Indication device

Abstract

To provide a display device that makes the internal structure difficult to see. [Solution] The display device 100 of the present invention comprises a housing 110, a display 120 housed within the housing 110, a polarizing beam splitter 130, an ND filter 140, a λ / 4 plate 150, and a retroreflective material 160. The λ / 4 plate 150 is placed on the surface of the retroreflective material 160, and the ND filter 140 is placed on the surface of the λ / 4 plate 150. Unwanted light Lb that does not contribute to the imaging of the aerial image P output from the display 120 is attenuated by the ND filter 140.

Description

Technical Field

[0001] The present invention relates to a display device that displays an aerial image by retroreflection. Background Art

[0002] Aerial Imaging by Retro-Reflection (AIRR) using retroreflection is known. The principle of displaying an aerial image (or aerial video) using retroreflection is that light emitted from a light source is reflected by a mirror toward a retroreflective material, and part of the glowing light that returns to the mirror again is transmitted to achieve re-imaging. For this reason, a half mirror with reduced reflectance, a polarizing beam splitter, or the like is used for this mirror (for example, Patent Document 1). Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Patent No. 7604079 Summary of the Invention Problems to be Solved by the Invention

[0004] FIG. 1(A) is a diagram showing a schematic configuration of a conventional display device that displays an aerial image. The display device 10 is configured to include, for example, a display 30, a polarizing beam splitter 40, a λ / 4 plate 50, and a retroreflective material 60 in a housing 20 such as a casing.

[0005] The display 30 outputs the original image of the aerial image P, and the polarizing beam splitter 40 reflects the incident light of the original image toward the retroreflective material 60. The λ / 4 plate 50 is a phase difference film that creates a λ / 4 phase difference and is attached to the surface of the retroreflective material 60. The light reflected by the polarizing beam splitter 40 passes through the λ / 4 plate 50 and is retroreflected by the retroreflective material 60 in the same direction as the incident light. The retroreflected light then passes through the λ / 4 plate 50 again and then passes through the polarizing beam splitter 40 to form the aerial image P.

[0006] Here, of the light output from the display 30, the light La reflected by the polarizing beam splitter 40 becomes light La' that passes through the optical path of the λ / 4 plate 50, retroreflective material 60, λ / 4 plate 50, and polarizing beam splitter 40, forming an aerial image P. On the other hand, among the light output from the display 30 in an oblique direction, there is light Lb that is incident directly on the λ / 4 plate 50 without incident on the polarizing beam splitter 40. Such light Lb becomes light Lb' that is reflected from the surface of the λ / 4 plate 50, for example, and does not contribute to the formation of the aerial image P. When such light Lb' reaches the observer U's eye, the internal structure such as the optical system inside the housing appears bright, which reduces the contrast of the aerial image P.

[0007] Furthermore, as shown in Figure 1(B), even within the light Lc that passes through the λ / 4 plate 50 and enters the retroreflective material 60, scattered light Lc' is generated that repeatedly reflects between the reflective portion (Al metal layer) 62 of the retroreflective material 60 and the λ / 4 plate 50 and does not undergo retroreflection. Such scattered light Lc' is also unwanted light that does not contribute to the formation of the aerial image P, and causes the same problems as described above. Note that light La is an example of the desired retroreflected light La'.

[0008] The present invention aims to solve these conventional problems and provide a display device that makes the internal structure difficult to see and improves the contrast of the aerial image. [Means for solving the problem]

[0009] The display device according to the present invention is capable of displaying an aerial image using retroreflection and comprises a light source, a polarizing beam splitter positioned at a location into which light from the light source is incident, a retroreflective material, a λ / 4 plate disposed on the surface of the retroreflective material, and a light-reducing filter disposed on the surface of the λ / 4 plate. The retroreflective material receives light reflected by the polarizing beam splitter via the light-reducing filter and the λ / 4 plate, and the polarizing beam splitter transmits the light retroreflected by the retroreflective material through the λ / 4 plate and the light-reducing filter to form the aerial image.

[0010] Furthermore, the display device according to the present invention is capable of displaying an aerial image using retroreflection and comprises a light source, a half mirror positioned at a location into which light from the light source is incident, a retroreflective material, and a polarizing plate positioned on the surface of the retroreflective material. The retroreflective material receives the light reflected by the half mirror through the polarizing plate, and the half mirror transmits the light retroreflected by the retroreflective material through the polarizing plate to form the aerial image. [Effects of the Invention]

[0011] According to the present invention, by arranging a light-reducing filter on the surface of the λ / 4 plate, light that does not contribute to the formation of an aerial image from the light source is reduced, thereby suppressing the appearance of brightness in the internal structure and improving the contrast between the aerial image and the background. Furthermore, according to the present invention, by arranging a polarizing plate on the surface of the retroreflective material, light that does not contribute to the formation of an aerial image from the light source is reduced, thereby suppressing the appearance of brightness in the internal structure and improving the contrast between the aerial image and the background. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1(A) shows a schematic configuration of a conventional display device for showing aerial images, and Figure 1(B) illustrates scattered light generated by a retroreflective material. [Figure 2] This figure shows a schematic configuration of a display device for displaying an aerial image according to the first embodiment of the present invention. [Figure 3] Figure 3(A) illustrates the reduction of unwanted light when an ND filter is placed on a conventional polarizing beam splitter, while Figure 3(B) illustrates the reduction of unwanted light according to this embodiment. [Figure 4] This figure shows a schematic configuration of a display device for displaying an aerial image according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0013] Next, embodiments of the present invention will be described. The display device according to this embodiment displays an aerial image using retroreflection, while preventing the inside of the housing from being brightly visible, thereby improving the appearance design of the display device and improving the visibility and brightness of the aerial image. It should be noted that the drawings referenced in the following description of the embodiments include exaggerated representations to facilitate understanding of the invention and do not represent the shape or scale of the actual product. [Examples]

[0014] Next, embodiments of the present invention will be described in detail with reference to the drawings. Figure 2 is a schematic diagram of a display device according to the first embodiment of the present invention. The display device 100 of this embodiment comprises a housing 110, a display 120 as a light source disposed within the housing 110, a polarizing beam splitter 130, an ND filter 140, a λ / 4 plate 150, and a retroreflective material 160, and displays an aerial image P floating in the air from the housing 110.

[0015] The housing 110 is not particularly limited in shape or material, but for example, it is a rectangular enclosure that houses optical elements such as a display 120, a polarizing beam splitter 130, and a retroreflective material 160 in its internal space. An opening or window 112 is formed on the upper surface of the housing 110 at a position opposite the polarizing beam splitter 130, allowing light from the polarizing beam splitter 130 to pass through. The opening 112 is appropriately selected according to the size of the aerial image P or the display 120. The opening 112 may be a cavity, or it may be covered by a cover or sheet made of a light-transmitting material.

[0016] The display 120 is a light source for generating the original image of the aerial image P. The display 120 is not particularly limited, but examples include LED or organic EL displays, projectors, and LED units in which multiple LEDs are arranged in two dimensions. In the first embodiment, the display 120 outputs light that is generally linearly polarized toward the polarization beam splitter 130. The angle between the normal (optical axis) of the display surface of the display 120 and the main surface of the polarization beam splitter 130 is, for example, 45 degrees.

[0017] The polarizing beam splitter 130 selectively reflects linearly polarized light that vibrates in a certain direction and transmits the component perpendicular to that linearly polarized light component. The polarizing beam splitter 130 is configured such that it reflects light received from the display 120 and transmits light received from the retroreflective material 160.

[0018] The retroreflective material 160 is an optical element that reflects light in the same direction as the incident light, and its configuration is not particularly limited, but for example, it can be composed of a triangular pyramidal retroreflective element, a full cube corner retroreflective element, etc. The retroreflective material 160 is, for example, a rectangular sheet-like or film-like member and is placed on the bottom surface of the housing 110.

[0019] The λ / 4 plate 150 is a sheet-shaped or film-shaped optical element that generates a λ / 4 phase difference between incident light and outgoing light. The λ / 4 plate 150 is, for example, attached to the retroreflective surface of the retroreflector 160, or disposed close to the surface of the retroreflector 160. For example, when linearly polarized light vibrating in a certain direction is incident on the λ / 4 plate 150, it emits light converted into circularly polarized light, or when circularly polarized light is incident thereon, it emits light converted into linearly polarized light.

[0020] The ND (Neutral Density) filter 140 is a dimming filter that uniformly reduces light of all incident wavelengths. The ND filter 140 has substantially the same planar shape as the λ / 4 plate 150, and for example, is attached to the surface of the λ / 4 plate 150 or disposed close to the surface thereof.

[0021] Next, the operation of the display device 100 of this embodiment will be described. The display 120 outputs an original image of the aerial image P, and the polarization beam splitter 130 reflects the light of the original image incident from the display 120 toward the retroreflector 160. The light intensity of the light reflected by the polarization beam splitter 130 is reduced by passing through the ND filter 140, then passes through the λ / 4 plate 150 and is incident on the retroreflector 160. The light incident on the retroreflector 160 is retroreflected in the same direction as the incident light, and after passing through the λ / 4 plate 150 again, the retroreflected light passes through the ND filter 140 again, whereby the light intensity is further reduced. The retroreflected light that has passed through the ND filter 140 transmits through the polarization beam splitter 130 and forms the aerial image P.

[0022] Here, of the light output from the display 120, the light La incident on the polarizing beam splitter 130 is retroreflected by the retroreflective material 160 and is the desirable light La' that forms the aerial image P. On the other hand, the light Lb output from the display 120 in an oblique direction and incident on the λ / 4 plate 150 without incident on the polarizing beam splitter 130 is unwanted light that does not contribute to the formation of the aerial image P. Such light Lb becomes light Lb', which has its light intensity reduced by passing through the ND filter 140 twice. Because the light intensity of light Lb' is reduced, when observer U observes the aerial image P, even if light Lb' reaches observer U's eyes, the internal structure of the housing 110 does not appear bright, and the contrast between the aerial image P and its background can be improved. Also, although not shown here, scattered light generated by the retroreflective material 160 as shown in Figure 1(B) is similarly attenuated by the ND filter 140, so the internal structure of the housing 110 does not appear bright.

[0023] In the above embodiment, the ND filter 140 is placed on the upper surface of the λ / 4 plate 150, but the configuration is not limited to this, and the ND filter 140 may be placed on the lower surface (or back surface) of the λ / 4 plate 150. In other words, the ND filter 140 is placed between the λ / 4 plate 150 and the retroreflective material 160. Even if the ND filter 140 is placed on the lower surface of the λ / 4 plate 150, the same effect as in the above embodiment can be obtained, and unwanted light Lb that does not form an image in the aerial image P is attenuated by the ND filter 140, the internal structure of the housing 110 does not appear bright, and the contrast between the aerial image P and its background is improved. The method of attaching the ND filter 140 is arbitrary, but for example, the ND filter 140 may be attached to the surface of the retroreflective material 160, and the λ / 4 plate 150 may be attached to the surface of the ND filter 140.

[0024] Figure 3(A) shows the attenuation of unwanted light when an ND filter is attached to a conventional polarizing beam splitter, while Figure 3(B) shows the attenuation of unwanted light when an ND filter is attached to the surface of a λ / 4 plate, as in this embodiment.

[0025] In a conventional structure, a λ / 4 plate 210 is placed on the surface of a retroreflective material 200, a polarizing beam splitter 220 is placed parallel to it oppositely, and an ND filter 230 is placed on the upper surface of the polarizing beam splitter 220. The polarizing beam splitter 220 reflects light La incident from a light source (not shown) toward the retroreflective material 200, and the light La' retroreflected by the retroreflective material 200 passes through the polarizing beam splitter 220 and the ND filter 230 to form an aerial image. On the other hand, unwanted light Ld that does not contribute to the formation of the aerial image (including light scattered by the retroreflective material 200 and light reflected from the surface of the λ / 4 plate 210) passes through the polarizing beam splitter 220 and the ND filter 230 and is emitted to the outside. However, since the unwanted light Ld only passes through the ND filter 230 once, the amount of light reduced is relatively small.

[0026] In contrast, in this embodiment, by attaching an ND filter 230 to the surface of the λ / 4 plate 210, unwanted light Le that does not contribute to the formation of the aerial image from the light source passes through the ND filter 230 twice, resulting in a greater reduction in the amount of light. Therefore, the internal structure of the housing 110 does not appear brighter, and the contrast of the aerial image is improved. Thus, by attaching the ND filter 230 to the surface side of the retroreflective material 200, unwanted light passes through the ND filter 230 twice, which reduces unwanted light more effectively compared to the conventional structure and leads to an improvement in the contrast of the aerial image.

[0027] Next, a second embodiment of the present invention will be described. Figure 4 is a schematic diagram showing the configuration of a display device according to the second embodiment, and the same reference numerals are used for the same components as in the first embodiment. The display device 100A of the second embodiment has a light source 120A which outputs unpolarized light as the original image of the aerial image P, a half mirror 300 used in place of the polarizing beam splitter 130 of the first embodiment, and an ND filter 310 attached to the surface of the retroreflective material 160 after removing the λ / 4 plate, and relates to an unpolarized optical system.

[0028] The half-mirror 300 is an optical element that separates incident light into reflected light and transmitted light. The polarizing plate 310 is an optical element that transmits light polarized in a specific direction. The half-mirror 300 receives random light from the light source 120A and reflects a portion of the incident light toward the retroreflective material 160. A portion of the light reflected by the half-mirror 300 is incident on the retroreflective material 160 via the polarizing plate 310, and the light retroreflected there is incident on the half-mirror 300 again via the polarizing plate 310, and the light La' that has passed through the half-mirror 300 forms an aerial image P.

[0029] On the other hand, light Lb that does not contribute to the imaging of the aerial image P output from the light source 120A is incident on the retroreflective material 160 via the polarizing plate 310, for example, without directly entering the half mirror 300, where scattered light is generated. As the amount of light Lb is reduced when it passes through the polarizing plate 310, the scattered light Lb' becomes weak light, which suppresses the appearance of the internal structure of the optical system in the housing as bright to the observer U, and can improve the contrast of the aerial image P.

[0030] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims. [Explanation of Symbols]

[0031] 100, 100A: Display device; 110: Housing 120: Display 130: Polarizing beam splitter 140: ND filter 150: λ / 4 plate 160: Retroreflective material 300: Half mirror 310: Polarizing plate

Claims

1. A display device capable of displaying an aerial image using retroreflection, Light source and A polarizing beam splitter is positioned at the location into which light from the aforementioned light source is incident, Retroreflective material, A λ / 4 plate is placed on the surface of the retroreflective material, The plate has a light-reducing filter arranged on the surface of the λ / 4 plate, The retroreflective material receives light reflected by the polarizing beam splitter through the attenuation filter and the λ / 4 plate, The polarizing beam splitter is a display device that transmits light retroreflective by the retroreflective material through the λ / 4 plate and the attenuation filter to form the aerial image.

2. The display device according to claim 1, wherein the light-reducing filter is an ND filter.

3. The display device according to claim 1, wherein the λ / 4 plate and the light-reducing filter are laminated on the surface of the retroreflective material.

4. The light-reducing filter is attached to the upper or lower surface of the λ / 4 plate, as described in claim 1 or 3.

5. A display device capable of displaying an aerial image using retroreflection, Light source and A half-mirror is positioned at the location into which light from the aforementioned light source is incident, Retroreflective material, The retroreflective material has a polarizing plate placed on its surface, The retroreflective material receives light reflected by the half-mirror through the polarizing plate, The half-mirror is a display device that transmits light retroreflective by the retroreflective material through the polarizing plate to form the aerial image.

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