Light source device and display device using the same

Abstract

To provide a more suitable display device that contributes to 3 health and well-being for all people of sustainable development goals (SDGs).SOLUTION: A display device includes: a display panel that emits image light to a projection member; a light source device that supplies light to the display panel; and a circular polarization conversion element on an image light emission surface side of the display panel. The display device reflects the image light from the display panel by the projection member and allows an image generated by the display panel to be visually recognized as a virtual image.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light source device and a display device using the same. [Background technology]

[0002] A known in-vehicle information display system is a HUD (Head up Display) as shown in Non-Patent Document 1, which displays an image on an image display device in the real view viewed by the driver while driving, and forms a virtual image through the action of a concave mirror, which is then reflected by the windshield to provide the driver with an enlarged image.

[0003] This HUD has two reflective surfaces, the inside surface of the windshield (referred to as the inside surface) and the outside surface of the windshield (referred to as the outside surface), so the virtual image appears to be a double image. In addition, the volume of the set is large, and an AR (Augmented Reality)-HUD, which obtains a large virtual image at a distance, exceeds 10 liters in volume, so it cannot be placed in the space between the steering wheel and the windshield. Furthermore, in the unlikely event that a malfunction occurs in the HUD, it cannot be easily replaced, and the degree of freedom in maintenance is low, which has been an obstacle to its widespread use. In addition, the maximum resolution of the displayed image is about 80 dots per degree of viewing angle, and the hardware configuration is difficult to respond to the advancement of the communication environment, such as not being able to display high-definition images. Furthermore, if a driver wears polarized sunglasses to protect their eyes from sunlight on a sunny day, the image cannot be seen. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] DENSO TECHNICAL REVIEW Vol.21 2016 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional projection type information display systems and devices do not take into consideration the efficient (effective) delivery of image light to an observer in a vehicle to improve the efficiency of light utilization, thereby reducing the power consumption of devices including light sources. In addition, no consideration was given to how to deal with the damage caused to the liquid crystal panel by sunlight entering the HUD device. Furthermore, there was no description of a configuration or arrangement for reducing the set volume of the HUD, for easy removal, for increasing the resolution of the obtained image, or even of a solution to the problem of not being able to see the virtual image formed by image light of a specific polarization when the observer, the driver, wears polarized sunglasses.

[0006] Therefore, the present invention provides a technique for a display device capable of displaying suitable images for the interior of a space (inside a vehicle). [Means for solving the problem]

[0007] In order to solve the above problems, for example, the configuration described in the claims is adopted. The present invention includes a plurality of means for solving the above problems, and as one example, a display device includes a display panel that emits image light to a projection member, a light source device that supplies light to the display panel, and a circular polarization conversion element on the image light emission surface side of the display panel, and the image light from the display panel is reflected by the projection member, and the image generated by the display panel is visually recognized as a virtual image. Effect of the Invention

[0008] According to the present invention, it is possible to suitably display an image inside a vehicle. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram showing a peripheral device configuration of the information display system according to the embodiment. [Diagram 2] FIG. 1 is a top view of a vehicle equipped with an information display system. [Diagram 3]FIG. 1 is a diagram showing different radii of curvature of windshields. [Figure 4A] FIG. 1 is an explanatory diagram illustrating the phenomenon in which the images of light entering the left and right eyes in binocular vision are misaligned, resulting in a double image. [Figure 4B] FIG. 2 is a schematic diagram showing distortion of left and right images caused by binocular vision. [Figure 4C] 1 is a schematic diagram showing a deviation between left and right images in binocular vision due to a difference in virtual image distance. [Diagram 5] This is a schematic diagram to explain the phenomenon in which the image of light entering one eyeball becomes misaligned and appears double. [Figure 6] FIG. 1 is a schematic diagram for explaining a mechanism by which a double image is generated by a windshield. [Figure 7] 1 is a schematic diagram showing an example of an information display system; [Figure 8] 1 is a cross-sectional view for explaining the principle of the present application of protecting against sunlight and reducing double images. [Figure 9] FIG. 1 is a graph showing the reflectance of P-polarized light, S-polarized light, and circularly polarized light of natural light such as sunlight against the angle of incidence on glass. [Figure 10] 1 is a characteristic diagram showing a wavelength distribution of natural light such as sunlight. [Figure 11] FIG. 2 is an explanatory diagram for explaining the position of an image displayed on a windshield by the image display device according to the embodiment. [Figure 12] FIG. 11 is a characteristic diagram summarizing the results of an experiment to determine the range of eye point movement when a driver looks ahead while driving. [Figure 13] FIG. 2 is an explanatory diagram for explaining the position of an image displayed on a windshield by the image display device according to the embodiment. [Figure 14] FIG. 1 is a diagram showing an example of a specific configuration of a video display device. [Figure 15] FIG. 2 is an explanatory diagram for explaining the position of an image displayed on a windshield by the image display device according to the embodiment. [Figure 16] FIG. 1 is a diagram showing an example of a specific configuration of a video display device. [Figure 17] FIG. 1 is a diagram showing an example of a specific configuration of a video display device. [Figure 18] 11A and 11B are diagrams illustrating the relationship between the image display position and the relative image size with respect to the actual scene viewed by the driver in the embodiment. [Figure 19] FIG. 2 is a schematic diagram illustrating an example of the arrangement when the image display device is mounted in an automobile. [Figure 20] FIG. 2 is a schematic diagram illustrating an example of the arrangement when the image display device is mounted in an automobile. [Figure 21] FIG. 2 is a diagram illustrating an example of a specific configuration of an image forming unit. [Figure 22] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Diagram 23] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 24] FIG. 1 is a cross-sectional view showing an example of a specific configuration of an image display device. [Diagram 25] FIG. 1 is a cross-sectional view showing an example of a specific configuration of an image display device. [Figure 26] FIG. 11 is a diagram showing another example of a specific configuration of the video display device. [Figure 27] FIG. 2 is a diagram illustrating an example of a specific configuration of a light source device. [Figure 28] FIG. 2 is a diagram illustrating an example of a specific configuration of a light source device. [Figure 29] FIG. 2 is a diagram illustrating an example of a specific configuration of a light source device. [Diagram 30] FIG. 4 is a diagram showing the image light diffusion characteristics of the image forming unit. [Diagram 31] FIG. 4 is a diagram showing the image light diffusion characteristics of the image forming unit. [Diagram 32] 1A to 1C are a perspective view, a top view, and a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 33A] FIG. 13 is a structural diagram showing another example of a specific configuration of a light source device of a different type. [Figure 33B] FIG. 13 is a diagram showing a part of another example of a specific configuration of a light source device of another type. [Figure 33C] FIG. 13 is a diagram showing a part of another example of a specific configuration of a light source device of another type. [Figure 33D]FIG. 13 is a diagram showing a part of another example of a specific configuration of a light source device of another type. [Figure 34A] FIG. 13 is a structural diagram showing another example of a specific configuration of a light source device of a different type. [Figure 34B] FIG. 13 is a diagram showing another example of a specific configuration of a light source device of a different type. [Figure 34C] 10 is a cross-sectional view showing an example of a specific configuration of a diffusion plate provided in the light source device. FIG. [Diagram 35] FIG. 2 is a diagram showing a coordinate system for measuring the visual characteristics of a liquid crystal display panel. [Diagram 36] FIG. 1 is a diagram showing the luminance angle characteristics (longitudinal direction) of a typical liquid crystal display panel. [Figure 37] FIG. 1 is a diagram showing the luminance angle characteristics (short side direction) of a typical liquid crystal display panel. [Figure 38] FIG. 1 is a diagram showing the angular characteristics (longitudinal direction) of contrast of a typical liquid crystal display panel. [Figure 39] FIG. 1 is a diagram showing the angular characteristics (short side direction) of contrast of a typical liquid crystal display panel. [Diagram 40] FIG. 1 is a characteristic diagram showing the emission spectrum of a typical white LED light source. [Diagram 41] FIG. 2 is a characteristic diagram showing the reflection characteristics of a reflector according to an embodiment of the present invention. [Diagram 42] 1 is a characteristic diagram showing the spectral transmittance of a polarizing plate used in a liquid crystal display panel. [Diagram 43] FIG. 2 is a cross-sectional view showing an example of the configuration of a polarizing plate. [Diagram 44] FIG. 4 is a characteristic diagram showing the reflection characteristics of a light guide according to an embodiment of the present invention. [Diagram 45] FIG. 1 is a characteristic diagram showing the spectral transmittance of a typical polarizing plate. [Figure 46] 4 is a cross-sectional view showing the configuration of a liquid crystal display panel, a polarizing plate provided on the image light exit side, and a circular polarization conversion element. FIG. [Figure 47] 1 is an explanatory diagram for explaining characteristics of a circular polarization conversion element according to an embodiment of the present invention. FIG. [Figure 48]3 is a chromaticity diagram showing chromaticity when white color is displayed in the image display device according to the embodiment of the present invention. FIG. [Figure 49] FIG. 2 is a chromaticity diagram showing the chromaticity when the image display device according to the embodiment of the present invention displays white, with MacAdam's color discrimination ellipse superimposed thereon. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The following embodiments relate to an information display system that can display an image generated by image light from a large-area image light source outside a store (space) by transmitting the image through a transparent member that divides the space, such as the glass of a show window. The embodiments also relate to a vehicle information display system that uses the information display system to project an image into the interior of a car or train (hereinafter collectively referred to as a "vehicle") through the front windshield, rear windshield, side windshield, and combiner. The front windshield, rear windshield, side windshield, and combiner may also be referred to as a projection member, projection element, reflection member, reflection element, etc.

[0011] According to the following embodiment, for example, high-resolution image information can be displayed on the glass surface of a show window, the rear glass, the front glass, or the side glass of a vehicle, or the combiner proposed in the embodiment, and the divergence angle of the emitted image light is made small, i.e., an acute angle, and further, by aligning it to a specific polarization, the image light is efficiently delivered to the observer and the light utilization efficiency is improved, thereby making it possible to provide a novel and highly usable information display system that can significantly reduce the power consumption of a device including a light source. In addition, for example, a so-called unidirectional display that is visible inside the vehicle through a shield glass including the front glass, rear glass, and side glass of the vehicle can be performed, and double images that occur on both sides of the window glass can be reduced. In addition, a vehicle information display system that has sufficient brightness and good color reproducibility even for an observer using polarized sunglasses and has sufficient protection against sunlight can be provided.

[0012] A typical vehicle information display system that displays real image information to the interior of the vehicle includes a system in which LED (Light Emitting Diode) chips are arranged in a matrix and light up in accordance with the image information. In such a system, (1) the diffusion angle of the LED chips is wide, so a large amount of power is required to obtain the desired brightness. In addition, (2) the individual dimensions of the LED chips that obtain the desired brightness are large, and high resolution cannot be obtained for an information display system that is small enough to be mounted on a vehicle. Furthermore, (3) if one tries to prevent the device from becoming too large, it is difficult to display images in color.

[0013] On the other hand, to realize an image display device that can display a virtual image enlarged by a concave mirror at a distance or over a wide range using a large liquid crystal panel capable of displaying color, a large concave mirror is required, and the set size becomes large in order to secure an optical path from the image display device to the concave mirror. In that case, it becomes impossible to store the information processing device in the space between the windshield 6 and the steering wheel 43 shown in FIG. 2, for example. In addition, if the range of the visual space (eye box) including both eyes of the driver or the horizontal and vertical components of the angle formed by the line segment connecting both eyes and the virtual image are expanded, it becomes necessary to further increase the dimensions of the concave mirror, which leads to the above-mentioned increase in the set size.

[0014] In contrast, the vehicle image display device of the present application uses a high-resolution liquid crystal panel and narrows the divergence angle of the light source device to achieve high brightness. Furthermore, to improve the efficiency of light utilization, S-polarized light, which has a high reflectance when obliquely incident on the windshield or combiner, is used as the image output.

[0015] Furthermore, to prevent sunlight concentrated through the concave mirror when the sun is at a specific angle as shown in Figures 7(a) and (b) from entering and damaging the image display panel 11 or the light beam direction conversion means 54 (see Figure 21), a filter that converts the polarization direction is provided on the windshield or combiner, thereby increasing the reflectance of sunlight and reducing the amount of light entering the LCD panel.

[0016] In addition, the double image that occurs when the image light is reflected twice, once on the image reflecting surface of the windshield 6 and once on the surface in contact with the outside of the vehicle, can be significantly reduced by the action of the above-mentioned filter.

[0017] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the description of the embodiments, 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. In addition, in all the drawings for explaining the present invention, the same reference numerals are given to parts having the same functions, and repeated explanations thereof may be omitted.

[0018] <Video information display system> Next, FIG. 1 shows a more specific configuration of the video information display system. The video information display system may be called an information display system, a display system, an information display device, a display device, or the like. The video display panel 11 constituting the video display device 49 is, for example, configured by a relatively large liquid crystal display panel with a screen size of more than 15 inches. The video display panel 11 of this embodiment may be called a display panel, a display element, or the like. In order to perform correction at a level that does not cause practical problems by distortion correction, the resolution of the panel is preferably 1280×720 dots or more, and in order to display still images or moving images of video information other than character information externally, a resolution of 1980×1080 dots or more is desirable. In addition, although not shown, it is also possible to achieve high resolution by combining multiple panels and using a blending function, and it is also possible to display different images on each video display device.

[0019] <First embodiment of the video information display system> The image display device 49 includes a light source device 48 constituting the light source thereof together with the image display panel 11, and an example of the configuration is shown in Fig. 21. In Fig. 21, the light source device 48 is shown as an exploded perspective view together with the image display panel 11. As shown by the arrow 30, the image display panel 11 has a narrow-angle diffusion characteristic due to the light from the light source device 48, which is a backlight device. That is, the light source device 48 obtains a surface-emitted illumination light flux that has strong directivity (straightness) and characteristics similar to laser light with a polarization plane aligned in one direction, and emits the image light modulated according to the input image signal toward the transparent sheet 7b provided on the surface of or inside the window glass shown in Fig. 8.

[0020] 21, the information display system is configured to include the image display panel 11, the light source device 48, and, if necessary, a light beam direction conversion means 54 for controlling the directional characteristics of the light beam emitted from the light source device 48, and a narrow-angle diffusion plate (not shown). The light beam direction conversion means 54 in the present invention may be called a light beam direction conversion element, a light beam direction conversion member, a light beam direction conversion sheet, or the like. In addition, a circular polarization conversion means (not shown) may be provided on the viewer side of the light beam direction conversion means 54 from which the image light is emitted in order to accommodate polarized sunglasses. The circular polarization conversion means may be called a circular polarization conversion member, a circular polarization conversion element, or the like. Polarizing plates having the configuration shown in FIG. 43 may be provided on both sides of the image display panel 11, and the image light of a specific polarized wave is output after modulating the light intensity by a video signal (see arrow 30 in FIG. 21). As a result, the desired image is projected onto the windshield 6 as light of a specific polarization with high directivity (linearity) via the light beam direction conversion means 54, and is reflected on its surface toward the viewer's eyes. It is also possible to control the angle of incidence of the image light with respect to the windshield 6 by tilting the image display device 49 with respect to the windshield 6 without providing the light beam direction conversion means 54 described above.

[0021] In this embodiment, in order to improve the utilization efficiency of the light flux emitted from the light source device 48 and to significantly reduce power consumption, in an image display device 49 including the light source device 48 and the image display panel 11, the light from the light source device 48 (see arrow 30 in FIG. 21) is transmitted through a transparent sheet 51 (see FIG. 14) provided on the surface of the windshield 6, thereby giving high directivity. In addition, optical components such as a lenticular lens and a transparent panel give high directivity to the brightness of the image light diffused from the image display device 49. With this, the image light from the image display device 49 efficiently reaches the observer inside the windshield 6 with high directivity (straightness) like laser light, and as a result, it is possible to display a high-quality image with high resolution and significantly reduce the power consumption of the image display device 49 including the LED elements 200 of the light source device 48.

[0022] <First embodiment of vehicle information display system> According to the above-mentioned embodiment, as shown in Fig. 1, the image light generated from the image display device 49 and emitted toward the windshield 6, which is the member to be projected, is (1) converted from divergent light from an LED into image light with a narrow diffusion angle (high linearity) and only specific polarization components, like the image light from an image source (light source device 48) that acts like a surface-emitting laser, by the optical system described below, thereby enabling a high-quality image to be displayed on the high-resolution image display panel 11, while improving the utilization efficiency of the emitted light and significantly reducing power consumption, and at the same time, (2) as is clear from the above-mentioned components, it is possible to configure the overall outer shape of the device in a flat (panel) shape. In Fig. 1, the vertical width (vertical screen dimension) of the image display panel is L'1.

[0023] Therefore, a storage space can be provided in a part of the console of the vehicle, and the display device can be installed later. Furthermore, since the image light from the image display device 49 has a narrow-angle diffusion characteristic, a high-luminance image can be realized with low power consumption. At this time, in order to allow the viewer 8 to view the image through the windshield 6 during the daytime as an in-vehicle information display system, if the image light is S-polarized, a luminance of 40,000 (nt) or more is required. On the other hand, since the image display device 49 of this embodiment has high luminance, it can be used not only for in-vehicle use but also as a tablet terminal for outdoor use. At this time, the required luminance is about 2000 (nt), and the power consumption is about 1 / 20, so that it can be driven for a long time with a small battery, and information from an information processing device such as a smartphone is wirelessly transmitted and displayed as an image, and the interaction function allows the selection of information and selectively proceeding to the depths of the information.

[0024] Fig. 19 shows the state where an image display device 49 according to an embodiment of the present invention is placed in the console part of the vehicle body. Compared to the conventional image display device 55 using the concave mirror 1 shown in Fig. 20, there is no space through which the image light passes, making it possible to make it more compact.

[0025] No optical components are required between the image display device 49 and the windshield 6, and compared to the conventional image display device 55 using the concave mirror 1 shown in Fig. 20, no spatial area through which image light passes is required, making it possible to make the device more compact. Furthermore, when the entire image display screen of the image display device 49 is used, the device is set so that images can be displayed in the entire display area d of the windshield 6 facing the driver as shown in Fig. 11, and the display positions of the display areas a, b, c, etc. are moved or optimally selected according to the driver's viewpoint using a camera (not shown) that detects the vehicle speed and the driver's viewpoint installed inside the vehicle. Furthermore, a driving support system in which the displayed images do not interfere with driving can be constructed by dividing the display areas to the left and right of the center of the viewpoint and providing a function to move or select the display positions according to the vehicle speed and the movement of the viewpoint.

[0026] In addition, in the stopped state, a large amount of video information can be displayed simultaneously by displaying video in the entire video display area.

[0027] On the other hand, the images displayed on the image display device 49 include navigation information, speed information from the driving assistance ECU, engine torque information, remaining power in an electric vehicle, remaining fuel information in a gasoline vehicle or hybrid vehicle, as well as visual information around the vehicle from an on-board camera and alert information to call attention. Furthermore, information from an information processing device such as a smartphone is also transmitted by wire or wirelessly and displayed as an image, and the interaction function allows the selection of information or selectively going deeper into the information. Various examples of so-called vehicular information display systems in which the information display system of the present invention is applied to vehicles such as automobiles, trains, and aircraft by utilizing these features will be described in detail below.

[0028] 2 and 3 show an example in which the above-mentioned image display device 49 and the like are mounted on a commercial vehicle, and an image from the image display device 49 is displayed on a part of the windshield 6 (above the steering wheel 43), a part of the side window 6'', or the whole of the same. FIGS. 2 and 3 show an example of an image display area.

[0029] As a specific means for displaying an image through (a part or all of) the windshield of an automobile, for example, an image display device 49 including a large image display panel 11 as shown in FIG. 1 is provided to correspond to the windshield of the vehicle body. A light source device 48 shown in FIG. 24 and FIG. 25 is provided on the back surface of the image display panel 11. The light source device 48 has a plurality of reflective light guides 304, and obtains image light with a narrow diffusion angle (high linearity) of light from a surface emitting laser light source and a uniform polarization plane. The light source may be a point light source. The light intensity of these light beams is modulated by the image display panel 11 according to the image signal, and the image is displayed inside or outside the vehicle through the windshield 6, rear glass 6', and side glass 6". The image display panel 11 can be a conventional TV panel, and a large liquid crystal panel or a high-resolution panel equivalent to 8k can also be used. A special specification panel in which a liquid crystal compatible with high light output is sealed in a conventional TV panel can also be used. In this case, a large liquid crystal panel or a high-resolution panel equivalent to 8k can also be used.

[0030] In addition, in applications such as commercial vehicles and ordinary cars as shown in Fig. 2, the windshield (front windshield, rear windshield, etc.) may be curved, and when an image is viewed from outside the vehicle through the glass, the image may be distorted due to the refraction of the glass. Similarly, even if the image light is reflected on the inner surface of the windshield, the reflected image will be distorted due to the curved shape of the windshield. In order to reproduce an image with a normal shape from the image viewing side, it is advisable to distort the original image into a corrected shape so that the image after passing through the glass will be a normal image.

[0031] Furthermore, in a vehicle information display system, since the vehicle itself is exposed to natural light including sunlight, it is necessary to take measures against such sunlight, but natural light such as sunlight is not only light in a wide wavelength range from ultraviolet to infrared, but also exists in a state of light with two types of polarization directions (hereinafter referred to as S-polarized and P-polarized) mixed together, that is, light with a vibration direction perpendicular to the light's traveling direction and light with a horizontal direction, as shown in Fig. 10. In particular, in areas where the angle of incidence on the windshield 6 exceeds 50 degrees, the reflectance on the glass surface differs depending on the type of polarization and the angle of incidence, as shown in Fig. 9.

[0032] Therefore, in this embodiment, taking into consideration that most of the sunlight that penetrates through the windshield 6 is a P-polarized component, it has been confirmed that in order to suppress external light, including sunlight, that is irradiated and penetrates the image display device, it is particularly effective to reduce the P-wave component, and in addition, it is effective to use the S-wave component as the image light that is emitted from the image display device and emitted outside the vehicle and recognized by the viewer. Also, in the information display system of this embodiment, the area where sunlight is incident on the image display panel 11 is sensed, and the LED of the light source device corresponding to this area is turned off, thereby not displaying the image, reducing the temperature rise of the image display device and improving reliability.

[0033] <Issues regarding vehicle image information display systems> The problems with the above-mentioned vehicle information display system will be described in detail below.

[0034] <The principle behind double images caused by binocular disparity> Fig. 4A is a schematic diagram for explaining the principle of double images caused by binocular parallax, which is the first problem. As shown in Fig. 4B, a discrepancy occurs between the image recognized by the viewer's right eye and the image recognized by the left eye. This is because the parallax caused by the difference in eyeball position causes the virtual images recognized by each eye to look different because the relative curvature of the windshield 6, which is a reflective surface, is different.

[0035] This is caused by the difference in the optical system that forms the virtual image due to the binocular parallax described above, and in order to solve this, the virtual image distance is moved farther away as shown in Fig. 4C, which reduces the angle at which the virtual image caused by the parallax due to the interpupillary distance (average 60 mm) is viewed, thereby reducing the effect of double images. The inventors have experimentally clarified that when the virtual image distance exceeds 8 m, it exceeds the discrimination range of a viewer with a visual acuity of 1.0, and at 13 m, it is difficult for a viewer with a visual acuity of 1.2 or more to discern.

[0036] <Vertical double image caused by reflection on two windshields> FIG. 5(a) is a schematic diagram showing the principle of vertical double images occurring due to the second problem that the reflected images at the two air interfaces of the windshield 6 are misaligned and pass through the viewer's pupil to form an image on the retina. To solve this problem, the virtual image distance should be moved farther away to reduce the angle at which the virtual image generated by the two reflecting surfaces of the windshield 6 is viewed, as shown in FIG. 5(b) and FIG. 6. The inventors experimentally determined the virtual image distance at which this double image is at a level that is practically problem-free. As a result, it was revealed that for a viewer with an average pupil diameter of 7 mm, when the virtual image distance exceeds 12 m, it is beyond the discrimination range even for a viewer with a visual acuity of 1.0, and at 15 m, it is difficult to discern even for a viewer with a visual acuity of 1.2 or more. The second solution for reducing the double image that occurs in principle as described above will be described later.

[0037] 7(a) shows a schematic cross-sectional structure of the vehicle information display system of the present application when it is installed inside the vehicle body. The image display device 49 is equipped with a light source device 48 that has narrow-angle diffusion characteristics and supplies a specific polarized wave to the image display panel 11, and the image display panel 11 obtains a desired image by modulating the output light intensity of the supplied light in accordance with the image signal. Therefore, compared to a HUD in which an image of the image display device 55 shown in FIG. 20 is magnified by a concave mirror 1 to obtain a virtual image, there is no space for an optical path, making it possible to make the system significantly more compact.

[0038] <Compatible with polarized sunglasses> In recent years, an increasing number of drivers are using polarized sunglasses to prevent glare from sunlight and headlights from oncoming vehicles from directly or indirectly entering their eyes when driving a vehicle. In the above-mentioned vehicle information display system using the image display device 49, when a liquid crystal panel is used as the image display panel 11 shown in Fig. 7(a), S-polarized image light with high reflectance on the windshield 6 is used. Therefore, when the driver views a virtual image display through polarized sunglasses, if the polarization axis is perpendicular, there is a fundamental problem that the polarized sunglasses block the light and the display image is almost unrecognizable.

[0039] FIG. 7(b) is a schematic layout diagram showing a situation where a viewer views a distant display image of the information display system using polarized sunglasses. In the second vehicle information display system of the present application shown in FIG. 7(b), the divergent light beam from the LED light source of the light source device 48 is converted into a substantially parallel light beam, and the light beam is polarized and converted by a polarization conversion optical element to a specific linearly polarized light (S-polarized light) with a small diffusion angle and is made incident. Therefore, the image display panel 11 can display an image with unprecedented high luminance (brightness). Therefore, the virtual image displayed by the vehicle information display system equipped with the light source device 48 can also be displayed with unprecedented high luminance. In the embodiment of the present application, a circular polarization conversion element 12 is provided on the image light output side of the image display panel 11 (liquid crystal panel) to convert linearly polarized light into circularly polarized light.

[0040] As a result, to allow sufficient brightness to be transmitted to a driver wearing polarized sunglasses, a circular polarization conversion element 12 that converts linearly polarized light into circularly polarized light is provided on the viewer side of the display surface of the image display panel 11, and S-polarized light (linearly polarized light) emitted from the image display panel 11 is converted into circularly polarized light. The information display system (information display device) shown in Fig. 7(b) is configured to emit light converted into circularly polarized light toward the viewer, making it possible for the viewer to view high-brightness images even when wearing polarized sunglasses. The reflectance of circularly polarized light on the windshield 6 is intermediate between the reflectance of P-polarized light and S-polarized light, as shown in Fig. 9.

[0041] <Information display system equipped with a circular polarization conversion element with high color reproducibility> In an image display panel that normally emits S-polarized (linearly polarized) image light, in order to convert the light emitted from the image display panel 11 into circularly polarized light, in the embodiment of the present application, as shown in FIG. 46, a λ / 4 plate is adhesively fixed to the surface of a polarizing plate provided on the image light emission side of a liquid crystal panel with an adhesive. The λ / 4 plate and the polarizing plate may be attached to a glass plate as separate members depending on the configuration of the optical system. As shown in FIG. 46, the liquid crystal panel, the polarizing plate, and the λ / 4 plate may be adhesively fixed to the liquid crystal panel with an adhesive. The polarizing plate and the liquid crystal panel may be attached via a glass plate. The circular polarization conversion element 12 is configured to include a λ / 4 plate (phase difference plate), and by providing an anti-reflection film on the air-side interface, reflection loss and deterioration of image quality due to reflected light at the interface can be suppressed.

[0042] The retardation plate (lambda / 4 plate) used in the examples of the present invention is obtained by stretching a polycarbonate substrate to a desired thickness. At this time, the thickness of the stretched substrate is determined based on 137.5 nm, which is 1 / 4 of 550 nm, which has a high relative luminosity factor. The inventors selected the lambda / 4 plate using color reproducibility as a new evaluation index.

[0043] FIG. 47 is a characteristic diagram showing the characteristics of a typical commercially available λ / 4 plate. The color reproducibility of the display image was evaluated using samples with different partial dispersions based on light at 550 nm. For a λ / 4 plate with normal positive wavelength dispersion obtained by stretching a normal polycarbonate substrate with respect to the ideal straight line of partial dispersion, the phase correction amount is insufficient for light in the blue region below 470 nm, and the efficiency of polarization conversion is significantly reduced. As a result, when a white display image was displayed as the display image displayed by the video display device 49, it became yellowish white.

[0044] It was found that the color temperature of this white image also decreased significantly with respect to the color temperature of the LED light source. Next, even when a λ / 4 plate having a flat wavelength dispersion shown in FIG. 47 was used, the phase correction amount was insufficient for light in the blue region below 470 nm, so that when a white display image was displayed, it became yellowish white. Further, as shown in FIG. 47, the same evaluation was performed for two types of λ / 4 plates (characteristics (a) and (b)) having an inverse wavelength dispersion characteristic showing characteristics close to the ideal straight line of the wavelength dispersion characteristic in the wavelength region shorter than the reference wavelength of 550 nm.

[0045] <LED light source> The light source described in the embodiments of the present invention is an LED as a surface light source having diffusion characteristics. Hereinafter, description will be made based on the light source device of the present invention shown in FIGS. 32 and 33A. The light source shown in the embodiments of the present invention is configured such that a surface-emitting white LED emits yellow phosphor using blue LED as excitation light and synthesizes to emit white light. FIG. 40 shows the emission spectrum.

[0046] In order to raise the color temperature of white light below the peak wavelength of blue light of 450 nm or less among the light source light from the surface-emitting white LED to a high region, among the samples of characteristics (a) and (b) having inverse wavelength dispersion characteristics in the blue-green and blue regions, the chromaticity of the white display image is moved in the direction of higher color temperature, and the characteristic that enables a more vivid white display is that the wavelength dispersion on the shorter wavelength side of the peak wavelength of the blue region of the light source light of the white LED is smaller, and the sample of characteristic (a) showed better performance. Also, since the wavelength dispersion on the long wavelength side is also close to the ideal curve, the color development of the red video light was improved.

[0047] From these results, as shown in the cross-sectional structure of Fig. 46, the priority order for selecting the λ / 4 plate provided on the image output surface of the image display device 49 is (1) that the wavelength dispersion is close to an ideal straight line, (2) that the wavelength dispersion in the blue region is particularly effective as it is smaller than the ideal straight line, and (3) that the color reproducibility of the entire system is further improved. For this purpose, it is even better to bring the wavelength dispersion in the red region and the long wavelength region of 650 nm or more closer to an ideal straight line.

[0048] <Absorptive polarizing plate> The spectral transmittance of a general absorptive polarizing plate provided on the transparent sheets 7b and 51 described above is shown in Fig. 45. Since the transmittance in the blue-green wavelength region of 500 nm or less is lower than the transmittance in the long wavelength region of 550 nm or more, the absorption in the blue region of the emission spectrum of the white LED shown in Fig. 40 is large, and the color temperature of white shifts to the low temperature side along the black body locus of the chromaticity diagram shown in Fig. 48, and the color reproduction range is narrowed. In addition, the spectral transmittance of the polarizing plate attached to the light source side and the image light emission surface side of the image display panel 11 is shown in Fig. 42, but the transmission axis transmittance is the same as the general absorptive polarizing plate described above, since the transmittance in the blue-green wavelength region of 500 nm or less is lower than the transmittance in the long wavelength region of 550 nm or more, the absorption in the blue region of the emission spectrum of the white LED shown in Fig. 40 is large, and the color temperature of white shifts to the low temperature side along the black body locus of the chromaticity diagram shown in Fig. 49.

[0049] Figure 43 shows the structure of a typical absorption-type polarizer and how it is attached to an LCD panel. Polarizers control the polarization characteristics for specific polarized waves by stretching PVA film in a specific direction and dyeing it with a dye. Because this PVA (Polyvinyl alcohol) is highly hydrophilic, it is sandwiched on both sides between TAC (Tri acetyl cellulose) films to reduce moisture absorption. The dye that controls the polarization characteristics increases absorption of short wavelengths below 500 nm when the degree of polarization (transmission axis transmittance / absorption axis transmittance) is improved.

[0050] Figure 48 shows a chromaticity diagram that indicates the chromaticity when the video information display device displays white. Figure 49 shows a chromaticity diagram that shows the chromaticity when the video information display device displays white, with the MacAdam color discrimination ellipse superimposed on it. The sensitivity of each coordinate region to chromaticity changes (CIE XY chromaticity coordinate system) as seen by the human eye is expressed by the MacAdam color matching ellipse, which indicates the region that is recognized as the same color depending on the amount of deviation from the center point of the ellipse on the XY chromaticity coordinates shown in Figures 48 and 49. The higher the color temperature, the higher the sensitivity to recognize subtle chromaticity changes, so great care will be needed when using a vivid white base in order to expand the color reproduction range of displayed images in the future.

[0051] As described above, in an optical system using a circular polarization conversion element provided in a liquid crystal display panel, the spectral transmittance in the blue-green wavelength region of 500 nm or less of the transmission polarizing plate and the circular polarization conversion element attached to the liquid crystal display panel used is lower than that for wavelengths in the green-red region, as shown in Fig. 45. Therefore, in order to ensure reproducibility of white color, it is essential to use a λ / 4 plate attached to the surface of the polarizing plate provided on the image light output side surface of the liquid crystal display panel used in the embodiment of the present invention that has the inverse wavelength dispersion characteristics shown in Fig. 47.

[0052] In addition, in the configuration of the embodiment of the present invention shown in Figure 7(b), when a driver wears polarized sunglasses and views the displayed image as a virtual image from the direction shown in the figure, a good displayed image (virtual image) that is bright and has excellent color reproducibility can be obtained due to the action of the above-mentioned circular polarization conversion element.

[0053] Furthermore, as a means different from the above-mentioned technical means, it is preferable to use S-polarized waves because the reflectance of the image light from the image display panel 11 on the windshield 6 can be made high in principle. However, as described above, if the viewer wears polarized sunglasses, the virtual image is reflected or absorbed by the polarized sunglasses. Therefore, a depolarizing element that optically converts part of the image light of a specific polarized wave into the other polarized wave and converts it into pseudo-natural light may be provided at the position of the circular polarization conversion element 12 in FIG. 7(b) instead of the circular polarization conversion element 12. As a result, the viewer can view a good displayed image even if he or she wears polarized sunglasses.

[0054] Commercially available depolarizing elements include, for example, Cosmoshine SRF (manufactured by Toyobo Co., Ltd.) and depolarizing adhesive (manufactured by Nagase & Co., Ltd.). In the case of Cosmoshine SRF (manufactured by Toyobo Co., Ltd.), by attaching the adhesive to the image display device, it is possible to reduce the reflection at the interface and improve the brightness. In the case of the depolarizing adhesive, a colorless transparent plate and the image display device are attached via the depolarizing adhesive. In this embodiment, as described above, the image display device 49 includes the image display panel 11 and the light source device 48 that generates light of a specific polarization having a narrow-angle diffusion characteristic.

[0055] If the windshield 6 is inclined by 45 degrees or more with respect to the horizontal axis, this image display device 49 must be inclined toward the windshield with respect to the horizontal axis (indicated by an inclination angle θ2 in FIGS. 7(a) and 7(b)) as shown in FIG. 7(a) and FIG. 7(b). The image display position in the vertical direction of the windshield can be arbitrarily determined by using the distance between the center of the image screen from the image display device and the bottom end of the windshield 6 and the above-mentioned θ2 as parameters. However, care must be taken when using θ2 as a parameter, because the reflection angle θ1 of the image light reflected by the windshield 6 changes. By widening the display area of ​​the image display device 49, almost the entire surface of the windshield 6 can be used as a reflective surface, so that the image can be displayed in an optimal position according to the output of a camera (not shown) that displays an image in a part of the display area and detects the viewpoint position of the driver who is the image viewer. Therefore, an information display system can be realized that does not need to be precisely attached to the vehicle body on the automobile manufacturing line, and can appropriately change the display position according to the customer's viewpoint at a dealership. At this time, the image distortion that occurs varies depending on the display position on the windshield, but by capturing the display image with a camera aligned with the customer's viewpoint and distorting and inversely correcting the image to be displayed on the image display device based on the obtained image information, distortion can be reduced in the image reflected on the windshield 6.

[0056] Image light from the image display device 49 is emitted through the protective cover 41 toward the windshield 6, where it is reflected to reach the viewer. The protective cover 41 not only protects the image display panel 11 from dirt and moisture, but may also have the effect of blocking ultraviolet rays and infrared rays, which are part of sunlight.

[0057] <Display position of video information> The first embodiment of the in-vehicle information display system of the present application will be described below with reference to FIG. 11 with regard to the image information display position (image reflection position on the windshield and virtual image formation position) and the display contents suitable for each display area. As shown in FIG. 11, the image display device 49 is placed between the steering wheel 43 and the windshield 6, and the surface is covered with a protective cover 41 to prevent dust, moisture, and the like from entering from the outside. In addition, the stress of sunlight on the image display device 49 is reduced by providing a filter characteristic that cuts near-infrared light, infrared light, P-polarized waves, and the like of sunlight. The protective cover 41 shown in FIG. 7 is removable like the image display device 49, and when the image display device 49 is taken out of the vehicle as the above-mentioned outdoor tablet terminal or when an image display device with the same panel size and high resolution is realized in the future, the image display device 49 can be easily made high-resolution by simply removing the protective cover 41.

[0058] The display area of ​​the image display device 49 is the right half of the outside world as seen through the windshield 6 in right-hand drive vehicles, that is, the front of the seat where the driver sits (shown as display area d), and displays necessary information in multiple areas (display area a, display area b, display area c) at the necessary time and timing as necessary. As for the displayed images, navigation information and outside information obtained by the in-vehicle camera 100 are analyzed by the peripheral observation device 63 shown in Fig. 1, and information that may be an obstacle to driving, such as obstacles or people, is selected, and alert information is generated and superimposed on the display device to call attention.

[0059] Figure 12 is a graph plotting the results of an investigation conducted by the inventors into the driver's line of sight or movement of the viewpoint when driving a passenger car (driving in urban areas at a speed of 50 km / h). The reference line is usually in the range of -3 degrees to 10 degrees (horizon) from 0 degrees (the driver's line of sight is approximately 20 m ahead of the driver), and moving the eyes to the speedometer or tachometer in the instrument panel makes it impossible to see the scenery ahead, which impedes safe driving. For this reason, it was found that there is extremely little movement of the viewpoint to the instrument panel area, except when the driver is consciously looking at it.

[0060] In addition, while the horizontal gaze shift is often directed toward the opposite lane where oncoming vehicles are driving, the gaze shift is also directed to the left side where pedestrians are, and is concentrated in a range of 10 degrees to the left and right (especially the right side is more frequent) from 20 m in front of the driver. For this reason, displaying an alert to events occurring outside this range to call attention is an important element in supporting safe driving. If the distance from the driver's eyes to the center of the image reflection position of the windshield 6 is 1 m, a driver driving on a general road at a speed of 50 km / h can usually see a range of ±10 degrees, so if alert information is displayed on the windshield at a location beyond the range of ±160 mm from the center of the line of sight, it will lead to the driver's awareness. In other words, it was found that by moving the display position of the alert information, which is not usually displayed when driving at high speed compared to when driving at low speed, to the inside of the driver's horizontal visibility range based on sensor information that detects the vehicle speed, it is possible to display attention-calling information while driving at the same level regardless of the vehicle speed.

[0061] Moreover, the optimal position for displaying on the HUD information necessary for driving the vehicle, such as speed information, engine RPM, remaining fuel and battery level, and coolant temperature, without interfering with driving, is display area c. Furthermore, in order to view navigation information and the like from a position far from a fork in the road, it is preferable to display it in display area a at the top of the screen, and when approaching a fork in the road, to display it in display area b. This is excellent in terms of both visibility and convenience, as it changes the display position depending on the road conditions and the vehicle's position.

[0062] On the other hand, when driving at high speeds, the driver's range of gaze movement (not shown) becomes even narrower (0 degrees is the baseline, with the line of sight approximately 40 m ahead of the driver), and in a similar evaluation result when driving at high speeds (driving at 100 km / h), it was found that the driver could see within a range of ±5 degrees to the left and right of the front, and that when driving in the driving lane, the driver frequently gazed at overtaking vehicles on the right, and when driving in the overtaking lane, the driver frequently gazed at the center divider. In addition, the degree of gaze at close and distant views was more than 90% of the time, with the driver looking at a distance of 2 degrees or more. The measurement results of the driver's gaze movement described above were evaluated under conditions where the driver was seated on the right side of the vehicle and driving on the left side.

[0063] To sum up, when driving at high speed, the driver's visibility is about ±5 degrees, and the viewing angle is more than 2 degrees ahead, and at 50 km / h the visibility is about ±10 degrees left and right, and the viewing angle is ±5 degrees. That is, it is better to change the display position of the image according to the vehicle speed, and therefore the required resolution is four times higher when driving at 50 km / h and 100 km / h. Also, when the vehicle is stopped, it is better to use the entire panel resolution of the image display device. That is, as described above, the viewer's visibility can be improved by changing the resolution of the displayed image according to the image reflection position on the windshield.

[0064] We conducted experiments to determine the necessary resolution depending on the image display position on the windshield. The results showed that a resolution of 80 dots / degree or less was sufficient at the top of the windshield (visibility of 5 degrees or more), and a resolution of 120 dots / degree or less was sufficient at the center (near visibility of 0 degrees). In order to satisfy the above conditions and obtain sufficient resolution for a tablet device when the vehicle is stopped, a resolution equivalent to WQXGA (1920 x 1200 dots) was required.

[0065] It was also found that a resolution of (1280 x 720 dots) is sufficient for dedicated use as an in-vehicle video display device.

[0066] <Second embodiment of the video display system> Next, with reference to FIG. 13, the display content suitable for the video information display position (the video reflection position and the virtual image formation position on the windshield) and by display area in the second embodiment of the in-vehicle information display system of the present application will be described below. The video display devices 49a and 49b (illustrated by broken lines) are arranged in parallel between the steering wheel 43 and the front windshield 6, and the surface is covered with the protective cover 41, thereby preventing dust, moisture, etc. from entering from the outside in the same manner as in the first embodiment. Further, by providing filter characteristics for cutting near-infrared and infrared light, P-polarized waves, etc. in sunlight, the stress of sunlight on the video display devices 49a and 49b is reduced.

[0067] The display areas of the video display devices 49a and 49b are the entire external area viewed through the front windshield 6 in front, that is, the entire front surface of the seat on which the driver is seated (illustrated by the display area f), and are positions that do not interfere with driving as the optimal display positions for displaying speed information necessary for vehicle operation, engine rotation speed, remaining fuel and battery levels, coolant temperature, etc. on the HUD (displayed as the display area e in the figure). As a result, the instrument panel portion in the vehicle shown in FIG. 13 becomes unnecessary, and a large space is created between the steering wheel and the front windshield 6, enabling the placement of a large video display device 49 (not shown) or the video display devices 49a and 49b. Since the video display devices 49a and 49b can be made thinner, parallel arrangement is also possible as shown in the figure. As a result, a virtual image V1 with the entire front windshield 6 as the reflection surface as shown in FIG. 14 can be displayed.

[0068] Also, in front of the passenger seat, it is also possible to display smartphone information, entertainment information such as movies and TV images, and area information during driving as needed within a range that does not interfere with driving. At this time, although there is a slight difference in the height in the vertical direction of the screen of the video display device 49 due to the inclination of the front windshield 6, it becomes almost equal to the height in the vertical cross-section of the front windshield 6. For this reason, as shown in FIG. 14, it becomes a liquid crystal panel with a large vertical width (screen vertical dimension). In FIG. 14, the vertical width (screen vertical dimension) of the video display panel 11 is set as L'2, and there is a relationship of L'1 < L'2 with respect to L'1 in FIG. 1.

[0069] On the other hand, since the aspect ratio of the windshield 6 when viewed by the viewer 8 is 2.5:1 or more in an ordinary passenger car, a single liquid crystal panel with the appropriate aspect ratio may be used, or it can be realized by using multiple liquid crystal panels for TVs with an aspect ratio of 16:9. Also, by providing transparent sheets 7b and 51 (described later) on the interior side of the windshield 6, it is possible to significantly reduce double images of the displayed image and damage to the image display device 49 due to the incidence of sunlight.

[0070] <Third embodiment of the video display system> A third embodiment of the in-vehicle information display system of the present application will be described with reference to Fig. 15. Image information is displayed on a combiner 301 provided between the windshield 6 and the steering wheel 43. An image display device 49 (not shown) is disposed between the steering wheel 43 and the windshield 6 as in the two embodiments described above, and its surface is covered with a protective cover 41 to prevent dust, moisture, and the like from entering from the outside. In addition, by providing a filter characteristic that cuts out near-infrared light, infrared light, P-polarized waves, and the like of sunlight, the stress of sunlight on the image display device 49 is reduced.

[0071] The display area of ​​the image display device 49 is the outside world area seen through the combiner 301, that is, the entire surface of the combiner facing the seat on which the driver sits (shown by display area g and display area h), and displays information necessary for driving the vehicle, such as speed information, engine RPM, remaining fuel and battery, and coolant temperature, at a position that does not interfere with driving (shown by display area h in the figure, virtual image V2 in FIG. 16) as an optimal display position for displaying on the HUD. In addition, information such as navigation is imaged at a position corresponding to the distant virtual image V1 and is displayed superimposed on the combiner 301 information. As a result, the instrument panel portion is not necessary in the vehicle shown in FIG. 15, and a large space is created between the steering wheel 43 and the windshield 6, allowing the large image display device 49 including the combiner 301 to be disposed. As a result, it is possible to display a virtual image V1 with the upper part of the entire surface of the combiner 301 as a reflective surface and a virtual image V2 with the lower part of the entire surface as a reflective area, as shown in FIG. 16.

[0072] In addition, in the front of the passenger seat, it is also possible to display smartphone information, entertainment information such as movies and TV images, and regional information during driving as needed within a range that does not interfere with driving. At this time, although there are slight differences in the height in the vertical direction of the screen of the video display device 49 due to the inclination of the windshield 6, it is almost equal to the height in the vertical cross-section of the windshield 6. For this reason, as shown in FIG. 14, it becomes a liquid crystal panel with a large vertical width (screen vertical dimension). In FIG. 14, the vertical width (screen vertical dimension) of the video display panel 11 is set as L'2, and there is a relationship of L'1 < L'2 with respect to L'1 in FIG. 1.

[0073] On the other hand, since the aspect ratio when viewed from the viewer 8 of the combiner 301 is 2.0:1 or more in a general passenger car, a liquid crystal panel with an adjusted aspect ratio may be used alone, or it can also be realized by using a plurality of liquid crystal panels for TVs with an aspect ratio of 16:9. In addition, by providing transparent sheets 7b and 51, which will be described later, on the indoor side surface of the windshield 6, double imaging of the displayed video and damage to the video display device 49 due to sunlight incidence can be significantly reduced.

[0074] The relationship between the virtual image distance L3, the image display position, and the optimal image display size in the three embodiments described above will be described with reference to Figs. 17 and 18. Fig. 17 is a schematic diagram showing a state in which the viewer 8 is viewing a virtual image V1 through the windshield 6 of the image information displayed on the image display device 49 of the present application. The size of the virtual image V1 is determined by the ratio of the virtual image distance L3 to (L1+L2). As shown in Fig. 18, when the display distance L3 of the virtual image is set to 2 m, the angle when the image is displayed 20 m away as shown in Fig. 12 is set as the reference angle (0 degrees), and the horizontal dimension of the image display device required to display a virtual image with a horizontal dimension of 20 inches at a virtual image display position of 2 m (recognized by a pupil movement equivalent to -2.5 degrees) is selected as 20 inches, the virtual image displayed at the display position of 20 m (reference angle 0 degrees) using the same image display device 49 will be equivalent to 200 inches. Similarly, at a virtual image display position of 40 m (recognized with a pupil movement equivalent to 2.4 degrees), a virtual image equivalent to 400 inches can be displayed (indicated by a ● mark in FIG. 18). That is, in this embodiment, the position at which the image light from image display device 49 is reflected on windshield 6 is used as a parameter, and at the same time, by changing the angle that image display device 49 makes with respect to windshield 6, an information display system can be realized with the unprecedented advantage of being able to arbitrarily determine the display distance of a virtual image and the size of the image.

[0075] 18, if the angle when an image is displayed 20 m away is set as the reference angle (0 degrees), and the horizontal dimension of the image display device required to display a virtual image of 7 inches at a virtual image display position of 2 m (recognized with a pupil movement equivalent to -2.5 degrees) is selected as 7 inches, the virtual image displayed at a display position of 20 m (reference angle 0 degrees) using the same image display device 49 will be equivalent to 95 inches. Similarly, at a virtual image display position of 40 m (recognized with a pupil movement equivalent to 2.4 degrees), a virtual image equivalent to 190 inches can be displayed (indicated by a triangle in FIG. 18). That is, in this embodiment, by using the position where the image light from the image display device 49 is reflected on the windshield 6 as a parameter, an information display system in which the FOV (Field of View) in which the observer 8 views the image is constant can be realized, and therefore, by using the display height as a parameter as a means for changing the display distance of the virtual image and the size of the image, that is, by using the mounting position of the image display device 49 disposed between the lower end of the windshield 6 and the steering wheel 43 and the angle with respect to the windshield 6 as parameters, an information display system with an unprecedented advantage that it can be arbitrarily determined can be realized. The reason why the information display system which is the embodiment of the present application described above can display desired virtual images at each position in response to the case where the FOV is constant and the virtual image display distance is a parameter is that the image light from the image display device 49 has a narrow divergence angle and radiates telecentric image light, as will be described later.

[0076] <Example of image display device 1> FIG. 22 shows an example of a specific configuration of the image display device 49. In FIG. 22, the image display panel 11 and the light beam direction conversion means 54 are arranged on the light source device 48 of FIG. 21. The light source device 48 is formed in a case shape, for example, from plastic, and is configured by storing the LED elements 200 and the light guide 203 inside as shown in the figure. The end surface of the light guide 203 is provided with a lens shape that has a cross-sectional area gradually increasing toward the opposite side to the light receiving part, and has a function of gradually decreasing the divergence angle by total reflection multiple times during propagation inside, in order to convert the divergent light from each LED element 200 into a substantially parallel light beam, as shown in FIG. 21. The image display panel 11 constituting the image display device 49 is attached to the upper surface. In addition, LED elements 200, which are semiconductor light sources, and an LED board 202, which has its control circuit mounted thereon, are attached to one side of the case of light source device 48 (the left end face in this example), and a heat sink, which is a member for cooling heat generated by the LED elements 200 and the control circuit, may be attached to the outer surface of the LED board 202.

[0077] In addition, the frame (not shown) of the image display panel 11 attached to the upper surface of the case of the light source device 48 is configured by attaching the image display panel 11 attached to the frame, and further by attaching an FPC (Flexible Printed Circuits) (not shown) electrically connected to the image display panel 11. That is, the image display panel 11 equipped with a liquid crystal display element generates a display image by modulating the intensity of transmitted light based on a control signal from a control circuit (not shown) constituting an electronic device together with the LED element 200 which is a solid light source. At this time, the generated image light has a narrow diffusion angle and contains only a specific polarized wave component, so that a new image display device that is similar to a surface-emitting laser image source driven by a video signal can be obtained. Note that, at present, it is technically and safety impossible to obtain a laser light beam of the same size as the image obtained by the above-mentioned image display device 49 by using a laser device. Therefore, in this embodiment, light similar to the above-mentioned surface-emitting laser image light is obtained from a light beam from a general light source equipped with an LED element, for example.

[0078] Next, the configuration of the optical system of the light source housed in the case of the light source device 48, which can be made thin, will be described in detail with reference to FIG. 22 and FIG.

[0079] 22 and 23 are cross-sectional views, and only one of the LED elements 200 constituting the light source is shown, and this is converted into approximately collimated light by the shape of the light-receiving end surface 203a of the light guide 203. For this reason, the light-receiving portion of the light guide end surface and the LED element are attached while maintaining a predetermined positional relationship. Each of the light guides 203 is formed of a light-transmitting resin such as acrylic. The LED light-receiving surface at the end of the light guide has, for example, a convex outer circumferential surface of a cone obtained by rotating a parabolic cross section, and at the top of the convex outer circumferential surface, a concave portion having a convex portion (i.e., a convex lens surface) formed in the center thereof, and a convex lens surface protruding outward (or a concave lens surface recessed inward) is provided in the center of the flat portion (not shown). The outer shape of the light receiving part of the light guide to which the LED element 200 is attached is a parabolic shape forming a conical outer surface, and is set within an angle range within which the light emitted from the LED element in the peripheral direction can be totally reflected within it, or a reflective surface is formed.

[0080] On the other hand, the LED elements 200 are arranged at predetermined positions on the surface of the LED substrate 202, which is the circuit substrate. The LED substrate 202 is arranged and fixed such that the LED elements 200 on the surface are located in the center of the recessed portion described above with respect to the LED collimator (light-receiving end surface 203a).

[0081] According to this configuration, the shape of light-receiving end surface 203a of light guide 203 makes it possible to extract the light emitted from LED element 200 as substantially parallel light, thereby improving the efficiency of use of the generated light.

[0082] As described above, the light source device 48 is configured by mounting a light source unit in which a plurality of LED elements 200 serving as light sources are arranged on the light receiving end surface 203a serving as a light receiving section provided on the end surface of the light guide 203, and converting the divergent light beam from the LED elements 200 into substantially parallel light by the lens shape of the light receiving end surface 203a of the end surface of the light guide, and guiding the light inside the light guide 203 as shown by the arrow (in a direction parallel to the drawing), and reflecting the light source light propagated substantially parallel to the light guide toward the image display panel 11 by the light beam direction conversion means 204 (in a direction perpendicular to the front side of the drawing). The image light whose light intensity is modulated by the image display panel 11 according to the image signal is directed to a desired direction by the light beam direction conversion means 54. The distribution (in-plane density) of the light source light beam is optimized by the shape of the inside or surface of the light guide, thereby controlling the uniformity of the light beam incident on the image display panel 11.

[0083] The light beam direction conversion means 204 described above emits the light beam propagated inside the light guide toward the image display panel 11 arranged substantially parallel to the light guide (in a direction perpendicular to the front of the drawing) by providing a portion with a different refractive index in the shape of the surface of the light guide or inside the light guide. In this case, when the image display panel 11 is faced directly at the center of the screen and the viewpoint is placed at the same position as the diagonal dimension of the screen, if the relative brightness ratio between the brightness at the center of the screen and the brightness at the periphery of the screen is 20% or more, there is no practical problem, and if it exceeds 30%, it will be an even better characteristic.

[0084] 22 is a cross-sectional layout diagram for explaining the configuration and operation of the light source of this embodiment that performs polarization conversion in light source device 48 including the above-mentioned light guide 203 and LED element 200. In Fig. 22, light source device 48 is composed of light guide 203 formed of, for example, plastic or the like and having light flux direction conversion means 204 on its surface or inside, LED element 200 as a light source, reflective sheet 205, retardation plate 309, lenticular lens, etc., and image display panel 11 having polarizing plates on the light source light entrance surface and image light exit surface is attached to the upper surface.

[0085] Moreover, a film or sheet-like reflective polarizing plate 52 is provided on the light source light incidence surface (lower surface in the figure) of the image display panel 11 corresponding to the light source device 48, and selectively reflects one polarized wave (e.g., P wave 212) of the natural light beam 210 emitted from the LED element 200, and the reflected light beam is reflected by a reflective sheet 205 provided on one surface (lower surface in the figure) of the light guide 203, and directed again toward the image display panel 11. Therefore, a retardation plate (λ / 4 plate) 309 is provided between the reflective sheet 205 and the light guide 203 or between the light guide 203 and the reflective polarizing plate 52, and the reflected light beam of one polarized wave is reflected by the reflective sheet 205 and passes through the reflected light beam twice, thereby converting the reflected light beam from P polarized light to S polarized light, thereby improving the utilization efficiency of the light source light. The image light whose light intensity has been modulated by the video signal in the image display panel 11 (arrow 215 in FIG. 22) is incident on the windshield 6 at a large angle of incidence, as shown in FIGS. 7 and 8, so that the reflectance at the transparent sheet 7b is large, and good characteristics can be obtained for viewing the image inside the vehicle.

[0086] Fig. 23, like Fig. 22, is a cross-sectional layout diagram for explaining the configuration and action of a light source of this embodiment that performs polarization conversion in a light source device 250 including a light guide 203 and an LED element 200. Similarly, the light source device 250 is composed of a light guide 203 formed of, for example, plastic and provided with a light flux direction conversion means 204 on its surface or inside, an LED element 200 as a light source, a reflection sheet 205, a retardation plate 309, a lenticular lens, etc., and on the upper surface thereof, an image display panel 11 having polarizing plates on the light source light entrance surface and the image light exit surface is attached as the image display panel 11.

[0087] In addition, a film or sheet-like reflective polarizing plate 52 is provided on the light source light incidence surface (lower surface in the figure) of the image display panel 11 corresponding to the light source device 48, and selectively reflects one polarized wave (for example, S wave 211) of the natural light beam 210 emitted from the LED element 200, and is reflected by a reflecting sheet 205 provided on one surface (lower surface in the figure) of the light guide 203, and then travels again toward the image display panel 11. It is also possible to provide a retardation plate (λ / 4 plate) 309 between the reflecting sheet 205 and the light guide 203 or between the light guide 203 and the reflective polarizing plate 52, and to polarize the reflected light beam by the reflecting sheet 205 and by passing the retardation plate 309 twice, thereby performing polarization conversion from S polarized light to P polarized light. As described above, in the present invention, the light source beam, which is natural light, can be made approximately parallel and simultaneously converted into a light beam of a specific polarization, so that it can be selected according to the characteristics of the image display panel 11, and as a result, the utilization efficiency of the light source light can be improved. As a result, the image light that has been intensity-modulated by the video signal in the image display panel 11 (arrow 214 in FIG. 23) is incident on the windshield 6 at a large angle of incidence, as shown in FIG. 7, so that the reflectance at the transparent sheet 7b is large, and good characteristics can be obtained for viewing images inside the vehicle.

[0088] In the light source device shown in FIG. 22 and FIG. 23, in addition to the action of the polarizing plate provided on the light incident surface of the corresponding image display panel 11, the reflective polarizing plate 52 reflects the polarized component on one side, so that the theoretically obtained contrast ratio is the reciprocal of the cross transmittance of the reflective polarizing plate 52 multiplied by the reciprocal of the cross transmittance obtained by the two polarizing plates attached to the liquid crystal display panel, and therefore high contrast performance is obtained. In fact, it was confirmed by an experiment that the contrast performance of the displayed image was improved by 10 times or more. As a result, a high-quality image comparable to that of a self-luminous organic EL was obtained. In addition, since the light source device 48 can be made thin, it is one of the technical means for realizing an image display device used in combination with the above-mentioned tablet terminal.

[0089] <Example of image display device 2> FIG. 26 shows another example of a specific configuration of the image display device 49. In the image display device 49 in FIG. 26, the light source device 48 in FIG. 1 is replaced with a light source device 101. As shown in the figure, the light source device 101 is formed of, for example, plastic in its case (see FIG. 26), and is configured by storing LEDs, a collimator, a composite diffusion block, a light guide, and the like inside, and the image display panel 11 is attached to its upper surface. In addition, an LED board 102 shown in FIG. 27 on which LEDs 14a and 14b, which are semiconductor light sources, and a control circuit for them are mounted are attached to one side of the case of the light source device 101, and a heat sink 103, which is a member for cooling heat generated by the LED elements and the control circuit, is attached to the outer side of the LED board 102.

[0090] The liquid crystal display panel frame attached to the top surface of the case is configured to have the image display panel 11 attached to the frame, and further, an FPC (Flexible Printed Circuits) 403 (see FIG. 26) electrically connected to the image display panel 11. That is, the image display panel 11 equipped with the liquid crystal display element generates a display image by modulating the intensity of transmitted light based on a control signal from a control circuit (not shown here) constituting an electronic device together with the LEDs 14a and 14b which are solid-state light sources.

[0091] <Example 3 of image display device> Next, another example of a specific configuration of the image display device 49 will be described with reference to Fig. 24(a). In the light source device 48 of this image display device 49, a divergent light flux of natural light (a mixture of P-polarized and S-polarized waves) from an LED is converted into a substantially parallel light flux by an LED collimator 18, and after passing through an optical element 303 that converts the diffusion characteristic, the light is reflected toward the image display panel 11 by a reflective light guide 304. The reflected light is incident on a reflective polarizing plate 52 disposed between the image display panel 11 and the reflective light guide 304. The reflective polarizing plate 52 reflects light of a specific polarized wave (e.g., S-polarized wave), and transmits light of the other specific polarized wave (e.g., P-polarized wave). Thereafter, the light transmitted through the reflective polarizing plate 52 is incident toward the image display panel 11.

[0092] As a result, the natural light from the LEDs is aligned to a specific polarized wave (for example, S polarized wave), enters the image display panel 11, and is luminance-modulated according to the image signal to display an image on the panel surface. As in the above example, a plurality of LEDs constituting the light source are shown (however, since they are vertical cross sections, only one LED is shown in Figs. 24(a) and (b)), and these are attached at a predetermined position relative to the LED collimator 18. Each of the LED collimators 18 is formed of, for example, a light-transmitting resin such as acrylic or glass. The LED collimator 18 has a cone-shaped outer peripheral surface obtained by rotating a parabolic cross section, and at the top of the LED collimator 18, a concave portion having a convex portion (i.e., a convex lens surface) formed in the center is formed. The center of the flat portion of the LED collimator 18 has a convex lens surface protruding outward (or may be a concave lens surface recessed inward). The parabolic surface forming the cone-shaped outer peripheral surface of the LED collimator 18 is set within an angle range in which the light emitted from the LEDs in the peripheral direction can be totally reflected inside the parabolic surface, or a reflective surface is formed.

[0093] The light converted into nearly parallel light by the LED collimator 18 is aligned to one side of polarization (e.g., S-polarized light) by the polarization conversion element 21 as shown in Fig. 24(b), and is then reflected by the reflective light guide 304, and the light of a specific polarization (e.g., S-polarized light) is transmitted by the action of the reflective polarizing plate 52, while the light of the other specific polarization (e.g., P-polarized light) is reflected. As a result, the degree of polarization can be increased, and high contrast can be achieved. It goes without saying that the same effects as those of the first embodiment can be obtained in the second embodiment of Fig. 24(b) even if the above-mentioned reflective polarizing plate 52 is omitted.

[0094] Next, another example of a specific configuration of the image display device 49 will be described with reference to Fig. 25(a). In the light source device 48 of this image display device 49, a divergent light beam of natural light (a mixture of P-polarized and S-polarized waves) emitted from an LED is converted into a substantially parallel light beam by an LED collimator 18, and the parallel light beam is reflected toward the image display panel 11 by a reflecting surface of a reflective light guide 304. Of the reflected light, a specific polarized wave (e.g., P-polarized wave) is reflected by a reflective polarizing plate 52 arranged between the image display panel 11 and the reflective light guide 304, and the light of the specific polarized wave transmitted through the transmitting portion of the reflective light guide 304 is reflected by a reflecting plate 310, passes twice through a λ / 4 plate (phase difference plate) 309 arranged between the reflective light guide 304 and the reflecting plate 310, is polarized and converted (e.g., S-polarized wave), and is transmitted through the reflective polarizing plate 52.

[0095] As a result, the natural light from the LEDs is aligned to a specific polarization (for example, S polarization) and enters the image display panel 11, where it is brightness-modulated according to the video signal to display an image on the image display panel surface, and the image light is given a desired directional characteristic after passing through optical element 330, which converts the diffusion characteristics. The image light is reflected by the windshield 6 and is visually recognized by the viewer. A λ / 2 plate (phase difference plate) is provided on the reflective surface of the windshield 6 and the transmitted S-polarized light is polarized and converted to P-polarized light, significantly reducing reflections on the surface of the windshield 6 that contacts the outside of the vehicle and reducing double images of the image light to a level that does not cause practical problems.

[0096] In contrast to the above-mentioned image display device 49, the embodiment shown in Fig. 25(b) has a polarization conversion element 21 between the LED collimator 18 and the reflective light guide 304 as a first polarization conversion section that performs polarization conversion, and a second polarization conversion section composed of a reflective polarizer 52, a retardation plate 309, and a reflector 310 provided in the latter stage is also provided. As a result, the degree of polarization can be increased, and high contrast can be achieved. It goes without saying that the same effects as those of the first embodiment can be obtained in the second embodiment of Fig. 25(b) even if the above-mentioned reflective polarizer 52 and wave plate (retardation plate) 309 are omitted.

[0097] Here, in a conventional TV set, the light emitted from the image display panel 11 has similar diffusion characteristics in both the horizontal direction of the screen (shown by the X-axis in FIG. 30(a)) and the vertical direction of the screen (shown by the Y-axis in FIG. 30(b)). In contrast, the diffusion characteristics of the light flux emitted from the image display panel 11 of the above-mentioned embodiment are, for example, as shown in Example 1 of FIG. 30, 1 / 5 of the conventional 62 degrees when the viewing angle at which the luminance is 50% of that when viewed from the front (angle 0 degrees) is set to 13 degrees. Similarly, the vertical viewing angle is optimized by optimizing the reflection angle of the reflective light guide and the area of ​​the reflection surface so that the viewing angle on the upper side is made uneven between the top and bottom and is suppressed to about 1 / 3 of the viewing angle on the lower side. As a result, the amount of image light heading in the viewing direction is significantly improved compared to conventional liquid crystal TVs, and the luminance is 50 times or more higher.

[0098] Furthermore, if the viewing angle characteristic shown in Example 2 of FIG. 31 is used, the viewing angle at which the luminance is 50% of that when viewed from the front (angle 0 degrees) is set to 5 degrees, which is 1 / 12 of the conventional 62 degrees. Similarly, the vertical viewing angle is equal from top to bottom, and the reflection angle and the area of ​​the reflection surface of the reflective light guide are optimized to suppress the viewing angle to about 1 / 12 of the conventional viewing angle. As a result, the amount of image light heading in the viewing direction is significantly improved compared to conventional LCD TVs, and the luminance is 100 times or more. As described above, by making the viewing angle narrow, the amount of light flux heading in the viewing direction can be concentrated, and the light utilization efficiency is significantly improved. As a result, even if a conventional TV image display panel is used, a significant improvement in luminance can be achieved with similar power consumption by controlling the light diffusion characteristics of the light source device, and an image display device compatible with an information display system for outdoor use can be obtained.

[0099] 7(a) and (b), the basic configuration is such that a light beam with a narrow angle of directivity is incident on the image display panel 11 by the light source device 48, and the luminance is modulated according to the image signal, so that the image information displayed on the screen of the image display panel 11 is displayed toward the driver and passengers inside the vehicle through the windshield 6. At this time, the image on the glass surface appears as a double image due to reflections on both sides of the glass, so it is advisable to provide a transparent sheet 51, which will be described later, to reduce this.

[0100] <Light source device example 1> Next, the configuration of the optical system housed in the case of the light source device 101 shown in FIG. 26 will be described in detail with reference to FIG. 27 as well as FIGS. 28(a) and (b).

[0101] 27 and 28 show a plurality of (two in this example) LEDs 14a and 14b constituting the light source, which are attached at predetermined positions relative to the LED collimator 15. Each of the LED collimators 15 is formed of a light-transmitting resin such as acrylic. As shown in FIG. 28(b), the LED collimator 15 has a cone-shaped outer peripheral surface 156 obtained by rotating a parabolic cross section, and has a concave portion 153 at its top with a convex portion (i.e., a convex lens surface 157) formed in its center. The center of the flat surface has a convex lens surface 154 protruding outward (or may be a concave lens surface recessed inward). The parabolic surface forming the cone-shaped outer peripheral surface 156 of the LED collimator 15 is set within an angle range that allows the light emitted from the LEDs 14a and 14b in the peripheral direction to be totally reflected therein, or a reflective surface is formed thereon.

[0102] The LEDs 14a and 14b are disposed at predetermined positions on the surface of the LED substrate 102, which is the circuit substrate. The LED substrate 102 is disposed and fixed to the LED collimator 15 such that the LEDs 14a and 14b on the surface are located at the center of the recess 153.

[0103] According to this configuration, the light emitted from the LED 14a or 14b by the above-mentioned LED collimator 15, particularly the light emitted from the central portion toward the upper side (to the right in the figure), is collected and made parallel by the two convex lens surfaces 157, 154 that form the outer shape of the LED collimator 15. The light emitted from the other portions toward the periphery is reflected by the parabolic surface that forms the conical outer circumferential surface of the LED collimator 15, and is similarly collected and made parallel. In other words, the LED collimator 15 that has a convex lens in its center and a parabolic surface formed on its periphery makes it possible to extract almost all of the light generated by the LED 14a or 14b as parallel light, and thus makes it possible to improve the utilization efficiency of the generated light.

[0104] A polarization conversion element 21 is provided on the light emission side of the LED collimator 15. As is clear from Fig. 28, this polarization conversion element 21 is configured by combining a columnar translucent member having a parallelogram cross section (hereinafter, parallelogram column) and a columnar translucent member having a triangular cross section (hereinafter, triangular column), and arranging them in an array in parallel to a plane perpendicular to the optical axis of the parallel light from the LED collimator 15. Furthermore, a polarization beam splitter film 221 and a reflection film 222 are alternately provided at the interface between adjacent translucent members arranged in the array, and a λ / 2 plate 213 is provided on the emission surface from which the light incident on the polarization conversion element 21 and transmitted through the polarization beam splitter film 221 is emitted.

[0105] 28(a) is provided on the exit surface of this polarization conversion element 21. That is, the light emitted from the LED 14a or 14b is converted into parallel light by the action of the LED collimator 15, enters the synthesizing diffusion block 16, is diffused by the texture 161 on the exit side, and then reaches the light guide 17.

[0106] The light guide 17 is a rod-shaped member made of a translucent resin such as acrylic and having a substantially triangular cross section (see Figure 28(b)), and, as is clear from Figure 27, is equipped with a light guide light entrance portion (surface) 171 facing the exit surface of the synthetic diffusion block 16 via a first diffusion plate 18a, a light guide light reflection portion (surface) 172 forming an inclined surface, and a light guide light exit portion (surface) 173 facing the image display panel 11 equipped with a liquid crystal display element via a second diffusion plate 18b.

[0107] 27, which is a partially enlarged view of the light guide 17, a number of reflective surfaces 172a and connecting surfaces 172b are alternately formed in a sawtooth shape on the light guide light reflecting portion (surface) 172 of the light guide 17. The reflective surface 172a (a line segment sloping upward to the right in the figure) forms an angle αn (n: natural number, e.g., 1 to 130 in this example) with the horizontal plane indicated by the dashed dotted line in the figure, and as an example, αn is set to 43 degrees or less (but 0 degree or more) here.

[0108] The light guide light incident portion (surface) 171 is formed in a curved convex shape inclined toward the light source side. Accordingly, the parallel light from the exit surface of the synthetic diffusion block 16 is diffused and enters through the first diffusion plate 18a, and as is clear from Fig. 27, the parallel light is slightly bent (deflected) upward by the light guide light incident portion (surface) 171 and reaches the light guide light reflecting portion (surface) 172, where it is reflected and reaches the image display panel 11 provided on the exit surface at the top of Fig. 27.

[0109] According to the image display device 49 described above in detail, it is possible to improve the light utilization efficiency and the uniform illumination characteristics, and at the same time, to manufacture the modularized S-polarized light source device in a small size and at low cost. In the above explanation, the polarization conversion element 21 is described as being attached after the LED collimator 15, but the present invention is not limited to this, and the same action and effect can be obtained by providing it in the optical path leading to the liquid crystal display panel.

[0110] 27, in the light guide light reflection portion (surface) 172, a number of reflection surfaces 172a and connecting surfaces 172b are alternately formed in a sawtooth shape, and the illumination light beam is totally reflected on each reflection surface 172a and directed upward, and furthermore, a narrow-angle diffusion plate is provided in the light guide light emission portion (surface) 173 to make the illumination light beam into a substantially parallel diffused light beam, which is incident on the light beam direction conversion means 54 that controls the directivity, and then is incident on the image display panel 11 from an oblique direction. In this embodiment, the light beam direction conversion means 54 is provided between the light guide light emission portion (surface) 173 and the image display panel 11, but the same effect can be obtained by providing the light beam direction conversion means 54 on the emission surface of the image display panel 11 as shown in FIG.

[0111] <Light source device example 2> Another example of the configuration of the optical system of the light source device 48 is shown in FIG. 29. As in the example shown in FIG. 28, a plurality of (two in this example) LEDs 14a and 14b constituting the light source are shown, and these are attached at predetermined positions relative to the LED collimator 15. Each of the LED collimators 15 is formed of a light-transmitting resin such as acrylic. As in the example shown in FIG. 28, the LED collimator 15 has a cone-shaped outer peripheral surface 156 obtained by rotating a parabolic cross section, and at the top of the LED collimator 15, a concave portion 153 having a convex portion (i.e., a convex lens surface 157) formed in the center is formed. Also, at the center of the flat portion, a convex lens surface 154 protruding outward (or a concave lens surface recessed inward may be used). The parabolic surface forming the cone-shaped outer peripheral surface 156 of the LED collimator 15 is set within an angle range that allows the light emitted from the LED 14a in the peripheral direction to be totally reflected therein, or a reflective surface is formed thereon.

[0112] The LEDs 14a and 14b are disposed at predetermined positions on the surface of the LED substrate 102, which is the circuit substrate. The LED substrate 102 is disposed and fixed to the LED collimator 15 such that the LEDs 14a and 14b on the surface are located at the center of the recess 153.

[0113] According to this configuration, the light emitted from the LED 14a or 14b by the above-mentioned LED collimator 15, particularly the light emitted from the central portion toward the upper side (to the right in the figure), is collected and made parallel by the two convex lens surfaces 157, 154 that form the outer shape of the LED collimator 15. The light emitted from the other portions toward the periphery is reflected by the parabolic surface that forms the conical outer circumferential surface of the LED collimator 15, and is similarly collected and made parallel. In other words, the LED collimator 15 that has a convex lens in its center and a parabolic surface formed on its periphery makes it possible to 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.

[0114] A light guide 170 is provided on the light emission side of the LED collimator 15 via a first diffusion plate 18a. The light guide 170 is a rod-shaped member having a substantially triangular cross section (see FIG. 29(a)) made of a light-transmitting resin such as acrylic, and as is clear from FIG. 29(a), the light guide 170 includes a light guide light incident portion (surface) 171 that faces the emission surface of the synthetic diffusion block 16 via the first diffusion plate 18a, a light guide light reflecting portion (surface) 172 that forms an inclined surface, and a light guide light emission portion (surface) 173 that faces the image display panel 11 having a liquid crystal display element via a reflective polarizing plate 252.

[0115] If this reflective polarizing plate 252 is selected to have, for example, the property of reflecting P polarized light (and transmitting S polarized light), it will reflect the P polarized light in the natural light emitted from the LED light source, pass through the λ / 4 plate 177 provided on the light guide light reflecting portion (surface) 172 shown in Figure 29 (b), be reflected by the reflecting surface 176, and then pass through the λ / 4 plate 177 again to be converted into S polarized light, and all the light beams entering the image display panel 11 will be unified into S polarized light.

[0116] Similarly, if a material having the property of reflecting S-polarized light (transmitting P-polarized light) is selected as reflective polarizer 252, it will reflect the S-polarized wave of the natural light emitted from the LED light source, pass through λ / 4 plate 177 provided on light guide light reflecting section (surface) 172 as shown in Fig. 29(b), be reflected by reflecting surface 176, and pass through λ / 4 plate 177 again to be converted into P-polarized wave, and all the light beams entering image display panel 11 will be unified into P-polarized waves. Polarization conversion can also be achieved with the configuration described above.

[0117] <Light source device example 3> Another example of the light source device is shown in Fig. 24 and Fig. 25. The arrangement of the light source device and the image display panel 11 of this example is also shown in Fig. 24 and Fig. 25. The light source device converts the divergent light flux of natural light (a mixture of P polarized waves and S polarized waves) from the LEDs into a substantially parallel light flux by the LED collimator 18, and reflects it toward the image display panel 11 by the reflective light guide 304. Of the reflected light, a specific polarized wave is reflected by the reflective polarizing plate 52 arranged between the image display panel 11 and the reflective light guide 304, while the other polarized wave is transmitted and enters the image display panel 11. The specific polarized wave (e.g., S polarized wave) reflected by the reflective polarizing plate 52 transmits through the transmitting portion of the reflective light guide 304 and is reflected by the reflector 310 provided on the opposite surface of the reflective light guide 304. A phase difference plate 309 is disposed between the reflective light guide 304 and the reflector 310 , and the light passes through the phase difference plate 309 twice to be converted into a polarized wave (eg, P polarized wave) that is transmitted through the reflective polarizer 52 .

[0118] As a result, the natural light from the LED is aligned to a specific polarization (for example, P polarization). As in the above example, a plurality of LED substrates 102 constituting the light source are shown (however, since the cross section is shown, only one is shown in Figs. 24 and 25), and these are attached to a predetermined position with respect to the LED collimator 18. Each of the LED collimators 18 is formed of, for example, a light-transmitting resin such as acrylic or glass. The LED collimator 18 has a cone-shaped outer peripheral surface obtained by rotating a parabolic cross section, and at the top of the LED collimator 18, a concave portion having a convex portion (i.e., a convex lens surface) formed in the center is formed. The center of the flat portion of the LED collimator 18 has a convex lens surface protruding outward (or may be a concave lens surface recessed inward). The parabolic surface forming the cone-shaped outer peripheral surface of the LED collimator 18 is set within an angle range in which the light emitted from the LED collimator 18 in the peripheral direction can be totally reflected inside the parabolic surface, or a reflective surface is formed.

[0119] The LEDs are arranged at predetermined positions on the surface of the circuit board, that is, the LED substrate 102. The LED substrate 102 is arranged and fixed to the LED collimator 18 such that the LEDs on the surface are located at the center of the recessed portion.

[0120] According to this configuration, the light emitted from the LEDs by the LED collimator 18, particularly the light emitted from the central part, is collected and made parallel by the two convex lens surfaces that form the outer shape of the LED collimator 18. The light emitted from the other parts toward the periphery is reflected by the parabolic surface that forms the outer peripheral surface of the cone shape of the LED collimator 18, and is similarly collected and made parallel. In other words, the LED collimator 18, which has a convex lens in its center and a parabolic surface formed on its periphery, makes it possible to extract almost all of the light generated by the LEDs as parallel light, and improves the utilization efficiency of the generated light.

[0121] 24(a) and 25(a), an optical element 303 may be provided on the light emission side of the LED collimator 18 to convert the diffusion characteristics in the vertical and horizontal directions (front and back directions, not shown) of the drawings. In order to efficiently irradiate the light onto the reflecting surface of the light guide, it is advisable to optimally design the number of LEDs and the divergence angle from the optical element 303 as design parameters so that the diffusion angle in the vertical direction of the screen matches the width of the vertical surface of the reflecting surface of the light guide, and the surface density of the light flux emitted from the image display panel 11 in the horizontal direction is uniform.

[0122] If the retardation plate 309 arranged between the reflective polarizing plate 52 and the reflective light guide 304 is selected to have the property of reflecting S-polarized light (transmitting P-polarized light), it will reflect the S-polarized light of the natural light emitted from the LED light source, pass through the wave plate shown in FIG. 24 and other figures, be reflected by the reflecting surface, and pass through the wave plate again to be converted into P-polarized light and enter the image display panel 11. The thickness of this wave plate must be optimally selected depending on the angle of incidence of the light beam to the wave plate, and the optimal value is in the range of λ / 16 to λ / 4. At this time, the reflection angle at the reflective light guide 304 is also a design parameter, and the angle of incidence on the image display panel 11 is designed to be constant over the entire screen area, thereby improving the uniformity of brightness. Alternatively, the reflection angle of the reflective light guide 304 is also a design parameter, and the angle of incidence on the image display panel 11 is designed to be constant over the entire screen area, thereby improving the uniformity of brightness.

[0123] In order to increase the degree of polarization and achieve high contrast, the light source device 48 in FIG. 24(b) and FIG. 25(b) may be provided with a polarization conversion element 21 on the light exit surface of the LED collimator 18.

[0124] Furthermore, by using the light source device according to this embodiment as described above, an image display device having narrow-angle diffusion characteristics as shown in Examples 1 and 2 in (a) and (b) of Fig. 31 can be realized. When the image display device 49 is used for mounting on a vehicle, the distance between the image display device 49 viewed through the windshield 6 and the driver's eyes is equivalent to 1 m, so when the panel size is 7 inches, the diffusion characteristics match those close to the middle between Examples 1 and 2 shown in Fig. 31. On the other hand, when used as a tablet terminal for outdoor use, the clear viewing distance is 0.3 m, so wide diffusion characteristics are required, and it is desirable to optimally design the surface shape and surface roughness of the light reflecting surface of the light guide as parameters according to the application, such as matching the characteristics of Example 2.

[0125] <Directivity characteristics of light emitted from liquid crystal panel> In a device used for a general TV, the light emitted from the video display panel 11 has similar diffusion characteristics in the horizontal direction of the screen (the display direction corresponding to the X-axis of the graph in FIG. 31(a)) and the vertical direction of the screen (the display direction corresponding to the Y-axis of the graph in FIG. 31(b)), as shown, for example, in the plot curves of "conventional characteristics (X direction)" in FIG. 31(a) and "conventional characteristics (Y direction)" in FIG. 31(b).

[0126] In contrast, the diffusion characteristics of the light beam emitted from the image display panel 11 of this embodiment are, for example, as shown in the plot curves of "Example 1 (X direction)" in FIG. 31(a) and "Example 1 (Y direction)" in FIG. 31(b).

[0127] In one specific example, when the viewing angle at which the luminance is 50% (luminance reduced to about half) of the luminance when viewed from the front (angle 0 degrees) is set to 13 degrees, the diffusion angle is about 1 / 5 of the diffusion characteristic of a typical home TV device (angle 62 degrees). Similarly, in one example of setting the vertical viewing angles unequally between the upper and lower sides, the reflection angle of the reflective light guide and the area of ​​the reflection surface are optimized so that the upper viewing angle is suppressed (narrowed) to about 1 / 3 of the lower viewing angle.

[0128] By setting the viewing angle and other settings as described above, the amount of light in the image directed in the user's viewing direction increases dramatically (greatly improving image brightness) compared to conventional LCD TVs, and the brightness of the image becomes more than 50 times higher.

[0129] Furthermore, in the case of the viewing angle characteristics shown in "Example 2" in Fig. 31, if the viewing angle at which the luminance of the image obtained when viewed from the front (angle 0 degrees) is 50% (luminance reduced to about half), is set to 5 degrees, the angle (narrow viewing angle) is about 1 / 12 of the diffusion characteristics (angle 62 degrees) of a typical home TV device. Similarly, in one example of setting the vertical viewing angle equally on the upper and lower sides, the reflection angle and the area of ​​the reflection surface of the reflective light guide are optimized to suppress (narrow) the vertical viewing angle to about 1 / 12 of the conventional angle.

[0130] By using these settings, the brightness (amount of light) of the image in the viewing direction (the direction of the user's line of sight) is significantly improved, becoming more than 100 times brighter, compared to conventional LCD TVs.

[0131] As described above, narrowing the viewing angle allows the amount of light flux heading in the viewing direction to be concentrated, greatly improving the efficiency of light utilization. As a result, even if a liquid crystal display panel for general TV applications is used, it is possible to achieve a significant improvement in brightness with similar power consumption by adjusting the light diffusion characteristics of the light source device, making it possible to create an image display device that is compatible with display systems facing bright outdoors.

[0132] <Light source light control method> In the present invention, the image display device 49 includes a light source device 48 and an image display panel 11. In this embodiment, in order to improve the efficiency of use of the light flux emitted from the light source device 48 and to significantly reduce power consumption, the light source device 48 emits image light rays that are luminance-modulated according to the image signal toward the windshield 6 after being incident on the image display panel 11 at an incident angle that maximizes the characteristics of the image display panel 11. At this time, if the light source device 48 can be made thin in order to reduce the set volume of the image display system, the degree of freedom in installing the image display device 49 can be increased. Furthermore, a technical means for controlling the directivity of the virtual image so that the reflected image (virtual image) can be viewed from a desired position after reflection on the windshield 6 will be described below.

[0133] By providing a transparent sheet made of optical components such as a linear Fresnel lens as a light direction conversion panel on the image display surface of the image display panel 11, the outgoing direction of the light beam incident on the windshield 6 can be controlled while maintaining high directivity, so that the image light can be directed to the position of the viewer's eyes according to the installation position and the inclination angle of the windshield 6. As a result, the degree of freedom in installation of the image display device 49 can be greatly improved. According to this configuration, the image light from the image display device 49 reaches the viewer efficiently with high directivity (straightness) like laser light. As a result, it is possible to display high-quality images at high resolution and to greatly reduce the power consumption of the image display device 49 including the light source device 48.

[0134] <Example 4 of image display device> FIG. 34A shows another example of a specific configuration of the image display device 49. In FIGS. 32 to 34A, light source device 13 is shown instead of light source device 48. Since the circular polarization conversion element 12 shown in FIGS. 32 to 34A has been described above, detailed description will be omitted. This light source device 13 is configured by storing LEDs, a collimator, a composite diffusion block, a light guide, etc. in a case made of, for example, plastic, and an image display panel 11 is attached to its upper surface. In addition, LED (Light Emitting Diode) elements 14, which are semiconductor light sources, and an LED board on which a control circuit is mounted are attached to one side of the case of the light source device 13, and a heat sink, which is a member for cooling heat generated by the LED elements and the control circuit, is attached to the outer side of the LED board (not shown).

[0135] The liquid crystal display panel frame attached to the top surface of the case is configured to have an image display panel 11 attached to the frame, and further, an FPC (Flexible Printed Circuits) (not shown) electrically connected to the image display panel 11, etc. That is, the image display panel 11, which is a liquid crystal display element, generates a display image by modulating the intensity of transmitted light based on a control signal from a control circuit (not shown here) constituting an electronic device together with the LED elements 14, which are solid-state light sources.

[0136] <Light Source Device Example 4> Next, the configuration of the optical system such as the light source device housed in the case will be described in detail with reference to Fig. 34A and Fig. 34B. Fig. 34A and Fig. 34B show LEDs 14 and 14b constituting the light source device 13, which are attached at predetermined positions relative to the collimator 18. Each of the collimators 18 is formed of a light-transmitting material such as glass or heat-resistant resin. As shown in Fig. 34B, the collimator 18 has a cone-shaped outer peripheral surface 156 obtained by rotating a parabolic cross section, and has a concave portion with a convex portion (i.e., a convex lens surface) 154 formed at the center of the apex (the side in contact with the LED substrate).

[0137] Also, the central part of the flat part (the side opposite to the apex) of the collimator 18 has a convex lens surface protruding outward (or may have a concave lens surface recessed inward) 154. The parabolic surface forming the outer peripheral surface of the cone shape of the collimator 18 is set within an angle range in which the light emitted from the LED 14 in the peripheral direction can be totally reflected therein, or a reflective surface is formed.

[0138] The LEDs 14 are disposed at predetermined positions on the surface of the LED substrate 102, which is the circuit substrate. The LED substrate 102 is disposed and fixed to the collimator 18 such that the LEDs 14 on the surface are located at the center of the recessed portion.

[0139] According to this configuration, the light emitted from the LED 14 or 14b by the collimator 18 described above, particularly the light emitted from the central portion toward the upper side (to the right in the drawing), is collected and made parallel by the convex lens surface 154 forming the outer shape of the collimator 18. The light emitted from the other portions toward the periphery is reflected by the parabolic surface forming the conical outer circumferential surface of the collimator 18, and is similarly collected and made parallel. In other words, according to the collimator 18 having a convex lens formed in its central portion and a parabolic surface formed in its peripheral portion, it is possible to extract almost all of the light generated by the LED 14 or 14b as parallel light, and it is possible to improve the utilization efficiency of the generated light.

[0140] A polarization conversion element 21 is provided on the light exit side of the collimator 18. The polarization conversion element 21 may be called a polarization conversion member. As is clear from FIG. 34B, the polarization conversion element 21 is configured by combining a columnar translucent member having a parallelogram cross section (hereinafter, a parallelogram column) and a columnar translucent member having a triangular cross section (hereinafter, a triangular column), and arranging them in an array in parallel to a plane perpendicular to the optical axis of the parallel light from the collimator 18. Furthermore, a polarizing beam splitter (hereinafter, abbreviated as "PBS film") and a reflective film are alternately provided at the interface between the adjacent translucent members arranged in the array, and a λ / 2 phase plate is provided on the exit surface from which the light incident on the polarization conversion element 21 and transmitted through the PBS film exits.

[0141] A number of other examples of the light source device will be described below. Any of these other examples of the light source device may be used in place of the light source device in the example of the image display device described above.

[0142] When using a large LCD panel, as mentioned above, the light around the screen can be directed inward toward the viewer when the viewer is facing the center of the screen, improving the overall brightness of the screen. However, binocular parallax occurs depending on whether the viewer uses the left or right eye to view the image. On the other hand, the smaller the panel size and the closer the viewing distance, the larger the convergence angle in binocular vision by the left and right eyes. In particular, when using a small panel of 7 inches or less, the convergence angle due to binocular parallax is an important requirement, so it is advisable to design the light source to have a directional characteristic or to have an optical diffusion characteristic to direct the image light toward the optimal viewing range of the system.

[0143] Furthermore, depending on the required specifications of the system, it may be necessary to optimally design the shape, surface roughness, inclination, etc. of the reflective surface of the light guide of the light source device 13 described above in order to obtain different directional and diffusion characteristics in the horizontal and vertical directions.

[0144] <Light Source Device Example 5> Next, another example of the light source device will be described with reference to Fig. 32. Figs. 32(a) and (b) are diagrams in which the image display panel 11 and the diffusion plate 206 are partially omitted in order to explain the light guide 311.

[0145] 32 shows a state in which the LEDs 14 constituting the light source are mounted on the LED substrate 102. The LEDs 14 and the LED substrate 102 are attached to a reflector 300 at predetermined positions.

[0146] 32, the LEDs 14 are arranged in a row in a direction parallel to the side (short side in this example) of the image display panel 11 on which the reflector 300 is arranged. In the example shown in the figure, the reflector 300 is arranged corresponding to the arrangement of the LEDs. Note that a plurality of reflectors 300 may be arranged.

[0147] In one embodiment, the reflectors 300 are each made of a plastic material. In other embodiments, the reflectors 300 may be made of a metal material or a glass material, but the plastic material is easier to mold, so the reflectors 300 are made of a plastic material in this embodiment.

[0148] As shown in FIG. 32(b), the inner surface (right side in the figure) of the reflector 300 has a reflection surface (hereinafter, sometimes referred to as a "parabolic surface") 305 having a shape obtained by cutting a parabolic surface by a meridian plane. The reflector 300 converts the divergent light emitted from the LED 14 into substantially parallel light by reflecting it on the reflection surface 305 (parabolic surface), and causes the converted light to enter the end surface of the light guide 311. In addition to the aluminum reflection film, a plurality of metal films such as Ti and SiO are formed on the reflection surface of the reflector 300 as reflection-enhancing films, so that the reflectance is increased and the dependency on the incident angle is reduced as shown in FIG. 41. In one specific example, the light guide 311 is a reflection type light guide.

[0149] The reflecting surface 321 of the reflector 300 has a shape asymmetric with respect to the optical axis of the emitted light of the LED 14. In addition, the reflecting surface 321 of the reflector 300 is a parabolic surface as described above, and the LED 14 is disposed at the focus of the parabolic surface to convert the reflected light flux into approximately parallel light.

[0150] Since the LED 14 is a surface light source, even if it is placed at the focus of a paraboloid, the divergent light from the LED 14 cannot be converted into completely parallel light, but this does not affect the performance of the light source of the present invention. The LED 14 and the reflector 300 form a pair. In order to ensure a predetermined performance when the LED 14 is attached to the LED board 102 with an attachment accuracy of ±40 μm, the number of LEDs 14 attached to the LED board 102 should be a maximum of 10 or less, and it is better to keep it to about 5 in consideration of mass productivity.

[0151] Although the LED 14 and the reflector 300 are partly close to each other, the temperature rise of the LED can be reduced because heat can be dissipated into the space on the opening side of the reflector 300. This makes it possible to use a plastic molded reflector 300. As a result, with this reflector 300, the shape precision of the reflective surface can be improved by 10 times or more compared to a reflector made of glass material, thereby improving the light utilization efficiency.

[0152] On the other hand, as shown in Fig. 32, a reflecting surface is provided on the bottom surface 302 of the light guide 311, and the light from the LEDs 14 is converted into a parallel light beam by the reflector 300, reflected by the reflecting surface, and emitted toward the image display panel 11 arranged opposite the light guide 311. As shown in Fig. 32, the reflecting surface provided on the bottom surface 302 has a plurality of surfaces with different inclinations in the traveling direction of the parallel light beam from the reflector 300, and the light is reflected toward the corresponding parts of the image display panel 11. Each of the plurality of surfaces with different inclinations may have a shape extending in a direction perpendicular to the traveling direction of the parallel light beam from the reflector 300.

[0153] Also, as shown in FIG. 32, the shape of the reflection surface provided on the bottom surface 302 may be flat. Furthermore, a diffusion plate 206 may be provided to more precisely control the diffusion characteristics of the light reflected by the reflection surface provided on the bottom surface 302 of the light guide 311 facing the image display panel 11. The diffusion plate 206 refracts the reflected light once by the surface shape and surface roughness of both sides, and can adjust the amount of light and the emission direction of the light beam toward the image display panel 11 with high precision, so that the amount of light incident on the image display panel 11 and the emission direction of the light emitted from the image display panel 11 can be controlled with high precision as well. Therefore, in the image display system using the image display device 49 having the above-mentioned configuration, the diffusion direction and diffusion angle of the image light of the display image can be set to a desired value. In this case, it is preferable to design the reflection film provided on the reflection surface to have a high reflectance and a reduced incidence angle dependency of the reflectance as shown in FIG. 44 by adding an increased reflection film of Ti and SiO to the aluminum reflection film. The aluminum reflective film described above has a lower reflectance in the blue-green wavelength region below 500 nm compared to the green-red region, so when designing an enhanced reflection film, it is also important to improve the purity of white in order to reduce the incidence angle dependency of reflectance and improve color reproducibility.

[0154] As shown in FIG. 32, the LED 14 is soldered to a metallic LED substrate 102. This allows heat generated by the LED 14 to be dissipated into the air via the LED substrate 102. The reflector 300 may be in contact with the LED substrate 102, or a space may be left therebetween. When a space is left therebetween, the reflector 300 is attached to the housing and disposed therebetween. By leaving a space therebetween, heat generated by the LED 14 can be dissipated into the air, improving the cooling effect. As a result, the operating temperature of the LED 14 can be reduced, making it possible to maintain the luminous efficiency and extend the lifespan.

[0155] In the light source device described above, the light utilization efficiency can be improved by 1.8 times by using the polarization conversion element 21. The configuration of the optical system related to this light source device will be described in detail below with reference to Figures 33A, 33B, 33C, and 33D.

[0156] 33A, 33B, and 33C show a state in which the LEDs 14 constituting the light source are mounted on the LED substrate 102, and these are configured as a unit 312 having a plurality of blocks, with the reflector 300 and the LEDs 14 forming a pair of blocks.

[0157] Among these, the base material 320 shown in Fig. 33A(2) is the base material of the LED substrate 102. In general, the metallic LED substrate 102 generates heat, so the base material 320 may be made of a plastic material or the like in order to insulate (thermally insulate) the heat of the LED substrate 102. A metal member may also be used to enhance heat dissipation.

[0158] Furthermore, the reflecting surface 321 of the reflector 300 may have an asymmetric shape with respect to the optical axis of the emitted light from the LED 14. The reason for this will be explained with reference to Fig. 33A(2). In this embodiment, the reflecting surface 321 of the reflector 300 is a parabolic surface, and the center of the light emitting surface of the LED 14, which is a surface light source, is located at the focal position of the parabolic surface.

[0159] In addition, due to the characteristics of the paraboloid, the light emitted from the four corners of the light emitting surface becomes approximately parallel light beams, and only the emission direction differs. Therefore, even if the light emitting part has an area, if the distance between the polarization conversion element 21 and the reflector 300 arranged in the latter stage is short, the amount of light incident on the polarization conversion element 21 and the conversion efficiency are hardly affected.

[0160] In addition, even if the mounting position of the LED 14 is shifted in the XY plane with respect to the focal point of the corresponding reflector 300, an optical system can be realized that can reduce the decrease in light conversion efficiency for the above-mentioned reasons. Furthermore, even if the mounting position of the LED 14 varies in the Z-axis direction, the converted parallel light beam only moves in the ZX plane, and the mounting accuracy of the LED 14, which is a surface light source, can be significantly reduced. In this embodiment, the reflector 300 having the reflective surface 321 in which a part of the paraboloid is meridionally cut out, has been described, but the LED may be arranged in a part of the cutout with the entire paraboloid as the reflective surface.

[0161] On the other hand, in this embodiment, as shown in Fig. 33B(1) and Fig. 33C, the divergent light from the LED 14 is reflected by the parabolic reflecting surface 321 to be converted into substantially parallel light, and then the light is made incident on the end face of the downstream polarization conversion element 21, and aligned into a specific polarization by the polarization conversion element 21. Due to this characteristic configuration, in this embodiment, the light utilization efficiency is 1.8 times that of the example in Fig. 32 described above, and a highly efficient light source can be realized.

[0162] At this time, the substantially parallel light resulting from the reflection of the divergent light from the LEDs 14 by the reflecting surface 321 is not all uniform. Therefore, by adjusting the angular distribution of the reflected light by the reflecting surface 307 having a plurality of inclinations, it is possible for the reflected light to be incident on the image display panel 11 in a direction perpendicular to the image display panel 11.

[0163] Here, in the example of this figure, the LEDs 14 are arranged so that the direction of light (principal light) entering the reflector 300 from the LEDs 14 is approximately parallel to the direction of light entering the image display panel 11. This arrangement is easy to arrange in terms of design, and the reflector 300 can significantly reduce the divergence angle from the LEDs 14 in the vertical direction of the drawing. As a result, the divergence angle in the horizontal direction of the screen incident on the image display panel 11 can be controlled more precisely than the divergence angle in the vertical direction of the screen. In the configuration shown in Fig. 33B, the LEDs 14, which are heat sources, are arranged below the light source device, but it goes without saying that the diffused light flux from the LEDs 14 can be similarly controlled even if the LEDs 14 are arranged above.

[0164] 33B(1), in order to improve the capture rate of the divergent light from the LED 14, the light beam that cannot be captured by the reflector 300 is reflected by a sub-reflector 308 provided on a light shielding plate 313 arranged on the upper part of the reflector 300, reflected by the inclined surface of a lower sub-reflector 315, and made to enter the effective area of ​​the subsequent polarization conversion element 21, thereby further improving the light utilization efficiency. That is, in this embodiment, a part of the light reflected by the reflector 300 is reflected by the sub-reflector 308, and the light reflected by the sub-reflector 308 is reflected by the sub-reflector 315 in a direction toward the reflective light guide 306.

[0165] In the light source of this embodiment, PBSs that reflect specific polarized waves are arranged vertically so that the change in luminance in the vertical direction of the screen is small in principle. The approximately parallel light beams aligned to specific polarized waves by this polarization conversion element 21 are reflected toward the image display panel 11 arranged opposite the reflective light guide 306 by the reflecting surface shape provided on the surface of the reflective light guide 306. At this time, the light amount distribution of the light beams incident on the image display panel 11 is optimally designed by the shape and arrangement of the reflector 300 described above, the reflecting surface shape (cross-sectional shape) of the reflective light guide 306, and the inclination and surface roughness of the reflecting surface 307.

[0166] The reflective surface shape provided on the surface of the reflective light guide 306 is such that a plurality of reflective surfaces 307 are arranged opposite the exit surface of the polarization conversion element 21, and the inclination, area, height and pitch of the reflective surfaces 307 are optimized according to the distance from the polarization conversion element 21, thereby making the light quantity distribution of the light beam incident on the image display panel 11 the desired value, as described above.

[0167] The reflecting surface 307 provided on the reflective light guide 306 can be configured to have multiple inclinations on one surface as shown in FIG. 33B(2), thereby realizing more accurate adjustment of reflected light6. As shown in FIG. 33B(2), the parallel light beam φ5 (R7-R10) from the reflector 300 is reflected by multiple surfaces (P7-P10) with different inclinations in the traveling direction and heads toward the corresponding parts of the image display panel 11. Note that, in the reflecting surface 307, the configuration in which one surface has multiple inclinations may be such that the area used as the reflecting surface 307 is a multiple surface, a multi-surface, or a curved surface. Furthermore, the diffusion effect of the diffusion plate 206 realizes a more uniform light amount distribution. The light incident on the diffusion plate 206 on the side closer to the LED 14 realizes a uniform light amount distribution by changing the inclination of the reflecting surface 307. As a result, the light amount and the emission direction of the light beam heading toward the image display panel 11 can be adjusted with high accuracy. As a result, the amount and direction of light incident on the image display panel 11 and the light emitted from the image display panel 11 can also be controlled with high precision, so that the diffusion direction and diffusion angle of the image light of the image information display device can be set to desired values.

[0168] In this embodiment, a plastic material such as heat-resistant polycarbonate is used as the base material of the reflecting surface 307. The angle of the reflecting surface 307 immediately after emission from the λ / 2 plate 213 changes depending on the distance between the λ / 2 plate and the reflecting surface.

[0169] In this embodiment, the LED 14 and the reflector 300 are also close to each other in some places, but the temperature rise of the LED can be reduced by dissipating heat into the space on the opening side of the reflector 300. It goes without saying that the same capture rate can be ensured even if the LED substrate 102 and the reflector 300 are arranged upside down as shown in Figures 33A, 33B, and 33C.

[0170] However, if the LED board 102 is placed on top, the LED board 102 will be close to the image display panel 11, which may make the layout difficult. Therefore, as shown in the figure, placing the LED board 102 on the lower side of the reflector 300 (the side farther from the image display panel 11) often results in a simpler configuration within the device.

[0171] A light shielding plate 410 may be provided on the light incidence surface of the polarization conversion element 21 to prevent unnecessary light from entering the optical system at the subsequent stage. With such a configuration, a light source device that suppresses temperature rise can be realized. In the polarizing plate provided on the light incidence surface of the image display panel 11, the temperature rise is reduced by absorption in the light flux with uniform polarization of the present invention, but when reflected by the reflective light guide 306, the polarization direction rotates and some of the light is absorbed by the incidence side polarizing plate. Furthermore, the temperature of the image display panel 11 also rises due to absorption by the liquid crystal itself and temperature rise caused by light incident on the electrode pattern, but there is a sufficient space between the reflective surface 307 of the reflective light guide 306 and the image display panel 11, allowing natural cooling.

[0172] Fig. 33D is a modified example of the light source device of Fig. 33B(1) and Fig. 33C. Fig. 33D(1) illustrates a modified example of a part of the light source device of Fig. 33B(1). The rest of the configuration is the same as the light source device described above in Fig. 33B(1), so illustrations and repeated explanations are omitted.

[0173] First, in the example shown in Fig. 33D(1), the height of recess 319 of sub-reflector 315 is adjusted to be lower than phosphor 114 so that the chief ray of fluorescence outputted laterally (in the X-axis direction) from phosphor 114 (see the straight line extending in a direction parallel to the X-axis in Fig. 33D(1)) passes through recess 319 of sub-reflector 315. Furthermore, the height of light-shielding plate 410 is adjusted to be lower in the Z-axis direction relative to the position of phosphor 114 so that the chief ray of fluorescence outputted laterally from phosphor 114 enters the effective area of ​​polarization conversion element 21 without being blocked by light-shielding plate 410.

[0174] Furthermore, the reflective surface of the convex portion of the unevenness on the top of the sub-reflector 315 reflects the light reflected by the sub-reflector 308 in order to guide the light reflected by the sub-reflector 308 to the reflective light guide 306. Therefore, the height of the convex portion 318 of the sub-reflector 315 is adjusted so that the light reflected by the sub-reflector 308 is reflected and made to enter the effective area of ​​the polarization conversion element 21 in the subsequent stage, thereby further improving the light utilization efficiency.

[0175] 33A(2), the sub-reflector 315 is arranged to extend in one direction and has an uneven shape. Furthermore, at the top of the sub-reflector 315, unevenness having one or more recesses 319 and protrusions 318 is periodically arranged along one direction. By using such an uneven shape, it is possible to configure the main ray of the fluorescence outputted horizontally from the phosphor 114 to be incident on the effective area of ​​the polarization conversion element 21.

[0176] Further, the uneven shape of the sub-reflector 315 is periodically arranged at a pitch where the recesses 319 are located at the positions where the LEDs 14 are located. That is, each of the phosphors 114 is periodically arranged along one direction corresponding to the arrangement pitch of the recesses of the uneven shape of the sub-reflector 315. Note that when the phosphor 114 is provided in the LED 14, the phosphor 114 may be expressed as a light-emitting portion of the light source.

[0177] Also, Fig. 33D(2) illustrates a modified example of a part of the light source device of Fig. 33C. The other configuration is the same as that of the light source device of Fig. 33C, so illustration and repeated explanation are omitted. As shown in Fig. 33D(2), the sub-reflector 315 is not necessary, but as in Fig. 33D(1), the height of the light shielding plate 410 is adjusted to be lower in the Z-axis direction relative to the position of the phosphor 114 so that the main ray of the fluorescence outputted horizontally from the phosphor 114 is not blocked by the light shielding plate 410 and enters the effective area of ​​the polarization conversion element 21.

[0178] 33A, 33B, 33C, and 33D, side walls 400 may be provided to prevent dust from entering the space between reflective surface 307 of reflective light guide 306 and image display panel 11, to prevent stray light from entering the light source device, and to prevent stray light from entering the light source device from the outside, as shown in Fig. 33A(1). When side walls 400 are provided, they are arranged to sandwich the space between reflective light guide 306 and diffusion plate 206.

[0179] The light exit surface of the polarization conversion element 21, which emits the light polarized by the polarization conversion element 21, faces the space surrounded by the side wall 400, the reflective light guide 306, the diffuser plate 206, and the polarization conversion element 21. In addition, of the inner surface of the side wall 400, a surface of a portion that covers the space from which the light is output from the exit surface of the polarization conversion element 21 (the space on the right side of the exit surface of the polarization conversion element 21 in FIG. 33B(1)) from the side is a reflective surface having a reflective film or the like. In other words, the surface of the side wall 400 facing the above-mentioned space has a reflective area having a reflective film. By making the portion of the inner surface of the side wall 400 a reflective surface, the light reflected by the reflective surface can be reused as light source light, and the brightness of the light source device can be improved.

[0180] Among the inner surfaces of the side wall 400, the surface of the portion covering the side of the polarization conversion element 21 is made to have low light reflectance (such as a black surface without a reflective film). This is because when light is reflected on the side of the polarization conversion element 21, light with an unexpected polarization state is generated, which causes stray light. In other words, by making the above surface a surface with low light reflectance, it is possible to prevent or suppress the occurrence of stray light in the image and light with an unexpected polarization state. Also, the side wall 400 may be configured to have a hole through which air can pass in part to improve the cooling effect.

[0181] 33A, 33B, 33C, and 33D have been described on the assumption that they are configured to use the polarization conversion element 21. However, these light source devices may be configured without the polarization conversion element 21. In this case, a cheaper light source device can be provided.

[0182] <Another example of light source device 2> Next, the configuration of the optical system for a light source device using a reflective light guide 304 based on the light source device shown in Example 1 of the light source device will be described in detail with reference to Figures 34A (1), (2), (3), and 34B.

[0183] 34A shows a state where the LEDs 14 constituting the light source are mounted on the LED substrate 102, and the collimator 18 and the LEDs 14 are arranged as a pair of blocks, and the unit 328 has a plurality of blocks. Since the collimator 18 in this embodiment is close to the LEDs 14, a glass material is used for the collimator 18 in consideration of heat resistance. In addition, a light shielding plate 317 is provided in the stage before the light enters the polarization conversion element 21, thereby preventing or suppressing unnecessary light from entering the optical system in the subsequent stage, and reducing the rise in temperature due to the unnecessary light.

[0184] Among the other configurations of the light source shown in FIG. 34B, the LED 14b and the polarization conversion part are different from the embodiment shown in FIG. 33, but the configurations and effects of each have been described above and will not be described here. The other configurations are the same as in FIG. 33A, FIG. 33B, FIG. 33C, and FIG. 33D, so repeated explanations will be omitted. The light source device in FIG. 34A may be provided with a side wall, as described in FIG. 33A, FIG. 33B, and FIG. 33C. The configuration and effects of the side wall have already been described, so repeated explanations will be omitted.

[0185] <Structure of the diffusion plate> Fig. 34C is a cross-sectional view showing an example of the shape of the diffusion plate 206. As described above, the divergent light output from the LED is converted into approximately parallel light by the reflector 300 or the collimator 18, converted into a specific polarized wave by the polarization conversion element 21, and then reflected by the light guide. The light beam reflected by the light guide passes through the flat portion of the incident surface of the diffusion plate 206 and enters the image display panel 11 (see the two solid arrows indicating "reflected light from the light guide" in Fig. 34C).

[0186] Furthermore, of the light emitted from the polarization conversion element 21, the divergent light beam is totally reflected by the inclined surface of a protrusion having an inclined surface provided on the incident surface of the diffusion plate 206, and enters the image display panel 11. In order to totally reflect the light emitted from the polarization conversion element 21 by the inclined surface of the protrusion of the diffusion plate 206, the angle of the inclined surface of the protrusion is changed based on the distance from the polarization conversion element 21. If the angle of the inclined surface of the protrusion on the side farther from the polarization conversion element 21 or the side farther from the LED is α, and the angle of the inclined surface of the protrusion on the side closer to the polarization conversion element 21 or the side closer to the LED is α', then α is smaller than α' (α<α'). By setting in this way, it becomes possible to effectively utilize the polarization-converted light beam.

[0187] <Technology for controlling diffusion characteristics of image display devices> As a method for adjusting the diffusion distribution of the image light from the image display panel 11, a lenticular lens may be provided between the light source device 13 (light source device 48) and the image display panel 11, or on the surface of the image display panel 11, and the shape of the lens may be optimized. That is, by optimizing the shape of the lenticular lens, it is possible to adjust the emission characteristics of the image light (hereinafter also referred to as "image light flux") emitted in one direction from the image display panel 11. The light source device 13 may be replaced with the light source device 48.

[0188] Alternatively or additionally, a microlens array may be arranged in a matrix on the surface of the image display panel 11 (or between the light source device 13 and the image display panel 11), and the manner of the arrangement may be adjusted. That is, by adjusting the arrangement of the microlens array, it is possible to adjust the emission characteristics in the X-axis and Y-axis directions of the image light emitted from the image display device 49, and as a result, it is possible to obtain an image display device having desired diffusion characteristics.

[0189] As a further configuration example, two lenticular lenses may be combined and arranged at a position where the image light emitted from the image display device 49 passes, or a sheet for adjusting the diffusion characteristics by arranging a microlens array in a matrix may be provided. By configuring the optical system in this way, the brightness (relative brightness) of the image light can be adjusted in the X-axis and Y-axis directions according to the reflection angle of the image light (reflection angle with the vertical reflection as the reference (0 degrees)).

[0190] In this embodiment, by using such a lenticular lens, it is possible to obtain excellent optical characteristics that are clearly different from the graphs (plot curves) of conventional characteristics, as shown in the graphs (plot curves) of "Example 1 (Y direction)" and "Example 2 (Y direction)" in Fig. 31(b). Specifically, in the plot curves of Example 1 (Y direction) and Example 2 (Y direction), the brightness characteristic in the vertical direction is made steep, and further, by changing the balance of the directional characteristics in the up and down directions (positive and negative directions of the Y axis), the brightness (relative brightness) of light due to reflection and diffusion can be increased.

[0191] Therefore, according to this embodiment, the image light has a narrow diffusion angle (high straightness) and contains only specific polarization components, like the image light from a surface-emitting laser image source, and can be adjusted so that the displayed image from the image display device 49 is efficiently delivered to the viewer's eyes.

[0192] Furthermore, the light source device described above can provide a directional characteristic with a significantly narrower angle in both the X-axis and Y-axis directions than the diffusion characteristic of light emitted from a general liquid crystal display panel shown in Figures 31(a) and (b) (indicated as "conventional characteristic" in the figure). In this embodiment, by providing such a narrow-angle directional characteristic, it is possible to realize an image display device that outputs image light that is nearly parallel toward a specific direction and outputs light of a specific polarization.

[0193] FIG. 30 shows an example of the characteristics of the lenticular lens used in this embodiment. In this example, the characteristics in the X direction (vertical direction) based on the Z axis are shown in particular, and the characteristic O shows a luminance characteristic that is symmetrical up and down, with the peak of the light emission direction at an angle of about 30 degrees upward from the vertical direction (0 degrees). The plot curves of the characteristics A and B shown in the graph of FIG. 30(b) further show an example of a characteristic in which the image light above the peak luminance is collected near 30 degrees to increase the luminance (relative luminance). For this reason, in these characteristics A and B, as can be seen by comparing with the plot curve of the characteristic O, the luminance (relative luminance) of light is suddenly reduced in the region where the inclination (angle θ) from the Z axis to the X direction exceeds 30 degrees (θ>30°).

[0194] That is, according to the optical system including the above-mentioned lenticular lens, when the image light from the image display device 49 is incident on the windshield, the emission angle and viewing angle of the image light aligned to a narrow angle by the light source device 13 can be adjusted, and the degree of freedom in installation of the image display device 49 can be significantly improved. As a result, the degree of freedom in the display position of the image displayed by the image display device 49 can be significantly improved. As a result, it is possible to efficiently reach the eyes of an observer outdoors or indoors as light with a narrow diffusion angle (high straightness) and only a specific polarized wave component. As a result, even if the intensity (brightness) of the image light from the image display device 49 is reduced, the observer can accurately recognize the image light and obtain information. In other words, by reducing the output of the image display device 49, a display system with low power consumption can be realized.

[0195] Various embodiments or examples (i.e., specific examples) to which the present invention is applied have been described above in detail. However, the present invention is not limited to only the above-mentioned embodiments (specific examples), and includes various modified examples. For example, the above-mentioned embodiments are detailed descriptions 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 of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0196] <Lenticular lens sheet and its function> In addition to the above-mentioned control of emitted light by the light source device, a second technical means for controlling the diffusion distribution of the image light from the image display panel 11 is to provide a lenticular lens between the light source device 48 and the image display panel 11 or on the surface of the image display panel 11, and optimize the lens shape to control the emission characteristics in one direction. Furthermore, by arranging a microlens array in a matrix, the emission characteristics of the image light from the image display device 49 in the X-axis and Y-axis directions can be controlled independently or simultaneously, and different directional characteristics can be provided in the center and periphery of the screen of the image display panel 11, thereby obtaining an image display device with desired diffusion characteristics.

[0197] Next, the action of the lenticular lens will be described. The lenticular lens optimizes the lens shape to control the directional characteristics of the light emitted from the image display device 49, and allows the light to be efficiently reflected or diffused on the transparent sheet 7b provided inside the windshield 6 or the transparent sheet 51 provided on the surface. That is, two lenticular lenses are combined or a microlens array is arranged in a matrix to provide a sheet for controlling the diffusion characteristics for the image light from the image display device 49, and the luminance (relative luminance) of the image light can be controlled in the X-axis and Y-axis directions according to the reflection angle (vertical direction is 0 degrees). In this embodiment, such a lenticular lens makes the luminance characteristics in the vertical direction steeper than in the conventional case, as shown in FIG. 31(b), and further changes the balance of the directional characteristics in the up and down directions (positive and negative directions of the Y-axis) to increase the luminance (relative luminance) of the light due to reflection or diffusion, so that the image light has a narrow diffusion angle (high straightness) and is composed of only a specific polarization component, like the image light from a surface-emitting laser image source, and efficiently reaches the viewer's eyes.

[0198] On the other hand, by using the light source device described above, it is possible to realize an image display device that emits light of a specific polarization that emits image light nearly parallel to a specific direction by achieving a directional characteristic that is significantly narrower in both the X-axis and Y-axis directions than the diffusion characteristic of the emitted light from a typical liquid crystal panel shown in Figures 31(a) and (b) (labeled as "conventional" in the figures).

[0199] FIG. 30 shows an example of the characteristics of the light source device adopted in this embodiment. The above-mentioned characteristics of the lenticular lens are added to tilt the peak luminance by 30 degrees in the X direction (vertical direction). Specifically, characteristic O shows a luminance characteristic that is symmetrical up and down, with the peak of the light emission direction at an angle of about 30 degrees upward from the vertical direction (0 degrees). Characteristics A and B in FIG. 30 show examples of characteristics in which the image light above the peak luminance is further concentrated near 30 degrees to increase the luminance (relative luminance). For this reason, in characteristics A and B, the luminance (relative luminance) of light is rapidly reduced at angles exceeding 30 degrees, compared to characteristic O.

[0200] According to the optical system including the light source device adopted in the present embodiment, as shown in FIG. 26, the image light from the image display device 49 can be reflected or diffused in a specific direction with its brightness increased (emphasized) through a transparent sheet 51 provided on the surface of the windshield 6 described below. This makes it possible to make the image light from the image display device 49 reach the eyes of an observer outside or inside the room efficiently as light with a narrow diffusion angle (high linearity) and only a specific polarization component, like the image light from a surface emitting laser image source. As a result, even if the intensity (brightness) of the image light from the image display device 49 is reduced, the observer can accurately recognize the image light and obtain information. In other words, by further reducing the output of the image display device 49, an information display system with low power consumption can be realized.

[0201] <LCD panel performance> Incidentally, in a typical TFT (Thin Film Transistor) liquid crystal panel, the brightness and contrast performance differs depending on the light emission direction due to the mutual characteristics of the liquid crystal and the polarizing plate. In an evaluation in the measurement environment shown in Fig. 35, the brightness and viewing angle characteristics in the short side (up and down) direction of the panel are superior at an angle slightly shifted from the emission angle perpendicular to the panel surface (emission angle 0 degrees) (+5 degrees in this embodiment) as shown in Fig. 37. The reason for this is that in the short side (up and down) direction of the liquid crystal panel, the light twisting characteristic does not become 0 degrees when the applied voltage is at its maximum.

[0202] On the other hand, the contrast performance in the short side (up and down) direction of the panel is excellent in the range of -15 degrees to +15 degrees, as shown in Figure 39. When combined with the luminance characteristics, the best characteristics are obtained when used in the range of ±10 degrees with 5 degrees as the center.

[0203] Furthermore, the brightness and viewing angle characteristics in the longitudinal (left-right) direction of the panel are superior at an emission angle perpendicular to the panel surface (emission angle of 0 degrees) as shown in Figure 36. The reason for this is that the light twisting characteristic in the longitudinal (left-right) direction of the liquid crystal panel becomes 0 degrees when the applied voltage is at its maximum.

[0204] Similarly, the contrast performance in the longitudinal (left-right) direction of the panel is excellent in the range of -5 degrees to -10 degrees as shown in Fig. 38, and when combined with the brightness characteristics, the best characteristics are obtained when used in the range of ±5 degrees with -5 degrees as the center. For this reason, the emission angle of the image light emitted from the liquid crystal panel is set by making the light enter the liquid crystal panel from the direction that provides the best characteristics by the light beam direction conversion means provided on the light guide of the light source device 13 described above, and modulating the light with a video signal, thereby improving the image quality and performance of the image display device 49.

[0205] In order to make the most of the brightness and contrast characteristics of the liquid crystal panel as an image display element, the image quality can be improved by setting the incident light from the light source to the liquid crystal panel within the above-mentioned range.

[0206] In order to bend the image light from the image display panel having the liquid crystal display element in a desired direction, it is advisable to provide light beam direction conversion means 54 using a lenticular lens sheet or the like on the exit surface of the liquid crystal display panel.

[0207] <Transparent sheet effect 1> A transparent sheet 7b is provided on the windshield 6 of the vehicle shown in Figs. 7(a) and (b) as an embodiment of the present application. A more detailed configuration and its effect will be described with reference to Figs. 8(a) and (b). The sunlight pouring into the interior of the vehicle is natural light containing a mixture of P-polarized waves and S-polarized waves. Of these, S-polarized waves are irradiated as light with a high ratio of P-polarized waves due to the high reflectance of the windshield 6. Fig. 8(a) shows the configuration of the transparent sheet 7b that reflects image light into the interior of the vehicle, and the principle of protecting against sunlight and reducing double images. Fig. 8(b) is a cross-sectional view for explaining the principle of protecting against sunlight and reducing double images when a viewer is wearing polarized sunglasses. The transparent sheet 7b is provided on the image light incident surface side of the shatterproof sheet 7 that prevents glass provided inside the windshield 6 from shattering if it is damaged. The transparent sheet 7b is provided with a retardation plate (lambda / 2 plate) that converts sunlight with a high ratio of P-polarized waves that has passed through it into S-polarized light, and converts the transmitted polarized light into S-polarized light. As a result, the light is reflected with high reflectance on the interior surface of the windshield 6 and heads outside the vehicle. At this time, it is converted to P-polarized light by passing through the retardation plate (λ / 2 plate) again, reducing reflection on the surface of the windshield 6 that contacts the exterior of the vehicle. As a result, the amount of sunlight entering the vehicle is significantly reduced, reducing stress on the image display panel 11 that constitutes the image display device 49. Note that transparent sheet 7b does not necessarily have to be provided.

[0208] <Transparent sheet effect 2> Next, the second effect of the transparent sheet described above will be explained. The image light, which is intensity-modulated by the image display device 49 according to the image signal, is reflected by the image light incident surface of the windshield 6 and moves toward the viewer. However, the light transmitted through the image light incident surface passes through the retardation plate (lambda / 2 plate) and is converted to P-polarized light. As a result, the reflectance is low on the surface of the windshield 6 that contacts the outside world, so that the double image caused by the reflection on both sides of the windshield 6 is reduced to a level that does not cause practical problems. The retardation plate (lambda / 2 plate) described above should be selected to have an optimal thickness depending on the incident angle and angular distribution of the image light from the image display device 49 to the windshield 6, and an optimal value should be selected according to the diffusion characteristics of the transparent diffusion sheet. When the incident angle is large, it is better to make the retardation plate thinner than in the case of perpendicular incidence to obtain better characteristics.

[0209] In addition, it was confirmed that by providing the above-mentioned transparent sheet 7b on the inside surface of the windshield 6 and providing its surface with a reflection-enhancing coating that increases the reflectivity for S-polarized waves, not only can a bright image be obtained, but the intensity of the double image caused by the reflected image can also be significantly reduced.

[0210] Furthermore, instead of the above-mentioned transparent sheet, for example, PDLC (Polymer Dispersed Liquid Crystal) by Suntec Display Co., Ltd. may be used for the rear glass 6', and when an image is displayed, no voltage is applied to disperse the image light, and when an image is not displayed, a voltage is applied to make the glass transparent, thereby substituting for a transparent sheet. Furthermore, the inventors have experimentally found that by varying the voltage applied to the PDLC to vary the dispersion characteristics, and by modulating the applied voltage in synchronization with the ON / OFF or strength of the image signal, a window glass with a screen function that can vary the transmittance according to the image can be realized. As a result, a video information display system with a desired viewing range can be realized by diffusing narrow-angle image light from the image display device vertically and horizontally toward the inside and outside of the automobile.

[0211] According to the embodiment described above in detail, the image light from the image display device 49 can be made to have a narrow diffusion angle (high linearity) and only a specific polarization component, like the image light from a surface emitting laser image source. This allows various information to be displayed inside or outside the vehicle, for example, by using the respective window glasses that separate the inside and outside of the vehicle, and it becomes possible to significantly improve the utilization efficiency of the automobile as a moving image advertisement. In addition, an information display system is realized that can display high-quality images with high resolution, and can improve the utilization efficiency of the light emitted from the light source to significantly reduce power consumption. In addition, when a larger image is to be displayed, a liquid crystal display device with an aspect ratio wider than 16:9 can be realized by combining multiple liquid crystal panels as the image display panel 11 that constitutes the image display device 49 together with the light source device 48.

[0212] In this case, a plurality of light source devices may be provided corresponding to the respective liquid crystal panels, and it is also possible to combine a plurality of liquid crystal panels with a different number of light source devices and use a large image display panel 11 which is integrated with a continuous joint. In this case, the light beam from the light source device 48 is directed in parallel to the above-mentioned transparent sheets 7b, 51 provided on the window glass, and is reflected and diffused in one direction by the transparent sheets, thereby making it possible to display enlarged image information while significantly reducing power consumption.

[0213] As described above, the light source device 48 includes a point-like or planar light source, an optical member that reduces the divergence angle of light from the light source, a polarization conversion element that aligns the light with the reduced divergence angle to light of a specific polarization, and a light guide having a reflective surface that reflects the light aligned to the specific polarization by the polarization conversion element and propagates to the image display panel. The light guide has a surface facing the image display panel, and the reflective surface of the light guide reflects the light beam from the light source toward the image display panel arranged opposite the light guide, and controls a part of the divergence angle of the light incident from the light source to the image display panel by the shape and surface roughness of the reflective surface. In addition, a λ / 4 plate is provided on the light exit surface of the liquid crystal panel to make the image light circularly polarized, so that the image can be viewed even when using polarized sunglasses. Furthermore, the dispersion characteristics of this λ / 4 plate are optimized to minimize coloring of the image, and since the image light is linearly polarized even when reflected on the exit surface of the λ / 4 plate, it can be absorbed by the polarizing plate on the incident side, so that deterioration of the reflected light can be reduced. Furthermore, the deterioration of image quality caused by reflected light can be reduced by providing an anti-reflection film on the reflecting surface.

[0214] As a result, a thin, high-brightness direct-view image display system (direct-view image display device) that outputs a specific polarized wave can be realized. An image display system is realized in which the image from the image display device 49 is reflected by the windshield 6, providing image information directly to the driver as a reflected image (virtual image). On the other hand, double images that occur due to the reduced reflectance of the windshield can also be reduced.

[0215] Although various embodiments have been described above in detail, the present invention is not limited to the above-described embodiments, and various modified examples are included. For example, the above-described embodiments are detailed descriptions of the entire system in order to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0216] The light source device described above is not limited to being applied to information display devices, but can also be applied to display devices such as HUDs, tablets, digital signage, and the like.

[0217] Furthermore, the technology according to the above-mentioned embodiment can display information necessary for driving, such as alert information when an oncoming vehicle or pedestrian is detected, in addition to navigation information such as destination and speed, in line with the actual scene through the windshield, and can prevent traffic accidents by providing an information display device (head-up display device) that reduces the driver's viewpoint movement and contributes to supporting safe driving. This contributes to the achievement of "Good health and well-being for all," one of the Sustainable Development Goals (SDGs) advocated by the United Nations. [Explanation of symbols]

[0218] 6...front glass, 6"...side glass, 11...image display panel, 15...LED collimator, 21...polarization conversion element, 43...steering wheel, 41...protective cover, 48, 13...light source device, 49, 49a, 49b...image display device, 7b, 51...transparent sheet, 54...light beam direction conversion means, 102...LED substrate, 12...circular polarization conversion element, 206...diffusion plate, 300...reflector, 213...λ / 2 plate, 308, 315...sub-reflector, 301...combiner, 200...LED element, 202...LED substrate, 203...light guide, 205...reflective sheet, 42...instrument panel.

Claims

1. A display device, comprising: A display panel that emits image light to a projection member; a light source device for supplying light to the display panel; a circular polarization conversion element on the image light exit surface side of the display panel, A display device in which image light from the display panel is reflected by the projection member, and the image generated by the display panel is viewed as a virtual image.

2. 2. The display device according to claim 1, The light source device is A point or surface light source; an optical member that reduces the divergence angle of light from the light source; a light guide having a reflective surface that reflects light from the light source and propagates the light to the display panel; a polarization conversion element between the light guide and the light source, a reflective surface of the light guide is disposed to reflect light from the light source and propagate the light to the display panel disposed opposite the light guide; a divergence angle of light incident on the display panel from the light source is adjusted in part or in whole by the shape and surface roughness of the reflecting surface of the light guide; The light source device supplies light of a specific linear polarization with a narrow divergence angle to the display panel.

3. 2. The display device according to claim 1, A display device in which, when the viewing angle at which the viewer views the image is constant, the position and / or angle of the display panel can be changed relative to the projection member, thereby changing the reflection position of the image light from the display panel on the projection member, thereby making it possible to change the display position of the image viewed by the viewer.

4. 2. The display device according to claim 1, The light source device is A point or surface light source; a reflector that reflects light from the light source; a light guide that guides the light from the reflector toward the display panel, A display device, wherein the reflecting surface of the reflector has an asymmetric shape with respect to the optical axis of the light emitted from the light source.

5. 2. The display device according to claim 1, The display device, wherein the circular polarization conversion element is a λ / 4 plate.

6. The display device according to claim 5 , The display device, wherein the λ / 4 plate has an inverse dispersion characteristic.

7. 5. The display device according to claim 4, The display device, wherein the light guide is a reflective light guide.

8. 5. The display device according to claim 4, A diffusion plate that diffuses light from the light guide; and side walls arranged to sandwich a space between the light guide and the diffusion plate. Display device.

9. 5. The display device according to claim 4, The reflector is made of a plastic material, a glass material, or a metal material. Display device.

10. 2. The display device according to claim 1, The light source device is A point or surface light source; a reflector that reflects light from the light source; a light guide that guides the light from the reflector toward the display panel, a reflecting surface provided on the light guide is disposed to reflect light from the light source and propagate the light to the display panel disposed opposite the light guide; a reflective polarizing plate is disposed between the reflective surface of the light guide and the display panel; the light reflected by the reflective polarizing plate is reflected by a reflector disposed in close proximity to and facing the surface of the light guide opposite the display panel side, the light passes twice through a retardation plate disposed between the light guide and the reflector, and the light is then polarized and converted; the light passes through the reflective polarizing plate and propagates to the display panel; A display device in which a divergence angle of light incident on the display panel from the light source is partially or entirely adjusted by changing the shape and surface roughness of a reflecting surface provided on the light guide.

11. The display device according to claim 10, A display device, wherein a divergence angle of light incident on the display panel is ±30 degrees or less.

12. The display device according to claim 10, A display device, wherein a divergence angle of light incident on the display panel is ±10 degrees or less.

13. The display device according to claim 10, A display device, wherein the horizontal diffusion angle and the vertical diffusion angle of light incident on the display panel are different from each other.

14. The display device according to claim 10, The display panel is a liquid crystal display element, and has a contrast performance obtained by multiplying the contrast obtained by the characteristics of the polarizing plates provided on the light entrance surface and light exit surface of the display panel by the inverse of the cross transmittance of the reflective polarizing plate.

15. 2. The display device according to claim 1, Equipped with a safe driving support system, The safe driving support system is a display device in which, when the viewpoint position when viewed from the front within the range of horizontal viewpoint movement of the observer is used as a reference axis, the position at which alert information is displayed for an event that occurs outside the view range of the observer moves in accordance with the vehicle's traveling speed.

16. 16. The display device according to claim 15, The safe driving support system is a display device that moves the display position of the alert information to be inside the viewer's horizontal visual range when the vehicle is traveling at high speeds compared to when the vehicle is traveling at low speeds, based on sensor information that detects the vehicle's traveling speed.

17. 16. The display device according to claim 15, The safe driving support system has an image correction function, A display device that changes the display position of the alert information to a pseudo-lower resolution of the displayed image when the vehicle is traveling at high speeds compared to when the vehicle is traveling at low speeds, based on sensor information that detects the vehicle's traveling speed.

Images