Head-up display

Abstract

To provide a head-up display capable of displaying an image formed from multiple display light beams with excellent visibility.SOLUTION: A head-up display 1 projects first polarization to a wind shield 10 from a side of an inner surface 10a of the wind shield 10 and reflects it and allows a virtual image pertaining to the first polarization to be visually recognized in a side of an outer surface 10b of the wind shield 10, or projects second polarization different from the first polarization to the wind shield 10 and reflects it and allows a real image to be visually recognized in a side of the inner surface 10a of the wind shield 10. The second polarization has a lower reflectance in the wind shield 10 than the first polarization, and the wind shield 10 has a double image suppression structure for suppressing a double image obtained by reflection light reflected on the inner surface pertaining to the projected first polarization and reflection light reflected on the outer surface, and a reflection polarizer layer 15 that is disposed in an area in which the second polarization is projected on the inner surface and has a higher reflectance than the reflectance of the second polarization of the wind shield 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, head-up displays have been known in which display light is reflected by a reflective member such as a windshield of a vehicle, allowing an image to be viewed inside and outside the vehicle. Because the reflective member has a certain thickness, there is a risk that the viewer will see a double image due to the display light reflected from one surface and the display light reflected from the other surface. Conventionally, a technique has been known to reduce the double image by varying the reflection angle on each surface of the reflective member (see, for example, Patent Document 1).

[0003] Also known is a technique for displaying images at multiple locations by varying the focal lengths of multiple display lights (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-156678 [Patent Document 2] Japanese Patent Application Publication No. 2017-056844 Summary of the Invention [Problem to be solved by the invention]

[0005] With the current widespread use of autonomous driving technology, head-up displays are required to be able to display not only information necessary for driving but also information with entertainment value. At the same time, high image visibility is also required. As described above, when attempting to form images based on multiple display lights by reflecting them from a common reflective member, measures to prevent double images are required for each display light. However, even if the technology shown in Patent Document 2 is applied, it can only reduce double images for specific display lights, but is not effective for all display lights.

[0006] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a head-up display that can display an image formed by a plurality of display lights with good visibility. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the head-up display of the present disclosure is a head-up display that projects a first polarized light from the inner surface side of the reflective member onto the reflective member and reflects it, causing a virtual image related to the first polarized light to be viewed on the outer surface side of the reflective member, or projects a second polarized light different from the first polarized light onto the reflective member and reflects it, causing a real image to be viewed on the inner surface side of the reflective member, wherein the second polarized light has a lower reflectance on the reflective member than the first polarized light, and the reflective member has a double image suppression structure that suppresses double images caused by reflected light related to the projected first polarized light reflected on the inner surface and reflected light reflected on the outer surface, and a high-reflection structure that is arranged in an area on the inner surface onto which the second polarized light is projected and has a reflectance higher than the reflectance of the second polarized light of the reflective member. [Effects of the Invention]

[0008] In the head-up display of the present disclosure, an image formed by a plurality of display lights can be displayed with good visibility. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the system configuration of an embodiment of a HUD according to the present disclosure, illustrating the display of a virtual image V. [Figure 2] FIG. 1 is a diagram showing an example of the system configuration of an embodiment of a HUD of the present disclosure, and is an explanatory diagram showing the display of a real image R. [Figure 3] 10 is an explanatory diagram illustrating the projection of display light onto a windshield having a wedge shape that becomes thinner as it goes downwards. FIG. [Figure 4] 4 is a diagram illustrating a case where display light is projected onto the windshield of FIG. 3. FIG. [Figure 5] 10A and 10B are diagrams illustrating a case where display light is projected onto a windshield having a wedge shape that becomes thinner as it goes upward. [Figure 6] 6 is a diagram illustrating a case where display light is projected onto the windshield of FIG. 5. FIG. [Figure 7] FIG. 10 is an explanatory diagram illustrating a case where display light related to S-polarized light is projected onto a windshield. [Figure 8] FIG. 10 is an explanatory diagram illustrating a case where display light related to P polarization is projected onto a windshield. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] 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.

[0012] 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.

[0013] In the following description, "front," "rear," "top," and "bottom" follow the definitions of "Fr.", "Re.", "To.", and "Bo." in Figures 1 to 8.

[0014] 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 polarization, S-polarization) on the outer surface 10b (front) of the windshield 10, i.e., outside the vehicle and 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 polarization, P-polarization) on the inner surface 10a (rear) of the windshield 10, i.e., inside the vehicle, for a viewer 3 to view.

[0015] The display light L1 relates to images that are displayed, for example, during manual driving of the 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 relates to characters (assistants, agents) that provide various information to support the driver as the viewer 3, and images (contents) that provide entertainment to the viewer 3, that are displayed, for example, during automatic driving of the vehicle or when the vehicle is stopped.

[0016] The HUD 1 includes a windshield 10 and a display device 20 .

[0017] The windshield 10 has an inner surface 10a and an outer surface 10b. The windshield 10 has a wedge-shaped cross section in the up-down direction as a double image suppression structure (see FIG. 7). Specifically, the windshield 10 has a wedge-shaped shape that becomes thinner in the up-down direction. This double image suppression structure is realized by the windshield 10 having the inner surface 10a and the outer surface 10b, which can suppress double images by controlling the reflection angle of the display light L1 incident on the inner surface 10a and the outer surface 10b. In other words, the inner surface 10a and the outer surface 10b are designed to suppress double images by controlling the deviation in the optical axis between the projected display light L1 reflected by the inner surface 10a and the outer surface 10b.

[0018] The windshield 10 has a reflective polarizer layer 15 as a high-reflectivity structure on a portion of the inner surface 10a. The reflective polarizer layer 15 is disposed on the inner surface 10a in an area onto which P-polarized light, i.e., display light L2, is projected. The reflective polarizer layer 15 has a higher reflectivity for P-polarized light, i.e., display light L2, than the reflectivity of the windshield 10. The reflective polarizer layer 15 is designed to reflect a large amount of P-polarized light and transmit a large portion of S-polarized light, with a reflectivity of 20% or more for P-polarized light and a reflectivity of 10% or less for S-polarized light, when the incident angle of the display light L2, determined by the relative positions of the display device 20 and the windshield 10, is between 55 and 60 degrees. The reflective polarizer layer 15 is formed on the inner surface 10a by, for example, coating or attaching a multilayer thin film.

[0019] 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.

[0020] The image generating unit 21 includes a light source 22 , a display element 23 , a switching element 24 , and a control unit 25 .

[0021] The light source 22 is, for example, a light-emitting diode mounted on a wiring board and emitting white light in the visible wavelength range. The light emitted from the light source 22 is homogenized by passing through optical members (not shown), such as a condenser lens, a lenticular lens, or a diffuser. The display element 23 is, for example, a TFT (Thin Film Transistor) liquid crystal display element. The switching element 24 extracts S-polarized light or P-polarized light as a specific polarization from the display light emitted from the display element 23. Specifically, the switching element 24 passes only the specific polarization while switching between the S-polarized component and the P-polarized component of the extracted display light. The switching element 24 switches the polarization component to be passed 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 23 is designated as display light L1, and the P-polarized component is designated as display light L2.

[0022] The control unit 25 controls the lighting of the light source 22. The control unit 25 also controls the display element 23 to generate display light related to a desired image. Furthermore, the control unit 25 controls the switching element 24 so that the display light emitted by the switching element 24 is switched between S-polarized light and P-polarized light.

[0023] 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.

[0024] 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 and emits them onto the windshield 10.

[0025] 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.

[0026] Next, the operation of the HUD 1 in this embodiment when displaying an aerial image will be described.

[0027] 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 25, the image generation unit 21 causes the display element 23 to generate an image using light emitted from the light source 22 to display the virtual image V, and further causes the switching element 24 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.

[0028] 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.

[0029] 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 25, the display element 23 generates an image using light emitted from the light source 22 to display the real image R, and the switching element 24 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.

[0030] 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.

[0031] 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.

[0032] Here, the HUD 1 in this embodiment reflects the display lights L1 and L2, which have different optical axes and form the virtual image V and real image R, on the windshield 10, which serves as a common reflecting member, and allows the viewer 3 to view them. The windshield 10, which serves as a reflecting member, has a thickness required for its function. For this reason, when projecting onto the windshield 10, it is necessary to take into consideration double images caused by reflection on the inner surface 10a and outer surface 10b. Naturally, the angles of the inner surface 10a and outer surface 10b of the windshield 10 cannot be changed depending on the display lights L1 and L2, so the HUD 1 is designed to be able to suppress double images of either of the display lights L1 and L2.

[0033] 3 is a diagram illustrating a case where display light L1 is projected onto a windshield 10 having a wedge shape that becomes thinner as it goes downward. FIG. 4 is a diagram illustrating a case where display light L2 is projected onto the windshield 10 of FIG. 3.

[0034] This wedge-shaped windshield 10 is designed to reduce the occurrence of double images, which are a virtual image Va formed by the display light L1a reflected by the inner surface 10a and a virtual image Vb formed by the display light L1b reflected by the outer surface 10b. This prevents significant misalignment between the display positions of the virtual images Va and Vb. However, when display light L2 is projected onto a similar windshield 10, a misalignment occurs between the display positions of the real image Ra formed by the display light L2a reflected by the inner surface 10a and the real image Rb formed by the display light L2b reflected by the outer surface 10b. This increases the occurrence of double images compared to when the windshield 10 is not wedge-shaped but has a constant thickness.

[0035] 5 is a diagram illustrating a case where display light L2 is projected onto a windshield 10 having a wedge shape that becomes thinner as it goes up. FIG. 6 is a diagram illustrating a case where display light L1 is projected onto the windshield 10 of FIG.

[0036] Such a wedge-shaped windshield 10 is designed to be suitable for suppressing the double images of real images Ra and Rb formed by display light L2. However, when display light L1 is projected onto a similar windshield 10, the display positions of virtual images Va and Vb are shifted, resulting in an increase in double images compared to when the windshield 10 has a constant thickness.

[0037] Furthermore, due to the nature of light, reflective materials such as the windshield 10 have different reflectances depending on the polarization. When attempting to display a virtual image V and a real image R using different polarized light, as in this embodiment, the difference in reflectance affects the visibility of the images. In the case of S-polarized and P-polarized light used in this embodiment, the S-polarized light has a higher reflectance in principle, which reduces the visibility of the real image R formed by the P-polarized light.

[0038] To address this issue, the HUD 1 of this embodiment has a double image suppression structure for the display light L1 by forming the windshield 10 in a wedge-shaped cross section that becomes thinner as it goes downward. Furthermore, the display light L1 is S-polarized and the display light L2 is P-polarized, and a reflective polarizer layer 15 that increases the reflectivity of the P-polarized display light L2 is formed on the inner surface 10a, resulting in a highly reflective member. This allows most of the display light L2 reflected by the windshield 10 to be reflected by the reflective polarizer layer 15, thereby preventing double images from occurring with respect to the display light L2. Furthermore, efficiently reflecting P-polarized light with the reflective polarizer layer 15 also solves the problem of insufficient brightness resulting from the lower reflectivity of the P-polarized light (display light L2) compared to the S-polarized light.

[0039] As a result, when HUD1 displays a virtual image V and a real image R using display light L1 and L2, it can simultaneously solve the problem of suppressing double images for display light having multiple optical axes and the problem of improving the reflectance of P-polarized light.

[0040] That is, when a virtual image V related to the display light L1 is displayed, as shown in FIG. 7, display light L1a, which is a portion of the display light L1, passes through the reflective polarizer layer 15, is reflected by the inner surface 10a of the windshield 10, and is directed toward the viewer 3. Meanwhile, display light L1b, which is a portion of the display light L1, enters the inside of the windshield 10, is reflected by the outer surface 10b, and is directed toward the viewer 3. Furthermore, a very small portion of the display light L1 is reflected by the reflective polarizer layer 15, but this amount is so small that it is difficult for the viewer 3 to see. As described above, the viewer 3 sees virtual images Va and Vb due to the display light L1a and L1b, but the windshield 10 has a double image suppression structure, so the formation of a double image due to the virtual images Va and Vb is suppressed.

[0041] Furthermore, when a real image R corresponding to the display light L2 is displayed, as shown in FIG. 8 , a portion of the display light L2, that is, display light L2a, is reflected by the reflective polarizer layer 15, which selectively reflects P-polarized light, and travels toward the viewer 3. A portion of the display light L2, that is, display light L2b, passes through the reflective polarizer layer 15, enters the interior of the windshield 10, and is reflected by the outer surface 10b. Because this reflected light is P-polarized, the reflectivity of the windshield 10 is not high, and the amount of reflected light is small. Although the amount of light reflected by the outer surface 10b is small, it is emitted from the inner surface 10a, but is reflected by the reflective polarizer layer 15, which has a high reflectivity for P-polarized light. Therefore, only a small amount of the light is transmitted and travels toward the viewer 3. As described above, the double image suppression structure is effective only for the display light L1. However, by including the reflective polarizer layer 15, most of the display light L2 is reflected by the reflective polarizer layer 15, thereby achieving the brightness required for visibility. Moreover, the display light L2 directed toward the other viewers 3 is light that is not visible to the viewers 3, and therefore, a double image is unlikely to be formed.

[0042] Therefore, the HUD 1 of this embodiment aims to provide a head-up display that can display an image formed by a plurality of display lights with good visibility.

[0043] 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.

[0044] 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 polarized light is not limited to S-polarized or P-polarized light, as long as the polarization angles of the first polarized light and the second polarized light are different. In this case, it is preferable that the difference in polarization angle between the first polarized light and the second polarized light be 22.5 degrees or more.

[0045] In addition, the switching element 24 may be a polarizing plate that is arranged on the display element 23 side, which is the incident side of the display light, and is electrically controlled to rotate around the optical axis direction of the display light as the rotation center axis, thereby switching between passing S-polarized and P-polarized components. [Explanation of symbols]

[0046] 1 Head Up Display (HUD) 3. Viewer 10 Windshield (reflective material) 10a Inner surface 10b External surface 15 Reflective polarizer layer (high reflective structure) 20 Display device 21 Image Generation Unit 22 Light source 23 Display element 24 Switching element 25 Control Unit 31 First Mirror 32 Second Mirror 33 Third Mirror 35 cabinet 36 Cover F1, F2 composite focus L1, L1a, L1b, L2, L2a, L2b display light R, Ra, Rb real images V, Va, Vb virtual image

Claims

1. A head-up display that projects a first polarized light from an inner surface side of a reflecting member onto the reflecting member, reflecting the first polarized light, and allows a virtual image related to the first polarized light to be viewed on an outer surface side of the reflecting member, or projects a second polarized light different from the first polarized light onto the reflecting member, reflecting the second polarized light, and allows a real image to be viewed on the inner surface side of the reflecting member, the second polarized light has a lower reflectance on the reflecting member than the first polarized light, The reflecting member is a double image suppression structure that suppresses double images caused by reflected light reflected on the inner surface and reflected light reflected on the outer surface, which are related to the projected first polarized light; A head-up display having a highly reflective structure disposed in an area on the inner surface where the second polarized light is projected, the highly reflective structure having a reflectivity higher than the reflectivity of the second polarized light of the reflective member.

2. the image according to the first polarization is a virtual image, The head-up display according to claim 1 , wherein the image according to the second polarization is a real image.

3. The head-up display of claim 2 , wherein the first polarization is S polarization.

4. The head-up display of claim 3 , wherein the second polarization is P polarization.

5. the reflecting member is a windshield, The head-up display according to claim 1 , wherein the double image suppression structure is the windshield having the inner surface and the outer surface that suppress the double image by controlling a reflection angle of incident light.

6. The head-up display according to claim 1 , wherein the highly reflective structure is a film attached to or a coating formed on the inner surface of the reflective member.

Images