WO2023185600A1 - Retroreflection assembly, retroreflector, and communication device - Google Patents

Abstract

The present application provides a retroreflection assembly, a retroreflector, and a communication device. The retroreflection assembly comprises a reflecting mirror, a convex lens, and a metasurface provided between the reflecting mirror and the convex lens; the reflecting mirror has a bottom surface and a reflecting surface, the convex lens is provided at the reflecting surface of the reflecting mirror, and the distance between the reflecting surface of the reflecting mirror and the convex lens is less than the focal length of the convex lens; the metasurface is used for modulating the phases of incident signals, so that incident signals, the incident paths of which are parallel to each other, can be converged at a same point on the reflecting surface. According to the retroreflector, the size of a retroreflector in an optical axis direction can be reduced, thereby facilitating implementation of light and thin design of a device.

Description

Retroreflective components, retroreflectors and communication equipment

Cross-references to related applications

This application claims priority to the Chinese patent application filed with the China Patent Office on March 28, 2022, with application number 202210314775.0 and the application name "Retroreflective Components, Retroreflectors and Communication Equipment", the entire content of which is incorporated by reference in in this application.

Technical field

The present application relates to the field of communication technology, and in particular to a retroreflective component, a retroreflector and communication equipment.

Background technique

A retroreflector is an optical or electromagnetic wave device that can reflect incident light or electromagnetic waves back, and the direction of the reflection path of the light or electromagnetic wave is parallel to and opposite to the incident path. Retroreflectors are widely used in wireless charging, communications, detection, etc.

In the existing technology, limited by module size requirements, retroreflectors have defects such as large thickness or low efficiency, which is not conducive to the development and practicality of retroreflectors.

Contents of the invention

This application provides a retroreflective component, a retroreflector and communication equipment to reduce the thickness of the device and achieve a thin and light design of the device.

In the first aspect, the present application provides a retroreflective component, which can be applied to communication, charging, detection and other occasions requiring signal feedback. The retroreflective component includes a reflective mirror, a convex lens, and a metasurface disposed between the reflective mirror and the convex lens. The reflecting mirror has a bottom surface and a reflecting surface, and the convex lens is arranged on the reflecting surface side of the reflecting mirror. When used, the bottom surface of the reflector faces the signal receiving end, and the convex lens faces the signal transmitting end. The incident signal can reach the reflective surface of the reflector through the convex lens and metasurface and be reflected, becoming a reflected signal. The metasurface located between the convex lens and the mirror can modulate the phase of the incident signal so that the incident signal can be focused on the reflective surface to meet the retroreflection requirements. Specifically, the distance between the reflecting surface of the mirror and the convex lens is smaller than the focal length of the convex lens, and the metasurface is used to modulate the phase of the incident signal so that the incident signals whose incident paths are parallel to each other can converge at the same point on the reflecting surface ( That is, the incident signals that are parallel to each other are focused on one point). According to the principle of reversible optical path, the reflected signal and the incident signal are parallel to each other, achieving retroreflection of the signal.

In the above-mentioned retroreflector, the incident signal is refracted and converged by the convex lens. The metasurface located between the convex lens and the mirror can change the amplitude, phase, polarization state and other characteristic parameters of the incident signal to control it, and guide and focus the incident signal to the reflected signal. surface, shortening the distance for the incident signal to reach the reflective surface, so that the distance between the reflector and the convex lens can be reduced to less than the focal length of the convex lens. The retroreflector can reduce the size of the retroreflector in the optical axis direction, which is beneficial to realizing a thin and light design of the device.

Among them, metasurface includes substrate and 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 reflector. In order to achieve retroreflection of signals, the refraction angle of the incident signal passing through the optical center of the convex lens in the substrate is set to θ ₂ , -3° ≤ _{θ 2} ≤ 3°. Should The angle range can optimize the metasurface and reduce the maximum exit angle deviation.

Ideally, there is a continuous change between the various modulation phases. Along the direction perpendicular to the optical axis of the retroreflective component, the phase gradient of the phase modulation structure satisfies the following rules:

in, is the phase gradient of the phase modulation structure, n ₁ is the refractive index of the structure located on the light incident side of the metasurface; n 2 is the refractive index of the substrate, and θ ₁ is the incident angle of the incident signal to the phase modulation structure. When the structure on the light incident side of the metasurface is a convex lens, n ₁ is specifically the refractive index of the convex lens. When θ ₂ is 0°, the retroreflective component can make the incident signal and the outgoing signal symmetrical about the secondary optical axis (or main optical axis).

In some possible implementations, a transparent spacing dielectric layer is also provided between the metasurface and the convex lens. In this structure, n ₁ is specifically the refractive index of the spacer dielectric layer. The spacing dielectric layer can provide support between the convex lens and the metasurface, so that the surface of the convex lens facing the metasurface and the surface of the metasurface facing the convex lens can remain relatively parallel.

In order to facilitate the realization of the metasurface structure, the phase modulation structure may specifically include multiple sub-wavelength units. Along the direction perpendicular to the optical axis of the retroreflective component, on the contour line of the cross-section of each sub-wavelength unit, the distance between any two points is less than the wavelength of the incident signal, and the distance between any two adjacent sub-wavelength units is The spacing is smaller than the wavelength of the incident signal.

In some possible implementations, the retroreflective component needs to transmit signals. At this time, a reflective area and a transmissive area can be set on the reflector. The reflective area is used to reflect signals, and the transmissive area is used to transmit signals. Specifically, the transmission area can be implemented in the form of a through hole, and the incident signal can pass through the through hole to reach the receiving end. The transmission area can also be realized in the form of a weak portion. The thickness of the weak portion is smaller than the thickness of the reflective area, and the incident signal can be transmitted through the weak area.

In a second aspect, embodiments of the present application also provide a retroreflector, which specifically includes a plurality of retroreflective components provided by the above technical solutions. An array of multiple retroreflective components can form a larger-area retroreflector to meet the retroreflective effect of a larger area.

In some possible implementations, gaps exist between multiple retroreflective components, and the gaps can be used for signals to pass through. For example, a retroreflector formed by a circular array of retroreflective components will form multiple gaps that can be used for signals to pass directly through. Therefore, this kind of retroreflector can be directly applied to scenarios where transmitted signals are required.

In a third aspect, embodiments of the present application also provide a communication device, including a transmitting module, a receiving module, and any of the above retroreflective components. The transmitting module is used to transmit signals, and the receiving module is used to receive signals. The retroreflective component is disposed on the side of the receiving module facing the transmitting module, and the reflector of the retroreflective component faces the receiving module, so that the signal transmitted by the transmitting module can be reflected back to the transmitting module.

Description of drawings

Figure 1 is a schematic structural diagram of a retroreflective component provided by an embodiment of the present application;

Figure 2 is a schematic structural diagram of a reflector in a retroreflective assembly provided by an embodiment of the present application;

Figure 3 is a schematic diagram of the working principle of a convex lens in a retroreflective assembly provided by an embodiment of the present application;

Figure 4 is a schematic diagram of the working principle of a retroreflective component provided by an embodiment of the present application;

Figure 5 is a schematic diagram of the reflection principle of an incident signal by a retroreflective component provided by an embodiment of the present application;

Figure 6 is a schematic structural diagram of a metasurface in a retroreflective component provided by an embodiment of the present application;

Figure 7 is a schematic diagram of the reflection principle of an incident signal by a retroreflective component provided by an embodiment of the present application;

Figures 8a to 8c are schematic diagrams of the reflection principle of incident signals by a retroreflective component provided by an embodiment of the present application;

Figure 9 is a schematic structural diagram of a metasurface in a retroreflective component provided by an embodiment of the present application;

Figure 10 is a schematic structural diagram of a sub-wavelength unit in a retroreflective component provided by an embodiment of the present application;

Figure 11 is a schematic diagram of the cross-sectional changes of the sub-wavelength unit in Figure 10;

Figure 12 is a schematic structural diagram of a sub-wavelength unit in a retroreflective component provided by an embodiment of the present application;

Figure 13 is a schematic diagram of the cross-sectional changes of the sub-wavelength unit in Figure 12;

Figure 14 is a schematic structural diagram of a metasurface in a retroreflective component provided by an embodiment of the present application;

Figure 15 is a schematic structural diagram of a metasurface in a retroreflective component provided by an embodiment of the present application;

Figure 16a is a schematic structural diagram of a convex lens in a retroreflective assembly provided by an embodiment of the present application;

Figure 16b is a schematic structural diagram of a retroreflective component provided by an embodiment of the present application;

Figure 17a is a schematic structural diagram of a convex lens in a retroreflective assembly provided by an embodiment of the present application;

Figure 17b is a schematic structural diagram of a retroreflective component provided by an embodiment of the present application;

Figure 18 is a schematic structural diagram of a convex lens in a retroreflective assembly provided by an embodiment of the present application;

Figure 19 is a schematic structural diagram of a convex lens in a retroreflective assembly provided by an embodiment of the present application;

Figure 20 is a schematic structural diagram of a reflector in a retroreflective assembly provided by an embodiment of the present application;

Figure 21 is a schematic structural diagram of a retroreflective component provided by an embodiment of the present application;

Figure 22 is a schematic structural diagram of a retroreflector provided by an embodiment of the present application;

Figure 23 is a schematic structural diagram of a retroreflector provided by an embodiment of the present application;

Figure 24 is a schematic structural diagram of a communication device provided by an embodiment of the present application.

Reference signs: 1-mirror; 11-reflection area; 12-transmission area; 2-convex lens; 3-metasurface; 31-substrate; 32-phase modulation structure; 321-subwavelength unit; 4-filler; 5- Spacer dielectric layer. 10-retroreflective component; 20-transmitting module; 30-receiving module; 100-retroreflector.

Detailed ways

A retroreflector, also known as a retroreflector, can reflect incident signals (including light and electromagnetic waves) back, and the reflection direction is parallel to the incident direction. Through the retroreflector, the side that transmits the signal can automatically obtain the position or angle state of the side that reflects the signal. Existing retroreflectors have the disadvantages of large size and low efficiency, and cannot meet the needs of retroreflection development.

Based on this, embodiments of the present application provide a retroreflective component, a retroreflector including the retroreflective component, and a communication device including the retroreflective component, which have a smaller closed structure, which is conducive to the lightweight and thin design of the device.

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

The terminology used in the following examples is for the purpose of describing specific embodiments only and is not intended to limit the application. As used in the specification and appended claims of this application, the singular expressions "a", "an", "said", "above", "the" and "the" are intended to also Expressions such as "one or more" are included unless the context clearly indicates otherwise.

Reference in this specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Therefore, the phrases "in one embodiment", "in some embodiments", "in other embodiments", "in other embodiments", etc. appearing in different places in this specification are not necessarily References are made to the same embodiment, but rather to "one or more but not all embodiments" unless specifically stated otherwise. The terms “including,” “includes,” “having,” and variations thereof all mean “including but not limited to,” unless otherwise specifically emphasized.

The embodiment of the present application provides a retroreflective component 10. The retroreflective component 10 can be used in laser charging or wireless communication system receiving terminals. Its main function is to reflect incident signals (light or electromagnetic waves) back. The reflection of the signal The direction of radiation is parallel and opposite to the direction of the incident signal. No additional alignment is required for signal transfer between the terminal transmitting the signal and the terminal receiving the signal.

As shown in FIG. 1 , the retroreflective component 10 includes a reflective mirror 1 , a convex lens 2 and a metasurface 3 disposed between the reflective mirror 1 and the convex lens 2 . The retroreflective component 10 serves as an optical system, and its optical axis P is parallel to the stacking direction of the reflector 1 , the metasurface 3 , and the convex lens 2 . When in use, the convex lens 2 faces the signal transmitting end to guide the incident signal from the transmitting end into the retroreflective component 10 . The reflector 1 is located at the receiving end of the signal. The incident signal passes through the convex lens 2 and the metasurface 3 and then reaches the reflector 1. The reflector 1 reflects the incident signal and then the reflected signal is emitted through the metasurface 3 and the convex lens 2.

Specifically, as shown in FIG. 2 , the reflecting mirror 1 has a bottom surface a1 and a reflecting surface a2 , and the convex lens 2 is provided on the reflecting surface a2 side of the reflecting surface 1 . When the incident signal reaches the reflective surface a2, the reflective surface a2 has a strong reflection effect on the incident signal, and a metal material can be selected. The angle between the incident signal and the normal line N perpendicular to the reflecting surface a2 is the incident angle α1, and the angle between the reflected signal and the normal line N perpendicular to the reflecting surface a2 is the reflection angle α2, α1=α2.

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 produce a certain convergence effect on the incident signal to facilitate the phase modulation of the incident signal by the metasurface 3.

Generally, as shown in Figure 3, mutually parallel incident signals (these incident signals have the same incident angle) will converge to a convergence point after passing through the convex lens 2. Incident signals from different incident directions will converge to different convergence points after passing through the convex lens 2 . Set the plane where the convex lens 2 is located to be 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 component 10 . The direction of the light passing through the optical center O of the convex lens 2 remains unchanged. Taking the incident signal A0, the incident signal A1 and the incident signal A2 with different incident directions as an example, the incident signal A0 has an incident direction perpendicular to the plane where the convex lens 2 is located. The light rays of the incident signal A0 will converge to the convergence point Q0, the light rays of the incident signal A1 will converge to the convergence point Q1, and the light rays of the incident signal A2 will converge to the convergence point Q2. The plane where these convergence points are located can be defined as the focal plane M0. Set the axis perpendicular to the plane M1 of the convex lens 2 and passing through the optical center O as the main optical axis L0 (the main optical axis L0 coincides with the optical axis P of the retroreflective component 10), and the intersection point of the main optical axis L0 and the focal plane M0 is The main focus (that is, the convergence point Q0). Other axes passing through the optical center O and not perpendicular to the plane M1 of the convex lens 2 are the secondary optical axes (the secondary optical axis L1 of the incident signal A1, and the secondary optical axis L2 of the incident signal A2). The focal point between the secondary optical axis and the focal plane M0 is the secondary focus, the secondary focus on the secondary optical axis L1 is the convergence point Q1, and the secondary focus on the secondary optical axis L2 is the convergence point Q2. The plane where the convex lens 2 is located is the distance between M1 and the focal plane M0, which is the focal length f of the convex lens 2. The signals in Figure 3 are all bidirectional arrows. When any convergence point is used as a transmitting end to transmit a signal to the convex lens 2, the signal path is the same as the signal path that can converge to the convergence point through the convex lens 2.

In the retroreflective assembly 10 provided by the embodiment of the present application, the reflector 1 is set such that the distance between the reflective surface a2 of the reflector 1 and the convex lens 2 is smaller than the focal length f of the convex lens 2 . To this end, a metasurface 3 is provided between the reflector 1 and the convex lens 2 to converge the signal passing through the convex lens 2 to the reflection surface a2 of the reflector 1 . The principle is that the incident signal is incident on the metasurface 3, and the metasurface 3 can phase modulate the incident signal, causing the phase of the incident signal to change, thereby causing refraction. This phenomenon of phase modulation of signals (light or electromagnetic waves) by the metasurface 3 to produce refraction can be expressed by the generalized Snell's law.

As shown in Figure 4, 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 metasurface 3 is located is M3. Taking an incident signal that is parallel to each other and not perpendicular to the plane M1 where the convex lens 2 is located as an example, the incident signal can be focused to the convergence point Q on the focal plane M0 through the convex lens 2 (dotted line example). 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 reflector 1 is located and the plane M1 where the convex lens 2 is located is f', and f' is smaller than f. The metasurface 3 can change the phase of the incident signal passing through the convex lens 2 so that the incident signal can converge at the convergence point Q' on the plane M2 where the reflector 1 is located (solid line example).

As shown in FIG. 5 , an incident signal that is not perpendicular to the plane M1 of the convex lens 2 is used as an example to introduce the reflection principle of the retroreflective component 10 provided in the embodiment of the present application. The incident signal is refracted by the convex lens 2. The refracted incident signal is phase-changed by the metasurface 3 and then incident on the convergence point Q’ (solid line example) on the plane M1 where the reflection surface a2 is located. The reflective surface a2 reflects the incident signal to form a reflected signal that reaches the metasurface 3 again. Between the plane M3 where the metasurface 3 is located and the plane M2 where the reflective surface a2 is located, the incident angle between the incident signal and the normal line N is the same as the reflection angle between the reflected signal and the normal line N. The metasurface 3 performs phase modulation on the reflected signal so that the reflected signal can be emitted after passing through the convex lens 2, and the emitting direction is parallel to the angle of incidence, thereby realizing retroreflection of the signal.

It can be seen that the retroreflective component 10 provided in the embodiment of the present application is provided between the reflector 1 and the convex lens 2 with a metasurface 3 that can phase modulate the incident signal. The incident signal is adjusted through the metasurface 3 so that the incident signal can be Converged on the reflective surface a2 of the reflector 1. The distance between the reflecting mirror 1 and the convex lens 2 can be reduced to less than the focal length f of the convex lens 2. The retroreflective component 10 can reduce the size of the retroreflective component 10 in the optical axis direction, which is beneficial to realizing a thin and light design of the device. It should be understood that the retroreflective component 10 provided in the embodiment of the present application has a relatively closed structure, has a high degree of structural integration, and can also avoid the problem of dust accumulation affecting device performance.

The structure of the metasurface 3 can be referred to as shown in Figure 6 . The metasurface 3 includes a substrate 31 and a phase modulation structure 32 . The phase modulation structure 32 can be specifically provided on the side of the substrate 31 facing the convex lens 2 , or can also be provided on the side of the substrate 31 facing the reflecting mirror 1 , which is not limited here. Among them, the phase modulation structure 32 can adjust the phase of the signal. As the signal passes through the substrate 31, it is refracted.

In order to increase the field of view 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, taking the incident signal at the optical center O of the hyperconvex lens 2 (the optical center O coincides with the optical axis P) as an example, after the incident signal is phase modulated by the phase modulation structure 32 of the metasurface 3, the incident signal enters the substrate. The bottom 31 is refracted within the substrate 31 . The angle between the incident signal and the normal line N in the substrate 31 is the incident angle θ ₁ . The angle between the incident signal and the normal line N in the substrate 31 is the refraction angle θ ₂ . The outgoing signal and the incident signal are parallel to each other, and the outgoing signal's exit point on the plane M1 where the convex lens 2 is located is close to the optical center O of the convex lens 2 .

θ ₂ here is approximately equal to 0°, and the specific range can be set to -3° ≤ _{θ 2} ≤ 3°. As shown in Figure 8a, the incident signal from the optical center O of the hyperconvex lens 2 is phase-adjusted by the phase modulation structure 32 of the metasurface 3, refracted in the substrate 31, and then refracted in the direction perpendicular to the mirror 1 (i.e. θ ₂ =0°) reaches the reflecting surface a2. The incident signal is reflected by the reflective surface a2 of the mirror 1 and then returns to the metasurface 3, and can return to the original path. That is, the incident signal and the reflected signal have the same path, and the signal realizes retroreflection of the original path.

As shown in Figure 8b, taking a set 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, and the incident signal located to the left 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 may be other multiple parallel signals between the first signal B1 and the center signal B0. Among them, the central signal B0 passes through the optical center of the convex lens 2 and is vertically incident on the reflective surface a2 relative to the reflective surface a2 (the path from the plane M3 where the metasurface 3 is located to the plane M2 where the reflector 1 is located coincides with the normal N). It should be understood that the retroreflection optical path of the central signal B0 is similar to that in Figure 8a and will not be described again. After the first signal B1 is refracted by the convex lens 2, the phase is adjusted by the phase modulation structure 32, and refracted by the substrate 31, it reaches the convergence point Q' of the reflective surface a2 and converges with the center signal B0. The first signal B1 is reflected by the reflective surface a2 and then emits to the right side of the normal line N, passes through the metasurface 3 and the convex lens 2 again, and then emits. According to the principle of reversible optical path, the directions of the emitted first signal B1 and the incident first signal B1 are parallel to each other. Moreover, the distance from the incident point O' of the first signal B1 to the convex lens 2 to the optical center O of the convex lens 2 is d, and the distance from the exit point O" of the first signal B1 from the convex lens 2 to the optical center O of the convex lens 2 is Also d. Located between the first signal B1 and the center signal B0 The signal incidence range of other paths between them is between the incident point O' and the optical center O, and the signal output 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 to say, as long as the range of the first signal B1 relative to the center signal B0 can be set, the retroreflection range of the set of signals can be limited to prevent unavailability problems caused by the outgoing signal exceeding the range of the convex lens 2 .

As shown in Figure 8c, taking a set 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, and the incident signal located to the left of the center signal B0 is the first signal B1. The incident signal located on the right side of the central 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 may be other multiple channels of parallel signals between the first signal B1 and the central signal B0, and there may be other multiple channels of parallel signals between the second signal B2 and the central signal B0. Among them, the central signal B0 passes through the optical center of the convex lens 2 and is vertically incident on the reflective surface a2 relative to the reflective surface a2. The first signal B1 is incident from the incident point O’ and emerges from the exit point O”. The incident point of the second signal B2 incident on the convex lens 2 coincides with the exit point O” of the first signal B1 from the convex lens 2 . According to the principle of reversible optical path, the incident point O' of the first signal B1 entering the convex lens 2 is also 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 also the second signal B2. The incident point of the convex lens 2. If the first signal B1 and the second signal B2 are defined as the signals at the extreme edge of the horizontal direction of the group of signals, then the incidence range of the group of signals coincides with the reflection range.

As can be seen from the above embodiments, the retroreflective component 10 provided by the embodiment of the present application can make the incident signal and the reflected signal symmetrical about the secondary optical axis (or main optical axis) by setting the position of the incident signal relative to the optical center of the convex lens 2. This limits the range of the reflected signal, avoids the problem of unusability caused by the outgoing signal exceeding the range of the convex lens 2, and increases the field of view of the retroreflective component 10.

In the embodiment of the present application, the phase modulation structure 32 has a continuously changing modulation phase, so that the phase modulation structure 32 can perform different phase modulation on different signals in the entire area, thereby achieving the above technical effects. It should be understood that under ideal conditions, the modulation phase changes of the phase modulation structure 32 are continuous. Specifically, as shown in FIG. 7 and FIGS. 8a to 8c , the phase modulation structure 32 is composed of many points along the plane where the metasurface 3 is located (that is, the plane perpendicular to the optical axis of the retroreflective component 10 ). Each point of 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 rules:

in, is the phase gradient of the phase modulation structure 32, n ₁ is the refractive index of the structure located on the light incident side of the metasurface 3 (here is the refractive index of the convex lens 2); n ₂ is the refractive index of the substrate 31, θ ₁ is the incident signal The angle of incidence into the phase modulation structure 32 .

In practical applications, the calculated phase value of the modulation phase corresponding to a certain position on the phase modulation structure 32 may be used. Specifically, the reference phase value of a reference position can be set, and the phase value of the target position adjacent to the reference position can be calculated according to the following formula:

Among them, α is the reference phase value of the reference position, β is the phase value with the target position, and L is the distance between the reference position and the target position. During calculation, you can first calculate the phase value of a target position based on this formula, and then use the phase value of the target position as the reference phase value to calculate the phase value of the next target position. By analogy, the phase value at any position on the phase modulation structure 32 can finally be determined.

Specifically, as shown in Figure 9, the phase modulation structure 32 specifically includes a plurality of sub-wavelength units 321. The plurality of sub-wavelength units 321 form an array structure. Each sub-wavelength unit 321 can correspond to the adjacent sub-wavelength unit 321. distance No restrictions. Along the direction perpendicular to the optical axis of the retroreflective component 10, the distance between any two points on the cross-section of each sub-wavelength unit 321 is smaller than the wavelength of the incident signal. Moreover, the distance between any two adjacent sub-wavelength units 321 is smaller than the wavelength of the incident signal, so that the sub-wavelength unit 321 can phase modulate the incident signal.

It should be understood that the phase change produced by the sub-wavelength unit 321 is related to the material, shape, size, etc. of the sub-wavelength unit 321 . During design, for a unit of a specific material, you can usually test the phase change value under a certain shape or size first, and then adjust the shape or size. Then test the corresponding phase change value, and finally obtain the corresponding shape or size within the phase range of 0 to 2π, and select according to the required phase change value. The material of the sub-wavelength unit 321 may be a transparent metal or dielectric material, such as titanium dioxide or silicon nitride.

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. As shown in FIG. 10 , a subwavelength unit 321 has a height (direction parallel to the optical axis of the retroreflective component 10 ) of 500 nm, and its cross section (direction perpendicular to the optical axis of the retroreflective component 10 ) is square. When the side lengths of the cross-section of the subwavelength unit 321 are 100 nm (shown as b1 in Figure 11), 200nm (shown as b2 in Figure 11), and 300nm (shown as b3 in Figure 11) respectively, compared with the reference phase, The phase change values corresponding to the sub-wavelength unit 321 are 0.3, 0.6, and 0.9. As shown in Figure 12, a sub-wavelength unit 321 has a height (direction parallel to the optical axis of the retroreflective component 10) of 600 nm, and a cross-section (direction perpendicular to the optical axis of the retroreflective component 10) of a "C" shape. . When the angles between the notch direction of "C" and the horizontal right direction are 0° (shown as c1 in Figure 13), 45° (shown as c2 in Figure 13), and 60° (shown as c3 in Figure 13), respectively, Compared with the reference phase, the phase change values corresponding to the sub-wavelength unit 321 are 0.2, 0.3, and 0.4.

Based on the top view of the metasurface 3 shown in FIG. 11 and FIG. 13 , as shown in FIG. 14 , each sub-wavelength unit 321 has the same shape and size, and its cross-section is elliptical. Different sub-wavelengths can be achieved by rotating each sub-wavelength unit 321 at different angles around the axis direction of each sub-wavelength unit 321 (the direction perpendicular to the substrate 31, that is, the direction of the optical axis of the retroreflective component 10). Unit 321 corresponds to different phase values. Or as shown in the top view of the metasurface 3 as shown in Figure 15, each sub-wavelength unit 321 has the same shape and height, and its cross-section is square. By changing the side length dimensions of the sub-wavelength units 321 at different positions, different phase values corresponding to the different sub-wavelength units 321 can be achieved.

That is to say, after combining the reference phase value and determining the phase change value corresponding to the sub-wavelength unit 321 at each position of the metasurface 3, the sub-wavelength unit 321 can be implemented according to the phase change value. That is, after the material is determined, it can be implemented according to a specific size or shape, so that the phase modulation structure 32 composed of multiple sub-wavelength units 321 can satisfy the phase modulation effect on the incident signal.

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

A biconvex lens as shown in Figure 16a. Along the direction of the optical axis W of the convex lens 2, both surfaces of the convex lens 2 are convex surfaces. When this kind of convex lens 2 is integrated into the retroreflective component 10, as shown in Figure 16b, the side of the convex lens 2 facing the metasurface 3 is a curved surface, and a filler 4 can be placed in the gap between the convex lens 2 and the metasurface 3 to maintain stable structure. This kind of convex lens 2 has the best focusing effect, but the integration degree and thickness of the convex lens 2 are limited by the convex surface.

A plano-convex lens as shown in Figure 17a. Along the direction of the optical axis W of the convex lens 2, one surface of the convex lens 2 is a convex surface and the other surface is a flat surface. In use, as shown in Figure 1, the plane can be docked with the metasurface 3. At this time, the signal is incident through the convex surface first, and the performance in terms of field of view will be better. Alternatively, as shown in Figure 17b, the convex surface can be connected to the metasurface 3 (in this case, a filler 4 can be provided between the convex lens 2 and the metasurface 3 to maintain structural stability). At this time, the signal first passes through the plane and is incident. For the retroreflective component 10, both surfaces along the optical axis direction are flat, which has high integration.

A Fresnel lenticular lens is shown in Figure 18. Along the direction of the optical axis W of the convex lens 2, one of the convex lenses 2 One face is a flat surface, and the other face is inscribed with concentric circles from small to large. The arrangement method can refer to the convex lens 2 illustrated in Figure 17a. Fresnel convex lenses are equivalent to convex lenses for infrared and visible light in some cases, with better light focusing effect and lower cost.

A meniscus lens as shown in Figure 19. Along the direction of the optical axis W of the convex lens 2, one surface of the convex lens 2 is a concave surface and the other surface is a convex surface, and the curvature of the convex surface is greater than the curvature of the concave surface. The arrangement method can refer to the convex lens 2 illustrated in Figure 17a.

It should be understood that in application, the convex lens 2 can be selected according to needs, as long as the above focusing effect can be achieved. Referring to Figure 1, Figure 16a, Figure 17a, Figure 18 and Figure 19, when the above-mentioned convex lens 2 is applied to the retroreflective component 10 provided by the embodiment of the present application, the optical axis W of the convex lens 2 and the retroreflective component 10 The optical axes P coincide.

As for the reflector 1, in some communication, charging and other application scenarios, 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 material of the reflective mirror 1 is low, a reflective area 11 and a transmissive area 12 can be provided on the reflective mirror 1 as shown in FIG. 20 . The reflective area 11 is used to reflect signals, and the transmissive area 12 is used to transmit signals. Specifically, the transmission area 12 can be a through hole, and the through hole can allow signals to directly pass through. Through holes can be achieved by drilling. Alternatively, the transmissive region 12 is a weak portion, and the thickness of the weak portion is smaller than the thickness of the reflective region 11 so that signals can be transmitted therethrough. The weak part can be formed by grinding and thinning.

A retroreflective component 10 as shown in Figure 21 includes a reflective mirror 1, a convex lens 2, a spacing dielectric layer 5 and a metasurface 3 stacked in sequence along the optical axis direction. The spacer dielectric layer 5 is a material transparent to signals (light or electromagnetic waves). The spacing dielectric layer 5 can provide support between the convex lens 2 and the metasurface 3 so that the surface of the convex lens 2 facing the metasurface 3 and the surface of the metasurface 3 facing the convex lens 2 can remain relatively parallel.

In the retroreflective component 10 shown in Figure 21, the phase gradient of the phase modulation structure 32 in the metasurface 3 also satisfies dφ/dx=2π/λ·(n ₁ sinθ ₁ -n ₂ sinθ ₂ ), where n ₁ is The refractive index of the structure located on the light incident side of metasurface 3. In the retroreflective component 10 , the spacer dielectric layer 5 is located on the light incident side of the metasurface 3 . Therefore, n ₁ here is the refractive index of the spacer dielectric layer 5 .

Based on the above retroreflective component 10, embodiments of the present application also provide a retroreflector 100, which can be used to achieve large-area retroreflection. Generally, if the retroreflector 100 has the structure shown in Figure 1, the difference in phase gradient at different points farther away from the center of the retroreflector 100 is smaller. In order to achieve the retroreflective effect, the phase modulation in the metasurface 3 is The preparation accuracy of structure 32 puts forward higher requirements. In order to avoid the above problems, the retroreflector 100 in the embodiment of the present application is specifically composed of a plurality of the above-mentioned retroreflective components 10. The plurality of retroreflective components 10 can be combined in an array to form a larger-area retroreflector 100.

Taking the retroreflector 100 shown in FIG. 22 as an example, the retroreflector 100 includes a plurality of hexagonal retroreflective components 10 of equal size. There is no gap between any adjacent retroreflective components 10 . Based on this idea, the retroreflective component 10 can also be in a triangular, rectangular, rhombus or other structure, all of which can achieve a gapless retroreflector 100.

In other embodiments, a retroreflector 100 is shown in FIG. 23 . The retroreflector 100 includes a plurality of circular retroreflective components 10 of equal size. Gaps M are formed between the plurality of retroreflective components 10 . The gap M can serve as a hole for signals to pass through when the retroreflector 100 is required to have a signal transmission function. It should be understood that other retroreflective assemblies 10 that cannot achieve a gapless array can also achieve this effect.

In addition, an embodiment of the present application also provides a communication device. As shown in FIG. 24 , the communication device specifically includes the above-mentioned transmitting module 20, the receiving module 30 and the above-mentioned retroreflective component 10. The transmitting module 20 is used to transmit and receive signals (light or electromagnetic waves), and the receiving module 30 is used to receive the signals sent by the transmitting module 20 . The retroreflective component 10 is disposed on the side of the receiving module 30 facing the transmitting module 20 and is used to reflect the signal sent by the transmitting module 20 to realize the reverse reflection of the signal. shoot. The reflective surface a2 of the reflector 1 of the retroreflective assembly 10 faces the receiving module 30 , and the convex lens 2 faces the transmitting module 20 .

Possibly, the retroreflective assembly 10 is used as a stand-alone device as shown in Figure 1 . Alternatively, the retroreflective assembly 10 may be spliced to form the retroreflector 100 shown in FIG. 21 or FIG. 22 . Just choose according to different needs.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the present application, and all of them should be covered. within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims (11)

1. A retroreflective component, characterized in that it includes a reflecting mirror, a convex lens, and a metasurface disposed between the reflecting mirror and the convex lens;

   The reflector has a bottom surface and a reflective surface, the convex lens is disposed on one side of the reflective surface of the reflector, and the distance between the reflective surface of the reflector and the convex lens is less than the focal length of the convex lens;

   The metasurface is used to modulate the phase of the incident signal so that the incident signals whose incident paths are parallel to each other can converge on the same point on the reflection surface.
2. The retroreflective component according to claim 1, wherein the metasurface includes a substrate and a phase modulation structure, and the phase modulation structure is disposed on a side of the substrate facing the convex lens or the substrate. The side facing the reflector;

   The refraction angle of the incident signal passing through the optical center of the convex lens in the substrate is θ ₂ , and -3°≤θ ₂ ≤3°.
3. The retroreflective component according to claim 2, characterized in that, along the direction perpendicular to the optical axis of the retroreflective component, the phase gradient of the phase modulation structure satisfies the following rules:
   

   in, is the phase gradient of the phase modulation structure, n ₁ is the refractive index of the structure located on the light incident side of the metasurface; n ₂ is the refractive index of the substrate, θ ₁ is the incident signal to the phase Modulates the angle of incidence of the structure.
4. The retroreflective component according to claim 2 or 3, wherein θ ₂ is 0°.
5. The retroreflective component according to any one of claims 2 to 4, wherein the phase modulation structure includes a plurality of sub-wavelength units; along a direction perpendicular to the optical axis of the retroreflective component, each of the On the cross-section of the sub-wavelength unit, the distance between any two points is less than the wavelength of the incident signal; and the distance between any two adjacent sub-wavelength units is less than the wavelength of the incident signal.
6. The retroreflective component according to any one of claims 1 to 5, further comprising a transparent spacing dielectric layer disposed between the convex lens and the metasurface.
7. The retroreflective component according to any one of claims 1 to 6, wherein the reflector has a reflective area and a transmissive area, and the transmissive area is used for signal transmission.
8. The retroreflective component according to claim 7, wherein the transmission area is a through hole or a weak portion, and the thickness of the weak portion is smaller than the thickness of the reflective area.
9. A retroreflector, characterized in that it includes a plurality of retroreflective components according to any one of claims 1 to 8, and a plurality of said retroreflective components are arranged in an array.
10. The retroreflector according to claim 9, characterized in that there are gaps between a plurality of the retroreflective components, and the gaps are used for signals to pass through.
11. A communication device, characterized by comprising a transmitting module, a receiving module and a retroreflective component according to any one of claims 1-8;

    The retroreflective component is disposed on the side of the receiving module facing the transmitting module, and the reflective surface of the reflector of the retroreflective component faces the receiving module.