged view of the connecting portion between the mirror driving portion 42 and the concave mirror 52. As shown in FIG.

The concave mirror 52 is arranged inside the upper housing 61 and the lower housing 65 so as to be rotatable within a slight angular range by a pair of shafts formed on the side surfaces thereof. Furthermore, at the bottom of the lower housing 65, along with the main controller 20, which is an electronic board, the mirror driving section 42 including a movement mechanism such as a motor, a worm gear, and a worm wheel is attached by an attachment/detachment mechanism such as screws. That is, the mirror driving section 42 changes the tilt angle of the concave mirror 52 within a small angular range.

As shown in FIG. 5A, the mirror drive unit 42 includes, in a case 421, at least an electric motor 422 whose rotational speed can be controlled over a wide range from high speed to low speed, a worm gear 423, and an output shaft of the electric motor 422. and a worm gear 423 (see FIG. 6).

As shown in FIGS. 5B and 6, a worm foil 411 is formed at the lower end of the concave mirror 52 . A worm gear 423 is attached so as to mesh with the worm wheel 411 through a partial notch.

The rotation of an electric motor 422 whose rotation can be controlled over a wide range from low speed to high speed by the mirror drive unit 42 is converted into a desired rotational speed and driving force via a plurality of gears 424 and transmitted to the worm gear 423. Further, the worm wheel 411 formed at the lower end of the concave mirror 52 moves the concave mirror 52 forward and backward while rotating around the rotation axis (see arrow A in FIG. 6), thereby moving the concave mirror 52 It can be adjusted to the desired tilt angle. In this figure, the plurality of gears 424 are shown spaced apart for ease of illustration, but they are actually in contact and mesh with each other.

Next, the adjustment of the display position of the virtual image on the HUD 1, the detailed configuration of which has been described above, will be described in detail below with reference to FIG. FIG. 7 is an explanatory diagram for adjusting the display position of the virtual image on the HUD 1. As shown in FIG.

The viewpoint detection device 6 captures an image including the eyes of the driver 5 (referred to as a “viewpoint image”), and transmits the image to the main control device using wireless communication such as CAN (Controller Area Network) or Ethernet (registered trademark) or wired communication. 20. Main controller 20 detects the position of the viewpoint of driver 5 based on the viewpoint image. The main controller 20 controls the tilt angle (also referred to as the rotation angle) of the concave mirror 52 according to the viewpoint position of the driver 5, thereby adjusting the position of the projection image projected onto the windshield 3 of the vehicle 2. . The figure also shows the inclined position of the concave mirror 52, the projection position of the projected image on the windshield 3, the driver's 5 viewpoint, and The positions of the virtual images seen from each starting point of the driver 5 are A, B, C, A', B', C', A'', B'', C'', A''', B'', respectively. ', C'''.

Here, as described above, the viewpoint positions A'', B'', and C'' of the driver detected by the viewpoint detection device 6, and the positions A''' and B''' of the virtual images seen by the driver. , C''' correspond one-to-one. Similarly, the positions A', B', and C' of the projection images projected on the windshield also have a one-to-one relationship with the driver's viewpoint positions A'', B'', and C''.

On the other hand, the projection image camera 28 has a function of quantitatively detecting the positions A', B', and C' and the shape of the projection image by photographing the projection image projected onto the windshield. have.

Therefore, it can be said that the viewpoint detection device 6 and the projection image camera 28 have a relationship of complementing each other's functions.

That is, the main controller 20 adjusts the position of the virtual image seen by the driver 5 by controlling the angle of the concave mirror 52 according to the change in the viewpoint of the driver 5 based on the viewpoint image from the viewpoint detection device 6. On the other hand, the main controller 20 captures a reference image captured by the projection image camera 28 on the windshield 3, and based on the captured data, determines the position of the projection image projected on the windshield 3, Also, the distortion of the projected image can be quantitatively detected, and based on this information (the position and distortion of the projected image), it is possible to contribute to the position adjustment and distortion correction of the image including the display content.

Functional configurations of the main controller 20 and the viewpoint detection device 6 will be described with reference to FIGS. 8A and 8B. FIG. 8A is a block diagram showing an example of connection between main controller 20 and various vehicle devices. FIG. 8B is a functional configuration diagram of main controller 20. As shown in FIG.

As shown in FIG. 8A, the main controller 20 is connected to an in-vehicle network (eg, CAN) 108 and acquires vehicle information 4 (see FIG. 8B) via the in-vehicle network 108 . The vehicle information 4 is obtained from information acquisition devices connected to an in-vehicle network, such as a vehicle speed sensor 101, a shift position sensor 102, a steering angle sensor 103, a headlight sensor 104, an illumination sensor 105, a chromaticity sensor 106, and an engine start sensor 109. , an acceleration sensor 110, a gyro sensor 111, a temperature sensor 112, a road-to-vehicle communication radio receiver 113, a vehicle-to-vehicle communication radio receiver 114, an exterior camera 116, a GPS receiver 117, and a VICS (registered trademark) receiver 118. .

As shown in FIG. 8B , the main controller 20 is configured using hardware including an ECU 21 configured from a CPU (Central Processing Unit), etc., a nonvolatile memory 22 and a memory 23 . The functions of the HUD 1 are realized by the ECU 21 executing software stored in the nonvolatile memory 22 and the memory 23 . It may be implemented by hardware such as a microcomputer or FPGA (Field Programmable Gate Array).

The main controller 20 also includes a viewpoint detection control section 34 , a projection image camera control section 24 , a light source adjustment section 25 , a distortion correction section 26 , a display element drive section 27 and a mirror adjustment section 29 . These include hardware such as a communication device and an amplifier, image processing, distance measurement processing, and software outputting to each actuator (for example, the light source 31, the display element 33, and the electric motor 422 of the mirror driving section 42).

The viewpoint detection device 6 includes a ranging sensor 603 , a viewpoint detection camera 604 and an infrared LED 615 .

The viewpoint detection control unit 34 controls the viewpoint detection camera 604 to photograph the face of the driver 5, analyzes the image by software or a hardware accelerator, and calculates the position of the viewpoint.

A distance measuring sensor 603 is provided to grasp the position of the driver 5 in the depth direction. That is, when the position of the driver 5 (for example, the head) is detected only by the camera image, the distance in the depth direction is unknown, and sufficient accuracy cannot be obtained. Therefore, the distance sensor 603 measures the distance to the head of the driver 5 and outputs the data to the viewpoint detection control unit 34 . The viewpoint detection control unit 34 detects the position of the viewpoint of the driver 5 viewed from the viewpoint detection device 6 by combining the image analysis result and the distance measurement data.

Further, when the illuminance detected by the illuminance sensor 105 becomes equal to or less than a predetermined illuminance threshold, the ECU 21 turns on the infrared LED 615 via the viewpoint detection control section 34 . Thereby, the viewpoint of the driver 5 is detected in a dark environment such as at night.

The ECU 21 stops the viewpoint detection device 6 when the steering angle of the steering wheel detected by the steering wheel steering angle sensor 103 is greater than or equal to a predetermined steering angle threshold value. Depending on the steering angle of the steering wheel, the viewpoint detection camera 604 may be hidden by the steering wheel, and the driver 5 cannot be recognized.

<Target position (display position of virtual image)>
Next, with reference to FIGS. 9 and 10, the optimal display position (hereinafter referred to as "target position") of the virtual image with respect to the viewpoint of the driver 5 will be described. FIG. 9 is an explanatory diagram showing the correspondence relationship between the target position on the HUD 1 and the position of the driver's head. FIG. 10 is an explanatory diagram showing the correspondence relationship between the target position and the depression angle θ on the HUD 1. As shown in FIG.

When displaying the projected image on the windshield 3, it is important to consider the position of the head of the driver 5 and the angle of depression θ from the viewpoint of the driver 5 (see FIG. 10). The depression angle θ is an angle for visualizing the virtual image at the optimum position. The AR-HUD superimposes (maps) a virtual image on the vehicle in front and on pedestrians and the like present around the vehicle. Therefore, it is necessary to define the depression angle θ in order to perform this mapping accurately.

First, the visual range of the virtual image changes according to the position of the driver's 5 head. For example, when the head of the driver 5 is in the upper position ((1) in FIGS. 9 and 10), the position of the concave mirror 52 (mirror position A, mirror position According to B), the position where the projected image is projected on the windshield 3, that is, the visual range of the virtual image is the range shown on the left side of the figure. On the other hand, when the head of the driver 5 is in the lower position ((2) in FIGS. 9 and 10), the position of the concave mirror 52 (mirror position A, mirror The visual range of the virtual image corresponding to the position B) is the range shown on the left side of the figure.

In addition, especially when it is optimal to display the virtual image at the position of the depression angle θ, it is preferable to set the target position as follows.
1. If the position of the depression angle θ is within the visual range of the virtual image, the depression angle θ is set as the target position.
2. If the position of the depression angle θ is lower than the lower limit of the visual range of the virtual image, the lower limit of the visual range of the virtual image is set as the target position.
3. When the position of the depression angle θ is higher than the upper limit of the visual range of the virtual image, the upper limit of the visual range of the virtual image is set as the target position.

That is, as shown in FIGS. 10A and 10B, the position of the depression angle θ within the visual range of the virtual image shown in FIGS. )), and if it is lower than the lower limit of the visual range of the virtual image, the lower limit of the visual range of the virtual image is set as the target position (see FIG. 10(b)). If the position is higher than the upper limit of the visual range of the virtual image, the upper limit of the visual range of the virtual image is set as the target position.

As described above, the visual range of the virtual image should be controlled so as to set the target position by controlling the position of the concave mirror 52 in consideration of the position of the head of the driver 5 and the position of the depression angle θ associated therewith. For example, it is possible to more preferably display a virtual image on the HUD.

<Distortion correction of projected image for each vehicle>
FIG. 11 is a diagram showing an example of a windshield shape that deviates from the design center value of the radius of curvature. In FIG. 11, the dashed line shows the windshield 301 which actually has a smaller radius of curvature Rv' than the windshield 3 which has the vertical radius of curvature Rv as its design center value. Note that FIG. 11 exaggerates the difference in radius of curvature. It is known that the normal windshield 3 has a shape variation of about ±10% with respect to the design value of the radius of curvature.

As is clear from FIG. 11, when the radius of curvature Rv' of the windshield is smaller than the radius of curvature Rv that is the design center value, the image projected on the windshield 301 deviates greatly upward from the driver's perspective. In addition, the shape of the image is shorter in the vertical direction than the image projected on the windshield 3 .

In the opposite case, that is, when the radius of curvature Rv' of the windshield is larger than the radius of curvature Rv which is the design center value, the image projected on the windshield is downward when viewed from the driver. It is displayed at a shifted position, and its shape is longer in the vertical direction than the image projected on the windshield 3 .

FIG. 12 is a view of the displacement of the projected image on the windshield and the distortion of the projected image observed from the driver's side (inside the vehicle). FIG. 12(a) is a diagram schematically showing how a display image projected onto the windshield 3 is seen from the driver, and FIG. 12(b) is a display image projected onto the windshield 301. FIG. is a diagram schematically showing the state seen from the driver's side as well.

As shown in FIG. 12(a), the image on the windshield 3 displayed without distortion is essentially rectangular in shape.

On the other hand, as shown in FIG. 12(b), the shape of the windshield 301 is significantly different from the original shape. It is shorter, and the lengths of the upper and lower sides are also different. In this case, the upper side is shorter than the lower side.

Further, as described with reference to FIG. 11, when the radius of curvature Rv′ of the windshield 301 is smaller than the original design center value, the projection on the windshield 301 becomes The image is also displayed with its display position shifted upward as viewed from the driver 5 .

Therefore, in order to correct the display position from the projection image 301a shown in FIG. Each step must be processed.

Next, display position correction and distortion correction processing of a projection image will be described with reference to FIGS. 13 and 15. FIG. FIG. 13 is a flowchart for explaining the flow of processing for correcting the display position of the projected image on the windshield 301 and correcting the distortion of the projected image. FIG. 14 is a flowchart showing details of projection image correction data generation processing. FIG. 15A is a diagram showing an example of a grid-shaped reference image, and FIG. 15B is a diagram showing an example of a concentric circle-shaped reference image.

As shown in FIG. 13, the processing for correcting the display position of the projected image and the image distortion due to the distortion of the windshield 3 unique to each vehicle can be roughly divided into the projection image correction according to the shape of the windshield 3 for each vehicle. There are a step (S1) of generating and storing data, and a step (S2) of correcting the display position and image distortion of the projection image using the projection image correction data during operation. Generating the projection image correction data corresponds to calibration processing of the virtual image display position of the HUD 1 .

The distortion correction of the projected image on the windshield 3 must be performed for each vehicle in the manufacturing process of the vehicle, for example. Alternatively, if the HUD 1 must be replaced for some reason, it will be necessary to correct the distortion of the projected image after the HUD 1 is attached to the vehicle. Therefore, in this embodiment, step S1 will be described as a step that is mainly executed in the vehicle factory.

However, it is conceivable that the image distortion of the projected image occurs due to some cause (for example, displacement of the mounting position of the HUD 1, change in the shape of the windshield 3 due to changes in temperature, etc.). Therefore, image distortion correction may be performed each time the vehicle is started to operate. In this case, step S1 is executed again after step S2.

Furthermore, even when the vehicle 2 is being driven, the shape of the optical components and the windshield 3 that make up the HUD 1 may change due to changes in the outside air temperature, even if the change is very small. When the vehicle is parked, while the vehicle is waiting for a signal, or according to the driver's operation, the distortion correction may be appropriately performed. In this case, step S2 and step S1 are alternately performed within a relatively short period of time.

Step S2 is a step of correcting the display position and image distortion of the projection image using the projection image correction data generated in step S1. This process is executed while the vehicle is actually being driven after shipment. Conventionally, for the same vehicle, projection image correction data is generated and stored based on the design center value, but this does not correct the variation in the shape inherent to the windshield 3 . This embodiment is characterized in that projection image correction data is generated and stored for each vehicle regardless of whether the vehicle is the same or different, and the projection image is corrected using the projection image correction data during driving. . Details will be described later.

The projection image correction data generation process will be described with reference to FIG.

The ECU 21 projects a reference image onto a first target position (xg1, yg1) on the windshield 3 ((xg, yg) are coordinates indicating a point on the windshield 3) in accordance with an operation instruction from the operator (S101 ). The ECU 21 temporarily stores in the memory 23 the angle α1 of the concave mirror 52 when the image light is emitted to the first target position (xg1, yg1). The reference image has a constant area, and a plurality of areas arranged at equal intervals in the reference image is used. For example, the reference image may be a grid-shaped reference image 3b (see FIG. 15A) or a concentric circular reference image 3c (see FIG. 15B). This makes it easier to measure the distortion in the horizontal and vertical directions of the position where the reference image is projected on the windshield 3 .

The ECU 21 causes the projection image camera 28 to capture a reference image projected onto the windshield 3 (S102). Next, the projection image camera 28 sends information on the captured projection image to the ECU 21 .

The ECU 21 detects the display position (xg1', yg1') indicating the position on the windshield 3 where the reference image is displayed from the projection image information sent from the projection image camera 28 (S103). Then, the amount of positional deviation (Δxg1′, Δyg1′) of the actual display position (xg1′, yg1′) with respect to the target position (xg, yg) is calculated. Then, a correction amount (-Δxg1', -Δyg1') that cancels out this positional deviation amount is calculated.

When the adjustment of the reference image position is completed, the ECU 21 calculates the distortion correction amount using the reference image (S104). The ECU 21 compares the projection image with the normal shape of the reference image for each rotation angle α of the concave mirror 52, and detects the image distortion amounts (ΔRv1, ΔRh1) at each display position. Then, distortion correction amounts (-ΔRv1, -ΔRh1) are calculated from horizontal and vertical enlargement/reduction ratios (amounts of curvature difference cancellation) that cancel out the image distortion.

The ECU 21 generates first target position projection image correction data (α1, −Δxg1′, −Δyg1′, −Δyg1′, -ΔRv1, -ΔRh1) are temporarily stored in the memory 23 (S105).

When using the grid-shaped reference image shown in FIG. 15A, it is necessary to align all the positions of the points where the line segments intersect with the reference position. However, there is an advantage that the distortion correction amounts (-ΔRv1, -ΔRh1) at a plurality of points can be calculated with respect to the display position (xg1, yg1).

On the other hand, when the concentric circular image shown in FIG. 15B is used as the reference image, a plurality of circles (here, three The ECU 21 first aligns the centers of the three circles, and then corrects the distortion so that the radii of the three circles match the reference value. than is possible.

Then, the processing from step S101 to step S105 is continuously performed until all angles αn at which the concave mirror 52 can rotate are completed (S106: No).

The ECU 21 adjusts the angle of the concave mirror 52 so that the rotation angle α2 corresponds to the second target position (xg2, yg2) (S107).

The mirror adjustment unit 29 generates a motor control signal for the electric motor 422 based on the information indicating the rotation angle α2 of the concave mirror 52 sent from the ECU 21 and sends the electric motor 422 . The electric motor 422 is driven according to the motor control signal to adjust the rotation angle of the concave mirror 52 . Through the above control, the concave mirror adjusts the reference image position.

After that, the process returns to step S101. When executing step S101 again, the ECU 21 analyzes the projection image information output by the projection image camera 28 to detect the display position of the reference image. You may make it detect whether it is settled in. The correction amount of the shape distortion of the windshield 3 at the second target position, that is, the second target position projection image correction data (α2, -Δxg2', -Δyg2', -ΔRv2, -ΔRh2) is temporarily stored in the memory 23. .

When all rotatable angles αn of concave mirror 52 are completed (S106: Yes), target position projection images (α1, −Δxg1′, −Δyg1′, −ΔRv1, −ΔRh1 ) to (αn, −Δxgn′, −Δygn′, −ΔRvn, −ΔRhn) are combined and written in the nonvolatile memory 22 as projection image correction data (S108). The nonvolatile memory 22 corresponds to a projection image correction data storage unit.

The projection image correction data may be the measurement data itself from (α1, -Δxg1, -Δyg1, -ΔRv1, -ΔRh1) to (αn, -Δxgn-Δ, ygn, -ΔRvn, -ΔRhn). This is because no correction is required below the angular resolution of the concave mirror 52, so even with measurement data consisting of discrete points, it is possible to correct the shape distortion unique to the windshield 3. FIG.

The ECU 21 may interpolate the non-measured points using actual measurement data, generate projection image correction data having continuity, and then write the data in the non-volatile memory 22 .

As described above, the ECU 21 refers to the projection image correction data to determine the rotation angle α of the concave mirror 52 for displaying the projection image at the desired point (xg, yg) on the windshield 3. It is possible to control the projection position on the windshield 3 of . Furthermore, by correcting the display content so as to cancel out the shape distortion of the windshield 3 at the rotation angle α and then projecting it, the projected image is the same as the display content regardless of the shape distortion of the windshield 3. It can be displayed in its original form.

Although the invention made by the present inventor has been specifically described above based on the embodiments, the present invention is not limited to the above embodiments, and can be variously modified without departing from the scope of the invention. Needless to say. For example, the above embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. That is, part of the configuration of the above embodiments can be deleted or replaced with other equivalent techniques.

1: HUD
2: Vehicle 3: Windshield 3a: Projected image 3b: Reference image 3c: Reference image 4: Vehicle information 5: Driver 6: Viewpoint detection device 20: Main control device 21: ECU
22 : non-volatile memory 23 : memory 24 : projection image camera control unit 25 : light source adjustment unit 26 : distortion correction unit 27 : display element drive unit 28 : projection image camera 29 : mirror adjustment unit 30 : image display device 31 : light source 33 : Display element 34 : Viewpoint detection control unit 42 : Mirror drive unit 43 : Free curved lens 52 : Concave mirror 61 : Upper housing 65 : Lower housing 101 : Vehicle speed sensor 102 : Shift position sensor 103 : Steering wheel steering angle sensor 104 : Headlight sensor 105 : Illuminance sensor 106 : Chromaticity sensor 108 : In-vehicle network 109 : Engine start sensor 110 : Acceleration sensor 111 : Gyro sensor 112 : Temperature sensor 113 : Wireless receiver for road-vehicle communication 114 : Wireless receiver for vehicle-to-vehicle communication Machine 116 : External camera 117 : GPS receiver 118 : Receiver 301 : Windshield 301a : Projected image 411 : Worm wheel 421 : Case 422 : Electric motor 423 : Worm gear 424 : Gear 603 : Ranging sensor 604 : Viewpoint detection camera 615 : Infrared LED

Claims (6)

A head-up display mounted on a vehicle,
a video display device that generates and emits video light including display content to be displayed as a virtual image;
a virtual image optical system that projects the image light toward the windshield of the vehicle;
a viewpoint detection device that detects the viewpoint of the observer of the virtual image;
A display position on the windshield of a projected image composed of an image of the display content connected to the video display device, the virtual image optical system, and the viewpoint detection device, and appearing when the video light is incident on the windshield. and a main controller that performs image distortion correction of the projected image,
The main control unit generates projection image correction data that defines a correction amount for offsetting the display position deviation of the projection image and the image distortion of the projection image due to the shape distortion specific to the windshield mounted on the vehicle. including a projection image correction data storage unit for storing,
The main controller determines a target position on the windshield where the image light is to be projected in accordance with the data obtained by detecting the viewpoint of the observer by the viewpoint detection device, and reproduces the projection image at the target position. correcting the image distortion of the display content using a correction amount for canceling the image distortion, emitting the image light including the display content corrected for the image distortion from the image display device, and The virtual image optical system uses a correction amount that offsets the amount of displacement of the projected image at the target position so that the image light including the display content corrected for the image distortion is reflected toward the target position. to control the
A head-up display characterized by In the head-up display according to claim 1,
further comprising a projection image camera that captures the projection image, the projection image camera being connected to the main controller;
With the head-up display mounted on the vehicle,
The image display device generates image light including a reference image having a known shape,
The virtual image optical system emits light toward each of a plurality of target positions of the windshield,
The projection image camera obtains the projection image obtained by capturing the reference image reflected on the windshield at each of the target positions,
Based on the projection images captured at each of the target positions, the main controller determines a positional deviation amount of the display position of the reference image captured in the projection image with respect to the target position, and a known value of the reference image. calculating an image distortion amount of the shape of the reference image captured in the projection image for the shape, calculating a projection image correction amount that offsets the positional deviation amount and the image distortion amount, and calculating the target position of the windshield; , generating the projection image correction data by associating the projection image correction amount calculated at the target position;
A head-up display characterized by In the head-up display according to claim 2,
The main controller generates the projection image correction data at a target position in the entire range in which the virtual image optical system can reflect the image light.
A head-up display characterized by In the head-up display according to claim 2,
The main controller controls, as the projection image correction amount at the target position, the distortion with respect to the design center value of the vertical radius of curvature of the windshield at the target position, and the design center of the horizontal radius of curvature of the windshield. calculate a correction amount that cancels out the distortion for the value,
A head-up display characterized by In the head-up display according to claim 3,
The virtual image optical system includes a concave mirror that reflects the image light emitted from the image display device toward the windshield, and a mirror driving unit that rotates the concave mirror around a rotation axis,
The main controller outputs a control signal to the mirror driving unit for rotating the concave mirror to an angle at which the image light is reflected toward the target position.
A head-up display characterized by A calibration method for a head-up display mounted on a vehicle, comprising:
a step of emitting video light including a reference image having a known shape from a head-up display mounted on a vehicle toward a first target position on the windshield of the vehicle;
capturing the reference image reflected on the windshield at the first target position to generate a projected image;
Based on the projection image imaged at the first target position, the displacement amount of the display position of the reference image imaged in the projection image with respect to the first target position, and the known shape of the reference image calculating an image distortion amount of the shape of the reference image captured in the projection image, calculating a projection image correction amount that offsets the positional deviation amount and the image distortion amount, and calculating the first target position of the windshield; generating first target position projection image correction data by associating the projection image correction amount calculated at the first target position;
a step of emitting video light including a reference image having a known shape from the head-up display toward a second target position different from the first target position;
capturing the reference image reflected on the windshield at the second target position to generate a projected image;
Based on the projection image imaged at the second target position, the positional deviation amount of the display position of the reference image imaged in the projection image with respect to the second target position and the known shape of the reference image calculating an image distortion amount of the shape of the reference image captured in the projection image, calculating a projection image correction amount that offsets the positional deviation amount and the image distortion amount, and calculating the second target position of the windshield; generating second target position projected image correction data by associating the projected image correction amount calculated at the second target position;
a step of generating and storing projection image correction data including the first target position projection image correction data and the second target position projection image correction data for correcting shape distortion inherent in the windshield mounted on the vehicle; ,
A calibration method for a head-up display, comprising:

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