An 18mm full-frame aerial lens

Abstract

The application discloses an 18mm full-frame aerial lens, and relates to the technical field of optical lenses, which comprises, in sequence from the object side to the image side, a first lens with negative focal length, a second lens with negative focal length, a third lens with positive focal length, a fourth lens with positive focal length, a diaphragm, a fifth lens with positive focal length, a sixth lens with positive focal length, a seventh lens with negative focal length and an eighth lens with positive focal length. The application can meet the full-frame shooting requirement.

Description

Technical Field

[0001] This application relates to the field of optical lens technology, and in particular to an 18mm full-frame aerial photography lens. Background Technology

[0002] With the development of civilian drone technology, aerial photography has become increasingly popular among young people. This has created a significant demand for optical systems suitable for aerial surveillance. To capture high-definition, uniformly sized images, lenses for aerial photography need to meet requirements such as high pixel count, low distortion, and high relative illumination. However, most aerial lenses on the market that meet these requirements have relatively small sensor sizes and cannot achieve full-frame resolution. Summary of the Invention

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an 18mm full-frame aerial lens that can meet the needs of full-frame shooting.

[0004] According to an embodiment of the first aspect of this application, an 18mm full-frame aerial lens includes, from the object side to the image side, a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, an aperture stop, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, and an eighth lens with positive optical power.

[0005] According to an embodiment of this application, an 18mm full-frame aerial lens has at least the following beneficial effects: The first lens has negative optical power, which can bring in light from a larger field of view into the system, reducing the field of view of the subsequent lens elements. The second lens also has negative optical power, which can again bring in light from a larger field of view into the system, further reducing the field of view of the subsequent lens elements. The first and second lenses first expand the field of view and correct distortion. The third, fourth, and fifth lenses, with positive optical power, correct aberrations introduced by the front group. The fifth and sixth lenses converge light and further improve image quality. The seventh lens effectively corrects field curvature and spherical aberration at large apertures. By placing the aperture stop in the center of the lens, the optical power can be more symmetrically distributed between the front and rear lens groups. This helps balance the lens size and avoids the front lens being too large and heavy, which is one of the key design features for achieving a compact and lightweight lens. Through the strong divergence of the two negative optical power lenses in the front group, large-angle off-axis light rays can enter the rear group, covering the image field of the full-frame sensor.

[0006] According to some embodiments of this application, the first lens is a meniscus lens, the second lens is a meniscus lens, the third lens is a biconvex lens, the fourth lens is a meniscus lens, the fifth lens is a meniscus lens, the sixth lens is a meniscus lens, the seventh lens is a meniscus lens, and the eighth lens is a meniscus lens.

[0007] According to some embodiments of this application, the following relationship is satisfied: -1.1 <f1 / f<-0.9; -1.5 <f2 / f<-1.3; 0.9 <f3 / f<1.1; 1.6 <f4 / f<2.0; 3.6 <f5 / f<4.2; 1.0 <f6 / f<1.2; -1.1 <f7 / f<-0.8; 4 <f8 / f<5; Where f is the focal length of the 18mm full-frame aerial lens, 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, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens.

[0008] According to some embodiments of this application, the following relationship is satisfied: 1.5 < Nd1 < 1.6; 1.9 < Nd2 < 2.0; 1.8 < Nd3 < 1.9; 1.6 < Nd4 < 1.7; 1.5 < Nd5 < 1.6; 1.5 < Nd6 < 1.6; 1.8 < Nd7 < 1.9; 1.4 < Nd8 < 1.6; Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, Nd4 is the refractive index of the fourth lens, Nd5 is the refractive index of the fifth lens, Nd6 is the refractive index of the sixth lens, Nd7 is the refractive index of the seventh lens, and Nd8 is the refractive index of the eighth lens.

[0009] According to some embodiments of this application, the following relationship is satisfied: 55 < Vd1 < 60; 16 < Vd2 < 20; 30 < Vd3 < 35; 55 < Vd4 < 65; 55 < Vd5 < 65; 65 < Vd6 < 75; 20 < Vd7 < 30; 55 < Vd8 < 65; Wherein, Vd1 is the dispersion coefficient of the first lens, Vd2 is the dispersion coefficient of the second lens, Vd3 is the dispersion coefficient of the third lens, Vd4 is the dispersion coefficient of the fourth lens, Vd5 is the dispersion coefficient of the fifth lens, Vd6 is the dispersion coefficient of the sixth lens, Vd7 is the dispersion coefficient of the seventh lens, and Vd8 is the dispersion coefficient of the eighth lens.

[0010] According to some embodiments of this application, the following relationship is satisfied: 0.02 <A01 / TL<0.03; 0.05 <A02 / TL<0.06; 0.04 <A03 / TL<0.05; 0.08 < (A1S + AS2) / TL < 0.09; 0.25 <A1S / AS2<0.35; 0.025 <A05 / TL<0.035; 0.001 <A06 / TL<0.002; 0.01 <A07 / TL<0.02; Wherein, A01 is the air gap between the first lens and the second lens, A02 is the air gap between the second lens and the third lens, A03 is the air gap between the third lens and the fourth lens, A1S is the air gap between the fourth lens and the aperture stop, AS2 is the air gap between the aperture stop and the fifth lens, A05 is the air gap between the fifth lens and the sixth lens, A06 is the air gap between the sixth lens and the seventh lens, A07 is the air gap between the seventh lens and the eighth lens, and TL is the length of the 18mm full-frame aerial lens.

[0011] According to some embodiments of this application, the following relationship is satisfied: 3.8 <TL / f<4; 0.2 < BF / TL < 0.3; Where f is the focal length of the 18mm full-frame aerial lens, BF is the back focal length of the 18mm full-frame aerial lens, and TL is the length of the 18mm full-frame aerial lens.

[0012] According to some embodiments of this application, the 18mm full-frame aerial lens further includes a lens barrel, and the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are mounted inside the lens barrel.

[0013] According to some embodiments of this application, the fifth lens and the eighth lens are aspherical lenses.

[0014] According to some embodiments of this application, the aspherical spherical curve equations of the fifth lens and the eighth lens are as follows: , Where Z is the surface elevation along the direction parallel to the optical axis, r is the radial distance from the optical axis, c is the vertex curvature, and k is the conic constant. α 1 represents the first-order aspherical coefficient. α 2 represents the second-order aspherical coefficient. α 3 represents the third-order aspherical coefficient. α 4 represents the fourth-order aspherical coefficient. α 5 represents the 5th order aspherical coefficient. α 6 represents the sixth-order aspherical coefficient. α 7 represents the 7th order aspherical coefficient.

[0015] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0016] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the optical structure of a lens according to an embodiment of this application; Figure 2 This is an MTF curve of a lens according to an embodiment of this application; Figure 3 This is a dot diagram of a lens according to one embodiment of this application; Figure 4 This is a schematic diagram of the field curvature and distortion curves of a lens according to an embodiment of this application; Figure 5 This is a schematic diagram of the vertical chromatic aberration of a lens according to an embodiment of this application.

[0017] Icon labels: First lens 100; Second lens 200; Third lens 300; Fourth lens 400, aperture 410; Fifth lens 500; Sixth lens 600; Seventh lens 700; Eighth lens 800; Protective glass 900, image sensor 910. Detailed Implementation

[0018] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0019] In the description of this application, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0020] In the description of this application, "multiple" refers to two or more. The use of "first" and "second" is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or the order in which the technical features are indicated.

[0021] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0022] Reference Figure 1As shown, one embodiment of this application discloses an 18mm full-frame aerial lens, which, from the object side to the image side, comprises: a first lens 100 with negative optical power, a second lens 200 with negative optical power, a third lens 300 with positive optical power, a fourth lens 400 with positive optical power, an aperture stop 410, a fifth lens 500 with positive optical power, a sixth lens 600 with positive optical power, a seventh lens 700 with negative optical power, and an eighth lens 800 with positive optical power. The first lens 100 has negative optical power, which can bring in light from a larger field of view into the system, thus reducing the field of view of the subsequent lens. The second lens 200 has negative optical power, which can again bring in light from a larger field of view into the system, thus reducing the field of view of the subsequent lens. The first lens 100 and the second lens 200 first expand the field of view and correct distortion. The third lens 300, the fourth lens 400, and the fifth lens 500, which have positive optical power, correct the aberrations introduced by the front group. The fifth lens 500 and the sixth lens 600 converge the light and further improve image quality, while the seventh lens 700 can effectively correct field curvature and spherical aberration at large apertures. By placing the aperture stop 410 in the center of the lens, the optical power can be distributed more symmetrically between the front and rear lens groups. This helps to balance the lens size and avoid the front lens being too large and heavy, which is one of the key design features for achieving a compact and lightweight lens. Through the strong divergence of the two negative optical power lenses in the front group, large-angle off-axis light rays can be quickly compressed and enter the rear group, achieving an image field that covers the entire frame sensor.

[0023] Reference Figure 1As shown, in some embodiments, the first lens 100 is a meniscus lens. The object-side surface of the first lens 100 is convex, and the image-side surface is concave, which is beneficial for collecting large-angle light rays. The second lens 200 is a meniscus lens, with the object-side surface being convex and the image-side surface being concave. The second lens 200, together with the first lens 100, reduces the lens's sensitivity to changes in the angle of incidence of light. The third lens 300 is a biconvex lens, with the object-side surface and the image-side surface having the same curvature, facilitating assembly. The fourth lens 400 is a meniscus lens, with the object-side surface being concave and the image-side surface being convex. The fifth lens 500 is a meniscus lens, with the object-side surface being convex and the image-side surface being concave. The fourth lens 400 and the fifth lens 500 together correct spherical aberration and coma. The sixth lens 600 is a meniscus lens, with its object-side surface being concave and its image-side surface being convex. The seventh lens 700 is also a meniscus lens, with its object-side surface being concave and its image-side surface being convex. The eighth lens 800 is also a meniscus lens, with its object-side surface being concave and its image-side surface being convex. The curvature directions of the two surfaces of the meniscus lens are the same, which makes the refraction angle of light more gradual, effectively reducing spherical aberration. This application, through the rational design of the meniscus lens, can effectively reduce the distortion generated by the lens during imaging, improving image sharpness and color reproduction.

[0024] Reference Figure 1 As shown, in some implementations, the 18mm full-frame aerial lens satisfies the following relationship: -1.1 <f1 / f<-0.9; -1.5 <f2 / f<-1.3; 0.9 <f3 / f<1.1; 1.6 <f4 / f<2.0; 3.6 <f5 / f<4.2; 1.0 <f6 / f<1.2; -1.1 <f7 / f<-0.8; 4 <f8 / f<5; Where f is the focal length of the 18mm full-frame aerial lens, f equals 18mm. TL is the length of the 18mm full-frame aerial lens. f1 is the focal length of the first lens 100, f2 is the focal length of the second lens 200, f3 is the focal length of the third lens 300, f4 is the focal length of the fourth lens 400, f5 is the focal length of the fifth lens 500, f6 is the focal length of the sixth lens 600, f7 is the focal length of the seventh lens 700, and f8 is the focal length of the eighth lens 800. Both the first lens 100 and the second lens 200 have negative optical power, and the ratio of their focal lengths to the total focal length of the system is constrained within the ranges of -1.1 to -0.9 and -1.5 to -1.3, respectively. The first lens 100 and the second lens 200 constitute the front diverging group, used to receive light rays with a large field of view and gently bend them. The absolute value of f1 / f is slightly greater than 1, indicating that this lens undertakes the main divergence function but not excessively; the absolute value of f2 / f is even larger, indicating that the second negative lens further enhances the divergence of light. This gradient distribution helps to avoid uncontrolled astigmatism and coma caused by excessive curvature of a single lens. The third lens 300 has positive power, which initially converges the divergent light from the previous group, while providing symmetrical incident angle conditions for aberration correction of subsequent lenses. The fourth lens 400 and the fifth lens 500 both have positive power, and their longer focal lengths are to fine-tune spherical aberration and off-axis aberrations without significantly changing the light path. The sixth lens 600 has positive power and a short focal length, reducing the beam cross-section and creating good incident conditions for the subsequent lenses. The seventh lens 700 and the eighth lens 800 are used for image correction.

[0025] Reference Figure 1 As shown, in some implementations, the 18mm full-frame aerial lens satisfies the following relationship: 1.5 < Nd1 < 1.6; 1.9 < Nd2 < 2.0; 1.8 < Nd3 < 1.9; 1.6 < Nd4 < 1.7; 1.5 < Nd5 < 1.6; 1.5 < Nd6 < 1.6; 1.8 < Nd7 < 1.9; 1.4 < Nd8 < 1.6; In this design, Nd1 is the refractive index of the first lens (100), Nd2 is the refractive index of the second lens (200), Nd3 is the refractive index of the third lens (300), Nd4 is the refractive index of the fourth lens (400), Nd5 is the refractive index of the fifth lens (500), Nd6 is the refractive index of the sixth lens (600), Nd7 is the refractive index of the seventh lens (700), and Nd8 is the refractive index of the eighth lens (800). The refractive index of the material is rationally selected based on the focal length of the lens design. The setting of the refractive index range takes into account both the maturity of the optical glass manufacturing process and the controllability of costs. Each selected refractive index range corresponds to optical material grades with stable market supply and good batch consistency. The eighth lens, 800, is the lens with the lowest refractive index. As a weakly positive lens at the end, the low refractive index allows it to fine-tune the light emission angle in a gentle manner, while reducing stray light from internal wall reflections caused by excessive differences in refractive indices between glass and air.

[0026] Reference Figure 1 As shown, in some implementations, the 18mm full-frame aerial lens satisfies the following relationship: 55 < Vd1 < 60; 16 < Vd2 < 20; 30 < Vd3 < 35; 55 < Vd4 < 65; 55 < Vd5 < 65; 65 < Vd6 < 75; 20 < Vd7 < 30; 55 < Vd8 < 65; In this design, Vd1 is the dispersion coefficient of the first lens (100), Vd2 is the dispersion coefficient of the second lens (200), Vd3 is the dispersion coefficient of the third lens (300), Vd4 is the dispersion coefficient of the fourth lens (400), Vd5 is the dispersion coefficient of the fifth lens (500), Vd6 is the dispersion coefficient of the sixth lens (600), Vd7 is the dispersion coefficient of the seventh lens (700), and Vd8 is the dispersion coefficient of the eighth lens (800). The combination of high refractive index and high dispersion of the second lens enables it to achieve strong negative optical power with a small curvature and to compensate for chromatic aberration. The combination of high refractive index and high dispersion of the seventh lens enables it to achieve field curvature correction with a gentle surface while simultaneously compensating for residual chromatic aberration. By using alternating combinations of high-dispersion and low-dispersion materials, the lens can simultaneously correct axial and transverse chromatic aberration in the 18mm ultra-wide-angle full-frame format, meeting the requirements of color reproduction and edge sharpness for aerial images.

[0027] Reference Figure 1 As shown, in some implementations, the 18mm full-frame aerial lens satisfies the following relationship: 0.02 <A01 / TL<0.03; 0.05 <A02 / TL<0.06; 0.04 <A03 / TL<0.05; 0.08 < (A1S + AS2) / TL < 0.09; 0.25 <A1S / AS2<0.35; 0.025 <A05 / TL<0.035; 0.001 <A06 / TL<0.002; 0.01 <A07 / TL<0.02; Wherein, A01 is the air gap between the first lens 100 and the second lens 200, A02 is the air gap between the second lens 200 and the third lens 300, A03 is the air gap between the third lens 300 and the fourth lens 400, A1S is the air gap between the fourth lens 400 and the aperture stop 410, AS2 is the air gap between the aperture stop 410 and the fifth lens 500, A05 is the air gap between the fifth lens 500 and the sixth lens 600, A06 is the air gap between the sixth lens 600 and the seventh lens 700, and A07 is the air gap between the seventh lens 700 and the eighth lens 800. The first lens 100 and the second lens 200 are relatively close together, and the two negative lenses are arranged adjacently so that they can work as a joint diverging group. The distance between the fifth lens 500 and the aperture stop 410 is smaller than the distance between the fourth lens 400 and the aperture stop 410. This asymmetrical arrangement allows light to enter the fifth lens 500 more quickly after passing through the aperture 410, which helps control the aperture of the off-axis beam and reduces vignetting at the edges of the field of view. The air gap between the sixth lens 600 and the seventh lens 700 is very small. This arrangement ensures that the seventh lens 700 can accurately correct the field curvature and residual aberrations accumulated by the previous group, without disrupting the already formed converging light path.

[0028] Reference Figure 1 As shown, in some implementations, the 18mm full-frame aerial lens satisfies the following relationship: 3.8 <TL / f<4; 0.2 < BF / TL < 0.3; Where f is the focal length of the 18mm full-frame aerial lens, BF is the back focal length of the 18mm full-frame aerial lens, and TL is the length of the 18mm full-frame aerial lens. The TL / f ratio range indicates that the total system length is controlled within 4 times the focal length, demonstrating the advantage of the retro-telephoto structure in achieving a large field of view within a limited space. This ratio allows the front negative lens to have sufficient space to fully diffuse light, while avoiding difficulties in adapting the aerial gimbal due to excessive increase in tube length.

[0029] Reference Figure 1As shown, in some embodiments, the 18mm full-frame aerial lens also includes a lens barrel, within which a first lens 100, a second lens 200, a third lens 300, a fourth lens 400, a fifth lens 500, a sixth lens 600, a seventh lens 700, and an eighth lens 800 are mounted. A photosensitive chip 910 is connected to the lens barrel, and the photosensitive chip 910 is covered with a protective glass 900. The lens barrel provides environmental protection and mechanical support. The actual shape of the lens barrel depends on the lens's operating environment and is therefore not shown in the accompanying drawings.

[0030] Reference Figure 1 As shown, in some embodiments, the fifth lens 500 and the eighth lens 800 are aspherical lenses. The fifth lens 500 is located after the aperture stop 410, on the critical path where light converges, and has a large positive power. The aspherical lens can specifically correct the optical path difference between peripheral and paraxial rays, allowing the entire light beam to converge at the same focal point, significantly improving the center sharpness and edge uniformity of the image. The eighth lens 800 is located at the end of the system, where the angle of incidence of light is complex. Using an aspherical lens helps control the angle of incidence of light reaching the image plane, thereby effectively increasing the optical path difference reaching the image plane, controlling lens imaging wavelet aberration, improving lens resolution performance, and controlling lens optical distortion.

[0031] Reference Figure 1 As shown, in some embodiments, the equations of the aspherical spherical curves of the fifth lens 500 and the eighth lens 800 are: , Where Z is the surface elevation along the direction parallel to the optical axis, r is the radial distance from the optical axis, c is the vertex curvature, and k is the conic constant. α 1 represents the first-order aspherical coefficient. α 2 represents the second-order aspherical coefficient. α 3 represents the third-order aspherical coefficient. α 4 represents the fourth-order aspherical coefficient. α 5 represents the 5th order aspherical coefficient. α 6 represents the sixth-order aspherical coefficient. α 7 represents the 7th order aspherical coefficient. α 1 and α The setting of the lower-order coefficients determines the lens's ability to correct principal aberrations, while α 3 to α The higher-order coefficients provide degrees of freedom for fine-tuning the light path.

[0032] Taking an example with an f-shape of 18mm, an aperture of f / 5.6, an actual imaging target diameter of 43.5mm, and a total lens length TTL of 70mm, the specific parameters of the optical system are shown in Table 1: Table 1

[0033] Among them, surface numbers S1 to S17 are the lens surface numbers arranged sequentially from the object side to the image side. S18 and S19 are the two surfaces of the protective glass 900.

[0034] The parameters of aspherical lenses are shown in Table 2: Table 2

[0035] In Table 2, A4 represents the second-order aspherical coefficient, A6 represents the third-order aspherical coefficient, A8 represents the fourth-order aspherical coefficient, A10 represents the fifth-order aspherical coefficient, A12 represents the sixth-order aspherical coefficient, and A14 represents the seventh-order aspherical coefficient.

[0036] Figure 2 and Figure 3 This is a chart showing the optical performance of the 18mm full-frame aerial lens in this embodiment. Figure 2 The MTF curve for an 18mm full-frame aerial lens is used to evaluate the resolving power of the optical system. Figure 3 As can be seen from the curves, the MTF curves of each field of view are relatively concentrated without large dispersion, indicating that the various aberrations of the optical system have been well corrected and the consistency of each field of view is good. Figure 3 For diffuse pattern, from Figure 3 As can be seen, the light rays in each field of view converge very closely, which is also close to the diffraction limit, further demonstrating that the system can achieve excellent imaging results. Figure 4 For the field curvature and distortion curves of the system, from Figure 4 As can be seen, the distortion is controlled at around 1%, which is very small and reaches the industrial level. Figure 5 The vertical axis chromatic aberration diagram of the system shows that all visible light rays are contained within the Airy disk, with no color overflow.

[0037] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. An 18mm full-frame aerial photography lens, characterized in that, From the object side to the image side, the lens consists of: a first lens (100) with negative optical power, a second lens (200) with negative optical power, a third lens (300) with positive optical power, a fourth lens (400) with positive optical power, an aperture stop (410), a fifth lens (500) with positive optical power, a sixth lens (600) with positive optical power, a seventh lens (700) with negative optical power, and an eighth lens (800) with positive optical power.

2. The 18mm full-frame aerial lens according to claim 1, characterized in that: The first lens (100) is a meniscus lens, the second lens (200) is a meniscus lens, the third lens (300) is a biconvex lens, the fourth lens (400) is a meniscus lens, the fifth lens (500) is a meniscus lens, the sixth lens (600) is a meniscus lens, the seventh lens (700) is a meniscus lens, and the eighth lens (800) is a meniscus lens.

3. The 18mm full-frame aerial lens according to claim 1, characterized in that: The following relationship must be satisfied: -1.1 <f1 / f<-0.9; -1.5 <f2 / f<-1.3; 0.9 <f3 / f<1.1; 1.6 <f4 / f<2.0; 3.6 <f5 / f<4.2; 1.0 <f6 / f<1.2; -1.1 <f7 / f<-0.8; 4 <f8 / f<5; Wherein, f is the focal length of the 18mm full-frame aerial lens, f1 is the focal length of the first lens (100), f2 is the focal length of the second lens (200), f3 is the focal length of the third lens (300), f4 is the focal length of the fourth lens (400), f5 is the focal length of the fifth lens (500), f6 is the focal length of the sixth lens (600), f7 is the focal length of the seventh lens (700), and f8 is the focal length of the eighth lens (800).

4. The 18mm full-frame aerial lens according to claim 1, characterized in that: The following relationship must be satisfied: 1.5 < Nd1 < 1.6; 1.9 < Nd2 < 2.0; 1.8 < Nd3 < 1.9; 1.6 < Nd4 < 1.7; 1.5 < Nd5 < 1.6; 1.5 < Nd6 < 1.6; 1.8 < Nd7 < 1.9; 1.4 < Nd8 < 1.6; Wherein, Nd1 is the refractive index of the first lens (100), Nd2 is the refractive index of the second lens (200), Nd3 is the refractive index of the third lens (300), Nd4 is the refractive index of the fourth lens (400), Nd5 is the refractive index of the fifth lens (500), Nd6 is the refractive index of the sixth lens (600), Nd7 is the refractive index of the seventh lens (700), and Nd8 is the refractive index of the eighth lens (800).

5. The 18mm full-frame aerial lens according to claim 1, characterized in that: The following relationship must be satisfied: 55 < Vd1 < 60; 16 < Vd2 < 20; 30 < Vd3 < 35; 55 < Vd4 < 65; 55 < Vd5 < 65; 65 < Vd6 < 75; 20 < Vd7 < 30; 55 < Vd8 < 65; Wherein, Vd1 is the dispersion coefficient of the first lens (100), Vd2 is the dispersion coefficient of the second lens (200), Vd3 is the dispersion coefficient of the third lens (300), Vd4 is the dispersion coefficient of the fourth lens (400), Vd5 is the dispersion coefficient of the fifth lens (500), Vd6 is the dispersion coefficient of the sixth lens (600), Vd7 is the dispersion coefficient of the seventh lens (700), and Vd8 is the dispersion coefficient of the eighth lens (800).

6. The 18mm full-frame aerial lens according to claim 5, characterized in that: The following relationship must be satisfied: 0.02 <A01 / TL<0.03; 0.05 <A02 / TL<0.06; 0.04 <A03 / TL<0.05; 0.08 < (A1S + AS2) / TL < 0.09; 0.25 <A1S / AS2<0.35; 0.025 <A05 / TL<0.035; 0.001 <A06 / TL<0.002; 0.01 <A07 / TL<0.02; Wherein, A01 is the air gap between the first lens (100) and the second lens (200), A02 is the air gap between the second lens (200) and the third lens (300), A03 is the air gap between the third lens (300) and the fourth lens (400), A1S is the air gap between the fourth lens (400) and the aperture (410), AS2 is the air gap between the aperture (410) and the fifth lens (500), A05 is the air gap between the fifth lens (500) and the sixth lens (600), A06 is the air gap between the sixth lens (600) and the seventh lens (700), A07 is the air gap between the seventh lens (700) and the eighth lens (800), and TL is the length of the 18mm full-frame aerial lens.

7. The 18mm full-frame aerial lens according to claim 1, characterized in that: The following relationship must be satisfied: 3.8 <TL / f<4; 0.2 < BF / TL < 0.3; Where f is the focal length of the 18mm full-frame aerial lens, BF is the back focal length of the 18mm full-frame aerial lens, and TL is the length of the 18mm full-frame aerial lens.

8. The 18mm full-frame aerial lens according to claim 1, characterized in that: The 18mm full-frame aerial lens also includes a lens barrel, in which the first lens (100), the second lens (200), the third lens (300), the fourth lens (400), the fifth lens (500), the sixth lens (600), the seventh lens (700), and the eighth lens (800) are mounted.

9. The 18mm full-frame aerial lens according to claim 1, characterized in that: The fifth lens (500) and the eighth lens (800) are aspherical lenses.

10. The 18mm full-frame aerial lens according to claim 9, characterized in that: The equations of the aspherical spherical curves of the fifth lens (500) and the eighth lens (800) are as follows: ， Where Z is the surface elevation along the direction parallel to the optical axis, r is the radial distance from the optical axis, c is the vertex curvature, and k is the conic constant. α 1 represents the first-order aspherical coefficient. α 2 represents the second-order aspherical coefficient. α 3 represents the third-order aspherical coefficient. α 4 represents the fourth-order aspherical coefficient. α 5 represents the 5th order aspherical coefficient. α 6 represents the sixth-order aspherical coefficient. α 7 represents the 7th order aspherical coefficient.

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