A large-array wide-angle uncooled infrared lens based on all-sulfur glass

Abstract

The utility model discloses a kind of big array wide-angle uncooled infrared lens based on all sulfur system glass, including first lens, second lens, third lens, fourth lens are sequentially arranged with the focus surface of detector from object plane to the direction along optical axis. Four pieces of lenses are all using sulfur system glass material, wherein first, second lens are all IG6 material, third lens is IG2 material, fourth lens is IG4 material, used sulfur system material is suitable for moulding process and batch efficiency is higher, process cost can be effectively controlled. The system has 80 ° full field of view, maximum optical distortion control is-12%, in the working temperature range of-40 ℃ to+60 ℃, defocus amount≤3 μm, with large field of view, low distortion, low cost, mass production efficiency and the like advantage. The utility model can be widely applied in various industrial security monitoring, vehicle auxiliary driving and other various product fields.

Description

Technical Field

[0001] This utility model relates to the field of long-wave infrared imaging lens design technology, specifically to a large-area array wide-angle uncooled infrared lens based on all-chalcogenide glass, and more particularly to a wide-angle unheated uncooled infrared lens based on all-chalcogenide glass material, adapted to an array size of 1280×1024@12μm and below. Background Technology

[0002] Infrared thermal imaging technology, as an important branch of modern optoelectronic detection, can convert the thermal radiation of an object's surface into a visual image, enabling all-weather monitoring without relying on ambient light. Due to their advantages in price, weight, and size, uncooled infrared detectors are widely used in various security and auxiliary observation fields.

[0003] With the rapid development of uncooled detector technology, the pixel size of current mainstream products has shrunk to 17μm and 12μm, while the array size continues to expand, with high-resolution configurations of 640×512 pixels, 1024×768 pixels, and even 1280×1024 pixels becoming increasingly common. This requires infrared lenses to have a matching large target surface design; otherwise, it can easily lead to problems such as image edge distortion and uneven energy distribution around the edges, directly affecting the overall performance of the imaging system.

[0004] In practical applications, the demand for wide-angle lenses in uncooled infrared imaging systems is experiencing explosive growth. Whether it's large-scale scene coverage in urban security or environmental perception for autonomous vehicles, wide-angle lenses, with their broad field of view, can effectively reduce blind spots and improve the efficiency of environmental information acquisition. However, large field-of-view designs often come with the challenge of increased difficulty in optical aberration correction. Furthermore, traditional lens designs often rely on high-cost infrared optical materials such as germanium and zinc selenide, and to meet complex optical performance requirements, multi-lens combinations and precision diffraction surface processing techniques are necessary. This results in high costs for material procurement, manufacturing, and assembly, limiting the large-scale application of these products in both military and civilian markets.

[0005] Based on this, a large-area wide-angle uncooled infrared lens based on low-cost materials is designed to solve the problems of existing lenses in terms of adapting to large-area detectors, imaging performance, cost control and temperature adaptability. It has important practical significance and application value, which will strongly promote the widespread application and development of uncooled infrared imaging technology in more fields. Utility Model Content

[0006] To meet the demand for low-cost and lightweight uncooled long-wave infrared wide-angle lenses in security monitoring, vehicle-mounted assisted driving, and other products, this utility model is designed using chalcogenide glass materials. It uses three materials, IG6, IG2, and IG4, for compatibility, resulting in four lenses of different optical powers. Due to their amorphous properties, chalcogenide glass can be processed using molding and turning processes. This characteristic allows for high yield rates in mass production of chalcogenide glass, effectively controlling costs.

[0007] A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass has a first lens, a second lens, a third lens, and a fourth lens respectively arranged along the optical axis from the object side to the detector focal plane. The first lens is a meniscus lens with its convex surface facing the object side, the second lens is a positive lens, the third lens is a negative lens, and the fourth lens is a positive lens.

[0008] Preferably, the focal length f1 of the first lens is -33.61mm, the focal length f2 of the second lens is 15.36mm, the focal length f3 of the third lens is -13.76mm, the focal length f4 of the fourth lens is 15.22mm, and the focal length f of the entire optical system composed of the first lens, the second lens, the third lens, and the fourth lens is 13.3mm.

[0009] Preferably, the infrared lens has a focal length of 13.3mm, and the dimensions of each lens along the optical axis are as follows: the air gap between the first lens and the second lens is 26.72mm, the air gap between the second lens and the third lens is 4.37mm, the air gap between the third lens and the fourth lens is 0.56mm, and the distance between the fourth lens and the focal plane of the infrared detector is 13.85mm.

[0010] Preferably, the curved surfaces of the first lens, second lens, third lens, and fourth lens along the object-side to image-side direction are labeled as S1, S2, S3, S4, S5, S6, S7, and S8, respectively; the center thickness of the first lens is 2.22 mm, the center thickness of the second lens is 4.09 mm, the center thickness of the third lens is 2.2 mm, and the center thickness of the fourth lens is 6.0 mm; the radius of curvature of S1 is 20.14 mm, the radius of curvature of S2 is 14.0 mm, the radius of curvature of S3 is 22.38 mm, the radius of curvature of S4 is 109.46 mm, the radius of curvature of S5 is -139.86, the radius of curvature of S6 is 24.38, the radius of curvature of S7 is 26.08, and the radius of curvature of S8 is -343.15.

[0011] Preferably, S1, S4, S6, and S7 are spherical surfaces, and S2, S3, S5, and S8 are aspherical surfaces, wherein S3 is an aspherical surface with an added diffraction surface design.

[0012] Preferably, the aspherical lens curves of the first lens, second lens, third lens, and fourth lens satisfy the following equation:

[0013]

[0014] Where r represents the height; Z represents the distance sag from the vertex of the aspherical surface at a position of height r along the incident direction of the light ray; c represents the radius of curvature; k represents the conic coefficient; a4, a6, a8, a 10 a 12 This represents the higher-order aspheric coefficients.

[0015] Preferably, the equation for the diffractive aspherical surface shape in the third lens satisfies the following equation:

[0016]

[0017] Where Z(r) represents the axial distance from a point on the surface to the vertex; n represents the refractive index of the material; λ represents the design center wavelength; c1 and c2 are diffraction phase coefficients; r represents the radial coordinate in the direction perpendicular to the optical axis; and HOR represents the diffraction order.

[0018] Preferably, the horizontal field of view is 64.3°, the vertical field of view is 52°, the total field of view is 80.1°, the maximum optical distortion is -12%, and the relative illumination is ≥82%.

[0019] Preferably, it is compatible with detector target surfaces with an array size of 15.36mm × 12.288mm or smaller, and is applicable to the 8~12μm uncooled long-wave infrared band; the lens has a defocusing amount ≤3μm within the operating temperature range of -40℃ to +60℃; the lens aperture number F≤1.2; the lens has all lenses coaxially fixedly installed in sequence through the lens barrel, and the lens barrel is provided with an aperture stop located on the surface of the second lens S3.

[0020] The mechanism and beneficial effects of this utility model are as follows:

[0021] (1) Conventional wide-angle lenses are difficult to correct due to their large incident angle, and usually use multiple lenses for aberration correction. However, increasing the number of lenses in an infrared lens can lead to a low overall transmittance. This utility model uses a four-glass design, simplifying the number of lenses and achieving a compact and lightweight structure that can be adapted to various observation products. This utility model uses a combination of aspherical and diffractive surfaces, with a full field of view of 80°, a horizontal field of view of 64°, a vertical field of view of 53°, and a maximum field of view optical distortion of -12%. This can solve the problems of narrow field of view and obvious distortion in most uncooled long-wave infrared lenses currently on the market.

[0022] (2) The present invention adopts a four-lens design, which enables the lens to be adapted to large-area uncooled detectors with a size of 1280×1024@12μm and target surfaces of smaller sizes, thus meeting the high resolution requirements of current vehicle driving systems and industrial security monitoring systems.

[0023] (3) This utility model adopts a full chalcogenide glass material with a low coefficient of thermal expansion, which meets the requirements of calorimetry design. It has excellent image quality in the working temperature range of -40℃ to +60℃ and defocusing amount ≤3μm.

[0024] (4) This utility model adopts a four-piece chalcogenide glass material design, which reduces the cost by about 30% compared with conventional lenses based on germanium and zinc selenide materials;

[0025] (4) The uniformity of all four glass elements being made of chalcogenide materials can significantly improve mass production efficiency and effectively reduce costs; the combination of aspherical and diffractive surfaces is used to optimize large field-of-view aberrations; the design is adapted to detectors of 1280×1024@12μm large array detectors and smaller; it has an 80° full field of view and a maximum optical distortion of -12%; it meets the high-resolution development trend of products such as industrial security monitoring, airborne / vehicle environment scene matching navigation / image fusion, and vehicle night driving assistance, and has broad market prospects. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the lens design system of this utility model.

[0027] Figure 2 The image quality analysis of this utility model includes MTF plots of the transfer function under normal temperature (a), low temperature (b), and high temperature (c) conditions.

[0028] Figure 3 This is a dot plot of the image quality analysis of this utility model under normal temperature (a), low temperature (b), and high temperature (c) conditions.

[0029] Figure 4 This is a schematic diagram of the image quality analysis of this utility model—diffusion spots under normal temperature, low temperature, and high temperature conditions.

[0030] Figure 5 This is a schematic diagram of field curvature and distortion under normal temperature conditions for image quality analysis of this utility model. Detailed Implementation

[0031] This utility model embodiment is applied to a lens case of an uncooled infrared detector with an array size of 1280×1024 and a pixel size of 12μm, operating in a temperature range of -40℃ to +60℃. It can also be adapted to detectors with an array size smaller than 1280×1024@12μm.

[0032] This utility model describes a large-area array wide-angle uncooled infrared lens based on all-chalcogenide glass. The lens structure is as follows: Figure 1 As shown, the front lens group includes a meniscus lens with its convex surface facing the object side. It is made of chalcogenide glass with negative optical power and paired with an aspherical surface to expand the field of view and complete the large field of view design.

[0033] The present invention describes a large-area wide-angle uncooled infrared lens based on all-chalcogenide glass, wherein the middle group is a chalcogenide positive lens glass, which adopts a combination of spherical and aspherical design to complete aberration correction.

[0034] The present invention describes a large-area wide-angle uncooled infrared lens based on all-chalcogenide glass. The rear lens group includes two aspherical chalcogenide glass lenses with a combination of positive and negative optical power. At the same time, a diffraction surface design is added to the aspherical design of the third lens. The diffraction surface can directly modulate the wavefront phase and suppress edge field aberrations, so as to complete the refraction and convergence of large-angle light rays to the focal plane of the detector.

[0035] The present invention describes a large-area wide-angle uncooled infrared lens based on all-chalcogenide glass. The first and second lenses are made of IG6 material, the third lens is made of IG2 material, and the fourth lens is made of IG4 material. The combination of the three chalcogenide materials can better correct the aberrations caused by the large field of view and eliminate the defocusing problem caused by the thermal expansion mismatch of multiple materials.

[0036] This invention discloses a large-area, wide-angle, uncooled infrared lens based on all-chalcogenide glass. The total optical length (from the first surface of the first lens to the focal plane of the detector) is 60mm. Increasing the field of view can lead to significant lens distortion; therefore, the lens length is appropriately increased to soften the light refraction angle and effectively correct lens distortion. The lens has a horizontal field of view of 64.2°, a vertical field of view of 52°, and a diagonal field of view of 80°, with the maximum optical distortion controlled at -12%. The lens has a compact and lightweight overall structure, with moderate lens thickness, resulting in a softer light refraction angle and meeting lightweight design requirements.

[0037] The present invention discloses a large-area array wide-angle uncooled infrared lens based on all-chalcogenide glass. In the long-wave infrared band range of 8~12μm, the blocking ratio of the first lens is appropriately controlled to be no greater than 0.85, so that the curvature of the lens is moderate, reducing the local incident angle of light reaching the image plane, and the relative illumination of the lens reaches 82% in this band.

[0038] Figure 2The figure shows the modulation transfer function (MTF) of the large-area wide-angle uncooled infrared lens based on all-chalcogenide glass in this embodiment under normal temperature, low temperature, and high temperature conditions. As can be seen from the figure, the MTF curves of each field of view are relatively uniformly distributed under each temperature condition. At normal temperature, the MTF value at the on-axis field of view is about 0.94 at 10 cyc / mm and about 0.48 at the threshold frequency of 34 cyc / mm. At the edge field of view, the value is about 0.76 at 10 cyc / mm and about 0.3 at the threshold frequency of 34 cyc / mm.

[0039] Figure 3 The image quality evaluation diagrams for this embodiment based on a large-area array wide-angle uncooled infrared lens using all-chalcogenide glass under normal temperature, low temperature, and high temperature conditions are shown in the dot plot diagrams. As can be seen from the diagrams, the average radius of the dot plot diagram in the on-axis field of view at normal temperature is about 5 μm, which is smaller than the radius of the Airy disk of the system; the radius of the dot plot diagram in the off-axis field of view is about 15 μm, which is close to the radius of the Airy disk of the system.

[0040] Figure 4 The relative illumination curve of the system is proportional to the fourth power of the cosine of the incident angle. Therefore, conventional wide-angle lenses have low relative illumination and poor imaging uniformity due to their large incident angle. This invention controls the blocking ratio of the first lens to be no greater than 0.85, increases the distance between the first and second lenses, and appropriately increases the length, so that the light refraction angle is stable and the lens relative illumination is ≥82%, which meets the requirements of human eyes for image observation.

[0041] Figure 5 The field curvature and distortion curves show that the maximum distortion of the system is less than -12%, and the field curvature is controlled within a range that is not easily perceptible to the human eye.

[0042] The third lens of the lens adopts a diffractive aspherical design, wherein the diffraction order is 1st, the phase coefficient c1 is -0.0006, and the phase coefficient c2 is -1.611e-08.

[0043] The optical parameters of the lens are shown in the table below:

[0044]

[0045] The aspherical parameters of the lens are shown in the table below:

[0046] .

Claims

1. A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass, characterized in that: A first lens, a second lens, a third lens, and a fourth lens are respectively arranged along the optical axis from the object side to the detector focal plane. The first lens is a meniscus lens with its convex surface facing the object side, the second lens is a positive lens, the third lens is a negative lens, and the fourth lens is a positive lens. The first and second lenses are made of IG6 material, the third lens is made of IG2 material, and the fourth lens is made of IG4 material. The combination of IG6, IG2 and IG4 materials is used to correct aberrations caused by a large field of view and to eliminate defocus caused by the thermal expansion of chalcogenide materials.

2. The large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to claim 1, characterized in that: The curved surfaces of the first lens, second lens, third lens, and fourth lens along the object-to-image direction are labeled as S1, S2, S3, S4, S5, S6, S7, and S8, respectively; among them, S1, S4, S6, and S7 are spherical surfaces, S2, S3, S5, and S8 are aspherical surfaces, and S3 is an aspherical surface with an added diffraction surface design.

3. The large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to claim 1, characterized in that: The focal length f1 of the first lens is -33.61mm, the focal length f2 of the second lens is 15.36mm, the focal length f3 of the third lens is -13.76mm, and the focal length f4 of the fourth lens is 15.22mm. The total focal length f of the entire optical system consisting of the first, second, third, and fourth lenses is 13.3mm.

4. The large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to claim 1, characterized in that: The dimensions of each lens along the optical axis are as follows: the air gap between the first and second lenses is 26.72 mm, the air gap between the second and third lenses is 4.37 mm, the air gap between the third and fourth lenses is 0.56 mm, and the distance between the fourth lens and the focal plane of the infrared detector is 13.85 mm.

5. A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to claim 2, characterized in that: The center thickness of the first lens is 2.22 mm, the center thickness of the second lens is 4.09 mm, the center thickness of the third lens is 2.2 mm, and the center thickness of the fourth lens is 6.0 mm; the radius of curvature of S1 is 20.14 mm, the radius of curvature of S2 is 14.0 mm, the radius of curvature of S3 is 22.38 mm, the radius of curvature of S4 is 109.46 mm, the radius of curvature of S5 is -139.86 mm, the radius of curvature of S6 is 24.38 mm, the radius of curvature of S7 is 26.08 mm, and the radius of curvature of S8 is -343.15 mm.

6. A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to claim 1, characterized in that: The aspherical lens curves of the first, second, third, and fourth lenses satisfy the following equation: ； Where r represents the height, Z represents the distance sag from the vertex of the aspherical surface at a position of height r along the incident direction of the light ray, c represents the radius of curvature, k represents the conic coefficients, and a4, a6, a8, a... 10 a 12 Represents higher-order aspheric coefficients; The equation for the diffraction aspherical surface shape in the third lens satisfies the following equation: ； Where Z(r) represents the axial distance from a point on the surface to the vertex, n represents the refractive index of the material, λ represents the design center wavelength, c1 and c2 are the diffraction phase coefficients, r represents the radial coordinate in the direction perpendicular to the optical axis, and HOR represents the diffraction order.

7. A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to claim 2, characterized in that: The lens has all the lenses coaxially fixed in sequence through the lens barrel. The lens barrel is equipped with an aperture stop, which is located on the surface of the second lens S3.

8. A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to any one of claims 1 to 7, characterized in that: The horizontal field of view is 64.3°, the vertical field of view is 52°, the total field of view is 80.1°, the maximum optical distortion is -12%, and the relative illumination is ≥82%.

9. A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to any one of claims 1 to 7, characterized in that: The lens has a defocusing amount of ≤3μm within the operating temperature range of -40℃ to +60℃. The lens aperture number F≤1.

2.

10. A large-area wide-angle uncooled infrared lens based on all-chalcogenide glass according to any one of claims 1 to 7, characterized in that: It is compatible with detector target surfaces with an array size of 15.36mm×12.288mm and smaller, and is applicable to the 8~12μm uncooled long-wave infrared band.

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