CN118011600A - A long-wave infrared microscope lens - Google Patents

Abstract

The present invention belongs to the field of infrared optical technology, and discloses a long-wave infrared microscope lens. The lens is provided with three lenses, namely, a first lens, a second lens, and a third lens, which are arranged in sequence along the transmission direction of the optical axis; the first lens is a positive meniscus lens with a convex surface facing the object side, the second lens is a negative meniscus lens with a convex surface facing the object side, and the third lens is a double convex positive lens. This long-wave infrared microscope lens has a small number of lenses, and also has the characteristics of a large target surface and clear imaging. The working band is 8μm-12μm, the object numerical aperture is 0.23, and the magnification is 0.6. It can be matched with a detector with a pixel number of 640×512 and a pixel size of 17μm.

Description

A long-wave infrared microscope lens

Technical Field

The invention belongs to the technical field of infrared optics, and in particular relates to a long-wave infrared microscope lens.

Background technique

Infrared thermal imager is a device that uses infrared thermal imaging technology to detect the infrared radiation of the target object and convert the image of the temperature distribution of the target object into a visible image by means of signal processing, photoelectric conversion, etc. The application fields of infrared thermal imagers are becoming more and more extensive, such as abnormal heating detection of laser optical fiber, thermal properties of integrated circuit components and semiconductor substrates, thermal imaging analysis in the biological field, and identification of criminal traces and physical evidence in the field of criminal investigation. Due to the limitations of working distance and magnification, it is impossible to image with high performance at close range and it is impossible to distinguish the details of the temperature distribution of the target object, so ordinary long-wave infrared lenses cannot meet the needs.

Since the price of long-wave infrared detectors is usually much lower than that of medium-wave infrared detectors, it is necessary to design corresponding long-wave infrared microscopes to meet the requirements of detail clarity. In order to obtain clear imaging, the existing technology often has multiple lenses, which is complex in structure and relatively costly.

Summary of the invention

In order to solve the above problems, the present invention proposes a long-wave infrared microscope lens, which has the characteristics of large target surface, clear imaging, and a small number of lenses; the specific technical scheme is as follows:

A long-wave infrared microscope lens, the lens is provided with three lenses, namely a first lens, a second lens, and a third lens arranged in sequence along the transmission direction of the optical axis; the first lens is a positive meniscus lens with a convex surface facing the object side, the second lens is a negative meniscus lens with a convex surface facing the object side, and the third lens is a double convex positive lens.

Furthermore, the center thickness of the first lens is 5 mm, the object side curvature radius is 57.99 mm, and the image side curvature radius is 179.95 mm; the center thickness of the second lens is 4 mm, the object side curvature radius is 102.53 mm, and the image side curvature radius is 34.18 mm; the center thickness of the third lens is 6.5 mm, the object side curvature radius is 535.36 mm, and the image side curvature radius is -75.51 mm.

Furthermore, the three lenses are all made of germanium single crystal.

Furthermore, the image side surface of the first lens and the object side surface of the second lens are aspherical surfaces and satisfy the aspherical surface formula:

Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1/R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, and E are high-order aspherical coefficients.

Furthermore, the object-side surface of the second lens is a diffraction surface, and satisfies the expression equation of the diffraction surface in Zemax: M(B ₁ ρ ² +B ₂ ρ ⁴ ); wherein M is the diffraction order, the diffraction order is 1, B ₁ and B ₂ are diffraction surface phase coefficients, B ₁ =-10.2148, B ₂ =1.0837, and the normalized radius ρ is 12.

Furthermore, a stop is provided between the first lens and the second lens.

Furthermore, the lens has an operating band of 8 μm-12 μm, an object-side numerical aperture of 0.23, a pixel number of 640×512, and a pixel size of 17 μm.

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 the present invention has the characteristics of a large target surface and clear imaging, and at the same time, the lens structure is simple and the number of lenses is only three.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

FIG1 is a diagram showing the lens composition of a long-wave infrared microscope lens of Example 1;

FIG2 is a light path diagram of the long-wave infrared microscope lens of Example 1;

FIG3 is a spot diagram of the long-wave infrared microscope lens of Example 1;

FIG. 4 is an MTF diagram of the long-wave infrared microscope lens of Example 1.

Reference numerals: 1, first lens; 2, aperture; 3, second lens; 4, third lens; 5, protective window; 6, image plane; 7, object plane.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in 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. It should be noted that the terms "first", "second" and "third" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features.

Example 1

As shown in Figure 1, this embodiment provides a long-wave infrared microscope lens, which is provided with three lenses, namely a first lens 1, a second lens 3, and a third lens 4 which are coaxially arranged in sequence along the transmission direction of the optical axis; the first lens 1 is a positive meniscus lens with a convex surface facing the object side, the second lens 3 is a negative meniscus lens with a convex surface facing the object side, and the third lens 4 is a double convex positive lens; an aperture 2 is provided between the first lens 1 and the second lens 2.

As shown in FIG. 2 , the light beam emitted from the object plane 7 passes through the first lens 1 , the aperture 2 , the second lens 3 , and the third lens 4 from left to right in sequence, and then forms an image on the image plane 6 through the protective window 5 .

As shown in Table 1, as a specific implementation, the center thickness T1 of the first lens 1 is 5mm, the object side curvature radius is 57.99mm, and the image side curvature radius is 179.95mm; the center thickness T3 of the second lens 3 is 4mm, the object side curvature radius is 102.53mm, and the image side curvature radius is 34.18mm; the center thickness T4 of the third lens 4 is 6.5mm, the object side curvature radius is 535.36mm, and the image side curvature radius is -75.51mm. The air gap between the first lens 1 and the second lens 2 is 15.17mm; the air gap between the second lens 3 and the third lens 4 is 8.88mm. The air gap between the object plane 7 and the first lens 1 is 80mm.

It can be understood that, from left to right along the optical axis, the left side is the object side and the right side is the image side, such as the S1 surface of the first lens 1 is the object side surface and the S2 surface is the image side surface. Other lenses are not described here.

Table 1 Parameters of each component

As a specific implementation, the material of the first lens 1 , the second lens 3 , and the third lens 4 is germanium single crystal.

Table 2 Aspheric surface data of lens

As a specific implementation, as shown in Table 2, the image side surface S2 of the first lens 1 and the object side surface S4 of the second lens 3 are aspherical surfaces and satisfy the aspherical surface formula:

Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1/R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, and E are high-order aspherical coefficients.

The object-side surface S4 of the second lens 3 is a diffraction surface, which satisfies the expression equation of the diffraction surface in Zemax: M(B ₁ ρ ² +B ₂ ρ ⁴ );

Wherein, M is the diffraction order, the diffraction order is 1, B ₁ and B ₂ are the diffraction surface phase coefficients, B ₁ =-10.2148, B2 =1.0837, and the normalized radius ρ is 12.

Figures 3 and 4 are the spot diagram and MTF diagram of the long-wave infrared microscope lens, respectively. In the MTF diagram, the horizontal axis represents different spatial frequencies and the vertical axis represents the modulation degree. All fields of view represent the MTF curve of the meridian 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.

The long-wave infrared microscope lens of this embodiment has an operating band of 8μm-12μm, an object numerical aperture of 0.23, an operating F number of 1.3, a magnification of 0.6, a pixel number of 640×512, and a pixel size of 17μm. The long-wave infrared microscope lens of this embodiment has a simple structure, a large target surface, and clear imaging.

Obviously, the above embodiments are merely examples for clearly explaining the technical solutions of the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the protection of the claims of the present invention.

Claims (7)

1. The long-wave infrared microscope lens is characterized in that the lens is provided with three lenses, namely a first lens, a second lens and a third lens which are sequentially arranged along the optical axis transmission direction; the first lens is a positive meniscus lens with a convex surface facing the object side, the second lens is a negative meniscus lens with a convex surface facing the object side, and the third lens is a biconvex positive lens.

2. The long-wave infrared microscope of claim 1, wherein the first lens has a center thickness of 5mm, an object-side radius of curvature of 57.99mm, and an image-side radius of curvature of 179.95mm; the center thickness of the second lens is 4mm, the curvature radius of the object side surface is 102.53mm, and the curvature radius of the image side surface is 34.18mm; the center thickness of the third lens is 6.5mm, the curvature radius of the object side surface is 535.36mm, and the curvature radius of the image side surface is-75.51 mm; the air space between the first lens and the second lens is 15.17mm; the air space between the second and third lenses was 8.88mm.

3. The long-wave infrared microscope of claim 1, wherein the three lenses are all germanium single crystals.

4. The long-wave infrared microscope of claim 1, wherein the image side of the first lens element and the object side of the second lens element are aspheric, and satisfy the aspheric formula:

Wherein Z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at the height r along the optical axis direction; c=1/R; r is the paraxial curvature fitting radius of the mirror surface; k is a conic coefficient; A. b, C, D, E is the higher order aspheric coefficient.

5. The long-wave infrared microscope of claim 1, wherein the object side surface of the second lens is a diffraction surface, and satisfies the expression equation of the diffraction surface in Zemax:

M(B₁ρ²+B₂ρ⁴)；

Wherein M is a diffraction order, the diffraction order is 1, B ₁、B₂ is a diffraction plane phase coefficient, B ₁ = -10.2148, b2= 1.0837, and the normalized radius ρ is 12.

6. The long-wave infrared microscope of claim 1, wherein a diaphragm is disposed between the first lens and the second lens.

7. The long-wave infrared microscope of any one of claims 1 to 6, wherein the working band of the lens is 8 μm-12 μm, the object side numerical aperture is 0.23, the number of pixels is 640 x 512, and the pixel size is 17 μm.