Refrigeration type monolithic annular aperture folded imaging optical system

Abstract

The invention discloses a refrigeration type monolithic annular aperture folded imaging optical system, relates to the technical field of refrigeration type infrared lenses, and aims to solve the problems that an existing infrared system is small in view field and large in size. The system is sequentially and coaxially provided with an annular aperture lens, a window, a cold diaphragm and an imaging plane; the window is located behind the annular aperture lens, and an incident light beam passes through the annular aperture lens, then passes through the window and the cold diaphragm and finally is focused on an imaging plane; the annular aperture lens sequentially comprises a first annular transmission surface, a first annular reflection surface, a second annular reflection surface, a third annular reflection surface, a fourth annular reflection surface and a second annular transmission surface from outside to inside. The optical system only adopts one annular aperture lens. Compared with a traditional optical system, the optical path can be folded through the special structure of the annular aperture system, the problem that the size of the traditional optical system is large is solved while the imaging quality is guaranteed, miniaturization of the system can be achieved, and the system is fewer in component and easy to install and adjust.

Description

Technical Field

[0001] The invention relates to the technical field of refrigerated infrared lenses, and in particular to a refrigerated single-chip annular aperture folded imaging optical system. Background Art

[0002] Infrared optical systems can detect the thermal radiation energy of the target and its surrounding environment. This type of optical system can detect the target in real time in various harsh environments, so it is widely used in military and civilian fields. In addition, cooled infrared detectors can greatly reduce the interference of their own thermal radiation and improve the final imaging quality, and are widely used in various detections.

[0003] Many current infrared cooling systems have problems such as large size and complex structure. Therefore, the existing technology has developed into annular aperture imaging system by optimizing the design of traditional reflective optical system. However, the existing infrared cooling annular aperture ultra-thin imaging system has a small field of view and a large size.

[0004] See the article "A Design of an Ultra-compact Monolithic Imaging Optical System" published by Yu Linyao et al. in Acta Optica Sinica. The system adopts an integrated dual-reflection structure, integrating the primary and secondary mirrors on the front and rear surfaces of a lens, and using only one lens to achieve optical system imaging. However, the system has a small field of view and a large volume, with a field of view of only 4.88°, and a long total optical length of 26mm, with a total length to system focal length ratio of 0.31. Summary of the invention

[0005] In order to solve the problems of small field of view and large volume of existing infrared systems, the present invention proposes a refrigerated single-chip annular aperture folded imaging optical system.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A cooling type single-piece annular aperture folded imaging optical system, wherein an annular aperture lens, a window, a cold diaphragm and an imaging plane are coaxially arranged in sequence; the window is located behind the annular aperture lens, and an incident light beam passes through the annular aperture lens, the window, the cold diaphragm and finally focuses on the imaging plane;

[0008] The annular aperture lens is composed of, from outside to inside: annular transmission surface 1, annular reflection surface 1, annular reflection surface 2, annular reflection surface 3, annular reflection surface 4 and annular transmission surface 2;

[0009] The annular transmission surface 1 of the annular aperture lens 1 is used to receive the incident light beam and transmit it out;

[0010] The annular reflective surface 1 of the annular aperture lens is used to receive the light beam transmitted by the annular transmittive surface 1 and perform a first reflection;

[0011] The annular reflection surface 2 of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface 1 and perform a second reflection;

[0012] The annular reflection surface three of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface two and perform a third reflection;

[0013] The annular reflection surface 4 of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface 3 and perform a fourth reflection;

[0014] The annular transmission surface 2 of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface 4 and focus the light beam.

[0015] The light beam is incident on the annular transmission surface one for transmission, the transmitted light is incident on the annular reflection surface one for the first reflection, the reflected light is incident on the annular reflection surface two for the second reflection, the light after the second reflection is incident on the annular reflection surface three for the third reflection, the light after the third reflection is incident on the annular reflection surface four for the fourth reflection, the light after the fourth reflection is incident on the annular transmission surface two for transmission, and the transmitted light passes through the window and the cold aperture and is finally focused on the imaging plane.

[0016] The material selected for the annular aperture lens and the window is germanium.

[0017] The annular reflective surface one, the annular reflective surface two, the annular reflective surface three and the annular reflective surface four are coated with a medium-wave infrared high reflective film layer, and the annular transmittance surface one and the annular transmittance surface two are coated with a medium-wave infrared high transmittance film layer.

[0018] The annular transmission surface 1, the annular reflection surface 1, the annular reflection surface 2, the annular reflection surface 3, the annular reflection surface 4 and the annular transmission surface 2 are all even-order aspherical surfaces, and the surface shape of the even-order aspherical surface satisfies the following relationship:

[0019]

[0020] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis; c is the surface curvature of the aspherical surface, where c = 1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D, and E are aspherical coefficients.

[0021] The beneficial effects of the present invention are as follows:

[0022] The refrigerated single-chip annular aperture folded imaging optical system of the present invention has a full field of view of 7°, is small in size and light in weight, has a short total length, a total optical length of 16.32 mm, a ratio of the total length of the optical element to the focal length of the system of only 0.16, and has a simple structure and is easy to assemble.

[0023] The optical system uses only one annular aperture lens. Compared with the traditional optical system, the special structure of the annular aperture system can fold the light path, which solves the problem of the large size of the traditional optical system while ensuring the imaging quality, and can realize the miniaturization of the system, and the system has fewer components and is easy to assemble and adjust. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the refrigerated single-chip annular aperture folded imaging optical system of the present invention;

[0025] Figure 2 The optical transfer function image of the present invention at the cutoff frequency of 21lp / mm; DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, a refrigerated single-piece annular aperture folded imaging optical system is provided, in which an annular aperture lens 1, a window 2, a cold aperture 3 and an imaging plane 4 are coaxially arranged in sequence.

[0028] The annular aperture lens 1 comprises, from outside to inside: annular transmission surface 1-1, annular reflection surface 1-2, annular reflection surface 2 1-3, annular reflection surface 3 1-4, annular reflection surface 4 1-5 and annular transmission surface 2 1-6.

[0029] The annular transmission surface 1-1 of the annular aperture lens 1 is used to receive the incident light beam and transmit it out;

[0030] The annular reflection surface 1-2 of the annular aperture lens is used to receive the light beam transmitted by the annular transmission surface 1-1 and perform the first reflection;

[0031] The annular reflection surface 2 1-3 of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface 1-2 and perform a second reflection;

[0032] The annular reflection surface three 1-4 of the annular aperture lens is used to receive the reflected light beam of the annular reflection surface two 1-3 and perform a third reflection;

[0033] The annular reflection surface four 1-5 of the annular aperture lens is used to receive the reflected light beam of the annular reflection surface three 1-4 and perform a fourth reflection;

[0034] The annular transmission surface 2 1-6 of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface 4 1-5 and focus the light beam.

[0035] The light beam is incident on the annular transmission surface 1-1 and is transmitted, the transmitted light is incident on the annular reflection surface 1-2 for the first reflection, the reflected light is incident on the annular reflection surface 1-3 for the second reflection, the second reflected light is incident on the annular reflection surface 1-4 for the third reflection, the third reflected light is incident on the annular reflection surface 1-5 for the fourth reflection, the fourth reflected light is incident on the annular transmission surface 1-6 for transmission, and the transmitted light passes through the window 2 and the cold aperture 3 and is finally focused on the imaging plane 4.

[0036] The annular aperture lens 1 is made of germanium, an infrared material that has high transmittance in the mid-wave infrared band and is easy to process.

[0037] The annular reflective surface 1-2, the annular reflective surface 2 1-3, the annular reflective surface 3 1-4, and the annular reflective surface 4 1-5 are coated with a medium-wave infrared high reflective film layer, and the annular transmission surface 1-1 and the annular transmission surface 2 1-6 are coated with a medium-wave infrared high reflective film layer;

[0038] The annular transmission surface 1-1, the annular reflection surface 1-2, the annular reflection surface 2 1-3, the annular reflection surface 3 1-4, the annular reflection surface 4 1-5 and the annular transmission surface 2 1-6 are all secondary aspherical surface types, and the vertices of each aspherical surface are located on the optical axis of the imaging system, and the aspherical surface type satisfies the following relationship:

[0039]

[0040] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis; c is the surface curvature of the aspherical surface, where c = 1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D, and E are aspherical coefficients.

[0041] Example:

[0042] The detector used in this device has an operating band of 3 to 5 μm, a resolution of 640×512, and a pixel size of 21 μm. The simulation is performed using the structural parameters shown in Table 1 and the even-order aspheric coefficients shown in Table 2:

[0043] Table 1 Structural parameters of optical surface

[0044] Optical surface Face type Radius of curvature thickness Material Semi-diameter Ring aperture 1 Aspheric -161.342 15.4 GERMANIUM 27 Ring aperture 2 Aspheric -57.415 -13.8 MIRROR 27 Ring aperture 3 Aspheric -83.753 11.13 MIRROR 16.5 Ring aperture 4 Aspheric 96.896 -11.78 MIRROR 16.5 Ring aperture 5 Aspheric -88.258 11.2 MIRROR 9.5 Ring aperture 6 Aspheric -514.569 2.44 7.7 window flat Inf 2 GERMANIUM 7.3 flat Inf 1 7.3 Aperture Inf 25.7 6.7 Image plane Inf 6.62

[0045] The radius of curvature in the table is the basic radius of curvature at the vertex of the optical surface, the thickness is the distance between adjacent optical surface vertices in the imaging light path, the material is the dielectric material between the optical surfaces, and the semi-diameter is the maximum light-clearance semi-aperture.

[0046] Table 2 Aspheric coefficients of optical surfaces

[0047] Optical surface A B C D E Ring aperture 1 2.717667E-06 2.683155E-09 -1.503153E-11 2.426834E-14 -1.257668E-17 Ring aperture 2 1.303332E-06 1.627886E-09 -8.034344E-12 1.275863E-14 -5.438443E-18 Ring aperture 3 -7.855453E-06 -1.348368E-08 -2.504575E-10 1.325592E-12 -1.583603E-15 Ring aperture 4 -8.014454E-05 3.027602E-07 -8.660505E-10 1.546838E-12 -1.198936E-15 Ring aperture 5 -8.364751E-05 -6.082801E-08 -7.881422E-10 8.665958E-11 -5.042862E-13 Ring aperture 6 -4.570646E-05 2.200717E-06 -4.588156E-08 5.401305E-10 -2.207453E-12

[0048] like Figure 2 As shown, at a spatial frequency of 21lp / mm, the field transfer functions of each embodiment of the present invention are greater than 0.27, approaching the diffraction limit, and the image quality is good.

Claims

1. A cooled monolithic annular aperture folded imaging optical system, characterized in that: It comprises an annular aperture lens (1), a window (2), a cold diaphragm (3) and an imaging plane (4) which are coaxially arranged in sequence; the window (2) is located behind the annular aperture lens (1); an incident light beam passes through the annular aperture lens (1), the window (2), the cold diaphragm (3), and finally focuses on the imaging plane (4); The annular aperture lens (1) comprises, from outside to inside: annular transmission surface one (1-1), annular reflection surface one (1-2), annular reflection surface two (1-3), annular reflection surface three (1-4), annular reflection surface four (1-5) and annular transmission surface two (1-6); The annular transmission surface 1 (1-1) of the annular aperture lens 1 is used to receive the incident light beam and transmit it out; The annular reflection surface 1 (1-2) of the annular aperture lens is used to receive the light beam transmitted by the annular transmission surface 1 (1-1) and perform a first reflection; The annular reflection surface 2 (1-3) of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface 1 (1-2) and perform a second reflection; The annular reflection surface three (1-4) of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface two (1-3) and perform a third reflection; The annular reflection surface four (1-5) of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface three (1-4) and perform a fourth reflection; The annular transmission surface 2 (1-6) of the annular aperture lens is used to receive the reflected light beam from the annular reflection surface 4 (1-5) and focus the light beam.

2. The refrigerated single-chip annular aperture folded imaging optical system according to claim 1, characterized in that: The light beam is incident on the annular transmission surface one (1-1) and is transmitted, the transmitted light is incident on the annular reflection surface one (1-2) for the first reflection, the reflected light is incident on the annular reflection surface two (1-3) for the second reflection, the second reflected light is incident on the annular reflection surface three (1-4) for the third reflection, the third reflected light is incident on the annular reflection surface four (1-5) for the fourth reflection, the fourth reflected light is incident on the annular transmission surface two (1-6) and is transmitted out, and the transmitted light passes through the window (2) and the cold aperture (3) and is finally focused on the imaging plane (4).

3. The refrigerated single-chip annular aperture folded imaging optical system according to claim 1, characterized in that: The material selected for the annular aperture lens (1) and the window (2) is germanium.

4. The refrigerated single-chip annular aperture folded imaging optical system according to claim 1, characterized in that: The annular reflective surface one (1-2), the annular reflective surface two (1-3), the annular reflective surface three (1-4), and the annular reflective surface four (1-5) are coated with a medium-wave infrared high reflective film layer, and the annular transmittance surface one (1-1) and the annular transmittance surface two (1-6) are coated with a medium-wave infrared high transmittance film layer.

5. The refrigerated single-chip annular aperture folded imaging optical system according to claim 1, characterized in that: The annular transmission surface one (1-1), the annular reflection surface one (1-2), the annular reflection surface two (1-3), the annular reflection surface three (1-4), the annular reflection surface four (1-5) and the annular transmission surface two (1-6) are all even-order aspheric surfaces, and the surface shape of the even-order aspheric surface satisfies the following relationship: Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis; c is the surface curvature of the aspherical surface, where c = 1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D, and E are aspherical coefficients.

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