Retroreflective assembly, retroreflector, and communication device

Abstract

The application provides a retro-reflection component, a retro-reflector and a communication device. The retro-reflection component comprises a mirror, a convex lens and a metasurface arranged between the mirror and the convex lens; the mirror has a bottom surface and a reflecting surface, the convex lens is arranged on one side of the reflecting surface of the mirror, and the distance between the reflecting surface of the mirror and the convex lens is less than the focal length of the convex lens; the metasurface is used for modulating the phase of an incident signal, so that incident signals with mutually parallel incident paths can converge on the same point on the reflecting surface. The retro-reflector can reduce the size in the direction of the optical axis of the retro-reflector, which is conducive to the lightweight design of the device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, in particular to a retro-reflection assembly, a retro-reflector and a communication device. BACKGROUND

[0002] The retro-reflector is an optical or electromagnetic wave device that can reflect the incident light or electromagnetic wave back, and the reflection path direction of the light or electromagnetic wave is parallel to the incident path and the method is opposite. The retro-reflector has a wide application in wireless charging, communication, detection and the like.

[0003] In the prior art, due to the limitation of module size requirement, the retro-reflector has the defects of large thickness or low efficiency, which is not conducive to the development and practicality of the retro-reflector. SUMMARY

[0004] The present application provides a retro-reflection assembly, a retro-reflector and a communication device to reduce the thickness of the device and realize the lightweight design of the device.

[0005] In a first aspect, the present application provides a retro-reflection assembly which can be applied to occasions requiring signal feedback such as communication, charging, detection and the like. The retro-reflection assembly comprises a reflector, a convex lens and a metasurface arranged between the reflector and the convex lens. The reflector has a bottom surface and a reflecting surface, and the convex lens is arranged on the side of the reflecting surface of the reflector. In application, the bottom surface of the reflector faces the signal receiving end, and the convex lens faces the signal transmitting end. The incident signal can be reflected on the reflecting surface of the reflector to become a reflected signal via the convex lens and the metasurface. The metasurface between the convex lens and the reflector can modulate the phase of the incident signal so that the incident signals with mutually parallel incident paths can converge at the same point on the reflecting surface (i.e. the incident signals with mutually parallel incident paths are focused at a point). According to the optical path reversibility principle, the reflected signal and the incident signal are mutually parallel, realizing the retro-reflection of the signal.

[0006] The above-mentioned retro-reflector can refract and converge the incident signal via the convex lens. The metasurface between the convex lens and the reflector can change the amplitude, phase, polarization state and other characteristic parameters of the incident signal for control, guide and focus the incident signal to the reflecting surface, shorten the distance of the incident signal to the reflecting surface, and reduce the distance between the reflector and the convex lens to less than the focal length of the convex lens. The retro-reflector can reduce the size of the optical axis direction, which is conducive to realizing the lightweight design of the device.

[0007] The super surface includes a substrate and a phase modulation structure. The phase modulation structure is arranged on the substrate, and the specific position is not limited, that is, the phase modulation structure is arranged on the side of the substrate facing the convex lens or the side of the substrate facing the mirror. In order to realize the reverse reflection of the signal, the refraction angle of the incident signal passing through the optical center of the convex lens in the substrate is θ2, and -3°≤θ2≤3°. The angle range can optimize the super surface and reduce the maximum deviation of the outgoing angle.

[0008] The ideal state between each modulation phase is continuously changed. Along the direction perpendicular to the optical axis of the reverse reflection component, the phase gradient of the phase modulation structure satisfies the following rule:

[0009]

[0010] Wherein, is the phase gradient of the phase modulation structure, n1 is the refractive index of the structure on the light side of the super surface; n2 is the refractive index of the substrate, θ1 is the incident angle of the incident signal to the phase modulation structure. When the structure on the light side of the super surface is a convex lens, n1 is specifically the refractive index of the convex lens. Wherein, when θ2 is 0°, the reverse reflection component can make the incident signal and the outgoing signal symmetric about the secondary optical axis (or the primary optical axis).

[0011] In some possible implementations, a transparent spacing medium layer is further arranged between the super surface and the convex lens. In this structure, n1 is specifically the refractive index of the spacing medium layer. The spacing medium layer can provide support between the convex lens and the super surface, so that the surface of the convex lens facing the super surface and the surface of the super surface facing the convex lens can remain relatively parallel.

[0012] In order to facilitate the implementation of the structure of the super surface, the phase modulation structure can specifically include a plurality of sub-wavelength units. Along the direction perpendicular to the optical axis of the reverse reflection component, the distance between any two points on the profile line of the cross section of each sub-wavelength unit is less than the wavelength of the incident signal, and the spacing between any two adjacent sub-wavelength units is less than the wavelength of the incident signal.

[0013] In some possible implementations, the reverse reflection component needs to realize the transmission of the signal. At this time, the reflecting mirror can be provided with a reflecting area and a transmitting area. The reflecting area is used for reflecting the signal, and the transmitting area is used for transmitting the signal. Specifically, the transmitting area can be realized in the form of a through hole, and the incident signal can pass through the through hole to reach the receiving end. The transmitting area can also be realized in the form of a weak part, and the thickness of the weak part is less than the thickness of the reflecting area, and the incident signal can pass through the weak area.

[0014] In a second aspect, the embodiments of the present application also provide a retroreflector, which specifically includes a plurality of reverse reflection components provided by the above technical solutions. The plurality of reverse reflection components are arranged in an array to form a larger area retroreflector, which can meet the reverse reflection effect of a larger area.

[0015] In some possible implementations, gaps exist between the plurality of retro-reflective components, which can be used for signal to pass through. For example, a retro-reflector formed by an array of circular retro-reflective components forms a plurality of gaps, which can be used for signal to pass through directly. Therefore, such a retro-reflector can be directly applied to a scenario where a transmitted signal is required.

[0016] In a third aspect, an embodiment of the present application further provides a communication device, comprising a transmitting module, a receiving module, and any of the retro-reflective components described above. The transmitting module is configured to transmit a signal, and the receiving module is configured to receive a signal. The retro-reflective component is arranged on a side of the receiving module facing the transmitting module, and a mirror of the retro-reflective component faces the receiving module, so that the signal transmitted by the transmitting module can be reflected back to the transmitting module. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A structural schematic diagram of a retro-reflective component provided by an embodiment of the present application;

[0018] Figure 2 A structural schematic diagram of a mirror in a retro-reflective component provided by an embodiment of the present application;

[0019] Figure 3 A working principle schematic diagram of a convex lens in a retro-reflective component provided by an embodiment of the present application;

[0020] Figure 4 A working principle schematic diagram of a retro-reflective component provided by an embodiment of the present application;

[0021] Figure 5 A reflection principle schematic diagram of a retro-reflective component provided by an embodiment of the present application on an incident signal;

[0022] Figure 6 A structural schematic diagram of a meta-surface in a retro-reflective component provided by an embodiment of the present application;

[0023] Figure 7 A reflection principle schematic diagram of a retro-reflective component provided by an embodiment of the present application on an incident signal;

[0024] Figures 8a to 8c A reflection principle schematic diagram of a retro-reflective component provided by an embodiment of the present application on an incident signal;

[0025] Figure 9 A structural schematic diagram of a meta-surface in a retro-reflective component provided by an embodiment of the present application;

[0026] Figure 10 A structural schematic diagram of a sub-wavelength unit in a retro-reflective component provided by an embodiment of the present application;

[0027] Figure 11 For Figure 10 Cross-sectional view of a sub-wavelength unit;

[0028] Figure 12 Structure diagram of a sub-wavelength unit in a retroreflective component provided by an embodiment of the present application;

[0029] Figure 13 For Figure 12 Cross-sectional view of a sub-wavelength unit;

[0030] Figure 14 Structure diagram of a metasurface in a retroreflective component provided by an embodiment of the present application;

[0031] Figure 15 Structure diagram of a metasurface in a retroreflective component provided by an embodiment of the present application;

[0032] Figure 16a Structure diagram of a convex lens in a retroreflective component provided by an embodiment of the present application;

[0033] Figure 16b Structure diagram of a retroreflective component provided by an embodiment of the present application;

[0034] Figure 17a Structure diagram of a convex lens in a retroreflective component provided by an embodiment of the present application;

[0035] Figure 17b Structure diagram of a retroreflective component provided by an embodiment of the present application;

[0036] Figure 18 Structure diagram of a convex lens in a retroreflective component provided by an embodiment of the present application;

[0037] Figure 19 Structure diagram of a convex lens in a retroreflective component provided by an embodiment of the present application;

[0038] Figure 20 Structure diagram of a mirror in a retroreflective component provided by an embodiment of the present application;

[0039] Figure 21 Structure diagram of a retroreflective component provided by an embodiment of the present application;

[0040] Figure 22 Structure diagram of a retroreflector provided by an embodiment of the present application;

[0041] Figure 23 Structure diagram of a retroreflector provided by an embodiment of the present application;

[0042] Figure 24 A structural schematic diagram of a communication device provided by an embodiment of the present application is shown.

[0043] Fig. 1 is a structural schematic diagram of a reflective mirror; Fig. 2 is a structural schematic diagram of a convex lens; Fig. 3 is a structural schematic diagram of a metasurface; Fig. 4 is a structural schematic diagram of a filler; Fig. 5 is a structural schematic diagram of a spacer medium layer; Fig. 6 is a structural schematic diagram of an inverse reflection assembly; Fig. 7 is a structural schematic diagram of a transmitting module; Fig. 8 is a structural schematic diagram of a receiving module; Fig. 9 is a structural schematic diagram of an inverse reflector; Fig. 10 is a structural schematic diagram of a communication device. DETAILED DESCRIPTION

[0044] The inverse reflector can also be referred to as a retroreflector, which can reflect the incident signal (including light and electromagnetic wave) back and the reflection direction is parallel to the incident direction. Through the inverse reflector, the position or angle state of the side of the reflected signal can be automatically acquired on the side of the transmitted signal. The existing inverse reflector has the defects of large size and low efficiency, which cannot meet the development needs of the retroreflection.

[0045] Based on this, the embodiments of the present application provide an inverse reflection assembly, an inverse reflector comprising the inverse reflection assembly, and a communication device comprising the inverse reflection assembly, which have a small closed structure and are beneficial to the lightweight design of the device.

[0046] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings.

[0047] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and the appended claims of the application, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0048] Reference herein to “one embodiment” or “some embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrases “in one embodiment,” “in some embodiments,” “in other embodiments,” “in additional embodiments,” and so on, in various places in the specification are not necessarily all referring to the same embodiment, unless otherwise specifically stated. The terms “comprise,” “comprising,” “include,” “including,” and “has” and their variants are meant to be construed as “including, but not limited to,” unless otherwise noted.

[0049] The present invention provides a retroreflective assembly 10 that can be used in a receiving terminal of a laser charging or wireless communication system. Its primary function is to reflect an incident signal (light or electromagnetic wave) back. The reflected signal is parallel to and opposite to the direction of the incident signal. No additional alignment is required when transmitting signals between the transmitting and receiving terminals.

[0050] like Figure 1 As shown, the retroreflective assembly 10 includes a reflector 1, a convex lens 2, and a metasurface 3 disposed between the reflector 1 and the convex lens 2. The retroreflective assembly 10 functions as an optical system, with its optical axis P parallel to the stacking direction of the reflector 1, the metasurface 3, and the convex lens 2. During use, the convex lens 2 faces the signal transmitting end to direct the incident signal from the transmitting end into the retroreflective assembly 10. The reflector 1 is located at the signal receiving end. The incident signal passes through the convex lens 2 and the metasurface 3 before reaching the reflector 1. The reflector 1 reflects the incident signal, and the reflected signal is then emitted through the metasurface 3 and the convex lens 2.

[0051] Specifically, if Figure 2 As shown, reflector 1 has a bottom surface a1 and a reflective surface a2. Convex lens 2 is positioned on the reflective surface a2 side of reflector 1. When an incident signal reaches reflective surface a2, reflective surface a2 strongly reflects the incident signal, and metal materials may be used. The angle between the incident signal and the normal N perpendicular to reflective surface a2 is incident angle α1, and the angle between the reflected signal and the normal N perpendicular to reflective surface a2 is reflection angle α2, where α1 = α2.

[0052] The convex lens 2 is made of a material that is transparent to the incident signal, usually a dielectric material. The convex lens 2 needs to have a certain focusing effect on the incident signal to facilitate the phase modulation of the incident signal by the metasurface 3.

[0053] In general, if Figure 3As shown, the mutually parallel incident signals (which have the same incident angle) converge to a convergence point after passing through the convex lens 2. Incident signals with different incident directions converge to different convergence points after passing through the convex lens 2. The plane where the convex lens 2 is located is M1. The optical center of the convex lens 2 is O, and the optical center of the convex lens 2 is located on the optical axis P of the retroreflective assembly 10. The direction of the light ray passing through the optical center O of the convex lens 2 does not change. Taking incident signals A0, incident signals A1 and incident signals A2 with different incident directions as examples, the incident direction of the incident signals A0 is perpendicular to the plane where the convex lens 2 is located. The light rays of the incident signals A0 converge to a convergence point Q0, the light rays of the incident signals A1 converge to a convergence point Q1, and the light rays of the incident signals A2 converge to a convergence point Q2. The plane where these convergence points are located can be defined as a focal plane M0. The axis perpendicular to the plane where the convex lens 2 is located M1 and passing through the optical center O is the main optical axis L0 (which coincides with the optical axis P of the retroreflective assembly 10), and the intersection of the main optical axis L0 and the focal plane M0 is the main focal point (that is, the convergence point Q0). The axes passing through the optical center O and not perpendicular to the plane where the convex lens 2 is located M1 are the auxiliary optical axes (auxiliary optical axis L1 of the incident signals A1, auxiliary optical axis L2 of the incident signals A2). The focal point of the auxiliary optical axis and the focal plane M0 is the auxiliary focal point, and the auxiliary focal point of the auxiliary optical axis L1 is the convergence point Q1, and the auxiliary focal point of the auxiliary optical axis L2 is the convergence point Q2. The distance between the plane where the convex lens 2 is located M1 and the focal plane M0 is the focal length f of the convex lens 2. Figure 3 The signals in FIG. 6 are bidirectional arrows. When any one convergence point is used as a transmitting end to transmit signals to the convex lens 2, the path of the signals is the same as the path of the signals that can converge on the convergence point through the convex lens 2.

[0054] The retroreflective assembly 10 provided in the embodiments of the present application sets the reflector 1 as follows: the distance between the reflecting surface a2 of the reflector 1 and the convex lens 2 is less than the focal length f of the convex lens 2. For this purpose, a metasurface 3 is arranged between the reflector 1 and the convex lens 2 to converge the signals passing through the convex lens 2 to the reflecting surface a2 of the reflector 1. The principle is that the incident signals are incident on the metasurface 3, and the metasurface 3 can modulate the phase of the incident signals, so that the phase of the incident signals changes and refraction occurs. This phenomenon of phase modulation of signals (light or electromagnetic waves) by the metasurface 3 to produce refraction can be described by the generalized Snell's law.

[0055] As shown in FIG. 7, the metasurface 3 is arranged between the convex lens 2 and the reflecting surface a2 of the reflector 1. The metasurface 3 is a two-dimensional surface structure, and the distance between the reflecting surface a2 of the reflector 1 and the metasurface 3 is less than the focal length f of the convex lens 2. The metasurface 3 is arranged to converge the signals passing through the convex lens 2 to the reflecting surface a2 of the reflector 1. Figure 4As shown, the plane where the convex lens 2 is located is M1, the plane where the reflecting surface a2 of the mirror 1 is located is M2, and the plane where the super surface 3 is located is M3. Taking a bundle of incident signals parallel to each other and not perpendicular to the plane M1 where the convex lens 2 is located as an example, the incident signals can be focused to a converging point Q (dashed line example) on the focal plane M0 after passing through the convex lens 2. The distance between the focal plane M0 and the plane M1 where the convex lens 2 is located is the focal length f of the convex lens 2. The distance between the plane M2 where the mirror 1 is located and the plane M1 where the convex lens 2 is located is f', which is less than f. The super surface 3 can change the phase of the incident signals passing through the convex lens 2, so that the incident signals can converge at a converging point Q' (solid line example) on the plane M2 where the mirror 1 is located.

[0056] As shown, the plane where the convex lens 2 is located is M1, the plane where the reflecting surface a2 of the mirror 1 is located is M2, and the plane where the super surface 3 is located is M3. Taking a bundle of incident signals parallel to each other and not perpendicular to the plane M1 where the convex lens 2 is located as an example, the incident signals can be focused to a converging point Q (dashed line example) on the focal plane M0 after passing through the convex lens 2. The distance between the focal plane M0 and the plane M1 where the convex lens 2 is located is the focal length f of the convex lens 2. The distance between the plane M2 where the mirror 1 is located and the plane M1 where the convex lens 2 is located is f', which is less than f. The super surface 3 can change the phase of the incident signals passing through the convex lens 2, so that the incident signals can converge at a converging point Q' (solid line example) on the plane M2 where the mirror 1 is located. Figure 5 As shown, the plane where the convex lens 2 is located is M1, the plane where the reflecting surface a2 of the mirror 1 is located is M2, and the plane where the super surface 3 is located is M3. Taking a bundle of incident signals parallel to each other and not perpendicular to the plane M1 where the convex lens 2 is located as an example, the incident signals can be focused to a converging point Q (dashed line example) on the focal plane M0 after passing through the convex lens 2. The distance between the focal plane M0 and the plane M1 where the convex lens 2 is located is the focal length f of the convex lens 2. The distance between the plane M2 where the mirror 1 is located and the plane M1 where the convex lens 2 is located is f', which is less than f. The super surface 3 can change the phase of the incident signals passing through the convex lens 2, so that the incident signals can converge at a converging point Q' (solid line example) on the plane M2 where the mirror 1 is located.

[0057] As shown, the plane where the convex lens 2 is located is M1, the plane where the reflecting surface a2 of the mirror 1 is located is M2, and the plane where the super surface 3 is located is M3. Taking a bundle of incident signals parallel to each other and not perpendicular to the plane M1 where the convex lens 2 is located as an example, the incident signals can be focused to a converging point Q (dashed line example) on the focal plane M0 after passing through the convex lens 2. The distance between the focal plane M0 and the plane M1 where the convex lens 2 is located is the focal length f of the convex lens 2. The distance between the plane M2 where the mirror 1 is located and the plane M1 where the convex lens 2 is located is f', which is less than f. The super surface 3 can change the phase of the incident signals passing through the convex lens 2, so that the incident signals can converge at a converging point Q' (solid line example) on the plane M2 where the mirror 1 is located.

[0058] As shown, the plane where the convex lens 2 is located is M1, the plane where the reflecting surface a2 of the mirror 1 is located is M2, and the plane where the super surface 3 is located is M3. Taking a bundle of incident signals parallel to each other and not perpendicular to the plane M1 where the convex lens 2 is located as an example, the incident signals can be focused to a converging point Q (dashed line example) on the focal plane M0 after passing through the convex lens 2. The distance between the focal plane M0 and the plane M1 where the convex lens 2 is located is the focal length f of the convex lens 2. The distance between the plane M2 where the mirror 1 is located and the plane M1 where the convex lens 2 is located is f', which is less than f. The super surface 3 can change the phase of the incident signals passing through the convex lens 2, so that the incident signals can converge at a converging point Q' (solid line example) on the plane M2 where the mirror 1 is located. Figure 6 As shown, the plane where the convex lens 2 is located is M1, the plane where the reflecting surface a2 of the mirror 1 is located is M2, and the plane where the super surface 3 is located is M3. Taking a bundle of incident signals parallel to each other and not perpendicular to the plane M1 where the convex lens 2 is located as an example, the incident signals can be focused to a converging point Q (dashed line example) on the focal plane M0 after passing through the convex lens 2. The distance between the focal plane M0 and the plane M1 where the convex lens 2 is located is the focal length f of the convex lens 2. The distance between the plane M2 where the mirror 1 is located and the plane M1 where the convex lens 2 is located is f', which is less than f. The super surface 3 can change the phase of the incident signals passing through the convex lens 2, so that the incident signals can converge at a converging point Q' (solid line example) on the plane M2 where the mirror 1 is located.

[0059] In order to increase the field of view angle range, the metasurface 3 adjusts the incident signal as follows: the refraction angle of the incident signal passing through the optical center of the convex lens 2 in the substrate 31 is almost 0. As shown in Figure 7 The incident signal passing through the optical center O of the convex lens 2 (the optical center O coincides with the optical axis P) is taken as an example. After the phase modulation of the phase modulation structure 32 of the metasurface 3, the incident signal enters the substrate 31 and is refracted in the substrate 31. The angle between the incident signal and the normal N in the substrate 31 is the incident angle θ1. The angle between the incident signal and the normal N in the substrate 31 is the refraction angle θ2. The emergent signal is parallel to the incident signal, and the emergent point of the emergent signal on the plane M1 where the convex lens 2 is located is close to the optical center O of the convex lens 2.

[0060] Here, θ2 is about 0°, and the specific range can be set to -3°≤θ2≤3°. As shown in Figure 8a The incident signal passing through the optical center O of the convex lens 2 is phase-adjusted by the phase modulation structure 32 of the metasurface 3, and is refracted in the substrate 31, and then reaches the reflecting surface a2 in a direction perpendicular to the mirror 1 (i.e. θ2=0°). After being reflected by the reflecting surface a2 of the mirror 1, the incident signal returns to the metasurface 3 and can return to the original path. That is, the incident signal and the reflected signal are in the same path, and the signal realizes the inverse reflection of the original path.

[0061] As shown in Figure 8b A group of mutually parallel incident signals are taken as an example. The incident signal passing through the optical center O of the convex lens 2 is defined as the center signal B0, and the incident signal on the left side of the center signal B0 is the first signal B1. The center signal B0 is the rightmost signal in the horizontal direction of the group of signals, and the first signal B1 is the leftmost signal in the horizontal direction of the group of signals. Along the horizontal direction, there can be other multiple signals parallel to each other between the first signal B1 and the center signal B0. Among them, the center signal B0 passes through the optical center of the convex lens 2 and is perpendicular to the reflecting surface a2 (the path from the plane M3 where the metasurface 3 is located to the plane M2 where the mirror 1 is located coincides with the normal N) to the reflecting surface a2. It should be understood that the inverse reflection path of the center signal B0 coincides with the path of the first signal B1. Figure 8aSimilar, no longer described. The first signal B1 is refracted by the convex lens 2, the phase is adjusted by the phase modulation structure 32, and the substrate 31 is refracted, and then reaches the convergence point Q' of the reflecting surface a2 and the center signal B0. The first signal B1 is reflected by the reflecting surface a2 and exits to the right of the normal N, and then exits again after passing through the super surface 3 and the convex lens 2. According to the optical path reversibility principle, the first signal B1 after exiting is parallel to the direction of the first signal B1 incident. And the distance between the incident point O' of the first signal B1 incident to the convex lens 2 and the optical center O of the convex lens 2 is d, and the distance between the exit point O" of the first signal B1 exiting from the convex lens 2 and the optical center O of the convex lens 2 is also d. The signal incident range of other paths between the first signal B1 and the center signal B0 is between the incident point O' and the optical center O, and the signal exit range of other paths between the first signal B1 and the center signal B0 is between the exit point O" and the optical center O. That is, as long as the range of the first signal B1 relative to the center signal B0 can be set, the reverse reflection range of the group of signals can be limited, and the problem of unavailability caused by the exit signal exceeding the range of the convex lens 2 can be prevented.

[0062] As shown in Figure 8c , taking a group of mutually parallel incident signals as an example, the incident signal passing through the optical center O of the convex lens 2 is defined as the center signal B0, the incident signal on the left side of the center signal B0 is the first signal B1, and the incident signal on the right side of the center signal B0 is the second signal B2. The first signal B1 is the leftmost signal in the horizontal direction of the group of signals, and the second signal B2 is the rightmost signal in the horizontal direction of the group of signals. Along the horizontal direction, there can be other multiple parallel signals between the first signal B1 and the center signal B0, and there can be other multiple parallel signals between the second signal B2 and the center signal B0. Among them, the center signal B0 passes through the optical center of the convex lens 2 and is perpendicular to the reflecting surface a2. The first signal B1 is incident from the incident point O', and is emitted from the exit point O". The incident point of the second signal B2 incident to the convex lens 2 coincides with the exit point O" of the first signal B1 from the convex lens 2. According to the optical path reversibility principle, the incident point O' of the first signal B1 incident to the convex lens 2 is the exit point of the second signal B2 from the convex lens 2, and the exit point O" of the first signal B1 from the convex lens 2 is the incident point of the second signal B2 incident to the convex lens 2. If the first signal B1 and the second signal B2 are defined as the signals at the edges of the group of signals in the horizontal direction, then the incident range of the group of signals coincides with the reflection range.

[0063] It can be known from the above embodiments that the retroreflective assembly 10 provided by the embodiments of the present application can set the position of the incident signal relative to the optical center of the convex lens 2, so that the incident signal and the reflected signal are symmetrical about the secondary optical axis (or the primary optical axis), thereby limiting the range of the reflected signal, avoiding the problem that the outgoing signal exceeds the range of the convex lens 2 and causes unavailability, and increasing the field of view angle of the retroreflective assembly 10.

[0064] In the embodiments of the present application, the phase modulation structure 32 has a continuously changing modulation phase, so that the phase modulation structure 32 can make different phase modulations to different signals in the whole area, thereby achieving the above technical effects. It should be understood that, in an ideal state, the modulation phase of the phase modulation structure 32 changes continuously. Specifically, the modulation phase of the phase modulation structure 32 can be determined according to the following formula: Figure 7 and Figures 8a to 8c As shown in FIG. 1 and FIG. 2, along the plane in which the super surface 3 is located (that is, the plane perpendicular to the optical axis of the retroreflective assembly 10), the phase modulation structure 32 is composed of a plurality of points, and each point of the phase modulation structure 32 corresponds to a modulation phase. According to the generalized Snell's law, the phase gradient of the phase modulation structure 32 satisfies the following rule:

[0065]

[0066] wherein, is the phase gradient of the phase modulation structure 32, n1 is the refractive index of the structure located on the light entering side of the super surface 3 (here, the refractive index of the convex lens 2); n2 is the refractive index of the substrate 31, and θ1 is the incident angle of the incident signal to the phase modulation structure 32.

[0067] In actual application, the phase value of the modulation phase corresponding to a certain position on the phase modulation structure 32 can be calculated. Specifically, a reference phase value of a reference position can be set, and the phase value of a target position adjacent to the reference position can be calculated according to the following formula:

[0068]

[0069] wherein, α is the reference phase value of the reference position, β is the phase value of the target position, and L is the distance between the reference position and the target position. In the calculation, the phase value of a target position can be calculated first according to the formula, and then the phase value of the next target position can be calculated by taking the phase value of the target position as the reference phase value. In this way, the phase value of any position on the phase modulation structure 32 can be finally determined.

[0070] Specifically, as shown in FIG. 3 and FIG. 4, Figure 9As shown, the phase modulation structure 32 specifically includes a plurality of subwavelength units 321, which form an array structure. The distance between each subwavelength unit 321 and adjacent subwavelength units 321 is not limited. Along a direction perpendicular to the optical axis of the retroreflective assembly 10, the distance between any two points on the cross-section of each subwavelength unit 321 is less than the wavelength of the incident signal. Furthermore, the spacing between any two adjacent subwavelength units 321 is less than the wavelength of the incident signal, enabling the subwavelength units 321 to phase modulate the incident signal.

[0071] It should be understood that the phase change produced by subwavelength element 321 is related to its material, shape, and size. During design, for a unit made of a specific material, one can typically first test the phase change value for a certain shape or size, then adjust the shape or size. The corresponding phase change value is then tested, and the shape or size corresponding to the phase range of 0 to 2π is determined. The desired phase change value can then be selected based on the desired shape or size. Subwavelength element 321 can be made of a transparent metal or a dielectric material, such as titanium dioxide or silicon nitride.

[0072] Among them, the sub-wavelength units 321 of different materials correspond to different phase values, and may have different shapes or sizes, which can be determined through testing or electromagnetic calculations. Figure 10 The height of the sub-wavelength unit 321 (parallel to the optical axis of the retroreflective component 10) is 500 nm, and its cross section (perpendicular to the optical axis of the retroreflective component 10) is a square. Figure 11 As shown in b1), 200nm( Figure 11 As shown in b2), 300nm( Figure 11 As shown in b3 in the figure, compared with the reference phase, the phase change values ​​corresponding to the sub-wavelength unit 321 are 0.3, 0.6, and 0.9. Figure 12 The sub-wavelength unit 321 shown in the example has a height (parallel to the optical axis of the retroreflective component 10) of 600 nm and a cross section (perpendicular to the optical axis of the retroreflective component 10) of "C". Figure 13 As shown in c1), 45°( Figure 13 As shown in c2), 60°( Figure 13 (as shown in c3 in FIG), compared with the reference phase, the phase change values ​​corresponding to the sub-wavelength unit 321 are 0.2, 0.3, and 0.4.

[0073] based on Figure 11 and Figure 13 As shown, Figure 14The top view of the super surface 3 is shown. The shape and size of each sub-wavelength unit 321 are the same, and the cross section is an ellipse. By rotating each sub-wavelength unit 321 by different angles around the axis direction of each sub-wavelength unit 321 (a direction perpendicular to the substrate 31, that is, a direction of the optical axis of the retroreflective component 10), different sub-wavelength units 321 can correspond to different phase values. Alternatively, as shown in Figure 15 The top view of the super surface 3 is shown. The shape and size of each sub-wavelength unit 321 are the same, and the cross section is an ellipse. By rotating each sub-wavelength unit 321 by different angles around the axis direction of each sub-wavelength unit 321 (a direction perpendicular to the substrate 31, that is, a direction of the optical axis of the retroreflective component 10), different sub-wavelength units 321 can correspond to different phase values. Alternatively, as shown in

[0074] That is, after the phase change values corresponding to the sub-wavelength units 321 at different positions of the super surface 3 are determined in combination with the reference phase values, the sub-wavelength units 321 can be implemented according to the phase change values. That is, after the material is determined, the sub-wavelength units 321 can be implemented according to specific sizes or shapes, so that the phase modulation structure 32 composed of the sub-wavelength units 321 can satisfy the phase modulation effect on the incident signal.

[0075] The structure of the convex lens 2 can refer to the following embodiments.

[0076] As shown in Figure 16a An example of a lenticular lens. Along the direction of the optical axis W of the convex lens 2, both surfaces of the convex lens 2 are convex. When this convex lens 2 is integrated into the retroreflective component 10, as shown in Figure 16b The side of the convex lens 2 facing the super surface 3 is curved, and a filler 4 can be arranged in the gap between the convex lens 2 and the super surface 3 to keep the structure stable. The focusing effect of this convex lens 2 is the best, but the integration and thickness of the convex lens 2 are limited by the convex surface.

[0077] As shown in Figure 17a An example of a plano-convex lens. Along the direction of the optical axis W of the convex lens 2, one surface of the convex lens 2 is convex, and the other surface is flat. In use, as shown in Figure 1 The flat surface can be butted against the super surface 3. At this time, the signal first passes through the convex surface and is incident, and the performance of the surface in terms of the field of view will be better. Alternatively, as shown in Figure 17b The convex surface can be butted against the super surface 3 (at this time, a filler 4 can be arranged between the convex lens 2 and the super surface 3 to keep the structure stable). At this time, the signal first passes through the flat surface and is incident. For the retroreflective component 10, both surfaces in the direction of the optical axis are flat, and the integration is high.

[0078] As shown in Figure 18 An example of a Fresnel lenticular lens. Along the direction of the optical axis W of the convex lens 2, one surface of the convex lens 2 is flat, and the other surface is engraved with concentric circles from small to large. The arrangement can refer toFigure 17a The convex lens 2 shown in the example. In some cases, the Fresnel convex lens is equivalent to the convex lens for infrared and visible light, has a good light focusing effect, and is low in cost.

[0079] like Figure 19 An example of a concave-convex lens. Along the direction of the optical axis W of the convex lens 2, one surface of the convex lens 2 is concave and the other surface is convex, and the curvature of the convex surface is greater than the curvature of the concave surface. The setting method can refer to Figure 17a The convex lens 2 shown in the example.

[0080] It should be understood that in application, the convex lens 2 can be selected according to the needs, as long as it can achieve the above-mentioned focusing effect. Figure 1 、 Figure 16a 、 Figure 17a 、 Figure 18 as well as Figure 19 As shown, when the convex lens 2 is applied to the retroreflective assembly 10 provided in the embodiment of the present application, the optical axis W of the convex lens 2 coincides with the optical axis P of the retroreflective assembly 10 .

[0081] For the reflector 1, in some application scenarios such as communication and charging, the reflector 1 needs to transmit a certain amount of incident signal to be captured by the receiving end, which requires the reflector 1 to have a certain transmittance. If the transmittance of the reflector 1 material itself is low, you can Figure 20 As shown, a reflector 1 is provided with a reflective region 11 and a transmissive region 12. The reflective region 11 is used to reflect signals, while the transmissive region 12 is used to transmit signals. Specifically, the transmissive region 12 may be a through hole that allows signals to pass directly through. The through hole can be formed by punching. Alternatively, the transmissive region 12 may be a weakened portion, the thickness of which is less than that of the reflective region 11, thereby allowing signals to pass through. The weakened portion can be formed by grinding and thinning.

[0082] like Figure 21 The retroreflective assembly 10 shown includes a reflector 1, a convex lens 2, a spacer dielectric layer 5, and a metasurface 3 stacked in sequence along the optical axis. The spacer dielectric layer 5 is a material transparent to signals (light or electromagnetic waves). The spacer dielectric layer 5 provides support between the convex lens 2 and the metasurface 3, allowing the surface of the convex lens 2 facing the metasurface 3 and the surface of the metasurface 3 facing the convex lens 2 to remain relatively parallel.

[0083] exist Figure 21 In the retroreflective component 10 shown, the phase gradient of the phase modulation structure 32 in the metasurface 3 also satisfies Here, n1 is the refractive index of the structure located on the light incident side of the metasurface 3. In the retroreflective assembly 10, the structure located on the light incident side of the metasurface 3 is the spacer dielectric layer 5, so n1 is the refractive index of the spacer dielectric layer 5.

[0084] Based on the above inverse reflection assembly 10, the embodiments of the present application also provide an inverse reflector 100, which can be used to realize large-area inverse reflection. Generally, if the inverse reflector 100 is of the structure shown in Figure 1 The phase gradient difference of different points far away from the center position of the inverse reflector 100 is smaller, and in order to achieve the inverse reflection effect, higher requirements are put forward for the preparation precision of the phase modulation structure 32 in the metasurface 3. In order to avoid the above problems, the inverse reflector 100 in the embodiments of the present application is specifically composed of a plurality of the above inverse reflection assemblies 10, and the plurality of inverse reflection assemblies 10 can be combined into a large-area inverse reflector 100 in an array manner.

[0085] For example, the inverse reflector 100 shown in Figure 22 includes a plurality of inverse reflection assemblies 10 of equal hexagons. There is no gap between any adjacent inverse reflection assemblies 10. Based on this idea, the inverse reflection assembly 10 can also be triangular, rectangular, rhombic or the like, all of which can realize the inverse reflector 100 without gaps.

[0086] In other embodiments, for example, the inverse reflector 100 shown in Figure 23 includes a plurality of inverse reflection assemblies 10 of equal circles. Gaps M are formed between the plurality of inverse reflection assemblies 10. The gap M can act as a pore for the signal to pass through when the inverse reflector 100 needs to have the signal transmission function. It should be understood that other inverse reflection assemblies 10 that cannot realize the gapless array can also achieve this effect.

[0087] In addition, the embodiments of the present application also provide a communication device, as shown in Figure 24 , which specifically includes the above transmitting module 20, receiving module 30 and the above inverse reflection assembly 10. The transmitting module 20 is used for transmitting signals (light or electromagnetic waves), and the receiving module 30 is used for receiving the signals transmitted by the transmitting module 20. The inverse reflection assembly 10 is arranged on the side of the receiving module 30 facing the transmitting module 20, and is used for reflecting the signals transmitted by the transmitting module 20 to realize the inverse reflection of the signals. Wherein, the reflecting surface a2 of the reflecting mirror 1 of the inverse reflection assembly 10 faces the receiving module 30, and the convex lens 2 faces the transmitting module 20.

[0088] Possibly, the inverse reflection assembly 10 is used as a separate device as shown in Figure 1 . Alternatively, the inverse reflection assembly 10 can be used in the inverse reflector 100 as shown in Figure 21 or Figure 22 . According to different needs, the selection can be made.

[0089] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A retroreflective assembly characterized by, The inverse reflection assembly comprises a mirror, a convex lens, and a metasurface arranged between the mirror and the convex lens. The mirror has a bottom surface and a reflecting surface, the convex lens is arranged on the side of the reflecting surface of the mirror, and the distance between the reflecting surface of the mirror and the convex lens is less than the focal length of the convex lens. The metasurface is used for modulating the phase of the incident signal, so that the incident signals with parallel incident paths can converge on the same point on the reflecting surface.

2. The retroreflective assembly of claim 1, wherein, The metasurface comprises a substrate and a phase modulation structure arranged on one side of the substrate facing the convex lens or one side of the substrate facing the mirror. The refraction angle of the incident signal passing through the optical center of the convex lens in the substrate is θ2, and -3°≤θ2≤3°.

3. The retroreflective assembly of claim 2, wherein, The phase modulation structure comprises a plurality of subwavelength units; in the direction perpendicular to the optical axis of the inverse reflection assembly, the distance between any two points in the cross section of each subwavelength unit is less than the wavelength of the incident signal; and the distance between any two adjacent subwavelength units is less than the wavelength of the incident signal.

4. The retroreflective assembly of claim 2, wherein, The θ2 is 0°.

5. The retroreflective assembly of claim 4, wherein, The phase modulation structure comprises a plurality of subwavelength units; in the direction perpendicular to the optical axis of the inverse reflection assembly, the distance between any two points in the cross section of each subwavelength unit is less than the wavelength of the incident signal; and the distance between any two adjacent subwavelength units is less than the wavelength of the incident signal.

6. The retroreflective assembly of claim 2, wherein, In the direction perpendicular to the optical axis of the inverse reflection assembly, the phase gradient of the phase modulation structure satisfies the following rule: wherein, is a phase gradient of the phase modulation structure, n1 is a refractive index of the structure located at the light entrance side of the metasurface; n2 is a refractive index of the substrate, and θ1 is an incident angle of the incident signal to the phase modulation structure.

7. The retroreflective assembly of claim 6, wherein, The phase modulation structure comprises a plurality of subwavelength units; in the direction perpendicular to the optical axis of the inverse reflection assembly, the distance between any two points in the cross section of each subwavelength unit is less than the wavelength of the incident signal; and the distance between any two adjacent subwavelength units is less than the wavelength of the incident signal.

8. The retroreflective assembly of claim 6, wherein, The θ2 is 0°.

9. The retroreflective assembly of claim 8, wherein, The phase modulation structure comprises a plurality of subwavelength units; in the direction perpendicular to the optical axis of the inverse reflection assembly, the distance between any two points in the cross section of each subwavelength unit is less than the wavelength of the incident signal; and the distance between any two adjacent subwavelength units is less than the wavelength of the incident signal.

10. The retroreflective assembly of claim 1, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

11. The retroreflective assembly of claim 2, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

12. The retroreflective assembly of claim 3, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

13. The retroreflective assembly of claim 4, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

14. The retroreflective assembly of claim 5, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

15. The retroreflective assembly of claim 6, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

16. The retroreflective assembly of claim 7, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

17. The retroreflective assembly of claim 8, wherein, A transparent spacing medium layer is further included, and the spacing medium layer is arranged between the convex lens and the metasurface.

18. The retroreflective assembly of claim 9, wherein, A transparent spacer medium layer is also included, disposed between the convex lens and the metasurface.

19. The retroreflective assembly of any of claims 1-18, wherein, The mirror has a reflective region and a transmissive region, the transmissive region being configured to transmit a signal.

20. The retroreflective assembly of claim 19, wherein, The transmissive region is a through hole or a weak region, the weak region having a thickness less than that of the reflective region.

21. A retroreflector, characterized by A plurality of retroreflective assemblies as claimed in any one of claims 1-20 are included, the plurality of retroreflective assemblies being arranged in an array.

22. The retroreflector of claim 21, wherein, Gaps are present between the plurality of retroreflective assemblies, the gaps being configured to transmit a signal.

23. A communications device, characterized by A transmitting module, a receiving module, and a retroreflective assembly as claimed in any one of claims 1-20 are included. The retroreflective assembly is disposed on a side of the receiving module facing the transmitting module, and a reflective surface of a mirror of the retroreflective assembly faces the receiving module.

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