Virtual image display device

Abstract

To reduce a size of a virtual image display device that suppresses occurrence of a double image.SOLUTION: A virtual image display device 10 comprises a display surface 20 that displays an image, and a projection optical system 14 that projects a light beam from the display surface 20 toward a transparent member 30. The projection optical system 14 includes a convex lens 16. A light path after reflection on a front face 32 of a first light beam L1 emitted from one point 22 of the display surface 20, passing through the convex lens 16, and reflected on the front face 32 of the transparent member 30, and a light path after emission from the front face 32 of a second light beam L2 emitted from one point 22, passing through the convex lens 16, reflected on the rear face 34 of the transparent member 30, and emitted from the front face 32 of the transparent member 30, match each other by refraction on the convex lens 16. An optical axis A of the convex lens 16 is inclined with respect to a reference axis Z that passes through one point 22 and extends in a direction orthogonal to the display surface 20. The display surface 20 is located between a center 16c of the convex lens 16 and a focal point 24 of the convex lens 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a virtual image display device. [Background technology]

[0002] Head-up displays are sometimes used as vehicle display devices. Head-up displays project image display light onto the windshield or other surface of a vehicle, and present a virtual image based on the image display light superimposed on the scenery outside the vehicle. A windshield has a front surface and a back surface, and the image display light reflected and viewed from the front surface and the back surface may be superimposed with a misalignment, resulting in the appearance of a double image. To prevent the occurrence of such double images, a configuration has been proposed in which the optical paths of a first light ray reflected from the front surface and a second light ray reflected from the back surface are aligned (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-92050 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned prior art, it is necessary to place the display unit at the focal point of the optical system, which has been a constraint on miniaturization of the virtual image display device.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a technique for miniaturizing a virtual image display device that suppresses the occurrence of double images. [Means for solving the problem]

[0006] A virtual image display device according to one embodiment of the present invention includes a display surface that displays an image, and a projection optical system that projects light rays from the display surface toward a transparent member having a front surface and a back surface that reflect a portion of the incident light rays. The projection optical system includes a convex lens disposed between the display surface and the transparent member. A first light ray that passes through the convex lens from a point on the display surface and reflects off the surface of the transparent member coincides with a second light ray that passes through the convex lens from the point, reflects off the back surface of the transparent member, and then exits the surface of the transparent member. The optical axis of the convex lens is inclined, within a plane that includes the first and second light rays, with respect to a reference axis that passes through the point and extends in a direction perpendicular to the display surface. The display surface is located between the center of the convex lens and the focus of the convex lens. A virtual image of an image is presented by the transparent member.

[0007] Any combination of the above components or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc. are also valid aspects of the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the size of a virtual image display device that suppresses the occurrence of double images. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram schematically illustrating a configuration of a virtual image display device according to an embodiment. [Figure 2] FIG. 10 is a diagram schematically illustrating a configuration of a virtual image display device according to a first modified example. [Figure 3] FIG. 10 is a diagram schematically illustrating a configuration of a virtual image display device according to a second modified example. [Figure 4] FIG. 10 is a diagram schematically illustrating a configuration of a virtual image display device according to a third modified example. [Figure 5] FIG. 10 is a diagram schematically illustrating a configuration of a virtual image display device according to a fourth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Specific numerical values and the like shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. Furthermore, in this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0011] 1 is a diagram schematically illustrating a configuration of a virtual image display device 10 according to an embodiment. The virtual image display device 10 is a so-called head-up display device. The virtual image display device 10 projects light rays from a display surface 20 onto a transparent member 30 to present a virtual image 40 in front of a user E. The virtual image display device 10 includes a display unit 12 and a projection optical system 14.

[0012] The display unit 12 has a display surface 20 that displays an image. The display unit 12 is an image display element such as a liquid crystal display (LCD) or an organic electroluminescence display (OLED). The display unit 12, for example, acquires an image signal, displays an image corresponding to the image signal on the display surface 20, and generates image display light. The display surface 20 may be a screen onto which an image is projected by a projector.

[0013] The projection optical system 14 projects image display light generated on the display surface 20 toward the transparent member 30. The projection optical system 14 includes a convex lens 16 and a projection mirror 18. The convex lens 16 is disposed on the optical path from the display surface 20 to the transparent member 30. The projection mirror 18 is disposed on the optical path from the convex lens 16 to the transparent member 30. The projection mirror 18 is a plane mirror that bends the light beam emitted from the convex lens 16 toward the transparent member 30. Note that the projection optical system 14 does not need to include the projection mirror 18, and may be configured so that the optical path is not bent by the projection mirror 18. The projection optical system 14 may further include an additional plane mirror, separate from the projection mirror 18, for bending the optical path.

[0014] The convex lens 16 is a lens having positive refractive power. The convex lens 16 is, for example, a plano-convex lens having a first surface 16a that is flat and a second surface 16b that is convex. The convex lens 16 is arranged so that the first surface 16a faces the display surface 20 and the second surface 16b faces the projection mirror 18 (or transparent member 30). The convex lens 16 may be a biconvex lens in which both the first surface 16a and the second surface 16b are convex. The convex lens 16 may be a convex meniscus lens in which the first surface 16a is concave and the second surface 16b is convex. The convex lens 16 is, for example, a spherical lens in which the convex surface (or concave surface) is spherical. The convex lens 16 may also be an aspherical lens in which the convex surface (or concave surface) is a free-form surface.

[0015] The transparent member 30 is a member that reflects a portion of incident light and transmits the remainder. The transparent member 30 reflects image display light toward the user E, thereby presenting the user E with a virtual image 40 corresponding to the image displayed on the display surface 20. The transparent member 30 is, for example, a windshield provided in a vehicle. The transparent member 30 may also be a combiner provided in the virtual image display device 10. The transparent member 30 is configured so that the front surface 32 and the back surface 34 are parallel and the thickness t between the front surface 32 and the back surface 34 is uniform. The transparent member 30 is, for example, configured from a flat or curved glass plate or resin plate. The transparent member 30 is different from wedge glass, in which the front surface 32 and the back surface 34 are non-parallel.

[0016] The image display light incident on the transparent member 30 includes a first light ray L1 that is reflected by the surface 32 of the transparent member 30 and travels toward the user E, and a second light ray L2 that is reflected by the back surface 34 of the transparent member 30 and travels toward the user E. The first light ray L1 is emitted from an arbitrary point on the display surface 20, passes through the convex lens 16, is reflected by the projection mirror 18, and is then reflected by the surface 32 of the transparent member 30 and travels toward the user E. The second light ray L2 is emitted from an arbitrary point on the display surface 20, passes through the convex lens 16, is reflected by the projection mirror 18, passes through the surface 32 of the transparent member 30, is reflected by the back surface 34 of the transparent member 30, and travels toward the user E from the surface 32 of the transparent member 30. When the first light ray L1 and the second light ray L2 traveling toward the user E coincide with each other, the user E can view a virtual image 40 without any double image caused by a misalignment between the first light ray L1 and the second light ray L2.

[0017] When the front surface 32 and the back surface 34 of the transparent member 30 are parallel, if the first light ray L1 and the second light ray L2 incident on the transparent member 30 are parallel, the directions (angles) of the first light ray L1 and the second light ray L2 heading toward the user E will match. In other words, the optical path of the first light ray L1 after reflection on the surface 32 of the transparent member 30 will match the optical path of the second light ray L2 after emission from the surface 32 of the transparent member 30. Here, "matching" preferably means perfect matching, but is not limited to this and may include a slight error to the extent that the user E does not perceive a double image. Similarly, "parallel" preferably means perfect parallel, but is not limited to this and may include a slight error to the extent that the user E does not perceive a double image.

[0018] In this embodiment, the optical path of a first light ray L1 that is emitted from a reference point (also referred to as a reference point 22) on the display surface 20 and heads toward the user E after being reflected by the surface 32 coincides with the optical path of a second light ray L2 that is emitted from the reference point 22 and heads toward the user E after being emitted from the surface 32. This embodiment is configured to cause the optical paths of the first light ray L1 and the second light ray L2 headed toward the user E to coincide, particularly by refraction at the convex lens 16, so that the user E does not perceive a double image.

[0019] Furthermore, in this embodiment, the display surface 20 is disposed closer to the convex lens 16 than the focal point 24 of the projection optical system 14. That is, the display surface 20 is located between the center 16c of the convex lens 16 and the focal point (front focal point) of the convex lens 16. As a result, the distance from the projection optical system 14 (or the convex lens 16) to the display surface 20 can be made shorter than when the display surface 20 is disposed at the focal point 24 of the projection optical system 14, and the virtual image display device 10 can be made smaller.

[0020] The following describes the positional relationship between the projection optical system 14 and the display surface 20, with reference to the position of the display surface 20. Specifically, in FIG. 1, the direction perpendicular to the display surface 20 is defined as the z direction, the direction perpendicular to the plane containing the first light ray L1 and the second light ray L2 is defined as the x direction, and the direction perpendicular to the x and z directions is defined as the y direction. FIG. 1 shows the yz plane containing the first light ray L1 and the second light ray L2. The axis extending from the reference point 22 in the z direction is referred to as the reference axis Z. The position of the reference point 22 on the display surface 20 is not particularly limited; for example, the reference point 22 can be near the center of the display surface 20 in the y direction. In the configuration of FIG. 1, the focal point 24 of the projection optical system 14 coincides with the front focal point of the convex lens 16.

[0021] The convex lens 16 is disposed decentered with respect to the reference axis Z in order to intentionally generate aberration due to decentering. Specifically, the convex lens 16 is disposed so that the center 16c of the convex lens 16 is shifted in the y direction from the reference axis Z in order to generate off-axis aberration due to decentering. The decentering amount d of the convex lens 16 is the distance in the y direction from the reference axis Z to the center 16c of the convex lens 16. Furthermore, the convex lens 16 is disposed so that the optical axis A of the convex lens 16 is tilted in the y direction with respect to the reference axis Z in order to generate decentering aberration due to tilt. The tilt angle θ of the convex lens 16 is the angle between the reference axis Z and the optical axis A of the convex lens 16.

[0022] In this embodiment, because the convex lens 16 is decentered, the first light ray L1 and the second light ray L2 pass through the convex lens 16 at a position away from the center 16c of the convex lens 16. As a result, due to the influence of off-axis aberration, the reference point 22, which is the intersection of the first light ray L1 and the second light ray L2, is located closer to the convex lens 16 than the focal point 24 of the projection optical system 14. Furthermore, because the convex lens 16 is tilted and decentered, the reference point 22, which is the intersection of the first light ray L1 and the second light ray L2, is located closer to the convex lens 16 than the focal point 24 of the projection optical system 14. In this way, by combining the decentering and tilting of the convex lens 16, it is possible to position the display surface 20 at a position closer to the convex lens 16 than the focal point 24 of the projection optical system 14, thereby achieving a compact virtual image display device 10.

[0023] The amount of decentering d and the tilt angle θ of the convex lens 16 can be set appropriately according to the specifications of the entire optical system related to the virtual image display device 10.

[0024] The amount of decentering d of the convex lens 16 is preferably 2% or more and 15% or less of the focal length of the projection optical system 14 (or the convex lens 16). If the amount of decentering d is less than 2% of the focal length, it is difficult to obtain the effect of downsizing due to decentering. Furthermore, if the amount of decentering d is greater than 15% of the focal length, image distortion due to off-axis aberration increases, making it difficult to optimize the image quality of the virtual image 40 presented to the user E. The amount of decentering d of the convex lens 16 may be, for example, 5% or more of the focal length of the projection optical system 14 (or the convex lens 16) or 10% or less of the focal length of the projection optical system 14 (or the convex lens 16).

[0025] The tilt angle θ of the convex lens 16 is preferably 3.5 degrees or more and 45 degrees or less. If the tilt angle θ is less than 3.5 degrees, it is difficult to obtain the effect of miniaturization due to tilt decentering. Furthermore, if the tilt angle θ is greater than 45 degrees, image distortion due to decentering distortion becomes significant, making it difficult to optimize the image quality of the virtual image 40 presented to the user E. The tilt angle θ of the convex lens 16 may be 5 degrees or more and 30 degrees or less.

[0026] In this embodiment, the direction of decentering of the convex lens 16 is preferably the same as the direction of tilting of the convex lens 16. For example, as shown in Fig. 1, if the direction of decentering of the convex lens 16 is the -y direction, it is preferable that the direction of tilting of the convex lens 16 is the -y direction. By making the decentering direction and tilting direction of the convex lens 16 the same, the effects of decentering and tilting can be combined, and the distance from the projection optical system 14 (or the convex lens 16) to the display surface 20 can be made shorter.

[0027] In this embodiment, the intersection of the optical axis A of the convex lens 16 and the reference axis Z is located on the display surface 20. By positioning the intersection of the optical axis A of the convex lens 16 and the reference axis Z on the display surface 20, it is possible to balance the effects of decentering and tilting, preventing either effect from becoming too large. As a result, it is possible to further enhance the effect of miniaturization while suppressing deterioration in the image quality of the virtual image 40.

[0028] (First Modification) FIG. 2 is a diagram schematically illustrating the configuration of a virtual image display device 10A according to a first modification. In the first modification, the decentering direction and tilt decentering direction of the convex lens 16 are opposite to those of the above-described embodiment. Specifically, in the first modification, the decentering direction of the convex lens 16 is the +y direction, and the decentering direction of the convex lens 16 is the +y direction. Other configurations according to the first modification may be similar to those of the above-described embodiment. The first modification can also achieve the same effects as those of the above-described embodiment.

[0029] (Second Modification) FIG. 3 is a diagram schematically illustrating the configuration of a virtual image display device 10B according to a second modified example. In the second modified example, the intersection of the optical axis A of the convex lens 16 and the reference axis Z is located farther from the display surface 20 as viewed from the convex lens 16. In the example of FIG. 3, the intersection of the optical axis A of the convex lens 16 and the reference axis Z coincides with the focal point 24 of the projection optical system 14. Other configurations according to the second modified example may be similar to those of the above-described embodiment. The second modified example can also achieve the same effects as those of the above-described embodiment.

[0030] In the second modification, the eccentricity d of the convex lens 16 B and tilt angle θ B may be the same as or different from the decentering amount d and tilt angle θ of the convex lens 16 in the above embodiment. For example, the decentering amount d of the convex lens 16 in the second modified example B may be larger than the amount of eccentricity d of the convex lens 16 in the embodiment. B may be smaller than the inclination angle θ of the convex lens 16 in the embodiment. In the second modified example, for example, a design can be considered in which the decentering is made relatively large and the tilting is made relatively small to balance the effects of both.

[0031] In the second modified example, the intersection of the optical axis A of the convex lens 16 and the reference axis Z may be located between the display surface 20 and the focal point 24 of the projection optical system 14. In the second modified example, the intersection of the optical axis A of the convex lens 16 and the reference axis Z may be located farther away from the focal point 24 of the projection optical system 14 as viewed from the convex lens 16. In the second modified example, the direction of decentering and tilting of the convex lens 16 may be the -y direction as in the embodiment, or the +y direction as in the first modified example.

[0032] (Third Modification) FIG. 4 is a diagram schematically illustrating the configuration of a virtual image display device 10C according to a third modified example. In the third modified example, the intersection 26 of the optical axis A of the convex lens 16 and the reference axis Z is located closer to the display surface 20 as viewed from the convex lens 16. In the example of FIG. 4, the intersection 26 of the optical axis A of the convex lens 16 and the reference axis Z is located near the midpoint between the center 16c of the convex lens 16 and the focal point 24 of the projection optical system 14. Other configurations according to the third modified example may be similar to those of the above-described embodiment. The third modified example can also achieve the same effects as those of the above-described embodiment.

[0033] In the third modified example, the eccentricity d of the convex lens 16 C and tilt angle θ C may be the same as or different from the decentering amount d and tilt angle θ of the convex lens 16 in the embodiment. For example, the decentering amount d of the convex lens 16 in the third modified example C may be smaller than the amount of eccentricity d of the convex lens 16 in the embodiment. C may be larger than the inclination angle θ of the convex lens 16 in the embodiment. In the third modified example, for example, a design can be considered in which the decentering is made relatively small and the tilting is made relatively large to balance the effects of both.

[0034] In the third modified example, the intersection 26 of the optical axis A of the convex lens 16 and the reference axis Z may be located closer to the display surface 20 than the convex lens 16, may be located midway between the convex lens 16 and the display surface 20, or may be located closer to the convex lens 16 than the display surface 20. In the third modified example, the direction of decentering and tilting of the convex lens 16 may be the -y direction as in the embodiment, or may be the +y direction as in the first modified example.

[0035] (Fourth Modification) 5 is a diagram schematically illustrating the configuration of a virtual image display device 10D according to a fourth modified example. In the fourth modified example, the optical axis A of the convex lens 16 is not inclined with respect to the reference axis Z, but is parallel to the reference axis Z. The fourth modified example can also achieve the same effects as those of the above-described embodiment.

[0036] In the fourth modification, the eccentricity d of the convex lens 16 D may be the same as or different from the decentering amount d of the convex lens 16 in the embodiment. For example, the decentering amount d of the convex lens 16 in the fourth modified example D may be larger than the amount of decentering d of the convex lens 16 in the embodiment. In the fourth modification, since there is no effect from tilt decentering, the same effect of miniaturization as in the embodiment can be achieved by relatively increasing decentering. In the fourth modification, the direction of decentering of the convex lens 16 may be the -y direction as in the above embodiment, or the +y direction as in the first modification.

[0037] The present invention has been described above with reference to the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, and appropriate combinations or substitutions of the configurations shown in each display example are also included in the present invention.

[0038] Several aspects of the present invention are described below.

[0039] A first aspect of the present invention is a virtual image display device including a display surface that displays an image, and a projection optical system that projects light rays from the display surface toward a transparent member having a front surface and a back surface that reflect a portion of the incident light rays. The projection optical system includes a convex lens disposed between the display surface and the transparent member, wherein an optical path of a first light ray that passes through the convex lens from a point on the display surface and is reflected by the surface of the transparent member and an optical path of a second light ray that passes through the convex lens from the point, is reflected by the back surface of the transparent member, and is then emitted from the surface of the transparent member are coincident due to refraction in the convex lens, the center of the convex lens is offset from a reference axis that passes through the point and extends in a direction perpendicular to the display surface, within a plane that includes the first light ray and the second light ray, and the display surface is located closer to the convex lens than a focus of the projection optical system, and a virtual image of the image is presented by the transparent member.

[0040] In the first aspect, the distance from the reference axis to the center of the convex lens may be 2% to 15% of the focal length of the projection optical system. The distance from the reference axis to the center of the convex lens may be 5% or more of the focal length of the projection optical system. The distance from the reference axis to the center of the convex lens may be 10% or less of the focal length of the projection optical system.

[0041] In the first aspect, the optical axis of the convex lens may be parallel to the reference axis in a plane that includes the first light ray and the second light ray.

[0042] In the first aspect, the optical axis of the convex lens may be inclined with respect to the reference axis in a plane including the first light ray and the second light ray. The inclination angle of the optical axis of the convex lens with respect to the reference axis may be 3.5 degrees or more and 45 degrees or less. The inclination angle of the optical axis of the convex lens with respect to the reference axis may be 5 degrees or more. The inclination angle of the optical axis of the convex lens with respect to the reference axis may be 30 degrees or less.

[0043] A second aspect of the present invention is a virtual image display device including a display surface that displays an image, and a projection optical system that projects light rays from the display surface toward a transparent member having a front surface and a back surface that reflect a portion of the incident light rays. The projection optical system includes a convex lens disposed between the display surface and the transparent member, wherein an optical path of a first light ray that passes through the convex lens from a point on the display surface and is reflected by the surface of the transparent member and an optical path of a second light ray that passes through the convex lens from the point, is reflected by the back surface of the transparent member, and is then emitted from the surface of the transparent member are coincident due to refraction in the convex lens, the optical axis of the convex lens is inclined with respect to a reference axis that passes through the point and extends in a direction perpendicular to the display surface, within a plane that includes the first light ray and the second light ray, and the display surface is located between the center of the convex lens and the focus of the convex lens, and a virtual image of the image is presented by the transparent member.

[0044] In the second aspect, the inclination angle of the optical axis of the convex lens with respect to the reference axis may be 3.5 degrees or more and 45 degrees or less. The inclination angle of the optical axis of the convex lens with respect to the reference axis may be 5 degrees or more. The inclination angle of the optical axis of the convex lens with respect to the reference axis may be 30 degrees or less.

[0045] In the second aspect, in a plane including the first light ray and the second light ray, the intersection of the optical axis of the convex lens and the reference axis may be located on the display surface. In a plane including the first light ray and the second light ray, the intersection of the optical axis of the convex lens and the reference axis may be located farther from the convex lens than the display surface. In a plane including the first light ray and the second light ray, the intersection of the optical axis of the convex lens and the reference axis may be located closer to the convex lens than the display surface.

[0046] In the first or second aspect, the first light ray and the second light ray may be transmitted through the convex lens at a position away from the center of the convex lens. The first light ray and the second light ray emerging from the convex lens may be inclined with respect to the optical axis of the convex lens. The first light ray incident on the transparent member may be parallel to the second light ray incident on the transparent member. The transparent member may have a uniform thickness between the front surface and the back surface. [Explanation of symbols]

[0047] 10...virtual image display device, 12...display unit, 14...projection optical system, 16...convex lens, 16c...center, 18...projection mirror, 20...display surface, 22...reference point, 24...focus, 30...transparent member, 32...surface, 34...back surface, 40...virtual image, E...user, L1...first light ray, L2...second light ray, Z...reference axis, A...optical axis.

Claims

1. a display surface for displaying an image; a projection optical system that projects light rays from the display surface toward a transparent member having a front surface and a back surface that reflect a part of the incident light rays; the projection optical system includes a convex lens disposed between the display surface and the transparent member; an optical path of a first light ray that passes through the convex lens from a point on the display surface and is reflected on the surface of the transparent member and an optical path of a second light ray that passes through the convex lens from the point, is reflected on the rear surface of the transparent member, and is then emitted from the surface of the transparent member, the optical path of the second light ray that passes through the convex lens from the point, is reflected on the rear surface of the transparent member, and is then emitted from the surface, the optical path of the second light ray that passes through the convex lens from the point, is reflected on the rear surface of the transparent member, and is then emitted from the surface, the optical path of the second light ray that is then emitted from the surface, the optical path of the second light ray that is the first light ray that is the second ... an optical axis of the convex lens is inclined with respect to a reference axis that passes through the point and extends in a direction perpendicular to the display surface, within a plane that includes the first light ray and the second light ray; the display surface is located between the center of the convex lens and the focal point of the convex lens; A virtual image display device that presents a virtual image of the image using the transparent member.

2. The virtual image display device according to claim 1 , wherein an inclination angle of the convex lens with respect to the reference axis is equal to or greater than 3.5 degrees and equal to or less than 45 degrees.

3. 3 . The virtual image display device according to claim 1 , wherein an intersection of the optical axis of the convex lens and the reference axis is located on the display surface in a plane including the first light ray and the second light ray.

4. 3. The virtual image display device according to claim 1, wherein, in a plane including the first light ray and the second light ray, an intersection of the optical axis of the convex lens and the reference axis is located farther from the convex lens than the display surface.

5. 3. The virtual image display device according to claim 1, wherein, in a plane including the first light ray and the second light ray, an intersection of the optical axis of the convex lens and the reference axis is located closer to the convex lens than to the display surface.

Images