WO2023024381A1

WO2023024381A1 - Metasurface optical element, design method and structured light projection module

Info

Publication number: WO2023024381A1
Application number: PCT/CN2021/142516
Authority: WO
Inventors: 汪肇坤; 伍未名; 刘风雷
Original assignee: 浙江水晶光电科技股份有限公司
Priority date: 2021-08-25
Filing date: 2021-12-29
Publication date: 2023-03-02

Abstract

The present application provides a metasurface optical element, a design method and a structured light projection module, which relate to the technical field of optics. The metasurface optical element comprises: a substrate and a plurality of nanometer antennas which are provided on the substrate and which modulate incident beams by means of transmission phases. The size of at least two nanometer antennas are different, and the plurality of nanometer antennas are distributed in an array on the substrate. The distance between the centers of two adjacent nanometer antennas is the same, and the transmission phase of each nanometer antenna is the superimposition of a collimation phase and a diffraction phase. Therefore, the formed metasurface optical element may have collimation and diffraction functions at the same time, that is, a collimation element and a diffraction element are integrated. Space occupied by existing collimation and diffraction elements as two independent optical elements is effectively reduced; meanwhile, since the alignment assembly of the collimation element and diffraction element is omitted, alignment error caused by the alignment assembly may thus be effectively reduced.

Description

A metasurface optical element, design method, and structured light projection module

Cross References to Related Applications

This application requires a Chinese patent application with the application number 202110980167.9 and titled "A Metasurface Optical Element and Design Method, Structured Light Projection Module" submitted to the State Intellectual Property Office of China on August 25, 2021 and filed on August 2021 The priority of the Chinese patent application with the application number 202110980751.4 and titled "A Metasurface Optical Element and Design Method, Structured Light Projection Module" submitted to the State Intellectual Property Office of China on April 25, the entire contents of which are incorporated herein by reference Applying.

technical field

The present application relates to the field of optical technology, in particular, to a metasurface optical element, a design method, and a structured light projection module.

Background technique

Structured light projects a specific pattern onto the surface of an object, collects it through the receiving module, calculates the position and depth information of the object according to the change of the light signal caused by the object, and then restores the entire depth space. The pattern can be designed as stripes, regular lattices, grids, speckles, codes, etc., or even more complex light shapes. With the development of optical technology, the application range of structured light is more and more extensive, such as face recognition, gesture recognition, projector, three-dimensional (Three-dimensional, 3D) outline reconstruction, depth measurement, anti-counterfeiting identification, etc. Therefore, how to provide a projection module that stably emits structured light has become the focus of people's research.

The structured light projection module in the related art mainly includes a light source, a collimator lens and a diffractive optical element. In the structured light projection module of the related art, the collimator mirror and the diffractive optical element are discrete components, so that the entire module takes up a large space and the alignment accuracy is low.

Contents of the invention

The present application provides a metasurface optical element, a design method, and a structured light projection module, so as to at least improve the problem that the structured light projection module in the related art occupies a large space and has low alignment accuracy.

In order to achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:

In some embodiments of the present application, a metasurface optical element is provided. The metasurface optical element may include a substrate, and a plurality of nanoantennas arranged on the substrate to modulate the incident light beam through transmission phase, at least two nanoantennas in size Different and multiple nano-antenna arrays are distributed on one side of the substrate, the distance between the centers of two adjacent nano-antennas is the same, and the transmission phase of each nano-antenna is the superposition of the collimation phase and the diffraction phase.

Optionally, the orthographic projection of the nano-antenna on the substrate may be a C4 rotationally symmetric figure.

Optionally, the orthographic projection of the nano-antenna can be circular.

Optionally, the orthographic projection of the nano-antenna can be a square.

Optionally, the plurality of nano-antennas may include a first antenna and a second antenna, the orthographic projection of the first antenna on the substrate may be a circle, and the orthographic projection of the second antenna on the substrate may be a square.

Optionally, when the nano-antenna is a square, the side length of the square may be 50nm to 500nm.

Optionally, when the nano-antenna is circular, the diameter of the circular shape may be 50nm to 500nm.

Optionally, when the nano-antenna is a square, the side length of the square may be 50nm to 500nm, and when the nano-antenna is circular, the diameter of the circle may be 50nm to 500nm.

Optionally, the center-to-center distance between two adjacent nano-antennas may be 200nm to 600nm.

Optionally, the heights of the multiple nano-antennas may be greater than 300nm.

Optionally, the heights of the multiple nano-antennas may be the same.

Optionally, the number of nanoantennas with different sizes may be greater than or equal to 4, and at least two nanoantennas have different sizes.

Optionally, the substrate may be a transparent substrate, and the material of the transparent substrate may be quartz, glass or silicon oxide film.

Optionally, the material of the nano-antenna can be silicon, titanium oxide, aluminum oxide or silicon nitride.

In addition, some embodiments of the present application provide a method for designing a metasurface optical element, the method may include:

Using the simulated collimation element presented by the metasurface optical element when realizing a single collimation function, obtaining the corresponding collimation phases of the plurality of first simulated nano-antennas arranged on the substrate;

Using the simulated diffraction element presented by the metasurface optical element when realizing a single diffraction function, obtain the respective diffraction phases of multiple second simulated nanoantennas set on the substrate, wherein the multiple first simulated nanoantennas and multiple second simulated nanoantennas The number of simulated nanoantennas corresponds one by one;

superimposing the alignment phases of multiple first simulated nanoantennas with the diffraction phases of their corresponding second simulated nanoantennas to obtain multiple simulated phases;

Multiple analog phases are discretized to obtain multiple discrete phases, wherein the number of multiple nano-antennas on the base of the metasurface optical element corresponds to the number of multiple discrete phases, and the transmission phases of multiple nano-antennas correspond to their corresponding The discrete phases are the same.

Optionally, after the multiple simulated phases are obtained by superimposing the alignment phases of the multiple first simulated nanoantennas with the diffraction phases of the corresponding second simulated nanoantennas, the multiple first simulated nanoantennas can be A simulated nano-antenna and the plurality of second simulated nano-antennas are fine-tuned to optimize the simulation results, thereby optimizing the superposition phase.

Optionally, obtaining the corresponding collimation phases of the plurality of first simulated nanoantennas arranged on the substrate may include:

Obtaining the simulated focal length of the simulated collimation element and the center-to-center distance of two adjacent first simulated nano-antennas;

The collimation phases corresponding to each of the plurality of first simulated nano-antennas are obtained according to the simulated focal length, the lens focusing equation and the distance between the centers of two adjacent first simulated nano-antennas.

Optionally, the center-to-center distance between two adjacent first simulated nanoantennas may be determined according to the preset working wavelength of the first simulated nanoantennas and the field angle to be realized.

Optionally, obtaining the respective diffraction phases corresponding to the plurality of second simulated nanoantennas arranged on the substrate may include:

Obtain the simulated viewing angle of the simulated diffraction element;

The diffraction phases corresponding to each of the plurality of second simulated nano-antennas are obtained according to the simulated viewing angle and a preset algorithm.

Optionally, before obtaining the collimation phases corresponding to the plurality of first simulated nano-antennas arranged on the substrate, the material of the metasurface optical element may be determined according to the required working wavelength.

Other embodiments of the present application provide a structured light projection module. The structured light projection module may include a light source and any of the above-mentioned metasurface optical elements. The light source is located on the light incident side of the metasurface optical element. The metasurface optics The element is used to collimate and diffract the light beam emitted by the light source.

The beneficial effects of the application at least include:

The present application provides a metasurface optical element and its design method, and a structured light projection module. The metasurface optical element includes a substrate, a plurality of nanoantennas arranged on the substrate to modulate the incident light beam through transmission phase, and at least two nanoantennas Multiple nano-antenna arrays with different sizes are distributed on one side of the substrate, the distance between the centers of two adjacent nano-antennas is the same, and the transmission phase of each nano-antenna is the superposition of the collimation phase and the diffraction phase. In this way, the formed metasurface optical element can have collimation and diffraction functions at the same time, that is, the collimation element and the diffraction element are integrated, which effectively reduces the space occupied by the existing collimation and diffraction independent of two optical elements. At the same time, since the alignment assembly of the collimation element and the diffraction element is canceled, the alignment error caused by it can be effectively reduced.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, so It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

FIG. 1 is one of the structural schematic diagrams of a metasurface optical element provided in the embodiment of the present application;

Fig. 2 is the second structural schematic diagram of a metasurface optical element provided by the embodiment of the present application;

Fig. 3 is the third structural schematic diagram of a metasurface optical element provided by the embodiment of the present application;

Fig. 4 is the fourth structural schematic diagram of a metasurface optical element provided by the embodiment of the present application;

Fig. 5 is the fifth structural schematic diagram of a metasurface optical element provided by the embodiment of the present application;

Fig. 6 is the sixth structural schematic diagram of a metasurface optical element provided by the embodiment of the present application;

FIG. 7 is a schematic structural diagram of a structured light projection module provided in an embodiment of the present application;

FIG. 8 is a schematic flowchart of a method for designing a metasurface optical element provided in an embodiment of the present application.

Icons: 10 - light source; 20 - speckle image; 100 - metasurface optical element; 110 - substrate; 120 - nanometer antenna; 121 - first antenna; 122 - second antenna.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of this application, not all of them. The components of the embodiments of the application generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Accordingly, the following detailed description of the embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. It should be noted that, in the case of no conflict, various features in the embodiments of the present application may be combined with each other, and the combined embodiments are still within the protection scope of the present application.

It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship that is usually placed when the application product is used, and is only for the convenience of describing the application and simplifying the description, rather than indicating or implying References to devices or elements must have a particular orientation, be constructed, and operate in a particular orientation and therefore should not be construed as limiting the application. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

Some embodiments of the present application provide a metasurface optical element. As shown in FIG. The phase of the light beam incident on the nano-antenna 120, wherein, the transmission phase refers to the phase adjustment achieved by the metasurface through the optical path difference generated during the transmission of electromagnetic waves. The specific principle is based on the theory of the equivalent refractive index of the medium. Using parameters such as length, width, and height, the nano-antennas 120 are arranged with different duty ratios to change the corresponding equivalent refractive index to achieve different transmission phases and achieve the purpose of adjusting the phase of the outgoing light.

Based on the principle of this transmission phase, by carefully designing the parameters such as the shape and geometric dimensions of the nano-antenna 120 in the metasurface optical element 100, different structures with the highest and equal transmittance and phase distribution between 0 and 2π can be selected. They are arranged at the same center-to-center distance to realize the metasurface optical element 100 with both collimation and beam splitting functions. In some embodiments, among the plurality of nanoantennas 120 disposed on the surface of the substrate 110 of the metasurface optical element 100, at least two nanoantennas 120 have different sizes, so that the nanoantennas 120 can have different transmission phases, thereby enabling Phase modulation is performed on the light beam incident on the nano-antenna 120 . Of course, as the number of nano-antennas with different sizes increases, the effect of achieving both collimation and diffraction functions is better.

As shown in Figures 1 and 4, multiple nanoantennas 120 can be distributed on the upper surface of the substrate 110 in the form of an array, and when multiple nanoantennas 120 are laid out on the upper surface of the substrate 110, the The transmission phase is arranged, and the transmission phase of each nano-antenna 120 can be the superposition of the collimation phase and the diffraction phase. Taking a nano-antenna 120 as an example: the collimation phase can be when the nano-antenna 120 realizes the collimation function alone In the same way, the diffraction phase can also be the diffraction phase when the nano-antenna 120 realizes the diffraction function alone, then, the transmission phase of the nano-antenna 120 can be the superposition of the alignment phase and the diffraction phase, thus obtaining If the transmission phase of the nano-antenna 120 is obtained, similarly, the respective transmission phases of the remaining nano-antennas 120 can be obtained, so that each nano-antenna 120 can be arranged on the surface of the substrate 110 according to the corresponding transmission phase of each nano-antenna 120, and more The transmission phase distribution of each nano-antenna 120 is between 0 and 2π, and the distance between the centers of two adjacent nano-antennas 120 is the same. In this way, the formed metasurface optical element 100 can have collimation and diffraction functions at the same time, that is, collimation The integration of the collimation element and the diffraction element effectively reduces the space occupied by the existing collimation and diffraction elements as two independent optical elements. At the same time, since the alignment assembly of the collimation element and the diffraction element is canceled, the The resulting alignment error.

It should be noted that, considering the difficulty of design and process manufacturing, after the superposition phases of multiple nano-antennas 120 obtained by superimposing the collimation phase and the diffraction phase (that is, the simulated phase in the subsequent method embodiment), it can be obtained according to the metasurface The number of nano-antennas 120 required by the optical element 100, the analog phase is discretized to obtain a discrete phase, the discrete phase is the same as the number of nano-antennas 120 required by the metasurface optical element 100, and each nano-antenna 120 is matched accordingly It has a discrete phase, and the discrete phase is the transmission phase of the nano-antenna 120. By arranging the nano-antennas 120 with the transmission phase, the metasurface optical element 100 with collimation and diffraction functions can be obtained.

After the simulated phase is obtained by the above superposition, in order to further improve the effect of the metasurface optical element when the collimation and diffraction functions are simultaneously realized, it is also possible to slightly fine-tune the multiple nano-antennas 120 that have obtained the simulated phase to optimize the simulation results, thereby optimizing the superposition phase. The specific optimization method may be performed through an algorithm, which is not limited in this application.

In addition, since the metasurface optical element 100 of the present application is based on a metasurface structure when realizing collimation and diffraction functions, it can also effectively improve diffraction efficiency and uniformity. At the same time, in terms of manufacturing process, the metasurface optical element 100 can be mass-produced by semiconductor chip technology, for example, templates can be made by photolithography such as electron beam or deep ultraviolet exposure, and then samples can be manufactured by dry etching and other processes.

In actual use, the substrate 110 can protect the metasurface optical element 100 and isolate dust, etc., without adding an additional cover, so the overall diffraction efficiency of the module will not be reduced. In addition, the surface on the other side of the transparent substrate 110 is a plane without optical elements, so other optical elements or film layers can be arranged on it to expand the performance of the metasurface optical element 100, for example, it can be coated on the other side of the glass substrate 110. Anti-reflective film or wear-resistant layer, etc. An ITO layer may also be plated on the surface of the transparent substrate 110 for protection.

Optionally, the orthographic projection of the nano-antenna 120 on the substrate 110 can be set as a C4 rotationally symmetric figure, that is, the orthographic projection rotated 90 degrees around the center point can coincide with the original figure.

In some embodiments, as shown in FIG. 2 and FIG. 5 , the nano-antenna 120 can be a cuboid structure, and its orthographic projection on the substrate 110 is a square. In this way, the side length L of the square is equal, so that the length of the square on two adjacent sides is The isotropy presented in the direction, the side length L of the square can be 50nm to 500nm.

In some implementations, as shown in FIG. 3 and FIG. 4 , the nanoantenna 120 can be a cylindrical structure, and its orthographic projection on the substrate 110 is a circle. In this way, using the property that the diameters of the circles are equal, the circles in each It is isotropic in the diameter direction, and the diameter of the circle can be 50nm to 500nm.

In some implementations, as shown in FIG. 6 , the nanoantenna 120 may include two parts, one part is a first antenna 121, and the other part is a second antenna 122. The orthographic projection of the first antenna 121 on the substrate is circular, and the second part is a circular antenna. The orthographic projection of the two antennas 122 on the substrate is a square, wherein the first antenna 121 and the second antenna 122 may be randomly distributed on the substrate 110 . The diameter of the circle may be 50nm to 500nm, and the side length L of the square may be 50nm to 500nm.

In the above-mentioned embodiments, since the nano-antennas 120 have a certain degree of isotropy, the metasurface optical element 100 of the present application can be made insensitive to the polarization of the incident light, which can solve the problem caused by the different polarization of the light source 10 caused by the traditional diffractive optical element. The problem of uneven beam splitting.

In some embodiments, the heights of two adjacent nano-antennas 120 are the same, and the pattern sizes of at least two nano-antennas 120 on the plane parallel to the substrate 110 are different. In this way, on the premise that a plurality of nano-columns have the same height, through Different sizes of the at least two nanocolumns form differences, so as to have different transmission phases, so as to realize the modulation of the incident light beam.

In some embodiments, the height of the nanoantenna (direction perpendicular to the substrate 110 ) is greater than 300 nm, for example, between 300 nm and 1000 nm.

In some embodiments, the center-to-center distance between two adjacent nanoantennas 120 is less than 600 nm. In this way, the performance of the metasurface optical element 100 can be effectively improved.

In some embodiments, the shapes of two adjacent nanoantennas 120 disposed on the substrate 110 may be different.

In some embodiments, the number of nano-antennas 120 with different sizes disposed on the substrate 110 is greater than or equal to 4, so that the obtained metasurface optical element 100 is at least equivalent to a fourth-order diffractive optical element, and has a higher diffraction efficiency. Of course, in other embodiments, the number of nano-antennas 120 with different sizes arranged on the substrate 110 may be greater than or equal to 8, so that the obtained metasurface optical element 100 is at least equivalent to an 8th-order diffractive optical element, have higher diffraction efficiency.

In some embodiments, the substrate 110 can be a transparent substrate 110 , so that the formed metasurface optical element 100 can have good light transmission. In some implementations, the material of the transparent substrate 110 may be quartz, glass or silicon oxide film.

In some embodiments, the material of the nano-antenna 120 may be silicon, titanium oxide, aluminum oxide or silicon nitride. In some implementations, when the nano-antenna 120 is made of silicon, it can be monocrystalline silicon, amorphous silicon, or polycrystalline silicon.

In some embodiments, nanoantenna 120 may be a sub-wavelength optical antenna.

In some embodiments, firstly, simulations are performed on nano-antenna pillars of different sizes and heights to obtain their transmittance and transmission phase distribution diagrams. When selecting the nano-antenna 120 , the selection is mainly based on the two requirements that the transmittance of the same polarization is the highest and equal, and the transmission phase is evenly distributed among 0-2π.

Another aspect of the present application provides a method for designing a metasurface optical element 100, as shown in FIG. 8 , the method may include:

S010: Obtain collimation phases corresponding to each of the plurality of first simulated nano-antennas disposed on the substrate of the simulated collimation element.

When designing the metasurface optical element 100, it can first be obtained that when the metasurface optical element 100 is used to simulate the collimation function separately (hereinafter referred to as the simulated collimation element for ease of distinction), a plurality of first simulated nanoantennas in the simulation The phase distribution on the substrate of the collimation element, that is, the collimation phase of each first simulated nano-antenna that can realize the collimation function.

S020: Obtain the diffraction phases corresponding to each of the multiple second simulated nanoantennas arranged on the base of the simulated diffraction element, wherein the multiple first simulated nanoantennas are in one-to-one correspondence with the multiple second simulated nanoantennas.

When designing the metasurface optical element 100, it can also be obtained that when the metasurface optical element 100 is used to simulate the diffraction function separately (for ease of distinction, hereinafter referred to as the simulated diffraction element), a plurality of second simulated antennas simulate collimation The phase distribution on the base of the element, that is, the diffraction phase of each second simulated nano-antenna capable of realizing the diffraction function. When executing S010 and S020, in different implementation manners, they may be performed in different orders.

Since both the simulated collimation element and the simulated diffraction element are structures presented by the metasurface optical element 100 when a single collimation or diffraction function is simulated, therefore, the arrangement of multiple first simulated nano-antennas of the simulated collimation element on the substrate There is a one-to-one correspondence with the layout of multiple second simulated nanoantennas of simulated diffraction elements on the substrate, that is, each first simulated nanoantenna is located on the substrate of a corresponding second simulated nanoantenna. The positions are the same, and the numbers of the first simulated nano-antennas and the second simulated nano-antennas are also the same.

S030: Superimpose the collimation phases of the multiple first simulated nanoantennas with the diffraction phases of the respective corresponding second simulated nanoantennas to obtain multiple simulated phases.

After the respective collimation phases of the multiple first simulated nanoantennas on the simulated collimation element and the respective diffraction phases of the multiple second simulated nanoantennas on the simulated diffraction element are obtained through S010 and S020, the multiple first simulated nanoantennas can be The collimated phases of the simulated nano-antennas and the corresponding diffraction phases of the second simulated nano-antennas are superimposed according to the corresponding relationship, so as to obtain multiple simulated phases.

After the simulated phase is obtained by the above superposition, in order to further improve the effect of the metasurface optical element 100 when the collimation and diffraction functions are simultaneously realized, it is also possible to slightly fine-tune the multiple nanoantennas 120 that have obtained the simulated phase to optimize the simulation results, thereby optimizing superimposed phase. The specific optimization method may be performed through an algorithm, which is not limited in this application.

S040: Discrete multiple analog phases to obtain multiple discrete phases, wherein the number of multiple nano-antennas on the substrate of the metasurface optical element corresponds to the number of multiple discrete phases, and the transmission phases of multiple nano-antennas correspond to their respective The corresponding discrete phases are the same.

According to the number of nano-antennas 120 required by the metasurface optical element 100, the simulated phase is discretized to obtain a discrete phase, the discrete phase is the same as the number of nano-antennas 120 required by the meta-surface optical element 100, and each nano-antenna 120 is The corresponding matching has a discrete phase, and the discrete phase is the transmission phase of the nano-antenna 120. By arranging the nano-antennas 120 with the transmission phase, a metasurface optical element with collimation and diffraction functions can be obtained. In this way, the arranged metasurface optical element 100 can realize the functions of collimation and diffraction at the same time, that is, integrate collimation and diffraction. It should be noted that when realizing the integration of collimation and diffraction functions, the optical transfer function can be used. When several imaging systems are connected in series, the optical transfer function of the combined system is the product of the optical transfer functions of the subsystems, that is, amplitude multiplication and phase superposition That's it.

In addition, since the metasurface optical element 100 of the present application is based on a metasurface structure when realizing collimation and diffraction functions, it can also effectively improve diffraction efficiency and uniformity. At the same time, in terms of manufacturing process, the metasurface optical element 100 can be mass-produced by semiconductor chip technology, for example, templates can be made by photolithography such as electron beam or deep ultraviolet exposure, and then samples can be manufactured by dry etching and other processes. Wherein the metasurface optical element 100, the simulated collimation element and the simulated diffraction element are all manufactured based on the metasurface process, therefore, the respective manufacturing processes of the three are the same, and the manufacturing cost is the same, that is, the metasurface optical element 100 of the present application is integrated with collimation and At the same time as the diffraction function, it can also avoid increasing costs.

In some implementations, when the collimation phases corresponding to the plurality of first simulated nano-antennas set on the base of the simulated collimation element are obtained through S010, the simulated focal length of the simulated collimation element and the simulated focal length of two adjacent first simulated nano-antennas can be obtained first. The distance between the centers of the nano-antennas, wherein the analog focal length can be preset, the center-to-center distances of two adjacent first simulated nano-antennas are the same, and the center-to-center distances of two adjacent first simulated nano-antennas can be based on the preset distance of the first simulated nano-antenna Set the working wavelength and the field angle to be realized. Then, according to the simulated focal length, the lens focusing equation and the distance between the centers of two adjacent first simulated nano-antennas, the respective collimation phases corresponding to each of the multiple first simulated nano-antennas are obtained. It should be noted that the center-to-center distance between two adjacent nano-antennas of the metasurface optical element is equal to the center-to-center distance between two adjacent first simulated nano-antennas.

In some embodiments, when the diffraction phases corresponding to the multiple second simulated nano-antennas provided on the base of the simulated diffraction element are obtained through S020, the simulated angle of view of the simulated diffraction element can be obtained first, and the simulated angle of view can be obtained according to requirements. reasonable assumptions. Then, the corresponding diffraction phases of the multiple second simulated nano-antennas are obtained according to the simulated viewing angle and a preset algorithm. In some implementation manners, the preset algorithm may be a Fourier iterative algorithm, a genetic algorithm, or the like.

In some embodiments, before S010, the material of the metasurface optical element 100 can be determined according to the required working wavelength, including the material of the substrate 110 and the material of the nano-antenna 120, and the nano-antenna 120 can be selected from a material with a high refractive index. material. The distance between the centers of two adjacent nano-antennas 120 on the substrate 110 of the metasurface optical element 100 can also be determined according to the working wavelength and the viewing angle, for example, set to be less than 600 nm. After determining the distance between the centers of the nano-antenna 120, use electromagnetic simulation software to simulate the nano-antenna 120 whose orthographic shape is a circle, a square or a square with rounded corners, etc., which have a certain degree of isotropic C4 rotational symmetry. , by optimizing the size and height of the nanostructures, multiple nanocolumns with the same height but different shapes and/or sizes are selected. The quantity can be 2, 4, 8 etc. In some embodiments, firstly, simulate nano-antenna pillars of different sizes and heights to obtain their transmittance and transmission phase distribution diagrams. When selecting the nano-antenna 120 , the selection is mainly based on the two requirements that the same polarization transmittance is the highest and equal, and the transmission phase is evenly distributed among 0-2π.

Some embodiments of the present application provide a structured light projection module. As shown in FIG. On the light-incident side of 100, the light beam emitted by the light source 10 enters the nano-antenna 120 of the metasurface optical element 100, and through the phase modulation of the nano-antenna 120, the incident light beam is collimated and diffracted before exiting the target area. When the light source 10 is a vertical cavity surface emitting laser, it can correspondingly project a speckle image 20 on the target area. Since the collimation and diffraction are integrated through the metasurface optical element 100, the overall volume of the structured light projection module is relatively small. In some embodiments, the light source 10 can also be an LD laser that generates a point source, the light source 10 is light of arbitrary polarization, and the wavelength is from the ultraviolet band to the terahertz band.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Industrial Applicability

In addition, it can be understood that the metasurface optical element, design method, and structured light projection module of the present application are reproducible and can be used in various industrial applications. For example, the metasurface optical element, design method, and structured light projection module of the present application can be used in the field of optical technology.

Claims

A metasurface optical element, characterized in that it includes a base, a plurality of nano-antennas arranged on the base through transmission phase modulation of incident light beams, at least two of the nano-antennas have different sizes and a plurality of the nano-antennas The array is distributed on one side of the substrate, the distance between the centers of two adjacent nano-antennas is the same, and the transmission phase of each nano-antenna is the superposition of the collimation phase and the diffraction phase.
The metasurface optical element according to claim 1, wherein the orthographic projection of the nano-antenna on the substrate is a C4 rotationally symmetric figure.
The metasurface optical element according to claim 2, wherein the orthographic projection of the nano-antenna is a circle; or, the orthographic projection of the nano-antenna is a square; or, a plurality of the nano-antennas include a first For the antenna and the second antenna, the orthographic projection of the first antenna on the base is a circle, and the orthographic projection of the second antenna on the base is a square.
The metasurface optical element according to claim 3, wherein when the nano-antenna is a square, the side length of the square is 50nm to 500nm; and/or, when the nano-antenna is circular, The diameter of the circle is 50nm to 500nm.
The metasurface optical element according to any one of claims 1 to 4, wherein the center-to-center distance between two adjacent nano-antennas is 200 nm to 600 nm; the heights of multiple nano-antennas are all greater than 300 nm.
The metasurface optical element according to any one of claims 1 to 5, wherein the heights of the plurality of nano-antennas are the same; the number of the nano-antennas with different sizes is greater than or equal to 4.
The metasurface optical element according to any one of claims 1 to 6, wherein the substrate is a transparent substrate, and the material of the transparent substrate is quartz, glass or silicon oxide film.
The metasurface optical element according to any one of claims 1 to 7, wherein the nano-antenna is made of silicon, titanium oxide, aluminum oxide or silicon nitride.
A method for designing a metasurface optical element, characterized in that the method comprises:

Using the simulated collimation element presented by the metasurface optical element when realizing a single collimation function, obtaining the corresponding collimation phases of the plurality of first simulated nano-antennas arranged on the substrate;

Using the simulated diffraction element presented by the metasurface optical element when realizing a single diffraction function, the respective diffraction phases corresponding to the multiple second simulated nano-antennas set on the substrate are obtained, wherein the multiple first simulated nano-antennas are the same as the The number of multiple second simulated nano-antennas corresponds to each other;

superimposing the collimated phases of the first simulated nanoantennas with the diffraction phases of the corresponding second simulated nanoantennas to obtain multiple simulated phases;

Discrete the multiple simulated phases to obtain multiple discrete phases, wherein the number of multiple nano-antennas on the base of the metasurface optical element corresponds to the number of the multiple discrete phases one-to-one, and the multiple nano-antennas The transmission phases of the antennas are the same as the respective discrete phases.
The method for designing a metasurface optical element according to claim 9, wherein the alignment phases of a plurality of the first simulated nanoantennas are superimposed with the diffraction phases of the respective corresponding second simulated nanoantennas to obtain the obtained After the plurality of simulated phases, the plurality of first simulated nanoantennas and the plurality of second simulated nanoantennas are fine-tuned to optimize the simulation results, thereby optimizing the superposition phase.
The metasurface optical element design method as claimed in claim 9 or 10, wherein the collimation phase corresponding to each of the plurality of first simulated nano-antennas provided on the acquisition substrate comprises:

Acquiring the simulated focal length of the simulated collimation element and the center-to-center distance of two adjacent first simulated nano-antennas;

The corresponding collimation phases of the plurality of first simulated nano-antennas are obtained according to the simulated focal length, the lens focusing equation and the center-to-center distance of the first simulated nano-antennas.
The method for designing a metasurface optical element according to claim 11, wherein the distance between the centers of two adjacent first simulated nanoantennas is based on the preset working wavelength and the field of view to be realized of the first simulated nanoantennas angle is fixed.
The metasurface optical element design method according to any one of claims 9 to 12, wherein said acquisition of the corresponding diffraction phases of a plurality of second simulated nano-antennas arranged on the substrate comprises:

Acquiring a simulated viewing angle of the simulated diffraction element;

The respective diffraction phases corresponding to the plurality of second simulated nano-antennas are obtained according to the simulated viewing angle and a preset algorithm.
The method for designing a metasurface optical element according to any one of claims 9 to 13, wherein, before acquiring the corresponding collimation phases of a plurality of first simulated nanoantennas arranged on the substrate, according to the required The working wavelength is used to determine the material of the metasurface optical element.
A structured light projection module, characterized in that it includes a light source and the metasurface optical element according to any one of claims 1 to 8, the light source is located on the light incident side of the metasurface optical element, and the metasurface optical element The surface optical element is used to collimate and diffract the light beam emitted by the light source.