Wide-spectrum athermalization long-wave infrared characteristic measuring lens

Abstract

The invention relates to the technical field of optical lenses, in particular to a wide-spectrum athermalization long-wave infrared characteristic measurement lens, which comprises an electromagnetic shielding window, an optical filter, a lens group, detector protection glass, a detector optical filter and a focal plane which are sequentially arranged along an optical axis from an object space to an image space, the lens group comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged along an optical axis from an object side to an image side; the first lens is an even-order aspheric negative lens; the second lens is an even-order aspheric positive lens; the third lens is a plano-concave even-order aspheric negative lens; the fourth lens is a plano-convex even-order aspheric positive lens. The lens has a wide spectrum band, a large athermalization range and an electromagnetic shielding function, has excellent environmental adaptability, can meet the use requirements of high-quality imaging in different space environments, and can be applied to acquisition of wide-spectrum infrared characteristic data of a target in the space environment.

Description

Technical Field

[0001] The invention relates to the technical field of optical lenses, in particular to a wide-band athermal long-wave infrared characteristic measurement lens. Background Art

[0002] Affected by the atmospheric window (long-wave infrared 8μm to 14μm), the spectral response range of commonly used cooled long-wave infrared detectors is 7.7μm to 9.5μm or 7.7μm to 10.3μm, and the spectral response range of uncooled long-wave detectors is 8μm to 14μm. In order to obtain richer characteristic data of the target, it is necessary to broaden the spectral response band of the detector, but ordinary infrared optical lenses are not suitable for wide-spectrum imaging. In addition, ordinary lenses generally only consider ground environmental conditions and can only achieve high-quality imaging in ground environments. They cannot meet the equipment's high-quality imaging and wide-spectrum characteristic observation and measurement requirements in space environments.

[0003] Therefore, there is an urgent need to provide a long-wave infrared characteristic measurement lens that can be used for observing and measuring wide-spectrum characteristics of space environments. Summary of the invention

[0004] In order to solve one or more technical problems in the prior art, the present invention provides a wide-band athermalization long-wave infrared characteristic measurement lens, which has a wide spectral band, a large athermalization range and an electromagnetic shielding function, has excellent environmental adaptability, can meet the use requirements of high-quality imaging in different space environments, and can be used to obtain wide-spectrum infrared characteristic data of targets in space environments, solving the problem that existing ordinary long-wave infrared optical lenses have a narrow spectral range and cannot be used for the observation and measurement of wide-spectrum characteristics of space environments.

[0005] In order to achieve the above-mentioned object, the present invention provides a wide-band athermal long-wave infrared characteristic measurement lens, comprising: an electromagnetic shielding window, a filter, a lens group, a detector protection glass, a detector filter and a focal plane arranged in sequence along the optical axis from the object side to the image side;

[0006] The lens group includes a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the optical axis from the object side to the image side; the first lens is an even-order aspheric negative lens; the second lens is an even-order aspheric positive lens; the third lens is a plano-concave even-order aspheric negative lens; the fourth lens is a plano-convex even-order aspheric positive lens; the lens group satisfies the following relationship:

[0007] BF / f=1.679

[0008] f1 / f=-0.95

[0009] f2 / f=1.58

[0010] f3 / f=-5.36

[0011] f4 / f=1.06

[0012] n1=n2=4, n3=2.21, n4=2.78

[0013] d1 / f=0.375

[0014] d2 / f=0.733

[0015] d3 / f=0.1

[0016] Wherein, BF is the back focus of the lens, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, n1 is the refractive index of the first lens, n2 is the refractive index of the second lens, n3 is the refractive index of the third lens, n4 is the refractive index of the fourth lens, d1 is the air spacing distance between the first lens and the second lens, d2 is the air spacing distance between the second lens and the third lens, and d3 is the air spacing distance between the third lens and the fourth lens.

[0017] In one possible design, the wide-band athermal long-wave infrared characteristic measurement lens has an operating band of 6μm to 12μm, a field of view of φ40°, a focal length of 24mm, an F number of 2, a distortion of less than 3%, an athermal temperature range of -40℃ to 60℃, and 100% cold aperture matching.

[0018] In a possible design, the electromagnetic shielding window is plated with a metal grid on one side close to the image side; the outer ring of the metal grid is plated with a metal ring; preferably, the electromagnetic shielding window has a diameter of 43 mm; the metal grid has a diameter of 40 mm; and the width of the metal ring is 1.5 mm.

[0019] In a possible design, both sides of the electromagnetic shielding window are coated with anti-reflection films; the electromagnetic shielding window has an average spectral transmittance of ≥86% in the 6μm to 12μm band, and an electric field radiation shielding effectiveness of ≥30dB in the 30MHz to 1.5GHz range.

[0020] In a possible design, the first lens has a spherical surface on the side close to the object and an even-order aspherical surface on the side close to the image.

[0021] The second lens has an even aspherical surface on the object side and a spherical surface on the image side.

[0022] The third lens has a flat surface on the object side and an even-order aspheric surface on the image side; and / or

[0023] The fourth lens has a flat surface close to the object side and an even-order aspherical surface close to the image side.

[0024] In a possible design, the radius of curvature of the first lens close to the object side is 38.678 mm, and the radius of curvature of the first lens close to the image side is 23.304 mm;

[0025] The curvature radius of the second lens close to the object side is 63.381mm, and the curvature radius of the second lens close to the image side is 137.128mm.

[0026] The radius of curvature of the image side of the third lens is 155.83 mm; and / or

[0027] The curvature radius of the fourth lens close to the image side is -45.354 mm.

[0028] In a possible design, the aspheric surfaces of the first lens near the image side, the second lens near the object side, the third lens near the image side, and the fourth lens near the image side meet the following formula:

[0029] Among them, Z is the vector height, c is the surface curvature, r is the radial distance from a point on the lens to the optical axis, k is the cone coefficient, and a2, a4, a6, and a8 are all aspherical coefficients.

[0030] In a possible design, the first lens near the image side satisfies: a2 = 0, a4 = -2.372E -6 , a6=-1.631E -8 , a8=6.877E -11 ;

[0031] The second lens close to the object side satisfies: a2 = 0, a4 = -2.453E -6 , a6=-1.168E -8 , a8=2.063E -11 ;

[0032] The third lens near the image side satisfies: a2 = 0, a4 = -3.249E -6 , a6=-2.884E -8 , a8=9.496E -11 ; and / or

[0033] The fourth lens near the image side satisfies: a2 = 0, a4 = 3.283E -6 , a6=1.372E -8 , a8=-4.716E -11 .

[0034] In one possible design, the thickness of the first lens is 3 mm;

[0035] The thickness of the second lens is 3.3 mm;

[0036] The thickness of the third lens is 6.8 mm; and / or

[0037] The thickness of the fourth lens is 4.7 mm.

[0038] In a possible design, the material of the first lens is germanium single crystal;

[0039] The material of the second lens is zinc sulfide;

[0040] The material of the third lens is germanium single crystal;

[0041] The material of the fourth lens is chalcogenide glass;

[0042] The material of the detector protection glass is germanium crystal; and / or

[0043] The material of the detector filter is germanium crystal.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] The present invention coordinates the parameters of each lens in the lens group (surface shape, focal length, refractive index, etc.) and the air spacing between the lenses to make the lens have a wide spectral band and a large athermal difference range, and has excellent environmental adaptability, which can meet the use requirements of high-quality imaging in different space environments and can be used to obtain wide-spectrum infrared characteristic data of targets in space environments, thus solving the problem that the existing ordinary long-wave infrared optical lenses have a narrow spectral range and cannot be used for observation and measurement of wide-spectrum characteristics in space environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 It is an optical path diagram of a wide-band athermal long-wave infrared characteristic measurement lens provided by the present invention;

[0048] Figure 2 It is a field curvature and distortion diagram of the wide-band athermal long-wave infrared characteristic measurement lens of the present invention at normal temperature and pressure;

[0049] Figure 3 It is the MTF curve diagram of the wide-band athermal long-wave infrared characteristic measurement lens of the present invention at normal temperature and pressure;

[0050] Figure 4It is the MTF curve of the wide-band athermal long-wave infrared characteristic measurement lens of the present invention at -40°C and normal pressure;

[0051] Figure 5 It is the MTF curve of the wide-band athermal long-wave infrared characteristic measurement lens of the present invention at 60°C and normal pressure;

[0052] Figure 6 It is the MTF curve diagram of the wide-band athermal long-wave infrared characteristic measurement lens of the present invention at normal temperature and pressure;

[0053] Figure 7 It is the MTF curve of the wide-band athermal long-wave infrared characteristic measurement lens of the present invention under -40°C vacuum;

[0054] Figure 8 It is the MTF curve diagram of the wide-band athermal long-wave infrared characteristic measurement lens of the present invention under 60°C vacuum.

[0055] Figure numerals: 1 - electromagnetic shielding window, 2 - filter, 3 - lens group, 31 - first lens, 32 - second lens, 33 - third lens, 34 - fourth lens, 4 - detector protection glass, 5 - detector filter, 6 - focal plane. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0057] like Figure 1 As shown, in order to achieve the above-mentioned purpose, the present invention provides a wide-band athermal long-wave infrared characteristic measurement lens, comprising: an electromagnetic shielding window 1, a filter 2, a lens group 3, a detector protection glass 4, a detector filter 5 and a focal plane 6 arranged in sequence along the optical axis from the object side to the image side;

[0058] The lens group includes a first lens 31, a second lens 32, a third lens 33 and a fourth lens 34 arranged in sequence along the optical axis from the object side to the image side; the first lens 31 is an even-order aspheric negative lens; the second lens 32 is an even-order aspheric positive lens; the third lens 33 is a plano-concave even-order aspheric negative lens; the fourth lens 34 is a plano-convex even-order aspheric positive lens; the lens group 3 satisfies the following relationship:

[0059] BF / f=1.679

[0060] f1 / f=-0.95, f2 / f=1.58, f3 / f=-5.36, f4 / f=1.06

[0061] n1=n2=4, n3=2.21, n4=2.78

[0062] d1 / f=0.375, d2 / f=0.733, d3 / f=0.1

[0063] Wherein, BF is the back focus of the lens, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, n1 is the refractive index of the first lens, n2 is the refractive index of the second lens, n3 is the refractive index of the third lens, n4 is the refractive index of the fourth lens, d1 is the air spacing distance between the first lens and the second lens, d2 is the air spacing distance between the second lens and the third lens, and d3 is the air spacing distance between the third lens and the fourth lens.

[0064] The present invention coordinates the parameters of each lens in the lens group (surface shape, focal length, refractive index, etc.) and the air spacing between the lenses to make the lens have a wide spectral band and a large athermal difference range, and has excellent environmental adaptability, which can meet the use requirements of high-quality imaging in different space environments and can be used to obtain wide-spectrum infrared characteristic data of targets in space environments, thus solving the problem that the existing ordinary long-wave infrared optical lenses have a narrow spectral range and cannot be used for observation and measurement of wide-spectrum characteristics in space environments.

[0065] In some preferred embodiments, the wide-band athermal long-wave infrared characteristic measurement lens has an operating band of 6 μm to 12 μm, a field of view of φ40°, a focal length of 24 mm, an F number of 2, a distortion of less than 3%, an athermal temperature range of -40°C to 60°C, and 100% cold stop matching. It should be noted that φ40° refers to a field of view with a cone angle of 40°.

[0066] In some preferred embodiments, the side of the electromagnetic shielding window 1 close to the image side is plated with a metal grid; the outer circle of the metal grid is plated with a metal ring; preferably, the diameter of the electromagnetic shielding window 1 is 43mm; the diameter of the metal grid is 40mm; the width of the metal ring is 1.5mm.

[0067] The electromagnetic shielding window of the present invention uses zinc sulfide as a substrate, and then a metal grid is plated on the surface of the zinc sulfide substrate to achieve electromagnetic shielding function, and then anti-reflection films are plated on both sides of the electromagnetic shielding window plated with the metal grid to increase the transmittance.

[0068] In some preferred embodiments, both sides of the electromagnetic shielding window 1 are coated with anti-reflection films; the electromagnetic shielding window has an average spectral transmittance of ≥86% in the 6μm to 12μm band, and an electric field radiation shielding effectiveness of ≥30dB in the 30MHz to 1.5GHz range.

[0069] In some preferred embodiments, the filter 2 can be for the 6μm-12μm band, or a smaller different band can be selected in the 6μm-12μm band, and the hotel filters corresponding to different bands can be installed on the filter wheel to achieve multi-band selection.

[0070] In some preferred embodiments, a surface of the first lens 31 close to the object side is a spherical surface, and a surface close to the image side is an even-order aspherical surface.

[0071] In some preferred embodiments, the second lens 32 has a surface close to the object side that is an even-order aspherical surface, and a surface close to the image side that is a spherical surface.

[0072] In some preferred embodiments, the third lens 33 has a surface close to the object side that is a plane, and a surface close to the image side that is an even-order aspheric surface.

[0073] In some preferred embodiments, the fourth lens 34 has a surface close to the object side that is a plane, and a surface close to the image side that is an even-order aspheric surface.

[0074] In some preferred embodiments, the radius of curvature of the first lens 31 close to the object side is 38.678 mm, and the radius of curvature of the first lens 31 close to the image side is 23.304 mm.

[0075] In some preferred embodiments, the curvature radius of the second lens 32 close to the object side is 63.381 mm, and the curvature radius of the second lens 32 close to the image side is 137.128 mm.

[0076] In some preferred embodiments, the radius of curvature of the surface of the third lens 33 close to the image side is 155.83 mm.

[0077] In some preferred embodiments, the curvature radius of the surface of the fourth lens 34 close to the image side is -45.354 mm.

[0078] In some preferred embodiments, the aspheric surfaces of the first lens 31 close to the image side, the second lens 32 close to the object side, the third lens 33 close to the image side, and the fourth lens 34 close to the image side meet the following formula:

[0079] Among them, Z is the vector height, c is the surface curvature, r is the radial distance from a point on the lens to the optical axis, k is the cone coefficient, and a2, a4, a6, and a8 are all aspherical coefficients.

[0080] In some preferred embodiments, the first lens 31 has a surface close to the image side that satisfies: a 2＝0 , a4=-2.372E -6 , a6=-1.631E -8 , a8=6.877E -11 .

[0081] In some preferred embodiments, the second lens 32 close to the object side satisfies: a 2＝0 , a4=-2.453E -6 , a6=-1.168E -8 , a8=2.063E -11 .

[0082] In some preferred embodiments, the third lens 33 has a surface close to the image side that satisfies: a 2＝0 , a4=-3.249E -6 , a6=-2.884E -8 , a8=9.496E -11 .

[0083] The fourth lens 34 has a surface close to the image side that satisfies: a 2＝0， a4=3.283E -6 , a6=1.372E -8 , a8=-4.716E -11 .

[0084] In some preferred embodiments, the thickness of the first lens 31 is 3 mm.

[0085] In some preferred embodiments, the thickness of the second lens 32 is 3.3 mm.

[0086] In some preferred embodiments, the thickness of the third lens 33 is 6.8 mm.

[0087] In some preferred embodiments, the thickness of the fourth lens 34 is 4.7 mm.

[0088] In some preferred embodiments, the material of the first lens 31 is germanium single crystal.

[0089] In some preferred embodiments, the material of the second lens 32 is zinc sulfide.

[0090] In some preferred embodiments, the material of the third lens 33 is germanium single crystal.

[0091] In some preferred embodiments, the material of the fourth lens 34 is chalcogenide glass, preferably Xinhuaguang chalcogenide glass IRG206.

[0092] In some preferred embodiments, the focal length of the first lens 31 is -22.8 mm.

[0093] In some preferred embodiments, the focal length of the second lens 32 is 37.92 mm.

[0094] In some preferred embodiments, the focal length of the third lens 33 is -128.64 mm.

[0095] In some preferred embodiments, the focal length of the fourth lens 34 is 25.44 mm.

[0096] In some preferred embodiments, the detector protection glass 4 is germanium crystal, and the thickness of the detector protection glass is preferably 2.5 mm.

[0097] In some preferred embodiments, the detector filter 5 is a germanium crystal, and the thickness of the detector filter is preferably 0.3 mm.

[0098] In a specific embodiment of the present invention, a wide-band athermal long-wave infrared characteristic measurement lens comprises: an electromagnetic shielding window 1, a filter 2, a lens group 3, a detector protection glass 4, a detector filter 5 and a focal plane 6 arranged in sequence along the optical axis from the object side to the image side;

[0099] The electromagnetic shielding window 1 (with zinc sulfide as the substrate and a diameter of 43mm) is coated with a metal grid (with a diameter of 40mm) on the side close to the image side; the outer circle of the metal grid is coated with a metal ring (with a width of 1.5mm); both sides of the electromagnetic shielding window are coated with anti-reflection films; the electromagnetic shielding window 1 has an average spectral transmittance of ≥86% in the 6μm~12μm band, and an electric field radiation shielding effectiveness of ≥30dB from 30MHz to 1.5GHz.

[0100] The lens group 3 includes a first lens 31 (a 3 mm thick germanium single crystal aspheric negative lens), a second lens 32 (a 3.3 mm thick zinc sulfide even-order aspheric positive lens), a third lens 33 (a 6.8 mm thick germanium single crystal plano-concave even-order aspheric negative lens) and a fourth lens 34 (a 4.7 mm thick chalcogenide glass plano-convex even-order aspheric positive lens) which are sequentially arranged along the optical axis from the object side to the image side.

[0101] The lens group satisfies the following relationship:

[0102] BF / f=1.679

[0103] f1 / f=-0.95, f2 / f=1.58, f3 / f=-5.36, f4 / f=1.06

[0104] n1=n2=4, n3=2.21, n4=2.78

[0105] d1 / f=0.375, d2 / f=0.733, d3 / f=0.1

[0106] Wherein, BF is the back focus of the lens, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, n1 is the refractive index of the first lens, n2 is the refractive index of the second lens, n3 is the refractive index of the third lens, n4 is the refractive index of the fourth lens, d1 is the air spacing distance between the first lens and the second lens, d2 is the air spacing distance between the second lens and the third lens, and d3 is the air spacing distance between the third lens and the fourth lens.

[0107] The first lens 31 has a spherical surface (with a curvature radius of 38.678 mm) on the object side and an even-order aspherical surface (with a curvature radius of 23.304 mm) on the image side; the second lens 32 has an even-order aspherical surface (with a curvature radius of 63.381 mm) on the object side and a spherical surface (with a curvature radius of 137.128 mm) on the image side; the third lens 33 has a plane surface (with a curvature radius of ∞) on the object side and an even-order aspherical surface (with a curvature radius of 155.83 mm) on the image side; the fourth lens 34 has a plane surface (with a curvature radius of ∞) on the object side and an even-order aspherical surface (with a curvature radius of -45.354 mm) on the image side.

[0108] The aspherical surfaces of the first lens 31 close to the image side, the second lens 32 close to the object side, the third lens 33 close to the image side, and the fourth lens 34 close to the image side meet the following formula: Among them, Z is the sag height, c is the surface curvature, r is the radial distance from a point on the lens to the optical axis, k is the cone coefficient, and a2, a4, a6, and a8 are all aspheric coefficients. Among them, the first lens close to the image side satisfies: a 2＝0 , a4=-2.372E -6 , a6=-1.631E -8 , a8=6.877E -11 ; The second lens close to the object side meets: a 2＝0 , a4=-2.453E -6 , a6=-1.168E -8 , a8=2.063E -11 ; The third lens close to the image side meets the following requirements: a 2＝0 , a4=-3.249E -6 , a6=-2.884E -8 , a8=9.496E -11 ; The fourth lens near the image side meets: a 2＝0 , a4=3.283E -6, a6=1.372E -8 , a8=-4.716E -11 .

[0109] The detector protection glass 4 is a germanium crystal with a thickness of 2.5 mm, the detector filter 5 is a germanium crystal with a thickness of 0.3 mm, and the focal plane 6 is the photosensitive surface of the detector for receiving infrared radiation signals.

[0110] The wide-band athermal long-wave infrared characteristic measurement lens has an operating band of 6μm to 12μm, a field of view of φ40°, a focal length of 24mm, an F number of 2, a distortion of less than 3%, an athermal temperature range of -40℃ to 60℃, and 100% cold aperture matching.

[0111] Depend on Figure 2 It can be seen that the wide-band athermal long-wave infrared characteristic measurement lens provided by the embodiment of the present invention has a small distortion (less than 3%). Figure 3-8 It can be seen that under the conditions of normal temperature and pressure, -40°C, 60°C normal pressure, normal temperature vacuum, -40°C vacuum and 60°C vacuum, the MTF curve of the lens is close to the diffraction limit curve, indicating that the lens can achieve athermalization under normal pressure and vacuum conditions of -40 to 60°C, and can meet high-quality imaging under normal pressure and vacuum conditions of -40 to 60°C. It can be seen that the wide-band athermal long-wave infrared characteristic measurement lens provided by the present invention has good environmental adaptability and can meet the high-quality imaging requirements under different environmental conditions.

[0112] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical factors in the process, method, article or device including the elements.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wide-band athermal long-wave infrared characteristic measurement lens, characterized in that: include: An electromagnetic shielding window, a filter, a lens group, a detector protection glass, a detector filter and a focal plane are arranged in sequence along the optical axis from the object side to the image side; The lens group includes a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the optical axis from the object side to the image side; the first lens is an even-order aspheric negative lens; the second lens is an even-order aspheric positive lens; the third lens is a plano-concave even-order aspheric negative lens; the fourth lens is a plano-convex even-order aspheric positive lens; the lens group satisfies the following relationship: BF / f=1.679 f1 / f=-0.95 f2 / f=1.58 f3 / f=-5.36 f4 / f=1.06 n1=n2=4, n3=2.21, n4=2.78 d1 / f=0.375 d2 / f=0.733 d3 / f=0.1 Wherein, BF is the back focus of the lens, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, n1 is the refractive index of the first lens, n2 is the refractive index of the second lens, n3 is the refractive index of the third lens, n4 is the refractive index of the fourth lens, d1 is the air spacing distance between the first lens and the second lens, d2 is the air spacing distance between the second lens and the third lens, and d3 is the air spacing distance between the third lens and the fourth lens.

2. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 1, characterized in that: The wide-band athermal long-wave infrared characteristic measurement lens has an operating band of 6 μm to 12 μm, a field of view of φ40°, a focal length of 24 mm, an F number of 2, a distortion of less than 3%, an athermal temperature range of -40°C to 60°C, and 100% cold stop matching.

3. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 1, characterized in that: The side of the electromagnetic shielding window close to the image side is plated with a metal grid; the outer circle of the metal grid is plated with a metal ring; preferably, the caliber of the electromagnetic shielding window is 43mm; the caliber of the metal grid is 40mm; and the width of the metal ring is 1.5mm.

4. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 1, characterized in that: Both sides of the electromagnetic shielding window are coated with anti-reflection films; within the 6μm-12μm band, the electromagnetic shielding window has an average spectral transmittance of ≥86%, and an electric field radiation shielding effectiveness of ≥30dB at 30MHz-1.5GHz.

5. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 1, characterized in that: The first lens has a spherical surface on the side close to the object and an even-order aspherical surface on the side close to the image; The second lens has an even-order aspheric surface on one side close to the object side and a spherical surface on the other side close to the image side; The third lens has a plane surface close to the object side and an even-order aspheric surface close to the image side; and / or The fourth lens has a surface close to the object side which is a plane, and a surface close to the image side which is an even-order aspherical surface.

6. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 5, characterized in that: The curvature radius of the first lens close to the object side is 38.678 mm, and the curvature radius of the first lens close to the image side is 23.304 mm; The curvature radius of the second lens close to the object side is 63.381 mm, and the curvature radius of the second lens close to the image side is 137.128 mm; The curvature radius of the third lens close to the image side is 155.83 mm; and / or The curvature radius of the fourth lens close to the image side is -45.354 mm.

7. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 5, characterized in that: The aspherical surfaces of the first lens close to the image side, the second lens close to the object side, the third lens close to the image side, and the fourth lens close to the image side meet the following formula: Among them, Z is the vector height, c is the surface curvature, r is the radial distance from a point on the lens to the optical axis, k is the cone coefficient, and a2, a4, a6, and a8 are all aspherical coefficients.

8. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 7, characterized in that: The first lens near the image side satisfies: a2 = 0, a4 = -2.372E -6 , a6=-1.631E -8 , a8=6.877E -11 ; The second lens near the object side satisfies: a2 = 0, a4 = -2.453E -6 , a6=-1.168E -8 , a8=2.063E -11 ; The third lens near the image side satisfies: a2=0, a4=-3.249E -6 , a6=-2.884E -8 , a8=9.496E -11 ; and / or The fourth lens near the image side satisfies: a2 = 0, a4 = 3.283E -6 , a6=1.372E -8 , a8=-4.716E -11 .

9. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 1, characterized in that: The thickness of the first lens is 3 mm; The thickness of the second lens is 3.3 mm; The thickness of the third lens is 6.8 mm; and / or The thickness of the fourth lens is 4.7 mm.

10. The wide-band athermal long-wave infrared characteristic measurement lens according to claim 1, characterized in that: The material of the first lens is germanium single crystal; The material of the second lens is zinc sulfide; The material of the third lens is germanium single crystal; The material of the fourth lens is chalcogenide glass; The material of the detector protection glass is germanium crystal; and / or The material of the detector filter is germanium crystal.

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