A hybrid refractive-diffractive middle wave infrared (MWIR) cooled optical lens

Abstract

A kind of fold-diffraction hybrid middle wave infrared refrigeration optical lens, including being arranged in order from left to right along the direction of optical axis successively: first single lens L1, second single lens L2, third single lens L3, fourth single lens L4, fifth single lens L5, sixth single lens L6, seventh single lens L7 and eighth single lens L8, the first single lens L1 is meniscus positive lens, the present application aims at solving the problems existing in prior art middle wave infrared imaging system, through the innovative fold-diffraction hybrid optical system design, high transmittance, large field of view, high resolution imaging performance is realized, while ensuring the stability in wide temperature range. Through careful design and reasonable selection of material to optical element, the lens of the application not only improves the imaging quality, but also reduces the processing cost, simplifies the difficulty of installation and adjustment, provides a new direction for the development of middle wave infrared imaging technology.

Description

Technical Field

[0001] This utility model relates to the field of optical lens technology, specifically to a mid-wave infrared cooled optical lens that combines refraction and diffraction. Background Technology

[0002] In the field of infrared imaging technology, mid-wave infrared imaging systems have attracted much attention due to their detection capabilities in the 3-5 micrometer wavelength range. Infrared radiation in this band can be absorbed by various materials and gases, thus finding wide applications in military reconnaissance, security monitoring, environmental monitoring, and industrial inspection. A mid-wave infrared imaging system typically includes key components such as an infrared detector, an optical system, a signal processor, and a display device. The optical system's role is to focus the infrared radiation from the target object onto the detector; its performance directly affects the quality of the entire imaging system. Traditional mid-wave infrared optical systems often face a series of challenges, including limitations on the selection of materials for specific infrared bands, system transmittance requirements, optical distortion control, and performance stability under extreme temperature conditions. To improve the system's sensitivity, signal-to-noise ratio, and resolution, cooled infrared detectors are usually required, further increasing the complexity of the system design. Cooled detectors need to operate at low temperatures to reduce thermal noise, requiring the optical system to consider cold stop efficiency to ensure that the detector only receives infrared radiation from the target, thereby achieving 100% cold stop efficiency. In optical system design, achieving large field-of-view, high-resolution imaging requires precise control of the curvature radius, thickness, and material parameters of optical components. Furthermore, due to the large coefficient of thermal expansion of infrared materials, the performance variations of the system at different temperatures also need to be controlled through athermal design. Athermal design aims to reduce the impact of temperature changes on the system's imaging quality, ensuring the system's stability and reliability over a wide temperature range. Utility Model Content

[0003] To address the shortcomings of existing technologies, this invention provides a mid-wave infrared cooled optical lens that combines refractive and diffractive technologies.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a refractive-diffraction hybrid mid-wave infrared cooled optical lens, comprising, coaxially arranged from left to right along the optical axis, a first single lens L1, a second single lens L2, a third single lens L3, a fourth single lens L4, a fifth single lens L5, a sixth single lens L6, a seventh single lens L7, and an eighth single lens L8, wherein the first single lens L1 is a meniscus positive lens with both surfaces being spherical; the second single lens L2 is a meniscus positive lens. The first single lens L3 is a meniscus negative lens with spherical surfaces on both sides; the second single lens L4 is a meniscus positive lens with spherical surfaces on both sides; the third single lens L5 is a meniscus positive lens with spherical surfaces on both sides; the fourth single lens L6 is a meniscus negative lens with spherical surfaces on both sides; the seventh single lens L7 is a meniscus positive lens with spherical surfaces on both sides; and the eighth single lens L8 is a biconvex positive lens with a spherical surface on the object side and a diffraction surface on the image side, with a thickness of 5.5 mm.

[0005] Furthermore, the improvements of this utility model include that the thickness of the first single lens L1 is 1.28 mm, the thickness of the second single lens L2 is 8.7 mm, the thickness of the third single lens L3 is 3.8 mm, the thickness of the fourth single lens L4 is 5 mm, the thickness of the fifth single lens L5 is 4.5 mm, the thickness of the sixth single lens L6 is 2.7 mm, the thickness of the seventh single lens L7 is 2.7 mm, and the thickness of the eighth single lens L8 is 5.5 mm.

[0006] Furthermore, the improvements of this utility model include: the air gap between the first single lens L1 and the second single lens L2 is 3.3-3.7 mm; the air gap between the second single lens L2 and the third single lens L3 is 1.1-1.9 mm; the air gap between the third single lens L3 and the fourth single lens L4 is 56.5-58.3 mm; the air gap between the fourth single lens L4 and the fifth single lens L5 is 9.2-10.1 mm; the air gap between the fifth single lens L5 and the sixth single lens L6 is 8.2-8.5 mm; the air gap between the sixth single lens L6 and the seventh single lens L7 is 0.1-0.15 mm; and the air gap between the seventh single lens L7 and the eighth single lens L8 is 0.6-0.9 mm.

[0007] Furthermore, an improvement of this invention is that the total length of the refractive-diffraction hybrid mid-wave infrared cooled optical lens is less than 180mm.

[0008] Furthermore, the improvements of this utility model include that the lens material of the first lens, the second lens, the fourth lens, the fifth lens, the seventh lens, and the eighth lens is silicon single crystal; and the lens material of the third lens and the sixth lens is germanium single crystal.

[0009] Furthermore, the present invention includes the following improvements: an object plane A is provided on the left side of the first lens, and a first window A, an aperture B, a second window C, and an image plane D are provided sequentially from left to right on the right side of the fifth lens.

[0010] Further improvements to this invention include: aperture B being -1.302E-9 to -2.037E-9, aperture C being -9.8E-13 to 9.8E-13, aperture D being -1.2E-15 to -1.8E-15, diffraction order HOR being 1, normalized radius being 16.797 mm, diffraction surface coefficients C1 being -23.753, and C2 being -1.571.

[0011] Compared with the prior art, this utility model provides a mid-wave infrared cooled optical lens with refractive-diffraction hybrid technology, which has the following advantages:

[0012] This invention aims to solve the problems existing in current mid-wave infrared imaging systems. Through an innovative hybrid refractive-diffraction optical system design, it achieves high transmittance, a large field of view, and high resolution imaging performance, while ensuring stability over a wide temperature range. Through meticulous design of optical components and rational selection of materials, the lens of this invention not only improves image quality but also reduces manufacturing costs and simplifies assembly and adjustment, providing a new direction for the development of mid-wave infrared imaging technology. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the optical structure in this utility model;

[0014] Figure 2 This is a distortion image of the hybrid refractive and diffractive mid-wave infrared cooling lens of this invention at -40 degrees Celsius.

[0015] Figure 3 The distortion image of the hybrid refractive-diffraction mid-wave infrared cooling lens of this utility model at 20 degrees Celsius;

[0016] Figure 4 The distortion image of the hybrid refractive-diffraction mid-wave infrared cooling lens of this utility model at 60 degrees Celsius;

[0017] Figure 5 This is a schematic diagram of the MTF curve of the hybrid refractive mid-wave infrared cooling lens of this utility model at a spatial frequency of 42p / mm at -40 degrees Celsius.

[0018] Figure 6 This is a schematic diagram of the MTF curve of the hybrid refractive mid-wave infrared cooling lens of this utility model at a spatial frequency of 42p / mm at 20 degrees Celsius.

[0019] Figure 7This is a schematic diagram of the MTF curve of the hybrid refractive mid-wave infrared cooling lens of this utility model at a spatial frequency of 42p / mm at 60 degrees Celsius.

[0020] Figure 8 This is a dot plot of the hybrid refractive and diffractive mid-wave infrared cooling lens of this utility model at -40 degrees Celsius.

[0021] Figure 9 This is a dot plot of the hybrid refractive and diffractive mid-wave infrared cooling lens of this utility model at 20 degrees Celsius.

[0022] Figure 10 This is a dot plot of the hybrid refractive-diffraction mid-wave infrared cooling lens of this invention at 60 degrees Celsius.

[0023] In the diagram: 1-First single lens L1, 2-Second single lens L2, 3-Third single lens L3, 4-Fourth single lens L4, 5-Fifth single lens L5, 6-Sixth single lens L6, 7-Seventh single lens L7, 8-Eighth single lens L8, 9-First window A, 10-Aperture B, 11-Second window C, 12-Image plane D. Detailed Implementation

[0024] 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.

[0025] Please see Figure 1-10 This utility model discloses a hybrid refractive-diffraction mid-wave infrared cooled optical lens, comprising, from left to right along the optical axis, a first single lens L1, a second single lens L2, a third single lens L3, a fourth single lens L4, a fifth single lens L5, a sixth single lens L6, a seventh single lens L7, and an eighth single lens L8. The first single lens L1 is a meniscus positive lens with both surfaces being spherical; the second single lens L2 is a meniscus positive lens with both surfaces being spherical; the third single lens L3 is a meniscus negative lens with both surfaces being spherical; the fourth single lens L4 is a meniscus positive lens with both surfaces being spherical; the fifth single lens L5 is a meniscus positive lens with both surfaces being spherical; the sixth single lens L6 is a meniscus negative lens with both surfaces being spherical; the seventh single lens L7 is a meniscus positive lens with both surfaces being spherical; and the eighth single lens L8 is a biconvex positive lens with a spherical surface on the object side and a diffraction surface on the image side, with a thickness of 5.5 mm.

[0026] The thickness of the first single lens L1 is 1.28 mm, the thickness of the second single lens L2 is 8.7 mm, the thickness of the third single lens L3 is 3.8 mm, the thickness of the fourth single lens L4 is 5 mm, the thickness of the fifth single lens L5 is 4.5 mm, the thickness of the sixth single lens L6 is 2.7 mm, the thickness of the seventh single lens L7 is 2.7 mm, and the thickness of the eighth single lens L8 is 5.5 mm.

[0027] The air gap between the first single lens L1 and the second single lens L2 is 3.3-3.7 mm; the air gap between the second single lens L2 and the third single lens L3 is 1.1-1.9 mm; the air gap between the third single lens L3 and the fourth single lens L4 is 56.5-58.3 mm; the air gap between the fourth single lens L4 and the fifth single lens L5 is 9.2-10.1 mm; the air gap between the fifth single lens L5 and the sixth single lens L6 is 8.2-8.5 mm; the air gap between the sixth single lens L6 and the seventh single lens L7 is 0.1-0.15 mm; and the air gap between the seventh single lens L7 and the eighth single lens L8 is 0.6-0.9 mm.

[0028] The total length of the mid-wave infrared cooled optical lens, which combines refractive and diffractive elements, is less than 180 mm.

[0029] The first lens, second lens, fourth lens, fifth lens, seventh lens, and eighth lens are made of silicon single crystal; the third lens and sixth lens are made of germanium single crystal.

[0030] The first lens has an object plane A on its left side, and the fifth lens has a first window A9, an aperture B10, a second window C11 and an image plane D arranged sequentially from left to right on its right side.

[0031] In optical systems, the shape of a binary surface satisfies the following formula:

[0032]

[0033] Where Z(r) is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis; c is the surface curvature of the aspherical surface, where c = 1 / R, and R is the radius of curvature of the aspherical surface; k is the conic coefficient; A, B, C, D, and E are aspherical coefficients; HOR is the diffraction order; C1 and C2 are diffraction surface coefficients; λ0 is the design center wavelength; n is the refractive index of the biconvex lens L8; and n is the refractive index of air.

[0034] The apertures are -1.302E-9 to -2.037E-9, C is -9.8E-13 to 9.8E-13, and D is -1.2E-15 to -1.8E-15. The diffraction order HOR is 1, the normalized radius is 16.797 mm, and the diffraction plane coefficients C1 and C2 are -23.753 and -1.571, respectively.

[0035] In this embodiment, a method for operating a mid-wave infrared cooled lens is described, which employs an eight-element mid-wave infrared cooled lens. Light passes sequentially from left to right through a first single lens L1, a second single lens L2, a third single lens L3, a fourth single lens L4, a fifth single lens L5, a sixth single lens L6, a seventh single lens L7, an eighth single lens L8, and a detector window to form an image.

[0036] The lens achieves the following performance indicators: (1) Spectral range: mid-infrared band of 3~5μm; (2) Focal length f'=165mm; (3) Full field of view of 6°; (4) F# of 1.57; (5) Applicable to cooled detectors with 1024×1024 pixels and 12 µm pixel size. The specific lens parameters are shown in the table below:

[0037] Table 1 Lens Parameters

[0038]

[0039] In this embodiment, the conic coefficients and higher-order aspheric coefficients of the two aspherical surfaces are shown in the table below.

[0040] Table 2 Optical parameters of the diffraction surface

[0041]

[0042] Figure 7 , 8 Figures 9 and 1 show the distortion of the refractive-diffraction hybrid mid-wave cooled infrared optical system of Example 1 at -40 degrees Celsius, 20 degrees Celsius, and 60 degrees Celsius. The horizontal axis represents the magnitude of the distortion, and the vertical axis represents the field of view. As can be seen from the figure, the maximum distortion is less than 1.1% in the temperature range of -40 to +60 degrees Celsius.

[0043] Figure 7 , 8 Figures 9 and 1 show the modulation transfer functions of the refractive-diffraction hybrid mid-wave cooled infrared optical system of Example 1 at -40°C, 20°C, and 60°C. As can be seen from the figure, within the temperature range of -40 to +60°C, at a spatial frequency of 42 lp / mm, the MTF is greater than 0.47 across the entire field of view.

[0044] Figure 4 , 5Figures 6 and 7 show the time points of the refraction-diffraction hybrid mid-wave cooled infrared optical system of Example 1 at -40 degrees Celsius, 20 degrees Celsius, and 60 degrees Celsius. They show that within the temperature range of -40 to +60 degrees Celsius, the root mean square radius of each field of view is close to the Airy disk radius, and the beam energy can be concentrated in a relatively small range.

[0045] The lens consists of 8 elements and adopts a secondary imaging structure. It uses only one diffraction surface, which enables a large relative aperture at low cost and achieves a heat-free design at -40℃ to +60℃.

[0046] In the description herein, it should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0047] 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.

Claims

1. A mid-wave infrared cooled optical lens with refractive-diffraction hybrid technology, characterized in that: The system includes, from left to right along the optical axis, a series of single lenses arranged coaxially: a first single lens L1 (1), a second single lens L2 (2), a third single lens L3 (3), a fourth single lens L4 (4), a fifth single lens L5 (5), a sixth single lens L6 (6), a seventh single lens L7 (7), and an eighth single lens L8 (8). The first single lens L1 (1) is a meniscus positive lens with both surfaces being spherical; the second single lens L2 (2) is a meniscus positive lens with both surfaces being spherical; the third single lens L4 (4) is a single lens arranged coaxially from left to right. Lens L3 (3) is a meniscus negative lens with spherical surfaces on both sides. The fourth single lens L4 (4) is a meniscus positive lens with spherical surfaces on both sides. The fifth single lens L5 (5) is a meniscus positive lens with spherical surfaces on both sides. The sixth single lens L6 (6) is a meniscus negative lens with spherical surfaces on both sides. The seventh single lens L7 (7) is a meniscus positive lens with spherical surfaces on both sides. The eighth single lens L8 (8) is a biconvex positive lens with a spherical surface on the object side and a diffraction surface on the image side, with a thickness of 5.5 mm.

2. The mid-wave infrared cooled optical lens according to claim 1, characterized in that: The thickness of the first single lens L1 (1) is 1.28 mm, the thickness of the second single lens L2 (2) is 8.7 mm, the thickness of the third single lens L3 (3) is 3.8 mm, the thickness of the fourth single lens L4 (4) is 5 mm, the thickness of the fifth single lens L5 (5) is 4.5 mm, the thickness of the sixth single lens L6 (6) is 2.7 mm, the thickness of the seventh single lens L7 (7) is 2.7 mm, and the thickness of the eighth single lens L8 (8) is 5.5 mm.

3. The mid-wave infrared cooled optical lens according to claim 2, characterized in that: The air gap between the first single lens L1 (1) and the second single lens L2 (2) is 3.3-3.7 mm; the air gap between the second single lens L2 (2) and the third single lens L3 (3) is 1.1-1.9 mm; the air gap between the third single lens L3 (3) and the fourth single lens L4 (4) is 56.5-58.3 mm; the air gap between the fourth single lens L4 (4) and the fifth single lens L5 (5) is 9.2-10.1 mm; the air gap between the fifth single lens L5 (5) and the sixth single lens L6 (6) is 8.2-8.5 mm; the air gap between the sixth single lens L6 (6) and the seventh single lens L7 (7) is 0.1-0.15 mm; and the air gap between the seventh single lens L7 (7) and the eighth single lens L8 (8) is 0.6-0.9 mm.

4. A mid-wave infrared cooled optical lens according to claim 3, characterized in that: The total length of the mid-wave infrared cooled optical lens, which combines refractive and diffractive elements, is less than 180 mm.

5. A mid-wave infrared cooled optical lens according to claim 4, characterized in that: The first single lens L1 (1), the second single lens L2 (2), the fourth single lens L4 (4), the fifth single lens L5 (5), the seventh single lens L7 (7) and the eighth single lens L8 (8) are made of silicon single crystal; the third single lens L3 (3) and the sixth single lens L6 (6) are made of germanium single crystal.

6. A mid-wave infrared cooled optical lens according to claim 5, characterized in that: The first single lens L1 (1) has an object plane A on its left side, and the fifth single lens L5 (5) has a first window A (9), an aperture B (10), a second window C (11) and an image plane D (12) arranged sequentially from left to right on its right side.

7. A mid-wave infrared cooled optical lens according to claim 6, characterized in that: The aperture B (10) is -1.302E-9 to -2.037E-9, C is -9.8E-13 to 9.8E-13, D is -1.2E-15 to -1.8E-15, the diffraction order HOR is 1, the normalized radius is 16.797 mm, the diffraction surface coefficients C1 and C2 are -23.753 and -1.571 respectively.

Images