Floating display device

Abstract

This invention relates to a levitating display device. The levitating display device includes: an image display unit having a display surface and emitting display light constituting an image from the display surface; a conjugate imaging element having a one-dimensional grating structure for converging the display light in a first direction; a relay light group disposed optically downstream of the image display unit; a beam expander light group disposed optically downstream of the relay light group and for expanding the display light only in a second direction; and an imaging light group disposed optically downstream of the beam expander light group and for converging the display light in the second direction, wherein a light beam emitted from a point on the display surface is converged in the first direction via the conjugate imaging element to a corresponding range on the image surface, and simultaneously converged in the second direction via the one-dimensional optical element to a corresponding range on the image surface, thereby causing the display light to form a levitating image on the image surface.

Description

Technical Field

[0001] The embodiments described herein generally relate to the field of optical display technology, and more specifically to a floating display device. Background Technology

[0002] Among the many display technologies, aerial levitation display technology has attracted much attention from researchers because it can display images in the air, bringing viewers a strong visual impact and a sensory experience that is both real and surreal.

[0003] Existing levitation display technologies mainly fall into three categories: The first category uses traditional optical lens imaging, such as a concave mirror and beam splitter structure. This optical structure was the earliest proposed solution for this type of display system. The illuminated real object or the content displayed on the LCD is reflected by the beam splitter into the concave mirror. The light is then converged by the concave mirror and passes through the beam splitter again to form an image on the other side. The observer then sees an image suspended in mid-air. This technology results in a small image size and severe distortion and aberrations. The second category utilizes integrated imaging principles. This type of solution consists of a microlens array and several image unit arrays. Light emitted from points displaying the same image information in the image unit converges in space through corresponding microlenses to form a levitation image point. The advantage of this solution is its ultra-thin display device, with a thickness essentially the same as a monitor. The disadvantages are low resolution and high cost.

[0004] The third type utilizes "negative refractive index screens" constructed with special microstructures for levitation imaging. These mainly include: a. Retroreflective structure with a beam splitter: This structure primarily consists of glass microspheres or microprism arrays. This structure achieves the effect that reflected light and incident light are parallel and opposite in direction. Light emitted from the display source is incident on the retroreflective structure via the beam splitter, and the reflected light passes through the retroreflective structure again in the opposite direction to the incident light, thus converging on the other side to form an image. b. Double-layer plane mirror array: This scheme consists of two layers of plane mirror arrays, with the plane mirror units between the two layers perpendicular to each other. Light emitted from the display source is reflected by this plane mirror array and converges on the other side to form an image. c. Micro-protrusion structure array: This scheme consists of a micro-protrusion structure array. Light emitted from the display source undergoes two reflections through the micro-protrusion structure and converges on the other side to form an image. The advantage of this type of technology is the absence of aberrations. The disadvantages are the presence of ghosting, high manufacturing cost of the "negative refractive index screen," and large system size.

[0005] Therefore, there is a need in this field for a new technical solution for levitation displays. Summary of the Invention

[0006] The purpose of exemplary embodiments of the present invention is to provide a levitation display device that can form levitation images in the air, while having a thinner and lighter design and a more flexible optical layout.

[0007] Specifically, an exemplary embodiment of the present invention provides a levitating display device, comprising: an image display unit having a display surface and emitting display light constituting an image from the display surface; a conjugate imaging element having a one-dimensional grating structure for converging the display light in a first direction; a relay light group disposed optically downstream of the image display unit, wherein a parallel light beam entering the relay light group in a second direction from the entrance pupil of the relay light group remains a parallel light beam in the second direction at its exit pupil after passing through the relay light group, the first direction and the second direction being orthogonal to the optical axis of the levitating display device; a beam expander light group disposed optically downstream of the relay light group and for expanding the display light only in the second direction; and an imaging light group disposed optically downstream of the beam expander light group and for converging the display light in the second direction, wherein a light beam emitted from a point on the display surface is converged in the first direction via the conjugate imaging element to a corresponding range on the image surface, and simultaneously converged in the second direction via the one-dimensional optical element to the corresponding range on the image surface, thereby causing the display light to form a levitating image on the image surface.

[0008] In the aforementioned levitated display device, the point beam on the display surface forms images with minimal (or no) aberrations along the first direction, and the image-side aperture angle is relatively large, satisfying the binocular parallax condition, thereby enabling the floating display of images. The optical systems in these levitated display devices are easy to manufacture, effectively reducing costs. Furthermore, by separately modulating the display light in the first and second directions, aberration problems present in existing technologies can be eliminated. In addition, beam expansion in the second direction achieves a thinner optical system.

[0009] Preferably, the image display unit is: a direct-view display source that directly displays the image on the display surface; or a projection display source that projects the light constituting the image onto the display surface, wherein the projection display source is configured such that the display light is parallel light in the second direction.

[0010] Preferably, when the image display unit is a direct-view display source, the floating display device further includes a collimating light group for converting light emitted from different light-emitting points on the display surface into parallel light at different angles in the second direction.

[0011] Preferably, when the image display unit is a projection display source, the suspended display device further includes a scattering screen for scattering light along the first direction. More preferably, the optical path between the scattering screen and the conjugate imaging element is set to be equal to the optical path between the conjugate imaging element and the image plane.

[0012] Preferably, the beam-expanding optical group includes a planar optical waveguide with multiple light deflection sections. The planar optical waveguide expands the incident light beam using total internal reflection, and the multiple light deflection sections are used to emit the light within the planar optical waveguide at different positions. Preferably, the planar optical waveguide is angularly positioned relative to the imaging optical group. The imaging optical group includes a one-dimensional imaging mirror, and the planar optical waveguide is disposed at the focal plane of the one-dimensional imaging mirror. Preferably, the imaging optical group includes a one-dimensional lens array, which is disposed on the surface of the light-emitting portion of the planar optical waveguide. Each one-dimensional lens in the one-dimensional lens array corresponds to one of the multiple light deflection sections and is used to change the angle of the light rays from the corresponding light deflection section.

[0013] Preferably, the conjugate imaging element is disposed optically downstream of the relay optical group. More preferably, the conjugate imaging element is disposed optically downstream of the beam expander optical group.

[0014] Preferably, the levitation display device has an aperture stop disposed between the imaging light group and the beam expander light group for confining light from the beam expander light group in the second direction. Attached Figure Description

[0015] The invention can be better understood by describing exemplary embodiments of the invention in conjunction with the accompanying drawings, in which:

[0016] Figure 1 A schematic block diagram of a floating display device 100 according to an embodiment of the present invention is shown;

[0017] Figure 2 A schematic diagram illustrating the principle of light propagation in the horizontal and vertical directions of a floating display device 100 according to an embodiment of the present invention is shown.

[0018] Figure 3 A schematic diagram of a relay optical array according to an embodiment of the present invention is shown;

[0019] Figure 4 Several typical structures of planar optical waveguides used for beam expansion are shown;

[0020] Figure 5 A schematic diagram showing the planar optical waveguide angularly positioned relative to the imaging light composition is provided.

[0021] Figure 6 A schematic diagram of a floating display device 600 according to a first example of the present invention is shown;

[0022] Figure 7 A schematic diagram of a floating display device 700 according to a second example of the present invention is shown;

[0023] Figures 8A-8B A schematic diagram of the floating display devices 800 and 800' according to a third example of the present invention is shown;

[0024] Figure 9 A schematic diagram of a floating display device 900 according to a fourth example of the present invention is shown;

[0025] Figure 10 A schematic diagram of a floating display device 1000 according to a fifth example of the present invention is shown;

[0026] Figure 11 An example structure of a one-dimensional retroreflector screen is shown;

[0027] Figure 12 Example of a one-dimensional lattice transmission array structure;

[0028] Figure 13A An example and a schematic diagram of optical modulation are shown for a planar optical waveguide with two types of microstructures.

[0029] Figure 13B An example of a microstructure composed of several smaller microstructures is shown;

[0030] Figure 14 A schematic diagram of a floating display device 1400 according to a sixth example of the present invention is shown;

[0031] Figure 15A A schematic diagram showing a floating display device 1500 according to a seventh example of the present invention; and

[0032] Figure 15B An example of a scattering screen employing a dual cylindrical microlens array is shown. Detailed Implementation

[0033] The following describes specific embodiments of the present invention. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. It should be understood that, in the actual implementation of any embodiment, just as in any engineering or design project, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and this can change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, some design, manufacturing, or production modifications based on the technical content disclosed herein are merely conventional technical means and should not be construed as insufficient content of this disclosure.

[0034] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in the patent application description and claims of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the element or object preceding "comprising" or "including" encompasses the element or object listed following "comprising" or "including" and its equivalents, and do not exclude other elements or objects. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0035] Figure 1 A schematic block diagram of a floating display device 100 according to an embodiment of the present invention is shown. Figure 2 A schematic diagram illustrating the principle of light propagation in the horizontal and vertical directions of a floating display device 100 according to an embodiment of the present invention is shown.

[0036] See Figure 1The levitation display device 100 according to an embodiment of the present invention may include an image display unit 110 and an optical system. The image display unit 110 has an image display surface and emits display light constituting an initial image from the display surface. The image display unit 110 may employ a direct light emission display method or an indirect projection method to directly display or indirectly project an image on the display surface. Indirect projection methods may include conventional projection methods, parallel light projection, laser MEMS scanning projection, etc. The optical system is arranged downstream of the image display unit 110 to receive the display light. The optical system receives the original light constituting the initial image, and then the original light is modulated by the optical system to form a levitation image (also referred to as an aerial image) at the image plane in the air. Alternatively, it is conceivable that one or more additional optical systems may exist between the image display unit 110 and the optical system, which can image the display surface of the image display unit 110 onto the object plane of the optical system; in this case, the object plane of the optical system 110 may be located at the image plane of the display surface of the image display unit 110 imaged by one or more additional optical systems.

[0037] For ease of description, light can be considered to propagate along the optical path from an optical "upstream" position to an optical "downstream" position within the beam. Therefore, the relative positions of optical elements within the optical path can also be described using these two terms. See, for example, [link to relevant documentation]. Figure 2 The relay light group 130 is located optically downstream of the image display unit 110 and optically upstream of the beam expander light group 140.

[0038] The optical system of the levitated display device 100 may include a conjugate imaging element 120, a relay light group 130, a beam expander light group 140, and an imaging light group 150. The display light from the image display unit 110 forms a levitated image at the image plane 20 in the air after propagating through the optical system, wherein the image aperture angle α in the x-direction may be greater than the image aperture angle β in the y-direction.

[0039] The conjugate imaging element 120 may have a one-dimensional grating structure for converging display light from the image display unit 110 in a first direction. As an example, the conjugate imaging element with a one-dimensional grating structure may be a one-dimensional retroreflective screen, a one-dimensional lattice transmission array, a one-dimensional holographic grating, etc. The advantage of using such a conjugate imaging element is that the positional relationship (object and image) is conjugate, the image is not magnified, and there are no aberrations. An example of a one-dimensional retroreflective screen is... Figure 11 As shown, when light rays arbitrarily strike the surface of a one-dimensional retroreflective screen, a portion of the light is reflected at the original angle. An example of a one-dimensional grating transmission array structure is shown below. Figure 12 As shown, a one-dimensional grid transmission array structure can be formed by bonding several parallel glass plates together, wherein the bonding surface is coated with a metal reflective film, and the object point o and the image point o' are optically conjugate. The object plane and the image plane of this structure are the same size and there are no aberrations.

[0040] The relay light group 130 is disposed optically downstream of the image display unit 110. In some embodiments of the present invention, parallel light beams of different incident angles (i.e., from different pixels) entering the relay light group 130 through its entrance pupil are still parallel light beams of different angles at their exit pupils after passing through the relay light group 130. Figure 3 As shown. The relay light group 130 can be used to limit the height (range) of the propagating light in the second direction, thereby contributing to the thinning of the suspended display device 100 in the second direction. The first direction can be the x-direction, and the second direction can be the y-direction, both orthogonal to the optical axis of the suspended display device 100.

[0041] The beam expander group 140 is positioned optically downstream of the relay group 130 and is used to expand the display light only in the second direction. For example... Figure 2 As shown, in the second direction (y direction), a narrower parallel beam entering the beam expander group 140 can be expanded into a wider parallel beam.

[0042] Imaging light group 150 is positioned optically downstream of beam expander light group 140 and is used to converge the expanded beam from beam expander light group 140 in a second direction. As an example, imaging light group 150 may include a cylindrical lens, concave mirror, etc., that has positive optical power in the second direction but no optical power in the first direction. Note that imaging light group 150 may be a single optical element or a combination of multiple optical elements.

[0043] In the levitation display device 100 of the present invention, a light beam emitted from a point on the display surface 10 converges in a first direction (x-direction) via a conjugate imaging element 120 to a corresponding range on the image surface 20, and simultaneously converges in a second direction (y-direction) via a one-dimensional optical element to a corresponding range on the image surface 20, thereby forming a levitation image on the image surface 20. Note that the corresponding range described here can be a point on the image surface 20, or it can be a small range centered on a point on the image surface 20 rather than being limited to that point. The corresponding range is sufficient as long as the following condition is met: the light beam emitted from a point on the display surface 10 converges in the first and second directions within the corresponding range, so that when the human eye moves in the second direction, the size and position of the observed levitation image in the second direction do not change significantly with the change of the human eye's observation position. It can be understood that, preferably, a light beam emitted from a point on the display surface 10 converges at a corresponding point on the image surface 20 via the conjugate imaging element 120 in the first direction (x direction), and also converges at the corresponding point on the image surface 20 via a one-dimensional optical element in the second direction (y direction).

[0044] A cross-sectional analysis of the beam propagation of the suspended display device 100 is performed in the first direction (x-direction) and the second direction (y-direction), respectively. See [link / reference]. Figure 2 If the image display unit 110 is a direct-view display source, then in the x-direction, the light rays emitted from object points a and b on the display surface 10 have a large divergence angle, and are imaged as a1 and b1 on the image surface 20 by the conjugate imaging element 120. If the image display unit 110 is a projection display source, then a scattering screen can be placed behind it to diverge the light rays in the x-direction to achieve a large divergence angle. In the y-direction, if the image display unit 110 is a direct-view display source, then the light rays emitted from object points a and b can be converted into parallel light of different angles in the y-direction by a collimating light group. If the image display unit 110 is a projection display source, then parallel light can be emitted directly from object points a and b. The parallel light of different angles remains parallel light of different angles after passing through the relay light group 130, but the angle can be changed to be coupled into the beam expander light group 140. The thin parallel beam is broadened into a coarse parallel beam in the y-direction by the beam expander light group 140, and then imaged as a1 and b1 on the image surface 20 by the imaging light group 150.

[0045] The above describes a levitation display device 100 according to an exemplary embodiment of the present invention. In the levitation display device 100, the image-side aperture angle of a point on the display surface 10 imaged along the x-direction by a conjugate imaging element is relatively large (preferably 30 degrees or more) to satisfy the binocular parallax condition, thereby forming a levitation image at the image surface 20. The image-side aperture angle of a point on the display surface 10 imaged along the y-direction by multiple light sources is relatively small, preferably within 30 degrees.

[0046] As described above, the display surface 10 can be a display screen of a self-emissive display or a projection surface generated by a projection display, and the light emitted by the display (i.e., the image source) can be set according to the light divergence angle requirements. In particular, the light emitted by the object point on the display surface 10 needs to have a certain object-side aperture angle in the first direction (e.g., 30 degrees to 180 degrees, specifically determined by the image-side aperture angle combined with the Laplace invariant formula as needed). This can be achieved through the inherent characteristics of the light source (i.e., the image source) or by modulating the light from the light source (i.e., the image source). For example, self-emissive displays such as OLEDs can emit light with a large divergence angle, so when their display screen is placed at the object surface (i.e., the display surface 10) of the aforementioned optical system, a floating display effect can be achieved. Optionally, if the light emitted by the object point on the display surface 10 does not have a large divergence angle in the first direction, a scattering screen can be provided to diffuse the light in the first direction, thereby making the light emitted from the scattering screen have a large divergence angle in the first direction.

[0047] Optionally, in some embodiments, the levitated display device 100 may further include a collimating light group. The collimating photon group may include a one-dimensional aperture stop for confining light rays from the object surface 10 in a second direction. For example, the one-dimensional aperture stop may be a slit grating. The one-dimensional aperture stop may be configured small enough to achieve a relatively large depth of focus in the second direction. The collimating light group may also include an optical element disposed between the display surface 10 and the one-dimensional aperture stop for converging light rays in the second direction, thereby allowing more light rays from the display surface 10 to pass through the one-dimensional aperture stop to improve imaging light intensity. The optical element may convert a beam of light from a point on the display surface 10 into approximately parallel light in the second direction, such that the beam divergence angle after passing through the aperture stop is close to 0. For example, the optical element may be a lens or a lens group.

[0048] Optionally, in some embodiments, if the image display unit 110 is a projection display source, the levitating display device may also have a relay image plane, which is the image plane of the projection display in the first direction. The scattering screen is placed at the relay image plane to scatter light in the first direction. In the second direction, the projection display may converge into an image point or not converge into an image point (specifically, it may present a line image in the second direction) at the relay image plane, which is beneficial for optical layout, improves the design freedom of the optical system, and facilitates the thin and light design of the optical system. In particular, because the conjugate imaging element 120 is used, the optical path between the scattering screen and the conjugate imaging element 120 in the first direction is set to be equal to the optical path between the conjugate imaging element 120 and the image plane in the first direction. Because a certain levitating image height is required, and a large image-side aperture angle in the first direction is desired to meet the binocular parallax conditions, the imaging unit has a large light-transmitting aperture in the first direction. The use of the conjugate imaging element 120 can effectively eliminate the aberrations generated by traditional optical elements and achieve high-quality levitating display.

[0049] Note that, although in Figure 2 The diagram shows a conjugate imaging element 120 positioned between the relay light group 130 and the beam expander light group 140. However, those skilled in the art will understand that the conjugate imaging element 120 can be positioned anywhere between the display surface 10 and the image plane 20, for example, between the display surface 10 and the relay light group 130, or between the beam expander light group 140 and the imaging light group 150. Therefore, the display light from the display surface 10 can diverge or converge in the first direction as it propagates in the beam expander light group 140 (depending on the position of the conjugate imaging element 120). In some embodiments, the display light from the display surface 10 can diverge in the first direction as it propagates in the relay light group 130.

[0050] It is understood that, in alternative embodiments of the present invention, the auxiliary imaging unit, scattering screen, one-dimensional aperture stop, or optical element may be integrated into the display source and not included in the optical system.

[0051] In some embodiments of the present invention, the beam expander 140 may be a combination of a lens and a scattering screen. Alternatively, the beam expander 140 may also be a planar optical waveguide with multiple light deflection sections, which utilizes total internal reflection to expand the incident light beam. See also Figure 4 This paper illustrates several typical structures of planar optical waveguides used for beam expansion. The planar optical waveguide can be a holographic waveguide, an arrayed waveguide, or a waveguide with microstructures. Specifically, an incident thin beam L propagates within the planar optical waveguide via total internal reflection. Each of the multiple beam deflectors deflects a portion of the thin beam L out of the waveguide at the same angle at different positions, thereby generating multiple outgoing beams L1, L2, L3…L… n Multiple emitted beams L1, L2, L3...L n This forms the outgoing coarse beam L', which is the expanded fine beam L.

[0052] Optionally, in some embodiments, the planar optical waveguide may be positioned at an angle relative to the imaging optical group 150°. See also Figure 5 A thin beam of light (represented by a solid line L or a dashed line M) enters from the coupler portion of a planar optical waveguide. After multiple reflections within the waveguide, it exits sequentially (e.g., the exit beams of L are represented as L1, L2, and L3; the exit beams of M are represented as M1, M2, and M3). The exit rays closer to the coupler portion (e.g., L1 and M1) travel a shorter distance within the waveguide, while the exit rays farther from the coupler portion (e.g., L3 and M3) travel a longer distance. Therefore, their equal-path wavefronts are AB, forming a certain angle with the planar waveguide. Thus, the imaging beam group 150 can be arranged parallel to the equal-path wavefronts, ensuring that the beams in the x and y directions ultimately converge to a single point in space.

[0053] Optionally, in some embodiments, the imaging beam group may include a one-dimensional imaging mirror, and when the beam expander beam group is a planar optical waveguide, the planar optical waveguide may be disposed at the focal plane of the one-dimensional imaging mirror, and parallel light of different angles emitted by the planar optical waveguide passes through the one-dimensional imaging mirror to form a suspended image in space.

[0054] Optionally, in an alternative embodiment of the invention, when the beam expander is a planar optical waveguide, the imaging optical group 150 can be formed on the light-emitting portion of the planar optical waveguide to integrate it with the planar optical waveguide. See also Figure 13AThe planar optical waveguide can include at least two types of microstructures: 1) Microstructure 1 (light deflection section) can have at least one inclined plane, with different angles for the inclined planes at different positions, used to control the overall light output direction of the beam coupled from the microstructure at a specific position, but without changing the divergence angle θ2 of the coupled beam (the angle between the small beams at different output angles); 2) Microstructure 2 (i.e., imaging beam group 150) is used to control the angle between the small beams emitted from each microstructure 1 at different angles. For example, microstructure 2 can be a cylindrical microlens (only changing the beam transmission in the y-direction), corresponding to different microstructures 1, with different focal lengths f, thus giving the light coupled from microstructure 1 at different positions different beam angles, such as... Figure 13A The values ​​θ1, θ2, and θ3 are shown. Microstructure 1 and microstructure 2 have a one-to-one correspondence. As an example, the imaging optical group 150 can be a one-dimensional lens array formed on the surface of the light-emitting part of the planar optical waveguide, wherein each one-dimensional lens (microstructure 2) in the one-dimensional lens array corresponds to one of the multiple light deflection parts (microstructure 1) and is used to change the angle of light rays from the corresponding light deflection part (microstructure 1). With this arrangement, light beams in the y-direction at different angles can be converged in space within different ranges to form a suspended image.

[0055] Optionally, the microstructure 2 unit can be composed of several smaller microstructures (such as...) Figure 13B As shown (in the diagram), similar to a lens transforming into a Fresnel lens, each tiny bevel individually controls the deflection of a thin beam of light, thereby controlling the angle between the thin beams coupled from the microstructure 1 in different directions. In this way, beams of light emitted from different directions from the waveguide can be converged in space into different suspended image points.

[0056] Optionally, considering the issue of uniformity of emitted light brightness, microstructure 1 and microstructure 2 can be arranged from sparse to dense starting from the waveguide's coupler end.

[0057] Optionally, the floating display device 100 can magnify the image on the display surface in the y direction, so the display surface can be set to be relatively small, thereby achieving a thinner optical system.

[0058] Optionally, the levitation display device 100 has an aperture stop disposed between the imaging light group 150 and the beam expander light group 140 to constrain the light from the beam expander light group 140 in the second direction. This arrangement can reduce aberrations in the second direction imaging while satisfying the viewing angle in the second direction, thereby improving the imaging quality of the levitation image.

[0059] In the following sections, several examples of a floating display device according to embodiments of the present invention will be described.

[0060] First Example

[0061] Figure 6 A schematic diagram of a floating display device 600 according to a first example of the present invention is shown. Several details of the floating display device 600 according to the first example are the same as those of the floating display device 100 described above, and will not be repeated here. The following mainly describes the special features of the floating display device 600 of the first example.

[0062] In the first example, the image display unit 610 is a projection display source configured such that light emitted from different positions of the image display unit 610 is parallel light at different angles in the x and y directions. The relay light group includes a first cylindrical mirror 631 and a lens 632, such that parallel beams of light from the image display unit 610 at different incident angles in the second direction, after passing through the first cylindrical mirror 631 and the lens 632, still produce parallel beams of light at different angles in the second direction at the exit pupil position. The conjugate imaging element is a one-dimensional retroreflective screen 620, which reflects light from the first cylindrical mirror 631 towards the lens 632. The lens 632 couples light from the one-dimensional retroreflective screen into the beam expander light group 640. The beam expander light group is an array-type planar optical waveguide 640, which expands the light beam only in the y direction. The imaging light group is a one-dimensional freeform mirror 650, which converges the expanded beam light only in the y direction and ensures that the suspended images a1, b1 form a certain angle with the display device. The levitation display device 600 also includes a second cylindrical mirror 661 and a one-dimensional scattering screen 662. The second cylindrical mirror 661 is used to change the angle of parallel light in the x-direction so that the parallel light in the x-direction is incident perpendicularly towards the one-dimensional retroreflection screen 620, thereby improving the imaging quality of the levitation image in the x-direction. The one-dimensional scattering screen 662 is disposed optically downstream of the second cylindrical mirror 661 to diffuse light only in the x-direction.

[0063] like Figure 6 As shown, the imaging process of the suspended display device 600 is as follows: Parallel light with different angles in both the x and y directions is emitted from the image display unit 610. In the x direction, the parallel light with different angles is redirected by the second cylindrical mirror 661, and forms an image magnified in the x direction on the one-dimensional scattering screen 662 (the relay image plane in the x direction). Then, it diverges in the x direction via the one-dimensional scattering screen 662 and enters the one-dimensional retroreflection screen 620, where it is converged onto the image plane 20. In the y direction, the parallel light with different angles propagates through the relay light group (the first cylindrical mirror 631 and the lens 632) and enters the planar optical waveguide 640. It is expanded by the planar optical waveguide 640 and exits towards the one-dimensional freeform mirror 650, where it is converged onto the image plane 20.

[0064] In this way, the beam emitted by the image display unit 610 has smaller aberrations in the x-direction and a relatively larger image-side aperture angle, satisfying the binocular parallax condition, thereby forming a suspended image at the image plane 20. The beam emitted by the image display unit 610 has a larger viewing angle in the y-direction due to the beam expansion by the planar optical waveguide 640.

[0065] Second example

[0066] Figure 7 A schematic diagram of a floating display device 700 according to a second example of the present invention is shown. Several details of the floating display device 700 according to the second example are the same as those of the floating display device 100 described above, and will not be repeated here. The following mainly describes the special features of the second example.

[0067] In the second example, the image display unit 710 is a direct-view display source, displaying images directly at the display surface 10. For example, the direct-view display source can be a flat panel display (such as OLED or LCD), whose emitted light has a large divergence angle. Specifically, the pixel ratio of the image display unit 710 in the x and y directions is not the conventional 1:1; but rather n:1. The floating display device 700 also includes a first cylindrical mirror 701 and an aperture stop 702. The first cylindrical mirror 701 and the aperture stop 702 can transform light from different pixels on the flat panel display into parallel narrow beams of light at different angles. The relay light group includes a second cylindrical mirror 731 and a lens 732, such that parallel beams of light from the image display unit 710 at different incident angles in the second direction, after passing through the second cylindrical mirror 731 and the lens 732, still produce parallel beams of light at different angles in the second direction at the exit pupil position. The conjugate imaging element is a one-dimensional retroreflective screen 720, which reflects light from the second cylindrical mirror 731 towards the lens 732. Lens 732 couples light from a one-dimensional retroreflector into beam expander group 740. Beam expander group is an arrayed planar optical waveguide 740 that expands the light only in the y-direction. Imaging group is a one-dimensional freeform mirror 750 that converges the expanded light only in the y-direction and makes the suspended images a1, b1 form a certain angle with the display device.

[0068] like Figure 7As shown, the imaging process of the suspended display device 700 is as follows: Display light with a large divergence angle is emitted from the image display unit 710. In the x-direction, since the first cylindrical mirror 701 and the second cylindrical mirror 731 are essentially inactive, the light with a large divergence angle in the x-direction does not change its light transmission path and illuminates the one-dimensional retroreflection screen 720, and is converged onto the image plane 20 by the one-dimensional retroreflection screen 720. In the y-direction, the light emitted from the image display unit 710 is converged by the first cylindrical mirror 701, passes through the aperture stop, so that the light from different pixels becomes parallel narrow beams at different angles, then propagates through the relay light group (the second cylindrical mirror 731 and the lens 732) and enters the planar optical waveguide 740, is expanded by the planar optical waveguide 740 and exits towards the one-dimensional freeform surface mirror 750, and is converged onto the image plane 20 by the one-dimensional freeform surface mirror 750.

[0069] In this way, the light beam emitted by the image display unit 710 has virtually no aberration in the x-direction and a relatively large image-side aperture angle, satisfying the binocular parallax condition, thereby forming a suspended image at the image plane 20. The light beam emitted by the image display unit 710 has a large viewing angle range in the y-direction due to the beam expansion by the planar optical waveguide 740.

[0070] Third Example

[0071] Figure 8A A schematic diagram of a floating display device 800 according to a third example of the present invention is shown. Several details of the floating display device 800 according to the third example are consistent with those described above. Figure 1 The floating display device 100 or 600 described in example 6 are the same and will not be repeated here. The following mainly describes the differences in the third example.

[0072] The image display unit 810 is a projection display source, configured such that the light emitted from the image display unit 810 is parallel light at different angles in the x and y directions. The relay light group includes a first cylindrical mirror 831 and a reflector 832, ensuring that parallel beams of light from the image display unit 810 at different incident angles in the second direction, after passing through the first cylindrical mirror 831 and the reflector 832, still exit at the exit pupil as parallel beams of light at different angles in the second direction. The conjugate imaging element is a one-dimensional lattice transmission array structure 820, which transmits light from the first cylindrical mirror 831 towards the reflector 832. The reflector 832 couples the light from the one-dimensional lattice transmission array structure 820 into the beam expander light group. The beam expander light group is an array-type planar optical waveguide 840, which expands the light beam only in the y direction. The imaging light group is a one-dimensional freeform surface mirror 850, which converges the expanded beam light only in the y direction and ensures that the suspended images a1, b1 form a certain angle with the display device. The levitated display device 800 also includes a one-dimensional scattering screen 801. The one-dimensional scattering screen 801 is disposed optically downstream of the image display unit 810 to scatter light only in the x-direction.

[0073] Specifically, in this example, such as Figure 8A As shown, the light emitted from the planar optical waveguide 840 will not pass through the planar optical waveguide 840 again. The suspended image on the image plane 20 is set at a certain angle with the planar glass, forming a visual effect of the suspended image being tilted.

[0074] Figure 8B A variant 800' of the floating display device 800 is shown, wherein the beam expander 840' is a combination of a scattering screen and a lens, replacing the planar optical waveguide 840. The beam expander includes a y-direction scattering screen 841, a curved mirror, and a semi-reflective lens 843 to expand the beam in the y-direction and exit to a reflecting mirror 802, which reflects the expanded beam from the beam expander 840' toward an imaging beam group 850. The imaging beam group 850 converges the reflected expanded beam at a corresponding point on the image plane 20. Note that the beam expander 840' described herein is not limited to replacing the planar optical waveguide 840 in the floating display device 800, but can also be applied to... Figure 6-7 The example floating display devices 600-700 and 900-1000 described in 9-10.

[0075] In this way, the light beam emitted by the image display unit 810 has smaller aberrations in the x-direction and a relatively larger image-side aperture angle, satisfying the binocular parallax condition, thereby forming a suspended image at the image plane 20. The light beam emitted by the image display unit 810 has a larger viewing angle range in the y-direction due to the beam expansion by the beam expander group 840'.

[0076] Fourth example

[0077] Figure 9 A schematic diagram of a floating display device 900 according to a fourth example of the present invention is shown. Several details of the floating display device 900 according to the fourth example are consistent with those described above. Figure 1 The floating display device 100 or 800 described in example 8 is the same and will not be repeated here. The following mainly describes the differences in the fourth example.

[0078] The image display unit 910 is a projection display source, configured such that the light emitted from the image display unit 910 is parallel light at different angles in the x and y directions. The relay light group includes a first cylindrical mirror 931 and a lens 932, such that parallel beams of light from the image display unit 910 at different incident angles in the second direction, after passing through the first cylindrical mirror 931 and the lens 932, still emerge as parallel beams of light at different angles in the second direction at the exit pupil position. The conjugate imaging element is a one-dimensional retroreflective screen 920, which reflects the light from the lens 932 toward the planar optical waveguide 940. The suspended display device 900 also includes a one-dimensional scattering screen 901 and an aperture stop. The aperture stop is disposed between the imaging light group 950 and the beam expander light group 940, used to constrain the light from the beam expander light group 940 in the y direction.

[0079] Specifically, in this example, such as Figure 9 As shown, the imaging optical group is a cylindrical mirror 950, which is easier to manufacture. The light emitted from the planar waveguide 940 is S-polarized light, which is reflected by the reflective polarizer 902, passes through a quarter-wave plate, and then illuminates the cylindrical mirror 950. The light reflected by the cylindrical mirror 950 illuminates the reflective polarizer 902 again and is emitted, forming a floating image. The floating image on the image plane 20 and the reflective polarizer 902 are set at a certain angle to create the visual effect of a tilted floating image.

[0080] In this way, the beam emitted by the image display unit 910 has smaller aberrations in the x-direction and a relatively larger image-side aperture angle, satisfying the binocular parallax condition, thereby forming a suspended image at the image plane 20. The beam emitted by the image display unit 910 has a larger viewing angle in the y-direction due to the beam expansion by the planar optical waveguide 940.

[0081] Fifth example

[0082] Figure 10 A schematic diagram of a floating display device 1000 according to a fifth example of the present invention is shown. Several details of the floating display device 1000 according to the fifth example are consistent with those described above. Figure 1-10 The described floating display devices 100 or 600-900 are the same and will not be repeated here. The following mainly describes the differences in the fifth example.

[0083] The image display unit 1010 is a projection display source, configured such that the light emitted from the image display unit 1010 is parallel light at different angles in the x and y directions. The relay light group includes a first cylindrical mirror 1031 and a lens 1032, such that parallel light beams from the image display unit 1010 at different incident angles in the second direction, after passing through the first cylindrical mirror 1031 and the lens 1032, still result in parallel light beams at different angles in the second direction at the exit pupil position. The image display unit 1010 also includes a one-dimensional scattering screen 1001 and a reflecting mirror 1002. The reflecting mirror 1002 reflects the light from the lens 1032 towards the one-dimensional retroreflection screen 1020, and the one-dimensional retroreflection screen 1020 reflects the light from the reflecting mirror 1002 into the planar optical waveguide 1040.

[0084] In this example, as shown in Figure 10, to reduce the thickness of the display device, an optical arrangement of a pancake (reflected optical path) structure is added to the imaging optical group. Specifically, the light emitted from the planar waveguide 1040 is circularly polarized light. The imaging optical group includes a cylindrical semi-reflective mirror 1051, a quarter-wave plate 1052, an APF 1053, and a polarizer 1054. The circularly polarized light passes through the cylindrical semi-reflective mirror 1051, is converted to s-polarized light by the quarter-wave plate 1052, is reflected by the APF 1053, is reflected again by the cylindrical semi-reflective mirror 1051, and is converted to p-polarized light again by the quarter-wave plate 1052. This p-polarized light then passes through the APF 1053 and the polarizer 1054, forming a suspended image in space. The planar waveguide 1040 and the imaging optical group are set at a certain angle to ensure that the optical path lengths at all points in the y-direction are the same, and that the light converges on the same horizontal plane after passing through the imaging optical group.

[0085] In this way, the light beam emitted by the image display unit 1010 has smaller aberrations in the x-direction and a relatively larger image-side aperture angle, satisfying the binocular parallax condition, thereby forming a suspended image at the image plane 20. The light beam emitted by the image display unit 1010 has a larger viewing angle range in the y-direction due to the beam expansion by the planar optical waveguide 1040.

[0086] Sixth example

[0087] Figure 14 A schematic diagram of a floating display device 1400 according to a sixth example of the present invention is shown. Several details of the floating display device 1400 according to the sixth example are the same as those of the floating display devices 100, 600-1000 described above, and will not be repeated here. The following mainly describes the differences of the sixth example.

[0088] See Figure 14The suspended display device 1400 includes an image display unit 1410, a one-dimensional retroreflective screen 1420, a relay light group (only lens 1432 is shown for simplicity), and a planar optical waveguide 1460 integrating the beam expander light group and the imaging light group. The planar optical waveguide 1460 has multiple light deflecting sections 1461 and corresponding multiple cylindrical microlenses 1462. Multiple cylindrical microlenses 1462 are formed on the surface of the light-emitting section of the planar optical waveguide 1460. Each cylindrical microlens (microstructure 2) corresponds to a specific light deflecting section (microstructure 1) among the multiple light deflecting sections and is used to change the angle of light rays from the corresponding light deflecting section (microstructure 1). A suspended image can be formed by expanding and converging fine parallel beams (from different pixels of the image display unit 1410) at different angles in a second direction onto a corresponding area on the image plane 20 using the following methods: 1. By setting the relative positional relationship between each light deflector 1461 and its corresponding cylindrical microlens 1462; 2. By setting the tilt angle of the light deflector 1461 at different positions, for example, gradually increasing the tilt angle of the light deflector 1461 from the coupling end of the waveguide; and / or 3. By setting the focal length f of the cylindrical microlens 1462 at different positions, for example, gradually decreasing the focal length f of the cylindrical microlens 1462 from the coupling end of the waveguide. In this way, the suspended image on the image plane 20 can be tilted relative to the waveguide light-emitting surface.

[0089] Seventh Example

[0090] Figure 15A A schematic diagram of a floating display device 1500 according to a seventh example of the present invention is shown. Several details of the floating display device 1500 according to the seventh example are the same as those of the floating display devices 100, 600-1000 or 1400 described above, and will not be repeated here. The following mainly describes the differences of the seventh example.

[0091] In the seventh example, the image display unit 1510 is a projection display source configured such that the light emitted from the image display unit 1510 is parallel light at different angles in the x and y directions. The relay light group includes a first cylindrical mirror 1531 and a lens 1532, such that the parallel light beams from the image display unit 1510 at different incident angles in the second direction, after passing through the first cylindrical mirror 1531 and the lens 1532, still result in parallel light beams at different angles in the second direction at the exit pupil position. The conjugate imaging element is a one-dimensional lattice transmission array structure 1520, which transmits light from the first cylindrical mirror 1531 towards the lens 1532. The lens 1532 couples the light from the one-dimensional lattice transmission array structure 1520 into the planar optical waveguide 1560. The planar optical waveguide 1560 has multiple light deflecting sections (not shown) and corresponding multiple cylindrical microlenses (not shown) for forming a suspended image at the image plane 20 that is tilted relative to the waveguide optical surface.

[0092] Unlike the first example, the floating display device 1500 includes a scattering screen 1501 employing a dual-cylindrical microlens array, such as Figure 15B As shown, the scattering screen 1501 employing a dual-cylindrical microlens array functions similarly to a combination of a collimating lens (e.g., cylindrical lens 661) and a single-cylindrical microlens array (e.g., scattering screen 662). This approach eliminates the need for a collimating lens, reducing manufacturing complexity and component costs when achieving large-size displays.

[0093] The foregoing describes in detail an exemplary embodiment of a levitation display device according to the present invention. Using these levitation display devices, the point beam on the display surface images along a first direction with minimal (or no) aberrations and a relatively large image-side aperture angle, satisfying the binocular parallax condition, thereby enabling the display of images in mid-air. The optical systems in these levitation display devices are easy to manufacture, effectively reducing costs. Furthermore, by separately modulating the display light in the x and y directions, aberration problems present in the prior art can be eliminated; by using a beam expander instead of a y-direction scattering screen, the positioning problem of the levitation image in the y-direction can be solved; or by magnifying the image in the y-direction, the optical system can be made thinner, and a more flexible optical layout can be achieved.

[0094] It should be understood that the above description is illustrative and not restrictive. For example, the above embodiments (and / or aspects thereof) can be used in combination with each other. Furthermore, many modifications can be made to adapt particular conditions or materials to the teachings of the various embodiments of the invention without departing from the scope of the invention. While the dimensions and types of materials described herein are used to define parameters of the various embodiments of the invention, the embodiments are not intended to be restrictive but are exemplary. Many other embodiments will become apparent to those skilled in the art upon reading the above description. Therefore, the scope of the various embodiments of the invention should be determined by reference to the appended claims and the full scope of their equivalents.

Claims

1. A floating display device, comprising: An image display unit having a display surface and emitting display light constituting an image from the display surface; A conjugate imaging element with a one-dimensional grating structure is used to converge the display light in a first direction; A relay light group is disposed downstream of the image display unit, wherein a parallel light beam entering the relay light group in a second direction through the entrance pupil of the relay light group is still a parallel light beam in the second direction at its exit pupil after passing through the relay light group, and the first direction and the second direction are respectively orthogonal to the optical axis of the floating display device. A beam expander is disposed downstream of the relay beam and is used to expand the display light only in the second direction to output a broadened display light. as well as An imaging beam group, positioned optically downstream of the beam expander beam group and used to converge the display light in the second direction. A light beam emitted from a point on the display surface converges in the first direction via the conjugate imaging element to a corresponding range on the image surface, and simultaneously converges in the second direction via the imaging light group to the corresponding range on the image surface, thereby causing the display light to form a floating image on the image surface.

2. The floating display device as described in claim 1, characterized in that, The image display unit is: A direct-view display source that displays the image directly on the display surface; or A projection display source that projects light constituting the image onto the display surface, wherein the projection display source is configured such that the display light is parallel light in the second direction.

3. The floating display device as described in claim 2, characterized in that, When the image display unit is a direct-view display source, the floating display device further includes a collimating light group for converting the light emitted from different light-emitting points on the display surface into parallel light at different angles in the second direction.

4. The floating display device as described in claim 2, characterized in that, When the image display unit is a projection display source, the floating display device further includes a scattering screen for scattering light along the first direction.

5. The floating display device as described in claim 4, characterized in that, The optical path between the scattering screen and the conjugate imaging element is set to be equal to the optical path between the conjugate imaging element and the image plane.

6. The floating display device as described in claim 1, characterized in that, The beam-expanding optical group includes a planar optical waveguide with multiple light deflection sections. The planar optical waveguide expands the incident light beam by total internal reflection, and the multiple light deflection sections are used to emit the light in the planar optical waveguide at different positions.

7. The floating display device as described in claim 6, characterized in that, The planar optical waveguide is angularly positioned relative to the imaging light composition.

8. The floating display device as described in claim 6, characterized in that, The imaging optical group includes a one-dimensional imaging mirror, and the planar optical waveguide is disposed at the focal plane of the one-dimensional imaging mirror.

9. The floating display device as described in claim 6, characterized in that, The imaging optical group includes a one-dimensional lens array disposed on the surface of the light-emitting part of the planar optical waveguide. Each one-dimensional lens in the one-dimensional lens array corresponds to one of the plurality of light deflection parts and is used to change the angle of light rays from the corresponding light deflection part.

10. The floating display device as claimed in claim 1, characterized in that, The suspended display device has an aperture stop disposed between the imaging light group and the beam expander light group for constraining light from the beam expander light group in the second direction.

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