A far-infrared optical system and a far-infrared optical lens

Abstract

The present application discloses a far-infrared optical system and a far-infrared optical lens. The far-infrared optical system includes: a refractive lens and a super lens in sequence from the object side to the image side along the optical axis. The refractive lens is a positive lens, and the surface of the refractive lens close to the object side is convex to the object side, and the surface of the refractive lens close to the image side is convex to the object side; the super lens is a positive lens, and the super lens includes a substrate and a micro-nano structure. The substrate is provided with micro-nano structures on both sides along the optical axis from the object side to the image side. The depth-to-width ratio of the micro-nano structure is greater than or equal to 5, so that the super lens has the expected deflection ability for light, and the far-infrared optical system has better imaging quality. The number of lenses used in the far-infrared optical system is relatively small, which can reduce the production cost of the far-infrared optical system. In addition, the total optical length of the far-infrared optical system is relatively short, which is conducive to the miniaturization of the lens corresponding to the far-infrared optical system.

Description

Technical Field

[0001] The present application relates to the field of far-infrared optical systems, and in particular to a far-infrared optical system and a far-infrared optical lens. Background Art

[0002] In order to obtain higher imaging quality, the far-infrared optical system in the prior art is usually equipped with multiple lenses, but the provision of multiple lenses usually increases the cost of the far-infrared optical system and also causes the volume of the far-infrared optical system to increase. That is, the far-infrared optical system in the prior art is usually difficult to simultaneously take into account the advantages of higher imaging quality, lower cost and smaller volume. Utility Model Content

[0003] In response to the above technical problems, the embodiments of the present application provide a far-infrared optical system and a far-infrared optical lens, aiming to provide a far-infrared optical system with high imaging quality, low cost and small size.

[0004] According to one aspect of an embodiment of the present application, a far-infrared optical system is disclosed, which includes, in sequence from the object side to the image side along the optical axis: a refractive lens and a super lens, wherein the refractive lens is a positive lens, and the surface of the refractive lens close to the object side is convex toward the object side, and the surface of the refractive lens close to the image side is convex toward the object side; the super lens is a positive lens, and the super lens includes a substrate and a micro-nano structure, and the micro-nano structure is provided on both sides of the substrate along the optical axis from the object side to the image side, the ratio of the height to the width of the micro-nano structure is the aspect ratio of the micro-nano structure, and the aspect ratio of the micro-nano structure is greater than or equal to 5.

[0005] In some embodiments, the refractive lens is an aspherical lens.

[0006] In some embodiments, the far-infrared optical system satisfies: Wherein, the surface of the refractive lens close to the object side is the front surface of the refractive lens, and the surface of the refractive lens close to the image side is the back surface of the refractive lens; r1 is the effective radius of the front surface of the refractive lens, r2 is the effective radius of the back surface of the refractive lens, R1 is the curvature radius of the front surface of the refractive lens, R2 is the curvature radius of the back surface of the refractive lens, f is the effective focal length of the far-infrared optical system, and f a1 is the focal length of the refractive lens.

[0007] In some embodiments, the metalens satisfies: The surface of the superlens close to the object side is the front surface of the superlens, and the surface of the superlens close to the image side is the back surface of the superlens; mR1is the effective radius of the front surface of the metalens, the f mR1 is the focal length of the front surface of the metalens, f is the effective focal length of the far-infrared optical system, is the absolute value of the maximum phase difference of the front surface of the metalens.

[0008] In some embodiments, the metalens satisfies: The surface of the superlens close to the object side is the front surface of the superlens, and the surface of the superlens close to the image side is the back surface of the superlens; mR2 is the effective radius of the rear surface of the metalens, the f mR2 is the focal length of the rear surface of the metalens, f is the effective focal length of the far-infrared optical system, is the absolute value of the maximum phase difference of the rear surface of the metalens.

[0009] In some embodiments, the metalens satisfies: The surface of the super lens close to the object side is the front surface of the super lens, and the surface of the super lens close to the image side is the back surface of the super lens; mR1 is the focal length of the front surface of the metalens, the f mR2 is the focal length of the rear surface of the metalens, is the absolute value of the maximum phase difference of the front surface of the metalens, is the absolute value of the maximum phase difference of the rear surface of the metalens.

[0010] In some embodiments, the far-infrared optical system satisfies: Wherein, f is the effective focal length of the far-infrared optical system, and D is the entrance pupil diameter of the far-infrared optical system.

[0011] In some embodiments,

[0012] In some embodiments, the far-infrared optical system satisfies: Wherein, BFL is the optical back focus of the far-infrared optical system, TTL is the total optical length of the far-infrared optical system, f is the effective focal length of the far-infrared optical system, and f a1 is the focal length of the refractive lens.

[0013] In some embodiments, the far-infrared optical system satisfies: Among them, f is the effective focal length of the far-infrared optical system, FOV is the field of view of the far-infrared optical system, and ImgH is half of the diagonal length of the imaging area of ​​the image plane of the far-infrared optical system.

[0014] In some embodiments, the far-infrared optical system further includes an aperture, and the aperture is disposed between the refractive lens and the superlens, or the aperture is disposed on a side of the refractive lens close to the object side.

[0015] A second aspect of an embodiment of the present application provides a far-infrared optical lens, which includes an imaging detector and a far-infrared optical system as described in any one of the above items.

[0016] The far-infrared optical system provided by the present application includes a refractive lens and a super lens. The number of lenses used in the far-infrared optical system is relatively small, which can reduce the production cost of the far-infrared optical system. Micro-nano structures are provided on both sides of the substrate along the optical axis from the object side to the image side, and the depth-to-width ratio of the micro-nano structure is greater than or equal to 5, so that the super lens has the expected deflection ability for light, so that the far-infrared optical system has better imaging quality. In addition, the total optical length of the far-infrared optical system is relatively short, which is conducive to the miniaturization of the lens corresponding to the far-infrared optical system. The far-infrared optical system provided by the present application can take into account the advantages of high imaging quality, low cost and small size at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

[0018] Figure 1 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0019] Figure 2 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0020] Figure 3 A field curvature diagram of a far-infrared optical system in an embodiment of the present application is shown.

[0021] Figure 4 A distortion diagram of a far-infrared optical system in an embodiment of the present application is shown.

[0022] Figure 5 A point diagram of a far-infrared optical system in one embodiment of the present application is shown.

[0023] Figure 6 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0024] Figure 7 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0025] Figure 8A field curvature diagram of a far-infrared optical system in an embodiment of the present application is shown.

[0026] Fig. 9 A distortion diagram of a far-infrared optical system in an embodiment of the present application is shown.

[0027] Fig.10 A point diagram of a far-infrared optical system in one embodiment of the present application is shown.

[0028] Fig.11 A schematic diagram of the architecture layout of a far-infrared optical system in a comparative example of the present application is shown.

[0029] Fig.12 The MTF field of view curve of the far-infrared optical system in the comparative example of the present application is shown.

[0030] Fig.13 The spot diagram of the far-infrared optical system in the comparative example of the present application is shown.

[0031] Reference numerals

[0032] 100. Far infrared optical system;

[0033] 1. Refractive lens;

[0034] 2. Super lens; 21. Substrate; 22. Micro-nano structure;

[0035] 3. Aperture;

[0036] 4. Optical protection parts;

[0037] A, object plane; B, image plane; S, optical axis. DETAILED DESCRIPTION

[0038] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these example embodiments are provided so that the description of the present application will be more comprehensive and complete and the concepts of the example embodiments will be fully conveyed to those skilled in the art. The accompanying drawings are only schematic illustrations of the present application and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0039] In addition, the described features, structures or characteristics may be combined in one or more example embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the example embodiments of the present application. However, those skilled in the art will appreciate that the technical solution of the present application may be practiced while omitting one or more of the specific details, or other modules, components, etc. may be adopted. In other cases, known structures, methods, implementations or operations are not shown or described in detail to avoid obscuring the present application and making the various aspects of the present application unclear.

[0040] The present application provides a far-infrared optical system. The optical system with the closest effective focal length to the present application is the optical system disclosed in Chinese patent CN117148547A. Although the imaging quality of the optical system is good, the optical system uses three lenses, and two of the lenses are aspherical lenses, which makes the production cost of the optical system relatively high. In addition, the total optical length of the optical system is 33 mm, which is not conducive to the miniaturization of the lens corresponding to the optical system.

[0041] See also Figure 1 , Figure 1 FIG. 1 shows a schematic diagram of the architecture layout of a far-infrared optical system 100 in an embodiment of the present application, wherein the optical axis S is the center line of the light beam. Figure 1 In the figure, the left side of the leftmost lens is the object side, and the object plane A is located on the object side; the right side of the rightmost lens is the image side, and the image plane B is located on the image side. Therefore, the direction from the object plane A to the image plane B along the optical axis S is consistent with the direction from the object side to the image side along the optical axis S. The far-infrared optical system 100 includes a refractive lens 1 and a super lens 2, and the refractive lens 1 and the super lens 2 are sequentially arranged along the optical axis S from the object plane A to the image plane B.

[0042] The refractive lens 1 is a positive lens. The surface of the refractive lens 1 close to the object side is convex toward the object side, and the surface of the refractive lens 1 close to the image side is convex toward the object side.

[0043] The superlens 2 is a positive lens. The superlens 2 includes a substrate 21 and a superstructure unit located on the surface of the substrate 21. The vertex and / or center of the superstructure unit is provided with a micro-nano structure 22. The filling material between the micro-nano structures 22 is air or other materials that are transparent in the working band. The ratio of the height to the width of the micro-nano structure 22 is the aspect ratio of the micro-nano structure 22. The aspect ratio of the micro-nano structure 22 is greater than or equal to 5, so that the superlens 2 has the expected modulation capability for the incident light.

[0044] The substrate 21 is provided with micro-nano structures 22 on both sides along the optical axis S from the object side to the image side. The surface of the substrate 21 close to the object side is provided with a layer of micro-nano structures 22, and the surface of the substrate 21 close to the image side is provided with a layer of micro-nano structures 22. It should be noted that although the surface of the substrate 21 close to the object side and the surface of the substrate 21 close to the image side are both provided with only one layer of micro-nano structures 22 in the present application, it cannot be understood that the number of layers of micro-nano structures 22 on the surface of the substrate 21 close to the object side and the number of layers of micro-nano structures 22 on the surface of the substrate 21 close to the image side can only be provided with one layer. In fact, whether it is the surface of the substrate 21 close to the object side or the surface of the substrate 21 close to the image side, the number of layers of micro-nano structures 22 thereon is not specifically limited, as long as the super lens 2 has the expected performance. In addition, the number of layers of micro-nano structures 22 on the surface of the substrate 21 close to the object side and the number of layers of micro-nano structures 22 on the surface of the substrate 21 close to the image side can be equal or unequal, as long as the super lens 2 has the expected performance. According to the phase modulation method adopted, the corresponding phase modulation formula can be adaptively used to configure various parameters of the micro-nano structure 22, so that the superlens 2 can achieve corresponding optical performance.

[0045] The far-infrared optical system 100 provided by the present application includes a refractive lens 1 and a super lens 2. The number of lenses used in the far-infrared optical system 100 is relatively small, which can reduce the production cost of the far-infrared optical system 100. Micro-nano structures 22 are provided on both sides of the substrate 21 along the optical axis S from the object side to the image side, and the aspect ratio of the micro-nano structure is greater than or equal to 5. Therefore, the super lens 2 has the expected deflection ability for light, so that the far-infrared optical system 100 has better imaging quality. In addition, the total optical length of the far-infrared optical system 100 is relatively short, which is conducive to the miniaturization of the lens corresponding to the far-infrared optical system 100. The far-infrared optical system 100 provided by the present application can take into account the advantages of high imaging quality, low cost and small size at the same time.

[0046] In some embodiments, two or more layers of micro-nano structures 22 are disposed on the surface of the substrate 21 close to the object side.

[0047] In some embodiments, two or more layers of micro-nano structures 22 are disposed on the surface of the substrate 21 close to the image side.

[0048] In some embodiments, the aspect ratio of the micro-nanostructure 22 of the superlens 2 is greater than 10 and less than 50, so that the superlens 2 has a desired modulation capability for incident light.

[0049] Furthermore, in some embodiments, the aspect ratio of the micro-nano structure 22 of the metalens 2 is greater than 15 and less than 40, so that the metalens 2 has the expected modulation capability for the incident light. At the same time, the metalens 2 also has better processability, because the aspect ratio of the micro-nano structure 22 is too large, which will cause the processing technology of the metalens 2 to be incompatible with the existing semiconductor processing technology, thereby making the metalens 2 with the micro-nano structure 22 having a large aspect ratio difficult to process.

[0050] In some embodiments, the refractive lens 1 is an aspherical lens. Since the aspherical lens has a strong advantage in aberration control, when the refractive lens 1 is an aspherical lens, the far-infrared optical system 100 has better performance in aberration control.

[0051] In some embodiments, the far-infrared optical system 100 satisfies Conditional Formula 1: Among them, the front surface of the refractive lens 1 and the back surface of the refractive lens 1 are defined based on the direction from the object side to the image side along the optical axis S, that is, the front surface of the refractive lens 1 in the present application refers to the surface of the refractive lens 1 close to the object side, and similarly, the back surface of the refractive lens 1 in the present application refers to the surface of the refractive lens 1 close to the image side. r1 is the effective radius of the front surface of the refractive lens 1, and the effective radius is the radius of the maximum light-transmitting area of ​​the lens, and the dimension of r1 is the unit of length. r2 is the effective radius of the back surface of the refractive lens 1, and the dimension of r2 is the unit of length. R1 is the radius of curvature of the front surface of the refractive lens 1, and the dimension of R1 is the unit of length. R2 is the radius of curvature of the back surface of the refractive lens 1, and the dimension of R2 is the unit of length. f is the effective focal length of the far-infrared optical system 100, and the dimension of f is the unit of length. f a1 is the focal length of the refractive lens 1, f a1 The dimension of is length unit. r1, r2, R1, R2, f and f a1 have the same dimension, for example, millimeters.

[0052] The lower limit of conditional formula 1 can ensure that the focal length of the refractive lens 1 accounts for a certain proportion of the focal length of the far-infrared optical system 100, and the upper limit of conditional formula 1 is to avoid the focal length of the refractive lens 1 being too large, or the upper limit of conditional formula 1 is to avoid the refractive lens 1 being difficult to process due to its semicircular surface shape.

[0053] In the present application, the surface of the superlens 2 close to the object side is the front surface, and the front surface of the superlens 2 refers to the substrate 21 and the micro-nano structure 22 located on the substrate 21 close to the object side. Similarly, the surface of the superlens 2 close to the image side is the rear surface, and the rear surface of the superlens 2 refers to the substrate 21 and the micro-nano structure 22 located on the substrate 21 close to the image side.

[0054] In some embodiments, the metalens 2 of the far-infrared optical system 100 satisfies conditional formula 2: Among them, R mR1 is the effective radius of the front surface of the metalens 2, where R mR1 The dimension of is the unit of length. mR1 is the focal length of the front surface of the metalens 2, f mR1 The dimension of is a length unit. f is the effective focal length of the far-infrared optical system 100, and the dimension of f is a length unit. is the absolute value of the maximum phase difference on the front surface of the metalens 2, The unit is rad.

[0055] The smaller the value of conditional expression 2 is, the greater the role of metalens 2 in light regulation is. The lower limit of conditional expression 2 indicates the maximum light regulation effect of metalens 2 in the far-infrared optical system 100. The upper limit of conditional expression 2 is to ensure that metalens 2 plays a role in the far-infrared optical system 100 to reduce chromatic aberration or other aberrations.

[0056] In some embodiments, the metalens 2 of the far-infrared optical system 100 satisfies conditional equation 3: Among them, R mR2 is the effective radius of the rear surface of the metalens 2, R mR2 The dimension of is the unit of length. mR2 is the focal length of the rear surface of the metalens 2, f mR2 The dimension of is a length unit. f is the effective focal length of the far-infrared optical system 100, and the dimension of f is a length unit. is the absolute value of the maximum phase difference of the rear surface of the metalens 2, The unit is rad.

[0057] The smaller the value of conditional expression 3, the greater the role of the metalens 2 in light regulation. The lower limit of conditional expression 3 indicates the maximum light regulation effect of the metalens 2 in the far-infrared optical system 100. The upper limit of conditional expression 3 is to ensure that the metalens 2 plays a role in the far-infrared optical system 100 to reduce chromatic aberration or other aberrations.

[0058] In some embodiments, the metalens 2 of the far-infrared optical system 100 satisfies conditional formula 4: Among them, f mR1 is the focal length of the front surface of the metalens 2, f mR1 The dimension of is the unit of length. mR2 is the focal length of the rear surface of the metalens 2, f mR2 The dimension of is the unit of length. is the absolute value of the maximum phase difference on the front surface of the metalens 2, The unit is rad. is the absolute value of the maximum phase difference of the rear surface of the metalens 2, The unit is rad.

[0059] The smaller the value of conditional expression 4, the greater the role of the metalens 2 in light regulation. The lower limit of conditional expression 4 indicates the maximum light regulation effect of the metalens 2 in the far-infrared optical system 100. The upper limit of conditional expression 4 is to ensure that the metalens 2 plays a role in the far-infrared optical system 100 to reduce chromatic aberration or other aberrations.

[0060] In some embodiments, the phase distribution of the metalens 2 satisfies the following formula:

[0061]

[0062] Wherein, r is the distance from the center of the superlens 2 to any micro-nanostructure 22, λ is the central wavelength of the working band of the superlens 2, is the phase constant, (x, y) is the two-dimensional coordinate of the surface of the metalens 2, and f m1 is the focal length of the superlens 2; a i and b i are real coefficients.

[0063] In some embodiments, the far-infrared optical system 100 satisfies Condition 5: Wherein, f is the effective focal length of the far-infrared optical system 100, and the dimension of f is a length unit. D is the entrance pupil diameter of the far-infrared optical system 100, and the dimension of D is a length unit. The dimensions of D and f are the same, for example, both are millimeters. Conditional formula 5 is used to represent the size range of the F number of the far-infrared optical system 100.

[0064] Furthermore, in some embodiments, the far-infrared optical system 100 satisfies conditional formula 6: That is, the far-infrared optical system 100 has a large aperture.

[0065] In some embodiments, the far-infrared optical system 100 satisfies conditional equation 7: Wherein, BFL is the optical back focus of the far-infrared optical system 100. In the present application, BFL is the distance between the surface of the metalens 2 close to the image plane B and the image plane B on the optical axis S, and the dimension of BFL is the unit of length. TTL is the total optical length of the far-infrared optical system 100. In the present application, TTL is the distance between the surface of the refractive lens 1 close to the object side and the image plane B on the optical axis S, and the dimension of TTL is the unit of length. f is the effective focal length of the far-infrared optical system 100, and the dimension of f is the unit of length. f a1 is the focal length of the refractive lens 1, f a1 The dimension is the unit of length. BFL, TTL, f, f a1 have the same dimension, for example, millimeters.

[0066] The lower limit of conditional expression 7 can ensure that the far-infrared optical system 100 can have a small volume while being able to clearly image. The upper limit of conditional expression 7 can ensure that the far-infrared optical system 100 has a certain length of back focal length to facilitate the assembly of the far-infrared optical system 100.

[0067] In some embodiments, the far-infrared optical system 100 satisfies Conditional Formula 8: Wherein, f is the effective focal length of the far-infrared optical system 100, and the dimension of f is the unit of length. FOV is the field of view of the far-infrared optical system 100, is the half viewing angle of the far-infrared optical system 100, The unit of ImgH is degree. ImgH is half of the diagonal length of the imaging area of ​​the image plane of the far-infrared optical system 100. The imaging area of ​​the image plane of the far-infrared optical system 100 is the same as the imaging area of ​​the matching image sensor. The unit of ImgH is the length unit. f and ImgH have the same dimension, for example, both are millimeters.

[0068] Conditional expression 8 represents the distortion of the far-infrared optical system 100, and the greater the value of conditional expression 8, the smaller the distortion of the far-infrared optical system 100. The value of conditional expression 8 is between 0.9 and 1, indicating that the far-infrared optical system 100 has a smaller distortion.

[0069] In some embodiments, the far-infrared optical system 100 further includes an aperture 3 , which is disposed between the refractive lens 1 and the superlens 2 , or the aperture 3 is disposed on a side of the refractive lens 1 close to the object side.

[0070] In some embodiments, the far-infrared optical lens further includes an optical protection member 4, which is located along the optical axis S on the side of the metalens 2 away from the refractive lens 1, and the optical protection member 4 can transmit light, and the optical protection member 4 is used to isolate the external environment, which can reduce the probability of damage to the device inside. The optical protection member 4 can be in the form of protective glass, but the optical protection member 4 is not limited to silicon glass. For example, the material of the optical protection member 4 can also be germanium glass.

[0071] In some embodiments, the far-infrared optical lens further includes a window material, and the window material is located on the side of the optical protection member 4 away from the metalens 2 along the optical axis S. The window material can be used to isolate the external environment to protect the internal device, and the window material has a high transmittance to light of a specific wavelength or wavelength range. In the present application, the window material has a high transmittance to far-infrared light and acts as a window.

[0072] The present application exemplarily provides two far-infrared optical lenses that meet the usage requirements in two embodiments. Next, the far-infrared optical lenses in each embodiment of the present application are introduced in detail.

[0073] Example 1

[0074] Figure 1 A schematic diagram of the architectural layout of the far-infrared optical system 100 in Example 1 is shown. In Example 1, the far-infrared optical system 100 includes, in sequence from the object side to the image side along the optical axis S: a refractive lens 1, an aperture 3, a super lens 2 and an optical protection member 4.

[0075] Table 1. Partial parameters of the far-infrared optical system 100 in Example 1

[0076] parameter data Total optical length (TTL) 27.6mm Field of view (2ω) 14° F-number 0.99 Effective focal length 25mm Working band Far infrared (8μm-12μm)

[0077] Table 1 shows some parameters of the far-infrared optical system 100. It can be seen from Table 1 that the far-infrared optical system 100 in this embodiment has an operating band of 8 microns to 12 microns, which meets the working requirements of the far-infrared band. The effective focal length of the far-infrared optical system 100 is 25 mm, the field angle of the far-infrared optical system 100 is 14°, and the total optical length of the far-infrared optical system 100 is 27.6 mm. The F number (aperture) of the far-infrared optical system 100 is 0.99, which can greatly increase the amount of light entering the far-infrared optical system 100, and collect as much energy as possible into the far-infrared optical system 100 when the image sensor has a low response to light energy, thereby ensuring excellent imaging quality.

[0078] Starting from the object plane A, along the optical axis S from the object side to the image side, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 2.

[0079] Table 2. Surface data of the far infrared optical system 100 in Example 1

[0080]

[0081]

[0082] For each surface in Table 2, surface 0 is object surface A. Surface 1 is the surface of the refractive lens 1 close to the object side, and surface 2 is the surface of the refractive lens 1 close to the image side. Surface 3 is aperture 3. Surface 4 is the surface of the superlens 2 close to the object side, and surface 5 is the surface of the superlens 2 close to the image side. Since the micro-nano structure 22 is provided on the surface of the superlens 2 close to the object side and the surface close to the image side, surface 4 and surface 5 are metasurfaces. Surface 6 is the surface of the optical protective member 4 close to the object side, and surface 7 is the surface of the optical protective member 4 close to the image side. Surface 8 is image surface B.

[0083] As can be seen from Table 2, the radius of curvature of surface 0 is infinite, that is, surface 0 is a plane, the distance between surface 0 and surface 1 is uncertain, and the material between surface 0 and surface 1 is air. Surface 1 is an aspheric surface, the radius of curvature of surface 1 is 19.71 mm, the distance between surface 1 and surface 2 is 2.88 mm, and the refractive index of the material between surface 1 and surface 2 is 4.004. Surface 2 is an aspheric surface, the radius of curvature of surface 2 is 23.29 mm, the distance between surface 2 and surface 3 is 13.64 mm, and the material between surface 2 and surface 3 is air. The radius of curvature of surface 3 is infinite, that is, surface 3 is a plane, the distance between surface 3 and surface 4 is 2.22 mm, and the material between surface 3 and surface 4 is air. Surface 4 is a metasurface, which is a plane, the distance between surface 4 and surface 5 is 0.30 mm, and the refractive index of the material between surface 4 and surface 5 is 3.421. Surface 5 is a metasurface, which is a plane. The distance between surface 5 and surface 6 is 6.58 mm, and the material between surface 5 and surface 6 is air. Surface 6 is a spherical surface, and the radius of curvature of surface 6 is infinite, that is, surface 6 is a plane. The distance between surface 6 and surface 7 is 1.00 mm, and the refractive index of the material between surface 6 and surface 7 is 4.004. Surface 7 is a spherical surface, and the radius of curvature of surface 7 is infinite, that is, surface 7 is a plane. The distance between surface 7 and surface 8 is 1.00 mm, and the material between surface 7 and surface 8 is air. The radius of curvature of surface 8 is infinite, that is, surface 8 is a plane.

[0084] Surface 1 and surface 2 are even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0085]

[0086] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S direction, c is the surface curvature of the aspherical surface, c=1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient, k, A, B, C, D, E, F, G... are the aspherical coefficients. The values ​​of k, A, B, C, D, E, F, G... of surface 1 and surface 2 can be obtained from Table 3.

[0087] Table 3. Coefficients of even-order aspheric surfaces in the far-infrared optical system 100 in Example 1

[0088]

[0089] Refer to Table 3, for surface 1, k is -2.021E-001, A is 1.411E-005, B is 3.171E-008, C is -1.424E-009, D is 1.948E-011, E is -1.478E-013, F is 4.287E-016, and G is -8.719E-019. For surface 2, k is 2.249E-001, A is 2.244E-005, B is -1.857E-007, C is 1.821E-009, D is -7.367E-012, E is 1.158E-013, F is -8.192E-016, and G is 1.880E-018.

[0090] See also Figure 2 , Figure 2 The MTF (Modulation Transfer Function, MTF for short) field of view curve of the far-infrared optical system 100 in Example 1 is shown. MTF is also called modulation transfer function, which is an important indicator for describing the imaging quality of the optical system. The larger the MTF value, the better the imaging quality. Figure 2 The horizontal axis in represents the field of view, and its unit is degree. Figure 2 The vertical axis is the MTF value. Figure 2 The sagittal curve S1 and the meridional curve T1 of the MTF of 21lp / mm spatial frequency as the field of view change, and the sagittal curve S2 and the meridional curve T2 of the MTF of 42lp / mm spatial frequency as the field of view change are listed in the figure. It can be seen from the above four curves that the MTF value within the 0.8 field of view (5.597°) is always greater than 0.3, and the MTF value within the full field of view is always greater than 0.2, which meets the requirements for MTF in the excellent imaging quality standard.

[0091] See also Figure 3 , Figure 3 1 shows a field curvature diagram of the far-infrared optical system 100 in Example 1, wherein: Figure 3 The horizontal axis in is the field curvature, and its unit is millimeters. Figure 3 The vertical axis in is the field of view angle, and its unit is degree. Figure 3The T1 curve is the field curvature of infrared light with a wavelength of 8 microns in the meridional direction, the T2 curve is the field curvature of infrared light with a wavelength of 9 microns in the meridional direction, the T3 curve is the field curvature of infrared light with a wavelength of 10 microns in the meridional direction, the T4 curve is the field curvature of infrared light with a wavelength of 11 microns in the meridional direction, the T5 curve is the field curvature of infrared light with a wavelength of 12 microns in the meridional direction, the S1 curve is the field curvature of infrared light with a wavelength of 8 microns in the sagittal direction, the S2 curve is the field curvature of infrared light with a wavelength of 9 microns in the sagittal direction, the S3 curve is the field curvature of infrared light with a wavelength of 10 microns in the sagittal direction, the S4 curve is the field curvature of infrared light with a wavelength of 11 microns in the sagittal direction, and the S5 curve is the field curvature of infrared light with a wavelength of 12 microns in the sagittal direction. Figure 3 It can be seen that the meridional field curvature is 0.3860 mm and the sagittal field curvature is 0.2010 mm in the full field of view, which meets the requirements for field curvature in the excellent imaging quality standard.

[0092] See also Figure 4 , Figure 4 The distortion diagram of the far-infrared optical system 100 in Example 1 under infrared light with wavelengths of 8 microns, 9 microns, 10 microns, 11 microns, and 12 microns is shown. Figure 6 The intervals between the five curves in are too small, so that the five curves are almost overlapped, and therefore, the five curves are not distinguished. Figure 4 The horizontal axis is the percentage of distortion. Figure 4 The vertical axis is the field of view, and its unit is degree. Figure 4 It can be seen that the maximum distortion is 1.52%, which meets the distortion requirement of the excellent imaging quality standard.

[0093] See also Figure 5 , Figure 5 FIG. 1 shows a point diagram of the far-infrared optical system 100 in Example 1, wherein: Figure 5 The middle line from top to bottom is the first row and the second row, the RMS radius (root mean square radius) of each sub-image along the first row from left to right is 7 microns, 7 microns, and 8 microns, respectively, and the RMS radius of each sub-image along the second row from left to right is 9 microns, 11 microns, and 13 microns, respectively. Among them, the Airy disk radius of the far-infrared optical system 100 in Example 1 is 12 microns, and the RMS radius of the second sub-image in the second row from left to right is 11 microns, which corresponds to a field of view of 6.4667 degrees, that is, a field of view of 0.9. It can be seen that the RMS radius within the field of view of 0.9 is smaller than the Airy disk radius, and the imaging quality of the far-infrared optical system 100 is excellent.

[0094] Example 2

[0095] Figure 6A schematic diagram of the architectural layout of the far-infrared optical system 100 in Example 2 is shown. In Example 2, the far-infrared optical system 100 includes, in sequence from the object side to the image side along the optical axis S: a refractive lens 1, an aperture 3, a super lens 2 and an optical protective member 4.

[0096] Table 4. Partial parameters of the far infrared optical system 100 in Example 2

[0097] parameter data Total optical length (TTL) 27.2mm Field of view (2ω) 14.8° F-number 0.95 Effective focal length 25mm Working band Far infrared (8μm-12μm)

[0098] Table 4 shows some parameters of the far-infrared optical system 100. It can be seen from Table 4 that the far-infrared optical system 100 in this embodiment has an operating band of 8 microns to 12 microns, which meets the working requirements of the far-infrared band. The effective focal length of the far-infrared optical system 100 is 25 mm, the field angle of the far-infrared optical system 100 is 14.8°, and the total optical length of the far-infrared optical system 100 is 27.2 mm. The F number (aperture) of the far-infrared optical system 100 is 0.95, which can greatly increase the amount of light entering the far-infrared optical system 100, and collect as much energy as possible into the far-infrared optical system 100 when the image sensor has a low response to light energy, thereby ensuring excellent imaging quality.

[0099] Starting from the object plane A, along the optical axis S from the object side to the image side, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 5.

[0100] Table 5. Surface data of the far infrared optical system 100 in Example 2

[0101] Surface serial number Surface type Curvature radius (mm) Thickness(mm) Refractive index of the material 0 Physical surface unlimited - - 1 Aspheric 18.77 3.79 4.004 2 Aspheric 20.83 13.38 - 3 Aperture 3 unlimited 1.26 - 4 Metasurface unlimited 0.30 3.421 5 Metasurface unlimited 6.49 - 6 Spherical unlimited 1.00 4.004 7 Spherical unlimited 1.00 - 8 Image plane unlimited - -

[0102] For each surface in Table 5, surface 0 is object surface A. Surface 1 is the surface of the refractive lens 1 close to the object side, and surface 2 is the surface of the refractive lens 1 close to the image side. Surface 3 is aperture 3. Surface 4 is the surface of the superlens 2 close to the object side, and surface 5 is the surface of the superlens 2 close to the image side. Since the micro-nano structure 22 is provided on the surface of the superlens 2 close to the object side and the surface close to the image side, surface 4 and surface 5 are metasurfaces. Surface 6 is the surface of the optical protective member 4 close to the object side, and surface 7 is the surface of the optical protective member 4 close to the image side. Surface 8 is image surface B.

[0103] It can be seen from Table 5 that the radius of curvature of surface 0 is infinite, that is, surface 0 is a plane, the distance between surface 0 and surface 1 is uncertain, and the material between surface 0 and surface 1 is air. Surface 1 is an aspherical surface, the radius of curvature of surface 1 is 18.77 mm, the distance between surface 1 and surface 2 is 3.79 mm, and the refractive index of the material between surface 1 and surface 2 is 4.004. Surface 2 is an aspherical surface, the radius of curvature of surface 2 is 20.83 mm, the distance between surface 2 and surface 3 is 13.38 mm, and the material between surface 2 and surface 3 is air. The radius of curvature of surface 3 is infinite, that is, surface 3 is a plane, the distance between surface 3 and surface 4 is 1.26 mm, and the material between surface 3 and surface 4 is air. Surface 4 is a metasurface, which is a plane, the distance between surface 4 and surface 5 is 0.30 mm, and the refractive index of the material between surface 4 and surface 5 is 3.421. Surface 5 is a metasurface, which is a plane. The distance between surface 5 and surface 6 is 6.49 mm, and the material between surface 5 and surface 6 is air. Surface 6 is a spherical surface, and the radius of curvature of surface 6 is infinite, that is, surface 6 is a plane. The distance between surface 6 and surface 7 is 1.00 mm, and the refractive index of the material between surface 6 and surface 7 is 4.004. Surface 7 is a spherical surface, and the radius of curvature of surface 7 is infinite, that is, surface 7 is a plane. The distance between surface 7 and surface 8 is 1.00 mm, and the material between surface 7 and surface 8 is air. The radius of curvature of surface 8 is infinite, that is, surface 8 is a plane.

[0104] Surface 1 and surface 2 are even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0105]

[0106] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S direction, c is the surface curvature of the aspherical surface, c=1 / R, R is the curvature radius of the aspherical surface; k is the cone coefficient, k, A, B, C, D, E, F, G... are the aspherical coefficients. The values ​​of k, A, B, C, D, E, F, G... of surface 1 and surface 2 can be obtained from Table 6.

[0107] Table 6. Coefficients of even-order aspheric surfaces in the far-infrared optical system 100 in Example 2

[0108]

[0109] Refer to Table 6, for surface 1, k is 6.946E-002, A is 1.288E-005, B is -1.422E-007, C is 1.174E-009, D is 2.797E-012, E is -6.746E-014, F is 2.758E-016, and G is -4.358E-019. For surface 2, k is 9.131E-001, A is 1.753E-005, B is -5.588E-007, C is 6.661E-009, D is -3.612E-011, E is 2.888E-014, F is 4.113E-016, and G is -1.525E-018.

[0110] See also Figure 7 , Figure 7 The MTF field of view curve of the far-infrared optical system 100 in Example 2 is shown, wherein: Figure 7 The horizontal axis in represents the field of view, and its unit is degree. Figure 7 The vertical axis is the MTF value. Figure 7 The sagittal curve S1 and the meridional curve T1 of the MTF of 21lp / mm spatial frequency as the field of view change, and the sagittal curve S2 and the meridional curve T2 of the MTF of 42lp / mm spatial frequency as the field of view change are listed in the figure. It can be seen from the above four curves that the MTF value within the 0.8 field of view (5.597°) is always greater than 0.29, which meets the requirements for MTF in the excellent imaging quality standard.

[0111] See also Figure 8 , Figure 8 1 shows a field curvature diagram of the far-infrared optical system 100 in Example 2, wherein: Figure 8 The horizontal axis in is the field curvature, and its unit is millimeters. Figure 8 The vertical axis in is the field of view angle, and its unit is degree. Figure 8 The T1 curve is the field curvature of infrared light with a wavelength of 8 microns in the meridional direction, the T2 curve is the field curvature of infrared light with a wavelength of 9 microns in the meridional direction, the T3 curve is the field curvature of infrared light with a wavelength of 10 microns in the meridional direction, the T4 curve is the field curvature of infrared light with a wavelength of 11 microns in the meridional direction, the T5 curve is the field curvature of infrared light with a wavelength of 12 microns in the meridional direction, the S1 curve is the field curvature of infrared light with a wavelength of 8 microns in the sagittal direction, the S2 curve is the field curvature of infrared light with a wavelength of 9 microns in the sagittal direction, the S3 curve is the field curvature of infrared light with a wavelength of 10 microns in the sagittal direction, the S4 curve is the field curvature of infrared light with a wavelength of 11 microns in the sagittal direction, and the S5 curve is the field curvature of infrared light with a wavelength of 12 microns in the sagittal direction. Figure 8 It can be seen that the meridional field curvature is 0.2625 mm and the sagittal field curvature is 0.0416 mm in the full field of view, which meets the requirements for field curvature in the excellent imaging quality standard.

[0112] See also Fig. 9 , Fig. 9 The distortion diagram of the far-infrared optical system 100 in Example 2 under infrared light with wavelengths of 8 microns, 9 microns, 10 microns, 11 microns, and 12 microns is shown. Fig. 9 The intervals between the five curves in are too small, so that the five curves are almost overlapped, and therefore, the five curves are not distinguished. Fig. 9 The horizontal axis is the percentage of distortion. Fig. 9 The vertical axis is the field of view, and its unit is degree. Fig. 9 It can be seen that the maximum distortion is 2.5%, which meets the distortion requirement of the excellent imaging quality standard.

[0113] See also Fig.10 , Fig.10 FIG. 1 shows a point diagram of the far-infrared optical system 100 in Example 2, wherein: Fig.10 The middle line from top to bottom is the first row, the second row, and the third row. The RMS radii of the sub-images in the first row from left to right are 8 microns and 8 microns respectively, the RMS radii of the sub-images in the second row from left to right are 9 microns, 10 microns, and 14 microns respectively, and the RMS radii of the sub-images in the third row from left to right are 16 microns and 17 microns respectively. Among them, the Airy disk radius of the far-infrared optical system 100 in Example 2 is 12 microns, and the RMS radius of the second sub-image in the second row from left to right is 10 microns, which corresponds to a field of view of 4.7450 degrees, that is, a 0.6 field of view. It can be seen that the RMS radius of the far-infrared optical system 100 within the 0.6 field of view is smaller than the Airy disk radius, and the imaging quality of the far-infrared optical system 100 is excellent.

[0114] In order to demonstrate the optical performance of the far-infrared optical system 100 provided by the present application, the present application also provides the following comparative example with the same specifications. The far-infrared optical system 100 in the comparative example is a single-sided superlens 2, and the micro-nano structure 22 of the superlens 2 is arranged on the surface of the substrate 21 facing the image side.

[0115] Comparative Example

[0116] Fig.11 A schematic diagram of the architectural layout of a far-infrared optical system 100 in a comparative example is shown. In the comparative example, the far-infrared optical system 100 includes, in sequence from the object side to the image side along the optical axis S: a refractive lens 1, an aperture 3, a superlens 2 and an optical protective member 4, wherein the refractive lens 1 is an aspherical lens.

[0117] Table 7. Some parameters of the far infrared optical system 100 in the comparative example

[0118]

[0119]

[0120] Table 7 shows some parameters of the far-infrared optical system 100 in the comparative example. It can be seen from Table 7 that in the comparative example, the working band of the far-infrared optical system 100 is 8 microns to 12 microns, which meets the working requirements of the far-infrared band. In the comparative example, the effective focal length of the far-infrared optical system 100 is 25.08 mm, the field angle of the far-infrared optical system 100 is 14.4°, and the total optical length of the far-infrared optical system 100 is 27.8 mm. The F number (aperture) of the far-infrared optical system 100 is 1.05.

[0121] Starting from the object plane A, along the optical axis S from the object side to the image side, each surface in the far-infrared optical system 100 in the comparative example is numbered, and the parameters of each surface are summarized to obtain the following Table 8.

[0122] Table 8 Surface data of far infrared optical system 100 in comparative example

[0123] Surface serial number Surface type Curvature radius (mm) Thickness(mm) Refractive index of the material 0 Physical surface unlimited - - 1 Aspheric 19.04 2.98 4.004 2 Aspheric 21.93 16.02 - 3 Aperture 3 unlimited 0.00 - 4 Spherical unlimited 0.30 3.421 5 Metasurface unlimited 6.50 - 6 Spherical unlimited 1.00 4.004 7 Spherical unlimited 1.00 - 8 Image plane unlimited - -

[0124] For each surface in Table 8, surface 0 is object surface A. Surface 1 is the surface of the refractive lens 1 close to the object side, and surface 2 is the surface of the refractive lens 1 close to the image side. Surface 3 is aperture 3. Surface 4 is the surface of the superlens 2 close to the object side, and surface 5 is the surface of the superlens 2 close to the image side. Since the micro-nano structure 22 is provided on the surface of the superlens 2 close to the object side and the surface close to the image side, surface 4 and surface 5 are metasurfaces. Surface 6 is the surface of the optical protective member 4 close to the object side, and surface 7 is the surface of the optical protective member 4 close to the image side. Surface 8 is image surface B.

[0125] The analysis of each surface in Table 8 can refer to Example 1, and this comparative example does not analyze each surface any more.

[0126] Surface 1 and surface 2 in Table 8 are even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0127]

[0128] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S direction, c is the surface curvature of the aspherical surface, c=1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient, k, A, B, C, D, E, F, G... are the aspherical coefficients. The values ​​of k, A, B, C, D, E, F, G... of surface 1 and surface 2 can be obtained from Table 9.

[0129] Table 9. Coefficients of even-order aspheric surfaces in the far-infrared optical system 100 in the comparative example

[0130]

[0131] Refer to Table 9, for surface 1, k is 2.986E-002, A is 4.514E-007, B is 1.425E-007, C is -1.612E-009, D is 1.329E-011, E is -8.140E-014, F is -2.068E-018, and G is -2.260E-019. For surface 2, k is 3.219E-001, A is 9.371E-006, B is 1.599E-007, C is -1.149E-009, D is -4.665E-012, E is -3.360E-014, F is -4.512E-016, and G is 1.405E-018.

[0132] See also Fig.12 , Fig.12 The MTF field of view curve of the far infrared optical system 100 in the comparative example is shown, wherein: Fig.12 The horizontal axis in represents the field of view, and its unit is degree. Fig.12 The vertical axis is the MTF value. Fig.12 The sagittal curve S1 and the meridional curve T1 of the MTF of 21lp / mm spatial frequency as the field of view changes, and the sagittal curve S2 and the meridional curve T2 of the MTF of 42lp / mm spatial frequency as the field of view changes are listed in the figure. It can be seen from the above four curves that the MTF value within the 0.8 field of view (5.597°) is always greater than 0.25.

[0133] See also Fig.12 and Figure 2 Compared with the far-infrared optical system 100 in the comparative example, at a spatial frequency of 42lp / mm, the MTF value of the far-infrared optical system 100 in Example 1 within a 0.8 field of view (5.597°) is always greater than 0.3, and the MTF value of the far-infrared optical system 100 in the comparative example within a 0.8 field of view (5.597°) is always greater than 0.25. At a spatial frequency of 42lp / mm, the MTF of the far-infrared optical system 100 in Example 1 at a 0 field of view is 0.41, and the MTF of the far-infrared optical system 100 in the comparative example at a 0 field of view is 0.3. Therefore, the imaging quality of the far-infrared optical system 100 in Example 1 is better than that of the far-infrared optical system 100 in the comparative example.

[0134] See also Fig.12 and Figure 7Compared with the far-infrared optical system 100 in the comparative example, at a spatial frequency of 42lp / mm, the MTF value of the far-infrared optical system 100 in Example 2 within a 0.8 field of view (5.597°) is always greater than 0.29, and the MTF value of the far-infrared optical system 100 in the comparative example within a 0.8 field of view (5.597°) is always greater than 0.25. At a spatial frequency of 42lp / mm, the MTF of the far-infrared optical system 100 in Example 2 at a 0 field of view is 0.48, and the MTF of the far-infrared optical system 100 in the comparative example at a 0 field of view is 0.3. Therefore, the imaging quality of the far-infrared optical system 100 in Example 2 is better than that of the far-infrared optical system 100 in the comparative example.

[0135] See also Fig.10 , Fig.10 The point diagram of the far-infrared optical system 100 in the comparative example is shown, wherein: Fig.10 From top to bottom, the middle line is the first row, the second row, and the third row. The RMS radii of the sub-images from left to right in the first row are 18 microns and 18 microns, respectively. The RMS radii of the sub-images from left to right in the second row are 18 microns, 19 microns, and 26 microns, respectively. The RMS radii of the sub-images from left to right in the third row are 34 microns and 42 microns, respectively. The Airy disk radius of the far-infrared optical system 100 in the comparison example is 13 microns. It can be seen that the RMS radius in the entire field of view is greater than the Airy disk radius.

[0136] The RMS radius of the far-infrared optical system 100 in Example 1 within the 0.9 field of view is smaller than the Airy disk radius, and the RMS radius of the far-infrared optical system 100 in Example 2 within the 0.6 field of view is smaller than the Airy disk radius. Therefore, the imaging quality of the far-infrared optical system 100 in Example 1 is higher than the imaging quality of the far-infrared optical system 100 in the comparative example, and the imaging quality of the far-infrared optical system 100 in Example 2 is higher than the imaging quality of the far-infrared optical system 100 in the comparative example.

[0137] The far-infrared optical system 100 in Example 1, the far-infrared optical system 100 in Example 2, and the far-infrared optical system 100 in the comparative example are all optical systems of the same specifications. The design difference between the far-infrared optical system 100 in Example 1, the far-infrared optical system 100 in Example 2 and the far-infrared optical system 100 in the comparative example is mainly that the far-infrared optical system 100 in Example 1 and the far-infrared optical system 100 in Example 2 are double-sided metalens 2, while the far-infrared optical system 100 in the comparative example is a single-sided metalens. Based on the comparison of the above MTF and the comparison of the point diagram, it can be seen that the imaging quality of the far-infrared optical system 100 in Example 1 and the far-infrared optical system 100 in Example 2 is higher than the imaging quality of the far-infrared optical system 100 in the comparative example, which also reflects that the use of the double-sided metalens 2 in the present application can improve the imaging quality of the far-infrared optical system 100 to a certain extent.

[0138] After summarizing the various parameters of the far-infrared optical system 100 provided in the above-mentioned embodiment 1, embodiment 2 and comparative example, the following Table 10 is obtained. The display of embodiment 1 and embodiment 2 in Table 10 is mainly used to illustrate that the various conditions satisfied by the far-infrared optical system 100 provided in each embodiment of the present application are all verified and supported by experiments. The display of the comparative example in Table 10 is mainly used to illustrate that the far-infrared optical system 100 provided in the comparative example is a far-infrared optical system 100 of the same specifications as those of embodiment 1 and embodiment 2.

[0139] Table 10. Summary of parameters of far-infrared optical system 100

[0140]

[0141]

[0142] The present application also provides a far-infrared optical lens (not shown), which includes an imaging detector and the above-mentioned far-infrared optical system 100, wherein the structure of the far-infrared optical system 100 can be found above and will not be described herein. The imaging detector is arranged on the image plane B of the far-infrared optical lens to receive light and form an image. The far-infrared optical lens provided by the present application can simultaneously take into account the advantages of high imaging quality, low cost and small size.

[0143] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the utility model disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the appended claims.

Claims

1. A far-infrared optical system, characterized in that: The far-infrared optical system includes, in sequence from the object side to the image side along the optical axis: a refractive lens and a super lens, wherein the refractive lens is a positive lens, and the surface of the refractive lens close to the object side is convex toward the object side, and the surface of the refractive lens close to the image side is convex toward the object side; the super lens is a positive lens, and the super lens includes a substrate and a micro-nano structure, and the micro-nano structure is provided on both sides of the substrate along the optical axis from the object side to the image side, and the ratio of the height to the width of the micro-nano structure is the aspect ratio of the micro-nano structure, and the aspect ratio of the micro-nano structure is greater than or equal to 5.

2. The far-infrared optical system according to claim 1, characterized in that: The refractive lens is an aspherical lens.

3. The far-infrared optical system according to claim 2, characterized in that: The far-infrared optical system meets the following requirements: Wherein, the surface of the refractive lens close to the object side is the front surface of the refractive lens, and the surface of the refractive lens close to the image side is the back surface of the refractive lens; r1 is the effective radius of the front surface of the refractive lens, r2 is the effective radius of the back surface of the refractive lens, R1 is the curvature radius of the front surface of the refractive lens, R2 is the curvature radius of the back surface of the refractive lens, f is the effective focal length of the far-infrared optical system, and f a1 is the focal length of the refractive lens.

4. The far-infrared optical system according to claim 2, characterized in that: The metalens satisfies: The surface of the superlens close to the object side is the front surface of the superlens, and the surface of the superlens close to the image side is the back surface of the superlens; mR1 is the effective radius of the front surface of the metalens, the f mR1 is the focal length of the front surface of the metalens, f is the effective focal length of the far-infrared optical system, is the absolute value of the maximum phase difference of the front surface of the metalens.

5. The far-infrared optical system according to claim 2, characterized in that: The metalens satisfies: The surface of the superlens close to the object side is the front surface of the superlens, and the surface of the superlens close to the image side is the back surface of the superlens; mR2 is the effective radius of the rear surface of the metalens, the f mR2 is the focal length of the rear surface of the metalens, f is the effective focal length of the far-infrared optical system, is the absolute value of the maximum phase difference of the rear surface of the metalens.

6. The far-infrared optical system according to claim 2, characterized in that: The metalens satisfies: The surface of the super lens close to the object side is the front surface of the super lens, and the surface of the super lens close to the image side is the back surface of the super lens; mR1 is the focal length of the front surface of the metalens, the f mR2 is the focal length of the rear surface of the metalens, is the absolute value of the maximum phase difference of the front surface of the metalens, is the absolute value of the maximum phase difference of the rear surface of the metalens.

7. The far-infrared optical system according to claim 2, characterized in that: The far-infrared optical system meets the following requirements: Wherein, f is the effective focal length of the far-infrared optical system, and D is the entrance pupil diameter of the far-infrared optical system.

8. The far-infrared optical system according to claim 7, characterized in that:

9. The far-infrared optical system according to claim 2, characterized in that: The far-infrared optical system meets the following requirements: Wherein, BFL is the optical back focus of the far-infrared optical system, TTL is the total optical length of the far-infrared optical system, f is the effective focal length of the far-infrared optical system, and f a1 is the focal length of the refractive lens.

10. The far-infrared optical system according to claim 2, characterized in that: The far-infrared optical system meets the following requirements: Among them, f is the effective focal length of the far-infrared optical system, FOV is the field of view of the far-infrared optical system, and ImgH is half of the diagonal length of the imaging area of ​​the image plane of the far-infrared optical system.

11. The far-infrared optical system according to any one of claims 1 to 10, characterized in that: The far-infrared optical system further includes an aperture, which is disposed between the refractive lens and the super lens, or the aperture is disposed on a side of the refractive lens close to the object side.

12. A far-infrared optical lens, characterized in that: It comprises an imaging detector and a far-infrared optical system as claimed in any one of claims 1 to 11.

Images