Light-weight large-aperture athermalization telephoto lens for unmanned aerial vehicle and electronic equipment

Abstract

The invention discloses a light-weight large-aperture athermalization telephoto lens for an unmanned aerial vehicle and electronic equipment. The first lens to the fourth lens are sequentially arranged from the object side to the image side along an optical axis. Wherein the first lens has a positive refractive index, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens has positive refractive index, the object side surface is a convex surface, and the image side surface is a concave surface; the third lens has a negative refractive index, the object side surface is a convex surface, and the image side surface is a concave surface; the fourth lens element with positive refractive index has a convex object-side surface and a concave image-side surface. According to the lens group, through positive-positive-negative-positive focal power distribution and convex-concave surface shape combination, monochromatic aberrations such as spherical aberration and coma aberration are effectively corrected, and field curvature and distortion are inhibited. The structure is favorable for realizing the design of a large aperture (such as F1.1), the introduction of the negative lens reduces the high-order aberration sensitivity, and a larger clear aperture is allowed without sacrificing the image quality, so that the requirement of high light incoming quantity in a weak light environment is met.

Description

Technical Field

[0001] This invention relates to the field of drone lens technology, and in particular to a lightweight, large-aperture, thermally amplified telephoto lens for drones and related electronic equipment. Background Technology

[0002] The widespread application of drones in surveying, monitoring, agriculture, rescue, and national defense has placed comprehensive and stringent performance demands on airborne optical systems. These demands are concentrated in several aspects, including lightweight and miniaturization, high resolution, large aperture, wide temperature range adaptability, and long focal length. Specifically, the limited payload capacity of drones requires compact and lightweight lens structures; high resolution is fundamental to ensuring clear capture of ground details from high altitudes; large apertures (such as F-numbers less than 1.1) can increase light intake and shorten exposure time in twilight or low-light environments, thereby suppressing motion blur; a wide operating temperature range (-40℃ to 80℃) must overcome problems such as defocusing, lens delamination, and image quality degradation that are common in ordinary lenses; and long focal length design is particularly crucial for long-distance observation and avoiding target interference, usually requiring the use of reasonable optical power allocation and aspherical lenses to correct advanced aberrations and improve image quality.

[0003] However, currently available drone lenses, especially in the telephoto range, generally struggle to achieve all of the aforementioned performance characteristics. Common issues include: large apertures (such as F2.0 and above) resulting in insufficient low-light imaging performance; inability to maintain image stability and sharpness under drastic temperature changes; or exceeding size and weight limits in pursuit of long focal lengths, making them unsuitable for drone payload constraints. These contradictions reflect a significant technological tension in achieving multiple objectives—long focal length, large aperture, high image quality, and high thermal stability—within limited size and weight constraints.

[0004] Therefore, the industry urgently needs to develop a new type of optical system that integrates long focal length, large aperture, high resolution, miniaturization, and high environmental stability. Such designs typically require the use of high-refractive-index glass, aspherical lenses (including plastic aspherical lenses introduced for weight reduction), and materials with low coefficients of thermal expansion to simultaneously address challenges such as aberration correction and thermal drift control. However, the introduction of these materials also leads to a significant increase in material and processing costs (coating, assembly, calibration), especially the difference in coefficients of thermal expansion between plastic aspherical lenses and glass materials, which presents additional optomechanical matching challenges in wide-temperature applications. How to achieve a breakthrough in comprehensive performance while controlling costs and ensuring reliability has become a key issue in the development of UAV-borne optical lenses. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a lightweight, large-aperture, thermally aggravated telephoto lens for unmanned aerial vehicles (UAVs) and an electronic device. This lens can at least solve one of the technical shortcomings mentioned in the background art. According to one aspect of the present invention, a lightweight, large-aperture, thermally aberration-corrected telephoto lens for unmanned aerial vehicles is provided, wherein the lens comprises, sequentially, a first lens to a fourth lens along an optical axis from the object side to the image side; wherein, The first lens has positive refractive index, with the object side being convex and the image side being concave; The second lens has positive refractive index, with a convex object-side surface and a concave image-side surface; The third lens has a negative refractive index, with the object side being convex and the image side being concave. The fourth lens has a positive refractive index, with a convex object side and a concave image side.

[0006] In the aforementioned technical solution, a four-element lens structure is proposed to address the optical performance requirements of telephoto lenses mounted on UAVs. From the object side to the image side, it comprises a positive refractive index convex-concave first lens, a positive refractive index convex-concave second lens, a negative refractive index convex-concave third lens, and a positive refractive index convex-concave fourth lens. This design partially solves the key issues mentioned in the background technology, such as large aperture, high resolution, and aberration correction. Regarding aberration correction and optical path control, this lens group effectively corrects monochromatic aberrations such as spherical aberration and coma by using a positive-positive-negative-positive power distribution and a combination of convex and concave surface shapes, while suppressing field curvature and distortion. The positive refractive index design of the first and second lenses provides the main power, achieving the foundation for long focal lengths; the negative refractive index of the third lens introduces negative spherical aberration compensation, balancing the aberrations generated by the previous group and improving off-axis imaging quality; the fourth lens further optimizes image plane flatness, ensuring consistency from the center to the edge of the image. This structure facilitates the design of large apertures (such as F1.1). The introduction of negative lenses reduces the sensitivity to advanced aberrations, allowing for a larger aperture without sacrificing image quality, thus supporting the high light intake requirements in low-light environments.

[0007] In some embodiments, the first lens and the second lens are made of high-refractive-index infrared glass material; the third lens and the fourth lens are made of low-refractive-index infrared glass material; and at least one of the first lens, the second lens, the third lens and the fourth lens has an aspherical surface.

[0008] In the above technical solution, improvements in optical performance, chromatic aberration correction, and environmental adaptability are achieved by introducing a combination of high / low refractive index infrared glass materials and at least one aspherical surface. Firstly, the combination of high and low refractive index glass plays a crucial role in image quality improvement and chromatic aberration correction. The first and second positive lenses use high refractive index materials, which, while bearing the main optical power, effectively reduce the lens's radius of curvature. This not only helps reduce higher aberrations such as spherical aberration but also contributes to system miniaturization. The third negative lens uses low refractive index materials, and combined with the front and rear positive lenses, it forms a classic "positive-positive-negative" partial chromatic aberration correction unit, capable of efficiently correcting axial chromatic aberration and magnification chromatic aberration. This material combination effectively suppresses the blurring problem of multicolor light imaging, which is particularly significant due to long focal lengths and large apertures, providing a crucial material foundation for the system to maintain a high MTF value at 42 lp / mm. Regarding system performance expansion and fine aberration correction, at least one lens surface is aspherical, providing a high degree of freedom for correcting higher aberrations that conventional spherical lenses cannot eliminate. Aspherical lenses can correct spherical aberration, coma, and even astigmatism, ensuring high contrast and clear imaging from the center to the edge of the image even at its widest aperture, thus fully utilizing the resolution of 20-30 megapixel sensors. Simultaneously, by replacing multiple spherical lenses with a single lens element, aspherical lenses further enable the system's lightweight and miniaturization. Regarding environmental adaptability and application range expansion, transmittance and dispersion have been optimized for the infrared band, allowing it to operate not only in the visible light range but also with better compatibility in the near-infrared band. This significantly improves the lens's penetration ability in adverse weather conditions such as fog and haze, and makes it suitable for drone monitoring systems using infrared illumination or night vision imaging, thereby indirectly enhancing its practical value in low-light environments such as dawn, dusk, and night.

[0009] In some embodiments, the lens satisfies the following condition: Nd1=Nd2 In the formula, Nd1 is the refractive index of the first lens and Nd2 is the refractive index of the second lens.

[0010] In the above technical solution, the first and second lenses have equal refractive indices and both have positive refractive indices. Using the same refractive index material ensures that the refractive behavior of light passing through these two key positive optical power elements is highly consistent. This greatly simplifies the correction process for spherical aberration and field curvature, eliminating aberration contributors caused by refractive index differences. This design provides a clear and stable starting point for subsequent introduction of negative lenses (such as a third lens) for chromatic aberration and astigmatism correction, reducing the complexity and sensitivity of aberration correction in the entire optical system. Furthermore, materials of the same or similar series often have similar thermo-optical properties (such as dn / dt) and coefficients of thermal expansion, reducing additional thermal aberrations caused by inconsistent thermal behavior of the first two lens sets over a wide temperature range (-40℃ to 80℃). This contributes to the system's fundamental stability in achieving "passive optical thermal aberration reduction," indirectly supporting the goal of "globally clear" imaging.

[0011] In some embodiments, the lens satisfies the following condition: Nd3=Nd4 In the formula, Nd3 is the refractive index of the third lens and Nd4 is the refractive index of the fourth lens.

[0012] In the above technical solution, the third lens has a negative refractive index, and the fourth lens has a positive refractive index, forming a classic "negative-positive" compensation group. With equal refractive indices, this compensation group maintains consistent fundamental ray deflection characteristics based on refractive index when the light path direction is changed (from divergent to convergent). This design ensures that when effectively compensating for residual field curvature and astigmatism in the first and second lenses, the lens group does not introduce additional, uncontrollable higher-order spherical aberrations due to refractive index differences, greatly simplifying the correction process and improving the stability and uniformity of off-axis field-of-view image quality at large apertures. Regarding thermal stability, lenses of the same material sequence typically have similar thermo-optical coefficients (dn / dt). This makes the thermally induced focus drift behavior of the third and fourth lens groups more synchronized and predictable when facing wide temperature ranges (-40℃ to 80℃), working well with the aforementioned active mechanical compensation mechanism to jointly suppress thermal defocusing and solidify the system's "all-around sharpness" imaging capability.

[0013] In some embodiments, the lens satisfies the following condition: 60mm <f1<75mm; 40mm <f2<50mm; -25mm <f3<-20mm; 50mm <f4<60mm; In the formula, 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.

[0014] In the above technical solution, the first lens undertakes the main task of converging light; the second lens, in conjunction with the first lens, establishes the focal length base axis. This architecture, with positive optical power distributed in the front group, allows the system to achieve a long focal length while effectively compressing subsequent optical paths, thus successfully controlling the total optical length within 82mm. The core function of the third lens is to correct the large amount of positive spherical aberration and positive Petzval field curvature generated by the first two groups of positive lenses, which is a prerequisite for achieving an F1.1 ultra-large aperture. If the focal length of the third lens is too short, although it can strongly correct aberrations, it will introduce significant negative distortion and increase the system's sensitivity; conversely, the correction capability will be insufficient. The current range ensures that while effectively correcting aberrations, it forms a smooth light transition with the front and rear positive lenses, laying the foundation for high image quality (high MTF value) at large apertures. The main function of the fourth lens is to finely adjust the image plane position, balance astigmatism and distortion, and further suppress residual aberrations. This focal length range ensures the mildness and controllability of its contribution, improves the system's tolerance performance, and facilitates production and assembly. Meanwhile, the "positive-positive-negative-positive" symmetrical structure formed by it together with the first three lenses helps the beam to flatten out at the end of the system, thereby obtaining a flat image plane and ensuring consistent high resolution from the center to the edge of the image.

[0015] In some embodiments, the lens barrel adopts a combined structure lens barrel, which contains at least two metal materials with different coefficients of thermal expansion.

[0016] In the above technical solution, a thermomechanical compensator is constructed by selecting metal materials with different coefficients of thermal expansion (such as aluminum alloy and magnesium alloy) and designing their mating structure and gaps. When the ambient temperature varies within the range of -40℃ to 80℃, the lens barrel components made of different materials will undergo differentiated axial expansion or contraction. This preset, calculable displacement is used to actively drive the key lens group (or image plane) to produce corresponding axial movement, thereby accurately compensating for the focus drift caused by changes in the refractive index (dn / dt) and glass thickness of the lens material due to temperature changes, effectively suppressing thermal defocusing and ensuring "all-around sharp" imaging performance across the entire temperature range. Magnesium alloy, as a high-strength, lightweight material, bears the main frame of the lens barrel, achieving extreme lightweighting (total weight <210g). The other metal introduced (such as aluminum alloy) not only serves as a thermal compensation element, but its composite structure with magnesium alloy also optimizes the overall stiffness and strength of the lens barrel. This combined design provides greater structural stability than single-material or all-plastic structures when dealing with vibrations and shocks during drone flight, thus ensuring that the precisely aligned lens optical axis does not shift under harsh mechanical conditions and maintains long-term stable high optical performance.

[0017] In some embodiments, the lens barrel has a hollow design.

[0018] In the aforementioned technical solution, the mass of the lens barrel is significantly reduced by selectively removing material from non-critical load-bearing components. Combined with the use of high-strength magnesium alloy, extremely high material utilization and structural efficiency are achieved. While ensuring the main rigidity of the lens barrel and the strength of the mounting interfaces, redundant mass is minimized, saving valuable space for the UAV payload and improving the aircraft's endurance and maneuverability. The hollow structure objectively increases the surface area to volume ratio of the lens barrel. The increased surface area promotes convective heat transfer between the inside and outside of the lens barrel, helping to equalize the temperature field of the entire lens system, reducing localized heat accumulation, and thus assisting in achieving thermal equilibrium more quickly and uniformly through thermal differential design. This characteristic plays a positive role in suppressing lens deformation or stress caused by temperature gradients and maintaining long-term thermal stability.

[0019] In some embodiments, the lens satisfies the following condition: TTL < 82; F#≤1.1; In the formula, TTL is the total optical length of the lens, and F# is the aperture number of the lens.

[0020] In the aforementioned technical solutions, TTL conditional mode not only significantly reduces the overall weight of the lens, but more importantly, it allows it to easily adapt to the limited payload space of drones, providing a crucial prerequisite for improving the aircraft's maneuverability and endurance. F# conditional mode allows the camera system to use lower ISO for shooting, thereby significantly suppressing image noise and improving the signal-to-noise ratio and dynamic range; at the same time, it enables the system to use shorter exposure times, significantly reducing motion blur caused by drone flight or target movement, which is crucial for applications such as monitoring and rescue.

[0021] According to another aspect of the present invention, an electronic device is provided, comprising the aforementioned lightweight, large-aperture, thermally aberrant telephoto lens for a drone; and An image sensor is configured to receive images formed by the telephoto lens of the lightweight, large-aperture, thermally absorbed UAV.

[0022] In the above technical solution, the advantage of this electronic device relies on a lightweight, large-aperture, thermally differentially controlled telephoto lens for drones, which will not be elaborated here. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of Example 1 of a lightweight, large-aperture, thermally amplified telephoto lens for a drone according to the present invention; Figure 2 This is the MTF curve of Example 1 of a lightweight, large-aperture, thermally amplified telephoto lens for a drone according to the present invention; Figure 3 This is a field curvature and distortion curve diagram of Example 1 of a lightweight, large-aperture, thermally abbreviated telephoto lens for UAVs according to the present invention; Figure 4 This is a dot diagram of Example 1 of a lightweight, large-aperture, thermally differential-controlled telephoto lens for a drone according to the present invention; Figure 5 This is a defocus MTF curve of Example 1 of a lightweight, large-aperture, thermally amplified telephoto lens for UAVs according to the present invention; Figure 6 This is a relative illumination diagram of Example 1 of a lightweight, large-aperture, thermally adiabatic telephoto lens for a drone according to the present invention; Figure 7 This is a schematic diagram of the structure of Example 2 of a lightweight, large-aperture, thermally amplified telephoto lens for UAVs according to the present invention; Figure 8 This is the MTF curve of Example 2 of a lightweight, large-aperture, thermally amplified telephoto lens for a drone according to the present invention; Figure 9 This is a field curvature and distortion curve diagram of Example 2 of a lightweight, large-aperture, thermally abbreviated telephoto lens for UAVs according to the present invention; Figure 10 This is a dot diagram of Example 2 of a lightweight, large-aperture, thermally differential-controlled telephoto lens for UAVs according to the present invention; Figure 11 This is a defocus MTF curve of Example 2 of a lightweight, large-aperture, thermally amplified telephoto lens for UAVs according to the present invention; Figure 12 This is a relative illumination diagram of Example 2 of a lightweight, large-aperture, thermally adiabatic telephoto lens for a drone according to the present invention; Figure 13 This is a structural schematic diagram of Example 3 of a lightweight, large-aperture, thermally amplified telephoto lens for UAVs according to the present invention; Figure 14 This is the MTF curve of Example 3 of a lightweight, large-aperture, thermally amplified telephoto lens for a drone according to the present invention; Figure 15 This is a field curvature and distortion curve diagram of Example 3 of a lightweight, large-aperture, thermally abbreviated telephoto lens for UAVs according to the present invention; Figure 16 This is a dot diagram of Example 3 of a lightweight, large-aperture, thermally differential-controlled telephoto lens for UAVs according to the present invention; Figure 17This is the defocus MTF curve of Example 3 of a lightweight, large-aperture, thermally amplified telephoto lens for UAVs according to the present invention; Figure 18 This is a relative illumination diagram of Example 3 of a lightweight, large-aperture, thermally amplified telephoto lens for a drone according to the present invention; Figure 19 This is a schematic diagram of the structure of Example 4 of the electronic device of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The purpose of this invention is to provide a lightweight, large-aperture, thermally aberration-controlled telephoto lens and electronic device for unmanned aerial vehicles (UAVs) with high optical performance. Embodiments according to the invention will now be described in detail with reference to the accompanying drawings.

[0027] Figure 1 , Figure 7 , Figure 13 These are cross-sectional views of the real-viewing lenses (optical systems) according to Examples 1 to 3. The real-viewing lenses according to each example are used in imaging equipment including digital cameras, digital still cameras, broadcast cameras, surveillance cameras, etc., and in electronic devices with interchangeable lenses. In each cross-sectional view, the left side is the object-side OBJ and the right side is the image-side IMA. In each cross-sectional view, Li represents the i-th lens, and ST represents the aperture stop (fixed aperture stop or visible aperture stop). IMA represents the image plane, and when the real-viewing lenses according to each example are used in the imaging optical system of a digital camera or digital still camera, a solid-state imaging element (photoelectric conversion element), such as a CMOS image sensor or a CCD image sensor, is arranged on the image plane IMA.

[0028] According to the examples of lightweight, large-aperture, thermally aberration-corrected telephoto lenses for drones, the lenses, from the object side to the image side along an optical axis, are sequentially arranged as a first lens to a fourth lens; wherein... The first lens L1 has positive refractive index, with a convex object-side surface and a concave image-side surface; The second lens L2 has a positive refractive index, with a convex object-side surface and a concave image-side surface; The third lens L3 has a negative refractive index, with a convex object-side surface and a concave image-side surface; The fourth lens L4 has a positive refractive index, with a convex object side and a concave image side.

[0029] The first lens L1 and the second lens L2 are made of high-refractive-index infrared glass material; the third lens L3 and the fourth lens L4 are made of low-refractive-index infrared glass material; and at least one of the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 has an aspherical surface.

[0030] The lens barrel employs a modular structure, incorporating at least two metallic materials with different coefficients of thermal expansion. The barrel is made of a hollowed-out magnesium alloy, achieving extremely low weight while maintaining structural strength. The total system weight is successfully controlled to 210g, and the total optical length to 82mm, saving valuable payload space for the drone and significantly improving its flight time and agility. Furthermore, a design combining passive optical thermal aberration mitigation with active mechanical compensation is employed. By selecting frame materials with different coefficients of thermal expansion (such as a combination of aluminum and magnesium alloys) and calculating and reserving thermal expansion gaps, the entire optical system can automatically maintain image plane stability under drastic temperature changes from -40℃ to 80℃, avoiding thermal focus shift and achieving "all-around sharpness." Simultaneously, the system's sealing is enhanced, providing dust and moisture protection and adapting to various harsh climates.

[0031] The lightweight, large-aperture, thermally abbreviated telephoto lens for drones in each example can satisfy at least one of the following settings 1) to 8): 1) Nd1 = Nd2; 2) Nd3 = Nd4; 3) 60mm <f1<75mm; 4) 40mm <f2<50mm; 5)-25mm <f3<-20mm; 6) 50mm <f4<60mm; 7) TTL < 39; 8) F#≤1.1; In the above conditional expressions, 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, 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, TTL is the total optical length of the lens, and F# is the aperture number of the lens.

[0032] A detailed description of lightweight, large-aperture, thermally aberration-correcting telephoto lenses for drones, based on various examples, will now be provided.

[0033] Please refer to the optical structure of Example 1. Figure 1The specific parameters for Example 1 are shown in Tables 1 and 2 below. In Example 1, the lens focal length f' = 84.95 and the aperture number F# = 1.1.

[0034] Table 1 Parameter Table for Example 1

[0035] Table 2 Aspheric Coefficient Parameter Table

[0036] Please see Figure 2 The MTF curve of Example 1 at 42 lp / mm shows that the design has reached the diffraction limit, indicating that the resolution in the central region is extremely high. The separation in the meridional and sagittal directions achieves a balance between high central sharpness and uniform image quality across the entire field of view within a small range. Figure 3 The above is the field curvature and distortion curve of Example 1. The distortion curve shows a slight pincushion distortion trend. At the maximum field of view (6.75°), the distortion value is about +2%. The curve is close to linear, without obvious inflection points or abnormal fluctuations, indicating that the distortion changes uniformly and controllably with the field of view. The overall performance is balanced and there are no obvious imaging geometric defects. Figure 4 This is a dot plot of Example 1; the spot size is extremely small, almost close to the Airy disk, the energy is highly concentrated, and the circles of confusion in the meridional and sagittal directions almost coincide, indicating that the on-axis aberrations are well controlled and the central sharpness is high. Figure 5 This is the defocus MTF curve of Example 1; the lens has good consistency in optimal focal plane imaging at a frequency of 21 lp / mm. Figure 6 This is the relative illumination diagram for Example 1; from the center field of view (0°) to the maximum field of view (6.75°), the relative illumination remains above 0.98 overall, with only a slight decrease at the edges. Therefore, this lens exhibits excellent relative illumination performance, with minimal illumination attenuation across the entire field of view and very good vignetting control. Please refer to the optical structure of Example 2. Figure 7 The specific parameters for Example 2 are shown in Tables 3 and 4 below. In Example 2, the lens focal length f' = 85.01 and the number of revolutions F# = 1.1.

[0037] Table 3 Parameter Table for Example 2

[0038] Table 4 Aspheric Coefficient Parameter Table

[0039] Please see Figure 8The MTF curve of Example 2 at 42 lp / mm shows that the design has reached the diffraction limit, indicating that the resolution in the central region is extremely high. The separation in the meridional and sagittal directions achieves a balance between high central sharpness and uniform image quality across the entire field of view within a small range. Figure 9 The field curvature and distortion curves are from Example 2. The distortion curve shows a slight pincushion distortion trend. At the maximum field of view (6.7°), the distortion value is about +2%. The curve is close to linear, without obvious inflection points or abnormal fluctuations, indicating that the distortion changes uniformly and controllably with the field of view. The overall performance is balanced and there are no obvious imaging geometric defects. Figure 10 This is the dot plot of Example 2; the spot size is extremely small, almost close to the Airy disk, the energy is highly concentrated, and the circles of confusion in the meridional and sagittal directions almost coincide, indicating that the on-axis aberrations are well controlled and the central sharpness is high. Figure 11 This is the defocus MTF curve of Example 2; the lens exhibits good consistency in optimal focal plane imaging at a frequency of 21 lp / mm. Figure 12 This is the relative illumination diagram for Example 2; from the center field of view (0°) to the maximum field of view (6.7°), the relative illumination remains above 0.98 overall, with only a slight decrease at the edges. Therefore, this lens exhibits excellent relative illumination performance, with minimal illumination attenuation across the entire field of view and very good vignetting control. Please refer to the optical structure of Example 3. Figure 13 The specific parameters for Example 3 are shown in Tables 5 and 6 below. In Example 3, the lens focal length f' = 84.99 and the aperture number F# = 1.1.

[0040] Table 5 Parameter Table for Example 3

[0041] Table 6 Aspheric Coefficient Parameter Table

[0042] Please see Figure 14 The MTF curve of Example 3 at 42 lp / mm shows that the design has reached the diffraction limit, indicating that the resolution in the central region is extremely high. The separation in the meridional and sagittal directions achieves a balance between high central sharpness and uniform image quality across the entire field of view within a small range. Figure 15 The field curvature and distortion curves are from Example 3. The distortion curve shows a slight pincushion distortion trend. At the maximum field of view (6.75°), the distortion value is about +2%. The curve is close to linear, without obvious inflection points or abnormal fluctuations, indicating that the distortion changes uniformly and controllably with the field of view. The overall performance is balanced, and there are no obvious imaging geometric defects. Figure 16This is the dot plot of Example 3; the spot size is extremely small, almost close to the Airy disk, the energy is highly concentrated, and the circles of confusion in the meridional and sagittal directions almost coincide, indicating that the on-axis aberrations are well controlled and the central sharpness is high. Figure 17 This is the defocus MTF curve of Example 3; the lens exhibits good consistency in optimal focal plane imaging at a frequency of 21 lp / mm. Figure 18 This is the relative illumination diagram for Example 3; from the center field of view (0°) to the maximum field of view (6.75°), the relative illumination remains above 0.98 overall, with only a slight decrease at the edges. Therefore, this lens exhibits excellent relative illumination performance, with minimal illumination attenuation across the entire field of view and very good vignetting control. Based on Examples 1 to 3, this case has the following advantages: Based on the aforementioned performance bottlenecks of UAV optical systems, this invention achieves a systematic breakthrough in terms of lightweighting, optical performance, and environmental adaptability by integrating innovative materials and composite thermal differential design. The specific technical advantages are as follows.

[0043] In terms of structural and lightweight design, this invention adopts a technical approach combining aspherical infrared lenses with a hollowed-out magnesium alloy lens barrel. The aspherical lenses effectively control the aperture and correct aberrations while significantly reducing the weight of the lens assembly; the lens barrel uses high-strength magnesium alloy material and features a hollowed-out structure design, achieving extreme lightweighting while ensuring overall rigidity and structural strength. Ultimately, the total weight of the system is successfully controlled to within 210g, and the total optical length does not exceed 82mm, saving crucial space for the UAV payload and contributing to improved flight endurance and maneuverability.

[0044] In terms of optical performance, this invention features an ultra-large F1.1 aperture, providing ample light intake in low-light environments such as dawn, dusk, night, or indoors. This allows the system to use lower ISO and shorter exposure times for shooting, effectively suppressing image noise, improving dynamic range, and significantly reducing motion blur. Furthermore, at a high spatial frequency of 42 lp / mm, the system's MTF value remains above 0.38, indicating excellent high-frequency information transmission capabilities. This fully leverages the imaging potential of 20-30 megapixel high-resolution sensors, meeting the detail requirements of professional aerial surveying and high-definition surveillance applications for consistent image quality from center to edge.

[0045] In terms of environmental adaptability and thermal stability, this invention integrates passive optical thermal aberration mitigation with active mechanical compensation mechanisms. By selecting frame materials with different coefficients of thermal expansion (such as a combination of aluminum and magnesium alloys) and precisely designing the thermal expansion gap, the system can automatically maintain image plane stability within a wide temperature range of -40℃ to 80℃, effectively suppressing thermal defocusing and achieving "all-around sharp" imaging. The system also possesses excellent sealing performance, providing dust and moisture protection and adapting to various harsh climatic conditions, thus ensuring reliable operation even in complex environments.

[0046] Example 4 For reference Figure 19 A description of an electronic device A according to Example 4 of the present invention will be given. Figure 19 This is a schematic diagram of an electronic device used in a camera optical system, based on any of the lightweight, large-aperture, thermally aberrant telephoto lenses for drones according to Examples 1 to 3.

[0047] exist Figure 19 In the figures, reference numeral A2 indicates the main body of the electronic device, and reference numeral A1 indicates any of the camera optical systems (interchangeable lenses) including the lightweight, large-aperture, thermally achromatic telephoto lenses for UAVs according to Examples 1 to 3. Reference numeral A3 indicates an image sensor (photoelectric conversion element) such as a CMOS image sensor or a CCD image sensor, which is built into the camera body A2 and receives light (the optical image formed by the camera optical system A1) from the camera optical system A1 and performs photoelectric conversion.

[0048] By using a lightweight, large-aperture, thermally aberrant drone telephoto lens according to any one of Examples 1 to 3 in an electronic device such as a digital still camera, an electronic device with a lightweight, large-aperture, thermally aberrant drone telephoto lens with high optical performance can be obtained.

[0049] Each example can provide electronic devices with high optical performance.

[0050] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims will be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A lightweight, large-aperture, thermally aberration-corrected telephoto lens for drones, characterized in that, The lens consists of four lenses, from the object side to the image side, arranged sequentially along an optical axis: the first lens to the fourth lens. The first lens has positive refractive index, with the object side being convex and the image side being concave; The second lens has positive refractive index, with a convex object-side surface and a concave image-side surface; The third lens has a negative refractive index, with the object side being convex and the image side being concave. The fourth lens has a positive refractive index, with a convex object side and a concave image side.

2. The lightweight, large-aperture, thermally aberration-reducing telephoto lens for UAVs as described in claim 1, characterized in that, The first lens and the second lens are made of high-refractive-index infrared glass material; the third lens and the fourth lens are made of low-refractive-index infrared glass material; and at least one of the first lens, the second lens, the third lens and the fourth lens has an aspherical surface.

3. The lightweight, large-aperture, thermally aberration-reducing telephoto lens for UAVs as described in claim 2, characterized in that... The lens satisfies the following condition: Nd1=Nd2 In the formula, Nd1 is the refractive index of the first lens and Nd2 is the refractive index of the second lens.

4. A lightweight, large-aperture, thermally aberration-reducing telephoto lens for UAVs as described in claim 2 or 3, characterized in that, The lens satisfies the following condition: Nd3=Nd4 In the formula, Nd3 is the refractive index of the third lens and Nd4 is the refractive index of the fourth lens.

5. A lightweight, large-aperture, thermally aberration-reducing telephoto lens for UAVs as described in claim 1, characterized in that, The lens satisfies the following condition: 60mm < f1 < 75mm; 40mm < f2 < 50mm; -25mm < f3 < -20mm; 50mm < f4 < 60mm; In the formula, 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.

6. The lightweight, large-aperture, thermally aberration-reducing telephoto lens for UAVs as described in claim 1, characterized in that, The lens barrel adopts a modular structure, which contains at least two metal materials with different coefficients of thermal expansion.

7. A lightweight, large-aperture, thermally aberration-reducing telephoto lens for UAVs as described in claim 6, characterized in that, The lens barrel features a hollow design.

8. A lightweight, large-aperture, thermally aberration-reducing telephoto lens for UAVs as described in claim 1, characterized in that, The lens satisfies the following condition: TTL < 39; F#≤1.1； In the formula, TTL is the total optical length of the lens, and F# is the aperture number of the lens.

9. An electronic device, characterized in that, A lightweight, large-aperture, thermally aberration-reduced telephoto lens for unmanned aerial vehicles according to any one of claims 1-8; and An image sensor is configured to receive images formed by the telephoto lens of the lightweight, large-aperture, thermally absorbed UAV.

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