Patent Description:
An aerial display that forms an image displayed on a display in the air using a retroreflective member or the like has been proposed. 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 disposed on an emission axis of a light source. In an image display device of <CIT>, in order to facilitate adjustment of an image forming position of an image, a semitransparent mirror, a retroreflective member, and an image output device are arranged parallel to each other, and a position of the semitransparent mirror or the image output device is changed so that the image forming position can be adjusted. In an image display device of <CIT>, in order to curb a decrease in visibility of an image, the number of times of light transmission through the phase difference member (λ/<NUM> plate) is reduced, and hardly any dust or the like is able to enter between a retroreflective member and a phase difference member. In an aerial video display device of <CIT>, in order to reduce the thickness of the device, a display and a retroreflective member are arranged parallel to a beam splitter, and a deflection optical element is disposed on the display.

<FIG> illustrates a schematic cross section of a display device using conventional retroreflection. As illustrated in the drawing, the display device <NUM> includes a display <NUM> that outputs an image, a beam splitter <NUM>, and a retroreflective member <NUM>. The light emitted from the display <NUM> is reflected by the beam splitter <NUM>, and the reflected light travels to the retroreflective member <NUM>. The retroreflective member <NUM> reflects light in the same direction as incident light, and the reflected light passes through the beam splitter <NUM>, and an aerial image <NUM> is displayed in a space in front of the observer's eyes. Such display of the aerial image <NUM> is known as an Aerial Imaging by Retro-Reflection (AIRR) method.

<FIG> is a schematic external view of the display device using the AIRR method. The display device <NUM> includes, for example, a rectangular parallelepiped housing <NUM> as illustrated in the drawing, the beam splitter <NUM> is disposed on the surface of the housing <NUM>, and the display <NUM> and the retroreflective member <NUM> are disposed inside the housing <NUM>. Since the housing <NUM> requires an internal space for the display <NUM> and the retroreflective member <NUM> to be inclined, the thickness T of the housing <NUM> increases.

In addition, the aerial image <NUM> that can be observed by the observer is limited to a range in which the observer can see the retroreflective member <NUM>. That is, the retroreflective member <NUM> needs to be present within the viewing angle of the observer. When <FIG> is taken as an example, the viewing angle θ at which the aerial image <NUM> can be observed is about ±<NUM> degrees to the left and right with respect to in front of the aerial image <NUM>, and there is a problem in that the viewing angle is narrow.

Further, the aerial image <NUM> is formed at a position symmetrical to the display <NUM> with respect to the surface of the beam splitter <NUM>. In a case where the display <NUM> is inclined at approximately <NUM> degrees with respect to the beam splitter <NUM>, the aerial image <NUM> observed by the observer is not a video of the display <NUM> viewed from in front but a video viewed from an oblique direction of <NUM> degrees.

An object of the present invention is to provide a display device capable of achieving thickness reduction, size reduction, and wide field of view, and enabling front viewing of a video of a light source, and a spatial input device using such display device.

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

The display device according to an aspect of the present invention capable of displaying a video in the air using retroreflection includes a transparent light guide plate including an original video of the video in the air, a light source configured to emit light from a side portion of the light guide plate toward the inside of the light guide plate, a polarization beam splitter disposed parallel to the light guide plate and above the light guide plate, a λ/<NUM> plate disposed below the light guide plate, and a retroreflective member disposed parallel to the light guide plate and below the λ/<NUM> plate, and retroreflects the original video to display the video in the air.

In one aspect, the display device further includes a polarizing member provided between the original video of the light guide plate and the polarization beam splitter, in which the polarizing member curbs transmission of light reflected by the original video through the polarization beam splitter. In one aspect, the polarizing member has a shape the same as or similar to a planar shape of the original video. In one aspect, the original video is formed on a bottom portion of the light guide plate, and the original video and an image in the air are at symmetrical positions with respect to a plane of the polarization beam splitter.

The spatial input device according to an aspect of the present invention includes a display device as described herein, and detection means configured to detect an approach of an object to a video in the air displayed by the display device. In one aspect, the detection means includes a capacitive sensor.

According to aspects of the present invention, since the light is emitted from the side portion of the transparent light guide plate on which the original video of the aerial image is formed, and the video in the air of the original video is displayed by the retroreflection of the retroreflective member disposed below the light guide plate in parallel with the light guide plate, the display device can be downsized and thinned, and the observer can observe the video in the air of the original video viewed from the front at a wide viewing angle.

Next, embodiments of the present invention will be described. The display device of the present invention displays a video using retroreflection in a three-dimensional space for which wearing special glasses or the like do not have to be worn. In an aspect, 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 the examples include exaggerated display in order to facilitate understanding of the invention, and do not directly represent the shape and scale of an actual product.

Next, an example of the present invention will be described in detail. <FIG> is a cross-sectional view illustrating a schematic configuration of a display device according to an example of the present invention. A display device <NUM> of the present example includes a light source <NUM>, a light guide plate <NUM>, a polarization beam splitter <NUM>, a λ/<NUM> plate <NUM>, a retroreflective member <NUM>, and a transparent protective member <NUM>. These members are accommodated in, for example, a rectangular parallelepiped housing, a housing, or the like.

The light source <NUM> emits light L having a constant emission angle (or oblique angle) in the X-direction. The emitted light L enters the inside from a side portion <NUM> of the transparent light guide plate <NUM>, and uniformly irradiates the inside of the light guide plate <NUM>. The light source <NUM> is not particularly limited, but for example, a light emitting diode, a laser diode, or the like may be used. If the side portion <NUM> of the light guide plate <NUM> has a certain length in the Y-direction, the plurality of light sources <NUM> may be arranged along the Y-direction of the side portion <NUM> of the light guide plate <NUM>. Here, light is incident from one side portion of the light guide plate <NUM>, but the light may be incident from a plurality of side portions.

The light guide plate <NUM> is a transparent plate-like optical member including a flat upper surface, a flat lower surface, and side surfaces connecting the upper surface and the lower surface. A known plate can be used as the light guide plate <NUM>, and may be, for example, an acrylic plastic plate, or a plate made of a polycarbonate resin, a cycloolefin-based resin, or the like. The light guide plate <NUM> has a constant thickness in the Z-direction in order to allow light L of the light source <NUM> to enter from the side portion <NUM>. A diffusion pattern for diffusing the incident light may be formed on the bottom portion or a bottom surface <NUM> of the light guide plate <NUM>. For example, a dot pattern may be formed by laser processing or printing. In this way, the light L incident from the side portion <NUM> of the light guide plate <NUM> is diffused or scattered by the diffusion pattern of the bottom portion <NUM> of the light guide plate <NUM>, and the light guide plate <NUM> functions as if it were a surface light source.

A light guide plate image <NUM> is further formed on the bottom portion or the bottom surface <NUM> of the light guide plate <NUM> as an original video P1 of the aerial image. A method of forming the light guide plate image <NUM> is not particularly limited, but for example, a two-dimensional image such as a groove or unevenness may be formed on the bottom portion <NUM> by laser processing, embossing, printing processing, or the like. When the light L is incident from the side portion of the light guide plate <NUM>, the light L is reflected by the light guide plate image <NUM>, and the two-dimensional original video P1 is generated. When it is desired to further increase the luminance of the light guide plate image <NUM>, the degree of diffusion or scattering of the bottom portion <NUM> in the region other than the light guide plate image <NUM> may be reduced.

The polarization beam splitter <NUM> is disposed on the upper portion of the light guide plate <NUM> in parallel with the light guide plate <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 L incident from the light source <NUM> is non-polarized light including various polarized components, a part of light L1 reflected by the bottom portion <NUM> of the light guide plate <NUM> or the light guide plate image <NUM> passes through the polarization beam splitter <NUM>, and most of the other light L2 is reflected by the polarization beam splitter <NUM>. If the light L 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 L, and most of the light L1 is reflected by the polarization beam splitter <NUM>.

The λ/<NUM> plate <NUM> is disposed below and parallel to the light guide plate <NUM>. The light L2 emitted from the light guide plate <NUM> is incident on the λ/<NUM> plate <NUM>, and a phase difference π/<NUM> (<NUM> degrees) is given to the incident light L2 to allow transmission of the incident light L2. 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 member <NUM> is disposed below and parallel to the λ/<NUM> plate <NUM>. The retroreflective member <NUM> reflects the light L2 transmitted through the λ/<NUM> plate <NUM> and the light L3 in the same direction as the incident light. The structure and material of the retroreflective member <NUM> are not particularly limited as long as the retroreflective member can reflect light in the same direction as the incident direction. The retroreflective member <NUM> includes, for example, prismatic retroreflective elements such as triangular pyramid retroreflective elements and full cube corner retroreflective elements, or bead retroreflective elements.

When the light L3 reflected by the retroreflective member <NUM> is transmitted through the λ/<NUM> plate <NUM> again, a phase difference π/<NUM> is given. Thus, the light L3 transmitted through the λ/<NUM> plate <NUM> has a phase difference π from the light L2 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 passing through the λ/<NUM> plate <NUM>, when the circularly polarized light is retroreflected an odd number of times by the retroreflective member <NUM>, the circularly polarized light becomes circularly polarized light in the opposite direction, and when this circularly polarized light in the opposite direction passes through the λ/<NUM> plate <NUM>, it becomes linear polarized light in a direction <NUM> degrees different from the original linear polarized light. Thus, when the light L3 transmitted through the λ/<NUM> plate <NUM> is incident on the polarization beam splitter <NUM>, most of the light L3 is transmitted through the polarization beam splitter <NUM>.

A transparent protective member <NUM> is disposed above the polarization beam splitter <NUM>. The transparent protective member <NUM> is made of, for example, a glass material or a plastic material. The transparent protective member <NUM> protects the surface of the polarization beam splitter <NUM>, and the arrangement thereof is arbitrary. The light L3 transmitted through the transparent protective member <NUM> forms an image in the air, and the observer can observe the aerial image <NUM> immediately in front from a viewpoint U. The aerial image <NUM> is a video P2 in which an original video P1 of the light guide plate image <NUM> is floated upward as it is. That is, the aerial image <NUM> is displayed at a position symmetrical to the light guide plate image <NUM> with respect to the plane of the polarization beam splitter <NUM>, and the observer can see the video P2 that is a front view of the original video P1.

<FIG> is a schematic external perspective view of the display device of the present example. In the display device <NUM>, for example, the transparent protective member <NUM> is disposed on the surface of the rectangular parallelepiped housing <NUM>, and the light source <NUM>, the light guide plate <NUM>, the polarization beam splitter <NUM>, the λ/<NUM> plate <NUM>, and the retroreflective member <NUM> are accommodated therein. Since the retroreflective member <NUM> is disposed in parallel to the light guide plate <NUM>, the polarization beam splitter <NUM>, and the λ/<NUM> plate <NUM> without inclining the retroreflective member as in the conventional display device, a thickness Ta of the housing <NUM> in the Z-direction can be reduced. In addition, since the light source <NUM> is disposed on the side portion of the light guide plate <NUM>, this also contributes to thinning of the housing <NUM>. Furthermore, since the retroreflective member <NUM> is disposed horizontally in the X-direction, the range in the X-direction in which the retroreflective member <NUM> can be observed from the viewpoint U of the observer is widened, so that the viewing angle θa in the X-direction in which the aerial image <NUM> can be viewed can be increased. The viewing angle θa of the present example is at least twice the viewing angle θ of the conventional display device <NUM> illustrated in <FIG>. Similarly, since the range in the Y-direction in which the retroreflective member <NUM> can be viewed from the viewpoint U is also widened, the viewing angle in the Y-direction is also widened.

Next, a second example of the present invention will be described. In the first example, since a part of the component of the light L1 reflected by the light guide plate image <NUM> is transmitted through the polarization beam splitter <NUM>, the observer views both the original video P1 by the transmitted light and the video P2 of the aerial image <NUM> by the retroreflection in a double manner. Therefore, in the second example, the original video P1 of the light transmitted through the polarization beam splitter <NUM> is made invisible.

<FIG> is a view illustrating a cross-sectional structure of a display device 100A according to a second example, and components the same as those in <FIG> are denoted by the same reference numerals. In the second example, a polarizing member (for example, a polarizing plate or a polarizing film) <NUM> having the same or similar shape as the light guide plate image <NUM> is disposed between the light guide plate image <NUM> and the polarization beam splitter <NUM>. For example, the polarizing member <NUM> is disposed on the upper portion of the light guide plate <NUM> as illustrated in the drawing. The polarizing member <NUM> curbs transmission of the reflected light L1 of the light guide plate image <NUM> through the polarization beam splitter <NUM>. For example, the polarizing member <NUM> transmits light in a direction different from the direction of linearly polarized light transmitted by the polarization beam splitter <NUM>.

As described above, according to the present example, since the polarizing member <NUM> for curbing transmission of the reflected light L1 of the light guide plate image <NUM> through the polarization beam splitter <NUM> is provided between the light guide plate image <NUM> and the polarization beam splitter <NUM>, the observer cannot see the original video P1, and the contrast and visibility of the aerial image <NUM> can be improved.

Next, a third example of the present invention will be described. A third example relates to a spatial input device in which the display device of the first or second example is applied to a user input interface. <FIG> is a diagram illustrating a schematic configuration of a spatial input device according to the third example. The spatial input device <NUM> includes a sensor <NUM> that detects an object (for example, a user's finger or the like) on the aerial image <NUM> and a controller <NUM> that receives a detection result from the sensor <NUM> and performs various controls.

The sensor <NUM> is not particularly limited as long as it can transmit the aerial image <NUM>, but for example, a non-contact capacitive sensor can be used. In this case, the transparent protective member <NUM> illustrated in <FIG> may be replaced with a capacitive sensor. The capacitive sensor detects a change in capacitance in a region where a conductor such as a user's finger approaches, like a capacitive touch panel. As illustrated in the drawing, when the user holds the finger F over the aerial image <NUM>, the capacitive sensor <NUM> detects the approach of the finger to the aerial image <NUM> and outputs the detection result to the controller <NUM>. As a result, the user can perform input in a non-contact manner. For example, a clean and hygienic input can be realized as compared with an input button touched by an unspecified person.

The spatial input device <NUM> of the present example 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>) as an image in the air using retroreflection, the display device (<NUM>) comprising:
a transparent light guide plate (<NUM>) including a light guide plate image (<NUM>) formed on a bottom portion (<NUM>) of the light guide plate (<NUM>) and configured to reflect light as an original video (P1) of the aerial image (<NUM>);
a light source (<NUM>) configured to emit light from a side portion (<NUM>) of the light guide plate (<NUM>) toward the inside of the light guide plate (<NUM>);
a polarization beam splitter (<NUM>) disposed parallel to the light guide plate (<NUM>) and above the light guide plate (<NUM>);
a λ/<NUM> plate (<NUM>) disposed below the light guide plate (<NUM>); and
a retroreflective member (<NUM>) disposed in parallel with the light guide plate (<NUM>) and below the λ/<NUM> plate (<NUM>),
wherein the display device (<NUM>) retroreflects the original video (P1) to display the aerial image (<NUM>).