20 million-pixel visible light refraction and reflection lens, camera module and terminal equipment

Abstract

The invention relates to a 20 million-pixel visible refractive and super lens, a camera module and a terminal device, and belongs to the field of optical lenses, the 20 million-pixel visible refractive and super lens comprises a diaphragm, a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object plane to an image plane along an optical axis; wherein at least one lens is a metasurface lens, and the other lenses are non-metasurface lenses. According to the 20 million-pixel visible light refraction and super lens, the contradictory barrier between miniaturization and high performance is broken through by fusing metasurface phase regulation and traditional refraction optics, an ultra-large field angle of 90 degrees or above is achieved under the front-end aperture of 0.81 mm, 20 million-pixel high-definition imaging is synchronously supported, and the total optical length is compressed to 2.6 mm or below; the nano-structure metasurface is compatible with a semiconductor process, has the advantages of low cost and mass production, and provides a solution for miniaturization and ultrathin development of front camera modules of portable electronic equipment such as mobile phones, computers and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of optical lenses, and particularly relates to a 2000-megapixel visible light folding super lens, a camera module and a terminal device. BACKGROUND

[0002] As an indispensable core component in modern optical systems, optical lenses exhibit unique value and function in information acquisition, imaging quality optimization, and system integration. Optical lenses effectively realize the imaging of objects and the accurate acquisition of information by precisely focusing the light of external objects on the photosensitive element. They play a key role in various optical imaging devices, such as mobile phone cameras, digital cameras, and surveillance cameras, and are the core components for obtaining high-quality image information. In addition, optical lenses have excellent compatibility and can be integrated with other optical and electronic components to form a complete optical system. For example, in laser processing equipment, optical lenses work together with lasers, mirrors, and other components to achieve high-precision laser processing of materials.

[0003] With the tide of technological development, portable electronic devices such as mobile phones and computers have deeply integrated into people's daily life, and their diverse functions and powerful performance continue to meet the growing needs of users. In particular, the camera modules, especially the front camera modules, carried by these portable devices not only meet the users' regular use scenarios in video calls and selfies, but also are widely used in advanced technology fields such as augmented reality (AR), virtual reality (VR), and biometric identification, becoming an important force driving the development of related technologies. A camera module is usually composed of an image sensor and an optical imaging lens. Modern camera modules mostly use CMOS sensors due to their low power consumption, high readout rate, and cost-effectiveness. Among the many factors that affect imaging quality, the pixel size and photosensitivity of the sensor are particularly critical. With technical means such as pixel four-in-one, the imaging performance of the camera module in low-light environments can be significantly improved, enhancing the clarity and brightness of the image. As a core component of the camera module, the optical imaging lens is mainly responsible for focusing and guiding light to ensure that light is accurately projected onto the image sensor. Generally, the lens adopts a multi-lens combination structure design, which effectively reduces the occurrence of aberration through the synergistic effect of each lens, thereby significantly improving the overall imaging quality. However, the current front camera module faces the challenge of achieving high-quality imaging in a limited space during the design process, and needs to meet the development trend of miniaturization and thinness of devices. Under this background, there is still room for improvement and optimization in the volume of traditional front camera modules.

[0004] As a new type of two-dimensional nano structure array, metasurface has attracted much attention due to its ability to precisely control the phase, amplitude and polarization state of light waves at subwavelength scale. As an important branch of nanophotonics and metamaterials research, the development of metasurface technology is mainly driven by the need to break through the limitations of traditional optical elements. Traditional optical elements are often limited by their large size and relatively single function, while the emergence of metasurface technology provides an innovative solution to these problems. Metasurface can realize all the functions of traditional optical elements at a very small subwavelength scale, thus having a unique advantage in significantly reducing the size and weight of optical systems, effectively replacing traditional thick lenses and realizing the transformation of ultra-thin and light optical design. In addition, metasurface technology also has the potential to achieve high-performance indicators that traditional optical elements cannot achieve, such as high numerical aperture (NA), high resolution and low aberration, which can significantly improve the imaging quality and performance of optical systems. At the same time, the manufacturing process of metasurface is highly compatible with existing semiconductor processing technology, and can be mass-produced through mature semiconductor manufacturing processes, thus showing high cost-effectiveness and market application prospects.

[0005] The fold-hybrid system formed by combining the metasurface lens and the traditional lens can well solve the problems existing in the traditional lens. The fold-hybrid system can usually achieve a high focal length and light path folding, so as to realize the required light path length in a relatively small optical system, which helps to reduce the volume and weight of the optical system, facilitates integration into equipment, and the imaging resolution can still reach a high level, while the manufacturing cost is relatively low. However, how to design the fold-hybrid lens to ensure 2000 million pixel high-quality image information while realizing the miniaturization and light weight of the optical system is still a challenge. SUMMARY

[0006] The present application provides a 2000 million pixel visible light fold-hybrid lens, a camera module and a terminal device, aiming to reduce the TTL (total optical length), volume and cost of the lens while ensuring the field of view and F number (aperture number), and realize non-thermal design.

[0007] To solve the above technical problems, the purpose of the present application is realized by the following technical scheme: the present application provides a 2000 million pixel visible light fold-hybrid lens, which comprises a stop, a first lens, a second lens, a third lens and a fourth lens arranged in order along the optical axis from the object plane to the image plane; wherein at least one lens is a metasurface lens, and the remaining lenses are non-metasurface lenses.

[0008] The 2000 million pixel visible light fold-hybrid lens meets the following requirements:

[0009]

[0010] Wherein, C1 represents the quadratic phase coefficient of the metasurface, R0 represents the root mean square radius size of the 0.9 field of view focusing spot, th1 represents the center thickness of the first lens, and th2 represents the center thickness of the second lens.

[0011] Further, the first lens, the third lens, and the fourth lens are all aspherical lenses; the second lens is a metasurface lens, and the metasurface lens comprises a substrate and a micro-nano structure arranged on the substrate.

[0012] Further, the first lens has positive refractive power, the object side surface of the first lens is a convex surface, the image side surface of the first lens is a concave surface, and the object side surface and the image side surface of the first lens are both aspherical surfaces.

[0013] The object side surface of the second lens is a plane, and the image side surface has a microstructure arrangement.

[0014] The third lens has positive refractive power, the object side surface of the third lens is a concave surface, the image side surface of the third lens is a convex surface, and the object side surface and the image side surface of the third lens are both aspherical surfaces.

[0015] The fourth lens has negative refractive power, the object side surface and the image side surface of the fourth lens are both concave surfaces in the paraxial region, and the object side surface and the image side surface of the fourth lens are both aspherical surfaces.

[0016] Optionally, the micro-nano structure material of the second lens is one of amorphous silicon, crystalline silicon, silicon dioxide, silicon nitride, and titanium dioxide; and the substrate material of the second lens is glass, and the substrate thickness satisfies 0.1mm≤th≤0.5mm.

[0017] Optionally, the materials of the first lens, the third lens, and the fourth lens are resin materials.

[0018] Further, the distance from the optical axis center of the object side surface of the diaphragm to the image surface satisfies: TTL≤2.50mm.

[0019] Further, the diaphragm is located before the first lens.

[0020] Optionally, the effective aperture D of the 2000-megapixel visible light hyper-lens at the front end satisfies: D eff ≤0.81mm. eff

[0021] Further, the field of view angle of the 2000-megapixel visible light hyper-lens satisfies: Fov≥90°.

[0022] Further, the working temperature of the 2000-megapixel visible light hyper-lens is -30℃-70℃.

[0023] ​The application further provides a camera module comprising the 20 million pixel visible light fold super lens.

[0024] The application further provides a terminal device comprising the camera module.

[0025] The 20 million pixel visible light fold super lens provided by the embodiment of the application adopts four lenses, three of which are made of resin material, and one of which is a super lens, so that the volume is small, the cost is saved, and the working temperature range is ensured. The total optical length of the 20 million pixel visible light fold super lens satisfies TTL≤2.60mm, and the overall field of view of the 20 million pixel visible light fold super lens is also large, Fov≥90°. Meanwhile, the imaging resolution is high, MTF≥0.4 in 110lp / mm, 0.8 field of view, and MTF≥0.7 in the central field of view, so that the problems of large volume and high cost existing in the prior art front camera lens are solved. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description are briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0027] Figure 1 A structure schematic diagram of the 20 million pixel visible light fold super lens provided by the embodiment of the application is shown in the figure.

[0028] Figure 2 An MTF schematic diagram of the 20 million pixel visible light fold super lens provided by the embodiment 1 of the application is shown in the figure.

[0029] Figure 3 A spot diagram of the 20 million pixel visible light fold super lens provided by the embodiment 1 of the application is shown in the figure.

[0030] Figure 4 A relative luminance schematic diagram of the 20 million pixel visible light fold super lens provided by the embodiment 1 of the application is shown in the figure.

[0031] Figure 5 An MTF schematic diagram of the 20 million pixel visible light fold super lens provided by the embodiment 2 of the application is shown in the figure.

[0032] Figure 6A schematic diagram of the diffuse spots of a 20-megapixel visible light refractive metalens provided in Example 2 of the present invention;

[0033] Figure 7 A schematic diagram of relative illumination of a 20-megapixel visible light refractive metalens provided in Example 2 of the present invention.

[0034] Description of reference numerals:

[0035] 110 , aperture; 120 , first lens; 130 , second lens; 140 , third lens; 150 , fourth lens; 160 , imaging surface. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0038] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0039] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0040] See also Figure 1 , a schematic structural diagram of a 20-megapixel visible light refractive metalens at room temperature provided by an embodiment of the present invention, including an aperture 110, a first lens 120, a second lens 130, a third lens 140, and a fourth lens 150 arranged in sequence along the optical axis from the object plane to the image plane.

[0041] In this embodiment, the visible light refractive metalens is configured to satisfy: TTL≤2.50mm, D eff≤0.81mm. Wherein, C1 represents the quadratic phase coefficient of the super surface, R0 represents the root mean square radius size of the 0.9 field of view focusing spot, th1 represents the center thickness of the first lens, th2 represents the center thickness of the second lens, the total optical length TTL is the distance from the optical axis center of the stop object side to the image surface, D eff represents the front effective aperture. Under the parameter specification, the 2000 million pixel visible light fold super lens has a shorter total optical length and smaller lens size, can correct spherical aberration, and balances the requirements of light efficiency and overall miniaturization of the lens. In addition, in the embodiment, the 2000 million pixel visible light fold super lens satisfies Fov≥90°, and the overall field of view is also larger, which can realize wide-angle imaging.

[0042] As a feasible implementation manner, at least one of the first lens 120, the second lens 130, the third lens 140 and the fourth lens 150 is a super surface lens.

[0043] Wherein, the super surface lens has an achromatic function, and by setting at least one lens in the 2000 million pixel visible light fold super lens as a super surface lens, chromatic aberration can be effectively corrected, thereby improving the image quality of the 2000 million pixel visible light fold super lens.

[0044] As a feasible implementation manner, the second lens 130 is a super surface lens, and the super surface lens includes a substrate and a micro-nano structure arranged on the substrate, wherein the micro-nano structure material includes but is not limited to amorphous silicon, crystalline silicon, silicon dioxide, silicon nitride, and titanium dioxide; the substrate material of the second lens is glass, and the substrate thickness is 0.1mm≤th≤0.5mm. The object side of the second lens 130 is a plane, and the image side has a microstructure arrangement.

[0045] As a feasible implementation manner, the materials of the first lens 120, the third lens 140 and the fourth lens 150 are resin.

[0046] Wherein, by setting the materials of the first lens 120, the third lens 140 and the fourth lens 150 as resin, and the material of the second lens 130 as glass, the 2000 million pixel visible light fold super lens has an achromatic function, so that the surround view lens can realize constant imaging quality within a certain range. In addition, by using the lens with matched material combination positive focal length temperature coefficient, the overall focal length drift is offset, the proportion of the focal power of each lens is adjusted, the total focal power of the system is not sensitive to temperature change, the athermal design is realized, the material cost is reduced, and the volume of the system is also reduced.

[0047] In the preferred embodiment, the first lens 120 is an aspherical lens with positive focal power, the object side is convex, the image side is concave, and both the object side and the image side of the first lens are aspherical; the second lens 130 is a super surface lens, the object side is flat, and the image side has a microstructure arrangement; the third lens 140 is an aspherical lens with positive focal power, the object side is concave, the image side is convex, and both the object side and the image side are aspherical; the fourth lens 150 is an aspherical lens with negative focal power, and both the object side and the image side are concave in the paraxial region; the diaphragm 110 is located before the first lens 120.

[0048] In the preferred embodiment, the positive focal power and specific surface shape of the first lens 120 help to converge light rays; the second lens 130 as a super surface lens can achieve more precise control of light rays through its flat object side and binary image side and the microstructure arrangement on the image side; the design of the surface shape of the third lens 130 and the fourth lens 140 takes into account a wider field of view, smaller lens size, and smaller optical system aberration; the placement position and aperture size of the diaphragm 110 are also optimized to effectively intercept and limit light rays. In summary, by matching different lenses and designing the surface shape and focal power of each lens, good imaging effect and optical performance can be achieved.

[0049] Based on the above scheme, the working temperature of the 20 million pixel visible light super-mirror lens is -30°C to 70°C, which can maintain stable performance and imaging quality and adapt to various extreme environmental conditions.

[0050] The following are two preferred embodiments based on the above examples, which detail the specific optical data parameters of each lens in the 20 million pixel visible light super-mirror lens provided by the embodiments of the present application.

[0051] Embodiment 1

[0052] Specifically, as shown in Figure 1 The 20 million pixel visible light super-mirror lens includes a diaphragm 110, a first lens 120, a second lens 130, a third lens 140, and a fourth lens 150 arranged in order along the optical axis from the object plane to the image plane; the second lens 130 is a super surface lens, and the remaining lenses are aspherical lenses made of resin; the incident light passes through the diaphragm 110, enters the object side of the first lens 120, passes through the second lens 130, and then passes through the third lens 140 and the fourth lens 150, and finally converges on the imaging plane 160.

[0053] The optical parameter data of the super-mirror hybrid lens can refer to the examples in Table 1.

[0054] Table 1

[0055]

[0056]

[0057] In Table 1, the surface number is numbered according to the surface sequence of each lens, for example, the surface number 1 represents the stop 110, the surface number 2 represents the object side surface of the first lens 120, the surface number 3 represents the image side surface of the first lens 120, and so on, and the last surface number 10 represents the imaging surface 160. Among them, the radius of curvature represents the bending degree of the lens surface, the positive value represents that the surface bends to the image side, and the negative value represents that the surface bends to the object side, the "Standard" represents the standard surface, the "Extended sphere" represents the extended aspherical surface, the "Binary2" represents the binary surface, and the "Infinity" represents that the surface is a plane; the interval represents the center axis distance from the current surface to the next surface, and the units of the radius of curvature and the interval are millimeters (mm).

[0058] The even aspherical surface satisfies the following equation:

[0059]

[0060] Wherein, z represents the distance of the aspherical surface along the optical axis direction from its vertex, r represents the height from the optical axis, c represents the curvature 1 / R, R represents the radius of curvature at the vertex of the lens; k represents the conic coefficient, Ai represents the aspherical high-order coefficient, and p represents the normalized radial coordinate.

[0061] In this embodiment, the conic coefficient k and the high-order coefficient Ai of the aspherical lens are as follows in Table 2.

[0062] Table 2

[0063]

[0064]

[0065] In Table 2, 5.08E+000 represents that the coefficient a2 of the surface number 2 is 5.08E+000, and so on.

[0066] In this embodiment, the phase of the metasurface lens can refer to Table 3.

[0067] Table 3

[0068]

[0069] In Table 3, R1 is the normalized radius of the binary surface of the metasurface lens.

[0070] In this embodiment, the quadratic phase coefficient of the metasurface, the root mean square radius size of the 0.9 field focusing spot, the center thickness of the first lens and the center thickness of the second lens satisfy The total length of the optical lens TTL satisfies TTL = 2.44 mm;

[0071] The working waveband of the 20 million pixel visible light fold super lens provided by the embodiment is 430-650 nm, the front effective aperture D eff satisfies D eff = 0.81 mm, and the full field of view is 92.6°, which satisfies the use requirement of the front camera module.

[0072] Figure 2 The MTF diagram of the 20 million pixel visible light fold super lens provided by the embodiment is shown, the 20 million pixel visible light fold super lens provided by the embodiment has high resolution, the MTF is greater than or equal to 0.4 in 0.8 field of view at 110 lp / mm, the MTF is greater than or equal to 0.7 in the central field of view, and the high-quality imaging requirement of the front camera lens can be satisfied.

[0073] Figure 3 The diffraction spot diagram of the 20 million pixel visible light fold super lens provided by the embodiment is shown, the 20 million pixel visible light fold super lens provided by the embodiment has a relatively concentrated diffraction pattern and uniform distribution in the entire long waveband, and the requirement of high-resolution imaging can be satisfied.

[0074] Figure 4 The relative luminance diagram of the 20 million pixel visible light fold super lens provided by the embodiment is shown, which represents the relative luminance values corresponding to different fields of view, as shown in the figure, the relative luminance of the 20 million pixel visible light fold super lens provided by the embodiment is greater than 25% in the 1.0 field of view in the working waveband, and the brightness is uniform. Figure 4

[0075] Embodiment 2

[0076] Exemplarily, the 20 million pixel visible light fold super lens in the embodiment includes, arranged in sequence along the optical axis from the object plane to the image plane, a diaphragm 110, a first lens 120, a second lens 130, a third lens 140, and a fourth lens 150; wherein the first lens 120 is an aspherical lens with positive focal power, the object side surface is convex, and the image side surface is concave; the second lens 130 is a super surface lens, the object side surface is a plane, and the image side surface has a microstructure arrangement; the third lens 140 is an aspherical lens with positive focal power, the object side surface is concave, and the image side surface is convex, and both the object side surface and the image side surface are aspherical; the fourth lens 150 is an aspherical lens with negative focal power, and both the object side surface and the image side surface are concave in the near-axis region; the diaphragm 110 is located before the first lens 120; the incident light passes through the diaphragm 110, enters from the object side surface of the first lens 120, passes through the second lens 130, and then passes through the third lens 140 and the fourth lens 150, and finally converges on the imaging surface 160.

[0077] ​The optical parameter data of the folded hyper-combined lens can refer to the examples in Table 4, and the optical data parameters in Table 4 correspond to Figure 1 The 2000-megapixel visible light folded hyper lens is shown.

[0078] Table 4

[0079] Surface No. Surface Type Radius of Curvature (mm) Pitch (mm) Material 1 STOP Standard Infinity -0.09 2 Evensphere 2.80 0.50 Resin 3 Evensphere 7.61 0.16 4 Standard Infinity 0.17 Glass 5 Binary2 Infinity 0.31 6 Evensphere -0.29 0.26 Resin 7 Evensphere 3.44 0.10 8 Evensphere -10.37 0.20 Resin 9 Evensphere 0.50 0.84 10 Standard Infinity -

[0080] In Table 4, the surface number is numbered according to the surface order of each lens, for example, surface number 1 represents the stop 110, surface number 2 represents the object side surface of the first lens 120, surface number 3 represents the image side surface of the first lens 120, and so on, and the last surface number 10 represents the imaging surface 160. Among them, the radius of curvature represents the bending degree of the lens surface, the positive value represents that the surface bends to the image side, and the negative value represents that the surface bends to the object side, and the "Standard" represents the standard surface, the "Extended sphere" represents the extended aspherical surface, the "Binary2" represents the binary surface, and the "Infinity" represents that the surface is a plane; the interval represents the center axis distance from the current surface to the next surface, and the units of the radius of curvature and the interval are millimeters (mm).

[0081] The even aspherical surface type satisfies the following equation:

[0082]

[0083] Where z represents the distance of the aspherical surface along the optical axis from its vertex, r represents the height from the optical axis, c represents the curvature 1 / R, R represents the radius of curvature at the vertex of the lens; k represents the conic coefficient, Ai represents the aspherical high-order coefficient, and p represents the normalized radial coordinate.

[0084] In the present embodiment, the conic coefficient k and the high-order coefficient Ai of the aspherical lens are as shown in the following Table 5.

[0085] Table 5

[0086]

[0087]

[0088] In Table 5, 5.08E+000 represents that the coefficient a2 of the surface number 2 is 5.08E+000, and so on.

[0089] In the present embodiment, the phase of the metasurface lens can refer to Table 6.

[0090] Table 6

[0091]

[0092] In Table 6, R1 is the normalized radius of the binary surface lens of the metasurface.

[0093] In the embodiment, the quadratic phase coefficient of the metasurface, the root mean square radius of the 0.9 field of view focusing spot, the center thickness of the first lens and the center thickness of the second lens satisfy the following relationship: The total length of the optical lens TTL satisfies TTL = 2.45mm;

[0094] The working waveband of the 20 million pixel visible light hyperbolic lens provided by the embodiment is 430-650nm, the front effective aperture D eff satisfies D eff = 0.80mm, the full field of view angle is 93.3°, and the use requirement of the front camera module is met.

[0095] Figure 5 The MTF diagram of the 20 million pixel visible light hyperbolic lens provided by the embodiment is shown, the 20 million pixel visible light hyperbolic lens provided by the embodiment has high resolution, the MTF is greater than or equal to 0.4 in 0.8 field of view at 110lp / mm, the central field of view MTF is greater than or equal to 0.7, and the high-quality imaging requirement of the front camera lens is met.

[0096] Figure 6 The diffraction spot diagram of the 20 million pixel visible light hyperbolic lens provided by the embodiment is shown, the 20 million pixel visible light hyperbolic lens provided by the embodiment has a relatively concentrated diffraction pattern and uniform distribution in the entire long waveband, and the requirement of high-resolution imaging is met.

[0097] Figure 7 The relative luminance diagram of the 20 million pixel visible light hyperbolic lens provided by the embodiment is shown, which represents the relative luminance values corresponding to different fields of view, as shown in the figure, the relative luminance of the 20 million pixel visible light hyperbolic lens provided by the embodiment is greater than 26% in the working waveband and in 1.0 field of view, and the brightness is uniform. Figure 7

[0098] In summary, the 20 million pixel visible light hyperbolic lens provided by the embodiment has a larger field of view angle, uniform brightness in the full field of view, clear imaging, and a smaller TTL, and can meet the requirements of high-resolution imaging and integration and lightness.

[0099] Embodiment 1 and embodiment 2 respectively satisfy the following relationship shown in Table 7:

[0100] Table 7

[0101]

[0102] The embodiment of the application also provides a camera module comprising the 20 million pixel visible light hyperbolic lens.​

[0103] The embodiment of the present application also provides a terminal device comprising the camera module.

[0104] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present disclosure, which should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A 20-megapixel visible light refractive metalens, characterized in that: The method comprises an aperture, a first lens, a second lens, a third lens, and a fourth lens, which are sequentially arranged along the optical axis from the object plane to the image plane; wherein at least one lens is a metasurface lens, and the remaining lenses are non-metasurface lenses; The 20-megapixel visible light refractive metalens meets the following requirements: Wherein, C1 represents the quadratic phase coefficient of the metasurface, R0 represents the root mean square radius of the 0.9 field of view focused spot, th1 represents the center thickness of the first lens, and th2 represents the center thickness of the second lens.

2. The 20-megapixel visible light refractive metalens according to claim 1, characterized in that: The first lens, the third lens, and the fourth lens are all aspherical lenses; the second lens is a metasurface lens, and the metasurface lens includes a substrate and a micro-nano structure provided on the substrate.

3. The 20-megapixel visible light refractive metalens according to claim 2, wherein: The first lens has positive refractive power, the object-side surface of the first lens is convex, the image-side surface of the first lens is concave, and both the object-side surface and the image-side surface of the first lens are aspherical surfaces; The object-side surface of the second lens is a plane, and the image-side surface of the second lens has a microstructure arrangement. The third lens has positive refractive power, the object side surface of the third lens is concave, the image side surface of the third lens is convex, and both the object side surface and the image side surface of the third lens are aspherical; The fourth lens has negative optical power, and in the paraxial region, the object side surface and the image side surface of the fourth lens are both concave surfaces, and the object side surface and the image side surface of the fourth lens are both aspherical surfaces.

4. The 20-megapixel visible light refractive metalens according to claim 3, wherein: The micro-nano structure material of the second lens is one of amorphous silicon, crystalline silicon, silicon dioxide, silicon nitride, and titanium dioxide; the base material of the second lens is glass, and the base thickness is 0.1 mm≤th≤0.5 mm.

5. The 20-megapixel visible light refractive metalens according to claim 3, wherein: The first, third and fourth lenses are made of resin.

6. The 20-megapixel visible light refractive metalens according to claim 1, wherein: The distance from the optical axis center of the object side of the first lens to the image plane is TTL, which satisfies the following conditions: TTL≤2.50 mm.

7. The 20-megapixel visible light refractive metalens according to claim 1, wherein: The aperture is located before the first lens.

8. The 20-megapixel visible light refractive metalens according to claim 1, wherein: The front effective aperture D of the 20-megapixel visible light refractive metalens is eff Satisfied: D eff ≤0.81mm.

9. The 20-megapixel visible light refractive metalens according to claim 1, wherein: The field of view (FOV) of the 20-megapixel visible light refractive metalens satisfies: Fov ≥ 90°.

10. The 20-megapixel visible light refractive metalens according to claim 1, wherein: The operating temperature of the 20-megapixel visible light refractive metalens is -30°C to 70°C.

11. A camera module, characterized in that: The method comprises the 20-megapixel visible light refractive metalens according to any one of claims 1 to 10.

12. A terminal device, characterized in that: Including the camera module as described in claim 11.

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