Head-up display

Abstract

To provide a head-up display that improves utilization efficiency of light.SOLUTION: A head-up display projects and reflects first display light on a reflection member having an inner surface and an outer surface to cause a viewer to visually recognize a virtual image associated with the first display light on the outer surface side, and projects and reflects second display light on the reflection member to cause the viewer to visually recognize a real image associated with the second display light on the inner surface side. The head-up display includes: a display unit that generates the first display light and the second display light; a light source that emits light to the display unit; and an optical member 25 that is disposed between the light source and the display unit and has a light distribution control unit 42 that emits incident light of the light source with different light distribution angles for the first display light and the second display light.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to head-up displays. [Background technology]

[0002] 2. Description of the Related Art Head-up displays are known in the art that reflect display light off a reflective member such as a windshield of a vehicle, allowing an image to be viewed both inside and outside the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 2] Japanese Patent Application Publication No. 2017-056844 Summary of the Invention [Problem to be solved by the invention]

[0004] A head-up display can switch the display position of an image between the inside and outside of a vehicle by, for example, changing the focal length of light emitted from a common light source and changing the arrangement of optical components. This allows the head-up display to create a visual effect depending on the content of the image. However, when attempting to display multiple images using a common light source, the light utilization efficiency may differ between each image. For example, while a wide light distribution can be obtained for a virtual image, the light distribution for a real image may be relatively narrow.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a head-up display that improves light utilization efficiency. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the head-up display of the present disclosure is a head-up display that projects and reflects first display light onto a reflective member having an inner surface and an outer surface, allowing a viewer to view a virtual image related to the first display light on the outer surface side, and projects and reflects second display light onto the reflective member, allowing a viewer to view a real image related to the second display light on the inner surface side, and includes: a display unit that generates the first display light and the second display light; a light source that emits light to the display unit; and an optical element that is arranged between the light source and the display unit and has a light distribution control unit that emits the incident light from the light source at different light distribution angles for the first display light and the second display light. [Effects of the Invention]

[0007] In the head-up display of the present disclosure, the image can be visually recognized favorably when switching between different display positions. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a system configuration of an embodiment of a HUD according to the present disclosure. [Figure 2] FIG. 1 is a diagram showing an example of a system configuration of an embodiment of a HUD according to the present disclosure. [Figure 3] FIG. 2 is an explanatory diagram conceptually showing the configuration of an image generation unit. [Figure 4] Cross-sectional view of a V-direction lenticular lens. [Figure 5] 10 is a conceptual diagram for explaining the light utilization efficiency in the V direction of a virtual image and a real image. [Figure 6] 10 is a conceptual diagram for explaining the light utilization efficiency of a virtual image and a real image in the H direction. [Figure 7] FIG. 10 is a cross-sectional view of a modified V-direction lenticular lens. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of a head-up display (hereinafter referred to as a "HUD") according to the present disclosure will be described with reference to the accompanying drawings. The HUD according to the present disclosure can be applied to HUDs mounted on vehicles such as automobiles, agricultural machinery, and construction machinery.

[0010] FIG. 1 is a diagram showing an example of the system configuration of an embodiment of a HUD according to the present disclosure, and is an explanatory diagram showing the display of a virtual image V.

[0011] FIG. 2 is a diagram showing an example of the system configuration of an embodiment of the HUD of the present disclosure, and is an explanatory diagram when a real image R is displayed.

[0012] In the following description, "front," "rear," "top," and "bottom" follow the definitions of "Fr.", "Re.", "To.", and "Bo." in Figures 1 and 2.

[0013] The HUD 1 is mounted, for example, in an instrument panel in front of the front seats of a vehicle. The HUD 1 projects and reflects display lights L1 and L2 from the rear and below onto a windshield 10 (a reflective member) of the vehicle. The HUD 1 displays an aerial image consisting of a virtual image V associated with the display light L1 (first display light) on the outer surface 10b (front) of the windshield 10, i.e., outside the vehicle, in front of the vehicle, for a viewer 3 (e.g., the driver) who is a passenger in the vehicle to view. The HUD 1 also displays an aerial image consisting of a real image R associated with the display light L2 (second display light) on the inner surface 10a (rear) of the windshield 10, i.e., inside the vehicle, for a viewer 3 to view. The HUD 1 forms an eyebox 4, which is an area where the viewer 3's viewpoint is expected to be located, and which is an area where the virtual image V and real image R are visible. The viewer 3 can view the virtual image V and real image R displayed by the HUD 1 by positioning their viewpoint within the eyebox 4. On the other hand, when the viewer 3 moves his / her viewpoint away from the eyebox 4, at least a part of the virtual image V and the real image R becomes unrecognizable (difficult to recognize).

[0014] The display light L1 (virtual image V) relates to an image that is displayed, for example, during manual driving of a vehicle, to provide information necessary for driving, such as driving speed, engine RPM, blind spot indicator, warning information such as speed limit exceeding warning, route guidance information, etc. The display light L2 (real image R) relates to a character (assistant, agent) that provides various information to support the driver as the viewer 3, or an image (content) that provides entertainment to the viewer 3, that is displayed, for example, during automatic driving of the vehicle or when the vehicle is stopped.

[0015] The HUD 1 includes a windshield 10 and a display device 20 .

[0016] The windshield 10 is a windshield of a vehicle, and has an inner surface 10a and an outer surface 10b.

[0017] The display device 20 includes an image generating unit 21, a first mirror 31, a second mirror 32, a third mirror 33, and a housing 35.

[0018] The image generation unit 21 generates display light L1 associated with a virtual image V and display light L2 associated with a real image R. Here, Fig. 3 is an explanatory diagram conceptually showing the configuration of the image generation unit 21. The image generation unit 21 has a light source 22, a condenser lens 23, an H-direction lenticular lens 24 (optical member), a V-direction lenticular lens 25 (optical member), a diffuser 26, a display element 27 (display section), a switching element 28, and a control section 29 (Fig. 1).

[0019] The light source 22 is, for example, a light-emitting diode (LED) that emits light in the visible wavelength range and is mounted on a wiring board. The light emitted from the light source 22 is homogenized by passing through optical members such as a condenser lens 23, H-direction and V-direction lenticular lenses 24 and 25, and a diffusion plate 26, and is then emitted to the display element 27.

[0020] The condenser lens 23 has a plurality of lenses arranged in an array, and collimates the light from the light source 22 to make the distribution uniform.

[0021] The H-directional lenticular lens 24 and the V-directional lenticular lens 25 are disposed between the light source 22 and the display element 27, and have a diffusion control unit 41 and a light distribution control unit 42. Here, Fig. 4 is a cross-sectional view of the V-directional lenticular lens 25. The V-directional lenticular lens 25 has a diffusion control unit 41 on the incident surface 25a (one of the incident surface 25a and the exit surface 25b) of the light L from the light source 22, and has a light distribution control unit 42 on the exit surface 25b (the other surface).

[0022] The diffusion control unit 41 outputs the incident light L from the light source 22 at different diffusion angles for display light L1 (first display light) and display light L2 (second display light). Specifically, the diffusion control unit 41 has a first lens 41a and a second lens 41b. The first lens 41a is a plurality of cylindrical concave lenses that emit light at a diffusion angle for display light L1 related to the virtual image V. The second lens 41b is a plurality of cylindrical concave lenses that emit light at a diffusion angle for display light L2 related to the real image R. The first lens 41a and the second lens 41b are lenticular lenses that have their major axes aligned in the H (Horizontal) direction of the image and are arranged alternately in the V (Vertical) direction.

[0023] The light distribution control unit 42 outputs the incident light L from the light source 22 at different light distribution angles for the display light L1 and the display light L2. Specifically, the light distribution control unit 42 has a first prism 42a and a second prism 42b, each of which has a surface inclined with respect to the optical axis of the light source 22 (the direction of the light L in FIG. 4). The first prism 42a is a plurality of prisms that emit light L01 according to the light distribution angle for the display light L1 associated with the virtual image V. The second prism 42b is a plurality of prisms that emit light L02 according to the light distribution angle for the display light L2 associated with the real image R. The second prism 42b is formed with a greater inclination than the first prism 42a, and the light L02 is refracted more than the light L01. The first prism 42a and the second prism 42b are a prism array in which the first prisms 42a and the second prisms 42b are alternately arranged with the major axis aligned with the V direction of the image.

[0024] The H-direction lenticular lens 24, like the V-direction lenticular lens 25, has a plurality of cylindrical lenses and a prism array, and is thus a lens having a required diffusion control section 41 and light distribution control section 42. Details of the H-direction lenticular lens 24 and the V-direction lenticular lens 25 will be described later.

[0025] The diffusion plate 26 further diffuses the light emitted from the V-direction lenticular lens 25 and emits it toward the display element 27 .

[0026] The display element 27 is, for example, a TFT (Thin Film Transistor) liquid crystal display element. The display element 27 generates light that becomes display light L1 related to the virtual image V and display light L2 related to the real image R, using light emitted from the optical member as backlight.

[0027] The switching element 28 extracts S-polarized light or P-polarized light as a specific polarization from the light emitted from the display element 27. Specifically, the switching element 28 switches the extracted light between an S-polarized component and a P-polarized component, and passes only one of the polarization components. The switching element 28 switches the polarization component to pass by electrical control based on whether or not a current is applied. Here, the S-polarized component of the display light emitted from the display element 27 is set as display light L1, and the P-polarized component is set as display light L2.

[0028] The control unit 29 controls the lighting of the light source 22. The control unit 29 also controls the display element 27 to generate required display light. Furthermore, the control unit 29 controls the switching element 28 so that the switching element 28 switches the display light that it emits.

[0029] The first mirror 31, the second mirror 32, and the third mirror 33 are flat or curved mirrors. The first mirror 31 reflects the display light L1, which is an S-polarized component, and transmits the display light L2, which is a P-polarized component. The second mirror 32 reflects the display light L2 that passes through the first mirror 31. As shown in FIG. 2, since the first mirror 31 is a mirror that transmits the display light L2, the display light L2 reflected by the second mirror 32 naturally passes from the back side to the front side of the first mirror 31. Therefore, the display light L2 reflected by the second mirror 32 passes through the first mirror 31 again and is guided to the third mirror 33. This allows the second mirror 32 to be disposed close to the first mirror 31, thereby preventing the housing 35 from becoming large.

[0030] The display lights L1 and L2 reflected by the first mirror 31 and the second mirror 32 are guided to the third mirror 33. The third mirror 33 reflects the display lights L1 and L2 toward the windshield 10. The third mirror 33 also has a drive unit (not shown) that is driven based on the control of the control unit 29, and rotates around a rotation axis 34. This allows the third mirror 33 to change the reflection direction of the incident light.

[0031] The housing 35 supports and houses the image generating unit 21, the first mirror 31, the second mirror 32, and the third mirror 33. The housing 35 has an opening at the top, through which the display lights L1 and L2 reflected by the third mirror 33 are emitted to the outside of the housing 35. The opening is covered with a cover 36 to prevent dust and other particles from entering the inside of the housing 35.

[0032] Next, the operation of the HUD 1 in this embodiment when displaying an aerial image will be described.

[0033] When the HUD 1 displays an aerial image consisting of a virtual image V, the image generation unit 21 emits display light L1 associated with the virtual image V, as shown in FIG. 1 . That is, under the control of the control unit 29, the image generation unit 21 causes the display element 27 to generate an image using light emitted from the light source 22 to display the virtual image V, and further causes the switching element 28 to emit display light L1 consisting of the S-polarized component of the display light. The display light L1 is reflected sequentially by the first mirror 31 and the third mirror 33, and is emitted from the opening. The emitted display light L1 is reflected by the windshield 10 toward the viewer 3, and is viewed by the viewer 3.

[0034] Here, when the first mirror 31, the third mirror 33, and the windshield 10 are considered to be a single imaging optical system, by arranging the image generating unit 21 sufficiently close to the first mirror 31, the composite focus F1 of the imaging optical system is positioned in front of the light source 22. By setting the position of the composite focus F1 in this way, the HUD 1 causes the virtual image V to be visible on the outer surface 10b side of the windshield 10, i.e., in front of the vehicle.

[0035] On the other hand, when the HUD 1 displays an aerial image consisting of a real image R, the image generation unit 21 emits display light L2 corresponding to the real image R, as shown in Fig. 2. That is, in the image generation unit 21, under the control of the control unit 29, the display element 27 generates an image using light emitted from the light source 22 to display the real image R, and the switching element 28 further emits display light L2 consisting of the P-polarized component of the display light. The display light L2 passes through the first mirror 31, is reflected successively by the second mirror 32 and the third mirror 33, and is emitted from the opening. The emitted display light L2 is reflected by the windshield 10 toward the viewer 3 and is viewed by the viewer 3.

[0036] Here, when the second mirror 32, the third mirror 33, and the windshield 10 are considered to be a single imaging optical system, by arranging the image generating unit 21 at a position sufficiently far from the second mirror 32, the composite focus F2 of the imaging optical system is positioned after the light source 22. By setting the position of the composite focus F2 in this way, the HUD 1 allows the real image R to be viewed on the inner surface 10a side of the windshield 10, i.e., inside the vehicle.

[0037] In this way, the HUD 1 (display device 20) projects and reflects display light L1 made of S-polarized light onto the windshield 10 from the inner surface 10a of the windshield 10, causing a virtual image V made of S-polarized light to be viewed on the outer surface 10b of the windshield 10. The HUD 1 also projects and reflects display light L2 made of P-polarized light onto the windshield 10 from the inner surface 10a of the windshield 10, causing a real image R to be viewed on the inner surface 10a of the windshield 10. The HUD 1 displays the virtual image V during manual driving and the real image R during automatic driving or when the vehicle is stopped, for example, based on control by a vehicle ECU that comprehensively controls the vehicle.

[0038] 5 is a conceptual diagram for explaining the light utilization efficiency in the V direction of the virtual image V and the real image R. FIG. 6 is a conceptual diagram for explaining the light utilization efficiency in the H direction of the virtual image V and the real image R.

[0039] 5, in the optical system of the HUD 1 of this embodiment, the display light L1 associated with the virtual image V emitted from the display element 27 is distributed so that the light becomes wider in the virtual image Vv in the V direction. On the other hand, the display light L2 associated with the real image R emitted from the display element 27 is distributed so that the light becomes narrower in the real image Rv in the V direction. That is, the light emitted from a certain range of the display light L2 forms an image in a narrower range than the display light L1, and the amount of light that does not contribute to image formation even when displayed on the display element 27 is increased.

[0040] 6, in the optical system of the HUD 1 of this embodiment, the display light L1 associated with the virtual image V emitted from the display element 27 is similarly distributed so as to be wide in the virtual image Vh in the H direction. On the other hand, the display light L2 associated with the real image R emitted from the display element 27 is distributed so as to be narrow in the real image Rh in the H direction. That is, the light emitted from a certain range of the display light L2 forms an image in a narrower range than the display light L1, and the amount of light that does not contribute to image formation even when displayed on the display element 27 is increased.

[0041] Therefore, in the HUD 1 of this embodiment, the V-directional lenticular lens 25 and the H-directional lenticular lens 24 are configured to efficiently emit light in the light distribution directions of the V and H directions of the image in order to efficiently utilize the light from the light source 22 to generate display light L1 and display light L2 and display the virtual image V and real image R. Specifically, the V-directional lenticular lens 25 and the H-directional lenticular lens 24 are provided with a diffusion control unit 41 and a light distribution control unit 42. The light distribution control unit 42 has a prism exit surface 25b configured to emit light at the light distribution angle shown in FIGS. 5 and 6 above. That is, as shown in FIG. 4, the light distribution control unit 42 of the V-directional lenticular lens 25 is suitably designed to appropriately set the light distribution angles of the light L01 that forms the display light L1 and the light L02 that forms the display light L2, so that the light from the light source 22 can be emitted in the desired direction. In addition, the diffusion control unit 41 ensures that light is reliably incident on each of the first prisms 42a and second prisms 42b by using each of the first lenses 41a and second lenses 41b, whose diffusion angles are suitably designed according to the width of the exit surface 25b of each of the first prisms 42a and second prisms 42b, to reliably diffuse light toward each of the first prisms 42a and second prisms 42b.

[0042] Although the illustration of the H-direction lenticular lens 24 corresponding to Figure 4 is omitted, by having a configuration similar to that of the V-direction lenticular lens 25 in order to efficiently distribute light at the light distribution angle shown in Figure 6, the light distribution angle and diffusion angle can be suitably controlled.

[0043] In the HUD1 of this embodiment, even when a virtual image V and a real image R are displayed using a common light source 22 with different focal lengths, the light L01 and L02 used as backlights to generate the display light L1 and the display light L2, respectively, can be controlled to be incident on the display element 27, thereby improving the light utilization efficiency.

[0044] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the claims. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions described in the claims and their equivalents.

[0045] For example, although the example has been described in which the first polarized light is S-polarized and the second polarized light is P-polarized, the first polarized light may be P-polarized and the second polarized light may be S-polarized. Furthermore, the first polarized light and the second polarized light are not limited to S-polarized and P-polarized light, as long as the polarization angles of the first polarized light and the second polarized light are different. In this case, for example, it is preferable that the difference in polarization angle between the first polarized light and the second polarized light is 22.5 degrees or more. Furthermore, the present invention is not limited to a method of switching between the real image R and the virtual image V by changing the polarization.

[0046] An example has been described in which the V-direction lenticular lens 25 and the H-direction lenticular lens 24 have a diffusion control unit 41 and a light distribution control unit 42, but if there is a large difference in the utilization efficiency of the display light L1 and L2 (see Figures 5 and 6), only the V-direction lenticular lens 25 may have a diffusion control unit 41 and a light distribution control unit 42 to improve the utilization efficiency only in the V direction of the image.

[0047] In addition, although an example has been described in which the diffusion control unit 41 is arranged on the incident surface of the V-direction lenticular lens 25 and the H-direction lenticular lens 24 and the light distribution control unit 42 is arranged on the exit surface, the light distribution control unit 42 may also be arranged on the incident surface and the diffusion control unit 41 may be arranged on the exit surface.

[0048] Taking into consideration the difference in utilization efficiency between the display light L1 and the display light L2, the amount of light L01 and L02 used as backlight for the display element 27 may be adjusted by adjusting the widths of the first lens 41a and the second lens 41b of the diffusion control unit 41 and the widths of the first prism 42a and the second prism 42b of the light distribution control unit 42. FIG. 7 is a cross-sectional view of a modified V-direction lenticular lens 25. As shown in FIG. 7, the widths of the second lens 41b and the second prism 42b may be made wider than the widths of the first lens 41a and the first prism 42a so as to increase the amount of light L02, which has a relatively low utilization efficiency. [Explanation of symbols]

[0049] 1 Head-Up Display (HUD) 3. Viewer 4 Eye Box 10 Windshield 10a Inner surface 10b External surface 20 Display device 21 Image Generation Unit 22 Light source 23 Condenser Lens 24 H-directional lenticular lens (optical component) 25 V-direction lenticular lens (optical component) 25a Incidence plane 25b Output surface 26 Diffuser 27 Display element (display unit) 28 Switching element 29 Control Unit 31 First Mirror 32 Second Mirror 33 Third Mirror 34 Rotation axis 35 cabinet 36 Cover 41 Diffusion control section 41a First lens 41b Second lens 42 Light distribution control section 42a First Prism 42b Second Prism F1 and F2 composite focus L, L01, L02 light L1 and L2 represent light R image V virtual image

Claims

1. A head-up display that projects and reflects first display light onto a reflecting member having an inner surface and an outer surface, allowing a viewer to view a virtual image related to the first display light on the outer surface side, and projects and reflects second display light onto the reflecting member, allowing the viewer to view a real image related to the second display light on the inner surface side, a display unit that generates the first display light and the second display light; a light source that emits light to the display unit; an optical element disposed between the light source and the display unit, the optical element having a light distribution control unit that outputs incident light from the light source at different light distribution angles for the first display light and the second display light.

2. The head-up display according to claim 1 , wherein the optical member further comprises a diffusion control section that causes the incident light from the light source to be emitted at different diffusion angles for the first display light and the second display light.

3. 3. The head-up display according to claim 2, wherein the light distribution control unit includes a plurality of first prisms that emit the light at a light distribution angle for the first display light and a plurality of second prisms that emit the light at a light distribution angle for the second display light, and is a prism array in which the first prisms and the second prisms are arranged.

4. 4. The head-up display of claim 3, wherein the diffusion control unit includes a plurality of first lenses that emit the light at a diffusion angle for the first display light and a plurality of second lenses that emit the light at a diffusion angle for the second display light, and is a lenticular lens in which the first lenses and the second lenses are arranged.

5. The head-up display according to claim 2 , wherein the optical member has the light distribution control section on one of an incident surface and an exit surface of the light from the light source, and has the diffusion control section on the other surface.

6. the optical member has the diffusion control section on an incident surface of the light from the light source and the light distribution control section on an exit surface of the light source, the diffusion control section is configured such that the first lenses and the second lenses, each of which is a cylindrical concave lens, are alternately arranged, 5. The head-up display according to claim 4, wherein the light distribution control unit is configured such that the first prism is disposed in front of the light diffused by the first lens and the second prism is disposed in front of the light diffused by the second lens.

Images