Optical element and display device

Abstract

To provide a display device in which light loss caused by a decorative layer is suppressed. Solution: The display device (100) of the present invention includes a display (110), a retro-reflective member (130), and a slit mirror (120) disposed at a position at which light from the display (110) is incident. The slit mirror (120) includes a plurality of mirrors (122) formed with a plurality of slits (126) and a decorative layer (124) disposed on the side of the reflecting surface of the mirrors (122) opposite the reflecting surface on one side. The reflecting surface on one side of the plurality of mirrors (122) reflects light from the display (110) toward the retro-reflective member (130), the reflecting surface on the other side reflects external light incident via the decorative layer (124), and the plurality of slits (126) transmit light retro-reflected by the retro-reflective member (130) to form an aerial image (P).

Description

Technical Field

[0001] The present invention relates to a display device for displaying aerial images by retroreflection, and particularly to an optical element for imaging aerial images. Background Technology

[0002] Aerial Imaging by Retro-Reflection (AIRR) is known. The principle behind this display is that a mirror reflects light generated from a light source towards a retroreflector, causing a portion of the light returning to the mirror to be transmitted, thus re-imaged. Therefore, this mirror uses a semi-reflective mirror with reduced reflectivity, a polarizing beam splitter, etc. (e.g., Patent Document 1). Furthermore, a decorative piece is placed between the imaging element of the aerial image and the imaging position, making the interior invisible from the outside (e.g., Patent Document 2).

[0003] Existing technical documents: Patent documents: Patent Document 1: Japanese Patent No. 7604079 Patent Document 2: Japanese Patent Application Publication No. 2020-76811. Summary of the Invention

[0004] The problem that the invention aims to solve: Figure 1 (A) is a schematic diagram showing the configuration of a conventional display device for displaying aerial images. The display device 10 is configured, for example, to include a display 20, a semi-reflective mirror 30, a retroreflective element 40, and a decorative layer 50 disposed on the upper surface side of the semi-reflective mirror 30 within a housing such as a frame.

[0005] The display 20 outputs the original image of the aerial image P. The semi-reflective mirror 30 reflects a portion of the incident light towards the retroreflector 40. The retroreflector 40 reflects the light in the same direction as the incident light. This reflected light passes through the semi-reflective mirror 30 and the decorative layer 50, forming the aerial image P. The decorative layer 50 is a decorative film or sheet printed with an appearance design and is a transparent medium with a certain transmittance. By providing the decorative layer 50 on the upper surface of the semi-reflective mirror 30, the interior of the housing is not visible from the outside, thus improving the aesthetic design.

[0006] When using a semi-reflective mirror 30, for example, if the semi-reflective mirror is one that reflects 50% of the light, the light is lost due to two passes through the semi-reflective mirror 30, one for reflection and one for transmission, which reduces the light utilization efficiency that contributes to imaging the aerial image P. To improve light utilization efficiency, in Figure 1In the display device 10A shown in (B), a λ / 4 waveplate 60 that generates a phase difference of λ / 4 is disposed on the upper surface of the retroreflector 40, and a polarizing beam splitter 70 is used instead of the semi-reflector 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 waveplate 60 and the retroreflector 40, so that the polarization direction of the light emitted from the λ / 4 waveplate 60 is aligned with the transmission axis of the polarizing beam splitter 70, thereby enabling the light transmitted through the polarizing beam splitter 70 and the decorative layer 50 to form an aerial image P.

[0007] However, in Figure 1 In the conventional display devices 10 and 10A shown in (A) and (B), the light reflected by the retroreflector 40 is transmitted through the decorative layer 50 after the transmissive semi-reflector 30 and the polarizing beam splitter 70. Therefore, there is a problem that the light loss caused by the decorative layer 50 will occur regardless, resulting in a decrease in the brightness of the aerial image.

[0008] The purpose of this invention is to solve such conventional problems and to provide an optical element and a display device that suppresses light loss caused by the decorative layer.

[0009] Methods used to solve problems: The display device of the present invention is capable of displaying an aerial image using retroreflection. The display device includes: a light source; a retroreflector; and an optical element disposed at a position where light from the light source is incident. The optical element includes: a plurality of reflective regions formed by a plurality of slits; and a decorative layer disposed on the reflective surface side of one of the reflective regions, opposite to the reflective surface of one of the reflective regions. The reflective surface of one of the plurality of reflective regions reflects light from the light source toward the retroreflector, and the reflective surface of the other reflects external light incident through the decorative layer. The plurality of slits transmit light retroreflected by the retroreflector to image the aerial image.

[0010] The optical element of the present invention uses retroreflection to image an aerial image, the optical element comprising: a transparent substrate; a plurality of reflective regions formed on the surface of the transparent substrate through a plurality of slits; and a decorative layer formed between the surface of the transparent substrate and the reflective regions.

[0011] Invention effects: According to the present invention, by distributing a decorative layer on the reflective surface side of the reflective region opposite to the reflective surface of one side, light reflected by the retroreflector does not pass through the decorative layer, thereby suppressing the loss of light that contributes to the imaging of the aerial image and displaying a high-brightness aerial image, while the decorative layer reflects external light, thus maintaining the aesthetic design. Attached Figure Description

[0012] Figure 1This is a schematic diagram illustrating the configuration of an existing display device for displaying aerial images.

[0013] Figure 2 (A) is a schematic diagram illustrating the configuration of a display device according to an embodiment of the present invention. Figure 2 (B) is Figure 2 The bottom view of the slit mirror shown in (A) Figure 2 (C) is Figure 2 (B) is a sectional view of the slit mirror along line AA.

[0014] Figure 3 (A) is a diagram illustrating the principle of the display device of this embodiment. Figure 3 (B) is a diagram illustrating the reflection and transmission based on a slit mirror.

[0015] Figure 4 Figure (A) is an example illustrating the light utilization efficiency in a conventional display device. Figure 4 (B) is a diagram illustrating an example of light utilization efficiency in the display device of this embodiment.

[0016] Figure 5 (A) is an explanation Figure 2 (A) shows a diagram of further improvements to the display device. Figure 5 (B) is a diagram illustrating a schematic configuration of a display device according to another embodiment.

[0017] Explanation of reference numerals in the attached figures: 100: Display device; 110: Display screen 120: Slit mirror; 122: Mirror 124: Decorative layer; 126: Slit 128: Transparent substrate; 130: Retroreflective element 200: λ / 4 waveplate; 210: Absorbing polarizer Detailed Implementation

[0018] Next, embodiments of the present invention will be described. In this embodiment, the display device uses a slit mirror structure with multiple reflective areas formed in a stripe pattern via multiple slits as an optical element for imaging an aerial image. By using the slit mirror structure, light utilization efficiency can be improved compared to conventional half-reflective mirrors, and dispersion can be suppressed compared to polarizing beam splitters. It should be noted that the accompanying drawings referred to in the following description of the embodiments contain exaggerated displays for ease of understanding of the invention and do not represent the shape or proportions of actual products.

[0019] [Example] Next, embodiments of the present invention will be described in detail. Figure 2 (A) is a schematic diagram showing the configuration of a display device according to a first embodiment of the present invention. The display device 100 of this embodiment is configured to include a display 110, a slit mirror 120 having a plurality of mirrors formed in a striped pattern via a slit, and a retroreflector 130. These components are disposed, for example, within a housing or frame, to display an aerial image P floating in the air from the housing.

[0020] Display 110 is a light source used to generate the original image of the aerial image P. Display 110 is not particularly limited; it can be, for example, an LED or organic EL display, a projector, or an LED unit with multiple LEDs arranged in a two-dimensional configuration. The light from the original image of the aerial image P generated by display 110 is output towards the slit mirror 120. For example, the angle between the normal (optical axis) of the display surface of display 110 and the principal surface of slit mirror 120 is 45 degrees.

[0021] The slit mirror 120 is an optical element consisting of alternating arrangements of each of a plurality of slits and each of a plurality of mirrors. The slit mirror 120 is positioned such that light from the display 110 is incident upon it, and reflects the light from the display 110 toward the retroreflector 130 via the plurality of mirrors, and transmits the light reflected by the retroreflector 130 via the plurality of slits, thereby forming an aerial image P.

[0022] Figure 2 (B) is the bottom view of the slit mirror. Figure 2 (C) is Figure 2 (B) is a cross-sectional view along line AA. As shown in the figure, the slit reflector 120 has a generally rectangular plane on which a plurality of elongated rectangular reflectors 122 extending in the column direction are formed, a plurality of decorative layers 124 disposed on the back side of the plurality of reflectors 122, and a plurality of slits 126 formed between the plurality of reflectors 122 and the plurality of decorative layers 124 respectively. The planar shape of the decorative layer 124 is the same as that of the reflector 122. The surface of the reflector 122 provides a reflective surface for reflecting light incident from the display 110, and its back side provides a reflective surface for reflecting light incident from the outside via the decorative layer 124. The decorative layer 124 provides the appearance design, and the slits 126 provide the transmission area for the light after retroreflection.

[0023] In one way, such as Figure 2 As shown in (C), the slit mirror 120 has a transparent film or plate-like transparent substrate 128 that allows light to pass through. A decorative layer 124 and a mirror 122 are formed on the bottom surface of the transparent substrate 128. The material of the transparent substrate 128 is not particularly limited, and may be, for example, plastic, glass, acrylic, etc.

[0024] The reflector 122 is, for example, a metal layer. The decorative layer 124 is a transparent layer with a certain transmittance to which an appearance design has been applied. The appearance design applied to the decorative layer 124 enhances the appearance design of the display device 100, and the colors, patterns, etc. constituting the appearance design are arbitrary.

[0025] The manufacturing method of the reflector 122 and the decorative layer 124 is not particularly limited. For example, a component with the decorative layer 124 printed on the surface of the metal layer serving as the reflector 122 can be glued to the transparent substrate 128. Alternatively, after forming the decorative layer on the entire surface of the transparent substrate 128, metal material can be vapor-deposited to cover the entire surface of the decorative layer, and then the material can be patterned by etching to form a striped reflector 122 and decorative layer 124. The area of ​​the transparent substrate 128 not covered by the metal layer provides the slit 126, i.e., the transmission area. The above-described method of manufacturing the reflector is an example, and the slit reflector 120 can also be constructed by other methods.

[0026] Alternatively, the slit 126 can also be a gap or space formed in the transparent substrate 128. As another option, the decorative layer 124 can also be formed on the surface side of the transparent substrate 128 in a manner that matches the position of the reflector 122. That is, the reflector 122 is formed directly on the bottom side of the transparent substrate 128, and the decorative layer 124 is formed on the surface side in a manner that precisely overlaps with the position of the reflector 122. In this case, the decorative layer 124 is printed on the surface of the transparent substrate 128, and the reflector 122 is printed on the bottom surface.

[0027] The retroreflector 130 is an optical element that reflects light in the same direction as the incident light. Its configuration is not particularly limited; for example, it can be composed of a triangular pyramidal retroreflector or a full cubical corner retroreflector. The retroreflector 130 reflects light incident on the incident light after it has been reflected by mirror 122 of the slit mirror 120 in the same direction. The light reflected back by the retroreflector 130 is parallel to the incident light, and a certain offset is generated between the reflected light and the incident light, as described later. The retroreflector 130 is aligned with the slit mirror 120 such that the reflected light passes through the slit 126 of the slit mirror 120. Thus, an aerial image P is formed by transmitting the reflected light through the slit 126 of the slit mirror 120.

[0028] Next, the operating principle of the display device 100 in this embodiment will be explained. Figure 3(A) is a projection diagram when the retroreflector is projected onto the slit mirror and the two are superimposed for observation. The retroreflector 130 comprises multiple retroreflection units arranged in a row and column direction, each retroreflection unit being, for example, a retroreflection prism. The retroreflection prism has three reflecting surfaces, and the incident light is internally reflected three times by the three reflecting surfaces, exiting in the same direction as the incident light. At this time, a certain amount of offset is necessarily produced between the incident light and the outgoing light (retroreflected light). The retroreflector 130 has three axes (hereinafter referred to as reversal axes) that produce outgoing light at positions symmetrical with respect to such incident light.

[0029] For example, if with Figure 3 Taking example (A) as an example, when viewing one regressive reflection unit from above, the regressive reflection unit is represented by an equilateral triangle. Multiple regressive reflection units are arranged in a matrix with alternating inversions of the equilateral triangles. In addition, the three bisecting lines from the vertices of the equilateral triangles toward the midpoint of the base are the inversion axes S1, S2, and S3.

[0030] like Figure 3 As shown in (A), light incident on retroreflector a exits from position a' symmetrical with respect to the reversal axis S2, light incident on b exits from position b' symmetrical with respect to the reversal axis S1, and light incident on c exits from position c' symmetrical with respect to the reversal axis S3. The reverse is also true (light incident on a' exits from a, light incident on b' exits from b, and light incident on c' exits from c). Thus, light incident on retroreflector exits from positions symmetrical with respect to the reversal axes S1, S2, and S3.

[0031] The retroreflector 130 is positioned relative to the slit mirror 120 such that one of the reversal axes S1, S2, S3 is parallel to the column direction (slit direction) of the mirror 122. Figure 3 In example (A), the retroreflector 130 is configured such that the reversal axis S1 is parallel to the slit direction of the slit mirror 120.

[0032] In a preferred embodiment, the spacing in the row direction between the reflectors 122 and slits 126 of the slit reflector 120 is set to be equal to the spacing in the row direction of the retroreflection unit. In this case, the width W1 in the row direction of the reflector 122 is equal to the width W2 in the row direction of the slit 126 (W1=W2), and the length Ws of one side of the equilateral triangle of the retroreflection unit is Ws=W1+W2. Furthermore, the width in the row direction of the decorative layer 124 is equal to the width W1 of the reflector 122.

[0033] In addition, in another aspect, when the pitch in the row direction between the reflecting mirror 122 and the slit 126 is equal to the pitch in the row direction of the retro-reflection units, the width W1 of the reflecting mirror may also not be equal to the width W2 of the slit (W1≠W2). For example, when W1>W2, the amount of reflected light may become relatively large, or conversely, when W1<W2, the amount of transmitted light may become relatively large. W1 and W2 may also be set according to the optical characteristics of the display device. In addition, the width of the decorative layer 124 in the row direction may also be equal to or slightly smaller than the width W1 of the reflecting mirror 122.

[0034] Figure 3 (B) is a diagram schematically showing the situation of 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, and the incident light L1 is separated into reflected light and transmitted light here. The incident light L1 becomes light L2 reflected by the reflecting mirror 122 toward the retro-reflector 130, and the light L2 is reflected by the retro-reflector 130 in the same direction as the incident light. The retro-reflected light L3 is reflected in the same direction as the incident light L2, but an offset T is generated between the incident light L2 and the reflected light L3, whereby the retro-reflected light L3 transmits through the slit 126 of the slit mirror 120 to form an aerial image P.

[0035] On the other hand, the decorative layer 124 is formed on the back side of the reflecting mirror 122, so external light L4 passes through the transparent substrate 128 and the decorative layer 124 and is reflected to the outside by the reflecting surface on the back side of the reflecting mirror 122. In this way, the brightness of the appearance design of the decorative layer 124 can be increased by the external light L4. On the other hand, the light L3 retro-reflected by the retro-reflector 130 does not transmit through the decorative layer 124, so it is not lost at the decorative layer 124 and is used for forming the aerial image P.

[0036] As described above, according to this embodiment, by disposing the decorative layer on the back side of the reflecting mirror in the slit mirror structure, providing the reflecting mirror inside the slit mirror structure and providing the appearance design on the outside, an aerial interface with invisible decoration that hardly generates light loss can be achieved.

[0037] The display device according to this embodiment has the following effects.

[0038] • In the conventional structure, since the retro-reflected light transmits through the decorative layer, about 50% to 80% of the light is lost. However, in this embodiment, adding the decorative layer on the back side of the reflecting mirror makes the retro-reflected light not transmit through the decorative layer, so there is no light loss caused by the decorative layer. As a result, the aerial image can be prevented from darkening.

[0039] • Since the decoration is provided on the upper part (back side) of the reflecting mirror made of a metal layer, high-brightness decoration for aerial images can be achieved by external light.

[0040] • A decorative aerial image reflector that can achieve the absence of chromatic aberration (color variation caused by viewing angle) that occurs when using a monitor, and offers high design flexibility for both the image and the background.

[0041] Figure 4 (A) is a diagram illustrating the light utilization efficiency when using a conventionally constructed decorative layer. Figure 4 (B) is a graph illustrating the light utilization efficiency when using the slit reflector 120 containing the decorative layer of this embodiment. Figure 4 In the conventional configuration shown in (A), if it is assumed that the transmittance of the semi-reflective mirror 30 is 50% and the reflectance is 50%, then the light emitted from the display 20 is separated into 50% reflected light and 50% transmitted light by the semi-reflective mirror 30. 50% of the reflected light is reflected back by the retroreflector 40, and the reflected light is transmitted through the semi-reflective mirror 30. Half of the light, 25%, is used to image the aerial image P.

[0042] On the other hand, Figure 4 In the display device 100 of this embodiment shown in (B), 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 retroreflected by the retroreflector 130, and the retroreflected 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 semi-reflective 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 the past, and as a result, the aerial image P can be displayed with high brightness.

[0043] Next, another embodiment of the present invention will be described. Figure 5 (B) is a schematic diagram illustrating the configuration of a display device according to another embodiment, which is related to... Figure 2 The components shown in (A) are identical in designation and have the same reference numerals.

[0044] like Figure 5 As shown in (A), when the slit mirror 120 is used, part of the light emitted from the display 110 is light Lx that transmits through the slit 126 of the slit mirror 120. This light Lx does not contribute to the imaging of the aerial image. In addition, if it is prominent as internal stray light, there is a concern that the problem of internal stray light, which is suppressed by using a polarizing beam splitter, will recur.

[0045] Therefore, in this embodiment, an absorptive polarizer 210 is provided on the upper surface of the slit mirror 120 to absorb light emitted from the display 110, which serves as the light source (polarized in the case of a typical LCD), thereby blocking the display 110 and internal scattered light, making it difficult to see from the outside. Simultaneously, since it is necessary to transmit light for imaging the aerial image P, a λ / 4 waveplate 200 is provided on the surface of the retroreflector 130 to change the polarization direction of the light from the aerial image P, thereby enabling lossless imaging of the aerial image. By combining the slit mirror 120 and the absorptive polarizer 210, the equivalent function of a polarizing reflector in an aerial image display device is achieved.

[0046] The λ / 4 waveplate 200 is, for example, a phase retardation film adhered to the surface of the retroreflector 130. The λ / 4 waveplate 200, for example, transforms linearly polarized light that vibrates in a certain direction into circularly polarized light when incident on it, or transforms circularly polarized light into linearly polarized light when incident on it.

[0047] The absorptive polarizer 210 is an absorptive polarizer that selectively transmits the component of linearly polarized light vibrating in a certain direction and absorbs the component of linearly polarized light orthogonal to that component. Therefore, the light emitted from the absorptive polarizer 210 is not absorbed and only becomes the polarized component transmitted therein. An absorptive polarizer is, for example, a polarizing film adhered to the top surface of the slit mirror 120. Furthermore, the direction of the linearly polarized light absorbed by the absorptive polarizer 210 is approximately the same as the direction of the linearly polarized light emitted from the display 110.

[0048] 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 transmitted through the slit mirror 120 is largely absorbed by the absorptive polarizer 210. On the other hand, the light reflected by the slit mirror 120 is directed toward the retroreflector 130, where it passes twice through the λ / 4 waveplate 200 and then toward the slit mirror 120 again. The retroreflected light is given a phase difference of λ / 2 by the λ / 4 waveplate 200, that is, the polarization direction is rotated by 90 degrees. Thus, the retroreflected light is transmitted through the slit 126 of the slit mirror 120 to the absorptive polarizer 210, forming an aerial image P.

[0049] Thus, according to this embodiment, by using an absorptive polarizer and a λ / 4 waveplate, the original image and internal scattering of the display 110 can be made difficult to see, thereby improving the visibility of the aerial image P. Furthermore, by combining the λ / 4 waveplate, the slit mirror, and the absorptive 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, reflective polarizers have low durability under high temperature and humidity conditions, making it easy to mount the display device of this embodiment in vehicles exposed to high-temperature environments.

[0050] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to specific embodiments. Various modifications and alterations can be made within the scope of the spirit of the invention as described in the claims.

Claims

1. A display device, wherein, The display device is capable of displaying aerial images using retroreflection and has the following features: light source; Reflective element; as well as Optical elements, positioned at the location where light from the light source is incident. The optical element includes: a plurality of reflective regions formed by a plurality of slits; and a decorative layer disposed on the reflective surface side of the reflective regions opposite to the reflective surface of one of the reflective regions. One of the multiple reflective areas reflects light from the light source toward the retroreflector, while the other reflects external light incident through the decorative layer. The multiple slits allow light reflected by the retroreflector to be transmitted, thus forming the aerial image.

2. The display device according to claim 1, wherein, The optical element further comprises a transparent substrate, on the surface of which the reflective area is formed through the decorative layer.

3. The display device as claimed in claim 1, wherein, The reflective area and the decorative layer are elongated regions extending along the column direction, and the slits are respectively formed between the various reflective areas of the plurality of reflective areas.

4. The display device as claimed in claim 1, wherein, The retroreflector includes a plurality of reversal axes that reverse incident light into reflected light, and the retroreflector is configured such that one of the reversal axes is parallel to the slit direction of the optical element.

5. The display device as claimed in claim 1, wherein, When the retroreflector is projected onto the optical element, the row spacing of the retroreflector units arranged in the row and column directions of the retroreflector is consistent with the row spacing of the reflection area and the slit of the optical element.

6. The display device as claimed in claim 1, wherein, The display device further includes a λ / 4 waveplate disposed on the upper surface side of the retroreflector and a polarizer disposed on the upper surface side of the optical element. The polarizer is an absorptive polarizer capable of absorbing the polarization component of light emitted from the light source, which allows the polarization component of the retroreflected light from the λ / 4 waveplate to be transmitted.

7. An optical element, wherein, Using retroreflection to create an image in the air, The optical element comprises: a transparent substrate; a plurality of reflective regions formed on the surface of the transparent substrate through a plurality of slits; and a decorative layer formed between the surface of the transparent substrate and the reflective regions.

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