Large-relative-aperture refrigeration long-wave system

Abstract

The invention relates to a large-relative-aperture refrigeration long-wave system. The system comprises a meniscus positive lens A, a meniscus negative lens B, a meniscus positive lens C, a meniscus positive lens D, a meniscus positive lens E and a meniscus positive lens F which are sequentially arranged in the direction of an optical path. The matched detector G is a refrigeration type long-wave infrared detector, the cold diaphragm is located at the tail end of the system so that the efficiency of the cold diaphragm can be 100%, stray light entering is reduced, and the detection sensitivity of the system is improved. The system adopts a secondary imaging structural form to compress the aperture of the system, combines aspheric surfaces, reasonably selects materials and distributes the focal power of each lens, and reduces the number of lenses and the weight of the system on the premise of ensuring that the system realizes a large relative aperture.

Description

Technical Field

[0001] The invention relates to a large relative aperture refrigeration long wave system. Background Art

[0002] As the working time of uncooled infrared detectors increases, the temperature of the body will rise, and the temperature change will form a noise signal, thus affecting the detection sensitivity of the system. Compared with uncooled infrared detectors, cooled infrared detectors need to add a cooling device to keep their focal planes working in a lower temperature environment. In a low temperature environment, the noise equivalent temperature difference of the detector is low, the detection sensitivity is high, and it can detect farther and fainter targets to cope with more complex scene requirements. Cooled long-wave infrared detectors also have shorter integration time, higher frame rate, wider dynamic range and faster search speed, and have superior performance in ground air defense and air early warning.

[0003] Currently, there are few literatures related to lenses that match cooled long-wave infrared detectors. Chinese patent CN 103631003B discloses a long-wave infrared cooled long focal length, large aperture, and large field of view lens. The optical system has an F number of 1.67 and a diagonal field of view of approximately 3°. Chinese patent CN 112415723 B discloses a cooled long-wave infrared wide-angle lens. The system has an F number of 2.0 and a horizontal field of view of approximately 100°. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a large relative aperture long-wave refrigerated infrared optical system, with an F number of 1.0, a diagonal field of view of about 10°, a matching refrigerated long-wave infrared detector, and a detector target imaging circle diameter of not less than Φ20.4mm. The system material is selected from several materials such as germanium single crystal and zinc selenide for reasonable matching, and several aspherical surfaces are used in combination to reasonably distribute the optical power of each lens to achieve the correction of system chromatic aberration and monochromatic aberration.

[0005] The present invention is implemented by the following scheme: a large relative aperture refrigeration long-wave system, comprising a meniscus positive lens A, a meniscus negative lens B, a meniscus positive lens C, a meniscus positive lens D, a meniscus positive lens E, and a meniscus positive lens F which are sequentially arranged along the light path direction.

[0006] Furthermore, the optical system also includes a detector G, which is a long-wave cooling detector with a pixel number of 640×512, a pixel size of 25 μm, and an F number of 1.0.

[0007] Furthermore, the air gap between the meniscus positive lens A and the meniscus negative lens B is 2.98 mm, the air gap between the meniscus negative lens B and the meniscus positive lens C is 162.51 mm, the air gap between the meniscus positive lens C and the meniscus positive lens D is 39.63 mm, the air gap between the meniscus positive lens D and the meniscus positive lens E is 16.19 mm, and the air gap between the meniscus positive lens E and the meniscus positive lens F is 2 mm.

[0008] Furthermore, the convex surface of the meniscus positive lens A faces the object plane, and the material is germanium single crystal; the convex surface of the meniscus negative lens B faces the object plane, and the material is zinc selenide; the convex surface of the meniscus positive lens C faces the object plane, and the material is germanium single crystal; the convex surface of the meniscus positive lens D faces the object plane, and the material is germanium single crystal; the concave surface of the meniscus positive lens E faces the object plane, and the material is GAAS; the convex surface of the meniscus positive lens F faces the object plane, and the material is germanium single crystal.

[0009] Further, the focal length of the optical system is f´, the focal length of the meniscus positive lens A is f1´, the focal length of the meniscus negative lens B is f2´, the focal length of the meniscus positive lens C is f3´, the focal length of the meniscus positive lens D is f4´, the focal length of the meniscus positive lens E is f5´, and the focal length of the meniscus positive lens F is f6´. The relationship between the focal length of each lens of the system and the focal length of the system is as follows: -5≤f1´ / f´≤0, 5≤f2´ / f´≤10, -5≤f3´ / f´≤0, -5≤f4´ / f´≤0, -5≤f5´ / f´≤0, -5≤f6´ / f´≤0.

[0010] Compared with the prior art, the present invention has the following beneficial effects: a) The F number of the optical system of the present invention is 1.0. Compared with the low F number system, the system makes full use of the light aperture of the existing focal length, increases the effective light area of ​​the system, and improves the detection sensitivity of the system; b) The optical system of the present invention matches a 640×512, 25um large-target-area refrigerated long-wave infrared detector, and the system has a shorter integration time, a higher frame rate, a wider dynamic range, a faster search speed, and a wider search range; c) The system of the present invention adopts a combination of materials with high refractive index, which can reduce the number of lenses in the system and reduce the weight of the system while meeting the image quality requirements.

[0011] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a structural diagram of an optical system of the present invention; Figure 2is a graph of the MTF of the optical system of the present invention; Figure 3 is a distortion curve diagram of the optical system of the present invention; Figure 4 It is the energy concentration curve diagram of the optical system of the present invention. DETAILED DESCRIPTION

[0013] like Figures 1 to 4 As shown, a large relative aperture refrigerated long-wave system includes a meniscus positive lens A, a meniscus negative lens B, a meniscus positive lens C, a meniscus positive lens D, a meniscus positive lens E, and a meniscus positive lens F, which are sequentially arranged along the optical path. This optical system adopts a secondary imaging structure consisting of six lenses. The matched detector G is a refrigerated long-wave infrared detector. The cold aperture is located at the end of the system to achieve 100% cold aperture efficiency, reduce stray light entry, and improve the detection sensitivity of the system. The system combines the use of aspheric surfaces and the reasonable selection of materials and distribution of the optical power of each lens, so that the system performance can be met with a smaller number of lenses and the system weight can be reduced.

[0014] In this embodiment, the air gap between the meniscus positive lens A and the meniscus negative lens B is 2.98 mm, the air gap between the meniscus negative lens B and the meniscus positive lens C is 162.51 mm, the air gap between the meniscus positive lens C and the meniscus positive lens D is 39.63 mm, the air gap between the meniscus positive lens D and the meniscus positive lens E is 16.19 mm, and the air gap between the meniscus positive lens E and the meniscus positive lens F is 2 mm.

[0015] In this embodiment, the convex surface of the meniscus positive lens A faces the object plane, and the material is germanium single crystal; the convex surface of the meniscus negative lens B faces the object plane, and the material is zinc selenide; the convex surface of the meniscus positive lens C faces the object plane, and the material is germanium single crystal; the convex surface of the meniscus positive lens D faces the object plane, and the material is germanium single crystal; the concave surface of the meniscus positive lens E faces the object plane, and the material is GAAS; the convex surface of the meniscus positive lens F faces the object plane, and the material is germanium single crystal.

[0016] In this embodiment, the focal length of the optical system is f´, the focal length of the positive meniscus lens A is f1´, the focal length of the negative meniscus lens B is f2´, the focal length of the positive meniscus lens C is f3´, the focal length of the positive meniscus lens D is f4´, the focal length of the positive meniscus lens E is f5´, and the focal length of the positive meniscus lens F is f6´. The relationship between the focal length of each lens of the system and the focal length of the system is as follows: -5≤f1´ / f´≤0, 5≤f2´ / f´≤10, -5≤f3´ / f´≤0, -5≤f4´ / f´≤0, -5≤f5´ / f´≤0, -5≤f6´ / f´≤0.

[0017] The specific parameters of each lens in the optical system of the present invention are shown in the following table: The aspheric surface equations of the above lenses are as follows: ; Z represents the position in the direction of the optical axis, r represents the height in the vertical direction relative to the optical axis, c represents the radius of curvature, and k represents the cone coefficient. Represents the aspheric coefficient.

[0018] Aspherical data of each lens:

[0019] The optical system composed of the above lenses achieves the following optical indicators: (1) Diagonal field of view: ≈ 10°; (2) Optical distortion: ≤5%; (3) Imaging circle diameter: not less than Ф20.4; (4) Working spectrum range: 8.0um~12um; (5) F number: 1.0 When optimizing the cooled infrared optical system, for surfaces with severe cold reflection, constraints on the radius of curvature are added to change the angles of the paraxial principal ray and the edge ray of the surface to reduce the value of cold reflection; the optical power is reasonably distributed and combined with the use of even-order aspherical surfaces to balance the system aberrations, and the sensitivity of each optical component is reduced by adjusting the curvature and thickness, making the lens easier to process and assemble.

[0020] Compared with the prior art, the present invention has the following beneficial effects: a) The F number of the optical system of the present invention is 1.0. Compared with the low F number system, the system makes full use of the light aperture of the existing focal length, increases the effective light area of ​​the system, and improves the detection sensitivity of the system; b) The optical system of the present invention matches a 640×512, 25um large-target-area refrigerated long-wave infrared detector, and the system has a shorter integration time, a higher frame rate, a wider dynamic range, a faster search speed, and a wider search range; c) The system of the present invention adopts a combination of materials with high refractive index, which can reduce the number of lenses in the system and reduce the weight of the system while meeting the image quality requirements.

[0021] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0022] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0023] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A large relative aperture refrigeration long wave system, characterized in that: It includes a meniscus positive lens A, a meniscus negative lens B, a meniscus positive lens C, a meniscus positive lens D, a meniscus positive lens E, and a meniscus positive lens F which are sequentially arranged along the optical path direction.

2. The large relative aperture refrigeration long wave system according to claim 1, characterized in that: The optical system further comprises a detector G, which is a long-wave cooling detector with a pixel number of 640×512, a pixel size of 25 μm, and an F number of 1.

0.

3. The large relative aperture refrigeration long wave system according to claim 1, characterized in that: The air gap between the meniscus positive lens A and the meniscus negative lens B is 2.98 mm, the air gap between the meniscus negative lens B and the meniscus positive lens C is 162.51 mm, the air gap between the meniscus positive lens C and the meniscus positive lens D is 39.63 mm, the air gap between the meniscus positive lens D and the meniscus positive lens E is 16.19 mm, and the air gap between the meniscus positive lens E and the meniscus positive lens F is 2 mm.

4. The large relative aperture refrigeration long wave system according to claim 1, characterized in that: The convex surface of the meniscus positive lens A faces the object plane, and the material is germanium single crystal; the convex surface of the meniscus negative lens B faces the object plane, and the material is zinc selenide; the convex surface of the meniscus positive lens C faces the object plane, and the material is germanium single crystal; the convex surface of the meniscus positive lens D faces the object plane, and the material is germanium single crystal; the concave surface of the meniscus positive lens E faces the object plane, and the material is GAAS; the convex surface of the meniscus positive lens F faces the object plane, and the material is germanium single crystal.

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