Aerial Image Display Device

Abstract

This invention provides an aerial image display device that can display aerial images with higher resolution than conventional devices. [Solution] An aerial image display device comprising: an image forming unit that emits a first image light; an optical element that transmits a portion of the incident light and reflects the remainder to form a second image light separated from the first image light; and a retroreflective element that retroreflectively reflects the second image light; a focusing optical system that directs the second image light formed by the optical element toward the retroreflective element and forms an aerial image by imaging the second image light reflected by the retroreflective element, wherein the focusing optical system forms an out-of-focus image of the second image light on the surface of the retroreflective element.

Description

Technical Field

[0006] , , ,

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

Background Art

[0002] Conventionally, display devices for displaying images or videos in the air have attracted attention as non-contact user interfaces and digital signage that provide a high sense of presence. In the following description, an image or video displayed in the air is referred to as an "aerial image". Also, a display device capable of displaying an aerial image is referred to as an "aerial image display device".

[0003] As an aerial image display device, a configuration using a retroreflective element is known (see, for example, Patent Document 1). In the aerial image display device described in Patent Document 1, an image displayed on the display device is reflected by an optical element having a beam splitter function, then incident on a retroreflective element, and a retroreflected light beam that exits in the same direction as the incident light beam is transmitted through the optical element having the beam splitter function to form an aerial image.

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

[0005] Therefore, in order to increase the resolution, a configuration using an optical element (such as a lens) having a light condensing function is known (see Patent Document 2). In Patent Document 2, an image displayed on the display device is incident on the reflection surface of the retroreflective element through an optical element having a light condensing function, so that it is incident on a relatively narrow range on the reflection surface of the retroreflective element. In Patent Document 2, it is stated that the aerial image can be increased in resolution by the above configuration.

Prior Art Documents

Patent Documents

Patent Document 1

[0007] However, as shown in Patent Document 2, simply installing an optical element (such as a lens) with a light-gathering function has limited effect on improving resolution, and there remains the problem that resolution may not improve under certain conditions. Therefore, there was a need for a display device that could reliably produce high-resolution aerial images.

[0008] This invention has been made in view of these circumstances, and aims to provide an aerial image display device that solves the aberration of the light-gathering optical element and enables the display of aerial images with higher resolution than conventional devices. [Means for solving the problem]

[0009] To solve the above problems, one aspect of the present invention includes the following aspects.

[0010] [1] An aerial image display device comprising: an image forming unit that emits a first image light; an optical element that transmits a portion of the incident light and reflects the remainder to form a second image light separated from the first image light; and a retroreflective element that retroreflectively reflects the second image light, wherein the second image light formed by the optical element is incident toward the retroreflective element, and the second image light reflected by the retroreflective element is imaged to form an aerial image, the focusing optical system forming an out-of-focus image of the second image light on the surface of the retroreflective element.

[0011] [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, the retroreflective element has a plurality of cells that perform retroreflection, and when the point image distribution function of the light-gathering optical system on the surface of the retroreflective element is f(x), the following equation (A) is satisfied. f(a)≧b…(A) (In the formula, a represents the size of the pixel, and b represents the size of the cell.)

[0012] [3] The aerial image display device according to [2], wherein the pixel has a plurality of subpixels and satisfies the following formula (B). f(c)≧b…(B) (In the formula, c represents the size of the subpixel, and b represents the size of the cell.)

[0013] [4] The aerial image display device according to any one of the items [1] to [3], wherein the optical element is a reflective polarizer.

[0014] [5] The aerial image display device according to [4], having a quarter-wave plate in the optical path between the retroreflective element and the focusing optical system.

[0015] [6] The aerial image display device according to [4] or [5], wherein the optical element has an absorbing polarizing plate on the optical path opposite to the focusing optical system, which absorbs polarization in the direction of vibration reflected by the optical element.

[0016] [7] The aerial image display device according to any one of [1] to [6], 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.

[0017] [8] The aerial image display device according to any one of [1] to [7], wherein the focusing optical system comprises a plurality of lenses arranged along the principal axis of the focusing optical system.

[0018] [9] The aerial image display device according to any one of [1] to [8], wherein the retroreflective element has a curved shape on the optical path side of the focusing optical system.

[0019]

[10] The aerial image display device according to any one of [1] to [9], wherein the image forming unit is positioned at a location that overlaps with the focal point on the image forming unit side of the light-gathering optical system.

[0020]

[11] The retroreflective element is arranged at a position farther from the condensing optical system than the condensing position on the side of the retroreflective element of the condensing optical system with respect to the condensing optical system. On the optical path between the condensing optical system and the retroreflective element, there is a separating element that refracts and separates the second image light in a first direction and a second direction. The retroreflective element has a first retroreflective element into which the second image light refracted in the first direction is incident, and a second retroreflective element into which the second image light refracted in the second direction is incident. The aerial image display device according to any one of [1] to

[10] .

[0021]

[12] The aerial image display device according to any one of [1] to

[11] , having a first reflecting element on the optical path between the condensing optical system and the retroreflective element.

[0022]

[13] On the optical path between the optical element and the condensing optical system, there is a second reflecting element that reflects the second image light in the direction of the optical element. The condensing optical system condenses the second image light emitted from the optical element through the second reflecting element. The aerial image display device according to any one of [1] to

[12] .

[0023]

[14] The optical element emits the first image light transmitted through the optical element as the second image light. The aerial image display device according to any one of [1] to

[13] .

Advantages of the Invention

[0024] According to the present invention, it is possible to provide an aerial image display device that solves the aberration of the condensing optical element and can display an aerial image with higher resolution than before.

Brief Description of the Drawings

[0025] [Figure 1] FIG. 1 is an explanatory diagram showing an aerial image display device 10A according to the first embodiment. [Figure 2] FIG. 2 is an explanatory diagram explaining problems occurring in the retroreflective element. [Figure 3] FIG. 3 is an explanatory diagram explaining the effects of the aerial image display device 10A. [Figure 4] Figure 4 is an explanatory diagram showing an aerial image display device 10B according to a modified example of the first embodiment. [Figure 5] Figure 5 is an explanatory diagram showing an aerial image display device 10C according to a modified example of the first embodiment. [Figure 6] Figure 6 is an explanatory diagram of the aerial image display device 10D according to the second embodiment. [Figure 7] Figure 7 is an explanatory diagram of the aerial image display device 10E according to the third embodiment. [Figure 8] Figure 8 is an explanatory diagram of the aerial image display device 10F according to the fourth embodiment. [Figure 9] Figure 9 is an explanatory diagram of the aerial image display device 10G according to the fifth embodiment. [Figure 10] Figure 10 is an explanatory diagram of the aerial image display device 10H according to the fifth embodiment. [Figure 11] Figure 11 is an explanatory diagram of the aerial image display device 10I according to the sixth embodiment. [Figure 12] Figure 12 is an explanatory diagram of the aerial image display device 10J according to the seventh embodiment. [Figure 13] Figure 13 is an explanatory diagram of the aerial image display device 10K according to the eighth embodiment. [Modes for carrying out the invention]

[0026] [First Embodiment] The aerial image display device according to the first embodiment will be described below with reference to Figures 1 to 5. Note that in all the following drawings, the dimensions and proportions of each component have been appropriately altered for clarity.

[0027] Figure 1 is an explanatory diagram showing an aerial image display device 10A according to the first embodiment. The aerial image display device 10A includes an image forming unit 1, an optical element 2, a condensing lens (condensing optical system) 3, and a retroreflective element 4. The aerial image display device 10A forms a second image light L2 from a first image light L1 emitted from the image forming unit 1, and forms an aerial image AI by imaging the second image light L2 in the air.

[0028] <Image Forming Section> The image forming unit 1 has a plurality of pixels P1 that emit a first image light L1. The plurality of pixels P1 are arranged, for example, in a matrix, and by emitting the first image light L1, they form the original image I1 of the aerial image AI.

[0029] The image forming unit 1 can employ various configurations as long as it is capable of emitting the first image light L1. For example, the image forming unit 1 may be a self-emissive display panel (display device), or a known display device formed by a combination of a light source and a light modulator that modulates the light emitted from the light source may be used.

[0030] As the light source for the above-mentioned display device, known light sources such as mercury lamps, laser light sources, and LEDs can be used. As the optical modulation device for the above-mentioned display device, known optical modulation devices such as liquid crystal panels and DMDs (Digital Micro-mirror Devices) can be used.

[0031] The first image light L1 emitted by the image forming unit 1 may be monochromatic, or it may be multiple colors including, for example, the three primary colors red (R), green (G), and blue (B). If the first image light L1 includes multiple colors, the image forming unit 1 may be a single display device, or it may use a different display device for each color of light emitted, and emit each color of light superimposed on the optical path.

[0032] The image forming unit 1 may have a projection optical system (not shown).

[0033] The first image light L1 emitted from the image forming unit 1 is incident on the optical element 2. Figure 1 shows the first image light L1 emitted from one pixel (point light source) of the image forming unit 1.

[0034] <Optical elements> The optical element 2 has the function of transmitting a portion of the incident light and reflecting the remainder. The optical element 2 divides the first image light L1 emitted from the image forming unit 1 to form the 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.

[0035] As the optical element 2, known beam splitters and reflective polarizers can be used.

[0036] The second image light L2 emitted from the optical element 2 enters the focusing lens 3.

[0037] <Concentrating lens> The focusing lens 3 directs the second image light L2 emitted from the optical element 2 towards the retroreflective element 4. In Figure 1, the focusing lens 3 is shown focusing the second image light L2 towards the retroreflective element 4.

[0038] The condensing lens 3 shown in Figure 1 is a magnifying optical system that magnifies and images the incident second image light L2. The condensing lens 3 is not limited to this; it may also be a reduction optical system that reduces and images the incident second image light L2. Furthermore, the condensing lens 3 can also employ a lens array.

[0039] <Retroreflective element> The retroreflective element 4 is an optical element that retroreflects the incident second image light L2. The retroreflective element 4 is located at the focusing position of the focusing lens 3. The retroreflective element 4 has a plurality of cells 41 that perform retroreflection.

[0040] A known configuration can be used for the retroreflective element 4. For example, the retroreflective element 4 can be a configuration in which a large number of corner cubes are arranged on the reflective surface (corner cube type or prism lens type), or a configuration in which a large number of glass beads are arranged on the reflective surface (glass bead type).

[0041] The multiple corner cubes and glass beads of the retroreflective element 4 each correspond to cells that perform retroreflection in the retroreflective element 4. A corner cube type configuration is preferred for the retroreflective element 4. Figure 1 shows the retroreflective element 4 as being of the corner cube type.

[0042] The second image light L2, reflected by the retroreflective element 4, enters the focusing lens 3 again. The focusing lens 3 focuses the second image light L2 to form an aerial image AI.

[0043] At this time, the second image light L2 retroreflectively reflected by the retroreflective element 4 passes through the same optical path as when it passed through the condensing lens 3 from the optical element 2 side, and then passes through the condensing lens 3 from the retroreflective element 4 side. If the condensing lens 3 has lens aberrations, the aberration when passing through the condensing lens 3 from the optical element 2 side and the aberration when passing through the condensing lens 3 from the retroreflective element 4 side cancel each other out. As a result, the lens aberrations in the condensing lens 3 are reduced in the second image light L2 emitted from the condensing lens 3.

[0044] The second image light L2, focused by the focusing lens 3, enters the optical element 2. Of the second image light L2 that enters the optical element 2, the component that passes through the optical element 2 is imaged at the focusing position of the focusing lens 3, forming an aerial image AI.

[0045] The user U of the device can acquire various information by viewing the aerial image AI.

[0046] Figure 2 is an explanatory diagram illustrating the problems that arise in retroreflective elements. Figure 2 shows a perspective view (Figure 2(a)) and a cross-sectional view (Figure 2(b)) of cell 41 of a corner cube-shaped retroreflective element 4. Similar problems also arise in retroreflective elements in which numerous glass beads are arranged on the reflective surface.

[0047] As shown in Figure 2(a), the cell 41 of the retroreflective element 4 is a triangular pyramidal shape with 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 meet to form the vertex of the triangular pyramidal shape.

[0048] The incident light IL entering such a cell 41 is reflected sequentially by, for example, the reflective surfaces 41a, 41b, and 41c, and the reflected light RL is emitted in the same direction as 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 shifted (optical path shift) due to reflections occurring within the cell 41. The amount of shift W1 between the incident light IL and the reflected light RL is larger the larger the cell 41 is.

[0049] On the other hand, as shown in Figure 2(b), when incident light IL is incident on the cell 41 of the retroreflective element 4, the incident light IL is diffracted by the cell 41 when it is reflected. As a result, the reflected light RL emitted from the cell 41 has a broadened shape as diffracted light. The amount of broadening W2 of the reflected light RL depends on the diffraction angle, so it becomes larger as the cell 41 becomes smaller.

[0050] In conventional aerial image display devices with retroreflective elements, the resolution of the aerial image was reduced due to these optical path shifts and diffractions.

[0051] In contrast, in the aerial image display device 10A, the focusing lens 3 forms an out-of-focus image OI of the second image light L2, i.e., an out-of-focus image, on the surface (reflective surface 4a) of the retroreflective element 4. In the aerial image display device 10A, the focal position of the focusing lens 3 on the retroreflective element 4 side is set on the opposite side of the retroreflective element 4 from the focusing lens 3.

[0052] Figure 3 is an explanatory diagram illustrating the effects of the aerial image display device 10A. Figure 3(a) compares the size of a pixel P1 in the image forming unit 1 (original image I1) with that of a cell 41, and Figure 3(b) compares the size of a pixel P2 in the out-of-focus image OI formed on the surface of the retroreflective element 4 with that of a cell 41. Pixel P1 has RGB subpixels SP1, and pixel P2 has RGB subpixels SP2.

[0053] Here, "pixel size" refers to the width of a pixel in the direction of the subpixel arrangement when one pixel is formed by three subpixels of RGB colors. "Subpixel size" refers to the width of a subpixel in the direction of the above arrangement. Furthermore, "cell size" refers to half the size of one side of the cell if the retroreflective element is a corner cube type, the size of one side of the cell if it is a full corner cube type, and the diameter of the bead if it is a bead type.

[0054] For example, as shown in Figure 3(a), when comparing the size of a pixel P1 in the image forming unit 1 with the size of a cell 41, the device configuration is such that the cell 41 is larger than the pixel P1 ([size of pixel P1 Wa] < [size of cell 41 Wb]). If the image light emitted from the pixel P1 of the image forming unit 1 enters the cell 41 while maintaining the size relationship as shown in Figure 3(a), there is a risk that the cell 41 will experience an optical path shift greater than the size of the pixel P1. In that case, problems such as the image light displaying a certain pixel overlapping with the image light displaying adjacent pixels may occur, leading to a decrease in the resolution of the resulting aerial image.

[0055] On the other hand, as shown in Figure 3(b), when an out-of-focus image OI of the second image light L2 is formed on the surface of the retroreflective element 4, the out-of-focus image OI is blurred and spread out more than the intermediate image formed when the second image light L2 is imaged.

[0056] In this case, even if the second image light L2 undergoes an optical path shift in cell 41, the shift in the second image light L2 is likely to remain within a single pixel. Therefore, problems such as the image light displaying one pixel overlapping with the image light displaying adjacent pixels are less likely to occur.

[0057] More specifically, the aerial image display device 10A satisfies the following equation (A), where f(x) is the point image distribution function of the focusing lens 3 on the surface of the retroreflective element 4. f(a)≧b…(A) (In the formula, a represents the size of pixel P1, and b represents the size of cell 41.)

[0058] In other words, as shown in Figure 1, the pixels P2 of the out-of-focus image OI of the second image light L2 formed on the reflective surface 4a of the retroreflective element 4 by the focusing lens 3 should be equal to or greater than the size of the cell 41 ([size of pixel P2 Wc] ≥ ​​[size of cell 41 Wb]).

[0059] For similar reasons, if pixel P1 has multiple sub-pixels SP1, it is preferable that it satisfies the following equation (B). f(c)≧b…(B) (In the formula, c represents the size of subpixel SP1, and b represents the size of cell 41.)

[0060] If equation (B) above is satisfied, even if the second image light L2 undergoes an optical path shift in cell 41, the shift in the second image light L2 is likely to remain within a single subpixel. Therefore, problems such as the image light used to display a certain pixel overlapping with the image light used to display an adjacent pixel are less likely to occur.

[0061] Furthermore, the diffusion of light generated in the retroreflective element, such as diffraction due to aperture limitation of the retroreflective element 4 and scattering at the vertices and edges of the prism structure, can be focused into the aerial image AI by the focusing optical system. In other words, the cell 41 constituting the retroreflective element can be made smaller. It should be noted that in a normal aerial image display device, it is known that, contrary to the aerial image display device 10A, it is better to make the cell larger in order to suppress the diffusion of light due to diffraction.

[0062] As a result, the aerial image display device 10A of this embodiment can display aerial images with a higher resolution than conventional devices.

[0063] In this embodiment, a single biconvex lens is illustrated and described as the light-gathering optical system, but it is not limited to this.

[0064] Figures 4 and 5 are explanatory diagrams showing an aerial image display device according to a modified example. The aerial image display device 10B shown in Figure 4 has a condensing optical system 30 composed of multiple lenses instead of a condensing lens 3. The condensing optical system 30 is composed of multiple lenses (not shown) arranged along the principal axis of the condensing optical system 30.

[0065] The focal position of the condensing optical system 30 on the retroreflective element 4 side is set on the opposite side of the condensing optical system 30 from the retroreflective element 4. In other words, the retroreflective element 4 is positioned closer to the condensing optical system 30 than the imaging position of the intermediate image I2 formed by the condensing optical system 30. An out-of-focus image OI of the second image light L2 is formed on the surface of the retroreflective element 4.

[0066] In addition to the effects of the invention described with reference to Figure 3, the aerial image display device 10B having such a light-gathering optical system 30 can improve imaging performance compared to using a single light-gathering lens, and can form aerial images AI with higher resolution. Furthermore, by using the light-gathering optical system 30, various effects can be obtained, such as changing the imaging position, shortening the coupling distance (spatial distance), and adjusting the brightness distribution of the entire lens.

[0067] The aerial image display device 10C shown in Figure 5 has a focusing optical system 31 composed of two lenses instead of a focusing lens 3. The focusing optical system 31 has a lens 3a located on the optical element 2 side and a lens 3b located on the retroreflective element 4 side. Lenses 3a and 3b are arranged along the principal axis of the focusing optical system 31. Lenses 3a and 3b are each one-sided telecentric optical systems, and the light rays between lens 3a and lens 3b are parallel light.

[0068] In addition to the effects of the invention described with reference to Figure 3, the aerial image display device 10C having such a light-gathering optical system 31 can improve imaging performance compared to using a single light-gathering lens, and can form aerial images AI with higher resolution.

[0069] [Second Embodiment] Figure 6 is an explanatory diagram of the aerial image display device 10D according to the second embodiment. In the following embodiments, components common to the previously described embodiments are denoted by the same reference numerals, and detailed descriptions are omitted.

[0070] The aerial image display device 10D comprises an image forming unit 1, an optical element 2, a condensing lens (condensing optical system) 3, and a retroreflective element 4. In the aerial image display device 10D, the light component transmitted through the optical element 2 is used as the second image light L2.

[0071] The second image light L2 emitted from the optical element 2 is incident on the retroreflective element 4 side via the focusing lens 3. The retroreflective element 4 is positioned closer to the focusing lens 3 than the imaging position of the intermediate image I2 formed by the focusing lens 3. An out-of-focus image OI of the second image light L2 is formed on the surface of the retroreflective element 4.

[0072] Furthermore, the second image light L2 is retroreflective by the retroreflective element 4 and incident on the focusing lens 3.

[0073] The second image light L2, focused by the focusing lens 3, enters the optical element 2. Of the second image light L2 that enters the optical element 2, the component reflected by the optical element 2 is imaged at the focusing position of the focusing lens 3, forming an aerial image AI.

[0074] The user U of the device can acquire various information by viewing the aerial image AI. In addition, the user U will also view the background B of the optical element 2 through the optical element 2. In other words, the aerial image display device 10D is a so-called see-through type display device, which allows the user U to view an image in which the aerial image AI and background B are superimposed.

[0075] With this aerial image display device 10D, the effects of the invention described using Figure 3 above enable the display of aerial images AI with higher resolution than conventional methods, and by allowing the user U to view the image including the background B, richer image representation becomes possible.

[0076] [Third Embodiment] Figure 7 is an explanatory diagram of the aerial image display device 10E according to the third embodiment. The aerial image display device 10E includes an image forming unit 1, an optical element 20, a focusing lens 3, a retroreflective element 4, a quarter-wave plate 5, and an absorbing polarizing plate 6.

[0077] The optical element 20 is a reflective polarizer. The optical element 20 separates the unpolarized first image light L1 into s-polarized and p-polarized light, transmits the s-polarized light, and reflects the p-polarized light as the second image light L2 in the direction of the focusing lens 3. If the image forming unit 1 is a liquid crystal panel and the first image light L1 is polarized light, it is preferable to configure the image forming unit 1 to emit p-polarized light as the first image light L1.

[0078] The quarter-wave plate 5 is positioned to cover the reflective surface 4a of the retroreflective element 4. A known configuration can be used for the quarter-wave plate 5.

[0079] The quarter-wave plate 5 converts the incident second image light L2 from linearly polarized (p-polarized) to circularly polarized. The second image light L2, converted to circular polarization, is reflected an odd number of times (3 times for a corner cube type, 1 time for a glass bead type) at the fixed end of the cell 41 of the retroreflective element 4, and its phase shifts by 180°.

[0080] The second image light L2, retroreflective within cell 41, is emitted from the retroreflective 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, because the phase of the second image light L2 has shifted due to reflection within cell 41, it is converted from the original p-polarized light to s-polarized light.

[0081] The s-polarized second image light L2 is focused by the focusing lens 3 and incident on the optical element 2. The second image light L2 that incident on the optical element 2 passes through the optical element 2 and forms an image at the focusing position of the focusing lens 3, forming an aerial image AI.

[0082] The absorbing polarizer 6 is positioned on the opposite side of the optical element 2 from the focusing lens 3. The absorbing polarizer 6 absorbs the polarization in the direction of vibration reflected by the optical element 20, i.e., p-polarized light, and transmits s-polarized light.

[0083] As described above, the optical element 20 is a reflective polarizer and has the function of reflecting p-polarized light and transmitting s-polarized light. However, in the aerial image display device 10E, the light is incident on the optical element 20 at an oblique angle, so the optical element 20 may not perform as designed and may transmit p-polarized light as well. In this case, by placing the absorbing polarizer 6, which absorbs p-polarized light, on the opposite side of the optical element 2 from the condensing lens 3, i.e., on the user U side, the p-polarized light that would otherwise pass through the optical element 20 can be absorbed by the absorbing polarizer 6.

[0084] With the aerial image display device 10E configured in this way, the effects of the invention described using Figure 3 above enable the display of aerial images AI with higher resolution than conventional devices. Furthermore, it is possible to suppress light loss in the optical path and improve visibility.

[0085] [Fourth Embodiment] Figure 8 is an explanatory diagram of the aerial image display device 10F according to the fourth embodiment. In the aerial image display device 10F, the optical axis 3ax of the condensing lens 3 is inclined with respect to the principal ray axis of the second image light L2 incident on the condensing lens 3. This prevents surface reflection of the retroreflective element 4, suppresses the generation of stray light, and improves visibility.

[0086] With the aerial image display device 10F configured in this way, the effects of the invention described using Figure 3 above enable the display of aerial images AI with higher resolution than conventional devices. Furthermore, the effects of lens aberrations can be eliminated regardless of the optical axis of the condensing lens 3. In addition, while off-axis optical systems with configurations offset from the optical axis may experience increased aberrations, this configuration offers the significant advantage of greater freedom in determining the image formation position.

[0087] [Fifth Embodiment] Figures 9 and 10 are explanatory diagrams of the aerial image display device according to the fifth embodiment. The aerial image display device 10G shown in Figure 9 has a first reflecting element 8 in the optical path between the focusing lens 3 and the retroreflective element 4.

[0088] The aerial image display device 10H shown in Figure 10 has a second reflecting element 9 on the optical path between the optical element 2 and the focusing lens 3, on the side opposite to the image forming unit 1 relative to the optical element 2. In the aerial image display device 10H, the 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 lens 3 is incident on the optical element 2 via the second reflecting element 9 and focuses the second image light L2 emitted from the optical element 2.

[0089] Known mirrors can be used as the first reflecting element 8 and the second reflecting element 9.

[0090] With the aerial image display devices 10G and 10H configured in this way, the effects of the invention described using Figure 3 above enable the display of aerial images AI with higher resolution than conventional devices. Furthermore, because the optical path within the device is bent by the first reflecting element 8 and the second reflecting element 9, the footprint of the entire optical system can be reduced, allowing the device to be miniaturized.

[0091] [Sixth Embodiment] Figure 11 is an explanatory diagram of the aerial image display device 10I according to the sixth embodiment. In the aerial image display device 10I, the image forming unit 1 is positioned at a location that coincides with the focal point of the condensing lens 3 on the image forming unit 1 side. As a result, the second image light L2 is converted into parallel light by the condensing lens 3, forming an intermediate image I2 at infinity.

[0092] In this case, the second image light L2 emitted from the point light source on the image forming unit 1 illuminates the entire illumination area of ​​the retroreflective element 4, and is retroreflective by all of the multiple cells present in that illumination area. This averages out the manufacturing errors of the retroreflective element 4, making it possible to display a high-resolution aerial image AI.

[0093] Furthermore, when the second image light L2 is irradiated across multiple cells of the retroreflective element 4, diffraction is expected to occur in the cells. However, since the second image light L2 is irradiated onto the retroreflective element 4 as parallel light, the resulting diffraction pattern can be considered to be constant regardless of the light incidence position in the retroreflective element 4. Therefore, by emitting the first image light L1 from the image forming unit 1 that has undergone inverse filtering processing that takes the diffraction pattern into account, the degradation of the image quality of the aerial image AI due to diffraction can be suppressed.

[0094] With the aerial image display device 10I configured in this way, the effects of the invention described using Figure 3 above enable the display of aerial images AI with higher resolution than conventional devices. The effects of manufacturing errors of the retroreflective element 4 are reduced, enabling the display of high-resolution aerial images AI.

[0095] [Seventh Embodiment] Figure 12 is an explanatory diagram of the aerial image display device 10J according to the seventh embodiment. The aerial image display device 10J includes an image forming unit 1, an optical element 2, a condensing lens 3, and a retroreflective element 40. The retroreflective element 40 has a curved shape in which the side of the optical path facing the condensing lens 3 is concave.

[0096] For the condensing lens 3, lenses that are generally considered to have large aberrations, such as thick-walled lenses, achromatic lenses, Fresnel lenses, and lens arrays, can be used.

[0097] The second image light L2 emitted from the optical element 2 is incident on the retroreflective element 40 side via the condensing lens 3. The retroreflective element 40 is positioned further away from the condensing lens 3 than the condensing position of the condensing lens 3 (the imaging position of the intermediate image I2). An out-of-focus image of the second image light L2 is formed on the surface of the retroreflective element 4.

[0098] The retroreflective element 40 has a curvature that takes into account the field curvature of the condensing lens 3 (condensing optical system) and is capable of forming an intermediate image I2 on the reflective surface 40a where the field curvature aberration is canceled out. Such a retroreflective element 40 can be designed by a known method based on the magnitude of the field curvature obtained after measuring or theoretically calculating the field curvature of the condensing lens 3.

[0099] With the aerial image display device 10J configured in this way, the effects of the invention described using Figure 3 above enable the display of aerial images AI with higher resolution than conventional devices. In addition, the retroreflective element 40 reduces the curvature of the image field of the focusing lens 3, enabling the display of aerial images AI with even higher resolution.

[0100] [Eighth Embodiment] Figure 13 is an explanatory diagram of the aerial image display device 10K according to the eighth embodiment. The aerial image display device 10J includes an image forming unit 1, an optical element 2, a focusing lens 3, a retroreflective element 42, and a separation element 45.

[0101] The second image light L2 emitted from the optical element 2 enters the retroreflective element 42 side via the condensing lens 3. The retroreflective element 42 is positioned further away from the condensing lens 3 than the condensing position of the condensing lens 3 (the imaging position of the intermediate image I2).

[0102] The separation element 45 is positioned in the optical path between the focusing lens 3 and the retroreflective element 42. The separation element 45 separates the second image light L2 by refracting it in a first direction and a second direction. For example, a prism can be used as the separation element 45.

[0103] The retroreflective element 42 includes a first retroreflective element 42a to which the second image light L21 refracted in a first direction is incident, and a second retroreflective element 42b to which the second image light L22 refracted in a second direction is incident. An out-of-focus image OI1 of the second image light L21 is formed on the surface of the first retroreflective element 42a. An out-of-focus image OI2 of the second image light L22 is formed on the surface of the second retroreflective element 42b.

[0104] The second image light L21 and L22, retroreflective by the retroreflective element 42, are coupled by the separation element 45 and emitted toward the focusing lens 3. The second image light L2 (second image light L21 and L22), focused by the focusing lens 3, is incident on the optical element 2. Of the second image light L2 incident on the optical element 2, the component that passes through the optical element 2 is imaged at the focusing position of the focusing lens 3, forming an aerial image AI.

[0105] With the aerial image display device 10K configured in this way, the effects of the invention described using Figure 3 above enable the display of aerial images AI with higher resolution than conventional devices. Furthermore, even when multiple retroreflective elements are used, the second image light L2 is incident while avoiding the boundaries between the retroreflective elements, enabling the display of a seamless aerial image AI.

[0106] The aerial image display devices of the embodiments described above do not have retroreflective elements placed at the imaging position of the image light emitted from the image forming unit. Therefore, even if displacement of each element occurs due to heat generation or vibration during operation of the device, it is still possible to display a suitable high-resolution aerial image. Taking advantage of this characteristic, it is expected that these devices can be mounted on mobile devices that experience vibration and heat generation, such as vehicles and robots, to display high-resolution aerial images.

[0107] In addition, it will be possible to display high-resolution aerial images for information displays such as traffic information, map information, facility guides, and explanations of exhibits, as well as for content displays in interpersonal services such as entertainment, nursing care, and medical care.

[0108] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design, specifications, etc., without departing from the spirit of the present invention.

[0109] Furthermore, each optical element shown in the above embodiment can be replaced with an optically equivalent element. For example, although a biconvex lens was shown as the focusing lens, a concave mirror may be used as the optical element with a focusing function. In addition, a light guide optical system may be appropriately provided for bending and curving the optical path. [Explanation of Symbols]

[0110] 1…Image forming unit, 2,20…Optical elements, 3…Focusing lens (Focusing optical system), 3a,3b…Lens, 3ax…Optical axis, 4,40,42…Retroreflective elements, 5…Waveplate, 6…Absorbing polarizer, 8…First reflecting element, 9…Second reflecting element, 10A,10B,10C,10D,10E,10F,10G,10H,10I,10J,10K…Air image display device, 30,31…Focusing optical system, 41…Cell, 42a…First retroreflective element, 42b…Second retroreflective element, 45…Separating element, AI…Air image, L1…First image light, L2,L21,L22…Second image light, OI,OI1,OI2…Out-of-focus image, P1,P2…Pixel, SP1,SP2…Sub-pixel, Wa,Wb…Size

Claims

1. An image forming unit that emits a first image light, An optical element that transmits a portion of the incident light and reflects the remainder to form a second image light separated from the first image light, The system comprises a retroreflective element that retroreflects the second image light, The optical system includes a light-gathering optical system that directs the second image light formed by the optical element toward the retroreflective element and forms an aerial image by imaging the second image light reflected by the retroreflective element, The light-gathering optical system is an aerial image display device that forms an out-of-focus image of the second image light on the surface of the retroreflective element.

2. The image forming unit has a plurality of pixels that emit the first image light, The retroreflective element has a plurality of cells that perform retroreflection, The aerial image display device according to claim 1, wherein the point image distribution function of the light-gathering optical system on the surface of the retroreflective element is f(x), and the following equation (A) is satisfied. f(a)≧b…(A) (In the formula, a represents the size of the pixel, and b represents the size of the cell.)

3. The aforementioned pixel has a plurality of subpixels, The aerial image display device according to claim 2, satisfying the following formula (B). f(c)≧b…(B) (In the formula, c represents the size of the subpixel, and b represents the size of the cell.)

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

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

6. The aerial image display device according to claim 4, further comprising an absorbing polarizing plate on the optical path opposite to the condensing optical system relative to the optical element, which absorbs polarization in the vibration direction reflected by the optical element.

7. The aerial image display device according to any one of claims 1 to 3, 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.

8. The aerial image display device according to any one of claims 1 to 3, wherein the light-gathering optical system is composed of a plurality of lenses arranged along the principal axis of the light-gathering optical system.

9. The aerial image display device according to any one of claims 1 to 3, wherein the retroreflective element has a curved shape in which the side of the light-gathering optical system on the optical path is concave.

10. The aerial image display device according to any one of claims 1 to 3, wherein the image forming unit is positioned at a location that overlaps with the focal point on the image forming unit side of the light-gathering optical system.

11. The retroreflective element is positioned at a location further away from the focusing position of the focusing optical system than the focusing position on the retroreflective element side of the focusing optical system. The optical path between the light-gathering optical system and the retroreflective element includes a separation element that refracts and separates the second image light in a first direction and a second direction. The aerial image display device according to any one of claims 1 to 3, wherein the retroreflective element comprises a first retroreflective element to which the second image light refracted in the first direction is incident, and a second retroreflective element to which the second image light refracted in the second direction is incident.

12. The aerial image display device according to any one of claims 1 to 3, further comprising a first reflector in the optical path between the light-gathering optical system and the retroreflective element.

13. A second reflecting element is provided in the optical path between the optical element and the light-gathering optical system, which reflects the second image light in the direction of the optical element. The aerial image display device according to any one of claims 1 to 3, wherein the light-gathering optical system gathers the second image light emitted from the optical element via the second reflecting element.

14. The aerial image display device according to any one of claims 1 to 3, wherein the optical element emits the first image light transmitted through the optical element as a second image light.

Images