Display device

Abstract

To provide a display device capable of reducing the thickness thereof.SOLUTION: An aerial image display device 100 includes: a housing 110; a beam splitter 120 formed on a surface of the housing 110; a retroreflective sheet 130 which is arranged so as to face the beam splitter 120 and on which a notch or an opening for generating a design of an original image of an aerial image is formed; a light source 140 that illuminates the retroreflective sheet 130 from a back surface side; and a metamaterial layer 150 which is arranged between the beam splitter 120 and the retroreflective sheet 130 and of which refractive index is less than 1. An aerial image P of a design Q illuminated by the light source 140 is displayed at a floating distance Lb (Lb>Lx) over the housing 110.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a display device having a function of displaying an image in the air by using retroreflection.

Background Art

[0002] Aerial Imaging by Retro-Reflection (AIRR) is known. For example, Patent Document 1 discloses a display device including a half mirror, an image output device that outputs light toward one surface of the half mirror, and a retroreflective member that is disposed between the image output device and the half mirror and has a plurality of openings formed therein. Further, Patent Document 2 discloses an aerial display device including a planar light emitter having a light emitting portion, a retroreflective sheet that is disposed on the emission surface side of the planar light emitter and has a plurality of through holes representing a figure for aerial display at positions corresponding to the light emitting portions, and a half mirror that is disposed on the emission surface side of the retroreflective sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As an AIRR-type aerial display system, there is one that uses an LED as a light source and displays a fixed display pattern in the air. In order to achieve miniaturization and thinning, such a display device is configured such that each optical component is arranged to face each other, and one configuration example is shown in FIG. 1.

[0005] FIG. 1(A) is a schematic plan view of a conventional aerial image display device, and FIG. 1(B) is a schematic cross-sectional view taken along line A-A thereof. The aerial image display device 10 includes a beam splitter 30 attached to the surface of a rectangular housing 20, a retroreflective sheet 40 disposed inside the housing 20 so as to face the beam splitter 30, and a light source 50 such as an LED. A notch or opening 42 is formed in the retroreflective sheet 40, and the notch 42 generates a design (fixed display pattern) Q that forms the original image of the aerial image P. The aerial image P in FIG. 1(A) exemplifies an icon representing the power on / off of the device.

[0006] When irradiated with the light source 50 from the back side of the retroreflective sheet 40, the light that has passed through the notch 42 is retroreflected between the retroreflective sheet 40 and the beam splitter 30, and the aerial image P of the design Q is displayed above the housing 20. The floating distance L1 of the aerial image P is equivalent to the distance L2 from the beam splitter 30 to the retroreflective sheet 40 (or the design Q). In order to reduce the thickness of the height H of the housing 20, when the distance L2 is reduced, there is a problem that the floating distance L1 of the aerial image P becomes short and the feeling that the aerial image P is floating becomes less.

[0007] An object of the present invention is to solve such a conventional problem and provide a display device capable of reducing the thickness while maintaining the floating distance of the aerial image.

Means for Solving the Problems

[0008] A display device capable of displaying an aerial image using retroreflection according to the present invention includes an optical member that transmits a part of the incident light and reflects the rest, a retroreflective member that is disposed so as to face the optical member and has a notch or opening formed therein for generating a design of the original image of the aerial image, a light source that irradiates the retroreflective member from the back side, and a transparent intermediate layer that is disposed between the optical member and the retroreflective member and is composed of a substance having a refractive index smaller than 1.

[0009] In one aspect, the transparent intermediate layer is composed of a metamaterial. In one aspect, the aerial image is displayed above the optical member at a floating distance corresponding to the refractive index of the transparent intermediate layer. In one aspect, the optical member is a half mirror, a beam splitter, or a polarizing beam splitter.

Advantages of the Invention

[0010] According to the present invention, by providing an intermediate layer having a refractive index smaller than 1 between the optical member and the retroreflective member, the refraction angle of the light transmitted through the optical member can be reduced, and the aerial image can be formed at a farther distance. Therefore, while reducing the distance between the optical member and the retroreflective member to make the display device thinner, the floating distance of the aerial image can be increased.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0012] The display device according to the present invention displays an aerial image using retroreflection in a three-dimensional space without wearing special glasses or the like. It should be noted that the drawings referred to in the following description of the embodiments include exaggerated displays for easy understanding of the invention, and do not represent the actual shape and scale of the product as it is.

Examples

[0013] Next, embodiments of the present invention will be described in detail. FIG. 2 is a schematic cross-sectional view of an aerial image display device according to an embodiment of the present invention, and this cross-sectional view corresponds to a cross-section taken along line A-A of FIG. 1(A).

[0014] The aerial image display device 100 of this embodiment includes, for example, a rectangular housing 110, a beam splitter 120 attached to the surface of the housing 110, a retroreflective sheet 130 attached in the housing 110 so as to face the beam splitter 120, a light source 140 disposed on the back side of the retroreflective sheet 130, and a metamaterial layer 150 disposed so as to fill the space between the beam splitter 120 and the retroreflective sheet 130.

[0015] The beam splitter 120 is an optical member that transmits a part of the incident light and reflects the rest, that is, an optical member that separates the incident light into transmitted light and reflected light at a certain ratio. The beam splitter 120 is, for example, a half mirror. Also, when polarized light is used, a polarization beam splitter is used as the beam splitter 120.

[0016] The retroreflective sheet 130 is disposed so as to face the beam splitter 120. The retroreflective sheet 130 is an optical member that reflects light in the same direction as the incident light, and is composed of, for example, a prism-type retroreflective element such as a triangular pyramid-type retroreflective element or a full cube corner-type retroreflective element, or a bead-type retroreflective element.

[0017] The shape and size of the retroreflective sheet 130 are not particularly limited, but a notch or opening for generating a design Q that is the original image of the aerial image P is formed in the retroreflective sheet 130. For example, as shown in FIG. 1(A), the design Q is an icon representing on / off of the power supply. However, the type (characters, icons, etc.) and number of designs formed on the retroreflective sheet 130 are arbitrary.

[0018] A light source 140 is arranged on the back side of the retroreflective sheet 130. The light source 140 is not particularly limited, and examples thereof include an LED light source, a display light source such as a liquid crystal, and a projection light source such as a projector. When using an LED light source, for example, a plurality of LEDs may be arranged linearly or in a planar shape so as to efficiently and evenly irradiate the entire back surface of the retroreflective sheet 130. Further, a diffusion plate or a diffusion sheet may be used in combination so that the back side of the retroreflective sheet 130 is uniformly irradiated.

[0019] A light-transmissive transparent substance having a refractive index smaller than 1, that is, a metamaterial layer 150, is filled or arranged between the beam splitter 120 and the retroreflective sheet 130. The metamaterial layer 150 is formed with a generally constant film thickness such that its upper surface is in contact with the beam splitter 120 and its bottom surface is in contact with the retroreflective sheet 130. However, the film thickness and shape of the metamaterial layer 150 are not particularly limited.

[0020] A metamaterial is an artificial substance or artificial material that exhibits behavior not found in natural substances, and here it has the property of having a refractive index smaller than 1. A metamaterial generally has a fine structure or pattern periodically arranged, by which it is possible to control the refraction of light. Components of a general metamaterial include, for example, metals, dielectrics, magnetic materials, carbon nanotubes and metal nanowires, silicon, and plastics. By interposing the metamaterial layer 150, the refraction angle of the light transmitted through the beam splitter 120 can be made smaller than the refractive index in the case of an air layer where the metamaterial layer 150 does not exist.

[0021] Next, the operation of the aerial image display device 100 of this embodiment will be described. The light from the light source 140 irradiates the back side of the retroreflective sheet 130, and the irradiated light passes through the notches or openings formed in the retroreflective sheet 130, thereby generating a design Q that is the original image of the aerial image P. The light that has passed through the notches or openings is partially reflected by the beam splitter 120 via the metamaterial layer 150. Then, the light retroreflected by the retroreflective sheet 130 passes through the beam splitter 120 via the metamaterial layer 150, and the aerial image Q of the design P is re-imaged.

[0022] By filling the space between the beam splitter 120 and the retroreflective sheet 130 with the metamaterial layer 150, the refraction angle of the light passing through the beam splitter 120 becomes smaller compared to when the space is an air layer, and the aerial image P can be imaged farther away, that is, the floating distance Lb can be increased.

[0023] As a comparative example, the aerial image P1 shown in FIG. 2 is the imaging position when there is an air layer without the metamaterial layer 150 between the beam splitter 120 and the retroreflective sheet 130. At that time, the floating distance La is equivalent to the distance Lx between the beam splitter 120 and the retroreflective sheet 130 (or the design Q) (La = Lx). On the other hand, the aerial image P is the imaging position when the space with the distance Lx between the beam splitter 120 and the retroreflective sheet 130 is filled with the metamaterial layer 150, and its floating distance Lb is larger than the floating distance La when there is no metamaterial layer 150 (Lb > La). The floating distance Lb is generally determined according to the refractive index of the metamaterial layer 150.

[0024] Thus, even if the interval Lx between the beam splitter 120 and the retroreflective sheet 130 is shortened, that is, even if the housing is made thinner, the floating distance Lb of the aerial image P can be extended, and a floating feeling can be produced.

[0025] In another aspect of this embodiment, the light source 140 may include a polarizing plate or a polarizing filter, and may irradiate the back surface side of the retroreflective sheet 130 with polarized light. In this case, a retardation film, for example, a λ / 4 film, is provided on the front surface side of the retroreflective sheet 130, and a polarizing beam splitter is used as the beam splitter 120. The polarizing beam splitter transmits part of the light in a certain polarization state and reflects the rest. The polarization state of the polarizing plate or the polarizing film is determined in relation to the polarization state of the polarizing beam splitter.

[0026] The upper side of FIG. 3 shows the simulation result of the aerial image generated by the conventional liquid crystal display device, and the lower side shows the simulation result of the aerial image generated by the liquid crystal display device of this embodiment. In the conventional liquid crystal display device, the space between the retroreflective sheet and the polarizing beam splitter is an air layer, and from the eye point, an aerial image generated at a floating distance equal to the thickness of the air layer is visible.

[0027] On the other hand, in the liquid crystal display device of this embodiment, instead of the air layer, a metamaterial layer, which is a transparent body with a refractive index less than 1, is embedded, so that an aerial image with an extended imaging position compared to the case of the air layer is displayed, and from the eye point, an aerial image with a larger floating distance than in the case of the air layer is visible.

[0028] The aerial image display device of this embodiment can be applied to the display of information of any device and user input. For example, it can be applied to computer devices, in-vehicle electronic devices, ATMs in banks, ticket vending machines at stations, input buttons of elevators, etc.

[0029] As described above, the preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to specific embodiments, and various modifications and changes are possible within the scope of the gist of the invention described in the claims.

Explanation of Reference Numerals

[0030] 100: Aerial image display device 110: Housing 120: Beam splitter 130: Retroreflective sheet 140: Light source 150: Metamaterial layer P: Virtual image in air Q: Design (original image)

Claims

1. A display device capable of displaying a virtual image by using retroreflection, comprising: an optical member that transmits part of the incident light and reflects the rest; a retroreflective member disposed to face the optical member and having a notch or aperture formed therein for generating a design of an original image of the virtual image; a light source that irradiates the retroreflective member from the back side; a transparent intermediate layer disposed between the optical member and the retroreflective member and composed of a substance having a refractive index smaller than 1; and a display device including the same.

2. The display device according to claim 1, wherein the transparent intermediate layer is composed of a metamaterial.

3. The display device according to claim 1, wherein the virtual image is displayed above the optical member at a floating distance corresponding to the refractive index of the transparent intermediate layer.

4. The display device according to claim 1, wherein the optical member is a half mirror, a beam splitter, or a polarizing beam splitter.

Images