Disclosure of Invention
The application aims to solve the problems and provides a light small-sized medium-wave infrared refrigeration zoom lens.
The application provides a light small-sized medium wave infrared refrigeration continuous zoom lens, wherein a lens arranged in the lens sequentially comprises a front fixed group, a zoom group, a compensation group, a focusing group, a rear fixed group and a detector from an object space to an image space;
the front fixed group comprises a first lens; the first lens has positive focal power, is a meniscus silicon single crystal positive lens with a convex surface facing an object space, and has two spherical surfaces;
the variable power group comprises a second lens; the second lens has negative focal power, is a biconcave germanium single crystal negative lens, and one side of the second lens facing the object space is an aspheric surface; the total moving stroke of the second lens is 27.779 mm;
the compensation group comprises a third lens; the third lens has positive focal power, is a biconvex zinc selenide positive lens, and has an aspheric surface on one side facing the image side; the total moving stroke of the third lens is 20.398 mm;
the focusing group comprises a fourth lens; the fourth lens has positive focal power, is a meniscus germanium single crystal positive lens with a convex surface facing the object space, and has a concave surface as a diffraction surface; the total moving stroke of the fourth lens is 0.55 mm;
the rear fixed group comprises a fifth lens and a sixth lens; the fifth lens has positive focal power, is a meniscus germanium single crystal positive lens with a convex surface facing to an image space, and has a diffraction surface; the sixth lens is positioned behind the fifth lens and is a meniscus germanium single crystal positive lens with a convex surface facing the image space, and the convex surface of the positive lens is an aspheric surface;
the detector comprises a protection window, a cold screen, a cold diaphragm and an image surface which are sequentially arranged; the cold stop remains constant during zooming.
According to the technical scheme provided by some embodiments of the present application, the lens satisfies the following parameters:
the effective focal length EFL of the lens is 30-240 mm, the F number is 4, the total length of the optical system is 142mm, the resolution of the adaptive detector is 640 multiplied by 512, the pixel size is 15 mu m, and the adaptive waveband is 3.7-4.8 mu m.
According to the technical scheme provided by some embodiments of the present application, the horizontal field angle range of the lens is as follows: 2W is 18.2 to 2.3 °.
According to the technical scheme provided by some embodiments of the present application, an aspheric surface in a lens of the lens satisfies the following expression:
wherein z is the height of the aspheric surface along the optical axisWhen the degree is the position of r, the rise of the distance from the vertex of the aspheric surface is obtained; c represents the apex curvature of the surface; k is a conic coefficient; alpha is alpha2、α3、α4、α5、α6Are high-order aspheric coefficients.
According to the technical scheme provided by some embodiments of the application, the diffraction surface in the lens of the lens meets the following expression:
Φ=A1ρ2+A2ρ4
where Φ is the phase of the diffraction plane, and ρ is r/rn,rnIs the planned radius of the diffraction plane, A1、A2Is the phase coefficient of the diffraction plane.
According to the technical scheme provided by certain embodiments of the application, the surface of the first lens close to the object side is plated with the diamond-like carbon film.
According to the technical scheme provided by some embodiments of the application, the average MTF of the full field of view of the lens is greater than 0.49@20 lp/mm.
Compared with the prior art, the beneficial effect of this application: the light small-sized medium wave infrared refrigeration continuous zoom lens totally adopts six lenses, has a zoom ratio of 8 times, has an optical system total length of 142mm and a maximum caliber of 66mm, has a compact structure, relatively reduces weight and volume, has a smooth zooming curve, has a maximum lens moving amount of 27.779mm, can realize continuous zooming in a larger range (30-240 mm), and has a good imaging effect in the whole zooming range; the zoom group and the compensation group only adopt one lens, so that the stability of an optical axis in the zooming process can be better ensured.
Detailed Description
The following detailed description of the present application is given for the purpose of enabling those skilled in the art to better understand the technical solutions of the present application, and the description in this section is only exemplary and explanatory, and should not be taken as limiting the scope of the present application in any way.
The embodiment is an example of the application of the method and the device in a staring focal plane detector with a medium wave refrigeration type resolution of 640 x 512 and a pixel size of 15 mu m.
Fig. 1 and fig. 5 are optical system diagrams of the light and small medium wave infrared refrigeration zoom lens provided by the present application at focal lengths of 240mm and 30mm, respectively, the structures of the lenses are the same, and one of the lenses is taken as an example to be specifically described as follows.
As shown in fig. 1, the present application provides a light and small medium wave infrared refrigeration zoom lens, where a lens set in the lens includes, in order from an object space to an image space, a front fixed group, a zoom group, a compensation group, a focusing group, a rear fixed group, and a detector; the direction from the object space to the image space is from front to back; the object space is an object space 100; the front fixed group includes a first lens L1; the first lens L1 has positive focal power, is a meniscus positive lens with a convex surface facing the object space, is made of silicon single crystal, and has spherical surfaces on two surfaces S1 and S2; the variable power group includes a second lens L2; the second lens L2 has negative focal power, is a double concave negative lens, is made of germanium single crystal, and has two surfaces of S3 and S4, wherein the surface of the second lens L2 facing the object side, namely the surface of S3, is aspheric; the second lens L2 is a movable lens which plays a role in zooming, the moving curve of the second lens is 8-time parabola, and the total moving stroke is 27.779 mm; the compensation group comprises a third lens L3; the third lens L3 has positive focal power, is a biconvex positive lens, is made of zinc selenide, and has two surfaces S5 and S6, wherein the side facing the image, i.e., the surface S6, is aspheric; the third lens L3 is a movable lens, when a variable power lens group, namely the second lens L2, moves, the third lens L3 correspondingly moves to ensure that the position of an image plane remains unchanged, the moving curve of the third lens L3 is a straight line, and the total moving stroke is 20.398 mm; the focusing group includes a fourth lens L4; the fourth lens L4 has positive focal power, is a meniscus positive lens with a convex surface facing the object space, is made of germanium single crystal, and has two surfaces S7 and S8 respectively, wherein the concave surface S8 surface is a diffraction surface; the fourth lens L4 is a moving lens, and can be used for refocusing when the target distance changes and the working temperature changes, and the total moving stroke of the fourth lens is 0.55 mm; the rear fixed group includes a fifth lens L5 and a sixth lens L6; the fifth lens L5 has positive focal power, is a meniscus positive lens with a convex surface facing the image space, is made of germanium single crystal, and has two surfaces S9 and S10 respectively, wherein the convex surface (the surface S10) is a diffractive aspheric surface; the sixth lens element L6 is located behind the fifth lens element L5, and is a positive meniscus lens with a convex surface facing the image space, the positive meniscus lens element is made of germanium single crystal, and two surfaces of the positive meniscus lens element are S11 and S12, respectively, wherein the convex surface, i.e., the surface of S12, is aspheric; the detector is a medium wave refrigeration detector and comprises a protection window 101, a cold screen 102, a cold diaphragm S13 and an image plane 103 which are sequentially arranged from left to right; the cold stop S13 remains constant during zooming.
Further, the lens satisfies the following parameters: the effective focal length EFL of the lens is 30-240 mm, the F number is 4, the total length of the optical system is 142mm, the adaptive detector resolution is 640 multiplied by 512, the pixel size is 15 mu m, the adaptive waveband is 3.7-4.8 mu m, and the imaging plane is 12.3 mm.
Further, the horizontal field angle range of the lens is as follows: 2W is 18.2 to 2.3 °.
Table 1 shows the optical structure parameters of the light and small medium wave infrared refrigeration zoom lens according to the present application at focal lengths of 240mm and 30 mm:
TABLE 1
Further, the aspheric surfaces of the six lenses, i.e., the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6, are even aspheric surfaces, and the expressions thereof are as follows:
wherein z is the rise of the distance from the vertex of the aspheric surface when the aspheric surface is at the position with the height of r along the optical axis direction; c represents the apex curvature of the surface; k is a conic coefficient; alpha is alpha2、α3、α4、α5、α6Are high-order aspheric coefficients.
Table 2 shows aspheric coefficients of the surfaces S3, S6, S8, S10, and S12:
TABLE 2
Surface of
|
4th
|
6th
|
8th
|
10th
|
12th
|
14th
|
S3
|
2.058E-06
|
-4.343E-09
|
2.636E-11
|
-1.032E-13
|
1.642E-16
|
0
|
S6
|
3.105E-06
|
-3.576E-09
|
1.591E-11
|
-4.666E-14
|
5.628E-17
|
0
|
S8
|
-3.664E-06
|
8.95E-07
|
-5.671E-08
|
2.154E-09
|
-4.164E-11
|
3.308E-13
|
S10
|
2.498E-04
|
8.437E-07
|
4.906E-07
|
-3.48E-08
|
1.577E-09
|
-2.569E-11
|
S12
|
-2.212E-05
|
3.731E-07
|
-9.152E-09
|
7.786E-11
|
-2.333E-13
|
0 |
Further, the diffraction surfaces mentioned in the six lenses of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 satisfy the following expressions:
Φ=A1ρ2+A2ρ4
where Φ is the phase of the diffraction plane, and ρ is r/rn,rnIs the planned radius of the diffraction plane, A1、A2Is the phase coefficient of the diffraction plane.
Table 3 is the diffraction coefficients for surface S10 and surface S12:
TABLE 3
Surface of
|
A1 |
A2 |
S10
|
-38.713
|
-8.146
|
S12
|
-55.058
|
-29.247 |
Furthermore, the surface of the first lens L1 close to the object space, namely the surface of S1, is plated with a diamond-like carbon film, because the surface of S1 is exposed, the diamond-like carbon film needs to be plated to play a role in protection, and the rest surfaces of S2-S12 are plated with antireflection films.
Further, the average MTF of the full field of view of the lens is >0.49@20 lp/mm.
The effects of the present application are described in further detail below with reference to aberration analysis charts.
Fig. 2-4 are aberration analysis graphs of the embodiment of the light, small-sized medium wave infrared refrigerating zoom lens in fig. 1 in a telephoto state, that is, a focal length of 240mm, where fig. 2 is a point diagram, fig. 3 is an MTF graph, and fig. 4 is a field curvature distortion graph.
Fig. 6-8 are aberration analysis graphs of the embodiment of the light, small-sized medium wave infrared refrigerating zoom lens system illustrated in fig. 5 in a short-focus state, i.e., a focal length of 30mm, wherein fig. 6 is a point diagram, fig. 7 is an MTF graph, and fig. 8 is a field curvature distortion graph.
It can be found from the figure that various aberrations of each focal segment are well corrected, the diffuse spots are all corrected to be close to the size of the Airy spots, the MTF is good, the distortion is less than 2%, and the human eyes have no obvious distortion feeling.
The light and small medium-wave infrared refrigeration continuous zoom lens provided by the embodiment of the application can be applied to a staring type focal plane detector with medium-wave refrigeration resolution of 640 multiplied by 512 and pixel size of 15 mu m; the light small-sized medium wave infrared refrigeration continuous zoom lens totally adopts six lenses, has a zoom ratio of 8 times, has an optical system total length of 142mm and a maximum caliber of 66mm, has a compact structure, relatively reduces weight and volume, has a smooth zooming curve, has a maximum lens moving amount of 27.779mm, can realize continuous zooming in a larger range (30-240 mm), and has a good imaging effect in the whole zooming range; the zoom group and the compensation group only adopt one lens, so that the stability of an optical axis in the zooming process can be better ensured.
The principles and embodiments of the present application are explained herein using specific examples, which are provided only to help understand the method and the core idea of the present application. The foregoing is only a preferred embodiment of the present application, and it should be noted that there are no specific structures which are objectively limitless due to the limited character expressions, and it will be apparent to those skilled in the art that a plurality of modifications, decorations or changes can be made without departing from the principle of the present invention, and the technical features mentioned above can be combined in a suitable manner; such modifications, variations, combinations, or adaptations of the invention in other instances, which may or may not be practiced, are intended to be within the scope of the present application.