A long-wave infrared microscope objective

Abstract

This invention belongs to the field of infrared optics technology and discloses a long-wave infrared microscope lens. The lens has four lenses: a first lens, a second lens, a third lens, and a fourth lens, coaxially arranged between the object plane and the image plane. The first, third, and fourth lenses are meniscus lenses with concave object-side surfaces, while the second lens is a meniscus lens with convex object-side surfaces. The optical power of the first, second, third, and fourth lenses is positive. This long-wave infrared microscope lens, while having a small number of lenses, also features a large target area and clear imaging. It operates in the 8μm-12μm wavelength range, has a magnification of 3.4, an object-side numerical aperture of 0.75, and can be used with detectors with a pixel count of 640×512 and a pixel size of 17μm.

Description

Technical Field

[0001] This invention belongs to the field of infrared optical technology, and specifically relates to a long-wave infrared microscope lens. Background Technology

[0002] An infrared microscope lens is a special type of lens that utilizes infrared light instead of visible light. Infrared thermal imagers equipped with infrared microscope lenses can reveal detailed images of objects, primarily used in power system and equipment maintenance and inspection for predictive detection of overheating faults in power and telecommunications equipment, thermal imaging analysis in the biological field, and forensic identification of criminal traces and physical evidence. Ordinary long-wave infrared imaging lenses, due to limitations in working distance and magnification, cannot achieve high-performance imaging at close range and cannot distinguish detailed temperature distribution patterns in objects.

[0003] To obtain clear images, existing infrared microscope lenses often have multiple lenses, resulting in complex structures and relatively high costs. Summary of the Invention

[0004] To address the above problems, this invention proposes a long-wave infrared microscope lens, which features a large target surface, clear imaging, and a small number of lenses; the specific technical solution is as follows: A long-wave infrared microscope lens, wherein the lens is provided with four lenses, namely a first lens, a second lens, a third lens, and a fourth lens arranged coaxially between the object plane and the image plane; the first lens, the third lens, and the fourth lens are meniscus lenses with concave object sides, and the second lens is a meniscus lens with convex object sides; the optical power of the first lens, the second lens, the third lens, and the fourth lens is positive.

[0005] Further, the first lens has a center thickness of 5.75 mm, an object-side radius of curvature of -44.964 mm, and an image-side radius of curvature of -35.573 mm; the second lens has a center thickness of 5.75 mm, an object-side radius of curvature of 57.771 mm, and an image-side radius of curvature of 60.751 mm; the third lens has a center thickness of 6.16 mm, an object-side radius of curvature of -83.810 mm, and an image-side radius of curvature of -71.010 mm; the fourth lens has a center thickness of 5.51 mm, an object-side radius of curvature of -157.741 mm, and an image-side radius of curvature of -121.822 mm; the air gap between the first and second lenses is 20.06 mm; the air gap between the second and third lenses is 25.22 mm; and the air gap between the third and fourth lenses is 5.17 mm.

[0006] Furthermore, the first lens, the third lens, and the fourth lens are made of germanium single crystal, while the second lens is made of zinc selenide.

[0007] Furthermore, the object-side surfaces of the first lens, the third lens, and the fourth lens are aspherical and satisfy the aspherical formula: Where 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 higher-order aspherical coefficients.

[0008] Furthermore, the object-side surface of the third lens is a diffraction surface, and satisfies the equation for the diffraction surface in Zemax: M(B1ρ 2 +B2ρ 4 ); where M is the diffraction order, the diffraction order is 1, B1 and B2 are the phase coefficients of the diffraction surface, B1 = -25.910, B2 = -10.807, and the normalized radius ρ is 27.

[0009] Furthermore, the object side of the third lens is provided with an aperture stop.

[0010] Furthermore, the lens operates in the 8μm-12μm wavelength range, has a magnification of 3.4, an object-side numerical aperture of 0.75, a pixel count of 640×512, and a pixel size of 17μm.

[0011] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: The lens of this invention features a large target surface and clear imaging, while having a simple structure and only four lenses. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a diagram showing the lens composition of the long-wave infrared microscope lens in Example 1; Figure 2 This is the optical path diagram of the long-wave infrared microscope head in Example 1; Figure 3 This is a dot plot of the long-wave infrared microscope lens from Example 1; Figure 4 This is the MTF image of the long-wave infrared microscope lens in Example 1.

[0014] Reference numerals in the attached figures: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Protective window; 6. Image plane; 7. Object plane. Detailed Implementation

[0015] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that the terms "first," "second," "third," and "fourth" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features.

[0016] Example 1 This embodiment provides a long-wave infrared microscope lens.

[0017] like Figure 1 As shown, the long-wave infrared microscope lens has four lenses, namely, lens 1, lens 2, lens 3, and lens 4, which are coaxially arranged between the object plane and the image plane. Lenses 1, 3, and 4 are meniscus lenses with concave object sides, while lens 2 is a meniscus lens with convex object sides. The optical power of lenses 1, 2, 3, and 4 is positive. Lens 3 has an aperture stop on its object side.

[0018] like Figure 2 As shown, the light beam passes through the first lens 1, the second lens 2, the aperture, the third lens 3, and the fourth lens 4 from left to right, and then forms an image on the image plane 6 through the protective window 5 of the detector.

[0019] As shown in Table 1, in one specific embodiment, the center thickness of the first lens 1 is 5.75 mm, the object-side radius of curvature is -44.964 mm, and the image-side radius of curvature is -35.573 mm; the center thickness of the second lens 2 is 5.75 mm, the object-side radius of curvature is 57.771 mm, and the image-side radius of curvature is 60.751 mm; the center thickness of the third lens 3 is 6.16 mm, the object-side radius of curvature is -83.810 mm, and the image-side radius of curvature is -71.010 mm; the center thickness of the fourth lens 4 is 5.51 mm, the object-side radius of curvature is -157.741 mm, and the image-side radius of curvature is -121.822 mm; the air gap between the first lens 1 and the second lens 2 is 20.06 mm; the air gap between the second lens 2 and the third lens 3 is 25.22 mm; and the air gap between the third lens 3 and the fourth lens 4 is 5.17 mm. The air gap between the object plane 7 and the first lens 1 is 20mm.

[0020] It is understandable that, along the optical axis from left to right, the left side is the object side and the right side is the image side. For example, in the first lens 1, surface S1 is the object side and surface S2 is the image side. Other lenses will not be described in detail here.

[0021] Table 1 Parameters of each component In a specific implementation, the first lens 1, the third lens 3, and the fourth lens 4 are made of germanium single crystal, and the second lens 2 is made of zinc selenide.

[0022] Table 2 Aspherical data of lenses As one specific implementation, as shown in Table 2, the object-side surface S1 of the first lens, the object-side surface S5 of the third lens, and the object-side surface S7 of the fourth lens are aspherical surfaces and satisfy the aspherical surface formula: Where 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 higher-order aspherical coefficients.

[0023] The object-side surface S5 of the third lens is a diffraction surface and satisfies the equation for the diffraction surface in Zemax: M(B1ρ 2 +B2ρ 4 ); where M is the diffraction order, the diffraction order is 1, B1 and B2 are the phase coefficients of the diffraction surface, B1 = -25.910, B2 = -10.807, and the normalized radius ρ is 27.

[0024] Figure 3 , Figure 4 The images show a dot plot and MTF plot of the long-wave infrared microscope lens at a magnification of 3.4. In the MTF plot, the horizontal axis represents different spatial frequencies, and the vertical axis represents modulation. All fields of view represent the MTF curves of the meridional plane. It can be seen that the MTF is close to the diffraction limit, the root mean square diameter of the diffuse spot is smaller than the Airy disk diameter, and the image quality is good.

[0025] The long-wave infrared microscope lens of this embodiment operates in the 8μm-12μm wavelength range, has a magnification of 3.4, an object-space numerical aperture of 0.75, a working F-number of 2.26, a pixel count of 640×512, and a pixel size of 17μm. This long-wave infrared microscope lens features a simple structure, a large target surface, and clear imaging.

[0026] Obviously, the above embodiments are merely examples to clearly illustrate the technical solutions of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A long-wave infrared microscope lens, characterized in that, The lens has four lenses, namely a first lens, a second lens, a third lens, and a fourth lens, which are coaxially arranged between the object plane and the image plane. The first lens, the third lens, and the fourth lens are meniscus lenses with a concave object side, and the second lens is a meniscus lens with a convex object side. The optical power of the first lens, the second lens, the third lens, and the fourth lens is positive.

2. The long-wave infrared microscope lens according to claim 1, characterized in that, The first lens has a center thickness of 5.75 mm, an object-side radius of curvature of -44.964 mm, and an image-side radius of curvature of -35.573 mm; the second lens has a center thickness of 5.75 mm, an object-side radius of curvature of 57.771 mm, and an image-side radius of curvature of 60.751 mm; the third lens has a center thickness of 6.16 mm, an object-side radius of curvature of -83.810 mm, and an image-side radius of curvature of -71.010 mm; the fourth lens has a center thickness of 5.51 mm, an object-side radius of curvature of -157.741 mm, and an image-side radius of curvature of -121.822 mm; the air gap between the first and second lenses is 20.06 mm; the air gap between the second and third lenses is 25.22 mm; and the air gap between the third and fourth lenses is 5.17 mm.

3. The long-wave infrared microscope lens according to claim 1, characterized in that, The first, third, and fourth lenses are made of germanium single crystal, while the second lens is made of zinc selenide.

4. The long-wave infrared microscope lens according to claim 1, characterized in that, The object-side surfaces of the first lens, the third lens, and the fourth lens are aspherical and satisfy the aspherical formula: Where 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 higher-order aspherical coefficients.

5. The long-wave infrared microscope lens according to claim 4, characterized in that, The object-side surface of the third lens is a diffraction surface, and satisfies the equation for the diffraction surface in Zemax: M(B1ρ) 2 +B2ρ 4 ); where M is the diffraction order, the diffraction order is 1, B1 and B2 are the phase coefficients of the diffraction surface, B1 = -25.910, B2 = -10.807, and the normalized radius ρ is 27.

6. The long-wave infrared microscope lens according to claim 1, characterized in that, The object side of the third lens is equipped with an aperture stop.

7. The long-wave infrared microscope lens according to any one of claims 1 to 6, characterized in that, The lens operates in the 8μm-12μm band, has a magnification of 3.4, an object-side numerical aperture of 0.75, a pixel count of 640×512, and a pixel size of 17μm.

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