High-overload-resistant infrared seeker optical system

Abstract

The invention discloses an anti-high overload infrared seeker optical system, which comprises a seeker shell, a lens endoscope frame, a pressing ring and an infrared lens assembly, the infrared lens assembly is composed of four infrared lenses, a first lens, a second lens, a third lens and a fourth lens are sequentially arranged along the light incident direction, the first lens is fixed at the front end of the seeker shell, the second lens is fixed at the rear end of the seeker shell, and the fourth lens is fixed at the front end of the seeker shell. The second lens, the third lens and the fourth lens are sequentially mounted on the lens endoscope frame; the lens endoscope frame is coaxially installed in the seeker shell and fixed through the pressing ring. The infrared lens assembly is a refractive optical system designed by an optical passive athermalization method; the central thickness range of the four lenses of the infrared lens assembly is [4 mm, 5 mm], the edge thickness range of the four lenses is [2.5 mm, 4.5 mm], the central air interval range among the four lenses is (1 mm, 5 mm), and the mechanical radius range of the four lenses is [10 mm, 11.5 mm]. According to the invention, continuous 15000g impact overload within 10ms can be resisted, the structure is simple and compact, the temperature stability is good, and the usability is high.

Description

Technical Field

[0001] The invention belongs to the technical field of seekers, and in particular relates to an infrared seeker optical system resistant to high overload, which can withstand an impact overload of 15000g for 10ms. Background Art

[0002] There are many types of infrared seekers in the prior art, including refractive, reentrant, reflective, and folding types. In practical applications, folding and folding types and other structures are mainly used. However, with the increase in the demand for overload resistance, traditional folding and folding types and other structures are increasingly unable to meet the design requirements. Specifically, the maximum overload of infrared seekers using folding and reentrant structures is 70g to 80g, and the infrared lens materials mostly use expensive infrared materials such as single crystal germanium and gallium arsenide, resulting in high cost of the seeker. When the impact overload reaches 15,000g, the optical system structure of the traditional infrared seeker cannot withstand the overload, and there is a high probability of fragmentation. Therefore, the infrared optical system of the traditional infrared seeker is not suitable for use in special application environments. Summary of the invention

[0003] The present invention proposes an infrared seeker optical system resistant to high overload, so as to meet the requirement that the infrared optical system of the seeker can resist an impact overload of 15000g lasting within 10ms.

[0004] The technical solution to realize the present invention is: an infrared seeker optical system resistant to high overload, including a seeker housing, a lens inner frame, an infrared lens assembly, and a pressure ring, wherein the infrared lens assembly includes a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the incident direction of light, the first lens is fixed to the front end surface of the seeker housing, and acts as a fairing, and the second lens, the third lens and the fourth lens are sequentially mounted on the lens inner frame; the lens inner frame is coaxially mounted in the seeker housing and fixed by a pressure ring; the infrared lens assembly adopts a refractive system structure; the center thickness range of the four lenses in the infrared lens assembly is [4mm, 5mm], the edge thickness range of the four lenses is [2.5mm, 4.5mm], the air spacing range between the four lenses is (1mm, 5mm), and the mechanical radius range of the four lenses is [10mm, 11.5mm].

[0005] Compared with the prior art, the present invention has the following significant advantages:

[0006] (1) When the infrared seeker optical system of the present invention withstands an overload of 15000g within 10ms, the safety factors of the lenses of the infrared lens assembly are: 3.45 for the first lens, 1.42 for the second lens, 3.25 for the third lens, and 1.38 for the fourth lens. The infrared lens assembly has good anti-overload performance.

[0007] (2) The total weight of the four lenses of the infrared lens assembly of the present invention is 26.78 grams, and the distance from the center of the front surface of the first lens to the center of the imaging surface is 33.8 mm. The infrared lens assembly has the advantages of being light and compact.

[0008] (3) The infrared lens assembly of the present invention has a working temperature range of -40°C to 60°C: the maximum focal length drift is 0.0284 mm, the temperature sensitivity is 0.000284 mm / °C; the optical transfer function (MFT) is not less than 0.3@42lp / mm; the RMS spot radius is less than the pixel size of 12 μm. The infrared lens assembly has good temperature stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a mechanical structure diagram of an example of the present invention.

[0010] Figure 2 Schematic diagram of the infrared seeker optical system that can withstand high overload.

[0011] Figure 3 This is the finite element simulation result diagram of the first lens.

[0012] Figure 4 This is the finite element simulation result diagram of the second lens.

[0013] Figure 5 This is the finite element simulation result diagram of the third lens.

[0014] Figure 6 This is the finite element simulation result diagram of the fourth lens.

[0015] In the figure: 1-first lens; 2-second lens; 3-third lens; 4-fourth lens; 5-seeker housing; 6-lens inner lens frame; 7-pressing ring; 8-imaging movement baffle; 9-imaging surface. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0018] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0019] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation" and the like should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; "connection" can be a mechanical connection or an electrical connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0021] The following will further introduce the specific implementation method, as well as the technical difficulties and inventive points of this invention in combination with this design example.

[0022] Combination Figure 1 , an infrared seeker optical system resistant to high overload, comprising a seeker housing 5, a lens inner frame 6, an infrared lens assembly, and a pressing ring 7, wherein the infrared lens assembly comprises a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4 arranged in sequence along the incident direction of light, the first lens 1 is fixed to the front end surface of the seeker housing 5, and acts as a fairing, the second lens 2, the third lens 3 and the fourth lens 4 are sequentially mounted on the lens inner frame 6; the lens inner frame 6 is coaxially mounted in the seeker housing 5 and fixed by the pressing ring 7; the infrared lens assembly adopts a refractive system structure; the center thickness range of the four lenses in the infrared lens assembly is [4mm, 5mm], the edge thickness range of the four lenses is [2.5mm, 4.5mm], the air spacing range between the four lenses is (1mm, 5mm), and the mechanical radius range of the four lenses is [10mm, 11.5mm].

[0023] The infrared lens assembly is optically designed based on the principle of optical passive athermalization. Within the operating temperature range of -40℃ to 60℃, the imaging quality of the infrared lens assembly meets the use requirements and has good temperature stability.

[0024] The four lenses in the infrared lens assembly are all made of infrared optical materials, which have good transmittance to light in the working band.

[0025] The first lens 1 is made of zinc sulfide material, the second lens 2 is made of IRG206 material, the third lens 3 is made of zinc selenide material, and the fourth lens 4 is made of IRG206 material. The lens materials are cost-effective, and the infrared lens assembly has the advantage of low cost.

[0026] The optical rear surfaces of the second lens 2, the third lens 3 and the fourth lens 4 all adopt even-order aspheric surfaces for aberration correction, and the infrared lens assembly has good aberration correction capability.

[0027] The first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 can all withstand an impact overload of 15000g for 10ms without breaking, and the infrared seeker optical system has good overload resistance.

[0028] The circumferential outer wall of the first lens 1 is mounted to the inner wall of the seeker housing 5 by gluing. The rear surface of the second lens 2 is mounted to the lens inner frame 6 by gluing. The rear surface of the third lens 3 is mounted to the lens inner frame 6 by gluing. The front surface of the fourth lens 4 is mounted to the lens inner frame 6 by gluing. The pressure ring 7 is fixed to the rear end surface of the seeker housing 5 by gluing to press the fourth lens 4. The infrared seeker optical system has the characteristics of simple and efficient assembly.

[0029] The load on the first lens 1 is pulled and transmitted by the guide head housing 5; the load on the second lens 2 and the third lens 3 is pushed and transmitted by the lens inner frame 6; the load on the fourth lens 4 is pulled by the lens inner frame 6 and pushed and transmitted by the pressure ring 7. The stress distribution of each lens is reasonable, and there is no dangerous stress concentration phenomenon.

[0030] The distance from the center of the front surface of the first lens 1 to the center of the imaging surface 9 is less than 40 mm, the total weight of the four lenses of the infrared lens assembly is less than 30 grams, and the infrared lens assembly has the characteristics of compact structure and light weight.

[0031] Embodiment 1:

[0032] In this example, the optical system of the infrared seeker has achieved the following technical indicators: ① working band: 8μm~13μm; ② focal length: 18mm; ③ the distance from the front surface of the first lens 1 of the infrared lens assembly to the imaging surface 9: 33.8mm; ④ F number: 1.08; ⑤ infrared detector: long-wave infrared cooling type 640×512, pixel size 12μm×12μm; ⑥ field of view: 24.08°×19.37°; ⑦ optical transfer function (MFT): not less than 0.3@42lp / mm at the cutoff frequency; ⑧RMS spot radius: less than the pixel size of 12μm; ⑨ overload resistance: the infrared lens assembly will not break under a continuous overload of 15000g within 10ms.

[0033] Combination Figure 2 , the net diameter of the front optical surface of the first lens 1 is 9mm, the net diameter of the rear optical surface is 7.78mm, the edge thickness is 4.3mm, and the center thickness is 4.5mm; the net diameter of the front optical surface of the second lens 2 is 8.5mm, the net diameter of the rear optical surface is 7.48mm, the edge thickness is 3.88mm, and the center thickness is 5mm; the net diameter of the front optical surface of the third lens 3 is 8mm, the net diameter of the rear optical surface is 5.98mm, the edge thickness is 4.42mm, and the center thickness is 4mm; the net diameter of the front optical surface of the fourth lens 4 is 8.62mm, the net diameter of the rear optical surface is 9mm, the edge thickness is 2.72mm, and the center thickness is 5mm. The air gap between the center of the rear surface of the first lens 1 and the center of the front surface of the second lens 2 is 1.5mm; the air gap between the center of the rear surface of the second lens 2 and the center of the front surface of the third lens 3 is 1.4mm; the air gap between the center of the rear surface of the third lens 3 and the center of the front surface of the fourth lens 4 is 4.5mm. The total weight of the four lenses is 26.78 grams. The imaging movement baffle 8 is a flat glass, which belongs to the movement packaging structure and is used to protect the movement imaging array.

[0034] The infrared lens assembly adopts an optical passive athermal design method to eliminate thermal differences. At 20°C, the focal length is 18.0219mm and the actual F number is 1.08485. In the operating temperature range of -40°C to 60°C: the maximum temperature drift of the focal length is 0.0284mm, and its temperature sensitivity is 0.000284mm / °C; the maximum temperature drift of the actual F number is 0.00005; the optical transfer function (MFT) is not less than 0.3@42lp / mm; the RMS spot radius is less than the pixel size of 12μm. The imaging quality of the infrared lens assembly meets the use requirements and has good temperature stability.

[0035] like Figure 3 to Figure 6 As shown in the figure, under the impact overload of 15000g for 10ms, the impact condition finite element simulation is carried out on the entire infrared seeker optical system, and the four lenses of the infrared lens assembly in the simulation results are analyzed: ① The first lens 1: the maximum equivalent stress is 19.943MPa, the safety factor is 3.45, and there is no risk of fragmentation; ② The second lens 2: the maximum equivalent stress is 21.154MPa, the safety factor is 1.42, and there is no risk of fragmentation; ③ The third lens 3: the maximum equivalent stress is 16.88MPa, the safety factor is 3.25, and there is no risk of fragmentation; ④ The fourth lens 4: the maximum equivalent stress is 21.781MPa, the safety factor is 1.38, and there is no risk of fragmentation. The infrared lens assembly has no risk of fragmentation under the expected overload conditions, and the infrared seeker optical system has good overload resistance.

Claims

1. An infrared seeker optical system resistant to high overload, characterized in that: The invention comprises a seeker housing (5), a lens inner frame (6), an infrared lens assembly, and a pressing ring (7), wherein the infrared lens assembly comprises a first lens (1), a second lens (2), a third lens (3), and a fourth lens (4) which are arranged in sequence along the incident direction of light, the first lens (1) being fixed on the front end surface of the seeker housing (5) and acting as a fairing, the second lens (2), the third lens (3), and the fourth lens (4) being mounted on the lens inner frame (6) in sequence; the lens inner frame (6) being coaxially mounted in the seeker housing (5) and being fixed by the pressing ring (7); the infrared lens assembly adopts a refractive system structure; the center thickness range of the four lenses in the infrared lens assembly is [4 mm, 5 mm], the edge thickness range of the four lenses is [2.5 mm, 4.5 mm], the air spacing range between the four lenses is (1 mm, 5 mm), and the mechanical radius range of the four lenses is [10 mm, 11.5 mm].

2. The infrared seeker optical system with high overload resistance according to claim 1, characterized in that: The infrared lens assembly is optically designed based on the principle of optical passive athermalization, and the system operating temperature range is -40℃~60℃.

3. The infrared seeker optical system with high overload resistance according to claim 2, characterized in that: The four lenses in the infrared lens assembly are all made of infrared optical materials.

4. The infrared seeker optical system with high overload resistance according to claim 3 is characterized in that: The first lens (1) is made of zinc sulfide material, the second lens (2) is made of IRG206 material, the third lens (3) is made of zinc selenide material, and the fourth lens (4) is made of IRG206 material.

5. The infrared seeker optical system with high overload resistance according to claim 4, characterized in that: The optical rear surfaces of the second lens (2), the third lens (3) and the fourth lens (4) are all even-order aspherical surfaces for aberration correction.

6. The infrared seeker optical system resistant to high overload according to claim 5, characterized in that: The first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) can all withstand an impact overload of 15000g for 10ms without being broken.

7. The infrared seeker optical system with high overload resistance according to claim 6, characterized in that: The circumferential outer wall of the first lens (1) is mounted to the inner wall of the seeker housing (5) by gluing; the rear surface of the second lens (2) is mounted on the lens inner frame (6) by gluing; the rear surface of the third lens (3) is mounted on the lens inner frame (6) by gluing; the front surface of the fourth lens (4) is mounted on the lens inner frame (6) by gluing; and the pressing ring (7) is fixed to the rear end surface of the seeker housing (5) by gluing to press the fourth lens (4).

8. The infrared seeker optical system with high overload resistance according to claim 1, characterized in that: The load on the first lens (1) is pulled and transmitted by the guide head housing (5); the load on the second lens (2) and the third lens (3) is pushed and transmitted by the lens inner frame (6); and the load on the fourth lens (4) is pulled by the lens inner frame (6) and pushed and transmitted by the pressure ring (7).

9. The infrared seeker optical system with high overload resistance according to claim 1, characterized in that: The distance from the center of the front surface of the first lens (1) to the center of the imaging surface (9) is less than 40 mm, and the total weight of the four lenses of the infrared lens assembly is less than 30 grams.

Images