JP2021152558A - Virtual image display device - Google Patents

Abstract

To improve the visibility of a virtual image to be presented.SOLUTION: A virtual image display device 10 presents a virtual image to a user via a virtual image presentation plate 22. The virtual image display device comprises: a display part 12 which generates image display light; and a projection optical system 14 including a projection mirror 16 for projecting the image display light to the virtual image presentation plate 22. The projection optical system 14 is configured such that a focal point 26m in a meridional surface and a focal point 26s in a sagittal surface of a synthesis optical system 20 constituted by the virtual image presentation plate 22 and the projection optical system 14 are different from each other. The virtual image display device 10 is configured such that a difference in inverse numbers of a first distance D1 and a second distance D2 is equal to or less than 0.25 [m-1] when the first distance to a sagittal image surface position 50s of a virtual image viewed from a user is D1 and a second distance to a meridional image surface position 50m of the virtual image is D2.SELECTED DRAWING: Figure 8

Description

The present invention relates to a virtual image display device.

In recent years, a head-up display may be used as a vehicle display device. The head-up display projects the image display light onto the windshield of the vehicle or the like, and superimposes and displays a virtual image based on the image display light on the scenery outside the vehicle. Since the windshield has two interfaces, the inside of the vehicle and the outside of the vehicle, the image display light reflected and visually recognized at each interface may be shifted and superimposed, resulting in a double image. In order to suppress the occurrence of such a double image, a mathematical formula for setting the viewing distance so that the amount of deviation of the double image is within the resolution of the human eye and obtaining an optical arrangement that realizes the viewing distance is used. It has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 62-225429

In the above technique, it is premised that the viewing distance to the presentation position of the virtual image seen in front of the user is about 20 m in order to reduce the double image. It is preferable that the generation of double images can be suitably reduced even when the virtual image is presented so that it can be seen at a closer position. Further, it is preferable that the virtual image can be presented in a natural way even when the height of the user's viewpoint changes.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for improving the visibility of a virtual image to be presented.

One aspect of the present invention is a virtual image display device for presenting a virtual image to a user via a virtual image presentation board. The virtual image display device includes a display unit that generates image display light, and a projection optical system that includes a projection mirror that projects the image display light toward the virtual image presentation plate. The projection optical system is configured so that the meridional in-plane focus and the sagittal in-plane focus of the synthetic optical system composed of the virtual image presentation plate and the projection optical system are different, and the meridional in-plane focus of the synthetic optical system is the meridional of the virtual image presentation plate. It is the focusing position of the parallel light beam when the parallel light beam is incident from the user toward the virtual image presentation plate along the surface, and the in-plane focus of the sagittal plane of the synthetic optical system is along the sagittal surface of the virtual image presentation plate. This is the focusing position of the parallel light beam when the parallel light beam is incident on the virtual image presentation plate. The virtual image display device has a first distance D1 and a second distance D2 when the first distance to the sagittal image plane position of the virtual image as seen by the user is D1 and the second distance to the meridional image plane position of the virtual image is D2. The difference between the reciprocals of is 0.25 [m ^-1 ] or less.

It should be noted that any combination of the above components or components and expressions of the present invention that are mutually replaced between methods, devices, systems, and the like are also effective as aspects of the present invention.

According to the present invention, it is possible to reduce the occurrence of double images and improve the visibility of virtual images.

It is a figure which shows typically the structure of the virtual image display device which concerns on embodiment. It is a figure which shows typically the generation of the double image caused by the virtual image presentation board. It is a figure which shows typically the suppression of a double image by a wedge glass. It is a figure which shows the optical arrangement of the virtual image display device which concerns on a comparative example. It is a figure which shows typically the change of the appearance of a virtual image when the height position of an eye changes in a comparative example. It is a figure which shows the optical arrangement of the virtual image display device which concerns on embodiment in detail. 7 (a) and 7 (b) are diagrams schematically showing astigmatism of a parallel light flux incident on a part of a concave curved surface. It is a figure which shows typically the change of the appearance of a virtual image when the height position of an eye changes in an embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The specific numerical values and the like shown in such embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are designated by the same reference numerals to omit duplicate description, and elements not directly related to the present invention are not shown. do.

FIG. 1 is a diagram schematically showing a configuration of a virtual image display device 10 according to an embodiment. In the present embodiment, the virtual image display device 10 is installed in the dashboard of the vehicle 60, which is an example of a moving body. The virtual image display device 10 is a so-called head-up display device. The virtual image display device 10 projects image display light onto the windshield 62, which is a virtual image presentation plate, and presents the virtual image 50 in front of the vehicle 60 in the traveling direction (right direction in FIG. 1). A user E such as a driver can visually recognize the virtual image 50 superimposed on the actual landscape through the windshield 62. Therefore, the user E can obtain the information shown in the virtual image 50 with almost no movement of the line of sight while the vehicle is traveling. In FIG. 1, the traveling direction (front-rear direction) of the vehicle 60 is the z direction, the top-bottom direction (vertical direction) of the vehicle 60 is the y direction, and the left-right direction of the vehicle 60 is the x direction.

The virtual image display device 10 includes an illumination unit 11, a display unit 12, a projection optical system 14, and a control unit 40. The illumination unit 11 is a light source for generating display light, and generates illumination light for illuminating the display unit 12. The illumination unit 11 includes a light emitting element such as an LED (Light Emitting Diode) or an LD (Laser Diode), and an optical element for adjusting the intensity distribution and the angle distribution of the output light from the light emitting element. The illumination unit 11 provides the display unit 12 with white light having substantially uniform brightness. The configuration of the illumination unit 11 is not particularly limited, but an optical element such as a light tunnel, a Fresnel lens, or a light diffusing plate can be used in order to adjust the output light from the light emitting element.

The display unit 12 modulates the illumination light from the illumination unit 11 to generate display light, and forms an intermediate image (real image) corresponding to the display content of the virtual image 50. The display unit 12 includes a transmissive image display element for generating display light, and includes a display device such as a transmissive liquid crystal panel. The image display element receives an image signal transmitted from the control unit 40 and generates an image display light having display contents corresponding to the image signal. The display unit 12 may further include an optical element for adjusting the direction and light distribution angle of the image display light. Further, the display unit 12 includes a projection unit such as a DMD (Digital Mirror Device) other than a transmissive liquid crystal panel, an LCOS (Liquid Crystal on Silicon), or an LSM (Laser Scanning Module) such as a MEMS (Micro Electro Mechanical Systems) system. , A transmissive screen such as a microlens array sheet or a light diffusing sheet may be combined.

The projection optical system 14 projects the image display light generated by the display unit 12 toward the windshield 62. The projection optical system 14 includes a transmissive optical element such as a convex lens and a reflective optical element such as a concave mirror. The specific configuration of the projection optical system 14 will be described later.

The control unit 40 generates a display image, and operates the illumination unit 11 and the display unit 12 so that the virtual image 50 corresponding to the display image is presented. The control unit 40 is connected to the external device 64 and generates a display image based on the information from the external device 64.

The external device 64 is a device that generates original data of an image displayed as a virtual image 50. The external device 64 is, for example, an electronic control unit (ECU) of the vehicle 60, a navigation device, a mobile device such as a mobile phone, a smartphone, or a tablet. The external device 64 transmits to the control unit 40 image data necessary for displaying the virtual image 50, information indicating the content and type of the image data, and information about the vehicle 60 such as the speed and the current position of the vehicle 60.

Hereinafter, the generation of the double image will be described with reference to a comparative example before the optical arrangement according to the embodiment is described in detail. One of the factors that cause the virtual image 50 to appear as a double image is that the image display light reflected and visually recognized at the two interfaces of the inside and outside of the windshield 62 is presented in a shifted manner.

FIG. 2 is a diagram schematically showing the generation of a double image caused by the virtual image presentation plate 22. In FIG. 2, for simplification of the description, an optical element such as a concave mirror arranged between the virtual image presentation plate 22 and the display unit 92 is omitted. The virtual image presentation plate 22 has a predetermined thickness t, and has a first surface 23 and a second surface 24. The first surface 23 corresponds to the interface inside the vehicle of the windshield 62, and the second surface 24 corresponds to the interface outside the vehicle of the windshield 62.

The image display light L reaching the user E from any one point of the display unit 92 mainly passes through the two optical paths L1 and L2. The first optical path L1 is an optical path that is reflected by the first surface 23 and heads toward the user E, and the second optical path L2 is refracted by the first surface 23 and reflected by the second surface 24, and then the first surface 23. It is an optical path that is refracted again and heads for user E. At this time, if an angle difference Δθ exists between the first optical path L1 and the second optical path L2 toward the user E, the image display light passing through each of the two optical paths L1 and L2 is shifted and visually recognized according to the angle difference Δθ. Then, a double image is generated in the virtual image 51. It should be noted that an optical path that is multiple-reflected between the first surface 23 and the second surface 24 and directed toward the user E can be assumed, but the component of the image display light that is multiple-reflected and directed toward the user E is small, and in a normal usage mode. It can be ignored.

FIG. 3 is a diagram schematically showing the suppression of the double image by the wedge glass. The virtual image presentation plate 82 of FIG. 3 is a so-called “wedge glass”, and the thickness of the virtual image presentation plate 82 is configured to change depending on the location. As a result, the first surface 83 and the second surface 84 of the virtual image presentation plate 82 have different inclination angles with respect to the line-of-sight direction of the user E, and an angle difference δ is provided. By using a wedge glass having an angle difference δ between the two surfaces 83 and 84, the angle difference Δθ between the first optical path L1 and the second optical path L2 as shown in FIG. 2 is corrected, and a double image is obtained. The suppressed virtual image 52 can be presented.

However, since such "wedge glass" needs to be formed by precisely controlling the angle difference δ, it is more expensive than ordinary glass having a uniform thickness t. Further, when the windshield 62 of the vehicle 60 is made of wedge glass, not only a special wedge glass corresponding to the shape of the vehicle 60 is required, but also the entire windshield 62 must be replaced, which is extremely difficult. It costs money. Therefore, it is preferable that the generation of double images can be reduced without using such a special wedge glass.

FIG. 4 is a diagram showing in detail the optical arrangement of the virtual image display device 90 according to the comparative example. The comparative example differs from the configuration of FIG. 4 in that a convex lens 94 is provided between the virtual image presentation plate 22 and the display unit 92. In this comparative example, by providing the convex lens 94, the first optical path L1 that starts from an arbitrary point of the display unit 92 and is reflected by the first surface 23 of the virtual image presentation plate 22 and the second optical path L1 of the virtual image presentation plate 22. The angle difference with the second optical path L2 reflected by the surface 24 can be reduced. In particular, by arranging the display unit 92 at the focal point of the composite optical system composed of the virtual image presentation plate 22 and the convex lens 94, the double image can be eliminated by eliminating the angle difference between the first optical path L1 and the second optical path L2. Can be done. In the comparative example of FIG. 4, since the display unit 92 is arranged at the focal point of the composite optical system, the presentation position of the virtual image 53 when viewed from the user E is at infinity or near infinity.

FIG. 5 is a diagram schematically showing a change in the appearance of the virtual image 53 when the height position of the eyes changes in the comparative example. In the comparative example, since the presentation position of the virtual image 53 is infinity, code E _A, E _B, also the height position of the user's eye as shown in E _C (eyepoint trough also referred) is changed in the vertical , the direction in which the virtual image 53 is visible (the image display light _{L A,} L B, the extending direction of the _{L C)} does not change. As a result, when _{the eye points of the users E A to} E _C move up and down, the virtual image 53 also appears to move up and down in parallel. That is, _{the vertical movement amount Δh of the eye points of the users E A to} E _C and the vertical movement amount Δk at the presentation position of the corresponding virtual image 53 are substantially the same. Such an appearance is different from when looking at an object at a finite distance such as several meters away, which may give the user a sense of discomfort. In particular, when the heights of the left and right eyes are different due to tilting the head, the presentation position of the virtual image 53 visually recognized by the left and right eyes shifts by the difference in the heights of the left and right eyes. There is a risk that the discomfort given will increase.

Therefore, in the present embodiment, in order to reduce the discomfort of the appearance of the virtual image that may occur due to the change in the height position of the eyes, the virtual image is presented at a finite distance when viewed from the user. That is, in the comparative example of FIG. 4, the display unit 92 is arranged at a position deviated from the focal point of the composite optical system. At this time, as the distance between the display unit 92 and the focal point of the composite optical system is increased, the presentation position of the virtual image can be arranged closer to the front side when viewed from the user, and the appearance of the virtual image due to the change in the height position of the eyes. The feeling of strangeness can be reduced. On the other hand, there is a trade-off that the larger the distance between the display unit 92 and the focal point of the composite optical system, the easier it is to perceive the double image caused by the virtual image presentation plate 22. Therefore, the present inventors pay attention to the astigmatism of the synthetic optical system, and by appropriately setting the meridional image plane position and the sagittal image plane position of the virtual image, the appearance of the virtual image due to the change in the height position of the eyes. We considered a method to alleviate the occurrence of double images while reducing the discomfort of. Details of astigmatism will be described later.

FIG. 6 is a diagram showing in detail the optical arrangement of the virtual image display device 10 according to the embodiment, and corresponds to the configuration of FIG. 1 described above. The projection optical system 14 of the virtual image display device 10 includes a concave mirror 16 and a convex lens 18. The concave mirror 16 projects the image display light L generated by the display unit 12 toward the virtual image presentation plate 22. The convex lens 18 is arranged between the display unit 12 and the concave mirror 16. The convex lens 18 adjusts the amount of astigmatism, the focal length, and the like of the synthetic optical system 20 composed of the virtual image presentation plate 22 and the projection optical system 14. The projection optical system 14 may not include the convex lens 18, and in addition to the illustrated optical element, another optical element such as a lens or a folded mirror may be added.

In the synthetic optical system 20, since the image display light L is obliquely incident on the concave mirror 16 at an angle θ, astigmatism (astigmatism) As occurs. As a result, a gap occurs between the meridional in-plane focal point 26 m of the composite optical system 20 and the sagittal in-plane focal point 26s. Specifically, since the sagittal in-plane focal length is longer than the meridional in-plane focal length, the sagittal in-plane focal length 26s is located farther from the concave mirror 16 than the meridional in-plane focal length 26m. Here, the “meridional plane” refers to a plane including the optical axis of the synthetic optical system 20 and the main ray of the image display light L, and the yz plane of FIG. 6 corresponds to the meridional plane. On the other hand, the "sagittal plane" is a plane including the optical axis of the composite optical system 20 and orthogonal to the meridional plane, and the xz plane of FIG. 6 corresponds to the sagittal plane.

7 (a) and 7 (b) are diagrams schematically showing the astigmatism of the parallel luminous flux incident on the partial region 98 of the concave curved surface 96, and are views from different viewpoints. FIG. 7 (a) shows the luminous flux in the meridional plane (yz plane) of the concave curved surface 96, and FIG. 7 (b) shows the luminous flux in the sagittal plane (xz plane) of the concave curved surface 96. As shown in the figure, the convergence positions Fm and Fs of the parallel luminous flux are different between the meridional plane and the sagittal plane, and the sagittal in-plane focus Fs is located farther from the concave curved surface 96 than the meridional in-plane focus Fm. This is because when a parallel light beam is obliquely incident on a concave mirror, the distance to the light convergence position (that is, the focal length) changes according to the incident angle. Assuming that the focal length of the concave mirror is f and the incident angle of the light incident on the concave mirror is φ, the focal length of the obliquely incident light is expressed as f · cosφ. .. That is, the focal length in the meridional plane in which the luminous flux is obliquely incident is shortened to f · cosφ. On the other hand, the focal length in the sagittal plane becomes long to f / cosφ.

The focal point of the synthetic optical system 20 of FIG. 6 is determined by the characteristics and arrangement of the concave mirror 16, the convex lens 18, and the virtual image presentation plate 22 constituting the synthetic optical system 20. Specifically, it is determined by the focal length of the concave mirror 16, the focal length of the convex lens 18, the focal length of the virtual image presentation plate 22, and the relative distance and orientation of the concave mirror 16, the convex lens 18 and the virtual image presentation plate 22. For example, when the virtual image presentation plate 22 has a predetermined curvature, the first surface 23 has a concave surface, and the second surface 24 has a convex surface, the image display light L is obliquely input and reflected by the virtual image presentation plate 22. Astigmatism can occur due to this. The virtual image presentation plate 22 may have a shape in which the first surface 23 and the second surface 24 are flat. Further, the positions of the focal points 26m and 26s of the composite optical system 20 shown in FIG. 6 are schematically shown, and do not indicate an accurate focal position based on the optical arrangement of the composite optical system 20.

In the present embodiment, the display unit 12 is arranged on the front side (convex lens 18 side) of the composite optical system 20 from the focal points 26m and 26s, and the display unit 12 is arranged on the front side by a distance d from the meridional in-plane focal point 26m. Will be done. Therefore, it seems that the virtual image 50 is presented to the user E at a finite viewing distance. Further, since there is an astigmatism difference As, the sagittal image plane 50s of the virtual image 50 which seems to be in focus in the horizontal direction (inside the sagittal plane) and the virtual image 50 which seems to be in focus in the vertical direction (inside the meridional plane) The meridional image plane 50 m is presented at different distances in the depth direction when viewed from the user E. Specifically, the virtual image 50 is presented so that the first distance D1 to the sagittal image plane 50s as seen from the user E is shorter than the second distance D2 to the meridional image plane 50 m. At this time, the user E mainly visually recognizes the virtual image formed at the position of the sagittal image plane 50s that can be seen on the front side.

FIG. 8 is a diagram schematically showing a change in the appearance of the virtual image 50 when the height position of the eyes changes in the embodiment. In the embodiment, the presentation position of the virtual image 50 is a finite distance, and the position where the meridional image plane 50 m can be seen does not change even if the eye points of the _{users E A to} E _{C move up and down.} That is, in the embodiment, the direction or angle of the virtual image 50 appear (image display light L _A, L _B, direction or angle extension of L _C) varies depending on the position of the eye point. At this time, the position where the sagittal image plane 50s on the front side, which is mainly visually recognized _{by the users E A to E C,} can be seen can change in the vertical direction according to the extending direction of the _{image display lights L A to} L _C. However, the amount of change Δk in the vertical direction of the sagittal image plane 50s is smaller than the amount of change Δh in the vertical direction of the eye point. Specifically, when the above-mentioned first distance D1 and second distance D2 are used, Δk = Δh · D1 / D2. Therefore, according to the present embodiment, the amount of movement of the virtual image 50 in the vertical direction due to the change in the vertical direction of the eye point can be reduced, and the discomfort in the appearance can be alleviated, as compared with the above-mentioned comparative example. ..

In order to achieve both the generation of the double image and the alleviation of the discomfort of the appearance due to the change of the eye point, the difference between the reciprocals of the first distance D1 and the second distance D2 is 0.25 [m ^-1. ] Or less (that is, (1 / D1)-(1 / D2) ≤ 0.25 [m ^-1 ]). By satisfying this relational expression, the eyes of the user E can be focused on both the meridional image plane 50 m and the sagittal image plane 50s, and it is possible to prevent the occurrence of discomfort such as dizziness.

To give a specific example, if the first distance D1 is 2 m, it is preferable to set the second distance D2 within the range of 2 m to 4 m. If the first distance D1 is 3 m, the second distance D2 is preferably set within the range of 3 m to 12 m, and if the first distance D1 is 4 m, the second distance D2 is a finite distance of about 4 m to 20 m. The distance is preferable.

Further, in order to reduce the amount of movement of the virtual image 50 in the vertical direction due to the change in the vertical direction of the eye point, it is preferable that the difference between the first distance D1 and the second distance D2 is small. For example, by setting the second distance D2 to be twice or less the first distance D1, the vertical movement of the virtual image 50 can be made less noticeable as compared with the case where the second distance D2 is not set.

Although the present invention has been described above with reference to the above-described embodiment, the present invention is not limited to the above-described embodiment, and the present invention is not limited to the above-described embodiment, and the configurations shown in each display example are appropriately combined or replaced. Is also included in the present invention.

10 ... Virtual image display device, 12 ... Display unit, 14 ... Projection optical system, 16 ... Concave mirror, 18 ... Convex lens, 20 ... Synthetic optical system, 22 ... Virtual image presentation plate, 26m ... Meridional in-plane focus, 26s ... Sagittal in-plane focus , 50 ... virtual image, 50m ... meridional image plane, 50s ... sagittal image plane.

Claims (2)

A virtual image display device for presenting a virtual image to a user via a virtual image presentation board.
A display unit that generates image display light and
A projection optical system including a projection mirror that projects the image display light toward the virtual image presentation plate is provided.
The projection optical system is configured such that the meridional in-plane focus and the sagittal in-plane focus of the synthetic optical system composed of the virtual image presentation plate and the projection optical system are different.
The meridional in-plane focal point of the synthetic optical system is a condensing position of the parallel light flux when a parallel light flux is incident from the user toward the virtual image presentation plate along the meridional surface of the virtual image presentation plate.
The sagittal in-plane focus of the synthetic optical system is a condensing position of the parallel light flux when a parallel light flux is incident from the user toward the virtual image presentation plate along the sagittal surface of the virtual image presentation plate.
When the first distance to the sagittal image plane position of the virtual image as seen from the user is D1 and the second distance to the meridional image plane position of the virtual image is D2, the first distance D1 and the second distance D2 A virtual image display device characterized in that the difference between the reciprocals of the above is 0.25 [m ^{-1] or less.} The virtual image display device according to claim 1, wherein the virtual image presentation plate is a windshield having a uniform thickness provided in a vehicle.

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