Display device

Abstract

To provide a display device which has a thin structure while maintaining a height for forming an aerial image.SOLUTION: A display device 100 includes: a light source 110; a diffuser plate 120; a polarizing plate 130; a retroreflection plate 140 including an opening for generating a design P as an original image of an aerial image Q; and a polarization beam splitter 150 having a curved surface which is arranged opposite to the retroreflection plate 140. The display device 100 displays the aerial image Q at a larger floating distance than when using a flat polarization beam splitter.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Aerial Imaging by Retro-Reflection (AIRR) is known. For example, Patent Document 1 discloses a display device that positions a light source and a retroreflective member so that light specularly reflected by the retroreflective member does not enter the user's observation range, improving the contrast and visibility of the aerial image. Further, Patent Document 2 discloses a display device that arranges a retroreflective portion at a position different from the emission direction of light emitted from a light source, enabling observation of an aerial image from a wide angle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] FIG. 1(A) is a perspective view of a display device aiming at thinning of the AIRR method, and FIG. 1(B) is a schematic cross-sectional view of the display device. As shown in FIG. 1(A), the display device 10 displays an aerial image Q at a position of height D from the surface of a housing such as a housing, and a user can visually recognize the aerial image Q at height D.

[0005] As shown in Fig. 1(B), the display device 10 is configured to include a light source 20, a diffusion layer 30, a polarizing plate 40, a retroreflective plate 50, and a polarization beam splitter 60. The polarization beam splitter 60 is arranged to face the retroreflective layer 50 in parallel, thus achieving a thinner profile of the display device. On the surface of the retroreflective plate 50, a phase adjustment film such as a λ / 4 film is formed, and a design P including an aperture (through-hole) 52 for generating the aerial image Q is formed. The design P including the aperture 52 is the original image of the aerial image Q representing an icon for user operation as shown in Fig. 1(A).

[0006] The light L emitted from the light source 20 is diffused by the diffusion layer 30 and then becomes polarized light by the polarizing plate 40 and irradiates the bottom side of the retroreflective plate 50. The light irradiating the bottom side of the retroreflective plate 50 passes through the aperture 52 and is reflected by the polarization beam splitter 60. The light is reflected by the retroreflective plate 50 in the same direction as the incident light, and the retroreflected light passes through the polarization beam splitter 60, and the aerial image Q of the design P is formed.

[0007] However, such a display device has the following problems. As shown in Fig. 1(B), the aerial image Q and the design P formed on the retroreflective plate 50 are geometrically symmetric about the polarization beam splitter 60. That is, the height D at which the aerial image Q is formed is the same as the distance between the retroreflective plate 50 constituting the design P and the polarization beam splitter 60.

[0008] In the commercialization of the display device, there is a need for a thin structure. However, when attempting to make the display device thinner, there is a problem that the imaging height D of the aerial image Q also becomes lower. In addition, the light reflected by the retroreflective plate 50 includes not only the light component of retroreflection but also a part of the light component of regular reflection. This also occurs when a phase adjustment film or the like is formed on the retroreflective plate.

[0009] Such regular reflection components undergo multiple reflections between the retroreflective plate 50 and the polarization beam splitter 60 and form higher-order virtual images at positions different from the original intended aerial image. It is desirable that this higher-order aerial image does not occur originally.

[0010] The present invention aims to solve the above-described conventional problems and provide a display device with a thin structure while maintaining the height at which an aerial image is formed.

Means for Solving the Problems

[0011] The display device according to the present invention displays an aerial image using retroreflection, and includes a generation means for generating light representing a design as an original image of the aerial image, a retroreflective member for retroreflecting the light representing the design, and a beam splitter having a curved curved surface, and the beam splitter is arranged such that the concave side faces the retroreflective member.

[0012] In one aspect, the retroreflective member has an opening for generating the design, the generation means includes a light source for irradiating the retroreflective member, and light representing the design is generated by irradiating the retroreflective member with the light source. In one aspect, the generation means further includes a diffusion plate and a polarizing plate between the light source and the retroreflective member, the light representing the design is polarized light, and the beam splitter is a polarizing beam splitter. In one aspect, the beam splitter is arranged such that when the light representing the design is incident, the incident angle > the reflection angle. In one aspect, the retroreflective member is arranged such that its main surface is orthogonal to an axis passing through the center of curvature of the beam splitter. In one aspect, the retroreflective member is arranged obliquely with respect to an axis passing through the center of curvature of the beam splitter. In one aspect, the generation means includes a display light source that emits an image as the design. In one aspect, the optical axis of the display light source is arranged obliquely with respect to an axis passing through the center of curvature of the beam splitter.

Effects of the Invention

[0013] According to the present invention, by using a beam splitter having a curved surface, the floating distance of the aerial image can be made larger than when using a planar beam splitter, and thus the display device can be made thinner. Furthermore, the visibility of the higher-order aerial image due to multiple reflections can be reduced.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0015] The display device according to the present invention displays an aerial video or an aerial image using retroreflection in a three-dimensional space that can be visually recognized without wearing special glasses or the like. In one aspect, the display device according to the present invention is applied to a user input interface using an aerial image. It should be noted that the drawings referred to in the following 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

[0016] Next, embodiments of the present invention will be described in detail. FIG. 2(A) is a schematic cross-sectional view showing the configuration of a display device according to a first embodiment of the present invention, and FIG. 2(B) is a diagram showing the optical path when a virtual image is formed in the display device of this embodiment.

[0017] As shown in FIG. 2(A), the display device 100 of this embodiment includes a light source 110, a diffusion plate 120, a polarizing plate 130, a retroreflective plate 140, and a polarizing beam splitter 150. Although these members are not shown here, they can be attached to, for example, a housing or a casing.

[0018] The light source 110 is disposed below the diffusion plate 120 and emits light having a certain emission angle (or radiation angle) toward the bottom surface of the diffusion plate 120. The light source 110 is not particularly limited, and for example, a light-emitting element such as a light-emitting diode or a laser diode can be used. Also, the number and arrangement of the light sources 110 are not particularly limited, but the light source 110 is arranged so as to effectively irradiate the region including the opening 142 formed in the retroreflective plate 140 from the bottom surface side of the retroreflective plate 140.

[0019] The diffusion plate 120 is, for example, a film-like, sheet-like, or plate-like optical member including a rectangular upper surface and a bottom surface facing the upper surface. The diffusion plate 120 allows the light L emitted by the light source 110 to enter from the bottom surface side, diffuses the incident light, and emits the diffused light from the upper surface side of the diffusion layer 120. The light emitted from the diffusion plate 120 irradiates the region including the opening 142 of the retroreflective plate 140 from the bottom surface side of the retroreflective plate 140 substantially uniformly.

[0020] The polarizing plate 130 is disposed on the upper surface side of the diffusion plate 120. The polarizing plate 130 is, for example, a rectangular film-like, sheet-like, or plate-like optical member, and is composed of, for example, a polarizing filter or a DBEF (reflection-type polarizing element). The polarizing plate 130 receives the light emitted from the upper surface side of the diffusion plate 120 and emits light in a certain polarization state (for example, linearly polarized light) from the incident light.

[0021] A retroreflector 140 is formed above the polarizing plate 130. The retroreflector 140 is a rectangular film-like, sheet-like, or plate-like optical member that reflects light in the same direction as the incident light, and is composed of, for example, prism-type retroreflective elements such as triangular pyramid-type retroreflective elements and full cube corner-type retroreflective elements, or bead-type retroreflective elements.

[0022] On the surface of the retroreflector 140, for example, a λ / 4 film or the like may be provided as a phase adjustment film for adjusting the phase. The phase adjustment film gives a phase difference between the incident light and the emitted light. For example, if it is a λ / 4 film, it gives a phase difference of λ / 4 between the incident light and the emitted light. When a λ / 4 film is provided, the retroreflected light passes through the λ / 4 film twice, so it has a phase difference of λ / 4×2 with respect to the incident light.

[0023] Furthermore, one or more openings (through holes) 142 for forming a design P, which is the original image of the aerial image Q, are formed in the retroreflector 140. The design P including the opening 142 is not particularly limited, and is, for example, any figure such as an icon, character, number, symbol, or a combination thereof as shown in FIG. 1(A).

[0024] Above the retroreflector 140, a polarizing beam splitter 150 is disposed via a gap. The beam splitter is an optical element that separates the incident light into transmitted light and reflected light. The polarizing beam splitter 150 is a polarization separation element that divides the incident light into a p-polarization component and an s-polarization component, transmits light of a certain polarization state, and reflects light of a certain polarization state. The polarization direction of the polarizing beam splitter 150 is determined in relation to the polarization direction of the polarizing plate 130. For example, the polarization direction of the polarizing plate 130 is substantially orthogonal to the polarization direction of the polarizing beam splitter 150.

[0025] What is characteristic in this embodiment is that the polarization beam splitter 150 has a curved surface or an arc-shaped surface. The appearance shape of the polarization beam splitter 150 in a plan view from the side is not particularly limited, and for example, it can be rectangular or circular. The polarization beam splitter 150 is arranged such that the curved surface on its convex side faces upward, in other words, the curved surface on its concave side faces the retroreflective plate 140. In the illustrated example, the polarization beam splitter 150 is arranged such that the axis passing through its center of curvature is aligned with the optical axis C that generally passes through the center of the light source 110, and the tangent line S that intersects the axis passing through the center of curvature of the polarization beam splitter 150 is perpendicular to the optical axis C. Further, the distance between the tangent line S of the polarization beam splitter 150 and the main surface of the retroreflective plate 140 is set to a size such that the light retroreflected from the retroreflective plate 140 can be incident on the polarization beam splitter 150.

[0026] The display device 100 configured as described above generates an aerial image Q of the design P above the polarization beam splitter 150 as shown in FIG. 2(B). That is, the light emitted from the light source 110 is diffused by the diffuser plate 120 and then becomes polarized light by the polarizer 130 and irradiates the bottom surface side of the retroreflective plate 140. The light irradiating the bottom surface side of the retroreflective plate 140 passes through the aperture 142 and generates light representing the design P. The light passing through the retroreflective plate 140 is reflected by the polarization beam splitter 150, and the reflected light is reflected by the retroreflective plate 140 in the same direction as the incident light. The retroreflected light passes through the polarization beam splitter 150 and forms an aerial image Q of the design P.

[0027] FIG. 3 is a diagram comparing the aerial image Q' generated by the conventional display device 10 shown in FIG. 1(B) with the aerial image Q generated by the display device 100 of this embodiment. In the conventional display device 10, a planar polarization beam splitter 60 (shown by a dashed line) is arranged parallel to the main surface of the retroreflective member 140, but in the display device 100 of this embodiment, a polarization beam splitter 150 having a curved surface is arranged to be generally parallel to the main surface of the retroreflective plate 140, thereby changing the reflection angle with respect to the incident angle with respect to the optical axis C in the polarization beam splitter 150.

[0028] In the conventional display device 10, the light L from the light source 110 is reflected by the polarization beam splitter 60 arranged so as to be orthogonal to the optical axis C, and then reflected in the incident direction by the retroreflector 140 to form an aerial image Q'. In the conventional display device 10, since the polarization beam splitter 60 is planar, the incident angle with respect to its optical axis C is equal to the reflection angle, and the aerial image Q' is formed at a position of an equal distance D on the opposite side of the distance D from the retroreflector 140 including the design P to the polarization beam splitter 60.

[0029] On the other hand, in the display device 100 of the present embodiment, since the polarization beam splitter 150 has a curved surface that is concave on the light source side, the incident angle θ1 and the reflection angle θ2 of the light L emitted from the light source with respect to the optical axis C have a relationship of θ2 < θ1. Therefore, with respect to the distance D from the retroreflector 140 including the design P to the polarization beam splitter 150, there is a relationship of imaging distance D1 = (sinθ1 / sinθ2)D. That is, in the conventional display device 10, in order to form the aerial image Q at the distance D1, a thickness of the distance D1 is required on the light source side with respect to the retroreflector 140. In the display device 100 of the present embodiment, since it can be realized with a thickness of the distance D on the light source side, it is possible to increase the floating distance D1 of the aerial image Q while reducing the thickness of the display device 100.

[0030] Next, the reduction in visibility of the higher-order aerial image due to multiple reflections in the display device of the present embodiment will be described. FIG. 4 is an enlarged view of one side of the optical axis C in FIG. 3, and illustrates the higher-order reflected light by the retroreflector 140. In the conventional display device 10, the incident angle θ1 = the reflection angle θ2 with respect to the optical axis C, and also the incident angle θ2 = the reflection angle θ3 with respect to the second-order reflected light. As a result, an aerial image 2Q associated with the second-order reflection is generated at a 3D distance. The imaging is the same for the third-order reflected light and subsequent, and an aerial image is generated at a distance of (2n - 1)D with respect to the nth-order reflected light.

[0031] In contrast, in the display device 100 of this embodiment, the imaging distance of the nth-order aerial image is the distance of (2n - 1)(sinθ1 / sinθ2)D. Also, when θ2 ≤ 0, the light does not form an image. That is, compared with the conventional display device 10, since the imaging distance of the higher-order reflected light is farther from the first-order imaging distance D1, it becomes difficult to visually recognize the higher-order aerial image.

[0032] Thus, according to this embodiment, by using the curved polarizing beam splitter, it is possible to increase the floating distance of the aerial image while reducing the thickness of the display device, and further reduce the visibility of the higher-order aerial image due to multiple reflections.

[0033] In the above embodiment, an example of displaying the aerial image Q using polarized light is shown. However, alternatively, the aerial image Q may be displayed using non-polarized light. In this case, the diffuser plate 120 and the polarizer plate 130 are unnecessary, and the light from the light source 110 directly irradiates the back side of the retroreflector 140. Also, instead of the polarizing beam splitter 150, a half mirror having a curved surface is used.

[0034] Next, a second embodiment of the present invention will be described. FIG. 5(A) is a schematic cross-sectional view showing the configuration of a display device according to the second embodiment. In the display device 100A of the second embodiment, the optical axes C of the light source 110, the diffusion plate 120, the polarizing plate 130, and the retroreflective plate 140 including the design P are arranged obliquely with respect to the axis passing through the center of curvature of the polarizing beam splitter 150, and another retroreflective plate 160 is also arranged obliquely with respect to the beam splitter 150 on the opposite side of the retroreflective plate 140. The retroreflective plate 160 may be arranged at a position symmetric with the retroreflective plate 140 with respect to the axis passing through the center of curvature of the polarizing beam splitter 150, but is not limited thereto, and may be arranged at an asymmetric position. In short, the retroreflective plate 160 may be arranged at a position where the light reflected by the polarizing beam splitter 150 is incident and the aerial image Q can be formed in the direction of retroreflection. The appearance shape of the retroreflective plate 160 in a plan view is, for example, generally the same as that of the retroreflective plate 140, but is not limited thereto. Further, unlike the retroreflective plate 140, the retroreflective plate 160 does not require an opening or a hole for generating the design P.

[0035] In the second embodiment, the light emitted from the opening 142 of the retroreflective plate 140 including the design P is reflected by the polarizing beam splitter 150, the reflected light is incident on the retroreflective plate 160, and is reflected in the same direction as the incident light there, and the retroreflected light passes through the polarizing beam splitter 150 and the aerial image Q is formed. The aerial image Q is formed farther than the aerial image Q' generated when the planar polarizing beam splitter 60A is used.

[0036] Thus, according to the second embodiment, even when the light source is arranged obliquely with respect to the polarizing beam splitter 150, the aerial image Q can be formed farther than in the case of using a planar polarizing beam splitter, as in the first embodiment, and the display device 100A can be made thinner. At the same time, it is also possible to reduce the visibility of the higher-order aerial image due to multiple reflections.

[0037] FIG. 5(B) is a schematic cross-sectional view showing the configuration of the display device according to the third embodiment. In the display device 100A of the second embodiment, the retroreflective plate 140 in which the holes 142 are formed is used to generate the design P. However, in the display device 100B of the third embodiment, instead of using such a retroreflective plate 140, a display light source 170 such as a display is used.

[0038] The display light source 170 is not particularly limited as long as it has a function of emitting an image or a picture. For example, it may be a liquid crystal display device (LCD), an organic EL display device, a projection display device, etc. For example, it emits an image (polarized light) in the normal direction (optical axis direction) of the rectangular emission surface. The display light source 170 is, for example, the screen of a portable terminal such as a smartphone, the screen of a personal computer, the screen of a projector, etc.

[0039] The display light source 170 is arranged such that its optical axis is inclined with respect to the axis passing through the center of curvature of the polarization beam splitter 150. The light emitted from the display light source 170 is reflected by the polarization beam splitter 150 and then retroreflected by another retroreflective plate 160, and an aerial image Q is formed by the light transmitted through the polarization beam splitter 150. Also in this embodiment, compared with the case of using the planar polarization beam splitter 60A, the aerial image Q is formed farther away than the aerial image Q'. Therefore, the thickness reduction of the display device 100B and the reduction in the visibility of the higher-order aerial image can be achieved.

[0040] Next, the specific effects of this embodiment will be described. FIG. 6(A) is a schematic diagram showing the positional relationship of the optical members of the display device, and FIG. 6(B) is a simulation result showing the imaging position of the aerial image. The upper optical system shows the case of using a planar beam splitter, and the lower optical system shows the case of using a beam splitter having a curved surface. Each part of FIG. 6(A) is as follows. O: Reference point (aerial display surface) R: Beam splitter radius of curvature F: Beam splitter focal length (0.5R) a: Distance from the light source (design) to the beam splitter ≒ device height b: Imaging distance

[0041] According to the imaging formula, the relationship (1 / a) - (1 / b) = 1 / F holds. If the radius of curvature R of the beam splitter is 2000 mm and a = 50 mm, then b = 52.6 mm, and a < b. The floating distance extends compared to the floating distance (b = 50 mm) in the case of a planar beam splitter. That is, the device height can be reduced with respect to the floating distance. By inverse calculation, if the floating distance b = 50 mm and the radius of curvature R of the beam splitter is 300 mm, then a = 37.5 mm, and a 25% thinning of the optical system part becomes possible.

[0042] When the aerial image is set to the same floating distance / the same size, the following accompanying effects occur. (1) Miniaturization of the original design is necessary (the size image in the air is enlarged from the light source size (design). Magnification = b / a) (2) Along with the effect of (1) above, when the luminance of the design is the same, a decrease in luminance occurs according to the magnification ratio. (3) Along with the effect of (1) above, when the resolution (DPI) of the design is the same, the resolution of the aerial image decreases according to the magnification ratio. (4) Since the design approaches the beam splitter side, the required area of the retroreflector can be reduced.

[0043] 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 Signs

[0044] 100, 100A, 100B: Display device 110, 170: Light source 120: Diffuser 130: Polarizer 140: Retroreflector 142: Aperture (through-hole) 150: Polarizing beam splitter

Claims

1. A display device capable of displaying a virtual image using retroreflection, comprising: generating means for generating light representing a design as the original image of the virtual image; a retroreflective member for retroreflecting the light representing the design; a beam splitter having a curved surface, wherein the beam splitter is arranged such that its concave side faces the retroreflective member.

2. The retroreflective member has an aperture for generating the design, the generating means includes a light source for irradiating the retroreflective member, and the display device according to claim 1, wherein the light representing the design is generated by irradiating the retroreflective member with the light source.

3. The generating means further includes a diffuser and a polarizer between the light source and the retroreflective member, the light representing the design is polarized light, and the beam splitter is a polarizing beam splitter. The display device according to claim 2.

4. The display device according to claim 1, wherein the beam splitter is arranged such that when the light representing the design is incident thereon, the incident angle > the reflection angle.

5. The display device according to claim 1, wherein the retroreflective member is arranged such that its main surface is orthogonal to the axis passing through the center of curvature of the beam splitter.

6. The display device according to claim 1, wherein the retroreflective member is arranged obliquely with respect to the axis passing through the center of curvature of the beam splitter.

7. The display device according to claim 1, wherein the generating means includes a display light source for emitting an image as the design.

8. The display device according to claim 7, wherein the optical axis of the display light source is arranged obliquely with respect to the axis passing through the center of curvature of the beam splitter.

Images