Aerial image display device

Abstract

This aerial image display device comprises: a display having first and second display surfaces arranged in a first direction and each facing a second direction; a first retroreflective material having a reflective surface facing the first direction and extending in the second direction; a reflective material having a reflective surface facing the first display surface; a first beam splitter that is inclined with respect to the first display surface and the first retroreflective material between the first display surface and the reflective material and intersects the first retroreflective material at a first starting point on the display side; a second retroreflective material that has a reflective surface facing the second display surface; and a second beam splitter that is inclined with respect to the second display surface and the second retroreflective material between the second display surface and the second retroreflective material and intersects the second retroreflective material at a second starting point on the first retroreflective material side. A third length of a difference between a first length from the first display surface to the first retroreflective material via the first beam splitter, the reflective material, and the first beam splitter, and a second length from the second display surface to the second retroreflective material via the second beam splitter is substantially equal to a fourth length between the first and second starting points in the first direction.

Description

Aerial image display device

[0001] The embodiment relates to an aerial image display device.

[0002] Aerial image display technologies have been proposed that display aerial images as if objects were actually present in empty space. For example, aerial image optical systems using retrotransmissive or retroreflective elements, such as dihedral corner reflector arrays (DCRAs) or micro mirror array plates (MMAPs), display real aerial images. Furthermore, aerial image optical systems using half mirrors display virtual aerial images.

[0003] A real aerial image is displayed closer to the user than a virtual aerial image, and therefore provides a greater sense of reality in space. However, because a real aerial image is a real image on a display, the aerial image itself does not provide a sense of three-dimensionality.

[0004] Therefore, as a method for presenting a real aerial image with a sense of three-dimensionality to a user, a method has been proposed in which a field of view is added to the aerial image by using a naked-eye 3D display.

[0005] Gun A. Lee, Hye Sun Park, Mark Billinghurst, “Optical-Reflection Type 3D Augmented Reality Mirrors,” In Proceedings of the 25th ACM Symposium on Virtual Reality Software and Technology, 2019. doi: 10.1145 / 3359996.3364782

[0006] However, the proposed method uses a naked-eye 3D display to display a real aerial image with a three-dimensional effect, which raises concerns about the device configuration becoming complicated.

[0007] The present invention has been made in light of the above-mentioned circumstances, and an object of the present invention is to provide a means for presenting a three-dimensional aerial image to a user using a simple device configuration.

[0008] An aerial image display device according to one embodiment includes a display, a first retroreflective material, a reflector, a first beam splitter, a second retroreflective material, a second beam splitter, a first wave plate, a second wave plate, and a third wave plate. The display has a first display surface and a second display surface aligned in a first direction and each facing a second direction intersecting the first direction. The first retroreflective material has a reflective surface facing the first direction and extending in the second direction. The reflective material has a reflective surface facing the first display surface. The first beam splitter is disposed between the first display surface and the reflector at an angle relative to the first display surface and the first retroreflective material, and intersects with the first retroreflective material or an extension of the first retroreflective material at a first starting point on the display side. The second retroreflective material has a reflective surface facing the second display surface. The second beam splitter is disposed between the second display surface and the second retroreflective material at an angle relative to the second display surface and the second retroreflective material, and intersects with the second retroreflective material or an extension of the second retroreflective material at a second starting point on the first retroreflective material side. The first wave plate is disposed between the first beam splitter and the first retroreflective material. The second wave plate is disposed between the first beam splitter and the reflector. The third wave plate is disposed between the second beam splitter and the second retroreflective material. A third length, which is the difference between a first length of the optical path from the first display surface that passes through the first beam splitter, is reflected by the reflective material, is reflected by the first beam splitter, and reaches the first retroreflective material, and a second length of the optical path from the second display surface that passes through the second beam splitter and reaches the second retroreflective material, is approximately equal to a fourth length from the first starting point to the second starting point in the first direction.

[0009] According to the embodiment, it is possible to provide a means for presenting a three-dimensional aerial image to a user with a simple device configuration.

[0010] FIG. 1 is a plan view showing an example of the configuration of an aerial image display device according to a first embodiment. FIG. 2 is a plan view showing an example of an aerial image displayed by the aerial image display device according to the first embodiment. FIG. 3 is a plan view showing an example of the configuration of an aerial image display device according to a second embodiment. FIG. 4 is a plan view showing an example of an aerial image displayed by the aerial image display device according to the second embodiment. FIG. 5 is a plan view showing an example of the configuration of an aerial image display device according to a third embodiment. FIG. 6 is a plan view showing an example of an aerial image displayed by the aerial image display device according to the third embodiment. FIG. 7 is a plan view showing an example of the configuration of an aerial image display device according to a fourth embodiment. FIG. 8 is a plan view showing an example of an aerial image displayed by the aerial image display device according to the fourth embodiment. FIG. 9 is a plan view showing an example of the configuration of an aerial image display device according to a fifth embodiment. FIG. 10 is a plan view showing an example of an aerial image displayed by the aerial image display device according to the fifth embodiment.

[0011] Hereinafter, several embodiments will be described with reference to the drawings. In the following description, components having the same functions and configurations will be given the same reference numerals.

[0012] The aerial image display device described below is a device equipped with a real image optical system configured to display two real aerial images in a multi-layered manner based on an image displayed on the display surface of a display. Each of the two real aerial images displayed by the aerial image display device is displayed in a direction substantially perpendicular to the display surface.

[0013] For ease of explanation, the plane parallel to the display surface of the display provided in the aerial image display device will be referred to as the XY plane below. Furthermore, the plane parallel to the display surface of the two real aerial images will be referred to as the YZ plane. The direction where the XY plane and the YZ plane intersect will be referred to as the Y direction. The direction perpendicular to the Y direction in the XY plane will be referred to as the X direction. The direction perpendicular to the Y direction in the YZ plane will be referred to as the Z direction. The opposite direction of the user's line of sight LOS (i.e., the direction approaching the user) will be considered to coincide with the X direction.

[0014] 1. First Embodiment An aerial image display device according to a first embodiment will be described.

[0015] 1.1 Configuration of the Aerial Image Display Device Fig. 1 is a plan view showing an example of an aerial image display device according to Embodiment 1. Fig. 1 shows the planar positional relationship of a display 10, a retroreflector 11, a beam splitter 12, a total reflector 13, a beam splitter 14, and a retroreflector 15 when viewed in the Y direction.

[0016] The aerial image display device 1 includes a display 10 , a retroreflective material 11 , a beam splitter 12 , a total reflector 13 , a beam splitter 14 , and a retroreflective material 15 .

[0017] The display 10 is a flat display arranged with its display surface facing inward of the aerial image display device 1. The display surface of the display 10 is divided into two partial display surfaces S1 and S2 aligned in the X direction. Each of the partial display surfaces S1 and S2 has a length H in the X direction (H is a positive real number). The partial display surfaces S1 and S2 are arranged so as to be tangent in the X direction. The display 10 is configured to be able to display images that are independent of each other on the partial display surfaces S1 and S2.

[0018] The retroreflective material 11 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 11 is arranged substantially perpendicular to the display 10 (i.e., substantially parallel to the YZ plane) so as to face in the direction from the partial display surface S1 to the partial display surface S2 of the display 10 (i.e., the X direction). The reflective surface of the retroreflective material 11 has a length H in the Z direction.

[0019] The beam splitter 12 is, for example, a non-polarizing beam splitter. The beam splitter 12 is disposed inside the aerial image display device 1 at an angle of approximately π / 4 with respect to the reflective surface of the retroreflective material 11 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 12 are aligned with both ends of the partial display surface S1 of the display 10. That is, the length of the beam splitter 12 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 12 intersects with one end of the retroreflective material 11 or an extension thereof on the display 10 side. In the first embodiment, the intersection point between the beam splitter 12 and the retroreflective material 11 is also referred to as the starting point A1. The starting point A1 also contacts the display surface of the display 10.

[0020] The total reflector 13 has a reflective surface configured to totally reflect incident light. The reflective surface of the total reflector 13 is arranged substantially parallel to the display 10 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1. The reflective surface of the total reflector 13 is arranged so as to sandwich the beam splitter 12 between itself and the partial display surface S1 of the display 10. When viewed in the Y direction, the reflective surface of the total reflector 13 is arranged at a position spaced a length s (s is a positive real number) in the Z direction from the other end of the retroreflective material 11 (the end opposite the starting point A1).

[0021] The beam splitter 14 is, for example, a non-polarizing beam splitter. The beam splitter 14 is disposed inside the aerial image display device 1 in a direction substantially perpendicular to the beam splitter 12 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 14 are aligned with both ends of the partial display surface S2 of the display 10. In other words, the length of the beam splitter 14 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 14 contacts the display surface of the display 10.

[0022] The retroreflective material 15 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 15 is arranged substantially parallel to the display 10 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1. The reflective surface of the retroreflective material 15 is arranged so as to sandwich the beam splitter 14 between the retroreflective material 15 and the partial display surface S2 of the display 10. The reflective surface of the retroreflective material 15 has a length H in the X direction. When viewed in the Y direction, one end of the retroreflective material 15 or its extension intersects with the other end of the beam splitter 14 (the end opposite the end on the display 10 side). In the first embodiment, the intersection of the beam splitter 14 and the retroreflective material 15 is also referred to as a starting point B1. The starting point B1 also contacts the other end of the beam splitter 12 (the end opposite the starting point A1).

[0023] 1.2 Display Position of Aerial Image Fig. 2 is a plan view showing an example of the display position of the aerial image displayed by the aerial image display device according to Embodiment 1. As shown in Fig. 2, the aerial image display device 1 displays display images DI1 and DI2 on partial display surfaces S1 and S2 of the display 10, respectively, thereby allowing the aerial images AI1 and AI2 to be displayed shifted in the line of sight LOS.

[0024] The display 10 displays a display image DI1 on the partial display surface S1, which is farther from the user out of the partial display surfaces S1 and S2.

[0025] The emitted light of the display image DI1 passes through the beam splitter 12 and is totally reflected by the total reflecting material 13. The light totally reflected by the total reflecting material 13 is reflected by the beam splitter 12 toward the retroreflecting material 11. The light reflected by the beam splitter 12 is retroreflected by the retroreflecting material 11. After passing through the beam splitter 12, the light retroreflected by the retroreflecting material 11 forms an aerial image AI1.

[0026] In the optical system described above, the optical path length from the display image DI1 to the retroreflective material 11 is 2(H+s). The optical path length from the retroreflective material 11 to the aerial image AI1 is equal to the optical path length from the display image DI1 to the retroreflective material 11, so the optical path length from the retroreflective material 11 to the aerial image AI1 is 2(H+s). In other words, the aerial image AI1 is formed at a position 2(H+s) away from the origin A1 in the X direction.

[0027] Furthermore, the display 10 displays a display image DI2 on the partial display surface S2, which is closer to the user out of the partial display surfaces S1 and S2.

[0028] The emitted light of the display image DI2 passes through the beam splitter 14 and is retroreflected by the retroreflector 15. The light retroreflected by the retroreflector 15 is reflected by the beam splitter 14 in the direction opposite to the retroreflector 11, and then forms an aerial image AI2.

[0029] In the optical system described above, the optical path length from the display image DI2 to the retroreflective material 15 is H. The optical path length from the retroreflective material 15 to the aerial image AI2 is equal to the optical path length from the display image DI2 to the retroreflective material 15, and therefore the optical path length from the retroreflective material 15 to the aerial image AI2 is H. In other words, the aerial image AI2 is formed at a position that is the length H away from the origin B1 in the X direction.

[0030] Here, origin B1 is located at a position away from origin A1 in the X direction by a length H. Therefore, aerial image AI1 is formed at a position away in the X direction from the imaging position of aerial image AI2 by a length 2s (i.e., a position closer to the user than the imaging position of aerial image AI2 by the length 2s).

[0031] 1.3 Effects of the First Embodiment According to the first embodiment, the partial display surfaces S1 and S2 of the display 10 are aligned in the X direction and face the Z direction. The retroreflective material 11 faces the X direction and has a reflective surface extending in the Z direction. The total reflective material 13 has a reflective surface facing the partial display surface S1. The beam splitter 12 is provided between the partial display surface S1 and the total reflective material 13 at an angle relative to the partial display surface S1 and the retroreflective material 11, and intersects with the retroreflective material 11 or an extension of the retroreflective material 11 at a starting point A1 on the display 10 side. The retroreflective material 15 has a reflective surface facing the partial display surface S2. The beam splitter 14 is provided between the partial display surface S2 and the retroreflective material 15 at an angle relative to the partial display surface S2 and the retroreflective material 15, and intersects with the retroreflective material 15 or an extension of the retroreflective material 15 at a starting point B1 on the retroreflective material 11 side. In this way, the aerial image display device 1 is configured using only one display 10 and does not require a control mechanism such as a time-division image display using a liquid crystal shutter, which allows for a simpler configuration.

[0032] Furthermore, in the aerial image display device 1, the difference between the length 2(H+s) of the optical path from partial display surface S1, passing through beam splitter 12, reflecting off total reflector 13, and then reflecting off beam splitter 12 to retroreflector 11 and the length H of the optical path from partial display surface S2, passing through beam splitter 14 to retroreflector 15, is a length H+2s, which is different from the length H from origin A1 to origin B1 in the X direction. That is, the difference H+2s between the two optical path lengths is longer than the length H between origins A1 and B1. As a result, an aerial image AI1 corresponding to display image DI1 on partial display surface S1 and an aerial image AI2 corresponding to display image DI2 on partial display surface S2 are formed at different positions as viewed by the user. Specifically, the aerial image AI1 is formed at a position closer to the user in the X direction by the length 2s than the aerial image AI2. This allows the user to be provided with aerial images AI1 and AI2 displayed in multiple layers in the depth direction.

[0033] Furthermore, the beam splitters 12 and 14 are disposed symmetrically with respect to the YZ plane, which allows the aerial images AI1 and AI2 to be displayed as aligned in the X direction without any misalignment in the Y and Z directions as viewed by the user.

[0034] 2. Second Embodiment Next, an aerial image display device according to a second embodiment will be described.

[0035] The second embodiment differs from the first embodiment in that the front-to-back relationship of the two aerial images as seen by the user is reversed. The following mainly describes the configuration that differs from the first embodiment.

[0036] 2.1 Configuration of the Aerial Image Display Device Fig. 3 is a plan view showing an example of an aerial image display device according to the second embodiment, which corresponds to Fig. 1 in the first embodiment.

[0037] The aerial image display device 1A includes a display 20, a retroreflector 21, a beam splitter 22, a total reflector 23, a beam splitter 24, and a retroreflector 25.

[0038] The display 20 is a flat display arranged with its display surface facing inward of the aerial image display device 1A. The display surface of the display 20 is divided into two partial display surfaces S3 and S4 aligned in the X direction. Each of the partial display surfaces S3 and S4 has a length H in the X direction. The partial display surfaces S3 and S4 are spaced apart by a length t in the X direction. The display 20 is configured to be able to display images that are independent of each other on the partial display surfaces S3 and S4.

[0039] The retroreflective material 21 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 21 is arranged substantially perpendicular to the display 20 (i.e., substantially parallel to the YZ plane) so as to face in the direction from the partial display surface S3 to the partial display surface S4 of the display 20 (i.e., the X direction). The reflective surface of the retroreflective material 21 has a length H in the Z direction.

[0040] The beam splitter 22 is, for example, a non-polarizing beam splitter. The beam splitter 22 is disposed inside the aerial image display device 1A at an angle of approximately π / 4 with respect to the reflective surface of the retroreflective material 21 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 22 are aligned with both ends of the partial display surface S3 of the display 20. That is, the length of the beam splitter 22 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 22 intersects with one end of the retroreflective material 21 or an extension thereof on the display 20 side. In the second embodiment, the intersection point between the beam splitter 22 and the retroreflective material 21 is also referred to as the starting point A2. The starting point A2 is separated from the display surface of the display 20 in the Z direction by a length t (t is a positive real number).

[0041] The total reflector 23 has a reflective surface configured to totally reflect incident light. The reflective surface of the total reflector 23 is arranged substantially parallel to the display 20 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1A. The reflective surface of the total reflector 23 is arranged so as to sandwich the beam splitter 22 between itself and the partial display surface S3 of the display 20. When viewed in the Y direction, the reflective surface of the total reflector 23 is in contact with the other end of the retroreflective material 21 (the end opposite the starting point A2).

[0042] The beam splitter 24 is, for example, a non-polarizing beam splitter. The beam splitter 24 is disposed inside the aerial image display device 1A in a direction approximately perpendicular to the beam splitter 22 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 24 are aligned with both ends of the partial display surface S4 of the display 20. In other words, the length of the beam splitter 24 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 24 is located at a distance of length t in the Z direction from the display surface of the display 20.

[0043] The retroreflective material 25 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 25 is arranged substantially parallel to the display 20 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1A. The reflective surface of the retroreflective material 25 is arranged so as to sandwich the beam splitter 24 between the retroreflective material 25 and the partial display surface S4 of the display 20. The reflective surface of the retroreflective material 25 has a length H in the X direction. When viewed in the Y direction, one end of the retroreflective material 25 or its extension intersects with the other end of the beam splitter 24 (the end opposite the end on the display 20 side). In the second embodiment, the intersection of the beam splitter 24 and the retroreflective material 25 is also referred to as starting point B2. Starting point B2 is located a length t away from the other end of the beam splitter 22 (the end opposite starting point A2) in the X direction.

[0044] 2.2 Display Position of Aerial Image Fig. 4 is a plan view showing an example of the display position of an aerial image displayed by the aerial image display device according to the second embodiment. Fig. 4 corresponds to Fig. 2 in the first embodiment. As shown in Fig. 4, the aerial image display device 1A displays display images DI3 and DI4 on partial display surfaces S3 and S4 of the display 20, respectively, thereby allowing the aerial images AI3 and AI4 to be displayed shifted in the line of sight LOS.

[0045] The display 20 displays a display image DI3 on ​​the partial display surface S3, which is farther from the user out of the partial display surfaces S3 and S4.

[0046] The emitted light of the display image DI3 passes through the beam splitter 22 and is totally reflected by the total reflecting material 23. The light totally reflected by the total reflecting material 23 is reflected by the beam splitter 22 towards the retroreflecting material 21. The light reflected by the beam splitter 22 is retroreflected by the retroreflecting material 21. After passing through the beam splitter 22, the light retroreflected by the retroreflecting material 21 forms an aerial image AI3.

[0047] In the optical system described above, the optical path length from the display image DI3 to the retroreflective material 21 is 2H+t. The optical path length from the retroreflective material 21 to the aerial image AI3 is equal to the optical path length from the display image DI3 to the retroreflective material 21, and therefore the optical path length from the retroreflective material 21 to the aerial image AI3 is 2H+t. In other words, the aerial image AI3 is formed at a position that is a length 2H+t away from the origin A2 in the X direction.

[0048] Furthermore, the display 20 displays a display image DI4 on the partial display surface S4, which is closer to the user out of the partial display surfaces S3 and S4.

[0049] The emitted light of the display image DI4 passes through the beam splitter 24 and is retroreflected by the retroreflector 25. The light retroreflected by the retroreflector 25 is reflected by the beam splitter 24 in the direction opposite to the retroreflector 21, and then forms an aerial image AI4.

[0050] In the optical system described above, the optical path length from the display image DI4 to the retroreflector 25 is H+t. The optical path length from the retroreflector 25 to the aerial image AI4 is equal to the optical path length from the display image DI4 to the retroreflector 25, and therefore the optical path length from the retroreflector 25 to the aerial image AI4 is H+t. In other words, the aerial image AI4 is formed at a position that is a length H+t away from the origin B2 in the X direction.

[0051] Here, starting point B2 is located at a position that is a length H+t away from starting point A2 in the X direction. Therefore, aerial image AI4 is formed at a position that is a length t away in the X direction from the position at which aerial image AI3 is formed (i.e., a position that is a length t closer to the user than the position at which aerial image AI3 is formed).

[0052] 2.3 Effects of the Second Embodiment According to the second embodiment, in the aerial image display device 1A, the difference H between the optical path length 2H+t from partial display surface S3, passing through beam splitter 22, reflecting off total reflector 23, and then reflecting off beam splitter 22 to retroreflector 21 and the optical path length H+t from partial display surface S4, passing through beam splitter 24 to retroreflector 25, is different from the length H+t from origin A2 to origin B2 in the X direction. That is, the difference H between the two optical path lengths is shorter than the length H+t between origins A2 and B2. As a result, the aerial image AI3 corresponding to display image DI3 on ​​partial display surface S3 is formed at a position farther from the user in the X direction by the length t than the aerial image AI4 corresponding to display image DI4 on partial display surface S4. This makes it possible to provide the user with aerial images AI3 and AI4 displayed in multiple layers in the depth direction.

[0053] Note that the light emitted from partial display surface S3 transmits and reflects once through beam splitter 22 and once through beam splitter 24, before forming an aerial image AI3. In contrast, the light emitted from partial display surface S4 transmits and reflects once through beam splitter 24, before forming an aerial image AI4. If the reflection losses at total reflector 23 and retroreflectors 21 and 25 can be ignored, and the transmittance and reflectance of beam splitters 22 and 24 are both 50%, the aerial image AI4 will be twice as bright as the aerial image AI3.

[0054] According to the second embodiment, the aerial image AI4 is displayed closer to the user than the aerial image AI3. This allows the aerial image with the relatively higher brightness to be in the foreground, thereby improving the user's visibility.

[0055] 3. Third Embodiment Next, an aerial image display device according to a third embodiment will be described.

[0056] The third embodiment differs from the second embodiment in that an aerial image displayed in front of the user can be displayed larger than an aerial image displayed behind the user. The following mainly describes the configuration that differs from the second embodiment.

[0057] 3.1 Configuration of the Aerial Image Display Device Fig. 5 is a plan view showing an example of an aerial image display device according to the third embodiment. Fig. 5 corresponds to Fig. 3 in the second embodiment.

[0058] The aerial image display device 1B includes a display 30, a retroreflector 31, a beam splitter 32, a total reflector 33, a beam splitter 34, and a retroreflector 35.

[0059] The display 30 is a flat display arranged with its display surface facing inward of the aerial image display device 1B. The display surface of the display 30 is divided into two partial display surfaces S5 and S6 aligned in the X direction. The partial display surfaces S5 and S6 have lengths H and H+t in the X direction, respectively. The partial display surfaces S5 and S6 are arranged to be tangent in the X direction. The display 30 is configured to be able to display images independent of each other on the partial display surfaces S5 and S6.

[0060] The retroreflective material 31 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 31 is arranged substantially perpendicular to the display 30 (i.e., substantially parallel to the YZ plane) so as to face in the direction from the partial display surface S5 to the partial display surface S6 of the display 30 (i.e., the X direction). The reflective surface of the retroreflective material 31 has a length H in the Z direction.

[0061] The beam splitter 32 is, for example, a non-polarizing beam splitter. The beam splitter 32 is disposed inside the aerial image display device 1B at an angle of approximately π / 4 with respect to the reflective surface of the retroreflective material 31 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 32 are aligned with both ends of the partial display surface S5 of the display 30. That is, the length of the beam splitter 32 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 32 intersects with one end of the retroreflective material 31 or an extension thereof on the display 30 side. In the third embodiment, the intersection point between the beam splitter 32 and the retroreflective material 31 is also referred to as starting point A3. Starting point A3 is separated from the display surface of the display 30 by a length t in the Z direction.

[0062] The total reflector 33 has a reflective surface configured to totally reflect incident light. The reflective surface of the total reflector 33 is arranged substantially parallel to the display 30 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1B. The reflective surface of the total reflector 33 is arranged so as to sandwich the beam splitter 32 between itself and the partial display surface S5 of the display 30. When viewed in the Y direction, the reflective surface of the total reflector 33 is in contact with the other end of the retroreflective material 31 (the end opposite the starting point A3).

[0063] The beam splitter 34 is, for example, a non-polarizing beam splitter. The beam splitter 34 is disposed inside the aerial image display device 1B in a direction substantially perpendicular to the beam splitter 32 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 34 are aligned with both ends of the partial display surface S6 of the display 30. In other words, the length of the beam splitter 34 when viewed in the Y direction is (H + t) × √2. When viewed in the Y direction, one end of the beam splitter 34 is located a distance t in the Z direction from the display surface of the display 30.

[0064] The retroreflective material 35 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 35 is arranged substantially parallel to the display 30 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1B. The reflective surface of the retroreflective material 35 is arranged so as to sandwich the beam splitter 34 between the retroreflective material 35 and the partial display surface S6 of the display 30. The reflective surface of the retroreflective material 35 has a length H+t in the X direction. When viewed in the Y direction, one end of the retroreflective material 35 or its extension intersects with the other end of the beam splitter 34 (the end opposite the end on the display 30 side). In the third embodiment, the intersection of the beam splitter 34 and the retroreflective material 35 is also referred to as starting point B3. Starting point B3 is located a length t away from the other end of the beam splitter 32 (the end opposite starting point A3) in the Z direction.

[0065] 3.2 Display Position of Aerial Image Fig. 6 is a plan view showing an example of the display position of an aerial image displayed by the aerial image display device according to the third embodiment. Fig. 6 corresponds to Fig. 4 in the second embodiment. As shown in Fig. 6, the aerial image display device 1B displays display images DI5 and DI6 on partial display surfaces S5 and S6 of the display 30, respectively, thereby allowing the aerial images AI5 and AI6 to be displayed shifted in the line of sight LOS.

[0066] The display 30 displays a display image DI5 on the partial display surface S5, which is farther from the user than the partial display surfaces S5 and S6.

[0067] The emitted light of the display image DI5 passes through the beam splitter 32 and is totally reflected by the total reflecting material 33. The light totally reflected by the total reflecting material 33 is reflected by the beam splitter 32 toward the retroreflecting material 31. The light reflected by the beam splitter 32 is retroreflected by the retroreflecting material 31. The light retroreflected by the retroreflecting material 31 passes through the beam splitter 32 and then forms an aerial image AI5.

[0068] In the optical system described above, the optical path length from the display image DI5 to the retroreflective material 31 is 2H+t. The optical path length from the retroreflective material 31 to the aerial image AI5 is equal to the optical path length from the display image DI5 to the retroreflective material 31, and therefore the optical path length from the retroreflective material 31 to the aerial image AI5 is 2H+t. In other words, the aerial image AI5 is formed at a position that is a length 2H+t away from the origin A3 in the X direction.

[0069] Furthermore, the display 30 displays a display image DI6 on the partial display surface S6, which is closer to the user out of the partial display surfaces S5 and S6.

[0070] The emitted light of the display image DI6 passes through the beam splitter 34 and is retroreflected by the retroreflector 35. The light retroreflected by the retroreflector 35 is reflected by the beam splitter 34 in the direction opposite to the retroreflector 31, and then forms an aerial image AI6.

[0071] In the optical system described above, the optical path length from the display image DI6 to the retroreflector 35 is H+2t. The optical path length from the retroreflector 35 to the aerial image AI6 is equal to the optical path length from the display image DI6 to the retroreflector 35, and therefore the optical path length from the retroreflector 35 to the aerial image AI6 is H+2t. In other words, the aerial image AI6 is formed at a position that is a length H+2t away from the origin B3 in the X direction.

[0072] Here, starting point B3 is located at a position away from starting point A3 in the X direction by a length H. Therefore, aerial image AI6 is formed at a position away from the imaging position of aerial image AI5 in the X direction by a length t (i.e., a position closer to the user than the imaging position of aerial image AI5 by the length t).

[0073] 3.3 Effects of the Third Embodiment According to the third embodiment, in the aerial image display device 1B, the difference between the optical path length 2H+t from partial display surface S5, passing through beam splitter 32, reflecting off total reflector 33, and then reflecting off beam splitter 32 to retroreflector 31 and the optical path length H+2t from partial display surface S6 to beam splitter 34 and then retroreflector 35 is a length H-t that is different from the length H from origin A3 to origin B3 in the X direction. In other words, the difference between the two optical path lengths H-t is shorter than the length H between origins A3 and B3. As a result, the aerial image AI5 corresponding to the display image DI5 on partial display surface S5 is formed at a position farther from the user in the X direction by the length t than the aerial image AI6 corresponding to the display image DI6 on partial display surface S6. This makes it possible to provide the user with aerial images AI5 and AI6 displayed in multiple layers in the depth direction.

[0074] As in the second embodiment, if the reflection losses at the total reflector 33 and the retroreflectors 31 and 35 can be ignored, and the transmittance and reflectance of the beam splitters 32 and 34 are both 50%, the aerial image AI6 will be twice as bright as the aerial image AI5.

[0075] According to the third embodiment, the aerial image AI6 is displayed closer to the user than the aerial image AI5. This allows the aerial image with the relatively higher brightness to be in the foreground, thereby improving the user's visibility.

[0076] Furthermore, partial display surface S6 is longer in the X direction than partial display surface S5. Accordingly, beam splitter 34 and retroreflector 35 are longer than beam splitter 32 and retroreflector 31, respectively. This allows the aerial image AI6 corresponding to the display image DI6 on partial display surface S6 to be larger than the aerial image AI5 corresponding to the display image DI5 on partial display surface S5. This allows the foreground to be displayed larger than the background, providing the user with an aerial image with a more three-dimensional feel.

[0077] 4. Fourth Embodiment An aerial image display device according to a fourth embodiment will be described.

[0078] The fourth embodiment differs from the first embodiment in that the loss of brightness when light passes through and is reflected by the beam splitter is reduced. The following mainly describes the configuration that differs from the first embodiment.

[0079] 4.1 Configuration of the Aerial Image Display Device Fig. 7 is a plan view showing an example of an aerial image display device according to the fourth embodiment. Fig. 7 corresponds to Fig. 1 in the first embodiment.

[0080] The aerial image display device 1C includes a display 40, a retroreflector 41, a beam splitter 42, a total reflector 43, a beam splitter 44, a retroreflector 45, a wave plate 46, a wave plate 47, a wave plate 48, and a polarizer 49.

[0081] The display 40 is a flat display arranged with its display surface facing inward of the aerial image display device 1C. The display surface of the display 40 is divided into two partial display surfaces S7 and S8 aligned in the X direction. Each of the partial display surfaces S7 and S8 has a length H in the X direction. The partial display surfaces S7 and S8 are arranged to be tangent in the X direction. The display 40 is configured to be able to display images that are independent of each other on the partial display surfaces S7 and S8. Furthermore, the partial display surfaces S7 and S8 of the display 40 are configured to be able to emit light of different polarization states.

[0082] The retroreflective material 41 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 41 is arranged substantially perpendicular to the display 40 (i.e., substantially parallel to the YZ plane) so as to face in the direction from the partial display surface S7 to the partial display surface S8 of the display 40 (i.e., the X direction). The reflective surface of the retroreflective material 41 has a length H in the Z direction.

[0083] The beam splitter 42 is, for example, a polarizing beam splitter. The beam splitter 42 is disposed inside the aerial image display device 1C at an angle of approximately π / 4 with respect to the reflective surface of the retroreflective material 41 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 42 are aligned with both ends of the partial display surface S7 of the display 40. That is, the length of the beam splitter 42 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 42 intersects with one end of the retroreflective material 41 or an extension thereof on the display 40 side. In the fourth embodiment, the intersection point between the beam splitter 42 and the retroreflective material 41 is also referred to as starting point A4. Starting point A4 also contacts the display surface of the display 40.

[0084] The total reflector 43 has a reflective surface configured to totally reflect incident light. The reflective surface of the total reflector 43 is arranged substantially parallel to the display 40 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1C. The reflective surface of the total reflector 43 is arranged so as to sandwich the beam splitter 42 between itself and the partial display surface S7 of the display 40. When viewed in the Y direction, the reflective surface of the total reflector 43 is arranged at a position spaced a length s in the Z direction from the other end of the retroreflective material 41 (the end opposite the starting point A4).

[0085] The beam splitter 44 is, for example, a polarizing beam splitter. The beam splitter 44 is disposed inside the aerial image display device 1C in a direction substantially perpendicular to the beam splitter 42 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 44 are aligned with both ends of the partial display surface S8 of the display 40. In other words, the length of the beam splitter 44 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 44 contacts the display surface of the display 40.

[0086] The beam splitters 42 and 44 transmit and reflect light of the same polarization state. Hereinafter, the polarization state of the light that transmits through the beam splitters 42 and 44 will be referred to as P-polarized light, and the polarization state of the light that is reflected by the beam splitters 42 and 44 will be referred to as S-polarized light.

[0087] The retroreflective material 45 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 45 is arranged substantially parallel to the display 40 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1C. The reflective surface of the retroreflective material 45 is arranged so as to sandwich the beam splitter 44 between the retroreflective material 45 and the partial display surface S8 of the display 40. The reflective surface of the retroreflective material 45 has a length H in the X direction. When viewed in the Y direction, one end of the retroreflective material 45 or its extension intersects with the other end of the beam splitter 44 (the end opposite the end on the display 40 side). In the fourth embodiment, the intersection of the beam splitter 44 and the retroreflective material 45 is also referred to as starting point B4. Starting point B4 also contacts the other end of the beam splitter 42 (the end opposite starting point A4).

[0088] Each of the wave plates 46, 47, and 48 is, for example, a λ / 4 wave plate. Each of the wave plates 46, 47, and 48 is configured to output incident light with a phase shift of π / 2 between P-polarized light and S-polarized light. The wave plate 46 is attached to the reflective surface of the retroreflective material 41. The wave plate 47 is attached to the reflective surface of the total reflector 43. The wave plate 48 is attached to the reflective surface of the retroreflective material 45.

[0089] The polarizing plate 49 is, for example, an absorbing polarizing plate. The polarizing plate 49 is configured to transmit, for example, P-polarized light and absorb light other than P-polarized light. The polarizing plate 49 is disposed, for example, between the beam splitters 42 and 44 and in parallel with the retroreflective material 41.

[0090] 4.2 Display Position of Aerial Image Fig. 8 is a plan view showing an example of the display position of an aerial image displayed by the aerial image display device according to the fourth embodiment. Fig. 8 corresponds to Fig. 2 in the first embodiment. As shown in Fig. 8, the aerial image display device 1C displays display images DI7 and DI8 on partial display surfaces S7 and S8 of the display 40, respectively, thereby allowing the aerial images AI7 and AI8 to be displayed shifted in the line of sight LOS.

[0091] The display 40 displays a display image DI7 on the partial display surface S7, which is farther from the user out of the partial display surfaces S7 and S8. The display 40 emits P-polarized light from the display image DI7.

[0092] The P-polarized outgoing light from the display image DI7 passes through the beam splitter 42 and is totally reflected by the total reflector 43 via the wave plate 47. As a result, the P-polarized outgoing light from the display image DI7 passes through the wave plate 47 twice during the total reflection process. Therefore, the light totally reflected by the total reflector 43 becomes S-polarized light due to a phase shift of π. The S-polarized reflected light from the total reflector 43 is reflected by the beam splitter 42 toward the retroreflector 41. The S-polarized reflected light from the beam splitter 42 is retroreflected by the retroreflector 41. As a result, the S-polarized reflected light from the beam splitter 42 passes through the wave plate 46 twice during the retroreflection process. Therefore, the light retroreflected by the retroreflector 41 becomes P-polarized light due to a phase shift of π. The P-polarized retroreflected light from the retroreflector 41 passes through the beam splitter 42 and the polarizing plate 49, and then forms an aerial image AI7.

[0093] In the optical system described above, the optical path length from the display image DI7 to the retroreflector 41 is 2(H+s). The optical path length from the retroreflector 41 to the aerial image AI7 is equal to the optical path length from the display image DI7 to the retroreflector 41, and therefore the optical path length from the retroreflector 41 to the aerial image AI7 is 2(H+s). That is, the aerial image AI7 is formed by P-polarized light at a position 2(H+s) away from the origin A4 in the X direction.

[0094] The display 40 also displays a display image DI8 on the partial display surface S8, which is closer to the user out of the partial display surfaces S7 and S8. The display 40 emits P-polarized light from the display image DI8.

[0095] The outgoing light of the display image DI8 passes through the beam splitter 44 and is retroreflected by the retroreflector 45 via the wave plate 48. As a result, the P-polarized outgoing light from the display image DI8 passes through the wave plate 48 twice during the retroreflection process. Therefore, the light retroreflected by the retroreflector 45 becomes S-polarized light due to a phase shift of π. The S-polarized reflected light from the retroreflector 45 is reflected by the beam splitter 44 in the direction opposite to the retroreflector 41, and then forms an aerial image AI8.

[0096] In the optical system described above, the optical path length from the display image DI8 to the retroreflector 45 is H. The optical path length from the retroreflector 45 to the aerial image AI8 is equal to the optical path length from the display image DI8 to the retroreflector 45, and therefore the optical path length from the retroreflector 45 to the aerial image AI8 is H. That is, the aerial image AI8 is formed by S-polarized light at a position distanced by the length H from the origin B4 in the X direction.

[0097] Here, starting point B4 is located at a position away from starting point A4 in the X direction by a length H. Therefore, aerial image AI7 is formed at a position away from the imaging position of aerial image AI8 in the X direction by a length 2s (i.e., a position closer to the user than the imaging position of aerial image AI8 by a length 2s).

[0098] 4.3 Effects of the Fourth Embodiment According to the fourth embodiment, in the aerial image display device 1C, the difference H+2s between the length 2(H+s) of the optical path from partial display surface S7, passing through beam splitter 42, reflecting off total reflector 43, and then reflecting off beam splitter 42 to retroreflector 41 and the length H of the optical path from partial display surface S8, passing through beam splitter 44 to retroreflector 45, is different from the length H from origin A4 to origin B4 in the X direction. That is, the difference H+2s between the two optical path lengths is longer than the length H between origins A4 and B4. As a result, the aerial image AI7 corresponding to the display image DI7 on partial display surface S7 is formed at a position closer to the user in the X direction by the length 2s than the aerial image AI8 corresponding to the display image DI8 on partial display surface S8. This makes it possible to provide the user with aerial images AI7 and AI8 displayed in multiple layers in the depth direction.

[0099] The aerial image display device 1C also includes a wave plate 46 between the beam splitter 42 and the retroreflector 41. A wave plate 47 is provided between the beam splitter 42 and the total reflector 43. A wave plate 48 is provided between the beam splitter 44 and the retroreflector 45. Each of the wave plates 46, 47, and 48 is a λ / 4 wave plate. The beam splitters 42 and 44 are polarizing beam splitters. As a result, when the beam splitters 42 and 44 are configured to transmit P-polarized light and reflect S-polarized light, and the partial display surfaces S7 and S8 are configured to emit P-polarized light, the aerial images AI7 and AI8 can be formed without loss due to transmission and reflection by the beam splitters 42 and 44. This allows the brightness of the aerial images AI7 and AI8 to be uniform and higher than when loss due to the beam splitters is incurred. This improves user visibility.

[0100] The aerial image display device 1C further includes a polarizing plate 49 between the beam splitters 42 and 44. The polarizing plate 49 is configured to selectively transmit light of the same polarization state as the light emitted from the partial display surface S7 and absorb light of other polarization states. This makes it possible to prevent stray light generated by the display image DI7, the retroreflective material 41, and the total reflective material 43 from leaking to the user.

[0101] 5. Fifth Embodiment An aerial image display device according to a fifth embodiment will be described.

[0102] The fifth embodiment differs from the fourth embodiment in that two aerial images are displayed at the same position as seen by the user, while providing the user with a three-dimensional aerial image. The following mainly describes the configuration that differs from the fourth embodiment.

[0103] 5.1 Configuration of the Aerial Image Display Device Fig. 9 is a plan view showing an example of an aerial image display device according to the fifth embodiment. Fig. 9 corresponds to Fig. 7 in the fourth embodiment.

[0104] The aerial image display device 1D includes a display 50, a retroreflector 51, a beam splitter 52, a total reflector 53, a beam splitter 54, a retroreflector 55, a wave plate 56, a wave plate 57, a wave plate 58, and a polarizer 59.

[0105] The display 50 is a flat display arranged with its display surface facing inward of the aerial image display device 1D. The display surface of the display 50 is divided into two partial display surfaces S9 and S10 aligned in the X direction. Each of the partial display surfaces S9 and S10 has a length H in the X direction. The partial display surfaces S9 and S10 are arranged to be tangent in the X direction. The display 50 is configured to be able to display images that are independent of each other on the partial display surfaces S9 and S10. Furthermore, the partial display surfaces S9 and S10 of the display 50 are configured to be able to emit light of different polarization states.

[0106] The retroreflective material 51 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 51 is arranged substantially perpendicular to the display 50 (i.e., substantially parallel to the YZ plane) so as to face in the direction from the partial display surface S9 toward the partial display surface S10 of the display 50 (i.e., the X direction). The reflective surface of the retroreflective material 51 has a length H in the Z direction.

[0107] The beam splitter 52 is, for example, a polarizing beam splitter. The beam splitter 52 is disposed inside the aerial image display device 1D at an angle of approximately π / 4 with respect to the reflective surface of the retroreflective material 51 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 52 are aligned with both ends of the partial display surface S9 of the display 50. That is, the length of the beam splitter 52 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 52 intersects with one end of the retroreflective material 51 or an extension thereof on the display 50 side. In the fifth embodiment, the intersection point between the beam splitter 52 and the retroreflective material 51 is also referred to as starting point A5. The starting point A5 is separated from the display surface of the display 50 by a length t in the Z direction.

[0108] The total reflector 53 has a reflective surface configured to totally reflect incident light. The reflective surface of the total reflector 53 is arranged substantially parallel to the display 50 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1D. The reflective surface of the total reflector 53 is arranged so as to sandwich the beam splitter 52 between itself and the partial display surface S9 of the display 50. When viewed in the Y direction, the reflective surface of the total reflector 53 is in contact with the other end of the retroreflective material 51 (the end opposite the starting point A5).

[0109] The beam splitter 54 is, for example, a polarizing beam splitter. The beam splitter 54 is disposed inside the aerial image display device 1D in a direction approximately perpendicular to the beam splitter 52 when viewed in the Y direction. When viewed in the Z direction, both ends of the beam splitter 54 are aligned with both ends of the partial display surface S10 of the display 50. In other words, the length of the beam splitter 54 when viewed in the Y direction is H × √2. When viewed in the Y direction, one end of the beam splitter 54 is located at a distance of length t in the Z direction from the display surface of the display 50.

[0110] The beam splitters 52 and 54 transmit light of the same polarization state (P polarization) and reflect light of the same polarization state (S polarization).

[0111] The retroreflective material 55 has a reflective surface configured to retroreflect incident light. The reflective surface of the retroreflective material 55 is arranged substantially parallel to the display 50 (i.e., substantially parallel to the XY plane) so as to face the inside of the aerial image display device 1D. The reflective surface of the retroreflective material 55 is arranged so as to sandwich the beam splitter 54 between the retroreflective material 55 and the partial display surface S10 of the display 50. The reflective surface of the retroreflective material 55 has a length H in the X direction. When viewed in the Y direction, one end of the retroreflective material 55 or its extension intersects with the other end of the beam splitter 54 (the end opposite the end on the display 50 side). In the fifth embodiment, the intersection of the beam splitter 54 and the retroreflective material 55 is also referred to as starting point B5. Starting point B5 also contacts the other end of the beam splitter 52 (the end opposite starting point A5).

[0112] Each of the wave plates 56, 57, and 58 is, for example, a λ / 4 wave plate. Each of the wave plates 56, 57, and 58 is configured to output incident light with a phase shift of π / 2 between P-polarized light and S-polarized light. The wave plate 56 is attached to the reflective surface of the retroreflective material 51. The wave plate 57 is attached to the reflective surface of the total reflector 53. The wave plate 58 is attached to the reflective surface of the retroreflective material 55.

[0113] The polarizing plate 59 is, for example, an absorbing polarizing plate. The polarizing plate 59 is configured to transmit, for example, P-polarized light and absorb light other than P-polarized light. The polarizing plate 59 is disposed, for example, between the beam splitters 52 and 54 and in parallel with the retroreflective material 51.

[0114] 5.2 Display Position of Aerial Image Fig. 10 is a plan view showing an example of the display position of an aerial image displayed by the aerial image display device according to the fifth embodiment. Fig. 10 corresponds to Fig. 8 in the fourth embodiment. As shown in Fig. 10, the aerial image display device 1D can display the aerial images AI9 and AI10 at the same position in the line of sight LOS by displaying the display images DI9 and DI10 on the partial display surfaces S9 and S10 of the display 50, respectively.

[0115] The display 50 displays a display image DI9 on the partial display surface S9, which is farther from the user out of the partial display surfaces S9 and S10. The display 50 emits P-polarized light from the display image DI9.

[0116] The P-polarized outgoing light from the display image DI9 passes through the beam splitter 52 and is totally reflected by the total reflector 53 via the wave plate 57. As a result, the P-polarized outgoing light from the display image DI9 passes through the wave plate 57 twice during the total reflection process. Therefore, the light totally reflected by the total reflector 53 becomes S-polarized light due to a phase shift of π. The S-polarized light reflected from the total reflector 53 is reflected by the beam splitter 52 toward the retroreflector 51. The S-polarized light reflected from the beam splitter 52 is retroreflected by the retroreflector 51. As a result, the S-polarized light reflected from the beam splitter 52 passes through the wave plate 56 twice during the retroreflection process. Therefore, the light retroreflected by the retroreflector 51 becomes P-polarized light due to a phase shift of π. The P-polarized retroreflected light from the retroreflector 51 passes through the beam splitter 52 and the polarizing plate 59, and then forms an aerial image AI9.

[0117] In the optical system described above, the optical path length from the display image DI9 to the retroreflector 51 is 2H+t. The optical path length from the retroreflector 51 to the aerial image AI9 is ​​equal to the optical path length from the display image DI9 to the retroreflector 51, and therefore the optical path length from the retroreflector 51 to the aerial image AI9 is ​​2H+t. That is, the aerial image AI9 is ​​formed by P-polarized light at a position 2H+t away from the starting point A5 in the X direction.

[0118] The display 50 also displays a display image DI10 on the partial display surface S10, which is closer to the user out of the partial display surfaces S9 and S10. The display 50 emits P-polarized light from the display image DI10.

[0119] The outgoing light of the display image DI10 passes through the beam splitter 54 and is retroreflected by the retroreflector 55 via the wave plate 58. As a result, the P-polarized outgoing light from the display image DI10 passes through the wave plate 58 twice during the retroreflection process. Therefore, the light retroreflected by the retroreflector 55 becomes S-polarized light due to a phase shift of π. The S-polarized reflected light from the retroreflector 55 is reflected by the beam splitter 54 in the direction opposite to the retroreflector 51, and then forms an aerial image AI10.

[0120] In the optical system described above, the optical path length from the display image DI10 to the retroreflector 55 is H+t. The optical path length from the retroreflector 55 to the aerial image AI10 is equal to the optical path length from the display image DI10 to the retroreflector 55, and therefore the optical path length from the retroreflector 55 to the aerial image AI10 is H+t. That is, the aerial image AI10 is formed by S-polarized light at a position a length H+t away from the origin B5 in the X direction.

[0121] Here, origin B5 is located at a position away from origin A5 in the X direction by a length H. Therefore, aerial images AI9 and AI10 are formed at the same position in the X direction (i.e., the same position as seen by the user).

[0122] A user views such aerial images AI9 and AI10 through two polarizing plates 60R and 60L. The polarizing plates 60R and 60L are absorption polarizing plates. The polarizing plate 60R is configured to selectively transmit light of one polarization state (e.g., P-polarized) of P-polarized and S-polarized light and absorb light of the other polarization state. The polarizing plate 60L is configured to selectively transmit light of the other polarization state (e.g., S-polarized) of P-polarized and S-polarized light and absorb light of the other polarization state.

[0123] The user views the aerial images AI9 and AI10 by associating polarizer 60R with the right eye and polarizer 60L with the left eye. This allows the user to view the P-polarized aerial image AI9 with the right eye and the S-polarized aerial image AI10 with the left eye. This allows the user to obtain parallax information from the aerial images AI9 and AI10.

[0124] 5.3 Effects of Fifth Embodiment According to the fifth embodiment, in the aerial image display device 1D, the difference H between the length 2H+t of the optical path from partial display surface S9, passing through beam splitter 52, reflecting off total reflector 53, and then reflecting off beam splitter 52 to reach retroreflector 51, and the length H+t of the optical path from partial display surface S10, passing through beam splitter 54 to reach retroreflector 55, is approximately equal to the length H from origin A5 to origin B5 in the X direction. As a result, an aerial image AI9 corresponding to display image DI9 on partial display surface S9 is formed at the same position in the X direction as an aerial image AI10 corresponding to display image DI10 on partial display surface S10.

[0125] The aerial image display device 1D also includes a wave plate 56 between the beam splitter 52 and the retroreflector 51. A wave plate 57 is provided between the beam splitter 52 and the total reflector 53. A wave plate 58 is provided between the beam splitter 54 and the retroreflector 55. Each of the wave plates 56, 57, and 58 is a λ / 4 wave plate. The beam splitters 52 and 54 are polarizing beam splitters. Thus, when the beam splitters 52 and 54 are configured to transmit P-polarized light and reflect S-polarized light, and the partial display surfaces S9 and S10 are configured to emit P-polarized light, the aerial images AI9 and AI10 can be formed without loss due to transmission and reflection by the beam splitters 52 and 54. This allows the brightness of the aerial images AI9 and AI10 to be uniform and higher than when loss due to the beam splitters is incurred. This improves user visibility.

[0126] The aerial image display device 1D also includes a polarizing plate 59 between the beam splitters 52 and 54. The polarizing plate 59 is configured to selectively transmit light of the same polarization state as the light emitted from the partial display surface S9 and absorb light of other polarization states. This makes it possible to prevent stray light generated by the display image DI9, the retroreflective material 51, and the total reflective material 53 from leaking to the user.

[0127] Furthermore, when the polarization states of the light emitted from partial display surfaces S9 and S10 are the same, the aerial images AI9 and AI10 have different polarization states. Specifically, when P-polarized light is emitted from partial display surfaces S9 and S10, the polarization states of aerial images AI9 and AI10 are P-polarized and S-polarized, respectively. Therefore, suggestive information can be provided by having the user view the aerial images AI9 and AI10 with their left and right eyes through polarizers 60R and 60L, which have different transmission axes.

[0128] Specifically, when the polarizer 60R corresponding to the right eye is configured to transmit P-polarized light while absorbing light other than P-polarized light, and the polarizer 60L corresponding to the left eye is configured to transmit S-polarized light while absorbing light other than S-polarized light, the user views the aerial image AI9 with their right eye and the aerial image AI10 with their left eye. As a result, if the aerial images AI9 and AI10 are the same image, the user can obtain visual field information from the real aerial images AI9 and AI10. This makes it possible to provide the user with an aerial image with a more three-dimensional feel.

[0129] 6. Modifications, etc. Various modifications can be applied to the first, second, third, fourth, and fifth embodiments described above.

[0130] In the fourth and fifth embodiments described above, the case where P-polarized light is emitted from the display has been described, but this is not limiting. For example, the light emitted from the display may be unpolarized, circularly polarized, or obliquely polarized. If the light emitted from the display is unpolarized, an absorbing polarizer that selectively transmits light of the polarization axis (e.g., P-polarized light) that is transmitted by the beam splitter may be provided between the display and the beam splitter. Furthermore, if the light emitted from the display is circularly polarized or obliquely polarized, a depolarizing film may be provided between the display and the beam splitter.

[0131] 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.

[0132] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D... Aerial image display device 10, 20, 30, 40, 50... Display 11, 15, 21, 25, 31, 35, 41, 45, 51, 55... Retroreflective material 12, 14, 22, 24, 32, 34, 42, 44, 52, 54... Beam splitter 13, 23, 33, 43, 53... Total reflector 46, 47, 48, 56, 57, 58... Wave plate 49, 59, 60R, 60L... Polarizing plate A, B... Starting point S... Display surface DI... Display image AI... Aerial image

Claims

1. A display having a first display surface and a second display surface aligned in a first direction and each facing a second direction intersecting the first direction; a first retroreflective material facing the first direction and having a reflective surface extending in the second direction; a reflective material having a reflective surface facing the first display surface; a first beam splitter disposed between the first display surface and the reflective material at an angle with respect to the first display surface and the first retroreflective material, and intersecting with the first retroreflective material or an extension of the first retroreflective material at a first starting point on the display side; a second retroreflective material having a reflective surface facing the second display surface; a second beam splitter disposed between the second display surface and the second retroreflective material at an angle with respect to the second display surface and the second retroreflective material, and intersecting with the second retroreflective material or an extension of the second retroreflective material at a second starting point on the first retroreflective material side; a first wave plate disposed between the first beam splitter and the first retroreflective material; an aerial image display device comprising: a second wave plate provided between the first beam splitter and the reflector; and a third wave plate provided between the second beam splitter and the second retroreflective material; wherein a third length which is a difference between a first length of an optical path that passes from the first display surface through the first beam splitter, is reflected by the reflector, is reflected by the first beam splitter, and reaches the first retroreflective material, and a second length of an optical path that passes from the second display surface through the second beam splitter and reaches the second retroreflective material, is approximately equal to a fourth length from the first starting point to the second starting point in the first direction.

2. An aerial image display device as described in claim 1, wherein a first aerial image corresponding to a first display image displayed on the first display surface and formed at a position separated by the first length in the first direction from the first origin, and a second aerial image corresponding to a second display image displayed on the second display surface and formed at a position separated by the second length in the first direction from the second origin have mutually different polarization states.

3. An aerial image display device according to claim 2, wherein the first beam splitter and the second beam splitter are polarizing beam splitters, and the first wave plate, the second wave plate and the third wave plate are λ / 4 wave plates.

4. An aerial image display device as described in claim 3, wherein each of the first beam splitter and the second beam splitter is configured to transmit a first linearly polarized light and reflect a second linearly polarized light that is perpendicular to the first linearly polarized light, and each of the first display surface and the second display surface is configured to emit the first linearly polarized light.

5. An aerial image display device as described in claim 4, wherein the first wave plate is configured to convert the light reflected by the reflective material from the first linearly polarized light to the second linearly polarized light, the second wave plate is configured to convert the light reflected by the first retroreflective material from the second linearly polarized light to the first linearly polarized light, and the third wave plate is configured to convert the light reflected by the second retroreflective material from the first linearly polarized light to the second linearly polarized light.

6. An aerial image display device according to claim 1, wherein the first beam splitter and the second beam splitter are disposed symmetrically with respect to a plane that intersects the first direction and includes the second direction.

7. The aerial image display device according to claim 1, further comprising a first polarizing plate provided between said first beam splitter and said second beam splitter.

8. An aerial image display device as described in claim 1, further comprising: a second polarizing plate provided between the first display surface and the first beam splitter; and a third polarizing plate provided between the second display surface and the second beam splitter.

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