Space-floating image display device

Abstract

To provide a technique desirable for indoor use, the technique displaying a high-visibility space floating picture and contributing to "3. Good Health and Well-Being" and "9. Industry, Innovation, and Infrastructure" in Sustainable Development Goals.SOLUTION: A space floating picture display device has a housing 106 storing a picture display device 1, which can be desirably set on such a surface of a table in a room. Outside the housing 106, there are a retroreflective member 2 provided with a λ / 4 plate 21 and a polarization separation member 101 (a beam splitter) arranged at a predetermined angle. Picture light as p-polarization from the picture display device 1 is converted into s-polarization through the polarization separation member 101 and the retroreflective member 2, for example, and a space floating picture 3 is displayed in a predetermined position on the basis of the picture light as S-polarization.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to a technology for a space floating image display device. [Background technology]

[0002] An example of a space floating image display device is disclosed in Japanese Patent Application Laid-Open No. 2019-128722 (Patent Document 1). Patent Document 1 states that "the CPU of the information processing device includes an approach direction detection unit that detects the direction from which the user approaches an image formed in the air, an input coordinate detection unit that detects the coordinates at which the input is detected, an operation reception unit that processes the reception of operations, and an operation screen update unit that updates the operation screen in accordance with the received operations. When the user approaches the image from a predetermined direction, the CPU receives the user's movement as an operation and executes processing in accordance with the operation." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-128722 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the space-floating image display device disclosed in Patent Document 1 can improve the operability of the space-floating image, it does not take into consideration the improvement of the apparent resolution and contrast of the space-floating image. There is a demand for further improvement in the image quality of the space-floating image.

[0005] The floating image display device has a wide range of applications. When used as signage (advertising billboards), the novelty of "displaying images floating in space," something not found in conventional flat displays, has the effect of attracting many people's attention. Furthermore, as described in Patent Document 1, if the floating image is used as a human interface for performing some kind of operation, its contactless feature can be effective in preventing viral infections mediated by touching parts such as push buttons. Furthermore, if the floating image display device can be easily installed in a home study, living room, or workplace, text, figures, and videos that were previously simply displayed on LCD screens can be displayed as floating images, which is visually appealing and suitable as an interior accessory.

[0006] On the other hand, when a space-floating image display device is used indoors, especially in a living room where a family gathers or an office where at least several people are present, it is desirable that the space-floating image be visible only to the specific individual using it (hereinafter referred to as the user). However, as will be described later, there is a problem in that the image light emitted from the image source that is the source of the space-floating image can be seen by people on the opposite side of the user's eyes. It has been desired to solve this problem, that is, to make the image light invisible to people other than the user who are on the opposite side of the user's eyes.

[0007] An object of the present disclosure is to provide a technology for a space-floating image display device that can prevent image light from being visible to a person on the opposite side of the user's eyes when the user views the space-floating image. Another object of the present disclosure is to provide a technology that is suitable for indoor use and can display a space-floating image with high visibility. [Means for solving the problem]

[0008] To solve the above problems, for example, the configuration described in the claims is adopted. The present application includes multiple means for solving the above problems, but one example is as follows. A space-floating image display device according to one embodiment displays a space-floating image, and includes: a retroreflective member disposed opposite the image display device and having a λ / 4 plate (a phase difference plate, a quarter-wave plate) provided on its retroreflective surface; and a polarization separation member disposed in a space connecting the image display device and the retroreflective member at a predetermined angle relative to the image display device and the retroreflective member. The image display device includes a light source device and a liquid crystal display panel as an image source. Image light of a specific polarization, specifically, P-polarized image light, emitted from the liquid crystal display panel passes through the polarization separation member (also called a beam splitter), is reflected by the retroreflective member, and passes through the λ / 4 plate twice, whereby it is polarization-converted into S-polarized image light. As a result, the S-polarized image light reflected by the retroreflection member is reflected by the polarization separation member, and a real image floating in space is displayed at a predetermined position based on the reflected image light.

[0009] Here, when the P-polarized image light passes through the beam splitter, a part of the P-polarized image light is reflected without passing through the beam splitter, which causes a problem that the part of the reflected image light reflected by the beam splitter can be seen by a person on the back side of the space-floating image display device, more specifically, on the opposite side of the eyes of the user viewing the space-floating image.

[0010] The space-floating image display device of this embodiment is configured so that the reflected image light reflected by the beam splitter is not generated or the amount of the reflected image light is sufficiently reduced. More specifically, the space-floating image display device of this embodiment is configured so that the reflected image light is not generated by setting the incident angle of the image light (P-polarized image light) to the beam splitter at a predetermined angle (Brewster angle: θB). [Effects of the Invention]

[0011] According to a representative embodiment of the present disclosure, when a user views a floating-in-space image, the image light can be made invisible to people on the opposite side of the user's eyes. Furthermore, according to a representative embodiment, a floating-in-space image suitable for indoor use can be displayed, which has high visibility. According to a representative embodiment, a bright floating-in-space image can be displayed, and reflected image light, which is generated when the image light that forms the floating-in-space image is reflected by a beam splitter, is not generated, or the amount of reflected image light is sufficiently reduced. This makes it possible to provide a floating-in-space image display device that has the effect of making the reflected image light invisible to people on the opposite side of the user's eyes. The above and other problems, as well as configurations for solving these problems and the effects thereof, will be made clear through the description of the following embodiments. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of a usage form of a space floating image display device according to an embodiment; [Figure 2] 1 is a diagram showing a V-shaped configuration as an example of a main part configuration of a space floating image display device according to an embodiment. [Figure 3] 1 is a diagram showing a Z-type configuration as an example of a main part configuration of a space floating image display device according to an embodiment. FIG. [Figure 4] 10A and 10B are diagrams illustrating an example of a detailed structure of a retroreflective member. [Figure 5] FIG. 1 is a characteristic diagram showing the relationship between the surface roughness of a retroreflective member and the amount of blur of a retroreflected image (a spatially floating image). [Figure 6] 1 is a diagram illustrating an example of the configuration of a video display device according to an embodiment; [Figure 7] 1 is a diagram showing an example of the external configuration of a space floating image display device according to an embodiment (first embodiment). [Figure 8] 1 is a diagram showing an example of the cross-sectional configuration of a space floating image display device according to one embodiment (first embodiment) as viewed from the side; [Figure 9]FIG. 1 is a perspective view showing an example of the external configuration of a space floating image display device according to an embodiment (second embodiment). [Figure 10] FIG. 10 is a diagram showing an example of the cross-sectional configuration of a space floating image display device according to an embodiment (second embodiment) as viewed from the side. [Figure 11] FIG. 1 is a diagram showing the relationship between the angle of incidence and reflectance, and the Brewster angle. [Figure 12] FIG. 10 is a perspective view showing an example of the external configuration of a space floating image display device according to an embodiment (third embodiment). [Figure 13] FIG. 10 is a diagram showing an example of the cross-sectional configuration of a space floating image display device according to an embodiment (third embodiment), as viewed from the side. [Figure 14] FIG. 10 is a diagram showing an example of mounting a λ / 2 plate in an image display device section in a space floating image display device according to one embodiment (a modified example of the second embodiment). DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present disclosure will be described in detail below with reference to the drawings. In the drawings, identical components are generally designated by the same reference numerals, and repeated description will be omitted. In the drawings, the actual position, size, shape, and scope of each component may not be depicted to facilitate understanding of the invention. For the purpose of explanation, when describing program-based processing, the program, functions, processing units, etc. may be described as the main focus. However, the main focus of these hardware components is a processor, or a controller, device, computer, system, etc., configured with the processor. A computer executes processing in accordance with a program loaded into memory using resources such as memory and communication interfaces as appropriate, thereby realizing predetermined functions, processing units, etc. The processor may be configured with semiconductor devices such as a CPU / MPU or GPU. The processor may be configured with devices or circuits capable of performing predetermined calculations. Processing is not limited to software program processing, but can also be implemented using dedicated circuits. Dedicated circuits such as FPGAs, ASICs, and CPLDs can be used. The program may be pre-installed on the target computer as data, or may be distributed as data from a program source to the target computer and installed. The program source may be a program distribution server on a communication network, or a non-transitory computer-readable storage medium such as a memory card or disk. The program may be composed of multiple modules. The computer system may be composed of multiple devices. The computer system may be composed of a client-server system, a cloud computing system, etc. Various data and information may be composed of structures such as, but not limited to, tables and lists. Expressions such as identification information, identifiers, IDs, names, and numbers are interchangeable.

[0014] <Embodiment> A space-floating image display device according to an embodiment includes an image display device, a beam splitter serving as a polarization separation member, and a retroreflective member having a λ / 4 plate (a phase difference plate, a quarter-wave plate) on its retroreflective surface. The image display device includes a light source device and a display panel or liquid crystal display panel serving as an image source (image display element) that emits image light of a specific polarization (e.g., P-polarized light). The light source device generates and supplies light as backlight to the liquid crystal display panel. A polarization separation member is disposed in the space connecting the liquid crystal display panel and the retroreflective member of the image display device. The polarization separation member transmits the image light of a specific polarization from the liquid crystal display panel toward the retroreflective member and reflects the image light of the other polarization (e.g., S-polarized light) after polarization conversion by the retroreflective member and the λ / 4 plate. The reflected image light of the other polarization generates and displays a space-floating image, which is a real image, at a predetermined position in a direction different from that of the image display device.

[0015] In order to improve the contrast performance of the spatially floating image, the image display device may be provided with a polarization conversion unit that aligns the light source light from the light source device to be polarized in a specific direction. For example, the light source device may include a point or planar light source, an optical element unit that reduces the divergence angle of the light from the light source, a polarization conversion unit (such as a polarization conversion element) that aligns the light from the light source to be polarized in a specific direction, and a light guide having a reflective surface that propagates the light from the light source to the liquid crystal display panel, and the image luminous flux of the image light from the liquid crystal display panel is controlled by the shape and surface roughness of the reflective surface of the light guide.

[0016] The space-floating image display device of the embodiment is configured to have an image display device unit with a housing that can be placed on a desk, and a space-floating image display unit made of a frame structure, with consideration given to use particularly indoors, although this is not limited thereto.

[0017] The video display device mainly comprises a liquid crystal display panel and a light source (backlight).

[0018] The space floating image display unit is configured to have an optical system made up of a polarization separation member, a retroreflection member, etc. The optical system of this embodiment has a structure supported by a frame made of metal or resin.

[0019] [Space-floating image display device] The following embodiments relate to a space-floating image display device that can display an image generated by image light from a large-area image light source as a space-floating image inside or outside a store space by transmitting the image through a transparent member that divides the space, such as the glass of a shop window. Also, apart from the above embodiments, a space-floating image display device is also provided that uses an optical system that includes a polarization separation member (in other words, a polarizing beam splitter, or simply a beam splitter) and a retroreflector, which will be described later, to display a space-floating image mainly indoors.

[0020] In the following description of the embodiments, an image floating in space is expressed by the term "space-floating image." Instead of this term, it may be expressed as "aerial image," "space-floating image," "space-floating optical image of displayed image," "space-floating optical image of displayed image," etc. The term "space-floating image" used in the description of the embodiments is used as a representative example of these terms.

[0021] According to the following embodiments, for example, high-resolution image information can be displayed in a state of floating in space on the glass surface of a shop window or a light-transmitting plate. Furthermore, the space-floating image display device of the embodiments can be installed in a relatively small space, such as on a desk in a study, on a table in a living room, or on a kitchen counter. Furthermore, according to the embodiments, it is possible to provide a space-floating image display device that prevents a user who can see the space-floating image from seeing the reflected image light (described in detail later) on the other side of the space-floating image display device. According to the embodiments, it is possible to provide a space-floating image display device that is particularly suitable as an interior accessory or a display device for an information device.

[0022] In the conventional floating image display device, an organic EL panel or a liquid crystal display panel is used as a high-resolution color display image source in combination with a retroreflective material. In the conventional floating image display device, the image light is diffused over a wide angle, which causes the following problems:

[0023] As shown in Figure 4, in the retroreflective member 2, the retroreflective portion 2a is a hexahedron, so in addition to the normally reflected light, ghost images are generated by image light that is incident on the retroreflective member 2 at an angle, which causes a problem of impairing the image quality of the floating image in space. The retroreflective member 2 is also called a retroreflective plate or retroreflective sheet.

[0024] Furthermore, as shown in Figure 5, the floating image obtained by reflecting the image light from the image display device, which is the image source, using the retroreflective member 2 has the problem that in addition to the ghost image mentioned above, blurring occurs in each pixel of the liquid crystal display panel.

[0025] FIG. 1 shows an example of a usage pattern and a configuration example of a space-floating image display device according to an embodiment. (A) of FIG. 1 shows the overall configuration of the space-floating image display device according to this embodiment. For example, in a store or the like, a space is partitioned by a show window (window glass) 105, which is a light-transmitting member (also referred to as a transparent member) such as glass. The space-floating information display device of this embodiment can transmit the transparent member and display a space-floating image in one direction to the outside of the store space. Specifically, light with a narrow-angle directivity and specific polarization is emitted from the image display device 1 of the space-floating information display device as an image beam, enters the retroreflective member 2, is retroreflected, and passes through the window glass 105 to form a space-floating image 3, which is a real image, outside the store space. (A) of FIG. 1 shows a case where, in the depth direction, the back side of the window glass 105 is the store space and the front side is the outside space (e.g., a sidewalk). On the other hand, by providing the window glass 105 with a means for reflecting a specific polarized wave (such as an optical member), it is possible to reflect the image light beam and form the floating image 3 in a desired position within the store.

[0026] FIG. 1B shows a block diagram of the image display device 1. The image display device 1 includes an image display unit 1a that displays the original image of the floating image 3, an image control unit 1b that converts the input image to match the resolution of the panel of the image display unit 1a, an image signal receiving unit 1c that receives the image signal, and a receiving antenna 1d. The image signal receiving unit 1c supports wired input signals such as USB (Universal Serial Bus: registered trademark) input and HDMI (High-Definition Multimedia Interface: registered trademark) input, as well as wireless input signals such as Wi-Fi (Wireless Fidelity: registered trademark). The image display device 1 can function independently as an image receiving and display device and can also display image information from an external PC, tablet, smartphone, etc. Furthermore, by connecting a stick PC or the like, the image display device 1 can be equipped with capabilities such as calculation processing and image analysis processing.

[0027] [V-type floating image display device] FIG. 2 shows an example of the configuration of the main components of a space-floating image display device according to one embodiment. The embodiment of FIG. 2 shows a configuration in which an image display device 1 and a retroreflective member (in other words, a retroreflector) 2 are arranged in a substantially V-shape (hereinafter referred to as a V-shape). As shown in FIG. 2, in the V-shape configuration, the image display device 1 is provided in an oblique direction (a direction corresponding to optical axis A1) relative to a transparent member 100 such as flat glass (which is arranged horizontally in this example). Furthermore, the retroreflective member 2 is provided in another oblique direction (a direction corresponding to optical axis A2) relative to the transparent member 100 such as flat glass. The image display device 1 is composed of a light source device 13, a liquid crystal display panel 11 which is a liquid crystal display element, an absorptive polarizer 12, etc.

[0028] 2, image light of a specific polarization emitted from a liquid crystal display panel 11 of an image display device 1 travels in the direction of optical axis A1, is reflected by a beam splitter 101 (polarization separating member) provided on a transparent member 100 and has a film that selectively reflects image light of a specific polarization, travels in the direction of optical axis A2, and is incident on a retroreflective member 2. In this example, the beam splitter 101 is formed in a sheet shape and is adhered to the lower surface of the transparent member 100, such as flat glass. Alternatively, the beam splitter 101 may be formed by evaporating an optical thin film directly onto the flat glass.

[0029] A λ / 4 plate 21 is provided on the image light incident surface (in other words, the retroreflective surface) of the retroreflective member 2. In other words, the λ / 4 plate 21 is a polarization conversion element, a phase difference plate, and a quarter-wave plate.

[0030] The image light on optical axis A2 from the beam splitter 101 is made to pass through the λ / 4 plate 21 twice, once upon entering the retroreflective member 2 and once upon exiting the retroreflective member 2, and is thereby polarization-converted from a specific polarization (one polarization) to the other polarization. Here, the beam splitter 101, which selectively reflects image light of a specific polarization, has the property of transmitting image light of the other polarization after polarization conversion. Therefore, the image light of the other polarization after polarization conversion passes through the beam splitter 101. The image light that has passed through the beam splitter 101 forms and displays a real image, a floating-in-space image 3, at a predetermined position outside the transparent member 100 in the direction of optical axis A3, which corresponds to the optical axis A2.

[0031] The light that forms the floating image 3 in space is a collection of light rays that converge from the retroreflective member 2 to the optical image of the floating image 3, and these light rays continue to travel in a straight line even after passing through the optical image of the floating image 3 in space. Therefore, in the configuration of FIG. 2, when a user views the floating image 3 from direction A indicated by the arrow, which corresponds to the optical axis A3, the floating image 3 is perceived as a bright image. However, when viewed by another person from direction B indicated by the arrow, for example, the floating image 3 cannot be perceived as an image at all. These characteristics are extremely suitable for use in systems that display images that require high security or highly confidential images that should be kept secret from people directly facing the user.

[0032] Depending on the performance of the retroreflective member 2, the polarization axis of the reflected image light may become misaligned. In this case, a portion of the image light with a misaligned polarization axis is reflected by the beam splitter 101 described above and returns to the image display device 1. This returned light may be re-reflected on the image display surface of the liquid crystal display panel 11 constituting the image display device 1, generating a ghost image and potentially degrading the image quality of the floating image 3. Therefore, in this embodiment, an absorbing polarizer 12 is provided on the image display surface of the image display device 1. The image light emitted from the image display device 1 is transmitted through the absorbing polarizer 12, and the reflected light returning from the beam splitter 101 is absorbed by the absorbing polarizer 12. This suppresses the re-reflection and prevents degradation of the image quality of the floating image 3 due to ghost images.

[0033] The above-mentioned beam splitter (polarization separation member) 101 is formed of, for example, a reflective polarizing plate or a metal multilayer film that reflects specific polarized waves. More specifically, the beam splitter 101 can be formed by evaporating an optical thin film onto flat glass (for example, quartz glass).

[0034] [Z-type floating image display device] Figure 3 shows an example of the configuration of the main parts of a space-floating image display device according to an embodiment different from the embodiment in Figure 2. The embodiment in Figure 3 shows a configuration in which an image display device 1 and a retroreflective member 2 (retroreflective plate) are arranged opposite each other, and a beam splitter 101 is arranged in the space connecting them at an angle of about 45 degrees to the image display device 1 and the retroreflective member 2, roughly in a Z shape (or an inverted Z shape) (hereinafter referred to as Z shape).

[0035] The Z-type configuration shown in Fig. 3 includes a transparent member 100 such as a glass plate and an absorptive polarizer 112 for the purpose of reducing the effect of external light incident from direction C on the retroreflective member 2 and image display device 1. As shown in Fig. 3, the image display device 1 and retroreflective member 2 are disposed at an angle of approximately 90 degrees to the transparent member 100 and the absorptive polarizer 112, and at an angle of approximately 45 degrees to the beam splitter 101. In this embodiment, the beam splitter 101 is disposed horizontally, and the position of the image displayed on the image display device 1, more specifically the liquid crystal display panel 11, and the position where the floating image 3 is formed are plane-symmetrical to the beam splitter 101.

[0036] [Retroreflective material] Figure 4(A) shows the surface shape of a typical retroreflective member 2 (retroreflector) manufactured by Nippon Carbide Industries Co., Ltd., used in this study. Figure 4(A) shows a top view, and Figure 4(B) shows a side view. The surface of the retroreflective member 2 has retroreflective sections 2a consisting of regularly arranged hexagonal prisms. Light rays entering the retroreflective sections 2a are reflected by the walls and bottom of the hexagonal prisms and exit as retroreflected light in a direction corresponding to the incident light. This exiting light forms a space-floating image 3 as a regular reflected image (regular image), for example, in the configuration shown in Figures 2 and 3. However, as shown in Figure 4(B), image light from the image display device 1 that is obliquely incident on the retroreflective member 2 forms a ghost image (not shown) at a position different from the regular image. This ghost image reduces the visibility of the space-floating image 3.

[0037] Therefore, in this embodiment (FIG. 3), a real image, a floating image 3, is displayed based on the image displayed on the image display device 1 without forming ghost images. The resolution of this floating image 3 depends not only on the resolution of the liquid crystal display panel 11 but also on the outer diameter D and pitch P of the retroreflective portion 2a of the retroreflective member 2 shown in FIG. 4A. For example, when using a 7-inch WUXGA (1920 × 1200 pixels) liquid crystal display panel 11, even if one pixel (one triplet) is approximately 80 μm, if the diameter D of the retroreflective portion 2a is 240 μm and the pitch P is 300 μm, one pixel of the floating image 3 will be equivalent to 300 μm. As a result, the effective resolution of the floating image 3 will be reduced to about one-third. Therefore, to make the resolution of the floating image 3 equivalent to that of the image display device 1, it is desirable to make the diameter D and pitch P of the retroreflective portion 2a closer to that of one pixel of the liquid crystal display panel. On the other hand, in order to suppress the occurrence of moire caused by the retroreflective member 2 and the pixels of the liquid crystal display panel 11, it is preferable to design the pitch ratio of each so that it is not an integral multiple of one pixel. Also, it is preferable to arrange the shape so that none of the sides of the retroreflective portion 2a overlaps with any of the sides of one pixel of the liquid crystal display panel 11.

[0038] The inventors conducted experiments to determine the relationship between the amount of blur l (small L) and pixel size L (large L) of the image of the floating image 3 that is acceptable for improving visibility. The image display device 1 was created by combining a liquid crystal display panel 11 with a pixel pitch of 40 μm and a light source device 13 with a narrow divergence angle (divergence angle of 15°) as in this embodiment. Figure 5 shows the experimental results. It was found that the amount of blur l, which deteriorates visibility, 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 acceptable is an average roughness of 160 nm or less within a measurement distance of 40 μm. To achieve a less noticeable amount of blur l, it was found that a surface roughness of 120 nm or less is desirable. Therefore, it is desirable to reduce the surface roughness of the retroreflective member 2 described above and to keep the surface roughness, including the reflective film and its protective film, that form the reflective surface below the above-mentioned value.

[0039] On the other hand, to manufacture the retroreflective member 2 at low cost, it is preferable to use a roll press method. Specifically, this method involves aligning the retroreflective portions 2a and forming them on a film. In this method, the reverse shape of the shape to be formed is formed on the surface of a roll, and a UV-curable resin is applied to a base material for fixing. The required shape is formed by passing the roll through the rolls, and then cured by irradiating with UV light to obtain the retroreflective member 2 of the desired shape.

[0040] The image display device 1 of this embodiment, using the liquid crystal display panel 11 and the light source device 13 (see FIG. 6 for details) as a light source that generates light of a specific polarization, reduces the possibility of image light being incident obliquely on the retroreflective member 2. As a result, the occurrence of ghost images is suppressed, and even if a ghost image occurs, the brightness of the ghost image is low, resulting in a structurally excellent system.

[0041] 3, the image display device 1, which is configured with a liquid crystal display panel 11, an absorptive polarizer 12, and a light source device 13, is disposed at a predetermined angle (for example, about 45 degrees with respect to the beam splitter 101 in the horizontal plane). The image light from the image display device 1 passes through the beam splitter 101 in the direction of optical axis B1 (diagonal to the beam splitter 101), and travels toward the retroreflective member 2 in the direction of optical axis B2 (corresponding to direction D) that corresponds to the optical axis B1.

[0042] Here, the image light from the image display device 1 is light of a specific polarization, for example, image light having the characteristics of P polarization (parallel polarization). The beam splitter 101 is a polarization separation member such as a reflective polarizer, and has the property of transmitting P polarization image light from the image display device 1 but reflecting S polarization (vertical polarization: Senkrecht polarization) image light. The beam splitter 101 is formed from a reflective polarizer or a metal multilayer film that reflects specific polarization. The beam splitter 101 can generally be formed by evaporating an optical thin film on a flat glass substrate. Therefore, the refractive index of the beam splitter 101 is substantially the same as the refractive index n of flat glass (n = approximately 1.5).

[0043] Meanwhile, a λ / 4 plate 21 is provided on the light incident surface (retroreflective surface) of the retroreflective member 2. P-polarized image light transmitted through the beam splitter 101 from the image display device 1 passes through the λ / 4 plate 21 twice in total, upon entering and exiting the retroreflective member 2, and is thereby converted from P-polarized to S-polarized light. As a result, the polarization-converted S-polarized image light from the retroreflective member 2 is reflected by the beam splitter 101 and travels toward the transparent member 100, etc. The reflected S-polarized image light travels in a direction corresponding to the optical axis B3 (a diagonal direction relative to the beam splitter 101), passes through the transparent member 100, such as a glass plate, and the absorptive polarizer 112, and generates and displays a real image, a floating-in-space image 3, at a predetermined position outside the transparent member 100, etc.

[0044] Here, in order to reduce degradation of image quality caused by sunlight or illumination light incident on an optical system composed of optical components such as the image display device 1, retroreflective member 2, and beam splitter 101, it is advisable to provide an absorptive polarizing plate 112 on the outer surface of the transparent member 100. Since the polarization axis may become misaligned when light is retroreflected by the retroreflective member 2, some of the image light may be reflected by the beam splitter 101 and returned to the image display device 1. This returned light is reflected again by the image display surface of the liquid crystal display panel 11 constituting the image display device 1, generating a ghost image and significantly degrading the image quality of the spatial floating image 3.

[0045] 2 and 3, an absorptive polarizer 12 is provided on the image display surface of the image display device 1. Alternatively, an anti-reflection film (not shown) may be provided on the image output side of the absorptive polarizer 12 provided on the surface of the image display device 1. This allows the absorptive polarizer 12 to absorb light that causes ghost images, thereby preventing degradation of image quality of the spatially floating image 3 due to ghost images.

[0046] Furthermore, in the Z-shaped configuration of FIG. 3, when external light directly enters the retroreflective member 2, a strong ghost image is generated. Therefore, to suppress and prevent the generation of this ghost image, in this embodiment, the retroreflective member 2 is tilted downward relative to the direction of incidence of the external light, thereby blocking the incidence of the external light. Specifically, the main incident direction of the external light is set to a direction (diagonal direction like the optical axis B3) corresponding to direction C indicated by the arrow (the direction in which the user views the floating image 3 from the front). In this case, the retroreflective member 2 is arranged so that the optical axis B2 is at an angle of, for example, about 90 degrees relative to direction C (optical axis B3). In other words, the main surface of the retroreflective member 2 is arranged so that the main surface of the transparent member 100 or the like is at an angle of, for example, about 90 degrees. As a result, external light incident in direction C does not directly enter the main surface (retroreflective surface) of the retroreflective member 2, thereby preventing the generation of ghost images.

[0047] Furthermore, the image display device 1 is also disposed in a direction different from the incident direction of external light (direction C). Specifically, the main surface (image light exit surface) of the image display device 1 is disposed in the same direction as (i.e., parallel to) the main surface of the retroreflective member 2, and the optical axis B1 of the image display device 1 is disposed at an angle of approximately 90 degrees with respect to the optical axis B3 corresponding to the incident direction of external light (direction C). Furthermore, when considering the range of the luminous flux when external light is incident in direction C on the main surface of the transparent member 100 functioning as an opening, the image display device 1 is disposed at a position slightly outside that range. These features reduce the occurrence of ghost images caused by re-reflection at the image display device 1.

[0048] [Video display device] FIG. 6 shows an example of the configuration of an image display device 1 that can be applied to the embodiments of FIGS. 2 and 3. This image display device 1 is configured to include a light source device 13, a liquid crystal display panel 11, a light redirection panel 54, etc. The image output surface side of the liquid crystal display panel 11 may be provided with the aforementioned absorptive polarizer 12. The light source device 13 is configured to include a plurality of LED elements 201 (LEDs: Light Emitting Diodes), which are semiconductor light sources (solid-state light sources) that make up the light source, and a light guide 203, etc. FIG. 6 shows, as an exploded perspective view, a state in which the liquid crystal display panel 11 and the light redirection panel 54 are arranged on the light output side of the light source device 13.

[0049] Light source device 13 is formed, for example, from a plastic case (not shown) and is configured to house LED elements 201 and light guide 203 inside. Light-receiving end surface 203a is provided on the light incident side of light guide 203 to convert divergent light from each LED element 201 into a substantially parallel beam. Light-receiving end surface 203a has a shape in which the cross-sectional area gradually increases toward the side opposite the light-receiving portion, and is provided with a lens shape that has the effect of gradually reducing the divergence angle by multiple total reflections as light propagates inside.

[0050] Furthermore, the liquid crystal display panel 11 is attached to the upper surface of the light guide 203, and is disposed approximately parallel to the light guide 203. The upper surface of the light guide 203 refers to the emission surface that emits light reflected by the light guide 203. Furthermore, a plurality of LED elements 201 are attached to one side surface (the lower side surface in FIG. 6) of the case of the light source device 13. The light from the plurality of LED elements 201 is converted into approximately collimated light (approximately 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 light-receiving end surface 203a and the LED elements 201 are attached while maintaining a predetermined positional relationship.

[0051] The light source device 13 is configured by attaching a light source unit, in which a plurality of LED elements 201 serving as light sources are arranged, to a light-receiving end surface 203a, which is a light-receiving section provided on the light incident side of a light guide 203. The divergent light beam from the LED elements 201 is converted into approximately collimated light by the lens shape of the light-receiving end surface 203a of the light guide 203. This approximately collimated light is guided inside the light guide 203 in direction A indicated by the arrow. Direction A is a direction approximately parallel to the liquid crystal display panel 11 (from bottom to top in the drawing). The light guided in direction A has its direction converted by a light beam direction conversion section 204 provided in the light guide 203, and is emitted in direction B indicated by the arrow toward the liquid crystal display panel 11, which is approximately parallel to the light guide 203. Direction B is a direction approximately perpendicular to the display surface of the liquid crystal display panel 11.

[0052] The light guide 203 has a configuration in which the distribution (in other words, density) of the light beam direction conversion portions 204 is optimized by the shape inside or on the surface of the light guide 203. This makes it possible to control the uniformity of light, which is the light beam emitted from the light source device 13 shown in direction B and incident on the liquid crystal display panel 11.

[0053] Furthermore, in the image display device 1 including the light source device 13 and the liquid crystal display panel 11, the directivity of the light emitted from the light source device 13 in the direction B can be controlled to improve the utilization efficiency of the light flux emitted from the light source device 13 in the direction B and significantly reduce power consumption. More specifically, a light source having a narrow divergence angle can be configured as the light source device 13. As a result, the image light from the image display device 1 reaches the viewer efficiently with high directivity (in other words, linearity) like laser light, and a high-quality floating image can be displayed with high resolution. At the same time, the power consumption of the image display device 1 including the LED elements 201 of the light source device 13 can be significantly reduced.

[0054] The liquid crystal display panel 11 is attached to a frame (not shown) of the liquid crystal display panel 11, which is attached to the top surface of a case (not shown) of the light source device 13. The liquid crystal display panel 11 is attached to the frame, and a flexible printed circuit (FPC) (not shown) and the like are attached, which are electrically connected to the liquid crystal display panel 11. The liquid crystal display panel 11, which is a liquid crystal display element, generates a display image together with the LED elements 201 by modulating the intensity of transmitted light based on a control signal from a control circuit (not shown) that constitutes the electronic device.

[0055] <Desktop-mounted (Z-type) floating image display device> Next, a desk-mounted type space-floating image display device according to one embodiment will be described with reference to Fig. 7 and subsequent figures. The space-floating image display device of each embodiment shown below has a basic configuration similar to the Z-type configuration shown in Fig. 3. In order to form the space-floating image 3, the components of the space-floating image display device (image display device 1, beam splitter 101, retroreflective member 2, etc.) are fixed to each other with a predetermined positional relationship.

[0056] [First Example] Fig. 7 shows an example of the external configuration of a space-floating image display device suitable for installation on a desk, according to one embodiment (hereinafter referred to as the first embodiment). The space-floating image display device of the first embodiment shown in Fig. 7 is roughly divided into an image display device unit 300 (corresponding housing 106) and a space-floating image display unit 400. The image display device unit 300 is mounted and housed in the housing 106 (in other words, the housing for the image display device 1). The space-floating image display unit 400 is made up of a retroreflective member 2, a λ / 4 plate 21, a beam splitter 101, and a frame 108 that supports these components.

[0057] In FIG. 7, if the illustrated XY plane is the desk surface (a horizontal plane in this example), a housing 106 is placed on the desk surface. The housing 106 is roughly rectangular and flat with a predetermined height. An image display device 1 is placed inside the housing 106 along the desk surface. A space-floating image display unit 400 is placed on top of the housing 106. A beam splitter 101 is placed diagonally with respect to the desk surface. A retroreflective member 2 and a λ / 4 plate 21 are placed on top of the beam splitter 101 along the desk surface. The λ / 4 plate 21 is placed facing downward relative to the retroreflective member 2 above. In other words, the λ / 4 plate 21 is placed on the light incident side of the retroreflective member 2. The space-floating image 3 is formed between the housing 106 and the retroreflective member 2, protruding from the beam splitter 101 to the front (Y direction) and standing vertically (XZ plane).

[0058] The space-floating image 3 is formed between the housing 106 and the retroreflective member 2, projecting from the beam splitter 101 to the front (Y direction) and standing in the vertical direction (XZ plane). The housing 106 of the space-floating image display device is not limited to being placed at the bottom. Depending on the situation, the positional relationship between the housing 106 and the retroreflective member 2 may be reversed, and they may be placed not only vertically but also horizontally. In other words, the beam splitter 101 is placed between the light-emitting side of the housing 106 and the retroreflective member 2, the light-emitting side of the housing 106 and the light-incident / exit side of the retroreflective member 2 are placed opposite each other, and the beam splitter 101 is placed at an angle to the light-incident / exit surface of the retroreflective member 2.

[0059] The frame 108 is a member that supports the beam splitter 101, the retroreflective member 2, and the λ / 4 plate 21. The frame 108 protrudes from two corners of the top surface of the housing 106, extends diagonally upward along the two hypotenuses of the beam splitter 101, bends in the horizontal direction (Y direction), extends along the two sides of the retroreflective member 2, etc., and then its ends extend along the X direction to close.

[0060] In this embodiment, the components of the image display device 1 as shown in FIG. 6, namely, the light source device 13, the liquid crystal display panel 11 which is a liquid crystal display element, the absorptive polarizer 12, etc., are housed and fixed in a housing 106. An opening 1061 is provided in the upper part of the housing 106. The opening 1061 is a portion through which image light passes. A transparent member or the like may be provided in the opening 1061. Image light corresponding to an image displayed on the image display device 1, more specifically, on the liquid crystal display panel 11, passes through this opening 1061 and travels toward the beam splitter 101 above.

[0061] 7 shows a perspective view of the appearance of the space-floating image display device as seen from above (diagonally above). The front of the device here is the surface corresponding to the direction in which a user can view the space-floating image 3 (shown in a dashed frame) formed by the space-floating image display unit 400 from the front. Direction F is the direction in which a user can view the space-floating image 3 from the front, and corresponds to the negative Y direction.

[0062] For the purpose of explanation, a coordinate system or direction such as (X, Y, Z) shown in the figure may be used. The Z direction is the vertical direction, or up-down direction (the vertical direction within the screen of the Floating in Space Image 3), the X direction and the Y direction are two horizontal directions, the X direction is the left-right direction (the horizontal direction within the screen of the Floating in Space Image 3), and the Y direction is the depth direction, or front-back direction (the direction in which the user views the Floating in Space Image 3).

[0063] In this embodiment, as shown in the figure, the space-floating image display unit 400 is configured such that the beam splitter 101, the retroreflective member 2, and other components are exposed and not covered by a housing. The housing 106 is also relatively small (compact) and thin, with a small thickness in the Z direction. In this embodiment, the space-floating image display unit 400 is disposed and fixed on the upper side of the housing 106 via a frame 108, which serves as a support, so as to support the beam splitter 101, the retroreflective member 2, and other components. Therefore, when a user views the space-floating image display unit 400 (particularly the space-floating image 3) from the Y direction, facing forward (direction F), the only housing that is visible to the user is the thin housing 106. Therefore, this embodiment has few obstructions to the user's view, enhancing the feeling of floating in the air of the space-floating image 3, making it ideal for use.

[0064] The beam splitter 101 and the retroreflective member 2 are sufficiently thin. The main surfaces of the retroreflective member 2, which is made of a resin material, are arranged along the X and Y directions (for example, the horizontal direction). Therefore, when the space-floating image 3 is viewed from the user's viewpoint in the Y direction, in front (direction F), the retroreflective member 2 is not very noticeable. Furthermore, when the space-floating image 3 is not displayed and the space-floating image display device is not being used, when the space-floating image display unit 400 is viewed from the user's viewpoint in the Y direction (direction F), the beam splitter 101 appears as a semitransparent plate, and the back side of the beam splitter 101 can be seen to some extent.

[0065] As already mentioned, beam splitter 101 has the property of transmitting P-polarized light and reflecting S-polarized light, and can be formed, for example, by depositing an optical thin film on a flat glass substrate. In this case, the angle of incidence of polarized light on beam splitter 101 is generally set to approximately 45 degrees ± 15 degrees. Furthermore, the image display device unit 300, beam splitter 101, retroreflective member 2, etc. are arranged and fixed in a predetermined positional relationship, similar to the Z-shaped configuration in FIG. 3.

[0066] As shown in Fig. 7, on the housing 106, i.e., on the upper side of the image display device unit 300 or on the light output side of the image display device unit 300, a beam splitter 101 is arranged via a frame 108, which is a support, so as to form an inclined surface with respect to the XY plane. Furthermore, a retroreflective member 2 and a λ / 4 plate 21 are arranged on the XY plane relative to the beam splitter 101 via the frame 108, which is a support. Here, the beam splitter 101 and the retroreflective member 2 are each fixed by bonding two or three sides of the rectangular main surface to the corresponding frame 108, which is a support. Then, as shown in the figure, a floating image 3 is formed at a predetermined position on the front side in the Y direction of the beam splitter 101.

[0067] 8 shows the internal structure of the image display device unit 300 and the space-floating image display unit 400 of FIG. 7 in a cross-sectional view when viewed from the side in the X direction (direction E in FIG. 7). As shown, this image display device unit 300 and the space-floating image display unit 400 have the Z-shaped structure of FIG. 3. If the configuration of FIG. 3 is rotated within the drawing so that direction D in FIG. 3 becomes the vertical direction (Z direction), the configuration of FIG. 3 and the configuration of FIG. 8 will be the same, except for the transparent member 100 and the absorbing polarizing plate 112.

[0068] 8, the image display device unit 300, i.e., the housing 106 and the image display device 1 housed within the housing 106, are arranged so that image light from the liquid crystal display panel 11 is emitted upward in the Z direction. That is, the image display surface of the liquid crystal display panel 11 is arranged on the XY plane (horizontal plane). Also, within the housing 106, the light source device 13, the liquid crystal display panel 11, and the absorptive polarizer 12 are arranged in this order from bottom to top. In FIG. 8, the image light emitted upward on the optical axis C1 from the image display device 1 through the opening 1061 is indicated by dashed arrows. The center of the three dashed arrows indicates the optical axis, and the left and right sides indicate the range of the light beam.

[0069] The image light emitted from the liquid crystal display panel 11 is assumed to be light having a predetermined polarization characteristic, for example, P-polarized light (parallel polarization: P stands for parallel). This P-polarized image light passes directly upward through the beam splitter 101 and travels toward the retroreflective member 2 on an optical axis C2 corresponding to the optical axis C1. The beam splitter 101 has the property of passing P-polarized light and reflecting S-polarized light (vertical polarization: S stands for Senkrecht). The beam splitter 101 is disposed so as to form an angle of, for example, approximately 45 degrees with the P-polarized image light (optical axis C1, Z direction). That is, the beam splitter 101 is disposed so that its principal surface forms an angle of approximately 45 degrees with respect to the Y direction of the principal surfaces of the liquid crystal display panel 11 and the retroreflective member 2.

[0070] Meanwhile, a λ / 4 plate 21 is provided on the light incident surface of the retroreflective member 2. The P-polarized image light on optical axis C2 emitted from the image display device 1 and transmitted through the beam splitter 101 passes through the λ / 4 plate 21 twice, once before and once after being reflected by the retroreflective member 2, and is thereby converted from P-polarized light to S-polarized light. As a result, the S-polarized image light that has traveled on optical axis C2 after being reflected by the retroreflective member 2 is reflected by the beam splitter 101 and travels on optical axis C3 in the Y direction. This S-polarized image light generates and displays a real image, a floating image in space 3, at a predetermined position on the near side in the Y direction, as shown in the figure.

[0071] The predetermined position where the floating image 3 is formed is determined according to the optical distance of the optical path of the optical system including the image display device 1, the beam splitter 101, and the polarization separation member 2. In this embodiment, the position where the floating image 3 is formed is a position in the depth direction (Y direction) near the front end of the area of ​​the main surface of the retroreflective member 2. This predetermined position can be adjusted by design. As described above, in this embodiment, the floating image 3 is generated by linearly polarized (S-polarized in this embodiment) image light. A user (an observer who observes the floating image 3) can easily view the floating image 3 from the front side in the Y direction, i.e., from the direction F indicated by the arrow.

[0072] In the above embodiment, the image display device 1, the beam splitter 101, and the retroreflective member 2 maintain a Z-shaped positional relationship as shown in Fig. 8, and can provide the user (observer) with a space-floating image 3 with excellent visibility. The space-floating image display device of the above embodiment can be suitably used when placed on a horizontal surface such as a desk, table, or shelf.

[0073] 8, when the beam splitter 101 is disposed at an angle of approximately 45 degrees with respect to the P-polarized image light (optical axis C1, Z direction), the image displayed on the image display device 1, i.e., on the liquid crystal display panel 11, is generated and displayed as a floating image in space 3 while maintaining its aspect ratio. More specifically, when a perfect circle is displayed on the liquid crystal display panel 11, the same perfect circle is also displayed as the floating image in space 3.

[0074] [Second Example] Here, when using the space-floating image display device of the first embodiment, if the user (observer) views the space-floating image display unit 400 in the Y direction (horizontal direction) from their viewpoint, that is, from direction F in FIG. 8, the beam splitter 101 looks like a semi-transparent plate. Therefore, the user can see to some extent what is happening behind the beam splitter 101 (the opposite side of the beam splitter 101 from the user's perspective) while observing the space-floating image 3. Conversely, this means that the user can see to some extent what is happening on the user's side through the beam splitter 101 from the rear side of the beam splitter 101, that is, from the opposite side of the beam splitter 101 from the user's perspective, that is, from direction G in FIG. 8. However, the space-floating image 3 itself, which is a real image, cannot be seen from direction G.

[0075] As already mentioned, beam splitter 101 has the property of transmitting P-polarized light and reflecting S-polarized light, and can be formed, for example, by depositing an optical thin film on a flat glass substrate. Therefore, when image light (here, P-polarized image light emitted from liquid crystal display panel 11 constituting image display device 1) is irradiated onto the surface of beam splitter 101, most of the light is transmitted through beam splitter 101, while at least a portion of the light irradiated onto beam splitter 101 is visually recognized as reflected light on beam splitter 101.

[0076] 8, when image light on optical axis C1 emitted from image display device 1 is irradiated onto beam splitter 101, most of the image light (approximately 90% or more) passes through beam splitter 101 and reaches retroreflective sheet 2, while a portion of the image light (approximately 5 to 10%) is reflected on beam splitter 101. This reflected light is shown as reflected image light R.

[0077] In other words, in Fig. 8, when the space-floating image display unit 400 is observed from a direction G opposite to the direction F of the user's original viewpoint, there is a problem that the image light reflected on the beam splitter 101 (reflected image light R in Fig. 8) can be seen. This reflected image light R can be more clearly seen when the brightness around the space-floating image display unit 400 is low, that is, when the room is dark.

[0078] A solution to this problem, that is, a method of making the reflected image light R invisible from direction G in FIG. 8 or reducing the brightness of the reflected image light R, will be described below.

[0079] 9 and 10 show an embodiment in which the space-floating image display unit 400 shown in FIGS. 7 and 8 has been modified to be more vertically elongated in order to solve the above-mentioned problems. These figures show perspective views of the appearance of the space-floating image display device as viewed from above (diagonally above). The height of the entire device in the Z direction in FIG. 9 is greater than the height of the entire device in the Z direction in FIG. 7. The angle B2 of the slope of the beam splitter 101 in FIG. 10 is greater than the angle B1 (approximately 45 degrees) in FIG. 8. As in FIG. 7, the front of the device here corresponds to the direction F in which the user can view the space-floating image 3 (shown in a dashed-line frame) formed by the space-floating image display unit 400 from approximately the front. In FIG. 9, the Z direction is the vertical direction, and the X and Y directions are two horizontal directions. The X direction is the left-right direction (the horizontal direction within the screen of the space-floating image 3), and the Y direction is the depth direction and the front-back direction (the direction in which the user views the space-floating image 3).

[0080] 9, similar to FIG. 7, the beam splitter 101 is arranged on the upper side of the housing 106, i.e., the image display device unit 300, via a frame 108 serving as a support, so as to form an inclined surface with respect to the XY plane (horizontal plane). Furthermore, a retroreflective member 2 and a λ / 4 plate 21 are arranged on the XY plane relative to the beam splitter 101 via the frame 108 serving as a support. Here, the beam splitter 101 and the retroreflective member 2 are each fixed by bonding two or three rectangular sides to the corresponding frame 108 serving as a support. As shown in the figure, the upper part of the space-floating image 3 is formed at a predetermined position on the front side of the beam splitter 101 in the Y direction so as to be slightly inclined toward the user. In other words, in the Z direction, the upper part of the space-floating image 3 is formed so as to be inclined toward the user more than the lower part of the space-floating image 3. As shown in the figure, the two sides extending in the Z direction of the space-floating image 3 are inclined at a predetermined angle γ with respect to the Z direction (vertical direction).

[0081] Fig. 10 is a schematic diagram of the space floating image display device shown in Fig. 9, viewed from the side, i.e., the X-axis direction, direction H in Fig. 9. In Fig. 10, the aforementioned direction F is also the negative direction of the Y direction, and direction F' is illustrated as the oblique direction when the space floating image 3 formed at a slight angle is viewed from the front (direction perpendicular to the surface).

[0082] In Fig. 10, the image light emitted from the liquid crystal display panel 11 is generally linearly polarized (S-polarized or P-polarized) image light. In the embodiment of Fig. 10, the image light emitted from the liquid crystal display panel 11 is P-polarized image light. In this embodiment, in order to allow the image light to pass through the beam splitter 101, if the image light emitted from the liquid crystal display panel 11 is P-polarized, it can be output to the beam splitter 101 as is. On the other hand, if the image light emitted from the liquid crystal display panel 11 is S-polarized, the S-polarized image light is passed through a λ / 2 plate 14 (Fig. 14) to convert it to P-polarized light.

[0083] 14 shows an example of the arrangement of the λ / 2 plate 14 in one embodiment (a modified example of the second embodiment) when the image light emitted from the liquid crystal display panel 11 is S-polarized. This λ / 2 plate 14 is a separate element from the λ / 4 plate 21 of the retroreflective member 2, and is a polarization conversion element, a retardation plate, and a half-wave plate that converts S-polarized light into P-polarized light. Here, the liquid crystal display panel 11 and the λ / 2 plate 14 are arranged, for example, at the position shown in the figure within the housing 106, together with the light source device 13 and the absorptive polarizer 12. In FIG. 14, the λ / 2 plate 14 is provided in contact with the upper side in the Z direction of the image light emission surface of the liquid crystal display panel 11, and the absorptive polarizer 12 is provided in contact with the upper side of the λ / 2 plate 14.

[0084] As another configuration example, other than the example of FIG. 14, a λ / 2 plate 14 may be provided on the lower surface of the transparent member in the opening 1061 of the housing 106.

[0085] In FIG. 10, the image light from the liquid crystal display panel 11 remains P-polarized, or in FIG. 14, the image light converted to P-polarized light by the λ / 2 plate 14 (P-polarized image light) passes through the beam splitter 101 in FIG. 10 and enters the retroreflective member 2 via the λ / 4 plate 21. At this time, the image light that enters the retroreflective member 2 passes through the λ / 4 plate 21 twice, once when it enters the retroreflective member 2 and once when it is reflected, and is therefore converted to S-polarized image light. As described above, the image light reflected by the retroreflective member 2 has been converted to S-polarized image light, and is therefore reflected by the beam splitter 101. As a result, a floating image 3 is generated at the position shown in FIG. 10.

[0086] In this case, in FIG. 10, when the image light from the liquid crystal display panel 11 remains P-polarized, or the image light converted to P-polarized after passing through the λ / 2 plate 14, is incident on the beam splitter 101, the rate at which it is reflected (reflectance) on the beam splitter 101 varies depending on the angle of incidence α onto the beam splitter 101.

[0087] The graph in Figure 11 shows the relationship between the angle of incidence and the reflectance (%R) at the glass surface when S-polarized and P-polarized light is incident from air onto glass with a refractive index of n = 1.5. In Figure 11, the dashed curve shows the change in reflectance as the angle of incidence of S-polarized image light increases, while the solid curve shows the change in reflectance as the angle of incidence of P-polarized image light increases. As Figure 11 shows, for S-polarized image light, the reflectance increases monotonically as the angle of incidence increases, whereas for P-polarized image light, the reflectance approaches zero as the angle of incidence increases, reaching zero at a certain angle, and then increasing again as the angle of incidence increases. Furthermore, the reflectance of S-polarized image light is always greater than that of P-polarized image light at the same angle of incidence.

[0088] As shown in Figure 11, the angle of incidence at which the reflectance of P-polarized image light becomes 0 is called the Brewster angle (θB). This Brewster angle θB is determined by the following equation 1 using the refractive indices of two materials (here, air and glass).

[0089] (Formula 1) θB=arctan(n2 / n1)

[0090] In Equation 1, n1 is the refractive index on the incident side (i.e., air), and n2 is the refractive index on the transmission side (i.e., glass). For example, the Brewster angle θB of light incident on glass with a refractive index of 1.5 from air with a refractive index of 1 is 56.3 degrees.

[0091] As is clear from Figure 11, with S-polarized image light, reflection occurs constantly even when the angle of incidence is changed, and with P-polarized image light, when the angle of incidence reaches the Brewster angle θB, it enters the material (glass) and is no longer reflected. In other words, at the Brewster angle θB, the reflectance (%R) has the property of being 0. On the other hand, as is clear from Equation 1, the Brewster angle changes depending on the refractive index of the material on which the light is incident, and the greater the refractive index on the transmission side relative to the incident side, the larger the Brewster angle.

[0092] As described above, when P-polarized image light is configured to be incident on beam splitter 101 at the Brewster angle calculated using Equation 1 from the refractive index (n2) on the transmission side according to the material of beam splitter 101, there is no reflection on beam splitter 101. As already mentioned, since beam splitter 101 is formed as an optical thin film on flat glass, for example, the Brewster angle θB of beam splitter 101 is the same value (56.3 degrees) as the Brewster angle θB of glass (more specifically, quartz glass).

[0093] As a result, in Fig. 10, if P-polarized image light emitted from the image display device 1 based on the image light from the liquid crystal display panel 11 is configured to be incident on the beam splitter 101 at the Brewster angle θB, the reflected image light R reflected on the beam splitter 101 will be almost zero. The reflected image light R will not be visible in the direction opposite to the direction in which the space-floating image 3 is formed, specifically, from the direction L in Fig. 10. This has the effect of making it difficult for others to see the image light that may be bothersome to others other than the user of the space-floating image display device, and on the other hand, the user can obtain the effect of preventing others from seeing the image light that they do not want others to see.

[0094] 11, even if the incident angle α of the image light on the beam splitter 101 is set to the Brewster angle θ (56.3 degrees) or a slightly smaller angle close to the Brewster angle θ (for example, an angle in the range of 50 degrees to less than 56.3 degrees) (50 degrees≦α<θ), the reflectance of the image light on the beam splitter 101 can be reduced to 2% or less, and the reflected image light R can be reduced to a level that is almost unrecognizable, even if the incident angle α on the beam splitter 101 is an angle away from the Brewster angle θ (for example, α<50 degrees), as can be seen from the graph of FIG. 11, the brightness of the reflected image light R can be reduced simply by converting the image light incident on the beam splitter 101 from S-polarized light to P-polarized light using, for example, the λ / 2 plate 14.

[0095] As described above, the angle of incidence α of the image light emitted from the image display device 1 when it enters the beam splitter 101 on the optical axis C1 is configured to be the Brewster angle θB (specifically, 56.3 degrees) or an angle within a range close to the Brewster angle θB (50 degrees≦α<θB). That is, the angles of arrangement of each component are specified as shown in FIG. 10. FIG. 10 shows an example where α=θB. In particular, the angle of arrangement of the inclined surface of the beam splitter 101 is angle β (β=90 degrees-θB=33.7 degrees) with respect to the Z direction (vertical direction) and angle B2 (B2=θB=56.3 degrees) with respect to the horizontal plane (Y direction).

[0096] This makes it possible to reduce the reflected image light R of the image light at the beam splitter 101 to zero or close to zero, to a level that does not cause any practical problems. In other words, when the beam splitter 101 is viewed from the opposite side (direction L) from the side where the space floating image 3 is visible, the reflected image light R can be reduced to a level that is not visible.

[0097] The specific incident angle α when incident on the beam splitter 101 is not limited to the Brewster angle θB, but if it is set to an angle within the range of 45 degrees to 60 degrees, an effect similar to that of the above embodiment can be obtained.

[0098] [Modification (Third Example)] Here, if the angle of incidence on the beam splitter 101 is set to Brewster's angle, a new problem will arise, as described below. As shown in Fig. 8, in the case of a configuration in which the beam splitter 101 is arranged to form approximately 45 degrees with respect to the P-polarized image light (optical axis C1, Z direction), the image displayed on the image display device 1, i.e., on the liquid crystal display panel 11, will maintain its aspect ratio, and the floating image 3 will be generated and displayed in the direction F corresponding to the expected line of sight of the user, i.e., the horizontal direction (Y direction).

[0099] On the other hand, as shown in Fig. 10, in a configuration in which the incident angle α of the P-polarized image light on the beam splitter 101 is set to 56.3 degrees, which is the Brewster angle θB, the floating image 3 in space is generated in a diagonally downward direction (a direction corresponding to direction F') as seen by the user (direction F). In Fig. 10, the S-polarized image light from the beam splitter 101 is reflected on an optical axis C3 having an angle corresponding to (θB × 2) with respect to the vertical direction (Z direction), as shown. Therefore, the surface of the floating image 3 in space is arranged as a slope with its upper side tilted downward, perpendicular to the direction of the optical axis C3, and having a predetermined angle γ (an angle determined in relation to θB and β) with respect to the XZ plane.

[0100] In this configuration, when a user views the space floating image 3 from direction F, not only does visibility deteriorate, but a new problem arises in that the space floating image 3 may not be visible depending on the position of the user's eyes.

[0101] 12 and 13 show an embodiment corresponding to a solution to the problem of the deterioration of visibility. FIG. 12 also shows a perspective view of the space-floating image display device of this embodiment. In FIG. 12, the housing 106 is modified so that the space-floating image 3 coincides with the XZ plane. Specifically, the height of the front surface 106s1 in the Y direction of the housing 106, corresponding to the side on which the space-floating image 3 is formed, is made higher than in FIG. 9, and the height of the rear surface 106s2, corresponding to the side opposite the side on which the space-floating image 3 is formed, is made lower. In the example of FIG. 9, the height of the housing 106 in the Z direction is 10 mm, the width in the X direction is 80 mm, and the depth in the Y direction is 30 mm. In contrast, in FIG. 12, the height of the surface 106s1 is 26 mm and the height of the surface 106s2 is 6 mm. As a result, in FIG. 12, the difference in height between the front and rear sides is 20 mm. Meanwhile, the depth between the front and rear sides is the same 30 mm. 12 is tilted backward by an angle of arctan(20 / 30), or 33.7 degrees. This 33.7 degrees corresponds to the angle β, which is the difference between 90 degrees and the Brewster angle θB of 56.3 degrees. Alternatively, the angle between the light exit surface of the liquid crystal display panel and the light incident surface of the retroreflective member 2 corresponds to the angle, which is the difference between 90 degrees and the Brewster angle θB.

[0102] FIG. 13 shows a cross-sectional view seen from direction H corresponding to FIG. 12. In FIGS. 12 and 13, the top surface of a housing 106, which has different heights at the front and rear surfaces, is inclined with respect to the XY plane, and above the top surface, a space-floating image display unit 400 is disposed in the same positional relationship as in FIGS. 9 and 10. When the light exit surface of the image display device 1 is disposed along the top surface of the housing 106, the image display device 1 is disposed obliquely within the housing 106 so as to form a Z-shape with respect to the beam splitter 101 and the retroreflective member 2. In other words, the light exit surface of the image display device 1 or the surface of the liquid crystal display panel is disposed obliquely, or the distance between the exit surface of the image display device 1 on the side of the housing 106 connected to the beam splitter 101 and the retroreflective member 2 is shorter than the distance between the exit surface of the image display device 1 on the side of the housing 106 not connected to the beam splitter 101 and the retroreflective member 2. Alternatively, the light exit surface of the image display device 1 or the light exit surface of the liquid crystal display panel has a shorter distance from the retroreflective member 2 on the side corresponding to the formed floating image in space than on the side facing the floating image in space.

[0103] Therefore, with the configuration of Fig. 12, the plane on which the floating image 3 is formed coincides with the XZ plane. When the user's line of sight is in the direction of the line of sight (direction M corresponding to the negative Y direction in Fig. 12), the floating image 3 has the best visibility from the user's perspective, i.e., it has high brightness, and the aspect ratio of the floating image 3 is the original aspect ratio (the same aspect ratio as the image displayed on the liquid crystal display panel 11).

[0104] As described above, when the angle of incidence of the P-polarized image light displayed on the liquid crystal display panel 11 on the beam splitter 101 is the Brewster angle θB of 56.3 degrees, the floating image 3 in space will be generated diagonally downward as shown in Figure 9, which will result in poor visibility for the user. Therefore, as shown in Figure 12, by making the front side of the housing 106 including the image display device 1 higher and the rear side lower, the plane on which the floating image 3 in space is formed can be made to coincide with the XZ plane. This optimizes the visibility of the floating image 3, making it suitable for use.

[0105] [Effects, etc.] As described above, the space-floating image display device of each embodiment and modification is suitable for use mainly indoors and can display a space-floating image with high visibility. Furthermore, it is possible to provide a space-floating image display device in which the brightness of the reflected image light, which is caused by the image light from the image display device 1 based on the image light from the liquid crystal display panel 11 being reflected on the beam splitter 101, is zero or reduced. As a result, from the perspective of a user who is in a position where the space-floating image can be observed, the reflected image light cannot be seen by people on the opposite side of the space-floating image display device. This has the effect of making it difficult to see image light that may be unnecessary or bothersome to people other than the user in a room where the space-floating image display device is installed.

[0106] Furthermore, in order to reduce or eliminate the brightness of the reflected image light, it is necessary to increase the angle of incidence of the image light on the beam splitter 101 from 45 degrees to 56.3 degrees, which is the Brewster angle θB, and this causes the floating image to tilt downward as seen by the user, resulting in a problem of poor visibility. To address this problem, by appropriately adjusting the heights of the front and rear sides of the housing 106 including the image display device 1, the surface on which the floating image 3 is formed can be made vertical, resulting in the effect of optimizing visibility.

[0107] Due to the above effects, the space-floating image display device of each embodiment and modified example can display bright, highly visible space-floating images without emitting unnecessary image light to people other than the user, even when used in a relatively small room, and because it is small and lightweight, it is suitable for easy installation on a desk, table, shelf, etc. indoors.

[0108] The technology in this embodiment displays high-resolution, high-brightness floating images in a floating state, making it possible to use these floating images as a contactless user interface, allowing users to operate them without worrying about contact infection. This contributes to the achievement of the United Nations' Sustainable Development Goals (SDGs), "Good health and well-being for all."

[0109] Furthermore, the technology of this embodiment reduces the divergence angle of the emitted image light and aligns it with a specific polarization, thereby efficiently reflecting only the normal reflected light from the retroreflective material, thereby enabling high light utilization efficiency and producing bright and clear floating images in space.The technology of this embodiment can provide a highly usable non-contact user interface that can significantly reduce power consumption.This contributes to the "9th Sustainable Development Goal (SDGs) - Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation" advocated by the United Nations.

[0110] Although the embodiments of the present disclosure have been specifically described above, they are not limited to the above-described embodiments and various modifications are possible without departing from the spirit of the present disclosure. Unless otherwise specified, each component may be singular or plural. Components of each embodiment may be added, deleted, or replaced, except for essential components. Forms combining each embodiment are also possible. [Explanation of symbols]

[0111] 1: image display device, 2: retroreflective member, 3: space-floating image, 11: liquid crystal display panel, 12, 112: absorption polarizer, 13: light source device, 21: λ / 4 plate, 100: transparent member, 101: beam splitter (polarization separation member), 106: housing, 108: frame, 300: image display device unit, 400: space-floating image display unit, 1061: opening.

Claims

1. A space floating image display device that displays a space floating image, a housing that houses a video display device; a retroreflective member disposed outside the housing opposite the image display device and having a λ / 4 plate provided on a retroreflective surface; a polarization separation member disposed at a predetermined angle with respect to the image display device and the retroreflective member in a space connecting the image display device and the retroreflective member outside the housing; Equipped with the image display device includes a light source device and a liquid crystal display panel as an image source, The image light of a specific polarization output from the liquid crystal display panel is incident on the polarization separation member at a specific incident angle, passes through the polarization separation member, is reflected by the retroreflective member, and is polarization-converted by passing through the λ / 4 plate to become image light of the other polarization, and the image light of the other polarization is reflected by the polarization separation member, and a space-floating image that is a real image is displayed at a predetermined position based on the reflected image light, When the surface on which the floating image in space is displayed is a vertical plane, the image light exit surface of the housing containing the image display device is disposed at an angle to a horizontal plane, and in the vertical direction of the vertical plane, the height of the housing on the side on which the floating image in space is formed is higher than the height of the housing on the side opposite to the side on which the floating image in space is formed, and the angle of incidence on the polarization separation member is greater than 50 degrees and smaller than the Brewster angle corresponding to the material of the polarization separation member; A floating image display device.

2. 2. The space floating image display device according to claim 1, The image light of the specific polarization incident on the polarization separation member is P-polarized light. A floating image display device.

3. 2. The space floating image display device according to claim 1, The specific incident angle of the light incident on the polarization separation member is an angle within a range of 60 degrees or less. A floating image display device.

4. 2. The space floating image display device according to claim 1, the polarization separating member and the retroreflective member are supported by a frame with respect to the housing in which the image display device is housed; A floating image display device.

5. 2. The space floating image display device according to claim 1, The polarization separation member is a reflective polarizing plate or a metal multilayer film that reflects specific polarized waves, which is formed as an optical thin film on a glass substrate. A floating image display device.

6. 2. The space floating image display device according to claim 1, The surface roughness of the retroreflective surface of the retroreflective member is set so that the ratio of the blur amount of the spatial floating image to the pixel size of the image display device is 40% or less, The light source device is a point or surface light source; an optical element unit that reduces the divergence angle of light from the light source; a polarization conversion unit that aligns the light from the light source to be polarized in a specific direction; a light guide having a reflective surface that propagates light from the light source to the liquid crystal display panel; Equipped with controlling the image luminous flux of the image light from the liquid crystal display panel by the shape and surface roughness of the reflecting surface; A floating image display device.

7. 3. The space floating image display device according to claim 2, the image light from the liquid crystal display panel is S-polarized light, a λ / 2 plate that converts S-polarized image light from the liquid crystal display panel into P-polarized light to be incident on the polarization separation member; A floating image display device.

Images