Optical elements and display devices

Abstract

To provide a display device that suppresses light loss due to the decorative layer. [Solution] The display device 100 of the present invention includes a display 110, a retroreflective material 130, and a slit mirror 120 positioned to receive light from the display 110. The slit mirror 120 includes a plurality of mirrors 122 formed through a plurality of slits 126, and a decorative layer 124 disposed on the other reflective surface side facing one of the reflective surfaces of the mirrors 122. One reflective surface of the plurality of mirrors 122 reflects light from the display 110 toward the retroreflective material 130, the other reflective surface reflects ambient light incident through the decorative layer 124, and the plurality of slits 124 transmit the light retroreflective by the retroreflective material 130 to form an aerial image P.

Description

[Technical Field]

[0001] The present invention relates to a display device that displays an aerial image by retroreflection, and particularly relates to an optical element for forming an aerial image. [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 as follows: light emitted from a light source is reflected by a mirror toward a retroreflective material, and part of the light that returns to the mirror again is transmitted to re-form an image. For this reason, this mirror uses a half mirror with reduced reflectance, a polarizing beam splitter, or the like (for example, Patent Document 1). Further, a decorative sheet is arranged between the imaging element for the aerial image and the imaging position, so that the interior cannot be observed from the outside (for example, Patent Document 2). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent No. 7604079 [Patent Document 2] Japanese Unexamined Patent Publication No. 2020-76811. [Summary of the Invention] [Problem 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 includes, for example, a display 20, a half mirror 30, a retroreflective material 40, and a decorative layer 50 provided on the upper surface side of the half mirror 30 in a housing such as a casing.

[0005] The display 20 outputs the original image of the aerial image P, and the half mirror 30 reflects a portion of the incident light from the original image toward the retroreflective material 40. The retroreflective material 40 reflects light in the same direction as the incident light, and the reflected light passes through the half mirror 30 and the decorative layer 50, forming an image of the aerial image P. The decorative layer 50 is a decorative film or decorative sheet with a printed design, and is a transparent medium with a certain transmittance. By providing the decorative layer 50 on the upper side of the half mirror 30, the inside of the housing is not visible from the outside, improving the appearance design.

[0006] When using a half-mirror 30, for example, if the half-mirror is a mirror that reflects 50% of the light, light is lost by passing through the half-mirror 30 twice for reflection and transmission, resulting in low utilization efficiency of light that contributes to the formation of the aerial image P. To improve the utilization efficiency of light, the display device 10A shown in Figure 1(B) has a λ / 4 plate 60 that creates a λ / 4 phase difference on the upper surface of the retroreflective material 40, and a polarizing beam splitter 70 is used instead of a half-mirror 30. In this case, the polarizing beam splitter 70 reflects the light of the original image incident from the display 20 toward the λ / 4 plate 60 and the retroreflective material 40, and aligns the polarization direction of the light emitted from the λ / 4 plate 60 with the transmission axis of the polarizing beam splitter 70, thereby forming an aerial image P on the light that has passed through the polarizing beam splitter 70 and the decorative layer 50.

[0007] However, in the conventional display devices 10 and 10A shown in Figures 1(A) and (B), the light retroreflective by the retroreflective material 40 passes through the half mirror 30 and the polarizing beam splitter 70 before passing through the decorative layer 50. As a result, light loss due to the decorative layer 50 inevitably occurs, leading to a problem of reduced brightness of the aerial image.

[0008] The present invention aims to solve these conventional problems and provide an optical element and a display device that suppress light loss due to the decorative layer. [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 retroreflective material, and an optical element positioned at a location into which light from the light source is incident. The optical element includes a plurality of reflective regions formed through a plurality of slits, and a decorative layer disposed on the side of the other reflective surface facing one of the reflective surfaces of the plurality of reflective regions. One reflective surface of the plurality of reflective regions reflects light from the light source toward the retroreflective material, and the other reflective surface reflects ambient light incident through the decorative layer. The plurality of slits transmit the light retroreflected by the retroreflective material to form the aerial image.

[0010] The optical element according to the present invention forms an aerial image using retroreflection, and the optical element includes a transparent substrate, a plurality of reflective regions formed on the surface of the transparent substrate via a plurality of slits, and a decorative layer formed between the surface of the transparent substrate and the reflective regions. [Effects of the Invention]

[0011] According to the present invention, by arranging a decorative layer on the side of the reflective surface opposite to one reflective surface in the reflective region, the light retroreflected by the retroreflective material is prevented from passing through the decorative layer, thereby suppressing the loss of light that contributes to the formation of an aerial image, allowing for the display of a high-brightness aerial image, while simultaneously maintaining aesthetic appeal by reflecting ambient light onto the decorative layer. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a schematic configuration of a conventional display device for showing aerial images. [Figure 2] Figure 2(A) shows a schematic configuration of a display device according to an embodiment of the present invention, Figure 2(B) is a bottom view of the slit mirror shown in Figure 2(A), and Figure 2(C) is a cross-sectional view of the slit mirror shown in Figure 2(B) along line AA. [Figure 3] Figure 3(A) is a diagram illustrating the principle of the display device according to this embodiment, and Figure 3(B) is a diagram illustrating the reflection and transmission by a slit mirror. [Figure 4]Figure 4(A) illustrates an example of the light utilization efficiency in a conventional display device, and Figure 4(B) illustrates an example of the light utilization efficiency in the display device according to this embodiment. [Figure 5] Figure 5(A) illustrates further improvements to the display device shown in Figure 2(A), and Figure 5(B) shows a schematic configuration of a display device according to another embodiment. [Modes for carrying out the invention]

[0013] Next, embodiments of the present invention will be described. In this embodiment, the display device uses a slit mirror structure in which multiple reflective regions are formed in a striped pattern through multiple slits as an optical element for forming an aerial image. By using a slit mirror structure, the light utilization efficiency can be improved compared to conventional half mirrors, and color dispersion can be suppressed compared to polarized beam splitters. It should be noted that the drawings referenced in the following description of embodiments include exaggerations 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. Figure 2(A) 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 display 110, a slit mirror 120 in which a plurality of mirrors are formed in a striped pattern via slits, and a retroreflective material 130. These components are arranged, for example, inside a housing or enclosure, and an aerial image P floating in the air from the housing is displayed.

[0015] The display 110 is a light source for generating an original image of the aerial image P. The display 110 is not particularly limited, and may be, for example, an LED or organic EL display, a projector, or an LED unit in which a plurality of LEDs are two-dimensionally arranged. The light of the original image of the aerial image P generated by the display 110 is output toward the slit mirror 120. For example, the angle formed by the normal line (optical axis) of the display surface of the display 110 and the main surface of the slit mirror 120 is 45 degrees.

[0016] The slit mirror 120 is an optical element in which each of a plurality of slits and each of a plurality of mirrors are alternately arranged. The slit mirror 120 is disposed at a position where light from the display 110 is incident, reflects the light from the display 110 toward the retroreflective material 130 via the plurality of mirrors, and transmits the light reflected by the retroreflective material 130 via the plurality of slits to form the aerial image P.

[0017] Fig. 2(B) is a bottom view of the slit mirror, and Fig. 2(C) is a cross-sectional view taken along line A-A of Fig. 2(B). As shown in the figure, the slit mirror 120 has a substantially rectangular flat surface, on which a plurality of elongated rectangular mirrors 122 extending in the column direction, a plurality of decorative layers 124 disposed on the back side of the plurality of mirrors 122, and a plurality of slits 126 formed between each of the plurality of mirrors 122 and the plurality of decorative layers 124 are formed. The planar shape of the decorative layer 124 is the same as that of the mirror 122. The surface of the mirror 122 provides a reflective surface that reflects light incident from the display 110, and the back surface of the mirror 122 provides a reflective surface that reflects light incident from the outside via the decorative layer 124. The decorative layer 124 provides a design, and the slits 126 provide a transmission region for retroreflected light.

[0018] In one aspect, as shown in Fig. 2(C), the slit mirror 120 has a transparent film-shaped or plate-shaped transparent base material 128 capable of transmitting light, and the laminated decorative layer 124 and mirror 122 are formed on the bottom surface of the transparent base material 128. The material of the transparent base material 128 is not particularly limited, and is, for example, plastic, glass, acrylic, or the like.

[0019] The mirror 122 is, for example, a metal layer. The decorative layer 124 is a transparent layer provided with a design and having a certain transmittance. The design provided on the decorative layer 124 improves the appearance design of the display device 100, and the colors, patterns, and the like constituting the design are arbitrary.

[0020] The method for manufacturing the mirror 122 and the decorative layer 124 is not particularly limited. For example, a product obtained by printing the decorative layer 124 on the surface of a metal layer serving as the mirror 122 may be adhered to a transparent substrate 128. Alternatively, after forming a decorative layer on the entire surface of the transparent substrate 128, a metal material may be deposited to cover the entire surface of the decorative layer, and then these materials are patterned by etching to form the striped mirror 122 and the striped decorative layer 124. The region of the transparent substrate 128 not covered by the metal layer provides the slits 126, that is, the transmission region. The above manufacturing method for the mirror is an example, and the slit mirror 120 may be configured by other methods.

[0021] In addition, as another aspect, the slits 124 may be voids or spaces formed in the transparent substrate 128. As still another aspect, the decorative layer 124 may be formed on the surface side of the transparent substrate 128 so as to align with the position of the mirror 122. That is, the mirror 122 is directly formed on the bottom surface side of the transparent substrate 128, and the decorative layer 124 is formed on the surface side so as to accurately overlap the position of the mirror 122. In this case, the decorative layer 124 is printed on the surface of the transparent substrate 128, and the mirror 122 is printed on the bottom surface thereof.

[0022] The retroreflective material 130 is an optical element that reflects light in the same direction as the incident light. 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 130 receives light reflected by the mirror 122 of the slit mirror 120 and reflects this light in the same direction as the incident light. The light retroreflected by the retroreflective material 130 is parallel to the incident light, and a certain offset occurs between the retroreflected light and the incident light, as will be described later. The retroreflective material 130 is positioned relative to the slit mirror 120 so that the retroreflected light passes through the slit 126 of the slit mirror 120. In this way, an aerial image P is formed by the retroreflected light that has passed through the slit 126 of the slit mirror 120.

[0023] Next, the operating principle of the display device 100 of this embodiment will be described. Figure 3(A) is a projection view when the retroreflective material is projected onto a slit mirror and the two are superimposed. The retroreflective material 130 includes a plurality of retroreflective units arranged in the matrix direction, and one retroreflective unit is composed of, for example, a retroreflective prism. The retroreflective prism has three reflective surfaces, and the incident light is internally reflected three times by the three reflective surfaces and emitted in the same direction as the incident light. At this time, a certain amount of offset always occurs between the incident light and the emitted light (retroreflective light). The retroreflective material 130 has three axes (hereinafter referred to as inversion axes) that produce emitted light at a position symmetric to the incident light.

[0024] For example, in the example shown in Figure 3(A), when a single retroreflective unit is viewed from above, it is represented as an equilateral triangle. Multiple retroreflective units are arranged in a matrix such that the equilateral triangles are alternately inverted. Furthermore, the three bisectors extending from the vertices of the equilateral triangles to the midpoint of the base are the inversion axes S1, S2, and S3.

[0025] As shown in FIG. 3(A), light incident on position a of the retroreflection unit exits from position a' which is symmetric with respect to the inversion axis S2, light incident on position b exits from position b' which is symmetric with respect to the inversion axis S1, and light incident on position c exits from position c' which is symmetric with respect to the inversion axis S3. The same applies in the reverse case (light incident on a' exits from a, light incident on b' exits from b, and light incident on c' exits from c). In this way, light incident on the retroreflection unit exits from positions that are symmetric with respect to the inversion axes S1, S2, and S3.

[0026] The retroreflective member 130 is positioned relative to the slit mirror 120 such that any one of the inversion axes S1, S2, and S3 is parallel to the column direction (slit direction) of the mirrors 122. In the example of FIG. 3(A), the retroreflective member 130 is arranged such that the inversion axis S1 is parallel to the slit direction of the slit mirror 120.

[0027] In a preferred embodiment, the pitch in the row direction between the mirrors 122 and the slits 126 of the slit mirror 120 is set to be equal to the pitch in the row direction of the retroreflection units. In this case, the width W1 of the mirror 122 in the row direction is equal to the width W2 of the slit 126 in the row direction (W1=W2), and the length Ws of one side of the equilateral triangle of the retroreflection unit satisfies Ws=W1+W2. Further, the width of the decorative layer 124 in the row direction is equal to the width W1 of the mirror 122.

[0028] In another embodiment, when the pitch in the row direction between the mirrors 122 and the slits 126 is equal to the pitch in the row direction of the retroreflection units, the width W1 of the mirror does not need to be equal to the width W2 of the slit (W1≠W2). For example, W1>W2 may be set to relatively increase the amount of reflected light, and conversely, W1<W2 may be set to relatively increase the amount of transmitted light. W1 and W2 may be set according to the optical characteristics of the display device. Further, the width of the decorative layer 124 in the row direction may be equal to or slightly smaller than the width W1 of the mirror 122.

[0029] Figure 3(B) schematically shows the reflection and transmission by the slit mirror 120. As shown in the figure, light L1 from the display 110 is incident on the slit mirror 120, where the incident light L1 is separated into reflected and transmitted light. The incident light L1 is reflected by the mirror 122 toward the retroreflective material 130 to become light L2, and light L2 is reflected by the retroreflective material 130 in the same direction as the incident light. The retroreflective light L3 is reflected in the same direction as the incident light L2, but an offset T occurs between the incident light L2 and the reflected light L3, and as a result the retroreflective light L3 passes through the slit 126 of the slit mirror 120 and forms an aerial image P.

[0030] On the other hand, since the decorative layer 124 is formed on the back side of the mirror 122, external light L4 is reflected to the outside by the reflective surface on the back side of the mirror 122 via the transparent substrate 128 and the decorative layer 124. In this way, the brightness of the design of the decorative layer 124 can be increased by the external light L4. On the other hand, the light L3 retroreflective by the retroreflective material 130 does not pass through the decorative layer 124, and is therefore used for forming the aerial image P without being lost in the decorative layer 124.

[0031] Thus, according to this embodiment, by arranging a decorative layer on the back surface of the mirror in the slit mirror structure, a mirror is provided inside the slit mirror structure and a design is provided on the outside, enabling a stealthy aerial interface with virtually no light loss.

[0032] The display device of this embodiment has the following effects. In conventional structures, approximately 50-80% of the light was lost because the retroreflected light passed through the decorative layer. However, in this embodiment, a decorative layer is added to the back side of the mirror, preventing the retroreflected light from passing through the decorative layer. As a result, there is no light loss due to the decorative layer, and consequently, the aerial image does not become dark. • By applying decoration to the upper (back) side of the mirror, which is composed of a metal layer, it is possible to achieve a high-brightness aerial image decoration using ambient light. This technology eliminates color dispersion (color variation depending on the viewing angle) when using a display, enabling the creation of decorative mirrors for aerial projection that offer high aesthetic appeal for both the image and the background.

[0033] Figure 4(A) illustrates the light utilization efficiency when using a conventional decorative layer, and Figure 4(B) illustrates the light utilization efficiency when using a slit mirror 120 including the decorative layer of this embodiment. In the conventional structure shown in Figure 4(A), assuming that the transmittance of the half mirror 30 is 50% and the reflectance is 50%, the light emitted from the display 20 is separated into 50% reflected light and 50% transmitted light by the half mirror 30, 50% of the reflected light is retroreflective by the retroreflective material 40, the retroreflective light passes through the half mirror 30, and half of the light, 25%, contributes to the formation of the aerial image P.

[0034] On the other hand, in the display device 100 of this embodiment shown in Figure 4(B), the light emitted from the display 110 is separated into reflected light and transmitted light by the slit mirror 120, 50% of the reflected light is retroreflective by the retroreflective material 130, and the retroreflective light passes through the slit 126 of the slit mirror 120 and the transparent substrate 128. At this time, no light loss occurs as with a half mirror, so 50% of the light contributes to the imaging of the aerial image P. In this way, by using the slit mirror 120, the light utilization efficiency can be greatly improved compared to conventional methods, and as a result, the aerial image P can be displayed with high brightness.

[0035] Next, another embodiment of the present invention will be described. Figure 5(B) is a schematic diagram showing the configuration of a display device according to another embodiment, and components identical to those shown in Figure 2(A) are given the same reference numerals.

[0036] As shown in Figure 5(A), when the slit mirror 120 is used, a portion of the light emitted from the display 110 is light Lx that passes through the slit 126 of the slit mirror 120. This light Lx does not contribute to the formation of an aerial image, and if it becomes noticeable as internal stray light, there is a concern that the problem of internal stray light, which had been suppressed by using a polarizing beam splitter, will resurface.

[0037] Therefore, in this embodiment, by installing an absorbing polarizing plate 210 on the upper surface of the slit mirror 120 to absorb the light emitted from the display 110, which is the light source (in the case of a typical LCD, the light is polarized), the display 110 and internal scattered light are blocked, making it difficult to see from the outside. At the same time, since it is necessary to transmit the light that forms the aerial image P, a λ / 4 plate 200 is installed on the surface of the retroreflective material 130, and by changing the polarization direction of the light of the aerial image P, it becomes possible to form the aerial image without loss. By combining the slit mirror 120 and the polarizing absorbing plate 210, a function equivalent to that of a polarizing reflector in an aerial image display device is realized.

[0038] The λ / 4 plate 200 is, for example, a phase difference film that is attached to the surface of the retroreflective material 130. The λ / 4 plate 200 emits light converted to circular polarization when linearly polarized light vibrating in a certain direction is incident on it, or emits light converted to linear polarization when circularly polarized light is incident on it.

[0039] The polarizing plate 210 is an absorptive polarizing plate that selectively transmits linearly polarized light components vibrating in a certain direction and absorbs linearly polarized light components perpendicular to those components. Therefore, the light output from the polarizing plate 310 consists only of the polarized light components that are transmitted through it without being absorbed. An absorptive polarizing plate is, for example, a polarizing film attached to the top surface of the slit mirror 120. Furthermore, the direction of linearly polarized light absorbed by the polarizing plate 210 generally coincides with the direction of linearly polarized light emitted from the display 110.

[0040] Figure 5(B) is a diagram illustrating the operation of the display device 100A. Light emitted from the display 110 is separated into reflected light and transmitted light by the slit mirror 120. The light that passes through the slit mirror 120 is largely absorbed by the absorbing polarizer 210. On the other hand, the light reflected by the slit mirror 120 goes towards the retroreflective material 130, where it passes through the λ / 4 plate 200 twice and returns to the slit mirror 120 again. The retroreflective light is given a phase difference of λ / 2 by the λ / 4 plate 200, that is, its polarization direction is rotated by 90 degrees, and as a result the retroreflective light passes through the slit 126 of the slit mirror 120 to the absorbing polarizer 210 and forms an aerial image P.

[0041] As described above, this embodiment makes it possible to make the original image and internal scattering of the display 110 difficult to see by using an absorbing polarizer and a λ / 4 plate, thereby improving the visibility of the aerial image P. Furthermore, by combining the λ / 4 plate, a slit mirror, and an absorbing polarizer, the same function as a polarizing beam splitter (reflective polarizer) can be added. Moreover, since reflective polarizers are expensive, the cost of the display device in this embodiment can be reduced. Furthermore, since reflective polarizers have low durability against high temperature and humidity, it becomes easier to mount the display device in this embodiment on vehicles exposed to high-temperature environments.

[0042] 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]

[0043] 100: Display device 110: Display 120: Slit mirror 122: Mirror 124: Decorative layer 126: Slit 128: Transparent substrate 130: Retroreflective material 300:λ / 4 plate 310:Polarizing plate

Claims

1. A display device capable of displaying an aerial image using retroreflection, Light source and Retroreflective material, It has an optical element positioned at a location into which light from the light source is incident, The optical element includes a plurality of reflective regions formed through a plurality of slits, and a decorative layer disposed on the side of the other reflective surface facing one of the reflective surfaces of the reflective regions. A display device wherein one reflective surface of the plurality of reflective regions reflects light from the light source toward the retroreflective material, the other reflective surface reflects ambient light incident through the decorative layer, and the plurality of slits transmit the light retroreflectiveed by the retroreflective material to form the aerial image.

2. The display device according to claim 1, wherein the optical element further includes a transparent substrate, and the reflective region is formed on the surface of the transparent substrate via the decorative layer.

3. The display device according to claim 1, wherein the reflective region and the decorative layer are elongated regions extending in the column direction, and each of the slits is formed between each of the plurality of reflective regions.

4. The display device according to claim 1, wherein the retroreflective material includes a plurality of reversal axes that reverse incident light into reflected light, and the retroreflective material is arranged such that any of the reversal axes are parallel to the slit direction of the optical element.

5. The display device according to claim 1, wherein when the retroreflective material is projected onto the optical element, the row-direction pitch of the retroreflective units arranged in the matrix direction of the retroreflective material matches the row-direction pitch of the reflective region and slit of the optical element.

6. The display device further includes a λ / 4 plate disposed on the upper side of the retroreflective material and a polarizing plate disposed on the upper side of the optical element. The display device according to claim 1, wherein the polarizing plate is an absorbing polarizing plate capable of absorbing the polarization component of light emitted from the light source, and the absorbing polarizing plate transmits the polarization component of light retroreflected from the λ / 4 plate.

7. An optical element that uses retroreflection to form an image of the air, The optical element comprises a transparent substrate, a plurality of reflective regions formed on the surface of the transparent substrate via a plurality of slits, and a decorative layer formed between the surface of the transparent substrate and the reflective regions.

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