Aerial image display device

Abstract

An aerial image display device characterized by comprising a first optical element and a second optical element, which are configured such that a plurality of triangular ridges including a first inclined surface and a second inclined surface are arranged on a first surface, a second surface is a flat surface, and a light flux entering the first surface at a predetermined incident angle is transmitted through the first inclined surface, is reflected by the second inclined surface, and is emitted from the second surface, and characterized in that the first optical element and the second optical element are laminated such that the arrangement directions of the ridges are orthogonal to each other.

Description

Aerial image display device

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

[0002] Aerial image display devices form real images in real space using lenses, concave mirrors, etc. Patent documents 1 to 3 propose displaying real images in the air by bonding two optical elements (mirror arrays) in which multiple mirrors are arranged in parallel so that the parallel directions of the mirrors are perpendicular to each other. Patent document 4 also proposes displaying real images in the air using an optical element (two-sided Conner reflector array) in which multiple square through-holes are provided and mirror films are formed on the inner walls of the through-holes.

[0003] JP 2011-81300 A JP 2011-81309 A JP 2013-109211 A JP 2008-158114 A WO 2017 / 171072

[0004] However, the above-mentioned aerial image display device has several problems.

[0005] First, the aerial image display devices of Patent Documents 1 to 3 are designed to reflect all light beams at a specific incident angle, as shown in Figure 14(A). However, if the angle deviates from the design angle, as shown in Figures 14(B) and 14(C), a portion of the incident light beam travels straight or is reflected twice. When a portion of the light beam that travels straight or is reflected twice by the first mirror array is reflected by the second mirror array, which is perpendicular to the first mirror array, or when the light beam reflected by the first mirror array travels straight or is reflected twice by the perpendicular mirror array, ghosts (one-dimensional real image, one-dimensional orthogonal virtual image) occur. Similarly, in the case of the aerial image display device using a two-sided Conner reflector array of Patent Document 4, light beams reflected by only one of the perpendicular side surfaces become the above-mentioned real and virtual ghost images. This ghost appears near the aerial image when the aerial image display device is close to the monitor or object. Therefore, when the field of view of the aerial image display devices of Patent Documents 1 to 3 and Patent Document 4 is widened, a distance from the monitor or object is required to avoid this ghost, resulting in a larger overall device size. Unlike lenses or concave mirrors, these aerial image display devices spread light beams at an angle roughly proportional to the angle desired from the position of the monitor or object placed on a single mirror array or two-sided Conner reflector array. Therefore, the greater the distance between the monitor or object and the aerial image display device, the lower the resolution. Furthermore, light beams that travel in a straight line through these aerial image display devices (transmitted or reflected twice by one of the mirror arrays) and ghosts of real and virtual images result in a loss of light, reducing the utilization rate of light. Furthermore, when external light is reflected from the surface of these aerial image display devices in the direction of the aerial image, glare reduces the visibility of the aerial image.

[0006] Second, the above-mentioned optical elements require many manufacturing processes, resulting in high manufacturing costs. Patent Documents 1 and 2 require many processes, such as stacking, cutting, and polishing mirror substrates. Patent Document 3 attempts to simplify the manufacturing process by stacking rectangular parallelepiped mirror units, but the process of stacking the mirror units requires high alignment precision, making the manufacturing process as complex as or even more complex than Patent Documents 1 and 2 and unsuitable for mass production. Patent Document 4 requires complex processes, such as producing a mold by cutting or electroforming, producing a main body by pressing or replica processing, forming a mirror film on the inner surface of the main body, and removing the mirror film attached to both surfaces of the main body.

[0007] In consideration of the above circumstances, the present invention aims to provide an aerial image display device that is less affected by ghosting even when placed closer to a monitor or object than conventional devices, produces bright aerial images, is small, has high resolution, and can be manufactured inexpensively.

[0008] A first aspect of the present invention is an aerial image display device comprising a first optical element and a second optical element, each having a first surface on which a plurality of triangular ridges, each including a first inclined surface and a second inclined surface, is arranged, the second surface being flat, and configured so that a light beam incident on the first surface at a predetermined angle of incidence passes through the first inclined surface, is reflected by the second inclined surface, and is emitted from the second surface, and the first optical element and the second optical element are stacked so that the arrangement directions of the ridges are perpendicular to each other.

[0009] According to the present invention, an aerial image display device can be provided that has a higher light utilization rate than conventional devices, resulting in a brighter aerial image, and does not generate ghosts between real and virtual images even when close to a monitor or object, resulting in high resolution, allowing the entire device to be made small, and can be manufactured inexpensively.

[0010] 6A and 6B are diagrams showing the structure of an aerial image display device according to an embodiment; a diagram explaining the structure of a triangular prism array constituting the aerial image display device according to an embodiment; a diagram showing an optical path in the aerial image display device according to an embodiment; a diagram showing an optical path in the aerial image display device according to an embodiment; a diagram showing an optical path in the aerial image display device according to an embodiment; a diagram showing an optical path in the aerial image display device according to an embodiment; a diagram showing an optical path in the aerial image display device according to an embodiment; a diagram showing an optical path in the aerial image display device according to an embodiment; a diagram explaining a manufacturing method of a triangular prism array constituting the aerial image display device according to an embodiment; a diagram showing an image displayed by an aerial image display device according to an embodiment and a conventional example; a diagram explaining the structure of a triangular prism array constituting the aerial image display device according to Modification 1; a diagram showing the structure of an aerial image display device according to Modification 2; a diagram explaining the shape of a triangular prism array suitable for Modification 2 of FIG. 6 and light beam propagation; a diagram explaining the shape of a triangular prism array constituting an aerial image display device according to Modification 3 and light beam propagation; a diagram explaining the shape of a triangular prism array constituting an aerial image display device according to Modification 3 and light beam propagation; a diagram explaining calculation of a magnification ratio in Modification 3. 1A to 1C are diagrams illustrating the structure of an aerial image display device according to an embodiment and the effect of canceling out color misalignment.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The components of the embodiments described below can be combined as appropriate.

[0012] [Configuration of Aerial Image Display Device] FIG. 1(A) is a diagram showing the structure of an aerial image display device 100 according to an embodiment of the present invention. As shown in the figure, the aerial image display device 100 is an orthogonal prism array configured by stacking two triangular prism arrays 1A and 1B. The triangular prism arrays 1A and 1B correspond to the first optical element and the second optical element in the present invention. FIG. 1(B) is a diagram showing the structure of the triangular prism arrays 1A and 1B. Hereinafter, the triangular prism array may be simply referred to as a prism array. Furthermore, the prism arrays 1A and 1B may be collectively referred to as a prism array 1.

[0013] 1(B), a plurality of triangular ridges 15 are arranged on a first surface 10 of the prism array 1, and a second surface 20 opposite the first surface 10 is flat. In the aerial image display device 100, the prism arrays 1A and 1B are stacked so that the surfaces on which the ridges 15 are provided face in the same direction and so that the longitudinal directions 16 of the ridges 15 are orthogonal to each other.

[0014] 2 is a diagram illustrating the structure of the prism array 1. The prism array 1 is a sawtooth triangular prism array. A first surface 10 of the prism array 1 is provided with a protrusion 15 including a first inclined surface 11 and a second inclined surface 12. A second surface 20 is flat.

[0015] A light beam incident on the first slope 11 of the first surface 10 at a predetermined angle of incidence is reflected by the second slope 12 and emerges from the second surface 20 at an emergence angle equal to the angle of incidence. In this way, the light beam is guided by reflection, so even if the refractive index of the prism array 1 is small, it can accommodate large angles of incidence and emergence. Furthermore, because the prism array 1 utilizes total reflection at the second slope 12, no light beam passes through the second slope 12, resulting in a high light utilization rate (see Patent Document 5).

[0016] 3A to 3D are diagrams illustrating the optical paths of the aerial image display device 100. As shown in Fig. 3A, the longitudinal direction of the protrusions of prism array 1B is the X-axis, the longitudinal direction of the protrusions of prism array 1A is the Y-axis, and the normal direction of first surfaces 10 of prism arrays 1A and 1B is the Z-axis.

[0017] 3(B) to 3(D), light 41 incident on the first surface 10 side of prism array 1A is reflected by prism array 1A and prism array 1B, respectively, and forms a real image in the air. Therefore, by using the aerial image display device 100, it is possible to project an object or a three-dimensional image in the air.

[0018] 4A to 4F are diagrams showing in more detail the optical paths of light incident on the prism array 1. In these diagrams, hatched areas indicate shadowed areas, solid lines indicate chief rays, and dashed lines indicate stray light.

[0019] Here, as an example, the prism array 1 is designed so that the refractive index inside the prism array is 1.49, the angle of incidence and the angle of emergence are both 45 degrees, the angle α of the first slope 11 is 58.6 degrees, the angle β of the second slope 12 is 79.4 degrees, and the angle γ between the first slope 11 and the second slope 12 is 42.0 degrees. The prism array 1 is also designed so that the incident light beam is reflected by a portion of the second slope 12. With this design, as shown in Figures 4(A) to 4(C) , all of the incident light beam can be reflected by the second slope 12 over a fairly wide range of angles of incidence close to the design value (41.6 to 49.7 degrees in this example).

[0020] If the incident angle becomes smaller than the design value, as shown in Figure 4(D), the light beam that is not reflected by the second slope of the prism array 1 is totally reflected by the back surface (second surface 20, exit surface) and exits from the second slope 12, or is reflected by the second slope 12 and exits from the first slope 11. In this way, stray light is not emitted to the back surface side, so it is less likely to cause ghosts. In this example, incident angles of 34 to 41.6° correspond to this case.

[0021] If the incident angle becomes even smaller, as shown in Figure 4(E), light emerges from the rear surface, causing ghosting. However, because the light emerges from the rear surface at a large refraction angle, this ghost appears at a position away from the aerial image, and the impact of the ghosting is minimal. In this example, this occurs when the incident angle is 34° or less.

[0022] Furthermore, if the incident angle is larger than the design value, as shown in Fig. 4(F), the light beam reflected by the second inclined surface 12 is reflected by the first inclined surface 11 and emerges from the rear surface at an angle close to that of the main light beam, causing a ghost. However, the intensity of this reflection is weak, so the impact of the ghost is small. In this example, this occurs when the incident angle is 49.7° or larger.

[0023] [Shape of Prism Array] An appropriate shape of the prism array 1 is determined depending on the incident angle, the exit angle, and the refractive index of the light beam. The shape of the prism array 1 when the above parameters are given will be described below.

[0024] In the following description, as shown in Figure 2, the angle formed between the first inclined surface 11 and the second surface 20 is represented as α, the angle formed between the second inclined surface 12 and the second surface 20 is represented as β, and the angle (vertex angle) formed between the first inclined surface 11 and the second inclined surface 12 is represented as γ (= 2R - α - β). The grating pitch of the first surface 10 is represented as Λ, and the grating height is represented as t. The refractive index of the medium filling the prism array 1 is represented as n.

[0025] First, a method for designing the angles α and β of the first inclined surface 11 and the second inclined surface 12 will be described with reference to FIG. ０ , the exit angle is θ ５ The incident angle θ ０ and the exit angle θ ５ are all defined by the angle with the normal to the second surface 20 (plane).

[0026] If the condition is given that the light beam reflected by the second inclined surface 12 propagates substantially parallel to the first inclined surface 11, the angles α and β are determined as follows.

[0027] However, since the incident light and the outgoing light have a certain degree of spread (for example, ±2.5°), it is preferable to set the angle α of the first inclined surface 11 smaller than the angle calculated by the above formula so that the light beam reflected by the second inclined surface 12 is not vignetted by the first inclined surface 11. It is preferable that the angle α is such that the light beam reflected by the second inclined surface 12 is not vignetted by the first inclined surface 11 and is closest to the value calculated by the above formula. Specifically, the closer the angle α is to the value calculated by the following formula, the more preferable it is. where φ is the divergence angle of the emitted light.

[0028] The grating pitch Λ is mainly determined by the resolution. The grating height t is determined once the angles α and β of the first inclined surface 11 and the second inclined surface 12 and the grating pitch Λ are determined. To read 12-point (4.2 mm) alphabets, it is desirable for the pitch Λ to be 0.4 mm or less.

[0029] On the other hand, as the pitch becomes finer, blurring due to diffraction (the spread of the angle of the emitted light) occurs. When the pitch Λ is 0.4 mm and the incident angle and exit angle are 45 degrees, the blurring of a light beam with a wavelength of 600 nm is 0.06°. In other words, when a document is observed 300 mm away from the prism array, it will blur by about 0.3 mm. This phenomenon also occurs in the aerial image display devices described in Patent Documents 1-3 and 4.

[0030] If the incident angle of the light beam on the second inclined surface 12 exceeds the critical angle, the light beam is totally reflected. However, if the incident angle is within the critical angle, the light beam is not totally reflected. In this case, it is preferable to provide a metallic or dielectric reflective film on the second inclined surface 12.

[0031] [Method for manufacturing a prism array] The prism array according to this embodiment may be manufactured by directly processing grooves into a hard resin material, or may be manufactured by replica processing, hot pressing, or roll pressing of a resin material using a metal mold.

[0032] The replica processing will be described below with reference to FIGS. 5(A) to 5(C).

[0033] First, a workpiece 101 is prepared, in which the surface of a metal substrate such as stainless steel, which has a linear expansion coefficient roughly equal to that of nickel-phosphorus, is plated with electroless nickel-phosphorus to a thickness of approximately 0.5 to 2 mm depending on the grating pitch Λ and apex angle γ. A diamond cutting tool 102, which is matched to the angle of the grooves of the prism array to be fabricated, is attached to an ultra-precision machining center and used for cutting (shaper or flycut) this workpiece 101 to fabricate a master grating 103, as shown in Figure 5(A).

[0034] 5B, a release agent is applied to the surface of the master grating 103, and then an ultraviolet-curable or two-component curable transparent resin 104 is poured into the surface to adhere the glass substrate 105. It is preferable to apply a silane coupling agent or the like to the surface of the glass substrate 105 to strengthen the bond with the resin 104.

[0035] The replica grating 106 made of the glass substrate 105 and the resin 104 is peeled off from the master grating 103, thereby completing the prism array 106 according to this embodiment, as shown in FIG. 5C.

[0036] Electroless nickel-phosphorus plating is amorphous and is an excellent material for molds for precision optical elements that are machined. Shaper and fly-cutting processes using precision machining equipment and diamond tools can precisely shape the cutting edge, making them ideal for manufacturing molds for the prism array of this embodiment.

[0037] In the case of direct processing, the prism array of this embodiment can be produced by fly-cutting a hard resin material with a diamond rotary tool.

[0038] [Advantageous Effects of the Present Embodiment] According to the present embodiment, as described above, ghosts do not occur, or even if they do occur, their intensity is weak or they occur at a position away from the aerial image, so the effects of ghosts can be suppressed.

[0039] Figures 6(A) and 6(B) show aerial images produced by the aerial image display devices of this embodiment and the conventional example (Patent Documents 1 and 2), both placed at the same distance from the object (monitor). While ghosts (one-dimensional real image, one-dimensional orthogonal virtual image) appear in the conventional example, no such ghosts appear in this embodiment. As a result, the aerial image display device can be placed closer to the object (monitor), allowing the device to be made smaller in this embodiment.

[0040] Furthermore, this embodiment has high resolution and utilizes total reflection inside the prism array, so that a bright aerial image can be projected due to a high light utilization rate.

[0041] Furthermore, the prism array of this embodiment is easy to manufacture and can be manufactured inexpensively. In particular, by performing replica processing, hot pressing, or roll pressing, it is possible to mass-produce prism arrays at low cost.

[0042] [Variation 1] In the aerial image display device 100 according to the above embodiment, the prism arrays 1A and 1B are stacked so that they face in the same direction, and the object light is incident from the surface on which the grooves are formed (first surface 10 of prism array 1A). However, the object light may be incident from the flat surface (second surface 20 of prism array 1B).

[0043] In this modification, prism arrays 1A and 1B are configured such that a light beam incident on second surface 20 at a predetermined angle of incidence is reflected by second inclined surface 12 and emerges from first surface 10 at an emergence angle equal to the angle of incidence. This condition can also be achieved using a prism array with the same shape as the above embodiment. However, it is preferable to employ a configuration that prevents vignetting within the prism array.

[0044] FIG. 7 shows the shape of the prism array 1 and the optical path of incident light in this modified example. It is designed so that all light beams incident on the second surface 20 exit without vignetting. While details are omitted, this modified example, like the above-described embodiment (FIGS. 4A to 4F), can reflect all incident light beams from the second slope 12 over a relatively wide range of incident angles close to the design value. However, in the example shown in FIG. 7, a portion of the light beams reflected from the second slope and exiting the first slope (shown by the dashed line) are vignetted by the adjacent second slope, causing ghosting. However, in FIG. 7, most of the vignetted light beams in the case of 45° incidence exit at approximately 70°, resulting in ghosting at a position distant from the principal ray exiting at 45.1°. This ghosting becomes stronger as the incident angle increases. On the other hand, when the incident angle is 42.4° or less, a weak ghost appears near the principal ray, and becomes stronger as the incident angle decreases, but the angle from the principal ray increases.

[0045] This modification can also achieve the same effects as the above embodiment. Furthermore, in this modification, since the first surface is disposed on the aerial image side (observer side), there is also the effect that external light reflection on the surface is less likely to occur.

[0046] [Variation 2] In the aerial image display device 100 according to the above embodiment and Variation 1, the prism arrays 1A and 1B are stacked so that they face the same direction, but this is not a limitation. As shown in Fig. 8, the prism arrays 1A and 1B may be stacked so that their flat surfaces (second surfaces 20) face each other and their grooved surfaces (first surfaces 10) face in opposite directions. Alternatively, the prism arrays 1A and 1B may be stacked so that their grooved surfaces face each other and their flat surfaces face in opposite directions.

[0047] In this modification, light is incident on the first surface 10 of one prism array 1, and light is incident on the second surface of the other prism array 1. If the light utilization rate differs between the first surface 10 and the second surface 20, the brightness of the aerial images for the right and left eyes may differ. Therefore, it is preferable that the utilization rate of light incident on the first surface 10 and the second surface 20 at a predetermined angle of incidence is the same. Specifically, it is preferable that the prism array 1 is configured so that the light beam incident on the first surface 10 and the second surface 20 at a predetermined angle of incidence is not vignetted within the prism array and exits from the second surface 20 and the first surface 10 at an exit angle equal to the angle of incidence. Note that such a prism array can be suitably used not only in this modification but also in the aerial image display device 100 of the above embodiment.

[0048] Figure 9 illustrates the shape of a prism array and the propagation of light beams suitable for an aerial image display device 100 in which the grooved surfaces (first surfaces 10) of a modified example are stacked in opposite directions, or for an aerial image display device 100 in which the grooved surfaces face each other and the flat surfaces are stacked in opposite directions. In Figure 9, when the refractive index inside the prism array is 1.49 (acrylic resin, etc.), and the incident angle and exit angle are approximately 34°, there is almost no vignetting regardless of whether light is incident from the protrusion side or the second surface side. Note that the condition for almost no vignetting, as shown in Figure 9, is uniquely determined by the exit angle and the shape of the prism array when the refractive index, apex angle, and incident angle inside the prism array are given.

[0049] 10 and 11 illustrate the shape of a prism array and the propagation of light beams suitable for an aerial image display device 100 in which the prism arrays are stacked so that the surfaces (first surfaces 10) on which the grooves are provided face in the same direction. As shown in FIG. 1 , when the prism arrays are stacked so that the first surfaces 10 face in the same direction, the incidence angle and the exit angle of the prism array 1 do not need to be the same. In this modification, the prism array 1 is configured so that a light beam incident on the first surface 10 at a first angle exits from the second surface 20 without vignetting within the prism array 1, and a light beam incident on the first surface 10 at a second angle exits from the second surface 20 without vignetting within the prism array 2. Here, the first angle and the second angle may be different.

[0050] FIG. 10 is a diagram illustrating the shape of a prism array that causes almost no vignetting inside and the propagation of light beams when the refractive index inside the prism array is 1.49 (acrylic resin, etc.), the incident angle is 37.3°, and the exit angle is 18.0°.

[0051] FIG. 11 is a diagram illustrating the shape of a prism array that causes almost no vignetting inside and the propagation of light beams when the refractive index inside the prism array is 1.49 (acrylic resin, etc.), the incident angle is 40.7°, and the exit angle is 0°.

[0052] The condition for almost no vignetting as shown in FIGS. 10 and 11 is determined by the output angle and the shape of the prism array when the refractive index, apex angle, and incident angle inside the prism array are given.

[0053] Furthermore, an aerial image display device using a prism array with different incident and outgoing angles as shown in Figures 10 and 11 can enlarge or reduce the aerial image because the distance from the monitor or object to the aerial image display device and the distance from the aerial image display device to the aerial image are different. The magnification ratio M of the aerial image is calculated by multiplying the distance between the object or monitor P in Figure 12. １ The distance f of the light beam from the aerial image display device １ and the angle of incidence θ1, object P １ The small angle δ1 from the aerial image display device to the distance d and the aerial image P ２ The distance f of the ray to ２ and the output angle θ2, the aerial image P２ A small angle δ seen from the distance d on the aerial image display device ２ It is expressed as follows using

[0054] The magnification ratio M of the aerial image is defined as M = f2 / f1.

[0055] Object P １ The distance d on the aerial image display device as viewed from is d = f1tanδ1 / cosθ1, d≪f1.

[0056] Real Image P ２ The distance d on the aerial image display device as viewed from is d = f2tanδ2 / cosθ2, d≪f2.

[0057] From the above formula, the magnification ratio M is given by M = f2 / f1 = (tanδ1cosθ2) / (tanδ2cosθ1).

[0058] In the aerial image display device of Figure 10, the magnification factor is approximately 0.67x when incident from the flat surface side and approximately 1.5x when incident from the prism side. Also, in the aerial image display device of Figure 11, the magnification factor is approximately 0.57x when incident from the flat surface side and approximately 1.74x when incident from the prism side. The aerial image display devices of Figures 4(B) and 7 have approximately the same incident and exit angles, but the magnification changes due to the effect of the prism. That is, in the aerial image display device of Figure 4(B), the magnification factor is approximately 1.22x when incident from the flat surface side and approximately 0.82x when incident from the prism side. Also, in the aerial image display device of Figure 7, the magnification factor is approximately 1.21x when incident from the flat surface side and approximately 0.83x when incident from the prism side.

[0059] In a configuration using a prism array with different incident and exit angles as shown in this modified example, when the prism arrays are stacked so that the first surfaces 10 face in opposite directions, i.e., the first surfaces 10 face each other, or when the second surfaces 20 face each other, the images for the right and left eyes are shifted vertically and flattened in a 45-degree direction.

[0060] [Variation 4] When an object is projected using an aerial image display device using a single prism array, as in the above-described embodiment, the unevenness of the object is inverted. Therefore, to faithfully project the object, two prism arrays must be used (see Patent Document 2). However, with conventional aerial image display devices using mirror arrays or two-sided Conner reflector arrays, ghosts of real and virtual images appear near the aerial image when the device is brought closer to the object. This necessitates increasing the distance from the object, which increases the device's size and results in a blurred aerial image. Furthermore, conventional aerial image display devices have a problem in that the aerial image becomes dark when used in two stages due to their low light utilization rate.

[0061] FIG. 13 shows the configuration of an aerial image display device 1200 according to this modification. The aerial image display device 1200 includes a first prism array pair 1201 and a second prism array pair 1202. The first prism array pair 1201 and the second prism array pair 1202 include a prism array 1A and a prism array 1B, respectively. The configurations of the prism array pair 1201 and the prism array pair 1202 may be any of those described in the above embodiments or modifications. FIG. 13 shows how light rays are imaged for each wavelength (color). When light rays emerge from an object position P, chromatic dispersion occurs as they pass through the first prism array pair 1201, resulting in images being formed at different positions for each wavelength. However, when light rays pass through the prism array pair 1202, the color shift is canceled out, and all wavelengths are imaged at a real image position P'. As a result, the aerial image display device can project aerial images of bright objects or holograms because it can be placed close to the object, and the entire device can be made compact.

[0062] [Other Modifications] The present invention is not limited to the above-described embodiment and modifications, and various modifications are possible. For example, a member other than a prism array, such as a plane-parallel filter, may be provided between the two prism arrays.

[0063] In the above embodiment, the two prism arrays are stacked so that the longitudinal directions of the ridges are perpendicular to each other, but an aerial image can be displayed if the ridges are stacked so that the longitudinal directions of the ridges intersect at an angle of 60 to 120°. However, because the aspect ratio of the aerial image changes as the intersection angle deviates from 90° (perpendicular), the intersection angle is preferably 80 to 100°, more preferably 85 to 95°, and even more preferably 90°.

[0064] 100: Aerial image display device 1 (1A, 1B): Triangular prism array, prism array 10: First surface 11: First inclined surface 12: Second inclined surface 20: Second surface (flat surface) 15: Protrusion 16: Longitudinal direction of protrusion

Claims

1. An aerial image display device comprising a first optical element and a second optical element, each having an array of triangular ridges, each including a first inclined surface and a second inclined surface, and a flat second surface, configured so that a light beam incident on the first surface at a predetermined angle of incidence passes through the first inclined surface, is reflected by the second inclined surface, and is emitted from the second surface, and wherein the first optical element and the second optical element are stacked so that the arrangement directions of the ridges intersect.

2. The aerial image display device according to claim 1, wherein the first optical element and the second optical element are stacked so that the arrangement directions of the protrusions are perpendicular to each other.

3. The aerial image display device according to claim 1, characterized in that the second surface of the first optical element and the first surface of the second optical element are arranged facing each other, and the first surface of the first optical element and the first surface of the second optical element face in the same direction.

4. The aerial image display device described in claim 3, characterized in that the light beam incident on the first surface of the first optical element at the predetermined incident angle is configured to exit from the second surface of the first optical element at an exit angle equal to the predetermined incident angle, to enter the first surface of the second optical element at the predetermined incident angle, and to exit from the second surface of the second optical element at an exit angle equal to the predetermined incident angle.

5. The aerial image display device described in claim 4, characterized in that the first optical element and the second optical element are configured so that a light beam incident on the first surface of the first optical element at the specified incident angle is emitted from the second optical element without being vignetted inside the first optical element and the second optical element.

6. The aerial image display device described in claim 3, characterized in that the light beam incident on the second surface of the second optical element at the predetermined incident angle is configured to exit from the first surface of the second optical element at an exit angle equal to the predetermined incident angle, to enter the second surface of the first optical element at the predetermined incident angle, and to exit from the first surface of the first optical element at an exit angle equal to the predetermined incident angle.

7. The aerial image display device described in claim 4, characterized in that the first optical element and the second optical element are configured so that a light beam incident on the second surface of the second optical element at the specified incident angle is emitted from the first optical element without being vignetted inside the first optical element and the second optical element.

8. The aerial image display device described in claim 3, characterized in that the first optical element and the second optical element are configured so that a light beam incident on the second surface of the second optical element at a first angle exits from the first surface of the second optical element at a second angle different from the first angle, and a light beam incident on the second surface of the first optical element at the second angle exits from the first surface of the first optical element at the first angle.

9. The aerial image display device described in claim 8, characterized in that the first optical element is configured so that the light beam incident on the second surface at the second angle exits the first optical element without vignetting occurring inside the first optical element, and the second optical element is configured so that the light beam incident on the second surface at the first angle exits the second optical element without vignetting occurring inside the first optical element.

10. The aerial image display device described in claim 3, characterized in that the first optical element and the second optical element are configured so that a light beam incident on the first surface of the first optical element at a first angle exits from the second surface of the first optical element at a second angle different from the first angle, and a light beam incident on the first surface of the second optical element at the second angle exits from the second surface of the second optical element at the first angle.

11. The aerial image display device described in claim 10, characterized in that the first optical element is configured so that the light beam incident on the first surface at the first angle exits the first optical element without vignetting occurring inside the first optical element, and the second optical element is configured so that the light beam incident on the first surface at the second angle exits the second optical element without vignetting occurring inside the first optical element.

12. The aerial image display device according to claim 1, wherein the first surface of the first optical element and the first surface of the second optical element are arranged facing in opposite directions.

13. The aerial image display device described in claim 12, characterized in that the first optical element and the second optical element are arranged with the second surfaces facing each other, and are configured so that a light beam incident on the first surface at the specified incident angle exits the second surface at an exit angle equal to the specified incident angle without vignetting occurring inside the optical element, and so that a light beam incident on the second surface at the specified incident angle exits the first surface at an exit angle equal to the specified incident angle without vignetting occurring inside the optical element.

14. The aerial image display device described in claim 12, characterized in that the first optical element and the second optical element are arranged with the first surfaces facing each other, and are configured so that a light beam incident on the second surface at the specified incident angle is emitted from the first surface at an exit angle equal to the specified incident angle without vignetting occurring inside the optical element, and so that a light beam incident on the first surface at the specified incident angle is emitted from the second surface at an exit angle equal to the specified incident angle without vignetting occurring inside the optical element.

15. The aerial image display device according to claim 1, wherein a reflective film is provided on the second inclined surface of at least one of the first optical element and the second optical element.

16. An aerial image display device as described in any one of claims 1 to 15, comprising: a first optical element pair including the first optical element and the second optical element; and a second optical element pair including the first optical element and the second optical element, wherein the first optical element pair and the second optical element pair are arranged so that a light beam incident on the first optical element pair at the predetermined angle is incident on the second optical element pair at the predetermined angle.

Images