Athermalized infrared lens

Abstract

Embodiments of the present application provide a kind of to eliminate heat difference infrared lens, including the first lens, second lens that are coaxially arranged in order from object side to image side;First lens is positive focal power meniscus lens, the object side surface of first lens is convex and shape is aspherical surface, the image side surface of first lens is concave and shape is aspherical surface, the object side surface of first lens is also provided with diaphragm;Second lens is positive focal power meniscus lens, the object side surface of second lens is concave and shape is binary surface, the image side surface of second lens is convex and shape is aspherical surface.The lens of this lens is used two, the number of lens is less, by reasonable focal power distribution, in combination with the design of aspherical surface and binary surface, so that it has the characteristics of high image quality, clear imaging.

Description

Technical Field

[0001] This application relates to the field of infrared lens technology, and in particular to a thermally differential infrared lens. Background Technology

[0002] Infrared imaging systems have advantages such as all-weather operation, no need for auxiliary lighting, good concealment, and good environmental adaptability, and have been widely used in military fields such as alarm, reconnaissance, and guidance, as well as in civilian engineering.

[0003] With technological advancements, the pixel size of uncooled infrared systems is continuously decreasing, and their sensitivity is constantly improving, while their price is gradually decreasing. Furthermore, because they do not require a cooling system, they offer high system reliability and can be miniaturized, leading to their increasingly widespread application in security monitoring, automotive, and other fields. During the use of infrared lenses, ambient temperature affects the refractive index of the lens material, causing changes in optical power and a shift in the optimal image plane, resulting in blurred images, decreased contrast, and reduced optical imaging quality, ultimately impacting the lens's imaging performance. In optical passive thermal aberration reduction technology, traditional lenses suffer from technical problems such as small target surface and unclear imaging. Summary of the Invention

[0004] The purpose of this application is to at least solve one of the aforementioned technical defects, particularly the problems of small target surface and unclear imaging in existing thermal differential infrared lenses.

[0005] This application provides a thermally ablated infrared lens, including a first lens and a second lens coaxially arranged from the object side to the image side;

[0006] The first lens is a meniscus lens with positive optical power. The object side of the first lens is convex and aspherical in shape, and the image side of the first lens is concave and aspherical in shape. An aperture is also provided on the object side of the first lens.

[0007] The second lens is a meniscus lens with positive optical power. The object side of the second lens is concave and has a binary shape, while the image side of the second lens is convex and has an aspherical shape.

[0008] In one embodiment, the thermally ablated infrared lens has a focal length of 13.6 mm and an operating wavelength of 8 μm-12 μm, making it suitable for infrared detectors with a resolution of 388×284 and a pixel size of 17 μm.

[0009] In one embodiment, a protective window is also included between the image plane and the second lens.

[0010] In one embodiment, the protective window is made of germanium.

[0011] In one embodiment, the center thickness of the protective window is 1 mm.

[0012] In one embodiment, the distance between the protective window and the second lens is 6.26 mm.

[0013] In one embodiment, the center thickness of the first lens is 5 mm, the center thickness of the second lens is 5.5 mm, the fitted radius of curvature of the object side of the first lens is 10.80 mm, and the fitted radius of curvature of the image side is 10.55 mm; the fitted radius of curvature of the object side of the second lens is -26.99 mm, and the fitted radius of curvature of the image side is -14.50 mm.

[0014] In one embodiment, the distance between the first lens and the second lens is 3.38 mm.

[0015] In one embodiment, the first lens and the second lens are made of chalcogenide glass.

[0016] In one embodiment, the first lens is made of IRG207 and the second lens is made of IRG206.

[0017] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0018] The thermally ablation infrared lens provided in this application uses two lenses, which is relatively few in number. Through reasonable optical power distribution and the design of aspherical and binary surfaces, it has the characteristics of excellent image quality and clear imaging. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a thermally ablated infrared lens provided in one embodiment of this application;

[0021] Figure 2 This is the MTF plot of a thermally differential infrared lens in one embodiment of this application operating at 20°C.

[0022] Figure 3 This is the MTF plot of a thermally differential infrared lens in one embodiment of this application operating at -40°C.

[0023] Figure 4 This is the MTF plot of a thermally differential infrared lens in one embodiment of this application operating at 60°C.

[0024] Figure 5 This is a dot plot of a thermally differential infrared lens in a 20°C operating environment according to one embodiment of this application;

[0025] Figure 6 This is a dot plot of a thermally differential infrared lens in an embodiment of this application operating in a -40°C environment;

[0026] Figure 7 This is a dot plot of a thermally differential infrared lens in a 60°C operating environment according to one embodiment of this application;

[0027] Labeling explanation: 1. First lens; 2. Second lens; 3. Protective window; 4. Infrared imaging array. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] In the description of the embodiments of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product is in use. These are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the use of terms such as "horizontal," "vertical," and "suspended" does not mean that the component is required to be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the embodiments of this invention, "a plurality of" means at least two.

[0032] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0033] Please see Figure 1 This application provides a thermally ablated infrared lens, including a first lens 1 and a second lens 2 coaxially arranged from the object side to the image side. Both the first lens 1 and the second lens 2 are meniscus lenses with positive optical power. Here, positive optical power refers to the lens's ability to converge light through refraction. A meniscus lens is a lens with concave and convex surfaces on its two sides. When imaging an object using this lens, the side closer to the object is the object side, and the side where the object is imaged is the image side. Figure 1 For example, an infrared imaging array 4 is set at the image plane S7, and a protective window 3 is set between the image plane S7 and the second lens 2. Figure 1 The left side is the object side, and the right side is the image side. Light enters from the object side S1 of the first lens 1, passes sequentially through the image side S2 of the first lens 1, the object side S3 of the second lens 2, the image side S4 of the second lens 2, and the protective window 3, and finally reaches the infrared imaging array 4 at the image plane S7 to form an image. In this embodiment, the object side S1 of the first lens 1 is convex and aspherical, and the image side S2 of the first lens 1 is concave and aspherical. The object side S1 of the first lens 1 is also provided with an aperture stop. The object side S3 of the second lens 2 is concave and binary, and the image side S4 of the second lens 2 is convex and aspherical. The aspherical surface can be expressed by the following formula:

[0034]

[0035] In the formula, Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are the aspherical coefficients corresponding to the fourth, sixth, eighth, tenth, and twelfth orders. The aspherical coefficients of the first lens 1 and the second lens 2 are shown in the table below:

[0036] Table 1 Aspheric coefficient data of lenses

[0037] S1 1.767e-05 1.767e-06 -8.997e-08 2.110e-09 -2.003e-11 S2 -1.995e-04 3.001e-06 -4.643e-07 2.556e-08 -6.267-10 S3 -3.900e-04 9.1930e-06 -1.303e-06 5.569e-08 -1.084e-09 S4 -4.349e-05 -5.005e-06 2.091e-07 -4.782e-09 4.194e-11

[0038] A binary surface can be represented by the following formula:

[0039] M(B1ρ 2 +B2ρ 4 )

[0040] Where M is the diffraction order, which is 1, and B1 and B2 are the binary phase coefficients for the object surface S3 of the second lens 2. Preferably, B1 = -12.753998, B2 = -0.74913564, and the normalized radius ρ is 4.

[0041] Preferably, the relevant parameters of the first lens 1 and the second lens 2 are as follows: the center thickness of the first lens 1 is 5 mm, the fitted radius of curvature of the object-side surface S1 of the first lens 1 is 10.80 mm, and the fitted radius of curvature of the image-side surface S2 of the first lens 1 is 10.55 mm. The air gap between the first lens 1 and the second lens 2 (i.e., the distance from the center of the image-side surface of the first lens 1 to the center of the object-side surface of the second lens 2) is 3.38 mm. The center thickness of the second lens 2 is 5.5 mm, the fitted radius of curvature of the object-side surface S3 of the second lens 2 is -26.99 mm, and the fitted radius of curvature of the image-side surface S4 of the second lens 2 is -14.50 mm. The materials of the first lens 1 and the second lens 2 are preferably chalcogenide glass. The selection of chalcogenide glass, combined with large-scale molding technology, not only reduces production costs but also gives the lens a smaller temperature refractive index coefficient and thermal expansion coefficient, thereby improving the thermal stability and optical performance of the lens. The first lens 1 can be made of IRG207, and the material of the second lens 2 can be IRG206.

[0042] In some embodiments, a protective window 3 is further provided between the second lens 2 and the image plane S7. The protective window 3 is a parallel flat glass, that is, the two sides S5 and S6 of the protective glass are mutually parallel planes. Preferably, the relevant parameters of the protective window 3 are: the center thickness of the protective window 3 is 1 mm, the distance between the protective window 3 and the second lens 2 is 6.26 mm, and the distance between the protective window 3 and the image plane S7 is 1.37 mm. The material of the protective window 3 can be germanium single crystal.

[0043] Figure 2 , Figure 3 , Figure 4 The images show the MTF plots of the thermally ablated infrared lens in operating environments of 20℃, -40℃, and 60℃. The horizontal axis represents different spatial frequencies, and the vertical axis represents the modulation index. Figure 5 , Figure 6 and Figure 7The dot plots represent the thermally differential infrared lens operating at 20℃, -40℃, and 60℃, respectively. The legends in the upper right corner of the figures are cross, intersecting, and rectangular, respectively. Based on the MTF chart and dot plots, it can be seen that the lens in this application has excellent image quality, achieving good resolution at different temperatures of 20℃, -40℃, and 60℃. The lens exhibits good overall imaging quality and strong thermal stability.

[0044] As can be seen from the above, the thermally ablated infrared lens in this application achieves the following optical specifications: working wavelength range of 8μm-12μm; focal length f′=13.6mm; resolution of 388×284, 17μm; and F number of 1.0.

[0045] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only 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 a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0046] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0047] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thermally ablated infrared lens, characterized in that, It consists of a first lens and a second lens arranged coaxially from the object side to the image side; The first lens is a meniscus lens with positive optical power. The object side of the first lens is convex and aspherical in shape, and the image side of the first lens is concave and aspherical in shape. An aperture is also provided on the object side of the first lens. The second lens is a meniscus lens with positive optical power. The object side of the second lens is concave and has a binary shape, while the image side of the second lens is convex and has an aspherical shape. The center thickness of the first lens is 5 mm, the center thickness of the second lens is 5.5 mm, the fitted radius of curvature of the object side of the first lens is 10.80 mm, and the fitted radius of curvature of the image side is 10.55 mm; the fitted radius of curvature of the object side of the second lens is -26.99 mm, and the fitted radius of curvature of the image side is -14.50 mm.

2. The thermally ablated infrared lens according to claim 1, characterized in that, The thermally ablated infrared lens has a focal length of 13.6mm and an operating wavelength of 8μm-12μm, making it suitable for infrared detectors with a resolution of 388×284 and a pixel size of 17μm.

3. The thermally ablated infrared lens according to claim 1, characterized in that, A protective window is also included between the image plane and the second lens.

4. The thermally ablated infrared lens according to claim 3, characterized in that, The protective window is made of germanium.

5. The thermally ablated infrared lens according to claim 3, characterized in that, The center thickness of the protective window is 1 mm.

6. The thermally ablated infrared lens according to claim 5, characterized in that, The distance between the protective window and the second lens is 6.26 mm.

7. The thermally ablated infrared lens according to claim 1, characterized in that, The distance between the first lens and the second lens is 3.38 mm.

8. The thermally ablated infrared lens according to claim 1, characterized in that, The first lens and the second lens are made of chalcogenide glass.

9. The thermally ablated infrared lens according to claim 8, characterized in that, The first lens is made of IRG207 material, and the second lens is made of IRG206 material.

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