JP7798596B2 - Space floating image display device and retroreflective member used therein - Google Patents

Description

The present invention relates to a space floating image display device and a retroreflective member used therein.

It is disclosed, for example, in Patent Document 1 as a retroreflective optical element used in an image display device that displays images in space in a spatial floating information display system.

Japanese Patent Application Laid-Open No. 2019-128722

In retroreflective optical elements of the prior art, after reflective surfaces are laminated and each reflective surface is adhesively fixed, changes in the temperature and humidity of the surrounding environment can allow liquids such as moisture to penetrate from the edge of the bonded surface, causing the bonded surface to separate and creating an interface. As a result, not only does this significantly reduce the retroreflective properties, but when an observer looks directly at the retroreflective element, external light is reflected from the interface, significantly reducing the quality of the floating image. Furthermore, reflections from this interface can make ordinary glass appear cracked, visually causing the floating information display system to malfunction. However, conventional retroreflective elements do not take into consideration the technical means or structure to prevent moisture and other liquids from penetrating from the edge of the bonded portion.

The object of the present invention is to provide a retroreflective member with excellent environmental resistance by providing technical means and a structure that prevents moisture and other substances from entering through the laminated end faces of the reflective surfaces of the retroreflective member used in a spatial floating information display system or a spatial floating image display device.

In order to solve the above problems, for example, the configuration described in the claims is adopted. This application includes multiple means for solving the above problems, and one example is a space-floating image display device using a retroreflective optical element, as described below. The retroreflective optical element used in the space-floating image information display system, which is an example of this application, has reflective surfaces that are laminated and adhesively fixed, and then the end faces are subjected to a bonding process or post-processing to prevent the penetration of moisture, etc. into the end faces.

The present invention makes it possible to realize a space-floating image information system with excellent environmental resistance. In particular, by preventing the intrusion of moisture or other substances from the end faces of the retroreflective material, which would cause the laminated and bonded reflective surfaces to separate and create an interface, the space-floating image information can be displayed optimally without any degradation in image quality. Other issues, configurations, and effects will become clear from the description of the embodiments below.

1A and 1B are diagrams illustrating the configuration of a retroreflective member according to an embodiment of the present invention and the position where a spatially floating image is generated. 1 is an explanatory diagram for explaining the mechanism by which a ghost image is generated by an extraordinary ray generated by retroreflection according to an embodiment of the present invention. FIG. 10 is an explanatory diagram for explaining the mechanism of generation of extraordinary rays generated by a retroreflective member used in another space floating image information system. FIG. 1 is an explanatory diagram for explaining the mechanism for eliminating extraordinary light rays that occur when external light is incident on a retroreflective member according to an embodiment of the present invention. FIG. 10 is a characteristic diagram showing the optimum use conditions of the retroreflective member in the space floating image information display system according to one embodiment of the present invention. FIG. 1 is a diagram showing an example of a main part configuration and a retroreflection part configuration of a space floating image information display system according to an embodiment of the present invention; 1 is a diagram showing a second embodiment of the main part configuration and retroreflection part configuration of a space floating image information display system according to an embodiment of the present invention; 10 is a diagram showing a third embodiment of the main part configuration and retroreflection part configuration of the space floating image information display system according to an embodiment of the present invention. FIG. 10 is a diagram showing a fourth embodiment of the main part configuration and retroreflection part configuration of the space floating image information display system according to an embodiment of the present invention; FIG. 1 is an explanatory diagram for explaining the operation principle of an optical member that refracts image light used in the space floating image information display system of the present invention. 1 is an explanatory diagram showing the structure and principle of a space floating image information display system using an optical element that refracts image light according to the present invention; 1 is an explanatory diagram for explaining the structure of an optical member that refracts image light used in the space floating image information display system of the present invention. FIG. 10 is an explanatory diagram for explaining the arrangement of an optical member and an image source used in the space floating image information display system of the present invention, which prevents a viewer from directly viewing the image displayed by the image source. FIG. 4 is a cross-sectional view showing the arrangement of a member that blocks extraordinary rays generated in a retroreflecting portion according to an embodiment of the present invention. FIG. 1 is a diagram showing a configuration of a main part of a first embodiment of a space floating image information display system according to an embodiment of the present invention; 10A and 10B are diagrams showing the appearance and main components of a second embodiment of a space floating image information display system according to an embodiment of the present invention; 10A and 10B are diagrams showing the appearance and main components of a second embodiment of another space floating image information display system according to an embodiment of the present invention; 1 is an explanatory diagram for explaining a sensing means provided in a space floating image information display system according to an embodiment of the present invention; FIG. 10 is a diagram showing another example of a specific configuration of a light source device of another type. FIG. 10 is a structural diagram showing another example of a specific configuration of a light source device of another type. FIG. 10 is a diagram illustrating a portion of another example of a specific configuration of a light source device of another type. FIG. 10 is a diagram illustrating a portion of another example of a specific configuration of a light source device of another type. FIG. 10 is a diagram illustrating a portion of another example of a specific configuration of a light source device of another type. FIG. 10 is a structural diagram showing another example of a specific configuration of a light source device of another type. FIG. 10 is a diagram showing another example of a specific configuration of a light source device of another type. 10 is an enlarged view showing the surface shape of a light guide diffusion portion of another example of a specific configuration of a light source device. FIG. FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. 3A and 3B are structural diagrams showing examples of specific configurations of light source devices. 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. 1A and 1B are perspective and top views showing an example of a specific configuration of a light source device. 10A and 10B are explanatory diagrams for explaining the light source diffusion characteristics of the image display device. 10A and 10B are explanatory diagrams for explaining the light source diffusion characteristics of the image display device. FIG. 10 is an explanatory diagram for explaining the diffusion characteristics of a video display device. FIG. 10 is an explanatory diagram for explaining the diffusion characteristics of a video display device. FIG. 1 is a diagram showing a coordinate system for measuring visual characteristics of a liquid crystal panel. FIG. 1 is a diagram showing the luminance angle characteristics (longitudinal direction) of a typical liquid crystal panel. FIG. 1 is a diagram showing the luminance angle characteristics (short side direction) of a typical liquid crystal panel. FIG. 1 is a diagram showing the angular characteristics (longitudinal direction) of contrast of a typical liquid crystal panel. FIG. 1 is a diagram showing the angular characteristics (short-side direction) of contrast of a typical liquid crystal panel. 1 is an explanatory diagram for explaining a structure for preventing performance degradation due to moisture absorption caused by retroreflection according to one embodiment of the present invention. FIG. 1 is an explanatory diagram for explaining the structure of a goods vending machine equipped with a space floating image information display system according to an embodiment of the present invention;

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the contents of the embodiments described below (hereinafter also referred to as "the present disclosure"). The present invention extends to the spirit of the invention and the scope of the technical ideas set forth in the claims, or equivalents thereof. Furthermore, the configurations of the embodiments (examples) described below are merely examples, and various changes and modifications may be made by those skilled in the art within the scope of the technical ideas disclosed in this specification.

In addition, in the drawings used to explain the present invention, components having the same or similar functions will be given the same reference numerals, and different names will be used as appropriate, while repeated explanations of functions, etc. may be omitted. In the following description of the embodiments, images that float in space will be referred to as "space-floating images." Instead of this term, other terms such as "aerial image," "spatial image," "floating-in-the-air image," "space-floating optical image of displayed image," and "floating-in-the-air optical image of displayed image" may also be used. The term "space-floating image," which is primarily used in the description of the embodiments, is used as a representative example of these terms.

This disclosure relates to an information display system that can display an image generated by image light from a large-area image light source as a floating image inside or outside a store (space) by transmitting the image through a transparent member that separates the space, such as the glass of a shop window. This disclosure also relates to a retroreflective member used in such an information display system.

According to the following embodiment, it is possible to display high-resolution video information in a state of floating in space, for example, on the glass surface of a shop window or on a light-transmitting plate. In this case, by making the divergence angle of the emitted video light small (i.e., acute) and further aligning it with a specific polarization, it is possible to efficiently reflect only the normal reflected light from the retroreflective material. This results in high light utilization efficiency, and it is possible to suppress ghost images that appear in addition to the main floating image in space, which was a problem with conventional retroreflective methods, thereby producing a clear floating image in space.

Furthermore, a device including the light source of the present disclosure can provide a novel, highly usable floating image information display system that can significantly reduce power consumption. Furthermore, the technology of the present disclosure can provide a floating image information display system for vehicles that can display so-called unidirectional floating images that can be viewed from outside the vehicle, for example, through shield glass, including the vehicle's windshield, rear window, or side window.

In contrast, conventional floating-space image information display systems combine an organic EL panel or liquid crystal display panel (LCD panel or display panel) with a retroreflective member as a high-resolution color display image source. The first retroreflective member 2 used in conventional floating-space image display devices diffuses image light over a wide angle. Therefore, in addition to the light reflected normally by the retroreflective member of the first embodiment, which is composed of a polyhedron as shown in Figure 3, the shape used for retroreflective member 2a, as shown in Figure 3, is hexahedral, and as a result, image light incident at an angle generates six ghost images, including ghost images 3a and 3f, impairing the image quality of the floating-space image. Furthermore, the same floating-space image, which is a ghost image, can be viewed by people other than the viewer, posing a major security issue.

Furthermore, as shown in Figure 1(A), the second retroreflective member 5 used in the space floating image display device is formed by arranging optical elements 20, each having a large number of band-shaped planar light-reflecting portions at a constant pitch, perpendicular to one side of the first light control panel 221 and the second light control panel 222, respectively, of transparent flat plates 18 and 17, each of which has a constant thickness. Here, the light-reflecting portions of the optical elements 20 constituting the first light control panel 221 and the second light control panel 222 are arranged so as to intersect (orthogonally in this embodiment) in a planar view.

Next, we will explain the function of the second retroreflective member used in the space-floating image display device and a specific example of a space-floating image display device. As shown in Figure 1(B), the second retroreflective member 5 is typically tilted at an angle of 40 to 50 degrees relative to the image display device 1. In this case, the space-floating image 3 exits the second retroreflective member 5 at the same angle as the angle at which the image light enters the second retroreflective member 5. In this case, the space-floating image is formed symmetrically, a distance equal to the distance L1 from the image display device 1 to the second retroreflective member 5.

The mechanism by which the space-floating image is formed will be explained in detail below using Figures 1 and 2. Image light emitted from the image display device 1 provided on one side of the second retroreflective member 5 is reflected by the planar light-reflecting portion C (the reflective surface of the light-reflecting member 20) of the second light control member 222, and then reflected by the planar light-reflecting portion C' (the reflective surface of the light-reflecting member 20) of the first light control member 221, thereby forming a space-floating image 3 (real image) at a position outside the second retroreflective member 5 (in the space on the other side). In other words, by using this second retroreflective member 5, a space-floating image information device is established, and the image of the image display device 1 can be displayed in space as a space-floating image.

As mentioned above, the second retroreflective member 5 has two reflective surfaces, and therefore generates two ghost images 3a and 3b in addition to the spatially floating image 3, depending on the number of reflective surfaces, as shown in Figures 2(A) and 2(B).

Furthermore, it was found that when the intensity of external light is high and it enters from the top surface of the second retroreflective member 5, the spacing between the reflective surfaces (300 μm or less) becomes shorter, causing optical interference, resulting in the observation of rainbow-colored reflected light and making the observer aware of the presence of the retroreflective member. Therefore, to prevent the interference light generated by the pitch of the reflective surfaces of the retroreflective member 5 due to the incidence of external light from being returned to the observer, the area where the interference light occurs was experimentally determined using the measurement environment shown in Figure 4, with the angle of incidence of the external light as a parameter. The results obtained are shown in Figure 5. It was found that when the reflective surface pitch is 300 μm and the reflective surface height is 300 μm, the interference light does not return to the observer if the inclination angle θYZ of the retroreflective member is 35 degrees or more.

On the other hand, it has been found that with the ratio (H/P) of the pitch P of the light-reflecting member 20 to the height H of the reflective surface described above, approximately 60% of the reflective surface forms a space-floating image due to retroreflection, while the remaining 40% becomes abnormally reflected light that generates ghost images. In order to improve the resolution of space-floating images in the future, it will be essential to shorten the pitch of the reflective surface. Additionally, in order to suppress the generation of ghost images, the height of the reflective surface must be made higher than it is currently, but due to manufacturing constraints on the second retroreflective member 5, it is best to select the ratio (H/P) of the pitch P of the reflective surface to the height H (H) in the range of 0.8 to 1.2, compared to the current value of 1.0.

As a result of the above-mentioned investigations, the inventors investigated a retroreflective optical system that achieves high-quality floating images in a floating image information display system using a second retroreflective member that, in principle, produces fewer ghost images, and arrived at the present invention. The present invention will be described in detail below with reference to the accompanying drawings.

<Configuration Example of First Retroreflection Optical System Forming the Space Floating Image Information Display System>
FIG. 6 is a diagram showing an example of the configuration of a retroreflecting optical system used to realize the space-floating image information display system of the present disclosure. FIG. 6 is also a diagram illustrating the overall configuration of the space-floating image information display system of the present disclosure. Referring to FIG. 6, for example, according to the space-floating information display system of the present disclosure (hereinafter also referred to as "the present system"), when the space-floating image information display system is placed on a desk, the person monitoring the space-floating image will view the space-floating image from below at an angle θ6. It has been found that the optimal position for monitoring the space-floating image is to arrange the image display device 1 so that the sum of the angle θ2 between the display surface and the retroreflective member 5 and the angle θ1 between the retroreflective member 5 and the space-floating image (θ2 + θ1) is approximately equal.

As mentioned above, the floating image is formed symmetrically to the image display device 1 with respect to the second retroreflective member 5, so the angles θ1 and θ2 formed by their respective arrangements are equal. Therefore, once the angle θ6 at which the observer looks into the floating image display system is determined, it is advisable to arrange the image display device 1 and the second retroreflective member 5 in the retroreflective optical system so that the angle θ2 = θ6/2. Furthermore, a predetermined distance L1 is required between the image display device 1 and the second retroreflective member 5 to increase the cooling efficiency of the image display device 1. Furthermore, in order to structurally obtain the aforementioned angle θ2, it is necessary to determine the distance L2 relative to L1.

The configuration of the spatially floating image information display system of the present disclosure will now be described in more detail. As shown in Figure 6, it comprises an image display device 1 that diverges image light of a specific polarization at a narrow angle, and a second retroreflective member 5. The image display device 1 comprises a liquid crystal display panel (hereinafter sometimes simply referred to as the liquid crystal panel) 11, and a light source device 13 that generates light of a specific polarization with narrow-angle diffusion characteristics.

The image light of a specific polarized wave from the image display device 1 is selectively transmitted through an absorptive polarizing sheet 101 with an anti-reflection film on the surface of the second retroreflective member 5 that faces the outside of the device (not shown), and the other polarized wave contained in the external light is absorbed, preventing the influence of light reflected from the surface of the second retroreflective member 5 on the resulting floating image in space.

Here, the absorptive polarizing sheet 101, which selectively transmits image light of a specific polarization, has the property of transmitting image light of a specific polarization, so the image light of a specific polarization passes through the absorptive polarizing sheet 101. The transmitted image light forms a floating image 3 in a position symmetrical to the retroreflective member 5.

The light that forms the floating image 3 is a collection of light rays that converge from the retroreflective member 5 onto the optical image of the floating image 3, and these light rays continue to travel in a straight line even after passing through the optical image of the floating image 3. Therefore, the floating image 3 is a highly directional image, unlike the diffused image light formed on a screen by a typical projector or the like.

Therefore, with the configuration shown in Figure 6, the floating image 3 appears as a bright image when viewed by a user from the direction shown in the figure, but when viewed by other people from above, below, or in front of the page, the floating image 3 cannot be seen as an image at all. This characteristic is highly suitable for use in systems that display images that require high security or highly confidential images that should be kept secret from people directly facing the user.

Depending on the performance of the retroreflective member 5, the polarization axis of the reflected image light may become misaligned. In this case, some of the image light with misaligned polarization axes is absorbed by the absorptive polarizing sheet 101 described above. This prevents unnecessary reflected light from being generated in the retroreflective optical system, preventing or minimizing degradation in the image quality of the spatially floating image.

Furthermore, in a space-floating image display device using the retroreflective optical system of the present disclosure, even when an observer looks into the space-floating image, the display screen of the image display device 1 is shielded from light by the reflective surface of the retroreflective member 5. Therefore, in this space-floating image display device, the image displayed on the image display device 1 is more difficult to see directly than when the image display device 1 and the retroreflective member are directly opposite each other.

<Configuration Example of Second Retroreflection Optical System Forming the Space Floating Image Information Display System>
7 is a diagram showing the main components of another example of a retro-optical system for realizing a space-floating image information display system according to an embodiment of the present invention. This space-floating image information display system is suitable for an observer to observe a space-floating image from diagonally above. The image display device 1 is configured with a liquid crystal display panel 11 as an image display element and a light source device 13 that generates light of a specific polarization with a narrow-angle diffusion characteristic. The liquid crystal display panel 11 is configured with a screen size ranging from a small one of about 5 inches to a large one exceeding 80 inches. The image light from the liquid crystal display panel 11 is emitted toward a retroreflective member (retroreflective portion or retroreflective plate) 5.

Light from a narrow-divergence light source device 13 (described later) is incident on the liquid crystal panel 11, generating a narrow-divergence image beam that is then incident on the retroreflective member 5 to produce the floating image 3. The floating image 3 is formed symmetrically on the image display device 1, with the retroreflective member 5 as the plane of symmetry. To eliminate ghost images and produce a high-quality floating image 3, an image light control sheet 334, the structure of which is shown in Figure 12(A), can be provided on the output side of the liquid crystal panel 11 to control the diffusion characteristics in unwanted directions. Furthermore, since the reflectivity of the image light from the liquid crystal panel 11 can be increased by reflective materials such as retroreflective members, it is generally preferable to use S-polarized light. However, if the observer wears polarized sunglasses, the floating image will be reflected or absorbed by the sunglasses. To address this issue, a depolarizing element 339 can be provided to optically convert a portion of the image light of a specific polarization into the other polarization, thereby simulating natural light, allowing the observer to observe a high-quality floating image even when wearing polarized sunglasses. When these are optically bonded with adhesive 338, no light reflecting surfaces are created, and the image quality of the floating image is not impaired.

Commercially available depolarizing elements include Cosmoshine SRF (manufactured by Toyobo Co., Ltd.) and depolarizing adhesive (manufactured by Nagase & Co., Ltd.). Cosmoshine SRF (manufactured by Toyobo Co., Ltd.) can be applied to an image display device to reduce interfacial reflection and improve brightness. Depolarizing adhesives are used by bonding a colorless, transparent plate to an image display device via the depolarizing adhesive. An image light control sheet 338 is also provided on the image output surface of the retroreflective member 5 to eliminate ghost images that appear on both sides of the normal image of the spatially floating image 3 due to unwanted light. In this embodiment, the retroreflective member 5 is positioned parallel to the horizontal plane in space, allowing the spatially floating image 3 to be displayed at an angle θ1 relative to the horizontal plane. To achieve this, the display surface of the image display device 1 is tilted θ1 away from the horizontal plane to the spatially floating image 3. Furthermore, in this embodiment, the image display device 1 is equipped with a light source device 13 that generates specifically polarized light with a diffusion characteristic that forms a narrow angle with the liquid crystal display panel 11.

<Configuration Example of Third Retroreflection Optical System Forming Space Floating Image Information Display System>
8 is a diagram showing another example of the configuration of the main components of a retroreflecting optical system for realizing a space-floating image information display system. This space-floating image information display system is suitable for an observer to observe a space-floating image from diagonally above in front. The image display device 1 is configured with a liquid crystal display panel 11 as an image display element and a light source device 13 that generates light of a specific polarization with narrow-angle diffusion characteristics. The liquid crystal display panel 11 is configured with a screen size ranging from a small one of about 5 inches to a large one exceeding 80 inches.

Image light from the liquid crystal display panel 11 is emitted toward the retroreflective member 5. Light from a narrow divergence angle light source device 13 (described below) is incident on the liquid crystal panel 11, generating an image light beam with a narrow divergence angle, which is then incident on the retroreflective member 5, resulting in a floating image 3. The floating image 3 is formed at a symmetrical position on the image display device 1, with the retroreflective member 5 as the plane of symmetry.

To eliminate ghost images generated by the space-floating image 3 and obtain a high-quality space-floating image 3, an image light control sheet 334 may be provided on the output side of the liquid crystal panel 11 shown in Figure 14(A) to control the diffusion characteristics in unnecessary directions. On the other hand, as shown in Figure 14(B), an image light control sheet 338 may also be provided on the image output surface of the retroreflective member 5 to eliminate ghost images generated on both sides of the normal image of the space-floating image 3 due to unnecessary light. By tilting the retroreflective sheet 5 (θ2) relative to the horizontal plane, the space-floating image 3 can be generated at an angle θ1 relative to the horizontal plane. Therefore, for example, if the configuration of Figure 8 is incorporated into the top of a kiosk terminal and a space-floating image is displayed as an avatar on the top end of the terminal, the image light will be directed toward the observer's eyes, allowing for the observation of a high-brightness space-floating image.

As with the first and second embodiments, to obtain the desired elevation angle and position for the floating image 3, it is sufficient to optimally design the inclination angle θ2 of the retroreflective member 5 and the inclination angle θ3 of the image display device 1, as well as their respective positions.

<Configuration example of the fourth retroreflection system forming the space floating image information display system>
9 is a diagram showing the main components of another example of a retroreflecting optical system for realizing a space-floating image information display system. This space-floating image information display system is suitable for an observer to observe a space-floating image from diagonally above. The image display device 1 is configured with a liquid crystal display panel 11 as an image display element and a light source device 13 that generates light of a specific polarization with a narrow-angle diffusion characteristic. The liquid crystal display panel 11 is configured with a screen size ranging from a small one of about 5 inches to a large one exceeding 80 inches.

In order to make the image light from the liquid crystal display panel 11 obliquely incident on the retroreflective member 5 placed directly opposite, a linear Fresnel sheet 105 such as the one shown in Figure 10 can be placed close to the image display surface of the liquid crystal panel 11 of the image display device 1 as the image light control sheet 334, and the image light can be refracted in the desired direction. In this case, a light-shielding layer can be provided on the vertical surface of the linear Fresnel to block the incidence of image light from sources other than the Fresnel lens, thereby suppressing the generation of unwanted light. Furthermore, by providing an anti-reflection film on the image light entrance and exit surfaces of the linear Fresnel sheet, the generation of unwanted light can be suppressed, resulting in favorable characteristics.

The image light is emitted toward the retroreflective member 5 by the image light control sheet 334 equipped with the linear Fresnel sheet 105 described above. Light from a narrow divergence angle light source device 13 (described later) is incident on the liquid crystal panel 11, generating an image light beam with a narrow divergence angle, which is then incident on the retroreflective member 5, resulting in a space-floating image 3. The space-floating image 3 is formed in a symmetrical position on the display surface of the image display device 1, with the retroreflective member 2 as the plane of symmetry. In this embodiment, the retroreflective member 2 and the image display device 1 are positioned directly opposite each other. Therefore, if an observer looks into the retroreflective member 5 of the space-floating image information display device, the image displayed on the liquid crystal panel 11 will overlap the space-floating image, significantly reducing the image quality of the space-floating image.

To prevent the above-mentioned image light from overlapping with the spatially floating image, an image light control sheet is provided on the image light output surface of the liquid crystal panel 11. For example, a viewing angle control film (VCF) from Shin-Etsu Polymer Co., Ltd. is suitable as this image light control sheet. Its structure is a sandwich structure in which transparent silicon and black silicon are alternately arranged with synthetic resin placed on the light input and output surfaces, and therefore it is expected to have the same effect as the ambient light control film of this example. In this case, since the viewing angle control film (VFC) has an alternating arrangement of transparent silicon and black silicon that stretch in a specific direction, it is recommended to tilt the extension direction of the transparent silicon and black silicon of the image light control sheet 334 relative to the vertical direction of the pixel arrangement direction of the liquid crystal panel 11 (θ10 in the figure) as shown in Figure 13 to reduce moiré that occurs due to the pitch between the pixels and the ambient light control film.

In the fourth embodiment, the retroreflective member 5 is positioned parallel to the bottom surface of the housing. As a result, external light enters the retroreflective member 5 and enters the housing, resulting in a degradation in the quality of the generated space-floating image 3. To eliminate ghost images generated in the space-floating image 3 and obtain a high-quality space-floating image 3, as in the second and third embodiments, an image light control sheet 334 may be provided on the exit side of the liquid crystal panel 11 to control the diffusion characteristics in unnecessary directions, as shown in Figures 14(A) and 14(B). On the other hand, an image light control sheet 338 may also be provided on the image exit surface of the retroreflective member 5 to eliminate ghost images generated on both sides of the normal image of the space-floating image 3 due to unnecessary light. By placing the above-described structures inside the housing, external light is prevented from entering the retroreflective member 5, preventing the generation of ghost images.

If the Fresnel angle of the linear Fresnel sheet 105 shown in Figure 10 is 20 degrees and the base material of the linear Fresnel sheet 105 is acrylic, the refractive index is 1.49 and the exit angle θ9 of the linear Fresnel sheet is 30 degrees. When the light beam emitted from the image display device 1 is emitted perpendicular to the display surface, if the divergence angle of the light beam is ±20 degrees, the angle of incidence on the exit surface will be a maximum of +40 degrees. As a result, the angle of the light beam emitted from the linear Fresnel sheet 105 will be a maximum of +70 degrees, which is 1.75 times larger. On the other hand, if the divergence angle is -20 degrees, the angle of incidence on the exit surface will be 10 degrees, and the divergence angle can be increased by 1.5 times from 20 degrees to 30 degrees.

Furthermore, we have discovered that the intensity of ghost images 3a and 3b that appear in addition to the spatially floating image 3 shown in (A) and (B) can be reduced; in other words, the brightness of ghost images 3a and 3b can be reduced because the diffusion angle of the abnormally reflected light reflected by the retroreflective member 5 is increased. Above, we have described the configuration and effects of an optical system in which the linear Fresnel sheet 105 shown in Figure 10 is placed between the retroreflective member 5 and the image display device 1 for the purposes of increasing the diffusion angle and reducing ghost images.

Next, an example of a housing using an optical system with a linear Fresnel sheet 105 in a space-floating image information display device will be described with reference to Figure 11. As mentioned above, the image light beam is refracted by the action of the linear Fresnel sheet 105. At this time, the direction of the light beam emitted from the image display device 1 is controlled so that the chief ray of the light beam (the ray with the highest brightness) is at the desired angle θ9 with respect to the space-floating image surface 3. At this time, as shown in Figure 10, the angle θ8 after refraction is calculated from the angle of incidence on the linear Fresnel sheet 105, the Fresnel angle, and the refractive index of the base material of the linear Fresnel sheet 105, and the exit angle θ9 after refraction at the air interface can also be uniquely determined.

As a result, the chief ray B1 of the image light emitted perpendicularly from the liquid crystal display panel 11 that constitutes the image display device 1 is refracted obliquely and enters the retroreflective member 5. After being reflected by two reflective surfaces, it forms a floating image 3 in a position symmetrical to the liquid crystal display panel 11. At this time, the image light beam has a narrow divergence angle due to the light source device 13 of the present invention (included in the image display device 1 shown in Figure 11), which has narrow-angle diffusion characteristics as shown in Figure 30, but the diffusion angle θ11 of one light beam B11 relative to the chief ray B1 is greatly expanded by the action of the Fresnel lens sheet 105. Furthermore, the other light beam B12 is diffused at a diffusion angle θ12 that is approximately equal to the original diffusion angle.

For this reason, when observing the floating image 3, the brightness is greatest when the image is viewed from the direction of the chief ray. For this reason, in a floating image information system having an optical system equipped with a linear Fresnel sheet 105, in order to direct the floating image of maximum brightness in the direction of the observer, a hinge 513 is provided on the housing base 516, which serves as the base, as a mechanism for holding the housing 511 and rotating it relative to the housing base 516 (see angle θ13 in Figure 11), and the housing 511 is connected to a support arm 512, one end of which is connected to the hinge 513. As a result, it is possible to rotate the housing 511 relative to the housing base 516, allowing the observer to observe the floating image 3 at maximum brightness.

Furthermore, by providing the above-mentioned mechanism, when the spatial floating image information display system is not in use, a compact storage configuration can be achieved by storing the housing 511 in the space provided by the housing base 516 and the housing cover 515 attached to the housing base 516. The housing 511 houses an image display device 1 equipped with a liquid crystal panel (not shown) and a light source (not shown), as well as a retroreflective member 5. In addition, the back cover 514 has an inclined surface near the hinge, which prevents the back cover 514 of the housing 511 from coming into contact with the housing base 516 when stored.

In contrast to the general form of a linear Fresnel sheet, in which Fresnel lenses are formed in a direction parallel to one side of the outer shape, in the first embodiment of the present invention, as shown in FIG. 12(A), the Fresnel lens shape has at least one boundary surface. FIG. 12(A) shows the boundary surface between inclined linear Fresnel sheet 517 and inclined linear Fresnel sheet 518. As a result, the image light beam from the image displayed on the flat display provided in image display device 1 arranged on the lower side in FIG. 13 is refracted in the direction indicated by the arrow in FIG. 12(A). As a result, the light output direction of the resulting floating image 3 in space can be set to two directions. Furthermore, if a linear Fresnel sheet is configured so that this boundary surface forms two surfaces, it goes without saying that the light output direction of the floating image 3 in space can be set to three directions.

Furthermore, as a second embodiment of the present invention, the decentered Fresnel sheet 519 shown in Figure 12(B) has an eccentric circular Fresnel sheet structure, and the lens action obtained by the Fresnel shape causes the light emitted from the floating image 3 to be emitted in a direction perpendicular to the Fresnel lens surface. As a result, the image light beam from the image displayed on the flat display provided in the image display device 1 located on the lower side in Figure 13 is refracted in the direction shown by the arrow in Figure 12(B). Here, in order to control the light emitted from the floating image 3, the eccentricity amount and Fresnel angle of the circular Fresnel sheet are used as parameters for optimal design. Furthermore, by keeping the Fresnel angles of the linear Fresnel sheet and circular Fresnel sheet constant, it is possible to achieve both control of the emitted light and a slim optical system set.

The above describes a technical means for controlling the emission direction of the image light beam from the image display device 1 using the action of a Fresnel lens, but it goes without saying that the same effect can be achieved by electrically changing the refractive index or shape to control the emission direction of the image light beam and control the emission direction and diffusion angle of light from the floating image. Furthermore, as will be described later, the same effect can be achieved by controlling the emission direction of the light source light beam incident on the liquid crystal panel 11 from the light source device 13.

<First Configuration Example of Space Floating Image Information Display System>
A first embodiment of a space-floating image information system using the four retroreflective optical systems described above is shown in Figure 15. A retroreflective member 5 is adhesively or glue-fixed to a transparent sheet 100. By adopting a structure that allows the distance between the image display device 1 and the retroreflective member 5 to be changed and the imaging position of the space-floating image 3 to be changed, it is possible to impart movement to the space-floating image, thereby realizing an image information display device that can display pseudo-three-dimensional space-floating images.

<Second Configuration Example of the Space Floating Image Information Display System>
A second embodiment of the space-floating image information display system will be described with reference to FIG. 16 . FIG. 16 shows a first embodiment in which a space-floating image display device 202 is incorporated into a tablet terminal. The space-floating image display device 202 and the flat display 200 are provided in the same housing 201. In addition, a sensing unit 203 that covers the entire display image 204 of the flat display 200 and the space-floating display 202 is provided at the end of the housing 201 where both the flat display 200 and the space-floating image display device 202 are located, on the same plane as the floating image 204. The sensing unit 203 can sense both the sensing area of the flat display 200 and the sensing area of the space-floating display 202 on the same plane, shown as sensing area 226 in FIG. 16 . In addition, when a configuration is provided with two or more sensing areas, such as the sensing area of the flat display 200 and the sensing area of the space-floating display 202, they may exist parallel to each other on a plane, above and below each other, or behind and before and after each other. They may also exist on the same plane. In this case, the sensing unit 203 may be divided and provided for each sensing area. The space-floating image display device 202 and the flat display 200 may be installed side by side in the same housing 201. While the present embodiment is described using the flat display 200, any display may be used, not limited to a flat display. In the second configuration example, the sensing area is positioned higher from the front of the device to the rear, and has a slope. This allows for an arrangement that facilitates input. The sensing unit will be described in detail below.

In this video information display system, if the wavelength of the light source of the TOF system, which is the ranging system of the sensing unit 203 used, is a long wavelength of 900 (nm) or more, it is less susceptible to the influence of external light. In this case, the user is given the illusion that the spatial operation input performed on the displayed floating image 204 can also be performed on the image display surface of the flat display 200. This allows spatial operation input to be performed without directly touching the display screen of the flat display 200.

Furthermore, the inventors conducted experiments to determine how far the flat display 200 and the sensing area 226 should be so that the operator's fingers do not touch the surface of the flat display 200 even when performing spatial operations based on the screen displayed on the flat display 200. As a result of this experiment, they found that by positioning the imaging position of the floating image 204 40 mm or more away from the flat display 200, the probability that the operator will directly touch the screen of the flat display 200 can be reduced to 50% or less. Furthermore, by positioning the sensing area 226 50 mm or more away, operations do not directly touch the flat display 200.

Note that the configuration described in Figure 16 is not limited to the tablet terminal described above, but may also be incorporated into various other display devices, such as ATMs, automatic ticket vending machines, kiosk terminals, and stationary display devices.

<Third Configuration Example of the Space Floating Image Information Display System>
A third embodiment of the space-floating image information display system will be described with reference to FIG. 17 . FIG. 17 shows a second embodiment in which a space-floating image display device 202 is incorporated into a tablet terminal. The space-floating image display device 202 and a flat display 200 are mounted in the same housing 201, and there is a first sensing unit 203a that senses a first sensing area (sensing region) 226a that covers the imaging area of the space-floating image 204 of the space-floating image display device 202, and a second sensing unit 203b that senses a second sensing area 226b that covers the image display area of the flat display 200. The first sensing area 226a and the second sensing area 226b are provided at the starting points of the space-floating image display device 202 and the flat display 200, respectively. Furthermore, the first sensing area 226a and the second sensing area 226b are arranged in close proximity to each other. The first sensing area and the second sensing area exist parallel to each other or in front and behind each other on a plane. As shown in FIG. 15, the first sensing area and the second sensing area may be configured to exist on the same plane. The space floating image display device 202 and the flat display 200 may be installed side by side in the same housing 201. In this embodiment, the flat display 200 is used for explanation, but any display may be used, not limited to a flat display. In this embodiment, the area is arranged approximately parallel to the image display surface of the flat display 200. The sensing unit used here will also be described in detail later.

In the third embodiment of the video information display system described above, the user is given the illusion that the spatial operation inputs made to the displayed floating-in-space image 204 can also be made to the image display surface of the flat display 200. This allows spatial operation inputs to be made without directly touching the display screen of the flat display 200.

In this regard, a prototype was used to evaluate finger contact with the flat display 200 using an actual device, and the results showed that by positioning the imaging position of the floating image 204 at a distance of 50 mm or more from the flat display 200, the operator was able to perform spatial operation inputs to the video information display system without directly touching the screen of the flat display 200.

As mentioned above, the configuration described in Figure 17 is not limited to tablet terminals, but may also be incorporated into various display devices such as ATMs, automatic ticket vending machines, kiosk terminals, and stationary display devices.

<Technical means for sensing spatial images>
In order to allow a monitor (operator) to be connected to an information system bidirectionally via a space-floating image display device, sensing technology for pseudo-operating the space-floating image will be described below.

In the space-floating video information system, sensing information is read along with the space-floating video using a two-dimensional sensor (described below), enabling image manipulation of the displayed video.

The following describes sensing technology for simulating the operation of floating images in space, enabling a monitor (operator) to connect bidirectionally to an information system via a floating image display device. Figure 18 is a diagram illustrating the principle of this sensing technology. A distance measuring device 203 incorporating a TOF (Time of Flight) system compatible with floating images in space is installed. A near-infrared LED (Light Emitting Diode) serving as the light source is activated in synchronization with the system's signal. An optical element for controlling the divergence angle is provided on the LED's light output side, and a pair of highly sensitive avalanche diodes with picosecond time resolution are used as light receiving elements, aligned horizontally to correspond to the area. The LED light source emits light in synchronization with the system signal, and the phase Δt is shifted by the time it takes for the light to reflect off the object to be measured (the monitor's fingertip) and return to the light receiving unit. The distance to the object is calculated from this time difference Δt, and the position and movement of the operator's finger are sensed as two-dimensional information in combination with the position information of multiple sensors arranged in parallel. Furthermore, a space-floating information display system or space-floating image display device can be realized that has sensing functions with few false detections for the display screen of a flat display and the space-floating image.

<Technical means for reducing ghost images>
A technical means for realizing a high-quality spatial image display device with reduced ghost images as a spatial floating image display device will be described with reference to Fig. 14. In order to control the divergence angle and divergence angle of the image light from the liquid crystal panel 13 as the image display element in a desired direction, it is advisable to provide an image light control sheet 334 on the exit surface of the liquid crystal panel 13, as shown in Fig. 14(A). Furthermore, the reflection light control sheet 334 is provided on the light exit surface or the light entrance surface or both of the retroreflective member to absorb abnormal light that generates ghost images.

Figures 14 (A) and (B) show a specific method for applying the image light control sheet 334 to a spatial image display device. The image light control sheet 334 is provided on the output surface of a liquid crystal panel 335, which is the image display element. In this case, the following two methods (1) and (2) are effective in reducing moiré that occurs due to interference between the pixels of the liquid crystal panel 13 and the pitch of the transmissive portions 336 and light absorbing portions 337 of the image light control sheet 334.

(1) As shown in Figure 13, the vertical stripes created by the transmissive and light-absorbing portions of the image light control sheet 334 and the pixel arrangement of the liquid crystal panel 335 (represented as liquid crystal panel 11 in Figure 15) are tilted by θ10.

(2) If the pixel size of the liquid crystal panel 335 is A (see double-headed arrow A in Figure 14(A)) and the pitch of the vertical stripes of the image light control sheet 334 is B (see double-headed arrow B in Figure 14(A)), then this ratio (B/A) is selected so as not to be an integer multiple.

One pixel 339 of the LCD panel consists of three color pixels (RGB) arranged in parallel, and is generally square, so the occurrence of the above-mentioned moire cannot be suppressed across the entire screen. For this reason, we experimentally determined that the tilt θ10 shown in (1) should be optimized between 5 and 25 degrees so that the position where moire occurs can be intentionally shifted to a location where the floating image is not displayed. While we have used an LCD panel as an example to reduce moire, the moire that occurs between the retroreflective member 5 and the image light control sheet 334 is a linear structure, so as shown in Figure 4, by optimally tilting the image light control sheet with respect to the X-axis, it is possible to reduce large, low-frequency moire that can be seen with the naked eye even at long wavelengths.

Figure 14 (A) is a vertical cross-sectional view of the image display device 1 of the present invention, in which an image light control sheet 334 is disposed on the image light output surface of a liquid crystal panel 335. The image light control sheet 334 is configured by alternately arranging light-transmitting portions 336 and light-absorbing portions 337, and is adhesively fixed to the image light output surface of the liquid crystal panel 335 by an adhesive layer 338.

Furthermore, as mentioned above, when a 7-inch WUXGA (1920 x 1200 pixels) LCD panel is used as the image display device 1, even if one pixel (one triplet) (the length of the double-headed arrow A shown in Figure 14(A)) is approximately 80 μm, the pitch B of the image light control sheet 334, consisting of a 300 μm transmissive portion d2 and a 40 μm light-absorbing portion d1, needs to be 340 μm. This configuration ensures sufficient transmittance and controls the diffusion characteristics of the image light from the image display device, which causes abnormal light, thereby reducing ghost images that appear on both sides of the spatially floating image. Furthermore, in this case, making the thickness of the image control sheet at least two-thirds of the pitch B significantly improves ghost reduction.

Figure 14 (B) is a vertical cross-sectional view of a retroreflective member of the present invention in which an image light control sheet 334 is disposed on the image light exit surface of the retroreflective member 5. The image light control sheet 334 is configured by alternatingly arranging light-transmitting portions 336 and light-absorbing portions 337, and is inclined at an inclination angle θ1 to match the exit direction of the retroreflected light. As a result, the abnormal light generated by the retroreflection described above is absorbed, while allowing the normally reflected light to pass through without loss.

When using a 7-inch WUXGA (1920 x 1200 pixels) LCD panel, even if one pixel (one triplet) (the length of the double-headed arrow A in Figure 14(A)) is approximately 80 μm, if the pitch B of the retroreflective part is 420 μm, for example, with a 400 μm transmissive portion d2 and a 20 μm light-absorbing portion d1, sufficient transmission characteristics are achieved, and the diffusion characteristics of the image light from the image display device, which causes abnormal light to be generated in the retroreflective member, are controlled, reducing ghost images that appear on both sides of the floating image.

The above-mentioned image light control sheet 334 also prevents external light from entering the interior of the spatial floating image display device, thereby improving the reliability of the components. A suitable example of this image light control sheet is Shin-Etsu Polymer Co., Ltd.'s viewing angle control film (VCF), which has a sandwich structure in which transparent silicone and black silicone are alternately arranged with synthetic resin placed on the light entrance and exit surfaces, so it can be expected to have the same effect as the external light control film of this example.

<LCD panel performance>
Incidentally, in a typical TFT (Thin Film Transistor) liquid crystal panel, the brightness and contrast performance differ depending on the light output direction due to the mutual characteristics of the liquid crystal and polarizer. In an evaluation in the measurement environment shown in Figure 31, the brightness and viewing angle characteristics in the short side (up and down) direction of the panel were superior at an angle slightly shifted (+5 degrees in this example) from the output angle perpendicular to the panel surface (output angle of 0 degrees), as shown in Figure 33. 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.

On the other hand, as shown in Figure 35, contrast performance in the short (up and down) direction of the panel is excellent in the range of -15 degrees to +15 degrees, and when combined with brightness characteristics, the best characteristics are obtained when used in the range of ±10 degrees with 5 degrees as the center.

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 32. 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.

Similarly, as shown in Figure 34, contrast performance in the longitudinal (left-right) direction of the panel is excellent in the range of -5 degrees to -10 degrees, and when combined with brightness characteristics, the best characteristics are obtained when used in a range of ±5 degrees with -5 degrees as the center. Therefore, the image quality and performance of the image display device 1 are improved by directing the light emitted from the liquid crystal panel from a direction that provides the best characteristics using the light beam direction conversion means (reflecting surfaces 307, 314, etc.) provided on the light guide of the light source device 13 described above, and modulating the light using a video signal.

In order to make the most of the brightness and contrast characteristics of the LCD panel as an image display element, the image quality of the floating images can be improved by setting the incident light from the light source to the LCD panel within the range described above.

<Light Source Light Control Method>
In this embodiment, in order to improve the utilization efficiency of the light beam emitted from the light source device 13 and significantly reduce power consumption, in the image display device 1 comprising the light source device 13 and the liquid crystal display panel 11, the light source device 13 enters the liquid crystal panel 11 at an incident angle that maximizes the characteristics of the liquid crystal panel 11, and then emits image light beams that have been brightness-modulated in accordance with the image signal toward the retroreflective member. At this time, in order to reduce the set volume of the spatial floating image information display system, it is desired to increase the degree of freedom in the arrangement of the liquid crystal panel 11 and the retroreflective member. Furthermore, in order to form the floating image at a desired position after retroreflection and ensure optimal directionality, the following technical means are used.

A transparent sheet made of optical components such as a linear Fresnel lens, as shown in Figures 10 and 12, is provided on the image display surface of the liquid crystal panel 11 as a light direction conversion panel. This controls the output direction of the incident light beam on the retroreflective optical element while providing high directivity, thereby determining the imaging position of the floating image in space. With this configuration, the image light from the image display device 1 reaches the observer efficiently with high directivity (straightness) like laser light, resulting in the display of high-quality floating images at high resolution while also significantly reducing the power consumption of the image display device 1, including the light source device 13.

<Example 1 of video display device>
Fig. 24 shows another example of the specific configuration of the image display device 1. The light source device 13 in Fig. 24 is similar to the light source device in Fig. 25 etc. This light source device 13 is configured by housing LEDs, a collimator, a composite diffusion block, a light guide, etc. in a case made of, for example, plastic, and has a liquid crystal display panel 11 attached to its upper surface. An LED board on which LED (Light Emitting Diode) elements 14a and 14b, which are semiconductor light sources, and their control circuits are mounted are attached to one side of the case of the light source device 13, and a heat sink (not shown), which is a member for cooling heat generated by the LED elements and the control circuit, is attached to the outer surface of the LED board.

The LCD panel frame attached to the top surface of the case contains the LCD panel 11 attached to the frame, as well as an FPC (Flexible Printed Circuit) (not shown) electrically connected to the LCD panel 11. In other words, the LCD panel 11, which is a liquid crystal display element, generates a display image by modulating the intensity of transmitted light together with the LED elements 14a and 14b, which are solid-state light sources, based on control signals from a control circuit (not shown) that constitutes the electronic device.

<Example 1 of Light Source Device of Example 1 of Image Display Device>
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 Figs. 23, 25(a) and 25(b). Figs. 23 and 24 show LEDs 14a and 14b constituting the light source, which are attached at predetermined positions relative to the collimator 15. Each collimator 15 is formed of a light-transmitting resin, such as acrylic. As shown in Fig. 22(b), the collimator 15 has a conical convex outer surface 156 obtained by rotating a parabolic cross section, and a recess 153 with a convex portion (i.e., a convex lens surface) 157 formed in the center of its apex (the side in contact with the LED substrate).

The center of the flat surface of the collimator 15 (the side opposite the apex) has a convex lens surface 154 that protrudes outward (or it may be a concave lens surface that is recessed inward). The parabolic surface 156 that forms the conical outer surface of the 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 within it, or a reflective surface is formed.

LEDs 14a and 14b are each arranged at a predetermined position on the surface of the circuit board, substrate 102. This substrate 102 is positioned and fixed to the collimator 15 so that LED 14a or 14b on its surface is located in the center of its recess 153.

With this configuration, the collimator 15 described above focuses the light emitted from LED 14a or 14b, particularly the light emitted upward from the center (toward the right in the figure), by the two convex lens surfaces 157, 154 that form the outer shape of the collimator 15, to form parallel light. Light emitted from other areas toward the periphery is reflected by the parabolic surface that forms the conical outer surface of the collimator 15, and similarly focuses and forms parallel light. In other words, a collimator 15 with a convex lens in its center and a parabolic surface around its periphery makes it possible to extract almost all of the light generated by LED 14a or 14b as parallel light, thereby improving the utilization efficiency of the generated light.

A polarization conversion element 21 is provided on the light exit side of the collimator 15. The polarization conversion element 21 may also be referred to as a polarization conversion member. As is clear from Figure 24(a), this polarization conversion element 21 is configured by combining a cylindrical light-transmitting member with a parallelogram cross section (hereinafter referred to as a parallelogram prism) and a cylindrical light-transmitting member with a triangular cross section (hereinafter referred to as a triangular prism), and these are arranged in an array parallel to a plane perpendicular to the optical axis of the collimated light from the collimator 15. Furthermore, polarizing beam splitters (hereinafter referred to as "PBS films") 211 and reflective films 212 are alternately provided at the interfaces between adjacent light-transmitting members arranged in the array. In addition, a λ/2 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.

The exit surface of this polarization conversion element 21 is further provided with a rectangular composite diffusion block 16, also shown in Figure 24(a). That is, the light emitted from LED 14a or 14b is converted into parallel light by the action of the collimator 15 and enters the composite diffusion block 16. After being diffused by the texture 161 on the exit side, the light reaches the light guide 17.

The light guide 17 is a rod-shaped member made of a translucent resin such as acrylic and having a roughly triangular cross section (see Figure 24(b)). As is clear from Figure 25, it comprises a light guide light incident portion (surface) 171 that faces the exit surface of the composite diffusion block 16 via a first diffuser plate 18a, a light guide light reflecting portion (surface) 172 that forms a slope, and a light guide light exit portion (surface) 173 that faces the liquid crystal display panel 11, which is a liquid crystal display element, via a second diffuser plate 18b.

As shown in Figure 23, which is an enlarged partial view, the light guide light reflecting portion (surface) 172 of this light guide 17 has a sawtooth pattern with numerous alternating reflecting surfaces 172a and connecting surfaces 172b. The reflecting surfaces 172a (the line segments sloping upward to the right in the figure) form an angle αn (n is a natural number, for example, 1 to 130 in this example) with respect to 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 degrees or greater).

The light guide entrance surface (surface) 171 is formed in a curved convex shape inclined toward the light source. As a result, parallel light from the exit surface of the composite diffusion block 16 is diffused and incident via the first diffuser plate 18a. As is clear from the figure, the light is slightly bent (deflected) upward by the light guide entrance surface (surface) 171 before reaching the light guide light reflection surface (surface) 172, where it is reflected and reaches the liquid crystal display panel 11 provided on the exit surface at the top of the figure.

The image display device 1 described above in detail not only improves light utilization efficiency and uniform illumination characteristics, but also enables compact, low-cost manufacturing, including of a modularized S-polarized light source device. While the above description describes the polarization conversion element 21 as being attached after the collimator 15, the present invention is not limited to this, and similar effects can be achieved by locating it in the optical path leading to the liquid crystal display panel 11.

The light guide light reflecting portion (surface) 172 has multiple reflective surfaces 172a and connecting surfaces 172b arranged alternately in a sawtooth pattern. The illumination light beam is totally reflected by each reflective surface 172a and directed upward. The light guide light exiting portion (surface) 173 is equipped with a narrow-angle diffuser to convert the light beam into a substantially parallel diffused beam, which then enters the light redirecting panel 54, which adjusts the directional characteristics, and then enters the LCD panel 11 at an angle. The light exiting the image display device 1 has its direction controlled by the light redirecting panel 54 mounted on the top surface of the light source device 13. As a result, the light exiting the LCD panel 11 is also controlled, thereby controlling the light diffusion direction of the spatially floating image produced by the spatially floating image information system using the image display device 1. In this embodiment, the light redirecting panel 54 is mounted between the light guide exiting surface 173 and the LCD panel 11, but similar effects can be achieved by mounting it on the exiting surface of the LCD panel 11.

In a typical TV device, the light emitted from the liquid crystal 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 Figure 30(A)) and the vertical direction of the screen (the display direction corresponding to the Y-axis of the graph in Figure 30(B)), as shown, for example, in the plot curves of "Conventional characteristics (X direction)" in Figure 30(A) and "Conventional characteristics (Y direction)" in Figure 30(B).

In contrast, the diffusion characteristics of the light beam emitted from the liquid crystal display panel of this embodiment are as shown, for example, in the plot curves of "Example 1 (X direction)" in Figure 30(A) and "Example 1 (Y direction)" in Figure 30(B).

In one specific example, if the viewing angle at which the brightness is 50% (brightness reduced to about half) of the brightness when viewed from the front (angle of 0 degrees) is set to 13 degrees, this is approximately 1/5 of the diffusion characteristics of a typical home TV (angle of 62 degrees). Similarly, in one example where the vertical viewing angles are set unevenly between the top and bottom, the reflection angle of the reflective light guide and the area of the reflective surface are optimized so that the upper viewing angle is kept (narrowed) to about 1/3 of the lower viewing angle.

By setting the viewing angle and other settings as described above, the amount of light in the image directed toward the user's viewing direction increases dramatically (significantly improving image brightness) compared to conventional LCD TVs, resulting in an image that is more than 50 times brighter.

Furthermore, when the viewing angle characteristics shown in "Example 2" in Figure 30 are used, if the viewing angle at which the brightness of the image obtained when viewed from the front (angle of 0 degrees) is 50% (brightness reduced to approximately half) is set to 5 degrees, this results in an angle (narrow viewing angle) that is approximately 1/12 of the diffusion characteristics (angle of 62 degrees) of a typical home TV device. Similarly, in an example where the vertical viewing angle is set equally on the top and bottom, the reflection angle and the area of the reflective surface of the reflective light guide are optimized so that the vertical viewing angle is reduced (narrowed) to approximately 1/12 of the conventional value.

By making 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 compared to conventional LCD TVs, with the brightness of such images being more than 100 times greater.

As described above, by setting the viewing angle to a narrow angle, the amount of luminous flux directed in the viewing direction can be concentrated, significantly improving light utilization efficiency. As a result, even when using a liquid crystal display panel for general TV applications, adjusting the light diffusion characteristics of the light source device makes it possible to achieve a significant improvement in brightness with similar power consumption, resulting in a video display device that is compatible with information display systems facing bright outdoor environments.

When using a large LCD display panel, the overall brightness of the screen can be improved by directing the light from the periphery of the screen inward so that it is directed toward the viewer when facing the center of the screen. Figure 27 shows the convergence angle between the long and short sides of the LCD display panel when the distance L from the LCD display panel to the viewer and the panel size of the image display device (screen ratio 16:10) are used as parameters. The upper diagram assumes that the image is viewed with the LCD display panel screen in portrait orientation (hereinafter also referred to as "portrait viewing"). In this case, the convergence angle can be set to match the short side of the LCD display panel (see arrow V in Figure 27 as appropriate).

As a more specific example, as shown in the plot graph in Figure 27, when a 22" panel is used vertically and the viewing distance is 0.8 m, by setting the convergence angle to 10 degrees, image light from each corner (four corners) of the screen can be effectively projected or output toward the viewer.

Similarly, when viewing a 15" panel in portrait orientation, a convergence angle of 7 degrees will allow image light from the four corners of the screen to be effectively directed toward the viewer at a viewing distance of 0.8 m. As described above, depending on the size of the LCD display panel and whether it is used portrait or landscape, image light from the periphery of the screen can be directed toward the viewer who is in the optimal position to view the center of the screen, improving the overall brightness of the screen.

As shown in Figure 30 above, the basic configuration involves a light source device directing a light beam with a narrow angle of directionality to the liquid crystal display panel 11, which is then luminance-modulated in accordance with the video signal. The video information displayed on the screen of the liquid crystal display panel 11 is then reflected by the retroreflective member, and the resulting floating image is displayed indoors or outdoors via the transparent member 100.

The following describes several other examples of light source devices. Any of these other examples of light source devices may be used in place of the light source device in the example of the image display device described above.

As mentioned above, when using a large LCD display panel, the light from the periphery of the screen can be directed inward toward the viewer when facing the center of the screen, improving the overall brightness of the screen. However, binocular parallax occurs depending on whether the viewer uses their left or right eye to view the image. Figure 28 shows the convergence angle between the long and short sides of the LCD display panel, calculated based on the positions of the left and right eyes, when the distance L from the LCD display panel to the viewer and the panel size of the video display device (screen ratio 16:10) are used as parameters.

The smaller the panel size and the closer the monitoring distance, the larger the convergence angle when viewing binocularly with both eyes. When using a small panel of 7 inches or less, the convergence angle due to binocular parallax is an important requirement. Therefore, for panels of 7 inches or less, for example, the light diffusion characteristics of the light source shown in Figure 30 should be expanded or given directional characteristics so that the image light is directed toward the system's optimal monitoring range.

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

<Example 1 of Light Source Device>
Next, another example of a light source device will be described with reference to Fig. 19. Figs. 19(a) and (b) are diagrams in which the liquid crystal display panel 11 and the diffuser plate 206 are partially omitted in order to explain the light guide 311.

Figure 19 shows the LEDs 14 that make up the light source mounted on the substrate 102. The LEDs 14 and substrate 102 are attached to a predetermined position relative to the reflector 15.

As shown in Figure 19(a), the LEDs 14 are arranged in a row parallel to the side of the liquid crystal display panel 11 on which the reflector 300 is arranged (in this example, the short side). In the example shown, the reflector 300 is arranged in correspondence with the arrangement of the LEDs. Note that multiple reflectors 300 may be arranged.

In one specific example, the reflectors 300 are each made of a plastic material. As another example, the reflectors 300 may be made of a metal or glass material, but because plastic materials are easier to mold, plastic materials are used in this example.

As shown in Figure 19(b), the inner surface of reflector 300 (the right side in the figure) has a reflective surface 305 (hereinafter sometimes referred to as a "paraboloid") shaped like a paraboloid cut at its meridian plane. Reflector 300 converts the divergent light emitted from LED 14 into approximately parallel light by reflecting it off reflective surface 305 (paraboloid), and directs the converted light to be incident on the end face of light guide 311. In one specific example, light guide 311 is a transmissive light guide.

The reflective surface of reflector 300 has an asymmetric shape with respect to the optical axis of the light emitted by LED 14. Furthermore, as mentioned above, reflective surface 305 of reflector 300 is a parabolic surface, and by placing the LED at the focus of this parabolic surface, the reflected light beam is converted into approximately parallel light.

Since the LED 14 is a surface light source, even if it is placed at the focus of a parabolic surface, the divergent light from the LED 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 reflector 300 form a pair. Furthermore, to ensure the specified performance when the LED 14 is attached to the substrate 102 with an accuracy of ±40 μm, the number of LEDs attached to the substrate should be limited to a maximum of 10 or less, and considering mass productivity, it is best to limit it to around 5.

Although the LED 14 and reflector 300 are close to each other in some areas, heat can be dissipated into the space on the opening side of the reflector 300, reducing the temperature rise of the LED. 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 more than 10 times compared to reflectors made of glass material, thereby improving light utilization efficiency.

Meanwhile, a reflective surface is provided on the bottom surface 303 of the light guide 311, and light from the LED 14 is converted into a parallel beam by the reflector 300, reflected by the reflective surface, and emitted toward the liquid crystal display panel 11 arranged opposite the light guide 311. As shown in Figure 19, the reflective surface provided on the bottom surface 303 may have multiple surfaces with different inclinations in the direction of travel of the parallel beam from the reflector 300. Each of the multiple surfaces with different inclinations may have a shape that extends in a direction perpendicular to the direction of travel of the parallel beam from the reflector 300.

The reflective surface on the bottom surface 303 may also be flat. In this case, the refractive surface 314 on the surface of the light guide 311 facing the liquid crystal display panel 11 refracts the light reflected by the reflective surface on the bottom surface 303 of the light guide 311, making it possible to adjust with high precision the amount of light and emission direction of the light beam heading toward the liquid crystal display panel 11. As a result, the amount and emission direction of light incident on and emitted from the liquid crystal display panel 11 can also be controlled with high precision, so in a spatial video information display system that uses an image display device that employs this light source, the diffusion direction and diffusion angle of the image light of the spatially floating image can be set to desired values.

As shown in Figures 19(a) and 19(b), the refractive surface 314 may have multiple surfaces with different inclinations in the direction of travel of the parallel light beam from the reflector 300. Each of the multiple surfaces with different inclinations may have a shape that extends in a direction perpendicular to the direction of travel of the parallel light beam from the reflector 300. The inclinations of the multiple surfaces refract light reflected by the reflective surface provided on the bottom surface 303 of the light guide 311 toward the liquid crystal display panel 11. The refractive surface 314 may also be a transmissive surface.

If a diffuser plate 206 is present in front of the LCD panel 11, the light reflected by the reflective surface is refracted toward the diffuser plate 206 due to the multiple inclinations of the refracting surface 314. In other words, the extension direction of the multiple surfaces with different inclinations of the refracting surface 314 is parallel to the extension direction of the multiple surfaces with different inclinations of the reflective surface provided on the bottom surface 303. By making the extension directions of both parallel, the angle of the light can be adjusted more appropriately. On the other hand, the LEDs 14 are soldered to the metallic substrate 102. This allows heat generated by the LEDs to be dissipated into the air via the substrate.

The reflector 300 may be in contact with the substrate 102, or a space may be left between them. If a space is left between them, the reflector 300 is attached to the housing. Leaving a space between them allows heat generated by the LED to be dissipated into the air, improving the cooling effect. As a result, the operating temperature of the LED can be reduced, maintaining luminous efficiency and extending its lifespan.

<Another example 2 of light source device>
Next, the configuration of an optical system relating to a light source device in which the light utilization efficiency is improved by 1.8 times by using polarization conversion compared to the light source device shown in Fig. 19 will be described in detail with reference to Fig. 20A, Fig. 20B, Fig. 20C, and Fig. 20D. Note that the sub-reflector 308 is not shown in Fig. 20A.

Figures 20, 20B, and 20C show the LEDs 14 that make up the light source mounted on the substrate 102, with the reflector 300 and LEDs 14 forming a pair of blocks, and the unit 312 having multiple blocks.

Of these, the base material 320 shown in Figure 20A (2) is the base material of the substrate 102. Generally, metallic substrates 102 generate heat, so in order to insulate (thermally insulate) the heat of the substrate 102, it is advisable to use a plastic material or the like for the base material 320. The material and shape of the reflective surface of the reflector 300 may be the same as those in the example of the light source device in Figure 28.

The reflective surface of reflector 300 may also have an asymmetric shape with respect to the optical axis of the light emitted from LED 14. The reason for this will be explained with reference to Figure 20A (2). In this embodiment, as with the example in Figure 19, the reflective surface of reflector 300 is a parabolic surface, and the center of the light-emitting surface of the LED, which is a surface light source, is located at the focal position of the parabolic surface.

Furthermore, due to the characteristics of the parabolic surface, the light emitted from the four corners of the light-emitting surface also becomes approximately parallel light beams; only the direction of emission differs. Therefore, even if the light-emitting section has an area, the amount of light incident on the polarization conversion element 21 and its conversion efficiency are hardly affected as long as the distance between the polarization conversion element and the reflector 300 located downstream is short.

In addition, for the reasons described above, an optical system can be realized that can reduce the decrease in light conversion efficiency even if the mounting position of the LED 14 is shifted in the XY plane relative to the focal point of the corresponding reflector 300. Furthermore, even if the mounting position of the LED 14 varies in the Z-axis direction, the converted parallel light beam simply moves in the ZX plane, significantly reducing the mounting precision required for the LED, which is a surface light source. In this embodiment, a reflector 300 is described that has a reflective surface formed by meridionally cutting out a portion of a paraboloid, but the LED may also be placed in a portion of the cutout, with the entire paraboloid as the reflective surface.

On the other hand, in this embodiment, as shown in Figures 20B(1) and 20C, the divergent light from the LED 14 is reflected by the parabolic surface 321 and converted into approximately parallel light, which is then incident on the end face of the polarization conversion element 21 in the subsequent stage 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 higher than the example in Figure 26 described above, realizing a highly efficient light source.

Note that the approximately parallel light resulting from the reflection of the divergent light from the LED 14 by the parabolic surface 321 is not all uniform. Therefore, by adjusting the angular distribution of the reflected light using the multiple inclined reflecting surfaces 307, the light can be directed toward the liquid crystal display panel 11 and incident perpendicularly to the liquid crystal display panel 11.

In the example shown in this diagram, the direction of light (principal rays) entering the reflector from the LED is approximately parallel to the direction of light entering the LCD panel. This arrangement is easy to design, and placing the heat source below the light source device is preferable because it allows air to escape upwards, reducing the temperature rise of the LED.

Furthermore, as shown in Figure 20B (1), in order to improve the capture rate of 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 309 located above the reflector, and is reflected by the slope of the lower sub-reflector 310, and is incident on the effective area of the subsequent polarization conversion element 21, further improving the light utilization efficiency. That is, in this embodiment, a portion 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 310 in a direction toward the light guide 306.

The approximately parallel light beam, aligned to a specific polarization by the polarization conversion element 21, is reflected by the reflective shape provided on the surface of the reflective light guide 306 toward the liquid crystal display panel 11, which is positioned opposite the light guide 306. At this time, the light intensity distribution of the light beam incident on the liquid crystal display panel 11 is optimally designed by the shape and arrangement of the reflector 300 described above, and the reflective surface shape (cross-sectional shape) of the reflective light guide, as well as the inclination and surface roughness of the reflective surface.

The reflective surface shape on the surface of the light guide 306 is such that multiple reflective surfaces are arranged opposite the exit surface of the polarization conversion element, and the inclination, area, height, and pitch of the reflective surfaces are optimized according to the distance from the polarization conversion element 21, thereby achieving the desired light intensity distribution of the light beam incident on the liquid crystal display panel 11, as described above.

As shown in Figure 20B (2), the reflective surface 307 on the reflective light guide can be configured with multiple inclinations on a single surface, allowing for more precise adjustment of reflected light. Note that a reflective surface with multiple inclinations on a single surface may have multiple surfaces, a polyhedral surface, or a curved surface. Furthermore, the diffusing action of the diffuser 206 achieves a more uniform light intensity distribution. Light incident on the diffuser plate closer to the LED achieves a more uniform light intensity distribution by changing the inclination of the reflective surface. As a result, the amount and direction of the light beam directed toward the liquid crystal display panel 11 can be adjusted with high precision. As a result, the amount and direction of light incident on and emitted from the liquid crystal display panel 11 can also be controlled with high precision. Therefore, in a spatial video information display system using an image display device with this light source, the diffusion direction and diffusion angle of the image light for a floating image can be set to desired values.

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

In this embodiment, the LED 14 and reflector 300 are also partially adjacent to each other, but heat can be dissipated into the space on the opening side of the reflector 300, reducing the temperature rise of the LED. Furthermore, the substrate 102 and reflector 300 may be arranged upside down compared to Figures 20A, 20B, and 20C.

However, if the substrate 102 is placed on top, it will be close to the liquid crystal display panel 11, which may make the layout difficult. Therefore, as shown in the figure, placing the substrate 102 below the reflector 300 (the side farther from the liquid crystal display panel 11) will simplify the internal configuration of the device.

A light-shielding plate 410 may be provided on the light-incident surface of the polarization conversion element 21 to prevent unnecessary light from entering the subsequent optical system. This configuration makes it possible to realize a light source device that suppresses temperature rise. The polarizer provided on the light-incident surface of the liquid crystal display panel 11 reduces temperature rise by absorbing the uniformly polarized light beam of the present invention, but when reflected by the reflective light guide, the polarization direction rotates and some of the light is absorbed by the incident-side polarizer. Furthermore, the temperature of the liquid crystal 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 sufficient space between the reflective surface of the reflective light guide 306 and the liquid crystal display panel 11, allowing for natural cooling.

Figure 20D is a modified example of the light source device of Figures 20B(1) and 20C. Figure 20D(1) illustrates a modified example of a portion of the light source device of Figure 20B(1). The rest of the configuration is the same as the light source device described above in Figure 20B(1), so illustrations and repeated explanations will be omitted.

First, in the example shown in Figure 20D (1), the height of the recess 319 of the sub-reflector 310 is adjusted to be lower than the phosphor 114 so that the chief ray of fluorescence output laterally (in the X-axis direction) from the phosphor 114 (see the straight line extending parallel to the X-axis in Figure 20D (1)) can exit through the recess 319 of the sub-reflector 310. Furthermore, 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 chief ray of fluorescence output laterally from the phosphor 114 is not blocked by the light-shielding plate 410 and enters the effective area of the polarization conversion element 21.

In addition, the reflective surface of the convex portion of the uneven top of the sub-reflector 310 reflects the light reflected by the sub-reflector 308 in order to guide the light reflected by the sub-reflector 308 to the light guide 306. Therefore, the height of the convex portion 318 of the sub-reflector 310 can be adjusted so that the light reflected by the sub-reflector 308 is reflected and incident on the effective area of the subsequent polarization conversion element 21, thereby further improving the light utilization efficiency.

As shown in Figure 20A (2), the sub-reflector 310 is arranged to extend in one direction and has an uneven shape. Furthermore, the top of the sub-reflector 310 has unevenness with one or more recesses periodically arranged in one direction. By using such an uneven shape, it is possible to configure the main ray of fluorescence output laterally from the phosphor 114 to enter the effective area of the polarization conversion element 21.

The uneven shape of the sub-reflector 310 is periodically arranged at a pitch such that the recesses 319 are located at the positions where the LEDs 14 are located. In other words, each phosphor 114 is periodically arranged in one direction corresponding to the pitch of the recesses in the uneven shape of the sub-reflector 310. Note that when the phosphor 114 is provided on the LED 14, the phosphor 114 may also be expressed as the light-emitting portion of the light source.

Figure 20D (2) also illustrates a modified version of a portion of the light source device in Figure 20C. The remaining configuration is the same as that of the light source device in Figure 20C, so illustration and repeated explanation will be omitted. As shown in Figure 20D (2), the sub-reflector 310 is not necessary, but as in Figure 20D (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 chief ray of fluorescence output laterally from the phosphor 114 is not blocked by the light-shielding plate 410 and enters the effective area of the polarization conversion element 21.

In addition, as shown in Figure 20A (1), for the light source devices of Figures 20A, 20B, 20C, and 20D, side walls 400 may be provided to prevent dust from entering the space between the reflective surface of the reflective light guide 306 and the liquid crystal display panel 11, to prevent stray light from being generated outside the light source device, and to prevent stray light from entering from outside the light source device. If side walls 400 are provided, they are positioned so as to sandwich the space between the light guide 306 and the diffuser plate 206.

The light exit surface of the polarization conversion element 21, which emits light polarized by the polarization conversion element 21, faces the space surrounded by the side wall 400, the light guide 306, the diffuser plate 206, and the polarization conversion element 21. Furthermore, a reflective surface having a reflective film or the like is used for the inner surface of the side wall 400 that laterally covers the space into which light is output from the exit surface of the polarization conversion element 21 (the space to the right of the exit surface of the polarization conversion element 21 in Figure 20B (1)). 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 this 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, thereby improving the brightness of the light source device.

Of the inner surfaces of the sidewall 400, the surface that covers the side of the polarization conversion element 21 is made to have low light reflectivity (such as a black surface without a reflective film). This is because if light is reflected from the side of the polarization conversion element 21, light with an unexpected polarization state will be generated, causing stray light. In other words, by making these surfaces have low light reflectivity, it is possible to prevent or suppress the occurrence of stray light in the image and light with an unexpected polarization state. In addition, the sidewall 400 may be configured with holes to allow air to pass through in some parts to improve the cooling effect.

Note that the light source devices in Figures 20A, 20B, 20C, and 20D have been described assuming a configuration that uses a polarization conversion element 21. However, these light source devices may be configured without the polarization conversion element 21. In this case, a light source device can be provided at a lower cost.

<Another example 3 of light source device>
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 21A (1), (2), (3) and Figure 21B.

Figure 21A shows the LEDs 14 that make up the light source mounted on the substrate 102, with the collimator 18 and LEDs 14 forming a pair of blocks, forming a unit 328 with multiple blocks. Because the collimator 18 in this embodiment is located close to the LEDs 14, a glass material is used for heat resistance. The shape of the collimator 18 is similar to that described for the collimator 15 in Figure 20. Furthermore, by providing a light shielding plate 317 before the light enters the polarization conversion element 21, unwanted light is prevented or suppressed from entering the optical system in the subsequent stage, reducing the temperature rise caused by the unwanted light.

The other configurations and effects of the light source shown in Figure 21A are the same as those in Figures 20A, 20B, 20C, and 20D, so repeated explanations will be omitted. The light source device in Figure 21A may be provided with side walls, as explained in Figures 20A, 20B, and 20C. The configurations and effects of the side walls have already been explained, so repeated explanations will be omitted.

Figure 21B is a cross-sectional view of Figure 21A (2). The configuration of the light source shown in Figure 21B is common to part of the structure of the light source in Figure 20, and has already been explained in Figure 18, so repeated explanation will be omitted.

<Another example 4 of light source device>
Next, the light source device of Fig. 25 is configured with a unit 328 having a plurality of blocks, each of which is a pair of the collimator 18 and LED 14 used in the light source device shown in Fig. 21. The configuration of the optical system relating to the light source device using LEDs and reflective light guides 504 arranged at both ends of the back surface of the liquid crystal display panel 11 will be described in detail with reference to Figs. 25(a), (b), and (c).

Figure 25 shows the LEDs 14 that make up the light source mounted on a substrate 505, which are configured as units 503 having multiple blocks, each paired with a collimator 18 and an LED 14. The units 503 are arranged at both ends of the rear surface of the liquid crystal display panel 11 (in this embodiment, three units are arranged side by side in the short side direction). Light output from the units 503 is reflected by the reflective light guide 504 and enters the liquid crystal display panel 11 (shown in Figure 25(c)) arranged opposite.

As shown in Figure 25(c), the reflective light guide 504 is divided into two blocks corresponding to the units located at each end, and is positioned so that the central part is the highest. Because the collimator 18 is located close to the LED 14, a glass material is used to ensure heat resistance to the heat emitted by the LED 14. The shape of the collimator 18 is the same as that described for the collimator 15 in Figure 20.

Light from the LED 14 enters the polarization conversion element 501 via the collimator 18. The shape of the optical element 81 is configured to adjust the distribution of light entering the subsequent reflective light guide 504. In other words, the light intensity distribution of the light beam entering the LCD panel 11 is optimally designed by adjusting the shape and position of the collimator 18 described above, the shape of the optical element 81, the diffusion characteristics, the shape (cross-sectional shape) of the reflective surface of the reflective light guide, the inclination of the reflective surface, and the surface roughness of the reflective surface.

As shown in Figure 25(b), the reflective surface shape on the surface of the reflective light guide 504 is such that multiple reflective surfaces are arranged opposite the exit surface of the polarization conversion element 21, and the inclination, area, height, and pitch of the reflective surfaces are optimized according to the distance from the polarization conversion element 21. Furthermore, by dividing the area of the same reflective surface (i.e., the surface facing the polarization conversion element) into a polyhedron, the light intensity distribution of the light beam incident on the liquid crystal display panel 11 can be adjusted (optimized) to a desired value, as described above. This allows the light intensity and exit direction of the light beam toward the liquid crystal display panel 11 to be adjusted with high precision. As a result, the light intensity and exit direction of the light incident on and exiting the liquid crystal display panel 11 can also be controlled with high precision. Therefore, in a spatial video information display system using an image display device that uses this light source, the diffusion direction and diffusion angle of the image light of the spatially floating image can be set to desired values (see the four solid arrows indicating "reflected light from the light guide" in Figure 26).

The reflective surface of the reflective light guide, like the reflective light guide described in Figure 20B, can be configured such that one surface (the area that reflects light) has a shape with multiple inclinations (in the example of Figure 25, the XY plane is divided into 14 sections with different inclinations), allowing for more precise adjustment of the reflected light. Furthermore, by providing a light-shielding wall 507 to prevent reflected light from the reflective light guide from leaking out the side of the light source device 13, it is possible to prevent light from leaking in any direction other than the desired direction (towards the liquid crystal display panel 11).

Furthermore, the units 503 arranged on the left and right sides of the reflective light guide 504 in Figure 25 may be replaced with the light source device in Figure 20. In other words, a configuration may be adopted in which multiple light source devices (substrate 102, reflector 300, LED 14, etc.) in Figure 20 are prepared and these multiple light source devices are arranged in positions facing each other, as shown in Figures 25(a), (b), and (c).

Figure 26(B) shows a light source device configured with six units 503 shown in Figure 26(A) arranged on the top and six on the bottom. The light source device shown in Figure 26(B) is configured as described above, with units 503, each with five LEDs arranged horizontally, and the desired brightness is achieved by current control using a single power supply. Therefore, as a light source device for illuminating an LCD panel, the light source brightness can be controlled for each area illuminated by each unit 503. The configuration shown in Figure 26 includes a reflective surface 222 and a reflective surface 502 that is different from the reflective surface 222. Of these, the reflective surface 222 has a horizontal lattice-like shape or a strip-like shape with a predetermined width. On the other hand, the reflective surface 502 has a vertical and horizontal lattice-like shape. By optimally designing the shape of these fine lattices and the inclination of the dividing surfaces, the desired output light distribution (output direction and diffusion characteristics of the output light) can be achieved. As a result, even when a single light source is used in the flat panel display and spatially floating image information device shown in Figures 16 and 17, the amount of light and emission direction of the light beam directed toward the liquid crystal display panel 11 can be adjusted with high precision. As a result, just like the two embodiments described above, the amount of light and emission direction of the light incident on the liquid crystal display panel 11 and the light emitted from the liquid crystal display panel 11 can be controlled with similar high precision, so in a spatial image information display system that uses an image display device that uses this light source, the diffusion direction and diffusion angle of the image light of the spatially floating image can be set to desired values.

Figure 22 is a cross-sectional view showing an example of the shape of the diffuser plate 206. As described above, the divergent light output from the LED is converted into approximately parallel light by the reflector 300 or collimator 18, converted into a specific polarization by the polarization conversion element 21, and then reflected by the light guide. The light beam reflected by the light guide then passes through the flat portion of the incident surface of the diffuser plate 206 and enters the liquid crystal display panel 11 (see the two solid arrows indicating "reflected light from the light guide" in Figure 22).

Furthermore, of the light emitted from the polarization conversion element 21, the divergent light beam is totally reflected by the slopes of the protrusions with inclined surfaces provided on the incident surface of the diffuser plate 206 and enters the liquid crystal display panel 11. In order to totally reflect the light emitted from the polarization conversion element 21 at the slopes of the protrusions of the diffuser plate 206, the angle of the slopes of the protrusions is changed based on the distance from the polarization conversion element 21. If the angle of the slope of the protrusions on the side farther from the polarization conversion element 21 or the LED is α, and the angle of the slope of the protrusions on the side closer to the polarization conversion element 21 or the LED is α', then α is smaller than α' (α < α'). By setting it in this way, it becomes possible to effectively utilize the polarization-converted light beam.

<Technology for controlling diffusion characteristics of video display devices>
One method for adjusting the diffusion distribution of the image light from the liquid crystal display panel 11 is to provide a lenticular lens between the light source device 13 and the liquid crystal display panel 11 or on the surface of the liquid crystal display panel 11 and optimize the shape of the lens. 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 luminous flux") emitted in one direction from the liquid crystal display panel 11.

Alternatively or additionally, a microlens array may be arranged in a matrix on the surface of the liquid crystal display panel 11 (or between the light source device 13 and the liquid crystal display panel 11), and the arrangement may be adjusted. In other words, 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 beam emitted from the image display device 1, thereby obtaining an image display device with the desired diffusion characteristics.

As a further configuration example, two lenticular lenses may be combined and placed at a position where the image light emitted from the image display device 1 passes, or a sheet may be provided in which a microlens array is arranged in a matrix to adjust the diffusion characteristics. By configuring the optical system in this way, the brightness (relative brightness) of the image light in the X-axis and Y-axis directions can be adjusted according to the reflection angle of the image light (reflection angle with vertical reflection as the reference (0 degrees)).

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 Figure 29(b). Specifically, in the plot curves of Example 1 (Y direction) and Example 2 (Y direction), the brightness characteristics in the vertical direction are made steeper, and further, by changing the balance of the directional characteristics in the up and down directions (positive and negative directions on the Y axis), it is possible to increase the brightness (relative brightness) of light due to reflection and diffusion.

For this reason, according to this embodiment, the image light has a narrow diffusion angle (high linearity) and contains only specific polarization components, like the image light from a surface-emitting laser image source, and can be adjusted to suppress the ghost images that occur in the retroreflective member when using image display devices based on conventional technology, and to efficiently deliver the spatially floating image caused by retroreflection to the viewer's eyes.

Furthermore, the light source device described above can provide significantly narrower angle directional characteristics in both the X-axis and Y-axis directions compared to the diffusion characteristics of light emitted from a typical liquid crystal display panel shown in Figures 30(A) and 30(B) (labeled "conventional characteristics" in the figures). In this embodiment, by providing such narrow angle directional characteristics, it is possible to realize an image display device that emits light of a specific polarization, emitting nearly parallel image light beams in a specific direction.

Figure 30 shows an example of the characteristics of the lenticular lens used in this embodiment. This example particularly shows the characteristics in the X direction (vertical direction) relative to the Z axis. Characteristic O shows a luminance characteristic that is symmetrical up and down, with the peak in the light emission direction at an angle of approximately 30 degrees above the vertical direction (0 degrees). Furthermore, the plot curves of characteristics A and B shown in the graph of Figure 30 show examples of characteristics in which the image light above the peak luminance is concentrated near 30 degrees, thereby increasing the luminance (relative luminance). Therefore, as can be seen by comparing Characteristics A and B with the plot curve of Characteristic O, the luminance (relative luminance) of light drops sharply in the region where the inclination (angle θ) from the Z axis to the X direction exceeds 30 degrees (θ > 30°).

In other words, with an optical system including the above-described lenticular lens, when the image light beam from the image display device 1 is incident on the retroreflective member, the emission angle and viewing angle of the image light aligned to a narrow angle by the light source device 13 can be adjusted, significantly improving the flexibility of retroreflective sheet installation. As a result, the flexibility of the relationship between the image position of the spatially floating image that is reflected or transmitted through the window glass and focused at the desired position can be greatly improved. As a result, it is possible to efficiently deliver light with a narrow diffusion angle (high linearity) and containing only specific polarization components to the eyes of an observer indoors or outdoors. As a result, even if the intensity (brightness) of the image light from the image display device 1 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 1, it is possible to realize an information display system with low power consumption.

<Structural example of retroreflective member>
FIG. 36 shows another configuration of the second retroreflective member 5 of the present invention. In the retroreflective member 50 of FIG. 36(A) or the retroreflective member 500 of FIG. 36(B), which are other examples of the second retroreflective member 5 of FIG. 2, the first light control panel 221 and the second light control panel 222 are formed by arranging optical elements 20 of a predetermined width or distance, each having a plurality of strip-shaped reflective portions perpendicular to one side of the flat plates 17 and 18. The first light control panel 221 and the second light control panel 222 are fixed to the transparent flat plates 17 and 18, which are disposed approximately perpendicular to the reflective portions of the optical elements 20. Here, the reflective portions of the optical elements 20 constituting the first light control panel 221 and the second light control panel 222 are arranged so as to intersect (orthogonal in this embodiment) in a planar view, and will hereinafter be referred to as a planar light reflective element 220. In this embodiment, the first light control panel 221 and the second light control panel 222 are bonded with an adhesive. The first light control panel 221 and the second light control panel 222 are adhered and fixed to the transparent flat plates 17 and 18. Although the transparent flat plates 17 and 18 are referred to as transparent flat plates in this specification, they are not limited to being transparent and may be non-transparent. The light control panels may also be referred to as light control members.

The first light control panel 221 will be described below. The first light control panel 221 has multiple optical elements 20 arranged in parallel, and a flat light reflecting section 220 provided on one surface of the optical elements 20. The flat light reflecting section 220 is generally formed by depositing a reflective film on the surface of the optical elements 20 using vapor deposition or sputtering techniques, and an easy-to-handle adhesive is used to secure them together. The first light control panel 221 and the transparent flat plate 17 are bonded and fixed with a UV-curable acrylic adhesive by irradiating UV rays from the transparent flat plate 17 side. Similarly, the second light control panel 222 has optical elements 20 arranged in parallel, and the optical elements 20 are bonded to each other. The second light control panel 222 is also bonded and fixed to the transparent flat plate 18. Experiments have shown that if a liquid such as water seeps into the end face of a retroreflective member 50 manufactured using the method described above, causing the adhesive surface to separate and creating an interface, allowing external light to enter the retroreflective member due to reflection at the adhesive/air interface in addition to the normal reflective surface, an observer will recognize this as an abnormal phenomenon and conclude that the member is faulty, due to the double reflective surface created by the interface.

To solve the above-mentioned problems, the inventors discovered that, as shown in Figure 36(A), a resin-based adhesive 217, which is normally used as an adhesive, can be applied to the joints on the end faces of the retroreflective member 50 to cover the exposed joints on the end faces, thereby preventing the penetration of moisture and other liquids. Even if the transparent flat plates 17, 18 are made of resin, silicone-based adhesives can expand and contract to accommodate changes in external dimensions due to expansion caused by temperature fluctuations or moisture absorption. This allows them to absorb changes in the shape of the transparent flat plates 17, 18, stably cover the joints, and prevent the penetration of liquids such as moisture. Furthermore, the resin-based adhesive 217 may be either transparent or opaque. Figure 36(A) uses a transparent resin-based adhesive 217, while the transparent resin-based adhesive 217 in this embodiment is an acrylic-modified silicone resin-based adhesive, such as Cemedine Super XG No. 777.

In addition to the edge treatment described above, it is also effective to prevent the intrusion of moisture and other liquids by adhering moisture-proof tape 218 to the edge of the retroreflective member 500, as shown in Figure 36 (B). Furthermore, if the edge is covered with the above-mentioned adhesive 217 and then moisture-proof tape 218 is adhered to it, creating a double-layered structure to prevent the intrusion of liquids such as moisture, an even more effective waterproofing effect can be achieved. Furthermore, the moisture-proof tape 218 may be either transparent or opaque; for example, Scotch Strong Waterproof Repair Tape BBT-50 is used. A spatial floating image information display system using the resulting retroreflective member can be realized as a system with excellent resistance to environmental changes.

<Method for manufacturing retroreflective member>
As described above, in the retroreflective member 50 or the retroreflective member 500, the optical members 20 of the respective light control members 221 and 222 are arranged in parallel and cross each other. Furthermore, the light control members 221 and 222 are fixed to the transparent flat plates 17 and 18 with an ultraviolet-curing adhesive.

Transparent flat plates 17 and 18 are generally made of plastic that does not contain UV absorbers (which absorb light of 400 nm or less) so that UV rays can pass through. However, in UV exposure tests conducted by the inventors, a problem occurred in which the plastic substrate reacted to UV rays and turned yellow. To address this problem, the transparent flat plate 17 placed on the side where external light enters is made of plastic that contains UV absorbers, and UV rays are irradiated from the opposite side of the transparent flat plate 17 to adhere the light control member 221 with a UV-curable adhesive. The other transparent flat plate 18 is made of plastic that does not contain UV absorbers, and the light control member 222 is adhered by irradiating UV rays from the direction of the transparent flat plate 18 and fixing it with a UV-curable adhesive.

As a result, the floating-in-space video information display system 2920 can also be applied to an outdoor vending machine 2900, as shown in Figure 37, which has a drink display section 2901, a bill slot 2902, a drink dispenser 2903, a change dispenser 2904, a coin dispenser 2905, etc.

In the example shown in Figure 37, for example, when selecting a product, concierge 2921 is displayed on the floating video information display system 2920, and a voice message is played saying, "Welcome. The screen will change to numeric buttons. Please select the product number you would like." Numeric buttons 2922 and decision button 2923 are then displayed, and when the product number is pressed using numeric buttons 2922 and decision button 2923 is pressed, the product with that product number is dispensed from the drink dispenser 2903, concierge 2921 is displayed again, and a voice message is played saying, for example, "Thank you. We look forward to seeing you again.", ending the process.

Above, various embodiments and examples (i.e., specific examples) to which the present invention is applied have been described in detail. However, the present invention is not limited to the above-described embodiments (specific examples) and includes various modifications. For example, the above-described embodiments are detailed descriptions of the entire system in order to clearly explain the present invention, and are not necessarily limited to systems that include all of the described configurations. Furthermore, it is possible to replace 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. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

The light source device described above is not limited to space-floating image display devices, but can also be applied to information display devices such as HUDs, tablets, digital signage, etc.

The technology according to this embodiment displays high-resolution, high-brightness floating images in a floating state, allowing users to operate the system without worrying about contact infection. Using the technology according to this embodiment in a system used by an unspecified number of users reduces the risk of contact infection and provides a contactless user interface that can be used without anxiety. The present invention, which provides such technology, contributes to "Good health and well-being" - one of the Sustainable Development Goals (SDGs) advocated by the United Nations.

Furthermore, the technology according to the above-described embodiment reduces the divergence angle of the emitted image light and aligns it with a specific polarization, thereby efficiently reflecting only the normal reflected light from the retroreflective material, resulting in high light utilization efficiency and enabling the production of bright, clear, floating images in space. The technology according to the present embodiment makes it possible to provide a highly usable non-contact user interface that can significantly reduce power consumption. The present invention, which provides such technology, contributes to the achievement of "9. Build resilient infrastructure, promote inclusive and sustainable industrialization, innovate and foster innovation" and "11. Make cities and towns inclusive and sustainable" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

Furthermore, the technology according to the above-described embodiment makes it possible to form floating images using highly directional (linear) video light. The technology according to this embodiment makes it possible to provide a non-contact user interface with low risk of people other than the user viewing the floating images, even when displaying images that require high security, such as those used in bank ATMs or train station ticket machines, or highly confidential images that should be kept secret from people directly facing the user, by displaying highly directional video light. By providing the above-described technology, the present invention contributes to "Sustainable Cities and Communities," one of the Sustainable Development Goals (SDGs) advocated by the United Nations.

1...image display device, 2...first retroreflective member, 5...second retroreflective member, 3...spatial image (space-floating image), 100...transmissive plate, 13...light source device, 54...light direction conversion panel, 105...linear Fresnel sheet, 101...absorptive polarizing sheet (absorptive polarizing plate), 200...flat display, 201...housing, 203...sensing system, 217...resin-based adhesive, 218...moisture-proof tape, 226...sensing area, 102...substrate, 11, 335...liquid crystal display panel, 206...diffuser, 21...polarization conversion element, 300...reflector, 213...λ/2 plate, 306...reflective light guide, 307...reflective surface, 308, 310...sub-reflector, 204...space-floating image, 334...image light control sheet 336...transmitting portion, 337...light absorbing portion, 81...optical element, 501...polarization conversion element, 503...unit, 507...light shielding wall, 401, 402...light shielding plate, 320...substrate, 511...housing, 512...support arm, 513...hinge, 514...back cover, 515...housing cover, 516...housing base, 517, 518...inclined linear Fresnel sheet, 519...eccentric Fresnel sheet, 2900...vending machine, 2901...drink display section, 2902...bill slot, 2903...drink outlet, 2904...change outlet, 2905...coin slot, 2920...space floating video information display system, 2921...concierge, 2922...number buttons, 2923...decision button.

Claims (23)

A space floating image display device,
a display panel for displaying images;
a light source device that emits light to the display panel;
a retroreflective member that reflects image light from the display panel and displays a real image floating in space in the air using the reflected light;
The retroreflective member includes two light control members, and the two light control members are bonded together with an adhesive;
The retroreflective member has moisture-proof tape attached to an end face of the joint where the two light control members are joined. 2. The space floating image display device according to claim 1,
The retroreflective member has an adhesive applied to the end face of the joint where the two light control members are joined, and the moisture-proof tape is further attached to the retroreflective member. 3. The space floating image display device according to claim 1,
A space floating image display device, wherein a silicone-based adhesive is applied as the adhesive to the end faces where the two light control members are joined. 4. The space floating image display device according to claim 1,
the light control member includes an optical member;
A reflective film is formed on one surface of the optical member by vapor deposition or sputtering technology. 5. The space floating image display device according to claim 1,
The light control member is adhered and fixed to the flat plate by ultraviolet light irradiation from the flat plate side with an ultraviolet-curing acrylic adhesive. 6. The space floating image display device according to claim 5,
The space floating image display device has two flat plates, one of which is made of plastic containing an ultraviolet absorbing material. A retroreflective member that reflects light from a light source device,
The retroreflective member includes two light control members,
the two light control members are bonded together with an adhesive;
The light control member includes optical members arranged in parallel and fixed to a flat plate provided substantially perpendicular to the reflecting portions of the optical members,
The retroreflective member has moisture-proof tape attached to an end face of the joint where the two light control members are joined. The retroreflective member according to claim 7,
The retroreflective member has an adhesive applied to the end face of the joint where the two light control members are joined, and further has the moisture-proof tape attached thereto. The retroreflective member according to claim 7 or 8,
A retroreflective member in which a silicone-based adhesive is applied as the adhesive to the end surface where the two light control members are joined. The retroreflective member according to any one of claims 7 to 9,
the light control member includes an optical member;
A retroreflective member in which a reflective film is formed on one surface of the optical member by vapor deposition or sputtering technology. The retroreflective member according to any one of claims 7 to 10,
The light control member is a retroreflective member that is bonded and fixed to the flat plate by irradiating ultraviolet rays from the flat plate side with an ultraviolet-curing acrylic adhesive. The retroreflective member according to any one of claims 7 to 11,
The retroreflective member has two flat plates, one of which uses a plastic containing an ultraviolet absorbing material. A space floating image display device,
a display panel for displaying images;
a light source device that emits light to the display panel;
a retroreflective member that reflects image light from the display panel and displays a real image floating in space in the air using the reflected light;
The retroreflective member includes two light control members, and the two light control members are bonded together with an adhesive;
the light control member is bonded and fixed to the flat plate by ultraviolet light irradiation from the flat plate side with an ultraviolet-curing acrylic adhesive;
There are two flat plates, and one of the flat plates is made of plastic containing an ultraviolet absorbing material,
The retroreflective member has an adhesive applied to the end face of the joint where the two light control members are joined, and further has moisture-proof tape attached thereto. A retroreflective member that reflects light from a light source device,
The retroreflective member includes two light control members,
the two light control members are bonded together with an adhesive;
The light control member includes optical members arranged in parallel and fixed to a flat plate provided substantially perpendicular to the reflecting portions of the optical members,
There are two flat plates, and one of the flat plates is made of plastic containing an ultraviolet absorbing material,
The retroreflective member has an adhesive applied to the end face of the joint where the two light control members are joined, and further has moisture-proof tape attached thereto. A space floating image display device,
a display panel for displaying images;
a light source device that emits light to the display panel;
a retroreflective member that reflects image light from the display panel and displays a real image floating in space in the air using the reflected light;
The retroreflective member includes two light control members, and the two light control members are bonded together with an adhesive;
The retroreflective member has an adhesive applied to the end face of the joint where the two light control members are joined, and further has moisture-proof tape attached thereto. 16. The space floating image display device according to claim 15 ,
A space floating image display device, wherein a silicone-based adhesive is applied as the adhesive to the end faces where the two light control members are joined. 17. The space floating image display device according to claim 15 or 16 ,
the light control member includes an optical member;
A reflective film is formed on one surface of the optical member by vapor deposition or sputtering technology. 18. The space floating image display device according to claim 15 ,
The light control member is adhered and fixed to the flat plate by ultraviolet light irradiation from the flat plate side with an ultraviolet-curing acrylic adhesive. 19. The space floating image display device according to claim 18 ,
The space floating image display device has two flat plates, one of which is made of plastic containing an ultraviolet absorbing material. A retroreflective member that reflects light from a light source device,
The retroreflective member includes two light control members,
the two light control members are bonded together with an adhesive;
The light control member includes optical members arranged in parallel and fixed to a flat plate provided substantially perpendicular to the reflecting portions of the optical members,
The retroreflective member has an adhesive applied to the end face of the joint where the two light control members are joined, and further has moisture-proof tape attached thereto. The retroreflective member according to claim 20 ,
A retroreflective member in which a silicone-based adhesive is applied as the adhesive to the end surface where the two light control members are joined. The retroreflective member according to claim 20 or 21 ,
the light control member includes an optical member;
A retroreflective member in which a reflective film is formed on one surface of the optical member by vapor deposition or sputtering technology. The retroreflective member according to any one of claims 20 to 22 ,
The light control member is a retroreflective member that is bonded and fixed to the flat plate by irradiating ultraviolet rays from the flat plate side with an ultraviolet-curing acrylic adhesive.