A middle wave infrared imaging relay lens group based on dyson improved concentric structure

Abstract

The application relates to an infrared imaging lens, in particular to a middle-wave infrared imaging relay lens based on a Dyson improved concentric structure, which is used for solving the problem that the object plane position and the image plane position of the Dyson concentric structure are both located near the curvature center of a concave mirror, so that the radial distance between the object plane and the image plane is difficult to be pulled apart, and the engineering application of the Dyson concentric structure is limited. The middle-wave infrared imaging relay lens based on the Dyson improved concentric structure adopts a plane mirror to replace the concave mirror, so that the processing and detection are simple, the radial distance between the object plane and the image plane can be pulled apart, the limited radial distance between the edges of the object plane and the image plane of the traditional Dyson concentric structure is overcome, the interference of the object plane and the image plane is avoided, and the range of the engineering application is widened.

Description

TECHNICAL FIELD

[0001] The present application relates to an infrared imaging lens, in particular to a middle wave infrared imaging relay lens based on a Dyson improved concentric structure. BACKGROUND

[0002] The middle wave infrared system is a kind of infrared thermal radiation detection and imaging technology, mainly receiving the infrared radiation energy of the target itself. The middle wave infrared system has important applications in civil industrial production, medical treatment and other fields. For example, in civil industrial production, it can be used for non-contact temperature monitoring and quality control of equipment; in medical treatment, it can be used for non-invasive detection of diseased tissues.

[0003] The Dyson concentric structure is a concentric structure composed of a plano-convex lens and a concave mirror, that is, the convex surface of the lens and the concave surface of the mirror have a common spherical center. The light beam emitted by the object point is imaged to the concave mirror through the plano-convex lens, and then reflected by the concave mirror and imaged to the image plane again through the plano-convex lens. This structure has the characteristic that the magnification of the object and image is -1, and the incident light beam and the exit light beam share the same optical system, thereby realizing optical path multiplexing. The concave mirror is the aperture stop of the system, and the concave mirror is located near the focal plane position of the plano-convex lens, so that the Dyson concentric structure has the imaging characteristics of double-telecentricity of the object side and the image side. The Seidel aberration of the system tends to zero, and has the advantages of simple and compact structure, small volume, light weight, large numerical aperture, etc.

[0004] The Dyson concentric structure has special application advantages in the infrared band. In the infrared band, the light absorption rate of the lens material is relatively high, and the high light flux characteristic of the Dyson concentric structure can well meet the requirement of high optical efficiency of the optical imaging system in the infrared band. However, since the object plane position and the image plane position of the Dyson concentric structure are both located near the curvature center of the concave mirror, it is difficult to pull apart the radial distance between the object plane and the image plane. This structure is too compact, which leads to easy interference of the object and the image, and it is difficult to increase the distance between the object plane and the image plane, thereby limiting the engineering application of the Dyson concentric structure. SUMMARY

[0005] The purpose of the present application is to solve the problem that the object plane position and the image plane position of the Dyson concentric structure are both located near the curvature center of the concave mirror, making it difficult to pull apart the radial distance between the object plane and the image plane, and limiting the engineering application of the Dyson concentric structure, and to provide a middle wave infrared imaging relay lens based on a Dyson improved concentric structure.

[0006] In order to solve the above-mentioned problems of the prior art, the present application provides the following technical solutions:

[0007] A kind of middle wave infrared imaging relay lens group based on Dyson improved concentric structure, it is special in that: including first lens, second lens, third lens and plane mirror;

[0008] The infrared beam of target radiation is projected to plane mirror by object plane in turn through first lens, second lens, third lens, is reflected after being reflected by plane mirror, again passes through third lens, second lens, first lens and is focused on image plane;

[0009] The first lens, second lens are positive focal length lens bent to plane mirror, for converging the infrared beam passing through it;The third lens is negative focal length lens bent to plane mirror, for diverging the infrared beam passing through it;The plane mirror is used to control the finite aperture range of the infrared beam reflected by it, and the infrared beam output by the third lens is reflected back to the third lens;

[0010] The radial distance at the edge of the object plane and image plane is greater than or equal to 30mm.

[0011] Further, one side of the first lens away from the second lens is 10 times even high-order aspherical surface.

[0012] Further, both sides of the third lens are 8 times even double high-order aspherical surface.

[0013] Further, the material of the first lens, second lens and third lens is Ge, Si and Ge respectively.

[0014] The middle wave infrared imaging relay lens group based on Dyson improved concentric structure according to claim 4, characterized in that:

[0015] The thickness of the first lens is 13.9mm, the distance between the first lens and the second lens is 50.24mm, the thickness of the second lens is 13.5mm, the distance between the second lens and the third lens is 1.68mm, the thickness of the third lens is 11.84mm, and the distance between the third lens and the image plane is 183.55mm.

[0016] Further, the radii of the two sides of the first lens are 96.8mm and 102.2mm respectively, the radii of the two sides of the second lens are 49.53mm and 110.5mm respectively, and the radii of the two sides of the third lens are 123.55mm and 50.48mm respectively.

[0017] Compared with the prior art, the beneficial effects of the present application are:

[0018] (1) The application is a middle wave infrared imaging relay lens group based on Dyson improved concentric structure, which adopts plane mirror to replace concave mirror, is simple to process and detect, and can pull apart the radial distance of object plane and image plane, overcomes the limited radial distance between the edges of object plane and image plane of traditional Dyson concentric structure, avoids the interference of object plane and image plane, and widens the range of engineering application.

[0019] (2) The application breaks the limited field of view of traditional Dyson concentric structure, realizes the ability of clear infrared imaging under wide field of view, and widens the imaging field of view.

[0020] (3) The application realizes the 'light path multiplexing' of incident light beam and outgoing light beam, is equivalent to a rotationally symmetric structure, and has the imaging characteristics of system distortion value of 0.

[0021] (4) The application has the pupil structure characteristics of object side and image side double telecentricity, which is beneficial to application in combined light path. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structure schematic view of the embodiment of the application, a middle wave infrared imaging relay lens group based on Dyson improved concentric structure.

[0023] Figure 1 Label explanation:

[0024] 1- object plane; 2- first lens; 3- second lens; 4- third lens; 5- plane mirror; 6- image plane.

[0025] Figure 2 It is the MTF (modulation transfer function) curve of the embodiment of the application;

[0026] Figure 3 It is the spot diagram of the embodiment of the application;

[0027] Figure 4 It is the performance diagram of astigmatic field curves and distortion of the embodiment of the application. DETAILED DESCRIPTION

[0028] The application will be further described below in combination with the drawings and exemplary embodiments.

[0029] Reference Figure 1 A middle wave infrared imaging relay lens group based on Dyson improved concentric structure, comprising a first lens 2, a second lens 3, a third lens 4 and a plane mirror 5.

[0030] The infrared beam of the target radiation is projected by the object plane 1 to the first plane (the plane far from the second lens 3) and the second plane of the first lens 2, the first plane and the second plane of the second lens 3, the first plane and the second plane of the third lens 4 in turn, and then focused and imaged on the image plane 6 by the plane mirror 5 after being reflected by the plane mirror 5 again. The present application realizes the "light path multiplexing" of the incident beam and the exit beam.

[0031] The first lens 2 is a positive focal power lens bent towards the plane mirror 5, and the first plane is a 10th-order even high-order aspheric surface, which is used for correcting aberration, expanding the field of view and improving the resolution. The second lens 3 is a positive focal power lens bent towards the plane mirror 5, and the third lens 4 is a negative focal power lens bent towards the plane mirror 5, and both planes are 8th-order even double high-order aspheric surfaces, which are used for further optimizing the transmission and focusing state of the light beam, reducing the aberration and distortion in the system, and ensuring the high-quality imaging effect. The plane mirror 5 is used for controlling the limited aperture range of the infrared light beam reflected thereby, and reflecting the infrared light beam output by the third lens 4 back to the third lens 4.

[0032] The parameters of the first lens 2, the second lens 3 and the third lens 4 are shown in Table 1:

[0033] Table 1

[0034]

[0035] The thickness of the first lens 2 is 13.9mm, the distance between the first lens 2 and the second lens 3 is 50.24mm, the thickness of the second lens 3 is 13.5mm, the distance between the second lens 3 and the third lens 4 is 1.68mm, the thickness of the third lens 4 is 11.84mm, and the distance between the third lens 4 and the image plane 6 is 183.55mm.

[0036] The materials of the first lens 2, the second lens 3 and the third lens 4 are Ge, Si and Ge respectively. The two infrared materials Ge and Si are matched with each other to correct the primary aberration, the high-order aspheric surface is added on the surface of Ge to correct the high-order aberration, the object side and the image side are designed to be double-telecentric, the radial distance between the edge of the pullable object plane 1 and the image plane 6 is 40mm. The total efficiency of the optical system is better than 82%, and the achievable object side imaging field of view is 15.36mm*19.2mm.

[0037] The magnification of the present application is -1 times, the F number is 2, the imaging field of view is 15.36mm*19.2mm (M*N), and the working spectral range is 3.7um-4.8um.

[0038] The adapted infrared detector is a refrigeration type HgCdTe detector, the working wave band is 3.7-4.8 mu m, the cold screen F number is 2, the pixel size is 15 mu m*15 mu m, and the target surface size is 9.6 mm*7.68 mm (M*N).

[0039] Figure 2 For the MTF curve of the embodiment of the application, the meridional / tangential MTF of the maximum off-axis field of view under each wave band and each field of view is better than 0.22 at a spatial frequency of 331 p / mm, and is close to the diffraction limit.

[0040] Figure 3 For the point column diagram of the embodiment of the application, the aberration characteristics of the system are judged by analyzing the distribution and size of the light spot under different field positions; the RMS (Root Mean Square) error is used to quantify the dispersion degree of the light spot in the point column diagram, and the smaller the value is, the better the imaging quality is; 100% represents the percentage of energy contained by the light spot. Figure 3 In the diagram, most of the light spots are concentrated in the ideal Airy disk, the maximum diffraction spot diameter is less than 12 mu m, the RMS value is small, and the imaging performance of the system is excellent.

[0041] Figure 4 The astigmatism curve (left side) and the performance diagram of distortion (right side) of the embodiment of the application; from the astigmatism curve in the left side diagram, it can be seen that the astigmatism curves of different wavelengths have a certain offset at different object heights, which shows that the system has a certain degree of astigmatism at different wavelengths, but overall, the offset amount of these curves is small, which shows that the astigmatism of the system is controlled within a good range. From the performance diagram of distortion, it can be seen that the green curve is almost coincided with the vertical axis, which shows that the distortion of the optical system is very small in the whole field of view range, close to zero, which shows that the system has very good geometric imaging performance.

Claims

1. A mid-wave infrared imaging relay mirror assembly based on a Dyson improved concentric structure, characterized in that: It includes a first lens (2), a second lens (3), a third lens (4), and a plane mirror (5); The infrared beam radiated by the target passes through the object surface (1) sequentially through the first lens (2), the second lens (3), and the third lens (4) and is projected onto the plane mirror (5). After being reflected by the plane mirror (5), it is focused onto the image plane (6) again through the third lens (4), the second lens (3), and the first lens (2). The first lens (2) and the second lens (3) are both positive power lenses bent toward the plane mirror (5) and are used to converge the infrared beam passing through it; the third lens (4) is a negative power lens bent toward the plane mirror (5) and is used to diverge the infrared beam passing through it; the plane mirror (5) is used to control the limited aperture range of the infrared beam reflected by it and to reflect the infrared beam output by the third lens (4) back to the third lens (4). The radial distance between the object plane (1) and the image plane (6) at their edges is greater than or equal to 30 mm.

2. The mid-wave infrared imaging relay mirror assembly based on a Dyson improved concentric structure according to claim 1, characterized in that: The side of the first lens (2) away from the second lens (3) is an aspherical surface containing even-order 10.

3. The mid-wave infrared imaging relay mirror assembly based on a Dyson improved concentric structure according to claim 2, characterized in that: Both sides of the third lens (4) are double-sided high-order aspherical surfaces containing even-order 8th order.

4. A mid-wave infrared imaging relay mirror assembly based on a Dyson improved concentric structure according to claim 3, characterized in that: The materials of the first lens (2), the second lens (3), and the third lens (4) are Ge, Si, and Ge, respectively.

5. A mid-wave infrared imaging relay mirror assembly based on a Dyson improved concentric structure according to claim 4, characterized in that: The thickness of the first lens (2) is 13.9 mm, the distance between the first lens (2) and the second lens (3) is 50.24 mm, the thickness of the second lens (3) is 13.5 mm, the distance between the second lens (3) and the third lens (4) is 1.68 mm, the thickness of the third lens (4) is 11.84 mm, and the distance between the third lens (4) and the image plane (6) is 183.55 mm.

6. A mid-wave infrared imaging relay mirror assembly based on a Dyson improved concentric structure according to claim 5, characterized in that: The radii of the two sides of the first lens (2) are 96.8 mm and 102.2 mm, the radii of the two sides of the second lens (3) are 49.53 mm and 110.5 mm, and the radii of the two sides of the third lens (4) are 123.55 mm and 50.48 mm, respectively.

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