Infrared imaging optical system, lens

Abstract

The application discloses an infrared imaging optical system and a lens, and relates to the technical field of infrared imaging. The optical system is composed of a super lens and a traditional refractive lens to form a fold super hybrid optical system. The super lens has the advantages of light weight, low cost, small size and planarization, so that the optical system is miniaturized, and the weight and cost of the optical system are reduced. A double-sided super lens is introduced into the optical system, so that the flexible phase control ability of the double-sided super lens can be used to effectively correct aberration, and the imaging quality of the optical system is improved. The first lens and the second lens are both lenses with positive focal power, so that the main surface position of the optical system is more forward, the total optical length of the system is reduced, the structure is more compact, and the miniaturization of the optical system is further realized. The optical system has the characteristics of a large relative aperture, a small focal length and a wide field of view.

Description

Technical Field

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

[0002] Infrared thermal imaging systems acquire information about the distribution of infrared thermal radiation in specific wavelengths of an object and convert it into an image that can be distinguished by the human eye. This imaging technology has advantages such as strong anti-interference capabilities and the ability to operate around the clock, and is widely used in important fields such as industry, military, medicine, and environmental protection.

[0003] With the development of infrared imaging optical systems, infrared imaging equipment is trending towards higher resolution, miniaturization, and smaller size. However, traditional infrared imaging optical systems are typically large, heavy, and expensive. In related infrared imaging technologies, the lenses in long-wave infrared wide-angle lenses are all traditional lenses, resulting in a relatively long overall length and large size of the optical system, which is not conducive to miniaturization. Furthermore, the optical system is heavy and costly.

[0004] Therefore, providing a new infrared imaging optical system that achieves miniaturization, light weight, and low cost is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide an infrared imaging optical system and lens to solve the technical problems of excessive length, large size, heavy weight, and high cost caused by the use of traditional lenses in optical systems.

[0006] To solve the above-mentioned technical problems, the present invention provides an infrared imaging optical system, comprising: a first lens with positive optical power, an aperture, a double-sided superlens, and a second lens with positive optical power, which are arranged sequentially from the object plane to the image plane along the optical axis.

[0007] For example, the optical system satisfies the following expression: 1.5 <f1 / f<5, Where f1 is the focal length of the first lens; and f is the focal length of the optical system.

[0008] For example, the optical system satisfies the following expression: 1 <f2 / f<1.5, Where f2 is the focal length of the second lens; and f is the focal length of the optical system.

[0009] For example, both the first and second surfaces of the first lens are aspherical, and both the first and second surfaces of the second lens are aspherical.

[0010] For example, both the first lens and the second lens are meniscus lenses, and both the first lens and the second lens are made of germanium.

[0011] For example, the double-sided superlens includes a first metasurface, a substrate layer, and a second metasurface; the substrate layer is located between the first metasurface and the second metasurface; the surface microstructure units of the first metasurface and the surface microstructure units of the second metasurface are arranged in a hexagonal lattice periodic array.

[0012] For example, the materials of the first metasurface, the substrate, and the second metasurface are all silicon.

[0013] For example, the surface microstructure units of the first metasurface and the surface microstructure units of the second metasurface are cylindrical structures, and the diameter of the cylindrical structure is on the subwavelength order.

[0014] For example, the height of the surface microstructure unit of the first metasurface and the height of the surface microstructure unit of the second metasurface are both 12 μm.

[0015] To address the aforementioned technical problems, the present invention also provides an infrared imaging lens, including the aforementioned infrared imaging optical system.

[0016] The infrared imaging optical system provided by this invention includes: a first lens with positive optical power, an aperture stop, a double-sided superlens, and a second lens with positive optical power, arranged sequentially along the optical axis from the object plane to the image plane. When the number of lenses in the hybrid refractive-superlens optical system provided by this invention, which combines a superlens with a traditional refractive lens, is the same as the number of lenses in an optical system composed solely of traditional lenses, it means that the invention uses a double-sided superlens to replace some of the traditional lenses. Since superlenses have advantages over traditional lenses in terms of light weight, low cost, small size, and planar design, the optical system provided by this invention, by combining a superlens with a traditional refractive lens to form a hybrid refractive-superlens optical system, improves the compactness of the entire optical system, achieving miniaturization and reducing the weight and cost of the optical system. Both the first and second lenses are lenses with positive optical power. This invention positions the principal plane of the optical system further forward, reducing the overall optical length and making the structure more compact, thus further miniaturizing the optical system. The introduction of a double-sided superlens allows for flexible phase adjustment to correct spherical and off-axis aberrations, enabling the optical system to achieve a large relative aperture of 1 / 0.96, a focal length of 3.2mm, and a wide field of view exceeding 68°. This improves the resolution of long-wave infrared (8μm-12μm) and allows for matching with a 256×192@12μm uncooled long-wave infrared detector. In short, this invention achieves imaging with a large relative aperture, short focal length, wide field of view, small overall optical length, and high image quality. In summary, the infrared imaging optical system provided by this invention achieves miniaturization and effectively reduces the weight and cost of the optical system while maintaining image quality.

[0017] In addition, the present invention also provides an infrared imaging lens that has the same or corresponding technical features as the infrared imaging optical system mentioned above, and has the same effect. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A structural diagram of an infrared imaging optical system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a double-sided superlens provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a structural unit of a double-sided superlens provided in an embodiment of the present invention; Figure 4 for Figure 1The MTF curve of the optical system shown is shown. Figure 5 for Figure 1 The diagram shows a dot matrix representation of the optical system. Figure 6 for Figure 1 The astigmatism curve of the optical system shown; Figure 7 for Figure 1 The distortion curve of the optical system shown; Figure 8 A phase distribution diagram of the first surface of a double-sided superlens provided in an embodiment of the present invention; Figure 9 The phase distribution diagram of the second surface of the double-sided superlens provided in the embodiment of the present invention.

[0020] The reference numerals in the attached figures are as follows: A is the first lens, B is the aperture stop, C is the double-sided superlens, D is the second lens, E is the window, F is the image plane, C1 is the first metasurface of the double-sided superlens C, C2 is the substrate layer, and C3 is the second metasurface of the double-sided superlens C. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0022] The core of this invention is to provide an infrared imaging optical system and lens to solve the technical problems caused by the use of traditional lenses in optical systems, which result in excessively long overall length, large volume, heavy weight, and high cost of the optical system.

[0023] A superlens is a novel optical element composed of subwavelength-spaced scattering structures at the interface. By appropriately adjusting their shape, size, position, and orientation, the fundamental properties of light can be controlled, allowing for arbitrary design of the wavefront. When applied in imaging optical systems, its free phase modulation capability enables imaging control functions that surpass those of traditional refractive lenses. Furthermore, superlenses offer advantages such as light weight, low cost, small size, and planar design.

[0024] In related infrared imaging technologies, long-wave infrared wide-angle lenses generally adopt three or more conventional lenses, which results in a relatively large total length of the optical system and a large overall volume of the optical system, which is not conducive to miniaturization, and the optical system has a relatively large weight and a relatively high cost. Therefore, in the present invention, a refractive-hybrid optical system is formed in combination with a conventional refractive lens, so as to improve the compactness of the entire optical system, and provide a new solution for the design of the optical system with microminiaturization, miniaturization, light weight, low cost and high resolution.

[0025] In order to enable those skilled in the art to better understand the solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementations. Figure 1 is a structural diagram of an infrared imaging optical system provided by an embodiment of the present invention, as shown in Figure 1 , the optical system includes: a first lens A with positive refractive power, a diaphragm B, a double-sided metalens C, and a second lens D with positive refractive power, which are sequentially arranged along the optical axis from the object plane to the image plane F.

[0026] The specific positions of the first lens A, the diaphragm B, the double-sided metalens C, and the second lens D in the optical structure are not limited, as long as the first lens A, the diaphragm B, the double-sided metalens C, and the second lens D are sequentially arranged along the optical axis from the object plane to the image plane F. In addition, the number of the first lens A, the number of the second lens D, and the number of the double-sided metalens C are not limited, and are determined according to actual conditions. In implementation, in order to reduce the structure of the optical system, a preferred implementation manner is that the number of the first lens A, the number of the double-sided metalens C, and the number of the second lens D are all one, that is, the infrared imaging optical system is composed of three lenses. The shape of the first lens A and the shape of the second lens D are not limited. To correct aberrations, both the first lens A and the second lens D are configured as meniscus lenses. At the same time, the material of the first lens A and the material of the second lens D are not limited. Since germanium material has the highest refractive index among infrared materials, aberration control can be achieved under the conditions of minimal curvature and small glass thickness. The small curvature reduces the processing difficulty, and the small thickness reduces the material cost. Therefore, in some embodiments, the material of the first lens A and the material of the second lens D are both germanium.

[0027] In order to reduce the total length of the optical system and reduce aberrations, the optical system satisfies the following expression: 1.5<f1 / f<5, wherein f1 is the focal length of the first lens A; f is the focal length of the optical system.

[0028] The first lens A has positive refractive power, and when the refractive power it bears is greater than the upper limit of the expression 1.5<f1 / f<5, excessive off-axis aberrations will be introduced, making it difficult to eliminate the aberrations.

[0029] The second lens D undertakes most of the optical power to realize the focusing of light rays, and by placing it at a position far away from the diaphragm B, the spherical aberration and coma introduced by the second lens D are reduced. In some embodiments, the optical system satisfies the following expression: 1<f2 / f<1.5, where f2 is the focal length of the second lens D; f is the focal length of the optical system.

[0030] When the optical power of the second lens D is less than the lower limit of the expression 1<f2 / f<1.5, it will cause the first lens A to undertake excessive optical power and introduce more aberrations.

[0031] Wide-angle lenses have large off-axis aberrations, and the use of spherical lenses will lead to reduced image quality. Therefore, in this embodiment, both the first surface and the second surface of the first lens A are aspheric, and both the first surface and the second surface of the second lens D are aspheric. Lenses with aspheric surfaces are used to better correct aberrations.

[0032] The metasurface can effectively and flexibly regulate the phase of incident light, control aberrations with high precision, and simultaneously undertake extremely small optical power to avoid its inherent chromatic aberration problem. The metalens adopted in the embodiments of the present invention is a double-sided metalens C, Figure 2 which is a schematic structural diagram of a double-sided metalens provided by an embodiment of the present invention, as shown in Figure 2 the figure, the double-sided metalens C includes a first metasurface C1, a substrate layer C2 and a second metasurface C3; the substrate layer C2 is located between the first metasurface C1 and the second metasurface C3, and the surface microstructure units of the first metasurface C1 and the surface microstructure units of the second metasurface C3 are arranged in a periodic array in a hexagonal lattice.

[0033] There is no limitation on the material of the first metasurface C1, the material of the substrate layer C2, and the material of the second metasurface C3. Since silicon material is compatible with standard semiconductor process fabrication and has low material and manufacturing costs, in some embodiments, the material of the first metasurface C1, the material of the substrate layer C2, and the material of the second metasurface C3 are all silicon.

[0034] The phase distribution of the first metasurface C1 and the phase distribution of the second metasurface C3 respectively satisfy the following expressions: ; ; where, ρ is the radial coordinate of the metasurface, R is the normalized radius, A 1, B 1, C 1, D 1, E 1,F 1 represents the coefficients of the second, fourth, sixth, eighth, tenth, and twelfth orders of the phase change of C1 on the first metasurface. A 2. B 2. C 2. D 2. E 2. F 2 represents the coefficients of the quadratic, quartic, septic, octogenetic, decimal, and twelfth-order terms of the phase change of the second metasurface C3. Different phase distributions are achieved by changing the parameters.

[0035] Since cylindrical structures are the easiest to fabricate and are among the most commonly used microstructures, their subwavelength diameter ensures high diffraction efficiency. Therefore, in some embodiments, the surface microstructure units of the first metasurface C1 and the surface microstructure units of the second metasurface C3 are cylindrical structures, and the diameter of the cylindrical structures is on the subwavelength order. Figure 3 This is a schematic diagram of a structural unit of a double-sided superlens provided in an embodiment of the present invention, combined with... Figure 2 and Figure 3 The surface microstructure units of the first metasurface C1 and the surface microstructure units of the second metasurface C3 of the double-sided superlens C are both cylindrical structures.

[0036] To ensure that the metasurface structure meets the phase modulation requirements of a double-sided metasurface in an optical system across the entire infrared band, in some embodiments, the height of the surface microstructure units of the first metasurface C1 and the second metasurface C3 is both 12 μm. Figure 3 The height shown is 12 μm.

[0037] The infrared imaging optical system provided in this invention includes: a first lens with positive optical power, an aperture stop, a double-sided superlens, and a second lens with positive optical power, arranged sequentially from the object plane to the image plane along the optical axis. When the number of lenses in the hybrid refractive-superlens optical system provided by this invention, which combines a superlens with a traditional refractive lens, is the same as the number of lenses in an optical system composed solely of traditional lenses, that is, the invention uses a double-sided superlens to replace some of the traditional lenses. Since superlenses have advantages over traditional lenses in terms of light weight, low cost, small size, and planar design, the optical system provided in this invention combines a superlens with a traditional refractive lens to form a hybrid refractive-superlens optical system, improving the compactness of the entire optical system, achieving miniaturization, and reducing the weight and cost of the optical system; both the first and second lenses have positive optical power. The lens positions the principal plane of the optical system further forward, reducing the overall optical length and making the structure more compact, further miniaturizing the optical system. The introduction of a double-sided superlens allows for flexible phase adjustment to correct spherical and off-axis aberrations, enabling the optical system to achieve a large relative aperture of 1 / 0.96, a focal length of 3.2mm, and a wide field of view exceeding 68°. This improves the resolution of long-wave infrared (8μm-12μm) and allows for matching with a 256×192@12μm uncooled long-wave infrared detector. In short, it achieves large relative aperture, small focal length, wide field of view, small overall optical length, and high image quality. In summary, the infrared imaging optical system provided by this invention achieves miniaturization and effectively reduces the weight and cost of the optical system while maintaining image quality.

[0038] The above describes an infrared imaging optical system. This embodiment also provides an infrared imaging lens, which includes the infrared imaging optical system described above.

[0039] In conjunction with the description above Figure 1 Along the optical axis from the object side to the image side, a meniscus-shaped first lens A with positive optical power, an aperture B, a double-sided superlens C, a meniscus-shaped second lens D with positive optical power, a window E, and an image plane F are arranged sequentially. Incident light passes through the first lens A, then through the aperture B into the double-sided superlens C, the second lens D, and finally into the image plane F with the window E.

[0040] The above optical system is applied to a lens, and the specific performance parameters of the lens are set as follows: (1) Operating wavelength: 8-12μm; (2) Focal length f = 3.12 mm; (3) The number of working Fs, WFNO, is 0.96; (4) Entrance pupil diameter d = 3.2 mm; (5) The focal length of the first lens A is 6.50 mm; (6) The focal length of the second lens D is 3.41 mm; (7) Field of view: 2ω≥68°; (8) Total optical length ≤ 5.3 mm, back cutoff ≥ 1.3 mm.

[0041] Based on the performance parameters of the lens described above, it can be seen that the infrared imaging optical system provided in this embodiment of the invention is a long-wave infrared refractive super hybrid short focal length wide-angle optical system.

[0042] Image plane F uses an uncooled long-wave infrared detector to image the lens, with a pixel size of 12μm and a pixel count or resolution of 256×192.

[0043] Table 1 shows... Figure 1 The optical structure parameters of the optical system are shown in Table 2. Table 2 shows the aspherical surface data. Table 3 shows the polynomial coefficients of the first and second metasurfaces, specifically including... A 1. B 1. C 1. D 1. A 2. B 2. C 2. D 2 and normalized radius R Detailed numerical values.

[0044] Table 1 Optical structure parameters of the optical system

[0045] Aspherical surfaces satisfy the following expression: ; in, Z The outline of an aspherical surface; r The distance from any point on the aspherical surface to the optical axis of the optical system; C The paraxial curvature of the aspherical surface is numerically equal to the reciprocal of the paraxial curvature of the aspherical surface; k For aspherical surfaces, the conicity coefficient is... X, Y, M These are the coefficients of the fourth, sixth, and eighth orders of the aspherical profile, respectively.

[0046] Table 2 Aspherical Data

[0047] Table 3 Polynomial coefficients of the first and second metasurfaces

[0048] Figure 4 for Figure 1The MTF curve of the optical system shown shows that, at a cutoff frequency of 42 lp / mm, the MTF values ​​in all fields of view are higher than 0.2, which meets the transfer function requirements of a 256×192@12μm uncooled long-wave infrared detector.

[0049] Figure 5 for Figure 1 The dot plot of the optical system shown indicates that the root mean square radius of the star points in this lens is close to the Airy disk radius, indicating concentrated energy and good image quality.

[0050] Figure 6 for Figure 1 The astigmatism curve of the optical system shown is as follows. Figure 7 for Figure 1 The distortion curves of the optical system shown are represented by three wavelengths: 8μm, 10μm, and 12μm. The astigmatism value is less than 0.2mm and the distortion value is less than 10%, which meets the imaging requirements. Figure 8 A phase distribution diagram of the first surface of a double-sided superlens provided in an embodiment of the present invention; Figure 9 This is a phase distribution diagram of the second surface of a double-sided superlens provided in an embodiment of the present invention. The unit is rad / 2π, and its phase distribution can be achieved by arranging the microstructure units of the superlens. It should be noted that in this embodiment, the first surface of the double-sided superlens is referred to as the front surface (closer to the object plane) of the double-sided superlens, and the second surface of the double-sided superlens is referred to as the rear surface (closer to the image plane) of the double-sided superlens.

[0051] In the infrared imaging optical system and infrared imaging lens provided in this embodiment of the invention, the optical path scheme adopts a configuration of two meniscus lenses with a double-sided superlens in between. The structure is simple, the number of lenses is small, and the cost and weight of the lens are effectively reduced while ensuring image quality. Both meniscus lenses bear positive optical power, so that the principal plane of the optical system is positioned further forward, reducing the overall optical length of the system, making the lens structure more compact, reducing the lens volume, and facilitating the application of the lens in miniaturized scenarios. The introduction of the double-sided superlens utilizes its flexible phase adjustment capability to correct spherical aberration and off-axis aberration, enabling the lens to achieve a large relative aperture of 1 / 0.96 and a large field of view of over 68°, improving the resolution of 8μm-12μm long-wave infrared, and can be matched with a 256×192@12μm uncooled long-wave infrared detector.

[0052] The infrared imaging optical system and lens provided by the present invention have been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0053] It should also be noted that, in 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 terms "comprising," "including," or any other variations thereof are intended to cover 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. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. An infrared imaging optical system, characterized in that, include: The first lens (A), the aperture (B), the double-sided superlens (C), and the second lens (D) with positive optical power are placed sequentially along the optical axis from the object plane to the image plane (F); the infrared imaging optical system has three lenses. The optical system satisfies the following expression: 1.5 <f1 / f<5, Where f1 is the focal length of the first lens (A); f is the focal length of the optical system; The optical system satisfies the following expression: 1 <f2 / f<1.5, Where f2 is the focal length of the second lens (D); f is the focal length of the optical system; Both the first lens (A) and the second lens (D) are meniscus lenses, and both the first lens (A) and the second lens (D) are made of germanium. The double-sided superlens (C) includes a first metasurface (C1), a substrate layer (C2), and a second metasurface (C3); the substrate layer (C2) is located between the first metasurface (C1) and the second metasurface (C3); the surface microstructure units of the first metasurface (C1) and the surface microstructure units of the second metasurface (C3) are arranged in a hexagonal lattice periodic array. The height of the surface microstructure unit of the first metasurface (C1) and the height of the surface microstructure unit of the second metasurface (C3) are both 12 μm.

2. The infrared imaging optical system according to claim 1, characterized in that, The first and second surfaces of the first lens (A) are both aspherical, and the first and second surfaces of the second lens (D) are both aspherical.

3. The infrared imaging optical system according to claim 1, characterized in that, The materials of the first metasurface (C1), the substrate layer (C2), and the second metasurface (C3) are all silicon.

4. The infrared imaging optical system according to claim 1, characterized in that, The surface microstructure units of the first metasurface (C1) and the surface microstructure units of the second metasurface (C3) are cylindrical structures, and the diameter of the cylindrical structure is on the subwavelength order.

5. An infrared imaging lens, characterized in that, Including the infrared imaging optical system according to any one of claims 1 to 4.

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