Information display device

Abstract

To provide an information display device capable of presenting navigation information and smartphone information to a driver without requiring the driver to move his / her gaze significantly away from a road surface.SOLUTION: An information display device is provided, comprising a backlight unit for generating an illumination light beam, a display panel for modulating the illumination light beam from the backlight unit to project image light onto a windshield, and a light direction conversion panel disposed in a light path near the display panel and configured to control directional characteristics of the image light.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to an information display system that projects an image onto a windshield or a combiner of an automobile, a train, an aircraft, etc. (hereinafter collectively referred to as "vehicles"), and a vehicle information display device that reflects the image back by the windshield to observe a real image or a virtual image like a mirror, and relates to the information display device.

Background Art

[0002] A so-called head-up display (HUD) device that projects video light onto a windshield or a combiner of an automobile to form a virtual image and displays traffic information such as route information and traffic jam information, and automobile information such as remaining fuel amount and coolant temperature has already been known from the following Patent Document 1.

[0003] In this type of information display device, while it is desirable to expand the area where the driver can view the virtual image, it is also an important performance factor that the virtual image has high resolution and high visibility.

[0004] The head-up display device provides a virtual image as an enlarged image to the driver using an optical system including a concave mirror (function of a convex lens) for the video displayed on the video display device, and a windshield or a combiner is always required as the final reflection surface.

[0005] As the video display device used in the above-described head-up display device, a liquid crystal display element (liquid crystal display panel) is often used because high-quality video can be easily obtained and it is inexpensive. On the other hand, in order to miniaturize the set, a small liquid crystal display element is used, so the resolution of the projected image obtained is insufficient, and a new problem has become clear that it is not suitable for displaying high-resolution video displayed on a smartphone or the like.

[0006] The present invention relates to a vehicle information display system that uses different technical means for each image display area to compensate for the resolution of the head-up display device described above, and to technical means for realizing an information display device, including an information display device used in such a system to provide high-resolution image information to the driver.

[0007] Furthermore, according to Patent Document 2 below, a head-up display device is already known that, in order to protect an inexpensive liquid crystal display panel used as an image source for an information display device from damage caused by sunlight, has a transmissive reflective member (hot mirror) that allows display light from the liquid crystal display panel to pass through and reflect infrared rays, which is provided at a distance from the front of the liquid crystal display panel in a non-parallel position.

[0008] On the other hand, as a head-up display device with a different structure, a device that mounts the main unit, including the combiner, near the roof (sun visor) of the automobile has already been proposed, as disclosed in Non-Patent Document 1 below. However, safety issues remain, such as the possibility of injuring the driver if the HUD device detaches in the event of a collision. For this reason, it is thought that the method of directly reflecting image light off the windshield will become the mainstream for head-up display devices in the future. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2015-194707 [Patent Document 2] Patent No. 4788882 [Non-patent literature]

[0010] [Non-Patent Document 1] PIONEER R&D (Vol. 22, 2013) [Overview of the project] [Problems that the invention aims to solve]

[0011] In the example of the head-up display device disclosed in Patent Document 1, which is a prior art invention, the device comprises a device for displaying an image and a projection optical system for projecting the image displayed on the display device. The projection optical system has a first mirror and a second mirror in the optical path from the display device to the viewer, and the device is realized by satisfying predetermined conditions regarding the relationship between the angle of incidence in the long axis direction of the image at the first mirror, the angle of incidence in the short axis direction of the image at the first mirror, the distance between the image display surface of the display device and the first mirror, and the horizontal width of the virtual image seen by the viewer. However, no specific solution for increasing the resolution of the image as described above is shown, and furthermore, there is no mention whatsoever of the new problem in which, under predetermined conditions during the daytime, sunlight passes through the windshield and is focused by the concave mirror, damaging the image on the liquid crystal panel and polarizer and significantly degrading performance.

[0012] In the future, the method described in Patent Document 1 above, which uses the windshield as the reflective surface, is expected to become mainstream. However, it completely fails to address the need to handle the increasing resolution of display images on information terminals such as smartphones. In addition, it completely fails to address a crucial issue for the practical application of vehicle information display devices: sunlight that passes through the windshield and is focused by a concave mirror occurs under certain daytime conditions. This sunlight is then focused onto a polarizing plate or the liquid crystal panel itself on the light-emitting side of the liquid crystal display device, causing it to deteriorate due to the heat and intensity of the sunlight, resulting in a malfunction known as "burning" (carbonization).

[0013] Similarly, in the technology disclosed in Non-Patent Document 1, where the final reflective surface is a combiner, no consideration was given to the new problem of increasing the resolution of the displayed image or, when the image display element is a liquid crystal panel, sunlight passes through the windshield and combiner under predetermined daytime conditions, is focused by the concave mirror, damaging the liquid crystal panel and polarizer and significantly degrading performance.

[0014] Furthermore, Patent Document 2 proposes placing a transmissive reflective member (hot mirror) in the optical path to selectively reflect infrared rays from sunlight in order to reduce the risk of damage to liquid crystal display panels caused by sunlight. However, incoming sunlight includes not only infrared rays but also visible and ultraviolet rays, and reducing infrared rays alone was insufficient to mitigate the damage caused to liquid crystal display elements and polarizers by sunlight. Moreover, no consideration was given to the adverse effects of the intrusion of external light, including visible light, such as a significant decrease in the quality of the image seen by the driver, particularly in contrast performance and apparent resolution, or to address the need for higher resolution displayed images.

[0015] Thus, in the case of head-up display devices, which provide video information to drivers using the conventional technology described above, it is necessary to use large liquid crystal display elements in order to obtain high-resolution display images. Therefore, the first challenge has become clear: it is not possible to achieve both miniaturization and high resolution at the same time.

[0016] Furthermore, a second challenge became clear regarding the liquid crystal panel used as the image display device for the head-up display system: when actually installed in a vehicle, under certain conditions during the daytime, sunlight passes through the windshield and is focused by the concave mirror, damaging the liquid crystal panel and polarizing plate, resulting in a significant decrease in performance.

[0017] This invention has been made in view of the problems of the prior art described above, and more specifically, aims to provide an in-vehicle information display system that can achieve both miniaturization and high resolution and is suitable for practical use, as well as an information display device for that system. [Means for solving the problem]

[0018] In order to achieve the above-mentioned objectives, the present invention provides a vehicle information display system that reflects image light onto the windshield of a vehicle to display image information to a viewer, comprising: a first information display device that reflects image light onto the windshield to allow the viewer to view a virtual image; and a second information display device that reflects image light onto the windshield to allow the viewer to view a reflected image, wherein the resolution of the image displayed by the first information display device is lower than the resolution of the image displayed by the second information display device.

[0019] Furthermore, the present invention provides an information display device for configuring an information display system that reflects image light onto the windshield of a vehicle to display image information to a viewer, the information display device comprising: an image light generation means for generating image light to display image information, an image light processing means for applying predetermined optical processing to the image light from the image light generation means, and a means for projecting the image light from the image light processing means through the opening of the housing so that the viewer perceives the image information as a virtual image in front of the windshield.

[0020] Furthermore, the present invention provides an information display device for configuring an information display system that reflects image light onto the windshield of a vehicle to display image information to a viewer, comprising: a backlight device that generates a highly directional illumination beam; a display panel that modulates the highly directional illumination beam from the backlight device according to the image information and emits it onto the windshield; and a light direction conversion panel provided on a part of the windshield that converts the image light from the display panel so that the viewer perceives it as a reflected image in front of the windshield. [Effects of the Invention]

[0021] According to the present invention described above, as an information display device that obtains video information reflected by the windshield on the external landscape viewed through the windshield when the driver drives a vehicle, a large-screen virtual image is displayed far away in a partial area of the windshield by a head-up display device. On the other hand, for example, in the lower end area of the windshield, a vehicle information display system can be provided in which the video of a large-sized high-resolution video display device is reflected by the windshield and the reflected image can be directly viewed by the driver and passengers. As a result, the driver can appropriately display videos with different resolutions and video sizes on the windshield for the necessary information.

[0022] On the other hand, according to the present invention described above, while realizing miniaturization of the head-up display device, it corrects distortion and aberration of the virtual image observed by the driver due to external light including sunlight, and at the same time, the concave mirror forming the virtual image optical system reduces the damage to the liquid crystal panel, polarizing plate, etc. which are video display devices caused by external light including sunlight (mostly P-polarized wave component) incident through the windshield and reduces the deterioration of performance. That is, it is possible to provide an information display device for a vehicle information display system that forms a virtual image with excellent performance by reducing the adverse effects caused by light with a wide range of wavelengths included in the external light including sunlight.

Brief Description of the Drawings

[0023] [Figure 1] It is a top view of an automobile equipped with the vehicle information display system of the present invention and a diagram explaining the difference in the curvature radius of the windshield. [Figure 2] It is a diagram showing a schematic configuration including the virtual image optical system of the first information display device according to an embodiment of the present invention. [Figure 3] It is a schematic configuration diagram showing the relationship between the first information display device, the second information display device, the windshield, the driver's viewpoint position, and sunlight. [Figure 4] It is a schematic configuration diagram showing the relationship between the first information display device of the vehicle information display system, the windshield, the image display position, the driver's viewpoint position, and sunlight. [Figure 5]This is a schematic diagram of the first information display device for a vehicle information display system. [Figure 6] This is a schematic diagram illustrating the operation of the components related to the first information display device of a vehicle information display system. [Figure 7] This is a schematic diagram showing the relationship between the second information display device of a vehicle information display system, the windshield, the image display position, the driver's viewpoint, and sunlight. [Figure 8] This is a schematic diagram of the second information display device for a vehicle information display system. [Figure 9] This is a cross-sectional view showing the configuration of the light source device related to the second information display device. [Figure 10] This is a top view and a cross-sectional view showing the configuration and operation of the light source device of the second information display device. [Figure 11] This is an explanatory diagram for illustrating the operation of the optical components constituting the light source device related to the second information display device. [Figure 12] This is a conceptual diagram illustrating the configuration of optical components related to the second information display device. [Figure 13] This is a schematic diagram showing an example of a car cockpit equipped with a first information display device and a second information display device that constitute a vehicle information display system. [Figure 14] This is a schematic diagram showing another example of a car cockpit equipped with a first information display device and a second information display device that constitute a vehicle information display system. [Figure 15] This diagram illustrates the structure of the film that adheres to the windshield in a vehicle information display system. [Figure 16] This is a schematic diagram illustrating the change in reflectivity of glass with respect to the angle of incidence due to S-polarization and P-polarization. [Figure 17] This is a diagram showing the spectral irradiance of sunlight. [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described in detail below with reference to the drawings and other figures. However, the present invention is not limited to the following description, and various changes and modifications are possible by those skilled in the art within the scope of the technical ideas disclosed herein. Furthermore, in all the figures used to illustrate the present invention, components having the same function are denoted by the same reference numerals, and repeated descriptions may be omitted.

[0025] <Overview of the Vehicle Information Display System> Figure 1(a) is a top view of the information display device 100 according to an embodiment of the present invention, described later, mounted on an automobile, train, aircraft, etc., in particular on an automobile. In front of the driver's seat of the automobile 1010, there is a windshield 6 as the projection target. The inclination angle of this windshield 6 relative to the vehicle body differs depending on the type of automobile. Furthermore, the inventors also investigated the radius of curvature in order to realize the optimal virtual image optical system. As a result, as shown in Figure 1(b), it was found that the radius of curvature of the windshield 6 differs between the horizontal radius of curvature Rh, which is horizontal to the ground surface of the automobile, and the radius of curvature Rv, which is perpendicular to the horizontal axis, and that the following relationship generally holds between Rh and Rv. Rh>Rv Furthermore, it was found that the difference in radius of curvature, specifically Rh relative to Rv, is often in the range of 1.5 to 2.5 times.

[0026] In this invention, video information is displayed by reflecting it off the windshield onto the external scenery that the driver views through the windshield while driving the vehicle. The information display device divides the windshield into multiple areas, and in one of these areas, a head-up display device displays a large virtual image at a distance. On the other hand, for example, in the lower edge area of ​​the windshield, the image of a large, high-resolution video display device is reflected off the windshield, and the reflected image is viewed directly by the driver and passengers. As a result, an information video system is provided that can appropriately display the information the driver needs, with different resolutions and image sizes depending on the display area on the windshield.

[0027] One example of such a head-up display device is an information display device that displays video information as a virtual image on a projection surface, and the information display device is provided that comprises: an image light generation means for generating image light for displaying video information, located inside a housing having an opening in part of it; a means for performing a predetermined optical process on the image light from the image light generation means; and a means for projecting the image light from the image light processing means onto the projection surface through the opening in the housing, so that the viewer can recognize the video information as a virtual image in front of the projection surface.

[0028] More specifically, as will be detailed below, in the information display device of the present invention, a polarizing plate that absorbs P-wave sunlight is provided in the glare stop 41 installed in the aperture. That is, the polarizing plate absorbs P-polarized sunlight and transmits S-polarized sunlight. The polarizing plate is, for example, a λ / 4 plate, a λ / 8 plate, or a λ / 16 plate. By having the glare stop 41 absorb the P-wave component, the following effects can be obtained. (1) Under predetermined daytime conditions, the P-polarized sunlight component that has passed through the windshield (and subsequently through the combiner in the combiner method) is absorbed in front of the concave mirror, thereby preventing the sunlight that has passed through the windshield from returning to the liquid crystal panel and polarizer. (2) When the information display device is not in use, the concave mirror is rotated to a predetermined angle to prevent sunlight from returning to the image display device, thereby preventing sunlight focused by the concave mirror from returning to the image display device.

[0029] Furthermore, a large, high-resolution video display device is installed on the dashboard at a position corresponding to the video display area in the lower edge region of the windshield. This provides an information video system in which the displayed image is reflected off the windshield, allowing the driver and passengers to directly view the reflected image. A transparent screen with the effect of scattering video light is installed on the windshield corresponding to the video display position, and by efficiently reflecting the light, the image can be provided to the driver and passengers at a level of image quality that is practically acceptable. Because the aforementioned large, high-resolution video display device is high-brightness, the direction of the emitted video light is controlled to prevent the video light from directly entering the eyes of the driver and passengers.

[0030] <The first information display device for vehicle information display systems> Figure 2 is a schematic diagram showing the peripheral equipment configuration of the first information display device of the vehicle information display device of the present invention. Here, as an example, an information display device 100 that projects an image onto the windshield 6 of an automobile will be described. The head-up display device, which is an embodiment of the present invention as an information display device 100, is a device (so-called HUD (Head-up Display)) that displays various information reflected by the projection member (in this embodiment, the inner surface of the windshield 6) as a virtual image VI (Virtual Image) in order to form a virtual image V1 in front of the vehicle at the driver's line of sight (eye point: to be described in detail later) 8. The illustrated control device 40 that constitutes such a HUD device acquires various information from the navigation system 61 as foreground information (i.e., information to be displayed in front of the vehicle by the virtual image) such as the speed limit and number of lanes of the road corresponding to the current position of the vehicle, and the planned route of the vehicle set in the navigation system 61.

[0031] Furthermore, the illustrated driver assistance ECU 62 is a control device for realizing driver assistance control by controlling the drive system and control system according to obstacles detected as a result of monitoring by the surrounding monitoring device 63. Such driver assistance control includes well-known technologies such as cruise control, adaptive cruise control, pre-collision safety, and lane keeping assist.

[0032] The illustrated surrounding monitoring device 63 is a device that monitors the conditions around the vehicle. Examples include a camera that detects objects present around the vehicle based on images taken of the surrounding area, and a search device that detects objects present around the vehicle based on the results of transmitting and receiving search waves.

[0033] The HUD device control unit 40 described above acquires information from the driver assistance ECU 62 (for example, the distance to the preceding vehicle, the direction of the preceding vehicle, the location of obstacles and signs, etc.) as foreground information. Furthermore, the control unit 40 receives an ignition (IG) signal and vehicle status information. Of this information, vehicle status information is information acquired as vehicle information and does not require high-resolution display, such as the remaining fuel level of the internal combustion engine and the temperature of the coolant, and includes warning information that indicates a predetermined abnormal state. It also includes the result of turn signal operation, the vehicle's driving speed, and shift position information. The control unit 40 described above is activated when an ignition signal is input. This concludes the description of the overall information display system of this embodiment.

[0034] The projected member can be any member onto which information is projected, and is not limited to the aforementioned windshield 6; it can also be a combiner or other component. In other words, in this embodiment, the information display device 100 can be any device that forms a virtual image in front of the vehicle within the driver's line of sight 8 and allows the driver to see it.

[0035] The information display device 100 having the above configuration includes an image display device 4 that projects image light to display information, and a corrective lens element 2 to correct distortions and aberrations that occur when a virtual image is formed by a concave (free-form) mirror 1 of the image displayed on the image display device 4. The image light beam from this information display device 100 is emitted from an aperture (not shown) toward the windshield 6.

[0036] Furthermore, the information display device 100 also includes a video display device 4 and a control device 40 that controls its backlight. The optical components, including the video display device 4 and the backlight, are a virtual image optical system, as described below, and include a concave mirror 1 that reflects light. The light reflected by this optical component is then reflected by the windshield 6, which is the projection target, and directed towards the driver's line of sight 8.

[0037] The above-mentioned video display device 4 can include, for example, an LCD (Liquid Crystal Display) with a backlight, as well as a self-emissive VFD (Vacuum Fluorescent Display).

[0038] Alternatively, instead of the aforementioned video display device 4, an image may be displayed on a screen using a projection device, turned into a virtual image by the aforementioned concave mirror 1, and reflected by the projected element, the windshield 6 or a combiner (not shown), and directed towards the driver's viewpoint 8.

[0039] Here, in order to reduce the distortion of the virtual image, the shape of the concave mirror 1 should be such that, as shown in Figure 1, the upper part (the area below the windshield 6 where light rays are reflected and the distance from the driver's viewpoint 8 is relatively short) has a relatively small radius of curvature so that the magnification is large, while the lower part (the area above the windshield 6 where light rays are reflected and the distance from the driver's viewpoint is relatively long) has a relatively large radius of curvature so that the magnification is small. Furthermore, by tilting the video display device 4 with respect to the optical axis of the concave mirror 1, the difference in virtual image magnification described above is corrected, thereby reducing the distortion itself, which can lead to even better correction.

[0040] On the other hand, as shown in Figure 1(b), the windshield 6 of a passenger car has different radii of curvature Rv in the vertical direction and Rh in the horizontal direction, and generally, Rh > Rv. Therefore, when the windshield 6 is considered as a reflective surface, it becomes the toroidal surface of the concave mirror 1. For this reason, in the information display device 100 of this embodiment, the shape of the concave mirror 1 should be such that it corrects the virtual image magnification due to the shape of the windshield 6, that is, it should have different mean radii of curvature in the horizontal and vertical directions to correct the difference in radii of curvature of the windshield 6 in the vertical and horizontal directions. In this case, if the shape of the concave mirror 1 is a spherical or aspherical shape symmetric to the optical axis (shown below as [Equation 2]), it is a function of the distance r from the optical axis, and the horizontal and vertical cross-sectional shapes at distant locations cannot be controlled individually. Therefore, it is preferable to correct it as a free-form surface as shown below as [Equation 1], as a function of the coordinates (x,y) of the surface of the mirror surface from the optical axis.

[0041]

number

[0042]

number

[0043] <Principles of preventing and suppressing the intrusion of sunlight into devices> Next, we will explain how sunlight enters the aforementioned information display device in the driver's seat of the vehicle. Figure 3 shows the state near the driver's seat of the vehicle. The information display device 100 is located below the windshield 6, which is mounted between the hood 44 and the roof panel 45 that make up the vehicle body. For example, it is positioned behind the dashboard, which includes instruments such as the speedometer 42 (towards the rear hood). This figure also shows the vehicle's steering wheel 43, the eyes 8 of the driver (the observer), and the daytime sun 60 above the vehicle. Figure 4 shows the configuration of Figure 3, mainly with the sun 60, windshield 6, and eyes 8 removed. Figure 5 shows the configuration of the information display device 100 housed within the casing 7.

[0044] In Figures 3 and 4, strong light from the sun 60 enters the vehicle's windshield 6 at an incident angle θ1, as indicated by the white arrows. After a portion of the light is reflected by the windshield 6, the remaining light enters the device through a glare stop 41 (see Figure 5), which is located in an opening at the top of the information display device 100 and blocks reflected light unrelated to the image reflected by optical elements and structures placed inside the housing. At this time, as is clear from Figure 4, especially at incident angles of 50 degrees or more, much of the S-polarized component (S-wave) of sunlight is reflected on the windshield 6, as shown in Figure 4. As a result, most of the sunlight entering the information display device 100 becomes the P-polarized component (P-wave).

[0045] On the other hand, the video light emitted from the information display device 100 is reflected by the windshield 6 or combiner (not shown) and incident on the viewer's eyes 8, as shown by the solid arrows in Figures 3 and 4.

[0046] More specifically, natural light such as sunlight, as shown in Figure 17, not only consists of light in a wide wavelength range from ultraviolet to infrared, but also exists in a mixed state with two types of polarization directions (hereinafter referred to as S-polarization and P-polarization): light with a vibration direction perpendicular to the direction of light propagation and light with a horizontal polarization direction. As mentioned above, in the region where the incident angle to the windshield 6 exceeds 50 degrees, as shown in Figure 16, the reflectivity on the glass surface differs depending on whether the light is S-polarized or P-polarized, and furthermore, on the incident angle.

[0047] Therefore, in this embodiment, based on the inventor's findings described above, that is, considering that most of the sunlight entering through the windshield 6 is P-polarized, it was confirmed that reducing the P-wave component is particularly effective in suppressing external light, including sunlight, entering the information display device 100, and that in addition, it is effective to use the S-wave component as the image light projected from the information display device 100.

[0048] <Specific Examples of the First Information Display Device> Next, the specific optical configuration of the information display device 100, which is constructed based on the findings described above, will be explained below.

[0049] The configuration of an information display device 100 as one embodiment of the present invention will be described with reference to Figure 3. A lens element 2, for example, is arranged between the video display device 4 and the concave mirror 1 as a transmissive optical component. The lens element 2 corrects distortion of the virtual image obtained in conjunction with the shape of the concave mirror 1 by controlling the direction of light rays emitted to the concave mirror 1, and at the same time corrects aberrations including astigmatism caused by the difference between the horizontal radius of curvature and the vertical radius of curvature of the windshield 6 mentioned above.

[0050] Furthermore, in order to further enhance the aberration correction capability, the lens element 2 described above may be composed of multiple lenses. Alternatively, a curved (free-form) mirror can be placed instead of the lens element 2, and distortion aberration can be reduced by using the curved mirror to fold back the optical path and simultaneously controlling the incident position of the light rays onto the concave mirror 1. As stated above, it goes without saying that even if an optical element optimally designed to further improve the aberration correction capability is placed between the concave mirror 1 and the image display device 4, it will not deviate from the technical idea or scope of the present invention. Furthermore, by changing the thickness of the lens element 2 in the optical axis direction, in addition to the original aberration correction, the optical distance between the concave mirror 1 and the image display device 4 can be changed, and the display position of the virtual image can be continuously changed from a far position to a close position.

[0051] Sunlight entering from outside the vehicle is reflected by the windshield 6 in terms of its S-polarized component, while the P-polarized component is transmitted into the vehicle and enters the information display device 100 through the opening. A polarizing plate is provided on one side of the glare stop 41 installed in the opening, which absorbs the P-wave component of the incident sunlight and transmits the S-polarized component. Furthermore, a reflective film that reflects ultraviolet and infrared light is provided on the other side of the glare stop 41 or on the sunlight incident surface of the polarizing plate. As a result, most of the P-polarized light in the visible light region and most of the light in the ultraviolet and infrared regions do not enter the image display device 4, and consequently, the damage to the image display device 4 from sunlight is reduced.

[0052] On the other hand, it is known that a factor that degrades the image quality of the information display device 100 is that the image light rays emitted from the image display device 4 toward the concave mirror 1 are reflected by the surface of the lens element 2 placed in between, return to the image display device 4, are reflected again, and are superimposed on the original image light, thereby degrading the image quality. For this reason, in this embodiment, it is preferable not only to suppress reflection by forming an anti-reflective film on the surface of the lens element 2, but also to design the lens surface shape of either the image light incident surface or the outgoing surface of the lens element 2 with constraints on its surface shape so that the reflected light described above does not concentrate on a part of the image display device 4 (for example, a shape with the concave surface facing the image display device 4).

[0053] The aforementioned glare stop 41 is equipped with a λ / 16 plate (optimally selected from λ / 4 or λ / 8 depending on the brightness) on the image display device 4 side of the polarizing plate, and a mechanism for adjusting its mounting angle is provided. For example, by moving it to the position shown by the dashed line in the figure, the polarization angle of the S-polarized image light output from the image display device 4 is changed. As a result, even if the driver is wearing polarized sunglasses, a virtual image with sufficient brightness and excellent overall color can be obtained by appropriately changing the mounting angle of the waveplate provided on the glare stop 41 of the present invention.

[0054] Furthermore, even if the polarizing plate installed in the glare stop 41 absorbs the P-polarized component of sunlight incident inside the vehicle, its reliability is not compromised because the area of ​​the polarizing plate receiving light is the same as that of the aperture. In addition, since this polarizing plate selectively transmits S-polarized light, it also has the effect of improving the contrast performance of the virtual image obtained by the information display device 100.

[0055] On the other hand, it is preferable to use a solid-state light source with a long product life as the light source device 10 used in the information display device 100 of the present invention shown in Figures 5 and 6. For example, it is preferable that the light source device 10 includes an LED (Light Emitting Diode) that exhibits little change in light output due to fluctuations in ambient temperature, and a polarizing beam splitter (PBS) equipped with optical means for reducing the light divergence angle, and that polarization conversion is performed by the PBS.

[0056] Polarizing plates (not shown here) are placed on the backlight side (light incident surface) and the lens element 2 side (light output surface) of the liquid crystal panel, thereby increasing the contrast ratio of the image light. By using an iodine-based polarizing plate with a high degree of polarization on the backlight side (light incident surface), a high contrast ratio can be obtained. On the other hand, by using a dye-based polarizing plate on the lens element 2 side (light output surface), high reliability can be obtained even when ambient light is incident or when the ambient temperature is high.

[0057] When a liquid crystal panel is used as the image display device 4, a problem occurs in which the image is not visible, especially when the driver is wearing polarized sunglasses, because certain polarizations are blocked. To prevent this, as described above, a λ / 4 plate, a λ / 8 plate, or a λ / 16 plate is placed on one side of the glare stop 41 provided at the opening to prevent glare generated inside the information display device from returning to the driver's line of sight. This plate aligns the glare to a specific polarization direction. Furthermore, it is preferable to rotate the glare stop 41 from the position shown in Figure 5 to the position 46 shown by the dashed line in Figure 6 to appropriately change the polarization angle of the image light, converting it to circular polarization or rotating the polarization axis of linear polarization to a polarization axis different from the polarization direction of the polarized sunglasses. On the other hand, if the polarization axis is rotated to approach circular polarization, the polarization axis of the image light from the information display device rotates from S polarization, which reduces the reflectivity of the windshield 6 and reduces the brightness of the image, so it is best to choose a balance between the two.

[0058] The inventors experimentally determined that, in order to reduce color unevenness in the resulting image (uniformity of color across the entire screen in a full-white display), it is effective to place a predetermined wavelength plate at the glare stop position where the image light beam is widest.

[0059] <The second information display device for vehicle information display systems> Next, the specific optical configuration of the second information display device of the information display system of the present invention will be described below.

[0060] <Specific Examples of the Second Information Display Device> As the second information display device of the present invention, the information display device 48, as shown in Figures 3 and 7, for example, a high-resolution image (image from a large high-resolution image display device) from a smartphone 300 or the like is reflected towards the viewer's eyes by a film (for example, a transparent film or sheet) 51 provided on the surface of the windshield 6, thereby displaying an image on the windshield in a simulated manner.

[0061] Next, the configuration of the information display device 48 will be explained using Figure 8. The image display element (liquid crystal display panel) 52 is composed of a relatively large liquid crystal display panel with a screen size exceeding 6 inches. Generally, the radius of curvature of the windshield 6 often differs in parts, so uneven distortion (vertical and horizontal) occurs in the displayed image depending on where the image is reflected. For this reason, distortion correction is necessary to obtain a correct image when the reflected image is viewed from the viewing direction. In order to achieve a level of correction that is not problematic in practice through this distortion correction, the panel resolution needs to be 1280 x 720 dots or higher.

[0062] Figure 9 shows the image display element 52, and below it, the light source device 101, which constitutes its light source, as an unfolded perspective view. The image display element (liquid crystal display panel) 52 obtains a highly directional illumination beam from the light source device 101, which is a backlight device, and emits modulated image light according to the image signal toward the film 51 provided on the windshield 6. In Figure 9, the information display device 48 is equipped with the image display element 52, as well as an optical direction conversion panel 54 and a second diffuser plate 18b that control the directional characteristics of the light beam 30 emitted from the light source device 101. That is, polarizing plates are provided on both sides of the information display device 48 (see Figure 8), and the configuration is such that image light with a specific polarization is emitted with the intensity of the light modulated by the image signal. As a result, high-resolution images from a smartphone 300 or the like (images from a large high-resolution image display device) are projected onto the windshield 6 and reflected toward the viewer's eyes by the film 51 provided on its surface.

[0063] Furthermore, the light source device 101 is formed of, for example, plastic. The light source device 101 includes a case (see Figure 8) that houses the LED, collimator, composite diffusion block, light guide, etc., which will be described in detail later. An information display device 48 and an image display element 52 are mounted on the top surface of the light source device 101. In addition, an LED substrate 102 (see Figures 9-10) on which a semiconductor light source LED (Light Emitting Diode) element and its control circuit are mounted is attached to one side of the case of the light source device 101, and a heat sink 103 for cooling the heat generated by the LED element and control circuit is attached to the outer surface of the LED substrate 102 (see Figure 8).

[0064] On the other hand, the image display element 52 mounted on the upper surface of the light source device 101 consists of a liquid crystal display panel frame, a liquid crystal display panel mounted on the frame, and an FPC (Flexible Printed Circuits) 403 (see Figure 8) electrically connected to the panel. In other words, as will be explained in detail later, the image display element 52 generates and controls the displayed image through control signals from a control circuit (not shown here) that constitutes the electronic device, together with an LED element which is a solid light source.

[0065] Next, the configuration of the light source device 101, that is, the optical system housed within the case of the light source device 101, will be described in detail below with reference to Figures 9 and 10.

[0066] Figures 9 and 10 show a plurality of LEDs 14a and 14b (not shown here) that constitute the light source (two in this example), which are attached to the LED collimator 15 at predetermined positions. Each LED collimator 15 is made of a translucent resin such as acrylic. As shown in Figure 10(b), the LED collimator 15 has a cone-shaped outer surface 156 obtained by rotating a parabolic cross section, and at its apex, it has a recess 153 with a convex lens portion (i.e., a convex lens surface) 157 formed in the center. The center of the convex lens portion 157 has a convex lens surface 154 that protrudes outward (or a concave lens surface that is recessed inward). The outer surface 156 that forms the cone-shaped outer surface of the LED collimator 15 is set within an angle range in which light emitted from the LED 14a in the peripheral direction can be totally reflected inside it, or a reflective surface is formed thereon.

[0067] On the other hand, LEDs 14a and 14b are each positioned at predetermined locations on the surface of the circuit board, so-called LED substrate 102. This LED substrate 102 is fixed to the LED collimator 15 such that LEDs 14a or 14b on its surface are positioned in the center of their respective recesses 153.

[0068] With this configuration, the LED collimator 15, as described above, focuses the light emitted from LED 14a or 14b, particularly the light emitted upward (to the right in the diagram) from its central portion, into parallel light by the convex lens portion 157 and convex lens surface 154 that form the outer shape of the LED collimator 15. In addition, the light emitted from other parts toward the periphery is reflected by the parabolic surface that forms the conical outer surface of the LED collimator 15, and similarly focuses into parallel light. In other words, with an LED collimator 15 that has a convex lens in its central portion and a parabolic surface formed on its periphery, it becomes possible to extract almost all of the light generated by LED 14a or 14b as parallel light, thereby improving the utilization efficiency of the generated light.

[0069] Furthermore, a polarization conversion element 21, which will be described in detail below, is provided on the light output side of the LED collimator 15. As is clear from the figure, this polarization conversion element 21 is constructed by combining a translucent member with a parallelogram cross-section (hereinafter referred to as a parallelogram prism) and a translucent member with a triangular cross-section (hereinafter referred to as a triangular prism), and arranging multiple such elements in an array parallel to a plane perpendicular to the optical axis of the parallel light from the LED collimator 15. In addition, a PBS film 211 and a reflective film 212 are alternately provided at the interfaces between adjacent translucent members arranged in this array, and a 1 / 2λ phase plate 213 is provided on the output surface from which light incident on the polarization conversion element 21 and transmitted through the PBS film 211 is emitted.

[0070] The emission surface of this polarization conversion element 21 is further provided with a rectangular composite diffusion block 16, as shown in Figure 10(a). That is, the light emitted from LED 14a or 14b becomes parallel light due to the action of the LED collimator 15, enters the composite diffusion block 16, is diffused by the emission-side texture 161, and then reaches the light guide 17 described below.

[0071] The light guide 17 is a rod-shaped member formed from a translucent resin such as acrylic, with a substantially triangular cross-section (see Figure 10(b)). As is clear from Figure 10(a), it comprises a light guide light incident portion (light guide light incident surface) 171 facing the emission surface of the composite diffusion block 16 via a first diffusion plate 18a, a light guide light reflection portion (light guide light reflection surface) 172 forming a slope, and a light guide light emission portion (light guide light emission surface) 173 facing the liquid crystal display panel including the image display element 52 via a second diffusion plate 18b.

[0072] As shown in Figure 9, a magnified view of a part thereof, the light-reflecting portion 172 of the light guide 17 has numerous reflective surfaces 172a and connecting surfaces 172b alternately formed in a sawtooth pattern. The reflective surfaces 172a (sloping line segments in the figure) form αn (n is a natural number, for example, 1 to 130) with respect to the horizontal plane shown by the dashed line in the figure. As an example, here αn is set to 43 degrees or less (but greater than or equal to 0 degrees).

[0073] As a result, the light-indicating portion 171 of the light guide is formed in a curved convex shape that is inclined toward the light source. With this configuration, parallel light from the exit surface of the composite diffusion block 16 is diffused through the first diffusion plate 18a and incident on the light guide 17. As is clear from the figure, the light reaches the light-reflecting portion 172 of the light guide while being slightly bent (deflected) upward by the light-indicating portion 171 of the light guide.

[0074] As detailed above, the information display device 48 of the present invention improves light utilization efficiency and its uniform illumination characteristics, while also enabling the manufacture of a modular S-polarized light source device in a compact and low-cost form factor. In the above description, the polarization conversion element 21 was described as being installed after the LED collimator 15, but this embodiment is not limited to this, and it will be obvious to those skilled in the art that similar effects can be obtained by installing it at any location in the optical path leading to the liquid crystal display panel.

[0075] The light guide's light-reflecting section 172 has numerous reflective surfaces 172a and connecting surfaces 172b formed alternately in a sawtooth pattern. The diffused light diffused through the first diffuser plate 18a is totally reflected on each reflective surface 172a and directed upward. The diffused light directed upward is incident on the optical direction conversion panel 54, which controls the directional characteristics, as a parallel diffused light beam via the light guide's light-emitting section 173 and the second diffuser plate 18b. The optical direction conversion panel 54 performs a light direction conversion on this diffused light beam. The diffused light beam, after the direction conversion, is emitted from the optical direction conversion panel 54 in a direction such as shown in Figure 9, and incident on the image display element 52 from an oblique direction.

[0076] Figure 11 is a schematic diagram illustrating the principle of the optical direction conversion panel 54 provided in the information display device 48 described above. The light beam from the light guide enters the optical direction conversion panel from the incident surface and is refracted in a desired direction θ3 by the lens action of the linear Fresnel lens provided on the exit surface. At this time, the desired direction θ3 is uniquely derived from Snell's law based on the incident angle θ2 of the light beam to the linear Fresnel lens, the Fresnel angle θ0 of the linear Fresnel lens, and the refractive index n of the substrate. As a result, it is possible to give directivity to the parallel light beam from the light guide in a desired direction.

[0077] Similarly, by providing a linear Fresnel lens with the structure shown in Figure 11 on the light-emitting surface of the image display device 48, the image light beam is directed toward the windshield 6, which becomes the reflective surface. As a result, even if the driver looks directly at the screen of the image display device 48, the image light does not directly reach their eyes, so it does not interfere with driving. The pitch of the linear Fresnel lens is preferably 1 / 3 or less of the pixel pitch of the image display device 48. For example, in order to reduce the moiré pattern generated by the pixel-to-linear Fresnel lens pitch ratio to a level that does not pose a practical problem, the pitch of the linear Fresnel lens is preferably 1 / 7 or less of the pixel pitch. In addition, a protective cover (shown by a dashed line) is provided on the surface to protect the linear Fresnel lens from wear and tear.

[0078] Figure 12 is a cross-sectional view showing the schematic configuration of the protective cover 50 that contacts the dashboard 47 of the information display device 48 described above. A black stripe 59 is provided on a portion of the light-emitting side of the substantially transparent substrate 56. The black stripe 59 reduces surface reflection of external light, including sunlight. For example, a black paint containing carbon black is used for the black stripe 59. In addition, an anti-reflective coating is provided on the parts where the black stripe is not provided to suppress surface reflection. The anti-reflective coating significantly reduces external light reflection on the surface of the protective cover 50, thereby reducing interference with the driver due to external light reflection when driving the vehicle.

[0079] On the other hand, a film or membrane 58 that absorbs or reflects the P-wave component of the sunlight beam is deposited or adhered to the light-incident side of the nearly transparent substrate 56. As a result, the P-wave component of sunlight does not incident on the information display device 48, significantly improving reliability in terms of light resistance and heat resistance. Meanwhile, the film 58 also has the properties of a filter that selectively transmits S-polarized video light output from the information display device 48, significantly improving the contrast performance of the resulting image.

[0080] Furthermore, since the image source of the aforementioned image display device 48 is a liquid crystal panel, similar to the information display device 100 mentioned above, if the driver is wearing polarized sunglasses, a problem occurs in which certain polarizations are blocked and the image cannot be seen. To prevent this, a phase difference plate 57, such as a λ / 4 plate, λ / 8 plate, or λ / 16 plate, is placed between the film 58 of the protective cover 50 of the information display device 48 and the base material 56. By providing the phase difference plate 57, the polarization direction of the light beam is aligned to a specific direction, and the image light is polarized at an optimal angle, shifting the polarization axis by a desired amount from the polarization direction of the polarized sunglasses.

[0081] On the other hand, rotating the polarization axis to approach circular polarization causes the polarization axis of the image light from the information display device to rotate from S polarization. As a result, the reflectivity of the front glass 6 decreases and the brightness of the image decreases, so it is best to choose a setting that balances both.

[0082] <Specific Examples of Vehicle Information Display Systems> Figure 13 shows an example of the arrangement of the information display system of the present invention, including the information display device 100 and the information display device 48 described above, in the cockpit of an automobile. Figure 13(a) shows a system corresponding to an automobile with the steering wheel on the left side, and Figure 13(b) shows a system corresponding to an automobile with the steering wheel on the right side. In the image display area 1(a) of the figure, the information display device 100 is used to reflect video information off the windshield 6, allowing the driver to view a virtual image. In the image display area 1(b), the video information displayed on the information display device 48 is reflected off the windshield, allowing the driver to view a real image. Alternatively, the video information may be reflected using a combiner equipped with a film 51.

[0083] As shown in Figure 3, the information display devices 100 and 48 are positioned between the windshield 6 and the steering wheel 43. Inside the dashboard 47, the video display device 48 and the information display device 100 are arranged sequentially from the windshield 6 towards the steering wheel 43. As a result, the external scenery that the driver views through the windshield 6 when driving the vehicle is displayed as an information display system that obtains video information by reflecting it off the windshield 6. The windshield 6 is divided into multiple areas, and in one area, the information display device 100 displays a large virtual image at a distance using a head-up display device. On the other hand, in the lower edge area of ​​the windshield (displaying an image within the area of ​​the vehicle's hood), for example, a second information display device is provided, which reflects the image of the large, high-resolution information display device 48 off the windshield 6, providing an information video system that the driver and passengers can directly view. As a result, the information the driver needs can be displayed appropriately with different resolutions and image sizes according to the display area of ​​the windshield 6.

[0084] Furthermore, the rearview mirror 71 in Figure 13 is equipped with a camera 72 that monitors the driver's condition and the interior of the vehicle, and controls the direction of the light emitted from the aforementioned information display device to match the driver's eye level, for example.

[0085] Figure 14 is a schematic diagram showing an information video system that also provides video information to a passenger in the front passenger seat. Similar to Figure 13, Figure 14(a) shows a system corresponding to a car with the steering wheel on the left side, and Figure 14(b) shows a system corresponding to a car with the steering wheel on the right side. In the image display area 1(a), the information display device 100 is used to reflect video information off the windshield, allowing the driver to view a virtual image. In the image display area 1(b), the video information displayed on the information display device 48 is reflected off the windshield, allowing the driver to view a real image. As a result, the passenger is shown video information displayed by a device (not shown) with a similar configuration to the video display device 48, which is reflected onto the image display area 1(c) on the windshield, allowing the driver to view a real image.

[0086] It is clear that the aforementioned film 51 (see Figure 7) is attached or bonded to the windshield 6 corresponding to image display area 1(b) and image display area 1(c).

[0087] Next, the structure of the film 51 will be explained with reference to Figure 15. Sunlight entering the windshield 6 (for the sake of explanation, it will be assumed to be horizontally positioned) from an oblique direction reflects its S-polarization and transmits its P-polarization towards the film 51. The film 51 is composed of a polarizing plate 55b that transmits S-waves and a transparent diffusion sheet 55a. The transparent diffusion sheet 55a is a film made by dissolving and stretching a thermoplastic polymer in which nanoparticles of zirconium or diamond with a high refractive index are dispersed, such as JXTG Energy's "Kaleidoscreen". By using the transparent diffusion sheet 55a, it is transparent when no image is displayed and does not obstruct the driver's view of the outside world (outside the car). On the other hand, when an image is displayed, it diffuses the image light, making it possible for the driver and passengers to see the image information.

[0088] The image light from the information display device 48 is S-polarized, but some of the image light scattered inside the transparent diffusion sheet 55a has its polarization direction rotated toward the windshield 6, and some of it becomes close to P-polarized. This light is absorbed by the polarizer 55b and is not reflected at the surface of the windshield 6 that is in contact with the outside world. For this reason, the image reflected by the film 51 does not become a double image caused by the reflected image on the windshield 6.

[0089] Similarly, it goes without saying that the same effect can be obtained by applying the aforementioned film 51 to the combiner instead of the windshield 6 as the reflective surface for the image.

[0090] In the information display system and the first information display device of the present invention described above, (1) under predetermined daytime conditions, the P-polarized sunlight component that has passed through the windshield (and subsequently through the combiner in the combiner method) is absorbed in front of the concave mirror so that it does not return to the liquid crystal panel and polarizer. (2) When the first information display device is not used, the concave mirror is rotated to a predetermined angle to prevent sunlight from returning to the image display device, thereby preventing sunlight focused by the concave mirror from returning to the image display device.

[0091] Furthermore, a large, high-resolution second information display device is installed on the dashboard at a position corresponding to the image display area in the lower edge region of the windshield. This provides an information video system in which the displayed image is reflected off the windshield, allowing the driver and passengers to directly view the reflected image. A transparent screen with the effect of scattering image light is installed on the windshield corresponding to the second image display position, and by efficiently reflecting the light, the image can be provided to the driver and passengers at a practically acceptable level of image quality. Because the aforementioned large, high-resolution second image display device is highly luminous, the direction of the emitted image light is controlled to prevent the image light from directly entering the eyes of the driver and passengers.

[0092] According to this embodiment, an in-vehicle information display system and information display device for the same purpose are provided, which is an information display device that obtains information by superimposing video information reflected by the windshield onto the external scenery viewed by the driver through the windshield when driving the vehicle. This system divides the windshield into multiple areas, and in one area a head-up display device displays a large virtual image at a distance. On the other hand, for example, in the area at the lower end of the windshield, the image of a large high-resolution video display device is reflected by the windshield, and the reflected image is viewed directly by the driver and passengers. As a result, a high-quality video information system that can handle the increasing resolution of display images on information terminals such as smartphones is provided.

[0093] Furthermore, even in large-scale, high-resolution video display devices, the energy of light incident on the display device is reduced by absorbing not only the infrared component of sunlight but also a portion of the P-polarized component of light across a wide range of wavelengths. Additionally, by providing a protective cover on the surface of a high-resolution video display device (e.g., a liquid crystal display panel) and equipping one side of the cover with a light-absorbing layer to absorb a portion of sunlight, and equipping the other side with a polarizing plate to absorb P-wave sunlight, it becomes possible to reduce the adverse effects on the polarizing plate integrated with the liquid crystal display device (e.g., a liquid crystal display panel).

[0094] Furthermore, the image light from large, high-resolution video display devices is designed to be directional, preventing direct light from entering the driver's eyes. By changing the image light from divergent light to a directional beam, the efficiency of light utilization can also be improved.

[0095] Although various embodiments have been described in detail above, the present invention is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above are detailed explanations of the entire system in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of Symbols]

[0096] 100... Information display device (first information display device), 1... Concave mirror, 2... Lens element, 4... Image display device (Liquid crystal display element, Liquid crystal display panel), 6... Windshield (projection target), 7... Housing, V1... Virtual image, 8... Eye point (observer's eye), 101... Light source device, 41... Glare stop, 43... Steering wheel, 47... Dashboard, 48... Information display device (second information display device), 50... Protective cover, 51... Film, 55a... Transparent diffusion sheet, 55b... Polarizing plate, 57... Phase difference plate, 58... Film, 52... Image display element, 59... Black stripe, 1010... Automobile, 300... Smartphone

Claims

1. An information display device for displaying an image to a viewer by reflecting image light onto the windshield of a vehicle, A backlight device that generates a luminous flux, A display panel that modulates the illumination beam from the backlight device and emits image light onto the windshield, An optical direction conversion panel is positioned in the optical path near the aforementioned display panel, Equipped with, The optical direction conversion panel includes a linear Fresnel lens that refracts the light beam in a desired direction, and controls the directional characteristics of the image light. The pitch of the linear Fresnel lens is 1 / 3 or less of the pixel pitch of the display panel. Information display device.

2. In the information display device according to claim 1, The display panel is provided with a substantially transparent substrate on the video display side, The display panel side of the substantially transparent substrate is provided with a layer that absorbs or reflects light of a predetermined polarization. Information display device.

3. In the information display device according to Claim 1, The linear Fresnel lens is provided with a protective cover, Information display device.

4. In the information display device according to claim 1, A polarizing plate is provided between the optical direction conversion panel and the display panel. Information display device.

5. In the information display device according to claim 1, The light source of the aforementioned backlight device is an LED. Information display device.

6. In the information display device according to claim 5, The backlight device includes a heat sink for cooling the LED. Information display device.

7. In the information display device according to claim 1, The backlight device has a polarization conversion element, Information display device.

8. In the information display device according to claim 1, The backlight device has an exterior made of plastic and houses a light guide. Information display device.

Images