Unmanned aerial vehicle-mounted wide-angle thermal infrared telephoto lens

Abstract

The invention provides an unmanned aerial vehicle-mounted wide-angle thermal infrared telephoto lens which comprises a first lens (1), a second lens (2), a third lens (4), a fourth lens (5) and an imaging target surface (6) which are sequentially arranged from left to right from the light incidence direction. The first lens (1), the second lens (2), the third lens (4) and the fourth lens (5) are all spherical glass lenses, the first lens (1) and the second lens (2) have negative focal power, and the third lens (4) and the fourth lens (5) have positive focal power; the spherical optical glass lens is used, the problem that the imaging quality of an optical system is reduced due to the fact that the high-altitude temperature difference is large is well avoided, and the large field angle solves the problems that the flight height is limited by new specifications of an unmanned aerial vehicle, the field angle of an existing lens is small, and the existing working efficiency cannot be met.

Description

Technical Field

[0001] The invention relates to the technical field of lenses, and in particular to a wide-angle thermal infrared telephoto lens carried by an unmanned aerial vehicle. Background Art

[0002] UAV technology is becoming more and more mature and widely used in the field of geological exploration. Its advantages of flexibility, rapid imaging and wide-ranging imaging have gradually become one of the main working methods of geologists. The thermal infrared hyperspectral imaging system carried by the drone can detect anhydrous silicates (frame, island, chain silicates), sulfates, phosphates and other minerals that cannot be detected in the visible-shortwave infrared spectrum. Rapid scanning of large areas saves human resources and time costs. It prevents geologists from working directly in some dangerous environments such as high altitudes, thereby improving safety.

[0003] Most existing thermal infrared telescopes use aspherical plastic lenses to reduce weight, but plastic lenses are not as stable as optical glass, especially in high-altitude working areas with large temperature differences. Temperature changes lead to reduced image quality. Aspherical lenses are more rigorous to process than spherical lenses and are more expensive. Many regulations clearly limit the flight altitude of drones, and the existing telescopes have a small field of view and cannot meet the needs of large-area rapid scanning. Summary of the invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a wide-angle thermal infrared telephoto lens for drones in view of the shortcomings of the prior art, so as to solve the problems of small field of view and temperature affecting imaging quality of infrared lenses in the prior art. The lens comprises: a first lens, a second lens, a third lens, a fourth lens and an imaging target surface arranged from left to right in sequence from the incident direction of the light;

[0005] The first lens, the second lens, the third lens and the fourth lens are all spherical glass lenses, wherein the first lens and the second lens have negative optical power, and the third lens and the fourth lens have positive optical power;

[0006] The first lens has a convex surface in the incident direction of the light and a concave surface in the opposite direction of the incident direction of the light;

[0007] The second lens has a convex surface in the incident direction of the light and a concave surface in the opposite direction of the incident direction of the light;

[0008] The third lens has a concave surface in the incident direction of the light and a convex surface in the opposite direction of the incident direction of the light;

[0009] The fourth lens is convex in the direction opposite to the incident direction of the light, and is flat in the direction opposite to the incident direction of the light.

[0010] The ratio ranges of the focal length of each lens to the total focal length of the lens are:

[0011] -3.9<f1′ / f<-2.9, -8.9<f2′ / f<-7.9, 6.9<f3′ / f<7.9, 2.8<f4′ / f<3.8;

[0012] Wherein 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 f4′ is the focal length of the fourth lens; and f is the focal length of the lens.

[0013] The total length of the optical system of the lens and the total focal length of the lens satisfy: TTL / f≤17.78; wherein, TTL is the total length of the optical system, and the total length of the optical system refers to the distance from the light incident direction surface of the first lens to the imaging target surface; the system composed of the first lens, the second lens, the aperture stop, the third lens, the fourth lens and the imaging target surface is the optical system, which is also the optical structure of the unmanned aerial vehicle-mounted wide-angle thermal infrared telescope lens. After the optical system is assembled with mechanical structural parts, it becomes the unmanned aerial vehicle-mounted wide-angle thermal infrared telescope lens.

[0014] The refractive index of the first lens is Nd1, and the refractive index of the second lens is Nd2, wherein MIN(Nd1, Nd2)≥2.4965, and MIN represents a minimum value.

[0015] The second lens is a concave lens, the third lens is a convex lens, the refractive index of the second lens is Nd2, and the refractive index of the third lens is Nd3, satisfying: 1.4126≤Nd3 / Nd2≤1.8809.

[0016] The lens further includes an aperture stop disposed between the second lens and the third lens.

[0017] The aperture stop (the definition of the aperture stop is: the metal disc that limits the aperture angle of the object point on the axis is called the aperture stop) distance satisfies 1.9<L2 / L3<2.2, where L2 is the distance from the opposite direction of the light incident surface of the second lens to the aperture stop, and L3 is the distance from the aperture stop to the light incident direction surface of the third lens.

[0018] The operating wavelength range of the lens is 8 to 12.5 um, and the field of view is 40°.

[0019] The present invention also provides a camera device, comprising:

[0020] The drone carries a wide-angle thermal infrared telescope lens;

[0021] An image pickup element is arranged on the image side of the lens and is used to convert the image formed by the lens into an electrical signal.

[0022] The imaging device further includes an image processor configured to correct aberrations contained in the electrical signal.

[0023] Beneficial effects: The present invention uses a spherical optical glass lens, which effectively avoids the problem of decreased imaging quality of the optical system caused by large temperature differences at high altitudes. The large field of view angle solves the problem that the new regulations on drones limit flight altitudes and the small field of view angle of existing lenses cannot meet existing work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0025] Figure 1 It is a structural diagram of the optical system.

[0026] Figure 2 is the transfer function graph.

[0027] Figure 3 It is a point diagram. DETAILED DESCRIPTION

[0028] like Figure 1 As shown, an embodiment of the present invention provides a wide-angle thermal infrared telephoto lens carried by an unmanned aerial vehicle, and the wide-angle thermal infrared telephoto lens carried by an unmanned aerial vehicle comprises: a first lens 1, a second lens 2, a third lens 4, a fourth lens 5 and an imaging target surface 6 arranged in sequence from left to right starting from the incident direction of light;

[0029] The first lens 1, the second lens 2, the third lens 4, and the fourth lens 5 are all spherical glass lenses, wherein the first lens 1 and the second lens 2 have negative optical power, and the third lens 4 and the fourth lens 5 have positive optical power;

[0030] The first lens 1 is convex in the direction of light incidence and concave in the opposite direction of light incidence;

[0031] The second lens 2 is convex in the direction of light incidence and concave in the opposite direction of light incidence;

[0032] The third lens 4 is concave in the incident direction of the light and is convex in the opposite direction of the incident direction of the light;

[0033] The fourth lens 5 is convex in the direction opposite to the incident direction of the light, and is flat in the direction opposite to the incident direction of the light.

[0034] The ratio ranges of the focal length of each lens to the total focal length of the lens system are:

[0035] -3.9<f1′ / f<-2.9, -8.9<f2′ / f<-7.9, 6.9<f3′ / f<7.9, 2.8<f4′ / f<3.8;

[0036] Among them, f1′ is the focal length of the first lens 1; f2′ is the focal length of the second lens 2; f3′ is the focal length of the third lens 4, f4′ is the focal length of the fourth lens 5; and f is the focal length of the wide-angle thermal infrared telescope lens on the drone.

[0037] The total length of the optical system of the lens and the total focal length of the lens system satisfy: TTL / f≤17.78; wherein TTL is the total length of the optical system.

[0038] The refractive index of the first lens 1 is Nd1, and the refractive index of the second lens 2 is Nd2, wherein MIN(Nd1, Nd2)≥2.4965, and MIN represents a minimum value.

[0039] The second lens 2 is a concave lens, the third lens 4 is a convex lens, the refractive index of the second lens 2 is Nd2, and the refractive index of the third lens 4 is Nd3, wherein: 1.4126≤Nd3 / Nd2≤1.8809.

[0040] The lens further comprises an aperture stop 3 , and the aperture stop 3 is arranged between the second lens 2 and the third lens 4 .

[0041] The aperture stop distance satisfies 1.9<L2 / L3<2.2,

[0042] Wherein L2 is the distance from the light incident reverse direction surface of the second lens 2 to the aperture stop, and L3 is the distance from the aperture stop 3 to the light incident direction surface of the third lens 4.

[0043] The working wavelength range of the lens of this embodiment is 8-12.5um, the field of view is 40°, the aperture diaphragm is STOP, and the imaging target surface is IMAGE.

[0044] Table 1

[0045] Surface number Surface type Radius of curvature Thickness / Gap Material Clear Aperture S11 Spherical 12.462 3.00 GERMANIUM 5.334 S12 Spherical 7.824 26.00 4.033 S21 Spherical 16.307 3.00 AMTIR1 3.277 S22 Spherical 10.966 2.00 2.867 STOP flat 1.00 3.004 S31 Spherical -22.657 3.00 GERMANIUM 3.153 S32 Spherical -19.87 11.10 3.681 S41 Spherical 39.872 3.00 GERMANIUM 5.681 S42 Spherical infinity 15.00 5.508 IMAGE flat infinity 1.360

[0046] In Table 1, S11 is the surface of the first lens 1 in the direction of light incidence, s12 is the surface of the first lens 1 in the opposite direction of light incidence; S21 is the surface of the second lens 2 in the direction of light incidence, s22 is the surface of the second lens 2 in the opposite direction of light incidence; S31 is the surface of the third lens 4 in the direction of light incidence, s32 is the surface of the third lens 4 in the opposite direction of light incidence; S41 is the surface of the fourth lens 5 in the direction of light incidence, s42 is the surface of the fourth lens 5 in the opposite direction of light incidence;

[0047] like Figure 2 As shown, by using the lens described in this embodiment, the optical modulation transfer function is close to the diffraction limit, higher than 0.2 at 30lp / mm, and the optical system has good imaging quality.

[0048] like Figure 3As shown, by using the lens described in this embodiment, the diffuse spot in each field of view is much smaller than the radius of the Airy disk, and the overall aberration is well corrected.

[0049] The present invention provides a wide-angle thermal infrared telephoto lens for drones. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the protection scope of the present invention. All components not specified in this embodiment can be implemented using existing technologies.

Claims

1. A wide-angle thermal infrared telephoto lens for drones, characterized in that: include: Starting from the incident direction of the light, the first lens (1), the second lens (2), the third lens (4), the fourth lens (5) and the imaging target surface (6) are arranged in sequence from left to right; The first lens (1), the second lens (2), the third lens (4) and the fourth lens (5) are all spherical glass lenses, wherein the first lens (1) and the second lens (2) have negative optical power, and the third lens (4) and the fourth lens (5) have positive optical power; The first lens (1) is convex in the direction of incident light and concave in the direction opposite to the incident light; The second lens (2) is convex in the direction of incident light and concave in the direction opposite to the incident light; The third lens (4) is concave in the direction of incident light and is convex in the direction opposite to the incident light. The fourth lens (5) is convex in the direction opposite to the incident direction of the light, and is flat in the direction opposite to the incident direction of the light.

2. The wide-angle thermal infrared telephoto lens for unmanned aerial vehicles according to claim 1, characterized in that: The ratio ranges of the focal length of each lens to the total focal length of the lens are: -3.9<f1′ / f<-2.9, -8.9<f2′ / f<-7.9, 6.9<f3′ / f<7.9, 2.8<f4′ / f<3.8; Wherein f1′ is the focal length of the first lens (1); f2′ is the focal length of the second lens (2); f3′ is the focal length of the third lens (4); f4′ is the focal length of the fourth lens (5); and f is the focal length of the lens.

3. The wide-angle thermal infrared telephoto lens for unmanned aerial vehicles according to claim 2, characterized in that: The total optical system length of the lens and the total focal length of the lens satisfy: TTL / f≤17.78; wherein TTL is the total optical system length, and the total optical system length refers to the distance from the light incident direction surface of the first lens (1) to the imaging target surface (6).

4. The wide-angle thermal infrared telephoto lens for unmanned aerial vehicles according to claim 3, characterized in that: The refractive index of the first lens (1) is Nd1, and the refractive index of the second lens (2) is Nd2, wherein MIN(Nd1, Nd2)≥2.4965, and MIN represents a minimum value.

5. The wide-angle thermal infrared telephoto lens for unmanned aerial vehicles according to claim 4, characterized in that: The second lens (2) is a concave lens, the third lens (4) is a convex lens, the refractive index of the second lens (2) is Nd2, and the refractive index of the third lens (4) is Nd3, satisfying: 1.4126≤Nd3 / Nd2≤1.8809.

6. The wide-angle thermal infrared telephoto lens for unmanned aerial vehicles according to claim 5, characterized in that: The lens also includes an aperture stop (3), and the aperture stop (3) is arranged between the second lens (2) and the third lens (4).

7. The wide-angle thermal infrared telephoto lens for unmanned aerial vehicles according to claim 6, characterized in that: The aperture stop distance satisfies 1.9<L2 / L3<2.2, wherein L2 is the distance from the light incident reverse direction surface of the second lens (2) to the aperture stop, and L3 is the distance from the aperture stop (3) to the light incident direction surface of the third lens (4).

8. The wide-angle thermal infrared telephoto lens for unmanned aerial vehicles according to claim 7, characterized in that: The operating wavelength range of the lens is 8 to 12.5 um, and the field of view is 40°.

9. A camera device, characterized in that: include: The lens as claimed in any one of claims 1 to 8; An imaging element is arranged on the image side of the lens and is used to convert the image formed by the lens into an electrical signal.

10. The camera device according to claim 9, characterized in that: An image processor is also included, and the image processor is used to correct the aberration contained in the electrical signal.

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