Aerial image display device

Abstract

This aerial image display device comprises: an image formation unit that emits first image light; an optical element that transmits a part of incident light and reflects the remaining part to form second image light divided from the first image light; a condensing optical system that condenses at least a part of the second image light; and a retroreflective element provided at a condensing position of the condensing optical system. The condensing optical system forms an aerial image by enlarging and imaging at least a part of the second image light on a surface of the retroreflective element and reducing and imaging the second image light reflected by the retroreflective element.

Description

Aerial image display device

[0001] The present invention relates to an aerial image display device. This application claims priority to Japanese Patent Application No. 2024-155307 filed on September 9, 2024, and Japanese Patent Application No. 2024-155308 filed on September 9, 2024, the contents of which are incorporated herein by reference.

[0002] Display devices that display images or videos in the air have been attracting attention as non-contact user interfaces and digital signage that provides a high level of realism. In the following description, an image or video displayed in the air will be referred to as an "aerial image." Furthermore, a display device capable of displaying an aerial image will be referred to as an "aerial image display device."

[0003] A configuration using a retroreflecting element is known as an aerial image display device (see, for example, Patent Document 1). In the aerial image display device described in Patent Document 1, an image displayed on a display device is reflected by an optical element having a beam splitter function, and then incident on the retroreflecting element. Retroreflected light rays that are emitted in the same direction as the incident light rays are transmitted through the optical element having the beam splitter function, thereby forming an aerial image.

[0004] However, it is known that the aerial image display device described in Patent Document 1 is prone to a decrease in resolution of the displayed image due to the characteristics of the retroreflective elements.

[0005] Therefore, in order to increase the resolution of the displayed image, an aerial image display device is known that uses a retroreflective element and an optical element (such as a lens) having a light-collecting function (see Patent Document 2). In the aerial image display device described in Patent Document 2, an image displayed on the display device is incident on the reflective surface of the retroreflective element via the optical element having a light-collecting function, so that the image is incident on a relatively narrow range on the reflective surface of the retroreflective element. The invention described in Patent Document 2 claims that this configuration can increase the resolution of the aerial image.

[0006] JP 2011-253128 A JP 2021-173873 A

[0007] However, as in the invention described in Patent Document 2, simply installing an optical element (such as a lens) with a light-condensing function only has a limited effect in improving resolution, and there remains the problem that the resolution does not improve under certain conditions. Therefore, there has been a demand for a display device that can reliably produce high-resolution aerial images.

[0008] The present invention has been made in view of the above circumstances, and has an object to provide an aerial image display device that can display an aerial image with a higher resolution than conventional devices.

[0009] The present invention includes the following aspects.

[0010] [A1] An aerial image display device comprising: an image forming unit that emits first image light; an optical element that transmits part of the incident light and reflects the remainder to form second image light split from the first image light; a focusing optical system that focuses the second image light; and a retroreflective element provided at a focusing position of the focusing optical system, wherein the focusing optical system focuses the second image light on the surface of the retroreflective element and reduces and focuses the second image light reflected by the retroreflective element to form an aerial image.

[0011] [A2] The aerial image display device according to [A1], wherein the image forming unit has a plurality of pixels that emit the first image light, and the retroreflecting element has a plurality of cells that perform retroreflection, and the following formula (A) is satisfied: [pixel size] × α ≥ [cell size] ... (A) (where α represents the magnification factor achieved by a focusing optical system arranged on the optical path from the image forming unit to the retroreflecting element).

[0012] [A3] The aerial image display device according to [A2], wherein the pixel has a plurality of sub-pixels and satisfies the following formula (B): [sub-pixel size]×α≧[cell size] (B), where α is the same as α in formula (A).

[0013] [A4] The aerial image display device according to any one of [A1] to [A3], wherein the optical element is a reflective polarizing plate.

[0014] [A5] The aerial image display device according to [A4], which has a quarter-wave plate on the optical path between the retroreflecting element and the focusing optical system.

[0015] [A6] An aerial image display device described in [A4] or [A5], which has an absorbing polarizer on the optical path opposite the focusing optical system with respect to the optical element, which absorbs polarized light in the vibration direction reflected by the optical element.

[0016] [A7] An aerial image display device described in any one of [A1] to [A6], wherein the optical axis of the focusing optical system is inclined with respect to the chief ray axis of the second image light incident on the focusing optical system, and the normal direction of the surface of the retroreflective element is inclined with respect to the chief ray axis of the second image light incident on the retroreflective element.

[0017] [A8] The aerial image display device according to [A7], which has an anti-reflection plate on the optical path between the retroreflecting element and the focusing optical system.

[0018] [A9] An aerial image display device described in any one of [A1] to [A8], wherein the focusing optical system is composed of a plurality of lenses arranged along the main axis of the focusing optical system.

[0019] [A10] An aerial image display device according to any one of [A1] to [A9], wherein the retroreflective element has a curved surface shape that is concave on the side of the focusing optical system on the optical path.

[0020] [A11] An aerial image display device according to any one of [A1] to [A10], which has a first reflecting element on the optical path between the focusing optical system and the retroreflecting element.

[0021] [A12] An aerial image display device described in any one of [A1] to [A11], which has a second reflecting element on the optical path between the optical element and the focusing optical system on the opposite side of the image forming unit from the optical element, which reflects the second image light in the direction of the optical element, and the focusing optical system focuses the second image light emitted from the optical element via the second reflecting element.

[0022] [A13] An aerial image display device according to any one of [A1] to [A11], wherein the optical element emits the first image light that has passed through the optical element as the second image light.

[0023] The present invention also includes the following aspects.

[0024] [B1] An aerial image display device comprising: an image forming unit that emits first image light; an optical element that transmits a portion of the incident light and reflects the remainder to form a second image light split from the first image light; a focusing optical system that collects a portion of the second image light; a first retroreflective element provided at a focusing position of the focusing optical system; and a second retroreflective element onto which the remainder of the second image light is incident; wherein the focusing optical system images the second image light incident on the surface of the first retroreflective element and images the second image light reflected by the first retroreflective element to form a first aerial image; and the second retroreflective element retroreflectively reflects the second image light incident on it to form a second aerial image.

[0025] [B2] The aerial image display device according to [B1], wherein the optical element is a reflective polarizing plate.

[0026] [B3] The aerial image display device according to [B2], which has a quarter-wave plate on the optical path between the first retroreflecting element and the focusing optical system.

[0027] [B4] An aerial image display device described in [B2] or [B3], which has an absorbing polarizer on the optical path opposite the focusing optical system with respect to the optical element, which absorbs polarized light in the vibration direction reflected by the optical element.

[0028] [B5] An aerial image display device described in any one of [B1] to [B3], wherein the optical axis of the focusing optical system is inclined with respect to the principal ray axis of the second image light incident on the focusing optical system.

[0029] [B6] The aerial image display device according to [B5], further comprising an anti-reflection plate on the optical path between the first retroreflection element and the focusing optical system.

[0030] [B7] An aerial image display device described in any one of [B1] to [B3], wherein the focusing optical system reduces and focuses a portion of the second image light onto the first retroreflective element.

[0031] [B8] An aerial image display device described in any one of [B1] to [B3], which has a third retroreflective element into which third image light, which is the remaining portion of the second image light split from the first image light, is incident in the optical element.

[0032] [B9] An aerial image display device described in any one of [B1] to [B3], wherein the optical element emits the first image light that has passed through the optical element as the second image light.

[0033] [B10] An aerial image display device described in any one of [B1] to [B9], wherein the second retroreflective element is arranged closer to the optical element than the first retroreflective element in the field of view seen from the optical element side.

[0034] [B11] An aerial image display device as described in [B10], which has a support for supporting the focusing optical system, and the second retroreflective element overlaps with the support in the field of view seen from the optical element side.

[0035] [B12] An aerial image display device described in any one of [B1] to [B11], which has a second focusing optical system that focuses the second image light incident on the surface of the second retroreflective element and focuses the second image light reflected by the second retroreflective element to form a second aerial image.

[0036] That is, the present invention includes the following aspects.

[0037] [1] An aerial image display device comprising: an image forming unit that emits first image light; an optical element that transmits a portion of the incident light and reflects the remainder to form a second image light split from the first image light; a focusing optical system that focuses at least a portion of the second image light; and a retroreflecting element provided at a focusing position of the focusing optical system, wherein the focusing optical system magnifies and images at least a portion of the second image light on the surface of the retroreflecting element, and reduces and images the second image light reflected by the retroreflecting element to form an aerial image.

[0038] [2] The aerial image display device according to [1], wherein the image forming unit has a plurality of pixels that emit the first image light, and the retroreflecting element has a plurality of cells that perform retroreflection, and the following formula (A) is satisfied: [pixel size] × α ≥ [cell size] ... (A) (where α represents the magnification factor of a focusing optical system arranged on the optical path from the image forming unit to the retroreflecting element).

[0039] [3] The aerial image display device according to [2], wherein the pixel has a plurality of sub-pixels and satisfies the following formula (B): [sub-pixel size] × α ≥ [cell size] (B), where α is the same as α in formula (A).

[0040] [4] The aerial image display device according to any one of [1] to [3], wherein the optical element is a reflective polarizing plate.

[0041] [5] The aerial image display device according to [4], which has a quarter-wave plate on the optical path between the retroreflecting element and the focusing optical system.

[0042] [6] An aerial image display device as described in [4], which has an absorbing polarizer on the optical path opposite the focusing optical system with respect to the optical element, which absorbs polarized light in the vibration direction reflected by the optical element.

[0043] [7] An aerial image display device described in any one of [1] to [6], wherein the optical axis of the focusing optical system is inclined with respect to the chief ray axis of the second image light incident on the focusing optical system, and the normal direction of the surface of the retroreflective element is inclined with respect to the chief ray axis of the second image light incident on the retroreflective element.

[0044] [8] The aerial image display device according to [7], which has an anti-reflection plate on the optical path between the retroreflecting element and the focusing optical system.

[0045] [9] An aerial image display device described in any one of [1] to [8], wherein the focusing optical system is composed of a plurality of lenses arranged along the main axis of the focusing optical system.

[0046]

[10] An aerial image display device according to any one of [1] to [9], wherein the retroreflective element has a curved surface shape that is concave on the side of the focusing optical system on the optical path.

[0047]

[11] An aerial image display device according to any one of [1] to

[10] , having a first reflecting element on the optical path between the focusing optical system and the retroreflecting element.

[0048]

[12] An aerial image display device described in any one of [1] to

[11] , which has a second reflecting element on the optical path between the optical element and the focusing optical system on the opposite side of the image forming unit from the optical element, which reflects the second image light in the direction of the optical element, and the focusing optical system focuses the second image light emitted from the optical element via the second reflecting element.

[0049]

[13] An aerial image display device described in any one of [1] to

[11] , wherein the optical element emits the first image light that has passed through the optical element as the second image light.

[0050]

[14] An aerial image display device as described in [1], comprising: a focusing optical system that focuses a portion of the second image light; a retroreflective element arranged at the focusing position of the focusing optical system; and a second retroreflective element onto which the remaining portion of the second image light is incident, wherein the focusing optical system magnifies the second image light incident on the surface of the retroreflective element and reduces the second image light reflected by the retroreflective element to form a first aerial image, and the second retroreflective element retroreflects the second image light incident on it to form a second aerial image.

[0051]

[15] The aerial image display device according to

[14] , wherein the optical element is a reflective polarizing plate.

[0052]

[16] The aerial image display device according to

[15] , which has a quarter-wave plate on the optical path between the retroreflecting element and the focusing optical system.

[0053]

[17] An aerial image display device as described in

[15] or

[16] , which has an absorbing polarizer on the optical path opposite the focusing optical system with respect to the optical element, which absorbs polarized light in the vibration direction reflected by the optical element.

[0054]

[18] An aerial image display device described in any one of

[14] to

[16] , wherein the optical axis of the focusing optical system is inclined with respect to the principal ray axis of the second image light incident on the focusing optical system.

[0055]

[19] The aerial image display device according to

[18] , which has an anti-reflection plate on the optical path between the retroreflecting element and the focusing optical system.

[0056]

[20] An aerial image display device described in any one of

[14] to

[16] , which has a third retroreflective element into which third image light, which is the remaining portion of the second image light split from the first image light, is incident in the optical element.

[0057]

[21] An aerial image display device described in any one of

[14] to

[16] , wherein the optical element emits the first image light that has passed through the optical element as the second image light.

[0058]

[22] An aerial image display device described in any one of

[14] to

[21] , wherein the second retroreflective element is arranged closer to the optical element than the retroreflective element in the field of view seen from the optical element side.

[0059]

[23] An aerial image display device as described in

[22] , which has a support for supporting the focusing optical system, and the second retroreflective element overlaps with the support in the field of view seen from the optical element side.

[0060]

[24] An aerial image display device described in any one of

[14] to

[23] , having a second focusing optical system that focuses the second image light incident on the surface of the second retroreflective element and focuses the second image light reflected by the second retroreflective element to form a second aerial image.

[0061] According to the present invention, it is possible to provide an aerial image display device that can display an aerial image with a higher resolution than conventional ones.

[0062] FIG. 1 is an explanatory diagram showing an aerial image display device 10A according to a first embodiment. FIG. 2 is an explanatory diagram illustrating a problem that occurs with a retroreflection element. FIG. 3 is an explanatory diagram illustrating an effect of the aerial image display device 10A. FIG. 4 is an explanatory diagram showing an aerial image display device 10B according to a modified example of the first embodiment. FIG. 5 is an explanatory diagram showing an aerial image display device 10C according to a modified example of the first embodiment. FIG. 6 is an explanatory diagram of an aerial image display device 10D according to a second embodiment. FIG. 7 is an explanatory diagram of an aerial image display device 10E according to a third embodiment. FIG. 8 is an explanatory diagram of an aerial image display device 10F according to a fourth embodiment. FIG. 9 is an explanatory diagram of an aerial image display device 10G according to a fifth embodiment. FIG. 10 is an explanatory diagram of an aerial image display device 10H according to the fifth embodiment. FIG. 11 is an explanatory diagram of an aerial image display device 10I according to a sixth embodiment. FIG. 12 is an explanatory diagram of an aerial image display device 10J according to a seventh embodiment. FIG. 13 is an explanatory diagram of an aerial image display device 10K according to a modified example. FIG. 14 is an explanatory diagram of an aerial image display device 10L according to an eighth embodiment. Fig. 15 is an explanatory diagram of an aerial image display device 10M according to a ninth embodiment. Fig. 16 is an explanatory diagram of an aerial image display device 10N according to a tenth embodiment. Fig. 17 is an explanatory diagram of an aerial image display device 10P according to an eleventh embodiment. Fig. 18 is an explanatory diagram of an aerial image display device 10Q according to a twelfth embodiment.

[0063] [First embodiment] An aerial image display device according to a first embodiment will be described below with reference to Figures 1 to 5. Note that in all of the following figures, the dimensions and proportions of the components have been appropriately changed to make the drawings easier to see.

[0064] 1 is an explanatory diagram showing an aerial image display device 10A according to a first embodiment. The aerial image display device 10A has an image forming unit 1, an optical element 2, a focusing optical system 3, and a retroreflection element 4. The aerial image display device 10A forms second image light L2 from first image light L1 emitted from the image forming unit 1, and forms an aerial image AI by focusing the second image light L2 in the air.

[0065] <Image Forming Unit> The image forming unit 1 has a plurality of pixels P1 that emit first image light L1. The plurality of pixels P1 are arranged, for example, in a matrix, and form an original image I1 of the aerial image AI by emitting the first image light L1.

[0066] Various configurations can be adopted for the image forming unit 1 as long as it is capable of emitting the first image light L1. For example, a self-luminous display panel (display device) may be used as the image forming unit 1, or a known display device formed by combining a light source and a light modulation device that modulates the light emitted from the light source may be used.

[0067] The light source of the display device may be a known light source device such as a mercury lamp, a laser light source, an LED, etc. The light modulation device of the display device may be a known light modulation device such as a liquid crystal panel, a DMD (Digital Micro-mirror Device), etc.

[0068] The first image light L1 emitted by the image forming unit 1 may be monochromatic or may be a plurality of colors including, for example, the three primary colors of red (R), green (G), and blue (B). When the first image light L1 includes a plurality of colors, the image forming unit 1 may be a single display device, or may use a different display device for each color of light to be emitted, and may emit the colored light in a superimposed manner on the optical path.

[0069] The image forming unit 1 may have a projection optical system (not shown).

[0070] The first image light L1 emitted from the image forming unit 1 is incident on the optical element 2. In Fig. 1, the first image light L1 emitted from one pixel (point light source) of the image forming unit 1 is shown.

[0071] <Optical Element> The optical element 2 has the function of transmitting a portion of incident light and reflecting the remainder. The optical element 2 splits the first image light L1 emitted from the image forming unit 1 to form second image light L2. In the aerial image display device 10A, the light component reflected by the optical element 2 is used as the second image light L2.

[0072] As the optical element 2, a known beam splitter or a reflective polarizing plate can be used.

[0073] The second image light L2 emitted from the optical element 2 is incident on the light-collecting optical system 3 .

[0074] <Light Concentrating Optical System> The light focusing optical system 3 focuses the second image light L2 emitted from the optical element 2, and forms an image on the surface (reflecting surface 4a) of the retroreflective element 4, which will be described later.

[0075] The focusing optical system 3 shown in Fig. 1 forms an aerial image by enlarging the second image light L2 incident from the optical element 2 side and by reducing the light incident from the retroreflective element 4 side. The focusing optical system 3 may be composed of a single lens or multiple lenses. Furthermore, the focusing optical system 3 may employ a lens array. In Fig. 1, the focusing optical system 3 is shown as a single lens.

[0076] <Retroreflective Element> The retroreflective element 4 is an optical element that retroreflects the incident second image light L2. The retroreflective element 4 is provided at a light collection position of the light collection optical system 3. The retroreflective element 4 has a plurality of cells 41 that perform retroreflection.

[0077] A known configuration can be used for the retroreflective element 4. For example, the retroreflective element 4 can have a configuration in which a large number of corner cubes are arranged on the reflective surface (corner cube type or prism lens type (full corner cube type)), or a configuration in which a plurality of transparent beads such as glass beads are arranged on the reflective surface (bead type).

[0078] The multiple corner cubes and beads that the retroreflective element 4 has correspond to cells that perform retroreflection in the retroreflective element 4. A corner cube type configuration is preferable for the retroreflective element 4. In Figure 1, the retroreflective element 4 is shown as being of the corner cube type.

[0079] The second image light L2 reflected by the retroreflective element 4 is again incident on the collecting optical system 3. At this time, the second image light L2 retroreflected by the retroreflective element 4 passes through the collecting optical system 3 from the retroreflective element 4 side, along the same optical path as when it passed through the collecting optical system 3 from the optical element 2 side. If the collecting optical system 3 has lens aberration, the aberration when passing through the collecting optical system 3 from the optical element 2 side and the aberration when passing through the collecting optical system 3 from the retroreflective element 4 side cancel each other out. Therefore, the lens aberration in the collecting optical system 3 is reduced in the second image light L2 emerging from the collecting optical system 3.

[0080] The second image light L2 collected by the collecting optical system 3 is incident on the optical element 2. Of the second image light L2 incident on the optical element 2, the component that has transmitted through the optical element 2 is focused at the collecting position of the collecting optical system 3, forming an aerial image AI.

[0081] A user U of the device can obtain various information by visually recognizing the aerial image AI.

[0082] 2A and 2B are explanatory diagrams illustrating problems that arise in retroreflective elements. In Fig. 2, a perspective view (Fig. 2A) and a cross-sectional view (Fig. 2B) of a cell 41 of a corner cube retroreflective element 4 are shown. Similar problems also arise in bead-type retroreflective elements in which a large number of glass beads are arranged on the reflective surface.

[0083] 2A, the cell 41 of the retroreflective element 4 is a triangular pyramid having three reflective surfaces 41a, 41b, and 41c. Each of the reflective surfaces 41a, 41b, and 41c is a right-angled triangle, and the right angles of each reflective surface come together to form the vertex of the triangular pyramid.

[0084] The incident light IL incident on such a cell 41 is reflected in order by, for example, reflecting surfaces 41a, 41b, and 41c, and is emitted as reflected light RL in the same direction as the incident direction of the incident light IL. At this time, the optical path of the incident light IL and the optical path of the reflected light RL are misaligned (optical path shifted) due to reflections occurring within the cell 41. The amount of shift W1 between the incident light IL and the reflected light RL increases as the cell 41 increases.

[0085] 2B, when incident light IL enters a cell 41 of the retroreflective element 4, the incident light IL is diffracted by the cell 41 upon reflection. As a result, reflected light RL emitted from the cell 41 has a spread as diffracted light. The spread amount W2 of the reflected light RL depends on the diffraction angle, and therefore increases as the cell 41 becomes smaller.

[0086] In conventional aerial image display devices having retroreflection elements, the resolution of the aerial image is reduced due to the optical path shift and diffraction.

[0087] In the invention described in Patent Document 2, a focusing optical element (lens) is installed on the optical path between the optical element 2 and the retroreflecting element 4 in the aerial image display device of this embodiment in order to increase the resolution. However, simply installing a lens on the optical path between the optical element and the retroreflecting element only has a limited effect on improving the resolution, and there remains the problem that the resolution may not be improved under certain conditions, so improvements have been sought.

[0088] In contrast, the aerial image display device 10A uses, as the focusing optical system 3, an optical system that enlarges and forms an image of the second image light L2 incident from the optical element 2 side and reduces and forms an image of the light incident from the retroreflecting element 4 side. As a result, the focusing optical system 3 functions as an optical system that reduces and forms an image of the retroreflected second image light L2, thereby suppressing the light ray shift caused by the size (pitch size) of the cells 41 of the retroreflecting element 4 as shown in Fig. 2(a). This suppresses the spread of the point image formed by the focusing optical system 3, and solves the problem of reduced resolution.

[0089] 2B, the diffracted light and scattered light generated on the retroreflective element 4 are focused at the position of the aerial image by the focusing optical system 3. This solves the problem of reduced resolution caused by the spread of light due to diffracted light, etc., generated on the retroreflective element 4.

[0090] As a result, the aerial image display device 10A can form an aerial image AI with a resolution that exceeds the diffraction limit of a conventional aerial imaging optical system that uses retroreflection.

[0091] Furthermore, in the aerial image display device 10A, the size of the original image I1 may be changed by the focusing optical system 3, which is arranged on the optical path from the image forming unit 1 to the retroreflecting element 4, so as to satisfy the following formula (A): [pixel size]×α≧[cell size] (A) (where α represents the magnification factor achieved by the focusing optical system 3, which is arranged on the optical path from the image forming unit 1 to the retroreflecting element 4).

[0092] That is, as shown in Figure 1, when an image (intermediate image I2) of the second image light L2 is formed on the reflecting surface 4a of the retroreflective element 4 by the focusing optical system 3, the pixel P2 of the intermediate image I2 is set to be equal to or larger than the size of the cell 41.

[0093] Here, "pixel size" refers to the width of a pixel in the direction of arrangement of the subpixels when one pixel is formed from three subpixels of RGB colors. "Subpixel size" refers to the width of the subpixel in the direction of arrangement. Furthermore, "cell size" refers to half the size of one side of a cell when the retroreflective element is a corner cube type, the size of one side of a cell when the retroreflective element is a full corner cube type, or the diameter of a bead when the retroreflective element is a bead type.

[0094] 3A and 3B are explanatory diagrams illustrating the effects of the aerial image display device 10A. Fig. 3A is a diagram comparing the size of a pixel P1 in the image forming unit 1 (original image I1) with that of a cell 41, and Fig. 3B is a diagram comparing the size of a pixel P2 in the intermediate image I2 with that of the cell 41. Pixel P1 has RGB sub-pixels SP1, and pixel P2 has RGB sub-pixels SP2.

[0095] For example, as shown in FIG. 3A , when comparing the sizes of pixel P1 of the image forming unit 1 and cell 41, the device configuration is such that cell 41 is larger than pixel P1 ([size Wa of pixel P1] < [size Wb of cell 41]). If image light emitted from pixel P1 of the image forming unit 1 is incident on cell 41 while maintaining the size relationship shown in FIG. 3A , there is a risk of an optical path shift occurring in cell 41 that is greater than the size of pixel P1. In this case, problems such as image light displaying a certain pixel overlapping with image light displaying an adjacent pixel occur, leading to a reduction in the resolution of the formed aerial image.

[0096] 3(b), the first image light L1 and the second image light L2 are magnified by the optical elements arranged on the optical path from the image forming unit 1 to the retroreflective element 4, and as a result, the pixel P2 of the intermediate image I2 is equal to or larger in size than the cell 41 ([size Wc of pixel P2]≧[size Wb of cell 41]). The [size Wc of pixel P2] can be calculated from the size of pixel P1 and the magnification of the focusing optical system 3 arranged on the optical path from the image forming unit 1 to the retroreflective element 4.

[0097] In this case, even if the optical path of the second image light L2 shifts in the cell 41, the shift of the second image light L2 is likely to be contained within a single pixel. Therefore, problems such as image light displaying a pixel overlapping with image light displaying an adjacent pixel are unlikely to occur.

[0098] For the same reason, when the pixel P1 has a plurality of subpixels SP1, it is preferable that the following formula (B) be satisfied: [subpixel size]×α≧[cell size] (in the formula, α represents the magnification factor of the focusing optical system 3 arranged on the optical path from the image forming unit 1 to the retroreflective element 4).

[0099] When the above formula (B) is satisfied, the shift of the second image light L2 is likely to be contained within a single sub-pixel even if the optical path of the second image light L2 shifts in the cell 41. Therefore, problems such as image light displaying a pixel overlapping with image light displaying an adjacent pixel are even less likely to occur.

[0100] Furthermore, the light spreading that occurs in the retroreflecting element 4, such as diffraction due to aperture restriction of the retroreflecting element 4 and scattering at the vertices and ridges of the prism structure, can be focused into the aerial image AI by the focusing optical system 3. In other words, the cells 41 that make up the retroreflecting element 4 can be made smaller. Note that in a typical aerial image display device, it is known that, contrary to the aerial image display device 10A, it is effective to increase the size of the cells in order to suppress the spreading of light due to diffraction.

[0101] As described above, by forming an intermediate image I2 such that the size of the pixels constituting the image forming unit 1 is equal to or greater than the size (opening size) of the cells 41 constituting the retroreflective element 4, the display content remains constant even if the wavefront of the second image light L2 (retroreflected light) emitted from each cell 41 is inverted, and a decrease in resolution can be suppressed.

[0102] As a result, the aerial image display device 10A of this embodiment can display an aerial image AI with a higher resolution than conventional devices.

[0103] In this embodiment, one biconvex lens is illustrated as the focusing optical system, but the present invention is not limited to this.

[0104] 4 and 5 are explanatory diagrams showing a modified aerial image display device. The aerial image display device 10B shown in Fig. 4 has a focusing optical system 30 composed of multiple lenses instead of the focusing optical system 3, which is a single lens. The focusing optical system 30 is composed of multiple lenses (not shown) arranged along the main axis of the focusing optical system 30.

[0105] 3, the aerial image display device 10B having such a focusing optical system 30 can improve imaging performance compared to when a single focusing lens is used, and can form an aerial image AI with higher resolution. Furthermore, by using the focusing optical system 30, various effects can be obtained, such as the ability to change the imaging position, shorten the imaging distance (spatial distance), and adjust the luminance distribution of the entire lens.

[0106] The aerial image display device 10C shown in Fig. 5 has a focusing optical system 31 composed of two lenses instead of the focusing optical system 3 which is a single lens. The focusing optical system 31 has a lens 3a arranged on the optical element 2 side and a lens 3b arranged on the retroreflecting element 4 side. The lenses 3a and 3b are arranged along the principal axis of the focusing optical system 31. The lenses 3a and 3b are each a one-sided telecentric optical system, and the light beam between the lenses 3a and 3b is parallel.

[0107] An aerial image display device 10C having such a focusing optical system 31 can improve imaging performance compared to when a single focusing lens is used, in addition to the effects of the invention described above using Figure 3, and can form an aerial image AI with higher resolution.

[0108] 6 is an explanatory diagram of an aerial image display device 10D according to a second embodiment. In the following embodiments, components common to the previous embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

[0109] The aerial image display device 10D includes an image forming unit 1, an optical element 2, a focusing optical system 3, and a retroreflection element 4. In the aerial image display device 10D, the light component that passes through the optical element 2 is used as second image light L2.

[0110] The second image light L2 emitted from the optical element 2 passes through the focusing optical system 3 and forms an image on the reflecting surface 4a of the retroreflecting element 4. The second image light L2 is retroreflected by the retroreflecting element 4 and enters the focusing optical system 3.

[0111] The second image light L2 collected by the collecting optical system 3 is incident on the optical element 2. Of the second image light L2 incident on the optical element 2, the component reflected by the optical element 2 is focused at the collecting position of the collecting optical system 3 to form an aerial image AI.

[0112] A user U of the device can obtain various information by viewing the aerial image AI. The user U can also view the background B of the optical element 2 through the optical element 2. That is, the aerial image display device 10D is a so-called see-through display device, and can allow the user U to view an image in which the aerial image AI and the background B are superimposed.

[0113] With such an aerial image display device 10D, the effects of the invention described above using Figure 3 make it possible to display an aerial image AI with higher resolution than conventional methods, and by allowing the user U to view an image including the background B, richer image expression is possible.

[0114] 7 is an explanatory diagram of an aerial image display device 10E according to a third embodiment. The aerial image display device 10E includes an image forming unit 1, an optical element 20, a focusing optical system 3, a retroreflection element 4, a quarter-wave plate 5, and an absorbing polarizer 6.

[0115] The optical element 20 is a reflective polarizing plate. The optical element 20 separates the unpolarized first image light L1 into s-polarized light and p-polarized light, transmits the s-polarized light, and reflects the p-polarized light as the second image light L2 toward the light-collecting optical system 3. When the image forming unit 1 is a liquid crystal panel and the first image light L1 is polarized light, it is preferable that the image forming unit 1 emits p-polarized light as the first image light L1.

[0116] The quarter-wave plate 5 is disposed so as to cover the reflecting surface 4a of the retroreflective element 4. The quarter-wave plate 5 may have a known structure.

[0117] The quarter-wave plate 5 converts the incident second image light L2 from linearly polarized light (p-polarized light) to circularly polarized light. The circularly polarized second image light L2 is reflected from the fixed ends of the cells 41 of the retroreflective element 4 an odd number of times (three times for a corner cube type, and once for a bead type) and is shifted in phase by 180°.

[0118] The second image light L2 retroreflected within the cell 41 is emitted from the retroreflecting element 4 and again incident on the quarter-wave plate 5, where it is converted from circularly polarized light to linearly polarized light. At this time, the second image light L2 has been phase-shifted due to reflection within the cell 41, and is therefore converted into s-polarized light instead of the original p-polarized light.

[0119] The second image light L2, which is s-polarized light, is collected by the collecting optical system 3 and enters the optical element 2. The second image light L2 that enters the optical element 2 passes through the optical element 2 and is focused at the collecting position of the collecting optical system 3, thereby forming an aerial image AI.

[0120] The absorbing polarizer 6 is disposed on the opposite side of the optical element 2 from the focusing optical system 3. The absorbing polarizer 6 absorbs polarized light in the vibration direction reflected by the optical element 20, i.e., p-polarized light, and transmits s-polarized light.

[0121] As described above, optical element 20 is a reflective polarizing plate that reflects p-polarized light and transmits s-polarized light. However, in aerial image display device 10E, light is obliquely incident on optical element 20, which may prevent optical element 20 from performing as designed and may transmit p-polarized light as well. In this case, by placing an absorbing polarizing plate 6 that absorbs p-polarized light on the opposite side of optical element 2 from the focusing optical system 3, i.e., on the user U side, the p-polarized light that would otherwise be transmitted through optical element 20 can be absorbed by absorbing polarizing plate 6.

[0122] The aerial image display device 10E configured as described above can display an aerial image AI with higher resolution than conventional ones due to the effects of the invention described above with reference to Fig. 3. In addition, it is possible to suppress light loss in the optical path and improve visibility.

[0123] 8 is an explanatory diagram of an aerial image display device 10F according to a fourth embodiment. In the aerial image display device 10F, the optical axis 3ax of the focusing optical system 3 is inclined with respect to the chief ray axis ax1 of the second image light L2 incident on the focusing optical system 3. Furthermore, the direction of the normal 4ax to the surface (reflective surface 4a) of the retroreflective element 4 is inclined with respect to the chief ray axis ax2 of the second image light L2 incident on the retroreflective element 4.

[0124] Furthermore, in the aerial image display device 10F, an anti-reflection plate 7 is provided on the optical path between the retroreflecting element 4 and the focusing optical system 3. This prevents surface reflection of the retroreflecting element 4, suppresses the generation of stray light, and improves visibility.

[0125] The aerial image display device 10F configured as described above can display an aerial image AI with higher resolution than conventional ones due to the effects of the invention described above with reference to Fig. 3. In addition, it is possible to suppress the generation of stray light and improve visibility.

[0126] 9 and 10 are explanatory diagrams of an aerial image display device according to a fifth embodiment. The aerial image display device 10G shown in Fig. 9 has a first reflecting element 8 on the optical path between the focusing optical system 3 and the retroreflecting element 4.

[0127] 10 has a second reflecting element 9 on the optical path between the optical element 2 and the focusing optical system 3, on the opposite side of the optical element 2 from the image forming unit 1. In the aerial image display device 10H, second image light L2 formed by passing through the optical element 2 is incident on the second reflecting element 9 and specularly reflected. The focusing optical system 3 focuses the second image light L2 that enters the optical element 2 via the second reflecting element 9 and is emitted from the optical element 2.

[0128] As the first reflecting element 8 and the second reflecting element 9, known mirrors can be used.

[0129] The aerial image display devices 10G, 10H configured as described above are capable of displaying aerial images AI with higher resolution than conventional devices due to the effects of the invention described above with reference to Fig. 3. Furthermore, because the optical path within the device is bent by the first reflecting element 8 and the second reflecting element 9, the contact area of ​​the entire optical system can be reduced, allowing for the device to be made more compact.

[0130] 11 is an explanatory diagram of an aerial image display device 10I according to a sixth embodiment. The aerial image display device 10I has an image forming unit 1, an optical element 2, a focusing optical system 3, and a retroreflecting element 40. The retroreflecting element 40 has a curved surface shape that is concave on the side of the optical path that faces the focusing optical system 3.

[0131] The retroreflective element 40 has a curvature that allows it to form an intermediate image I2 with the field curvature aberration canceled on the reflecting surface 40a, taking into account the field curvature of the focusing optical system 3. Such a retroreflective element 40 can be designed by a known method based on the magnitude of the obtained field curvature after measuring the field curvature of the focusing optical system 3 or calculating it using simulation software that uses ray tracing.

[0132] The aerial image display device 10I configured as described above can display an aerial image AI with higher resolution than conventional devices due to the effects of the invention described above with reference to Fig. 3. In addition, the retroreflecting element 40 reduces the field curvature of the focusing optical system 3, making it possible to display an aerial image AI with higher resolution.

[0133] 12 is an explanatory diagram showing an aerial image display device 10J according to a seventh embodiment. The aerial image display device 10J has an image forming unit 1, an optical element 2, a light collecting unit 3A, a first retroreflecting element 4A, and second retroreflecting elements 4B and 4C. The aerial image display device 10J forms second image light L2 from first image light L1 emitted from the image forming unit 1, and forms an aerial image AI by focusing the second image light L2 in the air.

[0134] <Light Concentrating Unit> The light focusing unit 3A forms an aerial image by enlarging and focusing the second image light L2 incident from the optical element 2 side and by reducing and focusing the light incident from the retroreflective element 4 side. The light focusing unit 3A focuses a portion of the second image light L2 emitted from the optical element 2 toward the first retroreflective element 4A. In Fig. 12, the light focusing unit 3A is shown as focusing the image light L21 toward the first retroreflective element 4A.

[0135] The light collecting unit 3A has a light collecting optical system 31 that collects a part of the second image light L2, and a support 32 that supports the light collecting optical system 31.

[0136] The focusing optical system 31 focuses a portion of the second image light L2 (image light L21) toward the first retroreflective element 4A, and forms an image on the surface (reflective surface 4a) of the first retroreflective element 4A.

[0137] The light-collecting optical system 31 may be configured with a single optical element, or may be configured with a plurality of optical elements (a plurality of lenses). The light-collecting optical system 31 may also employ a lens array.

[0138] The support 32 is disposed on the outer periphery of the condensing optical system 31 in the axial direction, and supports the condensing optical system 31. The support 32 may be a known lens barrel or lens bracket.

[0139] <First and Second Retroreflective Elements> The first retroreflective element 4A and the second retroreflective elements 4B, 4C are all optical elements that retroreflect the incident second image light L2. The first retroreflective element 4A is provided at a focusing position of the focusing optical system 31 of the light focusing unit 3A. The second retroreflective elements 4B, 4C are arranged closer to the optical element 2 than the first retroreflective element 4A in the field of view seen from the optical element 2 side, and are provided at positions where the remaining portion of the second image light L2 (image light L22) that did not enter the light focusing unit 3A is incident.

[0140] The first retroreflective element 4A and the second retroreflective elements 4B and 4C each have a plurality of cells 41 that perform retroreflection.

[0141] Known configurations can be used for the first retroreflective element 4A and the second retroreflective elements 4B and 4C, such as a configuration in which a number of corner cubes are arranged on the reflective surface (corner cube type or prism lens type) or a configuration in which a number of glass beads are arranged on the reflective surface (glass bead type).

[0142] The multiple corner cubes and glass beads of the retroreflective element correspond to cells that provide retroreflection in the retroreflective element. The first retroreflective element 4A and the second retroreflective elements 4B and 4C are preferably corner cube-shaped. In Figure 12, the first retroreflective element 4A and the second retroreflective elements 4B and 4C are each shown as being corner cube-shaped.

[0143] The first retroreflective element 4A and the second retroreflective elements 4B and 4C may have the same configuration or different configurations.

[0144] The image light L21 reflected by the first retroreflective element 4A is again incident on the collecting optical system 31. At this time, the image light L21 retroreflectively reflected by the first retroreflective element 4A passes through the collecting optical system 31 from the first retroreflective element 4A side, following the same optical path as when it passed through the collecting optical system 31 from the optical element 2 side. If the collecting optical system 31 has lens aberration, the aberration when passing through the collecting optical system 31 from the optical element 2 side and the aberration when passing through the collecting optical system 31 from the first retroreflective element 4A side cancel each other out. Therefore, the lens aberration in the collecting optical system 31 is reduced for the second image light L2 emitted from the collecting optical system 31.

[0145] The image light L21 collected by the light collecting optical system 31 is incident on the optical element 2. Of the image light L21 incident on the optical element 2, the component that has passed through the optical element 2 forms an image at the light collecting position of the light collecting optical system 31.

[0146] Furthermore, the image light L22 reflected by the second retroreflective elements 4B and 4C is incident on the optical element 2. Of the image light L22 incident on the optical element 2, the component that is transmitted through the optical element 2 forms an image at a spatial position symmetrical to the image forming unit 1 across the optical element 2.

[0147] The image light L21 formed by the focusing optical system 31 and the image light L22 formed by the second retroreflective elements 4B and 4C form a single aerial image AI.

[0148] To address the issues that arise with the retroreflective element described above using Figure 2, the aerial image display device 10J uses a focusing optical system 31 to focus a portion of the second image light L2 (image light L21) onto the first retroreflective element 4A, thereby optically shortening the diffraction distance, which is the distance from the image forming unit 1 to the first retroreflective element 4A.

[0149] In addition, by positioning the second retroreflective elements 4B and 4C closer to the optical element 2 than the first retroreflective element 4A in the field of view seen from the optical element 2 side, the diffraction distance, which is the distance from the image forming unit 1 to the second retroreflective elements 4B and 4C, is shortened.

[0150] As a result, the aerial image display device 10J can improve the resolution of both the image light L21 that passes through the focusing optical system 31 and the image light L22 that does not pass through the focusing optical system 31, thereby forming a high-resolution aerial image AI.

[0151] Furthermore, the aerial image display device 10J uses, as the focusing optical system 31, an optical system that enlarges and forms an image of the image light L21 incident from the optical element 2 side and reduces and forms an image of the light incident from the first retroreflective element 4A side. As a result, the focusing optical system 31 functions as an optical system that reduces and forms an image of the retroreflected image light L21, thereby suppressing the light ray shift caused by the size (pitch size) of the cells 41 of the first retroreflective element 4A, as shown in Figure 2(a). This suppresses the spread of the point image formed by the focusing optical system 31, thereby solving the problem of reduced resolution.

[0152] 2B, the diffracted light and scattered light generated on the first retroreflective element 4A are focused at the position of the aerial image by the focusing optical system 31. This solves the problem of reduced resolution caused by the spread of light generated by the diffracted light generated on the first retroreflective element 4A.

[0153] Furthermore, the size of the original image I1 may be changed by a focusing optical system 31 disposed on the optical path from the image forming unit 1 to the first retroreflective element 4A so as to satisfy the following formula (A): [pixel size]×α≧[cell size] (A) (where α represents the magnification factor achieved by the focusing optical system 31 disposed on the optical path from the image forming unit 1 to the first retroreflective element 4A).

[0154] That is, as shown in Figure 12, when an image (intermediate image I2) of image light L21 is formed on the reflective surface 4a of the first retroreflective element 4A by the focusing optical system 31, pixel P2 of the intermediate image I2 is set to be equal to or larger than the size of cell 41.

[0155] The effects of the aerial image display device 10J will be described with reference to FIG.

[0156] 3B, the second image light L2 is magnified by the focusing optical system 31 arranged on the optical path from the image forming unit 1 to the first retroreflective element 4A, and as a result, the pixel P2 of the intermediate image I2 is equal to or larger in size than the cell 41 ([size Wc of pixel P2]≧[size Wb of cell 41]). The [size Wc of pixel P2] can be calculated from the size of pixel P1 and the magnification ratio of the focusing optical system 31 arranged on the optical path from the image forming unit 1 to the first retroreflective element 4A.

[0157] In this case, even if the optical path of the image light L21 is shifted in the cell 41, the shift of the image light L21 is likely to be contained within a single pixel. Therefore, problems such as the image light displaying a pixel overlapping with the image light displaying an adjacent pixel are unlikely to occur.

[0158] For the same reason, when pixel P1 has multiple subpixels SP1, it is preferable that the following formula (B) be satisfied: [subpixel size]×α≧[cell size] (in the formula, α represents the magnification factor of the focusing optical system 31 arranged on the optical path from the image forming unit 1 to the first retroreflective element 4A).

[0159] When the above formula (B) is satisfied, the deviation of the image light L21 is likely to be contained within a single sub-pixel even if the optical path of the image light L21 is shifted in the cell 41. Therefore, problems such as the image light displaying a pixel overlapping with the image light displaying an adjacent pixel are even less likely to occur.

[0160] Furthermore, the light spreading that occurs in the retroreflective element, such as diffraction due to aperture restriction of the retroreflective element 4 and scattering at the vertices and ridges of the prism structure, can be focused onto the aerial image AI in the focusing optical system. In other words, the cells 41 that make up the retroreflective element can be made smaller. Note that in a typical aerial image display device, it is known that, contrary to the aerial image display device 10J, it is effective to increase the size of the cells in order to suppress the spreading of light due to diffraction.

[0161] Furthermore, in the aerial image display device 10J, the second retroreflective elements 4B, 4C overlap with the support 32 in the field of view seen from the optical element 2. This allows the second image light L2 irradiated onto the position of the support 32, which does not transmit light, to be used to form the aerial image AI.

[0162] The aerial image formed using the image light L21 has a higher resolution than the aerial image formed using the image light L22. Therefore, the aerial image AI displayed by the aerial image display device 10J has a display area capable of displaying at high resolution and a display area with a relatively low resolution.

[0163] Therefore, the aerial image display device 10J configured as described above can display an aerial image AI that includes a display area with higher resolution than conventional devices and that can be expressed in a variety of ways. The first retroreflective element 4A and the second retroreflective elements 4B and 4C can be selected appropriately depending on the content of the aerial image to be displayed.

[0164] 13 is an explanatory diagram showing a modified aerial image display device 10K. The aerial image display device 10K has a focusing optical system 31 (focusing unit 3A) that focuses the image light L21 on the surface of the first retroreflective element 4A. The aerial image display device 10K configured in this manner can reduce the contact area of ​​the entire optical system, thereby enabling the device to be made more compact.

[0165] 14 is an explanatory diagram of an aerial image display device 10L according to an eighth embodiment. The aerial image display device 10L has an image forming unit 1, an optical element 2, a light collecting unit 3A, a first retroreflecting element 4A, and second retroreflecting elements 4B and 4C. In the aerial image display device 10L, the light component that passes through the optical element 2 is used as second image light L2.

[0166] A portion of the second image light L2 (image light L21) emitted from the optical element 2 forms an image on the reflective surface 4a of the first retroreflective element 4A via the light collecting portion 3A. The image light L21 is retroreflected by the first retroreflective element 4A and enters the light collecting portion 3A.

[0167] The image light L21 collected by the light collecting section 3A is incident on the optical element 2. Of the image light L21 incident on the optical element 2, the component reflected by the optical element 2 forms an image at the light collecting position of the light collecting section 3A.

[0168] Furthermore, the image light L22 reflected by the second retroreflective elements 4B and 4C is incident on the optical element 2. Of the image light L22 incident on the optical element 2, the component reflected by the optical element 2 forms an image at a spatial position symmetrical to the image forming unit 1 across the optical element 2.

[0169] The image light L21 formed by the focusing optical system 31 and the image light L22 formed by the second retroreflective elements 4B and 4C form a single aerial image AI.

[0170] A user U of the device can obtain various information by viewing the aerial image AI. The user U also views the background B of the optical element 2 through the optical element 2. That is, the aerial image display device 10L is a so-called see-through display device, and can allow the user U to view an image in which the aerial image AI and the background B are superimposed.

[0171] Such an aerial image display device 10L can display an aerial image AI that includes a display area with higher resolution than conventional devices and allows for a variety of expressions, and by allowing the user U to view an image that includes the background B, it is possible to express a richer image.

[0172] 15 is an explanatory diagram of an aerial image display device 10M according to a ninth embodiment. The aerial image display device 10M includes an image forming unit 1, an optical element 20, a light collecting unit 3A, a first retroreflecting element 4A, second retroreflecting elements 4B and 4C, a quarter-wave plate 5, and an absorbing polarizing plate 6.

[0173] The optical element 20 is a reflective polarizing plate. The optical element 20 separates the unpolarized first image light L1 into s-polarized light and p-polarized light, transmits the s-polarized light, and reflects the p-polarized light as the second image light L2. When the image forming unit 1 is a liquid crystal panel and the first image light L1 is polarized light, it is preferable that the image forming unit 1 emits p-polarized light as the first image light L1.

[0174] The quarter-wave plate 5 is disposed so as to cover the reflecting surface 4a of the first retroreflective element 4A. The quarter-wave plate 5 may have a known structure.

[0175] The quarter-wave plate 5 converts the incident second image light L2 (image light L21) from linearly polarized light (p-polarized light) to circularly polarized light. The circularly polarized second image light L2 is reflected from the fixed end of the cells 41 of the first retroreflective element 4A an odd number of times (three times for a corner cube type, one time for a glass bead type) and is shifted in phase by 180°.

[0176] The image light L21 retroreflected within the cell 41 is emitted from the first retroreflecting element 4A and again incident on the quarter-wave plate 5, where it is converted from circularly polarized light to linearly polarized light. At this time, the image light L21 has been phase-shifted due to reflection within the cell 41, and is therefore converted into s-polarized light instead of the original p-polarized light.

[0177] The image light L21, which is s-polarized light, is collected by the collecting unit 3A and enters the optical element 20. The image light L21 that enters the optical element 20 passes through the optical element 20 and is focused at the collecting position of the collecting optical system 31, thereby forming an aerial image AI.

[0178] The absorbing polarizer 6 is disposed on the opposite side of the optical element 20 from the light collecting unit 3A. The absorbing polarizer 6 absorbs polarized light in the vibration direction reflected by the optical element 20, i.e., p-polarized light, and transmits s-polarized light.

[0179] As described above, optical element 20 is a reflective polarizing plate that reflects p-polarized light and transmits s-polarized light. However, in aerial image display device 10M, light is obliquely incident on optical element 20, which could prevent optical element 20 from performing as designed and cause p-polarized light to be transmitted. In this case, by placing an absorbing polarizing plate 6 that absorbs p-polarized light on the opposite side of optical element 2 from light-collecting unit 3A, i.e., on the user U side, the p-polarized light that would otherwise be transmitted through optical element 20 can be absorbed by absorbing polarizing plate 6.

[0180] With an aerial image display device 10M configured in this manner, it is possible to display an aerial image AI that includes a display area with higher resolution than conventional ones and that can be expressed in a variety of ways, while also suppressing light loss in the optical path and improving visibility.

[0181] 16 is an explanatory diagram of an aerial image display device 10N according to a tenth embodiment. In the aerial image display device 10N, the optical axis 3ax of the light concentrator 3A is inclined with respect to the chief ray axis of the image light L21 incident on the light concentrator 3A. Furthermore, the direction of the normal 4ax to the surface (reflective surface 4a) of the first retroreflecting element 4A is inclined with respect to the chief ray axis of the image light L21 incident on the first retroreflecting element 4A.

[0182] Furthermore, in aerial image display device 10N, an anti-reflection plate 7 is provided on the optical path between first retroreflection element 4A and light collecting unit 3A. This prevents surface reflection of first retroreflection element 4A, suppresses the generation of stray light, and improves visibility.

[0183] The aerial image display device 10N configured as described above can display an aerial image AI that includes a display area with higher resolution than conventional ones and allows for a variety of expressions. It can also suppress the generation of stray light and improve visibility.

[0184] 17 is an explanatory diagram of an aerial image display device 10P according to an eleventh embodiment. In the aerial image display device 10P, a third retroreflecting element 4D is disposed at a position where third image light L3, which is the remaining portion of the second image light L2 split from the first image light L1 in the optical element 2, is incident. The third retroreflecting element 4D can have a configuration similar to that of the first retroreflecting element 4A and the second retroreflecting elements 4B and 4C.

[0185] The third image light L3 incident on the third retroreflective element 4D is retroreflected and irradiated onto the optical element 2. Of the third image light L3 incident on the optical element 2, the component reflected by the optical element 2 forms an image at a spatial position symmetrical to the image forming unit 1 across the optical element 2. The image formed by the third image light L3 is superimposed on the images formed by the image light L21 and L22 to form an aerial image AI.

[0186] The aerial image display device 10P configured as described above can display an aerial image AI that includes a display area with higher resolution than conventional ones and allows for a variety of expressions.

[0187] 18 is an explanatory diagram of an aerial image display device 10Q according to a twelfth embodiment. The aerial image display device 10Q has condensing optical systems 31A, 31B, and 31C. The condensing optical system 31A corresponds to the condensing optical system 31 described above and has the same function.

[0188] The focusing optical systems 31B and 31C correspond to the "second focusing optical system" in the present invention. The focusing optical systems 31B and 31C are supported by supports 32B and 32C, respectively. The supports 32B and 32C may have the same configuration as the support 32 described above.

[0189] The focusing optical systems 31B and 31C focus the second image light (image light L22) incident thereon onto the surfaces of the second retroreflecting elements 4B and 4C, respectively, and also focus the image light L22 reflected by the second retroreflecting elements 4B and 4C to form a part of the aerial image AI (second aerial image). The focusing optical systems 31B and 31C can have a configuration similar to that of the focusing optical system 31 described above.

[0190] Retroreflecting elements 33A, 33B, and 33C are disposed on the optical element 2 side of supports 32A, 32B, and 32C, respectively. In the field of view from the optical element 2 side, retroreflecting elements 33A, 33B, and 33C overlap supports 32A, 32B, and 32C, respectively.

[0191] Furthermore, the focusing optical system 31B, the support 32B, and the retroreflective element 33B are arranged closer to the optical element 2 than the focusing optical system 31A, the support 32A, and the retroreflective element 33A. Furthermore, the focusing optical system 31A, the support 32A, and the retroreflective element 33A are arranged closer to the optical element 2 than the focusing optical system 31C, the support 32C, and the retroreflective element 33C.

[0192] In the field of view from the optical element 2 side, part of the support 32B and the retroreflective element 33B overlaps part of the support 32A and the retroreflective element 33A. Also, part of the support 32B and the retroreflective element 33B overlaps part of the support 32C and the retroreflective element 33C.

[0193] In this way, each support device overlaps with the other, and a retroreflective element is arranged overlapping the support device, so that the second image light L2 incident on the support device can be preferably reflected toward the user U, forming an aerial image AI.

[0194] The aerial image display device 10Q configured as described above can display an aerial image AI that includes a display area with higher resolution than conventional devices and allows for a variety of expressions. The functions of the focusing optical systems 31B and 31C can also form a high-resolution aerial image of the image light L22. Furthermore, by using multiple focusing optical systems, the high-resolution aerial image can be observed from multiple viewpoints.

[0195] The aerial image display devices of the first to sixth embodiments described above can display aerial images with higher resolution than conventional ones, and are therefore expected to be used as signage.

[0196] Furthermore, the aerial image display devices of the seventh to twelfth embodiments can display aerial images with appropriate resolution depending on the displayed information, for example, by forming an aerial image using image light L21 for information that requires high resolution, such as characters or detailed drawings, and forming an aerial image using image light L22 for areas that do not require high resolution, such as background patterns. Utilizing these characteristics, applications as high-resolution aerial signage are expected.

[0197] In addition, high-resolution aerial images can be displayed for traffic information, map information, facility guides, and information displays explaining exhibits, as well as content displays for personal services such as entertainment, nursing care, and medical care.

[0198] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on the design, specifications, etc., without departing from the spirit of the present invention.

[0199] Each optical element shown in the above embodiment can be replaced with an optically equivalent element. For example, although a biconvex lens is shown as the focusing lens, a concave mirror may be used as the optical element having the focusing function. Furthermore, a light-guiding optical system for bending or curving the optical path may be provided as appropriate.

[0200] REFERENCE SIGNS LIST 1...image forming unit, 2, 20...optical element, 3, 30, 31, 31A, 31B, 31C...light-collecting optical system, 3a, 3b...lens, 3ax...optical axis, 4, 33A, 33B, 33C, 40...retroreflective element, 4ax...normal, 4A...first retroreflective element, 4B, 4C...second retroreflective element, 4D...third retroreflective element, 5...quarter-wave plate, 6...absorbing polarizer, 7...antireflection plate, 8...first reflective element, 9...second reflective element, 10A, 10 B, 10C, 10D, 10E, 10F, 10G, 10H, 10I, 10J, 10K, 10L, 10M, 10N, 10P, 10Q... aerial image display device, 32, 32A, 32B, 32C... support, 41... cell, AI... aerial image, ax1, ax2... chief ray axis, L1... first image light, L2... second image light, L3... third image light, L21, L22... image light, P1, P2... pixel, SP1, SP2... sub-pixel, Wa, Wb, Wc... size

Claims

1. An aerial image display device comprising: an image forming unit that emits first image light; an optical element that transmits a portion of the incident light and reflects the remainder to form second image light split from the first image light; a focusing optical system that focuses at least a portion of the second image light; and a retroreflective element provided at the focusing position of the focusing optical system, wherein the focusing optical system forms an enlarged image of at least a portion of the second image light on the surface of the retroreflective element and forms a reduced image of the second image light reflected by the retroreflective element to form an aerial image.

2. The aerial image display device according to claim 1, wherein the image forming unit has a plurality of pixels that emit the first image light, and the retroreflecting element has a plurality of cells that perform retroreflection, and the following formula (A) is satisfied: [pixel size] x α ≥ [cell size] ... (A) (where α represents the magnification factor of a focusing optical system arranged on the optical path from the image forming unit to the retroreflecting element.) 3. The aerial image display device according to claim 2, wherein the pixel has a plurality of sub-pixels and satisfies the following formula (B): [Sub-pixel size] x α ≥ [Cell size] ... (B) (where α is the same as α in formula (A)).

4. The aerial image display device according to any one of claims 1 to 3, wherein the optical element is a reflective polarizing plate.

5. The aerial image display device according to claim 4, further comprising a quarter-wave plate on the optical path between the retroreflecting element and the focusing optical system.

6. An aerial image display device according to claim 4, further comprising an absorbing polarizing plate, which is disposed on the optical path opposite to said focusing optical system with respect to said optical element, for absorbing polarized light in the vibration direction reflected by said optical element.

7. An aerial image display device as described in any one of claims 1 to 3, wherein the optical axis of the focusing optical system is inclined with respect to the chief ray axis of the second image light incident on the focusing optical system, and the normal direction of the surface of the retroreflective element is inclined with respect to the chief ray axis of the second image light incident on the retroreflective element.

8. The aerial image display device according to claim 7, further comprising an anti-reflection plate on the optical path between said retroreflecting element and said focusing optical system.

9. An aerial image display device according to any one of claims 1 to 3, wherein the focusing optical system is composed of a plurality of lenses arranged along the main axis of the focusing optical system.

10. An aerial image display device according to any one of claims 1 to 3, wherein the retroreflective element has a curved surface shape that is concave on the side of the focusing optical system on the optical path.

11. An aerial image display device according to any one of claims 1 to 3, further comprising a first reflecting element on the optical path between the focusing optical system and the retroreflecting element.

12. An aerial image display device as described in any one of claims 1 to 3, which has a second reflecting element on the optical path between the optical element and the focusing optical system on the opposite side of the image forming unit from the optical element, which reflects the second image light in the direction of the optical element, and the focusing optical system focuses the second image light emitted from the optical element via the second reflecting element.

13. An aerial image display device according to any one of claims 1 to 3, wherein the optical element emits the first image light that has passed through the optical element as the second image light.

14. An aerial image display device as described in claim 1, comprising: the focusing optical system that focuses a portion of the second image light; the retroreflective element provided at the focusing position of the focusing optical system; and a second retroreflective element onto which the remainder of the second image light is incident, wherein the focusing optical system forms an enlarged image of the second image light incident on the surface of the retroreflective element and forms a reduced image of the second image light reflected by the retroreflective element to form a first aerial image, and the second retroreflective element retroreflects the second image light incident on it to form a second aerial image.

15. The aerial image display device according to claim 14, wherein the optical element is a reflective polarizing plate.

16. The aerial image display device according to claim 15, further comprising a quarter-wave plate on the optical path between the retroreflecting element and the focusing optical system.

17. An aerial image display device according to claim 15 or 16, further comprising an absorbing polarizing plate, which absorbs polarized light in the vibration direction reflected by said optical element, on the optical path opposite said focusing optical system with respect to said optical element.

18. An aerial image display device according to any one of claims 14 to 16, wherein the optical axis of the focusing optical system is tilted with respect to the principal ray axis of the second image light incident on the focusing optical system.

19. The aerial image display device according to claim 18, further comprising an anti-reflection plate on the optical path between the retroreflecting element and the focusing optical system.

20. An aerial image display device as described in any one of claims 14 to 16, which has a third retroreflective element into which third image light, which is the remaining portion of the second image light split from the first image light, is incident in the optical element.

21. An aerial image display device according to any one of claims 14 to 16, wherein the optical element emits the first image light that has passed through the optical element as the second image light.

22. An aerial image display device according to any one of claims 14 to 16, wherein the second retroreflective element is positioned closer to the optical element than the retroreflective element in the field of view seen from the optical element side.

23. An aerial image display device according to claim 22, further comprising a support for supporting the focusing optical system, wherein the second retroreflective element overlaps with the support in the field of view seen from the optical element side.

24. An aerial image display device as described in any one of claims 14 to 16, which has a second focusing optical system that focuses the second image light incident on the surface of the second retroreflective element and focuses the second image light reflected by the second retroreflective element to form a second aerial image.

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