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 the windshield or combiner of an automobile, train, airplane, etc. (hereinafter collectively referred to as "vehicle"), and to a vehicle information display device that reflects the image back on the windshield like a mirror, allowing the real or virtual image to be observed, and to the information display device. [Background technology]

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

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

[0004] A head-up display device uses an optical system including a concave mirror (which acts like a convex lens) to provide the driver with a virtual image of the image displayed on the image display device as an enlarged image, and a windshield or combiner is always required as the final reflecting surface.

[0005] Liquid crystal display elements (liquid crystal display panels) are often used as the image display devices used in the above-mentioned head-up display devices because they can easily produce high-quality images and are inexpensive. However, because small liquid crystal display elements are used to make the sets smaller, a new issue has emerged: the resolution of the resulting projected images is insufficient, making them unsuitable for displaying high-resolution images such as those displayed on smartphones.

[0006] The present invention relates to a vehicle information display system that uses a video information display device in combination with the above-mentioned head-up display device, using different technical means for each video display area for the external scenery viewed by the driver through the windshield, in order to compensate for the resolution of the head-up display device, and to technical means for realizing an information display device that is used in such a system and includes an information display device for providing the driver with high-resolution video information.

[0007] Furthermore, according to Patent Document 2 below, a head-up display device is already known in which a transparent reflective member (hot mirror) that passes display light from the liquid crystal display panel but reflects infrared rays is provided in front of the liquid crystal display panel in a non-parallel manner, in order to protect the inexpensive liquid crystal display panel used as the image source of the information display device from damage caused by sunlight.

[0008] Meanwhile, a head-up display device with a different structure has already been proposed, in which the main body including the combiner is attached near the roof (sun visor) of the vehicle, as disclosed in the following Non-Patent Document 1. However, there are still safety issues, such as the possibility of the driver being injured if the HUD device becomes detached in the event of a collision. For this reason, it is thought that a system in which image light is reflected directly on 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 Application Laid-Open No. 2015-194707 [Patent Document 2] Patent No. 4788882 [Non-patent literature]

[0010] [Non-Patent Document 1] PIONEER R&D (Vol. 22, 2013) Summary of the Invention [Problem to be solved by the invention]

[0011] The example of a head-up display device disclosed in Patent Document 1, which is the above-mentioned prior art, includes a device for displaying an image and a projection optical system for projecting the image displayed on the display device, and the projection optical system has a first mirror and a second mirror in an 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 on the first mirror in the image long axis direction and the angle of incidence on the first mirror in the image short axis direction, the distance between the image display surface of the display device and the first mirror, and the horizontal width of the virtual image viewed by the viewer. However, no specific solution to the problem of increasing the resolution of the above-mentioned image is disclosed, let alone a new problem that, under certain daytime conditions, sunlight passes through the windshield and is concentrated by the concave mirror, causing image damage to the liquid crystal panel and the polarizing plate, resulting in a significant decrease in performance.

[0012] It is expected that the method of using the windshield as a reflective surface, as described in Patent Document 1, will become mainstream in the future, but no consideration has been given at all to dealing with the increasing resolution of images displayed on information terminals such as smartphones.In addition, no consideration has been given at all to measures to prevent the occurrence of so-called burning (carbonization), which is a very important problem for the practical application of vehicle information display devices. This occurs under certain daytime conditions, when sunlight passes through the windshield and is concentrated by a concave mirror, and is concentrated on the polarizing plate or liquid crystal panel itself provided on the light-exiting side of the liquid crystal display device, causing deterioration due to the heat and light intensity of the sunlight and preventing the device from functioning normally.

[0013] Similarly, the technology disclosed in Non-Patent Document 1, in which the final reflecting surface is a combiner, does not take into consideration 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 certain daytime conditions and is concentrated by the concave mirror, damaging the liquid crystal panel and polarizer and significantly reducing performance.

[0014] Furthermore, Patent Document 2 above proposes placing a transmissive reflective member (hot mirror) in the optical path to selectively reflect infrared sunlight in order to reduce the risk of damage to the liquid crystal display panel caused by sunlight. However, the sunlight that penetrates the display contains not only infrared rays but also light rays in the visible and ultraviolet regions, and therefore, simply reducing infrared rays is insufficient to reduce damage caused by sunlight to the liquid crystal display element and polarizing plate. Furthermore, no consideration has been given to the new problem of the quality of the image seen by the driver, particularly the significant reduction in contrast performance and apparent resolution, which is a negative effect of the penetration of external light, including visible light, and to how to address the increasing resolution of displayed images.

[0015] As described above, in the head-up display device as an information display device that provides visual information to the driver using the conventional technology described above, a large liquid crystal display element is required to obtain a high-resolution display image, and therefore the first problem that the device cannot be made compact and have high resolution at the same time has become clear.

[0016] Furthermore, a second problem has become clear regarding the liquid crystal panel used as the image display device of a head-up display device: when actually mounted in a vehicle, sunlight passes through the windshield under certain daytime conditions and is concentrated by the concave mirror, damaging the liquid crystal panel and polarizing plate, resulting in a significant reduction in performance.

[0017] The present invention has been made in consideration of the problems in the conventional technology described above, and more specifically, an object of the present invention is to provide an in-vehicle information display system that is capable of achieving both miniaturization and high resolution and is suitable for practical use, and an information display device therefor. [Means for solving the problem]

[0018] In order to achieve the above-mentioned object, the present invention provides an information display system for a vehicle that reflects image light onto the windshield of a vehicle to display image information to a viewer, the information display system comprising: a first information display device that reflects image light off the windshield to allow the viewer to view a virtual image; and a second information display device that reflects image light off 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] The present invention also provides an information display device for constituting an information display system that reflects image light on the windshield of a vehicle and displays image information to a viewer, the information display device comprising: an image light generating means for generating image light that displays image information inside a housing having an opening in one part; an image light processing means for performing predetermined optical processing on the image light from the image light generating means; and a means for projecting the image light from the image light processing means through the opening in the housing so that the viewer recognizes the image information as a virtual image in front of the windshield.

[0020] Furthermore, the present invention provides an information display device for constituting an information display system that reflects image light on the windshield of a vehicle and displays image information to a viewer, the information display device comprising: a backlight device that generates a highly directional illumination light beam; a display panel that modulates the highly directional illumination light beam from the backlight device in accordance with the image information and emits it onto the windshield; and a light direction conversion panel that is provided in part of the windshield and 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, it is possible to provide a vehicle information display system in which a head-up display device displays a large-screen virtual image in the distance in a portion of the windshield as an information display device that provides video information by reflecting the external scenery viewed through the windshield when the driver is driving the vehicle, and on the other hand, an image from a large, high-resolution video display device is reflected by the windshield in, for example, the lower edge region of the windshield, allowing the driver and passengers to directly view the reflected image. As a result, it is possible to appropriately display images with different resolutions and image sizes on the windshield to provide the information the driver needs.

[0022] On the other hand, according to the present invention described above, it is possible to achieve a compact head-up display device while correcting distortions and aberrations in the virtual image observed by the driver caused by external light, including sunlight, and at the same time, the concave mirror that forms the virtual image optical system can reduce the damage caused to the liquid crystal panel and polarizing plate, which are image display devices, and the like, and the resulting degradation of performance by concentrating external light, including sunlight (mostly P-polarized components), that enters through the windshield.In other words, it is possible to provide an information display device for a vehicle information display system that reduces the adverse effects of light with a wide range of wavelengths contained in external light, including sunlight, and forms a virtual image with excellent performance. [Brief explanation of the drawings]

[0023] [Figure 1] 1A and 1B are top views of a vehicle equipped with the vehicular information display system of the present invention and diagrams illustrating differences in the radius of curvature of the windshield. [Figure 2] 1 is a diagram showing a schematic configuration including a virtual image optical system of a first information display device according to an embodiment of the present invention; [Figure 3] 3 is a schematic diagram showing the relationship between the first information display device, the second information display device, the windshield, the driver's viewpoint position, and sunlight. FIG. [Figure 4] 1 is a schematic diagram showing the relationship between a first information display device of a vehicle information display system, a windshield, an image display position, a driver's viewpoint position, and sunlight. [Figure 5]1 is a schematic configuration diagram of a first information display device of a vehicle information display system; [Figure 6] 3 is a schematic diagram for explaining the operation of components of the first information display device of the vehicle information display system; FIG. [Figure 7] 10 is a schematic diagram showing the relationship between the second information display device of the vehicle information display system, the windshield, the image display position, the driver's viewpoint position, and sunlight. FIG. [Figure 8] FIG. 2 is a schematic configuration diagram of a second information display device of the vehicle information display system. [Figure 9] FIG. 10 is a cross-sectional view showing the configuration of a light source device according to a second information display device. [Figure 10] 10A and 10B are a top view and a cross-sectional view showing the configuration and operation of a light source device of a second information display device. [Figure 11] 10A and 10B are explanatory diagrams for explaining the function of optical components that constitute the light source device according to the second information display device. [Figure 12] FIG. 10 is a conceptual diagram illustrating the configuration of an optical component according to a second information display device. [Figure 13] 1 is a schematic diagram showing an example of a vehicle cockpit provided with a first information display device and a second information display device that constitute a vehicle information display system; [Figure 14] FIG. 10 is a schematic diagram showing another example of an automobile cockpit provided with a first information display device and a second information display device that constitute a vehicle information display system. [Figure 15] 1A and 1B are diagrams illustrating the configuration of a film adhered to a windshield in a vehicle information display system. [Figure 16] FIG. 1 is a schematic diagram for explaining the change in reflectance of glass depending on the angle of incidence of S-polarized light and P-polarized light. [Figure 17] FIG. 1 is a diagram showing the spectral irradiance of sunlight. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings and the like. Note that the present invention is not limited to the following description, and various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the present invention, parts having the same function are designated by the same reference numerals, and repeated explanations thereof may be omitted.

[0025] <Outline of vehicle information display system> FIG. 1(a) is a top view of an information display device 100 according to an embodiment of the present invention, which will be described later, mounted on an automobile, train, airplane, or other vehicle, particularly an automobile. In front of the driver's seat of an automobile 1010, there is a windshield 6 as a projection target. The inclination angle of the windshield 6 relative to the body varies depending on the type of automobile. Furthermore, the inventors investigated the radius of curvature of the windshield 6 in order to realize an optimal virtual image optical system. As a result, as shown in FIG. 1(b), the windshield 6 has a radius of curvature Rh in the horizontal direction parallel to the vehicle's contact surface and a radius of curvature Rv in the direction perpendicular to the horizontal axis, which are different, and it was found that the following relationship generally holds between Rh and Rv: Rh>Rv It was also found that the difference in the radius of curvature, that is, the ratio of Rh to Rv, was in the range of 1.5 to 2.5 times in many cases.

[0026] In this invention, video information is displayed by reflecting it on the windshield as the driver views the external scenery through the windshield while driving the vehicle. The information display device divides the windshield into multiple areas, and a head-up display device displays a large-screen virtual image in the distance in some of the areas. On the other hand, an image from a large, high-resolution video display device is reflected by the windshield in, for example, the lower edge area of ​​the windshield, so that 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 by changing the resolution and image size depending on the display area of ​​the windshield.

[0027] One example of such a head-up display device is an information display device that displays video information on a projection surface as a virtual image, and is provided with an information display device that includes, inside a housing having an opening in one portion, a video light generating means that generates video light that displays the video information, a means for performing predetermined optical processing on the video light from the video light generating means, and a means for projecting the video light from the video light processing means onto the projection surface through the opening in the housing so that a viewer can recognize the video information as a virtual image in front of the projection surface.

[0028] More specifically, as will be described in detail below, in the information display device of the present invention, a polarizing plate that absorbs P-polarized sunlight is provided in the glare stopper 41 provided in the opening. 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 stopper 41 absorb the P-wave component, the following effects can be obtained. (1) Under specified daytime conditions, the P-polarized sunlight component that passes through the windshield (and then passes through the combiner in the case of the combiner method) is absorbed just before the concave mirror, preventing the sunlight that passes through the windshield from returning to the LCD panel and polarizing plate. (2) When the information display device is not in use, the concave mirror is rotated by a predetermined angle to prevent sunlight from returning to the image display device, thereby preventing sunlight collected by the concave mirror from returning to the image display device.

[0029] Furthermore, an information video system is provided in which a large, high-resolution video display device is installed in a position on the dashboard corresponding to the video display area in the lower edge region of the windshield, and the displayed video is reflected by the windshield, allowing the driver and passengers to view the reflected image directly. 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 video can be presented to the driver and passengers with a level of image quality that is practically acceptable. Because the large, high-resolution video display device described above is highly bright, controlling the direction of the video light output prevents the video light from directly entering the eyes of the driver and passengers.

[0030] <First information display device of vehicle information display system> FIG. 2 is a schematic diagram showing the peripheral device configuration of a first information display device of the vehicular 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 as the information display device 100 according to one embodiment of the present invention is a device (so-called HUD (Head-up Display)) that displays various information reflected from a projection target (in this embodiment, the inner surface of the windshield 6) as a virtual image VI (virtual image) to form a virtual image V1 in front of the vehicle at the driver's line of sight (eyepoint: described in detail later) 8. The illustrated control device 40 constituting such an HUD device acquires, from a navigation system 61, various pieces of information 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 travel of the vehicle set in the navigation system 61, as foreground information (i.e., information to be displayed in front of the vehicle as the virtual image).

[0031] The illustrated driving assistance ECU 62 is a control device for realizing driving assistance control by controlling the drive system and control system in accordance with obstacles detected as a result of monitoring by the surroundings monitoring device 63. Such driving assistance control includes well-known technologies such as cruise control, adaptive cruise control, pre-crash safety, and lane keeping assist.

[0032] The illustrated surroundings monitoring device 63 is a device that monitors the situation around the vehicle, and examples include a camera that detects objects around the vehicle based on images taken of the area around the vehicle, or an exploration device that detects objects around the vehicle based on the results of transmitting and receiving exploration waves.

[0033] The control device 40 of the HUD device described above acquires information from the driving assistance ECU 62 (e.g., the distance to the preceding vehicle, the direction of the preceding vehicle, the locations of obstacles and signs, etc.) as foreground information. Furthermore, an ignition (IG) signal and vehicle status information are input to the control device 40. Among these pieces of information, the vehicle status information is acquired as vehicle information and includes warning information indicating a predetermined abnormal state, such as the remaining amount of fuel in the internal combustion engine and the temperature of the coolant, which does not require high-resolution display. The information also includes the operation result of the turn signal, the vehicle's traveling speed, and even the gear position information. The control device 40 described above is activated when an ignition signal is input. This concludes the description of the overall information display device system of this embodiment.

[0034] The projection target may be any member onto which information is projected, and may be not only the windshield 6 but also a combiner. That is, the information display device 100 of this embodiment may be any member that forms a virtual image in front of the vehicle in the driver's line of sight 8 and allows the driver to view it.

[0035] Information display device 100 having the above-described configuration includes image display device 4 that projects image light for displaying information, and corrective lens element 2 for correcting distortion and aberration that occur when a virtual image is formed from the image displayed on image display device 4 using concave (free-form surface) mirror 1. The image light beam from information display device 100 is emitted toward windshield 6 from an opening (not shown).

[0036] The information display device 100 further includes a control device 40 that controls the image display device 4 and its backlight. The optical components including the image display device 4 and the backlight are a virtual image optical system, which will be described below, and include a concave mirror 1 that reflects light. The light reflected by this optical component is reflected by the windshield 6, which is the member onto which the light is projected, and heads toward the driver's line of sight 8.

[0037] The image display device 4 may be, for example, a self-luminous VFD (Vacuum Flourescent Display) in addition to a backlight-equipped LCD (Liquid Crystal Display).

[0038] On the other hand, instead of the above-mentioned image display device 4, an image may be displayed on a screen using a projection device, and then the image may be converted into a virtual image by the above-mentioned concave mirror 1, and reflected by the windshield 6 or a combiner (not shown), which is the projection target, toward the driver's viewpoint 8.

[0039] Here, in order to reduce distortion of the virtual image, the shape of the concave mirror 1 should be such that the radius of curvature is relatively small so that the magnification is large in the upper part (the region where light rays are reflected below the windshield 6, which is relatively close to the driver's viewpoint 8) shown in Fig. 1, and the radius of curvature is relatively large so that the magnification is small in the lower part (the region where light rays are reflected above the windshield 6, which is relatively far from the driver's viewpoint). Furthermore, even better correction can be achieved by tilting the image display device 4 with respect to the optical axis of the concave mirror 1 to correct the difference in virtual image magnification described above and reduce the distortion itself.

[0040] On the other hand, as shown in FIG. 1(b), the windshield 6 of a passenger vehicle has a different radius of curvature Rv in the vertical direction and a different radius of curvature Rh in the horizontal direction, with Rh > Rv generally being true. Therefore, when the windshield 6 is viewed as a reflective surface, it becomes a toroidal surface of the concave mirror 1. Therefore, in the information display device 100 of this embodiment, the shape of the concave mirror 1 is designed to compensate for the virtual image magnification due to the shape of the windshield 6, i.e., to compensate for the difference in the 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 surface symmetrical about the optical axis (shown below in 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 individually controlled. Therefore, it is preferable to correct the shape as a free-form surface shown below in Equation 1, as a function of the coordinates (x, y) of the mirror surface from the optical axis.

[0041]

number

[0042]

number

[0043] <The penetration of sunlight into the device and the principle of its suppression> Next, the penetration of sunlight into the information display device at the driver's seat of the vehicle will be described. Fig. 3 shows a state near the driver's seat of a vehicle, with the information display device 100 described above being disposed below a windshield 6 attached between a hood 44 and a ceiling panel 45 that constitute the vehicle body, behind a dashboard that includes instruments such as a speedometer 42 (on the rear hood side). This figure also shows the daytime sun 60 above the vehicle, along with the vehicle's steering wheel 43 and the driver's eye 8. Fig. 4 mainly shows the sun 60, the windshield 6, and the viewer's eye 8 extracted from the configuration of Fig. 3, and Fig. 5 shows a configuration in which the information display device 100 is housed in a housing 7.

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

[0045] On the other hand, the image light emitted from the information display device 100 is reflected by the windshield 6 or a combiner (not shown) and enters the viewer's eye 8, as indicated by the solid arrows in FIGS.

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

[0047] Therefore, in this embodiment, based on the findings of the inventors described above, i.e., taking into consideration that most of the sunlight that enters through the windshield 6 is a P-polarized component, it has been confirmed that reducing the P-wave component is particularly effective in suppressing external light, including sunlight, from entering the information display device 100, and in addition, it is effective to use the S-wave component as the image light projected from the information display device 100.

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

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

[0050] To further enhance the aberration correction capability, the lens element 2 may be composed of multiple lenses. Alternatively, a curved (free-form) mirror may be disposed in place of the lens element 2. The curved mirror may be used to fold the optical path while simultaneously controlling the position of incidence of the light beam on the concave mirror 1, thereby reducing distortion. As described above, it goes without saying that providing an optical element optimally designed to further improve the aberration correction capability between the concave mirror 1 and the image display device 4 does not deviate from the technical spirit 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 inherent aberration correction, the optical distance between the concave mirror 1 and the image display device 4 can be changed, thereby continuously varying the display position of the virtual image from a distant to a close position.

[0051] The S-polarized component of sunlight pouring in from outside the vehicle is reflected by the windshield 6, while the P-polarized component is transmitted toward the interior of the vehicle and enters the information display device 100 through the opening. One side of the glare stopper 41 installed at the opening is provided with a polarizing plate that absorbs the P-polarized component of the incident sunlight and transmits the S-polarized light. Furthermore, a reflective film that reflects light in the ultraviolet and infrared regions is provided on the other side of the glare stopper 41 or the sunlight incident surface of the polarizing plate. As a result, P-polarized waves in the visible light region and most light in the ultraviolet and infrared regions are prevented from entering the image display device 4, resulting in reduced damage to the image display device 4 from sunlight.

[0052] On the other hand, it is known that a factor that degrades the image quality of information display device 100 is that image light rays emitted from image display device 4 toward concave mirror 1 are reflected by the surface of lens element 2 arranged along the way, return to image display device 4, and are reflected again to be superimposed on the original image light, thereby degrading image quality. For this reason, in this embodiment, not only is an anti-reflection film formed on the surface of lens element 2 to suppress reflection, but it is also preferable to design the lens surface shape of either or both of the image light entrance surface and exit surface of lens element 2 with constraints on the surface shape so that the above-mentioned reflected light is not concentrated on a part of image display device 4 (for example, a shape with the concave surface facing image display device 4).

[0053] A λ / 16 plate (optimally selected from λ / 4, λ / 8, etc. depending on the balance with brightness) is provided on the image display device 4 side of the polarizing plate of the glare stop 41 described above, and a mechanism for adjusting the mounting angle is further 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 color overallness can be obtained by appropriately changing the mounting angle of the wave plate provided in the glare stop 41 of the present invention.

[0054] Furthermore, even if the polarizing plate provided in the glare stop 41 absorbs the P-polarized component of sunlight entering the vehicle, reliability is not impaired because the area of ​​the polarizing plate that receives the light is the same as the opening. Furthermore, this polarizing plate selectively transmits S-polarized light, which 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) whose light output changes little with fluctuations in ambient temperature, and a polarizing beam splitter (PBS) provided with optical means for reducing the divergence angle of light, and that the PBS performs polarization conversion.

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

[0057] When a liquid crystal panel is used as the image display device 4, a problem occurs, particularly when the driver is wearing polarized sunglasses, in which certain polarized waves are blocked, making the image invisible. To prevent this, as described above, a λ / 4 plate, λ / 8 plate, or λ / 16 plate is placed on one side of the glare stopper 41 installed 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, by rotating the glare stopper 41 from the position shown in Figure 5 to position 46 shown by the dashed line in Figure 6, the polarization angle of the image light can be appropriately changed, converting it to circular polarization or rotating the polarization axis of linear polarization to a polarization axis different from that of the polarized sunglasses. On the other hand, rotating the polarization axis to approach circular polarization rotates the polarization axis of the image light from the information display device from S-polarized light, reducing the reflectivity of the windshield 6 and reducing the brightness of the image. Therefore, it is best to strike a balance between these two.

[0058] The inventors have found through experiments that in order to reduce the color unevenness of the image obtained at this time (color uniformity across the entire screen when the entire screen is displayed in white), it is effective to place a specified wavelength plate at the position of the glare stop where the image light beam is most widespread.

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

[0060] <Specific Example of the Second Information Display Device> As shown in Figures 3 and 7, information display device 48, which is the second information display device of the present invention, displays a pseudo-image on the windshield by reflecting high-resolution images (images from a large, high-resolution image display device) from, for example, a smartphone 300 toward the viewer's eyes using a film (e.g., a transparent film or sheet) 51 provided on the surface of the windshield 6.

[0061] Next, the configuration of the information display device 48 will be described with reference to 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 of over 6 inches. Generally, the radius of curvature of the windshield 6 often varies in different parts, which causes uneven (vertical and horizontal) distortion in the displayed image depending on the location where the image is reflected. For this reason, distortion correction is required to obtain a correct image when the reflected image is viewed from the viewing direction. To perform this distortion correction at a level that is practically acceptable, the panel resolution must be 1280 x 720 dots or higher.

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

[0063] Furthermore, light source device 101 is formed from, for example, plastic. Light source device 101 includes a case (see FIG. 8) for light source device 101 that houses LEDs, a collimator, a composite diffusion block, a light guide, and the like, which will be described in detail later. Information display device 48 and image display element 52 are attached to the top surface of light source device 101. Furthermore, LED substrate 102 (see FIGS. 9-10) on which LED (Light Emitting Diode) elements, which are semiconductor light sources, and their control circuits are mounted is attached to one side of the case of light source device 101, and heat sink 103 for cooling heat generated by the LED elements and control circuit is attached to the outer surface of LED substrate 102 (see FIG. 8).

[0064] On the other hand, the image display element 52 attached to the upper surface of the light source device 101 is composed of a liquid crystal display panel frame, a liquid crystal display panel attached to the frame, and an FPC (Flexible Printed Circuits) 403 (see FIG. 8) electrically connected to the panel. That is, as will be described in detail later, the image displayed by the image display element 52, together with the LED elements that are solid-state light sources, is generated and controlled by control signals from a control circuit (not shown here) that constitutes the electronic device.

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

[0066] 9 and 10 show a plurality of (two in this example) LEDs 14a and 14b (not shown) constituting the light source, which are attached at predetermined positions relative to the LED collimator 15. Each of the LED collimators 15 is made of a light-transmitting resin, such as acrylic. As shown in FIG. 10(b), the LED collimator 15 has a cone-shaped outer peripheral surface 156 obtained by rotating a parabolic cross section, and a recess 153 at its apex, with a convex lens portion (i.e., a convex lens surface) 157 formed in its central portion. The convex lens portion 157 has a convex lens surface 154 (which may be a concave lens surface recessed inward) protruding outward at its central portion. The outer peripheral surface 156 forming the cone-shaped outer peripheral surface of the LED collimator 15 is set within an angle range that allows total reflection of the light emitted from the LED 14a in the peripheral direction, or a reflective surface is formed thereon.

[0067] On the other hand, the LEDs 14a and 14b are respectively arranged at predetermined positions on the surface of the circuit board, that is, the so-called LED substrate 102. The LED substrate 102 is arranged and fixed to the LED collimator 15 so that the LEDs 14a and 14b on the surface are respectively positioned at the center of the recess 153.

[0068] According to this configuration, the light emitted from the LED 14a or 14b by the LED collimator 15 described above, particularly the light emitted upward from the central portion (toward the right in the figure), is collected and converted into parallel light by the convex lens portion 157 and convex lens surface 154 that form the outer shape of the LED collimator 15. Furthermore, the light emitted from other portions toward the periphery is reflected by the parabolic surface that forms the conical outer surface of the LED collimator 15, and is similarly collected and converted into parallel light. In other words, the LED collimator 15, which has a convex lens in its center and a parabolic surface formed on its periphery, can extract almost all of the light generated by the LED 14a or 14b as parallel light, thereby improving the utilization efficiency of the generated light.

[0069] A polarization conversion element 21, which will be described in detail below, is provided on the light exit side of the LED collimator 15. As is clear from the drawing, this polarization conversion element 21 is configured by combining a columnar light-transmitting member having a parallelogram cross section (hereinafter referred to as a parallelogram prism) with a columnar light-transmitting member having a triangular cross section (hereinafter referred to as a triangular prism), and arranging a plurality of these in an array parallel to a plane perpendicular to the optical axis of the collimated light from the LED collimator 15. Furthermore, PBS films 211 and reflective films 212 are alternately provided at the interfaces between adjacent light-transmitting members arranged in the array, and a ½λ phase plate 213 is provided on the exit surface from which light that has entered the polarization conversion element 21 and passed through the PBS film 211 exits.

[0070] 10(a) is provided on the exit surface of this polarization conversion element 21. That is, the light emitted from LED 14a or 14b is converted into parallel light by the action of LED collimator 15, enters the combining / diffusing block 16, is diffused by texture 161 on the exit side, and then reaches light guide 17, which will be described below.

[0071] The light guide 17 is a rod-shaped member made of a translucent resin such as acrylic and having an approximately triangular cross section (see Figure 10(b)). As is clear from Figure 10(a), the light guide 17 comprises a light guide light incident portion (light guide light incident surface) 171 that faces the exit surface of the synthetic diffusion block 16 via a first diffusion plate 18a, a light guide light reflecting portion (light guide light reflecting surface) 172 that forms an inclined surface, and a light guide light exit portion (light guide light exit surface) 173 that faces the liquid crystal display panel including the image display element 52 via a second diffusion plate 18b.

[0072] 9, which is a partially enlarged view, a number of reflective surfaces 172a and connecting surfaces 172b are alternately formed in a sawtooth pattern on the light guide light reflecting portion 172 of the light guide 17. The reflective surfaces 172a (line segments sloping upward to the right in the figure) form an angle αn (n: natural number, e.g., 1 to 130 in this example) with respect to the horizontal plane indicated by the dashed dotted line in the figure. As an example, αn is set to 43 degrees or less (but 0 degree or more).

[0073] As a result, light guide light incident portion 171 is formed in a curved convex shape inclined toward the light source. Accordingly, the parallel light from the exit surface of synthetic diffusion block 16 is diffused by first diffuser plate 18a and enters light guide 17. As is clear from the figure, the parallel light is bent (deflected) slightly upward by light guide light incident portion 171 and reaches light guide light reflecting portion 172.

[0074] As described above in detail, information display device 48 according to the present invention described above can further improve light utilization efficiency and uniform illumination characteristics, while also enabling compact, low-cost manufacturing, including a modularized S-polarized light source device. While the above description has been given assuming that polarization conversion element 21 is attached after LED collimator 15, this embodiment is not limited to this, and it will be clear to those skilled in the art that similar actions and effects can be achieved by locating polarization conversion element 21 anywhere along the optical path leading to the liquid crystal display panel.

[0075] The light guide light reflecting section 172 has a number of alternating reflective surfaces 172a and connecting surfaces 172b formed in a sawtooth pattern. The diffused light diffused by the first diffuser plate 18a is totally reflected by each reflective surface 172a and directed upward. The upward diffused light passes through the light guide light emitting section 173 and the second diffuser plate 18b and enters the light redirecting panel 54, which controls the directivity, as a parallel diffused light beam. The light redirecting panel 54 redirects the light of this diffused light beam. The redirected diffused light beam is emitted from the light redirecting panel 54 in the direction shown in FIG. 9, for example, and enters the image display element 52 at an oblique angle.

[0076] FIG. 11 is a schematic diagram illustrating the principle of the light redirecting panel 54 provided in the information display device 48 described above. A light beam from the light guide enters the light redirecting panel's entrance surface and is refracted in the 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 using 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 impart directionality to the collimated light beam from the light guide in the desired direction.

[0077] Similarly, by providing a linear Fresnel lens having the structure shown in FIG. 11 on the light exit surface of the image display device 48, directivity is provided toward the windshield 6, which serves as a reflecting surface for the image light beam. As a result, even if the driver looks directly at the screen of the image display device 48, the image light does not reach the driver's eyes directly, so driving is not hindered. The pitch of the linear Fresnel lens is desirably 1 / 3 or less of the pixel pitch of the image display device 48. For example, to reduce the moire that occurs due to the pitch ratio between the pixels and the linear Fresnel lens to a practically acceptable level, the pitch of the linear Fresnel lens is desirably 1 / 7 or less of the pixel pitch. In addition, a protective cover (shown by a dashed line) is provided on the surface of the linear Fresnel lens to protect it from wear and tear.

[0078] FIG. 12 is a cross-sectional view showing a 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 a substantially transparent substrate 56. The black stripe 59 reduces surface reflection of external light, including sunlight. For example, black paint containing carbon black is used for the black stripe 59. Furthermore, an anti-reflection film is provided in the portion where the black stripe is not provided to suppress surface reflection. The anti-reflection film significantly reduces external light reflection on the surface of the protective cover 50, reducing the hindrance caused by external light reflection when the driver is driving the vehicle.

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

[0080] Since the image source of the image display device 48 described above is a liquid crystal panel, when the driver is wearing polarized sunglasses, certain polarized waves are blocked, making the image invisible, as with the information display device 100 described above. To prevent this, a retardation plate 57 such as a λ / 4 plate, λ / 8 plate, or λ / 16 plate is disposed between the film 58 of the protective cover 50 of the information display device 48 and the substrate 56. By providing the retardation plate 57, the polarization direction of the light beam can be aligned in a specific direction, and the polarization axis of the image light can be shifted by a desired amount from the polarization direction of the polarized sunglasses, providing an optimal polarization angle.

[0081] 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 will rotate from S-polarized light, which will reduce the reflectance of the windshield 6 and reduce the brightness of the image, so it is best to strike a balance between these two when making your selection.

[0082] <Specific Examples of Vehicle Information Display Systems> FIG. 13 shows an example of the arrangement in the cockpit of an automobile in which the information display system of the present invention, including the above-described information display device 100 and information display device 48, is arranged. FIG. 13(a) shows a system corresponding to an automobile in which the steering wheel is arranged on the left side, and FIG. 13(b) shows a system corresponding to an automobile in which the steering wheel is arranged on the right side. In the image display area 1(a) of the figure, video information is reflected by the windshield 6 using the information display device 100, and a virtual image is viewed by the driver. In the image display area 1(b), video information displayed on the information display device 48 is reflected by the windshield, and a real image is viewed by the driver. Note that the video information may also be reflected by a combiner provided with a film 51.

[0083] As shown in FIG. 3 , the information display device 100 and the information display device 48 are disposed between the windshield 6 and the steering wheel 43. Inside the dashboard 47, the image display device 48 and the information display device 100 are sequentially disposed from the windshield 6 toward the steering wheel 43. As a result, when the driver drives the vehicle, the external scenery viewed through the windshield 6 is reflected by the windshield 6 to obtain image information. The windshield 6 is divided into multiple regions as an information display system, and in some of the regions, a large-screen virtual image is displayed in the distance using a head-up display device as the information display device 100. On the other hand, in the lower end region of the windshield, for example (displaying an image within the hood of the vehicle), an image from the large, high-resolution information display device 48 is reflected by the windshield 6 as a second information display device, and the reflected image is directly viewed by the driver and passengers. This provides an information and image system. As a result, the information required by the driver can be displayed appropriately by varying the resolution and image size according to the display region of the windshield 6.

[0084] The rearview mirror 71 in FIG. 13 is provided with a camera 72 for monitoring the driver's condition and the state inside the vehicle, and the direction of emission of the image light from the information display device is controlled to match the driver's eye height, for example.

[0085] FIG. 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 FIG. 13, FIG. 14(a) shows a system suitable for a vehicle with a steering wheel located on the left side, and FIG. 14(b) shows a system suitable for a vehicle with a steering wheel located on the right side. In image display area 1(a), video information is reflected off the windshield using information display device 100, allowing the driver to view a virtual image. In image display area 1(b), video information displayed on information display device 48 is reflected off the windshield, allowing the driver to view a real image. As a result, for the passenger, video information displayed by a device (not shown) having a similar configuration to video display device 48 is reflected onto image display area 1(c) on the windshield, allowing the driver to view a real image.

[0086] It will be apparent that the film 51 (see FIG. 7) already described is adhered or bonded to the windshield 6 corresponding to the image display area 1(b) and the image display area 1(c).

[0087] Next, the structure of the film 51 will be described with reference to FIG. 15. When sunlight is incident obliquely on the windshield 6 (which is assumed to be horizontally disposed), its S-polarized waves are reflected, while its P-polarized waves are transmitted toward 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 melting and stretching a thermoplastic polymer in which nanoparticles of zirconium or diamond, which have a high refractive index, are dispersed, such as the "Kaleidoscreen" manufactured by JXTG Nippon Oil & Energy Corporation. The transparent diffusion sheet 55a is transparent when no image is displayed, and does not obstruct the driver's view of the outside world (outside the vehicle). On the other hand, when an image is displayed, the light from the image is diffused, allowing the driver and passengers to view the image information.

[0088] The image light from information display device 48 is S-polarized, but the polarization direction of part of the image light scattered inside transparent diffusion sheet 55a described above is rotated toward windshield 6, and part of this light becomes closer to P-polarized light. This light is absorbed by polarizing plate 55b and is not reflected by the surface of windshield 6 that is in contact with the outside world. Therefore, the image reflected by film 51 does not become a double image caused by the image reflected by windshield 6.

[0089] Similarly, it goes without saying that the same effect can be obtained by sticking the above-mentioned film 51 on the combiner instead of the windshield 6 as a reflection surface for the image.

[0090] In the information display system and first information display device of the present invention described above, (1) under specified daytime conditions, the P-polarized sunlight component that passes through the windshield (and then passes through the combiner in the case of the combiner method) is absorbed just before the concave mirror, preventing it from returning to the liquid crystal panel and polarizing plate. (2) When the first information display device is not in use, the concave mirror is rotated by a predetermined angle to prevent sunlight from returning to the image display device, thereby preventing sunlight concentrated by the concave mirror from returning to the image display device.

[0091] Furthermore, an information and video system is provided in which a large, high-resolution second information display device is installed in a position on the dashboard corresponding to the video display area in the lower edge region of the windshield, and the displayed video is reflected by the windshield so that the driver and passengers can directly view the reflected image. A transparent screen that scatters video light is installed on the windshield corresponding to the second video display position, and by efficiently reflecting the light, the driver and passengers can be provided with a practically acceptable level of image quality. Because the large, high-resolution second video display device described above is highly bright, the direction of the video light output can be controlled to prevent the video light from directly entering the eyes of the driver and passengers.

[0092] According to this embodiment, an information display device is provided that superimposes image information reflected by the windshield onto the external scenery viewed through the windshield by the driver while driving his or her own vehicle.The windshield is divided into multiple areas, and a head-up display device displays a large virtual image in the distance in some of the areas, while an image from a large, high-resolution image display device is reflected by the windshield in an area, for example, at the bottom of the windshield, so that the driver and passengers can directly view the reflected image.As a result, an in-vehicle information display system and an information display device therefor are provided that can obtain high-quality image information that can keep up with the increasing resolution of display images on information terminals such as smartphones.

[0093] Furthermore, even in large-scale, high-resolution image display devices, the energy of light incident on the image display device can be reduced by absorbing not only the infrared component of sunlight but also part of the P-polarized component of light over a wide range of wavelengths. Also, by providing a protective cover on the surface of a high-resolution image display device (e.g., a liquid crystal display panel), providing a light-absorbing layer on one side to absorb part of the sunlight, and providing a polarizing plate on the other side 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] In addition, the image light from large, high-resolution image displays is given directionality and positioned so that direct light does not enter the driver's eyes. Changing the image light from divergent light to a directional luminous flux can also improve light utilization efficiency.

[0095] Various embodiments have been described above in detail. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments are detailed descriptions of the entire system to clearly explain the present invention, and the present invention is not necessarily limited to a system including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part 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 (projected member), 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 on a windshield of a vehicle, a backlight device that generates an illumination light beam; a display panel that modulates the illumination light beam from the backlight device and emits image light onto the windshield; a light redirecting panel disposed in a light path adjacent to the display panel; Equipped with the light redirecting panel controls the directional characteristics of the image light; Information display device.

2. 2. The information display device according to claim 1, a substantially transparent substrate on the image display surface side of the display panel; a layer that absorbs or reflects light of a predetermined polarized wave is provided on the display panel side of the substantially transparent base material; Information display device.

3. 2. The information display device according to claim 1, The light redirecting panel includes a linear Fresnel lens in part to refract light beams in a desired direction. Information display device.

4. 2. The information display device according to claim 1, a polarizer between the light redirecting panel and the display panel; Information display device.

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

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

7. 2. The information display device according to claim 1, The backlight device includes a Fresnel lens in part. Information display device.

8. 2. 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