Ultra-thin medium-long wave infrared dual-waveband imaging system
阅读说明：本技术 超薄中长波红外双波段成像系统 (Ultra-thin medium-long wave infrared dual-waveband imaging system ) 是由 朴明旭 王�琦 张博 于 2020-08-12 设计创作，主要内容包括：超薄中长波红外双波段成像光学系统属于红外光学成像技术领域。现有超薄红外成像系统只能实现中波红外成像,现有中长波红外成像系统结构松散,不易制造和装配。本发明由镜体及分布在镜体两端的若干个镜面构成；在所述镜体的进光一侧,自周围至中间依次分布环带形折射镜面、环带形二次反射镜面、圆形四次反射镜面；在镜体的出光一侧,自周围至中间依次分布环带形一次反射镜面、环带形三次反射镜面、圆形折射镜面；所述六个镜面的面型均为高次非球面；所述六个镜面的高次非球面顶点均位于超薄中长波红外双波段成像光学系统光轴上；所述两个折射镜面镀有中长波红外增透膜,所述四个反射镜面镀有中长波红外反射膜；所述镜体的材质为红外硫系玻璃。(An ultra-thin medium-long wave infrared dual-waveband imaging optical system belongs to the technical field of infrared optical imaging. The existing ultrathin infrared imaging system can only realize medium-wave infrared imaging, and the existing medium-long wave infrared imaging system has a loose structure and is difficult to manufacture and assemble. The invention is composed of a mirror body and a plurality of mirror surfaces distributed at two ends of the mirror body; the light-entering side of the mirror body is sequentially provided with an annular refraction mirror surface, an annular secondary reflection mirror surface and a round four-time reflection mirror surface from the periphery to the middle; on the light emergent side of the mirror body, an annular primary reflecting mirror surface, an annular tertiary reflecting mirror surface and a circular refracting mirror surface are sequentially distributed from the periphery to the middle; the surface types of the six mirror surfaces are all high-order aspheric surfaces; the high-order aspheric vertexes of the six mirrors are all positioned on the optical axis of the ultrathin medium-long wave infrared dual-band imaging optical system; the two refraction mirror surfaces are plated with medium-long wave infrared antireflection films, and the four reflection mirror surfaces are plated with medium-long wave infrared reflection films; the mirror body is made of infrared chalcogenide glass.)
1. An ultra-thin medium-long wave infrared two-waveband imaging optical system comprises a mirror body (1) and a plurality of mirror surfaces distributed at two ends of the mirror body (1), and is characterized in that an annular refraction mirror surface (2), an annular secondary reflection mirror surface (3) and a round fourth reflection mirror surface (4) are sequentially distributed from the periphery to the middle on the light inlet side of the mirror body (1); the light-emitting side of the mirror body (1) is sequentially provided with an annular primary reflecting mirror surface (5), an annular tertiary reflecting mirror surface (6) and a circular refracting mirror surface (7) from the periphery to the middle; the surface types of the six mirror surfaces are all high-order aspheric surfaces, and the equation of the high-order aspheric surfaces is as follows:
in the formula, z is the rise of the high-order aspheric surface, c is the basic curvature at the vertex of the high-order aspheric surface, r is the radial coordinate of a point on the high-order aspheric surface, k is a conic constant, and A, B, C, D, E and … are aspheric coefficients; the high-order aspheric vertexes of the six mirrors are all positioned on the optical axis of the ultrathin medium-long wave infrared dual-band imaging optical system; the two refraction mirror surfaces are plated with medium-long wave infrared antireflection films, and the four reflection mirror surfaces are plated with medium-long wave infrared reflection films; the mirror body is made of infrared chalcogenide glass.
Technical Field
The invention relates to an ultra-thin medium-long wave infrared dual-waveband imaging optical system which is compact in optical structure and ultra-thin in mirror body and belongs to the technical field of infrared optical imaging.
Background
The infrared imaging technique uses the radiation temperature difference generated between the detected target and the background to collect information and form a corresponding scene image. With the development of the infrared imaging technology, the single-waveband infrared imaging optical system can not meet the detection requirement of a complex scene gradually and is easily interfered by external unstable factors, and the dual-waveband infrared imaging optical system can perform more comprehensive imaging on the scene from two wavebands and has stronger resistance to external interference. However, the conventional refractive dual-band infrared imaging optical system has a large size, and in some special occasions, such as an unmanned aerial vehicle, the size and the weight of the conventional refractive dual-band infrared imaging optical system are strictly limited, so that the conventional refractive dual-band infrared imaging optical system is difficult to meet the requirements of ultra-thinness and light weight.
The utility model discloses a chinese utility model patent that publication number is CN202421617U discloses a technical scheme named "infrared two band harmonic diffraction optical system", and this scheme comprises four lens, and wherein the front surface of second lens is the harmonic diffraction face, and all the other each faces are the sphere, and this scheme has realized the formation of image to two infrared bands of medium-long wave. Although the optical system introduces harmonic diffraction surfaces to simplify the optical system structure, the optical structure of the system is complicated by four lenses, and the ratio of the axial dimension of the system to the focal length of the system is as high as 1.28, which is far from the ultra-thin degree.
An article entitled "design of ultra-compact monolithic imaging optical system" published in optics journal (2015,35(04): 331-337) provides an ultra-compact monolithic imaging optical system suitable for medium-wave infrared, which is characterized in that the front surface and the rear surface of a monolithic lens are processed in regions, and are respectively coated with an internal reflection film and an anti-reflection film to form two reflection surfaces and two transmission surfaces to form a refraction and reflection integrated lens, and the whole optical system is integrated on one lens, so that the structure is simple. Although the ratio of the axial size of the system to the focal length of the system is reduced to 0.62 by adopting the secondary reflection mode, the ratio is close to the ultra-thin degree; in addition, the optical system can only realize imaging of a single waveband of medium-wave infrared.
The document "Design of an ultra-thin band-free system" (DuK, ChengX, LvQ, et al. Design of an ultra-thin band-free system [ C ]// Optical Design of testing VI. International Society for optics and photonics 2014:92720U-92720U-6.) proposes a four fold reflection ultra-thin dual band infrared system applying the folded Optical system to the field of infrared imaging. In order to maintain the collection of light, the multiple reflection type optical system has larger external aperture, is more suitable for being used as an uncooled image sensor in infrared optics, and can effectively reduce the cost and the weight of the optical system. Because the optical path is folded by multiple reflections, the optical system can be very compact while maintaining good image quality. The F number of the ultrathin dual-waveband infrared system is 2, the outer diameter is 80mm, and the ratio of the axial size of the system to the focal length of the system is further reduced to 0.233, which is consistent with the ultrathin system. The ultrathin dual-waveband infrared system also adopts four aluminum mirror body reflectors, and does not generate chromatic aberration. Nevertheless, the solution still has its unsatisfactory points, including that the four mirrors are different, which is not conducive to mass production; the four reflectors need to be installed and fixed by using a support, so that the installation and adjustment difficulty of the system is increased, the support is easy to deform after being stressed, and the imaging quality is reduced.
Disclosure of Invention
In order to realize medium-long wave infrared dual-band imaging, and simultaneously enable an imaging system to be compact in structure, easy to manufacture and assemble, high in imaging quality and stable, the invention provides an ultrathin medium-long wave infrared dual-band imaging optical system.
The ultra-thin medium-long wave infrared two-waveband imaging optical system consists of a
in the formula, z is the rise of the high-order aspheric surface, c is the basic curvature at the vertex of the high-order aspheric surface, r is the radial coordinate of a point on the high-order aspheric surface, k is a conic constant, and A, B, C, D, E and … are aspheric coefficients; the high-order aspheric vertexes of the six mirrors are all positioned on the optical axis of the ultrathin medium-long wave infrared dual-band imaging optical system; the two refraction mirror surfaces are plated with medium-long wave infrared antireflection films, and the four reflection mirror surfaces are plated with medium-long wave infrared reflection films; the mirror body is made of infrared chalcogenide glass.
The six mirror surfaces are integrated on the same mirror body and are line-symmetric revolution curved surfaces taking the optical axis as a symmetric line, the structure of the imaging system is very compact, although the structure is slightly complex, once the design is finished, and the material of the mirror body is infrared chalcogenide glass and is a material suitable for precision die pressing, so that the imaging optical system is an optical device capable of being manufactured in batches, and the manufacturing cost is also very low. The mirror surfaces forming the imaging optical system are integrated at two ends of one mirror body, and once manufacturing is finished, so that installation and debugging are not involved, and imaging quality reduction caused by structural change of the imaging optical system in the using process is avoided.
As shown in FIG. 1, the diaphragm of the ultra-thin medium-long wave infrared dual-band imaging optical system of the present invention is located at the
In the imaging process of double-folding and four-reflecting, all the mirror surfaces are high-order aspheric surfaces, and by combining an infrared coating technology and selection of mirror body materials, the invention realizes high-quality imaging in the medium-wave infrared band of 3-5 mu m and the long-wave infrared band of 7.7-10 mu m.
Drawings
FIG. 1 is a schematic sectional view of the structure of an ultra-thin medium-long wave infrared dual-band imaging optical system of the present invention, and is also a schematic view of an imaging optical path, which is also taken as an abstract figure. FIG. 2 is a perspective view of the light-entering side of the lens body of the ultra-thin medium-long wave infrared dual-band imaging optical system of the present invention. FIG. 3 is a perspective view of the light exit side of the lens body of the ultra-thin medium-long wave infrared dual-band imaging optical system of the present invention. FIG. 4 is a graph showing a 3-5 μm modulation transfer function curve of a mid-wave infrared band of the ultra-thin mid-long wave infrared dual-band imaging optical system of the present invention. FIG. 5 is a 7.7-10 μm long-wave infrared band modulation transfer function curve diagram of the ultra-thin medium-long-wave infrared two-band imaging optical system of the present invention.
Detailed Description
Part of parameters of a design example of the ultrathin medium-long wave infrared dual-waveband imaging optical system are shown as the following table:
c in the table is the basic curvature at the vertex of the high-order aspheric surface, the pitch in the table refers to the distance between the vertices of the adjacent mirror surfaces in the imaging optical path, and the material in the table is the dielectric material between the optical surfaces.
Aspherical surface coefficients of respective mirrors in the design example
Mirror surface
A
B
C
D
E
Annular
0.000
2.816E-007
-1.747E-010
9.717E-014
-5.795E-017
Annular primary reflecting
0.000
2.998E-007
6.490E-011
-4.079E-014
0.000
Annular secondary
0.000
2.726E-006
-1.647E-009
5.676E-013
0.000
Annular triple reflecting
0.000
1.203E-006
-1.849E-009
-8.699E-012
3.463E-014
Circular four-times reflecting
0.000
-2.732E-006
-1.238E-009
-5.972E-011
4.078E-013
Circular refracting mirror 7
0.000
-9.598E-005
4.670E-006
-1.023E-007
8.236E-010
In the design example, each mirror surface is an axisymmetric aspheric surface, and can correct off-axis aberration; the diaphragm is positioned at the annular
The modulation transfer function curves of all fields of view of the design example are close to the diffraction limit, the MTF value of 20 line pairs/mm of characteristic frequency in the middle-wave infrared band of 3-5 mu m is larger than 0.45, as shown in figure 4, the MTF value of 20 line pairs/mm of characteristic frequency in the long-wave infrared band of 7.7-10 mu m is larger than 0.30, as shown in figure 5, and high-quality imaging is achieved.