An athermalized long-wave infrared fisheye lens

Abstract

The application discloses an athermal long-wave infrared fisheye lens. The fisheye lens comprises, in sequence from an object side to an image side, a first lens, a second lens, a third lens and a fourth lens. The first lens has a negative refractive power, the object side is a convex surface, the surface type is a spherical surface, the image side is a concave surface and the surface type is a spherical surface. The second lens has a negative refractive power, the object side is a convex surface, the surface type is an aspherical surface, the image side is a concave surface and the surface type is an aspherical surface. The third lens has a positive refractive power, the object side is a convex surface, the surface type is an aspherical surface, the image side is a convex surface and the surface type is a binary diffractive surface. The fourth lens has a positive refractive power, the object side is a concave surface, the surface type is an aspherical surface, the image side is a convex surface and surface type is an aspherical surface. The fisheye lens has a good imaging effect in a long-wave band, is smaller in size than fisheye lenses of the same type, has fewer optical elements and is more economical and practical. The fisheye lens has a small number of lens pieces and a simple structure, and the purpose of miniaturization of the optical system is achieved.

Description

Technical Field

[0001] This invention relates to the field of infrared fisheye lens technology, and more particularly to a non-thermalized long-wave infrared fisheye lens. Background Technology

[0002] Infrared fisheye lenses are special lenses with a field of view of up to 180 degrees, playing an important role in sky monitoring, forest fire prevention, public security and border defense, regional monitoring (such as airport substations), and pipeline inspection. However, existing lenses have the following drawbacks: 1. Generally, infrared fisheye lenses have low edge resolution and low relative illumination; 2. Because the refractive index of infrared lenses is sensitive to temperature and has a large temperature coefficient, high and low temperatures have a significant impact on the optical system, causing image blurring; 3. Generally, infrared lenses are large in size, and infrared lenses are expensive, resulting in high lens costs. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a calorimetric long-wave infrared fisheye lens that can solve at least one of the technical problems mentioned in the background art.

[0004] According to one aspect of the present invention, a thermal-free long-wave infrared fisheye lens is provided, comprising, in sequence from the object side to the image side, a first lens, a second lens, a third lens, and a fourth lens;

[0005] The first lens has negative refractive power, the object side is convex and the surface type is spherical, the image side is concave and the surface type is spherical;

[0006] The second lens has negative refractive power, the object side is convex and the surface type is aspherical, and the image side is concave and the surface type is aspherical.

[0007] The third lens has positive diopter, the object side is convex and the surface type is aspherical, the image side is convex and the surface type is binary diffraction surface;

[0008] The fourth lens has positive refractive power, the object side is concave and the surface type is aspherical, the image side is convex and the surface type is aspherical.

[0009] In the above technical solution, this embodiment has a field of view of 180° and a horizontal field of view of 118°. The horizontal field of view H and the vertical field of view V are perfectly adapted to a 12µm detector with a pixel size of 1280*1024. It has good imaging effect in the long-wavelength band, and is smaller in size and uses fewer optical elements compared to similar lenses, making it more economical and practical. This solution has fewer lens elements and a simpler structure, achieving the goal of miniaturization of the optical system.

[0010] In some embodiments, the lens satisfies the following formula:

[0011] 7mm < T1 < 10mm

[0012] 5mm < T2 < 6mm

[0013] 7mm < T3 < 10mm

[0014] 5mm < T4 < 6mm

[0015] In the formula, T1, T2, T3, and T4 represent the center thicknesses of the first lens, the second lens, the third lens, and the fourth lens, respectively.

[0016] In the above technical solution, in order to improve the optical performance of the lens and reduce the cost of the optical lens, the center thickness of the lens is set.

[0017] In some embodiments, the radius of curvature of the first lens object surface is 30mm to 35mm;

[0018] The radius of curvature of the image measuring surface of the first lens is 15mm to 30mm;

[0019] The radius of curvature of the second lens's object surface is 50mm to 70mm;

[0020] The radius of curvature of the image measuring surface of the second lens is 40mm to 60mm;

[0021] The radius of curvature of the object measurement surface of the third lens is 50mm to 80mm;

[0022] The radius of curvature of the image measuring surface of the third lens is -40mm to -60mm;

[0023] The radius of curvature of the object measurement surface of the fourth lens is -50mm to -100mm;

[0024] The radius of curvature of the image measuring surface of the fourth lens is -30mm to -60mm.

[0025] In the above technical solution, in order to achieve low distortion, the optical power is reasonably configured, and heatless operation is achieved, the radius of curvature of the lens is set.

[0026] In some embodiments, the lens satisfies the following formula:

[0027] BFL>f

[0028] In the formula, BFL is the optical back focal length of the lens, and f is the effective focal length of the lens.

[0029] In the above technical solution, in order to enable the lens to have both wide-angle and long back focal length, this embodiment adopts a reverse telephoto optical structure, namely a reverse telephoto optical system.

[0030] In some embodiments, the first lens is made of germanium-based glass.

[0031] In the above technical solution, the first lens in this embodiment is a germanium meniscus lens made of high-refractive-index infrared material. Both the object-side and image-side surfaces of the first lens are made of spherical surfaces, which are simple to manufacture. The first lens can be coated with DLC film or hardened film, has high stability, and the high-refractive-index material is beneficial for reducing the aperture. The meniscus negative lens can ensure a large field of view, a large angle, and a large aperture ratio of the optical system, which is beneficial for compressing the aperture of subsequent optical elements to achieve lens miniaturization.

[0032] In some embodiments, the second lens is made of germanium-based glass.

[0033] In the above technical solution, the second lens is made of germanium and is a split lens of the first lens. In addition to balancing the subsequent third and fourth lenses, it also has a prism deflection effect, which makes the incident angle of the edge field of view rays on the subsequent optical elements smaller, realizing an imaging range greater than the hemispherical field of view, making its optical system structure compact and small in size.

[0034] In some embodiments, the third lens is made of chalcogenide glass;

[0035] The fourth lens is made of germanium-based glass or chalcogenide glass.

[0036] In the above technical solution, the third lens and the fourth lens are made of chalcogenide material IRG206 and germanium or sulfur, respectively. The lens center thickness is small and the cost is low. It can be produced by molding and is suitable for mass production.

[0037] In some embodiments, the first lens, the second lens, the third lens, and the fourth lens are respectively made of germanium-based glass, germanium-based glass, chalcogenide glass, and germanium-based glass.

[0038] In some embodiments, the first lens, the second lens, the third lens, and the fourth lens are respectively made of germanium-based glass, chalcogenide glass, chalcogenide glass, and chalcogenide glass.

[0039] In both of the above technical solutions, the lenses in the optical system utilize a combination of germanium and chalcogenide materials, both of which are common infrared optical materials. These raw materials are mass-produced by optical material manufacturers, ensuring the maturity and continuity of the technology. Furthermore, the combination of optical materials (germanium and chalcogenide) solves the problem of using only germanium in long-wavelength fisheye lenses. The use of optical materials (germanium and chalcogenide) that match the linear expansion coefficients of the lens barrel and spacer materials, along with the image-side surface of the third optical lens being set as a binary diffraction surface, allows for passive optical compensation of thermal differences across the entire temperature range of -45℃ to 85℃. This compensates for defocusing caused by thermal expansion and contraction due to temperature changes in the lens barrel and spacer materials, achieving a heat-free optical system. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0041] Figure 1 This is a schematic diagram of the lens structure of one embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0042] Figure 2 This is a lens optical path diagram of one embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0043] Figure 3 This is a distortion curve diagram of one embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0044] Figure 4 This is a room temperature MTF curve of one embodiment of the calorimetric long-wave infrared fisheye lens of the present invention;

[0045] Figure 5 This is a high-temperature 85°C MTF curve of one embodiment of the calorimetric long-wave infrared fisheye lens of the present invention;

[0046] Figure 6 This is a low-temperature -40℃ MTF curve of one embodiment of the calorimetric long-wave infrared fisheye lens of the present invention;

[0047] Figure 7 This is a relative illumination diagram of one embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0048] Figure 8 This is a schematic diagram of the lens structure of a second embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0049] Figure 9 This is a lens optical path diagram of a second embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0050] Figure 10 This is a distortion curve diagram of a second embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0051] Figure 11 This is a room temperature MTF curve of a second embodiment of the calorimetric long-wave infrared fisheye lens of the present invention;

[0052] Figure 12 This is a high-temperature 85°C MTF curve of the second embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0053] Figure 13This is a low-temperature -40℃ MTF curve of the second embodiment of the calorimetric long-wave infrared fisheye lens of the present invention;

[0054] Figure 14 This is a relative illumination diagram of a second embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0055] Figure 15 This is a schematic diagram of the lens structure of a third embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0056] Figure 16 This is the lens optical path diagram of the third embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0057] Figure 17 This is a distortion curve diagram of the third embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0058] Figure 18 This is a room temperature MTF curve of the third embodiment of the calorimetric long-wave infrared fisheye lens of the present invention;

[0059] Figure 19 This is a high-temperature 85°C MTF curve of the third embodiment of the athermalized long-wave infrared fisheye lens of the present invention;

[0060] Figure 20 This is a low-temperature -40℃ MTF curve of the third embodiment of the calorimetric long-wave infrared fisheye lens of the present invention;

[0061] Figure 21 This is a relative illumination diagram of the third embodiment of the athermalized long-wave infrared fisheye lens of the present invention. Detailed Implementation

[0062] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] This invention provides a calorimetric long-wave infrared fisheye lens that can solve at least one of the technical problems mentioned in the background art.

[0064] Example 1

[0065] Please see Figure 1 , Figure 2 , Figure 1 This is a schematic diagram of the lens structure in this embodiment. Figure 2This is the lens optical path diagram of this embodiment. From the object side OBJ to the image side IMA, it includes, in sequence, a first lens L1, a second lens L2, an aperture stop ST, a third lens L3, and a fourth lens L4;

[0066] The first lens L1 has negative refractive power and has a first lens object side 1 facing the object side and a first lens image side 2 facing the image side. The first lens object side 1 is convex and has a spherical surface type, and the first lens image side 2 is concave and has a spherical surface type.

[0067] The second lens L2 has negative refractive power and has an object-side surface 3 facing the object side and an image-side surface 4 facing the object side. The object-side surface 3 is convex and has an aspherical surface type, while the image-side surface 4 is concave and has an aspherical surface type.

[0068] The aperture ST has an aperture surface of 5.

[0069] The third lens L3 has positive diopter and has a third lens object side 6 facing the object side and a third lens image side 7 facing the image side. The third lens object side 6 is a convex surface and the surface type is aspherical. The third lens image side 7 is a convex surface and the surface type is a binary diffraction surface.

[0070] The fourth lens L4 has positive refractive power and has an object-side surface 8 facing the object side and an image-side surface 9 facing the image side. The object-side surface 8 is concave and has an aspherical surface type, while the image-side surface 9 is convex and has an aspherical surface type.

[0071] The protective glass G has an object-side protective glass 10 facing the object side and an image-side protective glass 11 facing the image side.

[0072] In this embodiment, the optical back focal length (BFL) of the lens is 12mm, the total lens length (TTL) is 81mm, and the ratio of optical back focal length to total lens length (BFL / TTL) is 0.1481 (retaining four decimal places).

[0073] In this embodiment, the effective focal length of the lens is 8mm, the focal length of the first lens is f1 -24mm, the focal length of the second lens is f2 -54mm, the focal length of the third lens is f3 -16mm, the focal length of the fourth lens is f4 -33mm, the focal length of the front group is -14.5mm, and the focal length of the rear group is 15.5mm.

[0074] Other parameters of the lens in this embodiment are as follows:

[0075] Table 1 Lens-related parameters for one of the embodiments

[0076] 1 First lens 33.96 9.00 germanium 27.12 2 18.12 12.30 16.06 3 Second lens 70.40 5.50 germanium 11.41 4 46.03 14.85 11.26 5 aperture unlimited 1.00 9.87 6 Third lens 70.74 10.00 Sulfur series 11.45 7 -44.80 10.30 13.61 8 Fourth lens -62.22 5.00 germanium 12.90 9 -40.52 10.54 13.38 10 Protective glass INF 0.50 germanium - 11 INF 1.00 - 12 Image

[0077] Table 2. Lens Aspheric Coefficient Table of One Embodiment

[0078] A4 -1.55E-05 -8.87E-06 -1.49E-05 -1.34E-06 -9.37E-06 1.88E-06 A6 -1.58E-07 -1.43E-07 -6.42E-08 -4.27E-08 2.19E-08 1.15E-08 A8 2.36E-10 -7.18E-10 2.38E-10 -4.73E-11 2.01E-10 1.06E-10 A10 -4.79E-12 2.86E-12 -2.75E-12 -2.64E-13 -1.51E-13 7.25E-14

[0079] See Figures 3 to 7 .from Figure 3 It can be seen that the system distortion changes linearly. Figures 4 to 6 These are the modulation transfer function curves of the fisheye lens in this embodiment at nine equal-area Y-fields of view, with the horizontal and vertical axes representing the MTF value and image plane spatial frequency, respectively. From Figure 7 It can be seen that the relative illumination of the lens in the entire field of view is greater than 85%. Relative illumination refers to the relative illumination RI of the radial field of view coordinates of a uniform Lambertian scene. The vertical and horizontal axes respectively represent the illumination intensity of a unit area of ​​the image plane (which can be reduced to the illumination of the point with the maximum illumination in the field of view) and the radial y-field of view.

[0080] Example 2

[0081] Please see Figure 8 , Figure 9 , Figure 8 This is a schematic diagram of the lens structure in this embodiment. Figure 9 This is the lens optical path diagram of this embodiment. From the object side OBJ to the image side IMA, it includes, in sequence, a first lens L1, a second lens L2, an aperture stop ST, a third lens L3, and a fourth lens L4;

[0082] The first lens L1 has negative refractive power and has a first lens object side 1 facing the object side and a first lens image side 2 facing the image side. The first lens object side 1 is convex and has a spherical surface type, and the first lens image side 2 is concave and has a spherical surface type.

[0083] The second lens L2 has negative refractive power and has an object-side surface 3 facing the object side and an image-side surface 4 facing the object side. The object-side surface 3 is convex and has an aspherical surface type, while the image-side surface 4 is concave and has an aspherical surface type.

[0084] The aperture ST has an aperture surface of 5.

[0085] The third lens L3 has positive diopter and has a third lens object side 6 facing the object side and a third lens image side 7 facing the image side. The third lens object side 6 is a convex surface and the surface type is aspherical. The third lens image side 7 is a convex surface and the surface type is a binary diffraction surface.

[0086] The fourth lens L4 has positive refractive power and has an object-side surface 8 facing the object side and an image-side surface 9 facing the image side. The object-side surface 8 is concave and has an aspherical surface type, while the image-side surface 9 is convex and has an aspherical surface type.

[0087] The protective glass G has an object-side protective glass 10 facing the object side and an image-side protective glass 11 facing the image side.

[0088] In this embodiment, the optical back focal length (BFL) of the lens is 13.02 mm, the total lens length (TTL) is 68.76 mm, and the ratio of optical back focal length to total lens length (BFL / TTL) is 0.1894 (rounded to four decimal places).

[0089] In this embodiment, the effective focal length of the lens is 8mm, the focal length of the first lens is f1 -19mm, the focal length of the second lens is f2 -83mm, the focal length of the third lens is f3 15mm, the focal length of the fourth lens is f4 30mm, the focal length of the front group is -13.65mm, and the focal length of the rear group is 13mm.

[0090] Other parameters of the lens in this embodiment are as follows:

[0091] Table 3 Lens-related parameters for Embodiment 2

[0092] 1 First lens 31.73 9.00 germanium 23.32 2 16.07 8.29 13.60 3 Second lens 58.17 6.63 germanium 11.37 4 43.13 12.00 10.06 5 aperture unlimited 1.04 9.14 6 Third lens 54.13 8.30 Sulfur series 11.72 7 -49.64 7.35 13.07 8 Fourth lens -84.11 3.13 germanium 12.35 9 -44.68 11.32 12.34 10 Protective glass INF 0.70 germanium - 11 INF 1.00 - 12 Image

[0093] Table 4. Lens Aspheric Coefficients in Example 2

[0094] A4 -3.67E-06 1.61E-05 -6.39E-06 9.77E-06 -6.28E-06 4.83E-06 A6 -3.20E-08 1.15E-07 4.09E-09 -3.62E-08 3.08E-08 4.22E-08 A8 -6.20E-12 -8.22E-10 -2.07E-10 -2.37E-10 2.69E-10 1.12E-10 A10 -4.79E-12 -8.51E-12 -2.14E-12 -4.95E-13 3.55E-13 1.20E-12

[0095] from Figure 10 It can be seen that the system distortion changes linearly. Figures 11 to 13 These are the modulation transfer function curves of the fisheye lens in this embodiment at nine equal-area Y-fields of view, with the horizontal and vertical axes representing the MTF value and image plane spatial frequency, respectively. From Figure 14 It can be seen that the relative illumination of the lens in the entire field of view is greater than 85%. Relative illumination refers to the relative illumination RI of the radial field of view coordinates of a uniform Lambertian scene. The vertical and horizontal axes respectively represent the illumination intensity of a unit area of ​​the image plane (which can be reduced to the illumination of the point with the maximum illumination in the field of view) and the radial y-field of view.

[0096] Example 3

[0097] Please see Figure 15 , Figure 16 , Figure 8 This is a schematic diagram of the lens structure in this embodiment. Figure 9 This is the lens optical path diagram of this embodiment. From the object side OBJ to the image side IMA, it includes, in sequence, a first lens L1, a second lens L2, an aperture stop ST, a third lens L3, and a fourth lens L4;

[0098] The first lens L1 has negative refractive power and has a first lens object side 1 facing the object side and a first lens image side 2 facing the image side. The first lens object side 1 is convex and has a spherical surface type, and the first lens image side 2 is concave and has a spherical surface type.

[0099] The second lens L2 has negative refractive power and has an object-side surface 3 facing the object side and an image-side surface 4 facing the object side. The object-side surface 3 is convex and has an aspherical surface type, while the image-side surface 4 is concave and has an aspherical surface type.

[0100] The aperture ST has an aperture surface of 5.

[0101] The third lens L3 has positive diopter and has a third lens object side 6 facing the object side and a third lens image side 7 facing the image side. The third lens object side 6 is a convex surface and the surface type is aspherical. The third lens image side 7 is a convex surface and the surface type is a binary diffraction surface.

[0102] The fourth lens L4 has positive refractive power and has an object-side surface 8 facing the object side and an image-side surface 9 facing the image side. The object-side surface 8 is concave and has an aspherical surface type, while the image-side surface 9 is convex and has an aspherical surface type.

[0103] The protective glass G has an object-side protective glass 10 facing the object side and an image-side protective glass 11 facing the image side.

[0104] In this embodiment, the optical back focal length (BFL) of the lens is 8.41mm, the total lens length (TTL) is 80mm, and the ratio of optical back focal length to total lens length (BFL / TTL) is 0.1051 (retaining four decimal places).

[0105] In this embodiment, the effective focal length of the lens is 7.5mm, the focal length of the first lens is f1 -19mm, the focal length of the second lens is f2 -145mm, the focal length of the third lens is f3 18mm, the focal length of the fourth lens is f4 25mm, the focal length of the front group is -16mm, and the focal length of the rear group is 18mm.

[0106] Other parameters of the lens in this embodiment are as follows:

[0107] Table 5. Parameters related to the three lenses in the embodiment.

[0108] 1 First lens 30.53 10.30 germanium 24.10 2 29.83 7.71 13.02 3 Second lens 208.19 2.32 Sulfur series 12.64 4 213.90 14.70 12.00 5 aperture INF 8.20 7.32 6 Third lens 291.50 11.00 Sulfur series 26.97 7 -574.00 14.46 26.26 8 Fourth lens -5066.68 2.90 Sulfur series 19.43 9 -368.98 6.71 19.42 10 Protective glass INF 0.70 germanium - 11 INF 1.00 - 12 Image

[0109] Table 6. Aspherical Coefficients of the Three Lenses in Embodiment 6

[0110] A4 -3.18E-05 -3.13E-05 3.27E-07 1.15E-05 -4.04E-05 -1.44E-05 A6 -8.12E-08 -1.52E-08 9.43E-10 -4.55E-09 1.21E-08 6.38E-09 A8 9.93E-11 9.45E-11 4.82E-15 -2.40E-13 3.60E-11 -3.41E-11 A10 5.57E-13 2.30E-12 1.46E-15 1.90E-15 1.16E-13 2.19E-13

[0111] Please see Figures 17 to 21 .from Figure 17 It can be seen that the system distortion changes linearly. Figures 18 to 20 These are the modulation transfer function curves of the fisheye lens in this embodiment at nine equal-area Y-fields of view, with the horizontal and vertical axes representing the MTF value and image plane spatial frequency, respectively. From Figure 21 It can be seen that the relative illumination of the lens in the entire field of view is greater than 85%. Relative illumination refers to the relative illumination RI of the radial field of view coordinates of a uniform Lambertian scene. The vertical and horizontal axes respectively represent the illumination intensity of a unit area of ​​the image plane (which can be reduced to the illumination of the point with the maximum illumination in the field of view) and the radial y-field of view.

[0112] Based on the above three embodiments, the advantages of the present invention are as follows:

[0113] 1. This invention provides an optical material combination (germanium and sulfur) that solves the problem of using only germanium in long-wavelength fisheye lenses. (The price of germanium raw materials is much higher than that of sulfur materials.) Three design examples are provided for the same optical specifications: a performance-oriented design (germanium, germanium, sulfur, germanium), a volumetric design (germanium, germanium, sulfur, germanium), and an economical design (germanium, sulfur, sulfur, sulfur).

[0114] 2. This invention features an ultra-wide field of view (180°), meeting the needs of wide-area spatial applications.

[0115] 3. This invention features a large relative aperture (F#=1), resulting in good imaging quality, high relative illumination, and high energy utilization, which is beneficial for detecting weak targets.

[0116] 4. This invention is perfectly compatible with long-wavelength detectors with large image size, such as 1280×1024 pixels, 12µm, with a maximum field of view of 2w = 180° and a horizontal field of view of 2w = 118°. Its optical performance across the entire field of view is close to the diffraction limit.

[0117] 5. The lens optical system of this invention features a heat-free design, enabling clear imaging within a temperature range of -40℃ to 80℃, demonstrating strong environmental adaptability.

[0118] 6. The lens of this invention has a small number of lenses and a simple structure, thus achieving the goal of miniaturization of the optical system;

[0119] 7. The parameters of the fisheye lens system of the present invention are: working wavelength range of 8um to 14um, 180° full field of view lens, lens viewpoint position D: 180°@19.67mm, H: 118°@15.36mm, V: 90°@12.288mm (angle tolerance ±3°), effective focal length of 8mm, entrance pupil diameter of 8mm, i.e. F#1, satisfying TTL < 85, lens diameter of all lenses less than 60, front aperture of the lens < 70, rear aperture of the lens < 40, BFL > 8 and < 14, where BFL is the rear focal length of the optical system, and TTL is the total length of the optical system; the optical system achieves miniaturization and reduces cost.

[0120] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A calorimetric long-wave infrared fisheye lens, characterized in that, From the object side to the image side, the lenses consist of a first lens, a second lens, a third lens, and a fourth lens, with a total of 4 lenses having refractive power. The first lens has negative refractive power, the object side is convex and the surface type is spherical, the image side is concave and the surface type is spherical; The second lens has negative refractive power, the object side is convex and the surface type is aspherical, and the image side is concave and the surface type is aspherical. The third lens has positive diopter, the object side is convex and the surface type is aspherical, the image side is convex and the surface type is binary diffraction surface; The fourth lens has positive refractive power, the object side is concave and the surface type is aspherical, the image side is convex and the surface type is aspherical; The radius of curvature of the first lens's object surface is 30mm to 35mm; The radius of curvature of the image measuring surface of the first lens is 15mm to 30mm; The radius of curvature of the second lens's object surface is 50mm to 70mm; The radius of curvature of the image measuring surface of the second lens is 40mm to 60mm; The radius of curvature of the object measurement surface of the third lens is 50mm to 80mm; The radius of curvature of the image measuring surface of the third lens is -40mm to -60mm; The radius of curvature of the object measurement surface of the fourth lens is -50mm to -100mm; The radius of curvature of the image measuring surface of the fourth lens is -30mm to -60mm.

2. The athermalized long-wave infrared fisheye lens as described in claim 1, characterized in that, The lens satisfies the following formula: 7mm < T1 < 10mm 5mm < T2 < 6mm 7mm < T3 < 10mm 5mm < T4 < 6mm In the formula, T1, T2, T3, and T4 represent the center thicknesses of the first lens, the second lens, the third lens, and the fourth lens, respectively.

3. The calorimetric long-wave infrared fisheye lens as described in claim 1, characterized in that, The lens satisfies the following formula: BFL>f In the formula, BFL is the optical back focal length of the lens, and f is the effective focal length of the lens.

4. The calorimetric long-wave infrared fisheye lens as described in claim 1, characterized in that, The first lens is made of germanium-based glass.

5. The calorimetric long-wave infrared fisheye lens as described in claim 1, characterized in that, The second lens is made of germanium-based glass.

6. The athermalized long-wave infrared fisheye lens as described in claim 1, characterized in that, The third lens is made of chalcogenide glass; The fourth lens is made of germanium-based glass or chalcogenide glass.

7. The calorimetric long-wave infrared fisheye lens as described in claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens are respectively made of germanium-based glass, germanium-based glass, chalcogenide glass, and germanium-based glass.

8. The calorimetric long-wave infrared fisheye lens as described in claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens are respectively made of germanium-based glass, chalcogenide glass, chalcogenide glass, and chalcogenide glass.

Images