Optical system

Abstract

Embodiments of the present application provide an optical system, which belongs to the technical field of optical systems. The optical system comprises a first lens, a second lens and a third lens arranged in order from an object side to an image side along an optical axis; wherein the first lens and the second lens are configured as super lenses; the first lens is configured as a stop of the optical system; the third lens is configured as a refractive lens, and the focal length of the refractive lens is positive; wherein the optical system at least satisfies: min{t 12 ,t 23}≥0.05mm; wherein f is the focal length of the optical system; f3 is the focal length of the third lens (3); t 12 is the distance between the first lens and the second lens; t 23 is the distance between the second lens (2) and the third lens; and min{t 12 ,t 23} is the minimum value of t 12 and t 23 . Embodiments of the present application realize miniaturization and light weight of the optical system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical systems, and in particular, the present application relates to an optical system. BACKGROUND

[0002] With the advancement of technology, users have increasingly high requirements for optical systems. On the basis of ensuring imaging quality, further pursuit of miniaturization and light weight of equipment is required.

[0003] In the prior art, optical systems are generally composed of three refractive lenses to save installation space in the equipment and promote the miniaturization of the equipment.

[0004] However, the miniaturization of the three-piece optical system is bottlenecked, and continued pursuit of miniaturization will lead to a decline in imaging quality, so a new optical system is urgently needed. SUMMARY

[0005] In order to solve the problem of decline in imaging quality caused by miniaturization of the optical system in the prior art, the embodiments of the present application provide an optical system.

[0006] In a first aspect, the embodiments of the present application provide an optical system, which comprises:

[0007] a first lens, a second lens and a third lens arranged in order from an object side to an image side along an optical axis;

[0008] The first lens and the second lens are configured as super lenses; the first lens is configured as a stop of the optical system;

[0009] The third lens is configured as a refractive lens, and the focal length of the refractive lens is positive;

[0010] The optical system at least satisfies:

[0011] ;

[0012] ;

[0013] Wherein, f is the focal length of the optical system; f2 is the focal length of the second lens; t 12 is the distance between the first lens and the second lens; t 23 is the distance between the second lens and the third lens; is the minimum value of t 12 and t 23 .

[0014] Optionally, the optical system further satisfies:

[0015] ;

[0016] ;

[0017] wherein f is a focal length of the optical system; f1 is a focal length of the first lens; and f3 is a focal length of the third lens.

[0018] Optionally, a radius of curvature of a surface of the third lens facing an object side is smaller than a radius of curvature of a surface of the third lens facing an image side.

[0019] Optionally, the surface of the third lens is spherical or aspherical.

[0020] Optionally, an extinction coefficient of a material of the third lens for a working waveband is less than 10 -4 .

[0021] Optionally, the material of the third lens comprises fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, or hydrogenated amorphous silicon.

[0022] Optionally, the superlens comprises a substrate and a nanostructure layer disposed on one side of the substrate.

[0023] wherein the nanostructure layer comprises periodically arranged nanostructures.

[0024] Optionally, the superlens further comprises a bonding layer.

[0025] The bonding layer is disposed between the substrate and the nanostructure layer.

[0026] Optionally, a phase of the superlens at least satisfies:

[0027] ; ; ; ;

[0028] wherein r is a distance from a center of the superlens to a center of the nanostructure; and λ is a working wavelength of the superlens. is an arbitrary constant phase; (x, y) are coordinates of a surface of the superlens; f i is a focal length of a single superlens, and i is a natural number.

[0029] Optionally, a range of an effective refractive index of the superlens is less than 2.

[0030] The range of the effective refractive index is equal to a maximum effective refractive index minus a minimum effective refractive index.

[0031] Optionally, the substrate of the superlens is made of the same material as the nanostructure.

[0032] Optionally, the substrate of the superlens is different from the nanostructured material.

[0033] Optionally, the refractive index of the nanostructure is greater than the refractive index of the substrate and the adhesive layer.

[0034] Optionally, the thickness of the adhesive layer is less than or equal to 20% of the central wavelength of the working waveband.

[0035] Optionally, the adhesive layer comprises a planar structure parallel to the substrate.

[0036] Optionally, the adhesive layer comprises a nano-adhesive column corresponding to the nanostructure.

[0037] Optionally, the superlens further comprises an anti-reflection film;

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

[0039] the anti-reflection film is arranged on the side of the nanostructure layer adjacent to air.

[0040] Optionally, the method is suitable for the superlens provided in any of the above embodiments, and the method comprises:

[0041] Step S1, coating the adhesive layer on the substrate;

[0042] Step S2, bonding the material wafer of the nanostructure layer to the substrate through the adhesive layer;

[0043] Step S3, thinning the material wafer to a reference thickness;

[0044] Step S4, coating photoresist on the thinned material wafer and exposing a reference structure on the photoresist;

[0045] Step S5, etching the nanostructure on the thinned material wafer based on the reference structure; wherein the etching stop layer is the adhesive layer or the substrate.

[0046] Optionally, the method further comprises:

[0047] Step S6, depositing a filling material between the nanostructures and making the filling material coincide with the surface of the nanostructure layer;

[0048] Optionally, the method further comprises:

[0049] Step S7, coating the anti-reflection film on the side of the substrate away from the adhesive layer; and / or,

[0050] Step S8, coating the anti-reflection film on the side of the nanostructure layer adjacent to air.

[0051] Optionally, the imaging device comprises the optical system and the photosensitive element provided in any of the above embodiments.

[0052] The photosensitive element is arranged on an image plane of the optical system.

[0053] Optionally, the electronic device comprises the imaging device provided in any of the above embodiments.

[0054] The optical system provided in the embodiments of the present application comprises a first lens and a second lens which are super lenses, and a third lens which is a refractive lens. The total length of the optical system is compressed by configuring the focal length ratio of the third lens to the whole optical system and setting the distance between the lens groups, so as to promote the miniaturization of the optical system. Moreover, the optical system introduces the super lens, so as to promote the light weight of the optical system. BRIEF DESCRIPTION OF DRAWINGS

[0055] 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.

[0056] Figure 1 An optional structural schematic diagram of the optical system provided in the embodiments of the present application is shown;

[0057] Figure 2 Another optional structural schematic diagram of the optical system provided in the embodiments of the present application is shown;

[0058] Figure 3 Still another optional structural schematic diagram of the optical system provided in the embodiments of the present application is shown;

[0059] Figure 4 An optional structural schematic diagram of the super lens provided in the embodiments of the present application is shown;

[0060] Figure 5 An optional perspective schematic diagram of the nanostructure of the super lens provided in the embodiments of the present application is shown;

[0061] Figure 6 Still another optional perspective schematic diagram of the nanostructure of the super lens provided in the embodiments of the present application is shown;

[0062] Figure 7 An optional arrangement mode of the nanostructure of the super lens provided in the embodiments of the present application is shown;

[0063] Figure 8 Still another optional arrangement mode of the nanostructure of the super lens provided in the embodiments of the present application is shown;

[0064] Figure 9 Another optional arrangement of the nanostructure of the superlens provided by the embodiments of the present application is shown;

[0065] Figure 10 An optional structural schematic diagram of the superlens provided by the embodiments of the present application is shown;

[0066] Figure 11 Another optional structural schematic diagram of the superlens provided by the embodiments of the present application is shown;

[0067] Figure 12 An optional modulation transfer function of the optical system provided by the embodiments of the present application is shown;

[0068] Figure 13 A wavelength phase map of the first lens in the optional optical system provided by the embodiments of the present application is shown;

[0069] Figure 14 A wavelength phase map of the second lens in the optional optical system provided by the embodiments of the present application is shown;

[0070] Figure 15 Another optional modulation transfer function of the optical system provided by the embodiments of the present application is shown;

[0071] Figure 16 Another wavelength phase map of the first lens in the optional optical system provided by the embodiments of the present application is shown;

[0072] Figure 17 Another wavelength phase map of the second lens in the optional optical system provided by the embodiments of the present application is shown;

[0073] Figure 18 Another optional modulation transfer function of the optical system provided by the embodiments of the present application is shown;

[0074] Figure 19 Another wavelength phase map of the first lens in the optional optical system provided by the embodiments of the present application is shown;

[0075] Figure 20 Another wavelength phase map of the second lens in the optional optical system provided by the embodiments of the present application is shown;

[0076] Figure 21 An optional flow chart of the preparation method of the superlens provided by the embodiments of the present application is shown;

[0077] Figure 22 Another optional flow chart of the preparation method of the superlens provided by the embodiments of the present application is shown;

[0078] Figure 23Another optional flow chart of the method for manufacturing the superlens provided by the embodiments of the present application is shown.

[0079] Figure 24 An optional phase diagram of the superlens provided by the embodiments of the present application is shown.

[0080] Figure 25 An optional transmittance diagram of the superlens provided by the embodiments of the present application is shown.

[0081] The reference signs in the drawings respectively represent:

[0082] 1 - first lens; 2 - second lens; 3 - third lens;

[0083] 11 - substrate; 12 - nanostructure layer; 13 - adhesive layer; 14 - antireflection film; 15 - filling material; 16 - photoresist layer;

[0084] 120 - material wafer of the nanostructure layer; 120' - material wafer of the nanostructure layer; 121 - nanostructure; 122 - superstructure unit; 131 - nano glue column. DETAILED DESCRIPTION

[0085] The present application will now be described more fully hereinafter with reference to the accompanying drawings, in which various 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.

[0086] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. For example, the term "a component" is intended to mean "at least one component". The term "at least one of" followed by a list of one or more components is intended to mean that at least one, but not necessarily including one, of the listed components is included. The term "or" means "and / or". The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0087] Unless otherwise defined, all terms used in this disclosure, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms, such as those defined in commonly used 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 in the specification.

[0088] The meaning of "including" or "comprising" indicates the presence of the stated feature, number, step, operation, component, component, or combination thereof, but does not exclude the presence or addition of other features, numbers, steps, operations, components, components, or combinations thereof.

[0089] Embodiments are described herein with reference to cross-sectional illustrations that are idealized embodiments. Consequentially, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments described herein are not to be construed as being limited to the particular shapes as illustrated herein but are to include deviations in shapes that result from, for example, manufacturing. For example, an area illustrated or described as flat can typically have rough and / or nonlinear features. Moreover, illustrated sharp angles can be rounded. Thus, the regions illustrated in the figures are schematic and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims.

[0090] Hereinafter, exemplary embodiments according to the present application will be described with reference to the accompanying drawings.

[0091] There is a technology in the prior art that combines a superlens with a refractive lens, and such an optical system can only correct on-axis chromatic aberration, far from meeting the needs of full aberration correction and full-spectrum clear imaging. Based on the foregoing prior art, a technical bias is formed that a superlens can only correct on-axis chromatic aberration and cannot be used for full aberration correction and full-spectrum imaging. With the miniaturization and lightness of electronic devices, the miniaturization and lightness of optical systems are increasingly important. The present application provides an optical system that realizes full-spectrum imaging and full aberration correction through a refractive lens and a superlens, and also reduces the weight of a three-piece optical system by two-thirds.

[0092] In a first aspect, the embodiments of the present application provide an optical system as shown in Figure 1 、 Figure 2 and Figure 3 . The optical system includes a first lens 1, a second lens 2, and a third lens 3 arranged in order from the object side to the image side along the same optical axis. Among them, the first lens 1 and the second lens 2 are configured as superlenses, and the third lens 3 is a positive focal length refractive lens. The first lens 1 is configured as the stop of the optical system. The third lens 3 is configured as a positive focal length refractive lens. And the optical system at least meets:

[0093] (1)

[0094] (2)

[0095] In the formulas (1) and (2), f is the focal length of the optical system; f2 is the focal length of the second lens 2; t 12 is the distance between the first lens 1 and the second lens 2; t 23 is the distance between the second lens 2 and the third lens 3; and t is the minimum value of t 12 and t 23 .

[0096] It should be noted that the distance between lenses in the embodiments of the present application refers to the distance between two adjacent surfaces of two adjacent lenses. Alternatively, in some cases, since the thickness of the nanostructure layer of the superlens surface is much smaller than the thickness of the substrate, the distance between the refractive lens (or superlens) and the adjacent superlens can be the distance from the surface of the refractive lens (or superlens) to the surface of the adjacent superlens substrate. The first lens 1 is configured as a stop, which is beneficial on the one hand to reduce the aperture of the superlens, thereby reducing the required equivalent refractive index range for designing the superlens; on the other hand, the first lens 1 configured as a stop is also beneficial to compress the aperture of the superlens and the entire optical system. Compressing the aperture of the superlens is also beneficial to simplify the production process of the superlens. For example, alternatively, after the aperture of the first lens 1 and the second lens 2 is compressed, single exposure can be used for processing, without involving complex layout process.

[0097] Referring to Figure 1 , Figure 2 and Figure 3 , the incident radiation is emitted from the first lens 1, and is modulated by the second lens 2 and the third lens 3 in turn, and finally forms an image on the image plane. According to the embodiments of the present application, the apertures and focal lengths of the first lens 1, the second lens 2 and the third lens 3 are D1, D2, D3 and f1, f2, f3 respectively; the distance between the first lens 1 and the second lens 2 is t 12 , and the distance between the second lens 2 and the third lens 3 is t 23 . The focal length of the optical system is f, and the back focal length is BFL.

[0098] Alternatively, the equivalent refractive index range of the superlens provided by the embodiments of the present application is less than 2. The equivalent refractive index range of the superlens refers to the maximum equivalent refractive index minus the minimum equivalent refractive index. In this way, the refractive index of the superlens can be prevented from being too large, which can cause the aberration to be intensified and the imaging quality to be reduced.

[0099] According to embodiments of the present application, the focal length of the first lens 1 and the second lens 2 is not specially required to be positive or negative. In another alternative embodiment, the optical system provided by the embodiments of the present application also satisfies:

[0100] ; (3)

[0101] ; (4)

[0102] In the formulas (3) and (4), f is the focal length of the optical system; f1 is the focal length of the first lens 1; and f3 is the focal length of the third lens 3.

[0103] According to embodiments of the present application, the third lens 3 is a refractive lens, and the radius of curvature of the surface of the third lens 3 facing the object side is smaller than the radius of curvature of the surface of the third lens 3 facing the image side. For example, the third lens 3 is a plano-convex lens, and the plane of the plano-convex lens faces the image side, and the curved surface faces the object side. For another example, the third lens 3 can be a biconvex lens or a meniscus lens, as long as the radius of curvature of the surface of the third lens 3 facing the object side is smaller than the radius of curvature of the surface of the third lens 3 facing the image side.

[0104] According to embodiments of the present application, the material of the third lens 3 is a material with high transmittance in the working waveband. Preferably, the extinction coefficient of the third lens 3 to the working waveband is less than 10 -4 . For example, the material of the third lens 3 includes one or more of fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, or hydrogenated amorphous silicon.

[0105] Next, the superlens used in the embodiments of the present application is described in detail as follows. Figures 4 to 11

[0106] The superlens is a specific application of the metasurface, and the superlens modulates the phase, amplitude, and polarization of the incident light through the periodic arrangement of nanometer structures with subwavelength size. Figures 4 to 9 As shown in the figure, the superlens includes a substrate 11 and a nanometer structure layer 12 arranged on one side of the substrate 11; wherein the nanometer structure layer 12 includes periodically arranged nanometer structures 121. Figure 5 and Figure 6 The figure shows an alternative perspective view of the nanometer structure 121 of the superlens used in the optical system provided by the embodiments of the present application.

[0107] As Figure 1 shown, the nanometer structure layer of the first lens 1 is arranged on the side of the substrate 11 facing the second lens 2; and the nanometer structure layer of the second lens 2 is arranged on the side of the substrate 11 facing the third lens 3. As Figure 2 ​As shown, the nanostructure layer of the first lens 1 is disposed on the side of the substrate 11 facing the second lens 2; the nanostructure layer 12 of the second lens 2 is disposed on the side of the substrate 11 facing the first lens 1. Without any theoretical limitations, the orientation of the nanostructure layer of either the first lens 1 or the second lens 2 can be either the side of the substrate 11 away from the image side or the side of the substrate 11 closer to the image side. Generally, the nanostructure layer 12 of the first lens 1 is disposed on the side of the optical system away from the object side to prevent wear and tear on the nanostructure layer 12 during use.

[0108] Optionally, the spaces between the nanostructures on the superlens may be filled with air or other materials that are transparent or translucent in the operating wavelength band, hereinafter referred to as filler material 15. Optionally, the extinction coefficient of filler material 15 for radiation in the operating wavelength band is less than 0.01. For example, filler material 15 may optionally include one or more of fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, or hydrogenated amorphous silicon.

[0109] According to embodiments of this application, the absolute value of the difference between the refractive index of the filler material 15 and the refractive index of the nanostructure 121 should be greater than or equal to 0.5. For example... Figure 5 As shown, nanostructure 121 can be a polarization-sensitive structure, which imposes a geometric phase on the incident light. Examples include elliptical cylinders, hollow elliptical cylinders, elliptical apertures, hollow elliptical apertures, rectangular prisms, rectangular apertures, hollow rectangular prisms, and hollow rectangular apertures. Figure 6 As shown, nanostructure 121 can be a polarization-insensitive structure, which imposes a propagation phase on the incident light. Examples include cylindrical, hollow cylindrical, circular aperture, hollow circular aperture, square prism, square aperture, hollow square prism, and hollow square aperture structures.

[0110] In some alternative embodiments, the nanostructure layer 12 includes periodically arranged superstructure units 122, which are close-packed patterns, and each superstructure unit 122 has a nanostructure 121 disposed at its center and / or vertex.

[0111] like Figure 7 As shown, according to an embodiment of this application, the superstructure units can be arranged in a fan shape. Figure 8 As shown, according to an embodiment of this application, the superstructure units can be arranged in a regular hexagonal array. Furthermore, as... Figure 9 As shown, according to embodiments of this application, the superstructure units can be arranged in a square array. Those skilled in the art will recognize that the superstructure units 122 included in the nanostructure layer 12 can also include other forms of array arrangement, and all such variations are covered within the scope of this application.

[0112] Optionally, the period of the superstructure element 122 is greater than or equal to 0.3λ. c And less than or equal to 2λ c ; where λ c λ is the center wavelength of the operating band; when the operating band is multi-band, λ c This is the center wavelength of the shortest operating band. Optionally, the height of nanostructure 121 is greater than or equal to 0.3λ. c And less than or equal to 5λ c ; where λ c λ is the center wavelength of the operating band; when the operating band is multi-band, λ c It is the center wavelength of the shortest wavelength operating band.

[0113] According to an embodiment of this application, the nanostructure 121 is an all-dielectric structural unit. The nanostructure is made of a material with high transmittance in the operating wavelength band of the optical system. Optionally, the extinction coefficient of the nanostructure 121 for radiation in the operating wavelength band is less than 0.01. Exemplarily, the material of the nanostructure 121 includes one or more of the following: fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, hydrogenated amorphous silicon, etc.

[0114] In one optional embodiment, the material of the substrate 11 is the same as the material of the nanostructure 121. In yet another optional embodiment, the material of the substrate 11 is different from the material of the nanostructure 121. The material of the substrate 11 is a material with high transmittance in the working wavelength band. Optionally, the extinction coefficient of the substrate 11 for radiation in the working wavelength band is less than 0.01. Exemplarily, the material of the substrate 11 can be one or more of the following: fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, hydrogenated amorphous silicon, etc.

[0115] In yet another alternative implementation, such as Figure 10 and Figure 11 As shown, the superlens provided in this embodiment further includes an adhesive layer 13, which is disposed between the substrate 11 and the nanostructure layer 12. In some cases, the nanostructure 121 is bonded to the substrate 11 by the adhesive layer 13. For example, in some cases, limitations in the fabrication process result in insufficient bonding between the material of the nanostructure 121 and the material of the substrate 11; in such cases, the adhesive layer 13 can make the bonding between the nanostructure 121 and the substrate 11 more stable. As another example, in some cases, the nanostructure 12 cannot be grown on the substrate 11 by a deposition process; in such cases, the nanostructure 12 can be grown on the substrate 11 by the adhesive layer 13. The superlens having the adhesive layer 13 will be referred to as a cemented superlens below.

[0116] According to embodiments of this application, the thickness of the adhesive layer 13 is less than or equal to 20% of the center wavelength of the superlens's operating band, thereby increasing the transmittance of incident radiation. If the thickness of the adhesive layer 13 is greater than 20% of the center wavelength of the operating band, the incident radiation will cause destructive interference within the adhesive layer 13, reducing the transmittance of the superlens to the operating band. In some optional embodiments, such as... Figure 11 As shown, the adhesive layer 13 includes a planar structure parallel to the substrate 11. In an alternative embodiment, as... Figure 11 As shown, the adhesive layer 13 includes nanopillars 131 corresponding to the nanostructure 121. For example, the adhesive layer 13 may consist entirely of nanopillars 131. Alternatively, at least a portion of the adhesive layer 13 may be nanopillars 131, each corresponding to a portion of the nanostructure 121. Exemplarily, the number, size, and shape of the nanopillars 131 are the same as those of the nanostructure 121. It should be understood that the dimensions (height, width, diameter, etc.) and shapes of the nanopillars 131 and the nanostructure 121 may be the same or different.

[0117] In some optional embodiments of this application, the superlens further includes an antireflective coating 14. The antireflective coating 14 is disposed on the side of the substrate 11 away from the adhesive layer 13 of the nanostructure layer 12; and / or, the antireflective coating 14 is disposed on the side of the nanostructure layer 12 adjacent to air. The antireflective coating 14 is used to increase the transmittance of incident radiation.

[0118] Optionally, the phase of the superlens provided in the embodiments of this application satisfies at least the following:

[0119] (5) (6) (7) (8)

[0120] Where r is the distance from the center of the superlens to the center of the nanostructure 121; λ is the operating wavelength of the superlens; f is an arbitrary constant phase; (x, y) are the coordinates of the surface of the superlens; i Let f be the focal length of a single superlens, where i is a natural number (e.g., the focal length of the first lens 1 is f1). It should be noted that the phase of the superlens can be expressed by a high-order polynomial, which includes both even-order and odd-order polynomials.

[0121] Example 1

[0122] This application provides an optical system, the principle and structure of which are as follows: Figure 2 As shown in the figure, the specific structural parameters are shown in Table 1. Among them, the substrate material of the first lens 1 and the second lens 2 is chalcogenide glass IRG01, and the material of the third lens 3 is single crystal germanium.

[0123] Table 1

[0124]

[0125] The imaging results of the optical system provided in Embodiment 1 are shown in Figures 12 to 14 . The modulation transfer functions of the optical system at 0 field of view, 0.5 field of view and 1 field of view are shown. As shown in Figure 12 , the modulation transfer functions of the optical system at different field of view are close to but not more than the diffraction limit. Therefore, the imaging quality of the optical system is excellent. Figure 12 The phase relationship diagrams of the incident radiation of different wavelengths along the superlens radius direction of the first lens 1 are shown. Figure 13 The phase relationship diagrams of the incident radiation of different wavelengths along the superlens radius direction of the second lens 2 are shown. Figure 14 The central wavelengths of the incident radiation in Figure 13 and Figure 14 are 8 μm, 10 μm and 12 μm respectively. As shown in Figure 13 and Figure 14 , the imaging quality of the optical system is excellent.

[0126] Example 2

[0127] Embodiments of the present application also provide an optical system, the principle and structure of which are shown in Figure 2 , and the specific structure parameters are shown in Table 2.

[0128] Table 2

[0129]

[0130] The imaging results of the optical system provided in Embodiment 2 are shown in Figures 15 to 17 . The modulation transfer functions of the optical system at 0 field of view, 0.5 field of view and 1 field of view are shown. As shown in Figure 15 , the modulation transfer functions of the optical system at different field of view are close to but not more than the diffraction limit. Therefore, the imaging quality of the optical system is excellent. Figure 15 The phase relationship diagrams of the incident radiation of different wavelengths along the superlens radius direction of the first lens 1 are shown. Figure 16 The phase relationship diagrams of the incident radiation of different wavelengths along the superlens radius direction of the second lens 2 are shown. Figure 17 The central wavelengths of the incident radiation in Figure 16 and Figure 17 are 8 μm, 10 μm and 12 μm respectively. As shown in Figure 16 and Figure 17 , the imaging quality of the optical system is excellent.

[0131] Embodiment 3

[0132] This application also provides an optical system, the principle and structure of which are as follows: Figure 3 As shown in Table 3, the specific structural parameters are as follows.

[0133] Table 3

[0134]

[0135] The imaging results of the optical system provided in Example 3 are shown in [reference]. Figures 18 to 20 . Figure 20 The modulation transfer functions of the optical system at 0, 0.5, and 1 field of view are shown. Figure 18 It can be seen that the modulation transfer function of this optical system is close to but does not exceed the diffraction limit in different fields of view. Therefore, the imaging quality of this optical system is excellent. Figure 19 The phase relationship diagram of incident radiation of different wavelengths along the radial direction of the first lens 1 is shown. Figure 20 The phase relationship diagram of incident radiation of different wavelengths along the radius of the superlens in the second lens 2 is shown. Figure 19 and Figure 20 The center wavelengths of the incident radiation are 8 μm, 10 μm, and 12 μm, respectively. Figure 19 and Figure 20 It is evident that the imaging quality of this optical system is excellent. It should be noted that the superlens provided in this embodiment can be fabricated using semiconductor technology, offering advantages such as light weight, thinness, simple structure and process, low cost, and high consistency in mass production.

[0136] It should be understood that the working bands of the superlens provided in the embodiments of this application include the visible light band, near-infrared band, mid-infrared band, far-infrared band, ultraviolet light band, deep ultraviolet light band, and extremely deep ultraviolet light band.

[0137] Secondly, embodiments of this application also provide a method for fabricating a superlens, used to process the cemented superlens provided in any of the above embodiments. For example... Figure 21 As shown, the preparation method includes at least the following steps S1 to S5.

[0138] Step S1: Apply adhesive layer 13 to substrate 11. Substrate 11 can be a plane or a curved surface. For example, substrate 11 can be a freeform surface.

[0139] In step S2, the material wafer 120 of the nanostructure layer is bonded to the substrate 11 using the adhesive layer 13. Optionally, the bonding between the material wafer 120 and the substrate 11 can be a permanent bonding or a temporary bonding.

[0140] Step S3, thinning the material wafer 120 to a reference height. Optionally, the thinning method of the material wafer 120 in the embodiments of the present application includes grinding and polishing. The reference height refers to a height that meets the target optical performance design of the glued superlens.

[0141] Step S4, coating photoresist on the thinned material wafer, exposing a reference structure on the photoresist to form a photoresist layer 16.

[0142] Step S5, etching the nanostructure 121 on the thinned material wafer 120' based on the reference structure. The etching stop layer is the glue layer 13 or the substrate 11. Optionally, the photoresist is removed after etching.

[0143] The superlens preparation method provided by the embodiments of the present application overcomes the limitations of the nanostructure material and the substrate material on the superlens by gluing the material wafer and the substrate after gluing the nanostructure material wafer and the substrate, thinning the material wafer, and improving the preparation process of the superlens. The method can break through the limitations of the material in the traditional superlens preparation, realize the combination of more materials through gluing, and thus break through the limitations of the nanostructure material and the substrate material on the imaging effect of the superlens.

[0144] According to the embodiments of the present application, as shown in Figure 22 Step S6, depositing a filling material 15 between the nanostructures 121 and making the filling material 15 coincide with the surface of the nanostructure layer 12. Optionally, the deposition method of the filling material 15 includes but is not limited to atomic layer deposition (ALD) and chemical vapor deposition (CVD).

[0145] In some optional embodiments of the present application, as shown in Figure 23 The method further includes:

[0146] Step S7, coating an antireflection film 14 on the side of the substrate 11 away from the glue layer 13; and / or, Step S8, coating an antireflection film 14 on the side of the nanostructure layer 12 adjacent to the air. That is, the antireflection film 14 can be arranged on both sides of the substrate 11. Optionally, the method of coating the antireflection film 14 includes but is not limited to evaporation.

[0147] Example 4

[0148] The embodiments of the present application provide an exemplary glued superlens prepared by the above steps S1 to S5. The material of the substrate 11 in the glued superlens is chalcogenide glass, the material of the glue layer 13 is bonding glue, and the material of the nanostructure 121 is crystalline silicon. The thickness of the glue layer 13 is 1 μm. Figure 24The phase diagram of the glued superlens is shown. Figure 25 The transmittance diagram of the glued superlens is shown.

[0149] In a third aspect, the embodiments of the present application further provide an imaging device, which comprises the optical system and the photosensitive element provided by any of the above embodiments. The photosensitive element is arranged on an image plane of the optical system.

[0150] In a fourth aspect, the embodiments of the present application further provide an electronic device, which comprises the imaging device provided by the above embodiments.

[0151] In summary, the optical system provided by the embodiments of the present application comprises a first lens and a second lens which are superlenses, and a third lens which is a refractive lens. The total length of the optical system is compressed by configuring the focal length ratio of the third lens to the whole optical system and setting the distance between the lens groups, thereby promoting the miniaturization of the optical system. Moreover, the optical system introduces superlenses, thereby promoting the light weight of the optical system. The optical system saves the installation space in the electronic device.

[0152] The superlens preparation method provided by the embodiments of the present application comprises gluing the nanometer-structured material wafer and the substrate through the glue layer and then thinning the material wafer, thereby overcoming the limitation of the nanometer-structured material and the substrate material on the superlens and improving the preparation process of the superlens.

[0153] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An optical system, characterized in that, The optical system includes: The first lens (1), the second lens (2), and the third lens (3) are arranged coaxially from the object side to the image side. Wherein, the first lens (1) and the second lens (2) are configured as superlenses; the first lens (1) is configured as the aperture stop of the optical system to reduce the aperture of the first lens (1), the second lens (2) and the optical system; The third lens (3) is configured as a refractive lens, and the focal length of the refractive lens is positive; The optical system shall at least satisfy the following: ； ； ； Where f is the focal length of the optical system; f1 is the focal length of the first lens (1); f2 is the focal length of the second lens (2); f3 is the focal length of the third lens (3); t 12 The distance between the first lens (1) and the second lens (2); t 23 The distance between the second lens (2) and the third lens (3); For t 12 and t 23 The minimum value in.

2. The optical system as described in claim 1, characterized in that, The optical system also satisfies: ； ； Where f is the focal length of the optical system; f1 is the focal length of the first lens (1); and f3 is the focal length of the third lens (3).

3. The optical system as described in claim 1, characterized in that, The radius of curvature of the surface of the third lens (3) facing the object side is smaller than the radius of curvature of the surface facing the image side.

4. The optical system as described in claim 3, characterized in that, The surface of the third lens (3) is either spherical or aspherical.

5. The optical system as described in any one of claims 1-4, characterized in that, The material of the third lens (3) has an extinction coefficient of less than 10 for the working wavelength band. -4 .

6. The optical system as described in any one of claims 1-4, characterized in that, The materials of the third lens (3) include fused silica, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, or hydrogenated amorphous silicon.

7. The optical system as claimed in claim 1, characterized in that, The superlens includes a substrate (11) and a nanostructure layer (12) disposed on one side of the substrate (11). The nanostructure layer (12) includes periodically arranged nanostructures (121).

8. The optical system as claimed in claim 7, characterized in that, The superlens also includes an adhesive layer (13); The adhesive layer (13) is disposed between the substrate (11) and the nanostructure layer (12).

9. The optical system as claimed in claim 8, characterized in that, The phase of the superlens satisfies one of the following formulas: ； ； ； ； Where r is the distance from the center of the superlens to the center of the nanostructure (121); λ is the operating wavelength of the superlens; f is an arbitrary constant phase; (x, y) are the coordinates of the surface of the superlens; i Let i be the focal length of a single superlens, where i is a natural number.

10. The optical system as claimed in claim 1, characterized in that, The effective refractive index of the superlens is less than 2. The range of the equivalent refractive index is equal to the maximum equivalent refractive index minus the minimum equivalent refractive index.

11. The optical system as claimed in claim 7 or 8, characterized in that, The substrate (11) of the superlens is made of the same material as the nanostructure (121).

12. The optical system as claimed in claim 7 or 8, characterized in that, The substrate (11) of the superlens is made of a different material than the nanostructure (121).

13. The optical system as claimed in claim 8, characterized in that, The refractive index of the nanostructure is greater than that of the substrate (11) and the adhesive layer (13).

14. The optical system as claimed in claim 8, characterized in that, The thickness of the adhesive layer (13) is less than or equal to 20% of the center wavelength of the working band.

15. The optical system as claimed in claim 14, characterized in that, The adhesive layer (13) includes a planar structure parallel to the substrate (11).

16. The optical system as claimed in claim 14, characterized in that, The adhesive layer (13) includes nanopillars (131) corresponding to the nanostructure (121).

17. The optical system as claimed in claim 7 or 8, characterized in that, The superlens also includes an anti-reflective coating (14). The antireflective film (14) is disposed on the side of the substrate (11) away from the nanostructure layer (12) or the adhesive layer (13); and / or, The antireflective membrane (14) is disposed on the side of the nanostructure layer (12) adjacent to air.

18. An imaging device, characterized in that, The imaging device includes the optical system and photosensitive element as described in any one of claims 1-17; The photosensitive element is disposed on the image plane of the optical system.

19. An electronic device, characterized in that, The electronic device includes the imaging apparatus as described in claim 18.

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