Space-floating image display device

Abstract

To provide a space-floating image display device capable of displaying pseudo-3D space-floating images contributing to sustainable development goals; I,e., "3 Health and Well-Being for All", "9 Build a Foundation for Industry and Innovation", and "11 Creating a Sustainable City".SOLUTION: The space-floating image display device includes: a display panel for displaying images; a retroreflective optical member that reflects image light from the display panel and displays space-floating images in the air with reflected light; and an image light control film on the surface of the retroreflective optical member.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a technology for a space-floating image display device that displays a space-floating image with high visibility even in a bright usage environment, and to a technology for a space-floating image display device that uses an optical system that allows multiple viewers to simultaneously observe the image of the space-floating image as a real image. [Background technology]

[0002] Patent No. 6632747 (Patent Document 1) has proposed a technique for reducing the size of a space floating image display device that displays images in the air and increasing the projection distance of the spatial image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6632747 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of image display device, it is desirable to increase the amount of projection (in other words, the amount of floating) of the floating image from the floating image display device to expand the visible range of the aerial image. On the other hand, in order to increase the size of the floating image, it is necessary to increase the size of the image displayed on the image display unit (display device). In that case, with conventional technology, the floating image display device (set) would end up being large.

[0005] An object of the present invention is to provide a space floating image display technology capable of more suitably displaying a space floating image. [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 a number of means for solving the above problems, but one example is as follows. A space-floating image display device that forms a three-dimensional space-floating image includes a display panel that displays an image, a retroreflective optical member that reflects image light from the display panel and displays a space-floating image in the air using the reflected light, and an image light control film on the surface of the retroreflective optical member. Effect of the Invention

[0007] According to the present invention, it is possible to provide a space floating image display technology capable of more suitably displaying a space floating image. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of a main part configuration and a retroreflective optical part configuration for explaining the principle of a space floating image display device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is an explanatory diagram showing a retroreflective optical member as a subject of a space floating image display device. [Diagram 3] 4 is a characteristic diagram showing the relationship between the surface roughness of a retroreflective optical member and the amount of blur of a retroreflected image. FIG. [Figure 4] 1 is a diagram showing the principle of a ghost image reduction means of a space floating image display device according to an embodiment of the present invention; [Diagram 5] 1 is a diagram showing the principle of a first embodiment of a depth reduction means of a space floating image display device; [Figure 6] 11A and 11B are diagrams illustrating the principle of a second embodiment of the depth reduction means of the space floating image display device. [Figure 7] 11 is a diagram showing the principle of a third embodiment of a set volume reduction means for a space floating image display device. FIG. [Figure 8] FIG. 13 is a diagram showing the principle of a fourth embodiment of the set volume reduction means of the space floating image display device. [Figure 9]FIG. 13 is a diagram showing the principle of the fifth embodiment of the set volume reduction means of the space floating image display device. [Figure 10] FIG. 13 is a diagram showing the principle of a sixth embodiment of the set volume reduction means of the space floating image display device. [Figure 11] FIG. 13 is a diagram showing the principle of the seventh embodiment of the set volume reduction means of the space floating image display device. [Figure 12] 1A and 1B are diagrams illustrating the principle of an optical element of a space floating image display device. [Figure 13] 1 is a diagram showing the principle of a first embodiment of a set volume reduction means for a space floating image display device; FIG. [Figure 14] 11 is a diagram showing the principle of a second embodiment of a set volume reduction means for a space floating image display device. FIG. [Figure 15] 11 is a diagram showing the principle of a third embodiment of a set volume reduction means for a space floating image display device. FIG. [Figure 16] FIG. 2 is a top view showing a first structure of an optical component of the space floating image display device. [Figure 17] 11 is a diagram showing an image surface shape of a first space floating image obtained by the space floating image display device. FIG. [Figure 18] FIG. 2 is a top view showing a second structure of the optical components of the space floating image display device. [Figure 19] 11 is a diagram showing a second image surface shape of the space floating image obtained by the space floating image display device. FIG. [Figure 20] 1 is an explanatory diagram of the principle of enlarging a space floating image of a space floating image display device. FIG. [Figure 21] 1 is a characteristic diagram showing the angular characteristics of light output from an image display device. [Figure 22] FIG. 2 is a diagram illustrating an example of a specific configuration of a light source device. [Diagram 23] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 24] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Diagram 25] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 26]FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 27] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 28] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Figure 29] FIG. 2 is an explanatory diagram of the diffusion characteristics of a display device. [Diagram 30] FIG. 2 is an explanatory diagram of the diffusion characteristics of a display device. [Diagram 31] FIG. 2 is a cross-sectional view showing an example of a specific configuration of a light source device. [Diagram 32] FIG. 2 is a diagram illustrating an example of a specific configuration of a light source device. [Diagram 33] 1 is a diagram showing an example of a usage form of a space floating image display device according to an embodiment; [Diagram 34] FIG. 11 is a diagram showing a second embodiment of the main configuration of a space floating image display device installed in a car. [Diagram 35] FIG. 1 is a characteristic diagram showing the reflection characteristics of glass with respect to the angle of incidence of light due to differences in polarization components. [Diagram 36] FIG. 2 is a characteristic diagram showing the spectral irradiance of sunlight. [Figure 37] FIG. 1 is a characteristic diagram showing the relative values ​​of the spectral radiance of a high-brightness white LED. [Figure 38] 1 is a characteristic diagram showing the radiation characteristics of a high-brightness white LED. [Figure 39] FIG. 11 is a characteristic diagram showing a filter characteristic for selecting blue light from a light source. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Conventional space floating image display device> Conventional floating image display devices use organic EL panels or liquid crystal display panels that have the property of diffusing image light as a high-resolution color image display source, and are configured in combination with retroreflective optical members. This floating image display device produces a planar floating image of the same size as the color image display source.

[0010] Moreover, the image light reflected by the retroreflective optical member has a wide-angle diffusion characteristic similar to that of the image display source. On the surface of the retroreflective optical member, hexahedral reflecting members are aligned as shown in Fig. 1(B). As shown in Fig. 2, since the reflecting surface of the retroreflective optical member 2 is a hexahedron, in addition to the reflected light 6002 caused by the normal image light (principal light beam of the image light) 6001, the reflected light 6004 caused by the image light (oblique light beam of the image light) 6003 obliquely incident on the retroreflective optical member 2 (reflecting members 2a, 2b, 2c, etc.) generates a ghost image, impairing the image quality of the floating image in space.

[0011] Since the reflecting member of the retroreflective optical member 2 shown as an example of the prior art is a hexahedron, in addition to the normal floating-in-space image, multiple ghost images from the first ghost image to the sixth ghost image (not shown) are generated. For this reason, people other than the viewer (user) can also view the ghost images, which are the same floating-in-space images, and there is a major problem that the apparent resolution of the floating-in-space image is significantly reduced. Here, an example of a structure that realizes retroreflection by reflection by a hexahedron shown in FIG. 1(B) is shown. Not limited to this, there is a problem that ghost images are generated for the same reason in optical members that obtain retroreflected images by at least two or more reflections that cause retroreflection. The above describes the case where the reflecting surface is a hexahedron with a protruding shape, but the same effect can be obtained with a hexahedron with a reflecting surface that is concave with respect to the surroundings.

[0012] In addition, there is a configuration in which image light from a display device having a narrow-angle directional characteristic described later is reflected by a retroreflective optical member, thereby obtaining a floating image in space. According to the inventor's experiment, in addition to the ghost image described above, the floating image in space obtained by this method was visually recognized as blurring for each pixel of the liquid crystal display panel, as shown in FIG.

[0013] <Outline of the space floating image display device> The configuration of the space floating image display device of this embodiment will be described more specifically with reference to FIG. 1. As shown in FIG. 1(A), a display device 1 that diverges image light of a specific polarization at a narrow angle is provided in an oblique direction (direction of optical axis 5001) of a transparent member 100 such as glass. This oblique direction is a predetermined direction having an angle that is oblique to the plane direction of the transparent member 100 and a direction perpendicular thereto, as shown in the figure. The display device 1 includes a display panel 11 that is an image source and emits image light, and a light source device 13 (in other words, a backlight) that generates light of a specific polarization having a narrow-angle diffusion characteristic. The display panel in this embodiment will be described using a liquid crystal display panel.

[0014] Image light of a specific polarization from the display device 1 is reflected by a polarization separation member 101 having a film that selectively reflects image light of a specific polarization provided on a transparent member 100, and the reflected light is incident on the retroreflective optical member 2 in the direction of an optical axis 5002. In the drawing, the polarization separation member 101 is formed in a sheet shape and is adhered to a surface of the transparent member 100 (the lower surface as shown in the figure). A λ / 4 plate 21 is provided on the image light incident surface of the retroreflective optical member 2. The image light is made to pass through the λ / 4 plate 21 twice in total, when it enters the retroreflective optical member 2 and when it exits, and is thereby polarization-converted from a specific (one) polarization to the other polarization.

[0015] Here, the polarization separation member 101, which selectively reflects image light of a specific polarization, has the property of transmitting polarized light of the other polarization that has been polarization-converted. Therefore, the image light of a specific polarization after polarization conversion is transmitted through the polarization separation member 101 in the direction of optical axis 5002. The image light transmitted through the polarization separation member 101 forms a real image, a floating-in-space image 220, at a predetermined position outside the transparent member 100 (upper side in the drawing), in the direction of optical axis 5003 corresponding to the optical axis 5002.

[0016] The light forming the space-floating image 220 is a collection of light rays that converge from the retroreflective optical member 2 to the optical image of the space-floating image 220, and these light rays continue to travel straight even after passing through the optical image of the space-floating image 220. Therefore, the space-floating image 220 is an image with high directivity, unlike the diffuse image light formed on a screen by a general projector or the like. Therefore, in the illustrated configuration, when a user (corresponding eye point) views the space-floating image 220 from the direction of the arrow A, the space-floating image 220 is viewed as a suitable bright image, but when another person views the space-floating image 220 from a direction different from the arrow A, for example, the arrow B, the space-floating image 220 cannot be viewed as an image at all.

[0017] This high directional characteristic is extremely advantageous when used in a system that displays necessary video information only to the driver (a user whose eye point corresponds to direction A), or in a system that displays highly confidential video that must be concealed from other people outside the vehicle facing the driver (for example, people whose eye point corresponds to direction B) or people in other positions inside the vehicle.

[0018] <Improvement of the performance of the space floating image display device according to the present invention> In the conventional space floating image display device, depending on the performance of the retroreflective optical member 2, the polarization axis of the reflected image light may become misaligned. In this case, a part of the image light with the misaligned polarization axis is reflected by the above-mentioned polarization separation member 101 and returns to the display device 1. This light may be reflected again on the image display surface of the liquid crystal display panel 11 constituting the display device 1, generating the above-mentioned ghost image, thereby degrading the image quality of the space floating image 220. Therefore, in this embodiment, an absorbing polarizing plate 12 is provided on the image display surface of the display device 1. The image light emitted from the display device 1 is transmitted through the absorbing polarizing plate 12, and the reflected light returning from the polarization separation member 101 is absorbed by the absorbing polarizing plate 12. This makes it possible to suppress the above-mentioned re-reflection, etc., and to prevent the degradation of image quality due to the ghost image of the space floating image 220.

[0019] The above-mentioned polarization separation member 101 may be, for example, a reflective polarizing plate or a metal multilayer film that reflects a specific polarized wave.

[0020] Next, FIG. 1(B) shows the surface shape of a retroreflective optical member manufactured by Nippon Carbide Industrial Co., Ltd., which was used in this study as a representative retroreflective optical member 2. This retroreflective optical member has hexagonal prisms (retroreflective parts) regularly arranged in the plane. A light ray incident on the interior of the regularly arranged hexagonal prisms is reflected by the walls and bottom of the hexagonal prisms, and is emitted as retroreflective light in a direction corresponding to the incident light, forming a normal image R1 (an image formed at a predetermined position) of the space floating image 220 shown in FIG. 1(A). The retroreflective optical member 2 can also have a similar effect by providing a reflective surface on the bottom surface so that the hexagonal prism is in contact with the air, forming a hexagonal corner surface on the upper part of the reflective surface, making the hexahedron and hexagonal prism hollow, and filling the remaining part with resin, as shown in FIG. 1(B).

[0021] On the other hand, as shown in FIG. 2, among the image light from the display device 1, the image light obliquely incident on the retroreflective optical member 2 forms a ghost image in addition to the normal image R1. The space-floating image display device of the present invention displays a space-floating image, which is a real image, based on the image displayed on the display device 1. The resolution of this space-floating image depends greatly on the outer shape D and pitch P of the hexagonal prism (retroreflective part) constituting the retroreflective optical member 2 shown in FIG. 1(B) in addition to the resolution of the liquid crystal display panel 11. For example, when a 7-inch WUXGA (1920×1200 pixels) liquid crystal display panel is used, even if one pixel (one triplet) is about 80 μm, if the diameter D of the hexagonal prism is 240 μm and the pitch P is 300 μm, one pixel of the space-floating image is equivalent to 300 μm. For this reason, the effective resolution of the space-floating image is reduced to about 1 / 3.

[0022] Therefore, in order to make the resolution of the spatial floating image equal to that of the display device 1, it is desirable to make the diameter D and pitch P of the hexagonal prisms of the retroreflective optical member 2 close to one pixel of the liquid crystal display panel 11. On the other hand, in order to suppress the occurrence of moire due to the hexagonal prisms of the retroreflective optical member 2 and the pixels of the liquid crystal display panel 11, it is preferable to design the pitch ratio of each to be a different integer multiple of one pixel. In addition, it is preferable to arrange the shape so that none of the sides of the hexagonal prisms of the retroreflective optical member 2 overlaps with any of the sides of one pixel of the liquid crystal display panel 11.

[0023] Furthermore, as shown in FIG. 2, when external light 6000 enters the retroreflective optical member 2 from an oblique direction, it is reflected by the surface of the retroreflective optical member 2 (hexagonal columns 2a, 2b, 2c, etc.), generating ghost images in various directions and significantly degrading the image quality of the floating image in space. The inventors experimentally determined the relationship between the amount of blur l (L) of the image of the floating image in space that is permissible for improving the image quality and visibility of the floating image in space and the pixel size L. In this case, the inventors created a display device 1 that combines a liquid crystal display panel with a pixel pitch of 40 μm with a light source device having the characteristics of a narrow divergence angle (for example, a divergence angle of 15°) of this embodiment, and determined the relationship.

[0024] It was found that the amount of blur l at which visibility is deteriorated is preferably 40% or less of the pixel size, and is barely noticeable if it is 15% or less. The surface roughness of the reflective surface at which the amount of blur l is tolerable (surface roughness 6010 of the retroreflective surface in FIG. 2) is an average roughness of 160 nm or less within a measurement distance of 40 μm, and it was found that the surface roughness of the reflective surface is preferably 120 nm or less to make the amount of blur l less noticeable. For this reason, it is desirable to reduce the surface roughness of the retroreflective optical member 2 described above, and to make the surface roughness of the reflective film and its protective film that form the reflective surface less than the above-mentioned value.

[0025] On the other hand, in order to manufacture the retroreflective optical member 2 at a low cost, it is preferable to use a roll press method for molding. Specifically, this is a method in which a plurality of retroreflective parts (hexagonal columns in FIG. 2) are aligned and shaped on a film. In this method, the inverse shape of the shape to be shaped is formed on the roll surface, an ultraviolet curable resin is applied onto a base material for fixing, and the required shape is formed by passing it between the rolls, and then the retroreflective optical member 2 of the desired shape is obtained by irradiating it with ultraviolet light and curing it.

[0026] The display device 1 of this embodiment shown in Fig. 1 can reduce the possibility of image light being incident obliquely (Fig. 2) on the above-mentioned retroreflective optical member 2 by using a liquid crystal display panel 11 and a light source device 13 that generates light of a specific polarized wave having a narrow-angle diffusion characteristic described in detail later. This results in a structurally excellent device in that even if a ghost image occurs, the ghost image is difficult to see because of its low brightness.

[0027] Furthermore, it is preferable to provide an image light control film (external light control film, optical sheet) 250 for narrowing the viewing angle on the surface of the retroreflective optical member 2 as shown in FIG. 4. This optical sheet 250 has transparent parts 251, which are light-transmitting members, and black parts 255, which are light-absorbing members (dot pattern areas in the drawing), arranged alternately in the surface direction. The light-absorbing members extend in the depth direction of FIG. 4. When diffuse light from the image source enters the retroreflective optical member 2 from an oblique direction, this optical sheet 250 blocks it with the black parts 255, and at the same time, even if the image light is scattered due to the surface roughness of the retroreflective optical member 2 (for example, scattering 253 and scattering 254 in FIG. 4), it is absorbed by the black parts 255. Therefore, it is possible to suppress the occurrence of ghost images of the floating image in space. Of the image light 4001 (image light close to perpendicular incidence) normally incident on the retroreflective optical member 2, the regular reflected light (retroreflected light 4002) that is not scattered passes through the transparent portion 251 to form a space floating image.

[0028] As the optical sheet 250 for suppressing the scattered light of the retroreflective optical member 2, for example, a view control film (VCF) of Shin-Etsu Polymer Co., Ltd. is suitable. Since the structure of this film is a structure in which transparent silicon and highly shielding black silicon in a louver shape are alternately arranged, the light incident from an oblique direction is absorbed by the black silicon. Therefore, the same effect as that of the optical sheet 250 of this embodiment (FIG. 4) can be expected.

[0029] In order to reduce the generation of ghost images of the spatially floating image, when using the above-described video light control film 250, the pitch Ps of the light transmission member (transparent portion 251) and the light absorption member (black portion 255) is desirably 10 times or less with respect to the pixels of the video displayed on the video source. When the thickness T of the video light control film 250 is desired to make the viewing angle α smaller than 45 degrees, h / w may be made larger than 1.0. In other words, it is preferable to select a video light control film 250 having a relationship of 0.5 < Ps / T < 2.0. Further, the inclination angle of the black portion 255 is preferably arranged perpendicular (inclination angle 0) to the retroreflective optical member 2. Also in the embodiments shown in FIGS. 33 and 34 described later, by providing the video light control film 250 on the surface of the retroreflective optical element 2100, the generation of ghost images can be significantly reduced.

[0030] <Principle 1 of Miniaturization of Spatially Floating Image Display Device> Using FIGS. 5 and 6, a first technical means for miniaturizing the spatially floating image display device will be described. FIG. 5 is an explanatory diagram of the principle of miniaturization. The display device 1 includes a light source device 13 having narrow-angle diffusion characteristics and a liquid crystal display panel 11 as a video display element. A λ / 2 plate 111 (half-wave plate) is provided in the right half region of the video display surface of the liquid crystal display panel 11. As a result, the video light emitted from the right half region and the left half region of FIG. 5 has different polarization directions, and is divided into the left polarization separation member 101 and the right polarization separation member 102, and reflection and transmission are divided corresponding to their respective polarization directions, thereby shortening the dimension in the thickness direction (depth direction; vertical direction in FIG. 5) of the spatially floating image display device.

[0031] More specifically, the image light on the right side of the drawing (half of the right side) of the liquid crystal display panel 11 is converted to S-polarized waves (shown by solid lines in the drawing) by providing a λ / 2 plate 111, and one (right) polarization separation member 102 has the property of reflecting S-polarized waves and transmitting P-polarized waves (shown by dashed lines in the drawing). Conversely, the image light on the left side of the drawing (half of the left side) of the liquid crystal display panel 11 is converted to P-polarized waves by not providing a λ / 2 plate 111, and the other (left) polarization separation member 101 has the property of transmitting S-polarized waves and reflecting P-polarized waves. In this way, the S-polarized image light reflected by the right polarization separation member 102 transmits through the left polarization separation member 101 and is incident on and reflected by the left retroreflective optical member 2 (2A), forming a floating image in space. Conversely, the P-polarized image light reflected by the left polarization separation member 101 passes through the right polarization separation member 102 and is incident on and reflected by the right retroreflective optical member 2B, thereby forming a floating image in space.

[0032] A λ / 4 plate 21 (phase difference plate, 1 / 4 wavelength plate) is provided on the surface of each of the left and right retroreflective optical members 2 (2A, 2B). The image light reflected by the left retroreflective optical member 2A passes through the λ / 4 plate 21 a total of two times and is converted into P-polarized light. The converted P-polarized image light is reflected by the left polarization separation member 101, passes through the transparent member 100, and displays a space-floating image 2201 (a space-floating image in the left region shown by the dashed line) at a predetermined position above. Similarly, the image light reflected by the right retroreflective optical member 2B passes through the λ / 4 plate 21 a total of two times and is converted into S-polarized light. The converted S-polarized image light is reflected by the right polarization separation member 102, passes through the transparent member 100, and displays a space-floating image 2202 (a space-floating image in the right region shown by the solid line) at a predetermined position above.

[0033] In addition, in the configuration of this embodiment, the position of the retroreflective optical members 2 (2A, 2B) is movable in the left-right direction of the arrow in the drawing. By moving the retroreflective optical members 2 (2A, 2B), the display position of the space-floating image 220 (also described as the image surface) can be changed to any position within a predetermined range in the thickness direction (up-down direction in FIG. 5). The interval (distance) L shown in the figure is the distance between the transparent member 100 and the image surface of the space-floating image 220 (2201, 2202) in the thickness direction. This distance L can be changed by moving. At this time, there is no need to change the dimension of the space-floating image display device in the thickness direction (up-down direction in FIG. 5). When changing the position of the image surface, for example, if the two left and right retroreflective optical members 2 (2A, 2B) are moved away from each other, the optical path length of the image light becomes longer below the transparent member 100, so that the position of the image surface becomes lower in the thickness direction. When the two left and right retroreflective optical members 2 (2A, 2B) are moved closer to each other, the optical path length of the image light becomes shorter below the transparent member 100, and the position of the image plane becomes higher in the thickness direction accordingly.

[0034] In addition, in the configuration of this embodiment, the position of the display device 1 may be configured to be movable in the up-down direction of the arrow in the drawing. By moving the display device 1, the display position of the floating image 220 can be changed to any position within a predetermined range in the thickness direction. In this case, it is not necessary to change the horizontal dimension of the floating image display device. For example, when the display device 1 is moved downward away from the polarization separation member, the optical path length of the image light becomes longer below the transparent member 100, and the position of the image plane becomes lower in the thickness direction accordingly.

[0035] A drive mechanism such as a motor may be used as the structure for moving the retroreflective optical member 2 and the display device 1. The controller of the space floating image display device may control the drive mechanism. Alternatively, the user may manually operate the structure to move the components.

[0036] As shown in FIG. 5, in this embodiment, the image displayed on the liquid crystal display panel 11 is inverted left and right by two polarization separation members (101, 102) functioning as mirrors. Therefore, the floating image 220 is inverted left and right with respect to the image on the liquid crystal display panel 11. Specifically, the image on the right side where the λ / 2 plate 111 is present is converted from S-polarized to P-polarized to become the floating image 2201 on the left side, and the image on the left side where the λ / 2 plate 111 is not present is converted from P-polarized to S-polarized to become the floating image 2202 on the right side. Therefore, taking the above-mentioned left and right inversion into consideration, the start position and display order of the image display for the image displayed on the liquid crystal display panel 11 may be appropriately selected depending on the number of divisions, the method, etc.

[0037] In this embodiment (FIG. 5), the image light emitted from the liquid crystal display panel 11 is P-polarized light, and the light emitted from the right half of the image display surface of the liquid crystal display panel 11 is S-polarized light by providing a λ / 2 plate 111 in the right half of the image display surface of the liquid crystal display panel 11. This is not limiting, and the image light emitted from the liquid crystal display panel 11 may be S-polarized light.

[0038] 5, a set of two left and right polarization separation members (left polarization separation member 101, right polarization separation member 102) is diagonally arranged at a predetermined position between a set of two left and right retroreflective optical members 2 (left retroreflective optical member 2A, right retroreflective optical member 2B) on the upper side of the display device 1. The two left and right polarization separation members and the two left and right retroreflective optical members 2 are arranged symmetrically with respect to the left and right center positions (boundary of the presence or absence of the λ / 2 plate 111) of the liquid crystal display panel 11 shown by the dashed dotted line in the figure. The right polarization separation member 102 is arranged above the right area where the λ / 2 plate 111 is present, and the left polarization separation member 101 is arranged above the left area where the λ / 2 plate 111 is not present.

[0039] Opposite the display device 1, a transparent member 100 (forming an opening) is disposed above them. The left-side polarization separation member 101 is disposed with its main surface in an oblique direction so as to reflect the image light from the left-side region toward the right-side polarization separation member 102 and the retroreflective optical member 2B (reflected at approximately 90 degrees in FIG. 5). The right-side polarization separation member 102 is disposed in an oblique direction different from that of the polarization separation member 101 so as to reflect the image light from the right-side region toward the left-side polarization separation member 101 and the retroreflective optical member 2A (reflected at approximately 90 degrees in FIG. 5). As shown in FIG. 5, the retroreflective optical members 2 (2A, 2B) are disposed almost perpendicular to the transparent member 100 of the opening of the space floating image display device. This can reduce ghost images caused by external light entering the retroreflective optical member 2.

[0040] A second technical means for further miniaturizing the space floating image display device will be described with reference to Fig. 6. In the first embodiment of Fig. 5, the screen of the liquid crystal display panel 11, which is the image source, is divided into two. In contrast, in the second embodiment shown in Fig. 6, the screen of the liquid crystal display panel 11, which is the image source, is divided into four. This allows for further miniaturization.

[0041] In FIG. 6, in the second embodiment, two retroreflective optical members 2 are arranged in the center of the screen (position of dashed line A) in comparison with the first embodiment in FIG. 5. In the second embodiment, two configurations like the first embodiment are arranged in parallel in the left-right direction of the screen of the display device 1. This divides the display screen of the liquid crystal display panel 11 into four, and as the space floating image 220, space floating images (2201, 2202, 2203, 2204) corresponding to each divided area can be obtained. In this embodiment, the image light emitted from the liquid crystal display panel 11 is P-polarized light (dashed line). In the left-right direction of FIG. 6 (the direction constituting the display plane), the rightmost 1 / 4 screen 601 and the central left 1 / 4 screen 603 can have the emitted light S-polarized light (solid line) by providing a λ / 2 plate 111 on the image display surface of the liquid crystal display panel 11.

[0042] Thus, in the second embodiment, a set of retroreflective optical members 2 (2A, 2B) and polarized light separating members (101, 102) are arranged in parallel in the direction of the screen (image display surface). As a result, by dividing reflection and transmission according to the respective polarization directions, the dimension in the thickness direction (vertical direction in FIG. 6) of the space floating image display device can be further shortened. In the configurations of FIG. 5 and FIG. 6, when the size of the screen (image display surface) is the same, the components of FIG. 6 (two sets of retroreflective optical members 2 and two sets of polarized light separating members) are smaller in size than the components of FIG. 5 (one set of retroreflective optical members 2 and one set of polarized light separating members), as shown in the figure. Therefore, the dimension in the thickness direction of the configuration of FIG. 6 is shorter than that of the configuration of FIG. 5.

[0043] Also, in the second embodiment, as in the first embodiment, the position of the retroreflective optical member 2 may be movable in the left-right direction of Fig. 6, and the position of the display device 1 may be movable in the up-down direction of Fig. 6. By these means, the display position of the floating image 220 can be changed to any position within a predetermined range in the up-down direction of Fig. 6. In this case, there is no need to change the dimension in the thickness direction of the floating image display device.

[0044] <Principle of miniaturization of the space floating image display device 2> A third technical means for miniaturizing the space floating image display device will be described with reference to FIG. 7 and FIG. 12. FIG. 7 is an explanatory diagram of the principle of miniaturization. The display device 1 is configured to have a light source device 13 having a narrow-angle diffusion characteristic and a liquid crystal display panel 11 as an image display element. In addition to the same components as in FIG. 5, the configuration of FIG. 7 has an optical element 2150 disposed at an upper position near the transparent member 100. The optical element 2150 has the effect of enlarging the space floating image. The lens effect of the optical element 2150 increases the area at the imaging position (virtual surface 700) of the space floating image 220 compared to the image display area of ​​the liquid crystal display panel 11, which is the image source. In addition, in this embodiment, the imaging position of the space floating image 220 can be appropriately selected by moving the display device 1 in the vertical direction in the drawing.

[0045] The optical element 2150 is an optical element having a diverging effect by making the emitted light telecentric with narrow-angle diffusion characteristics ("reference light distribution", "Example 1", "Example 2") shown in Fig. 21. At this time, the optical element 2150 controls the emission direction of the image light from the liquid crystal display panel 11 toward the area corresponding to each pixel assumed on the virtual surface 700 with respect to the original size 220a1 (solid line) and size 220a2 (dashed line) of the space floating image. As a result, the enlarged image 220b1 and the enlarged image 220b2 are obtained as the space floating image 220 at the desired position on the virtual surface 700.

[0046] The floating-in-space image (size 220a1) of the right-side region (solid line) in the original position is enlarged by the optical element 2150, becoming an enlarged image 220b1 of the right-side region (solid line) at the position of the virtual surface 700. The floating-in-space image (size 220a2) of the left-side region (dashed line) is enlarged by the optical element 2150, becoming an enlarged image 220b2 of the left-side region (dashed line). The original position of the floating-in-space image when the optical element 2150 is not provided is a position at a distance 701 from the transparent member 100 in the thickness direction. The position of the floating-in-space image 220 as an enlarged image when the optical element 2150 is provided is a position on the virtual surface 700 at a distance 702 further upward from the original position.

[0047] This embodiment has a structure capable of changing the optical distance between the image source and the retroreflective optical member 2. Specifically, it has a structure that moves the display device 1 up and down. By changing the optical distance with this structure, it is possible to change the position and size where the floating image 220 (magnified image) is formed.

[0048] A fourth technical means for miniaturizing the space-floating image display device will be described with reference to FIG. 8. In the fourth embodiment shown in FIG. 8, a microlens array 300 is arranged between the upper side of the display device 1 and the optical element 2150. The image light having a narrow angle of divergence emitted from each pixel of the liquid crystal display panel 11 of the display device 1, which is an image source, projects an image corresponding to each pixel in space by the action of the microlenses arranged in a matrix in the microlens array 300. At this time, in this embodiment, the position where the space-floating image 220 is formed (a collection of image forming points) is controlled by the focal length of the microlens. Therefore, in the fourth embodiment of FIG. 8, the space-floating image display device can be made smaller than the three methods (FIGS. 5, 6, and 7) using the retroreflective optical member 2 and the polarization separation member (101 and 102) described above.

[0049] In this embodiment, the focal length of microlens array 300 is increased to increase the floating amount (protrusion amount; distance in the thickness direction) of floating-in-space image 220, and optical element 2150, which is arranged between floating-in-space image 220 and microlens array 300 and has the effect of controlling the direction of the image light beam (divergence effect), changes the emission direction of the image light beam for each pixel with respect to the original size of the floating-in-space image, thereby obtaining an enlarged image of floating-in-space image 220 (enlarged image 801 at the position of virtual plane 700).

[0050] The optical element 2150 has the function of directing the pixels of the space floating image corresponding to each pixel on the image display surface of the liquid crystal display panel 11 to a desired position. This function will be described in detail with reference to FIG. 20. In the above-mentioned embodiment, the optical element 2150 is provided between the liquid crystal display panel 11, which is the image source, and the space floating image 220 (virtual surface 700), and controls the image formation position on the XY plane of the pixels (shown by broken lines in FIG. 20) of the space floating image 220 corresponding to the pixels (shown by solid lines in FIG. 20) arranged in a matrix on the liquid crystal display panel 11. On the other hand, the image formation position in the Z-axis direction (thickness direction) is uniquely determined by the interval (distance) L between the retroreflective optical member 2 and the liquid crystal display panel 11 in the first to third embodiments, and an image is formed at a predetermined position after reflection by the retroreflective optical member 2. In addition, in the method using the microlens array 300 in the fourth embodiment of FIG. 8, the image formation position can be controlled by the focal length of the microlens.

[0051] 20, the coordinate axes are shown with the center coordinates of the display area of ​​the liquid crystal display panel 11 as the origin of the XY plane, and the center coordinates of the screen of the corresponding floating-in-space image 220 as the origin of the XY plane. The pixels of the liquid crystal display panel 11 are arranged in a matrix in the horizontal direction (X) and vertical direction (Y) of the screen, and each pixel (hereinafter, one pixel is represented by three colors, RGB) has an address (Onn). On the other hand, the virtual surface 700 corresponding to the floating-in-space image 220 also has an address (Inn) corresponding to each pixel of the liquid crystal display panel 11, and the image light beam is directed to a desired position corresponding to the pixel on the XY plane of the displayed image by the lens action of the optical element 2150.

[0052] Specifically, in the optical system of the present invention shown in the first to third embodiments in which a space-floating image is obtained by making an image light beam having a narrow-angle diffusion characteristic incident on the retroreflective optical member 2 from each pixel of the liquid crystal display panel 11 and reflecting it, the most effective technical means for enlarging the space-floating image may be as follows. That is, the image light beam corresponding to each pixel (image light diverging from each pixel) may be incident on the optical element 2150 as an individual image light beam, and directed to a desired position on the XY plane by the lens action obtained by the shape of the entrance surface and the exit surface of the optical element 2150. At this time, the imaging position of the space-floating image 220 is uniquely determined by the distance L between the retroreflective optical member 2 and the liquid crystal display panel 11 described above, and the image is formed at a predetermined position after reflection by the retroreflective optical member 2. On the other hand, in the method using the microlens array 300 of the fourth embodiment, the imaging position can be controlled by the focal length of the microlens.

[0053] Next, the optimal diffusion characteristics of the image light emitted from each pixel of the liquid crystal display panel 11, which is the image source, will be described with reference to FIG. 21. If the narrow-angle characteristics are ±2 degrees or less as shown in the "reference light distribution" shown in FIG. 21, the ghost image generated by the retroreflective optical member 2 can be significantly reduced. On the other hand, in order to obtain uniform brightness to the periphery of the space-floating image, a moderate diffusion characteristic is required. Since the distance between the two eyes of the viewer is 65 mm on average, if the horizontal dimension of the screen is 65 mm or less, even with the reference light distribution shown in FIG. 21, if the space-floating image is reflected by the retroreflective optical member 2, brightness that does not cause practical problems can be obtained even at the periphery of the screen. In addition, in order to increase the magnification ratio of the space-floating image, as described above, the bending amount of the image light beam or the amount of space-floating is increased by the lens action of the optical element 2150, thereby controlling it. In this case, if the magnification is increased to more than twice the magnification of the liquid crystal display panel 11, which is the image source, and the image is given a spreading diffusion characteristic as shown in "Example 2," not only can sufficient brightness be obtained all the way to the periphery of the screen, but also sufficient brightness can be achieved all the way to the periphery of the screen even when the floating image is viewed from an oblique direction.

[0054] Furthermore, in the method for enlarging the floating image in space of the present invention, the pixels of the enlarged image are not enlarged, but each pixel is imaged at a desired position, so the distance between pixels is increased. In the "standard light distribution" characteristic shown in Fig. 21, a space larger than the size of a pixel is generated between each pixel. In order to reduce this, it is necessary to give the image a diffusion characteristic with a wide base as shown in "Example 1" and "Example 2". As a guideline, if the spread of the pixels due to the above-mentioned diffusion characteristic exceeds 30% of the distance between pixels of the floating image in space, there will be no sense of incongruity in the continuity of the image, and if it exceeds 80%, the pixels will overlap and the sense of focus of the floating image in space will decrease.

[0055] In addition, the optical element 2150 of this embodiment is disposed between the image source (display device 1) and the imaging position of the space-floating image, and has the effect of expanding the image light flux diverging from the pixels of the liquid crystal display panel 11. That is, the imaging point of the space-floating image itself is controlled toward the direction in which the image expands (the direction in which the coordinate value increases in the XY plane in FIG. 20). Furthermore, by displacing the optical axis of this optical element 2150 from the central axis of the image source (display device 1), the partial expansion ratio and imaging position of the enlarged image of the space-floating image 220 can be controlled, so that a space-floating image of a pseudo three-dimensional image can be obtained.

[0056] 9 shows the configuration of a space floating image display device of the fifth embodiment. In this embodiment, an image light beam 901 (dashed arrow) having a narrow angle diffusion characteristic (almost parallel light) emitted from each pixel of an image source (display device not shown) is expanded (diffuses the light beam) by a first optical element 2150, which is an optical element 2150, and the expanded image light beam 902 (dash-dotted arrow) is collected by a second optical element 2160 arranged on a virtual surface 700 and converted into an image light beam 903 (dashed arrow) which is parallel light. The image light beam 903 which is parallel light displays a space floating image 220b as an expanded image at a predetermined position 705. As a result, even when the space floating image 220b is viewed from the front or from an oblique direction, the image light beam can obtain sufficient brightness for practical use in the entire area from the center of the screen to the periphery of the screen. At this time, the space floating image becomes a space floating image 220b which is enlarged with respect to the size of the original space floating image 220a corresponding to the position of the first optical element 2150.

[0057] In FIG. 9, it is advisable to provide an AR coating on the light incident surface of the optical element 2150.

[0058] <Examples of optical elements that magnify floating images> A first specific example of an optical element for enlarging a space-floating image will be described with reference to FIG. 10. FIG. 10 shows an optical element 1100 as a first specific example of an optical element 2150. The configuration of the embodiment of FIG. 10 is the same as that of FIG. 9, in that the optical element 1100 has a function of diffusing an image light beam 1001 (dashed line) emitted from each pixel of an image source (display device not shown) and refracts the image light beam toward a desired position. This optical element 1100 has a circular Fresnel shape (in other words, a circular Fresnel lens) 2151 provided on the space-floating image generating side (upper surface side in FIG. 10) of a base material (substrate) 2152, and this lens function directs the image light beam 1002 toward a desired position to form a space-floating image 220 (enlarged image 1101, a three-dimensional space-floating image).

[0059] At this time, the reflected light on the Fresnel lens surface due to the circular Fresnel shape 2151 returns to the exit surface of the base material 2152 and is reflected again, and this reflected light is superimposed on the original light beam that forms the spatial floating image, generating a ghost image. In order to reduce this ghost image, it is preferable to form an anti-reflection film 2153 on the image light beam incident side of the base material 2152 (the lower surface side in FIG. 10). At this time, the Fresnel angle of the circular Fresnel lens provided on the base material 2152 changes depending on the distance l (e.g. l1, l2, l3) from the Fresnel center (dotted chain line) as shown in FIG. 12. Therefore, it is preferable that the anti-reflection film 2153 provided on the incident surface has a minimum reflectance at the angle at which the reflected light is incident on the incident surface of the base material 2152 after reflection, relative to the average Fresnel angle of the entire Fresnel lens. Furthermore, it is preferable to minimize the reflectance in the green light region (530 nm to 570 nm) where the relative luminous efficiency is maximum.

[0060] The optical element 1100 is disposed so that the center of the optical element 1100 is eccentric with respect to the optical axis connecting the center of the image display area of ​​the image source (liquid crystal display panel 11) and the center of the external shape of the retroreflective optical member 2, and the height center of the three-dimensional floating-in-space image (enlarged image 1103) exists on an extension line of the center of the decentered optical element 1100. The imaging position of the three-dimensional floating-in-space image 220 corresponds to a virtual surface that is approximately parallel to the lens surface of the optical element 1100 and has an area obtained by enlarging the lens surface. The optical element 1100 has the function of controlling the emission direction of the image light beam passing through the lens surface according to the inclination of the lens surface. The height direction coordinate information of the floating-in-space image determined by the interval between the image source and the retroreflective optical member 2 is added to the plane coordinate information in the virtual surface corresponding to the area through which the image light beam of the optical element 1100 passes, and the thickness within the area of ​​the optical element 1100 is set, thereby forming the three-dimensional floating-in-space image 220 (enlarged image 1103).

[0061] When the space-floating image 220 is enlarged at a high magnification by the optical element 2150 (optical element 1100) which is a magnifying optical element using the specific technique for obtaining the space-floating image 220 described above, the image surface of the space-floating image 220 (enlarged image 1103) is curved as shown in FIG. 10. In order to reduce this curvature (field curvature) by the optical element 2150 alone, the configuration of the optical element 2155 shown in FIG. 11 can be applied. In the configuration of FIG. 11, in order to correct the field curvature of the space-floating image 220, the thickness t5 of the peripheral part is changed in accordance with the lens action with respect to the center thickness t9 of the optical element 2155, and the thickness is optimized so that the optical path length (the product of the refractive index and the physical length) from the incident surface of the optical element 2155 to the image surface of the space-floating image 220 is equal in the optical path through which the image light beam corresponding to the pixel passes, thereby correcting the field curvature. In this case, the thickness may be changed by overlapping flat surfaces (flat surfaces) t6, t7, t8, etc. having different thicknesses as shown in the figure so that the incident surface of the optical element 2155 does not have a lens function.

[0062] In order to obtain the above-mentioned circular Fresnel lens shape, for example, a mold or replica is created and the optical element 2155 is molded by molding. At this time, depending on the Fresnel shape at the outermost periphery of the optical element 2155, the resistance to release from the mold increases, causing optical problems such as deformation of the base material and roughness of the lens surface. For this reason, in order to improve the mold releasability, it is necessary to provide the circular Fresnel shape 2151 with a draft angle θ0 as shown in the figure. Empirically, the draft angle θ0 should be 2 degrees or more, and if it exceeds 5 degrees, the area where light cannot be refracted in the normal direction increases, resulting in the generation of ghost images and a decrease in the brightness of the floating image in space.

[0063] In FIG. 10, it is advisable to provide an AR coating on the light incident surface of the optical element 2150.

[0064] <Technical means to increase design freedom regarding the display position and magnification of the floating image> Next, technical means for increasing the degree of freedom with respect to the display position of the space floating image will be described with reference to Figs.

[0065] FIG. 13 shows a first embodiment of the present invention that increases the degree of freedom for the display position and magnification of the floating image in space. FIG. 13 shows the structure of a floating image display device using a retroreflective optical member 2. The display device 1, which is an image source, is composed of a liquid crystal display panel 11 as an image display device and a light source device 13. The liquid crystal display panel 11 emits image light of a specific polarized wave. At this time, it is preferable to select a light source device 13 having a narrow divergence angle for the image light in order to reduce ghost images generated by the retroreflective optical member 2 as described above. As a result, the image light emitted from the display device 1 to the left of the drawing is reflected upward by the reflecting mirror 2120 without spreading and heads toward the polarized light separation member 2140a. The image light of the specific polarized wave is first reflected by the polarized light separation member 2140a, and then enters and is reflected by the retroreflective optical member 2 or the like in the left direction. A λ / 4 plate 21 is arranged on the surface of the retroreflective optical member 2. The image light of a specific polarized wave from the polarization separation member 2140a is reflected by the reflecting surface of the retroreflective optical member 2 and is simultaneously polarized and converted by passing through the λ / 4 plate 21. The image light of the other polarized wave after the conversion passes through the polarization separation member 2140a toward the right, and the space floating image 220 is displayed.

[0066] At this time, in this embodiment, an optical element 2150 having the function of enlarging the space-floating image 220 is disposed between the retroreflective optical member 2 and the space-floating image 220 (a virtual surface on which the enlarged image 1301 is formed). The optical element 2150 enlarges the space-floating image 220 to a desired size. The space-floating image 220 is displayed as the enlarged image 1301 at the position of the virtual surface. In addition, in this embodiment, the display device 1 is structured to be movable in the left-right direction (direction of the optical axis) of the drawing. By moving the display device 1 in the left-right direction, the optical path length of the image light (the optical distance between the display device 1 and the retroreflective optical member 2) changes, so that the imaging position of the space-floating image 220 can be changed. For example, when the display device 1 is moved to the left, it becomes like the changed virtual surface 1302. Then, by expanding the image light beam by the optical element 2150 disposed in the middle of the optical path, an enlarged spatial image can be obtained according to the desired imaging position. Alternatively, the position of the retroreflective optical member 2 may be structured to be movable in the left-right direction of the drawing, and the same effect can be obtained.

[0067] FIG. 14 shows a second embodiment that increases the degree of freedom for the display position and magnification of the space floating image. FIG. 14 shows the structure of a space floating image display device using a retroreflective optical member 2. The display device 1, which is an image source, is composed of a liquid crystal display panel 11 as an image display device and a light source device 13. The liquid crystal display panel 11 emits image light of a specific polarized wave. At this time, it is preferable to select a light source device 13 having a narrow divergence angle for the image light in order to reduce ghost images generated by the retroreflective optical member 2 as described above. As a result, the image light emitted upward from the display device 1 is reflected by the reflecting mirror 2120 and the reflecting mirror 2110 without spreading. The image light of a specific polarized wave reflected by the reflecting mirror 2110 heads toward the polarization separation member 2140a above. The image light first passes through the polarization separation member 2140a, and is incident on and reflected by the retroreflective optical member 2 above. A λ / 4 plate 21 is arranged on the surface of the retroreflective optical member 2. The image light of a specific polarized wave from the polarization separation member 2140a is reflected by the reflecting surface of the retroreflective optical member 2 and is simultaneously polarization-converted by the λ / 4 plate 21. The image light of the other polarized wave after the conversion is reflected by the polarization separation member 2140a and travels diagonally upward, passing through the optical element 2150 and displaying a floating image in space as the magnified image 220b.

[0068] In the second embodiment of FIG. 14, two reflecting mirrors (2120, 2110) are provided as reflecting mirrors (reflective optical elements), but this is not limiting. At least one reflecting mirror may be provided as a reflecting mirror in the optical path connecting the imaging position of the floating-in-space image and the polarization separation member 2. In the second embodiment, the number of reflecting mirrors is increased to increase the number of times the optical path is turned back, thereby increasing the degree of freedom in the shape and installation of the floating-in-space image device. In this case, the center of the optical action of the optical element 2150 that acts to magnify the floating-in-space image (for example, the center of the Fresnel lens) is decentered from the optical axis 1401 shown by the dashed dotted line, and is disposed between the retroreflective optical member 2 and the floating-in-space image (the virtual surface on which the magnified image 220b is formed). As a result, the floating-in-space image with a different magnification with respect to the optical axis can be magnified to a desired size. In the second embodiment, similar to the first embodiment, the position of the display device 1 is structured to be movable in the vertical direction (direction of the optical axis) of the drawing. By moving the display device 1 up and down, the imaging position of the spatially floating image can be changed in the direction of the image light corresponding to the optical axis 1401, and by spreading the image light beam using the optical element 2150, which is positioned off-center with respect to the optical axis 1401, an enlarged spatial image that is off-centered in the vertical direction of the screen can be obtained according to the imaging position.

[0069] Among the reflecting mirrors, the reflecting mirror arranged closest on the optical path to the imaging position of the spatially floating image (in this embodiment, reflecting mirror 2110) is preferably configured to be made of a metal multilayer film that reflects one polarized wave of the image light and transmits the other polarized wave.

[0070] FIG. 15 shows a third embodiment that similarly increases the degree of freedom for the display position and magnification of the space floating image. FIG. 15 shows the structure of a space floating image display device using a retroreflective optical member 2. The display device 1, which is an image source, is composed of a liquid crystal display panel 11 and a light source device 13. The liquid crystal display panel 11 emits image light of a specific polarized wave. At this time, as described above, it is preferable to select a light source device 13 having a narrow divergence angle of the image light in order to reduce ghost images generated by the retroreflective optical member 2. As a result, the image light is reflected by the reflecting mirror 2120 and the reflecting mirror 2110 without spreading, passes through the polarization separation member 2140a, and enters the retroreflective optical member 2, etc. A λ / 4 plate 21 is arranged on the surface of the retroreflective optical member 2. The image light of a specific polarized wave from the polarization separation member 2140a is reflected by the reflecting surface of the retroreflective optical member 2 and is simultaneously polarized and converted by the λ / 4 plate 21. The image light of the other polarized wave after the conversion is reflected by the polarization separation member 2140a, directed diagonally upward, and is displayed as a floating image in space as a magnified image 220b through the optical element 2150. Similarly, in the third embodiment of Fig. 15, the number of reflecting mirrors is increased to increase the number of times the optical path is folded back, thereby increasing the degree of freedom in the shape and installation of the floating image device in space.

[0071] At this time, the center of the optical action of the optical element 2150 having the effect of magnifying the floating image in space (for example, the center of the Fresnel lens) is decentered from the optical axis 1501 shown by the dashed line, and is disposed between the retroreflective optical member 2 and the floating image in space (the virtual surface on which the magnified image 220b is formed). The third embodiment of FIG. 15 is different from the second embodiment in that the second optical element 2160 is disposed between the first optical element 2150, which is the optical element 2150, and the floating image in space (the virtual surface). The action of this second optical element 2160 is as described in detail as the second optical element 2160 in the fifth embodiment shown in FIG. 9. In this third embodiment, since the center of the optical action of the first optical element 2150 is decentered with respect to the center of the outer shape, the floating image in space can be magnified to a desired size by disposing the center of magnification at a position different from the optical axis 1501, as shown in FIG.

[0072] In addition, in this third embodiment, the retroreflective optical member 2 is structured to be movable in the vertical direction (diagonal direction) in the drawing. By moving the position of the retroreflective optical member 2 in the vertical direction (diagonal direction), the imaging position of the floating image in space can be changed, and by expanding the image light beam by the optical element 2150 arranged eccentrically with respect to the optical axis 1501, an enlarged spatial image eccentric in the vertical direction of the screen according to the imaging position can be obtained.

[0073] <Advantages of enlarging the floating image> The advantage of enlarging the space-floating image will be described with reference to the aforementioned Fig. 7 showing the configuration of the space-floating image display device using the retroreflective optical member 2. In Fig. 7, the image light beam from the display device 1, which is the image source, is reflected by the retroreflective optical member 2, and passes through the transparent member 100 that separates the space-floating image display device body from the outside, and then an enlarged space-floating image 220 (220b1, 220b2) is obtained. Note that in Fig. 7, the transparent member 100 may be configured to double as the optical element 2150, in other words, may be configured as an integrated unit.

[0074] For this reason, in the configuration of FIG. 7, when the enlarged floating image is displayed, the viewer does not directly see the retroreflective optical member 2 through the transparent member 100 when viewing the enlarged floating image (220b1, 220b2) from the top to the bottom of the drawing. The surface of the retroreflective optical member 2 is a polyhedron with a mirror-like reflecting surface (FIG. 2), and when external light is incident, ghost images and scattered light are generated, which reduces the quality of the image and the quality of the device itself. For this reason, it is desirable to make the opening of the floating image display device (for example, the part where the transparent member 100 is arranged) as small as possible. For this purpose, it is preferable to increase the magnification ratio of the optical element 2150. The inventors conducted experiments to determine the brightness of the floating image required to suppress the deterioration of image quality due to external light to a level that does not cause problems in practical use. As a result, it was found that a brightness of 10 times or more is required compared to the brightness (brightness) around the device, and if it is 1000 (nt) or more, it is practically problem-free, and to obtain even better image quality, a brightness of 30 times, 3000 (nt), is required. Similarly, in order to create a sufficient sense of floating in space when the floating image is viewed from an oblique direction, the external light reflection must be more than 100 times that of the device itself, and it is desirable for the exterior of the device (a structure not shown that incorporates optical components, etc.) to be a blackish color that absorbs light.

[0075] <Technical means for obtaining three-dimensional floating images> As a technical means for increasing the design freedom with respect to the display position and magnification of the above-mentioned floating image in space, a Fresnel lens has been described as an optical element 2150 for magnifying the floating image in space. The original function of the optical element 2150 in this embodiment is to refract the image light beam emitted from each pixel of the liquid crystal display panel 11 as the image display element constituting the display device 1, which is the image source, in a desired direction. For this reason, a refracting surface corresponding to the location where the image light beam from each pixel reaches after refraction at the incident surface is provided on the exit surface of the optical element 2150. For this reason, ideally, it should be configured in a form in which polyhedrons are connected. However, in the case of this polyhedral shape, a lot of time is required to process the molding die. For this reason, in order to put it into practical use, it is better to obtain the coordinates within the surface by considering the inclination of adjacent surfaces, and to obtain the shape of the exit surface by, for example, regressing to a free-form surface formula. Furthermore, in order to reduce the processing time of the die, if a concentric Fresnel shape 2152a is used as shown in FIG. 16, the workability is further improved.

[0076] Fig. 17 is an explanatory diagram of the principle by which the floating-in-space image 220ba obtained by the action of the optical element 2150 shown in Fig. 16 appears three-dimensional. Methods for obtaining a floating-in-space image include (1) a retroreflection method in which the amount of floating of the image can be arbitrarily determined by the structure of the optical system, and (2) a microlens method in which the amount of floating of the image is uniquely determined by the focal length of the microlens. For the sake of simplicity, the following description will be given taking the retroreflection method as an example.

[0077] The optical element 2150 in the retroreflective system has the function of directing the pixels of the space-floating image corresponding to each pixel of the liquid crystal display panel 11 to a desired position. This function has been described in detail with reference to Fig. 20, but as shown in Fig. 20 etc., the optical element 2150 is provided between the liquid crystal display panel 11, which is an image source, and the space-floating image 220 (virtual surface), and controls the imaging position on the XY plane of the pixels (dashed lines) of the space-floating image 220 corresponding to the pixels (solid lines) arranged in a matrix on the liquid crystal display panel 11 in Fig. 20. On the other hand, the imaging position in the Z-axis direction is uniquely determined by the interval L between the retroreflective optical member 2 and the liquid crystal display panel 11, so that the image is formed at a predetermined position after reflection by the retroreflective optical member 2. As a result, the center of the screen is imaged at the position farthest from the reference plane (the xy plane in FIG. 17), and image points away from the center of the screen are closer to the reference plane, so that when the image points of the space-floating image are connected, they form a hemisphere (semicircle in cross section) as shown in FIG. 17, and even if the image information displayed on the liquid crystal display panel 11, which is the image source, is planar, the space-floating image 220 can be formed as a pseudo-three-dimensional image (three-dimensional space-floating image 220ba).

[0078] FIG. 18 shows a state where the optical center (center of the Fresnel lens) of the optical element 2150 is decentered. In this case, as shown in FIG. 19, the pseudo-stereoscopic image obtained is imaged at the apex O (center of the screen) at the position farthest from the reference plane (xy plane in FIG. 19), and the image points at the positions farther from the screen apex are closer to the reference plane, so that when the image points of the floating image are connected, they form an elliptical spherical shape. Even with flat image information displayed on the liquid crystal display panel 11, which is the image source, the floating image in space can be formed as a pseudo-stereoscopic image (three-dimensional floating image in space 220bb). As described above, in the embodiment shown in FIG. 15, the pseudo-stereoscopic image obtained by decentering the optical element 2150 can be formed by decentering it within the screen. In this case, the image position of the retroreflected image, which is determined by the distance between the retroreflecting optical member 2 and the liquid crystal display panel 11, is uniquely determined by the action of the optical element 2150.

[0079] Furthermore, as another technical means for forming a space-floating image, the same is true for a microlens array method in which a space image is formed by a microlens array corresponding to each pixel of the display device 1, which is the image source, and the focal length of each microlens is optimized to control the image formation position for each pixel. In addition, the image formation position and shape of the space-floating image are controlled by the action of the optical element 2150 described above to obtain a desired space-floating image. In the above, the optical element 2150 has been described on the assumption that it has a diverging effect in order to simplify the explanation, but depending on the desired shape, it may also have a so-called free-form lens shape that also has a lens shape that has a partial light-collecting effect.

[0080] <In-vehicle floating image display device> FIG. 33 is a schematic diagram for explaining the advantages of the space-floating image display device of the present invention for obtaining a space-floating image or a pseudo-stereoscopic space-floating image 220 when used for vehicle-mounted applications. Here, as an example, a space-floating image display device 1000 that can obtain an enlarged space-floating image without using a windshield 6 of a vehicle will be described. The space-floating image display device 1000 obtains a space-floating image 220, which is an enlarged space-floating image, in the internal space of the vehicle at an eye point 8 (described in detail later) corresponding to the driver's line of sight. This provides a visual effect similar to that of a virtual image V1 that is a pseudo-enlarged virtual image formed in front of the vehicle. Furthermore, in this configuration, it is possible to obtain a pseudo-stereoscopic image due to the shape of the optical element 2150, and it has been confirmed by an experiment that, in combination with image processing, the displayed spatial image can have a sense of depth. Below, an example of displaying a pseudo-stereoscopic space-floating image will be described in detail.

[0081] As shown in Fig. 33, when the expanded floating image 220 is viewed from the eye point 8, the virtual image V1 reflected by the projection target (in this embodiment, the inner surface of the windshield 6, the surface facing the driver in the vehicle) is viewed in a conventional head-up display (HUD), and the pseudo-three-dimensional floating image 220 (corresponding virtual image V1) can be superimposed on the actual scene viewed by the driver by the above-mentioned technical means. Information displayed as the pseudo-three-dimensional floating image 220 (also described as a three-dimensional space image) includes, for example, vehicle information, foreground information captured by a camera (not shown) such as a surveillance camera or an around viewer, the scenery around the vehicle before starting, a speedometer, an engine tachometer, an energy remaining display, etc., as well as a safe driving support system using video information and audio information such as displaying a character on the periphery of the screen and calling attention by audio (not shown).

[0082] In addition, in this embodiment, the space floating image display device 1000 includes a display device 1 that displays a three-dimensional image corresponding to information on a plane and projects the corresponding image light, and a retroreflective optical member 2100 (in other words, a retroreflective optical element) that reflects the image displayed on the display device 1 to form a three-dimensional space floating image 220. In addition, the display device 1 is made to have a structure that can be moved in space (shown as being movable left and right in the drawing). By moving the display device 1 left and right, the position where the three-dimensional space floating image 220 is formed can be moved in a diagonal up and down direction (roughly in the up and down direction) along the optical axis 3301 passing through the optical element 2150. As a result, the dip angle θe related to the virtual image V1 is changed by roughly moving up and down the position where the three-dimensional space floating image 220 viewed by the driver from the eye box (referring to a predetermined space including the eye point 8) is formed. This provides an effect equivalent to that of changing the display position of the virtual image in a conventional HUD. In addition, by detecting the movement of the driver's line of sight (eye point 8) using, for example, a monitor camera (not shown) inside the vehicle, the display position of the three-dimensional floating image 220 can be moved up, down, left, right, and so on in accordance with the movement of the line of sight.

[0083] In this embodiment, the position where the three-dimensional floating image 220 is formed is set to a position higher than the upper surface (not shown) of the dashboard (FIG. 34 described later) of the vehicle. Therefore, in this embodiment, the optical distance from the display device 1 to the retroreflective optical member 2100 is lengthened by folding back the image light from the display device 1 downward once by a reflection mirror (in other words, a folding mirror) 2110 provided on the optical path between the display device 1 and the retroreflective optical member 2100. With this configuration, the position of the three-dimensional floating image 220 obtained after reflection by the retroreflective optical member 2100 can be made higher in the diagonal up-down direction in the drawing, which corresponds to the virtual image V1 at a distant position as seen from the driver.

[0084] <Specific example 1 of a space floating image display device that obtains space floating images> An embodiment of the space-floating image display device for vehicle mounting of the present invention will be described with reference to Fig. 33. In this embodiment, a space-floating image display device 1000 is built into a dashboard (similar to Fig. 34) as a HUD. The space-floating image display device 1000 includes a display device 1, a retroreflective optical member 2100, and the like. The image displayed on the display device 1 is preferably displayed with emphasis on the shadows of the displayed image in order to emphasize the depth direction. As the image display element, a liquid crystal display panel 11 is used which modulates light supplied from a light source device 13 in accordance with an image signal and emits it as light of a specific polarization.

[0085] A specific polarized wave modulated by the liquid crystal display panel 11, in this example, an image of S polarized wave (solid line) passes through a beam splitter (or a reflective polarizing plate) 2140 having a characteristic of transmitting S polarized light and reflecting P polarized light, and enters the reflecting mirror 2110. The image light reflected downward by the reflecting mirror 2110 is reflected by a retroreflective optical member 2100 arranged near the bottom surface of the space floating image display device 1000, and forms a space floating image 220. A λ / 4 plate is provided on the image light incident surface of the retroreflective optical member 2100. This S polarized image light enters the retroreflective optical member 2100, is reflected, and passes through the λ / 4 plate twice, whereby it is converted to P polarized wave (dashed line). The P polarized image light is reflected again by the reflecting mirror 2110, turns back the optical path, and is reflected upward by the beam splitter 2140. The reflected P-polarized image light is reflected diagonally upward by a reflecting optical element (reflecting mirror) 2120 provided on the top of the space-floating image display device 1000, and a space-floating image or a pseudo-three-dimensional space-floating image 220 is obtained by the action of the optical element 2150.

[0086] If necessary, the shape of the transmission surface of the optical element 2150 is, for example, a concave shape toward the driver (a shape that has the effect of diverging light rays), so that the image light flux forming the space-floating image 220 is diverged, and at the same time, the image forming point of the obtained space-floating image 220 is curved forward in the peripheral area relative to the center of the screen, so that a space image with information in the depth direction pseudo-added when viewed from the driver is obtained. At this time, as described above, it is preferable to display the image on the display device 1 with emphasized shadows to emphasize the depth direction. Furthermore, when the displayed image is a person or the like, adding a shadow portion is preferable because the stereoscopic image is emphasized. As described above, the vehicle-mounted space-floating image display device 1000 of this embodiment forms a space-floating image or a stereoscopic space-floating image 220, and the driver can view the corresponding virtual image V1.

[0087] As shown in FIG. 34, the image light from the optical element 2150 is emitted from an opening 41 provided in the dashboard 48 to the outside, and a floating image or a three-dimensional floating image 220 in space can be obtained at the position shown in the figure (a position in front of the windshield 6 inside the vehicle). Returning to FIG. 33, the image formation position of the floating image or the three-dimensional floating image 220 in space obtained at this time is formed on a line segment connecting the optical element 2150 and the eye point 8, and the image is formed above the upper end of the optical element 2150. As a result, like the AR-HUD of the conventional technology, a three-dimensional image can be superimposed as a real image on the real scene observed by the driver while driving. At this time, unlike the conventional HUD, in this embodiment, the windshield (windshield 6) is not used as an optical system, so that even if the radius of curvature or the inclination of the windshield changes due to the design of the car, it is not affected, and is excellent in adaptability to different car models.

[0088] The reflective optical element 2120 may be a reflective film formed by coating or stepping a metal reflective film, a beam splitter that selectively reflects a specific polarized wave, or a reflective polarizing plate. This has the following effects. When the incident angle is large, the component of external light such as sunlight incident from the windshield 6 has a high reflectance of S-polarized light as shown in FIG. 35. Therefore, P-polarized components are incident inside the vehicle. The reflective optical element 2120 selectively reflects this P-polarized component. Therefore, external light is not incident on the optical components (the display device 1, the beam splitter 2140, the retroreflective optical member 2100, etc., as components in the structure of the space floating image display device 1000) that are located downstream of the reflective optical element 2120 (the lower side in the drawing). This prevents the reliability of the optical components, the display device 1, and the polarizing plate (not shown) arranged on the image light output side of the liquid crystal display panel 11 from being impaired.

[0089] Furthermore, it is even better if the reflecting optical element 2120 has a characteristic of reflecting light with a wavelength of 800 nm or more and ultraviolet rays, which contribute to temperature rise, among the spectral radiant energy of sunlight shown in FIG. 36. Also, in this embodiment, the display device 1 is structured to be movable in the left-right direction (direction of the optical axis) in the drawing, so that the position where the space floating image 220 is formed can be moved diagonally up and down. As a result, the depression angle of the space floating image 220 (corresponding virtual image V1) seen from the driver's eye point 8 changes, and the image display distance and size of the space floating image 220 can be changed in a pseudo manner with respect to the actual scene viewed by the driver. Furthermore, in this embodiment, a camera (not shown) for detecting the driver's line of sight may be provided to track and detect the driver's line of sight, so that the display position of the space floating image 220 can be linked to the line of sight position. Also, at this time, the image displayed as the space floating image 220 may be alert information that matches the actual scene viewed by the driver, thereby realizing attention while driving.

[0090] <Specific example 2 of a space floating image display device that obtains a space floating image> A second example of the in-vehicle floating image display device of the present invention will be described with reference to FIG. 34. As a display element constituting the display device 1 in the second example, a liquid crystal display panel 11 is used, which modulates light supplied from a light source device 13 in accordance with a video signal and outputs the light of a specific polarized wave, as in the first example. The image of a specific polarized wave (here, S-polarized wave) modulated by the liquid crystal display panel 11 passes through a beam splitter (or a reflective polarizing plate) 2140 having a characteristic of transmitting S-polarized light and reflecting P-polarized light, and is reflected by a retroreflective optical member 2100 to form a floating image 220. A λ / 4 plate is provided on the image light incident surface of the retroreflective optical member 2100. The S-polarized image light enters the retroreflective optical member 2100, is reflected, and passes through the λ / 4 plate twice to be converted to P-polarized wave. The P-polarized image light is reflected by a beam splitter (or a reflective polarizing plate) 2140, and is further reflected by a reflecting mirror (reflective optical element) 2120 provided on the upper part of the space-floating image display device 1000. The reflected light passes through an optical element 2150 to display a space-floating image 220 in an obliquely upward direction.

[0091] For example, if the surface shape of the optical element 2150 is concave toward the driver (a shape that has the effect of diverging light rays), the image light flux that forms the floating in space image is diverged, so that the image is enlarged on the imaging surface, and at the same time, the imaging point is curved toward the front in the peripheral area relative to the center of the screen, so that a spatial image with pseudo-depth information is obtained when viewed from the driver's perspective. In this case, as described above, it is preferable to display the image on the display device 1 with emphasized shadows to emphasize the depth direction. Furthermore, when the displayed image is of a person, etc., the stereoscopic image is emphasized by adding shadows.

[0092] The image light forming the above-mentioned floating image 220 is emitted from the opening 41 provided in the dashboard 48 of the vehicle. This allows the floating image 220 to be obtained at a predetermined position. In addition, if the above-mentioned optical element 2150 is used as a window through which the image light beam passes according to the shape of the opening 41, the number of parts can be reduced, which is even better. At this time, the image formation position of the obtained floating image 220 is formed on the line segment connecting the retroreflective optical member 2100, the optical element 2150, and the eye point 8, and the image is formed above the upper end of the optical element 2150. As a result, like the HUD of the conventional technology, the image can be superimposed as a real image on a part of the real scene observed by the driver while driving. At this time, unlike the conventional HUD, this floating image display device 1000 does not use the windshield (front glass 6) as an optical system, so it is not affected even if the radius of curvature or inclination of the windshield changes due to the design of the car, and it has excellent adaptability to different car models.

[0093] It is preferable to provide an anti-reflection film or an absorptive polarizing plate on the image light incident surface of the transparent member of the opening 41 .

[0094] It is also preferable that the image displayed on the liquid crystal display panel 11 is an image that corrects image distortion that occurs in the optical system that forms the floating in space image 220. The control device 40 (FIG. 33) performs image processing and the like to create an image to be displayed on the liquid crystal display panel 11 so that the image has corrected image distortion.

[0095] The reflective optical element (reflection mirror) 2120 can be the same as that in the first example. As a result, the reflective optical element 2120 selectively reflects the P-polarized light component entering the vehicle interior as described above. Therefore, external light does not enter the optical components subsequent to the reflective optical element 2120, and the reliability of the optical components and the liquid crystal display panel 11 is not impaired. Also, as in the above-mentioned example, the display device 1 (or the retroreflective optical member 2100) is structured to be movable in the left-right direction in the drawing (direction of the optical axis. A direction perpendicular to the image display surface). As a result, in this embodiment, the position where the space floating image or the three-dimensional space floating image 220 is formed can be moved in the diagonal up-down direction along the optical axis 3401 passing through the optical element 2150. As a result, the depression angle of the space floating image 220 (corresponding virtual image) seen from the driver's eye point 8 changes, and the image display distance and size of the space floating image or the pseudo-three-dimensional space floating image 220 can be changed with respect to the actual scene viewed by the driver.

[0096] According to the above-described embodiment, for example, a high-resolution image or a three-dimensional image can be displayed as a space-floating image 220 that can be seen floating in space on an extension line (optical axis 3401 passing through optical element 2150) of opening 41 on dashboard 48. At this time, in this embodiment, the divergence angle of the image light emitted from opening 41 of space-floating image display device 1000 is made small, that is, an acute angle, and further, it is configured to be aligned with a specific polarization. As a result, only the normal reflected light is efficiently reflected to retroreflective optical member 2100. Therefore, according to this embodiment, the light utilization efficiency is high, and the above-mentioned ghost image that was a problem in the conventional retroreflective method can be suppressed, and a clear space-floating image can be obtained. In addition, the configuration including the light source (light source device 13) of this embodiment can provide a new space-floating image display device that can significantly reduce power consumption and has excellent usability. In addition, as described above, it is possible to provide a vehicle-use space floating image display device capable of displaying a so-called unidirectional expanded space floating image or a three-dimensional space floating image that can be viewed inside or outside the vehicle through the windshield 6 of the vehicle.

[0097] In the above embodiment, the optical element 2150 having the function of diverging the image light beam to enlarge the space floating image has been described, but instead of providing this optical element 2150, a configuration in which the reflecting mirror (reflecting optical element) 2120 has the same function as the optical element 2150 may be used. In other words, the reflecting optical element 2120 and the optical element 2150 may be integrated into one element. However, if an optical element having a magnifying function is provided inside the structure of the space floating image display device 1000, it becomes necessary to increase the area of ​​the opening window 41, which increases the possibility that external light will enter the space floating image display device, thereby degrading the reliability of the parts and the image quality, and therefore, design consideration is required.

[0098] <Reflective polarizing plate> In the above-mentioned embodiment, when a reflective polarizing plate with a grid structure is used as the beam splitter 2140, the characteristics of this reflective polarizing plate for light from a direction perpendicular to the polarization axis are degraded. For this reason, it is desirable to use this reflective polarizing plate along the polarization axis, and the light source device 13 of this embodiment, which can emit the outgoing image light from the liquid crystal display panel 11 at a narrow angle, is an ideal light source. Similarly, the characteristics in the horizontal direction also degrade for light from an oblique angle. In consideration of the above characteristics, an embodiment will be described below in which a light source (light source device 13) capable of emitting the outgoing image light from the liquid crystal display panel 11 at a narrower angle is used as the backlight of the liquid crystal display panel 11. This makes it possible to provide a high-contrast floating image in space.

[0099] <Display device> The display device 1 of this embodiment will be described with reference to Fig. 22 etc. The display device 1 of this embodiment includes a liquid crystal display panel 11 which is an image display element, and a light source device 13 which constitutes a light source for the liquid crystal display panel 11. Fig. 22 shows the light source device 13 together with the liquid crystal display panel 11 as an exploded perspective view.

[0100] As shown by the arrow (emitted light beam) 30 in FIG. 22, the liquid crystal display panel 11, which is an image display element, obtains an illumination light beam having a narrow-angle diffusion characteristic, i.e., a strong directivity (in other words, a straight-line characteristic) and a characteristic similar to that of a laser beam with a polarization plane aligned in one direction, by light from the light source device 13, which is a backlight device, and emits image light modulated according to an input image signal. Then, the image light is reflected by the retroreflective optical member 2 and transmitted through the windshield (front glass) to form a real image, a floating image in space. In addition, the display device 1 of this embodiment is configured to include the liquid crystal display panel 11, a light direction conversion panel 54 that controls the directional characteristics of the emitted light beam from the light source device 13, and a narrow-angle diffusion plate (not shown) as necessary. That is, polarizing plates are provided on both sides of the liquid crystal display panel 11, and the image light of a specific polarization is configured to be modulated in light intensity by the image signal and emitted as shown by the arrow (emitted light beam) 30. As a result, the display device 1 of this embodiment projects a desired image as light of a specific polarization with high directionality (linearity) via the light direction conversion panel 54 toward the retroreflective optical member 2, and after being reflected by the retroreflective optical member 2, it transmits toward the eyes of a viewer inside / outside the vehicle space to form a space floating image. Note that a protective cover may be provided on the surface of the light direction conversion panel 54 described above.

[0101] In this embodiment, in order to improve the utilization efficiency of the emitted light beam 30 from the light source device 13 and to significantly reduce power consumption, the display device 1 including the light source device 13 and the liquid crystal display panel 11 can be configured as follows. That is, the display device 1 projects the light (emitted light beam 30) from the light source device 13 toward the retroreflective optical member 2, and after reflection by the retroreflective optical member 2, the display device 1 can control the directivity so that the floating image is formed at a desired position by a transparent sheet (not shown) provided on the surface of the windshield. Specifically, this transparent sheet controls the imaging position of the floating image while giving high directivity by optical components such as a Fresnel lens or a linear Fresnel lens. According to this, the image light from the display device 1 can efficiently reach the observer outside the windshield (for example, on the sidewalk) with high directivity (straightness) like laser light. As a result, it is possible to display a high-quality floating image with high resolution and to significantly reduce the power consumption of the display device 1 including the LED element 201 of the light source device 13.

[0102] <Display device example 1> FIG. 23 shows an example of a specific configuration of the display device 1. In FIG. 23, a liquid crystal display panel 11 and a light direction conversion panel 54 are arranged on the light source device 13 of FIG. 22. This light source device 13 is formed of, for example, plastic or the like, and is configured by storing an LED element 201 and a light guide 203 inside. In order to convert the divergent light from each LED element 201 into a substantially parallel light beam, an end face of the light guide 203 is provided with a lens shape having a shape in which the cross-sectional area gradually increases toward the opposite side to the light receiving part, and which has an effect of gradually decreasing the divergence angle by multiple total reflections during propagation inside. The liquid crystal display panel 11 is attached to the upper surface of the light guide 203. In addition, an LED element 201, which is a semiconductor light source, and an LED board 202 on which a control circuit for the LED element 201 is mounted are attached to one side (the left end face in this example). In addition, a heat sink, which is a member for cooling the heat generated by the LED elements 201 and the control circuit, may be attached to the outer surface of the LED substrate 202.

[0103] In addition, the frame (not shown) of the liquid crystal display panel 11 attached to the upper surface of the case of the light source device 13 is configured by attaching the liquid crystal display panel 11 attached to the frame, and further by attaching a flexible printed circuit (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 based on a control signal from a control circuit (not shown) constituting an electronic device together with the LED element 201, which is a solid light source. At this time, the generated image light has a narrow diffusion angle and contains only specific polarized components, so that a new display device that has not been seen before is obtained that is similar to a surface-emitting laser image source driven by an image signal. Note that, at present, it is technically and safety impossible to obtain a laser light beam of the same size as the image obtained by the above-mentioned display device 1 using a laser device. Therefore, in this embodiment, light similar to the above-mentioned surface-emitting laser image light is obtained from a light beam from a general light source equipped with an LED element, for example.

[0104] Next, the configuration of the optical system housed in the case of the light source device 13 will be described in detail with reference to FIG. 23 and FIG. 24. Since FIG. 23 and FIG. 24 are cross-sectional views, only one of the LED elements 201 constituting the light source is shown. The light from the LED elements 201 is converted into approximately collimated light (parallel light) by the shape of the light-receiving end surface 203a of the light guide 203. For this reason, the light-receiving portion of the end surface of the light guide 203 and the LED element 201 are attached while maintaining a predetermined positional relationship. Each of the light guides 203 is formed of a light-transmitting resin such as acrylic. The LED light receiving surface at the end of the light guide 203 has, for example, a cone-shaped convex outer circumferential surface obtained by rotating a parabolic cross section, and at the top of the outer circumferential surface, a concave portion with a convex portion (i.e., a convex lens surface) formed at the center of the top has a convex lens surface protruding outward (or a concave lens surface recessed inward) at the center of the flat portion of the light receiving end surface 203a of the light guide 203 (similar to FIG. 26 described later). The outer shape of the light receiving portion of the light guide 203 to which the LED element 201 is attached is a parabolic shape forming a cone-shaped outer circumferential surface, and is set within an angle range in which the light emitted from the LED element 201 in the peripheral direction can be totally reflected inside the outer circumferential surface, or a reflective surface is formed.

[0105] On the other hand, the LED elements 201 are arranged at predetermined positions on the surface of the LED substrate 202, which is a circuit board. The LED substrate 202 is arranged and fixed such that the LED elements 201 on the surface are located at the center of the recessed portion described above with respect to the light receiving end surface 203a, which is an LED collimator. With this configuration, the shape of the light receiving end surface 203a of the light guide 203 makes it possible to extract the light emitted from the LED elements 201 as substantially parallel light, thereby improving the efficiency of use of the generated light.

[0106] As described above, the light source device 13 in Fig. 22 and the like is configured by mounting a light source unit in which a plurality of LED elements 201 serving as light sources are arranged on the light receiving end surface 203a serving as a light receiving section provided on the end surface of the light guide 203. As a result, the divergent light beam from the LED elements 201 is converted into substantially parallel light by the lens shape of the light receiving end surface 203a of the light guide 203, guided inside the light guide 203 as indicated by the arrow (horizontal direction in Fig. 23 and the like), and emitted in a direction toward the liquid crystal display panel 11 arranged substantially parallel to the light guide 203 (vertical direction in Fig. 23 and the like) by the light beam direction conversion member 204 (emitted light beam 30 in Fig. 22). By optimizing the distribution (in other words, density) of the light beam direction conversion member 204 depending on the shape inside or on the surface of the light guide 203, the uniformity of the light beam incident on the liquid crystal display panel 11 can be controlled. The above-mentioned light beam direction conversion member 204 emits the light beam propagated inside the light guide 203 toward the liquid crystal display panel 11 arranged approximately parallel to the light guide 203 by changing the shape of the surface of the light guide 203 or by providing a portion with a different refractive index inside the light guide 203. At this time, when the liquid crystal display panel 11 is faced directly at the center of the screen and the viewpoint is placed at the same position as the diagonal dimension of the screen, if the relative luminance ratio between the center of the screen and the periphery of the screen is 20% or more, there is no practical problem, and if it exceeds 30%, it is an even more excellent characteristic.

[0107] 23 is a cross-sectional layout diagram for explaining the configuration and operation of a light source (light source device 13) of this embodiment that performs polarization conversion in light source device 13 including light guide 203 and LED element 201, as in FIG. 22. In FIG. 23, light source device 13 is composed of light guide 203 having light beam direction conversion member 204 on the surface or inside formed of plastic or the like, LED element 201 as a light source, reflection sheet 205, retardation plate 206, lenticular lens, etc. On the upper surface of light source device 13, liquid crystal display panel 11 having polarizing plates on the light source light entrance surface and the image light exit surface is attached.

[0108] The display device 1 may also be configured as follows. In FIG. 23, a film or sheet-like reflective polarizing plate 49 is provided on the light source light incidence surface (lower surface in the drawing) of the liquid crystal display panel 11 corresponding to the light source device 13. The light source device 13 selectively reflects one side of the polarized wave (e.g., P wave) 212 of the natural light beam 210 emitted from the LED element 201, and reflects it on a reflecting sheet 205 provided on one surface (lower surface in the drawing) of the light guide 203, and directs it again toward the liquid crystal display panel 11. Therefore, a λ / 4 plate, which is a retardation plate, is provided between the reflecting sheet 205 and the light guide 203, or between the light guide 203 and the reflective polarizing plate 49. With this configuration, the light is reflected by the reflecting sheet 205 and passes through the λ / 4 plate twice, thereby converting the reflected light beam from P polarized light to S polarized light, and improving the utilization efficiency of the light source light as image light. The image light beam (arrow 213 in Figure 23), whose light intensity has been modulated by the video signal in the liquid crystal display panel 11, is incident on the retroreflective optical element 2100 and reflected, as shown in Figure 33, for example, and then passes through the reflecting mirrors 2110 and 2120 to obtain a real, three-dimensional floating image in the space inside the vehicle in front of the windshield 6 or in the space outside the vehicle.

[0109] The display device 1 may also be configured as follows. In FIG. 23, a film or sheet-like reflective polarizing plate 49 is provided on the light source light incidence surface (lower surface in the drawing) of the liquid crystal display panel 11 corresponding to the light source device 13. The light source device 13 selectively reflects one side of the polarized wave (for example, S wave) 211 of the natural light beam 210 emitted from the LED element 201, and reflects it on a reflecting sheet 205 provided on one surface (lower surface in the drawing) of the light guide 203, and directs it again toward the liquid crystal display panel 11. A λ / 4 plate, which is a retardation plate, is provided between the reflecting sheet 205 and the light guide 203, or between the light guide 203 and the reflective polarizing plate 49. With this configuration, the light is reflected by the reflecting sheet 205 and passes through the λ / 4 plate twice, thereby converting the reflected light beam from S polarized light to P polarized light, and improving the utilization efficiency of the light source light as image light. The image light beam (arrow 214 in FIG. 24), which has been light intensity modulated by a video signal in the liquid crystal display panel 11, is incident on the retroreflective optical element 2100 and reflected, as shown in FIG. 33, for example, and passes through the reflecting mirrors 2110 and 2120 to obtain a real, floating image in the space inside the vehicle in front of the windshield 6 or in the space outside the vehicle.

[0110] In the light source device 13 shown in Fig. 23 and Fig. 24, in addition to the action of the polarizing plate provided on the light incident surface of the corresponding liquid crystal display panel 11, the polarized light component on one side is reflected by the reflective polarizing plate, so that the theoretically obtained contrast ratio is the product of the inverse of the cross transmittance of the reflective polarizing plate and the inverse of the cross transmittance obtained by the two polarizing plates attached to the liquid crystal display panel. This results in high contrast performance. In fact, it was confirmed by experiments that the contrast performance of the displayed image was improved by more than 10 times. As a result, a high-quality image was obtained that was comparable to that of a self-luminous organic EL.

[0111] <Display device example 2> Next, another example of the specific configuration of the display device 1 will be described with reference to Fig. 25. In the light source device of this display device 1, the divergent light flux of natural light (a mixture of P-polarized and S-polarized waves) from the LED 14 is converted into a substantially parallel light flux (a vertical light flux 19 in the drawing) by the LED collimator 18, and is reflected by the reflective light guide 304 toward the liquid crystal display panel 11 as a light flux in the horizontal direction in the drawing. The reflected light from the reflective light guide 304 is incident on the wave plate 206 and the reflective polarizing plate 49 arranged between the liquid crystal display panel 11 and the reflective light guide 304. A specific polarized wave (e.g., S-polarized wave) of the incident light is reflected by the reflective polarizing plate 49, and the phase of the reflected light is converted by the wave plate 206, returns to the reflecting surface of the reflective light guide 304, is reflected, passes through the wave plate 206 again, and is converted into a polarized wave (e.g., P-polarized wave) that transmits through the reflective polarizing plate 49.

[0112] As a result, the natural light from the LEDs 14 is aligned to a specific polarized wave (e.g., P polarized wave), enters the liquid crystal display panel 11, and is luminance-modulated according to the video signal to display an image on the video display surface of the liquid crystal display panel 11. In FIG. 25, as in the previous example, a plurality of LEDs 14 (only one is shown in FIG. 25 because it is a cross section) constituting a light source are provided, and these LEDs 14 are attached at a predetermined position relative to the LED collimator 18. Each of the LED collimators 18 is formed of a light-transmitting resin such as acrylic or glass. As in the previous example, the LED collimator 18 has a convex outer peripheral surface obtained by rotating a parabolic cross section, and at the top of the outer peripheral surface, a concave portion is formed with a convex portion (i.e., a convex lens surface) at the center of the top. The LED collimator 18 also has a convex lens surface protruding outward (or a concave lens surface recessed inward) at the center of the flat surface. The paraboloid that forms the conical outer surface of the LED collimator 18 is set within an angle range that allows the light emitted from the LED 14 in the peripheral direction to be totally reflected inside the outer surface, or a reflective surface is formed.

[0113] The configuration shown in FIG. 25 and the configuration of the light source device of the display device 1 shown in FIG. 31 are roughly similar. Furthermore, the light converted into approximately parallel light by the LED collimator 18 shown in FIG. 31 is reflected by the reflective light guide 304, and the light of a specific polarized wave is transmitted by the action of the reflective polarizing plate 49, while the other reflected polarized wave passes through the reflective light guide 304 again and is reflected by the reflector 271 provided on the other surface of the reflective light guide 304 that is not in contact with the liquid crystal display panel 11. At this time, the light is polarized and converted by passing twice through the λ / 4 plate 270, which is a retardation plate disposed between the reflector 271 and the liquid crystal display panel 11, and passes through the reflective light guide 304 again and the reflective polarizing plate 49 provided on the opposite surface, and is incident on the liquid crystal display panel 11 with the polarization direction aligned. As a result, in this configuration, all the light from the light source can be used, and the light utilization efficiency is doubled.

[0114] In a conventional TV set, as shown in Figs. 29 and 30, the light emitted from the liquid crystal display panel 11 has similar diffusion characteristics in both the horizontal direction of the screen (shown by the X-axis in Figs. 29(A) and 30(A)) and the vertical direction of the screen (shown by the Y-axis in Figs. 29(A) and 30(B)), and the angle at which the luminance is 50% of the front view is about 60 degrees, which is a wide angle, so that the image of the TV set can be seen from any position. In contrast, the diffusion characteristics of the light flux emitted from the liquid crystal display panel 11 of this embodiment are 1 / 15 of the directional characteristic of 60 degrees of a conventional TV by setting the viewing angle at which the luminance is 50% of the front view (angle 0 degrees) to 4 degrees, as shown in "Example 1" of Fig. 30(A). Similarly, the vertical viewing angle is optimized by optimizing the reflection angle of the reflective light guide 304 and the area of ​​the reflection surface so that the viewing angle in the upper direction is about 1 / 3 of the viewing angle in the lower direction, with the viewing angle being uneven between the top and bottom. In addition to this result, efficiency increases by 1.8 times by polarizing the light source light, so by combining the above technical means, the amount of image light heading in the viewing direction is significantly improved compared to conventional LCD TVs, and the brightness is more than 80 times higher. Note that the X and Y directions in Figure 30 are the same coordinates as Figure 29(A).

[0115] Furthermore, in the case of the viewing angle characteristic shown in "Example 2" in FIG. 30, the viewing angle at which the luminance is 50% of that when viewed from the front (angle 0 degrees) is set to 1 degree, which is 1 / 60 of the conventional 60 degrees. Similarly, the reflection angle and the area of ​​the reflection surface of the reflective light guide 304 are optimized so that the viewing angle in the vertical direction is kept equal up and down and is about 1 / 12 of the conventional viewing angle. As a result, in this embodiment, the amount of image light heading in the viewing direction is significantly improved compared to conventional liquid crystal TVs, and the luminance is 700 times or more. An image source that can obtain image light of a specific polarization can be obtained by providing a polarization conversion element that performs polarization conversion described later, aligning it to a specific polarization, using a light source similar to a laser surface light source with an extremely small divergence angle, and modulating the intensity of light according to the image signal on the liquid crystal display panel.

[0116] As described above, by setting the viewing angle to a narrow angle, the amount of light flux toward the viewing direction can be concentrated, and the light utilization efficiency is greatly improved. As a result, according to the embodiment, even if a conventional liquid crystal display panel for TV is used, it is possible to realize a significant improvement in brightness with the same power consumption by controlling the light diffusion characteristics of the light source device, and a display device capable of displaying images facing outdoors can be obtained.

[0117] The basic configuration of this embodiment is as shown in Figure 34 above, in which a light beam with a narrow-angle directional characteristic is incident on the liquid crystal display panel 11 by the light source device 13, and the brightness is modulated according to the video signal, so that the video information displayed on the screen of the liquid crystal display panel 11 is reflected by the retroreflective optical element 2100 to obtain a spatial floating image 220, which is displayed indoors or outdoors.

[0118] <Light source device example 1> Next, a detailed description will be given of an example of the configuration of an optical system including a light source device housed in a case with reference to FIG. 26 as well as FIGS. 27(A) and (B).

[0119] 26 and 27 show LEDs 14 (14a, 14b) constituting a light source. These LEDs 14 are attached at predetermined positions relative to the LED collimator 15. Each of the LED collimators 15 is formed of a light-transmitting resin such as acrylic. As shown in FIG. 27(B), the LED collimator 15 has a cone-shaped outer peripheral surface 156 obtained by rotating a parabolic cross section, and a concave portion 153 having a convex portion (i.e., a convex lens surface) 157 formed at the center of the top of the outer peripheral surface 156. The LED collimator 15 also has a convex lens surface (or a concave lens surface recessed inward) 154 protruding outward at the center of the flat surface. The parabolic surface 156 forming the cone-shaped outer peripheral surface of the LED collimator 15 is set within an angle range in which light emitted from the LEDs 14 in the peripheral direction can be totally reflected inside the parabolic surface 156 of the outer peripheral surface, or a reflective surface is formed.

[0120] The LEDs 14 (14a, 14b) are disposed at predetermined positions on the surface of the LED substrate 102, which is a circuit substrate. The LED substrate 102 is disposed and fixed to the LED collimator 15 so that the LEDs 14 on the surface are located at the center of the recess 153 of the LED collimator 15. According to this configuration, the light emitted from the LEDs 14 by the LED collimator 15, particularly the light emitted from the center of the LEDs 14 toward the upper side (the right direction in the drawing), is collected and made into parallel light by the two convex lens surfaces 157, 154 that form the outer shape of the LED collimator 15. The light emitted from the other parts toward the periphery is reflected by the parabolic surface 156 that forms the outer peripheral surface of the cone shape of the LED collimator 15, and is similarly collected and made into parallel light. In other words, the LED collimator 15, which has a convex lens in the center and a parabolic surface formed on the periphery, makes it possible to extract almost all of the light generated by the LED 14 as parallel light, thereby improving the utilization efficiency of the generated light.

[0121] In Fig. 26, a polarization conversion element 21 is provided on the light emission side of the LED collimator 15. As is clear from Fig. 27(A), this polarization conversion element 21 is configured by combining a columnar translucent member having a parallelogram cross section (hereinafter, parallelogram column) and a columnar translucent member having a triangular cross section (hereinafter, triangular column), and arranging them in an array in parallel to a plane perpendicular to the optical axis of the parallel light from the LED collimator 15. Furthermore, a polarizing beam splitter (hereinafter, PBS film) 2111 and a reflective film 2121 are alternately provided at the interface between the adjacent translucent members arranged in the array. In addition, a λ / 2 phase plate 213 is provided on the emission surface from which the light incident on the polarization conversion element 21 and transmitted through the PBS film 2111 is emitted.

[0122] 27(A) is provided on the exit surface of this polarization conversion element 21. That is, the light emitted from the LED 14 is converted into parallel light by the action of the LED collimator 15, enters the synthetic diffusion block 16, is diffused by the texture 161 on the exit side of the synthetic diffusion block 16, and then reaches the light guide 17.

[0123] Light guide 17 is a rod-shaped member made of a light-transmitting resin such as acrylic and having a substantially triangular cross section (FIG. 27(B)). Light guide 17 includes light guide light incident portion (including a light guide light incident surface) 171 facing the exit surface of synthetic diffusion block 16 via first diffusion plate 18a, light guide light reflecting portion (including a light guide light reflecting surface) 172 forming an inclined surface, and light guide light exit portion (including a light guide light exit surface) 173 facing liquid crystal display panel 11 via second diffusion plate 18b.

[0124] 26, a number of reflective surfaces 172a and connecting surfaces 172b are alternately formed in a sawtooth shape in the light guide light reflecting portion 172 of the light guide 17. The reflective surface 172a (a line segment sloping upward to the right in the drawing) forms an angle αn (n: natural number, 1 to 130 in this example) with the horizontal plane (left-right direction in the drawing) shown by the dashed line in the drawing. As an example, the angle αn is set to 43 degrees or less (but 0 degrees or more).

[0125] Light guide entrance portion 171 is formed in a curved convex shape inclined toward the light source side. Accordingly, parallel light from the exit surface of synthetic diffusion block 16 is diffused via first diffusion plate 18a and enters light guide entrance portion 171, and as is clear from the drawing, reaches light guide light reflecting portion 172 while being bent slightly upward (in other words, deflected) by light guide entrance portion 171. The light is reflected by light guide light reflecting portion 172 and reaches liquid crystal display panel 11 provided above light guide light exit portion 173 at the upper part of the drawing.

[0126] According to the display device 1 described above in detail, the light utilization efficiency and the uniform illumination characteristics are further improved, and at the same time, it is possible to manufacture the display device 1, including the modularized S-polarized light source device, in a small size and at low cost. In the above description, the polarization conversion element 21 is described as being attached after the LED collimator 15, but the present invention is not limited to this. The same action and effect can be obtained by providing the polarization conversion element 21 in the optical path leading to the liquid crystal display panel 11.

[0127] In addition, the light guide light reflection section 172 has a number of reflection surfaces 172a and connection surfaces 172b formed alternately in a sawtooth shape, and the illumination light beam is totally reflected on each reflection surface 172a and directed upward. Furthermore, a narrow-angle diffusion plate is provided in the light guide light emission section 173, and the illumination light beam is incident on the light direction conversion panel 54 that controls the directivity as a substantially parallel diffused light beam, and the directivity is controlled so that the illumination light beam is incident on the liquid crystal display panel 11 from an oblique direction as shown in Fig. 26. In this embodiment, the light direction conversion panel 54 is provided between the light guide emission surface 173 and the liquid crystal display panel 11, but the present invention is not limited to this, and the same effect can be obtained even if the light direction conversion panel 54 is provided on the emission surface of the liquid crystal display panel 11.

[0128] <Light source device example 2> Another example of the configuration of the optical system of the light source device 13 and the like is shown in FIG. 28. In FIG. 28, similar to the example shown in FIG. 26, a plurality of (two in this example) LEDs 14 (14a, 14b) constituting the light source are shown. These LEDs 14 are attached at predetermined positions with respect to the LED collimator 15. Each of the LED collimators 15 is formed of a light-transmitting resin such as acrylic. Similarly to the example shown in FIG. 26, the LED collimator 15 has a cone-shaped outer peripheral surface 156 obtained by rotating a parabolic cross section, and at the top of the outer peripheral surface 156, a concave portion 153 is formed with a convex portion (i.e., a convex lens surface) 157 at the center of the top. Also, the LED collimator 15 has a convex lens surface 154 protruding outward (or may have a concave lens surface recessed inward) at the center of the flat surface. In addition, the paraboloid 156 that forms the conical outer peripheral surface of the LED collimator 15 is set within an angle range that allows the light emitted from the LED 14 in the peripheral direction to be totally reflected inside the paraboloid 156, or a reflective surface is formed.

[0129] The LEDs 14 (14a, 14b) are disposed at predetermined positions on the surface of the LED substrate 102, which is a circuit substrate. The LED substrate 102 is disposed and fixed to the LED collimator 15 so that the LEDs 14 (14a, 14b) on the surface are located at the center of the recess 153. According to this configuration, the light emitted from the LEDs 14 by the LED collimator 15, particularly the light emitted from the center of the LED toward the upper side (the right direction in the drawing), is collected and made into parallel light by the two convex lens surfaces 157, 154 that form the outer shape of the LED collimator 15. The light emitted from the other parts toward the periphery is reflected by the parabolic surface 156 that forms the outer peripheral surface of the cone shape of the LED collimator 15, and is similarly collected and made into parallel light. In other words, the LED collimator 15, which has a convex lens in the center and a parabolic surface formed on the periphery, makes it possible to extract almost all of the light generated by the LED 14 as parallel light, thereby improving the utilization efficiency of the generated light.

[0130] In Fig. 28(A), a light guide 170 is provided on the light emission side of the LED collimator 15 via a first diffusion plate 18a. The light guide 170 is a member formed in a rod shape having a substantially triangular cross section, made of a light-transmitting resin such as acrylic. As is clear from Fig. 28(A), the light guide 170 includes a light guide entrance portion 171 of the light guide 170 that faces the emission surface of the diffusion block 16 via the first diffusion plate 18a, a light guide light reflection portion 172 that forms an inclined surface, and a light guide light emission portion 173 that faces the liquid crystal display panel 11, which is a liquid crystal display element, via a reflective polarizing plate 200.

[0131] For example, a material having the property of reflecting P-polarized light and transmitting S-polarized light is selected as the reflective polarizing plate 200. In this way, the reflective polarizing plate 200 reflects P-polarized light out of the natural light emitted from the LED serving as the light source, passes through the λ / 4 plate 2802 provided in the light guide light reflecting section 172 shown in Fig. 28(B), is reflected by the reflecting surface 2801, and passes through the λ / 4 plate 2802 again to be converted into S-polarized light. As a result, all the light beams incident on the liquid crystal display panel 11 are unified into S-polarized light.

[0132] Similarly, a material having the property of reflecting S-polarized light and transmitting P-polarized light may be selected as the reflective polarizing plate 200. In this case, the reflective polarizing plate 200 reflects S-polarized light from the natural light emitted from the LED light source, passes through the λ / 4 plate 2802 provided in the light guide light reflecting section 172 shown in FIG. 28(B), reflects it on the reflecting surface 2801, and passes through the λ / 4 plate 2802 again to be converted into P-polarized light. As a result, all the light beams incident on the liquid crystal display panel 11 are unified into P-polarized light. The above-mentioned configuration can also realize polarization conversion.

[0133] <Light source device example 3> Another example of the configuration of the optical system of the light source device, etc., will be described with reference to FIG. 25. In this example, as shown in FIG. 25, a divergent light beam of natural light (a mixture of P-polarized light and S-polarized light) from the LED 14 is converted into a substantially parallel light beam by the collimator lens 18, and is reflected toward the liquid crystal display panel 11 by the reflective light guide 304. The reflected light is incident on the reflective polarizing plate 206 arranged between the liquid crystal display panel 11 and the reflective light guide 304. A specific polarized wave (e.g., S-polarized wave) is reflected by the reflective polarizing plate 206, and the reflected light is transmitted through a surface connecting the reflective surfaces of the reflective light guide 304, reflected by a reflector 271 arranged facing the opposite surface of the reflective light guide 304, and is polarized and converted by transmitting twice through a λ / 4 wave plate 270, which is a phase plate. The polarized light (e.g., P-polarized wave) is transmitted through the reflective light guide 304 and the reflective polarizing plate 206, incident on the liquid crystal display panel 11, and modulated into image light. At this time, by combining the specific polarized wave with the polarized wave surface converted by the polarization conversion, the light utilization efficiency becomes twice as high as usual, and the degree of polarization (in other words, the extinction ratio) of the reflective polarizing plate 206 is also included in the extinction ratio of the entire system. Therefore, by using the light source device of this embodiment, the contrast ratio of the space floating image display device is significantly improved.

[0134] As a result, in this embodiment, the natural light from the LED 14 is aligned to a specific polarization (for example, P polarization). As in the previous example, in this embodiment, a plurality of LEDs 14 constituting a light source are provided, and these LEDs 14 are attached at a predetermined position relative to the LED collimator 18. Each of the LED collimators 18 is formed of, for example, a light-transmitting resin such as acrylic or glass. As in the previous example, the LED collimator 18 has a convex outer peripheral surface obtained by rotating a parabolic cross section, and at the top of the outer peripheral surface, a concave portion is formed with a convex portion (i.e., a convex lens surface) at the center. In addition, the center of the flat surface of the LED collimator 18 has a convex lens surface protruding outward (or may be a concave lens surface recessed inward). The parabolic surface forming the conical outer peripheral surface of the LED collimator 18 is set within an angle range in which the light emitted from the LED 14 in the peripheral direction can be totally reflected inside the parabolic surface, or a reflective surface is formed.

[0135] The LEDs 14 are disposed at predetermined positions on the surface of the LED board 102, which is a circuit board. The LED board 102 is disposed and fixed to the LED collimator 18 so that the LEDs 14 on the surface are located at the center of the recess of the LED collimator 18. According to this configuration, the LED collimator 18 collects the light emitted from the LEDs 14, particularly the light emitted from the central portion, into parallel light by the two convex lens surfaces that form the outer shape of the LED collimator 18. The light emitted from the other portions toward the periphery is reflected by the parabolic surface that forms the conical outer circumferential surface of the LED collimator 18, and is similarly collected into parallel light. In other words, the LED collimator 18, which has a convex lens formed in the center and a parabolic surface formed in the peripheral portion, makes it possible to extract almost all of the light generated by the LEDs 14 as parallel light, thereby improving the utilization efficiency of the generated light.

[0136] <Light source device example 4> Further, another example of the configuration of the optical system of the light source device or the like will be described with reference to FIG. 31. In FIG. 31, two optical sheets (in other words, diffusion sheets, diffusion films) 207 that convert the diffusion characteristics are used on the light emission side of the LED collimator 18, and the light from the LED collimator 18 is made to enter between these two optical sheets 207. The optical sheets 207 convert the diffusion characteristics in the up-down direction (vertical direction in the screen) and the front-back direction (horizontal direction in the screen) of the drawing that constitutes the surface. When the optical sheet 207 is configured with one sheet, the diffusion characteristics in the vertical direction and the horizontal direction are controlled by the fine shapes of the front and back surfaces of the sheet. Also, the optical sheet 207 may be a plurality of optical sheets that share the functions. Depending on the front and back shapes of the optical sheet 207, the diffusion angle of the light from the LED collimator 18 in the vertical direction of the screen may be adjusted to the width of the vertical surface of the reflecting surface of the optical sheet 207, and the surface density of the light beam emitted from the liquid crystal display panel 11 in the horizontal direction may be uniform. In other words, in this embodiment, the diffusion characteristics are controlled by the surface shape of one or more optical sheets 207, instead of the above-mentioned light guide 304. In this embodiment, the polarization conversion is performed in the same manner as in the above-mentioned example 3 of the light source device. Alternatively, a polarization conversion element 21 may be provided between the LED collimator 18 and the optical sheet 207, and the light source light may be made incident on the optical sheet 207 after the polarization conversion.

[0137] The above-mentioned reflective polarizing plate 206 is selected to have the property of reflecting S-polarized light and transmitting P-polarized light, for example. In this way, of the natural light emitted from the LED 14 serving as the light source, S-polarized light is reflected by the reflective polarizing plate 206, passes through the retardation plate 270, is reflected by the reflecting surface 271, passes through the retardation plate 270 again, is converted to P-polarized light, and enters the liquid crystal display panel 11. The thickness of this retardation plate 270 needs to be optimally selected depending on the angle of incidence of the light beam on the retardation plate 270, and the optimal value is in the range of λ / 16 to λ / 4.

[0138] <Light source device example 5> Another example of the configuration of the optical system of the light source device will be described with reference to FIG. 32. In this embodiment, the light source device 13 includes a polarization conversion element 501 on the light output side of the LED collimator 18, as shown in FIG. 32(C), and the polarization conversion element 501 aligns the natural light from the LED 14 (LED element) to a specific polarization, and the light is incident on the optical element 81 that controls the diffusion characteristics. The optical element 81 controls the diffusion characteristics of the incident light in the vertical direction (up and down direction in FIG. 32(C)) and the horizontal direction (front and back direction in FIG. 32(C)) of the screen, thereby optimizing the light distribution characteristics toward the reflection surface of the reflection type light guide 200. As shown in FIG. 32(B), a concave-convex pattern 502 is provided on the surface of the reflection type light guide 200, and the incident light from the optical element 81 is reflected toward the image display device (not shown) arranged on the opposing surface of the reflection type light guide 200, thereby obtaining the desired diffusion characteristics. The arrangement accuracy of the LED 14 and the LED collimator 18 of the light source greatly affects the efficiency of the light source. Therefore, the optical axis accuracy usually needs to be about 50 μm. Therefore, the inventors have come up with the following configuration as a countermeasure to the problem of the deterioration of the installation accuracy due to the expansion of the LED collimator 18 caused by the heat generated by the LEDs 14. That is, in this embodiment, as shown in Figs. 32(A) and (B), a single or multiple (three in this example) light source units 503 are used in the light source device as a structure of the light source unit 503 in which several LEDs 14 and the LED collimator 18 are integrated, thereby reducing the deterioration of the installation accuracy.

[0139] In the embodiment shown in Fig. 32(A), (B), and (C), a plurality of light source units 503 (total of six) each integrating an LED element and an LED collimator 18 are incorporated at both ends of the long side direction (left-right direction in the drawing) of the reflective light guide 200. In this embodiment, three light source units 503 are incorporated on each of the left and right sides of the reflective light guide 200 in the screen vertical direction (up-down direction in Fig. 32(B)). This realizes uniform luminance of the light source device 13. A plurality of concave-convex patterns 502 approximately parallel to the light source units 503 are formed on the reflection surface of the reflective light guide 200 (the surface on which the concave-convex pattern 502 is formed in Fig. 32(B)). The cross section on which the concave-convex pattern 502 is formed is the surface in Fig. 32(C), the concave-convex pattern 502 is repeated in the left-right direction in Fig. 32(B), and one concave-convex extends in the up-down direction in Fig. 32(B). A polyhedron is formed on the surface of even one concave-convex pattern 502. This makes it possible to control the amount of light incident on the image display device with high precision.

[0140] In this embodiment, the shape of the reflection surface of the reflection light guide 200 has been described as the uneven pattern 502, but the shape is not limited thereto, and may be a pattern in which shapes such as triangular surfaces and corrugated surfaces are regularly or irregularly arranged, and the light distribution pattern from the reflection light guide 200 toward the image display device may be controlled by the pattern surface shape. As shown in Fig. 32(A), a light shielding wall 504 may be provided on the side surface of the reflection light guide 200 (the side surface on which the light source unit 503 is not provided) to prevent the light controlled by the LED collimator 18 from leaking out from the light source device 13 to the outside, and the LED element (LED 14) may be designed to have improved heat dissipation by a metal base 505 provided on the outside.

[0141] <Lenticular lens> The following describes the action of the lenticular lens that controls the diffusion characteristics of light emitted from the display device 1. The lenticular lens can obtain a floating image in space in front of the windshield (FIG. 33) of the vehicle or in the space outside the vehicle by optimizing the lens shape. That is, in this embodiment, the brightness (in other words, the relative brightness) of the image light from the display device 1 can be controlled according to the reflection angle (vertical direction is 0 degrees) in the X-axis and Y-axis directions in the screen (FIG. 29) by combining two lenticular lenses or arranging a microlens array in a matrix to control the diffusion characteristics. In this embodiment, such a lenticular lens makes the brightness characteristics in the vertical direction (Y-axis) steeper than in the past, as shown in FIG. 29(B), and further changes the balance of the directional characteristics in the up and down directions (positive and negative directions of the Y-axis), thereby increasing the brightness (relative brightness) of light by reflection and diffusion. As a result, in this embodiment, the image light has a narrow diffusion angle (in other words, is highly directional) and contains only specific polarization components, like the image light from a surface-emitting laser image source, so that the ghost images that were generated by the retroreflective optical element when conventional technology was used can be suppressed and the spatially floating image caused by the retroreflection can be controlled to reach the viewer's eyes efficiently.

[0142] Furthermore, by using the light source device described above, it is possible to realize a display device that emits light of a specific polarization that emits an image light beam that is nearly parallel to a specific direction by achieving a directional characteristic with a significantly narrower angle in both the X-axis and Y-axis directions compared to the diffusion characteristic of the emitted light from a typical liquid crystal display panel shown in Figures 30(A) and (B) ("conventional characteristics" in the drawings).

[0143] FIG. 29 shows an example of the characteristics of the lenticular lens employed in this embodiment. In this example, the angle θ is particularly shown as the characteristics in the Y-axis direction (vertical direction) of FIG. 29(A). In FIG. 29(B), "characteristic O" shows a luminance characteristic that is symmetrical up and down, with the peak of the light emission direction at an angle of about 30 degrees upward from the vertical direction (0 degrees). Furthermore, "characteristic A" and "characteristic B" show examples of characteristics in which the image light above the peak luminance is further concentrated at about 30 degrees to increase the luminance (relative luminance). For this reason, in these characteristics A and B, the luminance (relative luminance) of light is rapidly reduced at angles exceeding 30 degrees, compared to characteristic O.

[0144] That is, according to the optical system including the above-mentioned lenticular lens, when the image light beam from the display device 1 is incident on the retroreflective optical member 2, the emission angle and viewing angle of the image light aligned to a narrow angle by the light source device 13 can be controlled, and the degree of freedom of installation of the retroreflective optical member 2 can be significantly improved. As a result, the degree of freedom of the relationship of the image formation position of the space floating image that is reflected or transmitted through the windshield and formed at the desired position can be significantly improved. As a result, it is possible to efficiently reach the eyes of the viewer outdoors or indoors as light with a narrow diffusion angle (high straightness) and only a specific polarized wave component. As a result, even if the intensity (corresponding brightness) of the image light from the 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 display device 1, it is possible to realize a display device with low power consumption.

[0145] According to this embodiment, instead of the conventional HUD device, it is possible to provide a space-floating image display device that can display the necessary image as a space-floating image inside the car, especially in the space between the windshield and the driver, without reflecting the image on the windshield. This makes it possible to provide a space-floating image display device that can be used between car models with different body designs.

[0146] In addition, according to this embodiment, it is possible to realize a space floating display device that can display a space floating image with high visibility, since it can be deployed among vehicles with different shapes and inclinations of windshields, which was an obstacle to installation in comparison with the conventional HUD.

[0147] The above-mentioned embodiment includes the following configuration. The space-floating image display device includes a liquid crystal display panel as an image source, and a light source device with a narrow divergence angle that supplies light with a specific polarization direction to the image source. The light source device includes a point-like or planar light source, an optical member that reduces the divergence angle of light from the light source, and a light guide having a reflective surface that propagates to the image source. The light guide is disposed opposite the image source, and has a reflective surface inside or on its surface that reflects light from the light source toward the image source, and propagates the light to the image source. The image source modulates the light intensity according to the image signal. The light source device controls a part or all of the divergence angle of the light beam incident from the light source to the image source by the shape and surface roughness of the reflective surface provided on the light source device. The space-floating image display device reflects or transmits the image light beam having a narrow divergence angle from the image source with a retroreflective optical member to form a space-floating image in the air.

[0148] Furthermore, the image light from the image source has a narrow angle divergence characteristic, and the generation of ghost images is reduced by considering the arrangement of the optical system so that external light does not enter the retroreflective optical element, and in addition, an optical sheet that controls the diffusion angle of the emitted light is provided on the light exit surface of the retroreflective optical element, the light exit surface of the liquid crystal display panel, or both light exit surfaces, so that the ghost light generated by the retroreflective optical element does not contribute to the imaging of the space floating image, thereby significantly improving the image quality of the obtained space floating image. Also, in order to reduce the ghost image generated by the external light entering the retroreflective optical element, the retroreflective optical element is arranged almost perpendicular to the opening of the space floating image display device.

[0149] On the other hand, the space floating image display device controls the image light flux passing through the opening of the space floating image display device to enlarge the space floating image so that the size of the space floating image is larger than the opening of the space floating image display device. More specifically, an image enlarging optical element (image light control film) that controls the outgoing direction according to pixels so as to enlarge the display screen is disposed between the retroreflective optical member and the viewer's eye point (the imaging position of the corresponding space floating image). This controls the size of the space floating image and the shape of the imaging surface.

[0150] In addition, since it is possible to control the imaging position of the re-imaged image corresponding to each pixel of the display device, information on the three-dimensional direction can be added to the image information. Also, by setting the surface roughness of the above-mentioned spatial image magnifying optical element to a predetermined roughness, the focus of the pixels of the spatial floating magnified image is controlled. Similarly, in order to reduce the amount of blurring of the spatial floating image, the surface roughness of the reflective surface of the retroreflective optical member is reduced to a predetermined value per unit length or less, thereby reducing the amount of blurring of the spatial floating image and improving visibility.

[0151] On the other hand, to miniaturize the space floating image display device, the liquid crystal display panel, which is the image source, is arranged so that the polarization direction of the image light emitted is changed for each image display area divided vertically or horizontally on the screen. As a result, the screen is divided into multiple areas and a space floating image is formed for each image in each area, making it possible to make the device thinner and to realize a smaller set.

[0152] Furthermore, the amount of protrusion (floating amount) of the space-floating image formed by the space-floating image display device is realized by controlling the imaging position of the re-imaged image corresponding to each pixel of the display device described above by the action of the image magnifying optical element.

[0153] Although various embodiments have been described above in detail, the present invention is not limited to the above-described embodiments and includes various modified examples. For example, the above-described embodiments are detailed descriptions of the entire device in order to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. It is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0154] The technology according to this embodiment displays high-resolution, high-brightness image information in a state of floating in space, which allows users to operate the system without worrying about contact infection. If the technology according to this embodiment is used in a system used by an unspecified number of users, it is possible to provide a contactless user interface that can be used without worry, reducing the risk of contact infection. This contributes to the achievement of "Good health and well-being for all," one of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0155] In addition, the technology according to this embodiment makes it possible to efficiently reflect only the normal reflected light from the retroreflective material by reducing the divergence angle of the emitted image light and aligning it to a specific polarization, which makes it possible to obtain a bright and clear floating image with high light utilization efficiency. The technology according to this embodiment makes it possible to provide a highly usable non-contact user interface that can significantly reduce power consumption. This contributes to the achievement of the Sustainable Development Goals (SDGs) proposed by the United Nations, "9 Build resilient infrastructure, promote inclusive and sustainable industrialization, and promote technological innovation" and "11 Make cities and towns sustainable and livable."

[0156] Furthermore, the technology according to this embodiment makes it possible to form a floating image using highly directional (linear) image light. The technology according to this embodiment makes it possible to provide a non-contact user interface with little risk of people other than the user looking at the floating image, even when displaying images that require high security, such as those in bank ATMs and ticket machines at train stations, or highly confidential images that should be hidden from people directly facing the user, by displaying highly directional image light. This contributes to "Sustainable cities and towns" in the Sustainable Development Goals (SDGs) proposed by the United Nations. [Explanation of symbols]

[0157] 1...display device, 2 (2A, 2B)...retroreflective optical element, 11...liquid crystal display panel, 13...light source device, 100...transparent element, 101, 102...polarized light separation element, 111...lambda / 2 plate, 220...space-floating image (three-dimensional space-floating image, enlarged image), 2150, 1100...optical element.

Claims

1. A space floating image display device, A display panel for displaying an image; A retroreflective optical member that reflects image light from the display panel and displays a space floating image in the air using the reflected light; An image light control film is provided on the surface of the retroreflective optical member. A floating image display device.

2. 2. The space floating image display device according to claim 1, The image light control film has light transmitting members and light absorbing members arranged alternately. A floating image display device.

3. 3. The space floating image display device according to claim 2, In the image light control film, the light transmitting members and the light absorbing members are arranged alternately at a predetermined period. When the period is Ps and the thickness of the image light control film is T, 0.5<Ps / T<2.0 Fulfilling A floating image display device.

4. 3. The space floating image display device according to claim 2, In the image light control film, the light absorbing member is provided so as to extend perpendicularly to the surface of the retroreflective optical member. A floating image display device.

5. 3. The space floating image display device according to claim 2, the light absorbing member absorbs a portion of light based on the image light from the display panel, and the light transmitting member transmits a portion of the light based on the image light from the display panel. A floating image display device.

6. 3. The space floating image display device according to claim 2, The light transmitting member is made of transparent silicon, and the light absorbing member is made of black silicon. A floating image display device.

7. 2. The space floating image display device according to claim 1, An opening is provided through which image light for forming the space floating image passes, The display panel is disposed at a position where the image light emitted from the display panel cannot be seen when the user views the opening from a direction in which the spatial floating image is viewed by the user. A floating image display device.

8. 2. The space floating image display device according to claim 1, An opening is provided through which image light for forming the space floating image passes, An anti-reflection film or an absorptive polarizing plate is provided on an image light incident surface of the transparent member of the opening. A floating image display device.

9. 2. The space floating image display device according to claim 1, An optical element is provided between the retroreflective optical member and the space floating image, The optical element is disposed such that the center of the optical element is decentered with respect to an optical axis connecting the center of the image display area of ​​the display panel and the center of the outer shape of the retroreflective optical member, The height center of the three-dimensional floating image is on an extension of the center of the decentered optical element. A floating image display device.

10. 2. The space floating image display device according to claim 1, a light source device for supplying light to the display panel; the light source device controls a part or the whole of a divergence angle of a light beam by changing a shape and a surface roughness of the reflecting surface of the light source device so that a divergence angle of a light beam of the display panel is within ±15 degrees; A floating image display device.

11. 2. The space floating image display device according to claim 1, a light source device for supplying light to the display panel; the light source device adjusts a part or the whole of a divergence angle of a light beam by changing a shape and a surface roughness of the reflecting surface of the light source device so that a horizontal divergence angle and a vertical divergence angle of a light beam of the display panel are different from each other. A floating image display device.

Images