Display device

Abstract

The present invention addresses the problem of providing a display device having a thin structure while maintaining the height at which an aerial image is formed. [Solution] This display device (100) is provided with a light source (110), a diffusion plate (120), a polarizer (130), a retroreflection plate (140) having an opening for generating a pattern (P) that is an original image of an aerial image (Q), and a polarization beam splitter (150) having a curved surface disposed so as to face the retroreflection plate (140). An aerial image (Q) having a larger suspension distance than when a planar polarization beam splitter is used is displayed.

Description

Technical Field

[0001] The present invention relates to a display device having a function of displaying a floating image 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 retroreflected by the retroreflective member does not enter the viewing range of a user, improving the contrast or visual recognition of the floating image. In addition, 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 the floating image to be observed from a wider angle.

[0003] Prior Art Documents:

[0004] Patent Documents:

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-150245

[0006] Patent Document 2: Japanese Patent No. 6927554 Summary of the Invention

[0007] Problems to be Solved by the Invention:

[0008] Figure 1 (A) of is a perspective view of a display device that realizes thinning of the AIRR method, Figure 1 (B) of is a schematic cross-sectional view of the display device. As shown in Figure 1 (A) of, the display device 10 displays a floating image Q at a height D from the surface of a housing such as a case, and the user can visually recognize the floating image Q at the height D.

[0009] As shown in Figure 1 (B) of, the display device 10 is configured to include a light source 20, a diffuser layer 30, a polarizer 40, a retroreflective plate 50, and a polarization beam splitter 60, and realizes thinning of the display device by arranging the polarization beam splitter 60 to face the retroreflective layer 50 in parallel. On the surface of the retroreflective plate 50, for example, a phase adjustment film such as a λ / 4 film is formed, and a pattern P including an opening (through hole) 52 for generating the floating image Q is formed. The pattern P including the opening 52 is the original image of the floating image Q that represents an icon for user operation as shown in Figure 1 (A) of.

[0010] The light L emitted from the light source 20 is diffused by the diffusing layer 30 and then becomes light in a certain polarization state at the polarizer 40 and irradiates the bottom surface side of the retroreflector 50. The light irradiating the bottom surface side of the retroreflector 50 is reflected by the polarization beam splitter 60 through the opening 52. This light is reflected by the retroreflector 50 in the same direction as the incident light, and the retroreflected light passes through the polarization beam splitter 60 to form the aerial image Q of the pattern P.

[0011] However, such a display device has the following problems. As shown in (B) of Figure 1 , the aerial image Q and the pattern P formed on the retroreflector 50 are geometrically symmetric with the polarization beam splitter 60 as the center. That is, the height D at which the aerial image Q is formed is the same as the distance between the retroreflector 50 constituting the pattern P and the polarization beam splitter 60.

[0012] When manufacturing the display device, a thin structure is required, but there is a problem that if the display device is thinned, the imaging height D of the aerial image Q also becomes lower. In addition, among the light reflected by the retroreflector 50, there is not only the retroreflected light component, but also a part of the light component that is specularly reflected. This also occurs when a phase adjustment thin film or the like is formed on the retroreflector.

[0013] Such a specular reflection component forms a high-order virtual image at a position different from the original target aerial image after multiple reflections between the retroreflector 50 and the polarization beam splitter 60, but it is preferably that such a high-order aerial image does not occur originally.

[0014] An object of the present invention is to solve the above-mentioned existing problems and provide a display device having a thin structure while maintaining the height at which the aerial image is formed.

[0015] Means for solving the problems:

[0016] The display device according to the present invention uses retroreflection to display an aerial image and includes: a generation mechanism that generates light representing a pattern of an original image serving as the aerial image; a retroreflective member that retroreflects the light representing the pattern; and a beam splitter having a curved surface, the beam splitter being arranged such that the concave side faces the retroreflective member.

[0017] In a certain mode, the retroreflective member has an opening for generating the pattern, and the generating mechanism includes a light source for irradiating the retroreflective member. By irradiating the retroreflective member with the light source, light representing the pattern is generated. In a certain mode, the generating mechanism further includes a diffuser plate and a polarizer between the light source and the retroreflective member, and the light representing the pattern is polarized light, and the beam splitter is a polarization beam splitter. In a certain mode, the beam splitter is configured such that when the light representing the pattern is incident, the incident angle > the reflection angle. In a certain mode, the retroreflective member is configured such that its main surface is orthogonal to the axis passing through the center of curvature of the beam splitter. In a certain mode, the retroreflective member is configured such that its main surface is inclined with respect to the axis passing through the center of curvature of the beam splitter. In a certain mode, the generating mechanism includes a display light source that emits an image as the pattern. In a certain mode, the display light source is configured such that its optical axis is inclined with respect to the axis passing through the center of curvature of the beam splitter.

[0018] Advantages of the Invention:

[0019] According to the present invention, by using a beam splitter having a curved surface, compared with using a planar beam splitter, the floating distance of the aerial image can be increased, and thus the thinning of the display device can also be achieved. Furthermore, the visual recognizability of the higher-order aerial image caused by multiple reflections can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 (A) of is a perspective view of a conventional display device, Figure 1 and (B) of is a schematic cross-sectional view of a conventional display device.

[0021] Figure 2 is a schematic cross-sectional view showing the configuration of a display device according to the first embodiment of the present invention.

[0022] Figure 3 is a diagram comparing the aerial image generated by the display device according to the present embodiment with the aerial image generated by a conventional display device.

[0023] Figure 4 is an enlarged view of one side of the optical axis of the display device according to the present embodiment, and is also a diagram for explaining the reduction of the visual recognizability of the higher-order aerial image.

[0024] Figure 5 (A) of is a schematic cross-sectional view showing the configuration of a display device according to the second embodiment of the present invention, Figure 5 (B) of is a schematic cross-sectional view showing the configuration of a display device according to the third embodiment of the present invention.

[0025] Figure 6(A) is a schematic diagram showing the positional relationship of the optical components of the display device. Figure 6 (B) is a diagram showing the optical simulation result when an aerial image is formed.

[0026] Description of reference numerals:

[0027] 100, 100A, 100B: Display devices 110, 170: Light sources

[0028] 120: Diffuser 130: Polarizer

[0029] 140: Retroreflector 142: Opening (through hole)

[0030] 150: Polarizing beam splitter Detailed implementation mode

[0031] The display device according to the present invention displays an aerial image or an aerial image formed by retroreflection in a three-dimensional space that can be visually recognized without wearing special glasses or the like. In a certain mode, the display device of the present invention is applicable to a user input interface using an aerial image. In addition, it should be noted that the drawings referred to in the following embodiments include displays exaggerated for easy understanding of the invention, and do not represent the actual shape or ratio of the product as it is.

[0032] [Embodiment]

[0033] Next, the embodiments of the present invention will be described in detail. Figure 2 (A) is a schematic cross-sectional view showing the configuration of the display device according to the first embodiment of the present invention. Figure 2 (B) is a diagram showing the optical path when an aerial image is formed in the display device of this embodiment.

[0034] As Figure 2 shown in (A), the display device 100 of this embodiment is configured to include a light source 110, a diffuser 120, a polarizer 130, a retroreflector 140, and a polarizing beam splitter 150. These components can be installed in, for example, a housing or a casing (not shown here).

[0035] The light source 110 is disposed below the diffuser 120 and emits light having a certain emission angle (or radiation angle) toward the bottom surface of the diffuser 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. In addition, the number or arrangement of the light sources 110 is not particularly limited, and the light sources 110 are arranged so as to be able to effectively irradiate the area including the opening 142 formed in the retroreflector 140 from the bottom surface side of the retroreflector 140.

[0036] The diffuser plate 120 is, for example, a film-like, sheet-like, or plate-like optical component including a rectangular upper surface and a bottom surface opposed to the upper surface. The diffuser plate 120 receives the light L emitted from the light source 110 from the bottom surface side, diffuses the incident light, and causes the diffused light to be emitted from the upper surface side of the diffuser plate 120. The light emitted from the diffuser plate 120 irradiates the region including the opening 142 of the retroreflector 140 substantially uniformly from the bottom surface side of the retroreflector 140.

[0037] A polarizer 130 is disposed on the upper surface side of the diffuser plate 120. The polarizer 130 is, for example, a rectangular film-like, sheet-like, or plate-like optical component, and is constituted by, for example, a polarization filter or a DBEF (reflection type polarization element). The polarizer 130 receives the light emitted from the upper surface side of the diffuser plate 120, and emits light in a certain polarization state (for example, linearly polarized light) from the incident light.

[0038] A retroreflector 140 is formed above the polarizer 130. The retroreflector 140 is a rectangular film-like, sheet-like, or plate-like optical component that reflects light in the same direction as the incident light, and is constituted by, for example, a prism type retroreflective element such as a triangular pyramid type retroreflective element or an all-solid angle type retroreflective element, or a bead type retroreflective element.

[0039] On the surface of the retroreflector 140, a phase adjustment film such as a λ / 4 film may be provided, for example, as a phase adjustment film for adjusting the phase. The phase adjustment film imparts a phase difference between the incident light and the emitted light. For example, if it is a λ / 4 film, a phase difference of λ / 4 is imparted between the incident light and the emitted light. In the case where a λ / 4 film is provided, the retroreflected light passes through the λ / 4 film twice, and thus has a phase difference of λ / 4×2 with respect to the incident light.

[0040] Furthermore, in the retroreflector 140, one or more openings (through holes) 142 for forming a pattern P that forms the original image of the aerial image Q are formed. The pattern P including the opening 142 is not particularly limited, and is, for example, any graphic such as an icon, character, number, symbol, or a combination thereof as shown in (A) of Figure 1 etc.

[0041] Above the retroreflector 140, a polarization beam splitter 150 is disposed with a gap therebetween. The beam splitter is an optical element that separates the incident light into transmitted light and reflected light, and the polarization beam splitter 150 is a polarization separation element that separates the incident light into a p-polarization component and an s-polarization component, transmits light in a certain polarization state, and reflects light in a certain polarization state. The polarization direction of the polarization beam splitter 150 is determined according to the relationship with the polarization direction of the polarizer 130. For example, the polarization direction of the polarizer 130 is substantially orthogonal to the polarization direction of the polarization beam splitter 150.

[0042] In this embodiment, it is characterized in that the polarization beam splitter 150 has a curved surface or an arc-shaped surface. The external shape of the plane sagittal view of the polarization beam splitter 150 is not particularly limited, and can be, for example, rectangular or circular. The polarization beam splitter 150 is configured such that the curved surface on its convex side faces upward, in other words, the curved surface on its concave side faces the retroreflector 140. In the illustrated example, the polarization beam splitter 150 is configured such that the axis passing through its center of curvature coincides with the optical axis C passing through the approximate center of the light source 110, and the tangent S intersecting the axis passing through the center of curvature of the polarization beam splitter 150 is orthogonal to the optical axis C. In addition, the distance between the tangent S of the polarization beam splitter 150 and the main surface of the retroreflector 140 is set to a size such that the light retroreflected from the retroreflector 140 can be incident on the polarization beam splitter 150.

[0043] The display device 100 configured in this way is as Figure 2 shown in (B). Above the polarization beam splitter 150, an aerial image Q of the pattern P is generated. That is, the light emitted from the light source 110 is diffused by the diffuser 120 and then becomes light in a certain polarization state on the polarizer 130 and irradiates the bottom surface side of the retroreflector 140. The light irradiating the bottom surface side of the retroreflector 140 passes through the opening 142 to generate light representing the pattern P. The light passing through the retroreflector 140 is reflected by the polarization beam splitter 150, the reflected light is reflected by the retroreflector 140 in the same direction as the incident light, the retroreflected light passes through the polarization beam splitter 150, and an aerial image Q of the pattern P is formed.

[0044] Figure 3 is a diagram for comparing the aerial image Q' generated by the Figure 1 conventional display device 10 shown in (B) with the aerial image Q generated by the display device 100 of this embodiment. In the conventional display device 10, the planar polarization beam splitter 60 (represented 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, the polarization beam splitter 150 having a curved surface is arranged substantially parallel to the main surface of the retroreflector 140, thereby changing the reflection angle corresponding to the incident angle of the polarization beam splitter 150 with respect to the optical axis C.

[0045] In the conventional display device 10, the light L from the light source 110 is reflected by the polarization beam splitter 60 arranged orthogonal to the optical axis C and then is reflected by the retroreflector 140 in the incident direction 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 at an equal distance D on the opposite side of the distance D from the retroreflector 140 including the pattern P to the polarization beam splitter 60.

[0046] In contrast, in the display device 100 of the present embodiment, the polarization beam splitter 150 has a curved surface that is concave on the light source side. As a result, the incident angle θ1 of the light L emitted from the light source with respect to the optical axis C and the reflection angle θ2 have a relationship of θ2 < θ1. Therefore, with respect to the distance D from the retroreflective plate 140 including the pattern 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 the retroreflective plate 140 as a reference. However, in the display device 100 of the present embodiment, it can be achieved with a thickness of the distance D on the light source side. Therefore, the suspension distance D1 of the aerial image Q can be increased and the display device 100 can be made thinner.

[0047] Next, the reduction in the visual recognition of the higher-order aerial images due to multiple reflections in the display device of the present embodiment will be described. Figure 4 is Figure 3 An enlarged view of one side of the optical axis C, illustrating the higher-order reflected light caused by the retroreflective plate 140. In the conventional display device 10, the incident angle θ1 = the reflection angle θ2 with respect to the optical axis C, and for the second-order reflected light, the incident angle θ2 = the reflection angle θ3. As a result, an aerial image 2Q associated with the second-order reflection is generated at a 3D distance. Similarly, imaging occurs for the third-order reflected light and subsequent ones. For the nth-order reflected light, an aerial image is generated at a distance of (2n - 1)D.

[0048] In contrast, in the display device 100 of the present embodiment, the imaging distance of the nth-order aerial image becomes a distance of (2n - 1)(sinθ1 / sinθ2)D. Additionally, when θ2 ≤ 0, this light does not form an image. That is, compared with the conventional display device 10, the imaging distance of the higher-order reflected light is farther from the first-order imaging distance D1. Therefore, it is not easy to visually recognize the higher-order aerial images.

[0049] As described above, according to the present embodiment, by using a curved polarization beam splitter, the suspension distance of the aerial image can be increased and the display device can be made thinner. Furthermore, the visual recognition of the higher-order aerial images due to multiple reflections can be reduced.

[0050] In addition, in the above embodiment, an example of using polarized light to display the aerial image Q is shown. However, in addition to this, unpolarized light can also be used to display the aerial image Q. In this case, the diffuser plate 120 or the polarizer 130 is not required, and the light from the light source 110 directly irradiates the back side of the retroreflective plate 140. Additionally, instead of the polarization beam splitter 150, a half mirror with a curved surface is used.

[0051] Next, a second embodiment of the present invention will be described. Figure 5(A) is a schematic cross-sectional view showing the configuration of the 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 diffuser plate 120, the polarizer 130, and the retroreflector 140 including the pattern P are arranged to be inclined with respect to the axis passing through the center of curvature of the polarization beam splitter 150. Further, another retroreflector 160 is arranged on the opposite side of the retroreflector 140 to be inclined with respect to the beam splitter 150. The retroreflector 160 may be arranged at a position symmetric to the retroreflector 140 with respect to the axis passing through the center of curvature of the polarization beam splitter 150, but is not limited thereto, and may be arranged at an asymmetric position. In short, the retroreflector 160 only needs to be arranged at a position where the light reflected by the polarization beam splitter 150 can be incident and an aerial image Q can be formed in the retroreflection direction. The external shape of the planar sagittal view of the retroreflector 160 has, for example, substantially the same shape as the retroreflector 140, but is not limited thereto. In addition, different from the retroreflector 140, the retroreflector 160 does not need an opening or a hole for generating the pattern P.

[0052] In the second embodiment, the light emitted from the opening 142 of the retroreflector 140 including the pattern P is reflected by the polarization beam splitter 150, and the reflected light is incident on the retroreflector 160 and is reflected in the same direction as the incident light here. The retroreflected light transmits through the polarization beam splitter 150 and forms an aerial image Q. The aerial image Q is imaged at a position farther than the aerial image Q' generated in the case of using the planar polarization beam splitter 60A.

[0053] In this way, according to the second embodiment, even when the light source is arranged to be inclined with respect to the polarization beam splitter 150, it is also possible to image the aerial image Q at a position farther than in the case of using a planar polarization beam splitter as in the first embodiment, and the display device 100A can be made thinner. At the same time, the visual recognizability of the higher-order aerial image caused by multiple reflections can also be reduced.

[0054] Figure 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 retroreflector 140 having a hole 142 formed for generating the pattern P is used, but in the display device 100B of the third embodiment, instead of using such a retroreflector 140, a display light source 170 such as a display is used.

[0055] The display light source 170 only needs to have the function of emitting an image or a picture, and is not particularly limited. For example, it is 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 smart phone, the screen of a personal computer, the screen of a projector, etc.

[0056] The display light source 170 is configured 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 retroreflected by another retroreflector 160 after being reflected by the polarization beam splitter 150, and the light passing through the transmission polarization beam splitter 150 forms an aerial image Q. In this embodiment, compared with the case of using the planar polarization beam splitter 60A, the aerial image Q is imaged at a farther distance than the aerial image Q'. Therefore, the thinning of the display device 100B can be achieved and the visual recognition of the higher-order aerial image can be reduced.

[0057] Next, the specific effects of this embodiment will be described. Figure 6 (A) of is a schematic diagram showing the positional relationship of the optical components of the display device, Figure 6 (B) of is a simulation result showing the imaging position of the aerial image, showing the case where the upper optical system uses a planar beam splitter and the lower optical system uses a beam splitter with a curved surface. Figure 6 Each part of (A) of is as follows.

[0058] O: Reference point (aerial display surface)

[0059] R: Curvature radius of the beam splitter

[0060] F: Focal length of the beam splitter (0.5R)

[0061] a: Distance from the light source (pattern) to the beam splitter ≈ device height

[0062] b: Imaging distance

[0063] By the mapping formula, the relationship becomes (1 / a) - (1 / b) = 1 / F.

[0064] Assuming that the curvature radius R of the beam splitter is 2000 mm and a = 50 mm, then b = 52.6 mm, a < b, and the suspension distance is extended compared with the suspension distance (b = 50 mm) in the case of the planar beam splitter. That is, the device height can be made smaller with respect to the suspension distance. By inverse calculation, if the suspension distance b = 50 mm and the curvature radius R of the beam splitter is 300 mm, then a = 37.5 mm, and a 25% thinning can be achieved in the optical system part.

[0065] When the aerial images are set to the same floating distance / same size, the following additional effects are produced:

[0066] (1) It is necessary to miniaturize the underlying pattern (the size of the aerial image is magnified compared to the size of the light source (pattern). Magnification ratio = b / a)

[0067] (2) Along with the effect of (1) above, when the brightness of the pattern is the same, the brightness decreases corresponding to the magnification ratio.

[0068] (3) Along with the effect of (1) above, when the resolution (DPI) of the pattern is the same, the resolution of the aerial image decreases corresponding to the magnification ratio.

[0069] (4) Since the pattern is close to the beam splitter side, the required area of the retroreflector can be reduced.

[0070] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to specific embodiments, and various modifications and changes can be made within the scope of the gist of the invention described in the claims.

Claims

1. A display device capable of displaying an aerial image by utilizing retroreflection, wherein: have: A generating mechanism that generates light of a pattern representing an original image as an aerial image; A retroreflective component that retroreflects light representing the pattern; as well as A beam splitter having a curved surface, The beam splitter is arranged so that the concave side faces the retroreflective member.

2. The display device according to claim 1, wherein: The retroreflective member has openings for generating the pattern, The generating mechanism comprises a light source for illuminating the retroreflective member, When the retroreflective member is illuminated by the light source, light representing the pattern is generated.

3. The display device according to claim 2, wherein: The generating mechanism further includes a diffusion plate and a polarizing plate between the light source and the retroreflective member, the light representing the pattern is polarized light, and the beam splitter is a polarization beam splitter.

4. The display device according to claim 1, wherein: The beam splitter is arranged so that, when light representing the pattern is incident, an incident angle > a reflection angle.

5. The display device according to claim 1, wherein: The retroreflective member is disposed so that a main surface of the retroreflective member is orthogonal to an axis passing through a center of curvature of the beam splitter.

6. The display device according to claim 1, wherein: The retroreflective member is arranged such that a main surface of the retroreflective member is inclined with respect to an axis passing through a center of curvature of the beam splitter.

7. The display device according to claim 1, wherein: The generating mechanism includes a display light source that emits an image serving as the pattern.

8. The display device according to claim 7, wherein: The display light source is configured such that an optical axis of the display light source is tilted relative to an axis passing through a center of curvature of the beam splitter.

Images