A long-wave infrared athermal objective lens based on refraction

Abstract

This invention discloses a refraction-based long-wave infrared athermalized objective lens. From the object side to the image side, it comprises, in order, a first lens, a second lens, a third lens, a fourth lens, an optical filter (ICR), and an imaging surface (IMA). The first lens is a negative meniscus lens, the second lens is a positive meniscus lens, and both the third and fourth lenses are meniscus lenses. This objective lens has a simple structure, a stable optical axis, and high system reliability. It can meet the requirements of high-definition image quality at infinity at ambient temperatures between -40°C and +50°C without requiring focusing.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging equipment, and in particular to a long-wave infrared athermal objective lens based on refraction. Background Art

[0002] With the rapid development of infrared night vision technology, uncooled infrared optical systems have gained widespread application in military and civilian applications. However, the refractive index temperature coefficient (dn / dT) of the materials used in infrared lenses is large. As the ambient temperature changes, the refractive index, the curvature and thickness of optical components, and the spacing between components all change, causing thermal defocusing in the infrared optical system and degrading the system's image quality. Therefore, athermalizing infrared optical systems has become a mainstream development direction for high-precision infrared optical systems. There are three main approaches to athermalizing infrared systems: the first is mechanical passive compensation, which utilizes the complementary effects of thermal deformation of structural components and thermal expansion of infrared materials for temperature compensation; the second is mechanical (electronic) active compensation, which uses traditional electric focusing for temperature compensation. Both mechanical passive and mechanical (electronic) active compensation methods result in complex system structures, low reliability, and inconvenient operation. The third is optical passive compensation, a common method that incorporates diffractive optical elements into the system. However, diffractive elements are complex to manufacture and assemble, resulting in high production costs and lower light transmittance than conventional optical elements. Summary of the Invention

[0003] The present invention aims to overcome the deficiencies of the prior art and to provide a refraction-based long-wave infrared athermal objective lens that can meet the requirements of high-definition image quality at infinity under environmental conditions of -40°C to +50°C without focusing.

[0004] To achieve the above-mentioned design objectives, the technical solution adopted by the present invention is: a refraction-based long-wave infrared athermal objective lens, which includes, from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, a filter (ICR) and an imaging surface (IMA), wherein the first lens is a negative meniscus lens, the second lens is a positive meniscus lens, and the third lens and the fourth lens are both meniscus lenses.

[0005] The concave surfaces of the second lens and the third lens are both aspherical.

[0006] The optical material of the first lens and the third lens is made of zinc sulfide crystal, and the optical material of the second lens and the fourth lens is made of chalcogenide glass.

[0007] The first lens, the second lens, the third lens and the fourth lens are all made of common chalcogenide infrared materials.

[0008] The present invention has the following beneficial effects: By combining four lenses, aberrations such as spherical aberration, chromatic aberration, field curvature, and distortion are eliminated, achieving aberration balance in the system. The image is then imaged on an infrared focal plane detector. By utilizing optical passive compensation methods, without using diffractive optical elements for temperature compensation, and by utilizing differences in the thermal properties of infrared materials, and by rationally selecting common infrared lens materials and allocating optical power, the entire infrared system is prevented from defocusing. This ensures that the optical system maintains clear imaging of scenes under varying ambient temperatures without the need for focusing. Furthermore, by utilizing the principle of refraction, excellent imaging quality is achieved over a wide temperature range. The present invention has a simple structure, a stable optical axis, and high system reliability. It can meet the requirements for high-definition image quality at infinity at ambient temperatures between -40°C and +50°C without the need for focusing. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is an arrangement diagram of the optical glass with light of the present invention;

[0010] Figure 2 This is the transfer function diagram of the present invention at 20°C;

[0011] Figure 3 This is the transfer function diagram of the present invention at -40°C;

[0012] Figure 4 This is the transfer function diagram of the present invention at 50°C;

[0013] Figure 5 This is the 20°C diffuse pattern of the present invention;

[0014] Figure 6 This is the -40℃ diffuse pattern of the present invention;

[0015] Figure 7 This is the 50°C diffusion pattern of the present invention. DETAILED DESCRIPTION

[0016] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Figure 1-7 As shown: A refraction-based long-wave infrared athermal objective lens, which includes, from the object side to the image side, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a filter (ICR) 5 and an imaging surface (IMA) 6. The first lens 1 is a negative meniscus lens, the second lens 2 is a positive meniscus lens, and the third lens 3 and the fourth lens 4 are both meniscus lenses.

[0017] The concave surfaces of the second lens 2 and the third lens 3 are both aspherical.

[0018] The optical material of the first lens 1 and the third lens 3 is made of zinc sulfide crystal, and the optical material of the second lens 2 and the fourth lens 4 is made of chalcogenide glass.

[0019] The first lens 1 , the second lens 2 , the third lens 3 and the fourth lens 4 are all made of common chalcogenide infrared materials.

[0020] The parameters of the f′=90mm / F1.0 non-focusing athermal infrared optical system are as follows:

[0021] Serial number radius Thickness (interval) caliber Material Remark 1 118 5 φ93 <![CDATA[ ZnS ]]> 2 101.1 1 φ89 3 78.34 13 φ90 IRG206 4 137.91 62.7 φ84 Aspheric 5 43 5 φ32 <![CDATA[ ZnS ]]> 6 32.5 11.1 φ28 Aspheric 7 28.75 5 φ25 IRG202 8 33.72 11 φ22 9 Image plane Infrared detector germanium window

[0022] The high-order aspheric equation of the fourth surface is:

[0023]

[0024] Where:

[0025] k=-1.92624

[0026] a1=0

[0027] a²=1.584656×10 -7

[0028] a4=2.649014×10 -12

[0029] a²=4.807491×10 -16

[0030] The quadratic aspheric equation of the sixth surface is:

[0031]

[0032] Where:

[0033] k=-0.99755

[0034] a1=0

[0035] a²=4.490302×10 -6

[0036] a4=2.019293×10 -9

[0037] a²=1.013826×10 -11 .

Claims

1. A long-wave infrared athermal objective lens based on refraction, characterized by: From the object side to the image side, it is composed of the first lens, the second lens, the third lens, the fourth lens, the filter (ICR) and the imaging surface (IMA). The first lens is a negative meniscus lens, the second lens is a positive meniscus lens, and the third lens and the fourth lens are both meniscus lenses. The object side curvature radius of the first lens is 118mm, the thickness is 5mm, the image side curvature radius is 101.1mm, the interval between the first lens and the second lens is 1mm, and the material of the first lens is ZnS; the object side curvature radius of the second lens is 78.34mm, the thickness is 13mm, and the image side curvature radius is 137.9 1mm, the distance between the second lens and the third lens is 62.7mm, and the material of the second lens is IRG206; the object side curvature radius of the third lens is 43mm, the thickness is 5mm, the image side curvature radius is 32.5mm, the distance between the third lens and the fourth lens is 11.1mm, and the material of the third lens is ZnS; the object side curvature radius of the fourth lens is 28.75mm, the thickness is 5mm, the image side curvature radius is 33.72mm, the distance between the fourth lens and the filter is 11mm, and the material of the fourth lens is IRG202; the concave surfaces of the second and third lenses are both aspherical.

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