Optical imaging system and electronic device

Abstract

The utility model discloses an optical imaging system and electronic equipment, and belongs to the technical field of optical imaging. The electronic equipment comprises an optical imaging system, the optical imaging system comprises a positive lens, a negative lens and a super-structure lens, the negative lens, the positive lens and the super-structure lens are sequentially arranged in the direction where the optical axis of the optical imaging system is located and in the direction from the object side to the imaging face, the negative lens is used for diffusing light, the positive lens is used for focusing the light, and the super-structure lens is used for focusing the light. At least one of the object side face and the image side face of the super-structure lens is a super surface, and the super surface comprises at least two microstructures arranged at intervals. Compared with a traditional optical imaging system formed by a refraction lens, the optical imaging system disclosed by the utility model is smaller in size.

Description

Technical Field

[0001] The present application belongs to the field of optical imaging technology, and specifically relates to an optical imaging system and electronic equipment. Background Art

[0002] In recent years, with the rapid development of portable electronic products with photographic functions, the requirements for miniaturized optical imaging systems have also increased.

[0003] However, in order to meet the needs of market development, traditional optical imaging systems often inevitably use more than three refractive lenses to ensure imaging quality, but this will cause the optical imaging system to be larger in size, which is not conducive to the miniaturization of portable electronic products. Utility Model Content

[0004] The purpose of the embodiments of the present application is to provide an optical imaging system and an electronic device, which can solve the problem of large size of the optical imaging system in the related art.

[0005] In a first aspect, an embodiment of the present application provides an optical imaging system, comprising: a positive lens, a negative lens and a meta-lens, wherein the negative lens, the positive lens and the meta-lens are arranged in sequence in the direction of the optical axis of the optical imaging system and in the direction from the object side to the imaging surface, the negative lens is used to diffuse light, the positive lens is used to focus light, at least one of the object side surface or the image side surface of the meta-lens is a meta-surface, and the meta-surface includes at least two micro-structures arranged at intervals.

[0006] In a second aspect, an embodiment of the present application provides an electronic device, including: the optical imaging system described above.

[0007] In an embodiment of the present application, the optical imaging system includes a meta-lens, and the metasurface of the meta-lens includes at least two spaced-apart microstructures. The phase of each position of the meta-lens can be adjusted by the structural parameters of the microstructure, which enables the meta-lens to have a large degree of freedom and can produce any phase surface shape, so that one meta-lens can replace at least two refractive lenses. In this way, under the same imaging requirements, the light imaging system provided by the embodiment of the present application is smaller in volume than the traditional optical imaging system composed of refractive lenses. In addition, since the volume of the meta-lens is smaller than that of the refractive lens, even if only one refractive lens is replaced by the meta-lens, the volume of the traditional optical imaging system can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A schematic diagram of ray tracing of an optical imaging system disclosed in an embodiment of the present application;

[0009] Figure 2This is a schematic diagram of the structure of the meta-lens disclosed in the embodiment of the present application at a first viewing angle;

[0010] Figure 3 A schematic diagram of the partial structure of the meta-lens disclosed in an embodiment of the present application at a second viewing angle;

[0011] Figure 4 A schematic diagram of the structure of the microstructure disclosed in the embodiment of the present application;

[0012] Figure 5 A schematic diagram of the arrangement of the microstructures disclosed in the embodiments of the present application;

[0013] Figure 6 A schematic diagram of the structure of the mask disclosed in the embodiment of the present application;

[0014] Figure 7 A design flow chart of the metasurface disclosed in the embodiments of the present application;

[0015] Figure 8 The modulation transfer function curve of the optical imaging system disclosed in the embodiment of the present application at an ambient temperature of 20° C. obtained by optical design software simulation;

[0016] Fig. 9 The modulation transfer function curve of the optical imaging system disclosed in the embodiment of the present application at an ambient temperature of 60° C. obtained by optical design software simulation;

[0017] Fig.10 The modulation transfer function curve of the optical imaging system disclosed in the embodiment of the present application at an ambient temperature of -40°C obtained by optical design software simulation;

[0018] Fig.11 The relative distortion curve diagram of the optical imaging system disclosed in the embodiment of the present application at an ambient temperature of 20° C. obtained by optical design software simulation;

[0019] Fig.12 The relative distortion curve diagram of the optical imaging system disclosed in the embodiment of the present application at an ambient temperature of 60° C. obtained by optical design software simulation;

[0020] Fig.13 The relative distortion curve diagram of the optical imaging system disclosed in the embodiment of the present application at an ambient temperature of -40°C obtained by optical design software simulation;

[0021] Fig.14 Schematic diagram of phase mutation and transmittance obtained at different diameters for the microstructure disclosed in the embodiment of the present application;

[0022] Fig.15 Schematic diagram of the phase difference between the reference phase at the central wavelength and the phase difference at the working band for microstructures with different diameters;

[0023] Fig.16 A target phase distribution diagram of the first metasurface microstructure array disclosed in an embodiment of the present application;

[0024] Fig.17 A target phase distribution diagram of the second metasurface microstructure array disclosed in an embodiment of the present application;

[0025] Fig.18 A target phase distribution diagram of the third metasurface microstructure array disclosed in an embodiment of the present application;

[0026] Fig.19 This is the target phase distribution diagram of the fourth metasurface microstructure array disclosed in the embodiment of the present application.

[0027] Description of reference numerals:

[0028] 100-positive lens, 100a-first positive lens, 100b-second positive lens, 100c-third positive lens;

[0029] 200-negative lens, 200a-first negative lens, 200b-second negative lens;

[0030] 300-meta-lens, 300a-first meta-lens, 300b-second meta-lens, 310-meta-surface, 311-microstructure, 320-substrate layer, 321-substrate;

[0031] 400-infrared focal plane detector, 410-detector window, 420-infrared focal plane array;

[0032] 500-light;

[0033] 600-mask, 610-exposure area. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0035] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0036] The optical imaging system and electronic device provided in the embodiments of the present application are described in detail below through specific embodiments and their application scenarios in conjunction with the accompanying drawings.

[0037] Please refer to Figures 1 to 5 As shown, an optical imaging system is disclosed in the embodiment of the present application. Specifically, the disclosed optical imaging system includes: a positive lens 100, a negative lens 200 and a meta-lens 300, and the positive lens 100 and the negative lens 200 are both a type of refractive lens. In the direction of the optical axis of the optical imaging system and from the object side to the imaging surface, that is, Figure 1 In the direction indicated by the middle arrow line, the negative lens 200, the positive lens 100 and the metalens 300 are arranged in sequence, the negative lens 200 is used to diffuse the light 500, the positive lens 100 is used to focus the light 500, at least one of the object side surface or the image side surface of the metalens 300 is a metasurface 310, and the metasurface 310 includes at least two spaced-apart microstructures 311. The metalens 300 is used, for example, to regulate the wavefront of the incident light.

[0038] In an embodiment of the present application, the optical imaging system includes a meta-lens 300, and the metasurface 310 of the meta-lens 300 includes at least two spaced microstructures 311, and the phase of each position of the meta-lens 300 can be adjusted by the structural parameters of the microstructure 311, which makes the meta-lens 300 have a large degree of freedom and can produce any phase surface shape, so that one meta-lens 300 can replace at least two refractive lenses. In this way, under the same imaging requirements, the optical imaging system provided by the embodiment of the present application is smaller in size than the traditional optical imaging system composed of refractive lenses. Furthermore, since the volume of the meta-lens 300 is smaller than the volume of the refractive lens, even if only one refractive lens is replaced by the meta-lens 300, the volume of the traditional optical imaging system can be reduced. In addition, compared with the traditional refractive lens, the meta-lens 300 is lighter and has a lower cost, so that the optical imaging system provided in the embodiment of the present application is lighter and has a lower cost.

[0039] In addition, during the specific use, the imaging beam, that is, Figure 1 The light 500 in the image is first diffused by the positive lens 100, then focused by the negative lens 200, and finally emitted after being regulated by the meta-lens 300. The overall light path of the optical imaging system is shown as Figure 1 The envelope-shaped trend of first diffusion and then focusing is shown, which is conducive to aberration correction, and the wavefront of the incident light is controlled by the meta-lens 300, so as to achieve high-resolution and substantially athermal imaging.

[0040] In another embodiment, reference Figure 1 As shown, the number of negative lenses 200 is, for example, at least two, including, for example, a first negative lens 200a and a second negative lens 200b, and in the direction of the optical axis and from the object side to the imaging surface, the first negative lens 200a, the second negative lens 200b and the positive lens 100 are, for example, arranged in sequence. During specific use, the first negative lens 200a and the second negative lens 200b cooperate with each other to achieve a preset light diffusion effect. The first negative lens 200a and the second negative lens 200b can, for example, continuously diffuse the light 500 in the direction of the optical axis and from the object side to the imaging surface.

[0041] It can be understood that the number of negative lenses 200 is not limited to at least two, but can be any number. For example, in other optional embodiments, the number of negative lenses 200 can be one, and is not limited to including the first negative lens 200a and the second negative lens 200b. This is just an example.

[0042] Further, as a specific implementation method, refer to Figure 1 As shown, the object side surface of the first negative lens 200a is, for example, a concave surface, and the image side surface of the first negative lens 200a is, for example, a convex surface. The object side surface of the second negative lens 200b is, for example, a convex surface, and the image side surface of the second negative lens 200b is, for example, a concave surface. In this way, the first negative lens 200a and the second negative lens 200b are both roughly meniscus-shaped, and the meniscus-shaped design can make the optical power of the first negative lens 200a and the second negative lens 200b more evenly distributed on the object side and the image side, so that the bending uniformity of the light on the two interfaces is better, thereby reducing spherical aberration. In addition, setting the side of the first negative lens 200a facing the image side as a convex surface can make the illumination of the imaging surface more uniform, and setting the side of the second negative lens 200b facing the object side as a convex surface can greatly reduce spherical aberration.

[0043] It should be noted that the present application does not limit the shapes of the object-side surface and the image-side surface of the first negative lens 200 a and the shapes of the object-side surface and the image-side surface of the second negative lens 200 b , which are only used as examples for illustration.

[0044] In another embodiment, reference Figure 1As shown, the number of positive lenses 100 is at least two, including a first positive lens 100a, a second positive lens 100b and a third positive lens 100c; in the direction of the optical axis and from the object side to the imaging surface, the negative lens 200, the first positive lens 100a, the second positive lens 100b, the third positive lens 100c and the meta-lens 300 are sequentially arranged. In the specific use process, the first positive lens 100a, the second positive lens 100b and the third positive lens 100c cooperate with each other to achieve a preset light diffusion effect.

[0045] It can be understood that the number of the positive lenses 100 is not limited to at least two, and can be any number. For example, in other optional embodiments, the number of the positive lens 100 can be one, and is not limited to including the first positive lens 100a, the second positive lens 100b and the third positive lens 100c mentioned above. The first positive lens 100a, the second positive lens 100b and the third positive lens 100c are only examples.

[0046] Further, as a specific implementation method, refer to Figure 1 As shown, the object side surface of the first positive lens 100a is, for example, a concave surface, and the image side surface of the first positive lens 100a is, for example, a convex surface; the object side surface of the second positive lens 100b is, for example, a convex surface, and the image side surface of the second positive lens 100b is, for example, a plane surface; the object side surface of the third positive lens 100c is, for example, a convex surface, and the image side surface of the third positive lens 100c is, for example, a concave surface. As described above, in this arrangement, the first positive lens 100a and the third positive lens 100c are both roughly meniscus-shaped, and the meniscus-shaped design can make the optical power of the first positive lens 100a and the third positive lens 100c more evenly distributed on the object side and the image side, so that the bending uniformity of the light on the two interfaces is better, thereby reducing spherical aberration. In addition, setting the side of the first positive lens 100a facing the image side as a convex surface can make the illumination of the imaging surface more uniform, and setting the side of the third positive lens 100c facing the object side as a convex surface can greatly reduce spherical aberration.

[0047] It should be noted that the present application does not limit the shapes of the object-side surface and the image-side surface of the first positive lens 100a, the object-side surface and the image-side surface of the second positive lens 100b, and the object-side surface and the image-side surface of the third positive lens 100c, and they are only used as examples for illustration.

[0048] Furthermore, the optical imaging system provided in this embodiment may also include the first negative lens 200a and the second negative lens 200b in the above embodiment. In this case, the first negative lens 200a, the second negative lens 200b, the first positive lens 100a, the second positive lens 100b, the third positive lens 100c and the meta-lens 300 are arranged in sequence in the direction of the optical axis and from the object side to the imaging surface.

[0049] Further, as a specific implementation method, refer to Figure 1 As shown, the object side surface and the image side surface of the first positive lens 100a and the object side surface and the image side surface of the third positive lens 100c are, for example, arc-shaped structures, and the curvature of the image side surface of the first positive lens 100a is, for example, smaller than the curvature of the object side surface of the third positive lens 100c.

[0050] In another embodiment, at least one of the object side surface and the image side surface of the positive lens 100 and one of the object side surface and the image side surface of the negative lens 200 are spherical mirror surfaces or even-order aspherical mirror surfaces. Both the spherical mirror surface and the even-order aspherical mirror surface are symmetrical structures, so that the processing and installation of the positive lens 100 and the negative lens 200 are relatively convenient.

[0051] Furthermore, the surface shape of the even-order aspheric mirror satisfies the following relationship:

[0052]

[0053] Wherein, z is the distance vector height from the vertex of the even-order aspheric mirror surface at the radial coordinate position r along the direction of the optical axis and from the object side to the imaging surface, c is the curvature of the even-order aspheric mirror surface, R is the radius of curvature of the even-order aspheric mirror surface, r is the radial coordinate perpendicular to the optical axis, that is, the radial coordinate perpendicular to the optical axis, k is the quadratic curve constant, N i is the coefficient of each order of even-order aspheric surface, and i is a positive integer. It should be noted that the vertex of the even-order aspheric surface refers to the intersection of the optical axis and the even-order aspheric surface.

[0054] Of course, in other optional embodiments, the surface shape of the even-order aspheric mirror surface may also satisfy other relationship expressions, and the embodiments of the present application do not limit this.

[0055] In another embodiment, both the object side and the image side of the metalens 300 are metasurfaces 310. With this arrangement, both the object side and the image side of the metalens 300 can regulate the light 500, so that the metalens 300 has better light regulation capability and can meet higher light regulation requirements.

[0056] In other optional embodiments, only one of the object-side surface and the image-side surface of the metalens 300 may be configured as the metasurface 310 .

[0057] In another embodiment, reference Figure 1As shown, the number of metalenses 300 is at least two, including a first metalens 300a and a second metalens 300b, and in the direction of the optical axis and from the object side to the imaging surface, the positive lens 100, the first metalens 300a and the second metalens 300b are sequentially arranged. In the solution adopted in this embodiment, both the first metalens 300a and the second metalens 300b can regulate the light 500, so that the optical imaging system has a strong light regulation capability and can meet higher imaging requirements.

[0058] In other optional embodiments, the number of the meta-lens 300 may also be one.

[0059] Furthermore, in this embodiment, the object side surface and the image side surface of each metalens 300 can both be a metasurface 310. In this way, the light control capability of the optical imaging system can be further enhanced.

[0060] Furthermore, the number of positive lenses 100 is, for example, at least two, and includes, for example, the first positive lens 100a, the second positive lens 100b, and the third positive lens 100c. In this case, in the direction of the optical axis and in the direction from the object side to the imaging surface, the first positive lens 100a, the second positive lens 100b, the third positive lens 100c, the first meta-lens 300a, and the second meta-lens 300b are, for example, arranged in sequence.

[0061] In another embodiment, the microstructure 311 is, for example, a cylindrical structure, and each microstructure 311 of the metasurface 310 is, for example, arranged in a tetragonal lattice periodic array. In this arrangement, the microstructure 311 itself and the arrangement of the microstructure 311 are symmetrical, so that the processing of the metasurface 310 is more convenient.

[0062] Specifically, the microstructure 311 is processed by, for example, step-by-step photolithography and inductively coupled plasma etching (ICP) and other processes. In order to compress the size of the layout file and facilitate mass production, only one mask 600 is used in the step-by-step photolithography process. Figure 6As shown, the layout design of the exposure area 610 on the mask 600 is a microstructure array in a fan-shaped area with the center of the metasurface 310 as the vertex angle and an angle of 90 degrees. The symmetry of the microstructure 311 and the arrangement of the microstructure 311 is utilized, and stepping lithography is performed four times, exposing a quarter circle area each time. After each exposure, the mask 600 is rotated 90 degrees to continue exposing the next quarter circle area, so that the four exposure areas 610 are spliced ​​into an exposure area of ​​a metalens 300, and a photoresist pattern of the microstructure array of the metasurface 310 is generated. The complete exposure area corresponding to the metalens 300 is a circular structure; ICP etching, for example, adopts a deep silicon etching process, and uses the photoresist pattern generated by stepping lithography as an etching mask to obtain a high aspect ratio metasurface 310 microstructure array.

[0063] refer to Figure 2 As shown, the metasurface 310 further includes a substrate layer 320, and each microstructure 311 is disposed on the object side of the substrate layer 320, so that the object side of the metalens 300 is the metasurface 310, and / or each microstructure 311 is disposed on the image side of the substrate layer 320, so that the image side of the metalens 300 is the metasurface 310. Figure 5 As shown, when the microstructures 311 are arranged in a tetragonal lattice periodic array, the base layer 320 can be equivalent to at least two sub-bases 321, and the cross-section of the sub-base 321 in the direction perpendicular to the optical axis is a square. The axial direction of the microstructure 311 is, for example, set along the thickness direction of the base layer 320. It should be noted that the diameter of the microstructure 311 is Figure 4 The height of the microstructure 311 is Figure 4 The array period of the microstructure 311 is Figure 5 It should be noted that the L in the array of the microstructures 311 refers to the distance between the axes of two adjacent microstructures 311 .

[0064] In another embodiment, the phase of the metasurface 310 The distribution of satisfies the following relationship:

[0065]

[0066] Wherein, ρ is the normalized radial coordinate of the metasurface 310, R is the normalized radius of the metasurface 310, A, B, C and D are the quadratic coefficient, quartic coefficient, sextic coefficient and octadic coefficient of the metasurface 310, respectively, and 2πrad is the phase Unit of.

[0067] In the case where the microstructure 311 is a cylindrical structure, for example, the microstructures 311 of the metasurface 310 are arranged in a tetragonal lattice periodic array, and the object side and image side of the positive lens 100 and the object side and image side of the negative lens 200 are all even-order aspherical mirror surfaces in the above-mentioned embodiment, Figure 7 As shown, the design method of the metasurface 310 includes, for example, the following steps:

[0068] S101, using a rigorous coupled wave analysis method, calculating the phase mutation and phase difference value distribution introduced by the microstructures 311 with different radii when light with a characteristic wavelength in the working band is incident, and obtaining a plurality of groups of radius-phase mutation-phase difference value distributions corresponding to each other to form a microstructure unit library, wherein the light with a characteristic wavelength in the working band is, for example, light with a characteristic wavelength of long-wave infrared;

[0069] S102, determining a target phase distribution of the tetragonal lattice periodic array of the metasurface 310 with the goal of enabling the metalens 300 to perform wavefront control on the incident light 500 and correct the higher-order aberrations of the incident light 500;

[0070] S103, for any tetragonal lattice, selecting multiple groups of radius-phase mutation-phase difference distributions corresponding to phase mutations from a microstructure unit library according to the target phase of the tetragonal lattice;

[0071] S104, with the goal of achieving the highest consistency in the distribution of phase difference values ​​of each tetragonal lattice in the same metasurface 310, the radius of the microstructure 311 at each tetragonal lattice is determined from the results selected in step S103.

[0072] It should be noted that the radius of the microstructure 311 in step S101 satisfies: the phase mutations corresponding to all radii cover 0-2π. For a microstructure 311 of any radius, calculating its phase difference value in the working band in S101 includes: calculating the phase mutation introduced by the microstructure 311 of any radius when the light in the working band is incident with the maximum wavelength, and the phase mutation introduced when the light in the working band is incident with the minimum wavelength; calculating the difference between the phase mutation corresponding to the maximum wavelength and the phase mutation corresponding to the minimum wavelength to obtain the phase difference value.

[0073] In another embodiment, the optical imaging system further includes an infrared focal plane detector 400. In the direction of the optical axis and from the object side to the imaging surface, the negative lens 200, the positive lens 100, the meta-lens 300 and the infrared focal plane detector 400 are sequentially arranged. During specific use, the infrared focal plane detector 400 can filter out stray light and light 500 outside the detection band, thereby improving the imaging quality.

[0074] In other optional embodiments, the optical imaging system may not be provided with the infrared focal plane detector 400 .

[0075] As a specific implementation method, refer to Figure 1 As shown, the infrared focal plane detector 400 includes, for example, a detector window 410 and an infrared focal plane array 420 which are sequentially arranged in the direction of the optical axis and in the direction from the object side to the imaging surface. The detector window 410 is used to filter out stray light of the optical imaging system and light outside the detection band, and the infrared focal plane array 420 is used to detect and image the focused infrared light incident light.

[0076] As a specific implementation, the material of the positive lens 100 is, for example, at least one of germanium, barium fluoride, zinc sulfide, zinc selenide, and chalcogenide glass. The material of the negative lens 200 is, for example, at least one of germanium, barium fluoride, zinc sulfide, zinc selenide, and chalcogenide glass. The material of the detector window 410 is, for example, at least one of germanium, barium fluoride, zinc sulfide, zinc selenide, and chalcogenide glass. The materials of the microstructure 311 and the base layer 320 are, for example, intrinsic single crystal silicon, and the chalcogenide glass is, for example, infrared glass (InfraRed Glass, IRG).

[0077] In a further embodiment, the number of negative lenses 200 is, for example, at least two, including the first negative lens 200a and the second negative lens 200b described above, the number of positive lenses 100 is, for example, at least two, including the first positive lens 100a, the second positive lens 100b and the third positive lens 100c described above, and the number of meta-lenses 300 is, for example, at least two, including the first meta-lens 300a and the second meta-lens 300b described above. At this time, referring to Figure 1 As shown, in the direction of the optical axis and from the object side to the imaging surface, the first negative lens 200a, the second negative lens 200b, the first positive lens 100a, the second positive lens 100b, the third positive lens 100c, the first metalens 300a, the second metalens 300b, the detector window 410 and the infrared focal plane array 420 are arranged in sequence.

[0078] In this embodiment, the positive lens 100 is made of, for example, an infrared germanium glass material, and the negative lens 200 is made of, for example, a chalcogenide glass material. The object side and image side of the first metalens 300a and the object side and image side of the second metalens 300b are, for example, both a metasurface 310. The microstructure 311 is, for example, a cylindrical structure, and each microstructure 311 of the metasurface 310 is, for example, arranged in a tetragonal lattice periodic array.

[0079] In this embodiment, the object side surface and the image side surface of the positive lens 100 and the object side surface and the image side surface of the negative lens 200 are, for example, even-order aspheric mirror surfaces, and the surface shapes of the even-order aspheric mirror surfaces satisfy the following relationship, for example:

[0080]

[0081] Wherein, z is the distance vector height from the vertex of the even-order aspheric mirror at the radial coordinate r position along the direction of the optical axis and from the object side to the imaging surface, c is the curvature of the best-fit sphere of the even-order aspheric mirror, r is the radial coordinate perpendicular to the optical axis, k is the quadratic curve constant, A is the second-order aspheric coefficient of the even-order aspheric mirror, B is the fourth-order aspheric coefficient of the even-order aspheric mirror, C is the sixth-order aspheric coefficient of the even-order aspheric mirror, and D is the eighth-order aspheric coefficient of the even-order aspheric mirror.

[0082] In this embodiment, the phase of the microstructure 311 The distribution of satisfies the following relationship:

[0083]

[0084] Wherein, ρ is the normalized radial coordinate of the hypersurface 310, R is the normalized radius of the hypersurface 310, and A, B, C and D are the quadratic coefficient, quartic coefficient, sixth coefficient and octadecane coefficient of the hypersurface 310, respectively.

[0085] The following table 1 shows the technical indicators achieved by this embodiment, wherein the calculation formula for the F number of the optical imaging system is f / D, f is the focal length of the optical imaging system, and D is the diameter of the entrance pupil. In addition, the optical structural parameters of the first negative lens 200a, the second negative lens 200b, the first positive lens 100a, the second positive lens 100b, and the third positive lens 100c are determined by the ray tracing method, as shown in the following table 2, the cone coefficients and the values ​​of the even-order aspheric coefficients of the first negative lens 200a, the second negative lens 200b, the first positive lens 100a, the second positive lens 100b, and the third positive lens 100c are shown in the following table 3, and the structural parameters of the metasurface are shown in the following table 4. For the convenience of description, in the direction of the optical axis and from the object side to the imaging surface, the two metasurfaces 310 of the first meta-lens 300a are defined as the first meta-surface and the second meta-surface, respectively, and the two meta-surfaces 310 of the second meta-lens 300b are defined as the third meta-surface and the fourth meta-surface, respectively, and A in Table 4 i , B i , C i , D i They respectively refer to the quadratic coefficient, the quartic coefficient, the sixth coefficient and the octadecane coefficient of the metasurface 310. In addition, IRG206 in the following Table 2 is a type of infrared glass.

[0086] Table 1 Technical indicators achieved by the embodiment

[0087]

[0088] Table 2 Light structure parameters of positive lens and negative lens

[0089]

[0090] Table 3 Conic coefficients of positive and negative lenses and values ​​of even-order aspheric coefficients of each order

[0091]

[0092] Table 4. Related parameters of metasurface

[0093] R(mm) <![CDATA[A i ]]> <![CDATA[B i ]]> <![CDATA[C i ]]> <![CDATA[D i ]]> First metasurface (i=1) 1.000 -1.643E+001 1.369E-002 -4.800E-005 6.376E-008 Second metasurface (i=2) 1.000 1.659E+001 -2.641E-002 9.449E-005 -1.098E-007 The third metasurface (i=2) 1.000 -4.251E-001 6.6230E-002 -2.121E-004 1.510E-007 The fourth metasurface (i=2) 1.000 3.078E-001 -5.084E-002 1.505E-004 -8.043E-008

[0094] Figure 8 is the modulation transfer function curve disclosed in the embodiment of the present application at an ambient temperature of 20° C. obtained by optical design software simulation. Fig. 9 The modulation transfer function curve disclosed in the embodiment of the present application at an ambient temperature of 60° C. obtained by optical design software simulation. Fig.10 The modulation transfer function curve disclosed in the embodiment of the present application at an ambient temperature of -40°C obtained by optical design software simulation is Figures 8 to 10 It can be seen that at the cutoff frequency of 42lp / mm corresponding to the detector with a pixel size of 12μm, the full-field modulation transfer function is greater than 0.4, close to the diffraction limit, and high-resolution imaging can be achieved. Figure 8 , Fig. 9 as well as Fig.10 The horizontal coordinates are all spatial frequencies, and the vertical coordinates are all modulation transfer functions. Figure 8 , Fig. 9 as well as Fig.10 The lines in the figure respectively indicate the modulation transfer function of the optical imaging system in the meridional direction under the diffraction limit, the modulation transfer function of the optical imaging system in the sagittal direction under the diffraction limit, the modulation transfer function of the optical imaging system in the meridional direction under zero field of view, the modulation transfer function of the optical imaging system in the sagittal direction under zero field of view, the modulation transfer function of the optical imaging system in the meridional direction under the maximum field of view, the modulation transfer function of the optical imaging system in the sagittal direction under the maximum field of view, the modulation transfer function of the optical imaging system in the meridional direction with field of view, and the modulation transfer function of the optical imaging system in the sagittal direction with field of view. It should be noted that Figure 8 , Fig. 9 as well as Fig.10 The modulation transfer function of the optical imaging system in the meridional direction under the medium diffraction limit coincides with the modulation transfer function of the optical imaging system in the sagittal direction under the diffraction limit, and the modulation transfer function of the optical imaging system in the meridional direction under zero field of view coincides with the modulation transfer function of the optical imaging system in the sagittal direction under zero field of view.

[0095] Fig.11 This is a relative distortion curve diagram of the optical imaging system provided by this embodiment at an ambient temperature of 20° C. obtained by optical design software simulation. Fig.12 This is a relative distortion curve diagram of the optical imaging system provided by this embodiment at an ambient temperature of 60° C. obtained by optical design software simulation. Fig.13 The relative distortion curve of the optical imaging system provided by this embodiment at an ambient temperature of -40°C obtained by optical design software simulation. Figures 11 to 13 It can be seen that the optical imaging system provided in this embodiment has barrel distortion, and the relative distortion of the entire field of view is less than 10%. Fig.11 , Fig.12 as well as Fig.13 The horizontal coordinates are the relative distortion of the optical imaging system, and the vertical coordinates are the field of view angles. Fig.11 , Fig.12 as well as Fig.13 The lines in the figure respectively indicate the relative distortion of the optical imaging system when the wavelength of the incident light is 8 μm, the relative distortion of the optical imaging system when the wavelength of the incident light is 10 μm, and the relative distortion of the optical imaging system when the wavelength of the incident light is 12 μm.

[0096] The method for designing the metasurface 310 of the optical imaging system provided in this embodiment includes, for example, the following steps:

[0097] S1, using the rigorous coupled wave analysis method, calculate the phase mutation and phase difference value distribution introduced by microstructures 311 of different radii when light of long-wave infrared characteristic wavelength is incident, and obtain multiple sets of corresponding radius-phase mutation-phase difference value distribution to form a microstructure unit library. The schematic diagram of microstructure 311 is shown in Figure 4 As shown in FIG. 1 , the radius, height, array period and other parameters of the microstructure 311 are optimized by using the vector electromagnetic field numerical simulation algorithm and the rigorous coupled wave analysis method, and the relationship between the radius and the phase is obtained. The phase mutation and transmittance of the microstructure 311 at different radii are shown in FIG. Fig.14 As shown, the height of the optimized microstructure 311 is 14 μm, and the period of the microstructure 311 is 2.7 μm.

[0098] In this embodiment, for a microstructure 311 of any radius, calculating its phase difference distribution in the long-wave infrared in step S1 includes: calculating the phase mutation introduced by the microstructure 311 of any radius when the long-wave infrared light is incident at the maximum wavelength, and the phase mutation introduced when the long-wave infrared light is incident at the minimum wavelength; calculating the difference between the phase mutation corresponding to the maximum wavelength and the phase mutation corresponding to the minimum wavelength, to obtain the phase difference distribution.

[0099] The radius of the microstructure 311 selected in step S1 satisfies: in the microstructure unit library, all phase mutations corresponding to the radii cover 0-2π. Phase mutations covering 0-2π means that for any phase mutation within the range of 0-2π, there are one or more radii corresponding to the phase mutation.

[0100] In this embodiment, assuming that the radius of the microstructure 311 is selected within the interval (d1, d2), the interval can be divided into several sub-intervals. In each sub-interval, the phase mutation increases as the radius increases, and the phase mutation in the sub-interval covers 0-2π. Therefore, any phase mutation within the range of 0-2π has several corresponding radii corresponding to it.

[0101] Taking the radius of microstructure 311 as d, the characteristic wavelength of long-wave infrared as 10 μm, the minimum wavelength of long-wave infrared as 8 μm, and the maximum wavelength of long-wave infrared as 12 μm as an example, in step S1, the phase mutation of microstructure 311 with radius d at 8 μm, 10 μm, and 12 μm is calculated by using the rigorous coupled wave analysis method. The phase mutation Φ at the characteristic wavelength of 10 μm is the reference phase. The difference between the phase mutation at the maximum wavelength of 12 μm and the phase mutation at the minimum wavelength of 10 μm is the phase difference distribution D. Based on this, a set of corresponding radius d-phase mutation Φ-phase difference distribution D is obtained. Select a new radius d multiple times and repeat the above steps to obtain multiple sets of radius d-phase mutation Φ-phase difference distribution D to form a microstructure unit library, such as Fig.15 shown.

[0102] Fig.15 Each data point in corresponds to a microstructure 311 of a specific radius, the horizontal axis value of the point reflects the corresponding phase mutation, and the vertical axis value reflects the corresponding phase difference value distribution. For example, the data point at the origin indicates that the phase mutation of the microstructure 311 with a radius of 0 nm is 0 and the phase difference value distribution is 0.

[0103] S2, with the goal of enabling the metalens 300 to perform wavefront control on the incident light 500 and correct the higher-order aberrations of the incident light 500, determine the target phase distribution of the tetragonal lattice periodic array of the metasurface 310.

[0104] The first metasurface, the second metasurface, the third metasurface, and the fourth metasurface are respectively composed of microstructure arrays arranged according to a certain phase distribution, and the phase distribution of the metasurface 310 satisfies the following relationship:

[0105]

[0106] Wherein, ρ is the normalized radial coordinate of the hypersurface 310, R is the normalized radius of the hypersurface 310, and A, B, C and D are the quadratic coefficient, quartic coefficient, sixth coefficient and octadecane coefficient of the hypersurface 310, respectively.

[0107] Specifically, in step S2, the second-order coefficient, fourth-order coefficient, sixth-order coefficient and eighth-order coefficient of the metasurface 310, that is, the above-mentioned A, B, C and D are optimized by ray tracing method, with the goal of enabling the metalens 300 to perform wavefront control on the incident light 500 and correct the higher-order aberrations of the incident light 500. For specific values, see Table 4 above, so as to determine the target phase distribution of the tetragonal lattice periodic arrays of the first metasurface, the second metasurface, the third metasurface and the fourth metasurface. The ray tracing schematic diagram of the optical imaging system provided in this embodiment is shown in FIG. Figure 1 The target phase distribution diagram of the first metasurface microstructure array obtained by optimization is shown in Fig.16 As shown, the target phase distribution diagram of the second metasurface microstructure array is as follows Fig.17 As shown, the target phase distribution diagram of the third metasurface microstructure array is as follows Fig.18 As shown, the target phase distribution diagram of the fourth metasurface microstructure array is as follows Fig.19 shown. Fig.16 , Fig.17 , Fig.18 as well as Fig.19 The horizontal axis represents the horizontal coordinate of a point on the metasurface 310, the vertical axis represents the vertical coordinate of a point on the metasurface 310, and the gray value represents the required phase value at the point.

[0108] S3, for any tetragonal lattice, multiple groups of radius-phase mutation-phase difference distributions of corresponding phase mutations are selected from the microstructure unit library according to the target phase of the tetragonal lattice.

[0109] There is a one-to-one correspondence between the target phase Φ′ and the phase mutation Φ, and one phase mutation Φ corresponds to multiple radii. Based on this, for any tetragonal lattice, according to its target phase, multiple sets of corresponding radius-phase mutation-phase difference distributions can be selected from the microstructure unit library. The phase mutations of these multiple sets of radius-phase mutation-phase difference distributions are the same and correspond to the target phase of the tetragonal lattice.

[0110] S4, with the goal of achieving the highest consistency in the distribution of phase difference values ​​of each tetragonal lattice in the same metasurface 310, the radius of the microstructure 311 at each tetragonal lattice is determined from the results selected in step S3.

[0111] In this embodiment, step S3 determines multiple sets of alternative solutions for the radius of the microstructure 311 at each tetragonal lattice.

[0112] Step S4 comprehensively considers the phase difference distribution of all tetragonal lattices, with the goal of making the phase difference distribution at each location the most consistent, and determines the corresponding optimal solution (optimal radius-phase mutation-phase difference distribution) for the radius of the microstructure 311 at each tetragonal lattice, and determines the radius in the optimal solution as the radius of the microstructure 311 at the corresponding tetragonal lattice.

[0113] An embodiment of the present application also provides an electronic device, which includes the optical imaging system described above, and the electronic device is, for example, a camera or a lens.

[0114] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. An optical imaging system, characterized in that: include: A positive lens (100), a negative lens (200) and a meta-lens (300), wherein the negative lens (200), the positive lens (100) and the meta-lens (300) are arranged in sequence in the direction of the optical axis of the optical imaging system and in the direction from the object side to the imaging surface, the negative lens (200) is used to diffuse the light (500), the positive lens (100) is used to focus the light (500), at least one of the object side surface or the image side surface of the meta-lens (300) is a meta-surface (310), and the meta-surface (310) includes at least two spaced-apart micro-structures (311).

2. The optical imaging system according to claim 1, characterized in that: The number of the negative lenses (200) is at least two, including a first negative lens (200a) and a second negative lens (200b); in the direction of the optical axis and in the direction from the object side to the imaging surface, the first negative lens (200a), the second negative lens (200b) and the positive lens (100) are arranged in sequence; the object side surface of the first negative lens (200a) is a concave surface, and the image side surface of the first negative lens (200a) is a convex surface; the object side surface of the second negative lens (200b) is a convex surface, and the image side surface of the second negative lens (200b) is a concave surface.

3. The optical imaging system according to claim 1, characterized in that: The number of the positive lenses (100) is at least two, including a first positive lens (100a), a second positive lens (100b) and a third positive lens (100c); in the direction of the optical axis and in the direction from the object side to the imaging surface, the negative lens (200), the first positive lens (100a), the second positive lens (100b), the third positive lens (100c) and the meta-lens (300) are arranged in sequence; the object side surface of the first positive lens (100a) is a concave surface, and the image side surface of the first positive lens (100a) is a convex surface; the object side surface of the second positive lens (100b) is a convex surface, and the image side surface of the second positive lens (100b) is a flat surface; the object side surface of the third positive lens (100c) is a convex surface, and the image side surface of the third positive lens (100c) is a concave surface.

4. The optical imaging system according to claim 3, characterized in that: The object side surface and the image side surface of the first positive lens (100a) and the object side surface and the image side surface of the third positive lens (100c) are all arc-shaped structures, and the curvature of the image side surface of the first positive lens (100a) is smaller than the curvature of the object side surface of the third positive lens (100c).

5. The optical imaging system according to claim 1, characterized in that: At least one of the object side surface and the image side surface of the positive lens (100) and one of the object side surface and the image side surface of the negative lens (200) are spherical mirror surfaces or even-order aspherical mirror surfaces, and the surface shape of the even-order aspherical mirror surface satisfies the following relationship: Wherein, z is the distance vector height from the vertex of the even-order aspheric mirror surface at the radial coordinate position r along the direction of the optical axis and from the object side to the imaging surface, c is the curvature of the best fitting sphere of the even-order aspheric mirror surface, r is the radial coordinate perpendicular to the optical axis, k is the quadratic curve constant, N i are the even-order aspheric coefficients of each order, and i is a positive integer.

6. The optical imaging system according to claim 1, characterized in that: The object side surface and the image side surface of the meta-lens (300) are both the meta-surface (310); And / or, the number of the metalens (300) is at least two, including a first metalens (300a) and a second metalens (300b), and in the direction of the optical axis and in the direction from the object side to the imaging surface, the positive lens (100), the first metalens (300a) and the second metalens (300b) are arranged in sequence.

7. The optical imaging system according to claim 1, characterized in that: The microstructure (311) is a cylindrical structure, and each of the microstructures (311) of the super surface (310) is arranged in a tetragonal lattice periodic array.

8. The optical imaging system according to claim 1, characterized in that: The phase of the metasurface (310) The distribution of satisfies the following relationship: Wherein, ρ is the normalized radial coordinate of the hypersurface (310), R is the normalized radius of the hypersurface (310), and A, B, C and D are the quadratic coefficient, quartic coefficient, sextic coefficient and octatic coefficient of the hypersurface (310), respectively.

9. The optical imaging system according to claim 1, characterized in that: The optical imaging system further comprises an infrared focal plane detector (400), wherein the negative lens (200), the positive lens (100), the meta-lens (300) and the infrared focal plane detector (400) are arranged in sequence in the direction of the optical axis and in the direction from the object side to the imaging surface.

10. An electronic device, characterized in that: Comprising the optical imaging system as described in any one of claims 1-9.

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