CN205809398U - A kind of large aperture long wave double-view field infrared optical lens - Google Patents

Abstract

The utility model discloses a kind of large aperture long wave double-view field infrared optical lens, described lens optical system is sequentially provided with from thing lateral image side incident direction along light before there is positive light coke and fixes group, for a piece of falcate germanium plus lens convex surface facing thing side；There is the zoom group of negative power, for a piece of concave concave germanium minus lens, be used for switching visual field；Group is fixed, for a piece of lenticular germanium plus lens after there is the first of positive light coke；Fix group after there is the second of positive light coke, form for a piece of falcate germanium plus lens convex surface facing image space.This optical system can in two visual fields of 50/150mm in image quality good, and be capable of focal length and be switched fast.

Description

A large-aperture long-wave dual-field infrared optical lens

technical field

The utility model relates to the field of optical technology, in particular to a large-aperture long-wave double-view infrared optical lens.

Background technique

Infrared technology can be applied to the detection of targets at night and under adverse weather conditions such as smoke, fog and dust, so as to realize all-weather observation.

The dual field of view infrared optical lens has two fields of view, wide and narrow, which can meet the functions of detection and identification respectively. The wide field of view is used for target detection and the narrow field of view is used for target identification.

For bad weather conditions, it is hoped that more energy will enter the optical system to be detected, thereby increasing the imaging contrast. In terms of optical principles, the Eliban diameter becomes smaller as the aperture increases, which means higher resolution. Therefore, a lens with a large aperture is required.

Contents of the invention

The utility model provides a large-aperture long-wave dual-field infrared optical lens, which solves the above-mentioned problems, and its technical scheme is as follows:

A long-wave infrared dual-field infrared optical lens, which sequentially includes a front fixed group, a zoom group, a first rear fixed group, and a second rear fixed group from the object side to the image side;

The front fixation group has a positive diopter and converges light, including a meniscus germanium positive lens with a convex surface facing the object side;

The zoom group has a negative diopter and is used for focal length switching, including a double-concave germanium negative lens; the second surface of the zoom group adopts a diffractive surface;

The first rear fixation group has a positive diopter and includes a biconvex germanium positive lens;

The second rear fixation group has a positive diopter and includes a positive meniscus germanium lens with a convex surface facing the image side.

The first surface of the first rear fixation group adopts a high-order aspheric surface.

The first surface of the second rear fixation group adopts a high-order aspheric surface.

The working band of the long-wave infrared dual-field infrared optical lens is 8-12um.

The long-wave infrared dual-field-of-view infrared optical lens has an F number of 1 when it is telephoto, and an F number of 0.9 when it is short.

Among them, F/# refers to the ratio of the diameter of the lens to the focal length, which is an optical term and has no unit.

The optical system is adapted to a detector with a resolution of 640×480 and a pixel size of 17 μm.

The optical system has good imaging quality in two fields of view of 50/150mm, and can realize fast switching of focal length.

Description of drawings

Fig. 1 is the utility model narrow field of view, long focal length optical path figure;

Fig. 2 is the optical path diagram of the utility model wide field of view and short focal length;

Fig. 3 is the narrow field of view of the utility model, long focal length diffuse pattern;

Fig. 4 is a wide field of view, short focal length diffuse pattern of the utility model;

Fig. 5 is the utility model narrow field of view, long focal length optical transfer function figure, and cut-off resolution is 2011p/mm;

Fig. 6 is the optical transfer function figure of the utility model wide field of view, short focal length, and the cut-off resolution is 2011p/mm;

Fig. 7 is the astigmatic distortion diagram of the utility model with a narrow field of view and a long focal length;

Fig. 8 is an astigmatic distortion diagram of the utility model with wide field of view and short focal length;

Among them, 110-object space, L1-front fixed group, 111-aperture, L2-zoom group, L3-first rear fixed group, L4-second rear fixed group, 112-protection window, 113-detector protection Window, 114-image plane, S1-S8 are the respective surfaces of the lens.

detailed description

In the utility model, the first meniscus positive lens L1, the second double-concave negative lens L2, the third double-convex positive lens L3, the fourth meniscus positive lens L4, the protection window 112 and the image surface 113 are arranged sequentially from the object side to the image side. , the second negative lens can move axially between the first lens L1 and the third lens L3 to respectively form a narrow field of view light path and a wide field of view light path.

When the optical system is in short focus, the external radiation converges to the focal plane of the detector through the front fixed group, zoom group and rear fixed group; when the optical system is in long focus, the external radiation passes through the front fixed group, zoom group, first rear fixed group The fixed group, the second rear fixed group converges on the detector focal plane.

The large-aperture long-wave dual-field infrared optical lens provided by the utility model adopts a high-order aspheric surface and a diffraction surface to improve the image quality of the system, so that the total length of the optical path of the system is shorter and the weight is lighter. Since the movement of a lens is used to realize the conversion of the field of view and focus compensation, the movement mechanism in the system is reduced, and the difficulty of installation and adjustment is reduced.

And meet the following parameters:

The effective focal length of the long-wave infrared dual-field optical lens is EFL=50/150mm, the F-number=0.9/1, the total length of the optical system=220mm, the resolution of the adapted detector is 640×480, and the pixel size is 17 μm.

Below in conjunction with accompanying drawing, the utility model is described in further detail through embodiment.

It should be understood that the specific embodiments described here are only used to explain the utility model, and are not limited to the utility model.

Fig. 1, Fig. 2 are respectively the optical system figure of the present utility model when the focal length is 150mm and 50mm, and the structure of described lens is the same, one of them is taken as an example as illustration.

As shown in Figure 1, this embodiment consists of a front fixed group L1 with positive refractive power, a zoom group L2 with negative refractive power, and rear fixed groups L3 and L4 with positive refractive power.

The front fixed group L1 is the first lens, which is a positive lens with a convex surface facing the object side. The material is germanium single crystal. This lens has a large aperture, so no aspheric surface is used;

The variable power group L2 is the second lens, which is a double-concave negative lens, and the material is germanium single crystal, and the surface of S4 is a diffractive surface. The lens is a moving lens, which plays the role of zooming and focusing, and the total moving stroke is 39.6mm;

The first rear fixed group L3 is the third lens, which is a biconvex positive lens, the material is germanium single crystal, and the surface of S5 is aspherical;

The second rear fixed group-L4 is the fourth lens, which is a meniscus positive lens with a convex surface facing the image side, and the material is germanium single crystal, and the surface of S7 is aspherical.

The light passes through the detector protection window 112 and is imaged on the image plane 113 with a resolution of 640x480 and a pixel size of 17μ.

Among the above four lenses, the surface of the first lens S1 is coated with a diamond-like carbon film. Because the surface is exposed, the carbon film needs to be coated with a diamond-like carbon film for protection.

Table 1 is the optical structure parameter of the utility model at focal length 150mm, 50mm:

Table 1

The aspheric surfaces mentioned in the above 4 lenses are all even-order aspheric surfaces, and their expressions are as follows:

$\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; cr</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}$

Where z is the distance sagittal height of the aspheric surface from the apex of the aspheric surface at a position of height r along the optical axis, c is the vertex curvature of the surface, k is the conical coefficient, α ₂ , α ₃ , α ₄ , α ₅ , α ₆ is the high-order aspheric coefficient.

Table 2 shows the aspheric coefficients of surfaces S4, S5, and S7:

Table 2

The expression of the diffractive surface mentioned in the above four lenses is as follows:

Φ＝A ₁ ρ ² +A ₂ ρ ⁴

Where Φ is the phase of the diffraction surface, ρ=r/r _n , r _n is the planned radius of the diffraction surface, and A1 and A2 are the phase coefficients of the diffraction surface.

Table 3 shows the diffraction coefficient of surface S3:

table 3

surface S4 -34.83 3.381

Finally, it should be noted that the above embodiments are only used to illustrate the utility model rather than limit the technical solution described in the utility model. Therefore, although the specification has described the utility model in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the utility model can still be modified or equivalently replaced; and everything does not depart from the utility model The technical solutions in the spirit and scope and their improvements should all be included in the scope of the claims of the present utility model.

Claims (6)

1. A long-wave infrared dual-field of view infrared optical lens is characterized in that, from the object side to the image side, it comprises successively a front fixed group, a zoom group, the first rear fixed group, and the second rear fixed group; The front fixation group has a positive diopter and converges light, including a meniscus germanium positive lens with a convex surface facing the object side; The zoom group has a negative diopter and is used for focal length switching, including a double-concave germanium negative lens; the second surface of the zoom group adopts a diffractive surface; The first rear fixation group has a positive diopter and includes a biconvex germanium positive lens; The second rear fixation group has a positive diopter and includes a positive meniscus germanium lens with a convex surface facing the image side. 2. The long-wave infrared dual-field infrared optical lens according to claim 1, wherein the first surface of the first rear fixing group adopts a high-order aspheric surface. 3. The long-wave infrared dual-field infrared optical lens according to claim 1, wherein the first surface of the second rear fixing group adopts a high-order aspheric surface. 4 . The long-wave infrared dual-field infrared optical lens according to claim 1 , characterized in that, the working band of the long-wave infrared dual-field infrared optical lens is 8-12um. 5. The long-wave infrared dual-field infrared optical lens according to claim 1, characterized in that, the long-wave infrared dual-field infrared optical lens has an F-number=1 when it is telephoto, and an F-number=0.9 when it is short-focus. 6. The long-wave infrared dual-field infrared optical lens according to claim 1, wherein the long-wave infrared dual-field infrared optical lens is adapted to a detector with a resolution of 640×480 and a pixel size of 17 μm.