WO2024239233A1 - Lens assembly and preparation method therefor, and lens module and electronic device - Google Patents

Abstract

A lens assembly (10) and a preparation method therefor, and a lens module and an electronic device. The lens assembly (10) comprises a substrate (1), an imaging structure (2) and a coating structure (3), wherein the imaging structure (2) and the coating structure (3) are respectively disposed on two sides of the substrate (1) in the thickness direction. The imaging structure (2) comprises a plurality of micro-structures (21), which are disposed in an array; and the coating structure (3) comprises a plurality of coatings (31), which are cyclically disposed in the thickness direction of the substrate (1) in a stacked manner. At least two coatings (31) which are made of different materials are comprised in each stacking cycle. The plurality of coatings (31) are arranged with a cycle greater than or equal to 2. The lens assembly (10) is a planar lens, which combines a metasurface with a multi-layer coating technique, such that the working efficiency of the lens assembly can be improved, stray light in a non-working waveband can be suppressed, and the imaging quality can be improved. In addition, the lens assembly (10) further has the advantages of being light and thin in terms of structure and being convenient to assemble.

Description

Lens assembly and preparation method thereof, lens module, and electronic device Technical Field

The present application relates to the field of optical technology, and in particular to a lens assembly and a preparation method thereof, a lens module, and an electronic device.

Background Art

Traditional lenses mainly use the principle of refraction to refract incident light, causing it to converge or diverge, thereby achieving functions such as imaging or energy collection. Unlike traditional lenses, planar lenses mainly use the diffraction effect of micro-nano structures to converge or diverge light. Compared with traditional refractive lenses, planar lenses have attracted widespread attention due to their unique optical properties and potential application value.

At present, planar lenses cannot take into account both bandwidth performance and ease of use, and their imaging performance cannot meet usage requirements.

Summary of the invention

The present application provides a lens assembly and a preparation method thereof, a lens module, and an electronic device. The lens assembly can meet the imaging performance requirements while having good performance in terms of bandwidth, thereby improving the imaging performance of the lens assembly.

In the first aspect, the present application provides a lens assembly, which can be used in the field of imaging, such as thermal infrared imaging, near-infrared imaging and the like. The lens assembly includes a substrate, an imaging structure and a film layer structure. The imaging structure and the film layer structure are respectively arranged on both sides of the thickness direction of the substrate, and the substrate provides support for the imaging structure and the film layer structure. Among them, the imaging structure includes a plurality of microstructures arranged in an array, and it can be considered that the imaging structure is a metasurface. The distance between the centers of any two microstructures is less than half of the target wavelength to suppress the high-order diffraction of the target wave, reduce the scattering of the target wave, and thus reduce the impact on the imaging quality. The target wave here can be considered as the working band of the lens assembly, which can be light or electromagnetic wave. When the target wave passes through the imaging structure, the plurality of microstructures can phase modulate the target wave, so that the phase of the target wave changes, thereby generating refraction to meet the imaging requirements. The film layer structure includes a plurality of film layers, and the plurality of film layers are periodically stacked along the thickness direction of the substrate. At least two film layers of different materials are included in each stacking period, and the at least two film layers have a certain stacking order, and the stacking order of the film layers in each period is the same. For the film layer structure, the arrangement period of multiple film layers is greater than or equal to 2. Based on the multi-layer coating technology, the target wave forms multi-layer interference in the working band, changes the bandwidth to achieve filtering, and can also enhance the transmittance of light in the working band. This film layer structure makes the planar lens more efficient in the working band, while suppressing the transmittance of the non-working band, so that the imaging performance of the lens is better.

The above lens assembly can be considered as a plane lens. The metasurface can realize the imaging function, and the multi-layer technology can realize the function of suppressing stray light. In application, according to different application scenarios, different film layers can be selected to improve the bandwidth performance of the lens assembly and broaden the application range of the lens assembly. In addition, the lens assembly combines the metasurface and multi-layer technology, which simplifies the structure of the lens assembly and facilitates the assembly and use of the lens assembly.

Specifically, the microstructure of the imaging structure may be implemented in a variety of ways. The microstructure may be a columnar body, and the distance between the centers of any two adjacent columns is less than half of the target wavelength. Alternatively, the microstructure may be a ring-shaped body, and multiple rings are distributed in concentric circles, and the distance between the center lines of any two adjacent rings is less than half of the target wavelength. The high-order diffraction of the target wave can be suppressed to optimize the imaging quality.

In one possible implementation, the lens assembly further includes a dielectric structure, which is disposed on a side of the imaging structure facing away from the substrate. The dielectric structure covers the surface of the imaging structure facing away from the substrate and fills the gaps between the plurality of microstructures. The refractive index of the dielectric structure is different from that of the microstructure, and can phase modulate the target wave when light or electromagnetic waves pass through it. Thereby achieving the expected imaging effect. Here, the medium structure may be a gas such as air, or a solid structure. Among them, the solid structure may specifically include a liquid or a solid. When the medium structure is a solid structure, it can be considered that the medium structure is wrapped around the surface of the microstructure, and the medium structure can play a certain protective role on the microstructure. In order to enhance the anti-reflection effect of the lens assembly, an anti-reflection layer can be provided on the side of the medium structure away from the substrate.

The substrate may be made of the same material as the microstructure of the imaging structure, and in this case, the substrate and the microstructure may have an integrated structure. Alternatively, the substrate may be made of the same material as the medium structure.

In the specific implementation, in order to make the lens assembly have good transmittance, the substrate, microstructure and film layer can all be selected from materials with low loss in the working band. Specifically, the absorption rate of the target wave by the low-loss material can be less than 40%, for example, the absorption rate of the target wave by the low-loss material can be 15-20%.

The lens assembly provided in the embodiment of the present application may be applied in various occasions, corresponding to different working bands. When the target wave is visible light or near infrared light, the material of the microstructure may be silicon nitride (SiN or Si ₃ N ₄ ) or titanium dioxide (TiO ₂ ), and the material of the film layer in the film layer structure may be at least two of silicon dioxide (SiO ₂ ), silicon nitride, titanium dioxide, tantalic oxide (Ta ₂ O ₅ ), magnesium fluoride (MgF ₂ ), barium fluoride (BaF ₂ ), aluminum oxide (Al ₂ O ₃ ), calcium chloride (CaCl ₂ ), sodium chloride (NaCl), potassium chloride (KCl), and potassium bromide (KBr). When the target wave is thermal infrared light, the material of the microstructure can be selected from one of germanium (Ge), silicon (Si), selenium sulfide (SeS), and zinc sulfide (ZnS), and the material of the film layer in the film layer structure can be selected from at least two of germanium, silicon, zinc selenide (ZnSe), zinc sulfide, gallium arsenide (GaAs), cadmium telluride (CdTe), barium fluoride, sodium chloride, potassium chloride, and potassium bromide.

In a second aspect, the present application provides a lens module, which includes a plurality of lens assemblies provided in the first aspect. The plurality of lens assemblies can be arranged in sequence along the thickness direction of the substrate, and the plurality of lens assemblies can be considered to be stacked. During the imaging process, the stacked combination of the plurality of lens assemblies can eliminate aberrations and optimize the imaging effect. Alternatively, the plurality of lens assemblies can also be arranged in sequence along the thickness direction perpendicular to the substrate, and the plurality of lens assemblies can be considered to be tiled, and during the imaging process, the tiled combination of the plurality of lens assemblies can achieve light field imaging.

In a third aspect, the present application provides an electronic device, which includes but is not limited to a near-infrared camera, a thermal infrared camera, a laser radar, a depth (time of flight, TOF) camera, etc. The electronic device includes a housing, an image sensor, and a lens unit, and the lens unit is the lens assembly provided in the first aspect or the lens module provided in the second aspect. The housing has an opening, the image sensor is arranged in the housing, and the lens unit is arranged on the side of the image sensor facing the opening. Specifically, the lens unit can be arranged at the opening, or it can be arranged between the image sensor and the opening. When the lens unit is arranged between the image sensor and the opening, the electronic device can be provided with a lens for light transmission at the opening of the housing. The lens unit here is used to focus the external light input into the opening to the image sensor.

In a fourth aspect, an embodiment of the present application provides a method for preparing a lens assembly, which can be used to prepare the lens assembly provided in the first aspect. Taking the example that the substrate and the microstructure of the imaging structure have an integrated structure, the preparation method may include the following steps:

Providing a substrate, the substrate having a first surface and a second surface, the first surface and the second surface are opposite to each other along a thickness direction of the substrate;

A plurality of film layers are arranged on the second surface of the substrate, and the plurality of film layers are periodically stacked along the thickness direction of the substrate; the stacking period of the plurality of film layers is greater than or equal to 2, and each stacking period includes at least two film layers of different materials;

A plurality of microstructures are formed on the first surface of the substrate, wherein the distance between the centers of any two microstructures is less than the target wavelength. half.

When the lens assembly is also provided with a dielectric structure of a solid structure, the dielectric structure can cover the surface of the microstructure away from the substrate and fill the gaps between the multiple microstructures. In this case, multiple microstructures and the dielectric structure can be firstly made on the first surface of the substrate, and then the film layer structure can be prepared on the second surface of the substrate after the substrate is inverted.

Specifically, forming a plurality of microstructures on the first surface of the substrate may include the following steps:

forming a plurality of first structures on a first surface of the substrate;

etching the substrate between any two first structures;

The first structure is removed.

There may be multiple implementations for forming a plurality of first structures on the first surface of the substrate.

When a plurality of first structures are formed by using a photolithography process, forming a plurality of first structures on the first surface of the substrate may include the following steps:

Coating a photoresist on a first surface of the substrate and curing the photoresist to form a sacrificial layer;

The sacrificial layer is irradiated by using a mask photolithography exposure process, so that the sacrificial layer forms a plurality of irradiated first structures and a second structure that is not irradiated, and the second structure is filled between the plurality of first structures;

The second structure is removed by developing technology.

When a plurality of first structures are formed by adopting a nanoimprint process, forming a plurality of first structures on a first surface of a substrate may include the following steps:

Coating a photoresist on a first surface of the substrate and forming a sacrificial layer;

The sacrificial layer is printed with a template and cured to divide the sacrificial layer into a plurality of first structures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a lens assembly provided in an embodiment of the present application;

FIG2 is a schematic structural diagram of an imaging structure and a substrate in a lens assembly provided in an embodiment of the present application;

FIG3a is a schematic diagram of a microstructure in a lens assembly provided in an embodiment of the present application;

FIG3 b is a schematic structural diagram of a microstructure in a lens assembly provided in an embodiment of the present application;

FIG3c is a schematic diagram of a microstructure in a lens assembly provided in an embodiment of the present application;

FIG3 d is a schematic structural diagram of a microstructure in a lens assembly provided in an embodiment of the present application;

FIG3e is a schematic diagram of a microstructure in a lens assembly provided in an embodiment of the present application;

FIG3f is a schematic structural diagram of a microstructure in a lens assembly provided in an embodiment of the present application;

FIG4a is a schematic structural diagram of an imaging structure and a substrate in a lens assembly provided in an embodiment of the present application;

FIG4b is an enlarged view of the R portion in FIG4a;

FIG5a is a schematic structural diagram of an imaging structure and a substrate in a lens assembly provided in an embodiment of the present application;

FIG5b is a schematic structural diagram of an imaging structure and a substrate in a lens assembly provided in an embodiment of the present application;

FIG6 is a schematic structural diagram of an imaging structure and a substrate in a lens assembly provided in an embodiment of the present application;

FIG7 is a schematic cross-sectional view of a film structure in a lens assembly provided in an embodiment of the present application;

FIG8a is a schematic cross-sectional structure diagram of a lens assembly provided in an embodiment of the present application;

FIG8b is a schematic cross-sectional structure diagram of a lens assembly provided in an embodiment of the present application;

FIG8c is a schematic cross-sectional structure diagram of a lens assembly provided in an embodiment of the present application;

FIG9 is a schematic cross-sectional structure diagram of a lens assembly provided in an embodiment of the present application;

FIG10 is a schematic diagram of a process for preparing a lens assembly according to an embodiment of the present application;

FIG11a is a schematic structural diagram of a substrate provided in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG. 11 b is a schematic structural diagram of providing a film layer structure on a substrate during a method for preparing a lens assembly provided in an embodiment of the present application;

FIG. 11c is a schematic structural diagram of providing an imaging structure on a substrate during a method for preparing a lens assembly provided in an embodiment of the present application;

FIG12 is a schematic diagram of a process for forming a microstructure in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG13a is a schematic cross-sectional structure diagram of a first structure formed on a substrate in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG13 b is a schematic cross-sectional view of a microstructure formed on a substrate in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG14 is a schematic diagram of a process for forming a first structure in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG15a is a schematic cross-sectional structure diagram of a sacrificial layer formed on a substrate in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG15 b is a schematic cross-sectional view of a method for preparing a lens assembly provided in an embodiment of the present application, in which a sacrificial layer is processed to form a first structure;

FIG16 is a schematic diagram of a process for forming a first structure in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG17a is a schematic cross-sectional view of a first structure formed on a substrate in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG17b is a schematic cross-sectional view of a first structure formed on a substrate in a method for preparing a lens assembly provided in an embodiment of the present application;

FIG18 is a schematic diagram of a process for preparing a lens assembly according to an embodiment of the present application;

FIG19a is a schematic cross-sectional structure diagram of a lens module provided in an embodiment of the present application;

FIG19b is a top view of a lens module provided in an embodiment of the present application;

FIG19c is a schematic diagram of a cross-sectional structure of a lens module provided in an embodiment of the present application;

FIG20a is a schematic diagram of an imaging principle of an electronic device provided in an embodiment of the present application;

FIG20 b is a schematic diagram of an imaging principle of an electronic device provided in an embodiment of the present application;

FIG21a is a schematic cross-sectional structure diagram of an electronic device provided in an embodiment of the present application;

FIG21 b is a schematic cross-sectional structure diagram of an electronic device provided in an embodiment of the present application;

Figure 21c is a schematic diagram of the cross-sectional structure of an electronic device provided in an embodiment of the present application.

DETAILED DESCRIPTION

In the field of optics, planar lenses have attracted widespread attention due to their lightweight structure and strong applicability. Specifically, meta-lens is a representative technology among planar lenses. Meta-lens is a planar lens based on meta-materials. It converges or diverges light through the diffraction effect of micro-nano structures on light. It has the advantages of being lighter, thinner, having higher design freedom, and its processing technology is compatible with semiconductor processes. However, the broadband performance of meta-lens is poor, which affects the imaging performance and limits the widespread application of this technology.

To this end, the embodiments of the present application provide a lens assembly and a preparation method thereof, a lens module, and an electronic device, wherein the lens assembly has good performance in bandwidth while meeting the imaging performance requirements, has better imaging performance, and is more applicable.

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

The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "a", "an", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context.

References to "one embodiment" or "some embodiments" etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear at different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

As shown in FIG1 , an embodiment of the present application provides a lens assembly 10, which can be used in the optical field, specifically including but not limited to imaging, detection and monitoring and other occasions. Specifically, the lens assembly 10 includes a substrate 1, an imaging structure 2 and a film layer structure 3. Along the thickness direction of the substrate 1, the imaging structure 2 and the film layer structure 3 are respectively arranged on both sides of the substrate 1. The imaging structure 2 includes a plurality of microstructures 21, and the plurality of microstructures 21 are arrayed on the surface of the back film layer structure 3 of the substrate 1. Here, the microstructures 21 can be arrayed according to a certain regularity or irregularly. The microstructure 21 is a sub-wavelength unit, and the imaging structure 2 can be considered as a metasurface. The film layer structure 3 includes a plurality of film layers 31, and the plurality of film layers 31 are periodically stacked along the thickness direction of the substrate 1. The filtering unit 3 is formed by a plurality of periodically stacked film layers 31, and the film layer structure 3 can be regarded as a structure for filtering using multi-film layer technology. The principle of multilayer film technology is to use the interference of light or electromagnetic waves between multilayer films to form a high transmission or high reflection function for a specific band. Specifically, when the target wave passes through the multi-film layer structure, the multi-film layer can make the target wave form multi-layer interference in the working band, change the bandwidth to achieve filtering. In addition, the multi-film layer structure can also enhance the transmittance of the light of the target wave.

In the lens assembly 10 provided in the embodiment of the present application, the imaging structure 2 can suppress the high-order diffraction of the target wave through multiple microstructures 21, reduce the heat dissipation of the target wave as much as possible, and reduce the influence of the scattering of the target wave on the imaging quality. The film layer structure 3 can make the target wave form multi-layer interference in the working band through multiple film layers 31, change the bandwidth to achieve filtering, and enhance the transmittance of the light of the target wave. For the film layer structure 3, the target wave can be incident light or transmitted light.

Among them, metasurfaces can also be called metasurfaces. Metasurfaces are structures formed by arrays of metamaterials. The broad definition of metamaterials refers to a complex of artificially designed unit structures with physical properties that traditional natural materials do not have. The physical properties of metamaterials are determined by the structure, arrangement and material of subwavelength units. Among them, subwavelength units refer to structures with radial dimensions much smaller than the target wavelength. Metasurfaces are a two-dimensional form of metamaterials, that is, surface structures composed of structures with subwavelength units. Based on the generalized laws of reflection and refraction, the transmission rules of light when passing through a metasurface are different from the transmission rules followed when passing through the interface of ordinary optical devices. Traditional optical elements rely on the phase that gradually accumulates during the propagation of light, and by introducing a sudden phase change within the wavelength range, the abnormal reflection and refraction phenomenon of linear phase change along the interface can be observed.

In order to make the lens assembly 10 have good light transmittance, the substrate 1, microstructure 21 and film layer 31 in the embodiment of the present application can be made of materials with low loss in the working band. The low loss here means that the material has very low absorption of the working wave in the working band, and specifically, it can be considered that the absorption rate of the material to the working wave is less than 40%. For example, the absorption rate of the material to the working wave is 15-20%.

Specifically, as shown in Figure 2, the microstructure 21 in the imaging structure 2 can be a columnar body. In an embodiment of the present application, the radial dimension d of the microstructure 21 is in the micrometer level or nanometer level. Among them, the radial dimension d refers to the dimension perpendicular to the thickness direction of the substrate 1. Multiple microstructures 21 can be arranged regularly or irregularly, and the distance D between the centers of any two microstructures 21 is less than half of the target wavelength. The target wave here refers to the light or electromagnetic wave allowed to pass through when the lens assembly 10 is working, that is, the working band of the lens assembly 10. When the target wave passes through the imaging structure 2, the multiple microstructures 21 can suppress the high-order diffraction of the target wave, reduce the scattering of the target wave, and avoid affecting the imaging quality as much as possible. In specific applications, the shape and arrangement of the microstructure 21 can be designed to achieve the desired imaging effect.

Among them, the shape of the microstructure 21 is not limited, and it can be any geometric form of a subwavelength unit. The microstructure 21 can be a regular geometric form or an irregular geometric form. Exemplarily, the microstructure 21 is one of a columnar, a quasi-columnar, a truncated cone, a quasi-truncated cone, a cone, a quasi-conical, a needle, and a quasi-needle. Exemplarily, the microstructure 21 may be a regular structure, such as the cube shown in FIG. 3a, the hexagonal prism shown in FIG. 3b, the cylindrical shape shown in FIG. 3c, and the truncated cone shown in FIG. 3d. The microstructure 21 may also be an irregular structure, such as the quasi-columnar shown in FIG. 3e and the quasi-truncated cone shown in FIG. 3f.

There may be many ways to arrange the multiple microstructures 21. For example, as shown in Fig. 4a, taking a cylindrical microstructure 21 as an example, the multiple microstructures 21 are arranged in an array in a manner similar to concentric circles. The substrate 1 is exemplified as a circle.

FIG4b shows an enlarged view of a portion of the structure of the R region within the dotted box in FIG4a. As shown in FIG4b, the plurality of microstructures 21 include a central microstructure 21a, and the central microstructure 21a can be located at the center of the substrate 1. The plurality of microstructures 21 also include a plurality of first microstructures 21b, a plurality of second microstructures 21c, a plurality of third microstructures 21d, a plurality of fourth microstructures 21e, and a plurality of fifth microstructures 21f. The plurality of first microstructures 21b are arranged in a circular array with the central microstructure 21a as the center, the plurality of second microstructures 21c are arranged in a circular array with the central microstructure 21a as the center, the plurality of third microstructures 21d are arranged in a circular array with the central microstructure 21a as the center, the plurality of fourth microstructures 21e are arranged in a circular array with the central microstructure 21a as the center, and the plurality of fifth microstructures 21f are arranged in a circular array with the central microstructure 21a as the center. From the center of the substrate 1 to the edge, the plurality of first microstructures 21b, the plurality of third microstructures 21d, the plurality of fourth microstructures 21e, and the plurality of fifth microstructures 21f are arranged in a concentric array. The diameters of the first microstructure 21 b , the second microstructure 21 c , the third microstructure 21 d , the fourth microstructure 21 e , and the fifth microstructure 21 f may be the same or different.

Of course, the microstructures 21 may have other arrangements. For example, as shown in FIG5a , the microstructure 21 is cylindrical, and multiple microstructures 21 are arranged in a hexagonal array. Alternatively, as shown in FIG5b , the microstructure 21 is cubic, and multiple microstructures 21 are arranged in a rectangular array.

In some embodiments, as shown in FIG6 , the microstructure 21 in the imaging structure 2 may be an annular body, and a plurality of annular bodies are distributed in concentric circles. For each microstructure 21, the annular body has an annular centerline. The annular centerline here refers to a line formed by the center points between the inner edge of the annular body and the outer edge of the annular body at any point along the radial direction of the annular body. Exemplarily, the annular centerlines of the two outermost annular bodies are shown by dotted lines in FIG6 . The distance D2 between the annular centerlines of any two adjacent annular bodies is less than half of the target wavelength in order to achieve a good imaging effect.

In the lens assembly 10 provided in the embodiment of the present application, the imaging structure 2 is formed by arranging a plurality of microstructures 21 , so that the imaging structure 2 can be planar.

As shown in FIG7 , the film layer structure 3 includes a plurality of film layers 31 stacked periodically, and each stacking period T includes at least two film layers 31 of different materials. In order to achieve a good imaging effect, the stacking period T of the plurality of film layers 31 can be set to at least 2. Exemplarily, the number of stacking periods T of the plurality of film layers 31 is 3, that is, the plurality of film layers 31 have 3 stacking periods T. Each stacking period T includes three film layers 31, and the three film layers 31 are respectively a first film layer 31, a second film layer 31, a third film layer 31, a fourth film layer 31, a fifth ... 31a, the second film layer 31b, the third film layer 31c, the materials of the film layers 31 in each stacking period T are different. Taking the structure shown in FIG7 as a reference, along the direction from the top to the bottom, the first film layer 31a, the second film layer 31b, and the third film layer 31c are repeatedly set as a fixed combination within a period T. In application, multiple film layers 31 are adaptively configured according to specific application requirements, so that the film layer structure 3 can suppress stray light in the non-working band in the working band of the lens assembly 10, thereby improving the transmittance, and then improving the imaging performance of the lens assembly 10.

The lens assembly 10 provided in the embodiment of the present application integrates the imaging structure 2 in the form of a metasurface and the membrane structure 3 of multi-layer technology on the substrate 1, with high integration and easy installation and disassembly during use. The lens assembly 10 can be in a planar shape with a relatively small size, and has the advantages of being light and thin. Among them, the imaging structure 2 can use multiple microstructures 21 to phase modulate the incident light, so that the incident wave converges or disperses to achieve the desired imaging effect. The multiple film layers 31 in the membrane structure 3 can be set to have functions such as high transmission or high reflection in a specific band as needed to match the corresponding bandwidth. In addition, the membrane structure 3 can also suppress the transmittance of non-working bands and improve the optical performance of the lens assembly 10. It can be considered that the above-mentioned specific band refers to the working band or target band of the lens assembly 10 adapted to the application scenario. Of course, the optical performance of the lens assembly 10 includes but is not limited to imaging performance.

As described above, the lens assembly 10 provided in the embodiment of the present application has a relatively wide range of application scenarios. Taking the target wave as visible light or near-infrared light as an example, the material of the microstructure 21 in the imaging structure 2 can be silicon nitride or titanium dioxide, and the material of the film layer 31 in the film layer structure 3 includes at least two of silicon dioxide, silicon nitride, titanium dioxide, tantalum pentoxide, magnesium fluoride, barium fluoride, aluminum trioxide, calcium fluoride, sodium chloride, potassium chloride, and potassium bromide. Taking the target wave as thermal infrared light as an example, the material of the microstructure 21 in the imaging structure 2 can be one of germanium, silicon, selenium sulfide, and zinc sulfide, and the material of the film layer 31 in the film layer structure 3 includes at least two of germanium, silicon, zinc selenide, zinc sulfide, gallium arsenide, cadmium telluride, barium fluoride, sodium chloride, potassium chloride, and potassium bromide.

It is worth noting that the microstructure 21 can be independent of the substrate 1 and fixed to the substrate 1, and the microstructure 21 can also be an integrated structure with the substrate 1, thereby saving costs. When the microstructure 21 and the substrate 1 have an integrated structure, the microstructure 21 and the substrate 1 can be made of silicon material at the same time, specifically polycrystalline silicon. The silicon material is abundant and the mining cost is extremely low, which can reduce the production cost. In addition, the processing technology of the silicon material is compatible with the standard semiconductor process, which can further reduce the production cost of the lens assembly 10.

As shown in FIG8a, in some embodiments, the lens assembly 10 further includes a dielectric structure 4, which is disposed on the side of the imaging structure 2 facing away from the substrate 1. The dielectric structure 4 covers the imaging structure 2 and fills between the multiple microstructures 21. It can be considered that the dielectric structure 4 can wrap the multiple microstructures 21 in the imaging structure 2. The dielectric structure 4 and the microstructure 21 have different refractive indices, and light or electromagnetic waves can refract when passing through the interface between the dielectric structure 4 and the microstructure 21, thereby satisfying the light modulation effect of the metasurface. Between the substrate 1, the imaging structure 2 and the dielectric structure 4, the substrate 1 can have the same material as the microstructure 21 of the imaging structure 2, and the substrate 1 can also have the same material as the dielectric structure 4. When the substrate 1 and the microstructure 21 have the same material, the substrate 1 and the imaging structure 21 can have an integrated structure.

The dielectric structure 4 may be solid, and the dielectric structure 4 may cover the surface of the microstructure 21 away from the substrate 1 and fill the gaps between the multiple microstructures 21, and the dielectric structure 4 may provide a certain protection for the microstructure 21. Alternatively, the dielectric structure 4 may also be liquid, and in this case, the liquid dielectric structure 4 needs to be kept within a certain range by means of a coating or other structure, so as to cover the surface of the microstructure 21 away from the substrate 1 and fill the gaps between the multiple microstructures 21.

In some embodiments, the surface of the dielectric structure 4 facing away from the substrate 1 may be a centrally symmetrical free-form surface. For example, as shown in FIG8b , the surface of the dielectric structure 4 facing away from the substrate 1 is a convex surface. Such a dielectric structure 4 can be considered to form a convex lens on the side of the imaging structure 2 facing away from the substrate 1, which can have a focusing effect on the target wave. Alternatively, as shown in FIG8c As shown, the surface of the medium structure 4 facing away from the substrate 1 is a concave surface. Such a medium structure 4 can be considered to form a concave lens on the side of the imaging structure 2 facing away from the substrate 1, which can have a divergent effect on the target wave. In addition, the structure of the medium structure 4 and the imaging structure 2 can also be adjusted to achieve the effect of eliminating chromatic aberration.

Taking the structure shown in FIG. 8 a as an example, as shown in FIG. 9 , in order to improve the anti-reflection effect of the lens assembly 10 , an anti-reflection layer 5 may be further provided on the surface of the dielectric structure 4 facing away from the substrate 1 .

Taking the substrate 1 and the microstructure 21 as an integrated structure as an example, the present application embodiment also provides a method for preparing a lens assembly, and FIG10 shows a schematic diagram of the preparation process of the preparation method. The preparation method may specifically include the following steps:

S1: Provide a substrate having a first surface and a second surface, wherein the first surface and the second surface are opposite to each other along a thickness direction of the substrate.

As shown in FIG. 11 a , the substrate 1 has a first surface a1 and a second surface a2 , wherein the second surface a2 of the substrate 1 faces upward and the first surface a1 faces downward.

S2: multiple film layers are arranged on the second surface of the substrate, and the multiple film layers are periodically stacked along the thickness direction of the substrate; the stacking period of the multiple film layers is greater than or equal to 2, and each stacking period includes at least two film layers of different materials.

As shown in FIG. 11b , a plurality of film layers 31 are sequentially stacked on the second surface a2 of the substrate 1, and the plurality of film layers 31 can form a film layer structure 3. The process of setting the film layer 31 includes but is not limited to evaporation, sputtering and other processes. The periodic stacking rule of the plurality of film layers 31 can be illustrated with reference to FIG. 7 .

S3: forming a plurality of microstructures on the first surface of the substrate, wherein the distance between the centers of any two microstructures is less than half of the target wavelength.

As shown in FIG11c, a plurality of microstructures 21 are formed on the first surface a1 of the substrate 1, and the plurality of microstructures 21 can form an imaging structure 2 to modulate the incident light or electromagnetic wave to meet the optical requirements. Here, the microstructure 21 is exemplarily a columnar body, and the distance between the centers of any two microstructures 21 is less than half of the target wavelength. The microstructure 21 can suppress the high-order diffraction of the target wave and reduce the scattering of the target wave to optimize the imaging quality. It should be understood that the microstructure 21 has an integrated structure with the substrate 1, and therefore, the surface of the microstructure 21 facing away from the substrate 1 is also the first surface a1 of the substrate 1.

Referring to FIG. 11b and FIG. 11c , when a plurality of microstructures 21 are provided, the film layer structure 3 is located at the bottom of the substrate 1. The microstructure 21 is a relatively small structure compared to the lens assembly 10. The film layer structure 3 is made first, and then the microstructure 21 is made. The microstructure 21 will not be located at the bottom of the substrate 1, and the microstructure 21 can be protected to a certain extent.

When the lens assembly 10 is also provided with a dielectric structure 4 of a solid structure, the dielectric structure 4 can cover the surface of the microstructure 21 away from the substrate 1 and fill the gaps between the multiple microstructures 21, and the dielectric structure 4 can provide a certain protection for the microstructure 21. At this time, multiple microstructures 21 and the dielectric structure 4 can be first made on the first surface a1 of the substrate 1, and then the substrate 1 can be inverted so that the dielectric structure 4 and the multiple microstructures 21 are located at the bottom of the substrate 1, and then the film layer structure 3 is prepared on the second surface a2 of the substrate 1. In this preparation process, it can be considered that the above steps S2 and S3 are successively inverted.

In a specific implementation, as shown in FIG. 12 , forming a plurality of microstructures arranged along the first surface on the first surface of the substrate as shown in the above step S3 may specifically include the following steps:

S31: forming a plurality of first structures on a first surface of a substrate.

As shown in FIG13a, a plurality of first structures 61 are arranged along the first surface a1 of the substrate 1. In the process design, the arrangement rule of the first structures 61 corresponds to the arrangement rule of the designed microstructure 21. Any two first structures 61 are isolated from each other, and it can be considered that the plurality of first structures 61 are a plurality of independent structures protruding from the first surface a1 of the substrate 1.

S32: Etching the substrate between the plurality of first structures.

Taking the plurality of first structures 61 as reference, the substrate 1 between the plurality of first structures 61 is etched so that the first surface of the substrate 1 A plurality of microstructures 21 are formed on the surface a1 , and the plurality of microstructures 21 correspond to the plurality of first structures 61 one by one.

S33: removing the first structure.

In this step, the first structure 61 in FIG. 13b can be removed by dissolving or the like, and finally the structure shown in FIG. 11c is obtained, that is, a plurality of microstructures 21 are formed on one side of the first surface a1 of the substrate 1, and the lens assembly 10 is completed.

It should be understood that the above preparation method is implemented based on the microstructure 21 and the substrate 1 having an integrated structure, that is, the microstructure 21 is formed by etching the first surface a1 of the substrate 1. When the microstructure 21 is a structure independent of the substrate 1, a structural layer for forming the microstructure 21 can be provided on the first surface a1 of the substrate 1, and the structural layer is etched with reference to the first structure 61 to form a plurality of microstructures 21.

As shown in FIG. 14 , forming a plurality of first structures on the first surface of the substrate in the above step S31 may include the following steps:

S3111: coating a photoresist on the first surface of the substrate and curing the photoresist to form a sacrificial layer.

Specifically, a photoresist can be applied to the first surface a1 of the substrate 1 by spin coating and cured. The structure after step S3111 can be shown in FIG. 15a, and the photoresist forms a sacrificial layer 6 covering the first surface a1 of the substrate 1. The type and thickness of the photoresist can be selected according to the manufacturing process. It should be understood that the photoresist is only a specific material of the sacrificial layer 6. In the specific manufacturing process, other materials may be replaced. The embodiment of the present application only limits the structure and function of the sacrificial layer 6. Of course, the sacrificial layer 6 may have other names, and its role is mainly reflected in the preparation process. The sacrificial layer 6 does not exist in the structure finally prepared.

S3112: using a mask exposure process to form a plurality of irradiated first structures and unirradiated second structures on the sacrificial layer, wherein the second structures are filled between the plurality of first structures.

As shown in FIG. 15b , the mask 7 has a hollow area. Light is applied to the side of the mask 7 away from the sacrificial layer 6. After the light passes through the hollow area on the mask 7, it can be irradiated onto the sacrificial layer 6. The sacrificial layer 6 irradiated by the light forms a plurality of first structures 61, and the sacrificial layer 6 not irradiated by the light forms a second structure 62. It can be considered that the second structure 62 is located between the gaps of the plurality of first structures 61, and the first structure 61 and the second structure 62 are complementary. Among them, the light indicated by the arrow can be ultraviolet light.

In a specific implementation, the size of the mask 7 is relatively large, while the size of the lens assembly 10 is relatively small. After passing through the mask 7 , the light can be reduced by the lens 8 of the photolithography machine and irradiated onto the sacrificial layer 6 in equal proportion.

S3113: removing the second structure using development technology.

Specifically, the structure shown in FIG. 15 b may be immersed in a developer, and the developer is used to dissolve the second structure 62 to obtain the structure shown in FIG. 13 a .

It should be understood that when the substrate 1 is etched with the first structure 61 as a reference to form the microstructure 21, the second structure 62 is a redundant structure and is removed by development. When the substrate 1 is etched with the second structure 62 as a reference to form the microstructure 21, the first structure 61 can be removed by development. Of course, the developer selected to remove the first structure 61 is different from the developer selected to remove the second structure 62.

In another preparation method, as shown in FIG. 16 , forming a plurality of first structures on the first surface of the substrate in the above step S31 may include the following steps:

S3121: Coating photoresist on the first surface of the substrate to form a sacrificial layer.

Specifically, a photoresist may be coated on the first surface a1 of the substrate 1 by spin coating to form a sacrificial layer 6, and its structure may be shown in FIG15a. It should be noted that the sacrificial layer 6 obtained after step S3111 shown in FIG15a is a photoresist cured, while the sacrificial layer 6 in step S3121 is a photoresist uncured state.

S3122: using a template to imprint a sacrificial layer and solidifying it to form a plurality of first structures.

Specifically, as shown in FIG17a, the template 9 includes a substrate 91 and a plurality of protrusions 92 disposed on the substrate 91. The plurality of protrusions 92 are directed toward the sacrificial layer 6. At this time, the sacrificial layer 6 is not cured and is relatively soft. The side of the template 9 with the protrusions 92 is pressed onto the sacrificial layer 6 and pressure is applied to the substrate 91. As shown in FIG17b, the plurality of protrusions 92 squeeze the sacrificial layer 6 until the plurality of protrusions 92 contact the first surface a1 of the substrate 1, and the plurality of protrusions 92 can squeeze and separate the sacrificial layer 6. After applying ultraviolet light curing, the template 9 is demoulded and removed, and the sacrificial layer 6 can form a plurality of first structures 61 as shown in FIG13a.

In some methods for preparing lens assemblies, as shown in FIG. 18 , after a plurality of film layers are disposed on the second surface of the substrate and before a plurality of microstructures arranged along the first surface are formed on the first surface of the substrate, the following steps are further included:

S2’: performing thinning processing on the first surface of the substrate.

By thinning the first surface a1 of the substrate 1 , a certain amount of inherent defects of the first surface a1 of the substrate 1 can be removed and repaired, thereby improving the quality of the first surface a1 and facilitating the formation of the microstructure 21 on the first surface a1 .

As shown in FIG. 19 a and FIG. 19 b , the embodiment of the present application further provides a lens module 100 , which includes a plurality of lens assemblies 10 in the above-mentioned embodiments.

FIG19a illustrates a lens module 100 in which a plurality of lens assemblies 10 are sequentially arranged along the thickness direction of the substrate 1, and a specific example includes three lens assemblies 10. In such a lens module 100, there may be a distance between any two lens assemblies 10 along the thickness direction of the lens assembly 10. When light or electromagnetic waves pass through the lens module 100, they will sequentially pass through a plurality of lens assemblies 10. By designing the structural parameters of the plurality of lens assemblies 10, the aberration problem in the imaging process can be eliminated, and a better imaging effect can be achieved. It should be understood that the plurality of lens assemblies 10 can be assembled and fixed by an external bracket 20. In a specific application scenario, the bracket 20 may be a structure such as the housing of an electronic device.

Figures 19b and 19c illustrate a lens module 100 in which a plurality of lens assemblies 10 are arranged in a plane. Specifically, there are 6 lens assemblies 10, and the 6 lens assemblies 10 are arrayed in 3 rows and 2 columns. Figure 19b shows a top view of the lens module 100. Combined with the front view of the lens module 100 shown in Figure 19c, a plurality of lens assemblies 10 are sequentially spliced along the plane where the lens assemblies 10 are located, and the plurality of lens assemblies 10 are almost kept in the same plane. At this time, for the convenience of manufacturing, the substrate 1 of the plurality of lens assemblies 10 can have an integrated structure. Of course, the splicing form of the plurality of lens assemblies 10 is not limited, and can also be honeycomb splicing, rectangular splicing, etc. In this lens module 100, the plurality of lens assemblies 10 can be used in light field imaging occasions.

An embodiment of the present application also provides an electronic device, which may be an imaging device capable of realizing imaging, and the imaging device may be an infrared camera, a thermal infrared camera, a laser radar, a depth camera, etc. Alternatively, the electronic device may also be an electronic product including an imaging device, such as a mobile phone, a laptop computer, a tablet computer, etc. Alternatively, the electronic device may also be an optical communication device. Here, taking the imaging device as a thermal infrared camera as an example, as shown in Figures 20a and 20b, the imaging device includes a housing 200, an image sensor 300 and a lens unit 400, wherein the image sensor 300 is specifically a thermal infrared sensor. Among them, the lens unit 400 may be any one of the lens assemblies 10 provided in the above-mentioned embodiments, and may also be any one of the lens modules 100 provided in the above-mentioned embodiments.

As shown in FIG. 20a , the housing 200 may be a box-shaped structure with an opening, and the lens unit 400 is disposed at the opening of the housing 200. The external environment has a person or object that can emit radiation light in the far-infrared range, and the far-infrared radiation light emitted by the person or object enters the lens unit 400 as a group of approximately parallel light rays after long-distance transmission. Here, the object side that emits infrared light is taken as an example of a person, and the infrared light emitted from a certain point P on the person is exemplified by light rays p1, light rays p2, light rays p3, light rays p4, and light rays p5. After being transported over a long distance, these light rays enter the lens unit 400 as a group of approximately parallel light rays. The group of light rays enters the lens unit 400 in a manner parallel to the optical axis Q of the lens unit 400. The image sensor 300 is disposed at the focusing surface of the lens unit 400, and the lens unit 400 can focus the group of light rays onto the image sensor 300 on the focusing surface. The image sensor 300 is used to capture radiation in the external far-infrared range and generate thermal imaging image data. It should be understood that in actual applications, there are multiple groups of light emitted from the object side, and when the multiple groups of light enter the lens unit 400, there are different angles between them and the optical axis Q, and each group of light can be focused by the lens unit 400 onto the focusing plane and captured by the image sensor 300. Different groups of light have different focus points on the focusing plane, and can be distributed at different positions on the focusing plane, so as to be captured by the image sensor 300.

As shown in FIG. 20b , the housing 200 may be a box-shaped structure with an opening, and the lens unit 400 and the image sensor 300 are both disposed in the housing 200, and the lens unit 400 is located at the opening between the image sensor 300 and the housing 200, and the opening of the housing 200 has a smaller diameter than the lens unit 400. Possibly, an aperture 500 may be disposed at the opening of the housing 200. Exemplarily, the infrared light emitted from a point P on a person's body includes light rays p1, p2, p3, p4, p5, p6, and p7. When the group of light rays passes through the opening of the housing 200, they are blocked by the opening of the housing 200 and a portion of the light rays are allowed to enter the housing 200. The light rays entering the housing 200 are focused on the focusing plane after passing through the lens unit 400 and are captured by the image sensor 300.

There may be a gap between the aperture 500 and the lens unit 400 to achieve better control of the field of view angle and further reduce stray light.

Exemplarily, as shown in FIG21a, when the lens unit 400 is a lens assembly 10, the lens assembly 10 can be installed in the housing 200, and the lens assembly 10 is located between the opening of the housing 200 and the image sensor 300. Specifically, the film layer structure 3 of the lens assembly 10 can be oriented toward the object side, and the imaging structure 2 of the lens assembly 10 can be oriented toward the image sensor 300. Of course, the specific orientation of the lens assembly 10 is only an example.

Exemplarily, as shown in FIG. 21b, when the lens unit 400 is a lens module 100, taking the lens module 100 composed of three lens assemblies 10 arranged in sequence along the thickness direction as an example, the three lens assemblies 10 are respectively a first lens assembly 10a, a second lens assembly 10b and a third lens assembly 10c. When the lens module 100 is mounted to the housing 200, the first lens assembly 10a can be mounted at the opening of the housing 200, and the second lens assembly 10b and the third lens assembly 10c can be mounted in sequence between the first lens assembly 10a and the image sensor 300. Among them, the third lens assembly 10c is adapted to the inner diameter of the housing 200 and fixed to the inner wall of the housing 200. The second lens assembly 10b is fixedly mounted by the mounting seat 201 in the housing 200.

In other embodiments, as shown in FIG. 21c, when the lens unit 400 includes a first lens assembly 10a, a second lens assembly 10b and a third lens assembly 10s. Among them, the first lens assembly 10a and the second lens assembly 10b are the lens assemblies 10 provided in the above-mentioned embodiments, and have an imaging structure 2 and a filtering structure 3. The third lens assembly 10s is an ordinary lens assembly. In other words, the lens assembly 10 provided in the embodiment of the present application can be used in combination with an ordinary lens assembly to achieve the required imaging effect. Such a design can reduce costs and structural volume and improve design freedom. It should be understood that the ordinary lens assembly in FIG. 21c is arranged in two lens assemblies 10 for exemplary purposes only, and the embodiment of the present application does not limit the number and position relationship of the lens assembly 10 combined with the ordinary lens assembly.

In summary, the lens assembly 10 provided in the embodiment of the present application combines the metasurface with the multi-film layer technology to realize a planar lens while achieving lightness and thinness. In application, according to different application scenarios, different film layer structures 3 are selected to improve the bandwidth performance of the lens assembly 10 and broaden the application scope of the lens assembly 10. When the lens assembly 10 is used alone or combined into a lens module 100, the imaging performance can be improved and a better imaging effect can be achieved. The imaging device with the lens assembly 10 is also easier to achieve miniaturization, which meets the development needs of current terminal devices.

The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (16)

A lens assembly, characterized in that it comprises: a substrate, an imaging structure and a film layer structure; along the thickness direction of the substrate, the imaging structure and the film layer structure are respectively located on two sides of the substrate; The imaging structure comprises a plurality of microstructures, wherein the plurality of microstructures are arrayed on the surface of the substrate, and the distance between the centers of any two of the microstructures is less than half of the target wavelength; The film layer structure includes a plurality of film layers, and the plurality of film layers are periodically stacked along the thickness direction of the substrate; the stacking period of the plurality of film layers is greater than or equal to 2, and each stacking period includes at least two film layers of different materials. The lens assembly as described in claim 1 is characterized in that the lens assembly includes a dielectric structure, which is arranged on a side of the imaging structure away from the substrate; the dielectric structure covers the surface of the imaging structure away from the substrate and fills the gaps between the plurality of microstructures; the dielectric structure and the microstructure have different refractive indices. The lens assembly as described in claim 2 is characterized in that the lens assembly includes an anti-reflection layer, and the anti-reflection layer is arranged on a side of the dielectric structure facing away from the substrate. The lens assembly according to claim 2 or 3, characterized in that the substrate is made of the same material as the microstructure; or the substrate is made of the same material as the dielectric structure. The lens assembly according to any one of claims 1 to 4, characterized in that the microstructure is a columnar body, and the distance between the centers of any two adjacent columns is less than half of the target wavelength. The lens assembly as described in any one of claims 1 to 4 is characterized in that the microstructure is an annular body, and a plurality of the annular bodies are distributed in concentric circles; and the distance between the center lines of any two adjacent annular bodies is less than half of the target wavelength. The lens assembly according to any one of claims 1 to 6, characterized in that when the target wave is visible light or near-infrared light, the material of the microstructure is silicon nitride or titanium dioxide; the material of the film layer of the film layer structure includes at least two of silicon dioxide, silicon nitride, titanium dioxide, tantalum pentoxide, magnesium fluoride, barium fluoride, aluminum oxide, calcium fluoride, sodium chloride, potassium chloride, and potassium bromide; When the target wave is thermal infrared light, the material of the microstructure is one of germanium, silicon, selenium sulfide, and zinc sulfide; the material of the film layer of the film layer structure includes at least two of germanium, silicon, selenium sulfide, zinc sulfide, gallium arsenide, cadmium telluride, barium fluoride, sodium chloride, potassium chloride, and potassium bromide. The lens assembly according to any one of claims 1 to 7, characterized in that the absorption rate of the target wave by the substrate, the microstructure and the film layer is less than 40%. A lens module, characterized in that it comprises a plurality of lens assemblies as described in any one of claims 1 to 8; the plurality of lens assemblies are arranged in sequence along the thickness direction of the substrate; or the plurality of lens assemblies are arranged in sequence along a thickness direction perpendicular to the substrate. An electronic device, characterized in that it comprises a housing, an image sensor and a lens unit, wherein the lens unit is the lens assembly according to any one of claims 1 to 8 or the lens module according to claim 9; The housing has an opening, and the image sensor is arranged in the housing; the lens unit is arranged on a side of the image sensor facing the opening, and the lens unit is used to focus external light entering the opening onto the image sensor. The electronic device as described in claim 10 is characterized in that the lens unit is fixed at the opening; or a lens is provided at the opening of the housing, and the lens unit is provided between the lens and the image sensor. A method for preparing a lens assembly, characterized in that it is used to prepare a lens assembly; the lens assembly includes a liner A substrate, an imaging structure and a film layer structure; along the thickness direction of the substrate, the imaging structure and the film layer structure are respectively located on both sides of the substrate; the preparation method comprises: Providing a substrate, the substrate having a first surface and a second surface, the first surface and the second surface are opposite to each other along a thickness direction of the substrate; A plurality of film layers are arranged on the second surface of the substrate, and the plurality of film layers are periodically stacked along the thickness direction of the substrate; the stacking period of the plurality of film layers is greater than or equal to 2, and each stacking period includes at least two film layers of different materials; A plurality of microstructures are formed on the first surface of the substrate, and the distance between the centers of any two of the microstructures is less than half of the target wavelength. The preparation method according to claim 12, characterized in that forming a plurality of microstructures on the first surface of the substrate comprises: forming a plurality of first structures on a first surface of the substrate; Etching the substrate between any two first structures; The first structure is removed. The preparation method according to claim 13, characterized in that forming a plurality of first structures on the first surface of the substrate comprises: Coating a photoresist on the first surface of the substrate and curing the photoresist to form a sacrificial layer; Using a mask exposure process, the sacrificial layer is formed into a plurality of irradiated first structures and a second structure that is not irradiated, wherein the second structure is filled between the plurality of first structures; The second structure is removed by using a developing technology. The preparation method according to claim 13, characterized in that forming a plurality of first structures on the first surface of the substrate comprises: Coating a photoresist on the first surface of the substrate and forming a sacrificial layer; The sacrificial layer is printed by using a template and cured to form a plurality of the first structures. The preparation method according to any one of claims 12 to 15 is characterized in that after arranging multiple film layers on the second surface of the substrate and before forming multiple microstructures on the first surface of the substrate, it also includes: thinning the first surface of the substrate.