Display device

Abstract

To provide a display device that suppresses stray light and improves the visibility and contrast of aerial images.SOLUTION: An aerial image display device 100 includes: a beam splitter 110; a retroreflective sheet 120 which is arranged so as to face the beam splitter 110 and on which a notch or an opening for generating a design Q of an original image of an aerial image; a transparent member (for example, an acrylic material) 130 which is arranged between the beam splitter 110 and the retroreflective sheet 120 and of which refractive index is greater than 1; and a light source 140 that illuminates the retroreflective sheet 120 from a back surface side. An aerial image P of the design Q illuminated by the light source 140 is displayed at a position floating over the beam splitter 110.SELECTED DRAWING: Figure 4

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 to be displayed in the air 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 has each optical component arranged in parallel so as to face each other, and one configuration example thereof is shown in FIG. 1.

[0005] Fig. 1(A) is a schematic perspective view of a conventional aerial image display device, and Fig. 1(B) is a schematic cross-sectional view thereof. The aerial image display device 10 includes, for example, a beam splitter 30 disposed on 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 disposed on the back side of the retroreflective sheet 40.

[0006] The retroreflective sheet 40 is an optical member or optical element that reflects light in the same direction as the incident light. A notch or aperture S is formed in the retroreflective sheet 40. The notch or aperture S 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) shows, for example, an icon indicating the rewinding direction of playback.

[0007] When irradiated with light from the light source 50 from the back side of the retroreflective sheet 40, the light that has passed through the notch S 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 beam splitter 30.

[0008] However, the conventional aerial image display device 10 has the following problems. Fig. 2(A) is a diagram illustrating the cross-sectional structure of the retroreflective sheet 40 and the surface reflection and internal reflection occurring inside the retroreflective sheet 40. The retroreflective sheet 40 includes a pattern forming portion 42 formed of a light transmissive material, a metal layer 44 (for example, Al, etc.) formed on the inclined surface of the pattern forming portion 42, an optical adhesive 46 applied on the upper surface of the pattern forming portion 42, and a phase plate (for example, λ / 4 plate) 48 attached on the optical adhesive 46. The metal layer 44 functions as a reflective layer, and the thickness including the optical adhesive 46 and the phase plate 48 is, for example, 1 mm or less.

[0009] Light L1: The light incident on the retroreflective sheet 40 is reflected multiple times by the metal layer 44, and the reflected light is reflected in the same direction as the incident light. Such a light ray L1 is a light ray that follows the optical characteristics of the retroreflective sheet 40 and is desirable light. Light L2: Part of the light incident on the retroreflective sheet 40 is reflected from the surface of the phase plate 48, and the reflected light is specularly reflected at a reflection angle equal to the incident angle. Such a light ray L2 is a light ray that does not conform to the optical characteristics of the retroreflective sheet 40 and is undesirable light. Light L3: Part of the light incident on the retroreflective sheet 40 is reflected by the metal layer 44, then internally reflected by the phase plate 48, and reflected again by the metal layer 44. Such a light ray L3 has a large optical path difference between the incident light and the reflected light, does not conform to the optical characteristics of the retroreflective sheet 40, and is undesirable light.

[0010] When undesirable lights L2 and L3 are generated by the retroreflective sheet 40, as shown in Fig. 2(B), stray light (or virtual image) V of the design Q is generated, and a pseudo aerial image W caused by the stray light (or virtual image) V is generated. As a result, as shown in Figs. 3(A) and (B), within the range where the user observes the aerial image P, a plurality of virtual images V and pseudo aerial images W are reflected around it, and the visibility and contrast of the aerial image P are reduced.

[0011] An object of the present invention is to solve such conventional problems, suppress stray light or pseudo aerial images, and provide a display device that improves the visibility and contrast of the aerial image.

Means for Solving the Problems

[0012] The display device according to the present invention is capable of displaying an aerial image using retroreflection, and includes an optical member that separates incident light into reflected light and transmitted light, a retroreflective member that faces the optical member and has a design formed by a notch or an opening, a light source disposed on the back side of the retroreflective member, and a transparent member disposed between the optical member and the retroreflective member and composed of a substance having a refractive index greater than 1.

[0013] In one aspect, the transparent member has a generally rectangular shape, with the upper surface of the transparent member in contact with the optical member and the bottom surface in contact with the retroreflective member. In one aspect, the transparent member is made of a material with a refractive index difference from the retroreflective member of approximately zero or less than a certain value. In one aspect, when the retroreflective member includes a phase member on its surface, the transparent member is made of a material with a refractive index difference from the phase member of approximately zero or less than a certain value. In one aspect, the transparent member is made of an acrylic material. In one aspect, the optical member is a half mirror, a beam splitter, or a polarizing beam splitter.

Advantages of the Invention

[0014] According to the present invention, by providing a transparent member with a refractive index greater than 1 between the optical member and the retroreflective member, the refractive index difference between the transparent member and the retroreflective member is reduced, and reflection at the interface between the transparent member and the retroreflective member is suppressed. As a result, the generation of stray light and pseudo virtual images is suppressed, and the visibility and contrast of the virtual image can be improved.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] The display device according to the present invention displays a virtual 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 ease of understanding of the invention, and do not represent the actual shape and scale of the product as it is.

Embodiment

[0017] Next, embodiments of the present invention will be described in detail. FIG. 4(A) is a schematic cross-sectional view of a virtual image display device according to an embodiment of the present invention, and FIG. 4(B) is a diagram for explaining the generation of a virtual image. The virtual image display device 100 of the present embodiment includes, for example, a beam splitter 110 disposed on the surface of a rectangular housing or casing, a retroreflective sheet 120 disposed opposite to the beam splitter 110, a transparent member 130 having a refractive index greater than 1 disposed between the beam splitter 110 and the retroreflective sheet 120, and a light source 140 disposed on the back side of the retroreflective sheet 120.

[0018] The beam splitter 110 is an optical member or optical element that separates incident light into reflected light and transmitted light. For the beam splitter 110, for example, a half mirror or, when using polarized light, a polarizing beam splitter is used.

[0019] The retroreflective sheet 120 is disposed to face the beam splitter 120. The retroreflective sheet 130 is an optical member or optical element 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. In one aspect, the retroreflective sheet 120 is configured in the same manner as the retroreflective sheet 40 shown in FIG. 2(A), that is, a pattern forming portion 42 formed of a light transmissive material, a metal layer 44 formed on the inclined surface of the pattern forming portion 42, an optical adhesive 46 applied on the upper surface of the pattern forming portion 42, and a phase plate (for example, a λ / 4 plate) 48 attached on the optical adhesive 46. However, the retroreflective sheet 120 is not limited to such a configuration and may not include the phase plate 48 on its surface.

[0020] The shape and size of the retroreflective sheet 120 are not particularly limited, but the retroreflective sheet 120 is formed with a notch or an opening for generating a design Q that is the original image of the aerial image P. For example, as shown in FIG. 1(A), the design Q is an icon representing the rewinding direction of reproduction. However, the type (characters, icons, etc.) and number of designs formed on the retroreflective sheet 120 are arbitrary.

[0021] A light source 140 is disposed on the back side of the retroreflective sheet 120. 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 plane so as to efficiently and evenly irradiate the entire back surface of the retroreflective sheet 120. In a certain aspect, a diffusion plate or a diffusion sheet may be used in combination so that the back side of the retroreflective sheet 120 is uniformly irradiated. Further, the light source 140 may include a polarizing plate or a polarizing film and irradiate the back surface of the retroreflective sheet 120 with polarized light. In this case, a polarizing beam splitter is used as the beam splitter 110, a λ / 4 film is provided on the surface of the retroreflective sheet 120, and the polarization state of the polarizing plate or the polarizing film is determined in relation to the polarization state of the polarizing beam splitter.

[0022] A transparent member 130 with a light transmittance and a refractive index greater than 1 is disposed between the beam splitter 110 and the retroreflective sheet 120. Preferably, a material having a refractive index approximating that of the retroreflective sheet 120 is selected for the transparent member 130, and the refractive index difference between the transparent member 130 and the retroreflective sheet 120 is made as small as possible. When a phase plate 48 is formed on the surface of the retroreflective sheet 120, a material having a refractive index approximating that of the phase plate 48 is selected. The approximating refractive index means that the refractive index difference between the two is as small as possible. For example, when a λ / 4 plate (or λ / 4 film) is formed, if the refractive index of the λ / 4 plate is about 1.5, an acrylic material is selected as the material for the transparent member 130 with a refractive index of about 1.5. In addition to the acrylic material, other plastic materials (for example, PC (refractive index 1.584), polystyrene (refractive index 1.592), PET (refractive index 1.576)) can also be used for the transparent member 130 according to the refractive indices of the retroreflective sheet 120 and the phase plate 48.

[0023] The transparent member 130 generally has a rectangular shape, with the beam splitter 110 formed on its upper surface and the retroreflective sheet 120 formed on its back surface. The beam splitter 110 may be formed by film deposition on the upper surface of the transparent member 130, or may be attached by an optical adhesive. Also, the retroreflective sheet 120 may be attached to the back surface of the transparent member 120, for example, by an optical adhesive.

[0024] Next, the operation of the aerial image display device 100 of this embodiment will be described. As shown in FIG. 4(B), the light from the light source 140 irradiates the back surface side of the retroreflective sheet 120, and the irradiated light passes through the notch or opening formed in the retroreflective sheet 120, and a design Q, which is the original image of the aerial image P, is generated. The light that has passed through the notch or opening is partially reflected by the beam splitter 110 through the transparent member 130, the reflected light is retroreflected by the retroreflective sheet 120, the retroreflected light passes through the beam splitter 110 through the transparent member 130, and the aerial image Q of the design P is re-imaged above the beam splitter 110.

[0025] By filling the space between the beam splitter 110 and the retroreflective sheet 120 with a transparent member 130 having a refractive index greater than 1, the refractive index difference between the transparent member 130 and the retroreflective sheet 120 is made as small as possible compared to the case where the space is an air layer, and the light incident on and exiting from the retroreflective sheet 120 can reduce the specular reflection on the surface of the retroreflective sheet 120 and the internal reflection occurring inside. Ideally, if the refractive indices of the transparent member 130 and the retroreflective sheet 120 are equal, the transparent member 130 and the retroreflective sheet 120 can be regarded as optically seamless and identical members. Therefore, as shown in FIGS. 2(A) and (B), unwanted lights L2 and L3 caused by the reflection occurring on the surface of the retroreflective sheet 120 can be suppressed, thereby suppressing the generation of the virtual image of the design Q and stray light V. As a result, the generation of the pseudo virtual image W is suppressed, and the visibility and contrast of the virtual image P can be improved.

[0026] Note that by interposing the transparent member 130 having a refractive index greater than 1, the refraction angle of the light transmitted through the beam splitter 110 becomes larger than that in the case of the air layer, and the floating distance of the virtual image P becomes somewhat smaller. Therefore, when displaying a virtual image with a large floating distance, it is necessary to consider the thickness of the transparent member 130.

[0027] The virtual image display device of the present embodiment can be applied to the display of information of any device and user input, and can be applied to, for example, a computer device, in-vehicle electronic equipment, an ATM such as a bank, a ticket vending machine at a station, an input button of an elevator, and the like.

[0028] 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

[0029] 100: Virtual image display device 110: Beam splitter 120: Retroreflective sheet 130: Transparent member 140: Light source P: Virtual image in the air Q: Design (original image)

Claims

1. A display device capable of displaying a virtual image using retroreflection, comprising: an optical member that separates incident light into reflected light and transmitted light; a retroreflective member that faces the optical member and has a design formed by a notch or an opening; a light source disposed on the back side of the retroreflective member; a transparent member disposed between the optical member and the retroreflective member and composed of a material having a refractive index greater than 1.

2. The display device according to claim 1, wherein the transparent member has a generally rectangular shape, an upper surface of the transparent member is in contact with the optical member, and a bottom surface thereof is in contact with the retroreflective member.

3. The display device according to claim 1, wherein the transparent member is composed of a material having a refractive index difference from the retroreflective member of approximately zero or less than a certain value.

4. The display device according to claim 1, wherein when the retroreflective member includes a phase member on its surface, the transparent member is composed of a material having a refractive index difference from the phase member of approximately zero or less than a certain value.

5. The display device according to claim 1, wherein the transparent member is composed of an acrylic material.

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

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