WO2020255982A1

WO2020255982A1 - Method for designing head-up display and head-up display

Info

Publication number: WO2020255982A1
Application number: PCT/JP2020/023666
Authority: WO
Inventors: 健川合
Original assignee: 日本精機株式会社
Priority date: 2019-06-20
Filing date: 2020-06-17
Publication date: 2020-12-24
Also published as: JPWO2020255982A1

Abstract

Provided are a method for designing a head-up display and a head-up display with which it is possible to maintain a high display quality of a display image regardless of the position of an eye point. The shape of an optical system (13) is determined to minimize the difference between a first calculated value for an index value (Mv) associated with a display image when viewed from a first eye point (EP1) lower than a standard eye point (EP) and a second calculated value for the index value (Mv) when viewed from a second eye point (EP2) higher than the standard eye point (EP) on the basis of information relating to the radius of curvature of a windshield (14).

Description

Head-up display design method and head-up display

This disclosure relates to a head-up display design method and a head-up display.

A head-up display having a display that emits display light and a concave mirror that is rotatably provided with respect to the vehicle body and reflects the display light emitted from the display toward a windshield (front windshield) is known. ing. The driver of the vehicle can obtain information necessary for driving by visually recognizing the display image (virtual image) of the display reflected on the windshield.

Normally, in a head-up display, the position of the viewpoint (eye point) where a virtual image can be visually recognized is adjusted to the height of the driver's eyes by changing the position of the windshield on which the display light is projected by rotating the concave mirror. Can be adjusted.

Japanese Unexamined Patent Publication No. 2003-107391

The conventional head-up display has a problem that the display quality of the virtual image differs within the adjustable eye point range.

An object of the present disclosure is to provide a head-up display design method and a head-up display that can maintain high display quality of a display image regardless of the position of the eye point.

On one side,
It is a design method of a head-up display (1) that projects a display image onto a windshield (14) via an optical system (13) that converges light.
Based on the radius of curvature information of the windshield (14), the first calculated value (Mv) of the index value (Mv) related to the display image when viewed from the first eye point (EP1) lower than the standard eye point (EP). The optical system (1) so as to minimize the difference between the index value (Mv) and the second calculated value when viewed from the second eye point (EP2) higher than the standard eye point (EP). A design method including the step of determining the shape of 13) is provided.

According to the present disclosure, a head-up display design method and a head-up display capable of obtaining high display quality regardless of the position of the eye point are provided.

It is a figure which shows the structure of the head-up display of this Example. It is a figure which shows the relationship between a virtual image and an eye box. It is a figure which shows the positional relationship of the eye points EP, EP1, EP2 and the corresponding virtual images IM, IM1, IM2 when the direction of the concave mirror 13 is changed according to the eye point. It is a figure which shows the parameter used in the design of a head-up display 1. It is a figure which shows the vertical radius Rci of a concave mirror 13. It is a figure which shows the part to be calculated. It is a figure which shows the state that the concave mirror 13 is rotated when the original eye point EP is changed to the temporary eye point EPA.

Hereinafter, each embodiment will be described in detail with reference to the attached drawings.

FIG. 1 is a diagram showing a configuration of a head-up display of this embodiment. The head-up display 1 includes a display 11, a plane mirror 12, and a concave mirror 13 as an optical system for converging light.

A predetermined display image (for example, a display image showing information necessary for driving a vehicle) is displayed on the display screen 11a of the display device 11. The display size of the display image displayed on the display screen 11a is variable for each display area. As a result, it is possible to suppress distortion of the display image finally viewed by the driver. For example, the display image can be displayed so that the display size (display magnification) in the vertical direction differs depending on the display area of the display image. The upper display size is enlarged or reduced than the lower display size. Similarly, the display size may be variable in the horizontal direction.

The display light emitted from the display screen 11a of the display 11 is converged and reflected by the concave mirror 13 rotatably attached to the vehicle body, and is irradiated to the windshield (front windshield) 14 of the vehicle. The concave mirror 13 has a function of magnifying the displayed image. Further, the concave mirror 13 has a function of suppressing distortion of the display image due to reflection by the windshield 14. Further, the concave mirror 13 has a function of equalizing the focal length (distance from the driver's eyes to the virtual image of the display image) in the entire display image so as to approach a predetermined distance. As the optical system for converging light, a lens optical system (for example, a convex lens) may be used instead of the concave mirror 13.

A part of the display light emitted to the windshield 14 is reflected by the windshield 14 and heads for the eye point EP. The eyepoint EP indicates, for example, the standard position of the eyes of the driver of the vehicle. Specifically, for example, it is the central position of the range of the eye point that can be adjusted by rotating the concave mirror 13. The driver can visually recognize the virtual image of the display image reflected on the windshield 14 from the vicinity of the eye point EP.

Note that in FIG. 1, the components of the head-up display 1 are two-dimensionally arranged on a flat surface (paper surface of FIG. 1). However, in reality, these components can be arranged three-dimensionally.

The eye point EP1 shown in FIG. 1 indicates a first eye point located at a lower position in the vertical direction of the vehicle than the eye point EP. The eye point EP1 corresponds to the lowest position in the vertical direction of the vehicle in the range of the eye point that can be adjusted by rotating the concave mirror 13. Further, the eye point EP2 shown in FIG. 1 indicates a second eye point located higher than the eye point EP in the vertical direction of the vehicle. The eye point EP2 corresponds to the highest position in the vertical direction of the vehicle in the range of the eye point that can be adjusted by rotating the concave mirror 13. The height of the eye point depends on the driver. The eye point EP1 corresponds to the case where the eye position is low, and the eye point EP2 corresponds to the case where the eye position is high.

FIG. 2 is a diagram showing the relationship between the virtual image and the eye box. In FIG. 2, the eye box EB shows a range in which the virtual image IM of the display image reflected on the windshield 14 can be visually recognized.

The concave mirror 13 can be rotated in a predetermined direction (for example, an axial direction orthogonal to the paper surface of FIG. 1). By changing the direction of the concave mirror 13, the eyebox EB is set at a position corresponding to the height of the driver's eyes.

FIG. 3 is a diagram showing the positional relationship between the eye points EP, EP1, EP2 and the corresponding virtual images IM, IM1, and IM2 when the orientation of the concave mirror 13 is changed according to the eye point. By changing the direction of the concave mirror 13 according to the height of the eyes in this way, the virtual images IM, IM1 and IM2 can always be reflected on the windshield 14. Instead of changing the direction of the concave mirror 13, a rotatable reflecting surface (not shown) may be provided in the optical path of the display light, and the direction of the reflecting surface may be changed. The same applies when a lens optical system is used instead of the concave mirror 13.

By the way, the radius of curvature of the windshield 14 is not constant in the entire windshield 14. For example, in the front windshield of a vehicle, the radius of curvature in the vertical direction at the upper part is often smaller than the radius of curvature at the lower part. The radius of curvature in the lateral direction of the front windshield also changes depending on the position in the lateral direction (width direction of the vehicle), but usually, the change in the vertical direction is particularly large. Therefore, when the height of the eye point changes, the display state of the display image tends to change significantly. That is, the height of the area where the front windshield is used as the reflective surface changes according to the height of the eye point. Therefore, since the radius of curvature in the vertical direction in the region changes, it becomes difficult to maintain the display quality when the height of the eye point changes. Specifically, astigmatism and image shift occur in the displayed image, making it difficult to clearly see the displayed image, or the displayed image is distorted and visually recognized.

This disclosure takes such a problem into consideration, and provides a method for designing a head-up display that can suppress deterioration of the display quality of the display image even when the height of the eye point changes.

The distribution of the radius of curvature in the windshield 14, especially the radius of curvature in the vertical direction, is known. For example, in manufacturing, the distribution of the radius of curvature of the windshield 14 is controlled to be a constant distribution. Alternatively, when designing the head-up display 1, the distribution of the radius of curvature in the windshield 14 is measured and stored in advance for at least the entire range used for displaying the display image.

Next, the design method of the head-up display 1 will be described.

FIG. 4 is a diagram showing parameters used in the design of the head-up display 1. In FIG. 4, the light ray 50 connecting the light emitting point 51 of the display screen 11a of the display 11 to the eye point EP is shown by a solid line. In FIG. 4, the components of the head-up display 1 are arranged on a virtual two-dimensional plane (paper surface) so that the light rays 50 are located on the paper surface. The vertical direction of FIG. 4 corresponds to the vertical direction of the windshield 14.

As shown in FIG. 4, a light ray 50 is emitted from a light emitting point 51 on the display screen 11a of the display 11. The light ray 50 is sequentially bent at the incident point 52 of the plane mirror 12 and the incident point 53 of the concave mirror 13. Further, the light ray 50 is bent at the incident point 54 of the windshield 14 to reach the eye point EP.

Here, the display distance L1 is the distance from the eye point EP to the virtual image IM. The distance L2 is the distance from the eye point EP to the incident point 54. The distance L3 is the distance from the incident point 54 to the incident point 53. The distance L4 is the distance from the incident point 53 to the light emitting point 51.

Further, the incident angle θ1 is the incident angle of the light ray 50 on the windshield 14. The incident angle θ2 is the angle of incidence of the light ray 50 on the concave mirror 13. The tilt angle θ3 is an angle formed by the normal line of the plane corresponding to the display screen 11a of the display 11 and the light ray 50. The incident angle θ1, the incident angle θ2, and the tilt angle θ3 are all angles corresponding to the vertical direction (vertical direction) of the windshield 14.

The vertical angle of view Vdo is the vertical angle of view at the eye point EP. The size Vmo is the ideal display image vertical size of the virtual image IM. The vertical radius Rwi is the vertical radius (radius in the vertical direction) of the windshield 14. The focal length Fw is the vertical focal length (focal length in the vertical direction) of the windshield 14. The distance L5 is the distance from the windshield 14 to the virtual image IM'formed by the concave mirror 13. The size Vc is the vertical size of the virtual image IM'formed by the concave mirror 13. The focal length Fc is the vertical focal length (focal length in the vertical direction) of the concave mirror 13. The vertical radius Rci is the vertical radius (radius in the vertical direction) of the concave mirror 13. The display size Di is a display size (display magnification) in the vertical direction of the display image displayed on the display screen 11a.

FIG. 5 is a diagram showing the vertical radius Rci of the concave mirror 13. As shown in FIG. 5, a circle having a radius Rci whose center is the point Pr comes into contact with the concave mirror 13 at the incident point 53. That is, the vertical radius Rci indicates the radius of curvature in the vertical direction at the incident point 53 of the concave mirror 13. Similarly, the longitudinal radius Rwi indicates the radius of curvature in the longitudinal direction at the incident point 54 of the windshield 14.

Next, an example of the procedure for designing the head-up display 1 is shown.

In this embodiment, the shape of the concave mirror 13 is calculated so that the display distance L1 is the same at a plurality of places in the display area (eye box). Specifically, the vertical radius Rci is calculated so that the same display distance L1 is obtained at each of the four corners of the display area (eye box). In addition, the display size Di at which the vertical angle of view Vdo at the eye point EP is obtained at each of the four corners of the display area is calculated.

FIG. 6 is a diagram showing a part to be calculated. That is, i = 1 indicates the upper left part, i = 2 indicates the upper right part, i = 3 indicates the lower left part, and i = 4 indicates the lower right part. The "i" attached to each parameter (vertical radius Rwi, vertical radius Rci, display size Di) indicates these parts. Although the part to be calculated is arbitrary, it is usually in the peripheral region of the display image that the distortion and astigmatism of the display image appear significantly. Therefore, it is desirable that the peripheral region of the display image, for example, the four corners of the display image or the parts close to the four corners are selected as the parts for performing the calculation.

As shown in FIG. 4, equation (1) holds.

Vmo = 2 × L1 × tan (Vdo / 2) ... (1) Equations (2) to (7) are established.

Here, for each of i = 1 to 4, the vertical radius Rci of the concave mirror 13 and the display size Di on the display screen 11a are calculated using the equations (1) to (7).

Next, using the vertical radius Rci of the concave mirror 13 obtained by the equations (6) and (7) and the display size Di on the display screen 11a, the scaling factor of the display image at the eyepoint EP1 and the eyepoint EP2 is calculated. To do. Here, too, the scaling factor of the displayed image is calculated for each of the four corners of the display area, that is, i = 1 to 4, for each of the displayed images at the eye point EP1 and the eye point EP2. This calculation is performed using equations (8) to (16).

Here, the magnifying magnification Mw is the magnifying magnification of the display image due to reflection by the windshield 14. The display image vertical size Vm is the vertical size (vertical size) of the display image. The display image vertical angle of view Mv of the formula (16) is a scaling factor (%) of the display image.
Next, the scaling factor of the displayed image at the eye point EP1 and the scaling factor of the displayed image at the eye point EP2 are compared. Then, among the four corners of the display area, that is, i = 1 to 4, the portion where the change in the scaling ratio of the display image is the largest is selected. Specifically, for i = 1 to 4, the difference between the scaling factor of the displayed image at the eye point EP1 and the scaling factor of the displayed image at the eye point EP2 is calculated. Then, the portion Pmax (for example, i = 1) having the largest absolute value of the difference is selected.

In this embodiment, it is aimed to equalize the scaling factor Mw of the displayed image at the site Pmax at the eye point EP1 and the scaling factor Mw of the displayed image at the site Pmax at the eye point EP2. That is, the goal is that the size of the displayed image at the site Pmax is the same regardless of whether the image is viewed from the eye point EP1 or the eye point EP2.

Therefore, it is necessary to obtain the vertical radius Rwi'of the windshield 14 at the temporary eye point EP'that makes the above difference zero. Therefore, in the equations (1) to (7), a calculation (simulation) is performed in which the vertical radius Rwi of the windshield 14 of the portion Pmax (for example, i = 1) is changed to the vertical radius Rw'(arbitrary value). By this calculation, the vertical radius Rc'of the concave mirror 13 and the display size D'on the display screen 11a are calculated.

Next, using the calculated vertical radius Rc'and the display size D'on the display screen 11a, the calculation is performed using the equations (8) to (16). By this calculation, the scaling factor Mv1'of the displayed image at the site Pmax at the eye point EP1 and the scaling factor Mv2'of the displayed image at the site Pmax at the eye point EP2 can be obtained.

In this way, while changing the provisional eye point EP', the scaling factor Mv1' of the displayed image at the site Pmax at the eye point EP1 and the scaling factor Mv2' of the displayed image at the site Pmax at the eye point EP2 are calculated. repeat. Finally, at the provisional eye point EP', where the scaling factor Mv1'of the displayed image at the site Pmax at the eye point EP1 and the scaling factor Mv2'of the displayed image at the site Pmax at the eye point EP2 are equal. The vertical radius RAwi of the windshield 14 is required. The algorithm for obtaining the solution of the longitudinal radius RAwi of the windshield 14 at which the scaling factors Mv'of the displayed image at the site Pmax are equal at the eye point EP1 and the eye point EP2 is arbitrary.

Next, if the vertical radius RAwi of the windshield 14 is determined, a temporary eye point EPA will be determined. In the temporary eye point EPA, the vertical radius at the intersection of the line connecting the eye box EB and the virtual image IM and the windshield 14 at the site Pmax is approximately the vertical radius RAwi of the windshield 14. It is a point. As a result, the angle of the concave mirror 13 at the temporary eye point EPA, the position of the eye box EB, and the position of the virtual image IM are determined. FIG. 7 is a diagram showing how the concave mirror 13 is rotated when the original eye point EP is changed to the temporary eye point EPA. In this way, the angle of the concave mirror 13 is set to an angle adjusted to the temporary eye point EPA. Instead of changing the direction of the concave mirror 13, a rotatable reflecting surface (not shown) may be provided in the optical path of the display light, and the direction of the reflecting surface may be changed. The same applies when a lens optical system is used instead of the concave mirror 13.

Once the temporary eye point EPA is determined, the shape of the concave mirror 13 is optimized. Specifically, the shape of the concave mirror 13 is adjusted so that the display distance when the virtual image IM is viewed from the eye box EB corresponding to the temporary eye point EPA matches the target distance (distance L1). Further, the shape of the concave mirror 13 is adjusted so that the distortion of the displayed image is reduced. Here, for example, while changing the radius of curvature (for example, the vertical radius Rc) of each part of the concave mirror 13 corresponding to each part of the display image (each part of the eyebox EBA corresponding to the eyepoint EPA), the equations (1) to (7). ) Repeat the simulation using the equation corresponding to the equation. Then, the optimum solution of the radius of curvature of each part of the optimum concave mirror 13 is obtained. Regarding the display size D of each part of the display image, the optimum solution may be obtained by simulation together with the radius of curvature of each part of the concave mirror 13.

As described above, in this embodiment, the eye point is set to the eye point EPA. Therefore, in the eye point EP1 and the eye point EP2, the region of the windshield 14 corresponding to the vertical radius so that the influence on the display distance (size of the display image) is even can be used. That is, the area of the windshield 14 can be used so that the influence on the display distance (size of the display image) is equal regardless of the height of the eye point. Therefore, excellent display quality can be obtained regardless of the height of the eye point. In particular, it is possible to suppress the difference in the display state between the eye point EP1 and the eye point EP2.

Further, in this embodiment, the curvature of the concave mirror 13 and the area of use of the windshield 14 are set based on the display state at the portion (site Pmax) where distortion of the display image and astigmatism are likely to occur. Therefore, it is possible to prevent the occurrence of a portion having a large astigmatism or a large distortion in the entire display image or the entire eye box.

Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes can be made within the scope of the claims. It is also possible to combine all or a plurality of the components of the above-described embodiment.

Regarding the above examples, the following additional notes will be disclosed.

[Appendix 1]
It is a design method of a head-up display (1) that projects a display image onto a windshield (14) via an optical system (13) that converges light.
Based on the radius of curvature information of the windshield (14), the first calculated value (Mv) of the index value (Mv) related to the display image when viewed from the first eye point (EP1) lower than the standard eye point (EP). The optical system (1) so as to minimize the difference between the index value (Mv) and the second calculated value when viewed from the second eye point (EP2) higher than the standard eye point (EP). A design method comprising the step of determining the shape of 13).

According to the configuration of Appendix 1, since the difference between the first calculated value and the second calculated value is minimized, the display image when viewed from the first eye point and the display image when viewed from the second eye point. The display quality of is made uniform. Therefore, the display quality of those display images including the display images when viewed from a standard eye point is made uniform.

[Appendix 2]
The index value (Mv) is the scaling factor (Mv1', Mv2') of the displayed image.
The design method according to Appendix 1, wherein in the step, the shape of the optical system (13) is determined so that the difference between the first calculated value and the second calculated value is minimized.

According to the configuration of Appendix 2, the difference between the scaling ratios of the displayed image, which is the first calculated value and the second calculated value, is minimized, so that the displayed image when viewed from the first eye point and the second eye point are used. Differences in the size of the displayed image when viewed and distortion of the image can be suppressed. Therefore, the display quality of those display images including the display images when viewed from a standard eye point is made uniform.

[Appendix 3]
In the step, the distance (L1) from the standard eye point (EP) to the virtual image of the display image formed on the windshield (14) when viewed from the standard eye point (EP). However, the shape of the optical system (13) is determined so as to be uniform in the display image, and the first calculated value and the second calculated value are used using the determined optical system (13). The design method according to

Appendix

1 or 2, wherein the method is calculated.

According to the configuration of Appendix 3, after determining the shape of the concave mirror so that the distance from the standard eye point to the virtual image formed on the windshield is uniform in the displayed image, the first calculated value and Since the second calculated value is calculated, astigmatism of the display image when viewed from the first eye point and the display image when viewed from the second eye point can be suppressed. Therefore, the display quality of those display images including the display images when viewed from a standard eye point is made uniform.

[Appendix 4]
In the above step
The radius of curvature in the vertical direction of the windshield (14) that minimizes the difference is derived.
The item described in any one of Supplementary note 1 to 3, wherein the optical path of the display light is set so that the display image is projected on the region of the windshield (14) having the derived radius of curvature (RAwi) in the vertical direction. Design method.

According to the configuration of Appendix 4, since the display image is projected on the area of the windshield having the radius of curvature in the vertical direction that minimizes the difference, the display image when viewed from the first eye point and the second eye point. Differences in the size of the displayed image when viewed from above and distortion of the image can be suppressed. Therefore, the display quality of those display images including the display images when viewed from a standard eye point is made uniform.

[Appendix 5]
The design method according to any one of Supplementary note 1 to 4, wherein the index value (Mv) is a value in the peripheral region of the display image.

According to the configuration of Appendix 5, the difference between the first calculated value and the second calculated value of the index value in the peripheral region of the displayed image where distortion and astigmatism of the displayed image are likely to occur is minimized, so that the first eye The display quality of the display image when viewed from the point and the display quality when viewed from the second eye point are effectively made uniform.

[Appendix 6]
A display (11) that emits display 6 and
It is provided with an optical system (13) that is rotatably provided with respect to the vehicle body and that converges the display light emitted from the display (11) toward the windshield (14).
The index value (Mv1') regarding the display image when viewed from the first eye point (EP1) lower than the standard eye point (EP) is higher than the standard eye point (EP). A head-up display configured to be substantially the same as the index value (Mv2') when viewed from (EP2).

According to the configuration of Appendix 6, since the index value related to the display image when viewed from the first eye point is substantially the same as the index value when viewed from the second eye point, when viewed from the first eye point. The display quality of the display image and the display image when viewed from the second eye point are made uniform. Therefore, the display quality of those display images including the display images when viewed from a standard eye point is made uniform.

[Appendix 7]
The head-up display according to Appendix 6, wherein the index value is a scaling factor (Mv1', Mv2') of the display image.

According to the configuration of Appendix 7, the difference between the scaling ratios of the displayed image, which is the first calculated value and the second calculated value, is minimized, so that the displayed image when viewed from the first eye point and the second eye point are used. Differences in the size of the displayed image when viewed and distortion of the image can be suppressed. Therefore, the display quality of those display images including the display images when viewed from a standard eye point is made uniform.

1 Head-up display 11 Display 13 Concave mirror (optical system)
14 Windshield EP Eyepoint (Standard Eyepoint)
EP1 eye point (1st eye point)
EP2 eye point (second eye point)
Mv1'scale ratio (index value)
Mv2'scale ratio (index value)
Rwi vertical radius (radius of curvature)
RAwi vertical radius (radius of curvature)

Claims

It is a design method of a head-up display (1) that projects a display image onto a windshield (14) via an optical system (13) that converges light.
Based on the radius of curvature information of the windshield (14), the first calculated value (Mv) of the index value (Mv) related to the display image when viewed from the first eye point (EP1) lower than the standard eye point (EP). The optical system (1) so as to minimize the difference between the index value (Mv) and the second calculated value when viewed from the second eye point (EP2) higher than the standard eye point (EP). A design method comprising the step of determining the shape of 13).
The index value (Mv) is the scaling factor (Mv1', Mv2') of the displayed image.
The design method according to claim 1, wherein in the step, the shape of the optical system (13) is determined so that the difference between the first calculated value and the second calculated value is minimized.
In the step, the distance (L1) from the standard eye point (EP) to the virtual image of the display image formed on the windshield (14) when viewed from the standard eye point (EP). However, the shape of the optical system (13) is determined so as to be uniform in the display image, and the first calculated value and the second calculated value are used using the determined optical system (13). The design method according to claim 1 or 2, wherein the method is calculated.
In the above step
The radius of curvature in the vertical direction of the windshield (14) that minimizes the difference is derived.
According to any one of claims 1 to 3, the optical path of the display light is set so that the display image is projected on the region of the windshield (14) having the derived radius of curvature (RAwi) in the vertical direction. Described design method.
The design method according to any one of claims 1 to 4, wherein the index value (Mv) is a value in the peripheral region of the display image.
A display (11) that emits display light and
It is provided with an optical system (13) that is rotatably provided with respect to the vehicle body and converges the display light emitted from the display (11) toward the windshield (14).
The index value (Mv) related to the display image when viewed from the first eye point (EP1), which is lower than the standard eye point (EP), is higher than the standard eye point (EP). A head-up display (1) configured to be substantially the same as the index value (Mv) when viewed from EP2).
The head-up display (1) according to claim 6, wherein the index value is a scaling factor (Mv1', Mv2') of the display image.