Portable floating image display system

Abstract

To provide a portable space floating image display system capable of suitably displaying images onto the outside of a space so as to contribute to sustainable development goals of "3. good health and well-being for all," "9. building a foundation for industry and technological innovation," and "11. creating sustainable cities."SOLUTION: A space floating image information display system is provided, comprising a housing accommodating a display panel and a light source device, a power supply unit provided with a power supply and coupled to the housing via a first linkage, and a frame structure holding a retroreflective member coupled to the housing via a second linkage.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a portable space floating image display system and an optical system used therein. [Background technology]

[0002] As a space floating image display system, an image display device that displays an image directly to the outside and a display method that displays it as a spatial screen are already known. In addition, a retroreflective member that displays a spatial image is disclosed, for example, in Patent Document 1. Furthermore, it is disclosed, for example, in Patent Document 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-067933 [Patent Document 2] Japanese Patent Application Publication No. 2019-133109 Summary of the Invention [Problem to be solved by the invention]

[0004] As a space-floating image display system, an image display device that displays an image directly to the outside and a display method that displays it as a spatial screen are already known. However, in the above-mentioned prior art space-floating image device, although there are descriptions of the configuration and arrangement of the retroreflective member that generates the space-floating image and the method of irradiating the image light from the image light source, there is no consideration of the design method for the configuration and realization technology of a portable space-floating image display system.

[0005] An object of the present invention is to provide a technique for realizing a portable space-floating image display system or space-floating image display device. [Means for solving the problem]

[0006] In order to solve the above problems, for example, the configuration described in the claims is adopted. The present application includes multiple means for solving the above problems, and the following provides an example of a space-floating image display device. The space-floating image display system as an example of the present application includes a housing that holds a display panel and a light source device, a power supply unit that has a power source and is connected to the housing via a first connecting part, and a frame structure that holds a retroreflective member that is movably connected to the housing via a second connecting part. [Effects of the Invention]

[0007] According to the present invention, a portable system can be realized in a space floating image display system or a space floating image display device. Other problems, configurations, and effects will become clear from the following description of the embodiments. [Brief explanation of the drawings]

[0008] [Figure 1A] 1A and 1B are diagrams illustrating the configuration of a transmissive retroreflective member according to an embodiment of the present invention and the position where a spatially floating image is generated. [Figure 1B] 1 is an explanatory diagram for explaining the characteristics of an optical member that constitutes a transmissive retroreflective member according to an embodiment of the present invention. FIG. [Figure 2] 1A and 1B are diagrams illustrating the configuration of a reflective retroreflective member according to an embodiment of the present invention and the position where a spatially floating image is generated. [Figure 3] 1 is a structural diagram showing an example of a specific configuration of a liquid crystal panel according to an embodiment of the present invention; [Figure 4] 1 is a structural diagram showing the arrangement of a light source device and a liquid crystal panel according to an embodiment of the present invention; [Figure 5] 1 is a side view showing the structure of a space floating image display system according to an embodiment of the present invention; [Figure 6] 1 is a top view showing the structure of a space floating image display system according to an embodiment of the present invention; [Figure 7] FIG. 2 is a second side view showing the structure of the space floating image display system according to an embodiment of the present invention. [Figure 8]FIG. 10 is a third side view showing the structure of the space floating image display system according to an embodiment of the present invention. [Figure 9] FIG. 4 is a fourth side view showing the structure of a space floating image display system according to an embodiment of the present invention. [Figure 10] 1 is a first front view showing the structure of a space floating image display system according to an embodiment of the present invention; [Figure 11] FIG. 5 is a fifth side view showing the structure of a space floating image display system according to an embodiment of the present invention. [Figure 12] FIG. 2 is a second front view showing the structure of the space floating image display system according to an embodiment of the present invention. [Figure 13A] 1 is a diagram illustrating the structure of a space floating image display system according to an embodiment of the present invention; [Figure 13B] 1 is a perspective view showing the structure of a space floating image display system according to an embodiment of the present invention; [Figure 13C] 1 is a front view showing the structure of a space floating image display system according to an embodiment of the present invention; [Figure 13D] 1 is a top view showing the structure of a space floating image display system according to an embodiment of the present invention, with a part of the housing being see-through; [Figure 13E] 1 is a side view showing the structure of a space floating image display system according to an embodiment of the present invention; [Figure 13F] 1 is a diagram illustrating the structure of a space floating image display system according to an embodiment of the present invention; [Figure 14] 1A to 1C are a perspective view, a top view, and a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 15A] FIG. 10 is a structural diagram showing another example of a specific configuration of a light source device of another type. [Figure 15B] FIG. 10 is a diagram illustrating a portion of another example of a specific configuration of a light source device of another type. [Figure 15C] FIG. 10 is a diagram illustrating a portion of another example of a specific configuration of a light source device of another type. [Figure 15D] FIG. 10 is a diagram illustrating a portion of another example of a specific configuration of a light source device of another type. [Figure 16A]FIG. 10 is a structural diagram showing another example of a specific configuration of a light source device of another type. [Figure 16B] FIG. 10 is a diagram showing another example of a specific configuration of a light source device of another type. [Figure 17] 10 is a cross-sectional view showing an example of a specific configuration of a diffusion plate provided in the light source device. FIG. [Figure 18] FIG. 10 is an explanatory diagram for explaining the diffusion characteristics of a video display device. [Figure 19] FIG. 10 is an explanatory diagram for explaining the diffusion characteristics of a video display device. [Figure 20] FIG. 1 is a diagram showing a coordinate system for measuring visual characteristics of a liquid crystal panel. [Figure 21] FIG. 1 is a diagram showing the luminance angle characteristics (longitudinal direction) of a typical liquid crystal panel. [Figure 22] FIG. 1 is a diagram showing the luminance angle characteristics (short side direction) of a typical liquid crystal panel. [Figure 23] FIG. 1 is a diagram showing the angle characteristics (longitudinal direction) of contrast of a typical liquid crystal panel. [Figure 24] FIG. 1 is a diagram showing the angle characteristics (short side direction) of contrast of a typical liquid crystal panel. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the contents of the embodiments described below (hereinafter also referred to as "the present disclosure"). The present invention also extends to the spirit of the invention and the scope of the technical ideas described 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.

[0010] Furthermore, in the drawings for explaining the present invention, components having the same or similar functions are given the same reference numerals, and different names are used as appropriate, while repeated explanations of functions, etc. may be omitted. In the following description of the embodiments, an image floating in space is expressed using the term "space-floating image." Instead of this term, it is also acceptable to express it as "aerial image," "spatial image," "floating image," "space-floating optical image of displayed image," "floating optical image of displayed image," etc. The term "space-floating image," which is mainly used in the description of the embodiments, is used as a representative example of these terms.

[0011] The present disclosure relates to a portable information terminal or the like that can display an image generated by image light from a small image light source as a floating image in space using a retroreflective member.

[0012] According to the following embodiment, for example, it is possible to display high-resolution images floating in space on the glass surface of a shop window or a light-transmitting plate. In this case, by making the divergence angle of the emitted image 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 makes it possible to obtain a portable, small, and low-power floating image display device with high light utilization efficiency, which was not possible with conventional retroreflective methods.

[0013] Furthermore, the device and optical system including the light source of the present disclosure can significantly reduce power consumption, and when combined with a new, small image display device (liquid crystal panel), a low-power, portable floating image display system can be provided. Furthermore, according to the technology of the present disclosure, it is possible to provide a floating image display system for vehicles that can display so-called unidirectional floating images that can be seen from outside the vehicle through shield glass, such as the vehicle's windshield, rear glass, and side glass.

[0014] Next, the function of the transmissive retroreflective member used in the space-floating image display device of the embodiment disclosed in the present invention and a specific embodiment of the space-floating image display device will be described. As shown in FIG. 1A(2), the transmissive retroreflective member 2 is generally disposed 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 transmissive retroreflective member 2 at the same angle as the angle at which the image light enters the transmissive retroreflective member 2. In this case, the space-floating image 3 is formed symmetrically at a distance equal to the distance L1 from the image display device 1 to the transmissive retroreflective member 2.

[0015] 1A and 1B, the mechanism by which a space-floating image is formed by an optical system using the transmissive retroreflective member 2 shown in FIG. 1A and FIG. 1B is used to explain in detail. Image light emitted from an image display device 1 provided on one side of the transmissive retroreflective member 2 is reflected by the flat light-reflecting portion C (the reflective surface of the light-reflecting member 20) of the second light control member 22, and then reflected by the flat light-reflecting portion C' (the reflective surface of the light-reflecting member 20) of the first light control member 21, thereby forming a space-floating image 3 (a real image) at a position outside the transmissive retroreflective member 2 (in the space on the other side). In other words, by using this transmissive retroreflective member 2, a space-floating image display device is established, and the image of the image display device 1 can be displayed in space as a space-floating image.

[0016] As described above, the transmissive retroreflective member 2 has two reflective surfaces, and therefore generates two ghost images 3a and 3b in accordance with the number of reflective surfaces in addition to the spatially floating image 3, as shown in Figures 1B(1) and (2).

[0017] Furthermore, it was found that when the intensity of external light is high and the light enters from the top surface of the transmissive retroreflective member 2, the spacing between the reflective surfaces (300 μm or less) becomes short, causing optical interference, resulting in the observation of rainbow-colored reflected light, which makes the viewer 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 returning to the viewer, the area where the interference light occurs was experimentally determined using the angle of incidence of external light as a parameter. It was found that when the pitch of the reflective surfaces is 300 μm and the height of the reflective surfaces is 300 μm, the interference light does not return to the viewer's side if the transmissive retroreflective member is tilted at an angle θ of 35 degrees or more with respect to the vertical plane.

[0018] On the other hand, it was 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 necessary to shorten the pitch of the reflective surface. Additionally, to suppress the generation of ghost images, the height of the reflective surface must be made higher than it is currently. However, due to manufacturing constraints on the second retroreflective member 2, 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.

[0019] 2 shows the configuration of a reflective retroreflective member according to one embodiment of the present invention and the basic configuration of a space-floating image display device using the reflective retroreflective member. As shown in Fig. 2, the device includes an image display device 1 that diverges image light of a specific polarization at a narrow angle in an oblique direction of a transparent member or transmissive plate 100 having light transmissivity such as glass. The image display device 1 includes a liquid crystal display panel 11 and a light source device 13 that generates light of a specific polarization with a narrow-angle diffusion characteristic.

[0020] Image light of a specific polarization from the image display device 1 is reflected by a polarization separator 101 (in the figure, the polarization separator 101 is formed in a sheet shape and adhered to the transparent member 100) that has a film that selectively reflects image light of a specific polarization and is provided on a transparent member 100, and then enters the retroreflective member 5. A λ / 4 plate 21 is provided on the image light incident surface of the retroreflective member 5. The image light is polarized and converted from the specific polarization to the other polarization by passing through the λ / 4 plate 21 twice, once when entering the retroreflective member 2 and once when exiting. Here, the polarization separator 101 that selectively reflects image light of a specific polarization has the property of transmitting polarized light of the other polarization that has been polarization-converted, so the image light of the specific polarization after polarization conversion passes through the polarization separator 101. The image light that has passed through the polarization separator 101 forms a space-floating image 3, which is a real image, outside the transparent member 100. The polarization separation member 101 may be formed of, for example, a reflective polarizing plate or a metal multilayer film that reflects specific polarized waves.

[0021] In the configuration of Figure 2, when viewed by a user from the direction of arrow A, the levitating image 3 appears as a bright image, but when viewed by another person from the direction of arrow B, the levitating image 3 cannot be seen at all. This characteristic is extremely suitable for use in a system that displays images that require high security or highly confidential images that should be kept secret from people directly facing the user.

[0022] In this embodiment, a configuration is described in which an absorptive polarizer 12 is provided on the image display surface of image display device 1. Absorptive polarizer 12 transmits image light emitted from image display device 1 and absorbs reflected light returning from polarization separation member 101, thereby suppressing re-reflection. Therefore, according to this embodiment using absorptive polarizer 12, it is possible to prevent or suppress degradation of image quality due to ghost images of a space-floating image in a space-floating image device using a reflective retroreflective member.

[0023] As a result of the above-mentioned investigations, the inventors have investigated a retroreflective optical system that improves the quality of the space-floating image obtained in a space-floating image display system using a transmissive retroreflective member or a reflective retroreflective member, while realizing a portable space-floating image display device that can be battery-powered with low power consumption in accordance with the small image display device 1, and have arrived at the present invention. The present invention will be described in detail below with reference to the drawings.

[0024] <Layout that achieves compactness> FIG. 3 shows a structure including a liquid crystal panel 11, an FPC (Flexible Printed Circuits) 249, and a circuit board 251. The liquid crystal panel 11 and the circuit board 251 are connected by the FPC 249. As shown in FIG. 4, light from LED chips, which are surface light sources arranged in a row parallel to the short sides of the liquid crystal panel 11, is converted into approximately parallel light by a reflector 300, and then polarized by a Polarizing Beam Splitter (PBS) 21 to enter a reflective light guide 311 as light of a specific polarization. The light is reflected by a reflecting surface 307 and enters the liquid crystal panel 11 at a desired angle and at a desired position on the liquid crystal panel 11. The reflective light guide 311 is inclined relative to the light source block 312 shown in FIG. 4, and the circuit board 251 is disposed below the reflective light guide 311 by bending the FPC 249 of the liquid crystal panel 11. The circuit board 251 can be made thinner if it is disposed along the back surface of the reflective light guide 311. This configuration reduces wasted space, making it possible to store the light source device 13 and the liquid crystal panel 11 in a compact housing.

[0025] 4 has been used to explain the layout in which the light source blocks 312 are arranged along the short side of the liquid crystal panel 11, but the same applies to a layout in which the light source blocks are arranged along the long side of the liquid crystal panel 11, and even when the light source blocks 312 are arranged facing each other on both the short side or long side of the liquid crystal panel 11, the liquid crystal panel 11, the FPC 249, and the circuit board 251 should be arranged in the same manner as above. By realizing this configuration, wasted space is reduced, and the light source device 13 and the liquid crystal panel 11 can be stored compactly in the housing.

[0026] <Example 1 of a small-sized floating image display device> 5 shows a structure in which the above-described liquid crystal panel 11 and light source device 13 are housed in a compact housing 253, and the housing 253 and power supply unit 256 are movably coupled or connected by a hinge 255. The power supply unit 256 may be, for example, a wirelessly powered battery pack. The transmissive retroreflective member 2 is held by a frame structure 252. With respect to the housing 253 as a reference, the frame structure 252 is movably connected to one side of the housing 253 via a second connecting member, and the power supply unit 256 is movably connected to the other side of the housing 253 via a first connecting member. In other words, with respect to the housing 253 as a reference, the frame structure 252 is movably connected to one side of the housing 253 via a hinge 254, and the power supply unit 256 is movably connected to the other side of the housing 253 via a hinge 255. The end of the housing 253 connected to the frame structure 252 and the end of the housing 253 connected to the power supply unit 256 face each other. Furthermore, the other side of power supply unit 256 that faces the end of power supply unit 256 connected to housing 253 via hinge 255 is not connected to frame structure 252, but when it is movable toward frame structure 252 via hinge 255, it can come into contact with one end of frame structure 252. As a result, transmissive retroreflective member 2 can be fixed at any angle to housing 253 that houses light source device 13 and liquid crystal display panel 11, and transmissive retroreflective member 2 can be moved arbitrarily.

[0027] When displaying the floating image 3, the other side of the frame structure 252 opposite the end connected to the hinge 254 can rotate around the hinge 254 as an axis toward the light output side of the liquid crystal display panel 11 built into the housing 253. Also, the other side of the power supply unit 256 opposite the end connected to the hinge 255 can rotate around the hinge 255 as an axis toward the floating image 3. As a result, the imaging position of the floating image 3 can be adjusted to the optimal position and direction toward the viewer's line of sight, that is, toward an angle of θ1 with respect to the vertical line in FIG. 5. The hinge 255 may be referred to as the first connecting part, and the hinge 254 may be referred to as the second connecting part. The first and second connecting parts may include a connecting member and a movable member.

[0028] FIG. 6 is a top view showing the structure of the space-floating image display system according to one embodiment of the present invention shown in FIG. 5. Because the top of the space-floating image 3 is not imaged above the line connecting the viewer's viewpoint and the top of the transmissive retroreflective member 2, in order to enhance the floating sensation, it is recommended to add a mark to the end of the frame structure 252 facing the viewer, particularly the top, i.e., the end not connected or joined to the housing 253 by the hinge 254, to facilitate movement of the viewpoint. Furthermore, the floating sensation can be enhanced by providing a black display area above the space-floating image 3. In FIGS. 5 and 6, metal fins 104 may be exposed to the outside of the housing or may be provided inside the housing to dissipate heat generated by the LEDs to the outside.

[0029] The floating image display device shown in FIG. 13A has a generally cylindrical, particularly cylindrical, housing, as shown. This floating image display device with a cylindrical housing is a retractable bottle holder (also called a drink holder) type, and is a relatively small (compact) and portable floating image display device. For example, such a floating image display device can be appropriately placed in a bottle holder (also called a drink holder) in a vehicle or on the dashboard. This cylindrical shape has an axis extending in the height direction (corresponding to the vertical direction) and a diameter extending in a direction perpendicular to the axis (corresponding to the horizontal direction). This cylindrical housing roughly has an upper housing portion and a lower housing portion, which are connected. Note that the upper housing portion and the lower housing portion may or may not be integrally connected. An optical system, a control circuit board, and, if necessary, a rechargeable battery are housed inside the housing.

[0030] FIG. 13A shows the structure of a drink-holder-type, space-floating image display system using a transmissive retroreflective member 2. FIG. 13A(1) is a perspective view of the drink-holder-type, space-floating image display system using a transmissive retroreflective member 2, FIG. 13A(2) is a front view of the drink-holder-type, space-floating image display system using a transmissive retroreflective member 2, and FIG. 13A(3) is a side view of the drink-holder-type, space-floating image display system using a transmissive retroreflective member 2. The space-floating image display device of this embodiment includes a housing 253 that incorporates a power supply unit 256, a frame structure 252, and an image display device. To maintain balance, this drink-holder-type, space-floating image device has the retroreflective member 2 and image display device disposed on the upper part of the housing, and the power supply unit 256 disposed on the lower part of the housing. The housing 253 incorporates a light source unit 13 and a liquid crystal panel 11. The frame structure 252 holds the transmissive retroreflective member 5. The image display device includes a light source unit and a liquid crystal display panel.

[0031] As shown in FIG. 13A , the housing 253 is disposed at an angle relative to the power supply unit 256. One end of the housing 253 is fixed to the support unit 258, and the other opposite end of the housing 253 is movably connected to the frame structure 252 via a hinge 260. In this embodiment, the end of the housing 253 connected to the support unit 258 is referred to as the lower portion, i.e., the power supply unit 256 side, and the end of the housing 253 connected to the frame structure 252 is referred to as the upper portion. A recess is formed in the support unit 258 in the vertical or height direction, and the housing 253 is fixed to the recess. As shown in FIG. 13A (3), the support unit 258 has a U-shape, but this shape is not limited to this and other shapes may be used depending on the design. The end of the housing 253 movably connected to the frame structure 252 via the hinge is at the same height as the upper portion of the support unit 258. In other words, the end of the housing 253 opposite the end of the housing 253 fixed to the recess is at the same height as the upper portion of the support unit 258. 13A(1), image light from an image display device built into housing 253 is transmitted through transmissive retroreflective member 2, and a floating image (not shown) is formed in the air on the opposite side of support portion 258 with frame structure 252 as the reference. To align with the user's line of sight, the end of frame structure 252 opposite the end connected to hinge 260 is in contact with support portion 258, and can rotate around hinge 260 as an axis toward the floating image side. Note that support portion 258 may also be referred to as a first coupling portion or a first connecting portion, and hinge 260 may also be referred to as a second coupling portion or a first connecting portion.

[0032] On the other hand, as another example of the arrangement of the drink-holder-type floating image device other than that shown in FIG. 13A , the image display device built into the housing 253 may be arranged in the height direction of the support portion 258. In this case, the end of the frame structure 252 is movably fixed to the upper part of the support portion 258 via the hinge 260, thereby increasing the movable range of the retroreflective member 2 held by the frame structure 252 and allowing the display position of the floating image to be adjusted to match the user's line of sight. Furthermore, to block external light, side walls may be provided on the sides of the housing 253 other than the side connected to the hinge 260 and the side connected to the support portion 258, thereby improving the visibility of the floating image. The side walls may be arranged on both sides of the space surrounded by the housing 253, the support portion 258, and the frame structure 252. The side walls may be detachable, foldable, or retractable. For example, the side walls may be arranged on both ends of the housing 253 where there are no hinges.

[0033] The above-mentioned configuration provides a space-floating image display system that is compact, portable, and low-power. The space-floating image display system incorporates a display panel that displays the image and a light source device for the display panel in the same housing, and a holding member that protects a transmissive retroreflective member that reflects the image light from the display panel and displays a real space-floating image in the air using the reflected light, and a mobile battery are connected with flanges. This makes it possible to change the system configuration depending on the usage style, making it portable, and significantly reducing power consumption by narrowing the directional characteristics of the light source device.

[0034] <How to fix the floating image in space> FIG. 7 is a second side view showing a structure for fixing the space-floating image 3 at an angle θ2 relative to the viewer's line of sight, i.e., the perpendicular line in FIG. 7, in a space-floating image display system according to an embodiment of the present invention. The housing 253 and the power supply unit 256 are connected by rotating with a hinge 255. The upper end of the frame structure 252, i.e., the end not connected or coupled to the housing 253 by the hinge 254, contacts the end of the power supply unit 256 not connected to the housing 253 by the hinge 255, thereby fixing the angle between the housing 253 and the transmissive retroreflective member 2 held by the frame structure 252. The power supply unit 256 may be, for example, a wirelessly powered battery pack. By providing hinges at both ends of the housing 253, which houses the liquid crystal panel 11 and the light source device 13, the space-floating image display system can be configured to suit different usage patterns. Furthermore, by providing side walls on the sides of the housing 253 other than the side connected to the hinge 260 and the side connected to the support 258 to block external light, the visibility of the floating image in space is improved. The side walls may be detachable, foldable, or retractable. For example, the side walls may be located at both ends of the housing 253 where there are no hinges. Furthermore, as shown in FIG. 7, by bringing the frame structure 252 holding the transmissive retroreflective member 2 closer to the housing 253 perpendicularly, the angle of the floating image in space 3 can be adjusted in a direction perpendicular to the bottom surface. This also makes it possible to adjust the position of the floating image in space 3 to match the viewer's viewpoint, i.e., θ3 relative to the perpendicular line in FIG. 8. Furthermore, in the installation shown in FIG. 8, external light incident on the rear of the transmissive retroreflective member 2 (the right side of the drawing), i.e., the light incident surface of the retroreflective member 2, can be blocked, as in FIG. 7, thereby significantly improving the image quality of the floating image in space 3, particularly the contrast performance.

[0035] <Example 2 of a small-sized floating image display device> FIG. 9 is a side view showing a second embodiment of a floating-in-space image display device. As with the first embodiment, the liquid crystal panel 11 and light source device 13 are housed in a compact housing 253, and the housing 253 and power supply unit 256 are connected or coupled by a hinge 255, creating a movable structure. The power supply unit 256 can be, for example, a wirelessly powered battery pack. The transmissive retroreflective member 2 is held by a frame structure 252 and connected to the housing 253 by a hinge 254 at the end not connected to the power supply unit 256 via a hinge 255 of the housing 253. As a result, the transmissive retroreflective member 2 can be fixed at any angle relative to the housing 253 incorporating the liquid crystal panel 11 and light source device 13, and is movable. As a result, the imaging position of the floating-in-space image 3 can be adjusted to the optimal position and direction toward the viewer's line of sight, that is, an angle θ1 relative to the perpendicular line in FIG. 9 . Hinge 255 may be referred to as a first connecting part, hinge 254 may be referred to as a second connecting part, or the hinge may be referred to as a connecting part. Also, in order to block external light, side walls are provided on both sides of the triangular prism-shaped space surrounded by housing 253, power supply unit 256, and frame structure 252, thereby improving the visibility of the floating image in space. The side walls may be detachable, foldable, or retractable.

[0036] <The effect of increasing the amount of floating in space due to the illusion> FIG. 10 is a front view showing the structure of the space-floating image display system according to one embodiment of the present invention shown in FIG. 9 . The top of the space-floating image 3, i.e., the side where the housing 253 is not located, is not imaged above the line connecting the viewer's viewpoint and the top of the transmissive retroreflective member 2, i.e., the side where the housing 253 is not located. Therefore, the inventors considered specific technical means to enhance the floating sensation of the space-floating image. As a result, mark 257-1 is added to the end of the frame structure 252 facing the viewer, particularly the upper part, i.e., the end not connected or joined to the housing 253 by the hinge 254, so that the viewer's viewpoint can easily move to that end. Furthermore, similar marks 257-2 and 257-3 are added to the side of the frame structure 252, i.e., the side opposite mark 257-1 that does not face the retroreflective member 2, to draw the viewer's attention to the mark. As a result, it was found that this has the effect of making the floating amount of the floating image 3 appear larger than it actually is. In Figures 9 and 10, unlike the first embodiment, metal fins 104 (not shown) that dissipate heat generated by the LED to the outside are arranged inside the housing and are not exposed. Note that the metal fins 104 may also be arranged outside the housing.

[0037] <Non-display state of the space floating image display device> 11 is a side view showing the state in which the space-floating image 3 of the space-floating image display device is not displayed. The liquid crystal panel 11 and the light source device 13 are housed in a compact housing 253, and the housing 253 and the power supply unit 256 are connected or coupled by a hinge 255 and arranged side by side. In other words, the housing 253 and the power supply unit 256 are movable by the hinge 255, but in FIG. 11, the angle between the housing 253 and the power supply unit 256 is approximately 180 degrees. A frame structure 252 holding a transmissive retroreflective member 2 above the housing 253 and the power supply unit 256 is connected to the housing 253 by a hinge 254 provided at the end of the housing 253 that is not connected to the power supply unit 256 by the hinge 255, and the hinge 254 enables the display to be folded. As a result, the transmissive retroreflective member 2 is stacked and fixed to the housing 253 and power supply unit 256 that house the liquid crystal panel 11 and light source device 13, resulting in the thinnest possible structure and a portable thickness. When the floating image 3 is not displayed, the other side of the frame structure 252 opposite the end connected to the hinge 254 may be rotated and folded toward the light-emitting side of the liquid crystal display panel 11 housed in the housing 253, or may be rotated and folded away from the light-emitting side of the liquid crystal panel 11. When the other side of the frame structure 252 opposite the end connected to the hinge 254 is rotated and folded toward the light-emitting side of the liquid crystal display panel 11, dust and the like can be prevented from adhering to the liquid crystal panel 11. On the other hand, when the other side of the frame structure 252 opposite the end connected to the hinge 254 is rotated and folded away from the light-emitting side of the liquid crystal panel 11, the length of the device can be shortened in the longitudinal direction, but the thickness increases. In this way, the folding method can be adjusted to suit the user's needs. The power supply unit 256 may be, for example, a wireless power supply type battery pack.

[0038] FIG. 12 is a perspective view of the floating image display system according to one embodiment of the present invention shown in FIG. 11, as seen from A. If the width, i.e., the vertical thickness, of the housing 253 and the power supply unit 256 are made the same, they will be integrated, thereby realizing a more portable floating image display system.

[0039] Furthermore, in the space-floating image display device of this embodiment, even when a viewer looks into the space-floating image 3, the image display surface of the liquid crystal display panel 11 is shielded from light by the reflective surface of the retroreflective member 2. Therefore, in this space-floating image display device, the liquid crystal display panel and the retroreflective member are arranged at an angle, making it difficult to view the image displayed on the liquid crystal display panel directly.

[0040] Furthermore, it is preferable to use S-polarized light because the image light from the liquid crystal panel 11 can theoretically have a high reflectance on reflective materials such as retroreflective materials. However, if the viewer wears polarized sunglasses, the floating image will be reflected or absorbed by the polarized sunglasses. To address this issue, a depolarizing element 103 can be provided on the viewer side of the transmissive retroreflective material 2, i.e., on the side of the material facing the floating image 3. This optically converts a portion of the image light of a specific polarization into the other polarization, thereby simulating natural light. As a result, a high-quality floating image can be viewed even when the viewer is wearing polarized sunglasses. When optically bonded to the transparent plate 100 with adhesive, no light reflection surface is created, and the image quality of the floating image is not impaired.

[0041] Commercially available depolarizing elements include Cosmoshine SRF (manufactured by Toyobo Co., Ltd.) and depolarizing adhesive (manufactured by Nagase & Co., Ltd.). In the case of Cosmoshine SRF (manufactured by Toyobo Co., Ltd.), by attaching the adhesive to the image display device, it is possible to reduce interfacial reflection and improve brightness. In addition, in the case of depolarizing adhesive, a colorless transparent plate and the image display device are attached via the depolarizing adhesive. As described above, in this embodiment, the image display device 1 is equipped with a light source device 13 that generates light of a specific polarization having diffusion characteristics at a narrow angle with the liquid crystal display panel 11.

[0042] <Example 3 of a small-sized floating image display device> 13B, 13C, 13D, and 13E show the structure of a space-floating image display system using a reflective retroreflective member 5. FIG. 13B is a perspective view of the space-floating image display system using a reflective retroreflective member 5. FIG. 13C is a front view of the space-floating image display system using a reflective retroreflective member 5, FIG. 13D is a top view of the space-floating image display system using a reflective retroreflective member 5, and FIG. 13E is a side view of the space-floating image display system using a reflective retroreflective member 5. FIG. 13D shows the contents of the housing 253, illustrating a part of the light source device 13. The light source device 13 includes an LED 14, a reflector 300, and a light guide 306. A detailed description of the light source device 13 will be provided below and will not be repeated here.

[0043] 13B to 13E show an embodiment corresponding to one example of the present invention shown in FIG. 2. A light source device 13 and a liquid crystal display panel 11 are built into a housing 253, which is movably connected or coupled to a power supply unit 256 via a hinge 255. A reflective retroreflective member 5 is disposed between a first coupling portion and a second coupling portion. The side of the power supply unit 256 on which the spatially floating image is formed is defined as the upper portion, and the reflective retroreflective member 5 is disposed above the power supply unit 256. The reflective retroreflective member 5 may be bonded to the power supply unit 256, or the reflective retroreflective member 5 may be fixed to a frame structure or the like and disposed above the power supply unit 256. The power supply unit 256 may be, for example, a wirelessly powered battery pack. The power supply unit 256 is connected to the transparent member 100 via a hinge 254. 13B, for example, hinge 255 is adjusted so that the angle between power supply unit 256 and housing 253 is approximately 90 degrees, and hinge 254 is adjusted so that transparent member 100 comes into contact with the end of housing 253 where hinge 255 is not attached. In this case, light from light source device 13 enters liquid crystal display panel 11, and the light from liquid crystal display panel 11 is reflected by polarization separation member 101 (not shown) provided on the light incident surface of transparent member 100. The reflected light is reflected by reflective retroreflective member 5, then passes through transparent member 100, and forms a floating image (not shown) in the air.

[0044] Furthermore, with respect to the power supply unit 256 as a reference, the transparent member 100 is movably connected to one side of the power supply unit 256 via a second connecting part, and the housing 253 is movably connected to the other side of the power supply unit 256 via a first connecting part. That is, with respect to the power supply unit 256 as a reference, the transparent member 100 is movably connected to one side of the power supply unit 256 via a hinge 254, and the housing 253 is movably connected to the other side of the power supply unit 256 via a hinge 255. The end of the power supply unit 256 connected to the transparent member 100 and the end of the power supply unit 256 connected to the housing 253 face each other. Furthermore, the other side of the housing 253 facing the end of the housing 253 connected to the power supply unit 256 via the hinge 255 is not connected to the transparent member 100, but when the housing 253 moves toward the transparent member 100 via the hinge 255, it can come into contact with one end of the transparent member 100. As a result, the transparent member 100 can be fixed at any angle relative to the power supply unit 256, and the transparent member 100 can be moved as desired. When displaying the floating image 3, the other side of the transparent member 100 opposite the end connected to the hinge 254 can rotate around the hinge 254 as an axis toward the light output side of the retroreflective member 5. Furthermore, the other side of the housing 253 opposite the end connected to the hinge 255 can rotate around the hinge 255 as an axis toward the floating image side. As a result, the imaging position of the floating image in space can be adjusted to the optimal position and direction toward the viewer's line of sight. The hinge 255 may be referred to as a first connecting part, and the hinge 254 may be referred to as a second connecting part. The first and second connecting parts may include a connecting member and a movable member.

[0045] Furthermore, the visibility of the floating image in space is improved by providing side walls on both sides of the triangular prism-shaped space surrounded by the housing 253, the power supply unit 256, and the transparent member 100 to block external light. The side walls may be detachable, foldable, or retractable. For example, the side walls may be appropriately disposed on the end of the power supply unit 256 or the housing 253 that does not have a hinge.

[0046] 13D and 13E show an embodiment corresponding to another example of the present invention shown in FIG. Housing 253 houses light source device 13 and liquid crystal display panel 11, and housing 253 is movable via hinge 255 and connected or coupled to power supply unit 256. Reflective retroreflective member 5 is coupled to transparent member 100 via hinge 254 and held in place by the restraining force of hinge 254. FIG. 13D is a top view of the example shown in FIG. 13E, but shows an example in which housing 253 is positioned in the opposite direction to that shown in FIG. 13E. A perspective view of the light source unit provided in housing 253 shows the arrangement of liquid crystal panel 11, reflective light guide 306, and drive circuit 251.

[0047] 13B to 13E, marks are added to the end of the transparent member 100 facing the viewer, particularly the upper end, i.e., the end not connected or joined to the power supply unit 256 by the hinge 254, so that the viewpoint can easily move to that end. Furthermore, by adding similar marks to the side of the transparent member 100, i.e., the side facing the marks that does not face the retroreflective member 5, the viewer's attention is drawn to the marks. This has been found to have the effect of making the floating amount of the floating image in space seem larger than it actually is. Metal fins (not shown) that dissipate heat generated by the LEDs to the outside are located inside the housing and are not exposed. The metal fins may also be located outside the housing.

[0048] When the floating image in space is not displayed, the angle between the housing 253 and the power supply unit 256 is approximately 180 degrees, and the transparent member 100 can be folded by the hinge 254 toward the light-emitting side of the liquid crystal display panel 11 built into the housing 253. As a result, the structure becomes the thinnest and has a thickness that is portable. Furthermore, when the floating image in space is not displayed, the transparent member 100 and the housing 253 that houses the image display device can be freely folded toward the opposite side by the hinges 254 and 255. On the other hand, if the other side of the transparent member 100 opposite the end connected to the hinge 254 is rotated toward the opposite side of the light-emitting side of the liquid crystal panel 11 and folded, the length of the device can be shortened in the longitudinal direction, but the thickness will increase. In this way, the folding method can be adjusted to suit the user's needs.

[0049] The floating image display device shown in FIG. 13F has a generally cylindrical, particularly cylindrical, housing, as shown. This floating image display device with a cylindrical housing is a retractable bottle holder (also called a drink holder) type, and is a relatively small (compact) and portable floating image display device. For example, such a floating image display device can be appropriately placed in a bottle holder (also called a drink holder) in a vehicle or on the dashboard. This cylindrical shape has an axis extending in the height direction (corresponding to the vertical direction) and a diameter extending in a direction perpendicular to the axis (corresponding to the horizontal direction). This cylindrical housing roughly has an upper housing portion and a lower housing portion, which are connected. Note that the upper housing portion and the lower housing portion may or may not be integrally connected. An optical system, a control circuit board, and, if necessary, a rechargeable battery are housed inside the housing.

[0050] FIG. 13F shows the structure of a space-floating image display system using the reflective retroreflective member 5 shown in FIG. 2, another embodiment of the present invention. FIG. 13F(1) is a perspective view of a drink-holder-type space-floating image display system using the reflective retroreflective member 5, FIG. 13F(2) is a side view of the drink-holder-type space-floating image display system using the reflective retroreflective member 5, and FIGS. 13F(3) and 13F(4) are side views of another example of a drink-holder-type space-floating image display system using the reflective retroreflective member 5. The power supply unit is omitted in FIGS. 13F(3) and 13F(4). The space-floating image display device of this embodiment is composed of a power supply unit 256, a reflective retroreflective member 5, and a housing 253 that houses an image display device. In this drink-holder-type space-floating image display device, the reflective retroreflective member 5 and image display device are arranged on the top of the housing to maintain balance, and the power supply unit 256 is arranged on the bottom of the housing. The housing 253 houses the light source device 13 and the liquid crystal panel 11. The floating image device also includes a transparent member 100.

[0051] 13F, the retroreflective member 5 is disposed on the support member 258 at an angle relative to the power supply unit 256. The housing 253 is disposed at an angle relative to the power supply unit 256, with one end of the housing 253 connected to the support member 258 and the other end movably connected to the transparent member 100 via a hinge 260. In this embodiment, the end of the housing 253 connected to the support member 258 is referred to as the lower portion, i.e., the power supply unit 256 side, and the end of the housing 253 connected to the transparent member 100 via the hinge 260 is referred to as the upper portion. A recess is formed in the support member 258 in the vertical direction or height direction, and one end of the housing 253 and one end of the retroreflective member 5 are fixed in the recess. As shown in FIG. 13F(2), the support member 258 has a U-shape, but is not limited to this shape and may have other shapes depending on the design. For example, as shown in Figures 13F(3) and 13F(4), the support parts may not be U-shaped, but may be arranged separately, such as support part 259a of the housing 253 and support part 259b of the retroreflective member 5. The connection part between the housing 253 and the retroreflective member 5 may be connected exactly to the side of the housing 253, or may be connected only partially. In Figures 13F(1) to 13F(4), the angle between the housing 253 and the retroreflective member 5 is 90 degrees. The display position of the floating image in space can be adjusted by the position of the transparent member 100, which can rotate around a hinge 260 toward the floating image (not shown). Also, Figure 13F(3) may be in a non-display state, and Figure 13F(4) may be in a display state, depending on the user's needs.

[0052] In addition, the end of the housing 253, which is movably connected to the transparent member 100 via the hinge 260, is at the same height as the top of the support portion 258. In other words, the end of the housing 253 opposite the end fixed to the recess is at the same height as the top of the support portion 258. The recess may be a through hole, in which case the end of the housing 253 and the end of the retroreflective member 5 pass through the hole in the support portion 258 and protrude. In FIG. 13F(1), image light from an image display device built into the housing 253 is reflected by a polarization separation member (not shown) provided on the light incident surface of the transparent member 100, the reflected light is reflected by the reflective retroreflective member 5, then passes through the transparent member 100, and forms a floating image (not shown) in the air on the opposite side of the support portion 258 with respect to the transparent member 100. The support portion 258 may be referred to as a first coupling portion or a first connecting portion, and the hinge 260 may be referred to as a second coupling portion or a first connecting portion. Furthermore, by providing side walls on both sides of the triangular prism-shaped space surrounded by the housing 253, the power supply portion 256, and the transparent member 100 to block external light, the visibility of the floating image in space is improved. The side walls may be detachable, foldable, or retractable. For example, the side walls may be appropriately disposed at the end of the power supply portion 256 or the housing 253 where there is no hinge.

[0053] The above-mentioned configuration provides a space-floating image display system that is compact, portable, and has low power consumption. The space-floating image display system incorporates a display panel that displays the image and a light source device for the display panel in the same housing, and a holding member that protects a reflective retroreflective member that reflects the image light from the display panel and displays a real space-floating image in the air using the reflected light, and a mobile battery are connected with flanges. This allows the system configuration to be changed depending on the usage style, making it portable, and the light source device's directional characteristics can be made narrow, making it possible to significantly reduce power consumption.

[0054] <Image light control sheet> In order to achieve different diffusion characteristics in the vertical and horizontal directions of the screen in the above-described image display device 1, an image light control sheet is provided on the image light exit 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 entrance and exit surfaces, and therefore it is expected to have the same effect as the ambient light control film of this embodiment. In this case, since the viewing angle control film (VCF) has an alternating arrangement of transparent silicon and black silicon stretched in a predetermined direction, it is recommended to tilt the stretching direction of the transparent silicon and black silicon of the image light control sheet 21 relative to the vertical direction of the pixel arrangement direction of the liquid crystal panel 11 to reduce moiré that occurs due to the pitch between the pixels and the ambient light control film.

[0055] (1) In order to reduce vertical stripes caused by the transmissive and light-absorbing parts of the image light control sheet and moire caused by the pixel arrangement of the liquid crystal panel 11, it is advisable to tilt the vertical stripes and pixel arrangement described above. Furthermore, (2) if the pixel size of the liquid crystal panel 11 is A and the pitch of the vertical stripes of the image light control sheet 12 is B, selecting a ratio (B / A) that is not an integer multiple can further reduce moire.

[0056] Each pixel on an LCD panel consists of three color pixels (RGB) arranged in parallel, and is generally square, so the occurrence of the aforementioned moire cannot be suppressed across the entire screen. For this reason, we experimentally determined that optimizing the tilted arrangement shown in (1) within a range of 5 to 25 degrees would be sufficient, so that the moire occurrence position could be intentionally shifted to a location where the spatial floating image would not be displayed. While we have used an LCD panel as an example to reduce moire, the moire that occurs between the retroreflective member 2 and the image light control sheet 250 occurs because both are linear structures. By optimally tilting the image light control sheet relative to the pixel arrangement of the LCD panel, it is possible to reduce large, low-frequency moire that is visible to the naked eye.

[0057] As shown in FIG. 3, the image light control sheet 250 is placed on the image light output surface of the liquid crystal panel 11 and is adhesively fixed to the image light output surface of the liquid crystal panel 11 with an adhesive material.

[0058] <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 20, 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 22. 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.

[0059] On the other hand, the contrast performance in the short side (up and down) direction of the panel is excellent in the range of -15 degrees to +15 degrees, as shown in Figure 24. When combined with the brightness characteristics, the best characteristics are obtained when used in the range of ±10 degrees with 5 degrees as the center.

[0060] Furthermore, the brightness and viewing angle characteristics in the longitudinal (left-right) direction of the panel are superior at an output angle perpendicular to the panel surface (output angle of 0 degrees), as shown in Figure 21. 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.

[0061] Similarly, the 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 the brightness characteristics, the best characteristics are obtained when used in the range of ±5 degrees with -5 degrees as the center. For this reason, the image quality and performance of the image display device 1 are improved by setting the emission angle of the image light emitted from the liquid crystal panel to be incident on the liquid crystal panel from a direction that provides the best characteristics using the light beam direction conversion means provided in the light guide of the light source device 13 described above, and modulating the light with a video signal.

[0062] In order to make the most of the brightness and contrast characteristics of the liquid crystal panel as an image display element, the image quality of the floating image can be improved by setting the incident light from the light source to the liquid crystal panel within the above-mentioned range.

[0063] <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 from the light source device 13 is incident on the liquid crystal panel 11 at an incident angle that maximizes the characteristics of the liquid crystal panel 11, and then the image light beam is luminance-modulated in accordance with the image signal and emitted toward the retroreflective member. At this time, in order to reduce the set volume of the spatial floating image 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 the desired position after retroreflection and ensure optimal directionality, the following technical means are used.

[0064] A transparent sheet made of optical components such as a linear Fresnel lens is provided on the image display surface of the liquid crystal panel 11 as a light direction conversion panel, and the image position of the floating image in space is determined by controlling the direction of emission of the incident light beam to the retroreflective optical element while providing high directivity. With this configuration, the image light from the image display device 1 reaches the observer efficiently with high directivity (straightness) like laser light, and as a result, it is possible to display high-quality floating images with high resolution and significantly reduce the power consumption of the image display device 1 including the light source device 13.

[0065] <Example 1 of video display device> 16A shows another example of the specific configuration of the image display device 1. 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. Also, an LED board on which LED (Light Emitting Diode) elements 14b, which are semiconductor light sources, and their control circuits are mounted are attached to one side of the case of 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.

[0066] The liquid crystal display panel frame attached to the top surface of the case is configured to have attached thereto a liquid crystal display panel 11 attached to the frame, and further to have attached thereto an FPC (Flexible Printed Circuits) (not shown) electrically connected to the liquid crystal display panel 11. That is, the liquid crystal display 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 14b, which are solid-state light sources, based on a control signal from a control circuit (not shown here) that constitutes the electronic device.

[0067] <Example 1 of Light Source Device for 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 Fig. 16A and Fig. 16B. Fig. 16A and Fig. 16B show LEDs 14 and 14b constituting light source 13, which are attached at predetermined positions relative to collimator 18. Each collimator 18 is formed of a light-transmitting material, such as glass or heat-resistant resin. As shown in Fig. 16B, collimator 18 has outer peripheral surface 156 of a conical convex shape obtained by rotating a parabolic cross section, and has, at the center of its apex (the side in contact with the LED substrate), recess 153 with convex portion (i.e., convex lens surface) 157 formed therein.

[0068] Furthermore, the central part of the flat part (the side opposite to the apex) of the collimator 18 has a convex lens surface 154 that protrudes outward (or may be a concave lens surface that is recessed inward). The parabolic surface 156 that forms the outer peripheral surface of the cone shape of the collimator 15 is set within an angle range that allows the light emitted from the LEDs 14, 14b in the peripheral direction to be totally reflected therein, or a reflective surface is formed thereon.

[0069] The LEDs 14 and 14b are arranged at predetermined positions on the surface of the circuit board, 102. The substrate 102 is positioned and fixed to the collimator 18 so that the LEDs 14 and 14b on the surface are located at the center of the recess 153.

[0070] According to this configuration, the collimator 18 described above condenses the light emitted from the LED 14 or 14b, particularly the light emitted upward from the central portion (toward the right in the drawing), into parallel light by the two convex lens surfaces 157, 154 that form the outer shape of the collimator 18. Light emitted from other portions toward the periphery is reflected by the parabolic surface that forms the conical outer surface of the collimator 18, and is similarly condensed into parallel light. In other words, the collimator 18, which has a convex lens in its center and a parabolic surface formed on its periphery, can extract almost all of the light generated by the LED 14 or 14b as parallel light, thereby improving the utilization efficiency of the generated light.

[0071] A polarization conversion element 21 is provided on the light exit side of the collimator 18. The polarization conversion element 21 may also be referred to as a polarization conversion member. As is clear from FIG. 16B , this polarization conversion element 21 is configured by combining a columnar light-transmitting member having a parallelogram cross section (hereinafter referred to as a parallelogram prism) and a columnar light-transmitting member having a triangular cross section (hereinafter referred to as a triangular prism), and arranging a plurality of these in an array parallel to a plane perpendicular to the optical axis of the collimated light from the collimator 18. Furthermore, a polarization beam splitter (hereinafter referred to as a "PBS film") and a reflective film are alternately provided at the interface between adjacent light-transmitting members arranged in the array, and a λ / 2 phase plate is provided on the exit surface from which light incident on the polarization conversion element 21 and transmitted through the PBS film exits.

[0072] <Directivity characteristics of light emitted from LCD panel> 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 FIG. 19(A)) and the vertical direction of the screen (the display direction corresponding to the Y-axis of the graph in FIG. 19(B)), as shown in the plot curves of "conventional characteristics (X direction)" in FIG. 19(A) and "conventional characteristics (Y direction)" in FIG. 19(B).

[0073] In contrast, the diffusion characteristics of the light beam emitted from the liquid crystal display panel of this embodiment are, for example, as shown in the plot curves of "Example 1 (X direction)" in FIG. 19(A) and "Example 1 (Y direction)" in FIG. 19(B).

[0074] In one specific example, when 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 angle is about 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 upper and lower sides, the reflection angle of the reflective light guide and the area of ​​the reflective surface are optimized so that the upper viewing angle is held down (narrowed) to about 1 / 3 of the lower viewing angle.

[0075] 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, and the brightness of the image becomes more than 50 times greater.

[0076] Furthermore, in the case of the viewing angle characteristics shown in "Example 2" in Fig. 19, 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 about half) is set to 5 degrees, the angle (narrow viewing angle) will be about 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 sides, 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 about 1 / 12 of the conventional value.

[0077] 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, and the brightness of the image is more than 100 times higher.

[0078] 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, by adjusting the light diffusion characteristics of the light source device, it is possible to achieve a significant improvement in brightness with similar power consumption, making it possible to create a video display device that is compatible with display systems facing bright outdoor environments.

[0079] When using a large liquid crystal display panel, the brightness of the screen can be improved by directing the light from the periphery of the screen inward so that it faces the viewer when the viewer is facing the center of the screen. On the other hand, when the panel size (screen ratio 16:10) of the image display device is 5 inches or less and in the portrait mode described in this embodiment (when the screen of the liquid crystal display panel is vertically long (hereinafter also referred to as "portrait use")), the horizontal directivity can be significantly narrowed to provide a floating image display device that achieves high brightness or low power consumption.

[0080] A number of other examples of the light source device will be described below, and any of these other examples of the light source device may be used in place of the light source device in the example of the image display device described above.

[0081] As mentioned above, when using a large LCD 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. Meanwhile, the smaller the panel size and the closer the viewing distance, the larger the convergence angle in binocular vision using the left and right eyes. Since the convergence angle due to binocular parallax is an important requirement, particularly when using small panels of 7 inches or less, it is advisable to design the light source to have a directional characteristic or to have an increased light diffusion characteristic so that the image light is directed to the optimal viewing range of the system.

[0082] Furthermore, depending on the required specifications of the system, it may be necessary to optimally design the shape, surface roughness, inclination, etc. of the reflective surface of the light guide of the light source device 13 described above in order to obtain horizontal and vertical directional characteristics and diffusion characteristics.

[0083] <Light source device example 1> Next, another example of the light source device will be described with reference to Fig. 14. Figs. 14(a) and (b) are diagrams in which the liquid crystal display panel 11 and the diffusion plate 206 are partially omitted in order to explain the light guide 311.

[0084] 14 shows a state in which the LEDs 14 constituting the light source are mounted on a substrate 102. The LEDs 14 and the substrate 102 are attached to a reflector 300 at predetermined positions.

[0085] 14, the LEDs 14 are arranged in a row in a direction parallel to the side (short side in this example) of the liquid crystal display panel 11 on which the reflector 300 is arranged. In the example shown in the figure, the reflector 300 is arranged corresponding to the arrangement of the LEDs. Note that a plurality of reflectors 300 may be arranged.

[0086] In one embodiment, the reflectors 300 are each made of a plastic material. Alternatively, the reflectors 300 may be made of a metal material or a glass material, but plastic materials are easier to mold, so in this embodiment, plastic materials are used.

[0087] As shown in FIG. 14(b), the inner surface of the reflector 300 (the right side in the figure) has a reflective surface (hereinafter sometimes referred to as a "paraboloid") 305, which has a shape obtained by cutting a paraboloid along a meridional plane. The reflector 300 converts the divergent light emitted from the LED 14 into approximately parallel light by reflecting it off the reflective surface 305 (paraboloid), and directs the converted light to the end face of the light guide 311. In addition to an aluminum reflective film, the reflective surface of the reflector 300 is designed to have multiple metal films, such as Ti and SiO films, formed as enhanced reflection films to increase reflectivity and reduce dependency on the incident angle. In one specific example, the light guide 311 is a reflective light guide.

[0088] The reflecting surface of reflector 300 has a shape asymmetric with respect to the optical axis of the light emitted from LED 14. Furthermore, reflecting surface 321 of reflector 300 is a parabolic surface as described above, and by placing the LED at the focus of the parabolic surface, the light flux after reflection is converted into approximately parallel light.

[0089] Because 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 production, it is best to limit it to around 5.

[0090] Although the LED 14 and reflector 300 are partly close to each other, 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 10 times or more compared to a reflector made of glass material, thereby improving light utilization efficiency.

[0091] 14, a reflective surface is provided on the bottom surface 303 of the light guide 311, and the 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 disposed opposite the light guide 311. As shown in Fig. 14, the reflective surface provided on the bottom surface 303 has a plurality of surfaces with different inclinations in the traveling direction of the parallel beam from the reflector 300, and the light is reflected toward the corresponding liquid crystal panel portion. Each of the plurality of surfaces with different inclinations may have a shape extending in a direction perpendicular to the traveling direction of the parallel beam from the reflector 300.

[0092] 14, the reflective surface on the bottom surface 303 may be flat. Furthermore, a diffuser 206 may be provided to more precisely control the diffusion characteristics of light reflected by the reflective surface on the bottom surface 303 of the light guide 311 facing the liquid crystal display panel 11. This diffuser 206 refracts the reflected light by adjusting the surface shape and roughness of both surfaces, thereby precisely adjusting the amount and direction of the light beam heading toward the liquid crystal display panel 11. This allows for similarly precise control of the amount and direction of light incident on and emitted from the liquid crystal display panel 11. Therefore, in a space-floating image display system using the image display device 1 configured as described above, the diffusion direction and diffusion angle of the image light of the space-floating image can be set to desired values. In this case, the reflective film on the reflective surface may be designed to have high reflectivity and reduce the dependency of the reflectivity on the incident angle by adding a Ti or SiO reflective coating to the aluminum reflective film. The aluminum reflective film described above has a lower reflectance in the blue-green wavelength region below 500 nm than in the green-red region, so when designing an enhanced reflection film, it is also important to improve the purity of white in order to reduce the dependency of reflectance on the angle of incidence and improve color reproducibility.

[0093] As shown in Figure 14, the LED 14 is soldered to a metallic substrate 102. This allows the heat generated by the LED 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. By leaving a space between them, the heat generated by the LED can be dissipated into the air, improving the cooling effect. As a result, the operating temperature of the LED can be reduced, thereby maintaining luminous efficiency and extending its lifespan.

[0094] In the light source device described above, the light utilization efficiency can be improved by 1.8 times by using the polarization conversion element 21. The configuration of the optical system related to this light source device will be described in detail below with reference to Figures 15A, 15B, 15C, and 15D.

[0095] 15A, 15B, and 15C show the state in which the LEDs 14 constituting the light source are mounted on the substrate 102, and these are configured as a unit 312 having a plurality of blocks, with the reflector 300 and the LEDs 14 forming a pair of blocks.

[0096] 15A(2) is the base material of the substrate 102. Generally, the metallic substrate 102 generates heat, so the base material 320 may be made of a plastic material or the like to insulate (thermally insulate) the heat of the substrate 102. It may also be made of a metal member to improve heat dissipation.

[0097] Furthermore, the reflecting surface 321 of the reflector 300 may have a shape that is asymmetric with respect to the optical axis of the light emitted from the LED 14. The reason for this will be explained with reference to Fig. 15A(2). In this embodiment, the reflecting surface of the 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.

[0098] 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, and the only difference is the direction of emission. Therefore, even if the light-emitting part has an area, if the distance between the polarization conversion element and the reflector 300 arranged in the subsequent stage is short, the amount of light incident on the polarization conversion element 21 and its conversion efficiency are hardly affected.

[0099] Furthermore, even if the mounting position of the LED 14 is shifted in the XY plane with respect to the focal point of the corresponding reflector 300, an optical system can be realized that can reduce the decrease in light conversion efficiency for the reasons described above. 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, and the mounting precision of the LED, which is a surface light source, can be significantly reduced. In this embodiment, the reflector 300 having a reflective surface formed by meridionally cutting out a portion of a paraboloid has been described, but the LED may also be placed in a portion of the cutout with the entire paraboloid as the reflective surface.

[0100] 15B(1) and 15C, the present embodiment is characterized in that the divergent light from the LED 14 is reflected by the parabolic surface 321 and converted into approximately parallel light, and then the parallel light is incident on the end face of the polarization conversion element 21 at the subsequent stage, and aligned into a specific polarization by the polarization conversion element 21. With this characteristic configuration, the present embodiment achieves a light utilization efficiency that is 1.8 times that of the example in FIG. 14 described above, thereby realizing a highly efficient light source.

[0101] At this time, the substantially 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 by the reflecting surface 307 having multiple inclinations, the light can be made to enter the liquid crystal display panel 11 in a direction perpendicular to the liquid crystal display panel 11.

[0102] In the example shown in this figure, the direction of the light (principal ray) entering the reflector from the LED is approximately parallel to the direction of the 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.

[0103] 15B(1), in order to improve the capture rate of divergent light from LED 14, the light beam that cannot be captured by reflector 300 is reflected by sub-reflector 308 provided on light-shielding plate 309 arranged above the reflector, reflected by the slope of sub-reflector 310 below, and made to enter the effective area of ​​polarization conversion element 21 in the subsequent stage, thereby further improving the light utilization efficiency. That is, in this embodiment, a part of the light reflected by reflector 300 is reflected by sub-reflector 308, and the light reflected by sub-reflector 308 is reflected by sub-reflector 310 in a direction toward light guide 306.

[0104] The substantially parallel light beams aligned to a specific polarization by the polarization conversion element 21 are reflected by a reflective shape provided on the surface of the reflective light guide 306 toward the liquid crystal display panel 11 arranged opposite the light guide 306. At this time, the light quantity distribution of the light beams incident on the liquid crystal display panel 11 is optimally designed by the shape and arrangement of the reflector 300 described above, and the shape (cross-sectional shape) of the reflective surface of the reflective light guide, as well as the inclination and surface roughness of the reflective surface.

[0105] The shape of the reflective surface provided 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.

[0106] As shown in FIG. 15B(2), the reflective surface 307 of the reflective light guide 306 can be configured to have multiple inclinations on one surface, thereby enabling more accurate adjustment of reflected light. As shown in FIG. 15B(2), the parallel light beam φ5 (R7-R10) from the reflector 300 is reflected by multiple surfaces (P7-P10) with different inclinations along its travel direction and directed toward the corresponding LCD panel portions. Note that the configuration of the reflective surface with multiple inclinations on one surface may also be achieved by using a multi-surface, polyhedral, or curved surface as the reflective surface. Furthermore, the diffusing effect of the diffuser 206 achieves a more uniform light intensity distribution. The light incident on the diffuser plate closer to the LED achieves a uniform light intensity distribution by changing the inclination of the reflective surface. As a result, the light intensity and emission direction of the light beam directed toward the LCD panel 11 can be adjusted with high accuracy. As a result, the amount and direction of light incident on the liquid crystal display panel 11 and the light emitted from the liquid crystal display panel 11 can also be controlled with high precision, so in a space-floating image display system using this image display device 1, the diffusion direction and diffusion angle of the image light of the space-floating image can be set to desired values.

[0107] In this embodiment, a plastic material such as heat-resistant polycarbonate is used for the base material of the reflecting surface 307. 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.

[0108] In this embodiment, the LED 14 and the reflector 300 are also partially adjacent to each other, but the temperature rise of the LED can be reduced by dissipating heat into the space on the opening side of the reflector 300. Furthermore, the substrate 102 and the reflector 300 may be arranged upside down compared to those in Figures 15A, 15B, and 15C.

[0109] However, if the substrate 102 is placed on top, the substrate 102 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 (on the side farther from the liquid crystal display panel 11) will simplify the internal configuration of the device.

[0110] 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 realizes a light source device with reduced 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. However, 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 light incident on the electrode pattern. However, 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.

[0111] Fig. 15D is a modified example of the light source device of Fig. 15B(1) and Fig. 15C. Fig. 15D(1) illustrates a modified example of a portion of the light source device of Fig. 15B(1). The other configuration is the same as that of the light source device described above in Fig. 15B(1), so illustration and repeated explanation will be omitted.

[0112] 15D(1), the height of recess 319 of sub-reflector 310 is adjusted to be lower than phosphor 114 so that the chief ray of fluorescence output laterally (in the X-axis direction) from phosphor 114 (see the straight line extending in a direction parallel to the X-axis in FIG. 15D(1)) can exit from recess 319 of sub-reflector 310. Furthermore, the height of light-shielding plate 410 is adjusted to be lower in the Z-axis direction relative to the position of phosphor 114 so that the chief ray of fluorescence output laterally from phosphor 114 can enter the effective area of ​​polarization conversion element 21 without being blocked by light-shielding plate 410.

[0113] Furthermore, 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 is adjusted so that the light reflected by the sub-reflector 308 is reflected and incident on the effective area of ​​the polarization conversion element 21 in the subsequent stage, thereby further improving the light utilization efficiency.

[0114] 15A(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, each having one or more recesses 319 and protrusions 318, periodically arranged in one direction. By using such an uneven shape, it is possible to configure the sub-reflector 310 so that the chief ray of the fluorescence output laterally from the phosphor 114 enters the effective area of ​​the polarization conversion element 21.

[0115] Furthermore, the concave and convex shapes of sub-reflector 310 are periodically arranged at a pitch such that concave portions 319 are located at positions where LEDs 14 are present. That is, each of phosphors 114 is periodically arranged in one direction corresponding to the pitch of the arrangement of concave portions of the concave and convex shapes of sub-reflector 310. Note that when phosphor 114 is provided in LED 14, phosphor 114 may be expressed as a light-emitting portion of the light source.

[0116] 15D(2) illustrates a modified example of a portion of the light source device of FIG. 15C. Other configurations are the same as those of the light source device of FIG. 15C, and therefore illustrations and repeated explanations are omitted. As shown in FIG. 15D(2), the sub-reflector 310 is not necessary, but as in FIG. 15D(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 the 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.

[0117] 15A, 15B, 15C, and 15D, side walls 400 may be provided as shown in Fig. 15A(1) 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. When side walls 400 are provided, they are arranged to sandwich the space between the light guide 306 and the diffuser plate 206.

[0118] The light exit surface of the polarization conversion element 21, which emits light that has been polarization-converted by the polarization conversion element 21, faces a 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 a portion of 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 FIG. 15B(1)). In other words, the surface of the side wall 400 facing the 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.

[0119] Of the inner surfaces of the side wall 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 surface of the polarization conversion element 21, light with an unexpected polarization state will be generated, causing stray light. In other words, by making the above surface a surface with 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. Furthermore, the side wall 400 may be configured to have holes in parts to allow air to pass through, thereby improving the cooling effect.

[0120] 15A, 15B, 15C, and 15D have been described assuming a configuration using the 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.

[0121] <Another example of light source device 2> Next, the configuration of the optical system for a light source device using a reflective light guide 304 based on the light source device shown in Example 1 of the light source device will be described in detail with reference to Figures 16A(1), (2), (3) and 16B.

[0122] 16A shows a state in which the LEDs 14 constituting the light source are mounted on the substrate 102, and these are configured as a unit 328 having a plurality of blocks, each of which is a pair of a collimator 18 and an LED 14. Since the collimator 18 in this embodiment is located close to the LED 14, a glass material is used for the collimator 18 in consideration of heat resistance. In addition, by providing a light shielding plate 317 in the stage before the light enters the polarization conversion element 21, it is possible to prevent or suppress unwanted light from entering the optical system in the subsequent stage, thereby reducing the temperature rise caused by the unwanted light.

[0123] Other configurations and effects of the light source shown in Fig. 16A are the same as those in Fig. 15A, Fig. 15B, Fig. 15C, and Fig. 15D, and therefore repeated explanations will be omitted. The light source device in Fig. 15A may be provided with side walls, as explained in Fig. 15A, Fig. 15B, and Fig. 15C. The configurations and effects of the side walls have already been explained, and therefore repeated explanations will be omitted.

[0124] Fig. 16B is a cross-sectional view of Fig. 16A(2). The configuration of the light source shown in Fig. 16B has already been described above in <Example 1 of Light Source Device of Example 1 of Image Display Device>, so repeated description will be omitted.

[0125] <Diffusion plate structure> 17 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 the collimator 18, converted into 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 FIG. 17).

[0126] Furthermore, of the light emitted from the polarization conversion element 21, the divergent light beam is totally reflected by the inclined surfaces of the protrusions having inclined surfaces provided on the incident surface of the diffuser plate 206, and then enters the liquid crystal display panel 11. In order to totally reflect the light emitted from the polarization conversion element 21 by the inclined surfaces of the protrusions of the diffuser plate 206, the angle of the inclined surfaces of the protrusions is changed based on the distance from the polarization conversion element 21. If the angle of the inclined surface of the protrusions on the side farther from the polarization conversion element 21 or farther from the LEDs is α, and the angle of the inclined surface of the protrusions on the side closer to the polarization conversion element 21 or closer to the LEDs is α', then α is smaller than α' (α<α'). By setting in this way, it becomes possible to effectively utilize the polarization-converted light beam.

[0127] <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.

[0128] 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. That is, by adjusting the arrangement of the microlens array, it is possible to adjust the emission characteristics in the X-axis and Y-axis directions of the image light beam emitted from the image display device 1, and as a result, it is possible to obtain an image display device with desired diffusion characteristics.

[0129] As a further configuration example, two lenticular lenses may be combined and arranged at a position where the image light emitted from the image display device 1 passes, or a sheet that adjusts the diffusion characteristics by arranging a microlens array in a matrix may be provided. By configuring the optical system in this way, the brightness (relative brightness) of the image light in the X-axis and Y-axis directions can be adjusted according to the reflection angle of the image light (reflection angle with the vertical reflection as the reference (0 degrees)).

[0130] In this example, 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 18(b). Specifically, in the plot curves of Example 1 (Y direction) and Example 2 (Y direction), the brightness characteristic in the vertical direction is made steeper, and further, by changing the balance of the directional characteristics in the up and down direction (positive and negative directions of the Y axis), it is possible to increase the brightness (relative brightness) of light due to reflection and diffusion.

[0131] Therefore, according to this embodiment, the image light has a narrow diffusion angle (high straightness) and contains only specific polarization components, like the image light from a surface-emitting laser image source, and can be adjusted to suppress the ghost images that would occur in the retroreflective member when using an image display device using conventional technology, and to efficiently deliver the spatially floating image caused by retroreflection to the viewer's eyes.

[0132] Furthermore, the light source device described above can provide directional characteristics with significantly narrower angles in both the X-axis and Y-axis directions compared to the diffusion characteristics of emitted light from a general liquid crystal display panel shown in (A) and (B) of Figure 19 (indicated as "conventional characteristics" in the figure). In this embodiment, by providing such narrow-angle directional characteristics, it is possible to realize an image display device that emits nearly parallel image light beams in a specific direction and emits light of a specific polarization.

[0133] FIG. 18 shows an example of the characteristics of the lenticular lens employed 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 vertically, with the peak of the light emission direction at an angle of approximately 30 degrees upward from the vertical direction (0 degrees). Furthermore, the plot curves of characteristic A and characteristic B shown in the graph of FIG. 18 show examples of characteristics in which the image light above the peak luminance is further concentrated at approximately 30 degrees to enhance the luminance (relative luminance). Therefore, in characteristic A and characteristic B, as can be seen by comparing them 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°).

[0134] That is, with the optical system including the lenticular lens described above, 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 image position of the floating image that is reflected or transmitted through the window glass and focused at the desired position can be significantly improved. As a result, it is possible to efficiently deliver light with a narrow diffusion angle (high linearity) and only specific polarization components to the eyes of viewers indoors or outdoors. As a result, even if the intensity (brightness) of the image light from the image display device 1 is reduced, the viewer can accurately recognize the image light and obtain information. In other words, by reducing the output of the image display device 1, a display system with low power consumption can be realized.

[0135] Various embodiments or examples (i.e., specific examples) to which the present invention is applied have been described in detail above. 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 to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, 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.

[0136] The light source device described above is not limited to the space floating image display device, but can also be applied to display devices such as HUDs, tablets, digital signage, and the like.

[0137] The technology according to this embodiment displays high-resolution, high-brightness floating images in a floating state, allowing users to operate the device 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 the "3 Good Health and Well-Being" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0138] 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 a bright, clear, floating image in space. The technology according to the present embodiment can 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 the United Nations' Sustainable Development Goals (SDGs): "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation" and "Make cities and towns sustainable."

[0139] Furthermore, the technology according to the above-described embodiment makes it possible to form a floating image in space using highly directional (linear) video light. The technology according to the fifth embodiment makes it possible to provide a non-contact user interface with less risk of people other than the user peeking at the floating image in space, even when displaying images that require high security, such as those in bank ATMs or ticket machines at train stations, 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" of the Sustainable Development Goals (SDGs) advocated by the United Nations. [Explanation of symbols]

[0140] 1...image display device, 2...transmissive retroreflective member, 3...spatial image (space-floating image), 3a, 3b...ghost image, 100...transmissive plate, 13...light source device, 250...light control sheet, 251...circuit board, 249...FPC, 252...frame structure, 256...power supply unit (mobile battery), 253...housing, 254...hinge (rotation mechanism), 102...substrate, 11...liquid crystal display panel, 206...diffuser, 21...polarization conversion element, 300...reflector, 213...λ / 2 plate, 306...reflective light guide, 308, 310...sub-reflector.

Claims

1. A space floating image display system, a housing that holds the display panel and the light source device; a power supply unit including a power source and connected to the housing via a first connecting portion; a frame structure that holds a retroreflective member that is movably connected to the housing via a second connecting portion; The housing and the power supply unit are movably connected via the first connecting portion. A floating video display system.

2. 2. The space floating image display system according to claim 1, The retroreflective member is a transmissive retroreflective member. A floating video display system.

3. A space floating image display system, a housing that houses the display panel and the light source device; a power supply unit including a power source and connected to the housing via a first connecting portion; a transparent member connected to the power supply unit via a second connecting portion; A retroreflective member is disposed above the power supply unit. A floating video display system.

4. 4. The space floating image display system according to claim 3, the housing and the power supply unit are movably connected via the first connecting portion, the power supply unit and the transparent member are movably connected via the second connecting unit; A floating video display system.

5. 4. The space floating image display system according to claim 3, The retroreflective member is a reflective retroreflective member. A floating video display system.

6. A space floating image display system, A display panel for displaying images and a light source device are housed in a housing, The display panel has a structure in which a retroreflective member is held by a frame structure, the retroreflective member reflecting the image light from the display panel and displaying a real image floating in the air using the reflected light, The frame structure and the housing are connected by a first connection portion; The structure allows the relative angle between the retroreflective member and the display panel built into the housing to be set arbitrarily, one end of the frame structure is connected to the housing by the first connection portion, The other end of the housing is connected to a power supply unit by a second connection part. A floating video display system.

7. 7. The space floating image display system according to claim 6, The housing and the power supply unit are connected by the second connection unit, and the driving power of the display panel and the light source device is supplied from the power supply unit.

8. 7. The space floating image display system according to claim 6, A space floating image display system, wherein the imaging position of the space floating image can be changed by setting the frame structure at any angle relative to the housing, with the housing being used as an installation surface.

9. 7. The space floating image display system according to claim 6, an image light control sheet for controlling the diffusion characteristics of image light is provided on the image display surface of the display panel; the image light control sheet is disposed between the retroreflective member and the display panel, the image light control sheet is a viewing angle control film for the display panel; A floating video display system.

10. 2. The space floating image display system according to claim 1, The diffusion angle and diffusion direction of the image light beam diffused from the space floating image are adjusted by the image light control sheet and the diffusion characteristics of the light source device. A floating video display system.

11. 7. The space floating image display system according to claim 6, The light source device is a point or surface light source; a reflector that reflects light from the light source; a light guide that guides the light from the reflector toward the display panel, The reflecting surface of the reflector has an asymmetric shape with respect to the optical axis of the light emitted from the light source. A floating video display system.

12. 12. The space floating image display system according to claim 11, The light guide is a reflective light guide. A floating video display system.

13. 12. The space floating image display system according to claim 11, The reflector is made of a plastic material, a glass material, or a metal material. A floating video display system.

14. A space floating image display system, a display panel for displaying an image and a light source device for the display panel are housed in a housing; The display panel has a structure in which a transmissive retroreflective member is held by a frame structure, the transmissive retroreflective member reflecting image light from the display panel and displaying a real image floating in the air using the reflected light, The frame structure and the housing are connected by a first connection portion; The structure is such that the relative angle between the transmissive retroreflective member and the display panel built into the housing can be set arbitrarily, The housing and the power supply unit are connected by a second connection unit, and when the space-floating image is displayed, the power supply unit is arranged approximately perpendicular to the housing, and the space-floating image display system is characterized by having a housing structure that can be arranged to block external light entering the transmissive retroreflective member.

15. A space floating image display system, a display panel for displaying an image and a light source device for the display panel are housed in a housing; The display panel has a structure in which a retroreflective member is held by a frame structure, the retroreflective member reflecting the image light from the display panel and displaying a real image floating in the air using the reflected light, The frame structure and the housing are connected by a connection portion, The structure is such that the relative angle between the retroreflective member and the display panel built into the housing can be set arbitrarily, The floating image display system has a portable structure in which the housing and the power supply unit are connected by a hinge unit, and the power supply unit and the housing are folded together with the frame structure.

16. A space floating image display system, A transparent member; a housing that houses a display panel and a light source device and is movably connected to the transparent member via a second connecting portion; a retroreflective member that reflects light from the display panel housed in the housing to the transparent member; a power supply unit including a power source, The retroreflective member is disposed between the housing and the power supply unit. A floating video display system.

Images