Athermal large target surface wide band short wave infrared refrigeration optical system

Abstract

This invention discloses a thermally cooled, large-target-area, wide-band short-wave infrared optical system, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side to the image side. The first lens is a biconvex spherical lens with positive optical power; the second lens is a biconcave double aspherical lens with negative optical power; the third lens is a biconcave spherical lens with negative optical power; the fourth lens is a biconvex single aspherical lens with positive optical power; the fifth lens is a biconvex spherical lens with positive optical power; the sixth lens is a meniscus aspherical lens with negative optical power and its convex surface curved towards the object side; the seventh lens is a biconvex single aspherical lens with positive optical power; and the eighth lens is a plano-concave aspherical lens with negative optical power. This optical system has a long applicable wavelength range, an ultra-large target-area field of view, and a large aperture, achieving a thermally cooled design from -40℃ to 80℃, and exhibits strong adaptability.

Description

Technical Field

[0001] This invention relates to a calorimetric large-target-area wide-band short-wave infrared cooling optical system, belonging to the technical field of wide-band short-wave infrared cooling optical systems. Background Technology

[0002] Short-wave infrared (SWI) lenses typically operate in the 0.9µm–2.5µm band, providing information beyond visible, mid-infrared, and long-infrared wavelengths. Due to material limitations and manufacturing costs, currently popular SWI lenses primarily use conventional glass materials, making wide-band chromatic aberration correction relatively difficult, and achieving passive, athermal optical cooling is also challenging. Most mainstream SWI lenses on the market are non-athermal designs in the 0.9µm–1.7µm band, rarely compatible with the 0.9µm–2.5µm wide band. Compared to uncooled SWIMP systems, cooled SWIMP systems operate at stable low temperatures, offering faster response times, higher sensitivity, stronger anti-interference capabilities, and suitability for extreme working environments.

[0003] Against this background, the present invention provides a cooled, athermalized shortwave optical system with a focal length of 50mm and an applicable wavelength range of 0.9um to 2.5um. It can be matched with a maximum F#2.0 and 2048*2848-10um shortwave cooled camera. It features a large field of view, high sensitivity, and strong anti-interference ability, and can be applied to multiple application fields such as security monitoring, medical imaging, biometric technology, space remote sensing, and machine vision. Summary of the Invention

[0004] This invention provides a wide-band short-wave infrared cooled athermal optical system with a large aperture and large target surface, which features good imaging quality, high sensitivity, and high resolution.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A thermalized, large-target, wide-band short-wave infrared cooling optical system includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 arranged sequentially from the object side to the image side. The first lens L1 is a biconvex spherical lens with positive optical power; the second lens L2 is a biconcave double aspherical lens with negative optical power; the third lens L3 is a biconcave spherical lens with negative optical power; the fourth lens L4 is a biconvex single aspherical lens with positive optical power; the fifth lens L5 is a biconvex spherical lens with positive optical power; the sixth lens L6 is a meniscus aspherical lens with negative optical power and its convex surface curved towards the object side; the seventh lens L7 is a biconvex single aspherical lens with positive optical power; and the eighth lens L8 is a plano-concave aspherical lens with negative optical power.

[0007] To further improve image quality, the above-mentioned calorimetric large-target wide-band short-wave infrared cooled optical system satisfies the following relationships: 5.0F < f1 < 5.2F; -1.2F < f2 < -1.1F; -1.3F < f3 < 1.0F; 1.6F < f4 < 1.9F; 1.3F < f5 < 1.75F; -1.5F < f6 < -1.2F; 0.5F < f7 < 0.8F; -4F < f8 < -2F; where F is the focal length of the optical system, f1 is the focal length of the first lens L1, f2 is the focal length of the second lens L2, f3 is the focal length of the third lens L3, f4 is the focal length of the fourth lens L4, f5 is the focal length of the fifth lens L5, f6 is the focal length of the sixth lens L6, f7 is the focal length of the seventh lens L7, and f8 is the focal length of the eighth lens L8.

[0008] To further improve image quality, the first lens L1 is made of magnesium fluoride, the second lens L2 is made of zinc selenide, the third lens L3 is made of calcium fluoride, the fourth lens L4 is made of sulfide IRG206, the fifth lens L5 is made of barium fluoride, the sixth lens L6 is made of sulfide IRG206, the seventh lens L7 is made of zinc sulfide, and the eighth lens L8 is made of sulfide IRG206.

[0009] The aperture of the optical system in this application is coincident with the aperture of the cooled camera to achieve 100% cold aperture efficiency. At the same time, the entire optical system preferably uses chalcogenide glass, zinc selenide, zinc sulfide, and fluoride glass as lens materials to achieve thermal imaging at -40℃ to 80℃.

[0010] To balance system stability and imaging performance, the center thickness of the first lens L1 is 14±0.0003mm; the center thickness of the second lens L2 is 3±0.0003mm; the center thickness of the third lens L3 is 5.26±0.0003mm; the center thickness of the fourth lens L4 is 5.48±0.0003mm; the center thickness of the fifth lens L5 is 12.5±0.0003mm; the center thickness of the sixth lens L6 is 5±0.0003mm; the center thickness of the seventh lens L7 is 10±0.0003mm; and the center thickness of the eighth lens L8 is 4±0.0003mm.

[0011] To further improve image quality, the center-to-center distance between the first lens L1 and the second lens L2 is 22.2641±0.0003mm; the center-to-center distance between the second lens L2 and the third lens L3 is 9.6574±0.0003mm; the center-to-center distance between the third lens L3 and the fourth lens L4 is 6.0136±0.0003mm; the center-to-center distance between the fourth lens L4 and the fifth lens L5 is 0.5406±0.0003mm; the center-to-center distance between the fifth lens L5 and the sixth lens L6 is 3.1511±0.0003mm; the center-to-center distance between the sixth lens L6 and the seventh lens L7 is 2.8644±0.0003mm; and the center-to-center distance between the seventh lens L7 and the eighth lens L8 is 0.3544±0.0003mm.

[0012] The first lens's incident surface S1 and exit surface S2 are both spherical; the second lens's incident surface S3 and exit surface S4 are both aspherical; the third lens's incident surface S5 and exit surface S6 are both spherical; the fourth lens's incident surface S7 is spherical, and the fourth lens's exit surface S8 is aspherical; the fifth lens's incident surface S9 and exit surface S10 are both spherical; the sixth lens's incident surface S11 is spherical, and the sixth lens's exit surface S12 is aspherical; the seventh lens's incident surface S13 is aspherical, and the seventh lens's exit surface S14 is spherical; the eighth lens's incident surface S15 is planar, and the eighth lens's exit surface S16 is aspherical.

[0013] To further improve image quality, the radius of curvature of the first lens's incident surface S1 is 118.8928±0.0003mm, and the radius of curvature of the first lens's exit surface S2 is -520.6900±0.0003mm; the radius of curvature of the second lens's incident surface S3 is -151.3956±0.0003mm, and the radius of curvature of the second lens's exit surface S4 is 192.2144±0.0003mm; the radius of curvature of the third lens's incident surface S5 is -37.7600±0.0003mm, and the radius of curvature of the third lens's exit surface S6 is 58.2000±0.0003mm; the radius of curvature of the fourth lens's incident surface S7 is 320.7000±0.0003mm, and the radius of curvature of the fourth lens's exit surface S8 is -320.61mm. The radius of curvature of the fifth lens's incident surface S9 is 70.5620±0.0003mm, and the radius of curvature of the fifth lens's exit surface S10 is -99.8211±0.0003mm; the radius of curvature of the sixth lens's incident surface S11 is 47.0000±0.0003mm, and the radius of curvature of the sixth lens's exit surface S12 is 31.5548±0.0003mm; the radius of curvature of the seventh lens's incident surface S13 is 46.3555±0.0003mm, and the radius of curvature of the seventh lens's exit surface S14 is -278.4599±0.0003mm; the radius of curvature of the eighth lens's incident surface S15 is infinite, and the radius of curvature of the eighth lens's exit surface S16 is 245.7861±0.0003mm.

[0014] The aforementioned athermalized large-target wide-band short-wave infrared cooled optical system has a focal length of 50mm, an applicable wavelength range of 0.9um to 2.5um, and can be matched with F#2.0 and 2048*2848-10um short-wave cooled cameras. It has a full field of view of 34° and features a large field of view, high sensitivity, and strong anti-interference ability. It can be applied in multiple fields such as security monitoring, medical imaging, biometric technology, space remote sensing, and machine vision.

[0015] Any techniques not mentioned in this invention are based on existing technologies.

[0016] The calorimetric large-target-area, wide-band short-wave infrared cooling optical system of the present invention has the following beneficial effects:

[0017] 1) The optical system of this invention achieves wide-band achromatic imaging of 0.9um to 2.5um, applicable to a long wavelength range.

[0018] 2) The optical system of this invention has an ultra-large target surface field of view, which can be matched with a shortwave camera with a target surface of H20.48mm×V20.48mm.

[0019] 3) The optical system of this invention is matched with a cooled camera for imaging, with a large aperture of F#2.0, sufficient energy, high sensitivity, fast response, high resolution, and strong anti-interference ability.

[0020] 4) This invention achieves a heatless design from -40℃ to 80℃, eliminating the need for multiple refocusing adjustments due to changes in ambient temperature during use, thus demonstrating strong adaptability. Attached Figure Description

[0021] Figure 1 This is the optical path diagram of the calorimetric large-target-area wide-band short-wave infrared cooling optical system of the present invention;

[0022] Figure 2 This is a schematic diagram of the structure of the calorimetric large target area wide-band short-wave infrared cooling optical system of the present invention;

[0023] Figure 3 The transfer function curve of the calorimetric large target area wide-band short-wave infrared cooling optical system of the present invention at an ambient temperature of 20°C is shown.

[0024] Figure 4 This is a transfer function curve of the calorimetric large target area wide-band short-wave infrared cooling optical system of the present invention at an ambient temperature of -40℃.

[0025] Figure 5 The transfer function curve of the calorimetric large target area wide-band short-wave infrared cooling optical system of the present invention at an ambient temperature of 80°C is shown.

[0026] Figure 6 This is a full-field distortion curve of the athermalized large-target-area wide-band short-wave infrared cooling optical system of the present invention. Detailed Implementation

[0027] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0028] like Figure 1-2 As shown, the calorimetric large target surface wide-band short-wave infrared cooling optical system includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7 and an eighth lens L8 arranged sequentially from the object side to the image side.

[0029] Let the focal length of the above-mentioned anechoic large-target wide-band short-wave infrared cooling optical system be F, and the focal lengths of the first to eighth lenses be f1, f2, f3, f4, f5, f6, f7, and f8, respectively. The characteristics of each lens are as follows:

[0030] The first lens L1 is a biconvex spherical lens with positive optical power, 5.0F < f1 < 5.2F;

[0031] The second lens L2 is a biconcave double aspherical lens with negative optical power, -1.2F < f2 < -1.1F;

[0032] The third lens L3 is a biconcave spherical lens with negative optical power, -1.3F < f3 < 1.0F;

[0033] The fourth lens L4 is a biconvex aspherical lens with positive optical power, 1.6F < f4 < 1.9F;

[0034] The fifth lens L5 is a biconvex spherical lens with positive optical power, 1.3F < f5 < 1.75F;

[0035] The sixth lens L6 is a meniscus aspherical lens with negative optical power and a convex surface bent towards the object side, -1.5F < f6 < -1.2F;

[0036] The seventh lens L7 is a biconvex aspherical lens with positive optical power, 0.5F < f7 < 0.8F;

[0037] The eighth lens L8 is a plano-concave aspherical lens with negative optical power, -4F < f8 < -2F;

[0038] Table 1. Specific optical parameters of the optical system:

[0039]

[0040]

[0041] In Table 1, radius of curvature refers to the radius of curvature of each lens surface, thickness or spacing refers to the center thickness of the lens or the center spacing between adjacent lenses, material refers to the material used for the lens, and air refers to the medium between two lenses being air.

[0042] To achieve better image quality in the optical system, even-order aspherical surfaces are used to reduce various aberrations, including chromatic aberration, and lens materials are appropriately matched to eliminate focus shift caused by changes in surface shape due to temperature variations.

[0043] Table 2. Aspheric coefficients used in optical systems.

[0044] surface k A B C D S3 0 -3.7113817E-007 -3.6808659E-010 -6.6998365E-013 7.8165295E-016 S4 0 -3.4196652E-007 -9.2507658E-010 1.9454130E-013 3.2562715E-016 S8 0 7.8569439E-007 8.2094316E-011 -2.0096584E-013 2.5688914E-016 S12 0 -5.6236308E-006 -3.4877680E-009 4.1079676E-012 -3.2060445E-015 S13 0 -3.4665201E-006 -3.2501538E-009 4.6454438E-012 -2.8548074E-016 S16 0 1.8589157E-006 -7.2189069E-010 2.5309552E-012 3.2625185E-015

[0045] The aspherical equations used for each surface in Table 2 are as follows:

[0046]

[0047] The meanings of each quantity are as follows:

[0048] ZA: The lens sagitta along the optical axis of the aspherical surface;

[0049] R: Radius of curvature at the intersection of the surface and the optical axis OO';

[0050] Y: Half-aperture of the lens perpendicular to the optical axis;

[0051] k: Conic coefficient;

[0052] A, B, C, D aspheric coefficients

[0053] Y: Half-aperture of the lens perpendicular to the optical axis;

[0054] Table 3 Technical Specifications of the Optical System

[0055]

[0056] Figure 3 The above optical system has a transfer function curve at room temperature (20°C). Figure 4 The above optical system has a transfer function curve at a low temperature of -40°C. Figure 5 The transfer function curve of the aforementioned optical system at a high temperature of 80°C is shown below. Figure 3 , 4 As shown in Figure 5, within the temperature range of -40℃ to 80℃, the transfer function of 50 lp / mm is greater than 0.4, indicating excellent image quality. From... Figure 6 It can be seen that the distortion across the entire field of view is ≤-5%.

Claims

1. A thermal-free, large-target, wide-band short-wave infrared cooling optical system, characterized in that: It is composed of a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 arranged sequentially from the object side to the image side; the first lens L1 is a biconvex spherical lens with positive optical power, the second lens L2 is a biconcave double aspherical lens with negative optical power, the third lens L3 is a biconcave spherical lens with negative optical power, the fourth lens L4 is a biconvex single aspherical lens with positive optical power, the fifth lens L5 is a biconvex spherical lens with positive optical power, the sixth lens L6 is a meniscus aspherical lens with negative optical power and its convex surface curved towards the object side, the seventh lens L7 is a biconvex single aspherical lens with positive optical power, and the eighth lens L8 is a plano-concave aspherical lens with negative optical power. The first lens's incident surface S1 and exit surface S2 are both spherical; the second lens's incident surface S3 and exit surface S4 are both aspherical; the third lens's incident surface S5 and exit surface S6 are both spherical; the fourth lens's incident surface S7 is spherical, and its exit surface S8 is aspherical; the fifth lens's incident surface S9 and exit surface S10 are both spherical; the sixth lens's incident surface S11 is spherical, and its exit surface S12 is aspherical; the seventh lens's incident surface S13 is aspherical, and its exit surface S14 is spherical; the eighth lens's incident surface S15 is planar, and its exit surface S16 is aspherical. A calorimetric, large-target, wide-band short-wave infrared cooled optical system satisfies the following relationships: 5.0F < f1 < 5.2F; -1.2F < f2 < -1.1F; -1.3F < f3 < 1.0F; 1.6F < f4 < 1.9F; 1.3F < f5 < 1.75F; -1.5F < f6 < -1.2F; 0.5F < f7 < 0.8F; -4F < f8 < -2F; where F is the focal length of the optical system, f1 is the focal length of the first lens L1, f2 is the focal length of the second lens L2, f3 is the focal length of the third lens L3, f4 is the focal length of the fourth lens L4, f5 is the focal length of the fifth lens L5, f6 is the focal length of the sixth lens L6, f7 is the focal length of the seventh lens L7, and f8 is the focal length of the eighth lens L8.

2. The athermalized large-target-area wide-band short-wave infrared cooling optical system as described in claim 1, characterized in that: The first lens L1 is made of magnesium fluoride, the second lens L2 is made of zinc selenide, the third lens L3 is made of calcium fluoride, the fourth lens L4 is made of sulfide IRG206, the fifth lens L5 is made of barium fluoride, the sixth lens L6 is made of sulfide IRG206, the seventh lens L7 is made of zinc sulfide, and the eighth lens L8 is made of sulfide IRG206.

3. The athermalized large-target-area wide-band short-wave infrared cooling optical system as described in claim 1 or 2, characterized in that: The center thickness of the first lens L1 is 14±0.0003mm; the center thickness of the second lens L2 is 3±0.0003mm; the center thickness of the third lens L3 is 5.26±0.0003mm; the center thickness of the fourth lens L4 is 5.48±0.0003mm; the center thickness of the fifth lens L5 is 12.5±0.0003mm; the center thickness of the sixth lens L6 is 5±0.0003mm; the center thickness of the seventh lens L7 is 10±0.0003mm; and the center thickness of the eighth lens L8 is 4±0.0003mm.

4. The athermalized large-target-area broadband short-wave infrared cooling optical system as described in claim 1 or 2, characterized in that: The center-to-center distance between the first lens L1 and the second lens L2 is 22.2641±0.0003mm; the center-to-center distance between the second lens L2 and the third lens L3 is 9.6574±0.0003mm; the center-to-center distance between the third lens L3 and the fourth lens L4 is 6.0136±0.0003mm; the center-to-center distance between the fourth lens L4 and the fifth lens L5 is 0.5406±0.0003mm; the center-to-center distance between the fifth lens L5 and the sixth lens L6 is 3.1511±0.0003mm; the center-to-center distance between the sixth lens L6 and the seventh lens L7 is 2.8644±0.0003mm; and the center-to-center distance between the seventh lens L7 and the eighth lens L8 is 0.3544±0.0003mm.

5. The athermalized large-target-area broadband short-wave infrared cooling optical system as described in claim 1 or 2, characterized in that: The radius of curvature of the incident surface S1 of the first lens is 118.8928±0.0003 mm, and the radius of curvature of the exit surface S2 of the first lens is -520.6900±0.0003 mm; the radius of curvature of the incident surface S3 of the second lens is -151.3956±0.0003 mm, and the radius of curvature of the exit surface S4 of the second lens is 192.2144±0.0003 mm; the radius of curvature of the incident surface S5 of the third lens is -37.7600±0.0003 mm, and the radius of curvature of the exit surface S6 of the third lens is 58.2000±0.0003 mm; the radius of curvature of the incident surface S7 of the fourth lens is 320.7000±0.0003 mm, and the radius of curvature of the exit surface S8 of the fourth lens is -320.6135±0.0 mm. The radius of curvature of the fifth lens's incident surface S9 is 70.5620±0.0003mm, and the radius of curvature of the fifth lens's exit surface S10 is -99.8211±0.0003mm; the radius of curvature of the sixth lens's incident surface S11 is 47.0000±0.0003mm, and the radius of curvature of the sixth lens's exit surface S12 is 31.5548±0.0003mm; the radius of curvature of the seventh lens's incident surface S13 is 46.3555±0.0003mm, and the radius of curvature of the seventh lens's exit surface S14 is -278.4599±0.0003mm; the radius of curvature of the eighth lens's incident surface S15 is infinite, and the radius of curvature of the eighth lens's exit surface S16 is 245.7861±0.0003mm.

6. The athermalized large-target-area broadband short-wave infrared cooling optical system as described in claim 1 or 2, characterized in that: The operating wavelength is 0.9um to 2.5um, the F / # is 2.0, and the full field of view is 34°.

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