CN217606168U - Long-wave infrared prime lens - Google Patents

Abstract

The utility model relates to an infrared detector technical field, concretely relates to infrared tight shot of long wave, including first lens, second lens, third lens, fourth lens, protection window and image planes, first lens, second lens, third lens, fourth lens, protection window and image planes set gradually along thing side to image side direction, and first lens has negative focal power, and the second lens has positive focal power, and the above structure sets up for this infrared tight shot of long wave has reduced the quantity of lens, thereby has practiced thrift the cost, and can use under abominable environment.

Description

Long-wave infrared prime lens

Technical Field

The utility model relates to an infrared detector technical field especially relates to an infrared tight shot of long wave.

Background

With the commercialization of uncooled infrared detectors, thermal infrared imaging is widely popularized in various industries, and compared with the traditional refrigerated infrared detectors, the uncooled infrared detectors are greatly reduced in cost and volume.

But compare in refrigeration infrared detector, uncooled infrared detector needs to match the lens that the clear aperture is big as far as possible, needs the lens to have less F number promptly, and the traditional camera lens that is used for refrigeration infrared detector can not adapt uncooled infrared detector.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide an infrared tight shot of long wave aims at solving the problem that the camera lens that the tradition was used for refrigeration infrared detector can not the uncooled infrared detector of adaptation.

In order to achieve the above object, the utility model provides a long wave infrared prime lens, including first lens, second lens, third lens, fourth lens, protection window and image planes, first lens the second lens the third lens the fourth lens the protection window with image planes sets gradually along thing side to image side direction, first lens has negative focal power, the second lens has positive focal power, the third lens has negative focal power, the fourth lens has positive focal power, protection window no focal power, protection window thing side and image side are the plane.

The long-wave infrared prime lens meets the following conditions: f/ENPD is more than 1.05mm and less than 1.15mm, wherein f is the effective focal length of the long-wave infrared fixed-focus lens, ENPD is the entrance pupil diameter of the long-wave infrared fixed-focus lens, and the focal length of the long-wave infrared fixed-focus lens is as follows: 11.5mm-13.5mm, the long-wave infrared focusing lens corrects aberration for long-wave infrared light with a spectral range of 8 μm-14 μm.

The first lens has a first lens object-side surface and a first lens image-side surface, the second lens has a second lens object-side surface and a second lens image-side surface, the third lens has a third lens object-side surface and a third lens image-side surface, the fourth lens has a fourth lens object-side surface and a fourth lens image-side surface, the first lens object-side surface and the second lens object-side surface are convex surfaces, the first lens image-side surface and the second lens image-side surface are concave surfaces, the first lens object-side surface, the first lens image-side surface, the second lens object-side surface, the second lens image-side surface, the fourth lens object-side surface and the fourth lens image-side surface are aspheric surfaces, and the third lens object-side surface and the third lens image-side surface are spherical surfaces.

Wherein the central thickness of the first lens is 1.976mm-2.184mm, the central thickness of the second lens is 3.5245mm-3.8955mm, the central thickness of the third lens is 2.071mm-2.289mm, the central thickness of the fourth lens is 3.306mm-3.654mm, and the central thickness of the protection window is 10.6935mm-0.7665mm.

Wherein, the distances of the air intervals between the first lens and each lens of the protection window on the optical axis are 21.489mm-23.751, 4.1515mm-4.5885, 9.5475mm-10.5525mm, 9.31mm-10.29mm and 0.7695mm-0.8505 in sequence.

The refractive index of the material of the first lens is 3.8mm-4.2mm, the refractive index of the material of the second lens is 2.4795mm-2.7405mm, the refractive index of the material of the third lens is 2.2515mm-2.4885mm, the refractive index of the material of the fourth lens is 3.8mm-4.2mm, and the refractive index of the material of the protection window is 3.23mm-3.57mm.

The utility model discloses an infrared fixed focus camera lens of long wave, through introducing multi-disc aspheric lens, compare traditional spherical lens, lens quantity has been reduced, the cost is practiced thrift, the aspheric surface far is superior to spherical lens to the ability of phase difference correction simultaneously, this infrared fixed focus camera lens of long wave all rectifies and balances various phase differences, this infrared fixed focus camera lens of long wave introduces aspheric lens, accomplish great logical light bore, it can make more infrared light formation of image at image plane to reach 1.05mm < f/ENPD < 1.15mm, simultaneously through infrared crystal material and infrared glass's reasonable collocation, realized passive athermalization under-40 ℃ -60 ℃ wide temperature, in abominable service environment, keep better imaging quality throughout, wherein, the wide temperature range to-40 ℃ -60 ℃ has carried out passive athermalization design, do not have the curve under the ordinary temperature infrared fixed focus camera lens of warm 20 ℃, low temperature-40 ℃, high temperature 60 ℃ MTF as shown in figure 3, figure 4, figure 5.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a long-wave infrared fixed-focus lens provided by the present invention.

Fig. 2 is a light path diagram of the long-wave infrared prime lens provided by the utility model.

Fig. 3 is a MTF diagram at normal temperature of 20 ℃ for a long-wave infrared prime lens provided by the present invention.

Fig. 4 is a MTF diagram at-40 ℃ of the long-wave infrared prime lens provided by the present invention.

Fig. 5 is an MTF diagram of the long-wave infrared prime lens at 60 ℃.

1-first lens, 2-second lens, 3-third lens, 4-fourth lens, 5-protective window, 6-image surface, 7-first lens object side surface, 8-first lens image side surface, 9-second lens object side surface, 10-second lens image side surface, 11-third lens object side surface, 12-third lens image side surface, 13-fourth lens object side surface and 14-fourth lens image side surface.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by referring to the drawings are exemplary intended for explaining the present invention, and should not be construed as limiting the present invention. In addition, in the description of the present invention, "a plurality" means two or more unless specifically limited otherwise.

Referring to fig. 1 to 5, the present invention provides a long-wave infrared fixed focus lens, including a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a protection window 5 and an image plane 6, wherein the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the protection window 5 and the image plane 6 are sequentially arranged along a direction from an object side to an image side, the first lens 1 has a negative focal power, the second lens 2 has a positive focal power, the third lens 3 has a negative focal power, the fourth lens 4 has a positive focal power, the protection window 5 has no focal power, and the object side and the image side of the protection window 5 are planar.

In the embodiment, by introducing a plurality of aspheric lenses, compared with the traditional spherical lens, the number of lenses is reduced, the cost is saved, meanwhile, the aspheric phase difference correction capability is far better than that of the spherical lens, the long-wave infrared fixed-focus lens corrects and balances various phase differences, the long-wave infrared fixed-focus lens introduces the aspheric lens, a large light-passing aperture is achieved, f/ENPD is more than 1.05mm and less than 1.15mm, more infrared rays can be imaged on an image surface, meanwhile, passive athermalization under wide temperature of-40 ℃ to 60 ℃ is realized through reasonable matching of infrared crystal materials and infrared glass, good imaging quality is always kept in a severe use environment, wherein passive athermalization is carried out on the wide temperature range of-40 ℃ to 60 ℃, and MTF curves of the long-wave infrared fixed-focus lens under the conditions of normal temperature, 20 ℃ at low temperature, 40 ℃ below zero and 60 ℃ at high temperature are shown in figures 3, 4 and 5.

Further, the long-wave infrared fixed-focus lens meets the following conditions: f/ENPD is more than 1.05mm and less than 1.15mm, wherein f is the effective focal length of the long-wave infrared focusing lens, ENPD is the entrance pupil diameter of the long-wave infrared focusing lens, and the focal length of the long-wave infrared focusing lens is as follows: 11.5mm-13.5mm, wherein the long-wave infrared focusing lens corrects aberration for long-wave infrared light with a spectral range of 8 μm-14 μm; the first lens element 1 has a first lens element object-side surface 7 and a first lens element image-side surface 8, the second lens element 2 has a second lens element object-side surface 9 and a second lens element image-side surface 10, the third lens element 3 has a third lens element object-side surface 11 and a third lens element image-side surface 12, the fourth lens element 4 has a fourth lens element object-side surface 14 and a fourth lens element image-side surface 15, the first lens element object-side surface 7 and the second lens element object-side surface 9 are both convex surfaces, the first lens element image-side surface 8 and the second lens element image-side surface 10 are both concave surfaces, the first lens element object-side surface 7, the first lens element image-side surface 8, the second lens element object-side surface 9, the second lens element image-side surface 10, the fourth lens element object-side surface 13, the fourth lens element image-side surface 14 is aspheric, and the third lens element object-side surface 11 and the third lens element image-side surface 12 are spherical surfaces.

In the present embodiment, from the first lens 1 to the protection window 5, the aspheric surface has a radius of curvature of 12.6825mm to 14.0175mm (i.e. 13.35mm ± 5%), 9.8135mm to 10.8465mm (i.e. 10.33mm ± 5%), 26.2485mm to 29.2485m (i.e. 27.63mm ± 5%), 566.1525mm to 625.7475m (i.e. 595.95mm ± 5%), 37.867mm to 41.853mm (i.e. 39.86mm ± 5%), 65.2175mm to 72.0825mm (i.e. 68.65mm ± 5%), and the spherical surface has a radius of curvature of: 38.9025mm-42.9975mm (namely 40.98mm +/-5%), 53.5325mm-59.1675mm (namely 56.35mm +/-5%), the long-wave infrared prime lens has a large clear aperture, the F number is 1.05-1.15, various phase differences are well corrected, the lens volume is reduced by adopting an aspheric surface and passive athermal design, good imaging quality is achieved in the temperature environment of-40 ℃ to 60 ℃, and a good lens is provided for a non-refrigeration infrared detector.

Further, the center thickness of the first lens 1 is 1.976mm-2.184mm, the center thickness of the second lens 2 is 3.5245mm-3.8955mm, the center thickness of the third lens 3 is 2.071mm-2.289mm, the center thickness of the fourth lens 4 is 3.306mm-3.654mm, and the center thickness of the protection window 5 is 10.6935mm-0.7665mm; the distances of the air intervals between the first lens 1 and the lenses of the protection window 5 on the optical axis are 21.489mm-23.751, 4.1515mm-4.5885, 9.5475mm-10.5525mm, 9.31mm-10.29mm and 0.7695mm-0.8505 in sequence; the refractive index of the material of the first lens 1 is 3.8mm-4.2mm, the refractive index of the material of the second lens 2 is 2.4795mm-2.7405mm, the refractive index of the material of the third lens 3 is 2.2515mm-2.4885mm, the refractive index of the material of the fourth lens 4 is 3.8mm-4.2mm, and the refractive index of the material of the protection window 5 is 3.23mm-3.57mm.

In this embodiment, the aspheric surface Z of the long-wave infrared fixed-focus lens adopts the following aspheric surface formula:

where Z is a distance vector from a fixed point of the aspheric surface when the aspheric surface is at a position having a height of R in the optical axis direction, c is a paraxial curvature of the aspheric surface, c =1/R (R is a curvature radius), k is a conic coefficient, and A2, A4, A6, A8, a10, a12, a14, and a16 are coefficients corresponding to high-order terms.

Table 1 high order coefficient of aspheric surface of the first lens, the second lens, the fourth lens.

Surface of

S1

S2

S3

S4

S7

S8

k

-2.01

-0.34

2.61

93.67

-93.73

-74.84

A2

0

0

0

0

0

0

A4

9.25E-05

1.28E-05

1.53E-06

1.38E-05

8.19E-05

-2.51E-05

A6

-1.06E-07

5.78E-07

-2.55E-07

-1.60E-07

-2.76E-06

-1.57E-06

A8

-6.86E-10

-2.09E-08

4.44E-09

3.69E-09

-2.36E-09

1.03E-08

A10

-1.48E-11

1.62E-10

-3.32E-11

-2.31E-11

4.69E-10

-1.57E-10

A12

8.96E-14

-1.11E-12

2.32E-14

-7.84E-14

-7.52E-12

1.32E-12

A14

-2.58E-17

4.27E-15

6.29E-16

1.22E-15

2.59E-14

-4.08E-15

A16

0

0

0

0

0

0

Wherein E-01 represents the power of-1 of 10, E-02 represents the power of-2 of 10, and so on, and E-N represents the power of-N of 10, and the figures and data show that the long-wave infrared prime lens has good correction on various aberrations of each focal segment and good imaging quality.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention.

Claims (5)

1. A long-wave infrared prime lens is characterized in that,

the optical lens comprises a first lens, a second lens, a third lens, a fourth lens, a protection window and an image plane, wherein the first lens, the second lens, the third lens, the fourth lens, the protection window and the image plane are sequentially arranged in the direction from an object side to an image side, the first lens has negative focal power, the second lens has positive focal power, the third lens has negative focal power, the fourth lens has positive focal power, the protection window has no focal power, and the object side and the image side of the protection window are both planes;

the long-wave infrared prime lens comprises: f/ENPD is more than 1.05mm and less than 1.15mm, wherein f is the effective focal length of the long-wave infrared focusing lens, ENPD is the entrance pupil diameter of the long-wave infrared focusing lens, and the focal length of the long-wave infrared focusing lens is as follows: 11.5mm-13.5mm, the long wave infrared fixed focus lens corrects aberration for long wave infrared light with a spectrum range of 8 μm-14 μm.

2. The long-wave infrared prime lens of claim 1,

the first lens has a first lens object side surface and a first lens image side surface, the second lens has a second lens object side surface and a second lens image side surface, the third lens has a third lens object side surface and a third lens image side surface, the fourth lens has a fourth lens object side surface and a fourth lens image side surface, the first lens object side surface and the second lens object side surface are convex surfaces, the first lens image side surface and the second lens image side surface are concave surfaces, the first lens object side surface, the first lens image side surface, the second lens object side surface, the second lens image side surface, the fourth lens object side surface and the fourth lens image side surface are aspheric surfaces, and the third lens object side surface and the third lens image side surface are spherical surfaces.

3. The long-wave infrared prime lens of claim 2,

the center thickness of the first lens is 1.976mm-2.184mm, the center thickness of the second lens is 3.5245mm-3.8955mm, the center thickness of the third lens is 2.071mm-2.289mm, the center thickness of the fourth lens is 3.306mm-3.654mm, and the center thickness of the protective window is 10.6935mm-0.7665mm.

4. The long-wave infrared prime lens of claim 3,

the distances of the air intervals between the first lens and the lenses of the protection window on the optical axis are 21.489mm-23.751, 4.1515mm-4.5885, 9.5475mm-10.5525mm, 9.31mm-10.29mm and 0.7695mm-0.8505 in sequence.

5. The long-wave infrared prime lens of claim 4,

the refractive index of the material of the first lens is 3.8mm-4.2mm, the refractive index of the material of the second lens is 2.4795mm-2.7405mm, the refractive index of the material of the third lens is 2.2515mm-2.4885mm, the refractive index of the material of the fourth lens is 3.8mm-4.2mm, and the refractive index of the material of the protection window is 3.23mm-3.57mm.

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