Unmanned aerial vehicle-mounted aspheric ultra-wide-angle long-wave infrared telephoto lens

Abstract

The invention provides an unmanned aerial vehicle-mounted aspheric ultra-wide-angle long-wave infrared telephoto lens. The unmanned aerial vehicle-mounted aspheric ultra-wide-angle long-wave infrared telephoto lens comprises a first lens, an aperture diaphragm, a second lens, a third lens and an imaging target surface which are sequentially arranged from a light incidence direction, the first lens is a spherical glass lens, and the second lens and the third lens are aspheric lenses. The first lens has negative focal power, and the second lens and the third lens have positive focal power; the first lens is a convex surface in a light incidence direction and is a concave surface in a light incidence opposite direction; the second lens is a convex surface in the light incidence direction and is a concave surface in the light incidence opposite direction; the third lens is a convex surface in the light incidence direction and is a concave surface in the light incidence opposite direction. According to the invention, a focal power negative-positive-positive structure is adopted to eliminate large-order aberration generated by a long-wave infrared band, the distortion is low, the characteristics of small size, light total mass and the like are considered, and the lens can be conveniently used on an unmanned aerial vehicle.

Description

Technical Field

[0001] This invention relates to the field of lens technology, specifically to an unmanned aerial vehicle (UAV) mounted aspherical ultra-wide-angle long-wave infrared telescope lens. Background Technology

[0002] Infrared spectroscopy is a novel research method for altered minerals in magmatic-hydrothermal deposits. The selective absorption of chemical bonds and functional group vibrations within the mineral lattice produces differentiated spectral characteristics, which can be used to quickly identify mineral types. The longwave infrared band, as an important atmospheric window and a significant coverage area for the spectral characteristics of ground features, can identify anhydrous silicates (framework, island, and chain silicates), sulfates, phosphates, and other minerals, thus greatly expanding the range of mineral classes and types that can be remotely sensed. Furthermore, it complements visible-shortwave infrared remote sensing.

[0003] Long-wave infrared hyperspectral imaging systems are a novel remote sensing technology integrating optics, spectroscopy, precision mechanics, electronics, and computer technology. They can acquire hundreds or thousands of continuous, detailed spectra across a wide spectral range, simultaneously collecting geometric, radiometric, and spectral information of targets. Integrating the capabilities of cameras, radiometers, and spectrometers, they form an image cube, obtaining the spectral characteristic curves of any pixel of a target, enabling target "fingerprint" identification. On one hand, long-wave infrared imaging detection technology can invert the temperature and emissivity information of ground objects; on the other hand, the emissivity spectral mixing in the long-wave infrared band exhibits linear mixing characteristics, making spectral interpretation relatively easier. Currently, long-wave infrared hyperspectral imaging systems are developing towards wider swath width and higher resolution to meet the needs of large-area rapid scanning, providing domestically produced equipment for my country's major strategic needs in deep space and Earth remote sensing, geology and mineral resources, ecological environment monitoring, and land quality surveys. They also support the new round of strategic actions for mineral exploration breakthroughs, carrying out upgrades and application demonstrations of geological and mineral exploration technologies and methods. To upgrade my country's geological exploration technology and equipment towards multi-parameter, high-precision, high-resolution, and rapid and efficient directions, and to comprehensively improve the modernization level of my country's geological exploration technology and equipment.

[0004] Unmanned aerial vehicle (UAV) technology is becoming increasingly mature and widely used in the field of geological exploration. Its advantages of maneuverability, speed, and wide-ranging imaging have gradually made it one of the main working tools for geologists. By using long-wave infrared hyperspectral imaging systems mounted on UAVs, large working areas can be quickly scanned, saving manpower and time costs, and avoiding direct work by geologists in dangerous environments such as high altitudes, thus improving safety. The acquisition of continuous spectral image data with many very narrow spectral bands enables geological prospectors to accurately locate new mineral deposits and effectively identify the differences between minerals and other substances.

[0005] Existing long-wave infrared telescopes generally have relatively small fields of view, and current regulations explicitly limit the flight altitude of drones, making them unsuitable for large-area rapid scanning. Furthermore, the large number of lenses typically results in heavy telescopes, preventing their mounting on small drone platforms. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing an unmanned aerial vehicle (UAV) aspherical ultra-wide-angle long-wave infrared telescope head, which includes a first lens, an aperture stop, a second lens, a third lens, and an imaging target surface arranged in sequence from the direction of light incident.

[0007] The first lens is a spherical glass lens, and the second and third lenses are aspherical lenses;

[0008] The first lens has negative optical power, while the second and third lenses have positive optical power;

[0009] The first lens is convex in the direction of light incidence and concave in the opposite direction of light incidence.

[0010] The second lens is convex in the direction of light incidence and concave in the opposite direction of light incidence; the third lens is convex in the direction of light incidence and concave in the opposite direction of light incidence.

[0011] The ratios of the focal lengths of each lens to the focal length of the UAV-borne aspherical ultra-wide-angle long-wave infrared telescope lens are as follows:

[0012] -3.52<f1′ / f<-3.32, 2.59<f2′ / f<2.79, 2.32<f3′ / f<2.52,

[0013] Where f1′ is the focal length of the first lens; f2′ is the focal length of the second lens; f3′ is the focal length of the third lens; and f is the focal length of the UAV-borne aspherical ultra-wide-angle long-wave infrared telescope, f = 6.4 mm.

[0014] The total length of the optical system formed by the lens and the focal length of the lens satisfy the following condition: TTL / f≤6.97; where TTL is the total length of the optical system, which refers to the distance from the first lens in the direction of light incidence to the imaging target surface.

[0015] The first, second, and third lenses are made of germanium glass with a refractive index of Nd, 4.003≤Nd≤4.0074, and a thermal Abbe number of 865.

[0016] The aperture stop is positioned between the first lens and the second lens.

[0017] The aperture stop distance satisfies 3.03 < L1 / L2 < 3.07, where L1 is the distance from the aperture stop to the surface of the first lens, and L2 is the distance from the aperture stop to the surface of the second lens.

[0018] The unmanned aerial vehicle-mounted aspherical ultra-wide-angle long-wave infrared telescope has a working wavelength range of 8–12.5 μm, a field of view of 100°, a numerical aperture of 1.9, and a maximum optical distortion of 30%.

[0019] The second lens and the third lens are aspherical in the direction of light incidence, and satisfy the following expression:

[0020]

[0021] Where c represents the paraxial radius of curvature, k represents the conic coefficient, α1, α2, α3, α4, α5, α6 represent higher-order aspherical coefficients, x represents the distance vector from a point on the aspherical surface to the optical axis, and Z represents the distance vector from a point on the aspherical surface to the vertex of the aspherical surface.

[0022] The aspherical coefficients α1, α2, α3, α4, α5, and α6 of the second lens in the direction of light incidence are 0, 7.328 × 10⁻⁶, and 7.328 × 10⁻⁶, respectively. -5 -7.51×10 -7 1.281×10 -8 -1.64×10 -10 8.678×10 -13 .

[0023] The aspherical coefficients α1, α2, α3, α4, α5, and α6 of the third lens in the direction of light incidence are 0, 3.875 × 10⁻⁶, and 3.875 × 10⁻⁶, respectively. -5 1.517×10 -7 -6.181×10 -9 3.304×10 -11 6.087×10 -14 .

[0024] Beneficial effects: This invention provides an aspherical ultra-wide-angle long-wave infrared telescope head for UAVs, with a field of view of 100°. The overall structure adopts a three-piece compact transmission structure and uses a "negative-positive-positive" optical power structure to eliminate the large-scale aberrations generated in the long-wave infrared band, resulting in low distortion. It also features small size and light weight, with the total weight of the optical system being 9g. The ultra-light optical system greatly optimizes the payload of equipment on UAVs and makes it easy to use on UAVs. Attached Figure Description

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0026] Figure 1 This is a structural diagram of the optical system of the lens of the present invention.

[0027] Figure 2 It is a transfer function graph.

[0028] Figure 3 It is a dot-matrix diagram.

[0029] Figure 4 It is an optical distortion diagram.

[0030] Explanation of reference numerals in the attached diagram: 1. First lens; 2. Aperture stop; 3. Second lens; 4. Third lens; 5. Imaging target surface. Detailed Implementation

[0031] like Figure 1 As shown, this embodiment of the invention provides an unmanned aerial vehicle (UAV) aspherical ultra-wide-angle long-wave infrared telescope head, including a first lens 1, an aperture stop 2, a second lens 3, a third lens 4, and an imaging target surface 5 arranged sequentially from the direction of light incidence.

[0032] The first lens is a spherical glass lens, and the second and third lenses are aspherical lenses. The first lens 1 has negative optical power, while the second and third lenses have positive optical power. The first lens 1 is convex in the direction of light incidence and concave in the opposite direction of light incidence; the second lens 3 is convex in the direction of light incidence and concave in the opposite direction of light incidence; and the third lens 4 is convex in the direction of light incidence and concave in the opposite direction of light incidence.

[0033] The ratios of the focal length of each lens to the total focal length of the lens system range as follows:

[0034] -3.52<f1′ / f<-3.32, 2.59<f2′ / f<2.79, 2.32<f3′ / f<2.52,

[0035] Where f1′ is the focal length of the first lens 1; f2′ is the focal length of the second lens 3; f3′ is the focal length of the third lens 4; and f is the focal length of the UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head, f = 6.4 mm.

[0036] The total length of the optical system formed by the lens and the total focal length of the lens system satisfy: TTL / f≤6.97; where TTL is the total length of the optical system and f is the focal length of the UAV-borne aspherical ultra-wide-angle long-wave infrared telescope.

[0037] The lens is made of germanium glass with a refractive index of Nd, 4.003≤Nd≤4.0074, and a thermal Abbe number of 865.

[0038] The lens also includes an aperture stop, which is disposed between the first lens and the second lens.

[0039] The aperture stop distance satisfies 3.03 < L1 / L2 < 3.07, where L1 is the distance from the aperture stop to the surface of the first lens, and L2 is the distance from the aperture stop to the surface of the second lens.

[0040] Operating wavelength range 8–12.5 μm, field of view 100°, numerical aperture 1.9, maximum optical distortion 30%.

[0041] Table 1

[0042] Surface number Surface type radius of curvature Thickness / Gap Material Light transmission aperture S11 spherical 12.910 2 GERMANIUM 10.76 S12 spherical 9.538 17.4 8.56 STO - - 5.7 2.85 S21 even aspherical surface 28.923 2 GERMANIUM 7.45 S22 spherical 62.085 7.5 7.36 S31 even aspherical surface 23.723 2 GERMANIUM 8.23 S32 spherical 45.296 8 7.95 IMA flat - - 5.54

[0043] Table 1 shows the specific parameters of the optical system of the UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head. S11 is the plane of the first lens 1 in the direction of light incidence, and s12 is the plane of the first lens 1 in the opposite direction of light incidence. STO is the aperture stop 2, S21 is the plane of the second lens 3 in the direction of light incidence, and s22 is the plane of the second lens 3 in the opposite direction of light incidence. S31 is the plane of the third lens 4 in the direction of light incidence, and s32 is the plane of the third lens 4 in the opposite direction of light incidence. IMA is the imaging target surface.

[0044] The second lens and the third lens are aspherical in the direction of light incidence, and satisfy the following expression:

[0045]

[0046] Where c represents the paraxial radius of curvature, k represents the conic coefficient, α1, α2, α3, α4, α5, and α6 represent higher-order aspherical coefficients, x represents the distance vector from a point on the aspherical surface to the optical axis, and Z represents the distance vector from a point on the aspherical surface to the vertex of the aspherical surface. The aspherical coefficients α1, α2, α3, α4, α5, and α6 of the second lens in the direction of ray incident are 0, 7.328 × 10⁻⁶, and 7.328 × 10⁻⁶, respectively. -5 -7.51×10 -7 1.281×10 -8 -1.64×10 -10 8.678×10 -13 The aspherical coefficients α1, α2, α3, α4, α5, and α6 of the third lens in the direction of light incidence are 0 and 3.875 × 10⁻⁶, respectively. -5 1.517×10 -7 -6.181×10 -9 3.304×10 -11 6.087×10 -14 .like Figure 2As shown (the vertical axis represents the transfer function, which can be understood as contrast; its value is a ratio and has no unit), the optical modulation transfer function is close to the diffraction limit, and the MTF curves in the meridional and sagittal directions are very close, with negligible difference. This indicates good imaging consistency in both meridional and sagittal directions, and the optical system has good imaging quality. Figure 3 As shown, the RMS blur spot size based on the centroid is used as the optimization evaluation function for the center wavelength. The circles in the figure represent the diffraction limit of the system, i.e., the Airy disk size. The blur spots in each field of view are much smaller than the Airy disk radius, and the overall aberrations are well corrected. Figure 4 The curves showing the distortion of the lens as a function of the field of view are shown in the figure. It can be seen from the figure that the maximum optical distortion is 30%.

[0047] This invention provides an unmanned aerial vehicle (UAV)-borne aspherical ultra-wide-angle long-wave infrared telescope. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head, characterized in that, It includes a first lens (1), an aperture stop (2), a second lens (3), a third lens (4), and an imaging target surface (5) arranged sequentially from the direction of light incidence; The first lens (1) is a spherical glass lens, and the second lens (3) and the third lens (4) are aspherical lenses; The first lens (1) has negative optical power, and the second lens (3) and the third lens (4) have positive optical power; The first lens (1) is convex in the direction of light incidence and concave in the opposite direction of light incidence; The second lens (3) is convex in the direction of light incidence and concave in the opposite direction of light incidence; the third lens (4) is convex in the direction of light incidence and concave in the opposite direction of light incidence.

2. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 1, characterized in that, The ratios of the focal lengths of each lens to the focal length of the UAV-borne aspherical ultra-wide-angle long-wave infrared telescope lens are as follows: -3.52<f1′ / f<-3.32, 2.59<f2′ / f<2.79, 2.32<f3′ / f<2.52, Where f1′ is the focal length of the first lens (1); f2′ is the focal length of the second lens (3); f3′ is the focal length of the third lens (4); f is the focal length of the UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head, f=6.4mm.

3. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 2, characterized in that, The total length of the optical system formed by the lens and the focal length of the lens satisfy: TTL / f≤6.97; where TTL is the total length of the optical system, which refers to the distance from the first lens (1) to the imaging target surface (5) in the direction of light incidence.

4. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 3, characterized in that, The first lens (1), the second lens (3) and the third lens (4) are made of germanium glass with a refractive index of Nd, 4.003≤Nd≤4.0074 and a thermal Abbe number of 865.

5. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 4, characterized in that, The aperture stop (2) is positioned between the first lens (1) and the second lens (3).

6. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 5, characterized in that, The distance between the aperture stop (2) and the first lens (1) is 3.03 < L1 / L2 < 3.07, where L1 is the distance between the aperture stop (2) and the first lens (1), and L2 is the distance between the aperture stop and the second lens (3).

7. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 6, characterized in that, The unmanned aerial vehicle-mounted aspherical ultra-wide-angle long-wave infrared telescope has a working wavelength range of 8–12.5 μm, a field of view of 100°, a numerical aperture of 1.9, and a maximum optical distortion of 30%.

8. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 7, characterized in that, The second lens (3) and the third lens (4) are aspherical in the direction of light incidence, and satisfy the following expression: Where c represents the paraxial radius of curvature, k represents the conic coefficient, α1, α2, α3, α4, α5, α6 represent higher-order aspherical coefficients, x represents the distance vector from a point on the aspherical surface to the optical axis, and Z represents the distance vector from a point on the aspherical surface to the vertex of the aspherical surface.

9. The UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 8, characterized in that, The aspherical coefficients α1, α2, α3, α4, α5, and α6 of the second lens (3) in the direction of light incidence are 0, 7.328 × 10⁻⁶, and 7.328 × 10⁻⁶, respectively. -5 -7.51×10 -7 1.281×10 -8 -1.64×10 -10 8.678×10 -13 .

10. A UAV-borne aspherical ultra-wide-angle long-wave infrared telescope head according to claim 8, characterized in that, The aspherical coefficients α1, α2, α3, α4, α5, and α6 of the third lens (4) in the direction of light incidence are 0, 3.875 × 10⁻⁶, and 3.875 × 10⁻⁶, respectively. -5 1.517×10 -7 -6.181×10 -9 3.304×10 -11 6.087×10 -14 .

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