CN114002808A - Infrared imaging optical system - Google Patents
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- 238000003331 infrared imaging Methods 0.000 title claims abstract description 29
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- 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
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- 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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Abstract
The application provides an infrared imaging optical system, relates to optics technical field, and its technical scheme main points are: includes, arranged in order from an object side to an image side along an optical axis: a first lens having a positive optical power; a second lens having a negative optical power; a third lens having a negative optical power; a fourth lens having a positive optical power; the focal power of the first lens is phi 1, the focal power of the whole optical system is phi, and the following conditions are met: phi 1/phi is more than or equal to 0.40 and less than or equal to 0.90; the combined focal power of the first lens and the second lens is phi 12, the focal power of the whole optical system is phi, and the following requirements are met: phi 12/phi is more than or equal to 0.35 and less than or equal to 0.52; the combined focal power of the third lens and the fourth lens is phi 34, the focal power of the whole optical system is phi, and the following requirements are met: phi 34/phi is more than or equal to 1.02 and less than or equal to 1.42. The infrared imaging optical system has the advantages of achieving complete common-path design of medium-wave infrared and long-wave infrared, reducing the space size of the optical system, and having large relative aperture imaging capacity, strong light condensation capacity and excellent imaging quality.
Description
Technical Field
The application relates to the technical field of optics, in particular to an infrared imaging optical system.
Background
The infrared spectrum has enhanced night vision and the capability of detecting and identifying targets all day long, so that the infrared imaging is widely applied to the military and civil fields. Infrared spectra can be classified into three major categories, short-wave infrared, medium-wave infrared and long-wave infrared, according to the "atmospheric window" in which infrared exists in atmospheric transmission. The medium wave infrared imaging and long wave infrared imaging detection target self heat radiation realizes imaging of a scene, and has the imaging capabilities of haze, fog, high humidity environment and all-day time. The medium wave infrared thermal imaging is suitable for detecting a target with higher temperature, and the long wave infrared is suitable for detecting a target with normal temperature or low temperature. In practical application, due to the fact that the scene has targets with different temperature distributions, clear, high-resolution and high-dynamic-range images can be obtained more conveniently by adopting a dual-band detection method, and the detection and identification capability of the targets is enhanced.
In the traditional mode, a single spectral band imaging is realized mostly by adopting a separate optical lens and a detector, and the system is large and complex; the visual axis consistency among different devices is difficult to ensure, and the use efficiency is poor. With the development and progress of infrared detector devices, the infrared bicolor detector can simultaneously output two images of medium wave infrared and long wave infrared, so that the mass of the infrared thermal imaging equipment is reduced; but the optical system is challenged, the optical system must collect the information of the medium wave infrared and long wave infrared ultra-wide spectrums to the target surface of the detector at the same time, and the design and development difficulty of the optical system is greatly increased. Although patent CN 109407273 a realizes common aperture design of visible light, medium wave and long wave infrared, the relative aperture of the optical system is only F/4, the light gathering capability is low, and it is difficult to obtain high-definition and high-resolution images. Design elements of a common-caliber infrared dual-band optical system are researched in the optical newspaper 'selection of medium-wave/long-wave bicolor infrared optical system materials' in 2015 by the aid of the intensity of the pairs and the like, but the obtained design result is still an optical system with a small relative aperture, and the requirements of an infrared imaging system on pursuing high light condensation capacity and high sensitivity are difficult to meet.
The common-caliber medium-long wave infrared imaging optical system is a key way for solving the problems of large volume and low precision of a discrete infrared optical system. In specific application, the design of a common-aperture imaging optical path faces the problems of chromatic aberration of ultra-wide spectrum and secondary spectrum correction; because the high-transmittance infrared material which simultaneously satisfies medium wave infrared and long wave infrared is very limited, the aberration correction difficulty is increased; furthermore, in order to improve the detection sensitivity of the infrared thermal imaging system and exert the performance of the infrared bicolor detector, the optical system needs to realize a large relative aperture design, and the difficulty in correcting and balancing optical aberration is increased.
In view of the above problems, improvements are needed.
Disclosure of Invention
The application aims to provide an infrared imaging optical system which has the advantages of achieving complete common-path design of medium-wave infrared and long-wave infrared, reducing the space size of the optical system, and having large relative aperture imaging capacity, strong light condensation capacity and excellent imaging quality.
In a first aspect, the present application provides an infrared imaging optical system, which has the following technical scheme:
the method comprises the following steps: arranged in order from an object side to an image side along an optical axis:
a first lens having a positive optical power;
a second lens having a negative optical power;
a third lens having a negative optical power;
a fourth lens having a positive optical power;
the focal power of the first lens is phi 1, the focal power of the whole optical system is phi, and the following conditions are met:
0.40≤Φ1/Φ≤0.90；
the combined focal power of the first lens and the second lens is phi 12, the focal power of the whole optical system is phi, and the following requirements are met:
0.35≤Φ12/Φ≤0.52；
the combined focal power of the third lens and the fourth lens is phi 34, the focal power of the whole optical system is phi, and the following requirements are met:
1.02≤Φ34/Φ≤1.42。
further, in the present application, Φ 12 and Φ satisfy:
0.35≤Φ12/Φ≤0.48；
the phi 34 and the phi satisfy:
1.02≤Φ34/Φ≤1.05。
further, in the present application, Φ 1 and Φ satisfy:
0.40≤Φ1/Φ≤0.55；
the focal power of the second lens is phi 2, the focal power of the whole optical system is phi, and the following requirements are met:
-0.075≤Φ2/Φ≤-0.045；
the phi 34 and the phi satisfy:
1.25≤Φ34/Φ≤1.42。
further, in this application, the one side that the first lens is close to the object side is the convex surface, and the one side that is close to image side is the convex surface, the one side that the first lens is close to the object side is the aspheric surface, the one side that the second lens is close to the object side is the concave surface, and the one side that is close to image side is the convex surface, and the one side that the third lens is close to the object side is the concave surface, the convex surface of third lens is the aspheric surface, the one side that the fourth lens is close to the object side is the convex surface, and the one side that is close to image side is the concave surface, the convex surface of fourth lens is the aspheric surface, and the aspheric surface satisfies the following expressions:
z is the distance rise 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 =1/R, R representing the paraxial radius of curvature of the mirror surface; k is a conic coefficient; A. b, C, D are high-order aspheric coefficients.
Further, in the present application, an aperture stop is provided between the second lens and the third lens.
Further, in the present application, a paraxial radius of curvature of the first lens on the side close to the object side is 109.792mm, a clear aperture is 55mm, a paraxial radius of curvature of the first lens on the side close to the image side is-924.698 mm, a clear aperture is 50.2mm, and a thickness of the first lens on the central axis is 10.17 mm;
the curvature radius of one surface, close to the object side, of the second lens is-51.957 mm, the clear aperture is 48.8mm, the curvature radius of one surface, close to the image side, of the second lens is-70.497 mm, the clear aperture is 46mm, the thickness of the second lens on the central axis is 5.288mm, and the interval between the second lens and the first lens on the central axis is 8.96 mm;
the clear aperture of the aperture stop 500 is 39.6mm, and the distance between the aperture stop and the second lens on the central axis is 1.15 mm;
the paraxial curvature radius of one surface, close to the object side, of the third lens is 88.948mm, the clear aperture is 43.1mm, the curvature radius of one surface, close to the image side, of the third lens is 26.108mm, the clear aperture is 38.1mm, the interval between the third lens and the aperture diaphragm on the central axis is 32.56mm, and the thickness of the third lens on the central axis is 8 mm;
the paraxial curvature radius that fourth lens is close to the one side of thing side is 26.125mm, clear aperture is 37.2mm, and the curvature radius that is close to the side of image is 48.498mm, clear aperture is 21.6mm, the thickness of fourth lens on the axis is 25mm, fourth lens with the interval of third lens on the axis is 2.08mm, fourth lens and the interval of image plane on the axis are 10.35 mm.
Further, in the present application, an aperture stop is disposed between the first lens and the object plane, and the aperture stop is disposed on a mirror surface of the first lens close to the object side.
Further, in this application, one surface of the first lens element close to the object side is a convex surface, one surface close to the image side is a concave surface, the convex surface and the concave surface of the first lens element are aspheric surfaces, one surface of the second lens element close to the object side is a convex surface, one surface close to the image side is a concave surface, one surface of the third lens element close to the object side is a convex surface, one surface close to the image side is a concave surface, one surface close to the object side of the fourth lens element is a convex surface, and one surface close to the image side is a concave surface, and the aspheric surface satisfies the following expressions:
z is the distance rise 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 =1/R, R representing the paraxial radius of curvature of the mirror surface; k is a conic coefficient; A. b, C, D are high-order aspheric coefficients.
Further, in the present application, a paraxial radius of curvature of the first lens on the side close to the object side is 116.638mm, a clear aperture is 50mm, a paraxial radius of curvature of the first lens on the side close to the image side is 232.206mm, a clear aperture is 48.6mm, and a thickness of the first lens on the central axis is 11.07 mm;
the aperture diaphragm is attached to the convex surface of the first lens, and the clear aperture of the aperture diaphragm is 50 mm;
the curvature radius of one surface, close to the object side, of the second lens is 32.636mm, the clear aperture is 45.8mm, the curvature radius of one surface, close to the image side, of the second lens is 23.058mm, the clear aperture is 32.6mm, the thickness of the second lens on the central axis is 14.68mm, and the distance between the second lens and the first lens on the central axis is 15.27 mm;
the curvature radius of one surface, close to the object side, of the third lens is 130.417mm, the clear aperture is 32mm, the curvature radius of one surface, close to the image side, of the third lens is 22.336mm, the clear aperture is 30.5mm, the thickness of the third lens on the central axis is 4mm, and the distance between the third lens and the second lens on the central axis is 10.86 mm;
the curvature radius of the fourth lens close to the object side is 28.078mm, the clear aperture is 33.2mm, the curvature radius of the fourth lens close to the image side is 345.258mm, the clear aperture is 26.9mm, the thickness of the fourth lens on the central axis is 17.36mm, the fourth lens and the interval of the third lens on the central axis are 4.37mm, and the interval of the fourth lens and the image plane on the central axis is 11.25 mm.
Further, in the present application, the material of the first lens is a chalcogenide glass material, the material of the second lens is a germanium material or a crystal material, the material of the third lens is a crystal material, and the material of the fourth lens is a crystal material.
Therefore, the infrared imaging optical system provided by the application corrects chromatic aberration and secondary spectrum of two wide spectral bands by adopting the four lenses, and is used for correcting aberrations such as spherical aberration, coma, astigmatism and field curvature by mutual cooperation between the lenses, so that imaging with excellent quality can be obtained while ensuring a common optical path of medium wave infrared and long wave infrared, and the infrared imaging optical system has the beneficial effects of realizing the design of the complete common optical path of the medium wave infrared and the long wave infrared, reducing the space size of the optical system, having large relative aperture imaging capability, strong light gathering capability and excellent imaging quality.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
Fig. 1 is a schematic view of an infrared imaging optical system in one embodiment provided in the present application.
FIG. 2 is a graph of the optical transfer function curve for the optical system of FIG. 1 in the mid-wave infrared.
FIG. 3 is a graph of the optical transfer function curve for the optical system of FIG. 1 in the long-wave infrared.
Fig. 4 is a schematic view of an infrared imaging optical system in another embodiment provided in the present application.
FIG. 5 is a graph of the optical transfer function curve for the optical system of FIG. 4 in the mid-wave infrared.
FIG. 6 is a graph of the optical transfer function curve for the optical system of FIG. 4 in the long-wave infrared.
In the figure: 100. a first lens; 200. a second lens; 300. a third lens; 400. a fourth lens; 500. and (4) an aperture diaphragm.
Detailed Description
The technical solutions in the present application will be described clearly and completely with reference to the drawings in the present application, and it should be understood that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. The components of the present application, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
Referring to fig. 1 to 6, an infrared imaging optical system specifically includes: arranged in order from an object side to an image side along an optical axis:
a first lens 100 having a positive optical power;
a second lens 200 having a negative optical power;
a third lens 300 having a negative optical power;
a fourth lens 400 having positive optical power;
the focal power of the first lens 100 is Φ 1, and the focal power of the entire optical system is Φ, which satisfies:
0.40≤Φ1/Φ≤0.90；
the combined focal power of the first lens 100 and the second lens 200 is phi 12, the focal power of the whole optical system is phi, and the following conditions are satisfied:
0.35≤Φ12/Φ≤0.52；
the combined focal power of the third lens 300 and the fourth lens 400 is phi 34, the focal power of the whole optical system is phi, and the following requirements are met:
1.02≤Φ34/Φ≤1.42。
through the technical scheme, under the condition that the conditional expressions are met, chromatic aberration and secondary spectrum of two wide spectral bands are corrected by utilizing the mutual cooperative matching among the first lens 100, the second lens 200, the third lens 300 and the fourth lens 400, and the chromatic aberration, the coma, the astigmatism, the field curvature and other aberrations are corrected, so that the common optical path of the medium wave infrared and the long wave infrared is achieved, imaging with excellent quality is obtained, the imaging quality is guaranteed, the size is reduced, the system is more compact, the manufacturing cost is reduced, the miniaturization and the popularization are facilitated, and the beneficial effects of realizing the complete common optical path design of the medium wave infrared and the long wave infrared, reducing the space size of the optical system, having the imaging capability with large relative aperture, strong light gathering capability and excellent imaging quality are achieved.
Further, as shown in fig. 1, the present application may further define that Φ 12 and Φ satisfy:
0.35≤Φ12/Φ≤0.48；
Φ 34 and Φ satisfy:
1.02≤Φ34/Φ≤1.05。
besides, the following relationship can be also used between Φ 12 and Φ:
0.32≤Φ12/Φ≤0.48；
the following relationship between Φ 34 and Φ may also be:
0.95≤Φ34/Φ≤1.05。
in this embodiment, a surface of the first lens element 100 close to the object side is a convex surface, a surface close to the image side is a convex surface, a surface of the first lens element 100 close to the object side is an aspheric surface, a surface of the second lens element 200 close to the object side is a concave surface, a surface close to the image side is a convex surface, a surface of the third lens element 300 close to the object side is a convex surface, a surface close to the image side is a concave surface, a convex surface of the third lens element 300 is an aspheric surface, a surface of the fourth lens element 400 close to the object side is a convex surface, a surface close to the image side is a concave surface, a convex surface of the fourth lens element 400 is an aspheric surface, and the aspheric surface satisfies the following expressions:
z is the distance rise 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 =1/R, R representing the paraxial radius of curvature of the mirror surface; k is a conic coefficient; A. b, C, D, the aspheric coefficients of high order are shown in the following table:
note that the mirror surfaces represented by the surface numbers correspond to the mirror surfaces of the respective lenses arranged in order from the object side to the image side along the optical axis.
Through the technical scheme, the convex surface of the first lens 100 close to the object side, the convex surface of the third lens 300 and the convex surface of the fourth lens 400 are set to be aspheric surfaces for correcting aberrations such as spherical aberration, coma, astigmatism and field curvature, the number of lenses is reduced, the size is reduced, a better imaging effect can be obtained, the design is simplified, and the cost is reduced
Further, in some of the embodiments, an aperture stop 500 is disposed between the second lens 200 and the third lens 300.
Through the above technical solution, the aperture stop 500 is arranged between the second lens 200 and the third lens 300 for adjusting the intensity of the light beam, and the aperture stop 500 is arranged between the second lens 200 and the third lens 300 to ensure the paraxial condition, improve the imaging quality, and correct the aberration.
Specifically, the paraxial radius of curvature of the surface, close to the object side, of the first lens 100 is 109.792mm, the clear aperture is 55mm, the paraxial radius of curvature of the surface, close to the image side, of the first lens is-924.698 mm, the clear aperture is 50.2mm, and the thickness of the first lens 100 on the central axis is 10.17 mm;
the curvature radius of the surface, close to the object side, of the second lens 200 is-51.957 mm, the clear aperture is 48.8mm, the curvature radius of the surface, close to the image side, of the second lens 200 is-70.497 mm, the clear aperture is 46mm, the thickness of the second lens 200 on the central axis is 5.288mm, and the interval between the second lens 200 and the first lens 100 on the central axis is 8.96 mm;
the clear aperture of the aperture stop 500 is 39.6mm, and the interval between the aperture stop 500 and the second lens 200 on the central axis is 1.15 mm;
the paraxial curvature radius of the surface, close to the object side, of the third lens 300 is 88.948mm, the clear aperture is 43.1mm, the curvature radius of the surface, close to the image side, of the third lens 300 is 26.108mm, the clear aperture is 38.1mm, the distance between the third lens 300 and the aperture stop 500 on the central axis is 32.56mm, and the thickness of the third lens 300 on the central axis is 8 mm;
the paraxial radius of curvature of the fourth lens 400 on the side close to the object side is 26.125mm, the clear aperture is 37.2mm, the radius of curvature of the side close to the image side is 48.498mm, the clear aperture is 21.6mm, the thickness of the fourth lens 400 on the central axis is 25mm, the distance between the fourth lens 400 and the third lens 300 on the central axis is 2.08mm, and the distance between the fourth lens 400 and the image plane on the central axis is 10.35 mm. Wherein the central axis coincides with the optical axis.
Through above-mentioned technical scheme, reduce the system size when guaranteeing that the imaging quality is outstanding, make the system compacter, save the cost, be favorable to using and promoting.
In some of these embodiments, the material of the first lens 100 is a chalcogenide glass material.
Through the technical scheme, the chalcogenide glass material has excellent infrared transmittance, a high refractive index and a low temperature coefficient of refractive index, so that the chalcogenide glass material is used as the material of the first lens 100.
Specifically, in some embodiments, the material of the first lens 100 may be IG4 glass or IG6 glass.
In some of these embodiments, the material of the second lens 200 is a germanium material.
Through the above technical solution, the germanium material has good mechanical properties and thermal conductivity, and thus is used as the material of the second lens 200.
In some of these embodiments, the material of the third lens 300 is a crystalline material.
Specifically, in some embodiments, the material of the third lens 300 is calcium fluoride or barium fluoride.
By the technical scheme, the calcium fluoride or the barium fluoride has high impact resistance and thermal shock resistance, has good transmittance in ultraviolet, visible light and infrared wave band ranges, and can eliminate secondary spectrum, so that the calcium fluoride or the barium fluoride is used as a material of the third lens 300.
In some of these embodiments, the material of the fourth lens 400 is a crystalline material.
Specifically, in some embodiments, the material of the fourth lens 400 is zinc selenide or zinc sulfide.
By the technical scheme, zinc selenide or zinc sulfide has good transmission performance within the range of 0.5-22 microns, has the characteristic of small light transmission loss, and provides high-quality optical performance through refractive index, homogeneity and uniformity, so that the zinc selenide or zinc sulfide is used as a material of the fourth lens 400.
As one of the preferred embodiments, the parameter settings of the optical system are shown in the following table:
through the parameter setting, the technical indexes of the optical system are as follows:
(1) the working wave band is as follows: 3.7-4.8 μm, 7.7-9.5 μm;
(2) focal length: 50 mm;
(3) a detector: 640 x 512, 17 μm;
(4) relative pore diameter: f/0.9.
In the technical scheme recorded in the embodiment, the optical system can be matched with a non-refrigeration double-color infrared detector, is used for various platforms such as aerospace or ground and the like, realizes multiband infrared imaging and is used for detection, monitoring and other tasks, the relative aperture can reach F/0.9, the relative aperture of the conventional double-wave detection optical system is only F/4, and through the scheme recorded in the application, the relative aperture can reach F/0.8-F/1.5, the small volume is ensured, the high-sensitivity detection effect is achieved, and meanwhile, the high-sensitivity detection optical system has very strong light-gathering capacity and is favorable for obtaining the high-sensitivity detection effect.
FIG. 2 shows the curve distribution of the optical transfer function of the optical system in the middle-wave infrared in this embodiment, and the average optical transfer function value reaches 0.7@30lp/mm, so that the imaging quality is excellent.
FIG. 3 shows the optical transfer function curve distribution of the optical system in the long-wave infrared in this embodiment, and the average optical transfer function value reaches 0.64@30lp/mm, so that the imaging quality is excellent.
Besides, as shown in fig. 4, the present application may further define that Φ 1 and Φ satisfy:
0.40≤Φ1/Φ≤0.55；
the focal power of the second lens 200 is Φ 2, and the focal power of the whole optical system is Φ, which satisfies:
-0.075≤Φ2/Φ≤-0.045；
Φ 34 and Φ satisfy:
1.25≤Φ34/Φ≤1.42。
besides, the following relationship can be also used between Φ 34 and Φ:
1.25≤Φ34/Φ≤1.45。
in this embodiment, a surface of the first lens element 100 close to the object side is a convex surface, a surface close to the image side is a concave surface, the convex surface and the concave surface of the first lens element 100 are aspheric surfaces, a surface of the second lens element 200 close to the object side is a convex surface, a surface close to the image side is a concave surface, a surface of the third lens element 300 close to the object side is a convex surface, a surface close to the image side is a concave surface, a surface of the fourth lens element 400 close to the object side is a convex surface, and a surface close to the image side is a concave surface, where the aspheric surfaces satisfy the following expressions:
z is the distance rise 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 =1/R, R representing the paraxial radius of curvature of the mirror surface; k is a conic coefficient; A. b, C, D are high-order aspheric coefficients, and the parameters of the aspheric coefficients are shown in the following table:
note that the mirror surfaces represented by the surface numbers correspond to the mirror surfaces of the respective lenses arranged in order from the object side to the image side along the optical axis.
Through above-mentioned technical scheme, set the convex surface and the concave surface of first lens 100 to the aspheric surface for aberration such as correction spherical aberration, coma, astigmatism and field curvature reduces lens quantity, can obtain better imaging effect when reducing the size, plays the effect of simplifying the design, reduce cost.
Further, in some embodiments, an aperture stop 500 is disposed between the first lens 100 and the object plane, and the aperture stop 500 is disposed on a mirror surface of the first lens 100 close to the object side.
Through the above technical solution, the aperture stop 500 is disposed on the mirror surface of the first lens 100 close to the object side for adjusting the intensity of the light beam, and meanwhile, for ensuring the paraxial condition, improving the imaging quality, and correcting the aberration, and the aperture stop is disposed on the convex surface of the first lens 100, which is beneficial to obtaining a compact, light and small layout design.
Specifically, the paraxial radius of curvature of the surface, close to the object side, of the first lens 100 is 116.638mm, the clear aperture is 50mm, the paraxial radius of curvature of the surface, close to the image side, of the first lens 100 is 232.206mm, the clear aperture is 48.6mm, and the thickness of the first lens 100 on the central axis is 11.07 mm;
the aperture diaphragm 500 is attached to the convex surface of the first lens 100, and the clear aperture of the aperture diaphragm 500 is 50 mm;
the curvature radius of the surface, close to the object side, of the second lens 200 is 32.636mm, the clear aperture is 45.8mm, the curvature radius of the surface, close to the image side, of the second lens 200 is 23.058mm, the clear aperture is 32.6mm, the thickness of the second lens 200 on the central axis is 14.68mm, and the distance between the second lens 200 and the first lens 100 on the central axis is 15.27 mm;
the curvature radius of the surface, close to the object side, of the third lens 300 is 130.417mm, the clear aperture is 32mm, the curvature radius of the surface, close to the image side, of the third lens 300 is 22.336mm, the clear aperture is 30.5mm, the thickness of the third lens 300 on the central axis is 4mm, and the distance between the third lens 300 and the second lens 200 on the central axis is 10.86 mm;
the curvature radius of the surface, close to the object side, of the fourth lens 400 is 28.078mm, the clear aperture is 33.2mm, the curvature radius of the surface, close to the image side, of the fourth lens 400 is 345.258mm, the clear aperture is 26.9mm, the thickness of the fourth lens 400 on the central axis is 17.36mm, the distance between the fourth lens 400 and the third lens 300 on the central axis is 4.37mm, and the distance between the fourth lens 400 and the image plane on the central axis is 11.25 mm. The central axis coincides with the optical axis.
Through above-mentioned technical scheme, reduce the system size when guaranteeing that the imaging quality is outstanding, make the system compacter, save the cost, be favorable to using and promoting.
In some of these embodiments, the material of the first lens 100 is a chalcogenide glass material.
Through the technical scheme, the chalcogenide glass material has excellent infrared transmittance, a high refractive index and a low temperature coefficient of refractive index, so that the chalcogenide glass material is used as the material of the first lens 100.
In some embodiments, the material of the first lens 100 may be selected to be IG6 glass.
In some of these embodiments, the material of the second lens 200 is a crystalline material.
Specifically, in some embodiments, the material of the second lens 200 may be zinc selenide.
By the technical scheme, the zinc selenide has good transmission performance within the range of 0.5-22 mu m, has the characteristic of small light transmission loss, and provides high-quality optical performance through refractive index, homogeneity and uniformity, so that the zinc selenide serves as a material of the second lens 200.
In some of these embodiments, the material of the third lens 300 is a crystalline material.
Specifically, in some embodiments, the material of the third lens 300 may be selected to be calcium fluoride or barium fluoride.
By the technical scheme, the calcium fluoride or the barium fluoride has high impact resistance and thermal shock resistance, has good transmittance in ultraviolet, visible light and infrared wave band ranges, and can eliminate secondary spectrum, so that the calcium fluoride or the barium fluoride is used as a material of the third lens 300.
In some of these embodiments, the material of the fourth lens 400 is a crystalline material.
Specifically, in some embodiments, the material of the fourth lens 400 may be selected to be zinc sulfide.
As one of the preferred technical solutions, the parameter settings of the optical system are shown in the following table:
through the parameter setting, the technical indexes of the optical system are as follows:
(1) the working wave band is as follows: 3.7-4.8 μm, 7.7-9.5 μm;
(2) focal length: 50 mm;
(3) a detector: 640 x 512, 17 μm;
(4) relative pore diameter: f/1.0.
In the scheme recorded in the embodiment of the application, the optical system can be matched with a non-refrigeration double-color infrared detector, is used for various platforms such as aerospace or ground and the like, realizes multiband infrared imaging and is used for detection, monitoring and other tasks, the relative aperture can reach F/1.0, the relative aperture of the conventional double-wave detection optical system is only F/4, and through the scheme recorded in the application, the relative aperture can reach F/0.8-F/1.5, the small volume is ensured, meanwhile, the high-sensitivity detection effect is achieved, and the strong light-gathering capacity is achieved, and the high-sensitivity detection effect is facilitated.
FIG. 5 shows the curve distribution of the optical transfer function of the optical system in the middle-wave infrared in this embodiment, and the average optical transfer function value reaches 0.63@30lp/mm, so that the imaging quality is excellent.
FIG. 6 shows the optical transfer function curve distribution of the optical system in the long-wave infrared in this embodiment, and the average optical transfer function value reaches 0.58@30lp/mm, so that the imaging quality is excellent.
The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. An infrared imaging optical system, comprising: arranged in order from an object side to an image side along an optical axis:
a first lens having a positive optical power;
a second lens having a negative optical power;
a third lens having a negative optical power;
a fourth lens having a positive optical power;
the focal power of the first lens is phi 1, the focal power of the whole optical system is phi, and the following conditions are met:
0.40≤Φ1/Φ≤0.90；
the combined focal power of the first lens and the second lens is phi 12, the focal power of the whole optical system is phi, and the following requirements are met:
0.35≤Φ12/Φ≤0.52；
the combined focal power of the third lens and the fourth lens is phi 34, the focal power of the whole optical system is phi, and the following requirements are met:
1.02≤Φ34/Φ≤1.42。
2. an infrared imaging optical system according to claim 1, characterized in that between Φ 12 and Φ:
0.35≤Φ12/Φ≤0.48；
the phi 34 and the phi satisfy:
1.02≤Φ34/Φ≤1.05。
3. an infrared imaging optical system according to claim 1, characterized in that between Φ 1 and Φ:
0.40≤Φ1/Φ≤0.55；
the focal power of the second lens is phi 2, the focal power of the whole optical system is phi, and the following requirements are met:
-0.075≤Φ2/Φ≤-0.045；
the phi 34 and the phi satisfy:
1.25≤Φ34/Φ≤1.42。
4. the infrared imaging optical system of claim 2, wherein one surface of the first lens element close to the object side is a convex surface, one surface of the first lens element close to the image side is a convex surface, one surface of the first lens element close to the object side is an aspheric surface, one surface of the second lens element close to the object side is a concave surface, one surface of the third lens element close to the image side is a convex surface, one surface of the third lens element close to the object side is a concave surface, the convex surface of the third lens element is an aspheric surface, one surface of the fourth lens element close to the object side is a convex surface, one surface of the fourth lens element close to the image side is a concave surface, and the convex surface of the fourth lens element is an aspheric surface, and the following expressions are satisfied:
z is the distance rise 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 =1/R, R representing the paraxial radius of curvature of the mirror surface; k is a conic coefficient; A. b, C, D are high-order aspheric coefficients.
5. The infrared imaging optical system according to claim 4, wherein an aperture stop is provided between the second lens and the third lens.
6. The infrared imaging optical system as claimed in claim 1, wherein the paraxial radius of curvature of the first lens on the side close to the object side is 109.792mm, the clear aperture is 55mm, the paraxial radius of curvature of the first lens on the side close to the image side is-924.698 mm, the clear aperture is 50.2mm, and the thickness of the first lens on the central axis is 10.17 mm;
the curvature radius of one surface, close to the object side, of the second lens is-51.957 mm, the clear aperture is 48.8mm, the curvature radius of one surface, close to the image side, of the second lens is-70.497 mm, the clear aperture is 46mm, the thickness of the second lens on the central axis is 5.288mm, and the interval between the second lens and the first lens on the central axis is 8.96 mm;
the clear aperture of the aperture diaphragm is 39.6mm, and the interval between the aperture diaphragm and the second lens on the central axis is 1.15 mm;
the paraxial curvature radius of one surface, close to the object side, of the third lens is 88.948mm, the clear aperture is 43.1mm, the curvature radius of one surface, close to the image side, of the third lens is 26.108mm, the clear aperture is 38.1mm, the interval between the third lens and the aperture diaphragm on the central axis is 32.56mm, and the thickness of the third lens on the central axis is 8 mm;
the paraxial curvature radius that fourth lens is close to the one side of thing side is 26.125mm, clear aperture is 37.2mm, and the curvature radius that is close to the side of image is 48.498mm, clear aperture is 21.6mm, the thickness of fourth lens on the axis is 25mm, fourth lens with the interval of third lens on the axis is 2.08mm, fourth lens and the interval of image plane on the axis are 10.35 mm.
7. The infrared imaging optical system as claimed in claim 3, wherein an aperture stop is disposed between the first lens and the object plane, and the aperture stop is disposed on a mirror surface of the first lens close to the object side.
8. The infrared imaging optical system of claim 7, wherein one surface of the first lens element close to the object side is a convex surface, one surface of the first lens element close to the image side is a concave surface, the convex surface and the concave surface of the first lens element are aspheric surfaces, one surface of the second lens element close to the object side is a convex surface, one surface of the third lens element close to the image side is a concave surface, one surface of the third lens element close to the object side is a convex surface, one surface of the fourth lens element close to the object side is a convex surface, and one surface of the fourth lens element close to the image side is a concave surface, the aspheric surfaces satisfy the following expressions:
z is the distance rise 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 =1/R, R representing the paraxial radius of curvature of the mirror surface; k is a conic coefficient; A. b, C, D are high-order aspheric coefficients.
9. The infrared imaging optical system as claimed in claim 8, wherein the paraxial radius of curvature of the first lens on the object side is 116.638mm, the clear aperture is 50mm, the paraxial radius of curvature of the first lens on the image side is 232.206mm, the clear aperture is 48.6mm, and the thickness of the first lens on the central axis is 11.07 mm;
the aperture diaphragm is attached to the convex surface of the first lens, and the clear aperture of the aperture diaphragm is 50 mm;
the curvature radius of one surface, close to the object side, of the second lens is 32.636mm, the clear aperture is 45.8mm, the curvature radius of one surface, close to the image side, of the second lens is 23.058mm, the clear aperture is 32.6mm, the thickness of the second lens on the central axis is 14.68mm, and the distance between the second lens and the first lens on the central axis is 15.27 mm;
the curvature radius of one surface, close to the object side, of the third lens is 130.417mm, the clear aperture is 32mm, the curvature radius of one surface, close to the image side, of the third lens is 22.336mm, the clear aperture is 30.5mm, the thickness of the third lens on the central axis is 4mm, and the distance between the third lens and the second lens on the central axis is 10.86 mm;
the curvature radius of the fourth lens close to the object side is 28.078mm, the clear aperture is 33.2mm, the curvature radius of the fourth lens close to the image side is 345.258mm, the clear aperture is 26.9mm, the thickness of the fourth lens on the central axis is 17.36mm, the fourth lens and the interval of the third lens on the central axis are 4.37mm, and the interval of the fourth lens and the image plane on the central axis is 11.25 mm.
10. The infrared imaging optical system as set forth in claim 1, wherein the first lens is made of chalcogenide glass, the second lens is made of germanium or crystal, the third lens is made of crystal, and the fourth lens is made of crystal.
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