Aerial video display device and aerial video display program

Abstract

An aerial video display device according to the present invention comprises a first aerial display unit (DU1) and a second aerial display unit (DU2). The first aerial display unit (DU1) includes a first retroreflective material (11A), a first beam splitter (12A), and a first display (13A), and is configured to display a first aerial image (14A) at a position on the first display (13A) in plane symmetry with respect to the first beam splitter (12A). The second aerial display unit (DU2) includes a second retroreflective material (11B), a second beam splitter (12B), and a second display (13B), and is configured to display a second aerial image (14B) at a position on the second display (13B) in plane symmetry with respect to the second beam splitter (12B). The first aerial display unit (DU1) and the second aerial display unit (DU2) are disposed such that the first aerial image (14A) and the second aerial image (14B) are displayed at the same position.

Description

Aerial image display device and aerial image display program

[0001] The embodiments relate to an aerial image display device and an aerial image display program.

[0002] There are known image display technologies that display images from displays as aerial images. One type of technology that realizes the display of aerial images is known as AIRR (Aerial Imaging by Retro-Reflection). AIRR aerial displays can display aerial images as real images using retroreflectors and beam splitters. There is a demand for the development of higher performance aerial displays that utilize AIRR.

[0003] Hirotsugu Yamamoto, "Aerial Display Using Aerial Imaging by Retroreflection (AIRR)", Journal of the Imaging Society of Japan, 2017, Vol. 56, No. 4, pp. 341-351

[0004] The present invention has been made in light of the above circumstances, and its purpose is to provide an aerial image display device and an aerial image display program that are capable of realizing a higher performance aerial display.

[0005] An embodiment of the aerial image display device includes a first aerial display unit, a second aerial display unit, and a control circuit. The first aerial display unit includes a first retroreflective material, a first beam splitter having a first surface and a second surface, and a first display. The first aerial display unit is configured to display a first aerial image at a plane-symmetrical position on the first display relative to the first beam splitter by reflecting at least a portion of a first output light based on the display of the first display from the first surface of the first beam splitter and retroreflecting it from the first retroreflective material, and by transmitting at least a portion of the retroreflected first output light through the first beam splitter to form an image. The second aerial display unit includes a second retroreflective material, a second beam splitter having a first surface and a second surface, and a second display. The second aerial display unit is configured to form a second aerial image at a plane-symmetrical position of the second display relative to the second beam splitter by causing at least a portion of the second emitted light based on the display of the second display to reflect off the first surface of the second beam splitter and retroreflect by the second retroreflector, and by causing at least a portion of the retroreflected second emitted light to transmit through the second beam splitter and form an image. The control circuit is configured to control the first aerial display unit and the second aerial display unit to display the same image on each of the first display and the second display, and to display the first aerial image and the second aerial image at the same position.

[0006] According to the embodiment, it is possible to provide an aerial image display device and an aerial image display program that can realize a higher performance aerial display.

[0007] FIG. 1 is a schematic diagram showing an example of the configuration of an aerial display unit that uses aerial imaging by retroreflection. FIG. 2 is a block diagram showing an example of the configuration of an aerial image display device according to the first embodiment. FIG. 3 is a schematic diagram showing an example of the configuration of a display unit provided in the aerial image display device according to the first embodiment. FIG. 4 is a schematic diagram showing an example of a method of controlling the display unit using a display position adjustment mechanism provided in the aerial image display device according to the first embodiment. FIG. 5 is a schematic diagram showing an example of a viewing angle corresponding to the viewing area of ​​the display unit provided in the aerial image display device according to the first embodiment. FIG. 6 is a graph showing an example of the relationship between angle θ and the horizontal viewing angle in the aerial image display device according to the first embodiment. FIG. 7 is a schematic diagram showing an example of the configuration of a display unit in a first modified example of the first embodiment. FIG. 8 is a schematic diagram showing an example of the configuration of a display unit in a second modified example of the first embodiment. FIG. 9 is a schematic diagram showing an example of the configuration of a display unit in a third modified example of the first embodiment. FIG. 10 is a schematic diagram showing an example of the configuration of a display unit in a fourth modified example of the first embodiment. FIG. 11 is a schematic diagram showing an example of the configuration of a display unit in the fourth modified example of the first embodiment. Fig. 12 is a schematic diagram showing an example of the configuration of a display unit provided in the aerial image display device according to the second embodiment. Fig. 13 is a schematic diagram showing an example of a method for controlling the display unit by the display position adjustment mechanism provided in the aerial image display device according to the second embodiment. Fig. 14 is a schematic diagram showing an example of a viewing angle corresponding to the viewing area of ​​the display unit provided in the aerial image display device according to the second embodiment. Fig. 15 is a schematic diagram showing an example of the configuration of a display unit in a first modified example of the second embodiment. Fig. 16 is a schematic diagram showing an example of the configuration of a display unit in a second modified example of the second embodiment. Fig. 17 is a schematic diagram showing an example of the configuration of a display unit in a third modified example of the second embodiment. Fig. 18 is a schematic diagram showing an example of the configuration of a display unit in a fourth modified example of the second embodiment. Fig. 19 is a schematic diagram showing an example of the configuration of a display unit in a fifth modified example of the second embodiment. Fig. 20 is a schematic diagram showing an example of the configuration of a display unit in a sixth modified example of the second embodiment.

[0008] Each embodiment will be described below with reference to the drawings. Each embodiment illustrates an apparatus or method for embodying the technical concept of the invention. The drawings are schematic or conceptual. The dimensions and proportions of the drawings are not necessarily the same as those of the actual apparatus. In the following description, components having the same function and configuration are assigned the same reference symbols. Numbers or letters added to the reference symbols are used to refer to the same reference symbols and to distinguish between similar elements. In the following description, two horizontal directions that intersect with each other are referred to as the "X direction" and the "Y direction," respectively. A direction that intersects with each of the X direction and the Y direction is referred to as the "Z direction." A plane parallel to each of the X direction and the Y direction is referred to as the "XY plane." A plane parallel to each of the X direction and the Z direction is referred to as the "XZ plane." A plane parallel to each of the X direction and the Y direction is referred to as the "YZ plane."

[0009] <0> Overview of Aerial Display by AIRR First, an overview of an aerial display that utilizes aerial imaging by AIRR will be described.

[0010] Fig. 1 is a schematic diagram showing an example of the configuration of an aerial display unit DU that uses aerial imaging by retroreflection. As shown in Fig. 1, the aerial display unit DU includes, for example, a retroreflector 11, a beam splitter 12, and a display 13, and is configured to display an aerial image 14 as a real image.

[0011] The retroreflective material 11 is an optical element that has the property of retroreflecting incident light. In this example, the reflective surface of the retroreflective material 11 is arranged along the XZ plane. In this example, the direction perpendicular to the reflective surface of the retroreflective material 11 corresponds to the Y direction.

[0012] The beam splitter 12 is an optical element that reflects a portion of incident light and transmits a portion of it. The beam splitter 12 has a first surface S1 and a second surface S2 opposite the first surface S1. The direction perpendicular to the first surface S1 of the beam splitter 12 intersects with the direction perpendicular to the reflective surface of the retroreflector 11. In the XY plane, the angle between the reflective surface of the retroreflector 11 and the first surface S1 of the beam splitter 12 is generally 45°. However, the angle between the reflective surface of the retroreflector 11 and the first surface S1 of the beam splitter 12 may be other values.

[0013] The display 13 is a device that displays images. In this example, the display surface of the display 13 is disposed along the YZ plane. The direction perpendicular to the display surface of the display 13 intersects with the direction perpendicular to the reflecting surface of the beam splitter 12. As a result, the outgoing light EL emitted from the display surface of the display 13 based on the image displayed by the display 13 is incident on the first surface S1 of the beam splitter 12. Note that the display method of the display 13 is not particularly limited. For example, a liquid crystal display or an organic electroluminescence (EL) display may be used as the display 13.

[0014] A portion of the output light EL from the display 13 is reflected by the first surface S1 of the beam splitter 12. A portion of the output light EL reflected by the first surface S1 of the beam splitter 12 is incident on the retroreflector 11 and is retroreflected by the retroreflector 11. A portion of the retroreflected light passes through the beam splitter 12 and forms an aerial image 14. In other words, the aerial image 14 is formed on the second surface S2 side of the beam splitter 12.

[0015] The relationship between the position of the aerial image 14 and the position of the display 13 is plane-symmetrical with respect to the beam splitter 12. In other words, the aerial display unit DU displays (forms) the aerial image 14 at a plane-symmetrical position of the display 13 with respect to the beam splitter 12. The aerial image 14 can be viewed by an observer within a viewing area VRA. The viewing area VRA corresponds to the range in which the observer can see the aerial image 14 without any omissions. The viewing angle φ1 (i.e., the horizontal viewing angle) corresponding to the viewing area VRA of the aerial display unit DU is calculated by the following equation (1).

[0016]

[0017] "r" in equation (1) corresponds to the width of the retroreflective material 11. "d" in equation (1) corresponds to the width of the display 13. In the aerial display unit DU, the retroreflective material 11 and the display 13 are each designed to satisfy "d<r". "L" in equation (1) corresponds to the distance between the back part of the aerial display unit DU and the aerial image 14. In this example, the back part of the aerial display unit DU corresponds to the reflective surface of the retroreflective material 11.

[0018] The aerial display unit DU referred to in each embodiment described below has a configuration similar to that described using Fig. 1. In this specification, a case will be described in which blocking of light retroreflected by the retroreflective material 11 by the display 13 in the aerial display unit DU is not taken into consideration.

[0019] <1> First Embodiment The first embodiment relates to an aerial image display device 1 that expands the viewing angle corresponding to the viewing area VRA of an aerial image 14 by combining two aerial image optical systems (aerial display units DU). Details of the aerial image display device 1 according to the first embodiment will be described below.

[0020] <1-1> Configuration First, the configuration of the aerial image display device 1 according to the first embodiment will be described.

[0021] <1-1-1> Hardware configuration of the aerial image display device 1 Figure 2 is a block diagram showing an example of the hardware configuration of the aerial image display device 1 according to the first embodiment. As shown in Figure 2, the aerial image display device 1 includes, for example, a display unit 10, a display position adjustment mechanism 20, a processor 30, a memory 40, and an input interface 50. The display unit 10, the display position adjustment mechanism 20, the processor 30, the memory 40, and the input interface 50 are configured to be able to communicate with each other.

[0022] The display unit 10 is configured to display one aerial image 14 as a real image using two aerial display units DU. The specific configuration of the display unit 10 will be described later. The display position adjustment mechanism 20 is configured to be able to adjust the position and installation angle of some of the components included in the display unit 10. The display position adjustment mechanism 20 can adjust, for example, the position and installation angle of the display 13 included in the aerial display unit DU, or the installation angle between the two aerial display units DU.

[0023] The processor 30 is an integrated circuit capable of executing various programs and controls the overall operation of the aerial image display device 1. The processor 30 is, for example, a CPU (Central Processing Unit). The memory 40 stores programs, control data, etc. for controlling the aerial image display device 1. The memory 40 may be used as a work area for the processor 30. The input interface 50 is an interface circuit that can input image data to be displayed on the aerial image display device 1 to the aerial image display device 1.

[0024] The aerial image display device 1 may be configured to display not only externally input image data but also image data stored in its own storage device. The aerial image display device 1 may include an MPU (Micro Processing Unit) instead of a CPU. The processing described in each embodiment may be realized by dedicated hardware. The processor 30 may also be called a control circuit. When the aerial image 14 is displayed at a fixed position, the display position adjustment mechanism 20 may be omitted from the aerial image display device 1.

[0025] <1-1-2> Configuration of Display Unit 10 Figure 3 is a schematic diagram showing an example of the configuration of the display unit 10 provided in the aerial image display device 1 according to the first embodiment. As shown in Figure 3, the display unit 10 includes aerial display units DU1 and DU2. Each of the aerial display units DU1 and DU2 has a configuration similar to that of the aerial display unit DU described using Figure 1.

[0026] Hereinafter, the reference numerals of the components associated with aerial display units DU1 and DU2 will have an "A" and a "B" suffix added, respectively. Specifically, aerial display unit DU1 includes a retroreflector 11A, a beam splitter 12A, and a display 13A, and is configured to display aerial image 14A as a real image. Aerial display unit DU2 includes a retroreflector 11B, a beam splitter 12A, and a display 13A, and is configured to display aerial image 14B as a real image.

[0027] The arrangement of aerial display unit DU1 is obtained by flipping the aerial display unit DU described using Fig. 1 in the X direction and appropriately rotating it around the Z axis. The arrangement of aerial display unit DU2 is obtained by appropriately rotating the aerial display unit DU described using Fig. 1 around the Z axis. The positional relationship between aerial display unit DU1 and aerial display unit DU2 is plane-symmetric with respect to the YZ plane.

[0028] A portion of the outgoing light EL1 emitted from the display surface of the display 13A is reflected by the beam splitter 12A and retroreflected by the retroreflector 11A. A portion of the retroreflected outgoing light EL1 then passes through the beam splitter 12A and forms an aerial image 14A. The positional relationship between the aerial image 14A and the display 13A is plane-symmetric with respect to the beam splitter 12A.

[0029] A portion of the output light EL2 emitted from the display surface of display 13B is reflected by beam splitter 12B and retroreflected by retroreflector 11B. A portion of the retroreflected output light EL2 then passes through beam splitter 12B and forms an aerial image 14B. The positional relationship between aerial image 14B and display 13B is plane-symmetric with respect to beam splitter 12B.

[0030] As described above, in display unit 10, output light EL1 from display 13A forms aerial image 14A at a position symmetrical with respect to beam splitter 12A, and output light EL2 from display 13B forms aerial image 14B at a position symmetrical with respect to beam splitter 12B. In the first embodiment, the image displayed by display 13A and the image displayed by display 13B are each composed of similar images. Display unit 10 is configured so that misalignment between aerial images 14A and 14B is suppressed by control of aerial display units DU1 and DU2 by display position adjustment mechanism 20, allowing a single aerial image 14 to be displayed.

[0031] <1-2> Operation Next, as the aerial image display method according to the first embodiment, we will explain the operation of the aerial image display device 1. The operation described below can be realized by the processor 30 of the aerial image display device 1 executing the aerial image display program.

[0032] <1-2-1> Control method of display unit 10 Figure 4 is a schematic diagram showing an example of a control method of display unit 10 by display position adjustment mechanism 20 provided in the aerial image display device 1 according to the first embodiment. Figure 4 shows the specific positions and installation angles of displays 13A and 13B controlled by display position adjustment mechanism 20 for the configuration of display unit 10 shown in Figure 3.

[0033] In the following description, the origin of the XY coordinate system is set at the rear of the display unit 10, between the aerial display units DU1 and DU2. "L" in FIG. 4 corresponds to the distance between the rear of the display unit 10 and the aerial image 14, i.e., the depth of the aerial image 14. "θ" in FIG. 4 corresponds to the installation angle between the two aerial display units DU1 and DU2. Specifically, "θ" corresponds to the angle formed in the XY plane between the second surface S2 of the beam splitter 12A of the aerial display unit DU1 and the second surface S2 of the beam splitter 12B of the aerial display unit DU2, i.e., the angle between the beam splitters 12A and 12B, and satisfies 0°<θ<90°.

[0034] As shown in FIG. 4 , when aerial image 14 is displayed at coordinates (0, -L), display 13A is controlled to be located at coordinates (X1, Y1) = (L * sin(θ), -L * cos(θ)) and to have an installation angle of θ degrees. The installation angle of display 13A corresponds to the angle between the display surface of display 13A and the X direction on the XY plane. In other words, display position adjustment mechanism 20 tilts the display surface of display 13A by θ degrees from the X direction (horizontal direction) and positions display 13A at coordinates (L * sin(θ), -L * cos(θ)).

[0035] Furthermore, when aerial image 14 is displayed at coordinates (0, -L), display 13B is controlled so that the coordinates (X2, Y2) on the XY plane are located at (-L*sin(θ), -L*cos(θ)) and the installation angle is θ°. The installation angle of display 13B corresponds to the angle between the display surface of display 13B and the X direction on the XY plane. In other words, display position adjustment mechanism 20 tilts the display surface of display 13B by θ° from the X direction (horizontal direction) and positions display 13B at coordinates (L*sin(θ), -L*cos(θ)).

[0036] Processor 30 can calculate changes in the positions of displays 13A and 13B that accompany changes in the position of aerial image 14 based on the image data input to aerial image display device 1. Processor 30 can then control display position adjustment mechanism 20 based on the position changes of displays 13A and 13B to adjust the positions of displays 13A and 13B. In this way, the aerial image display device 1 according to the first embodiment can display aerial image 14 as a real image at coordinates (0, -L), which is a combination of aerial image 14A displayed by aerial display unit DU1 and aerial image 14B displayed by aerial display unit DU2.

[0037] In the aerial image display device 1 according to the first embodiment, when the aerial image 14 is displayed at a fixed position and the positions of the displays 13A and 13B are not dynamically changed, the aerial display units DU1 and DU2 may be designed so that the above-described positional relationship between the aerial image 14 and the displays 13A and 13B is satisfied. In this case, the display position adjustment mechanism 20 may be omitted from the aerial image display device 1 according to the first embodiment.

[0038] <1-2-2> Viewing angle of display unit 10 Figure 5 is a schematic diagram showing an example of a viewing angle corresponding to the viewing area VRA of display unit 10 provided in the aerial image display device 1 according to the first embodiment. Figure 5 shows the viewing angle φ2 corresponding to the viewing area VRA of display unit 10 for the configuration of display unit 10 shown in Figure 3. As shown in Figure 5, the viewing angle φ2 corresponding to the viewing area VRA of display unit 10 is calculated using the following equation (2).

[0039]

[0040] "r" in equation (2) corresponds to the width of each of the retroreflective materials 11A and 11B. "d" in equation (2) corresponds to the width of each of the displays 13A and 13B. In the display unit 10, the retroreflective materials 11A and 11B and the displays 13A and 13B are each designed to satisfy "d<r." "L" in equation (2) corresponds to the distance between the back part of the display unit 10 and the aerial image 14.

[0041] That is, the viewing angle φ2 of the viewing area VRA in the XY plane of the display unit 10 can be calculated from the sizes of the displays 13A and 13B, the sizes of the retroreflectors 11A and 11B, the angle between the beam splitters 12A and 12B, and the depth of the aerial image 14. As shown in equation (2), the smaller θ is, the larger the viewing angle φ2 is. Therefore, when the minimum depth distance L of the aerial image 14 is known, the optimal θ (hereinafter referred to as "θmin") is calculated using the following equation (3).

[0042]

[0043] <1-3> Effects of the First Embodiment The aerial image display device 1 according to the first embodiment makes it possible to realize a high-performance aerial display that can display an aerial image 14 with a wide viewing angle. The effects of the first embodiment will be described in detail below.

[0044] Because aerial displays using AIRR can be easily enlarged, they are expected to be useful in applications such as allowing multiple people to view an aerial image simultaneously. However, with an aerial display using AIRR, the viewing angle at which the aerial image can be viewed is limited to the range in which both the beam splitter and the retroreflector can be viewed simultaneously. In other words, the viewing angle is limited depending on the arrangement of the beam splitter and the retroreflector, which may limit the number of people who can view the aerial image.

[0045] In contrast, the aerial image display device 1 according to the first embodiment has a configuration that combines two aerial image optical systems (i.e., aerial display units DU1 and DU2). Emitted light EL1 from display 13A forms an aerial image 14A at a plane-symmetric position relative to beam splitter 12A, and emitted light EL2 from display 13B forms an aerial image 14B at a plane-symmetric position relative to beam splitter 12B. Displays 13A and 13B are positioned so that the position of aerial image 14A formed by display 13A coincides with the position of aerial image 14B formed by display 13B. In other words, a display position adjustment mechanism 20 controls each of aerial display units DU1 and DU2 so as to align the positions of aerial images 14A and 14B.

[0046] As a result, the aerial image display device 1 according to the first embodiment displays aerial images 14A and 14B as a single aerial image 14, and the viewing angle of aerial image 14 can be configured by combining the viewing angles of aerial display units DU1 and DU2. Therefore, the aerial image display device 1 according to the first embodiment can widen the horizontal viewing angle in an AIRR-based aerial display, thereby achieving a high-performance aerial display.

[0047] Furthermore, in the aerial image display device 1, the positions of the aerial images 14A and 14B displaying the same image are aligned, thereby preventing the visual switching between the aerial images 14A and 14B as the viewpoint moves. The display position adjustment mechanism 20 can prevent misalignment of the aerial images 14A and 14B by adjusting the positions of the displays 13A and 13B in accordance with changes in the positions of the beam splitters 12A and 12B. The aerial image display device 1 can calculate optimal control values ​​for the aerial display units DU1 and DU2 from the position of the aerial image 14, and calculate the position change of the displays 13A and 13B in accordance with the change in the position of the aerial image 14.

[0048] FIG. 6 is a graph showing an example of the relationship between angle θ and horizontal viewing angle in the aerial image display device 1 according to the first embodiment. In FIG. 6, the dashed line indicates the horizontal viewing angle when a single aerial display unit DU is used under the same simulation conditions as in the comparative example. The simulation conditions used were r = 100 cm, d = 10 cm, and L = 100 cm. As shown in FIG. 6, the horizontal viewing angle in the aerial image display device 1 according to the first embodiment tends to narrow as θ increases. For example, the viewing angle in the comparative example is 48.4°, whereas in the first embodiment, the viewing angle when θ = 60° is 102.0° and when θ = 80° is 92.1°. Thus, the viewing angle in the first embodiment is wider than in the comparative example in the range of 0° < θ < 90°. Therefore, the combination of two aerial display units DU1 and DU2 can provide a wider viewing angle than when a single aerial display unit DU is used.

[0049] <1-4> Modifications of the First Embodiment The configuration of the display unit 10 described in the first embodiment can be modified as appropriate. Below, first to fifth modifications of the first embodiment will be described in order as modifications of the display unit 10 in the first embodiment. Note that the first to fifth modifications of the first embodiment may be combined to the extent possible.

[0050] <1-4-1> First Modification of First Embodiment Figure 7 is a schematic diagram showing an example of the configuration of the display unit 10a in a first modification of the first embodiment. As shown in Figure 7, the display unit 10a includes aerial display units DUa1 and DUa2. The aerial display unit DUa1 includes a retroreflector 11A, a beam splitter 12A, and a three-dimensional display 13aA. The aerial display unit DUa2 includes a retroreflector 11B, a beam splitter 12B, and a three-dimensional display 13aB.

[0051] Each of the three-dimensional displays 13aA and 13aB is a display capable of displaying a three-dimensional image. For example, a 3D holographic display is used as the three-dimensional displays 13aA and 13aB. The depth of the image displayed on each of the three-dimensional displays 13aA and 13aB needs to be inverted in order to correctly represent the depth in the aerial image 14. In other words, image data with inverted depth is input to each of the three-dimensional displays 13aA and 13aB. The other configurations of the display unit 10a in the first modification of the first embodiment are the same as those of the display unit 10 in the first embodiment.

[0052] The aerial image 14 displayed by the display unit 10 of the first embodiment tends to have a strong sense of flatness because it does not change with a change in viewpoint. In contrast, in the first modification of the first embodiment, the aerial image 14A formed by the light EL1 emitted from the stereoscopic display 13aA and the aerial image 14B formed by the light EL2 emitted from the stereoscopic display 13aB each have a three-dimensional appearance based on the display of the stereoscopic displays 13aA and 13aB. As a result, the aerial image 14 displayed by the display unit 10a changes with a change in viewpoint, creating a three-dimensional effect. Therefore, the display unit 10a in the first modification of the first embodiment can display a more three-dimensional aerial image 14 with a less flat appearance than the first embodiment.

[0053] Note that, as the display unit 10a in the first modified example of the first embodiment, a curved display may be used instead of the three-dimensional displays 13aA and 13aB. Even in such a case, the display unit 10a can display the aerial image 14 with a three-dimensional effect based on the shape of the curved display. Even when a curved display is used, it is preferable that the depth of the image displayed on the curved display be inverted. The processor 30 may generate depth-inverted image data based on the image data input via the input interface 50. Then, the processor 30 may input the depth-inverted image data to the display unit 10.

[0054] <1-4-2> Second Modification of First Embodiment Figure 8 is a schematic diagram showing an example of the configuration of the display unit 10b in a second modification of the first embodiment. As shown in Figure 8, the display unit 10b includes aerial display units DUb1 and DUb2. Aerial display unit DUb1 includes a retroreflector 11A, a beam splitter 12bA, a polarized display 13bA, and a quarter-wave plate 15A. Aerial display unit DUb2 includes a retroreflector 11B, a beam splitter 12bB, a polarized display 13bB, and a quarter-wave plate 15B.

[0055] Each of the beam splitters 12bA and 12bB is an optical element whose reflection and transmission characteristics change depending on the polarization direction. For example, a reflective polarizing film is used as the beam splitters 12bA and 12bB. The following describes a case where each of the beam splitters 12bA and 12bB has the characteristics of reflecting S-polarized light and transmitting P-polarized light.

[0056] The quarter-wave plate 15A covers the reflective surface of the retroreflector 11A. The polarized display 13bA is a display that displays an image using S-polarized emitted light EL1s. The emitted light EL1s is reflected by the first surface S1 of the beam splitter 12bA and retroreflected by the retroreflector 11A. The retroreflected emitted light EL1s is converted into P-polarized emitted light EL1p via the quarter-wave plate 15A. The emitted light EL1p passes through the beam splitter 12bA and forms an aerial image 14A.

[0057] The quarter-wave plate 15B covers the reflective surface of the retroreflector 11B. The polarized display 13bB is a display that displays an image using S-polarized emitted light EL2s. The emitted light EL1s is reflected by the first surface S1 of the beam splitter 12bB and retroreflected by the retroreflector 11B. The retroreflected emitted light EL2s is converted into P-polarized emitted light EL2p via the quarter-wave plate 15B. The emitted light EL2p passes through the beam splitter 12bB and forms an aerial image 14B.

[0058] Other configurations of the display unit 10b in the second modified example of the first embodiment are similar to those of the display unit 10 in the first embodiment.

[0059] The brightness of the aerial image 14 formed by the display unit 10 of the first embodiment is reduced by utilizing reflection and transmission by the beam splitter 12. For example, assume that no attenuation of brightness occurs in optical elements other than the beam splitter 12. In this case, the aerial image 14 in the display unit 10 using the beam splitter 12 with a reflectance of 50% and a transmittance of 50% is formed using 25% of the light EL emitted from the display 13.

[0060] In contrast, the display unit 10b in the second modification of the first embodiment improves brightness by utilizing polarization characteristics. For example, in the above configuration, by utilizing polarization characteristics, the aerial image 14A is formed using 100% of the light from the polarized display 13bA, and the aerial image 14B is formed using 100% of the light from the polarized display 13bB. As a result, the display unit 10b can display the aerial image 14 with higher brightness than the first embodiment.

[0061] In the display unit 10b, light that passes directly through the beam splitter 12bA from the polarizing display 13bA can be removed. Similarly, in the display unit 10b, light that passes directly through the beam splitter 12bB from the polarizing display 13bB can be removed. In the second modification of the first embodiment, the polarizing displays 13bA and 13bB may be displays that display images using P-polarized light. In this case, optical elements that reflect P-polarized light and transmit S-polarized light are used as the beam splitters 12bA and 12bB. Each of the polarizing displays 13bA and 13bB may be a combination of a display and a polarizing plate. For example, a combination of the display 13A and a polarizing plate that transmits S-polarized light is equivalent to the polarizing display 13bA that displays images using S-polarized light EL1s.

[0062] <1-4-3> Third Modification of First Embodiment FIG. 9 is a schematic diagram showing an example of the configuration of a display unit 10c in a third modification of the first embodiment. As shown in FIG. 9, the display unit 10c includes aerial display units DUc1 and DUc2. Aerial display unit DUc1 includes a retroreflector 11A, a beam splitter 12cA, a polarizing display 13cA, a quarter-wave plate 15A, and a polarizing absorption plate 16A. Aerial display unit DUc2 includes a retroreflector 11B, a beam splitter 12cB, a polarizing display 13cB, a quarter-wave plate 15B, and a polarizing absorption plate 16B.

[0063] The beam splitters 12cA and 12cB are optical elements whose reflection and transmission characteristics change depending on the polarization direction. The reflection and transmission characteristics of the beam splitters 12cA and 12cB differ from each other depending on the polarization direction. The polarizing absorption plate 16A is an optical element that absorbs one of S-polarized and P-polarized light, and the polarizing absorption plate 16B is an optical element that absorbs the other of S-polarized and P-polarized light. The polarizing absorption plate 16A is provided to cover the second surface S2 of the beam splitter 12cA. The polarizing absorption plate 16B is provided to cover the second surface S2 of the beam splitter 12cB.

[0064] In the following, a case will be described in which the beam splitter 12cA has the property of reflecting P-polarized light and transmitting S-polarized light, and the beam splitter 12cB has the property of reflecting S-polarized light and transmitting P-polarized light. In this case, the polarization absorption plate 16A is configured to have the property of absorbing P-polarized light, and the polarization absorption plate 16B is configured to have the property of absorbing S-polarized light.

[0065] The polarized display 13cA is a display that displays an image using P-polarized output light EL1p. The output light EL1p is reflected by the first surface S1 of the beam splitter 12cA and retroreflected by the retroreflector 11A. The retroreflected output light EL1p is converted into P-polarized output light EL1p via the quarter-wave plate 15A. The output light EL1p passes through the beam splitter 12cA and the polarization absorption plate 16A and forms an aerial image 14A.

[0066] The polarized display 13cB is a display that displays an image using S-polarized emitted light EL2s. The emitted light EL1s is reflected by the first surface S1 of the beam splitter 12cB and retroreflected by the retroreflector 11B. The retroreflected emitted light EL2s is converted into P-polarized emitted light EL2p via the quarter-wave plate 15B. The emitted light EL2p passes through the beam splitter 12cB and the polarization absorption plate 16B and forms an aerial image 14B.

[0067] Other configurations of the display unit 10c in the third modified example of the first embodiment are similar to those of the display unit 10b in the second modified example of the first embodiment.

[0068] In the display unit 10 of the first embodiment, stray light may occur due to unintended light behavior, such as surface reflection of the retroreflective materials 11A and 11B. In contrast, the display unit 10c of the third modified example of the first embodiment eliminates stray light by utilizing polarization characteristics. For example, in the above configuration, by utilizing polarization characteristics, the output light EL1s transmitted through the beam splitter 12cA and the polarization absorption plate 16A is absorbed when irradiated onto the polarization absorption plate 16B. Similarly, the output light EL2p transmitted through the beam splitter 12cB and the polarization absorption plate 16B is absorbed when irradiated onto the polarization absorption plate 16A. In this way, the display unit 10c can eliminate stray light and display an aerial image 14 of higher quality than the first embodiment.

[0069] In the third modification of the first embodiment, the polarized displays 13cA and 13cB may be displays that display images using S-polarized and P-polarized light, respectively. In this case, the beam splitter 12cA may be an optical element that reflects S-polarized light and transmits P-polarized light, and the beam splitter 12cB may be an optical element that reflects P-polarized light and transmits S-polarized light. Furthermore, the polarized light absorption plate 16A is configured to absorb S-polarized light, and the polarized light absorption plate 16B is configured to absorb P-polarized light. Each of the polarized displays 13cA and 13cB may be a combination of a display and a polarizing plate. In this case, in the third modification of the first embodiment, for example, a combination of the display 13A and a polarizing plate that transmits P-polarized light and a combination of the display 13B and a polarizing plate that transmits S-polarized light are used.

[0070] <1-4-4> Fourth Modification of First Embodiment Figure 10 is a schematic diagram showing an example of the configuration of a display unit 10d in a fourth modification of the first embodiment. As shown in Figure 10, the display unit 10d includes aerial display units DUd1 and DUd2. Aerial display unit DUd1 includes a retroreflector 11A, a beam splitter 12dA, a polarizing display 13dA, a quarter-wave plate 15A, and a polarization absorption plate 16dA. Aerial display unit DUd2 includes a retroreflector 11B, a beam splitter 12dB, a polarizing display 13dB, a quarter-wave plate 15B, and a polarization absorption plate 16dB.

[0071] The beam splitters 12dA and 12dB are optical elements whose reflection and transmission characteristics change depending on the polarization direction. The reflection and transmission characteristics of the beam splitters 12dA and 12dB differ from each other depending on the polarization direction. The polarizing absorption plate 16A is an optical element that absorbs one of left-diagonally polarized light and right-diagonally polarized light, and the polarizing absorption plate 16B is an optical element that absorbs the other of left-diagonally polarized light and right-diagonally polarized light. The polarizing absorption plate 16dA is provided to cover the second surface S2 of the beam splitter 12dA. The polarizing absorption plate 16dB is provided to cover the second surface S2 of the beam splitter 12dB.

[0072] In the following, a case will be described in which the beam splitter 12dA has the property of reflecting left-diagonally polarized light and transmitting right-diagonally polarized light, and the beam splitter 12cB has the property of reflecting right-diagonally polarized light and transmitting left-diagonally polarized light. In this case, the polarization absorption plate 16dA is configured to absorb left-diagonally polarized light, and the polarization absorption plate 16dB is configured to absorb right-diagonally polarized light.

[0073] The polarized display 13dA is a display that displays an image using left-diagonally polarized output light EL1dl. The output light EL1dl is reflected by the first surface S1 of the beam splitter 12dA and retroreflected by the retroreflector 11A. The retroreflected output light EL1dl is converted into right-diagonally polarized output light EL1dr via the quarter-wave plate 15A. The output light EL1dr passes through the beam splitter 12dA and the polarization absorption plate 16dA and forms an aerial image 14A.

[0074] The polarized display 13dB is a display that displays an image using right-diagonally polarized output light EL2dr. The output light EL1dr is reflected by the first surface S1 of the beam splitter 12dB and retroreflected by the retroreflector 11B. The retroreflected output light EL2dr is converted into left-diagonally polarized output light EL2dl via the quarter-wave plate 15B. The output light EL2dl passes through the beam splitter 12dB and the polarization absorption plate 16dB and forms an aerial image 14B.

[0075] Other configurations of the display unit 10d in the fourth modified example of the first embodiment are similar to those of the display unit 10c in the third modified example of the first embodiment.

[0076] In the display unit 10c according to the third modification of the first embodiment, stray light can be eliminated, but a difference in brightness between the left and right sides due to the difference in polarization direction can occur. In contrast, the display unit 10d according to the fourth modification of the first embodiment uses linearly polarized light at an oblique angle of 45°, and not only the components but also the polarization direction are provided symmetrically.

[0077] For example, in the above configuration, the output light EL1dr that has passed through the beam splitter 12dA and the polarization absorption plate 16dA is absorbed when it is irradiated onto the polarization absorption plate 16dB. Similarly, the output light EL2dl that has passed through the beam splitter 12dB and the polarization absorption plate 16dB is absorbed when it is irradiated onto the polarization absorption plate 16dA. In this way, the display unit 10d can remove stray light, similar to the third modification of the first embodiment.

[0078] Furthermore, in display unit 10d, the polarization directions of polarized displays 13dA and 13dB are tilted by 45°, so that the polarization directions of light coming from aerial display unit DUd1 and light coming from aerial display unit DUd2 are orthogonal yet symmetrical. This reduces the difference in brightness between the left and right sides of aerial image 14 in display unit 10d.

[0079] As described above, by using left-diagonal polarized light and right-diagonal polarized light, the display unit 10d can eliminate stray light and suppress the difference in luminance between the left and right sides of the aerial image 14. As a result, the display unit 10d in the fourth modification of the first embodiment can display an aerial image 14 of higher quality than the third modification of the first embodiment.

[0080] In the fourth modification of the first embodiment, the polarized displays 13dA and 13dB may be displays that display images using right-diagonally polarized and left-diagonally polarized light, respectively. In this case, the beam splitter 12dA may be an optical element that reflects right-diagonally polarized light and transmits left-diagonally polarized light, and the beam splitter 12dB may be an optical element that reflects left-diagonally polarized light and transmits right-diagonally polarized light. The polarized light absorption plate 16dA may be configured to absorb right-diagonally polarized light, and the polarized light absorption plate 16dB may be configured to absorb left-diagonally polarized light. Each of the polarized displays 13dA and 13dB may be a combination of a display and a polarizer. For example, the combination of the display 13A and a polarizer that transmits left-diagonally polarized light is equivalent to the polarized display 13dA that displays images using left-diagonally polarized light EL1dl. In this case, in the fourth modified example of the first embodiment, for example, a combination of the display 13A and a polarizing plate that transmits left-diagonally polarized light and a combination of the display 13B and a polarizing plate that transmits right-diagonally polarized light are used.

[0081] <1-4-5> Fifth Modification of First Embodiment Fig. 11 is a schematic diagram showing an example of the configuration of a display unit 10e in a fifth modification of the first embodiment. As shown in Fig. 11, the display unit 10e has a configuration in which a beam splitter 17 is added to the display unit 10 of the first embodiment. The beam splitter 17 is disposed on the movement path of the aerial image 14. The movement path of the aerial image 14 is based on the movable range of the displays 13A and 13B and the installation angle between the aerial display units DU1 and DU2.

[0082] The direction perpendicular to the surface of beam splitter 17 intersects with both the direction perpendicular to the second surface S2 of beam splitter 12A and the direction perpendicular to the second surface S2 of beam splitter 12B. In this example, display unit 10e forms a triangular area in the XY plane surrounded by beam splitters 12A, 12B, and 17. The other configurations of display unit 10e in the fifth modified example of the first embodiment are similar to those of display unit 10 in the first embodiment.

[0083] In the display unit 10e according to the fifth modified example of the first embodiment, a beam splitter 17 is disposed on the path of movement of the aerial image 14. This allows the display unit 10e to have both a mirror function and a function of displaying the aerial image 14. For example, by using the display unit 10e, the observer can simultaneously observe the aerial image 14 and the reflection in the mirror (beam splitter 17). Furthermore, the display unit 10e can also produce an effect in which the aerial image 14 moves back and forth between inside and outside the mirror. The display unit 10e according to the fifth modified example of the first embodiment can thus realize an aerial display with higher performance than that of the first embodiment.

[0084] <2> Second Embodiment The aerial image display device 1 according to the second embodiment improves the three-dimensional effect of the aerial image by combining two aerial image optical systems (aerial display units DU). The following describes the aerial image display device 1 according to the second embodiment, focusing on the differences from the first embodiment.

[0085] <2-1> Configuration First, the configuration of the aerial image display device 1 according to the second embodiment will be described.

[0086] Fig. 12 is a schematic diagram showing an example of the configuration of the display unit 10f included in the aerial image display device 1 according to the second embodiment. As shown in Fig. 12, the display unit 10f includes aerial display units DUf1 and DUf2. Each of the aerial display units DUf1 and DUf2 has a configuration similar to that of the aerial display unit DU described using Fig. 1, except for the installation angles of the displays 13A and 13B.

[0087] Specifically, aerial display unit DUf1 includes retroreflector 11A, beam splitter 12A, and display 13A, and is configured to display aerial image 14A as a real image. Aerial display unit DUf2 includes retroreflector 11B, beam splitter 12A, and display 13A, and is configured to display aerial image 14B as a real image.

[0088] In the second embodiment, displays 13A and 13B are configured to display different images. For example, displays 13A and 13B display images from different viewpoints. Display unit 10f then forms aerial image 14 by intersecting aerial images 14A and 14B through control of aerial display units DUf1 and DUf2 by display position adjustment mechanism 20. Other configurations of the aerial image display device 1 according to the second embodiment are the same as those of the first embodiment.

[0089] <2-2> Operation Next, as an aerial image display method according to the second embodiment, we will explain the operation of the aerial image display device 1. The operation described below can be realized by the processor 30 of the aerial image display device 1 executing the aerial image display program.

[0090] <2-2-1> Control method for display unit 10f Figure 13 is a schematic diagram showing an example of a control method for the display unit by display position adjustment mechanism 20 provided in the aerial image display device 1 according to the second embodiment. Figure 13 shows the specific positions and installation angles of displays 13A and 13B controlled by display position adjustment mechanism 20 for the configuration of display unit 10f shown in Figure 12.

[0091] As shown in FIG. 13 , when aerial image 14 is displayed at coordinates (0, −L), display 13A is controlled to be located at coordinates (X1, Y1) = (L * sin(θ), −L * cos(θ)) and to have an installation angle of β degrees. The installation angle of display 13A corresponds to the angle between the display surface of display 13A and the X direction on the XY plane, and is calculated as β = θ + α, where α is a value that can be changed as appropriate depending on the image to be displayed and the position of aerial image 14. Display position adjustment mechanism 20 tilts the display surface of display 13A by β degrees from the X direction (horizontal direction) to position display 13A at coordinates (L * sin(θ), −L * cos(θ)).

[0092] Furthermore, when aerial image 14 is displayed at coordinates (0, -L), display 13B is controlled to be located at coordinates (X2, Y2) = (-L * sin(θ), -L * cos(θ)) and to have an installation angle of β degrees. The installation angle of display 13B corresponds to the angle between the display surface of display 13B and the X direction on the XY plane, and is calculated as β = θ + α. Display position adjustment mechanism 20 tilts the display surface of display 13B by β degrees from the X direction (horizontal direction) and positions display 13B at coordinates (-L * sin(θ), -L * cos(θ)).

[0093] In the second embodiment, each of the aerial images 14A and 14B is displayed tilted by α° with respect to the X direction. In the second embodiment, the different aerial images 14A and 14B are displayed at the same position, and therefore the appearance of the aerial image 14 changes as the observer's viewpoint moves.

[0094] As in the first embodiment, the processor 30 of the second embodiment can calculate changes in the positions of the displays 13A and 13B that accompany changes in the position of the aerial image 14 based on the video data. The processor 30 can then control the display position adjustment mechanism 20 based on the changes in the positions of the displays 13A and 13B to adjust the positions and installation angles of the displays 13A and 13B. This allows the aerial image display device 1 of the second embodiment to display, as a real image at coordinates (0, -L), an aerial image 14 formed by the intersection of the aerial image 14A produced by the aerial display unit DUf1 and the aerial image 14B produced by the aerial display unit DUf2.

[0095] In the aerial image display device 1 according to the second embodiment, when the aerial image 14 is displayed at a fixed position and the positions of the displays 13A and 13B are not dynamically changed, it is sufficient that the aerial display units DUf1 and DUf2 are designed so that the above-described positional relationship between the aerial image 14 and the displays 13A and 13B is satisfied. In this case, the display position adjustment mechanism 20 can be omitted from the aerial image display device 1 according to the second embodiment.

[0096] <2-2-2> Viewing angle of display unit 10f Figure 14 is a schematic diagram showing an example of the viewing angle corresponding to the viewing area of ​​display unit 10f provided in the aerial image display device 1 according to embodiment 2. Figure 14 shows three types of viewing areas VRA1 to VRA3 formed by display unit 10f for the configuration of display unit 10f shown in Figure 12.

[0097] As shown in Figure 14, visual recognition area VRA1 is an area in which aerial image 14A based on the display of display 13A can be viewed. Visual recognition area VRA2 is an area in which aerial image 14B based on the display of display 13B can be viewed. Visual recognition area VRA3 is an area in which aerial image 14 composed of a portion of aerial image 14A and a portion of aerial image 14B can be viewed. By devising the display ranges of displays 13A and 13B, display unit 10f can eliminate the area in which one of the missing aerial images is visible.

[0098] The viewing angle φ3 corresponding to the viewing area VRA2 of the display unit 10 is calculated by the following equation (4).

[0099]

[0100] The viewing angle φ4 corresponding to the viewing area VRA3 of the display unit 10 is calculated by the following equation (5).

[0101]

[0102] "r" in equations (4) and (5) corresponds to the width of each of the retroreflectors 11A and 11B. "d" in equations (4) and (5) corresponds to the width of each of the displays 13A and 13B. In the display unit 10f, the retroreflectors 11A and 11B and the displays 13A and 13B are designed to satisfy "d<r". "L" in equations (4) and (5) corresponds to the distance between the back of the display unit 10f and the aerial image 14. "θ" in equation (4) is set in the range 0°<θ<90°. "α" in equations (4) and (5) corresponds to the tilt of the aerial image 14 in the XY plane.

[0103] Viewing angle φ3 corresponds to the range in which only one of aerial images 14A and 14B is visible. The viewing angle of viewing area VRA1 in the XY plane of display unit 10f is the same as that of viewing area VRA2. Viewing angle φ4 corresponds to the range in which both aerial images 14A and 14B are visible. In this way, the viewer can view aerial image 14, which changes as the viewpoint moves.

[0104] <2-3> Effects of the second embodiment When two aerial display units DU1 and DU2 are used as in the first embodiment, the horizontal viewing angle can be expanded, but since the aerial image 14 does not change as the viewpoint moves, the aerial image 14 tends to have a stronger flat appearance.

[0105] In contrast, the aerial image display device 1 according to the second embodiment adjusts the orientation and display content of displays 13A and 13B in a configuration that combines two aerial image optical systems (i.e., aerial display units DUf1 and DUf2). Specifically, in the second embodiment, aerial display units DUf1 and DUf2 each display aerial images from different viewpoints. As in the first embodiment, displays 13A and 13B are positioned so that the position of aerial image 14A displayed by display 13A coincides with the position of aerial image 14B displayed by display 13B.

[0106] As a result, the aerial image display device 1 according to the second embodiment can change the appearance of the aerial image 14 depending on the viewpoint. Therefore, the aerial image display device 1 according to the second embodiment can enhance the three-dimensional effect of the aerial image 14 in an AIRR aerial display, thereby achieving a high-performance aerial display.

[0107] Furthermore, similar to the first embodiment, the display position adjustment mechanism 20 in the second embodiment can suppress deviation of the aerial images 14A and 14B by adjusting the positions of the displays 13A and 13B in accordance with changes in the positions of the beam splitters 12A and 12B. Similarly, the aerial image display device 1 in the second embodiment can calculate optimal control values ​​for the aerial display units DU1 and DU2 from the position of the aerial image 14, and can calculate changes in the positions of the displays 13A and 13B in accordance with changes in the position of the aerial image 14.

[0108] <2-4> Modifications of the Second Embodiment The configuration of the display unit 10f described in the second embodiment can be modified as appropriate. Below, first to sixth modifications of the second embodiment will be described in order as modifications of the display unit 10f in the second embodiment. Note that the first to sixth modifications of the second embodiment may be combined to the extent possible.

[0109] <2-4-1> First Modification of Second Embodiment Figure 15 is a schematic diagram showing an example of the configuration of the display unit 10g in the first modification of the second embodiment. As shown in Figure 15, the display unit 10g includes aerial display units DUg1 and DUg2. The aerial display units DUg1 and DUg2 have the same configuration as the aerial display units DUa1 and DUa2 described using Figure 7, except for the installation angles of the stereoscopic displays 13aA and 13aB.

[0110] Specifically, the aerial display unit DUg1 includes a retroreflective material 11A, a beam splitter 12A, and a stereoscopic display 13aA. The aerial display unit DUg2 includes a retroreflective material 11B, a beam splitter 12B, and a stereoscopic display 13aB. The installation angles of the stereoscopic displays 13aA and 13aB on the display unit 10g are the same as the installation angles of the displays 13A and 13B on the display unit 10f of the second embodiment. The depth of the images displayed on the stereoscopic displays 13aA and 13aB must be inverted to correctly represent the depth in the aerial image 14. The other configurations of the display unit 10g in the first modified example of the second embodiment are the same as those in the first modified example of the first embodiment.

[0111] When viewed from the front, the display unit 10f of the second embodiment may show both the aerial image 14A from the display 13A and the aerial image 14B from the display 13B, potentially impairing the continuity of the aerial image as the viewpoint moves. In contrast, the display unit 10g of the first modified example of the second embodiment displays the aerial image 14A formed by the light EL1 emitted from the stereoscopic display 13aA and the aerial image 14B formed by the light EL2 emitted from the stereoscopic display 13aB, each with a three-dimensional effect based on the display of the stereoscopic displays 13aA and 13aB. The display unit 10g adjusts and displays the images so that the two aerial images 14A and 14B are consistent within the range in which they can be viewed. As a result, the aerial image 14 displayed by the display unit 10g maintains continuity as the viewpoint moves, allowing a stereoscopic image with a wide viewing area VRA to be observed. Therefore, the display unit 10g of the first modified example of the second embodiment can display a higher-quality aerial image 14 than the second embodiment.

[0112] Note that, as the display unit 10g in the first modified example of the second embodiment, a curved display may be used instead of the stereoscopic displays 13aA and 13aB. Even in such a case, the display unit 10g can display the aerial image 14 with a three-dimensional effect based on the shape of the curved display. Even when a curved display is used, it is preferable that the depth of the image displayed on the curved display be inverted. Furthermore, the processor 30 may generate depth-inverted image data based on image data input via the input interface 50. Then, the processor 30 may input the depth-inverted image data to the display unit 10g.

[0113] <2-4-2> Second Modification of Second Embodiment Figure 16 is a schematic diagram showing an example of the configuration of a display unit 10h in a second modification of the second embodiment. As shown in Figure 16, the display unit 10h includes aerial display units DUh1 and DUh2. The aerial display unit DUh1 includes a retroreflector 11A, a beam splitter 12A, and a directional display 13hA. The aerial display unit DUh2 includes a retroreflector 11B, a beam splitter 12B, and a directional display 13hB.

[0114] Each of the directional displays 13hA and 13hB is a display capable of displaying multiple types of images by utilizing directivity. The directional display 13hA emits output light EL1a toward one end of the beam splitter 12A (the origin side of the XY plane) and emits output light EL1b toward the other end of the beam splitter 12A. The output light EL1a and EL1b are included in the viewing areas VRA1 and VRA3, respectively. The directional display 13hA emits output light EL2a toward one end of the beam splitter 12B (the origin side of the XY plane) and emits output light EL2b toward the other end of the beam splitter 12B. The output light EL2a and EL2b are included in the viewing areas VRA2 and VRA3, respectively. In this way, the light emitted from each directional display 13h toward the origin reaches an observer in front of the aerial image 14 (an observer whose viewpoint position is included in the visible area VRA3).

[0115] It is preferable that the image displayed by directional display 13hA using emitted light EL1a and EL1b have continuity. Similarly, it is preferable that the image displayed by directional display 13hB using emitted light EL2a and EL2b have continuity. In the second modification of the second embodiment, display unit 10h displays the same image using emitted light EL1b and EL2b corresponding to the overlapping viewing area VRA3 between directional displays 13hA and 13hB. The other configurations of display unit 10a in the second modification of the second embodiment are the same as those of display unit 10f in the second embodiment.

[0116] When the aerial image 14 displayed by the display unit 10f of the second embodiment is viewed from the front of the display unit 10f (e.g., in the viewing area VRA3), the aerial images displayed by the displays 13A and 13B may be visible, resulting in a lack of consistency. In contrast, the display unit 10h of the second modified embodiment of the second embodiment uses the directional displays 13hA and 13hB as described above to display the same image in the viewing area VRA3. As a result, the display unit 10h of the second modified embodiment of the second embodiment can ensure the consistency of the aerial image 14 viewed from the front and can display different aerial images at three viewpoints (viewing areas VRA1 to VRA3). Therefore, the display unit 10 of the second modified embodiment of the second embodiment can display aerial images 14 of higher quality than the second embodiment.

[0117] The aerial image 14 displayed by the display unit 10h is observed as a bent shape due to the combination of two planes. Therefore, the display unit 10h may display a perspective projection image that appears as a single plane according to each viewing area VRA (the viewpoint position of the observer).

[0118] <2-4-3> Third Modification of Second Embodiment Figure 17 is a schematic diagram showing an example of the configuration of the display unit 10i in a third modification of the second embodiment. As shown in Figure 17, the display unit 10i includes aerial display units DUi1 and DUi2. The aerial display units DUi1 and DUi2 have the same configuration as the aerial display units DUb1 and DUb2 described using Figure 8, except for the installation angles of the polarized displays 13bA and 13bB.

[0119] Specifically, the aerial display unit DUi1 includes a retroreflector 11A, a beam splitter 12bA, a polarizing display 13bA, a quarter-wave plate 15A, and a polarizing absorption plate 16A. The aerial display unit DUi2 includes a retroreflector 11B, a beam splitter 12bB, a polarizing display 13bB, a quarter-wave plate 15B, and a polarizing absorption plate 16B. The installation angles of the polarizing displays 13bA and 13bB in the display unit 10i are the same as the installation angles of the displays 13A and 13B in the display unit 10f of the second embodiment. In the example shown in FIG. 17, the beam splitters 12bA and 12bB are each configured to reflect S-polarized light and transmit P-polarized light. The other configurations of the display unit 10i in the third variant of the second embodiment are the same as those in the second variant of the first embodiment.

[0120] The brightness of the aerial image 14 produced by the display unit 10f of the second embodiment is reduced by utilizing reflection and transmission by the beam splitter 12. In contrast, the display unit 10i of the third modified example of the second embodiment improves brightness by utilizing polarization characteristics, as in the second modified example of the first embodiment. For example, in the configuration shown in FIG. 17 , the aerial image 14A is formed using 100% of the light from the polarized display 13bA, and the aerial image 14B is formed using 100% of the light from the polarized display 13bB. As a result, the display unit 10i can display the aerial image 14 with higher brightness than the second embodiment.

[0121] In the display unit 10i, light that passes directly through the beam splitter 12bA from the polarizing display 13bA can be removed. Similarly, in the display unit 10i, light that passes directly through the beam splitter 12bB from the polarizing display 13bB can be removed. The polarizing displays 13bA and 13bB may be displays that display images using P-polarized light. In this case, optical elements that reflect P-polarized light and transmit S-polarized light are used as the beam splitters 12bA and 12bB. Each of the polarizing displays 13bA and 13bB in the third modification of the second embodiment may be a combination of a display and a polarizing plate.

[0122] <2-4-4> Fourth Modification of Second Embodiment Figure 18 is a schematic diagram showing an example of the configuration of a display unit 10j in a fourth modification of the second embodiment. As shown in Figure 18, the display unit 10j includes aerial display units DUj1 and DUj2. The aerial display units DUj1 and DUj2 have the same configuration as the aerial display units DUc1 and DUc2 described using Figure 9, except for the installation angles of the polarized displays 13cA and 13cB.

[0123] Specifically, the aerial display unit DUj1 includes a retroreflector 11A, a beam splitter 12cA, a polarizing display 13cA, a quarter-wave plate 15A, and a polarizing absorption plate 16A. The aerial display unit DUj2 includes a retroreflector 11B, a beam splitter 12cB, a polarizing display 13cB, a quarter-wave plate 15B, and a polarizing absorption plate 16B. The installation angles of the polarizing displays 13cA and 13cB in the display unit 10j are the same as the installation angles of the displays 13A and 13B in the display unit 10f of the second embodiment.

[0124] 18, beam splitter 12cA has the property of reflecting P-polarized light and transmitting S-polarized light, and beam splitter 12cB has the property of reflecting S-polarized light and transmitting P-polarized light. In this case, polarization absorption plate 16A is configured to have the property of absorbing P-polarized light, and polarization absorption plate 16B is configured to have the property of absorbing S-polarized light. The other configurations of display unit 10j in the fourth modification of the second embodiment are the same as those in the third modification of the first embodiment.

[0125] In the display unit 10f of the second embodiment, stray light may occur due to unintended light behavior, such as surface reflection of the retroreflective materials 11A and 11B. In contrast, the display unit 10j of the fourth modified example of the second embodiment eliminates stray light by utilizing polarization characteristics. For example, in the above configuration, by utilizing polarization characteristics, the output light EL1s transmitted through the beam splitter 12cA and the polarization absorption plate 16A is absorbed when irradiated onto the polarization absorption plate 16B. Similarly, the output light EL2p transmitted through the beam splitter 12cB and the polarization absorption plate 16B is absorbed when irradiated onto the polarization absorption plate 16A. As a result, the display unit 10j of the fourth modified example of the second embodiment can eliminate stray light and display aerial images 14 of higher quality than the second embodiment.

[0126] In the fourth modification of the second embodiment, the polarized displays 13cA and 13cB may be displays that display images using S-polarized and P-polarized light, respectively. In this case, the beam splitter 12cA uses an optical element that reflects S-polarized light and transmits P-polarized light, and the beam splitter 12cB uses an optical element that reflects P-polarized light and transmits S-polarized light. Furthermore, the polarized light absorption plate 16A is configured to absorb S-polarized light, and the polarized light absorption plate 16B is configured to absorb P-polarized light. Each of the polarized displays 13cA and 13cB in the third modification of the second embodiment may be a combination of a display and a polarizing plate.

[0127] <2-4-5> Fifth Modification of Second Embodiment Figure 19 is a schematic diagram showing an example of the configuration of a display unit 10k in a fifth modification of the second embodiment. As shown in Figure 19, the display unit 10k includes aerial display units DUk1 and DUk2. The aerial display units DUk1 and DUk2 have the same configuration as the aerial display units DUd1 and DUd2 described using Figure 10, except for the installation angles of the polarized displays 13dA and 13dB.

[0128] Specifically, the aerial display unit DUk1 includes a retroreflector 11A, a beam splitter 12dA, a polarizing display 13dA, a quarter-wave plate 15A, and a polarizing absorption plate 16dA. The aerial display unit DUk2 includes a retroreflector 11B, a beam splitter 12dB, a polarizing display 13dB, a quarter-wave plate 15B, and a polarizing absorption plate 16dB. The installation angles of the polarizing displays 13dA and 13dB in the display unit 10k are the same as the installation angles of the displays 13A and 13B in the display unit 10f of the second embodiment.

[0129] 19 , the beam splitter 12dA has the property of reflecting left-diagonally polarized light and transmitting right-diagonally polarized light, and the beam splitter 12dB has the property of reflecting right-diagonally polarized light and transmitting left-diagonally polarized light. In this case, the polarization absorption plate 16dA is configured to absorb left-diagonally polarized light, and the polarization absorption plate 16dB is configured to absorb right-diagonally polarized light. The other configurations of the display unit 10k in the fifth modification of the second embodiment are the same as those in the fourth modification of the first embodiment.

[0130] While the display unit 10j in the fourth modification of the second embodiment can eliminate stray light, a difference in brightness between the left and right sides may occur due to differences in polarization direction. In contrast, the display unit 10k in the fifth modification of the second embodiment, like the fourth modification of the first embodiment, uses linearly polarized light at a 45° angle, and not only the components but also the polarization direction are arranged symmetrically. As a result, like the fourth modification of the first embodiment, the display unit 10k in the fifth modification of the second embodiment can eliminate stray light and suppress a difference in brightness between the left and right sides of the aerial image 14. Therefore, the display unit 10k in the fifth modification of the second embodiment can display a higher quality aerial image 14 than the fourth modification of the second embodiment.

[0131] In the fifth modification of the second embodiment, the polarized displays 13dA and 13dB may be displays that display images using right-diagonally polarized and left-diagonally polarized light, respectively. In this case, the beam splitter 12dA may be an optical element that reflects right-diagonally polarized light and transmits left-diagonally polarized light, and the beam splitter 12dB may be an optical element that reflects left-diagonally polarized light and transmits right-diagonally polarized light. Furthermore, the polarized light absorption plate 16dA is configured to absorb right-diagonally polarized light, and the polarized light absorption plate 16dB is configured to absorb left-diagonally polarized light. Each of the polarized displays 13dA and 13dB in the fifth modification of the second embodiment may be a combination of a display and a polarizing plate.

[0132] <2-4-6> Sixth Modification of Second Embodiment Fig. 20 is a schematic diagram showing an example of the configuration of a display unit 10l in a sixth modification of the second embodiment. As shown in Fig. 19, the display unit 10l has a configuration in which a beam splitter 17 is added to the display unit 10f of the second embodiment. The beam splitter 17 is disposed on the movement path of the aerial image 14. The movement path of the aerial image 14 is based on the movable range of the displays 13A and 13B and the installation angle between the aerial display units DU1 and DU2.

[0133] The direction perpendicular to the surface of beam splitter 17 intersects with the direction perpendicular to the second surface S2 of beam splitter 12A and the direction perpendicular to the second surface S2 of beam splitter 12B. In this example, display unit 10k forms a triangular area in the XY plane surrounded by beam splitters 12A, 12B, and 17. The other configurations of display unit 10l in the sixth modification of the second embodiment are similar to those of display unit 10f in the second embodiment.

[0134] In the display unit 10l in the sixth modified example of the second embodiment, a beam splitter 17 is disposed on the movement path of the aerial image 14. This allows the display unit 10l to have both a function as a mirror and a function to display the aerial image 14. For example, by using the display unit 10l, the observer can simultaneously observe the aerial image 14 and the reflection in the mirror (beam splitter 17). Furthermore, the display unit 10l can also produce an effect in which the aerial image 14 moves back and forth between inside and outside the mirror. In this way, the display unit 10l in the sixth modified example of the second embodiment can realize an aerial display with higher performance than that of the second embodiment.

[0135] <3> Other In this specification, "planar view" means viewing the XY plane from above. In this specification, "width" corresponds to the longitudinal length of a component in a planar view. "depth" corresponds to the short-side direction of a component in a planar view. "Rear portion" corresponds to the rear portion of display unit 10 when an observer observes aerial image display device 1. "P-polarized light" corresponds to linearly polarized light in which the electric field oscillates parallel to the plane in which the incident light and the outgoing light exist. "S-polarized light" corresponds to linearly polarized light in which the electric field oscillates perpendicular to the plane in which the incident light and the outgoing light exist. "Right-angled polarized light" corresponds to linearly polarized light in which the oscillation direction of S-polarized light is tilted by 45°, for example. "Left-angled polarized light" corresponds to linearly polarized light in which the oscillation direction of S-polarized light is tilted by -45°, for example.

[0136] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention.

[0137] DESCRIPTION OF SYMBOLS 1...Aerial image display device 10, 10a to 10l...Display unit 11, 11A, 11B...Retroreflective material 12, 12A, 12B, 12bA, 12bB, 12cA, 12cB, 12dA, 12dB...Beam splitter 13, 13A, 13B...Display 13aA, 13aB...3D display 13bA, 13bB, 13cA, 13cB, 13dA, 13dB...Polarized display 13hA, 13hB...Directional display 14, 14A, 14B...Aerial image 15A, 15B...1 / 4 wavelength plate 16A, 16B, 16dA, 16dB...Polarizing absorption plate 17...Beam splitter 20...Display position adjustment mechanism 30...Processor 40...Memory 50...Input interface DU1, DU2, DUa1, DUa2, DUb1, DUc1, DUc2, DUd1, DUd2, DUf1, DUf2, DUg1, DUg2, DUh1, DUh2, DUi1, DUi2, DUj1, DUj2, DUk1, DUk2...Aerial display units EL1, EL2, EL1a, EL2a, EL1b, EL2b, EL1dl, EL2dl, EL1dr, EL2dr, EL1p, EL2p, EL1s, EL2s...Emitted light S1...First surface S2...Second surface VRA1, VRA2, VRA3...Visibility area

Claims

1. A first aerial display unit including a first retroreflective material, a first beam splitter having a first surface and a second surface, and a first display, wherein at least a portion of a first outgoing light based on a display of the first display is reflected by the first surface of the first beam splitter and retroreflected by the first retroreflective material, and at least a portion of the retroreflected first outgoing light passes through the first beam splitter to form an image, thereby displaying a first aerial image at a plane-symmetrical position of the first display with respect to the first beam splitter; An aerial image display device comprising: a second aerial display unit including a second retroreflective material, a second beam splitter having a first surface and a second surface, and a second display, wherein at least a portion of second output light based on a display of the second display is reflected by the first surface of the second beam splitter and retroreflected by the second retroreflective material, and at least a portion of the retroreflected second output light passes through the second beam splitter to form an image, thereby forming a second aerial image at a plane-symmetrical position with respect to the second beam splitter of the second display; and wherein the first aerial display unit and the second aerial display unit are arranged so that the first aerial image and the second aerial image are displayed in the same position.

2. The aerial image display device of claim 1, further comprising a control circuit configured to control the first aerial display unit and the second aerial display unit so as to display the same image on each of the first display and the second display, and so that the first aerial image and the second aerial image are displayed in the same position.

3. The aerial image display device according to claim 1, wherein each of the first display and the second display is a stereoscopic display.

4. The aerial image display device of claim 1, further comprising a first quarter-wave plate arranged to cover the reflective surface of the first retroreflective material, and a second quarter-wave plate arranged to cover the reflective surface of the second retroreflective material, wherein each of the first display and the second display is a polarized display, the first display configured to emit the first outgoing light with a first linear polarization and the second display configured to emit the second outgoing light with the first linear polarization, and each of the first beam splitter and the second beam splitter configured to reflect the first linearly polarized light and transmit second linearly polarized light that is linearly polarized in a direction perpendicular to the first linearly polarized light.

5. The display further comprises a first quarter-wave plate provided to cover the reflective surface of the first retroreflective material, a second quarter-wave plate provided to cover the reflective surface of the second retroreflective material, a first polarizing absorbing plate provided to cover the second surface of the first beam splitter, and a second polarizing absorbing plate provided to cover the second surface of the second beam splitter, each of the first display and the second display being a polarized display, the first display being configured to emit the first output light with a first linearly polarized light, and the second display being configured to emit the second output light with a second linearly polarized light that is linearly polarized in a direction perpendicular to the first linearly polarized light, the first beam splitter being configured to reflect the first linearly polarized light and transmit the second linearly polarized light, and the second beam splitter being configured to reflect the second linearly polarized light and transmit the first linearly polarized light, 2. The aerial image display device according to claim 1, wherein the first polarizing absorbing plate is configured to absorb the light of the first linear polarization, and the second polarizing absorbing plate is configured to absorb the light of the second linear polarization.

6. An aerial image display device as described in claim 5, wherein the first linearly polarized light is linearly polarized light whose vibration direction of S-polarized light is tilted by 45°, and the second linearly polarized light is linearly polarized light whose vibration direction of S-polarized light is tilted by -45°.

7. The aerial image display device according to claim 2, further comprising a third beam splitter arranged to intersect with the movement paths of the first aerial image and the second aerial image.

8. An aerial image display program for use in the aerial image display device described in claim 1, the aerial image display program causing a computer to execute the following: displaying the same image on each of the first display and the second display; and controlling the first aerial display unit and the second aerial display unit so that the first aerial image and the second aerial image are displayed in the same position.

Images