Patent Description:
<CIT> discloses a stereoscopic display that enables stereoscopic vision by imparting a lens structure or a prism structure as a configuration for obtaining stereoscopic effect on a display.

<CIT> discloses a backlight illuminated colour display device comprising a light guiding member constructed with a pair of wedge-shaped light guiding plates bonded together, light sources of different colors, each disposed facing one edge of each of said wedge-shaped light guiding plates, substantially transparent layers, each formed on a light emergence surface of each of said wedge-shaped light guiding plates and having a higher refractive index than said light guiding member, and a light scattering layer formed in a desired pattern on each of said transparent layers.

Further, aerial imaging by retro-reflection (AIRR) using retroreflection is known. <CIT> discloses an aerial image display device provided with at least one light source, and an optical system for forming a real image of the light source, wherein the optical system comprises a half mirror disposed on the front surface side, and a retroreflection member disposed opposite the half mirror and disposed on the back surface side, and forms the real image outside the half mirror.

<CIT> discloses an aerial image display system with an image display device provided with image display equipment for displaying an image on a screen on the basis of an acquired image signal, an image forming member which forms a real image in the air from image light including the image displayed on the screen, a wavelength-selective reflecting member which has properties to transmit visible light and reflect invisible light, and which is disposed on the same side of the image forming member as the surface thereof onto which the image light is incident, and an image capturing device which receives invisible light reflected from an object to be detected that is performing an input operation with respect to the real image, and captures an invisible light image of the object to be detected.

For example, in order to enable observation of an image formed in the air from a wider angle, the display device of <CIT> uses two retroreflective members, and one of the retroreflective members is arranged on the emission axis of the light source. In the image display device of <CIT>, in order to facilitate adjustment of an image forming position of an image, a half mirror, a retroreflective member, and an image output device are disposed in parallel and a position of the half mirror or the image output device is changed so that the image forming position can be adjusted. In the image display device of <CIT>, in order to minimize a decrease in visibility of an image, the number of times of light transmission through a phase difference member (λ/<NUM> plate) is reduced and it is made difficult for dust or the like to enter between a retroreflective member and the phase difference member. In the aerial image display device of <CIT>, in order to reduce a thickness of a device, a display and a retroreflective member are disposed parallel to a beam splitter and a deflection optical element is disposed on the display.

<FIG> illustrates an example in which a display device that displays an aerial image is applied to a spatial input device. The spatial input device <NUM> includes a housing (structure) <NUM> that accommodates a display device that generates an aerial image, and a three-dimensional distance sensor <NUM> that detects approach of an object (for example, a user's finger or the like) <NUM> to the aerial image <NUM> generated above the housing <NUM>. The aerial image <NUM> includes, for example, left and right scroll keys <NUM> and <NUM> and icon images <NUM> to <NUM> for instructing input as illustrated in <FIG>.

In a case where only the aerial image <NUM> is displayed, a situation often occurs in which, when the user sees the aerial image <NUM>, the user recognizes that the aerial image <NUM> is displayed on the structure <NUM> on a back surface, and does not recognize it as the aerial image <NUM> in the first place. This is related to a human cognitive process, and is caused by superimposing the aerial image <NUM> on a background object in the brain when viewing the aerial image. When the aerial image <NUM> is used as a non-contact device, it is necessary to make the user visually recognize the fact, and how to make the aerial image stand out and easily recognized is a problem in implementation.

An object of the present invention is to provide a display device capable of displaying an aerial image that is easily visually recognized, and a spatial input device using the display device.

The invention relates to a display device according to the appended claims. Embodiments are disclosed in the dependent claims.

A display device according to an aspect of the present invention is capable of displaying an aerial image using retroreflection, the display device including a first optical structure that forms a multiple image by light diffused or scattered by a first light diffusion surface of a first light guide layer, and a second optical structure that retroreflects light diffused or scattered by a second light diffusion surface of a second light guide layer to form an aerial image, in which the first optical structure and the second optical structure are in a stacked relationship, and the first light diffusion surface and the second light diffusion surface are disposed at positions not overlapping each other.

In one embodiment, the first optical structure includes reflection members formed on an upper surface side and a bottom surface side of the first light guide layer, and light incident from a side portion of the first light guide layer is diffused or scattered by the first light diffusion surface formed on a bottom surface or a bottom portion of the first light guide layer. In one embodiment, the second optical structure includes a retroreflective layer formed on a bottom surface side of the second light guide layer, and light incident from a side portion of the second light guide layer is diffused or scattered by the second light diffusion surface formed on a bottom surface or a bottom portion of the second light guide layer. In one embodiment, the second optical structure is stacked on the first optical structure, the first optical structure includes a reflection layer, a first light guide layer formed on the reflection layer, and a beam splitter formed on the first light guide layer, and the second optical structure includes a retroreflective layer, a second light guide layer formed on the retroreflective layer, and a beam splitter formed on the second light guide layer, and a multiple image formed by the first light diffusion surface of the first light guide layer and an aerial image formed by the second light diffusion surface of the second light guide layer can be simultaneously observed from above the second optical structure. In one embodiment, the first optical structure is stacked on the second optical structure, the second optical structure includes a retroreflective layer and a second light guide layer formed on the retroreflective layer, and the first optical structure includes a reflection layer, a first light guide layer formed on the reflection layer, and a beam splitter formed on the first light guide layer, and a multiple image formed by the first light diffusion surface of the first light guide layer and an aerial image formed by the second light diffusion surface of the second light guide layer can be simultaneously observed from above the first optical structure. In one embodiment, a color of light incident on the first light guide layer is different from a color of light incident on the second light guide layer. In one embodiment, the second optical structure further includes a λ/<NUM> plate between a second light guide layer and the retroreflective layer, and a beam splitter formed on an upper surface of the second light guide layer is a polarization beam splitter.

A spatial input device according to another aspect of the present invention includes a display device as described herein, and a detection unit that detects an approach of an object to an aerial video displayed by the display device.

According to aspects of the present invention, since the aerial image and the multiple image are simultaneously formed, a sense of depth or a stereoscopic effect is imparted to the aerial image by the multiple image, and the aerial image is made conspicuous, by which visual attraction of the aerial image is enhanced, and the aerial image is easily recognized.

A display device of embodiments of the present invention displays a video using retroreflection in a three-dimensional space without wearing special glasses or the like. In an embodiment, the display device of the present invention is applied to a user input interface using a video displayed in the air. It should be noted that the drawings referred to in the following description of embodiments include exaggerated display in order to facilitate understanding of the invention, and do not directly represent the shape and scale of an actual product.

An embodiment of the present invention will be described in detail below. <FIG> is a schematic cross-sectional view of a display device that displays an aerial image according to the first embodiment of the present invention, and <FIG> is a perspective view schematically illustrating designs of light diffusion surfaces formed in light guide layers.

In the display device of the present embodiment, two light guide layers are stacked, an aerial image is formed by a light diffusion surface of one of the light guide layers, and a multiple image with a sense of depth is formed around or outside the aerial image by a light diffusion surface of the other light guide layer, thereby making the aerial image conspicuous, enhancing visual attraction, and facilitating visual recognition of the aerial image.

As illustrated in the drawing, the display device <NUM> includes a first optical structure <NUM> and a second optical structure <NUM> disposed above the first optical structure <NUM>. The first optical structure <NUM> includes a light source <NUM>, a light guide layer <NUM>, a reflection layer <NUM> disposed below the light guide layer <NUM>, and a half mirror <NUM> disposed above the light guide layer <NUM>.

The light source <NUM> emits light L1 having a constant emission angle (or radiation angle) in the X direction. The emitted light L1 enters the inside from a side portion <NUM> of the transparent light guide layer <NUM>, and uniformly irradiates the inside of the light guide layer <NUM>. The light source <NUM> is not particularly limited, but for example, a light emitting diode, a laser diode, or the like is used. The color (wavelength) of the light L1 emitted from the light source <NUM> is not particularly limited, but may be the same as or different from the color of the light L2 emitted from the second light source <NUM>, for example. Further, in a case where the side portion <NUM> of the light guide layer <NUM> has a certain length in the Y direction, a plurality of the light sources <NUM> may be arranged along the Y direction of the side portion <NUM> of the light guide layer <NUM>. Furthermore, although the light L1 is incident from one side portion of the light guide layer <NUM>, the light may be incident from both side portions.

The light guide layer <NUM> is a transparent plate-like or film-like optical member including a flat upper surface, a flat lower surface, and side surfaces connecting the upper surface and the lower surface. As the light guide layer <NUM>, a known one can be used, and is made of, for example, glass, acrylic plastic, polycarbonate resin, cycloolefin-based resin, or the like. The light guide layer <NUM> has a constant thickness in the Z direction in order to allow the light L1 from the light source <NUM> to enter from the side portion <NUM>.

A light diffusion surface <NUM> for diffusion the incident light L1 in the Z direction is formed on a bottom portion or a bottom surface <NUM> of the light guide layer <NUM>. The light diffusion surface <NUM> is formed, for example, by performing laser processing or printing processing on the bottom surface <NUM> of the light guide layer <NUM>. The light diffusion surface <NUM> generates a design (original image) for forming a multiple image around or outside the aerial image, and the design is arbitrarily determined in relation to the aerial image. In the example of the drawings, the light diffusion surface <NUM> is processed to produce a ring-shaped or annular design P1.

The reflection layer <NUM> is disposed so as to be in contact with the bottom surface <NUM> of the light guide layer <NUM>. The reflection layer <NUM> is, for example, a plate-shaped, film-shaped, or thin-film-shaped member having the same shape as the bottom surface <NUM> of the light guide layer <NUM>, and the material thereof is not particularly limited. The reflection layer <NUM> totally reflects the light L1 incident on the light guide layer <NUM>.

The half mirror <NUM> is disposed so as to be in contact with the upper surface of the light guide layer <NUM>. The half mirror <NUM> is, for example, a transparent optical member having the same shape as the upper surface of the light guide layer <NUM> and separating incident light into reflected light and transmitted light. The half mirror <NUM> is configured by, for example, forming a dielectric multilayer film, an anti-reflection film, or the like on a front surface or a back surface of a substrate such as flat glass or plastic. Here, the half mirror <NUM> in which an amount of reflected light and an amount of transmitted light are equal to each other is exemplified, but a beam splitter in which a ratio between the amount of reflected light and the amount of transmitted light is different in accordance with the luminance of the light source <NUM> or the luminance of the aerial image may be used.

The light L1 incident from the side portion <NUM> of the light guide layer <NUM> travels in the X direction, is diffused or scattered in the Z direction by the light diffusion surface <NUM>, and the light diffused or scattered by the light diffusion surface <NUM> repeats multiple reflection between the reflection layer <NUM> and the half mirror <NUM>. When the user observes from a viewpoint U in the Z direction, a multiple virtual image of the design P1 is generated on the back surface of the first optical structure <NUM> due to the effect of facing mirrors.

The second optical structure <NUM> includes a light source <NUM>, a light guide layer <NUM>, a retroreflective layer <NUM> disposed below the light guide layer <NUM>, and a half mirror <NUM> disposed above the light guide layer <NUM>.

The light source <NUM> emits light L2 having a constant emission angle (or radiation angle) in the X direction. The emitted light L2 enters the inside from the side portion <NUM> of the transparent light guide layer <NUM>, and uniformly irradiates the inside of the light guide layer <NUM>. The light source <NUM> includes, similarly to the light source <NUM>, one or a plurality of light emitting diodes or laser diodes, for example. Note that in a case where the light L2 of the light source <NUM> and the light L1 of the light source <NUM> have the same color, light emitted from a single light source may be divided into two by a beam splitter or the like, and the divided light may be emitted to the light guide layers <NUM> and <NUM>, respectively.

The light guide layer <NUM> is a transparent plate-like or film-like optical member including a flat upper surface, a flat lower surface, and side surfaces connecting the upper surface and the lower surface, and is formed of a member similar to the light guide layer <NUM>. The light guide layer <NUM> has a constant thickness in the Z direction in order to allow the light L2 of the light source <NUM> to enter from the side portion <NUM>.

A light diffusion surface <NUM> for diffusing the incident light in the Z direction is formed on the bottom portion or a bottom surface <NUM> of the light guide layer <NUM>. The light diffusion surface <NUM> is formed, for example, by performing laser processing or printing processing on the bottom surface <NUM> of the light guide layer <NUM>. The light diffusion surface <NUM> generates a design (original image) for forming an aerial image, and the design is arbitrarily determined. In the example of the figure, the light diffusion surface <NUM> is located inside or on an inner periphery of the light diffusion surface <NUM>, and is processed so as to generate a triangular design P2 in which an opening is formed at the center.

The retroreflective layer <NUM> is formed so as to be in contact with the bottom surface of the light guide layer <NUM>. The retroreflective layer <NUM> is an optical member that reflects light in the same direction as the incident light, and is not particularly limited in its configuration but includes, for example, prismatic retroreflective elements such as triangular pyramid retroreflective elements and full cube corner retroreflective elements, or bead retroreflective elements. The retroreflective layer <NUM> is disposed at a position not interfering with the light diffusion surface <NUM>, that is, at a position inside the light diffusion surface <NUM>, and is disposed so as to substantially overlap the light diffusion surface <NUM> (here, since the design P2 has an opening at the center, the opening is shielded).

The half mirror <NUM> is disposed so as to be in contact with the upper surface of the light guide layer <NUM>. The half mirror <NUM> has, for example, the same shape as the upper surface of the light guide layer <NUM>, and is configured similarly to the half mirror <NUM>. Here, the half mirror <NUM> in which the amount of reflected light and the amount of transmitted light are equal to each other is exemplified, but a beam splitter in which a ratio between the amount of reflected light and the amount of transmitted light is different in accordance with the luminance of the light source <NUM> or the luminance of the aerial image may be used.

The light L2 incident from the side portion <NUM> of the light guide layer <NUM> travels in the X direction and is diffused or scattered in the X direction by the light diffusion surface <NUM>, a part of the diffused or scattered light is reflected by the half mirror <NUM>, and the reflected light is incident on the retroreflective layer <NUM>. The light incident on the retroreflective layer <NUM> is reflected in the same direction as the incident light, and a part thereof is transmitted through the half mirror <NUM> and forms an image again. An aerial image <NUM> of the design P2 floating up from the second optical structure <NUM> is observed from the viewpoint U of the user in the Z direction. Further, simultaneously with the aerial image <NUM>, a multiple image <NUM> of the design P1 generated on the outer periphery of the aerial image <NUM> is also observed.

<FIG> is a perspective view schematically illustrating a relationship between the multiple image <NUM> of the design P1 and the aerial image <NUM> of the design P2. The first optical structure <NUM> generates multiple reflection of the design P1 due to the effect of facing mirrors and produces the multiple virtual image <NUM> having a depth feeling equal to or greater than the thickness of a real object. The second optical structure <NUM> forms the aerial image <NUM> of the design P2 inside or around the multiple virtual image <NUM>. By representing the multiple virtual image <NUM> around the aerial image <NUM>, it is possible to achieve performance in which the aerial video floats at the center of the image having a sense of depth by the display device <NUM> having a small/thin stacked structure.

As described above, by optically arranging the design P1 of the first layer and the design P2 of the second layer in a thin aerial video element in which the two layers are combined so that the design P1 of the first layer and the design P2 of the second layer can be simultaneously viewed, the stereoscopic effect of the aerial image <NUM> is emphasized, the visual attraction is increased, and the probability of being recognized as the aerial display even at the first sight can be increased. Further, the aerial image <NUM> can be made more conspicuous by making the color of the light source <NUM> different from the color of the light source <NUM>.

Note that the second optical structure for generating the aerial image is not limited to the configuration of <FIG>, and may have a configuration as illustrated in <FIG>, for example. In a second optical structure 300A, the polarization beam splitter <NUM> is disposed on the upper portion of the light guide plate <NUM> instead of the half mirror <NUM>, and the λ/<NUM> plate <NUM> is disposed between the light guide layer <NUM> and the retroreflective layer <NUM>.

The polarization beam splitter <NUM> is a polarization separation element capable of dividing incident light into a p-polarization component and an s-polarization component, and can transmit a light component linearly polarized in a certain specific direction. If the light L2 incident from the light source <NUM> is unpolarized light including various polarization components, a part of the light reflected by the light diffusion surface <NUM> is transmitted through the polarization beam splitter <NUM>, and the other light is reflected by the polarization beam splitter <NUM>. If the light L2 incident from the light source <NUM> is linearly polarized light, the direction of the linearly polarized light transmitted by the polarization beam splitter <NUM> is set to be different from the direction of the linearly polarized light of the incident light L2, and most of the light L2 is reflected by the polarization beam splitter <NUM>.

The λ/<NUM> plate <NUM> gives a phase difference π/<NUM> (<NUM> degrees) to the light incident from the light guide layer <NUM> and transmits the light. For example, when linearly polarized light is incident, it is converted into circularly polarized light (or elliptically polarized light), and when circularly polarized light (or elliptically polarized light) is incident, it is converted into linearly polarized light.

The retroreflective layer <NUM> reflects the light transmitted through the λ/<NUM> plate <NUM> in the same direction as the incident light. When the light reflected by the retroreflective layer <NUM> is transmitted through the λ/<NUM> plate <NUM> again, a phase difference π/<NUM> is given. Thus, the light transmitted through the λ/<NUM> plate <NUM> has a phase difference π from the light incident on the λ/<NUM> plate <NUM>. For example, if the light incident on the λ/<NUM> plate <NUM> is linearly polarized light, the light becomes circularly polarized light (or elliptically polarized light) when it is transmitted through the λ/<NUM> plate <NUM>, when this circularly polarized light is retroreflected an odd number of times by the retroreflective layer <NUM>, the circularly polarized light becomes circularly polarized light in the opposite direction, and when this circularly polarized light in the opposite direction is transmitted through the λ/<NUM> plate <NUM>, it becomes linearly polarized light in a direction <NUM> degrees different from the original linearly polarized light. In this manner, when the light transmitted through the λ/<NUM> plate <NUM> is incident on the polarization beam splitter <NUM>, most of the reflected light is transmitted through the polarization beam splitter <NUM>, the transmitted light forms an image, and an aerial image is formed.

Next, a display device 100A according to a second embodiment of the present invention is illustrated in <FIG>. In the display device 100A of the present embodiment, the stacking direction is reversed from that of the first embodiment, and the first optical structure <NUM> is stacked above the second optical structure <NUM>. The light diffusion surface <NUM> is formed on the bottom surface <NUM> of the light guide layer <NUM> of the second optical structure <NUM>. The light diffusion surface <NUM> is processed to form the triangular design P2. The retroreflective layer <NUM> is disposed on the bottom surface of the light guide layer <NUM> so as to generate the aerial image <NUM> of the design P2.

On the other hand, the light diffusion surface <NUM> is formed on the outer peripheral portion of the bottom surface <NUM> of the light guide layer <NUM> of the first optical structure <NUM>. The light diffusion surface <NUM> is processed to form the ring-shaped design P1. The design P1 is formed at a position not overlapping with the design P2. A ring-shaped reflection layer <NUM> is formed below the light diffusion surface <NUM>. The opening <NUM> at the center of the reflection layer <NUM> has a size that exposes the light diffusion surface <NUM> and the retroreflective layer <NUM> so that the aerial image <NUM> is not shielded. That is, a part of the light diffused or scattered in the Z direction by the light diffusion surface <NUM> is reflected by the half mirror <NUM> of the first optical structure <NUM> via the opening <NUM>, the reflected light is incident on the retroreflective layer <NUM>, this incident light is reflected by the retroreflective layer <NUM> in the same direction, and a part of this reflected light is transmitted through the half mirror <NUM> to generate the aerial image <NUM>.

In this manner, in the video viewed from the viewpoint U of the user, the multiple virtual image <NUM> of the design P1 generated by the first optical structure <NUM> is projected around the aerial image <NUM> of the design P2 generated by the second optical structure <NUM>, the sense of depth is imparted to the aerial image <NUM>, and recognition of the aerial image becomes easy. Further, in the present embodiment, by arranging the second optical structure <NUM> below the first optical structure <NUM>, a distance D at which the aerial image <NUM> floats up can be made larger than that in the first embodiment, and an aerial image with a more stereoscopic effect can be displayed.

Next, a third embodiment of the present invention will be described. The third embodiment relates to a spatial input device in which the display device of the first or second embodiment is applied to a user input interface. As described with reference to <FIG>, the spatial input device includes a sensor that causes the display devices <NUM> and 100A of the present embodiment to display the aerial image <NUM> and detects an approach of an object (for example, a user's finger or the like) to the aerial image <NUM>. The configuration of the sensor is not particularly limited, but for example, the sensor detects the approach of an object by a three-dimensional distance sensor, or detects the proximity of an object by analyzing image data captured by an imaging camera.

The spatial input device of the present embodiment can be applied to any user input, and can be applied to, for example, a computer device, an in-vehicle electronic device, an ATM of a bank or the like, a ticket purchasing machine of a station or the like, an input button of an elevator, and the like.

Claim 1:
A display device (<NUM>) capable of displaying an aerial image (<NUM>) using retroreflection, the display device (<NUM>) comprising:
a first optical structure (<NUM>) configured to form a multiple image (<NUM>) by light diffused or scattered by a first light diffusion surface (<NUM>) of a first light guide layer (<NUM>);
a second optical structure (<NUM>) configured to retroreflect light diffused or scattered by a second light diffusion surface (<NUM>) of a second light guide layer (<NUM>) to form an aerial image (<NUM>), characterized in that
the first optical structure (<NUM>) and the second optical structure (<NUM>) are in a stacked relationship, and the first light diffusion surface (<NUM>) and the second light diffusion surface (<NUM>) are disposed at positions not overlapping each other.