Compound lens and optical system comprising the same

Abstract

The embodiment of the application provides a kind of composite lens and the optical system comprising it, belong to optical superlens technical field.The composite lens includes the first lens and the second lens sequentially arranged from object side to image side;Wherein, the first lens is the refractive lens with positive focal length;The second lens is superlens;The object side surface and the image side surface of the first lens are aspherical surface;The first lens and the second lens also satisfy: t 12 ≤0.5mm;R 1i >R 1O ;Wherein, t 12 The interval of the first lens and the second lens is f1;The focal length of the first lens is f2;The focal length of the second lens is R 1o The radius of curvature of the object side surface of the first lens is R 1i The radius of curvature of the image side surface of the first lens is used.The composite lens is used in optical system to promote the miniaturization and light weight of five-piece optical system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical superlenses, and in particular, the present application relates to a composite lens and an optical system comprising the same. BACKGROUND

[0002] With the development of technology, miniaturization and lightness of electronic devices are increasingly important. In the process of miniaturization of electronic devices, miniaturization and lightness of optical systems are an important link.

[0003] However, as users' requirements for the imaging quality of optical systems increase, the number of lenses needs to be increased in order to improve the imaging quality of optical systems. This in turn increases the total length of the optical system, which is not conducive to the miniaturization and lightness of electronic devices.

[0004] Therefore, there is an urgent need for a miniaturized optical system. SUMMARY

[0005] In order to solve the problem that the miniaturization of the optical system is limited by the number of lens pieces in the prior art, the embodiments of the present application provide a composite lens and an optical system comprising the same.

[0006] In a first aspect, the embodiments of the present application provide a composite lens, which comprises a first lens and a second lens arranged in order from an object side to an image side;

[0007] wherein the first lens is a refractive lens with a positive focal length; and the second lens is a superlens;

[0008] The object side surface and the image side surface of the first lens are both aspherical surfaces;

[0009] The first lens and the second lens also satisfy:

[0010] t 12 ≤ 0.5 mm;

[0011]

[0012] R 1i > 0; 1O

[0013] wherein t 12 is the distance between the first lens and the second lens; f1 is the focal length of the first lens; f2 is the focal length of the second lens; R 1o is the radius of curvature of the object side surface of the first lens; and R 1i is the radius of curvature of the image side surface of the first lens.

[0014] Optionally, the second lens comprises a substrate layer and at least one nanostructure layer arranged on the substrate layer.​

[0015] Each of the at least one nanostructure layer comprises periodically arranged nanostructures.

[0016] Optionally, the arrangement period of the nanostructures in any of the at least one nanostructure layer is greater than or equal to 0.3λ c and less than or equal to 2λ c .

[0017] wherein λ c is the center wavelength of the second lens working waveband.

[0018] Optionally, the height of the nanostructures in any of the at least one nanostructure layer is greater than or equal to 0.3λ c and less than or equal to 5λ c .

[0019] wherein λ c is the center wavelength of the second lens working waveband.

[0020] Optionally, any of the at least one nanostructure layer comprises superstructure units arranged in an array.

[0021] The superstructure units are a close-packed pattern, and the nanostructures are arranged at the vertex and / or center position of the close-packed pattern.

[0022] Optionally, the extinction coefficient of the material of the substrate layer to the working waveband is less than 0.01.

[0023] Optionally, the extinction coefficient of the material of the nanostructures to the working waveband is less than 0.01.

[0024] Optionally, the material of the substrate layer comprises fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon and hydrogenated amorphous silicon.

[0025] Optionally, the material of the nanostructures comprises fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon and hydrogenated amorphous silicon.

[0026] Optionally, the material of the nanostructures is different from the material of the substrate layer.

[0027] Optionally, the material of the nanostructures is the same as the material of the substrate layer.

[0028] Optionally, the shape of the nanostructures is a polarization-insensitive structure.

[0029] Optionally, the polarization-insensitive structure comprises a cylinder, a hollow cylinder, a circular hole, a hollow circular hole, a square cylinder, a square hole, a hollow square cylinder, and a hollow square hole.

[0030] Optionally, the second lens further comprises a filler;

[0031] The filler fills between the nanostructures.

[0032] And the extinction coefficient of the material of the filler to the working waveband is less than 0.01.

[0033] Optionally, the absolute value of the difference between the refractive index of the filler and the refractive index of the nanostructure is greater than or equal to 0.5.

[0034] Optionally, the filler comprises air, fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, and hydrogenated amorphous silicon.

[0035] Optionally, the material of the filler is different from the material of the substrate layer.

[0036] Optionally, the material of the filler is different from the material of the nanostructure.

[0037] Optionally, the second lens further comprises an anti-reflection film.

[0038] The anti-reflection film is arranged on the side of the substrate layer away from the nanostructure layer, and / or the side of the nanostructure layer away from the substrate layer.

[0039] Optionally, the wide-spectrum phase of the superstructure unit satisfies:

[0040]

[0041] Wherein, r is the radial coordinate of the second lens; r0 is the distance from any point on the second lens to the center of the second lens; λ is the working wavelength of the second lens.

[0042] Optionally, the second lens comprises at least two nanostructure layers;

[0043] Wherein, the nanostructures in any two adjacent nanostructure layers are coaxially arranged.

[0044] Optionally, the superlens comprises at least two nanostructure layers; wherein the nanostructures in any adjacent nanostructure layer are arranged in a staggered manner along a direction parallel to the substrate of the superlens.

[0045] Optionally, the phase of the second lens further satisfies:

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] wherein, r is the distance from the center of the second lens to any nanostructure; λ is the working wavelength of the second lens; is any phase related to the working wavelength of the second lens; (x, y) is the superlens lens coordinate, f2 is the focal length of the second lens; a i and b i are real coefficients.

[0055] In a second aspect, the embodiments of the present application further provide a processing method of a superlens, which is suitable for the second lens in the composite lens provided by any of the above embodiments, and the method comprises:

[0056] Step S1, setting a layer of structure layer material on the substrate layer;

[0057] Step S2, coating photoresist on the structure layer material and exposing a reference structure;

[0058] Step S3, etching the periodic nanostructures on the structure layer material according to the reference structure to form the nanostructure layer;

[0059] Step S4, setting the filler between the nanostructures;

[0060] Step S5, trimming the surface of the filler so that the surface of the filler coincides with the surface of the nanostructure.

[0061] Optionally, the method further comprises:

[0062] Step S6, repeating the steps S1 to S5 until the setting of all nanostructure layers is completed.

[0063] In a third aspect, the embodiments of the present application further provide an optical system, which comprises, in order from an object side to an image side, a stop, a composite lens provided by any of the above embodiments, a third lens, a fourth lens, and a fifth lens;

[0064] The third lens is a refractive lens, and a curvature radius of an object-side surface of the third lens is negative.

[0065] The fourth lens is a refractive lens, and an object-side surface of the fourth lens is a concave surface.

[0066] The fifth lens is a refractive lens, and an object-side surface of the fifth lens is a concave surface.

[0067] At least one of the object-side surface and the image-side surface of the third lens, the object-side surface and the image-side surface of the fourth lens, and the object-side surface and the image-side surface of the fifth lens is an aspheric surface, and the aspheric surface contains one inflection point.

[0068] The optical system further satisfies:

[0069] f / EPD<3;

[0070] 25°≤HFOV≤55°;

[0071] 0.05mm≤d2≤2mm;

[0072] Wherein, f is a focal length of the optical system; EPD is an entrance pupil diameter of the optical system; HFOV is one half of a maximum field of view of the optical system; and d2 is a thickness of the second lens.

[0073] Optionally, the optical system further satisfies:

[0074] 0.2≤R 1o / f1≤0.8

[0075] Wherein, R 1o is a curvature radius of an object-side surface of the first lens; and f1 is a focal length of the first lens.

[0076] Optionally, the optical system further satisfies:

[0077] (V1+V4) / 2-V3>20;

[0078] Wherein, V1 is an Abbe number of the first lens; V4 is an Abbe number of the fourth lens; and V3 is an Abbe number of the third lens.

[0079] Optionally, the optical system further satisfies:

[0080] 1.2<TTL / ImgH<1.8;

[0081] wherein TTL is a system total length of the optical system; and ImgH is a maximum imaging height of the optical system.

[0082] Optionally, the optical system further satisfies:

[0083]

[0084] wherein f2 is a focal length of the second lens in the optical system; and f is a focal length of the optical system.

[0085] In a fourth aspect, an embodiment of the present application further provides an imaging device, the imaging device comprising:

[0086] The optical system provided by any of the above embodiments and the electronic photosensitive element arranged on an image plane of the optical system.

[0087] In a fifth aspect, an embodiment of the present application further provides an electronic device, characterized in that the electronic device comprises the imaging device provided by the above embodiments.

[0088] The composite lens provided by the embodiments of the present application improves the design freedom of the optical system by combining the superlens and the refractive lens. The superlens processing method provided by the embodiments of the present application realizes the superlens structure of at least one nanostructure layer through layered processing, improves the aspect ratio of the nanostructure, and increases the design freedom of the superlens. The optical system provided by the embodiments of the present application uses the refractive lens and the superlens in the composite lens as the first lens and the second lens, so that the focal length of the optical system is greater than 3 mm, but the system total length is less than 3 mm, which promotes the miniaturization and light weight of the five-piece optical lens. BRIEF DESCRIPTION OF DRAWINGS

[0089] The accompanying drawings, which are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and together with the description serve to explain the principles of the present application.

[0090] Fig. 1 Fig. 1 shows an optional structural schematic diagram of a composite lens provided by an embodiment of the present application;

[0091] Fig. 2 Fig. 2 shows an optional structural schematic diagram of a superlens provided by an embodiment of the present application;

[0092] Fig. 3 Fig. 3 shows an optional structural schematic diagram of a nanostructure in a superlens provided by an embodiment of the present application;

[0093] Fig. 4Fig. 6 shows another optional structure diagram of the nanostructure in the superlens provided by the embodiment of the present application;

[0094] Fig. 5 Fig. 7 shows an optional arrangement mode diagram of the nanostructure in the superlens provided by the embodiment of the present application;

[0095] Fig. 6 Fig. 8 shows another optional arrangement mode diagram of the nanostructure in the superlens provided by the embodiment of the present application;

[0096] Fig. 7 Fig. 9 shows another optional arrangement mode diagram of the nanostructure in the superlens provided by the embodiment of the present application;

[0097] Fig. 8 Fig. 10 shows another optional structure diagram of the nanostructure in the superlens provided by the embodiment of the present application;

[0098] Fig. 9 Fig. 11 shows another optional structure diagram of the nanostructure in the superlens provided by the embodiment of the present application;

[0099] Fig. 10 Fig. 12 shows another optional structure diagram of the nanostructure in the superlens provided by the embodiment of the present application;

[0100] Fig. 11 Fig. 13 shows another optional structure diagram of the superlens provided by the embodiment of the present application;

[0101] Fig. 12 Fig. 14 shows another optional structure diagram of the superlens provided by the embodiment of the present application;

[0102] Fig. 13 Fig. 15 shows another optional structure diagram of the superlens provided by the embodiment of the present application;

[0103] Fig. 14 Fig. 16 shows an optional phase diagram of the superlens provided by the embodiment of the present application;

[0104] Fig. 15 Fig. 17 shows an optional transmittance diagram of the superlens provided by the embodiment of the present application;

[0105] Fig. 16 Fig. 18 shows another optional phase diagram of the superlens provided by the embodiment of the present application;

[0106] Fig. 17 Fig. 19 shows another optional transmittance diagram of the superlens provided by the embodiment of the present application;

[0107] Fig. 18An optional flow diagram of the superlens processing method provided by the embodiment of the present application is shown;

[0108] Fig. 19 Another optional flow diagram of the superlens processing method provided by the embodiment of the present application is shown;

[0109] Fig. 20 Another optional flow diagram of the superlens processing method provided by the embodiment of the present application is shown;

[0110] Fig. 21 An optional structural diagram of the optical system provided by the embodiment of the present application is shown;

[0111] Fig. 22 An optional phase modulation diagram of the second lens in the optical system provided by the embodiment of the present application at different wavelengths is shown;

[0112] Fig. 23 An astigmatism diagram of the optical system provided by the embodiment of the present application is shown;

[0113] Fig. 24 A distortion diagram of the optical system provided by the embodiment of the present application is shown;

[0114] Fig. 25 A modulation transfer function diagram of the optical system provided by the embodiment of the present application is shown;

[0115] Fig. 26 A broadband matching degree of the second lens in the optical system provided by the embodiment of the present application is shown;

[0116] Fig. 27 Another optional structural diagram of the optical system provided by the embodiment of the present application is shown;

[0117] Fig. 28 Another optional phase modulation diagram of the second lens in the optical system provided by the embodiment of the present application at different wavelengths is shown;

[0118] Fig. 29 Another astigmatism diagram of the optical system provided by the embodiment of the present application is shown;

[0119] Fig. 30 Another distortion diagram of the optical system provided by the embodiment of the present application is shown;

[0120] Fig. 31 Another modulation transfer function diagram of the optical system provided by the embodiment of the present application is shown;

[0121] Fig. 32A wideband matching degree of the second lens in an optional optical system provided by the embodiment of the application is shown;

[0122] Fig. 33 Another optional structural schematic diagram of an optical system provided by the embodiment of the application is shown;

[0123] Fig. 34 A phase modulation schematic diagram of the second lens in another optional optical system provided by the embodiment of the application at different wavelengths is shown;

[0124] Fig. 35 An astigmatism diagram of another optional optical system provided by the embodiment of the application is shown;

[0125] Fig. 36 A distortion diagram of another optional optical system provided by the embodiment of the application is shown;

[0126] Fig. 37 A modulation transfer function diagram of another optional optical system provided by the embodiment of the application is shown;

[0127] Fig. 38 A wideband matching degree of the second lens in an optional optical system provided by the embodiment of the application is shown;

[0128] Fig. 39 Another optional structural schematic diagram of an optical system provided by the embodiment of the application is shown;

[0129] Fig. 40 A phase modulation schematic diagram of the second lens in another optional optical system provided by the embodiment of the application at different wavelengths is shown;

[0130] Fig. 41 An astigmatism diagram of another optional optical system provided by the embodiment of the application is shown;

[0131] Fig. 42 A distortion diagram of another optional optical system provided by the embodiment of the application is shown;

[0132] Fig. 43 A modulation transfer function diagram of another optional optical system provided by the embodiment of the application is shown;

[0133] Fig. 44 A wideband matching degree of the second lens in an optional optical system provided by the embodiment of the application is shown.

[0134] The reference signs in the figures respectively represent:

[0135] 10-first lens; 20-second lens; 30-third lens; 40-fourth lens; 50-fifth lens; 60-diaphragm; 70-infrared filter

[0136] 201 - base layer; 202 - nanostructure layer; 203 - superstructure unit; 204 - antireflection coating; 2021 - nanostructure; 2022 - filler;

[0137] 202a - structure layer material; 205 - photoresist; 206 - reference structure. DETAILED DESCRIPTION

[0138] The present application will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments are shown. The present application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art. Like reference numerals refer to like elements throughout. Furthermore, in the drawings, the thickness of components, ratios, and dimensions are exaggerated for clarity.

[0139] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the terms "a," "one," "the," and "at least one" are not intended to refer to a limitation on the number of embodiments. Rather, these terms are intended to mean that there is at least one, but there can also be more than one. For example, "a" component can mean "at least one" component. "At least one" should be interpreted in the same manner as "one or more." "Or" means "and / or." The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0140] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by one of ordinary skill in the art. Terms, such as those defined in commonly utilized dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0141] "Include" or "comprise" means including but not limited to, and encompasses the case where the listed elements are among those that also comprise other elements.

[0142] This document describes embodiments with reference to cross-sectional views as idealized implementations. Thus, variations in shape relative to the illustrations are anticipated as a result of, for example, manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions shown herein, but should include deviations in shape due to, for example, manufacturing processes. For example, regions shown or described as flat may typically have rough and / or non-linear characteristics. Furthermore, acute angles shown may be rounded. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to show precise shapes of the regions and are not intended to limit the scope of the claims.

[0143] In the following description, exemplary embodiments according to this application will be described with reference to the accompanying drawings.

[0144] In the miniaturization of optical systems, optical systems using traditional plastic lenses face limitations in thickness and curvature due to the constraints of their injection molding process. This makes it difficult to achieve breakthroughs in the thickness of individual lenses, the spacing between lenses, and the overall system length in five-element lens structures. Furthermore, the limited availability of only a dozen or so materials for plastic lenses restricts the freedom of aberration correction in optical systems. While glass-resin hybrid lenses have addressed issues such as chromatic aberration to some extent, the injection molding process still significantly hinders the miniaturization and weight reduction of optical systems. Currently, reducing the overall length of an optical system by even 1 millimeter requires tremendous effort.

[0145] In a first aspect, embodiments of this application provide a composite lens, such as... Fig. 1 As shown, the compound lens includes a first lens 10 and a second lens 20 arranged sequentially from the object side to the image side. The first lens 10 is a refractive lens with a positive focal length, and the second lens 20 is a superlens. Both the object-side and image-side surfaces of the first lens 10 are aspherical. The first lens 10 and the second lens 20 also satisfy the following formula (1):

[0146] t 12 ≤0.5mm; (1-1)

[0147]

[0148] R 1i >R 1O (1-3)

[0149] In formulas (1-1) to (1-3), t 12 f1 is the distance between the first lens 10 and the second lens 20; f2 is the focal length of the first lens 10; f3 is the focal length of the second lens 20; R 1o R is the radius of curvature of the object-side surface of the first lens 10; 1iis the radius of curvature of the image-side surface of the first lens 10. It should be noted that the interval t 12 is less than a reference value. Optionally, when the composite lens is used in a consumer electronic device, t 12 is less than 0.5 mm.

[0150] The composite lens, by combining aspherical lenses with superlenses, can be used in a lens group with a lens number of not less than four to reduce the pressure on subsequent lens groups for aberration correction; secondly, if the second lens 20 adopts other lenses other than superlenses, the second lens 20 needs multiple inflection points and high-order curved surface structures to achieve similar results, but the existing processing technology does not support such complex design; and by virtue of the advantage that the thickness of the superlens is much smaller than that of the refractive lens, the total length (TTL, Total Tracking Length) of the optical system can be effectively reduced

[0151] According to the embodiments of the present application, the material of the first lens 10 can be optical glass, such as crown glass, flint glass, quartz glass, etc.; or various optical plastics, such as APL5514, OKP4HT, etc. Preferably, the first lens 10 is selected from optical plastics. The first lens 10 adopts optical plastics, which can realize mass production of aspherical lenses at low cost through injection molding.

[0152] According to the embodiments of the present application, optionally, the condensing power of the second lens 20 is less than that of the first lens 10. The role of the second lens 20 includes correcting the chromatic spherical aberration, other monochromatic aberrations and transverse chromatic aberration of the first lens 10. Preferably, the absolute value of the focal length ratio of the second lens 10 to the first lens 20 needs to be greater than 8.

[0153] Next, the superlens (i.e. the second lens 20) provided by the embodiments of the present application will be described. Figs. 2 to 17 Next, the superlens (i.e. the second lens 20) provided by the embodiments of the present application will be described.

[0154] Specifically, the superlens is a specific application of the super surface, which modulates the phase, amplitude and polarization of the incident light through the periodic arrangement of sub-wavelength size nano structures.

[0155] Fig. 2 An optional structural schematic diagram of the superlens provided by the embodiments of the present application is shown. Referring to Fig. 2 , the second lens 20 includes a substrate layer 201 and at least one nano structure layer 202 arranged on the substrate layer 201. Each of the at least one nano structure layer 202 includes a periodic arrangement of nano structures 2021.

[0156] According to the embodiments of the present application, in any of the at least one nano structure layer 202, the arrangement period of the nano structure 2021 is greater than or equal to 0.3λ cand less than or equal to 2λ c ; wherein λ c is the center wavelength of the working waveband of the second lens 20.

[0157] According to the embodiments of the present application, optionally, the height of the nanostructure 2021 in any one of the at least one nanostructure layer 202 is greater than or equal to 0.3λ c and less than or equal to 5λ c ; wherein λ c is the center wavelength of the working waveband of the second lens 20.

[0158] Fig. 3 and Fig. 4 shows a perspective view of the nanostructure 2021 in any one of the nanostructure layers 202 in the second lens 20. Optionally, Fig. 3 is a cylindrical structure. Optionally, Fig. 4 the nanostructure 2021 in the above-mentioned Fig. 1 and Fig. 4 , the second lens 20 further comprises a filler 2022, the filler 2022 fills between the nanostructures 2021, and the extinction coefficient of the material of the filler 2022 to the working waveband is less than 0.01. Optionally, the filler comprises air or other materials transparent or translucent in the working waveband. According to the embodiments of the present application, the absolute value of the difference between the refractive index of the material of the filler 2022 and the refractive index of the nanostructure 2021 should be greater than or equal to 0.5. When the superlens provided by the embodiments of the present application has at least two nanostructure layers 12, the filler 2022 in the nanostructure layer 202 farthest from the base layer 201 can be air.

[0159] In some optional embodiments of the present application, as shown in Figs. 5 to 7 , the at least one nanostructure layer 202 comprises a superstructure unit 203 arranged in an array in any one of the at least one nanostructure layer 202. The superstructure unit 203 is a close-packed pattern, and the vertex and / or center position of the close-packed pattern is provided with a nanostructure 2021. In the embodiments of the present application, the close-packed pattern refers to one or more patterns that can fill the entire plane without gaps and without overlapping.

[0160] As shown in Fig. 5 , according to the embodiments of the present application, the superstructure unit can be arranged in a fan shape. As shown in Fig. 6 , according to the embodiments of the present application, the superstructure unit can be arranged in a regular hexagonal array. In addition, as shown in Fig. 7As shown, according to embodiments of the present application, the super-structure units 203 can be arranged in a square array. Those skilled in the art should appreciate that the super-structure units 203 included in the nano-structure layer 202 can also include other forms of array arrangement, all of which are encompassed within the scope of the present application.

[0161] Optionally, the wide-spectrum phase of the super-structure units 203 and the working wavelength band of the super-lens also satisfy:

[0162]

[0163] In formula (2), r is the radial coordinate of the second lens 20; r0is the distance from any point on the second lens 20 to the center of the second lens 20; and λ is the working wavelength of the second lens 20.

[0164] Exemplarily, the nano-structure 2021 provided by embodiments of the present application can be a polarization-insensitive structure, which applies a propagation phase to the incident light. According to embodiments of the present application, as shown in Fig. 8 、 Fig. 9 and Fig. 10 , the nano-structure 2021 can be a positive structure or a negative structure. For example, the shape of the nano-structure 2021 includes a cylinder, a hollow cylinder, a square prism, a hollow square prism, etc.

[0165] More advantageously, as shown in Fig. 11 , the second lens 20 provided by embodiments of the present application includes at least two layers of nano-structure layers 202. Optionally, as shown in Fig. 12 (a), the nano-structures 2021 in adjacent nano-structure layers of the at least two layers of nano-structures 202 are arranged coaxially. The aforementioned coaxial arrangement means that the nano-structures 2021 in the adjacent two layers of nano-structure layers 12 have the same arrangement period; or the axes of the nano-structures 2021 at the same position in the adjacent two layers of nano-structure layers coincide. Optionally, as shown in Fig. 12 (b), the nano-structures 2021 in adjacent nano-structure layers of the at least two layers of nano-structures 202 are arranged in a staggered manner along a direction parallel to the substrate 201 of the super-lens. This arrangement is advantageous for breaking through the limitation of the aspect ratio of the nano-structures in the super-lens by the processing technology, thereby realizing higher design freedom. Fig. 11 The left view in FIG. 2 shows a perspective view of an optional three-layer nano-structure layer. Fig. 11 The right view in FIG. 2 shows a top view of each layer of nano-structure layer. According to embodiments of the present application, the shape, size or material of the nano-structures 2021 in adjacent nano-structure layers 202 can be the same or different. According to embodiments of the present application, the fillers 2022 in adjacent nano-structure layers 202 can be the same or different.

[0166] For example, Fig. 8 a to Fig. 8 The d in the figure shows that the shape of the nanostructure 2021 includes a cylinder, a hollow cylinder, a square cylinder, and a hollow square cylinder, and the nanostructure 2021 is surrounded by filler 2022. Fig. 8 In this embodiment, the nanostructure 2021 is positioned at the center of the quadrilateral superstructure unit 203. In an optional embodiment of this application, Fig. 9 a to Fig. 9 The d in the figure shows the shapes of the nanostructure 2021, including cylinder, hollow cylinder, square cylinder and hollow square cylinder, and there is no filler 2022 around the nanostructure 2021. Fig. 9 In this structure, nanostructure 2021 is positioned at the center of the quadrilateral superstructure unit 203.

[0167] According to the embodiments of this application, Fig. 10 a to Fig. 10 The d in the figure shows that the shape of the nanostructure 2021 includes a square column, a cylinder, a hollow square column, and a hollow cylinder, and there is no filler 2022 around the nanostructure 2021. Fig. 10 a to Fig. 10 In d, the nanostructure 2021 is positioned at the center of the hexagonal superstructure unit 203. Optionally, Fig. 10 e to Fig. 10 The h in the figure represents the nanostructures 2021, which are negative nanostructures, such as square pore pillars, circular pore pillars, square ring pillars, and circular ring pillars. Fig. 10 e to Fig. 13 In h, nanostructure 2021 is a negative structure located at the center of the superstructure unit 203 in a regular hexagon.

[0168] In one alternative implementation, such as Example 1 As shown, the second lens 20 provided in this embodiment further includes an antireflective coating 204. The antireflective coating 204 is disposed on the side of the substrate layer 201 away from at least one nanostructure layer 202; or, the antireflective coating 204 is disposed on the side of the at least one nanostructure layer 202 adjacent to air. The function of the antireflective coating 204 is to increase the transmission and reduce the reflection of incident radiation.

[0169] According to embodiments of the present application, the material of the substrate layer 201 is a material with extinction coefficient less than 0.01 in the working wavelength range. For example, the material of the substrate layer 201 includes fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, and hydrogenated amorphous silicon. For another example, when the working wavelength range of the second lens 20 is the visible light range, the material of the substrate layer 201 includes fused silica, quartz glass, crown glass, flint glass, sapphire, and alkali glass. In some embodiments of the present application, the material of the nanostructure 2021 is the same as the material of the substrate layer 201. In yet some embodiments of the present application, the material of the nanostructure 2021 is different from the material of the substrate layer 201. Optionally, the material of the filler 2022 is the same as the material of the substrate layer 201. Optionally, the material of the filler 2022 is different from the material of the substrate layer 201.

[0170] It should be understood that, in some optional embodiments of the present application, the material of the filler 2022 is the same as the material of the nanostructure 2021. In yet some optional embodiments of the present application, the material of the filler 2022 is different from the material of the nanostructure 2021. For example, the material of the filler 2022 is a high-transmittance material in the working wavelength range, with extinction coefficient less than 0.01. For example, the material of the filler 2022 includes fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, and hydrogenated amorphous silicon.

[0171] Optionally, the second lens 20 provided by embodiments of the present application has an equivalent refractive index range less than 2. The equivalent refractive index range is the maximum refractive index of the second lens 20 minus the minimum refractive index thereof. According to embodiments of the present application, the phase of the second lens 20 provided by embodiments of the present application also satisfies formula (3):

[0172]

[0173]

[0174]

[0175]

[0176]

[0177]

[0178]

[0179]

[0180] wherein r is the distance from the center of the second lens 20 to the center of any nanostructure; λ is the working wavelength of the second lens 20, for any phase related to the working wavelength, (x, y) is the coordinate on the second lens 20 (in some cases, it can be understood as the coordinate of the surface of the substrate layer 201), f2 is the focal length of the second lens 20, a i and b i are real coefficients. The phase of the superlens (i.e., the second lens 20) can be expressed by a high-order polynomial, which includes an odd-order polynomial and an even-order polynomial. In order not to destroy the rotational symmetry of the phase of the superlens, the phase corresponding to the even-order polynomial can usually be optimized only, which greatly reduces the design freedom of the superlens. However, in the above formulas (3-1) to (3-8), formulas (3-4) to (3-6) can optimize the phase satisfying the odd-order polynomial without destroying the rotational symmetry of the phase of the superlens, thereby greatly improving the optimization freedom of the superlens.

[0181] Optionally, the matching of the actual phase of the second lens 20 and the ideal phase provided by the embodiments of the present application is that the broadband phase matching degree of the second lens 20 is given by formula (4):

[0182]

[0183] In formula (4), λ max and λ min are the upper limit and the lower limit of the working wavelength range of the second lens 20, for example, λ max = 700 nm and λ min = 400 nm. and are the theoretical target phase and the actual database internal phase, respectively.

[0184] Fig. 14

[0185] In an exemplary embodiment, the embodiments of the present application provide a second lens 20. The second lens 20 includes a substrate layer 201 and two layers of nanostructure layers 202 arranged on the substrate layer 201. Among them, the two layers of nanostructure layers 202 are sequentially arranged in the direction away from the substrate layer 201 as the first nanostructure layer and the second nanostructure layer. The specific parameters of the second lens 20 are shown in Table 1. Fig. 14 The phase diagram of the second lens 20 provided by embodiment 1 is shown in FIG. 2, Fig. 15 the abscissa is the wavelength of the incident radiation, and the ordinate is the number of nanostructures 2021. Fig. 15 The transmittance diagram of the second lens 20 provided by embodiment 1 is shown in FIG. 3, Example 2 the abscissa is the wavelength of the incident radiation, and the ordinate is the number of nanostructures 2021.

[0186] In the embodiment 1, the wide spectrum phase of any superstructure unit 203 in the second lens 20 satisfies the following relationship with the wavelength:

[0187]

[0188] wherein, r is the coordinate of the second lens 20 along the radial direction; r0 is the distance from any point on the second lens 20 to the center of the second lens 20; and λ is the working wavelength of the second lens 20.

[0189] Table 1

[0190]

[0191] Fig. 16

[0192] In another exemplary embodiment, the embodiment of the present application provides a second lens 20. The second lens 20 comprises a substrate layer 201 and two nanostructure layers 202 arranged on the substrate layer 201. Among them, the two nanostructure layers 202 are sequentially arranged as a first nanostructure layer and a second nanostructure layer along the direction away from the substrate layer 201. The specific parameters of the second lens 20 are shown in Table 2. Fig. 16 The phase diagram of the second lens 20 provided by the embodiment 2 is shown in FIG. 2B, Fig. 17 wherein, the abscissa is the wavelength of the incident radiation, and the ordinate is the number of nanostructures 2021. Fig. 17 The transmittance diagram of the second lens 20 provided by the embodiment 2 is shown in FIG. 2C, Figs. 18 to 20 wherein, the abscissa is the wavelength of the incident radiation, and the ordinate is the number of nanostructures 2021.

[0193] In the embodiment 2, the wide spectrum phase of any superstructure unit 203 in the second lens 20 satisfies the following relationship with the wavelength:

[0194]

[0195] wherein, r is the coordinate of the second lens 20 along the radial direction; r0 is the distance from any point on the second lens 20 to the center of the second lens 20; and λ is the working wavelength of the second lens 20.

[0196] Table 2

[0197]

[0198]

[0199] In a second aspect, the embodiment of the present application also provides a processing method of a superlens, which is suitable for the second lens 20 provided by any embodiment of the present application. As shown in FIG. 6, Fig. 19 the method comprises at least steps S1 to S5.

[0200] Step S1, disposing a layer of structure layer material 202a on the base layer 201.

[0201] Step S2, coating photoresist 205 on the structure layer material 202a, and exposing a reference structure 206.

[0202] Step S3, etching a periodic arrangement of nanostructures 2021 in the structure layer material 202a according to the reference structure 206 to form a nanostructure layer 202.

[0203] Step S4, disposing a filler 2022 between the nanostructures 2021.

[0204] Step S5, trimming the surface of the filler 2022 so that the surface of the filler 2022 coincides with the surface of the nanostructures 2021.

[0205] Optionally, as shown in Fig. 21 , the method provided by the embodiments of the present application further includes:

[0206] Step S6, repeating steps S1 to S5 until the setting of all nanostructure layers is completed.

[0207] In a third aspect, the embodiments of the present application further provide an optical system, as shown in Fig. 27 , Fig. 33 , Fig. 35 , Fig. 39 and Example 3 , the optical system includes, in order from the object side to the image side, a stop 60, the composite lens provided by any of the embodiments described above, a third lens 30, a fourth lens 40, and a fifth lens 50.

[0208] Among them, the third lens 30 is a refractive lens, and the curvature radius of the object side surface of the third lens 30 is negative; the fourth lens 40 is a refractive lens, and the object side surface of the fourth lens 40 is a concave surface; the fifth lens 50 is a refractive lens, and the object side surface of the fifth lens 50 is a concave surface; and at least one of the object side surface and the image side surface of the third lens 30, the object side surface and the image side surface of the fourth lens 40, and the object side surface and the image side surface of the fifth lens 50 is an aspherical surface; the aspherical surface contains one inflection point.

[0209] Further, the optical system provided by the embodiments of the present application also satisfies the following formula (5):

[0210] f / EPD<3; (5-1)

[0211] 25°≤HFOV≤55°; (5-2)

[0212] 0.05mm≤d2≤2mm; (5-3)

[0213] wherein f is a focal length of the optical system; EPD is an entrance pupil diameter of the optical system; HFOV is a half field of view of a maximum field of view of the optical system; and d2 is a thickness of the second lens 20.

[0214] According to the optional embodiments of the present application, the optical system provided by the embodiments of the present application further satisfies:

[0215] 0.2≤R 1o / f1≤0.8; (6)

[0216] In formula (6), R 1o is a radius of curvature of an object side surface of the first lens 10; and f1 is a focal length of the first lens 10. According to the optional embodiments of the present application, the optical system provided by the embodiments of the present application further satisfies:

[0217] (V1+V4) / 2-V3>20; (7)

[0218] wherein V1 is an Abbe number of the first lens 10; V4 is an Abbe number of the fourth lens 40; and V3 is an Abbe number of the third lens 30.

[0219] In some example embodiments, the optical system provided by the embodiments of the present application further satisfies:

[0220] 1.2<TTL / ImgH<1.8; (8)

[0221] wherein TTL is a total tracking length of the optical system; and ImgH is a maximum imaging height of the optical system. The maximum imaging height refers to a half of a diagonal length of an effective sensing area of an electronic photosensitive element. In yet some example embodiments, the optical system provided by the embodiments of the present application further satisfies:

[0222]

[0223] wherein f2 is a focal length of the second lens 20 in the optical system; and f is a focal length of the optical system.

[0224] Further, in the optical system provided by the embodiments of the present application, the aspheric surfaces in the third lens 30, the fourth lens 40 and the fifth lens 50 satisfy:

[0225]

[0226] In formula (10), z represents a surface vector parallel to the z-axis, c is a center point curvature of the aspherical surface, k is a quadratic surface constant, A-J correspond to high order coefficients respectively, and the z-axis is an optical axis of the optical system provided by the embodiments of the present application.

[0227] According to the embodiments of the present application, the fifth lens 50 is used to correct optical aberrations of the first to fourth lenses, including but not limited to monochromatic aberrations and chromatic aberrations.

[0228] Fig. 21

[0229] Exemplarily, as shown in Fig. 22 The optical system provided by the embodiments of the present application includes, in order from the object side to the image side, a diaphragm 60, the composite lens provided by any of the embodiments described above, a third lens 30, a fourth lens 40 and a fifth lens 50.

[0230] The third lens 30 is a refractive lens, and the radius of curvature of the object side surface of the third lens 30 is negative; the fourth lens 40 is a refractive lens, and the object side surface of the fourth lens 40 is a concave surface; the fifth lens 50 is a refractive lens, and the object side surface of the fifth lens 50 is a concave surface; and at least one of the object side surface and the image side surface of the third lens 30, the object side surface and the image side surface of the fourth lens 40, and the object side surface and the image side surface of the fifth lens 50 is an aspherical surface; the aspherical surface contains one inflection point.

[0231] The optical system provided by the embodiment 3 also satisfies formula (5):

[0232] f / EPD<3; (5-1)

[0233] 25°≤HFOV≤55°; (5-2)

[0234] 0.05mm≤d2≤2mm; (5-3)

[0235] Wherein, f is the focal length of the optical system; EPD is the entrance pupil diameter of the optical system; HFOV is half of the maximum field of view of the optical system; and d2 is the thickness of the second lens 20.

[0236] The system parameters of the optical system provided by the embodiment 3 are shown in Table 3-1, and VIS in Table 3-1 represents the visible light band. The curvature, thickness and refractive index of the surface of each lens in the optical system are shown in Table 3-2. The aspherical surface coefficients of the surface of each lens in the optical system are shown in Table 3-3. Fig. 22The phase modulation of the second lens 20 in the optical system provided in Embodiment 3 at 486.13 nm, 587.56 nm and 656.27 nm is shown. It can be seen that the phase of the second lens 20 at different wavelengths covers 0-2π. Fig. 23 It can be seen that the phase of the second lens 20 at different wavelengths covers 0-2π. Fig. 23 The astigmatism of the optical system is shown. It can be seen that the meridional astigmatism of the optical system is not more than 0.05 mm, and the sagittal astigmatism is about 0. Fig. 24 The astigmatism of the optical system is shown. It can be seen that the meridional astigmatism of the optical system is not more than 0.05 mm, and the sagittal astigmatism is about 0. Fig. 24 The distortion (also referred to as the field curvature) of the optical system is shown. It can be seen that the distortion of the optical system within 0-1 field of view is not more than 5%. Fig. 25 The distortion (also referred to as the field curvature) of the optical system is shown. It can be seen that the distortion of the optical system within 0-1 field of view is not more than 5%. Fig. 25 The modulation transfer function (MTF) of the optical system is shown. According to Fig. 26 It can be seen that the modulation transfer functions of the optical system at different fields of view are close to the diffraction limit. Fig. 26 The broadband matching degree of the second lens 20 in the optical system provided in Embodiment 3 is shown. There are Parameter item It can be seen that the actual phase of the second lens 20 in Embodiment 3 matches the theoretical phase by more than 90%. It can be seen from the above that the optical system provided in Embodiment 3 has good imaging effect and excellent astigmatism and distortion control.

[0237] Table 3-1

[0238] Value Working wavelength (WL) VIS (400-700 nm) Equivalent focal length (EFL) 3 mm Field angle (2ω) F number 74° Image height (ImgH) 2.23 2.4 mm Total track length (TTL) 3 mm Example 4

[0239] Table 3-2

[0240]

[0241]

[0242] Table 3-3

[0243]

[0244]

[0245] Fig. 27

[0246] Exemplarily, as Fig. 28 shown, the optical system provided in the embodiments of the present application includes, arranged in order from the object side to the image side, an aperture 60, the composite lens provided in any of the embodiments described above, a third lens 30, a fourth lens 40 and a fifth lens 50.

[0247] The third lens 30 is a refractive lens, and the curvature radius of the object side surface of the third lens 30 is negative; the fourth lens 40 is a refractive lens, and the object side surface of the fourth lens 40 is a concave surface; the fifth lens 50 is a refractive lens, and the object side surface of the fifth lens 50 is a concave surface; and at least one surface of the object side surface and the image side surface of the third lens 30, the object side surface and the image side surface of the fourth lens 40, and the object side surface and the image side surface of the fifth lens 50 is an aspheric surface; the aspheric surface contains one inflection point.

[0248] The optical system provided by the embodiment 4 also satisfies formula (5):

[0249] f / EPD<3; (5-1)

[0250] 25°≤HFOV≤55°; (5-2)

[0251] 0.05mm≤d2≤2mm; (5-3)

[0252] Wherein, f is the focal length of the optical system; EPD is the entrance pupil diameter of the optical system; HFOV is half field of view of the maximum field of view of the optical system; d2 is the thickness of the second lens 20.

[0253] The system parameters of the optical system provided by the embodiment 4 are shown in Table 4-1, and VIS in Table 4-1 represents the visible light band. The curvature, thickness and refractive index of the surface of each lens in the optical system are shown in Table 4-2. The aspheric coefficients of the surface of each lens in the optical system are shown in Table 4-3. Fig. 28 The phase modulation diagrams of the second lens 20 in the optical system provided by the embodiment 4 at 486.13nm, 587.56nm and 656.27nm are shown. From the diagrams, it can be seen that the phase of the second lens 20 at different wavelengths covers 0-2π. Fig. 29 It can be seen that the phase of the second lens 20 at different wavelengths covers 0-2π. Fig. 29 The astigmatism diagram of the optical system is shown. From the diagram, it can be seen that the meridional astigmatism of the optical system is not more than 0.2mm, and the sagittal astigmatism is about 0. Fig. 30 It can be seen that the meridional astigmatism of the optical system is not more than 0.2mm, and the sagittal astigmatism is about 0. Fig. 30 The distortion diagram (also known as the field curvature diagram) of the optical system is shown. From the diagram, it can be seen that the distortion of the optical system within 0-1 field of view is not more than 10%. Fig. 31 It can be seen that the distortion of the optical system within 0-1 field of view is not more than 10%. Fig. 31 The modulation transfer function (MTF, Modulation Transfer Function) of the optical system is shown. According to the diagram, it can be seen that the modulation transfer functions of the optical system at different fields of view are close to the diffraction limit. Fig. 32 It can be seen that the modulation transfer functions of the optical system at different fields of view are close to the diffraction limit. Fig. 32The broadband matching degree of the second lens 20 in the optical system provided by Embodiment 4 is shown. There is Parameter item It can be seen that the actual phase matching degree of the second lens 20 in Embodiment 4 is greater than 90%. As can be seen from the above, the imaging effect of the optical system provided by Embodiment 4 is good, and the astigmatism and distortion control is excellent.

[0254] Table 4-1

[0255] Value Working wavelength (WL) VIS (400-700 nm) Equivalent focal length (EFL) 3 mm Field angle (2ω) F number 80° Image height (ImgH) 2.3 2.52 mm Total track length (TTL) 3 mm Example 5

[0256] Table 4-2

[0257]

[0258]

[0259] Table 4-3

[0260]

[0261] Fig. 33

[0262] Exemplarily, as Fig. 34 shown, the embodiment of the present application provides an optical system. The optical system comprises, arranged in order from the object side to the image side, a diaphragm 60, a composite lens provided by any of the above embodiments, a third lens 30, a fourth lens 40 and a fifth lens 50.

[0263] Wherein, the third lens 30 is a refractive lens, and the curvature radius of the object side surface of the third lens 30 is negative; the fourth lens 40 is a refractive lens, and the object side surface of the fourth lens 40 is a concave surface; the fifth lens 50 is a refractive lens, and the object side surface of the fifth lens 50 is a concave surface; and at least one surface of the object side surface and the image side surface of the third lens 30, the object side surface and the image side surface of the fourth lens 40 and the object side surface and the image side surface of the fifth lens 50 is aspherical; the aspherical surface contains one inflection point.

[0264] And the optical system provided by Embodiment 5 also satisfies formula (5):

[0265] f / EPD<3; (5-1)

[0266] 25°≤HFOV≤55°; (5-2)

[0267] 0.05mm≤d2≤2mm; (5-3)

[0268] Wherein, f is the focal length of the optical system; EPD is the entrance pupil diameter of the optical system; HFOV is half field of view of the optical system; and d2 is the thickness of the second lens 20.

[0269] The system parameters of the optical system provided in Embodiment 5 are shown in Table 5-1, where VIS represents the visible light band. The parameters such as the curvature, thickness and refractive index of each lens surface in the optical system are shown in Table 5-2. The aspheric coefficients of each lens surface in the optical system are shown in Table 5-3. Fig. 34 The phase modulation diagrams of the second lens 20 in the optical system provided in Embodiment 5 at 486.13 nm, 587.56 nm and 656.27 nm are shown. It can be seen that the phase of the second lens 20 at different wavelengths covers 0-2π. Fig. 35 The phase of the second lens 20 at different wavelengths covers 0-2π. Fig. 35 The astigmatism diagram of the optical system is shown. It can be seen that the meridional astigmatism of the optical system is not more than 0.4 mm, and the sagittal astigmatism is not more than 0.1 mm. Fig. 36 The astigmatism of the optical system is not more than 0.4 mm, and the sagittal astigmatism is not more than 0.1 mm. Fig. 36 The distortion diagram (also known as the field curvature diagram) of the optical system is shown. It can be seen that the distortion of the optical system within 0-1 field of view is not more than 5%. Fig. 37 The distortion of the optical system within 0-1 field of view is not more than 5%. Fig. 37 The modulation transfer function (MTF) of the optical system is shown. According to the formula: Fig. 38 The modulation transfer function of the optical system at different fields of view is close to the diffraction limit. Fig. 38 The broadband matching degree of the second lens 20 in the optical system provided in Embodiment 5 is shown. It can be seen that the actual phase of the second lens 20 in Embodiment 5 is greater than 90% matched with the theoretical phase. Parameter item The actual phase of the second lens 20 in Embodiment 5 is greater than 90% matched with the theoretical phase. It can be seen from the above that the optical system provided in Embodiment 5 has good imaging effect and excellent astigmatism and distortion control.

[0270] Table 5-1

[0271] Value Working wavelength (WL) VIS (400-700 nm) Equivalent focal length (EFL) 3.2 mm Field angle (2ω) F number 72° Image height (ImgH) 2.25 2.2 mm Total track length (TTL) 3.2 mm Example 6

[0272] Table 5-2

[0273]

[0274]

[0275] Table 5-3

[0276]

[0277] Fig. 39

[0278] Exemplarily, as shown in Fig. 40 The optical system provided by the embodiment of the present application comprises, in order from the object side to the image side, a stop 60, the composite lens provided by any one of the above embodiments, a third lens 30, a fourth lens 40 and a fifth lens 50.

[0279] The third lens 30 is a refractive lens, and the curvature radius of the object side surface of the third lens 30 is negative; the fourth lens 40 is a refractive lens, and the object side surface of the fourth lens 40 is a concave surface; the fifth lens 50 is a refractive lens, and the object side surface of the fifth lens 50 is a concave surface; and at least one surface of the object side surface and the image side surface of the third lens 30, the object side surface and the image side surface of the fourth lens 40 and the object side surface and the image side surface of the fifth lens 50 is an aspheric surface; the aspheric surface contains one inflection point.

[0280] The optical system provided by the embodiment 6 also satisfies formula (5):

[0281] f / EPD<3; (5-1)

[0282] 25°≤HFOV≤55°; (5-2)

[0283] 0.05mm≤d2≤2mm; (5-3)

[0284] Wherein, f is the focal length of the optical system; EPD is the entrance pupil diameter of the optical system; HFOV is half field of view of the maximum field of view of the optical system; d2 is the thickness of the second lens 20.

[0285] The system parameters of the optical system provided by the embodiment 6 are shown in Table 6-1, and VIS in Table 6-1 represents the visible light band. The curvature, thickness and refractive index of the surface of each lens in the optical system are shown in Table 6-2. The aspheric coefficients of the surface of each lens in the optical system are shown in Table 6-3. Fig. 40 The phase modulation diagrams of the second lens 20 in the optical system provided by the embodiment 6 at 486.13nm, 587.56nm and 656.27nm are shown. It can be seen from Fig. 41 that the phase of the second lens 20 at different wavelengths covers 0-2π. Fig. 41 The astigmatism diagram of the optical system is shown. It can be seen from Fig. 42 that the meridional astigmatism of the optical system is not more than 0.4mm, and the sagittal astigmatism is not more than 0.1mm. Fig. 42 The distortion diagram (also known as the field curvature diagram) of the optical system is shown. It can be seen from Fig. 43It can be seen that the optical system has an aberration of less than 5% in a 0 to 1 field of view. Fig. 43 The modulation transfer function (MTF) of the optical system is shown. According to the MTF curve, it can be seen that the modulation transfer function of the optical system is close to the diffraction limit at different fields of view. Fig. 44 It can be seen that the modulation transfer function of the optical system is close to the diffraction limit at different fields of view. Fig. 44 The broadband matching degree of the second lens 20 in the optical system provided in Embodiment 6 is shown. It can be seen that the actual phase of the second lens 20 in Embodiment 6 is close to the theoretical phase. ​ It can be seen that the actual phase of the second lens 20 in Embodiment 6 is close to the theoretical phase. It can be seen from the above that the optical system provided in Embodiment 6 has a good imaging effect, and the astigmatism and aberration are well controlled.

[0286] Table 6-1

[0287]

[0288]

[0289] Table 6-2

[0290]

[0291] Table 6-3

[0292]

[0293]

[0294] It can be understood that in some optional embodiments, the optical system provided in any of the above embodiments further comprises an infrared filter 70 arranged between the fifth lens 50 and the image plane of the optical system, for providing the imaging quality of the optical system in the visible light band. It should be noted that the superlens (i.e., the second lens 20) provided in the embodiments of the present application can be processed by a semiconductor process, and has the advantages of light weight, thin thickness, simple structure and process, low cost, and high consistency in mass production.

[0295] In summary, the composite lens provided in the embodiments of the present application improves the design freedom of the optical system by combining the superlens and the refractive lens. The superlens processing method provided in the embodiments of the present application realizes the superlens structure of at least one nanostructure layer through layered processing, improves the aspect ratio of the nanostructure, and increases the design freedom of the superlens. The optical system provided in the embodiments of the present application uses the refractive lens and the superlens in the composite lens as the first lens and the second lens, so that the focal length of the optical system is greater than 3 mm, and the total length of the system is less than 3 mm, which promotes the miniaturization and light weight of the five-piece optical lens.

[0296] The above merely describes the specific implementation of the embodiments of the present application, but the protection scope of the embodiments of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the embodiments of the present application, which should be covered in the protection scope of the embodiments of the present application. Therefore, the protection scope of the embodiments of the present application should be subject to the protection scope of the claims.

Claims

1. An optical system characterized by comprising: The optical system comprises, arranged in order from the object side to the image side, a composite lens, a third lens (30), a fourth lens (40), and a fifth lens (50); The composite lens comprises, arranged in order from the object side to the image side, a first lens (10) and a second lens (20); The first lens (10) is a refractive lens with a positive focal length; the object side surface and the image side surface of the first lens (10) are aspherical surfaces; The third lens (30) is a refractive lens, and the curvature radius of the object side surface of the third lens (30) is negative; The fourth lens (40) is a refractive lens, and the object side surface of the fourth lens (40) is a concave surface; The fifth lens (50) is a refractive lens, and the object side surface of the fifth lens (50) is a concave surface; The first lens (10) and the second lens (20) further satisfy: ； ； ； wherein t 12 is the distance between the first lens (10) and the second lens (20); f1 is the focal length of the first lens (10); f2 is the focal length of the second lens (20); R 1i is the radius of curvature of the image-side surface of the first lens (10); R 1o is the radius of curvature of the object-side surface of the first lens (10); The optical system further satisfies: ； Wherein, f is the focal length of the optical system; EPD is the entrance pupil diameter of the optical system.

2. The optical system of claim 1, wherein, The second lens (20) comprises a substrate layer (201) and at least one nanostructure layer (202) arranged on the substrate layer (201); Each of the at least one nanostructure layer (202) comprises periodically arranged nanostructures (2021).

3. The optical system of claim 2, wherein, the arrangement period of the nanostructures (2021) in any of the at least one nanostructured layer (202) is greater than or equal to 0.3λ c , and less than or equal to 2λ c ; where λ c is the center wavelength of the second lens (20) operating band.

4. The optical system of claim 2, wherein, a height of the nanostructures (2021) in any of the at least one nanostructured layer (202) is greater than or equal to 0.3λ c and less than or equal to 5λ c ; where λ c is the center wavelength of the second lens (20) operating wavelength band.

5. The optical system of claim 2, wherein, Any one of the at least one nanostructure layer (202) comprises arrayed superstructure units (203); The superstructure units (203) are close-packed patterns, and the vertices and / or center positions of the close-packed patterns are provided with the nanostructures (2021).

6. The optical system of claim 2, wherein, The extinction coefficient of the material of the substrate layer (201) to the working waveband is less than 0.

01.

7. The optical system of claim 2, wherein, The extinction coefficient of the material of the nanostructures (2021) to the working waveband is less than 0.

01.

8. The optical system of claim 6, wherein, The material of the substrate layer (201) comprises fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, and hydrogenated amorphous silicon.

9. The optical system of claim 7, wherein, The material of the nanostructures (2021) comprises fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, and hydrogenated amorphous silicon.

10. The optical system of any of claims 2-9, wherein, The material of the nanostructures (2021) is different from that of the substrate layer (201).

11. The optical system of any of claims 2-9, wherein, The material of the nanostructures (2021) is the same as that of the substrate layer (201).

12. The optical system of any one of claims 2-9, wherein, The shape of the nanostructures (2021) is a polarization-insensitive structure.

13. The optical system of claim 12, wherein, The polarization-insensitive structure comprises a cylindrical shape, a hollow cylindrical shape, a circular hole shape, a hollow circular hole shape, a square column shape, a square hole shape, a hollow square column shape, and a hollow square hole shape.

14. The optical system of any one of claims 2-9, wherein, The second lens (20) further comprises a filler (2022); The filler (2022) fills between the nanostructures (2021); And, the extinction coefficient of the material of the filler (2022) to the working waveband is less than 0.

01.

15. The optical system of claim 14, wherein, The absolute value of the difference between the refractive index of the filler (2022) and the refractive index of the nanostructures (2021) is greater than or equal to 0.

5.

16. The optical system of claim 14, wherein, The filler includes air, fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, and hydrogenated amorphous silicon.

17. The optical system of claim 16, wherein, The material of the filler is different from the material of the substrate layer (201).

18. The optical system of claim 16, wherein, The material of the filler is different from the material of the nanostructure (2021).

19. The optical system of any one of claims 2-9, wherein, The second lens (20) further comprises an antireflection film (204); The antireflection film (204) is arranged on the side of the substrate layer (201) away from the nanostructure layer (202), and / or the side of the nanostructure layer (202) away from the substrate layer (201).

20. The optical system of claim 5, wherein, The wide-spectrum phase of the superstructure unit (203) satisfies: ； Wherein, r is the coordinate of the second lens (20) along the radial direction; r0 is the distance from any point on the second lens to the center of the second lens (20); λ is the working wavelength of the second lens (20).

21. The optical system of any one of claims 2-9, wherein, The second lens (20) comprises at least two nanostructure layers (202); Wherein, the nanostructures in any two adjacent nanostructure layers (202) are coaxially arranged.

22. The optical system of any one of claims 2-9, wherein, The superlens comprises at least two nanostructure layers (202); wherein the nanostructures in any adjacent nanostructure layer (202) are arranged in a staggered manner along the direction parallel to the substrate of the superlens.

23. The optical system of claim 2, wherein, The phase of the second lens (20) further satisfies: ； ； ； ； ； ； ； ； where r is the distance from the center of the second lens (20) to any nanostructure; λ is the working wavelength of the second lens (20); φ0is any phase associated with the working wavelength of the second lens (20); (x, y) are the superlens lens coordinates; f2is the focal length of the second lens (20); a i and b i are real coefficients.

24. The optical system of claim 1, wherein, The optical system further comprises a diaphragm (60), the diaphragm (60), the composite lens, the third lens (30), the fourth lens (40), and the fifth lens (50) are arranged in order from the object side to the image side; At least one of the object side surface and the image side surface of the third lens (30), the object side surface and the image side surface of the fourth lens (40), and the object side surface and the image side surface of the fifth lens (50) is aspherical; the aspherical surface contains one inflection point; The optical system further satisfies: ； ； Wherein, HFOV is half of the maximum field of view of the optical system; d2 is the thickness of the second lens (20).

25. The optical system of claim 24, wherein, The optical system further satisfies: ； wherein R 1o is the radius of curvature of the object side surface of the first lens (10); and f1 is the focal length of the first lens (10).

26. The optical system of claim 24, wherein, The optical system further satisfies: ； Wherein, V1 is the Abbe number of the first lens (10); V4 is the Abbe number of the fourth lens (40); V3 is the Abbe number of the third lens (30).

27. The optical system of claim 24, wherein, The optical system further satisfies: ； Wherein, TTL is the total system length of the optical system; ImgH is the maximum imaging height of the optical system.

28. The optical system of claim 24, wherein, The optical system further satisfies: ； Wherein, f2 is the focal length of the second lens (20) in the optical system; f is the focal length of the optical system.

29. An imaging device, characterized by The imaging device comprises: The optical system according to any one of claims 24-28 and an electronic photosensitive element arranged on the image plane of the optical system.

30. An electronic device, comprising: The electronic device comprises the imaging device according to claim 29.

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