An infrared superconducting hybrid lens

Abstract

This invention discloses an infrared refractive-hybrid lens, relating to the field of infrared imaging technology. It includes a first lens with negative optical power, an aperture stop, a metalens, and a second lens with positive optical power, arranged sequentially from the object plane to the image plane along the optical axis. Positive chromatic aberration is obtained through a refractive spherical surface, and negative chromatic aberration is obtained through a diffractive surface; the optical power of these two is allocated to achieve chromatic aberration correction. A large portion of the optical power is handled by refractive elements with both positive and negative optical power, while the remaining chromatic aberration and spherical aberration are corrected using metasurface elements. This invention achieves a lightweight infrared imaging system with a large field of view and a large numerical aperture; utilizing the temperature insensitivity of the metalens, the system has a pyro-aberration reduction effect; and by eliminating the use of aspherical lenses and reducing the number of lenses, the weight and cost of the lens are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of infrared imaging technology, and in particular to an infrared-hybrid lens. Background Technology

[0002] Infrared imaging and identification have a wide range of practical applications. They can be used in areas such as human body temperature detection and civilian security monitoring, and are also an important component of guidance technology. With the development of science and technology and application needs, there is a greater demand for the integration, multi-functionality, and intelligence of these devices.

[0003] There is a growing demand for miniaturized and lightweight optical imaging systems while maintaining image quality; that is, imaging lens assemblies should be smaller and lighter, while effectively controlling production costs. Secondly, compatibility with CMOS architecture and integration will be a major trend in the future development of optical imaging systems. Although high-quality imaging has been achieved using traditional bulk geometric optical systems, there is limited room for further development in integration, requiring breakthroughs in theoretical design. Furthermore, the need for aspherical surfaces in the case of large apertures and large numerical apertures will increase the overall system cost. With further research, hybrid refractive and hyperplastic lenses have also been proposed for achieving miniaturization and integration of optical systems.

[0004] However, in traditional hybrid refractive and hyperlens designs, the refractive element is required to have multiple aspherical surfaces. This approach has high processing costs, limiting production applications and failing to fully utilize the wavefront modulation capability of the hyperlens. Therefore, this application provides a novel infrared hybrid refractive and hyperlens lens and its design method, achieving a miniaturized and low-cost infrared imaging optical system without using aspherical surfaces. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an infrared refractive-meta-chromatic hybrid lens. This invention achieves chromatic aberration correction by using a refractive spherical surface to obtain positive chromatic aberration and a diffractive surface to obtain negative chromatic aberration. The optical power of both is allocated to correct chromatic aberration. A large portion of the optical power is handled by a refractive element with both positive and negative optical power, while the remaining chromatic and spherical aberrations are corrected using a metasurface element. This fully leverages the advantages of both types of elements, achieving high imaging quality while meeting the requirements of low cost and miniaturization.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] An infrared hybrid lens includes a first lens, an aperture, a meta lens, and a second lens arranged sequentially from the object plane to the image plane along the optical axis; wherein the first lens has negative optical power and the second lens has positive optical power; the meta lens includes a substrate and microstructures arranged on the substrate, the microstructures being aperture-type structures located on the image side of the meta lens, and the microstructures being periodically arranged in an array on the substrate.

[0008] Preferably, both sides of the first lens are spherical, with the object side being concave and the image side being convex; the object side of the second lens is spherical and convex, and the image side is planar; the object side of the meta-lens is planar, and the image side is a diffraction surface, which has equal-group delay dispersion characteristics.

[0009] Preferably, the phase design method for the microstructure includes the following steps:

[0010] S1. Construct a polynomial expression for the phase profile Φ of the metasurface. Based on the polynomial formula, design the phase profile of the metasurface as needed. The polynomial expression for the phase profile Φ of the metasurface is as follows:

[0011]

[0012] In the formula, the diffraction order of the metasurface is M, the maximum number of terms is N, the normalized radius is R, and the coefficients of each term in the polynomial are A. i ;

[0013] S2. Adjust the arrangement period p and depth h of the microstructures. By traversing the structural parameters d of each microstructure, simulate the phase-wavelength curve of the microstructure, where 0.25≤d / p≤0.8. Calculate the group delay dispersion characteristics of the microstructure in the working band and the center wavelength phase of the microstructure.

[0014] S3. Select a set of structural parameters d for the microstructures to make the current metalens meet the design requirements. The design requirements include that the center wavelength phase of each microstructure is consistent with the phase profile determined in S1, and that the group delay dispersion characteristics of each microstructure are equal. If the microstructures cannot meet the design requirements, return to S2 to adjust the period and depth of the microstructures. Repeat S2 until the current metalens meets the design requirements.

[0015] S4. Based on the processing accuracy of the processing equipment, determine whether the current microstructure design can be processed. If it is determined that the microstructure cannot be processed, return to S2, change the microstructure parameters, and repeat S2-S3 until it is confirmed that the microstructure can be processed.

[0016] The beneficial effects of adopting the above technical solution are:

[0017] This invention utilizes two refracting spherical mirrors and one metalens to achieve a lightweight infrared imaging system with a large field of view and a large numerical aperture; it takes advantage of the temperature insensitivity of the metalens to achieve thermal aberration reduction; this invention has no aspherical lenses and requires fewer lens elements, effectively reducing lens weight and cost. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the optical system of an infrared superconducting hybrid lens provided by the present invention;

[0019] Figure 2 This is a schematic diagram of the optical path of an infrared refracting-hybrid lens provided in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of a meta-lens microstructure unit provided in an embodiment of the present invention;

[0021] Figure 4 yes Figure 2 The MTF curve of the optical system shown;

[0022] Figure 5 yes Figure 2 A dot diagram of the optical system shown.

[0023] Figure 6 yes Figure 2 The illuminance curve of the optical system shown.

[0024] Figure 7 yes Figure 2 Phase distribution diagram of the metalens in the optical system shown;

[0025] Figure 8 yes Figure 2 The MTF curves of the optical system shown are displayed at high and low temperatures.

[0026] Explanation of reference numerals in the attached figures: 101 is the first surface of the first lens; 102 is the second surface of the first lens; 200 is the aperture stop; 301 is the first surface of the meta-lens; 302 is the second surface of the meta-lens; 401 is the first surface of the second lens; 402 is the second surface of the second lens; 500 is the window plate; 600 is the image plane. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention or the claims of this invention without creative effort should fall within the scope of protection of this invention.

[0028] The present invention includes: an infrared hyperrefractive hybrid lens, referenced... Figure 1 This includes a first lens with negative optical power, an aperture, a metalens, and a second lens with positive optical power, arranged sequentially along the optical axis from the object plane to the image plane. Infrared refractive-meta-lens imaging is observed using a detector with a germanium window. For example... Figure 2The light rays, as shown, pass sequentially along the optical axis through a first lens, an aperture, a metalens, and a second lens, finally converging into a clear image through a germanium window on the detector surface. This embodiment of the invention uses a 160*120 detector with a pixel size of 17µm. It achieves an infrared refractive-hybrid lens with an f-number (F-number) of 1.08, a focal length of 3.1mm, a field of view (FOV) greater than 60°, and a total of 3 lens elements, operating in the 8µm–12µm wavelength range. By adjusting the curvature, thickness, and phase parameters of each lens, this embodiment can be used in environments ranging from -30℃ to 80℃, with a total lens length of less than 15mm. The lens performance parameters demonstrate that this embodiment of the invention manufactures an infrared refractive-hybrid short-focal-length wide-angle optical system.

[0029] As a preferred implementation method, such as Figure 1 , 2 As shown, the object-side surface of each lens is called the first surface, and the image-side surface is called the second surface. The first surface 101, the second surface 102 of the first lens, and the first surface 401 of the second lens are all spherical. The first lens is a meniscus lens, with its first surface 101 being concave and its second surface 402 being convex. The second lens is a plano-convex lens, with its first surface 401 being convex and its second surface 402 being planar. The meta-lens has a first surface 301 being planar and a second surface 302 being a diffraction surface. The meta-lens is a circular lens with uniform thickness, including a substrate and microstructures arranged on the substrate. The substrate is located on one side of the planar surface of the meta-lens, and the microstructures are located on one side of the diffraction surface. All microstructures are arranged in a periodic array on the substrate.

[0030] In a preferred embodiment, the equivalent focal length f of the infrared superconducting lens satisfies f≥3.1mm; the distance from the first surface 101 of the first lens to the image plane is the total optical length TTL; where 3≤TTL / f≤5.5.

[0031] In a preferred embodiment, the meta-lens is made of silicon and has a thickness of 0.5 mm, and both the first lens and the second lens are made of chalcogenide glass.

[0032] For example, Table 1 describes in detail the specific optical system parameters of each lens in the infrared hyperrefractive lens provided in the embodiment of the present invention at room temperature, according to a preferred embodiment.

[0033] Table 1. Optical System Structural Parameters

[0034]

[0035] Wherein, numbers 0-8 represent the first surface 101 and second surface 102 of the first lens, the first surface 301 (coinciding with the aperture stop 200) and second surface 302 of the meta-lens, the first surface 401 and second surface 402 of the second lens, the object-side surface of the window, the image-side surface, and the image plane 600, respectively. The phase profile Φ of the meta-lens is designed using the following polynomial:

[0036]

[0037] In the formula, M is the diffraction order of the metasurface, N is the maximum number of terms, R is the normalized radius, and A i These are the coefficients of the polynomial; for example, Table 2 details the phase of the metalens in this embodiment. Figure 7 The phase distribution diagram corresponds to the metalens, with units of rad / 2π.

[0038] Table 2 Polynomial Coefficients of the Superlens

[0039]

[0040] Figure 3 This is a schematic diagram of the microstructure of the metalens in this embodiment. The dashed lines represent invisible lines. To achieve equal group delay characteristics, this embodiment uses a aperture-type microstructure with a period of 4 μm. The structural parameter d (d represents the aperture diameter for a circular aperture and the side length for a square aperture) is in the range of 1.5 μm to 3 μm, and the aperture depth h = 12 μm. Circular apertures are the most commonly used due to their lower fabrication difficulty. This embodiment also uses square or cross-shaped apertures to expand the phase dispersion library of the microstructure. Furthermore, the use of a subwavelength microstructure arrangement period achieves high diffraction efficiency and improves overall transmission efficiency. The use of a 12 μm deep microstructure effectively ensures the equal group delay requirement of 2π phase coverage at the center wavelength.

[0041] The microstructure diffraction surface of the metalens exhibits equal-group retardation dispersion characteristics, and the phase design method of the microstructure includes the following steps:

[0042] S1. Define the phase profile Φ of the meta-lens by a polynomial formula, and obtain the ideal phase profile Φ of the meta-lens by iterative optimization according to the basic parameter requirements of lens optical design.

[0043] S2. Adjust the arrangement period and depth of the microstructure, and calculate the group delay dispersion characteristics of the microstructure in the working band (8~12um) and the center wavelength phase of the microstructure by simulating the phase-wavelength curve of the microstructure; the arrangement period is the spacing distance of each row / column of microstructure.

[0044] S3. Combine the phase profile Φ determined in S1 to match and determine the microstructures at each radius of the meta-lens. Each microstructure needs to satisfy that the center wavelength phase is consistent with the phase profile and that the group delay dispersion characteristics of each microstructure are equal. If it is determined that the microstructure cannot completely match the phase profile requirements, return to S2, change the microstructure arrangement period and depth, and repeat S2 until the microstructure can completely match the designed phase profile.

[0045] S4. Based on the distribution of matched microstructure parameters, determine the microstructure layout for processing. Observe the processing results to determine whether the current design can be processed. If it is determined that the microstructure cannot be processed (such as detachment, excessive aperture error, etc.), return to S2, change the microstructure parameters, and repeat S2-3 until it is confirmed that the microstructure can be processed.

[0046] Figure 4 This is a schematic diagram of the MTF curve of an embodiment of the present invention at room temperature, which achieves a transfer function greater than 0.4 at 35 mm / lp. Figure 5 The image shown is a dot plot of an embodiment of the present invention at room temperature. The dot plot is concentrated and can be matched with an uncooled long-wave infrared detector. Both the MTF curve and the dot plot indicate that this embodiment is close to the diffraction limit and has high imaging quality. Figure 6 This is a dot plot illuminance curve of an embodiment of the present invention under normal temperature conditions, which can meet the requirement of more than 95% relative illuminance under a 30-degree field of view.

[0047] Figure 8 This is a schematic diagram of the MTF curves of an embodiment of the present invention at high and low temperatures. As shown in the figure, at both low temperature (-30℃) and high temperature (80℃), the transfer function remains above 0.4 at 35 lp / mm, achieving a passive heat loss reduction effect.

[0048] In summary, the infrared refractive-hybrid lens of this invention utilizes the positive and negative dispersion effects of the refractive spherical surface and the diffractive surface, and achieves chromatic aberration correction by distributing the optical power between the two. It employs one refractive element each with positive and negative optical power to handle a large optical power, and uses a single-sided metasurface element to correct the remaining chromatic aberration and spherical aberration, fully leveraging the advantages of both elements. This reduces the types of materials used, the number of lenses, and the number of aspherical surfaces, effectively lowering costs. The system achieves near-diffraction-limited imaging quality with a field of view exceeding 60° and an F-number of 1.08, effectively enabling environmental detection in a wide temperature range (-30℃ to 80℃).

[0049] It should be noted that in the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the term "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0050] Those skilled in the art will recognize that the embodiments described herein are intended to help readers understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the essence of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. An infrared-hybrid superconducting lens, characterized in that, It consists of a first lens, an aperture, a metalens, and a second lens arranged sequentially from the object plane to the image plane along the optical axis; wherein the first lens has negative optical power and the second lens has positive optical power; both surfaces of the first lens are spherical, with the object side being concave and the image side being convex; the object side of the second lens is spherical and convex, and the image side is planar; the object side of the metalens is planar, and the image side is a diffraction surface with equal group retardation dispersion characteristics; the metalens includes a substrate and microstructures arranged on the substrate, the microstructures being aperture-type structures located on the image side of the metalens, and the microstructures being periodically arranged in an array on the substrate; The following relationship exists between the focal length f1 of the first lens, the focal length f2 of the second lens, and the equivalent focal length f of the infrared superconducting lens: -18 ≤ f1 / f ≤ 0, and 0 ≤ f2 / f ≤ 5.5; the distance between the first lens and the super lens is ≥ 2 mm, the distance between the super lens and the second lens is ≥ 0.5 mm, and the optical back focal length of the lens is ≥ 3.5 mm; the equivalent focal length f of the infrared superconducting lens satisfies f ≥ 3.1 mm; the distance from the object side of the first lens to the image plane of the lens is the total optical length TTL, satisfying 3 ≤ TTL / f ≤ 5.5; The microstructure is arranged periodically according to a tetragonal lattice, and the microstructure is an open structure with the direction of the opening parallel to the optical axis. The phase design method for the microstructure includes the following steps: S1. Construct a polynomial expression for the phase profile φ of the metasurface. Based on the polynomial formula, design the phase profile of the metasurface as needed. The polynomial expression for the phase profile φ of the metasurface is as follows: In the formula, M is the diffraction order of the metasurface, N is the maximum number of terms, R is the normalized radius, and A i These are the coefficients of the terms in the polynomial; S2. Adjust the arrangement period p and depth h of the microstructures. By traversing the structural parameters d of each microstructure, simulate the phase-wavelength curve of the microstructure, where 0.25≤d / p≤0.

8. Calculate the group delay dispersion characteristics of the microstructure in the working band and the center wavelength phase of the microstructure. S3. Select a set of structural parameters d for the microstructures to make the current metalens meet the design requirements. The design requirements include that the center wavelength phase of each microstructure is consistent with the phase profile determined in S1, and that the group delay dispersion characteristics of each microstructure are equal. If the microstructures cannot meet the design requirements, return to S2 to adjust the period and depth of the microstructures. Repeat S2 until the current metalens meets the design requirements. S4. Based on the processing accuracy of the processing equipment, determine whether the current microstructure design can be processed. If it is determined that the microstructure cannot be processed, return to S2, change the microstructure parameters, and repeat S2-S3 until it is confirmed that the microstructure can be processed.

2. The infrared-hybrid refractive-hyper-lens lens according to claim 1, characterized in that: The aperture is positioned to coincide with the object side of the metalens.

3. The infrared-hybrid refractive-hyper-lens lens according to claim 1, characterized in that: The openings of the microstructures are all round or square holes.

4. The infrared hyperrefractive hybrid lens according to claim 1, characterized in that: The meta-lens is made of silicon and has a thickness of 0.5 mm. Both the first lens and the second lens are made of chalcogenide glass.

5. A hybrid long-wave infrared lens according to claim 1, characterized in that: The field of view (FOV) of the infrared refracting-hybrid lens is ≥60°; the operating temperature of the infrared refracting-hybrid lens is -30℃ to 80℃.

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