Information display device

Abstract

The present invention provides an information display device with high contrast and significantly improved light resistance to sunlight. To address the aforementioned issues, an information display device is provided that displays image information on a projection surface using a virtual image. The device comprises, within a housing having a partially opened portion, an image light generating unit that generates image light for displaying the image information; an image light processing unit that performs predetermined optical processing on the image light from the image light generating unit; and an image projection unit that projects the image light from the image light processing unit onto the projection surface through the opening in the housing, allowing an observer to perceive the image information as a virtual image in front of the projection surface. An optical element, obtained by attaching a reflective polarizer to a transmissive substrate, is provided in the optical path within the housing as a unit that selectively reflects the P-polarized component of light in the visible light band.

Description

Technical Field

[0001] The present invention relates to an information display device for projecting images onto a vehicle's windshield or combiner, and more particularly to an information display device realized by using a projection optical system that enables images to be observed as virtual images across the windshield. Background Art

[0002] Head-up displays (HUDs) are known. They project image light onto the windshield or a stacking mirror of vehicles such as automobiles, trains, and aircraft, creating a virtual image. These devices display traffic information such as route and congestion information, as well as vehicle information such as remaining fuel and cooling water temperature. While expanding the area visible to the driver is desirable, high resolution and visibility are also important performance factors for these displays.

[0003] A head-up display (HUD) uses an optical system including a concave reflector (functioning as a convex lens) to present the image displayed on the image display device to the driver as a magnified virtual image. The windshield or stacking mirror is essential as the final reflective surface. Liquid crystal display elements are often used as image display devices because they easily produce high-quality images and are inexpensive.

[0004] In this regard, the head-up display device disclosed in Patent Document 1 is configured to include a device for displaying an image and a projection optical system for projecting the image displayed on the display device. The projection optical system has a first reflector and a second reflector on the optical path from the display device to the observer, and the relationship between the incident angle of the image on the first reflector in the long axis direction and the incident angle of the image on the first reflector in the short axis direction, as well as the relationship between the interval between the image display surface of the display device and the first reflector and the horizontal width of the virtual image seen by the observer meet specified conditions.

[0005] In addition, the head-up display device disclosed in Patent Document 2 is configured such that, in order to reduce the risk of damage to the liquid crystal display panel caused by sunlight, a transmissive reflective component (heat reflector) is provided at a distance in front of the liquid crystal display panel, not parallel to the liquid crystal display panel, to allow display light from the liquid crystal display panel to pass through and to reflect infrared rays.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-194707

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-065011 Summary of the Invention

[0010] Technical problem to be solved by the invention

[0011] As described in Patent Document 1, the use of the front window glass as a reflective surface is expected to become mainstream in the future. However, this approach requires highly recognizable images during the day, especially on sunny days. Furthermore, sunlight passing through the front window glass and focused by the concave reflector under specified daytime conditions may cause so-called burns (carbonization). This means that the polarizer and the liquid crystal panel on the light-emitting side of the liquid crystal display device may deteriorate due to the heat and intensity of the focused sunlight, rendering them incapable of functioning properly. This means that, under the aforementioned high-contrast technology and specified daytime conditions, a new technical problem arises: sunlight passing through the front window glass and focused by the concave reflector may damage the liquid crystal panel and polarizer, significantly reducing performance.

[0012] Similarly, in a structure where the final reflecting surface is a stacked mirror, under specified daytime conditions, sunlight will pass through the front window glass and the stacked mirror and then be converged by the concave reflector, causing damage to the liquid crystal panel and polarizer, resulting in a significant reduction in performance.

[0013] Furthermore, in the example of the head-up display device disclosed in Patent Document 1, a device for displaying an image and a projection optical system for projecting the image displayed on the display device are provided. The projection optical system is constructed by providing a first reflector and a second reflector in the optical path from the display device to the viewer. No optical element is disposed between the concave reflector and the liquid crystal panel serving as the image display device. Therefore, in addition to the aforementioned problems, a new problem arises: light that passes through the windshield, is focused by the concave reflector, and then reflects off the surface of the optical element disposed between the liquid crystal panel and the concave reflector, returning to the driver's eyes and overlapping with the virtual image generated by the image display device, significantly degrading the quality of the image viewed by the driver, particularly contrast performance and visual resolution.

[0014] Furthermore, the solution proposed in Patent Document 2 is to place a transflective reflective component (heat reflector) in the optical path to selectively reflect infrared rays from sunlight in order to reduce the risk of sunlight damaging the liquid crystal display panel. However, the incoming sunlight contains not only infrared rays, but also light in the visible and ultraviolet regions. To mitigate sunlight damage to the liquid crystal display element and polarizer, simply reducing the infrared wavelength band is not enough. In addition, the adverse effects of the entry of external light, including visible light, also create a new problem: the quality of the image viewed by the driver, particularly the contrast performance and visual resolution, is significantly reduced.

[0015] As such, liquid crystal display elements are often used as image display devices in head-up displays. However, when used as an image source for heads-up displays that superimpose images on a landscape, these elements present two new problems: low contrast performance, and, under typical daytime conditions, sunlight passing through the windshield and focused by the concave reflector can damage the liquid crystal panel and polarizer, significantly degrading performance.

[0016] Furthermore, it was also clarified that, in order to miniaturize the head-up display device, an optical element is arranged between the concave reflector and the image display device. Surface reflection from this optical element causes a portion of sunlight to return to the driver's viewpoint (eyes), overlapping with the virtual image obtained by the image display device. This results in a significant reduction in the quality of the image observed by the driver, particularly the contrast performance and visual resolution.

[0017] The present invention relates to a technical means for solving two problems when using a liquid crystal display panel as the image source of the above-mentioned head-up display device, and has high contrast and can reduce damage caused by sunlight to the liquid crystal display element and polarizer, which can minimize the impact on the imaging performance of the optical system including the concave reflector.

[0018] The present invention is made in view of the above-mentioned problems of the prior art. More specifically, its main purpose is to provide an information display device that reduces the energy of light incident on the image display device by reflecting not only the infrared component of sunlight but also the P-polarized component of light in a wide range of wavelengths. As a result, the adverse effects on the liquid crystal display element and the polarizer can also be reduced.

[0019] In addition, the present invention also aims to provide an information display device that can block only specific polarized light to solve the following problem: during the day or at night, high-intensity external light at a specific incident angle is reflected on the surface of an optical element arranged between an image display device and a concave reflector forming the information display device and returns to the driver's eyes, overlapping with the virtual image obtained through the image display device, thereby causing the quality of the image observed by the driver, especially the contrast performance and visual resolution, to be greatly reduced.

[0020] Technical means to solve the problem

[0021] To achieve the above-mentioned objectives, the present invention provides, as one example, an information display device for displaying image information on a projection surface using a virtual image. The device is characterized in that the device comprises, within a housing having a partial opening, an image light generating unit for generating image light for displaying the image information; an image light processing unit for performing predetermined optical processing on the image light from the image light generating unit; and an image projection unit for projecting the image light from the image light processing unit onto the projection surface through the opening of the housing, such that an observer can perceive the image information as a virtual image in front of the projection surface. An optical element is provided in a portion of the optical path within the housing as a unit for selectively reflecting a P-polarized component of light in the visible light band, comprising a reflective polarizer attached to a transmissive substrate using an adhesive or a pressure-sensitive adhesive, wherein a moisture-proof film is provided on the surface of the reflective polarizer.

[0022] Effects of the Invention

[0023] The present invention can achieve device miniaturization while correcting distortion and aberration of the virtual image observed by the driver caused by external light, including sunlight. It also mitigates the phenomenon in which external light, including sunlight (mostly consisting of P-polarized light), incident through the windshield is concentrated by the concave reflector in the virtual image optical system, potentially damaging the liquid crystal panel and polarizing plate of the image display device, leading to performance degradation. In other words, it is possible to provide an information display device for forming virtual images that mitigates the adverse effects of broad wavelengths of light contained in external light, including sunlight, while also improving contrast performance and resistance to ambient air. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the peripheral equipment structure including the information display device.

[0025] Figure 2 This is a top view of a passenger car equipped with an information display device.

[0026] Figure 3 It is a diagram explaining the difference in the curvature radius on the windshield glass.

[0027] Figure 4 3 is a diagram showing the relationship between the information display device and the driver's viewpoint position.

[0028] Figure 5 This diagram shows the relationship between sunlight, windshield glass, and the driver's viewpoint.

[0029] Figure 6 This is a diagram illustrating the reflectivity of glass for S-polarized light and P-polarized light.

[0030] Figure 7 It is a diagram showing a specific example of lens data of an optical system.

[0031] Figure 8 This is a graph showing the free surface coefficients of the reflective mirror surface.

[0032] Figure 9 This is a diagram schematically showing the overall structure of the optical system.

[0033] Figure 10 This is a schematic diagram showing an enlarged portion of the optical system.

[0034] Figure 11 This is a diagram showing the amount of distortion in an optical system.

[0035] Figure 12 It is a diagram showing the imaging performance (spot image) of the optical system.

[0036] Figure 13 It is an enlarged view showing the overall structure of the information display device.

[0037] Figure 14 It is a diagram schematically showing the structure of an optical element including a reflective polarizing plate.

[0038] Figure 15 This is a cross-sectional view illustrating the function of a reflective polarizing plate.

[0039] Figure 16 It is a cross-sectional view showing the specific structure of a reflective polarizing plate.

[0040] Figure 17 This is a diagram showing the effect of the moisture-proof film.

[0041] Figure 18 It is a characteristic diagram showing the spectral irradiance of sunlight.

[0042] Figure 19 This is a structural diagram showing the arrangement of an image display device and a light source device.

[0043] Figure 20 This is a schematic structural diagram showing the structure of a light source device.

[0044] Figure 21 It is a cross-sectional view showing the propagation of light in the light source device.

[0045] Figure 22 It is a schematic structural diagram showing the shape of a polarization conversion element.

[0046] Figure 23 This is a schematic diagram showing the structure of a synthetic diffusion block.

[0047] Figure 24 It is a diagram showing the detailed structure of the light guide.

[0048] Figure 25 This is an enlarged view of the light reflecting portion (surface) of the light guide.

[0049] Figure 26 This is an enlarged view of the light reflecting portion (surface) of the light guide.

[0050] Figure 27 This is a diagram showing the structure of a light guide using a polarization conversion element.

[0051] Figure 28 This diagram shows a structure for preventing sunlight from reaching the image display device.

[0052] Figure 29 This is a diagram explaining the principle of obtaining a virtual image using a concave reflecting mirror. DETAILED DESCRIPTION

[0053] The following describes embodiments of the present invention in detail using the accompanying drawings. The present invention is not limited to the following description, and those skilled in the art can implement various modifications and corrections within the scope of the technical concept disclosed in this specification. In all figures used to illustrate the present invention, parts with the same function are marked with the same reference numerals, and repeated descriptions may be omitted.

[0054] <Overview of Information Display Device>

[0055] Figure 1 1 is a schematic diagram showing the peripheral configuration of an information display device according to an embodiment of the present invention. Here, as an example, an information display device 100 for projecting images on the front window glass (also called windshield) of an automobile is described.

[0056] like Figure 1 As shown, the information display device 100 is a device that displays various information reflected from a projection element 6 (in this embodiment, the inner surface of the windshield) as a virtual image VI in front of the vehicle, so as to form a virtual image VI in front of the vehicle from the driver's (observer's) eyepoint 8. This device is a so-called head-up display. The projection element 6 can be any component onto which information can be projected, and it can be anything other than the windshield as described above, or even a combiner (not shown). Specifically, the information display device 100 can be any device that can form a virtual image in front of the vehicle at the driver's eyepoint 8 for the driver to observe. Information that can be displayed as a virtual image naturally includes, for example, vehicle information and foreground information captured by a surveillance camera or panoramic camera (not shown).

[0057] The information display device 100 is provided with a light source device 10, an image display device 4, a concave (free-form surface) reflector 1, a correction lens element 2 and an optical element (not shown) between the correction lens element 2 and the image display device 4 to prevent sunlight from being converged by the concave reflector 1 and returning to the image display device 4, wherein the image display device 4 projects image light for displaying information, the concave (free-form surface) reflector 1 reflects the image displayed on the image display device 4 toward the projected component 6, and the lens element 2 is used to correct the distortion and aberration generated when a virtual image is formed using the concave reflector 1.

[0058] The information display device 100 includes a control device 40 for controlling the image display device 4 and driving the light source device 10 (backlight). The optical components, including the image display device 4 and the light source device 10, constitute the virtual image optical system described later, and include a concave reflector 1 for reflecting light. Light reflected from these optical components is reflected by the projection unit 6 and then travels to the driver's viewpoint 8. The image display device 4 may include a liquid crystal display (LCD) with a backlight or a self-luminous fluorescent display (VFD).

[0059] Instead of the image display device 4, an image may be displayed on a screen by a projection device, and the image is formed into a virtual image by the concave reflector 1 and reflected on the projection member 6, i.e., the windshield or a stacking mirror, and then directed to the driver's viewpoint 8. Such a screen may be constructed, for example, using a microlens array in which microlenses are arranged two-dimensionally.

[0060] Here, in order to reduce the distortion of the virtual image, the concave reflecting mirror 1 may be in such a shape that Figure 1 The upper portion (the region where light is reflected below the portion of the windshield 6 that is relatively close to the driver's viewpoint 8) shown has a relatively small radius of curvature to increase the magnification. On the other hand, the lower portion (the region where light is reflected below the portion of the windshield 6 that is relatively close to the driver's viewpoint 8) has a relatively large radius of curvature to reduce the magnification. Furthermore, by tilting the image display device 4 relative to the optical axis of the concave reflector 1, the distortion caused by correcting the aforementioned difference in virtual image magnification is reduced, thereby enabling better correction.

[0061] On the other hand, the front window glass 6 of the passenger car is as shown in FIG. Figure 2 、 Figure 3As shown, the curvature radius Rv in the vertical direction of the vehicle body is different from the curvature radius Rh in the horizontal direction, and generally has the relationship of Rh>Rv. Therefore, if the front window glass 6 is used as the reflecting surface, it constitutes a toroidal surface of the concave reflector 1. Therefore, in the information display device 100 of this embodiment, the shape of the concave reflector 1 adopts different average curvature radii in the horizontal direction and the vertical direction to correct the virtual image magnification affected by the shape of the front window glass 6, that is, to correct the difference in the curvature radius of the front window glass 6 in the vertical direction and the horizontal direction. At this time, if the shape of the concave reflector 1 is a spherical or aspherical shape symmetrical about the optical axis (expressed by the following formula 2), it is a function of the distance r from the optical axis, and the horizontal and vertical cross-sectional shapes of farther parts cannot be individually controlled. Therefore, it is preferable to adopt the free-form surface shape shown in the following formula 1 and perform correction as a function of the surface coordinates (x, y) from the optical axis of the reflector surface.

[0062]

[0063]

[0064] Back to Figure 1 A lens element 2 is further provided as a transmissive optical component between the image display device 4 and the concave reflector 1 to control the direction of light emitted toward the concave reflector 1. This corrects distortion aberrations according to the shape of the concave reflector 1, and simultaneously corrects aberrations of the virtual image, including astigmatism caused by the difference between the horizontal and vertical curvature radii of the front window glass 6.

[0065] In addition, in order to further improve the aberration correction capability, the lens element 2 can be replaced with a multi-lens lens. Alternatively, a curved (free-form surface) reflector can be configured in place of the lens element 2 to control the incident position of the light on the concave reflector 1 while folding the light path, thereby also reducing the distortion aberration. Furthermore, an optical element optimized for improving the aberration correction capability can be provided between the concave reflector 1 and the image display device 4. In addition, by changing the thickness of the lens element 2 in the optical axis direction to change the optical distance between the concave reflector 1 and the image display device 4, in addition to the original aberration correction, the display position of the virtual image can be continuously changed from far to near.

[0066] Alternatively, the image display device 4 may be arranged to be tilted relative to the normal to the optical axis of the concave reflector 1 to correct for vertical magnification differences in the virtual image. Furthermore, an optical element (not shown here) may be provided between the concave reflector 1 and the image display device 4 to reflect or absorb P-polarized light in the visible wavelength range, as well as light in the ultraviolet and infrared wavelength ranges, from the sunlight that has passed through the windshield 6 and is concentrated by the concave reflector 1, thereby reducing the amount of light returning to the image display device 4.

[0067] On the other hand, it is known that a factor that degrades the image quality of the information display device 100 is that the image light emitted from the image display device 4 toward the concave reflector 1 is reflected by the surface of the lens element 2 disposed along the way and returns to the image display device 4. There, it is reflected again and superimposed with the original image light, resulting in degraded image quality. Therefore, in this embodiment, an anti-reflection film is formed on the surface of the lens element 2 to suppress reflection. Furthermore, the lens surface shape of one or both of the image light incident surface and the image light exit surface of the lens element 2 is restricted so that the reflected light is not focused on a portion of the image display device 4 (for example, a shape in which the concave surface faces the image display device 4).

[0068] Furthermore, the inventors of the present application studied the properties of the antireflection film provided on the surface of the lens element 2. As a result, they experimentally confirmed that by suppressing the reflectivity in the green wavelength band (where visual sensitivity is highest) to 0.2% or less, the reflectivity in the red wavelength band to 0.6% or less, and the reflectivity in the blue wavelength band to 1.0% or less, even if sunlight is reflected on the surface of the optical element, it will not affect the quality of the virtual image.

[0069] Furthermore, in the image display device 4, in addition to the first polarizer positioned close to the liquid crystal panel to absorb reflected light from the lens element 2, a second polarizer is also positioned separately from the liquid crystal panel. By using the light source device of this embodiment, which generates polarized light in a specific direction (described later), the polarization degree can be increased by approximately 10 times compared to the two polarizers typically included with a liquid crystal image display element, significantly improving contrast performance. Furthermore, when sunlight passing through the front window 6 is focused by the concave reflector 1 and incident on the liquid crystal panel, the amount of light is reduced by absorption or reflection by the first and second polarizers, thereby improving the reliability of the liquid crystal panel.

[0070] On the other hand, Figure 4 As shown, an optical element 3 (also referred to as an optical unit) having the function of reflecting the P-polarized component is disposed between the lens element 2 and the concave reflector 1. The optical element 3 is disposed so as to be inclined relative to the optical axis formed by the concave reflector 1 and the image display device 4. This allows the P-polarized component of sunlight incident from the windshield 6 to be reflected and focused at a position offset from the concave reflector 1. This prevents the reflected light from returning to the driver's viewpoint 8, thereby preventing it from hindering the driver's driving.

[0071] Image display device 4 uses a liquid crystal display element to modulate the brightness of light from a light source that only produces light of a specific polarization, in accordance with the image signal. The resulting image light is S-polarized light. Since optical element 3 (reflective polarizer) also transmits S-polarized image light, thereby increasing its polarization, it also has the advantage of improving the contrast of the image viewed by the driver. Furthermore, the light in the image light that is totally reflected on the surface of lens element 2 is converted from S-polarized light to P-polarized light, and therefore reflects off optical element 3 without adversely affecting the image viewed by the driver.

[0072] Next, as an image display device 4, if a second polaroid is configured separately from the liquid crystal panel in addition to the first polaroid configured close to the liquid crystal panel to absorb the reflected light from the lens element 2, the degradation of image quality can be alleviated. In addition, for the backlight of the liquid crystal panel, the incident direction of the light incident on the liquid crystal panel is controlled in a manner that allows the image light to efficiently enter the entrance pupil of the concave reflector 1. At this time, by reducing the divergence angle of the light beam incident on the liquid crystal panel, not only can the image light efficiently reach the driver's viewpoint, but also a high-contrast, highly recognizable image can be obtained. The contrast performance of the image corresponding to the divergence angle is more significant in the horizontal direction, and excellent characteristics can be obtained within ±20 degrees. To further improve the contrast performance, a light beam within ±10 degrees can be used.

[0073] On the other hand, a solid-state light source with a long product life is preferably used as the light source device 10. In particular, it is preferable to use a light emitting diode (LED) whose light output changes less with ambient temperature fluctuations and a polarizing beam splitter (PBS) equipped with an optical unit to reduce the divergence angle of light for polarization conversion.

[0074] Polarizers (not shown) are placed on the backlight side (light incident surface) and the lens element 2 side (light exit surface) of the liquid crystal panel to improve the contrast of the image light. Using an iodine-based polarizer with a high degree of polarization as the polarizer on the backlight side (light incident surface) can achieve high contrast. On the other hand, using a dye-based polarizer on the lens element 2 side (light exit surface) can achieve higher reliability even in the presence of external light and at high ambient temperatures.

[0075] When a liquid crystal panel is used as the image display device 4, especially when the driver is wearing polarized sunglasses, a problem may occur in which specific polarized light is blocked, preventing the image from being visible. To prevent this problem, it is preferable to place a λ / 4 wave plate on the optical element side of the polarizer disposed on the lens element 2 side of the liquid crystal panel. This converts the image light uniformly polarized in a specific direction into circularly polarized light, or to make the polarization axis different from the polarization direction of the polarized sunglasses.

[0076] Back to Figure 1 The control device 40 obtains various information from the navigation system 61, such as the speed limit and number of lanes on the road corresponding to the current position of the vehicle, the planned movement path of the vehicle set in the navigation system 61, and uses this information as foreground information (i.e., information displayed in front of the vehicle using the virtual image described above).

[0077] The driving assistance ECU (Electronic Control Unit) 62 is a device for driving assistance control that controls the drive system and control system based on obstacles detected by the surrounding monitoring device 63. Driving assistance control includes well-known technologies such as cruise control, adaptive cruise control, collision avoidance, and lane keeping assist.

[0078] The surrounding monitoring device 63 is a device that monitors the situation around the vehicle. For example, it includes a camera that detects objects around the vehicle based on images taken around the vehicle, or a detection device that detects objects around the vehicle based on the results of transmitting and receiving detection waves.

[0079] The control device 40 obtains information from such a driving assistance ECU 62 (such as the distance to the vehicle in front and the direction of the vehicle in front, the location of obstacles and signs, etc.) as foreground information. Furthermore, the ignition (IG) signal and the vehicle status information are input to the control device 40. The control device 40 starts when the ignition signal is input. The vehicle status information is vehicle information obtained by various sensors, such as warning information indicating that the remaining amount of fuel in the internal combustion engine and the temperature of the cooling water have reached a predetermined abnormal state. In addition, it also includes the operation results of the turn signal and the driving speed of the vehicle, and further includes gear information, etc. The above is the structure of the entire system including the information display device 100 of this embodiment.

[0080] <Sunlight Entry and Suppression Principles in the Device>

[0081] Next, the entry of sunlight into the information display device from the driver's seat of the vehicle will be described.

[0082] Figure 4Indicates the state of the vehicle near the driver's seat. The information display device 100 is arranged below the windshield 6, for example, on the back side (the rear engine cover side) of the instrument panel 42 including the speedometer and other measuring instruments, wherein the windshield 6 is installed between the engine cover 44 and the ceiling panel 45 constituting the vehicle body. In addition, the figure shows the steering wheel 43 of the vehicle, the driver's viewpoint 8, and the daytime sun 50 above the vehicle. In addition, Figure 5 express Figure 4 In particular, the relationship between the sun 50, the windshield 6 and the driver's viewpoint 8 in the state.

[0083] Figure 4 and Figure 5 In FIG. 1 , the image light emitted from the information display device 100 is reflected by the windshield 6 or the stacking mirror (not shown) as indicated by the solid arrow, and enters the viewpoint 8 of the observer.

[0084] On the other hand, as indicated by the hollow arrow, strong light from the sun 50 is incident at an incident angle θ relative to the front windshield 6 of the vehicle, and after a portion of it is reflected by the front windshield 6, the remaining light enters the interior of the device through the opening portion 41 provided at the upper portion of the information display device 100. Here, natural light such as sunlight exists in a state of a mixture of P-polarized light and S-polarized light. At this time, especially when the incident angle θ is above 50 degrees, most of the S-polarized component (S light) of the sunlight is reflected on the front windshield 6. As a result, most of the sunlight entering the information display device 100 is P-polarized component (P light). The reason for this is that the reflectivity of the glass exhibits the following characteristics: Figure 6 That is, in a region where the incident angle θ on the windshield 6 exceeds 50 degrees, the reflectivity on the glass surface differs between S-polarized light and P-polarized light, and the refractive index of S-polarized light is greater than that of P-polarized light.

[0085] In this embodiment, based on the aforementioned findings of the present inventors, it is considered that most of the sunlight entering through the windshield 6 is a P-polarized component. Specifically, the invention is based on the fact that, in order to suppress external light, including sunlight, from entering the information display device 100, it is particularly effective to reduce the P-light component, and further, it is effective to use the S-light component as the image light projected from the image display device 100.

[0086] <Specific Example of Optical System of Information Display Device>

[0087] Figure 7This figure shows a specific example of lens data for the optical system that constitutes information display device 100. In the lens data, a positive sign for the radius of curvature indicates that the center of the radius of curvature is located in the direction of travel, and the inter-surface distance indicates the distance on the optical axis from the vertex of each surface to the vertex of the next surface. In a reflective optical system, the sign of the radius of curvature is reversed at locations where the inter-surface distance is a negative value.

[0088] "Eccentricity" refers to the values in the X-axis, Y-axis, and Z-axis directions, and "Tilt" refers to the rotation around the X-axis, the Y-axis, and the Z-axis. "Eccentricity and Tilt" apply to the surface in the order of eccentricity first and then tilt. "Basic eccentricity" means that the next surface is positioned at the distance between the surfaces in the new coordinate system after the "Eccentricity and Tilt" are applied. The eccentricity and tilt of "Eccentricity and Regression" only apply to this surface and do not affect the next surface. In addition, rotation around the X-axis is positive when viewed clockwise from the positive X-axis direction, rotation around the Y-axis is positive when viewed clockwise from the positive Y-axis direction, and rotation around the Z-axis is positive when viewed counterclockwise from the positive Z-axis direction.

[0089] The glass material name "50.30" indicates a material with a refractive index of 1.50 and an Abbe number of 30, and the glass material name "52.649" indicates a material with a refractive index of 1.52 and an Abbe number of 60. In this embodiment, by forming the concave reflecting mirror and the returning mirror into free-form surfaces, excellent distortion performance and spot pattern are achieved while ensuring telecentricity, as described later.

[0090] Figure 8 express Figure 7 The free surface coefficient of the reflective mirror surface in the lens data is obtained using Equation 1.

[0091]

[0092] The free-form surface coefficient Cj is a shape that is not rotationally symmetric about each optical axis (Z axis), and is defined by the components of the conic terms and the components of the X and Y polynomial terms. For example, when X is quadratic (m = 2) and Y is cubic (n = 3), the coefficient Cj corresponds to j = {(2 + 3)2 + 2 + 3 × 3} / 2 + 1 = 19, which is C19. In addition, the position of each optical axis of the free-form surface is given by Figure 7 The lens data is determined by the amount of decentering and tilt.

[0093] Figure 9 : is a diagram showing the configuration of the entire optical system, (a) is a diagram observed from the horizontal direction (X-axis direction), and (b) is a diagram observed from the vertical direction (Y-axis direction). Figure 10 This is an enlarged view of its main parts. Figure 10As shown, the visual optical system 5 is composed of a polarizing unit 51, a concave lens 52, a folding mirror 53, a concave reflector 54 with positive optical power, and a front window glass 6 arranged from the side of the liquid crystal display panel 4. For the polarizing unit 51, a polarizing plate is selected to suppress the P light component of sunlight entering the device under specific conditions (incident angle) to protect the liquid crystal display panel 4. In particular, in order to reduce the damage to the polarizing plate caused by sunlight, it is better to select a reflective polarizing plate. In this embodiment, by making the concave reflector 54 and the folding mirror 53 into a free-form surface shape, good distortion performance and imaging performance (spot image) are achieved while ensuring telecentricity.

[0094] As various parameters of the visual optical system of this embodiment, values such as the eyebox size and the viewing angle are shown below in the order of the horizontal direction and the vertical direction.

[0095] Eyebox size: 130×40mm

[0096] The effective size of the image light on the LCD panel is 68.0×25.2mm

[0097] Virtual image size 3500×943mm

[0098] Field of view (full viewing angle) 10.0×2.7 degrees

[0099] Depression angle 2.376 degrees

[0100] Virtual image distance 20.0m

[0101] Furthermore, the optical performance of the information display device 100 of this embodiment will be described. Figure 11 This graph shows the distortion performance of an information display device. It shows the amount of distortion at each position within the eyebox. Figure 12 The imaging performance of the information display device is shown using spot images. Spot images of various colors are shown at various positions within the field of view. As these results demonstrate, good distortion performance and imaging performance (spot images) can be achieved. Furthermore, in this embodiment, the illumination optical system is configured to be tilted 14 degrees relative to the liquid crystal display panel 4. Thus, according to this embodiment, the projection optical system using the concave lens 52 and the concave reflector 54 can provide an information display device 100 with a large virtual image distance.

[0102] <Specific Example of Information Display Device>

[0103] Next, a more specific configuration of the optical system of the information display device 100 constructed based on the above-described findings will be described.

[0104] Figure 13The overall structure of the information display device 100 is shown in an enlarged manner. As described above, the concave reflector 1 for projecting image light to form a virtual image through the front window glass 6, the lens element (lens group) 2 for correcting the distortion and aberration generated at this time, the optical element 3 for suppressing (reflecting) the P light component, the image display device 4, and the light source device 10 constituting the backlight are provided in order from the downstream side. In addition, this structure shows that the return mirror 53 (see Figure 10 ) is an example of an optical system with a short optical path. Here, optical element 3 is used to suppress the P-light component of sunlight entering the information display device 100. A reflective polarizer is provided between lens element 2 and image display device 4. This adds the polarization intensity of the reflective polarizer to the polarizers on both sides of the liquid crystal panel of image display device 4 on which light enters and exits, thereby producing a high-contrast image. Furthermore, optical element 3 (reflective polarizer) is arranged to be tilted relative to the optical axis of the virtual image optical system, preventing reflected light from entering the driver's eyes through windshield 6 and obstructing driving.

[0105] First, the concave reflector 1, which projects image light, has the function of reflecting visible light (wavelength: approximately 400-700 nm) while removing light components that are unnecessary for the information display device and could damage it. For example, it can remove infrared (IR) and ultraviolet (UV) rays from sunlight, which encompasses a wide spectrum of wavelengths. By achieving a visible light reflectivity of 95% or higher, a virtual image optical system with high light utilization efficiency can be achieved.

[0106] then, Figure 14 This is a longitudinal cross-sectional view schematically illustrating the structure of a reflective polarizer serving as optical element 3. Substrate 3a of optical element 3 is made of a highly transparent material to prevent absorption of wavelengths in the visible region of sunlight. A reflective polarizer 3b is then formed on the surface of substrate 3a.

[0107] As a method for obtaining the reflective polarizer 3b, there is a conventional method (1) of forming an aluminum pattern on a glass substrate using a photolithography film forming process. In addition, in recent years, a method (2) has become known in which an aluminum pattern is formed by nanoimprinting, thereby obtaining a reflective polarizer at a lower cost than (1). A representative example of (2) is the reflective polarizer film WGF (registered trademark) produced by Asahi Kasei E-Materials.

[0108] Asahi Kasei E-Materials' method for manufacturing a reflective polarizer, according to the company's technical documentation, involves printing a UV-curable resin on the surface of a TAC film using a roll-to-roll process using nanoimprinting, and then forming an aluminum film on the surface (including the sides) to produce a reflective polarizer. The polarization characteristics (parallel light transmittance and orthogonal transmittance) obtained in this manner are uniquely determined by the height and spacing of the formed protrusions, similar to the reflective polarizer described in (1). The following illustrates, using the accompanying drawings, the problems and solutions encountered when applying the method (2), which achieves a low price and a significant price advantage, such as the reflective polarizer WGF (registered trademark) described above.

[0109] Figure 14 、 Figure 15 、 Figure 16 3a and 3b are cross-sectional views showing the structure of a reflective polarizer. As shown in these figures, in this embodiment, a reflective polarizer 3b is provided on the side where sunlight is incident. More specifically, the reflective polarizer 3b is adhered to the substrate 3a with an adhesive or a glue 3h (see Figure 15 ). Then, in order to improve the light transmittance of the reflective polarizer 3b including the substrate 3a, a SiO (silicon oxide) film can be formed as a moisture-proof film 3d having an anti-reflection effect on the surface of the reflective polarizer 3b and the opposite side of the adhesive surface. However, when the substrate 3a is a glass base material, a general anti-reflection film can be provided.

[0110] More preferably, the moisture-proof film 3d has an anti-reflection property by setting its thickness to one-quarter of the wavelength. Since the majority of light emitted from the LED used as the light source for the information display device 100 falls within the wavelength range of 450nm to 650nm, the thickness of the moisture-proof film 3d, which also provides an anti-reflection effect with a center wavelength of 550nm, can be set to between 130nm and 145nm. Furthermore, an anti-reflection film 3c can be formed on the surface of the substrate 3a opposite the surface where the reflective polarizer 3b is provided, thereby reducing the generation of unwanted light.

[0111] like Figure 15As shown, the image light can be arranged in the optical path in such a way that it is incident from the opposite side of the adhesive surface of the reflective polarizer 3b. The reason for this is that, as mentioned above, most of the sunlight incident into the car is P-polarized light, so the optical path of the reflected light reflected on the reflective polarizer 3b is as follows. (1) It returns normally on the optical path and is reflected on the front window glass 6 to become regular reflected light returning to the driver's side. (2) In addition, sunlight incident from a more oblique direction is reflected on the side of the reflective polarizer 3b and becomes stray light. In order to reduce this light, an anti-reflection film 3c is provided on the sunlight incident surface of the substrate 3a, thereby reducing the reflected light generated on the incident and outgoing surfaces of the reflective polarizer 3b, suppressing the generation of glare, and thus reducing the degradation of image quality. In addition, because the reflective polarizer 3b has the structure described below, it is best to be provided on the sunlight incident side relative to the substrate 3a.

[0112] Figure 16 This is a cross-sectional view showing the specific structure of the reflective polarizer 3 of this embodiment. A reflective polarizer 3b is adhered and fixed to one surface of a glass substrate 3a using an adhesive or pressure-sensitive adhesive 3h. For example, the reflective polarizer 3b is WGF (registered trademark) sold by Asahi Kasei E-Materials. Regarding the manufacturing method of WGF (registered trademark), the technical documentation states that the reflective polarizer 3b is obtained by printing a roll-to-roll ultraviolet-curable resin 3j onto the surface of a TAC (triacetylcellulose) film 3f, which serves as a substrate, using nanoimprinting. An aluminum film 3k is then formed on the surface (including the sides) of the film to form the reflective polarizer 3b.

[0113] Generally speaking, the TAC film has reliability problems such as yellowing due to ultraviolet rays contained in sunlight and a significant decrease in transmittance. Therefore, the inventors of the present application have made the following changes in the structure of the reflective polarizer 3b: Figure 16 As shown, the entire surface of the reflective polarizer 3b is covered with an acrylic ultraviolet-curable resin 3j, and the surface to which the reflective polarizer 3b is attached faces the sunlight incident side. Specifically, since the acrylic ultraviolet-curable resin 3j is arranged so as to cover the TAC film 3f, it absorbs the ultraviolet component of sunlight, thereby preventing degradation of the TAC film 3f due to the ultraviolet component.

[0114] In addition, as the formation Figure 16The conditions for the moisture-proof film 3d in the film, the inventors of the present application considered the stability after film formation, focused on the temperature in the furnace during film formation, and found the optimal conditions. During the film-forming process of the moisture-proof film 3d, stress may be generated due to the difference in linear expansion coefficient between the TAC (triacetyl cellulose) film 3f, the substrate of the reflective polarizer 3b, and the acrylic ultraviolet curing resin 3j, causing the acrylic ultraviolet curing resin 3j to peel off from the TAC film 3f. In order to prevent this, a SiO (silicon oxide) film is formed on the surface as the moisture-proof film 3d by evaporation or sputtering at a low temperature. At this time, the temperature in the furnace of the evaporation device or sputtering device is preferably below 70°C near the substrate, and if evaporation or sputtering is performed below 50°C, the performance can be maintained more stably without changing the structure of the reflective polarizer 3b.

[0115] More preferably, the thickness of the moisture-proof film 3d formed at this time is set to a thickness equivalent to 1 / 4 of the wavelength contained in the transmitted light, as described above, to provide anti-reflection properties. Similarly, by forming an anti-reflection film 3c on the opposite side of the substrate 3a to which the reflective polarizer 3b is attached, the generation of unwanted light can be reduced. Furthermore, as described above, by providing a multilayer anti-reflection film 3c on the surface opposite to the surface on which the reflective polarizer 3b is attached to achieve an anti-reflection effect, interfacial reflection can be reduced without compromising the quality of the displayed image.

[0116] Figure 17 This is a diagram showing the effect of the moisture-proof film 3d. The sample for evaluating the moisture barrier properties of the moisture-proof film 3d was placed in a high temperature / high humidity environment of 85°C and 85% RH, and the change in transmittance relative to the initial value was evaluated as a relative value. At this time, the film thickness of the moisture-proof film 3d was used as a parameter for evaluation. The result was that, compared with the sample without a protective film, the greater the thickness of the moisture-proof film 3d, the less the transmittance decreased (deteriorated). Compared with the sample without a protective film (only a reflective polarizer), the transmittance degradation at the time point of 1500 hours was reduced by about 6% when the film thickness was 20nm. Furthermore, at a film thickness of around 140nm, which can achieve an anti-reflection effect, the initial transmittance can be improved by about 1.5%, and the relative value degradation after 1500 hours is reduced to 4% (not shown). On the other hand, when the thickness of the moisture-proof film 3d exceeds 500nm and is placed in an atmosphere with a high temperature exceeding 90°C for a long time, the stress generated between the three components increases due to the difference in linear expansion coefficients between the moisture-proof film 3d, the TAC film 3f, and the ultraviolet curing resin 3j, resulting in the inability to maintain the shape.

[0117] In addition, as the substrate 3a of the above-mentioned reflective polarizer 3b, a substrate with high transparency can be selected in addition to a glass substrate. In addition, the above-mentioned reflective polarizer 3b can also be set on an aspheric lens or a free-form lens made of plastic. In this case, the materials with high transparency include (1) ZEONEX (registered trademark) of Japan Zeon Co., Ltd., (2) polycarbonate, and (3) acrylic resin. ZEONEX (registered trademark) of (1) has a water absorption rate of approximately 0% and a high heat deformation temperature, which is the best, but the price is high. Acrylic resin of (3) has the best formability and is low in price, but it needs to be provided with a moisture-proof film to suppress moisture absorption during use.

[0118] Furthermore, in the opening 41 (see Figure 13 ), a light-transmitting plate (not shown) having the function of suppressing / removing at least one of the above-mentioned infrared rays and ultraviolet rays may also be provided. In addition to suppressing infrared rays and ultraviolet rays, the light-transmitting plate may also have the function of preventing external dust from entering the interior of the information display device 100.

[0119] In this way, it is possible to remove the components that are not necessary for the information display device 100 from the sunlight containing a large number of spectral components that enters the information display device 100 through the opening 41, and selectively extract mainly the visible light component. Figure 18 The spectral radiance characteristics of sunlight are shown in Figure 2.

[0120] then, Figure 29 This diagram illustrates the principle of producing a virtual image using a concave reflector in an information display device. By positioning object point AB inward of focal point F (focal length f) relative to point O on the optical axis of concave reflector 1′, a virtual image can be produced by concave reflector 1′. For ease of explanation, concave reflector 1′ is treated as a convex lens with uniform positive refractive power. The diagram shows the relationship between the object point, the convex lens (herein, referred to as a concave reflector for ease of explanation), and the resulting virtual image.

[0121] When the driver observes the virtual image generated by the information display device, it is desirable to ensure the focusing performance of both the virtual image (to be superimposed on the distant scenery) reflected from the upper portion of the windshield 6 and seen by the driver and the virtual image (to be superimposed on the nearby scenery) reflected from the lower portion of the windshield 6 and seen by the driver. Figure 29 The optical axis LL′ of the concave (free-form surface) reflector 1′ (corresponding to AB in the figure, in this embodiment, the liquid crystal panel) and the image display device (AB) can be tilted. This is also to simultaneously satisfy the magnification M = b / a of the virtual image produced by the liquid crystal panel and the concave (free-form surface) reflector 1′.

[0122] According to the optical structure of the information display device 100 described above, the optical element 3 can effectively reduce the P-light component (p-polarized light) in sunlight entering the device through the front window glass 6. Specifically, the optical element 3 prevents sunlight entering the information display device 100 through the upper opening 41 from causing adverse effects such as carbonization on the image display device 4 and surrounding polarizers disposed therein. This reduces damage to the liquid crystal display element and polarizers, suppressing degradation of the information display device 100's performance caused by sunlight. Furthermore, by providing a moisture-proof film on the optical element 3, it is possible to reduce the adverse effects of moisture, sulfides contained in exhaust gas, and the like on the image display device 4 and surrounding polarizers.

[0123] <Light source device for image display device>

[0124] As described above, in the optical system of the information display device 100, sunlight incident from the outside into the device via the windshield 6 is attenuated by the optical element 3. At the same time, the image light used to generate the virtual image of various image information displayed in front of the vehicle is as described above. Figure 4 and Figure 5 As shown by the solid arrow, the image light is emitted from the image display device 4 and reaches the front window glass 6 via the lens element 2 and the concave reflector 1. At this time, the image light also passes through the optical element 3, but as mentioned above, the image light uses the S light component (s-polarized light).

[0125] Therefore, the image display device 4 and the light source device 10 thereof for generating image light of the S light component will be described in detail below.

[0126] Figure 19 1 is a block diagram showing the arrangement of the image display device 4 and the light source device 10. Here, the image display device 4 is shown with a liquid crystal display element and the light source device 10 constituting its light source in a developed perspective view below.

[0127] The light source device 10 includes a light source device housing 101, which is formed of, for example, plastic and houses the LEDs, collimator, composite diffuser, light guide, and other components described below. A liquid crystal display element, serving as the image display device 4, is mounted on its top surface. Furthermore, an LED circuit board 102, which houses the LED elements serving as semiconductor light sources and their control circuitry, is mounted on one side of the light source device housing 101. A heat sink 103 is mounted on the outer side of the LED circuit board 102 to cool the heat generated by the LED elements and control circuitry.

[0128] Meanwhile, the liquid crystal display element, serving as image display device 4, mounted on the upper surface of light source device housing 101, comprises a liquid crystal display panel frame 401, a liquid crystal display panel 402 mounted on the frame, and a flexible printed circuit (FPC) 403 electrically connected to the panel. Specifically, as will be described later, liquid crystal display panel 402, along with LED elements serving as solid-state light sources, generates and controls the image to be displayed in accordance with control signals from a control circuit (not shown) constituting the electronic device.

[0129] Next, the internal structure of the light source device 10 , that is, the optical system housed in the light source device housing 101 , will be described in detail with reference to the accompanying drawings.

[0130] Figure 20 1 is a schematic structural diagram showing the structure of the light source device 10. Figure 21 It is a cross-sectional view showing the propagation of light in the light source device 10 . Figure 22 This is a schematic diagram showing the structure of the polarization conversion element in the light source device 10. In this example, a plurality of (two in this example) LEDs 14a and 14b constituting the light source are shown, which are mounted at predetermined positions relative to the LED collimator 15. Each LED collimator 15 is formed of a light-transmitting resin such as acrylic resin. Figure 21 As shown, it has an outer peripheral surface 156 in the shape of a convex cone obtained by rotating a cross section of a roughly parabola, and has a recess 153 at its top, with a convex portion (i.e., a convex lens surface) 157 formed in the center of the recess 153. In addition, a convex lens surface 154 convex outwardly (or, alternatively, a concave lens surface concave inwardly) is provided in the center of its planar portion. In addition, the conical outer peripheral surface (parabola) 156 of the LED collimator 15 is set within an angle range that allows light emitted from the LEDs 14a and 14b in the surrounding direction to be totally reflected within it, or a reflective surface is formed on the outer peripheral surface.

[0131] Meanwhile, LEDs 14a and 14b are arranged at predetermined positions on the surface of LED circuit board 102, which is a circuit substrate. LED circuit board 102 is arranged and fixed to LED collimator 15 so that LED 14a or 14b on its surface is located in the center of recess 153 thereof.

[0132] With this structure, using the aforementioned LED collimator 15, the light emitted from LEDs 14a and 14b, particularly the light emitted upward (to the right in the figure) from their central portions, is converged into parallel light by the two convex lens surfaces 157 and 154 that form the outer shape of the LED collimator 15. Furthermore, light emitted from other portions in peripheral directions is reflected by the paraboloidal surface that forms the conical outer surface of the LED collimator 15 and similarly converged into parallel light. In other words, using the LED collimator 15, whose central portion forms a convex lens and whose peripheral portion forms a paraboloidal surface, it is possible to extract substantially all of the light generated by LEDs 14a and 14b as parallel light, thereby improving the efficiency of utilizing the generated light.

[0133] like Figure 20 、 Figure 22 As shown, a polarization conversion element 21 is provided on the light exit side of the LED collimator 15. This polarization conversion element 21 is constructed by combining a translucent member having a parallelogram-shaped cross section (hereinafter referred to as a parallelogram-shaped column) and a translucent member having a triangular cross section (hereinafter referred to as a triangular column). Multiple translucent members are arranged in parallel in an array on a plane perpendicular to the optical axis of the parallel light from the LED collimator 15. Furthermore, polarization beam splitting (PBS) films 211 and reflective films 212 are alternately provided on the interfaces between adjacent translucent members arranged in the array. Furthermore, a 1 / 2λ phase plate 213 is provided on the exit surface, from which light incident on the polarization conversion element 21 and transmitted through the PBS film 211 exits.

[0134] The polarization conversion element 21 is also provided with a Figure 20 The rectangular composite diffusion block 16 is shown. That is, the light emitted from the LED 14a or 14b is converted into parallel light by the LED collimator 15 and enters the composite diffusion block 16. Figure 23 This is a schematic diagram showing the structure of the synthetic diffusion block 16. The light incident on the synthetic diffusion block 16 is diffused by the texture 161 on the exit side and reaches Figure 20 The light guide 17 is shown.

[0135] Figure 20 In the figure, a prismatic light guide 17 with a roughly triangular cross-section is positioned on the exit surface of the composite diffuser block 16, sandwiched between a first diffuser 18a and a second diffuser 18b. Consequently, the horizontal light from the LED collimator 15 is reflected upward in the figure by the light guide 17 and directed toward the incident surface of the liquid crystal display element. The intensity of the incident light is then uniformed by the first and second diffusers 18a and 18b.

[0136] Figure 241 and 2 are diagrams showing the detailed structure of the light guide 17. (a) is a perspective view showing the entire light guide 17, (b) is a cross-sectional view thereof, and (c) and (d) are partial enlarged views showing details of the cross section.

[0137] The light guide 17 is formed of a light-transmitting resin such as acrylic resin and has a substantially triangular cross section (see Figure 24 (b)) rod-shaped components. Figure 24 (a) shown, including the synthetic diffusion block 16 (refer to Figure 20 ) of the light guide body light incident portion (surface) 171 opposite to the first diffuser 18a, the light guide body light reflecting portion (surface) 172 forming an inclined surface, and the liquid crystal display panel 402 (refer to Figure 19 ) is opposite to the light emitting portion (surface) 173 of the light guide.

[0138] In addition, if Figure 24 As shown in the partially enlarged views (c) and (d) of the middle section, a large number of reflective surfaces 172a and connecting surfaces 172b are alternately formed in a zigzag pattern on the light guide light reflecting portion (surface) 172 of the light guide 17. Furthermore, the reflective surfaces 172a (the rightward-rising line segments in the figure) form an angle αn (n is a natural number, e.g., 1 to 130 in this example) with the horizontal plane indicated by the dotted line in the figure. As an example, αn is set to 43 degrees or less (but not less than 0 degrees).

[0139] On the other hand, the connecting surface 172b (the line segment descending to the right in the figure) forms βn (n is a natural number, 1 to 130 in this example) relative to the reflecting surface. That is, the connecting surface 172b of the reflecting portion is inclined at such an angle that the connecting surface 172b is located in the shadow of the incident light within the range of the half-value angle of the scatterer described later. As described later, αn is the elevation angle of the reflecting surface, and βn is the relative angle between the reflecting surface and the connecting surface. As an example, the relative angle βn is set to be greater than 90 degrees (but less than 180 degrees), and in this example, all are equal (β1=β2=β3=…=β130).

[0140] Figure 25 and Figure 26 This is an enlarged view of the light guide light reflecting portion (surface) 172 of the light guide 17. For ease of explanation, the size of the reflecting surface 172a and the connecting surface 172b are relatively enlarged compared to the size of the light guide 17. Figure 26As shown in (b), the main light rays are deflected by δ at the light guide light incident portion (surface) 171 of the light guide 17, in a direction that increases the angle of incidence on the reflective surface 172a. Specifically, the light guide light incident portion (surface) 171 is formed into a curved convex shape that tilts toward the light source. As a result, parallel light from the exit surface of the composite diffuser block 16 is diffused and incident via the first diffuser 18a. As can be seen in the figure, it is slightly bent (deflected) upward by the light guide light incident portion (surface) 171 and reaches the light guide light reflective portion (surface) 172.

[0141] On the light guide light reflecting portion (surface) 172, a large number of reflecting surfaces 172a and connecting surfaces 172b are alternately formed in a sawtooth shape. The diffused light from the first diffuser 18a is totally reflected on each reflecting surface 172a and goes upward, and then passes through the light guide light emitting portion (surface) 173 and the second diffuser 18b ( Figure 25 As shown, the light is incident on the liquid crystal display panel 402 of the liquid crystal display element as parallel diffused light. Therefore, the reflection surface elevation angle αn is set so that each reflection surface 172a is at an angle greater than the critical angle with respect to the diffused light. Meanwhile, the relative angle βn between the reflection surface 172a and the connecting surface 172b is set to a constant angle, preferably greater than 90 degrees, as described above.

[0142] With the above structure, each reflecting surface 172a always has an angle greater than a critical angle relative to the diffused light. Therefore, total reflection can occur even without forming a reflective film such as metal on the light guide light reflecting portion 172, thereby realizing a low-cost light source device 10.

[0143] In addition, the reflection surface elevation angle αn is set to a value that gradually increases slightly as it moves from the lower part to the upper part of the light guide body light reflecting portion (surface) 172. This is because the light after passing through the liquid crystal display panel 402 of the liquid crystal display element has a certain degree of divergence angle, so part of the light after passing through the peripheral part of the liquid crystal display panel 402 will be blocked by the edge of the reflector arranged downstream, resulting in so-called dark corners (edge dimming), and this phenomenon needs to be prevented. That is, if Figure 25 As shown in the light 30, vignetting is prevented by adopting a structure that slightly deflects the light in the peripheral portion toward the central axis.

[0144] in addition, Figure 25In the figure, Lr1, Lr2, Lr3... represent the projection lengths of the reflecting surface 172a on the horizontal plane, and Lc1, Lc2, Lc3... represent the projection lengths of the connecting surface 172b on the horizontal plane, so that the ratio Lr / Lc of the projection lengths of the reflecting surface 172a and the connecting surface 172b can change with the position. The intensity distribution of the main light 30 incident on the light guide 17 is not necessarily consistent with the intensity distribution required on the incident surface of the liquid crystal display panel. Therefore, the ratio Lr / Lc of the reflecting surface 172a and the connecting surface 172b is used to adjust the intensity distribution. The higher the ratio, the higher the average intensity of the reflected light in this part. Generally speaking, the light source 30 incident on the light guide 17 tends to be stronger in the central part. In order to correct this, the above-mentioned ratio Lr / Lc is made different with the position, especially reduced in the central part. Since the ratio Lr / Lc is different depending on the position and the elevation angle αn of the reflecting surface is different depending on the position, the envelope 172c showing the approximate shape of the light guide light reflecting portion 172 is as shown in FIG. Figure 25 The performance is shown as a curve shape.

[0145] Furthermore, regarding the projected lengths Lr and Lc of the reflecting surface 172a and the connecting surface 172b, the sum of the two, Lr+Lc, is set to a constant value at each position and is less than 0.6 mm. That is, the relationship Lr1+Lc1=Lr2+Lc2=…≤0.6 mm is set. By adopting this structure, the repetitive spacing of the reflecting surfaces viewed from the light guide light exit surface 173 of the light guide 17 can be made the same. In addition, because this spacing is less than 0.6 mm, it is superimposed with the functions and effects of the diffusers 18a and 18b, and when observed through the liquid crystal display panel 402, the various exit surfaces do not appear to be separated but rather appear to be continuous surfaces. As a result, uniformity of spatial brightness across the liquid crystal display panel 402 is achieved, thereby improving display characteristics. That is, according to this structure, the intensity distribution of incident light on the liquid crystal display panel 402 can be made uniform. If the value of Lr+Lc is too small, not only will the machining time increase, but it will also be difficult to machine each reflecting surface 172a with high precision. Therefore, the lower limit of Lr+Lc is preferably 0.2 mm for practical purposes.

[0146] The shape of the light guide reflective portion (surface) 172 of the light guide 17 described above satisfies the conditions for total reflection of the primary light. This eliminates the need for a reflective film, such as aluminum, on the light guide reflective portion 172, enabling efficient light reflection. Furthermore, the need for vapor deposition of aluminum thin film, which increases manufacturing costs, is eliminated, enabling a brighter S-light component (s-polarized light) light source to be realized at a lower cost. Furthermore, the relative angles β are set so that the connecting surface 172b lies within the shadow of the light 30 diffused by the synthetic scattering block 16 and the diffuser 18a. This suppresses the incidence of unwanted light on the connecting surface 172b, thereby reducing the reflection of unwanted light and achieving a light source device with excellent characteristics.

[0147] In addition, according to the above-mentioned light guide 17, by appropriately setting the reflection surface elevation angle αn, the length of the light guide light emitting surface 173 in the optical axis direction can be freely changed. Thus, it is possible to realize a light source device in which the size (surface size) of the light guide light emitting surface 173 can be appropriately changed to a suitable size (surface size) suitable for devices such as the liquid crystal display panel 402 relative to the light guide incident portion (surface) 171. Thus, the light guide light emitting surface 173 can be made into the required size without depending on the configuration shape of the LEDs 14a and 14b constituting the light source, so a planar light source of the required size can be obtained. Furthermore, the design freedom including the configuration of the LEDs 14a and 14b constituting the light source is also ensured, which is beneficial to the miniaturization of the entire device.

[0148] Figure 27 The following shows a case where a polarization conversion element is used as the above-mentioned light guide. That is, instead of the usual translucent resin, a polarization conversion element is used to form the light guide 17 arranged behind the synthetic diffusion block 16, which is represented as light guide 17'. In the light guide 17', a triangular column translucent component 211' and a parallelogram column translucent component 212' are combined, and a PBS film 211 is formed on their boundary surface. The PBS film 211 reflects the S-polarized light (refer to the mark (×) in the figure) of the incident light emitted from the LED 14 and converted into parallel light by the LED collimator 15, but transmits the P-polarized light (refer to the upper and lower arrows in the figure). A 1 / 2λ phase plate 213 is formed on the upper surface of the parallelogram column translucent component 212', and a reflective film 212 is formed on its side surface.

[0149] With this structure, incident light emitted from LED 14 and converted to parallel light by LED collimator 15 is then directed upward from the upper surface of light guide 17', which is formed of a polarization conversion element, as S-polarized light. This structure eliminates the need for light guide 17, typically made of a translucent resin, leading to significant device miniaturization and reduced manufacturing costs.

[0150] By using the aforementioned light source device 10 as the light source for the image display device 4, i.e., a liquid crystal display element, a compact, highly efficient, modular s-polarized light source device can be realized with fewer light sources (number of LEDs, power consumption). Furthermore, the aforementioned concave reflector 1 and optical element 3 can remove unnecessary infrared (IR) and ultraviolet (UV) rays, effectively reducing the p-light component (p-polarized light) that can cause adverse effects such as carbonization on the image display device 4 and surrounding polarizers. This enables the realization of an information display device 100 that reduces damage caused by sunlight and, by utilizing the s-light component (s-polarized light), provides superior information display.

[0151] As described in detail above, the information display device 100 according to this embodiment can further improve light utilization efficiency and uniform illumination characteristics while also enabling compact and cost-effective manufacturing, including modular S-polarized light source devices. Furthermore, while the above description describes the polarization conversion element 21 being installed after the LED collimator 15, the present invention is not limited to this configuration. Similar functions and effects can be achieved by installing the polarization conversion element 21 in the optical path before it reaches the liquid crystal display element.

[0152] <Other structures>

[0153] According to the above-described information display device 100, during operation, the concave reflector 1 and optical element 3 can remove unnecessary IR light, UV light, and P-polarized light from sunlight. However, when the vehicle is parked in a parking lot, for example, and the engine key is off, the information display device 100 does not need to operate. Therefore, in this state, incoming sunlight is excluded from the normal optical path. In other words, the optical path that enters the information display device 100 through the upper opening 41 and reaches the image display device 4 and the polarizers disposed before and after it is blocked.

[0154] Figure 28 This figure shows an example of a structure for preventing sunlight from reaching the image display device 4. This is an expanded perspective view of the information display device 100, viewed from the back side, with the components disassembled. A concave reflector 1 is rotatably mounted within the housing, i.e., the casing 46, 47. The position of the concave reflector 1 can be adjusted by a concave reflector drive unit 48, which is comprised of a motor or the like, to a predetermined position. In this position, the concave reflector reflects incoming sunlight in a direction that prevents it from reaching the image display device 4 (a direction different from the normal optical path).

[0155] That is, when the information display device 100 is not used, the concave reflector 1 is rotated by a predetermined angle so that the sunlight does not return to the image display device 4, thereby preventing the sunlight concentrated by the concave reflector 1 from returning to the image display device 4. Figure 1 The control device 40 shown is implemented by the CPU 35 included in the controller 40 executing software stored in advance in the ROM 34 .

[0156] According to this structure, when the vehicle is stopped and incoming sunlight becomes a problem, especially under strong sunlight in seasons such as midsummer, it is possible to more reliably prevent sunlight from causing damage or deterioration to the optical components of the information display device 100, namely the image display device 4 and the surrounding polarizers and the light source device 10.

[0157] The features of the information display device of the present embodiment described above are summarized as follows. In the virtual image optical system from the concave reflector to the image display device (liquid crystal panel):

[0158] (1) Under specified conditions during the day, even if the P-polarized light in the sunlight component that passes through the front window glass (in the case of the stacking mirror method, it also passes through the stacking mirror) is focused by the concave reflector, the P-light component can be suppressed by the optical unit (element), i.e., the reflective polarizer, provided in the optical system so that it is reflected and does not return to the liquid crystal panel and the polarizer.

[0159] (2) When the information display device is not used, the concave reflector is rotated by a predetermined angle so that the sunlight does not return to the image display device, thereby preventing the sunlight concentrated by the concave reflector from returning to the image display device.

[0160] (3) By providing an optical element that prevents a portion of sunlight from returning to the driver's viewpoint (eyes), an information display device is provided that has significantly improved resistance to external light including sunlight and image quality degradation.

[0161] (4) By simultaneously providing a reflective polarizer and a light source that provides light of a specific polarization, the polarization degree of the image light can be increased, thereby improving contrast performance.

[0162] (5) In order to obtain high reliability of the reflective polarizer against temperature, humidity, sulfur compounds, etc., a moisture-proof film (protective film) is provided on the surface to reduce the degradation of characteristics caused by changes in the structure due to the influence of external air.

[0163] While various embodiments have been described in detail above, the present invention is not limited to these embodiments and includes various variations. For example, the above embodiments describe the entire system in detail to facilitate understanding of the present invention, but are not limited to necessarily including all of the described structures. Furthermore, it is possible to replace a portion of the structure of one embodiment with a structure of another embodiment, or to add a structure of another embodiment to a structure of one embodiment. Furthermore, it is possible to add, delete, or replace a portion of the structure of each embodiment with another structure.

[0164] Description of Reference Numerals

[0165] 1...concave reflecting mirror, 2...lens element, 3...optical element (reflective polarizing plate, P-light component suppression optical unit), 3a...substrate (glass substrate), 3b...reflective polarizing plate, 3d...moisture-proof film, 3h...adhesive (adhesive), 4...image display device (liquid crystal display element, liquid crystal display panel), 6...projected component (front window glass), 7...housing, 8...eye point (observer's viewpoint), 10...light source device, 14...LED, 15...LED collimator, 16...synthetic diffuser, 17...light guide, 18a, 18b...diffuser, 21...polarization conversion element, 41...opening, 48...concave reflecting mirror drive unit, 100...information display device, VI...virtual image.

Claims

1. An information display device for displaying image information on a projection surface using a virtual image, characterized in that: The interior of the housing partially provided with an opening includes: an image light generating unit for generating image light for displaying image information; an image light processing unit that performs predetermined optical processing on the image light from the image light generating unit; and an image projection unit that projects the image light from the image light processing unit onto the projection surface through the opening of the housing so that an observer can recognize the image information as a virtual image in front of the projection surface; An optical element is provided in a portion of the optical path inside the housing as a means for selectively reflecting a P-polarized component of light in the visible light band, wherein a moisture-proof film is provided on a surface of the reflective polarizer. The moisture-proof film is formed on the surface of the reflective polarizer of the optical element with a film thickness of 130 nm to 145 nm, which corresponds to 1 / 4 of the wavelength of the image light, thereby also having anti-reflection properties.

2. The information display device according to claim 1, wherein: The reflective polarizer selectively reflects the P-polarized component of light in the visible light band and transmits the S-polarized component at a specific transmittance, thereby increasing the polarization degree of the image light from the image light generating unit and improving contrast performance.

3. The information display device according to claim 1, wherein: A unit for suppressing at least one of infrared and ultraviolet light is provided on the optical path inside the housing. The image light generating unit includes a unit that selectively generates image light using S-polarized light.

4. The information display device according to claim 1, wherein: The image light generating unit includes an S-polarized solid light source.

5. An information display device for displaying image information on a projection surface using a virtual image, characterized in that: The interior of the housing partially provided with an opening includes: an image light generating unit for generating image light for displaying image information; an image light processing unit that performs predetermined optical processing on the image light from the image light generating unit; and an image projection unit that projects the image light from the image light processing unit onto the projection surface through the opening of the housing so that an observer can recognize the image information as a virtual image in front of the projection surface; An optical element is provided on the optical path inside the housing as a means for selectively reflecting the P-polarized component of light in the visible light band. The optical element is obtained by fixing a reflective polarizer to a transmissive substrate via an adhesive or a pressure-sensitive adhesive. The substrate is made of a transmissive resin and its shape enables aberration correction of a virtual image. A moisture-proof film is provided on the surface of the reflective polarizer. The moisture-proof film is formed on the surface of the reflective polarizer of the optical element with a film thickness of 130 nm to 145 nm, which corresponds to 1 / 4 of the wavelength of the image light, thereby also having anti-reflection properties.

6. The information display device according to claim 5, wherein: The reflective polarizer selectively reflects the P-polarized component of light in the visible light band and transmits the S-polarized component at a specific transmittance, thereby increasing the polarization degree of the image light from the image light generating unit and improving contrast performance.

Images