An ultra-wideband large-aperture mid-wave infrared lens

Abstract

The utility model relates to infrared lens technical field, concretely to a kind of super wide waveband big image plane mid-wave refrigeration lens, comprising: first lens, second lens, third lens, fourth lens are sequentially arranged along the direction of light propagation, and detector, the inside of the detector is provided with first protective window, second protective window, diaphragm, image surface.The utility model selects silicon, germanium, IG6 three kinds of infrared materials by reasonable choice, 2 non-spherical surface is matched to optimize aberration, without using diffraction surface;It is adapted to 1024×1024 image element mid-wave refrigeration detector, working waveband 2.5~5.4 μm, F number 2.0, horizontal field of view 8.77 °, circular field of view 12.32 °, optical total length is less than 134 mm, can be in 0 ℃~30 ℃ range without focusing clear imaging, image distortion is less than 1%, applicable to civil security and other long-distance small target monitoring scene.

Description

Technical Field

[0001] This utility model relates to the field of infrared lens technology, specifically to an ultra-wideband large image plane mid-wave cooled lens. Background Technology

[0002] Infrared thermal imaging lenses, based on passive infrared night vision technology, collect the infrared radiation energy of objects and convert it into an image visible to the human eye. They are widely used in both military and civilian fields. Among them, mid-wave cooled lenses, due to their high imaging clarity, have become core equipment for long-distance, large-image-area observation needs in the civilian security field. For example, a mid-wave lens adapted to a 1024×1024 pixel resolution detector can meet the requirement of clear observation of small targets at a distance.

[0003] However, existing mid-wave thermal imaging lenses have the following technical drawbacks: (1) Poor temperature adaptability: When the temperature changes, the thermal expansion and contraction of the lens and lens barrel materials and the change of the lens refractive index will cause the lens focal length to shift, resulting in serious aberrations and defocus. Frequent focusing is required to maintain image quality. It cannot adapt to the daily ambient temperature fluctuations of 0℃~30℃. (2) Narrow working band: Conventional medium wave lenses have limited working bands and cannot fully collect the infrared radiation energy of the target, which is not conducive to the detection of weak signal targets at long distances; (3) Image quality is easily affected: Some lenses use diffraction surfaces to eliminate chromatic aberration, but the engraved rings will generate stray light to participate in imaging, destroying the uniformity of the image surface and reducing the clarity of the target image.

[0004] To address the aforementioned problems, we propose an ultra-wideband large-image-plane mid-wave cooled lens. Utility Model Content

[0005] The purpose of this invention is to provide an ultra-wideband large image plane mid-wave cooled lens to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: An ultra-wideband large-image-plane mid-wave cooled lens includes: A first lens, a second lens, a third lens, a fourth lens, and a detector are arranged sequentially along the direction of light propagation. The detector is internally provided with a first protective window, a second protective window, an aperture, and an image plane. The first lens is made of silicon. It is a meniscus negative lens with its convex surface facing the object side, and all its light-transmitting surfaces are spherical. The second lens is made of germanium. It is a plano-concave negative lens with its concave surface facing the image side. Its front surface is a plane and its rear surface is an aspherical surface. The highest order of the aspherical coefficient is 8th. The third lens is made of IG6. The third lens is a meniscus negative lens with its convex surface facing the object side. Its rear surface is an aspherical surface with the highest order of the aspherical surface being 6th order. The fourth lens is made of silicon. It is a meniscus positive lens with its convex surface facing the object side, and all its light-transmitting surfaces are spherical. The ultra-wideband large-image-size mid-wave cooled lens operates in the band of 2.5~5.4μm and is compatible with mid-wave cooled detectors with 1024×1024 pixels and 15μm pixel size. The horizontal field of view of the ultra-wideband large-image-size mid-wave cooled lens is 8.77° and the circular field of view is 12.32°.

[0007] Compared with the prior art, the beneficial effects of this utility model are: This invention achieves passive optical thermal aberration by complementing the refractive index temperature coefficients of silicon, germanium and IG6 materials, enabling clear imaging without focusing within the range of 0℃~30℃ and adapting to daily ambient temperature fluctuations. The working band of this utility model is 2.5 to 5.4 μm, which has a wider coverage range than conventional medium-wave lenses, can collect more infrared radiation energy from targets, and improve the detection sensitivity of small targets at a distance. This invention uses two aspherical surfaces (8th order on the L2 back surface and 6th order on the L3 back surface) to optimize aberrations, resulting in image distortion of less than 1%; it is compatible with a 1024×1024 (15μm) detector, with a horizontal field of view of 8.77° and a circular field of view of 12.32°, balancing a large field of view with high resolution. This invention does not employ a diffraction surface, thus avoiding stray light generated by the etched rings, ensuring image plane uniformity, while simultaneously enhancing resistance to non-target interference and providing stronger penetration of smoke and haze. This invention consists of only 4 lenses, with a small number of aspherical surfaces (2), reducing processing and assembly costs; the total optical length is less than 134mm, making it compact and easy to integrate into various monitoring devices. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the optical path of the ultra-wideband large image plane mid-wave cooling lens of this utility model; Figure 2 This is the 0°C transfer function diagram of the present invention; Figure 3 This is the 20°C transfer function diagram of the present invention; Figure 4 This is the 30°C transfer function diagram of the present invention; Figure 5 This is the 0°C dot plot of the present invention; Figure 6 This is a 20°C dot plot of the present invention; Figure 7 This is a 30°C dot plot of the present invention; Figure 8 This is a distorted schematic diagram of the present invention; Figure 9 This is the relative illumination diagram of the present invention.

[0009] In the picture: First lens 1, second lens 2, third lens 3, fourth lens 4, first protective window 5, second protective window 6, aperture 7, image plane 8. Detailed Implementation

[0010] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0011] Please see Figure 1-9 An ultra-wideband large-image-plane mid-wave cooled lens, comprising: The detector is arranged in sequence along the direction of light propagation, including a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a detector. The detector is equipped with a first protective window 5, a second protective window 6, an aperture 7, and an image plane 8.

[0012] The first lens 1 is made of silicon. The first lens 1 is a meniscus negative lens with its convex surface facing the object side. Its optical power is about -0.014. All light-transmitting surfaces are spherical. The radius of curvature of the front surface is 100.003 mm, and the radius of curvature of the rear surface is 17.73 mm. Silicon material has good temperature stability of refractive index, which can help eliminate thermal differences.

[0013] The second lens 2 is made of germanium. It is a plano-concave negative lens with its concave surface facing the image side. Its optical power is approximately -0.014. The front surface is a plane, and the rear surface is an aspherical surface with the highest order of aspherical coefficient being 8th. The radius of curvature of the rear surface is 13.77 mm. The 8th order aspherical surface can significantly correct aberrations such as spherical aberration and coma caused by a large image plane.

[0014] The third lens 3 is made of IG6. The third lens 3 is a meniscus negative lens with its convex surface facing the object side. Its optical power is approximately -0.001. The rear surface is aspherical, and the highest order of the aspherical surface is 6. The radius of curvature of the front surface is 57.998 mm, and the radius of curvature of the rear surface is 49.328 mm. The refractive index temperature coefficient of IG6 is complementary to that of silicon and germanium, making it a key material for achieving passive thermal ablation.

[0015] The fourth lens 4 is made of silicon. It is a meniscus positive lens with its convex surface facing the object side. Its optical power is about 0.013, and all light-transmitting surfaces are spherical. The radius of curvature of the front surface is 115.14 mm, and the radius of curvature of the rear surface is 284.275 mm. It is used to compensate for the optical power of the preceding lens and further optimize the system aberrations.

[0016] The lens is compatible with a mid-wave cooled staring focal plane detector with a resolution of 1024×1024 and a pixel size of 15μm; the operating wavelength is 2.5~5.4μm (ultra-wide mid-wave band); the F number is 2.0 (high light intake, which is beneficial for imaging in low-light environments); the horizontal field of view is 8.77° and the circular field of view is 12.32° (large image plane); the total optical length is less than 134mm (compact structure, easy to integrate).

[0017] like Figures 5-9 As shown, the assembled lens underwent performance testing, and the results are as follows: Temperature adaptability: At 0℃, 20℃, and 30℃, the MTF value of the polychromatic light diffraction at the lens edge field of view at a spatial frequency of 33 lp / mm is greater than 0.25 (e.g., Figures 2-4 As shown, it meets the industry standard for infrared lens imaging quality and can produce clear images without focusing; Image quality indicators: Dot plot tests show that the RMS radius of different fields of view at various temperatures is smaller than the radius of the Airy disk (8.64 μm) (e.g. Figures 5-7 As shown), the imaging spot is concentrated; distortion tests show that the maximum distortion value is 0.7310% (as shown). Figure 8 As shown in the figure, it is far less than the design target of 1%, and the image surface shows no obvious deformation. Band and adaptability: The infrared transmittance is stable in the 2.5 to 5.4 μm band; it is well adapted to a 1024×1024 pixel (15 μm) mid-wave cooled detector, with a horizontal field of view of 8.77° and a circular field of view of 12.32°, which meets the requirements of large image area monitoring. Structural dimensions: The measured total optical length is 132mm (less than the design limit of 134mm), which is compact and can be integrated into civilian security monitoring equipment.

[0018] The ultra-wideband large-image-size mid-wave cooled lens of this embodiment can be directly applied to long-distance monitoring systems in the field of civilian security, such as border patrol, security of large factory areas, and forest fire prevention. In outdoor environments of 0℃ to 30℃, it can achieve clear imaging with a resolution of 1024×1024 within a horizontal field of view of 8.77° without manual or automatic focusing. At the same time, it has a strong ability to penetrate smoke and haze and can effectively detect small targets at a distance (such as people and vehicles).

[0019] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A medium-wave cooled lens with an ultra-wideband large image plane, characterized in that, include: A first lens (1), a second lens (2), a third lens (3), a fourth lens (4) arranged sequentially along the direction of light propagation, and a detector, wherein the detector is provided with a first protective window (5), a second protective window (6), an aperture (7), and an image plane (8); The first lens (1) is made of silicon. The first lens (1) is a meniscus negative lens with its convex surface facing the object side. All light-transmitting surfaces are spherical. The material of the second lens (2) is germanium. The second lens (2) is a plano-concave negative lens with the concave surface facing the image side. The front surface is a plane and the rear surface is an aspherical surface. The highest order of the aspherical coefficient is 8. The material of the third lens (3) is IG6. The third lens (3) is a meniscus negative lens with the convex surface facing the object side. The rear surface is aspherical and the highest order of the aspherical surface is 6th order. The material of the fourth lens (4) is silicon. The fourth lens (4) is a meniscus positive lens with the convex surface facing the object side, and all light-transmitting surfaces are spherical. The ultra-wideband large-image-size mid-wave cooled lens operates in the band of 2.5~5.4μm and is compatible with mid-wave cooled detectors with 1024×1024 pixels and 15μm pixel size. The horizontal field of view of the ultra-wideband large-image-size mid-wave cooled lens is 8.77° and the circular field of view is 12.32°.

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