CN115356826A - Large-target-surface low-distortion athermal infrared lens - Google Patents
Large-target-surface low-distortion athermal infrared lens Download PDFInfo
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- CN115356826A CN115356826A CN202210953591.9A CN202210953591A CN115356826A CN 115356826 A CN115356826 A CN 115356826A CN 202210953591 A CN202210953591 A CN 202210953591A CN 115356826 A CN115356826 A CN 115356826A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
- G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
- G02B13/004—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having four lenses
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/008—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras designed for infrared light
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/06—Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
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Abstract
The invention belongs to the technical field of infrared optics and discloses a large-target-surface low-distortion heat difference eliminating infrared lens. The lens comprises a first lens, a second lens, a third lens and a fourth lens which are coaxially arranged from an object side to an image side in sequence; the first lens is a meniscus lens with negative focal power and a convex surface facing to the object side; the second lens is a meniscus lens with positive focal power and a convex surface facing the object side; the third lens is a meniscus lens with positive focal power and a convex surface facing to the image side; the fourth lens has a meniscus lens with a positive focal power and a convex surface facing the image side. The lens has wide field range, large target surface and low distortion, can effectively correct aberration, and has good marginal image quality and clear observation; the heat dissipation effect is good, the temperature requirement of a working environment from minus 40 ℃ to 80 ℃ can be met, and the thermal stability is good; the method is particularly suitable for large-range monitoring in the field of security monitoring.
Description
Technical Field
The invention belongs to the technical field of infrared optics, and particularly relates to a large-target-surface low-distortion athermal infrared lens.
Background
As security monitoring systems become more and more popular and high-end, various performances of the monitoring lens, including field angle, clear aperture, pixels, image plane size, etc., need to be further optimized. As one of the monitoring lenses, the wide-angle infrared lens has the characteristic of wide short-focus field coverage, and is increasingly widely applied. However, the distortion is high, the well-controlled distortion is generally between 40% and 50%, the resolution of the edge of the image surface is not high, the aberration is difficult to correct, the quality of the edge image is difficult to control, and the difficulty of the optical design is large.
Moreover, temperature has a certain influence on both optical materials and mechanical materials, which causes focal length variation, image plane drift, optical imaging quality degradation, image blur, and finally affects the imaging performance of the lens. In order to adapt the lens to different environments, the lens needs to have certain temperature adaptability.
Therefore, how to realize large target surface and low distortion while ensuring the heat dissipation difference is a difficult problem to be solved urgently in the field at the present stage.
Disclosure of Invention
In order to solve the problems, the invention provides the infrared lens with the large target surface and the low distortion athermal difference, which can realize passive athermal difference elimination and has the characteristics of large field angle range, large target surface and small distortion. The specific technical scheme is as follows.
A large-target-surface low-distortion athermal infrared lens comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object space to an image space, wherein the first lens is a meniscus lens with negative focal power, and a convex surface facing the object side; the second lens is a meniscus lens with positive focal power and a convex surface facing to the object side; the third lens is a meniscus lens with positive focal power and a convex surface facing the image side; the fourth lens is a meniscus lens with positive focal power and a convex surface facing the image side. From an object space to an image space along an optical axis, two surfaces of the first lens are a first object side surface and a first image side surface in sequence, two surfaces of the second lens are a second object side surface and a second image side surface in sequence, two surfaces of the third lens are a third object side surface and a third image side surface in sequence, two surfaces of the fourth lens are a fourth object side surface and a fourth image side surface in sequence, and the first image side surface, the third image side surface and the fourth object side surface are aspheric surfaces.
Preferably, the aspheric surfaces of the first image-side surface, the third image-side surface and the fourth object-side surface all satisfy the following formula,
wherein, Z is the distance rise from the vertex of the aspheric surface when the aspheric surface is at the position of the height r along the optical axis direction; c =1/R, R being the paraxial curvature fitting radius of the mirror surface; k is a conic coefficient; a, B, C, D and E are high-order aspheric coefficients.
Preferably, the first lens is a germanium material, the second lens is a zinc sulfide material, the third lens is an IRG206 material, and the fourth lens is an IRG209 material.
Preferably, the curvature radius of the first object-side surface is 20.37mm, the fitted curvature radius of the first image-side surface is 12.33mm, the curvature radius of the second object-side surface is 31.35mm, the fitted curvature radius of the second image-side surface is 60.71mm, the curvature radius of the third object-side surface is-119.8 mm, the fitted curvature radius of the third object-side surface is-27 mm, the curvature radius of the fourth object-side surface is-43.3 mm, and the fitted curvature radius of the fourth object-side surface is-27.86 mm.
Preferably, the central thickness of the first lens is 4mm, the central thickness of the second lens is 6mm,
the third lens has a central thickness of 4mm and the fourth lens has a central thickness of 3mm.
Preferably, the center distance between the first lens and the second lens is 13.26mm, the diaphragm is arranged between the second lens and the third lens, the center distance between the second lens and the diaphragm is 2.8mm, the center distance between the diaphragm and the third lens is 2.32mm, and the center distance between the third lens and the fourth lens is 7.84mm.
Preferably, a germanium protection window and a detector image plane are sequentially arranged on the image side of the fourth lens, and the distance between the fourth lens and the focal plane is 12.73mm.
Preferably, the second image-side surface is a binary surface, the expression of which is,
where M is a diffraction order, the diffraction order is 1, B1 and B2 are binary surface phase coefficients, B1= -106.16, B2=53.22, and the value of the normalization radius ρ is 10.
Preferably, the working waveband of the lens is 8-12 μm, the F number is 1.2, the horizontal field angle is 70 degrees, and the vertical field angle is 58 degrees.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention realizes large target surface and low distortion, the focal length of the lens is 9.5mm, the distortion can be controlled at 8 percent, and the distortion is controlled to be very small; can effectively correct aberration and has good marginal image quality.
2. The field range is large, the horizontal field angle can reach 70 degrees, observation is clear, the device is particularly suitable for large-scale monitoring, the device is applied to the field of security monitoring, the arrangement number of lenses can be reduced, and the cost is reduced.
3. The heat dissipation effect is good, the temperature requirement of the working environment from minus 40 ℃ to 80 ℃ can be met, and the thermal stability is good.
The working waveband of the lens is 8-12 mu m, and the lens can be matched with a detector with the resolution of 1280 multiplied by 1024 and 10 mu m for use.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a light path diagram of a large target surface low distortion athermal infrared lens in an embodiment of the present invention;
FIG. 2 is an MTF diagram of a large-target-surface low-distortion athermal infrared lens in a working environment at 20 ℃ according to an embodiment of the present invention;
FIG. 3 is a Spot plot of a large-target-surface low-distortion athermal infrared lens in a 20 ℃ working environment in accordance with embodiments of the present invention;
FIG. 4 is an MTF diagram of a large-target-surface low-distortion athermal infrared lens in a working environment at-40 ℃ in accordance with an embodiment of the present invention;
FIG. 5 is a plot of a work environment at-40 ℃ for a large target surface low distortion athermal infrared lens in accordance with an embodiment of the present invention;
FIG. 6 is an MTF graph of a large-target-surface low-distortion athermal infrared lens in an operating environment of 80 ℃ in accordance with an embodiment of the present invention;
fig. 7 is a Spot diagram of the large-target-surface low-distortion athermal infrared lens in the embodiment of the invention in a working environment of 80 ℃.
Fig. 8 is a field curvature distortion diagram of a large-target low-distortion athermal infrared lens in an embodiment of the invention.
The figure number: 1. a first lens; 2. a second lens; 3. a diaphragm; 4. a third lens; 5. a fourth lens; 6. a germanium protection window; 7. and (5) a detector image surface.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
As shown in fig. 1 of the present application, the present embodiment provides a large-target low-distortion athermal infrared lens, which includes four lenses, in order from an object side to an image side along an optical axis, a first lens 1, a second lens 2, a third lens 4, and a fourth lens 5. The first lens 1 is a meniscus lens with negative focal power and a convex surface facing to the object side; the second lens 2 is a meniscus lens with positive focal power and convex surface facing the object side; the third lens 4 is a meniscus lens with positive focal power and a convex surface facing the image side; the fourth lens 5 is a meniscus lens having a positive refractive power with a convex surface facing the image side.
Wherein the parameters of the four lenses 1 to 4 are shown in Table 1.
The radius of curvature of first object-side surface S1 is 20.37mm, the fitted radius of curvature of first image-side surface S2 is 12.33mm, the radius of curvature of second object-side surface S3 is 31.35mm, the fitted radius of curvature of second image-side surface S4 is 60.71mm, the radius of curvature of third object-side surface S5 is-119.8 mm, the fitted radius of curvature of third image-side surface S6 is-27 mm, the radius of curvature of fourth object-side surface S7 is-43.3 mm, and the fitted radius of curvature of fourth image-side surface S8 is-27.86 mm.
The center thickness of the first lens 1 is 4mm, the center thickness of the second lens 2 is 6mm, the center thickness of the third lens 4 is 4mm, and the center thickness of the fourth lens 5 is 3mm.
The center interval between the first lens 1 and the second lens 2 is 13.26mm, the diaphragm 3 is arranged between the second lens 2 and the third lens 4, the center interval between the second lens 2 and the diaphragm 3 is 2.8mm, the center interval between the diaphragm 3 and the third lens 4 is 2.32mm, the center interval between the third lens 4 and the fourth lens 5 is 7.84mm, and the image side of the fourth lens 5 is sequentially provided with a germanium protection window 6 and a detector image surface 7. The spacing between the fourth lens 5 and the focal plane is 12.73mm.
In one embodiment of the preferred embodiment, the material of the first lens 1 is germanium, the material of the second lens 2 is ZnS, the materials of the third lens 4 and the lens 5 are chalcogenide glasses, specifically, IRG206 is used for the third lens 4, and IRG209 is used for the fourth lens 5.
TABLE 1 parameters of lenses 1 to 4
As a preferred embodiment of the present invention, the first image-side surface S2, the third image-side surface S6 and the fourth object-side surface S8 are aspheric, and satisfy the following formula,
wherein, Z is the distance rise from the vertex of the aspheric surface when the aspheric surface is at the position of the height r along the optical axis direction; c =1/R, R being the paraxial curvature fitting radius of the mirror surface; k is a conic coefficient; a, B, C, D, E are high-order aspheric coefficients, and aspheric data of each lens is shown in Table 2.
TABLE 2 aspherical surface coefficient data of each lens
The image side surface S4 of the second lens 2 is a binary surface, and the expression equation of the binary surface in Zemax is:
where M is a diffraction order, the diffraction order is 1, B1 and B2 are binary surface phase coefficients, B1= -106.16, B2=53.22, and the value of the normalization radius ρ is 10.
In the embodiment, the lens realizes large target surface and low distortion through material matching of germanium-zinc sulfide-chalcogenide glass and reasonable design of focal power, aspheric surface and binary surface, has an ultrashort focal length of 9.5mm, and can control the distortion within 8%; aberration can be effectively corrected, and the edge image quality is good; the field range is large, the horizontal field angle can reach 70 degrees, the observation is clear, the method is particularly suitable for large-range monitoring, and is applied to the field of security monitoring, the arrangement number of lenses can be reduced, and the cost is reduced.
Fig. 2, 4 and 6 are MTF graphs of the thermal difference elimination infrared lens in operating environments of 20 ℃, -40 ℃ and 80 ℃, respectively, where the horizontal axis represents different spatial frequencies and the vertical axis represents modulation. All fields of view represent the MTF curves of the meridian planes, as indicated by the curve T in the figure, and the MTF curves of the sagittal planes, as indicated by the curve S in the figure, as diff. FIG. 3, FIG. 5, and FIG. 7 are the Spot plots of the thermal difference eliminating IR lens at 20 deg.C, -40 deg.C, and 80 deg.C working environment, respectively. Fig. 8 shows the field of view and distortion of an athermal infrared lens in an embodiment. As can be seen from fig. 2 to 7, the MTF is close to the diffraction limit, the root mean square diameter of the diffuse spot is smaller than that of the airy disk, and the image quality is good. The embodiment can reduce the distortion to below 8% through reasonable optical structure design. The lens provided by the embodiment has a good heat elimination effect, can meet the temperature requirement of a working environment ranging from-40 ℃ to 80 ℃, and has good thermal stability.
Therefore, the thermal difference elimination infrared lens composed of the above lenses provided by the embodiment achieves the following optical indexes.
The working wave band is as follows: 8-12 μm;
focal length: f' =9.5mm;
resolution ratio: 1280x1024, 10 μm;
f number: 1.2;
horizontal field angle: 70 °, vertical field angle: 58 deg.
The lens of the embodiment has good heat difference eliminating effect, can meet the requirement of a working temperature range of-40 ℃ to 80 ℃, has the advantages of double fields of view and ultralow distortion, and can be matched with a large target surface detector with the resolution of 1280 multiplied by 1024 and the diameter of 10 mu m for use.
It should be understood that the above examples are only for clearly illustrating the technical solutions of the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection of the claims of the present invention.
Claims (9)
1. The large-target-surface low-distortion athermal infrared lens is characterized by comprising a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object space to an image space, wherein the first lens is a meniscus lens with negative focal power, and a convex surface facing the object side; the second lens is a meniscus lens with positive focal power and a convex surface facing the object side; the third lens is a meniscus lens with positive focal power and a convex surface facing to the image side; the fourth lens is a meniscus lens with positive focal power and a convex surface facing to the image side; from an object space to an image space along an optical axis, two surfaces of the first lens are a first object side surface and a first image side surface in sequence, two surfaces of the second lens are a second object side surface and a second image side surface in sequence, two surfaces of the third lens are a third object side surface and a third image side surface in sequence, two surfaces of the fourth lens are a fourth object side surface and a fourth image side surface in sequence, and the first image side surface, the third image side surface and the fourth object side surface are aspheric surfaces.
2. The large-target-surface low-distortion athermal infrared lens as defined in claim 1 wherein the aspheric surfaces of the first image side, the third image side and the fourth object side all satisfy the following formula,
wherein, Z is the distance rise from the vertex of the aspheric surface when the aspheric surface is at the position of the height r along the optical axis direction; c =1/R, R being the paraxial curvature radius of the mirror; k is a conic coefficient; a, B, C, D and E are high-order aspheric coefficients.
3. The large-target-surface low-distortion athermal infrared lens of claim 1, wherein said first lens is germanium material, said second lens is zinc sulfide material, said third lens is IRG206 material, and said fourth lens is IRG209 material.
4. The large-target-surface low-distortion athermal infrared lens according to claim 1, wherein the radius of curvature of the first object-side surface is 20.37mm, the fitted radius of curvature of the first image-side surface is 12.33mm, the radius of curvature of the second object-side surface is 31.35mm, the fitted radius of curvature of the second image-side surface is 60.71mm, the radius of curvature of the third object-side surface is-119.8 mm, the fitted radius of curvature of the third image-side surface is-27 mm, the radius of curvature of the fourth object-side surface is-43.3 mm, and the fitted radius of curvature of the fourth image-side surface is-27.86 mm.
5. The large-target low-distortion athermal infrared lens of claim 1, wherein the first lens has a center thickness of 4mm, the second lens has a center thickness of 6mm, the third lens has a center thickness of 4mm, and the fourth lens has a center thickness of 3mm.
6. The large-target-surface low-distortion athermal infrared lens of claim 1, wherein the center-to-center distance between the first lens and the second lens is 13.26mm, the second lens and the third lens have a diaphragm therebetween, the center-to-center distance between the second lens and the diaphragm is 2.8mm, the center-to-center distance between the diaphragm and the third lens is 2.32mm, and the center-to-center distance between the third lens and the fourth lens is 7.84mm.
7. The large-target-surface low-distortion athermal infrared lens as claimed in claim 6, wherein a germanium protection window and a detector image plane are sequentially arranged on the image side of the fourth lens, and the distance between the fourth lens and the focal plane is 12.73mm.
8. The large-target-surface low-distortion athermal infrared lens as set forth in claim 1, wherein the second image side surface is a binary surface, the expression of the binary surface is,
where M is the diffraction order, the diffraction order is 1, B1 and B2 are binary planar phase coefficients, B1= -106.16, B2=53.22, and the normalized radius ρ has a value of 10.
9. The large-target-surface low-distortion athermal infrared lens as claimed in claim 1, wherein the working waveband of the lens is 8 μm to 12 μm, the F number is 1.2, the horizontal field angle is 70 °, and the vertical field angle is 58 °.
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| CN202210953591.9A CN115356826A (en) | 2022-08-10 | 2022-08-10 | Large-target-surface low-distortion athermal infrared lens |
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| CN202210953591.9A CN115356826A (en) | 2022-08-10 | 2022-08-10 | Large-target-surface low-distortion athermal infrared lens |
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